Like this paper and download? You can publish your own PDF file online for free in a few minutes!Sign Up
File loading please wait...
Citation preview
Textbook of Radiology & Imaging Edition 8 Volume 2 David Sutton Rodney Reznek, Janet Murfitt Adaptation Editor Bharat Aggarwal Director, Radiology Services, Max Healthcare, New Delhi, India Adjunct Professor, Koita Centre for Digital Health (KCDH) of Indian Institute of Technology, Bombay
Associate Editors Amit Kumar Sahu Consultant
Department of Radiology Max Superspeciality Hospital, Saket
New Delhi, India
Akshay D. Baheti Professor Department of Radiodiagnosis Tata Memorial Center and Homi Bhabha National University Mumbai, Maharashtra, India
Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
Subba R. Digumarthy Associate Professor of Radiology
Harvard Medical School
Boston, MA, United States Head of Thoracic Oncology Imaging Division of Thoracic Imaging and Intervention
Massachusetts General Hospital Boston, MA, United States
Sujit Vaidya Consultant Radiologist
The Royal London Hospital, Barts Health NHS Trust
Queen Mary University of London, London, United Kingdom
Suresh K. Mukerji
Professor of Radiology & Radiation Oncology
University of Louisville & University of Illinois, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, United States. Faculty, Otolaryngology Head Neck Surgery, Michigan State University National Director of Head & Neck Radiology; Pro
Scan Imaging
Bruce Bradley Fellow; The Leapfrog Group
Suyash Mohan Associate Professor of Radiology & Neurosurgery, Perelman School of Medicine at the University of Pennsylvania
Philadelphia, PA, United States
Formerly, Clinical Lecturer-II University of Michigan, Ann Arbor, MI, United States
Copyright Elsevier RELX India Pvt. Ltd. Registered Office: 818, 8th floor, Indraprakash Building, 21, Barakhamba Road, New Delhi-110 001 Corporate Office: 14th Floor, Building No. 10B, DLF Cyber City, Phase II, Gurgaon-122 002, Haryana, India Textbook of Radiology & Imaging, 2 Volume Set, 7e, David Sutton, Rodney Reznek,
Set e-ISBN: 978-81-312-5962-7 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notice The adaptation has been undertaken by RELX India Pvt. Ltd and its sole responsibility. Medical Students, radiology residents, practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds or experiments described herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made. To the fullest extent of the law, no responsibility is assumed by Elsevier, authors, editors or contributors in relation to the adaptation or for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Although all advertising material is expected to conform to ethical (medical) standards, inclusion in this publication does not constitute a guarantee or endorsement of the quality or value of such product or of the claims made of it by its manufacturer. Authorised Territory for Print form only is India, Pakistan, Bangladesh, Nepal, Srilanka, Bhutan, Maldives, Singapore, Malaysia, Brunei, Indonesia, Philippines, Thailand, Vietnam, Cambodia, Laos and Myanmar.
Publisher’s `e-book’ shall have `World’ rights for selling globally through 3PP websites as approved by Proprietor. Content Strategist: Mrinalini Bakshi Content project Manager: Shivani Pal
Senior Production Executive: Dhan Singh Senior Graphic Artist: Gopalakrishnan Venkatraman
Typeset by Aptara Printed in India by xxx
Table of Contents Cover image Title page Copyright Foreword Preface Contributors Chapter 52: Arthritis Degenerative and Erosive OA Inflammatory Arthropathies Connective Tissue Diseases of Joints Crystal-Induced Arthropathies Metabolic, Hematologic, and Other Miscellaneous Causes of Arthritis
Summary Suggested Readings References Chapter 53: Endocrine and Metabolic Bone Diseases Homeostasis of Bone Role of Imaging Dual X-ray Absorptiometry Generalized Osteoporosis Regional Osteoporosis Biochemistry of Bone Metabolism Rickets and Osteomalacia Parathyroid Disorders Renal Osteodystrophy Tumoral Calcinosis Metal and Drug Toxicity Approach to Qualitative Imaging Approach to Quantitative Imaging Suggested Readings References
Chapter 54: Lymphoreticular and Hematopoietic Bone Diseases Introduction Diseases Primarily Involving Red Blood Cells Diseases Primarily Involving White Blood Cells Diseases of the Lymphoreticular System Diseases of the Coagulation System Bone Marrow Changes Suggested Readings References Chapter 55: Musculoskeletal Infections Introduction Soft-Tissue Infection Osteomyelitis Postoperative Joint Infection Brucellosis Actinomycosis Hydatid Disease (Echinococcus) Cysticercosis Cat-scratch Disease Syphilis
Elbow Imaging Elbow Pathology Elbow Arthritis Bursitis Neuropathies Suggested Readings References Chapter 58: Imaging of the Wrist and Hand Introduction Functional Anatomy Nerves of the Hand and Wrist Imaging Modalities and Protocols Conclusion Suggested Readings References Chapter 59: Hip Introduction Functional Anatomy Imaging Techniques and Protocol
Joint Pathology Conclusion/Overall Approach Suggested Readings References Chapter 60: Knee Overview of the Function of the Knee Joint Anatomy Imaging Protocols Effusion Synovial Pathologies Impingement of the Fat Pads Around the Knee Joint Chondral and Osteochondral Abnormalities Meniscus Cruciate Ligaments Anterior Knee Medial Knee and Posteromedial Corner of Knee Lateral Knee and Posterolateral Corner of Knee Tennis Leg Osteoarthritis of Knee Knee Arthroplasty
Summary Suggested Readings References Chapter 61: Ankle and foot Introduction Imaging Techniques and Protocol Normal Anatomy Abnormal Alignment Tarsal Coalition Ligament Abnormalities Stress Fractures Abnormal Tendons Ankle Impingement Syndromes Other Hindfoot Abnormalities Abnormalities of the Forefoot Nerve Abnormalities Arthroplasty, Arthrodesis, and Alignment Correction Surgeries Foreign Bodies Practical Approach to Imaging the Foot and Ankle Suggested Readings
References Chapter 62: Bone Tumors Introduction General Diagnostic Approach to Bone Tumors Primary Bone Tumors Other Primary Bone Tumors Metastatic Tumor Involvement of Bone Suggested Readings References Chapter 63: Bone Tumor Mimics Introduction Normal Variants Congenital and Developmental Abnormalities Trauma-Related Lesions Infection Metabolic and Degenerative Diseases Miscellaneous Overall Approach Suggested Readings
References Chapter 65: Oral Cavity and Pharynx Section 1: Oral Cavit Diseases of The Oral Cavity Section 2: Pharynx Nasopharynx Oropharynx and Hypopharynx Other Malignancies Non-Neoplastic Lesions Pharyngeal Trauma Take Home Points: Oral Cavity Take Home Points—Pharynx Suggested Readings References Chapter 66: Larynx Introduction Imaging Anatomy Imaging Techniques and Protocols Tumors of the Larynx
Non-Tumorous Lesions Post-Treatment Evaluation Summary Suggested Readings References Chapter 67: Neck Nodes Introduction Imaging Techniques and Appropriateness Anatomical Location of Nodes Lymphatic Drainage of the Head and Neck Region Differentials of a Neck Mass and How to Ascertain That the Lesion is a Node Imaging Features of a Normal and an Abnormal Node Etiologies Malignant Neck Nodes With Unknown Primary—Guidelines From AJCC 8th Edition Suggested Readings References Chapter 68: Neck Spaces Introduction
Approach to Diagnosis of a Suprahyoid Neck Space Mass [1,2] Masticator Space Buccal Space Parapharyngeal Space Parotid Space Carotid Space Retropharyngeal Space Perivertebral Space Posterior Cervical Space Sublingual and Submandibular Spaces Conclusion Suggested Readings References Chapter 69: Thyroid and Parathyroids Introduction Embryology Anatomy Imaging Methods Pathology Anatomy, Embryology, and Physiology
Introduction Echoes Membranes Tumors Trauma Ultrasonography of the Extraocular Region Conclusion Suggested Readings References Chapter 72: Temporal Bone Introduction Imaging Techniques Radiological Anatomy Normal Variants External Ear Pathologies Middle Ear and Mastoid Pathologies Inner Ear Pathologies Suggested Readings References
Chapter 73: Skull Base Introduction Skull Base Anatomy Embryologic Development Imaging Technique Pathology Malignant Neoplasms Benign Neoplasms Infectious and Inflammatory Processes Suggested Readings References Chapter 74: Oral and Dentomaxillofacial Radiology Introduction Anatomy Pathologies Radiographic Analysis of the TMJs Suggested Readings References Chapter 75: Benign Brain Lesions and Epilepsy
Introduction Cerebral Hemispheres Basal Ganglia Thalamus and Hypothalamus Limbic Structures Neuroendocrine Structures Brainstem Cerebellum Sensory Pathways Motor Pathways Cerebellar Networks Language Networks Olfactory System Visual System Auditory System Additional Sensory and Motor Cranial Nerves CT and MRI Image Display Contrast Enhancement Field Strength MRI Protocols
MR Techniques Using Tissue Properties Other Than Magnetic Relaxivity Positron Emission Tomography Extra-Axial Versus Intra-Axial Mass Effect Volume Loss Gray Matter Versus White Matter and Cortical Versus Subcortical Focal Versus Multiple Versus Diffuse Homogeneous Versus Heterogeneous and Cystic Versus Solid Benign Cysts Neuroendocrine Diseases Vascular Lesions CNS Infections Demyelinating Diseases Neuroinflammatory Lesions Epilepsy Suggested Readings References Chapter 76: Metabolic and Degenerative Diseases Introduction
Metabolic Disorders Toxic Disorders Pathophysiology Approach to the Diagnosis of Toxic and Metabolic Disorders of the Brain Neurodegenerative Disorders Summary References Chapter 77: Stroke and Vascular Abnormalities Introduction Pathophysiology, Mechanisms, Classification, Management Acute Stroke Imaging Protocols Clinical Scenarios Conclusion Suggested Readings References Chapter 78: Brain Tumors Introduction 2016 WHO Classification of Central Nervous System (CNS) Tumors
Brain Tumor Imaging Protocol Suggested Readings References Chapter 79: Spine Imaging Techniques of the Spine Anatomy Diseases Suggested Readings References Chapter 80: Pediatric Brain and Spine Introduction Embryology and Normal Prenatal Brain Development Brain Myelination Inherited Neurometabolic Disorders/Leukodystrophies Hypoxic Ischemic Encephalopathy Congenital and Developmental Supratentorial Brain Anomalies Congenital and Developmental Infratentorial Brain Anomalies Pediatric Brain Tumors Extra-axial Neoplasms
Ultrasound of the Infant Brain Ultrasound of the Infant Spine Phakomatoses Suggested Readings References Chapter 81: Pediatric Head and Neck Introduction Imaging Techniques and Protocols Pediatric Skull Base Paranasal Sinuses and Nasal Cavity (Table 81.3) Pediatric Temporal Bone Orbit and Lacrimal Glands (Table 81.5 and Box 81.3) Lacrimal Gland Pediatric Neck Masses (Box 81.4) Imaging of Thyroid/Parathyroid and Salivary Glands Pediatric Upper Airway Disorders; Pediatric Sleep and Voice Disorders; Velopharyngeal Insufficiency (Box 81.7) Pediatric Head & Neck Emergencies Syndromes in Children With Head & Neck Manifestations Pediatric Jaw Lesions
Suggested Readings References Chapter 82: Pediatric Congenital Heart Disease Introduction Normal Fetal Circulation Role of Advanced Imaging Segmental Approach to Congenital Heart Disease Classification of Congenital Heart Disease Overall Approach to CHD Suggested Readings References Chapter 83: Pediatric Chest Introduction Congenital Thoracic Abnormalities Intrathoracic Neoplasms and Masses Neonatal Chest Lung Pathologies in the Older Child Suggested Readings References
Chapter 84: Pediatric Gastrointestinal Tract and Hepatobiliary System Normal Embryology Imaging Techniques Upper Gastrointestinal Tract Anomalies Lower Gastrointestinal Tract Anomalies Approach to Neonatal Bowel Obstruction Acute and Inflammatory Disorders of the Gastrointestinal Tract Abdominal Wall Defects Disorders of Biliary System, Liver, and Pancreas Burkitt Lymphoma Suggested Readings References Chapter 85: Pediatric Genitourinary Tract Embryology Normal Anatomy and Anatomic Variants Diagnostic Procedures Developmental Anomalies of the Kidney and Urinary Tract Abnormalities of Fusion Congenital Anomalies of the Pelvicalyceal System and Ureter Cystic Renal Diseases in Children
Infectious and Inflammatory Diseases Congenital Lesions of The Urethra Congenital Scrotal Disorders The Acute Scrotum Renal Neoplasms in Children Disorders of Sex Development Suggested Readings References Chapter 86: Pediatric Musculoskeletal System Introduction Normal Pediatric Skeletal Anatomy and Development Upper Limb Disorders Pelvis and Lower Limb Disorders of the Axial Skeleton Multifocal Disorders: Infectious, Inflammatory, and Pseudoneoplastic Generalized Skeletal Disorders: Genomic and Chromosomal Generalized Skeletal Disorders: Metabolic Skeletal Findings in Haemoglobinopathies Nonaccidental Injury
Bone Age Assessment in Children (Also See the Appendix of Bone Age Estimation) Suggested Readings References Chapter 87: Skeletal Trauma Introduction Terminology Associated Soft-Tissue Abnormalities Fracture Healing Evaluation of Skeletal Trauma Complications of Fracture Arterial Injury Joint Injuries Other Forms of Trauma Chronic Trauma to the Joints (Neuropathic Arthropathy) Osteochondritis Dissecans (Osteochondral Fractures) Salter-Harris Fractures Fractures at the Elbow Slipped Upper Femoral Epiphysis Major Trauma
Pathological Fractures Suspected Physical Abuse Classic Metaphyseal Lesions Long Bone Fractures in Non-Ambulant Infants Spiral Fractures Rib Fractures Fracture Age Mimics of Physical Abuse Birth Injuries Upper Limb Fractures: the Shoulder and Upper Arm The Elbow The Wrist Carpal Fractures The Lower Limb Suggested Readings References Chapter 88: Neuro, Head, and Neck Trauma Introduction Intracranial Trauma Skull Including the Skull Base
Temporal Bone Trauma Facial Trauma—Midface, Orbits, Nasoseptal, and Mandible Craniocervical Junction, Subaxial Cervical Spine, and Thoracolumbar Spine Trauma Fractures and Key Injury Patterns Blunt Cerebrovascular Injury (BCVI) Penetrating Neck Trauma Suggested Readings References Chapter 89: Trauma of the Torso Introduction Imaging of the Severely Injured Patient Thoracic Trauma Abdominal Trauma Summary Suggested Readings References Chapter 90: Acute Neurological Emergencies Introduction Acute Onset Headache
Comatose Patient Septic Patient Neurological Emergencies in the Pregnant/Postpartum Patient Acute Onset Cranial Nerve Deficit(s) Acute Spinal Cord Syndrome Summary Suggested Readings References Chapter 91: Acute Chest Radiological Techniques Nontraumatic Chest Emergencies Adult Respiratory Distress Syndrome (ARDS) Summary Suggested Readings References Chapter 92: Acute Abdomen Chest and Abdominal X-Rays (CXR and AXR) Hepatobiliary Gallbladder and Billiary System
Liver Pancreas Spleen Gastrointestinal Tract Conclusion Suggested Readings References Chapter 93: Introduction to Interventional Radiology History Preprocedure Checklists Postprocedure Checklist Overall Contraindications Basics of Fine-Needle Aspiration Cytology or Biopsy Basics of Aspiration Basics of Drainage Procedures Basics of Vascular Access Summary Suggested Readings References
Chapter 94: Abdominal Interventions Acute Cholecystitis Liver Abscess Hydatid Disease of Liver Liver Trauma Biliary Interventions in Obstructive Jaundice Percutaneous Stone Extraction Through T-Tube Track Introduction Hepatic Venous Pressure Gradient Transjugular Intrahepatic Portosystemic Shunt Shunt Surveillance Balloon-Occluded Retrograde Transvenous Obliteration (BRTO) Introduction Locoregional Therapies in Hepatocellular Carcinoma Conclusion [51] Introduction Indication and Timing of Intervention Percutaneous Radiological Drainage Procedure Infected Walled-Off Necrosis Drainage (Fig. 94.11) Minimally Invasive Necrosectomy
Pancreatic Fistula Conclusion Percutaneous Gastrojejunostomy Percutaneous Jejunostomy Percutaneous Cecostomy Balloon Dilation of Gastrointestinal Stricture Metallic Stent Placement Gastrointestinal Bleeding Relevant Anatomy Kidney Location Pelvicalyceal Anatomy Renal Vascular Anatomy Relation With Surrounding Structures Patient Preparation Percutaneous Nephrostomy Image Guidance General Technique Complications of Percutaneous Nephrostomy Specific Scenarios Transplant Kidney
Horseshoe Kidney Nondilated Calyceal System Percutaneous Nephrostomy in Pediatric Patients Percutaneous Nephrostomy in Pregnant Patients Antegrade Ureteral Stenting Technique Complications of Antegrade Ureteral Stenting Balloon Dilation of Ureteric Stricture Percutaneous Drainage of Perinephric Abscess Percutaneous Renal Biopsy Technique Transjugular Renal Biopsy Technique Renal Aneurysm and Pseudoaneurysm Technique Renal Arterio-Venous Shunts Renal Tumor Embolization Technique Renal Tumor Ablation Technique
Radiofrequency Ablation Microwave Ablation Cryoablation Laser Ablation High-Intensity Focused Ultrasonography Chemical Ablation Nonchemical Nonthermal Ablation: Irreversible Electroporation Postprocedural Follow-Up After Ablation Interventions in Transplant Kidneys Indications Contraindications Preprocedural Workup and Assessment Vascular Procedures Nonvascular Procedures Uterine Artery Embolization Role of Uterine Artery Embolization in Adenomyosis Role of Uterine Artery Embolization in PPH Pelvic Congestion Syndrome Fallopian Tube Recanalization Suggested Readings
References Chapter 95: Aortic and Peripheral Vascular Interventions and Interventions in the Chest Normal Anatomy and Variants Spectrum of Acquired Aortic Pathologies Requiring Intervention Spectrum of Peripheral Arterial Disease and Natural History Diagnostic and Imaging Modalities Management Strategies Normal Anatomy Spectrum of Pathology and Their Management Pulmonary Embolism Pulmonary Artery Stenosis Pulmonary Arteriovenous Malformation Pulmonary Artery Aneurysms and Pseudoaneurysms Percutaneous Retrieval of Foreign Body Normal Anatomy [89,90] Spectrum of Pathology and Indications of Interventions [91] Central Airway Obstruction Emphysematous Disease Asthma
Bronchopleural Fistula Tracheoesophageal Fistula Sampling of Peritracheal Tissue Newer Advances and Works in Progress Embryology and Anatomy of theBronchial Arteries Bronchial Artery Embolization Technique [147–156] Outcomes Complications Conclusion Suggested Readings References Chapter 96: Neurointervention Introduction Cerebral Angiography Cerebral Aneurysms Acute Ischemic Stroke Carotid Stenosis Arteriovenous Malformation Dural Arteriovenous Fistula Vein of Galen Malformation
Venous and Lymphatic Malformation Tumors Head and Neck Hemorrhage Spinal Vascular Interventions Vertebroplasty and Vertebral Augmentation Future Directions Suggested Readings References Chapter 97: Musculoskeletal Interventional Radiology Introduction Basic Principles of Musculoskeletal Intervention Preparation for Musculoskeletal Interventional Procedures Range of Technique and Evidence Choice of Technique Practical Tips Individual Procedures Choice of Injectate Post-Procedural Care Suggested Readings References
Chapter 98: Conventional Nuclear Medicine Imaging Introduction Musculoskeletal System Endocrine System Genitourinary System Pulmonary System Hepatobiliary System Neuroimaging Nuclear Cardiology Lymphoscintigraphy Miscellaneous Investigations Suggested Readings References Chapter 99: Positron Emission Tomography/Computed Tomography Introduction Fluorine-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Oncology Nononcologic Uses of Positron Emission Tomography/Computed Tomography Positron Emission Tomography/Magnetic Resonance Imaging
Conclusion Suggested Readings References Centres of Ossification Index
Foreword When I was a resident in the late 1980s, the only general radiology textbook we referred to was Dr. David Sutton’s Textbook of Radiology. My copy was heavily underlined and annotated and dog-eared and had multiple short, “xeroxed” pages of newer information from journals stuck to the original pages by tape or gum, increasing the weight of the textbook significantly. Even though in the later years, other textbooks became popular, Sutton was always the first book that would come to mind when we wanted residents to read up on a specific topic. In those days, with no Internet, no Pubmed, no Radiopaedia, and no other online resources, our only avenues to learn were general radiology and specialty textbooks and the popular grey and yellow journals, which in India, we would receive only about 6-9 months after publication. Dr. Sutton died in 2002. The last (7th) edition of his book was also published in 2002. Given its immense popularity, it is no wonder that Elsevier has decided to resurrect an 8th edition of this book, in a new avatar, especially for a South Asian audience. This is no mean task. Radiology has advanced by leaps and bounds since the time Dr. Sutton updated his book. Residents, fellows, and consultants now have access to a large number of online teaching resources, some very good, many free, and some behind paywalls, but all available at the click of a mouse or the touch of a thumb. The large language models such as Chat-GPT4 are also increasing access to textual knowledge, especially for specifically structured questions. Textbooks therefore now face significant competition for eyeballs and money. Elsevier was wise and I would say lucky to find and choose my friend Dr. Bharat Aggarwal to helm this project to bring to life this 8th edition. A third-generation radiologist, Bharat is one of the finest radiologists I have
known over the last 30 years. He understands the nuances of the subject, is widely read and traveled, and hence has been able to put together an enviable roster of renowned radiologists of Indian origin, both in India and from the US and the UK, as Associate and Section Editors. His Associate Editors, Drs. Amit Sahu, Akshay Baheti, and Varsha Joshi are radiologists I have known for the last many years, all of them passionate teachers and educators. His Section Editors are all internationally renowned experts in their field. Drs. Suyash Mohan, Suresh Mukherji, Sandeep Hedgire, Mukesh Harisinghani, Sujit Vaidya, Subba Digamurthy, Girish Gandikota, and Puneet Bhargava have all put tremendous effort into their individual sections to bring the book to fruition. It has taken about 4 years, two of which were during the challenging COVID-19 times, to make sure that each chapter in the book is as good, if not better than any online resource, with new images, algorithms, flowcharts, and tables. Some new sections have been added including Women’s, Pediatric Imaging, and Interventional Radiology. It is a complete textbook that would give residents most of the information they need during their residency days and clear their examinations. It has taken a lot of effort to maintain the flavor, language, and flow of the original book, while still ensuring that every statement of fact has been vetted and that all information is current up to the date of publication. I congratulate Dr. Bharat Aggarwal and his team for this effort and I am sure that the book will serve as a popular and invaluable resource, not only for residents, but even for consultants, who can use this as a quick reference resource when stuck on a specific subject. Dr Bhavin Jankharia
Preface Radiology is a continuously evolving field. With each passing year, advancements in technology enable greater precision and improved safety. The adoption of digital tools, artificial intelligence and machine learning, coupled with a better understanding of the molecular basis of disease, has enabled the introduction of new therapies and altered decision pathways for patient care. The role of the radiologist is now central to treatment planning and disease monitoring, therefore making it vital for radiologists to not only provide diagnoses but also actively contribute to decision-making in patient care. The modern radiologist now, more than ever before, must have a strong foundational knowledge while adapting to the evolving technological advances. It is with this premise that we have adapted this new edition of Sutton’s Textbook of Radiology. It has been an honor to be invited by Elsevier to edit and update Sutton’s Textbook of Radiology, the gold standard and a key reference book for practicing radiologists over multiple generations. I have attempted to share my experiences as a radiologist, a journey that began when I learned radiology from my father, Dr. Sudarshan K. Aggarwal, perhaps one of the greatest visionaries of Indian Radiology. The Diwan Chand Aggarwal Imaging Center, started by my grandfather in 1924 and taken forward by my uncle Dr. Satyapal Aggarwal, was scaled to an institution under the stewardship of my father, and managed under one core tenet—patient first. This created an academic environment and pushed the institute to be a teaching center from where over 100 radiology residents completed their training and are now leading radiologists across the globe. I continue to follow this philosophy of combining high-quality clinical care and academic pursuit in my ongoing tenure at Max Healthcare, one of the largest healthcare providers in India.
Despite the fact that the last revision of this book was in 2002, it has continued to be a favorite textbook among radiology residents, mainly because of the comprehensive coverage of each topic and the presentation style. We have preserved the unique style of the textbook and retained material that continues to be relevant even two decades later. This edition of Sutton is aimed at recreating an exhaustive resource and reference text for radiologists to solve diverse clinical scenarios using the latest and most appropriate technology, and develop a sound process-driven approach. New sections on radiology physics and techniques, pediatric radiology, interventional radiology, and emergency radiology have been added to make the book comprehensive. The first section includes chapters on quality assurance, structured reporting, information technology in radiology, and a primer in artificial intelligence—knowledge of which is now extremely important to practicing radiologists. The remaining sections have been reorganized to emphasize the need for sub-specialty radiology. Chapters on nuclear medicine and dental radiology provide the practicing radiologist with an understanding of all imaging-based diagnostic techniques available today. The evolving radiology lexicons that radiologists should use in their daily practice to communicate their findings for consistent care have also been incorporated into the book. This book was put together through the COVID-19 pandemic, the biggest medical calamity faced by our generation. I want to extend my heartfelt gratitude to all the contributors who, despite being personally and professionally impacted by COVID-19 at the frontlines during the pandemic, stood true to their commitment and contributed high-quality material that will lay the foundation for the careers of the radiologists of the future. I acknowledge the proactivity, guidance, and support extended by the section editors, all of whom are leaders in their fields—a big thanks to Dr. Suresh Mukherji, Dr. Suyash Mohan, Dr. Girish Gandikota, Dr. Sandeep Hedgire, Dr. Mukesh Harisinghani, Dr. Sujit Vaidya, Dr. Puneet Bhargava, and Dr. Subba Digumarthy. I would also like to thank Dr. Rajesh Gothi and Dr. Shivani Khanna for editorial support, and the management of Max Healthcare for their support. I would have been unable to complete this project without the commitment shown by my associate editors, Dr. Amit Sahu and Dr.
Akshay Baheti, right from the acceptance of this challenge to its planning and smooth execution, along with Dr. Varsha Joshi. Most importantly I thank the patient community that my family has served over almost a century, for shaping my professional career and encouraging me to be a better doctor. There are absolutely no words to describe the encouragement and support I have received from my wife, Suman, and children, Samir and Divya, in this extended, almost four-year journey of editing Sutton and the endless personal time ungrudgingly shared. This book is my contribution to the legacy of my family and to the specialty of Radiology. Dr Bharat Aggarwal
Contributors Amogh N Hegde
Senior Consultant Radiologist
Raffles Hospital, Singapore Abhay Kumar Kapoor
Senior Consultant & Head
Department of Interventional Oncology, RGCI & RC
Delhi, India Aditi Chandra
Senior Consultant, Tata Medical CenterKolkata, India Aditya S. Pandey
Professor and Chair, Department of Neurosurgery
Professor, Neurological Surgery, Radiology, Otolaryngology Head and Neck Surgery
Surgical Director, Comprehensive Stroke Center
Director, Strategic Vision and Outside Collaborations Neurosurgery
Ann Arbor, MI, United States Ali Rashidi
Department of Radiology, Molecular Imaging Program at Stanford (MIPS)
Stanford University School of Medicine
Stanford, CA, United States Alistair D. Calder
Radiology Department, Great Ormond Street Hospital
London, United Kingdom Late Allan Midyet
Imaging Institute for Neuroradiology
Anagha Rajeev Joshi
Professor and Head of Department
Department of Radiology
Lokmanya Tilak Municipal Medical College and General Hospital
Sion, Mumbai, Maharashtra, India Anand Kirwadi
Consultant Musculoskeletal Radiologist
Manchester University Hospitals Foundation Trust
Manchester, United Kingdom Anbarasu Arangasamy
Consultant Radiologist & Director Aran Diagnostic Imaging
Coimbatore, Tamil Nadu, India Anisha Gehani
Junior Consultant
Tata Medical Center
Kolkata, West Bengal, India Ankit Balani
Consultant Radiologist
Vijaya Diagnostic Center Pvt. Ltd
Hyderabad, Telangana, India Anu Eapen
Professor, Department of Radiodiagnosis
Christian Medical College
Vellore, Tamil Nadu, India Anuj Jain
Locum Consultant Radiologist, Department of Radiology & Nuclear Medicine
North Cumbria Integrated Care
Carlisle, United Kingdom Argha Chatterjee
PDCC Gastro-Radiology, SGPGIMS
Lucknow, Uttar Pradesh, IndiaAssociate Consultant
Tata Medical Center
Kolkata, West Bengal, India Arman Parsai
Consultant Radiologist at Barts Health
London, United Kingdom Ashok Adams
Consultant Radiologist at Barts Health
London, United Kingdom Betty Simon
Professor, Department of Clinical Radiology
Christian Medical College
Vellore, Tamil Nadu, India Bhawan Paunipagar
Partner and Consultant Radiologist, Sai Scans (3T MRI), Akshay PET-CT, Akshay CT
Sangli and Kolhapur, Maharashtra, India Bojan Kovacina
Radiologist
Jewish General HospitalAssistant Professor
McGill University
Montreal, QC, Canada Colbey W. Freeman
Currently, Instructor of Radiology
Perelman School of Medicine at the University of Pennsylvania
Philadelphia, PA, United States Curtis Offiah
Consultant Radiologist at Barts Health
London, United Kingdom Dania Tamimi
Oral and Maxillofacial Radiology Consultant, Private Practice
Orlando, FL, United States Adjunct Assistant Professor, Department of Comprehensive Dentistry
University of Texas Health Science center
San Antonio, TX, United States
Clinical Assistant Professor, Department of Prosthodontics and Digital Technology Deepak Bhatt
Director, UBM Institute
Mumbai, Maharashtra, India Dheeraj Gandhi
Professor of Radiology, Neurology and NeurosurgeryVice Chair for Academic Affairs
Director, Interventional NeuroradiologyClinical Director, CMIT Center
University of Maryland School of Medicine
Baltimore, MD, United States Dina Pefanis
Consultant Radiologist at Barts Health
London, United Kingdom Diva Siddharth Shah Senior Consultant Radiologist, HCG Cancer Center
Ahmedabad, Gujarat, India Esther Park
Faculty Radiologist in Cardiothoracic Imaging
Allegheny Health Network
Pittsburgh, PA, United States Garvit Khatri
University of Washington Medical Center
Seattle, WA, United States Girish Gandikote
Professor, Radiology; Professor, Rheumatology; Chair, Clinical Competency Committee
Division of Musculoskeletal Radiology; University of Michigan
Ann Arbor, MI, United States Girish Kumar Parida
Assistant Professor
Department of Nuclear Medicine
All India Institute of Medical Sciences
Bhubaneswar, Odisha, India
Gopinath Gnanasegaran
Consultant, Nuclear Medicine
Department of Nuclear Medicine, Royal Free London NHS Foundation Trust
London, United Kingdom Harish Bhujade
Assistant Professor
Postgraduate Institute of Medical Education and Research (PGIMER)
Chandigarh, India Hassan Aboughalia
University of Washington Medical Center
Seattle, WA, United States Hemant A. Parmar
Professors of Radiology at University of Michigan
Ann Arbor, MI, United States Husniye Demirturk
Adjunct Assistant Professor, Department of General Dental Science
Marquette University, School of Dentistry
Milwaukee, WI, United StatesOral and Maxillofacial Radiology Consultant, Private Practice
Wexford, PA, United States Ilya M. Nasrallah
Assistant Professor of Radiology
University of Pennsylvania
Philadelphia, PA, United States Jagadeesh Rampal Singh
Director of Interventional Radiolog,
AIG Hospitals
Hyderabad, Telangana, India James Kho
Department of Radiology
Bristol Royal Infirmary
Bristol, United Kingdom
Jan Fritz
Associate Professor of Radiology
Chief, Division of Musculoskeletal Radiology
NYU Grossman School of Medicine
Department of Radiology
New York, NY, United States Jason M.O. Hostetter
Assistant Professor
Department of Radiology
University of Maryland School of Medicine
Baltimore, MD, United States Janan Jeyatheesan
Barts Health NHS Trust
London, United Kingdom Jeffrey Ware
Associate Professor of Radiology
Perelman School of Medicine at the University of Pennsylvania
Philadelphia, PA, United States Jena N. Depetris
Department of Radiology
Ronald Reagan UCLA Medical Center and UCLA Santa Monica Medical Center
Los Angeles, CA, United States Jenn Shiunn Wong
Queen Alexandra Hospital
Portsmouth Hospitals University
NHS Trust, Portsmouth, United Kingdom Joel M. Stein
Department of Radiology, Perelman School of Medicine
University of Pennsylvania
Philadelphia, PA, United States John H. Woo
Associate Professor of Radiology
Perelman School of Medicine at the University of Pennsylvania
Philadelphia, PA, United States
Staff Radiologist
Corporal Michael J. Crescenz Veterans Affairs Medical Center
Philadelphia, PA, United States Joseph J. Gemmete
Clinical Professor, Radiology and Neurosurgery
University of Michigan – Michigan Medicine
Ann Arbor, MI, United States Joy Barber
Consultant Radiologist
St George’s University Hospitals NHS Foundation Trust
London, United Kingdom Julia Crim
Professor of Radiology
University of Missouri at Columbia
Columbia, MO, United States Jyoti Kumar
Director Professor, Department of Radio-diagnosis
Maulana Azad Medical College
New Delhi, India Kalpana Bhatt
Co-director, UBM Institute
Mumbai, Maharashtra, India Kanhaiyalal Agrawal
Additional Professor and Head
Department of Nuclear Medicine
All India Institute of Medical Sciences
Bhubaneswar, Odisha, India Kara Gaetke-Udager
Clinical Assistant Professor, Musculoskeletal Radiology
Diagnostic Radiology Residency Program Director, University of Michigan
Departments of Radiology, Neurosurgery, Neurology & Otorhinolaryngology
Michigan Medicine, Ann Arbor, Michigan, USA Pankaj Watal
Department of Radiology, Nemours Children's Hospital, Florida
Orlando, FL, United States Priya Ghosh
Associate Consultant
Department of Radiology
Tata Medical Center
Kolkata, West Bengal, India Priya Pathak
Abdominal Imaging Fellow, University of Washington
Seattle, WA, United States Radhesh Lalam
The Robert Jones and Agnes Hunt Orthopaedic Hospital NHS Foundation Trust
Oswestry, United Kingdom Raj Chari
Consultant Musculoskeletal Radiologist
Nuffield Orthopaedic Centre
Oxford University Hospitals
Oxford, United Kingdom Rajan Jain
Professor of Radiology
NYU
New York, NY, United States Rajendra Solanki
Consultant Radiologist, Suyog Imaging Center
Mehsana & Radiscan Diagnostics
Ahmedabad, Gujarat, India
Rajesh Botchu
Department of Musculoskeletal Radiology, Royal Orthopedic Hospital
Birmingham, United Kingdom Ramanan Rajakulasingam
Department of Musculoskeletal Radiology
Royal National Orthopedic Hospital
Stanmore, London, United Kingdom Ramy Mansour
Clinical Lead of MSK Imaging
Oxford University HospitalsRoyal College of Radiologists Global Ambassador Reena Tanna
London North West University Healthcare NHS Trust
London, United Kingdom Robin Proctor
Consultant MSK Radiologist
University Hospitals Of Morecambe Bay, NHS Rohit Khandelwal
Sr Consultant, Interventional Radiology, Narayana Health Group Hospital, Kolkata Roy Wheeler
Consultant Radiologist at Barts Health
London, United Kingdom Ryan B. Peterson
Associate Professor, Division of Neuroradiology
Assistant Chief of Radiology Services, Grady Memorial Hospital
Clinical Site Director of Neuroradiology, Grady Memorial Hospital
Program Director, Diagnostic Radiology Residency
Associate Program Director, Transitional Year Internship Sanjay Baijal
Chairman Departments of Interventional Radiology and Radiology, Medanta – The Medicity
Sanjay Vaid
Chief, Division of Head Neck & ENT Imaging
Director, AcademicsStar Imaging & Research Center
Pune, Maharashtra, India Sanjeev Kumar
Presently, Additional Professor, Cardiovascular Radiology & Endovascular Intervention, AIIMS
New Delhi, India Sanjiv Sharma
Pro Chancellor & HOD, Intervention Radiology, NIMSJaipur, Rajasthan, India Saugata Sen
Senior Consultant, Department of Radiology and Imaging Sciences
Tata Medical Center
Kolkata, West Bengal, India Scott D. WuertzerProfessor of Radiology Division Chief of Musculoskeletal Imaging Wake Forest School of Medicine
Medical Center Boulevard
Winston-Salem, NC, United States Shobhit Garg
Currently, Consultant Radiologist
William Harvey Hospital, Ashford, Kent
East Kent Hospitals University Foundation Trust
United, Kingdom Sneha Deshpande
Associate Professor, Department of Radiology
Lokmanya Tilak Municipal Medical College and General Hospital
Sion, Mumbai, Maharashtra, India Sophie West
Consultant Radiologist, East Kent Hospitals University NHS Trust
,
Canterbury, United Kingdom Sridhar Gibikote
Professor, Department of Radiodiagnosis
Christian Medical College
Vellore, Tamil Nadu, India Stephen Judge
Musculoskeletal Radiology Fellow at Hofstra
Northwell School of Medicine, Illinois Steven James
Department of Musculoskeletal Radiology
Royal Orthopedic Hospital
Birmingham, United Kingdom Supreeta Arya
Consultant Radiologist
Last Opinion @5C networkMember, Expert Committee
National Cancer Grid, India Susan Cross
Consultant Radiologist at Barts Health
London, United Kingdom Timothy R. Miller
University of Maryland, School of Medicine
Department of Diagnostic Radiology and Nuclear Medicine
Baltimore, MD, United States Tushar Chandra
Department of Radiology
Nemours Children’s Hospital, Florida
Orlando, FL, United States Vaidehi Bhatt
Consultant
Mumbai, Maharashtra, India Vijay Papineni
Consultant Radiologist
MSK Radiology Lead, Sheikh Shakhbout Medical City (Mayo Clinic)
Abu Dhabi, United Arab EmiratesConsultant Musculoskeletal Radiologist
Radiology Department, Manchester University HospitalsNHS Foundation Trust
Manchester, United Kingdom
Vivek Gupta
Chief of Neuroradiology, Mayo Clinic
Jacksonville, FL, United States Zachary Wilseck
Clinical Assistant Professor, Radiology
University of Michigan – Michigan Medicine
Ann Arbor, MI, United States
CHAPTER 52
Arthritis Stephen Judge, Michael Brooks, Lauren Goldman, Girish Gandikote
Radiographic examinations for joint and back pain are ubiquitous in both general and subspecialty radiology practices and become essential for the interpreting radiologist to differentiate inflammatory from degenerative causes of joint disease, having implications for patient management. Degenerative, or osteoarthritis (OA), is characterized by asymmetric chondral wear resulting in nonuniform joint space narrowing. As the joint space narrows, abnormal motion across the joint surfaces causes bony productive change in the form of subchondral sclerosis and osteophyte formation, as well as subchondral cysts or geodes. In contrast, there are imaging findings and concepts that are shared among the inflammatory arthritides. Recognizing the radiographic hallmarks of inflammatory arthritis, including marginal bone erosions, uniform joint space narrowing, and regional soft-tissue swelling, will allow the radiologist to offer more definitive radiological diagnoses. Focal discontinuity of subchondral bone indicates osseous erosion, which indicates underlying joint inflammation. Specifically, understanding the concept of periarticular or marginal erosions is considered one of the most important imaging features in being able to distinguish an inflammatory arthropathy from OA. Joint inflammation will initially produce erosions at the margins or periphery of joints,
known as the “bare area,” representing the portion of the joint that is intra-articular, but not covered or essentially not protected by hyaline cartilage (Fig. 52.1). Eventually, destruction of the articular cartilage is uniform throughout the joint space, which leads to symmetric joint space narrowing, rather than asymmetric patterns seen in degenerative arthritis [1].
FIGURE 52.1 (A) Illustration of synovial joint shows joint fluid (f) and articular cartilage (c). (B) Illustration and (C) radiograph show inflammatory arthritis, synovitis, and pannus (P) causing cartilage destruction. Marginal erosions (arrows) are seen where subchondral bone plate is exposed to intraarticular synovitis.
Additionally, and of equal importance, understanding the classic distribution tendencies will lead the radiologist down different diagnostic pathways. In monoarticular arthropathy, excluding infection is imperative before suggesting inflammatory arthropathy from a separate etiology. Successful diagnosis of a suspected inflammatory arthropathy that involves multiple joints should be tackled utilizing a distribution approach. For example, proximal distribution process of the hands or feet without bony proliferative changes suggests rheumatoid arthritis; however a distal distribution process of the hands or feet with associated bone proliferation suggests a seronegative arthropathy. Imaging and distribution characteristics of both degenerative OA and inflammatory arthritides will be addressed throughout this chapter, while offering a framework or an approach to be utilized during image interpretation to increase diagnostic accuracy (Fig. 52.2).
FIGURE 52.2 Approach to the radiographic evaluation of arthropathies, using the distal extremities as a model. CMC, carpometacarpal; CPPD, calcium pyrophosphate dihydrate crystal deposition disease; CRA, chronic reactive arthritis; DIP, distal interphalangeal; IP, interphalangeal; MCP, metacarpophalangeal; MTP, metatarsophalangeal; OA, osteoarthritis; PIP, proximal interphalangeal; PVNS, pigmented villonodular synovitis; RA, rheumatoid arthritis; TMT, tarsometatarsal.
Degenerative and Erosive OA Overview OA, also known as degenerative joint disease, is considered the most prevalent chronic joint disease. The overall disease prevalence of OA is thought to be on the rise, in part due to an aging population, but also due to the increasing prevalence of obesity [2]. The condition is most notably a noninflammatory arthropathy characterized by progressive cartilage degeneration with resultant hypertrophic bony proliferation, osteophyte formation, which far outpaces the body’s intrinsic ability for cartilage repair.
Pathology Although the pathophysiology underlying OA is not completely understood, it is thought to be fundamentally attributable to multiple intrinsic and extrinsic factors, including but not limited to repetitive mechanical stresses, history of trauma and/or instability, normal aging processes within articular cartilage, genetic factors predisposing to premature cartilage destruction, and in some cases even to hormonal factors such as low estrogen levels [3]. Even as part of the normal aging process, chondrocytes decrease in number resulting in increased fragility of the cartilage matrix due to decreasing proteoglycan production. Increased degradative enzymes may result from this process and contribute to the rapidity of onset.
Imaging Appearance Several imaging manifestations of OA, although not necessarily unique to this entity, are so widespread within osteoarthritic disease processes that they serve to markedly narrow the differential diagnosis of joint pathology, especially when seen simultaneously. Such findings include:
Additional imaging manifestations seen in OA can most easily be assessed based on anatomic location.
Hands/Wrists First, identifying the distribution of joint involvement in the hands and wrists is essential in narrowing the differential diagnosis for various arthritides. OA is known to affect the interphalangeal joints of the hand (Fig. 52.3), with special predilection for the distal interphalangeal (DIP) joint. Additionally, primary OA targets the first carpometacarpal joint and scapho-trapezial-
trapezoid articulations. Nodular deformities from osteophytes and soft-tissue swelling at the distal (Heberden nodes) and proximal (Bouchard nodes) interphalangeal joints are common clinical findings [4].
FIGURE 52.3 Classic osteoarthritis of the hands. PA (A) and lateral (B) radiographs demonstrate 2nd-5th DIP joint space narrowing with prominent marginal osteophytes (arrowheads), as well as severe narrowing at the 1st CMC joint (arrow) with subchondral sclerosis and osteophyte formation.
Erosive OA—It is an inflammatory variant of OA. It has marked female predilection. Typically presenting in the peri- and postmenopausal patient. Distribution pattern in the hands and feet is essentially the same as encountered in primary OA, manifesting as mixed erosive and productive changes of the interphalangeal joints. The first carpometacarpal joint is commonly involved, and less commonly the scapho-trapezial-trapezoid. It has pathognomonic central subchondral erosions resulting in a “gullwing deformity” (Fig. 52.4) [5].
FIGURE 52.4 Erosive osteoarthritis. Frontal radiograph of the hands in a 76-year-old female demonstrating central subchondral erosions of the 2nd–5th DIP joints resulting in the classic gullwing deformity (white arrow) seen in erosive osteoarthritis. Also, note the atypical distribution of 2nd and 3rd MCP narrowing with subchondral cystic change and chondrocalcinosis (arrowhead), suggestive of coexistent CPPD arthropathy.
Differential Pearls The hallmark of asymmetric joint space narrowing, resulting in hypertrophic osteophyte formation, and lack of erosions involving the small joints of the hand should raise suspicion for underlying
osteoarthritic change rather than and inflammatory arthropathy. Erosive OA with DIP involvement can be mistaken for psoriatic arthritis (PsA); however, careful assessment for “gull-wing” deformity with lack of periarticular erosions leans toward erosive OA. Rheumatoid arthritis rarely involves the DIP joints. If radiographic findings are similar in appearance to OA, but are in encountered in an atypical joint distribution, or advanced changes in a younger patient, then other causes of atypical or secondary OA (post-traumatic arthrosis, crystal-induced arthritis, hemophilic and neuropathic arthropathy) should be entertained.
Shoulders
◾Most Primary OA—No specific cause. Related to age, gender, and genetic factors. commonly seen in patients over the age of 50, with women being affected more often than men ◾dislocations, Secondary OA—Has a known cause (i.e., previous injury or shoulder infection, or rotator cuff tear)
Superomedial aspect of the humeral head is frequently the earliest site of osteoarthritic cartilage loss in the glenohumeral joint (Fig. 52.5). Marginal osteophyte formation is seen at the inferior humeral head-neck junction (Fig. 52.5).
FIGURE 52.5 Classic glenohumeral arthritis. Frontal radiograph (A) of the shoulder demonstrates joints space narrowing, glenoid subchondral sclerosis, inferior glenoid rim, and inferomedial humeral head–anatomic neck osteophyte formation (arrows). Coronal proton density fat-saturated MR image (B) in the same patient showing focal high-grade chondral wear along the superomedial aspect of the humeral head (arrowheads), as well as inferomedial humeral head osteophyte formation.
◾neurologic Large size of inferomedial humeral head osteophytes may even result in symptoms if they impinge on the axillary nerve as it courses through the quadrilateral space ◾articular Small fragments of osteophytes may additionally fracture and result in intrabodies Joint degeneration can be accelerated in the presence of accompanying soft-tissue abnormality, including but not limited to rotator cuff pathology and/or shoulder instability. Glenohumeral OA superimposed upon severe rotator cuff disease can result in rotator cuff arthropathy, a specific form of OA that results in superior displacement of the humeral head with respect to the glenoid. Abnormal articulation of the humerus with the acromion leads to rounding of the greater tuberosity (femoralization) with associated concave erosion of the undersurface of the acromion (acetabularization). The acromioclavicular (AC) joint is also a common site of OA, with typical findings of joint space narrowing, subchondral sclerosis and cystic change, and osteophyte formation.
Hips Classic OA of the hip results from progressive cartilage degeneration with following typical radiographic imaging manifestations (Fig. 52.6) [6]:
◾weight-bearing Superolateral femoral head subluxation and joint space narrowing along the portion of the joint is seen in 80% of cases, whereas medial subluxation/narrowing (protrusio) is seen in 20% of hip OA cases ◾ Subchondral sclerosis and cyst formation ◾ Osseous productive change ⚬ Femoral head–neck junction ring osteophytes ⚬ Acetabular osteophytes ⚬ Femoral neck (calcar) buttressing
FIGURE 52.6 Classic OA of the hip. AP (A) and frog leg lateral (B) radiographs demonstrate severe superolateral joint space narrowing of the right hip joint with bone-on-bone articulation, subchondral sclerosis, subchondral cyst (*), calcar buttressing (arrowheads), prominent acetabular spurring (arrow in A), and femoral head–neck junction ring osteophytes.
OA in young adults is often associated with underlying morphologic abnormalities:
◾ impingement ◾ Femoroacetabular Developmental dysplasia of the hip
One of the earliest imaging manifestations of OA of the hip is frequently a singular acetabular cyst, or Egger cyst, resulting from bone contusion ultimately giving rise to microfractures and intrusion of synovial fluid within the superior acetabulum (Fig. 52.7). More advanced OA may include superolateral femoral head subluxation which is found to occur in 80% of cases (though protrusion is also noted in a minority of OA cases, occasionally attributed to a variant of OA of the hip known as Otto disease) (Fig. 52.8).
FIGURE 52.7 Egger cyst. Coronal STIR MR image of the right hip demonstrating a large singular acetabular subchondral cyst known as an Egger cyst (*), an early hallmark of hip osteoarthritis.
FIGURE 52.8 Bilateral acetabular protrusio due to Otto disease. Coronal (A) and axial (B) CT images demonstrate medial intrapelvic convexity of the medial acetabular wall, with concentric joint space loss, subchondral cystic change, and osteophyte formation.
The differential diagnosis of hip pain is broad, which can present diagnostic challenges; however, MRI has become an invaluable tool in assessing patients with hip pain who have normal or inconclusive radiographs [7] including subchondral insufficiency fractures (Fig. 52.9), early chondral wear, labral tear and degeneration (Fig. 52.10), occult fractures, transient migratory osteoporosis, septic arthritis, and bone lesions.
FIGURE 52.9 Subchondral fracture with underlying avascular necrosis. Normal appearing frontal AP radiograph (A) of the right hip in a 67-year-old female presenting with acute hip pain. Axial T2-fat suppression image (B) demonstrates curvilinear hyperintense T2 signal undercutting the subarticular surface of the femoral head (white arrow) with associated intense subchondral bone marrow edema extending into the femoral neck on the coronal IR image (C) (*), compatible with an acute subchondral insufficiency fracture. Coronal PD image (D) demonstrates femoral head avascular necrosis with classic double-line sign (arrowheads).
FIGURE 52.10 Acetabular labral tear and chondral degeneration. Sagittal proton density fat-suppressed MR image in a 58-year-old female with left hip pain demonstrating degenerative tearing of the anterosuperior acetabular labrum (arrow) and high-grade thinning of the acetabular (arrowheads) and femoral head cartilage, compatible with osteoarthritis. Radiographs of the left hip were normal.
Rapidly progressing OA of the hip should prompt a search for underlying pathology, most commonly an insufficiency fracture of the superior subchondral femoral head surface (Fig. 52.11).
FIGURE 52.11 Rapidly destructive osteoarthritis of the hip. Initial AP radiograph (A) of the right hip demonstrated mild superolateral joint space narrowing. AP radiograph of the right hip obtained 6 months later (B) demonstrated interval boneon-bone articulation, subchondral cystic change, and collapse of the femoral head (arrow), compatible with rapidly progressive osteoarthritis.
Knees The knees are the most commonly affected joint in clinical practice and consists of three separate compartments—medial tibiofemoral, lateral tibiofemoral, and patellofemoral. Radiographs are the first-line imaging modality for evaluation; typical findings include:
◾approximately Joint space narrowing (typically demonstrated on notch views with the knee in 40 degrees of flexion) ◾ Prominent periarticular osteophyte formation ◾ cysts ◾ Subchondral Joint malalignment; most commonly varus (Fig. 52.12) [8]
FIGURE 52.12 Classic case of OA of the knees. Frontal radiographs demonstrating bone-on-bone articulation of the medial tibiofemoral compartments with subchondral sclerosis and osteophyte formation (arrows) resulting in genu varus alignment.
The patellofemoral joint can be assessed radiographically utilizing a dedicated sunrise view, which involves flexion of the knee to 45 degrees and imaging with placement of the x-ray beam aiming inferiorly to superiorly from the patient’s feet. Magnetic resonance imaging (MRI) can play an important role both in determining early cartilage degeneration (Fig. 52.13), and in assessing for mitigating factors in the development or progression of knee OA, such as subchondral insufficiency fractures (Fig. 52.14) and/or meniscal degeneration (Fig. 52.15).
FIGURE 52.13 Early osteoarthritic change on MRI. AP radiograph (A) demonstrated mild narrowing of the medial tibiofemoral compartment with small osteophytes. Coronal PD fat-suppression image (B) demonstrates diffuse chondral thinning overlying the central surfaces of the medial femoral condyle and medial tibial plateau (arrowheads).
FIGURE 52.14 Subchondral insufficiency fracture. AP radiograph (A) demonstrates a linear subchondral lucency along the medical femoral condyle (arrow), compatible with a subchondral insufficiency fracture. Coronal T1 (B) and T2 fatsuppression (C) images demonstrate subchondral linear hypointense T1 and T2 signal corresponding to the radiographic lucency (arrows), outlined by intense bone marrow edema, compatible with an acute subchondral insufficiency fracture. Note the normal appearing underlying articular cartilage.
FIGURE 52.15 Advanced OA on MRI. Coronal proton density fat-saturated MR image demonstrating degeneration and extrusion of the medial meniscal body (arrow), with associated complete, diffuse full thickness medial tibiofemoral compartment cartilage loss, marginal osteophytes, cystic change, and reactive subchondral bone marrow edema (arrowhead).
Ankles/Feet The subtalar joint is most involved; posterior subtalar compartment oftentimes being the most severely affected (Fig. 52.16). Involvement of the tibiotalar joint can also be seen
especially in the setting of previous trauma and/or recurrent ankle instability. Disease may be more widespread, involving many or all joints of the midfoot, including the tarsometatarsal joints (Fig. 52.17). OA of the forefoot typically presents with involvement of the first metatarsophalangeal (MTP) joint and can lead to malalignment and severe motion restriction, known as hallux rigidus (Fig. 52.18). The presence of alignment deformities of this joint (e.g., hallux valgus) should prompt a search for associated early or advanced degenerative changes, especially on more advanced cross-sectional imaging.
FIGURE 52.16 OA of the subtalar joint. Lateral radiograph of the ankle/hindfoot demonstrating severe degenerative changes of the subtalar joint, as well as the visualized joints of the midfoot and hindfoot.
FIGURE 52.17 Midfoot OA. AP radiograph of the left foot demonstrates severe narrowing across the 2nd and 3rd tarsometatarsal joints (arrows) with subchondral sclerosis, cystic change, and prominent dorsal osteophyte formation.
FIGURE 52.18 1st MTP OA. AP (A) and lateral (B) radiographs of the left foot demonstrate severe osteoarthritis of the 1st MTP joint with prominent dorsal osteophytes (arrows), compatible with radiographic evidence of hallux rigidus.
Spine Degenerative processes of the spine are exceedingly common and frequently visualized on radiographic imaging. More commonly, manifestations of OA of the lumbar spine include intervertebral disc space narrowing, subchondral endplate sclerosis, horizontal osteophyte formation, and facet degenerative changes, which may ultimately give rise to associated spinal canal and neuroforaminal narrowing (Fig. 52.19). Specific entities associated with OA of the spine include Baastrup’s disease, a condition in which the spinous processes are in closer approximation resulting in enlargement, flattening, and sclerosis of apposing interspinous surfaces [9]. Uncovertebral joint (apophyseal) osteophytes and facet joint OA in the cervical spine contribute to neuroforaminal narrowing. MRI is particularly useful in the setting of degenerative disc disease both to quantify the extent of degeneration, and to further clarify associated pathology such as disc herniation and/or annular tears, ligamentum flavum hypertrophy, or facet cyst formation, all of which may ultimately contribute to severity of patient symptoms including pain and/or radiculopathy.
FIGURE 52.19 Degenerative disc disease. Lateral radiograph of the lumbar spine in an 82-year-old female with back pain demonstrating moderate-to-severe narrowing at L45 and L5-S1 (black arrows) with subchondral endplate sclerosis, as well as anterior marginal and posterolateral osteophytes, which in combination with facet arthrosis likely contributes to neuroforaminal narrowing. There is also squaring of the spinous processes with narrowing of the interspinous spaces demonstrating subchondral irregularity and sclerosis, compatible with Baastrup’s disease (white arrow).
Inflammatory Arthropathies Rheumatoid Arthritis
Overview Rheumatoid arthritis is an autoimmune systemic inflammatory arthropathy that predominantly affects the musculoskeletal system, with imaging findings reflecting the underlying pathophysiology of the disease process. RA is seen in all age groups, but is most likely to present between ages 20 and 55, with women more commonly affected than men at a ratio of 3:1. Prevalence is quite high at approximately 1% of the worldwide population, and is particularly prevalent among some Native American populations. Although there is some debate regarding the pathogenesis of rheumatoid arthritis, it is generally felt that genetic predisposition accounts for nearly half of the risk of development of the disease [10], with 70% of patients being HLADR4 positive [11]. Additionally, presumed environmental triggers have been reported, including smoking, periodontal disease, and alterations in gut microbiome [1,12]. Pathology Synovitis or inflammation of the synovium lining joint surfaces, tendon sheaths, and bursae, can be seen in infection, noninfectious inflammatory processes, and degenerative conditions, is thought to be the primary underlying pathologic process in RA. Hypertrophied synovial proliferation, known as pannus, can be characterized as either hypervascular due active hyperemia, or hypovascular due to chronic inactive proliferation. Synovitis and pannus formation can ultimately result in periarticular marginal erosions, as the outer margins of synovial joints, known as “bare areas,” because they are not covered or protected by hyaline cartilage (Fig. 52.1). Hypertrophied synovium, which may involve joints, tendon sheaths, or bursae, is invasive inflammatory tissue, leading to eventual erosion of contiguous bone and cartilage surfaces, fibrous/osseous ankylosis, and ligamentous laxity/rupture [13]. Similarly, synovial proliferation within the tendon sheath results in tenosynovitis, and if severe, can lead to tendon failure and/or rupture. Imaging Findings
Along with a thorough clinical examination and laboratory markers, imaging evaluation can offer invaluable clues to the early diagnosis of RA, as well as monitoring of disease remission or progression depending on the imaging modality utilized for the assessment. Radiography remains the initial imaging modality in the evaluation of RA; however MRI and ultrasonography (USG) have emerged as critical tools in the assessment of early disease and monitoring of therapy. Throughout this section, multiple examples will illustrate early changes related to RA, including synovitis, tenosynovitis, joint effusions, bone marrow edema, and early erosions all of which are largely imperceptible upon radiographic examination [11]. Given that early pathological changes are related to the synovium, both USG and MRI have emerged as superior imaging modalities for the detection of early changes related to RA and other inflammatory arthridities compared with CT and radiography. When performed by an adept sonographer or trained musculoskeletal radiologist, USG has proved to be highly accurate in identifying both osseous and softtissue inflammatory changes, and is highly sensitive in detecting osseous erosions compared with radiography. USG and MRI are comparable in their ability to detect early osseous erosions [13]. In addition, USG is incredibly useful in detecting intra-articular synovitis (and tenosynovitis) manifest by noncompressible hypoechogenic synovial hypertrophy with or without power Doppler activity. Increased power Doppler activity indicates hyperemia and is a marker of acute inflammation. Similarly, MRI also demonstrates synovitis with high sensitivity compared with USG, as evidence by synovial thickening that can be detected as relative hypointense proliferative material outlined by hyperintense joint fluid. However, synovium and joint fluid can have similar appearing signal intensities on unenhanced MR images. The addition of IV gadolinium-based contrast agents adds specificity, as inflamed synovium will demonstrate enhancement, while bland joint fluid will not. Furthermore, when compared with radiography, CT, and USG, MRI provides a unique look at underlying subchondral inflammation, as evidenced by bone marrow edema changes and enhancement of subchondral bone,
which if identified has been shown to be an indicator of erosion formation. The wide spectrum of imaging findings encountered in patents with RA will be described based upon location and pathophysiology with corresponding imaging manifestations across multiple imaging modalities. Classic feature of RA is a bilateral symmetric inflammatory arthritis involving more than three joints with the absence of bony proliferation, helping to differentiate from OA and seronegative spondyloarthropathies. Additionally, over 60% of patients present with symmetric arthritis of the small joints of the hand. Erosive changes with predominant proximal distribution and the absence of periarticular bony productive changes are findings indicative of rheumatoid arthritis. Typical Patterns and Distribution of RA
Upper Extremity Hands and Wrists
◾ Bilateral, symmetric, and polyarticular process ◾erosions Commonly affected joints include the metacarpophalangeal (MCP) joints with of the second and third, as well as the third proximal interphalangeal (PIP) joint ◾ All wrist joints, ulnar and radial styloid ◾ DIP joints are rarely involved
Earliest, but subtle radiographic findings include soft-tissue swelling and periarticular osteopenia and thought to be the result of subchondral osteoclast activation secondary to regional synovitis and inflammation, which can easily identified by MR imaging or USG. Synovitis leads to subtle radiographic findings of initial joint space widening due joint effusions, as well as periarticular cortical thinning, indistinctness, and bone loss, known as the dot-dash appearance, and eventually contributing to erosions (Fig. 52.20).
FIGURE 52.20 Early radiographic findings in a patient with RA with USG confirmation. PA coned down view (A) of the right 2nd and 3rd MCP joints demonstrates subtle widening of the 2nd MCP joint indicating joint capsule distension with fluid and synovitis. Localized osteopenia of the 2nd and 3rd metacarpal heads with subtle irregularity and discontinuity of the cortex (white arrows), described as the “dot-dash” appearance of early erosive change. Also note the early erosions at the base of the 3rd proximal phalanx and head of the 3rd metacarpal (yellow arrows). Corresponding USG images in the same patient demonstrate 2nd and 3rd MCP joint capsular distension with synovitis, erosion at the base of the 2nd proximal phalanx (B—yellow arrow) which is not appreciated on the radiographs, and confirmation of the 3rd MCP joint erosions (C—red arrows) as seen on the radiographs.
Early in the disease process, the most involved joints include the second and third MCP and the third PIP joints of the hand (Fig. 52.20), which may be inconspicuous at radiography, but clear on USG (Figs. 52.20 and 52.21) and MR imaging (Fig. 52.22).
FIGURE 52.21 Erosions in patient with RA. USG images clearly demonstrate osseous erosions of the left (A and B) and right (C and D) 2nd metacarpal heads (yellow arrows) which are less conspicuous on AP (E) and lateral (F) radiographs (white arrows).
FIGURE 52.22 Synovitis and erosions in a woman with rheumatoid arthritis. Coronal PD fat-suppression (A) and axial T2 fat-suppression (B) images demonstrate periarticular erosions (arrows) at the 2nd–5th metacarpal heads, radial base of the 2nd proximal phalanx, and at the base of the 2nd metacarpal.
MRI findings of early rheumatoid arthritis in the hand and wrist include the following:
◾pannus Periarticular and/or marginal erosions, as well as ulnar styloid erosions and formation are typical (Figs. 52.22 and 52.23) ◾ Pannus formation outlined by joint effusions (Fig. 52.23) ◾ Tenosynovitis of flexor or extensor tendons ◾erosive Subchondral bone marrow edema, which may reflect an early manifestation of disease (Fig. 52.23) ◾ Enhancement of synovium and tendon sheaths on postcontrast imaging
FIGURE 52.23 MR imaging findings in early RA. Coronal PD (A) and coronal (B, C, D) and axial (E and F) PD-weighted fatsuppressed images demonstrate a triquetral erosion (black arrow), with extensive dorsal carpal, ulnocarpal, radiocarpal, and pisotriquetral recess synovitis (white arrows) manifest as intermediate-signal intensity outlined by high-signal joint fluid. Additionally, patchy areas of bone marrow edema and scattered erosions are seen throughout the carpal bones (arrowhead).
USG is complimentary to radiography and MRI, playing a critical role in the evaluation of early rheumatoid arthritis. There is excellent ability to detect early effusions and erosions of small joints (Figs. 52.20 and 52.21).
◾surface Erosions in USG are defined as periarticular cortical discontinuity of the bone visible in two perpendicular planes [14]. Acute erosions demonstrate irregular margin, poorly defined osseous base, and associated active synovitis.
The absence of synovitis may reflect chronic erosion [15]. Power Doppler imaging can be used to detect hyperemia and synovitis (Fig. 52.24) Joint effusion is identified as abnormal hypoechoic or anechoic intra-articular fluid that is displaceable and compressible, without demonstration of Doppler signal Synovitis is abnormal hypoechoic intra-articular tissue that is nondisplaceable, poorly compressible, with possible Doppler signal. It can be detected early in the disease course and is considered a strong predictor of bone erosion development
◾ ◾
FIGURE 52.24 Hyperemia and active synovitis on USG. A 66-year-old male patient presenting with wrist pain and normal radiographs. Longitudinal USG image acquired of the dorsal carpal recesses of the left wrist demonstrates abnormal, noncompressible intra-articular tissue surrounded by joint fluid, compatible with synovial hypertrophy (arrows), exhibiting increased power Doppler signal, consistent with active synovitis.
Following features allow USG to be used as a screening tool for the diagnosis of early inflammatory arthritis:
◾Tenosynovitis Ease of detection of tenosynovitis and tendon rupture (Fig. 52.25). is abnormal anechoic/hypoechoic tendon sheath thickening or
distention, related to the presence of abnormal tenosynovial fluid and/or synovial hypertrophy Superiority in the evaluation of rheumatoid nodules, which may be below the resolution of other forms of cross-sectional imaging
◾
FIGURE 52.25 USG findings in early presentation of RA. Longitudinal USG images (A and B) acquired of the left wrist demonstrate abnormal tenosynovial thickening of the extensor carpi ulnaris tendon (arrows) with increased power Doppler signal, compatible with tenosynovitis. Longitudinal (C) and transverse (D) USG images demonstrate tenosynovitis of the 3rd flexor tendon (arrows).
Later disease manifestations include uniform joint space narrowing and destruction, ulnar capping and translocation (with carpal bones subluxing ulnarly such that the lunate articulates with the ulna), as well as volar subluxation of the carpal bones upon the radius (Fig. 52.26). Ulnar capping refers to productive bone changes seen at the ulnar styloid sometimes seen with long-term rheumatoid arthritis. Scapholunate dissociation leads to volar intercalated segmental instability or dorsal intercalated segmental instability. Ulnar drift and volar subluxation is often present involving the metacarpal joints. “Hitchhiker’s thumb” results in flexion deformity at the thumb MCP joint with extension at the interphalangeal joint (Fig. 52.27). Swan-neck deformity refers to PIP joint hyperextension and DIP joint hyperflexion (Fig. 52.28).
FIGURE 52.26 Later stage findings in RA. AP radiographs of the wrists (A) show ulnar capping and ulnar translocation. Zoomed in AP radiograph of the left ulnar styloid (B) highlights the ulnar capping, which refers to productive bone changes seen at the ulnar styloid sometimes seen with long-term rheumatoid arthritis. Ulnar translocation involves volar subluxation of the carpal bones upon the radius.
FIGURE 52.27 Late-stage changes in RA. Radiographs demonstrate uniform joint space narrowing of the MCP joints with ulnar subluxation (arrows), periarticular erosions at the base of the left 3rd middle phalanx and base of the right 4th middle phalanx (arrowheads). Hitchhiker thumb is also demonstrated.
FIGURE 52.28 Late-stage changes in RA. AP (A) and lateral (B) radiographs demonstrate swan-neck deformity of the 5th finger (arrow in A). Also note volar subluxations (arrow in B) and periarticular osteopenia of the MCP joints.
Late severe destruction of osseous structures may give pencil-incup appearance in phalanges and may destroy distal ulna or proximal carpal row (Fig. 52.29).
FIGURE 52.29 Advanced RA changes. Radiographs demonstrate severe uniform, bilateral symmetric joint space narrowing of the 2nd MCP joints with ulnar deviation and volar subluxation, erosion of the left ulnar head and styloid, distal radioulnar joint erosions with scalloping along the ulnar aspect of the distal radius, and extensive carpal ankyloses.
Differential Pearls 1. Systemic lupus erythematosus (SLE) differs from RA in that associated arthropathy is nonerosive and joint subluxations are reducible. 2. Erosive OA may be differentiated as it typically follows the distribution of OA, with predominantly DIP involvement as well as involvement of the first carpometacarpal and scapho-trapezium-trapezoid joints. 3. Psoriatic arthropathy is more apt to have associated periostitis, with a distribution favoring the DIP joints. 4. The absence of DIP involvement, subchondral sclerosis, and osteophyte formation excludes OA.
Shoulder and Elbow. The AC joint may demonstrate erosions on both sides of the joint, with end-stage penciling of the clavicle as well as resorption at the coracoclavicular ligament insertions. Glenohumeral joint involvement typically begins with erosions at the junction of the cartilage-covered humeral head and the greater tuberosity (Fig. 52.30).
◾ Later stages result in uniform disruption of the glenohumeral joint ◾against Hatchet-like mechanical erosions at the medial surgical neck due to impaction the inferior glenoid may result ◾subacromial/subdeltoid Concomitant rotator cuff pathology may result in synovitis extending into the bursa
FIGURE 52.30 Glenohumeral RA. (A) Focal bone marrow edema (arrow) along the superior humeral head subjacent to the rotator cuff insertion, suggestive of early erosive change. Subsequent radiographs (B) and MRI (C) acquired 2 years later demonstrate osseous erosions of the superior humeral head in the previous sites of osteitis (arrows).
Elbow involvement may demonstrate joint effusions, olecranon bursitis, and/or diffuse erosive changes. Decompression of synovial fluid through weak joint capsules of large joints is common, and presumably related to the associated higher pressure of the inflammatory arthropathy (Fig. 52.31).
FIGURE 52.31 Elbow RA. AP (A) and lateral (B) radiographs show severe uniform joint space narrowing of the radiocapitellar and ulnotrochelar articulations with subchondral erosions of the capitellum, trochlea, radial head, and olecranon without bony productive change. Images also demonstrate diffuse osteopenia and large joint effusion, the findings of which are typical of RA. Coronal T2-weighted fatsuppressed (C) and PD fat-suppressed (D) images in the same patient demonstrate complete uniform cartilage loss of the radiocapitellar and ulnotrochelar joints, with osseous erosions. Axial (E) and sagittal (F) T2-weighted fatsuppressed images also show a large effusion surrounding exuberant lobulated low-signal hyperplastic synovial tissue, pannus (*), significantly distending the joint capsule and bicipital-radial bursa, as well as synovitis and joint fluid decompressing through weakened joint capsule (white arrows).
Lower Extremity
Hip and Knee: Typical imaging findings for hip and knee involvement include bilateral, symmetric, and uniform cartilage space narrowing, acetabular protrusio deformity (Fig. 52.32), periarticular osteopenia, and possible associated insufficiency fractures.
FIGURE 52.32 (A) Rheumatoid arthritis—extreme protrusio with medial migration and erosion of the femoral heads (B and C). Foot RA. AP (A) and lateral (B) views of the foot demonstrate calcaneal tubercle (arrow) and 5th metatarsal head periarticular erosions (arrowhead).
Ankle and Foot
◾ Tibiotalar and MTP joint effusions are relatively common ◾ Retrocalcaneal bursitis may be seen ◾posterior Earliest erosive changes are typically demonstrated at the fifth MTP joint and calcaneal tubercle (Fig. 52.32)
Axial Skeleton Erosive changes are most commonly seen at the C1–C2 level and are typically centered around the dens (Fig. 52.33). Atlantoaxial subluxation may result from disruption of the transverse ligament by inflammatory pannus formation, with normal atlantodens interval measuring less than 4 mm.
FIGURE 52.33 Cervical spine RA. Sagittal T1 (A) and T2 (B) MR images show extensive pannus formation surrounding the odontoid (white arrows) with effacement of the thecal sac and posterior displacement of the spinal cord, as well as erosion of the dens (black arrow). Corresponding CT image (C) demonstrates confirms odontoid erosions, as well as advanced erosive change across the C1–C2 facets (D— yellow arrows).
◾seen Flexion views will demonstrate maximal atlantoaxial subluxation, which is in up to 30% of patients with chronic rheumatoid arthritis ◾spondyloarthropathies, Note that subluxation may also be present in other seronegative but in this setting would likely be accompanied by syndesmophytes and/or vertebral body fusion
Atlantoaxial impaction results from erosions and collapse of the C1–C2 facets, which may result in protrusion of the dens through the foramen magnum. This may ultimately result in clinical symptoms of spinal cord compression. Other imaging manifestations of RA in the spine may include facet joint erosive change and thinning of the spinous processes. Sacroiliac joint changes are less common and severe than those in seronegative spondyloarthropathies but may be seen in up to
30% of those with long-standing disease. Such changes are more commonly seen in women and rarely result in fusion.
Seronegative Spondyloarthropathies The term seronegative spondyloarthropathy refers to a group of inflammatory arthritides that were initially characterized as rheumatoid arthritis, but which lacked serum rheumatoid factors [16]. Ankylosing spondylitis (AS) is the prototypical disease described in the spectrum of seronegative spondyloarthopathies, but other disorders in this category include PsA, arthritis-related inflammatory bowel disease (IBD), reactive arthritis, uveitisrelated to HLA-B27, and other undifferentiated or indistinguishable forms of these diseases. As this initial description, additional diagnostic criteria for this category of arthritides include axial and peripheral articular involvement, and an association with human leukocyte antigen HLA-B27. The overall prevalence is estimated at 1%, making this group of inflammatory arthritides more common than rheumatoid arthritis [17]. The predominant imaging approach to recognizing a seronegative inflammatory process includes polyarticular joint space narrowing, with predominant distal distribution of the hands and feet, and the addition of bony proliferation. Additionally, this group of diseases is characterized by enthesitis, or inflammation of enthesis, which are osseous attachment sites for ligaments and tendons. Diagnostic classification criteria set forth by the Assessment of SpondyloArthritis international Society for patients younger than 45 presenting with low back pain includes the following: 1. Either MRI or radiographic evidence of sacroiliitis and at least one clinical finding (mucosal ulcerations involving the mouth, intestines, or genitals, infections, erythema nodosum, inflammatory back pain, arthritis, Achilles enthesitis, dactylitis, uveitis, psoriasis, Crohn’s disease/ulcerative colitis, good response to nonsteroidal anti-inflammatory medications, family history of spondyloarthropathy, positive HLA-B27, and elevated C-reactive protein); OR 2. HLA-B27 positive and at least two clinical findings
MRI is an essential tool in the diagnostic algorithm and is included in the criteria because both the sensitivity and specificity
for the diagnosis of axial spondyloarthropathy is greater than 90% when there is MRI evidence of sacroiliitis combined with one specific clinical feature.
Ankylosing Spondylitis Overview AS is an inflammatory condition predominantly affecting the spine and sacroiliac joints. The peak onset typically occurs between 15 and 30 years of age, with males being more commonly affected than females at a 4:1 ratio. The prevalence in the general population is relatively low at 0.1%. Serum HLA-B27 positivity is detected in over 90% of patients afflicted with this condition. Pathology Pathophysiology of AS involves both synovial changes and entheseal inflammation, with fibrous ankylosis reflecting a relatively late manifestation. Imaging Radiographic findings of AS typically consist of bilateral, symmetric sacroiliitis (though asymmetric involvement is a common manifestation early in the disease process) (Fig. 52.34). Erosive changes are initially identified along the inferior one-third of the SI joints, which is the synovial portion of the joint, as well demonstrating an iliac-sided predominance due to the thinner hyaline cartilage layer in comparison to the sacrum, eventually leading to subchondral sclerosis and fusion across the SI joints later in the disease process.
FIGURE 52.34 Bilateral sacroilitis in patient with ankylosing spondylitis. Frontal radiograph of the pelvis demonstrating bilateral symmetric sacroiliac joint widening and cortical indistinctness compatible with sacroiliitis in a patient with ankylosing spondylitis.
Characteristic radiographic findings of the axial skeleton include the following:
◾spondylitis) Romanus lesions or corner entheseal erosions (active inflammatory at the anterior-superior and anterior-inferior aspects of the vertebral body endplates, at the attachment sites of the annulus fibrosus (Fig. 52.35), which appear as focal edema/enthesitis on MRI Osteitis or “shiny corner” sign reflecting reactive sclerotic repair or healing secondary to inflammatory Romanus erosions at the anterior-superior and anterior-inferior aspects of the vertebral body endplates (Fig. 52.36) Healing new bone formation at the annulus fibrosus enthesis results in vertical syndesmophyte formation, which is ossification of the outer margin of the annulus (Fig. 52.37) Thin syndesmophytes bridging the outer layer of the annulus fibrosis and ossification of the posterior interspinous ligaments produces a dense linear line known as the dagger sign, which in combination with fused facets results in what is known as the trolley track sign (Fig. 52.38) Eventually leads to long column fusion which creates the “bamboo spine” appearance Careful attention should be directed toward the evaluation of the posttraumatic AS patient [18], even in the setting of minimal or low-grade trauma, as the
◾ ◾ ◾ ◾ ◾
fused spine acts as a lever arm placing great stress on the spine, which can result in a transverse “carrot-stick” fracture (Fig. 52.39) across disco-vertebral junctions. Carrot-stick fractures can cause significant comorbidity if coupled with an unstable fracture pattern or epidural hematoma
FIGURE 52.35 Spondylitis in a patient with AS. Corner entheseal erosions (active inflammatory spondylitis) at the anterior-superior and anterior-inferior aspects of the T12 and L5 vertebral body endplates (arrowheads), at the attachment sites of the annulus fibrosus, which appear as focal edema/enthesitis on MRI.
FIGURE 52.36 Shiny corners in a patient with AS. AP radiograph of the lumbar spine (A) in a 25-year-old male demonstrates fusion of the sacroiliac joints (arrows). Lateral view (B) demonstrating osteitis or “shiny corners” appearing as increased sclerosis (arrowheads) of the anterosuperior endplates of the L4 and L5 vertebral bodies.
FIGURE 52.37 Ankylosing spondylitis. AP radiograph (A) demonstrates bilateral and symmetric sacroiliitis (white arrows). Lateral radiograph (B) demonstrates corner erosions of the anterior superior endplate of L2 and L4 (white arrowheads) which occur exactly at the site of attachment of the annulus fibrosus to the vertebral endplate, indicating a Romanus erosion, while there are corner foci of sclerotic repair at L2 and L5 (black arrows), compatible with osteitis or shiny corners. There is also healing new bone formation at the annulus fibrosus enthesis that results in vertical syndesmophyte formation (yellow arrows), which is ossification of the outer margin of the annulus.
FIGURE 52.38 Syndesmophytes in AS. AP and lateral radiographs demonstrate fusion across the SI joints, thin syndesmophytes bridging the outer layer of the annulus fibrosis (white arrowheads) resulting in the classic bamboo spine appearance, and ossification of the posterior interspinous ligaments (white arrow) produces a dense linear line known as the dagger sign, which in combination with fused facets results in what is known as the trolley track sign.
FIGURE 52.39 “Carrot-stick” facture in patient with AS. Sagittal CT image in a patient with known ankylosing spondylitis and subsequent transverse (“carrot stick”) fracture through the superior C6 vertebral body (arrow) and posterior elements.
Inflammatory spondylodiscitis, known as Andersson lesions, is a noninfectious disco-vertebral process seen in patients with AS. MR imaging can detect early changes of spondylodiscitis, typically revealing hemispherical increased signal intensity along adjacent subchondral endplates, as well as increased intradiscal signal, which can mimic discitis-osteomyelitis (Fig. 52.40). Both Romanus and Anderson lesions may demonstrate postcontrast enhancement, presumably related to the resulting associated local inflammatory hyperemia. More distal peripheral disease is less common and often seen with inadequate treatment. Unlike sacroiliac joint involvement, AS of peripheral joints is typically asymmetric.
FIGURE 52.40 Inflammatory spondylodiscitis. Sagittal (A) and coronal oblique (B) T2-weighted fat-suppressed images through the sacrum demonstrate hemispherical increased signal intensity along adjacent L5 and S1 subchondral endplates (yellow arrows), as well as increased intradiscal signal, compatible with inflammatory spondylodiscitis (Anderson lesion). Additionally, there is bilateral subchondral bone marrow edema along the SI joints compatible with sacroiliitis.
Differential Pearls Bilateral and symmetric sacroiliitis.
Inflammatory Bowel Disease Overview IBD is well known to be associated with peripheral arthritis and spondyloarthropathy, among other causes of musculoskeletal system-related pain, which occur in up to 53% of patients [19]. IBD-related spondyloarthropathy, which can be categorized as axial versus peripheral arthropathy, is considered one of the most common extraintestinal manifestations of IBD, occurring in up to 30% of patients with IBD [20]. Pathology
Serum HLA-B27 positivity is detected in over 50% of patients with enteropathic arthropathy, most commonly in those with axial skeletal involvement. It is felt that predisposing genetic factors may also play a role in disease and symptom onset. IBD-related spondyloarthropathy consists of both axial arthropathy (sacroiliitis, inflammatory back pain, and ankylosing spondylitis) and peripheral arthropathy (nondeforming arthritis that waxes and wanes with bowel activity and flares) [21]. Imaging Axial arthropathy includes sacroiliitis and spondylitis is common and indistinguishable from AS, appearing as bilateral and symmetric, as well as Romanus lesions and shiny corners, noninfectious spondylodiscitis, and thin bridging vertical syndesmophytes (Fig. 52.41). Additional synovial inflammatory changes can be seen along the facet joints, costosternal, costovertebral, and costotransverse joints.
FIGURE 52.41 IBD-related spondyloarthropathy. AP preliminary radiograph in a 65-year-old male with Crohn’s disease obtained for small bowel series demonstrates classic thin bridging vertical syndesmophytes (arrowheads) and fused SI joints, (arrows), indistinguishable from AS.
MR imaging can detect acute inflammatory spondylitis and sacroiliitis earlier than radiographs, allowing for potential treatments before progressive structural damage. MR findings of acute inflammatory sacroiliitis include the following (Fig. 52.42):
◾T2-weighted Subchondral bone marrow edema seen as a hyperintense signal on STIR or fat-suppressed images along the subchondral surface of the SI
joints, as well as subchondral enhancement, which be seen in association with erosions (Fig. 52.42) Synovitis of the SI joints manifested by intra-articular enhancement Enthesitis of the interosseous SI joint ligaments as evidenced by hyperintense signal seen on STIR or T2-weighted fat-suppressed Later findings and structural changes related chronic sacroiliitis, which can be appreciated on radiographs and MRI include subchondral sclerosis, erosions, periarticular fat deposition due to chronic inflammation, and bony bridging (ankylosis)
◾ ◾ ◾
FIGURE 52.42 IBD-related spondyloarthropathy. Coronal (A) and axial oblique IR (B) images demonstrate bilateral sacroiliac joint bone marrow edema, erosions, and fluid accumulation with SI joints, left greater than right, as well as inferior predominance involving the synovial portions of the SI joints (arrowheads). Axial PD fat-suppressed images (C and D) demonstrate multifocal entheseal bone marrow edema (white arrows), compatible with enthesitis at the hamstring tendon origins, adductor insertions, gluteal tendon insertions, and the L4–L5 endplates at the attachment sites of the annulus fibrosus.
Peripheral IBD-related arthropathy manifestation included dactylitis and enthesitis.
◾periarticular Radiographic findings are usually nonspecific and normal, but can show osteopenia, soft-tissue swelling, and rarely erosions of the MCP joints, as well as arthropathy of large weight-bearing joints ◾attachment Enthesitis, focal inflammation at a tendon, ligament, or joint capsule osseous site, are common findings in all patients with seronegative
spondyloarthropathies (6–50% of patients), manifested as bone marrow edema on MR imaging at enthesis sites (Fig. 52.42)
Other musculoskeletal manifestations of IBD-related spondyloarthropathy include osteonecrosis, which may be encountered more frequently due to high incidence of steroid use in this population, and osteomyelitis of the pelvic bones and spine due to direct extension from intra-abdominal abscess and fistulas.
Psoriatic Arthropathy Overview Psoriatic arthropathy (PsA) is considered under the category of seronegative spondyloarthropathy, presenting with peripheral joint involvement and affecting the axial skeleton including the sacroiliac joint and spine. Most patients, approximately 70%, develop psoriatic skin lesions several years before experiencing musculoskeletal symptoms, while 15% of patients develop arthritis before skin changes, and the remaining patients report arthritis and skin changes developing simultaneously. Patient symptoms clinically overlap with rheumatoid arthritis, including joint stiffness, pain, and swelling, limited range of motion, morning stiffness, and fatigue; however, patients with psoriatic arthropathy present with nail psoriasis and dactylitis and usually test negative for rheumatoid factor. Additionally, contrary to RA, patients with PsA, exhibit an asymmetric and distal distribution pattern in the extremities. In 2005, Moll and Wright classified PsA into five subtypes: 1. Classic PsA or predominant DIP joint arthritis of the hands and feet: It manifests as distinct periarticular erosive changes of the DIP joints with bony proliferative changes, often associated with nail dystrophy 2. Arthritis mutilans: A destructive form of PsA with extensive osteolysis of the DIP and PIP joints of the hands and feet resulting is severe digital abnormalities including “pencil-in-cup” and “opera glass” deformities 3. Symmetrical peripheral polyarthritis resembling RA: It affects more than five joints of the fingers, wrists, and toes with erosions and ankyloses of the interphalangeal joints. 15–20% of cases cannot be distinguished from RA (although patients are RF negative) 4. Asymmetrical mono or oligarthritis usually involving the knees or peripheral small joints: It is the most common form of PsA (70% of cases), affecting less than five joints, exhibiting an asymmetric distribution of both small and large joints, including the classic finding of “sausage digit”
5. Axial spondyloarthropathy: These findings are similar to AS, including spondylitis, bulky asymmetric syndesmophytes, and asymmetric sacroiliitis
Pathology Although the precise pathophysiology of psoriatic arthropathy has yet to be delineated, the development of psoriatic arthropathy is likely due to combination of hereditary and environmental factors. It has been postulated that this process may represent a reactive arthropathy from psoriatic plaque flora. Serum HLA-B27 positivity is detected in approximately 60% of patients who demonstrate peripheral and axial involvement. Imaging A plethora of radiographic findings are associated with psoriatic arthropathy and can be subdivided based on peripheral and axial distributions of inflammatory changes. Peripheral Joints
Hand/Wrists (Involved in 25%)
◾ Row pattern: Classic DIP prevalence with asymmetric distribution
⚬ Begins as periarticular or marginal erosions of the DIP joints with peripheral bony productive change at the joint borders, coined the “mouse-ear” deformity (Fig. 52.43) ⚬ More advanced changes include distal phalangeal tuft erosions, acroosteolysis (Box 52.1), as well as DIP and PIP joint ankyloses (Fig. 52.44)
◾including: Progressive osseous erosions lead to other advanced findings seen in PsA
⚬ “Pencil-in-cup” deformity: It is described as marked thinning/erosion of the distal aspect of the proximal phalanx exhibiting a pointed end and accompanied bone resorption at the base of the distal phalanx creating a concave appearance (Fig. 52.45) [22]. Typical radiographic finding in PsA, but not specific as it can be seen in other inflammatory arthropathies ⚬ Five percent of patients may develop arthritis mutilans resulting from osteolysis and articular collapse of the phalanges. This can be associated with the clinical manifestation of “telescoping fingers” Ray pattern: Early PsA of the hands and feet can result in dactylitis, known as a “sausage digit,” manifest as soft-tissue swelling of an entire digit and periostitis due to inflammation and synovitis about the DIP and PIP joints, as well as flexor tenosynovitis (Fig. 52.46)
◾
⚬ The MCP joints are typically spared early in the disease process, although can be eventually involved if untreated ⚬ A combination of endosteal and periosteal bone proliferation can lead to an “ivory” phalanx [22], which results in increased radiodensity of an entire phalanx (Fig. 52.47) ⚬ Any compartment of the wrist may be involved; fairly nonspecific
FIGURE 52.43 Psoriatic arthritis. AP radiographs of the hands demonstrated asymmetric distribution of periarticular erosions with bony productive change at the right 3rd DIP joint, known as “mouse-ear” deformity (arrows). Periarticular erosions are identified at the right 5th DIP, 3rd PIP, joint and 2nd and 3rd MCP joints. Early periarticular erosions at the left 2nd DIP joint, 2nd PIP joint, and 2nd MCP joint.
FIGURE 52.44 Psoriatic arthritis. AP radiographs of the hands demonstrate asymmetric erosive changes with bony productive change as well as ankyloses across multiple DIP joints (arrows).
FIGURE 52.45 Advanced changes in psoriatic arthritis. AP (A) and oblique (B) radiographs of the hands demonstrate marked erosive changes of the left 2nd and 3rd DIP and right 3rd and 4th DIP joints, resulting in the appearance of the pencil-in-cup deformity (arrows) and shortening of the middle phalanges with subluxation of the right 1st IP joint resulting in telescoping fingers, as well as flexion deformities of the right hand. Additionally periarticular erosions are also identified about the 1st MCP joints, and metacarpal heads.
FIGURE 52.46 Dactylitis in a psoriatic arthritis. AP radiograph (A) of the left hand in a 58-year-old male with history of psoriasis, demonstrating fusiform swelling of the 3rd digit (sausage digit) with periosteal proliferation along the 3rd proximal phalanx (arrows). Corresponding axial (B) and sagittal T2-fat-suppression (C) MR sequences demonstrate tenosynovitis of the 3rd flexor tendon (arrow) with regional soft-tissue edema, intense bone marrow edema within the 3rd proximal phalanx, 3rd MCP joint effusion, and erosion dorsal aspect of the 3rd metacarpal head (arrowhead).
FIGURE 52.47 Ivory phalanx. Frontal radiograph of the hand in an 80-year-old female with history of psoriasis demonstrating diffusely increased density within the 3rd digit distal phalanx (arrow) compatible with an “ivory phalanx.”
Feet/Ankles Overall, the features and distribution are same as seen in the hands (Fig. 52.48). Typically manifests as interphalangeal joint involvement, with ivory phalanx commonly observed in the distal phalanx of the great toe. Commonly observed erosive changes are seen at the posterior tubercle of the calcaneus, but is nonspecific as it can also be a typical finding in patients with chronic reactive arthritis. Enthesitis is a commonly observed imaging finding at the malleoli, Achilles tendon insertion, and plantar aponeurosis.
FIGURE 52.48 Psoriatic arthritis. AP (A) and oblique (B) radiographs of the right foot demonstrate 2nd, 3rd, and 4th DIP joint periarticular erosions (arrowheads), as well as at the bases of the 2nd and 3rd proximal phalanges.
Axial Manifestations
◾ Sacroiliitis ◾ ◾
⚬ Common finding in patients with PsA ⚬ Initially appears as bilateral and asymmetric, but progresses to symmetric involvement later in the disease process (Figs. 52.49and 52.50) ⚬ Late manifestations include bilateral ankylosis, although this is less common than in AS Spondylitis ⚬ Syndesmophytes present as bulky vertical/nonmarginal paravertebral ossifications that may be asymmetric with “skipped bodies” Enthesitis ⚬ Considered a hallmark clinical and imaging finding in seronegative spondyloarthropathies, including PsA ⚬ Most commonly identified at the Achilles tendon insertion, origin of the plantar aponeurosis, and tendinous attachment sites about the pelvis
FIGURE 52.49 Asymmetric sacroilitis in patient with psoriatic arthropathy. AP view of the sacrum demonstrates asymmetric left-sided sacroiliac joint subchondral irregularity, erosions, sclerosis, and partial fusion (black arrow), compatible with asymmetric sacroiliitis.
FIGURE 52.50 Psoriatic arthritis. AP radiograph of the pelvis demonstrating asymmetric sacroilitis, left greater than right as evidenced by subchondral sclerosis and indistinctness of the subchondral margins (arrows) due to underlying erosions with an iliac-sided predominance, as well as partial ankyloses. Additionally, note the concentric bilateral hip joint space narrowing, more commonly seen in inflammatory arthropathies compared with superolateral and inferomedial joint space narrowing commonly seen in osteoarthritis.
Diagnostic Pearls
◾change Distal, asymmetric distribution in the hands and feet with bony productive and the absence of periarticular osteopenia can help to differentiate psoriatic and rheumatoid arthritis ◾between PsA may be distinguished radiographically from chronic reactive arthritis (CRA) due to the propensity of CRA to involve a single articulation of the foot ◾ Bilateral and asymmetric sacroiliitis seen in PsA versus AS
Chronic Reactive Arthropathy
Overview The term chronic reactive arthropathy (CRA) refers to the triad of arthritis, urethritis, and conjunctivitis [23]. From a musculoskeletal standpoint this condition often presents with heel pain as an initial manifestation, following an enteric or urogenital infection. Pathology There is a strong association of CRA with HLA-B27 positivity. There has also been a demonstrable association between this condition and HIV-positive status, and is thought to be triggered by a preceding gastrointestinal or genitourinary infection, which may have a subclinical presentation. Additionally, joint fluid and synovial cultures are sterile, hence the term “reactive.” Imaging Radiographic findings are nonspecific, but are similar to other forms of seronegative spondyloarthropathies, such as PsA, including irregular erosions, enthesitis, bone proliferation, periostitis, and digital soft-tissue swelling, either presenting as unilateral or bilateral, as well as asymmetric distributions. However, compared with PsA, CRA more often targets the joint of the feet rather than the hands. Imaging features include:
◾insertion Erosions of the posterior tubercle of the calcaneus at the Achilles tendon (Fig. 52.51) in conjunction with erosions of the MTP joints and
interphalangeal joint of the great toe ⚬ Lower extremity predominance: MTP joints, first interphalangeal joint, and the calcaneus are the most frequent targeted sites in the foot Enthesitis Sausage digit with associated periostitis Bulky paravertebral osteophytes syndesmophytes, indistinguishable from PsA Asymmetric sacroiliitis
◾ ◾ ◾ ◾
FIGURE 52.51 Chronic reactive arthritis. Erosions of the posterior calcaneal tubercle (arrow).
Differential Pearls Radiographic changes are identical to PsA; however, the predominant distal distribution and feet greater than hands in CRA, as well as clinical history allows for a more accurate diagnosis of CRA versus PsA.
Connective Tissue Diseases of Joints Systemic Lupus Erythematosus Overview
SLE is an autoimmune disorder characterized by inflammation, immune complex deposition, vasculitis, and vasculopathy [24]. It affects 1 in 700 white females and roughly 1 in 245 Black females. The condition may affect individuals of all ages, although the peak onset is typically between 10 and 40 years of age [25,26]. Pathology The underlying pathophysiology of SLE is thought to be related to autoantibodies reacting with components of various cell nuclei, ultimately resulting in deposition of immune complexes within end organs. Cells affected by the disorder are often present within synovial fluid, which likely gives rise to the majority of musculoskeletal manifestations of lupus. Imaging Findings It is mostly considered a symmetric, polyarticular disease. The most frequent findings in the hands and wrists consist of reducible, deforming, but nonerosive arthropathy due to ligamentous laxity and muscle contracture, distinguishing SLE from RA (Fig. 52.52).
FIGURE 52.52 SLE-related arthropathy. AP (A) and lateral (B) radiographs demonstrate hyperextension deformity involving the 2nd through 5th proximal interphalangeal joints with associated compensatory flexion deformity at the distal interphalangeal joints, compatible with swan-neck deformity, as well as 1st CMC joint subluxation.
◾compensatory Swan-neck deformity: Hyperextension deformity of the PIP joint with flexion deformity at the DIP joint ◾extension Boutonniere deformity: Flexion contracture of the PIP joint with compensatory deformity at the DIP joint ◾ MCP joint subluxation with ulnar deviation ◾ Subluxation of the first carpometacarpal (CMC) joint ◾tendons Tenosynovitis is a common presenting sign, typically involving the flexor of the hand. Tendon ruptures may occur later in the disease process ◾toIncreased incidence of septic arthritis may be seen in this population, thought be due increased steroid treatments ◾theAvascular necrosis and insufficiency fractures are common, usually involving hips, knees, and shoulders. It may result from steroid therapy and/or osteopenia, but given the high incidence (10%), there is likely an underlying component related directly to the disease itself. Widespread osteonecrosis in unusual locations should suggest SLE as a possible etiology
Jaccoud’s arthropathy is a disease entity characterized by a deforming, nonerosive arthritis that occurs in approximately 10– 35% of SLE patients [27]. This condition does not involve the synovium but causes capsular fibrosis. Imaging Findings
◾weight-bearing; Lateral deviation of the hands and feet may be seen when examined without with pressure, these deformities vanish ◾ Joint spaces are mainly preserved ◾capsular “Hook” erosions of the metacarpal heads may possibly be due to local pressure; true erosions are not typically found
Scleroderma/Progressive Systemic Sclerosis Overview Scleroderma is a multisystem disorder characterized by skin thickening and vasculitis. It mostly affects younger patients, with roughly 50% of patients presenting before the age of 40. It has a strong female predominance of roughly 80%. Pathology Though the underlying etiology is unknown, characteristic antibodies associated with the disease (ANA, anticentromere) suggest an underlying immunologic abnormality. Vascular damage is considered to be the primary event in disease onset, with endothelial cell activation, intimal thickening, and vascular narrowing ultimately giving rise to an impaired angiogenic response. Imaging Findings
◾with Best diagnostic clue is acro-osteolysis (Figs. 52.53and 52.54) in conjunction soft-tissue calcification (Fig. 52.54) ◾changes Early skin changes usually appear as soft-tissue swelling. Mid-disease skin include tapering of the skin at the ends of digits. Late-disease skin changes include marked contractures ◾most Calcinosis appears as punctate, globular, or sheet-like areas of mineralization, commonly affecting the hands [28]
◾considered Tenosynovitis, occasionally with the presence of fibrotic nodules, is an early finding ◾may Muscular fibrosis and atrophy may occur later in the disease; early myopathy also occur but is virtually indistinguishable from other etiologies ◾disease Arthritis is uncommon early in the disease; erosions may develop later in the process, as may other signs of end-stage joint involvement including: ⚬ DIP joint ankylosis ⚬ Subluxation and erosion of the trapezium/base of first metacarpal ⚬ Radial and proximal migration of the first carpometacarpal joint is thought to be a hallmark of progressive systemic sclerosis
◾have Hyperparathyroidism, thermal injury/burns, and PsA can all similar appearances on imaging and should be maintained in the differential diagnosis
FIGURE 52.53 Acro-osteolysis in scleroderma. AP (A) and lateral (B) radiographs demonstrate distal phalangeal acroosteolysis (arrows).
FIGURE 52.54 Acro-osteolysis + soft-tissue calcifications in scleroderma. AP (A) and lateral (B) radiographs demonstrate acro-osteolysis of the right 1st and 2nd distal phalanx, left 2nd and 3rd distal phalanges, distal phalangeal soft-tissue calcification, as well as advanced 1st CMC arthrosis with radial migration of the 1st metacarpal.
Crystal-Induced Arthropathies Gout Overview This disease entity is due to a biochemical derangement in which hyperuricemia results in monosodium urate or uric acid crystal deposition within periarticular soft tissues, cartilage, and bone. Although most cases are idiopathic, there may be a familial component and in some cases a relation to chronic disease (typically renal pathology or conditions creating high rates of cellular turnover, such as widespread tumor). Pathology Hyperuricemia ultimately gives rise to sodium urate crystal deposition in soft tissues and joints. The underlying cause of the primary gout is thought to be abnormal purine metabolism, whereas the secondary gout is believed to be attributable to increased serum uric acid levels.
Imaging Findings Initial clinical presentation is usually of monoarticular joint involvement, commonly the foot. Although any joint can be affected, the first MTP joint is most commonly affected with gout, followed by the first interphalangeal and tarsometatarsal joints. Erosive changes as will be described can be mono- or polyarticular, and usually exhibit an asymmetric distribution. Similarly, any of the joints of the hand and wrist can be involved; the carpometacarpal and intercarpal joints are most frequently affected. Various imaging findings seen in gout can be subdivided based on modality.
Radiographic Findings
◾andPain,onlyerythema, and regional periarticular soft-tissue swelling may be the first radiographic finding encountered in an acute gouty attack ◾ Known as “podagra” if affecting the first MTP joint ◾sharp Juxta-articular erosions, away from the joint, characterized as well-defined sclerotic margins and overhanging edges (rat-bite erosions) are the typical appearance of gouty erosions (Fig. 52.55) ◾result Urate crystal deposits within the soft tissues, often seen with chronic gout, in dense nodules due to crystal deposition, sometimes with internal calcifications and/or cloudy amorphous density, known as tophus. Tophus and adjacent joint erosion may exist synchronously (Figs. 52.56–52.59) Preservation of the joint space until late in the disease process
◾
FIGURE 52.55 Gout. AP radiograph of the foot demonstrating the hallmark findings of gout including classic juxta-articular erosions of the 1st metatarsal head with overhanging edges (arrow), normal bone density, and preservation of the 1st MTP joint space. Additionally, there are punched out erosions across the 2nd DIP joint (white arrowhead), as well as erosions along the medial aspect of the naviculocuneiform articulation (black arrowhead).
FIGURE 52.56 Tophaceous gout. Oblique radiograph of the left foot (A) and AP radiograph of the right foot (B) demonstrates tophus formation with the soft tissues adjacent to the 1st MTP joints, associated with typical juxta-articular erosions of the 1st metatarsal heads (arrows).
FIGURE 52.57 Tophaceous gout. Lateral radiograph of the elbow demonstrates soft-tissue swelling localized to the olecranon bursa containing amorphous calcifications (arrow, typical of tophaceous gout-related olecranon bursitis).
FIGURE 52.58 Gout. AP radiograph of the wrist demonstrates a well-defined punched erosion of the ulnar styloid (arrow) with associated tophus formation.
FIGURE 52.59 Gout. AP radiographs demonstrate periarticular erosions at the left 5th DIP and PIP joints, ulnar margin of the 1st interphalangeal joint, and carpal bones bilaterally, as well as diffuse tophus deposition is seen adjacent to the 2nd metacarpal heads.
USG Finding
◾Erosions Typically demonstrate joint effusions, tophi, and periarticular erosions [29]. in gout are usually deeper and more destructive compared with RA erosions ◾thinTophianechoic appear as inhomogeneous hypoechoic to hyperechoic surrounded by rim, may exhibit a nodular or infiltrative appearance, and can cause posterior acoustic enhancement due to attenuation of the sound beam and calcifications (Figs. 52.60and 52.61) Tendon involvement is usually peritendinous or around the tendon, but can be seen as intratendinous deposit. Common tendons include the Achilles and peroneal tendons in the foot, as well as the popliteus tendon insertion and along the intercondylar groove associated with cruciate ligaments are common intraarticular sites within the knee. Additionally, the patellar tendon and infrapatellar fat pad are site of tophus formation Double contour sign refers to the sonographic appearance of hyperechoic linear crystal deposits with the underlying hyperechoic line of subchondral bone (Fig. 52.62) Hyperechoic aggregates may also be visualized within joint fluid
◾ ◾ ◾
FIGURE 52.60 Tophaceous gout with ultrasound correlation. On x-ray and USG, AP (A) and lateral (B) radiographs demonstrate soft-tissue prominence along the dorsum of the hand at the level of the 4th metacarpal head with associated amorphous cloudy mineralization most compatible with tophus (arrow), as well as concomitant juxta-articular erosive changes more pronounced along the ulnar margin base of the 4th proximal phalanx and the dorsal ulnar margin 4th metacarpal head (arrowheads). Corresponding USG (C and D) images demonstrate a heterogeneous echogenic soft-tissue mass (*) with diffuse punctate echogenic foci, cloud-like morphology, and localized hyperemia (D), compatible with tophus as seen on the radiographs.
FIGURE 52.61 Double contour sign, tophus, and dualenergy CT. Longitudinal USG image of the 1st MTP joint (A) demonstrated double contour sign of urate crystal deposition along the head of the 1st metatarsal (white arrows). Dualenergy CT images with color mapping (B, C, and D) confirm the USG findings and clearly demonstrate urate deposits (green foci demarcated by white arrows) adjacent to the 1st metatarsal head and a small juxta-articular erosion (back arrow).
FIGURE 52.62 Gout with double contour sign. Longitudinal USG images acquired of the 2nd MCP joint demonstrate a smooth echogenic line along the outer surface of the metacarpal head (white arrows) overlying the anechoic cartilage paralleling the subchondral bone due to the deposition of monosodium urate crystals along the surface of the hyaline cartilage.
CT Findings
◾deposition Dual-energy CT can be highly valuable in distinguishing urate crystal from calcium depositions, which may otherwise have very similar appearances on other imaging modalities (Fig. 52.61) [30]
MRI Findings: Can identify intraosseous tophus deposits; however, although MRI is very sensitive in the detection of soft tissue and bone pathology, the findings may not be specific as the erosive changes can mimic septic joint-osteomyelitis. The site of involvement, distribution,
radiographic, and clinical correlation are often necessary to conclude the correct diagnosis.
◾ MR imaging feature are as follows:
⚬ Tophi often demonstrate a hypointense-to-intermediate signal on T1weighted images and heterogeneous signal intensity on T2-weighted images depending on the amount of calcium within the tophus ⚬ Tophi can be intra-articular (Fig. 52.63), extra-articular, or intraosseous ⚬ Osseous erosions adjacent to or in direct continuity with tophi can produce bone marrow edema, simulating osteomyelitis (Fig. 52.64); however, the location such as the first MTP joint and lack of an adjacent soft-tissue ulcer should favor gout rather an osteomyelitis
FIGURE 52.63 Gout AP radiograph (A) demonstrates increased calcified soft density adjacent to popliteus tendon origin and erosion in popliteal groove (black arrow). Corresponding coronal PD (B) and axial T2-weighted fatsuppressed (C) images demonstrate intermediate signal tophus at the origin of the popliteus tendon with erosion of the popliteal groove (black arrows).
FIGURE 52.64 Gout versus osteomyelitis. AP radiograph of the right foot (A) demonstrates punched out erosion of the 4th DIP joint with associated amorphous partially calcified softtissue mass (white arrow). Patient had a history of gout and diabetes but no draining soft-tissue wound or ulcer. Sagittal T1 and IR (B and C) sequences demonstrate a gouty tophus infiltrating and eroding the 4th DIP joint (white arrows), with resultant bone marrow edema. Long-axis T1 and T2 fatsuppressed image (D and E) demonstrate corresponding juxta-articular erosion seen on the radiographs with tophus exhibiting intermediate signal on both sequences eroding the adjacent bone. Surgical pathology confirmed gouty tophus status post amputation. Additionally, note the 1st MTP joint erosions (red arrows) and adjacent low-to-intermediate signal tophus (yellow arrows).
Differential Pearls
◾ If exhibiting a proximal distribution pattern, gout can mimic RA ◾well-defined Unlike RA, gouty erosions and joint involvement is asymmetric, erosions are with sclerotic margins, and tophus may be present ◾joint OA can be seen superimposed upon gouty changes, especially of the first MTP and tarsometatarsal joints ◾ulcer Septic arthritis can mimic gout, but location, history, and lack of soft-tissue should render a correct imaging diagnosis. Image-guided aspiration may need to be performed in equivocal clinical situations, which would yield needle-shaped crystals with negative birefringence Tophi can also mimic rheumatoid nodules and xanthomas
◾
Calcium Pyrophosphate Deposition Disease Overview Calcium pyrophosphate disease (CPPD) is a crystal-induced arthropathy due to the deposition of calcium pyrophosphate crystals into articular tissues, deposition known as chondrocalcinosis [31], which can present as an acute inflammatory monoarticular arthritis similar to gout (or septic joint), thus formerly known as pseudogout (not a radiological diagnosis). CPPD or pyrophosphate arthropathy is described as joint damage or pathology due to intra-articular or para-articular crystal deposition. The most common sites of involvement are the knees, pubic symphysis, wrists (TFCC and radiocarpal joints), second and third MCP joints, shoulder, and hips. Pathology The underlying pathology of pseudogout is felt to be mostly idiopathic, although hereditary and even secondary causes such as hemochromatosis, hyperparathyroidism, hypothyroidism, and ochronosis have been theorized, which have been shown to have increased association with CPPD. The pseudogout crystals may be pathologically distinguished from other disease processes and crystal deposition diseases through the characteristic rhomboid positive birefringence CPPD crystals observed on polarized light microscopy. Imaging Findings Chondrocalcinosis is a pathognomonic radiographic finding that corresponds to crystal deposition into hyaline or fibrocartilaginous structures, appearing as punctate and linear calcifications.
◾⚬Typical locations of chondrocalcinosis include: TFCC
⚬ Hyaline cartilage and fibrocartilage (menisci) of the knee ⚬ Pubic symphysis ⚬ Glenohumeral joint
◾chondrocalcinosis Typical locations of tendon include:
⚬ Gastrocnemius, quadriceps, and Achilles tendons (the most common) ⚬ Triceps, rotator cuff, and cruciate ligaments (less common) Distribution of arthropathy: ⚬ Knee: Patellofemoral compartment may manifest as isolated disease, or out of proportion compared with the tibiofemoral compartments (Fig. 52.65) ⚬ Wrist: Radiocarpal articulation ⚬ Hands: Second and third MCP joints ⚬ Spine: Usually surrounding the dens and anterior arch of C1, discogenic calcifications
◾
FIGURE 52.65 Isolated patellofemoral arthrosis CPPD. AP (A) and lateral (B) views of the knee demonstrate tricompartmental chondrocalcinosis (arrowhead) with advanced arthrosis of the patellofemoral joint (arrow).
Radiographic appearance (Fig. 52.66):
◾ Chondrocalcinosis ◾formation Joint space narrowing, subchondral sclerosis, subchondral cysts, and geode ◾ osteophytes emanating from the metacarpal heads ◾ Hooked-like Cause of scapholunate advanced collapse (SLAC wrist)
FIGURE 52.66 CPPD arthropathy. PA radiograph (A) of the right hand demonstrates radiocarpal and TFCC chondrocalcinosis (arrowheads) with carpal geodes (*). There is also narrowing of the 2nd and 3rd MCP joint with subchondral sclerosis and hooked osteophyte emanating from the 3rd metacarpal head (arrow). Corresponding USG of the 3rd MCP joint (B) demonstrated an irregular pattern of calcium deposition along the 3rd metacarpal head (arrowheads).
USG appearance: The pseudogout may demonstrate a thin echogenic band, which is often interrupted, within the mid-zone of the articular cartilage (Figs. 52.66 and 52.67) [32].
FIGURE 52.67 CPPD arthropathy. Oblique radiograph of the left wrist (A) demonstrated TFCC chondrocalcinosis and softtissue swelling (arrow). USG images (B and C) show rounded echogenic foci with the dorsal carpal recesses, outlined by joint fluid, compatible with chondrocalcinosis as seen on the radiographs (arrowheads), demonstrating increased power Doppler signal, indicating acute inflammation and synovitis. The patient presented with acute left wrist pain and cellulitis, the findings of which likely reflect the clinical presentation of acute CPPD arthritis.
◾layer In contrast to gout, calcium pyrophosphate crystals aggregate in the middle of cartilage, appearing as hyperechoic irregular foci of a variable length embedded within anechoic appearing hyaline cartilage ◾fibrocartilaginous Punctate, round echogenic foci may also be demonstrated within structures (e.g., TFCC or menisci) ◾butMayunlike demonstrate echogenic intra-articular aggregates as can be seen in gout, gout these aggregates are uniformly round with sharply defined outer margins (Fig. 52.67)
Crowned dens syndrome is a typical manifestation of the pseudogout involvement of the spine (Fig. 52.68).
FIGURE 52.68 CPPD crowned dens syndrome. Sagittal (A) and axial (B) CT images show a calcified mass surrounding the dens (arrows), as well as discogenic and interspinous calcifications (arrowheads), the findings of which are characteristic of crystal deposition, most commonly CPPD. Rheumatoid arthritis pannus is excluded by the presence of calcifications.
Differential Pearls 1. Septic arthritis a. Clinical presentation and imaging findings can often be indistinguishable from CPPD arthritis, thus joint aspiration may be necessary in those clinical situations 2. CPPD versus RA a. The absence of MCP erosions would favor CPPD versus RA b. Erosions of the dens and mass-like deposition around the C1–C2 articulations can mimic pannus formation in RA; however, CT imaging can be used to identify calcifications that would be present in CPPD but not associated with pannus in a patient with RA 3. CPPD results in chondral destruction, producing an imaging appearance similar to OA a. CPPD distribution is different compared with OA b. Radiocarpal, glenohumeral, and, the second and third MCP joints are more commonly affected in CPPD c. Geodes and joint destruction encountered in CPPD is often more severe compared with OA d. Metacarpal head hooked osteophytes are commonly seen in CPPD, and may be more prominent in cases of hemochromatosis
Hydroxyapatite Deposition Disease/Calcific Tendinosis Overview Hydroxyapatite deposition disease (HADD) is caused by pathological deposition of calcium hydroxyapatite crystals in tendons, peritendinous and periligamentous tissues, and bursae. The peak incidence occurs between 30 and 50 years of age, with a slight male predominance, and can be observed in up to 3% of the general population. It is generally monoarticular, with the shoulder being the most frequent site of involvement in up to 69% of cases [33]. Interestingly, most cases of HADD are asymptomatic and frequently encountered on radiographs as an incidental finding; however, is a common cause of nontraumatic joint pain. Distribution and Location HADD presents as a monoarticular process, with the shoulder and hip known to be the most common site of involvement. However, when patients present with a painful monoarticular process in an atypical location, treating physicians must rely on radiological interpretation and clinical presentation to avoid misdiagnosing HADD as another possibly more ominous process.
Shoulder
◾(supraspinatus Common locations: Rotator cuff tendons are most common site of HADD > infraspinatus > subscapularis > teres minor) ◾subacromial–subdeltoid Uncommon locations: Biceps tendon, pectoralis major tendon insertion, and bursa
Hip
◾ Common locations: Gluteal tendon insertion
⚬ Greater trochanter: Gluteus medius and minimus tendon insertions ⚬ Gluteal tuberosity: Gluteus maximus tendon insertion
◾ Uncommon locations around the hip:
⚬ Rectus femoris origin ⚬ Iliopsoas insertion ⚬ Common hamstring tendon origins ⚬ Labrum and/or hip capsule (rare)
Elbow
◾ Common locations: Flexor and extensor tendon complex origins ◾ Uncommon locations: ⚬ Ulnar and radial collateral ligaments ⚬ Biceps and triceps tendon insertions
Wrist/Hand
◾ Common locations:
⚬ Flexor carpi ulnaris tendon insertion upon the pisiform is the most common site in the wrist ⚬ Periarticular regions of the MCP and interphalangeal joints
Knee
◾ Usually an uncommon or atypical site for HADD
⚬ Occur adjacent to the femoral condyles, fibular head, prepatellar region, popliteus tendon, and collateral ligaments
Foot/Ankle
◾ Usually an uncommon or atypical site for HADD
⚬ Seen in the flexor hallucis longus and brevis tendons, as well as the peroneus muscles ⚬ Adjacent to the MTP joints known as acute calcific periarthritis/hydroxyapatite pseudopodagra Often mistaken for acute tophaceous gout
◾
Neck
◾ Usually an uncommon or atypical site for HADD
⚬ Longus coli muscle and tendon with calcific deposition anterior to C2 ⚬ Present with acute onset of neck pain, stiffness, and odynophagia ⚬ Must differentiate from retropharyngeal abscess
Pathophysiology The underlying pathology is thought to be the result of microtrauma and/or stress within the tendon, which ultimately gives rise to regional hypovascularity, predisposing to degenerative tearing along with subsequent necrosis and calcification. There are four pathological stages of HADD: 1. Precalcific/formative stage: Local hypoxia resulting in fibrocartilaginous transformation. 2. Calcific stage: Resting period where the initial inflammatory process results in calcium being excreted from cells, coalescing into calcium deposits, which may appear well-defined and homogeneous on x-ray. 3. Resorptive stage: Calcific deposits liquefy, causing increased intratendinous pressure with localized acute inflammation, and possible rupture into adjacent bursa or localized soft tissues, as well as local cortical bone erosions. a. Most painful stage b. Fluffy, hazy appearance with ill-defined edges on radiographic evaluation c. Cortical erosions and bone marrow edema in this phase lead to aggressive appearance and misleading diagnosis d. Typical clinical manifestation includes acute pain and tenderness, decreased range of motion, and in some cases fever and elevated inflammatory markers (ESR and CRP), thus mimicking infection e. Unlike patients with infection, patients presenting with HADD have normal WBC counts 4. Reparative/postcalcific stage: Fibroblasts restore a normal tendon collagen pattern with residual shell deposit or linear calcifications
Imaging Findings Radiographic Findings: Typically appears as a globular, homogeneous calcific density, usually in the distribution of a tendon or bursa (Fig. 52.69). It can be associated with cortical erosions (most common with rotator cuff, pectoralis, or gluteal involvement) or intraosseous extension, particularly raising concern for a surface chondroid lesion.
FIGURE 52.69 Calcific tendinosis. AP radiographs of the shoulder and hip demonstrate globular homogenous calcific deposits along the course of the rotator cuff (arrow in A) and the gluteal tendon insertions (arrow in B).
Milwaukee shoulder (Fig. 52.70) is destructive shoulder arthropathy secondary to HADD [36]. It has high levels of activated collagenase and neutral protease enzymes resulting in sever thinning of cartilage, narrowing of the glenohumeral joint, and destruction of subchondral bone. Although HADD has a male predilection, this condition primarily affects elderly women. It resembles a neuropathic joint on radiographs and has high incidence of rotator cuff tear.
FIGURE 52.70 Milwaukee shoulder. AP radiograph of the right shoulder demonstrates uniform narrowing of the glenohumeral joint space, diffuse subchondral sclerosis, and intra-articular calcifications. Differential consideration would include chondrocalcinosis from calcium pyrophosphate deposition. Joint aspiration confirmed diagnosis of calcium hydroxyapatite crystals.
CT Findings: CT can confirm HADD along the path of tendinous insertions. It can provide additional information related to osseous/cortical erosion or intramedullary extension. It is useful for the evaluation of less common or atypical locations. CT can differentiate between calcification and ossification based on HU values. Comet
tail appearance with tapering along tendons and/or ligaments can be appreciated. MRI Findings: It can evaluate the extent of soft-tissue abnormalities and exclude other pathologies. Calcifications will appear hypointense on all pulse sequences, and demonstrate blooming on gradient-echo sequences. In the resorptive phase, migration of HADD triggers a localized inflammatory response, resulting in hyperintense T2 signal representing reactive edema and inflammatory response within the tendon proper, peritendinous tissues, or adjacent bursa (Fig. 52.71) [37]. Aggressive picture at MR imaging with extensive localized inflammatory response, enhancement, and osseous involvement can mimic tumor.
FIGURE 52.71 Calcific periarthritis. A 35-year-old male presenting with atraumatic hip pin and normal white blood cell count. AP radiograph (A) demonstrates a globular cloud-like calcification adjacent to the acetabulum (arrow). Axial CT image (B) demonstrates the focus of calcification adjacent to the posterior acetabular rim along the posterior joint capsule. Axial (C) and sagittal (D) PD fat-suppression MR images demonstrate the pericapsular/intra-articular calcification along the posterior aspect of the joint capsule, with associated reactive acetabular marrow edema, and reactive joint effusion. Differential consideration included septic joint, however aspiration confirmed negative culture.
◾ Edema may be extensive and can mimic infection or focal mass ◾resulting Soft-tissue calcification with cortical erosion and intraosseous migration in bone marrow edema and periostitis may raise concern for neoplasm, particularly surface chondroid lesions (Figs. 52.72and 52.73)
FIGURE 52.72 Calcific tendinosis with cortical erosion. A 55year-old male with shoulder pain and limited range of motion. Scapular Y-view of the right shoulder (A) showing focal area of calcification along the course of the subscapularis. Axial PD fat suppression MR image (B) and gradient echo image (C) of the right shoulder in the same patient shows a focus of low signal with blooming artifact within the superior fibers of the subscapularis tendon with subjacent cortical erosion and bone marrow edema (arrows), compatible with calcific tendinosis with subcortical erosion rather than chondroid surface lesion. Diagnostic ultrasound (D) shows the corresponding hyperechoic calcification (arrow) surrounding by bursal fluid (*). Mechanical barbotage (E) with mechanical disruption (blue arrow indicating needle) of the calcification with numerous passes after aspiration and then followed with steroid injection.
FIGURE 52.73 Atypical calcific tendinosis. A 55-year-old female with right knee pain and tenderness to palpation over the lateral joint space. Initial radiograph (A) demonstrates globular calcification adjacent to the lateral femoral condyle (arrow). Coronal proton density fat-saturated MR image (B) demonstrating marked edema of the lateral femoral condyle with low-signal intensity deposit/mineralization of the proximal lateral collateral ligament (arrow) compatible with acute calcific periarthritis.
Correlation with radiographs and/or CT is crucial in rendering the correct diagnosis in the setting of neoplasm versus HADD. USG Findings: Appears as echogenic foci within the tendon, with or without posterior acoustic shadowing (Fig. 52.74). USG can be utilized to perform diagnostic exams and therapeutic procedures (barbotage) [34]. Barbotage refers to a percutaneous intervention that allows for fragmentation and aspiration of calcific material within a joint or bursa.
FIGURE 52.74 Calcific tendinosis on USG. Diagnostic USG image demonstrated hyperechoic calcium deposit with the supraspinatus tendon (arrow) with posterior acoustic shadowing (*).
Differential Pearls Potential pitfalls and mimics in the acute setting 1. Infection a. Clinical manifestation of localized pain and in some cases fever b. Patients presenting with HADD will typically have normal WBC counts, but can elevated inflammatory markers c. MR imaging of calcium extrusion into the peribursal soft tissues/bursa aids in the diagnosis d. Acute onset of neck with stiffness and odynophagia (Fig. 52.75) i. Longus coli calcific tendinosis can mimic retropharangeal abscess [35] 2. Tumor a. Bone marrow edema associated with adjacent soft-tissue calcification and cortical destruction may raise concern for neoplasm, particularly surface chondroid lesions 3. Crystalline arthropathy (i.e., gout) a. Gouty tophi typically are more faintly calcified b. Elevated urate levels are seen in gout and not HADD c. MRI appearance of a tophus maybe indistinguishable from HADD 4. Other osseous mimics a. Avulsion fractures: Usually history of trauma or sports-related injury b. Post-traumatic ossification: Pellegrini-Stieda and myositis ossificans
c. Accessory ossicles d. Juxtacortical chondromas
FIGURE 52.75 Longus colli calcific tendinosis. A 42-year-old female with neck pain and difficulty swallowing. Lateral radiograph (A) and sagittal reformatted CT image (B) of the cervical spine showing amorphous calcification (arrows) anterior to the C2 vertebral body. Corresponding postcontrast axial CT image (C) showing reactive fluid anterior to the calcification (arrow) without rim enhancement or abnormal adenopathy, the findings of which are compatible with longus colli calcific tendinosis.
Radiographic correlation is essential when encountered with a potential case of HADD. CT is superior to radiographs to depict continuity between the tendinous, cortical, and medullary processes. MRI offers superior resolution to assess the degree of tendon, bursal, and osseous involvement. Factors that can aid in making the diagnosis of calcific tendinosis/HADD include: 1. Location within or adjacent to tendon or ligament 2. The absence of joint fluid or soft-tissue mass 3. Relatively acute clinical presentation
Metabolic, Hematologic, and Other Miscellaneous Causes of Arthritis
Hemochromatosis Overview Primary hemochromatosis is an autosomal recessive disorder caused by a single-site mutation on HFE gene, which allows cellular uptake of iron-based transferrin. Secondary hemochromatosis has a variety of causes but usually results from hemosiderosis from multiple blood transfusions. Pathology Increased GI uptake of iron and cellular uptake manifests as a progressive increase in total body iron stores, ultimately resulting in abnormal iron deposition in multiple organs. Imaging Findings The best diagnostic clue on imaging is typically the large hooked osteophytes involving the second and third metacarpal heads/MCP joints with associated joint space narrowing, subchondral sclerosis, and subchondral cyst formation (Fig. 52.76).
FIGURE 52.76 Hemochromatosis. AP (A) and oblique (B) demonstrate narrowing of the 2nd MCP joint with sclerosis, cystic change, and hooked/beaked-like osteophytes emanating from the 2nd metacarpal head (arrows). Additionally, are advanced arthritic changes in the 3rd PIP joint, geode formation with the head of the 3rd distal phalanx, and erosions of the ulna.
Differential Pearls
◾present Hooked osteophytes in hemochromatosis are typically larger than those in CPPD ◾(especially If an arthritic pattern suggestive of CPPD develops in a young adult a male), hemochromatosis should be considered as a potential cause ◾hooked MCP involvement can also be difficult to distinguish from RA; however, osteophytes would not be expected in a patient with RA ◾theDistal sites in the hands are more commonly seen with OA changes rather than more proximal distribution of hemochromatosis [38]
Hemodialysis-Associated Amyloid Arthropathy
Overview Amyloidosis is a multisystem disorder caused by deposition of amyloid fibrillary protein aggregates in patients on long-term hemodialysis (HD) targeting the musculoskeletal system, manifested by erosive peripheral arthropathy, spondyloarthropathy, and carpal tunnel syndrome. Pathology HD-related amyloid arthropathy is thought to be due insufficient elimination of β2 microglobulin, resulting in amyloid fibril deposition into bone, joints, muscle, tendons, and bursae, thus contributing to arthritis and tendon pathologies. However, the pathogenesis is likely multifactorial, including chronicity of renal failure, as well as the duration of HD. Distribution The most commonly affected locations include the shoulders, hips, and wrists, with imaging findings resembling that of inflammatory arthropathies, while spinal involvement may masquerade as discitis-osteomyelitis. Imaging Findings Erosive and destructive peripheral arthropathy.
Radiographic Appearance
◾usually Juxta-articular erosions and subchondral cysts/geodes of variable sizes, demonstrating well-defined sclerotic margins at the sites of tendon and ligament attachments ◾contractures Eventually can lead to a destructive arthropathy with subluxations and joint ◾ Most commonly seen around the hips, shoulders, and carpal bones
USG Appearance
◾echogenic Amyloid deposits appear as intra-articular, intrabursal, periarticular lobulated masses with associated joint effusions, synovitis, and bursitis (Fig.
◾52.77) Tenosynovial amyloid deposition with the flexor and extensor tendons of the wrist
FIGURE 52.77 HD-related amyloidosis in a patient with ESRD on long-term HD. Axial T1 (A) and T2 (B) fatsuppressed images extensive lobulated intra-articular synovial mass throughout the left hip joint (white *), demonstrating hypointense T1 and predominantly low-to-intermediate signal on T2-weighted sequences, the imaging characteristics of which are suggestive of intra-articular amyloid deposition/dialysis-related amyloidosis. There is an osseous erosion along the fovea capitis and anteromedial aspect (yellow arrows) of the femoral head–neck junction, with amyloid deposition infiltrating in continuity within the osseous erosions, demonstrating associated perierosional edema adjacent to the femoral neck erosion. Corresponding USG (C) in the same patient demonstrates with intra-articular mass (*) as lobulated and echogenic.
MRI Appearance
◾synovial Amyloid deposition can be identified along intra-articular, bursal, and tendon surfaces, eroding and communicating with osseous cysts, and extension into periarticular soft tissues ◾lobulated Intra-articular amyloid deposition appears as an abnormal intra-articular mass with capsular distension and joint effusion, demonstrating a hypointense signal on T1-weighted images, with variable but usually hypointense-to-intermediate signal on T2-weighted sequences (Fig. 52.77) Erosions, cysts, and intraosseous lesions demonstrate amyloid deposits that are in continuity with intra-articular deposits, exhibiting signal characteristics of low-signal intensity on all pulse sequences
◾
◾
⚬ No paramagnetic effect on gradient echo imaging (no blooming) MRI findings usually demonstrate periarticular tendon thickening with lowsignal intensity infiltration of the tendons, particularly at the shoulder and flexor tendons of the wrist ⚬ Infiltration of the carpal tunnel is commonly associated with carpal tunnel syndrome
Spondyloarthropathy: Amyloid deposits have been identified as soft-tissue masses within the intervertebral discs or within the facet joints, as well as the ligamentum flavum, atlanto-occipital, and atlantoaxial joints of the cervical spine [39]. Subchondral endplate erosions with intervertebral disc space narrowing and lack of prominent osteophytes can mimic discitisosteomyelitis; however, the process will usually be identified at multiple disc levels. Subchondral edema along the endplates with persistent intradiscal low signal suggest HD-related process, rather than infection. Biopsy may still be required in ambiguous clinical scenarios. Amyloid deposits and erosions can be identified in expected locations, usually demonstrating the amyloid tissue to be low signal on all sequences. Amyloid-induced atlantoaxial synovial hypertrophy can produce a soft tissue, partially calcified mass encasing and eroding the dens (Fig. 52.78), that may indistinguishable from rheumatoid arthritis pannus formation or crowned-dens findings in CPPD. However, calcifications in RA pannus formation are absent.
FIGURE 52.78 HD-related spondyloarthropathy. Amyloid and crystal deposition in patient with ESRD on long-term HD. Sagittal (A) and coronal (B) CT images demonstrate a partially calcified soft-tissue mass encasing the odontoid and displacing the spinal cord (white *), with well-defined punched out erosions involving the C1–C2 articulation, base of the odontoid, and facet joints (black arrows). Sagittal T1 (C) and T2 (D) MR images demonstrate the C1–C2 mass to be of low T1 and T2 signal (white arrows).
Differential Pearls 1. Differential considerations for this condition on an imaging basis should include multiple myeloma, metastatic disease, gouty erosions, brown tumors, hemophilic arthropathy, or pigmented villonodular synovitis (PVNS) Biopsy may be required for definitive diagnosis 2. Imaging finding in combination with clinical history can help rendering an accurate diagnosis of HD-related arthropathy Be aware of HD-related complications including pathological factures and compressive myelopathy 3. Tendon and joint capsule thickening in the setting of low-signal intensity erosions in a patient on long-term HD may also suggest amyloidosis
◾ ◾
Ochronosis (Alkaptonuria) Overview Alkaptonuria is a genetic autosomal recessive metabolic disorder that results in pathologic blue–black pigmentation of connective tissues in patients due to an underlying enzymatic deficiency of homogentisic acid oxidase [41]. Musculoskeletal manifestations of alkaptonuria may be referred to as ochronosis due the yellow (ocher) histological appearance of connective tissues. Pathology The absence of homogentisic acid oxidase enzyme leads excessive homogentisic acid, which binds to collagen in connective tissues, leading to inflammation, degeneration, and progressive arthropathy. Imaging Findings
Spine
◾discogenic The most common imaging manifestation is multilevel thoracic and lumbar calcification, disc space narrowing with endplate sclerosis, bridging osteophytes, and osteoporosis [40] (Fig. 52.79A) ◾ and pubic symphysis are also commonly affected ◾ SIThejoints differential diagnosis for discogenic calcifications included
⚬ OA, CPPD, AS, ochronosis, hemochromatosis, hyperparathyroidism, and amyloidosis
FIGURE 52.79 (A) Ochronosis. The intervertebral disc spaces are narrowed and calcified. (B) Multicentric reticulohistiocytosis. Erosive changes with radial subluxation of the 1st distal phalanges, erosive changes at the 2nd DIP joints bilaterally, and the right 5th DIP joint (arrows).
Peripheral Joints
◾narrowing, Large joints may also be involved with demonstration of cartilage space subchondral sclerosis, and possible intra-articular osteochondral fragments ◾shoulder Knee is the most commonly involved peripheral joint, followed by hip and
Differential Pearls Lack of osteophyte formation as well as advanced degenerative changes in a younger patient can help differentiate from OA; however, in some cases still may indistinguishable from OA.
Multicentric Reticulohistiocytosis (Also Known as Lipoid Dermatoarthritis) Overview This rare condition results from infiltration of lipid-laden histiocytes into various tissues including skin, bone, cartilage, and synovium. Pathology Abnormal accumulation results in soft-tissue nodules, acroosteolysis, and chronic destructive polyarthritis. Imaging Findings
◾hand Symmetric well-defined marginal erosions involving the DIP joints of the are typically seen (Fig. 52.79B) [42] ◾affected, MCP joints and carpal bones, as well as larger peripheral joints are also but less frequent than the DIP joints ◾ Noncalcified soft-tissue nodules
Differential Pearls
◾ DIP distribution less likely to be seen with RA ◾ Erosions encountered in gout and PsA are usually asymmetric ◾seen Erosions with overhanging edges and calcified soft-tissue nodules (tophi) are with gout
Hemophilic Arthropathy Overview Hemophilic arthropathy is a destructive arthropathy triggered by acute on chronic hemarthrosis and chronic synovitis that can lead to chronic pain, limited range of motion, and decreased quality of life. Approximately 50–80% of patients the hemophilia will develop a severe arthropathy. Pathology
Hemophilia A (the absence of clotting factor VIII) and hemophilia B (the absence of clotting factor IX) are both X-linked recessive bleeding disorders with intra-articular spontaneous bleeding and recurrent hemarthroses contributing to synovitis, chronic inflammation, and fibrosis, leading to chondral degeneration and subchondral bone destruction. Abnormal bleeding and clotting within joint spaces preferentially affects large joints including the knee, elbow, ankle, and hip. Imaging Findings
Radiographic Appearance
◾predominantly Large effusions are often noted, typically with increased density due to a hemorrhagic component and/or hemosiderin deposits within the in the case of chronic bleeding ◾synovium Knee ⚬ Epiphyseal overgrowth (ballooning) due to hyperemia, flat condylar ◾ Elbow surfaces, and widening of the intercondylar notch (Fig. 52.80) [43] ⚬ Enlarged radial head and widening of the trochlea notch ◾loss, Secondary osteoarthritic changes as evidenced by symmetrical joint space erosions, subchondral sclerosis, cysts, and osteophytes ◾ Typical gracile appearance of long bone diaphyses
FIGURE 52.80 Hemophilia arthropathy. A 20-year-old male patient with AP radiographs of the knees demonstrate epiphyseal overgrowth, squaring/flattening of the condyles (arrows), widening of the intercondylar notch, and advanced secondary osteoarthritic changes.
MRI
◾and/or Shown to demonstrate heterogeneous signal intensity within joint effusions fluid–fluid levels due to blood products, as well low-signal intensity and susceptibility artifact lining the synovium due to hemosiderin deposition
Differential Pearls
◾arthritis; Radiographic features may be indistinguishable from juvenile idiopathic however, hemosiderin deposits can be demonstrated MR imaging
◾hypointense Pigmented villonodular synovitis and hemophilia will both exhibit persistently signal of the synovium on all sequences and blooming on gradient echo images; however, PVNS tends to manifest as a more focal nodular pattern, rather than a diffuse intra-articular process, and the radiographic findings encountered with hemophilia will be absent in a patient with PVNS
Sarcoidosis Overview Sarcoidosis is a systemic chronic granulomatous disease characterized by noncaseating granulomas in multiple organs, including the heart and lungs, abdominal organs, central nervous system, and the musculoskeletal system including bone, joints, and soft tissues. Joint involvement is a commonly encountered clinical presentation, classified as either acute arthritis or chronic/recurrent arthritis. Acute sarcoidosis, known as Lofgren syndrome, is a syndrome characterized by erythema nodosum, hilar adenopathy, constitutional symptoms, and polyarthritis involving the ankles, wrist, PIP and MCP joint, and the elbows. Pathology Sarcoidosis is an immune-mediated disease resulting from an antigenic stimulation that triggers inflammatory response. An inflammatory response is caused by CD4(+) T cells that interact with antigen-presenting cells to initiate formation and maintenance of granulomas. The synovial granuloma formation incites an intra-articular inflammatory response, synovitis, and osseous erosions. Distribution Musculoskeletal sarcoidosis with osseous involvement is found in approximately 5% of patients with sarcoid. Although sarcoid can involve any site of the axial or appendicular skeleton, the most commonly encountered sites are the distal and middle phalanges of the second and third digits. Long bone and vertebral body involvement are less common, but must be differentiated from a metastatic or bone marrow hematological process.
Imaging Findings
Radiographic Findings
◾ Lacy trabecular configuration considered pathognomonic (Fig. 52.81) [44] ◾ Characteristically no periosteal reaction ◾dactylitis) Granulomas extend into the soft tissues, causing diffuse swelling (sausage
FIGURE 52.81 Musculoskeletal sarcoidosis. Radiographs demonstrate phalangeal expansion, trabecular thickening, and lucencies resulting in a lace-like pattern of osseous destruction (arrows).
Differential Pearls The abnormal lace-like trabecular pattern of phalangeal osteolysis and destruction is considered pathognomonic. If acro-osteolysis is observed, scleroderma may be considered in the differential, but patients with scleroderma will exhibit soft-tissue calcifications.
Pigmented Villonodular Synovitis Overview PVNS is considered a benign neoplastic process of synovial hyperplasia, which can be villous, nodular, or villonodular demonstrating synovial hemosiderin deposition [45]. Given the synovial etiology, not only can PVNS involve intra-articular synovial lining, but can also be extra-articular, seen along tendon sheaths and bursae. Pathology The etiology of PVNS is of neoplastic synovial proliferation. Repeated hemorrhagic effusions and intra-articular inflammation result in synovial iron deposition in synovium and nodules. With continued proliferation of abnormal synovium, focal erosions and subchondral cysts develop. Distribution PVNS presents as a monoarticular arthropathy, most commonly involves the knee joint (80% of cases), either the localized intraarticular nodular variant or the diffuse intra-articular form, followed by the hip joint. Ankle, shoulder, and elbow are also sites of potential PVNS, as is virtually any synovial joint. When encountered along a tendon sheath, the lesion is referred to as tenosynovial giant cell tumor and pigmented villonodular bursitis when identified within a bursa. Imaging Findings
Radiographic Appearance
◾preserved Joint effusion, soft-tissue swelling, extrinsic erosions, subchondral cysts, and joint space ◾ The absence of calcification [45]
MRI Appearance
◾ Focal nodular mass or diffuse villonodular proliferation (Fig. 52.82) ◾weighted Lesion predominantly demonstrates low-to-intermediate signal on T1- and T2images (Fig. 52.82). Increased signal on T2-weighted images is likely due to intralesional joint fluid or regional synovitis (Fig. 52.82) ◾artifact The associated hemosiderin-laden nodules produce characteristic blooming on gradient MRI sequences ◾based The typical MRI appearance consists of a large joint effusion with synovialmasses exhibiting blooming effect on gradient echo sequences ◾ Postcontrast images demonstrate, variable inhomogeneous enhancement
FIGURE 52.82 Localized intra-articular PVNS of the knee. Lateral radiograph (A) shows a noncalcified soft-tissue density within Hoffa fat pad (white arrow). Sagittal PD (B) and T2weighted fat-suppressed sequences (C) reveal a focal nodular soft-tissue mass within Hoffa’s fat pad (yellow arrows) demonstrating hypointense-to-intermediate signal on the PD image and heterogeneous increased signal and perilesional synovitis on the T2-weighted image, while the sagittal gradient echo image (D) clearly exhibits hypointense signal compatible with blooming artifact of hemosiderin.
Differential Pearls Differential consideration of intra-articular soft-tissue masses: 1. Intra-articular nodular synovitis a. Similar MR appearance to PVNS, but generally less hemosiderin deposition and smaller joint effusions 2. Gout a. Can appear similar to PVNS with extrinsic erosions; however, calcified gouty tophus on radiographs should exclude PVNS
3. Amyloid a. Can appear similar to PVNS, but blooming artifact not identified 4. Hemophilic arthropathy a. Diffuse hypointense synovial proliferation on T1- and T2-weighted sequences, as well as blooming artifact can be indistinguishable from diffuse intra-articular PVNS; however radiographic appearance and clinical history help to decipher the two conditions 5. Synovial chondromatosis a. Low-signal masses can be confused with PVNS, but if calcified on radiographic evaluation, excludes PVNS b. Chondral bodies will not exhibit blooming on gradient echo images
Synovial Chondromatosis Overview Synovial chondromatosis is a benign neoplasm that causes synovial membrane proliferation and the formation of cartilaginous or osseous bodies within a joint, bursa, or tenosynovial structure. It is classified into two subtypes: primary is usually monoarticular and is of unknown etiology, whereas secondary is usually a result of degeneration, trauma, or neuropathic arthropathy. Pathology Genetic features suggest synovial chondromatosis is of benign neoplastic etiology. Synovial membranes over proliferate creating nodular densities (which range from millimeters to greater than 2 cm) which may remain attached to synovium and develop blood supply and may become osseous, or become loose within a joint and become cartilaginous. In the ladder, the cartilage is provided nutrients through the synovial fluid. The underlying articular cartilage destruction is most likely mechanical in origin; not inflammatory. Distribution The distribution is commonly monoarticular and predominantly intra-articular, particularly in large joints. From most to least commonly involved joints: knee (50–65%) > hip > shoulder > elbow. The most common bursal locations are subdeltoid and
popliteal. Tenosynovial chondromatosis most commonly involves the hands and feet. Extracapsular spread is a potential risk through the usual sites of joint decompression; across rotator cuff tear into subacromial/subdeltoid bursa, from hip into iliopsoas bursa, and rare extension into adjacent muscle and fascial tissue. The round bodies of synovial chondromatosis are generally similar in size and may appear lamellated, with concentric rings of calcification. Occasionally will form conglomerate mass within joint or extend into extracapsular tissue. Imaging Findings
Radiographic Findings
◾fociMultiple round bodies (Fig. 52.83) of similar size which may range from small of speckled calcifications to large round, lamellated cartilage or ossified bodies ◾ These may conglomerate or be free floating [46] ◾mechanical/degenerative May or may not have associated osseous erosions, which are likely in etiology ◾ May be difficult to visualize on radiograph (20–50%)
FIGURE 52.83 Synovial chondromatosis. Lateral radiograph of knee (A) shows multiple round bodies in anterior and posterior joint space. Coronal CT image (B) of a different patient shows an enlarged obturator bursa with multiple calcified intrabursal bodies. Corresponding coronal T2 (C) demonstrates high-signal fluid distending the bursa, outlining innumerable foci of uniform shape and size low signal within the bursa corresponding to the areas of mineralization. The coronal T1 postcontrast image (D) demonstrates peripheral enhancement of the bursa without any internal enhancement.
MRI Findings
◾ Eighty percent of patients have degenerative erosions detectable by MR ◾ Large effusion (hyperintense on fluid-sensitive sequences, low signal on T1)
◾chondroid, Bodies are of variable MR signal, depending on proportion of calcium, and mature ossific tissue ⚬ The majority (77%) have low-to-intermediate T1 signal, with hyperintense T2 signal intensity (Fig. 52.83) T1WI FS with contrast shows enhancing hyperplastic synovium, surrounding low-signal effusion and bodies Malignant transformation to chondrosarcoma is unusual (5% of cases) and, although difficult to distinguish from benign disease, is suggested by multiple recurrences and marrow invasion [47]
◾ ◾
Lipoma Arborescens Overview Lipoma arborescens involves infiltration of fat tissue in synovium forming frond-like masses. Pathology Chronic synovial irritation leads to inappropriate proliferation of fat. Can be seen from both degenerative and inflammatory arthropathies, as well as with previous trauma. Mature adipocytes proliferate within subsynovium generating enlarged synovial fronds [47, 48]. Additionally, may see osseous or chondroid metaplasia in some cases. Imaging
Radiographic Findings
◾ ◾ Limited Joint distension ± visible fat density
CT Findings
◾ Fat density synovial masses
MR Findings
◾subcutaneous High-signal intensity synovial masses on T1 that match intensity of fat. These enhance on T1 contrast-enhanced images (Fig. 52.84) ◾ Low-signal intensity on STIR/any fat-suppressed sequence
FIGURE 52.84 Lipoma arborescens. Axial T2FS (A) shows a low intensity frond-like structures (yellow arrow) in the suprapatellar recess outlined by joint fluid. Sagittal T1 (B) and T2FS (C) confirm the signal to be equivalent to adipose fat.
Hypertrophic Osteoarthropathy Overview/Pathology Syndrome characterized by proliferation of skin (1°) and bone (1° and 2°) in distal extremities of an indeterminate cause. Genetic inheritance is classified as primary HOA. Pachydermoperiostosis is a rare disorder with autosomal recessive inheritance, which involves primary HOA, thickening of the skin of the face (pachyderma), excessive sweating (hyperhidrosis), and rheumatological symptoms (joint effusion, arthritis, acro-
osteolysis, periosteal ossification). The secondary HOA has multiple mechanisms that can be broken down by organ system as follows:
◾ Periosteal reaction without underlying osseous lesion or injury
⚬ Commonly symmetric [49] (Fig. 52.85) ⚬ Thickness/extent dependent on disease duration Shorter duration of disease → diaphyseal; later extends to metaphyses and epiphyses [50] Acro-osteolysis more commonly seen in patients with primary HOA and cyanotic heart disease Joints ⚬ Findings limited to soft-tissue swelling → clubbing of digits ⚬ No joint space narrowing or osseous erosions
◾ ◾
⚫
FIGURE 52.85 Hypertrophic osteoarthropathy. AP radiographs of the bilateral hips (A and B) and bilateral femurs (C and D) demonstrate smooth, benign-appearing thick periosteal reaction along both femoral diaphyses, which is bilaterally symmetric and consistent with hypertrophic pulmonary osteoarthropathy (HPOA). Specifically, this reflects HPOA in this patient with reported history of chronic pulmonary hypertension/interstitial lung disease.
MR Findings
◾ Normal marrow signal ◾ T1 hypointense periosteal reaction ◾sideFluid-sensitive sequences show linear high signal that may be seen on either of low-signal periosteal reaction
Diffuse Idiopathic Skeletal Hyperostosis Overview/Pathology Disease entity defines by flowing/uninterrupted coarse osteophytes bridging four adjacent vertebral bodies without severe loss of intervertebral disc height and without degeneration of apophyseal and sacroiliac (SI) joints. The cause for this exaggerated response is unknown, although has possible
associations with diabetes mellitus, dyslipidemia, hyperuricemia, alcohol intake, and poor dietary habits. This is a disease of middle-aged to older adults and is very uncommon before age 50. Imaging
Radiography
◾ Uninterrupted anterior vertebral ossification (Fig. 52.86) ⚬ New bone formation begins adjacent to midvertebral body [51] ◾ Preservation of disc spaces and facets (relative) [52]
FIGURE 52.86 Diffuse idiopathic skeletal hyperostosis. Lateral radiographs of cervical (A) and dorsal (B) spine of two different patients show diffuse, flowing ossification of the anterior longitudinal ligaments compatible with diffuse idiopathic skeletal hyperostosis.
MR Findings
◾may T1WI will show flowing ossification of the anterior longitudinal ligament that be difficult to distinguish from the anterior vertebral body ⚬ Hypointense if predominantly calcified
◾
⚬ Isointense or hyperintense if marrow fat present ⚬ May show minimal enhancement (similar to vertebral marrow) on contrast-enhanced images T2WI ⚬ Anterior longitudinal ligament ossification may be hypointense unless substantial fatty marrow content
Summary Differentiating inflammatory from degenerative causes of joint disease significantly impacts patient management (Fig. 52.87). Assessing for symmetric (inflammatory vs infectious) versus asymmetric (degenerative) joint space narrowing and identifying the distribution of joints involved are the first steps in leading a radiologist down the correct diagnostic pathway. Additionally, examining for periarticular or marginal erosions is essential to correctly distinguishing an inflammatory arthropathy from OA. Successfully implementing the systematic approach that has been outlined to recognize the radiographic hallmarks allows a prompt and confident diagnosis by the interpreter and subsequently appropriate management for the patient.
FIGURE 52.87 Summary of systematic approach to arthritis.
Suggested Readings • Eric Y. Chang, Karen C. Chen, Brady K. Huang, and Arthur Kavanaugh. Adult Inflammatory Arthritides: What the Radiologist Should Know. RadioGraphics 2016 36:6, 1849-1870 • Bijlsma JW, Berenbaum F, Lafeber FP. Osteoarthritis: an update with relevance for clinical practice. Lancet. 2011 Jun 18;377(9783):2115-26. doi: 10.1016/S0140-6736(11)60243-2. PMID: 21684382. • Taljanovic MS, Melville DM, Gimber LH, Scalcione LR, Miller MD, Kwoh CK, Klauser AS. High-Resolution US of Rheumatologic Diseases. Radiographics. 2015 Nov-Dec;35(7):2026-48. doi: 10.1148/rg.2015140250. PMID: 26562235. • Moll JM, Haslock I, Macrae IF, Wright V. Associations between ankylosing spondylitis, psoriatic arthritis, Reiter's disease, the intestinal arthropathies, and Behcet's syndrome. Medicine (Baltimore). 1974 Sep;53(5):343-64. doi: 10.1097/00005792-197409000-00002. PMID: 4604133. • Girish G, Glazebrook KN, Jacobson JA. Advanced imaging in gout. AJR Am J Roentgenol. 2013 Sep;201(3):515-25. doi: 10.2214/AJR.13.10776. PMID: 23971443.
References [1] EY Chang, KC Chen, BK Huang, A Kavanaugh, Adult inflammatory arthritides: what the radiologist should know, Radiographics 36 (6) (2016) 1849–1870.
[2] JW Bijlsma, F Berenbaum, FP Lafeber, Osteoarthritis: an update with relevance for clinical practice, Lancet 377 (9783) (2011) 2115–2126. 10.1016/S0140-6736(11)602432. [3] B Xia, D Chen, J Zhang, S Hu, H Jin, P Tong, Osteoarthritis pathogenesis: a review of molecular mechanisms, Calcif Tissue Int 95 (6) (2014) 495–505. 10.1007/s00223-014-9917-9. Epub 2014 Oct 14. [4] R Altman, G Alarcon, D Appelrouth, D Bloch, D Borenstein, K Brandt, et al., The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hand, Arthritis Rheum 33 (1990) 1601–1610. [5] A Anandarajah, Erosive osteoarthritis, Discov Med 9 (48) (2010) 468–477. [6] NJ Murphy, JP Eyles, DJ Hunter, Hip osteoarthritis: etiopathogenesis and implications for management, Adv Ther 33 (11) (2016) 1921–1946. 10.1007/s12325-0160409-3. Epub 2016 Sep 26. [7] MD Crema, GJ Watts, A Guermazi, YJ Kim, R Kijowski, FW., Roemer, A narrative overview of the current status of MRI of the hip and its relevance for osteoarthritis research – what we know, what has changed and where are we going?, Osteoarthri Cartil 25 (1) (2017) 1–13. 10.1016/j.joca.2016.08.015. Epub 2016 Sep 13. [8] S Farrokhi, CA Voycheck, JA Gustafson, GK Fitzgerald, S Tashman, Knee joint contact mechanics during downhill gait and its relationship with varus/valgus motion and muscle strength in patients with knee osteoarthritis, Knee 23 (1) (2016) 49–56. 10.1016/j.knee.2015.07.011. [9] BM Clark, TJ Lamer, Successful relief of back pain From Baastrup disease (Kissing Spines) by interspinous radiofrequency lesioning: a case report, A A Pract 11 (3) (2018) 79–81. 10.1213/XAA.0000000000000745. [10] DL Scott, F Wolfe, TW Huizinga, Rheumatoid arthritis, Lancet. 376 (9746) (2010) 1094–1108. 10.1016/S01406736(10)60826-4.
[11] JA Narvaez, J Narváez, E De Lama, M De Albert, MR imaging of early rheumatoid arthritis, Radiographics 30 (1) (2010) 143–163. [12] IB McInnes, G Schett, The pathogenesis of rheumatoid arthritis, N Engl J Med 365 (23) (2011) 2205–2219. 10.1056/NEJMra1004965. [13] MS Taljanovic, DM Melville, LH Gimber, LR Scalcione, MD Miller, CK Kwoh, et al., High-resolution US of rheumatologic diseases, Radiographics 35 (7) (2015) 2026–2048. 10.1148/rg.2015140250. [14] RJ Wakefield, PV Balint, M Szkudlarek, E Filippucci, M Backhaus, MA D’Agostino, et al., Musculoskeletal ultrasound including definitions for ultrasonographic pathology, J Rheumatol 32 (12) (2005) 2485–2487. Erratum. In: J Rheumatol 2006 Feb;33(2):440. Bruyn, George [corrected to Bruyn, George AW]. [15] M Backhaus, T Kamradt, D Sandrock, D Loreck, J Fritz, KJ Wolf, et al., Arthritis of the finger joints: a comprehensive approach comparing conventional radiography, scintigraphy, ultrasound, and contrastenhanced magnetic resonance imaging, Arthritis Rheum 42 (6) (1999) 1232–1245. 10.1002/15290131(199906)42:63.0.CO;2-3. [16] JM Moll, I Haslock, IF Macrae, V Wright, Associations between ankylosing spondylitis, psoriatic arthritis, Reiter’s disease, the intestinal arthropathies, and Behcet’s syndrome, Medicine (Baltimore) 53 (5) (1974) 343–364. 10.1097/00005792-197409000-00002. [17] L Hamilton, A Macgregor, A Toms, V Warmington, E Pinch, K Gaffney, The prevalence of axial spondyloarthritis in the UK: a cross-sectional cohort study, BMC Musculoskelet Disord 16 (2015) 392. 10.1186/s12891-015-0853-2. [18] R Campagna, E Pessis, A Feydy, H Guerini, F Thévenin, A Chevrot, et al., Fractures of the ankylosed spine: MDCT and MRI with emphasis on individual
anatomic spinal structures, Am J Roentgenol 192 (4) (2009) 987–995. 10.2214/AJR.08.1616. [19] JS Levine, R Burakoff, Extraintestinal manifestations of inflammatory bowel disease, Gastroenterol Hepatol (NY) 7 (4) (2011) 235–241. [20] SL Arvikar, MC Fisher, Inflammatory bowel disease associated arthropathy, Curr Rev Musculoskelet Med 4 (3) (2011) 123–131. 10.1007/s12178-011-9085-8. [21] JD Olpin, BP Sjoberg, SE Stilwill, LE Jensen, M Rezvani, AM Shaaban, Beyond the bowel: extraintestinal manifestations of inflammatory bowel disease, Radiographics 37 (4) (2017) 1135–1160. 10.1148/rg.2017160121. Epub 2017 May 26. [22] I Sudoł-Szopińska, G Matuszewska, B Kwiatkowska, G Pracoń, Diagnostic imaging of psoriatic arthritis. Part I: etiopathogenesis, classifications and radiographic features, J Ultrason 16 (64) (2016) 65–77. 10.15557/JoU.2016.0007. Epub 2016 Mar 29. [23] PP Lew, SS Ngai, R Hamidi, JK Cho, RA Birnbaum, DH Peng, et al., Imaging of disorders affecting the bone and skin, Radiographics 34 (1) (2014) 197–216. [24] CC Mok, CS Lau, Pathogenesis of systemic lupus erythematosus, J Clin Pathol 56 (7) (2003) 481–490. 10.1136/jcp.56.7.481. [25] MR Arbuckle, MT McClain, MV Rubertone, RH Scofield, GJ Dennis, JA James, et al., Development of autoantibodies before the clinical onset of systemic lupus erythematosus, N Engl J Med 349 (16) (2003) 1526–1533. 10.1056/NEJMoa021933. [26] TA Lalani, JP Kanne, GA Hatfield, P Chen, Imaging findings in systemic lupus erythematosus, Radiographics 24 (4) (2004) 1069–1086. 10.1148/rg.244985082. [27] J Cruz Whitley, P Aronowitz, Jaccoud’s arthropathy, J Gen Intern Med 33 (9) (2018) 1583. 10.1007/s11606-0184559-7.
[28] YE Izquierdo, E Calvo Páramo, LM Castañeda, SV Gómez, FS Zambrano, Radiographic changes of the distal phalangeal tuft of the hands in subjects with systemic sclerosis. Systematic review, Reumatol Clin 14 (1) (2018) 20–26. 10.1016/j.reuma.2016.08.009. English, Spanish Epub 2016 Oct 13. [29] G Girish, KN Glazebrook, JA Jacobson, Advanced imaging in gout, Am J Roentgenol 201 (3) (2013) 515– 525. 10.2214/AJR.13.10776. [30] HJ Rech, A Cavallaro, Dual-energycomputertomographie-Diagnostikbeigicht [Dual-energy computed tomography diagnostics for gout], Z Rheumatol 76 (7) (2017) 580–588. 10.1007/s00393-017-0341-1. German. [31] AK Tausche, M Aringer, Chondrokalzinosedurch Kalziumpyrophosphat-Dihydrat-Ablagerung (CPPD): VomradiologischenZufallsbefundzur CPPDKristallarthritis [Chondrocalcinosis due to calcium pyrophosphate deposition (CPPD). From incidental radiographic findings to CPPD crystal arthritis], Z Rheumatol (4) (2014) 349–357. 10.1007/s00393-0141364-5. [32] P Vele, SP Simon, L Damian, I Felea, L Muntean, I Filipescu, et al., Clinical and ultrasound findings in patients with calcium pyrophosphate dihydrate deposition disease, Med Ultrason 20 (2) (2018) 159–163. 10.11152/mu-1193. [33] GM Garcia, GC McCord, R Kumar, Hydroxyapatite crystal deposition disease, Semin Musculoskelet Radiol 7 (3) (2003) 187–193. 10.1055/s-2003-43229. [34] F Del Castillo-González, JJ Ramos-Álvarez, G Rodríguez-Fabián, J González-Pérez, J Calderón-Montero, Treatment of the calcific tendinopathy of the rotator cuff by ultrasound-guided percutaneous needle lavage. Two years prospective study, Muscles Ligaments Tendons J 4 (4) (2015) 407–412.
[35] N Gabra, M Belair, T Ayad, Retropharyngeal calcific tendinitis mimicking a retropharyngeal phlegmon, Case Rep Otolaryngol 2013 (2013) 912628. 10.1155/2013/912628. Epub 2013 Jun 3. [36] O Epis, E Viola, E Bruschi, F Benazzo, C Montecucco, Milwaukee shoulder syndrome (artropatiadestruente apatite-associata): aspettiterapeutici [Milwaukee shoulder syndrome (apatite associated destructive arthritis): therapeutic aspects], Reumatismo 57 (2) (2005) 69–77. doi:10.4081/reumatismo.2005.69. Italian. [37] LT Bui-Mansfield, M Moak, Magnetic resonance appearance of bone marrow edema associated with hydroxyapatite deposition disease without cortical erosion, J Comput Assist Tomogr 29 (1) (2005) 103–107. 10.1097/01.0000145861.13963.66. [38] T Dallos, E Sahinbegovic, T Stamm, E Aigner, R Axmann, A Stadlmayr, et al., Idiopathic hand osteoarthritis vs haemochromatosis arthropathy–-a clinical, functional and radiographic study, Rheumatology (Oxford) 52 (5) (2013) 910–915. 10.1093/rheumatology/kes392. Epub 2013 Jan 12. [39] E Kiss, G Keusch, M Zanetti, T Jung, A Schwarz, M Schocke, et al., Dialysis-related amyloidosis revisited, Am J Roentgenol 185 (6) (2005) 1460–1467. 10.2214/AJR.04.1309. [40] JA Gil, J Wawrzynski, GR Waryasz, Orthopedic manifestations of ochronosis: pathophysiology, presentation, diagnosis, and management, Am J Med 129 (5) (2016) 536.e1-6. 10.1016/j.amjmed.2016.01.010. Epub 2016 Feb 1. [41] A Zatkova, L Ranganath, L Kadasi, Alkaptonuria: current perspectives, Appl Clin Genet 13 (2020) 37–47. 10.2147/TACG.S186773. [42] D Santilli, A Lo Monaco, PL Cavazzini, F Trotta, Multicentric reticulohistiocytosis: a rare cause of erosive arthropathy of the distal interphalangeal finger joints, Ann Rheum Dis 61 (6) (2002) 485–487. 10.1136/ard.61.6.485.
[43] R Kerr, Imaging of musculoskeletal complications of hemophilia, Semin Musculoskelet Radiol 7 (2) (2003) 127–136. 10.1055/s-2003-41346. [44] D Ganeshan, CO Menias, MG Lubner, PJ Pickhardt, K Sandrasegaran, S Bhalla, Sarcoidosis from head to toe: what the radiologist needs to know, Radiographics 38 (4) (2018) 1180–1200. [45] HW Garner, CJ Ortiguera, RE Nakhleh, Pigmented villonodular synovitis, Radiographics 28 (5) (2008) 1519– 1523. [46] MD Murphey, JA Vidal, JC Fanburg-Smith, DA Gajewski, Imaging of synovial chondromatosis with radiologic-pathologic correlation, Radiographics 27 (5) (2007) 1465–1488. 10.1148/rg.275075116. [47] RS Ryan, AC Harris, JX O’Connell, PL Munk, Synovial osteochondromatosis: the spectrum of imaging findings, Australas Radiol 49 (2) (2005) 95–100. 10.1111/j.1440-1673.2005.01416.x. [48] EA White, R Omid, GR Matcuk, et al., Lipoma arborescens of the biceps tendon sheath, Skeletal Radiol 42 (10) (2013) 1461–1464. 10.1007/s00256-013-1638-z. [49] D Resnick, RE: radiographic features of osteoarthropathy, Radiology 157 (2) (1985) 553–554. 10.1148/radiology.157.2.4048472. [50] CJ Pineda, M Martinez-Lavin, JE Goobar, DJ Sartoris, P Clopton, D Resnick, Periostitis in hypertrophic osteoarthropathy: relationship to disease duration, Am J Roentgenol 148 (4) (1987) 773–778. 10.2214/ajr.148.4.773. [51] JS Kuperus, SF Oudkerk, W Foppen, et al., Criteria for early-phase diffuse idiopathic skeletal hyperostosis: development and validation, Radiology 291 (2) (2019) 420–426. 10.1148/radiol.2019181695. [52] R Mader, Diffuse idiopathic skeletal hyperostosis: a distinct clinical entity, Isr Med Assoc J 5 (7) (2003) 506– 508.
Chapter 53
Endocrine and Metabolic Bone Diseases Scott D. Wuertzer, Leon Lenchik
Homeostasis of Bone In general, metabolic bone diseases affect the skeleton in one of two ways: there is either too much or too little bone (Fig. 53.1). The latter, which comprises most of the metabolic bone diseases, is due to some combination of a decrease in the amount of bone formed and an increase in the amount of bone resorbed. This shift typically occurs from abnormal vitamin D and calcium metabolism, resulting from abnormal diet, renal or endocrine dysfunction, or drug therapy.
Figure 53.1 Homeostasis of bone. Metabolic and endocrine disorders of the skeleton are the result of too much or too little calcium. There is a critical balance between formation of bone and the resorption of bone. Most disease involves resorption of bone from abnormalities of vitamin D and calcium metabolism.
Role of Imaging Conventional radiographs are used to evaluate metabolic bone disorders due to their wide availability and low cost (Fig. 53.2). Depending on the ratio of bone formation to resorption, the bone may appear normal, radiodense (osteosclerosis), or
radiolucent (osteopenia). Because metabolic processes usually involve the entire skeleton, the radiographic findings are usually diffuse or multifocal. On occasion, focal lesions may be found, such as brown tumors in hyperparathyroidism (Fig. 53.3). In osteopenic patients, radiographs help establish a differential diagnosis and serve an important role in the diagnosis and management of fractures [1].
Figure 53.2 Role of imaging. The imaging of patients with metabolic and endocrine disorders should begin with radiographs, which provide a qualitative assessment, and progress to more advanced imaging (CT, MRI, or scintigraphy). In osteoporotic patients, clinical management
Figure 53.3 Brown tumors. Patient with a parathyroid adenoma. A lateral radiograph of the tibia and fibula shows a well-defined, mildly expansile lesion in the mid tibia consistent with a brown tumor. Smaller brown tumors are noted in the proximal and distal tibia.
More advanced imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy, are often used for the early diagnosis of specific disorders [2]. In particular, CT is more sensitive than radiographs for the diagnosis of nondisplaced fractures, bony erosions, and soft-tissue findings. MRI is more sensitive than radiographs for the diagnosis of occult fractures, bone and soft-tissue neoplasms, infection, and osteonecrosis. MRI is also more sensitive and specific for the evaluation of ligament, tendon, and muscle injuries. Bone scintigraphy, which uses a physiologic marker (methylene diphosphonate), is more sensitive to bone turnover than radiographs or CT. Because it can screen the entire body, bone scintigraphy is often used for determining the location and distribution of disease. For the evaluation of osteoporosis, clinical management often necessitates quantitative imaging. Conventional radiographs can be subject to technical errors and interpreter subjectivity. For example, an osteoporotic patient may appear normal if an improper technique has been used during image acquisition. Likewise, the same radiographs on a
patient may be interpreted as normal by one radiologist and osteopenic by another. For this reason, various quantitative methods for measuring bone mass have been developed, with dual x-ray absorptiometry (DXA) and quantitative CT (QCT) being the most widely used. QCT is a volumetric technique that expresses bone mineral density (BMD) in mg/cm3. In contrast, DXA is an area-based twodimensional technique that expresses BMD in g/cm2. Over the last decade, DXA has gained a higher acceptance rate over QCT, due to lower radiation dose, higher precision, and ease of use [3].
Dual X-ray Absorptiometry DXA is routinely used for the diagnosis of osteoporosis, assessment of fracture risk, and monitoring of drug therapy [4]. A DXA scanner produces x-rays with two energy peaks, allowing a differential absorption of radiation by bone and soft tissue, from which the BMD is calculated. A typical DXA scan consists of a BMD measurement in the lumbar spine and the proximal femur, which are the most common sites of osteoporotic fractures. When
the patient exceeds the weight limit of the table, or the hip and spine measurements are invalid, BMD can be measured in the nondominant forearm (Table 53.1). Table 53.1 When to Add the Forearm to Dual X-ray Absorptiometry Spine Hardware artifacts Multilevel vertebroplasty
◾ ◾ ◾ Severe scoliosis ◾ Severe degenerative changes
Vertebral fracture(s) Hip artifacts
◾ Congenital or post-traumatic deformity ◾ Hardware
Patient exceeds weight limit of scanner
In pediatric patients, a hip scan is usually not appropriate, and instead, a whole-body scan is obtained. Because the skull contains mostly cortical bone, the head is typically excluded from the final analysis, when whole-body scans are reported. For point-of-care diagnosis of vertebral fractures, lateral evaluation of the thoracic and lumbar spine can be obtained, known as vertebral fracture assessment (VFA). VFA should be performed in patients with height loss, history of vertebral fracture, or chronic steroid therapy (>5 mg, >3 months). BMD measurements are expressed as the number of standard deviations from the young-adult mean (Tscore) or the age-matched mean (Z-score). The World Health Organization (WHO) defines osteoporosis as a T-score, which is 2.5 standard deviations or more below the young–adult mean (Table 53.2). Table 53.2 WHO Criteria for Osteoporosis Diagnosis T-Score Normal
≥−1
Diagnosis
T-Score
Osteopenia
Between −1 and −2.5
Osteoporosis
≤−2.5, without fractures
Severe (established) osteoporosis
≤−2.5, with fractures
The printout from a DXA scan includes images of the spine, hip, or forearm, which should be inspected for proper patient positioning, proper scan analysis, and artifacts. Artifacts may falsely increase or decrease BMD. When possible, the spine, hip, or forearm artifacts should be removed from the region of interest. Other artifacts may be external to the patient, which should be removed before scanning (Table 53.3). Table 53.3
◾
Potential Artifacts on Dual X-ray Absorptiometry Increase bone mineral Degenerative density disease
◾
Decrease bone mineral density
◾ Fracture ◾ Vertebroplasty ◾ Sclerotic metastases ◾ Paget disease of bone ◾ Vascular calcifications ◾ Overlying objects ◾ Contrast in bowel ◾ Patient motion ◾ Laminectomy defects ◾ Lytic metastases ◾ Contrast in bowel ◾
◾ Patient motion Although low BMD is the single best predictor for future fracture in postmenopausal women and older men, fractures are multifactorial in origin. In fact, in the study of osteoporotic fractures, 54% of the patients were not osteoporotic by BMD. These patients, however, could benefit from treatment, and the WHO introduced the Fracture Risk Assessment Tool (FRAX) in 2008 [5]. FRAX is a tool that calculates the 10-year probability of osteoporotic fractures based on widely validated clinical risk factors, including BMD as an input. FRAX has models for more than 50 countries and is considered the gold standard for fracture risk assessment. In the United States, the National Osteoporosis Foundation and the International Society for Clinical Densitometry provide guidance on how FRAX should be used (Table 53.4). Table 53.4 National Osteoporosis Foundation and International Society for Clinical Densitometry Guidelines for
FRAX
◾ Should only be used in patients with osteopenia by dual x-ray absorptiometry ◾ Should NOT be used in patients on therapy ◾ Should NOT be used in patients osteomalacia, Children: Effects of rickets >2° HPT
Rugger-jersey spine, periostitis, soft tissue and vascular calcification, osteopenia
Metal and drug toxicity
Fluorosis, hypervitaminosi s A and D toxicity, heavy metal toxicity
Approach to Quantitative Imaging The evaluation of patients with metabolic and endocrine disorders often requires an assessment with both qualitative and quantitative imaging. Quantitative imaging, which is an invaluable tool for clinical management, can help diagnose osteoporosis, assess the risk of fracture, identify patients for drug therapy, and monitor therapy. To produce an accurate report with clinically relevant information, a checklist approach can be applied to DXA interpretation (Fig. 53.53). The results should then be reported with a structured template (Fig. 53.54).
Suggested Readings • Fan Y, Peh W. Radiology of Osteoporosis: Old and New Findings. Semin Musculoskelet Radiol. 2016 Oct 14;20(03):235–45. • Chang CY, Rosenthal DI, Mitchell DM, Handa A, Kattapuram SV, Huang AJ. Imaging Findings of Metabolic Bone Disease. RadioGraphics. 2016 Oct;36(6):1871–87. • Proisy M, Rouil A, Raoult H, Rozel C, Guggenbuhl P, Jacob D, et al. Imaging of Musculoskeletal Disorders Related to Pregnancy. American Journal of Roentgenology. 2014 Apr;202(4):828–38. • Chanchlani R, Nemer P, Sinha R, Nemer L, Krishnappa V, Sochett E, et al. An Overview of Rickets in Children. Kidney International Reports. 2020 Jul;5(7):980–90. • Sellami M, Riahi H, Maatallah K, Ferjani H, Bouaziz MC, Ladeb MF. Skeletal fluorosis: don't
miss the diagnosis! Skeletal Radiol. 2020 Mar;49(3):345–57.
References [1] Y Fan, W Peh, Radiology of osteoporosis: old and new findings, Semin Musculoskelet Radiol 20 (03) (2016) 235–245. [2] G Guglielmi, S Muscarella, A Bazzocchi, Integrated imaging approach to osteoporosis: stateof-the-art review and update, RadioGraphics 31 (5) (2011) 1343–1364. [3] C Messina, L Sconfienza, M Bandirali, G Guglielmi, F Ulivieri, Adult dual-energy x-ray absorptiometry in clinical practice: How I Report it, Semin Musculoskelet Radiol 20 (03) (2016) 246– 253. [4] LG Dasher, CD Newton, L Lenchik, Dual X-ray absorptiometry in today’s clinical practice, Radiol Clin North America 48 (3) (2010) 541–560.
[5] JA Kanis, H Johansson, NC Harvey, EV McCloskey, A brief history of FRAX, Arch Osteoporos 13 (1) (2018) 118. [6] BC Silva, WD Leslie, H Resch, O Lamy, O Lesnyak, N Binkley, et al., Trabecular bone score: a noninvasive analytical method based upon the DXA image, J Bone Miner Res 29 (3) (2014) 518–530. [7] CY Chang, DI Rosenthal, DM Mitchell, A Handa, SV Kattapuram, AJ Huang, Imaging findings of metabolic bone disease, RadioGraphics 36 (6) (2016) 1871–1887. [8] E Shane, D Burr, B Abrahamsen, RA Adler, TD Brown, AM Cheung, et al., Atypical subtrochanteric and diaphyseal femoral fractures: second report of a task force of the American Society for Bone and Mineral Research, J Bone Miner Res 29 (1) (2014) 1–23. [9] JD Isaacs, L Shidiak, IA Harris, ZL Szomor, Femoral insufficiency fractures associated with prolonged bisphosphonate therapy, Clin Orthop Relat Res 468 (12) (2010) 3384–3392.
[10] A Imerci, U Canbek, S Haghari, L Sürer, M Kocak, Idiopathic juvenile osteoporosis: a case report and review of the literature, Int J Surg Case Reports 9 (2015) 127–129. [11] M Proisy, A Rouil, H Raoult, C Rozel, P Guggenbuhl, D Jacob, et al., Imaging of musculoskeletal disorders related to pregnancy, Am J Roentgenol 202 (4) (2014) 828–838. [12] A Rao, G Gandikota, Beyond ulcers and osteomyelitis: imaging of less common musculoskeletal complications in diabetes mellitus, Br J Radiol (2018) 20170301. [13] JC Baker, JL Demertzis, NG Rhodes, DE Wessell, DA Rubin, Diabetic musculoskeletal complications and their imaging mimics, RadioGraphics 32 (7) (2012) 1959–1974. [14] M Al Muderis, T Azzopardi, P Cundy, Zebra lines of pamidronate therapy in children, J Bone Joint Surg 89 (7) (2007) 1511–1516. [15] JM Joyce, TE Keats, Disuse osteoporosis: mimic of neoplastic disease, Skeletal Radiol 15 (2) (1986)
129–132. [16] L Nardo, DN Sandman, W Virayavanich, L Zhang, RB Souza, L Steinbach, et al., Bone marrow changes related to disuse, Eur Radiol 23 (12) (2013) 3422–3431. [17] A Rupasov, U Cain, S Montoya, JG Blickman, Imaging of posttraumatic arthritis, avascular necrosis, septic arthritis, complex regional pain syndrome, and cancer mimicking arthritis, Radiol Clin North Am 55 (5) (2017) 1111–1130. [18] EE Vassalou, K Spanakis, IP Tsifountoudis, AH Karantanas, MR imaging of the hip: an update on bone marrow edema, Semin Musculoskelet Radiol 23 (03) (2019) 276–288. [19] S-T Quek, WC.G Peh, Radiology of osteoporosis, Semin Musculoskelet Radiol 6 (3) (2002) 10. [20] R Chanchlani, P Nemer, R Sinha, L Nemer, V Krishnappa, E Sochett, et al., An overview of rickets in children, Kidney Int Rep 5 (7) (2020) 980–990.
[21] D Regina John, PP Suthar, Radiological features of long-standing hypoparathyroidism, Pol J Radiol 81 (2016) 42–45. [22] MD Murphey, DJ Sartoris, JL Quale, MN Pathria, NL Martin, Musculoskeletal manifestations of chronic renal insufficiency, RadioGraphics 13 (2) (1993) 357–379. [23] JG Bonchak, KK Park, T Vethanayagamony, MM Sheikh, LS Winterfield, Calciphylaxis: a case series and the role of radiology in diagnosis, Int J Dermatol 55 (5) (2016) e275–e279. [24] KM Olsen, FS Chew, Tumoral calcinosis: pearls, polemics, and alternative possibilities, RadioGraphics 26 (3) (2006) 871–885. [25] HS Sidhu, N Venkatanarasimha, G Bhatnagar, V Vardhanabhuti, BM Fox, SP Suresh, Imaging features of therapeutic drug–induced musculoskeletal abnormalities, RadioGraphics 32 (1) (2012) 105–127. [26] M Sellami, H Riahi, K Maatallah, H Ferjani, MC Bouaziz, MF Ladeb, Skeletal fluorosis: don’t
miss the diagnosis!, Skeletal Radiol 49 (3) (2020) 345–357.
Chapter 54
Lymphoreticular and Hematopoietic Bone Diseases Ali Rashidi, Jan Fritz
Introduction This important group of disorders is responsible for some of the most challenging and feature-rich radiological abnormalities encountered in the skeleton. In this chapter, the diseases affecting cells and systems and the role of imaging in diagnosing hematopoietic and bone marrow disorders will be detailed.
Diseases Primarily Involving Red Blood Cells In the infant, red marrow extends throughout the medullary cavities of the whole skeleton, except for the epiphyses and apophyses. During the first few months of life, red blood cells are also produced by the spleen and liver, described as extramedullary erythropoiesis. As the physiological requirement for erythrocyte production diminishes progressively during the years of growth, a cessation of this function occurs in the liver and spleen and later by regression of the red marrow areas in the peripheral skeleton. By the age of 20, red marrow is normally confined to the proximal ends of the femur and humerus and the axial skeleton. Residual areas of fatty nonhematopoietic marrow in the appendicular skeleton, as well as the liver and spleen, maybe reactivated should the need arise. Such a response normally occurs after severe bleeding but can also be seen with obesity. These episodes are insufficiently prolonged to cause conventional radiographic changes, although this reconversion from fatty to red marrow is readily identified on MRI. Table 54.1 summarizes the most important radiologic findings of chronic anemias. Table 54.1 Chronic
Radiological Findings of Chronic Anemia Radiologic Findings
Anemia Thalassemia
Sickle cell disease
◾Medullary trabeculae destruction and cortex thinning ◾ “Hair-on-end” appearance of the skull due to gross thinning of the outer table ◾ Development of the air space of the skull which causes “rodent” facies clinical manifestation
◾ Generalized osteoporotic appearance specifically in the axial skeleton ◾ “Bone within a bone” appearance resulting from the separation of inward cortical thickened by a thin zone of translucency
◾ Osteopenia and progressive microfractures which represent bone infarction ◾ Bone marrow hypointensity on T1-weighted and hyperintensity on T2-weighted MR images is suspicious for osteomyelitis Erythroblast osis fetalis
◾ Development of transverse metaphyseal translucencies in the long bones (nonspecific)
Chronic Hemolytic Anemias In many instances, these anemias, in which red blood cells suffer extensive destruction, are followed by such a degree of marrow hyperplasia that striking skeletal abnormalities result. The great majority of these diseases are congenital and hereditary in origin. The red blood cells are abnormal in shape, fragility, and the type of hemoglobin that they contain. The clinical picture is that of any chronic anemias. Dyspnea, pallor, fatigue, and weakness are often accompanied by jaundice due to erythrocyte destruction. If extramedullary hematopoiesis occurs, the liver and spleen may be enlarged, particularly the latter, especially when the anemia is profound. Cardiac enlargement and failure may occur, and many of the more severely affected patients die before puberty.
Radiological Changes Radiological changes in the skeleton resulting from marrow hyperplasia vary greatly with disease severity. In children, the changes are widespread and are usually demonstrated most easily in the extremities and the skull. To some degree, marrow hyperplasia destroys many of the medullary trabeculae, which is followed by thinning and expansion and even perforation of the overlying cortex. This hyperplasia achieves its compensatory objective in many patients so that a state of erythrocytic balance is reached. The areas of bone destruction show repair features by forming fibrous tissue and the development of reactive bone sclerosis. The latter thickens the remaining trabeculae and, in some, the endosteal aspect of the cortex to produce an overall increase in bone density. As age advances, the peripheral bones, now in a state of balance, tend to revert to a normal appearance, but some residual increase in density may remain. Evidence of continued erythropoiesis to a greater degree than normal is then confined to the physiological red marrow areas. Extramedullary hematopoiesis, in addition to hepatosplenomegaly, may be revealed by radiologic findings (Fig. 54.1). A hypovascular, heterogeneous softtissue mass in computed tomography (CT) or a solid mass with internal vascularity in ultrasonography (USG) can represent extramedullary hematopoiesis. On MRI, extramedullary hematopoiesis is a heterogeneous mass with lipid component and variable T1- and T2-weighted appearance and microscopic fat on chemical shift images. The presence of a predominantly fatty lesion can indicate an inactive hematopoietic mass.
The most common location of extramedullary hematopoiesis, after hepatosplenomegaly, is paravertebral masses. These masses mostly find incidentally and are more common in the thoracic vertebra than the abdominal or pelvis area. Lymphoma, neurogenic tumors, and Castleman’s disease are the differential diagnosis of a mass in the posterior mediastinum. Unlike lymphoma, extramedullary hematopoiesis presents bilaterally, and in contrast to neurogenic tumors, is not associated with osseous erosions. Also, the discrimination of extramedullary hematopoiesis and Castleman’s disease is simplified by the heterogeneity of extramedullary hematopoiesis masses. Extramedullary hematopoiesis masses that involve the spinal canal may cause neurological compression symptoms [1].
Thalassemia (Cooley’s Anemia) As described by Cooley in 1927, this condition, known as Mediterranean anemia, is common in Mediterranean countries or races. The geographical distribution of this condition extends eastward in a broad band through Asia and West Africa. It is commonplace in such areas and may be encountered anywhere in the world in individuals having heredity originating from these areas. The disease is due to abnormalities of the hemoglobin molecule. Homozygous subjects, who have inherited the trait from both parents, develop the more severe form of the disease, known clinically as thalassemia major, whereas heterozygous subjects develop a minor form. Both may vary greatly in severity so that the distinction between them and other hematological variants is of relatively little radiological importance. Severe forms usually become manifest in the first 2 years of life. Although the majority of these patients die before puberty, some survive in early adult life. Those with the less severe disease live longer, and minimal manifestations may be found only by examining the blood of individuals who otherwise appear entirely normal. The important clinical features, in addition to those of other anemias, are dwarfing, delay in the development of secondary sexual characteristics, and either “mongoloid” or “rodent” facies due to the expansion of the underlying facial bones because of erythroblastic hypertrophy. Radiologic Changes:
Hyperplasia of the marrow destroys many of the medullary trabeculae and expands and thins the overlying cortex. This is evident in children, especially in the hands, when the shafts of the phalanges and metacarpals become biconvex instead of being biconcave (Fig. 54.2). The feet are affected in the same way.
Figure 54.2 Thalassemia (boy aged 7). Gross marrow hyperplasia has expanded and thinned overlying cortical bone. Medullary trabeculae have been destroyed and the residual bones are coarsened. Inset—early changes of the same type in a finger of a child aged 4. Similar abnormalities in the ribs (Fig. 54.3) and long bones (Fig. 54.4) may produce an apparent failure of modeling with, for example, a flask-shaped femur (Fig. 54.5).
Figure 54.3 Thalassemia (boy aged 15). A chest film shows gross expansion of bone structures due to marrow hyperplasia. Note particularly involvement of the ribs and scapulae.
Figure 54.4 Thalassemia. Considerable bone expansion, cortical thinning, and simplification of trabecular pattern are demonstrated in the forearm of a 15-year-old boy.
Figure 54.5 Thalassemia. Considerable marrow expansion has produced a flask shape of the distal femur. The coarsened trabecular pattern and cortical thinning are obvious. In the skull, the diploic space is widened, and the gross thinning of the outer table may be followed by marked diploic thickening, starting in the frontal region, but usually exempting the occipital bone, the marrow content is minimal (Fig. 54.6). These marrow changes result in the “classical” appearance of the “hair-on-end” in the skull imaging, distinguished by cortical erosions (Fig. 54.7). In the skull radiograph, gross thinning of the cortical bone, coarse trabeculation, and widening of marrow space are prominent features that are better visualized on CT images. On MR images, bone marrow expansion with T1-weighted signal hypointensity is a secondary finding to red marrow hyperplasia [2].
Figure 54.6 Thalassemia. Thickening of the outer table of the skull in the frontal area with perpendicular striation—“hairbrush sign.”
Figure 54.7 Classical “hair-on-end” appearance. Sagittal (A) and coronal (B) CT images of the skull in a patient with thalassemia major (Cooley’s anemia) show thinning of the outer and inner cortical bones, coarse linear trabeculation of cancellous bone, and widening of marrow space. CT, computed tomography. Development of the skull’s air spaces, especially the maxillary and the mastoids, is impaired because of hyperplasia of the marrow, accounting for the clinical manifestation of “rodent” facies, with malocclusion. The spine shows only diffuse demineralization with the same generalized coarsened trabecular pattern observed in the appendicular skeleton.
Although osteoporosis and osteopenia are common causes of morbidity in thalassemia major [3], vertebral collapse is uncommon. Osseous abnormalities of this type may also be observed in fewer forms of thalassemia and its variants, including those associated with other abnormal hemoglobins and the sickle cell trait. However, in all these conditions, the changes tend to be much less prominent than in thalassemia major.
Sickle Cell Disease This chronic hemolytic anemia is congenital and hereditary in origin and results from a single gene mutation. The erythrocytes, when hypoxic, become abnormal in shape, being unusually long and slender. The abnormal hemoglobin that they contain has a reduced oxygen-carrying capacity. The disease occurs almost exclusively in black-skinned races, especially those in Central Africa or their descendants, who are homozygous for the sickling trait. This trait may be crossed with normal or abnormal hemoglobins, including thalassemia. In these crossed types, the patient is less severely affected, both clinically and radiologically. Differentiation of the true homozygous state from the variants (combined with hemoglobin C is the most common) is of some importance. The former group’s median survival age is 42 and 48 for men and women, respectively, whereas the latter may have a normal lifespan. The homozygous sickle cell disease is characterized clinically by early onset of the severe anemic picture, with frequent skeletal and abdominal crises. These acutely painful episodes, lasting for several days, are due essentially to infarction, attributed to vascular blockage by collections of erythrocytes that have undergone sickling in areas of capillary stasis, with resultant hypoxia. Infarcts may affect many systems. The fundamental skeletal abnormalities consist of marrow hyperplasia with superimposition of bone necrosis areas due to infarction and subsequent growth disparities. A further clinical complication is the development of infection within these infarcts, particularly in lesions developing in children’s long bones.
Radiological Changes
The chronic hemolytic state is reflected by the development of characteristic and diagnostic radiological abnormalities, affecting primarily the erythropoietic skeleton and the soft tissues involved by extramedullary hematopoiesis. The frequency with which abnormalities are discovered increases with age. All variants of sickle cell disease produce essentially similar radiological abnormalities. 1. Marrow hyperplasia is fundamental. However, in this disease, the effects on the skeleton, which are so prominent in thalassemia major, occur in modified form, even in its worst clinical manifestations being less severe. A generalized osteoporotic appearance is evident throughout the hematopoietic areas of the skeleton, but even in infants and children, it is recognized more easily in the axial than in the peripheral skeleton. Decreased T1 signal intensity equal to or less than intervertebral disc can be diagnosed in MRI [4]. This feature is not diagnostic, but in a black-skinned child should arouse suspicion. Unlike severe thalassemia, significant modeling abnormalities are uncommon so that the air spaces of the paranasal sinuses are rarely affected. The diploic space of the skull may be widened, with consequent bossing. If a state of erythrocytic balance is achieved, diffuse trabecular thickening is likely to develop. Such an appearance may be seen incidentally in an asymptomatic adult sickle cell trait carrier. A coarse medullary pattern is associated with enlarged vascular channels in bone, especially in proximal or middle phalanges in more advanced cases 2. Endosteal apposition of bone: Inward cortical thickening is separated occasionally by a thin zone of translucency to result in the appearance in the long bones of “a bone within a bone” (Fig. 54.8). This sign may be observed in other conditions, including Gaucher’s disease. In severe cases, the medullary cavities may ultimately be grossly narrowed and almost obliterated so that a diffuse and generalized increase in bone density results. This does not occur in the axial skeleton, which is a persistent red marrow area, and this provides an important diagnostic feature even in the absence of other signs 3. Avascular necrosis/infarction of bone provides the diagnostic hallmark of this disease. Infarction of various tissues, which results from vaso-occlusion, is considered the cause of the classic clinical episodes of sickle cell crises. Unlike thalassemia, in which infarction is virtually unknown, this type of skeleton involvement is common. The consequent radiological abnormalities are comparable to those observed in other systemic disorders such as
dysbaric osteonecrosis (Caisson disease) and Gaucher’s disease. Such infarcts are usually multiple and most commonly affect the humeral and femoral heads (Fig. 54.9) and medullary bone. Medullary infarcts may be of two varieties, with either sharply defined margins or producing diffuse sclerosis. In their mildest form, they may be recognized in an asymptomatic patient. The classic “snow cap” sign refers to the subarticular area of increased density, particularly in humeral and femoral heads, reflecting the revascularization of an area of bone that has been necrotic (Figs. 54.10 and 54.11). At this phase of development, bone scans are usually abnormal with increased activity. On the radiographs and CT imaging, osteopenia and progressive microfractures are the most common findings which result in abnormal sclerosis and fragmentation. On MRI, a linear signal hypointensity on T1-weighted images demonstrates avascular necrosis. On T2-weighted MRI, in addition to the linear hypointensity, an inner line of signal hyperintensity makes a “double line sign” as a clue for avascular necrosis [4]. Nevertheless, in acute infarction, a photon deficiency is often present within 24 hours of the insult. However, repairing bone is brittle and fractures easily—varying from “osteochondritis dissecans” to complete collapse
Figure 54.8 “Bone-within-a-bone” appearance of a patient with sickle cell disease. Left humerus anteroposterior radiograph (A) and axial T1weighted MR image demonstrate separation and thickening of the cortical bone, resembling a dual layering of cortex with interposition of a thin zone without mineralization (arrows). Note the presence of a “snow cap” sign of the humeral head (asterisk), indicating avascular necrosis.
Figure 54.9 Sickle cell disease. Infarction in the proximal femoral metaphysis has produced a large defect with avascular necrosis of the femoral head. These features are similar to those of Perthes disease.
Figure 54.10 Avascular necrosis and “snow cap” sign of the shoulder in a patient with sickle cell disease. Left shoulder anteroposterior radiograph shows subarticular areas of increased density (arrows) indicating sclerotic bone due to recurring episodes of ischemia and infarction in the proximal left humerus.
Figure 54.11 Avascular necrosis and “snow cap” sign of the hip in a patient with sickle cell disease. Left hip anteroposterior (A) and lateral (B) radiographs show subarticular areas of increased density (arrows), indicating sclerotic bone due to recurring episodes of ischemia and infarction in the femoral head, which is referred to as a “snow cap” sign. Right coronal hip proton-density-weighted (C) and axial fat-suppressed T2-weighted (D) MR images show the subarticular areas of bone infarction (), which are characterized by areas of edema pattern indicating osseous ischemia and necrosis, as well as a geographic demarcation zone that has the characteristic double line with adjacent healthy cancellous bone and normal MRI signal of bone marrow. Femoral heads affected in childhood present an appearance exactly comparable to Perthes disease. In young black children, the areas with a preference for infarctions are the small tubular bones of the hands and feet, causing destructive changes accompanied by massive and painful soft-tissue swellings and periosteal reactions, which may be florid and reflect associated infarction of cortical bone (sickle cell dactylitis or “hand–foot” syndrome). These findings may indicate the correct diagnosis, but other causes of infantile periosteal reactions, such as cortical hyperostosis of the infantile or traumatic types, tuberculous dactylitis, or possibly hypervitaminosis A, may require consideration. The formation of perpendicular bony spicules on the skull, uncommon even in thalassemia, is distinctly unusual. More important is the possibility of a superadded infection, which is discussed later. Infarcts of vertebral bodies are another characteristic of radiological stigma. Generalized depressions of the central portions of the vertebral end-plates are
common and may be demonstrated in an asymptomatic patient. The depressions are often concave and rounded, initially simulating an ordinary nucleus pulposus impression on an already porotic bone. Infarction may be diagnosed when the center of the depression is flat and the sides slope obliquely, producing characteristic H-shaped vertebrae (Fig. 54.12). The diaphysis of the long bones, especially in the older child and the adolescent, are predilection sites for infarction. Typically, they involve the zones between the mid diaphysis and the metaphysis, the so-called “intermediate fifths.” When the metaphysis is involved, significant deformities may occur due to growth arrest.
Figure 54.12 Classic “H-shaped” or “Lincoln log” appearance of the vertebrae with sickle cell disease. Lateral radiograph (A), sagittal CT image (B), and sagittal MR image (C) of the thoracolumbar spine in a patient with sickle cell disease demonstrate effects of vertebral endplate bone infarctions during development, manifesting as focal depressions of the center of the upper and lower endplates (arrows), resembling the shape of the letter H or a “Lincoln log,” which are square-notched miniature toy logs used to build small buildings and blockhouses. CT, computed tomography. Central metaphyseal defects and lucencies are typical. These, in turn, may produce fragmentation and deformity of the epiphyses. They may also be the sites of pathological fractures. Infarcts may be massive, causing bone destruction, sequestration, reactive sclerosis, and even involucrum formation. The pattern may suggest acute pyogenic osteomyelitis. Superimposed infection/secondary osteomyelitis: The areas of bone necrosis caused by infarction are especially susceptible to infection, classically by salmonella organisms of the paratyphoid B group. Differentiation between the
pure infarct and those infected in this way may be extremely difficult both radiologically and pathologically since cultures are often sterile. Such lesions are liable to occur, especially in the tubular bones of the hands (Fig. 54.13) and feet in infants and the long bones (Fig. 54.14) and the spine of older children.
Figure 54.13 Sickle cell disease. Soft-tissue swelling surrounds an expanded proximal phalanx. Medullary expansion is present with simplification of trabecular pattern and penetration of the cortex. The distinction between these changes and osteomyelitis is extremely difficult.
Figure 54.14 Sickle cell disease with salmonella osteomyelitis (Nigerian boy aged 4). Extreme destructive changes in the long bones have been caused by infection superimposed upon infarction. Numerous sequestra are present. (Courtesy: Mr. Geoffrey Walker.) In the adult, septic arthritis may be superimposed on an adjacent infarct. Radiographs are mostly normal, and CT shows a different marrow density between the normal bone marrow and the infection. However, MRI has high sensitivity and specificity for the diagnosis of osteomyelitis. Bone marrow hypointensity on T1-weighted and hyperintensity on T2-weighted images are in favor of the diagnosis of osteomyelitis. With appropriate treatment, either by conservative antibiotic therapy or by active surgical measures, including sequestrectomy, healing usually occurs with remarkable rapidity. Soft-tissue involvement may be seen in other chronic hemolytic anemias and such disorders of the marrow as Gaucher’s disease. These may consist of heterotopic masses of hematopoietic tissue in the dorsal paravertebral areas and hepatosplenomegaly, renal papillary necrosis, or bowel infarction. Heterotopic masses of hematopoietic tissue may develop in the dorsal paravertebral areas.
The release of iron pigments by accelerated destruction of erythrocytes may accelerate the formation of biliary calculi.
Erythroblastosis Fetalis (Hemolytic Disease of the Newborn) Hemolytic anemia occurring in the fetus and newborn results from an immunological incompatibility between the mother and fetus’s blood, most commonly due to the Rh factor, although other hematological errors of this type are known. The severity may vary widely, from mild anemia to icterus neonatorum and fetal hydrops. The Rh-positive erythrocytes of the fetus, crossing the placental barrier in a mother without Rh antigen, stimulate the maternal formation of anti-Rh antibodies that traverse the placenta to enter the fetal circulation, there to hemolysis the fetal red blood cells. The danger of infants being affected by this incompatibility increases with the number of conceptions, but early recognition of the disorder and the adoption of prophylactic measures has greatly reduced its incidence. Radiological Changes:
The only skeletal abnormality is the development of transverse metaphyseal translucencies in the long bones. These translucencies are nonspecific, as they may also occur with other severe maternal illnesses during pregnancy and in congenital syphilis. With successful treatment, the translucent areas ossify with residual growth lines. In the spine, such growth lines often cause “ghost shadows” within the vertebral bodies. Fetal hydrops may be diagnosed sonographically by the detection of growth retardation, effusions, and subcutaneous edema. The enlargement of the placenta displaces the fetus.
Other Chronic Anemias
Iron Deficiency Anemia The anemia of infants suffering from iron deficiency may produces radiological changes in the skull due to marrow hyperplasia similar to those of the less severe congenital anemias. An inadequate diet is a usual cause, but malabsorption or abnormal loss of iron may be important factors. The widening of the diploic space and the subsequent bossing of the skull vault is again characteristic, but the
disease has never been reported to cause changes sufficiently severe to involve the long bones and facial bones.
Hereditary Spherocytosis This is an inherited defect in which the red blood cells are of an abnormal round shape. The anemia in which results may produce mild changes comparable to the other congenital anemias. Removal of the spleen permits the bone structures to revert to a normal appearance.
Fanconi’s Anemia This syndrome of congenital aplastic anemia with multiple congenital anomalies (not to be confused with the other syndrome described by the same author and concerned with osteomalacia and an abnormal renal tubular mechanism) is of interest in that the hematological changes are unlikely to appear before the age of 2 years. These consist of hypoplastic anemia, marrow hypoplasia, and skin pigmentation. The defect is inherited, and congenital abnormalities of the skeleton are associated, such as the deficient formation of the thumb bones, first metacarpal, and radius; other abnormalities, including congenital dislocation of the hip and club foot, short stature, and microcephaly, have also been observed. These are evident long before the hematological abnormalities become apparent, and the latter is not responsible for any skeletal abnormalities. Some cases have been terminated in leukemia.
Polycythemia This condition is due to an increased level of erythropoietin and the overproduction of red blood cells. Although occasionally responsible for bone infarction, it produces no characteristic radiological changes in the skeleton. Transition to myeloid metaplasia is common. Pulmonary abnormalities in polycythemia may occur in the form of increased reticulation or fine mottling.
Diseases Primarily Involving White Blood Cells
Leukemia Children are most commonly affected, almost invariably by an acute form of leukemia. In adults, the disease may also be acute, but it is more commonly chronic. Hematopoietic tissue is widely distributed throughout the skeleton of a child but is confined in the adult to the “red marrow” areas of the axial skeleton and the proximal ends of the humeri and femur. Thus, radiological changes in the bones are common in the younger age groups. More than half of the children affected show skeletal abnormalities, while in adults, these are found in fewer than 10% of cases. Although the diagnosis is usually confirmed by examining the blood and sternal marrow, bone changes may precede the development of a grossly pathological blood picture, especially in the so-called aleukemic type. Differentiation between myeloid and lymphatic types of leukemia cannot be made by radiological examination.
Radiological Changes These are observed mainly in children and consist of the following (Table 54.2) 1. Metaphyseal translucencies. In children, the most characteristic sign occurring in up to 90% of cases is the presence of bands of translucency running transversely across the metaphysis (Fig. 54.15). Such bands may be narrow and incomplete in the early stages of the disease, but they may be found to traverse the metaphysis completely and be as much as 5 mm in width in a few weeks. The most rapidly growing areas—knees, wrists, and ankles—are commonly affected first, but later the metaphysis of the shoulders, hips, and vertebral bodies also may be involved. With treatment, remission may occur, and the bands of translucency resolve 2. Metaphyseal cortical erosions (leukemic lines) on the medial side of the proximal ends of the humeral (Fig. 54.16) and tibial shafts sometimes occur as an early feature. They are usually bilateral 3. Osteolytic lesions develop in over half of the cases. Usually, they are punctuating and diffusely scattered, although solitary and larger lesions may occur. Although such leukemic deposits may involve any portion of the skeleton, they are commonest in the shafts of the long bones. When the vertebral bodies are involved, collapse often occurs before specific areas of
rarefaction can be identified. Prominent convolution marking and sutural widening can demonstrate skull involvement 4. Periosteal reactions are usually associated with underlying bony lesions and are distinguished by a sunburst pattern of periosteal reaction 5. Osteosclerosis of the metaphysis is a rare but well-recognized primary manifestation. It may develop during treatment Table 54.2 Radiological Findings of Diseases Involving the White Blood Cells Disease Radiologic Findings Leukemia
Myeloid metaplasia
◾ Bands of translucency running transversely across the metaphysis ◾Cortical erosion of metaphysis (leukemic lines) ◾ Diffusely scattered osteolytic lesions; mostly common in the shafts of the long bones ◾ Periosteal reaction with sunburst pattern associated with underlying bony lesions ◾ Patchy or diffuse bone density increase with areas of relative translucency due to fibrosis ◾ Irregular periosteal reactions, particularly near the ends of long bones
Figure 54.15 Metaphyseal translucent band in a child with leukemia. Lateral radiograph of the left knee shows a translucent band transversing the metaphysis of the distal left femur metaphysis (arrows).
Figure 54.16 Lymphatic leukemia. (A) Erosions of the medial side of the proximal metaphyses (arrow) of both humeri were present in this 8-yearold child. The disease was in an aleukemic phase, not an uncommon finding even when skeletal changes are present. (B) The same child complained of back pain. Multiple vertebral collapses are shown with the
preservation of disc-space height. Overall, bone density is reduced with a simplified trabecular pattern. In metastatic neuroblastoma, skeletal changes take place, which may be indistinguishable from leukemia. Separation of the sutures of the skull in the former condition is a helpful differentiating sign. In adults, skeletal lesions are rare. As has been stressed before, the deposits occur essentially in red marrow areas. Changes include osteoporosis, translucent areas of leukemic bone destruction (which tend to be oval with the long axis parallel to the shaft), and vertebral destruction and collapse. Periosteal reactions are unusual. Occasionally, generalized osteosclerosis of the marrow area is evident. This is likely to be caused by trabecular thickening during remission periods and may be patchy in type. However, in some instances, the leukemic changes may be a secondary and terminal process in myeloid metaplasia. On MRI, signal hypointensity in T1-weighted and hyperintensity in T2-weighted and short-tau inversion recovery (STIR) sequences, compared with normal bone marrow, are expected findings.
Myeloid Metaplasia (Myelofibrosis/Myelosclerosis) This syndrome occurs by replacing bone marrow tissue with fibrous tissue due to an unknown etiology and is characterized by the triad of myelofibrosis, myeloid metaplasia, and features in the peripheral blood film, which simulate leukemia. The relation between myeloid metaplasia, myelosclerosis, and other diseases, including polycythemia vera and chronic myeloid leukemia, is intimate. The typical patient is a middle-aged or elderly adult, the primary disorder being metaplasia of the marrow cells to fibrous tissue. The usual presenting complaints are fatigue and abdominal fullness due to hepatosplenomegaly. Obliteration of the hematopoietic tissue results in progressive anemia, the appearance of immature red and white cells in the peripheral blood, and compensatory splenomegaly. In the later stages of the disease, the fibrous tissue becomes converted to bone, and endosteal cortical thickening develops. Polycythemia may be followed by myeloid metaplasia, and it appears probable that nearly half of the developed cases of myeloid metaplasia previously had some form of this blood disorder. Purine hypermetabolism may manifest itself as secondary gout.
Radiological Changes In the sclerotic stage of the disease, the increased density of the bones may be diffuse or patchy (Table 54.2). Areas of relative translucency due to fibrosis may persist (Fig. 54.17). The increased density is due to new bone deposition on the trabeculae and the endosteal cortical thickening with the loss of the normal cortico medullary distinction. Narrowing of the medullary space becomes visible and resembles the later bones of sickle cell anemia in the long bones. Irregular periosteal reactions may occur, particularly near the ends of long bones. These may be well organized and continuous with the cortex or separated from it by a translucency zone. Although the red marrow areas (particularly the pelvis) are especially subject to these pathological changes, the entire skeleton may be affected. The density of the skull is associated with obliteration of the diploic space, although some persistent areas of fibrosis may remain translucent. Splenomegaly is almost invariably evident (Fig. 54.18). On MRI, T1- and T2weighted sequences demonstrate hypointense marrow.
Figure 54.17 Myeloid metaplasia. Widespread but patchy areas of sclerosis are shown throughout the pelvis and lumbar spine.
Figure 54.18 Myeloid metaplasia (woman aged 63). All the bones are diffusely dense, with lack of distinction between cortical and medullary bone. The spleen is grossly enlarged (arrows). Differentiation must be made from other conditions causing a generalized increase of bone density. The congenital sclerosing dysplasias, including osteopetrosis, are likely to be encountered in adult life only as an incidental finding or associated with a pathological fracture. Fluorosis is likely to occur in an endemic area. Mastocytosis may cause some confusion, but the lesions are usually less diffuse and are accompanied by urticaria pigmentosa. Sclerosing and widespread metastasis, particularly prostatic, should not be forgotten.
Myelodysplastic Syndrome Myelodysplastic syndrome (MDS) [5] is a clonal disorder of hematopoietic, specifically myeloid, stem cells, which leads to a group of hematologic neoplasms. The chance of transformation to acute myeloid leukemia increased in
some of the patients. MDS frequently affects patients over 65 years’ age and is more common in males. Although mostly asymptomatic, clinical manifestations resulting from pancytopenia, including fatigue, shortness of breath, petechiae or bleeding, and infection. Following the exclusion of other cytopenia causes, a bone marrow aspirate and biopsy are utilized for diagnosis. Low-dose wholebody multidetector computed tomography [6] and MRI [7] providing valuable information and are used as prognostic predictors in patients with MDS. Prognosis ultimately depends on multiple factors such as the severity of cytopenias and the percentage of blasts in the bone marrow.
Diseases of the Lymphoreticular System Four main groups of the disorder will be considered, divided for convenience as follows: 1. Lymphomas: Hodgkin’s, non-Hodgkin’s lymphomas, mastocytosis 2. Plasma-cell disease: Plasmacytoma, multiple myeloma, Waldenström macroglobulinemia (WM), POEMS syndrome 3. Histiocytosis: Langerhans cell histiocytosis, Erdheim–Chester disease, Rosai–Dorfman disease, Juvenile Xanthogranuloma 4. Storage disorders: Gaucher’s disease, Niemann–Pick disease, Tay–Sachs disease, Fabry disease
Lymphomas Lymphomas are a common type of blood cancer that primarily affects B-cell, Tcell, and natural killer cells. The most common subtypes of lymphoma and their main radiologic findings are summarized in Table 54.3. Table 54.3 Lymphomas
Hodgkin’s disease
Radiological Findings of Lymphomas Commonly Radiologic Findings Involved Skeleton Areas ▪
Thoracolum bar spine (most common) ▪ Long bones ▪ Ribs and sternum ▪ Skull, clavicle, and scapulae
▪ Osteolytic, sclerotic, or mixed-type bone involvement ▪ Thoracolumbar spine (most frequently involved area): ⚬ Anterior scalloping of a vertebral body (rare and specific) ⚬ Ivory vertebral body (sclerotic type): a solitary dense vertebra ⚬ The intervertebral discs are usually spared ▪ Long bones: ⚬ The osteolytic type identifies as the predilection sites that are the red marrow areas in the proximal portions of the femora and humerus ⚬ Small oval translucencies in the long axis of the bone, extended throughout the marrow cavity associated with endosteal scalloping of the cortex ▪ Ribs and sternum: ⚬ Usually osteolytic and expanding in type
NonHodgkin’ s lymphom a
Lowgrade nonHodgki n’s
▪ Knee (with associated synovial effusion)
▪ The earliest finding: diffuse patchy medullary destruction or sclerosis with very poorly defined margins
lympho ma
▪ Proximal end of the humerus
Highgrade nonHodgki n’s lympho ma
▪ Primary skeletal involvement is probably extremely rare
▪ Resemble very closely to osteolytic type of Hodgkin’s disease
▪ Can be solitary or multiple
▪ Pathologic fractures in the femoral and humeral necks, and vertebral bodies
▪ Large and diffuse irregular margins with scalloping of the inner aspects of the cortex
▪ Cortex erosions followed by the formation of large associated softtissue masses with relatively little periosteal reaction Burkitt lympho ma
▪ Mandible and maxilla (most common) ▪ Spine and long bones
Mastocyt osis
Hodgkin’s Disease
▪ Spine, ribs, pelvis, skull, and tubular bones
▪ Large destructive, purely osteolytic, and rapidly growing lesions ▪ In long bones, the permeative lytic nature of the tumor, particularly with cortical erosions, may resemble an Ewing’s sarcoma ▪ The initial finding: osteopenia and osteoporosis ▪ Diffuse areas of lytic and sclerotic lesions
This defined tumor has an agreed classification on histological grounds, named after Rye. This comprises nodular sclerosis Hodgkin’s disease, a complaint of young women involving intrathoracic lymph nodes, and three categories, lymphocyte-predominant Hodgkin’s disease, mixed cellularity Hodgkin’s disease, and lymphocyte-depleted Hodgkin’s disease. The last three comprise a spectrum with, in the order listed, a worsening outlook. Bone involvement always implies a less favorable prognosis. It is a feature of widespread disease and has been found at postmortem in more than half of the cases. Skeletal lesions at presentation are far less common. Primary Hodgkin’s disease of bone probably does not occur. There is no correlation between the variety of Hodgkin’s disease and the nature of the individual bony lesions it produces. The age of onset varies widely from childhood to old age, but the diagnosis is most commonly made in young adults. The red marrow areas are the most frequent presentation sites, the majority of lesions being found in the spine, thoracic cage, and pelvis. Bone pain may precede, by several months, the development of these lesions, and the importance of serial radiological examination, either radiographic or scintigraphic, must be stressed. Radiological Changes:
In the skeleton, most early bone lesions are destructive and often large when they are first observed, either from direct involvement from affected soft tissues, particularly lymph nodes, or infiltration of bone marrow. About a third are essentially osteolytic in type (Fig. 54.19). The majority is, however, of mixed type with patchy sclerosis and destruction. Diffuse trabecular thickening causes sclerotic lesions in the remainder. Such an appearance may develop in a few months, being preceded by bone pain, and may well show no preliminary bone destruction. It may also follow the treatment of a formerly osteolytic lesion. Conversely, some sclerotic lesions may be observed to become osteolytic or normal following treatment. Whereas the osteolytic lesions may thin, displace, and erode the overlying cortex and develop associated soft-tissue masses, the primary sclerotic lesion does not cause enlargement of the affected bone.
Figure 54.19 Hodgkin’s disease. An expanding, destructive lesion involves the body of the sternum, with anterior and posterior soft-tissue masses. Bizarre changes in this bone should always arouse suspicion of lymphoma. Positron emission tomography (PET)/CT is a sensitive means of detecting the presence of bony lesions, particularly when sclerotic deposits have developed. With this method, bone marrow biopsy is no longer performed for adults in most trials, and instead, three positive foci detected by PET are considered bone involvement. PET/CT scans also increase disease staging sensitivity and improve the clinical outcomes in children [8]. MRI is extremely sensitive in the diagnosis of Hodgkin’s disease. Whole-body MRI (WB-MRI) and PET/CT are valuable diagnostic techniques in assessing bone marrow involvement in patients with lymphoma [9]. When CT and PET scans do not yield a definite diagnosis, MRI is often helpful to diagnose bone
involvement [8]. A T1 hypointensity and T2 hyperintensity suggest bone involvement on MRI [10]. ▪ The thoracolumbar spine is the most frequently involved area. A rare but more specific diagnostic feature is anterior scalloping of a vertebral body, attributed to the long-standing mass effect of adjacent paravertebral lymph nodes. Several vertebrae may be affected. The sclerotic type shows a diffuse increase of density, possibly also with some anterior vertebral scalloping. A solitary dense vertebra, the so-called ivory vertebral body, is suggestive of this disease (Fig. 54.20). In all these types, the intervertebral discs are usually spared, aiding differentiation from an infection. Even in the rare cases where a disc space does become narrowed, preservation of density of the vertebral end-plates usually permits differentiation from an infective discitis where the loss of this density is an early diagnostic sign ▪ The ribs lesions may be observed on chest radiographs, which are usually osteolytic and expanding in type ▪ The sternum is also a not-infrequent site for a lesion to appear, again usually osteolytic, but sometimes mixed in type with perpendicular spicules of new bone ▪ In the pelvis, mixed or sclerosing types tend to predominate. Osteolytic lesions, rather nonspecific in appearance, are not uncommon in the ischia, and change from either type to the mixed pattern may be observed in serial examinations ▪ In the long bones, the predilection sites are the red marrow areas in the proximal portions of the femora and humerus. These are usually of the osteolytic type and many small translucencies, oval in the long axis of the bone, extend throughout the marrow cavity associated with endosteal scalloping of the cortex. Although such an appearance is a feature of this disease, it may also be seen in non-Hodgkin’s lymphoma, leukemia, and Gaucher’s disease. The fusion of such areas may produce a “honeycomb pattern,” with coarse residual trabeculation, like the medullary changes of Gaucher’s disease. Organized periosteal reactions are not infrequent. Such a feature is rare in Gaucher’s disease ▪ The skull, clavicles, and scapulae are sometimes affected. Pathological fractures are uncommon. With sclerosing lesions in elderly individuals, confusion with Paget’s disease may easily arise, but the characteristic enlargement of the affected bone in that disease will probably be absent. Differentiation in all these lesions must be made from metastasis.
Intrathoracic disease may present with hypertrophic osteoarthropathy (Fig. 54.21)
Figure 54.20 Ivory vertebral body in lymphoma. Anteroposterior radiograph (A) and lateral radiograph (B) of the lumbar spine show a markedly sclerotic, dense vertebral body (arrows), which is called an “ivory” vertebral body indicating neoplastic disease.
Figure 54.21 Hypertrophic osteoarthropathy in a patient with thoracic Hodgkin’s disease. Right femur anteroposterior radiograph shows hypertrophic osteoarthropathy (arrows) of femur diaphysis characterized by mineralized periosteal thickening, which can be a sign of neoplastic pulmonary disease.
Non-Hodgkin’s Lymphoma This forms a much more difficult spectrum of disease with a continually evolving classification. That commonly used is based on lymph node histology and cytoimmuno chemistry. As a simplification, non-Hodgkin’s lymphomas (NHLs) are categorized according to the histological architecture of the tumor into follicular or diffuse forms and according to their cell type into B-cell and Tcell tumors. As a working formulation, the tumor is then classified as low, medium, or high grade. In general, low-grade tumors tend to be follicular B-cell lymphomas, and high-grade tumors tend to be diffuse T-cell lymphomas.
It is difficult to assess how many patients present with primary skeletal nonHodgkin’s lymphoma; the proportion is probably less than one-third. The majority of patients have diffuse disease at diagnosis. Experience suggests that low-grade NHL may present as a primary bone tumor, although it can be multifocal and systemic in older patients. It is unlikely that high-grade NHL ever presents primarily in the skeleton. Low-Grade Non-Hodgkin’s Lymphoma:
Skeletal involvement by low-grade NHL may be with localized pain and swelling, often over a protracted period. The tumor may be asymptomatic or presenting with pathological fracture. Males are affected twice as commonly as females. The majority is observed in the third and fourth decades, although presentation during later years is not unusual. The lesions may be multifocal in the older age group. These tumors may be confused with other malignancies, including osteosarcoma, metastasis, and malignant round cell tumors. Differentiation between these tumors in a young adult may be extremely difficult, not only on clinical and radiological grounds but also histologically. The lesion may arise as a primary tumor within the bone marrow and tend to remain confined to the skeleton, although it may spread to other bones and only at a later stage to lymph nodes and viscera. The condition is localized to a single bone with a marked predilection for the long bones in their primary form. Nearly half of the cases occur near the knee (Fig. 54.22), often with an associated synovial effusion. The proximal end of the humerus is another common site, and about a third of cases are found in the flat bones of the axial skeleton. Spinal, rib, and pelvic involvement tend to occur with the extra skeletal form and the older age group.
Figure 54.22 Non-Hodgkin’s lymphoma. A purely destructive lesion is present in the distal femur of a woman patient. The margins are illdefined with cortical destruction. Periosteal new bone formation is present adjacent to this destruction. These appearances resemble metastasis and osteosarcoma. The tumor may be extremely radiosensitive, and radiotherapy alone or in combination with surgery has resulted in many long survivals. Although a primary lesion may have regressed entirely with radiotherapy, generalized skeletal dissemination is likely to occur eventually. The earliest evidence of the tumor is diffuse medullary destruction or sclerosis of a patchy nature with very poorly defined margins. At this stage, it may be impossible to differentiate the lesion radiologically from any other aggressive neoplasm. In particular, an osteolytic metastasis is likely to present the greatest difficulty. The lesion may resemble other primary malignant neoplasms stimulating little or no reactive bone formation, such as Ewing’s tumor, fibrosarcoma, or malignant fibrous histiocytoma.
Radiological confusion with osteomyelitis may also arise, particularly as the overlying periosteal reaction is present in half of the cases (Fig. 54.22). The periosteal reaction may be present before medullary changes become evident. Scintigraphically, the features are unremarkable. Usually, increased activity is detected, or multifocal lesions may be found. Radiologically, the area of destruction spreads widely through the marrow cavity and remains patchy. Much of the adjacent cortex undergoes resorption with the development of welldefined soft-tissue swelling from soft-tissue tumor extension. Cortical thickening and reactive sclerosis are not prominent features, although they may occur exceptionally. In the generalized form of the disease, lesions may be detected throughout the skeleton, and each presents the same characteristics as a solitary focus. High-Grade Non-Hodgkin’s Lymphoma:
This malignant tumor is rarer than Hodgkin’s disease and mainly affects older patients in the fifth and sixth decades. Nonetheless, several cases have been observed in children, and a male sex preponderance has been found. A proportion of these patients develop frank lymphocytic leukemia. The incidence of bone lesions is 10–20%, although more are detected at postmortem. Prognostically, bone lesions imply a poor outcome. Primary skeletal involvement is probably extremely rare. In the skeleton, these resemble very closely to those of Hodgkin’s disease; other lesions grow more rapidly and are almost always osteolytic in type. Areas of destruction, commonly in red marrow areas, may be large with diffuse and irregular margins and with scalloping of the inner aspects of the cortex. They may be solitary or multiple and, because of their osteolytic nature, pathological fractures are common. The latter affects especially the femoral and humeral necks and may cause the collapse of vertebral bodies. When the lesions are multiple, they all tend to be of the same osteolytic type, unlike Hodgkin’s disease, when all the different bone change types may be present. Erosion of the cortex is likely to be followed by the formation of large associated soft-tissue masses with relatively little periosteal reaction. Such erosions usually occur through an area of the cortex that has already been thinned and expanded by the
underlying pathological process, emphasizing the radiological similarity of the individual lesions to Ewing’s sarcoma. Burkitt Lymphoma
Burkitt’s tumor is an exceptional and particularly aggressive form of nonHodgkin’s lymphoma common in African children. The disease is associated with Epstein–Barr virus and is especially prevalent in endemic malarial areas. Large, destructive lesions develop, especially in the mandible and maxilla (Fig. 54.23). Radiologically, these lesions are purely osteolytic and grow rapidly. The jaw lesions are characterized by the resorption of the lamina dura with multiple lytic foci that eventually merge with radiating spicules of bone. Spinal lesions are characterized by lytic, ill-defined destructive foci with paravertebral masses. In long bones, the permeative lytic nature of the tumor, particularly with cortical erosions, may resemble an Ewing’s sarcoma. Foci develop in soft tissues, particularly the kidneys, ovaries, and abdominal lymph nodes. Regression can occur following the use of cytotoxic drugs.
Figure 54.23 Burkitt’s tumor. A large destructive lesion in the mandible of this African child is typical of this form of lymphoma.
Mastocytosis The rare condition of urticaria pigmentosa is associated with enlargement of the liver, spleen, and lymph nodes due to the proliferation of mast cells. The disease is relatively benign, but a few instances of leukemic termination have been recorded. Bone changes are usually identified in early adult life. Radiological Changes
In 70% of cases, skeletal changes, which are mostly generalized, are present. The most common presentations in the initial steps are osteopenia and osteoporosis [11]. There are diffuse areas of lytic and sclerotic lesions throughout the axial and appendicular skeleton (Fig. 54.24). Any bone may be affected; however, spine, ribs, pelvis, skull, and tubular bones are more to have lytic lesions [12]. The expansion of some trabeculae and the thickening of others may cause the osseous structures to have a coarse pattern. The appearance may closely resemble sickle cell anemia, the sclerosing types of leukemia, Gaucher’s disease, and osteopetrosis. Occasionally the dense areas are sharply defined, of considerable size, and localized to a few areas. Particularly in young adults, differentiation from Hodgkin’s disease must be made.
Figure 54.24 Mastocytosis of the spine. Sagittal CT image of the lumbosacral spine shows an abnormal pattern of cancellous bone, characterized by areas of lytic (white arrows) and sclerotic (black arrow) lesions in all vertebral bodies. CT, computed tomography.
Plasma Cell Diseases Plasma cells represent the end product of B-lymphocyte maturation. Pathological proliferation produces either a local tumor (plasmacytoma) or disseminated disease (myelomatosis). Table 54.4 summarizes the main radiologic findings of plasma cell diseases. Table 54.4 Radiological Findings of Plasma-Cell Diseases
Plasma-Cell Disease
Commonly Involved Skeleton Areas
Plasmacytoma
▪ Vertebral bodies, especially in the thoracolumb ar and lumbar regions(most common) ▪ Pelvis, especially the ilium, ribs, femur, and humerus, is the next most commonly involved sites
Radiologic Findings
▪ These lesions arise in areas of red marrow function ▪ Bone expansion: may be considered thinning of the overlying cortex ▪ Vertebral body collapse ▪ Well defined and sharply demarcated margins, characteristically without a sclerotic reaction ▪ Network appearance in the area of destruction due to coarse trabecular strands of increased density
Plasma-Cell Disease
Multiple myeloma
Commonly Involved Skeleton Areas ▪ The axial skeleton is affected predominant ly ▪ Shafts of long bones and the skull
Radiologic Findings
▪ Generalized reduction in bone density ▪ Localized radiolucency areas in red marrow areas ▪ The rounded and oval defects characteristically have sharply defined edges ▪ Classic lesion: punched-out “raindrop” lesions, circular defects varying in diameter from a few millimeters to 2 or 3 cm ▪ Myelomatous lesions may erode the cortex and extend into the adjacent soft tissues. (The resulting soft-tissue masses help differentiate the advanced forms of the disease from metastatic carcinoma lesions, which much less commonly produce extension into the soft tissues.) ▪ Vertebral body collapse which resulted in paravertebral soft-tissue shadows ▪ Pathologic fractures with remarkably quick healing and massive callus and new bone formation without any evidence of reactive sclerosis
Waldenström macroglobuline mia
▪ Spine
▪ Diffuse demineralization and compression fracture of the spine due to bone marrow infiltration
Plasmacytoma This condition is unifocal, causing a localized destructive lesion in a red marrow area of the skeleton. Many other descriptive terms (such as solitary myeloma) for this localized lesion have been used. Although it may remain localized for many years and without health disturbance, it ultimately transitions to generalized myelomatosis. A latent interval of 5–10 years is usual; consequently, the outlook is better than multiple myeloma. Compared with the latter, these lesions are uncommon, but the exact incidence is difficult to assess as they are frequently asymptomatic. For example, a plasmacytoma in a rib may be noted incidentally on a routine examination of the chest (Fig. 54.25).
Figure 54.25 Plasmacytoma of the rib. Axial chest CT image shows a plasmacytoma in the posterior eighth rib, characterized by destructive osteolysis with expansile soft-tissue components (arrows) extending beyond the destructed cortex of the rib. CT, computed tomography.
When symptoms occur, they are commonly those of bone pain, particularly backache. The vertebral bodies, especially in the thoracolumbar and lumbar regions, are the most common sites for these lesions and are likely to undergo partial collapse. The pelvis, especially the ilium, ribs, femur, and humerus, is the next most commonly involved sites. The vast majority of affected individuals are between the fifth and seventh decade of age. The differential diagnosis always includes a solitary osteolytic metastasis. Differential diagnosis of these tumors may be difficult. Given the age group, osteolytic metastasis is the most common differential diagnosis. In vertebrae, such metastases are likely to involve the pedicles more commonly. Metastatic disease apart, the development of a solitary osteolytic lesion in a vertebral body in a late middle age patient should always be considered a plasmacytoma (Fig. 54.26). Chordoma may also produce similar features. Other differential diagnoses to be considered, especially with an expanding lytic focus in a rib, are fibrous dysplasia, a “brown” tumor of hyperparathyroidism, and, particularly when the lesion is adjacent to an articular surface, a giant cell tumor. The resemblance to a giant cell tumor may be close; however, these lesions are found in early adult life and have a different distribution, commonly affecting the appendicular skeleton, whereas plasmacytoma is more likely to be axial.
Figure 54.26 Plasmacytoma presenting with paraparesis. Conventional radiograph of the thoracic spine showing vertebra plana (arrows). Radiological Changes
These lesions arise in areas of red marrow function. Bone expansion, which may be considered thinning of the overlying cortex, is common, but when a vertebral body is affected, collapse may precede such apparent expansions. On MRI, this appearance has been described as “mini-brain” sign. The margins are usually well defined and sharply demarcated, and characteristically without a sclerotic reaction. Coarse trabecular strands of increased density may give a network appearance in the area of destruction, and exceptionally the lesion may be entirely sclerotic. Large lesions in flat bones may assume a “soap-bubble” appearance (Fig. 54.27).
Figure 54.27 Plasmacytoma of pelvis. This very extensive lesion was unaccompanied by any systemic abnormality. Bone expansion is associated with coarse trabeculation, producing a soap-bubble appearance. Scintigraphy and CT afford no specific diagnostic features. Increased activity is observed in the blood-pool phase of a bone scan, while the delayed phase shows increased activity around the margins. CT confirms the extent of these tumors but does not afford tissue-specific information. WB-MRI with diffusion-weighted imaging is the most sensitive imaging technique in evaluating plasmacytoma and multiple myeloma. According to recent International Myeloma Working Group guidance, WB-MRI, or fluorodeoxyglucose (FDG)-PET CT, suggested as the first-line technique in the assessment of plasmacytoma [13].
Multiple Myeloma The disseminated or generalized form of plasma cell infiltration of bone marrow is known as multiple myeloma. This entity may be preceded by a solitary plasmacytoma or arise de novo. It is much more common for the widespread form to present radiologically as a fully developed entity in the over-40 age group. Men are affected twice as often as women. Persistent bone pain or a pathological fracture is usually the first complaint. Plasma cell proliferation causes elevation of the total serum proteins due to the production of abnormal immunoglobulins. Such proliferation eventually occurs at the expense of all other marrow functions so that nonspecific leukopenia and secondary anemia develop. In about half of the cases, the presence of an abnormal urinary protein constituent, Bence Jones protein, may be demonstrated. Abnormal proteinuria causes cast formation in the renal tubules with impairment of renal function. Hypercalcemia, hypercalciuria, and amyloidosis occur, the last in about 10% of all cases, and resemble the distribution of primary amyloidosis. The hypercalcemia and hypercalciuria are unassociated with an elevation of either the serum alkaline phosphatase or phosphate levels. The bone destruction pattern may vary from diffuse osteoporosis, through small and almost insignificant areas of translucency, to rounded or oval defects with sharply defined margins. The last, regarded as characteristic, develops relatively late. Frequently the defects coalesce to produce even larger areas of osteolysis. Radiological Changes
The two cardinal features are generalized reduction in bone density and localized radiolucency areas in red marrow areas. The axial skeleton, therefore, is affected predominantly. Lesions may also be observed in the shafts of long bones and the skull. Despite positive bone marrow aspiration, radiological features may be absent in as many as one-third of cases, at least at the initial presentation. This group of patients tends to develop generalized osteoporosis. Radiology plays an important part in the initial diagnosis of the disease. Whether a skeletal survey is relevant will depend on the clinician’s approach to therapy; many will rely solely on the level of abnormal immunoglobulin to monitor treatment. If necessary, a radiographic skeletal survey is superior to scintigraphic
investigation using a bone-scanning agent because the lesions are essentially osteolytic with no bone reaction. However, a bone scan is superior in detecting lesions in the ribs because the associated fractures are demonstrated more easily. Diffuse osteoporosis alone can cause suspicion of the disease in an elderly patient. Even though age-related osteoporosis may be expected, the possibility of myelomatosis always merits consideration, particularly when symptomatic bone pain is present. The smaller areas of radiolucency are poorly demarcated and appear to be irregular accentuations of the generalized osteoporotic process. The rounded and oval defects characteristically have sharply defined edges (Fig. 54.28).
Figure 54.28 Typically localized lesions of myeloma are demonstrated in the upper femur of an adult woman. The sharply defined rounded defects with endosteal erosion of the cortex are characteristic. Bone lesions can also be diffuse with irregular margins. Exceptionally, however, sclerosing changes have been reported. These have varied, some resembling focal lesions of prostatic metastases, some the speculation of osteosarcoma, and
some a generalized diffuse increase in density. This very rare form of multiple myeloma occurs in probably 2% of cases and is frequently accompanied by peripheral neuropathy. Treatment, as in other conditions, may alter these appearances and, during its course, it is common to observe some lesions resolving while others evolve. The distribution of lesions is very widespread, and destructive foci are commonly located in the long bones in addition to the axial skeleton. ▪ The involvement of the skull is variable. Diffuse and irregular translucencies with generalized osteoporosis are not uncommon. Such changes eventually become pronounced and extensive. The disease will not always be evident by the presence of the classic punched-out “raindrop” lesions, circular defects varying in diameter from a few millimeters to 2 or 3 cm. Indeed, the skull may be normal, even in the presence of many lesions elsewhere in the skeleton ▪ Areas of osteolysis may also be observed in the mandible, a site only rarely affected by metastasis (Table 54.5). Myelomatous lesions may erode the cortex and extend into the adjacent soft tissues. The resulting soft-tissue masses help differentiate the advanced forms of the disease from metastatic carcinoma lesions, which much less commonly produce extension into the soft tissues ▪ The spine is often merely osteoporotic, but as the disease advances, multiple foci of destruction, almost invariably accompanied by some degree of collapse of the affected bodies, are likely to be present. With such collapse, paravertebral soft-tissue shadows are common. Differentiation from inflammatory lesions can be made, as the intervertebral disc spaces and the articular surfaces are not affected. The pedicles and posterior elements are involved less frequently and at a later stage than occurs with metastases ▪ A destructive rib lesion with a large associated soft-tissue mass is much more suggestive of multiple myeloma than of a plasmacytoma in the thorax. Diffuse involvement, however, is more usual; numerous characteristic lytic lesions being present ▪ The clavicles and scapulae may also show these destructive changes; indeed, such a lesion in the clavicle is far more likely to be due to myeloma than metastasis
▪ The long bones are affected most commonly in the persistent red marrow areas of the proximal ends of the humeri and femur. However, lesions are by no means found only in such areas, and irregular or punched-out translucencies in the shafts of other bones may be the first radiological manifestation of the disease Table 54.5 Radiological Differentiation of Multiple Myeloma From Metastases Multiple Myeloma Metastases ▪ More commonly affect the vertebral bodies
▪ Characteristic lytic lesions commonly involve the clavicles and scapulae
▪ Characteristic lytic lesions rarely involve the clavicles and scapulae
▪ May have a normal appearance in bone scan
▪ Rarely have a normal appearance in bone scan
In some advanced cases, lytic defects may be due also to secondary amyloidosis, which can complicate many chronic disorders such as rheumatoid disease and long-standing infections. Pathological fractures are very often the initiating factor in the diagnosis of the disease. These fractures heal remarkably quickly and soundly with massive callus and new bone formation. This response is somewhat surprising given the numerous cystic lesions and widespread osteoporosis, which are likely to be present without any evidence of reactive sclerosis. Whole-body radiography and traditional bone scintigraphy are techniques with low accuracy in evaluating skeletal involvement in multiple myeloma.
Whole-body low-dose (WBLD) CT is more sensitive than whole-body radiography and is recommended as the initial diagnostic procedure for diagnosing lytic bone lesions in multiple myeloma patients (Fig. 54.29).
Figure 54.29 Multiple myeloma of the spine. Sagittal CT image of the lumbosacral spine shows multiple areas of lytic vertebral bone lesions (arrows). CT, computed tomography. Whole-body MRI is the best technique for the assessment of bone marrow involvement in patients with multiple myeloma. Moreover, whole-body MRI is more sensitive than PET/CT to reveal focal or diffuse bone involvement. Multiple myeloma bone lesions have T1-weighted hypointensity and T2weighted intermediate to hyperintensity in the MRI [14].
Waldenström Macroglobulinemia
Waldenström macroglobulinemia (WM) is a rare malignant subtype of the lymphoplasmacytic lymphoma with immunoglobulinM (IgM) monoclonal gammopathy infiltrating bone marrow. It mostly affects older patients. The median age of patients is usually between 63 and 68, and males are more prone to get the disease [15]. Although serum hyperviscosity, due to the circulating IgM, is the most distinguishing presentation of WM and can lead to high-output cardiac failure, the most common disease manifestation is anemia, resulting from bone marrow infiltration. Infiltration and deposition of IgM in organs distinguished by lymphadenopathy and hepatosplenomegaly in the physical examination [16]. A rare complication of WM is Bing–Neel syndrome, which is characterized by infiltration of CNS and presenting with headache, ataxia, vertigo, diplopia, and nystagmus. Bone marrow infiltration may cause diffuse demineralization and a compression fracture of the spine. Although rare, the lytic bone disease may be visible on the bone surveys. On MRI, iso-/hypo-intensity to muscle and abnormal marrow enhancement can be noticed on TI-weighted images.
POEMS Syndrome An uncommon condition with the acronym POEMS is characterized by chronic progressive polyneuropathy, organomegaly (hepatosplenomegaly), endocrinopathy (commonly diabetes mellitus), M-proteins (plasma-cell dyscrasia), and skin changes (hirsutism, pigmentation, edema). The pick incidence of the disease is in the fifth and sixth decades of life. Bone pain and fractures are rare [17] and radiologically presents with multiple sclerotic lesions, most commonly in the spine and pelvis.
Histiocytosis The basic pathological abnormality in this group of diseases is a proliferation of histiocytic cells occurring particularly in the bone marrow, spleen, liver, lymphatic glands, and lungs. In the more chronic forms, these cells become swollen with lipid deposits, essentially cholesterol (although the blood cholesterol level remains normal), and they present the pathological appearances of “foam cells.” Some of these become necrotic and are replaced by fibrous tissue.
Various forms of the condition have been regarded as separate entities in the past, which are outlined in Table 54.6. Table 54.6 Disease
Langerha ns cell histiocyt osis
Radiological Findings of Histiocytosis Commonly Radiologic Findings Involved Skeleton Areas
Eosinoph ilic granulom a
▪ Thoracic spine ▪ Diaphysis or metaphysis of longbones
▪ Mostly presents as a solitary lesion ▪ Characteristic finding: translucent bone destruction areas, with sharply defined margins and considerable size ▪ Partial or complete collapse of spine presents as a classic fining: vertebra plana. (Consider DDX: Ewing’s tumor, neuroblastoma metastasis, benign osteoblastoma, atypical tuberculous focus) ▪ No sclerotic margin in the active phase, peripheral sclerosis around the lesion in the healing phase
Disease
Hand– Schüller– Christian disease
Commonly Involved Skeleton Areas ▪ Skull, mandible, and maxilla ▪ Vertebrae and pelvis ▪ Long bones (less common)
Radiologic Findings
▪ Similar finding as those of eosinophilic granulomas with far more numerous lesions ▪ “Geographical skull”: Merging of numerous bone lesions to produce widespread irregular defects usually likened to a map ▪ “Float in air” appearance: lesions in the mandible and maxilla around the tooth roots with dense and unaffected teeth
Letterer– Siwe disease
▪ Widely spread in the flat bones
▪ Purely lytic lesions, indistinguishable from Hand– Schüller–Christian disease
Disease
Erdheim–Chester disease
Commonly Involved Skeleton Areas
Radiologic Findings
▪ Distal ends of the femurs and proximal and distal tibia (The most characteristic in differentiating from Langerhans cell histiocytosis)
▪ Pathognomonic bilateral, symmetric cortical osteosclerosis of the diaphyseal and metaphyseal regions of the distal ends of lower—and sometimes upper limbs (epiphyses classically spare) ▪ Osteosclerosis of long bones differentiate it from Langerhans cell histiocytosis, which mostly presents with sharply defined lytic lesions in the axial skeleton
▪ Extensive fatty marrow replacement by signal hypointensity on T1weighted images, and the heterogeneous signal on T2weighted images/STIR Rosai–Dorfman disease
▪ Long bones (metaphysis, diaphysis, or epiphysis), skull, and spine
Langerhans Cell Histiocytosis
▪ Osteolytic and intramedullary lesions
Langerhans cell histiocytosis (LCH) is an idiopathic condition with unknown pathophysiology that involves dendritic antigen-presenting cells, although a neoplastic or an abnormal reactive process was defined as possible etiologies. The disease may involve bone marrow, lungs, liver, spleen, lymph nodes, gastrointestinal (GI) tract, pituitary gland, and a widespread disease increase mortality. LCH is a rare disease that mostly occurs in children 11-mm total or >2-mm asymmetry [13]; could also suggest an acetabular fracture
Anatomy
Disruption Suggestive of:
Shento n’s line
Inferior border of superior pubic ramus to inferomedial border of femoral neck
Femoral neck fracture or developmental dysplasia of the hip
Aceta bular roof
Border of superior acetabulum
Fracture
Anteri or acetab ular rim
Projects over the posterior rim
If projecting laterally compared with the posterior rim, suggestive of pincer-type deformity (“crossover sign”)
Posteri or acetab ular rim
Posterior portion of acetabular wall
Prominent posterior acetabular rim suggests over-coverage (“posterior wall sign”)
Sacral arcuat e lines
Inferior surfaces of bone that form the roofs of sacral foramina
Sacral fracture
Cartilage The femoral head is covered by hyaline cartilage, except for the fovea, which is a central depression in which the ligamentum teres arises (Fig. 59.1) [8]. The acetabulum contains horseshoe-shaped hyaline cartilage with a depression in the central roof called the “acetabular fossa.” The cartilage in the hip joint can be difficult to evaluate on imaging, as it is a covered curved surface and is relatively thin compared with other large joints like the knee. MR arthrography is typically the imaging study of choice and has a sensitivity of 50–79% and specificity of 77–84% for cartilage defects [16]. Labrum
The labrum is made of fibrocartilage and is attached to the osseous rim of the acetabulum. It is thickest superiorly and posteriorly. The labrum blends inferiorly with the transverse ligament along the edges of the acetabular notch (Fig. 59.1). The labrum attaches to the acetabulum near the joint capsule, and the small gap between the two can be seen on imaging as a perilabral sulcus. There is controversy over the etiology of a cleft at the interface between the labrum and hyaline cartilage in the anterosuperior quadrant, with some authors considering this to be a normal variant but others report this as a tear [8]. A normal labrum has a triangular configuration in cross section and low signal on T1-weighted images [17] (Fig. 59.6). Symptomatic tears most commonly involve the anterosuperior labrum.
Tendons There are numerous tendon attachments in the pelvis and hips. Table 59.2 gives details regarding these tendons, and Fig. 59.7 shows the tendon attachment sites on a pelvic radiograph. On MRI, tendons should appear as low signal, linear structures. Any intrasubstance high signal, thickening, or fluid-signal clefts on MRI suggest pathology such as tendinosis or tear [18]. One potential pitfall on MRI is the “magic angle” artifact. Dense, fibrillary structures, such as tendons, will appear falsely high in signal on specific sequences (proton density, T1-weighted, and gradient echo) when at an angle of 55 degrees to the main magnetic field. Findings should be confirmed or rejected based on cumulative appearances on other sequences, such as T2weighted sequences. This magic angle artifact on MRI corresponds to the anisotropy artifact on USG. On USG, tendons should have a fibrillar appearance and linear configuration; toggling the USG probe can change the appearance from hypo to hyperechoic, which is an artifact known as anisotropy. Table 59.2 Tendon Attachments in the Pelvis and Hips Sartorius
Proximal Attachment
Distal Attachment
Anterior superior iliac spine
Proximal, medial tibia
Quadriceps Tendons Rectus femoris Direct head Indirect head
Pubofemoral portion: lower gluteal line and linea aspera Ischiocondylar portion: adductor tubercle
Adductor brevis
Inferior pubic ramus
Linea aspera
Adductor Tendons
Iliopsoas Tendon
Proximal Attachment
Distal Attachment
Iliacus
Iliac fossa/crest, anterior ligaments of SI joint, lumbosacral, and iliosacral ligaments
Lesser trochanter
Psoas
Transverse processes of lumbar vertebrae
Lesser trochanter
Tensor fascia latae
Lateral edge of iliac crest, anterior superior iliac spine, sacrotuberous ligament, sacrum/coccyx
Middle third of the femur
Iliotibial tract
Thickened fascia originates from tensor fascia latae and gluteus maximus muscles
Gerdy’s tubercle
FIGURE 59.7 Pelvic radiograph with superimposed tendon attachment sites.
Pubic Symphysis The pubic symphysis is a nonsynovial joint formed by the confluence of the two pubic bones with an intervening fibrocartilaginous disk (Fig. 59.8). The medial surfaces of the pubic bones are covered by hyaline cartilage, and four ligaments are surrounding the joint (superior, arcuate/inferior, and anterior, posterior). Superiorly, the rectus abdominus and external oblique aponeurosis merge with the superficial layer of the anterior ligament. Inferiorly, the adductor longus and gracilis proximal attachments also merge with the aponeurosis, which attaches to the pubic bone.
FIGURE 59.8 Illustration of pubic symphysis anatomy (A) and muscle attachments (B).
Bursas There are numerous bursas in pelvis and hip region (Fig. 59.9). Anatomic (native) bursas are synovial-lined structures, while adventitial (non-native) bursts do not have a synovial lining and can develop at sites of pressure and friction. Bursas can be filled with fluid, but the term “bursitis” should not be used unless there is imaging evidence of inflammation [19]. Some commonly encountered bursas in the pelvis and hips are described in Table 59.3.
FIGURE 59.9 Illustration of bursas about the hip (A) and ischial tuberosity (B).
Table 59.3 Commonly Encountered Bursas in the Pelvis and Hips Associate d Tendons
Comments
Associate d Tendons
Comments
Iliopsoas
Iliopsoas
Communicates with the joint in 10–15% [20]
Subgluteus minimus
Gluteus minimus
Subgluteus medius
Gluteus medius
Subgluteus maximus
Gluteus maximus
Largest in the region; often called “greater trochanteric” bursa
Ischioglute al
Hamstring tendons
In proximity to sciatic and posterior femoral cutaneous nerves
Summary of Teaching Points: Functional Anatomy Section
◾ The hip is a ball-and-socket-type, synovial joint with a capsule extending over a relatively large span, including the femoral head and much of the femoral neck. Capsular thickening (7 mm or more) indicates intra-articular pathology (synovitis, joint effusion, etc.), can have clinical manifestations, including a limited range of motion.
◾ Normal marrow appearance in the pelvis should be bilateral and symmetric. ◾ Red marrow reconversion follows a predictable pattern, from first to last: proximal metaphysis, distal metaphysis, diaphysis, epiphysis (usually spared)
◾ On radiographs, trace symmetric lines on both sides of the pelvis and proximal femurs; if lines are disrupted or asymmetric, consider fracture or another source of pathology
◾ A normal labrum has a triangular configuration in cross– section and low signal on T1-weighted images. The labrum blends with the transverse ligament inferiorly. Sulci can be formed at the labral–capsular junctions, which can mimic tears. Symptomatic tears most commonly involve the anterosuperior labrum.
◾On MRI, tendons should appear as linear, low signal structures;
consider “magic angle” artifact on certain MRI sequences when the tendon is at a 55-degree angle.
◾ At the pubic symphysis, the rectus aponeurosis attaches to bone and blends inferiorly with the adductor aponeurosis. ◾ Native/anatomic bursas are synovial-lined structures; adventitial bursas develop at sites of friction) and do not have a synovial lining.
Imaging Techniques and Protocol Radiographs Radiographs remain the first-line study for evaluating most conditions in the pelvis and hip, including acute trauma, chronic conditions, such as arthritis, and the workup of any unknown cause of pain. Table 59.4 lists radiographic views of the hip and describes patient positioning and typical pathology that is best seen on each view [21,22]. Table 59.4 Radiographic Views of the Hip Radiographic View
Internal rotation, contralateral hip flexed 90 degrees (out of the way)
Injury in trauma patients; head–neck junction and anterior/posteri or dislocation
False profile
Patient standing, pelvis rotated at 65 degrees
Shape of acetabulum, anterior coverage of femoral head, impingement, measurement of anterior centeredge angle
Radiographic View
Positioning
Judet
Two projections: Iliac oblique in which unaffected side is rotated 45 degrees anterior Obt urator oblique in which affected side is rotated 45 degrees anterior
◾
◾
Helps Evaluate/Ident ify Acetabular fracture; iliac oblique shows anterior acetabulum and ilioischial column, while obturator oblique shows posterior acetabulum and posterior acetabular rim
Radiographic View
Positioning
Helps Evaluate/Ident ify
Inlet–outlet
Supine, beam tilted caudally and cranially
Inlet view: posterior displacement of pelvic ring, pubic symphyseal disruptionOutle t view: vertical shift
FAI, femoroacetabular impingement; SCFE, slipped capital femoral epiphysis.
Computed Tomography (CT) CT is a useful tool in evaluating the pelvis and hips, especially when osseous detail is required. It is typically used in acute trauma, to assess fracture healing and hardware, or for preoperative measurements. However, it can also help evaluate osseous and soft-tissue tumors as well as an infection. CT may give even better details than radiographs of the cortex, matrix mineralization, and soft-tissue calcifications [23]. High resolution is crucial in musculoskeletal (MSK) CT, and often the thinnest slices possible are desirable. However, this must be balanced with the need to keep the radiation dose as low as possible. Some considerations are as follows:
◾osseous Thin sections can help identify femoral neck and acetabular fractures and help evaluate bridging and fracture healing. ◾fractures. Three-dimensional reconstructions can be used for preoperative planning and evaluation of
◾postcontrast Intravenous contrast is typically given for the evaluation of neoplasm and infection; images alone are often sufficient in MSK CT to significantly reduce dose in younger patients. ◾through Metal can cause beam hardening or the loss of lower-energy photons as the beam passes an object, resulting in streaks and dark bands [24]. Hardware suppression protocols are thus beneficial in the presence of hip arthroplasties and other metallic hardware [24]. ◾ The use of dual-energy CT is limited in the hip due to depth. Ultrasonography (USG) Although some structures of the pelvis and hip are relatively deep, USG can be utilized for the evaluation of most of these structures. Typically, a linear 5–12 MHz probe is used in MSK USG. Still, a curvilinear 4–9 MHz probe is often helpful when evaluating the hip, as the lower frequency gives more penetration, although lower resolution. The patient is placed supine to scan the hip and anterior thigh and prone to scan the posterior thigh and hamstring tendons. Tables 59.5 describes primary indications in which hip USG can be diagnostic and when it can be limited, and Table 59.6 describes common USG interventions. Table 59.5 Utility of Hip USG Indications
Limitations
Hip joint effusion
Intra-articular pathology
Fluid collections
Labral tears
Tendons and tendinosis
Posterior hip
Snapping Hip
Osseous evaluation
Bursal distention and bursitis
Patient obesity
Greater trochanteric pain syndrome
Fatty infiltration of muscles
Inguinal and femoral hernias
Table 59.6 Common Hip USG Interventions Procedure
Clinical Setting
Procedure
Clinical Setting
Hip joint aspiration
Suspected infection
Hip joint injection
Hip pain and/or arthritis
Aspiration of fluid collections
Suspected infection
Injection of iliopsoas peritendon
Hip pain
Bursal injection (trochanteric or iliopsoas)
Bursitis/pain
Needling/tenotomy
Tendinosis
Platelet-rich plasma injection
Tendinosis
Magnetic Resonance Imaging (MRI) MRI is frequently used in MSK imaging of the pelvis and hips and provides excellent soft tissue and bone marrow detail. Common indications include occult hip fractures, stress/insufficiency fractures, avascular necrosis, and labral and tendon pathology, as well as neoplasm and infection. Most pelvis and hip MRI protocols include coronal views of the entire pelvis, typically with both T1-weighted and a fat-saturated, fluid-sensitive sequence, such as short-T1 inversion recovery (STIR). This allows evaluation for symmetry. If the MRI evaluation is focused on a single hip, it is helpful to get a sequence in all three planes (axial, coronal, and sagittal). Coronal sequences are best for detecting hip fractures, but other planes help to confirm the fracture and allow evaluation of other structures. Proton density (PD) sequences, especially with fat-saturation allow excellent evaluation of soft-tissue anatomy, and are frequently used. If there is a suspicion of infection or mass, gadolinium contrast can be useful; pre- and postcontrast, fat-saturated, T1weighted sequences tend to show the contrast better. Some special sequences can be utilized for problem solving, such as T1 inand opposed-phase coronal sequences of the entire pelvis, which helps to distinguish red marrow reconversion (loses signal on out-of-phase sequence, appearing dark) from a pathologic process like neoplasm (does not lose signal). MR arthrography of the hip is used in younger individuals to evaluate intra-articular pathology and labral tears. This involves a separate injection of gadolinium contrast into hip joint (under fluoroscopic or USG guidance) just before MRI. The operator should take care to avoid air in the injectate, which appears as low signal areas on the MRI (Table 59.7). Table 59.7
A Sample MRI Reporting Template of Hip MRI of the hip Clinical information: Technique: (description of protocol, sequences, and use of contrast) Comparison studies: Findings: Osseous Joints Labrum Tendons Muscles Bursas Other (lymph nodes, neurovascular, incidental findings) Impression
Nuclear Medicine Although nuclear imaging is less frequently used than other techniques when evaluating the hip, bone scan, typically utilizing technetium-99m-labeled diphosphonate can be helpful in the evaluation of stress and insufficiency fractures, avascular necrosis, osseous metastatic disease, and prosthetic loosening. One finding worth mentioning is that of a “superscan,” in which intense, symmetric radiotracer uptake is seen in the bones, with relative paucity of uptake in the soft tissues and kidneys. This condition can be seen in the setting of diffuse osseous metastatic disease and other diffuse processes that affect the bones, such as hyperparathyroidism, renal osteodystrophy, and osteomalacia. Single photon emission computed tomography (SPECT) can be used for better localization if bladder uptake obscures the pathology. A labeled white blood cell (WBC) scan can be useful in evaluating osteomyelitis, especially in patients who cannot undergo MRI because of a pacemaker or other implant. Summary of Teaching Points: Imaging Techniques and Protocol Section
◾ Radiographs are the first-line study for most hip and pelvis imaging ◾
◾CT is useful to evaluate osseous detail and orthopedic hardware ◾ US can be especially helpful to evaluate for joint effusion, tendon pathology, fluid collections, and bursitis ◾ MRI is an excellent tool for soft tissue and bone marrow evaluation ◾ Nuclear medicine can be helpful for problem solving, including labeled WBC scan for osteomyelitis Joint Pathology Central/Hip Joint Region Patients with pathology in the hip joint and/or central region will often present with groin pain or hip pain. Radiographs are the first-line imaging technique to assess for joint and/or osseous involvement, but cross-sectional imaging, including MRI or potentially an MR arthrogram, may need to be considered. Hip Joint Hip joint-based processes, such as arthritis, are well evaluated on imaging, and accurate diagnosis also depends on the clinical scenario. Osteoarthrosis (OA) is due to degeneration and abnormality of hyaline cartilage, and its primary form is usually due to overuse and/or old age. Secondary OA is a similar process but resulting after some insult, such as trauma, hip dislocation, or hip dysplasia. The hallmarks of OA on imaging are:
Because the hip is a weight-bearing joint, and the cartilage on the weightbearing surfaces wears out first, there is often asymmetric joint space narrowing in the areas of greatest force, usually the superior joint (Fig. 59.10).
FIGURE 59.10 Osteoarthrosis. A frontal radiograph of the hip shows complete, asymmetric joint space loss in the superior hip joint with bone-on-bone articulation, sclerosis, and osteophyte formation, consistent with severe osteoarthrosis.
Inflammatory arthritis, in contrast, results from inflammation and synovial proliferation in the hip joint, which can lead to erosions and effusion. Marginal erosions occur when inflammatory synovial tissue (pannus) erodes the bone in the “bare area” of the intra-articular bone, where there is no hyaline cartilage. Joint space narrowing is typically concentric or involving the entire joint (Fig. 59.11). In the hip, this can appear as axial femoral head migration and remodeling in the central acetabulum, causing protrusion, or displacement of the femoral head into the pelvis, past the ilioischial line. Coxa profunda, in contrast, refers to the acetabulum being medial to the ilioischial line. A well-centered pelvic radiograph is essential for evaluation.
FIGURE 59.11 Rheumatoid arthritis. An anteroposterior (AP) radiograph of the hip shows severe, concentric joint space narrowing with only mild sclerosis and small osteophytes, atypical for osteoarthrosis. This patient was only 35 years old, but had a history of rheumatoid arthritis.
Rheumatoid arthritis (RA), common inflammatory arthritis, has a different clinical presentation than OA, with:
◾ Women more affected than men ◾ Patients typically diagnosed in their 20–40 years of age ◾joints Patients having joint stiffness in the morning with pain and swelling in multiple, symmetric ◾ Positive rheumatoid factor in blood
Seronegative spondyloarthropathies, especially ankylosing spondylitis, may involve the hip, although rheumatoid factor should be negative in these patients. Table 59.8 lists a comparison of imaging features between OA and RA. It is important to note that some patients with RA will also have secondary OA with osteophytes and more severe joint space narrowing on the weightbearing surface.
Table 59.8 Imaging Features of Osteoarthrosis Compared to Inflammatory Athritis Osteoarthrosis
Inflammatory Arthritis
Radiog raphic finding s
Osteophytes Joint space narrowing Subchondral cysts Sclerosis
Erosions (possibly marginal) Joint space narrowing Periarticular osteopenia
Joint effusio n
Sometimes
Yes (often)
Joint space narrowi ng
Typically worst on weightbearing surfaces; asymmetric
Entire joint (concentric)
Clinical present ation
Hip pain, often in older/elderly patients and/or due to previous trauma or overuse
Hip pain and stiffness, worse in the morning, women > men in 20s–40s
Radiologists should be aware of the recent discussion in the literature of the entity known as rapidly destructive osteoarthritis (RDOA) of hip, which is a progression of degenerative changes over 6–12 months to complete joint destruction [25]. This entity is typically unilateral and most often seen in elderly patients, especially women. Some authors have suggested that RDOA of the hip may be related to steroid injection, with a faster progression to arthroplasty after the procedure [26,27]. Although the literature is not entirely conclusive, the possibility of RDOA should be discussed with patients who underwent hip steroid injection before the procedure and during consent. Septic Joint A septic hip is an orthopedic emergency, as an acute infection can irreversibly destroy native hip cartilage within hours. The radiologist can make a difference in clinical management and outcome by helping to identify this entity early in its course. The clinical presentation is crucial when interpreting imaging studies. Patients with an acute septic hip will often present with an acute onset of joint pain, extreme limitation of movement, swelling, redness, and a feeling of heat in the joint. Patients might have a flexion deformity of the hip and be unable to bear weight.
The progression of a septic hip is shown in Fig. 59.12. Although radiographs are the first-line evaluation tool, a negative radiograph does not necessarily exclude a septic joint, and cross-sectional imaging should be considered when there is high clinical suspicion. CT or MRI might show only joint effusion even in the setting of a septic hip (Fig. 59.13). These techniques can also help to rule out other pathologies, such as a hip fracture or soft-tissue process. If there is clinical suspicion of an acute septic hip and a joint effusion is seen, emergent joint aspiration is warranted, and this is frequently done with fluoroscopic or USG guidance. Typically a large-bore needle is used to allow for aspirate that could be viscous, and initially lavage should be avoided to allow for proper cell count. Lidocaine injection into the joint is contraindicated, as the solution can be antimicrobial. A positive diagnosis of a septic joint typically prompts a surgical washout procedure, which can prevent additional joint destruction.
FIGURE 59.12 Flowchart for pathophysiology of septic hip with imaging correlates.
FIGURE 59.13 Septic hip. Initial radiograph is normal (A). Coronal STIR MR image (B) left hip joint effusion, without marrow signal changes.
Labral Tear Suspected labral tears are a common indication for hip imaging. Patients tend to be in the younger age group (teens to 30s) and are often active. Presenting symptoms include hip or groin pain with catching and/or locking of the hip. Labral tears can be caused by trauma, overuse, FAI, and hip dysplasia, although labral degeneration is common with increasing age. Especially in patients older than 40, labral tears can an asymptomatic and/or incidental finding, which can add confusion when reviewing the study for a source of pain. It may be prudent to describe the findings with different verbiage than the word “tear” in such situations [28]. MR arthrogram is the study of choice to evaluate for labral tears, on which they will appear as a contrast-filled defect within the normally low-signal labrum (Fig. 59.14) [8]. Tears are most common in the anterior or anterosuperior region, with some studies showing as many as 86% of tears in this location [29]. On a non-MR arthrogram, labral tears can appear as linear, increased signal intensity in the labrum or at the chondro-labral junction, but may also be seen as surface irregularity or truncation of the normal morphology. Tears at the chondral junction may suggest adjacent cartilage damage. Paralabral cysts, which appear as multiloculated fluid signal on MRI, are highly suggestive of tears.
FIGURE 59.14 Labral tear. Sagittal proton density fat-saturated (PDFS) MR image of the hip shows high signal and abnormal morphology of the anterosuperior labrum (arrowhead) with fluid-signal, multiloculated paralabral cyst (arrow) emanating from the tear.
Femoroacetabular Impingement FAI is a result of altered morphology of bone involving the hip, causing abnormal contact of the femur and acetabulum. Repetitive microtrauma of bone on the cartilage and labrum causes cartilage degeneration and early OA of the hip as well as labral degeneration and tearing. Patients tend to be younger (teens to 30s) and active, and they may present with hip pain and restricted range of motion. The process is often bilateral and symmetric [30]. Physical examination tests that might suggest FAI include the anterior impingement test, in which the flexed hip is forced into adduction and
internal rotation, and the “FABER” test, in which the patient’s leg is placed into flexion, abduction, and external rotation, and the distance from the knee to the examination table is measured [31]. There are two main categories of FAI, although some patients can have both (mixed) (Fig. 59.13A):
◾ Cam impingement
◾
◾
⚬ Caused by broad osseous protuberance at the anterolateral femoral head–neck junction, causing loss of normal concavity that looks like a pistol grip (Figs. 59.15A1 and 59.15B) ⚬ Protuberant bone repeatedly strikes the labrum and acetabulum during flexion, which can lead to labral tear and eventually osteoarthrosis ⚬ Usually seen in young, active men ⚬ Many patients will develop a small, cystic area at the femoral head–neck junction, called a “synovial herniation pit” ⚬ Decreased femoral head–neck offset Pincer impingement ⚬ Overcoverage of the femoral head by the laterally extending superolateral acetabulum, involving the anterosuperior quadrant (Figs. 59.15A2 and 59.15C) ⚬ Often associated with acetabular retroversion ⚬ More common in women ⚬ Underlying labrum and cartilage are pinched during the normal range of motion, resulting in labral tearing and degenerative changes ⚬ Synovial herniation pits also seen Mixed-type cam/pincer impingement (Fig. 59.15A3) ⚬ More common than individual types ⚬ Slipped capital femoral epiphysis (SCFE) is said to increase susceptibility for future impingement
FIGURE 59.15 Appearance of FAI. (A) Illustration of cam (1), pincer (2), and mixed-type (3) FAI. (B) Cam deformity. Frog-leg radiographic view of the right hip shows osseous protuberance along the femoral head–neck junction. (C) Pincer deformity. Frontal radiograph of the right hip shows over-coverage of the acetabulum, with “crossover sign.”
Radiographic evaluation can help evaluate osseous morphology and allows the radiologist to provide measurements, including the amount of over coverage. The alpha angle issued to assess the presence of a cam deformity, and this is often seen best on CT or MRI (Fig. 59.16). To perform this measurement, two lines are drawn: one along the central axis of the femoral neck on an oblique view and one from the center of femoral head to the point where femoral head sphericity is first lost. An angle greater than 55 degrees is abnormal and confirms a cam deformity; clinical correlation for pain is essential.
FIGURE 59.16 Cam deformity with abnormal alpha angle. Sagittal oblique, T1-weighted MR arthrogram image of the hip shows the measurements that reveal an alpha angle of 70 degrees, which is greater than normal (55 degrees), consistent with a cam deformity. The osseous protuberance along the femoral head–neck junction is visible (arrow).
Occult Hip Fracture The osseous structure of the proximal femur includes both cortical and trabecular bone, and both are strongest when exposed to longitudinal force and weaker when exposed to tension and shear forces. Multiple vertically oriented compressive trabeculae radiate superiorly to the weight-bearing portion of the femoral head, while a second group of compressive trabeculae radiates obliquely from the lesser trochanter toward the greater trochanter. Multiple horizontally oriented tensile trabeculae run from the intertrochanteric region to the femoral head. It is these tensile trabeculae that are at increased risk of fracture due to tensile force, which places them at a greater risk of displacement, and thus necessitates surgical fixation [32].
Proper identification of an occult hip fracture is crucial, because a nondisplaced fracture can be stabilized with an intramedullary rod, thus sparing the hip joint, whereas an undiagnosed, nondisplaced fracture can eventually progress to a displaced fracture, which requires a hip arthroplasty. When there is strong clinical suspicion of a hip fracture because the patient is in severe pain, holding the leg in external rotation, and/or unable to bear weight, CT or MRI should be performed if the radiographs are negative. One study showed that 4.4% of patients in the emergency department with clinical suspicion of a hip fracture, but negative radiographs were proved to have an occult fracture on subsequent cross-sectional imaging (Fig. 59.17) [33]. MRI has the best sensitivity for nondisplaced fractures [34], although CT is often adequate, is easy to obtain, and can be used when there is a contraindication to MRI. Nondisplaced fractures are occasionally not detected on CT [35,36], although recent literature has shown that dualenergy CT increases sensitively for nondisplaced hip fractures by showing marrow edema at the occult fracture site [37].
FIGURE 59.17 Occult hip fracture. (A) Frontal radiograph of the pelvis is normal. MRI shows bone marrow edema (C, arrow) and linear, lowsignal (B, arrowhead) in the right femoral head and neck region, consistent with a nondisplaced fracture.
Insufficiency and Stress Fractures Patients with stress and insufficiency fractures of the hip may present with hip or groin pain that worsens with weight-bearing activity. Stress fractures occur in patients who experience an abnormal amount of stress on normal bone, such as long-distance runners, while insufficiency fractures occur with normal stress on abnormal (e.g., osteopenic) bone. The proximal femoral shaft is the most common site, and the fracture line is usually medial, as this is the area of greatest weight bearing. Radiographs exhibit a progression of bone injury, with focal periosteal reaction relatively early, sclerosis, and eventually a lucent fracture line.
Medial femoral neck buttressing, or cortical thickening with an overlying segment of smooth periosteal reaction, is in the differential diagnosis in the early phases of stress-related injury, although a fracture should not be seen; this process is thought due to altered hip mechanics [38]. MRI is the most sensitive technique and allows earlier diagnosis, before radiographic changes are visible (Fig. 59.18).
FIGURE 59.18 Coronal STIR MR image shows bone marrow edema in the medial, proximal left femur with linear, low signal (arrow) consistent with a fracture.
Bisphosphonate-related insufficiency fractures are a special category of proximal femoral fractures, which have been shown to occur in patients who underwent bisphosphonate therapy due to impaired bone remodeling in small numbers of patients [39]. These tend to be located along the lateral,
proximal femoral diaphysis with cortical thickening and possibly a visible fracture line [40] (Fig. 59.19).
FIGURE 59.19 Frontal radiograph of the pelvis shows bilateral, focal cortical thickening along with the lateral aspects of the femoral diaphysis in a patient who underwent bisphosphonate therapy. These were later shown to represent insufficiency fractures on MRI.
Avascular Necrosis Patients with avascular necrosis of the hip may present with hip or groin pain. Because the condition results from interruption of the blood supply with resulting necrosis of the marrow, medullary bone, and cortex, certain patients are predisposed, such as those with a history of steroid use, trauma, sickle cell anemia, alcoholism, radiation therapy, chemotherapy, and lupus. Avascular necrosis is commonly seen in the anterosuperior femoral head, as this is an area of relatively limited blood supply. Initially, radiographs can appear normal, with a crescentic subchondral lucency (Fig. 59.20) and/or mixed lucency and sclerosis sometimes appearing later in the course. The typical appearance on MRI is that of smooth, linear geographic signal abnormality, typically concave to the articular surface, with central fat and both low- and high-signal lines of demarcation (“double line sign”); there can be marrow edema, and eventual subchondral collapse/fracture is possible. A differential diagnosis could include a subchondral insufficiency
fracture, in which the fracture line on MRI tends to be irregular, disconnected to the cortex, and convex to the articular surface, transient osteoporosis of the hip, discussed in the next section, or stress reaction/fracture [41]. Table 59.9 lists the staging of imaging findings on both radiographs and MRI in the Ficat system, the most widely used categorization system; Fig. 59.21 shows the progression of MRI findings. The Mitchell classification system, based on MRI signal characteristics within the center of the lesion, is also used in some instances [42]. Contrastenhanced MRI can also help with evaluation, with decreased or nonenhancement in the area of avascular necrosis [43].
FIGURE 59.20 Frog-leg radiograph of the pelvis shows a crescentic, subchondral lucency (arrow) along with the superior femoral head, also known as the “crescent sign.”
Table 59.9 Ficat and Arlet Staging System for AVN of Hip
S t a g e
Radiographs/C T
MRI
Clinical Symptom s
0
Normal
Normal
None
1
Normal or minor osteopenia
Bone marrow edema
Pain
2
Sclerosis
Geographic signal abnormality (“double line sign”: adjacent low- and high-signal lines)
Pain and stiffness
3
Subchondral lucency (“crescent sign”) and flattening
Bone marrow edema, subchondral fracture/fluid
Pain radiating to knee, stiffness, limp
4
Femoral head collapse, evidence of osteoarthrosis
Bone marrow edema, femoral head collapse
Pain, stiffness, limp
(Adapted from Jawad MU, et al., Clin Orthop Relat Res 470 (9) (2012) 2636– 2639.)
FIGURE 59.21 Avascular necrosis. (A) Ficat stage 1: bone marrow edema seen in the subchondral region of the femoral head on this coronal PDFS MR image. (B) Ficat stage 2: coronal STIR MR image shows linear, geographic signal abnormality in the bilateral superior femoral heads (arrows) with central fat signal, as well as linear high and low signal, representing the “double line sign.” (C) Ficat stage 3: coronal PDFS MR image shows subchondral flattening/fracture of the femoral head superior articular surface with underlying marrow edema and fluid. (D) Ficat stage 4: coronal PDFS MR image shows marrow edema, flattening, and remodeling of the superior femoral head, consistent with collapse, with background avascular necrosis that is seen as faint geographic signal abnormality in the superior femoral head.
Depending on the size and location of the lesion, pharmacologic agents can be considered for treatment. Preservation of the femoral head might be attempted in younger patients without head collapse by using core decompression with bone grafts, bone morphogenic proteins, stem cells, or rotational osteotomies. When femoral head collapse is present, arthroplasty is the primary option [44]. Transient Osteoporosis of the Hip This entity was first described in patients in the third trimester of pregnancy, with onset of hip pain that resolves spontaneously after delivery, but this can also occur in nonpregnant patients. There is controversy as to the pathophysiology, with subchondral stress fracture as well as ischemia that does progress to necrosis offered as possible explanations, among others. Imaging findings include osteopenia of the femoral head on radiographs and CT and edema of the femoral head on MRI, mimicking AVN (Fig. 59.22). If post contrast sequences are obtained, the area of edema should enhance on postcontrast images in TOH, while in AVN these areas would show decreased or nonenhancement. TOH also typically spares the subchondral region of the femoral head. These findings and the patient’s symptoms should eventually resolve spontaneously with conservative management [45,46].
FIGURE 59.22 Transient osteoporosis of the hip. Coronal STIR (A) and axial T2-fat-saturated (B) MR images of the pelvis show marrow edema in the left femoral head (arrows) that resolved spontaneously on follow-up imaging.
Paget’s Disease of Bone Paget’s disease is a non-neoplastic condition that is characterized by abnormal bone remodeling. It can occur anywhere in the body, but the pelvis and proximal femur are common locations. It typically has three stages, as described in Table 59.10. There is often asymmetric involvement of the pelvis with cortical thickening, coarsened trabeculations, sclerosis, and acetabular protrusion. In the proximal femur, there can also be lateral bowing, possibly with the “blade of grass” sign, in which an area of subchondral lucency extends toward the diaphysis in a V-shape (Fig. 59.23) [47]. Although there is cortical thickening and sclerosis, it is essential to note that the bone structure is actually weakened from remodeling, which predisposes to fractures. Metastatic disease should be considered and excluded, especially given the mixed lytic and blastic appearance. There is a low (1%) risk of degeneration to osteosarcoma [48]. Table 59.10 Stages of Paget’s Disease of Bone Stage
Pathology
Early
Osteoclasts; active, lytic
Intermediate stage
Osteoblasts and osteoclasts; prominence of osteoblasts
Late stage
Osteosclerotic phase; inactive
FIGURE 59.23 Paget’s disease of the proximal femur. Frontal radiograph shows cortical thickening, coarse trabeculations, “blade of grass” sign (arrow), and an insufficiency fracture of the lateral cortex (arrowhead).
Fibrous Dysplasia Fibrous dysplasia is a non-neoplastic congenital process and is often asymptomatic, but can become symptomatic, such as with a pathologic fracture. As this lesion is classically identified as a “long lesion in a long bone,” it is most commonly seen in the pelvis in the proximal femur (Fig. 59.24); this is the second most common location in the body, after the ribs. Pathologically, there is replacement of normal bone with fibrous stroma and islands of immature, woven bone [47]. Radiographically, fibrous dysplasia appears as well-defined, bubbly lesion, sometimes with endosteal scalloping and cortical thinning, and there might be central ground-glass matrix and/or sclerosis. In the hip, a large lesion can cause bowing and coxa varus angulation referred to as a “shepherd’s crook” deformity.
FIGURE 59.24 Fibrous dysplasia. This patient has multiple lucent, well-defined lesions (arrows) in the proximal femur seen on this frog-leg radiograph, some of which show cortical thinning (arrowhead).
The differential diagnosis can be broad, as fibrous dysplasia has a variable appearance. Fibro-osseous lesions, such as a nonossifying fibroma, can sometimes have overlapping radiographic features, such as having multiple loculations, a well-defined rim, and peripheral sclerosis. Bone islands are another type of fibro-osseous lesion. However, these are typically distinguishable by their speculated margin and very dense sclerosis, which has been shown to have a mean attenuation over 885 Hounsfield units and a CT [49]. Summary of Teaching Points: Central Hip Region
◾ The hallmarks of OA are: osteophytes, joint space narrowing (asymmetric), subchondral sclerosis, subchondral cysts ◾ In inflammatory arthritis, joint space narrowing is typically concentric (symmetric) ◾
◾ A suspected native, septic hip is a true emergency; joint aspiration should be attempted as soon as possible. A negative radiograph does not exclude a septic joint
◾ Paralabral cysts are highly suggestive of the presence of a labral tear ◾ In FAI, repetitive microtrauma of bone on the labrum causes labral degeneration and tearing as well as cartilage degeneration and early OA of the hip
◾ Cam deformity refers to osseous protuberance at the anterosuperior femoral head–neck junction, while pincer deformity refers to acetabular over coverage; some patients have both (mixed-type FAI)
◾ If there is strong clinical suspicion of a hip fracture, but negative radiographs, MRI, or CT should be obtained ◾ Proximal femoral stress fractures appear as periosteal thickening, sclerosis, and possibly a linear lucency; these typically occur medially due to weight-bearing stress, with lateral injuries typical of patients with a history of bisphosphonate use
◾ Avascular necrosis appears as geographic signal abnormality with central fat and both high- and low-signal linear demarcation (“double line sign”)
◾ Transient osteoporosis of the hip will appear as marrow edema, which should spontaneously resolve ◾ Paget’s disease is due to abnormal bone remodeling and appears as cortical thickening and coarse trabeculations; weakened bone structure predisposes to fracture
Anterior Hip Region Tendons Tendinosis/Tendon Tear/Avulsion Injuries/Calcific Tendinosis: Tendon pathology in the anterior hip can present in several ways, including acute injury (tendon tear or avulsion) or chronic pain (tendinosis or chronic tear). Tendinosis appears as thickening and high signal within the tendon on
fluid-sensitive MRI sequences, or similarly as thickening and hypoechogenicity on US. A tendon tear will appear as a fluid-filled gap on MRI or a hypoechoic area on US with the absence of the normal fibrillary pattern. Tears can be partial-thickness, with disruption of only some of the tendon fibers, or full-thickness, in which all tendon fibers are torn. Tears can occur at the attachment site (typically referred to as “avulsions”), in the midportion of the tendon, or at the musculotendinous junction. Avulsion injuries can occur due to forceful muscular contraction. These are common in pediatric patients, in which they are a type of Salter–Harris I injury. These typically occur as a single event and cause acute pain, possibly with loss of function of the involved muscle. Initial radiographs can be normal, although if ossification has occurred, a displaced bone fragment can sometimes be seen. MRI is the most sensitive technique, as the soft-tissue findings of an avulsed tendon stump and marrow and soft-tissue edema are visible as well (Fig. 59.25) [30]. USG can also show the tendon injury with hypoechogenicity in the surrounding soft tissues, sometimes with a displaced osseous fragment. Displacement of the fragment by more than 2 cm is often treated surgically [50].
FIGURE 59.25 Rectus femoris avulsion. This coronal, fat-saturated, proton density MR image shows avulsion of the direct head of the rectus femoris tendon (arrow) from the anterior inferior iliac spine. A small osseous fragment (arrowhead) remains attached to the proximal tendon stump. There is surrounding soft-tissue edema.
Calcific tendinosis is another common type of tendon pathology in the pelvis and hips and will be discussed later. Snapping Hip There are multiple causes of a snapping hip, including extra-articular and intra-articular, with extra-articular being the most common. Extra-articular causes include soft-tissue structures sliding over osseous protuberances, such as the inter-tendinous iliopsoas tendon snapping or the iliotibial band, the gluteus maximus sliding over the greater trochanter, or the iliofemoral ligament snapping over the femoral head. Intra-articular causes would include such entities as labral tears or intra-articular bodies. USG is a useful evaluation tool given its ability to visualize tendons or ligaments during
patient movement, provided that the patient can recreate the snap. MRI is also useful, as it can confirm any intra-articular cause of a snapping hip [51]. Hernia Patients with lower abdominal/pelvic area hernias can present with groin or hip pain and/or a feeling of pressure or fullness in the hip area, which can prompt an imaging investigation. CT or MRI with and without valsalva can also help to identify hernias. USG is an excellent evaluation tool and allows dynamic imaging, repositioning of patient, and repeated attempts to elicit the hernia. Specific USG findings, such as fluid in the hernia sac, focal pain with transducer pressure, nonreduction of the hernia, or bowel content, suggest a more urgent clinical picture of obstructed hernia that might require immediate surgical intervention. Multiple types of hernias can be assessed, including umbilical hernias, spigelian hernias, indirect inguinal hernias, direct inguinal hernias, and femoral hernias. The locations, defined by the where the neck of hernia is present, are better depicted in Fig. 59.26.
FIGURE 59.26 Illustration of common hernia locations (in green). This perspective is that of the reader standing within the abdomen, looking in an anterior direction at the abdominal wall.
Pseudoaneurysm Vascular pathology can occur anywhere in the body, but one crucial entity in the hip region is a femoral artery pseudoaneurysm. This can happen after catheterization, usually when the puncture is too inferior. The
pseudoaneurysm appears as a rounded lesion, contained by a sac with a thin neck/connection to the vessel. Noncontrast CT will show an oval or spherical structure, possibly with high attenuation material adjacent to or within the sac. The contrast-filled sac should be visible on CTA, sometimes with thrombosis, which appears as low attenuation material. On USG, there is typically a to-and-fro pattern on spectral Doppler evaluation. Treatment is often image-guided and can include USG-guided compression, thrombin injection, stent placement, or surgery. Lymph Nodes Lymph nodes can be incidentally seen in the pelvic and inguinal region. The main chains are the common, internal, and external iliac, and inguinal. Lymph nodes that measure up to 1.5 cm in shortest dimension in the inguinal area and up to 1 cm in other sites are considered to be in the normal range [52]. Larger nodes, or nodes with abnormal morphology, such as the fatty hilum replacement, should be viewed as suspicious findings, and further imaging and/or biopsy may be warranted. Summary of Teaching Points: Anterior Hip Region
◾ Tendinosis appears as a thickening and high signal within the tendon on MRI or as hypoechogenicity on US ◾ US is an excellent technique to assess for lower abdominal/pelvic region hernias ◾ On US, pseudoaneurysm will appear as a to-and-fro pattern on spectral Doppler evaluation
Posterior Hip Region Hamstring Origin Region Pathology of the hamstring tendons is similar to the discussion above regarding the anterior hip region, but there are a few notable points. Hamstring tendon pathology can present clinically as hip or buttock pain, possibly with tenderness over the ischial tuberosity [18]. Injury to the hamstring tendons tends to occur when the hip is flexed and the knee is extended. Ischial bone stress-related injuries can show edema around the proximal hamstring tendon attachments on MRI, so it is important to distinguish this process from a true tendon injury.
The proximal hamstring attachment at the ischial tuberosity consists of the semimembranosus tendon anterolaterally and the conjoint tendon posteromedially. Conjoint tendon is a combination of the biceps femoris and semitendinosis fibers. The proximal semimembranosus tendon is more prone to tendinosis, which can chronically progress to tear, whereas the conjoint tendon is more prone to avulsion following trauma [53]. Of note, the “mini hamstring,” or ischiocondylar portion of the adductor magnus that has a tendinous attachment to the ischial tuberosity, is generally intact after a complete avulsion of the conjoint tendon, and should not be confused as representing an intact conjoint tendon [54]. The ischial tuberosity/proximal hamstring attachment area also contains the ischiogluteal bursa between the gluteus maximus and ischial tuberosity. Occupations that require prolonged sitting and/or excessive weight loss can predispose patients to ischiogluteal bursitis (Fig. 59.27), which can cause pain in the mid-buttock region. This is often termed “weaver’s bottom” because weavers could develop this condition due to many continuous hours of sitting at their job. The differential diagnosis includes a herniated lumbar disk and piriformis syndrome, which refers to a controversial clinical entity that includes a variety of piriformis muscle pathologies resulting in compression of the sciatic nerve and resulting symptoms [55]. Common causes attributed to piriformis syndrome include bulky piriformis (Fig. 59.28) an uncommon anatomic variation with sciatic nerve taking a deviant course through the piriformis muscle. USG or MRI can be useful in distinguishing these entities.
FIGURE 59.27 Ischiogluteal bursitis. Axial T2 fat-saturated (A) and T1 fat-saturated postcontrast (B) MR images show distention of the ischiogluteal bursa with layering fluid (A, arrow) and thin, peripheral postcontrast enhancement (B, arrowhead).
FIGURE 59.28 Piriformis syndrome. Axial T2 fat-saturated MR image shows thick and edematous right piriformis muscle (arrow) compared with left.
Nerves The sciatic nerve is located in the posterior hip region, exiting the pelvis through the greater sciatic foramen entering the gluteal region. “Sciatica” or
sciatic nerve pain is a common clinical problem in which patients have pain, tingling, or numbness in the buttock region, radiating down the posterior leg. This may be caused by compression or inflammation of the sciatic nerve. In some cases, the sciatic nerve will appear enlarged and/or edematous on MRI (Fig. 59.29), or there might be evidence of compression. Other possible abnormalities of the sciatic nerve include transection, which will appear on imaging as a discontinuity with swelling and/or nerve retraction. Because the sciatic nerve is intimately associated with the proximal hamstring attachments, hamstring injuries/tears can cause sciatic nerve damage and resulting symptoms [56]. In the setting of a proximal thigh amputation, sciatic neuromas can develop.
FIGURE 59.29 Axial T2 MR image shows thickened left sciatic nerve (arrow) due to post-traumatic tear of hamstring muscle (arrowhead).
Summary of Teaching Points: Posterior Hip Region
◾Ischiogluteal bursitis can occur due to prolonged sitting ◾ Posterior hip/buttock pain can be caused by sciatic nerve compression or inflammation; in some cases, there can be enlargement, edema, or compression seen on MRI
Medial Hip Region Athletic Pubalgia Athletic pubalgia is the term given to groin pain centered over the symphysis pubis region in athletes, and it can be due to a spectrum of injuries, as described later. The term “sports hernia” is misleading, as there is no true hernia present in this condition. Radiographs are helpful to evaluate the pubic symphysis for fracture and osseous irregularity, but MRI is helpful for the evaluation of soft-tissue injuries and bone marrow edema.
◾mechanical Osteitis pubis: This controversial entity is likely multifactorial and maybe a combination of and inflammatory processes involving the pubic symphysis and surrounding
muscle attachments. Radiographs show osseous irregularity (Fig. 59.30), which can progress to chronic remodeling and osteophyte formation, and there is typically marrow edema on both sides of the symphysis on MRI [57]. Patients can have true instability at symphysis, exacerbated by activity and sometimes made worse by pregnancy. Management is conservative. Rectus abdominis distal attachment injury: The distal fibers of the rectus abdominis muscle attach to the anteroinferior pubic bone, approximately 1-cm lateral to the symphysis. A tear in the attaching fibers can lead to a fluid-filled gap visible on MRI, best seen on sagittal images (Fig. 59.31); this is also known as the “superior cleft sign,” which appears as high signal on fluid-sensitive sequences that runs parallel to the inferior margin of the superior pubic ramus on coronal MRI [58]. The tear may extend inferiorly to involve the adductor muscle fibers. Bone marrow edema is also sometimes seen, but it tends to be anterior near the muscle attachment, not diffuse like in osteitis pubis. Adductor muscle injury: This may include chronic, degenerative tendinopathy or acute muscle tears or strains. Patients with adductor longus muscle injury tend not to have bone marrow edema or rectus abdominis insertional disorder. The “secondary cleft sign” refers to microtearing at the short adductor muscle segments and appears as high signal on fluidsensitive sequences along the inferior margin of the inferior pubic ramus seen on coronal MRI [58]. Muscle and/or tendon injuries typically respond to conservative measures.
◾ ◾
FIGURE 59.30 Osteitis pubis. Frontal radiograph of the pelvis shows osseous irregularity on both sides of the pubic symphysis.
FIGURE 59.31 Sagittal (A) and axial (B) proton density fat-saturated MR images show separation of the rectus abdominis aponeurosis from the pubic bone with intervening edema (arrow). There is an underlying marrow edema (arrowheads).
Adductor Insertion Avulsion/Thigh Splints “Thigh splints” refers to a painful condition in which there are repeated avulsive stresses to the adductor muscle attachments of the proximal to the mid femoral diaphysis. Radiographs can be normal, or periosteal reaction can be seen along the femur at the area of muscle attachment. On MRI, there might be soft-tissue edema in the adductor musculature or the adjacent bone (Fig. 59.32). The pain is often relieved with rest, and given that thigh splints might represent an early stage of osseous stress reaction/fracture, athletes with this condition must be cautious about continuing with training [59].
FIGURE 59.32 Thigh splints. Coronal STIR (A) and axial proton density fat-saturated (B) images of the left thigh show periosteal edema (arrows) along the proximal femoral diaphysis with underlying marrow edema.
Summary of Teaching Points: Medial Hip Region
◾ Athletic pubalgia refers to a spectrum of injuries that result in symphysis pubis pain; the term “sports hernia” is misleading ◾ A tear in the rectus abdominis aponeurosis can be seen as a fluid-filled cleft on MRI; sagittal images are typically the most revealing
◾ “Thigh splints” refers to repeated avulsive stress of the adductor muscle attachments at the femoral diaphysis; MRI will typically show periosteal edema
Lateral Hip Region Greater Trochanteric Pain Syndrome Patients who experience chronic pain and tenderness along the lateral hip may be given a clinical diagnosis of greater trochanteric pain syndrome, more commonly in women. Although this has often been equated with greater trochanteric bursitis, it is probably more often related to tendinosis and/or tears of the gluteal tendons, possibly in addition to bursitis, with similar imaging findings in regards to tendon pathology as described previously (Fig. 59.33). Other pathologic conditions that might contribute to symptoms at the greater trochanter include thickening of the proximal iliotibial band, which could snap over the greater trochanter.
FIGURE 59.33 Greater trochanteric pain syndrome. Axial (A) and coronal (B) proton density fat-saturated MR images show high signal and thickening of the gluteus minimus tendon (arrowheads) and fluid and synovial stranding in the greater trochanteric bursa (arrows).
Multiple bursas are surrounding the greater trochanter, and it is important to note that bursal distention with fluid is not equivalent to bursitis. Bursitis indicates an inflammatory or infectious process, with synovial thickening and irregularity plus fluid on MRI and USG, with USG also showing hyperemia. Management of greater trochanteric pain syndrome is typically conservative, targeting the specific reason for pain.
Calcific Tendinosis Calcific tendinosis is another entity that can affect tendons about the pelvis and hips. This occurs due to the deposition of calcium hydroxyapatite in the tendon fibers. Although it can occur anywhere in the body, the hip tendons that are more likely to be affected include the reflected head of the rectus femoris along superolateral and Gluteus maximus attachment over the posterior proximal femur. Patients can present with acute, severe pain and tenderness around the greater trochanter, which can mimic lumbar radiculopathy, although the pain can also be chronic. On radiographs, there may be calcification in the expected location of a tendon, and these can appear hazy, fluffy, or amorphous in the resorptive (acute) stage of the disease or homogeneous and well defined in the formative/calcific (chronic) stage [60]. Calcifications within the tendon can also be seen on USG or MRI. USG-guided aspiration/lavage (or “barbotage”) can be used for treatment, in which a needle is repeatedly inserted into the calcification with an injection of saline or lidocaine solution. Lateral Femoral Cutaneous Nerve Syndrome Lateral femoral cutaneous nerve syndrome, or “meralgia paresthetica,” is characterized by lateral and anterior thigh-burning, tingling, and numbness, often worsening with standing, walking, hip extension, and lying prone. The course of the nerve is variable. Typically it has a horizontal intrapelvic course along the anterior aspect of the iliacus muscle, courses vertically into the subcutaneous tissues at the level of the inguinal ligament, and branches into the subcutaneous tissues of the upper thigh. When there is clinical suspicion of nerve injury or entrapment, USG can be used for further evaluation. This may show nerve swelling and hypoechogenicity at the entrapment site, most commonly at the inguinal ligament–anterior superior iliac spine junction, which becomes symptomatic with transducer pressure [61]. Summary of Teaching Points: Lateral Hip Region
◾ Greater trochanteric pain syndrome is likely more often related to gluteal tendinopathy, sometimes in addition to trochanteric bursitis
◾ Bursal distention is not equivalent to bursitis; synovial thickening in addition to fluid and hyperemia on US, are suggestive of bursitis
◾ US-guided aspiration/lavage (“barbotage”) can be used to treat calcific tendinosis, which is most commonly seen involving the
gluteal or rectus femoris tendons in the hips
Sacrum Insufficiency Fractures One common type of pathology seen in the sacrum is insufficiency fractures. These often present in an elderly patient with back pain, and an insufficiency fracture might not be clinically suspected. Osteopenia is a significant risk factor, as are before radiation, steroid use, and rheumatoid arthritis. Radiographs can be negative or show vague, roughly linear sclerosis in the location of the fracture. MRI is the best technique for identifying insufficiency fractures, and they appear as linear/band-like low signal intensity on T1-weighted images, with surrounding edema on T2-weighted images (Fig. 59.34) [62]. The fracture lines in the sacrum usually parallel the sacral aspect of the SI joint, although occasionally, there is also a horizontally oriented band (Fig. 59.35) shows common sites in the sacrum, pelvis, and hips). Bone scans can also help identify these fractures, with radiotracer uptake sometimes taking on the “Honda sign,” in which uptake at the fracture sites appears similar to the “H” in the brand’s logo (Fig. 59.36).
FIGURE 59.34 Sacral insufficiency fracture. Coronal T1-weighted (A) and STIR (B) MR images of the pelvis show bone marrow edema in the left sacrum (B) with linear, low signal on both sequences (arrows).
FIGURE 59.35 Common sites of insufficiency fractures in the pelvis/sacrum and hips. The site in the lateral proximal femoral diaphysis is associated with bisphosphonate use, as described in the text.
FIGURE 59.36 “Honda sign” seen on technetium-99m diphosphonate bone scan. Insufficiency fractures in the sacrum, with two vertical lines laterally and a horizontally oriented line in the middle, cause radiotracer uptake (outlined in white) that appears similar in configuration to the brand’s “H” logo.
Osteomyelitis Osteomyelitis can occur in any area of the body, but it often affects the sacrum and pelvis in bedridden patients with pressure ulcers. On imaging, skin ulcers and/or surgical incisions can help guide the radiologist to the underlying osseous involvement. On radiographs, osseous erosion is the key finding to suggest osteomyelitis, and an overlying gas-filled tract leading from the skin surface to the bone is a helpful finding. MRI is typically used both for confirmation and to look for soft-tissue complications, such as abscess, fistula, and cellulitis. Osteomyelitis is confirmed when there is true marrow replacement underlying a known ulcer/soft-tissue infection; this will appear as a signal lower than skeletal muscle on T1-weighted images and higher than muscle on T2-weighted images. Post contrast enhancement of
the marrow in this region is helpful, but not necessary, finding to confirm osteomyelitis (Fig. 59.37). Marrow signal changes, such as edema and enhancement, without marrow replacement is suspicious for early osteomyelitis if there is an overlying infection. A tagged WBC scan can be used to confirm osteomyelitis if the patient cannot get an MRI done.
FIGURE 59.37 Sacral osteomyelitis. Sagittal T1-weighted (A) and T1weighted fat-saturated postcontrast (B) MR images show marrow replacement at the tip of the residual coccyx (A, arrow) consistent with osteomyelitis. There is also postcontrast enhancement in this area (B, arrowhead); note that the diagnosis can be made with the A image alone.
Summary of Teaching Points: Sacrum
◾ Sacral insufficiency fractures can be seen in osteopenic patients; they are often not clinically suspected ◾ MRI allows excellent evaluation of osteomyelitis and softtissue complications ◾ Marrow signal changes, even without marrow replacement, is suspicious for early osteomyelitis in the setting of overlying softtissue changes
Arthroplasties Hip arthroplasty is a common procedure, and there are many different types of surgical hardware. Radiographs are the first-line study and help detect hardware complications, fractures, and infection (Fig. 59.38). CT without contrast and with metal suppression technique can help evaluate suspected component malposition, particle disease, and other pathology (Fig. 59.39). MRI can also be used to detect particle disease, infection, and surrounding abnormalities. To reduce metal susceptibility artifact, MR imaging should utilize intermediate-weighted, fast SE pulse sequences. These sequences provide high-resolution images, fluid sensitivity, and high contrast-to-noise ratio to show periprosthetic tissue and bone. If an infection is suspected, imaging evaluation with radiographs followed by contrast-enhanced CT or MRI should be performed. Aspiration may be needed to confirm infected fluid. In-111 WBC and Tc-99m sulfur colloid scan can also be used to detect infection [63,64].
FIGURE 59.38 Complication of hip arthroplasty. Frontal radiograph of the pelvis shows bilateral total hip arthroplasties. The femoral head component on the left is superiorly located consistent with liner wear, and there are multiple osseous and metallic fragments in the soft tissues.
FIGURE 59.39 Sagittal reconstruction of a noncontrast CT performed with metal suppression protocol, showing a lucent lesion causing cortical thinning (arrow) at the tip of the femoral stem component of the hip arthroplasty. Without metal suppression technique, this lesion might have been more difficult, or even impossible, to see.
There are several main types of hip arthroplasties and many different brands and variations. Total hip arthroplasty involves replacing both the acetabulum and femoral head, while with a hemiarthroplasty, only the femoral head and neck are replaced. Total hip arthroplasties typically have a head and an acetabular liner, often made of polyethylene. Some are fixed with screws or cement, while others are cementless with a porous coating for bone ingrowth. Table 59.11 lists the most common types, with example images and primary descriptors [65]. Table 59.11
Common Types of Hip Arthroplasties Hemi
Total
Resurfacing
Femoral head/nec k
Replaced
Replace d
Replaced
Acetabul um
Native
Replace d
Replaced (surface only)
Clinical indicatio n
Femoral neck fracture
Osteoart hrosis
Young patients, preserves bone stock
Image
Common Postoperative Complications
◾ Periprosthetic fracture
◾
⚬ Incidence as high as 18%, during or after surgery ⚬ The calcar is a frequent site of intra-operative periprosthetic fracture in cementless total hip arthroplasty [66] ⚬ Risk factors: bone resorption, osteolysis, implant loosening, osteoporosis, trauma ⚬ Radiographs are a first-line study (Fig. 59.40) ⚬ On MRI, look for edema in marrow and cortex, fracture line, periosteal thickening ⚬ Potential mimic: edema from reaming, which causes a periprosthetic high signal that can persist for months Instability and dislocation ⚬ Loosening is seen as lucency on radiographs or CT surrounding the hardware; lucency measuring greater than 2 mm in thickness is usually considered clinically significant ⚬ A thin fibrous layer, appearing as a lucency of 1–2 mm, often forms at the bone– hardware interface and is considered normal if stable (after 1–2 years) and in some regions of the prosthesis ⚬ Classification systems help to identify, which areas are involved with lucency/loosening; note that these are targeted for radiographic evaluation Acetabular region: De Lee and Charnley system [63] Zones I, II, and III adjacent to acetabular component (Fig. 59.41A) Zone I (superolateral acetabulum) commonly shows a lucency Zones II (medial) and III (inferomedial) typically should not show lucencies Femoral region: Gruen zones [67] Zones 1–7 surrounding the femoral component (Table 59.12) (Fig. 59.41B) Common to see lucency in zone 1, or occasionally in zone 7 Lucency in zones 2–6 should be viewed with suspicion ⚬ Risk factors: component malposition, implant design, surgical approach, abductor mechanism, extent of soft-tissue dissection at surgery ⚬ High integrity of posterior joint capsule and musculature can be protective Adverse local tissue reaction ⚬ Umbrella term to describe reactions to arthroplasty-related metal products (metallosis) and reactive tissue inflammation (synonymous with pseudotumor) ⚬ Often resembles type IV hypersensitivity reaction ⚬ Can cause aggressive soft-tissue destruction ⚬ Poor correlation between symptoms and metallic ion levels in the blood ⚬ Prevalence may be as much as 39–66% Hematoma formation Synovitis Infection Heterotopic ossification Nerve injury
◾ ◽ ◽ ◽ ◾ ◽ ◽ ◽
◾ ◾ ◾ ◾ ◾ ◾
FIGURE 59.40 Frontal radiograph of the hip shows an oblique, periprosthetic fracture through the proximal femoral diaphysis.
FIGURE 59.41 Classification systems for the evaluation of loosening on postarthroplasty radiographs. De Lee and Charnley acetabular (A) and Gruen femoral (B) zones help to evaluate and describe areas of lucency on postoperative radiographs.
Table 59.12 Gruen Zones or Radiographic Changes Diagnostic of Loosening of the Femoral Component After Total Hip Arthroplasty Zo ne
Area of Proximal Femur
1
Superolateral (involving greater trochanter)
2
Midlateral femur
3
Inferolateral femur
4
Distal tip
5
Inferomedial femur
6
Midmedial femur (includes lesser trochanter)
7
Superomedial (includes calcar)
Summary of Teaching Points: Arthroplasties
◾Radiographs are first-line imaging study, but CT with metal
suppression can help further to evaluate hardware and the surrounding bone and soft tissues
◾ Lucency greater than 2 mm in thickness surrounding the hardware is suggestive of clinically significant loosening. De Lee and Charnley (acetabular) and Gruen (femoral) zones help evaluate and describe the perihardware areas of lucency radiographically
◾ Resurfacing arthroplasty is favored in young patients to preserve bone stock ◾ Postoperative complications include periprosthetic fracture, instability/dislocation, and adverse local tissue reaction Summary of Imaging Evaluation of the Hip Structure/pathology
Preferred investigation
Secondary option
Occult fracture
MRI
CT
Tendon pathology (e.g., tendinosis)
MRI or US
Labral tear
MR arthrography
MRI
Arthritis
Radiograph
MRI or CT
Stress fracture
Radiograph, MRI
Bone scan
FAI
CT, radiographs
Snapping hip
US
Bursitis
MRI or US
Insufficiency fracture
MRI
Bone scan or CT
Hip arthroplasty—no infection
Radiographs
CT, MRI
Structure/pathology
Preferred investigation
Secondary option
Hip arthroplasty— infection
Radiographs, aspiration
In-111 WBC and Tc-99m sulfur colloid
Conclusion/Overall Approach Imaging of the hip allows the radiologist to evaluate the patient’s anatomy and a myriad of pathological conditions. Fig. 59.42 shows an overall approach to the imaging evaluation of hip pain.
FIGURE 59.42 Flowchart that shows imaging workup of hip pain.
Suggested Readings • CA Petersilge, Chronic adult hip pain: MR arthrography of the hip, Radiographics 20 (Suppl_1) (2000) S43–S52 [Internet]. • DR Armfield, JD Towers, DD Robertson, Radiographic and MR imaging of the athletic hip, Clin Sports Med 25 (2) (2006) 211–239. • H Mulcahy, FS Chew, Current concepts of hip arthroplasty for radiologists: parts 1 and 2, AJR 199 (3) (2012) 559–569 and 570–580. • TM Hegazi, JA Belair, EJ McCarthy, JB Roedl, WB Morrison, Sports injuries about the hip: what the radiologist should know, Radiographics 36 (6) (2016) 1717–1745.
• S Lim, Y Park, Plain radiography of the hip: a review of radiographic techniques and image features, Hip Pelvis 27 (3) (2015) 125–134. • M Tannast, KA Siebenrock, SE Anderson, Femoroacetabular impingement: radiographic diagnosis – what the radiologist should know, AJR 188 (6) (2007) 1540–1552.
References [1] JA Stevens, RA Rudd, The impact of decreasing U.S. hip fracture rates on future hip fracture estimates, Osteoporos Int 24 (10) (2013) 2725–2728, [Internet]. [2] ML Wolford, K Palso, A Bercovitz, Hospitalization for total hip replacement among inpatients aged 45 and over: United States, 2000–2010. NCHS Data Brief 186 (2015 Feb) 1–8. [3] MS Silva, AR.C Fernandes, FN Cardoso, CH Longo, AY Aihara, Radiography, CT, and MRI of hip and lower limb disorders in children and adolescents, Radiographics 39 (3) (2019 May–June) 779–794. [4] CY Chang, AJ Huang, MR Imaging of normal hip anatomy, Magn Reson Imaging Clin N Am (2013) 1–19.. [5] CA Myers, BC Register, P Lertwanich, L Ejnisman, WW Pennington, JE Giphart, et al., Role of the acetabular labrum and the iliofemoral ligament in hip stability: an in vitro biplane fluoroscopy study, Am J Sports Med 39 (Suppl_1) (2011) 85S–91S, [Internet]. [6] M Tsutsumi, A Nimura, K Akita, New insight into the iliofemoral ligament based on the anatomical study of the hip joint capsule, J Anat 236 (5) (2020) 946–953, [Internet]. [7] DF DuBois, IM Omar, MR imaging of the hip: normal anatomic variants and imaging pitfalls, Magn Reson Imaging Clin N Am 18 (2010) 663–674. [8] CA Petersilge, Chronic adult hip pain: MR arthrography of the hip, Radiographics 20 (Suppl_1) (2000) S43–S52, [Internet]. [9] NV Bardakos, RN Villar, The ligamentum teres of the adult hip, J Bone Joint Surg Br 91 (2009) 8–15. [10] K Ito, MA Minka, M Leunig, S Werlen, R Ganz, Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset, J Bone Joint Surg Br 83 (2) (2001) 171–176, [Internet]. [11] PD Fabricant, KG Fields, SA Taylor, E Magennis, A Bedi, BT Kelly, The effect of femoral and acetabular version on clinical outcomes after arthroscopic femoroacetabular impingement surgery, J Bone Joint Surg Am 97 (2015) 537–543. [12] CL Andrews, From the RSNA refresher courses. Radiological Society of North America. Evaluation of the marrow space in the
adult hip, Radiographics (2000), Oct; 20 Spec No:S27-42. [13] S Delaunay, RG Dussault, PA Kaplan, BA Alford, Radiographic measurements of dysplastic adult hips, Skeletal Radiol 26 (2) (1997) 75–81, [Internet]. [14] S Monazzam, JD Bomar, K Cidambi, P Kruk, H Hosalkar, Lateral center-edge angle on conventional radiography and computed tomography hip, Clin Orthop Relat Res 471 (7) (2013) 2233–2237, [Internet]. [15] TR Yochum, LJ Rowe, Essentials of Skeletal Radiology, third ed., Lippincott Williams & Wilkins, Philadelphia, 2005, p. 1373. [16] MR Schmid, HP Nötzli, M Zanetti, TF Wyss, J Hodler, Cartilage lesions in the hip: diagnostic effectiveness of MR arthrography, Radiology 226 (2) (2003) 382–386. [17] RM Seldes, V Tan, J Hunt, M Katz, R Winiarsky, RH Fitzgerald, Anatomy, histologic features, and vascularity of the adult acetabular labrum, Clin Orthop Relat Res 382 (2001) 232–240. [18] LW Bancroft, DG Blankenbaker, Imaging of the tendons about the pelvis, AJR Am J Roentgenol 195 (2010) 605–617. [19] T Ruangchaijatuporn, K Gaetke-Udager, JA Jacobson, CM Yablon, Y Morag, Ultrasound evaluation of bursae: anatomy and pathological appearances, Skeletal radiol, 2017, 445–462. [20] JA Jacobson, V Khoury, CJ Brandon, Ultrasound of the groin: techniques, pathology, and pitfalls, Am J Roentgenol 205 (3) (2015) 513–523, [Internet]. [21] S-J Lim, Y-S Park, Plain radiography of the hip: a review of radiographic techniques and image features, Hip Pelvis 27 (3) (2015) 125 [Internet]. [22] WM Ricci, C Mamczak, M Tynan, P Streubel, M Gardner, Pelvic inlet and outlet radiographs redefined, J Bone Joint Surg Am 92 (10) (2010) 1947–1953, [Internet]. [23] RV O’Toole, G Cox, K Shanmuganathan, RC Castillo, CH Turen, MF Sciadini, et al., Evaluation of computed tomography for determining the diagnosis of acetabular fractures, J Orthop Trauma 24 (5) (2010) 284–290, [Internet]. [24] PI Mallinson, TM Coupal, PD McLaughlin, S Nicolaou, PL Munk, HA Ouellette, Dual-energy CT for the musculoskeletal system, Radiology 281 (3) (2016) 690–707. [25] ZS Rosenberg, S Shankman, GC Steiner, DK Kastenbaum, A Norman, MG Lazansky, Rapid destructive osteoarthritis: clinical, radiographic, and pathologic features, Radiology 182 (1) (1992) 213–216, [Internet].
[26] SR Hess, RS O’Connell, CP Bednarz, AC Waligora, GJ Golladay, WA Jiranek, Association of rapidly destructive osteoarthritis of the hip with intra-articular steroid injections, Arthroplast Today 4 (2) (2018) 205–209, [Internet]. [27] A Tiwari, Y Karkhur, JA Keeney, A Aggarwal, Rapid destructive osteoarthritis of the Hip after intra-articular steroid injection, Arthroplast Today 4 (2) (2018) 184–186, [Internet]. [28] I Amber, S Mohan, Preventing overdiagnosis of acetabular labral “tears” in 40-plus-year-old patients: shouldn’t these be called labral “fissures” instead?, Acad Radiol 25 (3) (2018) 387–390, [Internet]. [29] JC McCarthy, PC Noble, MR Schuck, J Wright, J Lee, The role of labral lesions to development of early degenerative hip disease, Clin Orthop Relat Res, 2001, 25–37, Philadelphia. [30] TM Hegazi, JA Belair, EJ McCarthy, JB Roedl, WB Morrison, Sports injuries about the hip: what the radiologist should know, Radiographics 36 (6) (2016) 1717–1745, [Internet]. [31] A Pacheco-Carrillo, I Medina-Porqueres, Physical examination tests for the diagnosis of femoroacetabular impingement. A systematic review, Phys t sport 21, 2016, 87–93. [32] SE Sheehan, JY Shyu, MJ Weaver, AD Sodickson, B Khurana, Proximal femoral fractures: what the orthopedic surgeon wants to know, Radiographics 35 (5) (2015) 1563–1584, [Internet]. [33] S Dominguez, P Liu, C Roberts, M Mandell, PB Richman, Prevalence of traumatic hip and pelvic fractures in patients with suspected hip fracture and negative initial standard radiographs – a study of emergency department patients, Acad Emerg Med 12 (4) (2005) 366–369, [Internet]. [34] MW Kirby, C Spritzer, Radiographic detection of Hip and pelvic fractures in the emergency department, Am J Roentgenol 194 (4) (2010) 1054–1060, [Internet]. [35] E Eggenberger, G Hildebrand, S Vang, A Ly, C Ward, Use of CT vs. MRI for diagnosis of hip or pelvic fractures in elderly patients after low energy trauma, Iowa Orthop J 39 (1) (2019) 179–183, [Internet]. [36] JC Mandell, MJ Weaver, B Khurana, Computed tomography for occult fractures of the proximal femur, pelvis, and sacrum in clinical practice: single institution, dual-site experience, Emerg Radiol 25 (3) (2018) 265–273. [37] TT Kellock, S Nicolaou, SS.Y Kim, S Al-Busaidi, LJ Louis, TW O’Connell, et al., Detection of bone marrow edema in nondisplaced hip fractures: utility of a virtual noncalcium dual-energy CT application, Radiology 284 (3) (2017) 798–805, [Internet].
[38] T Dixon, J Benjamin, P Lund, A Graham, E Krupinski, Femoral neck buttressing: a radiographic and histologic analysis, Skeletal Radiol 29 (10) (2000) 587–592, [Internet]. [39] TA Einhorn, Y Bogdan, P Tornetta, Bisphosphonate-associated fractures of the femur: pathophysiology and treatment, Orthopaed Trauma 28 (2014) 433–438, [cited 2020 Aug 10]. [40] A Saleh, VV Hegde, AG Potty, JM Lane, Bisphosphonate therapy and atypical fractures, Orthop Clin North Am 44 (2013) 137–151. [41] T Yamamoto, Subchondral insufficiency fractures of the femoral head, Clin Orthop Surg 4 (2012) 173–180. [42] DG Mitchell, VM Rao, MK Dalinka, CE Spritzer, A Alavi, ME Steinberg, et al., Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings, Radiology 162 (3) (1987) 709–715, [Internet]. [43] BJ Manaster, From the RSNA refresher courses: adult chronic hip pain: radiographic evaluation, Radiographics 2000 Oct;20 Spec No:S3–S25. [44] CG Zalavras, JR Lieberman, Osteonecrosis of the femoral head: evaluation and treatment, J Am Acad Orthop Surg 22 (2014) 455– 464. [45] C Mourad, P Omoumi, J Malghem, BC Vande Berg, Conventional radiography of the hip revisited: correlation with advanced imaging, Magn Reson Imaging C Am 27, 2019, 661–683. [46] KN Malizos, AH Zibis, Z Dailiana, M Hantes, T Karahalios, AH Karantanas, MR imaging findings in transient osteoporosis of the hip, Eur J Radiol 50 (3) (2004) 238–244, [Internet]. [47] JL Bloem, II Reidsma, Bone and soft tissue tumors of hip and pelvis, Eur J Radiol 81 (12) (2012) 3793–3801, [Internet]. [48] MR Wick, GP Siegal, KK Unni, RA McLeod, HG Greditzer, Sarcomas of bone complicating osteitis deformans (Paget’s disease). Fifty years’ experience, Am J Surg Pathol 5 (1) (1981) 47–59, [Internet]. [49] A Ulano, MA Bredella, P Burke, I Chebib, FJ Simeone, AJ Huang, et al., Distinguishing untreated osteoblastic metastases from enostoses using CT attenuation measurements, AJR Am J Roentgenol 207 (2) (2016) 362–368. [50] S Esser, D Jantz, MF Hurdle, W Taylor, Proximal rectus femoris avulsion: ultrasonic diagnosis and nonoperative management, J Athl Train 50 (7) (2015) 778–780, [Internet]. [51] V Pelsser, É Cardinal, R Hobden, B Aubin, M Lafortune, Extraarticular snapping hip, Am J Roentgenol 176 (1) (2001) 67–
73, [Internet]. [52] DM Koh, M Hughes, JE Husband, Cross-sectional imaging of nodal metastases in the abdomen and pelvis, Abdom Imaging 31 (6) (2006) 632–643, [Internet]. [53] RM Degen, Proximal hamstring injuries: management of tendinopathy and avulsion injuries, Curr Rev Musculoskelet Med 12 (2019) 138–146. [54] SM Broski, NS Murthy, AJ Krych, MR Obey, MS Collins, The adductor magnus “mini-hamstring”: MRI appearance and potential pitfalls, Skeletal Radiol 45 (2) (2016) 213–219, [Internet]. [55] EE Vassalou, P Katonis, AH Karantanas, Piriformis muscle syndrome: a cross-sectional imaging study in 116 patients and evaluation of therapeutic outcome, Eur Radiol 28 (2) (2018) 447– 458, [Internet]. [56] TJ Wilson, RJ Spinner, R Mohan, CM Gibbs, AJ Krych, Sciatic nerve injury after proximal hamstring avulsion and repair, Orthop J Sport Med 5 (7) (2017) 1–8. [57] AC Zoga, EC Kavanagh, IM Omar, WB Morrison, G Koulouris, H Lopez, et al., Athletic pubalgia and the “sports hernia”: MR imaging findings, Radiology 247 (3) (2008) 797–807. [58] CA Byrne, DJ Bowden, A Alkhayat, EC Kavanagh, SJ Eustace, Sports-related groin pain secondary to symphysis pubis disorders: correlation between MRI findings and outcome after fluoroscopyguided injection of steroid and local anesthetic, Am J Roentgenol 209 (2) (2017) 380–388, [Internet]. [59] MW Anderson, PA Kaplan, RG Dussault, Adductor insertion avulsion syndrome (thigh splints): spectrum of MR imaging features, Am J Roentgenol 177 (3) (2001) 673–675, [Internet]. [60] DS Siegal, JS Wu, JS Newman, JL del Cura, MG Hochman, Calcific tendinitis: a pictorial review, Can Assoc Radiol J 60 (5) (2009) 263–272. [61] CN Petchprapa, ZS Rosenberg, LM Sconfienza, CF.A Cavalcanti, R la Rocca Vieira, JS Zember, MR imaging of entrapment neuropathies of the lower extremity: part 1. The pelvis and hip, Radiographics 30 (4) (2010) 983–1000, [Internet]. [62] SK Brahme, V Cervilla, V Vint, K Cooper, K Kortman, D Resnick, Magnetic resonance appearance of sacral insufficiency fractures, Skeletal Radiol 19 (7) (1990) 489–493, [Internet]. [63] J Fritz, B Lurie, TT Miller, HG Potter, MR imaging of hip arthroplasty implants, Radiographics 34 (4) (2014) E106–E132. [64] BN Weissman, CJ Palestro, M Appel, SJ Baccei, JT Bencardino, IB Fries, MG Hochman, JA Jacobson, DN Mintz, GW Mlady, MD
Murphey, JS Newman, ZS Rosenberg, DA Rubin, Small KM EP on MI. ACR appropriateness criteria imaging after total hip arthroplasty, Am Coll Radiol (2015) 24. [65] H Mulcahy, FS Chew, Current concepts of hip arthroplasty for radiologists: part 1, features and radiographic assessment, AJR Am J Roentgenol 199 (2012) 559–569. [66] SS.A Miettinen, TJ Mäkinen, I Kostensalo, K Mäkelä, H Huhtala, JS Kettunen, et al., Risk factors for intraoperative calcar fracture in cementless total hip arthroplasty, Acta Orthop 87 (2) (2016) 113–119, [Internet]. [67] PA Banaszkiewicz, Modes of failure of cemented stem-type femoral components: a radiographic analysis of loosening, Classic Papers in Orthopaedics, Springer-Verlag, London Ltd, 2014, 35–38, [Internet].
Chapter 60
Knee Amit Kumar Sahu The knee joint is the body’s largest synovial joint. Normal knee joint contains less than 5 mL of fluid. Given its significant role in ambulation, it is vulnerable to various mechanical injuries, internal derangements, and osteoarthritis. Knee instability and pain is a common presenting complaint in athletes and nonathletes alike; as well as in young and old. Imaging also has a crucial complementary role to clinical examination in a large number of nontraumatic pathologies associated with the knee joint. The radiograph is the primary imaging technique in most pathology. Ultrasonography (USG) is a readily available technique that is helpful in assessing joint effusion, pathologies of large tendons, and ligaments around the knee, and in guiding intervention. It is gaining a more significant presence in the imaging algorithm. Magnetic resonance imaging (MRI) stands as the gold standard imaging
technique for most of the soft tissue and marrow pathologies. CT has an essential role in assessing fractures.
Overview of the Function of the Knee Joint The knee joint comprises predominantly of the weight-bearing femorotibial articulation and the patellofemoral articulation. The latter creates a frictionless transfer over the knee of the forces generated by contraction of the quadriceps femoris muscle. In 10% of cases, the knee joint space communicates with the proximal tibiofibular joint [1]. Movements in the knee joint include flexion, extension, internal, and external rotation. Abduction and adduction movements are limited and can only be achieved in a flexed knee. Any degree of abduction and adduction in an extended knee is considered to be sign of knee laxity. In a large part, the knee joint’s stability is maintained by the capsule, intrinsic ligaments and tendons.
Muscles producing movements of the knee are as follows:
◾ Flexion—biceps femoris, semitendinosus, and semimembranosus assisted by the gracilis, sartorius, and popliteus (and with the foot on the ground, the gastrocnemius and plantaris) Extension—quadriceps femoris, assisted by the tensor fasciae latae Medial rotation of the flexed leg—popliteus, semimembranosus, and semitendinosus assisted by the sartorius and gracilis Lateral rotation of the flexed leg—biceps femoris
◾ ◾ ◾
Anatomy Osseous and articular anatomy: The three bones forming the knee joint are the femur, tibia, and patella. The knee joint primarily has two components, femorotibial and patellofemoral (Fig. 60.1).
Figure 60.1 Diagrammatic representation of osseous components of the knee joint demonstrating various ligament attachments. The distal end of the femur has a large, oval medial condyle, and a small circular lateral condyle, separated by the intercondylar region. There are two small bony projections on either side of the distal femur condyles, called the medial and lateral epicondyles. Superior to the medial epicondyle lies
the adductor tubercle, which provides the attachment site for the tendinous part of the adductor magnus muscle. The anterior aspect of the distal femur has a saddle-shaped patellar surface called trochlear groove, forming the patellofemoral articulation. The patella is an oval-shaped sesamoid bone embedded within the tendon of quadriceps femoris. It has no direct role in the weight bearing of the knee joint. The articular surface of the patella is oval and is separated into smaller, more vertical medial, and larger more horizontal lateral facets by a vertical ridge. This vertical ridge fits into the corresponding trochlear groove in the anterior aspect of the femur. Contact between the patellar articular facets and femur varies with different positions of knee. During forced extension of the knee joint, the patella has a tendency to be displaced laterally, given the more horizontal orientation of the lateral facet. The patellar tendon is the inferior continuation of the quadriceps tendon and attaches to the tibial tuberosity. It is also called patellar ligament, as it extends between two bones.
The proximal tibia has an oval medial tibial condyle with its long axis in the sagittal plane and the circular and the smaller lateral tibial condyle. This topography helps in internal rotation of the femur on the fixed tibia as the knee approaches extension. Between the tibial condyles is the intercondylar area, which, from anterior to posterior, serves as attachments to
◾ anterior root ligament of the lateral meniscus; ◾ anterior cruciate ligament (ACL); ◾ anterior root ligament of the medial meniscus; ◾ posterior root ligament of the lateral meniscus; ◾ posterior root ligament of the medial meniscus; and ◾ posterior cruciate ligament (PCL).
Capsular and Synovial Anatomy The articular capsule of the knee joint consists of a thick outer fibrous capsule and a thin inner synovial membrane. The knee joint is a common joint space that is subdivided by synovial membranes into several interconnected compartments. Synovial recesses are extensions of the synovial membrane
between different anatomical structures that reduce friction during the motion of these structures (Fig. 60.2).
Figure 60.2 Diagrammatic representation of articular capsule attachment and recesses around the knee joint. The anatomy of anterior, medial, lateral, and central structures is discussed separately under individual sections later in this chapter.
Imaging Protocols Radiograph
Radiograph is the primary technique for all knee imaging. Basic radiographic views and their purpose are mentioned in Table 60.1. Table 60.1 Basic Radiographic Views of Knee Views Purpose AP view (weight bearing)
Axial view or sunrise view (30–45 degrees flexion)
Patella position, patellofemoral joint space, peripheral bony erosions in patella
Intercondylar view
Intercondylar space, tibial plateau fracture
Note: Additional views which can be obtained for patella and patellofemoral joint are Skyline Merchant view (superior-inferior projection of the patella in
supine position) and Skyline Laurel view (inferiorsuperior projection of the patella in semirecumbent position).
USG Protocol Localized evaluation of a different anatomical aspect of knee is done in both long and short axes (Table 60.2). Table 60.2 Basic Imaging Protocol of USG Knee Protoco Structures Evaluated l Anterior Extensor mechanism (quadriceps knee tendon, patella, and patellar tendon), patellar retinaculum, suprapatellar joint (patient recess, medial and lateral joint recesses, supine, anterior knee bursae, and femoral knee articular cartilage flexed 30 degrees)
Protoco l
Structures Evaluated
Medial knee (patient supine, knee full extensio n)
Medial collateral ligament, the body and anterior horn of the medial meniscus, and the pes anserine tendons (sartorius, gracilis, and semitendinosus)
Lateral knee (patient supine, knee full extensio n)
Iliotibial band, lateral collateral ligament, biceps femoris, common peroneal nerve, popliteus, and body and anterior horn of the lateral meniscus
Protoco l
Structures Evaluated
Posterio Baker cyst, the posterior horns of the r knee menisci, posterior cruciate ligament, and (patient the popliteal neurovascular bundle prone, knee full extensio n)
All reformats should include entire field of view of the source images. a
◾ Positioning: Patient supine, knee being imaged is centered in the scanner ◾ Field of view must include: Entire patella, both femoral condyles, and proximal tibia to just past the fibular head. In the case of a metal prosthesis, scan the entire length of the femoral and tibial components Practical indication of the CT scan of the knee is in the evaluation of fractures. In metal prosthesis, projection-based metal artifact reduction (MAR) algorithms are used to better evaluate the hardware and the periprosthetic bone
◾
MRI Protocol
Position
◾ Supine with feet first ◾ Position the knee in knee coil in 15-degree flexion with cushion below the knee for stability. In unavailability of knee coil, flex coil can be used ◾ Center the laser beam localizer over the lower border of patella
Although the imaging protocols for knee vary substantially across institutions the objectives remain the same. A representative MR knee protocol may include some combination of the following sequences (this is only a guide as protocols depend on institutional preferences and local practices) (Table 60.4). Table 60.4 Basic Imaging Protocol of MRI Knee Sequence Purpose
Sequence
Purpose
PDFS coronal
Synovial pathologies; meniscal tear; collateral ligaments; tendon pathologies; femoral and tibial articular cartilage; and cystic lesions around the knee
PDFS sagittal
Cruciate ligament pathologies; meniscal tear; quadriceps and patellar tendons
T1 characteristics of any incidental bone or soft-tissue lesion; avulsion fractures; intra-articular bodies
T2 FS Meniscal root tear; fat-saturation helps coronal reveal fluid, marrow edema, fat pad (optional) edema, bursitis, parameniscal cyst Gradient Calcification and hemorrhage (optional) Pre and Synovitis, osteomyelitis, tumors Postcontr ast T1 FS (optional)
MR arthrography of the knee is an invasive procedure that is done by injecting diluted gadolinium contrast into the joint followed by MR imaging. Although not a routine protocol, it is used for the detection of osteochondral lesions and evaluation of postoperative meniscus in current practice. MR cartigram is used to evaluate the articular cartilage. It uses quantitative cartilage imaging techniques such as T2 mapping sequences to detect changes in the water and collagen content and the three-dimensional ultrastructure of cartilage.
Effusion Joint Effusion Physiological fluid is noted in synovial joints, not sufficient to distend the joint cavity. Accumulation of excess fluid within the joint is called synovial effusion and leads to distention of synovial joint recess.
Imaging Features Radiograph: Properly obtained lateral radiograph of the knee is sensitive for detecting effusion. It is appreciated as distention of the suprapatellar joint recess, leading to separation of the suprapatellar and prefemoral fat pads by more than 5 mm [2] (Fig. 60.3).
Figure 60.3 Joint effusion versus synovitis. (A and B) Joint effusion: lateral view radiograph shows distension of the suprapatellar space (asterisk) separating suprapatellar fat pad (white arrow) from prefemoral fat pad (back arrow). Axial PDFS MR image showing excess fluid in the knee joint cavity (asterisk in B) with smooth synovium (arrowhead). (C) Synovitis: sagittal PDFS MR image showing excess fluid in suprapatellar recess (asterisk) with thickening of
the synovium (arrowhead). (D) Axial postcontrast T1FS image of a different patient shows diffuse central enhancement (white arrow). USG and MRI are equally sensitive in detecting synovial effusion. On USG, fluid is anechoic, compressible, and displaceable on dynamic evaluation. No intrinsic vascularity is seen. USG is also useful in guiding the aspiration of fluid both for diagnostic as well as therapeutic purposes. MRI is an excellent technique for assessment, given its sensitivity to fluid and fat. MRI signal will vary depending on fluid, blood, or fat content of the synovial fluid. Both effusion and synovitis can have low signal intensity on T1 and high signal intensity on T2-weighted images (Fig. 60.3). Administration of contrast (gadolinium) is often necessary to tell the difference between synovitis and effusion.
Hemarthrosis and Lipohemarthrosis
The presence of blood in the synovial cavity is termed hemarthrosis. Lipohemarthrosis denotes the presence of marrow fat and blood in the synovial cavity, often a consequence of fracture. This may take 3 hours to appear after trauma. Fat component in the synovial fluid represents seepage of marrow fat (from femur or tibia) into the joint due to fracture, ligament avulsion, or osteochondral abnormality [3]. Other causes of hemarthrosis include:
Imaging Features Radiograph often cannot differentiate between synovial effusion and hemarthrosis or lipohemarthrosis. However, if a lateral view (erect or supine trans-lateral) is obtained after 5–10 minutes of
the patient lying down, fat–fluid levels can be seen in lipohemarthrosis (Fig. 60.4).
Figure 60.4 Lipohemarthrosis. Radiograph lateral view (A), Axial PDFS MR image (B) and USG (C) in supine position of a traumatic knee showing distension of suprapatellar recess with three-layer appearance of superficial fat (white arrow), middle serum (white arrowhead), and deep red cells (black arrow). There is fracture of tibial plateau (black arrowheads in A). USG can differentiate between fat and blood. Fat is seen as echogenic nondependent globules within the synovial fluid and blood appears as floating echoes or as dependent echogenic sediment (Fig. 60.4). MRI: Three-layer fluid–fluid levels are seen consisting of nondependent marrow fat in the top layer, plasma serum in the middle layer, and
dependent blood cells (erythrocytes and leucocytes) in the most dependent portion forming the deepest layer (Fig 60.4). Acute hemorrhagic effusion (7 days) will have low signal intensity on both T1- and T2weighted images due to hemosiderin deposition.
Synovial Pathologies Synovitis Synovitis is the inflammation of the synovium, which causes hyperplasia of the synovial lining. It can be focal or diffuse and can lead to the appearance of frond-like projections into the synovial cavity. It is essential to differentiate between joint effusion and synovitis for treatment.
Imaging Features
A radiograph cannot usually differentiate between joint effusion and synovitis. USG: Areas of synovial hyperplasia can be seen as thick and echogenic synovium with increased color uptake on Doppler study. USG-guided synovial biopsy is performed in the case of nonconclusive imaging features. MRI holds some advantage in differentiating these two conditions. Synovitis and effusion can coexist. Synovitis is seen as an intermediate signal on T1 as against low signal in joint effusion. T2 signal is higher in synovitis than in joint effusion. Synovitis demonstrates diffuse postcontrast central enhancement (Fig. 60.3), while joint effusion may show peripheral enhancement.
Synovial Plicae These are band-like structures that are remnants of synovial tissue from early development and are normally seen in 90% of arthroscopies [4]. These are usually of no consequence but become symptomatic
when thickened (>2 mm) and then are called as plica syndrome. Commonly seen plicae in adults are:
Common causes of plica syndrome are trauma, strenuous exercise, osteochondritis dissecans, injuries to the meniscus, and intra-articular bodies. Patient usually presents with dull, aching pain aggravated by flexion; clicking sensation without locking or giving way; palpable or audible snap on knee movement.
Imaging Features Normal or thickened plica is seen in CT and MRI as a band-like fibrous structure (Fig. 60.5). Thickened plica may be asymptomatic while symptomatic plica may show secondary signs of erosions in condyles and patellar cartilage and associated joint effusion may also be present.
Figure 60.5 Medial patellar plica syndrome. Axial PDFS MR image showing a thick dark band of tissue (arrowhead) in the medial patellar recess extending from periphery to deep into the joint cavity. Joint effusion is also present (arrow). Treatment: Chronically thickened and symptomatic plicae are resected surgically, usually arthroscopically.
Synovial and Ganglion Cysts
Baker’s cyst or popliteal cyst is the most common synovial cyst of the knee with a true synovial lining. It is seen in medial popliteal fossa and communicates with the joint through a small neck between the tendons of the medial head of gastrocnemius and semimembranosus (Fig. 60.6). Other synovial cysts are located beneath the popliteus tendon and in between the tendons of the lateral head of gastrocnemius and biceps femoris.
Figure 60.6 PDFS MR images showing synovial and ganglion cysts. (A) Baker’s cyst: cystic lesion (white arrow) is seen in medial popliteal fossa having superficial and deep extension through a neck in between the tendons of medial head of gastronemius (white arrowhead) and semimembranosus (asterisk). (B) Periarticular ganglion cyst: lobulated cystic lesion (white arrow) is seen in proximal tibio-fibular joint with intraosseous extension (black arrow) into
the lateral tibial plateau. (C) Intra-articular ganglion cyst: lobulated and septated cystic lesion (arrow) in the infrapatellar location. (D) Ruptured Baker’s cyst: fluid tracking in the myofascial plane (white arrow) of calf region. Periarticular ganglion cyst is most commonly located close to the proximal tibio-fibular joint (Fig. 60.6) and may cause compression to the common peroneal nerve. They may arise from muscle bundles or tendon sheaths. Intra-articular ganglion cyst is rare, and two common sites are alar folds in the infrapatellar region and around cruciate ligaments (Fig. 60.6) [5]. They can have intraosseous extension into the femur or tibia and are called intraosseous ganglion cysts. The ganglion cyst in infrapatellar location may cause severe pain and mimic meniscal tear.
Imaging Features Radiograph can appreciate localized soft-tissue swelling if the cyst is large. Sometimes calcified
bodies can be seen within the Baker’s cyst. USG can identify localized fluid-filled sacs around the knee joint. MRI helps in detecting the communication of the cysts with the joint cavity. Ruptured Baker’s cyst can be identified as fluid tracking into the myofascial plane of the calf region (Fig. 60.6) and muscle edema. MRI is also sensitive in detecting small ganglion cysts and intraosseous extension of the ganglion cysts. Treatment: Most of these cysts are treated conservatively. Chances of recurrence prevail in surgical resection if the primary etiology, such as arthritis, is not treated. Tumor and tumor-like lesions of the synovium are discussed in the chapters on tumors (Chapter 62), tumor-like conditions (Chapter 63), and in arthritis (Chapter 52).
Bursitis
Bursa is a normal fluid-filled, sac-like structure present around large joints to decrease the friction between adjacent mobile structures. The bursae around the knee are demonstrated in Fig. 60.7. Inflammation of the bursa is called bursitis.
Figure 60.7 (A) Locations of bursitis around the knee. Prepatellar (house maid’s knee)— between the patella and overlying subcutaneous tissue. Superficial infrapatellar (Clergyman’s knee)—between tibial tubercle and overlying subcutaneous tissue. Deep infrapatellar— between the posterior aspect of the patellar tendon and the tibia. Suprapatellar—between the quadriceps tendon and the femur. Pes anserine—between the pes anserine tendons and the subjacent distal portion of the tibial collateral ligament and the bony surface of the medial tibial condyle. Medial collateral ligament—between the superficial and deep
layers of the medial collateral ligament. Iliotibial—between the distal part of the iliotibial band near its insertion on Gerdy tubercle and the adjacent tibial surface. (B and C) Prepatellar bursitis: Radiograph lateral view (B) shows large soft-tissue swelling anterior to the patella (white arrow). Axial PDFS MR image (C) shows large cystic lesion anterior to the patella with thick walls (black arrow) and internal intermediate signal fluid (asterisk). Common causes are trauma, infection, overuse, hemorrhage, collagen vascular disease, inflammatory arthropathy, and occupational. Patient usually presents with swelling and pain at a localized site. Superadded infection may, at times, present with localized erythema and hyperemia.
Imaging Features Radiograph can demonstrate localized soft-tissue swelling.
USG shows thick-walled, anechoic, or occasionally septated and fluid-filled sac at specific locations. MRI shows localized fluid signal with thick walls and occasionally internal septae (Fig. 60.7). Signs of inflammation include soft-tissue edema around the bursa. Blooming on gradient sequence indicates hemorrhage within the bursa. Treatment: USG-guided aspiration with simultaneous injection of steroid has promising results. Large recurrent bursitis may be surgically removed and has a low recurrence rate.
Impingement of the Fat Pads Around the Knee Joint The fat pads around the knee joint are located between the joint capsule and synovium. Impingement and friction involving these fat pads have different etiologies based on location (Table 60.5). Commonly they present with anterior knee pain. Table 60.5
Fat Pad Impingement Around the Knee Joint and Its Causes Suprapatellar Developmental cause related to the (quadriceps) anatomy of the extensor fat pad mechanism or maybe related to impingement abnormal mechanics Infrapatellar fat pad impingement (Hoffa’s disease)
Single or repetitive traumatic episodes. There is inflammation of the fat pad, which later becomes hypertrophied and predisposes to impingement [6]
Patellar tendon— lateral femoral condyle fat pad impingement syndrome
Overuse injury, with the patellar tendon chronically rubbing against the lateral femoral condyle and compressing the lateral aspect of Hoffa’s fat pad. Patellar maltracking (lateral subluxation) or malalignment (patella alta) is usually an associated finding [7]
Pericruciate fat pad impingement (inflammatio n of the fat
The cause is uncertain but is thought to be related to impingement of pericruciate fat pad during knee flexion, for example, squatting in weight lifters
pad posterior to the posterior cruciate ligament)
Imaging Features MRI demonstrates a focal area of high signal on T2 and PDFS images within the fat pad locations (Fig. 60.8). Fluid, calcification, and hemorrhage can be seen and there can be surrounding soft-tissue edema.
Figure 60.8 Young patients with anterior knee pain due to fat pad impingement. White arrows demonstrating edema in the fat pads. (A) Suprapatellar fat pad impingement. (B) Infrapatellar
fat pad impingement (Hoffa’s disease). Edema is also seen in inferior pole of patella (arrowhead). (C) Patellar tendon—lateral femoral condyle fat pad impingement syndrome. Asterisk marks the patellar tendon. Treatment: Conservative management is the choice, along with modified weight bearing.
Chondral and Osteochondral Abnormalities Anatomy: Articular hyaline cartilage is composed primarily of collagen and proteoglycans. Histologically, it is organized into four layers: superficial, transitional, deep (radial), and calcified layers. The deepest calcified cartilage layer is located at the interface with the subchondral bone plate. The compact subchondral bone and calcified cartilage are collectively termed the subchondral plate. Pathology: Several conditions may manifest as chondral and osteochondral lesions of the knee, a
localized abnormality of the articular cartilage, subchondral marrow, and subchondral bone [8].
Imaging Features Radiographs: Cartilage loss can be determined in weight-bearing compartments adequately as reduced joint space, but are less reliable for nonweightbearing compartments. Subchondral bony irregularity, cystic changes, and sclerosis can be appreciated in osteochondral pathologies. Separated bone fragments from parent articular margin can be appreciated in unstable osteochondral dissecans (Fig. 60.9).
Figure 60.9 PDFS MR coronal images showing chondral and osteochondral abnormalities. (A) Acute osteochondral fracture. Subchondral bone plate depression (arrow) with surrounding marrow edema in medial femoral condyle (B) subchondral insufficiency fracture. Subchondral incomplete fracture (arrowhead) with surrounding diffuse marrow edema (arrow) in medial femoral condyle. (C) Primary osteonecrosis. Well-marginated subchondral geographical areas (arrows) in femoral condyles. (D and E) Osteochondral dissecans.
Radiograph shows a small separated bone fragment along the articular margin of medial femoral condyle (arrow in D). MRI of different patient shows subchondral cyst with overlying articular cartilage thinning (arrow in E). USG assessment for articular cartilage is limited to assess the cartilage and is not practically indicated. However, in full flexion, the articular cartilage of the femoral condyles and trochlea can be evaluated for decreased thickness and focal defects in the cartilage. MRI: MRI is the technique of choice for imaging articular cartilage. Table 60.6 describes the MRI findings of different pathologies leading to osteochondral lesions (Fig. 60.9). Table 60.6 MRI Appearance of Pathologies Causing Osteochondral Lesions Pathologies MRI Appearance
Pathologies
MRI Appearance
Acute osteochondral fracture
Subchondral marrow edema, osteochondral fracture, subchondral bone plate depression, articular surface disruption and fragmentation, or a combination of these features
Subchondral insufficiency fracture; previously known as spontaneous osteonecrosis of the knee (SONK)
Marrow edema immediately subjacent to subchondral bone plate; incomplete subchondral fracture; focal depression in subchondral bone plate; fluid-filled cleft underlying the subchondral bone plate
Primary osteonecrosis (avascular necrosis)
Subchondral geographical area marginated by double-line in T1, T2, and PDFS images
Pathologies
MRI Appearance
Osteochondral dissecans: most common location is the lateral (intercondylar) aspect of the medial femoral condyle. There is separated and detached osteochondral fragment
MRI signs of instability of osteochondral dissecans lesion:
◾ high-signal-intensity rim at the interface
between the fragment and the adjacent bone on T2weighted images
◾ fluid-filled cysts beneath the lesion ◾ a high-signal-intensity line extending through the articular cartilage overlying the lesion
◾ focal osteochondral defect filled with joint fluid, indicating complete detachment of the fragment
Pathologies
MRI Appearance
Osteoarthritis (see details in Chapter 52)
Varied thickness cartilage loss; subchondral bone changes (cysts, compression, and sclerosis)
Intra-Articular Bodies Various structures of origin of intra-articular bodies are seen depending on the etiology. They can be seen in any synovial joint, but the knee joint is probably the most common site. Causes
Imaging Features Radiograph shows discrete foci of calcification, usually less than 5 in number and less than 1 cm in size. Noncalcified bodies are missed in radiographs and are well seen on MRI. In primary synovial osteochondromatosis, more than five bodies of uniform size can be seen (Fig. 60.10).
Figure 60.10 Intra-articular bodies. (A) Radiograph lateral view of an osteoarthritic knee shows a large calcified intra-articular body (arrow) in suprapatellar space. PDFS MR sagittal image (B) of the same patient shows isoto hypointense body (arrow) with joint effusion (asterisk). (C) Primary synovial osteochondromatosis. Radiograph lateral view shows multiple uniform size bodies (arrow) in
posterior knee space having central dense area and peripheral lucent rim. USG can successfully demonstrate large bodies as hypoechoic structures within the synovial fluid. MRI is sensitive in identifying calcified and noncalcified bodies in the presence of joint effusion. Filling defects can be seen within the effusion (Fig. 60.10). Treatment: Symptomatic bodies are removed arthroscopically if needed.
Meniscus Anatomy The menisci (medial and lateral) are semilunar, wedge-shaped fibrocartilagenous structures placed between the articular surfaces of femoral condyles and tibial plateaus. Their function is to provide stability to the joint by absorbing shock, distributing axial load, assisting in joint lubrication, and also in facilitating nutrient distribution [9].
Both menisci are stabilized by the transverse ligament. The meniscocapsular ligaments including the meniscofemoral and meniscotibial ligaments attach the menisci to the posterior femur and posterior tibial plateau. The lateral meniscus is stabilized by the coronary ligament, meniscofemoral ligament, arcuate ligament, and meniscotibial ligament (Fig. 60.11). If any of these supporting ligaments or the meniscus itself degenerates or is torn, the meniscus may become unstable.
Figure 60.11 Diagrammatic representation of inferior knee through superior view
demonstrating normal anatomy of meniscus and various ligaments attached to the menisci. Both menisci have anterior horn, body, posterior horn, and roots. Only the periphery of the meniscus remains vascularized in adults (called “red zone”), occupying 15% of the meniscus [10]. Tears that occur within the meniscus’ red zone are more likely to heal than those in the avascular, “white zone.”
Anatomical Variation in Meniscus
Discoid Meniscus It is the congenital variable enlargement of the meniscus body, often with thickening of the meniscus. Seen in 3% of knees and is 10–20 times more common in the lateral than in the medial meniscus [11]. Usually asymptomatic but are prone to cystic degeneration and tear. On MRI, the body of discoid meniscus measures 15 mm or more on a midline coronal image and sagittal MR images. The body of meniscus is seen in three or more contiguous slices (Fig. 60.12).
Figure 60.12 (A) Discoid lateral meniscus. There is thickening of the lateral meniscus (arrow) as seen in the coronal PDFS MR image of a 28-year male. (B) Meniscal flounce. Wavy appearance of the free inner edge of the medial meniscus (arrow) seen in sagittal PDFS MR image. (C) Meniscal ossicle. Focal calcification seen as hyperintense signal in posterior horn of medial meniscus (arrow) in sagittal T1 MR image.
Meniscal Flounce Wavy appearance of the free inner edge of the meniscus on coronal and sagittal MR images (Fig. 60.12). This is secondary to flexion of the knee where the free edge of the meniscus is redundant. It
is more common in the medial meniscus and it may mimic a radial tear in coronal MR images.
Meniscal Ossicle This is a focus of calcification or ossification seen with a predilection for the posterior horn of medial meniscus (Fig. 60.12). It may be developmental, degenerative, or post-traumatic. On radiographs, the ossicle can be mistaken for an intra-articular body, while at MR imaging, its increased signal intensity can mimic a tear.
Pathologies of Meniscus A tear is the most common pathology encountered in the meniscus. Developmental, inflammatory, infectious, neoplastic, and metabolic pathologies also affect the meniscus.
Meniscal Tears
Two common categories of pathologies responsible for meniscal tears are traumatic and degenerative. As it is difficult to differentiate between the two, categorization is based on clinical history, age of patient, gross morphology of the meniscus, and secondary imaging findings. Meniscal tear is defined as linear intrameniscal signal that contacts the superior, inferior or free articular margins of the meniscus or if there is a defect in the normal shape of the meniscus. Once the tear is identified, the description of the tear should be documented to categorize it into specific type. There are different terminologies used for meniscal tear classification, without consensus. However, the common classification of meniscal tears is based on the direction of tear [11]:
◾ Horizontal (parallel or oblique) ◾ Longitudinal vertical ◾ Radial
For general consideration: Longitudinal tears and less commonly, horizontal oblique tears are traumatic in nature. Degenerative tears are typically horizontal
cleavage lesions that generally occupy the posterior half of the menisci. Clinical presentation
◾ Joint pain (at the joint line) ◾ Giving way on walking ◾ Clicking on movement ◾ Joint effusion ◾ Locking (which may occur immediately after displacement of a meniscal fragment) ◾ Pseudolocking (secondary to hamstring muscle spasms)
Imaging Features Radiograph is not useful in the diagnosis of meniscal injuries. However, it may be indicated in elderly patients to obtain a differential diagnosis of osteoarthritis, which often develops in association with meniscal degeneration. AP and lateral radiographs may show joint space narrowing in clinically symptomatic meniscal injury. A radiograph
can also exclude unsuspected lesions such as osteochondritis or intra-articular bodies. CT is less sensitive in diagnosing meniscal tears. However, CT arthrography provides an accurate diagnosis of meniscal and cartilage injuries in patients who cannot undergo MRI. USG is not a routine test for meniscal imaging. Secondary signs such as extrusion and parameniscal cyst can be detected. Therapeutic USG-guided aspiration is performed in the symptomatic parameniscal cysts. MRI is the gold standard in diagnosing meniscal tears. It also helps in the evaluation of associated injuries, complications, and the postoperative meniscus. MRI characteristics of pathological meniscus [12] include: (A) Alteration in signal: Normal meniscus is characterized by low signal intensity on all sequences. Abnormal high signal on T2 and PDFS images is graded as shown in Fig. 60.13.
Figure 60.13 MRI grading of meniscus signal represented by arrows in sagittal PDFS images. (A) Grade 1—nonarticular focal or globular intrasubstance increased signal intensity. This signal correlates with early meniscal degeneration. Myxoid or hyaline degeneration are both used to describe these signal alteration. (B) Grade 2—horizontal, linear intrasubstance increased signal intensity usually extending from the capsular periphery of the meniscus without involving an articular meniscal surface. (C) Grade 3—area of increased signal intensity communicating or extending to at least one articular surface. Grade 3 signal is considered to be meniscal tear and a meniscus may contain multiple areas of grade 3 signal intensity.
(B) Alteration in morphology: Normal morphology of a meniscus is triangular with a sharp central tip apparent in both the coronal and sagittal planes (bowtie configuration). This triangular configuration is distorted in tear. Indirect signs of meniscal tear:
◾ Subchondral bone marrow edema beneath a meniscus in the absence of meniscectomy ◾ Presence of a parameniscal cyst ◾ Meniscal extrusion (when the meniscus is >3 mm outside the peripheral margin of the tibial plateau)
Nuances in the diagnosis of meniscal tear [12]
◾ Two-slice-touch rule: If intrameniscal signal contacts the meniscus surface on two or more images, there is 90–96% likelihood that a meniscal tear would be identified at arthroscopy. The signal to the surface must be in the same area of the meniscus on the two images, but one image can be in the coronal plane and other in the sagittal plane Meniscal Fraying is not a typical tear and may involve the free edge of the meniscus. This may
◾
appear as ill-defined margin of meniscus with horizontal signal alteration on one or two sequential MR images (sagittal or coronal) Mimics of meniscal tears Normal anatomical variations:
◾ Anterior transverse meniscal ligament of the knee ◾ Oblique meniscomeniscal ligaments of the knee ◾ Lateral inferior genicular artery ◾ Popliteus tendon ◾ Meniscofemoral ligaments ◾ Bursa of the medial collateral ligament (MCL) ◾ Tibial attachment site of the ACL ◾ Meniscal root ligaments
Physiological appearance:
◾ Meniscal flounce
Horizontal Tear
It runs parallel or oblique to the tibial plateau, contacts the articular surface(s) or the central free edge, and extends toward the periphery, dividing the meniscus into superior and inferior halves (Fig. 60.14). It usually occurs in patients older than 40 years in the setting of underlying degenerative joint disease. However, horizontal oblique tears can be post-traumatic. Typical MRI appearance is a horizontally oriented line of high signal intensity that contacts the meniscal surface or free edge. Parameniscal cyst (Fig. 60.15) formation is associated with complete horizontal tears that extend to the periphery, presumably secondary to direct communication with the joint fluid.
Figure 60.14 Types of meniscal tear based on direction of tear as indicated by arrows. Diagrammatic representation (first row), sagittal (B, D) and axial (F) PDFS MR images (second row) showing tear in posterior horn of medial meniscus in three different patients. (A and B) Horizontal oblique tear, (C and D) longitudinal vertical tear, and (E and F) radial tear.
Figure 60.15 Sagittal PDFS MRI image shows horizontal tear of posterior horn of medial meniscus (white arrow) with parameniscal cyst formation (black arrow).
Longitudinal Vertical Tear It runs perpendicular to the tibial plateau and parallel to the long axis of the meniscus and divides the meniscus into central and peripheral halves (Fig. 60.14). Unlike horizontal or radial tears, pure longitudinal tears do not involve the free edge of the meniscus. Often occur in younger patients after knee trauma and usually involve the peripheral third of the meniscus and posterior horns. Typical MRI appearance is a vertically oriented line of high signal intensity that contacts one or both articular surfaces. They usually involve the peripheral red zone and occur in posterior horn. There is a close association between peripheral longitudinal tear of either or both menisci and ACL tear. Longitudinal vertical tear of the peripheral capsular attachment of the posterior horn of the medial
meniscus at the meniscocapsular junction is termed as Ramp lesion. This lesion most frequently occurs in the setting of a pivot shift mechanism of injury. It is possibly due to disruption of the meniscotibial ligaments, or as a result of a tear of the peripheral attachment of the posterior horn of the medial meniscus.
Radial Tear It runs perpendicular to both the tibial plateau and the long axis of the meniscus and extends from the free edge toward the periphery (Fig. 60.14). In contrast to horizontal and longitudinal tears, radial tears disrupt the meniscal hoop strength, resulting in a dramatic loss of function and possible meniscal extrusion. These commonly involve the posterior horn of the medial meniscus or the junction of the anterior horn and body of the lateral meniscus. Surgical repair is usually not considered because they are located within the avascular “white zone.” MRI signs of radial tear:
◾
◾ Truncated meniscus represents a truncation of the free edge, with preservation of its peripheral portion, often due to a partial-thickness tear ◾ Ghost meniscus has no in-plane residual normal meniscus, often as a result of a fullthickness tear ◾ Marching cleft: tear that appears to progress away from the free edge on contiguous MR images and is seen in the junction of the horn and body (obliquely oriented to both coronal and sagittal planes) On coronal MR images, if the cleft is within the body, it results from a longitudinal tear. If the cleft is within the horn, it is the result of a radial tear. The opposite combination holds true on sagittal MR images.
Root Tear It is typically a radial-type tear and has received increased recognition in recent years, partially because of its previous underdiagnoses at both MR imaging and arthroscopy. On coronal MRI, if the root
is not seen over its respective tibial plateau on at least one image, tear is suspected (Fig. 60.16). On sagittal MRI, if the posterior root of the medial meniscus is not detected just medial to the PCL, a root tear should be suspected. Complete root tears have a high association with meniscal extrusion, mainly when the tear occurs in the medial meniscus. When an ACL tear is present, there is an increased incidence of lateral root tears.
Figure 60.16 PDFS MR images demonstrating different types of meniscal tear. (A) Root tear:
there is tear at the posterior root attachment of medial meniscus (white arrow) as seen in coronal image. (B) Complex tear: sagittal image showing tears in horizontal (black arrow) as well as in vertical orientation (white arrow). (C) Displaced tear: tear of the posterior horn of medial meniscus with posterior displacement of the torn fragment (white arrow) as seen in sagittal image. (D–F) Bucket-handle tear of the medial meniscus leading to PCL (black arrow in D) and centrally migrated meniscus fragment (white arrow in D) seen parallel to each other (double PCL appearance) on sagittal image. Coronal image shows torn fragment displaced in intercondylar notch (white arrow in E). Sagittal image shows double anterior horn (white arrow in F) and small posterior horn (black arrow in F) resulting in absent of normal bow-tie configuration.
Complex Tear It includes radial, horizontal, and longitudinal components (any two or all three). Often the
meniscus appears fragmented, with the tear extending in more than one plane (Fig. 60.16).
Displaced Tear Displaced tears are categorized into: free fragments, displaced flap tears, and bucket-handle tears. Small free fragments and flaps can be missed at arthroscopy, and retention of a meniscal flap often results in persistent pain and potential knee locking. Flap tears occur more frequently in the medial meniscus. In two-thirds of cases, fragments are displaced posteriorly, near or posterior to the PCL; in the remaining cases, fragments course into either the intercondylar notch or superior recess (Fig. 60.16).
Bucket-Handle Tear It is a longitudinal tear with central migration of the inner “handle” fragment. This tear pattern occurs more frequently in the medial meniscus.
◾
MRI signs of bucket-handle tear (Fig. 60.16):
◾ Absent normal bow-tie configuration ◾ Torn fragment within the intercondylar notch ◾ Double PCL appearance (PCL and centrally migrated meniscus fragment are seen parallel to each other on sagittal image) ◾ Double anterior horn or flipped meniscus ◾ Disproportionally small posterior horn A bucket-handle tear of the lateral meniscus can rarely manifest with a double ACL sign, where the fragment is located just posterior to the ACL. Mimics of the above signs:
◾ Absent bow-tie configuration: small meniscus; pediatric patient; radial tear of the body; macerated meniscus; or previous partial meniscectomy ◾ Double PCL sign: prominent ligament of Humphry; meniscomeniscal ligament; or intercondylar osseous bodies
Treatment: Principles of treatment focus on meniscal conservation, selective intervention, only intervening if there are symptoms of locking, displaced fragment, or potential for displacement. Surgical options
include open meniscal repair, meniscectomy, and meniscal transplantation.
Postoperative Appearance and Complications of the Meniscus The postoperative evaluation of partial meniscectomies and primary repair offers unique challenges in diagnosing a retear or persistent tear or normal healing response to the meniscal fibrocartilage. Attenuated but intact meniscus without any cleft rules out re-tear or persistent tear. Intrinsic signal abnormality can persist for few weeks as a normal healing response. Signs of re-tear include [13]:
◾ Displaced meniscal fragment(s) ◾ Increased signal intensity on PDFS or T2weighted images at a new location or site relative to the repair (Fig. 60.17)
Figure 60.17 Re-tear in repaired meniscus in a 25-year male seen as high signal intensity in the posterior horn of medial meniscus reaching inferior articular margin (arrow) in sagittal PDFS MR image.
Cruciate Ligaments
The anterior and posterior cruciate ligaments are intracapsular extra synovial structures being enveloped by a synovial fold. Generally, PCL is longer and stronger than ACL.
Anterior Cruciate Ligament
Anatomy ACL is proximally attached to a fossa on the posterior aspect of the medial surface of the lateral femoral condyle and distally to the tibial intercondylar eminence. Its tibial attachment is stronger than femoral attachment. It has two groups of fascicles:
◾ the anteromedial bundle is longest in flexion and resists anterior displacement of the tibia in flexion ◾ posterolateral bundle is longest in extension and resists hyperextension.
It is the primary restraint to anterior displacement of tibia; secondary restraint to internal tibial rotation in
full extension and minor restraint to varus-valgus angulation in full extension.
Mechanism of Injury Classic mechanism of injury is pivot-shift injury where there is indirect trauma related to deceleration, hyperextension, or twisting forces, which is frequently seen in skiers and American football players. Other mechanisms involve dashboard injury (applied force to anterior proximal tibia with knee in flexion); hyperextension injury (direct force applied to the anterior tibia with a planted foot); clip injury (contact injury secondary to pure valgus stress to a partially flexed knee).
Clinical Presentation
◾ Pain which varies with the severity of injury ◾ Swelling is usually due to hemarthrosis and 41–75% of knee hemarthrosis is attributed to ACL injury [14]. However, this cause of swelling takes 6–24 hours to develop and in the case of rapidly
developing hemarthrosis, osteochondral fracture should be considered as the primary differential diagnosis Sensation of “pop” is usually the most common clinical presentation in ACL tear than in any other ligament tear of the knee True locking is due to displacement of the distal segment of the torn ligament into the intercondylar region Pseudolocking is related to hematoma in posterior joint capsule, collateral ligament rigidity, and extrinsic muscle spasm Two important tests for ACL integrity are the Lachman test and the pivot shift test
◾ ◾ ◾ ◾
Imaging Features Radiograph and CT
◾ Anterior tibial translation: when the tangential line drawn along the posterior margin of femoral condyle does not intersect with the posterior aspect of tibia
◾
◾ Avulsion fracture of the tibial site of attachment is common in children and adolescents rather than in older age (Fig. 60.18). Avulsion fracture at the femoral attachment site is rare Segond fracture: discussed later Subtle posterior fractures of the lateral or medial tibial plateau due to avulsion at the attachment site of posterior portion of joint capsule and attachment site of semimembranosus which is seen in lateral radiographs Osteochondral fracture of the lateral femoral condyle (lateral notch sign) is considered to be 100% specific for complete tear of ACL when the depth of the notch is more than 2 mm. However, it is less sensitive as it is only seen in 5% of ACL tear [15]
◾ ◾ ◾
Figure 60.18 Anterior cruciate ligament (ACL) injury. (A) ACL avulsion fracture. Sagittal CT image shows avulsed bone fragment (arrow) from the tibial attachment site of ACL. Sagittal PDFS MR image shows (B) high signal in ACL with tear in anteromedial bundle (arrow), suggesting partial thickness tear while in (C) there is nonvisualization of ACL due to fullthickness tear (arrow). MRI: ACL is best seen in sagittal images as low signal band of fibers in all sequences which usually has high signal than the PCL. The posterolateral fascicle bundle has relatively higher signal than the anteromedial fascicle bundle. MRI diagnosing of ACL injury is documented by the following: (a) Abnormalities within the ACL: there are two types of alterations in the ligament itself that indicate injury —alteration in morphology or orientation and alteration in signal intensity (Fig. 60.18).
Full-thickness tear is evident by complete disruption of fibers and wavy appearance on sagittal images. Complete absence of ACL in coronal images through the intercondylar notch (empty notch sign) is an important indicator of complete tear. Partial tear is sometimes difficult to diagnose and one should be dependent on secondary signs. Anteromedial bundle is commonly involved. Focal or long segment edema within the ligament and in surrounding fat planes seen as high signal intensity in PDFS and T2weighted images. In chronic tears edema is usually absent, but fluid in the joint cavity may mimic edema within the ligament. False-positive diagnoses may occur because of the following:
◾ mucinous or myxoid change in the ligament, ◾ partial volume averaging of the ACL with the lateral femoral condyle or with periligamentous fat, and ◾ suboptimal selection of the sagittal imaging plane.
False-negative diagnoses may result from the following:
◾ formation of scar tissue and adherence to the PCL, and ◾ partial tears in which residual intact fibers lead to the appearance of a normal ACL.
(b) Alteration in appearance of other soft-tissue structures is attributed to the anterior displacement of the tibia in relation to femur and includes the following:
◾ Uncovered lateral meniscus sign—tangential line drawn along the posterior cortical margin of
lateral tibial plateau in sagittal MR images intersects any part of the posterior horn of lateral meniscus. This sign is negative if the line does not intersect the meniscus or lie posterior to it Positive posterior cruciate sign—line drawn along inferior portion of PCL when extended superiorly on sagittal MR images goes parallel to the femur and does not intersect it. Normally this line is seen to intersect the medullary cavity of femur
◾ ◾
◾ Lateral collateral ligament (LCL) seen in entirety in single coronal image is a valuable sign for ACL tear (c) Abnormalities from bone impaction and avulsion forces can be categorized as follows:
◾ Chondral, subchondral, and osteochondral lesions-sites being mid-portion of the lateral
femoral condyle and posterior aspect of lateral tibial plateau. The involvement of the posterior aspect of the medial femoral condyle and posterior aspect of medial tibial plateau, can be attributed to countercoup injury Avulsion fractures—Segond fracture, avulsion at tibial attachment, and avulsion of the tibial insertion of the semimembranosus tendon
◾
(d) Miscellaneous abnormalities include:
◾ Hoffa’s fat pad injury—linear high signal intensity in the middle of the infrapatellar fat pad body in sagittal MR images ◾ Fluid in the extra synovial triangular space between the cruciate ligaments is seen in the tear of any or both of the cruciate ligaments
Treatment: Conservative management involves functional bracing and modification in lifestyle. In cases of associated injuries to the meniscus and collateral ligament, surgical management is usually opted. Autogenous, allograft, and synthetic tissues are used. Patellar tendon (bone-tendon-bone [BTB]), quadrupled hamstring tendon, and double-bundle reconstruction using hamstring are the commonly used autografts. Imaging Appearance of Anterior Cruciate Ligament Reconstruction [16] In ACL reconstruction, the graft is placed in the newly drilled femoral and tibial tunnels. Correct positioning of these tunnels (Figs. 60.19 and 60.20), mimicking the direction of native ACL is essential for maintaining the isometry and stability of the graft.
Figure 60.19 Femoral tunnel positioning must be assessed in both the sagittal and coronal planes. (A) In AP radiograph the femoral tunnel (line a) should open superiorly above the lines joining femoral condyles (line b) at the 10–11o’clock position in the right knee (A) and at the 1–2-o’clock position in the left knee (not shown). (B) In lateral radiograph a line along the posterior cortex of the femur and another line along the roof of the intercondylar notch (Blumensaat line) is drawn. The inferior portion of the tunnel should be located at the intersection of these two lines (arrow).
Figure 60.20 Tibial tunnel should be oriented parallel to the projected slope of the intercondylar roof (the Blumensaat line). (A) In AP radiograph the tibial tunnel should open at the intercondylar eminence (arrow). (B) In lateral radiograph the opening of the proximal tibial tunnel (arrow) should be posterior to the intersection of the Blumensaat line and the tibia (black line). MRI Appearance of Anterior Cruciate Ligament Graft
High signal intensity is seen in the early postoperative period (7 mm in sagittal diameter) with high signal (but not fluid strength) on PDFS and T2 images within the tendon (Fig. 60.26), adjacent proximal infrapatellar fat, and inferior pole of the patella [19]. As patellar tendon does not have a tendon sheath but only a paratenon composed of loose areolar tissue, the earliest changes (6 weeks) there is thickening of tendon fibers with low to equivocal signal on T1 images and high signal on PDFS and T2 images.
Figure 60.26 (A) Patellar tendinosis. T2 sagittal image of a young patient showing diffuse thickening of the patellar tendon (arrow) with intermediate signal intensity. (B) Patellar tendon
tear. Sagittal STIR MR image of a young patient with history of recent trauma showing full thickness tear of the patellar tendon (arrow) at its attachment to inferior pole of patella. The tendon is retracted and appears wavy. (C) Quadriceps tendon tear. Sagittal PDFS MR image shows full thickness tear of quadriceps tendon (arrow) at its patellar attachment. The patellar tendon can also appear thickened after arthroscopy. Treatment: Conservative management (patient education, modifications in physical activity, exercises that lead to increased muscle strength) is the rule.
Patellar and Quadriceps Tendon Tear This is usually due to chronic tendinosis, direct trauma, or underlying systemic cause such as rheumatoid arthritis, gout, renal failure, diabetes, and systemic lupus erythematosus. Quadriceps tendon tear is more common than patellar tendon tear. Most
common site for the tear is adjoining the patella. Fullthickness quadriceps tendon tear (Fig. 60.26) leads to an inferior position of the patella (patella Baja). In contrast, full-thickness patellar tendon tear leads to a superior position of the patella (patella alta). Partial tears are not associated with abnormal position of the patella.
Imaging Features Radiograph in partial tears has a similar appearance as tendinosis. Full-thickness tear may show the abnormal position of the patella. Avulsion fracture can also be appreciated. USG: Partial-thickness will show hypoechoic areas within the tendon, while in full-thickness tear, there will be full-thickness disruption of the fiber continuity. MRI: Partial tear will have increased PDFS signal in the tendon with fluid strength. Edema will be seen in the fat pad and at the attachment site of patella. Fullthickness tear will have complete disruption with
residual tendon retracted and wavy in appearance (Fig. 60.26). Bony fragments, with or without marrow edema, can be identified in an avulsion injury with gradient images being more sensitive to small avulsed bony fragments. Treatment: Partial tears may be managed conservatively based on the extent of instability on clinical examination. Complete tears are intervened by direct tendon repair, reconstruction with the semitendinosus tendon, or bony reattachment. Rupture, chronic pain, and dysfunction are complications of repair.
Patellar Malalignment and Instability The major stabilizers of the patella are the quadriceps and patellar tendons and the medial and lateral patellao-femoral ligaments. Abnormality in these components leads to abnormal patellar position. Patellar malalignment is the term used when there is rotational or translational deviation relative to the long axis. It can be attributed to extensor mechanism
abnormality, arthritis, infection, bursitis, plica, and stress fractures. Patellar instability is a specific condition where there is subluxation or dislocation of the patella. This has a mechanical basis and can be caused by injury, congenital abnormality in patellar position and shape of the trochlea (trochlear dysplasia), ligament laxity, adjoining muscle abnormality, or malalignment of the whole lower limb. Patellar instability can be classified based on pattern of dislocation (superior, inferior, medial, lateral), acute or chronic; and single or recurrent episodes.
Patella Alta and Patella Baja Vertical position of the patella has clinical significance in assessing the stability of the anterior knee. High-riding patella (patella alta) is considered when the inferior pole of patella is above the femoral trochlear groove while low-riding patella (patella baja or patella infera) is considered when the whole of patella is below the femoral trochlear groove.
Patella alta is attributed to recurrent patellar dislocation, chondromalacia patellae, Sinding–Larsen disease, full-thickness patellar tendon tear, and large joint effusion. Patella baja is identified in achondroplasia, neuromuscular disorders, full thickness quadriceps tendon tear, and surgical transfer of tibial tuberosity.
Imaging Features Insall-Salvatiratio is ratio of the length of the patellar tendon to the maximum length of patella. Value of 1:1 is considered to be normal. Ratios defined for patella alta and baja are 1.52 and 0.79, respectively, in females and 1.32 and 0.74 in males (Fig. 60.27) [20].
Figure 60.27 (A) Normal vertical position of patella: Insall–Salvati ratio [patellar tendon length (TL) to patellar length (PL)] is normal (1:1). (B) Patella alta: ratio is greater than 1.32. (C) Patella baja: ratio is less than 0.74.
Patellar Shape Patellar shape is not constant. Three different patellar types have been described by Wiberg (types I, II, and III) based on the asymmetry between the medial and lateral patellar facets (Fig. 60.28). Increasing number type indicates a larger degree of asymmetry and type III is thought to be associated with trochlear dysplasia (described later).
Figure 60.28 Wiberg classification of patellar shape. (A) Type I: medial (M) and lateral (L) patellar facet length are equal. (B) Type II: slightly smaller size of medial facet. (C) Type
III: Significantly smaller size of medial patellar facet.
Acute Patellar Dislocation and Subluxation Complete displacement of patella from the trochlear groove is termed dislocation while partial displacement from the trochlear groove is termed subluxation, with both the terms used interchangeably on clinical examination. Lateral patellar dislocation is a more common entity than medial dislocation.
Lateral Patellar Dislocation Flexed knee in internal rotation on planted foot and valgus component is the usual mechanism of injury. The process of dislocation and relocation causes injury to the medial retinaculum, medial patellofemoral ligament (MPFL) along with osseous and cartilaginous injuries.
Imaging Findings Radiograph: Axial view demonstrates laterally placed patella in relation to trochlear groove. Occasionally avulsion fracture from the lateral surface of the patella, intra-articular bodies, and joint effusion are seen. USG: Full thickness or partial thickness tear of the MPFL can be seen. An avulsed bone fragment may be present at the site of injury. Joint effusion can be appreciated when present. MRI helps to detect the abnormalities and determine mechanism of injury, as the clinical examination is confusing in this scenario (Fig. 60.29) [21].
Figure 60.29 Acute lateral patellar dislocation: Axial PDFS MR image showing lateral subluxation of patella. There is cortical breach and marrow edema in medial pole of patella (white arrowhead), marrow edema in lateral condyle of femur (white arrow); full thickness tear of the MPFL (black arrow) and joint effusion (asterisk). A fractured bone fragment is also seen in lateral joint space (black arrowhead). Bone and cartilage injury: Marrow edema is seen in the anterior aspect of lateral femoral condyle and in
medial patellar facet. Fractures or avulsed bone and chondral intra-articular bodies are present. Osteochondral injury can be present in the lateral aspect of femoral trochlea, the dome of the patella and medial patellar facet. Medial patello-femoral ligament (MPFL) Injury: Partial or full-thickness tear of the MPFL can be seen at its anterior third (patellar attachment), middle third (mid substance), or posterior third (femoral attachment). Partial-thickness tear leads to attenuation of the ligament with high signal on PDFS images. Full-thickness tear demonstrates complete disruption of the ligament with wavy and retracted fibers surrounded by soft-tissue edema and fluid. Other findings: Joint effusion is reported in 55–95% [21]. Injury to the distal fibers of vastus medialis (where it confluences with MPFL) can be seen as intramuscular edema and surrounding fluid intensity. MPFL tear, when associated with O’Donoghue triad (injury to ACL, medial meniscus, and medial collateral ligament), is termed as O’Donoghue tetrad.
Treatment: Nonsurgical management includes bracing, physical therapy, and strengthening of medial muscles for a first-time dislocation with the absence of complete MPFL tear. However, cases of recurrent dislocations, severe trochlear dysplasia, and presence of complete MPFL tear are usually managed surgically.
Recurrent Lateral Patellar Dislocation These patients are usually young, and anatomic factors are usually associated with such recurrent episodes. It has been found that more than 85% of patients with a history of a true patellar dislocation had evidence of trochlear dysplasia [22]. The findings pertaining to injury are the same as in acute dislocation but are of more severity.
Trochlear Dysplasia It is defined as pathologic alteration in the shape of the femoral trochlea, which may be shallower than
usual or even flat or convex, thus predisposing the patella to lateral subluxation or even dislocation.
Imaging Findings Radiograph: Based on different findings, trochlear dysplasia has been classified into four morphological types [23,24]. Radiographic findings of each type are detailed in Table 60.8 and demonstrated in Fig. 60.30. Table 60.8 Classification of Trochlear Dysplasia and Their Radiographic Findings Type A “Crossing sign” in the lateral (shallow view (line which represents the trochlear deepest part of the trochlear groove) groove crosses the anterior border of the two condyles), a shallow trochlea, and a sulcus angle >145 degree on the 30 degree flexion axial view Type B (flat or
“Crossing sign” and
convex trochlea)
supratrochlear spur (angular projection of the most proximal portion of the trochlea) on lateral view
Type C (asymmetric trochlear facets, with the lateral facet being too high and the medial facet being hypoplastic)
“Crossing sign” and a “double contour sign” (contour of the medial femoral condyle is significantly smaller than that of the lateral femoral condyle) on the lateral view
Type D “Crossing sign,” supratrochlear (asymmetry of spur, and “double contour sign” trochlear facets plus vertical join and cliff pattern)
Figure 60.30 Classification of trochlear dysplasia. (A) Type A dysplasia. The “crossing sign” (black arrow) is evident. (B) Type B dysplasia. Evidence of crossing sign and supratrochlear spur (black arrow). (C) Type C dysplasia. Evidence of crossing sign and double contour (black arrow). (D) Type D dysplasia. Concomitant presence of crossing sign (white arrowhead), supratrochlear spur (white arrow), and double contour (black arrow). CT and MRI: These modalities have higher sensitivity in diagnosing trochlear dysplasia than a radiograph. MRI features of trochlear dysplasia include reduction in the trochlear depth, lateral trochlear inclination, and facet asymmetry [25]. These are evaluated on the most cranial axial image showing cartilage, approximately 3 cm above the joint line.
◾
◾ Facet asymmetry is determined by calculating the asymmetry in the length of the medial to the lateral femoral facets and expressed in percentage (Fig. 60.31A). Asymmetry of 35°). Bunion refers to a medial bony prominence of first metatarsal head. In severe cases, the first and second toes may show crossover, which should be noted in reports. Bunionette refers to a lateral bony prominence of fifth MT head, often associated with >5° difference in the axis between fifth MT and proximal phalanx. Flexion deformities of the lesser toes are divided into claw and hammer toes. Both types show dorsiflexion (extension) at the MTP joint, usually due to the laxity of the MTP plantar plate. Claw toes are flexed at the PIP and DIP joints. Hammer toes are flexed at the PIP joint but extended at the DIP joint. Causes of pes planus: normal variant, tarsal coalition, PTT, and spring ligament insufficiency, neuromuscular disorder (most commonly cerebral palsy),
neuropathic arthropathy. Causes of pes cavus: normal variant, neuromuscular disorder (most commonly cerebral palsy or Charcot–Marie–Tooth disease). Causes of hallux valgus: genetic predisposition, tight shoes, unstable first TMT joint, pes planus, the medial inclination of first cuneiform, inflammatory arthritis, cerebral palsy. Causes of flexion deformities of the toes: tight shoes, neuromuscular disorders, inflammatory arthritis, gout, or connective tissue disorders. They are often associated with pes cavus. Morton foot configuration is significant shortening of first MT than the second; different criteria are used for diagnosis. A short first MT transfers weight-bearing stress to the second and third digits.
◾Freiberg This can result in transfer metatarsalgia (painful second and third digits) metatarsal stress fracture, infraction (Fig. 61.13), and instability of second and third MTP joints
FIGURE 61.13 Freiberg infraction. (A) AP radiograph shows mottled sclerosis of the second metatarsal head, indicative of Freiberg infraction. In this case, a fracture is visible through the area of abnormality, and there is slight cortical depression. (B) Axial 1WI shows low-signal intensity edema in the second metatarsal head and neck. The fracture line (arrow) is visible as a jagged line of lower signal within the edematous region. (C) Axial T2WIFS shows the fracture line (arrow). The bone marrow distal to the fracture is low-signal intensity, due to sclerotic reaction. The bone marrow proximal to the fracture shows high-signal intensity edema. Note edema is also present in the soft tissues around the metatarsal.
Tarsal Coalition A tarsal coalition is an abnormal bony, cartilaginous, or fibrous bridge between two or more tarsal bones [2], and is found in about 1–3% of the population. The coalition restricts motion and causes pain. About 50% of cases show flatfoot
deformity. Traditionally, these were believe to present in the second decade of life, but the presentation is often later. A common presentation is repeated ankle sprains. The two most common coalitions are talocalcaneal and calcaneonavicular.
Talocalcaneal Coalition Talocalcaneal coalition is detectable on lateral radiographs of the ankle utilizing several, variably present signs (Fig. 61.14A). The talar beak is a superior flaring of the articular surface of the talar head, which develops because of restricted subtalar motion. It must be distinguished from the normal talar ridge (Fig. 61.1B). The Csign is a curved, continuous contour of the medial posterior talus and the enlarged sustentaculum tali, which has an inferior convex contour. It can also be seen in a pronated foot, without a coalition [3]. Blunting of the lateral process of the talus compared with its normal sharp “V” shape inferiorly is an underutilized but useful sign as well. A bony coalition is easily spotted on coronal MRI or CT, which shows bony continuity between an enlarged medial talus and the sustentaculum tali (Fig. 61.14B). A nonbony coalition is more common than a bony one, and is evident on MRI or CT as an overgrown medial articulating facet of the talus, which forms an oblique and irregular bridge to a malformed sustentaculum tali (Fig. 61.14C).
FIGURE 61.14 Talocalcaneal coalition. (A) Lateral XR shows the classic signs of subtalar coalition. The C-sign (arrowheads) is a continuous contour from the medial margin of the talar body along the sustentaculum tali. This sign can also be seen in the absence of coalition, if the patient has a pronated foot. The white arrow marks the talar beak, and the blunting of the lateral process is shown by the black arrow. (B) Coronal T1W MRI shows bony continuity between the medial talus and the sustentaculum tali. The bone marrow edema reflects altered hindfoot stresses because of the coalition. The patient had multiple ankle ligament tears. (C) Coronal T1W MRI shows malformed medial talus and sustentaculum tali. An oblique, fibrous, or cartilaginous bridge is seen. It is strikingly different from the normal, smooth, horizontal contour of the middle facet (compare Fig. 61.3D).
Calcaneonavicular Coalition Calcaneonavicular coalition can be seen on all three routine views of the foot. Normally, the calcaneus does not articulate with the navicular. The space between the anterior process of the calcaneus and the navicular varies, but a small space is normally present. The most characteristic finding is the anteater sign, where the anterior process of the calcaneus is elongated and has a blunt tip analogous to an anteater’s snout (Fig. 61.15A, B). Older patients with flatfoot deformity may develop bony remodeling of the anterior process due to impingement against the navicular, which may mimic coalition.
FIGURE 61.15 Calcaneonavicular coalition. (A) Lateral XR show the broadened, blunt tip of the anterior process of the calcaneus, referred to as the anteater sign. (B) Oblique XR shows the abnormal articulation between the broadened anterior process of the calcaneus, and the elongated lateral margin of the navicular, called the reverse anteater sign. Compare with normal anterior process as shown in Fig. 61.1C. (C) AP XR shows the lateral navicular elongation, and the irregularly contoured coalition, which partly overlies the calcaneocuboid joint. (D) Axial T1 MR shows the elongated, broad anterior process of the calcaneus abutting the lateral margin of the navicular. The nonbony coalition has a characteristic, irregular contour which looks quite different from a normal, smooth articular surface. (E) Coronal T1 MR shows the navicular abutting the enlarged anterior process of the calcaneus. The navicular and calcaneus normally lie in close proximity without contacting each other.
The reverse anteater sign (Fig. 61.15C) refers to the elongation of the lateral margin of the navicular, seen on the AP radiograph. Calcaneonavicular coalitions are often less conspicuous on advanced imaging (Fig. 61.15D) than on radiographs.
Lateral collateral ligament sprain is a very common injury due to ankle inversion. Most cases heal with conservative management, although some patients develop chronic instability. The components of the lateral collateral ligament typically tear in a defined order: anterior talofibular ligament (ATFL) is torn first, then calcaneofibular ligament, then posterior talofibular ligament. Isolated ATFL tear is common, and often asymptomatic. XR shows lateral soft-tissue swelling centered at the tip of the lateral malleolus, and often a joint effusion. A tiny avulsion fragment of the tip of the fibula by the calcaneofibular ligament is still generally considered an ankle sprain. Stress radiographs may show tibiotalar tilt (superior joint space widened from medial to lateral, Fig. 61.16A), and an anterior drawer sign (talus subluxates anteriorly when anterior stress is applied).
FIGURE 61.16 Lateral collateral ligament injury. (A) AP XR with inversion stress manually applied shows tibiotalar tilt. The operator’s hands are not gloved, but a glove should be used to reduce radiation exposure. The weightbearing portion of the joint is widened laterally (arrow), indicating insufficiency of the CFL. (B) Axial PDFSW MR aligned with axis of talus shows amorphous highsignal intensity in the expected course of the ATFL (arrow). White arrowheads point to the stumps of the torn ligament. PTFL (black arrowhead) is rarely torn, and is intact in this case. (C) Coronal T2FSW MR shows the CFL is wavy and discontinuous, displaced medially from its normal attachment to the tip of the fibula. The peroneal tendons are displaced slightly medially, a useful secondary sign of CFL tear. PTFL is intact. Note normal deep deltoid is taut and well defined, and has a striated appearance due to multiple ligamentous bands. Multifocal bone bruises are present. C, calcaneus; CFL, calcaneofibular ligament; PB, peroneus brevis; PL, palmaris longus; PTFL, posterior talofibular ligament; T, talus.
MRI (Fig. 61.16B, C) shows ligament discontinuity either at attachment or midsubstance [4], and often shows medial and superior displacement of the
peroneal tendons beneath the tip of the fibula.
Deltoid Ligament Deltoid ligament sprain [5] usually occurs due to eversion injury, in which case it may be associated with syndesmosis injury, posterior malleolar fractures, or Maisonneuve fracture of the proximal fibula. Injuries are usually treated conservatively. XR may be normal or may show widening of the medial clear space of the ankle more than 6 mm. This can be better shown on the stress view (Fig. 61.17A). The deep deltoid ligament is sparsely accessible to USG, but is well seen on coronal MRI images (Fig. 61.17B). Superficial deltoid injury is usually an avulsion from the medial malleolus and can be evaluated on both USG and MRI (Fig. 61.17C). An alternative injury mechanism leading to tearing of the superficial deltoid ligament is inversion + twist injury, in which case the deep deltoid ligament is often intact, but the lateral collateral ligament is injured [6].
FIGURE 61.17 Syndesmosis and deltoid ligament tears. (A) AP gravity stress XR shows complete loss of overlap (normally 1 cm on AP view) between tibia and fibula (arrow) indicating syndesmosis tear. There is borderline widening of the medial clear space (arrowhead), suspicious for deltoid ligament tear. To obtain this view, the patient lies on the affected side with a support under the leg,
but the ankle is not supported. (B) Coronal T2FSW MR shows the torn deep deltoid. Along the expected course of the ligament between the deep surface of the medial malleolus and the medial talus, the normal fiber bands are replaced by amorphous intermediate-signal intensity material. (C) Axial T2FSW MR shows the superficial deltoid is detached from the medial malleolus. This is the most common site of superficial deltoid tear. The syndesmosis is also injured. The AITFL appears discontinuous, but this must be confirmed on adjacent images, since the ligament is obliquely oriented. The PITFL is partially detached from the fibula. (D) Axial T2FSW MR is slightly superior to previous image, and better shows the syndesmosis injury. The AITFL and PITFL are thick, heterogeneous, and discontinuous. There is amorphous high-signal intensity in the expected location of the interosseous ligament. (E) Transverse ultrasound shows loss of the normal fibers of the AITFL. There is only amorphous tissue between the anterior margins of the fibula and tibia at the expected level of the ligament. Compare with Fig. 61.4A. AITFL, anterior inferior tibiofibular ligament; LM, lateral malleolus; MM, medial malleolus; PITFL, posterior inferior tibiofibular ligament; PT, posterior tibial tendon.
Syndesmotic Ligament Syndesmotic ligament sprain (high ankle sprain) occurs due to eversion injury, often in association with a deltoid ligament injury. Depending on the severity, it may be treated conservatively or with fixation screw or fiber tape fixation between the tibia and fibula to restore the normal width of the syndesmosis. XR shows softtissue swelling centered at the level of the syndesmosis (i.e., superior to the softtissue swelling visible on ankle sprains), and may show syndesmosis widening (Fig. 61.17A). Discontinuity of the ligaments is visible on MRI or USG (Figs. 61.17C–E).
Lisfranc Ligament Lisfranc ligament tear (midfoot sprain) occurs due to severe plantar flexion of the TMT joints, occurring when the forefoot folds under the hindfoot, either in sports or due to injury going downstairs or stepping off a curb. Although disruption of the Lisfranc ligament is a seemingly small injury, it destabilizes the TMT joint and needs to be fixed surgically [7]. Weight-bearing XR in cases of Lisfranc ligament tear usually shows slight lateral displacement of the second metatarsal relative to the middle cuneiform (Fig. 61.18A). A small bony avulsion fragment may be present. MRI shows discontinuity of the ligament on axial and coronal images (Fig. 61.18B).
FIGURE 61.18 Lisfranc ligament injury. (A) AP weight-bearing XR. Arrow points to lateral displacement of second MT relative to second cuneiform. The medial cortices of the two bones should always be aligned, and lateral displacement is specific for Lisfranc ligament injury. (B) Lisfranc ligament injury axial PDFSW MR. Arrow points to amorphous, high-signal intensity material along the expected location of the Lisfranc ligament.
Stress Fractures Stress fractures are common in the calcaneus, navicular, and metatarsals, and may not be visible on XR for 1–2 weeks after onset of pain. At that time, a sclerotic or lucent line is usually discernible, and there may be a cortical break and periosteal callus formation (Fig. 61.19A). Most are readily diagnosed clinically when patients present with sharp, focal pain after increased activity. It is good management to treat these patients presumptively with a flat bottom, stiff shoe/boot, and to repeat radiographs to confirm the diagnosis, rather than performing an expensive MRI. An exception is the navicular stress fracture, which occurs in runners, and presents with vague midfoot soreness; XR is negative until late in the clinical course, and MRI or CT is useful for the diagnosis (Fig. 61.19B). If left untreated, navicular stress fractures can progress to complete fracture and to osteonecrosis of the navicular (Mueller Weiss syndrome) [8].
FIGURE 61.19 Stress fractures. (A) Stress fracture of the third MT. Initial XR was normal. AP XR obtained 2 weeks later shows cortical break (arrow) and periosteal reaction. (B) Navicular stress fracture axial PDFSW MR. Arrow points to low-signal intensity incomplete fracture line, surrounded by edema. Stress fractures of the navicular always occur in the mid navicular, starting at the dorsal, proximal, margin of the bone.
Abnormal Tendons Tendinosis (also called tendinopathy) is collagen degeneration of a tendon due to overuse and aging. Tenosynovitis is seen as abnormal fluid within a tendon sheath, due to inflammation or overuse. Tendon tear is usually due to chronic overuse but may be due to acute trauma. It may be partial or complete. Most tendon tears happen at the site of pre-existent tendinosis. Radiological assessment of commonly injured tendons is discussed in Table 61.3. Table 61.3 Assessment of Commonly Injured Tendons Te nd on
Normal Size
Primary Insertio n
Abnormalities Associated With Dysfunction
Te nd on
Normal Size
Primary Insertio n
Abnormalities Associated With Dysfunction
Ac hill es
8 mm. There is a focal area suggestive of low-grade partial tear (arrow) at the anterior margin of the tendon. A small rim of fluid around the tendon is indicative of peritendinosis. (B) Achilles tendon tear. Long-axis panoramic USG shows a 6-cm defect in the tendon. Arrows point to the torn tendon ends. Amorphous material between the tendon ends represents blood and injured tissue.
Unique imaging findings of Achilles tendon injury: Enlargement of the superior margin of the calcaneus posterior process is known as a Haglund deformity (Fig. 61.21), and is associated with insertional tendinosis. Congenital and stress response has been attributed as a cause of this deformity. Symptomatic patients usually show marrow edema within the deformity on MRI. Pre-Achilles bursitis is seen on USG or MRI as a focal fluid collection between the calcaneus and Achilles. An adventitious bursa, the retro-Achilles bursa, may develop in patients with tendon impingement. Together, it is termed as Haglund syndrome.
FIGURE 61.21 Haglund deformity. (A) Lateral XR. The Haglund deformity refers to bony overgrowth of the superior margin of the posterior process of the calcaneus, and is a response to chronic stress. Achilles tendon is sharply outlined against the pre-Achilles fat. It becomes progressively thickened as it extends caudally toward its insertion. It contains calcifications and ossifications consistent with insertional tendonitis. Edema is seen as increased density in the pre-Achilles fat. (B) Sagittal STIR MR. There is bone marrow edema secondary to impingement by the Haglund deformity. The pre-Achilles bursa is distended. Thickening and streaks of high signal within the Achilles tendon indicate insertional tendinitis and early interstitial tearing.
Posterior Tibial Tendon PTT acts to invert and plantarflex the foot, maintain the medial arch and provide dynamic foot stability. It is held behind the medial malleolus by the flexor retinaculum. It attaches primarily to the median eminence of the navicular, with small slips to multiple bones of the midfoot. PTT dysfunction is most commonly seen in obese, middle-aged women with a pre-existing flatfoot deformity [14]. PTT is also very commonly involved in rheumatoid arthritis. Dysfunction progresses from tenosynovitis and tendinopathy to partial tear (Fig. 61.22) to complete tear. Elongation and insufficiency of the spring ligament also develops. Tears of the PTT lead to adult-acquired flatfoot, hindfoot valgus deformity, and dorsolateral peritalar subluxation (Fig. 61.23). Mild dysfunction may be treated with orthotics, walking boot, or brace. Partial or complete tears may be treated with surgical repair, corrective osteotomies to realign the hindfoot, and tendon transfers.
FIGURE 61.22 High-grade partial tear of posterior tibial tendon. (A) Axial PDFS MRI shows severe thinning of the PTT (arrow) and fluid in the tendon sheath surrounding the tendon. The peroneus brevis tendon PB (arrow) also shows mild splitting, which is often asymptomatic. (B) Short-axis USG at the level of the talar neck shows an irregularly shaped PTT within a tendon sheath which is distended with anechoic fluid. C, calcaneus; PB, peroneus brevis; PTT, posterior tibial tendon; T, talus.
FIGURE 61.23 XR findings of advanced PTT dysfunction. Although the talus is the bone which is displaced, by convention malalignment is designated by the distal part affected. Therefore, this deformity is known as dorsolateral peritalar subluxation. (A) Lateral XR shows the head of the talus is positioned inferior to the dorsal margin of the navicular, due to loss of support by the PTT and the spring ligament. (B) AP XR shows the head of the talus is rotated, and subluxated medially (arrow).
Unique imaging findings of PTT injury: The type 2 accessory navicular predisposes the PTT to injury. If the patient has a type 2 accessory navicular, PTT injury may disrupt the synchondrosis between the navicular and the ossicle, leading to edema in the ossicle or proximal displacement (Fig. 61.24). Radiographs of advanced PTT dysfunction show lateral and dorsal subluxation of the navicular relative to the head of the talus (Fig. 61.23). Rarely, the traumatic tear of the flexor retinaculum may destabilize the tendon as it passes behind the medial malleolus. Dynamic USG with inversion maneuver will show anteromedial subluxation of the tendon.
FIGURE 61.24 Painful accessory navicular. Sagittal T1W (A) and STIR (B) MR show edema in the type II accessory navicular, and fluid in the PTT sheath. Patient was treated with excision of the ossicle and reattachment of the tendon. PTT, posterior tibial tendon.
Peroneal Tendons Peroneal tendons act to evert and plantarflex the foot and assist in maintaining ankle stability. They are held behind the lateral malleolus by the peroneal retinaculum. A sesamoid bone, the os peroneum, is often present in the peroneus longus tendon distal to the calcaneal–cuboid joint line. It may be bipartite or multipartite, and can sometimes develop a painful sesamoiditis. Peroneal tendon tears often develop in patients with chronic ankle instability or injury to the peroneal retinaculum. Longitudinal splits (Fig. 61.25) may be repaired (“tubularized”) to regain a rounded contour. More severe injuries are often treated with tenodesis of the torn tendon to its companion peroneal tendon. Peroneal tendon abnormalities can also be seen in inflammatory arthropathy.
FIGURE 61.25 Splitting of the peroneal tendons. (A) Short-axis USG along lateral margin of calcaneus shows the PB (arrow) has an irregular contour due to longitudinal splitting. The PL (arrowhead) shows mildly irregular contour. Fluid surrounds the tendons within their shared tendon sheath. (B) Coronal T2FS MR at the level of the posterior subtalar joint in a different patient shows that the PB is severely split, and forms a V-shape which cups the peroneus longus tendon. Fluid and amorphous material are seen in the tendon sheaths. (C) Coronal T2FS MR (same patient as Fig. 61.22B) at the level of the anterior subtalar joint shows that splitting involves the PL as well as the PB. The PB is less severely affected at this level. PB, peroneus brevis; PL, palmaris longus.
Unique imaging findings of peroneal tendon injury: Severe splits of the PB tendon often cause it to form a V-shape, with tendon fibers lying on either side of the PL tendon inferior to it (Fig. 61.25B). Peroneal retinaculum injury may result in anterolateral dislocation of the peroneal tendons. Instability may not be visible on MRI and is best seen on dynamic ultrasound when the foot is everted (Fig. 61.26). An os peroneum displaced proximal to the calcaneocuboid joint indicates tear of the peroneus longus (Fig. 61.27). Peroneus brevis tendon normally becomes thin and ribbonlike near its insertion, and this should not be mistaken for partial tear.
FIGURE 61.26 Lateral subluxation of the peroneus longus on short-axis USG. The retinaculum (arrowhead) has been previously injured, and has reattached along the lateral margin of the lateral malleolus. This allows dynamic subluxation of the tendon around the corner of the fibula into the lateral subcutaneous region, when the foot is everted. LM, lateral malleolus; PB, peroneus brevis; PL, palmaris longus.
FIGURE 61.27 Complete tear of the peroneus longus tendon. (A) Oblique XR shows os peroneum (arrow) along the lateral margin of the calcaneus. Arrowhead points to its normal location, at the level of the calcaneocuboid joint or slightly distal to it. Proximal displacement is a reliable XR sign of complete tear. (B) Axial MR T2FS shows the displaced ossicle (white arrow) and the empty PL tendon sheath distal to it (black arrow). PL, peroneus longus.
Ankle Impingement Syndromes Limitation of ankle motion may occur in a variety of locations around the joint, and from a variety of causes [15]. In addition to the causes listed below, also consider decreased motion due to tarsal coalition, synovitis, or intra-articular bodies. Imaging can never diagnose impingement, which is a clinical diagnosis. Imaging can only suggest that findings are present, which may result in impingement.
Anterior Impingement Anterior impingement refers to limited ankle dorsiflexion, usually due to anterior osteophytes of the tibiotalar joint.
Anterolateral Impingement Anterolateral impingement refers to lateral pain and limited ankle dorsiflexion + eversion. It is caused by scarring in the anterolateral joint recess
after chronic tear of the ATFL or the AITFL. Axial MRI shows a “meniscoid” lesion, a triangular scar, in the anterolateral joint recess (Fig. 61.28).
FIGURE 61.28 Anterolateral impingement. Axial PDFS MR shows meniscoid lesion (arrow) representing scarring of chronically torn anterior talofibular ligament. This can cause pain and limit motion when the patient dorsiflexes and everts the foot.
Anteromedial Impingement Anteromedial impingement refers to anteromedial ankle pain and limited motion with ankle dorsiflexion + inversion. It is caused by osteophytes or by chronic tear and scarring of the superficial deltoid ligament. Axial MRI or USG show rounded scar at the anterior margin of medial malleolus, at the level of the joint.
Posterior Impingement Posterior impingement refers to posterior ankle pain and limited plantar flexion (Fig. 61.29). It is seen primarily in athletes who repeatedly maximally plantarflex the foot, for example, dancers and basketball players. It may be due to posterior
ligament scarring and synovitis, or to a large os trigonum (os trigonum syndrome). The FHL tendon suffers impingement at the level of the posterior process of the talus. MRI signs of os trigonum syndrome include bone marrow edema in the os trigonum, and focal fluid in the FHL sheath adjacent to the ossicle.
FIGURE 61.29 Os trigonum syndrome. (A) Lateral XR shows os trigonum (arrow). Cysts within the ossicle suggest abnormal motion. (B) Sagittal STIR MR shows high signal bone marrow edema in the os trigonum (arrow) and subjacent talar body. There is focal fluid in the FHL tendon sheath (white arrowhead) and the posterior subtalar recess (black arrowhead). Although it is normal to see a small amount of fluid in the FHL tendon sheath, a focal collection extending superiorly from the level of the os trigonum is suggestive of impingement.
Other Hindfoot Abnormalities Osteochondral Lesion of the Talus Osteochondral lesion (OCL) of the talus (Figs. 61.30 and 61.31) is a general term referring to a spectrum of acute and chronic injury to articular cartilage together with the underlying subchondral bone. On imaging, OCL can be characterized as stable lesions (Fig. 61.30), where a bone bruise or fracture line is present but is not complete, and unstable lesions (Fig. 61.31), where the osteochondral fragment is separated from the underlying bone. The unstable fragment may displace and
present as a loose body in the ankle joint. Chronic OCL may develop central cystic degeneration, and this is a sign that the lesion is unlikely to heal.
FIGURE 61.30 Stable OCL talus. (A) Mortise XR shows fracture line (arrow) across lateral margin of talar dome, which may be due to acute or chronic injury. Arrowheads point to normal subtalar joint. (B) Coronal T2FS MR shows that the fracture (arrow) is stable, because there is no fluid-filled cleft around it. Patient also has injuries of the deep (white arrowhead) and superficial (black arrowhead) deltoid ligament. Although OCL is associated most strongly with LCL injury, other ligament injuries commonly occur as well. Note also the multiple areas of bone bruising.
FIGURE 61.31 Unstable OCL talus. (A) Sagittal T1W MRI shows a bowlshaped transchondral fracture line (arrow). Low signal in the central fragment suggests a chronic lesion which has undergone osteonecrosis. A joint effusion is present. (B) Sagittal STIR shows the central fragment is surrounded by fluid, indicating the fragment is unstable, and vulnerable to displacement.
The most common site for OCL in the foot is the medial or lateral talar dome. It may also occur in the tibia. Both injuries occur with ankle sprains. OCL is rare in other locations. Heel pain may occur due to abnormalities of the Achilles tendon, tarsal tunnel syndrome, stress fracture, plantar fasciitis, tarsal sinus syndrome, or heel pad syndrome [16].
Plantar Fasciitis (or Plantar Fasciosus) It is a commonly seen painful condition of the plantar fascia, due to chronic stress. The central band, overlying the flexor digitorum brevis, is most commonly affected, and the abnormality is centered at the origin of the fascia close to calcaneal tuberosity. Plantar fasciitis is seen most commonly in obese patients and runners, but it can also be associated with seronegative spondyloarthropathy. It is treated with stretching exercises or corticosteroid injection. The XR finding of a heel spur does not have a strong association with plantar fasciitis. MR in cases of plantar fasciitis shows thickened plantar fascia and increased T1 and T2 signal of the fascia as well as the underlying muscle, adjacent bone marrow edema (Fig. 61.32A). Ultrasound shows thickened origin (>4 mm)of the plantar fascia, decreased echogenicity in the affected region, and edema in the superficial soft tissues (Fig. 61.32B). Plantar fasciitis may cause impingement of Baxter’s nerve (the inferior calcaneal nerve which is the first branch of the lateral
plantar nerve), which leads to isolated atrophy of the abductor digiti minimi muscle.
FIGURE 61.32 Plantar fasciitis. (A) Sagittal STIR shows thickening of the plantar fascia at the calcaneal origin. Edema is present not only in the fascia, but also the subjacent fat, flexor digitorum brevis muscle, and calcaneus. (B) Longaxis USG shows thickening of the plantar fascia at its origin from the posterior process of the calcaneus. A small bone spur is visible, and there are small calcifications in the fascial origin. Note edema in the fat pad (arrowhead) adjacent to the plantar fascia origin. FDB, flexor digitorum brevis.
Plantar Fascia Tear Plantar fascia tear is rare. It may be caused by steroid injection or athletic activity (Fig. 61.33).
FIGURE 61.33 Partial tear of plantar fascia on USG in a patient complaining of a painful nodule. Long-axis view in area of patient’s pain shows focal thickening of fascia in the center of the image, fiber discontinuity, and low echogenicity fluid between the torn fibers. Compare with the normal appearance of the fascia on the left side of the image (arrowhead).
Tarsal Sinus Syndrome (Sinus Tarsi Syndrome) Sinus tarsi is a cylindrical cavity located between the talus and calcaneus on the lateral aspect of the foot, distal and slightly anterior to the lateral malleolus. The syndrome is a poorly defined entity where patients have pain in the lateral hindfoot, which can be attributed to inflammation or scar in the tarsal sinus. There is often a subjective feeling of instability. The cervical ligament in the sinus tarsi is sometimes injured (Fig. 61.34). Synovitis emanating from the posterior subtalar joint may also contribute to pain. It is commonly associated with lateral ankle ligament sprain.
FIGURE 61.34 Tarsal sinus syndrome. (A) Coronal T1 MR shows that the normal high-signal intensity fat in the tarsal sinus has been replaced with lowsignal intensity material. (B) Coronal T2 MR at the same level shows heterogeneous material filling the tarsal sinus. The patient also has plantar fasciitis. C, calcaneus; T, talus.
Chronic Instability Chronic instability occurs when ligament tears fail to heal. Bone marrow edema patterns are useful to suggest abnormal motion, usually at the tibiotalar joint, but sometimes at the subtalar joint (Fig. 61.35). The presence of bone marrow edema should prompt a careful evaluation of ligamentous integrity.
FIGURE 61.35 Subtalar instability. An 18-year-old male athlete with feeling of “giving way.” Ankle ligaments were intact. (A) Coronal T2FS image shows bone marrow edema (arrowheads) on both sides of the posterior subtalar joint, suggesting abnormal motion. (B) Coronal T2FS image anterior to previous image, through tarsal sinus, shows absent cervical ligament, and shows bone marrow edema centered at the ligament attachments.
Heel Pad Syndrome Heel pad syndrome is atrophy of the fat of the plantar heel pad, generally due to obesity and diabetes. MR shows replacement of normal fat with fibrous tissue (low T1, intermediate to high T2 signal).
Abnormalities of the Forefoot Plantar Fibromatosis Plantar fibromatosis is a nodular thickening of the plantar fascia, which usually occurs in the forefoot. It causes a palpable lump and is painful when the patient bears weight. The nodules may be single or multiple. Treatment starts with cushioning pads around the lesion to decrease pressure. Corticosteroid injection and surgical removal are sometimes used. USG and MRI show focal, fusiform nodules in the plantar fascia (Fig. 61.36).
FIGURE 61.36 Plantar fibroma. Long-axis USG shows a fibroma (arrow) arising from the plantar fascia. It has a fusiform shape. Its margins taper into the normal adjacent fascia. It is usually isoechoic to the fascia.
Sesamoiditis Sesamoiditis refers to pain resulting from chronic stress on one or both of the sesamoids lying plantar to the first metatarsal head. The condition may progress to stress fracture. Treatment centers on offloading stress to the sesamoids. MRI shows bone marrow edema in the affected sesamoid.
Lesser Metatarsalgia Lesser metatarsalgia refers to pain in the MT other than the first. It most commonly affects the second and third MT. Lesser metatarsalgia is usually due to increased stress. The increased stress may occur because the first MT is either short or affected by hallux valgus, and in these cases the pain in the lesser metatarsals is often called transfer metatarsalgia. Pointed toe, high-heeled shoes
also contribute to lesser metatarsalgia. Imaging may show stress fractures, Morton neuroma, Freiberg infraction, or dorsal subluxation of the MTP joint.
Freiberg Infraction Freiberg infraction is an osteochondral injury (some authors believe it represents osteonecrosis) of the MT head, usually the second or third (Fig. 61.37).
FIGURE 61.37 Freiberg infraction. (A) AP XR shows concave contour of the MT head articular surface, and mottled subchondral sclerosis, surrounded in more advanced cases such as this one by a bowl-shaped sclerotic rim. Note that the lateral sesamoid of the first MT is bipartite, a normal variant. (B) Axial T2FS MRI in same patient shows the collapsed, sclerotic, low signal intensity area of Freiberg infraction, with surrounding high signal representing reactive edema and/or reparative tissue.
Nerve Abnormalities Patients with symptoms related to nerve abnormalities present with altered sensation and/or muscle weakness. A Tinel’s sign (tingling in the distribution of the abnormal nerve when the nerve is tapped) is typical. Nerve abnormalities may occur due to peripheral neuropathy, nerve injury, or entrapment.
Imaging of Nerves
Neuritis is evident on USG or MRI as nerve enlargement and edema of the nerve fascicles (Fig. 61.38) [17]. MRI shows changes in muscles innervated by a nerve. The first MR sign is a high T2 signal, “denervation edema,” in the affected muscles. Diffuse muscle fatty atrophy occurs later in the course.
FIGURE 61.38 Tarsal tunnel syndrome. (A) Coronal STIR MR shows the enlarged medial (black arrow) and lateral (short white arrow) branches of the tibial nerve. Denervation edema is visible in the abductor hallucis (black arrowhead) and abductor digiti minimi (white arrowhead) muscles. Note degradation of image by artifact from fixation hardware (long white arrow). Becoming proficient at MR interpretation requires learning to “read around” artifacts such as this, in addition to altering technique to reduce artifact. (B) Coronal PDFSW MR in another patient shows a synovial cyst arising from the subtalar joint, and deviating the medial plantar nerve. The patient had pain and a positive Tinel sign, but no changes are seen in the plantar muscles. (C) Cor T1W MRI shows fatty atrophy which is limited to the abductor digiti minimi muscle. This is due to impingement of the Baxter nerve, the first nerve branch of the lateral plantar nerve. (D) Coronal T2FSW MRI shows diffusely increased signal in the abductor digiti minimi. This pattern is characteristic of denervation edema.
◾trauma Denervation edema can be distinguished from increased T2 signal related to infection and muscle because, unlike in those entities, the normal architecture of the muscle is preserved (Fig. 61.38C, D).
Tarsal Tunnel Syndrome Tarsal tunnel syndrome is entrapment of the tibial nerve or its branches and is the most common location for nerve impingement in the foot. The tarsal tunnel lies deep to the flexor retinaculum in the hindfoot, and contains the tibial nerve and its branches, as well as vessels, flexor tendons, and quadratus plantae muscle. Compression of nerve may occur due to neoplasm, venous varicosities, synovial cysts, tenosynovitis, accessory muscles, tarsal coalition, osteophytes, posttraumatic deformity, or scar (Fig. 61.38).
Baxter Neuropathy Baxter neuropathy refers to isolated neuropathy of the nerve to the abductor digiti minimi, which is innervated by the first branch of the tibial nerve in the tarsal tunnel. It is often due to plantar fasciitis, with the nerve getting compressed between plantar fascia and underlying calcaneum. MRI shows isolated edema and fatty atrophy of the abductor digiti minimi.
Peripheral Neuropathy Peripheral neuropathy is common in diabetic patients, also seen in Charcot–Marie– Tooth syndrome. It is often described as a “stocking-glove” pattern and involves the small peripheral nerves. Patients experience burning pain and decreased sensation and proprioception. The intrinsic muscles of the foot show diffuse atrophy (Fig. 61.39).
FIGURE 61.39 Advanced denervation changes in the forefoot due to peripheral neuropathy. (A) Axial T1 shows nearly complete fatty replacement of the oblique head of the adductor hallucis muscle (arrow). The few fibers of remaining muscle are intermediate-signal intensity. (B) Axial PDFS shows that the remaining muscle fibers (arrow) are high-signal intensity, reflecting denervation edema. Denervation edema occurs rapidly after muscle denervation, while fatty atrophy is a chronic finding. Note that the residual muscle fibers have a straight course, and do not show the focal disruption that will be present in muscle injury. (C) Coronal T1 shows the fatty atrophy involves all of the intrinsic muscles of the forefoot. The distribution of muscle involvement is a helpful clue to etiology.
Morton Neuroma Morton neuroma is a traumatic neuroma due to chronic compression of the interdigital nerves at the level of the metatarsal (Fig. 61.40A, B) along the plantar aspect. It is most common in women, due to compression from pointed-toe and high-heel shoes. Common differential is an intermetatarsal bursa (Fig. 61.40C) which is a fluid distension in the web space.
FIGURE 61.40 Morton neuroma. (A) Long-axis USG shows a hypoechoic, 1cm fusiform mass (between the calipers) which tapers (arrow) into the interdigital nerve. The neuroma lies between the MT heads, and visualization especially of smaller neuromas is improved using a small hockey-stick transducer, imaging from the plantar side of the foot, and applying pressure to the dorsum of the foot with the other hand to push the MT heads apart. (B) Axial postcontrast T1 fatsaturated MR image shows an enhancing nodular lesion in second web space (arrow). (C) Intermetatarsal bursa. Axial STIR MR image shows a fluid signal lesion in second web space (arrow).
Arthroplasty, Arthrodesis, and Alignment Correction Surgeries Arthroplasty is not commonly employed in the foot and ankle to treat arthritis; arthrodesis remains more desirable. There are a large number of arthroplasty designs that have been developed for the ankle, however (Fig. 61.41), as in other joints, the concern of the radiologist is to monitor for particle disease, subsidence, loosening, and infection. Particle disease refers to a granulomatous reaction due to release of small polyethylene, cement, or metal particles from the prosthesis and manifests as more than 2-mm periprosthetic lucency.
FIGURE 61.41 Ankle arthroplasty. (A) AP XR shows arthroplasty which appears well positioned. A lucency above the tibial component (arrow) is suspicious for particle disease. (B) Coronal CT performed at the same time shows the extent of the particle disease (arrows) is much greater than evident on radiographs.
Arthrodesis can relieve pain but can increase stress on adjacent joints. Radiographs and CT are utilized to evaluate for bony bridging across a joint and hardware failure (Fig. 61.42), and for accelerated osteoarthritis in adjacent joints.
FIGURE 61.42 Failed ankle and subtalar arthrodesis. Lateral radiograph shows a retrograde nail has been placed from the plantar surface of the calcaneus, across the subtalar and tibiotalar joints. Both joints show no bridging bone. One of the interlocking screws is fractured, and there are lucent haloes (arrowheads) around the nail and the more inferior screw. These signs indicate motion across the sites of attempted arthrodesis.
Hindfoot valgus or varus can be corrected by osteotomies of the calcaneus and often the medial cuneiform. Hallux valgus correction varies according to the site of abnormality. The bony prominence (bunion) is resected at the same time that the deformity of the first digit is corrected. If the patient has an oblique or hypermobile first TMT joint, the fusion of the TMT joint may be performed. The orientation of the first MT and first PP can be corrected with a variety of osteotomies (Fig. 61.43).
FIGURE 61.43 Hallux valgus surgery. (A) AP XR shows a straight contour of the medial first MT head (arrow), indicating the bony bunion has been resected. Fixation screws are in place across a chevron (V-shaped) osteotomy, which is poorly seen on this view. (B) Lateral XR shows a chevron osteotomy (arrows). The distal MT can be moved medially across the chevron.
Foreign Bodies The foot is vulnerable to puncture by foreign bodies, and it can be difficult to localize on physical exam. In some cases, they are visible on XR or MRI. However, foreign bodies may be obscured on MRI due to the high-signal intensity of the surrounding inflammatory reaction. Glass can be commonly identified on radiographs. The technique of choice to image foreign bodies is USG (Fig. 61.44). Thin slivers can be detected when the USG transducer is aligned along their long axis. In our clinic, the skin is marked at the site of the foreign body seen on ultrasound. The patient then goes to the clinic for removal, and removal is guided by the mark.
FIGURE 61.44 Foreign body (thorn) on USG. The thorn is outlined by calipers. It shows moderate shadowing deep to it.
Practical Approach to Imaging the Foot and Ankle Always start with weight-bearing radiographs. These will give the best evaluation of alignment, and will additionally provide a good screening for bone trauma, bone tumors, infection, and arthritis, important causes of pain which are not covered in this chapter. Ultrasound is an excellent tool, but to utilize it effectively, the operator needs to have a high level of understanding of normal anatomy to visualize the small, obliquely oriented structures of the foot. Another advantage of ultrasound is the ability to perform dynamic maneuvers. MRI is best for evaluating bony abnormalities and for obtaining a global picture of the entire region. The MRI template given here can be used as a guide to reviewing MRIs in a systematic fashion. Evaluating every study using the same search pattern, in the same order, reduces errors. It is also important to remember that one problem in the foot and ankle can lead to other problems. For example, hallux valgus can lead to Freiberg infraction.
MR Template Technique: Describe area of coverage, contrast if given. Comparison: Always compare with previous radiographs, and advanced imaging. Lateral collateral ligament: Describe injuries to components separately. Syndesmotic and deltoid ligaments: Describe injuries to components separately. Intertarsal and TMT ligaments: Always specify Lisfranc ligament intact or injured. Can group other ligaments together as being normal, without naming specific ligaments, unless injured. Achilles tendon: Describe as normal, tendinopathy, peritendinosis, or tear. Give AP diameter of tendon if abnormal. Describe bursitis, Haglund deformity, and pre-Achilles fat if abnormal. Deep flexor tendons: Describe as normal, or describe tenosynovitis, tendinopathy, partial or complete tear. Describe any injury to flexor retinaculum here. Describe accessory navicular if present. Peroneal tendons: Describe as normal, or describe tenosynovitis, tendinopathy, partial or complete tear. Describe any injury to peroneal retinaculum here. Describe os peroneum if present. Extensor tendons Describe as normal, or describe tenosynovitis, tendinopathy, partial or complete tear. Describe extensor bursitis if present. Intrinsic muscle and plantar fascia: Describe as normal, or describe injury or denervation edema. Joints: Describe as no evidence of articular abnormality, or precisely and briefly describe osteophytes, erosions or joint effusions. Describe any evidence of impingement on a joint. Bones: Describe fracture, bone marrow edema, stress fracture, or marrow replacement process. Neurovascular structures: Describe as normal, or describe vascular abnormalities or evidence of nerve injury/impingement. Impression: This should be a short, succinct, numerical list, in order of importance of findings.
Suggested Readings
• J Crim, Imaging of tarsal coalition, Radiol Clin North Am 46 (2008) 1017–1026, vi. • T Alves, Q Dong, J Jacobson, C Yablon, G Gandikota, Normal and injured ankle ligaments on ultrasonography with magnetic resonance imaging correlation, J Ultrasound Med 38 (2019) 513– 528. • A Donovan, ZS Rosenberg, JT Bencardino, ZR Velez, DB Blonder, GA Ciavarra, et al., Plantar tendons of the foot: MR imaging and US, Radiographics 33 (7) (2013) 2065–2085. • SB Soliman, PJ Spicer, MT van Holsbeeck, Sonographic and radiographic findings of posterior tibial tendon dysfunction: a practical step forward, Skeletal Radiol 48 (2019) 11–27. • DV Flores, C Mejia Gomez, M Fernandez Hernando, MA Davis, MN Pathria, Adult acquired flatfoot deformity: anatomy, biomechanics, staging, and imaging findings, Radiographics 39 (2019) 1437– 1460.
References [1] S Bianchi, C Martinoli, C Gaignot, R De Gautard, JM Meyer, Ultrasound of the ankle: anatomy of the tendons, bursae, and ligaments, Semin Musculoskelet Radiol 9 (2005) 243–259. [2] J Crim, Imaging of tarsal coalition, Radiol Clin North Am 46 (2008) 1017–1026, vi. [3] RR Brown, ZS Rosenberg, BA Thornhill, The C sign: more specific for flatfoot deformity than subtalar coalition, Skeletal Radiol 30 (2001) 84– 87. [4] T Alves, Q Dong, J Jacobson, C Yablon, G Gandikota, Normal and injured ankle ligaments on ultrasonography with magnetic resonance imaging correlation, J Ultrasound Med 38 (2019) 513–528. [5] J Crim, Medial-sided ankle pain: deltoid ligament and beyond, Magn Reson Imaging Clin N Am 25 (2017) 63–77. [6] JR Crim, TC Beals, F Nickisch, A Schannen, CL Saltzman, Deltoid ligament abnormalities in chronic lateral ankle instability, Foot Ankle Int 32 (2011) 873–878. [7] J Crim, MR imaging evaluation of subtle Lisfranc injuries: the midfoot sprain, Magn Reson Imaging Clin N Am 16 (2008) 19–27, v. [8] JA Mann, DI Pedowitz, Evaluation and treatment of navicular stress fractures, including nonunions, revision surgery, and persistent pain after treatment, Foot Ankle Clin 14 (2009) 187–204. [9] A Donovan, ZS Rosenberg, JT Bencardino, ZR Velez, DB Blonder, GA Ciavarra, et al., Plantar tendons of the foot: MR imaging and US, Radiographics 33 (7) (2013) 2065–2085. [10] SB Soliman, PJ Spicer, MT van Holsbeeck, Sonographic and radiographic findings of posterior tibial tendon dysfunction: a practical step forward, Skeletal Radiol 48 (2019) 11–27. [11] MS Taljanovic, JN Alcala, LH Gimber, JD Rieke, MM Chilvers, LD Latt, High-resolution US and MR imaging of peroneal tendon injuries—
erratum, Radiographics 35 (2015) 651. [12] S Bianchi, C Martinoli, IF Abdelwahab, Ultrasound of tendon tears. Part 1: general considerations and upper extremity, Skeletal Radiol 34 (2005) 500–512. [13] S Bianchi, PA Poletti, C Martinoli, IF Abdelwahab, Ultrasound appearance of tendon tears. Part 2: lower extremity and myotendinous tears, Skeletal Radiol 35 (2006) 63–77. [14] DV Flores, C Mejia Gomez, M Fernandez Hernando, MA Davis, MN Pathria, Adult acquired flatfoot deformity: anatomy, biomechanics, staging, and imaging findings, Radiographics 39 (2019) 1437–1460. [15] P Robinson, LM White, Soft-tissue and osseous impingement syndromes of the ankle: role of imaging in diagnosis and management, Radiographics 22 (2002) 1457–1469, discussion 70–71. [16] CD Chang, JS Wu, MR imaging findings in heel pain, Magn Reson Imaging Clin N Am 25 (2017) 79–93. [17] M De Maeseneer, H Madani, L Lenchik, M Kalume Brigido, M Shahabpour, S Marcelis, et al., Normal Anatomy and Compression Areas of Nerves of the Foot and Ankle: US and MR Imaging with Anatomic Correlation, Radiographics 35 (5) (2015) 1469–1482.
CHAPTER 62
Bone Tumors James Kho, Rajesh Botchu, Steven James
Introduction Imaging plays a central role in the diagnosis and management of suspected bone tumors. For many suspected bone tumors, a definitive diagnosis or narrow differential diagnosis is possible from the imaging appearances alone. It is imperative that a radiological diagnosis is made as far as possible to avoid unwarranted biopsies of lesions with pathognomic radiological appearances, such as bone cysts. In other bone lesions, correlation with histopathological examination of the lesion may be required to establish the diagnosis. However, even in these cases, imaging should be regarded as complementary to histopathological opinion, particularly if this is based on biopsy material rather than the sectioning of a resection specimen. Inadequate investigations have occasionally been responsible for erroneous diagnoses of benign lesions as malignant, resulting in unnecessary surgical procedures, including iatrogenic disasters, such as amputation. Beyond establishing the diagnosis, imaging is important for surgical planning, oncological staging, and image-guided treatment such as radiofrequency ablation and follow-up. It is recognized that bone tumors can present as a considerable diagnostic challenge. Although benign and innocuous lesions such as fibrous cortical defects are common, and may occur in up to 30% of normal children, primary malignant tumors of bone are relatively rare and are responsible for only 1% of all deaths from neoplasia. Consequently, most radiologists will see comparatively few cases. Furthermore, there are a large number of recognized types of primary bone tumors, with varying radiological appearances. With these challenges in mind, this chapter begins with a discussion of a general diagnostic approach to bone lesions, irrespective of etiology.
Following this, the clinical and imaging characteristics of individual primary bone tumors (i.e., bone lesions of neoplastic or uncertain etiology) will be discussed, followed by metastatic bone disease. However, it is important to recognize that neoplastic bone lesions, whether benign or malignant, only represent a subset of bone lesions. Bone lesions may also arise from a myriad of non-neoplastic pathophysiological processes, including trauma, hematological diseases, autoimmune disorders, and metabolic disorders.
General Diagnostic Approach to Bone Tumors Radiographic Features The radiograph is vital in establishing the diagnosis or differential diagnosis of a bone lesion and is supplemented where necessary by further imaging including magnetic resonance imaging (MRI), computed tomography (CT), and nuclear medicine studies. Many of the characteristic imaging features of bone lesions were initially described on conventional radiographs given the long history of this technique. Radiographs are most frequently the initial technique used and it is therefore important to be able to assess bone lesions on radiographs to decide if further imaging is indicated. Finally, many of the principles of assessing a lesion on radiographs such as nature of periosteal reaction and lesion margins are applicable across imaging techniques. A systematic approach should be adopted in the radiographic assessment of any bone lesion. The key features that need to be assessed are the age of the patient, the location of the lesion, and the lesion appearances (Table 62.1). Table 62.1 Systematic Assessment of Bone Lesions Features to Be Assessed on Any Bone Lesion Age of patient Location of lesion • Which bone is affected? • Where is the lesion within the bone?
Features to Be Assessed on Any Bone Lesion Lesion appearances • Is lesion lytic or sclerotic? • Is there matrix calcification? • Are there any aggressive features? ○ Margins within the bone ○ Cortex ○ Periosteum ○ Soft-tissue
Age of the Patient The patient’s age should always be taken into account when formulating the differential diagnosis of any bone lesion because the prevalence of different bone lesions changes considerably with age. For example, a lytic lesion confined to the epiphysis is likely to reflect infection or chondroblastoma in a child before growth plate fusion, whereas if this is encountered in an adult over 50 years, alternate diagnosis such as a geode needs to be considered. As a general rule, with increasing age, bone metastasis, and myeloma become more likely causes of bone lesions than primary bone tumors. Nonetheless, on very rare occasions, lesions may be found outside the typical age groups. Some tumors such as osteosarcomas classically have a dual peak in incidence—the primary idiopathic form occurring in younger patients, and the secondary form occurring in older patients in association with Paget’s or previous irradiation. In clinical practice, the patient’s age should be readily available clinical information, but in the absence of this, the approximate patient’s age may be discerned from the state of physeal closure and the presence or absence of degenerative joint disease. The following diagram summarizes the tumors by age (Fig. 62.1).
FIGURE 62.1 Incidence of bone tumors by age.
Lesion Location The prevalence of bone lesions varies between different bones and between specific locations within bones. Primary bone lesions often show a predilection for certain types of bones (e.g., osteoid osteomas usually occur in long bones, not flat bones). Some lesions almost always occur in a specific bone (e.g., osteofibrous dysplasia [OFD] and adamantinoma in the tibia). The importance of considering the location in formulating a differential is exemplified by the example of central cartilage tumors— intramedullary cartilage-forming lesions with no aggressive imaging features in the phalanges, proximal humeri, and distal femur are most likely to be enchondromas, but lesions with similar imaging appearances in the axial skeleton should be considered suspicious for low-grade chondrosarcomas. The specific bone favored by each lesion will be discussed under the relevant subsection for that lesion later in this chapter. The location of the lesion within a bone should be noted in relation to the physis (diaphysis, metaphysis, epiphysis, apophysis), and in relation to the cortex and medulla (surface or periosteal lesion, intracortical, intramedullary). Intramedullary lesions may also be described as either
central or eccentric. For example, nonossifying fibroma and fibrous cortical defects are cortically based lesions, located at the metadiaphysis of a long bone. The following diagrams summarize the distribution of bone lesions by their location (Figs. 62.2 and 62.3).
FIGURE 62.2 Distribution of bone tumors by location relative to the physis.
FIGURE 62.3 Distribution of bone tumors by location relative to the cortex and medulla.
Epiphyseal lesions also occur in epiphyseal equivalents which include apophyses (e.g., greater trochanter of the femur) and certain bones such as the patella, talus and calcaneum. For example, the most common primary bone tumors of the patella are chondroblastoma and giant cell tumor (GCT). In addition to the location of the lesion, the radiograph should also be reviewed for any further bone lesions. Most primary bone tumors are confined to a single bone at the time of presentation in the absence of an underlying syndromic predisposition such as the multiple osteochondromas of hereditary multiple exostosis (HME) and multiple cartilage tumors in Ollier disease/Maffucci syndrome. Direct tumoral spread across a joint is rare but is well described at the sacroiliac joints with benign lesions such as GCT of the bone, as well as malignant tumors such as osteosarcoma. Imaging should include the entirety of the bone containing the lesion (i.e., from the joint proximal to the lesion, until the joint distal to the lesion), to evaluate for skip metastasis or multifocal lesions within a bone. Skip
metastases refer to metastatic lesions either within the same bone of the primary lesion or across a single joint in an adjacent bone, in the absence of widespread systemic metastatic disease. Skip metastases can occur in all high-grade sarcomas arising from the bone, but are most typically associated with osteosarcoma, chondrosarcoma, and Ewing sarcoma.
Lesion Appearances A comprehensive description of the radiographic appearances of a suspected bone tumor, in combination with the age and location of the lesion as described earlier, will often allow the radiologist to narrow the differential down to one or a few possibilities. The radiographic appearances can be subdivided and each category should be assessed for and described in every lesion. Is the Lesion Lytic or Sclerotic? This is, essentially, whether the lesion results in increased or decreased density relative to normal bone. Some lesions will be of mixed lytic and sclerotic components. Sclerotic components in a bone lesion are not a sign of benignity, as a gamut of lesions of varying aggressiveness, ranging from benign bone islands to malignant high-grade osteosarcoma may be sclerotic in nature. Likewise, the differential for lytic lesions includes completely benign entities such as simple bone cyst, and highly malignant entities such as Ewing sarcoma. Is There Matrix Calcification or Mineralization? The matrix refers to the internal substance of a lesion. On radiographs, the terminology matrix is usually applied to the pattern of calcification or mineralization, from which the nature of a lesion may be inferred. Two primary patterns of mineralization are recognized—chondroid and osteoid (Fig. 62.4). A chondroid matrix refers to ring, arc, or popcorn pattern of calcification and implies a cartilage-forming lesion. An osteoid matrix refers to denser mineralization in a rounded or amorphous pattern, and implies a bone-forming lesion. If the lesion extends into the surrounding soft-tissue, matrix calcification may be visualized better in the extraosseous component than in the intraosseous component. The terminology “ground-glass matrix” is sometimes used to refer to the relatively homogenous hazy density characteristically seen in fibrous dysplasia.
FIGURE 62.4 Matrix. (A) Ring and arc calcification of chondroid matrix, (B) dense mineralization of osteoid matrix, and (C) homogenous hazy density of ground-glass matrix.
Are There Any Aggressive Features? It is generally preferable to describe lesions based on the presence or absence of aggressive features rather than having malignant or benign features. Infection and histologically benign lesions such as GCT can have aggressive features on imaging. Conversely, small intramedullary bone metastases may not show any aggressive appearances. With regard to the aggressive features, the lesion should be reviewed in terms of its margins within the bone, followed by any changes in surrounding tissue starting from the closest to most distant (namely the bone cortex, periosteum, and softtissue). In practice, the presence of any single aggressive feature in a lesion generally warrants concern, requiring further clinical and radiological workup, although it should be emphasized that not all lesions demonstrating aggressive features will be malignant.
Margins Within the Bone (Zone of Transition) The margins of a bone lesion are often described based on the width of the zone of transition, that is the region between normal bone and the lesion (Fig. 62.5). An abrupt change at the margin of the lesion to normal bone is a narrow zone of transition. Some lesions have a thin surrounding rim of sclerosis which by definition is a narrow zone of transition. If the margin with normal bone is ill-defined, with a gradual change from lesional tissue to normal bone, this is a wide zone of transition. Occasionally, lesions will
have a permeative pattern, where the lesion and normal bone appear interspersed with no boundary between normal and abnormal bone. A wide zone of transition and a permeative pattern are both considered aggressive features in a focal bone lesion, although a permeative pattern may also be seen in metabolic diseases such as osteoporosis.
FIGURE 62.5 Zone of transition. Narrow (A), wide (B), and permeative pattern (C).
Cortex The cortex should be examined to determine if it is intact, or whether there is endosteal scalloping or cortical destruction (Fig. 62.6). Cortical destruction is an aggressive feature. Endosteal scalloping generally implies a slowgrowing bone lesion but in the setting of a central cartilage tumor, endosteal scalloping raises the possibility of a low-grade chondrosarcoma.
FIGURE 62.6 Cortical destruction (A) and endosteal scalloping (B).
The cortex should also be reviewed for other changes that do not imply aggressiveness or otherwise but may help narrow the differential diagnosis. Expansile lesions result in bowing (outward convexity) of the cortex, often associated with cortical thinning. Cortical thickening suggests exuberant periosteal bone formation, and is associated with osteoid osteomas, infection, and stress fractures. A focal step or linear lucency in the cortex overlying the lesion should raise concern for a pathological fracture. Pathological fractures occur in both benign and malignant lesions and are not an indicator of lesion aggressiveness. Lesions arising from the surface of the bone or in the adjacent soft-tissue can cause smooth scalloping or remodeling of the cortex of the bone that is sometimes referred to as saucerization.
Periosteum
The periosteum is a layer of thick connective tissue that covers the surface of all bones, except in its intra-articular portion. Periosteal reaction that is lamellated, spiculated, or interrupted are considered to be aggressive features, as is the Codman’s triangle (Fig. 62.7). Continuous, smooth, or wavy periosteal reactions are not considered to be indicative of an aggressive pathology, and are sometimes referred to as “benign” periosteal reactions. A pathological fracture is a possible cause of a periosteal reaction in proximity to a bone lesion but periosteal reactions resulting from fracture callus formation should never display aggressive morphology on radiographs.
FIGURE 62.7 Periosteal reaction. (A) Smooth, thin, (B) lamellated, (C) spiculated, and (D) interrupted with Codman’s triangle (arrow).
Soft-Tissue Increased soft-tissue density around a bone lesion implies extraosseous extension into the soft-tissue which is an aggressive feature.
Further Imaging and Biopsy Based on the age of the patient, the lesion location and its radiographic appearances, a diagnosis or differential diagnosis should be formulated. At this stage, further imaging may be warranted depending on the differential
diagnosis. Indications for further imaging include further characterization of the lesion, for oncological staging, treatment planning, and follow-up. Imaging investigations for lesion characterization should be performed before any biopsy of a lesion as such procedures may alter imaging appearances. The role of biopsies will also be briefly discussed in this section as image-guided biopsies are increasingly being performed by radiologists under imaging guidance rather than by surgeons in the operating theatre. Magnetic Resonance Imaging Although radiograph is essential for the diagnosis of bone tumor, MRI defines better, the extent of involvement in terms of marrow and soft-tissues. Therefore, tumor measurements, radiation, and resection planning are more accurately undertaken based on MRI (usually with contrast). MRI provides high spatial resolution images with excellent tissue discrimination in multiple planes. In terms of lesion characterization, the following imaging features are particularly well visualized on MRI, and are helpful in discriminating between different lesions.
◾ Precise anatomical location and extent of the lesion ◾ Extent of perilesional edema—both bone marrow edema and soft-tissue edema ◾neurovascular Extent of extraosseous extension into surrounding soft-tissue, and assessment of and joint involvement ◾ Signal characteristics of lesion to identify specific tissue components
The precise delineation of lesion from perilesional edema can be challenging, particularly on fluid-sensitive sequences, and therefore T1weighted images are often most helpful for this (Fig. 62.8). Neurovascular involvement should be considered when there is loss of the normal fat plane separating these structures lesion, particularly when there is encasement. Signal characteristics help distinguish between solid and cystic lesions, and allow for the identification of specific components that may be present within a lesion, namely fat, cartilage, hemorrhage, and calcification (Table 62.2). However, in the absence of these specific tissue types within a lesion, bone lesions on MRI can show considerable overlap in signal characteristics.
FIGURE 62.8 Lesion delineation on T1-weighted MRI image. Replacement of normal high signal fat in bone marrow by low-signal tumoral tissue (white arrows). Perilesional edema (asterisk) typically remains hyperintense relative to the skeletal muscle (arrowhead) on T1 as fat remains present.
Table 62.2 Intralesional Signal Characteristics on Magnetic Resonance Imaging Composition of Intralesional Foci
T1
T2
Example Lesion Containing the Intralesional Foci
Composition of Intralesional Foci
T1
T2
Example Lesion Containing the Intralesional Foci
Fat
Hyperi ntense
Hyperinte nse
Hemangioma, marrow fat in osteochondroma
Cartilage
Hypoin tense
Homogen ously hyperinten se
Enchondroma, chondrosarcoma
Calcification
Hypoin tense
Hypointen se
Most bone and cartilageforming primary bone lesions
Hemorrhage (recent)
Hyperi ntense
Variable
Aneurysmal bone cyst
Hemorrhage (old, hemosiderin)
Hypoin tense
Hypointen se
Giant cell tumor
Imaging protocols vary between institutions, but a combination of T1 imaging and fluid-sensitive sequences (e.g., T2, PDFS, STIR) in different planes are required at the minimum. An example of an imaging protocol at the authors’ institution is provided in Table 62.3. Table 62.3 Example Magnetic Resonance Imaging Protocol for the Evaluation of a Suspected Bone Tumor Imaging Plane
Sequence
Axial
T1
Axial
T2 fat-suppressed
Coronal
T1
Coronal
STIR
Gadolinium-enhanced MRI sequences can provide additional information, in particular, to distinguish between solid components within a lesion that generally enhance and necrotic/cystic components within a lesion that do not enhance. Dynamic contrast enhancement may also help in discriminating
higher grade from lower-grade lesions, based on the principle that highergrade lesions enhance more rapidly than lower-grade lesions. There is, however, debate as to whether routine use of contrast-enhanced sequences is necessary. Whole-body MR imaging is sometimes used for oncological staging of bone tumors, particularly childhood bone tumors such as Ewing sarcoma. Whole-body MRI briefly involves acquisition of wide-field of view images over large body regions using limited sequences, such that the entire body from head to toe is imaged. Typically, a sequence that is considered to be sensitive for the detection of metastatic lesions such as STIR, DIXON, or diffusion-weighted imaging is employed. Potentially metastatic lesions identified on whole-body MRI may need further imaging and/or sampling to determine their nature. In addition to avoiding ionizing radiation exposure, whole-body MRI is particularly valuable in identifying small intramedullary bone metastasis that may be occult on CT and planar nuclear imaging. Computed Tomography The principles of the evaluation of a bone lesion on CT are as on conventional radiographs. However, the lack of overlapping structures means that CT is often superior for detecting subtle calcification, intralesional fat, and extraosseous extension compared with radiographs. Visualization of lesions involving the axial skeleton, in particular, is superior on CT compared with radiographs. Although MRI is generally more helpful for lesion characterization, CT can be a valuable problem-solving tool to demonstrate patterns of calcification or ossification, or fine osseous detail which may not be visualized on MRI. Examples where CT may be employed in this fashion include distinguishing between a surface osteosarcoma and periostitis ossificans by the pattern of ossification, or demonstrating the tiny nidus within an osteoid osteoma to confirm this diagnosis. Due to the need for fine osseous detail, CT reconstructions with thin slice thickness (0.5–1.5mm) and using high-frequency kernels (bone kernels) are essential. Contrast medium enhancement is of limited value on CT in the diagnosis of bone lesions, because most tumors do not enhance on CT in a diagnostically useful fashion. CT is also the primary technique used to exclude the presence of a thoracic or abdominopelvic visceral primary lesion where bone metastasis is suspected. The lungs are the most common site of metastases for the majority of malignant primary bone tumors, and a noncontrast CT is more sensitive in the detection of pulmonary metastases that a chest radiograph. Radionuclide Imaging
The bone scan (planar scintigraphy with technetium-99m-labeled bisphosphonate) is commonly used to establish whether or not the lesion is solitary. Abnormal foci subsequently detected may then require radiographic examination or MRI to confirm their etiology. The delayed phase of the bone scan is obtained 2–3 hours after injection of the Tc-99m-labeled bisphosphonate, when the agent has localized to osteoblastic activity in bone. Tc-99m-labeled bisphosphonate uptake into bone depends on the rate of new bone formation. Some bone lesions such as myeloma bone deposits are characteristically not accompanied by any osteoblastic activity; these lesions are thus photopenic and not well visualized on bone scans. Bone scans allow for imaging of the whole body including the appendicular skeleton and are widely available. Both benign and malignant bone lesions may demonstrate uptake on a bone scan, although the specific pattern of uptake on the blood-pool or delayed phases of a bone scan can sometimes be helpful for lesion characterization. The specificity of Tc-99mlabeled bisphosphonate scintigraphy in discriminating lesional uptake from degenerative changes, particularly in certain anatomical regions such as the spine, can be improved by using single-photon emission computerized tomography (SPECT) instead of planar scintigraphy, particularly in the form of SPECT/CT, where CT is performed at the same time. It is important to recognize that the extent of increased uptake on a bone scan does not necessarily reflect the true tumor limits; uptake beyond the tumor margins even into adjacent joints can occur due to hyperemia or reactive bone formation [1]. F-fluorodeoxyglucose (FDG)-PET/CT is a further radionuclide imaging technique of relevance to bone lesions. In contrast to bone scans, uptake on FDG-PET/CT localizes to regions of increased metabolic activity, rather than new bone formation. Uptake on FDG-PET/CT within a bone lesion can be semiquantified as a standardized uptake value (SUV). Malignant lesions generally exhibit greater uptake and hence SUV. However, uptake varies too greatly between different primary bone lesions for there to be a single SUV cutoff to discriminate between benign and malignant lesions. Instead, FDGPET/CT is useful to detect bone metastasis with higher accuracy than a planar bone scan, but at a cost of increased radiation dose exposure. Angiography It is doubtful whether angiography now contributes significantly to the assessment of primary tumors and their extent. Historically, two signs— localized vessel narrowing by tumor encasement, and the presence of irregular branching tumor vessels—are described to occur with greater frequency in malignant tumors. Interventional angiography, however, has an important role in the embolization of highly vascular tumors, such as the metastatic bone deposit of renal cell carcinoma, before surgical treatment.
Image-Guided Biopsy Biopsies of bone lesions are performed either as open surgical biopsies, or as percutaneous needle biopsies under image guidance. CT is often used to guide biopsies of bone lesions, although ultrasound (US) guidance is also feasible in some circumstances, particularly for lesions with extraosseous extension into the soft-tissues. With primary bone tumors, there is a risk of seeding of tumoral tissue into the biopsy tract. To minimize the risk of local recurrence from this tumoral seeding, biopsy tracts need to be excised at the time of surgery. A poorly placed biopsy tract could therefore result in a patient needing far more extensive surgery with greater morbidity. It is imperative that radiologists consider the planned surgical approach before biopsy of any suspected primary bone tumor, ideally through discussion with the orthopedic oncology surgeon. Biopsy tracts should be planned to pass through as few muscular compartments as possible (Fig. 62.9). Some centers advocate the use of ink marking of the skin to highlight the biopsy site to facilitate excision at the time of surgery.
FIGURE 62.9 CT-guided biopsy of a lesion in the proximal femur. The biopsy course has been planned through the lateral aspect of the proximal femur to avoid passage through the quadriceps muscle compartment anteriorly, and the gluteal and hamstring compartments posteriorly.
Seeding is less of a clinical concern in the context of metastatic bone lesions. Generally, the most direct biopsy tract that avoids critical structures, such as the nerves, vessels, and joints, may be employed where a primary bone tumor has been excluded by the presence of multiple lesions. If a suspected metastasis is solitary, biopsy principles should follow those of a suspected primary bone tumor.
Diagnostic Imaging Pathway The diagnosis of a bone lesion is perhaps best thought of as a diagnostic pathway involving different imaging techniques and sometimes biopsy. It would not be uncommon that a definitive diagnosis cannot be reached using a single technique alone, even with MRI. The correct diagnosis of a specific bone lesion on imaging often requires a synthesis of different imaging features, observed on different techniques.
A suggested imaging pathway utilizing the different imaging techniques is presented in the following chart (Fig. 62.10). This pathway may be taken as a general guide, but a decision on the best imaging investigation to undertake next should always be tailored to the precise clinical or imaging question that requires answering.
FIGURE 62.10 Diagnostic imaging pathway for a suspected bone lesion.
Treatment of Bone Tumors The treatment of bone tumors is beyond the scope of this chapter and varies between lesions. Briefly, conservative management with clinical or imaging follow-up may be employed for asymptomatic or minimally symptomatic benign tumors such as simple bone cysts. At the other end of the spectrum, high-grade malignant primary tumors such as osteosarcoma and Ewing sarcoma require excision with wide margins, often in conjunction with chemotherapy. Allografts or endoprosthetic replacements may be used for reconstruction following surgical excision. Where tumoral spread is more extensive, wide surgical excision to clear margins may necessitate partial or complete amputation. For symptomatic or locally aggressive benign tumors, a range of treatments have been used, such as intralesional curettage, phenol injection and cementation, or image-guided ablation. Some tumors may even respond
to medical therapy, for example, bisphosponates or denosumab for GCTs of the bone.
Primary Bone Tumors Many different primary bone tumors are recognized, varying in their mode of clinical presentation, pathology, and clinical behavior. Their etiology remains obscure. Some appear to be superimposed upon a pre-existing disease such as Paget’s disease or bone infarction. An increased incidence of both benign and malignant neoplasms is known to follow radiation therapy. A radiologically unusual metastasis is more common, particularly in older patients, than a primary bone tumor. Metastatic bone disease is discussed later in this chapter. Bone lesions associated with hematopoietic and lymphoreticular elements of the bone, such as lymphoma, are discussed elsewhere (see Chapter 54).
Classification of Primary Bone Tumors The classification of bone tumors used in this chapter is presented in Table 62.4. This classification is adapted from the World Health Organization (WHO) classification [2], with modifications to emphasize lesions with similar radiological appearances. Classification of certain bone lesions reflects the cells that predominate in the developed lesion, rather than its cell of origin as the latter is not always known. Given the uncertain etiology of some primary bone lesions (e.g., neoplastic vs developmental), it is not possible to limit the definition of bone tumors to strictly neoplastic lesions. As such and in line with the WHO classification, primary bone lesions such as fibrous cortical defects (FCDs) and simple bone cysts are considered to be primary bone tumors, although they are likely non-neoplastic in origin. Table 62.4 Classification of Primary Bone Lesions Cartilageforming
Includes locally aggressive lesions with nonexistent or very low metastatic potential.
A brief description of the clinical features of individual primary bone tumors, followed by their imaging features and differential diagnosis are presented in the following section. It is advised that equal emphasis should be placed on reviewing the images as the text, to get a “feel” for the appearances of each lesion.
Cartilage-Forming Tumors Chondromas Chondromas are benign cartilaginous tumors, consisting histologically of well-differentiated cartilage with low mitotic activity. Chondromas are commonly subclassified according to their location; enchondromas when they occur within a bone, and periosteal chondromas when they arise from
the surface of a bone. Chondromas can also arise within the soft-tissues, as soft-tissue chondromas. Enchondromas Enchondromas present clinically either as an incidental imaging finding or occasionally as a pathological fracture. Classically, these lesions are thought of as being most common in the hands and feet, based on conventional radiographs. With increasing MRI utilization, it is now apparent that up to 2–3% of all knee MRIs demonstrate incidental enchondromas, many of which may be occult on radiographs [3,4]. Treatment is conservative, except in rare circumstances where the risk of fracture is considered to be high. Imaging Features: On radiographs, enchondromas are well-defined metadiaphyseal lytic lesions, often eccentrically located in the medullary cavity (Fig. 62.11). They may be mildly expansile, particularly when located in a narrow tubular bone, for example, fibula or phalanges, with associated endosteal scalloping and cortical thinning. A chondroid (ring and arc) pattern of matrix mineralization is almost invariably present, except in the small bones of the hands and feet, where they may be purely lytic. As a benign lesion, an enchondroma should exhibit no aggressive features radiologically. Any aggressive feature such as cortical destruction, extraosseous extension, or periosteal reaction (in the absence of a fracture) is in keeping with a chondrosarcoma.
FIGURE 62.11 Enchondroma. Well-defined, lytic, mildly expansile lesion in the proximal phalanx of the little finger.
On MRI, enchondromas demonstrate low T1 and high T2 signals in keeping with well-differentiated cartilage (Fig. 62.12). The lesion is usually uniform in signal, aside from small foci of low signal on all sequences representing chondroid calcification. No perilesional edema should be present. Peripheral enhancement occurs after administration of contrast. Enchondromas may show uptake on the bone scan but uptake is more often demonstrated with chondrosarcomas.
FIGURE 62.12 Enchondroma. (A) Ring and arc calcification in proximal humeral enchondroma on radiograph. (B) Noncalcified cartilage within enchondroma is high signal on fluid-sensitive images, while calcified cartilage is low signal.
Sometimes, intramedullary cartilaginous tumors do not demonstrate gross aggressive imaging features but exhibit more clinically aggressive behavior. These lesions represent atypical cartilaginous tumors or low-grade chondrosarcomas, rather than enchondromas. Low-grade chondrosarcomas rarely metastasize to the lungs and the bones, with an 83–89% 10-year survival rate [5]. In practice, distinguishing between enchondroma and low-grade central chondrosarcoma can sometimes be difficult, as both these lesions may demonstrate similar features radiologically and histologically [6]. There are however several imaging features that can be helpful. It is critical to appreciate that enchondromas are common in tubular bones, but uncommon in flat bones, such that an “enchondroma” of a flat bone should be regarded as a probable low-grade chondrosarcoma. Conversely, it is very unusual for central cartilaginous tumors in the hands and feet to demonstrate aggressive behavior, and the diagnosis of enchondroma in these sites can often be made on radiographs alone. Second, any interval change in size or radiological appearances on serial imaging should raise concern for chondrosarcoma. Third, larger lesions, particularly greater than 5 cm, are more likely to represent chondrosarcomas. Lastly, deep (>2/3 cortical thickness) or circumferential endosteal scalloping favors chondrosarcoma over enchondroma (Fig. 62.13).
FIGURE 62.13 Low-grade chondrosarcoma in the humerus demonstrating marked craniocaudal extension within the proximal-tomid diaphysis and deep endosteal scalloping along the lateral cortex (arrow, A), which is magnified in the image (B).
Differential Diagnosis
◾interval Low-grade central chondrosarcoma (consider if large >5 cm, deep endosteal scalloping, change, or uncommon location). ◾ High-grade central chondrosarcoma (aggressive features present). ◾orOnaneurysmal radiographs alone, if purely lytic in small tubular bones, consider GCT (if subarticular) bone cyst (ABC). MRI differentiates. ◾calcification Occasionally serpiginous calcification of bone infarcts may be confused for ring and arc of enchondroma.
Periosteal Chondroma Periosteal chondromas, also known as juxtacortical or surface chondromas, are much less common than enchondromas. These benign lesions are histologically similar to enchondromas and have predilection to the same bones as enchondromas. Given their more superficial location, periosteal
chondromas tend to present clinically as hard lumps. They occur frequently in association with Ollier disease. Imaging Features: On radiographs and CT, periosteal chondromas are typically visualized as a soft-tissue density lesion arising from the surface of bone, with mild erosion of the cortex. A chondroid matrix pattern of calcification may be present. Reactive periosteal bone formation at the interface of this lesion with the cortex is typical (Fig. 62.14). On MRI, periosteal chondromas demonstrate cartilage signal (hypointense on T1, uniformly hyperintense on T2), with or without markedly hypointense signal foci representing calcification.
FIGURE 62.14 Periosteal chondroma, proximal humerus. (A) Periosteal reaction and mild cortical erosion at the interface of the lesion with the bone cortex. (B) Axial MRI T2 image demonstrates the lesion comprises largely of hyperintense signal of well-differentiated cartilage (arrow), with small internal hypointense regions representing calcification. Note absence of medullary involvement.
Differential Diagnosis
◾deep Periosteal chondrosarcomas (rare malignant counterpart), consider if greater than 3 cm or if cortical surface erosion. ◾exhibit Other periosteal lesions may mimic periosteal chondroma on radiographs but these do not cartilage signal on MRI.
Syndromic Forms
◾multiple Ollier disease (Enchondromatosis) is a sporadic (nonhereditary) syndrome characterized by enchondromas, although periosteal chondromas may also be present (Fig. 62.15). Enchondroma distribution is usually similar to nonsyndromic solitary enchondromas, with additional involvement of other sites such as the pelvis. The severity of the presentation varies between patients but may be large with associated deformity and limb growth abnormality. An increased risk of chondrosarcomatous change has been reported, with an estimated lifetime risk of chondrosarcoma of 25–40% [7,8]. Chondrosarcoma should be considered if interval change occurs in a lesion after skeletal maturity. Lesions of Ollier disease are more hypercellular than nonsyndromic enchondromas, and can mimic chondrosarcoma histologically. Maffucci syndrome is the association of multiple enchondromas with multiple soft-tissue hemangiomas. On radiographs, the soft-tissue hemangiomas are characteristically recognized by the presence of soft-tissue masses containing phleboliths (Fig. 62.16). An increased lifetime risk of chondrosarcoma of 15–50% has been reported [7–9].
◾
FIGURE 62.15 Ollier disease. Multiple enchondromas with associated deformity are present. A periosteal chondroma is also present on the third metacarpal.
FIGURE 62.16 Maffucci syndrome. In addition to multiple enchondromas, note the ovoid calcific densities within the soft-tissues which are phleboliths within soft-tissue hemangiomas.
Chondroblastoma This chondroid tumor arises in the epiphysis of the tubular bones, or epiphyseal equivalent (e.g., apophysis or patella). Chondroblastoma usually occurs in children or young adults before growth plate fusion [10], in contrast to GCTs which occur after growth plate fusion. Presentation is of pain around the joint which may be of long duration and there may be limitation of joint movement. Treatment is by image-guided ablation for small lesions or curettage for larger ones. Imaging Features: On radiographs, a chondroblastoma is typically a rounded or oval lytic lesion with a thin sclerotic rim in the epiphysis or other epiphyseal equivalent. Larger lesions may extend into the metaphysis (Fig. 62.17).
Approximately half of lesions will have a demonstrable chondroid matrix pattern of calcification [10]. No aggressive features are present, but a benign periosteal reaction and joint effusion in the adjacent joint may be demonstrated [11].
FIGURE 62.17 Chondroblastoma in the proximal tibia. Although chondroblastomas arise in the epiphysis, extension into the metaphysis is not uncommon, as depicted in (A). Florid surrounding marrow edema (asterisk) typical of chondroblastomas is demonstrated on the coronal MRI STIR image in (B).
On MRI, chondroblastomas demonstrate variable signal characteristics. In addition to its epiphyseal location, a distinguishing imaging feature is the presence of a local surrounding inflammatory response. Surrounding marrow edema is common, as is soft-tissue edema (Fig. 62.17). Fluid–fluid levels may be present in some chondroblastomas reflecting secondary ABC formation. On bone scans, there is marked increased uptake on blood-pool phase. Differential Diagnosis: Other epiphyseal lesions in patients of a young age are the main differentials:
◾plate GCT does not typically demonstrate such florid edema and is uncommon before growth fusion. No sclerotic rim or matrix mineralization is present with GCT. ◾presence Osteomyelitis is usually readily distinguished from chondroblastoma on MRI due to the of a peripheral rim of mildly increased T1 signal (penumbra sign) around the intraosseous abscess, the presence of a sequestrum, sinus, or soft-tissue collection.
Chondromyxoid Fibroma
Chondromyxoid fibroma (CMF) is a very rare benign chondroid tumor, comprising 1.5 cm or interval growth after skeletal maturity.
FIGURE 62.25 Secondary peripheral chondrosarcoma. (A) Large lesion with chondroid calcification arising from the posterior tibia. (B) Axial T2FS MRI image depicting the markedly thickened cartilage cap (arrows) of the chondrosarcoma, arising from an underlying osteochondroma (asterisk).
Dedifferentiated Chondrosarcoma: Dedifferentiated chondro-sarcoma refers to the development of a high-grade nonchondrogenic sarcoma, within a low- to intermediate-grade chondroid tumor. The high-grade sarcoma is usually undifferentiated pleomorphic sarcoma (UPS), but osteosarcoma and other sarcoma types are known to occur. This occurs in approximately 7–20% of low- to intermediate-grade chondrosarcomas and is associated with a poor prognosis [20]. Dedifferentiated chondrosarcoma occurs in older patients, with a mean of approximately 60 years of age. The most common sites are the femur and pelvis. Radiologically, the diagnosis of dedifferentiation may be recognized as an area of osteolytic destruction developing adjacent to low-grade chondrosarcoma, which may destroy part of the pre-existing cartilaginous tumor (Fig. 62.26).
FIGURE 62.26 Dedifferentiated chondrosarcoma. Known low-grade chondrosarcoma of femur on follow-up with new ill-defined lytic focus at its inferiormost portion (arrow), corresponding to dedifferentiated sarcoma.
Mesenchymal Chondrosarcoma: This malignant cartilage tumor is rare. Histologically, it is characterized by islands of cartilage among undifferentiated spindle or round cell mesenchymal tissue. Craniofacial lesions are more common than in conventional chondrosarcoma. About a third of these tumors arise in the soft-tissues, especially in the extremities (thigh and calf). The imaging features of mesenchymal chondrosarcoma are similar to conventional chondrosarcoma, although these lesions often show more aggressive features (large soft-tissue mass, permeative pattern) at presentation, as well as a more prominent enhancement. Clear Cell Chondrosarcoma: This is an uncommon variant of chondrosarcoma that is typically located within the epiphysis, usually occurring within the proximal humerus, femur or tibia. Clear cell chondrosarcoma is frequently low-grade histologically. Clear cell chondrosarcoma occurs at 30–50 years of age. On radiographs, clear cell chondrosarcoma resembles chondroblastoma, resulting in a well-defined osteolytic lesion in the epiphysis that may have a sclerotic border (Fig. 62.27). Internal chondroid calcification is sometimes present. Unlike chondroblastoma, clear cell chondrosarcoma is not associated with surrounding inflammatory reaction, and therefore joint effusion, periosteal reaction, and bone marrow edema are absent or minimal
on MRI. In differentiating clear cell chondrosarcoma from chondroblastoma, considering patient age is critical.
FIGURE 62.27 Clear cell chondrosarcoma of femur. (A) Radiograph demonstrates typical appearances as a well-defined lytic epiphyseal lesion with thin sclerotic margin. The absence of degenerative hip arthropathy makes a geode unlikely. (B) Small intralesional foci of chondroid calcification demonstrated on CT.
Bone-Forming Tumors Bone Island (Enostosis) A bone island is a deposit of compact lamellar bone (normally found in cortex) within the cancellous bone of the medullary cavity. Bone islands are benign and asymptomatic, and probably hamartomatous or developmental rather than neoplastic in origin. They may be solitary or multiple. Imaging Features: On radiographs and CT, bone islands are uniformly dense, round or oval, and characteristically have radiating thorn-like spicules representing trabeculae, extending into the surrounding medullary cavity (Fig. 62.28).
FIGURE 62.28 Bone island (A) Dense, well-demarcated bone island with typical spicules in the distal femur. (B) Bone island in the iliac bone of a different patient, illustrating similar CT density to the cortical bone. (C) Homogenous markedly hypointense signal of the bone island depicted on coronal PD MRI image.
Bone islands usually measure less than 15 mm in diameter, but occasionally may be much larger. Bone islands over 2 cm in size are sometimes referred to as giant bone islands. Bone islands may grow in size up to the age of skeletal maturity but only rarely thereafter. MRI is not usually needed but may confirm the lack of bone marrow edema or other aggressive features. On MRI, bone islands are markedly hypointense on all sequences, in a similar manner to bone cortex. On bone scintigraphs, they show similar or minimally increased activity compared with normal bone. Occasionally giant bone islands may show move avid activity on bone scans. Osteopoikilosis refers to the condition of having numerous bone islands (Fig. 62.29).
FIGURE 62.29 Osteopoikilosis. Multiple bilateral bone islands, predominantly in the proximal femora.
Differential Diagnosis: Sclerotic metastases are the primary imaging differential diagnosis. Such metastasis typically
◾islands) are less uniformly dense (density >885 Hounsfield units on CT strongly favors bone [21], ◾ lack spicules of bone islands, ◾ demonstrate more avid uptake on bone scintigraphy.
Osteoma Osteomas are benign slow-growing lesions that arise from the surface of a bone, comprising compact lamellar bone, as well as a variable amount of cancellous bone. Like bone islands, they are benign and may represent hamartomas or reactive change rather than true neoplasms. The vast majority of these lesions arise from the craniofacial bones where they represent the most common benign bone lesion. These may arise from the outer or inner table of the skull, as well as within the sinuses. In contrast, osteomas of noncraniofacial bones are exceedingly rare (3.3 cm (which provides better sensitivity); or >6.6 cm (better specificity)
◾ Irregular margins ◾ Fascial invasion ◾ Presence of tumor necrosis ◾ Perilesional edema ◾ involvement ◾ Bone Neurovascular involvement Contrast-enhanced MRI can be helpful in distinguishing between benign and malignant lesions, but similarly, it is not a perfect parameter. Enhancement, either moderate or intense, can be seen in both benign and malignant lesions. Dynamic contrast enhancement has also been studied. Generally, malignant lesions tend to demonstrate rapid contrast uptake compared to benign lesions [9]. Van der Woude et al. reported a sensitivity of 91%, specificity 72% based on start of early enhancement ≤6 seconds [10]. Histological Characterization of Tumor The success of histological characterization of a soft tissue tumor based on MRI appearances is generally poor [6,7]. Gielen et al. reported success rate at predicting the histology on MRI in 50%, which decreases to 38% if benign lesions were excluded [6]. Nevertheless, it is worthwhile to consider some of the listed features below which can be useful to help arrive at a sensible differential diagnosis: 1. Masses with very high T1w signal There are five types of material (listed below) that can produce very high T1w signal, almost similar to subcutaneous fat. In the presence of high T1w signal, one should correlate with a fat suppressed sequence—fat-containing lesions will demonstrate decreased signal intensity, whereas other materials (proteinaceous, methemoglobin, melanin, and gadolinium) will remain hyperintense.
◾liposarcoma, Fat. Fat-containing lesions include lipoma, lipoma variants, lipoblastoma, lipomatosis of nerve, hibernoma,
hemangioma, marrow-containing lesions such as mature myositis ossificans Proteinaceous material. Ganglion or abscess can sometimes contain enough protein content to exhibit high T1w signal Methemoglobin in subacute hematoma, or even hemorrhage secondary to underlying tumor Melanin. High T1w signal reflecting presence of melanin can be seen in melanotic melanoma (Fig. 64.11), clear cell sarcoma (in around half of the cases), melanotic schwannoma Gadolinium contrast material 2. Masses with very low T2w signal
◾ ◾ ◾ ◾
Lesions with lower T2w signal similar to bony cortex can generally be considered to contain one or more of these components:
◾
◾desmoid, Fibrosis, such as plantar fibroma, GCT of tendon sheath, fibroma, fibrosarcoma ◾phleboliths Calcification, such as gouty tophi, chondroid mineralization, (venous malformation) ◾villonodular Hemosiderin, such as GCT of tendon sheath, pigmented synovitis (PVNS), hematoma. It is worth keeping in mind that not all of these lesions have sufficient hemosiderin at the time of scanning to produce a low T2w signal. Hemosiderin will also produce a blooming artifact on T2*-weighted gradientecho images (Fig. 64.12) Flow-voids, seen in high flow lesions such as arterial malformation and hemangioma 3. Masses with very high T2w signal
◾
Majority of soft tissue lesions demonstrates high T2w signal in a heterogenous fashion which does not particularly lead to a specific characterization. However, a very high T2w signal (similar to water) can help with characterization of lesions. Some lesions have homogenous bright T2w signal, and can represent true cystic lesions (such as ganglion and bursa), or cyst-appearing lesion which are actually solid lesions (such as myxoid tumors, PNST, vascular tumors, glomus tumors, synovial sarcoma) (Table 64.3). True cystic lesions can demonstrate enhancement in the periphery of the lesion (but not internally). Myxoid lesions on the other hand will have internal enhancement. Focal areas of high T2w signal in otherwise solid tumors are suggestive of necrosis, the presence of which may indicate a highgrade malignant tumor.
4. Diagnosis based on location and relationship with particular structures As discussed in the “USG ” section above, there are several tumors whereby a diagnosis can be made based on their characteristic location. They include Dupuytren’s nodule and plantar fibroma in palmar and plantar aponeurosis respectively; elastofibroma in a subscapular location; PNST arising from a nerve.
◾
FIGURE 64.11 Example of a melanoma with high T1w signal in the right thigh, seen in (A) T1w and (B) STIR coronal images. This lesion has a varying degree of melanin distribution. In the caudal aspect of the lesion (white arrow), there is a round focus of high T1w signal, corresponding with a rim of very low STIR signal (reflecting signal drop out due to paramagnetic property of melanin). At the middle level (arrowhead), there remains some patchy areas of increased T1w, corresponding with patchy varying high and low STIR signal, reflecting presence of patchy distribution of melanin, but not as dense as the former. Finally, at the cranial third (black arrow), there is low T1w area, corresponding to increased STIR, reflecting an amelanotic portion of this lesion.
FIGURE 64.12 Blooming artifact. (A) T1w and (B) STIR sagittal images demonstrating a synovial-based mass in the ankle joint posterolateral recess. (C) Note the blooming artifact on the T2*w sagittal sequence, reflecting presence of superparamagnetic hemosiderin, lending confidence to the diagnosis of PVNS.
Table 64.3 Masses With Cystic-Appearing Hyperintense T2W Signal and Their Differentiating Features Cate gory
Types of Lesions
Differentiating Imaging Features
True cysti c lesio ns (beni gn)
Ganglion, bursa
Both ganglion and bursa will occur in typical locations. For example, typical location for a ganglion is in the hands and wrists.
Epidermoid cyst
This has twinkling artifact on USG.
Abscess, hematoma, postsurgical seroma
Differentiation is possible based on accompanying history. High T1w areas can be seen in abscess and hematoma (due to proteinaceous or blood products respectively).
Intramuscula r myxoma
The solid nature of this lesion is reflected by the presence of contrast enhancement. Lesions can have internal T2w hypointense septal and nodular areas. USG will demonstrate a hypoechoic solid lesion, rather than a truly anechoic cystic lesion.
Myxoid liposarcoma
Fat can be seen in the lesion on T1w images, but not always.
Extraskeletal myxoid chondrosarco ma
Matrix mineralization can be seen on MRI and even USG, but better appreciated on radiograph or CT.
Myxofibrosa rcoma
Curvilinear extension or “tails” along fascial planes.
Myx oid tumo rs (beni gn and mali gnan t)
Cate gory
Types of Lesions
Differentiating Imaging Features
Othe rs (beni gn and mali gnan t)
Vascular lesions
Lymphatic malformation can be truly cystic or multiseptated. Flow-voids in high-flow malformation. Phleboliths in venous malformation and hemangioma. Hemangioma can have interspersed fat in the lesion seen on T1w images.
Peripheral nerve sheath tumor
Round or ovoid lesions arising along the nerves. Target sign.
Synovial sarcoma
This lesion typically occurs near a joint (but not intra-articular), most commonly near the knee.
Local Staging There are two main staging systems for soft tissue sarcoma: TNM system (by the American Joint Committee on Cancer Staging), and Enneking system (by Musculoskeletal Tumour Society), the former of which is more widely utilized. There are a few differences between the two systems. For example, Enneking system takes into account the site of tumor (intracompartmental or extracompartmental), and disregards presence of nodal involvement (in contradistinction to TNM system). Regardless of which staging system is used by the institution, the reporting radiologist should consistently report on the following:
◾ Size of tumor (in three dimensions) ◾extracompartmental) Location (superficial/deep to the deep fascia, retroperitoneal, mediastinum; intra- or ◾ Extracompartmental invasion ◾ Bone or joint involvement ◾ bundle involvement ◾ Neurovascular Lymph node involvement
DWI/ADC Diffusion-weighted imaging (DWI) is a functional imaging technique that measures the Brownian motion of water molecules. During acquisition of a DWI image, different amount of diffusion weighting (expressed as b values) can be applied. The higher the b value, the more sensitive the image is to molecular motion. DWI should be performed with at least two or three
different b values (b = 50, b = 400, b = 900 s/mm2, for example). The signal intensity of every voxel will decrease in an exponential manner with increasing b values; and the rate of this decrease can be calculated, voxel by voxel, using logarithmic regression analysis to produce an apparent diffusion coefficient (ADC) value. The ADC values are displayed as an image (also known as ADC map), which can then be analyzed in a quantitative manner. There are a few applications for DWI/ADC, all of which bring a new layer of information that can be used to augment routine MRI sequences. These DWI/ADC can be used to: 1. Differentiate malignant from benign lesions
This operates on the premise that malignant lesions are more cellular than benign lesions, thereby causing significant restriction to the diffusion mobility of water. Malignant tumors have been shown to have significantly lower ADC values than benign lesions. For example in one study, a threshold ADC value of 1.34 × 10−3 mm2/s has been proposed to differentiate between malignant and benign lesions with 94% sensitivity and 88% specificity [11]. Nevertheless, others have found significant overlap in the ADC values in malignant and benign lesions [12]. 2. Differentiate cystic from solid masses
Using a minimum ADC value of 1.8 × 10−3 mm2/s or mean value of 2.5 × 10−3 mm2/s yielded 100% specificity in determining a cyst from a solid tumor. This can be useful in differentiating a myxoid tumor (which has cystlike appearances) from true cysts [13], providing an alternative from using MRI contrast enhancement or USG (Fig. 64.13). 3. Monitor disease response following chemotherapy or radiotherapy
FIGURE 64.13 Use of ADC in determining cystic nature of a soft tissue mass. (A) PD FS axial image of the distal femur demonstrated a high signal lesion. (B) Mean ADC value of this lesion is 2.8 × 10−3 mm2/s, above the quoted minimum threshold ADC value, reflecting its cystic nature.
DWI/ADC can be used to monitor response to chemotherapy or radiotherapy [14]. This operates on the premise that malignant lesions following chemotherapy or radiotherapy will have lower tumor cell density, thereby allowing greater water molecule motion, reflected in an increase in ADC values. An increase in ADC value can also be seen in necrotic area post-therapy [12]. Interestingly, Moustafa et al. have reported that they found an inverted trend in fibromatosis lesions, where lesions with favorable response would show lower ADC values than those with progressive disease. The authors suggested that fibromatosis with favorable response will lead to progressive collagenization, which typically have low ADC values [14]. 4. Differentiate true recurrence/residual tumor from postsurgical scar tissue
Detection of tumor recurrence on static contrast-enhanced MRI has a reported sensitivity 87.5–100%, but with a poor specificity of 52–55.6% owing to their similar appearance of mass-like enhancement. However, with the addition of DWI/ADC, specificity is increased to 97–100% [15,16]. Further, larger studies will be required to substantiate the value of functional imaging in tumor follow-up. Of note, the value of DWI/ADC does not extend to myxoid sarcomatous tumor recurrence which may show elevated ADC similar to that seen in postoperative changes, thereby providing false reassurance [15]. Role of Contrast-Enhanced MRI
Gadolinium contrast-enhanced MRI can be part of the routine sequences in a tumor workup protocol, but this is not universal across every institution. Some institutions choose to omit this from their routine protocol because: a. they use USG for initial workup of all soft tissue tumors which can assess the vascularity and cystic nature of tumors; b. majority of lesions can be adequately characterized on routine sequences, for example, lipoma, PNST, vascular malformation, to name a few.
Patients can of course be recalled if it later transpires that there are unexpected findings or uncertainties requiring a contrast-enhanced study. This approach vastly reduces the number of patients receiving gadolinium injections and their associated risks. In general, there are a few instances where contrast-enhanced MRI is useful, or indeed strongly advised: 1. Postneoadjuvant chemotherapy or radiotherapy
While contrast-enhanced MRI is not routinely performed during initial tumor work up, contrast-enhanced sequences must be performed after neoadjuvant chemotherapy or radiotherapy. Following neoadjuvant therapy, as many as 31% of lesions can increase in size, the majority of which correlates with histopathological changes such as intralesional necrosis, cystic change, or hemorrhage [17]. Contrast-enhanced MRI sequences will be able to accurately distinguish viable tumor from nonviable areas. Nevertheless, the true challenge lies in distinguishing viable tumor from post therapy granulation tissue, due to similar T1w and T2w characteristics and their enhancing nature. For this purpose, dynamic-enhanced contrast MRI may be more useful, being able to differentiate early contrast uptake in viable tumor, from slower contrast uptake in granulation tissue [18]. 2. Postoperative follow-up
MRI is the preferred technique if follow-up imaging for locoregional recurrence is required postoperatively. The challenge is differentiating postoperative inflammation and scarring from true tumor recurrence. Tumor recurrence may have a more nodular or mass-like postcontrast enhancement, although scar tissue may have the same appearance on static postcontrastenhanced study. Dynamic postcontrast study can resolve this as tumor recurrence will show rapid arterial enhancement (Fig. 64.14). Contrast enhancement with subtraction imaging can also improve detection of tumor recurrence. 3. Distinguishing cystic from solid (but cystic appearing) lesion
FIGURE 64.14 Recurrence of myxofibrosarcoma. (A) T1w and (B) PD FS axial images demonstrating a new mass a few months after surgical resection. (C) ROI 1 (arrow) placed over the lesion demonstrates early contrast uptake and washout on the (D) time intensity curve (solid line), in keeping with a recurrence. ROI 2 and 3 (dashed and dotted lines, respectively) are placed in normal muscles and are used as controls, demonstrating general slow uptake.
Some solid tumors may have high T2w signal, mimicking a cyst. When faced with such lesions, solid tumors will have features such as thick-wall or internal complexity (inhomogeneity, thick septation, or nodularity), whereupon postcontrast MRI should be performed to assess for lesional enhancement to confirm its solid nature (Fig. 64.15). While USG can perform this assessment for superficial tumors, MRI with contrast is preferable for deeper lesions to assess cystic versus solid areas.
Another circumstance to consider contrast enhancement is in the presence of a hemorrhage—
a tumor may hemorrhage and lead to a large hematoma which may be incorrectly dismissed as a simple hematoma. Contrast enhancement is sometimes necessary to unveil the tumor nodule. 4. Selecting an appropriate site for biopsy
Contrast-enhanced MRI can identify solid and well-vascularized areas in the lesion, which should be targeted during biopsy. Nonviable, nonenhancing, necrotic areas should be avoided (Fig. 64.16).
FIGURE 64.15 Intramuscular myxoma mimicking a cyst. (A) T1w, (B) PD FS axial images demonstrating an ovoid, well-defined lesion with low T1w and high PD FS signal, mimicking a cyst (asterisks). (C) STIR coronal image demonstrates internal complexity, reflecting that this is not a simple cyst. Perilesional edema is typically seen at the poles of an intramuscular myxoma (arrows). (D) T1w FS postcontrast image demonstrates typical enhancement in a peripheral and septal pattern, confirming the solid nature of this mass.
FIGURE 64.16 Prebiopsy planning. Large mass in the left proximal thigh, with (A) high STIR signal mass and (B) peripheral enhancement on this T1w FS image, in keeping with a necrotic mass. Presence of necrosis is suggestive of a high-grade lesion, as in this grade 3 rhabdomyosarcoma. Biopsy of the necrotic component should be avoided due to low diagnostic yield. (C) On the cranial aspect of the lesion, this T1w FS image shows an area of viable, enhancing tissue (asterisk), correlating with (D) intermediate signal on this coronal STIR image. This is the area that should be targeted for biopsy.
Radiograph Radiograph has poor contrast resolution when it comes to assessing a soft tissue lesion. Vast majority of soft tissue lesions are isodense to muscles, therefore generally not appreciable on radiograph—unless when the lesion is large, which by extension makes it more likely to be a malignant tumor. About 64% of soft tissue lesions visible on radiographs are malignant [19]. Fat-containing lesions on the other hand are hypodense relative to adjacent muscles.
Radiograph is often unfairly dismissed as unimportant in the assessment of soft tissue lesions. However, despite its shortcomings, there are instances where it can be useful, specifically by assessing for lesional calcification and underlying bone involvement. Presence of calcification in a soft tissue lesion can provide invaluable information in narrowing the differential diagnoses of the lesion, and even clinching the diagnosis in some instances. There are a few patterns of calcification (Fig. 64.17):
◾ Ossification
FIGURE 64.17 Different types of calcification on radiographs. (A) Ossification with internal marrow and trabecular formation, seen in this long-standing myositis ossificans. (B) Chondroid calcification in a soft tissue chondroma of the finger demonstrating an amorphous appearance. (C) Several rounded phleboliths with lucent center in a vascular malformation in the calf.
The term ossification refers to bone formation and is reserved for when bony trabeculae are visible. Ossification can be seen in myositis ossificans where the mineralization is focused on the periphery, as opposed to central ossification in extraskeletal osteosarcoma.
◾ Chondroid
Mineralization in chondroid lesions, whether benign or malignant can have a stippled, punctate or ring, and arc appearance.
◾ Phleboliths
Phleboliths are typically rounded mineralization with a lucent center. Their presence in a soft tissue tumor is highly suggestive of a slow-flow venous
malformation. Bone involvement can be easily assessed on radiograph (although some limited assessment can also be performed on USG) (Fig. 64.18). The absence of bone involvement is obviously reassuring (and confirms the lesion to be originating in the soft tissue, rather than osseous lesion with extraosseous extension), while the presence of underlying bone involvement may provide clues as to the aggressiveness of the lesion:
◾ cortical bone destruction is highly concerning for an aggressive lesion ◾forIll-defined Conversely, well-defined pressure erosion is more suggestive of a slow-growing process, example, PVNS, GCT, and PNST ◾hemangioma Periosteal reaction can be seen in both benign and malignant lesions, for example, and sarcoma, respectively
FIGURE 64.18 Different forms of underlying bone involvement. (A) Radiograph demonstrating a large soft tissue mass centered on the medial side of the midfoot. Underlying bony destruction seen involving the cuneiforms, navicular, and base of several metatarsals, particularly the third metatarsal. This was a synovial sarcoma. In another patient (B) pressure erosion is seen on the lateral cortex of the femur (arrows) due to an adjacent soft tissue mass (arteriovenous malformation), suggesting a slow, nonaggressive growth of the lesion.
Computed Tomography CT generally has a limited role in the evaluation of soft tissue sarcoma. However, like radiograph, it is well-suited for visualizing presence of calcification and underlying bone involvement. It may be particularly useful in the assessment of myositis ossificans where peripheral calcification can be easily visualized. CT is also preferable to radiographs in the assessment of relationship of soft tissue tumors to the axial skeleton.
Positron Emission Tomography
Positron emission tomography (PET) is most commonly performed with radiotracer [18F]fluorodeoxyglucose as a mean of quantifying the metabolic activity of a tumor. Malignant lesions generally have higher standardized uptake values (SUVs) compared to benign lesions, although there are overlaps. For example, malignant synovial sarcoma and liposarcoma may not demonstrate increased SUVs, whereas benign GCT of tendon sheath can have increased SUVs [20]. Furthermore, distinction between benign and low-grade tumors is not reliable. While not routinely performed in the initial imaging workup of a soft tissue sarcoma, PET can be utilized to guide biopsy by highlighting the most metabolically active portion of the tumor. Whole-body staging with PET can also be considered in certain soft tissue sarcomas (discussed in later section) [5]. It can also be used to detect local recurrence and distant metastasis.
Compartmental Anatomy Radiologists should have some understanding of compartmental anatomy in context of soft tissue sarcoma reporting which is part of the Enneking staging system. Tumors tend to grow along the path of least resistance, spreading easily along the planes of fat and muscles, within the confines of the fascia which is an effective barrier. Presence of extracompartmental breach will not only adversely affect the staging of the tumor, but is also reflective of the high-grade nature of the lesion (which is an adverse prognostic factor) [21]. When biopsying a suspected soft tissue sarcoma, one must ensure the compartmental boundaries are respected (this will be discussed in later section “Biopsy”). Compartmental anatomy is discussed below and summarized in Table 64.4 and following figures. Table 64.4 Anatomic Compartments in the Upper and Lower Limbs [22,23,25,27,28] Anatomic Compartments and Their Muscles Ar m
Anterior
Posterior
Biceps, brachialis, coracobrachialis
Triceps
Anatomic Compartments and Their Muscles Fo re ar m
Extensor digitoru m brevis, extensor hallucis brevis
In the arm (Fig. 64.19), there are two soft tissue anatomic compartments: anterior and posterior. The anterior compartment consists of biceps brachii, brachialis, and coracobrachialis. The posterior compartment contains the triceps and anconeus [22].
FIGURE 64.19 Anatomical compartments and neurovascular bundles in the arm (left side).
In the forearm (Fig. 64.20), there are broadly five compartments: volar and dorsal (both of which can be further subdivided into deep and superficial compartments), and the mobile wad. The volar and dorsal compartments are separated by the interosseous membrane. The mobile wad is also known as the lateral compartment, and is found on the dorsolateral side of the forearm, is termed as such due to its relative ability to be displaced to permit access to deeper structures during surgery. The distal boundary of the forearm compartments is the flexor and extensor retinacula of the wrist [23].
FIGURE 64.20 Anatomical compartments and neurovascular bundles in the forearm (left side).
Compartmental anatomy in the hand is complex, with a total of 11 compartments: four dorsal interossei, three volar interossei, thenar, hypothenar, adductor, and mid-palm compartments. The intimate relationship of multiple vital structures in the hand presents a unique challenge to the surgical management. Lesions which would have been considered small if occurred elsewhere, would easily occupy more than one compartment in the hand. It can be difficult to obtain a wide surgical margin without sacrificing important structures. Compromise of the anatomical boundaries is also common as muscles and neurovascular structures pass through different compartments in the hand. It is best to discuss individual cases in multidisciplinary team meeting (MDT) to determine the best biopsy approach on a case by case basis. In the thigh (Fig. 64.21), there are three compartments: anterior, posterior, and medial. Of note is the sartorius muscle, a long strap muscle with an oblique course across the thigh. It originates anteriorly, and as it courses down, it becomes more medial and posterior in relation to the femur. Sartorius is generally considered to be an anterior compartment structure. Nevertheless, care should be taken when planning a biopsy route that may traverse this muscle, for several reasons. First, there are debates and interest in the oncology literature in excluding sartorius when irradiating the anterior compartment [24], made possible due to it being enclosed within its own
fascial sheath. Second, sartorius can be used in muscle transfer for soft tissue reconstruction of large residual surgical defects. On a similar note, rectus femoris and vastus intermedius are important muscles for functional outcome and should not be traversed if possible. These points serve as a reminder to the importance of discussing each individual case in a fully complemented multidisciplinary team.
FIGURE 64.21 Anatomical compartments and neurovascular bundles in the thigh (left side).
In the leg (Fig. 64.22), there are four compartments: anterior, lateral, superficial posterior, and deep posterior. The compartmental anatomy in the foot is more complex, with a varying number of compartments described in the literature. The foot can be divided into dorsal and plantar compartment. The plantar compartment in particular is complex, not least because intermuscular septa can be incomplete due to natural perforation by tendons. In a simpler categorization, the plantar side of the foot can be divided into three compartments: medial, lateral, and central [22,25].
FIGURE 64.22 Anatomical compartments and neurovascular bundles in the leg (left side).
Extracompartmental Space One should be aware of the two different connotations of “extracompartmental”: lesions that arise de novo as an extracompartmental space lesion (Fig. 64.23), or lesions that arise intracompartmentally but has breached through its anatomic compartment. As described earlier, extracompartmental invasion upstages a tumor (depending on the staging system used) and is an independent adverse prognostic factor [21]. On the other hand, oncological outcome for de novo extracompartmental space sarcoma is inconsistent; poor outcome has been reported, but several studies have shown a comparable outcome with intracompartmental lesions when managed with adjuvant therapy and surgical excision after adjusting for lesion size, presence of metastasis and histologic grade [26].
FIGURE 64.23 Extracompartmental mass. (A) and (B) PD FS axial images demonstrating a large extracompartmental mass arising in the right thigh adductor canal, centered on the femoral vein, and completely occluding it, the close association of which brings leiomyosarcoma into the differential. The femoral artery (arrow) is also being enveloped. Subfascial edema (arrowhead) about the vastus medialis suggests tumoral invasion.
Examples of true extracompartment spaces are the axilla, antecubital fossa, popliteal space, subsartorial canal, and femoral triangle. In general, extracompartmental space lesions are not restrained by the tight muscle fascia, allowing the lesions to extend with little resistance. Extracompartmental space lesions are surgically challenging due to their close proximity to vessels and nerves, limiting the ability to obtain a wide surgical margin.
WHO Classification The 2020 World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone lists more than 100 histological subtypes of soft tissue tumors. This long list is intimidating, but it is less daunting to appreciate that in practice, the majority of tumors, either benign (70%) or malignant (80%), are made up of only a handful of tumors (Table 64.5) [29,30]. The list of tumors in Table 64.5 is based on referral to a specialist tumor center. In a more generalist practice, lesions such as ganglia, lipoma, post-traumatic lesions, skin gland lesions, and normal variants form an even higher proportion of the soft tissue lumps assessed. Table 64.5 Most Frequent Benign and Malignant Soft Tissue Tumors Constituting
the Majority of Tumors Encountered in Practice Benign Tumors
Malignant Tumors
Lipoma (16%)
Malignant fibrous histiocytoma (24%) (see following paragraph)
Fibrous histiocytoma (13%)
Liposarcoma (14%)
Nodular fasciitis (11%)
Leiomyosarcoma (8%)
Hemangioma (8%)
Malignant schwannoma (6%)
Fibromatosis (7%)
Dermatofibrosarcoma protuberans (6%)
Neurofibroma (5%)
Synovial sarcoma (5%)
Schwannoma (5%)
Adult fibrosarcoma (5%)
Giant cell tumor of tendon sheath (4%)
Extraskeletal chondrosarcoma (2%)
Myxoma (3%)
Not further specified (12%)
The 2020 WHO Classification of Tumours of Soft Tissue and Bone is the fifth and latest edition, published in the first half of year 2020. Every edition brings with it updated classifications and diagnostic criteria, detailing new knowledge ranging from genetic markers to immunohistochemistry advances. For example, one of the changes in this latest edition is the introduction of a new entity called atypical spindle cell/pleomorphic lipomatous tumor, an adipocytic tumor with a nonaggressive clinical course. One noteworthy change introduced in the previous fourth edition released in 2013, was the removal of the term malignant fibrous histiocytoma (MFH). MFH had previously been thought to be a distinct tumor category, but with evolving knowledge in immunohistochemical and molecular genetics, a lot of previously diagnosed MFH can actually be reclassified into a specific tumor category [31]. In addition, tumors that do not exhibit any identifiable line of differentiation were classed under a newly introduced category of “undifferentiated/unclassified sarcomas” in the 2013 edition. The following section will discuss lesions from different categories of soft tissue tumors. It is not intended to be an all-inclusive write-up but aims to provide an overview of these lesions, where diagnosis of some can be suggested based on imaging features.
Adipocytic Tumors
Benign Adipocytic Tumors Lipoma Lipoma is the commonest benign soft tissue tumor, making up just under half of all the benign soft tissue tumors [1]. Histologically, they are lobules of mature adipocytes. They are most frequently located superficially in the subcutaneous plane, with around 5% located deep to the deep fascia, either intra- or intermuscularly. Lipoma is generally painless. They can increase in size during their initial growth period but should only demonstrate minimal increment after that. Patients who have lost weight may also report their lipoma becoming larger, which is made more prominent due to reduced surrounding fat. USG is a useful technique to diagnose a superficial lipoma with diagnostic accuracy of 96% [32]. On USG, a benign lipoma is (Fig. 64.24)
◾ typically ovoid or spindle in shape; ◾ homogenous; ◾either variable echogenicity, ranging from hypoechoic, to isoechoic, or hyperechoic compared to adjacent subcutaneous tissue or skeletal muscle [32]; ◾ can have minimal internal blood flow seen on Doppler USG.
FIGURE 64.24 Benign lipomas (in different patients). (A) On USG, lipomas typically have an ovoid or spindle shape (arrows) with homogenous echotexture. This lesion has a isoechoic echogenicity to adjacent subcutaneous tissue, but they can be variable. (B) Lipomas can have thin septations, as shown in this axial T1w of the right shoulder (curved arrows). (C) Intramuscular lipomas can demonstrate interdigitation with muscles (arrowhead), as seen on this coronal T1w image of the left forearm (deltoid muscle). (D) They should have complete fat suppression as seen on this PD FS axial image.
MRI features are:
◾ Homogenous high T1w signal, and completely suppresses on fat-suppressed sequences ◾ Thin septa can be seen, and should be 90%) in their middle-age (mean >55 years)
[34]. They consist of mature adipocytes and bland spindled cells, on background of collagen fibers or myxoid matrix [33]. The proportion of these bland spindled cells is variable, ranging from a few spindle cells to a lesion with predominant spindle cell and little fat cells. This will affect the amount of fat visible on MRI, with some lesions demonstrating little to no T1w signal. In addition, MRI appearance of a spindle cell lipoma varies greatly (Fig. 64.26), and unfortunately overlaps with that of a liposarcoma:
◾ septa in the lesion can be thin or thick, and there may be nonadipose areas in the lesion ◾ The Both the septa and nonadipose area can demonstrate enhancement
FIGURE 64.26 Spindle cell lipoma in a typical location over the shoulder in a middle-aged male patient. (A) T1w sagittal demonstrating an adipocytic lesion (arrow) with multiple thick septae. On image (B) T2w FS, there is little to no signal suppression in the lesion, suggesting dominating nonadipose material in the lesion. Imaging appearances warrants a biopsy, and was shown to be a spindle cell lipoma, containing dense collagenous tissue in a myxoid stroma.
While presence of the above imaging features should always prompt a biopsy, one should however consider this benign variant of lipoma when faced with a well-defined fatty mass, even though complex appearing, in the subcutaneous plane at the posterior neck, in a middle-aged male patient. Chondroid Lipoma Chondroid lipoma consists of adipocytes on a background of myxoid/chondroid matrix. On MRI, the lesion is well-defined and lobulated, with variable and nonspecific signal properties. Visualization of T1w signal will depend on the proportion of the adipocytic component. T2w signal can be prominent owing to the myxoid/chondroid components in the lesion (Fig. 64.27). Calcification can be present on radiographs and CT. Similar to
spindle cell lipoma, a specific diagnosis cannot be made with confidence based on imaging alone, and biopsy should be considered.
FIGURE 64.27 Chondroid lipoma. This is a rare benign lipoma variant, seen as a lesion (arrows) with little area of fat on this (A) T1w coronal. (B) Note the predominant high signal intensity on this STIR axial image, reflecting the background myxochondroid matrix. Small punctate areas of fat can be seen as low signal focus, also seen on (C) CT image. There is no mineralization seen in this lesion.
Lipomatosis of Nerve: Lipomatosis of nerve is also known as neural fibroma, or fibrolipomatous hamartoma (or variations thereof such as lipofibromatous hamartoma, or lipofibrohamartoma) of a nerve. It is a benign neoplastic process, characterized by proliferation of adipose or fibrous tissue within the epineurium of a nerve. The median nerve is by far the most involved nerve (upward of 80%), and has also been reported to involve the ulnar nerve, radial nerve, brachial plexus, cranial nerve, and sciatic nerve. There are several characteristic features in lipomatosis of nerve (Fig. 64.28):
◾lipomatosa) Macrodactyly can occur in 32% of cases (leading to another synonym of macrodystrophia [35], where there is hypertrophy of the skin, subcutaneous tissue, and bones of the affected nerve territory ◾andMRIthickened appearance is pathognomonic whereby one can see the hypointense (T1w and T2w) nerve fascicles, interspersed within hypertrophied fibroadipose tissue, producing a characteristic cable-like appearance ◾ USG can also be used to visualize the thickened nerve fascicle
FIGURE 64.28 Lipomatosis of the median nerve. (A) T1w axial image (at the level of the PIPJ) demonstrating thickened digital branches of the median nerve (arrows) in the index and middle finger (radial side only), enveloped by hypertrophied adipose tissue. As on the MRI, macrodactyly can also be seen on the radiograph (B), affecting mainly the index finger, and a little of the middle finger (radial side) and thumb. Association with exostosis formation is recognized (seen in the thumb IPJ; and index finger MCPJ, IPJs).
FIGURE 64.29 Hibernoma. Commonly found in the thigh, hibernoma (asterisks) has characteristics (A) high T1w signal (but just slightly lower than subcutaneous fat), (B) and signal suppression (though not as suppressed as subcutaneous fat) as seen on this T2w SPAIR coronal image. (C) T1w FS postcontrast demonstrates heterogenous enhancement, with a feeding/draining vessel visible (arrowheads).
Management of this condition is mainly conservative, with surgical intervention focused on decompressing the compromised nerve to relieve pain and paraesthesia, for example, by carpal tunnel decompression in the context of the median nerve involvement.
Hibernoma: Hibernoma is rare, accounting for only 1.6% of all benign lipomatous tumors [33]. It is composed of mature adipose tissue with variable proportions of brown fat cells. The thigh is the commonest site for hibernoma (though with a wide range of reported frequency in the literature (29–83%), followed by the shoulder) [36,37]. Imaging features of hibernoma (Fig. 64.29):
◾higher On CT, a hibernoma can be visualized as a fat-containing lesion, though is typically of attenuation than the subcutaneous fat ◾partial On T1w MRI, it is of high signal, but slightly lower than that of subcutaneous fat, with suppression on fat-suppressed sequences. Hibernoma typically appear homogenous on imaging, though a small proportion can be heterogenous ◾itsContrast enhancement is present on both CT and MRI, and can be heterogenous, reflecting hypervascularity. Indeed prominent serpentine vessels can sometimes be seen in the lesion, and may demonstrate flow-void on MRI [37]. Some investigators advocate using MR angiography to visualize the feeding and draining vessels to aid surgical planning [38] On PET/CT, hibernomas demonstrate intense uptake, much higher than that reported in lipoma and liposarcoma. This reflects the vascularity and large number of mitochondria, which interestingly lends itself to a feeling of warmth during clinical examination over a hibernoma, in contradistinction to the cool feeling over a lipoma
◾
Malignant Adipocytic Tumors (Liposarcoma) Liposarcoma is the second most common soft tissue sarcoma, comprising of 14% of all malignant soft tissue tumors, trailing behind MFH (24%) (this entity does not exist anymore, now renamed to undifferentiated pleomorphic sarcoma) [30]. WHO recognizes four subtypes of malignant lipomatous neoplasm. They are: 1. atypical lipomatous tumor (ALT), also known as well-differentiated lipoma-like liposarcoma (WDLLL); 2. dedifferentiated liposarcoma (DDL); 3. myxoid liposarcoma; 4. pleomorphic liposarcoma [33].
Atypical Lipoma/Well-Differentiated Lipoma-Like Liposarcoma ALT/WDLLL is the most common form of liposarcoma. Like lipoma, they are composed of mature adipocytes, but they are distinct in that there is significant variation in cell sizes and presence of hyperchromatic nuclei. They occur most commonly in the thigh (intramuscular) and in the retroperitoneum, and rarely superficially in the subcutaneous plane [33]. They have no metastatic potential if they remain as ALT/WDLLL. It is important to distinguish an ALT/WDLLL from a simple lipoma for two reasons. First, ALT/WDLLL has the potential to dedifferentiate and therefore metastasize (lungs being the most common target). Second, and more relevant to a “central-body” ALT/WDLLL (retroperitoneum, mediastinum, spermatic cord), is the extreme difficulty to obtain a clear
surgical margin in these locations. This translates to a high recurrence rate (86–92%) and can occasionally cause morbidity. This is in contradistinction to extremity lesions where the risk of recurrence is much lower (9–43%) [39,40]. While ALT/WDLLL are synonyms, it is for this reason that in practice, the term WDLLL should be reserved for “central-body” lesions, and ALT for extremity lesions. On CT and MRI examinations, an ALT/WDLLL can have attenuation and signal intensities similar to that of subcutaneous fat, and differentiating an ALT/WDLLL from a lipoma may not always be straightforward. MRI is the preferred technique to assess an ALT/WDLLL, whereby presence of features listed here may increase the likelihood of the lesion being a ALT/WDLLL, rather than a lipoma (Fig. 64.30):
◾T2w Thick and nodular septa (>2 mm), hyperintense septa or nodules on STIR or fat-suppressed sequences ◾ Avidly enhancing septa (rather than weakly enhancing) ◾ areas in the lesion ◾ Nonadipose Large tumor size >10 cm
FIGURE 64.30 Atypical lipomatous tumor/well-differentiated lipomalike liposarcoma. (A) T1w image demonstrates a large lipomatous tumor with thick septae, which are hyperintense on the (B) STIR sequence. T1w FS (C) precontrast and (D) postcontrast images demonstrate enhancement about the lesion and the septae. There is also background inhomogeneity which also enhances.
These imaging feature are not perfectly specific to ALT/WDLLL and can sometimes overlap with benign lipoma variants. However, this overlap should not impact our immediate management, that is, any lesions with suspicious imaging features should lead to the lesion being regarded as such, and biopsied at the very least. It is worth discussing briefly the use of immunohistochemical and molecular testing, specifically the role of MDM2 in the diagnosis of ALT/WDLLL. Just as there is limitation in the ability of imaging in differentiating lipoma from ALT/WDLLL, histologically the degree of cytologic atypia can be equivocal and fall short in clinching the diagnosis of an ALT/WDLLL; this is one of the circumstances when MDM2 is useful.
MDM2 amplification is a characteristic feature of ALT/WDL and DDL (also present in some nonadipocytic sarcomas), and is not present in a benign lipoma or lipoma variant. MDM2 protein overexpression can be detected with immunohistochemistry, though a more superior test is utilizing fluorescence in situ hybridization to demonstrate amplification of the MDM2 gene (100% sensitivity and 100% specificity) [41], though at higher cost, slower turnaround time, and not available to every center. Fluorescence in situ hybridization testing is also recommended for recurrent lipoma, large deep lipomas >15 cm without features of atypia, to rule out possibility of ALT/WDLLL [42]. Dedifferentiated Liposarcoma DDL describes a lesion which was originally an ALT/WDLLL, which has undergone nonlipogenic sarcomatous dedifferentiation. A previously resected ALT/WDLLL can also transform into a DDL at the time of recurrence. The risk of dedifferentiation is thought to be higher in lesions located in a “central body location” (retroperitoneum, mediastinum, spermatic cord) (22%), compared to extremity lesions (7%) [40]. However, it is thought more likely that this risk of dedifferentiation is “timedependent” rather than “site-dependent,” due to the higher risk of persistent disease in the retroperitoneum. Most DDL is located in the retroperitoneum (70%), followed by 21% in the extremities and trunk, and the rest in scrotum/spermatic cord (9%) [43]. DDL can also occur in the subcutaneous tissue, although rare. Risk of metastasis from DDL is widely variable in the literature, ranging from 2% to 17% [43,44]. Local recurrence and disease-related mortality are reported at 41% and 28%, respectively, with lesions in the retroperitoneum carrying the worst survival [43]. On imaging, DDL (Fig. 64.31):
◾Occasionally, Often have features of an ALT/WDL, with focal variably sized areas of dedifferentiation. the original lipomatous areas may not be visible on imaging ◾andTheCTdedifferentiated area will appear as a nodular, nonlipomatous component on both MRI ◾dedifferentiated On MRI, the dedifferentiated area will reflect the signal characteristics specific to the tissue, but generally is low/intermediate on T1w, and intermediate-high on T2w ◾ On CT, this component can have a variable CT attenuation and is nonspecific ◾ dedifferentiated component will enhance on either CT or MRI ◾ This Mineralization can sometimes be appreciated on CT or on radiographs
FIGURE 64.31 Dedifferentiated liposarcoma. (A) T1w coronal and (B) STIR coronal images demonstrating a large area of sarcomatous dedifferentiation (asterisks) on background of atypical lipomatous tumor in the left thigh (cross). (C) T1w axial demonstrating the ALT/WDLLL component with thick nodular septae. More caudally, (D) T1w and (E) T2w axial through the dedifferentiated component with low signal, which on histology is composed of “fibrotic” tissue with few vacuolated adipocytes (arrowheads).
Myxoid Liposarcoma Myxoid liposarcoma is the second most common form of liposarcoma, accounting for around 25% of all liposarcoma, trailing behind the most common well-differentiated type (48%) [30]. It typically represents as a painless mass, affecting patients of mean age 42 years. It can also occur in younger patients; indeed, while rare in the pediatric population, it is the most common subtype of liposarcoma in patients 75%) are located in the lower extremity, with the thigh being the most common location [30]. Myxoid liposarcoma has a prominent myxoid matrix with a delicate vascular network, admixed with variable amount of lipoblasts, and round or oval nonlipogenic cells. The amount of fat is variable and can range from 5% of round cells). Tateishi and colleagues reported that presence of significant contrast enhancement, and with globular and nodular pattern, are predictive of an intermediate or high-grade tumor, probably a reflection of the amount round cells in the lesion. This will in turn influence prognosis adversely. Low-
grade tumors on the other hand are likely to have thin septa or has a tumor capsule. Myxoid liposarcoma metastases are more likely to be extrapulmonary, in contradistinction to most other sarcomas and other forms of liposarcoma which tend to metastasize to the lungs first. For example, in a series, 81% of first metastatic site from myxoid liposarcoma are extrapulmonary, involving a variety of areas including limb muscles, subcutaneous tissue, retroperitoneal, and chest wall [46]. For this reason, staging for this type of sarcoma often involves whole-body imaging in the form of MRI, CT, or PET/CT. At the senior author’s institution, we perform whole-body MRI for routine staging of myxoid liposarcoma (Fig. 64.34).
FIGURE 64.34 Myxoid liposarcoma and their tendency for extrapulmonary metastases. (A and B) STIR coronal of whole-body MRI of a patient with myxoid liposarcoma diagnosed 2 years earlier. Despite the diffuse skeletal and soft tissue metastases, there is no pulmonary metastasis demonstrated on the concurrent CT thorax (not shown).
Myxoid liposarcoma, given their substantial myxoid stroma, can mimic a cyst or other myxoid tumor on imaging, such as intramuscular myxoma or myxoid chondrosarcoma and myxofibrosarcoma. Pleomorphic Liposarcoma Pleomorphic liposarcoma is the rarest of all liposarcoma, accounting for 6% of all cases, affecting patients with mean age of 60 years [30]. The lower extremity is the most common location (38–47% of cases). Other sites include the upper limb (14–18%), retroperitoneum (7–15%), and trunk (8– 14%) [30,47]. Around a quarter of cases can occur superficially (in the subcutaneous tissue or skin) [47]. On MRI, imaging features may be similar to that of other high-grade sarcomas (heterogenous high T2w signal, with postcontrast enhancement). Furthermore, there may only be a little amount of fat visible, in line with histological findings of variable amount of lipoblasts even between areas within the same tumor [33]. This highlights the importance of intralesional targeting during biopsy, to also sample the lipogenic component to enable histological diagnosis of pleomorphic liposarcoma, which otherwise may be interpreted as undifferentiated pleomorphic sarcoma.
Fibroblastic/Myofibroblastic Tumors Nodular Fasciitis Nodular fasciitis is a benign proliferation of fibroblasts and myofibroblasts. It usually presents as a rapidly growing mass or nodule in a span of few weeks, and together with high cellularity and mitotic activity, leads to common misdiagnosis as sarcoma [48]. The nodules can be a little painful, and measure around 2 cm in size. It is more commonly found in adults (20– 50 years), and most frequently located in the forearm (27%), thigh (17%), upper arm (12%), followed by trunk, and head and neck [49,50]. Nodular fasciitis, as the name suggests, involves the fascia (either superficial or deep fascia). Lesions can be sited in the subcutaneous plane (most common), intramuscular plane, or along the fascia. Intramuscular lesions are usually slightly larger (around 2.5 cm in size). On MRI, nodular fasciitis appears (Fig. 64.35):
◾cellularity Variable MR signal depending on the amount of myxoid and fibrous stroma, and also the of the lesion. Myxoid stroma will produce iso T1w, high T2w signal; fibrous stroma low T1w and T2w signal; cellular lesion has slightly increased T1w, high T2w signal ◾ or oval in shape ◾ Round Fascial tail
◾(myxoid Variable contrast enhancement. Enhancement patterns documented include homogenous lesions), heterogenous (cellular lesions), and periperal (fibrous lesions)
FIGURE 64.35 Nodular fasciitis in the leg of a 39-year-old patient. (A) T1w axial, (B) PD FS axial, (C) STIR sagittal images demonstrating a lesion based on the deep fascia, with a nodule penetrating through this fascia into the tibialis anterior muscle (arrow). Note the fascial tails (arrowheads) extending from the nodule.
Differential diagnoses for nodular fasciitis include extra-abdominal desmoid lesion, fibrous histiocytoma, PNST, and sarcoma (myxofibrosarcoma or fibrosarcoma). Nodular fasciitis has a few rare variants, one of which is ossifying fasciitis where metaplastic ossification can be seen, bringing in other differentials such as extraosseous osteosarcoma and myositis ossificans.
Elastofibroma Elastofibroma is a benign proliferation of fibrocollagenous tissue with prominent elastic fibers, characteristically located deep to the inferomedial border of the scapula and superficial to the posterior chest wall. It has a reported prevalence as high as 18% in an autopsy study (although a separate CT study revealed a prevalence of only 2%) [51,52]. It is a disease affecting patients almost exclusively over the age of 55 years old, with higher prevalence in female. Elastofibroma can be bilateral in about half of the cases [51]. Up to half of the patients will experience enough symptoms (pain, stiffness, “clunking” sensation) to require surgical excision. On imaging (Fig. 64.36):
◾ The lesion lies deep to the scapula and muscles, and superficial to the ribs ◾ It can have a convex posterolateral margin [52] ◾with On MRI, the lesion is demonstrated as a nonencapsulated heterogenous soft tissue mass, low T1w and T2w signal (reflecting its fibrous content), and interlaced with areas of fat ◾ Enhancement can be subtle on MRI
◾fatOn CT, the lesion has attenuation similar to that of muscles, again interlaced with areas of ◾overlying USG will demonstrate interspersed linearities within the lesion, similar to that of the muscles. Dynamic USG is useful by asking the patient to perform movements that will elicit the symptoms, typically by abducting the shoulder (while the patient is lying prone), to protrude the mass beyond the inferior border of the scapula
FIGURE 64.36 Elastofibroma. (A) T1w and (B) PD FS axial images demonstrating a nonencapsulated mass (asterisks) lying in between serratus anterior and the ribs, on the inferomedial border of the scapula (arrow). The fibrocollagenous content of elastofibroma has a relatively isointense signal to muscles. Interlaced areas of internal fat (arrowheads) can also be seen as slivers of signal suppression on image (B).
Superficial Fibromatoses Both palmar and plantar fibromatoses are superficial fibromatoses, characterized by infiltrative fibroblastic proliferation of the palmar and plantar aponeurosis, respectively. These are classified as intermediate malignancy by WHO, being locally aggressive though without metastatic potential [33]. Palmar Fibromatosis Palmar fibromatoses (Dupuytren’s contracture) represent the most common form of superficial fibromatoses. There is a predilection or male patients, with increasing prevalence with increasing age, ranging from 2% under 40 years old, to 20% in over 60 years old in a study [53]. It can also occur bilaterally. Palmar fibromatosis initially manifests as a palpable firm nodule, most commonly on the ulnar side on the fourth digit (36%), followed by the third (29%) and fifth digits (20%) [54], and mostly occurring at the level of the distal metacarpal. With time, there may be bands or cordlike indurations
developing between the nodules and adjacent fingers, leading to the characteristic flexion contracture. Diagnosis of palmar fibromatosis can be made on USG. It has:
◾ hypoechoic nodular or cord appearance; ◾toamajority of palmar fibromatosis lies at the level of the distal metacarpal, directly superficial the flexor tendons; ◾ intralesional vascularity or calcification can be seen rarely.
On MRI (Fig. 64.37), the nodules or cords are mostly low signal on T1w and T2w images, shown to represent the hypocellular and dense collagen nature of the lesion [55]. However, some lesions can be of intermediate T1w and T2w signals, reflecting their higher cellularity and minimal collagen content, representing the earlier proliferative stage of the disease [48,55].
FIGURE 64.37 Dupuytren’s nodule. A 56-year-old female presented with a painless, slow-growing, solitary lump in her little finger, at the level of the proximal phalanx neck. (A) USG demonstrated a superficial solid fusiform mass (arrows), a distance away from the underlying flexor tendon (asterisk). No intralesional vascularity. (B) T1w axial, (C) PD SPIR MRI demonstrate the lump (arrows) to have a low signal intensity, which can be seen to be related to a thickened palmar aponeurosis (arrowhead). (D) PDW SPIR sagittal image demonstrates the resultant contracture of the finger. The patient reported another lump in her contralateral palm a few months later (not shown).
Treatment-wise, there is limited evidence in conservative measurements in preventing progression to contracture. Intralesional corticosteroid injection, for example, has been reported to soften and decrease the size of the nodules (although 50% risk of recurrence), but has not been shown to improve or prevent a contracture [56]. Radiation therapy is another form of noninvasive option which can improve pain related to the nodules (also for plantar fibromatosis) [57,58]. In the presence of contracture, percutaneous needle fasciotomy to rupture the cord is a minimally invasive option, with recurrence of around 50% [59]. Surgical fasciectomy is the mainstay treatment and can range from regional fasciectomy to more extensive dermofasciectomy requiring skin grafting; there is a wide range in the risk of recurrence reported in literature. Another form of treatment is enzymatic fasciotomy with collagenase injection, which is proving to be a promising
nonsurgical alternative, shown to improve contracture and improve hand function, and may have a role as first-line intervention for contracture [60]. Plantar Fibromatosis Plantar fibromatosis (Ledderhose disease) usually arises in the central or medial cord of the plantar arch. There is a higher incidence in younger population, with up to 44% of cases seen before 30 years old [61]. Patients can complain of pain which can be exacerbated by walking or standing, or just of a palpable lump without actual symptoms [62]. In contradistinction to its palmar counterpart, contracture is not a typical feature in plantar fibromatosis, and can be seen rarely in the hallux. On USG, plantar fibromatosis:
◾ Appear as a fusiform nodule of hypo- or mixed echogenicity ◾ Located on either the medial or central bands of the fascia at the mid- or forefoot [62,63] ◾demonstrating A fifth of the lesions can have moderate or marked vascularity, with the remaining majority little to no vascularity [63] ◾isoechoic Larger lesions can demonstrate the comb-sign where there is alternating bands of hypo- and bands in the lesion (relative to plantar fascia) [63]
On MRI, the lesion appears (Fig. 64.38):
◾ As a well-defined nodule located along the plantar fascia ◾collagen Similar to palmar fibromatosis, the signal characteristics depends on the amount of and cellularity, varying between low and intermediate on T1w and T2w images
FIGURE 64.38 Plantar fibromatosis. (A) T1w sagittal, (B) STIR sagittal, (C) T2w short axial images showing a fusiform mass (arrows) arising from the central band of the plantar fascia. It has a low T1w signal and intermediate/high signal on STIR and T2w images. This patient also has bilateral plantar fibromas (not shown).
Symptoms of plantar fibromatosis generally improve over time. Therefore, it is best managed conservatively with physiotherapy and orthotics. Other
noninvasive management for painful nodules includes intralesional corticosteroid injection and radiation therapy. Surgical intervention can be offered for severe intractable cases, with a variable risk of recurrence depending on the extent of the surgery; local excision is associated with 100% recurrence rate, compared with 25% in total plantar fasciectomy [64].
Deep Fibromatoses Deep fibromatoses are also known as desmoid tumors. These are rare, accounting for around 0.4% of all benign soft tissue tumors [1]. Similar to superficial fibromatoses, these are also of intermediate malignancy being locally aggressive with no potential for metastasis. Deep fibromatoses demonstrate a more aggressive behavior compared to superficial fibromatoses with infiltrative growth pattern and high risk of recurrence. Lesions can also be multicentral and metachronous [65]. Deep fibromatoses are composed of spindle-shaped myofibroblastic cells embedded in a collagenous matrix. There can also be a variable degree of myxoid matrix [48]. Deep fibromatoses can be divided into three subtypes based on their location: 1. Extra-abdominal fibromatosis. This is commonly found in the lower limbs (particularly the foot, followed by hip and thigh, and the lower leg), shoulder, chest wall, and back (Fig. 64.39). Metachronous lesions can be seen in around 10% of cases, and tend to arise in the same limb in a more proximal location [65,66] 2. Abdominal fibromatosis. This has a tendency to affect women of child-bearing age, and can arise or demonstrate rapid growth during pregnancy or in the postpartum period. Lesions can arise from the aponeuroses or muscles of the anterior abdominal wall, particularly the rectus abdominis and internal oblique muscles or fascia (Fig. 64.40) 3. Intra-abdominal fibromatosis. Lesions typically arise from the mesentery of the small bowels or from the retroperitoneum. As a whole, majority of desmoid lesions are incidental, but there is an association with familial adenomatous polyposis (Gardner syndrome), where around 10% of patients can develop desmoid lesions, the majority of which are intraabdominal desmoids [67]
FIGURE 64.39 Extra-abdominal desmoid type fibromatosis in the calf of a 27-year-old woman. (A) STIR coronal, (B) T1w axial, (C) T2w axial, (D) T1w SPIR axial postcontrast demonstrating a large deep juxtacortical desmoid tumor related to posterior aspect of the tibia. Low signal areas across all sequences are compatible with areas of collagen distribution. The increased signal areas on (A) and (C), and intermediate on (B) correspond to areas of enhancement seen on postcontrast image (D) (one example area labeled with asterisk), and reflects the more cellular component of the lesion.
FIGURE 64.40 Abdominal wall fibromatosis in a 42-year-old woman. (A) Panoramic USG demonstrating an ovoid hypoechoic lesion, centered on the right rectus abdominis muscle. Low signal intensity linear bands can be seen on both (B) T1w and (C) T2w axial images (arrows), representing collagenized fibrous tissue. (B) Central intermediate–high signal is compatible with area of cellularity in the lesion. Another radiological differential would be an endometrioma which will have similar location and appearance, especially if it is related to previous caesarean scar and if there are cyclical symptoms. T2*w sequence will be useful in demonstrating blooming due to the presence of hemosiderin in endometrioma.
On MRI, desmoid tumors appear:
◾margins Either well-defined or irregular borders. Some lesions can also demonstrate infiltrative and growth. This can be appreciated, for example, by its spiculated margins, growth along the fascia (fascial tail), or through the fascia and invading compartmental anatomy. Extracompartmental involvement has been reported in 70% in a series [66]. Bone invasion can also be seen, especially in recurrent lesions Isointense on T1w (near homogenous). On T2w, the lesion is hyperintense (though less than that of fat signal), and is heterogenous [66]. Dark T2w bands can be seen Heterogeneity on T2w is influenced by collagen content and cellularity of the lesion— collagen produces low signal on T2w; cellularity leads to high signal on T2w, while low cellularity decreases T2w signal [66]. Vandevenne et al. reported that as desmoid tumors evolve, they become less cellular with more collagen deposition, changes of which will lead to growth of low T2w areas [66] Contrast enhancement can be moderate to strong, although the areas of collagen deposition and acellularity (depicted as low T2w areas) will be spared [66]
◾ ◾ ◾
USG appearance of desmoid tumors is nonspecific and variable; lesions can be hypoechoic, isoechoic, or hyperechoic, and either homogenous or heterogenous echotexture, reflecting its variable histological composition. Doppler flow can be demonstrated. Similarly on CT, desmoid tumors can be variable in their attenuation.
Intermediate (Rarely Metastasizing) and Malignant Fibroblastic/Myofibroblastic Tumors Within fibroblastic/myofibroblastic tumors, in addition to benign, and intermediate (locally aggressive) categories, there are intermediate (rarely
metastasizing) and malignant categories. Examples of intermediate (rarely metastasizing) lesions include dermatofibrosarcoma protuberans (DFSP). Examples of malignant lesions include fibrosarcoma and myxofibrosarcoma. Dermatofibrosarcoma Protuberans DFSP is a fibroblastic, nodular cutaneous tumor affecting patients with mean age of 40 years, most frequently sited on the trunk, head and neck, and lower extremities [68]. It accounts for 6% of all soft tissue sarcoma [30]. DFSP has an infiltrative growth pattern locally, with high risk of recurrence (as high as 50% in earlier series, though can be as low as 0% with micrographic surgery achieving clear surgical margins) [68]. Risk of metastasis is very low. As DFSP usually presents as small cutaneous lesions arising in the dermis, they are typically diagnosed based on their clinical appearances and biopsied without imaging studies. However, very rarely DFSP can arise within the subcutaneous tissue with or without dermal involvement. Imaging is also required in larger lesions and if there is suspicion of involvement beyond the subcutaneous tissue. On USG, the lesion appears (Fig. 64.41):
◾ Superficially located, closely related to the dermis ◾ or oval in shape. Well-defined with mild lobulated margins ◾(inRound Depending on the composition of the tumor, the lesion can be homogenously hypoechoic cellular lesions) or heterogenous (in mixed cellular and fibrous tissue) ◾ Posterior acoustic enhancement is present [69] ◾the“Claw” sign has been reported, describing a fine tapering extension from the main tumor at lesion/skin interface. This sign can be seen on USG, CT and MRI, and reflects tumor of the skin ◾involvement Moderate Doppler vascularity, more in the periphery of the lesion [69]
FIGURE 64.41 DFSP. (A) USG demonstrating a well-defined oval lesion centered on the dermis with typical peripheral vascularity. It has a hypoechoic and homogenous echotexture, reflecting its cellular state as seen on histology. There is posterior acoustic enhancement. (B) T1w and (C) PD FS images reflect the sonographic findings of homogenous signal throughout.
In addition to the shape/margin and “claw” sign as described above, on MRI, the lesion appears:
◾intensity). Isointense T1w, increased T2w signal (either similar to subcutaneous fat or higher T2w signal intensity can be higher in lesions with prominent myxoid stroma ◾ Contrast enhancement can be seen throughout the lesion or focused in the periphery
Adult Fibrosarcoma Fibrosarcoma can be divided into congenital/infantile form, and the adult form; the former of which has a more favorable outcome. Adult fibrosarcoma affects patients with median age 52.5 years, and most commonly found in the lower extremities, followed by head and neck, and the upper extremities [70]. The incidence of fibrosarcoma has declined dramatically in the past decades due to evolving diagnostic classification and development of new immunohistochemistry and molecular diagnosis; adult fibrosarcoma now accounts for 2 cm but ≤4 cm and ≤10 mm DOI
T 3
Tumor >4 cm OR any tumor >10 mm DOI
T 4
Moderately advanced or very advanced local disease
T 4 a
Moderately advanced local disease Tumor invades adjacent structures only (e.g., through cortical bone of the mandible or maxilla, or involves the maxillary sinus or skin of the face) Note: Superficial erosion of bone/tooth socket (alone) by a gingival primary is not sufficient to classify a tumor as T4
T 4 b
Very advanced local disease Tumor invades masticator space, pterygoid plates, or skull base and/or encases internal carotid artery
SCC in each subsite of the oral cavity displays nearly expected spread patterns. The objectives of imaging in SCC include defining the depth and extent of the lesion, defining potential routes of spread on basis of primary site of tumor within the oral cavity and providing pretreatment staging and evaluating the metastatic nodes in the neck. Table 65.2 is a compilation of the spread pattern of SCC of each subsite of the oral cavity with preferred choice of imaging technique, their advantages and disadvantages [16–23]. Table 65.2 Oral SCC: Spread Patterns and Preferred Imaging Techniques Subsi te
Spread Patterns and CheckList
Preferre d Imaging Techniq ue
Advantages
Disadvantages
Oral
Tongue
CE MRI
Excellent
Longer
tongu Subsi eteand floor of mout h (Fig. 65.15 )
Spread Patterns and CheckList cancers: Tumor thickness Whether localized to one side, reaches or crosses the midline Inferior extent— sublingual space and mylohoid muscle (FOM), lingual vessels Posterior extent— base of tongue, tonsil, oropharyn x, preepiglott ic space, hyoid Posterosup erior extent— retromolar trigone and
PETCT Preferre and d CEMRI Imaging in Techniq locoregi ue onally advance d cases
Advantages
Disadvantages
soft tissue and contrast resolution [16,17] Clearly defines extrinsic muscle and FOM invasion from tongue cancers Clearly defined posterior and inferior soft tissue extent in base of tongue Sensitive for bone erosion (which occur in less than 10% of oral tongue cancer) [16]
acquisition time Motion and metallic denture artifacts. Although good sensitivity for marrow changes, however specificity for marrow invasion is less due to inflammation by dental and periodontal conditions [18]
Subsi te
Spread Patterns and CheckList masticator space Bone erosion: lingual cortex of mandible Floor of mouth cancers: Whether crosses the midline Involveme nt of lingual vessels, base of tongue, valleculae, preepiglott ic space Lingual cortex of mandible, hyoid bone
Faster scan, reduces image acquisition time Oblique multiplanar bone
Dental amalgam artifacts, miss the small oral cavity lesions and cannot delineate true extent and
and Subsi lip te cance r (Fig. 65.16 )
Spread Patterns and CheckList dermal, and subdermal region of cheek Maxillary sinus Retromola r trigone Masticator space— Infranotch or supranotch disease* Retromola r trigone cancers: Maxilla, mandible erosion Gingivobu ccal mucosa and buccal space Masticator space— Infranotch or supranotch disease* Base of tongue, palatine tonsils
CE MRI Preferre for d suspecte Imaging dTechniq perineur ue al spread and postoper ative patients For smaller buccal mucosal lesions and in operated oral cancers, MRI with water distensio n maneuve r (Fig. 65.18)
Advantages
Disadvantages
algorithm evaluates the bony erosions and extent precisely [19,20] Adequate information about posterior and superior extent in relation to the mandibular notch [30– 32] Puffed cheek maneuver helps in delineating precise location and extent of gingivabuccal sulcus (GBS) and buccal mucosa (BM) lesions [22]
depth of the lesion CECT can miss perineural spread along inferior alveolar nerve and in skull base foramina, CEMRI is imaging technique of choice (Fig. 65.19)
Subsi te
Spread Patterns and CheckList Perineural spread along V2 or V3 division of trigeminal nerve or along auriculote mporal nerve (Fig. 65.17) *Infranotc h compartm ent—low masticator space containing medial pterygoid Supranotc h compartm ent—high masticator space containing lateral pterygoid and superior part of temporalis muscle
Preferre d Imaging Techniq ue
Advantages
Disadvantages
Subsi te
Spread Patterns and CheckList (Fig. 65.16)
Preferre d Imaging Techniq ue
Advantages
Disadvantages
Hard palate
Superiorly —nasal cavity and maxillary sinus Laterally —upper alveolus Posteriorly —soft palate or perineural spread along greater and lesser palatine foramina and in skull base foramina
CE MRI with open mouth maneuve r
Evaluate perineural spread along palatal and skull base foramina [34] Access marrow changes in hard palate precisely
Longer acquisition time Motion and metallic denture artifacts
Lymphoma: This is the second most common oral malignancy after SCC [24–25]. It commonly occurs in SMS as nodal non-Hodgkin lymphoma, but can also involve gingiva of palate. Perineural spread is very rare. Solitary or multiple enlarged homogenously enhancing discrete non-necrotic nodes are seen in SMS. Extranodal lymphoma involving oral or palatal submucosa or mandible is extremely rare and cannot be differentiated from carcinoma on cross-sectional imaging [26] (Fig. 65.20).
FIGURE 65.20 Non-Hodgkin’s lymphoma of mandible. Axial contrastenhanced CT scan (A), axial (B), and coronal (C). PET-CT shows metabolically active mildly enhancing large paramandibular soft tissue lesion with marrow infiltration (arrow).
Malignant Salivary Gland Tumors: These include primarily the Adenoid cystic carcinomas (ADCs) and the mucoepidermoid carcinomas (MECs). These malignant salivary gland cancers arise from minor salivary gland rests found in the oral cavity and are generally seen in the sixth to seventh decades of life. They are commonly seen in the hard palate and least frequently in the buccal mucosa [40]. They are slow growing lesions and histologically graded as low-, intermediate-, and high-grade carcinomas [27]. Low-grade neoplasms are wellcircumscribed lesions with presence of capsule and have predominantly cystic component [28]. High-grade tumors appear as infiltrative heterogeneously enhancing soft tissue masses on cross-sectional imaging and cannot be differentiated from SCC of oral cavity [29,30]. They have a high propensity for anterograde perineural spread along the second and third divisions of the fifth cranial nerve. Lymphatic spread to neck nodes is uncommon, however they have tendency for hematogenous spread to the lung and liver. Sarcoma: Liposarcoma, leiomyosarcoma, and rhabdomyosarcoma are rare groups of malignant neoplasms affecting oral cavity and seen in less than 1% of head and neck cancers [31]. On cross-sectional imaging these tumors appear as large ill-defined and infiltrating masses, showing heterogenous enhancement. Metastases: These are extremely rare tumors of oral cavity and arise from primary malignancies of the lung, breast, kidney, thyroid melanoma, and kidneys
[31,33]. Imaging findings are nonspecific and often associated with findings of metastatic deposits elsewhere in the body. Postoperative Oral Cavity Imaging of the postoperative oral cavity is crucial and radiologist must have knowledge of various imaging appearances of post-treatment oral cavity including anatomic distortion, appearance of flap reconstructions as well as postsurgical fibrosis from recurrent disease. Goals of postoperative imaging include: 1. Evaluation of postoperative bed 2. Evaluation of post-treatment short-term and long-term complications 3. Evaluation of disease recurrence at operative bed side and at flap mucosal junction
Imaging pearls of postoperative bed evaluation on cross-sectional imaging [34].
◾raises Any asymmetry or thickening at operative site or nodular/irregular contour of operated area the suspicion of recurrent malignant disease and should always be correlated with clinical examination findings ◾almost Enhancing soft tissue lesion at operative bed or involving the flap mucosal junction is definitive of recurrent malignant lesion (Fig. 65.21) ◾injection) DW-MRI and delayed contrast-enhanced MDCT/MRI (taken after 10 minutes of contrast helps at times to differentiate benign changes from recurrent disease spread (Fig. 65.22) ◾metastatic FDG PET-CT is valuable tool to evaluate recurrence and restaging for oral cavity cancers, neck node of unknown primary; however dental streak artifacts hinder the evaluation of oral cavity. Combining PET and MRI gives unique metabolic information and excellent soft tissue contrast as well as morphologic data [35,36] (Fig. 65.23)
FIGURE 65.21 Operated case of right buccal mucosa with flap reconstruction. Reformatted coronal (A) and sagittal (B) postcontrast CT images showing enhancing soft tissue (arrows) in superior aspect of flap (arrowhead) with intrasinus extension in residual right maxilla.
FIGURE 65.22 Operated case of carcinoma of left buccal mucosa, presented with pus discharge from oral cavity. (A) Sagittal PET-CT image shows hypermetabolic area at flap site (arrow). Postcontrast sagittal T1 fat suppressed image (B) shows inflamed flap with peripherally enhancing oroantral fistula (arrowhead) and DWI (C) with ADC (D) images show no restriction with high ADC value (asterisk).
FIGURE 65.23 Floor of mouth cancer. Axial PET-CT image (A) shows metabolically active metastatic left level II (arrow), axial PET-MRI fusion (B) shows metabolically active metastatic left level II node (arrow) and small lesion in left side of floor mouth (large arrow). Biopsy showed moderately differentiated SCC from ulcer in floor of mouth.
Section 2: Pharynx Pharynx is a long musculomembranous tube which extends from base of the skull cranially to the lower border of cricoid cartilage. It is subdivided into three parts, nasopharynx, oropharynx, and hypopharynx.
Anatomy Nasopharynx: It is the superior most part of pharynx which is situated below the skull base, posterior to the nasal cavity, anterior to clivus and bound by parapharyngeal space laterally and carotid space posterolaterally on either side and extends inferiorly up to the level of the line passing through the hard and soft palates. The lateral wall of nasopharynx shows two fossae and one mucosal projection on either side. The eustachian tube (ET) opening is located along the upper part of its lateral wall through which nasopharynx communicates with middle ear. Torus tubarius, a mucosal projection formed by cartilaginous portion of ET is located posterior to ET opening and the fossa of Rosenmuller is situated posterior to the torus tubarius (Fig. 65.24). The fossa of Rosenmuller and surrounding area is a frequent site for origin of nasopharyngeal carcinoma (NPC).
FIGURE 65.24 Normal anatomy of the nasopharynx. Axial CT section shows (1) Eustachian tube opening (thick black arrow), (2) torus tubarius (thin black arrow), (3) fossa of Rosenmuller (arrowhead), (4) and parapharyngeal space (asterisk).
Oropharynx: Oropharynx is located behind the oral cavity, and comprises the palatine tonsils with anterior and posterior pillars which are made up of palatoglossus and palatopharyngeus muscles, respectively, base of tongue and lingual tonsil, soft palate, posterior oropharyngeal wall related to second and third cervical vertebral bodies and vallecula formed by median glossoepiglottic fold and laterally by lateral glossoepiglottic fold [1] (Figs. 65.25 and 65.26). Oropharyngeal subsites usually contain lymphoid tissue in variable degree. This is the reason for lymphoma being a common diagnostic differential of oropharyngeal SCC (OPSCC).
FIGURE 65.25 Normal anatomy of oropharynx. (A) Base of tongue (solid black arrows). Postcontrast CT image showing differential enhancement than rest of the tongue due to presence of lymphoid tissue. It is located just above preepiglottic fat (dotted white arrow). On T1 W image (B) and on T2 fat saturated image (C), differential signal in base of tongue is seen due to presence of lymphoid tissue. Junction of soft and hard palate demarcates anterior boundary of oropharynx superiorly.
FIGURE 65.26 Normal anatomy of oropharynx. Axial (A) and coronal (B and C) anatomy shows bilateral palatine tonsils (solid white arrows) on medial aspect of parapharyngeal fat (solid black arrows). Medial pterygoid muscles (dotted black arrows) are located just lateral to parapharyngeal fat. Anterolaterally, retromolar trigone comes in relation with palatine tonsils.
Hypopharynx: Hypopharynx is located below oropharynx and extends caudally till the inferior margin of cricoid cartilage (Figs. 65.27, 65.28, and 65.29). It continues below as cervical esophagus. Hypopharynx is made up of three components namely pyriform fossa, postcricoid region, and posterior hypopharyngeal wall.
FIGURE 65.27 Pyriform fossa anatomy. Pyriform fossa is indicated by solid black arrows. Anteriorly, it comes in relation with paraglottic fat (dotted white arrows). Medially, it is related to aryepiglottic fold (solid white arrows). Laterally, it comes in relation with thyrohyoid membrane superiorly. In inferior part, pyriform fossa tapers as pyriform apex. Pyriform apex is located at the level of true vocal cord and cricoarytenoid joint. In image B, normal pyriform apex is seen on either side (solid black arrows).
FIGURE 65.28 Postcricoid region layered arrangement. Comparison of two different patients in axial CT scan images. Just behind the cricoid cartilage, first layer is posterior cricoarytenoid muscle (curved black arrows). Second layer is anterior submucosal fat plane (solid black arrows). Third layer is hypopharyngeal mucosa/opposed lumen (dotted black arrows). Fourth layer is second submucosal fat plane (solid white arrows). Inferior constrictor muscle of pharynx (dotted white arrows) is located behind second submucosal fat plane and anterior to longus capitis muscle.
FIGURE 65.29 Postcricoid region. (A) Sections at the level of thyroid gland (T) and trachea-esophageal groove. (B) As we go toward esophagus from hypopharynx, hypopharynx starts to change shape from flat to round and (C) becomes completely round in shape at level of esophagus. TR, trachea.
Visceral fascia is located behind the constrictor muscle of pharynx, posterior to which is retropharyngeal fat plane. Fat plane in retropharyngeal region is an important landmark while evaluating prevertebral fixation in cases of malignancy [37,38].
Imaging Techniques In the era of CT scan and MRI, plain radiographs and barium procedures are almost obsolete for imaging of these malignancies, except for screening [3942]. USG can be used to detect metastatic lymphadenopathy and for performing a few ultrasound-guided interventional procedures. MDCT and MRI are well-established imaging techniques for evaluation of pharyngeal pathologies. Mucosal abnormality of pharynx can be demonstrated on clinical evaluation or by endoscopy. The primary goal of imaging is to define the submucosal spread and locoregional extent into adjacent spaces. PET-CT is very useful and a gold standard for staging in conditions like lymphoma as well as residual, recurrent, and postoperative cases of pharyngeal malignancies. Commonly used imaging techniques for evaluation of pharyngeal pathology are given in Table 65.3. Table 65.3 Commonly Used Imaging Techniques for Evaluation of Pharyngeal Pathology
Subsite s
Technique
Nasoph arynx
MRI is preferred over CT PET CT
Oropha rynx
MRI is preferred over CT Contrast CT combined with MR imaging has highest degree of sensitivity [1]
Hypoph arynx
CT is preferred over MRI
Nasopharynx Various pathologies that affect the nasopharynx are given in Table 65.4. Table 65.4 Nasopharynx—Common Diseases Non-neoplastic
Neoplastic Direct extension of malignant sino nasal tumors or skull base tumor, e.g., chordoma, Extramedullary plasmacytoma
Common pathologies involving nasopharynx in the pediatric age group are adenoid hyperplasia and juvenile nasopharyngeal angiofibroma (JNA), while in adult it is NPC. An adult presenting with metastatic neck node(s) with carcinoma from unknown primary as initial presentation or nonresolving serous otitis media must be evaluated for NPC.
Neoplastic Lesions Juvenile Nasopharyngeal Angiofibroma It is commonest benign, but locally aggressive vascular tumor that may extend into the nasopharynx and exclusively occurs in adolescent males. Nasal obstruction and recurrent epistaxis are the commonest clinical presentations. Cross-sectional imaging (CT and/or MRI) are the main stay of imaging not only for confirmation of diagnosis of JNA but for its locoregional extension. This is followed by preoperative angiography with embolization. JNA originates from a vascular nidus in the posterolateral wall of nasal cavity near the superior margin of the sphenopalatine foramen, thus the term “nasopharyngeal” is a misnomer as it is only secondarily involved by this tumor [43,44]. The role of imaging is to determine exact site, extent and very importantly to know feeding arteries of this tumor before surgery, since surgery is the mainstay of treatment. Contrast-enhanced MDCT is the primary baseline imaging technique for mapping of tumor as well as to see intracranial extension, skull base erosion, and status of pterygoid plates. MRI should be reserved in cases with intracranial extension and engulfment of internal carotid artery [43–45]. On cross-sectional imaging JNA has a classical appearance of soft tissue density polypoidal mass showing avid enhancement. The lesion is centered at the sphenopalatine foramen. It can extend anteriorly into nasal cavity and nasopharynx, laterally into infratemporal fossa, masticator space through pterygopalatine fossa, and pterygomaxillary fissure. It causes anterior bowing of posterior wall of maxillary sinus known as “Holman–Miller sign” (Antral sign) [43,44] (Fig. 65.30). In 2017, Janakiram et al. have analyzed imaging findings of 242 patients of JNA and suggested that all primary cases
of JNA show marked widening of pterygoid wedge which is a junction of medial and lateral pterygoid plates. This sign is known as “Ram–Haran” sign (Fig. 65.31), and in follow up postoperative imaging shows two parallel lines of pterygoid plates due to drilling of cancellous bone in pterygoid wedge. This sign is known as “chopstick sign” [45]. At the time of imaging, most of the tumors are fairly large in size. They show signals that are isointense to muscle on T1 images and are heterogeneously hyperintense on T2 images. Presence of prominent flow voids leads to “salt and pepper” appearance at MRI. Moderate enhancement is seen on the contrast study.
FIGURE 65.30 Juvenile nasopharyngeal angiofibroma (JNA). Postcontrast axial CT scan shows classical signs of JNA. Widening of right sphenopalatine foramen (asterisk) with extension of tumor into pterygopalatine fossa and pterygomaxillary fissure (large arrow) and anterior bowing of posterolateral wall of right maxillary sinus (arrowhead).
FIGURE 65.31 Juvenile nasopharyngeal angiofibroma (JNA). Coronal CT reformatted image shows an intensely enhancing JNA (stage II) with marked widening of right pterygoid wedge—“Ram–Haran sign” (white arrow) and normal pterygoid wedge on left side (black arrow).
The purpose of preoperative angiography in this vascular tumor is for identifying the feeding vessels of the tumor, followed by elective embolization of feeders, which helps to reduce intraoperative bleeding (Fig. 65.32) [46].
FIGURE 65.32 Juvenile nasopharyngeal angiofibroma (JNA). Sagittal (A) and coronal (B) digital subtraction angiography images show blush of contrast in JNA (arrows), postembolization, sagittal (C) and coronal (D) digital subtraction angiography images show no blush of contrast at tumor site (arrowheads).
FIGURE 65.33 Nasopharyngeal carcinoma. Coronal (A) and sagittal (B) postcontrast reformatted CT images show stage IV nasopharyngeal carcinoma with intrasinus (asterisk) and intracranial (long arrows) extension on left side and bone reformatted image (C) shows erosion of foramen ovale (short arrow).
Arterial feeders in JNA are given in Table 65.5. Table 65.5 Arterial Feeders in JNA ECA—external carotid artery (major)
Nasopharyngeal Carcinoma NPC is a silent head and neck malignant tumor with approximately 60–85% presenting as metastatic neck nodes. Other presenting symptoms include headache, nasal obstruction, epistaxis, and cranial nerve palsy. The tumor occurs in adults, with male to female ratio being 3:1 and shows bimodal peak between second and sixth decades. It rarely affects children below 6 years of age. The diagnosis of NPC is usually done by endoscopy and biopsy. NPC starts in fossa of Rosenmuller and spreads submucosally. The primary goal of imaging is to know the entire extent of spread, especially in patients with ambiguous endoscopy findings, where tumor resembles hypertrophied lymphoid tissue or if the lesion is entirely submucosal. On CT, very early NPC may not be appreciated or can be seen fossa of Rosenmuller obliteration while in advanced NPC, the tumor is seen as a soft tissue density homogenously or heterogeneously enhancing lesion. On MRI
it is seen as low signal intensity lesion on T1-weighted images and intermediate to hyperintense signal mass on T2-weighted images with hypoenhancement than the normal mucosa on contrast T1-weighted images. Patterns of spread of NPC are shown in Table 65.6. Table 65.6 Patterns of Spread of NPC Exte nsio n
Involvement
Ante rior
Posterior aspect of nasal cavity. It can cause widening and/or erosion of sphenopalatine foramen with further spread of tumor into pterygopalatine fossa and pterygomaxillary maxillary fissure. NPC with limited spread to nasal cavity is considered as T1 stage. Inferior extension of the tumor into oropharynx rarely occurs.
Late ral
Extension through levatorpalatini muscle and pharyngobasilar fascia into the parapharyngeal space (PPS) [47]. Invasion of this space can lead to high incidence of distant metastasis and from this space the lesion can encase or invade internal carotid artery and further anterolateral spread occurs into the masticator space and infratemporal fossa. PPS extension is considered as T2 stage.
Supe rior
Invasion of the skull base and skull base foramina (foramen lacerum, ovale, and vidian canal) is best appreciated on coronal and axial postcontrast T1W fat saturated images. Erosion of clivus, body of sphenoid, and pterygoid bones is fairly common and better seen on MDCT. Paranasal sinus involvement occurs as direct extension, with sphenoid sinus involvement being the commonest. MRI can differentiate intrasinus extension from retained secretions [47]. Skull base and paranasal sinus extension of NPC is considered as stage T3 disease. Intracranial dural extension or infiltration, meningeal involvement or extension into the cavernous sinus are considered as T4 disease (Fig. 65.33)
Exte nsio n
Involvement
Post erior
NPC infiltrates the prevertebral muscle posteriorly via infiltration of longus coli muscle. Hematogenous spread occurs frequently after infiltration of prevertebral space by the lesion as space is rich in the venous plexus [48]. Extensively rich submucosal capillary lymphatic plexus of nasopharynx explains high incidence of cervical nodal metastasis. Nodal metastases occur commonly to retropharyngeal nodes followed by jugulodigastric nodes from level II to V.
Post-Treatment NPC Evaluation: NPC is a radiosensitive malignancy and radiation therapy is the mainstay of treatment for early disease and chemoradiation is preferred in locally advanced cases. Post-treatment MRI in NPC reveals diffusely thickened enhancing mucosa and submucosa of nasopharynx due to radiation induce edema and mucositis [49] (Fig. 65.34). Contrast-enhanced MRI is superior in evaluating post-treatment changes and recurrent nasopharyngeal tumors. PET-CT or PET-MRI is superior imaging techniques in equivocal follow-up cases of NPC, where MRI findings are not clearly diagnostic [50,51] (Fig. 65.35). Apart from information about distant metastasis, PET-CT is also valuable when MRI shows equivocal neck nodes. Recurrent or residual disease shows uptake of radionuclide tracer on PET imaging while on MRI, it appears as intermediate to high T2 signal intensity with inhomogeneous postcontrast enhancement. Combining PET and MRI significantly improves diagnostic accuracy in evaluation of recurrent disease with an advantage of combined metabolic and morphologic information.
FIGURE 65.34 Nasopharyngeal cancer post-treatment. Axial T2W (A) and postcontrast T1W (B) images show diffusely enhancing edematous symmetrical thickened nasopharyngeal wall (arrows) following chemoradiation for nasopharyngeal cancer.
FIGURE 65.35 Recurrent nasopharyngeal cancer. Follow-up MRI postcontrast T1W fat saturated (A) image shows mild asymmetric thickening of posterolateral wall of nasopharynx (arrow). PET MRI fusion image (B) shows focal metabolic activity in the thickened left posterolateral wall (arrow). Biopsy was suggestive of recurrent squamous cell carcinoma.
Lymphoma of Nasopharynx This is the second most common malignancy of nasopharynx. On imaging, it appears as a diffuse homogenous symmetrical enlargement of walls of nasopharynx with bulky masses and florid lymphadenopathy [52]. PET-CT is valuable in staging and restaging of lymphoma. Lymphoma is usually
differentiated from NPC on the basis of midline location with symmetrical involvement and uncommon bony invasion. On MRI, lymphoma shows low ADC values due to high cellularity.
Non-Neoplastic Lesions Adenoid Hyperplasia It is the commonest benign lesions of children and one of the common causes of upper airway obstruction. Lateral radiograph in an extended neck is sufficient to demonstrate adenoid hyperplasia, seen as a radio-opacity in the roof of nasopharynx. No other imaging is generally required. It is often seen as incidental finding in CT and MRI scans of the brain in children performed for various other reasons. Nasopharyngeal Cysts Cystic lesions like mucous retention cyst and Thornwaldt’s cysts are incidentally seen on head and neck imaging. Mucous retention cyst is seen in posterolateral wall of nasopharynx, while Thornwaldt’s cyst is a developmental cyst seen in midline due to failure of closure of nasopharyngeal bursa [53]. Encephalocoele/Meningocoele These are uncommon pathologies involving the nasopharynx [54]. Encephalocoele/meningocoeles are more commonly seen in nasal, frontoethmoidal regions, or occipital region, and are usually associated with a defect in the skull base. CT is good to identity the bony defect and MRI for the contents and its intracranial connection. Antrochoanal Polyp These are sinonasal polyps which originate from the maxillary sinus and extend from the maxillary ostium, nasal cavity, and posterior choana into the nasopharynx. CT shows a hypodense well-defined mass with associated widening of the maxillary ostium (Fig. 65.36). Contrast-enhanced computed tomography (CECT) may show peripheral enhancement. MRI reveals a T1 hypointense and T2 homogenously hyperintense mass which shows peripheral enhancement.
FIGURE 65.36 Antrochoanal polyp. Axial (A), coronal (B, C) CT reformations show complete polypoidal opacification of right maxillary sinus with widening of right osteometal complex (arrow) and extension posteriorly, bulging into nasopharynx (arrowhead).
Oropharynx and Hypopharynx Various pathologies that affect the oropharynx and hypopharynx are given in Table 65.7. Table 65.7 Oropharynx and Hypopharynx—Common Diseases Non-Neoplastic
Neoplastic
Congenital/developmen tal Lingual thyroid Thyroglossal duct cyst Venolymphatic malformation
Neoplasms Most common tumors occurring in oropharynx are carcinomas, minor salivary gland tumors, and lymphomas. Oropharyngeal Squamous Cell Carcinoma Oropharyngeal mucosa is lined by squamous epithelium of endodermal origin, which gives rise to high grade or poorly differentiated carcinomas, as compared to the oral cavity which is lined by squamous epithelium of ectodermal origin that gives rise to relatively well-differentiated carcinomas [1]. Oropharyngeal cancers rank as sixth most common cancer worldwide and cancers in each subsite have been described below. As per the eighth edition of the American Joint Committee on Cancer Staging Manual, published in 2017, OPSCCs are divided into two categories—HPV positive and HPV negative. HPV positive OPSCCs are positive for p16 immunostaining and have better prognosis than HPV negative OPSCCs [55]. Base of Tongue Cancers in the base of tongue have an indolent course, often attaining large sizes, crossing midline and presenting with deep cervical lymphadenopathy
(Fig. 65.37). Tongue base malignancy has tendency to remain localized without local spread except when tumors are located laterally. Laterally located tumors spread to tonsils. Otherwise, tonsillar spread is less common. Extrinsic muscle of the tongue involvement upgrades the stage to T4a [56,57].
FIGURE 65.37 Base of tongue cancer. Axial (A) and sagittal (B) fat saturated T2W images show the mass lesion centered at the base of tongue, extending anteriorly into genioglossus muscle on left side (solid black arrows in images A and B). The mass is infiltrating intrinsic muscles of tongue, crossing midline, and infiltrating posterior edge of right genioglossus muscle. It encases left lingual artery (dotted white arrow in A). Preepiglottic fat is normal in sagittal T1W image (solid black arrow in C).
When the lesion spreads across the midline, there are higher chances of bilateral lymphatic invasion. Also, for partial glossectomy surgery, one has to preserve at least one lingual artery and hypoglossal nerve. Involvement of the contralateral neurovascular bundle involvement contradicts hemi glossectomy for initial treatment at most institutions. Preepiglottic fat involvement suggests laryngeal involvement and may warrant laryngectomy with hemiglossectomy. Preepiglottic fat is rich in lymphatics and its involvement leads to significant lymphatic spread. Osseous involvement is rare in the base of tongue malignancy. Level II nodes are primary echelon drainage nodes for the base of tongue lesions followed by level III and IV nodes. Submandibular nodes are enlarged when there is involvement of oral tongue. Submental nodes are not involved in base of tongue carcinoma. Bilateral nodes are common, especially in tumors that have crossed the midline [58]. Tonsil Palatine tonsil is the commonest site for origin of carcinoma, followed by anterior tonsillar pillar (Figs. 65.38 and 65.39). Posterior pillar cancer in isolation is rare [1].
FIGURE 65.38 Tonsillar fossa cancer. Axial plain CT (A) and contrast CT (B) images show a mildly enhancing left tonsillar globular mass with effacement of glossotonsillar sulcus (dotted white arrows). Left-sided parapharyngeal fat is invaded (curved black arrow) and lesion abuts left medial pterygoid muscle (indicated by solid black arrows). The same tumor is seen in the coronal CT image (C).
FIGURE 65.39 Tonsillar lymphoma. Axial (A and B) and coronal (C) postcontrast CT images depict bilateral symmetrical enlargement of tonsils with kissing tonsil configuration and marked oropharyngeal lumen narrowing. Biopsy proven of case of non-Hodgkin’s lymphoma.
Tonsillar carcinomas can be infiltrative, exophytic, or ulcerative. Superiorly, these tumors can ascend along anterior tonsillar pillar while inferiorly, they can involve tongue base. Anterior extension to oral cavity is also common, while posterior extension leads to posterior oropharyngeal wall involvement. Laterally, parapharyngeal fat and RMT are susceptible for invasion. RMT can give access to spread of the disease into the masticator space and buccal space. Pharyngobasilar fascia invasion gives tumor access toward skull base [59]. The tonsil is often the site of origin for metastasis of unknown origin in neck, especially in the region of the glossotonsillar sulcus. The involved
tonsil can be small as compared to opposite tonsil and may be low signal on T2W images in malignancy. The reason for this dark signal is the crypted structure of tonsil that can harbor malignancy in the depth of its crypt which can give rise to cervical lymphadenopathy. Also, highly fibrous nature of the tumor can give rise to low signal on T2W images. Interestingly, in these cases random tonsillar biopsy is negative, only tonsillectomy can give correct estimate of malignancy. As nodal spread can occur on either side of neck, tonsils may have to be removed bilaterally in such cases as part of surveillance [60]. Soft Palate Soft palate is a distinct combination of muscles, epithelium, and minor salivary glands [1,61] (Figs. 65.40 and 65.41). SCC, ADC, and MEC are common tumors of soft palate. These tumors are detected earlier in the course of disease. MRI is preferred for the evaluation of soft palate cancer and the disease is best assessed on sagittal and coronal planes. In advanced cases, these cancers can spread to tonsillar pillars, hard palate, and base of tongue and along palate muscles to the skull base. Radiotherapy is the treatment of choice in early stages of disease, while advanced cases are treated with combination of chemotherapy and radiotherapy.
FIGURE 65.40 Soft palate cancer. Axial (A) and sagittal (B) noncontrast CT show well-defined lobulated soft tissue density lesion is noted in soft palate (solid black arrow in image A) on right side, right tonsillar fossa involving anterior tonsillar pillar (solid black arrow in image B).
FIGURE 65.41 Pleomorphic adenoma of the soft palate. Axial (A) and sagittal (B) postcontrast CT images show well-defined inhomogeneously enhancing hypodense lesion involving soft palate and pharyngomucosal space (solid black arrows) along right pharyngeal wall. Biopsy specimen seen in (C).
Posterior Pharyngeal Wall Isolated cancers of the posterior oropharyngeal wall are rare. In these cases, prevertebral fixation by tumor is very common, which is a contraindication to tumor resection. Lesions can spread to nasopharynx superiorly, hypopharynx inferiorly, and can involve the base of tongue. MRI is more important to evaluate prevertebral fixation by tumors [1]. Checklist for oropharyngeal carcinoma is given in Table 65.8. Table 65.8 Checklist for Oropharyngeal Carcinoma Base of Tongue [1,57]
Tonsil [1,59,60]
Soft Palate [1,61]
Submuco sal spread and deeper extent
Submucosal spread and deeper extent
Submuco sal spread and deeper extent
Base of Tongue [1,57]
Tonsil [1,59,60]
Soft Palate [1,61]
Extrinsic muscle involvem ent
Pterygoid muscle or plates involvement
Hard palate involvem ent
Midline crossing
Paradoxical small and dark tonsil, which can turn out to be carcinoma harboring site in evaluating metastasis of unknown origin
Tonsillar pillars involvem ent
Preepiglo ttic fat involvem ent
Pterygomandibular raphe involvement
Base of tongue involvem ent
Hyoid bone involvem ent
Pterygoid plates involvement
Hard palate involvem ent
Nodal disease
Nodal disease
Nodal disease
Retromolar trigone and masticator space involvement Foramen ovale and mandibular nerve invasion for perineural spread (less common)
Hypopharyngeal Cancers Pyriform Fossa: These cancers tend to remain silent for long time and invade the adjacent structures (Fig. 65.42). These tumors very often involve the larynx due to the close anatomical proximity. Tumors arising in lateral wall of pyriform fossa often spread to invade the thyroid cartilage. Medial tumors commonly involve the aryepiglottic fold with endolaryngeal extension. Anteriorly the lesions can spread to paraglottic space and cause laryngeal fixation. Inferiorly, the cancer can extend to the pyriform apex that is located at the level of the true cord.
FIGURE 65.42 Pyriform fossa malignancy. Axial T2W fat saturated images (A) and (B). Image in (A) shows a large left piriform sinus tumor with invasion of paraglottic fat (solid white arrows). Image B shows invasion of left lamina of thyroid cartilage with extralaryngeal soft tissue (solid white arrows). (C) Axial T1W image shows normal T1 hyperintensity of the right thyroid lamina with corticated margins (dotted white arrow). Compare with the diseased left lamina that is hypointense (white arrow) and shows extralaryngeal soft tissue.
Checklist for pyriform fossa malignancy: 1. Involvement of anterior, medial, lateral walls, or posterior walls as well as pyriform sinus apex if involved 2. Laryngeal fixation: Invasion of paraglottic space, true or false cord, cricoarytenoid joint involvement and trachea-esophageal groove extension leading to hemilaryngeal fixation. Sometimes, there is exaggerated peritumoral inflammation causing edema in the surrounding structures, which may cause laryngeal fixation 3. Cartilage infiltration 4. Posterior fixation: This is seen as obliteration of fat plane in retropharyngeal region with adherence to the prevertebral space and is a contraindication to surgery. It is better appreciated on MR images 5. Carotid artery/thyroid gland involvement 6. Superior oropharyngeal extension 7. Nodal disease: Commonly level II, IV, and V nodes are involved
Postcricoid Region: Tumors in this region are flat, often silent and patients present in advance stages (Fig. 65.43). These cancers are commonly associated with Plummer Vinson syndrome. Esophageal involvement is an important concern in case of postcricoid malignancy, as its surgical management requires partial esophagectomy. Nodal drainage is commonly to level III, IV, and retropharyngeal nodes. Hypopharygeal ultrasonography (Fig. 65.44A) yields good results in cases of postcricoid region malignancy, especially when mass is at the level of thyroid gland. Thyroid gland gives the necessary window to evaluate the postcricoid region which gets hindered by the bone, cartilage, and air interfaces. Biopsy can be done through transthyroid approach when tumor is not approachable on endoscopy or in cases of failed biopsy (Fig. 65.44B) [62].
FIGURE 65.43 Hypopharyngeal cancer. Axial postcontrast (A and B) and sagittal postcontrast (C) CT images show postcricoid region mass lesion (black arrows) at the level of thyroid gland with extension into trachea-esophageal groove and anterior bowing of trachea. Lesion is extending into esophagus in cervical part (solid white arrow in C).
FIGURE 65.44 Transthyroid postcricoid region biopsy for failed endoscopic biopsy of same patient of CT scan in Fig. 65.43. (A) Right lobe of thyroid is indicated by solid black arrow, mass lesion is indicated by dotted arrow. (B) Needle position is indicated by solid white arrow. Biopsy confirmed squamous cell carcinoma of postcricoid region.
Posterior Hypopharyngeal Wall: Tumors in this region are rare; however widespread malignancies may involve oropharynx and esophagus. Posterior prevertebral fixation is also common with tumors of this region. Nodal drainage is to level III and IV nodes as well as paratracheal nodes.
Other Malignancies Lymphoma Non-Hodgkin lymphomas dominate in head and neck in non-nodal primary sites of lymphoma, where they mimic SCC and must always be included in the list of diagnostic differentials. Waldeyer’s lymphatic ring in nasopharynx and hypopharynx is a common site for occurrence of lymphoma. Palatine tonsil, lingual tonsil, and lateral pharyngeal wall are commonly involved sites in oropharynx. Palatine tonsillar lymphomas (Fig. 65.39) commonly mimic tonsillar abscess but often have very clear margin with no surrounding infiltration. Unlike SCC, they are less infiltrative and base of tongue is less commonly involved. Lingual tonsillar carcinomas protrude in oropharyngeal lumen rather than invading base of tongue muscles as seen in
SCC. Lateral pharyngeal wall lymphomas are less common. PET-CT is preferred technique in cases of lymphoma to detect extranodal spread as well as other organs. Recurrence and surveillance are also better evaluated at PET CT [63].
Rhabdomyosarcomas It is a common pediatric age group malignancy and commonly involves the nasopharynx, soft palate, oropharynx, and hypopharyngeal walls. It is very rapidly progressive malignancy with extensive infiltration and destruction. On T1W images, it is usually isointense to muscle and on T2W images, it shows hyperintense signal. It shows heterogeneous enhancement with variable degree of necrosis [64].
Minor Salivary Gland Tumors Two major types of minor salivary gland tumors occur in oropharynx—MEC and ADC (Fig. 65.41). CT and MRI provide good delineation of the tumor and perineural spread details. ADCs have tendency to spread along greater and lesser palatine nerves to pterygopalatine fossa. Similarly, they can spread along branches of trigeminal nerve toward cavernous sinus and Meckel’s cave. Neural involvement can be seen in discontinuous manner, so vigilant inspection along the course of nerves is mandatory. Recurrence of these tumors even after complete cure is high due to perineural spread as well as early lymphatic involvement. Other tumors include acinic cell carcinoma, malignant mixed tumor, and pleomorphic adenoma [65].
Non-Neoplastic Lesions
◾results Lingual thyroid: Failure of thyroid tissue to descend from foramen caecum to lower neck in presence of thyroid rest cells in foramen caecum or along the course of the thyroglossal duct tract [11–13]. Foramen caecum in the base of the tongue is the most common location of ectopic thyroid tissue. On CT imaging it is seen as round or ovoid hyperdense lesion with attenuation similar to that of the normal thyroid gland (Fig. 65.45). On MRI it is usually solid in appearance, mildly hyperintense or isointense to the muscle on T1W images and are avidly enhancing masses. Parent thyroid bed in most cases shows absent normal thyroid [66] Peritonsillar abscess/quinsy: It is defined as pus collection between capsule of tonsil and superior pharyngeal constrictor muscle, occurring due to underlying tonsillitis. Usually imaging is not done for tonsillitis. Imaging diagnosis is supportive to clinical suspicion of abscess and CT is preferred. Low-density center with enhancing rim on CT scan easily diagnoses the abscess. Chronic tonsillitis often reveals presence of tonsilloliths (Fig. 65.46) and is seen an incidental finding in neck or brain CT performed for other indications [67] Zenker’s diverticulum: It is type of “pulsion pseudodiverticulum,” formed by bulging of mucosa and submucosa through a defect in cricopharyngeus muscle, at a potentially weak site between transverse and oblique parts of cricopharyngeus muscle, due to rising
◾ ◾
esophageal pressure. It appears on posterior and lateral aspect, mostly on left side. The diverticulum is best identified during swallowing and is best seen on the lateral view on barium studies, on which the diverticulum is typically noted at the C5-6 level [68]
FIGURE 65.45 Ectopic thyroid. Noncontrast axial (A) and postcontrast axial (B) and sagittal (C) reformations shows a hyperdense enhancing lesion in the region of foramen caecum (arrow) and absent thyroid gland in normal position (arrowhead in C).
FIGURE 65.46 Tonsilloliths. Axial postcontrast (A) and coronal postcontrast (B) images show case of chronic tonsillitis with bilateral tonsilloliths (indicated by solid arrows).
Pharyngeal Trauma It may be blunt, penetrating, or iatrogenic trauma. In accidental injuries, most commonly there is presence of retropharyngeal hematoma formation, which can be life threatening. Hypopharyngeal hematoma occurs in
instrumental injury. Foreign body entrapment is common event and hypopharynx–esophageal junction is very common site. It is also seen in vallecula, tonsillar fossa, and rarely in pyriform fossa. Plain CT evaluation is preferred for foreign body evaluation (Fig. 65.47). Penetrating injury can complete perforation of pharynx and lead to abscess formation [69].
FIGURE 65.47 Foreign body. Axial postcontrast (A) image shows hypopharyngeal foreign body (solid black arrow) in left pyriform fossa.
Take Home Points: Oral Cavity
◾subsites Spaces of oral cavity communicate with each other. Infection and malignancy of different of the oral cavity can spread into adjacent spaces ◾cavity Contrast MDCT and contrast MRI are imaging techniques of choice in evaluation of oral lesions. PET-CT scan is preferred in locoregionally advanced cancers of oral cavity and also helps in response evaluation of oral cancers ◾metabolic PET-MRI is an emerging hybrid imaging technique that combines the advantages of and morphologic information and is therefore useful in recurrent disease
Take Home Points—Pharynx
◾commonest JNA and adenoid hyperplasia are the commonest adolescent lesions while NPC is adult tumor of nasopharynx ◾onJNACTisand/or the commonest benign hypervascular tumor of adolescent male with classic signs MRI. Preoperative angiography for embolization is necessary before surgery of JNA ◾serous In an adult, with cervical metastatic lymph node from unknown origin or with unresolving otitis media, one should consider NPC unless proved otherwise ◾skull NPC has four major spread of pattern, they being parapharyngeal space, masticator space, base invasion, and invasion of neural foramina ◾associated Nodal involvement is very common in NPC, particularly with undifferentiated EBVNPC ◾inMRIequivocal is choice of imaging for evaluation of post-treatment NPC, while PET-CT is valuable cases of recurrent NPC and in evaluation of distant metastasis ◾ Carcinomas are commonest diseases seen in oropharynx and hypopharynx ◾lymphoma Oropharyngeal subsites usually contain lymphoid tissue in variable degree hence is a common diagnostic differential for SCC in these regions ◾canTonsilbe small is again a common site for metastasis of unknown origin in neck, and involved tonsil as compared to opposite tonsil, is dark or very dark on T2W images in case of malignancy
Suggested Readings • M Anthony, B Sharat, T Bruno, VB M, D Reordan, Nasopharynx. In: MC W, editor. Head and Neck Imaging – A Teaching File, 2nd ed., Philadelphia, Lippincott Williams & Wilkins, 2012, 285–296. • AJ MacDonald, HR Harnsberger, RH Wiggins, PA Hudgins, MA Michel, JD Swartz, Diagnostic Imaging: Head and Neck, 3rd ed., Salt Lake City, UT, Amirsys, 2004, 42–45. • PM Som, Head and Neck Imaging, 5th ed., PM Som, editor. St. Louis, Missouri, Elsevier Mosby, 2012, 1617–1642. • VHVS Bhat, Contemporary Oral Oncology, 1st ed., Kuriakose MA, editor, Buffalo, USA, 2017, 23–79.
References [1] HE Stambuk, S Karimi, N Lee, SG Patel, Oral cavity and oropharynx tumors, Radiol Clin North Am 45 (1) (2007) 1–20. [2] R Hermans, M Lenz, Imaging of the oropharynx and oral cavity part I: normal anatomy, Eur Radiol 6 (3) (1996) 362–368. [3] AJ MacDonald, HR Harnsberger, RH Wiggins, PA Hudgins, MA Michel, JD.H Swartz, Diagnostic Imaging: Head and Neck, 3rd ed., Amirsys, Salt Lake City, UT, 2004, 42–45. [4] R O’Rahilly, FCS Muller, Basic Human Anatomy – A Regional Study of Human Structure, Swenson R, editor, WB Saunders; 1983, Elsevier, the USA. [5] WS Fang, RH Wiggins, A Illner, BE Hamilton, GL Hedlund, JP Hunt, et al., Primary lesions of the root of the tongue,
Radiographics 31 (7) (2011) 1907–1922. [6] KK Koeller, L Alamo, CF Adair, JG Smirniotopoulos, From the archives of the AFIP. Congenital cystic masses of the neck: radiologic-pathologic correlation, Radiographics 19 (1) (1999) 121– 146. [7] IR Meesa, A Srinivasan, Imaging of the oral cavity, Radiol Clin North Am [Internet] 53 (1) (2015) 99–114, doi:. 10.1016/j.rcl.2014.09.003. [8] PL Narendra, NS Vishal, B Jenkins, Ludwig’s angina: need for including airways and larynx in ultrasound evaluation, BMJ Case Rep 2014 (2014) 10–13. [9] WJ Gallo, M Moss, DN.G.J.V Shapiro, Neurilemoma: review of the literature and report of Five cases, J Oral Surg (Chic) 35 (3) (1977) 235–236. [10] M Cohen, MB Wang, Schwannoma of the tongue: two case reports and review of the literature, Eur Arch Oto-Rhino-Laryngol 266 (11) (2009) 1823–1829. [11] RK Lingam, AA Daghir, E Nigar, SA.B Abbas, M Kumar, Pleomorphic adenoma (benign mixed tumour) of the salivary glands: its diverse clinical, radiological, and histopathological presentation, Br J Oral Maxillofac Surg [Internet] 49 (1) (2011) 14– 20, doi:. 10.1016/j.bjoms.2009.09.014. [12] J Lechner Goyault, S Riehm, A Neuville, A Gentine, F Veillon, Intérêt des séquences de diffusion et de l’IRM dynamique pour le diagnostic des tumeurs parotidiennes, J Neuroradiol [Internet] 38 (2) (2011) 77–89, doi:. 10.1016/j.neurad.2009.10.005. [13] TJ Ow, JN Myers, Current management of advanced resectable oral cavity squamous cell carcinoma, Clin Exp Otorhinolaryngol 4 (1) (2011) 1–10. [14] BM Trotta, CS Pease, JJ Rasamny, P Raghavan, S Mukherjee, Oral cavity and oropharyngeal squamous cell cancer: key imaging findings for staging and treatment planning, Radiographics 31 (2) (2011) 339–354. [15] LP Kowalski, HF Köhler, Relevant changes in the AJCC 8th edition staging manual for oral cavity cancer and future implications, Chin Clin Oncol 8 (Suppl 1) (2019) 8–11. [16] S Arya, P Rane, A Deshmukh, Oral cavity squamous cell carcinoma: role of pretreatment imaging and its influence on management, Clin Radiol [Internet] 69 (9) (2014) 916–930, doi:. 10.1016/j.crad.2014.04.013. [17] F Dammann, M Horger, M Mueller-Berg, H Schlemmer, C Claussen, J Hoffman, et al., Rational diagnosis of squamous cell carcinoma of the head and neck region: comparative evaluation of
CT, MRI, and 18FDG PET, Am J Roentgenol 184 (4) (2005) 1326– 1331. [18] A Nae, G O’Leary, L Feeley, C Fives, B Fitzgerald, E Chiriac, et al., Utility of CT and MRI in assessment of mandibular involvement in oral cavity cancer, World J Otorhinolaryngol - Head Neck Surg [Internet] 5 (2) (2019) 71–75, doi:. 10.1016/j.wjorl.2019.02.001. [19] SK Mukherji, DL Isaacs, A Creager, W Shockley, M Weissler, D Armao, CT detection of mandibular invasion by squamous cell carcinoma of the oral cavity, Am J Roentgenol 177 (1) (2001) 237– 243. [20] SM.A Mohiyuddin, P Harsha, S Maruvala, KR Sumanth, TN Suresh, GN Manjunath, et al., Outcome of compartment resection of locally advanced oral cancers extending to infratemporal fossa: a tertiary rural hospital experience, Eur Arch Oto-Rhino-Laryngol [Internet] 275 (11) (2018) 2843–2850, doi:. 10.1007/s00405-0185124-z. [21] CT Liao, SH Ng, JT.C Chang, HM Wang, C Hsueh, LY Lee, et al., T4b oral cavity cancer below the mandibular notch is resectable with a favorable outcome, Oral Oncol 43 (6) (2007) 570–579. [22] JL Weissman, RL Carrau, “Puffed-cheek” CT improves evaluation of the oral cavity, Am J Neuroradiol 22 (4) (2001) 741– 744. [23] CS Cox, DG Stallworth, KA Ahmed, J Trad, B Wenig, CH Chung, et al., Perineural tumor spread involving the trigeminal and facial nerves: a review of critical imaging findings, Ann Otolaryngol Rhinol 4 (5) (2017) 1177. [24] JB Epstein, JD Epstein, ND Le, M Gorsky, Characteristics of oral and paraoral malignant lymphoma: a population-based review of 361 cases, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 92 (5) (2001) 519–525. [25] S Kemp, G Gallagher, S Kabani, V Noonan, C O’Hara, Oral nonHodgkin’s lymphoma: review of the literature and World Health Organization classification with reference to 40 cases, Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol 105 (2) (2008) 194– 201. [26] AL Weber, A Rahemtullah, JA Ferry, Hodgkin and non-Hodgkin lymphoma of the head and neck: clinical, pathologic, and imaging evaluation, Neuroimaging Clin N Am 13 (3) (2003) 371–392. [27] K Triantafillidou, J Dimitrakopoulos, F Iordanidis, D Koufogiannis, Mucoepidermoid carcinoma of minor salivary glands: a clinical study of 16 cases and review of the literature, Oral Dis 12 (4) (2006) 364–370.
[28] M Okahara, H Kiyosue, Y Hori, A Matsumoto, H Mori, S Yokoyama, Parotid tumors: MR imaging with pathological correlation, Eur Radiol 13 (Suppl 4) (2003). [29] H Kokemueller, A Eckardt, P Brachvogel, JE Hausamen, Adenoid cystic carcinoma of the head and neck: a 20 years experience, Int J Oral Maxillofac Surg 33 (1) (2004) 25–31. [30] WT Ju, TC Zhao, Y Liu, YR Tan, MJ Dong, Q Sun, et al., Computed tomographic features of adenoid cystic carcinoma in the palate, Cancer Imaging 19 (1) (2019) 1–9. [31] A Vidiri, D Curione, F Piludu, A Guerrisi, B Pichi, G Mercante, et al., Non-squamous tumors of the oropharynx and oral cavity: CT and MR imaging findings with clinical-pathologic correlation, Curr Med Imaging Rev 13 (2) (2017) 166–175. [32] PA Hu, ZR Zhou, Clinical, pathological and unusual MRI features of five synovial sarcomas in head and neck, Br J Radiol 88 (1050) (2015) 1–7. [33] BC Jham, AR Salama, SA McClure, RA Ord, Metastatic tumors to the oral cavity: a clinical study of 18 cases, Head Neck Pathol 5 (4) (2011) 355–358. [34] MR.T Garcia, UL Passos, TA Ezzedine, HB Zuppani, RL.E Gomes, EM.S Gebrim, Postsurgical imaging of the oral cavity and oropharynx: what radiologists need to know, Radiographics 35 (3) (2015) 804–818. [35] TM Blodgett, MB Fukui, CH Snyderman, IV. .B.F Branstetter, BM McCook, DW Townsend, et al., Combined PET-CT in the head and neck: part 1. Physiologic, altered physiologic, and artifactual FDG uptake, Radiographics 25 (4) (2005) 897–912. [36] M Becker, H Zaidi, Imaging in head and neck squamous cell carcinoma: the potential role of PET/MRI, Br J Radiol 87 (1036) (2014). [37] M Becker, K Burkhardt, P Dulguerov, A Allal, Imaging of the larynx and hypopharynx, Eur J Radiol 66 (3) (2008) 460–479. [38] ND Wycliffe, RS Grover, PD Kim, A Simental Jr., Hypopharyngeal cancer, Top Magn Reson Imaging 18 (4) (2007) 243–258. [39] DW Tshering Vogel, HC Thoeny, Cross-sectional imaging in cancers of the head and neck: how we review and report, Cancer Imaging [Internet] 16 (1) (2016) 1–15, doi:. 10.1186/s40644-0160075-3. [40] AL Weber, S Al Arayedh, A Rashid, Nasopharynx: clinical, pathologic, and radiologic assessment, Neuroimaging Clin N Am 13 (3) (2003) 465–483.
[41] M Comoretto, L Balestreri, E Borsatti, M Cimitan, G Franchin, M Lise, Detection and restaging of residual and/or recurrent nasopharyngeal carcinoma after chemotherapy and radiation therapy: comparison of MR imaging and FDG PET/CT1, Radiology 249 (1) (2008) 203–211. [42] A Siddiqui, SE.J Connor, Imaging of the pharynx and larynx, Imaging 19 (1) (2007) 83–103. [43] J Gaurav, M Timonthy, R Prashant, D Gandhi, Imaging evaluation and treatment of vascular lesions at the skull base, Radiol Clin North Am 55 (1) (2017) 151–166. [44] B Schick, G Kahle, Review article radiological findings in angiofibroma, Acta Radiol 41 (2000) 585–593. [45] TN Janakiram, SB Sharma, UC Samavedam, O Deshmukh, B Rajalingam, Imaging in juvenile nasopharyngeal angiofibroma: clinical significance of Ramharan and Chopstick sign, Indian J Otolaryngol Head Neck Surg 69 (1) (2017) 81–87. [46] J Lutz, M Holtmannspötter, W Flatz, A Meier-Bender, A Berghaus, H Brückmann, et al., Preoperative embolization to improve the surgical management and outcome of juvenile nasopharyngeal angiofibroma (JNA) in a single center: 10-year experience, Clin Neuroradiol 26 (4) (2016) 405–413. [47] F Dubrulle, R Souillard, R Hermans, Extension patterns of nasopharyngeal carcinoma, Eur Radiol 17 (10) (2007) 2622–2630. [48] WM Lydiatt, SG Patel, B O’Sullivan, MS Brandwein, JA Ridge, JC Migliacci, et al., Head and neck cancers–major changes in the American Joint Committee on Cancer eighth edition cancer staging manual, CA Cancer J Clin 67 (2) (2017) 122–137. [49] AD King, Magnetic resonance imaging staging of nasopharyngeal carcinoma in the head and neck, World J Radiol 2 (5) (2010) 159. [50] B Tantiwongkosi, Role of 18 F-FDG PET/CT in pre and post treatment evaluation in head and neck carcinoma, World J Radiol 6 (5) (2014) 177. [51] S Ak, C Kiliç, S Özlügedik, Correlation of PET-CT, MRI and histopathology findings in the follow-up of patients with nasopharyngeal cancer, Braz J Otorhinolaryngol (2021), 643–648. [52] XW Liu, CM Xie, YX Mo, R Zhang, H Li, ZL Huang, et al., Magnetic resonance imaging features of nasopharyngeal carcinoma and nasopharyngeal non-Hodgkin’s lymphoma: are there differences?, Eur J Radiol [Internet] 81 (6) (2012) 1146–1154, doi:. 10.1016/j.ejrad.2011.03.066.
[53] K Sekiya, M Watanabe, RN Nadgir, K Buch, EN Flower, T Kaneda, et al., Nasopharyngeal cystic lesions: Tornwaldt and mucous retention cysts of the nasopharynx: findings on MR imaging, J Comput Assist Tomogr 38 (1) (2014) 9–13. [54] ER Friedman, SD John, Imaging of pediatric neck masses, Radiol Clin North Am [Internet] 49 (4) (2011) 617–632, doi:. 10.1016/j.rcl.2011.05.005. [55] MW Chan, et al., Morphologic and topographic radiologic features of human papillomavirus related and unrelated oropharyngeal carcinoma, Head Neck 39 (8) (2017) 1524–1534. [56] AL Weber, L Romo, S Hashmi, Malignant tumors of the oral cavity and oropharynx: clinical, pathologic, and radiologic evaluation, Neuroimaging Clin N Am 13 (3) (2003) 443–464. [57] AC Chi, TA Day, BW Neville, Oral cavity and oropharyngeal squamous cell carcinoma-an update, CA Cancer J Clin 65 (5) (2015) 401–421. [58] A Singh, CL Thukral, K Gupta, AS Sood, H Singla, K Singh, Role of MRI in evaluation of malignant lesions of tongue and oral cavity, Pol J Radiol 82 (2017) 92–99. [59] ME Guay, P Lavertu, Tonsillar carcinoma, Eur Arch Otorhinolaryngol 252 (5) (1995) 259. [60] JR Jumper, NJ Fischbein, MJ Kaplan, HZ Klein, WP Dillon, The “small, dark tonsil” in patients presenting with metastatic cervical lymphadenopathy from an unknown primary, AJNR Am J Neuroradiol 26 (2) (2005) 411–413. [61] SK Mukherji, HR Pillsbury, M Castillo, Imaging squamous cell carcinomas of the upper aerodigestive tract: what clinicians need to know?, Radiology 205 (3) (1997) 629–646. [62] T Fukuhara, E Matsuda, Y Hattori, et al., Usefulness of ultrasound for assessing the primary tumor of hypopharyngeal carcinoma, Laryngoscope Invest Otolaryngol 2 (6) (2017) 390–394. [63] SF Huang, LF Zhang, X He, WR Shen, ZY Gu, Imaging features of Waldeyer’s ring in non-Hodgkin’s lymphoma and its clinical significance, Ai Zheng 23 (11) (2004) 1325–1328. [64] EM Sturgis, BO Potter, Sarcomas of the head and neck region, Curr Opin Oncol 15 (3) (2003) 239–252. [65] M Guzzo, LD Locati, FJ Prott, G Gatta, M McGurk, L Licitra, Major and minor salivary gland tumors, Crit Rev Oncol Hematol 74 (2) (2010) 134–148. [66] DA Zander, WR Smoker, Imaging of ectopic thyroid tissue and thyroglossal duct cysts, Radiographics 34 (1) (2014) 37–50.
[67] RS Rana, G Moonis, Head and neck infection and inflammation, Radiol Clin North Am 49 (1) (2011) 165–182. [68] R Law, DA Katzka, TH Baron, Zenker’s diverticulum, Clin Gastroenterol Hepatol 12 (11) (2014) 1773–1782. [69] D Radkowski, TJ Mcgill, GB Healy, DT Jones, Penetrating trauma of the oropharynx in children, Laryngoscope 103 (9) (1993) 991–994.
Introduction The larynx or the “voice box” is a midline organ in the anterior neck located below the oropharynx and continuous inferiorly with the trachea. It is a key organ in phonation, facilitates respiration, and protects the lower respiratory tract from food and foreign particles. Patients with laryngeal abnormalities present to the otorhinolaryngologist with change in voice, hoarseness, or even neck lumps. An indirect or direct laryngoscopy is generally the first investigation for laryngeal diseases. The entire laryngeal mucosa can be optimally visualized at endoscopy, and imaging is usually done after a diagnosis has already been made at endoscopy or endoscopic biopsy. Cross-sectional imaging plays a very important complementary role in the diagnostic evaluation of laryngeal diseases and significantly impacts the therapeutic options for the patient.
Imaging Anatomy A clear understanding of the laryngeal anatomy is fundamental to the interpretation of imaging studies of patients with laryngeal diseases. The larynx comprises a cartilaginous skeleton that is held together by ligaments, membranes, and muscles. It is lined by a mucous membrane and is suspended from the hyoid bone by a ligamentous framework. Key features of clinicoradiological relevance are discussed in the following paragraphs [1,2] (Figs. 66.1–66.3).
FIGURE 66.1 Larynx anatomy. (A) Frontal view. (B) Lateral view. (C) Lateral view with one thyroid lamina removed.
FIGURE 66.2 Axial CECT images through larynx depict normal laryngeal anatomy. (A) Tip of epiglottis is seen in the midline (thin white arrow) before the hyoid bone appears. Note the median glossoepiglottic fold (block white arrow). (B) Paired valleculae (elbow white arrows) on either side of median glossoepiglottic fold (block white arrow). Note the lateral glossoepiglottic folds on either side (block black arrow). Epiglottis is seen in the midline (thin white arrow). The hyoid bone H is seen anteriorly in the midline. (C) The laminae of the thyroid cartilage are seen (notched white arrows). The pre-epiglottic space (white star) is seen anterior to the epiglottis (thin white arrow) and the paraglottic fat space is seen laterally on either side (white cross). Note the aryepiglottic folds (white arrowhead) and the piriform sinuses (curved white arrows). (D) The stem of the epiglottis is seen attaching to the inner surface of the thyroid cartilage in the midline by the thyroepiglottic ligament (thin white arrow). The aryepiglottic folds (white arrowheads), piriform sinuses (curved white arrows), pre-epiglottic fat (white star), and paraglottic fat spaces (white cross) are seen. The laminae of the thyroid cartilage are seen (notched white arrows). (E) The tip of the arytenoid cartilages (thin black arrows) and the false cords (double headed white arrow) are seen. The paraglottic fat spaces (white cross) are seen deep to the false cords. The laminae of the thyroid cartilage are seen (notched white arrows). Note the piriform sinuses (curved white arrows). This section represents the superior margin of the laryngeal ventricular complex. (F) The cricoid cartilage (black arrowheads) and arytenoid cartilages (thin black arrows) are seen forming the cricoarytenoid joints. The true cords are seen with the soft tissue density of the thyroarytenoid (double headed block white arrow) at this level. Note the anterior commissure (curved black arrow) and the posterior commissure (block white arrow). (G) Axial section through the subglottis shows the cricoid cartilage (black arrowheads) and the outer thyroid cartilage laminae (notched white arrows).
FIGURE 66.3 Larynx anatomy. (A) Sagittal CT image shows the epiglottis (white arrowhead) and the pre-epiglottic fat space (thick white arrow). Note the close relationship of the base of tongue (elbow white arrow) with the epiglottis. (B) Sagittal MR image shows the epiglottis (white arrowhead) and the preepiglottic fat space (thick white arrow). Note the close relationship of the base of tongue (elbow white arrow) with the epiglottis. (C) Coronal CT image through the larynx. Note the epiglottis (curved white arrow), false cord (white arrow head), laryngeal ventricle (white star), true cord (black arrowhead), and paraglottic fat space (small black arrows).
Laryngeal Cartilages The larynx comprises six cartilages—three paired and three unpaired. The paired cartilages are the arytenoid, cuneiform, and corniculate cartilages. Of these, the cuneiform and corniculate cartilages are tiny, inconsistently visualized within the aryepiglottic folds at imaging and do not contribute significantly to the imaging of laryngeal pathology. The unpaired cartilages are the epiglottis, thyroid, and the cricoid cartilages. The larynx extends from the tip of the epiglottis to the inferior margin of the cricoid cartilage.
◾ofThetheepiglottis is the superior-most, midline, leaf-shaped cartilage that forms the anterior boundary laryngeal entrance. It is divided into suprahyoid or free and infrahyoid or fixed portions. The hyoepiglottic ligament attaches the free epiglottic margin to the hyoid bone and the thyroepiglottic ligament attaches the epiglottic stem to the inner surface of the thyroid cartilage. The median glossoepiglottic fold overlies the hyoepiglottic ligament. On either side of the median glossoepiglottic fold are the valleculae that separate the larynx from the tongue base. Aryepiglottic folds arise from the inferolateral edges of epiglottis and sweep caudally to attach to the arytenoid cartilage separating the supraglottis from the piriform sinuses. Note that the superior tip of the epiglottis projects higher than the hyoid bone. Hence, while viewing serial axial computed
tomography (CT) or magnetic resonance imaging (MRI) images of the neck, the free epiglottic margin is always seen before the hyoid is visualized The thyroid cartilage is the largest laryngeal cartilage made of two laminae fused anteriorly in the midline at a prominent angle called the “Adam’s apple” and enlarged posteriorly to form the superior and inferior cornua. The superior cornua provide attachment to the thyrohyoid membrane and the infrahyoid muscles. The inferior cornua articulate medially with the sides of the cricoid cartilage at the cricothyroid joint The cricoid is the caudal ring-shaped laryngeal cartilage located below the thyroid cartilage and articulates with the inferior cornu of the thyroid cartilage. It is the foundation of the larynx with a narrow anterior arch and broad posterior lamina. The lower margin of the cricoid forms the lower margin of the larynx The arytenoid cartilages are located at the upper margin of the cricoid lamina, forming the cricoarytenoid joints, medial to the articulation of the inferior cornua of thyroid with the cricoid. The vertical height of the arytenoid spans the laryngeal ventricle. Each arytenoid has an apex and a base. The apex of the arytenoid attaches the vestibular ligament and corresponds to the level of the false cords. The base of the arytenoid projects the vocal process anteriorly, that attaches the vocal ligament running along the inner margin of true vocal cords
◾ ◾ ◾
The imaging appearance of these cartilages depends on their ossification. The epiglottis and vocal process of arytenoids are fibrocartilages that generally do not ossify. The thyroid, cricoid, and arytenoid are hyaline cartilages that ossify with advancing age. Ossification is first observed in the thyroid cartilage after 20 years of age, followed by the cricoid and arytenoid in the third decade [3,4]. Nonossified cartilages have soft tissue attenuation on CT and intermediate signal intensity on T1-weighted (T1W) and T2-weighted (T2W) MRI images. The ossified cartilages have hyperdense inner and outer margins with hypodense central medullary cavity on CT scans. At MRI, the ossified cortical margins are of low signal and the fat-filled medullary cavity is of high signal on T1W and T2W images.
Laryngeal Ventricular Complex (LVC) The laryngeal ventricular complex is the key component in organizing the larynx into the supraglottis, glottis, and subglottis. It comprises the false and true vocal cords and the intervening laryngeal ventricle. 1. False vocal cords are fixed and comprise the vestibular ligament with a fold of mucous membrane over it and the paraglottic space (PGS) deep to it. These are seen at the level of the apex of the arytenoid cartilage on axial images. 2. True cords are mobile and comprise the vocal ligament, the vocalis, and thyroarytenoid muscles deep to the ligament with the fold of mucous membrane over them. The thyroarytenoid muscle is the deepest portion of the true cord. The true cords are seen at the level of the base of the arytenoids and the cricoarytenoid joint on axial images parallel to the plane of hyoid bone. At histology, a superficial gel like layer of lamina propria is seen just below the epithelium. This is called the Reinke’s space. 3. The ventricle is a small air-filled outpouching between the false and true vocal cords. A small recess of the ventricle extends upward into the PGS of the supraglottic larynx and is called the saccule. The laryngeal ventricle is best seen on coronal plane.
Above the false cords, the mucosa is continuous with the aryepiglottic folds. Below the true cords, the mucosa continues downward to the subglottic area and the trachea. The laryngeal compartments and their contents are enlisted in Table 66.1. Table 66.1 Laryngeal Subdivisions Subdi vision
Extent
Conten ts
Supra glottis
Tip of epiglottis to laryngeal ventricle
Epiglot tis Aryten oid cartila ge Aryepi glottic folds Preepiglot tic fat space Paragl ottic fat space False vocal cords Laryng eal ventric le Vestib ule
Subdi vision
Extent
Conten ts
Glottis
Inferior margin of laryngeal ventricle to an imaginary plane approximately 1 cm below it
True vocal cord Anteri or commi ssure Posteri or commi ssure
Subgl ottis
From imaginary plane approximately 1 cm below the laryngeal ventricle to inferior surface of cricoid cartilage
Conus elasticu s
Anterior and Posterior Commissures The two vocal cords meet in midline anteriorly at the anterior commissure. It comprises the anterior ends of vocal cords and their junction, the thyroid cartilage and Broyle’s ligament that connects the vocal ligaments to the thyroid cartilage. The inner perichondrium is absent at the site where Broyle’s ligament inserts into the thyroid cartilage making the cartilage in this region vulnerable to tumor invasion. Posteriorly the mucosal surface along the cricoid cartilage between the arytenoid cartilage and true vocal cords is called as posterior commissure. Both the commissures are best seen on axial images.
The Paraglottic Space (PGS) and the Preepiglottic Space (PES) The PGS are paired, symmetric fat-filled spaces deep to the mucosal surface of the false cords and the thyroarytenoid muscle of the true cords, bound laterally by thyroid and cricoid cartilages. They extend down to the under surface of the true cords and their entire extent is seen best on coronal images. They are also seen well on axial CT and MR sections through the supraglottis, where they are entirely composed of fat. At the level of the false cords thin strands of muscle are seen in the paraglottic fat. At the glottic level, they are not distinctly visualized as
the fat is compressed between thyroarytenoid muscle and the thyroid cartilage. PGS is very well seen on axial and coronal images. The PES is a fat-filled space, rich in lymphatics, bound superiorly by the hyoepiglottic ligament, anteriorly by the thyrohyoid membrane, inferiorly by the thyroepiglottic ligament and posteriorly by the epiglottis. The PES and PGS communicate with each other superiorly. Sagittal images are best suited to delineate the entire extent of the PES. It is seen well on axial images also.
Ligaments and Muscles Of the many intrinsic and extrinsic laryngeal muscles, the muscle that is of relevance to the radiologist is the thyroarytenoid muscle. It stretches from the arytenoid cartilage to the anterior aspect of the thyroid cartilage and makes the bulk of the true cord allowing its identification at axial imaging. The hyoepiglottic and the thyroepiglottic ligaments have been discussed in the earlier paragraphs. The cricothyroid ligament courses between the cricoid and thyroid cartilages. Its thickened midline component is called the median cricothyroid ligament. Its lateral component is called the conus elasticus and extends from the superior border of cricoid to the inferior margin of the vocal ligament. These key radiologically relevant anatomical features are summarized in Box 66.1. Box 66.1
Salient Anatomical Features i. Four important cartilages of the larynx are the epiglottis, thyroid, cricoid and the arytenoid cartilages ii. The paraglottic space (PGS) and pre-epiglottic space (PES) are clinical blind spots but depicted exquisitely at imaging iii. The laryngeal ventricular complex (LVC) comprises the false cords, laryngeal ventricle and the true cords. It is identified best in coronal and axial
images and organizes the larynx into its three subdivisions iv. On axial images the tip of the epiglottis is always visualized above the level of the hyoid bone v. In an axial plane parallel to the hyoid bone, the LVC is seen as below Superior margin of the LVC is identified at the level of arytenoid apex, the false cords and the PGS The inferior margin of LVC is identified at the level of the cricoarytenoid joints, the true cords and the thyroarytenoid muscles There is a clear transition of the paraglottic fat to soft tissue density of the thyroarytenoid muscle from the superior to the inferior margins of the LVC
◾ ◾ ◾
Imaging Techniques and Protocols Plain Radiography Low kV and low mAs radiographs are preferred to enhance the contrast of the soft tissues of the neck. High kV end-inspiratory radiographs are used to delineate the air-filled cavities. In the current times, plain radiography has a limited role in laryngeal evaluation.
Ultrasonography Ultrasonography (USG) of the larynx is performed using high-frequency linear and sector transducers in the midline transverse, paramedian transverse, and longitudinal views with the patient preferably in supine or seated position. It is widely available, relatively inexpensive, noninvasive, radiation free imaging
technique that provides real-time imaging and high-resolution images of the larynx coupled with the advantage of a guided biopsy as and when required [5]. It is however highly user dependent and if not performed properly, may lead to interpretation errors.
CT Contrast-enhanced multidetector CT scan of the neck is performed from the skull base down to the aortic arch, in quiet breathing with the patient in supine position, neck slightly hyperextended, shoulders lowered as much as possible and refraining from coughing or swallowing. Quiet breathing is preferred to keep the vocal cords in open position. The recommended dose of contrast is about 0.4 g/kg body weight of iodine, and about 75–100 mL of iodinated CT contrast is used in adult population. Following the injection of contrast, vascular and nodal enhancement occurs during the “early” interstitial phase, but tumoral enhancement requires more time and occurs in the “late” interstitial phase. To enable optimum visualization of all of these structures, different imaging protocols have been described [6–8]. In the monophasic contrast protocol, a single contrast injection of 75–100 mL is followed by scanning at 90 seconds allowing a neck CT with only a single phase contrast enhancement, or dual scanning at 60 and 120 seconds that allows acquisition in both the phases, but at the risk of increased radiation to the patient. In the biphasic contrast protocol, about 50 mL of contrast is injected in the first phase followed by the remaining 30–50 mL after an interval of about 30 seconds. The patient is scanned at 90–120 seconds after the start of the first injection, allowing image acquisition in both the early and late interstitial phases simultaneously at a reduced radiation dose. The biphasic protocol has been found to more useful and is recommended over the monophasic contrast protocol [8]. After scanning, the images are reconstructed with a slice thickness that ranges from 0.75 mm to 3 mm to ensure high quality multiplanar reformations [9]. Axial reformations are obtained along the plane of the hyoid bone since the true cords run parallel to this plane. All images are reviewed with soft tissue and bone algorithms. Additionally, CT scan may be performed with the patient producing a high pitched “e” sound causing the vocal cords to adduct and distend the laryngeal ventricle and piriform sinuses. This e-phonation maneuver is used to assess vocal cord mobility and better evaluate the laryngeal ventricle, piriform sinuses, and the aryepiglottic folds [10].
MRI
A high field MRI scanner using a dedicated neck coil is preferred. Patient positioning and instructions are similar to that of CT scan. A combination of multiplanar, noncontrast diffusion-weighted imaging, T1W, T2W, and T2W fat saturation images with postcontrast T1W fat-suppressed images are used. It is important to take the T1 and T2 sections at the same levels. A section thickness of 4 mm is preferred with an interslice gap of 0–1 mm. The entire examination takes about 30–40 minutes. T1W images offer a high anatomical detail and T2W images better identify pathologic tissue and their interface with normal tissues.
FDG PET-CT The techniques and protocols of this technique are discussed in detail elsewhere in this textbook. A summary on the use of the various imaging techniques in laryngeal imaging is provided in Box 66.2. Box 66.2
Imaging Techniques for Larynx i. Multidetector CT allows excellent depiction of the laryngeal anatomy, mapping of the disease extent, and addresses all the relevant imaging issues that impact the therapeutic management of patients with laryngeal diseases. It offers the distinct advantages of speed coupled with high quality images that allow exquisite multiplanar reformations. CT is the preferred technique for laryngeal imaging ii. MRI has a similar ability to CT for laryngeal evaluation but takes a longer time to perform and can be difficult in restless patients with laryngeal tumors. It plays a complementary role and is often used as a problem solving tool when CT does not provide all
the information before therapy. It is mostly used if there is questionable cartilage involvement that is critical to therapeutic decisions or if there are contraindications to use of iodinated contrast media iii. The choice between CT and MRI in routine clinical practice is often subject to the availability of the technique, the expertise in interpretation and the choice of the treating surgeon. High-resolution USG for evaluating laryngeal abnormalities has been reported to provide information near comparable to CT and MRI in the assessment of laryngeal abnormalities and may be used when performing a CT or MRI scan is a challenge for some reason iv. The use of FDG PET CT for pretherapeutic evaluation of patients with advanced laryngeal cancer remains largely institution dependent. It however plays an important role in post-treatment evaluation of the larynx [11–13]
Tumors of the Larynx A variety of tumors affecting the larynx have been described and are enlisted in Table 66.2 [14]. They can be mucosal or submucosal. More than 95% are malignant and true benign tumors comprise less than 5% of laryngeal tumors [15]. Table 66.2 Laryngeal Tumors [14]
Histological Type
Benign
Malignant
Squamous cell tumor
Papilloma
Conventional squamous cell cancer (SCC) Verrucous SCC Spindle cell SCC
Mucosal Tumors Laryngeal Papilloma Papilloma is the commonest benign squamous cell neoplasm of the larynx seen as a smooth polypoid lesion at CT and MRI. It is commonly seen in the true vocal cord followed by subglottis and inferior aspect of epiglottis. The juvenile form, also called as laryngotracheobronchial papillomatosis, occurs in children, is not premalignant, occasionally recurrent and is associated with HPV infection. Adult papilloma is solitary, commoner in men and smokers and may be a premalignant condition [16]. Laryngeal Squamous Cell Cancer Laryngeal cancers constitute about 25–30% of all malignant head and neck tumors [17]. They commonly present in adults between 50 and 70 years and show a
strong male predominance [17,18]. The incidence and mortality rates due to laryngeal cancer are higher in Europe. It constitutes about 3–6% of all cancers in Indian men and is the seventh commonest cause of cancer in them [18,19]. Cigarette smoking and alcohol consumption are associated with higher risks for laryngeal cancers [20]. Patients with laryngeal squamous cell cancer (SCC) have a higher risk for synchronous or metachronous malignancies arising from the lung and upper aerodigestive tract [21]. Clinical examination followed by endoscopy is always the first step in patient evaluation and T-staging of laryngeal SCC. Small superficial mucosal tumors visualized at endoscopy may not be appreciated at CT or MRI, and hence it is always advisable to perform endoscopy before any imaging study. Except for some very rare small tumors arising deep within the laryngeal ventricle, these cancers are almost always detected at endoscopy. Cross-sectional imaging with CT or MRI is performed to define the submucosal extent and deeper margins of the tumor. Integration of cross-sectional imaging with endoscopy findings significantly improves the accuracy of T staging and impacts the therapeutic management of the patient [22]. Additionally, imaging provides information about the nodal disease, systemic metastases, any synchronous tumors and recurrent disease. Tables 66.3, 66.4, 66.5 provide the eighth edition of TNM classification laid down by the American Joint Commission on Cancer that is universally accepted for staging laryngeal cancer [23]. It incorporates all information available before treatment, including the clinical examination, endoscopy, endoscopic biopsy, and cross-sectional imaging. No recommendation is made regarding the preference of one imaging technique over the other. Table 66.3 T-Staging of Supraglottic Cancers T x
Primary tumor cannot be assessed
T i s
Carcinoma in situ
T 1
Tumor limited to one subsite of supraglottis with normal cord mobility (suprahyoid epiglottis, laryngeal aspect of aryepiglottic folds, infrahyoid epiglottis, false vocal cords, arytenoids)
T
Tumor invades mucosa of more than one adjacent subsite of supraglottis
2
or glottis or region outside the supraglottis (e.g., mucosa of base of tongue, vallecula, medial wall of piriform sinus) without fixation of the larynx
T 3
Tumor limited to larynx with vocal cord fixation or invades any of the following: pre-epiglottic space, paraglottic space, postcricoid area, or inner cortex of thyroid cartilage
T 4 a
Moderately advanced local disease: invades through the outer cortex thyroid cartilage, invades cricoid cartilage, or invades tissues beyond the larynx (e.g., trachea, soft tissues of neck including deep extrinsic muscle of tongue, strap muscles, thyroid, or esophagus)
T 4 b
Very advanced local disease: invades prevertebral space, encases carotid artery, or invades mediastinal structure
Table 66.4 T-Staging of Glottic Cancers T i s
Carcinoma in situ
T 1
Tumor limited to the vocal cord(s) (may involve anterior or posterior commissure) with normal mobility T1a: Limited to one vocal cord T1b: Involves both vocal cords
T 2
Tumor extends to supraglottis or subglottis or with impaired vocal cord mobility
T 3
Tumor limited to the larynx with vocal cord fixation or invasion of paraglottic space or inner cortex of the thyroid cartilage
T 4 a
Moderately advanced local disease: invades through the outer cortex thyroid cartilage, invades cricoid cartilage, or invades tissues beyond the larynx (e.g., trachea, soft tissues of neck including deep extrinsic muscle of tongue, strap muscles, thyroid, or esophagus)
T 4
Very advanced local disease: invades prevertebral space, encases carotid artery, or invades mediastinal structure
b
Table 66.5 T-Staging of Subglottic Cancers T x
Primary tumor cannot be assessed
T i s
Carcinoma in situ
T 1
Tumor limited to subglottis
T 2
Tumor extends to vocal cord(s) with normal or impaired mobility
T 3
Tumor limited to larynx with vocal cord fixation or invasion of paraglottic space or inner cortex of the thyroid cartilage
T 4 a
Moderately advanced local disease: invades through the outer cortex thyroid cartilage, invades cricoid cartilage or invades tissues beyond the larynx (e.g., trachea, soft tissues of neck including deep extrinsic muscle of tongue, strap muscles, thyroid, or esophagus)
T 4 b
Very advanced local disease: invades prevertebral space, encases carotid artery or invades mediastinal structure
Laryngeal SCC in each laryngeal compartment exhibits some characteristic spread patterns that have been detailed in the following paragraphs [24–27]. Supraglottic SCC: Supraglottic cancers constitute about 30% of all laryngeal cancers. These patients often present in advanced stage because hoarseness due to vocal cord involvement occurs late. Neck lumps due to nodal metastases (level II and III nodes) are frequent as the supraglottis enjoys a rich lymphatic network. Supraglottic SCC have three main subsites and are categorized as anterior compartment (epiglottis) or the posterolateral compartment (aryepiglottic fold and false cords) cancers.
Epiglottic cancers are anterior midline cancers that are likely to invade into the PES through the tiny perforations in the epiglottis. While the SCCs arising from the mobile portion of the epiglottis may spread from the PES further into the base of tongue and laterally into the aryepiglottic fold and PGS, those arising from the caudal portion often invade the low PES and via the anterior commissure, reach the glottis or subglottis (Figs. 66.4 and 66.5). The primary sign of PES invasion at imaging is replacement of the normal fat by abnormal enhancing soft tissue and is very well delineated at CT and MR imaging (Figs. 66.5B, G, 66.7A, C). Aryepiglottic fold (AE fold) cancers present as exophytic or infiltrative posterolateral masses. They expand the AE fold and spread into the PGS (Figs. 66.4C, 66.5C, 66.6, 66.7A, 66.8A). They may spread further anteriorly into the PES or posteriorly to invade the piriform sinus (Fig. 66.7A). False cord cancers are lateral masses with a strong predilection for submucosal spread into the PGS (Fig. 66.5D, 66.7B, 66.8B, 66.9). More extensive tumor may destroy the thyroid cartilage and spread into the extralaryngeal soft tissues or transglottically into the glottis and subglottis (Fig. 66.5, 66.8, 66.9). Tumor spread to the PGS on CT or MRI is seen as replacement of the normal paraglottic fat by the enhancing tumor (Figs. 66.5C, D, H, 66.6, 66.7A, B, 66.8A, B, C, 66.9).
FIGURE 66.4 Supraglottic cancer—epiglottis and aryepiglottic fold. (A) Axial CECT image shows the abnormal thickened enhancing free edge of the epiglottis (straight white arrow) and the thickened median glossoepiglottic fold (white arrowhead). (B) The thickened enhancing free edge of epiglottis (straight white arrow) is seen with enhancing mass invading the right vallecula (black arrowhead), the median glossoepiglottic fold (white arrowhead) and the base of tongue (straight black arrow). (C) The tumor extends into the right aryepiglottic fold that is thickened and enhancing (curved white arrow). (D) Midline sagittal section shows the epiglottic tumor (straight white arrow) with enhancement along the glossoepiglottic fold (white arrowhead) extending into the base of tongue (straight black arrows).
FIGURE 66.5 Transglottic cancer. (A) Axial CECT image shows abnormal thickening of the epiglottis (white arrowhead) with the soft tissue mass filling the right vallecula (straight white arrow). (B) The soft tissue mass is seen in fairly central location within the pre-epiglottic fat (white star). (C) Caudal image shows the soft tissue extending into the pre-epiglottic fat (white star), the right paralaryngeal fat (white cross) and the right aryepiglottic fold (block white arrow). Note the normal left paralaryngeal fat (straight black arrow). (D) Extension of the mass into the paraglottic fat deep to the right false cord is seen (white cross). The right piriform sinus is narrowed (curved white arrow). The tip of right arytenoid cartilage shows mild sclerosis (black arrowhead). (E) Mass extends into the right true cord (white cross). Note the sclerosis of right arytenoid cartilage (black arrowhead) and widened right thyroarytenoid space (curved black arrow). (F) There is subglottic spread of the mass to the right lateral wall of subglottis (white arrowhead). (G) Sagittal image very nicely shows the mass in the pre-epiglottic fat (white star) with thickened free edge of the epiglottis (white arrowhead). (H) Coronal image depicts the transglottic tumor with mass in the right paraglottic space (white cross).
FIGURE 66.6 Supraglottic cancer—aryepiglottic fold. Tumor is seen in the right aryepiglottic fold (white star) extending into the right paralaryngeal fat (white arrowhead).
FIGURE 66.7 Supraglottic cancer—aryepiglottic fold and false cord. (A) Large lobulated enhancing mass is seen in the left aryepiglottic fold (white arrowhead) extending into the epiglottis and filling the pre-epiglottic fat (white star). Tumor is also seen in the left paraglottic space (white arrowhead). Note the enlarged level II nodes (white arrow). (B) Tumor extends into the false cord and is seen in the paraglottic fat and the laryngeal ventricle (white cross). Note the enlarged level II nodes (white arrow). (C) Sagittal CT section shows a large tumor in the pre-epiglottic fat (white star).
FIGURE 66.8 Transglottic cancer with extralaryngeal spread. (A) Heterogeneously enhancing tumor in right aryepiglottic fold (black cross) extending into the right paralaryngeal fat (black star) and further posterolaterally to encase the walls of the right piriform sinus (curved black arrow). Note the erosion of the right thyroid lamina and extralaryngeal tumor spread into the overlying strap muscles (black arrowheads). (B) Large heterogenously enhancing tumor is seen in the right paralaryngeal fat (black star) with erosion of the right lamina of thyroid cartilage (black elbow arrow) and extralaryngeal extension of the mass into the strap muscles of the neck (black arrowheads). (C) The tumor involves the right true cord (black star) with erosion of the right lamina of thyroid cartilage (black elbow arrow) and extralaryngeal extension of the mass into the strap muscles of the neck (black arrowheads) across the cartilage and the widened thyroarytenoid gap (curved black arrow). (D) White arrowhead shows subglottic tumor in right lateral wall of subglottis. Complete erosion of the right lamina of thyroid cartilage is seen with deep subglottic extension into the soft tissues of the neck (black arrowheads).
FIGURE 66.9 Supraglottic cancer—false cord. Bulky tumor is seen in the right false cord and the paraglottic fat (white cross) with erosion of the right lamina of the thyroid cartilage and extralaryngeal extension into the overlying strap muscles (straight black arrow). Enhancing soft tissue extends into the preepiglottic fat (white asterisk). Sclerosis of the right arytenoid is seen (small white arrow). The right thyroarytenoid gap is widened (curved black arrow). Note level II adenopathy with extranodal disease spreading into right sternocleidomastoid muscle (black arrowhead).
Glottic SCC: About 65% of laryngeal cancers arise in the glottis and patients present early with hoarseness due to early involvement of true cords. Metastatic nodal disease is rare due to sparse lymphatic drainage. The anterior third of the cords is more commonly involved with spread of disease to anterior commissure identified on cross-sectional imaging as soft tissue thickening of more than 1 mm. From the anterior commissure, the tumor may spread further into the contralateral cord and the thyroid cartilage or posteriorly into the posterior commissure, the arytenoids, cricoarytenoid joint, and the cricoid. Involvement of cricoarytenoid joint or interarytenoid space suggests vocal cord fixation. The tumor may spread superiorly to access the PES and the PGS, or inferiorly reach the subglottis along the cricothyroid membrane. Extralaryngeal spread may occur through the cricothyroid membrane (Figs. 66.8C, 66.10, 66.11).
FIGURE 66.10 Glottic cancer with subglottic extension. (A) Axial CECT image shows a large enhancing tumor in the right true cord (white star) with widening of the thyroarytenoid gap (curved black arrow) and extralaryngeal spread of tumor abutting the right carotid artery (black arrow heads). Mild sclerosis of the right lamina of thyroid cartilage is seen (white arrow). (B) Caudal extension of the mass is seen in the right lateral wall of the subglottis (white arrowhead).
FIGURE 66.11 Glottic cancer. CECT scan of the larynx in a patient with clinically staged T1 glottis cancer. (A) Axial CECT image shows an enhancing mass in the anterior third of left true cord (white arrowhead) reaching the anterior commissure (black arrowhead). Note the cartilage erosion (black arrow). (B) CT image in bone algorithm confirms erosion of the inner cortex of the thyroid cartilage (black arrow) upstaging the tumor to T3.
FIGURE 66.12 Cartilage invasion and extralaryngeal spread—MRI. (A) Axial T1W image shows a large right false cord tumor with extralaryngeal spread (white star). The right lamina of cartilage is not seen separate from the soft tissue. Note the appearance of normal ossified left lamina of thyroid cartilage (straight white arrow). (B) Axial T2W image shows the hyperintense signal of the mass. Note the erosion of the right lamina of thyroid cartilage with irregular cortical margins and near similar intramedullary signal as the soft tissue mass (white arrowhead). (C) Contrast T1 axial image with fat suppression in another patient shows enhancing tumor in the subglottis (black stars). Note the enhancement in the cartilage (white arrows) along with the extralaryngeal soft tissue enhancement (white arrowheads), the intensity being similar to the tumoral enhancement.
Subglottic SCC: Primary subglottic cancers are rare, accounting for only 5% of all laryngeal cancers, clinically silent, present late in the course of the disease and have a poor prognosis. Nodal metastases are common and affect the pre and paratracheal nodes. Subglottic cancer is usually a caudal spread of the glottis cancer. Subglottic cancer is diagnosed if any tissue thickening more than 1 mm is noted between the airway and the cricoid ring (Figs. 66.5F, 66.8D, 66.10B). Due to their late presentation, invasion of the thyroid cartilage, cricoid cartilage, trachea, the cervical esophagus with extralaryngeal spread are common findings at imaging. Spread may occur through the cricothyroid membrane.
Laryngeal Cancer—Structuring a Clinically Relevant Report The treatment options for patients with laryngeal cancers include primary radiation, surgery, chemotherapy, and combinations of these depending on the cancer staging. While mapping the deep extent of the tumor on the neck scans, accurate assessment of a few key areas and patterns of disease spread is fundamental to generate a report that impacts the staging and hence the prognosis and management options of a patient with laryngeal cancer [24–27].
Submucosal Spread of Tumor Into PES and PGS While disease spread into the PGS is fairly common in supraglottic and glottic cancers, involvement of the PES is commoner in supraglottic cancers. Tumor in these spaces upstages the disease to T3 has increased incidence of nodal metastases and high risk of recurrence following radiation. Bulky tumor in these spaces precludes radiotherapy, local laser resections, and partial laryngectomy procedures. This form of disease spread cannot be assessed clinically or at endoscopy, but is very well seen at imaging. Hence, it is imperative to assess this tumor spread accurately on the scan. Cartilage Invasion Cartilage disease in laryngeal cancer cannot be assessed at endoscopy and is associated with a higher risk of tumor recurrence, poor response to radiation, and increased risk of later complications. Depending on the extent of the erosion, the tumor is upstaged to T3 or T4 disease and thus impacts the therapeutic options. Cricoid cartilage invasion always requires a total laryngectomy. Both CT and MRI can depict cartilage disease very well. MRI has a high sensitivity, lower specificity, and a very high negative predictive value for detection of cartilage disease as compared to CT, the overall accuracy of CT and MRI is nearly the same for cartilage invasion [22]. Box 66.3 summarizes the CT and MRI features of cartilage invasion in laryngeal cancer [28]. Box 66.3
Cartilage Disease in Laryngeal Cancer [28] CT
◾ Cartilage sclerosis Highly sensitive but lacks specificity as it may be due to reactive bone formation adjacent to tumorSpecificity is highest for thyroid cartilage (Figs. 66.5D, E, 66.10)
MRI Unenhanced and enhanced T1W images Tumor invasion is seen as abnormal soft tissue intensity within the bright signal of medullary fat of ossified cartilages, that enhances on the contrast study similar to the adjacent tumor (Fig. 66.12)
CT
MRI
High specificity but lower sensitivity as they are seen later in the course of the disease (Figs. 66.8, 66.9, 66.11)
T2W images Tumor invasion is seen as hyperintense signal within the cartilage, paralleling the signal of the tumor. If the hyperintensity is more than the tumor, it is likely to suggest peritumoral edema
◾ Cartilage erosion, lysis and extralaryngeal spread
Very recently, the use of dual energy CT using iodine overlay images has been found to have higher specificity and acceptable sensitivity when compared with MRI for assessment of neoplastic cartilage invasion [29]. USG is also reported to be comparable in sensitivity and specificity to CT or MRI in the detection of cartilage invasion [5]. Transglottic Spread of Cancer Laryngeal SCC encroaching on both, the glottis and supraglottis, with or without subglottic component and when the site of origin is unclear, is termed as transglottic tumor. This tumor spread is frequently submucosal through the PGS and hence may be missed at endoscopy. It is readily identified on coronal and axial images (Figs. 66.5, 66.8). This type of disease spread is again, a negative indicator for primary radiotherapy, contraindicates partial laryngectomy procedures and is frequently accompanied by nodal disease. Spread Across the Commissure This disease is best assessed at axial images obtained during quiet breathing. Thickening of more than 1 mm is suggestive of disease (Fig. 66.11). Diagnosis of this spread impacts the options of voice conserving surgeries available for the patient. Spread of a glottis cancer across the anterior commissure to involve more than a third of the contralateral cord precludes a vertical hemilaryngectomy and disease in the posterior commissure may obviate a supracricoid laryngectomy. Extralaryngeal Spread Extralaryngeal spread implies deep spread beyond the laryngeal boundaries into the soft tissues of the neck and represents T4 disease that contraindicates primary radiation or partial laryngectomy and requires extensive surgery. This form of spread can occur through the thyroarytenoid gap posteriorly, the cricothyroid and thyrohyoid membranes anterolaterally and across the thyroid and
cricoid cartilages and hence it is important to do a careful assessment of all these regions while interpreting the neck scans [30] (Figs. 66.8, 66.9, 66.10). Furthermore, if the extralaryngeal disease surrounds the carotid artery subtending an angle greater than 270°, it must be conveyed to the operating surgeon, since the artery may not be salvaged at surgery [31]. Nodal Metastases While assessing the T-stage of the disease in the neck scans, it is very important to look for cervical nodal metastases since it is an important indicator of prognosis and has implications on long term survival of these patients. This topic is discussed in further detail in another chapter in this section. Lungs followed by liver are the common metastatic sites for laryngeal cancer and these are usually seen in advanced cases. Box 66.4 summarizes the key assessment areas while interpreting neck scans in patients with laryngeal cancer. Box 66.4
Imaging Checklist While Reporting Scans for Laryngeal Cancers
◾ Submucosal disease in PES and PGS ◾ Cartilage invasion ◾ Transglottic spread ◾ Commissure spread ◾ Extralaryngeal spread ◾ Nodal metastases ◾ Submucosal tumors
Submucosal Tumors Although the vast majority of laryngeal tumors are mucosal, a bunch of nonsquamous cell tumors arising from the nonepithelial elements of the larynx may present as submucosal laryngeal masses—Table 66.2. These do not present with obvious mucosal abnormalities at endoscopy and are seen as a submucosal
bulge under an intact mucosa necessitating cross-sectional imaging to characterize them and guide an appropriate site for biopsy. When such a mass is referred for imaging, a good approach is to begin by first assessing the possibility of a cartilaginous or a vasculogenic neoplasm because these tumors have fairly characteristic imaging features that allow a precise diagnosis to be made [31,32]. The other soft tissue submucosal tumors do not display any specific imaging characteristics. Chondroid tumors of the larynx show a striking male predilection and are commonly seen in older men between 50 and 70 years of age. About 70% arise in the cricoid cartilage, the next common site being the thyroid cartilage. They are seen as hypodense masses at CT, with stippled or coarse calcifications which are the diagnostic feature of these tumors. The cartilage may be expanded suggesting that the lesion is arising from within the cartilage rather than eroding the cartilage from outside (Fig. 66.13). CT scores over plain radiography and MRI in detection of even very subtle intratumoral calcifications and is easily the preferred investigation [33,34].
FIGURE 66.13 Chondroid tumor. Axial CECT image shows a calcified expansile tumor arising from the right lateral wall of the cricoid ring. (Courtesy: Suresh Mukherji.)
On MRI, the tumor is intensely hyperintense on T2W images due to high water content and low cellularity of hyaline cartilage. Small foci of T1 and T2 hypointensity may be seen that represent stippled calcifications. While chondrosarcomas are commoner than chondromas, it may be difficult to differentiate between them at imaging. Laryngeal chondrosarcomas are low grade tumors and rarely metastasize. Laryngeal hemangiomas are seen as characteristic intensely enhancing submucosal masses due to the rapid filling of vessels within [35] (Fig. 66.14). Any narrowing of the airway is clearly depicted at imaging. Infantile and adult types are described. Infantile hemangioma is commoner in girls and generally presents before 6 months of age with some form of respiratory distress. It is commonly located in the subglottic region. Adult hemangiomas are commoner in males. An association between the subglottic hemangioma and a cutaneous hemangioma elsewhere in the body particularly in the head and neck in the
“beard” distribution and cardiovascular anomalies like coarctation and right-sided aortic arch has been described [36].
FIGURE 66.14 Subglottic hemangioma. Axial CECT image in a neonate who presented with stridor shows an intensely enhancing lesion in the subglottis on the left side, bulging slightly into the lumen (white arrowhead).
Non-Tumorous Lesions A few important nontumorous diseases where imaging plays an important role will be discussed here. Laryngeal trauma has been discussed under the section of “Trauma and emergency radiology.”
Laryngocele
Laryngocele is an abnormal dilatation of the saccule of the laryngeal ventricle that extends upward within the false vocal cord and is in communication with the laryngeal lumen. Laryngoceles are commonly unilateral and seen in adults. They may be spontaneous or a sequelae to increased intralaryngeal pressures as in glass blowers and wind instrument players. Another important cause is a mechanical obstruction at the outlet of the saccule due to a tumor or chronic inflammation [37,38]. CT shows the laryngocele as an air or fluid density blind-ending tubular lesion extending cranially into the paraglottic fat. When this is confined to the PGS medial to the thyrohyoid membrane, it is called as internal laryngocele. When the laryngocele herniates upward across the thyrohyoid membrane above the superior border of the thyroid cartilage into the soft tissues of the neck, it is called as a combined laryngocele (Fig. 66.15). Hence, combined laryngocele has an internal component medial to the thyrohyoid membrane and an external component that is lateral to the thyrohyoid membrane. Fluid-filled laryngocele is also called a laryngomucocele and when it gets infected a pyolaryngocele forms. CT is useful not only for the diagnosis but to map the entire extent, differentiate the internal and mixed varieties and delineate any enhancing tumor or obstruction at the saccular outlet. Pyolaryngoceles additionally show mucosal thickening, rim enhancement, and inflammatory changes in paralaryngeal soft tissues. Air-filled laryngoceles show a signal void on T1W and T2W images with blooming on susceptibility imaging. Fluid-filled laryngoceles are hypointense on T1W and hyperintense on T2W images. Chronic proteinaceous fluid contents are iso to mildly hyperintense on T1W images.
FIGURE 66.15 Laryngocele. (A) Axial CECT image through supraglottis shows the internal component of the laryngocele (small white arrowhead). Another air-filled component is seen in the paralaryngeal soft tissues of the neck on the left side (large white arrowhead). (B) Coronal image shows the combined laryngocele with the internal and external components. (C) Axial CECT image in another patient at the level of the supraglottis shows a fluidfilled combined laryngocele with mildly hypodense contents and thin enhancing walls.
The closest diagnostic differential is that of a saccular cyst when the laryngocele is fluid filled. The latter is mucous filled and commoner in children and very importantly shows no endolaryngeal communication.
Vocal Cord Paralysis Vocal cord paralysis (VCP) occurs due to disruption of nerve impulses to the larynx from the recurrent laryngeal nerve (RLN), a branch of the vagus nerve. Knowledge of certain key issues about the anatomy of the vagus nerve is crucial to understand VCP. The vagus nerves arise from the medulla and exit the skull base at the jugular foramen, descending in the neck in the carotid space to finally reach the superior mediastinum where they lie ventral to the subclavian arteries. The right RLN branches from the vagus nerve just caudal to right subclavian artery and left RLN arises under the aortic arch in the aortopulmonary window. The RLNs then course cranially in the tracheoesophageal groove to enter larynx at the level of cricothyroid joint.
Hence, VCP may occur secondary to lesions affecting the brainstem, the skull base, the neck, and additionally the mediastinum in cases of left-sided VCP. Unilateral paralysis is commoner with the left side being commoner due to the longer course of the left RLN [39,40]. While majority of the cases of RLN dysfunction are idiopathic or of a toxic nature, other common causes include nerve injury during thyroid or parathyroid surgery, trauma following intubation and nerve involvement by locally aggressive thyroid or esophageal malignancies. The diagnosis of VCP can easily be made at laryngoscopy and imaging is performed to identify any treatable cause of VCP. Imaging also helps in the diagnosis of VCP in clinically unsuspected cases. Box 66.5 enlists the various signs of VCP at cross-sectional imaging that are seen due to atrophy of the thyroarytenoid muscle [39,40] (Fig. 66.16). Box 66.5
Vocal Cord Palsy—Signs at CT and MRI Signs at axial CT during quiet breathing
◾ Widening of ipsilateral laryngeal ventricle ◾aryepiglottic Medial deviation and thickening of ipsilateral fold ◾ Dilatation of ipsilateral piriform sinus ◾ Slight anteromedial rotation of arytenoid and
medialization of posterior aspect of true cord. Along with ipsilateral laryngeal ventricular dilatation, this results in the residual airway having a shape similar to a ship’s sail—“sail sign” Fullness of ipsilateral subglottis due to sagging of the ipsilateral true cord
◾
Signs at axial CT during breath-hold
◾
◾compensatory The paralyzed vocal cord fails to adduct with movement by contralateral unaffected vocal cord that shows bowed appearance, convex margin toward the involved cord and may even cross the midline Signs on coronal CT
◾images—this Loss of ipsilateral “subglottic arch” on coronal arch is the superolateral concave contour formed by the lateral wall of the trachea with the undersurface of the true cord Pointed appearance of ipsilateral vocal cord due to atrophy
◾
Additional sign at axial CT that may indicate a proximal vagal cause
◾wallOutward bowing of the ipsilateral oropharyngeal due to atrophy of the pharyngeal constrictor muscles that are supplied by the superior laryngeal nerve which is a branch of the vagus nerve Uvular deviation toward opposite side
◾
FIGURE 66.16 Vocal cord palsy. (A) Axial CECT image shows medial deviation and slight thickening of the left aryepiglottic fold (white arrowhead) with dilatation of the left piriform sinus (white star). (B) A caudal image shows slight medial rotation of the left arytenoid cartilage with abnormal dilatation of the left laryngeal ventricle (white cross). (C) Axial CECT chest image shows a nodal mass (N) in the left aortopulmonary window (thick white arrowhead).
Tuberculous Laryngitis Laryngeal tuberculosis (TB) is a complication of pulmonary TB and a rare cause of chronic laryngitis. Patients present with hoarseness, cough, and odynophagia. It is extremely contagious and hence an early diagnosis is essential. Acute TB laryngitis shows fairly nonspecific bilateral diffuse thickening of the vocal cords, epiglottis, and paralaryngeal spaces. Chronic TB laryngitis may present as a focal asymmetric thickening resembling a mass (Fig. 66.17). Neck lymphadenopathy may be present. However to establish a definitive diagnosis, chest radiographs or CT, acid fast sputum smears, and bacteriologic cultures may be necessary [41,42].
FIGURE 66.17 Tuberculous laryngitis. Patient with pulmonary tuberculosis presented with severe breathing difficulty. (A) CECT scan of the neck shows thickened epiglottis (white arrowhead) with level II nodes on either side (straight arrows) in images. (B) Near symmetric diffuse thickening of the false cords with marked narrowing of the lumen. (C) Near symmetric diffuse thickening of the true cords with marked stenosis of the glottis lumen.
Miscellaneous Lesions Reinke’s edema implies accumulation of fluid in Reinke’s space of the true cords. It may be unilateral or bilateral, has no premalignant potential and is commonly seen in longstanding smokers [43]. Imaging is not required to diagnose Reinke’s edema, as the diagnosis is fairly evident on laryngoscopy. However, it is important for the radiologist to be aware of this entity as Reinke’s edema may be mistaken for tumor infiltration of the true cords by adjacent malignancies. CT reveals diffuse thickening of vocal folds and paraglottic fat with no evidence of any enhancing mass or erosions of overlying cartilage. Vocal cord nodules are bilateral, symmetric tiny nodular lesions of the true vocal cord, generally less than 3 mm in size that occur due to repetitive cord insult from vocal overuse. They are most commonly encountered in teachers, singers, and hawkers. They are typically seen as slight bulges along the free margin of the true cords at the junction of the anterior one-third and posterior two-thirds of the free margin of the true vocal cord as this is the site of maximum vibration and bearing the maximum brunt of vocal overuse [44] (Fig. 66.18).
FIGURE 66.18 Vocal nodules. Axial NECT image shows small symmetric bulges (white arrows) along the undersurface of the anterior thirds of the true cords on either side.
Vocal cord polyps are unilateral, pedunculated small lesions along the free margin of the true vocal cord, generally more than 3 mm in size that are also associated with chronic vocal abuse or trauma due to excessive shouting and screaming. They are seen as polypoid, exophytic, cystic, or fluid density lesion arising from the inner margin of the true vocal cord, protruding into the endolaryngeal lumen at CT or MRI [44] (Fig. 66.19).
FIGURE 66.19 Vocal cord polyp. Axial CECT image through the glottis shows a well-defined hypodense polypoid lesion (P) arising from the anterior aspect of the medial margin of the right vocal cord, protruding into the laryngeal lumen.
Two types of laryngeal cysts may be encountered—saccular cyst or mucosal cyst. Saccular cyst is fluid-filled dilatation of the saccule and is often used interchangeably with a fluid-filled internal laryngocele [31]. However it is not a true laryngocele as it does not communicate with the larynx. Mucosal cyst can occur anywhere where there is mucosa.
Post-Treatment Evaluation Interpretation of post-treatment neck scans can be challenging because of the postsurgical anatomical distortion and radiation induced changes in the soft tissues of the neck. Knowledge of these expected alterations and an optimal imaging interval following treatment can help the radiologist to avoid misinterpretation of normal post-treatment changes as recurrent or persistent disease.
Postirradiation changes are seen within all the soft tissues that are included within the radiation port and have been enlisted in Box 66.6. If the patient has been operated upon, it is always good to know the type of resection and any reconstruction performed and assess the appearance of structures that are visualized or not visualized. Scans following a total laryngectomy will show the absence of all laryngeal structures leaving behind a remnant of the thyroid gland, midline position of the neopharynx, and esophagus in place of the larynx just below the subcutaneous fat and a characteristic “rounded” appearance of the esophagus that mimics the larynx, due to lack of compression by the cartilaginous supporting structures and the thyroid gland [46] (Fig. 66.20). Box 66.6
Normal Postradiation Changes in the Neck at Imaging [45,47,48]
◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾
A. Early reactions (within 90 days) Thickening of the skin and platysma muscle Reticulation of the subcutaneous fat Enhancement of the pharyngeal mucosa, thickening of the posterior pharyngeal wall, retropharyngeal space edema Increased enhancement and size of the major salivary glands Thickening of the laryngeal structures with increased density and stippling of the fat in the pre-epiglottic and paralaryngeal spaces. B. Late reactions (after 90 days) Atrophy of the salivary glands Thickening of the skin and platysma Thickening of the pharyngeal muscles
FIGURE 66.20 Postlaryngectomy CT. Axial CECT image shows the normal appearance at CT following a total laryngectomy. The neopharynx is seen in the midline with a rounded appearance (white arrow). The isthmus of thyroid gland is not seen. Only small remnants of the thyroid gland (T) are seen. (Courtesy: Saugata Sen.)
The best time to obtain a post-treatment scan has been recommended approximately 3–4 months following the completion of the treatment [47–49]. While complete resolution of the primary mass strongly suggests a positive result, a persistent unchanged mass indicates treatment failure and a partial resolution of a mass on the post-treatment CT study is an indeterminate finding and requires further imaging [47,48] (Fig. 66.21). Stability of the mass on follow-up imaging over a 2-year period is suggestive of fibrosis and scarring [47,48].
FIGURE 66.21 Postradiation response. (A) Axial CECT image shows a midline lobulated epiglottic tumor (white star). (B) Axial CECT image obtained after radiation shows a smooth slightly thickened epiglottis indicating a successful control of primary tumor (white star). (Courtesy: Suresh Mukherji.)
Recurrent disease following radiation is seen as a nodular thickening or soft tissue at the primary site. Postsurgical recurrence manifests as focal areas of nodularity or soft tissue in the surgical bed, commonly at the cut margins of the surgery where the tumor was previously located (Fig. 66.22). Progressive sclerosis of laryngeal cartilages on post-treatment scans is likely to suggest local tumor recurrence whereas resolution of pretreatment cartilage sclerosis favors disease control [47,48]. While CT and diffusion-weighted imaging at MRI are used for assessment of post-treatment patients, FDG PET/CT imaging is a highly sensitive technique with superior diagnostic accuracy compared with CT and MRI in detection of recurrent head and neck cancer [50–53].
FIGURE 66.22 Postlaryngectomy CT—recurrence. Post total laryngectomy axial CECT shows a recurrence in the operative bed (white star) flattening the rounded neopharnx (white arrow). A myocutaneous flap is seen (white cross). (Courtesy: Suresh Mukherji.)
Summary Cross-sectional imaging plays an indispensable complementary role to clinical endoscopy in imaging of laryngeal diseases. Determination of the precise extent of cancer spread within the larynx (T staging) is the single-most critical factor guiding the management in patients with localized laryngeal cancer. A clear understanding of the standard imaging techniques and protocols for imaging the larynx, and familiarity with the key anatomical features and characteristic patterns of tumor spread within the different regions of the larynx, are fundamental to the interpretation of CT and MRI scans of these patients.
Suggested Readings
• V Joshi, V Wadhwa, S Mukherji, Imaging in laryngeal cancers, Indian J Radiol Imaging 22 (3) (2012) 209–226. • S Connor, Laryngeal cancer: how does the radiologist help? Cancer Imaging 7 (1) (2007) 93–103. • CM Paquette, DC Manos, BJ Psooy, Unilateral vocal cord paralysis: a review of CT findings, mediastinal causes, and the course of the recurrent laryngeal nerves, Radiographics 32 (3) (2012) 721–740. • SK Mukherji, WJ Weadock, Imaging of the post-treatment larynx, Eur J Radiol 44 (2002) 108–119. • V Saito, RN Nadgir, M Nakahira, M Takahashi, A Uchino, F Kimura, et al., Posttreatment CT and MR imaging in head and neck cancer: what the radiologist needs to know, Radiographics 32 (2012) 1261–1282.
References [1] HD Curtin, Anatomy, imaging and pathology of the larynx, in: Som PM, Curtin HD (eds.), Head and Neck Imaging, fifth ed., Philadelphia: Mosby, 2011; pp. 1905–2039. [2] R Hermans, Laryngeal neoplasms, in: Hermans R (ed.), Head and Neck Cancer Imaging, first ed., New York: Springer, 2006; pp. 43–80. [3] AG Jurik, Ossification and calcification of the laryngeal skeleton, Acta Radiol Diagn (Stockh) 25 (1) (1984) 17–22. [4] LM Turk, DA Hogg, Age changes in the human laryngeal cartilages, Clin Anat 6 (3) (1993) 154–162. [5] T Beale, VM Twigg, M Horta, S Morley, High-resolution laryngeal US: imaging technique, normal anatomy, and spectrum of disease, Radiographics 40 (2020) 775–790. [6] M Keberle, A Tschammler, K Berning, D Hahn, Spiral CT of the neck: when do neck malignancies delineate best during contrast enhancement? Eur Radiol 11 (10) (2001) 1986–1990. [7] BH Bartz, IC Case, A Srinivasan, SK Mukherji, Delayed MDCT imaging results in increased enhancement in patients with head and neck neoplasms, J Comput Assist Tomogr 30 (6) (2006) 972–974. [8] JH Lee, CW Ryu, SM Kim, EJ Kim, WS Choi, Usefulness of biphasic contrast injection in multidetector CT of the head and neck: a comparison with monophasic contrast injection, J Korean Soc Radiol 67 (2) (2012) 85–92. [9] MM Lell, C Gmelin, C Panknin, KT Eckel, M Schmid, WA Bautz, and H Greess, Thin-slice MDCT of the neck: impact on cancer staging, Am J Roentgenol 190 (3) (2008) 785–789. [10] I Celebi, A Oz, M Sasani, P Bayindir, E Sozen, C Vural, et al., Using dynamic maneuvers in the CT/MR assessment of lesions of the head and neck, Can Assoc Radiol J 64 (2013) 351–357. [11] NCCN guidelines version 1. 2018, Cancer of the supraglottic and glottis larynx.
[12] MM Chu, A Kositwattanarerk, DJ Lee, JS Makkar, EM Genden, J Kao, SH Packer, PM Som, L Kostakoglu, FDG PET with contrast-enhanced CT: a critical imaging tool for laryngeal carcinoma, Radiographics 30 (2010) 1353–1372. [13] EA Chu, YJ Kim, Laryngeal cancer: diagnosis and preoperative workup, Otolaryngol Clin N Am 41 (2008) 673–695. [14] M Becker, G Moulin, et al., Non-squamous cell neoplasms of the larynx: radiologic-pathologic correlation, Radiographics 18 (5) (1998) 1189–209. [15] NS Mastronikolis, TA Papadas, PD Goumas, IE Triantaphyllidou, DA Theocharis, N Papageorgakopoulou, et al., Head, neck: laryngeal tumors: an overview, Atlas Genet Cytogenet Oncol Hematol 13 (11) (2009) 888– 893. [16] JM Ko, JI Jung, SH Park, KY Lee, MH Chung, MI Ahn, et al., Benign tumors of the tracheobronchial tree: CT-pathologic correlation, Am J Roentgenol 186 (5) (2006) 1304–1313. [17] F Bray, J Ferlay, DM Parkin, P Pisani, International Agency for Research on Cancer, GLOBOCAN 2000: Cancer Incidence, Mortality and Prevalence Worldwide, International Agency for Research on Cancer, Lyon. 2001. [18] A Jain, G Balasubramanium, Epidemiological review of laryngeal cancer: an Indian perspective, Indian J Med Paediatr Ocol 36 (3) (2015) 154–160. [19] R Nocini, G Molteni, C Matiuzzi, G Lippi, Updates on larynx cancer epidemiology, Chin J Cancer Res 32 (1) (2020) 18–25. [20] M Hashibe, P Boffetta, D Zaridze, O Shangina, Szeszenia-Dabrowska N, D Mates, et al., Contribution of tobacco and alcohol to the high rates of squamous cell carcinoma of the supraglottis and glottis in central Europe, Am J Epidemiol 165 (2007) 814–820. [21] AC Nikolaou, CD Markou, DG Petridis, IC Daniilidis, Second primary neoplasms in patients with laryngeal carcinoma, Laryngoscope 110 (2000) 58–64. [22] P Zbaren, M Becker, H Läng, Pretherapeutic staging of laryngeal carcinoma: clinical findings, CT and MRI with histopathology, Cancer 77 (1996) 1263–1273. [23] American Joint Committee on Cancer: Larynx, in: Amin M, Edge SB, Greene FL (eds.), American Joint Committee on Cancer: AJCC staging manual, eighth ed., New York: Springer, 2018; p. 52–59. [24] M Becker, K Burkhardt, P Dulguerov, A Allal, Imaging of the larynx and the hypopharynx, Eur J Radiol 66 (2008) 460–479.
[25] S Connor, Laryngeal cancer: how does the radiologist help? Cancer Imaging 7 (2007) 93–103. [26] M Becker, K Burkhardt, et al., Imaging of the larynx and hypopharynx, Eur J Radiol 66 (2008) 460–479. [27] DM Yousem, RP Tufano, Laryngeal imaging, Magn Reson Imaging Clin N Am 10 (2002) 451–465. [28] M Becker, P Zbären, JW Casselman, R Kohler, P Dulguerov, CD Becker, Neoplastic invasion of laryngeal cartilage: reassessment of criteria for diagnosis at MR imaging, Radiology 249 (2008) 551–619. [29] H Kuno, K Sakamaki, et al., Comparison of MR imaging and dual energy CT for the evaluation of cartilage invasion by laryngeal and hypopharyngeal squamous cell carcinoma, Am J Neuroradiol 25 (2018) 1–7. [30] SA Chen, S Muller, AY Chen, PA Hudgin’s, DM Shin, F Khuri, et al., Patterns of extralaryngeal spread of cancer, Cancer 117 (22) (2011) 5047– 5051. [31] HD Curtin, Larynx, in: Haaga JR, Boll DT (eds.), CT and MRI of the Whole Body, sixth ed., Philadelphia, PA: Elsevier; 2015. pp. 732–753. [32] L Ash, A Srinivasan, SK Mukherj, Radiological reasoning: submucosal laryngeal mass, Am J Roentgenol 191 (3_suppl) (2008) S18–S21. [33] FJ Wippold, JG Smirniotopoulos, et al., Chondrosarcoma of the larynx —CT features, AJNR 14 (1993) 453–459. [34] A Ferlito, KO Devaney, et al., Differing characteristics of cartiliginous lesions of the larynx, Eur Arch Oto-Rhino-Laryngol 276 (10) (2019) 2635–2647. [35] BZ Koplewitz, C Springer, et al., CT of hemangiomas of upper airway in children, AJR 184 (2005) 663–670. [36] S Orlow, M Isakoff et al., Increased risk of symptomatic hemangiomas of the airway in association with cutaneous hemangiomas in a “beard” distribution, J Pediatr 131 (1991) 643–646. [37] LD Holinger, DR Barnes, et al., Laryngocele and saccular cysts, Ann Otolo Rhinol Laryngol 87 (5, part 1) (1978) pp. 675–685. [38] M Amin, AGD Maran, The aetiology of laryngocele, Clin Otolaryngol 13 (1988) 267–272. [39] CM Paquette, DC Manos, BJ Psooy, Unilateral vocal cord paralysis: a review of CT findings, mediastinal causes, and the course of the recurrent laryngeal nerves, Radiographics 32 (3) (2012) 721–740. [40] JW Dankbaar,FA Pameijer, Vocal cord paralysis: anatomy, imaging and pathology, Insights Imaging 5 (6) (2014) 743–751. [41] A Soda, Rubio H et al., Tuberculosis of the larynx: clinical aspects in 19 patients, Laryngoscope 99 (1989) 1147–1150.
[42] WK Moon, MH Han, et al., Laryngeal tuberculosis: CT findings. AJR 166 (1996) 445–449. [43] R Tavalac, H Herman, et al., Does Reinke’s edema grade determine premalignant potential? Ann Oto Rhin Laryngol 127 (2008) 812–816. [44] D Vasconcelos, AOC Gomes, CMT Araújo, Vocal fold polyps: literature review, Int Arch Otorhinolaryngol 23 (1) (2019) 116–124. [45] HB Stone, CN Coleman, MS Anscher, WH McBride, Effects of radiation on normal tissue: consequences and mechanisms, Lancet Oncol 4 (9) (2003) 529–536. [46] AC Ferriero, JL Jimenez, Martinez SJM et al., CT findings after laryngectomy, Radiographics 28 (2008) 869–882. [47] SK Mukherji, AA Mancuso, IM Kotzur, WM Mendenhall, PS Kubilis, RP Tart, et al., Radiologic appearance of the irradiated larynx. Part 1. Expected changes, Radiology 193 (1994) 141–148. [48] SK Mukherji, AA Mancuso, IM Kotzur, WM Mendenhall, PS Kubilis, RP Tart, et al. Radiologic appearance of the irradiated larynx. Part 2. Primary site response, Radiology 193 (1994) 149–154. [49] K Manikantan, S Khode, RC Dwivedi, et al., Making sense of posttreatment surveillance in head and neck cancer: when and what of followup, Cancer Treat Rev 35 (8) (2009) 744–753. [50] V Vandecaveye, De F Keyzer, S Nuyts, et al., Detection of head and neck squamous cell carcinoma with diffusion weighted MRI after (chemo)radiotherapy correlation between radiologic and histopathologic findings, Int J Radiat Oncol biol Phys 67 (4) (2007) 960–971. [51] Y Kitagawa, S Nishizawa, K Sano, et al., Prospective comparison of 18F-FDG PET with conventional imaging modalities (MRI, CT, and 67Ga scintigraphy) in assessment of combined intraarterial chemotherapy and radiotherapy for head and neck carcinoma, J Nucl Med 44 (2) (2003) 198–206, 53. [52] RS Andrade, DE Heron, B Degirmenci, et al., Posttreatment assessment of response using FDG-PET/CT for patients treated with definitive radiation therapy for head and neck cancers, Int J Radiat Oncol Biol Phys 65 (5) (2006) 1315–1322. [53] MG Isles, C McConkey, HM Mehanna, A systematic review and metaanalysis of the role of positron emission tomography in the follow up of head and neck squamous cell carcinoma following radiotherapy or chemoradiotherapy, Clin Otolaryngol 33 (3) (2008) 210–222.
CHAPTER 67
Neck Nodes Saugata Sen, Anisha Gehani, Argha Chatterjee Priya Ghosh
Introduction Neck nodes are ubiquitous and there are reports of over 300 nodes in the neck out of the 800 odd, which are present in the body [1]. Hence, 40% of the nodes of the human body are located in 20% of the volume of the body [2]. This very high concentration of nodes in the neck is related to exposure of the aerodigestive tract to environmental infective agents and carcinogens [2]. Nodes can be pathologically involved for a variety of reasons, such as infection, malignancy, or even as a reaction to acute systemic inflammation. Due to the very high prevalence of pathological involvement of neck nodes, a thorough knowledge is essential for diagnosis, description, and intervention. A radiologist is expected to recognize and report a pathological node from various criteria described in the literature. Localization and staging are mandatory for planning therapy and prognostication. Imageguided sampling is also within the domain of the radiologist. This chapter will discuss the techniques of imaging and their optimal use, the criteria of a pathological node, localization and staging of malignant nodes, and certain important clinical scenarios. Metastatic neck nodes are key to disease prognosis and treatment in malignancies of the head and neck region. This topic has been studied and published extensively. We will deal with metastatic neck nodes in detail in this chapter.
Imaging Techniques and Appropriateness Even though cervical lymph nodes can easily be palpated, imaging is essential in assessing the extent of disease due to the following reasons:
1. Many regions in the neck are not palpable, for example, retropharyngeal nodes (RPNs) (Fig. 67.1A and B). 2. Postsurgery and radiotherapy, neck can be difficult to palpate (Fig. 67.2). 3. Clinical palpation is inadequate for pretreatment assessment and may result in suboptimal management. 4. Oftentimes, imaging guidance is required to sample a lymph node (Fig. 67.3). 5. Imaging helps exclude other neck disorders, for example, a branchial cleft cyst.
FIGURE 67.2 Post modified radical left neck dissection. Axial CECT image shows soft tissue cuffing around the left carotid sheath (white arrow) which can cause small nodes to be impalpable in the region.
FIGURE 67.3 USG-guided FNAC from a pathological cervical node. Note the advancing needle tip (white arrow) within the thickened cortex of the node (asterisk).
Ultrasonography The initial and sometimes only technique required to assess the neck nodes is ultrasonography (USG). This technique is comparatively less expensive and easily available. Linear transducers of 7–12 MHz are used for the studies. USG has very high sensitivity and specificity to diagnose abnormal cervical nodes [3]. Even in the setting of postsurgical or postradiation neck, USG has high sensitivity and specificity for detection of abnormal nodes [3]. It is very useful for nodal sampling and can also be used as a problemsolving tool when computed tomography (CT) or magnetic resonance imaging (MRI) provide equivocal information. US elastography is a relatively new technique that also has the ability to characterize nodes, on the premise, that malignant (carcinomatous) nodes are stiffer [4–6]. Contrast-enhanced USG is another new technique with limited
use for assessment of neck nodes [7]. The drawback of USG is its inability to examine deep areas such as the retropharyngeal region.
Computed Tomography Contrast-enhanced CT (CECT) has been the most widely used technique for evaluating cervical lymph nodes for a malignant etiology and can evaluate any region in the neck unlike palpation or USG. Since malignant etiologies of the head and neck region are some of the commonest causes of cervical lymphadenopathy, both the primary site and the regional nodes can be staged in a single exam. The contrast delivery (90–120 mL in adults) is crucial and must follow one of the following protocols (Fig. 67.4).
FIGURE 67.4 Axial CECT image shows bilateral cervical level II nodes (asterisks) distinctly visualized from carotid arteries (thin white arrows) and internal jugular veins (thick white arrows).
a. Image with a 60-second delay after beginning contrast injection with a flow rate of 2–3 mL/s [8]. b. Initial bolus of 60 mL at 2–3 mL/s. A delay of 30 seconds followed by another 30 mL of contrast at 2–3 mL/s. Image after another 10–12 seconds delay. A saline chase can be used, but is not mandatory [8].
On CT, cervical nodes should be differentiated from the vascular structures. The above protocols are optimum with the fast scanners that are in use in modern times. As per American College of Radiology guidelines, caution should be exercised before administration of contrast to an individual with estimated glomerular filtration rate of less than 60 mL/s. There have been many controversies about radiation exposure in CT scans. In the head and neck region, concerns were raised about exposure to the lens and the thyroid gland. It has, however, conclusively been proven that even after multiple scans, the risks are significantly low, especially in the era of multidetector CT [9].
Magnetic Resonance Imaging The lack of ionizing radiation and better soft tissue resolution are advantages of MRI in cross-sectional imaging. Higher expenses and motion artifact (swallowing and respiration related) as well as long scan durations are some of the limitations. Thyroid cancers (papillary) and human papilloma virus (HPV) positive oropharyngeal cancers develop cystic lymph nodes that appear as hyperintense on T2WI. T1 hyperintensities are seen in thyroid cancers due to the presence of hemorrhagic or proteinaceous products. Contrast-enhanced MRI (CEMRI) is also a competent technique in detecting subtle extranodal extension (ENE) [10].
(18F) Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (18F) Fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) is a more recent addition to imaging and has a major role in malignancies. The technique has the ability to detect and stage disease, detect recurrence, and assess response. It has a higher specificity and sensitivity than CT or MRI for pathological neck nodes [11]. However, reactive nodes may also show FDG avidity [12]. For nodes less than 1 cm in size, the sensitivity of FDG PET-CT is much lower than the larger nodes [13] (Fig. 67.5A and B).
FIGURE 67.5 A 58-year-old woman with carcinoma right lateral border of tongue. (A) Axial PET CT and (B) corresponding axial CECT images show a rounded left cervical level IB node (arrow) showing FDG avidity. FNAC suggested reactive changes without any malignant cells.
Choice of Appropriate Imaging Technique The choice of imaging technique depends on the presentation, clinical features, and probable treatment of the primary pathology. Infective or inflammatory nodes may only be imaged if there is no response to initial therapy to document extent of disease and for sampling. This may be achieved by USG. If a malignant etiology is suspected, USG is used to sample the node, but staging would require cross-sectional imaging. The following scenarios are envisaged in the setting of malignant disease. a. Nasopharyngeal carcinoma (NPC): MRI is usually the first imaging method used. CT sections may be made available to assess skull base invasion by NPC. If size of node is more than 6 cm or nodes are observed below the level of the lower border of the cricoid cartilage, the disease is at high risk of distant metastasis. In such conditions, either PET-CT or CT scan of Thorax, Abdomen and Pelvis is recommended [14–16]. b. Thyroid cancer: Initial imaging technique is USG, which is also used for sampling. Before surgery, CT scan of neck is commonly performed as a roadmap. If thyroid cancers show nodal disease in the retropharyngeal region, the disease is at high risk of distant metastasis and CECT scan of thorax, abdomen, and pelvis is recommended. Imaging to search for distant metastasis is also warranted in cases of locally invasive disease, bulky or extensive nodal disease, symptoms of distant metastasis and anaplastic thyroid cancers [17]. c. Head and neck squamous cell carcinoma (HNSCC): CECT scan is preferred for most subsites. CEMRI is recommended for the tongue and also for laryngeal cancers to exclude the involvement of thyroid cartilage. However, practice differs between institutions and both techniques are used as per local expertise and preference. d. Lymphoma: FDG PET-CT scan is the imaging technique of choice. In lymphoma, excision biopsy is the standard practice. If excision biopsy is not possible, USG-guided neck node biopsy may be recommended. e. Recurrence: For HNSCC, NPC, and thyroid cancers, CT and MRI can both be used. FDG PET-CT may be used for HNSCC. For lymphoma, FDG PET-CT is always the first choice.
Imaging Technique
Any cross-sectional imaging of the head and neck region should cover the region between skull base and the carina to image level VII nodes and retrosternal thyroid. CT sections should be between 0.6 and 1.25 mm. On MRI, 3 mm sections are recommended. A small field of view is standard practice for optimal resolution. T1, T2, and contrast images are obtained on MRI on all three axes along with a fat saturated sequence in at least one axis [8].
Anatomical Location of Nodes The first detailed description of the human lymphatic system was published by Prof. H. Rouviere in 1938 in Paris, France (Anatomie des Lymphatiques de l’Homme) [1]. His description included a craniocaudal and transverse set of chains for a superficial system. The transverse chains consisted of occipital, mastoid, parotid, facial, RPN, submaxillary, and sublingual nodes. Two craniocaudal chains described were the anterior and lateral cervical chains. The deep system consisted of the internal jugular chain, the spinal accessory chain, and a transverse cervical chain. The final pathway of drainage of the lymph from the cervical region is the IJV chain. Anatomic location of nodes is principally important from the surgical standpoint. The Memorial Sloan Kettering surgical group proposed a simplified labeling of neck nodes as a set of seven levels [18] (Fig. 67.6). This was modified over time by imaging groups [19]. This system has been accepted by the American Joint Committee for Cancer (AJCC) system [17] as well, and is commonly used for staging of malignant neck nodes. Table 67.1 enumerates the levels of neck nodes as described by Som et al. [19] (Fig. 67.7A–C).
FIGURE 67.6 Cervical neck node levels.
Table 67.1 Levels of Neck Nodes L e v e l
Location Description
L e v e l I
These nodes lie above the hyoid bone, below the mylohyoid muscle and anterior to the back of the submandibular gland (previously classified as the submental and submandibular nodes).
L e v e l
Location Description
L e v e l I A
These nodes lie between the medial margins of the anterior bellies of the digastric muscles above the hyoid bone and below the mylohyoid muscles (previously known as submental nodes).
L e v e l I B
On each side of the neck, these nodes lie lateral to the level IA nodes and anterior to the back of each submandibular gland.
L e v e l I I
These nodes extend from the skull base to the level of the bottom of the body of the hyoid bone. They are posterior to the back of the submandibular gland and anterior to the back of the sternocleidomastoid muscle.
L e v e l I I A
These nodes are level II nodes that lie either anterior, lateral, medial, or posterior to the internal jugular vein. If posterior to the vein, the nodes are inseparable from the vein (previously classified as upper internal jugular nodes).
L e v e l
Location Description
L e v e l I I B
These are level II nodes that lie posterior to the internal jugular vein with a fat plane separating the nodes and the vein (previously classified as upper spinal accessory nodes).
L e v e l I I I
These nodes extend from the level of the bottom of the body of the hyoid bone to the level of the bottom of the cricoid arch. They lie anterior to the back of the sternocleidomastoid muscle (previously known as the mid-jugular nodes).
L e v e l I V
These nodes extend from the level of the bottom of the cricoid arch to the level of the clavicle. They lie anterior to a line connecting the back of the sternocleidomastoid muscle and the posterior-lateral margin of the anterior scalene muscle. They are also lateral to the carotid arteries (previously known as the low jugular nodes).
L e v e l V
These nodes lie posterior to the back of the sternocleidomastoid muscle from the skull base to the level of the bottom of the cricoid arch. From the level of the bottom of the cricoid arch to the level of the clavicle as seen on each axial scan, they lie posterior to a line connecting the back of the sternocleidomastoid muscle and the posterior-lateral margin of the anterior scalene muscle. They also lie anterior to the anterior edge of the trapezius muscle.
L e v e l
Location Description
L e v e l V A
Upper level V nodes extend from the skull base to the level of the bottom of the cricoid arch. They are posterior to the back of the sternocleidomastoid muscle.
L e v e l V B
Lower level V nodes extend from the level of the bottom of the cricoid arch to the level of the clavicle as seen on each axial scan. They are posterior to a line connecting the back of the sternocleidomastoid muscle and the posterior-lateral margin of the anterior scalene muscle.
L e v e l V I
These nodes lie between the carotid arteries from the level of the bottom of the body of the hyoid bone to the level of the top of the manubrium (previously known as the visceral nodes).
L e v e l V I I
These nodes lie between the carotid arteries below the level of the top of the manubrium and above the level of the innominate vein (previously known as the superior mediastinal nodes).
FIGURE 67.7 (A) Axial CECT of neck shows anatomical demarcation of level IA lymph nodes (white arrow) between the anterior bellies of the digastric muscles, level IB, IIA, IIB, and VA nodes. (B) Axial CECT of neck shows demarcation of the cervical levels below the cricoid cartilage into levels VI, IV, and VB. (C) Sagittal reformatted CECT of neck shows demarcation of cervical node levels III, IV, and VII by lower margin of hyoid, lower margin of cricoid, and upper margin of the manubrium of sternum, respectively.
Several regions that were surgically not amenable and not included in the above-mentioned system are still termed according to the anatomic location. They are as follows: 1. RPN 2. Facial 3. Pre- and postauricular and parotid 4. Occipital
Lymphatic Drainage of the Head and Neck Region Table 67.2 is adapted from the 8th edition of AJCC and shows the lymphatic drainage pathways of the head and neck region [17]. Table 67.2
Nodal Drainage of the Head and Neck Region L ev el
Hypopharynx, thyroid, cervical esophagus, and larynx.
V A an d V B
Nasopharynx, oropharynx, cutaneous structures of the posterior scalp and neck.
V I
Thyroid, glottic and subglottic larynx, apex of pyriform fossa, cervical esophagus.
V II
Thyroid cancer, esophageal cancer.
Differentials of a Neck Mass and How to Ascertain That the Lesion is a Node When a patient presents with a neck mass, it must be determined if the lesion is indeed a lymph node. In the pediatric population, branchial cleft cysts and various venolymphatic malformations are among the differentials. In adults,
infective and inflammatory masses may mimic lymph nodes. An enlarged submandibular gland is commonly mistaken for a lymph node. USG is a great technique to solve the problem and sample the lesion (Fig. 67.8A and B).
FIGURE 67.8 (A) Axial CECT and (B) USG images show a reactive right cervical level IB node (white arrowhead) and right submandibular gland (white arrow).
Suboptimal cross-sectional imaging can lead to vascular structures and muscles to be incorrectly diagnosed as nodes. The imaging techniques and administration of contrast must be standardized to mitigate the errors (Fig. 67.4).
Imaging Features of a Normal and an Abnormal Node The normal node has a reniform shape with an eccentrically placed hilum containing fat. The other parts of a node are the cortex placed at the periphery and medulla placed centrally. There is a covering by capsule, which is pierced by lymphatic and blood vessels for entry and exit into the node at the hilum. A normal node shows intact hilar fat that appears hypodense on CT and echogenic on USG. Blood vessels that enter through the hilum can also be detected by USG and the blood flow by colored Doppler (Fig. 67.9A and B).
FIGURE 67.9 (A) USG and (B) axial CECT images show a normal node with reniform shape and eccentrically placed hilum containing fat appearing echogenic on USG (asterisk in A) and hypodense with central vessels on CT (white arrowhead in B).
When a node is infected or infiltrated by tumor, certain changes occur both at the microscopic and macroscopic level. Some macroscopic changes can be detected by imaging. There is change in size and shape of the node. Malignant lymphatic emboli usually lodge within the medullary cortex of the node resulting in eccentric cortical thickening. Subcortical necrotic foci, capsular thickening, and breach are other features. Fat in the hilum may be replaced by disease process. The imaging features of a pathological node are as follows (Fig. 67.10):
FIGURE 67.10 Pictorial representation of features of pathological nodes.
Increase in Size A pathological lymph node may show alteration in size. The size criteria to stamp a node as pathological have been debated and are a matter of controversy. In a seminal article by Curtin et al., a 1.0 cm cutoff in the largest diameter in the axial section achieved a sensitivity of 88% and specificity of 39%. When the cutoff was increased to 1.5 cm, the sensitivity dropped to 56% and specificity increased to 84% [20]. It must be emphasized that about 50% of nodes less than 5 mm harbor pathology [21]. Again, 25% of nodes with ENE measure less than 10 mm [21]. About 20% of nodes more than 10 mm are not pathological [21]. Though all the data mentioned here are from studies that considered only malignant involvement, nonetheless, it does make a reasonable argument of not using size as the only or most important criteria of pathological neck nodes.
In practice, a node may not be diagnosed by size criteria alone. The size of a node in long axis on axial sections may help the radiologist arrive at a conclusive diagnosis in conjunction with other imaging features. Measurement of size of a malignant node, however, is of paramount importance in staging malignancies of the head and neck region.
Change in Shape of a Node The change in shape of a lymph node can help distinguish between normal and abnormal lymph nodes. Benign lymph nodes appear to be of reniform shape with the length more than the breadth, that is, the long axis to short axis ratio is more than 2 [22]. When a node is infiltrated or involved by malignant disease, there is change in shape to a more rounded form. A long to short axis diameter 6 cm Belo w the inferi or borde r of the cricoi d
Nx
N0
N1
N2
N3
HNSCC, P16/HPV +ve
Re gio nal nod es can not be ass ess ed
No nodal metastase s
Ipsilateral
Bilater al Contra lateral
>6 cm
HNSCC, P16/HPV −ve
Re gio nal nod es can not be ass ess ed
No nodal metastase s
One ipsilateral, ≤3 cm
One ipsilate ral, >3 cm, ≤6 cm Multip le ipsilat eral, ≤6 cm Bilater al Contra lateral
>6 cm (N3a) Clinic al or pathol ogical ENE (N3b)
Nx
N0
N1
N2
N3
Thyroid cancer
Re gio nal nod es can not be ass ess ed
No evidence of locoregio nal lymph node N0a— One or more patholog ically confirme d benign nodes N0b— No clinical or radiologi cal evidence of nodes
Metastasis to regional lymph nodes N1a— Metastasis to levels VI and VII, this can be unilateral or bilateral disease N1b— Metastasis to levels I to V, unilateral, bilateral, or contralater al or RPN
–
–
a. Nasopharyngeal carcinoma. b. Oropharyngeal carcinoma, HPV/P16 positive SCC. c. Oropharyngeal carcinoma, HPV/P16 negative SCC, SCC of other subsites in the head and neck region. d. Thyroid carcinoma.
The AJCC staging system emphasizes two important points that need special mention. 1. Any node that is central or in the midline in the neck has to be considered unilateral, that is, on the same side of the primary disease process. 2. The “uncertainty principle” states that in case of any uncertainty about the stage (T, N, or M), the lower of the two possible categories should be attributed to the patient. In other words, if there is equivocal opinion between stage N1a and N1b, stage N1a should be the correct category for the patient. However, this principle should not be used as a substitute for missing information. Hence, if there is missing information of nodal disease about any cancer, the disease cannot be labeled N0. The “uncertainty principle” is applicable for all cancers [32].
Malignant Neck Nodes With Unknown Primary—Guidelines From AJCC 8th Edition Before the publication of AJCC 8th, in a patient with malignant neck nodes without a known primary, a proper definition, standardized workflow, or guideline was not available. This recent AJCC 8th edition formulated a specific workflow pattern and definition of malignant neck nodes with unknown primary. A pathologically proven malignant node in the neck should undergo thorough clinical examinations of the nasopharynx, oral cavity, oropharynx, hypopharynx, and larynx. Examination with endoscopy (Hopkins) is also a part of the primary examination protocol. If a primary cancer remains undiagnosed, biopsy is performed from the nasopharynx and oropharynx including the tonsillar fossa on both sides in a random fashion. The tissue has to be subjected to HPV/P16 and EBV status. In case these examinations are negative too, the patient is labeled as neck nodal secondary with unknown primary. PET-CT may be requested for further investigation of a primary. In case a primary remains elusive, the lesion is termed T0, that is, an unknown primary.
Operability of a Malignant Neck Node HNSCC and thyroid cancer with pathological neck nodes may be offered a curative surgical option. Preoperative assessment of nodes is best performed by CECT or CEMRI. Traditionally, a more than 270 degree encasement of the carotid artery is considered inoperable disease [33] (Fig. 67.16). USG can be used as a problem solving tool as well. Oftentimes, a small degree of encasement of a node may be inoperable, where a part of the vessel (usually the artery), is pinched by nodal disease.
FIGURE 67.16 A 57-year-old man with left buccal mucosa carcinoma and ipsilateral cervical lymphadenopathy. Axial CECT image shows encasement of left carotid sheath (white arrow) by large necrotic left cervical level II node (white arrowheads) rendering it inoperable.
Suggested Readings • Head and Neck Imaging, 5th Ed. By Peter M. Som and Hugh D. Curtin. St. Louis, MO: Mosby. • ACR Neck Imaging Reporting and Data Systems (NI-RADS). • ACR Appropriateness Criteria. Neck mass / adenopathy. • JK Hoang, J Vanka, BJ Ludwig, CM Glastonbury, Evaluation of cervical lymph nodes in head and neck cancer with CT and MRI: tips, traps, and a systematic approach, AJR Am J Roentgenol 200 (1) (2013) W17–25. doi: 10.2214/AJR.12.8960. PMID: 23255768. • LB Eisenmenger, RH Wiggins 3rd, Imaging of head and neck lymph nodes, Radiol Clin North Am 53 (1) (2015) 115–132. • V Chong, Cervical lymphadenopathy: what radiologists need to know, Cancer Imaging 4 (2) (2004) 116–120.
References [1] H Rouviere, in: H Rouviere(Eds.) Anatomy of the Human Lymphatic System, Lymphatic System of the Head and Neck, Edwards Brothers, Ann Arbor, MI, 1938. [2] PM Som, MS Brandwein-Gensler, in: PM Som, HD Curtin (Eds.) Lymph Nodes of the Neck, Head and Neck Imaging, Vol. 2, Elsevier, St Louis, MO, 2011. [3] AT Ahuja, M Ying, SY Ho, G Antonio, YP Lee, AD King, et al., Ultrasound of malignant cervical lymph nodes, Cancer Imaging 8 (2008) 48–56. [4] YJ Choi, JH Lee, JH Baek, Ultrasound elastography for evaluation of cervical lymph nodes, Ultrasonography 34 (3) (2015) 157–164. [5] SY Chae, Jung HN, Ryoo I, Suh S, Differentiating cervical metastatic lymphadenopathy and lymphoma by shear wave elastography. Sci Rep 9 (1) (2019) 12396, doi: 10.1038/s41598019-48705-0. Accessed October 12, 2020. [6] M Ghajarzadeh, M Mohammadifar, K Azarkhish, SH., EmamiRazavi, Sono-elastography for differentiating benign and malignant cervical lymph nodes: a systematic review and meta-analysis, Int J Prev Med 5 (12) (2014) 1521–1528. [7] C Dudau, S Hameed, D Gibson, S Muthu, A Sandison, RJ Eckersley, et al., Can contrast-enhanced ultrasound distinguish malignant from reactive lymph nodes in patients with head and neck cancers?, Ultrasound Med Biol 40 (4) (2014) 747–754. [8] LB Eisenmenger, RH Wiggins 3rd., Imaging of head and neck lymph nodes, Radiol Clin North Am 53 (1) (2015) 115–132. [9] GM Fatterpekar, BN Delman, PM., Som, Imaging the paranasal sinuses: where we are and where we are going, Anat Rec 291 (11) (2008) 1564–1572. [10] AD King, GM.K Tse, EH.Y Yuen, EW.H To, AC Vlantis, B Zee, et al., Comparison of CT and MR imaging for the detection of extranodal neoplastic spread in metastatic neck nodes, Eur J Radiol 52 (3) (2004) 264–270. [11] H-S Jeong, C-H Baek, Y-I Son, M Ki Chung, D Kyung Lee, J Young Choi, et al., Use of integrated 18F-FDG PET/CT to improve the accuracy of initial cervical nodal evaluation in patients with head and neck squamous cell carcinoma, Head Neck 29 (3) (2007) 203–210. [12] T Nakagawa, M Yamada, Y Suzuki, 18F-FDG uptake in reactive neck lymph nodes of oral cancer: relationship to lymphoid follicles, J Nucl Med 49 (7) (2008) 1053–1059.
[13] I Brink, T Klenzner, T Krause, M Mix, UH Ross, E Moser, et al., Lymph node staging in extracranial head and neck cancer with FDG PET—appropriate uptake period and size-dependence of the results, Nuklearmedizin 41 (2) (2002) 108–113. [14] C Xu, Y Zhang, L Peng, X Liu, W-F Li, Y Sun, et al., Optimal modality for detecting distant metastasis in primary nasopharyngeal carcinoma during initial staging: a systemic review and metaanalysis of 1774 patients, J Cancer 8 (7) (2017) 1238–1248. [15] M Pastor, A Lopez Pousa, E Del Barco, P Perez Segura, BG Astorga, B Castelo, et al., SEOM clinical guideline in nasopharynx cancer (2017), Clin Transl Oncol 20 (1) (2018) 84–88. [16] AT.C Chan, V Grégoire, J-L Lefebvre, L Licitra, EP Hui, SF Leung, et al., Nasopharyngeal cancer: EHNS-ESMO-ESTRO clinical practice guidelines for diagnosis, treatment and follow-up, Ann Oncol 23 (Suppl 7) (2012), vii83–5. [17] MB Amin, S Edge, F Greene, DR Byrd, RK Brookland, MK Washington, AJCC Cancer Staging Manual, Springer Cham, Midtown Manhattan, New York, (2017). [18] JP Shah, E Strong, RH Spiro, B Vikram, Surgical grand rounds. Neck dissection: current status and future possibilities, Clin Bull 11 (1) (1981) 25–33. [19] PM Som, HD Curtin, AA Mancuso, An imaging-based classification for the cervical nodes designed as an adjunct to recent clinically based nodal classifications, Arch Otolaryngol Head Neck Surg 125 (4) (1999) 388–396. [20] HD Curtin, H Ishwaran, AA Mancuso, RW Dalley, DJ Caudry, BJ McNeil, Comparison of CT and MR imaging in staging of neck metastases, Radiology 207 (1) (1998) 123–130. [21] V Chong, Cervical lymphadenopathy: what radiologists need to know, Cancer Imaging 4 (2) (2004) 116–120. [22] HJ Steinkamp, M Cornehl, N Hosten, W Pegios, T Vogl, R Felix, Cervical lymphadenopathy: ratio of long- to short-axis diameter as a predictor of malignancy, Br J Radiol 68 (807) (1995) 266–270. [23] SE Song, BK Seo, SH Lee, A Yie, KY Lee, KR Cho, et al., Classification of metastatic versus non-metastatic axillary nodes in breast cancer patients: value of cortex-hilum area ratio with ultrasound, J Breast Cancer 15 (1) (2012) 65–70. [24] F Yan, YJ Byun, SA Nguyen, ST Stalcup, TA Day, Predictive value of computed tomography in identifying extranodal extension in human papillomavirus-positive versus human papillomavirusnegative head and neck cancer, Head Neck 42 (9) (2020) 2687– 2695, doi: 10.1002/hed.26281. Accessed October 16, 2020.
[25] F Faraji, N Aygun, SF Coquia, CG Gourin, M Tan, LM Rooper, et al., Computed tomography performance in predicting extranodal extension in HPV-positive oropharynx cancer, Laryngoscope 130 (6) (2020) 1479–1486. [26] ME Spector, KK Gallagher, E Light, M Ibrahim, EJ Chanowski, JS Moyer, et al., Matted nodes: poor prognostic marker in oropharyngeal squamous cell carcinoma independent of HPV and EGFR status, Head Neck 34 (12) (2012) 1727–1733. [27] JH Maxwell, TJ Rath, JK Byrd, WG Albergotti, H Wang, U Duvvuri, et al., Accuracy of computed tomography to predict extracapsular spread in p16-positive squamous cell carcinoma, Laryngoscope 125 (7) (2015) 1613–1618. [28] M Geltzeiler, D Clayburgh, J Gleysteen, ND Gross, B Hamilton, P Andersen, et al., Predictors of extracapsular extension in HPVassociated oropharyngeal cancer treated surgically, Oral Oncol 65 (2017) 89–93. [29] G Papaioannou, K McHugh, Neuroblastoma in childhood: review and radiological findings, Cancer Imaging 5 (2005) 116– 127. [30] A Ahuja, M Ying, Sonography of neck lymph nodes. Part II: abnormal lymph nodes, Clin Radiol 58 (5) (2003) 359–366. [31] A Karandikar, KM Gummalla, SC Loke, J Goh, TY Tan, Approach to intensely enhancing neck nodes, Diagn Interv Radiol 22 (2) (2016) 168–172. [32] DM Gress, SB Edge, FL Greene, MK Washington, EA Asare, JD Brierley, et al., Principles of cancer staging, MB Amin, SB Edge, FL Greene, DR Byrd, RK Brookland, MK Washington (Eds.), AJCC Cancer Staging Manual, Springer International Publishing, Cham, 2017, 3–30. [33] DM Yousem, H Hatabu, RW Hurst, HM Seigerman, KT Montone, GS Weinstein, et al., Carotid artery invasion by head and neck masses: prediction with MR imaging, Radiology 195 (3) (1995) 715–720.
Introduction The neck, which extends from the skull base to the cervicothoracic junction, is broadly divided craniocaudally by the hyoid bone, into two parts, the suprahyoid neck and the infrahyoid neck. The suprahyoid and infrahyoid neck are further cleaved into multiple compartments by the three layers of the deep cervical fascia. Therefore to understand the formation of the deep spaces of the neck, it is necessary to have an overview of the deep cervical fascia.
Cervical Fascia The deep cervical fascia has three layers: (1) the superficial layer also called the investing fascia; (2) the middle layer, also called buccopharyngeal fascia (in the suprahyoid neck) and visceral/pretracheal fascia (in the infrahyoid neck); and (3) the deep layer or prevertebral fascia [1,2]. The fascial layers are not seen on cross-sectional imaging, but knowledge of their location on the computed tomography/magnetic resonance imaging (CT/MRI) image helps demarcate the spaces they define (Fig. 68.1).
FIGURE 68.1 Axial CT image of the suprahyoid neck at the level of palate shows layers of deep cervical fascia as dashed lines. Investing layer (white), middle layer (yellow), and deep layer (red). The fascial layers enclose spaces, BS, buccal space; CS, carotid space; MS, masticator space; PMS, pharyngeal mucosal space; PS, parotid space; PVS, perivertebral space which has an anterior prevertebral compartment (pv) and posterior paraspinal compartment. The asterisk on each side shows the parapharyngeal space (PPS). The tensor vascular styloid fascia is a slip of middle layer (orange) passing from medial pterygoid plate to styloid process, which separates PPS from CS. The caret symbol shows the potential retropharyngeal space between the middle layer and prevertebral fascia. The CS sheath is composed of all three layers, but predominantly the deep layer.
These fascial layers provide support to the visceral structures of the neck also forming the tough carotid sheath that protects the neck vessels. They form natural barriers between various structures. They also allow flexibility so that structures in the neck can glide over each other smoothly during sideto-side movement of the neck and during swallowing.
The investing layer surrounds the entire neck like a collar and invests the sternocleidomastoid and trapezius muscles. Anteriorly it splits to enclose the parotid and submandibular glands. This layer is attached to the cranial base superiorly and inferiorly to the manubrium of the sternum, spine, and acromion of the scapula and the clavicles. Posteriorly, it is attached to the ligamentum nuchae. The middle layer of the cervical fascia encloses the strap muscles, the pharynx, larynx, trachea, esophagus, thyroid, and parathyroid glands. The part of the middle layer that invests the pharyngeal constrictors and the buccinators is called the buccopharyngeal fascia. The deep layer or the prevertebral fascia envelops the cervical vertebrae, the muscles of the vertebral column, and the cervical portion of the sympathetic trunk ganglia. Alar fascia, a thin slip of the prevertebral fascia spanning the midline, is located anterior to the prevertebral fascia and posterior to the buccopharyngeal fascia. Lastly, the carotid sheath is a tough tubular fascial envelope surrounding the carotid arteries, internal jugular vein (IJV), vagus nerve, and sympathetic nerve fibers. It receives fibers from all three layers (investing fascia, middle layer, and prevertebral fascia) [1,2].
Suprahyoid Neck Spaces: Overview The course of the cervical fascial layers in the suprahyoid and infrahyoid neck results in the formation of the deep neck spaces, which are actually compartments. They were initially discovered on anatomical dissection of cadavers and later rediscovered by surgeons while dissecting pus pockets. These spaces form natural barriers for the spread of infection, as well as early tumors. Each space has its specific contents and based on these, a distinct set of pathological entities can arise [1]. The spaces of the suprahyoid neck are imaged comprehensively only on cross-sectional imaging with CT/MRI and many spaces are not accessible to ultrasonography (USG). The investing fascia splits at the lower border of the mandible into two layers (medial and lateral) to enclose the mandible and masticator muscles forming the masticator space (MS) on each side. The medial fascial slip passes deep to the pterygoid muscles and inserts at the skull base, medial to the foramen ovale. Thus, this space extends from the skull base to the lower border of the mandible and communicates with the cranial cavity through the foramen ovale (Fig. 68.2). Anterior to the MS is a space filled with loose areolar tissue on each side called the buccal space (BS). The parotid space (PS) on each side lies posterior and lateral to the MS and is formed by the investing fascia enveloping the parotid gland (Fig. 68.1) [2].
FIGURE 68.2 Coronal CT reformation shows the investing fascia splitting at the lower border of the mandible to medial and lateral slips (dashed white lines) to enclose the masticator space containing the ramus of mandible (m) and the muscles: masseter (M), medial pterygoid (MP), and lateral pterygoid (LP) with the foramen ovale in the roof (arrow). The parapharyngeal space (asterisk) is seen between the middle layer of the deep cervical fascia (yellow dashed line) and the medial slip of the investing layer; and communicates with the submandibular space (SMS) inferiorly that contains the submandibular gland (outlined).
Pharyngeal mucosal space/visceral space is a midline space and is formed by the buccopharyngeal fascia enclosing the pharynx. This space includes the nasopharynx and oropharynx in the suprahyoid neck. Lateral to this space and medial to the MS is a fat-filled space called the parapharyngeal space (PPS). This space extends from the skull base up to the hyoid below and does not extend into the infrahyoid neck (Fig. 68.2). Posterior to the PPS is the carotid space (CS) on either side containing the carotid sheath and jugular nodes. This space extends down into the infrahyoid neck. Immediately behind the pharyngeal mucosal space is a potential space called the retropharyngeal space (RPS). This space has two compartments. The anterior compartment is located between the posterior layer of the buccopharyngeal fascia and the alar fascia and extends from the skull base to
the infrahyoid neck and further down into the mediastinum. The posterior compartment is another potential space called the danger space and is located between the alar fascia and the prevertebral fascia. It extends from the skull base into the posterior mediastinum up to the diaphragm. Far posterior in the midline, behind the RPS lies the perivertebral space (PVS) enclosed by the prevertebral fascia that envelops the muscles around the vertebral column. It has an anteriorly located prevertebral space component and a posteriorly located paraspinal space component and also extends into the infrahyoid neck (Fig. 68.1). The posterior cervical space (PCS) that lies lateral to the PVS also continues into the infrahyoid neck (Fig. 68.3). This chapter will discuss all the suprahyoid spaces, except for the pharyngeal mucosal space, which is discussed as nasopharynx, and oropharynx in a separate chapter. Two other spaces, sublingual space (SLS) and submandibular space (SMS), are part of the oral cavity but will be discussed in this chapter.
FIGURE 68.3 Axial CT image of the infrahyoid neck at the level of supraglottic larynx shows layers of deep cervical fascia as dashed lines. Investing layer (white); middle layer (yellow), and deep layer (red). The fascial layers enclose spaces. CS, carotid space; PCS, posterior cervical space; PVS, perivertebral space; VS, visceral space; the asterisk shows the potential retropharyngeal space between the middle layer and deep layer/prevertebral fascia. The investing layer encloses the sternomastoid (stm) and trapezius (tr). The CS sheath is composed of all three layers, but predominantly the deep layer.
Infrahyoid Neck Spaces: Overview The cervical fascial layers cleave the infrahyoid neck into five tightly packed spaces (Fig. 68.3). The central space is the visceral space surrounded by the middle layer of deep cervical fascia and contains not only the hypopharynx (which is a continuation of the suprahyoid pharyngeal mucosal space), but also the larynx, thyroid, parathyroid glands, trachea, and esophagus. These contents will be discussed elsewhere. The other spaces continuing from the suprahyoid neck are the CS, the RPS, the PVS, and the PCS. The PCS is a triangular fat-filled space between the carotid vessels anteriorly, sternocleidomastoid muscle laterally, and paraspinal muscles
posteromedially. Table 68.1 shows the various spaces of the suprahyoid and infrahyoid neck. Table 68.1 Spaces of the Necka Median spaces
Lateral spaces
Suprahyoid Neck
Infrahyoid Neck
Pharyngeal mucosal space/visceral space
Visceral space
Retropharyngeal space
Retropharyngeal space
Perivertebral space
Perivertebral space
Masticator space Parotid space Buccal space Parapharyngeal Space Carotid space
Carotid space
Posterior cervical space
Posterior cervical space
a
Sublingual space and Submandibular space are parts of the oral cavity.
Approach to Diagnosis of a Suprahyoid Neck Space Mass [1,2] The head and neck region usually has exquisite symmetry. The absence of symmetry should alert the radiologist to the region of asymmetry, which is often the location of the lesion. After identification of the lesion, the next step is to localize its epicenter to a neck space if possible. In the suprahyoid neck, the fat-filled PPS has a crucial location being surrounded by other spaces. Displacement of the PPS is a useful clue to the epicenter of the mass. For example, a MS mass will displace the PPS posteromedially while a CS mass will displace it anteriorly. A PS mass will displace it anteromedially while a pharyngeal mucosal space mass will displace it laterally. Deciding
the epicenter between the two midline spaces, PVS and RPS, requires examination of the location of the prevertebral muscles. RPS masses displace the prevertebral muscles posteriorly while PVS masses displace them anteriorly. The origin of a mass from the SLS or SMS is decided by studying its relationship with the mylohyoid muscle (in the floor of the mouth). SLS masses are located superomedial to the mylohyoid muscle while SMS masses are seen inferior and lateral to it. Once the epicenter is located, the differential diagnosis can be formed based on the knowledge of the various contents of that space and the list of lesions characteristic to that location. The differential diagnosis can be further narrowed, using a combination of the patient’s age, clinical history, and specific imaging features of the lesion. For example, an intensely enhancing nasopharyngeal mass in an adolescent male is typically a juvenile nasopharyngeal angiofibroma. An aggressive destructive pediatric soft tissue tumor in the MS is often a rhabdomyosarcoma. Hence, thorough knowledge of the boundaries and contents of the spaces, lesions specific to them and their imaging features together with the clinical history help devise a systematic approach to a neck mass.
Masticator Space Boundaries MS has its floor at the lower border of the mandible and its roof at the skull base (Fig. 68.2). The foramina ovale and spinosum are located in the roof of the MS. Medially, it is limited by the medial layer of investing fascia (also called medial pterygoid fascia). The lateral layer of investing fascia, which closely abuts the superficial part of the masseter and reaches up to the zygomatic arch, forms the lateral boundary of the MS. This layer continues further cranially over the temporalis muscle. Hence, laterally the MS extends further above the zygomatic arch, as a recess, called the suprazygomatic MS or the temporal fossa (by the surgeons). Anteriorly, the MS has an incomplete boundary with the BS. Posteriorly, it is bounded by the PS [1,2].
Contents The contents of the MS are:
◾ Ramus and body of the mandible ◾ Muscles of mastication ◾ Mandibular nerve and branches ◾ alveolar nerve ◾ Inferior Inferior alveolar artery and vein
The ramus and body of the mandible form the central strut in the MS. The muscles of mastication are the medial pterygoid muscle, lateral pterygoid muscle, temporalis, and masseter. The mandibular nerve or V3 nerve (third division of the trigeminal nerve) gives branches to the masticator muscles. The mandibular nerve trunk is located in the central part of MS in between the medial and lateral pterygoid muscles. The inferior alveolar nerve, the largest division of the mandibular nerve, is a sensory nerve that accompanies the inferior alveolar artery and vein. These structures enter the mandibular foramen to run within the inferior alveolar canal in the mandibular shaft [1,2].
Lesions of the MS The lesions of the MS can be classified as developmental, inflammatory, tumors, and miscellaneous (Table 68.2) [3]. Table 68.2 Lesions of the Masticator Space Developmental
Vascular anomalies a. Hemangioma* (pediatric) b. Vascular malformations High flow (AVMs and AVFs) Low flow* (venous/lymphatic/mixed malformation)
◾ ◾
Inflammatory
a. Masticator space abscess from odontogenic focus*/spread from adjacent spaces b. Mandibular osteomyelitis
Benign tumor
Nerve origin a. Schwannoma* b. Neurofibroma Bony origin a. Odontogenic origin* Dentigerous cysts, odontogenic keratocyst, ameloblastoma b. Nonodontogenic Simple bone cysts, aneurysmal bone cystsFibro-osseous lesionsFibrous dysplasia,
Intrinsic a. Neurogenic origin—malignant peripheral nerve sheath tumor b. Bony origin—osteosarcoma, chondrosarcoma, Ewing’s sarcoma, and metastases c. Soft tissue—rhabdomyosarcoma* (in children), malignant fibrous histiocytoma, fibrosarcoma, synovial sarcoma d. Non-Hodgkin’s lymphoma Extrinsic a. Tumor spread from adjacent spaces*— oral cavity, pharynx, parotid space, skull base b. Perineural tumor spread along V3 to the foramen ovale (via inferior alveolar nerve or auriculotemporal nerve) a. Benign masseteric hypertrophy* b. Accessory parotid gland* c. V3 denervation atrophy (acute and subacute phase)
Imaging Methods for MS Lesions CT and MRI are the commonly used methods for imaging MS lesions, except in case of vascular malformations where USG is the first-line diagnostic imaging. CT is superior for detecting cortical erosion and characterizing tumor matrix and mineralization. CT is the investigation of choice in suspected MS infection as it demonstrates mandibular osteomyelitis and MS abscess along with the cause of infection (odontogenic focus/parotid calculi). However, MRI is the preferred investigation in neoplasia as it depicts muscle and soft tissue invasion better due to superior soft tissue resolution. MRI is also superior for demonstrating mandibular marrow invasion and perineural tumor spread [1–4].
Imaging Features of Common MS Lesions Infections Infections are more common than tumors and are usually due to odontogenic causes, such as dental caries, gingivitis, or tooth extraction. Less commonly, the infection can also extend from an infected parotid gland or a tonsillar focus. Well-defined fluid collections with enhancing walls may be seen in the MS representing abscesses that may extend into adjacent spaces [3]. Masseteric abscess may not always be seen as a collection, instead, the muscle may appear enlarged, show heterogeneous enhancement, and the adjacent mandible may show sclerosis [5]. Suppurative osteomyelitis of the mandible is seen as an osteolytic pattern in the mandible with a lamellated periosteal reaction. Developmental Lesions The developmental lesions seen in the MS are vascular anomalies (Table 68.2). USG is the first-line imaging method for these and can differentiate between hemangioma and vascular malformations by depicting the parenchymal component in the former. Color Doppler USG (CDUSG) can also demonstrate the high-velocity flow in arteriovenous malformations and the low-velocity flow in venous and lymphatic malformations (LMs) [4]. The commonest benign pediatric tumor of the MS is a hemangioma. Two types exist, infantile hemangioma (a true neoplasm) and congenital hemangioma. USG with CDUSG is used for superficial lesions and shows a highly vascular soft tissue mass. Cross-sectional imaging is useful for studying large or deeply located masses. On MR imaging, hemangioma is seen as a soft tissue mass, which in the proliferating phase is seen as a lobulated, well-circumscribed, homogeneous mass that is intermediate in signal on T1-weighted images. Homogeneous hyperintense signal on T2weighted images is noted with homogeneous postcontrast enhancement. Heterogeneity is seen in the involutional phase [4]. Venous malformations (VMs) appear as compressible lesions with poorly defined margins on USG without arterial waveform on CDUS. Calcified phleboliths, best seen, as high attenuation foci on CT, are diagnostic of VMs (Fig. 68.4). Remodeling of adjacent bone may be typically seen in VMs, that is unusual in hemangiomas. On MRI, hypo to isointense homogeneous signal on T1-weighted images is usual except when thrombosis or hemorrhage is seen. T2-weighted images show high signal intensity when the vascular channels are large and intermediate signal when these are smaller. Heterogeneous delayed enhancement is seen on the postcontrast study (Fig. 68.5). Flow voids are not seen [4].
FIGURE 68.4 Venous malformation (VM), coronal CT reformation in a clinically soft compressible swelling of the left jaw shows mild heterogeneous enhancement in the masseter with phleboliths (arrow), which are pathognomonic of VM.
FIGURE 68.5 (A and B) MRI in venous malformation. (A) Fatsuppressed T2W axial image shows high signal intensity lesion (arrow) in the masticator space within the substance of the masseter muscle. (B) Fat-suppressed postcontrast T1W axial image shows delayed heterogeneous enhancement in the lesion (arrow), not usually seen in the cysts of lymphatic malformation. (C and D) MRI in lymphatic malformation (macrocystic). (C) Fat-suppressed T2W axial image shows a cystic lesion (arrow) in the masticator space within the substance of the masseter muscle. (D) Fat-suppressed postcontrast T1W axial image shows no enhancement of the cystic spaces which is typical of a lymphatic malformation.
LMs can be microcystic, macrocystic, or mixed types. Macrocystic lesions appear as septated cystic structures on both MRI and USG with fluid–fluid levels when there is hemorrhage within. A T1-weighted postcontrast fatsaturated sequence shows that the cysts do not enhance while the internal septae do and is useful to differentiate from a VM which shows delayed heterogeneous enhancement. Microcystic LMs have tiny cysts within and appear hyperechoic on USG. The tiny cysts show crowding of the walls, which are T2 hypointense and show postcontrast enhancement and this may make the lesion appear enhancing and solid on MRI [4]. Mixed malformations show a combination of all the above components. Arteriovenous malformations show a tangle of vessels without any parenchymal component and large flow voids on both T1- and T2-weighted images. They do not show high signal on T2-weighted sequences. Large feeding arteries and draining veins without intervening capillary components are characteristic, with intense early venous enhancement. The posterior body and ramus of the mandible may also be involved resulting in bony expansion and erosion of margins [4]. Benign and Malignant Tumors The common benign tumor of the MS is a schwannoma of the mandibular nerve or its branches. It is seen as a fusiform well-defined soft tissue intensity mass appearing hypointense on T1-weighted and hyperintense on T2-weighted images. Cystic degeneration is common in large tumors, which appear heterogeneous. Postcontrast enhancement can be homogenous or heterogeneous. Extension intracranially produces a dumbbell-shaped tumor with a waist at the foramen ovale (Fig. 68.6) [2].
FIGURE 68.6 Schwannoma with cystic degeneration. Coronal fatsuppressed postcontrast T1W MRI shows a dumbbell-shaped solidcystic mass (asterisk) in the masticator space (MS) closely apposed to the mandibular ramus (long arrow) extending through the foramen ovale intracranially (short arrow). Parapharyngeal fat that is compressed medially (arrowhead) confirms epicenter in the MS.
Neurofibromas (NFs) may be solitary or multiple (when associated with neurofibromatosis type 1). NFs show high T2 signal intensity and may exhibit either strong or heterogeneous postgadolinium enhancement (Fig. 68.7). Solitary NFs may show the typical target sign with central low signal intensity on T2-weighted images and peripheral hyperintense rim [6]. Plexiform NFs can involve multiple adjacent spaces.
FIGURE 68.7 Neurofibroma in the masticator space. (A) Axial T2W MRI shows a hyperintense mass with epicenter in the masticator space (solid arrows), also extending laterally into the parotid gland (arrowhead) and medially into the parapharyngeal space (dashed arrow). (B) Contrast-enhanced axial T1W MRI shows heterogeneous enhancement in the lesion (solid arrow) with a focus of cystic degeneration (dashed arrow). (Courtesy: Suresh K. Mukherji.)
Malignant peripheral nerve sheath tumor that arise de novo from schwannomas or NFs may have similar imaging appearance, but greater heterogeneity, foraminal erosion, and rapid increase in size may suggest malignant peripheral nerve sheath tumor [1,2]. Rhabdomyosarcoma is the most common malignant tumor of MS in children. It appears as an infiltrating soft tissue mass with bony destruction or erosion. Non-Hodgkin lymphoma (NHL) occurs as a part of systemic NHL and has no specific imaging features; the mass is fairly homogenous with well-defined margins, is more likely to mould than infiltrate bone, destruction being rare. Soft tissue sarcomas of the MS have no specific imaging features [1,2]. Odontogenic and nonodontogenic bone lesions are beyond the scope of this chapter. Tumor extension into the MS from the adjacent oral cavity, particularly from buccal and retromolar trigone cancers, is common and this causes upstaging of the primary disease. Other tumors that can spread into MS are nasopharyngeal carcinoma, tonsillar carcinomas, and parotid malignancies. This may be seen as direct tumor extension or as perineural spread (PNS) that is seen along the nerves, either in continuity with the primary in the adjacent space or as skip lesions. Malignant parotid tumors can spread along the auriculotemporal nerve and oral cavity tumors along the inferior alveolar nerve to reach the V3 nerve extending up to the foramen ovale and beyond (Fig. 68.8). Contrast-enhanced MR imaging best demonstrates the direct signs of PNS as nerve enlargement, excessive enhancement of the nerve, and loss of fat adjacent to the foraminae. Fullness and enhancement of Meckel’s
cave and cavernous sinus may be seen. CT demonstrates more advanced cases, showing foraminal erosion and soft tissue density obliterating the fat adjacent to foraminae.
FIGURE 68.8 Adenoid cystic carcinoma with perineural spread (PNS). Fat-suppressed postcontrast T1W MRI. (A) Coronal image shows enhancing parotid mass (long arrow) and PNS along V3 (short arrows) reaching foramen ovale (arrowhead). (B) Axial section. Arrowheads show the PNS along auriculotemporal nerve course (behind mandibular ramus) to reach V3 at mandibular foramen (white arrow).
Miscellaneous Lesions (Pseudolesions) Indirect signs of PNS are denervation atrophy of the masticator muscles. These show increased enhancement, T2 hyperintensity, and enlargement in the acute–subacute phase that should not be misinterpreted as a tumor. Benign masseteric hypertrophy may be unilateral or bilateral. The etiology remains unclear although bruxism, jaw malocclusion, and temporomandibular joint disorders have been implicated. Homogeneous enlargement of the entire muscle is seen on imaging without any focal masslike lesion. There may be associated hypertrophy of the pterygoid and temporalis muscles too (Fig. 68.9).
FIGURE 68.9 Benign hypertrophy of right masseter (solid arrow) and medial pterygoid (dashed arrow) seen on axial T2W MRI. Note the normal left-sided masseter (asterisk) and medial pterygoid (caret symbol).
An accessory parotid gland is seen just superficial to the masseter muscle and is usually unilateral. It is morphologically identical with the main parotid gland and should not be mistaken for a mass lesion. The characteristic density/intensity similar to the adjacent parotid gland is an important clue to correct diagnosis [1,2].
Teaching Points
◾when MS lesion is either located anterior/anterolateral to the PPS and large displaces the PPS posteriorly/posteromedially ◾baseOptimal imaging of an MS lesion extends from above the skull (level of the pons) to below the mandible and in case of suspected malignancy up to the root of the neck ◾andMRICTisisthethepreferred method of imaging for suspected malignancy preferred method of imaging for suspected infection of the MS
Buccal Space Boundaries The BS is located anterior to the MS and separated from it by an incomplete fascial boundary. It lies lateral to the buccinator muscle (and oral cavity) and medial to the zygomaticus major (Fig. 68.10). Lateral to the zygomaticus major muscle lies the subcutaneous fat under the skin of the cheek and this is not a part of the BS. Superiorly, the BS fat merges with the retroantral fat (part of infratemporal fossa) while inferiorly the BS merges with the SMS [1,7].
FIGURE 68.10 Buccal space (BS) anatomy. Axial CT image shows BS bounded by zygomaticus major muscle (solid arrow), buccinator muscle (dashed arrow), and masseter (m) in the masticator space (outlined). The terminal end of the parotid duct (arrowhead) divides the buccal fat pad into anterior and posterior parts.
The central adipose tissue is called the buccal fat pad. The terminal end of the parotid duct traverses the buccal fat pad transversely to pierce the buccinator opposite the upper second molar. This divides the buccal fat pad into two equal anterior and posterior compartments (Fig. 68.10). The buccal fat pad has other extensions. A lateral extension is seen along the parotid duct, a medial and superior extension is seen between the posterior wall of maxillary sinus and ramus of the mandible and an anterior extension is seen anterior to the maxillary sinus. The minor salivary gland rests, the nerves and lymphatic channels are not seen on imaging [7]. Lesions of the BS are listed in Table 68.3. Table 68.3 Lesions of the Buccal Space Developmental
Vascular anomalies a. Hemangiomas b. Vascular malformations* High flow (AVMs and AVFs) Low flow* (venous/lymphatic/mixed malformation)
◾ ◾
Inflammatory/inf ection
Cellulitis/abscess* due to a. Dental infections/salivary calculi b. Spread of infection from complicated sinusitis c. Spread of infection from masticator space
Benign tumor
Minor salivary gland tumor a. Pleomorphic adenoma* Nerve origin a. Schwannoma b. Neurofibroma*
Soft tissue lesions a. Lipoma b. Rhabdomyoma Malignant tumor
Intrinsic a. Adenoid cystic carcinoma b. Non-Hodgkin lymphoma c. Rhabdomyosarcoma (children) Extrinsic a. Tumor spread from adjacent spaces*—oral cavity, masticator space b. Nodal metastases from SCC*
*Represents the common lesions. AVF, arteriovenous fistula; AVM, arteriovenous malformation.
Imaging Features of BS Lesions Infections BS infections are either from adjacent infected dental foci/parotid calculi or extension of infection from adjacent MS. Invasive fungal sinusitis of the maxillary antrum is another focus of infection and all the above cause buccal fat infiltration. Cellulitis is manifested as stranding of the buccal and overlying subcutaneous fat with thickening of skin and enlargement of adjacent muscles while abscess appears characteristically as a fluid collection with enhancing walls. Vascular Anomalies Vascular malformations encountered in the BS could be VMs (more frequent) or LMs (Fig. 68.11).
FIGURE 68.11 Lymphatic malformation (macrocystic and microcystic components) in the right buccal space. Axial T2W MRI. Cystic components (black arrows) with fluid–fluid level (dashed arrow) indicate the macrocystic component. The anteriorly located intermediate signal intensity areas (white arrow) represent crowded walls of tiny cysts in the microcystic component.
Benign and Malignant Tumors Minor salivary gland rests (not seen on imaging) could give rise to the benign pleomorphic adenoma or the malignant adenoid cystic carcinoma (ACC) or mucoepidermoid carcinoma (MEC). MRI is the preferred method for characterizing neoplasms of the BS. The pleomorphic adenomas typically have low signal on T1-weighted images and high signal on T2weighted images and are often homogeneous when small. Ill-defined infiltrative margins and areas of low signal intensity are seen in malignant salivary neoplasms [7]. Lipomas show the typical fat density or intensity.
Malignancies of the oral cavity vestibule (gingival-buccal mucosa and retromolar trigone) when advanced, invade the BS after invading the buccinator. Further spread can reach the skin laterally or MS posteriorly (Fig. 68.12) upstaging the “T” category of the oral cancer.
FIGURE 68.12 Oral cancer extension. Axial CT section at the level of upper alveolus shows tumor extension into the buccal space (solid arrow) and masticator space (dashed arrow) from an advanced right upper alveolar oral cancer that destroys the bony alveolus (asterisk) and pterygoid plates.
Teaching Points
◾ BS is anterior to the MS and separated by an incomplete fascia ◾ BS is located lateral to the buccinator and oral cavity ◾theBSoralcancavity be a conduit for the spread of squamous carcinoma from to MS, which upstages disease (to T4b category)
Parapharyngeal Space Boundaries The PPS is an inverted pyramidal-shaped space with its base superiorly at the skull base (undersurface of temporal bone) and its apex inferiorly at the junction of the greater cornu of hyoid bone and the posterior belly of digastric muscle. On coronal imaging, it is seen located between the MS (lined by the medial slip of investing fascia) and the naso-oropharynx lined by the buccopharyngeal fascia; and communicates inferiorly with the SMS of the oral cavity (Fig. 68.2). On the axial imaging section, the pterygoid muscles and mandibular ramus (in the MS) are located anterolateral to it while posteriorly the tensor– vascular styloid fascia, a slip of the middle layer of cervical fascia (not seen on imaging), separates the PPS from the CS (Fig. 68.1). The posterolateral border of the PPS abuts the PS in the region of the deep lobe of the parotid [1,2,8].
The pterygoid venous plexus is a cluster of venules that are counterparts of branches of the maxillary artery. It is located in the PPS along the medial margin of the lateral pterygoid muscle and eventually forms the retromandibular vein [2].
Lesions of the PPS The lesions of the PPS can be classified as developmental, pseudomasses, inflammatory lesions, and tumors (Table 68.4) [1,2]. Table 68.4 Lesions of the Parapharyngeal Space Develop
Atypical second branchial cleft cyst*
mental Pseudom ass
Asymmetric pterygoid venous plexus*
Inflamma tory
Abscess spreading from adjacent deep spaces* a. masticator space (dental focus) b. parotid space (calculous disease) and c. pharyngeal mucosal space (tonsillar focus)
Benign tumor
Minor salivary gland tumor Pleomorphic adenoma* Fat Lipoma
Malignan t tumor
Intrinsic a. Adenoid cystic carcinoma b. Mucoepidermoid carcinoma Extrinsic a. Tumor spread from adjacent spaces*—parotid space, masticator space, and pharyngeal mucosal space
*Represents the more common lesions.
Imaging Features of Common PPS Lesions Infections Infections of the PPS are always due to spread from adjacent spaces and hence abscesses seen are multicompartmental (Fig. 68.13).
FIGURE 68.13 Tonsillar and peritonsillar abscess reaching the parapharyngeal space (PPS) and masticator space. Contrast-enhanced axial MRI shows the PPS abscess as a fluid-containing cavity (black arrow) with surrounding enhancement reaching up to the mandible. The right tonsil is enlarged and shows a nonenhancing central focus (white arrow) suggestive of a tonsillar abscess.
Developmental Lesions An atypical second branchial cleft cyst (BCC) is seen in the PPS. This entity encountered in the pediatric age group or young adults is seen as an ovoid cystic mass of water density/intensity, within the PPS, reaching the skull base superiorly. Inferiorly, it abuts the pharyngeal wall. Pseudomass When the pterygoid venous plexus is asymmetrically enlarged on one side, it appears as an enhancing cluster of vessels and should not be mistaken for a vascular tumor (Fig. 68.14).
FIGURE 68.14 Axial CT section at the level of nasopharynx shows prominent pterygoid venous plexus (arrows) in parapharyngeal spaces (normal content). An asymmetrically enlarged plexus should not be misinterpreted as a tumor.
Benign and Malignant Tumors As a general rule, the larger the salivary gland, the lower the incidence of malignancy with the highest incidence observed in the minor salivary gland rests. However, when it comes to the PPS salivary rests, benign tumors are much more common than malignant tumors [8]. Pleomorphic adenoma of the PPS is seen as round or oval soft tissue density mass on CT with very high signal on T2-weighted images. The mass is sharply circumscribed, centered in the PPS, and shows a well-defined fat plane all around the periphery if arising de novo from the PPS rests (Fig. 68.15A). On the other
hand, a pleomorphic adenoma arising from the adjacent deep lobe of the parotid and extending secondarily into the PPS shows a fat plane only along the medial margin of the mass and would be inseparable from the deep parotid lobe (Fig. 68.15B). This difference is important to recognize and convey, as the surgical approach for a parotid mass is trans-parotid, while a de novo PPS mass can be approached from an oral or submandibular approach. A large de novo PPS mass may push the parotid deep lobe laterally, however is very unlikely to reach the superficial parotid lobe (which is very likely with a deep lobe tumor). Also, multifocal masses are more likely to be parotid in origin while PPS masses are unifocal [1,2].
FIGURE 68.15 De novo parapharyngeal space (PPS) mass versus parotid mass. (A) Noncontrast axial T1W MRI shows a de novo left PPS mass with fat plane all around the mass (arrows), also separating it from the deep lobe parotid (P). (B) Axial T2W fat-suppressed image shows a hyperintense tumor (pleomorphic adenoma) inseparable from the deep lobe of the left parotid gland (P) extending into left PPS with widening of the stylomandibular tunnel (arrows).
Adenoid cystic or mucoepidermoid cancers of the PPS can show infiltrative margins. PNS to foramen ovale if visible is diagnostic of a malignant tumor (Fig. 68.16) [8].
FIGURE 68.16 Mucoepidermoid carcinoma of parapharyngeal space (PPS). A. Coronal T2W MRI and B & C. Axial contrast enhanced T1W MRI, show a well-defined heterogeneously enhancing mass in the left PPS in A (asterisk) and B. Subtle perineural spread (PNS) to the foramen ovale (arrow in A) is confirmed in C (arrow). The mass is separate from the parotid (outlined in B), displaces medial pterygoid muscle anterolaterally (arrow in B) establishing the epicenter in the PPS. Salivary neoplasms of the PPS are rarely malignant, but the presence of PNS is a pointer to malignancy.
Malignant lesions of the nasopharynx and tonsil (squamous carcinomas, lymphomas, and minor salivary gland malignancies) can also invade the PPS fat and displace it laterally. Sarcomas of the MS may extend into the PPS displacing the fat posteriorly and medially.
Teaching Points
◾neck. PPS mass has a strategic location on each side of the suprahyoid Its displacement helps decide the epicenter of a lateral suprahyoid neck lesion ◾novo It is important to differentiate between a salivary tumor arising de from the PPS salivary rests and a deep lobe parotid tumor as this can change the surgical approach ◾andMRICTisisthethepreferred method of imaging for suspected malignancy preferred method of imaging for suspected infection of the PPS
Parotid Space Boundaries
The PS extends superiorly from the external auditory canal and mastoid tip to the angle of the mandible inferiorly. The superficial layer of the deep cervical fascia encloses the PS; and the MS lies directly anterior to it (Fig. 68.1). PPS lies anteromedial to the PS while the CS which is posteromedial to it is separated by the posterior belly of the digastric muscle [1,2].
The PS contains the parotid gland, the largest salivary gland in the body. The facial nerve passes through this gland entering through its posterior border and arbitrarily divides the parotid gland into the superficial and deep lobes. The facial nerve divides into five terminal branches within the gland that innervate the muscles of facial expression; however, the parotid does not receive innervation from the VII nerve. The facial nerve is not identified on standard imaging. Hence, the retromandibular vein that passes through the parotid and lies just medial to the facial nerve is used as an imaging landmark to demarcate the superficial from the deep lobe. This information is important as a benign tumor localized only to the superficial lobe requires superficial parotidectomy alone. A line passing along the lateral margin of the retromandibular vein extending up to the posterior belly of digastric approximates the plane of the facial nerve (Fig. 68.17) [9]. The external carotid artery also passes through the parotid gland, and divides into its terminal branches, the superficial temporal and internal maxillary artery. The retromandibular vein is seen lateral to the external carotid artery (Fig. 68.17).
FIGURE 68.17 Parotid space anatomy. Axial CT shows fatty replacement in the parotid gland. Arrows show the retromandibular veins (RMV) and approximate location of the facial nerve (curved dashed lines) lateral to the RMV. The facial nerve divides the gland into a deep lobe (medial) and superficial lobe (lateral).
The parotid gland also contains about 20 intraparotid lymph nodes, which receive drainage from the adjacent scalp, cheek, and external auditory canal. This is the only salivary gland to contain lymph nodes within, owing to late encapsulation of the gland embryologically. Lesions of the PS are shown in Table 68.5. Table 68.5 Lesions of the Parotid space Developmental
Epithelial cyst a. First branchial cleft cyst Vascular anomalies a. Hemangiomas* (in infants)
◾ ◾
b. Vascular malformations* High flow (AVMs and AVFs) Low flow (venous/lymphatic/mixed malformation) Infections and inflammatory
a. Parotitis—acute and chronic b. Benign lymphoepithelial lesions in HIV c. Sjogren’s syndrome d. Reactive adenopathy e. Sarcoidosis
Benign tumor
a. Benign mixed tumor* b. Warthin tumor* c. Oncocytoma d. Myoepithelioma e. Monomorphic adenoma f. Basal cell adenoma g. Schwannoma/neurofibroma (seventh nerve) h. Lipoma
Malignant tumor
a. Mucoepidermoid carcinoma* b. Adenoid cystic carcinoma* c. Acinic cell carcinoma d. Adenocarcinoma e. Squamous cell carcinoma f. Lymphoma g. Metastases
Imaging Methods for PS Lesions CT, MRI, and USG have nearly completely replaced plain films and sialograms for imaging PS lesions. CT is the technique of choice for inflammatory lesions of the PS. CT is superior for detecting calcifications and calculi within the parotid gland and its ductal system. For evaluation of salivary gland masses, contrast-enhanced MRI is the preferred technique, although CT may also be used. MRI is superior in depicting the perineural
and intracranial spread of disease. Diffusion-weighted imaging with apparent diffusion coefficient (ADC) value calculation helps differentiation between benign and malignant tumors. Dynamic contrast enhanced MR imaging is another promising tool to aid differentiation of benign and malignant tumours using time intensity curve pattern of enhancement and washout. USG can well delineate the pathology of the superficial parotid gland but cannot demonstrate lesions of the deep lobe of the parotid gland. However, USG is a useful technique to evaluate superficial parotid lesions in pregnant women and children. USG is also useful to guide fine needle aspiration cytology/biopsy.
Imaging Features of Common PS Lesions Developmental Lesions The imaging features of vascular anomalies have already been discussed in earlier sections. Hemangiomas are the most common salivary gland masses in infants. First BCC is seen within the parotid and around the parotid/external auditory canal region. It appears as a cystic lesion when uncomplicated. When the cyst is infected, enhancing wall thickening and fluid levels may be seen and a sinus tract may be seen up to the external auditory canal [9]. Inflammatory Lesions/Infections Parotitis or inflammation of the parotid gland may be acute or chronic in nature. Acute parotitis can result from infection or obstruction of the parotid duct due to a calculus. Obstructive causes are not as common in the inflammation of the parotid gland as in the submandibular gland. This is because the submandibular gland has more viscous and alkaline secretions and an uphill course of its duct that predisposes to calculi formation, unlike the parotid gland. Infectious causes include bacteria (Staphylococcus aureus), and viruses (Paramyxovirus), and uncommonly, mycobacteria and fungi [10]. Bacterial parotitis predominates in neonates and adults greater than 50 years of age. Bacterial parotitis is usually unilateral, often seen in debilitated patients with poor oral hygiene. Dehydration is also a predisposing factor for bacterial parotitis. Viral parotitis is most frequently encountered in children with a peak age between 5 and 8 years. Two-thirds of these cases are bilateral [11]. Acute parotitis manifests as an enlarged heterogeneous parotid gland with well-defined or ill-defined margins. Surrounding fat and platysma show infiltration. Intraparotid abscesses may be seen which originates from the
necrotic intraparotid lymph nodes. Chronic parotitis arises from recurrent infections, as well as noninfectious causes like autoimmune disease and prior radiation therapy. It may also be idiopathic. In chronic parotitis, the gland may be enlarged and heterogeneous with a dilated ductal system. Endstage chronic parotitis is characterized by atrophy of the gland with small calcific foci within [11]. Chronic recurrent parotitis is a rare inflammatory disease, which usually has an onset between the ages of 2 and 6 years. The pathogenesis is unclear. It may be seen as unilateral or bilateral disease with recurrent episodes of inflammation. The glands appear enlarged and heterogeneous with hyperintense foci on T2-weighted MR images. Differential diagnosis includes benign lymphoepithelial lesions of human immunodeficiency viruses (HIV) and Sjogren syndrome [12]. Benign lymphoepithelial lesions of HIV are seen as cystic and solid lesions involving bilateral enlarged parotid glands (Fig. 68.18). Additional findings of cervical adenopathy, enlarged adenoids, faucial, and lingual tonsillar hypertrophy in a patient with HIV can provide a clue to the correct diagnosis [9].
FIGURE 68.18 Benign lymphoepithelial cysts. Axial T2W MRI shows well-defined cysts in bilateral parotid glands (arrows). No mural nodules are seen.
Sjogren syndrome is a chronic autoimmune disorder that primarily affects the salivary glands. The early stage is characterized by bilaterally enlarged parotid glands with hyperdense parenchyma on CT. With disease progression, gland destruction and fat deposition occur leading to atrophied glands with multiple punctate calcific specks/microliths. MRI may show inhomogeneous parenchyma with salt and pepper appearance on T1weighted images, salt representing fatty areas and pepper the calcified specks [13]. In advanced stages, a multicystic honeycomb or miliary pattern may be seen involving the atrophied glands and is diagnostic (Fig. 68.19). Primary Sjogren syndrome has a greater risk of development of NHL [9].
FIGURE 68.19 Sjogren’s disease. Axial T2W MRI. Arrows show bilateral parotids with a multicystic honeycomb appearance (miliary pattern, arrows), which is diagnostic and represents advanced disease.
Tumors Tumors of the PS may be benign or malignant. About 80% of tumors involving the parotid gland are benign and 80% of benign parotid tumors occur in the superficial parotid gland. Pleomorphic adenoma is the most
common benign parotid tumor comprising 70–80% of benign tumors. It is also known as benign mixed tumor (BMT) reflecting the heterogeneous contents of the tumor on histology. It is seen more often in middle-aged females. While small tumors are well defined and homogeneous, larger tumors are lobulated and heterogeneous in appearance [9,14]. On MR, BMT is hypointense on T1W images and hyperintense on T2W images. Intense high signal on T2-weighted images with homogeneity can resemble a parotid cystic lesion. However, the tumor enhances avidly on contrast administration that can help distinguish it from a cyst. Diffusionweighted MRI reveals facilitated diffusion with a high ADC value (Fig. 68.20). The presence of dystrophic calcification within a parotid mass highly favors the diagnosis of BMT. When BMT is seen to arise from the deep lobe of the parotid gland, anteromedial deviation of the parapharyngeal fat, and widening of the stylomandibular tunnel are the pointers to the origin of the mass (Fig. 68.15B).
FIGURE 68.20 Pleomorphic adenoma (benign mixed tumor). (A) Axial T2W MRI shows well-defined cystic appearing hyperintense mass in the parotid superficial lobe (arrows) that shows homogeneous postcontrast enhancement in B and facilitated diffusion on the ADC image in C.
Despite being benign, BMT is surgically resected owing to cosmetic reasons and the risk of malignant transformation. When resection is not complete, there is a high chance of tumor recurrence. Recurrence is seen as small clusters of soft tissue masses. Malignant transformation of BMT can occur in up to 15% of tumors, the risk of which is proportional to the duration of the lesion in situ (10–15 years), size of the lesion, and age of the patient. The risk is also higher in recurrent tumors. Malignant transformation may be suspected when there is rapid growth or fresh onset of facial palsy/pain in a pre-existing parotid mass [15]. Three malignant derivatives are known, carcinoma ex pleomorphic adenoma , which is the commonest, malignant mixed tumor (carcinosarcoma) and metastasizing pleomorphic adenoma. Carcinoma ex
pleomorphic adenoma develops in a preexisting long-standing pleomorphic adenoma or a case of previously operated pleomorphic adenoma. On imaging, irregular and focal/completely invasive margins can be seen in a previously well-circumscribed parotid mass along with heterogeneous T2 signal on MRI. Low T2 signal intensity areas are typical with some high T2 signal intensity foci representing pre-existing benign areas (Fig. 68.21). Diffusion MRI reveals restriction and low ADC values in contrast to BMT. In metastasizing pleomorphic adenoma, the least common type, multiple metastases are seen involving the lungs, bones and soft tissues while the histological appearance is “benign” [9,15].
FIGURE 68.21 Carcinoma ex pleomorphic adenoma. Axial T2W MRI in a long-standing case of left parotid pleomorphic adenoma shows malignant transformation seen as areas of T2 low signal (small arrows) interspersed with high-intensity foci that represent pre-existing benign elements (long arrow). The lobulated mass has invaded parapharyngeal space and displaced the lateral pharyngeal wall to the right.
Warthin tumor (papillary cystadenoma lymphomatosum/adenolymphoma) is the second most common tumor involving the parotid gland, accounting for 5–10% of parotid tumors. It is exclusive to the parotid gland and the periparotid or upper cervical lymph nodes, as it is believed to arise from salivary duct remnants entrapped within these lymph nodes. It is typically seen in middle-aged men with a history of smoking. Most often, it is seen in the tail of the parotid or the pretragal location, the common sites of intraparotid lymph nodes. Although most often single, multiple Warthin tumors, unilateral or bilateral may be seen in approximately 10% of patients. Internal heterogeneity is a key imaging finding and the tumor appears as a
well-circumscribed solid-cystic mass [16]. Enhancing mural nodule (Fig. 68.22) favors the diagnosis of Warthin tumor over BCC or lymphoepithelial cyst of the parotid. Diffusion-weighted MRI reveals low ADC values in the solid component that overlap with malignancy [9].
FIGURE 68.22 Warthin tumor. Coronal CT reformation shows a welldefined solid-cystic lesion in the tail of the right parotid (solid arrow), with enhancing mural nodule (dashed arrow).
Other uncommon benign tumors of the parotid gland include oncocytoma, myoepithelioma, monomorphic adenoma, and basal cell adenoma. These have no characteristic imaging features and need histopathology for an accurate diagnosis. Rarely, parotid lipoma and intraparotid facial nerve schwannomas may be encountered [9]. Schwannomas are hypovascular, may appear heterogeneous, show cystic degeneration and at times display the target sign, previously described in NFs (in lesions of MS). The mass may be seen extending along the stylomastoid foramen [17]. The most common malignant tumors of the parotid gland are MEC and ACC. Other uncommon malignancies to involve the parotid gland include acinic cell carcinoma, adenocarcinoma, and squamous cell carcinoma. Features that suggest malignancy are ill-defined/irregular borders,
heterogeneous enhancement, infiltration into surrounding structures, and PNS. However, the appearance varies with the grade of the tumor and a lowgrade malignant mass can depict well-defined margins with a homogeneous bright signal on T2-weighted images, making it difficult to distinguish it from a benign tumor. Enlarged lymph nodes when present also favour the diagnosis of malignancy. MEC, the most common malignant parotid tumor, has a propensity to develop lymph nodal spread, mainly to level II cervical lymph nodes. Intraparotid lymph nodes may also be enlarged. ACC, the second commonest malignant lesion of the parotid gland, has a greater tendency toward PNS than MEC (Fig. 68.8). Metastasis to lungs and bones are more frequent than lymph nodal metastases in ACC [16]. When a parotid malignancy is suspected or known, a careful evaluation of V and VII cranial nerves must be done to look for PNS, which is associated with decreased survival and increased risk of recurrence and metastases. The auriculotemporal nerve (branch of the mandibular division of trigeminal nerve) coursing between the sphenomandibular ligament and neck of the mandible can act as a conduit of the spread of disease between the VII and V cranial nerves in case of parotid malignancy (Fig. 68.8). PNS can be seen on CT as widening of skull foramen and replacement of fat in the foramen. PNS is best assessed on MRI using nonfat-saturated T1W images and contrastenhanced fat-saturated T1W images, which depict replacement of fat in the skull foramina and irregular thickening with enhancement of the involved nerve [9]. Lymphoma and metastases are also known to involve the parotid gland, can show multiplicity, and have unilateral/bilateral involvement. No characteristic imaging features are seen. Pseudolesion With age, the parotid gland undergoes fatty change (Fig. 68.17). Sometimes, premature asymmetric fatty change of the parotid gland occurs and this should not be mistaken for pathology either in the same gland or as a lesion in the contralateral gland [1,2].
Teaching Points
◾deviation A deep lobe parotid tumor typically causes anteromedial of the parapharyngeal fat and widening of the stylomandibular notch ◾weighted Irregular and invasive margins and areas of low signal on T2images are highly suggestive of parotid malignancy ◾
◾must When parotid malignancy is known or suspected, careful attention be paid to the V and VII cranial nerves to rule out PNS ◾toThin section fat-saturated postcontrast MRI is the best technique evaluate perineural tumor spread ◾Warthin Differential diagnoses of bilateral and multifocal tumors include tumors, NHL, acinic cell carcinoma, oncocytoma, and metastatic nodes
Carotid Space Boundaries The CS extends from the skull base to the aortic arch, its superior margin reaching into the jugular foramen. Craniocaudally, the CS can be divided into the suprahyoid portion, the infrahyoid portion, and the mediastinal part. In the suprahyoid neck, its anterior boundary is the PPS and styloid process while its lateral boundary is the PS from, which, is separated by the posterior belly of the digastric muscle. Medially, it is bordered by the lateral extension of the RPS (Fig. 68.1) [1,2].
Contents The contents of the CS are:
◾ Internal carotid artery (ICA, in suprahyoid CS up to carotid bifurcation) ◾ Common carotid artery (in infrahyoid and mediastinal CS; ends at carotid bifurcation) ◾ IJV (suprahyoid and infrahyoid CS) ◾ IX, XI, XII nerves (at the level of nasopharynx up to soft palate) ◾ X nerve (entire CS) ◾ Sympathetic plexus (entire CS) ◾ (from skull base to carotid bifurcation) ◾ Paraganglia Nodes (entire CS)
The carotid sheath that envelops the above contents has all the three layers of the cervical fascia. The IX, XI, and XII nerves exit the CS at the level of the soft palate, while the X nerve continues in the CS and is located in a posterior groove between the carotid artery and IJV. The sympathetic plexus is located along the posteromedial wall of the fascial sheath of the CS. Paraganglia are groups of chromaffin secretory cells of neural crest origin and may be sympathetic or parasympathetic. In the extracranial head–neck region, paraganglia, including the jugulotympanicum, vagal and laryngeal
paraganglia, and carotid bodies, are parasympathetic and are distributed along the IX and X nerves and their branches.
Lesions of the CS The lesions of the CS can be classified as pseudolesions, vascular, inflammatory/infective, and tumors (Table 68.6) [1,2]. Table 68.6 Lesions of the Carotid Space Pseudolesi ons
a. Asymmetric internal jugular vein* b. Ectasia of internal or common carotid artery*
Vascular
Inflammato ry
Benign tumor
Malignant tumor
Internal carotid artery a. Thrombosis b. Aneurysm c. Pseudoaneurysm* d. Dissection Internal jugular vein a. Thrombosis b. Thrombophlebitis a. Cellulitis b. Abscess c. Adenopathy* Reactive/suppurative/tuberculous
◾
Nerve origin a. Schwannoma* b. Neurofibroma Paraganglia a. Glomus jugulare* b. Glomus vagale c. Carotid body tumor* a. Metastatic nodes (thyroid cancer*, squamous cell carcinoma*) b. Neuroblastoma (children)* c. Malignant peripheral nerve sheath tumor d. Malignant paragangliomas
e. Sarcomas f. Non-Hodgkin lymphoma g. Extramedullary plasmacystoma *Represents the more common lesions.
Imaging Methods for CS Lesions CT and MRI are complementary methods for imaging CS lesions. While CT is best for showing calcification and relation to bony structures, MRI is superior for soft tissue characterization, to see the relation with the vessels, and for demonstrating intracranial extension. MRI may also help diagnose paragangliomas by depicting characteristic features (described below). Contrast-enhanced MR angiography is useful to rule out multiplicity in paragangliomas. Conventional angiography is performed in large vagal paragangliomas and carotid body tumors and helps demonstrate multicentricity, blood supply, and feeders for preoperative embolization. Angiography with balloon occlusion test is performed if carotid sacrifice is anticipated in the treatment for paragangliomas/aneurysms. Nuclear medicine has a role to play in cases where CT and MRI are equivocal and unable to distinguish between paragangliomas and schwannomas. Somatostatin receptor-based SPECT/PET scanning (using IIIindium or 68Ga), octreotide (somatostatin analog) scintigraphy, and 18FDOPA PET imaging have very high sensitivity for detecting paragangliomas [18].
Imaging Features of CS Lesions Pseudolesions Nearly 60% of patients have an asymmetric IJV with the right vein being larger in 68%. USG is very useful for demonstrating the enlarged IJV and helps choose the safe side for blind catheterization [19]. An ectatic ICA may appear as a pulsatile mass in the neck but is easily diagnosed as a tubular enhancing structure on CT/MRI. The finding of ectasia should always be conveyed especially when the artery is seen coursing beneath the pharyngeal mucosa to avoid inadvertent biopsy of a clinically suspected mass. Vascular Lesions IJV thrombosis is extremely rare and the commonest cause is due to catheterization. USG with Doppler depicts the hyperechoic thrombus with high sensitivity and specificity. CT shows the filling defect and MRI shows
the loss of flow void with high T1 signal in the subacute phase due to the methemoglobin. Acute thrombophlebitis is seen as enhancement of the walls of the vein [2]. ICA thrombus may present with cerebrovascular accident and is seen as complete/partial luminal occlusion. True aneurysm of the extracranial carotid artery is rare, can affect any segment of the ICA and common carotid artery, and when present represents a serious clinical condition. Surgical treatment is warranted as conservative management has high mortality rates due to rupture. Aneurysms of the common carotid bifurcation are the commonest and show fusiform dilatation of the segment, while aneurysms of the middle and distal ICA are saccular. The lumen may be partially or completely thrombosed, with risk of distal embolization and stroke in such cases. CT and MRI angiography are often used for diagnosis, but conventional digital subtraction angiography is the gold standard [20]. Pseudoaneurysms are formed due to penetrating trauma. Infections Cellulitis of the CS is seen as stranding of the fat surrounding the vessels or loss of soft tissue definition around structures. Infections of the CS are usually due to extension from adjacent spaces and are usually seen in extremely sick patients. A CS abscess is seen as a focal fluid collection with enhancing walls and represents a surgical emergency. Tuberculous CS nodes are more often seen in the lower neck and the supraclavicular region. Benign Tumors A recent systematic review revealed that the vast majority of the CS tumors were benign with the bulk formed by paragangliomas and neurogenic tumors. In their series of 455 CS tumors, paragangliomas formed 52%, schwannomas 27%, and NFs 9% [18]. These masses grow slowly over the years and along with a palpable neck mass, present with symptoms of compressive neuropathy of the cranial nerves (hoarseness, dysphagia, and paralysis of the tongue). Sympathetic plexus involvement can give rise to Horner’s syndrome [18]. Paragangliomas are named according to their location with glomus jugulare seen centered in the jugular foramen (Fig. 68.23), carotid body tumor seen typically splaying the crotch of the carotid bifurcation (Fig. 68.24), and glomus vagale seen along the vagal paraganglia located below the skull base and above the carotid bifurcation (Fig. 68.25). Multicentric paragangliomas are seen in less than 10% of patients, but the incidence is higher in familial cases (30%) [21]. Paragangliomas may become large in size and a glomus jugulare can extend both intracranially into the basal cisterns and extracranially toward the carotid bifurcation. Carotid body tumors can also extend superiorly toward the skull base and inferiorly spill
below the carotid bifurcation. Paragangliomas though do not originate in the infrahyoid neck below the carotid bifurcation as paraganglia are absent in this region [2]. Nerve sheath tumors however can occur anywhere in the CS from the jugular foramen to the root of the neck (Fig. 68.26). Despite the large size, the benign CS tumors are well-circumscribed and noninfiltrative.
FIGURE 68.23 Glomus jugulare. (A) Coronal dynamic CT reformation shows brightly enhancing mass eroding jugular foramen (short arrow), also extending into the hypoglossal canal (long arrow). (B) Axial CT shows resultant hemiatrophy of the tongue on the right side seen as fatty replacement (arrow).
FIGURE 68.24 Carotid body tumor. (A) Axial T2W MRI shows a brightly hyperintense mass at the carotid bifurcation. (B) MR angiogram. Note splaying of the internal carotid artery (long arrows) and external carotid artery (short arrows) in A and B.
FIGURE 68.25 Glomus vagale. (A) Contrast-enhanced axial T1W image. (B) Coronal T2W image show characteristic internal flow voids seen as dark spots and serpiginous channels (arrows). Location of the tumor below the skull base and above the carotid bifurcation indicate a diagnosis of glomus vagale.
FIGURE 68.26 Schwannoma with degeneration and calcification. (A) Axial contrast CT. (B) Coronal CT reformation shows a large sharply defined mass with coarse calcification (black arrows) in the suprahyoid and infrahyoid carotid space (CS) displacing the common carotid artery (long arrow) anteriorly, typical of a CS mass. The internal jugular vein is severely compressed and not seen. The short white arrow shows the external jugular vein. Images acquired in the early phase after contrast injection show no enhancement of the mass reflecting the hypovascular nature. The mass abuts the thyroid (T) in B but does not invade.
It is useful to differentiate neurogenic tumors from paragangliomas, as biopsy is avoidable in the latter. Also, planning surgery for carotid body tumors may require studying the extent of its contact with the ICA on MRI/CT. Circumferential contact of more than three-fourths of the circumference of the ICA with the tumor may require carotid sacrifice and grafting if surgery is contemplated and needs to be mentioned [22]. Characteristic MRI appearances of paragangliomas, particularly when larger than 2 cm in size, are internal flow voids (Fig. 68.25) in a T2 hyperintense mass (due to high flow serpiginous vessels), as well as the “salt and pepper” appearance on T1-weighted images. Salt represents the slow flow or hemorrhagic areas whereas pepper represents the flow voids. Postcontrast images show intense homogeneous early enhancement [1,2,23]. Large schwannomas are slightly hyperintense on T2-weighted MRI, with heterogeneous enhancement due to cystic degeneration and at times may display calcification (Fig. 68.26). Although hypovascular, marked enhancement may be seen in a schwannoma on delayed contrast-enhanced T1-weighted images acquired after 60 seconds due to poor venous drainage and contrast pooling. Hence, dynamic biphasic CT or MRI may be valuable in differentiating paragangliomas from schwannomas. The early arterial phase at 25–35 seconds will reveal the hypovascular nature of a schwannoma (Fig. 68.26). Paragangliomas on the other hand show striking
enhancement in the arterial phase with progressive washout which is maximum on the delayed phase after 3 minutes [23]. When CT and MRI are still equivocal, nuclear medicine may resolve the dilemma as discussed earlier [18]. Both glomus vagale and vagal schwannomas displace the carotid sheath anteriorly/anterolaterally, however vagal schwannoma is also known to splay the ICA and IJV [24]. Sympathetic plexus schwannomas can displace the carotid sheath laterally [1,23]. Glomus jugulare and schwannoma of the jugular foramen can also be differentiated by the pattern of bone involvement. While a glomus tumor causes permeative lytic erosion of the surrounding bone with moth-eaten appearance, a schwannoma causes smooth scalloping of the jugular foramen [2]. Occasionally, extracranial meningiomas may be seen in the CS including at the jugular foramen. These are hypovascular tumors often showing specks or amorphous dense calcification within. They may have an intracranial component giving a dumbbell shape to the mass or show a dural tail. If located at the skull base, hyperostosis of bony margins or at times erosion may be seen [2,23]. Malignant Tumors Primary malignant tumors account for only 13% of tumors of the CS (Table 68.6). Malignant paragangliomas form less than 10% of head and neck paragangliomas. The criterion for malignancy in paragangliomas is the presence of distant metastasis in non-neuroendocrine tissue, although the primary tumor may look similar to a benign paraganglioma [21]. NHL may present as homogenous single/multiple noninfiltrative masses. The other primary malignant neoplasms do not have characteristic imaging appearances but display infiltrative margins with an invasion of adjacent structures. Any CS mass with unusual features raising suspicion of malignancy warrants a biopsy [18]. Metastases in deep cervical nodes are the other more common malignant lesions of the CS. When the metastases are seen in level II–III lymph nodes with/without the involvement of level IV nodes, the primary lesion is most likely squamous cancer of the tongue base, palatine tonsil, larynx, and hypopharynx. When the metastases are seen in level II and level V nodes, the likely primary is the nasopharynx. However, if the metastatic nodes are localized to level IV and supraclavicular region alone, the primary could be in the thyroid or elsewhere in the thorax or abdomen (particularly if the left supraclavicular node is involved).
Teaching Points
◾
◾located A CS lesion is seen centered in the area of the ICA and IJV and posterior to the PPS ◾typically Common CS tumors are paragangliomas and schwannomas; most displace the carotid sheath anterolaterally, except for sympathetic plexus schwannomas that displace the sheath laterally. In contrast, the PPS lesions or deep lobe PS lesions displace the carotid sheath posteriorly Characteristic imaging features aided with optimal imaging technique helps differentiate paragangliomas from the hypovascular nerve sheath tumors Diagnosis of a paraganglioma should ideally prompt a search for other synchronous lesions. Contrast-enhanced MR angiography is useful for demonstrating multiplicity
◾ ◾
Retropharyngeal Space Boundaries RPS is a potential space that extends superiorly from the skull base to the mediastinum inferiorly. It lies between the middle layer of cervical fascia/visceral fascia anteriorly and the prevertebral fascia posteriorly. A thin slip of deep layer of deep cervical fascia (alar fascia) divides the RPS into two parts, the RPS proper anteriorly and danger space posteriorly. A median raphe may sometimes separate the RPS proper into two halves [25]. RPS proper terminates inferiorly where the alar fascia fuses with the anterior layer of the visceral fascia. The site of fusion is variable, lying between T1 and T6 vertebrae. The danger space extends further inferiorly up to the diaphragm. Infection arising in this space can extend inferiorly into the posterior mediastinum, giving the danger space its name. As alar fascia is an incomplete barrier, RPS proper and danger space are often clubbed together as RPS from an imaging perspective [25]. RPS is bordered anteriorly by pharyngeal mucosal space, posteriorly by the PVS, and laterally on either side by the CS.
Contents The contents of the RPS are: Suprahyoid RPS
◾ tissue ◾ Adipose Lymph nodes (medial and lateral group)
Infrahyoid RPS
◾ Adipose tissue
While the suprahyoid part of RPS contains both adipose tissue and lymph nodes, the infrahyoid part of RPS contains only adipose tissue. The retropharyngeal (RP) lymph nodes are categorized into two groups-medial and lateral. The medial group of lymph nodes lies close to the midline and atrophy before puberty. The lateral group of lymph nodes, also called the nodes of Rouviere, is located ventral/ventrolateral to the longus colli and medial to the CS. They persist during adulthood [26].
Lesions of the RPS The lesions of the RPS are shown in Table 68.7. Table 68.7 Lesions of the Retropharyngeal Space Develop mental
Inflamma tory
Vascular anomalies a. Hemangioma b. Vascular malformations High flow (AVMs) Low flow (venous/lymphatic/mixed malformation)
◾ ◾
a. Retropharyngeal edema/fluid* b. Reactive lymph node enlargement* c. Suppurative adenitis* d. Retropharyngeal abscess*
Benign tumor
a. Lipoma b. Schwannoma
Malignan t tumor
a. Direct invasion from nasopharyngeal carcinoma*/oropharyngeal carcinoma/nasopharyngeal non-Hodgkin lymphoma* rhadomyosarcoma b. Retropharyngeal nodal metastasis from Carcinoma nasopharynx* Squamous cell carcinoma oropharynx/hypopharynx* Papillary thyroid carcinoma* Sinonasal carcinoma Melanoma c. Non-Hodgkin lymphoma in retropharyngeal nodes
Imaging Methods for RPS Lesions Contrast-enhanced CT is the best tool to evaluate infection of RPS. Also, CT is advantageous in the detection of foreign bodies, calcification of longus colli tendon, and bony destruction in osteomyelitis that can affect the adjacent PVS. In the case of a RP abscess, imaging must extend into the posterior mediastinum, ideally up to the domes of the diaphragm to depict the inferior extent of the abscess. MR shows greater sensitivity in the detection of RPS adenopathy than CT.
Imaging Features of Common RPS Lesions Retropharyngeal Edema/Fluid Nonabscess fluid or edema in the RPS is seen as fluid without enhancement or mass effect (Fig. 68.27A). It can be attributed to a variety of inflammatory and noninflammatory causes [27].
FIGURE 68.27 (A) Retropharyngeal (RP) edema. Contrast CT shows fluid in the RP space (arrows). (B) Suppurative adenitis. Contrastenhanced MRI shows a right RP node with central fluid intensity and enhancing rim (long arrow). Surrounding inflammation is seen as enhancement (short arrows).
The various causes of RPS edema/nonabscess fluid are:
◾ Acute pharyngitis/tonsillitis ◾ Acute calcific tendinitis of longus colli muscle ◾ Acute thrombosis of IJV ◾ Prior surgery/radiation ◾ Trauma resulting in RPS hemorrhage ◾ ◾ Angioedema Kawasaki disease
Acute pharyngitis/tonsillitis is an uncommon cause of RPS edema in children. Diffuse swelling of the pharyngeal mucosa can be seen if there is accompanying acute pharyngitis. Enlarged tonsils with striated enhancement patterns are suggestive of acute tonsillitis. Pharyngitis and tonsillitis may also be encountered together [28]. Acute calcific tendinitis of longus colli tendon secondary to hydroxyapatite crystals deposition can result in an inflammatory response and RPS edema. This is best seen on CT as calcific foci within the longus colli tendons, typically at the C1–C2 level. The longus colli muscle belly may be enlarged but with preserved muscle striations. This is a self-limiting condition that responds to conservative management with nonsteroidal antiinflammatory drugs and steroids [29,30]. IJV thrombosis is another cause of fluid in RPS that can result from an indwelling catheter, infection, malignancy, and hypercoagulable states. Prior radiation and surgery can result in RPS fluid owing to lymphatic distension. RP hematoma can result from trauma. Other causes of RP fluid are angioedema and Kawasaki disease. Angioedema can be hereditary, anaphylactic, or idiopathic in nature, and
results in rapid airway compromise. Kawasaki disease is an acute systemic vasculitis of medium and small-sized arteries, typically seen in children less than 5 years of age [27,30]. Due to varied causes of RPS edema, it is important to actively look for all the ancillary features that can enable a correct diagnosis and aid appropriate management. When fluid is seen in the RPS, it must also be distinguished from RP abscess as the latter requires emergency surgical drainage. Reactive Adenopathy and Suppurative Retropharyngeal Adenitis RP nodes can get infected secondary to infection from tonsils/pharynx, paranasal sinus, middle ear, and PVS. These nodes enlarge as inflammatory cells proliferate within these nodes leading to reactive adenopathy. Reactive nodes are seen as mildly enlarged (usually 1 cm), low density/fluid intensity rounded or oval nodes with thin rim enhancement seen on either side of the RPS. Surrounding inflammation and loss of fat planes can be seen accompanying the suppurative node (Fig. 68.27B) [31]. Suppurative RP nodes can enlarge and subsequently rupture leading to RP abscess formation (Fig. 68.28). It is important to differentiate between suppurative RP adenitis and RP abscess formation. While suppurative adenitis is treated with medical therapy, prompt surgical drainage is done for an RP abscess.
FIGURE 68.28 Retropharyngeal (RP) abscess. (A) Sagittal CT reformation shows RP abscess extending from suprahyoid to infrahyoid neck (arrows). (B) Axial CT shows RP abscess displaces airspace of the pharynx (asterisk) anteriorly and extends from side to side (white arrows). An incomplete median raphe cleaves it in the midline. The black arrow shows the longus colli muscle to be displaced posteriorly by the RP abscess.
Retropharyngeal Abscess RP abscess mainly results from rupture of suppurative RP adenitis. The other causes are the spread of infection from contiguous PVS, pharyngeal penetrating foreign body, or trauma. RP abscess usually shows thick enhancing walls (Fig. 68.28A and B) and may also have air foci within. There is mass effect on the pharynx anteriorly and prevertebral muscles are flattened posteriorly. This is in contrast to RP edema that does not show mass effect/enhancement (Fig. 68.27A). Unlike suppurative adenitis, which is seen on either side of the RPS, RP abscess fills the RPS from side to side (Fig. 68.28B) [31]. RP abscess can extend into the danger space and then inferiorly up to the inferior mediastinum leading to mediastinitis, pericarditis, and empyema. Other complications include the extension of infection into airway, spine, and CS. As these complications can result in significant morbidity and mortality, emergency surgical drainage is done for an RP abscess. Retropharyngeal Space Tumors Neoplasms in the RPS are uncommon. Primary benign tumors may rarely be encountered such as a lipoma, which shows the ovoid configuration and fat attenuation within. Rarely, enlarged thyroid may extend into the RPS. Malignant masses in the RPS are more common than benign lesions. These involve the RPS either by direct invasion from adjacent spaces or as
nodal metastasis. Squamous cell cancers of the pharynx can directly invade the RPS and extend in a craniocaudal direction up to the skull base superiorly [25]. When RP nodes are seen in an adult greater than 30 years of age, the probability of metastasis needs to be considered. RP nodes are the first echelon of nodal spread from nasopharyngeal cancer. Nodal metastases are seen as enlarged rounded to ovoid nodes. They may or may not have central necrosis/extranodal extension. RPS may be the only site of nodal metastases from papillary thyroid cancer. Cystic/heterogeneous nodes with foci of calcification may be seen. These nodes can depict hyperintensity on T1weighted MR images. RP nodes may also be seen in 10% of HPV-positive oropharyngeal cancers and these nodes are typically cystic. Other primary malignancies that can spread to RP nodes include squamous cancers of the hypopharynx and oropharynx, nasal cavity cancers, and melanoma [25]. NHL can also involve the RPS. NHL nodes are seen as enlarged, homogeneously enhancing nodes with involvement of other nodal chains. High-grade NHL can depict necrosis and extranodal spread. Other primary malignancies of the RPS are rare. Pseudolesion Ectatic/tortuous carotid artery can project into the RPS and may be mistaken for a mass on inspection, especially in elderly patients. Careful evaluation of CT/MRI is important to prevent inadvertent biopsy.
Teaching Points
◾displacing A lesion can be localized to RPS when it is seen medial to the CS, the carotid vessels posterolaterally and parapharyngeal fat anterolaterally ◾posteriorly, Pathology of RPS displaces/flattens the prevertebral muscles while pathology of PVS displaces the prevertebral muscles anteriorly ◾from RP edema/nonabscess fluid in the RPS must be distinguished a RP abscess for appropriate triage in the emergency setting ◾implications Various causes of fluid in the RPS have different clinical and management. Ancillary findings that can provide clue to the correct diagnosis must be actively looked for ◾atheWhen RP nodes are seen in an adult greater than 30 years of age, probability of metastasis needs to be considered (especially from pharynx/thyroid primary)
Perivertebral Space Boundaries The PVS extends from the skull base to the level of T4 vertebra in the posterior mediastinum. A thin slip of the deep layer of cervical fascia extends to the transverse processes of the vertebrae, cleaving the space into the anterior prevertebral and posterior paraspinal spaces (Figs. 68.1 and 68.3). The deep layer of deep cervical fascia encloses the prevertebral muscles anteriorly and the paraspinal muscles posteriorly, attaching to the ligamentum nuchae behind [1,2]. The RPS sits just anterior to the PVS. CS is anterolateral to the PVS and the PCS (discussed later) is lateral to the PVS.
Contents Contents of the PVS are: Prevertebral space
◾ Vertebral body and intervertebral disks ◾ Prevertebral muscles (longus colli and capitis) ◾ Scalene muscles (anterior, middle, and posterior) ◾ Vertebral artery and vein ◾ nerve ◾ Phrenic Brachial plexus
Paraspinal space
◾ elements of vertebrae ◾ Posterior Paraspinal musculature
The vertebral arteries and the veins run in the transverse foramina of the vertebral bodies and are the major vessels that supply and drain the posterior cranial fossa and occipital lobes. The phrenic nerve originates from the cervical spinal roots of C3–C5 and crosses the anterior scalene muscle. The roots of the brachial plexus (ventral rami of C5 to T1 nerves) traverse between the anterior and middle scalene muscles and then interrupt the deep layer of cervical fascia to pass into the PCS and then the axilla. The posterior paraspinal portion of the PVS contains the posterior elements of the vertebrae and the paraspinal musculature. The paraspinal muscles include symmetrical small muscles (multifidus, longissimus capitis, splenius capitis, semispinalis, levator scapulae) on either side of the median interspinalis muscle and ligamentum nuchae.
Lesions of the PVS The lesions of the PVS are enumerated in Table 68.8. Table 68.8 Lesions of the Perivertebral Space Vascular (trauma)
a. Vertebral artery dissection b. Vertebral artery aneurysm/pseudoaneurysm c. Prevertebral hematoma
Inflammatory/inf ective
a. Osteomyelitis of spine (tubercular/pyogenic)* b. Longus colli tendinitis c. Rheumatoid arthritis
Benign tumor
Bony origin a. Giant cell tumor b. Osteochondroma and osteoblastoma c. Aneurysmal bone cyst d. Eosinophilic granuloma e. Hemangioma Nerve origin (from brachial plexus) a. Schwannoma b. Neurofibroma
Malignant tumor
Bony origin a. Vertebral metastases* b. Chordoma* c. Multiple myeloma d. Primary malignant tumors of vertebrae (osteosarcoma, Ewing’s sarcoma, chondrosarcoma) Mesenchymal origin a. Mesenchymal tumor of paraspinal musculature (rhabdomyosarcoma in children) Direct invasion from a. Squamous carcinoma of pharynx/larynx b. Non-Hodgkin lymphoma
Degenerative
a. Anterior spinal osteophytes* b. Anterior disk herniation* and discitis c. Hypertrophied facet/uncovertebral joint
Pseudolesion
a. Asymmetric hypertrophy of levator scapulae muscle b. Cervical rib
*Represents the more common lesions.
Imaging Methods for PVS Lesions Plain radiographs provide a quick view of the prevertebral soft tissue thickness. CT and MRI have replaced these and provide a more comprehensive evaluation. Contrast administration is important for delineation of the entire extent of infection/malignancy. Evaluation of the scan on different window settings on CT is important to highlight the lesions of bones as well as soft tissues. The correct window setting helps in accurate diagnosis, for example, calcific tendinitis of longus colli can be entirely missed if bone window settings are not used. MR is an excellent tool to delineate extension into the epidural space.
Imaging Features of Common PVS Lesions Infections/Inflammatory Lesions Spondylodiscitis/osteomyelitis is a common pathology of the PVS. It can occur as a result of pyogenic or tubercular infection. Vertebral endplate erosive changes and disk space narrowing are helpful clues to the diagnosis. Enhancing soft tissue/abscess in prevertebral, paraspinal regions, and epidural space with vertebral body destruction are the other imaging findings (Fig. 68.29). Progressively, there can be vertebral collapse and deformity.
FIGURE 68.29 Perivertebral abscess due to tubercular osteomyelitis. A & B. Sagittal fat-suppressed contrast-enhanced T1W MR images. A shows an abscess with thick enhancing walls (arrows) closely apposed to cervical vertebrae. B shows C4 and C5 vertebrae with altered signal, endplate destruction, and reduced height (arrows). Intervening disk is involved. (C). Axial T2W MRI shows perivertebral space hematoma (dashed arrow) typically lifting the prevertebral muscles anteriorly (solid arrows).
Rheumatoid arthritis can affect the atlantoaxial region of the cervical spine. Erosive changes and inflamed synovium (pannus) can occur around the odontoid process of C2 vertebra. Longus colli tendinitis is best seen on CT as calcific deposits within the longus colli tendon [32]. Trauma and Vascular Lesions Blunt trauma can result in bony, as well as ligamentous injury and result in a perivertebral hematoma (Fig. 68.29C). Vertebral artery (VA) dissection is a common vascular injury in the setting of blunt trauma due to a tear in the arterial wall. This can result in an intramural hematoma when blood collects between intima and media and causes narrowing of the arterial lumen (stenotic VA dissection). When blood collects between the media and adventitia, it results in aneurysmal dilatation of the artery (aneurysmal VA dissection). CT angiography demonstrates the lesions with high sensitivity. MRI is now replacing conventional angiography in demonstrating these lesions. On MRI the hematoma appears as a crescent with hyperintense signal on both T1- and T2-weighted images, adjacent to the vessel lumen [33]. Benign Tumors Brachial plexus schwannoma/NF can involve the PVS. It is seen as a wellcircumscribed mass characteristically situated between anterior and middle scalene muscles. Due to its benign and slow-growing nature, the adjacent bone may show remodeling and the neural foramen may be enlarged (Fig.
68.30). It can be seen as a mass in the extradural space or can be located in both intradural and extradural spaces [29].
FIGURE 68.30 Brachial plexus schwannoma. Axial T2W MRI shows a well-circumscribed solid-cystic mass (thick arrow) between anterior scalene (dashed arrow) and middle scalene muscles (dotted arrow) also causing widening of the cervical intervertebral neural foramen (small arrows).
Malignant Tumors Multiple destructive vertebral lesions can be seen with metastases and multiple myeloma. Metastatic disease is the most common disease of PVS. Metastases may be lytic, sclerotic, or mixed lytic–sclerotic in appearance. They may involve the vertebral body as well as posterior elements. In contrast to spondylodiscitis, disks are typically spared in metastatic disease [1,2]. A diagnosis of chordoma should be considered when a mass is centered in the midline of the spine. Although more common in the sacrococcygeal and spheno-occipital regions, chordoma may also involve the C2–C5 vertebrae. Destruction of vertebral bodies along with the involvement of intervertebral disks and a large accompanying well-defined T2 hyperintense enhancing soft tissue mass is the characteristic imaging appearance of a chordoma [34]. Pseudolesion
Levator scapulae muscle can hypertrophy to help lift the arm in case of atrophy of sternocleidomastoid and trapezius muscles, secondary to injury to the spinal accessory nerve. This hypertrophy must not be misinterpreted as a mass.
Teaching Points
◾prevertebral A lesion can be localized to the PVS when it is seen to lift the muscles anteriorly and/or depicts vertebral body destruction. This is in contrast to a lesion in the RPS, which flattens the prevertebral muscles posteriorly A lesion in the PVS bows out the fat in the PCS, while a lesion in the PCS results in mass effect on the paraspinal musculature If there is an infection/malignancy in PVS, epidural space extension must be looked for. Epidural extension is the path of least resistance for disease spread from PVS, as the deep layer of cervical fascia acts as a barrier to the spread of disease anteriorly into the RPS
◾ ◾
Posterior Cervical Space Boundaries The bulk of the PCS is located in the infrahyoid neck with a small part extending into the lower part of the suprahyoid neck. This space can be studied by cross-sectional imaging as well as USG [2]. In the infrahyoid neck it is seen as a triangular area bounded anteromedially by the carotid sheath, anterolaterally by the sternocleidomastoid muscle, and posteriorly and medially by the perivertebral muscles (Fig. 68.3).
Lesions of the PCS The lesions are shown in Table 68.9. Table 68.9 Lesions of the Posterior Cervical Space Developmental
Epithelial cyst a. Third branchial cleft cyst Vascular anomalies a. Hemangiomas b. Vascular malformations High flow (AVMs and AVFs) Low flow (venous*/lymphatic*/mixed malformation)
◾ ◾
Inflammatory/infe ction
a. Cellulitis/abscess b. Adenopathy* Reactive/suppurative/tuberculous
Benign tumor
Nerve origin a. Schwannoma b. Neurofibroma Fat a. Lipoma*
Malignant tumor
Pseudolesion
a. Metastatic adenopathy from squamous carcinoma* b. Non-Hodgkin/Hodgkin lymphoma* c. Liposarcoma (rare) a. Cervical rib
Imaging Features of PCS Lesions Infections Infective processes of the PCS involve the nodes. Tuberculous nodes appear enlarged and heterogeneous, with necrosis and calcification. The
characteristic feature is matting of the nodes with surrounding fat showing inflammatory changes. USG with Color Doppler is very useful for evaluating the nodes. In addition to the above-described features visible on grayscale USG, the reactive and tuberculous nodes show prominent central/hilar vascularity while metastatic nodes show absent or peripheral vascularity. USG also helps guide fine needle aspiration of the nodes. Developmental Lesions LMs are very common in the PCS and their features have been described in the MS lesions. A unilocular thin-walled cystic lesion in the PCS suggests the diagnosis of third BCC. Although LMs are usually multilocular, a unilocular LM may mimic a BCC (Fig. 68.31).
FIGURE 68.31 Lymphatic malformation of posterior cervical space (PCS). (A) Axial T2W MRI shows well-defined septated cystic PCS lesion. (B) Axial fat-suppressed contrast-enhanced T1W MRI shows no enhancement of the cyst except for the wall (long arrow) and a septa (short arrow). A venous malformation would show delayed heterogeneous enhancement.
Benign and Malignant Tumors Benign nerve sheath tumors are infrequent and have a similar appearance as described previously. Tracing the origin of the mass from the brachial plexus between the anterior and middle scalene muscles can be a clue to the correct diagnosis. About 25% of lipomas occur in the head neck and are commonly seen in the PCS. They show homogeneous fat density or intensity. Welldifferentiated liposarcomas or atypical lipomatous tumors of the head and
neck region are rare. These are locally aggressive tumors with intermediate malignant potential. Features that suggest this diagnosis are (1) presence of nonlipomatous areas interspersed within lipomatous components, (2) >2 mm thick enhancing septae, (3) contrast enhancement, (4) presence of nodules, and (5) lesion size >10 cm [35]. Hence any deviation from the typical appearance of a lipoma needs biopsy evaluation. Metastatic adenopathy is considered localized to the PCS if there is a fat plane between the node and the carotid sheath. If the node closely abuts the carotid sheath, it is considered to be a CS lesion [2]. This distinction though is theoretical as the nodes in this region are usually labeled as level II, III, and IV nodes as per the AJCC classification. Entirely cystic rounded structures in the PCS could represent metastatic nodes from thyroid cancer and may mimic a third BCC.
Teaching Points
◾there A lesion is localized in the PCS if it is centered in the PCS fat and is a clear fat plane between the mass and the carotid sheath ◾sternocleidomastoid A PCS lesion flattens the paraspinal musculature and lifts the muscle
Sublingual and Submandibular Spaces Boundaries The oral cavity has two small but significant submucosal spaces, the sublingual space (SLS) and the submandibular space (SMS). The mylohyoid muscle, which forms the floor of the mouth, separates these spaces from each other. The mylohyoid muscle is sling like and extends from the mylohyoid ridge on the inner aspect of the mandible on one side to the ridge on the opposite side (Fig. 68.32). The SLS lies superior and medial to the mylohyoid muscle while the SMS lies inferior and lateral to it [1,2].
FIGURE 68.32 Anatomy of the sublingual and submandibular spaces. The yellow arrows point to the teacup-shaped sublingual spaces (outlined in yellow) which is bounded medially by the genioglossus muscles (green) and inferolaterally by the mylohyoid sling (textured red) extending from one mylohyoid ridge of the mandible to the other (black arrows). Below the mylohyoid sling is the horseshoe-shaped outlined (in red) submandibular space (SMS). The lower boundary of the SMS is the platysma muscle (arrowheads).
Sublingual Space As the name suggests the SLS is located beneath the oral tongue mucosa and intrinsic tongue muscles. They are paired teacup-shaped potential spaces on either side with critical tongue contents and are not lined by fascia [2]. Each SLS is bounded medially by the genioglossus muscle and inferolaterally by the mylohyoid muscle (Fig. 68.32). The paired SLS communicate with each other anteriorly under the frenulum of the tongue.
Submandibular Space The SMS is a horseshoe-shaped space that lies inferior to the mylohyoid muscle and superior to the platysma muscle. It is a fascia-lined space bounded by the layers of the investing layer of deep cervical fascia except
posteriorly. The investing layer of cervical fascia splits into two layers while enclosing the SMS; the superior slip invests the outer surface of the mylohyoid and the inferior/superficial slip runs along the inner aspect of the platysma muscle of the neck. However, the fascia is deficient posteriorly and the posterior parts of SMS and SLS communicate with each other along the free posterior edge of the mylohyoid muscle. The posterior part of SMS also communicates with the PPS superiorly. Hence SLS, SMS, and PPS are contiguous spaces allowing the spread of pathology between them [2].
Contents Sublingual space The contents of the SLS [1] are:
◾ Anterior part of the hyoglossus muscle ◾ Sublingual gland and duct ◾ Lingual artery and vein ◾ Lingual nerve (branch of cranial nerve V) ◾ Glossopharyngeal nerve (cranial nerve IX) and hypoglossal nerve (cranial nerve XII) ◾ Deep portion of the submandibular gland ◾ duct (Wharton’s duct) ◾ Submandibular Fat
The hyoglossus muscle (Fig. 68.33) is an important landmark separating the lingual artery and vein that lie medial to it and the Wharton’s duct, hypoglossal nerve, and lingual nerve that lie lateral to this muscle. Wharton’s duct emerges from the deep portion of the submandibular gland and runs anteriorly to drain just lateral to the frenulum of the tongue. It may be visible when dilated (Fig. 68.33).
FIGURE 68.33 Contents of sublingual space (SLS) and submandibular space (SMS). (A) Axial T2W MRI shows hyoglossus muscles (arrows) in the SLS. (B) Axial T2W MRI shows a dilated submandibular duct (arrow) in the SLS. (C) Coronal T2W MRI shows the anterior part of SMS bounded inferiorly by platysma (arrowheads) and containing the anterior belly of digastric muscles (dashed arrows) that border the submental region (asterisk). Long arrow shows the lingual artery in the SLS. (D) Coronal T1W MRI shows the posterior part of SMS containing the submandibular glands (arrows).
Submandibular space The contents of the SMS [1] are:
◾ Anterior belly of the digastric muscle ◾ Superficial portion of the submandibular gland ◾ Facial artery and vein ◾ Level IA and IB lymph nodes ◾ loop of the hypoglossal nerve (cranial nerve 12) ◾ Inferior Fat
Fig. 68.33C and D shows the anatomy of the SMS. The small triangular region between the medial borders of the anterior belly of digastric muscles is the submental region of the SMS. This is the midline anterior-most part of the horseshoe-shaped SMS and contains fat and level IA lymph nodes. The region of the SMS posterolateral to the medial border of the anterior belly of
the digastric muscle contains level IB lymph nodes in addition to fat, the facial artery, facial vein, hypoglossal nerve loop, and superficial part of the submandibular gland.
Lesions of the SLS and SMS A lesion is considered to be a SLS lesion when its epicenter is within the SLS superior and medial to the mylohyoid muscle while a SMS lesion has an epicenter inferolateral to the mylohyoid muscle. Occasionally, an SLS lesion might extend backward and reach into the SMS along the free posterior edge of the mylohyoid appearing as a primary SMS lesion. However, it is rare for SMS lesions to extend into the SLS. At times a lesion in the tail of the parotid gland, when pedunculated can extend into the posterior SMS. Careful examination of consecutive axial sections as well as multiplanar reformations, with aid of clinical examination at times is essential to avoid labeling a primary PS mass as a SMS mass. Tables 68.10 and 68.11 enumerate the lesions of the SLS and SMS, respectively. Table 68.10 Lesions of the Sublingual Space Developmental
Vascular anomalies* a. Hemangioma (pediatric) b. Vascular malformations High flow (AVMs and AVFs) Low flow* (venous/lymphatic/mixed malformation) Epidermoid/dermoidLingual thyroid*
◾ ◾
Inflammatory
a. Cellulitis*/abscess/Ludwig’s angina b. Ranula*—simple or diving c. Dilated Wharton’s (submandibular) duct secondary to calculus or stenosis
Benign tumor
Benign mixed tumor/ pleomorphic adenoma of the sublingual gland
Malignant tumor
a. Squamous carcinoma of tongue base or oral tongue invading sublingual space* b. Primary sublingual gland tumor (rare) Adenoid cystic carcinoma
Table 68.11 Lesions of the Submandibular Space Developmental
Epithelial cysts a. Second branchial cleft cyst* b. Epidermoid/dermoid c. Suprahyoid thyroglossal duct cyst Vascular anomalies* a. Hemangioma (pediatric) b. Vascular malformations High flow (AVMs and AVFs) Low flow* (venous/lymphatic/mixed malformation)
◾ ◾
Inflammatory
a. Reactive adenopathy* b. Cellulitis*/abscess*/Ludwig’s angina c. Diving ranula* d. Submandibular gland inflammation due to submandibular duct obstruction by calculus, stenosis, or tumor e. Acute submandibular sialadenitis (bacterial, viral) f. Chronic infective adenitis g. Granulomatous sialadenitis—tubercular h. Chronic sialadenitis secondary to IgG4related disease (Kuttner’s disease) i. Post-treatment sialadenitis—postradioiodine therapy for thyroid cancer/postradiation therapy
Benign tumor
a. Benign mixed tumor/pleomorphic
adenoma of the sublingual gland b. Lipoma Malignant tumor
Miscellaneous/pseudol esions
a. Level IA and IB nodal metastasis from oral cavity squamous carcinoma* b. Nodal lymphoma* c. Direct invasion by squamous cell carcinoma of tongue d. Primary submandibular gland tumor (rare) Adenoid cystic carcinoma Mucoepidermoid carcinoma Acinic cell carcinoma
◾ ◾ ◾
Mandibular division of trigeminal nerve denervation and atrophy (contralateral side may be mistaken for tumor)
Imaging Methods for SLS and SMS Lesions CT and MR are complementary techniques to evaluate these spaces. CT is advantageous in terms of faster acquisition, wide availability, and better assessment of cortical bone and can clearly demonstrate calculi, phleboliths, and mandibular osteomyelitis. It is the preferred method for evaluating infections. MRI has superior contrast resolution and depicts better the soft tissue extent of a tumor/lesion, bone marrow involvement, and PNS. Dental amalgam artifacts can compromise the image quality of both CT and MRI, more so the former. Repeat limited scans in the plane of the mandible (along the amalgam) can be acquired on CT to minimize the artifacts. USG can be used to evaluate the SMS and to guide biopsy from this region.
Imaging Features of SLS and SMS Lesions Developmental Lesions Vascular malformations are common in both SLS and SMS and often tend to be multispatial. The imaging features of these have been described previously. Fig. 68.34 shows a VM of the right SLS with posterior and inferior extension into the SMS. A lesion classically seen in the SLS is an
epidermoid, while the dermoid has a predilection for the SMS. Epidermoids are seen as unilocular lesions with epicenter in the SLS and have fluid density/intensity (Fig. 68.35A), while dermoids have mixed signal intensity and may have an area of fat intensity/density [2].
FIGURE 68.34 Venous malformation (VM) in sublingual space (SLS) and submandibular space (SMS). (A) Axial T2W MRI shows a brightly hyperintense lesion in the SLS (arrows) extending posteriorly into the SMS. (B) Coronal T2 W MRI shows the hyperintense mass in the SLS (solid arrow) extending into the SMS where a darkly hypointense focus (dashed arrow) is seen suggestive of a phlebolith. (C) Contrastenhanced axial CT shows multiple phleboliths (dashed arrows) in the SMS component confirming the diagnosis of VM.
FIGURE 68.35 (A) Epidermoid cyst. Coronal postcontrast T1W MRI shows a unilocular cystic lesion in the right sublingual space (arrow) superior to the mylohyoid (asterisk). Differential diagnoses include a ranula and lymphatic malformation which may appear similar. (B) Second branchial cleft cyst (BCC). Axial contrast-enhanced MRI shows a unilocular cystic lesion with thick enhancing walls (solid arrow) in a typical location, that is, anteromedial to the sternomastoid muscle (sm), posterolateral to the submandibular gland (dashed arrow), and lateral to the carotid bifurcation flow voids (arrowhead). The thickened walls suggest a possibility of an infected second BCC.
Second BCC is the commonest lesion of the SMS in children. There are two peak incidences for second BCC, one seen in childhood and the second in young adults. On imaging, an uncomplicated second BCC appears as a thin-walled unilocular cystic lesion with a typical location at the angle of the mandible. As the cyst grows in size, it displaces the submandibular gland anteromedially and the sternocleidomastoid muscle posteriorly and laterally, the carotid sheath further posteromedially and comes to lie in the suprahyoid part of the PCS (Fig. 68.35B). One feature highly suggestive of a second BCC is the “notch sign/beak sign/tail sign” which is an extension of the cyst wall medially to the interval between the internal and external carotid arteries, although this sign was also reported in a cystic schwannoma [36]. Lingual thyroid is another lesion that can extend into the SLS from a midline mucosal location in the base tongue (region of foramen cecum). It occurs due to the failure of the normal descent of the thyroid gland from the foramen cecum to the lower neck. The characteristic feature is the thyroid density of the lesion, appearing hyperdense both on enhanced and nonenhanced CT sections. Thyroglossal duct cysts (TDCs) are commonly in an infrahyoid location and only one-fifth of the cases occur in a suprahyoid location. Infrahyoid TDCs are described in further detail in another chapter. A suprahyoid TDC can extend into the posterior SMS from the level of the
hyoid and appears as a cystic lesion in the midline (much less commonly in a paramedian location). Rarely TDC may be seen extending across the posterior SLS up to the foramen cecum [2]. Inflammatory/Infective Lesions Cellulitis and abscess can affect both SLS and SMS. The usual causes are spread of infection from odontogenic infections or from submandibular or sublingual gland infection (secondary to stenosis or calculus obstruction). Suppurative nodes are another cause of infection in the SMS. Imaging features of cellulitis are diffuse edema seen as fat stranding and ill-defined soft tissue thickening, while abscesses are seen as organized fluid collections with enhancement of the walls. Ludwig’s angina is the most serious of all the infective processes and is a severe form of cellulitis that involves both SLS and SMS. Streptococcus viridans and Staphylococcus aureus are some of the causative organisms. The patient presents with swelling of the SMS and may have pain during swallowing progressing to induration in the neck, trismus, tongue elevation, and in severe cases to respiratory distress. The cellulitis rapidly progresses spreading to the entire neck and can cause airway compromise making this a surgical emergency requiring airway management. Hence, imaging is usually done to see airway patency and look for underlying odontogenic abscess or less commonly submandibular gland inflammation. Rarely Ludwig’s angina can be complicated with craniocervical necrotizing fasciitis resulting in gangrene and gas formation in the soft tissues [37] (Fig. 68.36).
FIGURE 68.36 Ludwig’s angina with necrotizing fasciitis. (A) Axial Contrast enhanced CT shows swelling in the submandibular space with gas formation (arrows). (B) Sagittal CT reformation shows extension into the infrahyoid neck (arrow). (Courtesy: Suresh K. Mukherji.)
Reactive nodes are very common lesions in the SMS. USG is commonly used to image these palpable nodes and reveals ovoid enlarged nodes but with homogeneous internal echotexture and well-defined hila. Nodes in the SMS are extraglandular and not within the submandibular gland, unlike the parotid gland that has nodes encapsulated within. A dilated submandibular duct is another entity seen in the SLS and the cause is distal obstruction by calculus, stenosis, or tumor. Resultant submandibular gland inflammation is seen in the SMS and imaging reveals an enlarged gland with increased enhancement, heterogeneous signal intensity, and indistinct margins (Fig. 68.37).
FIGURE 68.37 Contrast-enhanced axial CT showing sialolith with obstructive sialadenitis. A shows a radiodense calculus in the left Wharton’s duct (black arrow) with proximal ductal dilatation (dashed arrows in A and B). Note the left submandibular gland (solid white arrows in A and B) shows increased enhancement and appears enlarged as compared to the right gland. It also shows indistinct medial margins in A; all the above features suggest resultant sialadenitis. (Courtesy: Suresh K. Mukherji.)
Other causes of (submandibular) sialadenitis may be acute bacterial, acute viral (occurs in less than 10% of cases and bilateral submandibular glands are involved), tuberculosis (incidence of 27% as compared to parotid involvement in 70%), chronic adult sialadenitis (glandular destruction due to repeated acute inflammatory episodes), chronic sialadenitis due to IgG4related disease (Kuttner tumor), or chronic sialadenitis as a complication of radiation treatment or radio-iodine therapy (for thyroid cancer). Acute sialadenitis, as well as tuberculous sialadenitis, may show an enlarged gland with heterogeneous enhancement with or without abscess formation. Adjacent fat stranding and thickening of adjacent deep cervical fascia may be seen. Kuttner tumor is typically seen as bilateral symmetric enlargement of submandibular glands that appear homogeneous in signal intensity with low to intermediate T2 signal and homogeneous enhancement. USG examination in Kuttner tumor shows enlarged submandibular glands with a poorly demarcated mass showing increased vascularity (Fig. 68.38). Endstage chronic adult sialadenitis and postradio-iodine therapy sialadenitis show small shrunken glands with low to intermediate T2 signal intensity (due to fibrosis) and ductal ectasia [38].
FIGURE 68.38 Ultrasound (USG) features of Kuttner tumor. (A) Grayscale USG shows poorly marginated hypoechoic mass in the submandibular gland (arrows). (B) Color Doppler USG shows increased vascularity seen as increased color signal (arrows). (Courtesy: Suresh K. Mukherji.)
A common lesion in the SLS is a simple ranula, which is a postinflammatory retention cyst of the sublingual gland and is lined by epithelium. It appears as a unilocular cystic lesion in the SLS and cannot be differentiated from an epidermoid cyst or a unilocular LM (Fig. 68.39A). Infected simple ranulas can appear like abscesses. A simple ranula can rupture if it becomes large and extend posteriorly and inferiorly into the SMS (and even further into the PPS) and is then called a diving or plunging ranula (Fig. 68.39B–D). Once the ranula ruptures, the bulk of it is seen in the SMS (Fig. 68.39B) with a collapsed sublingual portion showing the origin
from the SLS and this is called the “tail sign” of the diving ranula (Fig. 68.39C). Diving ranula is not epithelial lined and is a pseudocyst [2].
FIGURE 68.39 Ranula of the sublingual space (SLS) and its extensions into the submandibular space (SMS) and parapharyngeal space (PPS). (A) Contrast enhanced axial CT shows a well-defined unilocular cyst with thin walls (ranula) beginning in the SLS (black arrow) with extension into the SMS (white arrow) but not reaching the lower limit of PPS (dashed arrow). B Diving ranula. The bulk of the cystic lesion is in the SMS (solid arrow) and also extends into the adjacent lower PPS (dashed arrow). (C) Axial T2W MRI. Arrow shows the collapsed sublingual portion of the diving ranula, demonstrating its origin from the SLS and this is called the “tail sign” of the diving ranula. (D) Coronal T2W MRI shows extension of the diving ranula from the SMS (solid arrow) into the PPS (dashed arrow). (Courtesy: Suresh K. Mukherji.)
Tumors Squamous cell carcinoma is the commonest lesion of the SLS [1] and is an extension from the mucosal component in the dorsum/lateral border of the oral tongue or the mucosa of the base tongue. Contrast-enhanced MRI best shows the complete extent of the tumor. The tumors appear infiltrating with invasion of the neurovascular bundle and spread across the midline (Fig. 68.40). Minor salivary gland tumors of the sublingual gland such as ACC or MEC are rare lesions [2]. Infrequently neurogenic tumors (schwannomas) may be seen arising from the lingual or hypoglossal nerve [1]. They appear well defined with smooth margins, hypovascular, and may show cystic degeneration. Benign pleomorphic adenomas of the sublingual gland are extremely rare with a reported incidence ratio of 1 sublingual tumor to 100 parotid tumors [39].
FIGURE 68.40 Contrast-enhanced coronal MRI shows squamous cell carcinoma (SCC) of the mucosa of the oral tongue with epicenter on the right but crossing midline and showing ulceration in the dorsum (asterisk). The SCC is seen reaching inferiorly into the sublingual space and encasing the lingual artery flow void (dashed arrow). Solid arrows show bilateral level IB nodes in the submandibular space. The nodes are enlarged, rounded, enhancing, without visible hila and the inferior margin of the left IB node is slightly lobulated. Nodal features suggest metastatic nodes. SCC of the tongue that crosses midline can give rise to contralateral nodal metastases.
Tumors of the SMS can be benign or malignant. The benign tumors include lipoma and pleomorphic adenoma (BMT) of the submandibular gland. Pleomorphic adenomas are infrequent with only 8% involving the submandibular gland, while 84% are seen in the parotid [40]. Small tumors are homogeneous with marked enhancement, while larger pleomorphic adenomas appear as well-defined heterogeneous masses involving the submandibular gland and may show delayed enhancement, areas of cystic degeneration and foci of calcification [40]. Malignant tumors of the submandibular gland are rare, the commonest being an ACC [2]. SMS is more likely to be involved by oral tongue
squamous cell carcinoma by direct invasion across the mylohyoid muscle. The commonest malignancy of the SMS though is metastatic adenopathy from squamous cell carcinoma of the oral cavity [1]. On imaging, a metastatic node appears enlarged and rounded (rather than ovoid) with increased enhancement on CT (Fig. 68.40) and internal heterogeneity on MRI and the hilum may not be seen. Necrosis when present is the most reliable criterion of metastasis. Presence of ill-defined or indistinct margins suggests extracapsular spread. The other common malignant lesion of the SMS is nodal lymphoma in which multiple enlarged homogenous nodes with well-defined margins are seen not only at level IA and level IB but also at other levels (II–V) bilaterally. Pseudomass Occasionally, cranial nerve palsies may cause ipsilateral denervation atrophy that can result in the contralateral side being mistaken for a tumor. Injury to the hypoglossal nerve can cause ipsilateral volume loss of the tongue with fat replacement in the tongue muscles. On imaging, the contralateral normal tongue can be mistaken for a tumor in the SLS. When the mandibular division of the trigeminal nerve is injured/invaded by the tumor, the mylohyoid muscle and anterior belly of the digastric supplied by the mylohyoid branch undergo atrophy and fatty infiltration. The contralateral normal nonatrophied muscles should not be mistaken for a tumor [2].
Teaching Points
◾mylohyoid A lesion is primary to the SLS if it is seen superomedial to the muscle, while a lesion is primary to the SMS if it is inferolateral to the muscle ◾located SLS and SMS communicate with each other along the free posterior edge of the mylohyoid muscle and hence, lesions can extend from the SLS to the SMS. A diving ranula typically extends from the SLS to the SMS Primary involvement of the sublingual and submandibular glands by benign and malignant tumors is not very common; secondary invasion by squamous cell carcinoma of the oral cavity is the commonest tumor of the SLS A second BCC is the commonest SMS lesion in children while metastatic adenopathy from squamous carcinoma of the oral cavity is the commonest SMS lesion in adults
◾ ◾
Conclusion The neck spaces represent elegant natural barriers while protecting vital structures. For the radiologist too, it is useful to divide the complex region of the neck into various spaces to devise a systematic approach to a neck lesion. Knowledge of the anatomic boundaries and contents of each space helps generate a list of differential diagnoses unique to each space. The characteristic imaging findings and clinical information can help further refine the diagnosis.
Suggested Readings • SK Mukherji, M Castillo, A simplified approach to the spaces of the suprahyoid neck, Radiol Clin North Am 36 (5) (1998) 761–780. • AH Baer, HA Parmar, MA DiPietro, SJ Kasten, SK Mukherji, Hemangiomas and vascular malformations of the head and neck: a simplified approach, Neuroimaging Clin 21 (3) (2011) 641–658. • A Abdullah, FFR Rivas, A Srinivasan, Imaging of the salivary glands, Semin Roentgenol 48 (1) (2013) 65–74. • S Arya, V Rao, S Juvekar, AK Dcruz, Carotid body tumors: objective criteria to predict the Shamblin group on MR imaging, Am J Neuroradiol 29 (7) (2008) 1349–1354. • VFH Chong, YF Fan, Radiology of the retropharyngeal space: pictorial review, Clin Radiol 55 (10) (2000) 740.
References [1] SK Mukherji, M Castillo, A simplified approach to the spaces of the suprahyoid neck, Radiol Clin North Am 36 (5) (1998) 761–780. [2] HR Harnsberger, Handbook of Head and Neck Imaging, second ed., Mosby, St Louis, 1995. [3] T Fernandes, JC Lobo, R Castro, MI Oliveira, PM Som, Anatomy and pathology of the masticator space, Insights Imaging 4 (5) (2013) 605–616. [4] AH Baer, HA Parmar, MA DiPietro, SJ Kasten, SK Mukherji, Hemangiomas and vascular malformations of the head and neck: a simplified approach, Neuroimaging Clin 21 (3) (2011) 641–658. [5] KC Jones, J Silver, WS Millar, L Mandel, Chronic submasseteric abscess: anatomic, radiologic, and pathologic features, AJNR Am J Neuroradiol 24 (6) (2003) 1159–1163. [6] WH Jee, SN Oh, T McCauley, KN Ryu, JS Suh, JH Lee, et al., Extraaxial neurofibromas versus neurilemmomas: discrimination with MRI, AJR Am J Roentgenol 183 (3) (2004) 629–633. [7] HC Kim, MH Han, MH Moon, JH Kim, IO Kim, KH Chang, CT and MR imaging of the buccal space: normal anatomy and
abnormalities, Korean J Radiol 6 (1) (2005) 22–30. [8] PM Som, HD Curtin, Parapharyngeal and masticator space lesions, Head Neck Imaging Vol. 2, Mosby, St. Louis, 2003, 1955– 1987. [9] A Abdullah, FF.R Rivas, A Srinivasan, Imaging of the salivary glands, Semin Roentgenol 48 (1) (2013) 65–74. [10] EJ Inarejos Clemente, M Navallas, M Tolend, M Suñol Capella, J Rubio-Palau, A Albert Cazalla, et al., Imaging evaluation of pediatric parotid gland abnormalities, Radiographics 38 (5) (2018) 1552–1575. [11] SG Kanekar, K Mannion, T Zacharia, M Showalter, Parotid space: anatomic imaging, Otolaryngol Clin North Am 45 (6) (2012) 1253. [12] A Gadodia, A Seith, R Sharma, A Thakar, MRI and MR sialography of juvenile recurrent parotitis, Pediatr Radiol 40 (8) (2010) 1405–1410. [13] C Baldini, A Zabotti, N Filipovic, A Vukicevic, N Luciano, F Ferro, et al., Imaging in primary Sjögren’s syndrome: the “obsolete and the new”, Clin Exp Rheumatol 36 (Suppl 112) (2018) S215– S221. [14] JL Weissman, Imaging of the salivary glands, Semin Ultrasound CT MRI 16, (6), 1995, 546–568. [15] H Kato, M Kanematsu, K Mizuta, Y Ito, Y Hirose, Carcinoma ex pleomorphic adenoma of the parotid gland: radiologic-pathologic correlation with MR imaging including diffusion-weighted imaging, Am J Neuroradiol 29 (5) (2008) 865–867. [16] DM Yousem, MA Kraut, AA Chalian, Major salivary gland imaging, Radiology 216 (1) (2000) 19–29. [17] K Shimizu, H Iwai, K Ikeda, N Sakaida, S Sawada, Intraparotid facial nerve schwannoma: a report of five cases and an analysis of MR imaging results, Am J Neuroradiol 26 (6) (2005) 1328–1330. [18] F Riffat, RC Dwivedi, C Palme, B Fish, P Jani, A systematic review of 1143 parapharyngeal space tumors reported over 20 years, Oral Oncol 50 (5) (2014) 421–430. [19] D Lichtenstein, R Saifi, R Augarde, S Prin, JM Schmitt, B Page, et al., The internal jugular veins are asymmetric. Usefulness of ultrasound before catheterization, Intensive Care Med 27 (1) (2001) 301–305. [20] RK Sharma, AM Asiri, Y Yamada, T Kawase, Y Kato, Extracranial internal carotid artery aneurysm: challenges in the management: a case report and review literature, Asian J Neurosurg 14 (3) (2019) 970.
[21] A Szymańska, M Szymański, E Czekajska-Chehab, W Gołąbek, M Szczerbo-Trojanowska, Diagnosis and management of multiple paragangliomas of the head and neck, Eur Arch Oto-RhinoLaryngol 272 (8) (2015) 1991–1999. [22] S Arya, V Rao, S Juvekar, AK Dcruz, Carotid body tumors: objective criteria to predict the Shamblin group on MR imaging, Am J Neuroradiol 29 (7) (2008) 1349–1354. [23] PM Som, M Sacher, AL Stollman, HF Biller, W Lawson, Common tumors of the parapharyngeal space: refined imaging diagnosis, Radiology 169 (1) (1988) 81–85. [24] M Furukawa, MK Furukawa, K Katoh, M Tsukuda, Differentiation between schwannoma of the vagus nerve and schwannoma of the cervical sympathetic chain by imaging diagnosis, Laryngoscope 106 (12) (1996) 1548–1552. [25] VF.H Chong, YF Fan, Radiology of the retropharyngeal space: pictorial review, Clin Radiol 55 (10) (2000) 740–748. [26] JM Debnam, N Guha-Thakurta, Retropharyngeal and prevertebral spaces: anatomic imaging and diagnosis, Otolaryngol Clin North Am 45 (6) (2012) 1293–1310. [27] AA Bhatt, Non-traumatic causes of fluid in the retropharyngeal space, Emerg Radiol 25 (5) (2018) 547–551. [28] MR Klein, Infections of the oropharynx, Emerg Med Clin North Am 37 (1) (2019) 69–80. [29] MK Mills, LM Shah, Imaging of the perivertebral space, Radiol Clin North Am 53 (1) (2015) 163–180. [30] H Tomita, T Yamashiro, H Ikeda, A Fujikawa, Y Kurihara, Y Nakajima, Fluid collection in the retropharyngeal space: a wide spectrum of various emergency diseases, Eur J Radiol 85 (7) (2016) 1247–1256. [31] JK Hoang, BF Branstetter IV, JD Eastwood, CM Glastonbury, Multiplanar CT and MRI of collections in the retropharyngeal space: is it an abscess?, Am J Roentgenol 196 (4) (2011) W426– W432. [32] AG Jurik, Imaging the spine in arthritis: a pictorial review, Insights Imaging 2 (2) (2011) 177–191. [33] KW Park, JS Park, SC Hwang, SB Im, WH Shin, BT Kim, Vertebral artery dissection: natural history, clinical features and therapeutic considerations, J Korean Neurosurg Soc 44 (3) (2008) 109. [34] DM Sciubba, JH Chi, LD Rhines, ZL Gokaslan, Chordoma of the spinal column, Neurosurg Clin N Am 19 (1) (2008) 5–15.
[35] C Knebel, J Neuman, BJ Schwaiger, DC Karampinos, D Pfeiffer, K Specht, et al., Differentiating atypical lipomatous tumors from lipomas with magnetic resonance imaging: a comparison with MDM2 gene amplification status, BMC Cancer 19 (2019) 309. [36] PD Lanham, C Wushensky, Second branchial cleft cyst mimic: case report, AJNR 26 (7) (2005) 1862–1864. [37] M Vallée, B Gaborit, J Meyer, O Malard, D Boutoille, F Raffi, et al., Ludwig’s angina: a diagnostic and surgical priority, Int J Infect Dis 93 (2020) 160–162. [38] AA Razek, SK Mukherji, Imaging of sialadenitis, Neuroradiol J 30 (3) (2017) 205–215. [39] R Zdanowski, FL Dias, MM Barbosa, RA Lima, PA Faria, AM Loyola, et al., Sublingual gland tumors: clinical pathologic and therapeutic analysis of 13 patients treated in a single institution, Head Neck 33 (2011) 476–481. [40] HC Thoeny, Imaging of salivary gland tumours, Cancer Imaging 7 (2007) 52–62.
CHAPTER 69
Thyroid and Parathyroids Sneha Deshpande, Anuj Jain, Supreeta Arya
Thyroid Introduction Thyroid lesions are very common, which include focal lesions to generalized parenchymal involvement. Focal lesions range from benign “touch-me-not” lesions to aggressive malignancies with locoregional and distant spread. Accurate characterization of thyroid lesions aids in institution of timely and appropriate treatment. Also, thyroid hormonal imbalance is a major cause of morbidity, ranging from subclinical disease to florid thyroid dysfunction.
Embryology Thyroid gland consists of two types of cells: thyroxin (T4) and triiodothyronine (T3) producing follicular cells and calcitonin producing parafollicular cells (“C” cells). Thyroid follicular cells originate from the median thyroid anlage, which arises during the third week of embryonic development as an endodermal thickening between the first and second pharyngeal arches [1]. This thickening then forms the thyroid bud, a small pit which elongates into a bilobed diverticulum. It courses anteriorly to the primordial hyoid bone, loops inferiorly and posteriorly to the hyoid (due to rotation and fusion of hyoid anlage) and descends caudally, reaching its anatomical position in the anterior midline infrahyoid neck by the end of
seventh week [1]. A small channel, the thyroglossal duct, temporarily persists as a connection between the pharynx and the caudally migrating thyroid primordium which later involutes. The inferior portion of the thyroglossal duct may differentiate into the pyramidal lobe. The lateral thyroid anlagen, known as the ultimobranchial bodies, arise laterally along the fourth pharyngeal pouch and give rise to parafollicular cells. The lateral anlagen merge with median anlage after descent into the infrahyoid neck [1,2].
Anatomy Thyroid is an anterior midline neck structure composed of two lobes connected by the isthmus, which crosses the trachea anteriorly at the level of second and third tracheal rings. Thyroid gland and the posteriorly located trachea and esophagus are bound by the pretracheal fascia (part of middle layer of cervical fascia) and located within the visceral space of the neck. Thyroid is bound anteriorly by the sternothyroid and sternohyoid (strap) muscles, superior belly of omohyoid and anterior border of sternocleidomastoid and posterolaterally by the common carotid arteries and internal jugular veins, on either side. Thyroid gland size varies with age, gender, pregnancy, and disease states. Average dimensions of a thyroid lobe are 4–6 cm in height and 1–2 cm in width and thickness [1]. The isthmus varies from 1 to 2 cm in height [1]. Superior thyroid artery which is a branch of external carotid artery and the inferior thyroid artery which is a branch of the thyrocervical trunk provide a rich blood supply to the thyroid gland. In few individuals, there is an additional artery known as the thyroid ima artery which has variable origin, commonly from the aortic arch or brachiocephalic trunk. Venous drainage of thyroid is via the superior, middle, and inferior thyroid veins.
Imaging Methods Ultrasonography (USG) USG is a noninvasive, nonionizing widely available tool with high sensitivity and spatial resolution for thyroid evaluation. Also, superficial location of the thyroid gland makes it easily accessible to USG. Hence, USG is the first radiological investigation of choice in all suspected thyroid lesions [3]. All patients are scanned in supine position with hyperextended neck, using a high-frequency linear-array transducer and both, grayscale and color Doppler imaging (CDI) techniques are used. On USG, normal thyroid
appears homogenous with a medium to high-level echogenicity with an echogenic thin capsule. According to the American Thyroid Association (ATA) 2015 guidelines, USG with survey of the cervical lymph nodes should be performed in all patients with known or suspected thyroid nodules (strong recommendation, high-quality evidence), to confirm the presence, to localize, to accurately measure and characterize the lesion/s; thus assess the risk of malignancy and guide fine-needle aspiration (FNA) from suspicious thyroid nodules [3]. USG also helps to differentiate thyroid nodules from other cervical masses. In thyroid malignancies, preoperative USG is required to assess the status of the contralateral lobe and detect suspicious cervical lymphadenopathy while postoperative USG is indicated to detect residual or recurrent disease in the thyroid bed or the lymph nodes. USG is used to screen high-risk patients for thyroid malignancy with history of multiple endocrine neoplasia (MEN) type II, familial thyroid cancer, and neck irradiation in childhood. USG helps in assessing gland size, parenchymal echotexture, and vascularity in diffuse thyroid diseases. USG is also the initial technique of choice for evaluation of congenital neck masses, suspected to be of thyroid origin. USG is the technique of choice to evaluate thyroid incidentalomas (TI) seen on other imaging techniques.
Computed tomography (CT) and magnetic resonance imaging (MRI) Normal thyroid appears hyperdense to adjacent muscles on CT, due to high intrinsic iodine content. On contrast-enhanced CT, it shows homogenous avid enhancement. On MRI, thyroid appears isointense to mildly hyperintense on T1-weighted images (T1WI), mildly hyperintense on T2weighted images (T2WI), and shows homogenous avid enhancement on gadolinium-enhanced MR. According to the ATA 2015 guidelines, use of cross-sectional imaging studies (CT, MRI) with intravenous contrast is recommended as an adjunct to USG in (a) assessment of the extent of advanced thyroid malignancies including invasive primary tumor, (b) clinically suspected multiple or bulky cervical lymph nodes to look for involvement of atypical lymph node stations and extra-nodal spread, and (c) clinically suspected distant metastases (Fig. 69.1) [3]. The initial nodal metastases from thyroid malignancy are to the central compartment nodes, level VI and VII (which include pretracheal, paratracheal, prelaryngeal/Delphian nodes, or upper mediastinal nodes). It can also metastasize to lateral compartment lymph nodes (level I–V). A peculiar metastatic spread may also occur to the retropharyngeal nodes (Fig. 69.2). Cross-sectional imaging has limited role
in diffuse thyroid diseases, except in more extensive forms like Riedel’s thyroiditis (RT) or acute suppurative thyroiditis. Congenital thyroid abnormalities like ectopic thyroid or thyroglossal duct cysts (TDCs), are often evaluated with CT or MRI to confirm the diagnosis, assess the extent, and associated complications.
FIGURE 69.1 Invasive thyroid carcinoma. (A) Axial postcontrast CT image showing heterogeneously enhancing mass in the right thyroid lobe and isthmus (long solid arrow) with extrathyroidal extension, tracheal invasion (short solid arrow), and esophageal infiltration (dashed arrow). (B) Sagittal postcontrast CT brain showing an osseous calvarial lesion with associated soft tissue (long solid arrow) suggestive of osseous metastases.
FIGURE 69.2 Papillary thyroid carcinoma with retropharyngeal nodal metastasis. (A) Axial postcontrast CT image showing a heterogeneously enhancing lesion in the lower pole of the right thyroid lobe (arrow). (B) Axial postcontrast CT image showing a heterogeneously enhancing enlarged right retropharyngeal node (arrow).
Scintigraphy Radionuclide scan/scintigraphy produces a visual display of functional thyroid tissue by selective uptake of injected radionuclides, thus providing both, anatomical and functional information. It has an essential role in evaluating clinically suspected thyroid nodule with low serum thyrotropin (TSH) levels (seen in hyperfunctioning or “hot” nodule) [3]. Other common clinical indications include evaluation of thyrotoxicosis to differentiate diffuse thyroid disease and toxic nodule/s and congenital thyroid disorders. Due to easy availability, low cost, less radiation exposure, and good imaging characteristics, Tc99m pertechnetate is the most commonly used radiopharmaceutical. Tc99m pertechnetate is trapped by thyroid gland in an identical manner as iodide, but is not organified or incorporated into thyroid hormone. Thyroid image is acquired after 20–30 minutes of intravenous injection of 3–5 mCi of Tc99m pertechnetate, which shows uptake in the thyroid gland along with some normal uptake in salivary glands and oral cavity. The other radiopharmaceuticals for thyroid scintigraphy are I131 and I123. Due to high radiation dose, clinical use of I131 is largely limited to the postoperative therapeutic and whole-body diagnostic scanning of differentiated thyroid carcinoma (DTC). I123, if available, can be used in place of Tc99m pertechnetate and I131.
Positron Emission Tomography/Computed Tomography (PET/CT) Use of 18F-fluoro-2-deoxyglucose (18F-FDG)-PET/CT and other PET tracers in the evaluation of thyroid disorders is limited. ATA guidelines state that use of 18F-FDG-PET/CT for routine evaluation of nodules suspicious for malignancy on USG or for staging of diagnosed DTC is not recommended [3]. It is however recommended for staging of anaplastic carcinomas [4]. An incidentally detected focal uptake in the thyroid, seen on a PET scan is suspicious for malignancy [3]. Diffuse PET uptake in a thyroid is usually inflammatory, especially if USG too is corroborative.
Pathology Thyroid Dysgenesis Congenital developmental defects of the thyroid gland like aplasia (absent gland), hypoplasia (small gland), hemiagenesis (absent lobe; Fig. 69.3), and ectopia (abnormal location) are collectively called thyroid dysgenesis.
FIGURE 69.3 Axial postcontrast CT image showing left thyroid lobe agenesis (long arrow) with normal right thyroid lobe and isthmus (short arrows).
Ectopic Thyroid Tissue Stalled migration at any stage of the migratory path of the thyroid during embryological development or erroneous migratory course can lead to variant locations of thyroid tissue [5]. Thyroid ectopia is commonly seen at: (1) the base of the tongue, being the most common site; (2) adjacent to the hyoid bone; (3) the midline infrahyoid portion of the neck [2]. Ectopic thyroid tissue has rarely been reported in locations such as the lateral part of the neck, pharynx, esophagus, trachea, mediastinum, heart, lungs, breast, adrenal glands, bowel, and ovaries [2,5]. Ectopic thyroid tissue appears identical to the native thyroid gland on all imaging techniques, except the characteristic shape. It may show parenchymal nodules and can develop any of the abnormalities akin to thyroid gland, including malignancy. Orthotopic thyroid tissue is absent in 70–80% of the cases [2,5]. USG demonstrates absent orthotopic thyroid tissue and may indicate presence of ectopic thyroid. Ectopic thyroid is often evaluated with CT or MRI to confirm diagnosis and evaluate complications. Radionuclide scans are usually confirmatory to demonstrate ectopic thyroid tissue and absence of functioning orthotopic thyroid tissue (Fig. 69.4).
FIGURE 69.4 Ectopic thyroid (dual ectopia). (A) Sagittal reformation CT image showing homogenously enhancing well-defined ectopic thyroid tissue at the base of the tongue (solid white arrow) and adjacent to hyoid bone in infrahyoid location (dashed white arrow). (B) Radionuclide thyroid scan shows functioning thyroid tissue in these corresponding regions (black long solid arrow and dashed black arrow, respectively) with no functioning thyroid tissue in thyroid bed (short black solid arrow).
Thyroglossal Duct Cyst (TDC) TDC is the most common congenital neck mass, which results from remnants of the thyroglossal duct, anywhere along its course and may be associated with ectopic thyroid tissue [2,6]. It manifests usually in childhood as gradually increasing painless neck swelling which moves with deglutition and tongue protrusion. It may present in infrahyoid, suprahyoid or juxtahyoid and rarely intralingual locations [6]. Suprahyoid TDCs are usually midline, while infrahyoid TDCs may be paramedian in location, usually deeply embedded within or splaying the strap muscles. Preoperative imaging is performed to identify the anatomic extent of the cyst, identify ectopic thyroid tissue, and evaluate for potential malignancy within the cyst. USG reveals a well-circumscribed anechoic cyst with posterior enhancement, with some internal debris due to proteinaceous contents and may sometimes show a pseudosolid echogenic pattern. At CT, TDCs are seen as thin-walled well-circumscribed lesions with fluid attenuation or may sometimes show higher attenuation (Fig. 69.5). At MR
imaging, they appear hypointense to isointense on T1WI and hyperintense on T2WI. Infected TDCs may show thick enhancing wall and internal septations on CT and MRI. Fistula may develop in cases of external cyst rupture, recurrence after resection, or may rarely be congenital. Malignancy in TDCs is rare; most common type being papillary carcinoma. Imaging features which warrant evaluation for malignancy are enhancing wall nodularity and calcification (Fig. 69.5).
FIGURE 69.5 (A) Sagittal reformation CT image showing a welldefined thin-walled fluid density cystic lesion (arrow) in the juxtahyoid location reaching the posterior aspect of the hyoid bone suggesting a thyroglossal duct cyst (TDC). (B) Sagittal reformation CT image showing a juxtahyoid TDC (long solid arrow) with enhancing solid mural nodule (dashed arrow) and multiple foci of calcifications (short solid arrow). A case of papillary carcinoma in TDC.
Pearls
◾neck Ectopic thyroid and TDC are common differentials of anterior masses presenting in children and young adults ◾andTypical location along the line of decent of thyroid primordium characteristic imaging features clinch the diagnosis
Focal Thyroid Lesions/Thyroid Nodules
A thyroid nodule is defined by the ATA as “a discrete lesion within the thyroid gland that is radiologically distinct from the surrounding thyroid parenchyma” [3]. Thyroid nodules can be completely asymptomatic, may present with hormonal imbalance, compressive symptoms due to mass effect, or may harbor malignancy. During the initial evaluation of a patient with a clinically suspected thyroid nodule, serum TSH is measured [3]. If the serum TSH is subnormal (hyperthyroidism), the ATA guidelines recommend a radionuclide thyroid scan to assess whether the nodule is hyperfunctioning (“hot”), isofunctioning (“warm”), or nonfunctioning (“cold”) [3]. Hyperfunctioning nodules rarely harbor malignancy, and hence, no cytologic evaluation is recommended. In all patients with nodularity detected on thyroid scintigraphy, USG should be performed to confirm the presence of nodules corresponding to the hyperfunctioning areas on the scan and to evaluate other “warm” and “cold” nodules. In patients where the serum TSH is normal or elevated, a radionuclide scan should not be performed. Instead, USG of the thyroid and neck nodes is recommended in all such patients, as elevated serum TSH level is associated with increased risk of malignancy in a thyroid nodule, as well as a more advanced stage of thyroid cancer [3]. Thyroid nodules can be benign or malignant, with the incidence of benign nodules being significantly higher than malignancies. Various benign pathologies affect thyroid gland, like benign follicular nodules, follicular adenomas, or focal thyroiditis [7]. The malignant pathologies affecting thyroid are papillary thyroid carcinomas (PTCs) and follicular thyroid carcinomas (FTCs), which together are called differentiated thyroid malignancies (DTCs), medullary and anaplastic carcinomas, lymphomas, and metastases [7]. However, due to the high incidence of thyroid nodules, low incidence of thyroid malignancy, patient anxiety, and economic point of view, it is not feasible to biopsy every thyroid nodule. Hence, recommendations have been put forth by numerous committees for risk stratification and management decision making. One of them is the Thyroid Imaging Reporting and Data System (TI-RADS), which has several versions, the most widely used being that put forth by American College of Radiology (ACR). ACR TI-RADS ACR TI-RADS is based on the evaluation of USG features of thyroid nodules in five lexicon categories—composition, echogenicity, margin, shape, and echogenic foci (Table 69.1) [8]. Features in the first category (composition) are assigned 0–2 points while that in the other four categories are assigned 0–3 points, with more suspicious features awarded more points. When evaluating a thyroid nodule, one feature is selected from each of the first four categories, and all the features that are applicable to the nodule are
selected from the fifth category (echogenic foci). The total score, which is a sum of points assigned to all five categories, determines the ACR-TIRADS risk level (TR level) of the nodule, and the nodule is categorized as benign (TR1), not suspicious (TR2), mildly suspicious (TR3), moderately suspicious (TR4), or highly suspicious for malignancy (TR5). TR level in conjunction with the maximum nodule diameter dictates the management recommendations, like FNA, follow-up USG, or no further action [8]. ACR TI-RADS recommends reporting up to four thyroid nodules with the highest TR level [8,9]. Associated suspicious cervical lymphadenopathy or distant metastases suspected to be of thyroid origin are important factors guiding the decision to sample a thyroid nodule, irrespective of the size. The USG evaluation of each of these ACR-TIRADS lexicon categories is discussed below. Table 69.1 USG Evaluation of a Thyroid Nodule According to ACR-TIRADS ACR TIRADS Compos ition (Choose Any 1)
Echoge nicity (Choos e Any 1)
Margins (Choose Any 1)
Shap e (Cho ose Any 1)
Echogenic Foci (Choose All Features That Apply)
ACR TIRADS Compos ition (Choose Any 1)
Echoge nicity (Choos e Any 1)
Margins (Choose Any 1)
Shap e (Cho ose Any 1)
Echogenic Foci (Choose All Features That Apply)
Cystic or almost complete ly cystic: 0 points Spongif orm: 0 points Mixed solidcystic: 1 point Solid or almost complet ely solid: 2 points
Anecho ic: 0 points Iso or hypere choic: 1 point Hypoe choic: 2 points Very hypoec hoic: 3 points
Wide rthantall: 0 point s Talle rthanwide: 3 point s
None or large comet-tail artifacts: 0 points Macrocalcificat ions: 1 point Peripheral (rim) calcifications: 2 points Punctate echogenic foci: 3 points
Sum of Points Assigned to All Five Categories 0 points
2 points
3 points
4–6 point s
7 points or more
TR1 Benign
TR2 Not suspici ous
TR3 Mildly suspicious
TR4 Mod eratel y suspi cious
TR5 Highly suspicious
ACR TIRADS Compos ition (Choose Any 1)
Echoge nicity (Choos e Any 1)
Margins (Choose Any 1)
Shap e (Cho ose Any 1)
Echogenic Foci (Choose All Features That Apply)
No FNA required
No FNA require d
FNA if ≥2.5 cm Follow if ≥1.5 cm
FNA if ≥1.5 cm Follo w if ≥1 cm
FNA if ≥1 cm Follow if ≥0.5 cm
Adapted from ACR-TIRADS White Paper 2017 [8].
Composition: According to ACR-TIRADS, the composition of a thyroid nodule is classified as cystic or almost completely cystic (0 points), spongiform (0 points), mixed solid-cystic (1 point), and solid or almost completely solid (2 points) [8]. Purely cystic or almost completely cystic lesions are highly likely to be benign [3]. As per the ACR TIRADS lexicon, a “spongiform” appearance of a thyroid nodule, defined as the aggregation of multiple microcystic components in more than 50% of the volume of the nodule, is strongly correlated with benignancy (Fig. 69.6) [3,8,9]. Majority (82–91%) of thyroid cancers are solid or almost completely solid [3]. Solid nodule that contains minimal cystic component, which occupies no more than approximately 5% of the overall volume, should be classified as “almost completely solid” and is given similar points as a solid nodule [9]. Also, nodules with dense shadowing calcifications that preclude assessment of their composition are assumed to be solid [8,9]. If nodule contains both solid and cystic components, it is classified as a mixed solid-cystic nodule and the appearance of the solid component with the nodule’s maximum dimension, determines management (Fig. 69.6) [3,9]. The features of a solid-cystic thyroid nodule, which are suspicious for malignancy, are an eccentric hypoechoic solid component forming an acute angle with the cyst wall, microcalcifications, irregular margins, and extrathyroidal spread [3,9].
Lobulated margins and increased vascularity in the solid component are suspicious features, though less robust [3].
FIGURE 69.6 USG image showing: (A) A well-defined nodule (arrows) with smooth margins and aggregation of multiple microcysts in the entire nodule which suggests a “Spongiform nodule.” (B) A well-defined mixed solid-cystic nodule (arrows) in the left thyroid lobe with isoechoic solid component, shows smooth margins, wider-than-tall shape and no echogenic foci. The nodule was assigned a total of 2 points (TR2).
Echogenicity: According to ACR-TIRADS, echogenicity of a nodule is classified as anechoic (0 points), iso or hyperechoic (1 point), hypoechoic (2 points), or very hypoechoic (3 points) [8]. Anechoic nodules represent cystic or almost completely cystic nodules. Isoechoic or hyperechoic solid nodules (Fig. 69.7) prompt low suspicion for malignancy since only approximately 15– 20% of thyroid cancers are iso- or hyperechoic, and are generally the FTCs or follicular variant of PTCs [3]. Nodules that are less reflective than the adjacent thyroid parenchyma are classified as hypoechoic, while those that are less reflective than the strap muscles are classified as very hypoechoic (Fig. 69.8) [8,9]. Mixed echogenicity nodules are assessed based on the predominant echogenicity, and described as predominantly hypoechoic, isoechoic, or hyperechoic [8]. If dense calcification precludes the assessment of a nodule’s echogenicity, it is assumed to be at least isoechoic or hyperechoic and is assigned 1 point [9].
FIGURE 69.7 USG image showing almost completely solid nodules (10 ng/mL) and negative whole-body radioiodine scanning [3].
Thyroid Incidentalomas (TI) TI is defined as an unsuspected, asymptomatic thyroid lesion that is discovered on an investigation unrelated to the thyroid gland [14]. TIs detected on USG are managed similar to a clinically apparent thyroid nodule, according to the standard recommendations. TIs on cross-sectional imaging are a growing problem due to its high incidence and lack of definitive imaging feature to identify malignant thyroid nodules, except in the presence of frank local invasion. The ACR (2015) has proposed recommendations, which states that an incidentally detected thyroid nodule is recommended for further evaluation by thyroid USG, if it shows focal thyroid uptake on FDG-PET, shows signs of local invasion or associated suspicious cervical lymphadenopathy, thyroid nodule ≥1 cm (in axial plane) in patients 1 cm [3].
Diffuse Thyroid Diseases Multinodular goiter (MNG) MNG results due to recurrent episodes of hyperplasia and involution leading to irregular enlargement of the thyroid gland, caused by variations in response of follicular cells to external stimuli such as trophic hormones. USG reveals focal or diffuse irregular enlargement of the thyroid with a heterogeneous appearance due to conglomeration of multiple nodules with variable composition and echogenicity, without or with minimal intervening normal parenchyma (Fig. 69.17). The nodules may show presence of calcification, cystic changes, and hemorrhage. Calcifications (present in 15– 25%) may be peripheral or macrocalcifications; few nodules showing “large comet-tail artifacts,” which are suggestive of colloid nodules [16]. The nodules show variable vascularity on Doppler imaging; however, most commonly show peripheral vascularity. Role of USG in MNG is to detect suspicious nodules, cervical lymphadenopathy, to guide FNA and assess the extent of enlargement in cases presenting with mass effect. Each nodule in MNG is evaluated individually, based on its internal features and managed accordingly. Papillary carcinoma is the most common cancer in MNG [16]. CT and MRI, though not routinely used, aid in assessment of large goiters
with suspected substernal extension, and/or those with mass effect leading to obstructive or pressure symptoms (Fig. 69.18).
FIGURE 69.17 Multinodular goiter. USG reveals diffuse enlargement of the thyroid with a heterogeneous appearance due to conglomeration of multiple spongiform and iso to hyperechoic solid nodules (arrows) without intervening normal parenchyma.
FIGURE 69.18 (A) Sagittal and (B) axial postcontrast CT images showing multinodular goiter with a large hypodense heterogeneously enhancing nodule (long arrow) arising from the inferior pole of the left thyroid lobe which shows rim calcification (dotted arrow). It shows retrosternal extension with significant tracheal compression (short solid arrow).
Hashimoto’s Thyroiditis (Ht) (Chronic Lymphocytic Thyroiditis) HT is a chronic, autoimmune-mediated lymphocytic inflammatory disease leading to hypothyroidism, frequently affecting older women [16]. In early stages, USG reveals diffusely enlarged hypoechoic gland with heterogenous, coarse echotexture, and fine linear echogenic fibrotic bands. Multiple hypoechoic solid micronodules or pseudonodules with ill-defined margins may be seen ranging from 1 to 7 mm in size representing focal lymphocytic infiltration surrounded by echogenic rim of fibrosis (Fig. 69.19). This appearance is highly specific for HT with a positive predictive value of 95% [17]. CDI shows mild- to markedly increased gland vascularity. The hypoechoic pseudonodules do not show increased vascularity, while isoechoic normal thyroid parenchyma, especially along areas of fibrosis shows increased vascular flow. In late stages, USG shows heterogenous atrophic gland due to intense fibrosis with reduced or absent vascularity. It may also present with diffuse gland enlargement with or without formation of nodules. Nodular form of HT is also described, which has variable USG appearance; however, studies have reported solid hyperechoic nodules with regular or ill-defined margins to be common [18,19]. USG aids in detecting focal lesions in HT and differentiating them from PTC and primary thyroid lymphoma, which are possible complications of HT (Fig. 69.19).
FIGURE 69.19 Hashimoto’s thyroiditis. (A) USG reveals hypoechoic gland with heterogenous echotexture and multiple hypoechoic solid micronodules with ill-defined margins surrounded by echogenic rim of fibrosis (arrows). (B) USG reveals enlarged thyroid gland with heterogenous echotexture and fine linear echogenic strands (long arrow). A solid very hypoechoic nodule, wider-than-tall showing lobulated margins and no echogenic foci, is noted in the right thyroid lobe (short arrows). Hashimoto’s thyroiditis with papillary carcinoma.
Subacute Thyroiditis (De Quervain’s Thyroiditis) Subacute thyroiditis is a self-limiting disease presumed to be triggered by viral infection [16]. It presents as painful goiter with the anterior neck pain radiating to the ears and jaw; and may be accompanied by systemic symptoms like fever, fatigue, and weight loss. USG reveals diffuse tender thyroid enlargement, with initial unilateral involvement followed by symmetric or asymmetric involvement of contralateral lobe. Ill-defined hypoechoic heterogeneous predominantly subcapsular confluent areas showing centripetal reduction in echogenicity are noted, with no discrete mass formation, characteristically defined as “lava flow.” CDI shows no significant internal vascularity (Fig. 69.20) [16,20]. Follow-up USG reveals resolution of radiological changes on recovery or gland atrophy. Scintigraphy commonly shows diffusely reduced tracer uptake in thyroid gland.
FIGURE 69.20 Subacute thyroiditis. (A) Transverse (B) longitudinal USG image reveals ill-defined hypoechoic heterogeneous predominantly subcapsular confluent areas showing centripetal reduction in echogenicity (arrows). (C) Color Doppler image shows no significant internal vascularity.
Graves’ Disease Graves’ disease is an autoimmune disease characterized by stimulatory autoantibodies to the TSH receptors (long-acting thyroid-stimulating antibodies) and is the most common cause of hyperthyroidism. It is clinically characterized by diffuse goiter, ophthalmopathy with exophthalmos, and pretibial myxoedema (dermopathy). USG reveals diffuse nontender, symmetrical thyroid enlargement with hypoechoic, heterogeneous, and coarse parenchymal echotexture. Hypoechoic micronodular appearance may be noted. CDI shows markedly increased parenchymal vascularity (turbulent flow with arteriovenous shunting), which is called “thyroid inferno” (Fig. 69.21) [16,21]. Scintigraphy shows diffusely enlarged both lobes of thyroid gland with significantly increased tracer uptake and suppressed background and salivary gland activity (Fig. 69.21).
FIGURE 69.21 Graves’ disease. (A) USG reveals hypoechoic thyroid gland with heterogenous echotexture. (B) Power Doppler image showing marked vascularity within the gland. (C) Radionuclide thyroid scan showing intense uptake in thyroid (black arrows) with suppressed uptake in salivary glands.
Acute Suppurative Thyroiditis
Acute suppurative thyroiditis and thyroid abscesses are rare since thyroid has rich blood supply and lymphatic drainage, a high iodine level which has bactericidal effects and a complete fibrous capsule that contributes to the high resistance of thyroid to infection. Acute suppurative thyroiditis is more commonly seen in immunosuppressed individuals, due to local or hematogenous spread of infection or in children with third or fourth branchial fistula (pyriform sinus fistula), where infection tends to be recurrent (Fig. 69.22) [16,22]. USG reveals diffuse goiter with heterogenous parenchymal echotexture. Focal poorly defined hypoechoic lesions or localized heterogenous fluid collections with internal echoes and septations may be seen suggesting abscess formation, with or without air foci within; air foci leading to posterior shadowing. CDI shows normal or increased gland vascularity, and no significant internal vascularity within the parenchymal abscesses. Inflammatory changes may be noted in the strap muscles and periglandular area [16]. CT, preferred over MRI, is done to delineate and assess extent of inflammatory lesions, depict thyroid gland involvement, look for sinus or fistulous tracts, and detect air foci (Fig. 69.23).
FIGURE 69.22 Acute suppurative thyroiditis secondary to pyriform sinus fistula. Axial postcontrast CT images showing: (A) Soft tissue swelling and enhancement involving the left pyriform sinus (long solid arrow) and adjacent soft tissues with an air focus (short solid arrow). (B) Peripherally enhancing abscess noted in the perithyroidal region (dotted arrow). (C) The left thyroid lobe appears enlarged, shows heterogeneous enhancement with few hypoattenuating areas and poorly defined margins (short solid arrows). (Courtesy: Suresh K. Mukherji, MD, MBA, FACR.)
FIGURE 69.23 Acute suppurative thyroiditis. Axial postcontrast CT images showing a peripherally enhancing abscess involving the left thyroid lobe and perithyroidal region (arrow) which shows air fluid level (dotted arrow). (Courtesy: Suresh K. Mukherji, MD, MBA, FACR.)
Riedel’s thyroiditis (RT) RT, also known as invasive fibrosing thyroiditis, is characterized by densely fibrotic inflammatory process involving thyroid and the surrounding structures. RT has been proven with immunohistochemical staining to be part of the IgG4-related disease spectrum and may be associated with mediastinal and retroperitoneal fibrosis, orbital pseudotumor, or sclerosing cholangitis [23]. RT presents as stony hard nontender goiter, with or without symptoms of adjacent organ involvement. USG reveals hypoechoic, homogenous, or heterogeneous hypovascular mass which may show extrathyroidal extension characterized by encasement of vessels or involvement of trachea and esophagus [24]. CT or MRI is done to assess vascular and adjacent organ involvement. CT reveals an enlarged heterogeneous thyroid gland with lower to normal density. MR signal and postcontrast enhancement on CT and MR may change with the activity of
inflammation. Presence of mature fibrosis leads to hypointense signal on both T1 and T2WI and decreased postcontrast enhancement while immature fibrosis with inflammation in the early stages leads to variable heterogenous signal intensity on T2WI and variable postcontrast enhancement depending on its vascularity [24]. Differentials of RT include invasive thyroid carcinoma, lymphoma or fibrotic variant of HT.
Pearls Clinical, biochemical, immunological, and radiological evaluation together contribute to the final diagnosis of diffuse thyroid diseases
Parathyroid Anatomy, Embryology, and Physiology In 85% individuals, there are four parathyroid glands, two superior and two inferior, oval in shape, measuring approximately 3–6 mm in length, 2–4 mm in width, and 1–3 mm in thickness [1]. Supernumerary fifth gland can occur in 2.5–13% of the population with few studies reporting higher incidence [1,25]. Normal parathyroid glands are not seen on imaging, and are visualized if pathological. Superior parathyroid glands arise from fourth branchial pouch, migrate caudally along with thyroid gland, and are located along the posterior aspect of the upper pole or mid portion of the thyroid lobes. Inferior parathyroid glands arise from the third branchial pouch, have a common origin and migrate with the thymus gland, and most commonly found inferior to the posterior aspect of the lower poles of thyroid lobes [1]. The common locations of ectopic parathyroid glands are mediastinal, retropharyngeal, retroesophageal, or trachea-esophageal grove [1,26]. Chief cells of the parathyroid gland produce parathyroid hormone (PTH), which is largely responsible for maintenance of calcium homeostasis. PTH leads to increase in serum calcium level by enhancement of renal tubular calcium reabsorption, inhibition of renal tubular phosphate reabsorption, and stimulation of osteoclastic bone resorption. PTH stimulates the renal hydroxylation of 25-hydroxy–vitamin D, which further increases calcium absorption from intestines.
Pathology Hyperparathyroidism Hyperparathyroidism (HPT) is subdivided on the basis of etiopathogenesis into primary, secondary, and tertiary HPT. Primary HPT represents autonomous overproduction of PTH, resulting from parathyroid adenomas (PTAs; approximately 80% of cases), primary parathyroid hyperplasia (PH; less than 20% of cases), or parathyroid carcinoma (PaTC; approximately 1%) [1]. Secondary HPT is caused by any condition associated with chronic low levels of serum calcium, most commonly from chronic renal insufficiency. Vitamin D deficiency and dietary calcium deficiency can also lead to secondary HPT. When one or more hyperplastic glands in a case of secondary HPT become autonomously functioning, it is called as tertiary HPT. Definitive treatment for primary HPT is surgery. Traditional bilateral cervical dissection or four-gland exploration requires no preoperative imaging. However, preoperative imaging for accurate localization of pathological parathyroid gland and establishment of solitary or multigland involvement is vital for minimally invasive/focused parathyroidectomy. Other subgroup which requires imaging evaluation is patients with persistent/recurrent HPT. In general, USG and Tc99m-sestamibi scanning are more commonly used as primary techniques. 4D CT, MRI, and PET/CT are used in more difficult, recurrent cases or when results of primary imaging techniques are not helpful. Parathyroid Adenoma (PTA) PTAs are benign parathyroid tumors; commonly involving a single gland; however multigland involvement has been described. Various “anatomical” and “functional” imaging techniques are used in conjunction to detect and localize PTAs. Ultrasonography: USG accurately evaluates PTAs in eutopic glands and also assesses multigland involvement/multiple areas of uptake on radionuclide scanning, concomitant thyroid disease, and cervical lymphadenopathy. USG may also aid in cases of persistent or recurrent HPT postsurgery and in MEN syndromes. On USG, PTA appears as round to oval or rarely multilobulated, homogenously hypoechoic solid mass with well-defined margins. Some PTAs may show heterogeneous echotexture and cystic areas within. An echogenic line is seen separating thyroid and parathyroid tissue (Fig. 69.24). On CDI, these lesions are highly vascular and show a prominent “polar feeding
vessel” that arises from the branches of the inferior thyroidal artery. This vessel tends to branch along the periphery of the lesion before penetrating the lesion, covering 90–270° arc and gives the characteristic appearance of a “vascular arc”; which is a specific sign of PTA (Fig. 69.24) [27]. The adjacent thyroid parenchyma may also show asymmetrically increased vascularity.
FIGURE 69.24 Parathyroid adenoma. (A) USG reveals an oval hypoechoic solid mass posterior to the thyroid lobe, with lobulated margins (solid arrows). An echogenic line is seen separating thyroid and parathyroid tissue (dashed arrow). (B) Color Doppler image shows a peripheral “vascular arc” (arrows).
Imaging differentials of PTA on USG are enlarged cervical lymph nodes and thyroid nodules. Cervical lymph nodes show hilar vascularity and are more lateral in the neck. Thyroid nodules are usually of mixed echogenicity, including calcification and cystic component, are within the echogenic thyroid capsule and show variable peripheral or intranodular vascularity. Dual Phase Tc99m-Sestamibi Scan: Tc99m-sestamibi is a cationic complex which localizes into cellular mitochondria. Since PTAs have larger number of mitochondria, Tc99msestamibi is taken up more avidly in adenomatous tissue than the thyroid or normal parathyroid gland and is followed by slower release. Dual phase Tc99m-sestamibi scan involves acquisition of early and delayed planar images of neck and thorax after an intravenous injection of Tc99m-sestamibi. Abnormal parathyroid gland shows increased focal uptake in early images and retained tracer in delayed phase, while thyroid or normal parathyroid gland show physiological uptake of tracer in early phase and faster washout. SPECT or SPECT/CT images can be performed for better localization (Fig. 69.25).
FIGURE 69.25 Parathyroid adenoma. (A) Early and (B) delayed planar images of Tc99m-sestamibi scan show focal tracer uptake in mediastinum in the early phase (arrow) with retained tracer uptake in delayed phase (arrow). Corresponding (C) CT and (D) SPECT/CT axial sections show a well-defined soft tissue density lesion (arrow) with increased tracer uptake in anterior mediastinum (arrow) suggestive of ectopic parathyroid adenoma.
4D-Computed Tomography: 4D-computed tomography (4D-CT) is a technique used for preoperative localization of PTAs in eutopic or ectopic locations. Multiplanar CT (axial acquisition with coronal and sagittal reformations) forms the first three “dimensions” of 4D-CT and provides the anatomical information. Change in enhancement from non–contrast-enhanced, arterial, and venous phase imaging constitutes the fourth “dimension” of 4D-CT and provides the perfusion information [28]. Characteristic imaging appearance of PTAs on 4D-CT is low attenuation on the non–contrast-enhanced images, peak enhancement on the arterial phase (greater than thyroid gland) and contrast washout seen on venous phase images (Fig. 69.26). These characteristic imaging features help to differentiate PTAs from thyroid nodules or lymph
nodes. However, other enhancement patterns that may be noted in PTAs are —not higher in attenuation than thyroid in the arterial phase but lower in attenuation than thyroid in the delayed phase; or neither higher in attenuation than thyroid in the arterial phase nor lower in attenuation than thyroid in the delayed phase [29]. CT may also demonstrate the “polar vessel sign” in the form of a prominent vascular channel seen on the arterial phase of imaging, terminating in a parathyroid lesion, which is larger than contralateral neck vessels in a corresponding location.
FIGURE 69.26 Parathyroid adenoma. (A) Noncontrast CT shows the thyroid gland which appears hyperdense on NCCT. A well-defined hypodense lesion is noted posterior to the right thyroid lobe (arrow). The lesion (arrow) is (B) hyperattenuating to thyroid on arterial and (C) hypoattenuating to thyroid on venous phase.
MRI: MRI is rarely used for preoperative localization of PTAs. It may be used in persistent or recurrent HPT to locate residual abnormal parathyroid tissue, in neck or ectopic locations. Parathyroid appears isointense to hypointense on T1WI and hyperintense on T2WI. Attempts have been made to evaluate 4DMRI to localize PTAs, where they show similar enhancement characteristics as that on 4D-CT [30]. PET-CT: Few PET tracers like F18 choline and C11 methionine have been employed for preoperative planning of parathyroid surgery, however these are considered second-line techniques. F18 choline appears to be a promising tracer due to excellent detection rates and better availability as compared to C11 methionine. Parathyroid Carcinoma (PaTC) PaTC is an extremely rare malignant tumor and presents with palpable neck mass with severe HPT. On USG, PaTC tends to be larger than PTAs with an average size of 3 cm or more [31]. It appears as a round to oval hypoechoic
mass, with heterogeneous echotexture, irregular shape, lobulated or noncircumscribed margins, thick capsule, internal vascularity, and may show intralesional calcifications and cystic changes [31]. It commonly shows features of local invasion and may be associated with metastatic cervical lymphadenopathy [31]. CT and MRI may be used to assess for local invasion, metastatic disease, and postsurgical recurrence. Parathyroid Hyperplasia (PH) PH involves symmetric or asymmetric enlargement of two or more glands, most commonly seen secondary to chronic renal insufficiency. Differentiation of PTA and hyperplasia on USG is difficult due to similar morphological features, however each gland tends to be smaller in PH than adenoma. 4D-CT shows similar features as that of PTAs and may be used for preoperative evaluation. Parathyroid Cyst (PC) PCs are rare lesions which may be found in the neck or mediastinum; majority arising from the inferior parathyroid glands. They are classified as functioning or nonfunctioning PCs; nonfunctioning PCs being more common. On USG, PCs appear as anechoic round to oval wellcircumscribed lesions at the sites of parathyroid glands and may show an echogenic capsule. CT and MRI show a well-circumscribed cystic lesion and are useful in mediastinal lesions.
Pearls
◾hypoparathyroidism, Hyperparathyroidism is a more common clinical entity than with PTA being the commonest cause ◾primary USG and Tc -sestamibi scanning are the commonly used imaging techniques to evaluate PTAs 99m
Hypoparathyroidism Hypoparathyroidism is diagnosed mainly on clinical and biochemical grounds; parathyroid gland imaging plays a limited role in its evaluation.
Conclusion Thyroid and parathyroid diseases are common in clinical practice. A detailed clinical history, methodical imaging evaluation with a thorough knowledge
of the recommendations, is pivotal in accurate diagnosis and management.
Suggested Readings • BR Haugen, EK Alexander, KC Bible, et al., 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: the American Thyroid Association guidelines task force on thyroid nodules and differentiated thyroid cancer, Thyroid 26 (1) (2016) 1–133. • AC Nachiappan, ZA Metwalli, BS Hailey, RA Patel, ML Ostrowski, DM Wynne, The thyroid: review of imaging features and biopsy techniques with radiologic-pathologic correlation, Radiographics 34 (2) (2014) 276–293. • FN Tessler, WD Middleton, EG Grant, et al., ACR thyroid imaging, reporting and data system (TI-RADS): white paper of the ACR TI-RADS committee, J Am Coll Radiol 14 (5) (2017) 587–595. • HY Yuen, KT Wong, AT Ahuja, Sonography of diffuse thyroid disease, Australas J Ultrasound Med 19 (1) (2016) 13–29. • JK Hoang, W Sung, M Bahl, CD Phillips, How to perform parathyroid 4D CT: tips and traps for technique and interpretation, Radiology 270 (1) (2014) 15–24.
References [1] PM Som, HD Curtin, Head and Neck Imaging, Elsevier Health Sciences; 2011. [2] DA Zander, WRK Smoker, Imaging of ectopic thyroid tissue and thyroglossal duct cysts, Radiographics 34 (1) (2014) 37–50. [3] BR Haugen, EK Alexander, KC Bible, et al., 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: the American Thyroid Association guidelines task force on thyroid nodules and differentiated thyroid cancer, Thyroid 26 (1) (2016) 1–133. [4] RC Smallridge, KB Ain, SL Asa, et al., American Thyroid Association guidelines for management of patients with anaplastic thyroid cancer, Thyroid 22 (11) (2012) 1104–39. [5] G Noussios, P Anagnostis, DG Goulis, D Lappas, K Natsis, Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity, Eur J Endocrinol 165 (3) (2011) 375. [6] S Patel, AA Bhatt, Thyroglossal duct pathology and mimics, Insights Imaging 10 (1) (2019) 1–12. [7] AC Nachiappan, ZA Metwalli, BS Hailey, RA Patel, ML Ostrowski, DM Wynne, The thyroid: review of imaging features and biopsy techniques with radiologic-pathologic correlation, Radiographics 34 (2) (2014) 276–93. [8] FN Tessler, WD Middleton, EG Grant, et al., ACR Thyroid Imaging, Reporting and Data System (TI-RADS): white paper of
the ACR TI-RADS committee, J Am Coll Radiol 14 (5) (2017) 587–95. [9] FN Tessler, WD Middleton, EG Grant, Thyroid imaging reporting and data system (TI-RADS): a user’s guide, Radiology 287 (1) (2018) 29–36. [10] JK Hoang, WK Lee, M Lee, D Johnson, S Farrell, US features of thyroid malignancy: pearls and pitfalls, Radiographics 27 (3) (2007) 847–860. [11] M Iacobone, S Jansson, M Barczyński, P Goretzki, Multifocal papillary thyroid carcinoma: a consensus report of the European Society of Endocrine Surgeons (ESES), Langenbeck’s Arch Surg 399 (2) (2014) 141–54. [12] S-H Kim, B-S Kim, S-L Jung, et al., Ultrasonographic findings of medullary thyroid carcinoma: a comparison with papillary thyroid carcinoma, Korean J Radiol 10 (2) (2009) 101–105. [13] JH Lee, HK Lee, DH Lee, et al., Ultrasonographic findings of a newly detected nodule on the thyroid bed in postoperative patients for thyroid carcinoma: correlation with the results of ultrasonography-guided fine-needle aspiration biopsy, Clin Imaging 31 (2) (2007) 109–13. doi:10.1016/j.clinimag.2006.11.001 [14] J Jin, CR McHenry, Thyroid incidentaloma. Best Pract Res Clin Endocrinol Metab 26 (1) (2012) 83–96. doi:10.1016/j.beem.2011.06.004 [15] JK Hoang, JE Langer, WD Middleton, et al. Managing incidental thyroid nodules detected on imaging: white paper of the ACR Incidental Thyroid Findings Committee, J Am Coll Radiol 12 (2) (2015) 143–150. [16] HY Yuen, KT Wong, AT Ahuja, Sonography of diffuse thyroid disease, Australas J Ultrasound Med 19 (1) (2016) 13–29. [17] Yeh H-C, W Futterweit, P Gilbert, Micronodulation: ultrasonographic sign of Hashimoto thyroiditis, J Ultrasound Med 15 (12) (1996) 813–819. [18] JE Langer, A Khan, HL Nisenbaum, et al. Sonographic appearance of focal thyroiditis, Am J Roentgenol 176 (3) (2001) 751–754. [19] JW Zhang, ZJ Chen, A Gopinathan, Focal nodular hashimoto’s thyroiditis: comparison of ultrasonographic features with malignant and other benign nodules, Ann Acad Med Singapore 45 (8) (2016) 357–363. [20] C Cappelli, I Pirola, E Gandossi, AM Formenti, B Agosti, M Castellano, Ultrasound findings of subacute thyroiditis: a single institution retrospective review, Acta Radiol 55 (4) (2014) 429–433.
[21] PW Ralls, DS Mayekawa, KP Lee, et al., Color-flow Doppler sonography in Graves disease: “thyroid inferno”, Am J Roentgenol 150 (4) (1988) 781–784. [22] H Masuoka, A Miyauchi, C Tomoda, et al., Imaging studies in sixty patients with acute suppurative thyroiditis, Thyroid 21 (10) (2011) 1075–1080. [23] M Dahlgren, A Khosroshahi, GP Nielsen, V Deshpande, JH Stone, Riedel’s thyroiditis and multifocal fibrosclerosis are part of the IgG4-related systemic disease spectrum, Arthritis Care Res (Hoboken) 62 (9) (2010) 1312–1318. [24] M Ozbayrak, F Kantarci, DC Olgun, C Akman, I Mihmanli, P Kadioglu, Riedel thyroiditis associated with massive neck fibrosis, J Ultrasound Med 28 (2) (2009) 267–271. [25] d’AF Alessandro, de FLM Montenegro, LG Brandão, Lourenço DM Jr, de SA Toledo, AC Cordeiro, Supernumerary parathyroid glands in hyperparathyroidism associated with multiple endocrine neoplasia type 1, Rev Assoc Med Bras 58 (3) (2012) 323–327. [26] G Noussios, P Anagnostis, K Natsis, Ectopic parathyroid glands and their anatomical, clinical and surgical implications, Exp Clin Endocrinol Diab 120 (10) (2012) 604–610. [27] RJ Wolf, JJ Cronan, JM Monchik, Color Doppler sonography: an adjunctive technique in assessment of parathyroid adenomas, J Ultrasound Med 13 (4) (1994) 303–308. [28] JK Hoang, W Sung, M Bahl, CD Phillips, How to perform parathyroid 4D CT: tips and traps for technique and interpretation, Radiology 270 (1) (2014) 15–24. [29] M Bahl, AR Sepahdari, JA Sosa, JK Hoang, Parathyroid adenomas and hyperplasia on four-dimensional CT scans: three patterns of enhancement relative to the thyroid gland justify a threephase protocol, Radiology 277 (2) (2015) 454–462. [30] K Nael, J Hur, A Bauer, et al., Dynamic 4D MRI for characterization of parathyroid adenomas: multiparametric analysis, Am J Neuroradiol 36 (11) (2015) 2147–2152. [31] V Ferraro, LI Sgaramella, Di G Meo, et al., Current concepts in parathyroid carcinoma: a single centre experience, BMC Endocr Disord 19 (1) (2019) 1–9.
CHAPTER 70
Paranasal Sinuses Priya Ghosh, Aditi Chandra, Saugata Sen
Introduction The sinonasal space consists of the nose, the nasal cavity, and the paranasal sinuses, namely, the paired maxillary, ethmoid, frontal, and sphenoid sinuses. The sinonasal spaces share a common embryological development pathway. The entire sinonasal region consists of mucous lined closely connected airfilled spaces that show commonality of pathology, as well as easy regional spread of disease processes. Being exposed to the external environment, they are vulnerable to a variety of traumatic, infectious, inflammatory, and neoplastic diseases.
Imaging Techniques Radiography The indication and the need for plain x-rays in diagnosis and further management have declined over the last decade as cross-sectional imaging with multiplanar reconstructions create a near-perfect anatomical simulation for the treating physician. There is still a limited role for plain films of the paranasal sinuses in acute infection. This is limited to a single occipitomental view (Fig. 70.1), which is considered adequate for the basic assessment of the maxillary antra, the frontal sinuses, and the sphenoid sinus but is poor at excluding pathology of the ethmoid air cells or providing minute bony detail.
FIGURE 70.1 X-ray occipitomental view showing normal aerated paranasal sinuses in a 54-year-old woman. F, left frontal sinus; M, left maxillary sinus; E, right ethmoid sinuses; N, left nasal cavity; white arrowhead, nasal septum. Correct positioning is indicated by projection of the petrous ridge (dotted line) inferior to the maxillary sinus (M).
Computed Tomography (CT) Scan CT is the initial and most common technique for imaging the sinonasal space. Modern CT scanners are fast, readily available, and have very little radiation exposure. Excellent detail is available regarding the anatomy, anatomical variants, and pathology. Both soft tissue and bony detail can be observed in respective windows. Technique Modern multidetector scanners can reconstruct images in any plane from the raw data with no loss of detail. Hence, only axial sections are acquired
followed by multiplanar reconstructions in coronal and sagittal planes. The lesser scan time and radiation dose results in better patient compliance. The scan plane being parallel to the hard palate helps obviate dental artifacts to a large extent as well. This was not possible when direct coronal images were acquired with older single detector scanners. Images are usually reconstructed at 2.5–3 mm and 0.625–1 mm intervals. Reconstructions in both bone and soft tissue algorithms are required. For diseases such as congenital abnormalities, infections, inflammations, and granulomatous pathologies, the scan extends from the hard palate to the skull base. The decision to administer intravenous contrast should depend on the disease entity and should be performed for the evaluation of neoplasms and aggressive infectious and inflammatory disorders.
Magnetic Resonance Imaging (MRI) In the sinonasal region, MRI is reserved for neoplasms and any other sinonasal pathology that involves the orbits or brain. The assessment of the brain, meninges, and orbits, as well as perineural spread is superior with contrastenhanced MRI. MRI is superior to CT due to better soft tissue resolution and multiparametric imaging, but is expensive and has longer acquisition times. CT is superior to MRI for evaluating bony architecture, calcification, and periosteal reaction. Standard head coil is used for MR imaging of the sinonasal region using a 1.5T or 3T magnet. High-resolution T1-weighted and T2-weighted FSE sequences performed in the axial, coronal, and sagittal planes are the mainstay of sinonasal imaging. T2-weighted fat-saturated or STIR sequences are used as an adjunct to increase tumor conspicuity. Slice thickness of 3 mm is maintained, with interslice gap of 0–0.3 mm. Axial images are obtained parallel to the hard palate and the other sections perpendicular to the axial plane. Diffusion-weighted imaging is also routinely performed with images acquired at three b values, usually b50, b500, and b1000 that also generate apparent diffusion coefficient (ADC) maps. Most malignant tumors show diffusion restriction due to high cellularity. T1-weighted fat-saturated pre- and post-IV-gadolinium images are obtained, which help identify tumor extension, perineural, intraorbital, and intracranial spread, meningeal involvement. MRI is also helpful for assessing intracranial complications of infectious or inflammatory diseases, such as intracranial abscesses or orbital cellulitis.
Nuclear Medicine 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is not indicated for routine sinonasal imaging. In oncology, FDG-PET is not useful for evaluating the primary site, but it is useful for assessing distant disease (“M stage”). FDG-PET is commonly used
to assess recurrent or residual neoplastic disease following treatment, and also in monitoring response [1] (Fig. 70.2). A key disadvantage of FDG PET CT in the sinonasal region is its high false-positive rate, as inflammatory changes following therapy may also show FDG avidity [2].
FIGURE 70.2 Axial PET-CT image in a 40-year-old woman with sinonasal PNET (peripheral neuroectodermal tumor) shows mass in the right nasal cavity invading right maxillary sinus with high metabolic activity signified by increased FDG uptake (asterisk).
American College of Radiology (ACR) appropriateness criteria for imaging in sinonasal diseases [3] are shown in Table 70.1.
Table 70.1 ACR Appropriateness Criteria for Imaging in Sinonasal Diseases Clinical Presentation
Usually Appropria te Investigati on
Acute ( mandibl e involve ment Associat ions: Paget’s disease, retinobla stoma, irradiatio n Poorer prognosi s of radiation induced OS
1–4% of ES arise in head and neck Site: Mandibl e> maxilla > calvariu m> cervical spine. Rare within sinonasa l cavities Associat ions: Irradiati on followin g retinobl astoma
Imaging
Rhabdomyosarc oma (RMS) (Fig. 70.51)
Chondrosar coma (CS)
Osteosar coma (OS)
Ewing’s Sarcom a (ES)/PN ET
Nonspecific features: usually homogeneous, enhancing, associated with bone remodeling/destr uction
Marginal bone erosion seen, characteristi c chondroid calcification is diagnostic if present High T2 signals, intense enhanceme nt
Sunburst periosteal reaction, bone destructi on seen, dense sclerotic bone may be present T1 and T2 signals vary dependin g on bone content Enhance ment is less than CS
Destruct ive soft tissue mass, rarely expansil e mass Onionpeel perioste al reaction
Secondary Tumors: Metastases to the sinonasal cavity are uncommon. Usually a single sinus is involved and imaging features may mimic a primary. Primary malignancies metastasizing to the sinonasal cavity are renal cell cancer (50%), breast, colon, prostate, thyroid, female genital tract cancers [99]. Renal cell cancer metastases are often hypervascular and patients may present with epistaxis.
Suggested Readings • S Vaid, N Vaid, S Rawat, AT Ahuja, An imaging checklist for pre-FESS CT: framing a surgically relevant report, Clin Radiol 66 (5) (2011) 459–470. • WT O’Brien Sr, S Hamelin, EK Weitzel, The preoperative sinus CT: avoiding a “CLOSE” call with surgical complications, Radiology 281 (2016) 10–21.
• VM Joshi, R Sansi, Imaging in sinonasal inflammatory disease, Neuroimaging Clin N Am 25 (2015) 549–568. • S Sen, A Chandra, S Mukhopadhyay, P Ghosh, Imaging approach to sinonasal neoplasms, Neuroimaging Clin N Am 25 (2015) 577–593. • S Sen, A Chandra, S Mukhopadhyay, P Ghosh, CT and MRI in imaging sinonasal neoplasms, Neuroimaging Clin N Am 25 (2015) 595–618.
References [1] HB Eggesbø, Imaging of sinonasal tumours, Cancer Imaging 12 (2012) 136–152. [2] GW Goerres, GK Von Schulthess, TF Hany, Positron emission tomography and PET CT of the head and neck: FDG uptake in normal anatomy, in benign lesions, and in changes resulting from treatment, AJR Am J Roentgenol 179 (2002) 1337–1343. [3] Expert Panel on Neurologic Imaging. CF.E Kirsch, J Bykowski, JM Aulino, KL Berger, AF Choudhri, et al., ACR Appropriateness Criteria® sinonasal disease, J Am Coll Radiol 14 (2017) S550–S559. [4] PM Som, TP Naidich, Illustrated review of the embryology and development of the facial region, part 1: early face and lateral nasal cavities, AJNR Am J Neuroradiol 34 (2013) 2233–2240. [5] ZJ Cappello, K Minutello, AB Dublin, Anatomy, Head and Neck, Nose Paranasal Sinuses, StatPearls Publishing, StatPearls, Treasure Island, FL, 2020. [6] G Wolf, W Anderhuber, F Kuhn, Development of the paranasal sinuses in children: implications for paranasal sinus surgery, Ann Otol Rhinol Laryngol 102 (1993) 705–711. [7] TJ Beale, G Madani, SJ Morley, Imaging of the paranasal sinuses and nasal cavity: normal anatomy and clinically relevant anatomical variants, Semin Ultrasound CT MR 30 (2009) 2–16. [8] I Serifoglu, İ.İ Oz, M Damar, MC Buyukuysal, A Tosun, Ö Tokgöz, Relationship between the degree and direction of nasal septum deviation and nasal bone morphology, Head Face Med 13 (2017) 3. [9] DW Hsu, JD Suh, Anatomy and physiology of nasal obstruction, Otolaryngol Clin North Am 51 (2018) 853–865. [10] P Keros, On the practical value of differences in the level of the lamina cribrosa of the ethmoid, Z Laryngol Rhinol Otol 41 (1962) 809–813. [11] R Gera, F Mozzanica, A Karligkiotis, A Preti, F Bandi, S Gallo, et al., Lateral lamella of the cribriform plate, a keystone landmark: proposal for a novel classification system, Rhinology 56 (2018) 65– 72. [12] VF Chong, YF Fan, D Lau, DS Sethi, Functional endoscopic sinus surgery (FESS): what radiologists need to know, Clin Radiol 53 (1998) 650–658.
[13] R Kalaiarasi, V Ramakrishnan, S Poyyamoli, Anatomical variations of the middle turbinate concha bullosa and its relationship with chronic sinusitis: a prospective radiologic study, Int Arch Otorhinolaryngol 22 (2018) 297–302. [14] MW El-Anwar, AH Ali, RM Almolla, G Abdulmonaem, A Raafat, ME Hassan, Radiological middle turbinate variations and their relation to nasal septum deviation in asymptomatic adult, Egypt J Radiol Nucl Med 51 (2020) 104. [15] S Shalini, T Gopal, Paradoxical curvature of middle turbinate: a computed tomographic study, Int J Contemp Med Res [IJCMR] 5 (2018). 10.21276/ijcmr.2018.5.9.22. [16] T Gichner, IARC monographs on the evaluation of carcinogenic risks to humans. Volume 62. Wood dust and formaldehyde, Biol Plant 37 (1995) 500, –500. 10.1007/bf02908826. [17] MH Al-Bar, SM Lieberman, RR Casiano, Surgical anatomy and embryology of the frontal sinus, SE Kountakis, BA Senior, W Draf (Eds.) The Frontal Sinus, Springer, Berlin, Heidelberg, 2016, 15–33. [18] WE Bolger, CA Butzin, DS Parsons, Paranasal sinus bony anatomic variations and mucosal abnormalities: CT analysis for endoscopic sinus surgery, Laryngoscope 101 (1991) 56–64. [19] AZ Eweiss, HS Khalil, The prevalence of frontal cells and their relation to frontal sinusitis: a radiological study of the frontal recess area, ISRN Otolaryngol 2013 (2013) 687582. [20] JM DelGaudio, PA Hudgins, G Venkatraman, A Beningfield, Multiplanar computed tomographic analysis of frontal recess cells, Arch Otolaryngol–Head Neck Surg 131 (2005) 230. 10.1001/archotol.131.3.230. [21] JP Bent, C Cuilty-Siller, FA Kuhn, The frontal cell as a cause of frontal sinus obstruction, Am J Rhinol 8 (1994) 185–192. [22] S Lafci Fahrioglu, N VanKampen, C Andaloro, Anatomy, Head and Neck, Sinus Function and Development, StatPearls Publishing, StatPearls, Treasure Island, FL, 2020. [23] LP Chmielik, A Chmielik, The prevalence of the Onodi cell: most suitable method of CT evaluation in its detection, Int J Pediatr Otorhinolaryngol 97 (2017) 202–205. [24] D Sharma, N Sharma, V Sharma, Sinonasal cancers: diagnosis and management, T-C Wang (Eds.) Challenging Issues on Paranasal Sinuses, London, UK, pp. 95–113, 2019. [25] SB Hiremath, AA Gautam, K Sheeja, G Benjamin, Assessment of variations in sphenoid sinus pneumatization in Indian population: a multidetector computed tomography study, Indian J Radiol Imaging 28 (2018) 273–279. [26] MC DeLano, FY Fun, SJ Zinreich, Relationship of the optic nerve to the posterior paranasal sinuses: a CT anatomic study, AJNR Am J
Neuroradiol 17 (1996) 669–675. [27] AG Osborn, The nasal arteries, AJR Am J Roentgenol 130 (1978) 89–97. [28] AG Osborn, Craniofacial venous plexuses: angiographic study, AJR Am J Roentgenol 136 (1981) 139–143. [29] G Paff, Anatomy of the head and neck, G Paff (Eds.) Anatomy of the Head and Neck, WB Saunders, Philadelphia, 1973, 183–203. [30] AG Beule, Physiology and pathophysiology of respiratory mucosa of the nose and the paranasal sinuses, GMS Curr Top Otorhinolaryngol Head Neck Surg 9 (2010), Doc07. [31] R Kahana-Zweig, M Geva-Sagiv, A Weissbrod, L Secundo, N Soroker, N Sobel, Measuring and characterizing the human nasal cycle, PLoS One 11 (2016) e0162918. [32] RM Rosenfeld, JF Piccirillo, SS Chandrasekhar, I Brook, K Ashok Kumar, M Kramper, et al., Clinical practice guideline (update): adult sinusitis, Otolaryngol Head Neck Surg 152 (2015) S1–39. [33] RM Rosenfeld, D Andes, N Bhattacharyya, D Cheung, S Eisenberg, TG Ganiats, et al., Clinical practice guideline: adult sinusitis, Otolaryngol Head Neck Surg 137 (2007) S1–31. [34] T Heikkinen, A Järvinen, The common cold, Lancet 361 (2003) 51–59. [35] DE Low, M Desrosiers, J McSherry, G Garber, JW Williams Jr., H Remy, et al., A practical guide for the diagnosis and treatment of acute sinusitis, CMAJ 156 (1997) S1–14. [36] CJ Ito, RS Jackson, M Castro-Borobio, S Nanjappa, O Klinkova, V Phommachanh, et al., Microbiology of acute rhinosinusitis in immunosuppressed patients, Infect Dis Clin Pract 25 (2017) 260. [37] VD Nguyen, AK Singh, WB Altmeyer, B Tantiwongkosi, Demystifying orbital emergencies: a pictorial review, Radiographics 37 (2017) 947–962. [38] H Bhatia, R Kaur, R Bedi, MR imaging of cavernous sinus thrombosis, Eur J Radiol Open 7 (2020) 100226. [39] PM Som, HD Curtin, Head and Neck Imaging E-book, Elsevier Health Sciences, Amsterdam, The Netherlands, 2011. [40] VM Rao, KI el-Noueam, Sinonasal imaging. Anatomy and pathology, Radiol Clin North Am 36 (1998) 921–939, vi. [41] PM Som, WP Dillon, GD Fullerton, RA Zimmerman, B Rajagopalan, Z Marom, Chronically obstructed sinonasal secretions: observations on T1 and T2 shortening, Radiology 172 (1989) 515– 520. [42] WP Dillon, PM Som, GD Fullerton, Hypointense MR signal in chronically inspissated sinonasal secretions, Radiology 174 (1990) 73–78.
[43] PM Som, WP Dillon, HD Curtin, GD Fullerton, M Lidov, Hypointense paranasal sinus foci: differential diagnosis with MR imaging and relation to CT findings, Radiology 176 (1990) 777–781. 10.1148/radiology.176.3.2389036. [44] RW Babbel, HR Harnsberger, J Sonkens, S Hunt, Recurring patterns of inflammatory sinonasal disease demonstrated on screening sinus CT, AJNR Am J Neuroradiol 13 (1992) 903–912. [45] JW Sonkens, HR Harnsberger, GM Blanch, RW Babbel, S Hunt, The impact of screening sinus CT on the planning of functional endoscopic sinus surgery, Otolaryngol Head Neck Surg 105 (1991) 802–813. [46] KT Montone, Pathology of fungal rhinosinusitis: a review, Head Neck Pathol 10 (2016) 40–46. [47] J Gavito-Higuera, CB Mullins, L Ramos-Duran, H Sandoval, N Akle, R Figueroa, Sinonasal fungal infections and complications: a pictorial review, J Clin Imaging Sci 6 (2016) 23. [48] E Raz, W Win, M Hagiwara, YW Lui, B Cohen, GM Fatterpekar, Fungal sinusitis, Neuroimaging Clin N Am 25 (2015) 569–576. [49] M Aribandi, VA McCoy, C Bazan 3rd., Imaging features of invasive and noninvasive fungal sinusitis: a review, Radiographics 27 (2007) 1283–1296. [50] A Raut, NT Huy, Rising incidence of mucormycosis in patients with COVID-19: another challenge for India amidst the second wave?, Lancet Respir Med (2021). 10.1016/S2213-2600(21)00265-4. [51] ER Groppo, IH El-Sayed, AH Aiken, CM Glastonbury, Computed tomography and magnetic resonance imaging characteristics of acute invasive fungal sinusitis, Arch Otolaryngol Head Neck Surg 137 (2011) 1005–1010. [52] JH Yoon, DG Na, HS Byun, YH Koh, SK Chung, HJ Dong, Calcification in chronic maxillary sinusitis: comparison of CT findings with histopathologic results, AJNR Am J Neuroradiol 20 (1999) 571–574. [53] I De Gaudemar, P Contencin, T Van den Abbeele, A Munck, J Navarro, P Narcy, Is nasal polyposis in cystic fibrosis a direct manifestation of genetic mutation or a complication of chronic infection?, Rhinology 34 (1996) 194–197. [54] R Bouatay, L Aouf, B Hmida, A El Korbi, N Kolsi, K Harrathi, et al., The role of imaging in the management of sinonasal mucoceles, Pan Afr Med J 34 (2019) 3. [55] GG Capra, PN Carbone, DP Mullin, Paranasal sinus mucocele, Head Neck Pathol 6 (2012) 369–372. [56] A Illner, HC Davidson, HR Harnsberger, J Hoffman, The silent sinus syndrome: clinical and radiographic findings, AJR Am J Roentgenol 178 (2002) 503–506.
[57] H Tatekawa, T Shimono, M Ohsawa, S Doishita, S Sakamoto, Y Miki, Imaging features of benign mass lesions in the nasal cavity and paranasal sinuses according to the 2017 WHO classification, Jpn J Radiol 36 (2018) 361–381. [58] K Moturi, V Kaila, Cervicofacial actinomycosis and its management, Ann Maxillofac Surg 8 (2018) 361–364. [59] B D’Anza, CA Langford, R Sindwani, Sinonasal imaging findings in granulomatosis with polyangiitis (Wegener granulomatosis): a systematic review, Am J Rhinol Allergy 31 (2017) 16–21. [60] DW Kennedy, SJ Zinreich, AE Rosenbaum, ME Johns, Functional endoscopic sinus surgery. Theory and diagnostic evaluation, Arch Otolaryngol 111 (1985) 576–582. [61] H Stammberger, Endoscopic endonasal surgery: concepts in treatment of recurring rhinosinusitis. Part I. Anatomic and pathophysiologic considerations, Otolaryngol Head Neck Surg 94 (1986) 143–147. [62] EC Cashman, PJ MacMahon, D Smyth, Computed tomography scans of paranasal sinuses before functional endoscopic sinus surgery, World J Radiol 3 (2011) 199. [63] WT O’Brien Sr., S Hamelin, EK Weitzel, The preoperative sinus CT: avoiding a “CLOSE” call with surgical complications, Radiology 281 (2016) 10–21. [64] A Walker, P Surda, C Hopkins, Improving paranasal sinus computed tomography reporting prior to functional endoscopic sinus surgery: an ENT-UK panel perspective, J Laryngol Otol 131 (2017) 280–281. [65] JK Hoang, JD Eastwood, CL Tebbit, CM Glastonbury, Multiplanar sinus CT: a systematic approach to imaging before functional endoscopic sinus surgery, AJR Am J Roentgenol 194 (2010) W527– W536. [66] DR Youlden, SM Cramb, S Peters, SV Porceddu, H Møller, L Fritschi, et al., International comparisons of the incidence and mortality of sinonasal cancer, Cancer Epidemiol 37 (2013) 770–779. [67] PE Robin, DJ Powell, JM Stansbie, Carcinoma of the nasal cavity and paranasal sinuses: incidence and presentation of different histological types, Clin Otolaryngol Allied Sci 4 (1979) 431–456. [68] JL Llorente, F López, C Suárez, MA Hermsen, Sinonasal carcinoma: clinical, pathological, genetic and therapeutic advances, Nat Rev Clin Oncol 11 (2014) 460–472. [69] AK El-Naggar, JK.C Chan, JR Grandis, T Takata, PJ Slootweg, WHO Classification of Head and Neck Tumours, International Agency for Research on Cancer, Lyon, France, 2017. [70] S Tashi, BS Purohit, M Becker, P Mundada, The pterygopalatine fossa: imaging anatomy, communications, and pathology revisited,
Insights Imaging 7 (2016) 589–599. [71] MW van den Brekel, JA Castelijns, HV Stel, J Valk, GA Croll, RP Golding, et al., Detection and characterization of metastatic cervical adenopathy by MR imaging: comparison of different MR techniques, J Comput Assist Tomogr 14 (1990) 581–589. [72] S Sen, A Chandra, S Mukhopadhyay, P Ghosh, Imaging approach to sinonasal neoplasms, Neuroimaging Clin N Am 25 (2015) 577– 593. [73] JW Dankbaar, FA Pameijer, J Hendrikse, IM Schmalfuss, Easily detected signs of perineural tumour spread in head and neck cancer, Insights Imaging 9 (2018) 1089–1095. [74] G Madani, TJ Beale, VJ Lund, Imaging of sinonasal tumors, Semin Ultrasound CT MR 30 (2009) 25–38. [75] DP Vrabec, The inverted Schneiderian papilloma: a 25-year study, Laryngoscope 104 (1994) 582–605. [76] MR Kaufman, MS Brandwein, W Lawson, Sinonasal papillomas: clinicopathologic review of 40 patients with inverted and oncocytic Schneiderian papillomas, Laryngoscope 112 (2002) 1372–1377. 10.1097/00005537-200208000-00009. [77] N Vorasubin, D Vira, JD Suh, S Bhuta, MB Wang, Schneiderian papillomas: comparative review of exophytic, oncocytic, and inverted types, Am J Rhinol Allergy 27 (2013) 287–292. [78] JS Lewis Jr., Sinonasal squamous cell carcinoma: a review with emphasis on emerging histologic subtypes and the role of human papillomavirus, Head Neck Pathol 10 (2016) 60–67. [79] L Barnes, R Verbin, D Gnepp, Diseases of the nose, paranasal sinuses and nasopharynx in: L Barnes (ed.), Surgical Pathology of the Head and Neck, Marcel Dekker, 1985. [80] TM Davidson, Tumors of the Head and Neck: Clinical and Pathological Considerations vol. 3, Williams & Wilkins Co., Baltimore, MD, 1979, 2nd edition by JG Batsakis, 573 pp., illus 1980. [81] MB Amin, SB Edge, AJCC Cancer Staging Manual, Springer, 2017. [82] M Kawaguchi, H Kato, H Tomita, K Mizuta, M Aoki, A Hara, et al., Imaging characteristics of malignant sinonasal tumors, J Clin Med Res 6 (2017). 10.3390/jcm6120116. [83] RH Spiro, LG Koss, SI Hajdu, EW Strong, Tumors of minor salivary origin, Cancer 31 (1973) 117–129. [84] M Dréno, M Georges, F Espitalier, C Ferron, A Charnolé, B Dréno, et al., Sinonasal mucosal melanoma: a 44-case study and literature analysis, Eur Ann Otorhinolaryngol Head Neck Dis 134 (2017) 237– 242. [85] F López, JP Rodrigo, A Cardesa, A Triantafyllou, KO Devaney, WM Mendenhall, et al., Update on primary head and neck mucosal
melanoma, Head Neck 38 (2016) 147–155. [86] B Khademi, A Moradi, S Hoseini, M Mohammadianpanah, Malignant neoplasms of the sinonasal tract: report of 71 patients and literature review and analysis, Oral Maxillofac Surg 13 (2009) 191– 199. [87] Y-K Kim, JW Choi, H-J Kim, HY Kim, GM Park, Y-H Ko, et al., Melanoma of the sinonasal tract: value of a septate pattern on precontrast T1-weighted MR imaging, AJNR Am J Neuroradiol 39 (2018) 762–767. [88] S Kadish, M Goodman, CC Wang, Olfactory neuroblastoma: a clinical analysis of 17 cases, Cancer 37 (1976) 1571–1576. [89] AB Dublin, M Bobinski, Imaging characteristics of olfactory neuroblastoma (Esthesioneuroblastoma), J Neurol Surg B Skull Base 77 (2016) 1–5. [90] VA Budu, M Tuşaliu, T Decuseară, IA Bulescu, CG Popp, A Panfiloiu, et al., Sinonasal non-Hodgkin’s malignant lymphoma: review of a clinical case, Rom J Morphol Embryol 58 (2017) 181– 185. [91] H Kato, M Kanematsu, H Watanabe, S Kawaguchi, K Mizuta, M Aoki, Differentiation of extranodal non-Hodgkins lymphoma from squamous cell carcinoma of the maxillary sinus: a multimodality imaging approach, Springerplus 4 (2015) 228. [92] HJ Lee, J-G Im, JM Goo, KW Kim, BI Choi, KH Chang, et al., Peripheral T-cell lymphoma: spectrum of imaging findings with clinical and pathologic features, Radiographics 23 (2003) 7–26, discussion 26–28. [93] MC Neves, MM Lessa, RL Voegels, O Butugan, Primary nonHodgkin’s lymphoma of the frontal sinus: case report and review of the literature, Ear Nose Throat J 84 (2005) 47–51. [94] J Itami, M Itami, A Mikata, J Tamaru, T Kaneko, H Ogata, et al., Non-Hodgkin’s lymphoma confined to the nasal cavity: its relationship to the polymorphic reticulosis and results of radiation therapy, Int J Radiat Oncol Biol Phys 20 (1991) 797–802. [95] JK Chan, CS Ng, WH Lau, ST Lo, Most nasal/nasopharyngeal lymphomas are peripheral T-cell neoplasms, Am J Surg Pathol 11 (1987) 418–429. [96] J Suzuki, Y Harazaki, S Morita, Y Kaga, K Nomura, M Sugawara, et al., Myeloid sarcoma of the paranasal sinuses in a patient with acute myeloid leukemia, Tohoku J Exp Med 246 (2018) 141–146. [97] AB Shinagare, KM Krajewski, JL Hornick, K Zukotynski, V Kurra, JP Jagannathan, et al., MRI for evaluation of myeloid sarcoma in adults: a single-institution 10-year experience, AJR Am J Roentgenol 199 (2012) 1193–1198.
[98] E Cantone, AM Di Lullo, L Marano, E Guadagno, G Mansueto, P Capriglione, et al., Strategy for the treatment and follow-up of sinonasal solitary extramedullary plasmacytoma: a case series, J Med Case Rep 11 (2017) 219. [99] F López, KO Devaney, EY Hanna, A Rinaldo, A Ferlito, Metastases to nasal cavity and paranasal sinuses, Head Neck 38 (2016) 1847–1854.
CHAPTER 71
Orbit Allan Midyet, Deepak Bhatt, Suresh K. Mukherji
71.1
Technique While the orbit’s observable share of skull volume sometimes seems small, their central role in visual function clearly causes them to commandeer a critical function. Modern orbital imaging has come to rely on a current a triad of tried and true techniques of ultrasonography (USG), computed tomography (CT), and magnetic resonance imaging (MRI). Imaging techniques tried in yesteryear have largely been replaced, although they are sometimes resurrected in special circumstances, including catheter angiography, fluoroscopy, plain film radiography, nuclear medicine, orbital venography, and dacryocystography. Within CT & MRI there are powerful specialized subtechniques, including CT angiography (CTA) and MR angiography (MRA). With the choice of multiple techniques, it is more important than ever that orbital imaging is directed by individuals who can correlate clinical history and physical examination to perform and interpret these often elaborate examinations. CT is frequently the first technique performed in trauma cases, often because these patients have trauma to more than just the orbit, and CT is their initial study. CT excels in cases needing exquisite bony detail. In complex orbital cases, CT and MRI are commonly complimentary. MRI: Probably the procedure of choice for evaluation of visual impairment or suspected cranial nerve abnormality allowing assessment of entire cranial nerves and visual pathways. While T1 Gd images with fat saturation are sometimes superb, most neuroradiologists have found that fat is the imager’s
friend and that T1 images without contrast are essential in evaluating marrow signal in skull base and orbital foramina. Continued progress in protocols and coil design show significant strides shifting some avoid artifacts while others exploit them. Every effort should be made to eliminate eye makeups which contain ferromagnetic particles. As always, all absolute contraindications to MRI should be observed including but not limited to noncompliant intracranial devices. Imaging sequences should be tailored to the individual imaging situation but in general include T1, T2, and T1 Gd. Postcontrast fat saturation frequently improves conspicuity of subtle lesions. MRA and/or MRV sometimes show abnormality involving the arteries and veins. 2D and 3D time of flight and phase contrast techniques should be tailored to the suspected abnormality. USG is discussed in detail elsewhere in this text. Various lesser used techniques for the orbit include plain films, dacryocystography, angiography, PET CT, and PET MRI and are discussed further in this chapter and elsewhere in this text.
Anatomy Bony orbits: Resemble conical cones, with ice cream at its base and a small posterior apex. The four sides form a floor, a roof with lateral and medial walls which are loosely lined with periorbital periosteum contiguous with intracranial dura.
◾lesser The orbital roof is formed anteriorly by the frontal bone and posteriorly by the sphenoid’s wing ◾posteriorly The lateral wall forms from the zygoma anteriorly and the sphenoid’s greater wing ◾several The orbital floor and medial walls exhibit complex embryologic origins evolving from segments of sphenoid, maxilla, zygoma, palatine, ethmoid, lacrimal bones. These are thinner and predisposed to fracture, particularly the paper-thin lamina papyracea of the medial wall
Principal posterior openings include the optic canal, as well as superior and inferior orbital fissures (IOFs). Cylindrical optic canals connect the middle cranial fossa to the orbit and convey the ophthalmic artery and optic nerve with supplementary sympathetic fibers. Located lateral and caudal to the optic canal, the superior orbital fissure (SOF) comprises a craggy orbital apex cleft connecting the orbit to the middle cranial fossa conveying essential structures, including CN III, IV, V1, VI. The IOF enters the orbit caudal the SOF opening onto the posterolateral orbital floor. The IOF transmits the infraorbital and zygomatic nerves, the infraorbital artery (and vein), orbital ganglionic branches of the pterygopalatine ganglion, a branch of the inferior ophthalmic vein and various venous emissaries to the pterygoid plexus. The supraorbital and infraorbital foramina are important
structures superiorly and inferiorly. Important medial foramina include the anterior and posterior ethmoidal foramina which convey the anterior and posterior ethmoidal nerves, arteries, and veins. Embryologically, the bony orbits manifest a montage of no less than seven different bones including the frontal, ethmoid, sphenoid, maxilla, zygoma, lacrimal, and last but not least, the palatine bones [1]. Optic pathway: The posteriorly pointing orbital apex conveys the ophthalmic (artery and veins) and cranial nerves (II, III, IV, V1, and V2, VI) through three optic openings including the optic canal and outlets through the superior and IOFs which form a V with a medially pointing apex. Before forming the base of the anterior clinoid process, the optic strut separates the optic canal from the SOF. CN II is surrounded by meninges continuous with visceral dura forming the optic nerve sheath containing varying quantities of CSF within the perioptic subarachnoid space. Retinal axions pierce the choroid and sclera to connect with the optic nerve. The ophthalmic artery courses into the optic canal inferior to the optic nerve then crosses over its midsegment coursing anteriorly and medially supplying terminal twigs to the globe, nerve sheath, eyelid, muscles, and lacrimal gland. Small vessels pierce the sclera to supply the posterior choroid. The superior ophthalmic vein (SOV) connects the facial venous plexus to the orbit joining the inferior ophthalmic vein at the orbital apex to the SOF into the cavernous sinus [2]. Extraocular muscles (EOMs) comprise the group of muscles which move they eye and include the inferior, superior, lateral, and medial recti, the superior and inferior obliques, and the levator palpebrae. Fascia forms a familiar anatomic “muscle cone” around the four rectus muscles, with the two extraconal oblique muscles in the superomedial and inferomedial orbit. The fascial muscle cone extends posteriorly to form a dense fibrous band (the annulus of Zinn) which surrounds the optic nerve, ophthalmic artery, CN III, V1, VI, and related structures. It attaches anterior to the globe’s equator at Tenon’s capsule [1]. Orbital septum formed by palpebral fascia is a membranous sheet which anchors at Tenon’s capsule extending peripherally to the orbital rim’s periosteum forming three spaces. The preseptal space is contiguous with the face. The intraconal and extraconal spaces are postseptal. It is extremely important for imagers to identify pathologic processes which violate the orbital septum. Innervation: CN IV (Trochlear) supplies the superior oblique muscle. CN VI (Abducens) supplies the lateral rectus muscle. All other EOMs are innervated by CN III (Oculomotor), including the levator palpebrae. The globe is formed from a fibrous tunic outer sclera, an in inner neural retina, and a middle layer of uveal/vascular tunic. The interleaved layer of choroid, ciliary body, and iris is collectively called the uvea. The ciliary body assists
the lens to focus transmitted light from the cornea onto the retina. The anterior and posterior chambers contain aqueous humor. The lens separates the smaller anterior and posterior chambers from the larger vitreous chamber posteriorly which is conspicuously imaged with its collection of vitreous humor. Like in a camera’s lens, the iris regulates light reaching the retina [3]. Lacrimal glands: The paired elliptical lacrimal glands lodge in the lacrimal fossa’s superolateral postseptal extraconal space supplying lubrication to the anterior globe. Tears traverse the globe anteromedially storing surplus in the lacrimal sacs via upper and lower puncta. The preseptal lacrimal sacs drain through nasolacrimal ducts into the inferior meatus caudal to the inferior turbinates [4].
Trauma It has long been acknowledged that the orbit seems to be a “sitting duck” inviting an assortment of trauma. While a plethora of protective equipment has been devised, alas, unfortunate patients are often not wearing protective gear when the offending occasion occurred. The orbit appears plagued with blunt and penetrating injury with equal incidence. CT shows soft tissue and bony injury, air, and some foreign bodies. While CT excels when foreign bodies have high or low Hounsfield units, it sometimes struggles when foreign bodies are isodense to surrounding structures as is sometimes seen with wood, most glass, and some plastics. MRI can be complementary to CT in many cases but is clearly contraindicated in cases with metallic foreign bodies [5]. There are two commonly held theories for blow-out fractures. The “hydraulic theory” contends that pressure on orbital contents raises to the point that contents “blow-out” through the weakest point. The “buckling theory” purports that direct force proceeds through the orbit to cause the fracture. Whichever theory is correct, “blow-out fractures” are common and are frequently found medially (Fig. 71.1) and inferiorly (Fig. 71.2), although they occasionally involve the orbital roof. As originally described by Smith and Regan in 1957, blow-out fractures occur with intact orbital rims [5]. It is the radiologist’s responsibility to define the anatomy and identify which patients have significant extrusion and/or entrapment of orbital structures. Orbital “trapdoor” fractures are reported more frequently found in children ostensibly related to better bone elasticity. Whatever the cause, prompt identification of these fractures is important as urgent surgical repair reduces morbidity (and malpractice suits) [6]. There is a significant spectrum of post-traumatic global injury which ranges from minor to severe. Laceration, rupture, global deformity, and decreased ocular volume are conspicuous
while anterior chamber leaks and lens dislocations are sometimes subtle and initially overlooked (Figs. 71.3 and 71.4).
FIGURE 71.1 Medial blow-out fracture. Coronal (A) and axial (B) noncontrast CT shows dehiscent medial wall with orbital contents herniating inferiorly and medially (arrows in A & B resepectively).
FIGURE 71.2 Inferior blow-out fracture. Coronal (A) and sagittal (B) Noncontrast CT shows comminuted depressed left orbital floor fracture (arrows in A & B).
FIGURE 71.3 Anterior chamber perforation. Axial NECT shows narrowing of the space between right lens and cornea secondary to loss of fluid from anterior chamber perforation (arrow).
FIGURE 71.4 Ocular lens displacement. Axial NECT shows clear posterior displacement of calcified right lens (arrow).
Ruptured globe is usually well depicted by imaging and modern diagnostic and surgical techniques have increased the chances of visual salvage (Fig. 71.5). However, phthisis bulbi is the unfortunate end-result of various vicious orbital oddities showing a small, shrunken, misshapen globe which is insensitive to light revealing redundant, thickened, dense scleral calcifications. The characteristic imaging appearance is shown in Fig. 71.6.
FIGURE 71.5 Ruptured globe. Axial NECT demonstrates traumatic rupture of the left globe (arrow).
FIGURE 71.6 Phthisis bulbi. Axial NECT 1A shows a small shrunken, left globe with thickened sclera, large coarse dystrophic calcifications, increased vitreous attenuation, and enophthalmos from phthisis bulbi (arrow).
Ocular prostheses present a gamut of finding for imagers ranging in conspicuity from blatantly obvious to virtually invisible depending on the material and the technique. In general, many are hyperdense on CT demonstrating a signal void on MRI and some show artifacts on one or more techniques. While glass and plastic spheres have been mainstays, newer low attenuation integrated hydroxyapatite implants made of denatured coral have allowed direct attachment to the EOMs with fibrovascular ingrowth. Evaluation of this implant’s assimilation is sometimes assessed on T1 Gd or nuclear medicine uptake (Fig. 71.7).
FIGURE 71.7 Ocular prosthesis. (A) Lateral radiograph reveals an opaque, spherical aluminum oxide right orbital prosthesis (arrow). Sagittal T1 (B) an ocular implant surrounded by orbital fat (arrow). Noncontrast CT (C) obtained in a different patient shows a high attenuation ocular implant (arrow).
Retinal detachments occur when the globes inner retinal layer peals away from the middle choroidal layer permitting fluid accumulation in the previously present potential space. This is a true medical emergency which progresses to permanent vision loss and blindness if not repaired in 24–72 hours. The retina is tethered posteriorly to the optic nerve’s insertion and anteriorly to the ora serrata at the retinal/scleral junction. This results in retinal detachments demonstrating a “tulip-shaped” intraocular mass on USG, CT, and MRI (Fig. 71.8) [7].
FIGURE 71.8 Retinal detachment. Axial NECT conveys classic “tulip” appearance of retinal detachment containing both high attenuation blood and low attenuation vitreous humor beneath detached retinal stopping at the ora serrata and not extending to limbus (arrow). Prior cataract removal of the right globe with lens replacement.
Neoplasms Cavernous venous malformations of the orbit (AKA orbital cavernous hemangiomas) comprise the most common orbital vascular lesion in adults. Newer nomenclature by International Society for Study of Vascular Anomalies classifies them as “slow flow venous malformations.” These are benign, slow growing, encapsulated, vascular abnormalities usually presenting with progressive, painless proptosis. These are associated with Sturge–Weber syndrome and may result in spontaneous hemorrhage and retinal detachment. Venous malformations are typically unilateral, well circumscribed, enhancing, intraconal masses in adults. CT shows an intraconal mass that may have delayed enhancement. MRI shows T1 isointense, T2 hyperintense, avidly enhancing lesions that may have “blooming” effect on gradient echo or susceptibility-weighted imaging [8] (Fig. 71.9).
FIGURE 71.9 Cavernous venous malformation (arrows). (A) Axial T1 confirms well-circumscribed intraconal mass isointense to muscle. (B) Axial T1 Gd parades pattern of “mulberry” enhancement. (C) Axial T2 confirms characteristic sharp, low signal pseudocapsule.
Optic nerve gliomas (ONGs) are usually grade I juvenile pilocytic astrocytomas and most commonly present in children and young adults. In adults, they often appear as aggressive malignant optic gliomas arising from foci near the optic chiasm and have a poor prognosis. Contrast-enhanced MRI is the preferred technique for evaluating the optic nerves and chiasm. Since 90% of ONGs arise outside the orbit, the field of view must include the entire visual pathway. The characteristic findings are diffuse enlargement of this optic nerves which avidly enhances. The retrobulbar optic nerve is most commonly involved, but the lesion can extend posteriorly to the chiasm in more advanced cases. Bilateral ONGs are pathognomonic for neurofibromatosis type 1 [9] (Fig. 71.10).
FIGURE 71.10 Optic nerve glioma (arrows). (A) Axial T1 shows fusiform enlargement of right ON from the globe through the orbital apex. (B) Coronal T1 exhibits enlargement of right ON with mass effect on adjacent structures. (C) Coronal T2 shows increased signal within the mass. (D) Axial T1 Gd exhibits avid, homogeneous enhancement of ON through the orbital apex.
Optic nerve meningiomas are rare, benign tumors arising from arachnoid cap cells in the meninges covering the optic nerve. CT shows a high attenuation mass surrounding the optic nerve causing calcification in 20–
50% of cases. Optic nerve meningioma is usually idiopathic, however, 10% of patients with ONM may have neurofibromatosis type 2. The “tram track” or “sandwich” sign is the characteristic finding best appreciated on fatsuppressed contrast-enhanced T1W images. While “tram track” perineural enhancement is classic, it is not pathognomonic and this findings can be mimicked by pathologies that cause diffuse leptomeningeal enhancement, such as lymphoma, sarcoid, and leptomeningeal metastases [10] (Fig. 71.11).
FIGURE 71.11 Optic nerve meningioma. (A and B) Axial T1 images exhibit tubular enlargement of ON’s from globe through the orbital apices (arrows).
Orbital schwannomas usually present in middle-aged adults as well defined, encapsulated, slowly growing benign tumors arising from peripheral nerve Schwann cells and comprise 1% to orbital tumors. Orbital schwannomas do not arise from the optic nerves since the optic nerve is not a “real” cranial nerve and is not surrounded by schwann cells. Rather, orbital schwannomas are thought to arise from distal branches of cranial nerves which innervate the extraocular muscles and felt to most likely arise from intraorbital branches of cranial nerve III [11] (Fig. 71.12).
FIGURE 71.12 Orbital schwannoma. (Arrows) (A) Coronal NECT shows large heterogeneous left intraconal mass. (B) Axial CECT exhibits large mildly enhancing heterogeneous oval intraconal mass extending from posterior globe to orbital apex. (C) Axial T1 Gd exhibits large isointense mass with areas of avid “ring” enhancement extending from the posterior globe to the orbital apex producing exophthalmos.
Orbital lymphoma is a frequent orbital tumors in adults and account for 50% of all orbital malignancies. These malignancies usually arise in older patients presenting with progressive ptosis, exophthalmos, diplopia, and restricted extraocular movement. Imaging shows restricted diffusion. ADC may represent a noninvasive surrogate biomarker to measure treatment response [12] (Fig. 71.13).
FIGURE 71.13 Orbital lymphoma. (A) Axial CECT shows ill-defined infiltrative enhancing mass invading the medial left orbit, deforming and deviating left globe and medial rectus muscle with pre- and postseptal involvement (arrow). Axial T1 (B) and (C) T1 Gd performed in a different patient demonstrate an avidly enhancing aggressive mass invading the right orbit and ethmoid sinus extending posteriorly through the orbital apex (arrows).
Ocular melanoma (OM) is the most common adult intraocular malignancy. OM can be detected on both CT and MR as either focal or en plaque lesion abutting the retina. OMs are sometimes seen as an incidental findings on CT and are usually high attenuation masses that enhance with contrast. While there are variations between melanotic and amelanotic tumors, OM typically shows bright T1, dark T2, and moderate enhancement on T1 Gd. MRI is the technique of choice for complete evaluation, particularly when the lesion is
large. Amelanotic tumors resemble other soft tissue masses like metastases. MRI is excellent in sorting out effusions which are sometimes slightly bright on T1 [13] (Fig. 71.14).
FIGURE 71.14 Ocular melanoma (arrows). (A) Real-timeUSGsector scan shows small, focal, raised melanoma protruding into posterior vitreous chamber. Axial contrast-enhanced CT (B and C) shows a large heterogeneously enhancing soft tissue mass filling a significant portion of the vitreous chamber, and extending into the retrobulbar region exhibiting exophthalmos.
Retinoblastoma (RB) is the most common intraocular tumor in children. The most common clinical finding is loss of the red reflex resulting in leukocoria. Most cases are autosomal recessive with a mutation in RB1 on chromosome 13. One-third of patients present with bilateral lesions with autosomal dominant inheritance. Sporadic (90% with only intraocular disease but 1.5 mm in its mid-segment (Fig. 72.32). On MRI, the vestibular aqueduct is said to be dilated when the diameter is more than the ascending segment of the posterior SCC. They result in high-frequency hearing loss and can be an isolated abnormality or seen in association with cystic cochlear apex, enlarged vestibules, and abnormal semicircular canals. Pendred syndrome, CHARGE syndrome, and congenital viral infections are associated with enlarged vestibular aqueducts.
FIGURE 72.32 (A and B) Enlarged vestibular aqueduct—left temporal bone CT images show isolated dilated vestibular aqueduct (asterisks in A and B).
Semicircular Canal Anomalies The semicircular canal development starts between 6 and 8 weeks of gestational age, to complete between 19 and 22 weeks. The superior semicircular canal develops initially, followed by the posterior and lateral semicircular canal. Hence, hypoplasia most commonly involves the lateral semicircular canal (Fig. 72.33). The malformed semicircular canals are often broad and short but may also be narrow. The semicircular canal dysplasia involving the vestibule and the lateral SCC presents as a broad cystic space with absent or small intervening bone island and enlarged vestibule. The lateral SCC dysplasia may be associated with cochlear malformations depending on the stage of inner ear development and embryonic arrest. Semicircular canal aplasia is often associated with CHARGE syndrome.
FIGURE 72.33 Lateral semicircular canal dysplasia—right temporal bone CT image shows fusion of vestibule and lateral semicircular canal with the absence of normal intervening bone island (arrow).
Superior SCC dehiscence [7] occurs due to thinning or defect of the arcuate eminence overlying the superior semicircular canal, resulting in formation of “third window” (Fig. 72.34).
FIGURE 72.34 Superior semicircular canal dehiscence—right temporal bone CT image in Poschl’s view shows dehiscence of the superior semicircular canal (arrow).
The third window abnormalities typically present with noise-induced vertigo, also called Tullio’s phenomenon. Although SCC dehiscence has a genetic and syndromic association, it is also seen in the elderly, suggesting an acquired etiology. Similar dehiscence of the posterior SCC may be seen with a high-riding jugular bulb and fibrous dysplasia of the temporal bone. Surgical exploration through a middle cranial fossa approach with canal plugging is associated with long-term symptom control.
Congenital Internal Auditory Canal Anomalies The internal auditory canal may be atretic with a nonvisualized internal auditory canal or stenotic, with a diameter of less than 2 mm. The duplication of the internal auditory canal is a rare anomaly associated with the bony septum resulting in two separate canals, the anterosuperior canal continuous with the labyrinthine segment
of the facial nerve and the posteroinferior canal continuous with cochlea and the vestibule (Fig. 72.35). The duplication of the internal auditory canal is commonly isolated but rarely associated with Klippel–Feil syndrome and pontine tegmental cap dysplasia.
FIGURE 72.35 Duplication of internal auditory canal—right temporal bone CT image shows bony bar (arrow) separating the superior and inferior compartments of the internal auditory canal.
Cochlear Nerve Anomalies The internal auditory canal atresia or stenosis may suggest an associated cochlear nerve anomaly and mandates a high-resolution T2W MRI for optimal cochlear nerve assessment. Various subtypes of cochlear nerve malformations are based on
aplasia or hypoplasia of the nerve (Fig. 72.36) and its association with inner ear anomalies.
FIGURE 72.36 High-resolution T2 oblique sagittal view shows absence of cochlear division of VIII cranial nerve (n – nerve) at the anteroinferior compartment of IAC.
Genetic and Syndromic Association of Inner Ear Anomalies Hereditary causes account for approximately 50% of congenital sensorineural hearing loss and syndromic associations. Cochlear hypoplasia and semicircular canal aplasia are seen in CHARGE syndrome. Cochlear hypoplasia is also associated with the branchio-oto-renal syndrome, Waardenburg syndrome, and Down’s syndrome. The type II incomplete partition is associated with Pendred
syndrome (SLC26A mutations) and type III incomplete partition with X-linked deafness (POU3F4 mutations). Other congenital syndromes commonly associated with the inner ear malformations include Apert syndrome, Treacher Collins syndrome, and Pierre Robin sequence.
Labyrinthine Disorders Labyrinthitis Labyrinthitis refers to inflammation of the inner ear involving one or more compartments of the membranous labyrinth. It is either due to inner ear infection secondary to the bacterial, fungal, viral, and protozoal invasion of labyrinthine structures or noninfective inflammation secondary to autoimmune disorders and vasculitis. Based on the origin, it is classified into hematogenic, meningogenic, and otogenic labyrinthitis. Typically, otogenic labyrinthitis is unilateral and secondary to the spread of infections or toxins to the inner ear through the round or the oval window. Meningogenic labyrinthitis is common in the pediatric population. It is usually bilateral and occurs due to infection spread through the cochlear aqueduct and internal auditory canal. Radiologically, labyrinthitis is classified into three stages: acute, fibrous, and osseous (labyrinthitis ossificans) stages.
◾labyrinthine The acute phase is due to purulent infection that presents with an intense enhancement of the structures on post-contrast T1W images ◾onTheT2Wintermediate fibrous stage is characterized by fibrous replacement leading to hypointense signal images with mild enhancement on post-contrast T1W images ◾fluid The late osseous stage manifests with ossific deposition in the inner ear with loss of normal bright signal on T2W images and hyperdense replacement of inner ear on CT. CT allows for an optimal assessment of the location and extent of the ossification before cochlear implantation
Labyrinthitis Ossificans Labyrinthitis ossificans also develops secondary to chronic middle and inner ear infections, temporal bone fractures, and bacterial meningitis. Fibroblastic proliferation, which eventually differentiates into osteoblasts, appears on imaging as initial fibrosis and progresses to ossific deposits in the membranous labyrinth. MR imaging with high-resolution T2W and post-contrast T1W sequences is optimal for diagnosing labyrinthitis in the initial stages. In comparison, the highresolution CT is best for evaluating the extent and location of osseous replacement and dense sclerosis of labyrinthine structures later in the disease process (Fig. 72.37).
FIGURE 72.37 (A and B) Labyrinthitis ossificans—CT and MR images of the temporal bone shows dense sclerosis and osseous replacement of the vestibule (arrow in A) on CT with loss of normal fluid signal (arrow in B) on CISS images.
The salient imaging findings include cochlear stenosis, fibrous and ossific deposition in the cochlea. Rarely, labyrinthitis ossificans is also associated with obliteration of semicircular canals. Round window stenosis secondary to osseous deposits may lead to difficult and suboptimal cochlear implant placement.
Otosclerosis (Otospongiosis) Otosclerosis is autosomal dominant osteodystrophy that occurs due to spongy vascular bone replacing the normal dense endochondral bone. It commonly occurs
in the second to fourth decades of life, usually bilateral (85%), and shows female preponderance. Otosclerosis is of two types: the common fenestral and the rare retrofenestral type.
◾connective Fenestral otosclerosis typically involves the fissula ante fenestrum (which is a small fold of tissue anterior to the oval window) and gradually progresses to involve the round
window, oval window, and cochlear turns with late pericochlear involvement (Fig. 72.38). HRCT of the temporal bone is the imaging technique of choice that demonstrates bone rarefaction anterior to the oval window. The disease progression may lead to otosclerotic plaque formation, which may cause round window stenosis, stapes fixation, and rarely torsional subluxation of the incus. The grading of the extent and location of otosclerosis is by Symon and Fanning classification Retrofenestral otosclerosis is a rare subtype, typically bilateral, symmetrical, and almost always associated with the fenestral otosclerosis. It appears with a typical hypodense pericochlear hypodense double ring sign (aka fourth ring of valvassori). MR imaging may reveal hypointense signal on T1W with mild-to-moderate enhancement on post-contrast T1W images
◾
FIGURE 72.38 (A and B) Otosclerosis (otospongiosis). Fenestral otosclerosis —right temporal bone CT shows bone rarefaction with hypodensity in right fissula ante fenestrum (arrow in A). Retrofenestral otosclerosis—right temporal bone CT shows pericochlear hypodense ring sign (arrow in B).
The differential diagnoses include osteogenesis imperfecta, and rarely fibrous dysplasia, and Paget’s disease.
Meniere’s Disease Meniere’s disease is a clinical entity presenting with spontaneous episodes of vertigo, sensorineural hearing loss, and tinnitus that presents adults with a peak
incidence in the fourth to fifth decade. Endolymphatic hydrops (Eh) occurs due to the distension of endolymphatic compartments causing secondary compression of perilymphatic structures. This can be demonstrated by high resolution MRI imaging, mainly using 3T with delayed post IV Gadolinium (Gd) contrast FLAIR (fluid attenuated inversion recovery) sequence; post-contrast enhancement is seen best on 4 hour delayed imaging at the perilymphatic space. This enhanced space is compressed or obliterated in Eh. On HRCT, absent visualization of vestibular aqueduct predicts hydrops in more than 90% of subjects. Similarly, the cochlear hydrops shows dilatation of the scala media with partial or complete obliteration of the scala vestibuli.
Intralabyrinthine Schwannomas Schwannomas typically arise from the vestibular ganglion near the fundus of the internal auditory canal and frequently extend into the cerebellopontine angle. Rarely, they may arise from the terminal ends of the eighth cranial nerve in the vestibule, cochlea, and semicircular canals. The intralabyrinthine schwannomas (Fig. 72.39) include
◾ intracochlear (confined to the cochlea); ◾ transmodiolar (cochlear origin with IAC extension through modiolus); ◾ intravestibular (confined to vestibule ± semicircular canals); ◾ transmacular (vestibular origin with IAC extension through macula cribrosa); ◾ vestibulocochlear (confined to vestibule and cochlea) and ◾ transotic (labyrinthine schwannomas with IAC and middle ear extension) subtypes.
FIGURE 72.39 Labyrinthine schwannoma—axial CISS and coronal T1 postcontrast images of temporal bone show loss of normal fluid signal in the vestibule (arrow in A) and small enhancing mass in the vestibule (arrow in B).
On MR imaging, they are hypointense or replace the typical bright fluid signal on high-resolution T2W images with intense enhancement on post-contrast T1W images.
Bell’s Palsy Bell’s palsy typically presents acute onset of infranuclear facial palsy, accounting for approximately 70% of facial nerve paralysis. It is likely due to reactivation of the herpes simplex infection in the geniculate ganglion resulting in the inflammatory edema and likely ischemia of the labyrinthine segment in the tight
fallopian canal. MR imaging characteristically demonstrates enhancement of the canalicular and labyrinthine segments of the facial nerve (Fig. 72.40) in many patients. Similar imaging findings may be seen in Ramsay hunt syndrome (herpes zoster oticus) due to reactivation of varicella-zoster infection in the geniculate ganglion along with vesicular eruption in the external ear. Thickening and enhancement of the tympanic segment of the facial nerve raise concern for neoplastic etiology.
FIGURE 72.40 Bell’s palsy—axial post-contrast T1 image shows asymmetric increased enhancement of the cisternal segment of right facial nerve (arrow).
Any atypical presentation, including insidious onset, delayed recovery, progressive facial palsy, and recurrent Bell’s palsy, necessitates further evaluation to rule out other inflammatory or neoplastic etiology along the course of the nerve.
Precochlear Implant Imaging The presurgical mapping is essential for planning the route of cochlear implant electrode placement. CT and MRI provide critical information about the anatomical variations and imaging findings that may complicate surgical access and lead to iatrogenic complications. Simple mastoidectomy with a posterior tympanotomy is considered the classical approach that may be associated with round window enlargement or separate “cochleostomy,” aimed to access the scala tympani for electrode placement. Suprameatal approach, transcanal approach, middle cranial fossa approach with
apical turn cochleostomy are some of the alternative routes, but less commonly used. In cases with chronic suppurative otitis media, unstable mastoid cavities with recurrent otorrhea, partially ossified cochleae, tympanosclerosis, and some inner ear dysplasias, an alternative to the classic route may be considered. Both CT and MRI are needed for patient selection, side selection, and anatomical assessment. The common anatomical variations to be assessed include: 1. Vascular anatomy
FIGURE 72.41 (A and B) Precochlear implantation. Yellow line in the first image depicting the course of electrode insertion from mastoid margin to the round window niche. Arrow in the second image shows anterolateral projection of the sigmoid sinus with thinning of the overlying bony plate, a variation that affecting the surgical plan of electrode insertion in this path.
Cochlear or vestibulocochlear nerve hypoplasia or aplasia. Post-implant assessment usually includes a radiographic evaluation (Fig. 72.42) with CT or cone beam CT that is utilized as a problem-solving tool in doubtful/complicated cases. The assessment includes careful evaluation of the location and number of electrodes within the cochlea, course of the wire, electrode displacement/fractures and associated complications [1–13].
FIGURE 72.42 Cochlear implant. Radiograph (A) shows the parts of cochlear implant with electrodes located within the cochlea. Coronal CT image (B) shows tiny electrodes located in array noted within the cochlea; the number and exact location within the cochlear turns are important for hearing rehabilitation.
Suggested Readings • AF Juliano, DT Ginat, G Moonis, Imaging review of the temporal bone: part I, Anatomy and inflammatory and neoplastic processes, Radiology 269 (1) (2013 Oct) 17–33.
• SK Mukherji, consulting editor. Update on temporal bone imaging with emphasis on clinical and surgical perspectives, Neuroimag Clin 29 (1) (2019 Feb 1) xv. • BM Allanson, TH Low, JR Clark, R Gupta, Squamous cell carcinoma of the external auditory canal and temporal bone: an update, Head Neck Pathol 12 (3) (2018) 407–418. • JT Castle, Cholesteatoma Pearls: practical points and update. Head Neck Pathol 12 (3) (2018) 419– 429. • YY Kurihara, A Fujikawa, N Tachizawa, M Takaya, H Ikeda, J Starkey, Temporal bone trauma: typical ct and mri appearances and important points for evaluation, Radiographics 40 (2020) 1148– 1162. • P Touska, SEJ Connor, Imaging of the temporal bone, Clin Radiol 75 (9) (2020 Sept 1) 658–674.
References [1] S Mittal, S Singal, A Mittal, R Singal, G Jindal, Identification of foramen of Huschke with reversible herniation of temporomandibular joint soft tissue into the external auditory canal on multidetector computed tomography, Proc (Bayl Univ Med Cent) 30 (1) (2017 Jan) 92–93. [2] MS Al Aaraj, C Kelley, Malignant otitis externa. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK556138/ [3] Y Aswani, R Varma, G Achuthan, Spontaneous external auditory canal cholesteatoma in a young male: Imaging findings and differential diagnoses, Indian J Radiol Imaging 26 (2) (2016) 237–240. [4] EM Gassner, A Mallouhi, RW Jaschke, Preoperative evaluation of external auditory canal atresia on high-resolution CT, American Journal of Roentgenology 182 (5) (2004) 1305–1312. [5] A Anbarasu K Chandrasekaran, S Balakrishnan, Soft tissue attenuation in middle ear on HRCT: pictorial review, IJRI 22 (4) (2012 Oct-Dec) 298– 304. [6] M Gulati, S Gupta, A Prakash, et al., HRCT imaging of acquired cholesteatoma: a pictorial review, Insights Imaging 10 (2019) 92. [7] L Sennaroğlu, M Demir Bajin, Classification and current management of inner ear malformations, Balk Med J 34 (5) (2017 Sep) 397–411. [8] MM Lemmerling, B De Foer, BM Verbist, V VandeVyver, Imaging of inflammatory and infectious diseases in the temporal bone, Neuroimaging Clin N Am 19 (3) (2009 Aug) 321–337. [9] TN Booth, P Roland, JW Kutz, K Lee, B Isaacson, High-resolution 3-D T2-weighted imaging in the diagnosis of labyrinthitis ossificans: emphasis on subtle cochlear involvement, Pediatr Radiol 43 (12) (2013 Dec) 1584– 1590. [10] B Purohit, R Hermans, K Op de Beeck, Imaging in otosclerosis: a pictorial review, Insights Imaging 5 (2) (2014 Apr) 245–252.
[11] AR Sepahdari, G Ishiyama, N Vorasubin, KA Peng, M Linetsky, A Ishiyama, Delayed intravenous contrast-enhanced 3D FLAIR MRI in Meniere’s disease: correlation of quantitative measures of endolymphatic hydrops with hearing, Clin Imaging 39 (1) (2015 Jan-Feb) 26–31. [12] KL Salzman, AM Childs, HC Davidson, RJ Kennedy, C Shelton, HR Harnsberger, Intralabyrinthine schwannomas: imaging diagnosis and classification, AJNR Am J Neuroradiol 33 (1) (2012 Jan) 104–109. [13] P Raghavan, S Mukherjee, CD Phillips, Imaging of the facial nerve, Neuroimaging Clin N Am 19 (3) (2009 Aug) 407–425.
Chapter 73
Skull Base Mohannad Ibrahim, Hemant A. Parmar, Suresh K. Mukherji
Introduction Skull base comprises a complex area between the neurocranium and head and neck region, which is not always well accessible to clinicians for inspection. Advances in imaging over last few decades now allow radiologists to identify normal anatomy of the skull base in precise details. Imaging also helps to identify imaging characteristics of different pathology, staging of neoplasms, define extent of tumor spread, plan surgical approach, and evaluate tumor recurrence. Radiologists interpreting imaging studies in patients with skull base lesions need to be familiar with anatomy of this region and utilize correct imaging protocols.
In this chapter, we will outline the basic but critical anatomy of the skull base. We will discuss important and commonly used imaging techniques, protocols, and highlight some of the newer emerging tools. We will then focus on the various pathologies of the skull base. Discussion of the skull base lesions in this chapter is based on the nature of the lesions: congenital, benign neoplastic, malignant neoplastic, or infectious/inflammatory lesions. Tables of various lesions involving anterior, middle, or posterior skull base are also provided for easy reference.
Skull Base Anatomy The floor of the cranial cavity separates the brain from the face and neck structures. It is divided by the sphenoid ridge anteriorly and the petrous ridge posteriorly into three distinct depressions, the anterior cranial fossa (ACF), middle cranial fossa (MCF), and posterior cranial fossa (PCF) (Fig. 73.1).
Figure 73.1 Endocranium view of the skull base. 3-D CT of the skull base showing subdivision into anterior (A), middle (M), and posterior (P) cranial fossa. The lesser wing of sphenoid with anterior clinoid process separates anterior from middle cranial fossa. The petrous ridge shows the approximate position of the tentorium cerebelli which divides middle from posterior cranial fossa.
Anterior Cranial Fossa The ACF is a depression along the floor of the anterior cranial base that houses the orbitofrontal gyri of the frontal lobes, olfactory bulbs, and olfactory
tracts. The ACF extends anteriorly from the posterior walls of the frontal sinuses and posteriorly to the sphenoidal limbus (the anterior margin of the chiasmatic groove) and the lesser sphenoid wings. The majority of the floor of the anterior fossa is formed by the orbital plates of the frontal bone. Between them is the thin cribriform pate of the ethmoid bone. The frontal crest, an osseous ridge in the midline frontal bone, along with the crista galli, situated in the midline of the ethmoid bone, acts as an attachment site for the falx cerebri. On either side of the crista galli is the cribriform plate, forming the floor of the olfactory groove, which has numerous foramina that transmit vessels and nerves (Fig. 73.2A,B).
Figure 73.2 Normal anatomy—anterior skull base. (A) Coronal CT of the anterior skull base show crista galli (black arrow) with cribriform plates (small white arrow) on either side and orbital plates of frontal bone (large white arrows). (B) Coronal T2-weighted MRI through the same level show normal position of the olfactory bulb (arrow).
Middle Cranial Fossa The MCF is butterfly shaped with a central narrow part that accommodates the pituitary gland along with two lateral parts that accommodate the temporal lobes of the brain. The central part of the MCF contains the sella turcica (Latin for Turkish saddle) that holds and support the pituitary gland. The sella turcica consists of the tuberculum sellae, pituitary fossa, and dorsum sellae (Fig. 73.3A). It is bordered anteriorly by the chiasmatic groove and surrounded by the anterior and posterior clinoid processes on each side. The anterior clinoid processes arise from the lesser sphenoidal wings and project posterolaterally. The posterior clinoid processes are superolateral bony projections that serve as
attachment points for the tentorium cerebelli which forms the superior boundary of the PCF.
Figure 73.3 Normal anatomy—middle skull base. (A) Sagittal CT through the midline of middle cranial fossa shows depression of sella turcica (large white arrow) which bounded anteriorly by tuberculum sella (small white arrow) and posteriorly by dorsum sella (black arrowhead). (B) Coronal CT through the middle cranial fossa foramen rotundum (large arrow) and Vidian canal which is inferior and medial (small arrow). (C) Axial CT at the level of floor of middle cranial fossa show larger foramen ovale (large arrow) and smaller foramen spinosum (small arrow). There are many foramina that transmit vascular structures and nerves into and out of the MCF. The optic canals are situated anteriorly and superiorly
transmitting the optic nerves and ophthalmic arteries into the orbits. The superior orbital fissures are located immediately inferior to the optic canals. Each of the superior orbital fissure transmits the oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic branch of the trigeminal nerve (CN V1), the abducens nerve (CN VI), ophthalmic veins, and sympathetic tracts. The foramen rotundum transmits the maxillary branch of the trigeminal nerve (CN V2) into the pterygopalatine fossa (Fig. 73.3B). The foramen ovale and foramen spinosum both open into the infratemporal fossa transmitting the mandibular branch of the trigeminal nerve (CN V3) and accessory meningeal artery, respectively (Fig. 73.3C).
Posterior Cranial Fossa The PCF is the most posterior and deepest of the cranial fossae, accommodating the brainstem and cerebellum. Along with the brainstem and cerebellum, the PCF also accommodates the vertebrobasilar arteries, cranial nerves, and dural venous sinuses. The dorsum sellae and the two petrous ridges are the anteromedial and anterolateral
boundaries, respectively, separating the MCF and the PCF. The foramen magnum, the largest opening in the floor of the fossa, is located centrally in the PCF. It transmits the medulla oblongata along with the vertebral arteries, dural veins, and the anterior and posterior spinal arteries. The jugular foramina are situated on either side of the foramen magnum. Each jugular foramen is divided into anterior part (pars nervosa) that transmits the glossopharyngeal nerve and inferior petrosal sinus. The larger posterior part (pars vascularis) transmits vagus nerve, spinal accessory nerve, sigmoid sinus continuing into internal jugular vein and meningeal branches of the ascending pharyngeal and occipital arteries (Fig. 73.4). Immediately superior and medial to the jugular fossa is the hypoglossal canal, which transmits the hypoglossal nerve.
Figure 73.4 Normal anatomy—posterior skull base. Axial CT through the posterior cranial fossa shows jugular foramen that is divided by jugular spike into smaller pars nervosa anteriorly (small arrow) and larger pars vascularis posteriorly (large arrow).
Embryologic Development The skull base, also known as the chondrocranium, is formed mostly through endochondral ossification, in contrast to the neurocranium or the cranial vault that is formed by intramembranous ossification [1]. The formation of the chondrocranium is almost complete
by the eight week [1], which is then ensued by endochondral ossification between 12 and 17 weeks [1,2], that progress from posterior to anterior in a well-defined pattern [2]. The notochord, a defining structure in the development of the neural plate, has an intimate relationship with the central skull base [1]. It develops between the third and fourth weeks of gestation and is a major regulator of embryonic patterning. The notochord develops along a tract that extends from Rathke’s pouch to the buccopharyngeal membrane and further caudally in the vertebral column (Fig. 73.5). The notochord regresses as the axial skeleton develops, eventually contributing to the formation of the nucleus pulposus of the intervertebral disks. Regression of the notochord can sometimes be variable, particularly at the ends of the axial skeleton at the skull base and sacrococcygeal regions, which results in the persistence of a variety of vestigial notochordal remnants.
Figure 73.5 Embryology of the notochord. Midplane sagittal section of the skull base demonstrating the position of the notochord within the skull base.
Imaging Technique CT scan and MRI are the primary modalities used to evaluate the anterior skull base and these complement each other. For example, benign fibroosseous lesions are fairly commonly seen at the skull base. They can appear like an aggressive lesion on MRI, but CT is often diagnostic.
CT provides excellent bony anatomic detail and is useful for evaluating the bony margins surrounding the lesion to characterize aggressive or benign growth pattern [3]. CT is useful to evaluate subtle changes in the fat planes around various skull base foramina. CT (without or with intrathecal contrast) is also useful in evaluation of cerebrospinal fluid (CSF) leaks (more details in section of CSF leak). Most of the skull base CT is obtained by helical acquisition technique using submillimeter slice thickness and covering entire skull base. The raw data can be processed to provide reconstructions in any imaging plane from a single acquisition. Although orthogonal axes are most commonly used (axial, sagittal, and coronal), oblique planes can be used to correct for head tilt or provide optimal visualization of a specific structure. CT source data can also be subjected to sharpening algorithms (with more targeted field of view) to enhance osseous details. MRI provides excellent soft tissue detail and most of the lesions involving skull base require different imaging protocol compared to that of brain. MRI protocol is based on the suspected abnormality, the available imaging equipment, and local imaging
expertise. Most of the skull base protocols require smaller field of view with thinner (3 mm or less) slice thickness. Most commonly followed protocol includes T1- and T2-weighted sequences in axial and coronal planes followed by post-contrast enhanced T1-weighted sequence in multiple planes. Due to its intrinsic bright signal, fat provides excellent contrast with low-intensity structures, such as nerves and vessels on pre-contrast T1-weighted sequence [3,4]. This is helpful to check replacement of normal fat around the skull base foramina in cases with suspected perineural spread (PNS) of tumor. MRI, especially T2-weighted sequence, is helpful to separate mucosal thickening and retained secretions in the paranasal sinuses from tumor [3]. Replacement of normal marrow in osseous structures is also well evaluated by T1-weighted MRI scan (particularly helpful when there are no cortical erosive changes seen on CT). Fat suppression technique is another chosen technique for evaluation of skull base lesions that can be applied for T2 and post-contrast enhanced T1-weighted technique. This is especially helpful in evaluation of areas with intrinsic high T1 signal. However, caution should be exercised when using fat suppression as susceptibility artifacts from the bone
and air can extend into important soft tissues and obscure it. It may be a good idea to obtain postcontrast enhanced images without and with fat suppression to minimize this problem. A newer generation of fat free sequences can provide nonsaturated and fat saturated T1- and T2-weighted images based on chemical shift imaging with inphase/out-of-phase cycling of fat and water. Finally, MRI is also helpful for evaluation of dural, pial, or brain parenchymal enhancement in case of intracranial extension of skull base disease process. Diffusion-weighted imaging (DWI) is well recognized for its ability to characterize abscesses and head and neck tumors, and to differentiate cholesteatoma from granulation tissue. Other emerging applications for DWI include staging of neoplasms and differentiating tumor recurrence from post-treatment changes [5]. Another emerging MRI technique is perfusion imaging that can be used to characterize metastatic lymph nodes and to differentiate tumor recurrence from posttreatment changes. Among the different techniques of performing perfusion imaging such as
dynamic susceptibility contrast (DSC), dynamic contrast-enhanced (DCE), and arterial spin labeling (ASL) available today, DCE perfusion has been studied the most for skull base applications due to the significant susceptibility artifact arising from the DSC technique and relatively long acquisition time with ASL technique [5]. High-resolution fluid-sensitive balanced steady-state free precession sequences, called by different propriety names by vendors such as FIESTA (fast imaging employing steady state acquisition, CISS (constructive interference in steady state) are extremely useful sequences obtained using thin-slice acquisitions (less than 1 mm) and can be reconstructed in different planes. This allows to image cisternal segments of the cranial nerves and their relationship to adjacent structures/lesions [6], which may not be readily seen on routine sequences. Although not commonly utilized, conventional angiography remains an important tool for confirming the diagnosis of suspected vascular lesions such as carotid-cavernous fistula (often performed after CT or MR angiogram). It can also
serve as a therapeutic option in many cases, either on its own or for presurgical embolization. PET/CT is now a routine component of clinical practice for staging head and neck cancers and evaluation of tumor recurrent at many institutions. Nuclear medicine studies, such as Indium-111 labeled octreotide single-photon emission CT (SPECT) scan can also help confirm whether a tumor has a neuroendocrine origin, such as in glomus tumors/paragangliomas.
Pathology Lesions of the skull base can be challenging to group and classify due to a wide array of pathology that may be encountered. Some of these pathologies can be unique to part of the skull base (e.g., esthesioneuroblastoma in the ACF or paraganglioma in the PCF), compared to other pathologies that can be seen throughout the skull base (i.e., infectious process or congenital lesions). General categorical classifications of pathologies of the skull base include grouping the lesions as congenital, neoplastic, infectious, or others. Such pathologic
processes can be seen in the ACF (Table 73.1), MCF (Table 73.2), or the PCF (Table 73.3). Modern imaging techniques have increased the radiologist’s ability in characterizing skull base lesions and determine a diagnosis. Table 73.1
Notochord Remnants There is a wide spectrum of anatomical variants and developmental defects related to the notochord development within the skull base [1,7]. Notochord-
related lesions may be benign or malignant with variable locations, either submucosal in the nasopharynx, intraosseous/transosseous lesions, or intracranial lesions in the epidural, subdural, or subarachnoid spaces. Therefore, such lesions can often present a diagnostic dilemma with complex clinical presentation. Some of these lesions are benign “do not touch” lesions and mostly have no clinical significance. Clinical complications have been rarely reported in some of these benign embryonic remnants such as CSF leak [7], meningitis, otitis media related to compression of the Eustachian tube, or even neck pain and stiffness.
Canalis Basilaris Medianus The canalis basilaris medianus (CBM), also known as chordal canal, or clival canal, refers to variety of midline canals, most commonly in the basioccipital region [7,8]. The CBM is thought to represent a vestigial notochord remnant. However, some studies of the canal contents have found no notochordal remnants but only venous channels emanating from the basilar plexus toward the vertebral venous plexus
or veins located at the inferior aspect of the skull base [8] (Fig. 73.6).
Figure 73.6 Median basal canal. Sagittal CT through the midline shows a small linear channel at the tip of the bony clivus suggestive of median basal canal (arrows).
Fossa Navicularis Magna Fossa navicularis, or fossa navicularis magna, is a variant osseous depression that is oval shaped or round on the ventral surface of the basioccipital clivus, located superior to the pharyngeal tubercle
[1,7]. This anatomic variant is thought to represent the persistent cephalic end of the notochord. Although sometimes confusing, but this is typically a larger defect compared to the smaller and linear CBM (Fig. 73.7A,B).
Figure 73.7 Fossa navicularis. (A) Axial and (B) sagittal CT through the central skull base level shows a well-defined, oval lytic lesion involving the clivus suggestive of fossa navicularis (arrows).
Tornwaldt Cyst Tornwaldt cyst is an incidental midline mucosal cyst of the nasopharynx, typically seen in the adult patients [9]. The lesion is developmental and mostly
asymptomatic, though it can present with halitosis or middle ear symptoms [1]. Tornwaldt cyst represents a communication between notochord remnants and the pharyngeal endoderm, with gradual accumulation of fluid within the cyst related to occlusion of the orifice of the pharyngeal bursa. Tornwaldt cyst presents as well-circumscribed, submucosal lesion in the midline nasopharynx in between the longus colli muscles. A typical Tornwaldt cyst measures 2–10 mm in size, however it can be large measuring few centimeters in diameter [9]. On CT it appears as well-circumscribed, nonenhancing hypodense lesion. A protein-rich cyst may appear hyperdense. The MR signal characteristics depend on the protein content ranging from isointense to hyperintense on T1W images, and hyperintense on T2W images [9] (Fig. 73.8A,B).
Figure 73.8 Tornwaldt cyst. (A) Axial T2 and (B) axial T1-weighted MRI at the level of nasopharynx show a well-defined oval lesion at the midline posterior nasopharyngeal mucosal space (arrows). The lesion was hyperintense on both sequences.
Ecchordosis Physaliphora Ecchordosis physaliphora (EP) is an ectopic notochordal remnant, located anywhere from the skull base to the sacrum, but characteristically presenting as retroclival, intradural lesion [10]. Unlike chordomas that are often symptomatic due to
brainstem or cranial nerve compression, patients with EP and benign notochord cell tumor (BNCT) (discussed later) are usually asymptomatic. EP lesions are typically less than 2 cm in size [10]. There is controversy in differentiating large EP and intradural chordoma. Some authors used giant or symptomatic EP to describe intradural, extraosseous physaliphorous cell growth [11], while others suggested using the term intradural chordoma [10]. Assessment of EP is limited on CT scan due to its near CSF density and artifacts within the posterior fossa. Occasionally a pathognomonic osseous stalk can be seen at the base of the lesion, or it could appear as smoothly corticated osseous defect extending within the clivus [10] (Fig. 73.9A). EP lesions can sometimes hard to be seen. They are typically T1 hypointense, T2 hyperintense, and have no enhancement with gadolinium (Fig. 73.9B,C). A distinct pedicle, the hallmark of EP, is commonly seen and is typically T2 hypointense [10].
Figure 73.9 Ecchordosis physaliphora: (A) Axial CT image show a well-defined lytic lesion of the basisphenoid (arrows). This lesion was hypointense on sagittal T1 (B) and hyperintense on axial T2- weighted MRI images (C) (arrows). It was stable over multiple MRI exams over 10 years and was presumed for ecchordosis. Since it was an incidental finding, there was no pathology available for this lesion.
Craniopharyngeal Canal Persistent craniopharyngeal canal, also known as the hypophyseal canal, is a rare congenital osseous defect extending through the central skull base from the floor of the sella to the nasopharyngeal roof. Craniopharyngeal canals can be asymptomatic incidental canals (type 1), or associated with ectopic
adenohypophysis (type 2) [1,12]. Type 3 craniopharyngeal canals are associated with cephaloceles (type 3A), tumors (type 3B), or both (type 3C), including pituitary adenoma, craniopharyngioma, dermoid, teratoma, and glioma [1,12].
Encephalocele Encephaloceles are uncommon lesions characterized by herniation of the meninges and cerebral tissues through a cranial osseous defect [1]. Congenital encephalocele represents a form of neural tube defect secondary to failure of fusion during embryogenesis. However, there is no clear-cut explanation for most of the neural tube maldevelopment leading to such defect. The majority of encephaloceles in adults are either posttraumatic or iatrogenic, related mostly to idiopathic intracranial hypertension. Most of the encephaloceles are midline, either occipital (75%) or sincipital (15%) in location, and the rest are basal (10%) or parietal encephaloceles [13]. Atretic cephalocele contains dura, fibrous
tissue, and degenerated brain. Most encephaloceles are sporadic without underlying genetic abnormality. Earlier descriptions of the encephalocele were based on the herniated tract of the encephalocele; however, later classification systems described the encephalocele depending on many aspects such as the content or the site of the cranial defect, the location of the encephalocele, or whether the encephalocele is occult or overt (Table 73.4). Table 73.4 Types of Encephalocele 1. According to Etiology
◾ Congenital ◾ Acquired 2. Location
◾ Sincipital encephalocele a. Frontoethmoidal (nasoethmoidal, naso-frontal, nasoobrital)
b. Interfrontal
◾ Occipital or suboccipital encephalocele ◾ Basal a. Transsphenoidal b. Transethmoidal c. Intranasal d. Sphenoorbital e. Transtemporal
○ Intranasal ○ Intraorbital ○ Intratemporal ○ Intradiploic Osseous pits related to arachnoid granulations are common incidental findings [14], most often located
in the greater wing of the sphenoid bone or the posterior wall of the temporal bone. An empty or partially empty sella is commonly seen in association with these pits, suggesting that altered CSF dynamics have a role in their development [14,15]. The rare temporal lobe encephaloceles, type II lateral sphenoid cephalocele, involve only the greater sphenoid wing without extension into the sphenoid sinus. It can occasionally exist in asymptomatic patients or present with headache, meningitis, or cranial neuropathy; however, it can present a diagnostic challenge during imaging work-up for epilepsy [14]. The more medially located, type I lateral sphenoid cephalocele herniates into a pneumatized lateral recess of the sphenoid sinus and typically presenting with CSF leak or headache [14]. The radiographic features of encephaloceles depend on their contents, ranging from purely cystic lesions (meningocele) or brain matter and meninges in case of meningoencephalocele (Fig. 73.10A,B). Ultrasound may demonstrate purely cystic, hypoechoic mass or may contain echoes related to herniated brain tissue. High-resolution CT is typically used to display the osseous defects and
characterize the bone anatomy (Fig. 73.10C,D). The contents of the cephalocele are best defined with MRI, which aids in determining the prognosis and surgical planning.
Figure 73.10 Frontonasal meningoencephalocele. (A) Axial and (B) coronal T2-weighted MRI shows a large frontonasal meningoencephalocele in an infant,
with a large meningeal component on the left. (C) Sagittal CT shows a large osseous defect at the level of primitive foramen cecum (arrow). (D) 3-D rendered CT image shows marked enlargement and remodeling of the left bony orbit. High-resolution MRI, preferably coronal 3 mm T1W images, with matching fat-suppressed T2W images, and gadolinium-enhanced T1W spin-echo sequences, is often recommended to determine the contents of the soft tissue within the nasal cavity or sinus air cell, to distinguish between a meningocele and meningoencephalocele.
CSF Leak CSF rhinorrhea or otorrhea occurs due to osteodural disruption between subarachnoid space and pneumatized structure. Any clinically suspected CSF leak should first be confirmed with testing for beta-2 transferrin, a protein specific to CSF. The presence of β-trace protein (β-TP) in CSF is an alternative and cheaper method to test for CSF leak [16].
CSF leaks can be classified as acquired or congenital. The acquired CSF leak is further classified as traumatic, nontraumatic, or spontaneous [15]. Spontaneous CSF leak is considered to result from multifactorial process and is mostly associated with idiopathic intracranial hypertension [14,15]. This process occurs most commonly in areas of structural weakness in the ethmoid roof, sphenoid sinus, and temporal bone related to underlying anatomic predisposition and thinning of the cranial base [15]. The cribriform plate is the commonest site of spontaneous CSF fistulas [15]. CSF leak in the sphenoid sinus region is typically located in the parasellar region or the lateral recess of the sphenoid sinus, classically in middle aged female, and is probably related to arachnoid granulations [14,15]. CSF leak in the temporal region, typically seen in the seventh decade of life, is most frequently present in the tegmen tympani and mastoideum, likely associated with arachnoid granulations [15]. High-resolution unenhanced CT scan of the sinonasal and skull base region is the initial recommended imaging modality for patients with suspected CSF leak. Coronal and sagittal reformatted images are
very helpful to assess the site of CSF leak. The presence of an osseous defect with an opacified air cell and olfactory recess/nasal cavity below the defect are findings that predict a CSF leak (Fig. 73.11A). The presence of a single osseous defect in patients with positive beta-2 transferrin will negate the need for a cisternogram [17]. CT cisternogram can be helpful to determine the culprit site of CSF leak in the presence of multiple osseous defects [17] (Fig. 73.11B).
Figure 73.11 Traumatic CSF leak. (A) Coronal CT images in a bone window algorithm show a larger osseous defect at the level of roof of the left sphenoid sinus (arrow). (B) After CT cisternogram, there was clear CSF leak through
the defect over the left sphenoid sinus (arrowhead).
Dermoid and Epidermoid Cysts Dermoid and epidermoid cysts are uncommon congenital lesions related to inclusion of ectodermal elements during neural tube closure. Epidermoid cysts, comprising 0.2–1.8% of primary intracranial tumors, are four to nine times as common as dermoid cysts. They can present in a variety of intracranial locations or as intraosseous lesions associated with the sutures or the skull [12,18]. The majority of epidermoid cysts are intradural (90%), most frequently in the cerebellopontine angle cistern (40– 50%), with 10% of the cysts being extradural in the skull or in the spine [18]. Dermoid cysts tend to occur in the midline at the anterior fontanelle, frontonasal region, or sellar/parasellar region. Nasal dermal sinuses with dermoid and epidermoid cysts occur at multiple locations from the foramen cecum to the columella Additionally, dermoid cysts can occur in the skull base along the craniopharyngeal canal [12].
Epidermoids have a thin capsule of stratified squamous epithelium, with internal components filled with desquamated epithelial keratin and cholesterol crystals, which accounts for their unique imaging characteristics (Fig. 73.12A,B). Dermoids have a similar stratified squamous epithelium, but contain epidermal appendages in addition to the ectodermal elements such as hair follicles, sweat glands, and sebaceous glands (Fig. 73.13A,B). Dermoids or epidermoids are ectodermal and do not contain adipose tissue, as lipocytes are mesodermal in origin.
Figure 73.12 Epidermoid of anterior skull base. Sagittal T2-weighted MRI shows a well-defined T2 hyperintense lesion extending from the tip of the nose to the anterior skull base near the level
of foramen cecum (arrows). There was remodeling the bony margins on sagittal CT image (arrows).
Figure 73.13 Dermoid of anterior skull base. Sagittal T1-weighted MRI shows a large welldefined T1 hyperintense lesion at the level of anterior skull base/glabella consistent with dermoid (arrows). Axial CT image shows osseous defect with thin stalk extending toward the crista galli (arrows). The content of the lesion will determine its CT attenuation. Epidermoid cysts have fluid attenuation, compared to dermoid cysts that have fatty attenuation (Fig. 73.13A,B). Calcification may be present in the
cyst wall. Enhancement is uncommon, and typically appears as a thin peripheral rim. Very rarely epidermoid cyst may demonstrate hyperdensity, which is probably related to saponification, microcalcification, and blood products [18]. This most often occurs when present in the posterior fossa, although the reason is uncertain. Similarly, the signal intensity on MR imaging depends on the contents of the cyst, with fluid signal intensity (hypointense or isointense on T1 weighted and hyperintense on T2 weighted) in epidermoid, with often heterogeneous hyperintense signal on FLAIR images. Epidermoids typically have bright signal intensity on isotropic diffusion-weighted MR images. Dermoids have more complex signal intensity (hyperintense on T1 weighted due to cholesterol components and variable hypointense or hyperintense signal on T2 weighted) (Fig. 73.13A,B). Cyst rupture is the most common complication and appears as T1 hyperintense droplets in the subarachnoid spaces. To better delineate the ectodermal elements associated with nasal sinus tract in the prenasal space or the foramen cecum, thin (2–3 mm) sagittal T1-weighted or heavily T2-weighted
images and preferably sagittal DWI are optimal imaging techniques to consider.
Malignant Neoplasms Sinonasal Neoplasms There is a variety of neoplastic processes arising in the sinonasal region, most of which are malignant (Table 73.5). Many of these lesions can involve the skull base and present with neurological complications. CT and MRI are complementary modalities in evaluating sinonasal lesions. CT scan is essential to assess the osseous structures and should be performed with thin, 1 mm, slices with coronal and sagittal reformations. CT typically demonstrates heterogeneously enhancing, poorly defined mass, and is particularly effective in delineating the extent of osseous changes and the pattern of bone invasion. Intralesional calcifications are seen in certain pathologies, such as olfactory neuroblastoma, adenocarcinoma, inverted papilloma, cartilaginous tumors, or fibro-osseous lesions such as fibrous dysplasia (FD), osteoma, and osteosarcoma [19].
Characteristic osseous changes can help predict the tumor histology. Extensive osseous destruction is typically seen in high-grade malignancies (Fig. 73.14A), compared to permeative changes associated with small round cell tumors. The slow growth associated with low-grade malignancies and benign lesions may result in bony remodeling. Table 73.5
Figure 73.14 Squamous cell carcinoma. (A) Axial CT image at the level of central skull base shows a large, destructive mass that was Epstein-Barr virus–related nasopharyngeal cancer invading the skull base (arrows). The lesion was isointense on axial T1 (B), relatively hypointense on T2-weighted MRI (C) (arrows). The lesion had mild diffusion hyperintensity (D), with low signal on corresponding apparent diffusion coefficient images (E), particularly at the periphery of the mass (arrows). (F) MR perfusion show increased perfusion at the periphery of the lesion (arrows), corresponding to the area of reduced diffusion signal and
suggestive of more cellular component of the mass. MRI provides better characterization of the soft tissue components of the tumor and helps in differentiating the tumor from adjacent retained secretions. While tumor’s signal intensity can slightly vary based on their components, however the MR imaging characteristics are generally nonspecific with relative hypointense/isointense T1 signal and hyperintense T2 signal [19,20] (Fig. 73.14B). Mucinous or cartilaginous tumors may demonstrate marked T2 hyperintensity, compared to tumors with calcification or highly cellular tumors that demonstrate T2 isointensity or hypointensity (Fig. 73.14C). Intratumoral T1 hyperintensity indicates the presence of methemoglobin, melanin, protein, and sometimes intralesional mineralization or calcification [19,20]. DWI and the value of diffusion coefficient (apparent diffusion coefficient [ADC] maps) can serve as useful imaging biomarkers [20] (Fig. 73.14D). LowADC lesions typically indicate hypercellularity, desiccated secretions, or hemorrhage, whereas high-
ADC lesions indicate hypocellularity, “hydrated” mucus, or fluid/necrosis (Fig. 73.14E). A relatively low ADC values (0.87–1.10 × 10−3 mm2/s) is typically seen in malignant sinonasal tumors, compared to a higher ADC values of benign sinonasal lesions (1.35–1.78 × 10−3 mm2/s) [20]. MR perfusion can often show areas of increased perfusion (Fig. 73.14F). Lesions that cause dural invasion and perineural spread (PNS) are best characterized using contrast-enhanced MRI. Intracranial involvement is typically seen as an area of dural thickening >5 mm, pial enhancement, or the presence of focal dural nodules, in contrast to linear dural enhancement alone which is not a conclusive sign of dural invasion [20].
Esthesioneuroblastoma Olfactory neuroblastoma or esthesioneuroblastoma is an important type of sinonasal malignant tumor. It is a rare neuroectodermal tumor arising of the olfactory epithelium [3,20]. There is bimodal age distribution in the second and sixth decades of life, with no recognized gender predilection. Esthesioneuroblastomas are slowly growing lesions,
mostly seen at advanced stage as large lesions in the ACF and sinonasal region [3,20,21]. The CT imaging features are nonspecific, with smaller, intranasal, lesions appearing as polypoid soft tissue lesion that widens the olfactory recess [21]. Large esthesioneuroblastoma results in osseous destruction, or less frequently bony remodeling, and appears relatively isodense with intralesional focal calcifications, and scattered necrosis [20,21]. MRI signal characteristics can be variable but mostly heterogeneously T1 and T2 isointense, with variable enhancement [20] (Fig. 73.15A–C). Peritumoral cysts can be seen in larger lesions with intracranial extension; however, this is not pathognomonic for esthesioneuroblastoma [20]. Cervical and retropharyngeal nodal metastases are present in 10– 44% of cases at diagnosis, with relatively poor prognosis [20]. PET-CT and metaiodobenzlyguanidine (MIBG) scans are useful adjunct to conventional imaging in the initial staging and restaging of esthesioneuroblastoma.
Figure 73.15 Esthesioneuroblastoma. Coronal T2 (A), T1 (B), and contrast-enhanced T1weighted MRI shows an aggressive mass occupying the left nasal cavity and invading the left orbit (arrows). There was mild enhancement of the dura in the left anterior skull base (arrowhead), without parenchymal invasion.
Chordoma Chordoma is uncommon locally invasive tumor of the axial skeleton that originates from the embryonic remnants of the primitive notochord [22,23]. It can be histologically indistinguishable from EP, except by identifying infiltrative growth pattern along the margins of the chordoma. Chordomas are found along the axial skeleton with relatively even distribution among three locations, either the spheno-
occipital (30–35%), sacrococcygeal (30–50%), or vertebral body (15–30%) [22]. Within the clivus, chordoma is classically centrally located, intraosseous and extraosseous lesion that projects posteriorly indenting the pons with “thumb sign” or thumbing of the pons appearance. BNCT is a poorly recognized entity, usually asymptomatic and discovered incidentally on imaging of the head or spine. The majority of BNCTs are intraosseous lesions with 50% of the lesions involving the skull base. Apart from the characteristic location of these lesions (intraosseous vs intra/extraosseous), the imaging findings can be confusing. Chordomas are typically well-circumscribed expansile lesion and show variable osteolysis (Fig. 73.16A), sometimes with marginal sclerosis. Irregular intratumoral calcifications can be seen, thought to represent sequestra of normal bone, with intralesional hemorrhage or necrosis [22,24]. Chordomas are T1 hypo- or isointense and mostly T2 hyperintense [22,24] (Fig. 73.16B). Intralesional heterogeneity with small foci of T1 hyperintensity can be seen related to intratumoral hemorrhage or mucus pool. Susceptibility weighted imaging (SWI)
or gradient recalled echo (GRE)images will demonstrate variable blooming artifact related to the intralesional hemorrhage. There is heterogeneous enhancement following the administration of gadolinium with a honeycomb appearance corresponding to low T1 signal areas within the tumor [22,24] (Fig. 73.16C). Greater intralesional enhancement has been associated with poorer prognosis [25]. All BNCTs demonstrate mild osteosclerosis without associated osteolytic changes, and are typically T1 hypo- or isointense with hyperintense T2 signal, usually without enhancement or restricted diffusion [24].
Figure 73.16 Chordoma. Sagittal CT (A) through the midline show large irregularly marginated and mixed lytic and sclerotic lesion of the bony clivus (arrows). The lesion has heterogeneous appearance on axial T2-weighted
(B) and enhancement on post-contrast enhanced T1 sequence (C), respectively.
Chondrosarcoma Chondrosarcomas of the skull base are rare tumors most commonly located off the midline compared to chordomas that are usually midline [23,26]. Clinical presentation is usually due to mass effect, either on the adjacent brainstem and brain, or cranial neuropathy. Chondrosarcomas probably arise from embryonal rest cells, most commonly at the petrooccipital synchondrosis or at the sphenoethmoidal junction and sella turcica [26,27]. Rare cases of chondrosarcoma have been reported arising from the choroid plexus, or dura matter [28], presumably from heterotopic cartilaginous rests or metaplasia. Just like many other pathologies of the skull base, CT and MRI are complementary in imaging of chondrosarcoma. CT scan can characterize the relationship to the skull base structures, and exquisitely depicts intralesional calcification with osteolytic changes of the contiguous skull base [26,27] (Fig. 73.17A). There is typically minimal-to-
moderate contrast enhancement. MRI can better characterize the extent of the lesion and relationship to neural structures [26]. MRI will demonstrate T1 hypointensity and T2 hyperintensity with heterogeneous enhancement (Fig. 73.17B–C). Hypointense or heterogeneous T2 signal is likely caused by matrix mineralization, intralesional hemorrhage, and fibrocartilaginous elements [27]. There are no reliable imaging characteristics to differentiate chondrosarcoma from chordoma, apart from their location.
Figure 73.17 Chondrosarcoma. (A) Axial CT image shows a lytic mass centered near the right petro-clival fissure (arrows). The lesion has intralesion calcifications. The lesion is markedly hyperintense on axial T2 (B) and show “stippled” type of enhancement post-contrast enhanced T1-weighted MRI (C).
Plasmacytoma Plasmacytoma is a rare solitary tumor of neoplastic monoclonal plasma cells, most commonly occurs in bone (∼70%), and less frequently presents as extramedullary lesion (∼30%). It is typically associated with latent systemic disease with minimal or no systemic features. Involvement of the skull base is a rare entity mostly seen in the sphenoclival and petrous apex regions [29]. It is part of a larger differential diagnosis that includes chordoma, nasopharyngeal carcinoma, metastatic carcinoma, lymphoma, and multiple myeloma. CT scan can demonstrate osteolytic lesion or soft tissue mass (Fig. 73.18A). MRI features are nonspecific with T1 isointensity and T2 hyperintensity with heterogeneous enhancement [29,30] (Fig. 73.18B).
Figure 73.18 Plasmacytoma. (A) Axial CT at the level of central skull base and sphenoid sinus show a large aggressive lytic lesion involving the bony clivus (arrows). The lesion is iso to mildly hypointense on coronal T2-weighted MRI (not shown) and show moderate to avid post-contrast enhancement (B). The pituitary gland was elevated by this mass, but was separate.
Perineural Spread PNS is an important imaging feature of head and neck malignancies, with significant impact on management and prognosis. It is important to realize that PNS differs from perineural invasion, with the
former is a radiological finding, compared to later which is a histological finding of tumor cell infiltration [3,30]. PNS can be seen in any of the head and neck malignancies, with adenoid cystic carcinomas of the salivary glands is the most notorious for producing PNS [3,30]. Mucosal and cutaneous squamous cell carcinomas are the most frequent malignancies associated with PNS, mostly due to its common incidence (Fig. 73.19A).
Figure 73.19 Perineural spread of squamous cell carcinoma. (A) Axial and coronal (B, C) postcontrast enhanced T1-weighted MRI shows an enhancing mass anterior to the left maxillary sinus which was proven for squamous cell carcinoma (arrow). On further inspection, there is retrograde extension of tumor though the second (V2) division of left trigeminal nerve with mild asymmetric enhancement of the left
Meckel cave (arrow). Antegrade extension of cancer along the third (V3) division of left trigeminal nerve (arrow in C) is also seen. Typical imaging findings of PNS on CT scan include foraminal enlargement with or without destruction, and abnormal enhancement within the foramen or canal [3,30]. MRI is superior to CT for evaluation of PNS, demonstrating nerve thickening, loss of the fat surrounding the nerve, and abnormal neural contrast enhancement (Fig. 73.19B–C).
Benign Neoplasms Schwannoma Intracranial schwannomas are common benign tumors, mostly sporadic, with few syndromic associations seen in neurofibromatosis type II and schwannomatosis syndrome. Schwannomas are most frequently encountered in middle-aged and elderly adults with recognized female predilection [31]. Clinical presentation depends on the nerve involved and the location of involvement. Larger tumors can result in symptoms related to mass effect on the
surrounding structures. Any cranial nerve can be involved, though involvement of the sensory nerves is more common compared to the uncommon involvement of the pure motor nerves. The vast majority of intracranial schwannomas arises from the vestibular division of the vestibulocochlear cranial nerve, and less frequently in the trigeminal, facial, and glossopharyngeal nerves [31] (Figs. 73.20A–B and 73.21A–B).
Figure 73.20 Trigeminal nerve schwannoma. (A) Axial T2 and (B) sagittal post-contrast enhanced T1-weighted MRI shows large and well-defined soft tissue mass at the level of right middle cranial fossa along the course of the trigeminal nerve extending toward right Meckel cave (arrows). The lesion is hyperintense with
mild heterogeneity on T2 image and shows avid post-contrast enhancement.
Figure 73.21 Jugular foramen schwannoma. (A) Axial T1, (B) axial T2, and (C) coronal postcontrast enhanced T1-weighted MRI shows a large well-defined soft tissue mass at the level of left jugular foramen extending into the left carotid space (arrows). The lesion is hypointense on T1, hyperintense with mild heterogeneity on T2 image and show marked post-contrast enhancement. The slow growth of intracranial schwannomas results in its typical imaging features with well-defined margins (Fig. 73.20A) and smooth expansion of osseous foramina, with deformation of the brain in large lesions. CT demonstrates isodense or hypodense lesion, with variable enhancement [31]. Intralesional cystic changes can be seen as prominent
hypodense areas. MRI characteristics of individual schwannomas are typically related to its composition and the nerve of origin. Schwannomas typically have hyperintense or isointense T2 signal [23,30]. The presence of heterogeneous T2 hyperintense signal is attributed to the tumor’s composition with regions of compactly arranged cells (Antoni type A) which demonstrate slightly darker T2 signal, adjacent to distinct loosely arranged cells (Antoni type B) which have brighter T2 signal [32] (Figs. 73.20A and 73.21B). The target sign typically seen in peripheral neurogenic tumors is essentially never seen at imaging of intracranial schwannomas [31]. On T1weighted images, these lesions have isointense or hypointense signal and demonstrate avid, mostly heterogeneous, enhancement after contrast material administration, with or without cystic changes [23– 30] (Fig. 73.20B). Larger lesions commonly have heterogeneous enhancement, cystic spaces, and intralesional hemorrhage, and sometimes peritumoral cysts [23,30] (Fig. 73.21C).
Meningioma
Meningiomas are nonglial neoplasm that originates from the meningocytes or arachnoid cap cells of the meninges. Meningiomas are common primary intradural lesions, located anywhere that meninges are present, or can rarely present as primary extradural or ectopic extracranial lesions related to rest cells [33]. The majority of meningiomas have typical radiologic appearance with benign course; however there is a wide array of histological variants resulting in variable imaging features with, uncommonly, an aggressive biological behavior. Meningiomas are more common in female, with a female-to-male ratio of approximately 2:1. Many small meningiomas are entirely asymptomatic. Meningiomas may also become symptomatic due to mass effect, particularly lesions at the skull base as they involve the sphenoid ridge, juxtasellar or olfactory groove/planum sphenoidale region (Fig. 73.22A–B). Based on the WHO classification for CNS tumors, meningiomas are graded into benign grade I (70%), atypical grade II (30%), or anaplastic grade III (∼1%) lesions [33].
Figure 73.22 Planum sphenoidale meningioma. (A) Coronal T2, (B) sagittal T1, and (C) coronal post-contrast enhanced T1-weighted MRI show a large, well-defined, extraaxial soft tissue mass at the level of planum sphenoidale/anterior skull base (arrows). The lesion is isointense on T1, iso to mildly hyperintense on T2 and shows marked post-contrast enhancement. Noncontrast CT typically demonstrate slightly hyperdense lesion compared to normal brain (60%), while the rest are relatively isodense [34,35], or rarely hypodense [34]. Up to one-third of the lesions have intralesional calcification. The majority of meningiomas demonstrate homogeneously contrast enhancement (Figs. 73.22C and 73.23A), with malignant or cystic variants demonstrate more heterogeneity/less intense enhancement. Bony hyperostosis is typically seen associated with skull base meningioma [35]. This is different than
intraosseous meningioma, a rare meningioma subtype, that represents primary extradural meningioma with osteoblastic changes [35] or less frequently osteolytic changes [36] (Fig. 73.23B). Osteolytic and destructive changes are typically seen in higher grade tumors.
Figure 73.23 Intraosseous meningioma. (A) Axial post-contrast enhanced T1-weighted MRI shows a large, extra-axial soft tissue mass along the right greater wing of sphenoid bone (large arrow) with extension in the overlying right masticator space (small arrow). (B) Axial CT through the same level shows expansion and sclerosis suggesting intraosseous extension (arrows).
Signal changes on T1-weighted images are not particularly useful in discriminating pathologic subtype of meningiomas, with the majority of the lesions being isointense or hypointense [34, 37]. Signal intensity on T2-weighted images has a higher correlation with the histopathologic findings [37]. Predominantly fibroblastic or transitional meningiomas typically demonstrate T2 hypointense signal compared to the cortex (Fig. 73.22A), compared to syncytial or angioblastic meningiomas that are typically T2 hyperintense [37]. The appearance of meningiomas on DWI images is variable; however, the ADC value has no significance in determining histological behavior or in differentiating histopathological subtypes of meningiomas [38]. Dural tail is most commonly seen in meningiomas (60–72%), though it is not pathognomonic and can be seen with a variety of intraaxial and extraaxial pathologies [39]. A variable amount of vasogenic edema in the adjacent brain parenchyma is seen in up to 75% of the lesions [35]. Some meningioma variants can vary dramatically in their imaging appearance. A burnt-out meningioma, typically psammomatous meningioma or osseous
metaplastic subtype, describes a meningioma that is completely calcified/ossified. Cystic meningioma is uncommon variant characterized by intratumoral cyst formation, peritumoral cysts, or reactive intraparenchymal cysts [35]. Cystic meningiomas should not be confused with the rare microcystic meningiomas, a distinct variant, in which the cysts are microscopic. Microcystic meningiomas are typically hypodense on CT scan with bony hyperostosis. The lesion is fluid isointense on T1and T2-weighted images with avid enhancement, related to its abundant vascularity.
Benign Fibro-osseous Lesions A multitude of fibro-osseous lesions can involve the skull base, including FD, ossifying fibroma, or Paget disease. Contrary to Paget disease that mostly involves the calvarium, FD is a disease of the medullary cavity, involving the maxillofacial, skull base, and calvarial osseous structures [40]. FD is seen in children and young adults, compared to late presentation of Paget disease that is typically seen after the fifth decade of life [30]. Ossifying fibroma represent an aggressive monostotic form of FD [30].
FD is related to localized defect in osteoblastic differentiation and maturation, with replacement of normal marrow with large fibrous stroma and islands of immature woven bone. The underlying cause of FD is not fully understood, though it is probably caused by de novo mutation in a GNAS1 gene [41]. Craniofacial involvement in FD occurs in 50% of the patients, with variable radiographic appearance. Plain radiographs demonstrate bony expansion with displacement of the outer table and relative sparing of the inner table, in contrast to Paget disease that typically involve the inner table [40]. The affected bones in FD appear either sclerotic or demonstrate bubbly cystic changes. It commonly crosses the sutures, and results in obliteration of the paranasal sinuses. CT scan will demonstrate a thin cortical outline with loss of the normal corticomedullary differentiation in the affected bones [40], with homogeneous pagetoid, or ground glass appearance (56%), homogeneous sclerotic pattern (23%), or a cystic variety (21%) (Fig. 73.24A). Histologic correlates have shown an equal mixture of fibrous tissue and woven trabecular bone in pagetoid lesions, compared to predominance of osseous elements in
sclerotic type and fibrous elements in cystic variety [41]. The MRI features of FD can be sometimes confusing and resemble that of tumors, in contrast with the distinctive features of FD seen on radiography and CT (Fig. 73.24B,C). The signal intensity on T1- and T2-weighted images and the degree of contrast enhancement depend on the underlying histologic changes and the amounts of bony trabeculae, cellularity, or collagen [41]. FD lesions show well-defined borders with intermediateto-low signal intensity on T1 and intermediate-tohigh intensity on T2-weighted images [41]. A lower T2 signal is typically associated with higher bony trabeculae, whereas higher T2 signal is associated with fewer bony trabeculae. A cystic variant of FD lesions will appear T2 hyperintense. FD lesions typically demonstrate some degree of enhancement following gadolinium administration.
Figure 73.24 Fibrous dysplasia. (A) Axial CT mage at the level of central skull base shows a well-defined expansile lesion involving the sphenoid sinuses and basisphenoid (arrows). The lesion has well-defined margins and “hazy” internal matrix, which is highly suggestive for fibrous dysplasia. The lesion has heterogeneous appearance on axial T2 (B) and post-contrast enhanced T1-weighted MRI (C), mimicking a more aggressive lesion.
Cholesterol Granuloma Cholesterol granuloma is the most common cystic lesion of the petrous apex, though it can occur in the mastoid segment or the middle ear [42,43]. On otoscopy, it may appear as a “blue lesion” [42], hence the name blue-domed cyst [43]. The cyst is filled with viscous brown fluid and cholesterol crystals, with granulation tissues, which are often contained within a thick fibrous capsule that lacks a true epithelial lining. The exact pathogenesis of cholesterol granuloma is unknown. It is probably related to Eustachian tube dysfunction causing inadequate ventilation of petrous apex air cells,
which results in negative pressure, mucosal congestion, and repeated hemorrhage [43]. There is a foreign-body reaction that is typically seen related to local tissue breakdown and cholesterol formation. A newer theory suggests that hyperplastic mucosa leads to invasion of the underlying bone and exposure of bone marrow [44], which might hemorrhage resulting in subsequent cyst formation. There are multiple pathological processes that involve the petrous apex (Table 73.6). Petrous apex effusion or trapped fluid, a “leave me alone” lesion, is a common incidental finding on routine imaging studies [45], probably related to middle ear infection resulting in obstruction of the air cell track pathways, with subsequent trapping of fluid in the petrous apex [45]. Cholesterol granuloma is pathologically different compared to mucocele, a rare entity at the petrous apex, which is characterized by an obstructed air cell containing respiratory epithelium. Congenital cholesteatoma of the petrous apex is uncommon, related to aberrant ectoderm trapped during embryogenesis. This is more common compared to the rare acquired cholesteatoma. Cholesteatoma
contains keratinized, desquamated epithelial collection, without cholesterol or lipids. Table 73.6
◾ ◾Cholesterol granuloma ◾Congenital cholesteatoma ◾Mucocele of the petrous apex ◾Petrous apex cephalocele ◾Petrous apicitis ◾ Malignant tumors: skull base chondrosarcoma, chordoma, or metastasis Petrous Apex Lesions Asymmetric marrow/asymmetric pneumatization
Cholesterol granuloma on CT scan appears expansile, well-marginated lesion with thin overlying bone, reflecting its slow growth [42,43] (Fig. 73.25A). The
lesion is isodense to brain, and sometimes demonstrates a peripheral rim of enhancement. There may be osseous dehiscence when the lesion is large. On MR images, the cholesterol granuloma will be hyperintense on T1- and T2-weighted images and may contain low signal linear areas compatible with septations [42] (Fig. 73.25B,C). This is likely related to the lesion’s contents with paramagnetic effect of extracellular methemoglobin from blood breakdown products. Faint peripheral enhancement may be seen. In contrast to cholesterol granuloma, trapped fluid in the petrous apex appears hypo- or isointense on T1 and hyperintense on T2-weighted images, with no enhancement with gadolinium [45]. MRI appearance of petrous apex cholesteatoma is distinctive with CSF isointense collection on T1- and T2-weighted images, along with hyperintense signal on FLAIR and diffusion weighted images [42,43].
Figure 73.25 Petrous apex cholesterol granuloma. (A) Axial CT image show a welldefined, lytic lesion of the left petrous temporal bone with bony remodeling along the margins (arrows). (B) Axial T2 and (C) axial T1weighted MRI shows hyperintense signal from the lesion. There was no enhancement noted (not shown).
Glomus Tumors Paraganglioma of the skull base typically occurs in the jugular fossa (glomus jugulare) or arising from the tympanic plexus in the middle ear cavity (glomus tympanicum). The majority of the lesions present in adults with pulsatile tinnitus, hearing loss, or multiple cranial neuropathies depending on the lesion’s size. Only 3% of all head-neck paragangliomas secrete catecholamines. CT typically demonstrates irregularly erosive changes of the jugular fossa [46] (Fig. 73.26A). Erosion of the caroticojugular spine between the carotid canal and jugular fossa (Phelp sign) and jugular spine can be seen as the tumor enlarges,
differentiating paraganglioma from jugular fossa pseudolesions. Tumor can extend within the petrous bone, encasing the ossicular chain, though destruction of the ossicular chain is not typical [46]. Angiographic appearance is typically of a hypervascular lesion, with enlarged arterial feeders, mostly the ascending pharyngeal artery, along with early draining veins [46]. Preoperative embolization, typically 1–2 days prior to surgery, can be supportive in patient management.
Figure 73.26 Glomus jugulare: [A] Axial CT image show a large mass with permeative bony destruction at the level of left jugular foramen (arrows). The lesion is hyperintense on T2 weighted MRI [B] and reveals marked postcontrast enhancement [C] with prominent flow voids (arrowhead) within the lesion.
Glomus tumors are typically T1 hypointense and T2 hyperintense with marked enhancement following gadolinium [46] (Fig. 73.26B,C). The so-called “salt and pepper” appearance is typically seen with lesions greater than 2 cm, with the salt representing blood products from slow flow or intralesional hemorrhage, and the pepper representing flow voids due to high vascularity. This appearance is not pathognomonic for glomus tumors and can be encountered in other hypervascular lesions (e.g. renal metastases). Avid fluorodeoxyglucose (FDG) uptake can be seen on 18FDG PET scan, creating confusion with more aggressive or malignant lesions. Indium-111 labeled octreotide SPECT scan will demonstrate tumoral uptake due to the presence of somatostatin receptors, which is seen in tumors greater than 1.5 cm in diameter [47].
Endolymphatic Sac Tumors Endolymphatic sac tumors (ELSTs) are very rare tumors of the petrous temporal bone, located in the region of the vestibular aqueduct. ELSTs are most often associated with von Hippel–Lindau disease (VHL), with the presence of bilateral involvement in
30% of VHL patients. CT demonstrates locally aggressive lesion with erosion of petrous bone in an infiltrative or “moth-eaten” pattern with intralesional calcification and intense enhancement [48] (Fig. 73.27A). MRI demonstrates a hypervascular tumor with T1 hyperintensity, with heterogeneous T2 signal and avid enhancement in the noncystic component of the tumor (Fig. 73.27B,C). Tumors larger than 2 cm usually have intralesional flow voids [48].
Figure 73.27 Endolymphatic sac tumor. (A) Axial CT show a large expansile and lytic abnormality along the posterior aspect of the left petrous temporal bone (arrows). This lesion is heterogeneous on axial T2-weighted MRI (B) and show moderate post-contrast enhancement (C).
Infectious and Inflammatory Processes Infectious Osteomyelitis Skull base osteomyelitis (SBO) is uncommon but potentially serious, most commonly seen in older diabetic or immunocompromised patients [49]. It typically arises as a complication of sinusitis, ear infection, or can be odontogenic in origin. It results in osseous destruction of the skull base and involves the skull base foramina, causing cranial neuropathies. Intracranial extension can result in epidural abscess, subdural empyema, meningitis, or even cerebritis and cerebral abscess formation. Staphylococcus aureus and Pseudomonas aeruginosa were the two most common causative pathogens [49]. Radiologic features of SBO may be similar to those of the neoplastic processes, presenting a diagnostic dilemma. CT changes during early stage can be normal or with nonspecific osseous demineralization, along with soft tissue swelling and obliteration of the fat planes. Osseous destruction and bony
sequestration are relatively late phenomena (Fig. 73.28A,B). Bone SPECT scintigraphy and MRI are more sensitive in detecting early osseous changes and determining the extent of the disease [50]. MRI is superior in the evaluation of disease spread to the soft tissues and involvement of the fat planes, dural and cranial nerve involvement, or intracranial complication [50] (Fig. 73.29A–D). The most consistent imaging findings on MRI are T1 hypointensity of the marrow with gadolinium enhancement. Diffusivity values on ADC maps are typically higher compared to those of malignant lesions [51]. Ischemic coagulative necrosis is a distinctive MR finding of angioinvasive fungal osteomyelitis, that is characterized by lack of enhancement with relatively low T2 signal of the involved soft tissues (Fig. 73.30A–C). Tc99 m methylene diphosphonate (MDP) bone SPECT scintigraphy and Tc-99m hexamethylpropyleneamine oxime (HMPAO) labeled white blood cell are sensitive but poorly specific techniques that are rarely used in the assessment of SBO [50].
Figure 73.28 Skull base osteomyelitis. (A) Axial CT through the right petrous apex and skull base show an ill-defined lytic abnormality involving the right petrous apex, right basisphenoid level (arrows). Postsurgical changes are noted in the right mastoid bone (arrowhead). (B) CT angiogram show focal outpouching from the petrous segment of the right internal carotid artery suggestive for pseudoaneurysm (arrowhead), a complication from skull base osteomyelitis.
Figure 73.29 Skull base osteomyelitis, Axial T2 (A), T1 (B), and (C) post-contrast enhanced T1weighted MRI showing ill-defined, infiltrative signal abnormality due to extensive osteomyelitis from left mastoid bone. It involved left posterior skull base and extended toward the clivus and also involving upper cervical vertebra. The lesion is hypointense on T1 and hyperintense on T2 with marked post-
contrast enhancement. (D) Maximum intensity projection image of MR venogram shows obstruction of the left sigmoid sinus (arrow) by the disease process.
Figure 73.30 Invasive fungal sinusitis. (A) Coronal T2, (B) T1, and (C) post-contrast enhanced T1-weighted MRI showing soft tissue lesion at the level of left sphenoid sinus extending toward the left cavernous sinus. The lesion is hypointense on T2 (arrow) and isointense on T1 sequence. Large portion of this lesion show no post-contrast enhancement (arrow). Potts puffy tumor is a rare clinical complication of acute frontal sinusitis. It is characterized by osteomyelitis of the frontal bone with subgaleal collection and subperiosteal abscess formation [13]. CT scan will demonstrate opacification of the frontal
sinuses with swelling of the overlying scalp [13] and sometimes bony sequestration. Intracranial involvement is better evaluated on MRI with thickening and enhancement of the dura, epidural abscess or subdural empyema, and sometimes cerebritis or focal cerebral abscess [13] (Fig. 73.31A–C).
Figure 73.31 Pott puffy tumor. (A) Axial FLAIR and (B) axial diffusion–weighted MRI through the anterior skull base level show abnormal soft tissue swelling in the midline frontal scalp with fluid collection (arrows). This fluid reveals diffusion hyperintensity (arrowhead). There is similar fluid signal in the right frontal epidural space. (C) Sagittal post-contrast enhanced T1weighted MRI shows obstructed left frontal sinus as a source of this infection. There is enhancement of the dura (arrowhead) and pia (arrows) in the frontal regions.
Noninfectious Inflammatory Process Hypertrophic pachymeningitis is uncommon condition characterized by localized or diffuse inflammatory thickening of the dura. On imaging, it presents as a localized, multifocal, or diffuse dural thickening, and sometimes has a mass-like tumefactive appearance [52]. Early reports were described in relation to tuberculosis or syphilis; however, hypertrophic pachymeningitis has diverse etiology (Table 73.7). Its presentation is nonspecific with progressive cranial nerve palsies, headaches, and cerebellar dysfunction [52], and rarely with seizure. A thickened, hyperdense dura is typically seen on nonenhanced CT scans, involving the tentorium, falx, and retroclival region, with marked enhancement on contrast administration [52]. The thickened dura will appear hypointense on T1- and T2-weighted images with avid enhancement following gadolinium administration [52]. Table 73.7 Etiologies of Hypertrophic Pachymeningitis
1.Idiopathic 2.Neurosarcoidosis 3.IgG-4- related pachymeningitis 4.Neurosyphilis/CNS tuberculosis 5.Granulomatosis with polyangiitis 6.Polyarteritis nodosa 7.Rheumatoid arthritis 8.Neuro Behcet disease 9.Rosai- Dorfman disease Neurosarcoidosis: Involvement of the central nervous system is relatively common among patients with systemic sarcoidosis [53]. It typically presents with a wide array of manifestations, with lesions potentially involving the leptomeninges,
pachymeninges, pituitary gland, and cerebral or spinal parenchyma (Fig. 73.32A–D). Focal or diffuse pachymeningeal thickening may be observed, with isointense signal on T1, hypointense signal on T2weighted images, and moderate-to-intense contrast enhancement [53]. Simultaneous dural and leptomeningeal involvement is uncommonly observed [53].
Figure 73.32 (A) Axial FLAIR, (B) T1 and (C) post-contrast enhanced T1- weighted MRI show a large, enhancing extra-axial lesion involving
the right middle and posterior cranial fossa (arrows). (D) In addition, there is abnormal pial enhancement covering the lower brainstem and also at the surface of the left cerebellar hemisphere and covering the spinal cord (arrows). Erdheim–Chester disease: Erdheim–Chester disease is a rare non-Langerhans cell, multisystemic histiocytosis, most commonly presenting as multifocal sclerotic lesions, with or without widespread manifestations. Neurologic involvement can be seen in up to half of the cases. Infiltration can involve the intraaxial and extraaxial compartments of the CNS, which can be symptomatic or asymptomatic [54]. The imaging features of intracranial lesions can have infiltrative pattern, widespread or focal meningeal pattern, or composite pattern of infiltrative and meningeal lesions [54]. IgG4-related disease: Immunoglobulin G4 (IgG4) related disease is a fibroinflammatory condition that can affect nearly any organ system. It was recognized as a systemic disease in 2003, characterized by fibroinflammatory lesions rich in IgG4-positive plasma
cells and often elevated serum IgG4 concentrations [55]. Central nervous system (CNS) involvement is uncommon, with hypopituitarism secondary to IgG4related hypophysitis and pachymeningitis being the most common manifestations. MRI will demonstrate localized or less often diffuse dural thickening (Fig. 73.33). Tumefactive hypertrophic pachymeningitis is uncommon mass–like thickening of the dura [52].
MRI showing focal thickening and enhancing dural/pachymeningeal lesion at the retro-clival space (arrows).
Suggested Readings • AM Blitz, N Aygun, DA Herzka, M Ishii, GL Gallaia, High resolution three-dimensional MR Imaging of the skull base: compartments, boundaries, and critical structures, Radiol Clin North Am 55 (2017) 17–30. • E Dickerson, A Srinivasan, Advanced imaging techniques of the skull base, Radiol Clin North Am 55 (2017) 189–200. • HA Parmar, S Gujar, G Shah, SK Mukherji, Imaging of the anterior skull base, Neuroimaging Clin N Am 19 (2009) 427–439. • E Erdem, EC Angtuaco, R Hemert, JS Park, O Al-Mefty, Comprehensive review of intracranial chordoma, Radiographics 23 (2003) 995–1009. • GA Christoforidis, EM Spickler, MV Recio, BM Mehta, MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and
response to treatment, AJNR Am J Neuroradiol 20 (1999) 655–669. • MP Buetow, PC Buetow, JG Smirniotopoulos, Typical, atypical, and misleading features in meningioma, Radiographics 11 (1991) 1087–1106.
References [1] LM Conley, CD Phillips, Imaging of the central skull base, Radiol Clin North Am 55 (1) (2017) 53– 67. [2] WR Nemzek, et al., MR, CT, and plain film imaging of the developing skull base in fetal specimens, Am J Neuroradiol 21 (9) (2000) 1699– 1706. [3] H Parmar, et al., Imaging of the anterior skull base, Neuroimaging Clin N Am 19 (3) (2009) 427– 439. [4] HR Kelly, HD Curtin, Imaging of skull base lesions, Handb Clin Neurol 135 (2016) 637–657.
[5] E Dickerson, A Srinivasan, Advanced imaging techniques of the skull base, Radiol Clin North Am 55 (1) (2017) 189–200. [6] AM Blitz, et al., High resolution threedimensional MR Imaging of the skull base: compartments, boundaries, and critical structures, Radiol Clin North Am 55 (1) (2017) 17–30. [7] S Bayrak, D Goller Bulut, K Orhan, Prevalence of anatomical variants in the clivus: fossa navicularis magna, canalis basilaris medianus, and craniopharyngeal canal, Surg Radiol Anat 41 (4) (2019) 477–483. [8] GK Paraskevas, PP Tsitsopoulos, OM Ioannidis, Incidence and purpose of the clival canal, a “neglected” skull base canal, Acta Neurochir (Wien) 155 (1) (2013) 139–140. [9] I Ikushima, et al., MR imaging of Tornwaldt’s cysts, Am J Roentgenol 172 (6) (1999) 1663–1665. [10] HH Park, et al., Ecchordosis physaliphora: typical and atypical radiologic features, Neurosurg Rev 40 (1) (2017) 87–94.
[11] KM Krisht, et al., Giant ecchordosis physaliphora in an adolescent girl: case report, J Neurosurg Pediatr 12 (4) (2013) 328–333. [12] TA Abele, et al., Craniopharyngeal canal and its spectrum of pathology, Am J Neuroradiol 35 (4) (2014) 772–777. [13] FE Moron, et al., Lumps and bumps on the head in children: use of CT and MR imaging in solving the clinical diagnostic dilemma, Radiographics 24 (6) (2004) 1655–1674. [14] F Settecase, et al., Spontaneous lateral sphenoid cephaloceles: anatomic factors contributing to pathogenesis and proposed classification, Am J Neuroradiol 35 (4) (2014) 784–789. [15] RC Alonso, et al., Spontaneous skull base meningoencephaloceles and cerebrospinal fluid fistulas, Radiographics 33 (2) (2013) 553–570. [16] MH Sampaio, et al., Predictability of quantification of beta-trace protein for diagnosis of cerebrospinal fluid leak: cutoff determination in nasal
fluids with two control groups, Am J Rhinol Allergy 23 (6) (2009) 585–590. [17] PA Hudgins, KL Baugnon, Head and neck: skull base imaging, Neurosurgery 82 (3) (2018) 255–267. [18] AG Osborn, MT Preece, Intracranial cysts: radiologic-pathologic correlation and imaging approach, Radiology 239 (3) (2006) 650–664. [19] KK Koeller, Radiologic features of sinonasal tumors, Head Neck Pathol 10 (1) (2016) 1–12. [20] M Kawaguchi, et al., Imaging characteristics of malignant sinonasal tumors, J Clin Med 6 (12) (2017) 116. [21] ME Peckham, et al., Intranasal esthesioneuroblastoma: CT patterns aid in preventing routine nasal polypectomy, Am J Neuroradiol 39 (2) (2018) 344–349. [22] E Erdem, et al., Comprehensive review of intracranial chordoma, Radiographics 23 (4) (2003) 995–1009.
[23] AF Choudhri, et al., Lesions of the skull base: imaging for diagnosis and treatment, Otolaryngol Clin North Am 45 (6) (2012) 1385–1404. [24] T Nishiguchi, et al., Differentiating benign notochordal cell tumors from chordomas: radiographic features on MRI, CT, and tomography, Am J Roentgenol 196 (3) (2011) 644–650. [25] E Lin, et al., Prognostic implications of gadolinium enhancement of skull base chordomas, Am J Neuroradiol 39 (8) (2018) 1509–1514. [26] RF Oot, et al., The role of MR and CT in evaluating clival chordomas and chondrosarcomas, Am J Roentgenol 151 (3) (1988) 567–575. [27] SP Meyers, et al., Chondrosarcomas of the skull base: MR imaging features, Radiology 184 (1) (1992) 103–108. [28] JH Park, et al., Intracranial extraskeletal myxoid chondrosarcoma: case report and literature review, J Kor Neurosurg Soc 52 (3) (2012) 246–249.
[29] A Siyag, et al., Plasmacytoma of the skull-base: a rare tumor, Cureus 10 (1) (2018) e2073. [30] A Borges, Imaging of the central skull base, Neuroimaging Clin N Am 19 (4) (2009) 669–696. [31] AD Skolnik, et al., Cranial nerve Schwannomas: diagnostic imaging approach., Radiographics 36 (5) (2016) 1463–1477. [32] FJ Wippold 2nd. et al., Neuropathology for the neuroradiologist: Antoni A and Antoni B tissue patterns, Am J Neuroradiol 28 (9) (2007) 1633–1638. [33] DN Louis, H Ohgaki, OD Wiestler, et al., Acta Neuropathol 114 (2007) 97–109. [34] D Saloner, et al., Modern meningioma imaging techniques, J Neurooncol 99 (3) (2010) 333–340. [35] MP Buetow, P Buetow, J Smirniotopoulos, Typical, atypical, and misleading features in meningioma, Radiographics 11 (6) (1991) 1087– 1106.
[36] V Agrawal, et al., Intraosseous intracranial meningioma, Am J Neuroradiol 28 (2) (2007) 314– 315. [37] AD Elster, et al., Meningiomas: MR and histopathologic features, Radiology 170 (3 Pt 1) (1989) 857–862. [38] SE Sanverdi, et al., Is diffusion-weighted imaging useful in grading and differentiating histopathological subtypes of meningiomas?, Eur J Radiol 81 (9) (2012) 2389–2395. [39] M Wen, et al., Immunohistochemical profile of the dural tail in intracranial meningiomas, Acta Neurochir (Wien) 156 (12) (2014) 2263–2273. [40] J Tehranzadeh, et al., Computed tomography of Paget disease of the skull versus fibrous dysplasia, Skeletal Radiol 27 (12) (1998) 664–672. [41] YS Kushchayeva, et al., Fibrous dysplasia for radiologists: beyond ground glass bone matrix, Insights Imaging 9 (6) (2018) 1035–1056.
[42] MJ Pisaneschi, B Langer, Congenital cholesteatoma and cholesterol granuloma of the temporal bone: role of magnetic resonance imaging, Top Magn Reson Imaging 11 (2) (2000) 87–97. [43] B Isaacson, J Kutz, P Roland, Lesions of the petrous apex: diagnosis and management, Otolaryngol Clin North Am 40 (3) (2007) 479–519,, viii. [44] RK Jackler, M Cho, A new theory to explain the genesis of petrous apex cholesterol granuloma, Otol Neurotol 24 (1) (2003) 96–106, discussion 106. [45] MA Arriaga, Petrous apex effusion: a clinical disorder, Laryngoscope 116 (8) (2006) 1349–1356. [46] AB Rao, KK Koeller, CF Adair, From the archives of the AFIP. Paragangliomas of the head and neck: radiologic-pathologic correlation. Armed Forces Institute of Pathology, Radiographics 19 (6) (1999) 1605–1632. [47] ML Whiteman, et al., 111In octreotide scintigraphy in the evaluation of head and neck lesions, Am J Neuroradiol 18 (6) (1997) 1073–1080.
[48] SK Mukherji, et al., Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients, Radiology 202 (3) (1997) 801–808. [49] AK Johnson, PS Batra, Central skull base osteomyelitis: an emerging clinical entity, Laryngoscope 124 (5) (2014) 1083–1087. [50] A van Kroonenburgh, et al., Advanced imaging techniques in skull base osteomyelitis due to malignant otitis externa, Curr Radiol Rep 6 (1) (2018) 3. [51] B Ozgen, KK Oguz, A Cila, Diffusion MR imaging features of skull base osteomyelitis compared with skull base malignancy, Am J Neuroradiol 32 (1) (2011) 179–184. [52] IA Kazem, et al., Best cases from the AFIP: idiopathic tumefactive hypertrophic pachymeningitis, Radiographics 25 (4) (2005) 1075–1080. [53] GA Christoforidis, et al., MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and response to treatment, Am J Neuroradiol 20 (4) (1999) 655–669.
[54] F Lachenal, et al., Neurological manifestations and neuroradiological presentation of ErdheimChester disease: report of 6 cases and systematic review of the literature, J Neurol 253 (10) (2006) 1267–1277. [55] V Deshpande, et al., Consensus statement on the pathology of IgG4-related disease, Mod Pathol 25 (9) (2012) 1181–1192.
CHAPTER 74
Oral and Dentomaxillofacial Radiology Dania Tamimi, Husniye Demirturk
Introduction Oral and dentomaxillofacial radiology is a specialty in dentistry that covers the radiographic evaluation of the teeth, the jaws, the temporomandibular joints (TMJs), the facial bones, and the upper respiratory tract for dental treatment. To communicate with the referring dentist or dental surgeon, the radiologist must learn the correct dental and maxillofacial terminology, know the pathology that occurs in the maxillofacial complex and have a basic understanding of the treatments unique to this area. This chapter will introduce the radiologists to some of the pathology encountered in oral and dentomaxillofacial radiology (otherwise known as “dental radiology”) with the intent to facilitate communication with the referring dentist and to increase the radiologists’ confidence when reading images of this area. The anatomy and diagnosis of the TMJs will also be covered.
Anatomy Dental Anatomy and Nomenclature There are two sets of dentitions in humans: a primary dentition (20 teeth) and a permanent dentition (32 teeth), with half of these teeth in the maxillary arch and the other in the mandibular arch. Each arch is further divided into a right and left side (quadrant), with four quadrants in total in the mouth. Each quadrant has five primary teeth and eight permanent teeth.
a. A primary dentition quadrant contains a central incisor, a lateral incisor, a canine and a first molar and second molar. b. A permanent quadrant has a central incisor, a lateral incisor, a canine, a first and second premolar, and a first, second, and third molar.
These teeth can be named or numbered to facilitate communication [1]. There are multiple different tooth numbering systems used around the world, with the most common being the FDI (Federation Dentaire Internationale) system being the most widespread. This tooth numbering system is widely used globally and adopted by the World Health Organization and the International Association of Dental Research [2]. Unless the reader interprets cases for the United States (where the American Dental Association system prevails), the FDI system can be used on radiology reports for most of the world, or the teeth can be named. The FDI system gives each quadrant a number. In the permanent dentition, the maxillary right is quadrant 1, maxillary left is quadrant 2, mandibular left is quadrant 3, and mandibular right is quadrant 4 (Fig. 74.1). The permanent teeth are numbered from 1 to 8, starting from the midline. In the primary dentition, the maxillary right is quadrant 5, maxillary left is quadrant 6, mandibular left is quadrant 7, and the mandibular right is quadrant 8, and the primary teeth are numbered from 1 to 5, also starting at the midline. So a permanent maxillary right central incisor would be tooth number 11 (pronounced “one-one”), a maxillary right lateral incisors would be tooth number 12 “one-two” and a maxillary right third molar would be tooth number 18 “one-eight.” This continues for all other quadrants, with the quadrant number first then the tooth number. A primary mandibular left canine would be tooth #73 “seven-three” (Figs. 74.2and74.3). If the numbering system is confusing, a radiologist can name the teeth, first by identifying which dentition the tooth belongs to (primary or permanent), then the jaw (maxillary or mandibular) then the side (right or left) then the tooth name (central or lateral incisor, canine, first or second premolar, or first, second, or third molars (Fig. 74.4).
FIGURE 74.1 Graphic drawing demonstrating the division of the oral cavity into four quadrants. (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
FIGURE 74.2 (A) FDI (Federation Dentaire Internationale) numbering system for permanent teeth. (B) FDI numbering system for primary teeth. (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
FIGURE 74.3 Axial CBCT and panoramic reformation show how to count teeth on the radiographic imaging. (A) FDI tooth numbering on a panoramic radiograph of the permanent (adult) dentition (Courtesy: Dr. S. Bayrak). (B) FDI
tooth numbering on a panoramic radiograph in the mixed dentition phase (Courtesy: Dr. U. Seki). (C) FDI tooth numbering on a CBCT (applies to CT and MRI) axial view of the permanent teeth in the maxilla. (D) FDI tooth numbering on a CBCT (applied to CT and MRI) axial view of the permanent in the mandible. Quadrant 1: upper right, Quadrant 2: upper left, Quadrant 3: lower left, Quadrant 4: lower right. Tooth counting starts from the midline with the central incisor = 1 to the third molar = 8.
FIGURE 74.4 (A) Types of permanent teeth (incisors, canines, premolars, and molars) and (B) primary teeth (incisors, canines, and molars) found is each quadrant. The teeth are repeated in each quadrant. (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
Dental Anatomic Relationships The description of lesions and conditions surrounding teeth does not follow the conventional anatomic position descriptors (inferior, superior, medial, lateral, etc.). Instead, it puts the teeth in the center of the universe and structures surrounding the teeth are described in relation to the teeth. A special midline is considered between the central incisors that bisects the anterior maxillary and mandibular arches. This is different from the sagittal plane and the true anatomic midline of the jaws. Using the dental arch as a reference, the structures and tooth surfaces that are closer to this dental midline along this arch are “mesial” and those further away from this midline are “distal.” Structures and surfaces toward the face are “facial,” or more specifically “labial” in the anterior region and “buccal” in the posterior portion of
the arch. Structures on the inside the teeth toward the tongue are “lingual” in both arches, but more specifically “palatal” in the maxillary arch. Lesions above the crown of a tooth are “coronal” and those beneath the apices of the roots are “apical” [1,3] (Fig. 74.5).
FIGURE 74.5 Common terminology used to specify tooth surfaces and structures in relation to teeth: mesial/distal, facial/lingual, and occlusal/incisal. (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
Dental Anatomy Teeth:
There are four distinct tissues that make up tooth structure: enamel, dentin, cementum, and pulp. Enamel is the hardest and most mineralized tissue in the body (about 95%) thus the highest in attenuation on x-ray imaging. It covers the coronal portion of the tooth and protects the underlying dentin. Dentin is softer than enamel (75% mineralized) and comprises the majority of the crown and root portions of the tooth. Cementum is isodense to dentin and covers the surfaces of the root. The pulp is encased by the dentin and comprises of blood vessels and nerves that exit through the apical foramen of the root. The pulp is the least attenuating portion of the tooth [1–3] (Figs. 74.6and74.7).
FIGURE 74.6 A graphic representation of a molar tooth shows the various dental tissues that compose the tooth (enamel, dentin, cementum, and pulp) as well as the distinction between the crown and roots. The components of the periodontium (gingiva, alveolar bone, and periodontal ligament are identified). (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
FIGURE 74.7 Sagittal cone beam CT cross section of the mandibular right canine shows various dental tissues and periodontal tissues. (Adapted from: MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11.)
A tooth is made up of crown (coronal) and root (radicular) portions. The crown is covered by enamel that terminates in a point called the “cementoenamel junction” (CEJ). Cementum covers the external surface of the roots. Teeth can have a single root (anterior teeth and mandibular premolars) or multiple roots (molars and maxillary premolars). Multiple roots come together on a tooth in an area called the “furcation.” These roots are names according to the location in relation to the dental midline and arch (mesial, distal, lingual, and buccal; and in some cases mesiobuccal and distobuccal). Teeth that are developing within the alveolar process show a small and uniform follicle space that surrounds the crown and attaches to the CEJ. An enlarged or offcenter follicle that does not attach to the CEJ should raise suspicion for pathology. A developing root apex has a “blunderbuss” appearance as the apex has not closed yet. Periodontium: These are the tissues that surround the teeth whose primary function is to support and stabilize the dentition. The tissues of the periodontium are the gingiva “the gums,” periodontal bone/alveolar process and the periodontal ligament (PDL). The gingiva is a soft tissue structure and cannot be reliably evaluated on imaging. The PDLs are multidirectional fibers that attach the tooth to its socket in the alveolar bone. The radiographic appearance of a healthy PDL space is that of a thin lowdensity line that runs parallel to the root surface and the socket. If this line is thickened focally (such as at the apices in the case of periapical inflammation) or generally (such as in the case of attachment loss in periodontal disease) this is an indication of an abnormal PDL. The bone on the inner surface of the socket shows a thin radiopaque line called the “lamina dura.” If this line loses uniformity, one should suspect pathology [1–3].
Oral and Maxillofacial Panoramic Anatomy Accurate radiographic interpretation necessitates a thorough knowledge of normal anatomy, variations of normal, and pathologic changes [4]. Oral and maxillofacial anatomy is complicated and best assessed through different types of imaging techniques. This chapter summarizes the radiographic appearances of several anatomic structures utilizing panoramic radiography images. In dentistry, extraoral radiographs are used to assess regions not totally covered by intraoral radiographs or to assess the face, cervical spine, or cranium. Cephalometric (standardized extraoral) radiographs additionally help in assessing the development, and growth of the face, the relationship between several dental and orofacial structures, and treatment progress [5].
Identification of normal radiographic anatomy and normal anatomic variations is the first step in the analysis of radiographic images and detecting pathology [5]. Lack of landmarks or changes in anatomy should alert the clinician for a possible anomaly or pathology [4]. Extraoral Anatomy of Maxillofacial Region and Evaluation of Panoramic Radiographs Interpretation of extraoral radiographs should be careful, thorough, and meticulous and be done with a methodical, and systematic style [5]. Panoramic Imaging Of the extraoral radiographs described in this chapter, the panoramic radiograph (also called orthopantomography) is the most frequently used in dentistry. It can be considered as a curvilinear variant of conventional tomography such that it selectively generates tomographic image of a particular structure. Indications of panoramic radiograph include assessment of mandible, TMJ, maxilla, teeth, and zygomatic bone. The major disadvantage of panoramic radiology is its low spatial resolution comparing to intra-oral radiographs following by geometric distortion and unequal magnification of up to 20% throughout the image [4,5]. Panoramic radiography has imaging concepts which are vital to remember to understand the image formation and make accurate interpretation [4,6–8]. Concept #1: Structures are flattened and spread out. Concept #2: Midline structures may be projected in two ways:
Concept #3: Ghost images are formed which are larger, more fuzzy/blurry, positioned on the opposite side and above the real image. Concept #4: Soft-tissue shadows are seen. Concept #5: Air spaces are seen. Concept #6: Structures adjacent to the jaws (i.e., calcified lymph nodes, salivary stones, vascular calfications) are seen. Concept #7: Relative radiolucencies and radiopacities are seen.
◾ Air obscures bone and teeth, so hard tissues overlapped by air seem more radiolucent ◾ Soft tissue obscures air, so air spaces overlapped by soft tissue seem less radiolucent ◾ and teeth obscure soft tissue, so soft tissues overlapped by hard tissue seem more radiopaque ◾ Bone Ghost images obscure everything
The panoramic image represents the curved jaw which is flattened and spread out onto a flat plane. It shows a coronal view of the jaw in the anterior area while
sowing a sagittal view in the posterior [5]. As in all other radiographs, interpretation of panoramic radiograph needs a systematic and methodologic approach. To begin, the image can be separated into zones which permit comparison of bilateral structures (Table 74.1 and Fig. 74.8). Table 74.1 This Table Shows Anatomic Structures That Can Be Easily Seen on Panoramic Radiograph [6] Z o n e s
Assess
Z o n e 1
Dentition Alveolar bone Inferior border of maxillary sinus Lip markings (in the middle of the film)
Z o n e 2
Orbit Maxillary sinus Nasal fossa Hard palate Zygomatic process of maxilla Posterior wall of maxilla Nasal septum
Z o n e 3
Mandibular body Inferior border of mandible Hyoid bone Chin rest
Z o n e 4
Temporomandibular joint (head of condyle, neck of condyle, articular space, articular tubercle) Zygomatic arch Coronoid process
Z o n e s
Assess
Z o n e 5
Stylohyoid process Spine Ramus of mandible Angle of mandible Mandibular canal Oropharyngeal and nasopharyngeal air space
Z o n e 6
Hyoid bone (true image of hyoid bone, ghost image of opposite hyoid bone) Side guides of the machine Inferior border of the mandible
Note that bilateral structures must be compared with each other for any type of variation of normal or pathology (i.e., asymmetry). Adapted and modified from: O Langland, R Langlais, WD McDavid, A Delbalso, Panoramic Radiology, second ed., Lea & Febiger, Philadelphia, 1989 [6].
Table 74.2 List of Odontogenic and Nonodontogenic Lesions That Occur in the Jaws According to Location on a Tooth and Radiographic Appearance Atten uation
ABC, hemangioma, cherubism, central mucoepidermoid carcinoma
Odontoma, hypercement osis, CB
Idiopathic osteosclerosis, sclerosing osteitis, POD/FOD, enostosis, exostosis, osteoid osteoma, OF
High
Periap ical
Atten uation
Mixed
Locati on
Borde r
Odontogenic
Perico ronal
Odontoma
Interradicul ar
Retained root
Periapical, pericoronal
AOT, CCOT CEOT, AFO
Intraos seous
Nonodontogenic
POD/FOD, OF OF
ABC, aneurysmal bone cyst; AF, ameloblastic fibroma; AFO, ameloblastic fibroodontoma; AMB, ameloblastoma; AOT, adenomatoid odontogenic tumor; CB, cementoblastoma; CCOT, calcifying cystic odontogenic tumor; CEOT, calcifying epithelial odontogenic tumor; CGCG, central giant cell granuloma; DC, dentigerous cyst; EG, eosinophilic granuloma; FOD, florid osseous dysplasia; GOC, glandular odontogenic cyst; LPC, lateral periodontal cyst; MIC, mandibular infected cyst; MM, multiple myeloma; MNTI, melanotic neuroectodermal tumor of infancy; OF, ossifying fibroma; OM, odontogenic myxoma; OKC, odontogenic keratocyst; POD, periapical osseous dysplasia; RC, radicular cyst; SBC, simple bone cavity. (Adapted from: WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45–62.)
Table 74.3 Støre and Boysen’s Classification of Osteoradionecrosis (ORN) [21] S t a g e
Criteria
0
Only mucosa defect
S t a g e
Criteria
1
Radiologically detectable necrotic bone with intact mucosa
2
Positive radiographic findings with intraoral exposed bone
3
Clinically exposed necrotic bone, confirmed by imaging, infection, and skin fistula
Adapted and modified from: G Støre, M Boysen, Mandibular osteoradionecrosis: clinical behaviour and diagnostic aspects, Clin Otolaryngol Allied Sci 25 (5) (2000) 378–384 [21] and SM Mallya, S Tetradis, Imaging of radiation- and medication-related osteonecrosis. Radiol Clin North Am 56 (1) (2018) 77–89. doi:10.1016/j.rcl.2017.08.006 [18].
Table 74.4 Staging of Medication-Related Osteonecrosis of the Jaws (MRONJ) [18,23] S t a g e
Necrotic or Exposed Bone
A t r i s k
No clinical evidence
History and Clinical Findings
S t a g e
Necrotic or Exposed Bone
History and Clinical Findings
S t a g e 0
No clinical evidence
Nonspecific radiologic and clinical findings
S t a g e 1
Necrotic and exposed bone or fistulae that probes to bone
Asymptomatic, no infection
S t a g e 2
Necrotic and exposed bone or fistulae that probes to bone
Erythema, pain and infection in exposed bone region with or without purulent drainage
S t a g e 3
Necrotic and exposed bone or fistulae that probes to bone
Infection, pain, and one or more of the following: • Necrotic and exposed bone extending further than alveolar bone with the presence of pathologic fracture • Oroantral or oronasal communication, extraoral fistula • Lytic alterations extending to the floor of the maxillary sinus or inferior border of the mandible
Adapted and modified from: SL Ruggiero, TB Dodson, J Fantasia, et al., American Association of Oral and Maxillofacial Surgeons position paper on medicationrelated osteonecrosis of the jaw–2014 update, J Oral Maxillofac Surg 72 (10)
(2014) 1938–1956 [23] and SM Mallya, S Tetradis, Imaging of radiation- and medication-related osteonecrosis, Radiol Clin North Am 56 (1) (2018) 77–89 [18].
Table 74.5 A Classification for Severity of Condylar Fractures T y p e
Fracture Position
Condylar Position
T y p e I
Neck
Slight displacement of the condyle; angle between the condyle and the axis of the ramus between 10° and 45°
T y p e I I
Neck
Angle from 45° to 90°, resulting in tearing of the medial portion of the capsule
T y p e I I I
Neck/subcond ylar
Fragments not in contact; displaced medially and forward
T y p e I V
Neck/subcond ylar
Condyle articulates on or in a forward position with regard to the articular eminence
T y p e
Fracture Position
Condylar Position
T y p e V
Vertical or oblique through the condyle
Fragment can be displaced or within the fossa
FIGURE 74.8 Anatomic landmarks seen in the panoramic radiograph. (1) Hard palate, (2) nasal septum, (3) maxillary sinus, (4) mastoid process, (5) anterior nasal spine, (6) ramus of the mandible, (7) inferior nasal concha, (8) infraorbital canal, (9) zygomatic process of the maxilla, (10) posterior wall of the maxillary sinus, (11) right zygomatic arch, (12) maxillary central incisor, (13) mandibular central incisor, (14) soft palate (uvula), (15) calcified stylohyoid ligament, (16) anterior arch of atlas, (17) mandibular condyle, (18) articular eminence, (19) glenoid cavity, (20) epiglottis, (21) mental foramen, (22) mandibular cortex (inferior wall of the mandible), (23) hyoid bone, (24) mandibular canal, (25) mandibular foramen, (26) external auditory meatus, (27) Sella Turcica, (28) pterygomaxillary fissure, (29) orbit (Case courtesy: Dr. S. Bayrak).
Pathologies Odontogenic Infection Odontogenic infection is the most commonly encountered pathology in the oral and maxillofacial complex. It is a spectrum of diseases that can affect all ages, genders, and races equally and is highly dependent on lack or inadequacy of oral hygiene measures. They have diverse clinical courses and may remain localized or may spread to the adjacent anatomic structures, such as the maxillary sinuses, oral mucosa, submandibular and sublingual spaces, etc. These can be painful, especially in the acute phase of the infection. Imaging can help localize the infection to single or multiple teeth and also to determine if the infection has spread to adjacent structures. Dentists often use intraoral 2D imaging and clinical testing of the teeth for such evaluation, but more recently have added cone beam computed tomography (CBCT) to their diagnostic tests, as the ability to visualize an infectious process on any surface of the tooth root in 3D is important in the diagnosis and management of the infection. 3D imaging also assists the radiologist to determine the relation of the infection with adjacent structures, such as the development of odontogenic sinusitis due to the spread of the odontogenic infection from a maxillary posterior tooth to the lumen of the sinus. CT or magnetic resonance imaging (MRI) (T2 or STIR) can provide information about space infection and edema [9,10]. Odontogenic infection has two main origins and can be categorized in two main groups: pulpal and periodontal. a) Pulpal: The etiology of pulpal infections is often caries (tooth decay) or may be due to pulp death as a result of chemical or mechanical insult. Large coronal restorations encroaching upon the pulp and fractures may result in pulp irritation and subsequent death. Caries appears radiographically as irregular demineralization of tooth structure that is exposed to the oral cavity flora. The treatment of pulp necrosis resulting in periapical inflammation is root canal therapy when the tooth is salvageable and restorable. If too much of the tooth structure has been destroyed, then tooth extraction is used to resolve the infection. Periapical inflammatory disease has multiple presentations and is a manifestation of bacteria extending into the periapical tissues by way of the apical foramen or lateral radicular foramina [15]. The earliest presentation is a widening of the periapical PDL with effacement of the lamina dura (Fig. 74.9). On CT, this can be appreciated on either axial cuts through the apices of the teeth (Fig. 74.10B) or on sagittal reformations, providing that the slice thickness and interval are small. As minute as this change is, it can be exquisitely painful and is a manifestation of the acute active phase of the process. As time passes, there can be further accumulation of infectious material in the periapical tissues
resulting in a larger low-density lesion, either a periapical (radicular) abscess, cyst, or granuloma (Fig. 74.11). These can be indistinguishable radiographically when they are small, but radicular cysts tend to be more hydraulic in their growth and become large enough to displace teeth and expand bony cortices. Periapical inflammatory lesions may erode the cortical bone of the alveolar process and extend into the facial or lingual soft tissues, presenting clinically as a gum boil or draining parulis (Fig. 74.10A). An acute inflammatory process usually presents as rarefaction of bone (rarefying osteitis) whereas a more chronic low-grade inflammatory process presents as bone sclerosis (sclerosing osteitis) (Fig. 74.12). Chronic infection can result in sclerosis or the bone with may be solitary or in combination with a periapical radiolucency. Periapical infection can also lift and erode the floor of the maxillary sinuses, allowing communication between the periapical inflammation and the lumen of the sinus, resulting in odontogenic sinusitis (Fig. 74.10A). This cause of sinusitis is often overlooked by primary care physicians and ENTs and as a result, if often treated pharmacologically and surgically with no subsequent resolution of the infection. The correct treatment would be to identify the correct etiology and treat the offending tooth, which the radiologist and the dentist can assist with [11]. Periapical infection can take a serious course as well. The roots of the mandibular molars lie lower than the level of the mylohyoid muscle attachment. Infection coming from these teeth can erode the lingual cortex of the bone and extend into the submandibular space. The resulting space infection can affect the submandibular gland (sialadenitis) or can travel along the fascial planes surrounding the oropharynx, which may lead to Ludwig’s angina, which constitutes a medical emergency due to the threat of asphyxiation. CT in the soft-tissue window and contrast-enhanced CT will aid in evaluating such space infections. Another serious outcome of dental infection is osteomyelitis, which is an inflammation of bone and bone marrow. In the early stages, there may be pain but no radiographic findings on CT and CBCT. Early findings on MRI are low-signal intensity on T1 and high-signal intensity on T2 and STIR. As the disease progresses, there will be rarefaction of bone and development of periosteal reaction or periosteal new bone formation, which may or may not be present in early cases. In infection that also affects soft tissue with any swelling of the face, fat stranding, and opacification is commonly seen in the subdermal fat. Bony sequestration is also a pathognomonic finding. Sequestra are pieces of necrotic bone that have become isolated from the adjacent infected bone (Fig. 74.13). Chronic osteomyelitis can appear differently, with sequestration, mixed density presentation, and periosteal reaction that is more prominent. Sequestra will have low-signal intensity on T1 and STIR and the surrounding tissue will have high-signal intensity on T2 and STIR (Fig. 74.14). Nuclear medicine imaging using three-phase bone scintigraphy with Tc-99m-labeled methyl disphosphonate can be useful in diagnosing early osteomyelitis. 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) can be used in cases of chronic osteomyelitis [12] (Fig. 74.15).
b) Periodontal inflammation: This is inflammation of the supporting structures of teeth. Periodontal disease starts with gingivitis (a clinical diagnosis) which may progress to periodontal bone loss. The bone loss may be mild, moderate, or severe and may affect the furcation area (Fig. 74.16). Severe bone loss can result in tooth loss, thus prevention through good oral hygiene practices and early diagnosis of gingivitis and periodontitis is important. The biggest consideration for a general radiologist is to make the distinction between bone loss due to periodontal disease and that due to malignancy.
FIGURE 74.9 High-resolution small field of view CBCT sagittal cross section shows a widening of the periapical PDL space with mild surrounding sclerosis (arrow) suggestive of early periapical inflammation. (Adapted from: S Mardini, A Gohel, Imaging of odontogenic infections, Radiol Clin North Am 56 (1) (2018) 31–44.)
FIGURE 74.10 Axial and coronal CBCT cross sections show (A) a large periapical low-density inflammatory lesion that is effacing the buccal cortex of the alveolar process, suggestive of spread of the odontogenic infection to the gingiva, and lifting and thinning of the floor of the maxillary sinus. (B) On the axial view, a marked circumferential widening of the PDL surrounding the lingual root of the maxillary left first molar. This is a good projection to evaluate for early PDL widening. (Adapted from: S Mardini, A Gohel, Imaging of odontogenic infections, Radiol Clin North Am 56 (1) (2018) 31–44.)
FIGURE 74.11 Periapical radiograph of a maxillary lateral incisor shows periapical rarefaction suggestive of a periapical (radicular) cyst or granuloma. (Adapted from: S Mardini, A Gohel, Imaging of odontogenic infections, Radiol Clin North Am 56 (1) (2018) 31–44.)
FIGURE 74.12 Panoramic reformat of CBCT shows an endodontically treated tooth with periodontal bone loss, widening of the periapical PDL (open arrow), and surrounding periapical sclerosing osteitis (arrow). (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
FIGURE 74.13 Axial bone CT shows the ill-defined, moth eaten appearance of osteomyelitis in the right mandible. The cortex is destroyed in some areas (arrow), and there is evidence of lingual periosteal reaction (open arrow) and evidence of sequestrate (curved arrow), which help differentiate from malignancy. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
FIGURE 74.14 (A) Coronal T1WI MR shows 79-year-old with recurrent masticator space abscess 12 weeks after initial diagnosis and previous drainage. Normal high-signal marrow fat has been completely replaced in the left mandible consistent with osteomyelitis (arrows). (B) Axial T1Wi C+ fat-saturated MR in the same patient reveals diffuse enhancement of the left marrow space (arrow) with masticator space enhancement (phlegmon) (open arrow) and small lateral compartment abscess (curved arrow). (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
FIGURE 74.15 Anterior Tc-99m bone scan of a patient with osteomyelitis of the right mandible shows profound uptake of the tracer. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
FIGURE 74.16 Intraoral periapical radiograph of the mandibular left first molar shows moderate periodontal bone loss (open arrow) with root furcation involvement (curved arrrow). (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Benign Odontogenic Lesions The inflammatory benign lesions of the jaws arise from embryonic histologic structures that give rise to dental tissues. These are either ectodermal or ectomesenchymal cells. The ectodermal cells give rise to tooth enamel and the ectomesenchymal cells give rise to dentin, cementum, and the dental papilla that is the origin of the periodontium [13,14]. Benign odontogenic lesions can be divided into cysts and tumors. The cysts can be inflammatory or noninflammatory. One of
the inflammatory cysts, the radicular cyst was covered previously in the previous section. It is important to note that because of the nature of the oral cavity with its flora, caries/pulp necrosis process, and numerous dental procedures, any noninflammatory cyst can become secondarily infected, and one should look for signs of that inflammation (marked sclerosis of the borders). It should also be noted that, very rarely, some benign odontogenic lesions can undergo malignant transformation and the borders of a seemingly benign lesion should be evaluated carefully for a discontinuity. Because there are so many lesions in this category, it is often confusing to try to remember them all. Rather than list these entities according to histologic classification, which is the classic way of presenting them, this section will review them in a manner that makes sense to the radiologist and that is according to their appearance (low density, mixed density, or high density), location, and relation to teeth (periapical, pericoronal, inter-radicular, and intraosseous) as seen on osseous (CT/CBCT) imaging [15]. Low-Density Lesions
Periapical Radicular Cyst: This is an inflammatory cyst that was covered in the previous section. The etiology is pulp necrosis, so look for large carious lesions, restorations/root canal therapy, or fractures of the crown (Fig. 74.17). If these are not present, consider the differential diagnosis of periapical osseous dysplasia (see the Fibro-osseous Lesions section later) or other benign odontogenic cysts/tumors.
FIGURE 74.17 Sagittal CBCT shows a large radicular cyst lifting the floor of the maxillary sinus (blue arrow) and occupying the inferior third of the sinus. Note the inflammatory changes within the sinus (white arrows) which may be secondary to the odontogenic inflammation. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Pericoronal Dentigerous (Follicular) Cysts: These are the second most common cysts following the radicular cysts. They are well-defined, well-corticated, and unilocular lesions that surround the crown of an
unerupted tooth and attach to the tooth at the CEJ. When small, it is difficult to differentiate this entity from a normal dental follicle. A follicle space that is asymmetric or larger than 3 mm should raise the suspicion for cystic degeneration. This lesion can displace the associated tooth dramatically and resorb the adjacent tooth roots (Fig. 74.18). In long-standing cases, the cyst may detach from the CEJ and migrate more apically, making differentiating it from an odontogenic keratocyst (OKC) and other benign lesions difficult. The cyst can be secondarily infected, which may present clinically as pain and sclerosis of the adjacent bone radiographically. In rare cases, the epithelium may convert to other benign entities, such as an OKC and unicystic ameloblastoma, or, even more rarely, to squamous cell carcinoma or mucoepidermoid carcinoma. The borders of the lesion should be carefully inspected to rule out secondary infection and other neoplasia. On T1weighted MR imaging, dentigerous cysts are homogenous isointense and on T2weighted imaging they are homogenous or heterogenous hyperintense. They may show rim enhancement on postgadolinium sequences [16].
FIGURE 74.18 Axial CBCT shows a buccally displaced second molar with a well-defined unilocular low-density dentigerous cyst. The cyst attached to the cementoenamel junction of the tooth (arrows), a hallmark of this cyst. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Odontogenic Keratocyst: This is a well-defined, corticated entity that tends to occur more commonly in the mandible. This may occur pericoronally or within the alveolar bone independent of the tooth structure. One of its pathognomonic features is “growing in the length of the bone,” which describes its appearance as being longer in the anteroposterior dimension that the mediolateral dimension as the mediolateral expansion is minimal. It can resorb and displace teeth and displaces the inferior alveolar nerve
canal inferiorly. These lesions are largely low attenuating and unilocular, but can have thin and curved septations that mimic the soap bubble appearance of an ameloblastoma (Fig. 74.19). Multiple OKCs can be seen in basal cell nevus (Fig. 74.20) syndrome. The MR imaging appearance is different from a dentigerous cyst because of the high keratin content within its lumen. The T1-weighted imaging appearance is heterogenous hypointense or mildly hyperintense. On T2-weighted imaging, they are heterogenous or homogenous hyperintense. Focal inflammation and ulceration can result in rim enhancement. Histologically, this lesion can have peripheral soft tissue intramedullary extension called “daughter cysts” which contribute to the high recurrence rate. Mandatory periodic radiographic monitoring annually for 5 years postexcision then every 2–3 years is recommended [1,5,15,17].
FIGURE 74.19 Axial bone CT shows an OKC “growing in the length of the bone”: the AP growth is greater than the mediolateral growth. There is slight expansion and thinning of the cortices (white arrows) when compared with the AP dimension. This is characteristic of this lesion. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
FIGURE 74.20 Axial (A) and coronal (B) images of the maxilla and mandible show multiple multilocular hypoattenuating lesions suggestive of odontogenic keratocysts in basal cell nevus syndrome. (Adapted from: WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45–62.)
Ameloblastoma: This odontogenic tumor arises from the enamel epithelium, an ectodermal layer of cells responsible for the formation of enamel. It is a benign but locally aggressive lesion and is the second most common odontogenic tumor (after odontomas). It can occur pericoronally or within the alveolus, and may present unilocularly (also called “unicystic ameloblastoma”) or multilocularly. Unicystic ameloblastomas occur in younger age groups and present pericoronally. It can be difficult to differentiate from a dentigerous cyst, but with T1-weighted imaging, enhancement of mural nodules confirms the diagnosis of unicystic ameloblastoma. The multilocular lesions have a “soap-bubble” or “honey-comb” appearance. This may displace and resorb teeth and cause considerable expansion of the jaws that is evident clinically. The inferior alveolar nerve canal can be displaced, eroded, or may disappear within the lesion. Radiographic characterization can assist in choosing the correct treatment technique in relation to the variant (unicystic or multilocular), size, location, and involvement of the surrounding anatomy (Fig. 74.21). Contrast-enhanced CT shows irregular peripheral enhancement, septation, and solid and cystic mural nodule components within the lesion. T1-weighted MR shows a low to intermedial signal lesion, and on T2-weighted images the signal is
intermediate to high. Contrast-enhanced T1-weighted imaging reveals a hyperintense signal in the solid components. Recurrence of this lesion is high [1,5,14,15].
FIGURE 74.21 CBCT reformatted dental panoramic (A), axial view of the mandible at the level of the midroot (B) and sagittal view (C) of an ameloblastoma in the left ramus of a 34-year-old show a well-defined multilocular expansile lesion with scalloped borders developing pericoronal to the mandibular third molar. Thinning and erosion of the buccal and lingual cortical plates and knife-edge root resorption on the adjacent teeth is noted. The cortices of the inferior alveolar canal are not traceable within the lesion. (Adapted from: WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45–62.)
Ameloblastic Fibroma/Fibroodontoma: Radiographically, an ameloblastic fibroma looks very similar to an ameloblastoma, except that it occurs in childhood and adolescence (if it looks like an ameloblastoma and it is in a child, then consider ameloblastic fibroma). It is a rare mixed ectodermal and ectomesenchymal lesion. It is well-defined, corticated lowdensity lesion that most commonly occurs in the posterior mandible (Fig. 74.22). Sometimes, tooth density structures occur within the stroma, giving a mixed attenuation appearance. This changes the diagnosis to ameloblastic fibroodontoma, but the management is similar. Malignant transformation occurs in about 10% of pediatric cases [1,5,15,22].
FIGURE 74.22 Conventional panoramic radiography (A) axial bone (B) and soft-tissue (C) window and coronal bone (D) and soft-tissue (E) CT images of a 14-year-old girl with an asymptomatic large multilocular expansion of the left mandible involving the body, angle, and ramus. Soft-tissue images show heterogenous contents consistent with ameloblastic fibroma. (Adapted from: WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45–62.)
Inter-Radicular: Any odontogenic lesions (within the exception of the dentigerous cyst and the unicystic ameloblastoma) and nonodontogenic lesions (Table 74.2) can occur interradicularly. Listed below are a few lesions that occur exclusively inter-radicularly. Mandibular Infected Cyst (Buccal Bifurcation Cyst): This is a rare inflammatory odontogenic cyst that occurs in the buccal aspect of the mandibular first or second molars in the pediatric population. This presents clinically as swelling, pain, and local suppuration. Radiographically, it is a welldefined and corticated unilocular low-density lesion that may resorb or displace the involved tooth or delay its eruption. Its presence on the buccal aspect of the tooth furcation causes the tooth roots to tip lingually sometime thinning or going through the lingual cortex of the mandible, a hallmark presentation of this lesion (Fig. 74.23). This is best visualized on CT or CBCT axial cross sections [1,5,15].
FIGURE 74.23 Axial CBCT (A) shows a well-defined low-density lesion (open arrow) centered in the buccal aspect of the furcation of the permanent mandibular right second molar. This was incidentally found in a 17-year-old boy. Note the displacement of the tooth roots lingually into the lingual cortex of the mandible (arrows). The cross section (B) shows the tipping of the roots lingually (arrow) and the occlusal table buccally, making the lingual cusp of the molar more prominent. This is typical of a buccal bifurcation cyst. (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: Oral and maxillofacial, second ed., Elsevier; 2017.)
Lateral Periodontal Cyst: This is a noninflammatory developmental cyst that presents radiographically as a small, well-defined unilocular low-density lesion associated with the proximal surfaces of the teeth. The most common location is the mandibular lateral incisor to second premolar regions. A botryoid cyst is a multilocular variant of this cyst (Fig. 74.24). The teeth may be displaced but are vital, indicating that this is not an inflammatory process due to pulpal necrosis [1,5,15].
FIGURE 74.24 Periapical radiograph of the right mandibular premolars and molar (A) shows a lateral periodontal cyst with a classic tear-drop shape between the first and second premolars (white arrow). CBCT cross sections (B) of another patient show the botryoid variety of a lateral periodontal cyst: a small well-defined multilocular lesion in the canine premolar region (white arrow) that resembles a bunch of grapes, hence the name “botryoid cyst”. (Adapted from: LM Koenig, D Tamimi, et al. Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Intraosseous: Again, any odontogenic lesion with the exceptions listed above can present intraosseously in the tooth-bearing regions (alveolar processes) of the jaws. In the mandible, this means that the odontogenic lesions cannot occur inferior to the inferior alveolar canals. Nonodontogenic lesions can occur above or below the canals, and this anatomic landmark helps the radiologist further narrow down the list of differential diagnoses. Residual Cysts: This is a radicular cyst that is left behind after the extraction of a tooth. It is a welldefined, round, corticated low-density lesion that is located in an edentulous area (Fig. 74.25). These do not recur after complete excision.
FIGURE 74.25 Reformatted panoramic (A), axial (B) and cross-sectional (C) CBCT images show a round well-defined low-density lesion in the area of the missing left lateral incisor (arrow), consistent with a residual cyst. Note the continuity and proximity of the tooth socket on (A), indicating a possible causation of periapical odontogenic inflammation that was left behind with the extraction of the tooth. (Adapted from: WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45– 62.)
Odontogenic Myxoma: This is a rare benign odontogenic tumor of ectodermal origin. It occurs mostly in the posterior mandible. Radiographically, it is a multilocular low-density lesion with well-developed locules and scalloped borders which may be corticated or noncorticated. The septations are thin and can be arranged at right angles in a “step ladder” or “tennis racquet” appearance (pathognomonic feature). The septae can be coarse or curved. The lesion tends to scallop between the roots (Fig. 74.26). It has a high recurrence rate and should be followed up post-op [1,5,15].
FIGURE 74.26 Axial bone CT shows an odontogenic myxoma with straight septa (open arrow) and radiating wisps of bone (arrow) at the periphery of the lesion. The thin corticated margin (curved arrow) can be discerned and helps us differentiate from an osteosarcoma. (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017. Courtesy: S. Kalathingal.)
Glandular Odontogenic Cyst: These are rare aggressive cysts of ectodermal origin. They are most common in the anterior mandible and maxilla. They are low-density multilocular cysts with scalloped cortical margins and can cause expansion and perforation of the cortices of the alveolar process and displacement of the teeth. Recurrence is high [1,5,15]. High-Density Lesions
Periapical Periapical Sclerosing Osteitis: This is a sequela of dental inflammation as described in the previous section on infection. This is a hyperattenuating area of bone associated with the apex of a necrosing or necrotic tooth. This high-density area is a bone reaction to chronic low-grade inflammation. The tooth is nonvital and requires root canal therapy in most cases. Idiopathic osteosclerosis: This is a dense bone island located either at the apex of a tooth or anywhere in the jaws. This is isodense to cortical bone and blends into the adjacent cortical outline of the bone without expanding it (Fig. 74.27). An associated tooth is vital. No intervention is needed for this finding [1,5].
FIGURE 74.27 Axial (A) and cross-sectional (B) CBCT images of the mandibular left canine show a hyperdense area of bone that blends into the lingual cortex of the mandible without expanding it. This is a common finding in the jaws (idiopathic osteosclerosis or dense bone) and requires no intervention. (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Odontoma:
This is the most common benign odontogenic tumor in the jaws. The lesion stems from both ectodermal and ectomesenchymal cells and forms mature enamel, dentin, cementum, and pulp. These may be arranged to resemble a “bag of teeth,” small teeth in low-density sac (compound odontomas) or may be haphazardly arranged to appear as an amorphous high-density mass surrounded by a lowdensity rim (complex odontomas) (Fig. 74.28). These lesions are asymptomatic and are often discovered when a tooth fails to erupt if they present pericoronally. This lesion is self-limiting and does not cause gross expansion [1,5,15].
FIGURE 74.28 CBCT cross section shows a compound odontoma presenting pericoronal to the maxillary central incisor (arrow) and appearing as a bag of teeth. (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Hypercementosis: The cementum surrounding the roots of the teeth may respond to external stimuli such as chronic infection or occlusal trauma by producing a non-neoplastic proliferation of the cementum, resulting in an irregular and sometimes bulbous
root outline that is contained within the PDL and lamina dura (Fig. 74.29). This condition can occur in florid osseous dysplasia and Paget disease as well [1,5,15].
FIGURE 74.29 CBCT shows an impacted third molar with hypercementosis (white arrow). Note the normal higher density dentin outline can be seen within the lower density cementum (open arrows). (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Cementoblastoma: This is a rare ectomesenchymal neoplasm of cementum that presents as a solitary round hyperattenuating structure that is attached to the root of a tooth, most commonly the mandibular molars. It is surrounded by a low-density rim and exhibits a sunburst pattern within the high-density mass [1,5,15] (Fig. 74.30).
FIGURE 74.30 Sagittally reformatted CBCT shows a cementoblastoma (open arrows) on the distal root of the mandibular left first molar. There is root resorption and attachment to the root (white arrow). (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Pericoronal Odontomas: As previously noted, these lesions can occur around or close to the crown of a developing tooth and may impede its eruption. These pericoronal presentations occur more commonly in the anterior maxilla.
Inter-Radicular Tooth Roots:
Extraction of teeth is sometimes incomplete and a portion of the root is left behind. If the radiologist comes across these root tips, they should be evaluated for widening of the PDL space or development of infection surrounding it. If the root shows no signs of pathology, it is generally left alone. Supernumerary Teeth: Extra teeth can develop anywhere in the arches. The most common type of supernumerary is the mesiodens, which is a small peg-shaped tooth that occurs in the midline between or palatal to the maxillary central incisors. If they do not cause impaction of the other teeth, complicate esthetics or orthodontic treatment and do not have associated pathology, they are generally left alone [1,5]. Mixed Density Lesions Periapical: Other that complex odontomas, no odontogenic conditions appear as periapical mixed attenuating lesions. When faced with such a lesion in this location, one should consider a fibroosseous lesion (these are described in the Fibroosseous section later).
Pericoronal Calcifying Epithelial Odontogenic Tumor: These are rare neoplasms that can occur at any age, but are most commonly seen in middle-age. It is more common in men. Painless jaw expansion is often the only clinical symptom. It occurs more frequently in the posterior mandible, with half of them associated with an impacted tooth. It is well defined and expansile with a cyst-like cortex, and it may be unilocular or multilocular with numerous scattered radiopaque foci or varying size and density (Fig. 74.31). The calcifications come very close to the crown of the associated tooth [1,5,15].
FIGURE 74.31 Axial bone CT shows a calcifying epithelial odontogenic tumor presenting as a large, expansile, mixed density lesion in the right maxilla. There is a large focus of calcification noted in the lesion in addition to multiple small flecks of calcification. (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017.)
Adenomatoid Odontogenic Tumor: This is a rare nonaggressive tumor of mixed ectodermal and ectomesenchymal origin that mostly occurs in the second decade of life. Most of these tumors develop surrounding the crown of an unerupted tooth and impede its eruption. About 75% of these tumors occur in the maxilla, especially in the area of the incisors, canines, and premolars. It is well defined with a corticated border with varying degrees of internal calcifications that can resemble small pebbles or appear as dense clusters of ill-defined opacities [1,5,15] (Fig. 74.32).
FIGURE 74.32 Sagittal CBCT shows an adenomatoid odontogenic tumor associated with a maxillary premolar (block arrow). The corticated boundary of the lesion is attached to the midroot of the tooth. There are multiple small calcified fleck noted within the lesion (white arrow). (Adapted from: LM Koenig, D Tamimi, et al., Diagnostic imaging: oral and maxillofacial, second ed., Elsevier; 2017. Courtesy: M. Noujeim DDS.)
Ameloblastic Fibroodontoma: These lesions were covered previously in the discussion of ameloblastic fibroma, which is technically the same tumor without the calcified dental material. Calcifying Cystic Odontogenic Tumor: This was previously classified as a cyst and called “calcifying odontogenic cyst.” This is a rare tumor that is slow growing and that has a wide age distribution, with peaks at the second and seventh decades of life. Most occur anterior to the first molar. The periphery can vary from well defined and corticated to ill defined and irregular. The internal aspect may be completely radiolucent, or may show small flecks of calcified material that may coalesce and form larger solid masses. It is expansile but not-aggressive [1,5,15].
Radiation and Medication-Related Osteonecrosis of the Jaws Osteonecrosis generally refers to the bone devitalization and subsequent lytic alterations. Histologically, bone necrosis is characterized by the lack of osteocytes inside the lacuna. Balance between osteoclastic and osteoblastic activities result in continuous bone turnover. In the jaws, osteonecrosis is a pathological consequence of some antiresorptive medications or previous radiotherapy (osteoradionecrosis [ORN]) which disturb this balance. Additionally, oral cavity situation and teeth can affect the changed bone homeostasis negatively [18]. Osteonecrosis is frequently a result of altered vascularity causing avascular (aseptic) necrosis at few sites like femoral head. However, ORN and medicationrelated osteonecrosis of the jaws (MRONJ) are different pathologies than avascular necrosis. Furthermore, despite the similarity in their treatment-associated causation, MRONJ, and ORN are different pathologies. They are characterized by distinct but often overlapping radiographic and clinical features and are treated differently [18]. Osteoradionecrosis of the Jaws ORN is described as a region of irradiated and exposed bone which fails to heal for at least 3 months after radiation therapy (Fig. 74.33A–C) and in the absence of recurrent or residual tumor after other causes of osteonecrosis are excluded [19,20]. The pathogenesis of ORN is not yet clear. Commonly accepted theory is radiation produces microvascular alterations that generate hypovascularity, hypoxia, and hypocellularity disrupting bone homeostasis and causing to a chronic, nonhealing wound [19].
FIGURE 74.33 Osteoradionecrosis. (A) CBCT panoramic reconstruction of a patient with history of radiation therapy for salivary gland cancer showing irregular lytic changes in the right posterior mandible extending to partially interrupt the cortical margins of the mandibular canal. The bone between the
area of the right mandibular first molar and the mid-height of the ramus is remarkably sclerotic with the presence of an irregular in shape low-density area at the level of the angle of mandible. (B) CBCT cross-sectional views showing the lesion interrupting both buccal and lingual cortices with no expansion. The sclerotic bone around the low-density area presents with multiple small round low-density regions with some detached bone fragments. The lesion is situated inferior to the mandibular canal. No periosteal reaction noted. (C) CBCT 3D reconstruction sagittal view showing the extent and effect of the lesion on surrounding structures (Case courtesy: Dr. M. Noujeim).
ORN may occur any time after radiotherapy, and usually expresses 6–12 months after radiation therapy. Yet, the time to onset varies from months to years. Mandible is affected more than the maxilla likely owing to its relatively lower vascular supply [18]. Even though any regions of the jaws are susceptible, the posterior mandible is more frequently affected than other regions as it is often in the direct field of the radiation therapy due to the vicinity of primary and metastatic lesions in lymph nodes being treated [5,20]. Although not common, maxillary osteonecrosis can occur frequently secondary to radiotherapy for nasopharyngeal cancer [18]. Total radiation dose, therapeutic field size, distance between the tumor and bone, simultaneous chemotherapy, dental appliance and denture trauma, tooth extraction, surgical procedures of the irradiated region, alcohol abuse, smoking, and poor oral hygiene modulate ORN risk. A determining factor is the total radiation dose. ORN is unlikely to develop if the patient receives radiation dose less than 60 Gy and is rare at doses less than 50 Gy. For doses exceeding 66 Gy, the risk for ORN is increased 11-fold [18]. Staging of the Osteoradionecrosis of the Jaws: There is no universal staging system for ORN and present staging systems of ORN considers the degree of the osseous necrotic alterations, hyperbaric oxygen therapy response, and clinical and radiological factors [18,19,21]. This chapter uses the staging system suggested by “Støre and Boysen” [21], which is an efficient tool for the radiologist to score the disease status for the referring clinician (Table 74.3). Imaging Goals and Protocols: Generally, small to medium field of view (FOV) CBCT or CT is sufficient to visualize the area of interest. Scan FOV must involve the unaffected contralateral side to compare due to the significant variation of the trabecular bone architecture and density in the jaws. MDCT must be the technique of choice if evaluation of the adjacent soft tissues needed (i.e., soft-tissue mass suggestive of recurrent malignancy, superimposed cellulitis, and osteomyelitis). The FOV of MDCT should include the area from frontal sinus to mandible. Axial images parallel to the
dental occlusal plane should be acquired and evaluated applying soft-tissue and bone windows. Sinus walls and mandibular canal can be better seen in the coronal and sagittal reconstruction images [5,18]. Radiological Characteristics of Osteoradionecrosis: The first changes of ORN manifest as subtle regions of altered trabecular structure and rarefaction [18]. The altered bone can present with poorly defined, noncorticated border, with the presence of sclerosis and ill-defined, irregular areas of bone resorption. An early change observed in the mandibular cortex is a clearly defined bone resorption region. In the maxilla, portions of the maxillary sinus cortical walls might be missing [20]. Markedly, in the irradiated alveolar processes of the jaws, the most commonly developing alteration is a uniform but irregular widening of the PDL space surrounding the teeth. Moreover, the observed widening does not have a distinct epicenter and there is no bone loss. This is a frequent finding and does not require management in the lack of adjacent bone destruction [18,20]. Radiologic detection of ORN depends on the detection of sequestra which is a dead bone and positive patient history (Fig. 74.34A and B). Radiographically, sequestra may be seen as patchy, low-density area with dense islands of necrotic bone, contrasted against the low-density lytic alterations. Contrary to osteomyelitis, generally, there is no/minimal periosteal bone reaction in most of the patients. The existence of a pathologic fracture suggests ORN (Fig. 74.35) [20]. However, radiographic expression of ORN is not specific, and therefore must be distinguished from recurrent malignancy, osteomyelitis, and other bone necrosis [18]. If recurrent malignancy is suspected, MRI and CT can be utilized to identify an accompanying soft-tissue mass. Differentiating ORN from sclerotic pathologies (i.e., chronic osteomyelitis) is easier due to the history of radiotherapy [20].
FIGURE 74.34 (A) CBCT panoramic reconstruction of a patient with history of radiation therapy showing lytic changes with the presence of sequestra at the center in the right posterior mandible extending to partially interrupt the cortical margins of the mandibular canal. The bone between the area of the right mandibular canine and second molar is significantly sclerotic. (B) Coronal CBCT view of the same patient showing sequestra surrounded by the lytic area in the right posterior mandible. Note the significant sclerosis of the trabecular bone comparing to the left side (Case courtesy: Dr. K. Orhan).
FIGURE 74.35 Panoramic radiograph showing osteoradionecrosis and pathologic fracture (white arrow) in the left mandibular posterior region in a patient with a history of radiotherapy due to squamous cell carcinoma. Note the step defect in the fracture line (arrow) and radiopaque entity suggestive of submandibular sialolith or lymph node calcification (arrowhead) inferior to the fracture region (Case courtesy: Dr. B. Kan).
MRI has the ability to detect early ORN-induced bone marrow changes before being clinically visible. These changes are seen as decreased bone marrow signal on T1-weighted images and increased bone marrow signal on T2-weighted images.
Cortical destruction and surrounding soft-tissue changes can also be detected with MRI [18,22]. Medication-Related Osteonecrosis of the Jaws MRONJ is an osteonecrosis related to antiangiogenic or antiresorptive therapy [23]. Certain medications such as bisphosphonates and receptor activator of nuclear factor-κB ligand inhibitors (i.e., Denosumab) can produce chemical insult in the bone, changing the osteoclastic and osteoblastic balance activity, generating the disease. Similar to radiation therapy, most of the imaging characteristics (i.e., nonhealing, exposed bone) in MRONJ overlap with osteomyelitis [20]. To clarify its difference from other causes of exposed bone, the American Academy of Oral and Maxillofacial Surgery has established a diagnostic criterion to differentiate MRONJ-related bone exposure from other cause of exposed bone [23]. The diagnostic criteria for MRONJ are [23]:
◾ Previous or current antiangiogenic or antiresorptive treatment ◾more Exposed bone or bone which may be probed through an extraoral or intraoral fistula(e) persisted than 8 weeks ◾ No clear metastatic disease or history of radiotherapy to the jaws
The American Academy of Oral and Maxillofacial Surgery has also developed a staging system for preclinical and clinical MRONJ (Table 74.4) [23]. Imaging Goals and Protocols: Despite nonspecific imaging findings associated with the clinically exposed bone, imaging can show detachment, sequestra, increased sclerosis, thickening of lamina dura and PDL space widening (Fig. 74.36A) [20]. MDCT and CBCT protocols are the same with ORN. Regular examinations of asymptomatic cases give a baseline to watch future subtle alterations which can allow detection of early necrotic bone alterations. When clinical findings indicate the presence of MRONJ (stages 1–3), 3D imaging (i.e., CT or CBCT) should be performed to examine the extension of the alterations as well as the possibility of complications like interruption of the maxillary sinus and nasal cavity or pathologic fracture (Fig. 74.36B–E). MRI can show early trabecular bone changes which may result in preclinical disease detection [18].
FIGURE 74.36 (A) CBCT panoramic reconstruction of a patient with history of bisphosphonates treatment showing a well-defined, low-density area with a tunnel like appearance (arrow) in the right maxillary posterior region extending from area of missing #15 posteriorly to the area of missing #18 through the maxillary alveolar bone above the apical region of #16. (B) CBCT crosssectional views taken from right posterior maxilla showing buccal and palatal interruptions making the bony area below the low density similar to an island (bone sequestrum). The trabecular structure of the sequestrum is sclerotic with large bone marrow spaces. Note the presence of sinus reaction and possible sinus floor interruption. (C–E) CBCT sagittal (C), axial (D), and 3D reconstruction (E) views showing extension of the lesion with destruction of the buccal and lingual cortices (arrows) (Case courtesy: Dr. M. Noujeim).
Radiological Characteristics of Medication-Related Osteonecrosis of the Jaws: Radiologic findings show lytic and sclerotic bone changes (Fig. 74.37). Early lytic changes are seen as altered trabecular bone density and structure, following by patchy bone destruction and cortical interruption. The lytic alterations may progress to pathological fracture. Surgical defects and nonhealing extraction sockets must be detected (Fig. 74.38A and B). In the osteonecrosis of the jaws sclerotic alterations usually manifest as limited to extensive diffuse osteosclerosis, with the presence of periosteal reaction. When the necrotic changes progress and combine, sequestrate are formed [18].
FIGURE 74.37 (A) CBCT panoramic reconstruction of a patient with history of Denosumab use for the treatment of osteoporosis showing diffuse sclerotic bone area in the right mandible mainly between the canine and third molar teeth with the presence of multiple small punctate low-density areas within the thickened and sclerotic bone (B) CBCT sagittal view of the same patient showing remarkable sclerosis extending from the alveolar crest to reach the basal cortex with multiple small punctate low-density areas (arrows) (Case courtesy: Dr. M. Noujeim).
FIGURE 74.38 (A and B) Panoramic radiograph of a patient on a bisphosphate treatment with multiple extraction sockets (arrows) in the anterior maxilla and right maxillary premolar-molar region (A). Intraoral picture of the same patient with the development of MRONJ following extractions. Note the exposed bone (white arrowhead), swelling (black arrowhead) and redness (B) (Case courtesy: Dr. B. Kan).
Even though MRONJ and ORN have similar radiographic features, generally in MRONJ, increased cortical and trabecular bone density with associated significant periosteal reaction due to the inhibition of osteoclastic activity predominate (Fig. 74.39). In contrast, rarefaction, cortical interruption, and trabecular density loss as a result of increased osteoclastic and decreased osteoblastic activity dominate the ORN. Lytic lesions of MRONJ must be distinguished from the metastatic lesion and recurrent malignancy. Both malignant lesion and MRONJ can produce periosteal new bone formation. However, in metastatic malignancy, the periosteal reaction is irregular with radiating spicules of new bone perpendicular to the cortex. On the contrary, in MRONJ, the periosteal reaction is more organized, and paralleling the cortex. Assuming that large number of MRONJ patients are treated for metastatic pathology, this differentiation is very important [18].
FIGURE 74.39 Axial (A), coronal (B), views showing MRONJ in the body of the left mandible. Note increased sclerosis of the area with the presence of partially detached bone (arrow) which possibly will proceed to sequestra. (Case courtesy: Dr. U Seki).
Fibroosseous and Other Bone Lesions of the Jaws Fibroosseous Lesions Fibroosseous lesions of the jaws can be very problematic for radiologists that are not used to looking at conditions of the jaws. They range in appearance, location, and demographic distribution. Without adequate training, it would be difficult to recognize that these lesions belong to the same group of lesions. Their pathophysiology ranges from simple dysplasia to reactive lesions to formal neoplasms. The management of these lesions also varies greatly and differ from other lesions that they mimic, so reaching a correct diagnosis is important to plan the clinical course of the treatment [1,5,24]. Periapical Osseous Dysplasia: This type of dysplasia was recently renamed after being previously called “periapical cemental or cementoosseous dysplasia.” As they are considered, “do not touch” lesions, biopsies of these areas are not advised as the risk of infection is high. They tend to occur in middle-aged African women but can occur in other populations as well. There are no signs or symptoms associated with the teeth and they are vital (no pulpal necrosis), an important diagnostic point to consider when
differentiating them from periapical inflammation. They most commonly occur at the apices of the mandible anterior teeth, but can occur anywhere. Lesions limited to a few teeth are called focal osseous dysplasia. When more than two quadrants are involved, the term “florid osseous dysplasia” is used. Large lesions can displace the inferior alveolar canal inferiorly and the floor of the maxillary sinus superiorly. In these cases, the homogenous high-density foci are surrounded by wide areas of well-defined, noncorticated low densities. The concern with these lesions is secondary infection, either due to caries from an associated tooth or surgery, such as biopsy. Osteomyelitis develops easily in these lesions due to poor vascularity. Radiographically, periapical osseous dysplasia goes through three stages. In all three stages, the teeth are not resorbed or displaced. Larger lesions may expand and thin the alveolar cortices. The stages are: 1. Early: completely radiolucent, usually oval, round or lobular, and stays limited to the apices. This is the stage when they are most commonly mistaken for periapical inflammatory lesions. 2. Mixed stage: mixed density lesions with homogenous opacity with irregular margins (Fig. 74.40). 3. Late stage: completely radiopaque with homogenous density and with a thin low-density line between the border and the opacity [25].
FIGURE 74.40 Cone beam CT cross section of a mandibular incisor shows a mixed density stage periapical osseous dysplasia with preservation of the peripheral lucent rim of varying thickness and definition (arrows). Portions of the buccal and lingual cortical plates are thinned. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Fibrous Dysplasia: This is a developmental condition that behaves similar to a tumor is its expansion and displacement of structures. It replaces the normal medullary bone with a combination of fibrous tissue and abnormal bone. It can affect one bone (monostotic) or multiple bones (polyostotic). The polyostotic type usually occurs in children under the age of 10 in McCune–Albright syndrome [26]. Mandibular lesions are mostly monostotic. Maxillary lesions are often polyostotic, extending
into the adjacent bones. The course of this process becomes slow or static after the completion of skeletal grown, but may reactivate with pregnancy or the use of oral contraceptive. The margin of the lesion gradually blends into the normal trabecular bone without signs of a cortical boundary, making the extent of involvement difficult to determine radiographically. In the early phases, it is low or mixed density is appearance. The granular appearance of the bone is termed, “ground glass” appearance. Other descriptors used are “orange peel” or “cotton wool” mixed density appearance. Nonconcentric expansion of the cortical outlines of the bone is common (Fig. 74.41). Displacement of the adjacent structures, including the teeth is common. A hallmark of this lesion is the superior displacement of the inferior alveolar canal, which does not occur with odontogenic lesions. Tooth eruption is often impaired. Fibrous dysplasia can be confused with malignancy and not easily characterized and identified if it is viewed only on MR imaging, but evaluation of the CT or CBCT data can easily identify it is fibrous dysplasia. The MR imaging appearance on T1-weighted imaging shows low–intermediate signals depending on the ration or fibrous and mineralized contents. On T2-weighted imaging, the fibrous component has a bright signal that increases in intensity with gadolinium due to the high vascularity content [1,5,24].
FIGURE 74.41 (A) Volumetric CT rendering of a patient with polyostotic fibrous dysplasia superficially evident in the right mandible. (B) Axial CT section demonstrating noncentric expansion of the right portion of the ethmoid bone, sphenoid, and nasal bones. The right ethmoid air cells have been almost completely remodeled and replaced with grainy-appearing heterogenous bone. (C) Axial CT section of the right mandible shows nonconcentric expansion. Note the variable appearance of the altered trabecular bone from a more uniform radiopaque “ground glass” appearance to a more radiolucent appearance with irregular calcifications. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Ossifying Fibroma: This is a true neoplasm that is similar histologically and radiographically to bone dysplasias. It is exclusive to the jaws and does not occur anywhere else in the body. There are two types:1.ossifying fibroma of odontogenic origin (cementoossifying fibroma) and2.juvenile aggressive ossifying fibroma, which is rare. The cemento-ossifying fibroma mostly affects women in their 20s and 30s, whereas the juvenile aggressive variant occurs in younger individuals. It is often asymptomatic. In the initial stage, it is small and low attenuating, as it grows, it enters the mixed density stage. In the late stage, the high-density lesion is separated from the surrounding bone by a thin low-density capsule. This thin lowdensity line helps differentiate the lesion from fibrous dysplasia, which does not have this demarcation. The expansion of the cortical plates is concentric, unlike fibrous dysplasia (Fig. 74.42). The lesions have a low- to high-signal intensity on T1-weighted MR imaging, postgadolinium MR imaging may reveal uniform contrast enhancement for a mixed appearance [1,5,24,27].
FIGURE 74.42 Cropped panoramic radiography (A) and coronal (B) CBCT section show mostly rounded expansion of a well-defined lesion with heterogenous calcifications and peripheral lucent band, suggestive of a late stage ossifying fibroma. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91– 104.)
Other Bone Lesions Central Giant Cell Granuloma:
This reactive lesion is often seen in the first to third decades of life and is more common in females. Most are seen in the mandible. Central giant cell granuloma (CGCG) is largely asymptomatic, and is slow growing, but there is an aggressive variant that tends to resorb teeth and cause pain due to rapid growth. It can be a unilocular or multilocular low-density lesion that occurs in either jaw, tends to favor the posterior mandible but in younger individuals can occur in the anterior jaws, sometimes crossing the midline. When a lesion is multilocular, the septations are wispy and are at right angles to the border of the lesion, which is a pathognomonic finding for CGCG. Irregular and significant expansion is noted in larger lesion (Fig. 74.43). Root resorption and tooth displacement can also occur with larger lesions. They exhibit a homogenous intermediate signal intensity on T1-weighted imaging. Postgadolinium MR imaging can have enhanced contrast intensity [1,5,24].
FIGURE 74.43 (A) Cropped panoramic radiograph of a central giant cell granuloma in the left maxilla (arrows) shows that the lesion has displaced the developing third molar tooth superiorly into the maxillary sinus. (B) Coronal and CBCT section demonstrate irregular expansion into the sinus superiorly. Note the ill-defined septa that meet the border at right angles (arrow). (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Aneurysmal Bone Cyst: This is a reactive bone lesion that occurs in patients younger than 30 years old. It can affect either jaw, with the mandible having a higher incidence. It is a rapidly
expanding lesion that may exhibit pain and tenderness. Most aneurysmal bone cysts (ABCs) are well defined and round, and larger lesions may have wispy septations that may be at a right angle to the lesion border, making it difficult to distinguish from CGCG. On cross-sectional imaging, a balloon-like expansion of the lesion is more in line with an ABC (Fig. 74.44). Tooth displacement and resorption is common. T2-weighted imaging can be helpful in diagnosis where ABC has a high-signal intensity with fluid level [1,5,24,28].
FIGURE 74.44 (A) Cropped lateral skull radiograph of an aneurysmal bone cyst in a teenage patient shows a circular, well-defined, and expansile lesion in the anterior mandible (B) mandibular occlusal radiograph shows displacement of the anterior teeth and the presence of faint septa within the lesion. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Cherubism: This is a rare autosomal-dominant developmental condition that results is marked expansion of the jaws bilaterally, leading to an angelic or cherub-like round face. It is a disease of childhood, and has a male:female ratio of 2:1. The presence of bilateral, well-defined, multilocular, and markedly expansile low attenuation areas in the jaws is pathognomonic (Fig. 74.45). If the maxilla is involved, the maxillary sinus floors are elevated and the maxillary tuberosities enlarged. The associated teeth may be displaced or delayed in eruption [1,5,24,29].
FIGURE 74.45 (A) Panoramic radiograph of a child with cherubism shows bilateral, multilocular expansile lesions in the anterior and posterior jaws that are characteristic of this condition. Multiple teeth have been displaced. (B, C) Axial and coronal cone beam computed tomography section demonstrate significant bony expansion bilaterally in both jaws. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Paget Disease of Bone: This is an autosomal-dominant condition that is characterized by a discrepancy in the rate of resorption and apposition of bone that leads to distortion and weakening of the bone. It occurs in middle-age or older individuals, twice as often in males. It can affect multiple bones, with the jaw bone being less likely to be affects that other bones. The maxilla is more likely to be affected than the mandible. It has three radiographic stages1.the radiolucent (resorptive) stage,2.the granular stage, and3.radiopaque stage (Fig. 74.46).
FIGURE 74.46 Reconstructed panoramic radiograph of a middle-aged male with Paget disease of bone shows irregular and heterogenous regions of calcification of the medullary bone present bilaterally. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Tooth hypercementosis can be seen in association with this entity [1,5,24,30]. Simple (Idiopathic) Bone Cavity: This is a common condition with no known cause. It tends to occur in the first two decades of life and is asymptomatic. It most commonly occurs in the mandible, especially the posterior aspect. It is a well-defined low-density lesion that may be septated, corticated, or noncorticated, and tends to scallop between the roots of the teeth (Fig. 74.47). Expansion of the cortices is rare. Occasionally, simple bone cavities can occur in cases of fibrous dysplasia and florid osseous dysplasia [1,5,24,31].
FIGURE 74.47 (A) Cropped panoramic radiograph of a 17-year-old male with a simple bone cavity in the right mandible. Inferiorly, the lesion seems thinly corticated and noncorticated superiorly. The lesion is scalloping between the teeth roots with no tooth displacement or resorption. (B) Axial CBCT shows thinning of the buccal and lingual cortices with minimal expansion. (Adapted from: M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104.)
Radiographic Analysis of the TMJs Anatomy of the TMJs The temporomandibular joint (TMJ) is among the most complex and poorly understood joints in the body. The complexity of this diarthrodial joint leads to much controversy regarding its diagnosis and treatment. To further complicate matters, there are two TMJs that work together to move a single piece of bone, the mandible, and create multidirectional and multifunctional movements. An understanding of the radiographic anatomy of the TMJ will help the radiologist become more familiar with identifying and diagnosing TMJ dysfunction. This review will cover the intracapsular components of the TMJs, which are generally visible and diagnosable on radiographic imaging. To evaluate the TMJs correctly, one must obtain the correct cross sections. These images should be axially corrected sagittal and coronal oblique images of the TMJs along the long axes of the condyles and perpendicular to them (Fig. 74.48). This is true whether the imaging is CT, CBCT, or MRI. CT and CBCT imaging will show the osseous components of the TMJs as well as any resulting changes in
the facial skeleton. MRI will give information about the soft-tissue condition, such as disc position and condition in the closed and open mouth positions, the presence of joint effusion and bone marrow edema, as well as the osseous contours and bone marrow homogeneity. It is important that the imaging be performed with the teeth in maximum intercuspation as a baseline image. This allows for the evaluation of spatial relation of the condyle and fossa on CT/CBCT and the relation of the disc to the osseous components on MRI [32].
FIGURE 74.48 (A) CBCT axial view with schematic plane lines to show the orientation of the axially corrected, (B) sagittal oblique (same plane as the red line on (A)), and (C) coronal oblique (same plane as the yellow line on (A)) cross sections. These cross sections are correct and appropriate for the evaluation of the anatomy and spatial relations of the osseous structures. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Osseous Components Condyle: The condyle should have a rounded articular surface with the posterior height of contour lower than the anterior height of contour (Fig. 74.49). This is an important diagnostic point, as it enables the reviewer to distinguish whether a small condyle is due to a condylar hypoplasia (where the contours are normal but the condyle is small or short) from end stage degenerative joint disease (where the condyle is small and short, but the articular surface is flattened and the heights of contour are approximately at the same level). The articular cortex between these heights of contour is egg-shell thin. Flattening of the articular surface indicates functional remodeling and thickening of this cortex indicates subchondral sclerosis, both of which are results of increased biomechanical loading. The articular cortices should be continuous, rounded, and thin. Breaks in the cortices may indicate active
degenerative joint disease, rheumatoid arthritis or, rarely, malignancy. The bone marrow spaces should be homogenous on CT and MRI.
FIGURE 74.49 CBCT axially corrected (A) sagittal oblique and (B) coronal oblique cross sections show the position of the condylar heights of contours (arrows) in relation to one another in a normal condyle. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Fossa: The articular surface of the glenoid fossa is the roof of the fossa, the posterior slope of the eminence and the crest of the eminence. The posterior slope of the eminence should be smooth and rounded and the crest of the eminence is normally broad and rounded. The roof of the fossa can vary in thickness. Spatial Relations: When MRI is not available, evaluating the condylar relation to the fossa on CT or CBCT can be useful provided the teeth are in maximum intercuspation on the scan and the correct cross sections are used. It is a good exercise to envision the outlines of a disc in between the osseous components (Fig. 74.50). If the space is narrowed to a point where the components of a disc cannot fit in the space, or the condyle is posteriorly, medially, laterally, or superiorly positioned in the fossa, the disc is most likely displaced, but this cannot be verified without soft-tissue imaging and clinical evaluation.
FIGURE 74.50 CBCT axially corrected sagittal cross sections in (A) closed and (B) open mouth positions show the normal spatial relations of the osseous structures. (A) A normal-shaped biconcave disc can be imagined in the joint space by the examiner, indicating that the spatial relations are within normal limits (the disc cannot be visualized or diagnosed without MRI). (B) The condyle translates to a point inferior and slightly anterior to the crest of the eminence (range of motion within normal limits). (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Soft-Tissue Components The intracapsular soft-tissue structures that are evaluated on MRI are the disc, the attachments and the synovial fluid-filled joint compartments. In the closed mouth position and on the sagittal oblique view (Fig. 74.51), the disc is biconcave with the thick posterior band of the disc positioned at the 12 o’clock position to the condyle, the intermediate zone positioned between the heights of maximum curvature of the condyle and the posterior slope of the eminence, and the anterior band positioned anterior to the condyle. On the coronal oblique view, the disc resembles a crescent moon that tapes toward the poles and attaches to the lateral aspects of the condylar neck through the medial and lateral collateral ligaments (Fig. 74.52). The disc also attached to the condyle through the condylar posterior attachment (inferior lamina). The disc is attached to the fossa through the temporal posterior attachment (superior lamina). There are two joint compartments between the disc and the osseous surfaces: the superior and inferior joint compartments. A mild amount of joint effusion visualized on T2-weighted or STIR MRI is within normal limits, but larger fluid collections can be pathologic and symptomatic [33– 35].
FIGURE 74.51 MRI axially corrected sagittal oblique cross section shows the normal anatomic relations of the disc with the osseous structures. (Adapted from: D Tamimi, DC Hatcher. Specialty imaging: temporomandibular joint. Salt Lake City, UT: Elsevier; 2016.)
FIGURE 74.52 MRI axially corrected coronal oblique cross section shows the normal anatomic relations of the disc with the osseous structures. (Adapted from: D Tamimi, DC Hatcher. Specialty imaging: temporomandibular joint. Salt Lake City, UT: Elsevier; 2016.)
In the open mouth position the condyle should translate to a point inferior to the crest of the eminence. As is does this, the disc should move along with it, with the normal open mouth relation being the junction between the anterior band and the intermediate zone being interposed between the articular surfaces of the TMJ (Fig. 74.53). In the case of disc displacement with reduction, the disc/articular surface relation should be normal in the open mouth position.
FIGURE 74.53 T1 MRI axially corrected cross sections shows the normal range of motion of the condyle and the disc. (A) indicates the closed mouth position. In the open mouth position (B), the part of the disc interposed between the condyle and the eminence is the junction between the anterior band and intermediate zones of the disc.
TMJ Imaging of Pathology Internal Derangement and Degenerative Joint Disease Soft-Tissue Changes: The TMJ is designed to withstand high multidirectional biomechanical forces. When the biomechanical demands exceed the biomechanical threshold of the disc, a loss of structural integrity of the disc and attachments occurs [32]. This leads to a gradual slipping (displacement) of the posterior band of the disc from the normal 11–12 o’clock position. If the biomechanical insult continues and increases, further damage can occur to these soft tissues and further displacement can occur. If the normal disc–condyle relation is restored in the open mouth position, this is called “disc displacement with reduction”; if it does not, then this is called “disc displacement without reduction” [32,36–38] (Fig. 74.54). TMJ discs can become displaced in multiple directions, such as the anterior, anteromedial, and anterolateral rotational and sideways (pure medial or lateral) (Fig. 74.55). Some authors advocate the presence of posterior disc displacement, but it is this author’s opinion that this is most likely a false-positive appearance created by the formation of a “pseudodisc,” a thickening and fibrosis of the posterior attachment area that give a morphologically thick low signal similar to that of the disc [7]. Obtaining axially corrected sagittal oblique and coronal oblique cross sections is crucial for
the correct evaluation and diagnosis of the direction of a disc displacement [32,36,37].
FIGURE 74.54 MR images show (A, B) disc displacement with reduction and (C, D) disc displacement without reduction. (A) T1WI shows a biconcave disc that has maintained its anteroposterior dimension positioned anterior to the condyle. (B) T1WI in the same patient shows recapture of the disc by the condyle and translation of the condyle to normal range of motion. (C) T2WI shows a disc that is anteriorly displaced and appears morphologically altered. (D) T2WI in the same patient show lack of recapture of the disc by the condyle and limitation of condylar range of motion. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
FIGURE 74.55 MR images show some of the different directions of disc displacement: (A) anterior displacement, (B) lateral displacement, (C) medial displacement, and (D, E) anterior rotational displacement, where (D) the disc is in the correct position in the center of the condyle and (E) it is displaced anteriorly off the lateral aspect of the condyle. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Osseous Changes: The soft-tissue changes described previously precede the osseous changes seen in degenerative joint disease in both adults (DJD) and children (progressive condylar resorption/idiopathic condylar resorption). The morphology of the condyles at the end stage of the degenerative change is different for adults and children, but the process of destruction is similar. When the biomechanical threshold of the fibrocartilage and the articular surfaces is met, morphologic changes occur to the articular surfaces to adapt and to distribute these forces over a large surface area. These changes include thickening and sclerosis of the articular cortex and flattening of the articular surfaces (formation of congruent articulations). When the biomechanical threshold is exceeded, cortical breakdown (erosion) occurs (Fig. 74.56). The erosions destroy the articular surface and reduce its volume, and when the forces are alleviated or when the body adapts to their presence, the articular surfaces start to repair and recorticate. The lost bone, however, cannot be rebuilt, hence resulting in reduction of condylar height and volume with corticated
surfaces and condylar heights of contour that have changed in relation to the fossa, while the repair process is complete. In adult DJD, it is common to see osteophytes as a method of increasing surface area for load distribution (Fig. 74.57A). Subchondral bone cysts can also be seen in adult DJD [32–35]. In both adults and children, changes to the mandibular and facial morphology can be expected, but it is more severe if the degenerative joint disease occurs in a growing individual as the growth plates of the condyles are affected (Fig. 74.57C).
FIGURE 74.56 Axially corrected sagittal (A) and coronal (B) CBCT cross sections show erosion and volume loss on the articular surface of the condyle, indicating active degenerative changes. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
FIGURE 74.57 CBCT reformations show the effect of end-stage degenerative changes on the condylar dimensions and the facial skeleton. (A) Serial sagittal cross sections show reduction of condylar height and the formation of an osteophyte anteriorly on each condyle. (B) The coronal view shows a reduction of the condylar height. (C) Lateral 3D rendering shows the effect of the reduction of condylar height bilaterally on the mandible: posterior rotation of the mandible, small mandible, and a steep mandibular plane. This can result in a convex facial profile. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Range of Motion: Condylar hypermobility is characterized by a condyle that moves more than 2-mm anterior and superior to the crest of the eminence. This occurs when there is elongation of the posterior attachments and the sphenomandibular and stylomandibular ligaments. This may be seen in some early cases of internal derangement of the joint, or in cases of Ehlers–Danlos syndrome [39]. It can manifest as subluxation of the condyle, where the condyle can return to the closed position, or dislocation, where the condyle cannot return and the patient is in an open lock (Fig. 74.58). Condylar restriction is characterized by a condyle that
remains posterior and superior to the crest of the eminence. It can occur with internal derangement. Disc displacement with reduction usually has a normal range of motion, but an acute closed lock is usually experienced in the acute phase of disc displacement without reduction. As the condition becomes more chronic, range of motion may be restored. Disc adhesions can occur due to trauma or due to disc displacement (Fig. 74.59). Synovitis can lead to fibrin deposition and hence decrease in lubrication that results in the stiction effect (two solid objects pressed against each other but not sliding), reduced disc mobility and further increase in fibrin depositions and formation of fibrous adhesions. This most commonly occurs in the superior joint compartment (where the translation motion of the TMJ occurs), but can occur in the inferior compartment (where the rotation motion of the condyle occurs). Thus, adhesions of the superior compartment manifest as more limitation of opening than those of the inferior compartment [32,36,37,39]. When investigating limited oral opening, coronoid hyperplasia should be ruled out as a causative factor.
FIGURE 74.58 MR T1WI shows a hypermobile condyle (yellow arrow). The condyle is positioned anterior and superior to the crest of the eminence (white arrow). The portion of the disc between the condyle and fossa is the anterior band. This condyle is anterior to the normal position in relation to the disc (hypermobile). (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
FIGURE 74.59 MR T2WI in the (A) closed and (B) open positions shows that the disc position does not change in relation to the fossa, indicating a fibrous adhesion in the superior compartment. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Inflammatory Diseases Rheumatoid Arthritis: This is a chronic inflammatory disease that manifests as synovial membrane inflammation in many joints and can affect the TMJs. The inflammation of the synovial lining of the TMJ capsule in its chronic stages forms a granulomatous pannus that erodes the articular surface fibrocartilage and underlying bone. This results in an irregular resorption of the articular surfaces with subsequent flattening of the anterior and posterior aspects of the condyle, giving it a “sharpened pencil” appearance (Fig. 74.60A, B). In some late stages, fibrous or bony ankylosis may occur. On T1- and T2-weighted images, the pannus has an intermediate signal intensity that can displace the temporal posterior attachment inferiorly and the condylar posterior attachment superiorly (Fig. 74.60C). Because this is often a bilateral condition, the reduction of condylar height often leads to posterior rotation of the mandible around a second molar fulcrum resulting in an anterior open bite. This can also occur unilaterally leading to mandibular asymmetry [32,36,37].
FIGURE 74.60 (A) and (B) CBCT sagittal oblique cross sections show flattening of the condyles with a sharpened pencil appearance often seen with rheumatoid arthritis. (C) MR T1WI in another patient shows an intermediate signal mass in the joint space representing pannus formation. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Juvenile Idiopathic Arthritis: This is an autoimmune musculoskeletal inflammatory disease of childhood. It occurs primarily in large joints, but can affect the TMJs. When it does, it usually destroys the condyle, resulting in a condylar stump appearance and a wide and flat glenoid fossa. The condyle may reposition anteriorly and superiorly because of the flattening of the eminence. This condylar height reduction results in retardation of the growth of the mandible, resulting in a small mandible and a convex facial profile. On contrast-enhanced T1WI, there is enhancement of the joint compartment, which allows for the diagnosis to be made before the bone destruction and the subsequent facial growth problems [32,36,37] (Fig. 74.61).
FIGURE 74.61 CBCT panoramic reformat shows the left half of the mandible of a 15-year-old female with bilateral JIA. The coronoid process is elongated and the condylar process is stump-like. The antegonial notch is deepened. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Tenosynovial Giant Cell Tumor: It is a locally aggressive tumefactive disease of the synovium that is rare in the TMJ. When it does occur it presents as an aggressive lesion destroying the condyle and the fossa and invading into the middle cranial fossa. Bone CT shows erosion of the condyle and glenoid fossa. On T1- and T2-weighted imaging, a low to intermediate signal with a peripheral low-signal rim is seen. With contrastenhancement, some portions of the mass mildly enhance [32,36,37] (Fig. 74.62).
FIGURE 74.62 (A) Axial bone CT shows widening of the right TMJ space and multiple rounded erosions of the adjacent skull base. (B) Coronal MR T1WI shows a hypointense right TMJ mass with peripheral lower signal intensity. There is a contiguous middle cranial fossa extra-axial mass with a similar markedly low-signal intensity peripheral rim. This is consistent with pigmented villonodular synovitis. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Traumatic Changes Neonatal Fracture: This is a specific type of fracture that is caused by forceps delivery perinatally. The condylar neck fractures and the fragment becomes anteriorly dislocated. Remodeling occurs and the result is mandibular notch with an acute angle that gives the classic “pair of scissors” sign [32,36,37] (Fig. 74.63).
FIGURE 74.63 CBCT panoramic reformat of the right half of the mandible shows anterior positioning of the condylar process. The condylar cortex traverses the ramus. There is an acute angle between the condylar process and the coronoid process giving the “scissors sign” typical of a neonatal fracture after forceps delivery. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Subcondylar and Condylar Fracture: These types of fractures can occur in childhood or adulthood. Table 74.5 classifies condylar fractures according to severity (Fig. 74.64).
FIGURE 74.64 CBCT coronal (A), surface rendering (B), and sagittal (C) show condylar neck fracture (arrow) with limited anterior displacement due to the lodging of the fragment into the neck. (Adapted from: R Alimohammadi, Imaging of dentoalveolar and jaw trauma, Radiol Clin North Am 56 (1) (2018) 105–124.)
Bifid Condyle: This is a rare entity characterized by partial division of the mandibular condyle. It can have congenital, developmental, or acquired cause and can be secondary to trauma. The findings range from a heart-shaped condyle, a vertical depression in the superior surface of the condyle (best visualized on a coronal oblique view) to duplication of the condyle (one condyle in front of the other) in the sagittal oblique view [32,36,37] (Fig. 74.65).
FIGURE 74.65 CBCT (A) coronal oblique and (B) sagittal oblique cross sections show a bifid condyle. Image (A) shows the typical appearance of a deep groove in the superior aspect of the condyle. Image (B) shows the radiographic appearance of “one condyle in front of the other” that can be seen on panoramic plain film imaging and CBCT reformations. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Ankylosis: This can be fibrous or bony and is usually secondary to an insult to the joint. Trauma is the most common cause, followed by inflammatory arthritides, previous joint surgery, and infection. These present clinically as marked limitation of opening, with bony ankylosis being more severe. On bone CT, a fibrous ankylosis maintains a soft-tissue separation between the irregular articular surfaces. Bony ankylosis fuses the condyle to the fossa at varying degrees [32,36,37] (Fig. 74.66).
FIGURE 74.66 (A) CBCT sagittal oblique view shows abnormal remodeling of the left condyle and fossa following trauma. There is maintenance of a thin lowdensity band between the temporal and mandibular components, suggestive of a fibrous union, not a bony one. (B) Coronal bone CT shows gross enlargement of the right condyle and bony fusion with the temporal bone. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Benign Neoplasia Osteochondroma This is a benign, cartilage-capped, exophytic lesion arising from bone. It can arise from the condyle and from the coronoid process. It can present as a pedunculated mass of mixed density attached to the condyle that often extends from the anterior or anteromedial surface of the condyle at the attachment of the lateral pterygoid muscle and can grow in the direction of the muscle fibers (Fig. 74.67). When it is small, it is difficult to distinguish from osteophytes caused by degenerative joint disease. When large, it can displace the condyle in the fossa and displace the mandible inferiorly and contralaterally, resulting in an ipsilateral posterior open bite and a contralateral cross bite [32,36,37].
FIGURE 74.67 (A) CBCT panoramic reformat shows how an osteochondroma can mimic an osteophyte. The normal condylar outline is seen but it is inferiorly displaced by the lesion. The fossa contours are within normal limits. (B) Axial view shows orientation of the lesion with fibers of the lateral pterygoid muscle fibers. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Osteoma: This is a benign slow-growing bone-forming tumor characterized by proliferation of either compact or cancellous bone. It usually originates from the surfaces of the condyle that are covered with periosteum (nonarticular surfaces). It appears as a pedunculated, homogenous, well-defined high-density mass. It may be compact or cancellous and the bone pattern is normal (Fig. 74.68). This lesion can also cause displacement of the condyle and mandible if it is large enough [32,36,37].
FIGURE 74.68 Coronal CBCT shows a large pedunculated high-density mass arising from the neck of the condyle, suggestive of an osteoma. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Malignant Neoplasia Chondrosarcoma: This is a malignant tumor that more commonly occurs in the skull base in the head and neck. It can occur centrally within the condylar or temporal bone, parosteally or in the soft tissues of the TMJs. On bone CT, a nonenhancing mass with flocculent calcifications around the condyle and the joint space that may or may not destroy the bone is observed. The joint space is widened, and the condyle may appear enlarged or lengthened. There can be a ringlet pattern of calcification in and around the condyle. Periosteal reaction may or may not be present. On T2WI, it shows a high-signal intensity and the hypointense foci signifying calcification may not be as prominent as the calcified appearance on CT. With contrast, a heterogeneously enhancing mass with whorls of intensifying lines within the tumor are often seen [32,36,37] (Fig. 74.69).
FIGURE 74.69 Chondrosarcoma: (A) Bone CT shows increased sclerosis of the right condyle and the presence of small calcifications lateral to the condyle. (B) Coronal view shows ring-like calcifications lateral to the condyle and destruction of the glenoid fossa. (C) Sagittal MR T1WI shows a lobulated mass extending into the middle cranial fossa. (D) Axial contrast-enhanced T1WI shows extensive solid enhancement of the lesion, indicating that is not inflammatory. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
Osteosarcoma and Others: This has been discussed earlier under Effect of Malignancies on the Dentomaxillofacial complex. Miscellaneous Conditions Synovial Chondromatosis: Synovial chondromatosis can be primary (unrelated to DJD) or secondary to DJD. In the primary form, there is development of cartilaginous nodules within the subsynovial connective tissue that subsequently detach, ossify, and form loose articular bodies in the joint space. This is not a neoplastic entity but has a mass effect in widening the joint space, remodeling the surrounding bone and displacing the condyle. On bone CT, multiple calcified nodules can be seen surrounding the condyle with widening of the joint space. On T1-weighted imaging, the tissue planes between the mass and the surrounding soft tissues can be defined. Multiple hypointense loose articular bodies may be observed. On T2-weighted imaging the joint space in which these nodules reside is hyperintense due to fluid accumulation. Contrast-enhanced T1 MR imaging shows an enhancing synovium (Fig. 74.70).
FIGURE 74.70 (A) Noncontrast-enhanced CT in a patient with synovial chondromatosis shows multiple small loos calcified articular bodies surrounding the left condyle. (B) Sagittal oblique T2WI MR shows high-signal mass with small low-density bodies within. (Adapted from: D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018) 157–175.)
In the form secondary to DJD, there is production of 1 or more cartilaginous or osseous fragments along with irritation and metaplasia of the synovial membrane following unrelated breakdown of the articular surfaces caused by DJD. There are signs of advanced DJD (congruent articulation, osteophyte formation, joint space narrowing, and possible subchondral bone cyst formation). This form of synovial chondromatosis does not produce a mass effect, a point that is useful in distinguishing the two entities [32,36,37]. Calcium Pyrophosphate Dehydrate Deposition Disease: This is a metabolic disease in which calcium pyrophosphate crystals as deposited in the synovial fluid, resulting in calcification of the articular cartilage and leading to acute arthritis in some patients. Tumoral calcium pyrophosphate dehydrate deposition disease (CPPDD) is the most prevalent type in the TMJs. It differs from gout, in which uric acid crystals are precipitated, therefore it is called pseudogout. On bone CT, early CPPDD presents as fine, cloud-like calcifications with even distribution in the joint space, often encircling the condyle. Late CPPDD presents as a chunky, diffusely calcified mass that may have a ground glass appearance. There can be associated bone remodeling and mass effect that may mimic malignancy because of extensive bone destruction, which makes it difficult to distinguish from chondrosarcoma. On MR imaging T1W shows a low-signal to intermediate-signal lesion because of the soft-tissue mass in the joint space. Expansion of the joint capsule can be seen. Contrast enhancement yields a heterogeneously enhancing mass [32,36,37] (Fig. 74.71).
FIGURE 74.71 (A) Axial bone CT of a patient with CPPDD disease shows a large erosive defect in the medial aspect of the condyle and fine granular softtissue calcifications surrounding the condyle. (B) Axial MR T2WI FS shows a heterogenous but predominantly low-signal intensity lesion anterior to the condyle. Joint effusion is noted. (C) Coronal contrast-enhanced T1WI FS in the same patient shows enhancement of the inferolateral mass.
Suggested Readings • LJ Koenig, D Tamimi, G Petrikowski, SE Perschbacher, A Ruprecht, BW Benson, et al., Diagnostic Imaging: Oral and Maxillofacial, second ed., Elsevier, Philadelphia, 2017. • SMLE Mallya, White and Pharoah’s Oral Radiology Principles and Interpretation, eighth ed., Elsevier, St Louis, 2019. • D Tamimi, Oral and Maxillofacial Radiology, Radiol Clin North Am 56 (1) (2018). • WM Scarfe, C Angelopolous, Maxillofacial Cone Beam Computed Tomography. Springer; 2018, Switzerland. • O Langland, R Langlais, Principles of Dental Imaging. Williams & Wilkins; 1997, Baltimore, Maryland, USA.
References [1] LJ Koenig, D Tamimi, G Petrikowski, SE Perschbacher, A Ruprecht, BW Benson, et al., Diagnostic Imaging: Oral and Maxillofacial, second ed., Elsevier, Philadelphia, 2017. [2] SJ Nelson, Wheeler’s Dental Anatomy, Physiology and Occlusion, Elsevier Health Sciences, St. Louis, MO, 2014. [3] MA Husain, Dental anatomy and nomenclature for the radiologist, Radiol Clin North Am 56 (1) (2018) 1–11. [4] M Sadrameli, M Mupparapu, Oral and maxillofacial anatomy, Radiol Clin North Am 56 (1) (2018) 13–29. [5] SC.P.M White, Oral Radiology Principles and Interpretation, Elsevier Mosby, St Louis, MO, 2014.
[6] OL.R Langland, WD McDavid, A Delbalso, Panoramic Radiology, second ed., Lea & Febiger, Philadelphia, 1989. [7] OL.R Langland, J Preece, Principles of Dental Imaging, second ed., Lippincott Williams & Wilkins, Philadelphia, 2002. [8] M Mupparapu, C Nadeau, Oral and maxillofacial imaging, Dent Clin North Am 60 (1) (2016) 1–37. [9] A Gonzalez-Beicos, D Nunez, Imaging of acute head and neck infections, Radiol Clin North Am 50 (1) (2012) 73–83. [10] N Thayil, MN Chapman, N Saito, A Fujita, O Sakai, Magnetic resonance imaging of acute head and neck infections, Magn Reson Imaging Clin N Am 24 (2) (2016) 345–367. [11] S Mardini, A Gohel, Imaging of odontogenic infections, Radiol Clin North Am 56 (1) (2018) 31–44. [12] YJ Lee, S Sadigh, K Mankad, N Kapse, G Rajeswaran, The imaging of osteomyelitis, Quant Imaging Med Surg 6 (2) (2016) 184–198. [13] EA Bilodeau, BM Collins, Odontogenic cysts and neoplasms, Surg Pathol Clin 10 (1) (2017) 177–222. [14] RA Robinson, Diagnosing the most common odontogenic cystic and osseous lesions of the jaws for the practicing pathologist, Mod Pathol 30 (s1) (2017) S96–S103. [15] WC Scarfe, S Toghyani, B Azevedo, Imaging of benign odontogenic lesions, Radiol Clin North Am 56 (1) (2018) 45–62. [16] FW Costa, TS Viana, GM Cavalcante, PG de Barros Silva, RB Cavalcante, AS Nogueira, et al., A clinicoradiographic and pathological study of pericoronal follicles associated to mandibular third molars, J Craniofac Surg 25 (3) (2014) e283–e287. [17] A Borghesi, C Nardi, C Giannitto, A Tironi, R Maroldi, F Di Bartolomeo, et al., Odontogenic keratocyst: imaging features of a benign lesion with an aggressive behaviour, Insights Imaging 9 (5) (2018) 883– 897. [18] SM Mallya, S Tetradis, Imaging of radiation- and medication-related osteonecrosis, Radiol Clin North Am 56 (1) (2018) 77–89. [19] RE Marx, Osteoradionecrosis: a new concept of its pathophysiology, J Oral Maxillofac Surg 41 (5) (1983) 283–288. [20] SM.L.E Mallya, White and Pharoah’s Oral Radiology Principles and Interpretation, eighth ed., Elsevier, St Louis, 2019. [21] G Støre, M Boysen, Mandibular osteoradionecrosis: clinical behaviour and diagnostic aspects, Clin Otolaryngol Allied Sci 25 (5) (2000) 378– 384. [22] J Chong, LK Hinckley, LE Ginsberg, Masticator space abnormalities associated with mandibular osteoradionecrosis: MR and CT findings in
five patients, AJNR Am J Neuroradiol 21 (1) (2000) 175–178. [23] SL Ruggiero, TB Dodson, J Fantasia, R Goodday, T Aghaloo, B Mehrotra, et al., American Association of Oral and Maxillofacial Surgeons position paper on medication-related osteonecrosis of the jaw—2014 update, J Oral Maxillofac Surg 72 (10) (2014) 1938–1956. [24] M Ahmad, L Gaalaas, Fibro-osseous and other lesions of bone in the jaws, Radiol Clin North Am 56 (1) (2018) 91–104. [25] GN Mainville, DP Turgeon, A Kauzman, Diagnosis and management of benign fibro-osseous lesions of the jaws: a current review for the dental clinician, Oral Dis 23 (4) (2017) 440–450. [26] MM Cohen Jr., RE Howell, Etiology of fibrous dysplasia and McCuneAlbright syndrome, Int J Oral Maxillofac Surg 28 (5) (1999) 366–371. [27] LR Eversole, PW Merrell, D Strub, Radiographic characteristics of central ossifying fibroma, Oral Surg Oral Med Oral Pathol 59 (5) (1985) 522–527. [28] J Asaumi, H Konouchi, M Hisatomi, H Matsuzaki, H Shigehara, Y Honda, et al., MR features of aneurysmal bone cyst of the mandible and characteristics distinguishing it from other lesions, Eur J Radiol 45 (2) (2003) 108–112. [29] M Redfors, JL Jensen, K Storhaug, T Prescott, TA Larheim, Cherubism: panoramic and CT features in adults, Dentomaxillofac Radiol 42 (10) (2013) 20130034. [30] N Winn, R Lalam, V Cassar-Pullicino, Imaging of Paget’s disease of bone, Wien Med Wochenschr 167 (1-2) (2017) 9–17. [31] ME Peacock, R Krishna, JW Gustin, MR Stevens, RM Arce, RA Abdelsayed, Retrospective study on idiopathic bone cavity and its association with cementoosseous dysplasia, Oral Surg Oral Med Oral Pathol Oral Radiol 119 (4) (2015) e246–e251. [32] D Tamimi, DC Hatcher, Specialty Imaging: Temporomandibular Joint, Elsevier, Salt Lake City, UT, 2016. [33] RW Katzberg, RH Tallents, Normal and abnormal temporomandibular joint disc and posterior attachment as depicted by magnetic resonance imaging in symptomatic and asymptomatic subjects, J Oral Maxillofac Surg 63 (8) (2005 Aug) 1155–1161. [34] TA Larheim, RW Katzberg, PL Westesson, RH Tallents, ME Moss, MR evidence of temporomandibular joint fluid and condyle marrow alterations: occurrence in asymptomatic volunteers and symptomatic patients, Int J Oral Maxillofac Surg 30 (2) (2001 Apr) 113–117. [35] RW Katzberg, J Schenck, D Roberts, RH Tallents, JV Manzione, HR Hart, et al., Magnetic resonance imaging of the temporomandibular joint meniscus, Oral Surg Oral Med Oral Pathol 59 (4) (1985 Apr) 332–335.
[36] D Tamimi, E Jalali, D Hatcher, Temporomandibular joint imaging, Radiol Clin North Am 56 (1) (2018 Jan) 157–175. [37] D Tamimi, HD Kocasarac, S Mardini, Imaging of the temporomandibular joint, Semin Roentgenol 54 (3) (2019 Jul) 282–301. [38] F Perrini, RH Tallents, RW Katzberg, RF Ribeiro, S Kyrkanides, ME Moss, Generalized joint laxity and temporomandibular disorders, J Orofac Pain 11 (3) (1997) 215–221, Summer. [39] M Ahmad, L Hollender, Q Anderson, K Kartha, R Ohrbach, EL Truelove, et al., Research diagnostic criteria for temporomandibular disorders (RDC/TMD): development of image analysis criteria and examiner reliability for image analysis, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 107 (6) (2009 Jun) 844–860.
CHAPTER 75
Benign Brain Lesions and Epilepsy Michael Tran Duong, Joel M. Stein, Vivek Gupta
Introduction The human brain, with an estimated 86 billion neurons [1], enables sensation, motion, emotion, memory, cognition, and consciousness, presenting great challenges to understanding its structure, function, and dysfunction. The brain’s complexity both empowers and impedes the pursuit toward the Greek aphorism “to know thyself.” Sealed in the cranial vault and guarded by the blood–brain barrier, the secrets of the brain have been slow to unravel. In his 1817 article, “An Essay on the Shaking Palsy,” James Parkinson thanked “those who humanely employ anatomical examination in detecting the causes and nature of disease… To such research, the healing art is already much indebted for the enlargement of its power of lessening the evils of suffering humanity” [2]. For much of the history of medicine, such “anatomical examination” required pathological dissection or surgical vivisection. However, with the advent of successively more sophisticated imaging techniques, exploration of the brain today heavily relies on biomedical imaging technology, not only for diagnosis and management of neurological disorders, but also for advancement of the frontiers of neurobiology [3].
75.1
Review of Structural and Functional Anatomy
The following is an overview of structural and functional anatomy of the brain and central nervous system (CNS) (Figs. 75.1–75.6).
FIGURE 75.4 Cross sections of the pontomesencephalic junction and basal cisterns (suprasellar and interpeduncular cisterns in G) to the midbrain. Occipital lobe (1). Cerebellar vermis (2). Cerebral aqueduct of Sylvius (3). Pontomesencephalic junction (4). Medial temporal lobe (5). Temporal horn of the lateral ventricles adjacent to the hippocampus and medial temporal lobe (6). Pituitary stalk (7). Optic nerve (8). Globe (9). Midbrain (10). Cerebral peduncles (containing corticospinal tracts) (11). Cortical gray matter (12). Subcortical/juxtacortical white matter (13). Mammillary bodies (14). Optic chiasm (15). Olfactory bulbs and cortex (16). Red nucleus (17). Orbitofrontal cortex (18). Atrium of the lateral ventricles (19).
FIGURE 75.5 Cross sections of the basal ganglia and thalami to the lateral ventricles. Occipital lobe (1). Atrium of the lateral ventricles (2). Third ventricle (3). Fornix (4). Thalamus (5). Temporal lobe (6). Insular cortex (7). Head of the caudate (8). Putamen (9). Globus pallidus (10). Frontal horn of the lateral ventricles (11). Frontal lobe (12). Genu (13) and splenium of the corpus callosum (14). Septum pellucidum (15). Anterior limb (16), genu (17), and posterior limb of the internal capsule (18) (posterior limb contains motor fibers of corticospinal tract). External capsule (19). Note: globus pallidus + putamen = lentiform nucleus. Putamen + caudate nucleus = striatum.
FIGURE 75.6 Cross sections of the lateral ventricles to the superior cortex. Parieto-occipital region (1). Parietal lobe (2). Frontal lobe (3). Lateral ventricle (4). Septum pellucidum (5). Choroid plexus of the ventricles (6). Corona radiata, the afferent projection fibers to the cortex (7). Cingulate gyrus (8).
Cerebral Hemispheres The cerebral cortex, containing about 20 billion neurons [1], refers to the thin, highly convoluted layer of gray matter encapsulating the white matter. Only a relatively small portion of the cortex is involved in the specific functions of receiving sensory input from the special senses or projecting motor outputs to the spinal cord. Over 80% of the cortex, known as the association cortex, is involved in more general information processing for higher cortical functions of cognition, language, and reasoning. Converging evidence from many different investigative approaches is beginning to reveal that the organization of human brain involves specialization of spatial function and integration of these regions into task-defined networks [4]. Cortical regions and subcortical nuclei act as processing modules, each with a distinct cytoarchitecture and connectivity profile specialized to process and relay-specific categories and hierarchies of input information [4]. Thus, each perceptual, executive, and motor task engages a subset of these modules into a network determined by input type (visual, auditory, and somatosensory, etc.) and output target (i.e., pattern recognition, motor response, etc.). Hence, the cortical regions may be construed as serial and parallel processors, while white matter tracts are cables for information flow across the network [4,5]. The cerebrum (forebrain or telencephalon) (Figs. 75.1–75.6) is divided into two hemispheres by the interhemispheric fissure, and each hemisphere is subdivided into four main lobes [5].
◾ The frontal lobe governs executive and articulatory functions ◾ The parietal lobe processes sensory and visuospatial information [6] ◾ The temporal lobe regulates language, emotions, and memories ◾ occipital lobe processes visual input ◾ The The insular cortex, as the least understood lobe, may be involved in visceral sensorimotor, language, cognitive, and socioemotional functions
Fissures and sulci separate these lobes anatomically. The sylvian fissure separates the temporal lobe from the frontal and parietal lobes on the lateral cerebral surface. The insula lies in the depth of the sylvian fissure, covered by frontal, temporal, and parietal opercula (“lids”). The central sulcus divides the frontal and parietal lobes on the superior and lateral surface. The parietooccipital fissure separates the parietal and occipital lobes on the medial surface. However, it must be noted that these lobes are neither embryologically, nor functionally separate entities, and many distant areas of the cortex show greater connectivity than neighboring regions [4]. A detailed account of functional cortical specialization organization into networks is beyond the scope of this chapter [5].
Basal Ganglia
The basal ganglia, gray matter nuclei deep to the cerebral cortex, relay dopaminergic signaling from the substantia nigra to the thalamus and motor cortex through direct (cortex–putamen–globus pallidus interna–thalamus– cortex) and indirect (cortex–putamen–globus pallidus externa–subthalamic nucleus–globus pallidus interna–thalamus-cortex) pathways (Fig. 75.5) [5]. The structures in the basal ganglia include the caudate nucleus, putamen, globus pallidus, claustrum, and surrounding white matter tracts divided into internal and external capsules. Other nomenclature associated with basal ganglia nuclei include lentiform nucleus (globus pallidus and putamen flanked by internal and external capsules) and corpus striatum (caudate nucleus and putamen). The basal ganglia are responsible primarily for motor control but also play a role in motor learning, executive function, and emotional states [4]. Disorders of the basal ganglia are characterized by hypokinesia with rigidity and tremor (Parkinson disease, corticobasal degeneration) as well as hyperkinetic involuntary movements in essential tremor and choreoathetosis (Huntington disease) [5,7]. The basal ganglia are supplied by lenticulostriate vessels from the middle and to a lesser extent anterior cerebral arteries [8,9].
Thalamus and Hypothalamus The thalamus (meaning “chamber” in Greek) relays sensory input to cortical association areas, except for olfactory input which relays directly to the entorhinal cortex (Fig. 75.5) [5]. It is a paired paramedian ovoid structure located above the midbrain, immediately medial to the posterior limb of the internal capsule. It extends anteriorly to the foramen of Monro and medially to the third ventricle. In addition to being a relay station for sensory techniques, it receives motor connections from the cerebellum and basal ganglia en route to the cortex. The thalamus also has key connections with the limbic system, assigning it an important role in emotions and memory. There are several thalamic nuclei, each receiving input from specific sensory techniques and relaying to distinct cortical regions. For example, the ventroposterolateral (VPL) nucleus receives pain and temperature information from anterolateral spinothalamic fibers and position and vibration sense from the dorsal column-medial lemniscal pathway; it then outputs this information to the somatosensory cortex [4]. The ventroposteromedial nucleus receives facial sensory information from the trigeminothalamic tracts and afferent taste sensation from the solitary tracts (which sends data to the gustatory cortex) [4]. The lateral geniculate nucleus receives visual information from the optic tracts and relays information to the primary visual cortex along the calcarine fissure [4]. Likewise, the medial geniculate nucleus receives auditory information from the cochlear nerve nucleus and relays to the primary auditory cortex in the temporal lobe
(Heschl’s and superior temporal gyri). The ventral anterior and ventral lateral are the motor nuclei of the thalamus, whereas the anterior and lateral dorsal nuclei are part of the limbic system [5,7]. The thalamus is supplied by several branches arising from the posterior communicating and posterior cerebral arteries [9]. The hypothalamus (meaning “under chamber” in Greek) is similarly comprised of several small nuclei located anteriorly and inferiorly to the floor of the third ventricle and is separated from the thalamus by the hypothalamic sulcus in the wall of the third ventricle [10]. These nuclei govern several important functions including generation of the circadian rhythms through melatonin secretion (suprachiasmatic nucleus), stimulation of the anterior pituitary (arcuate nucleus) and posterior pituitary gland (supraoptic and paraventricular nuclei), regulation of hunger and satiety (lateral and ventromedial nuclei), and control of body temperature (anterior and posterior nuclei). The hypothalamus is functionally connected directly to the posterior pituitary gland through the infundibulum and indirectly to the anterior pituitary gland through local venous connections known as the hypothalamic–hypophyseal portal system [5,10].
Limbic Structures The hippocampus, named after its shape and meaning “seahorse” in Greek, plays an essential role in short-term memory and memory consolidation (Fig. 75.4) [4,11]. The amygdala regulates emotions, particularly fear conditioning. The limbic system is comprised of the medial temporal lobe (the amygdala, hippocampus, entorhinal and parahippocampal cortex), fornix, mammillary bodies, anterior thalamic nuclei, and cingulate cortex. This system is impaired in a variety of disorders, such as Alzheimer disease (AD), Limbicpredominant Age-related TDP-43 Encephalopathy (LATE), mesial temporal sclerosis (MTS) and Kluver–Bucy syndrome. Thiamine (B1) deficiency causes mammillary body degeneration resulting in Wernicke–Korsakoff syndrome [4–6].
Neuroendocrine Structures The pituitary gland is the master regulator of the endocrine system (Figs. 75.3 and 75.4). It is located in the sella turcica (Latin for “Turkish seat”) and secretes several hormones and hormone-releasing factors. This gland, along with the circumventricular organs (subfornical organ, organum vasculosum, and area postrema), is one of the few regions of the brain without a blood– brain barrier, thereby allowing for chemoregulation and hormone secretion. The area postrema of the medulla (chemotactic trigger zone) regulates
vomiting due to noxious toxin ingestion [4]. The pineal gland, a common site for benign calcification, was used as an important radiographic landmark before the advent of CT and MR imaging [3]. Furthermore, pineal masses may compress the midbrain and superior colliculi, leading to Parinaud syndrome, which is marked clinically by vertical gaze palsy, eyelid retraction, and convergence-retraction nystagmus [5,6,12].
Brainstem The brainstem is a complex highway of white matter tracts interspersed with gray matter nuclei. It is divided from superior to inferior into the midbrain, pons, and medulla (Figs. 75.2–75.4). The anterior midbrain is defined by the cerebral peduncles, two large fiber bundles [4,5]. Medially, the paired oculomotor nerves emerge from the interpeduncular fossa. The posterior midbrain consists of the quadrageminal plate, formed by two paired structures: superior colliculi and inferior colliculi. Immediately below the inferior colliculi, the paired trochlear nerves cross and exit the dorsal surface of the midbrain and traverse the perimesencephalic cistern [12]. The pons is characterized by a ventral “belly” or basis pontis containing the corticospinal, corticobulbar, and corticopontine tracts and a dorsal pontine tegmentum which includes the reticular formation, central tegmental tracts, and medial to lateral: the medial lemniscus, trigeminothalamic tract, and spinothalamic tract. The paired trigeminal nerves emerge from the anterolateral surface of the pontine belly and course through the prepontine cistern to reach Meckel’s cave, a dural recess containing the Gasserian (trigeminal) ganglion. The medial longitudinal fasciculus lies paramedially on the dorsal pontine surface and is flanked by the abducens nucleus [13–15]. The medial longitudinal fasciculus is critical for conjugate gaze and damage due to demyelination or infarct results in internuclear ophthalmoplegia. Facial colliculi mark the location of the motor fibers of the seventh nerve passing over the abducens nuclei along the floor of the fourth ventricle in the lower pontine tegmentum. Along the ventral (anterior) medulla are paired protrusion called the pyramids, which contain motor fibers (corticospinal and corticobulbar—the pyramidal tracts). The pyramids are separated by a median fissure that continues along the spinal cord, briefly interrupted where the pyramidal tracts decussate (cross the midline) at the spinomedullary junction. Lateral to the pyramids, separated by ventrolateral sulci, are the olivary bodies, containing superior and inferior olivary nuclei. Posterior to the olives are the dorsolateral sulci. The hypoglossal nerves (cranial nerve 12) exit the medulla in the ventrolateral sulci while the roots of cranial nerves 9, 10, and 11 exit through the dorsolateral sulci. Dorsally, the gracile and cuneate tubercles mark the location of the corresponding nuclei [5,12].
Cerebellum The cerebellum (“little brain”) is responsible for coordination of movement. Structurally, it can be visualized by two paired lobes of white matter core and projections covered by thin convolutions of cortex called folia (Figs. 75.1– 75.3). The motor and premotor cerebral cortex relay information about planned movements to the cerebellar cortex, while somatosensory, visual, and vestibular systems input into the cerebellar cortex to allow for the assessment of progressing motor task status [4]. After processing this complex information, the cerebellar cortex sends its output back to the cerebral cortex through the deep cerebellar nuclei. Midline cerebellar vermis damage (as in chronic alcoholism) causes truncal ataxia, while lesions of cerebellar hemispheres lead to dysmetria (impaired finger-to-nose/heal-to-shin testing), limb ataxia, intention tremor, and dysdiadochokinesia [4,6]. Recent evidence has also implicated the cerebellum in a few nonmotor functions, including cognition. The deep cerebellar white matter core contains four pairs of nuclei, located lateral to medial: the dentate, emboliform, globose, and fastigial nuclei. Of these, the dentate nucleus is the most clinically relevant as it relays the motor control output from the cerebellar hemispheres [5].
Sensory Pathways Spinothalamic (anterolateral) tract: This tract includes pain and temperature fibers. Sensory input from the dorsal root ganglia travels through Lissauer’s tract from the spinal cord, crosses through the anterior white commissure to the contralateral anterolateral pathway, ascends to synapse in the VPL nucleus of the thalamus, and projects through the corona radiata to somatosensory cortex [4]. Syringomyelia can affect this more centrally located tract in the spinal cord, causing bilateral cape-like dissociated sensory loss but sparing fine touch and proprioception [5,6]. Dorsal column-medial lemniscal tract: This tract includes vibration and proprioception fibers. Sensory input travels through dorsal columns, to gracile or cuneate fasciculi and nuclei, crosses in the dorsal medulla, ascends in the medial lemniscus to the VPL nucleus of the thalamus, and projects through the corona radiata to somatosensory cortex [4]. These tracts are affected in tabes dorsalis, a form of tertiary neurosyphilis and subacute combined degeneration caused by B12 deficiency, which leads to loss of proprioception and vibration perception and a positive Romberg sign [6]. These tracts are supplied by the posterior spinal arteries and therefore spared in anterior cord syndrome secondary to anterior spinal artery occlusion [5].
Motor Pathways Corticospinal tracts: These tracts serve as descending pathways for voluntary motor control. These fibers originate from the pyramidal cells of the primary motor cortex and travel through the posterior limb of the internal capsule, cerebral peduncle, and pontine belly to the medullary pyramid, where 90% of the fibers decussate to the contralateral side and descend in the lateral corticospinal tracts. Only about 10% of fibers remain ipsilateral in the anterior corticospinal tract (Fig. 75.7A) [4]. Motor tracts are affected in amyotrophic lateral sclerosis, corticobasal degeneration, and vitamin B12 deficiency. Wallerian degeneration is often seen distally in motor tracts when there is injury either to the pyramidal cells in the primary motor cortex (i.e., cortical infarction, tumor or amyotrophic lateral sclerosis), or to the more proximal descending axons (i.e., lacunar infarct in the coronal radiata or internal capsule) (Fig. 75.7B–F) [5,6].
FIGURE 75.7 Schematic anatomy of the corticospinal tracts (A) (Adapted from Henry Gray, Gray’s Anatomy, 1918). Acute Wallerian degeneration manifesting as long segment restricted diffusion (arrow) in the corticospinal tract: corona radiata (B), cerebral peduncle (C), pons (D), and medulla (E, F).
Cerebellar Networks Pontocerebellar tracts originate in the pons, cross the midline, and enter the cerebellum through the middle cerebellar peduncle (brachium pontis), which brings the input of the corticopontine fibers into the contralateral cerebellar cortex [4]. Ventral and dorsal spinocerebellar tracts bring sensory input from the spinal cord through the brainstem to the ipsilateral cerebellum through the superior and inferior cerebellar peduncles. These tracts are affected in vitamin B12 deficiency and spinocerebellar ataxia [6]. The cerebellar output to
cerebral cortex is carried although the superior cerebellar peduncle (brachium conjunctivum) into thalamic ventral anterior and ventral lateral nuclei after decussating in midbrain. The dentate nucleus, projecting to the contralateral red nucleus through the superior cerebellar peduncle, also decussates in the midbrain [5]. The red nucleus sends projections to the ipsilateral inferior olivary nucleus through the central tegmental tract, while the inferior olivary nucleus then projects back to the contralateral dentate nucleus through the inferior cerebellar peduncle. Interruptions of this pathway, also known as the “triangle of Guillain and Mollaret,” result in hypertrophic olivary degeneration, a type of trans-synaptic degeneration [16].
Language Networks The initial cortical processing of speech occurs in Heschl’s gyrus, along the superior temporal surface. The information then projects to the cortex flanking the posterior half of the superior temporal sulcus for phonological processing and representation. From here, language processing is carried along two distinct pathways, the ventral conceptual-semantic network and the dorsal articulatory pathway [4]. The dorsal articulatory pathway comprises the traditionally described strongly left dominant language network, which posteriorly includes Wernicke’s area at the lateral parieto-temporal junction. This region projects anteriorly through arcuate and superior longitudinal fasciculi onto the inferior frontal gyrus (Broca area) and superiorly onto the dorsolateral prefrontal cortex in the middle frontal gyrus, immediately in front of the precentral sulcus. The more recently understood ventral stream is relatively less left hemispheric dominant. This stream includes the posterior middle and inferior temporal gyri, which serve as lexical interface between phonological and semantic processing, and the anterior middle frontal gyrus and inferior frontal gyrus, which serve as part of the syntactical network [6]. Language networks are classically disrupted in middle cerebral artery infarcts and posterior temporal lobe and inferolateral frontal lobe tumors [17,18].
Olfactory System The olfactory system is comprised of numerous free nerve endings in the nasal mucosa that pass through the cribriform plate as the olfactory nerves and synapse in the olfactory bulb on each side. The nerve fibers then travel from the olfactory bulbs through the olfactory tracts located immediately below the gyrus rectus to reach the ipsilateral primary olfactory (piriform) cortex [4]. Olfaction is the only sensory technique that remains uncrossed in reaching the brain [19,22]. The olfactory nerve is considered the first of the 12 paired cranial nerves that pass through skull base foramina. However, like
the optic nerve it is not a peripheral nerve but rather part of the CNS and connects to the cerebrum instead of the brainstem.
Visual System Axons of the retinal ganglion cells converge at the optic disks and exit each globe as the optic nerves. Considered the second cranial nerve (CN II), the optic nerve is again embryologically part of the CNS and structurally a tract, surrounded by a CSF-containing meningeal sheath and myelinated by oligodendroglia instead of Schwann cells [4]. The optic nerve is frequently involved in CNS demyelinating disorders such as multiple sclerosis (MS) and neuromyelitis optica [6,19]. The arrangement of optic nerve fibers preserves the spatial orientation of light hitting different parts of the retina (visual somatotopy). The optic nerves enter the cranium through the optic canal, meet at the optic chiasm, and continue as the optic tracts. Fibers from the nasal (medial) portion of each retina cross to the contralateral side at the chiasm so that each optic tract carries fibers from the nasal half of the contralateral retina and the temporal half of the ipsilateral retina. The tracts project to the lateral geniculate nuclei of the thalamus and superior colliculi (located in the tectum or roof of the midbrain and mediating conjugate eye movements such as convergence and saccades) and to the calcarine cortex (also known as the primary visual cortex) through the optic radiations. The so-called direct pathway, representing the lower visual field, projects to the cortex on the superior bank of the calcarine fissure. The indirect pathway, representing the upper visual field and better known as Meyer’s loop, makes a “U” turn in the temporal lobe before terminating in the cortex on the lower bank of the calcarine cortex [5,20].
Auditory System Auditory information is carried by the cochlear nerve (also known as the auditory or acoustic nerve and part of the vestibulocochlear nerve, CN VIII). Cochlear nerve cell bodies are located in the spiral ganglion along the modiolus of the cochlea. The cochlear nerve passes through the internal auditory canal, immediately below the facial nerve and anterior to the superior and inferior divisions of the vestibular nerve, to synapse in the cochlear nucleus of the upper medulla. Most auditory input crosses into the contralateral superior olivary complex. From here, the lateral lemniscus ascends through the brainstem into the inferior colliculi and thereafter projects to the primary auditory cortex through the medial geniculate nucleus of the thalamus [4]. Many neurons in the auditory pathways cross at every
level of the auditory system. Thus, each auditory cortex receives input from both ears [5,21].
Additional Sensory and Motor Cranial Nerves The oculomotor nucleus is located in the midbrain ventral to the cerebral aqueduct and receives afferent input from cerebral cortex, cerebellum, pons, and medulla [12]. It consists of subnuclei innervating ipsilateral inferior rectus, inferior oblique and medial rectus, contralateral superior rectus, and both levator palpebrae superioris muscles. The nerve fibers travel anteriorly to exit the midbrain in the interpeduncular cistern [4]. These fibers merge with the preganglionic parasympathetic fibers from the Edinger–Westphal nucleus to form the oculomotor nerve (CN III). The nerve then courses anteriorly between the superior cerebellar and posterior cerebral arteries in the suprasellar cistern, immediately below the posterior communicating artery to the cavernous sinus along with trochlear nerve (CN IV) [5]. Note that the cavernous sinus contains the cranial nerves III, IV, V1, V2, and VI [35]. Inflammation or focal demyelination of the oculomotor nerve typically occurs near the root exit zone in the interpeduncular fossa and can be seen in ophthalmoplegic migraine, a type of cranial neuralgia presenting with headache and diplopia in children and young adults (Fig. 75.8). Compression by a ruptured or less commonly unruptured posterior communicating artery aneurysm is a well-known cause of acute, often partial, third cranial nerve palsy. This presents as ipsilateral pupillary dilatation (Fig. 75.9) [19,22].
FIGURE 75.8 Focal inflammatory enhancement of the left oculomotor nerve at the root exit zone (arrow) in a 10-year-old boy with ophthalmoplegic migraine. Note the normal appearance and course of the right oculomotor nerve (arrowhead).
FIGURE 75.9 Partial oculomotor palsy resulting from a partially thrombosed aneurysm of the left posterior communicating artery (arrowheads) seen on a time-of-flight MRA. The right oculomotor nerve (arrow) can be seen emerging below the posterior cerebral artery.
The trochlear nerve nucleus is situated near the midline, ventral to the cerebral aqueduct, while the fibers pass dorsally around the cerebral aqueduct. Decussating in the superior medullary velum, the trochlear nerve exits the dorsal surface of the midbrain, below the inferior colliculus. It then wraps anteriorly in the ambient cistern near the free edge of the tentorium and reaches the cavernous sinus immediately below the oculomotor nerve [4]. In the cavernous sinus, the trochlear nerve runs along the lateral wall immediately below the third nerve. Due to its very small caliber, the trochlear nerve is not consistently identified on 3 Tesla (T) MRI but can often be seen on high-resolution 7 T MRI (Fig. 75.10). Isolated trochlear nerve palsies can rarely result from compression by lesions of the quadrigeminal plate and ambient cisterns [19,22,24].
FIGURE 75.10 Right trochlear nerve (arrow) in the ambient cistern adjacent to the free edge of the tentorium (arrowhead) seen on a coronal T2-weighted 7 Tesla MR image. The superior cerebellar artery, posterior cerebral artery and basal vein of Rosenthal can be visualized in caudocranial order immediately above the nerve in the ambient cistern.
The abducens nerve (CN VI) innervates the lateral rectus muscle and abducts the ipsilateral eye. The sixth cranial nerve nucleus is located under the facial colliculus in the floor of the fourth ventricle. The seventh facial nerve (CN VII) motor nucleus is anterolateral to the sixth nerve nucleus in the lower pontine tegmentum. Fibers leaving the seventh nerve motor nucleus course posteromedially in the pons to pass around the sixth nerve nucleus in the facial colliculus [4,24]. The sixth nerve fibers pass anteriorly near the midline in the pontine belly and exit at the level of the pontomedullary junction. The sixth nerve then courses through the prepontine cistern and enters a small fibrous canal along the surface of the petrous apex, known as Dorello’s canal (Fig. 75.11). In Dorello’s canal, the sixth nerve is vulnerable to trauma and compression by increased intracranial pressure and petrous apex lesions. Proximity of the trigeminal and abducens nerves can result in
facial pain or dysesthesia in petrous apex lesions. The sixth nerve then enters the cavernous sinus, where it runs between the carotid artery and the trigeminal nerve branches [5]. The sixth nerve enters the orbit through the superior orbital fissure along with V1, oculomotor and trochlear nerves [19,22].
FIGURE 75.11 Abducens nerve (arrowheads) entering (A) and traversing (B) through the Dorello’s canal at the petroclival synchondrosis (arrows). Left petrous apex granuloma (C) expanding the petrous apex and obliterating the left Dorello’s canal; compare with normal right intracranial opening of the right Dorello’s canal (arrow). (Courtesy: Dr. Amit Agarwal, Mayo Clinic, Florida.)
The glossopharyngeal nerve (CN IX) is primarily a sensory nerve to the pharynx and posterior one-third of the tongue. It has two ganglia (superior and inferior) located near the jugular foramen [4,24]. The nerve leaves the medulla along with the vagus nerve in the retro-olivary sulcus and exits through the jugular foramen through the pars nervosa (Fig. 75.12) to run in the cervical carotid sheath. It receives contributions from the spinal trigeminal nucleus, the nucleus solitarius, the nucleus ambiguous, and the inferior salivatory nucleus [5,19,22].
FIGURE 75.12 Axial T2 (A) and gadolinium-enhanced T1-weighted MR images (B) depicting schwannoma of the left glossopharyngeal nerve. Note the normal course of the right glossopharyngeal nerve (arrowheads in A) from the retro-olivary sulcus to the pars nervosa of the jugular foramen. The schwannoma (S) can be seen extending in the pars nervosa medial and anterior to the jugular bulb (asterisk).
The vagus nerve (CN X) is a mixed sensory and motor nerve with general sensory afferent (external ear, tympanic membrane, and infratentorial dura), general visceral afferent (mucous membranes of the pharynx, larynx, trachea, esophagus, and gut to the splenic flexure of the colon), special visceral afferent (taste from epiglottis), special visceral efferent (muscles of larynx, pharynx, proximal esophagus levator veli palatine, and palatoglossus muscle), and general visceral efferent (preganglionic parasympathetic fibers to heart and abdominal organs) components [5,24]. It is the major motor nerve to the pharynx and larynx, thus serving critical functions in swallowing and speech. Also, it is the major source of parasympathetic innervation to the heart and abdominal organs [4]. Like CN IX, it has both a superior and inferior ganglion (called the nodose ganglion), which are located on the vagus nerve at the level of the jugular foramen. The vagus nerve exits the medulla immediately below the glossopharyngeal nerve and passes posteromedial to the glossopharyngeal nerve and posterior to the inferior petrosal sinus in the jugular foramen through the pars vasculosa (Fig. 75.13) [19,22,23].
FIGURE 75.13 A patient with neurofibromatosis type II. Oblique coronal reformatted T2 MR image (A) showing the vagus nerve coursing immediately below a schwannoma (arrow) affecting the glossopharyngeal nerve in the lateral medullary cistern. Axial black blood T1-weighted MR (B) image depicting small schwannomas of the left glossopharyngeal nerve (arrow) and vagus nerve in the jugular foramen (dotted arrow). Schwannomas of bilateral intradural spinal accessory (arrowheads) nerves and right hypoglossal nerve (curved arrow) can also be seen. Long thin arrow: inferior petrosal sinus. Internal carotid artery (labeled C); jugular bulb (labeled J).
The spinal accessory nerve (CN XI) is a pure motor nerve, innervating the sternocleidomastoid muscle and the superior component of the trapezius. CN XI arises from the spinal accessory nucleus, located in the high cervical cord from C1 to C5 [4]. The rootlets form a common trunk running superiorly to enter the skull through the foramen magnum and exit through the jugular foramen with CN IX and X (Fig. 75.13). Injury to this nerve typically occurs in the foramen magnum, jugular foramen, or in the carotid sheath [19,22,24]. Due to their proximity in the jugular foramen, CNs IX, X, and XI may be simultaneously involved in lesions of the posterior skull base such as metastasis, meningioma, jugular paraganglioma, and schwannoma [6]. The hypoglossal nerve (CN XII) is a pure motor nerve [5,6]. Hypoglossal nuclei are located in the posterior medulla, just anterior to the floor of the fourth ventricle. The hypoglossal nerve leaves the medulla in the ventrolateral sulcus between the pyramid and olive. The nerve then travels in the perimedullary cistern and exits through the hypoglossal canal in the skull base. The main function is to innervate the extrinsic and intrinsic muscles of the tongue. Its lesions cause hemiatrophy with fatty replacement, so-called “fatty atrophy” of the tongue. Hypoglossal nerve dysfunction may occur secondary to brainstem stroke, tumors involving the nerve and skull base, basilar meningitis, carotid dissection, trauma, inflammatory demyelinating neuropathy, and motor neuron disease. Synovial cysts, arising from the
craniovertebral junction and extending into the hypoglossal canal (Fig. 75.14), are a recently recognized cause of hypoglossal nerve palsy [19,22,24].
FIGURE 75.14 Axial T2 (A) and gadolinium-enhanced T1 (B); and coronal T2 (C) images showing a craniovertebral junction synovial cyst (arrows) encroaching upon the right hypoglossal nerve entering the hypoglossal canal (arrowheads) leading to hypoglossal nerve palsy. Note the normal left hypoglossal nerve entering the hypoglossal canal (curved arrow).
75.2
Brief Introduction to Neuroimaging Techniques Computed tomography (CT) and magnetic resonance imaging (MRI) are now the techniques of choice for imaging most suspected lesions of the brain. This and the following chapter are mainly devoted to their use in investigating intracranial pathology. Arteriography (CTA, MRA) and digital subtraction angiography (DSA): Modern technology has allowed the spatial resolution of computed tomography angiography (CTA) and magnetic resonance angiography (MRA) to become comparable to that of the “gold-standard” DSA [25]. CTA and MRA also provide additional information not available on DSA, such as status of the vessel wall and relation of vessels to adjacent intracranial structures. Therefore, noninvasive imaging, with the additional benefits of increased access and ease of acquisition, has become the preferred method for evaluating vascular lesions such as vaso-occlusive disease and aneurysms.
DSA is usually reserved for definitive diagnosis of select vascular lesions (i.e., dural arteriovenous fistula) and for endovascular procedures [26].
CT and MRI Image Display CT and MRI utilize a ray grayscale for depiction of cross-sectional anatomy in which the pixel brightness is proportional to either the x-ray attenuation coefficient or nuclear magnetic resonance (NMR) signal intensity of each corresponding tissue voxel (volume element). The ray grayscale intensity range, that is, the “window” (W) and the central intensity level (L) can be arbitrarily adjusted to optimize visualization. Standardizing W and L is of crucial importance in CT; the range of imaging options and signal variation in MRI mitigates against rigorous standardization although the basic principles still apply. Fig. 75.15 shows the relative density on the Hounsfield unit (HU) scale of the normal body tissues at CT. This HU is a universal ad hoc scale with air at −1000 HU and water at 0 HU as reference points. The cerebral white matter ranges between 25 and 35 HU, gray matter between 35 and 40 HU, and acute clotted blood between 60 and 70 HU. To optimize the visualization of brain on routine CT, L is typically chosen at 35 HU and W is spread over 80 HU to maximize gray and white matter contrast with tolerable perceived noise. The W can be narrowed arbitrarily to increase gray–white contrast, that is, in the detection of acute ischemic stroke but at the cost of greater perceived noise. Likewise, for optimal detection of extradural or subdural hemorrhage, the L is typically raised to 50–60 HU and W widened to 130–150 HU. Although tissue contrast in MRI depends mainly upon proton density and T1 and T2 relaxation times, other mechanisms also come into play, and absolute values show considerable variation according to acquisition technique and equipment used. Therefore, the default MR image display relies primarily on intrinsic tissue MR signal and contrast [3,26].
FIGURE 75.15 Hounsfield (HU) CT scale. The full scale extends below 0 HU to −1000 HU (the true zero of this scale, i.e., the attenuation of air). Head scans are obtained routinely at a window level (L) of 34–40 HU and a window width (W) of 0–80 HU.
Contrast Enhancement The signal arising from many normal structures and pathological conditions can be augmented using intravenous contrast material [3]. In CT, such enhancement is obtained by administration of a water-soluble iodinated compound; its relatively high atomic number (53), considerably increases the intravoxel electron density and leads to increased attenuation of the x-ray beam [26]. In MRI, this signal augmentation is commonly obtained with gadolinium-containing compounds, which lead to paramagnetic T1 shortening of nearby protons and signal increase on T1-weighted (T1w) MRI. These contrast agents do not penetrate the normal blood–brain barrier. A variety of brain conditions, including a majority of inflammatory and many neoplastic lesions, leads to the blood–brain barrier disruption, which then allows contrast agents to enter into the extracellular compartment of the
brain as well as pathological tissue. A much smaller amount of gadolinium is required to achieve enhancement on MRI compared with the concentration of iodine needed to achieve a similar result on CT. Therefore, contrast-enhanced MRI is much more sensitive than contrast-enhanced CT. Blood vessels, aneurysms, and vascular malformation enhance with contrast. This is the same for vascular structures such as choroid plexus [3]. Since gray matter contains considerably more blood than white matter, contrast between gray and white matter is accentuated by intravenous contrast agent administration. Generally, dura including the falx and tentorium normally demonstrate thin enhancement on volumetric or 3D T1-weighted MRI, particularly at 3T and higher field strengths. Leptomeningeal enhancement follows the surface contours of the gyri, sulci, and basal cisterns. In contrast, dural enhancement does not. Leptomeningeal enhancement typically results from infection (meningitis), inflammatory disorders such as sarcoidosis, leptomeningeal carcinomatosis, lymphomatosis, and conditions leading to gadolinium leakage through the leptomeninges such as acute arterial infarctions [27]. Dural or pachymeningeal enhancement may be seen with craniospinal hypotension, infections, metastasis, and pachymeningitis (idiopathic- or sarcoidosis-induced, granulomatous polyangiitis, and IgG4 disease, etc.) [28–30]. Outside CTA for the detection of vascular lesions (Fig. 75.16) or CT perfusion for characterizing ischemia, contrast is rarely utilized in brain CT imaging, as gadolinium-enhanced T1-weighted MRI is vastly superior for most other applications. Due to signal loss caused by susceptibility arising from its strong paramagnetic properties, gadolinium can also be used as a negative contrast agent on T2*-weighted MRI, that is, dynamic susceptibility contrast (DSC) MR perfusion imaging [3,26].
FIGURE 75.16 Cerebrovascular anatomy on CT angiography (CTA) in sagittal (A) and axial (B) views.
Aneurysms and vascular structures are best imaged immediately after contrast injection when blood concentrations of iodine are highest. Enhancement of lesions due to blood–brain barrier breakdown usually peaks 10–15 minutes after contrast injection [26]. Administration of intrathecal contrast allows performance of cisternography and myelography by CT and MRI. Although nonionic iodinated agents are routinely used for CT myelography and cisternography, safety of gadolinium-based agents is not yet established for MR applications and such usage remains off-label [26,31].
Field Strength Routine clinical MRI is performed at magnetic field strengths of 1.5 and 3T. Broadly speaking, while 1.5T MR is adequate for imaging of most routine brain conditions, 3T is superior for MRA and high-resolution MRI of cortex and hippocampus in epilepsy [11]. Higher field strength also accentuates T2* or susceptibility-weighted contrast and therefore, is also superior for susceptibility-weighted imaging (SWI), DSC perfusion, and blood oxygen level-dependent (BOLD) fMRI. Increasing the magnetic field strength increases the proportion of magnetized protons, thus improving the signal-tonoise ratio and allowing for greater spatial resolution with shorter scan duration. Hence, higher field strength scanners, especially 7T or higher, can better resolve finer anatomical details, particularly those of the hippocampus and cerebral cortex. However, ultrahigh field strength also leads to increased signal inhomogeneity due to magnet (B0) and radiofrequency (B1) field distortions and reduced contrast on T1-weighted sequences caused by
prolongation of T1 at higher fields. Further, ultrahigh-resolution imaging is also more susceptible to both subject and physiologic motion artifacts [31].
MRI Protocols Protocol choice in MRI is much wider than in CT. Most modern units no longer use conventional spin-echo sequences but instead use one or more of the newer fast scanning techniques. In practice, this generally entails the use of gradient-recalled echo (GRE) imaging for three-dimensional (3D) or volumetric acquisitions and fast spin-echo (FSE) for multislice (2D) acquisitions [3]. Also, FSE techniques are used mainly to demonstrate proton density and T2-weighted contrast. T1-weighted contrast is best displayed by inversion recovery (IR) or magnetization-prepared GRE techniques [39]. FSE acquisitions can be used to acquire dual echoes by generating proton density and T2-weighted images from each excitation as in conventional spin-echo techniques. In the head, GRE techniques are used mainly for volumetric acquisitions with T1-weighted contrast and usually with some form of tissue magnetization preparation, of which the simplest is IR preparation. IRprepared GRE (MPRAGE, BRAVO, IR-SPGR, etc.) is highly valuable in accentuating gray–white matter contrast, thereby allowing better detection of subtle cortical abnormalities such as focal cortical dysplasia (FCD) and more accurate segmentation of gray and white matter for volumetric analysis and voxel-based morphometry. Fluid-attenuated inversion recovery (FLAIR) depends on conventional T2weighted contrast and produces heavily T2-weighted CSF-nulled images by coupling an inversion pulse followed by a long inversion time with a long echo time [3]. FLAIR can enhance detection of lesions with conventional T2weighted spin-echo sequences and retain sensitivity of T1 relaxation, thus allowing enhancement with gadolinium-based contrast agents. Contrastenhanced FLAIR has exquisite sensitivity in detecting subtle changes in CSF composition and therefore, is ideally suited for evaluating leptomeningeal disease [28]. T2* GRE, particularly SWI, is sensitive to T2* signal decay caused by iron deposition and is routinely used to detect cerebral microbleeds seen in amyloid angiopathy and amyloid-related imaging abnormalities and chronic hypertension, superficial siderosis due to leptomeningeal hemosiderin deposition, and abnormal brain iron accumulation in neurodegenerative conditions such as multisystem atrophy and neuroferritinopathy [13]. More recently, fast spin-echo based MR techniques with variable flip angle evolution such as sampling perfection with application-optimized contrasts (SPACE and CUBE) have become available for 3D volumetric imaging for a variety of T1 and T2 image contrasts [32,33]. The routine MR brain examination in most centers remains a sagittal scout image or 3D T1-weighted GRE acquisition followed by an axial diffusion-
weighted imaging (DWI), T2*-weighted GRE or SWI, and FSE T2 and FLAIR acquisition. Postcontrast T1-weighted imaging is performed with 2D T1 SE or FSE in axial and coronal planes or with a single sagittal 3D T1weighted GRE or SPACE/CUBE, reformatted in axial and coronal planes as necessary [32,33]. Acquisition in the coronal plane is preferred in special situations, such as for hippocampal assessment in patients with epilepsy and dementia [11], detailed imaging of the pituitary gland and skull base [34] or better localization of lesions shown on other sequences. 3D magnetizationprepared GRE is preferred when specialized postprocessing is required, such as volumetry, morphometry, or surface rendering or registration. Highresolution 3D GRE or FSE imaging with submillimeter voxels, such as constructive interference steady state, fast imaging employing steady-state acquisition and SPACE are ideally suited for imaging of cranial nerves [35], vessel wall [36], membranous labyrinth [37], and the scolex in neurocysticercosis [38]. Two-dimensional, thin-slice, high inplane-resolution techniques can also be used for imaging small structures such as the pituitary gland, cranial nerves or internal auditory meatuses. Perfusion-weighted imaging can be produced by analyzing the signal change over time in region of interest after the administration of a bolus of intravenous contrast medium on both CT and MRI. Perfusion can also be assessed with techniques such as BOLD or arterial spin tagging [3,13]. Both T1 (dynamic contrast enhancement) and T2* (DSC) contrast properties of gadolinium-based agents can be exploited to achieve perfusion weighting. Highly accelerated T2* imaging for DSC and BOLD can be performed using echo-planar imaging. BOLD imaging has become routine in task-activation studies for presurgical functional brain mapping in tumors and epilepsy [31].
MR Techniques Using Tissue Properties Other Than Magnetic Relaxivity DWI and diffusion tensor imaging are achieved using strong magnetic gradients, typically with echo-planar imaging in routine clinical use [3,39]. Such strong gradients can lead to signal loss by incoherent phase shifts and consequent signal loss in tissues with rapid diffusion of water molecules, that is, the contrast depends on the diffusion coefficient of water. Diffusion behavior in brain is anisotropic, especially in white matter, and is greatest along the direction of the white matter tracts. Anisotropy is typically characterized by an elliptical diffusion tensor, the direction of which defines the longitudinal orientation of white matter tracts. Scalar DWI was initially used mainly in the evaluation of acute stroke but has also found widespread
clinical applications in characterization of disease processes. Interpretation of DWI and apparent diffusion coefficient (ADC) is summarized in Table 75.1. Diffusion tensor-based mapping of white matter tracts or tractography has become routine in surgical planning to prevent injury to critical motor and language networks [3,26]. Table 75.1 DWI and ADC Interpretation (White Block: High Signal, Black Block: Low Signal) D W I Diffusion restriction: acute ischemia, acute demyelination, abscess, inflammation, epidermoid, lymphoma, GBM Increased diffusion: CSF, cystic tumors, astrocytoma, vasogenic edema, gliosis, chronic demyelination T2 shine-through: many tumors, subacute infarct, subacute demyelination
Magnetic resonance spectroscopy integrates data from MRI and NMR. NMR can detect tissue metabolites such as N-acetylaspartate (NAA, a neuronal marker), choline (cell membrane), creatine (metabolism), lipids (necrosis), and lactate (anaerobic glycolysis), based on subtle variations in resonances of protons based on their specific molecular environments. Typically, tumors present with decreased NAA and elevated choline and lactate. Abscess typically shows decreased NAA and choline and elevated lactate, amino acid, and lipid peaks [40]. Detection of elevated lactate can also be useful in the diagnosis of mitochondrial encephalopathies such as Leigh’s disease, myoclonic epilepsy with ragged-red fibers and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. Similarly, detection of elevated glycine and NAA can characterize leukoencephalopathies due to nonketotic hyperglycinemia and Canavan disease, respectively [26]. Magnetization transfer contrast imaging exploits contrast from reduction in relaxed T1 magnetization induced by a broad-spectrum off-resonance prepulse [3]. This prepulse saturates the tightly bound water fraction in normal tissues and causes signal loss on T1-weighted imaging. In pathological tissues, this fraction of water bound to macromolecules/membranes is reduced, resulting in less reduction of relaxed
A D C
T1 magnetization. Magnetization transfer contrast is typically used to increase conspicuity of plaques in MS and corticospinal tract degeneration in amyotrophic lateral sclerosis [26].
Positron Emission Tomography Positron emission tomography (PET) imaging is based upon positronemitting radionuclide tracers such as 18F (i.e., 18F-fluorodeoxyglucose) and 11C isotopes (i.e., 11C-acetate or 11C-raclopride). The tracer, differentially taken up by the tissues, decays by emitting positrons [41]. The positrons collide with electrons to produce two antiparallel gamma rays, are detected as a coincidence by a circular array of detectors and are mapped onto a CT or MR image [41]. Based upon differences in glucose metabolism and molecular biosynthesis, PET can help differentiate tumors from non-neoplastic conditions including post-treatment changes in the brain. PET, using 18Ffluorodeoxyglucose, and amyloid and tau binding agents (i.e., 18Fflorbetaben, 18F-flortaucipir), is of considerable value in the diagnosis of Alzheimer’s disease and other neurodegenerative disorders, optimization of their clinical management and prognostication of outcomes in patients with mild cognitive impairment [42,43].
75.3
Basic Pattern Recognition Knowledge of brain anatomy is essential to identifying structural changes caused by intracranial disease. Even though a wide variety of pathological conditions can affect the brain, from the neuroimaging standpoint their appearances can be classified into a few essential patterns. Interpretation of brain images begins by identifying these basic patterns to broadly define the nature of the disease process. Thereafter, searching for progressively more specific or characteristic features helps narrow down the list of possibilities. Generating a final diagnosis or a narrow list of possibilities also requires the consideration of key features of clinical history, physical exam, laboratory findings, and change of imaging features over time. For example, a subacute infarct can be radiographically indistinguishable from a tumor, and a history of abrupt onset of symptoms can be the principal distinguishing criterion. Similarly, a rapidly growing ring-enhancing intra-axial lesion in a patient with bacteremia is more likely to be an abscess than metastasis. Many a
times, radiological interpretation serves as a guide to more tailored history and physical exam, strategies for high-yield laboratory tests, and further radiological imaging and tissue biopsy, if necessary [14,15]. That said, typical patterns in lesion locations and imaging characteristics allow an accurate detection and differential diagnosis in most cases by radiologists or even increasingly by automated methods [44–50].
Extra-Axial Versus Intra-Axial Radiographic characterization of an intracranial disease begins with determining whether it is intra-axial or extra-axial in location. Intra-axial processes are within the substance of the brain, while extra-axial processes occur outside the brain and pia mater [13,14]. Classic patterns of extra-axial and intra-axial pathology are exemplified by hematomas, which can occur in each location (Fig. 75.17). Extra-axial hematomas may occur in the epidural, subdural, or subarachnoid compartments; it is worth knowing classic features that differentiate these different types of hematomas (Table 75.2) and also considering other processes that occur in the different extra-axial compartments.
FIGURE 75.17 Extra-axial and intra-axial acute hematomas appearing hyperdense on CT. Biconvex epidural hematoma (A), crescentic subdural hematoma (B), and lobular parenchymal hematoma (C). The extra-axial epidural and subdural hematomas push the adjacent brain to the left or right. The intra-axial parenchymal hematoma is completely surrounded by brain tissue with low-density edema.
Table 75.2 Common Characteristics of Intracranial Extra-Axial Hemorrhage
Characte ristic
Epidural Hematoma
Subdural Hematoma
Subarachnoid Hemorrhage
Populatio n
Children, adults
Infants, elderly
Any
Incidence
Uncommon
Common
Common
Clinical presentati on
Lucid interval followed by unconsciousness
In older adults: fall with gradual decline In children: nonaccidental injury
Trauma, thunderclap headache, sudden onset of symptoms
Etiology
Trauma with skull fracture, lacerated middle meningeal artery
Between skull and dura, most commonly supratentorial
Between dura and arachnoid, most commonly supratentori al
Between arachnoid and pia, in cisterns, layering along the sylvian fissures or other sulci
Shape
Biconvex (lentiform)
Crescentic or curvilinear
Focal curvilinear in sulci
Cross suture lines
Usually no, but can cross, for example, the sagittal suture with a fracture at the vertex
Can cross
Characte ristic
Epidural Hematoma
Subdural Hematoma
Cross falx or tentorium
Can cross
Usually no, but can have unconnecte d hematomas
Subarachnoid Hemorrhage
A. Epidural processes which occur between the skull and dura: these processes include hematoma, abscess, and tumors of the skull such as metastasis and myeloma that may extend intracranially. Epidural lesions typically appear biconvex (lens shaped) and usually do not extend beyond sutures where the dura is tightly adherent to the skull. B. Subdural processes which occur between the dura and the arachnoid: these lesions include hematoma, empyema and hygroma. These lesions classically appear crescentic, cross suture lines, and follow dural reflections such as the falx and tentorium. Meningiomas and many other dural-based intracranial masses also occur in this space although rarely described as belonging to this compartment. C. Subarachnoid processes which occur between the arachnoid and pia in spaces typically containing CSF (sulci, cisterns such as the suprasellar and cerebellopontine angle cisterns, and fissures such as the interhemispheric and sylvian fissures): the typical pathologies of this compartment include subarachnoid hemorrhage, suprasellar and pineal tumors, arachnoid cysts, aneurysms and nerve sheath tumors.
Intraventricular lesions are considered extra-axial processes. The imaging features of extra-axial processes may include: peripheral location; incomplete confinement by the normal brain; effacement, compression, and displacement rather than brain infiltration; sharp interface between brain and lesion; broad dural base and obtuse angle at the lesion edge; contrast enhancement of the adjacent dura, the so-called “dural tail” sign [51]; involvement of two adjacent intracranial compartments; extension across the midline (exceptions include intra-axial lesions affecting commissures such as corpus callosum and third ventricle); and adjacent skull involvement. Meningioma is not only the most common extra-axial mass but is also the most frequent intracranial tumor [13]. With few exceptions such as metastasis, lymphoma, gliosarcomas, and malignant meningiomas, most intracranial tumors remain confined to their space of origin over time, that is, maintain their intra- or extra-axial localization. In large intracranial masses, intra- versus extra-axial determination can be challenging. Intra-axial processes occur within the brain parenchyma and include infarcts and hemorrhages, traumatic contusions, gliomas, metastasis, cysts, abscess, demyelination, neurodegeneration, vascular malformations, etc. [13]. Intra-axial disease processes frequently lead to disruption of the blood–brain barrier and produce expansion of the extracellular compartment in the surrounding brain by fluid leakage from the capillary bed known as “vasogenic edema.” Vasogenic edema primarily affects the white matter and
is characterized by hypodensity on CT and T2 hyperintensity on MRI, which follows the distribution of white matter tracts and subcortical U fibers. Although vasogenic edema is primarily seen surrounding intra-axial lesions, it is often also associated with extra-axial tumors and subdural empyemas [40]. Many intra-axial processes such as cerebritis and infiltrative gliomas are ill-circumscribed and blend imperceptibly; conversely, circumscribed gliomas, metastasis, demyelination, and abscesses have more distinct margins. In malignant gliomas, the infiltrative tumor can be impossible to distinguish from vasogenic edema. Rarely, an intra-axial mass can have “exophytic” growth into extra-axial space and be indistinguishable from primary extra-axial tumors. Location of the intra-axial lesions can help narrow down the differential diagnosis. For example:
◾ In MS there is preponderance of periventricular and callosal lesions ◾ Progressive multifocal leukoencephalopathy typically affects subcortical white matter ◾intracortical Isolated focal gyriform cortical involvement may be seen in arterial infarcts, certain tumors such as dysembryoplastic neuroepithelial tumor (DNET), seizures, or encephalitis ◾majority Traumatic brain contusions usually occur in cortex along the external surfaces, with the in frontobasal, temporal pole, and posteroinferior temporal locations ◾epidermoid) Midline posterior fossa masses either arise in the fourth ventricle (ependymoma, or cerebellar vermis (medulloblastoma) ◾ A slowly growing infiltrative mass in the pons is characteristic of a midline glioma ◾infarcts Bilateral paramedian cortical and subcortical hemorrhages are quite characteristic of venous due to sagittal sinus thrombosis ◾thrombosis Similarly, bilateral thalamic enlargement may be due to vein of Galen/straight sinus or rarely bithalamic glioma or lymphoma or bilateral arterial infarction due to occlusion of the basilar artery summit or the artery of Percheron [7,8,14]
Mass Effect Characteristically, hemorrhage, inflammatory processes, and tumors lead to increase in local tissue volume due to their intrinsic expansile nature as well as induction of vasogenic edema in the adjacent brain. Many other processes such as brain infarcts and traumatic contusions also lead to the development of the brain edema during their evolution, thus creating mass effect [15]. In the closed compartment of the cranium, mass effect not only leads to displacement and distortion of surrounding structures but also compression and decreased tissue compliance. This leads to reduced perfusion and venous congestion when severe. The primary source of mass effect could be within the brain (intra-axial) or ventricles (intra-ventricular) or outside the brain (extra-axial) in the meninges, CSF spaces, and skull. Although intra-axial mass lesions lead to compression and effacement of the CSF spaces (sulci and cisterns) in all directions, extra-axial masses lead to asymmetric expansion and effacement of these compartments.
Mass effect, midline shift, and herniation are essential features to assess in all brain images. Intracranial mass effect describes how a lesion displaces and compresses the adjacent structures. Lesions with mass effect can also cause midline shift or displacement of hemispheres across the midline, breaking the symmetry of the brain across the midsagittal plane. The term “herniation” is used to describe the displacement of brain structures in certain distinct locations, such as cerebellar tonsillar herniation below the foramen magnum and central herniation of the brainstem, which obliterates the perimesencephalic and perimedullary cisterns [4]. Transtentorial herniation occurs when the midbrain is displaced and compressed in the tentorial hiatus by the medial and downward displacement of the uncus and parahippocampal gyrus (Fig. 75.18A, B). As a result of severe crowding and compression against the tentorial free edge, uncal or transtentorial herniation can be complicated by posterior cerebral artery infarction, oculomotor nerve dysfunction leading to fixed dilated pupil and ipsilateral hemiparesis from compression of the cerebral peduncle against the tentorial free edge. Duret hemorrhage (Fig. 75.18C) can also occur in the midbrain or pons from venous compression in the setting of transtentorial herniation [12,14]. Ascending transtentorial herniation is sometimes used to describe upward displacement of the cerebellar vermis through the tentorial hiatus in posterior fossa mass lesions [13].
FIGURE 75.18 Transtentorial and subfalcine herniation on axial T2/FLAIR MRI (A, B). High-grade glioma with mass effect causes uncal and parahippocampal gyrus herniating below the free edge of tentorium cerebelli and compressing the midbrain (black arrow) and subfalcine herniation below the free edge of falx cerebri (white arrow). Duret hemorrhage (curved arrow) in midbrain complicating transtentorial herniation caused by large right intracerebral hematoma (C).
Subfalcine herniation occurs when the cingulate gyrus is displaced across the midline below the free edge of the falx cerebri and can later progress to additional structures including the corpus callosum and subcortical nuclei.
One clinical complication of subfalcine herniation is lower limb hemiparesis due to compression of the anterior cerebral artery branches supplying the paracentral lobule [4,6].
Volume Loss Brain tissue volume loss characterizes neurodegenerative processes and is typically accompanied by astrocytic gliosis in late stages of inflammatory disease, infarcts, intra-axial hematomas, and trauma [14]. Astrocytic gliosis is hypodense on CT and hyperintense on T2-weighted MRI. Diffuse or regional brain volume loss or cerebral atrophy, in the absence of an antecedent process such as trauma, infarct or inflammation, is a typical feature of aging and neurodegeneration. Distinct patterns of regional or lobar cortical atrophy in patients with cognitive decline or behavioral disturbances serve as markers of neurodegenerative conditions, such as Alzheimer disease (AD) and frontotemporal dementia (FTD) [4,42]. Distinct variants of AD include posterior cortical atrophy or logopenic variant primary progressive aphasia. Additional forms of neurodegeneration with etiologies distinct from Alzheimer pathology include vascular contributions to cognitive impairment and dementia (i.e., sequelae of atherosclerosis, small vessel ischemic disease, and infarcts), Lewy body disease, LATE, FTD, corticobasal syndrome, and progressive supranuclear palsy [55]. Encephalomalacia (brain softening) refers to end-stage astrocytic gliosis and cavitation ensuing from neural tissue loss from infection, ischemia, and hemorrhage, etc. Demyelinating diseases and blunt head trauma can also lead to diffuse brain atrophy [6]. Because the skull forms a rigid closed compartment, CSF spaces (ventricles, sulci, and cisterns) expand to make up brain volume loss. Ventricular enlargement of this type is called ex vacuo dilatation or hydrocephalus ex vacuo (Fig. 75.19) and should be distinguished from hydrocephalus caused by a blockage of CSF circulation or resorption [15].
FIGURE 75.19 Hydrocephalus ex vacuo and cortical atrophy on FLAIR MRI can be bilateral (A) for example due to diffuse adrenoleukodystrophy or unilateral (B) (right) due to periventricular multiple sclerosis, causing right lateral ventricle expansion.
Gray Matter Versus White Matter and Cortical Versus Subcortical Many diseases predominantly affect the cortical gray matter while certain disease processes are relatively restricted to white matter (Table 75.3 and Fig. 75.20) [13–15]. Table 75.3 Neurological Diseases by Gray/White Matter Localization Predominantly Cortical Gray Matter
▪ Microvascular ischemia or Binswanger disease ▪ Microangiopathy: Susac syndrome
Predominantly Cortical Gray Matter
Predominantly White Matter
Neurodegenerative conditions: AD and FTD
Prototypical demyelination: multiple sclerosis and neuromyelitis optica
Mesial temporal sclerosis
Rare/uncommon demyelination: osmotic demyelination and Marchiafavi–Bignami disease
Cortically based neoplasms: dysembryoplastic neuroectodermal tumor and ganglioglioma
Inherited metabolic: adrenoleukodystrophy and metachromatic leukodystrophy
Acute hypoxemic–ischemic and hypoglycemic injury
Viral and postviral demyelination: acute disseminated encephalomyelitis and progressive multifocal leukoencephalopathy
Metastases and abscesses tend to occur at the junction of gray and white matter (Fig. 75.20) [13].
FIGURE 75.20 Juxtacortical metastases (arrow) on postcontrast FLAIR MRI appearing as ring-enhancing metastasis at the border of gray and white matter with surrounding FLAIR hyperintense vasogenic edema in the left anterior temporal lobe. Vasogenic edema is also seen in the left frontal lobe due to another metastatic lesion not included in this image.
However, many disease processes, such as infarcts, contusions, and infiltrative gliomas, can affect both gray and white matter. MS demonstrates white matter disease early in its course and later onset of gray matter atrophy after repeated periods of relapses or progression [52,53]. Some pathologies are generally localized to subcortical structures like the basal ganglia and thalami. Some processes are usually unilateral (although
can also be bilateral), whereas others predominantly involve bilateral subcortical structures (Fig. 75.21 and Table 75.4) [7].
FIGURE 75.21 Bilateral subcortical lesions (arrows). CADASIL can show FLAIR hyperintensity of the lentiform nucleus due to lenticulostriate arteries vasculopathy (A). Artery of Percheron supplies both thalami from a single posterior cerebral artery, so infarct causes bilateral thalamic FLAIR hyperintensities (B). Calcinosis of the striatum in Fahr disease appears T1 hyperintense (C). Manganese in the globi pallidi is T1 hyperintense (D).
Table 75.4 Neurological Diseases of Subcortical Gray Matter Structures With Either Predominantly Unilateral or Bilateral Localization Predominantly Unilateral Subcortical Structures (Can Be Bilateral)
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)
Cerebrotoxoplas mosis: basal ganglia
Arboviral encephalitis: West Nile or Eastern equine encephalitis virus
Predominantly Unilateral Subcortical Structures (Can Be Bilateral)
Predominantly Bilateral Subcortical Structures
Hypertensive hemorrhage: basal ganglia and thalami
Wilson disease: bilateral basal ganglia and anterolateral thalami
Lenticulostriate and thalamostriate infarcts
Toluene poisoning: thalami
Midline glioma: thalamus (and brainstem)
Carbon monoxide poisoning: globi pallidi
▪ Paramagnetic mineral deposition: calcium in striatum (Fahr disease), manganese in globi pallidi, neurodegeneration with brain iron accumulation (NBIA): globus pallidus eye of the tiger sign ▪ Leigh disease: putamen, cerebral peduncles, periaqueductal gray
Some pathologies have unique cortical and subcortical features. Creutzfeldt–Jakob disease causes hyperintensity on DWI and hypointensity on ADC (diffusion restriction) and T2 hyperintensity of both the cortex (“cortical ribboning”) and basal ganglia (Fig. 75.22) [6,7]. Diffusion restriction in acute hypoxic ischemic encephalopathy can occur in gray matter throughout the brain. Infarcts, tumors, and many additional pathologies can also span both cortical and subcortical locations [7].
FIGURE 75.22 Creutzfeldt–Jakob disease. DWI (A) and FLAIR T2 (B) MR showing cortical ribboning (arrowheads) and bilateral caudate and putaminal hyperintensity in a patient with rapidly progressive behavioral change, rigidity and gait disturbance.
Focal Versus Multiple Versus Diffuse Many lesions are generally focal (single or solitary), such as most primary brain tumors and hypertensive hemorrhage. Other lesions are typically multiple, such as small vessel ischemic disease, MS, neurocysticercosis, toxoplasmosis, etc. [13]. Metastases are usually multiple but could be solitary. Bacterial abscesses tend to be solitary but could be multiple. Infarcts and lymphoma can be single or multiple. Glioblastoma can appear focal or multifocal/multicentric on imaging but may in fact be more diffuse histologically. High-grade primary brain tumors and metastatic disease can also disseminate in the CSF space. A leukodystrophy would be an example of a disease process affecting white matter fairly diffusely [15].
Homogeneous Versus Heterogeneous and Cystic Versus Solid Homogeneous signal denotes lesions with relatively uniform MR signal and density. Meningiomas are typically homogenous on both CT and MRI, whereas glioblastomas are typically heterogenous. Heterogeneous signal occurs in lesions that have mixed tissue elements, necrosis, hemorrhage,
calcification, or cystic change. Heterogeneity is best assessed on MRI (Fig. 75.23) [13].
FIGURE 75.23 Heterogeneous appearances of glioblastoma. Ringed FLAIR hyperintensities of a biopsied midline tumor lesion (A, arrow). Heterogeneous lesion with mass effect and edema (B, arrow). Classic “butterfly-shaped pattern” of high-grade glioma crossing the splenium of the corpus callosum (C, arrow).
Cystic brain lesions are fluid-filled sacs that may contain CSF, pus, serous, or serosanguinous fluid. Besides true cysts, the following can have a cystic appearance: primary brain tumors, metastasis, abscess, tuberculoma, and neurocysticercosis, etc. On CT and MRI, cystic lesions frequently show ring enhancement of the cyst wall. Purely CSF-containing cysts like arachnoid cysts follow CSF signal intensity on MRI and typically do not show wall enhancement [54]. Other cystic lesions are often hyperintense on T2/FLAIR due to the presence of proteins and other macromolecules in the fluid content [13]. Peripheral or ring enhancement after contrast administration is frequent in many disease processes. A helpful mnemonic is MAGIC DR, which stands for the following (Fig. 75.24 and Table 75.5).
FIGURE 75.24 Ring enhancement on postcontrast T1 MRI. Bilateral cerebellar metastases (A, arrow). Multifocal primary CNS lymphoma (B, arrows). Toxoplasma abscess with ring and partially ring-enhancing lesions (C, arrows). Acute demyelination in multiple sclerosis (D, arrow).
Survey of Benign Brain Lesions Here, we explore a diverse array of benign brain abnormalities, including cysts, neuroendocrine diseases, vascular, infectious, demyelinating and inflammatory lesions, and epilepsy.
Benign Cysts
Benign Cysts Arachnoid Cyst Arachnoid cysts are congenital arachnoid-lined non-neoplastic cysts that expand by CSF accumulation between arachnoid membranes. They may be found anywhere around the brain but are seen commonly along the cerebral convexities (especially at the temporal pole, in the sylvian fissure, cerebellomedullary cistern, and suprasellar region [3]. Arachnoid cysts are usually unilocular, but septated cysts can occur [54,56]. Acquired subarachnoid cysts can also occur secondary to traumatic or inflammatory conditions result from trapping of CSF by arachnoid scarring and loculation. Arachnoid cysts follow CSF density and signal on CT and MRI, respectively, which helps distinguish them from other types of cysts or posttraumatic or postinflammatory collections. Hypoplasia of underlying cerebral tissue such as the temporal pole is considered by some to be representation of coexistent congenital malformation and by others as consequence of mass effect. Large cysts can cause cranial asymmetry due to osseous remodeling [54,56]. Cysts may be associated with headaches, seizures, focal neurologic deficits, and developmental delay; however, note that most arachnoid cysts are found incidentally on imaging [3]. In neonates or small infants, the cysts may be diagnosed by ultrasound, but in older children and adults, they are diagnosed by CT or MRI (Fig. 75.25). They usually lie in one of the classic sites mentioned above, are of CSF density, and have no enhancing capsule or adjacent calcification on CT [3,54,56].
FIGURE 75.25 Arachnoid cysts. Axial CT showing a left temporal pole cyst (A). Axial MRI showing a supracerebellar cyst (B).
With suprasellar arachnoid cysts, the differential diagnosis includes Rathke’s cleft cyst, craniopharyngioma, and occasionally a grossly dilated third ventricle. In the quadrigeminal cistern, a dilated suprapineal recess or cystic pineal tumor may need consideration [10,54,56]. Localized trapping of CSF within cerebral sulci or along the interhemispheric fissure in adults [54,56] may mimic arachnoid cysts. Such localized ballooning of sulci may be accompanied by dilatation of the sylvian fissures and enlargement of ventricles in nonobstructive, normal pressure hydrocephalus (Fig. 75.26).
FIGURE 75.26 Dilated “trapped” sulcus mimicking arachnoid cyst on CT in the left parietal lobe before (A) and after (B) cyst and ventriculoperitoneal shunt placements in a patient with progressive cognitive impairment, “magnetic gait” and urinary incontinence, consistent with normal pressure hydrocephalus.
Colloid Cyst These cysts likely derive from the paraphysis and have been termed paraphyseal cysts. The paraphysis is a gland normally found in the human fetus at one stage of development but later disappears; its function is unknown. The cyst lies in the roof of the third ventricle behind the foramen of Monro and contains amorphous gelatinous material (colloid). Because of its position, the cyst can give rise to intermittent obstruction of the foramen of Monro and hydrocephalus even when quite small [57]. These cysts usually present in adults at any age but are also seen in children. They are usually 1–2 cm in diameter [3,54,56,57]. CT appearance is usually diagnostic on unenhanced scans, showing a small high-density spherical cyst at the base of the septum pellucidum in the region of the foramen of Monro (Fig. 75.27A), with or without enlargement of the lateral ventricles [3].
FIGURE 75.27 Colloid cyst. Unenhanced CT (A) with typical round hyperdense colloid cyst (arrow) at the foramen of Monro. FLAIR (B) and postcontrast T1-weighted (C) MRI images from a different patient show a cyst at the foramen of Monro causing obstructive hydrocephalus with enlarged ventricles and periventricular (transependymal) edema. The cyst does not enhance but there are displaced vessels along its margins.
On MRI, colloid cysts show variable hyperintense signal on T2 and FLAIR images, sometimes with a low signal center (Fig. 75.27B) and are iso- to hyperintense to surrounding brain on T1-weighted images. Marginal enhancement may rarely be seen either reflecting the cyst capsule or surrounding stretched veins (Fig. 75.27C) [54,57]. Cyst of the Septum Pellucidum The double septum or fifth ventricle is due to the abnormal persistence of the fetal cavum septi pellucidi. Ultrasound shows that this is present in over one-
third of neonates. The incidence falls rapidly through childhood but nevertheless the condition persists in 1–2% of adults as a normal variant on CT or MRI (Figs. 75.28A and 75.29A) [54,56] or may occur due trauma.
FIGURE 75.28 Cavum septi pellucidi (A): C, corpus callosum; F, fornix; CS, cavum septi pellucidi. Cavum septi pellucidi and cavum vergae (B): V.I., velum interpositum; CV, cavum vergae; 3, third ventricle. From [3].
FIGURE 75.29 Cyst of the septum pellucidum (A, arrow) that is continuous with cyst of the cavum vergae (B, arrow) in a patient with diffuse white matter hyperintensity secondary to HIV encephalopathy on axial T2/FLAIR MRI.
Cyst of the Cavum Vergae This so-called “sixth ventricle” is a backward extension of the septal cyst, only rarely seen in isolation. Anatomically, it lies beneath the posterior part of the corpus callosum with the velum interpositum below (Fig. 75.28B). On axial MR sections, the cavum vergae appears as a rectangular structure continuous with a septal cyst anteriorly, both following CSF signal (Fig. 75.29B). It should not be confused with the velum interpositum (Fig. 75.28), another CSF-filled space above the third ventricle that can be enlarged. On axial images, the latter is triangular in shape with the apex lying anteriorly, below the columns of the fornix with the internal cerebral veins along its inferior aspect. Fig. 75.30 shows a cyst of the velum interpositum [3,56].
FIGURE 75.30 Velum interpositum cyst (asterisks). Sagittal T1weighted (A) and axial T2-weighted MRI (B) images show an enlarged cystic space (asterisks in A, B) at the midline between the posterior corpus callosum, lateral ventricles, and third ventricle. The fornices are elevated and internal cerebral veins are displaced inferiorly around the cyst.
Rathke Cleft Cyst Rathke cleft cysts are benign mucoid epithelial cysts arising from the remnants of Rathke’s pouch and primarily occurring within the sella turcica [10], located between the anterior and posterior lobes of the pituitary gland (Fig. 75.31). They are usually asymptomatic unless large in size, when they may cause pituitary endocrine dysfunction, visual disturbances, or headaches.
Intrasellar Rathke’s cleft cysts should be differentiated from cystic pituitary adenomas and rarer suprasellar Rathke’s cleft cysts from craniopharyngiomas. Rathke’s cleft cysts are benign thin-walled unilocular cysts, which do not recur after simple excision. They have no solid components and do not calcify. Histologically, they are lined with cuboidal or columnar epithelium and contain mucinous cyst fluid, often brownish in color. Craniopharyngiomas, in contrast, are lined by squamous or basal cell line epithelium [10,58].
FIGURE 75.31 Typical intrasellar Rathke cleft cyst (A and B, arrows) located immediately beneath the infundibular attachment between adenohypophysis anteriorly and neurohypophysis posteriorly. The cyst is intrinsically hyperintense on unenhanced T1-weighted sagittal MR image and shows enhancement of only the cyst wall. Suprasellar Rathke cleft cyst located immediately anterior to the posteriorly displaced infundibulum (C and D). Enhancement of the thin cyst wall can be seen on sagittal T1-weighted midline MR image (C) and highly characteristic intracystic low signal nodule is present on T2-weighted coronal MR image (D, arrow).
The density and signal characteristics of the cyst on imaging will depend on its content. CT shows a round mass in the sella or suprasellar cistern without calcification. Density varies from that of CSF to more solid-looking when the contents are viscid and proteinaceous. The capsule may then enhance slightly, resembling a cystic craniopharyngioma [10,58]. On MRI, cysts with serous fluid are of similar signal characteristics to CSF, but those with proteinaceous fluid are of high T1 signal. An inconsistently present dark intracystic nodule on T2-weighted MRI is quite pathognomonic. Their characteristic midline location helps to distinguish intrasellar Rathke cleft cysts from cystic adenomas, which tend to be eccentric in location and
may show hemorrhage with fluid–fluid levels [59]. Thin cyst wall enhancement may be seen with Rathke’s cleft, but there is no nodular enhancing component as in craniopharyngioma. Displacement of the infundibulum is easily detectable on MRI (Fig. 75.31) [10,54,58]. Ependymal Cyst These very rare cysts are lined by a thin wall of ependyma and can be intraor paraventricular. The latter can resemble a hydatid cyst on CT and show no marginal enhancement [3]. Large intraventricular ependymal cysts can resemble unilateral hydrocephalus since they usually occur in the lateral ventricle and their wall is difficult to define on CT. Intrathecal/intraventricular contrast has been used to establish a diagnosis by outlining the cyst within the opacified ventricle [54].
Benign Tumor-Like Cysts Epidermoid Cyst Histologically, epidermoid cysts have a thin capsule of epidermis (squamous keratinized epithelium) and contain desquamated epithelial debris and cholesterol, which lead to their metallic or “pearly” sheen. They usually present in adults and are most commonly seen in the cerebellopontine angle or suprasellar region in the subarachnoid space. Other sites include the sylvian fissure and in the ventricles. The exact site of origin is often difficult to determine as these lesions can extend around blood vessels and nerves as they grow in the subarachnoid space. The margins may be irregular although sharp, and there is no true invasion of adjacent brain [3]. On CT, the cysts usually have low density, that of CSF or slightly higher, depending on the contents. Calcification is unusual but flecks of calcification have occasionally been noted in the capsule. They may be difficult to differentiate from arachnoid cysts [3,14]. MRI signal characteristics and appearances depend on relative proportions of cholesterol (short T1) and keratin (long T1) within the cyst. They are usually isointense or slightly hyperintense to CSF on T1 and bright like CSF on T2-weighted images. On heavily T2-weighted and FLAIR MR images, their internal keratinized matrix can often be appreciated (Fig. 75.32). On T2/FLAIR, their signal typically does not fully suppress due to proteinaceous contents, unlike the signal of arachnoid cysts, which does suppress like that of CSF. Diffusion-weighted sequences may also be helpful in differentiating epidermoid cysts from arachnoid cysts. Since arachnoid cysts have free water diffusion, they completely lose their T2 signal on DWI. Epidermoid cysts have more restricted diffusion due to the presence of epithelial debris; hence, their T2 signal is partially retained, and they typically appear hyper- or isointense
to the brain on DWI. Epidermoids often expand the cisterns from which they arise and distort adjacent brain structures creating lobulated or scalloped margins (Fig. 75.32). Although extra-axial origin remains apparent, the larger lesions may invaginate deeply and falsely appear to invade the parenchyma. Surgical resection of such epidermoids is, therefore, often incomplete. There is complete lack of enhancement except for along the margin on occasion [54].
FIGURE 75.32 Epidermoid cyst. Axial MR images show mass effect from a left cerebellopontine angle cistern epidermoid cyst (asterisk). The cyst is bright on T2-weighted imaging (A) but does not lose signal like CSF on FLAIR (B) and is notable bright on diffusion-weighted imaging (C) due to diffusion restriction.
Dermoid Cyst Dermoid cysts are more complex than epidermoids and more slow-growing. As rare entities, they arise from entrapment of embryonic ectoderm into the neural tube in early gestation and typically occur near the midline. Their wall contains full-width dermis, which may contain hair and sebaceous glands, and an outer layer of connective tissue and capsule. The cyst may contain matted hair and glandular secretions as well as desquamated keratinized epithelium. These lesions usually present in the third decade of life with chronic headache and other nonspecific symptoms [3]. Occasionally, they may be associated with seizures, focal neurologic deficits, and aseptic meningitis. Gradual enlargement may occur from glandular secretions and epithelial debris accumulation. Rupture of dermoid cysts spontaneously or iatrogenically at surgery can result in severe chemical meningitis that can be complicated by vasospasm and infarction. They can present in children in the midline at the base of the brain or near the fourth ventricle. The latter may show an occipital skin dimple with a stalk leading through bone and can become infected [54,56]. Arc-like calcification, occurring in the capsule, is seen in 20% of cases [54].
On CT, dermoid cysts are well-circumscribed fat density masses without contrast enhancement and are usually more rounded than epidermoids (Fig. 75.33). They are seen in the posterior fossa near the midline or above the floor of the anterior fossa, but they can occur over the convexity and elsewhere. Capsular calcification occurs more commonly than with epidermoids [3]. Rupture of a cyst may occur, with escape of the fatty contents into the CSF, resulting in chemical meningitis followed by arachnoid scarring and hydrocephalus; rupture into the ventricle has also been reported, and this has been recognized at CT by a fat–fluid level [14,54].
FIGURE 75.33 Ruptured dermoid in quadrigeminal plate cistern with scattered intraventricular fat droplets. Axial CT (A), axial-unenhanced T1-weighted (B), and axial T2-weighted (C and D) MR sections with demonstrate a mass with fat density (A) and high T1 signal (B) and intraventricular fat droplets (arrows). Chemical shift artifact due to fat causes bright and dark borders along the anterior and posterior margins of the primary mass and the intraventricular droplets (C and D: arrowheads).
On MRI, dermoids show high signal on T1-weighted images due to the presence of fat and vary from hypo- to hyperintense on T2-weighted images. Chemical shift artifact is frequently visible, indicating the presence of fat on T2-weighted images. There is typically no contrast enhancement or vasogenic edema in the surrounding brain. Serpiginous hypointensities may be seen if containing hair. Mural calcification can sometimes be identified on MR [3,56]. On both CT and MR images, fat density and high T1 signal droplets may be seen scattered throughout the subarachnoid space, often remote from the lesion or in the ventricular system if rupture has taken place. Dermoids without fat or calcification may be indistinguishable from epidermoids or arachnoid cysts; the presence of material other than fat within a lesion is also useful in distinguishing dermoids from intracranial lipomas. See Table 75.6 for further comparison of epidermoid and dermoid cysts [54]. Table 75.6
Comparison of Epidermoid and Dermoid Cysts Epidermoid
Dermoid
Path olog y
Ectodermal inclusion cyst with keratin and cholesterol but no dermal structures and rarely rupture
Ectodermal inclusion cyst with keratin, cholesterol, and dermal structures (hair, sebaceous glands) and may rupture
NECT: low density (like CSF) with uncommon calcification CECT: occasionally enhancing peripherally
NECT: low density (like fat) with common calcification CECT: no enhancement
MRI
Often isointense with CSF
T1 hyperintense, T2 hypo- to hyperintense
Neuroendocrine Diseases Pituitary Apoplexy This condition results from ischemia or hemorrhage of the pituitary gland, typically due to a previously undiagnosed pituitary adenoma (Fig. 75.34). Additional causes and predisposing associations include hypertension, trauma, and medications (anticoagulation, hormones). The classic clinical presentation involves acute headache, visual field defects due to compression of the optic chiasm, and diplopia if involving the cavernous sinus [60,61]. Long-term symptoms include endocrine dysfunction secondary to hypopituitarism and adrenal insufficiency. MRI, particularly DWI and GRE, reveals infarct and/or hemorrhage [61–63].
FIGURE 75.34 Pituitary apoplexy. CT showing a markedly expanded sella due to large pituitary adenoma (A, arrow) extending into the suprasellar cistern in a patient who presented with acute onset headache, visual field defects, and right abducens palsy. On sagittal T1unenhanced MRI, the sellar/suprasellar mass shows large subacute hemorrhage appearing as high signal T1 (B, arrow) and a fluid level with mixed high and low signal on axial T2 MR (C, arrowhead), indicating the presence of deoxyhemoglobin and methemoglobin in the subacute hemorrhage. Involvement of the right cavernous sinus accounts for the right abducens palsy (C, arrow).
Sheehan Syndrome This is a rare but potentially life-threatening condition associated with postpartum hemorrhage and/or hypovolemic shock, which triggers ischemic necrosis of the pituitary gland. Neuroendocrine sequelae include failure of lactation and rapidly developing panhypopituitarism. Variable pituitary gland enlargement with abnormal signal due to patchy central ischemic necrosis and hemorrhage and an abnormal lack of enhancement in the central portions of the gland (Fig. 75.35) are the typical radiologic findings of acute Sheehan’s syndrome. In chronic stage, there is marked glandular atrophy with an empty appearing sella [62,64]. Commonly on the differential diagnosis is peripartum/postpartum lymphocytic hypophysitis [64,65].
FIGURE 75.35 Sheehan syndrome. Postpartum necrosis of the pituitary gland appearing as lack of central enhancement on coronalenhanced T1-weighted MRI.
Empty Sella The “empty sella syndrome” rarely causes neuroendocrine sequelae (Fig. 75.36). An empty sella may be classified as primary or secondary.
FIGURE 75.36 Empty sella in a patient with pseudotumor cerebri. Sagittal CT reformat (A, arrow) showing moderately expanded fluid dense sella without visible pituitary gland. Sagittal T1 (B, arrow) and coronal T2 (C) MRI shows the normal pituitary gland flattened against the sellar floor by intrasellar herniation of the suprasellar cistern.
◾through Primary empty sella is caused by herniation of suprasellar arachnoid and CSF into the sella the normal opening in the diaphragm sellae for passage of the infundibulum. The pituitary gland is compressed against the back and floor of the sella causing much or most of the sella to be occupied by CSF. An empty sella may be asymptomatic and an incidental finding at imaging or autopsy for other causes. However, an empty sella should be recognized as evidence of elevated intracranial pressure that can cause headaches (idiopathic intracranial hypertension, aka pseudotumor cerebri), particularly in middle-aged women and associated with obesity [67]. Visual field defects can occur due to prolapse of the optic nerve or chiasmal tissue into the empty sella. The sella itself is often enlarged, presumably from pulsating CSF, and this, together with the clinical findings, can lead to an erroneous diagnosis of pituitary cyst [66] Secondary empty sella may occur after hypophysectomy or tumor removal, spontaneous pituitary infarction (i.e., Sheehan syndrome), radiation therapy, immune checkpoint inhibitorassociated hypophysitis or infectious/autoimmune etiologies [3,62,67]
◾
Vascular Lesions Vascular Compression of Cranial Nerves by Dolichoectatic Arteries Dolichoectasia is the dilation and kinking of a tortuous vessel due to abnormal vessel shape and flow, which can lead to compression of cranial nerves and brain parenchyma. Direct observations at surgery led to the theory that tortuous vessels compressing the trigeminal nerve root exit zones can be a cause of trigeminal neuralgia. The compression is usually due to a tortuous branch of the superior cerebellar artery. Advances in MRA and highresolution imaging have made noninvasive detection possible [3,8,13]. It is also now well recognized that hemifacial spasm can also be due to tortuous arteries arching into the pontomedullary junction and impinging on the facial nerve exit zone. The arteries implicated are either the vertebral artery, the anterior inferior cerebellar artery or the posterior inferior cerebellar artery. Other cranial nerves which may be affected by vascular compression
include the vestibulocochlear nerve, giving rise to tinnitus and vertigo, and the glossopharyngeal nerve, leading to glossopharyngeal neuralgia. It is thought that dolichoectasia of the vertebrobasilar system may also cause tension in small-caliber arteries (such as pontine perforator arteries), thereby decreasing flow to the brainstem and potentially causing stroke or basilar migraine [3,8].
Arteriovenous Malformation Arteriovenous malformations (AVMs) are abnormal intra-axial connections between cerebral arteries and veins without a capillary bed and involve the brain parenchyma and overlying meninges. Sometimes incidentally found, they may present with acute intraparenchymal or subarachnoid hemorrhage. Other manifestations include headache and seizures [68,69]. Patients presenting with hemorrhage will usually show an intracerebral hematoma recognizable by its characteristic density; blood may also be seen in the basal cisterns, ventricles, or sulci. Patients without subarachnoid hemorrhage will show no obvious lesion in 10–20% of unenhanced CT scans; this happens when the lesion is relatively small and superficial. However, a noncontrast CT scan may show characteristic serpiginous high-density structures suggestive of thrombosed enlarged vessels or hypertrophied veins. Characteristic ring-like or curvilinear and serpiginous calcification may also be shown. The appearance of the vessels in a large AVM will vary depending on the angle relative to the tomographic sections. Usually, tubular or vermiform densities may be recognized when sectioned longitudinally and rounded or ovoid densities when sectioned transversely [3]. CT low-density and T2 MR hyperintensity in brain parenchyma adjacent to the malformation can represent posthemorrhagic cysts or chronic ischemic gliosis, which along with dilated vessels in the vicinity can give rise to a mottled appearance [69]. After contrast injection, characteristic tortuous vascular structures are more easily recognized. Large lesions may penetrate deeply into the brain like wedges although the majority remain superficial. Most AVMs produce little mass effect unless there has also been a large hemorrhage. Nevertheless, it is possible to mistake the appearance for that of gliomas or infarcts, and the differential diagnosis should expand when appearances are not characteristic [3]. Although the diagnosis of AVMs is often established on CT and MR, most cases will require DSA before surgery or endovascular embolization to define the detailed anatomy of feeding and draining vessels [8]. CT shows an irregular hyperdense intraparenchymal lesion with calcification in about 30% of cases. Unless there is evidence of thrombosis or
hemorrhage, the AVMs show homogeneous intense enhancement in the arterial phase of the intravenous bolus [3]. When superficial, they can resemble meningiomas but without edema or mass effect [69]. MRI shows characteristic round, tubular or punctate low signal areas due to vascular flow voids, especially on T2-weighted images. Large arteries and draining veins usually appear as signal voids although may be hyperintense on T1-weighted images due to flow-related enhancement. There may be regional brain atrophy or occasionally some local mass effect. Intracerebral hematoma may be shown in or adjacent to the malformation, usually clearly evident on MR with variable signal or edema depending on acuity. Frequently, there are areas of low signal on T2-weighted images, secondary to hemosiderin tissue deposition. Calcification can also manifest as low signal although more apparent on CT. High signal on T2/FLAIR may be seen in the adjacent brain due to gliosis (Fig. 75.37) [8]. Refer to Spetzler–Martin grading scale for AVMs in Table 75.7, which correlates to clinical outcomes [70,71].
FIGURE 75.37 An arteriovenous malformation (AVM, arrow) mainly in the left temporal lobe appears as dilated tortuous vessels on T2weighted MRI.
Eloquent areas include sensorimotor, language and visual cortex, thalamus, hypothalamus, internal capsule, brainstem, cerebellar peduncles, and deep cerebellar nuclei.
Arteriovenous fistulas (AVFs) occur most commonly in the dura mater, frequently near or in the wall of a dural venous sinus. Dural AVFs, unlike AVMs, are direct arteriovenous shunts without an intervening nidus and are supplied primarily by the meningeal arteries and dural branches of the external and internal carotid arteries [3]. The drainage occurs usually through the dural venous sinuses (Fig 75.38) and occasionally through other superficial veins in the dura, orbit or scalp. Occasionally, dural AVFs drain or reflux intradurally into the cortical veins, causing enlarged tortuous cerebral veins to be visible (Fig. 75.39). Such AVFs carry high risk of rupture and intracranial hemorrhage [69].
FIGURE 75.38 Dural arteriovenous fistula causing pulsatile tinnitus. CT angiogram (A) shows abnormal vessels along the right lateral tentorium and abnormal drainage into the sigmoid sinus (arrow) in the arterial phase. Maximum intensity projection image from time-of-flight MR angiogram (B) shows high flow in the right sigmoid sinus (arrow) and prominent vessels and external artery carotid branches extending to the fistula at the right lateral tentorium. Conventional angiogram (C) shows occipital (arrow) and middle meningeal artery (arrowhead) branch feeders to the fistula (asterisk).
FIGURE 75.39 Dural AVF causing headache and pulsatile tinnitus. Axial T2 MRI (A) and contrast-enhanced CT (B) show dilated cortical veins in the left occipital lobe. Left external carotid DSA (C) shows a dural AVF of the transverse sinus (asterisk) supplied by a massively enlarged occipital artery (arrows) with venous reflux into occipital cortical veins. Cortical venous reflux significantly increases the risk of intracranial hemorrhage in dural AVF.
It is often difficult to detect dural AVFs on routine CT and MRI due to their proximity to the bony vault or skull base but enlarged draining cortical veins may be seen in some cases (Fig. 75.39) [8,69]. Dural AVFs are acquired lesions, often idiopathic but thought to be induced by previous known or unknown sinus thrombosis. More generally, AVFs may
be acquired from trauma (for example, caroticocavernous fistula) or surgery. In the pediatric period, a cerebral AVF involving a persistent median prosencephalic vein (vein of Galen malformation) can present dramatically with cardiac failure or hydrocephalus [3,69].
Cerebral Cavernous Malformations Cerebral cavernous malformations, cavernous angiomas, or cavernomas are vascular hamartomatous lesions comprised of sinusoidal spaces without intervening brain parenchyma. When occurring in familial syndromes caused by mutations in cerebral cavernous malformation 1, 2, or 3 genes, they are usually multiple [8,68]. Cavernomas are frequently asymptomatic and found incidentally on imaging. Seizures, headache, and hemorrhage are their most frequent clinical presentation when found in the cerebral hemispheres, whereas cavernomas of the brainstem typically present with focal neurological deficits. They commonly appear as small circumscribed intraaxial “popcorn”-like lesions with mixture of hypointense and hyperintense intralesional foci on T1- and T2-weighted MRI depending upon the presence of and stages of intralesional hemorrhages. Due to hemosiderin, lesions appear to bloom on susceptibility; cavernomas generally appear larger on T2* GRE or SWI than on T1 MRI or CT [3]. Very small cavernomas, therefore, may only be visualized on T2* GRE or SWI images. On CT, cavernomas are typically hyperdense with varying degrees of calcification. Sometimes, recent hemorrhage may be visible within or in the vicinity of the lesion. Rarely, underlying cavernomas may present only as an intracerebral, cerebellar or brainstem hematoma and may not be visualized on imaging. Cavernomas are characteristically invisible on DSA [8] (Fig. 75.40).
FIGURE 75.40 Cavernous malformation. T1-weighted (A) and T2weighted MR (B) images show a round left lateral temporal cavernous malformation with typical heterogenous, “popcorn-like” areas of high and low internal signal and a low signal rim. A sequence sensitive to the magnetic effects of blood products shows even more pronounced low signal related to the malformation (C). There is no surrounding edema to indicate recent hemorrhage.
Capillary telangiectasia is a benign, asymptomatic, and small (few millimeters to 2 cm) intraparenchymal vascular lesion composed of dilated endothelium-lined capillary type vessels. Brain capillary telangiectasias most frequently occur in the pons but may also be encountered in the medulla, basal ganglia, and cerebral hemispheres. They are usually solitary but can be multiple in hereditary hemorrhagic telangiectasia (Osler–Weber–Rendu syndrome), ataxia–telangiectasia, and Sturge–Weber syndrome [3,8]. Capillary telangiectasias, usually hypointense or isointense on T1-weighted MR and slightly hyperintense on T2-weighted MR, can appear variable but typically show faint feathery or cloud-like enhancement in otherwise normal appearing brain parenchyma without mass effect [72]. Capillary telangiectasias also show susceptibility-related signal loss on T2* GRE and SWI due to higher levels of deoxyhemoglobin in the blood of their dilated capillary bed (Fig. 75.41) [8,69].
FIGURE 75.41 Pontine capillary telangiectasia (white arrow). Characteristic feathery or cloud-like hyperintensity on T2 (A), signal dropout on T2* GRE (B) and enhancement on T1 (C) MRI. Note the absence of mass effect in this incidentally identified lesion.
Developmental Venous Anomalies Developmental venous anomalies or venous angiomas are simply aberrant venous drainage and are not pathological entities. On MRI, they appear as a curvilinear structure representing a large intraparenchymal draining vein onto which numerous smaller veins converge. They are often incidental findings but may be associated with cavernomas, parenchymal hemorrhage, or focal gliosis (Fig. 75.42).
Generally normal Mass effect, slow flow, and subtle shunting
Calcification and variable enhancement
Mixed signal
Dural AVF
Enlarged dural arteries with shunting Dural sinus stenosis or thrombosis
Generally normal Enlarged intradural veins
Generally normal Enlarged intradural veins MRA: enlarged dural arteries shunting into a venous sinus
CCM
Generally normal
NECT: iso/hyperdense CECT: minimal enhancement Variable calcification No mass effect
“Popcorn”-like, mixed signal with reticulated core, hemosiderin rim on T2 T2*GRE/SWI: blooming Often multiple lesions
Malfor mation
DSA
CT
MRI
Capillary telangiec tasia
Often normal
NECT: normal CECT: focal enhancement No edema or mass effect
Iso to hyperintense on T2 and hypointense on T2*GRE or SWI Feathery enhancement
DVA
Normal arterial phase Enlarged medullary veins (“Medusa head”)
NECT: normal CECT: tuft of periventricular vessels and dilated draining vein
Stellate, tubular, and convergent enhancing veins Occasionally adjacent gliosis and hemorrhage
Vein of Galen malform ation
Enlarged choroidal and thalamoperforati ng arteries Aneurysmal enlargement of vein of Galen Accessory sinus seen Straight sinus atresia and altered flow
NECT: iso/hyperdense mass in third ventricle CECT: strong enhancement Often obstructive hydrocephalus and encephalomala cia
CNS Infections Abscess and Cerebritis Abscess may be pyogenic, tuberculous, fungal, or parasitic. Pyogenic abscesses are collections of granulocytic exudate and are most frequently encountered in adults under 40 and children between 4 and 7. The male-tofemale ratio is greater than 2:1 [40,73,74]. Common presentations include headache, altered mental status, and focal neurologic deficits that precede headaches by days to weeks. Abscess may occur secondary to local spread
from paranasal sinus or mastoid infection; abscess can also occur secondary to hematogenous spread from endocarditis, suppurative chest diseases such as bronchiectasis and lung abscesses, or intra-abdominal sepsis. Intravenous drug use and immunocompromised status are also major predisposing factors in the development of brain abscesses [6,40]. Cerebritis precedes abscess formation whereby microbes cause localized inflammation leading to vasogenic edema, vascular congestion, petechial hemorrhage, and inflammatory exudate. Cerebritis and abscesses may occur anywhere in the brain [75]. Temporal lobe and cerebellar involvement can result as complications of suppurative otitis media and mastoiditis. Subdural and epidural abscess can also occur from skull osteomyelitis and septic thrombophlebitis of draining emissary veins (which lack valves) in paranasal infections. Post-traumatic or postsurgical dural tears involving the skull base can also lead to subdural empyemas and brain abscesses (Fig. 75.43). CT may provide more direct evidence by showing bone defects or opaque sinuses and air cells. In children, congenital malformations such as meningomyeloceles, encephaloceles, ectodermal defects, and right to left cardiac shunt diseases can predispose to intracranial abscess formation [40].
FIGURE 75.43 Orbitofrontal subdural empyema complicating fracture of the right ethmoid roof. Loculated subfrontal extra-axial hyperintense fluid collection on coronal T2 MR (A) along with reactive vasogenic edema in the adjacent brain. The collection shows typical peripheral enhancement on sagittal T1 MR (B).
On imaging, cerebritis is poorly localized and shows mass effect due to vasogenic edema and variable nodular to ring-like contrast enhancement. As the cerebritis progresses, an abscess develops once there is a central,
liquefied necrotic zone surrounded by a collagen capsule and gliosis. The capsule, which matures in about 2 weeks, is often less well formed on the side closer to the ventricle and tends to be thinner and more uniform than the capsule of a cystic/necrotic tumor [40]. Abscesses can be unilocular or multilocular. Those resulting from hematogenous spread tend to occur at gray–white matter junction, usually in the frontal or parietal lobes. Complications include satellite abscess formation, ventriculitis, choroid plexitis, and purulent leptomeningitis [27,76]. Ventriculitis or extension of inflammation to the ventricles is a poor prognostic sign. CT shows focal hypodensity in most cases, and CECT demonstrates the abscess capsule as a thin-walled regular ring of enhancement [40,77]. Occasionally the lesion is multilocular. The capsule may sometimes be seen as a ring of increased density before enhancement, but this is not a universal feature of abscesses. Vasogenic edema may be the most prominent feature, and edema and mass effect in proximity to opacified paranasal sinuses or mastoid air cells should prompt careful evaluation of the intervening bone and further imaging with MRI. Gas may be present adjacent to or within an abscess and usually indicates that the cavity has been surgically accessed. In rare cases, gas is present preoperatively, where it may indicate the presence of either gas-forming organisms or, more commonly, a fistulous connection with the scalp or paranasal sinuses [40,75]. MRI better demonstrates abscess than CT, with notable T2/FLAIR hyperintense and T1 hypointense lesions. Appearance varies by stage. The central zone of liquefying necrosis in a mature abscess is slightly hyperintense to CSF on T1-weighted images and isointense to CSF on T2weighted images with hyperintense surrounding vasogenic edema on T2 MRI. On unenhanced images, collagenous capsules are commonly T1iso/hyperintense and T2-hypointense to parenchyma, likely attributable to paramagnetic-free radicals [40,75]. As with CT, the abscess capsule enhances intensely on MRI; therefore, intravenous contrast is important in recognizing whether the abscess cavity is unilocular or multilocular, which has surgical implications [74]. Even after successful abscess drainage, enhancement of the capsule may persist for weeks to months. Although the sensitivity of MRI is greater than CT in detecting an abscess, the radiological differential of a ring-enhancing lesion includes glioma, metastasis, lymphoma, septic and aseptic infarcts, subacute hematoma, thrombosed aneurysm, and MS plaques (refer to Table 75.5 MAGIC DR). DWI can assist in differentiating an abscess from a liquefied/cystic tumor. Pyogenic abscesses demonstrate restricted diffusion, leading to bright signal on DWI with a low ADC; this is presumably due to viscosity of the cavity contents (Fig. 75.44). Conversely, necrotic tumors typically have increased free water diffusion with increased ADC [79,80].
FIGURE 75.44 Pyogenic cerebral abscess. T2-weighted (A) and postcontrast T1-weighted axial MR (B) images show a left parietotemporal collection with a well-defined enhancing rim and prominent surrounding edema. Diffusion-weighted image (C) and ADC maps (D) show diffusion restriction of the abscess contents.
Magnetic resonance spectroscopy of abscess may portray decreased NAA and choline/creatine ratio with elevated lactate, amino acids, and lipids. Comparatively, tumors show elevated choline/creatine (see Table 75.9). Table 75.9 Summary of MRS Characteristics of CNS Infections [27] Decreased Neuron Metabolites ▪N-acetyl-aspartate (2.0 ppm) ▪Creatine (3.0 ppm) ▪Choline (3.2 ppm
Increased Inflammation ▪Lactate (1.3 ppm) ▪Lipids (0.9–1.3 ppm) Elevated and Specific to Infection ▪Valine, leucine, isoleucine (0.9 ppm) ▪Succinate (2.4 ppm) ▪Acetate (1.9 ppm)
Ventriculitis is an uncommon but serious complication of brain abscess located near the ependymal surface. It may follow spontaneous or iatrogenic abscess rupture into the ventricles and may sometimes result from leptomeningitis or shunt infection. It is characterized on CT or MRI by linear contrast enhancement outlining the ventricular wall. Ventriculomegaly, septation, adhesions, and trapping of the ventricles may also be seen. Other associated features may include transependymal CSF transudation manifesting as increased periventricular T2 signal and abnormally swollen choroid plexi indicative of a choroid plexitis. In chronic ventriculitis, parenchymal periventricular calcification may be present, particularly seen in neonatal ventriculitis and classically seen in TORCH infections (Toxoplasma, other, rubella, cytomegalovirus, HIV, HSV) [27,77].
Meningitis Meningitis can occur in several extra-axial locations: leptomeningitis of pia and arachnoid or pachymeningitis of the dura. A potential complication of meningitis is ventriculitis of the ependyma and CSF in the subarachnoid space. Leptomeningitis is often associated with parenchymal inflammation known as meningoencephalitis [78]. Clinical presentation includes fever, altered mental status, nuchal rigidity, and Kernig/Brudzinsky signs. As with cerebral abscesses, meningitis can be classified as acute (pyogenic or bacterial vs viral or aseptic) or chronic (pyogenic fungal or parasitic) [81,82]. Imaging is usually not indicated except for detecting complications such as hydrocephalus, venous thrombosis, or infarction. Acute meningitis is usually occult on CT and MR imaging; however, contrast-enhanced T2/FLAIR can often show leptomeningeal or sulcal hyperintensity reflecting leptomeningeal inflammation [27,28,77] (Fig. 75.45).
FIGURE 75.45 Pyogenic meningitis due to pneumococcus. Contrastenhanced T1W axial MR image (A) shows diffuse leptomeningeal enhancement of the midbrain, medial temporal lobe, and sylvian fissures. Axial T2 FLAIR (B) shows diffuse hyperintensity of CSF in basal cisterns owing to lack of CSF suppression resulting from increased CSF protein and cellularity. Markedly dilated temporal horns with surrounding T2 hyperintensity from transependymal CSF flow are indicative of acute obstructive hydrocephalus (arrows, A, B). Significant resolution of the above abnormalities (C and D) after antibiotic therapy and ventriculostomy (not shown) can be seen on the same MR sequences 3 weeks later.
Viral Meningitis This is usually a self-limiting infection. The most common pathogen is an enterovirus such as echovirus, coxsackievirus (both A and B), and nonparalytic poliovirus. In most cases, CT and MRI are normal, unless associated with viral encephalitis. Sulcal/leptomeningeal enhancement (particularly on enhanced T2/FLAIR) and parenchymal edema may be seen on MRI [27,83].
Pyogenic Meningitis Causative organisms will vary according to the age of the patient [27,81,82].
◾ Newborns 0–6 months: group B streptococci, E. coli, Listeria ◾ Older children: Strep. pneumoniae, N. meningitidis, H. influenzae type B in unvaccinated ◾ adults: N. meningitidis > Strep. pneumoniae ◾ Young Older adults: Strep. pneumoniae, Listeria
In untreated or partially treated pyogenic meningitis, there may be obliteration of subarachnoid (or basal) cisterns, cerebral sulci, and cerebellar sulci due to inflammatory exudate and edema. Cisternal or leptomeningeal enhancing exudates are appreciated better on contrast-enhanced MRI than CT [40]. Communicating hydrocephalus is the most common complication of meningitis, resulting not only from interrupted CSF flow but also from impaired CSF resorption by arachnoid villi due to inflammation and plugging by cellular and macromolecular debris floating in the CSF. Leptomeningeal– ependymal fibrosis may be a later complication resulting in irreversible communicating-obstructive hydrocephalus. Subdural effusions (infected or sterile) are sometimes seen with acute meningitis. Most common are sterile hygromas, likely secondary to irritation of dura or subdural veins [81,83]. Subdural Abscess (Empyema) Paranasal sinusitis is the most common cause of subdural empyema [27]. The cerebral convexities and interhemispheric fissure are the most common locations; on CT, these are seen as crescentic or lentiform collections of variable hypodensity with marked enhancement of margins and occasionally the contents (Fig. 75.46). The outer enhancing rim represents hyperemic dura, and the inner enhancing membrane represents inflammatory granulation tissue on the leptomeningeal surface. Hypodensity of the adjacent brain may result from reactive vasogenic edema or from secondary thrombophlebitis of the subdural bridging veins, which can lead to venous infarction. MRI may be useful in differentiating sterile from infected subdural collection, as the former is more likely to be isointense to CSF on T1, whereas the latter is often more hyperintense due to proteinaceous contents [40,73]. Similar to brain abscess, DWI is extremely valuable in differentiating infected (empyema) from reactive subdural (hygroma) collections. The enhancing internal and external inflammatory membranes are easily appreciated with MRI. When subdural empyemas are adjacent to the tentorium, coronal sections may be indicated to show whether the lesion is supra- or infratentorial. They are readily detected by coronal MRI, especially T2, where the collection is variably hyperintense with respect to normal brain.
FIGURE 75.46 Epidural abscess and subdural empyema complicating sinusitis. Axial T2-weighted (A), diffusion-weighted (B), and postcontrast T1-weighted MR (C) images show a small left frontal epidural collection (arrows in A, B, C) and a more lateral subdural collection with diffusion restriction and adjacent meningeal enhancement (arrowheads in A, B, C). There is also involvement of the left frontal scalp.
Epidural Abscess When associated with meningitis, these are usually a result of direct extension from an external source such as skull osteomyelitis, frontal sinusitis and petromastoiditis, but they also occur after surgery or penetrating trauma [6,74]. On CT and MRI, the fluid collection is usually of slightly higher density and signal intensity than CSF, and the involved dura is markedly thickened and enhances. The underlying brain is usually normal as the dura resists intracranial dissemination of infection, but with advanced cases, retrograde thrombophlebitis may occur [27,40]. Tuberculosis CNS infection with Mycobacterium tuberculosis occurs more often in immunocompromised patients, that is, patients with HIV and alcohol or IV drug abuse. Spread is often hematogenous, and intracranial manifestations include meningitis (most common manifestation), cerebritis, and tuberculomas [27]. Tuberculous meningitis primarily affects the basal meninges, resulting in thick proliferative arachnoiditis and meningeal exudate. This may lead to communicating or even obstructive hydrocephalus. Traversing arteries and veins may become involved, resulting in infarctions [84]. On CT, the basal cisterns appear obliterated by iso/hyperdense exudates. Thick enhancement of basal leptomeninges extending into ambient, sylvian,
pontine, and chiasmatic cisterns can be seen with rare extension over cerebral and cerebellar hemispheres. Hydrocephalus is present in many patients at diagnosis [85]. MRI is more sensitive in detecting the presence of cisternal and leptomeningeal exudates and adjacent parenchymal granulomas. Infarcts due to vasculitis are most frequently seen in the basal ganglia due to involvement of the perforating arteries but may also occur in the cerebral cortex, pons, and cerebellum [86]. The imaging differential of tuberculosis (TB) meningitis includes late pyogenic, carcinomatous and fungal meningitis, and neurosarcoidosis [28,84]. Granulomatous basal meningitis is an uncommon presentation of tubercular meningitis. Diffuse granulomatous involvement of the basal meninges may result in visual disturbances by compression of the optic nerve/chiasm. On CT and MRI, there is dense basal meningeal enhancement with irregularly enhancing nodular masses. Chronic tuberculous pachymeningitis results from focal or diffuse involvement of the dura, more frequently affecting the cavernous sinus, floor of the middle cranial fossa, cerebral convexities, falx, and tentorium. The dura becomes plaque-like, thickened, and often calcified, appearing hyperdense on CT and iso- to hypointense on T1 and T2 MRI, with marked contrast enhancement [77].
Parenchymal Tuberculosis Parenchymal TB can be isolated or associated with TB meningitis, with the spectrum including cerebritis, TB granuloma (tuberculoma), abscess, and miliary TB [77]. Intracranial tuberculomas have variable quantity, size, and location (Fig. 75.47). Tuberculomas may be accompanied by meningitis [77]. The intraparenchymal tuberculous nidus begins as focal cerebritis and is hypodense on CT and hyperintense on T2-weighted MRI; there may not be T1 signal change or enhancement. Then, cerebritis progresses to a focal noncaseating granuloma, which is isodense or mildly hyperdense on CT, surrounded by perilesional low-density edema [3]. CECT shows dense nodular enhancement. On MRI, these solid granulomas are slightly hypo- to isointense on T1 MR and iso- to slightly hyperintense on T2 MR with nodular enhancement [77].
FIGURE 75.47 Tuberculoma. Axial T2 MRI (A) showing a hypointense caseating tuberculous granuloma in the right frontal lobe in association with vasogenic edema. The lesion is situated at the gray–white matter junction and on the postcontrast T1 axial image (B) has a multiloculated ring-enhancing appearance. Irregular enhancing tuberculoma within the pons on postcontrast axial T1 MRI (C). The lesion is of relatively low signal on the T2 axial image (D) and there shows extensive vasogenic edema and some modest mass effect with distortion of the 4th ventricle. Axial T2-weighted MR (E) demonstrates hydrocephalus. On the coronal T1 postcontrast image (F), there is leptomeningeal thickening and enhancement in the ambient cistern and aqueduct.
As caseation occurs, the granuloma reverts to isodense or slightly hypodense signal on CT. On MRI, the caseating granuloma remains T1 iso/hypointense but becomes T2 hypointense. The lesion will show ringenhancement and perilesional edema on both CT and MRI. The radiological differential of such ring-enhancing lesions includes abscess, neurocysticercosis, glioma, metastases, lymphoma, and other granulomatous processes such as sarcoid (Fig. 75.47) [27,77]. In miliary tuberculosis, multiple enhancing small (0 to ≤50% filling of occluded territory
2 – Moderate collaterals
>50 to 10
seconds divided by the volume of tissue with Tmax >6 seconds, has been shown to correlate with quality of collateral flow, with lower HIR 6 seconds has been reported as the threshold best correlating to salvageable penumbra [43]. The DEFUSE 3 trial, which helped establish criteria for thrombectomy up to 16 hours after onset, also used the 6 second threshold for selecting patients, and this value is most often used clinically [8].
CBF represents blood flow within the target tissue in mL/100 g/min. The relative CBF (rCBF) has been found to be the closest approximation for core infarct, or unsalvageable tissue. A threshold of ≤30% rCBF (compared to the contralateral hemisphere) is used to determine core infarction [44]. The combination of Tmax and rCBF give accurate measurements of core infarction and at-risk penumbra, which are used clinically to determine the course of action in stroke management. A large mismatch between the core and penumbra (ratio of penumbra to core of ≥1.8 in the DEFUSE 3 study) is a prerequisite for endovascular therapy in the extended time window (Fig. 77.6) [8].
Figure 77.6 A patient with left hemispheric stroke in the delayed window (A) and left ICA occlusion (arrow). CT perfusion demonstrates a large area of prolonged Tmax (>10 seconds) with a hypoperfusion intensity ratio of 0.7 denoting poor collateral flow and likely rapid growth of the infarct core (B). Mismatch maps (C) showing a small core infarction in the left MCA territory (purple), and a large volume of ischemic, at-risk penumbra involving the left MCA and bilateral ACA territories (green).
Additional parameters are commonly calculated in CT perfusion studies, including cerebral blood volume (CBV), and mean transit time (MTT). Decreased CBV has also been used in the past as a proxy for core infarct and usually closely tracks CBF, although CBF has been reported to better match diffusion abnormality on MRI [44]. MTT represents a measure of the average time for an erythrocyte to transit a volume of tissue and may be used as a marker of vasodilation. Autoregulation leads to vasodilation in oligemic and ischemic tissues, reducing the speed of transit through capillary beds to allow for maximal oxygen extraction. Areas of prolonged MTT will often overlap with areas of prolonged Tmax. Key Point Current guidelines in perfusion imaging define core infarction as ≤30% rCBF, and ischemic penumbra as Tmax >6 seconds. Perfusion imaging is a critical tool in decision making for stroke patients who are potential thrombectomy candidates in the extended window, 6–24 hours from last known well.
MR Perfusion The same perfusion principles apply to MR perfusion as in CT perfusion regarding calculation of timecontrast curves for voxels of brain tissue and the resulting main derived perfusion parameters, however there are multiple methods by which to acquire the images. The most commonly used method in stroke imaging is dynamic susceptibility contrast (DSC) perfusion, wherein a gadolinium-based contrast agent is injected intravenously and a T2 or T2* weighted sequence is performed continuously throughout the wash-in and wash-out phases. The paramagnetic effects of the intravascular gadolinium cause susceptibility artifact and signal loss proportional to the concentration of contrast. The time-intensity curves are then used to derive perfusion parameters in a fashion similar to CT perfusion (Fig. 77.7).
Figure 77.7 MRI perfusion with core-penumbra mismatch. (A) Diffusion weighted and (B) time to peak (TTP) perfusion image of the brain demonstrating a small area of diffusion restriction in the right corona radiata denoting core infarction with a larger area of prolonged TTP representing penumbra. Arterial spin labeled (ASL) perfusion imaging is a noncontrast method for acquiring perfusion images. The ASL technique utilizes magnetic labeling of upstream blood to quantify flow into the tissue of interest. In the case of brain imaging, this means labeling blood in the cervical vessels and acquiring signal from the labeled blood as it reaches the brain.
This technique is attractive as it is simple to implement, non-invasive, and gives quantitative CBF values. ASL is often used when imaging pediatric patients as it does not require intravenous contrast and can be repeated multiple times if initial imaging is suboptimal. The technique is limited, however, as other perfusion parameters including Tmax, CBV, and MTT cannot be derived from ASL data using current clinically available techniques [45]. A third MR perfusion technique, dynamic contrastenhanced (DCE) perfusion, is similar in technique to DSC perfusion, but utilizes a T1 weighted sequence during acquisition instead of a T2 or T2* weighted sequence. This approach uses increases in signal intensity rather than signal loss to construct the timeintensity curve and calculate perfusion parameters. The DCE technique brings an added ability to quantify vessel permeability, a measure that has been used in neuro-oncologic imaging [46]. DCE is not commonly employed in stroke imaging.
Automation
As imaging of penumbra has become an integral part of ischemic stroke management during the extended time window (>6 hours from stroke onset), methods to standardize and automate calculation of perfusion parameters have become more commonplace. The perfusion thresholds used in the DEFUSE 3 trial have become the basis for automated clinical decisionsupport tools, such as RAPID (iSchemaView), the tool used by the DEFUSE 3 investigators. The RAPID platform uses algorithms to automatically process source CT perfusion data, generate maps of the critical perfusion parameters, and calculate volumes of core infarction and penumbra. These automated tools also automatically alert members of the stroke team to the perfusion imaging and offer immediate access to the results, thereby helping to reduce the time needed to determine if a patient is eligible for thrombectomy.
Clinical Scenarios Large Vessel Occlusion and Thromboembolism
Acute thromboembolic infarction results from the occlusion of a cerebral artery by embolic thrombus from a more proximal or central vessel, commonly the heart or carotid arteries. A large vessel occlusion (LVO), or occlusion of the proximal intracranial anterior or posterior circulation, accounts for approximately 24–46% of acute ischemic strokes. Major risk factors include hypertension, diabetes mellitus, arrhythmias, and smoking, among others. Less frequently, emboli may arise from deep veins in the setting of a patent foramen ovale, resulting in the so-called “paradoxical embolus.” The MCA is the most common vessel for an embolus to occlude [47].
Acute Ischemic Stroke Management In the setting of acute ischemic stroke, the earlier an intervention can be safely performed, the higher the chance of a good clinical outcome [3,4,48]. Imaging plays a central role in multiple critical decision points in the management of acute ischemic stroke. First, the decision to give IV tPA must be made. Early IV tPA administration has been shown to increase odds of good outcome when given less than 3 hours from
stroke onset, and up to 4.5 hours in select patients [31,49]. Unenhanced head CT is therefore performed prior to its administration to exclude acute intracranial hemorrhage, major established infarction, or other contraindications to its use (e.g., evidence of a vascular malformation).
ASPECTS The Alberta Stroke Programme Early CT Score (ASPECTS) was developed to help with the rapid estimation of core infarct volume on unenhanced CT in patients experiencing a middle cerebral artery stroke [50]. Previously, the definition of a “major infarction” was loosely defined as “greater than onethird the volume of the MCA territory”, which is difficult for radiologists to accurately estimate. To help standardize this estimation and improve interreader reliability, the ASPECTS divides the MCA territory into 10 sections: C = Caudate nucleus; L = Lentiform nuclei; IC = Internal capsule; M1 = Anterior-inferior MCA cortex; M2 = MCA cortex lateral to the insular ribbon; M3 = Posteriorinferior insular cortex; M4 = Anterior-superior MCA
Figure 77.8 ASPECTS score [50] in axial CT images A & B at different levels. C = Caudate nucleus; I = insular ribbon; IC = Internal capsule; L = Lentiform nuclei; M1 = Anteriorinferior MCA cortex; M2 = MCA cortex lateral to the insular ribbon; M3 = Posterior-inferior insular cortex; M4 = Anterior-superior MCA cortex; M5 = Lateral-superior MCA cortex; M6 = Posterior-superior MCA cortex. The ASPECTS is calculated by assigning 1 point for each of the 10 sections and subtracting a point for
each section that shows early ischemic changes, such as edema or hypoattenuation. Therefore, a higher score denotes a smaller infarction with a score of 10 meaning no evidence of infarction. An ASPECTS of 7 or less is associated with a significantly increased risk of functional dependence or death, and correlates well with the “1/3 MCA territory rule” in predicting risk of symptomatic hemorrhage [50].
Vascular Imaging and Indications for Thrombectomy Following unenhanced CT, IV tPA is immediately administered if there are no contraindications identified. At this time, vessel imaging should be performed with either CTA or MRA. Depending on the time since stroke onset or last-known-well (LKW), imaging may or may not be performed with perfusion. Prior to 6 hours from onset, if a large vessel occlusion is identified on vessel imaging and there are no contraindications, evidence supports interventional thrombectomy regardless of perfusion imaging [4–6,31,51–54].
If more than 6 hours have passed since stroke onset, recent data have shown that patients may still benefit from intervention with thrombectomy, up to 24 hours after LKW [7,8,55]. These findings have significantly increased the number of patients who may be candidates for intervention, as patients who have unwitnessed stroke onset or who wake from sleep with a neurologic deficit (and therefore, onset time is not known) can still be eligible if certain criteria are met. The criteria for thrombectomy in the extended 6 to 24-hour window relies heavily on imaging. The main goal of imaging in this setting is establishing the presence of a small volume, or core of completed infarction, with a large area of at-risk brain tissue (i.e., the penumbra). The penumbra can either be assessed directly with quantitative perfusion imaging, or by identifying a mismatch between the clinical stroke symptoms (NIH Stroke Scale) and the core infarct volume on imaging (either by diffusion weighted MRI or perfusion imaging). A high NIH Stroke Scale score, denoting a severe clinical deficit(s), in the setting of a small core infarct on imaging, implies the presence of a large penumbra of
ischemic, but viable, brain tissue. As previously discussed, the specific protocol an institution uses to assess these parameters with imaging varies, and the use of either CTA or diffusion weighted MR, with or without perfusion imaging, are both reasonable options [31]. Once the decision has been made to proceed with thrombectomy, every effort is taken to perform the procedure and reperfuse the ischemic penumbra as quickly as possible. Multiple devices may be utilized for thrombectomy, the most common currently used include direct aspiration and stent retriever systems. A combination of techniques may also be used depending on the particulars of the case. Direct aspiration involves navigating an aspiration catheter to the site of thrombus (with or without the assistance of a microcatheter) and suctioning the thrombus into the catheter for retrieval [56,57]. Stent retrievers involve deploying a modified metallic mesh stent across the thrombus, which after allowing time for clot integration, is then removed from the body (Fig. 77.9].
Figure 77.9 (A) Pre-thrombectomy DSA image showing occlusion (arrow) of the proximal right M1 MCA segment. (B) Post-thrombectomy showing recanalization of the previously occluded segment.
Grading Reperfusion The most widely used method for grading reperfusion on DSA after thrombectomy is the modified Thrombolysis in Cerebral Infarction (mTICI) scale, which has superseded prior grading scales such as AOL and TIMI [58–60]. The scale is
based on real-time intraoperative arteriography of the territory distal to the occluded segment, immediately following thrombectomy (Table 77.3). Grades 2b, 2c and 3 have shown higher rates of good outcome and less infarct growth compared to Grades 1 and 2a [58,61]. Table 77.3 Modified TICI Scale for Reperfusion Grading After Thrombectomy mTI DSA Findings CI Gra de Grad e0
No perfusion
Grad e1
Antegrade perfusion beyond the initial occlusion, but limited distal filling and slow perfusion
Grad e 2a
Antegrade reperfusion of less than half of the occluded target artery previously ischemic territory (e.g., in 1 major division of the MCA and its territory)
mTI CI Gra de
DSA Findings
Grad e 2b
Antegrade reperfusion of more than half of the previously occluded target artery ischemic territory (e.g., in 2 major divisions of the MCA and their territories)
Grad e 2c
Near-complete perfusion except for slow flow in a few distal cortical vessels or presence of small distal cortical emboli
Grad e3
Complete antegrade reperfusion of the previously occluded target artery ischemic territory, with absence of visualized occlusion in all distal branches
Imaging Findings Post-Thrombectomy Follow up imaging studies are routinely performed after thrombectomy to assess final infarct volume, monitor edema and mass effect resulting from the infarction, and to assess for potential complications, including subarachnoid hemorrhage and hemorrhagic
conversion. If additional vascular imaging is performed in the post-thrombectomy setting, sequelae of the procedure may be evident, including focal spasm of the arteries adjacent to the original occlusion and/or vessel wall enhancement on contrast enhanced black blood MRI. Focal postprocedural vasospasm may be difficult to differentiate from residual thrombus. However, comparison with intraoperative DSA images is often helpful in this setting as spasm is often present immediately following thrombectomy and evident on DSA imaging. Monitoring edema of the infarcted territory is also important, as up to 10% of patients will manifest a so-called “malignant infarction” wherein severe edema and mass effect leads to neurologic deterioration, usually between days 2 and 5 after stroke onset [62]. In this setting, decompressive craniectomy may be performed in select patients, preferentially within 48 hours of stroke onset [31,62]. Postintervention imaging at approximately 24 hours is recommended, in part to exclude hemorrhage prior to initiation of anti-thrombotic treatment for
secondary prevention. CT imaging after thrombectomy often will demonstrate hyperdensity within infarcted tissue due to bloodbrain barrier breakdown and parenchyma contrast staining. This may pose a diagnostic dilemma as contrast staining may mimic and/or obscure true hemorrhage. Dualenergy CT may be used in this setting to create virtual non-contrast images and/or iodine map images, allowing simple separation of contrast from acute blood products (Fig. 77.10) [63].
Figure 77.10 Dual energy axial noncontrast (A) and virtual monoenergetic 190 keV (B) images in a patient 2 hours post thrombectomy in the right middle cerebral artery. Standard noncontrast images show extensive
parenchymal hyperattenuation in the right anterior MCA distribution. Virtual monoenergetic images at 190 keV show complete suppression of the hyperattenuation, indicating contrast staining rather than hemorrhage.
Cervical Imaging
Atherosclerosis Imaging of atherosclerotic disease involves using ultrasound, CT, MRI, or DSA to image the vessel lumen and determine if there is stenosis. The degree of luminal stenosis alone can predict risk of neurologic ischemic events as reported in the seminal NASCET trial in 1991, wherein those patients with a history of a hemispheric TIA or nondisabling stroke as well as ipsilateral carotid stenosis of 70–99% benefitted from endarterectomy [64,65]. The NASCET criteria and method of stenosis measurement is still used to stratify patients for surgical management, although recommendations have evolved to include asymptomatic patients with
stenosis ≥75%, or symptomatic patients with stenosis ≥50% [66,67]. The NASCET style measurement was initially described on catheter directed carotid angiograms, however the same method is now used for CTA and MRA Eq. (77.1). The measurement is performed as follows:Percent stenosis = 100 × (1 – [minimum residuallumen diameter (MRL)/distal lumen diameter (DL)]),where MRL is measured on the view or plane showing the smallest diameter, and DL is the lumen diameter at the next normal appearing arterial segment [66]. Cross sectional imaging and advanced techniques have opened many new areas of study beyond simply evaluating luminal diameter. CT, MRI and ultrasound all have an advantage over DSA in that the vessel wall and associated atherosclerotic plaque can be directly imaged in addition to the lumen. Plaque composition has been shown to affect risk of rupture and thrombosis, and both CT and MRI can be used to evaluate plaque composition. Plaques with certain features, including a thin fibrous cap, lipid-rich necrotic core, and/or intraplaque hemorrhage represent unstable lesions vulnerable to rupture [68– 71]. CT Hounsfield unit thresholds have been used to
characterize fibrous, calcified, lipid, and hemorrhagic components of carotid plaques. Prior investigations have suggested an increased risk of subsequent rupture in plaques demonstrating lower attenuation (≤25 HU) suggestive of fatty composition, while calcified lesions had a significantly decreased risk of neurologic events [71–74]. MRI is also very useful in differentiating fibrous cap from lipid core in atherosclerotic plaques. The fibrous cap will demonstrate avid enhancement on postcontrast T1 weighted images, whereas the avascular lipid core will not enhance [75,76]. The morphology of the plaque also has implications for stroke risk. Irregular or ulcerated surfaces are considered risk factors for TIA and stroke, as these may expose the pro-thrombotic lipid core of the plaque to the vessel lumen [72]. Key Point Cross-sectional imaging in atherosclerosis has allowed evaluation of many parameters beyond luminal diameter, including plaque composition and morphology, allowing better risk stratification.
Dissection Arterial dissection of a cervical artery is the most common cause of stroke in young and middle aged adults [77,78]. Dissection occurs when a defect in the intima allows flowing blood to enter between the layers of the arterial wall, often leading to compression and narrowing of the vessel lumen. The blood within the vessel wall may thrombose due to the exposed, thrombogenic adventitial and medial layers, resulting in intramural hematoma. This thrombogenicity may cause acute thrombus to form in the true lumen, resulting in occlusion of the dissected vessel, and, or embolization of clot to distal vascular territories. The latter is the most common cause of ischemic stroke in the setting of dissection [79]. Dissection may be spontaneous or result from direct vessel trauma. 80% of patients present with headache or neck pain, and 67% with neurologic symptoms of TIA or stroke [80]. Headache and neck pain may precede onset of neurologic symptoms, potentially serving as a warning sign [81]. Horner’s syndrome and other cranial nerve palsies ipsilateral to the
dissection have also been described in up to 25% of patients with extracranial ICA dissection, possibly due to stretching of nerves adjacent to the carotid or interruption of blood supply to the nerves [80,82]. CTA and MRA are most commonly used when dissection is suspected. Cervical artery dissection rarely manifests with a clearly visible intimal flap or patent false lumen as is often seen in aortic dissection [83]. The classic appearance of ICA dissection is a tapered, eccentric occlusion or stenosis just distal to the carotid bulb, appearing similar to a flame on coronal or sagittal views, known as the “flame sign.” However, any intimal irregularity with or without associated luminal narrowing may be suggestive of dissection. A dissection that extends towards the vessel adventitia may form an associated pseudoaneurysm, which may also act as a nidus for distal thromboembolism [83]. Vertebral dissection most often manifests as irregular focal narrowing of the vessel or abrupt occlusion. This can be difficult to differentiate from atherosclerotic occlusion or thromboembolism, and in these cases patient history and demographics are helpful, for example, a young
person or a history of recent neck trauma would be more suggestive of vertebral artery dissection. With MRI, one can directly visualize intramural hematomas associated with the dissection. When dissection is a consideration, the MRA protocol should include an axial precontrast T1 sequence with fat suppression. This allows the intrinsically T1 hyperintense blood products in the vessel wall to stand out against the dark intraluminal blood and suppressed perivascular fat, appearing as a crescent of high T1 signal (Fig. 77.11).
Figure 77.11 Left ICA dissection with a crescent of T1 hyperintensity surrounding the vessel lumen related to intramural hematoma (arrow). DSA is also helpful in evaluation of dissection, both in diagnosis and potentially treatment. Carotid dissection again classically appears as a tapered occlusion or stenosis, sometimes with a long distal segment of severe stenosis with a tiny patent true lumen known as the “string sign.” If the stenosis is able to be traversed with a microcatheter, stenting
may optionally be performed to restore normal vessel caliber [84]. Key Point Headache and/or neck pain with ipsilateral cranial nerve palsies may be a sign of carotid dissection. Fatsuppressed T1 weighted MRI may be used to directly visualize intramural hematoma in the setting of dissection.
Fibromuscular Dysplasia Fibromuscular dysplasia (FMD) is an idiopathic arteriopathy with a strong female predilection resulting in concentric hypertrophy of smooth muscle resulting in irregular segments of stenosis and dilation. The cervical vessels are the second most common site of involvement with FMD, after the renal arteries [83,85]. Most lesions occur in the midto-distal cervical internal carotid and vertebral arteries; the vertebral arteries are less commonly involved than the ICA’s. The proximal ICA and carotid bifurcation is nearly always spared, helping to
distinguish this entity from atherosclerotic disease. Bilateral involvement is common, being present in 60–85% of cases. On imaging, FMD manifests as irregular, segmental stenoses and dilations, resulting in a “string-ofbeads” appearance (Fig. 77.12). On DSA, this should be distinguished from the “standing wave” phenomenon commonly seen as an artifact of contrast power injection.
Figure 77.12 Coronal (A) and sagittal (B) reformatted maximum intensity projection CTA images of the neck showing string-of-beads appearance (arrows) of the bilateral cervical internal carotid arteries (A). Sagittal image (B)
shows involvement of the left ICA (arrows) as well as the adjacent left vertebral artery (arrowhead). FMD may cause hemodynamic compromise leading to stroke or TIA either through severe narrowing of the vessel, or spontaneous dissection of the affected segment [86]. Medical management is generally preferred in patients with FMD, including antihypertensive and antiplatelet therapy. In some severe cases, endovascular angioplasty may be offered as a surgical treatment [87]. Key Point FMD is most common in women, and the distal cervical arteries are commonly involved, second only to the renal arteries.
Carotid Web A carotid web manifests radiologically as a shelf-like linear filling defect projecting into the carotid lumen at the posterior wall of the proximal internal carotid artery (Fig. 77.13). These lesions all show the classic
location and appearance, are often bilateral, and have been found histopathologically to reflect fibrous intimal thickening resulting from an intimal variant of FMD [88]. Carotid webs should be distinguished from ulcerated atheromatous plaques or dissection flaps, lesions which may occur in the same location. Stasis and turbulence of blood flow just distal to the flap is thought to induce thrombus formation which may lead to TIA or ischemic stroke [88]. Carotid webs have been found to be associated with “cryptogenic strokes,” particularly in young African American women [89]. Endarterectomy may be performed in symptomatic patients.
Figure 77.13 Coronal reformatted CTA of the neck with a shelf-like filling defect (arrow)
projecting from the intima of the left carotid bulb, consistent with a web.
Small Vessel Ischemic Disease Small vessel ischemic disease (SVID), commonly referring to a combination of white matter gliotic changes otherwise known as leukoaraiosis, and/or lacunar infarctions, is often seen involving the white matter and deep gray structures of older patients. The proposed mechanism of these changes is narrowing or occlusion of small perforating arteries primarily due to chronic hypertension, however other cardiac risk factors may also play a role [90,91]. Leukoaraiosis results from small vessel narrowing resulting in chronic ischemia and gliosis of the white matter, while a true lacunar infarction results from a small perforating artery occlusion. Lacunar infarctions are often clinically silent, however changes of SVID is associated with an increased risk of symptomatic stroke [92]. Leukoaraiosis manifests as patchy, symmetric white matter hypoattenuation or T2 hyperintensity most commonly involving the periventricular white matter
of the lateral ventricles, the hemispheric subcortical white matter, and the central pontine white matter. Lacunar infarctions most commonly involve the basal ganglia, thalami, corona radiata, and pons, and may demonstrate central encephalomalacia with attenuation/signal equal to that of CSF. A common diagnostic dilemma in CT imaging is distinguishing an acute or subacute lacunar infarction from a chronic infarction in the setting of new onset neurologic symptoms. As these lesions are small, features such as edema in acute lesions or encephalomalacia in chronic lesions are often difficult or impossible to distinguish. In these cases, prior imaging can be helpful for lesion aging. However, MRI with diffusion weighted images is ultimately most useful to assess acuity.
Intrinsic Disease of the Intracranial Arteries
Intracranial Atherosclerosis
Intracranial atherosclerotic disease (ICAD) is one of the most common causes of stroke worldwide, and the most common cause in patients of Asian descent [93]. These lesions typically involve proximal intracranial arteries resulting in vessel stenosis or occlusion and are associated with a high risk of recurrent stroke. Medical therapy was the mainstay of ICAD management, however as many patients continued to develop disabling strokes despite medical management, an interest arose in angioplasty and stenting for severe lesions. However, the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis Trial (SAMPRIS) in 2011 established the superiority of aggressive medical management in the treatment of intracranial atherosclerotic lesions, both due to the increased risk of early stroke in the interventional arm, and a lower than expected risk of stroke with aggressive medical therapy [94]. Aggressive medical management, as defined in the SAMMPRIS trial, involves dual antiplatelet therapy with aspirin and clopidogrel, management of primary stroke risk factors including hypertension and elevated LDL, management of secondary risk factors including diabetes, smoking, and obesity.
Imaging of intracranial atherosclerotic plaques remains largely focused on the degree of stenosis, however plaque imaging techniques similar to those used in the cervical arteries have been used to image intracranial lesions as well, potentially providing additional risk stratification for stroke. In particular, plaques imaged with contrast enhanced black blood MRI sequences showing plaque enhancement, arterial positive remodeling, and plaque surface irregularity are associated with stroke events in the corresponding territory [93,95]. Key Point Intracranial atherosclerosis is treated medically rather than with interventional techniques.
Vasculitis Stroke may also manifest as a complication of vasculitis or other intrinsic vasculopathies resulting in arterial narrowing or occlusion. CNS vasculitis is generally divided into two categories: primary angiitis of the CNS (confined to the CNS without
involvement of other areas), and secondary. Secondary causes of CNS vasculitis include a wide range of diseases such as Takayasu arteritis, sarcoidosis, polyarteritis nodosa, systemic lupus erythematosus, and many others, with the primary diagnosis relying on combination of patient history, imaging, and various biomarkers from blood or CSF analysis [96,97]. Vascular imaging by DSA, CTA, or MRA in severe cases will classically show multifocal segmental narrowing of small and medium sized vessels, occlusions, and occasionally pseudoaneurysms. MRA and DSA are considered the most sensitive modalities, however sensitivity and specificity remain poor [98,99]. CT and MRI may show complications of vessel stenoses, including territorial or watershed infarctions, parenchymal hemorrhages, and nonspecific leukoencephalopathy. Black blood vessel wall MRI is very helpful in the evaluation of CNS vasculitis, particularly in distinguishing vasculitis from other causes of vessel narrowing. Active vasculitic lesions will show avid vessel wall enhancement most often in a smooth,
concentric fashion, as opposed to the heterogeneous and eccentric enhancement that may be seen with atherosclerotic disease. Other potential causes of narrowing, including reversible cerebral vasoconstriction syndrome (RCVS) and Moyamoya disease may show no enhancement or mild enhancement, although research in this area is ongoing [100].
Reversible Cerebral Vasoconstriction Syndrome Reversible cerebral vasoconstriction syndrome (RCVS) is a clinical and imaging syndrome characterized by sudden onset severe headache with segmental intracranial vasoconstriction that resolves by 3 months [101]. While most commonly a benign process, some cases may result in intracranial hemorrhage or stroke. Women are more frequently affected, and patients typically range from 20 to 50 years old. More than half of RCVS cases are associated with use of vasoactive drugs or the
postpartum state, although many other potential triggers have also been proposed. DSA remains the gold standard for evaluation of RCVS, however noninvasive CTA and MRA are commonly used. The classic appearance on imaging is of multi-territorial segmental vasoconstriction resulting in a beaded appearance of medium-to-large arteries (Fig. 77.14). Affected segments are interspersed with normal appearing segments [102]. Imaging may be normal early in the disease, possibly due to a distal-to-proximal progression of affected vascular segments with later involvement of larger vessels that are more easily visualized [102].
Figure 77.14 Lateral and PA DSA images showing multifocal vasoconstriction (arrows) resulting in a beaded appearance compatible with RCVS in a patient with acute onset headache and left extremity weakness. Imaging with CT or MRI may reveal watershed infarcts due to restricted blood flow, most often bilateral, as well as subarachnoid hemorrhage. Black blood vessel wall MRI may show significant thickening of the vessel walls in affected segments, however only a minority will display enhancement. Abnormalities are also typically transient, resolving over a few months, in contradistinction to CNS vasculitis [100,102]. Key Point RCVS most commonly affects young to middle-aged women, and while usually benign, can result in hemorrhagic or ischemic stroke.
Moyamoya Disease
Moyamoya disease is an idiopathic, progressive stenosis of the carotid terminus leading to development of a network of abnormal collateral vessels at the base of the brain [103]. While the term “Moyamoya disease” is reserved for idiopathic cases, “Moyamoya syndrome” or “Moyamoya” phenomenon may be used to describe an array of conditions leading to a similar pathological appearance, including atherosclerotic stenosis, sickle cell vasculopathy, radiation-induced vasculopathy, and others. Vascular imaging will show severe stenosis or occlusion of the carotid terminus, usually bilaterally with enlarged, abnormal collateral vessels in the parasellar region, perimesencephalic cisterns, and within the basal ganglia. The angiographic appearance of these collateral vessels produced the name “Moyamoya”, translated from Japanese as “hazy, as a puff of smoke” (Fig. 77.15) [103].
Figure 77.15 Moyamoya syndrome. (A) AP and (B) Lateral DSA views of the left internal carotid demonstrating chronic occlusion of the carotid terminus. Adjacent extensive opacification of tortuous collateral vessels (arrows). (C, D) Axial T2 spin echo MRI images in a different patient with Moyamoya show prominent flow voids from dilated lenticulostriate vessels along the expected
course of the left MCA (A) and in the bilateral suprasellar cistern (B). Parenchymal imaging may show multifocal territorial or watershed infarctions of the anterior circulation. The “ivy sign” of engorged leptomeningeal collateral vessels manifesting as hyperintensity within the sulci on T2 FLAIR or T1 postcontrast images is also a classic finding [104,105]. Only a minority of patients with Moyamoya will show vessel wall thickening or enhancement on black blood vessel wall imaging, however those cases which do show enhancement or thickening are associated with ischemic events [106].
Global Ischemic and Hypoxemic Injuries Global ischemic and hypoxemic events can result in devastating neurologic injury, depending on the degree and duration of the insult, as well as a patient’s individual physiology. Common etiologies include cardiac arrest, trauma, or asphyxiation. Generically termed “hypoxic-ischemic injury” (HII) or the clinical correlate “hypoxic-ischemic
encephalopathy” (HIE), injuries may present radiologically with many different patterns depending on patient age, severity of the injury, and timing of imaging following the injury. HII in infants and children is more likely to be due to asphyxiation, whereas in adults, cardiac arrest or cerebrovascular disease are more common [107]. In older children and adults, mild to moderate global ischemia usually results in watershed zone infarcts. Watershed zones represent boundary regions between major vascular territories, such as in the anterior frontal lobes between ACA and MCA vascular distributions, or in the occipital lobes between MCA and PCA supply. The exact location of watershed zones varies between individuals due to normal anatomic variations in the size and distribution of the cerebral vessels. As the watershed zones are farthest from the large afferent arteries supplying the brain, they are relatively hypo-perfused and therefore susceptible to episodes of decreased cerebral perfusion. Watershed infarctions are most commonly seen involving the white matter and cortex bordering the ACA, MCA, and PCA territories in a roughly parallel parasagittal orientation, however PCA/MCA
watershed infarctions in the temporal lobes can also be seen, again reflecting anatomic variation in the cerebral vessels. Severe HII in adults primarily affects the gray matter structures including the basal ganglia, thalami, cerebellum, hippocampi and cortex, particularly the pre- and postcentral gyri. These gray matter structures are more metabolically active due to synaptic activity than white matter, and are more susceptible to the effects of neuronal excitotoxicity [107]. Imaging of HII can be particularly difficult, as early post-injury studies may be completely normal, or show only the subtlest of abnormalities. Furthermore, abnormalities are often symmetric, which may mask subtle parenchymal changes. Fogging and pseudonormalization of CT and MRI may also mask even severe injuries if a study is acquired 1–3 weeks postinjury. Consequently, history is often very helpful to alert the radiologist to the possibility of a HII. CT imaging may initially demonstrate hypoattenuation in involved structures secondary to
edema, which may manifest as blurring of the border between gray and white matter in a diffuse or patchy manner. In severe cases, global cerebral edema may be present, with narrowing of the sulci and Sylvian fissures, decreased ventricular size, and effacement of the basal cisterns. The injured basal ganglia may become edematous and enlarged symmetrically. These changes may produce the “reversal sign,” or an inversion of the normal attenuation relationship between gray and white matter as a result of diffuse gray matter edema. The deep gray structures, brainstem and cerebellum in some cases may appear relatively spared, producing the “white cerebellum” sign [108]. The cause of this apparent sparing is poorly understood and may reflect any combination of preferential maintenance of blood flow to the posterior circulation, postischemic hypervascularity, distention of deep medullary veins, petechial hemorrhage, or other potential explanations. MRI will show restricted diffusion of injured structures acutely, and later edema. Cortical laminar necrosis of injured cortex may develop in the subacute to chronic period, manifesting as gyriform
CT hyperattenuation and associated T1 hyperintensity. Delayed changes may also be seen in the weeks and months after injury in those patients who survive the initial insult. Post anoxic leukoencephalopathy is a delayed white matter injury occurring in 2–3% of patients suffering hypoxic-ischemic events, manifesting as either progressive neurologic decline or an acute decline after 2–3 weeks of clinical stability [107]. On MRI, diffusion images will show diffuse white matter diffusion restriction and T2 hyperintensity [109]. The majority (75%) of these patients go on to complete or near-complete recovery over the following 6–12 months [107]. Patients surviving hypoxic-ischemic injuries may also develop progressive global cerebral atrophy in the weeks and months after the event. Also see Chapter 76 Key Point Imaging findings in HII are heterogeneous, and depend on patient age, severity and length of insult,
and other factors. History is very helpful in identifying subtle cases.
Fat and Air Emboli Cerebral fat embolism (CFE) typically occurs 24–48 hours after fractures of large, lower extremity long bones such as the femur, but may also be encountered following small bone fractures and, or orthopedic manipulations. The classic syndrome of fat embolism involves multiple other organ systems, including the lungs and skin, with major criteria for diagnosis including a petechial rash, respiratory insufficiency, and abnormal mental status [110]. Initial unenhanced head CT often appears on remarkable, however diffuse edema may be present in severe cases, as well as scattered areas of hypoattenuation and, or hemorrhage. On MRI, the classic “star field pattern” is produced on DWI with numerous small hyperintense foci throughout the cerebral hemispheres, deep gray structures, brainstem and cerebellum, with a predilection for the watershed zones. Susceptibility images (SWI) may show corresponding punctate hemorrhages (Fig. 77.16).
Figure 77.16 Axial FLAIR (A), susceptibility weighted minimum intensity projection (B), and diffusion weighted at the level of temporal lobes (C), basal ganglia (D) and centrum semiovale (E) MRI sequences in a patient with cerebral fat embolism after trauma. Multifocal T2 hyperintensities in the bilateral watershed distribution with innumerable foci of restricted diffusion bilaterally (starfield pattern) as well as diffuse punctate hemorrhages.
Cerebral air embolism (CAE) is a potentially catastrophic complication of vascular procedures. Cerebral arterial air may result from direct manipulation of the arterial system during surgery or catheterization, or by a paradoxical venous route via a patent foramen ovale [111]. Arterial air may occlude small arteries in the brain and cause diffuse ischemic injury, leading to cerebral edema and death. Larger air emboli may be visible on unenhanced head CT as tubular, serpiginous air densities within the brain parenchyma (Fig. 77.17).
Figure 77.17 Air density in a distal right anterior MCA branch (arrow). Edema of the visible MCA territory parenchyma due to evolving infarction. Small amounts of cerebral venous air are often present on routine imaging, likely due to bubbles of air injected during IV contrast or medication
administration floating retrograde to the larger cerebral venous structures including the cavernous sinuses and superior sagittal sinus. These small venous air emboli are generally of no clinical significance [112].
Venous Infarction Although arterial pathology, such as arterial stenosis or occlusion, is the most common and widely recognized causes of interruption of blood flow to the brain leading to infarction, downstream venous occlusion may also precipitate acute ischemic stroke. Various venous pathologies—including traumatic or iatrogenic venous thrombus or occlusion, venous hypertension related to a dural arteriovenous fistula, or occlusion of a developmental venous anomaly— may interrupt or slow venous drainage from the upstream parenchyma [113]. Without a pathway for venous drainage, intravascular pressures rise and eventually equal that of the cerebral perfusion pressure, preventing arterial blood from flowing into the territory and leading to ischemia and infarction. Venous infarction is rare, accounting for only 0.5% of all stroke [114] and clinical presentations as well as
underlying predisposing factors may vary greatly. However, when compared to arterial thromboembolism, affected individuals tend to be younger and present more often with headache and diffuse encephalopathy rather than with a painless focal neurologic deficit. Pregnancy, malignancy, steroid or oral contraceptive use, or any underlying prothrombotic condition are all known risk factors, among many others [114,115]. In addition to variability in clinical presentation, venous infarctions have a varied appearance on imaging, which can add to diagnostic difficulty. Parenchymal lesions will commonly cross arterial vascular boundaries and may be bilateral or symmetric if a midline venous structure is affected, such as the superior sagittal sinus or straight sinus. Hemorrhagic complications of venous infarctions are much more common compared to arterial infarctions, occurring in up to 40% of patients with cerebral venous thrombosis, presumably as a result of the underlying venous hypertension in the affected region [115].
The location of parenchymal changes corresponds to the causative thrombosed venous structure:
◾ Frontal and parietal paramedian lesions will be seen with superior sagittal sinus occlusion ◾ Temporal lesions with transverse sinus and vein of Labbe occlusion ◾ Bilateral thalamic lesions with straight sinus and vein of Galen occlusion
Parenchymal changes of venous infarction include edema, commonly with superimposed hemorrhage within the infarcted territory. Adjacent thrombosed venous structures will appear hyperattenuating on CT or show blooming artifact on susceptibility weighted MRI, described as the “cord sign” when involving cortical veins (Fig. 77.18).
Figure 77.18 Right parietal hematoma with adjacent thrombosed cortical vein (arrows) showing hyperattenuation on CT (A) and blooming artifact on MRI (B). MRI may show patchy restricted diffusion, often to a lesser degree and more heterogeneous than that encountered with arterial infarction [116]. Vascular congestion within the affected parenchyma may lead to heterogeneous parenchymal and leptomeningeal enhancement, as well as increased cerebral blood volume (CBV) on perfusion imaging [115,117].
Associated venous thrombus may be visible as blooming artifact on susceptibility weighted or T2* images, absence of the normal flow void on T2 weighted images, or as T1 hyperintensity along an adjacent cortical vein or dural sinus. CTV and contrast-enhanced MRV are also very helpful in these cases to delineate the degree of thrombus propagation as well as to monitor improvement if anticoagulation is initiated. The classically described “empty delta sign” may be seen on CTV or contrast-enhanced MRI/MRV in superior sagittal sinus thrombosis, describing the lack of central contrast filling of the triangular sinus, with peripheral enhancement [118]. Key Point Venous infarctions tend to cross arterial territory boundaries and have a high incidence of hemorrhage compared to arterial infarctions.
Arterial Vasospasm Cerebral arterial vasospasm may occur following an insult to the intracranial arteries, most commonly after aneurysmal subarachnoid hemorrhage where
vasospasm may be encountered in up to 50–90% of cases on DSA [119]. Vasospasm following aneurysm rupture may begin a few days after hemorrhage and typically peaks around 1-week post ictus. Involvement may be focal or diffuse, and vary in severity from mild and asymptomatic to severe with resulting focal neurologic deficits and, or acute infarctions. A large volume of subarachnoid clot is the best predictor for spasm, and the modified Fisher scale may be used to stratify risk (Table 77.4). Other predictors of spasm include slow clearance of hemorrhage from the subarachnoid space, intraventricular hematoma, poor neurologic condition on admission, and other vascular risk factors such as history of smoking, diabetes, or hypertension [119]. Symptomatic vasospasm after aneurysm rupture may be treated with endovascular techniques including balloon angioplasty and/or infusion of vasodilators at the site of spasm, or nonendovascular therapies such as intrathecal nimodipine. Table 77.4 Modified Fisher Scale for Stratifying Risk of Vasospasm After Subarachnoid Hemorrhage
Gra de
SAH
IVH
Risk of Vasospasm
0
None
None Very low risk
1
Focal or diffuse thin layer
None Low risk
2
Focal or diffuse thin layer
Prese Moderate risk nt
3
Focal or diffuse thick layer
None High risk
4
Focal or diffuse thick layer
Prese Very high nt risk
Modified Fisher Scale Vascular imaging in suspected vasospasm cases is commonly performed with transcranial Doppler ultrasound (TCD), CTA, and DSA. TCD is used to detect increased flow velocities in the proximal branches of the circle of Willis. While TCD is more operator dependent than cross sectional imaging and may not detect areas of more distal spasm, evaluation is low cost and may be helpful for surveillance [119].
CTA is very useful in vasospasm evaluation, owing to wide availability, repeatability, and the ability to perform concurrent perfusion studies. CTA will show concentric focal, segmental, or diffuse narrowing of the affected intracranial arteries. The most severely involved arteries often correspond to areas of greatest subarachnoid clot, which tends to be centered around the circle of Willis due to the predilection of aneurysms to originate from this region. The degree of stenosis is evaluated in comparison with prespasm imaging, most often CTA performed on admission. Without comparison imaging, vasospasm can be difficult to differentiate from congenitally hypoplastic segments or pre-existing stenoses from atherosclerosis or other causes. Perfusion imaging is commonly used in conjunction with CTA to assess the functional effect of stenosis on the distal territory, helping to delineate areas of infarction or ischemic penumbra in severe cases. DSA is reserved for severe cases when intra-arterial therapy is being considered.
Conclusion
Acute ischemic stroke remains a large source of morbidity and mortality across the globe, and recent developments in diagnosis and management have increased access to life-saving therapies. Diagnostic imaging and image-guided interventions remain the bedrock of stroke management, and familiarity with new imaging techniques and workflows are required for swift and accurate decision making during timesensitive stroke management.
Suggested Readings • JL Saver, GC Fonarow, EE Smith, MJ Reeves, MV Grau-Sepulveda, W Pan, et al., Time to treatment with intravenous tissue plasminogen activator and outcome from acute ischemic stroke, JAMA 309 (23) (2013 Jun) 2480. • M Goyal, AP Jadhav, A Bonafe, H Diener, V Mendes Pereira, E Levy, et al., Analysis of workflow and time to treatment and the effects on outcome in endovascular treatment of acute ischemic stroke: results from the SWIFT PRIME Randomized Controlled Trial, Radiology 279 (3) (2016 Jun) 888–897.
• RG Nogueira, AP Jadhav, DC Haussen, A Bonafe, RF Budzik, P Bhuva, et al., Thrombectomy 6 to 24 hours after stroke with a mismatch between deficit and infarct, N Engl J Med 378 (1) (2018 Jan) 11–21. • American College of Radiology, ACR Appropriateness Criteria: Cerebrovascular Disease, American College of Radiology, 2016. • BK Menon, CD d’Esterre, EM Qazi, M Almekhlafi, L Hahn, AM Demchuk, et al., Multiphase CT angiography: a new tool for the imaging triage of patients with acute ischemic stroke, Radiology 275 (2) (2015 May) 510–520. • TG Jovin, A Chamorro, E Cobo, MA de Miquel, CA Molina, A Rovira, et al., Thrombectomy within 8 hours after symptom onset in ischemic stroke, N Engl J Med 372 (24) (2015 Jun) 2296– 2306. • C Virapongse, C Cazenave, R Quisling, M Sarwar, S Hunter, The empty delta sign: frequency and significance in 76 cases of dural sinus thrombosis, Radiology 162 (3) (1987 Mar) 779– 785.
References
[1] CDC, Stroke facts [Internet]. Centers for Disease Control and Prevention; [cited 2021 Jan 7]. Available from: https://www.cdc.gov/stroke/facts.htm [2] MJ O’Donnell, D Xavier, L Liu, H Zhang, SL Chin, P Rao-Melacini, et al., Risk factors for ischaemic and intracerebral haemorrhagic stroke in 22 countries (the INTERSTROKE study): a casecontrol study, The Lancet 376 (9735) (2010 Jul) 112– 123. [3] JL Saver, GC Fonarow, EE Smith, MJ Reeves, MV Grau-Sepulveda, W Pan, et al., Time to treatment with intravenous tissue plasminogen activator and outcome from acute ischemic stroke, JAMA 309 (23) (2013 Jun) 2480. [4] JL Saver, M Goyal, A van der Lugt, BK Menon, CB.L.M Majoie, DW Dippel, et al., Time to treatment with endovascular thrombectomy and outcomes from ischemic stroke: a meta-analysis, JAMA 316 (12) (2016 Sep) 1279. [5] M Goyal, AP Jadhav, A Bonafe, H Diener, V Mendes Pereira, E Levy, et al., Analysis of workflow and time to treatment and the effects on outcome in
endovascular treatment of acute ischemic stroke: results from the SWIFT PRIME Randomized Controlled Trial, Radiology 279 (3) (2016 Jun) 888– 897. [6] BK Menon, TT Sajobi, Y Zhang, JL Rempel, A Shuaib, J Thornton, et al., Analysis of workflow and time to treatment on thrombectomy outcome in the Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) Randomized, Controlled Trial, Circulation 133 (23) (2016 Jun) 2279–2286. [7] RG Nogueira, AP Jadhav, DC Haussen, A Bonafe, RF Budzik, P Bhuva, et al., Thrombectomy 6 to 24 hours after stroke with a mismatch between deficit and infarct, N Engl J Med 378 (1) (2018 Jan) 11–21. [8] GW Albers, MP Marks, S Kemp, S Christensen, JP Tsai, S Ortega-Gutierrez, et al., Thrombectomy for stroke at 6 to 16 hours with selection by perfusion imaging, N Engl J Med 378 (8) (2018 Feb) 708–718. [9] HP Adams, BH Bendixen, LJ Kappelle, J Biller, BB Love, DL Gordon, et al., Classification of
subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment, Stroke 24 (1) (1993 Jan) 35–41. [10] SE Sacco, JP Whisnant, JP Broderick, SJ Phillips, WM O’Fallon, Epidemiological characteristics of lacunar infarcts in a population, Stroke 22 (10) (1991 Oct) 1236–1241. [11] J Bogousslavsky, G Van Melle, F Regli, The Lausanne Stroke Registry: analysis of 1,000 consecutive patients with first stroke, Stroke 19 (9) (1988 Sep) 1083–1092. [12] JI Sage, RL Van Uitert, Risk of recurrent stroke in patients with atrial fibrillation and non-valvular heart disease, Stroke 14 (4) (1983 Aug) 537–540. [13] LR Caplan, DB Hier, I D’Cruz, Cerebral embolism in the Michael Reese Stroke Registry, Stroke 14 (4) (1983 Aug) 530–536. [14] RL Koller, Recurrent embolic cerebral infarction and anticoagulation, Neurology 32 (3) (1982 Mar) 283–285.
[15] American College of Radiology, ACR Appropriateness Criteria: Cerebrovascular Disease, American College of Radiology, (2016). [16] JA Chalela, CS Kidwell, LM Nentwich, M Luby, JA Butman, M Demchuk, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison, Lancet 369 (9558) (2007 Jan 27) 293–298. [17] C Provost, M Soudant, L Legrand, W Ben Hassen, Y Xie, S Soize, et al., Magnetic resonance imaging or computed tomography before treatment in acute ischemic stroke: effect on workflow and functional outcome, Stroke 50 (3) (2019 Mar) 659– 664. [18] DS Liebeskind, N Sanossian, WH Yong, S Starkman, MP Tsang, AL Moya, et al., CT and MRI early vessel signs reflect clot composition in acute stroke, Stroke 42 (5) (2011 May) 1237–1243. [19] A Arboix, J Alioc, Cardioembolic stroke: clinical features, specific cardiac disorders and
prognosis, Curr Cardiol Rev 6 (3) (2010 Aug) 150– 161. [20] D Toni, M Fiorelli, S Bastianello, ML Sacchetti, G Sette, C Argentino, et al., Hemorrhagic transformation of brain infarct: predictability in the first 5 hours from stroke onset and influence on clinical outcome, Neurology 46 (2) (1996 Feb) 341– 345. [21] V Larrue, R von Kummer, A Müller, E Bluhmki, Risk factors for severe hemorrhagic transformation in ischemic stroke patients treated with recombinant tissue plasminogen activator: a secondary analysis of the European-Australasian Acute Stroke Study (ECASS II), Stroke 32 (2) (2001 Feb) 438–441. [22] A Scuotto, S Cappabianca, MB Melone, G Puoti, MRI “fogging” in cerebellar ischaemia: case report, Neuroradiology 39 (11) (1997 Nov) 785–787. [23] H Becker, H Desch, H Hacker, A Pencz, CT fogging effect with ischemic cerebral infarcts, Neuroradiology 18 (4) (1979) 185–192.
[24] JA Chalela, SE Kasner, The fogging effect, Neurology 55 (2) (2000 Jul) 315. [25] M Augustin, R Bammer, J Simbrunner, R Stollberger, H-P Hartung, F Fazekas. Diffusionweighted imaging of patients with subacute cerebral ischemia: comparison with conventional and contrast-enhanced MR imaging, AJNR Am J Neuroradiol 21 (9) (2000 Oct) 1596–1602. [26] CA.C Wijman, VL Babikian, IC.A Matjucha, B Koleini, C Hyde, MR Winter, et al., Cerebral microembolism in patients with retinal ischemia, Stroke 29 (6) (1998 Jun) 1139–1143. [27] AM Demchuk, I Christou, TH Wein, RA Felberg, M Malkoff, JC Grotta, et al., Accuracy and criteria for localizing arterial occlusion with transcranial doppler, J Neuroimaging 10 (1) (2000 Jan) 1–12. [28] K Rajamani, M Gorman, Trancranial Doppler in stroke, Biomed Pharmacother 55 (5) (2001 Jun) 247– 257.
[29] A Nacu, CE Kvistad, H Naess, H Øygarden, N Logallo, J Assmus, et al., NOR-SASS (Norwegian Sonothrombolysis in Acute Stroke Study): randomized controlled contrast-enhanced sonothrombolysis in an unselected acute ischemic stroke population, Stroke 48 (2) (2017 Feb) 335–341. [30] AV Alexandrov, M Köhrmann, L Soinne, G Tsivgoulis, AD Barreto, AM Demchuk, et al., Safety and efficacy of sonothrombolysis for acute ischaemic stroke: a multicentre, double-blind, phase 3, randomised controlled trial, Lancet Neurol 18 (4) (2019 Apr) 338–347. [31] WJ Powers, AA Rabinstein, T Ackerson, OM Adeoye, NC Bambakidis, K Becker, et al., Guidelines for the early management of patients with acute ischemic stroke: 2019 update to the 2018 guidelines for the early management of acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association, Stroke [Internet] 50 (12) (2019 Dec), Available from:. https://www.ahajournals.org/doi/10.1161/STR.00000 00000000211.
[32] SH Baik, JW Kim, BM Kim, DJ Kim, Significance of angiographic clot meniscus sign in mechanical thrombectomy of basilar artery stroke, J Neurointerv Surg 12 (5) (2020 May) 477–482. [33] BK Menon, E Qazi, V Nambiar, LD Foster, SD Yeatts, D Liebeskind, et al., Differential effect of baseline computed tomographic angiography collaterals on clinical outcome in patients enrolled in the interventional management of stroke III trial, Stroke 46 (5) (2015 May) 1239–1244. [34] OA Berkhemer, IG.H Jansen, D Beumer, PS.S Fransen, LA van den Berg, AJ Yoo, et al., Collateral status on baseline computed tomographic angiography and intra-arterial treatment effect in patients with proximal anterior circulation stroke, Stroke 47 (3) (2016 Mar) 768–776. [35] M Goyal, AM Demchuk, BK Menon, M Eesa, JL Rempel, J Thornton, et al., Randomized assessment of rapid endovascular treatment of ischemic stroke, N Engl J Med 372 (11) (2015 Mar) 1019–1030.
[36] BK Menon, CD d’Esterre, EM Qazi, M Almekhlafi, L Hahn, AM Demchuk, et al., Multiphase CT angiography: a new tool for the imaging triage of patients with acute ischemic stroke, Radiology 275 (2) (2015 May) 510–520. [37] JM Olivot, M Mlynash, M Inoue, MP Marks, HM Wheeler, S Kemp, et al., Hypoperfusion intensity ratio predicts infarct progression and functional outcome in the DEFUSE 2 cohort, Stroke 45 (4) (2014 Apr) 1018–1023. [38] A Guenego, M Mlynash, S Christensen, S Kemp, JJ Heit, MG Lansberg, et al., Hypoperfusion ratio predicts infarct growth during transfer for thrombectomy: HIR predicts infarct growth, Ann Neurol 84 (4) (2018 Oct) 616–620. [39] L Lin, C Chen, H Tian, A Bivard, N Spratt, CR Levi, et al., Perfusion computed tomography accurately quantifies collateral flow after acute ischemic stroke, Stroke 51 (3) (2020 Mar) 1006– 1009. [40] X Tian, B Tian, Z Shi, X Wu, W Peng, X Zhang, et al., Assessment of intracranial atherosclerotic
plaques using 3D black-blood MRI: comparison with 3D time-of-flight MRA and DSA, J Magn Reson Imaging 53 (2) (2021 Feb) 469–478. [41] RA Willinsky, SM Taylor, K terBrugge, RI Farb, G Tomlinson, W Montanera, Neurologic complications of cerebral angiography: prospective analysis of 2,899 procedures and review of the literature, Radiology 227 (2) (2003 May) 522–528. [42] IG.H Jansen, OA Berkhemer, AJ Yoo, JA Vos, GJ Lycklama à Nijeholt, ME.S Sprengers, et al., Comparison of CTA- and DSA-based collateral flow assessment in patients with anterior circulation stroke, Am J Neuroradiol 37 (11) (2016 Nov) 2037– 2042. [43] J-M Olivot, M Mlynash, VN Thijs, S Kemp, MG Lansberg, L Wechsler, et al., Optimal Tmax threshold for predicting penumbral tissue in acute stroke, Stroke 40 (2) (2009 Feb) 469–475. [44] BC.V Campbell, S Christensen, CR Levi, PM Desmond, GA Donnan, SM Davis, et al., Cerebral blood flow is the optimal CT perfusion parameter for
assessing infarct core, Stroke 42 (12) (2011 Dec) 3435–3440. [45] J-C Ferré, E Bannier, H Raoult, G Mineur, B Carsin-Nicol, J-Y Gauvrit, Arterial spin labeling (ASL) perfusion: techniques and clinical use, Diagn Interv Imaging 94 (12) (2013 Dec) 1211–1223. [46] S Okuchi, A Rojas-Garcia, A Ulyte, I Lopez, J Ušinskienė, M Lewis, et al., Diagnostic accuracy of dynamic contrast-enhanced perfusion MRI in stratifying gliomas: a systematic review and metaanalysis, Cancer Med 8 (12) (2019 Sep) 5564–5573. [47] M Waqas, M Mokin, CT Primiani, AD Gong, HH Rai, F Chin, et al., Large vessel occlusion in acute ischemic stroke patients: a dual-center estimate based on a broad definition of occlusion site, J Stroke Cerebrovasc Dis 29 Feb (2) (2020) 104504. [48] KR Lees, J Emberson, L Blackwell, E Bluhmki, SM Davis, GA Donnan, et al., Effects of alteplase for acute stroke on the distribution of functional outcomes: a pooled analysis of 9 trials, Stroke 47 (9) (2016 Sep) 2373–2379.
[49] J Emberson, KR Lees, P Lyden, L Blackwell, G Albers, E Bluhmki, et al., Effect of treatment delay, age, and stroke severity on the effects of intravenous thrombolysis with alteplase for acute ischaemic stroke: a meta-analysis of individual patient data from randomised trials, The Lancet 384 (9958) (2014 Nov) 1929–1935. [50] PA Barber, AM Demchuk, J Zhang, AM Buchan, Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy, The Lancet 355 (9216) (2000 May) 1670–1674. [51] BC.V Campbell, PJ Mitchell, TJ Kleinig, HM Dewey, L Churilov, N Yassi, et al., Endovascular therapy for ischemic stroke with perfusion-imaging selection, N Engl J Med 372 (11) (2015 Mar) 1009– 1018. [52] TG Jovin, A Chamorro, E Cobo, MA de Miquel, CA Molina, A Rovira, et al., Thrombectomy within 8 hours after symptom onset in ischemic stroke, N Engl J Med 372 (24) (2015 Jun) 2296–2306.
[53] S Bracard, X Ducrocq, JL Mas, M Soudant, C Oppenheim, T Moulin, et al., Mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke (THRACE): a randomised controlled trial, Lancet Neurol 15 (11) (2016 Oct) 1138–1147. [54] OA Berkhemer, PS.S Fransen, D Beumer, LA van den Berg, HF Lingsma, AJ Yoo, et al., A randomized trial of intraarterial treatment for acute ischemic stroke, N Engl J Med 372 (1) (2015 Jan) 11–20. [55] W Hacke, A New DAWN for Imaging-based selection in the treatment of acute stroke, N Engl J Med 378 (1) (2018 Jan) 81–83. [56] AS Turk, A Siddiqui, JT Fifi, RA De Leacy, DJ Fiorella, E Gu, et al., Aspiration thrombectomy versus stent retriever thrombectomy as first-line approach for large vessel occlusion (COMPASS): a multicentre, randomised, open label, blinded outcome, non-inferiority trial, The Lancet 393 (10175) (2019 Mar) 998–1008.
[57] W Boisseau, S Escalard, R Fahed, B Lapergue, S Smajda, B Maier, et al., Direct aspiration stroke thrombectomy: a comprehensive review, J Neurointerv Surg 12 (11) (2020 Nov) 1099–1106. [58] MP Marks, MG Lansberg, M Mlynash, S Kemp, R McTaggart, G Zaharchuk, et al., Correlation of AOL recanalization, TIMI reperfusion and TICI reperfusion with infarct growth and clinical outcome, J Neurointerv Surg 6 (10) (2014 Dec) 724–728. [59] JE Fugate, AM Klunder, DF Kallmes, What is meant by “TICI”?, Am J Neuroradiol 34 (9) (2013 Sep) 1792–1797. [60] OO Zaidat, AJ Yoo, P Khatri, TA Tomsick, R von Kummer, JL Saver, et al., Recommendations on angiographic revascularization grading standards for acute ischemic stroke: a consensus statement, Stroke 44 (9) (2013 Sep) 2650–2663. [61] KM Jang, TK Nam, MJ Ko, HH Choi, JT Kwon, SW Park, et al., Thrombolysis in cerebral infarction grade 2c or 3 represents a better outcome than 2b for endovascular thrombectomy in acute ischemic stroke:
a network meta-analysis, World Neurosurg, 136 (2020 Apr) e419–e439. [62] K Vahedi, J Hofmeijer, E Juettler, E Vicaut, B George, A Algra, et al., Early decompressive surgery in malignant infarction of the middle cerebral artery: a pooled analysis of three randomised controlled trials, Lancet Neurol 6 (3) (2007 Mar) 215–222. [63] H Almqvist, S Holmin, MV Mazya, Dual energy CT after stroke thrombectomy alters assessment of hemorrhagic complications, Neurology 93 (11) (2019 Sep) e1068–e1075. [64] North American Symptomatic Carotid Endarterectomy Trial Collaborators, Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis, N Engl J Med 325 (7) (1991 Aug) 445–453. [65] GG Ferguson, M Eliasziw, HW.K Barr, GP Clagett, RW Barnes, MC Wallace, et al., The North American Symptomatic Carotid Endarterectomy Trial: surgical results in 1415 patients, Stroke 30 (9) (1999 Sep) 1751–1758.
[66] Endarterectomy for asymptomatic carotid artery stenosis, Executive Committee for the Asymptomatic Carotid Atherosclerosis Study, JAMA J Am Med Assoc 273 (18) (1995 May) 1421–1428. [67] WS Moore, HJ.M Barnett, HG Beebe, EF Bernstein, BJ Brener, T Brott, et al., Guidelines for carotid endarterectomy: a multidisciplinary consensus statement from the ad hoc committee, american heart association, Circulation 91 (2) (1995 Jan) 566–579. [68] HS Bassiouny, Y Sakaguchi, SA Mikucki, JF McKinsey, G Piano, BL Gewertz, et al., Juxtalumenal location of plaque necrosis and neoformation in symptomatic carotid stenosis, J Vasc Surg 26 (4) (1997 Oct) 585–594. [69] S Carr, A Farb, WH Pearce, R Virmani, JS Yao, Atherosclerotic plaque rupture in symptomatic carotid artery stenosis, J Vasc Surg 23 (5) (1996 May) 755–765, discussion 765-766. [70] RJ Lusby, LD Ferrell, WK Ehrenfeld, RJ Stoney, EJ Wylie, Carotid plaque hemorrhage. Its role in
production of cerebral ischemia, Arch Surg Chic Ill 117 (11) (1960 Nov) 1479–1488. [71] L Saba, G Micheletti, W Brinjikji, P Garofalo, R Montisci, A Balestrieri, et al., Carotid intraplaquehemorrhage volume and its association with cerebrovascular events, Am J Neuroradiol (2019 Sep). [72] L Saba, C Yuan, TS Hatsukami, N Balu, Y Qiao, JK DeMarco, et al., Carotid artery wall imaging: perspective and guidelines from the ASNR Vessel Wall Imaging Study Group and Expert Consensus Recommendations of the American Society of Neuroradiology, Am J Neuroradiol 39 (2) (2018 Feb) E9–31. [73] TT de Weert, M Ouhlous, E Meijering, PE Zondervan, JM Hendriks, MR.H.M van Sambeek, et al., In vivo characterization and quantification of atherosclerotic carotid plaque components with multidetector computed tomography and histopathological correlation, Arterioscler Thromb Vasc Biol 26 (10) (2006 Oct) 2366–2372.
[74] KR Nandalur, E Baskurt, KD Hagspiel, CD Phillips, CM Kramer, Calcified carotid atherosclerotic plaque is associated less with ischemic symptoms than is noncalcified plaque on MDCT, Am J Roentgenol 184 (1) (2005 Jan) 295– 298. [75] J Cai, TS Hatsukami, MS Ferguson, WS Kerwin, T Saam, B Chu, et al., In vivo quantitative measurement of intact fibrous cap and lipid-rich necrotic core size in atherosclerotic carotid plaque: comparison of high-resolution, contrast-enhanced magnetic resonance imaging and histology, Circulation 112 (22) (2005 Nov) 3437–3444. [76] BA Wasserman, WI Smith, HH Trout, RO Cannon, RS Balaban, AE Arai, Carotid artery atherosclerosis: in vivo morphologic characterization with gadolinium-enhanced double-oblique MR imaging—initial results, Radiology 223 (2) (2002 May) 566–573. [77] Q Li, J Wang, H Chen, X Gong, N Ma, K Gao, et al., Characterization of craniocervical artery dissection by simultaneous MR noncontrast
angiography and intraplaque hemorrhage imaging at 3T, Am J Neuroradiol 36 (9) (2015 Sep) 1769–1775. [78] D Leys, L Bandu, H Hénon, C Lucas, F Mounier-Vehier, P Rondepierre, et al., Clinical outcome in 287 consecutive young adults (15 to 45 years) with ischemic stroke, Neurology 59 (1) (2002 Jul) 26–33. [79] DH Benninger, D Georgiadis, C Kremer, A Studer, K Nedeltchev, RW Baumgartner, Mechanism of ischemic infarct in spontaneous carotid dissection, Stroke 35 (2) (2004 Feb) 482–485. [80] VH Lee, RD Brown, JN Mandrekar, B Mokri, Incidence and outcome of cervical artery dissection: a population-based study, Neurology 67 (10) (2006 Nov) 1809–1812. [81] R Dziewas, C Konrad, B Dräger, S Evers, M Besselmann, P Lüdemann, et al., Cervical artery dissection: clinical features, risk factors, therapy and outcome in 126 patients, J Neurol 250 (10) (2003 Oct) 1179–1184.
[82] B Mokri, PL Silbert, WI Schievink, Piepgras DG. Cranial nerve palsy in spontaneous dissection of the extracranial internal carotid artery, Neurology 46 (2) (1996 Feb) 356–359. [83] MH Rodallec, V Marteau, S Gerber, L Desmottes, M Zins, Craniocervical arterial dissection: spectrum of imaging findings and differential diagnosis, Radiographics 28 (6) (2008 Oct) 1711–1728. [84] Y Kadkhodayan, DT Jeck, CJ Moran, CP Derdeyn, Angioplasty and stenting in carotid dissection with or without associated pseudoaneurysm, AJNR Am J Neuroradiol 26 (9) (2005 Oct), 2328–2335. [85] AG Osborn, RE Anderson, Angiographic spectrum of cervical and intracranial fibromuscular dysplasia, Stroke 8 (5) (1977 Sep) 617–626. [86] E Touzé, C Oppenheim, D Trystram, G Nokam, M Pasquini, S Alamowitch, et al., Fibromuscular dysplasia of cervical and intracranial arteries, Int J Stroke 5 (4) (2010 Aug) 296–305.
[87] JW Olin, HL Gornik, JM Bacharach, J Biller, LJ Fine, BH Gray, et al., Fibromuscular dysplasia: state of the science and critical unanswered questions: a scientific statement from the, American Heart Association. Circulation. 129 (9) (2014 Mar) 1048– 1078. [88] PM.C Choi, D Singh, A Trivedi, E Qazi, D George, J Wong, et al., Carotid webs and recurrent ischemic strokes in the era of ct angiography, Am J Neuroradiol 36 (11) (2015 Nov) 2134–2139. [89] PI Sajedi, JN Gonzalez, CA Cronin, T Kouo, A Steven, J Zhuo, et al., Carotid bulb webs as a cause of “cryptogenic” ischemic stroke, Am J Neuroradiol 38 (7) (2017 Jul) 1399–1404. [90] L Pantoni, JH Garcia, Pathogenesis of leukoaraiosis: a review, Stroke 28 (3) (1997 Mar) 652–659. [91] FE de Leeuw, JC de Groot, M Oudkerk, JC Witteman, A Hofman, J van Gijn, et al., A follow-up study of blood pressure and cerebral white matter lesions, Ann Neurol 46 (6) (1999 Dec) 827–833.
[92] LH Kuller, WT Longstreth, AM Arnold, C Bernick, RN Bryan, NJ Beauchamp, White matter hyperintensity on cranial magnetic resonance imaging: a predictor of stroke, Stroke 35 (8) (2004 Aug) 1821–1825. [93] JF Arenillas, Intracranial Atherosclerosis: current concepts, Stroke 42 (Supplement 1) (2011 Jan) S20–S23. [94] MI Chimowitz, MJ Lynn, CP Derdeyn, TN Turan, D Fiorella, BF Lane, et al., Stenting versus aggressive medical therapy for intracranial arterial stenosis, N Engl J Med 365 (11) (2011 Sep) 993– 1003. [95] HN Lee, C-W Ryu, Yu.n SJ, Vessel-Wall Magnetic resonance imaging of intracranial atherosclerotic plaque and ischemic stroke: a systematic review and meta-analysis, Front Neurol 9 (2018 Dec) 1032. [96] P Berlit, Review: diagnosis and treatment of cerebral vasculitis, Ther Adv Neurol Disord 3 (1) (2010 Jan) 29–42.
[97] G Bathla, P Watal, S Gupta, P Nagpal, S Mohan, T Moritani, Cerebrovascular manifestations of neurosarcoidosis: an underrecognized aspect of the imaging spectrum, Am J Neuroradiol 39 (7) (2018 Jul) 1194–1200. [98] Y Kadkhodayan, A Alreshaid, CJ Moran, DT Cross, WJ Powers, CP Derdeyn, Primary angiitis of the central nervous system at conventional angiography, Radiology 233 (3) (2004 Dec) 878–882. [99] TR Cupps, PM Moore, AS Fauci, Isolated angiitis of the central nervous system. Prospective diagnostic and therapeutic experience, Am J Med 74 (1) (1983 Jan) 97–105. [100] DM Mandell, M Mossa-Basha, Y Qiao, CP Hess, F Hui, C Matouk, et al., Intracranial vessel wall MRI: principles and expert consensus recommendations of the american society of neuroradiology, Am J Neuroradiol 38 (2) (2017 Feb) 218–229. [101] TR Miller, R Shivashankar, M Mossa-Basha, D Gandhi, Reversible cerebral vasoconstriction syndrome, part 1: epidemiology, pathogenesis, and
clinical course, Am J Neuroradiol 36 (8) (2015 Aug) 1392–1399. [102] TR Miller, R Shivashankar, M Mossa-Basha, D Gandhi, Reversible cerebral vasoconstriction syndrome, part 2: diagnostic work-up, imaging evaluation, and differential diagnosis, Am J Neuroradiol 36 (9) (2015 Sep) 1580–1588. [103] J Suzuki, A Takaku, Cerebrovascular “Moyamoya” disease: disease showing abnormal netlike vessels in base of brain, Arch Neurol 20 (3) (1969) 288–299. [104] N Mori, S Mugikura, S Higano, T Kaneta, M Fujimura, A Umetsu, et al., The leptomeningeal “ivy sign” on fluid-attenuated inversion recovery MR imaging in moyamoya disease: a sign of decreased cerebral vascular reserve?, Am J Neuroradiol 30 (5) (2009 May) 930–935. [105] H-K Yoon, H-J Shin, YW Chang, Ivy sign in childhood Moyamoya disease: depiction on FLAIR and contrast-enhanced T1-weighted MR images, Radiology 223 (2) (2002 May) 384–389.
[106] A Kathuveetil, PN Sylaja, S Senthilvelan, K Chandrasekharan, M Banerjee, B Jayanand Sudhir, Vessel wall thickening and enhancement in highresolution intracranial vessel wall imaging: a predictor of future ischemic events in Moyamoya disease, Am J Neuroradiol 41 (1) (2020 Jan) 100– 105. [107] BY Huang, M Castillo, Hypoxic-ischemic brain injury: imaging findings from birth to adulthood, Radiographics 28 (2) (2008 Mar) 417– 439. [108] EC Kavanagh, The reversal sign, Radiology 245 (3) (2007 Dec) 914–915. [109] J Kim, K-H Chang, IC Song, KH Kim, BJ Kwon, H-C Kim, et al. Delayed encephalopathy of acute carbon monoxide intoxication: diffusivity of cerebral white matter lesions, AJNR Am J Neuroradiol 24 (8) (2003 Sep) 1592–1597. [110] DA Godoy, M Di Napoli, AA Rabinstein, Cerebral fat embolism: recognition, complications, and prognosis, Neurocrit Care 29 (3) (2018 Dec) 358–365.
[111] R Mishra, P Reddy, M Khaja, Fatal cerebral air embolism: a case series and literature review, Case Rep Crit Care 2016 (2016) 1–4. [112] D Rubinstein, D Symonds, Gas in the cavernous sinus, AJNR Am J Neuroradiol 15 (3) (1994 Mar) 561–566. [113] J Inamasu, R Shiobara, T Kawase, J Kanzaki, Haemorrhagic venous infarction following the posterior petrosal approach for acoustic neurinoma surgery: a report of two cases, Eur Arch Otorhinolaryngol 259 (3) (2002 Mar) 162–165. [114] M-G Bousser, JM Ferro, Cerebral venous thrombosis: an update, Lancet Neurol 6 (2) (2007 Feb) 162–170. [115] G Saposnik, F Barinagarrementeria, RD Brown, CD Bushnell, B Cucchiara, M Cushman, et al., Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association, Stroke 42 (4) (2011 Apr) 1158– 1192.
[116] E Keller, S Flacke, H Urbach, HH Schild, Diffusion- and perfusion-weighted magnetic resonance imaging in deep cerebral venous thrombosis, Stroke 30 (5) (1999 May) 1144–1146. [117] M Gotoh, T Ohmoto, H Kuyama, Experimental study of venous circulatory disturbance by dural sinus occlusion, Acta Neurochir (Wien) 124 (2–4) (1993 Jun) 120–126. [118] C Virapongse, C Cazenave, R Quisling, M Sarwar, S Hunter, The empty delta sign: frequency and significance in 76 cases of dural sinus thrombosis, Radiology 162 (3) (1987 Mar) 779–785. [119] JM Findlay, J Nisar, T Darsaut, Cerebral vasospasm: a review, Can J Neurol Sci J Can Sci Neurol 43 (1) (2016 Jan) 15–32.
CHAPTER 78
Brain Tumors Shobhit Garg, Jeffrey Ware, Suyash Mohan, Rajan Jain
Introduction Imaging plays a pivotal role in the diagnosis and management of brain tumors. In the past decade, there has been a substantial change in the approach to many brain tumors with refinements in histological classification and increasing use of molecular markers to define biologic behavior, prognosis, and therapy. Imaging can play an important role by predicting molecular markers for these brain tumors preoperatively. Many conventional and advanced imaging techniques have been shown to correlate with tumor genotypes [1]. Neuroradiologists are at the forefront of this dynamic change in brain tumor imaging. It is important for radiologists to identify the conventional imaging signs as well as use advanced imaging techniques to identify tumors, and if possible, determine the molecular make up of these tumors for guiding therapy. Metastatic brain tumors are at least twice as common as malignant primary brain tumors [2]. Meningiomas are the most common benign primary brain tumors and the most common primary malignant brain tumor is glioblastoma [3].
2016 WHO Classification of Central Nervous System (CNS) Tumors The 2016 World Health Organization Classification of Tumors of the Central Nervous System has significantly changed since 2007 with the incorporation of molecular parameters in addition to histology to define many tumor entities [4]. In the new classification, there has been a restructuring of the
diffuse gliomas, medulloblastomas, and other embryonal tumors based on genomic markers.
◾inTheclassification most striking change is incorporation of IDH mutational status and 1p/19q codeletion of diffuse gliomas. In these cases, molecular markers have been given more importance than histological phenotype [4] ◾classification Medulloblastomas have been divided into distinct molecular subgroups in the new ◾single Solitary fibrous tumor of the dura has now been combined with hemangiopericytoma as a entity [4] ◾leptomeningeal Many new entities have been introduced including epithelioid glioblastoma, diffuse glioneuronal tumor, diffuse midline glioma (H3K27M-mutant), embryonal tumor with multilayered rosettes (ETMR), ependymoma RELA fusion-positive, and medulloblastoma WNT Some entities which no longer have diagnostic and/or biologic relevance have been removed. These include gliomatosis cerebri, protoplasmic astrocytoma, fibrillary astrocytoma, primitive neuroectodermal tumor, ependymoblastoma, and cellular variant of ependymoma
◾
Overall, this appears to be a more practical and logical system in terms of prognosis and treatment options for brain tumors, which share similar genetics and biologic behavior rather than just histopathology.
Brain Tumor Imaging Protocol Magnetic resonance imaging (MRI) is the current standard of care for brain tumor imaging. Although brain tumor imaging protocols vary substantially across institutions, the objectives remain the same. These include, tumor detection and depiction of its extent, estimation of tumor burden, guidance for biopsy/treatment, assessment of treatment response, and differentiation of treatment-induced changes from recurrence (true progression vs pseudoprogression). In the recent years, imaging has also played a key role in identifying genotype and molecular markers of brain tumors preoperatively (radiogenomics) [5]. A representative brain tumor MR protocol may include some combination of the following sequences (this is only a guide as protocols depend on institutional preferences and local practices).
◾ T1W axial and sagittal or 3D volumetric T1 ◾ T2W axial ◾ FLAIR (2D or 3D) ◾ Diffusion axial (DWI) ◾ T2* (gradient or susceptibility-weighted imaging) ◾sequence Postcontrast T1 spin echo in at least two different planes or postcontrast volumetric 3D T1 ◾ Functional imaging—perfusion (physiologic measure), spectroscopy (metabolic), fMRI ◾ tensor imaging ◾ Tractography/diffusion Hybrid MR-PET
Diffuse Gliomas (Diffuse Astrocytic and Oligodendroglial Tumors) Diffusely infiltrating gliomas (astrocytic and oligodendroglial) have been grouped together in the new 2016 WHO classification on the basis of their growth pattern as well as IDH gene mutation status [4]. Diffuse Astrocytoma Diffuse astrocytomas are WHO grade 2 and grade 3 infiltrative tumors of the brain. They are now divided into IDH mutant, IDH wild type, and NOS (if IDH mutational status is unavailable) categories. Approximately 70–80% of WHO grade 2 and grade 3 astrocytomas possess IDH mutations and rest are IDH wild type [6]. IDH mutant astrocytomas have a favorable prognosis compared with IDH wild type astrocytomas [4]. Diffuse astrocytomas (WHO grade 2) are more commonly seen in young adults. Anaplastic astrocytomas (WHO grade 3) occur in a slightly older population than the lower grade astrocytomas with peak incidence between 40 and 50 years of age. These tumors more frequently arise in the cerebral hemispheres although the cerebellum and brainstem may also be affected. Seizure is the most common presenting symptom. On CT, diffuse astrocytoma is a relatively poorly marginated, isodense to hypodense, nonenhancing lesion with mass effect. Calcification and hemorrhage are not common. On MRI, these are infiltrative mass lesions, isointense to hypointense compared with white matter on T1 and hyperintense on T2W images. There is no restriction of diffusion and usually no enhancement on postcontrast imaging (Fig. 78.1). Necrosis is usually absent. Enhancement, vasogenic edema and mass effect may be seen in WHO grade 3 anaplastic astrocytomas (Fig. 78.2). A subgroup of these astrocytomas may exhibit the “T2-FLAIR mismatch sign” that has been described as homogeneously hyperintense signal on T2 and relative suppression (hypointense signal) on FLAIR, with the exception of a FLAIR hyperintense peripheral rim (Fig. 78.3). The T2-FLAIR mismatch sign has shown very high specificity for diagnosing IDH mutant, 1p19q noncodeleted astrocytomas [7–10].
FIGURE 78.1 Diffuse astrocytoma (WHO grade 2). (A) Axial T2, (B) axial FLAIR, and (C) axial T1 postcontrast images demonstrate a poorly defined, infiltrative, T2, and FLAIR hyperintense, nonenhancing mass in the left frontal lobe extending across the genu of corpus callosum into contralateral white matter with mild mass effect on the frontal horns of the lateral ventricles.
FIGURE 78.2 Anaplastic astrocytoma (IDH mutant). (A) Axial T2, (B) axial FLAIR, and (C) axial T1 postcontrast images demonstrate a T2 and FLAIR hyperintense, nonenhancing infiltrative, and expansile mass in the left insula with mass effect on the left lentiform nucleus.
FIGURE 78.3 IDH mutant astrocytoma 1p19q noncodeleted. (A) Axial T2, (B) axial FLAIR, and (C) axial T1 postcontrast images demonstrate a T2 hyperintense, nonenhancing, infiltrative, and expansile mass in the left temporal lobe exhibiting the “T2-FLAIR mismatch sign.”
MR spectroscopy typically shows elevated choline, low N-acetyl aspartate (NAA), elevated choline/creatine ratio, elevated myoinositol, and the absence of lactate (due to the absence of necrosis). There is no increase in relative cerebral blood volume (rCBV) on MR perfusion in lower grade (WHO grade 2) astrocytomas. Anaplastic astrocytomas (WHO grade 3) can show elevated rCBV on perfusion imaging. Tumors with rCBV above 1.75 demonstrate higher grade and rapid progression [11].
Key Point Diffuse gliomas are usually T2 hyperintense nonenhancing lesions with mass effect and infiltrative features (enhancement could suggest dedifferentiation into a higher grade). In lower-grade (WHO grade 2 and grade 3) gliomas, T2-FLAIR mismatch sign represents a highly specific imaging biomarker for the IDH mutant, 1p/19q noncodeleted molecular subtype.
Glioblastoma Glioblastomas are aggressive, poorly differentiated, WHO grade 4 astrocytic tumors accounting for 16% of all primary brain tumors [12]. Primary glioblastomas develop rapidly de novo in elderly patients, without clinical or histologic evidence of a lower-grade precursor lesion. Secondary glioblastomas arise from a pre-existing low-grade diffuse astrocytoma in younger patients and are preferentially located in the frontal lobe [13]. Despite a similar histologic appearance, primary and secondary glioblastomas are distinct tumor entities that originate from different
precursor cells [13]. In the 2016 WHO classification, glioblastomas are divided into 1. glioblastoma, IDH wild type (about 90% of cases), which corresponds most frequently with the clinically defined primary or de novo glioblastoma, and 2. glioblastoma, IDH mutant (about 10% of cases) correspond closely to so-called “secondary” glioblastomas, almost always are IDH mutated and MGMT methylated [14].
The differences between the two are listed in Table 78.1. Secondary IDH mutant glioblastomas are less aggressive and carry a better prognosis than primary glioblastomas. On CT and MR, glioblastomas are heterogeneous tumors with thick irregular enhancing margins and central necrosis (Fig. 78.4). These lesions can have intratumoral vessels and hemorrhage. T2 signal abnormality surrounding the enhancing component of the tumor typically reflects a combination of vasogenic edema and infiltrative neoplastic cells. Solid enhancing component of the tumor can show heterogenous signal on diffusion imaging with variable areas of diffusion restriction. Necrotic glioblastomas show incomplete, irregular, hypointense rim on SWI which is frequently found at the inner aspect of the contrast enhancing rim due to random deposition of hemorrhagic products at the edge of necrotic cavity [15].
FIGURE 78.4 Glioblastoma IDH wild type. (A) Axial FLAIR and (B) axial T1 postcontrast images demonstrate a large and markedly heterogeneous right frontoparietal tumor with thick irregular enhancing margins, central necrosis, surrounding edema, and mass effect.
MR perfusion shows elevated rCBV. IDH wild type gliomas are more proangiogenic than IDH mutant tumors, and will typically show higher cerebral blood flow [16–18]. MR spectroscopy shows elevated choline, decreased NAA, decreased myoinositol, and a lipid/lactate peak (due to necrosis). PET shows increased FDG uptake to a level higher than gray matter. Glioblastomas can invade the corpus callosum and cross midline in a butterfly configuration. They can be multifocal or multicentric. Secondary glioblastoma may also arise in the background of a gliomatosis pattern (diffuse glioma with involvement of more than two lobes) (Fig. 78.5).
FIGURE 78.5 Secondary glioblastoma IDH mutant with background infiltrative tumor (gliomatosis pattern). (A, B, C) Axial FLAIR and (D) axial T1 postcontrast images demonstrate a heterogeneously enhancing mass (yellow arrow) in the right temporal lobe with central necrosis. Poorly defined, infiltrative FLAIR hyperintense signal diffusely involving multiple lobes in the right cerebral hemisphere represents a background gliomatosis pattern of diffuse glioma.
These tumors have a poor prognosis with a median survival rate of less than 2 years [19]. The presence of MGMT methylation is significantly correlated with longer overall survival for newly diagnosed glioblastoma patients [20,21]. GBM patients with less necrosis and less tumoral enhancement on preoperative MRI have better prognosis and survival than patients with greater amounts of necrosis and tumoral enhancement [22].
Key Point Primary glioblastoma is usually a large heterogenous tumor with thick irregular enhancing wall, central necrosis, hemorrhage, neovascularity, and other aggressive features typically arising in older patients. Table 78.1
Difference Between GBM, IDH Mutant and GBM, IDH Wild Type GBM, IDH Mutant
◾ 10% of GBM ◾ Younger ◾ Better prognosis ◾ More likely MGMT methylated ◾ Most “secondary” GBM ◾ Amenable to targeted therapies
GBM, IDH Wild Type
◾ 90% of GBM ◾ Older ◾ Poorer prognosis ◾ Most “primary” GBM
Gliosarcoma Gliosarcoma is an aggressive WHO grade 4 tumor consisting of glial as well as mesenchymal/sarcomatous components. It is seen in adults as a sharply marginated heterogeneous mass showing hemorrhage, necrosis, and thick irregular rim enhancement with surrounding edema. It can be difficult to differentiate from glioblastomas on imaging; however, gliosarcomas more commonly exhibit dural involvement owing to their peripheral location (Fig. 78.6).
FIGURE 78.6 Gliosarcoma. (A) Axial T2, (B) axial FLAIR, (C) axial T1 postcontrast, and (D) sagittal T1 postcontrast images demonstrate a large heterogeneously enhancing mass in the peripheral aspect of the anterior right temporal lobe with involvement of the overlying dura (yellow arrow).
Diffuse Midline Glioma Diffuse midline glioma (H3K27M-mutant) is a new entity in the 2016 WHO classification of CNS tumors [4]. This includes majority of tumors that were previously called diffuse intrinsic pontine gliomas. These aggressive WHO grade 4 tumors are more commonly found in young children but may also occur in adults. As implied by the name these arise from midline structures, most commonly the pons but they may also arise from elsewhere in the
brainstem, thalamus, cerebellum, and spinal cord. Brainstem tumors can present with cranial nerve palsies. The typical CT appearance is a hypodense, expansile, nonenhancing mass. On MRI, the typical appearance is a T1 hypointense, T2 hyperintense nonenhancing mass lesion expanding the pons (Fig. 78.7) with displacement of the basilar artery flow void and effacement of the fourth ventricle. Enhancement and mild diffusion restriction may occasionally be present (Fig. 78.8). Craniocaudal extension of the tumor and leptomeningeal spread may be seen [23] and usually carries a very poor prognosis.
FIGURE 78.7 Diffuse midline glioma (H3K27 mutant). (A) Axial T2, (B) axial FLAIR, (C) axial T1 postcontrast, and (D) coronal T2 images demonstrate a large expansile nonenhancing mass of the pons with partial effacement of the prepontine cistern.
FIGURE 78.8 Diffuse midline glioma (H3K27 mutant). (A) Sagittal T2, (B) sagittal T1 postcontrast, and (C) axial T1 postcontrast images demonstrate a large expansile mass of the pons with a central enhancing and necrotic component.
Key Point Usually a child with midline lesion expanding the pons, displacing the basilar artery flow void, and flattening the floor of the fourth ventricle with variable enhancement.
Tectal Glioma Tectal glioma is a rare low-grade tumor occurring predominantly in the pediatric population. It involves the superior and inferior colliculi of the brainstem. It can compress the aqueduct often causing obstructive hydrocephalus. These patients can present with headache, diplopia, or Parinaud syndrome. Typical imaging appearance is a T1 isointense, T2 hyperintense, nonenhancing expansile mass in the tectal plate (Figs. 78.9 and 78.10).
FIGURE 78.9 Tectal glioma. (A) Axial T2, (B) axial FLAIR, (C) axial T1 postcontrast, and (D) sagittal precontrast T1 images demonstrate a circumscribed, mildly expansile nonenhancing mass of the tectum surrounding the cerebral aqueduct.
FIGURE 78.10 Tectal glioma. (A) Sagittal FLAIR and (B) sagittal T1 postcontrast images demonstrate an expansile nonenhancing mass arising in the tectum and compressing the cerebral aqueduct.
Oligodendroglioma Oligodendrogliomas are diffuse infiltrating glial tumors arising from oligodendrocytes, which demonstrate IDH mutation as well as 1p/19q codeletion [23]. The term oligodendroglioma NOS (not otherwise specified) is used when there is insufficient information to assign a specific code such as in institutions lacking facility of molecular diagnostic testing. Oligodendrogliomas can be either well-differentiated WHO grade 2 oligodendrogliomas or WHO grade 3 anaplastic oligodendrogliomas. Oligodendroglioma is the third most common glial neoplasm and most commonly arises in the frontal lobe [24]. It occurs in males more frequently with a peak between 40 and 60 years of age. A majority of patients present with seizures as the first symptom due to cortical gray matter involvement [24]. They are slowly growing, nonencapsulated, and exhibit a predilection for infiltrating the overlying cortex. Other typical imaging features of oligodendrogliomas include indistinct tumor margins, heterogeneous signal intensity, and calcifications. Tumors that histologically show oligodendroglial features but are 1p/19q intact tend to be more wellcircumscribed, homogeneous and noncalcified [25]. These 1p/19q intact tumors are no longer classified as oligodendrogliomas. In this instance genotype trumps the histological phenotype, necessitating a diagnosis of diffuse astrocytoma, IDH mutant rather than oligodendroglioma [4]. On CT, oligodendrogliomas are isodense to hypodense tumors with calcification in up to 90% cases (Fig. 78.11). On MRI, these tumors appear hypointense to gray matter on T1 and hyperintense to gray matter on T2W
images. They generally do not enhance after contrast (Fig. 78.12). Mild to moderate patchy enhancement may be seen in up to 50% cases although it is a poorly reliable indicator of tumor grade (Fig. 78.11). Usually, they do not show restricted diffusion. Vasogenic edema is not a striking feature.
FIGURE 78.11 Oligodendroglioma (WHO grade 3). (A) Axial CT, (B) axial T2, (C) axial FLAIR, and (D) axial T1 postcontrast images demonstrate a partially calcified and mostly nonenhancing mass in the left frontal lobe infiltrating the overlying cortex and exhibiting low-level central enhancement.
FIGURE 78.12 Oligodendroglioma (WHO grade 2). (A) Axial T2, (B) axial FLAIR, and (C) axial T1 postcontrast images demonstrate a nonenhancing mass in the left frontal lobe infiltrating and expanding the overlying cortex.
MR perfusion may show elevated rCBV even in grade 2 oligodendrogliomas. MR spectroscopy shows moderately elevated Cho, decreased NAA without a lactate peak. The absence of a lipid/lactate peak may help in differentiating oligodendroglioma from anaplastic oligodendroglioma [26]. Treatment is surgical, with adjuvant radiotherapy and chemotherapy. Local recurrence is common due to infiltration at the margins. Neuropathology is
less predictive of outcome to chemotherapy than 1p/19q status [27].
Key Point Oligodendrogliomas show frontal lobe predilection and typical imaging features like indistinct tumor margin, cortical infiltration, and calcifications. It is important to identify these tumors as these are characterized by slowly progressive growth, better prognosis and better response to chemotherapy. Enhancement is not a reliable indicator of tumor grade.
Other Astrocytic Tumors Pilocytic Astrocytoma Pilocytic astrocytoma (PA) is the prototype of the low-grade (WHO grade 1) well-circumscribed astrocytoma [28]. It is the most common primary brain tumor in children accounting for 70–85% of all cerebellar astrocytomas and 15% of all pediatric brain tumors [29]. It usually presents in childhood between the ages of 5 and 15 years. It has a strong association with NF1. PA typically presents as a cystic mass with enhancing mural nodule in the cerebellum or as an infiltrative lesion along the optic pathway that elongates and widens the optic nerve [28]. Involvement of optic nerves is a feature of neurofibromatosis type I. It is difficult to diagnose when in atypical locations as it can resemble more aggressive and infiltrative lesions. On imaging, cystic lesion with enhancing mural nodule is more common than purely solid lesions (Fig. 78.13). About 10–20% lesions can show calcification. Cystic component shows fluid signal with enhancement of cyst wall in 50% cases. Solid mural nodule is hypointense on T1, hyperintense on T2 and shows intense enhancement. There is usually little or no surrounding edema. Infiltrative pattern is seen in optic pathway and hypothalamic lesions. The tumors involving the chiasm or hypothalamus are often large, lobulated, and well circumscribed at presentation and can be partially cystic.
FIGURE 78.13 Pilocytic astrocytoma. (A) Axial T2, (B) axial FLAIR, and (C) axial T1 postcontrast images demonstrate a well-circumscribed, cystic mass with an enhancing mural nodule.
Key Point Pilocytic astrocytoma typically presents in children as an expansile cystic mass lesion with enhancing mural nodule in the cerebellum.
Pilomyxoid Astrocytoma This neoplasm was previously considered just a “juvenile” variant of PA. It is now recognized as a distinct entity with unique clinical characteristics and histological appearance. It is an aggressive neoplasm usually seen in very young children with mean age at diagnosis being 18 months. It can occur anywhere along the neuraxis, however, these lesions have a strong predilection for the suprasellar region. Hypothalamus/optic chiasm is the most common location [30]. On imaging, majority of pilomyxoid astrocytomas (PMAs) are large, wellcircumscribed, lobulated, homogeneously enhancing solid mass lesions. Some lesions may show minimal cystic component [30]. They can expand from midline into both temporal lobes. Imaging findings are somewhat similar to PA; however, PMAs are brighter on T2 due to higher proportion of myxoid matrix (Fig. 78.14). PMA may show intratumoral hemorrhage on T2* images, which is very rare in PA. The most prominent imaging characteristic that suggests PMA versus PA is the presence of intratumoral hemorrhage [31]. CSF dissemination is common with PMA, so the entire neuraxis should be imaged.
FIGURE 78.14 Pilomyxoid astrocytoma (WHO grade 2). (A) Axial T2, (B) axial FLAIR, (C) axial T2*, and (D) axial T1 postcontrast images demonstrate an expansile, markedly T2 hyperintense and relatively well-circumscribed mass with heterogeneous enhancement in the left medial temporal lobe. There is a small focus of susceptibility within the center of the mass (yellow arrow).
Key Point Features which may differentiate PMA from PA include young age (3 spine levels)
Focal, multifocal, or confluent
Involves >2/3 of axial spinal cord area
Postinfectio us
MS
NMO
ADEM
Brain Yes involveme nt
Uncommon
Suggestiv e laboratory findings
Anti-AQP4, – anti-NF, or antiMOG antibodies
Oligoclonal bands of IgG in CSF
Yes
Figure 79.40 Neuromyelitis optica (NMO). Sagittal T2weighted image (A) shows hyperintense signal (white arrows) extending through the thoracic cord. The vertical
height is “long-segment,” about nine vertebral body heights, classic for this disease. Postcontrast fat-saturated T1-weighted image (B) shows patchy cord enhancement (black arrows).
Figure 79.41 Multiple sclerosis. Sagittal STIR image (A) shows a focus of hyperintense signal in the posterior cord at C4 (white arrow), and a smaller lesion at C2 (black arrow). The lesions are “short-segment,” meaning two vertebral bodies or less in vertical height. Axial T2weighted image (B) at the C4 level again shows the posterior lesion (black arrowhead) as well as another lesion in the left lateral cord (black arrow).
Figure 79.42 Sarcoid myelopathy. Sagittal T2-weighted image (A) shows long-segment signal abnormality in the thoracic cord (black arrows) with mild expansion. Sagittal postcontrast T1-weighted image (B) shows corresponding parenchymal enhancement (white arrows), primarily in the posterior cord. Axial postcontrast T1-weighted image (C) shows enhancement of the central cord as well as the posterior subpial cord (white arrows), the so-called “trident sign” that is characteristic of sarcoid myelopathy. Hirayama disease represents a rare form of compressive myelopathy. The diagnosis may be questioned in the appropriate patient setting on neutral-position MRI, with focal myelomalacia in the anterior lower cervical cord, but the diagnosis is often confirmed using flexion MRI. With patients positioned in hyperflexion, the posterior epidural space enlarges, and the cervical spinal cord is compressed anteriorly against the posterior vertebral bodies (Fig. 79.43).
Figure 79.43 Hirayama disease. Sagittal T2-weighted image (A) shows mild volume loss of the cord at the C6-7 level (black arrow). Normally, the lower cervical cord has thicker cross section than superiorly or inferiorly, the socalled “cervical enlargement,” so the apparent cord thinning at this level (confirmed on axial images, not shown) is abnormal. There is no stenosis at this level in the neutral position. However, a sagittal T2-weighted image (B) with neck flexion shows significant narrowing due to anterior displacement of the posterior dura (white arrows), and associated enlargement of the epidural space (asterisk). SACD, HIV-related vacuolar myelopathy, and tabes dorsalis produce signal abnormality in the dorsal columns. In SACD, the dorsal columns will demonstrate bilateral T2 hyperintensity,
occasionally producing an “inverted V,” with or without enhancement (Fig. 79.44). Abnormal signal may be present in the lateral cord as well. Bilateral dorsal column signal abnormality is seen in HIV-related vacuolar myelopathy, but is associated with cord atrophy and mostly commonly presents in the cervical and thoracic cord. Enhancement is rarely seen.
Figure 79.44 Subacute combined degeneration. Sagittal T2-weighted image (A) shows hyperintense signal (black arrows) in the posterior cord extending from approximately C2 through C5. Axial T2-weighted image (B) localizes the signal to the posterior columns (black arrows). Spinal cord infarct, while not a primary inflammatory or demyelinating process, can mimic the above entities on imaging, although cases will in general have a more rapid onset of
symptoms. Infarcts tend to occur more in the mid-to-lower thoracic cord or conus, where the vascular supply is more tenuous. Abnormal T2 prolongation will be seen in the area of the infarct, along with cord swelling in the acute phase (Fig. 79.45). If DWI is performed, the infarct will restrict acutely. As with brain infarcts, enhancement can be seen in the subacute phase. The presence of enhancement in the acute phase militates against the diagnosis of spinal cord ischemia, but supports other etiologies such as demyelinating or inflammatory disease. The “owl eye” appearance of an anterior spinal artery infarction is classically described, although it is nonspecific and can be seen in other settings, such as compressive myelopathy (Fig. 79.46). Ancillary features that favor infarct include vertebral infarction, which can present as bone marrow edema-like signal with T2 prolongation along the posterior aspect of the vertebral bodies.
Figure 79.45 Cord infarct. Sagittal STIR image (A) shows hyperintense signal (black arrow) in the conus. Note also
the hyperintense signal (white arrows) in the nearby posterior vertebral bodies, consistent with osseous infarct. The axial T2-weighted image (B), although degraded by artifacts, confirms the hyperintense signal (black arrows) in the conus, more on the left than the right.
Figure 79.46 “Owl eye” sign. Sagittal T2-weighted image (A) demonstrates thin, linear T2 hyperintense signal in the cervical spinal cord (white arrow). Axial T2-weighted image (B) shows bilateral symmetric ovoid foci of T2 hyperintense signal (white arrows) in a patient with chronic compressive myelopathy. Spinal cord herniation is best seen on MRI or CT myelography as a focal ventral displacement of the spinal cord with associated focal “kinking” and loss of the CSF space between the cord and ventral theca (Fig. 79.47). This typically occurs in the upper- to mid-thoracic region. The differential diagnosis for ventral cord displacement includes dorsal arachnoid cyst, adhesive arachnoiditis, and dorsal arachnoid web; however, visualization of cord parenchyma in the ventral epidural space is diagnostic
for cord herniation. Abnormal signal within the cord is indicative of myelopathy.
Figure 79.47 Anterior spinal cord herniation. Sagittal fatsaturated T2-weighted image (A) shows anterior cord displacement (black arrow) at a level where a welldefined defect (white arrow) is noted at the posterior margin of the vertebral body. Axial high-resolution MR myelographic (FIESTA-C) image (B) shows the spinal cord rotated to the right (black arrow), with complete loss of ventral cerebrospinal fluid, and cord parenchyma herniated ventrally into the dural defect (white arrow). Arachnoid webs can be visualized with CT myelography or MRI as a focal dorsal depression of the spinal cord. This indent can resemble the curved contour of a #10 scalpel blade, producing the “scalpel sign” (Fig. 79.48). Abnormal spinal cord signal may
be seen with myelopathy, and syrinx formation is a potential consequence.
Figure 79.48 Dorsal arachnoid web. Sagittal T2-weighted image (A) of the thoracic spine shows a focal dorsal deflection of the spinal cord, with a smooth posterior contour, where the cerebrospinal fluid space (asterisk) resembles a scalpel blade, the so-called “scalpel sign.” Note the syrinx (white arrows) within the cord superiorly. Sagittal CT myelogram image (B) shows a similar scalpellike shape of the posterior cerebrospinal fluid space (asterisk).
Angiography is the gold standard for evaluating arteriovenous fistulae and will demonstrate the abnormal vascular connections and early venous drainage. However, these patients will often present with myelopathic or other neurologic symptoms and therefore be initially evaluated with cross-sectional imaging, particularly MRI. Intradural flow voids on T2-weighted images with enhancement of the abnormal vessels on postcontrast T1weighted images can be seen, representing enlarged arterialized perimedullary veins (Fig. 79.49). T2 abnormal hyperintense signal within the cord is indicative of venous ischemia, which can enhance with contrast. Importantly, contrast-enhanced MRA may be used to evaluate these entities, to identify potential sites for arteriovenous communication and thereby expedite diagnostic angiography, but to date, cannot be used to exclude them. With epidural arteriovenous fistulae, the engorged epidural venous plexus may present as space-occupying mass lesions on MRI or CT.
Figure 79.49 Dural arteriovenous fistula with myelopathy from venous hypertension. Magnified sagittal fat-saturated T2-weighted image (A) shows hyperintense signal in the conus medullaris (white arrow). The flow voids, small
black rounded intradural signal foci around the cord (black arrows) are suggestive of an underlying vascular anomaly. Postcontrast fat-saturated T1-weighted image (B) confirms numerous enhancing vessels around the conus, indicating dilated perimedullary veins, and suggesting venous hypertension as the cause of myelopathy. A coronal maximum-intensity-projection image from an MR angiogram (C) confirms multiple dilated intradural vessels (white arrows) and also suggests the site of fistula at a right foramen (white arrowhead). Selective angiogram (D) at that level confirms multiple dilated perimedullary veins (black arrows).
What the Referring Physician Wants to Know Myelopathy is a broad clinical entity, and the imaging appearances of causative disease processes can have significant overlap (Table 79.2). However, there are some characteristic MRI appearances, such as posterior cord involvement or longsegment lesions, that help to narrow the diagnosis and guide referring physicians. In addition, the radiologist must always evaluate for cord compression and arteriovenous malformation/fistula as a cause of the myelopathy; if the latter is suspected, conventional angiography should be performed next to confirm or refute the diagnosis. For MRI, abnormal cord signal should always be reported and the presence of flow voids or enhancing vessels documented to lead to appropriate further angiographic evaluation and treatment.
Table 79.2 Common Causes of Myelopathy Category Typical Comment Onset Compressive Degenerative
Acute/subac ute
Disc, osteophyte, ligaments
Neoplastic
Acute
Most commonly extradural (metastasis)
Infectious
Acute
Abscess, phlegmon
Traumatic
Acute
Hematoma, disc, fracture fragments
Other
Subacute
Arachnoid cyst, arachnoid web, Hirayama disease
Demyelinating
Acute
MS, NMO spectrum disorders, ADEM
Systemic disease
Acute
Sarcoid, systemic lupus erythematosus, Sjogren’s
Infectious myelitis
Acute
Usually viral; bacterial/fungal/parasitic less common
Arterial
Acute
Atherosclerotic, aortic dissection/surgery
Venous
Subacute
AVF/AVM
Ischemic
Category
Typical Onset
Comment
Postradiation
Acute
Months-to-years after treatment
Paraneoplastic
Subacute
Overlap with autoimmune myelitides
Metabolic
Subacute
B12, copper, or vit E deficiency Nitrous oxide/zinc toxicity
Epidemiology and Clinical Presentation Neoplastic processes of the spinal canal are categorized by location: intramedullary (Fig. 79.41), intradural–extramedullary (Fig. 79.42), and extradural (Fig. 79.43).
◾
◾ Intramedullary neoplasms, located within the spinal cord parenchyma, include ependymoma, astrocytoma, and hemangioblastoma. The most common of these is the ependymoma, constituting 60% of intramedullary neoplasms [32]. Astrocytomas are overall approximately half as common as ependymomas [32] and are associated with neurofibromatosis type 1. The demographics of these tumors are important: ependymomas are more common in adults, whereas astrocytomas predominate in children. Hemangioblastomas constitute approximately 5% of intramedullary tumors and are associated with Von Hippel Lindau [33]. Intramedullary cavernomas are similarly rare, representing approximately 5% of intramedullary neoplasms [34]. Clinical presentation of intramedullary masses includes hydrocephalus, neck pain, back pain, and myelopathic symptoms. The intradural–extramedullary neoplasms, located within the dura but outside the spinal cord, are more common than intramedullary ones and include meningioma, myxopapillary ependymoma, and nerve sheath tumors, such as the schwannoma, neurofibroma, and malignant peripheral nerve sheath tumors. Meningiomas are the most common of these, approximately 30%, with ependymomas and nerve sheath tumors each contributing approximately 15% [35]. Meningiomas are also more common in females. Meningiomas and schwannomas are multiple when associated with neurofibromatosis type 2, whereas neurofibromas are more associated with neurofibromatosis type 1. Pain is common, resulting from either spinal cord or nerve root compression. If nerve roots are involved, the pain
◾
may be radicular in nature. Malignant peripheral nerve sheath tumors are more common in patients with neurofibromatosis type 1, in which case they may result from degeneration of plexiform neurofibromas. The most common extradural neoplasms are either metastatic or osteogenic in nature. Osteoid osteoma classically presents as pain, predominantly at night, that improves with aspirin administration. Osteoblastoma is less likely to respond to anti-inflammatory pain medications. There may be pain associated with aneurysmal bone cysts and giant cell tumors. Giant cell tumors occur almost exclusively in individuals with closed growth plates (i.e., adults). The presentation of a chordoma may vary depending on which structures it compresses as it grows.
◾
Pathophysiology Intramedullary tumors are most commonly gliomas, arising from cells found within the spinal cord, such as the ependymal cells lining the central canal and astrocytes supporting the neurons and axons of the cord. Hemangioblastomas arise from vascular stromal cells and intervening blood vessels. Cavernomas comprise vessels without normal intervening brain parenchyma. The intradural–extramedullary meningioma arises from arachnoid cap cells of the arachnoid villi. The myxopapillary ependymoma is a subtype of ependymoma. Both schwannomas and neurofibromas arise from Schwann cells.
Most extradural masses are metastatic in etiology. Osteoid osteomas, osteoblastomas, and giant cell tumors are osteogenic in origin with predilection for the neural arches. The chordoma specifically arises from notochord remnants.
Imaging Features In the setting of suspected malignancy or mass, MRI with contrast is the most appropriate imaging study, with a noncontrast MRI being an alternative if contrast cannot be used [12]. If MRI cannot be performed, CT with contrast is the next best option, although CT myelography may be needed to diagnose cord or cauda equina compression, particularly if urgent treatment is needed. Radiography has a limited role in evaluating these masses and may only show secondary osseous changes. Localizing the spinal spatial compartment of a mass lesion is best done with MRI, with myelography or CT myelography as a second choice, to visualize the relation between the mass, the spinal cord, and the surrounding CSF. The appearance of a mass lesion often depends upon its size. If small, an intramedullary mass, originating from within the spinal cord, will be surrounded by spinal cord parenchyma on MRI. If large, an intramedullary mass will expand the spinal cord, subsequently narrowing the surrounding CSF spaces, easily shown on MRI (Fig. 79.50) or CT myelography. In contrast, intradural/extramedullary masses, originating between the dura and the cord, produce a filling defect within the CSF column,
and sometimes, a CSF cleft or meniscus sign is visible (Fig. 79.51). If large enough, intradural/extramedullary masses will expand the CSF column ipsilateral to the mass, displacing the cord toward the other side. This important imaging feature can help localize large mass lesions to the intradural/extramedullary compartment, and should be sought by evaluating the CSF above and below the site of the primary mass. Finally, extradural mass lesions, originating outside the dura, will be centered within the vertebra, disc, or epidural fat, and when large, will narrow the nearby CSF space (Fig. 79.52).
Figure 79.50 Intramedullary neoplasm, anaplastic astrocytoma. Sagittal T2-weighted image (A) shows intramedullary hyperintensity (asterisk) of the neoplasm. Mild cord expansion with narrowing of the subarachnoid spaces superior and inferior to the neoplasm (black
arrows) indicates the intramedullary location. An incidental disc herniation (white arrow) is also visible. Sagittal fat-saturated postcontrast T1-weighted image (B) shows the patchy enhancement of the neoplasm (asterisks). Again, the subarachnoid spaces are narrowed (white arrows) above and below the neoplasm.
Figure 79.51 Intradural–extramedullary neoplasm. Magnified sagittal T2-weighted image (A) shows intradural–extramedullary mass (asterisk) dorsal to the spinal cord, which is displaced anteriorly. The subarachnoid spaces are mildly widened (white arrows) superior and inferior to the mask. A “meniscus” containing cerebrospinal fluid is visible (black arrows) at the interfaces between the mass, the spinal cord, and the posterior dura. Axial postcontrast T1-weighted image (B) shows the enhancing mass (asterisk) posterior and to the left of the cord, displaced anteriorly.
Figure 79.52 Extradural neoplasm, angiolipoma. Sagittal T2-weighted image (A) shows a heterogeneous posterior mass lesion (asterisk) compressing the spinal cord. The subarachnoid space inferiorly (black arrows) is narrowed; however, at a first glance, superiorly it may appear widened (white arrows), which may mistakenly place the mass as intradural–extramedullary in location. Sagittal T1weighted image (B) clarifies the location of the mass (asterisk), as superiorly there is thickened epidural fat (white arrowhead), which appears similarly hyperintense on the T2-weighted image. The subarachnoid space is narrowed as expected (white arrows). Indeed, the involvement of epidural fat (white arrowhead) proves that the mass lies within the epidural space. The angiolipoma
(asterisk) has both fatty and vascular elements, accounting for its heterogeneous signal. Of course, the reader should take care to visualize these relations in at least two orthogonal planes (e.g., axial and sagittal), for accurate localization. For example, an epidural mass lesion compressing the cord from both the left and right sides may impersonate an intramedullary process on a sagittal midline image by appearing to expand the cord and narrow the surrounding CSF. Radiographs have a limited role in the evaluation of intramedullary masses, but if performed, may uncommonly show findings. Enlargement of the cord by ependymoma (Fig. 79.53) or astrocytoma may cause expansion of the spinal canal with remodeling of adjacent bony structures, including the posterior aspect of the vertebral body and neural arch structures. These osseous features are also discernible on CT, and the tumor will enhance with contrast. MRI is the modality of choice, demonstrating an intramedullary T2-hyperintense mass with enhancement and surrounding cord edema. Beyond demographics differences, some imaging features differentiate ependymoma and astrocytoma. Ependymomas extend the length of 3–4 vertebral bodies, are most often cervical, are highly associated with syringomyelia, are more commonly associated with intramedullary cysts, and have a higher rate of hemorrhage. The “cap sign” refers to areas of T2 hypointensity at the superior and inferior aspects of the mass. Astrocytoma is more common in thoracic spine, less strongly associated with
syrinx and cysts, and extend the length of approximately seven vertebral bodies.
Figure 79.53 Ependymoma. Sagittal T2-weighted image (A) shows heterogeneous mass (asterisk) expanding the cord and narrowing the subarachnoid spaces (black arrows). Sagittal fat-saturated postcontrast image (B) shows that the mass enhances (asterisk), and is centrally located with well-defined margins. Hemangioblastoma is more common in the cervical spine and is strongly correlated with cyst formation and syringomyelia. The solid, nodular component of a hemangioblastoma, commonly eccentrically located on the pial surface of the cord, will enhance on CT and MRI, and it can occasionally be differentiated from other intramedullary lesions by its nidus of
flow voids (Fig. 79.54). The nidus is also generally visible on angiography. Surgical resection is the treatment of choice, with radiotherapy being an adjunct if total resection is unachievable or the neoplasm is malignant.
Figure 79.54 Spinal hemangioblastoma. Sagittal T1weighted image (A) shows expansion of the cord, with narrowing of the subarachnoid spaces superiorly (white arrows). Multilevel centrally located hypointense signal extending the length of the cervical cord (white asterisk) suggests edema or an underlying syrinx. Off-midline sagittal fat-saturated T2-weighted image (B) confirms cord expansion with abnormal cord signal (black asterisk), as well as a focal hypointense nodule (white arrow), located in the posterior cord, with an associated cyst extending superiorly (black arrow). Postcontrast fatsaturated T1-weighted sagittal (C) and axial (D) images show that the posterior nodule enhances (asterisk) and abuts the pial surface of the cord. A cystic mass associated
with a pial-based enhancing nodule is a classic appearance for hemangioblastoma. The intramedullary cavernoma demonstrates heterogeneous signal intensity on T1- and T2-weighted sequences reminiscent of “popcorn” with blooming artifact on gradient-echo sequences associated with susceptibility from blood products. A comparison of features of the common intramedullary neoplasms is shown in Table 79.3. Table 79.3 Comparison of Intramedullary Neoplasms of the Spinal Cord Astrocytom Ependymo Hemangioblasto a ma ma Age range
Childhood
Adulthood
Adulthood (sporadic form)
Appearance
Heterogene ous enhancemen t
More homogeneo us enhancemen t
Nodular enhancement, flow voids
Location
Thoracic
Cervical
Cervical
Extent of cord T2 hyperintens ity
Up to 7 vertebral bodies in length
Up to 3–4 vertebral bodies in length
–
Ancillary findings
Astrocytom a
Ependymo ma
Hemangioblasto ma
Cysts and syringomyel ia less common
Syringomye lia
Syringomeylia
Hemorrhage less common
Intramedull ary cysts
Intramedullary cysts Hemorrhage
Hemorrhage “Cap sign”
Syrinx, while not technically a neoplasm, is an important finding associated with intramedullary masses. The term “syrinx” encompasses both syringomyelia, a predominantly glial lined fluid-filled cavity within the spinal cord, and hydromyelia, which refers to enlargement of the central canal and is lined by ependymal cells. On MRI, the syrinx will follow the intensity of CSF on all sequences, will have well-defined margins, may be centrally or eccentrically positioned with the cord, and will not enhance (Fig. 79.55). Enhancement should raise concern for an associated intramedullary neoplasm. Of note, a smooth fusiform slit-like dilation of the central canal of up to 2 mm in an asymptomatic patient without known reason for syrinx (e.g., Chiari I malformation) is considered to represent a normal anatomic variant (“prominent central canal”) and not a syrinx that may otherwise require postcontrast or follow-up imaging (Fig. 79.56).
Figure 79.55 Syrinx. Sagittal T2-weighted (A) and T1weighted (B) images show spindle-shaped fluid space within the spinal cord (asterisk). It measured about 5 mm in diameter. A Chiari I malformation is also visible on these images.
Figure 79.56 Prominent central canal. Sagittal T1weighted image (A) shows thin linear longitudinal signal within the cord (white arrows), which shows hyperintensity (black arrows) on the sagittal T2-weighted image (B). The axial T2-weighted image (C) confirms its central location, round shape, and small size of only 1–2 mm (white arrow). Intramedullary spinal cord metastases may be difficult to distinguish from primary spinal cord neoplasms. The “rim sign,” a thin peripheral rim of enhancement around a lesion, and the “flame sign,” a flame-shaped area of enhancement extending beyond the rim of the lesion into adjacent cord, are sometimes present in spinal cord metastasis, but not in primary cord neoplasia. The intradural–extramedullary masses include meningioma, myxopapillary ependymoma, Schwannoma, neurofibroma, and malignant peripheral nerve sheath tumors. These masses may cause osseous remodeling similar to or even greater in extent than the cord expansion caused by intramedullary lesions. Total surgical resection represents the standard of care. Meningiomas are most common in the thoracic spine, often posterolateral to the cord. As in intracranial meningiomas, they enhance avidly, often possess a dural tail (Fig. 79.57), and rarely calcify or have cystic degeneration. They are cellular and may be hyperdense on CT. The myxopapillary ependymoma classically arises in the lumbosacral region as a T2-hyperintense mass with peripheral hypointensity and marked enhancement.
Figure 79.57 Spinal meningioma. Sagittal T2-weighted image (A) shows an intradural–extramedullary mass (asterisk) expanding the ventral subarachnoid space, and displacing the cord posteriorly. Sagittal fat-saturated postcontrast image (B) shows that the mass (asterisk) enhances homogeneously, with dural tails (black arrows). All nerve sheath tumors may extend into a neural foramen, giving it a “dumbbell”-shaped appearance and indirectly allowing imaging detection if the foramen is enlarged (Fig. 79.58). Schwannomas are also T2-hyperintense and vividly enhance. They may calcify. These will arise from a nerve and may be more paracentral or lateral in location, although this may
be different to discern if the mass is large. Neurofibromas will be hypodense on CT and hyperintense on T2-weighted MRI sequences. Enhancement will be less intense than the other intradural–extramedullary masses. The “target sign” refers to an area of central low T2 signal intensity surrounded by T2 hyperintensity. The “fascicular sign” refers to the appearance of multiple ring-like areas within the tumor that resemble fascicles. This sign may also be seen with schwannoma. Plexiform neurofibromas are seen in neurofibromatosis type 1 and are large, internally complex, and multilobulated. Schwannomas and neurofibromas that extend beyond the spinal canal are potential causes of lumbar paraspinal shadow on plain films. The malignant peripheral nerve sheath tumors are infiltrative and not well circumscribed. Their appearance on CT and MRI is markedly heterogeneous with internal blood products and necrosis. Necrotic areas, more commonly central, will not enhance, producing a pattern of peripheral enhancement.
Figure 79.58 Schwannoma. Axial T2-weighted image (A) shows a heterogenous mass with components inside and external to the spinal canal, extending through an enlarged right neural foramen to create the “dumbbell sign” (asterisk). Axial T1-weighted postcontrast image (B)
shows vivid peripheral enhancement of the mass (asterisk). This patient had neurofibromatosis type 2. An intradural arachnoid cyst is a loculated and expanding collection of CSF, which communicates with the free subarachnoid space through a narrow neck. They are evident on MRI as masses giving signals of either similar or slightly greater intensity than the subarachnoid CSF (Fig. 79.59).
Figure 79.59 Arachnoid cyst. Sagittal T2-weighted image (A) shows anterior displacement of the cord (white arrows) over 3–4 vertebral body lengths. Posteriorly, there is a suggestion of rounded contours of an intradural–
extramedullary cystic mass (black arrowheads). Also note the loss of CSF flow artifact within the cyst (asterisks). Sagittal CT myelogram image (B) confirms the intradural–extramedullary-filling defect (black arrows). The cyst partially fills with contrast (asterisk), confirming communication with the subarachnoid space. Chordomas most commonly arise in the sacrococcygeal region and occasionally the clivus, but they may occur at any segment of the spine. The tumor causes bone lysis, which tends to involve several segments of the spine and to be associated with expansion and some sclerotic reaction. Calcification or residual bone fragments within the tumors are not infrequently present. CT and MRI are particularly valuable in delineating the extent of the sacral chordomas, which may be entirely below the level of the spinal theca; higher tumors cause nonspecific extradural compression. Appearance on MRI is variable, but they are generally very hyperintense on T2-weighted imaging, which can be a helpful feature for diagnosis as well as when assessing paraspinal spread or recurrence after treatment (Fig. 79.60).
Figure 79.60 Sacrococcygeal chordoma. Sagittal T1weighted image (A) shows marrow replacement in the sacrum and coccyx by a mass (asterisks), with extraosseous paraspinal spread both anteriorly and posteriorly (black arrows). Sagittal STIR image (B) shows both osseous (asterisk) and extraosseous (white arrows) neoplasm with heterogeneously hyperintense signal. Sagittal fat-saturated postcontrast T1-weighted image (C) shows enhancement of the neoplasm (asterisk). Osteoid osteoma (Fig. 79.61) and osteoblastoma typically involve the neural arch. Sclerosis and expansion of the affected part of the neural arch may be better demonstrated with CT than plain x-rays. A low-density nidus with or without a sclerotic center is generally evident on CT. The two are differentiated by size, with osteoblastomas being greater than 2 cm in diameter.
Figure 79.61 Osteoid osteoma. Axial CT image shows a lucent lesion in the left pars interarticularis (white arrow) with a central sclerotic focus. Aneurysmal bone cysts arising in the spine usually involve the neural arch. Radiographs and CT will reveal expansile, lytic lesions. Fluid–fluid levels are classic and typically seen on MRI, although they may be discernible on CT (Fig. 79.62).
Figure 79.62 Aneurysmal bone cyst. Axial CT image (A) shows a lucent mass of the left sacrum with a large anterior paraspinal component (white arrows). Note the partial rim of calcification (white arrowhead) suggesting that the process is expansile and nonaggressive, not destructive. Sagittal T2-weighted image (B) shows that the mass is heterogeneous, with multiple cystic components (asterisks). Sagittal fat-saturated postcontrast T1-weighted image (C) shows rim-enhancement of these cystic components (white arrows). An axial fat-saturated T2-weighted image (D) shows a horizontal blood-fluid level (black arrows), a classic feature of aneurysmal bone cysts.
Giant cell tumors have a predilection for metaphyses of bones with extension to the epiphysis. In the spine, they are most common in the sacrum or the vertebral bodies of other spine segments and present as lytic, expansile neoplasms on radiograph and CT. A soft-tissue component may be identified on CT or MRI. On MRI, the neoplasm is isointense to hypointense compared with spinal cord on T1-weighted sequences and heterogeneous and variable intensity on T2weighted sequences. Areas of hypointense signal are related to internal blood products or connective tissue, and a cystic component may be present. Heterogeneous enhancement is common (Fig. 79.63).
Figure 79.63 Giant cell tumor. Lateral radiograph (A) shows collapse and lucency of the C7 vertebral body (asterisk). Sagittal T1-weighted image (B) shows an extradural mass posterior to the vertebral body (asterisk), compressing the cord. Sagittal T2-weighted image (C) shows that the extradural mass has primarily iso- to hypointense signal (asterisk). The sagittal postcontrast T1-
weighted image (D) shows solid enhancement of the mass (white arrows). Vertebral hemangiomas are most commonly intraosseous and demonstrate marked trabeculation or striation, the “corduroy sign,” on radiograph and CT. Their lipid content contributes to hyperintensity on T1-weighted sequences, and their water content produces T2 hyperintensity. They may enhance. Atypical hemangiomas are hypointense on T1-weighted images and hyperintense on T2-weighted images. Their appearance on radiograph and CT helps to clarify the diagnosis. Aggressive hemangiomas occur predominantly in the mid-thoracic spine and cause expansion of the vertebral body with extravertebral extension, including into the epidural space (Fig. 79.64).
Figure 79.64 Aggressive hemangioma. Sagittal STIR image (A) shows slight height loss of a thoracic vertebral body, with abnormal hyperintense signal (asterisk), associated with a hyperintense epidural mass lesion (black arrows) compressing the cord. Sagittal postcontrast T1weighted image (B) shows solid enhancement of the epidural mass (white arrows). Axial T2-weighted image (C) shows thickened and intact trabeculae (black arrows)
within the vertebral body, characteristic of the diagnosis of hemangioma. Sagittal CT image (D) confirms the internal architecture of the hemangioma, with thickened vertical trabeculae (black arrows). Metastases to the spine are most often vertebral (Fig. 79.65), but extension from contiguous structures, infiltration of the meninges, and even spread to the intramedullary spinal cord itself are also possible. Spinal canal extension of metastasis is variable in appearance, but usually presents as a heterogeneously enhancing mass or masses centered on an adjacent osseous structure with extension into the spinal canal. Sometimes the metastasis is limited to the epidural space. In either case, the spinal canal can be narrowed and the cord displaced or compressed.
Figure 79.65 Lytic metastasis from renal cell cancer. Axial CT image (A) shows a lucent mass within the vertebral body (asterisk). Cortical erosion anteriorly (white arrows) indicates an aggressive process. Sagittal CT image (B) confirms the lytic mass (asterisk) with cortical erosion
(white arrows). An incidental Schmorl’s node is also visible inferiorly (white arrowhead). Sagittal T1-weighted image (C) confirms abnormal marrow signal throughout the vertebral body (asterisk), consistent with metastasis. Most metastases are lytic, including those from renal, lung, and thyroid carcinomas; multiple myeloma, Burkitt’s lymphosarcoma, and Ewing’s sarcoma cause similar destructive lesions, although the latter may cause periosteal reaction and bone expansion. In common with most tumors, metastases cause T1 hypointensity and T2 hyperintensity at MRI. The T2 signal is often most evidence on fat-saturated or STIR sequences. Melanoma is an exception; melanin is paramagnetic and may cause high signal on T1-weighted images and low signal on T2weighted sequences. Blastic metastases are most commonly of prostate origin in males, and breast cancer metastases can be either blastic or lytic. In some cases, tumor spreads to or arises within the epidural space directly. Although metastatic disease most commonly spreads to the epidural space through extension from an adjacent osseous metastasis, tumor can also spread hematogenously to the epidural space. These metastases are occasionally centered on the basivertebral veins located centrally within each vertebral body. Lymphoma may arise in the epidural space as a primary lesion or in association with systemic disease. Epidural lymphoma is generally of intermediate signal on T1-weighted images and hyperintense signal on T2-weighted images. It will enhance homogeneously after contrast administration (Fig. 79.66).
Figure 79.66 Epidural lymphoma. Sagittal T2-weighted image (A) shows a posterior epidural mass (asterisk) compressing the spinal cord. Sagittal T1-weighted image (B) confirms the epidural mass (asterisk). Note the loss of epidural fat (white arrows), compared with the normal hyperintense epidural fat signal at other levels (white arrowheads), confirming that the mass lesion lies within the epidural space. The sagittal postcontrast T1-weighted image (C) shows that the mass enhances homogeneously (asterisk). Nonosseous metastases to the spinal meninges are also less common than metastases to the vertebral column. With leptomeningeal involvement, the leptomeninges and/or intradural nerve roots can be nodular or thickened in appearance with associated enhancement. Sometimes there is “sugar coating” with linear enhancement along the surfaces of the cord; both axial and sagittal images need to be evaluated to distinguish this enhancement pattern from normal enhancing
vessels that will have a tubular configuration. Abnormal T2 prolongation within the cord may be associated.
What the Referring Physician Wants to Know Malignant spinal cord or cauda equina compression may require urgent treatment, whether surgical decompression or radiation. In cases of metastatic disease to the spinal column, the radiology report should focus on 1. whether epidural neoplasm is present, 2. whether there is mass effect on the thecal sac, spinal cord contact, and/or spinal cord deformity, 3. whether there is myelographic block, and 4. whether there is signal abnormality within the cord. In many cases, the spinal neoplasm can be identified, or at least a short differential can be given, based on its imaging appearance and localization to the intramedullary, intradural– extramedullary, or extradural compartment. Sometimes, further imaging studies should be recommended; for example, noncontrast CT may clarify indeterminate findings on MRI, and bone scintigraphy may help determine malignant likelihood. With some cases, tissue diagnosis, whether by percutaneous sampling or surgical biopsy, is necessary.
Suggested Readings
• Diehn FE, Maus TP, Morris JM, Carr CM, Kotsenas AL, Luetmer PH, et al. Uncommon manifestations of intervertebral disk pathologic conditions. Radiographics. 2016;36(3):801-23. • Hong SH, Choi JY, Lee JW, Kim NR, Choi JA, Kang HS. MR imaging assessment of the spine: infection or an imitation. Radiographics. 2009;29(2):599-612. • Koeller KK, Shih RY. Intradural extramedullary spinal neoplasms: radiologic-pathologic correlation. Radiographics. 2019;39(2):468-90. • Lee MJ, Aronberg R, Manganaro MS, Ibrahim M, Parmar HA. Diagnostic approach to intrinsic abnormality of spinal cord signal intensity. RadioGraphics. 2019;39(6):1824-39. • Patel DM, Weinberg BD, Hoch MJ. CT myelography: clinical indications and imaging findings. Radiographics. 2020;40(2):470-84. • Rodallec MH, Feydy A, Larousserie F, Anract P, Campagna R, Babinet A, et al. Diagnostic imaging of solitary tumors of the spine: what to do and say. RadioGraphics. 2008;28(4):1019-41. • Rutherford EE, Tarplett LJ, Davies EM, Harley JM, King LJ. Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 2007;27(6):1737-49. • Shih RY, Koeller KK. Intramedullary masses of the spinal cord: radiologic-pathologic correlation. Radiographics. 2020;40(4):1125-45. • Smith EB, Gardner K, Talekar KS, Flanders AE, Zoga AC. Oh, my aching back! A review of spinal arthropathies: musculoskeletal imaging. Radiographics. 2016;36(3):935-6.
• Young PM, Berquist TH, Bancroft LW, Peterson JJ. Complications of spinal instrumentation. Radiographics. 2007;27(3):775-89.
References [1] ST Cochran, K Bomyea, JW Sayre, Trends in adverse events after IV administration of contrast media, AJR Am J Roentgenol 176 (6) (2001) 1385–1388. [2] JS McDonald, RJ McDonald, RE Carter, RW Katzberg, DF Kallmes, EE Williamson, Risk of intravenous contrast materialmediated acute kidney injury: a propensity score-matched study stratified by baseline-estimated glomerular filtration rate, Radiology 271 (1) (2014) 65–73. [3] JS Hinson, MR Ehmann, DM Fine, EK Fishman, MF Toerper, RE Rothman, et al., Risk of acute kidney injury after intravenous contrast media administration, Ann Emerg Med 69 (5) (2017) 577–586, e4. [4] LK Young, SZ Matthew, JG Houston, Absence of potential gadolinium toxicity symptoms following 22,897 gadoteric acid (Dotarem®) examinations, including 3,209 performed on renally insufficient individuals, Eur Radiol 29 (4) (2019) 1922– 1930. [5] SA Woolen, PR Shankar, JJ Gagnier, MP MacEachern, L Singer, MS Davenport, Risk of nephrogenic systemic fibrosis in patients with stage 4 or 5 chronic kidney disease receiving a
group II gadolinium-based contrast agent: a systematic review and meta-analysis, JAMA Intern Med 180 (2) (2020) 223–230. [6] RG McWilliams, JV Frabizzio, AI De Backer, A Grinberg, BD Maes, BB Zobel, et al., Observational study on the incidence of nephrogenic systemic fibrosis in patients with renal impairment following gadoterate meglumine administration: the NSsaFe study, J Magn Reson Imaging 51 (2) (2020) 607–614. [7] M Krupa, H Salts, F Mihlon, It is not necessary to discontinue seizure threshold-lowering medications prior to myelography, AJNR Am J Neuroradiol 40 (5) (2019) 916–919. [8] Y Ishimoto, N Yoshimura, S Muraki, H Yamada, K Nagata, H Hashizume, et al., Associations between radiographic lumbar spinal stenosis and clinical symptoms in the general population: the Wakayama Spine Study, Osteoarthritis Cartilage 21 (6) (2013) 783–788. [9] L Kalichman, R Cole, DH Kim, L Li, P Suri, A Guermazi, et al., Spinal stenosis prevalence and association with symptoms: the Framingham Study, Spine J 9 (7) (2009) 545–550. [10] MJ Lee, EH Cassinelli, KD Riew, Prevalence of cervical spine stenosis. Anatomic study in cadavers, J Bone Joint Surg Am 89 (2) (2007) 376–380. [11] MA McDonald, CF.E Kirsch, BY Amin, JM Aulino, AM Bell, RC Cassidy, et al., ACR appropriateness criteria® cervical neck pain or cervical radiculopathy, J Am Coll Radiol 16 (5S) (2019) S57–S76.
[12] ND Patel, DF Broderick, J Burns, TK Deshmukh, IB Fries, HB Harvey, et al., ACR appropriateness criteria low back pain, J Am Coll Radiol 13 (9) (2016) 1069–1078. [13] DF Fardon, AL Williams, EJ Dohring, FR Murtagh, SL Gabriel Rothman, GK Sze, Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology, Spine J 14 (11) (2014) 2525–2545. [14] CW Pfirrmann, C Dora, MR Schmid, M Zanetti, J Hodler, N Boos, MR image-based grading of lumbar nerve root compromise due to disk herniation: reliability study with surgical correlation, Radiology 230 (2) (2004) 583–588. [15] EP Flanagan, KN Krecke, RW Marsh, C Giannini, BM Keegan, BG Weinshenker, Specific pattern of gadolinium enhancement in spondylotic myelopathy, Ann Neurol 76 (1) (2014) 54–65. [16] RM Kurtz, Babatunde VD, Schmitt JE, Berger JR, Mohan S, Spinal cord sarcoidosis cccurring at sites of spondylotic stenosis, mimicking spondylotic myelopathy: a case series and review of the literature, AJNR Am J Neuroradiol 44 (1) (2023) 105–110. [17] J Urrutia, T Zamora, J Cuellar, Does the prevalence of spondylolysis and spina bifida occulta observed in pediatric patients remain stable in adults, Clin Spine Surg 30 (8) (2017 Oct) E1117–E1121.
[18] M Shin, LM Besser, C Siffel, JE Kucik, GM Shaw, C Lu, et al., Prevalence of spina bifida among children and adolescents in 10 regions in the United States, Pediatrics 126 (2) (2010) 274– 279. [19] I Goldstein, IR Makhoul, A Weissman, A Drugan, Hemivertebra: prenatal diagnosis, incidence and characteristics, Fetal Diagn Ther 20 (2) (2005) 121–126. [20] PG Passias, GW Poorman, CM Jalai, BG Diebo, S Vira, SR Horn, et al., Incidence of congenital spinal abnormalities among pediatric patients and their association with scoliosis and systemic anomalies, J Pediatr Orthop 39 (8) (2019) e608–e613. [21] JD Colmenero, ME Jiménez-Mejías, FJ Sánchez-Lora, JM Reguera, J Palomino-Nicás, F Martos, et al., Pyogenic, tuberculous, and brucellar vertebral osteomyelitis: a descriptive and comparative study of 219 cases, Ann Rheum Dis 56 (12) (1997) 709–715. [22] KP Bhavan, J Marschall, MA Olsen, VJ Fraser, NM Wright, DK Warren, The epidemiology of hematogenous vertebral osteomyelitis: a cohort study in a tertiary care hospital, BMC Infect Dis 10 (2010) 158. [23] PA Swanson, DB McGavern, Viral diseases of the central nervous system, Curr Opin Virol 11 (2015) 44–54. [24] MC Thigpen, CG Whitney, NE Messonnier, ER Zell, R Lynfield, JL Hadler, et al., Bacterial meningitis in the United States, 1998-2007, N Engl J Med 364 (21) (2011) 2016–2025.
[25] LN Ledbetter, KL Salzman, LM Shah, Imaging psoas sign in lumbar spinal infections: evaluation of diagnostic accuracy and comparison with established imaging characteristics, AJNR Am J Neuroradiol 37 (4) (2016) 736–741. [26] KB Patel, MM Poplawski, PS Pawha, TP Naidich, LN Tanenbaum, Diffusion-weighted MRI “claw sign” improves differentiation of infectious from degenerative modic type 1 signal changes of the spine, AJNR Am J Neuroradiol 35 (8) (2014) 1647–1652. [27] MT Wallin, WJ Culpepper, E Nichols, ZA Bhutta, TT Gebrehiwot, SI Hay, et al., Global, regional, and national burden of multiple sclerosis 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016, Lancet Neurol 18 (3) (2019) 269–285. [28] RA Marrie, C Gryba, The incidence and prevalence of neuromyelitis optica: a systematic review, Int J MS Care 15 (3) (2013) 113–118. [29] D Lacomis, Neurosarcoidosis, CN 9 (3) (2011) 429–436. [30] N Soni, G Bathla, R Pillenahalli Maheshwarappa, Imaging findings in spinal sarcoidosis: a report of 18 cases and review of the current literature, Neuroradiol J 32 (1) (2019) 17–28. [31] CJ Roth, PD Angevine, JM Aulino, KL Berger, AF Choudhri, IB Fries, et al., ACR appropriateness criteria myelopathy, J Am Coll Radiol 13 (1) (2016) 38–44.
[32] L Ferrante, L Mastronardi, P Celli, P Lunardi, M Acqui, A Fortuna, Intramedullary spinal cord ependymomas ? A study of 45 cases with long-term follow-up, Acta Neurochir 119 (1-4) (1992) 74–79. [33] DJ Miller, IE McCutcheon, Hemangioblastomas and other uncommon intramedullary tumors, J Neuro-Oncol 47 (3) (2000) 253–270. [34] H Maslehaty, H Barth, AK Petridis, A Doukas, HM Mehdorn, Symptomatic spinal cavernous malformations: indication for microsurgical treatment and outcome, Eur Spine J 20 (10) (2011) 1765–1770. [35] HJ Westwick, MF Shamji, Effects of sex on the incidence and prognosis of spinal meningiomas: a surveillance, epidemiology, and end results study, J Neurosurg Spine 23 (3) (2015) 368–373.
CHAPTER 80
Pediatric Brain and Spine Tushar Chandra, Pankaj Watal, Manish Bajaj, Laura Hayes
Introduction Imaging of the pediatric brain has rapidly evolved over the last few decades. There have been significant strides in both the quality of imaging and the understanding of disease processes that involve the pediatric central nervous system (CNS) along with a paradigm shift toward identifying the genetic basis of various disorders. Understanding the embryology, growth, developmental as well as maturation of the pediatric brain provides a fundamental basis for assessing the pediatric brain abnormalities.
Embryology and Normal Prenatal Brain Development Brain development begins in the third gestational week with dedifferentiation of neural progenitor cells. By the end of the embryonic period, the rudimentary structures of brain and CNS are established. The stages of brain development are as follows: 1. Dorsal induction 2. Ventral induction 3. Proliferation 4. Migration 5. Organization 6. Myelination
The first step in the human brain development is differentiation of the progenitor cells. The early CNS begins a simple neural plate in the dorsal midline of the embryo, which forms as thickening of the ectoderm. The neural plate folds to form a neural groove and the sides of the neural groove,
known as the neural folds come together and join to form the neural tube. The neural tube is formed by the 20th day of gestation and begins to close in the early stages of neurulation. The brain forms at the rostral end of the neural tube and three distinct primary vesicles are formed by the fourth week of gestation.
◾andThehindbrain three primary vesicles are the forebrain (prosencephalon), midbrain (mesencephalon), (rhombencephalon). The secondary vesicles arise from the primary vesicles ◾ The prosencephalon divides into telencephalon anteriorly and diencephalon posteriorly ◾myelencephalon The rhombencephalon divides into anterior metencephalon and the posterior ◾ The mesencephalon remains a single vesicle ◾mesencephalon, The lateral ventricles develop in the prosencephalon, the third ventricle develops in the and the fourth ventricle in the rhombencephalon
The telencephalon expands and differentiates to form the cerebral hemispheres by the 11th week of gestation, through a process of neuronal proliferation. Migration of the neuronal cells continues to about the 35th week. Through the process of operculization, the insular cortex and Sylvian fissures are formed. The lobes of the cerebral hemispheres and the sulci and gyri start forming and continue to the 35th week. The diencephalon develops into thalamus, hypothalamus, epithalamus, globi pallidi, pineal gland, and neurohypophysis of the pituitary gland. The cerebral commissures of the telencephalon begin to form and are the site of origin of the anterior commissure and the corpus callosum. The progression of formation of corpus callosum begins with the posterior aspect of genu, followed by the body, splenium, anterior genu, and rostrum during weeks 10–12 of gestation. The sequence of these events is somewhat controversial and has been challenged by some authors. The mesencephalon forms the superior and inferior colliculi of the tectum, cerebral peduncles, optic lobes, and tegmentum. The metencephalon portion of the rhombencephalon gives rise to the cerebellum and pons. The myelencephalon portion of the rhombencephalon develops into the medulla oblongata and the rostral neural tube is contiguous with the myelencephalon and forms the spinal cord. Although the brain continues to grow and myelinate after birth, structurally, the brain at birth is similar to the adult brain.
Brain Myelination Assessment of myelination is an integral part of evaluation of the pediatric brain. Myelin is produced by the oligodendrocytes and contains approximately 70% lipid and 30% protein [1]. MRI allows for a reliable and quick estimation of the degree of myelination of the brain, which can be
categorized as normal for age, delayed, or abnormal. This has greatly enhanced of our ability to evaluate pathologies that are associated with abnormalities of myelination, such as leukodystrophies and neurometabolic abnormalities. It is important to understand that anatomical regions in the brain that are responsible for more primitive and basic functions myelinate earlier than anatomic structures that are responsible for more advanced functions. Brain myelination, therefore is a sequential process that occurs in an orderly and predictable course. In general, brain myelination progresses from caudal to cephalad, dorsal to ventral, and from central to peripheral areas of the brain. For example, the brainstem myelinates before the deep gray matter structures and the cerebellum, and the cerebral hemispheres myelinate even later. Furthermore, projection tracts within the brain generally myelinate before the association tracts. However, it is also important for the reader to be aware that these are general rules and exceptions do exist. For example, the more cranially located perirolandic cortex myelinates before the more caudally located anterior limb of internal capsule and the more ventrally located frontal poles myelinate before the more dorsally located temporal poles. Myelination can be adequately assessed using routine T1- and T2weighted sequences. Progressive myelination is associated with both T1 and T2 shortening, thereby resulting in T1 hyperintensity and T2 hypointensity of myelinated structures, compared with structures that are unmyelinated [2,3].
T1-Weighted Images Generally, from birth to the first 6 months of life, T1-weighted images (T1WI) provided a more accurate assessment of myelination than T2weighted images (T2WI). This is because with progressive myelination, there is an earlier and more pronounced T1 shortening than T2 shortening. Brain structures that demonstrate myelination on T1WI at birth include the medulla, dorsal pons, midbrain, posterior limb of internal capsule, and perirolandic cortex. At about 3 months of age, the deep cerebellar white matter myelinates, followed by the splenium of corpus callosum by 4 months and the genu of corpus callosum by 6 months. With increasing age, T2WI more closely parallel the development of myelination.
T2-Weighted Images The splenium of corpus callosum myelinates at around 6 months of age on T2WI. By 8 months of age, the genu of the corpus callosum is completely myelinated and by 10–11 months of age, the anterior limb of internal capsule demonstrates myelination on T2-weighted sequence. By 12–14 months of
age, there is myelination of the frontal white matter, while the temporal white matter is still not completely myelinated. Most of the temporal white matter myelination is completed at around 16 months of age; however the terminal, subcortical U fibers are myelinated by 18–24 months of age. By 2 years of age, myelination of the brain is nearly complete and the myelination pattern on neuroimaging resembles that of an adult brain (Figs. 80.1 and 80.2).
FIGURE 80.1 Axial T1W (A–D) and T2W (E–H) images in a full-term newborn demonstrate normal myelination pattern. Note T1 hyperintensity and T2 hypointensity of the dorsal brainstem, posterior limb of internal capsule, and perirolandic cortex.
FIGURE 80.2 Axial T1W (A–D) and T2W (E–H) images in a 24-month old demonstrate myelination pattern resembling that of an adult. Note terminal zones of myelination (white arrows in G).
Terminal Zones of Myelination Symmetric areas of T2 hyperintense signal can be observed in the peritrigonal region beyond 2 years of age. These areas are termed as “terminal zones of myelination” and are thought to reflect a combination of prominent perivascular spaces as well as delayed myelination. Another region, the subcortical U fibers at the temporal lobes are also considered as terminal zones of myelination as these regions can also show persistent T2 hyperintense signals beyond 2 years of age [3].
Inherited Neurometabolic Disorders/Leukodystrophies A diverse group of both inherited and acquired abnormalities of myelination involve the brain in the pediatric age group. The accurate diagnosis can be challenging, as the clinical presentation is often nonspecific. They can present in various forms that can be seen with single versus multiple enzyme defects. The presentations can vary with the age of presentation and the same disease can have different imaging presentation in the infant, juvenile, or adult age group. Furthermore, there is considerable overlap in the imaging
appearance of different disorders and they may look similar on imaging at an advanced stage. MRI is more sensitive than CT in the demonstration of these disorders. Integration of clinical data, laboratory tests, imaging appearance, and genetic tests is usually needed for an accurate diagnosis. At the cellular level, these disorders can be caused by abnormalities in genes that code for important enzymes involved in various cellular processes in cell organelles such as lysosomes, peroxisomes, and mitochondria, etc. A faulty gene leads to a defective protein that in turn causes an enzyme defect. This enzyme defect leads to abnormal products that can cause direct toxicity to myelin or can interfere with neuronal function. Leukoencephalopathies is a broad term, generally encompassing all disorders that affect the white matter of the brain. Genetically determined leukoencephalopathies are called leukodystrophies. These disorders are underlined by pathological processes leading to abnormal development or destruction of myelin within the CNS. Several terms are sometimes loosely attributed to white matter disorders and therefore proper understanding of what these stand for is essential.
◾retarded. Delayed myelination is used when the process of myelination is progressing, but is Delayed myelination is a nonspecific feature that can be observed in children with development delay of any cause ◾inDysmyelination is a term that refers to an abnormality in the myelination process, resulting abnormal, patchy, or irregular myelination ◾myelin Demyelination is a term which is used when there is loss/destruction of already formed ◾ Hypomyelination is a term which means that there is paucity of myelin in the brain for age
Hypomyelinating Leukodystrophies This group of disorders is characterized by the absence or near absence of myelination in the brain. The MRI criteria for the diagnosis of hypomyelination are an unchanged pattern of myelination on two successive MRI studies done at least 6 months apart. One of these should have been obtained at the age more than 1 year [4]. Pelizaeus–Merzbacher Disease This is the classical hypomyelinating disorder, which is caused by mutations in the PLP1 gene. This leads to abnormal protein folding and death of oligodendrocytes, thereby causing nearly complete absence of myelin. Classic Pelizaeus–Merzbacher disease is X-linked recessive and exclusively seen in males, while other forms are autosomal recessive. It presents mainly in infancy, but can begin later. There is progressive dementia, ataxia, and nystagmus, often with extrapyramidal features such as dystonic postures and
torsion spasms. On imaging, there is complete lack of myelin that can be seen on both T1- and T2-weighted sequences [5] (Fig. 80.3).
FIGURE 80.3 Pelizeas–Merzbacher disease. Axial T1W (A) and T2W (B) images demonstrate complete lack of myelination in this 5-year-old male.
Other hypomyelinating leukodystrophies include:
◾which Pelizaeus–Merzbacher-like disease, also called hypomyelinating leukodystrophy type 2, is autosomal recessive, but otherwise similar to Pelizaeus–Merzbacher disease ◾mutations Pol III-related leukodystrophies are autosomal recessive disorders characterize by in POLR3A and POLR3B genes. In this disorder, apart from homogeneous hypomyelination, there are hyperintense signals in the globus pallidus and thalami on T2weighted sequences and cerebellar atrophy Hypomyelination with congenital cataracts is another rare, autosomal recessive disorder that is caused by a mutation in FAM126A gene. Patients with this order presented with developmental delay and congenital or childhood cataracts. On imaging, there is heterogeneous hypomyelination with T2 hyperintense signal more increased in the periventricular white matter compared with the subcortical and deep white matter [6] Hypomyelination with atrophy of basal ganglia and cerebellum is a sporadic disorder characterized by mutation in the TUBB4A gene, which is characterized by homogeneous hypomyelination along with atrophy of the cerebellum, putamen, and caudate nucleus, as the name suggests [7] Hypomyelination with brainstem and spinal cord involvement and leg spasticity is characterized by muscle spasticity in the legs that worsens over time along with other symptoms such as nystagmus, hypertonia, and mild intellectual disability. This is caused by DARS gene mutation that affects amino acids. On imaging there is homogeneous hypomyelination involving the cerebrum, brainstem, cerebellum, and spinal cord. The pyramidal tracts and dorsal columns are primarily affected by this condition [8]
◾ ◾ ◾
Metachromatic Leukodystrophy
This is one of the commoner hereditary leukodystrophies; clinical symptoms usually commence in infancy, although they can be delayed into adolescence or later. This is a lysosomal disorder caused by a deficiency of the enzyme arylsulfatase A. There is mental retardation or regression and other neurological signs, which are progressively fatal. On MRI, the classical appearances confluent and symmetric hyperintense T2 signals that involve the periventricular and deep white matter related to sparing of the subcortical U fibers. There is relative sparing of the perivenular myelin leading to a tigroid pattern. In late stages that can be involvement of subcortical U fibers, corpus callosum, and descending pyramidal tracts with atrophy.
Globoid Leukodystrophy (Krabbe’s Disease) This is also a lysosomal disorder, characterized by a lack of the enzyme Pgalactocerebrosidase. It presents in infancy with retardation and spasticity, and is usually fatal by the second year. Rarely, it presents in later childhood with a more chronic course and early visual failure. On CT, symmetric hyperdensity can be seen in basal ganglia, thalami, cerebellum, and corona radiata. On MRI there is confluent, symmetric T2 hyperintense signal in the periventricular and deep white matter along with alternating hyperintense, hypointense, and hyperintense signals in the cerebellar white matter around the dentate nuclei. Furthermore, there can be enlargement and postcontrast enhancement of the cranial nerves as well as cauda equina nerve roots.
Adrenoleukodystrophy This is an inherited X-linked peroxisomal disorders caused by ABCD1 mutation that results in accumulation of very long chain fatty acids in the white matter. The classic form of X-linked ALD primarily affects boys of 5– 12 years age. On MR imaging, there is involvement of the splenium of corpus callosum, peritrigonal periventricular and deep white matter, corticospinal tracts, and visual and auditory pathways. The classic imaging feature is confluent T2 hyperintense signal involving the periventricular and deep white matter in the peritrigonal regions with marked rim enhancement on postcontrast T1 images of the leading edge. Contrast enhancement represents perivascular inflammation at the margins of the demyelinating process (Fig. 80.4).
FIGURE 80.4 X-linked adrenoleukodystrophy. Coronal FLAIR (A) and axial FLAIR (B) images demonstrate confluent hyperintense signal in the peritrigonal white matter. Postcontrast T1 (C) image enhancement along the leading edge.
Alexander’s Disease This disease is inherited sporadically and is characterized histopathologically by the abundant presence of Rosenthal fibers in the affected brain. There are three clinical forms: infantile, juvenile, and adult. The infantile form is most common and these patients present with macrocephaly. There is a variable rate of progression and the disease is invariably fatal. On MR imaging, that is characteristic T2 hyperintense signal that involves bifrontal white matter (Fig. 80.5). In early disease, intense postcontrast enhancement may be observed.
FIGURE 80.5 Alexander’s disease. Axial T1(A), T2 (B), and FLAIR (C) images demonstrate confluent and symmetric T1 hypointense and T2/FLAIR hyperintense signal in the frontal white matter bilaterally.
Organic Acidemias and Aminoacidopathies This is a wide group of metabolic disorders caused by defects in the intermediate metabolic path results of amino acid, carbohydrate, and fatty acid oxidation. They present in infants and with improved methods of biochemical assay many different types have now been defined. The diagnosis is usually made biochemically but imaging may help by showing the degree of myelin damage or the effect of treatment on progression. This group of disorders includes conditions such as propionic acidemia, methylmalonic acidemia, multiple carboxylase deficiency, Canavan disease, glutaric aciduria, phenylketonuria, maple syrup urine disease, nonketotic hyperglycemia, homocystinuria, sulfite oxidase deficiency, etc. (Fig. 80.6).
Canavan Disease This is an autosomal recessive disorder characterized by deficiency of aspartoacylase enzyme which results in increased N-acetyl aspartate (NAA) in the brain, causing spongiform degeneration of the white matter, globus pallidus, and thalami. Patients present with macrocephaly and hypotonia which is evident in the first few months of life. On MRI there is involvement of the subcortical U fibers, thalamus, and globus pallidus with relative sparing of the internal capsules and putamen. The characteristic finding on MR spectroscopy is increase in NAA. Phenylketonuria
This is an autosomal recessive disorder of amino acid metabolism caused by mutation in PAH gene, leading to the absence of phenylalanine hydroxylase which hydrolyses phenylalanine to tyrosine. Severe mental impairment may ensue if the condition is unrecognized and untreated, and there are alterations in the hemisphere myelin resembling leukodystrophy. On MRI, T2/FLAIR hyperintensity can be seen in periventricular or subcortical white matter.
Mitochondrial Disorders This is a group of diseases that have in common a defect in mitochondria, with consequent deficiency of enzymes controlling oxidative phosphorylation and/or the respiratory chain. As the spermatozoa are deficient of mitochondria, these diseases have maternal inheritance. The affected persons are often short in stature. The histopathology includes subacute necrotizing encephalomyelopathy associated with proliferation of capillaries and glia and with spongiform degeneration. The distribution, reflected in the MRI appearances, includes symmetric necrosis in the basal ganglia, spongiform change with increase in T1 and T2 in the thalamus, brainstem, and/or hemispheric white matter. There is frequent involvement of muscles resulting in a proximal myopathy. Involvement of the CNS can result in varied clinical presentations, associated with elevation of the serum and cerebrospinal fluid (CSF) lactate.
◾DNA Leigh’s syndrome or subacute necrotizing encephalomyelopathy is caused by mitochondrial mutations. Typical MRI findings include symmetrical areas of T2 prolongation
involving bilateral caudate nuclei and lentiform nuclei with less common involvement of the thalami, periaqueductal gray matter, tegmentum, red nuclei, and dentate nuclei (Fig. 80.7). The T2 hyperintense signals are thought to reflect spongiform changes and vacuolization of gray matter structures. As the disease progresses, global atrophy can be seen and basal ganglia can show volume loss. On MR spectroscopy, there is a characteristic lactate doublet at 1.3 ppm (Fig. 80.8) Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode is another progressive neurodegenerative disorder caused by mitochondrial DNA mutation. On MRI, the classical findings are acute stroke-like cortical lesions that crosses vascular territories and may appear, disappear, and then reappear elsewhere. As the disease becomes chronic, it may lead to brain atrophy Myoclonic epilepsy with ragged red fibers is another mitochondrial disorder that has a predilection for basal ganglia and can present with watershed ischemia/infarction Kearnes–Sayre syndrome is characterized by a triad of ataxia, ophthalmoplegia, and retinitis pigmentosa. There are calcifications in bilateral basal ganglia, caudate nucleus, and subcortical white matter. On MRI, there may be T1 and T2 hyperintense signal within the basal ganglia and cerebellar white matter
◾ ◾ ◾
FIGURE 80.7 Leigh disease. Axial T2 (A and B) images demonstrate symmetric T2 hyperintense signals involving bilateral caudate nuclei and dorsal brainstem. DWI images (C and D) demonstrate restricted diffusion in those regions.
Hypoxic Ischemic Encephalopathy HIE is one of the major causes of cerebral palsy and severe neurological deficits in the pediatric age group. Neonatal encephalopathy can result from a diverse number of underlying conditions. Encephalopathy due to hypoxic ischemic injury presents within the first few hours after birth. If encephalopathy develops later (e.g., a few days after birth), infectious and metabolic causes should be considered. It is also important to remember that encephalopathy is a clinical term characterized by a low Apgar score and
clinical signs such as bradycardia, poor respiratory effort, hypotonia, and absent or weak cry at birth [9]. In terms of imaging, while describing the anatomical findings, hypoxic ischemic injury is a more appropriate term to use than HIE. Perinatal asphyxia leading to hypoxia and hypercapnia is the underlying pathophysiological mechanism for HIE. Hypoxia with loss of cerebral autoregulation leads to decreased cerebral blood flow and through a cascade of abnormal pathogenic mechanisms. This causes acidosis, release of inflammatory mediators and excitatory neurotransmitters, free radical formation, and lipid peroxidation, eventually leading to neuronal death [9,10]. The reasons for imaging patients with suspected HIE include confirmation of the diagnosis, exclusion of other structural abnormalities and assessing the extent of the injury for predicting the neurodevelopmental outcome. The patterns of injury depend on three primary factors: 1. Maturation of the brain (preterm vs term) 2. Duration of the insult 3. Severity of the insult
The vascular supply of the brain evolves as the brain matures. In the preterm neonate (36 weeks), the vascular border zone moves more peripherally in a more parasagittal location and HIE results in involvement of vascular watershed zones, with involvement of the cortex and the deep white matter. Severe and more prolonged injury results in greater involvement of deep gray matter structures such as the thalami and basal ganglia, cerebellum, and brainstem in both preterm as well as term infants. Furthermore, actively myelinating structures are more prone to hypoxic injury compared with other regions of the brain. Ultrasound of the neonatal brain is the initial investigation that helps in the detection of germinal matrix hemorrhage and hydrocephalus. However, ultrasound is not the preferred technique for the detection of changes of HIE in the early stages. It is operator defendant and has low sensitivity for the detection of cortical and brainstem abnormalities. In the more chronic setting, ultrasound can be used for the detection of periventricular leukomalacia. MRI is the most sensitive and specific technique for evaluation of suspected HIE. The most useful sequences on MR imaging are diffusionweighted (DW) sequence and T1 sequence. DW sequence demonstrates the cytotoxic edema caused by neuronal death as restricted diffusion. If performed within 24 hours of hypoxic injury, DW sequence may be falsely
negative. DW changes last for 10–12 days after hypoxic injury and thereafter pseudonormalization occurs [9]. T1 sequences are also useful for the detection of injury to the deep gray matter structures as well as the cortex. Deep gray matter injury is characterized by T1 hyperintense signal in the basal ganglia and thalamus. In the term neonate, this is accompanied by the absence of the normal T1 hyper intensity of the posterior limb of internal capsule (which should be present due to myelination in a normal term infant). T1 hyperintensity may also be seen along the cortex in cases with cortical injury. MR spectroscopy can be very useful in the evaluation of HIE. There is elevation of lactate with reduction of NAA (Figs. 80.9 and 80.10). An elevated lactate to creatine ratio on first day of life is a predictor of adverse outcome [11]. Caution must be used while interpreting MR spectroscopy findings in a preterm neonate as a high lactate and low NAA are normal findings in this age. The treatment of HIE is usually supportive and involves therapeutic hypothermia.
FIGURE 80.9 Hypoxic ischemic encephalopathy. Axial DWI (A) and ADC (B) images demonstrate restricted diffusion involving bilateral thalami and splenium of corpus callosum. MR spectroscopy (C) demonstrates elevated lipid-lactate (white arrow) and decreased NAA.
FIGURE 80.10 Severe hypoxic ischemic encephalopathy. Axial DWI (A) and ADC (B) images demonstrate extensive restricted diffusion involving bilateral deep gray matter, white matter, and the cortex. Note relative sparing of medial occipital lobes. MR spectroscopy (C) demonstrates elevated lipid-lactate (white arrow) and decreased NAA.
Congenital and Developmental Supratentorial Brain Anomalies There is a wide array of congenital supratentorial brain abnormalities. Patients often present with seizures or developmental delay, and prognosis is variable. Congenital brain malformations are best demonstrated with MRI. It is important for the radiologist to identify the abnormalities to help prognosticate outcomes and assist in surgical planning in some cases.
Pertinent Embryology Supratentorial brain development is a series of very complex, carefully orchestrated events that are beyond the scope of this chapter, and therefore a simplified review is included herein. The basic events that occur embryologically during development of the brain are neurulation, neuronal proliferation, and neuronal migration. The development of gyri and sulci takes place after the 11th week of gestation. Cortical neurons are formed in the embryonal germinal matrix which lies along the inner margins of the lateral ventricles. These neuroblasts migrate centrifugally out along the radial glial cells to the surface of the brain, where they form the cerebral cortex, the deeper layers being constituted first. Interruption of this process, which takes place primarily between the 11th and 15th fetal weeks, may give rise to various cortical anomalies including heterotopias, focal cortical dysplasias (FCDs), and lissencephaly.
Anomalies of the Cortex Lissencephaly (from the Greek language meaning “smooth brain”) is characterized by the absence of sulci and convolutions in the cortex, resembling the normal fetal brain before the seventh month of gestation (Fig. 80.11). Lissencephaly may be spontaneous or inherited. LIS1, DCX, and TUBA1A mutations are associated with the lissencephaly spectrum of disorders. Clinically these patients usually demonstrate developmental delay and seizures. Lissencephaly can involve the entire brain or only a portion of the hemispheres, most often in the parieto-occipital region. Some degree of pachygyria (meaning “thick brain”) with abnormally broad and thick convolutions may also be present [12]. Subcortical band heterotopia, also called “double cortex” syndrome, is the mildest form of classic lissencephaly.
FIGURE 80.11 Lissencephaly. Axial T2 (A) and sagittal T1 (B) images demonstrate broad gyri with paucity of sulci resulting in smooth appearance of the brain. Note a small Dandy–Walker cyst communicating with the fourth ventricle in the posterior fossa (arrow).
Holoprosencephaly (Fig. 80.12) is a complex craniocerebral and facial anomaly classified in grades of severity from alobar through semilobar to lobar, which is the least severe. It results from a failure of normal development of the forebrain (prosencephalon).
FIGURE 80.12 Holoprosencephaly. Coronal T2-weighted image (A) and axial T1-weighted image (B) demonstrate absent interhemispheric fissure (arrow) and fused frontal lobes in keeping with holoprosencephaly. A dilated monoventricle with a thin cortical mantle is present.
◾multiple The severe alobar form is incompatible with survival beyond infancy. The child has craniofacial anomalies (cleft lip and palate, hypotelorism, anophthalmia, or cyclopia). Intracranially, the midline structures (falx, corpus callosum, septum pellucidum, and olfactory bulbs) are absent and the two hemispheres are replaced by a single large ventricle with a thin rim of cortical mantle. The thalami are fused, unlike hydranencephaly (Fig. 80.13), where they remain normal and the falx is present Semilobar holoprosencephaly (Fig. 80.14), the intermediate form, shows less severe facial deformity and the brain has a thicker mantle with recognizable occipital horns In the mildest (lobar) type there are well-formed lateral ventricles and a recognizable third ventricle, although the septum and Sylvian fissures are usually absent. The grosser forms may be suspected from the clinical appearance of the infant, but imaging is required in all varieties to delineate the intracranial anomalies
◾ ◾
FIGURE 80.13 (A–C) Hydranencephaly.
FIGURE 80.14 (A and B) Semilobar holoprosencephaly.
Heterotopias may be observed as an isolated phenomenon due to arrest of migrating neurons in the form of small masses of gray matter. They may form subependymal nodules protruding into the lateral ventricles similar to those seen in tuberous sclerosis or lie in the deep or subcortical white matter (Fig. 80.15). Gray matter heterotopias may be nodular or band-like.
FIGURE 80.15 Heterotopia. Coronal T1 inversion recovery (A) and axial T1-weighted image (B) demonstrate a nodular focus of gray matter in the right parietal lobe, in keeping with a subependymal nodular gray matter heterotopia.
White Matter Anomalies With Cortical Malformation Hemimegalencephaly is a condition with unilateral enlargement of the skull. The asymmetrical skull is secondary to a congenital unilateral enlargement of the brain, and is associated with seizures, hemiplegia, and hemianopsia. There are migrational abnormalities with thickening of the gray matter and white matter with abnormal shallow sulci on the affected side (Figs. 80.16 and 80.17). The ventricle in the enlarged hemisphere is also enlarged.
FIGURE 80.16 Hemimegalencephaly. Axial T2 (A), axial FLAIR (B), and sagittal T2 (C) images demonstrate an enlarged right occipital lobe with increased T2 signal in the periventricular white matter. The ventricle is enlarged in this affected area.
FIGURE 80.17 Hemimegalencephaly. Postcontrast coronal T1 (A) image demonstrates asymmetrically enlarged right occipital lobe. 3D ASL (B) image demonstrated decreased perfusion in the abnormal brain parenchyma in the right occipital lobe.
Cobblestone lissencephaly, or cobblestone cortical malformation, is characterized by a nodular surface of the brain resembling a cobblestone street. The malformation is caused by defects in the limiting pial basement membrane. Overmigration of neuroblasts through these breaches results in an extracortical layer of aberrant gray matter nodules. Nearly all cases are part of a congenital muscular dystrophy syndrome and have associated ocular anomalies such as staphylomas. Most of these are dystroglycanopathies (Fig. 80.18).
FIGURE 80.18 Cobblestone lissencephaly. Axial T2-weighted images demonstrate a “cobblestone” appearance of the cortex (arrow in A), ventriculomegaly (B), staphylomas (asterisk in C), and dysplastic cerebellar hemispheres with small cysts (arrow in D).
Polymicrogyria (PMG) is a cortical malformation that occurs in the late migrational or early postmigrational periods. Three characteristics are usually seen: abnormal gyral pattern, thickened cortex, and irregular gray– white junction due to packing of gyri (Fig. 80.19). PMG is most commonly seen in the posterior aspect of the Sylvian fissures but can be unilateral or bilateral, focal or multifocal/diffuse, symmetric or asymmetric. Volumetric MR images are most helpful to detect PMG.
FIGURE 80.19 Polymicrogyria. Axial T2-weighted image demonstrates irregular cortex with small gyri along the right cingulate gyrus (arrow).
Prenatal cytomegalovirus (CMV) infection can lead to cortical malformations and congenital hearing loss. Numerous patterns can be seen depending on the phase of brain development at the time of the viral exposure in utero. Very early insults cause the most severe malformations. Cortical malformations associated with prenatal CMV infection include PMG, cortical infoldings in abnormal positions, thickened cortical ribbon, blurring of the gray–white junctions, schizencephaly, and porencephaly (Fig. 80.20). Hippocampal dysplasia with verticalization can also be seen. Dilatation of the temporal horns and anterior temporal cysts/pseudocysts are highly predictive of prenatal CMV infection. Parenchymal calcifications
may or may not be present, and if present are most common in the periventricular regions [13].
FIGURE 80.20 Congenital CMV infection. Noncontrast CT (A and B) and T2W MRI (C and D) demonstrate calcifications, microcephaly, migration anomalies (white arrow in D), and white matter lesions (white arrows in C).
Focal cortical dysplasia (FCD) is a cortical malformation that involves the cortex and adjacent white matter. Three types of FCD have been described. Type I FCD is defined as isolated alterations in cortical organization and lamination. Type II FCD is defined as isolated alteration in cortical organization and lamination with dysmorphic neurons. Type III is FCD in association with other lesions such as hippocampal sclerosis, tumors, or vascular lesions. The most common variant is FCD type II, that is divided into a and b types. Type II b is differentiated from type IIa as there are balloon cells present in type IIb on histopathology, in addition to dysmorphic neurons. FCDIIb is more conspicuous on MRI than type a. There is abnormal thickening of the cortex with blurring of the gray/white junction and a tail of T2 hyperintensity extending from the cortex into the white matter (Fig. 80.21). The transmantle sign refers to white matter signal tapering from the subcortical region to the ventricular margin. FCDIIb is most common in the frontal lobes and are most conspicuous on volumetric coronal T2 FLAIR and double inversion recovery MRI sequences.
FIGURE 80.21 Focal cortical dysplasia. Coronal T2 (A) and coronal T2 FLAIR (B and C) images demonstrate focal cortical dysplasias in the right middle frontal gyrus (A and B) and left superior frontal gyrus (C).
Anomalies Associated With Absent Septum Pellucidum Septal agenesis can occur as an isolated lesion giving rise to a single ventricle communicating across the midline. A similar appearance can be seen with chronic hydrocephalus due to autofenestration of the septum. Septo-optic dysplasia (SOD) is an abnormality characterized by the absence of the septum pellucidum and hypoplasia of the optic pathways (Fig. 80.22). There is squaring off of the frontal horns with a prominent chiasmatic cistern. The anatomical features are best demonstrated with MRI including high-resolution, thin-slice T2WI of the optic nerves and chiasm.
FIGURE 80.22 Septo-optic dysplasia. Ectopic pituitary bright spot on sagittal T1-weighted image (arrow in A) and absent septum pellucidum (arrow in B) with optic nerve hypoplasia on coronal T2-weighted image.
When the septum pellucidum is absent a search for schizencephaly should be made as it is often associated with SOD. Schizencephaly is a congenital anomaly in which gray matter-lined clefts, sometimes bilateral, extend from
the ventricles to the convexity often in the frontoparietal regions (Fig. 80.23). Injury to the germinal matrix in the early stage of gestation may result in loss of the full thickness of cerebral substance, with a cleft extending from the ventricle to the convexity subarachnoid space. Schizencephalies may be open- or closed-lip, with the former having a wide space between the cleft.
FIGURE 80.23 Axial T2-weighted image (A) of a patient with bilateral schizencephaly. The clefts radiate out from the lateral ventricles to the surface of the hemispheres and are lined by gray matter. The cleft on the right is close-lipped whereas the one on the left is open-lipped and this is evident on the more superior axial T1-weighted image (B).
Anomalies of the cerebral commissures are the most common of all congenital brain malformations. Agenesis of the corpus callosum is usually partial but may be complete. It can be seen as an isolated finding or in association with other malformations (Table 80.1). Complete agenesis is characterized by separation of the medial borders of the lateral ventricles with a high-riding third ventricle and enlargement of the occipital horns (porencephaly) (Fig. 80.24). Midline and paramedian MR images demonstrate the abnormality best. The third ventricle extends upward into and above the position of the absent corpus callosum. A “spoke-wheel” gyral pattern can be seen on sagittal images. The axons which fail to cross form symmetrical longitudinal bundles along the medial surfaces of the hemispheres and impress the medial aspects of the ventricles. Thus, the frontal horns and bodies are laterally displaced and small. The atria and occipital horns are large and rounded due to lack of the normal forceps
major impressions. Interhemispheric cysts may be present above the third ventricle and can be large. These may or may not communicate with the ventricles. Table 80.1 Malformations and Syndromes Associated With Callosal Dysgenesis [5] Malformations Chiari 2 Dandy–Walker Frontonasal dysplasia/clefts Cerebellar hypoplasia/dysplasia Hypothalamic–pituitary axis malformations Malformations of cortical development Inherited Syndromes Aicardi syndrome (females) Apert syndrome CRASH syndrome 22q11.2 deletion syndrome (DiGeorge) Morning glory syndrome
FIGURE 80.24 Agenesis of corpus callosum. Fetal MRI (A) and postnatal MR images (B and C). Note the “bull’s horn” configuration of the ventricles on coronal T2-weighted (B) and “box-car” configuration on the axial T1 image (C).
With hypogenesis of the corpus callosum the rostrum and splenium are often absent related to the absent cingulate gyri. Thickening of the corpus callosum is a rare anomaly associated with a few genetic disorders including neurofibromatosis type I, FG syndrome, and Cohen syndrome. Diffusion-tensor MR images, especially the color fractional anisotropy maps, can be very helpful to determine if there are any crossing white matter fibers (Fig. 80.25). The normal red (right to left) color of the CC is absent and the prominent green (front to back) tracts of the Probst bundles are seen. High-resolution, heavily T2-weighted 3D images may also be helpful to detect any crossing fibers. There may be an interhemispheric cyst (Fig. 80.26). A lipoma may be present at the site of the absent/dysgenetic corpus callosum.
FIGURE 80.25 Near-complete agenesis of the corpus callosum with some intact fibers in the rudimentary splenium on sagittal T1-weighted image (A) and axial diffusion tensor color fractional anisotropy map (B).
FIGURE 80.26 Agenesis of the corpus callosum associated with a large interhemispheric cyst.
Intracranial lipomas are relatively rare lesions that occur most commonly in relation to the corpus callosum, but can also occur elsewhere including the suprasellar and pineal regions. They may lie above a normal corpus callosum but are associated with partial or complete agenesis in 40% of cases (Fig. 80.27). There is often marginal calcification where they merge with adjacent cortical tissue—this can be of a characteristic “brackets” appearance which may be apparent on CT or even radiographs. The pericallosal arteries are usually incorporated in the lipoma and may be fused (azygos or single anterior cerebral artery). Low-attenuation fat density allows the lipomas to be readily identifiable on CT scans. Adjacent calcification is often seen, but this may be minimal or absent, particularly with small lesions. The single anterior cerebral artery may be visible at MRI on T2WI and MR angiography.
FIGURE 80.27 Callosal lipoma. Thick, curvilinear, T1 hyperintense lipoma (white arrow) associated with a hypoplastic corpus callosum.
Imaging Techniques and Analysis Supratentorial brain malformations are often detected on prenatal ultrasound examinations, and some cases may benefit from further characterization with fetal MR imaging. Postnatal MRI is the study of choice for evaluating the brain for supratentorial malformations. Postnatal ultrasound encephalography has limited utility in evaluating malformations of the brain. Ultrasound can be helpful to identify the absence of the septum pellucidum, mass effect, and ventriculomegaly. Noncontrast CT can be helpful to confirm the presence of calcifications but is less sensitive to detecting cortical and white matter abnormalities than MRI. IV contrast is not usually indicated in the evaluation for brain malformations but may be helpful if there is concern for a neurocutaneous disorder such as Sturge–Weber syndrome. The following approach to analyzing MR imaging studies of the brain is modified and adapted from A. James Barkovich’s guidelines [14,15]. Sagittal Images
Begin with the midline section of the T1-weighted sequence. Evaluate the corpus callosum, and if abnormal look closely for other midline anomalies such as an ectopic pituitary bright spot. Look for other lesions such as lipomas and cysts which are often midline or paramidline. Lipomas are hyperintense on T1WI and can be associated with calcifications that bloom on susceptibility-weighted sequences. Sagittal images are also helpful to evaluate the cortex. As you scroll through the images, evaluate the gyral pattern and cortex looking for signs of malformations such as PMG and schizencephaly, and look for subependymal nodular gray matter heterotopias. Coronal Images Coronal images make side to side comparison relatively simple. Malformations of cortical development are common around the Sylvian fissures. Look along the interhemispheric fissure for possible contiguity of the hemispheres that is present with holoprosencephaly. T2 FLAIR and double inversion recovery images (especially 3D images) are helpful to look for areas of FCD. Identify the septum pellucidum, and if absent look for other signs of SOD such as schizencephaly, fusion of the anterior columns of the fornix, and optic nerve/chiasm hypoplasia. The absence of the septum pellucidum can be suggested by a box-like frontal horns of the lateral ventricles. Confirm the presence of the crossing fibers of the corpus callosum. If the corpus callosum is absent, a bull’s-horn appearance of the frontal horns will be present. Closely look at the hippocampal formations and temporal horns to confirm that they are normally folded and not vertically oriented as can be seen with holoprosencephaly, lissencephaly, callosal anomalies, and malformations of cortical development. Axial Images T1- and T2-weighted axial images are helpful to evaluate myelination of the brain. At term, the posterior limb of the internal capsule should be myelinated and appear hyperintense on T1WI. Myelination occurs front to back in general and is discussed previously. Axial images are also helpful to evaluate the size and configuration of the ventricles and thickness and configuration of the cortical mantle. If the corpus callosum is absent, a box-car shape of the ventricles can be seen. Evaluate the cerebellum and brainstem to look for signs of dysgenesis that can be associated with supratentorial malformations. For instance, rhombencephalosynapsis can be associated with other midline anomalies and a “Z-shaped” brainstem can be seen with dystroglycanopathies.
Indications for Surgical Referral Hydrocephalus Hydrocephalus is often associated with supratentorial brain malformations, often detected prenatally, and may require shunting. Epilepsy Surgery Patients with intractable epilepsy refractory to treatment and with focal, resectable lesions (such as FCD) often benefit from resection of the seizure focus. Conventional MR imaging can be coupled with diffusion-tensor imaging (DTI)/tractography and functional MRI to aid in surgical planning and attempt to avoid areas with eloquent functions such as language, vision, or motor areas.
Key Teaching Points
◾varyTherebasedis aonwidethearray of supratentorial brain malformations. These timing of the insult during brain development ◾infections The most common etiologies are genetic mutations and in utero ◾brain MRI is the best imaging technique to evaluate for supratentorial malformations, preferably using volumetric 3D sequences ◾butMany malformations are detected on prenatal ultrasound studies, others may be detected after birth when imaging is performed for seizures, atypical facies, abnormal head circumference, hypo/hypertonia, or developmental delay Brain malformations may be incidental findings when the brain is imaged for other reasons, such as head trauma. For example, asymptomatic callosal lipomas Pay close attention to the midline structures. If abnormal, look for other malformations as they are often associated
◾ ◾
Congenital and Developmental Infratentorial Brain Anomalies Congenital and developmental infratentorial lesions result from alteration in normal development of cerebellum and brainstem. Malformation, by definition, implies congenital anomaly of a single organ or body part caused
by disruption of primary developmental program that is nonprogressive. MR imaging using both conventional and advanced techniques plays a pivotal role in delineating normal anatomy of posterior fossa and identifying and classifying malformations. On the basis of neuroimaging pattern, malformations can be classified into: 1. Predominantly cerebellar malformations 2. Cerebellar and brainstem malformations 3. Predominantly brainstem malformations
Predominantly Cerebellar Malformations Dandy–Walker Malformation This results from more or less complete membranous obstruction to the foramina of Magendie and Luschka, which causes cystic dilatation of the fourth ventricle. There is hypoplasia or agenesis of cerebellar vermis, particularly the inferior portion, although superior portion may also be affected [16–18]. There is upward and counterclockwise rotation of hypoplastic vermis. The grossly dilated fourth ventricle extends upward to and above the tentorium and also backward to the occipital bone, which is thinned and bulging, expanding the posterior fossa. Cerebellar hemispheres are hypoplastic and displaced anterolaterally (Fig. 80.28). Most children present in infancy with symptoms of increased intracranial pressure consequent to hydrocephalus.
FIGURE 80.28 Dandy–Walker malformation. (A) CT scan and (B) T1 axial MR image shows large posterior fossa cyst in open communication with the fourth ventricle. (C) and (D) T1 Sagittal midline and a lateral image showing absent vermis and hypoplastic upturned hemispheres with elevation of torcular herophili (arrow) and large posterior fossa.
CT or MRI shows the anatomical features described and permits an immediate diagnosis. In the neonate or small infant, the diagnosis may be made by ultrasound. Differentials include other cystic posterior fossa
malformations such as giant cisterna magna, posterior fossa arachnoid cyst, and Blake pouch cyst. Mega Cisterna Magna In this condition the cisterna magna appears abnormally large or dilated (>10 mm on midsagittal images) and the posterior fossa may be enlarged [18,19]. The fourth ventricle, cerebellum, and vermis, however, are seen to be normal. This is usually an incidental finding without any clinical relevance. Posterior Fossa Arachnoid Cyst Arachnoid cysts are usually unilocular, but septated cysts may occur. They may be retrocerebellar (located posterior or posteroinferior to vermis), supravermian (superior to vermis), anterior or lateral to hemispheres or brainstem. They can present in adults but more usually they present in infants or children, particularly if large enough to produce a mass effect or obstructive hydrocephalus. On MRI, these are well-circumscribed extraaxial fluid collections following CSF on all pulse sequences. Lack of communication with ventricular system and subarachnoid spaces is characteristic [20,21]. Blake Pouch Cyst This results from failure of regression of the Blake pouch due to nonfenestration of foramen of Magendie. Patients may be asymptomatic or show symptoms of raised intracranial pressure or macrocephaly. MRI reveals a retrocerebellar or infravermian cyst that represents a diverticulum of the fourth ventricle. It does not communicate with subarachnoid space and almost always results in tetraventricular hydrocephalus. Choroid plexus may curve under the vermis into the superior portion of the cyst, a characteristic feature, that can be seen best on sagittal T1 postcontrast MR images. Of note, the vermis is normally developed. Rhombencephalosynapsis This is believed to result from disruption in dorsoventral patterning in the rostral dorsal midline region of Rhombomere 1. The condition is sporadic with low recurrence risk. Clinical presentation is with truncal and/or limb ataxia, stereotypical head movements, and delayed motor development. Key findings on neuroimaging are agenesis/hypogenesis of vermis with continuous cerebellar hemispheres across midline. MRI shows horizontal folial pattern in the coronal images, whereas midline fusion of dentate nuclei and often superior cerebellar peduncles can be seen on axial and sagittal images (Fig. 80.29). The condition may be associated with hydrocephalus secondary to aqueductal stenosis and forebrain anomalies, such as absent
septum pellucidum, dysgenetic corpus callosum, the absence of olfactory bulbs, and rarely holoprosencephaly.
FIGURE 80.29 Rhombencephalosynapsis. (A) T1 axial and (B) T2 axial images showing continuation of cerebellar hemispheres across midline with the absence of vermis. (C) Coronal T2W image depicting the same finding.
Cerebellar and Brainstem Malformations Pontocerebellar Hypoplasia This is a diverse group of entities with characteristic findings of reduction in volume of both cerebellum and pons. There may be hypoplasia with superimposed atrophy of the cerebellum and significant reduction of pontine prominence (best appreciated on sagittal MR Images). Cerebellar cavitation (cysts) may be seen. Cerebellar hemispheric and vermian volume loss may be symmetric, but predominant hemispheric involvement with preserved vermis may result in a “dragonfly appearance.” Ten subtypes with different phenotypes and pathogenesis have been described. Multiple genes including TSEN54, CASK (X-linked recessive inheritance), RELN, and VLDLR have been implicated in pathogenesis. Clinical presentation includes ataxia, nystagmus, microcephaly, cognitive impairment, seizures, deafness, retinopathy, and sometimes cataracts. Alpha-Dystroglycanopathies These refer to a group of congenital muscular dystrophies resulting from defective O-glycosylation, or rarely N-glycosylation of alpha-dystroglycan. Clinically, there is variable involvement of muscle (weakness, increased creatine kinase values), eye (microphthalmia, optic nerve hypoplasia, coloboma), and brain (seizures, intellectual impairment). Characteristic
neuroimaging findings include pontocerebellar hypoplasia, cysts involving cerebellum, dysplasia of midbrain tectum, ventral cleft involving pons, and kinking of pontomesencephalic junction. Tubulinopathies These are a group of malformations resulting from mutations in genes encoding for microtubule formation and function. Posterior fossa involvement is in the form of pontocerebellar hypoplasia, dysplasia of the cerebellum, and midbrain tectum, with asymmetry of midbrain and pons. Cerebellar involvement is seen as diagonal folia seen on axial images, crossing the midline. Associated characteristic supratentorial imaging findings include dysmorphic basal ganglia with the absence of anterior limb of internal capsule, lissencephaly, and PMG. Clinical manifestations are wide including intellectual disability, cerebral palsy, microcephaly, and intractable seizures. Joubert Syndrome This is a malformation with classical imaging findings described as “molartooth” configuration of superior cerebellar peduncles that are thick, elongated, and horizontally oriented along with a deep interpeduncular fossa. It is consistently associated with hypoplasia and dysplasia of vermis. The fourth ventricle appears large and triangular with the apex pointing backward at its midportion, and large and “bat’s wing” at a higher level (Fig. 80.30). Up to one-third of affected individuals may have supratentorial involvement in the form of callosal dysgenesis, hippocampal malrotation, cephaloceles, and ventriculomegaly. DTI and tractography may reveal the absence of decussation of superior cerebellar peduncle and corticospinal tracts. This condition is characterized clinically by ataxia, mental retardation, episodic hyperpnoea, and abnormal eye movements, and is due to total aplasia of the cerebellar vermis.
FIGURE 80.30 Joubert syndrome. (A) Axial T2W and axial T1W (B) images at the level of superior cerebellar peduncles demonstrating “molar-tooth” appearance.
Predominant Brainstem Malformations Pontine Tegmental Cap Dysplasia This is a rare sporadic brainstem malformation with pathognomic conventional neuroimaging findings including flattening of ventral pons, “cap”-like vaulted pontine tegmentum, partial absent middle and inferior cerebellar peduncles, hypoplastic vermis, and molar-tooth configuration of pontomesencephalic junction along with the absence of inferior olivary prominence. Associations include duplicated internal auditory canals and hypoplastic cranial nerves. Clinical presentation is with hearing loss, facial paralysis, difficulty in swallowing, anesthesia in trigeminal nerve distribution and ataxia. Intellectual prognosis appears to correlate with imaging findings: mildly affected individuals have a rounded “cap”-like configuration of tectum while more severe developmental disability is seen with more angular “beak”-like brainstem protrusion. Horizontal Gaze Palsy With Progressive Scoliosis This is a rare disorder caused by mutation in ROBO3 gene with autosomal recessive inheritance. Pathognomic neuroimaging findings include butterflyshaped medulla (due to the absence of gracile and cuneate nuclei prominence), and inferior olivary prominence. There is associated hypoplasia of pons with a dorsal midline cleft. Brainstem Disconnection
Rostral and caudal brainstem segments in this abnormality are connected only by a thin cord of the tissue. Characteristic imaging findings are appreciated on sagittal images and supratentorial abnormalities are unusual. Clinical presentation is absent or weak suck and swallow at birth, central respiratory insufficiency, poor visual fixation, and hypo/hypertonia.
Chiari Malformations These were originally described by Chiari in 1891 and 1896, and were graded types 1–4 according to degree of deformity. Chiari Type 1: This is the least obvious clinically and may not be diagnosed until adult life. It consists of tonsillar herniation through the foramen magnum with or without varying degrees of elongation of the medulla oblongata and fourth ventricle (Fig. 80.31). There is associated crowding at the level of foramen magnum with paucity of CSF flow craniocaudally across the cervicomedullary junction, that can be assessed using cine flow MRI technique. Syringohydromyelia is associated with the condition in up to 70% of cases. The patients do not present clinically until adult life when the symptoms and signs of syringohydromyelia develop; less typically, symptoms suggesting involvement of the lower cranial or cervical nerves are seen, and very rarely patients present with hydrocephalus. Bony anomalies of the craniovertebral junction can be present, particularly assimilation of the atlas. Basilar invagination and dysplasias of the vault are other rare associations.
FIGURE 80.31 Chiari 1 malformation. (A) Sagittal T2 image showing tonsillar herniation below the foramen magnum. Axial T1W image (B) shows crowding at the level of foramen magnum.
The diagnosis is best confirmed by MRI, which also shows the syrinx. Caution is required when interpreting sagittal images of the craniovertebral junction as partial volume effects result in visualization of 3–4 mm of cerebellar tissue apparently lying below the foramen magnum in 15–20% of normal individuals [21]. Coronal imaging is helpful in equivocal cases. Differential consideration is tonsillar descent in cases of intracranial hypotension. Chiari Type 2: This presents in neonates or infants, virtually always with a thoracolumbar myelomeningocele. The associated brain deformities consist of caudal herniation of the medulla and vermis with a caudally displaced and elongated fourth ventricle, a small posterior fossa and low-lying torcula. A backward kink may be seen at the caudally displaced junction of cervical cord and medulla. Hydrocephalus may be due to associated aqueduct stenosis or to occlusion of the ambient cisterns. Associated malformations include hypoplasia or the absence of the falx and tentorium with interdigitation of the cerebral hemispheres; absence of the corpus callosum with forward pointing of the frontal horns; beaked tectum, medullar spur and kink, enlargement of the cerebellar vermis, and forward protrusion of the cerebellar hemispheres as pointed projections around the brainstem; gyral malformations, and other lesions. Many of these brain deformities can be identified by CT or MRI, and some by neonatal ultrasound. Skull x-ray may show a lacunar skull and forward bowing of the petrous bones and clivus. Chiari Types 3 and 4 have major deformities with cerebellar hypoplasia and downward displacement of the brainstem and a high cervical or occipital encephalocele.
Imaging Techniques and Analysis MR imaging on midline sag T1WI and T2WI is ideal for the evaluation of posterior fossa size, shape and size of vermis, morphology and size of the fourth ventricle and brainstem. The craniocaudal length of pons is roughly twice that of midbrain (third ventricle to ventral midbrain-pons junction) and medulla (obex to ventral pontomedullary junction). Parasagittal images provide good visualization of hemispheres and peduncles, whereas axial images are best for evaluating vermian morphology and size, dentate nuclei and superior and middle cerebellar peduncles. Coronal images show radiating folia and also help in the assessment of size, symmetry and contour of cerebellar peduncles. Advanced imaging techniques such as DTI may provide detailed information on white matter tracts noninvasively in children with posterior fossa malformations. This has allowed clinicians to delve into depths of pathogenesis of certain posterior fossa malformations such as Joubert syndrome and pontine tegmental cap dysplasia.
Key Teaching Points
◾classification The diagnosis of posterior fossa malformations as well as is based on neuroimaging findings ◾multiplanar MRI is the best technique for evaluation of posterior fossa and evaluation on conventional sequences may help identify malformations ◾available Well-defined criteria for the diagnosis and classification are for various malformations and should be used ◾additional Advanced techniques such as DTI and tractography may provide information in understanding pathogenesis of cerebellar and brainstem malformations
Pediatric Brain Tumors Introduction Primary brain tumors constitute about one-third of all neoplasms in the pediatric population [22]. Neoplasms of the CNS are the most common type of solid tumors in children in the age group 0–19 years. The overall incidence of primary CNS tumors in the United States is approximately 6 per 100,000 across all pediatric age groups. The age groups 0–4 and 15–19 years show maximum incidence of primary CNS tumors within the pediatric population [2].
Approach to an Intracranial Mass The fundamental imaging approach to a mass in the central neural axis is essentially similar in both adults and pediatric patients. Spatial localization of any intracranial mass and its relation to surrounding anatomical structures is the first key step in further characterization of a mass in the intracranial compartment. The determination of whether the mass is in intra-axial or extra-axial (extraparenchymal) location should be the first objective of any radiologist in such a scenario. The definitive imaging findings that point to extra-axial location of a mass are elucidated in Table 80.2. Table 80.2 High Yield Imaging Signs That Aid in Localization of an Extra-
axial Mass
◾ Cerebrospinal fluid strip between the mass and the brain parenchyma, may be seen as dark cleft on the fluid-attenuated inversion recovery (FLAIR) imaging. ◾ Vascular structures interposed between the brain and mass, identified as flow voids on spin echo sequences. ◾ The presence of cortical mantle between the mass and underlying brain parenchyma especially white matter.
Adapted from: SW Atlas, ed. Magnetic Resonance Imaging of the Brain and Spine, fourth ed., Vol. 1 and 2, Lippincott Williams & Wilkins, 2008.
The incidence of extra-axial lesions or masses in pediatric population is much lower than adults. The localization of a mass or lesion to extra-axial compartment in a pediatric patient considerably narrows the differential diagnosis. The characterization of an intraparenchymal mass in a child can be aided by precise anatomical location of the mass and age of the patient in combination with imaging appearance of the mass. The commonest site of an intra-axial primary CNS tumor in the pediatric age group is cerebellum. The commonest extra-axial location is pituitary region [23].
World Health Organization 2016 Classification of Tumors of Central Nervous System The concept of tumor pathogenesis driven by genetic makeup of the neoplastic cell has been well known in the literature. For the first time since the introduction of World Health Organization (WHO) CNS tumor classification system, this concept was incorporated into the 2016 WHO classification of CNS tumors. The classification thus recommended use of molecular characteristics, in addition to histologic features of tumor tissue, to define CNS tumor entities. The aim is to create a classification system with homogeneous and sharply defined groups or subgroups. The classification introduced the term “integrated” diagnosis for CNS tumors based on a combination of both phenotypic and genotypic information. The classification also recommended deletion of certain nomenclature including primitive neuroectodermal tumor, gliomatosis cerebri, protoplasmic and fibrillary astrocytoma, and cellular ependymoma. Importantly, the classification does not recommend exclusive use of genetic information for definition of CNS tumor entities [24]. Expectedly, the 2016 classification led to the creation of loosely defined category of tumors, with designation not
otherwise specified, that did not meet the narrow criteria prescribed in the new classification [24]. Consortium to inform molecular and practical approaches to CNS tumor taxonomy (cIMPACT-NOW or cIMPACT) updates: After the release of WHO 2016 CNS tumor classification, a group of expert neuropathologists and oncologists set up a formal working group, outside the realm of WHO. The aim of the group was to recommend updates and changes to CNS tumor classification in the time interval between WHO classification updates [25]. The cIMPACT updates that specifically apply to CNS tumors in the pediatric population are summarized in Table 80.3. Table 80.3 Summary of cIMPACT Updates as Applicable to Pediatric CNS Tumors U p d at e
Proposed Update
1
Use of the term NEC (not elsewhere classified) when the available pathologic information (molecular or histologic) is NOT enough to assign a specific WHO diagnosis. Not otherwise specified (NOS) term should be used exclusively when required pathologic information to assign a specific WHO diagnosis is NOT available. For example, embryonal tumor with multilayered rosettes that shows the absence of C19MC alteration on testing should be designated as ETMR, NEC [25]
2
The diagnostic entity diffuse midline glioma, H3 K27M-mutant diagnosis must be exclusively used for a CNS tumor that involves midline structures, is diffuse or infiltrating in appearance, a glioma, and positive for H3 K27M-mutation. Even though the H3 K27Mmutation is not exclusive to diffuse midline glioma, H3 K27M-mutant CNS tumor; however, this nomenclature should NOT be used for other pediatric tumors (pilocytic astrocytomas, diffuse astrocytomas, and gangliogliomas) that may sometimes bear H3 K27M-mutation such as [26]
U p d at e
Proposed Update
4
Delineation of molecular alterations that can be used for further classification of IDH-wild type H3-wild type WHO grade II diffuse pediatric gliomas, with emphasis on integrated diagnosis. This would involve analysis of tumors for alterations in the BRAFV600E, MYB, or MYBL1, FGFR1 genes and/or genes resulting in activation of MAPK pathway [27]
5
Introduction of newly recognized CNS tumor diagnostic entities in pediatric population including CNS neuroblastoma, FOXR2activated; Diffuse glioma, H3.3 G34-mutant, polymorphous lowgrade neuroepithelial tumor of the young. Introduction of key principles related to CNS tumor classification, nomenclature, and grading, for example proposed classification for pediatric-type glial/glioneuronal tumors [28]
6
Molecular or genetic criteria used for the classification of supratentorial, posterior fossa, and spinal cord ependymomas and their clinical implications. For example, MYCN amplified spinal cord ependymomas is a distinctive subgroup with a poor outcome [29]
Gliomas Gliomas represent the most common type of pediatric brain tumors. Based on clinicopathologic characteristics and long-term prognosis, these are classified into two broad categories—low-grade glioma and high-grade glioma [30]. High-grade gliomas in children show a higher rate and varied spectrum of mutations compared with low-grade gliomas [9]. Low-grade gliomas represent about 30% of all pediatric CNS tumors [30]. Common pathological subtypes of this group are detailed in Table 80.4. Table 80.4 Common Pathologic Subtypes of Pediatric Low-Grade Gliomas
◾ Pilocytic astrocytoma ◾ Ganglioglioma ◾
◾ Pleomorphic xanthoastrocytoma ◾ Dysembryoplastic neuroepithelial tumor ◾ Diffuse astrocytoma (angiocentric type) The most common molecular defect in pediatric low-grade gliomas is BRAF proto-oncogene mutation, either a BRAF V600E point mutation or BRAF fusion (KIAA1549:BRAF fusion). The common end result of these mutations is dysregulation of MAPK pathway [30]. The major differences between pediatric and adult low-grade gliomas are detailed in Table 80.5. Table 80.5 Clinicopathologic Differences Between Pediatric and Adult Low-Grade Gliomas Pediatric
Adult
Lower frequency of mutations
Higher mutation burden
Mutation profile is limited
Wide spectrum of mutation such as frequent IDH1 mutation and 1p/19q codeletion
Risk of malignant transformation is low
Risk of transformation to high-grade glioma higher
Pilocytic astrocytoma is the most common type of low-grade glioma reported in children. The most frequent site of involvement is the cerebellum and hypothalamus-chiasm followed by supratentorial structures. The typical appearance is a circumscribed complex solid cystic mass with enhancing solid component (Fig. 80.32). Usually, pilocytic astrocytoma in the hypothalamus-chiasm region present as predominantly solid, less sharply defined infiltrative mass with minimal to no contrast enhancement. Infrequently, pilocytic astrocytoma can have imaging features which may be mistaken for aggressive brain tumors (Fig. 80.33). These are detailed in Table 80.6 [31,32].
FIGURE 80.32 A 11-year-old male complained of left side weakness. Axial (A) and coronal T2 magnetic resonance (MR) image (B) demonstrated a large circumscribed solid cystic mass centered in paramedian frontal lobe. Coronal contrast-enhanced MR image (C) showed intense enhancement of solid component with internal areas of necrosis. This was later confirmed as pilocytic astrocytoma on histopathology.
FIGURE 80.33 A 9-year-old female presented with severe headache and vomiting. Nonenhanced axial computed tomography image (A) showed focus of hemorrhage in right cerebellar hemisphere at the level of inferior cerebellar peduncle. Axial contrast-enhanced MR image (B) demonstrated a mass-like lesion with suspicious peripheral nodular enhancement. Follow-up axial contrast-enhanced MR image at 9 months (C) clearly revealed a mass lesion with significant contrast enhancement. Histopathological examination confirmed pilocytic astrocytoma.
FIGURE 80.34 A 6-year-old male presented with severe headache, emesis, and altered mental status. Coronal T2 MR image (A) showed an irregular T2 hyperintense mass centered in suprasellar cistern and hypothalamic-chiasmatic region. Note the low signal along tumor periphery representing blood products (white arrow). Contrast-enhanced coronal and sagittal MR images demonstrated heterogeneous enhancement of the mass (B and C). Histopathologically proved case of pilomyxoid astrocytoma.
Table 80.6 Atypical Imaging Features of Pilocytic Astrocytoma [33,34]
◾ Complex solid cystic mass, with significant internal necrosis within the solid component. ◾ Predominantly solid appearing mass with minimal or no cystic areas. ◾ The presence of calcification and hemorrhage (alternative entities should be considered). ◾ In some series up to half of PAs may present as infiltrative solid masses on imaging making distinction from high-grade gliomas challenging.
Diffusion-weighted imaging is critical in differentiating low-grade gliomas from other aggressive neoplasms. The ADC is uniformly high in all pilocytic astrocytoma correlating with large volume of extracellular matrix [31,32,35]. MR spectroscopy and perfusion MRI should be utilized cautiously in pilocytic astrocytoma. The data for pilocytic astrocytoma from these advanced imaging tools must be correlated with conventional imaging features [31,32]. The differential diagnostic entities for pilocytic astrocytoma are elucidated in Table 80.7. Table 80.7
2. Ganglioglioma or pleomorphic xanthoastrocytoma 3. Hemangioblastoma
4. Medulloblastoma, ATRT, or ependymoma
◾ Chiasmatic hypothalamic region ◾ Solid and more infiltrative appearance ◾ Higher incidence of intratumoral hemorrhage, local recurrence, and CSF dissemination ◾ Relative homogenous contrast enhancement ◾ Suspected supratentorial pilocytic astrocytoma with intratumoral calcification or hemorrhage ◾ Absence of meningeal involvement ◾ Older child or teenager with cystic cerebellar mass ◾ Prominent flow voids ◾ Significantly high rCBV values on perfusion MRI ◾ Suspected infratentorial pilocytic astrocytoma with intratumoral calcification or hemorrhage ◾ Age of child
Focal well-circumscribed gliomas based in the brainstem gliomas are usually low-grade gliomas. These are typically centered in the dorsal or dorsolateral brainstem with relative sparing of ventral such as tectal glioma (Fig. 80.35), posterior cervicomedullary pilocytic astrocytoma. They can show unusual exophytic growth pattern [32,36].
FIGURE 80.35 A 2-year-old male with increasing head circumference. Axial T2 MR image (A) showed partly exophytic mild T2 hyperintense expansile mass involving dorsal mid brain (white arrow). The mass protrudes into the quadrigeminal cistern. On contrast-enhanced sagittal MR image mass showed minimal to absent contrast enhancement (white arrow in B). Histopathologically proved low-grade glioma.
Ho et al. analyzed TSITC data from DSC perfusion in pediatric brain tumors reporting high positive predictive value of T1 dominant leakage pattern (continuing above baseline or high percent signal recovery pattern) for low-grade gliomas specifically pilocytic astrocytoma [22]. The oligodendroglioma entity in children is unique since these frequently show lack of IDH mutation and 1p/19q codeletion. This is unlike adults where IDH mutation and 1p/19q deletion form the basis for the diagnosis of oligodendroglioma [38]. Recent literature has shown that the frequency of surveillance imaging and overall duration of surveillance in cerebellar grade 1 astrocytomas can be reduced if complete resection can be achieved. Importantly the data for noncerebellar tumors were considered inadequate and authors suggested continuing with practice of 6 monthly follow-up imaging in this group [39]. When gross total resection of a pilocytic astrocytoma is not achieved, surveillance imaging has been recommended at defined intervals such as 6, 12, or 24 months. On follow-up imaging PAs may show spontaneous fluctuations in contrast enhancement in the absence of any recent therapy. In the absence of corresponding change in tumor dimensions, these random findings are not favored to represent tumor progression or regression [32]. Malignant transformation of a pilocytic astrocytoma is a very rare event with few reported cases [34]. Dissemination of PA to other CNS sites is extremely rare with less than 100 reported cases in English language literature (Fig. 80.36) [39,35]. None of the documented patients demonstrated malignant
transformation of the primary site. It is not clear if the dissemination leads to increased mortality. The most common associated risk factor reported in these patients is subtotal resection with residual tumor in the operative bed and location of primary tumor site close to CSF [39].
FIGURE 80.36 A 7-year-old male presented with seizures and vomiting. Axial T2 MR image showed a large heterogenous mass based in temporal region (A) with intense enhancement of solid component on axial contrast-enhanced MR image (B). Follow-up imaging 6 years later, contrast-enhanced axial MR image of brain and contrast-enhanced sagittal lumbar spine MR image (C and D) showed evidence of leptomeningeal metastatic dissemination (white arrows). The primary intracranial mass was a proved pilocytic astrocytoma on histopathology.
High-grade gliomas constitute about 15% of pediatric CNS tumors. The most common site of involvement is brainstem. This is in contradistinction to adults where most high-grade gliomas are seen in the supratentorial space [30,37]. WHO 2016 classification introduced a new entity diffuse midline glioma, a grade IV tumor (Fig. 80.37). The diagnosis is based on K27M mutation in H3 histone gene, irrespective of histopathology. The classification includes diffuse intrinsic pontine glioma as a subtype of diffuse midline gliomas, H3K27M mutant. About 60–80% of DIPG show this mutation [37]. Somatic mutations in histone gene complex are highly specific genetic alterations reported in pediatric high-grade gliomas. The most common types are K27M and G34R/V mutations in histone 3 variants with downstream consequence of dysregulation of glial differentiation [30,40].
FIGURE 80.37 A 14-year old with headache, paresthesia, and vomiting. Coronal T1 MR image (A) showed a large heterogenous mass filling the left lateral ventricle. Axial T2 MR image (B) delineated the exophytic nature of mass originating from paramedian basal ganglia structures. Note the T2 hypointense focus representing blood product or calcification. Axial contrast-enhanced MR image (C) showed very heterogenous enhancement of the mass with numerous internal areas of necrosis. Histopathologic examination and molecular analysis confirmed high-grade glioma with H3K27M mutation.
Diffuse intrinsic pontine glioma is based in ventral pons with expansion and infiltration into adjacent structures like midbrain, medulla, brachium pontis. Contrast enhancement is minimal to none in most cases. Exophytic component in anterolateral aspect may be associated with basilar artery encasement. No significant differences in imaging feature have been reported between H3K27M mutant and wild type diffuse midline gliomas. Atypical imaging findings of heterogenous contrast enhancement with areas of necrosis and CSF spread to distant sites have been reported [40]. Noncontiguous involvement of supratentorial structures has also been reported. This may mimic gliomatosis on imaging [37]. Diffuse intrinsic pontine glioma is currently an imaging diagnosis with rare use of biopsy for histopathological proof except under clinical trial protocols [41]. Imaging findings may be used for guiding prognosis as mentioned in Table 80.8. Table 80.8 Imaging Features With Prognostic Significance in Diffuse Intrinsic Pontine Glioma [42] Increased Progression-Free Survival and Overall Survival
Reduced Progression-Free Survival and Overall Survival
Increased Progression-Free Survival and Overall Survival
Reduced Progression-Free Survival and Overall Survival
Reduction in tumor volume by at least 25% compared with preradiotherapy imaging
The presence of enhancement within mass at baseline Progressive increase in enhancement on follow-up imaging
Embryonal Tumors Medulloblastoma Medulloblastoma is the most common primary CNS malignancy affecting pediatric population. The age group most affected is between 3 and 7 years of age. Medulloblastoma accounts for about 65% of all pediatric embryonal tumors [30,43,44]. In young children with medulloblastoma presence of falcine/tentorial calcification at an early age (specifically male
Age
Children >3 years
Spatial location
Dorsolateral brainstem, level of middle cerebellar peduncle or fourth ventricle or inferior [46]
Histopathology
Classic [37]
Cerebrospinal fluid dissemination
Extremely rare
Prognosis
Excellent [30,40]. The presence of metastatic disease does not change the favorable outcome [30]
Sonic hedgehog medulloblastoma is associated with inactivating gene mutations in PTCHD1 [patched-1] gene and SUFU gene and/or amplification of gene MYCN and GLI gene. These are typically centered in the cerebellar cortex (Fig. 80.39). The tumors involving flocculus and
nodulus may present as a mass in the cerebellopontine angle and fourth ventricle, respectively. Uncommonly this subtype may also present as multifocal cerebellar cortical nodules or masses (Fig. 80.40). The involvement of the midline structures such as vermis is highly uncommon, except in the first year of life [37,46,48]. Intense contrast enhancement is a characteristic imaging feature of vast majority of sonic hedgehog medulloblastomas [48,49]. These tumors may be associated with nevoid basal cell carcinoma syndrome [30]. The clinical and pathological characteristics are detailed in Table 80.12.
FIGURE 80.39 A 17-year-old female with vomiting and headache. Axial T1 (A) and T2 MR images (B) showed a circumscribed heterogenous mass based in the periphery of cerebellar hemisphere or cerebellar cortex. Note buckling of white matter and collapsed fourth ventricle (white arrow) displaced away from the mass (A and B). Sagittal and coronal contrast-enhanced MR images showed intense enhancement within the mass lesion (C and D). Note the additional mildly enhancing cortical nodular mass on coronal contrast-enhanced MR image (white arrow in D). Histopathologic examination confirmed SHH type medulloblastoma.
FIGURE 80.40 A 12-year-old male presented with headache and dizziness for 2 months. Sagittal T1 MR image (A) showed a circumscribed mass centered in the fourth ventricle extending to the foramen magnum. Axial T2 MR image (B) demonstrated the midline location of the mass. ADC showed mildly reduced diffusivity values within the mass (C). Axial contrast-enhanced MR image (D) showed minimal to mild patchy enhancement of the mass (white arrow). Histopathologic examination confirmed non-WNT non-SHH group 4 medulloblastoma.
Table 80.12 Clinicopathologic Characteristics of Sonic Hedgehog Type Medulloblastoma Gender
Male = Female
Age
Children > midline-vermis (overall) Desmoplastic/nodular variant—cortex >> vermis [48] Medulloblastoma with extensive nodularity—vermis >> hemisphere
Histopatholo gy
TP53 wild type—children > Female
Gender
Male >> Female
Age
All age groups
Spatial location
Midline/fourth ventricle including vermis [50]
Histopathology
Classic; large cell/anaplastic pattern uncommon [49]
Cerebrospinal fluid dissemination
Frequent
Prognosis
Pediatric—intermediateAdult—worse
Uncommon imaging features of medulloblastoma include extension into the cerebellopontine angle cistern and porous acusticus, mimicking a vestibular schwannoma [44]. The presence of multiple intratumoral flow voids in adolescent or young adult patient should raise concern for other differential consideration such as a hemangioblastoma [44]. Rarely imaging features of medulloblastoma may mimic Lhermitte–Duclos disease (dysplastic cerebellar gangliocytoma). The presence of abnormally high choline levels on MR spectroscopy would favor the diagnosis of high-grade tumors such as embryonal tumors in these situations [52]. Imaging findings observed in histologically defined medulloblastoma variants are elucidated in Table 80.15. Table 80.15 Imaging Findings of Histologically Defined Medulloblastoma Subtypes Classic
High ADC values
Large cell/anaplastic
Ring enhancement Leptomeningeal enhancement Intratumoral hemorrhage Low ADC values
Medulloblastoma with extensive nodularity (previously cerebellar neuroblastoma)
Enhancing multinodular mass with racemose appearance (pathologic correlation to reticulinrich nodular areas with neuronal differentiation)
Desmoplastic/nodular
Focal abnormal leptomeningeal enhancement overlying mass (involvement of overlying dura or meninges)
The prevalence of leptomeningeal metastatic disease is about 20–35% and 30–50% of all medulloblastoma patients at the initial diagnosis and during follow-up surveillance, respectively [43,48,53]. Baseline imaging assessment for leptomeningeal metastatic disease is important before surgical resection, for optimal disease staging. If not feasible, postoperative assessment within 72 hours or more than 2 weeks after surgery is recommended to avoid false-positive imaging findings related to operative procedure[53]. The most common location of spinal metastases is along the posterior surface of spinal cord. Extraneural metastasis is rare in medulloblastoma, bone being the most common site followed by lymph nodes [44]. A significant proportion of patients may develop metastatic disease in the peritoneal cavity through ventriculoperitoneal shunt [44]. Recurrent medulloblastoma is most common within first 2 years after completion of treatment [44]. The imaging patterns of metastatic disease in non-WNT/nonSHH subtypes of medulloblastoma are detailed in Table 80.16. Table 80.16 Imaging Patterns of Metastatic Disease in Non-WNT/Non-SHH Medulloblastoma Subtypes Group 3
Group 4
Late metastatic disease common (distant sites in central nervous system without recurrence in treated primary site) [48] Local recurrence in a treated non-WNT/non-SHH medulloblastoma suspicious for radiation-induced tumor like high-grade glioma [30] Laminar metastatic pattern
Nodular metastatic disease
Matching pattern (both subarachnoid space and ependymal metastases show diffusion restriction and contrast enhancement)
Metastases in the anterior third ventricle or suprasellar region Mismatching pattern (ependymal metastases like primary tumor [restriction, no enhancement], in contrast to subarachnoid space metastatic disease [restriction and enhancement])
Posterior fossa syndrome is a clinical condition reported in up to one-third of patients after posterior fossa tumor surgery such as resection of medulloblastoma. Hypertrophic olivary degeneration is a MR imaging marker of posterior fossa syndrome, manifested as abnormal signal in inferior olivary nuclei (less commonly dentate nucleus and superior
cerebellar peduncle) especially on Proton density imaging. These patients typically present with cerebellar mutism after few days of surgery [54,55]. Susceptibility weighted imaging may reveal significant asymmetry at the level of midbrain with loss of expected T2 hypointensity within the red nucleus (compared with substantia nigra) [56]. Atypical Teratoid Rhabdoid Tumor Atypical teratoid rhabdoid tumor (ATRT) is a high-grade embryonal tumor commonly affecting children less than 4 years of age specifically within first year of life. The distinctive genetic alteration is loss of SMARCB1 (BAF47/hSNF5/INI1) tumor suppressor gene. An inherited germline deletion of the SMARCB1 tumor suppressor gene is associated with rhabdoid tumor predisposition syndrome (combination of ATRT and rhabdoid tumors outside CNS) [44,57]. A significant proportion of these tumors are based in the supratentorial space. The classical presentation is a markedly heterogenous intra-axial tumor in the posterior fossa in the infantile age showing combination of solid component, internal necrosis, calcification, and blood products (Fig. 80.41). Leptomeningeal metastatic disease is frequently observed as with other embryonal tumors [57]. The imaging findings specific for ATRT include presence of peripheral cysts, thick band-like wavy enhancement or involvement of the adjacent native dura, calvarium, or skull base by an intra-axial mass, however these may be seen only in a minority of patients [58]. Rare imaging presentation such as extra-axial location, cranial nerve origin, primary diffuse leptomeningeal disease have been reported [57].
FIGURE 80.41 A 14-month-old boy complained of vomiting and head tilt. Coronal T1 (A) and T2 MR images (B) showed a markedly heterogenous solid mass centered in the left cerebellar hemisphere. The mass appears to protrude into the fourth ventricle and through the foramen of Luschka. The T1 hyperintense and T2 hypointense areas in the mass represent blood products. The mass showed reduced ADC values (C). Axial contrast-enhanced MR image (D) showed near homogenous enhancement of the mass. The age of the patient favors the diagnosis of atypical teratoid rhabdoid tumor (ATRT). The differential diagnosis includes medulloblastoma. Histopathologic examination confirmed ATRT.
Embryonal Tumor With Multilayered Rosettes The diagnostic molecular defect in this tumor is amplification of a microRNA cluster at long arm of chromosome 19 (C19MC) and LIN28A overexpression. There is significant overlap of clinical and imaging features with other embryonal tumors, specifically AT/RT, such as predominantly affecting infants and children less than 4 years, heterogenous intra-axial hypercellular mass, and frequent metastatic spread along CSF. In contrast to other embryonal tumors, embryonal tumor with multilayered rosettes is usually well circumscribed with minimal to mild contrast enhancement (Fig. 80.42) [59]. Cerebral hemisphere is the most common site observed in majority of tumors (supratentorial > infratentorial > spinal) [37].
FIGURE 80.42 A 1-year-old-female patient presented with seizures. Coronal T2 MR image (A) demonstrated a large circumscribed homogenous hyperintense mass centered within the right frontotemporal lobe. The mass showed restricted diffusion (B and C) suggestive of hypercellularity and complete absence of enhancement on axial contrast-enhanced MR image (D). Given patient’s age and features including significant restricted diffusion and lack of contrast enhancement, findings suggestive of ETMR which was histopathologically confirmed.
FIGURE 80.43 A 3-year-old male complained of headache, difficulty walking, and right leg pain. Axial T2 MR image (A) showed a heterogenous mass centered in lateral recess or foramen of Luschka. Note the extension into the cerebellopontine angle cistern and contralateral brainstem displacement (white arrow). Sagittal T2 MR image (B) demonstrated the absence of obex involvement. Susceptibility weighted imaging (SWI) showed foci of hypointensity (C) representing calcifications. Coronal contrast-enhanced MR image (D) showed heterogeneously enhancing mass displacing the brainstem laterally (white arrow). Histopathologic examination confirmed ependymoma.
FIGURE 80.44 An 8-year-old male with headache. Coronal T2 MR image (A) showed a large complex cystic mass based in parietal lobe. The predominantly cystic mass showed a peripheral rim of solid component (white arrow). The solid component demonstrated along the periphery of mass showed reduced ADC values (B). Axial contrastenhanced MR image (C and D) showed intense enhancement of the solid portion of intra-axial mass. The intracranial mass was proved ependymoma on histopathology.
FIGURE 80.45 A 12-year-old male patient presented with headache. Axial (A) and coronal (B) T2 MR images demonstrated a focal predominantly hyperintense bubbly appearing mass lesion centered within the left temporal lobe. The mass showed facilitated diffusion on ADC (C). There is minimal to no enhancement of the mass on coronal contrast-enhanced MR image (D). Histopathologically proved case of ganglioglioma.
FIGURE 80.46 A 13-year-old male with seizures. Axial T1 (A) and coronal T2 (B) MR images demonstrated a circumscribed homogenous T1 hypointense and T2 hyperintense mass centered within the right frontal lobe cortex. The mass revealed the absence of enhancement on coronal contrast-enhanced MR image (C). Histopathologically proved case of dysembryoplastic neuroepithelial tumor.
FIGURE 80.47 An 8-month-old female with seizures. Axial T2 MR image (A) demonstrated a large solid cystic mass in right temporal region. Note significant surrounding edema. Coronal contrast-enhanced MR image (B) showed the nonenhancing cystic component and intensely enhancing solid component. Note that the solid component appears dural based on coronal and sagittal contrast-enhanced MR images (white arrows in B and C). The enhancing solid component with surrounding edema caused significant mass effect and contralateral displacement of cerebral and brainstem structures on coronal and axial contrast-enhanced MR images (B and D). Histopathologically proved case of desmoplastic infantile ganglioglioma.
Ependymal Tumors Ependymoma is an ependymal origin primary pediatric brain neoplasm typically reported in the age group of 1–5 years [37]. The majority (up to two-thirds) of ependymomas are based in the posterior fossa. The posterior fossa ependymomas typically present as an intraventricular mass. Calcification is a common feature of infratentorial ependymomas, in contrast to other posterior fossa tumors, seen in up to half of all such tumors.
Infrequently, intratumoral hemorrhagic residue may be observed. Baseline imaging of the craniospinal axis is critical to search for the presence of leptomeningeal metastatic disease, since there is a definite risk of spread through CSF [60]. The cIMPACT group does not recommend use of histologic subtyping for the purpose of pathologic classification of classic ependymomas since they are of no clinical benefit [29]. MR imaging evaluation of precise location and extent of posterior fossa ependymomas is used to classify these tumors into two groups. These are further detailed in Table 80.17. Table 80.17 Clinical and Imaging Features of Posterior Fossa Ependymomas [63] Lateral Type (Posterior Fossa Type A) (Fig. 80.43)
Midfloor Type (Posterior Fossa Type B)
Young children
Older children, adolescents
Based in foramen of Luschka/lateral recess
Mass in midline within the fourth ventricle
◾ absence of obex involvement ◾ lateral displacement of the brainstem (axial imaging plane)
◾ involvement of the obex ◾ anteroposterior brainstem
displacement (sagittal plane) Complete resection less feasible (extension into adjacent cisterns, encasement of neurovascular structures)
More amenable to complete surgical resection
Higher risk of residual tumor
Lower risk of residual tumor (better prognosis)
Supratentorial ependymomas represent about one-third of all intracranial ependymomas. These tumors are commonly extraventricular in location [63]. The WHO 2016 classification of supratentorial ependymomas is elucidated in Table 80.18 with associated clinical and imaging features. Table 80.18
WHO 2016 Classification of Supratentorial Ependymomas With Elucidation of Clinical and Imaging Features RELA Fusion Ependymomas [63] (Fig. 80.44)
YAP1-MAMLD1 Ependymomas [64]
Specific translocation between RELAand C11orf95-forming oncogenic fusion gene resulting in pathological activation of NFkB (nuclear factor k of B cells) signaling pathway (70%)
Fusion gene
Older children poorer outcomes [30]
Female patients less than 3 years of age
Predominantly cystic unilocular or multilocular lesion centered in the cerebral cortex with smooth peripheral enhancement
Large T2 isointense mass with prominent cystic component in an intra- or paraventricular location with heterogeneous contrast enhancement
Diffusion restriction demonstrated by reduced ADC values has been reported in the solid enhancing portion of supratentorial tumors
Multinodular appearance of the solid component, with often associated hemorrhage
Non-RELA/non-YAP1 ependymomas typically present as large predominantly solid tumors in midline, with internal necrotic areas [63]. Diffusion-weighted imaging is a useful tool in distinguishing the major posterior fossa tumor types. Multiple cut-off values of ADC-based metrics (mean ADC, minimum ADC, and ADC ratio) have been proposed for each major tumor type (including pilocytic astrocytomas, ependymomas, and embryonal tumors) [43]. The role of diffusion imaging in differentiating pilocytic astrocytoma from embryonal tumors (including medulloblastoma) has been evident. However, there is significant overlap in ADC values of ependymomas with the other tumor types, to the extent that literature suggests that use of diffusion imaging may not have significant impact on accurately diagnosing ependymomas irrespective of level of reader experience. Therefore DWI has limited utility in accurately differentiating ependymomas from other common posterior fossa tumors [65–67].
Neuronal and Mixed Neuronal-Glial Tumors Neuronal and mixed neuronal-glial tumors are rare tumors of the CNS composed of cell lineages that have in common cells of neuronal and
sometimes of glial differentiation. The WHO 2016 classification of this heterogenous tumor group is detailed in Table 80.19. Gangliogliomas are the most common tumor subtype in this group [68,69]. Table 80.19 2016 WHO CNS Tumor Classification; Neuronal and Mixed Neuronal-Glial Tumors Ganglioglioma and gangliocytoma Desmoplastic infantile ganglioglioma/astrocytoma Dysembryoplastic neuroepithelial tumor Central and extraventricular neurocytoma Papillary glioneuronal tumor Rosette-forming glioneuronal tumor Diffuse leptomeningeal glioneuronal tumor Dysplastic cerebellar gangliocytoma (Lhermitte–Duclos disease) Anaplastic ganglioglioma
*
Cerebellar liponeurocytoma
*
Paraganglioma
* *
Tumors exclusively seen in adult age group.
Ganglioglioma and gangliocytoma tumors in temporal lobe are particularly epileptogenic, long-standing seizures being the most common clinical presentation. Anaplastic ganglioglioma is a distinct pathological entity characterized by malignant degeneration of the glial component, corresponding to grade III of WHO classification [70]. Dedifferentiation of a benign appearing ganglioglioma into a more aggressive high-grade glioma is very rare but has been well documented [71]. Clinical and imaging features of different subtypes of glioneuronal tumors are summarized in Table 80.20. Table 80.20 Clinical and Imaging Characteristics of Neuronal and Mixed NeuronalGlial Tumors
Tumor Type
Clinicopath ologic Features
Imaging Features
Gangliogliom as (Fig. 80.45) and gangliocytoma s
Children and young adults Grade I BRAF V600E mutation is common
Supratentorial, temporal lobe commonest site Complex solid cystic mass Calcifications very common. Variable enhancement Hemorrhage rare Smooth scalloping of inner table of skull Associated FCD
Dysembryopla stic neuroepithelia l tumor (Fig. 80.46)
Commonly associated with epilepsy Grade I FGFR1 and BRAF V600E
Cortical based cystic or a multicystic lesion Calcification rare Lack of peritumoral edema and mass effect Stable or very slow growing
Desmoplastic infantile astrocytoma and desmoplastic infantile ganglioglioma (Fig. 80.47)
First year of life Grade I
Cerebral cortex and leptomeninges Frequently dural attachment with desmoplastic reaction (persistent enhancement on delayed images)
Tumor Type
Clinicopath ologic Features
Imaging Features
Central neurocytoma [72]
Young adult Grade II
Ventricular system close to midline, commonest site lateral ventricle Broad-based contact of mass with septum pellucidum or superior wall of lateral ventricle absence of parenchymal invasion Characteristic peripheral cystic areas, frequently associated with wavy appearance of lateral ventricle walls Fluid–fluid levels on T2 images Minimal to mild enhancement except few foci of intense enhancement
Extraventricul ar neurocytoma [73,74]
Young adults > children Poorer outcome Similar to central neurocytom a; frequent ganglionic differentiati on
Cerebral hemisphere > sella Circumscribed complex cystic mass with calcification Often hemorrhage and peritumoral edema Variable enhancement
Tumor Type
Clinicopath ologic Features
Imaging Features
Papillary glioneuronal tumor [75,76]
Young adults Grade I
Supratentorial periventricular, temporal lobe commonest site; uncommonly pineal gland and intraventricular Solid or solid cystic lesion with internal septation Frequent calcification and hemorrhage (rarely superficial siderosis) Facilitated diffusion typically Heterogenous enhancement including enhancement of septations and cyst walls
Rosetteforming glioneuronal tumor [77,78]
Young adults, children Grade I
Midline posterior fossa (fourth ventricle commonest site), pineal region Solid cystic mass Frequent peripheral heterogenous enhancement: green bell paper sign: central mucoid tissue—lack of enhancement; adjacent solid tissue— ring enhancement; peripheral loose tissue—minimal or no enhancement Variable intratumoral hemorrhage Infrequent satellite lesions and CSF dissemination Calcification uncommon
Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a new entity described in the new WHO classification of 2016. These tumors are characterized by predominant and widespread leptomeningeal growth and oligodendroglia like cytology with elements of neuronal differentiation. These tumors are difficult to diagnose because of a wide spectrum of radiological and histological features. The entity is associated with MAPK activation associated with either solitary 1p deletion or 1p/19q codeletion in the absence of IDH mutation. Pathological features of DLGNT are not specific, and differential diagnoses include pilocytic astrocytoma, ganglioglioma, or extraventricular neurocytoma. The diagnosis may be
difficult to make in the cases lacking leptomeningeal dissemination. The cIMPACT-NOW has suggested that DLGNT should be considered as a distinct tumor type with two distinct subtypes recognized based on DNAmethylation profiling [28]. The characteristic imaging finding of DLGNT is diffuse intracranial and intraspinal nodular leptomeningeal thickening and enhancement. However, many cases without the typical imaging features have been reported.
Pineal Tumors Pineal tumors may represent up to 9% of all pediatric brain tumors in Asia, however the incidence of these tumors is much less common in North America. The clinical presentation is generally related to mass effect on surrounding structures such as dorsal midbrain or aqueduct [79]. Germ cell tumors are the most common type of pineal neoplasms [80]. The classification, clinical, and imaging features of pineal tumors are further detailed in Table 80.21. Germinoma, the commonest germ cell tumor subtype, represents nearly 40% of pineal neoplasms (Fig. 80.48) [79]. Unusual imaging appearances of germinoma include ill-defined areas of signal abnormality in basal ganglia with or without contrast enhancement and hemiatrophy of ipsilateral brainstem structures [59]. Pineal parenchymal origin tumors represent up to 30% of all pineal neoplasms. Pineoblastoma is the most common tumor type in this group (Fig. 80.49). This is a neuroectodermal origin WHO grade 4 malignancy [79]. WHO classification of germ cell tumors and respective imaging features are detailed in Table 80.22. Table 80.21 Classification of Pineal Tumors [80] Type of Neoplas m
Germ cell tumors
Pineal parenchymal origin tumors [pineoblastoma, pineocytoma, pineal parenchymal tumor of intermediate differentiation, and papillary tumor of pineal origin]
Age
Adolescent age group, male > female
Pineoblastoma (first 5 years of life) [81]
Type of Neoplas m
Germ cell tumors
Pineal parenchymal origin tumors [pineoblastoma, pineocytoma, pineal parenchymal tumor of intermediate differentiation, and papillary tumor of pineal origin]
Laborato ry markers
Serum and CSF elevated tumor markers (specifically, NGGCTs show elevated alphafetoprotein and beta-human chorionic gonadotropin)
Rare
CSF dissemin ation
Very common
Frequently in pineoblastoma Rare in other tumors
Imaging pattern of calcificat ion within the pineal mass [79]
Germinomas— predominantly central, appear immersed within the mass
Peripheral calcification (exploding pattern)
Imaging [79]
Heterogeneous appearance, enhancing solid or solid/cystic mass
Typically, solid appearing mass
Syndrom ic associati on
Not known
Hereditary retinoblastoma
FIGURE 80.48 A 7-year-old male with 3-month history of polyuria and polydipsia. Sagittal T1 MR image (A) showed the presence of focal mass in the pineal region. Note the thickening of pituitary infundibulum (white arrow). Sagittal contrast-enhanced MR image (B) showed intense heterogenous enhancement of pineal region mass with concomitant diffuse enhancement of the pituitary infundibulum or stalk (white arrow). The pattern is most concerning for germinoma. Histopathologically proved case of germinoma.
FIGURE 80.49 A 12-year-old male presented with photophobia, phonophobia, diplopia, and dizziness. Coronal T2 MR image (A) showed the presence of iso- to mildly hypointense mass in the pineal region (white arrow). Sagittal (B) and axial (C) contrast-enhanced MR images showed intense enhancement of pineal region mass. Histopathologically proved case of pineoblastoma.
FIGURE 80.50 A 11-year-old male presented with vomiting and headache. Axial T2 MR image (A) showed a solid cystic mass in the pineal region with proximal hydrocephalus. Note the presence of T2 hypointense foci within the mass representing either blood products or calcifications. ADC map (B) revealed the absence of significant reduction in the ADC values. Sagittal (C) contrast-enhanced MR image showed intense enhancement of solid component and nonenhancing cystic component. Histopathologically proved case of nongerminomatous germ cell tumor.
Table 80.22 WHO Classification of Germ Cell Tumors and Relevant Imaging Features [80] Germinomas
Nongerminomatous Germ Cell Tumors (Fig. 80.50)
Locatio n
Sellar/suprasellar and pineal region especially presence of simultaneous masses
Cerebral hemispheric mass, isolated pineal tumors
Appear ance
Mass with infiltration into adjacent structures
Tumor with intralesional hyperintense foci (fat and calcification) on T1-weighted imaging
Diffusi on imagin g
Low ADC values
High ADC values
Contra st enhanc ement
Germinomas
Nongerminomatous Germ Cell Tumors (Fig. 80.50)
Minimal to mild
Moderate to intense
DWI may be serve as useful tool in discriminating between pineoblastomas from germ cell tumors, specifically nongerminomatous germ cell tumors. The mean ADC of pineoblastoma is reportedly significantly lower than nongerminomatous germ cell tumor. However, ADC values in a significant percentage of germinomas appear to overlap with pineoblastomas [82]. Studies have reported that incidental pineal cysts may be seen in up to 40% of the population, specifically when data included adolescent and adult age groups (Fig. 80.51). Use of MR imaging to discriminate small solid or cystic pineal tumors from pineal cysts or normal pineal tissue is challenging (similar signal intensity and enhancement pattern), although this may be of paramount importance to patient management specifically in patients with known retinoblastoma. Recent literature suggests close correlation between size of the solid portion of the pineal gland with patients age which could be used to differentiate between progressively enlarging tumors from stablesized pineal tissue [62,81]. Physiological changes in pineal gland size are detailed in Table 80.23.
FIGURE 80.51 Pineal cyst. A 15-year-old male complained of dizziness and syncope. Axial T2 MR image (A) showed a circumscribed CSF isointense large cystic lesion in the pineal region (white arrow). Axial (B) and sagittal (C) contrast-enhanced MR images showed thin peripheral enhancement of cyst wall without enhancement of the cyst contents. The large size of simple appearing cyst obstructed the CSF flow with proximal hydrocephalus. The cyst has been stable over 3 years of follow-up (not shown). White arrows delineate the pineal cyst.
Table 80.23 Expected Imaging Findings and Changes in Normal Solid and Cystic Appearing Pineal Gland in Children 0–5 Years of Age [83,81]
◾ Close identifiable association between the size parameters of pineal gland parenchyma (solid portion as seen on thin-slice MRI) and age of the child, independent of sex. ◾ Increase in the size of cyst or pineal gland between first and second year of life (increasing melatonin). ◾ Decrease in the size of cyst or pineal gland after age 3 (decreasing melatonin).
Extra-axial Neoplasms Choroid Plexus Tumors Choroid plexus neoplasms are rare and represent about 2–6% of all pediatric brain tumors. Up to four-fifths of all choroid plexus tumors are seen in pediatric population. The peak incidence is seen in infantile population [84,85]. The typical tumor presents as an extra-axial mass in the intraventricular compartment. The commonest sites in pediatric population
are atrium of the lateral ventricle and fourth ventricle [86]. WHO 2016 classification of CNS tumors categorizes these as choroid plexus papilloma (grade 1), atypical choroid plexus papilloma (grade 2), and choroid plexus carcinoma (grade 3) based on histologic grade [85]. These tumors commonly present as hydrocephalus observed in up to 80% of patients, likely from combination of overproduction of CSF and obstruction to CSF flow [85,87]. On MR imaging these tumors present as homogenously enhancing lobulated masses with papillary or frond-like appearance (Fig. 80.52). Calcification is commonly seen on CT. The presence of intratumoral flow voids is common and represents hypervascular nature of the tumor [85,87]. Imaging cannot reliably differentiate between the different grades, however the presence of invasion of brain parenchyma is highly suggestive of choroid plexus carcinoma [85]. Imaging of whole spine is essential at baseline since the presence of CSF spread is common especially with choroid plexus carcinoma [85,87]. Rarely choroid plexus tumors may be localized in an extraventricular location. Cerebellopontine angle is a common location for such tumors [88]. Lower ADC values and larger tumor volumes at presentation have been shown to correlate with higher grade tumor and poorer prognosis [89].
FIGURE 80.52 A one-year-old male presented with altered mental status. Axial T2 MR image (A) showed the presence of lobular mass in the left occipital horn. Note the papillary appearance of the surface of the mass. Susceptibility weighted image (SWI) showed foci of hypointensity (B) representing calcifications. Axial contrast-enhanced MR image (C) showed intense homogenous enhancement of mass. Histopathologically proved case of choroid plexus papilloma.
Meningiomas
Meningiomas are extremely rare tumors in pediatric population representing about 1–2% of primary CNS tumors in this cohort and less than 1% of meningiomas across all age groups. The tumors in prepubertal population show clear male predilection, unlike female predominance in adult meningiomas. The prevalence of spinal meningiomas is also significant higher in children compared with adult population. The genetic and molecular profile of pediatric meningiomas show significant differences compared with adults [90,91]. The imaging appearance is essentially similar to adult counterparts presenting as a homogenously enhancing extra-axial dural based mass. More importantly more common alternative diagnoses should be considered as detailed in Table 80.24. If there is no history a detailed evaluation for the presence of underlying genetic syndrome such as neurofibromatosis 2 (NF2) and Gorlin syndrome is appropriate [91]. Based on recent analysis of Surveillance, Epidemiology, and End Results dataset, a subset of pediatric meningiomas may demonstrate aggressive biologic behavior however overall prognosis and outcome appear similar to young adults [90]. Table 80.24 Differential Diagnostic Considerations for Meningiomas and/or Extra-axial Masses in Pediatric Population
Schwannomas Schwannoma (neurilemmoma) is an extremely rare tumor in children. These are typically associated with NF2 syndrome in the pediatric age group, although reports of sporadic unilateral schwannomas in pediatric population are documented. Schwannomas in children represent about 0.7% of all such tumors across all age groups [92]. Schwannomatosis is a genetic disorder presenting with schwannomas of multiple peripheral and intracranial nerves (distinct from NF2). The most common site for intracranial schwannoma is facial-vestibulocochlear nerve complex [92]. Sporadic intracranial schwannomas in children have been reported to present with cranial nerve weakness and relative lack of audiological symptoms [72]. On imaging these are well circumscribed predominantly solid tumors with occasional cystic
changes. The typical appearance is heterogeneously hyperintense on T2weighted imaging with relatively homogenous enhancement on postcontrast imaging. CT may reveal remodeling of the bony spaces containing the tumor, such as internal auditory canal or Meckel’s cave, however frank erosion is very uncommon [93].
Pituitary Region Neoplasms Pituitary region tumors constitute about 10% of all pediatric brain tumors. The most common type of pituitary region masses in children are craniopharyngioma and Rathke cleft cyst [94]. Craniopharyngioma represents about 5.5–13% of all pediatric intracranial tumors [95]. Among the histological subtypes of craniopharyngioma, adamantinomatous type is seen predominantly in pediatric population. The adamantinomatous type is believed to arise from the squamous epithelium of Rathke pouch remnant along the craniopharyngeal duct path, anywhere from nasopharynx to the third ventricle [94,96]. The peak incidence is seen in the age group of 5–14 years [95]. The typical imaging appearance is a predominantly cystic mass with solid component involving both sellar and suprasellar compartments (Fig. 80.53). Suprasellar component is identified in vast majority of craniopharyngiomas. Isolated intrasellar location is seen in only 5% of craniopharyngiomas [94,96]. The adamantinomatous type appears as a lobulated calcified mass with nonenhancing T1 hyperintense cystic component and enhancing solid component. Calcification is seen in about 90% of such tumors [94,96]. A pseudofluid–fluid or fluid–debris may be observed. This may be helpful in distinguishing these from hemorrhagic pituitary adenomas which show a fluid–fluid level [95,97]. The imaging findings important for preoperative planning are summarized in Table 80.25.
FIGURE 80.53 A 10-year-old male presented with headache and decreased vision. Coronal T1 (A) and sagittal T2 (B) MR image showed a lobulated T1 mildly hyperintense and T2 hyperintense mass in sellar region with suprasellar extension. The pituitary gland is not separately identified. Note the fluid–blood or fluid–debris level (white arrow) on T2weighted images (B and C). Contrast-enhanced axial MR image (D) showed peripheral nodular enhancement (white arrow) within the lesion. Histopathologically proved case of craniopharyngioma.
Table 80.25 Imaging Features Relevant to Surgical Planning in Craniopharyngiomas [94,96]
◾ Predilection for vascular encasement ◾ Delineation of the full spatial extent of the mass to the surrounding structures
Rathke cleft cysts arise from failure of involution of Rathke pouch (craniopharyngeal duct) remnant between the anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis) of pituitary gland. Rathke cleft cysts are observed in about 11% of population in the autopsy series and about 1.2% in pediatric population (based on nondedicated imaging) and 3.4% of all age groups on imaging series [94,96]. The classical MR imaging appearance is a well-circumscribed homogenous nonenhancing cystic lesion in intrasellar location (Fig. 80.54). The cyst signal pattern is variable dependent on protein concentration, with high protein cyst showing hyperintense T1 signal and intermediate/hypointense T2 signal. The characteristic midline location and reniform shape is best identified on axial plane imaging. Suprasellar extension of a sella-based Rathke cleft cyst is not uncommon. Isolated suprasellar lesions are rare. The presence of intracystic nonenhancing T1 hyperintense, T2 hypointense nodules is a specific imaging feature of Rathke cleft cysts, best seen on T2-weighted imaging. The presence of calcification, fluid–debris level or enhancing solid component is very atypical and should direct search for alterative diagnoses [97]. The clinical and imaging differences between Rathke cleft cysts and craniopharyngiomas are summarized in Table 80.26.
FIGURE 80.54 A 10-year-old female presented with headache and decreased vision. Sagittal T1 (A), coronal T1 (B), and coronal T2 (C) MR images showed a lobulated T1 hyperintense and T2 intermediate signal mass in sellar region with suprasellar extension. Note the internal T1 iso- to mildly hypointense nodule along anterior and lateral wall of the mass. Contrast-enhanced sagittal MR image (D) showed the absence of any enhancement within the lesion. Histopathologically proved case of inflamed Rathke cleft cyst.
Table 80.26 Differences Between Common Pituitary Lesions/Masses in Pediatric Population Craniopharyngio ma
Rathke Cleft Cyst
Squamous cell epithelium
Simple or pseudostratified columnar or cuboidal epithelium lining.
Irregular wall with frequent calcification, enhancing solid component
Thin uniform cyst wall without contrast enhancement. Apparent wall enhancement is pseudoenhancement from enhancing normal gland surrounding the cyst.
Pituitary adenomas are much less common in children, compared with adult population. The reported prevalence is variable, representing between 1% and 10% of pediatric brain tumors.
Ultrasound of the Infant Brain Technique The ideal equipment for the examination of the infant brain is a highresolution sector real-time scanner, fitted with a 7–12 MHz transducer. The scan head should ideally be as small and maneuverable as possible which is
suited for showing the maximum area of information through a small acoustic window. The transducer applied to the head through a port-hole in the incubator. In this way the baby is almost undisturbed by the examination. In each examination a series of closely spaced scans is made in both the coronal and sagittal planes by altering the angulation of the transducer to the fontanelle. The aim is to include as much as possible of the brain on each scan. A more limited access may also be possible through the posterior fontanelle and through the sutures. Occasionally, it may be of value to image directly through the skull vault. The ultrasound studies of the brain are most valuable in the first 6 months of life.
Indications The two most common abnormalities of the neonatal brain requiring confirmation or exclusion by imaging techniques are hydrocephalus and intracranial hemorrhage. The success of the procedure and the early complications such as shunt failure may also be followed by ultrasound. Meningitis is a comparatively common infection in some parts of the world. The common complications are ventricular enlargement, subdural effusions, and cerebral edema, all of which may be well shown with transfontanellar scanning.
Normal Appearances Ultrasound is able to demonstrate the normal brain structure in considerable detail. The coronal sections are particularly valuable for showing focal abnormalities as advantage may be taken of the brain’s symmetry. A series of landmarks in both coronal and sagittal planes has been described which allows recognition of the position at which the scan has been taken, and subsequently the acquisition of standard reproducible sections (Fig. 80.55). Within the brain, structures containing CSF, such as the ventricles and cisterns, appear anechoic; normal brain tissue generates low- to mid-level echoes; higher-level echoes are generated from the cerebellum, the sulci and vascular structures. One of the most echogenic intracerebral structures seen with ultrasound is choroid plexus. The bones of the vault also produce highly echogenic reflections and so may be useful as landmarks.
FIGURE 80.55 Diagram showing three standard sagittal sections (A) and six coronal sections (B).
◾section The first coronal plane the transducer is angled anteriorly in the fontanelle, producing a through the frontal lobes, seen separated centrally by the interhemispheric fissures and the falx. The far field landmark is the high-amplitude echoes from the orbital roofs and the central echoes from the ethmoid complex extending downward to a lower level. The second position the far field landmark changes so that the lesser wings of the sphenoid, with the greater wings of the sphenoid behind, are seen forming the anterior floor of the temporal fossa. The anterior horns of the lateral ventricles may be seen in this section as small slit-like spaces either side of the central midline echo. The third coronal section where the most prominent landmarks are the Sylvian fissures (Fig. 80.56). These are seen just behind the lesser wings of the sphenoid and run laterally and outward, becoming Y-shaped between the temporal and frontal lobes. Within this echo complex, pulsation from branches of the middle cerebral artery will be readily seen. Between the lateral ventricles the echo-free box-like structure of the cavum septi pellucidi may be seen. It is seen more commonly in premature infants. Its incidence decreases sharply with age, and by 6 months compares with the low percentage reported in adults. The roof of the lateral ventricle is formed by the corpus callosum, which is echogenic, and the floor by the head of the caudate nucleus, with lower-level echoes. The fourth coronal plane passes through the third ventricle which is not usually resolved in this plane when of normal size. A very prominent far field landmark is formed by the paired C-shaped echoes from the parahippocampal gyri and medial surface of the temporal lobes (Fig. 80.57). The bodies of the lateral ventricles now lie more horizontally and reflections from the choroid plexus may be seen in the floor of the ventricles At the fifth coronal section the prominent landmark is the highly echogenic tentorium and cerebellum shaped like an inverted V The sixth coronal section will bring into view the echogenic divergent bands characteristic of the glomus of the choroid plexus (Fig. 80.58). In the normal infant the choroid plexus will always be seen in this section, although the fluid-filled ventricles will not always be separately distinguished around the choroid
◾ ◾
◾ ◾ ◾
FIGURE 80.56 A coronal section in the third position showing the bodies of the lateral ventricles (V) and the Sylvian fissures (SF). Lying between the lateral ventricles is the cavum septi pellucidi (CSP).
FIGURE 80.57 A coronal section in the fourth position showing the prominent landmark of the parahippocampal gyri (HG). V, lateral ventricles.
FIGURE 80.58 A coronal section in the sixth position showing the characteristic echogenic choroid plexus (CP).
Rotating the transducer through 90° into the sagittal plane the sagittal sections are taken.
◾sulcal The first sagittal section is taken in the midline (Fig. 80.59). The detail is usually prominent and the cingulate sulcus containing the branches of the anterior cerebral artery can be identified. The echogenic cerebellum is seen posteriorly, and anterior to this the fourth ventricle can be recognized. Above this the third ventricle and the massa intermedia are demonstrated, and often the aqueduct of Sylvius is outlined. The clivus forms the far field landmark. The second parasagittal section is angled about 15° away from the midline and shows almost the full sweep of the lateral ventricle containing the echogenic choroid plexus. Within the sweep of the ventricles the rounded mass is formed by the thalamus and caudate nucleus. The far field landmark is the floor of the middle fossa
◾ ◾
◾toThethe third parasagittal section is angled outward about 30°, lateral ventricle and through the Sylvian fissure
FIGURE 80.59 A sagittal section in the midline showing the echogenic cerebellum and the fourth ventricle (arrow) posteriorly.
Hydrocephalus and Cystic Lesions The lateral ventricles in the normal neonate may be small and difficult to define accurately. The mean width of the lateral ventricle in the full-term infant is 12 mm and in the 30-week premature infant 9 mm, measured at the level of the body of the lateral ventricle. Ultrasound has proved to be accurate and reliable in detecting (Fig. 80.60) and grading the severity of hydrocephalus and is ideally suited to following progress. Further evaluation of hydrocephalus to establish a precise etiology may require diagnostic procedures in addition to ultrasound. However, in certain instances,
ultrasound may provide most or all of the answers. In addition to the diagnosis and follow-up of hydrocephalus, ultrasound may also be helpful in following shunt procedures, particularly in the evaluation of complications.
FIGURE 80.60 A coronal section showing the typical appearance of hydrocephalus involving the lateral and third ventricles. The section is through the foramen of Monro. Echogenic hemorrhage is within the ventricle.
Besides hydrocephalus other cystic lesions within the brain may show well. In hydranencephaly no brain parenchyma is present above the level of the midbrain and no cortical mantle is seen. The Dandy–Walker syndrome has a characteristic appearance where cystic dilatation of the fourth ventricle can be recognized. This condition must, however, be distinguished from a retrocerebellar arachnoid cyst which may produce a similar appearance. In the latter instance, however, a normal fourth ventricle is identified compressed anteriorly by the cyst.
Hemorrhage The germinal matrix is a neural vascular tissue in the fetus which is normally involuted by term. It is situated subependymally in the ventricles
and is prominent in the groove between caudate nucleus and thalamus. This is a frequent site for hemorrhage in premature infants (Fig. 80.61).
FIGURE 80.61 A coronal section in a premature infant showing a typical reflective hemorrhage (H) from the germinal matrix. A mass effect from the hemorrhage is distorting and elevating the lateral ventricle on this side.
The vascular choroid is also an important site for cranial hemorrhage in infants. The shape of the choroid plexus as it surrounds the caudate nucleus and thalamus is fairly constant so that any irregular increase in size is suspicious of hemorrhage. The symmetry of the two sides may also be of value in detecting abnormality. The diagnosis of intracerebral, periventricular, and intraventricular hemorrhages may be made reliably using ultrasound where the hemorrhage shows as a brightly reflective area. This is mainly due to the fibrin mesh formed, which produces multiple reflecting interfaces for the ultrasound beam. Subarachnoid hemorrhage is not reliably demonstrated using ultrasound, but subdural hemorrhage is usually shown as a crescentic echopoor region separating brain from the skull vault. Hemorrhage, particularly in premature infants, may rupture into the lateral ventricles. This may
enlarge the ventricles, either due to brain tissue loss and atrophy or to hydrocephalus due to CSF flow obstruction. The combination of both may occur, and monitoring to show progress or stabilization is important in these circumstances. Trauma to the infant brain due to birth or accidental injury produces a combination of the types of hemorrhagic or ischemic change already described. Nonaccidental injury to the brain may produce pathognomonic shearing injuries at the gray–white matter interface. This appears typically as small linear slit-like cavities, optimally demonstrated with the linear-array transducers.
Ultrasound of the Infant Spine Technique Pediatric spinal ultrasound is performed with a high resolution, 7–12 MHz linear-array transducer. These studies are usually performed with the infant lying in a prone position or with the infant in the lap of the parent or caregiver. The posterior elements begin to ossify after 3–4 months and therefore after that period spinal ultrasound is suboptimal or technically challenging. Ideally the studies are performed following a feeding without sedation. It is important to identify vertebral levels on ultrasound and there are a few ways to accomplish this. Probably the easiest and most reproducible methods are to identify the lumbosacral junction and then label lumbar vertebrae by counting in a superior fashion. Alternatively, the last ribbearing vertebra can be identified, which presumably indicates T12 and then counting can be done caudally. Although these and other methods can be used for counting; however, if sufficient doubt still persists, correlation with previous radiographs may be necessary.
Anatomy The most superficial tissue just deep to the skin surface is the subcutaneous fat, which shows intermediate echogenicity, lower in echogenicity than the dermis and the fascial planes but brighter than the paraspinal muscles. The ossified portions of the vertebra are brightly echogenic with posterior acoustic shadowing. There are portions of vertebra that are unossified cartilage and these are predominantly hypoechoic on ultrasound. Typically, the coccyx is entirely unossified cartilage at birth. The epidural space contains a small amount of echogenic fat, which may appear prominent in some infants. The thecal sac appears as a linear echogenic structure, which
typically terminates at the S2 level. Deep to the thecal sac is anechoic CSF and echogenic nerve roots within the subarachnoid space. On longitudinal images the nerve roots appear as linear echogenic structures coursing inferiorly from the spinal cord. In the central portion of the cord there is a “central echogenic complex” that is linear on longitudinal images and appears as a small central dot on transverse images. This is attributed to a small amount of fluid in the central spinal canal. The filum terminale extends inferiorly from the conus. The filum is centrally hypoechoic with increased echogenicity in the periphery at the interface of its margins with CSF. CSF pulsations cause normal motion, which are observable on real-time ultrasound of the filum terminale, surrounding cauda equina and conus. M-mode ultrasound can be used to document if this normal motion is present. Absent or nearly absent motion can be seen with cord tethering.
Normal Variants Many normal variants can be encountered during ultrasound evaluation of pediatric spine. Understanding these variants is important so as to avoid erroneous interpretation and unnecessary follow-up imaging or clinical evaluation. Some of the common variants are discussed as follows. Ventriculus Terminalis Ventriculus terminalis refers to ependymal-lined mild cystic dilatation of terminal spinal cord canal. It is also known as the terminal ventricle or the fifth ventricle. On ultrasound, this is seen as anechoic central canal dilatation. This structure has a transverse diameter of 2–4 mm and extends craniocaudally for approximately 8–10 mm [98]. This is an incidental finding with no clinical symptoms attributable to this abnormality. On follow-up imaging, most lesions are either stable in size or spontaneously regress. Transient Dilatation of Central Canal This is another incidental finding that can be seen incidentally in healthy newborns and disappears during first few weeks of life. Filar Cyst This lesion is seen as a well-defined, ovoid anechoic lesion within the filum terminale, just below the conus. These are also incidental findings that are not well seen on MR and have not been reported in adults. Pseudosinus Tract
This is seen as a linear or curvilinear hypoechoic tract extending from a skin dimple to the coccyx. Real dermal sinus tracts are usually seen more cranially and rarely occur at the tip of coccyx.
Pathology Tethered Cord Tethered cord refers to a stretched, thinned cord with low-lying conus and a thickened filum terminale. The diagnosis of tethered spinal cord is clinical and tethering may be present in spite of normal location of conus. Imaging is useful for finding associated abnormalities and detection of low-lying conus and thick filum terminale along with associated abnormalities. Typical symptoms include pain, neurological deficits in the lower extremities, and bladder and bowel dysfunction. Ultrasound findings include low position of conus (L3 or below), thickened filum terminale (more than 2 mm) and abnormal, dorsally positioned conus medullaris within the spinal canal. There is reduced or absent pulsatile spinal cord and nerve root motion on Mmode ultrasound examination. MRI is useful to confirm these findings and demonstrate dorsal positioning of the cord on supine images with the absence of anterior movement of the cord on prone images in these cases. Treatment of tethered cord consists of surgical release of filum. Spinal Lipoma Spinal lipomas are caused by premature disjunction resulting in mesoderm to be trapped between neural folds. These are not true neoplasms. Spinal lipomas may be intradural, extradural or a combination of both. On Ultrasound, these lesions appear as uniformly echogenic masses. Fibrolipoma of filum terminale is a unique form of spinal lipoma. The characteristic ultrasound finding is echogenic, thickened filum terminale (>2 mm). Dorsal Dermal Sinus Dorsal dermal sinus refers to an epithelial-lined midline/paramidline sinus tract extending from the skin surface to varying distances toward the spinal canal. The cause is incomplete disjunction of cutaneous ectoderm from neuroectoderm. The commonest location is in the lumbosacral region, followed by occipital region. There can be an associated intrathecal mass, which can be a dermoid or an epidermoid. These sinus tracts may result in spread of cutaneous infection to the spine, causing intraspinal abscess and meningitis. Ultrasound can demonstrates the entire length of tract. The subcutaneous tract is usually hypoechoic, whereas the subarachnoid tract is
echogenic. There may be associated findings of low-lying conus, thick filum terminale and an intrathecal mass. Spinal Dysraphism Ultrasound of the spine can detect defects in the posterior elements and contents of an open spinal dysraphism sac. The ability to see the cord also helps detect anomalies within the spinal canal like split cord in diastematomyelia (Fig. 80.62).
FIGURE 80.62 Short- (A) and long-axis (B) ultrasound showing diastematomyelia (arrow in A) with meningomyelocele (arrow in B). Axial T1-weighted MR scans of the same patient showing the split cord (arrow in C), meningomyelocele (arrow in D).
Phakomatoses The phakomatoses are a heterogenous group of neurocutaneous disorders characterized by the involvement of structures that arise from the embryonic ectoderm.
Neurofibromatosis Type 1 (NF1) This is the most common phakomatosis, also known as von Recklinghausen disease. The NF1 gene locus is on chromosome 17q11.2. The clinical diagnosis requires the presence of two or more of the following seven features:
◾prepubertal Six or more café-au-lait spots or hyperpigmented macules greater than 5 mm in diameter in children and greater than 15 mm in postpubertal individuals ◾ Axillary or inguinal freckles (>2 freckles) ◾ Two or more typical neurofibromas or one plexiform neurofibroma ◾ Optic pathway glioma ◾ Two or more iris hamartomas (Lisch nodules) ◾ wing dysplasia or typical long-bone abnormalities such as pseudarthrosis ◾ Sphenoid First-degree relative (e.g., mother, father, sister, brother) with a diagnosis of NF1
In the CNS, the disease is characterized by both neoplastic lesions and hamartomas. Optic pathway gliomas are the most common CNS neoplasms and are seen as areas of fusiform enlargement along the optic pathway (Fig. 80.63). Low-grade gliomas can also occur in the tectum, brainstem, basal ganglia, or cerebellum. Non-neoplastic white matter lesions known as foci of abnormal signal are seen as T2/FLAIR hyperintense signals and represent regions of myelin vacuolization or hamartomas. Bony dysplasia involving the greater wing of sphenoid is another characteristic finding seen with NF1.
FIGURE 80.63 Axial MRI (T1-weighted) shows right optic nerve glioma as low-signal rounded mass in a patient with neurofibromatosis.
Neurofibromatosis Type 2 (NF2) NF2 is an autosomal dominant disorder transmitted on chromosome 22 (22q12). It typically presents in adolescence or young adulthood, and the most common clinical presentation is bilateral sensorineural hearing loss as
a result of vestibular schwannomas. The diagnostic criteria require any one of the following two conditions:
◾ vestibular schwannomas ◾ Bilateral Family history of NF2 plus 1. Unilateral vestibular schwannoma
2. Any two of: glioma, meningioma, neurofibroma, schwannoma, or juvenile posterior subcapsular lenticular opacities.
These features give rise to the acronym MISME, which describes Multiple Inherited Schwannomas Meningiomas, and Ependymomas. Unlike NF1, cutaneous manifestations in NF2 are rare. CNS tumors are present in virtually 100% of patients with NF2. Schwannomas most commonly involve cranial nerve VIII and V cranial nerve is the next most common site for schwannomas. Other imaging findings that may be present in NF2 include prominent calcifications along the choroid plexus, or occasionally along the cerebral or cerebellar cortex. Lesions within the spinal canal are common and include schwannomas and meningiomas. Intramedullary tumors are typically ependymomas [99].
Tuberous Sclerosis This condition is characterized by a triad of seizures, mental retardation, and skin lesions. Hamartomas are seen in CNS, skin, kidneys, eyes, and lungs. Intracranial manifestations include cortical tubers (please see Fig. 75.71, Chapter 75) or hamartomas, subependymal nodules, and subependymal giant cell astrocytomas (SEGA). SEGA (please see Fig. 78.15, Chapter 78) present as enlarging masses at foramen of Monro and can cause obstructive hydrocephalus. Interval growth in size is the most important criteria to differentiate SEGA from subependymal nodules.
Sturge–Weber Syndrome This neurocutaneous syndrome is also called encephalotrigeminal angiomatosis and affects the vasculature of leptomeninges, face, and eyes. There is a port wine stain (facial angioma), that is seen along the distribution of the ophthalmic division of the trigeminal nerve and is present at birth. Intracranial manifestations include a leptomeningeal angioma, which causes paucity of the superficial cortical drainage leading to venous ischemia, cerebral cortical atrophy, and characteristic tram-track calcification along the affected cortex Fig. 80.64. Calcification and enlargement of ipsilateral choroid plexus may be present [100].
FIGURE 80.64 Axial T2-weighted image (A) in a patient with Sturge– Weber syndrome shows atrophy of the left cerebral hemisphere. Cortical T2 low signal in the left occipital region is consistent with calcification. There is also some thickening of the calvarium in the left frontal region. On the postcontrast T1 axial image (B) there is marked superficial enhancement in the occipital and temporal regions due to the presence of a pial angioma.
Von Hippel–Lindau Syndrome This is a neurocutaneous syndrome that is inherited in an autosomal dominant fashion due to inactivation of a tumor suppression gene located on chromosome 3p25.5. Hemangioblastomas are typical CNS neoplasms that can involve the spinal cord and the brain (please see Figs. 78.49–78.51, Chapter 78. In the brain, typical sites that are involved are the cerebellum and brainstem. On imaging, these tumors are seen as cystic lesions with enhancing mural nodules. Outside the CNS, manifestations include pancreatic cysts, renal cysts, renal cell carcinoma, pheochromocytoma, etc.
Suggested Readings • A Barkovich, James and Raybaud, Charles, “Pediatric Neuroimaging, sixth ed.” (2019). • BR Korf, The phakomatoses, Neuroimaging Clin N Am, 14 (2) (2004) 139–148, vii. doi: 10.1016/j.nic.2004.03.008.
• M Severino, TAGM Huisman, Posterior Fossa Malformations, Neuroimaging Clin N Am 29 (3) (2019) 367–383. • AB Meyers, T Chandra, M Epelman, Sonographic spinal imaging of normal anatomy, pathology and magnetic growing rods in children, Pediatr Radiol 47 (9) (2017) 1046–1057. • A Poretti, E Boltshauser, TA Huisman, Congenital brain abnormalities: an update on malformations of cortical development and infratentorial malformations, Semin Neurol 34 (3) (2014) 239–248. • BM Kline-Fath, MA Calvo-Garcia, Prenatal imaging of congenital malformations of the brain, Semin Ultrasound CT MR 32 (3) (2011) 167–188.
References [1] AJ Barkovich, S Deon, Hypomyelinating disorders: an MRI approach, Neurobiol Dis 87 (2016) 50–58. [2] NK Desai, ME Mullins, An imaging approach to diffuse white matter changes, Radiol Clin North Am 52 (2) (2014) 263–278. [3] S Guleria, TG Kelly, Myelin, myelination, and corresponding magnetic resonance imaging changes, Radiol Clin North Am 52 (2) (2014) 227–239. [4] R Schiffmann, MS van der Knaap, Invited article: an MRI-based approach to the diagnosis of white matter disorders, Neurology 72 (8) (2009) 750–759. [5] Y Numata, L Gotoh, A Iwaki, K Kurosawa, J Takanashi, K Deguchi, et al., Epidemiological, clinical, and genetic landscapes of hypomyelinating leukodystrophies, J Neurol 261 (4) (2014) 752– 758. [6] M Traverso, S Assereto, E Gazzerro, S Savasta, EM Abdalla, et al., Novel FAM126A mutations in hypomyelination and congenital cataract disease, Biochem Biophys Res Commun 439 (3) (2013) 369–372. [7] A Pizzino, TM Pierson, Y Guo, G Helman, S Fortini, K Guerrero, et al., TUBB4A de novo mutations cause isolated hypomyelination, Neurology 83 (10) (2014) 898–902. [8] J Zhang, M Liu, L Zhou, ZB Zhang, JM Wang, YW Jiang, et al., DARS mutations responsible for hypomyelination with brain stem and spinal cord involvement and leg spasticity: report of two cases and review of literature, Zhonghua Er Ke Za Zhi 56 (3) (2018) 211– 215. [9] S Bano, V Chaudhary, UC Garga, Neonatal hypoxic-ischemic encephalopathy: a radiological review, J Pediatr Neurosci 12 (1) (2017) 1–6. [10] CP Chao, CG Zaleski, AC Patton, Neonatal hypoxic-ischemic encephalopathy: multimodality imaging findings, Radiographics 26 (Suppl 1) (2006) S159–S172.
[11] AJ Barkovich, KD Westmark, HS Bedi, JC Partridge, DM Ferriero, DB Vigneron, Proton spectroscopy and diffusion imaging on the first day of life after perinatal asphyxia: preliminary report, AJNR Am J Neuroradiol 22 (9) (2001) 1786–1794. [12] B Battal, Malformations of cortical development: 3T magnetic resonance imaging features, World J Radiol 7 (10) (2015) 329. [13] MC Diogo, S Glatter, J Binder, H Kiss, D Prayer, The MRI spectrum of congenital cytomegalovirus infection, Prenatal Diagn 40 (1) (2020) 110–124. [14] AJ Barkovich, R Guerrini, RI Kuzniecky, GD Jackson, WB Dobyns, A developmental and genetic classification for malformations of cortical development: update 2012, Brain [Internet] 135 (5) (2012) 1348–1369, doi. 10.1093/ brain/aws019. [15] A Barkovich, et al., James and Raybaud, sixth ed, “Pediatric Neuroimaging, 2019. [16] T Bosemani, G Orman, E Boltshauser, A Tekes, TA Huisman, A Poretti, Congenital abnormalities of the posterior fossa, Radiographics 35 (1) (2015) 200–220. 10.1148/rg.351140038. [17] C Cotes, E Bonfante, J Lazor, S Jadhav, M Caldas, L Swischuk, et al., Congenital basis of posterior fossa anomalies, Neuroradiol J 28 (3) (2015) 238–253. 10.1177/1971400915576665. [18] SS Kollias, WS Ball Jr., EC Prenger, Cystic malformations of the posterior fossa: differential diagnosis clarified through embryologic analysis, Radiographics 13 (6) (1993) 1211–1231. 10.1148/radiographics.13.6.8031352. [19] AJ Robinson, S Blaser, A Toi, D Chitayat, W Halliday, S Pantazi, et al., The fetal cerebellar vermis: assessment for abnormal development by ultrasonography and magnetic resonance imaging, Ultrasound Q 23 (3) (2007) 211–223. 10.1097/RUQ.0b013e31814b162c. [20] R Ber, O Bar-Yosef, C Hoffmann, D Shashar, R Achiron, E Katorza, Normal fetal posterior fossa in MR imaging: new biometric data and possible clinical significance, AJNR Am J Neuroradiol 36 (4) (2015) 795–802. 10.3174/ajnr.A4258. Epub 2015 Feb 5. [21] A Poretti, E Boltshauser, TA Huisman, Cerebellar and brainstem malformations, Neuroimaging Clin N Am 26 (3) (2016) 341–357. [22] CY Ho, JS Cardinal, AP Kamer, C Lin, SF Kralik, Contrast leakage patterns from dynamic susceptibility contrast perfusion MRI in the grading of primary pediatric brain tumors, AJNR Am J Neuroradiol 37 (3) (2016) 544–551. [23] Q Ostrom, University hospitals health system, Neuro Oncol 22 (S1) (2020) 1–96, [Internet] [cited 2020 Nov 6]. Available from.
https://academic.oup.com/neurooncology/article/22/Supplement_1/iv1/5943281. [24] DN Louis, A Perry, G Reifenberger, A von Deimling, D Figarella-Branger, WK Cavenee, et al., The 2016 World Health Organization classification of tumors of the central nervous system: a summary, Acta Neuropathol 131 (6) (2016) 803–820. [25] DN Louis, P Wesseling, W Paulus, C Giannini, TT Batchelor, JG Cairncross, et al., cIMPACT-NOW update 1: not otherwise specified (NOS) and not elsewhere classified (NEC) [Internet], Acta Neuropathol 135 (2018) 481–484, [cited 2020 Dec 6]. Available from. https://pubmed.ncbi.nlm.nih.gov/29372318/. [26] DN Louis, C Giannini, D Capper, W Paulus, D FigarellaBranger, MB Lopes, et al., cIMPACT-NOW update 2: diagnostic clarifications for diffuse midline glioma, H3 K27M-mutant and diffuse astrocytoma/anaplastic astrocytoma, IDH-mutant, Acta Neuropathol [Internet] 135 (4) (2018) 639–642, Available from. https://doi.org/10.1007/s00401-018-1826-y. [27] DW Ellison, C Hawkins, DT.W Jones, A Onar-Thomas, SM Pfister, G Reifenberger, et al., cIMPACT-NOW update 4: diffuse gliomas characterized by MYB, MYBL1, or FGFR1 alterations or BRAF V600E mutation [Internet], Acta Neuropathol 137 (2019) 683–687, [cited 2020 Dec 6]. Available from. https://pubmed.ncbi.nlm.nih.gov/30848347/. [28] DN Louis, P Wesseling, K Aldape, DJ Brat, D Capper, IA Cree, et al., cIMPACT-NOW update 6: new entity and diagnostic principle recommendations of the cIMPACT-Utrecht meeting on future CNS tumor classification and grading, Brain Pathol 30 (4) (2020) 844–856, [Internet] [cited 2020 Dec 6]. Available from. https://pubmed.ncbi.nlm.nih.gov/32307792/. [29] DW Ellison, KD Aldape, D Capper, M Fouladi, MR Gilbert, RJ Gilbertson, et al., cIMPACT-NOW update 7: advancing the molecular classification of ependymal tumors [Internet], Brain Pathol 30 (2020) 863–866, [cited 2020 Dec 6]. Available from. https://pubmed.ncbi.nlm.nih.gov/32502305/. [30] J Alrayahi, M Zapotocky, V Ramaswamy, P Hanagandi, H Branson, W Mubarak, et al., Pediatric brain tumor genetics: what radiologists need to know, Radiographics 38 (7) (2018) 2102–2122. [31] D Chourmouzi, E Papadopoulou, M Konstantinidis, V Syrris, K Kouskouras, A Haritanti, et al., Manifestations of pilocytic astrocytoma: a pictorial review, Insights Imaging 5 (3) (2014) 387– 402.
[32] S Gaudino, M Martucci, R Russo, E Visconti, E Gangemi, F D’Argento, et al., MR imaging of brain pilocytic astrocytoma: beyond the stereotype of benign astrocytoma, Child’s Nerv Syst 33 (1) (2017) 35–54. [33] F D’Arco, F Khan, K Mankad, M Ganau, P Caro-Dominguez, S Bisdas, Differential diagnosis of posterior fossa tumours in children: new insights, Pediatr Radiol 48 (13) (2018) 1955–1963. 10.1007/s00247-018-4224-7. [34] M De Fatima Vasco Aragao, M Law, D Batista De Almeida, G Fatterpekar, B Delman, AS Bader, et al., Comparison of perfusion, diffusion, and MR spectroscopy between low-grade enhancing pilocytic astrocytomas and high-grade astrocytomas, Am J Neuroradiol 35 (8) (2014) 1495–1502. [35] AF Choudhri, A Siddiqui, P Klimo, Pediatric cerebellar tumors: emerging imaging techniques and advances in understanding of genetic features, Magn Reson Imaging Clin N Am [Internet] 24 (4) (2016) 811–821. [36] J Tisnado, R Young, KK Peck, S Haque, Conventional and advanced imaging of diffuse intrinsic pontine glioma, J Child Neurol 31 (2016) 1386–1393. [37] DR Johnson, JB Guerin, C Giannini, JM Morris, LJ Eckel, TJ Kaufmann, 2016 Updates to the WHO brain tumor classification system: what the radiologist needs to know, Radiographics 37 (2017) 2164–2180. [38] T Campion, B Quirk, J Cooper, K Phipps, S Toescu, K Aquilina, et al., Surveillance imaging of grade 1 astrocytomas in children: can duration and frequency of follow-up imaging and the use of contrast agents be reduced?, Neuroradiology (2020) 1, [Internet] [cited 2021 Feb 23] 953–958. Available from: /pmc/articles/PMC7688203/. [39] SX Bian, MF McAleer, TS Vats, A Mahajan, DR Grosshans, Pilocytic astrocytoma with leptomeningeal dissemination, Child’s Nerv Syst 29 (3) (2013) 441–450. [40] MS Aboian, DA Solomon, E Felton, MC Mabray, JE VillanuevaMeyer, S Mueller, et al., Imaging characteristics of pediatric diffuse midline gliomas with histone H3 K27M mutation, Am J Neuroradiol 38 (4) (2017) 795–800. [41] FE El-Khouly, SE.M Veldhuijzen van Zanten, V Santa-Maria Lopez, NH Hendrikse, GJ.L Kaspers, G Loizos, et al., Diagnostics and treatment of diffuse intrinsic pontine glioma: where do we stand?, J Neurooncol 145 (1) (2019) 177–184, [Internet] [cited 2020 Jan 18]. Available from. http://link.springer.com/10.1007/s11060019-03287-9.
[42] TY Poussaint, M Kocak, S Vajapeyam, RI Packer, RL Robertson, R Geyer, et al., MRI as a central component of clinical trials analysis in brainstem glioma: a report from the Pediatric Brain Tumor Consortium (PBTC), Neuro Oncol 13 (4) (2011) 417–427. [43] RY Shih, KK Koeller, Embryonal tumors of the central nervous system, Radiographics 38 (2) (2018) 525–541. [44] KK Koeller, EJ Rushing, From the archives of the AFIP -, medulloblastoma: a comprehensive review with radiologicpathologic correlation, Radiographics (2003) 1613–1637. [45] T Stavrou, EC Dubovsky, GH Reaman, AM Goldstein, G Vezina, Intracranial calcifications in childhood medulloblastoma: relation to nevoid basal cell carcinoma syndrome, AJNR Am J Neuroradiol 21 (4) (2000) 790–794, [Internet] [cited 2020 Jan 28]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/10782799. [46] Z Patay, LA DeSain, SN Hwang, A Coan, Y Li, DW Ellison, MR imaging characteristics of wingless-type-subgroup pediatric medulloblastoma, Am J Neuroradiol 36 (12) (2015) 2386–2393, [Internet] [cited 2020 Feb 9]. [47] A Stock, M Mynarek, T Pietsch, SM Pfister, SC Clifford, T Goschzik, et al., Imaging characteristics of wingless pathway subgroup medulloblastomas: Results from the German HIT/SIOPtrial cohort, Am J Neuroradiol 40 (11) (2019) 1811–1817, [Internet] [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/31649159. [48] D Mata-Mbemba, M Zapotocky, S Laughlin, MD Taylor, V Ramaswamy, C Raybaud, MRI characteristics of primary tumors and metastatic lesions in molecular subgroups of pediatric medulloblastoma: a single-center study, AJNR Am J Neuroradiol 39 (5) (2018) 949–955. [49] KW Yeom, BC Mobley, RM Lober, JB Andre, S Partap, H Vogel, et al., Distinctive MRI features of pediatric medulloblastoma subtypes, Am J Roentgenol 200 (4) (2013) 895–903. [50] M Iv, M Zhou, K Shpanskaya, S Perreault, Z Wang, E Tranvinh, et al., MR imaging-based radiomic signatures of distinct molecular subgroups of medulloblastoma, Am J Neuroradiol 40 (1) (2019) 154–161, [Internet] [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/30523141. [51] S Perreault, V Ramaswamy, AS Achrol, K Chao, TT Liu, D Shih, et al., MRI surrogates for molecular subgroups of medulloblastoma, Am J Neuroradiol 35 (7) (2014 Jul) 1263–1269, [Internet] [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/24831600.
[52] AC Douglas-Akinwande, TD Payner, EM Hattab, Medulloblastoma mimicking Lhermitte-Duclos disease on MRI and CT, Clin Neurol Neurosurg 111 (6) (2009) 536–539. [53] J Bennett, R Ashmawy, V Ramaswamy, D Stephens, E Bouffet, N Laperriere, et al., The clinical significance of equivocal findings on spinal MRI in children with medulloblastoma, Pediatr Blood Cancer 64 (8) (2017). [54] Z Patay, J Enterkin, JH Harreld, Y Yuan, U Löbel, Z Rumboldt, et al., MR imaging evaluation of inferior olivary nuclei: comparison of postoperative subjects with and without posterior fossa syndrome, Am J Neuroradiol 35 (4) (2014) 797–802, [Internet] [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/24184519. [55] SM Toescu, S Hettige, K Phipps, RP Smith, V Haffenden, C Clark, et al., Post-operative paediatric cerebellar mutism syndrome: time to move beyond structural MRI, Child’s Nerv Syst [Internet] 34 (11) (2018) 2249–2257, [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/29926177. [56] A Vossough, P Ziai, JA Chatzkel, Red nucleus degeneration in hypertrophic olivary degeneration after pediatric posterior fossa tumor resection: use of susceptibility-weighted imaging (SWI), Pediatr Radiol [Internet] 42 (4) (2012) 481–485, [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/ 22218736. [57] SP Meyers, SL Wildenhain, JK Chang, EC Bourekas, PF Beattie, DN Korones, et al., Postoperative evaluation for disseminated medulloblastoma involving the spine: contrast-enhanced MR findings, CSF cytologic analysis, timing of disease occurrence, and patient outcomes, AJNR Am J Neuroradiol 21 (9) (2000) 1757– 1765, [Internet] [cited 2020 Jan 28]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/11039362. [58] M Warmuth-Metz, B Bison, NU Gerber, T Pietsch, M Hasselblatt, MC Frühwald, Bone involvement in atypical teratoid/rhabdoid tumors of the CNS, Am J Neuroradiol 34 (10) (2013) 2039–2042. [59] J Nowak, C Seidel, F Berg, T Pietsch, C Friedrich, K Von Hoff, et al., MRI characteristics of ependymoblastoma: results from 22 centrally reviewed cases, Am J Neuroradiol 35 (2014) 1996–2001. [60] S Muly, S Liu, R Lee, S Nicolaou, R Rojas, F Khosa, MRI of intracranial intraventricular lesions, Clin Imaging [Internet] 52 (May 2018) (2018) 226–239, doi. 10.1016/j.clinimag.2018.07.021. [61] L Vandesteen, A Drier, D Galanaud, F Clarençon, D Leclercq, C Karachi, et al., Imaging findings of intraventricular and ependymal lesions, J Neuroradiol 40 (4) (2013) 229–244.
[62] JM U-King-Im, MD Taylor, C Raybaud, Posterior fossa ependymomas: new radiological classification with surgical correlation, Child’s Nerv Syst 26 (12) (2010) 1765–1772. [63] M Pagès, KW Pajtler, S Puget, D Castel, N Boddaert, A Tauziède-Espariat, et al., Diagnostics of pediatric supratentorial RELA ependymomas: integration of information from histopathology, genetics, DNA methylation and imaging, Brain Pathol 29 (3) (2019) 325–335. [64] F Andreiuolo, P Varlet, A Tauziède-Espariat, ST Jünger, E Dörner, V Dreschmann, et al., Childhood supratentorial ependymomas with YAP1-MAMLD1 fusion: an entity with characteristic clinical, radiological, cytogenetic and histopathological features, Brain Pathol 29 (2) (2019) 205–216. [65] K Koral, D Mathis, B Gimi, L Gargan, B Weprin, DC Bowers, et al., Common pediatric cerebellar tumors: correlation between cell densities and apparent diffusion coefficient metrics, Radiology 268 (2) (2013) 532–537. [66] K Koral, S Zhang, L Gargan, W Moore, B Garvey, M Fiesta, et al., Diffusion MRI improves the accuracy of preoperative diagnosis of common pediatric cerebellar tumors among reviewers with different experience levels, Am J Neuroradiol 34 (12) (2013) 2360– 2365. [67] JL Jaremko, LB.O Jans, LT Coleman, MR Ditchfield, Value and limitations of diffusion-weighted imaging in grading and diagnosis of pediatric posterior fossa tumors, Am J Neuroradiol 31 (9) (2010) 1613–1616, [Internet] [cited 2020 Feb 9]. Available from. http://www.ncbi.nlm.nih.gov/pubmed/20538820. [68] I Blümcke, OD Wiestler, Gangliogliomas: an intriguing tumor entity associated with focal epilepsies, J Neuropathol Exp Neurol 61 (7) (2002) 575–584, [Internet] [cited 2020 Dec 22]. Available from. https://academic.oup.com/jnen/article-lookup/doi/10.1093/ jnen/61.7.575. [69] HC Ulutin, Ö Öngürü, Y Pak, Postoperative radiotherapy for ganglioglioma; report of three cases and review of the literature, Minim Invasive Neurosurg 45 (4) (2002) 224–227, [Internet] [cited 2020 Dec 22]. Available from. http://www.thiemeconnect.de/DOI/DOI?10.1055/s-2002-36202. [70] X Chen, C Pan, P Zhang, C Xu, Y Sun, H Yu, et al., BRAF V600E mutation is a significant prognosticator of the tumour regrowth rate in brainstem gangliogliomas, J Clin Neurosci 46 (2017) 50–57. [71] G Riesberg, G Bathla, S Gupta, P Watal, T Moritani, Malignant transformation and leptomeningeal spread of recurrent
ganglioglioma: case report and review of literature, Clin Imaging 48 (2018) 7–11, [Internet] [cited 2021 Feb 27]. Available from. http://www.clinicalimaging.org/article/S0899707117301778/fulltext . [72] X Li, L Guo, S Sheng, Y Xu, L Ma, X Xiao, et al., Diagnostic value of six MRI features for central neurocytoma, Eur Radiol 28 (10) (2018) 4306–4313, [Internet] [cited 2021 Feb 23], doi. 10.1007/s00330-018-5442. [73] GF Yang, SY Wu, LJ Zhang, GM Lu, W Tian, K Shah, Imaging findings of extraventricular neurocytoma: report of 3 cases and review of the literature, Am J Neuroradiol 30 (3) (2009) 581–585, [Internet] [cited 2021 Feb 23]. Available from: /pmc/articles/PMC7051427/. [74] P Tortori-Donati, MP Fondelli, A Rossi, A Cama, M Brisigotti, G Pellicanò, Extraventricular neurocytoma with ganglionic differentiation associated with complex partial seizures, Am J Neuroradiol 20 (4) (1999) 724–727, [Internet] [cited 2021 Feb 23]. Available from: /pmc/articles/PMC7056012/. [75] N Yadav, S Rao, J Saini, C Prasad, A Mahadevan, N Sadashiva, Papillary glioneuronal tumors: a radiopathologic correlation, Eur J Radiol 97 (2017) 44–52, [Internet] [cited 2021 Feb 24]. Available from. https://pubmed.ncbi.nlm.nih.gov/29153366/. [76] H Xiao, L Ma, X Lou, Q Gui, Papillary glioneuronal tumor: radiological evidence of a newly established tumor entity, J Neuroimaging 21 (3) (2011) 297–302, [Internet] [cited 2021 Feb 27]. Available from. http://doi.wiley.com/10.1111/j.15526569.2010.00478.x. [77] G Medhi, C Prasad, J Saini, H Pendharkar, MD Bhat, P Pandey, et al., Imaging features of rosette-forming glioneuronal tumours (RGNTs): a series of seven cases, Eur Radiol 26 (1) (2016) 262– 270, [Internet] [cited 2021 Feb 24]. Available from. https://linkspringer-com.ezproxy.med.ucf.edu/article/10.1007/s00330-0153808-y. [78] L Gao, F Han, Y Jin, J Xiong, Y Lv, Z Yao, et al., Imaging features of rosette-forming glioneuronal tumours, Clin Radiol 73 (3) (2018) 275–282. [79] B Tamrazi, M Nelson, S Blüml, Pineal region masses in pediatric patients, Neuroimaging Clin N Am 27 (1) (2017) 85–97, [Internet], doi. 10.1016/j.nic.2016.08.002. [80] CC Wu, WY Guo, FC Chang, CB Luo, HJ Lee, YW Chen, et al., MRI features of pediatric intracranial germ cell tumor subtypes, J Neurooncol 134 (1) (2017) 221–230.
[81] P Galluzzi, MC de Jong, S Sirin, P Maeder, P Piu, A Cerase, et al., MRI-based assessment of the pineal gland in a large population of children aged 0–5 years and comparison with pineoblastoma: part I, the solid gland, Neuroradiology 58 (7) (2016) 705–712. [82] AF Choudhri, MT Whitehead, A Siddiqui, P Klimo, FA Boop, Diffusion characteristics of pediatric pineal tumors, Neuroradiol J 28 (2) (2015) 209–216. [83] S Sirin, MC de Jong, P Galluzzi, P Maeder, HJ Brisse, JA Castelijns, et al., MRI-based assessment of the pineal gland in a large population of children aged 0–5 years and comparison with pineoblastoma: part II, the cystic gland, Neuroradiology 58 (7) (2016) 713–721, [Internet] [cited 2020 Nov 9]. Available from. https://pubmed.ncbi.nlm.nih.gov/27130617/. [84] V Dangouloff-Ros, D Grevent, M Pagès, T Blauwblomme, R Calmon, C Elie, et al., Choroid plexus neoplasms: toward a distinction between carcinoma and papilloma using arterial spinlabeling, Am J Neuroradiol 36 (9) (2015) 1786–1790, [Internet] [cited 2020 Nov 8]. Available from. https://pubmed.ncbi.nlm.nih.gov/26021621/. [85] M Tenenbaum, Extraparenchymal lesions in pediatric patients, Neuroimaging Clin N Am 27 (1) (2017) 123–134. [86] AB Smith, JG Smirniotopoulos, I Horkanyne-Szakaly, From the radiologic pathology archives: intraventricular neoplasms: radiologic-pathologic correlation, Radiographics 33 (1) (2013) 21– 43, [Internet] [cited 2020 Nov 9]. Available from. https://pubmed.ncbi.nlm.nih.gov/23322825/. [87] KV Shekdar, ES Schwartz, Brain tumors in the neonate, Neuroimaging Clin N Am 27 (1) (2017) 69–83, [Internet], doi. 10.1016/j.nic.2016.09.001. [88] YZ Shi, ZQ Wang, YM Xu, YF Lin, MR findings of primary choroid plexus papilloma of the cerebellopontine angle: report of three cases and literature reviews, Clin Neuroradiol 24 (3) (2014) 263–267, [Internet] [cited 2020 Nov 9]. Available from. https://pubmed.ncbi.nlm.nih.gov/23736865/. [89] T Sasaki, J Kim, T Moritani, AA Capizzano, SP Sato, Y Sato, et al., Roles of the apparent diffusion coefficient and tumor volume in predicting tumor grade in patients with choroid plexus tumors, Neuroradiology 60 (5) (2018) 479–486, [Internet] [cited 2020 Nov 9]. Available from. https://pubmed.ncbi.nlm.nih.gov/29546484/. [90] RW.R Dudley, MR Torok, S Randall, B Béland, MH Handler, JM Mulcahy-Levy, et al., Pediatric versus adult meningioma: comparison of epidemiology, treatments, and outcomes using the
Surveillance, Epidemiology, and End Results database, J Neurooncol 137 (3) (2018) 621–629, [Internet] [cited 2021 Jan 29]. Available from. https://pubmed.ncbi.nlm.nih.gov/29520612/. [91] A Toland, SN McNulty, M Pekmezci, M Evenson, K Huntoon, CR Pierson, et al., Pediatric meningioma: a clinicopathologic and molecular study with potential grading implications, Brain Pathol 30 (6) (2020) 1134–1143, [Internet] [cited 2021 Jan 29]. Available from. https://pubmed.ncbi.nlm.nih.gov/32716568/. [92] T Tihan, Schwannoma, Atlas of Pediatric Brain Tumors [Internet], Springer, New York, 2010, 145–152, [cited 2021 Feb 1]. Available from. https://link.springer.com/chapter/10.1007/978-14419-1062-2_13. [93] VB Pothula, T Lesser, C Mallucci, P May, P Foy, Vestibular schwannomas in children, Otol Neurotol 22 (6) (2001) 903–907, [Internet] [cited 2021 Feb 1]. Available from. https://pubmed.ncbi.nlm.nih.gov/11698816/. [94] JW Schroeder, LG Vezina, Pediatric sellar and suprasellar lesions [Internet], Pediatr Radiol 41 (2011) 287–298, [cited 2020 Nov 10]. Available from. https://pubmed.ncbi.nlm.nih.gov/21267556/. [95] BY Huang, M Castillo, Nonadenomatous tumors of the pituitary and sella turcica, Top Magn Reson Imaging 16 (4) (2005) 289–299. [96] PR Chapman, A Singhal, S Gaddamanugu, V Prattipati, Neuroimaging of the pituitary gland: practical anatomy and pathology, Radiol Clin North Am [Internet] 58 (6) (2020) 1115– 1133, doi. 10.1016/j.rcl.2020.07.009. [97] F Bonneville, F Cattin, K Marsot-Dupuch, D Dormant, JF Bonneville, J Chiras, T1 signal hyperintensity in the sellar region: spectrum of findings, Radiographics 26 (1) (2006) 93–113, [Internet] [cited 2020 Nov 10]. Available from. www.rsna.org/rsnarights. [98] R Sigal, A Denys, P Halimi, L Shapiro, D Doyon, F Boudghene, Ventriculus terminalis of the conus medullaris: MR imaging in four patients with congenital dilatation, AJNR Am J Neuroradiol 12 (1991) 733–737. [99] S Borofsky, LM Levy, Neurofibromatosis: types 1 and 2, AJNR Am J Neuroradiol 34 (12) (2013) 2250–2251. [100] JG Smirniotopoulos, FM Murphy, The phakomatoses, AJNR Am J Neuroradiol 13 (2) (1992) 725–746.
CHAPTER 81
Pediatric Head and Neck Sanjay Vaid, Bhawan Paunipagar
Introduction The aim of this chapter is to provide an overview of the various head and neck pathologies that the radiographers and trainee radiologists would have to deal with in the pediatric population. The head and neck is a challenging region of the body to image due to its very heterogeneous contents and actively changing geometric shape. It is also prone to a range of artifacts leading to suboptimal image quality. A prudent choice of the right imaging technique, region-specific protocols, and appropriate use of contrast medium is vital in pediatric head and neck imaging to address the clinical condition definitively. Children of different age groups need varying agespecific techniques to ensure they co-operate for any radiological investigation from a simple plain radiograph/video fluoroscopy to a more advanced imaging like magnetic resonance imaging (MRI) or an interventional radiology procedure. These issues can be solved by effective distraction of the child, making the radiology suite child friendly, adequate but safe immobilization and sedation/short-acting anesthesia as a last resort (Box 81.1) [1]. Box 81.1
Key Safety Concerns Radiation Safety
◾ prone Children are more sensitive to the harmful effects of radiation, especially those more to DNA damage and who are likely to have repeated examinations over an extended period. ◾ possible. Use of a technique that does not involve radiation should be considered first as far as ◾ involving The ALARA (as low as reasonably achievable) principle should guide all studies radiation to achieve images of diagnostic (and not superlative) quality in children using dedicated pediatric protocols, radiation protection devices, and supervising studies to avoid unnecessary repeat scans.
Contrast Medium
◾tolerability. Choice of the appropriate contrast agent based on its safety, efficacy, and ◾compared Adverse/allergic reactions to intravenous contrast medium rare in children with adults, with similar manifestations and if occur should be treated as such. ◾candidate Child with abnormal renal function still to be considered as a potential high-risk for development of contrast-induced nephropathy/nephrogenic systemic fibrosis following intravenous contrast administration [4].
Sedation
◾associations Mandatory sedation program in concordance with approved guidelines set by like the American Academy of Pediatrics. The sedation program must have presedation protocols, use approved sedative agents, adequate monitoring devices, and a specific postsedation recovery/discharge checklist [3]. Essential to have MRI compatible emergency equipment available within the gantry room and trained expert staff to handle any adverse event. Use of safe and modern sedative/short-acting anesthetic agents.
◾ ◾
MRI Safety
◾examinations Most present-day otologic implants are MR compatible, however MRI of children with cochlear implants, cardiac pacemakers, nerve stimulators, or any other ferromagnetic implants/metallic foreign bodies should be undertaken after detailed assessment and background of the surgery and type of implant used [5]. Older versions of implants can malfunction, cause pain and physical damage to surrounding structures due to excessive heating/torque generation and nerve stimulation. Higher risk of radiofrequency heating effects due to poorly developed thermoregulatory mechanisms in children, high basal temperatures, and relatively higher surface area to weight ratio.
◾ ◾
Multiple age-related factors such as weight of the child and cardiac output play an essential role in determining the dose (as most dosages are related to weight), rate, and technique of infusion of the contrast medium and can also impact technical imaging factors such as the scan coverage, slice thickness, kVp, and mAs. The radiologist also needs to be aware of the changes within normal anatomical structures in a growing child. A specific set of differential diagnoses exists for different age groups within the pediatric population. A similar imaging finding may have a completely different diagnosis in the child and the adult [2].
Imaging Techniques and Protocols The techniques available for imaging include, computed and digital plain radiography and video fluoroscopy; ultrasonography (USG) and Doppler; multidetector computed tomography (MDCT); Cone beam computed tomography (CBCT)); MRI; nuclear medicine/positron emission tomography–computed tomography (PET-CT); digital subtraction angiography (DSA); and interventional radiology [1,2] (Table 81.1). Table 81.1 Imaging Modalities for Pediatric Head and Neck N Technique o .
Technique of Choice and Advantages
Disadvantages
Remarks
N Technique o .
Technique of Choice and Advantages
Disadvantages
Remarks
1 .
Conventio nal radiograph y and video fluoroscop y
Acute airway obstructive pathologies, foreign body, cervical spine assessment Video fluoroscopy: dynamic assessment of airway in OSAS Barium esophagogram: foreign body, vascular slings and webs/penetrating trauma of oropharynx, swallowing disorders Intra/postoperative confirmation of cochlear implant. Adv: Availability, quick overview of required anatomy (especially in trauma setting)
No information about soft tissues Prone to misinterpretation errors due to positioning and respiratory motion, crying and swallowing Most commonly detected foreign bodies are nonradiopaque
Lateral neck radiograph of the neck in upright position with neck in extension Avoid overcalling artifactual increased retropharyngeal soft-tissue thickness Be well versed with normal appearances and positions of implants
2 .
Ultrasonog raphy (USG) and Doppler
Technique of choice for pediatric extracranial head and neck masses Color Doppler for vascularity within and surrounding the lesion Adv: Ready availability, avoidance of ionizing radiation and sedation. Can be performed at bedside. Real-time assessment of IJV phlebectasia/laryng oceles possible. Repeat studies possible
Cannot assess deeper structures or deep extension of pathologies making cross-sectional imaging necessary Not useful in skull base/retropharyngeal/ph aryngeal mucosal space lesions
Examination in supine position with extended neck High-frequency linear array probes (12–5, 17–5 MHz) for superficial structures Curvilinear transducer for larger lesions and a “hockey stick” (17–5 io MHz) linear probe for very small superficial lesions
N Technique o .
Technique of Choice and Advantages
Disadvantages
Remarks
3 .
Multidetec tor computed tomograph y (MDCT)
First technique of choice in acute infections with suspected deep/trans-spatial spread, trauma with fractures, and vascular/penetrating injuries Adv: Highresolution, rapid multiplanar examination of the entire neck. Excellent assessment of bony/air-filled structures (paranasal sinuses/temporal bone/skull base) and accurate depiction of calcification, hemorrhage or fat within a lesion
High radiation dose especially where repeat examinations needed Adverse effects of sedation (if required) and contrast administration May not accurately differentiate necrotic phlegmonous collections from drainable abscess fluid
Adhere to ALARA (as low as reasonably achievable) principle using dedicated pediatric CT protocols Supine scanning with the neck in the neutral/mildly hyperextended position Scan range: top of the sphenoid sinus to the sternoclavicular joints
4 .
Cone beam computed tomograph y (CBCT)
Different beam geometry and processing from MDCT Adv: Less irradiation (up to 30% less) than MDCT. High isotropic spatial resolution: temporal bone, paranasal sinuses and faciomaxillary region. Less susceptible to metal artifacts
Earlier scanners could not scan children in supine position Poor contrast resolution resulting in suboptimal examination of larger, high volume soft-tissue regions like neck and body
Scanners can be incorporated into clinics/office settings as they require less space and powe requirements New generation CBCT models can scan in complete supine position
N Technique o .
Technique of Choice and Advantages
Disadvantages
Remarks
5 .
Head and neck masses, temporal bone, skull base, paranasal sinuses, orbits, TM joints and sleep disorders Intracranial extension of neck disease/perineural and perivascular spread/extra nodal extension in metastatic cervical lymphadenopathy of head neck malignancies Adv: Superior contrast resolution, noncontrast angiographic techniques, and lack of ionizing radiation with capability of dynamic imaging for functional evaluation of the airway and TM joints. Biomarker imaging capabilities in head neck oncology
Limited availability of high field strength MR scanners, pediatric coils Longer scan times and high susceptibility to motion-related artifacts makes sedation/anesthesia necessary in certain age groups Expensive especially if repeat examinations needed
Use surface coils to increase resolution Dedicated sedation program Customize sequences to specific regions, fat suppressed postcontrast acquisitions/CI SS/SS non-EPI TSE DWI provide valuable information
Magnetic resonance imaging (MRI) [6]
N Technique o .
Technique of Choice and Advantages
Disadvantages
Remarks
6 .
Nuclear medicine/p ositron emission tomograph ycomputed tomograph y (PETCT) [7]
Technetium-99m pertechnetate used in thyroid and parathyroid pathologies PET-CT used for staging, therapy planning and follow-up of pediatric malignancies
High radiation dose Need for sedation/anesthesia PET-CT is not readily available and is an expensive investigation Technically challenging due to smaller body mass, dosimetric restrictions, and physiological factors that can affect the FDG uptake
Brown adipose tissue (brown fat) can have intense FDG activity difficult to distinguish from cervical/supracl avicular nodesUse of an anxiolytic agent and keeping the child warm in winters before the examination can reduce FDG activity in brown fat SUV based on body surface area should be considered in pediatric patients (more uniform parameter than SUV based on body weight)
7 .
Digital subtraction angiograp hy (DSA) and interventio nal radiology (IR) [8]
Preoperative vascular mapping and embolization: Juvenile nasopharyngeal angiofibroma, vascular malformations, and tumors IR procedures: image-guided biopsies and drainage of abscesses/collectio ns/cysts, providing image-guided vascular access
Significant radiation dose Need for sedation Invasive procedure
Consider an alternative noninvasive technique like MRI with Dynamic Contrast Imaging Pediatric IR requires a multidisciplinar y approach with capability of treating complications
Adv, Advantage.
Irrespective of the imaging techniques available at any given time, the choice of a particular technique and the protocols used depends on the clinical presentation, the availability of safe sedation and the technique best suited to answer the clinical questions in the shortest possible time. USG, CT, and MRI provide the mainstay of imaging head and neck pathologies in children. USG is particularly useful in examining superficial structures whereas CT and MRI are helpful to evaluate deeper lesions [1,2].
Pediatric Skull Base Radiologists should be aware of the rapid developmental changes that occur in the pediatric skull base as these changes impact therapy planning and surgical approaches for many pathologies [9] (Box 81.2). A combination of a contrast-enhanced MRI and a limited bone HRCT is ideal for lesion characterization, differential diagnosis, and presurgical planning (Table 81.2). Additionally, DSA may be useful for preoperative embolization of hypervascular lesions, and PET/CT for treatment response and surveillance in malignancies and lymphoma. Box 81.2
Pediatric Skull Base Imaging Issues Key differences between pediatric and adult skull base lesions [9,10]:
◾ Rarer than in adults ◾ Benign pathologies more common (developmental/vascular) than malignancies ◾ Mesenchymal pathologies (benign: nerve sheath tumors and juvenile nasopharyngeal angiofibroma, and malignant: sarcomas) more common than epithelial lesions ◾ Located more in the central skull base as against anterior skull base in adults ◾ Better post-treatment outcomes than in adults due to benign nature and plasticity of the maturing nervous system
Avoiding the imaging pitfalls:
1. Small unossified gaps in the anterior skull base on CT in children under 3 years of age are normal (Fig. 81.1). 2. Fossa navicularis magna: notch-like defect in the midline basiocciput. 3. Prominent arachnoid granulations common in the greater wing of the sphenoid bone. 4. Ecchordosis physaliphora: notochordal remnant extending exophytically from the dorsal aspect of clivus.
5. Unossified/large foramen cecum. 6. Synchondrosis between anterior and posterior ossification centers of the sphenoid can sometimes be mistaken for Rathke’s pouch and canal. 7. Red marrow in the medullary cavity of the pediatric skull base exhibits a uniformly low T1W signal intensity/heterogeneous appearance till adolescence and should not be interpreted as an abnormal marrow infiltrative process.
Table 81.2 Imaging-Based Classification of Pediatric Skull Base Lesions [10,11] Neck and Sinus Lesions Extending Superiorly (From Below Upward)
Lymphoma Lymphomas most commonly present between the ages of 2 and 19 years. The lesions are characteristically hyperdense on CT and avidly enhance with contrast. They are associated with permeative bone destruction with relatively preserved bony trabeculation without chondroid or osteoid matrix formation. On MR, they are isointense on T1W and T2W isointense and enhance with contrast. Lymphomas typically have increase DWI signal and have restricted ADC suggesting high cellularity of the tumor (Fig. 81.2). The differential diagnosis includes rhabdomyosarcoma (RMS), primitive neuroectodermal tumor, Ewing’s sarcoma, neuroblastoma (NB), and metastatic Wilms’ tumor. Extensive homogeneous abnormal cervical lymphadenopathy suggests lymphoma.
FIGURE 81.1 Coronal (A) and midline sagittal (B) CT images of a 2-month-old infant depicting normal unossified gaps in the anterior skull base (arrows).
FIGURE 81.2 Lymphoma. Axial T1W (A) and axial T2W (B) images showing a large lobulated central skull base mass (M) with typical low T2W signal intensity characteristic of a hypercellular neoplasm. Axial (C) and coronal (D) postcontrast images show homogenous enhancement. Destruction of central skull base bony structures, sphenoid sinus, pituitary fossa, and left petrous apex is seen (oblique arrows) with encasement of cavernous/supraclinoid segment of the left internal carotid artery (horizontal arrows) and left intraorbital extension (block arrows).
Pearls: Non-Hodgkin lymphoma is more common than Hodgkin lymphoma in pediatric skull base and is seen in immunosuppressed children [10,12]. An aggressive form of NHL, T-cell
lymphoma has a high association of Epstein–Barr virus (EBV). It can exhibit necrosis, extranodal extension and can present with naso/oropharyngeal ulcers. Burkitt lymphoma is a type of non-Hodgkin B-cell lymphoma seen specifically in children (9–12 years) [10]. Two distinct entities are known:
◾ patients The “endemic” form usually presents in younger children in equatorial Africa, with positive serology for EBV characteristically present with an enlarging facial mass originating from the maxilla and involving the paranasal sinuses/palate. ◾ theThesporadic “sporadic” type occurs in older children with abdominal masses. Facial involvement is relatively uncommon in form (25%) [10,12]
Sarcomas Sarcomas are the most common head neck malignancies in children with >50% involving the skull base [10,12]. RMSs are histologically classified into four types:
The embryonal RMS is the most common subtype in the skull base region [10,12]. More than 50% of pediatric cases of RMS occur in children 50% are below 4 years of age). It occurs subsequent to ethmoid sinusitis, orbital trauma, or obstructed nasolacrimal duct. Classified as periorbital (preseptal location) and orbital (postseptal location) cellulitis. Preseptal cellulitis presents with edematous eyelid, inflamed lacrimal apparatus, and ocular adnexa. CT shows discontinuity in lamina papyracea, enhancement of periorbital tissues, intraorbital fat stranding, and identifies subperiosteal abscess (SPA) (Fig. 81.14). Contrast-
enhanced MRI helps evaluate the extent of the SPA, intracranial complications, cavernous sinus involvement which are facilitated by the valveless ethmoidal veins which facilitate spread of ethmoid infection through the thin lamina papyracea leading to orbital cellulitis, SPA formation and superior ophthalmic vein thrombosis. Thrombophlebitis of superior ophthalmic vein is a common complication and can lead to cavernous sinus thrombosis [19]. This can be associated with reactive inflammation of extraocular muscles (EOMs) leading to limited eye movements and lateral displacement of the medial rectus muscle. If untreated this can lead to severe acute to subacute proptosis and decreased vision. CECT and CE-MRI can also help in guiding drainage of SPA.
FIGURE 81.14 Orbital cellulitis with SPA. Axial (A) and coronal (B and C) images of the orbit show inflammatory changes in left ethmoid sinus and left orbit with a thin lenticularshaped subperiosteal abscess (white arrows). Coronal CT image (D) in bone windows shows breach in the left lamina papyracea (black arrows) allowing spread of infection into the orbit (postseptal orbital cellulitis).
Chandler Classification of Orbital Cellulitis I. Preseptal cellulitis: Inflammation anterior to orbital septum with eyelid edema, nontender, visual loss, or impaired EOM motility (ophthalmoplegia) II. Orbital cellulitis without abscess: diffuse postseptal edema of orbital fat III. Orbital cellulitis with SPA: Proptosis, impaired vision, or limited EOM motility IV. Orbital cellulitis with intraorbital abscess: Usually severe proptosis, reduced vision, and limited EOM motility V. Cavernous sinus thrombosis secondary to orbital phlebitis: Bilateral or unilateral
Differential diagnosis: Inflammatory pseudotumor, orbital neoplasm.
Inflammatory Pseudotumor
Uncommon inflammatory process in pediatric population (about 7–16%) arises from an idiopathic nongranulomatous inflammatory process with variable degree of fibrosis and infiltration of lymphocytic cells mostly involving lacrimal gland and EOM. CECT or CE MRI reveals homogenous contrast enhancement of the involved intra/extraconal soft tissues and the EOM [20].
Acute Proptosis Causes of acute proptosis include trauma, infection (periorbital and postseptal cellulitis), vascular malformations, and neoplasms (Fig. 81.15). Neurofibromatosis II, retinoblastomas, and acute lymphoblastic leukemia may also cause unilateral or bilateral acute proptosis in children [21]. Contrast-enhanced CT and MRI helps to assess the degree and extent of inflammation, abscess formation, the involvement of the intra/extraconal structures, compressive effect on structures in optic canal and ophthalmic fissures as well as presence of any intracranial vascular complications.
FIGURE 81.15 Spectrum of pathologies causing acute proptosis. Lymphatic malformation: Axial T2W FS (A and B) a 10-year-old girl with subacute to acute proptosis show a multiseptated retro-orbital intraconal lesion with fluid–fluid levels due to Hb breakdown products (FFL). Neurofibromatosis II: Axial CECT (C) of the orbit reveals mildly enhancing infiltrative plexiform neurofibroma on the right side (arrows). Insinuating around the structures of the superior orbit and into the temporal soft tissues. Acute myeloid leukemia (Type M3): Axial T2W (E) and contrast-enhanced image T1W FS (D, F) show smooth, homogenous T2W hypointense enhancing lesions in the intraconal and extraconal compartments of both orbits (arrows) due to acute infiltration caused by the myeloid tissue. (Courtesy: Dr. Anand Rahalkar, Pune India.)
Orbital Neoplasms and Other Masses Orbital tumors in the pediatric age group are mostly benign in nature, however, intraorbital masses need immediate attention to avoid irreversible deterioration in vision. Dermoid Cysts and Epidermoid Inclusion Cysts Dermoid Cysts (DCs) present mainly along embryonic fusion lines and consist of epitheliumlined cavities filled with skin appendage elements such as hair, fat, and sebaceous glands. Epidermoid cysts (ECs) consist of epithelial elements only and present as a cystic fluid-filled mass. ECs are slow growing, painless orbital lesions along frontozygomatic suture. Presentation depends on the location and vector of growth (outward or inward). These are soft fluctuant
masses, generally not affecting vision, but may hinder the EOM movement. EC and DC are most commonly situated in the orbit (50%), however also occur in the floor of mouth (23%), neck (14%), and nose (13%), anterior midline neck, submandibular space, and sinonasal region. Imaging Features: USG identifies the echo pattern and intrinsic vascularity of superficial DC (Fig. 81.16). CT demonstrates any sudden increase in the size, fat content, calcification, bony changes. EC shows uniform echogenicity with midlevel internal echoes and posterior acoustic enhancement if cystic. DCs show a more complex appearance due to associated lipomatous and calcific components. Cross-sectional imaging shows that DC to have heterogenous intensity due to the presence of fat and/or calcification). EC appear as hypodense lesions with predominantly cystic appearance. EC show diffusion restriction on MRI, and both lesions may show minimal peripheral marginal enhancement. These lesions may remodel the adjacent bony structures. Contrast-enhanced MRI is useful to identify intracranial extension and rare complications which may include meningitis or abscess.
FIGURE 81.16 Dermoid cyst. Transverse ultrasound Doppler image (A) at the level of the superomedial aspect of the orbit of a 5-year-old, showing a cystic mass lesion (C) with midlevel internal echoes and absent internal vascularity. Sagittal (B) and axial (C) CT images of the orbit reveal the extraconal fat-containing dermoid cyst (DC) with mass effect on the globe. Note smooth scalloping and remodeling of the orbit roof (arrows). Epidermoid cyst. Axial T2W FS (D) and T1W (E) images show a well-defined ovoid mass lesion (EC) in the superior and lateral aspect of the right orbit, in relation to the frontozygomatic suture of the right orbit. (Images of epidermoid cyst courtesy: Dr. Foram Gala, Mumbai, India.)
Intraocular Neoplasms Retinoblastoma (RB) is the most common intraocular neoplasm below 3 years of age. They are unilateral in 60% and bilateral in 40% of cases [22]. Retinoblastoma may be familial and may present earlier. RB may be bilateral or, “trilateral” (additional primary midline pineal tumor), and “quadrilateral” (second midline or paramidline sellar/parasellar tumor) variants due to embryogenic neuroectodermal origin. Nonfamilial cases usually present later and are often unilateral. White eye (leukocoria) is the most striking clinical sign for diagnosing retinoblastoma, associated with decreased vision, proptosis, and redness. Ultrasounds shows a posterior chamber lobulated calcified masses, heterogeneous in echo pattern, exhibiting
posterior acoustic shadowing. Diffuse retinal thickening and micronodules are better visualized on USG. CECT and CE MRI show calcified intraocular masses, usually bilateral, in posterior chamber of the eyeball with variable degree of tumor calcification and moderately enhancing noncalcified tumors (Figs. 81.17 and 81.18). MRI is superior to CT for assessment of accompanying retinal detachment, optic nerve involvement as well as trilateral/quadrilateral pattern of disease. DW imaging reveals restriction due to cellular nature of this neoplasm.
FIGURE 81.17 Retinoblastoma. Axial noncontrast CT image (A) shows a densely calcified intraocular mass in the center of the posterior chamber (arrows) indicating endophytic growth pattern of the retinoblastoma. Transverse ultrasound image of the orbit (B) demonstrates a polypoidal mass lesion in the posterior chamber (arrows) with irregular eccentric calcification. Axial noncontrast CT (C) shows bilateral intraocular retinoblastomas (R) in a 14-month-old child. Note the crumpled involuted globes on both sides with depletion of the vitreous material. On the left side the nodular partly calcified lesion tends to breach the posterior limits of the globe to encroach into the retrobulbar region along the course of the optic nerve (arrows). (CT image of bilateral retinoblastomas courtesy: Dr. Foram Gala, Mumbai, India.)
FIGURE 81.18 Retinoblastoma. Clinical photograph (B) of a 19-month-old girl child with an exophytic pattern of retinoblastoma involving the preseptal soft tissues of the right eye. Grayscale (A) and color Doppler (C) ultrasound of the same patient shows the aggressive, infiltrative nature of the solid tumor (R) distorting the morphology of the globe. Axial and coronal CT images (D, E) reveal significant intra- and extra-orbital spread of the tumor (R).
Extraocular Neoplasms Orbital NB metastases are often the only manifestation of the disease in patients below 2 years of age [23]. Tumor hemorrhage and ecchymosis result in acute proptosis in 8% of NB patients. CT reveals ill-defined hyperdense lesions along the posterolateral orbital wall with epidural neoplastic deposits that widen adjacent orbital sutures (Fig. 81.19). On MRI, NB deposits exhibit low T1W and inhomogeneous T2W signal intensity due to subtle intralesional hemorrhages or tissue necrosis. Contrast study reveals hypervascular lesions with nonenhancing foci due to intralesional hemorrhages. MIBG scans and PET-CT are useful in staging and disease monitoring.
FIGURE 81.19 Metastatic neuroblastoma. Axial CECT image (A), bone window algorithm (B) shows classical permeative destruction with periosteal new bone formation (arrows) involving the left sphenoid bone and the cribriform plate. Note the encroachment into the contralateral orbit (black arrow). Axial T1W FS+C image (C) of the orbits shows large associated enhancing mass adjacent to the bone involvement (M) with resultant left side exophthalmos. Coronal T1W FSC image (D) shows the craniocaudal extension of the osseous metastatic deposit (M) with extensive calvarial deposits (arrows). (Courtesy: Department of Radiodiagnosis, BVMC, Pune, India.)
Lacrimal Gland Nasolacrimal Duct Mucocele These can present as unilateral or bilateral, well-defined cystic masses along the medial can thus, due to obstruction of the distal duct by the Hasner membrane. The swelling usually presents very early (3–4 days after birth) and may undergo inflammation with cellulitis (dacryocystitis). CECT shows a thin imperceptible wall of nonenhancing cystic lesion unless infected. Chronic lesions scallop or remodel the bony margins. MRI can help differentiate the T2W hyperintense mucoceles from proximally situated lacrimal sacs.
Dacryocystitis Obstruction to normal drainage of secretions from the lacrimal gland results in dacryocystocele formation. A superimposed infection is termed dacryocystitis with exacerbation of clinical symptoms. USG may reveal intracystic debris with perilesional vascularity. CT and MRI
demonstrate heterogenous appearance with peripheral enhancement in the case of abscess formation.
Pediatric Neck Masses (Box 81.4) Box 81.4
Approach to a Pediatric Neck Mass
◾ History: present at birth, accompanying pain/fever, any change in size over time. ◾ Examination: location, fixed/mobile, compressibility, texture (smooth or irregular), associated tenderness, raised temperature or erythema. ◾ USG and Doppler: initial technique of choice except in airway/infection-related emergencies. ◾ CT/MRI: in emergent situations/large mass with deep space extension/if the mass exhibits suspicious features for malignancy.
Diagrammatic representation of the location of commonly encountered head, neck, and face lesions in the pediatric age group (Fig. 81.20).
FIGURE 81.20 Diagrammatic representation of the location of commonly encountered head, neck, and face lesions in the pediatric age group. TGDC, thyroglossal duct cyst.
FIGURE 81.21 First BCA: STIR axial (A and B) and coronal (C) images show tubular hyperintense structure coursing parallel to the left external auditory canal (small green arrows) representing sinus tract of Work type I first BCA within the preauricular soft tissues. Postcontrast FS axial (D and E) and coronal (F) images show peripherally enhancing lesion in the right periparotid soft tissues (arrows) representing infected Work type II first BCA.
FIGURE 81.22 Second BCA: Postcontrast axial (A), coronal (B), and sagittal (C) CT images show well-defined nonenhancing cystic lesion (arrows) in the infrahyoid neck on the right side inferior to the right submandibular gland (SMG) and anterior to the right sternocleidomastoid muscle (SCM) representing Bailey’s type II second BCA.
FIGURE 81.23 Third BCA: STIR axial (A) and coronal (C) images show well-defined tubular cystic hyperintense lesion (c) in the left posterior cervical space with thin marginal rim enhancement on postcontrast FS axial (B) and coronal (D) images (arrows).
FIGURE 81.24 Fourth BCA: Transverse grayscale (A) image of the neck demonstrates irregular margins of left thyroid lobe with peripherally located hypoechoic lesions (arrows) representing focal thyroiditis. A large heterogenous mixed echoic complex lesion is seen abutting the left lobe (A) with scattered peripheral increased vascularity (arrows) on color Doppler (B). Postcontrast axial (C) and coronal (D) CT images show large well-defined enhancing lesion with focal areas of liquefaction (A) representing an abscess formation.
FIGURE 81.25 Thyroglossal duct cyst (TDC): T1W axial (A), STIR axial (B), and STIR sagittal (C, D) images show a well-defined oval-shaped infrahyoid cystic lesion (TDC) embedded in the left strap muscles with focal extension into the posterior hyoid space (white arrow in D). High T1W signal represents increased proteinaceous content of the fluid and green arrows in C show contained fluid level.
Masses of Developmental Origin in Children Common developmental masses in children include branchial cleft anomalies, thyroglossal duct cyst, congenital hemangioma, ectopic thyroid, vascular malformations, cervical thymic cyst, dermoid/epidermoid cyst, congenital muscular torticollis, neurenteric cyst, meningocele congenital midline cervical cleft, congenital cervical teratoma, epignathus, congenital benign granular cell tumor (epulis), hairy polyp (rare fat-containing lesion), and congenital goiter [24] (Box 81.5). Box 81.5
Key Features and Imaging Appearances of the Common Masses of Developmental Origin [25] Branchial cleft anomalies (BCA)
Thyroglossal duct cyst (TDC)
Congenital malformations of the branchial apparatus
Most common congenital pediatric neck mass due to failure of involution of the thyroglossal duct
Branchial cleft anomalies (BCA)
Thyroglossal duct cyst (TDC)
(branchial arches, pharyngeal pouches, branchial grooves/membranes). Labeled as first, second, third, and fourth arch anomalies according to the pouch or cleft of origin and can present as fistulas, sinuses, and cysts. Imaging: 1. First BCAs (Fig. 81.21): Can be cysts or sinuses and the location depends on the subtype: Work type I: periauricular. Work type II: periparotid in location. High index of suspicion in a patient with chronic, unexplained otorrhea or recurrent parotid gland abscesses. Surgery of the anomaly may be complicated in Wok Type II cases due to proximity to Cr Nv VII. 2. Second BCAs (Fig. 81.22): Can be cyst, sinus, or fistula. Typically seen as a cystic neck masses posterolateral to submandibular gland, lateral to carotid space, anterior (or anteromedial) to the sternocleidomastoid muscle. Bailey classification: Type I–IV (Type II: Most common, cystic remnant of cervical sinus of His) based on superficial to deep location from the subplatysmal soft tissues
(which extends from the foramen cecum at the base of the tongue to the pyramidal lobe of the thyroid gland). Location: 50% at the level of the hyoid bone and the remaining 50% in the suprahyoid and infrahyoid region each. Suprahyoid/hyoid TDCs tend to be in the midline while the infrahyoid TDCs are mostly paramedian. The tract can have a small outpouching that hooks inferior and posterior to the hyoid bone. Imaging (Fig. 81.25): Goal: Confirm the presence of normal thyroid/ectopic thyroid tissue before planning surgery. Important to evaluate the posterior hyoid space [26] before surgery for complete resection of the central hyoid bone/abnormal tissue— additional component to the “Modified Sistrunk procedure” (the standard treatment for the TDC). Identify enhancing soft tissue/chunky nodular calcifications which could indicate a papillary carcinoma (seen in less than 1% of cases). Findings: USG: well-marginated hypo-anechoic oval/rounded lesion with posterior enhancement in relation to the hyoid bone in the anterior neck. Internal echoes indicate previous infections/hemorrhage/inspissated material high in protein content. CT/MRI: TDC may show peripheral enhancement after contrast administration if associated inflammation/infection or a high precontrast T1W signal due to high proteinaceous content.
Branchial cleft anomalies (BCA)
Thyroglossal duct cyst (TDC)
to the lateral pharyngeal wall. The second peak in demographics occurs in second or third decade: Consider a cystic metastatic squamous cell carcinoma node as a differential diagnosis in adults. 3. Third BCAs (Fig. 81.23): Can be cyst, sinus or fistula An ovoid/round cystic mass in the upper posterior cervical space/lower anterior neck. Less common in the pediatric age group. High index of suspicion if recurrent abscess in posterior neck. 4. Fourth BCAs (Fig. 81.24): Most are sinus tracts and fistulas coursing from the apex of the pyriform sinus to the upper aspect of the left thyroid lobe. Fourth BCAs will always be located in the left lower neck within or in close proximity to the left thyroid lobe. High index of suspicion if there are recurrent leftsided neck abscesses in children or recurrent focal thyroiditis/suppurative thyroiditis on the left side.
Congenital Muscular Torticollis (Sternocleidomastoid Pseudotumor of Infancy)
A congenital fibrotic process, generally unilateral (more on the right side and seen more in male babies) seen as a sequel to trauma during birth (breech presentation/forceps delivery) due to obstructed venous outflow in the sternocleidomastoid muscle leading to necrosis and fibrosis in the muscle fibers. Ultrasound shows fusiform enlargement and secondary shortening of the sternocleidomastoid muscle leading to torticollis (Fig. 81.26). Echogenicity may vary depending on the presence/absence of calcification. MRI shows a well-defined signal alteration within the normal muscle with increased signal on both T1 weighted and T2 sequences.
FIGURE 81.26 Congenital muscular torticollis. Longitudinal grayscale image of the neck (A) parallel to the longitudinal axis of the sternocleidomastoid muscle reveals diffuse fusiform thickening of the belly of the sternocleidomastoid muscle (CMT). Dynamic ultrasound revealed synchronous movement of the focal thickening with the normal uninvolved muscle fibers. Color Doppler (B) revealed increased intrinsic vascularity with a high resistance waveform (arrows). (Courtesy: Dr. Asif Momin, Mumbai, India.)
Masses of Lymph Nodal Origin in Children (Box 81.6 and Table 81.6) Box 81.6
Key Points 1. Up to 90% of healthy children in the age group of 4–8 years have palpable cervical nodes. 2. Assess the duration of the lymphadenopathy: acute (6 weeks). Acute: likely reactive/infectious causes. Chronic: likely neoplastic or metabolic causes. 3. Indications for imaging: Large, nontender, nonmobile, firm to hard nodes. No response to empirical treatment with antibiotics (4–6 weeks course)/increasing size and number of nodes. Accompanied by systemic symptoms. 4. Technique: USG/Doppler. Other techniques like CT, MRI, and PET-CT may be used depending on the clinical picture, information required for further management, and the appropriateness criteria (ACR).
Table 81.6 Causes of Abnormal Neck Nodes in Children [27]
Storage disorders (amyloido sis, Gaucher’s) Hypersen sitivity to drugs
Lymp homa Leuk emia Meta stase s
Masses of Non-Nodal Origin in Children (Table 81.7) Table 81.7 Classification of Non-Nodal Masses Vascular Pathology
Infections/Inflammatory Pathology
◾ Vascular malformations and hemangiomas ◾ Vasoproliferative disorders (lesions/tumors of vascular origin) ◾ vein phlebectasia ◾ Jugular Lemierre syndrome
◾ Retropharyngeal and other neck space abscesses ◾ Abscesses in the neck secondary to mastoid infections ◾ Langerhans cell histiocytosis ◾ Acute/recurrent parotitis and parotid abscess ◾ Ranula
Vascular Malformations and Hemangiomas
Tumors and Tumor-Like Lesions
◾ Rhabdomyosarcom as and other sarcomas Leukemia and lymphoma
Vascular pathologies must be identified accurately as the diagnosis, further natural progression and management differs significantly in this diverse group of diseases. Vascular malformations differ from vasoproliferative lesions in that they do not exhibit mitosis and endothelial cell turnover and are endothelial cell glucose transporter 1 (GLUT1) isoform protein negative (International Society for the Study of Vascular Anomalies) [28]. Lymphatic Malformation: Lymphatic malformations (LM) are low flow malformations. The older terminology which should be avoided includes lymphangioma and cystic hygroma. May be unifocal or trans-spatial, unilocular or multilocular. Histologically, they may be microcystic or macrocystic. LM do not have a well-defined capsule and do not enhance unless infected or combined with a venous (venoLM [VLM]) or capillary (lymphocapillary) malformations. USG and MRI using short tau inversion recovery or fat-saturated T2W sequences are considered optimal to evaluate the internal fluid, fluid–fluid, or blood–fluid levels, and the extent of the lesion (Fig. 81.27). LVA may be associated with developmental venous anomaly and other intracranial vascular anomalies if located in periorbital location.
FIGURE 81.27 Lymphatic malformation (LM): T1W (A) and STIR (B) reveal a large LM involving entire left parotid gland (LM) conforming to the shape of the gland. Postcontrast FS axial (C and D) images show minimal enhancement of the margins and the thin internal septae.
Capillary Malformation: There are two main types of capillary malformation. One is the classic “port-wine stain” associated with Sturge–Weber syndrome and the other is telangiectasia. The port-wine stain is the most common head and neck capillary malformation. These lesions are superficial and imaging is not routinely performed to evaluate these low flow vascular malformations unless there is concern for an associated intracranial anomaly. Venous Malformation:
Venous malformations (VMs) are low flow malformation and were previously known as cavernous malformation and cavernous hemangioma. The characteristic finding of a pure VM is a well-defined lesion that involves the muscle and may be associated with phleboliths. MRI using short tau inversion recovery or fat-saturated T2W is considered optimal to demonstrate the extent of the lesion, assess for skip lesions, and evaluate for airway involvement. Characteristically the lesions are very hyperintense on these sequences. Typical features include the presence of phleboliths, osseous remodeling in adjacent bone, and fat hypertrophy in adjacent soft tissues (Fig. 81.28). The degree of enhancement depends on the number and size of venous channels, the rate of venous blood flow within, and the presence of lymphatic tissue component (VLM) (Fig. 81.29). VMs and VLMs are easily differentiated from high-flow arteriovenous malformations using color Doppler, dynamic postcontrast CT, and MR imaging as well as DSA studies (Fig. 81.30).
FIGURE 81.28 Trans-spatial venous malformation (VM). Noncontrast axial (A) and coronal (B) CT reveal multifocal soft-tissue density superficial and deep situated lesions with multiple phleboliths (arrows). STIR axial (C), coronal (D), and coronal postcontrast FS (E) images show brilliantly hyperintense densely enhancing multifocal trans-spatial lesions (VM) with focal hypointense phleboliths (arrows).
FIGURE 81.29 Mixed venolymphatic malformation (VLM): Grayscale ultrasound image (A) and power Doppler image (B) of a large VLM with avascular multiloculated hypoechoic component, internal septae, and mobile internal midlevel echoes representing the lymphatic malformation (LM). Doppler image shows interspersed vascularity due to the venous component (VM). STIR coronal images (C and D) reveal the large hyperintense VLM in soft tissues of the left shoulder with internal fluid blood–fluid levels (arrows in D). Postcontrast FS coronal (E) image shows enhancement of the margins and the venous component of the VLM (arrows).
FIGURE 81.30 Mandibular arteriovenous malformation (AVM): Color Doppler image (A) of a complex mixed echoic lesion in soft tissues overlying the right mandible (arrows) in a 13-year-old girl showing tubular serpiginous high flow velocity arterial structures. STIR coronal (B) image reveals large signal abnormality showing flow voids (arrows) on lateral and medial aspect of the right mandible. CT angiography (C and D) and DSA (E) a large right mandibular AVM with an intraosseous component (arrows) supplied by a hypertrophied right facial artery (green arrows in C).
Hemangioma Congenital Hemangioma: The two subtypes include rapidly involuting congenital hemangioma, which involutes by 8–14 months and the noninvoluting congenital hemangioma. GLUT-1-negative status on immunohistochemistry differentiates this entity from the infantile hemangioma. Infantile Hemangioma: Infantile hemangioma (capillary hemangioma) usually presents within 3 months of birth and with most resolving by 9 years of age. Two phases of development include the proliferative phase and the involuting phase. These hemangiomas are GLUT-1-positive on immunohistochemistry [26]. The goal of imaging is to differentiate isolated (CN V distribution) pathology from multifocal disease (Fig. 81.31), identify deep extension (orbit and airway) and assess post-treatment response and evaluate associated anomalies (PHACES syndrome). These are well-defined intensely enhancing mass that are devoid of calcification and do not erode bone. The proliferative phase may have multiple internal flow voids (Fig. 81.32) which involute and have fatty replacement during involuting phase.
FIGURE 81.31 Hemangiomas at multiple sites: Transverse grayscale ultrasound (A) and longitudinal color Doppler image (B) shows a focal isohypoechoic appearance of a parotid gland hemangioma (H, arrows) with diffuse increase in the intrinsic vascularity. Right buccal space hemangioma (H) on coronal postcontrast FS MR (C). Left intraorbital hemangioma (H) on STIR axial MR (D). Right masticator space hemangioma (H) on axial postcontrast FS MR (E).
FIGURE 81.32 Hemangioma in oral cavity: STIR axial (A) and coronal (C) images and postcontrast FS axial (B) and coronal images (B, D, E & F) reveal a large hemangioma in the proliferative phase (H) with multiple intralesional enlarged vessels in image D and E (arrows), intense enhancement and infiltrating multiple oral cavity subsites.
Rhabdomyosarcomas (Refer Skull Base Section for More Details) RMS is the most common soft-tissue malignancy in the pediatric age group (50–70% of all childhood sarcomas), manifesting before 12 years of age. In the head and neck region, the most common sites of origin, in descending order of frequency, are the orbit, masticator space nasopharynx, middle earmastoid region, and sinonasal cavities [29]. Reporting must follow the TNM classification of RMS modified by the Intergroup Rhabdomyosarcoma Study Group [29]. Nonrhabdomyosarcoma Tumors Non-RMS tumors account for 3–5% of all malignant neoplasms in children and include soft-tissue fibrosarcoma (Fig. 81.33), osteosarcoma, nonskeletal Ewing’s sarcoma PNET: primitive neuroectodermal tumor, synovial sarcoma, and chondrosarcoma. Non-RMS tumors also include benign softtissue tumors like lipomas, myxomas, fibromas, leiomyomas, and desmoidtype fibromatosis (Fig. 81.34).
FIGURE 81.33 Soft-tissue sarcoma: Axial (A–C) and coronal (D–F) postcontrast FS MR images show a large infiltrative enhancing mass (M) in the left infra- and suprazygomatic masticator space (vertical black arrows in A and B) with intraorbital (black asterisks in E), left buccal space (horizontal white arrow in A) extension, and involvement of leftsided premaxillary soft tissues (vertical white arrow in C). Perineural spread is seen involving branches of the maxillary division of left trigeminal nerve (curved black arrow in C) with enhancing left infraorbital nerve (vertical block arrow in E), and left Vidian nerve (horizontal block arrow in F).
FIGURE 81.34 Infantile fibromatosis (desmoid type): Large lobulated left parapharyngeal space (arrows), causing marked indentation on the oropharynx and lateral oropharyngeal wall. It appears hypointense on T1W axial image (A), hyperintense on STIR axial image (B) with scattered hypointense components (arrows). Postcontrast FS axial and sagittal images (C–D) reveal dense heterogenous enhancement with large nonenhancing foci (arrows).
Neuroblastoma Primary cervical NB is comparatively rare (1–5%) compared with metastatic NB and arises from primitive neural crest cells of the sympathetic nervous system. Metastatic NB is the third most common pediatric malignancy and is the most common extracranial solid malignancy in children under 5 years of age. Most metastatic cervical NB arise from sites below the diaphragm, with additional primary sites being the skull, orbit, maxilla, and mandible [29]. Primary cervical NB presents as confluent adenopathy or large discrete nodes typically medial or posteromedial to the carotid sheath with/without calcifications (Fig. 81.35). Metastatic cervical NB exhibit spiculated “hair on end” periosteal reaction in the orbit, skull base, temporal bone with associated enhancing soft-tissue mass. CT helps in bone evaluation and contrast-enhanced MRI identifies associated soft tissue, dural, and other intracranial pathology. Abdominal imaging (USG, CT, MRI) is essential to identify the primary pathology and is staged according to the International Neuroblastoma Staging System [29].
FIGURE 81.35 Cervical sympathetic chain neuroblastoma: STIR axial (A), postcontrast FS axial (B), and sagittal (C) images of a 2-year-old show a large well-defined tubular-shaped enhancing mass (N) infiltrating the right suprahyoid and infrahyoid carotid space insinuating between the vessels (arrows). Extensive bilateral multilevel reactive cervical lymphadenopathy is noted (straight arrows). The mass shows diffusion restriction (D) with hypointense appearance on ADC images (arrows in D and E) and low ADC values measuring 0.84–0.87 × 10−3 mm2/s (E).
Imaging of Thyroid/Parathyroid and Salivary Glands Thyroid Gland Introduction Most childhood thyroid disorders are treatable endocrine disorders (Table 81.8). The thyroid gland achieves adult size by 15 years of age. Thyroglossal duct cyst is one of the most common developmental anomalies in children (see Developmental neck masses). Table 81.8 Classification of Pediatric Thyroid Disorders Infancy
Diffuse Thyroid Disease Chronic Lymphocytic Thyroiditis: Autoimmune thyroid disease with lymphocytic infiltration results in endocrine abnormalities (Fig. 81.36) and may be associated with other autoimmune diseases, type I diabetes, Graves’ disease [30], and neoplasms. On USG, the swollen thyroid gland is diffusely heterogeneous with
hypervascular parenchyma and multiple subcentimeter hypoechoic nodules [31].
FIGURE 81.36 Chronic lymphocytic thyroiditis. Longitudinal grayscale ultrasound (A) reveals diffuse heterogenous mixed hypoechoic appearance of an enlarged thyroid gland with lobulated contour, numerous poorly defined hypoechoic foci with prominent intervening hyperechoic septae. Longitudinal color Doppler (B) examination reveals moderate increase in the intrinsic vascularity of the entire thyroid gland. Note: Important to exclude any dominant nodule that could have a potential to undergo malignant transformation. (Courtesy: Dr. Varsha Sarda, Nagpur, India.)
Painful Thyroid Gland: A painful, tender, asymmetrically enlarged thyroid gland can be caused by infection, leading to acute suppurative and subacute nonsuppurative thyroiditis (secondary to a fourth BCA). Ultrasonography detects the heterogeneous echogenicity, evolving focal abscesses [32], and inflammation in adjacent structures. Ectopic Thyroid Lingual thyroid accounts >90% of all ectopic thyroid tissue with female preponderance. It may cause dysphagia, dyspnea, and globus. Empty native thyroid bed is determined by USG neck and CECT or MRI can identify determine the presence of orthotopic thyroid tissue [33]. At times, ectopic thyroid tissue may be the only functioning tissue in the body (Fig. 81.37).
FIGURE 81.37 Dual ectopic thyroid: Clinical photograph (A) of a 14year-old female with a midline neck swelling (arrow). Transverse grayscale ultrasound (B) and longitudinal color Doppler examination (C) reveal a lesion of heterogenous echogenicity with scattered hypoechoic foci (arrow) showing diffuse increase in the intrinsic vascularity. Postcontrast sagittal (D) and axial (E, F) images reveal a heterogeneously enhancing infrahyoid anterior midline lesion (arrows in D and E) representing ectopic thyroid tissue (within a likely thyroglossal duct cyst) and presence of a lingual thyroid (arrow in F). Technetium99m pertechnetate thyroid scan (G) reveals uptake in the lingual thyroid (arrow) and ectopic thyroid tissue (arrow head) without any uptake within the normal thyroid bed (asterisk).
Parathyroid Gland Parathyroid gland pathologies are uncommon in children. Familial causes include congenital absence of parathyroid gland or dysfunctional parathyroid gland. Multiple abnormal parathyroid glands may develop into single or multiple parathyroid adenomas. Adolescent primary hyperparathyroidism results from hyperplastic glands. Pediatric hypoparathyroidism is uncommon. A hypoechoic well-circumscribed lesion on sonography represents parathyroid adenoma. 4D CT determines the pattern of vascularity of these lesions in various phases of contrast enhancement [34]. An undetected ectopic parathyroid adenoma can be identified by a Tc-99m sestamibi scan.
Pediatric Salivary Glands The salivary glands are best evaluated initially with ultrasonography. CT is useful in deep extension of salivary gland pathologies inaccessible to the USG probe. MRI addition-ally identifies perineural spread and skull base invasion. Conventional sialography has now been replaced by MR sialography (Table 81.9) [35]. Table 81.9 Classification of Pathologies Development al
Viral Sialadenitis Mumps is a common cause for bilateral inflammation of parotid glands [36], submandibular, and sublingual glands being less commonly involved. USG reveals enlarged glands with diffuse heterogeneous echogenicity, entrapped secretions, and enlarged intraparotid nodes. Juvenile Recurrent Parotitis
Juvenile recurrent parotitis is a commonly encountered nonobstructive, nonsuppurative parotid gland inflammatory disorder with predominantly unilateral involvement (in two-thirds of patients). Inflammatory episodes are known to recur every 3–4 months. The disease is thought to be familial or autoimmune in nature [37]. USG reveals distortion of normal ductal anatomy due to lymphocytic infiltration within the connective tissue of gland and localized fibrosis/traction-induced multifocal ductal ectasia (Fig. 81.38). MR sialography aids in visualizing the entire salivary ductal system.
FIGURE 81.38 Juvenile recurrent parotitis. Transverse grayscale ultrasound (A) reveals diffusely heterogenous echo pattern of the parotid gland with multiple hypoechoic foci (asterisks). Axial (B) and coronal (C) STIR images show diffuse increase in size and heterogenous signal intensity of right parotid gland (arrow). Axial (D) and coronal (E) postcontrast FS images show dense homogeneous enhancement without any focal lesion. Bilateral multilevel cervical lymphadenopathy is seen (short angulated arrows). (Ultrasound image courtesy: Dr. Ankit Shah, Mumbai, India).
IgG4-Related Disease Disorder with recurrent infections of salivary glands in children under 12 years due to an autoimmune process, commonly involving the submandibular gland. USG reveals diffuse parenchymal changes, multiple lobulated hypoechoic foci on heterogeneously hyperechoic background, and mildly increased vascularity along compressed pseudoseptae. CT and MRI reveal a homogeneous appearance of the lobulated gland with postcontrast enhancement. MRI features include an intermediate T1W signal, with a hypo- to isointense T2W signal. The differential diagnosis includes malignant neoplasm and lymphoma. Salivary Gland Non-Neoplastic Cysts
Obstruction of the sublingual gland duct causes extravasation of mucousforming pseudocysts or mucoceles termed as ranulas. This can be a simple ranula if restricted to the floor of mouth or a “diving/plunging” ranula if it extends to the submandibular space behind or through the mylohyoid muscle [38]. The differential diagnosis includes LM. Salivary Gland Tumors These account for 20 mm
The adenoidal–nasopharyngeal ratio described in the earlier literature is no longer considered as a clinically useful parameter of airway obstruction. Soft-tissue shadows of the lingual and palatine tonsils can be observed indenting the airway on the lateral neck radiograph. However, no specific measurements are available as references. Video fluoroscopic studies are no longer considered useful in the work-up of OSA. Dynamic/cine MRI provides an accurate estimation of airway compromise during sleep state and additional useful information regarding the lateral pharyngeal walls’ softtissue thickening at the level of the velopharynx that contributes to the airway narrowing. It also evaluates the degree of glossoptosis and airway compromise at the level of the base of the tongue and hyoid bone. It is especially useful to evaluate airway obstruction at multiple levels (Trisomy 21 and craniofacial anomalies). CT cephalometric measurements provide an estimation of craniofacial abnormalities, such as a low-placed hyoid bone in OSA cases and the presence of an elongated and thickened soft palate.
Pediatric Velopharyngeal Insufficiency Velopharyngeal insufficiency occurs due to inadequate closure of the velopharynx and due to anatomical defects resulting in abnormal speech with typical nasal twang and inability to enunciate certain sounds [45]. Usually, it is diagnosed on physical examination, nasopharyngoscopy, and nasometry. Real-time phonation-linked cine MRI imaging helps to identify the type of velopharyngeal closure and structural and functional abnormalities of the levator veli palatini muscle. MR angiography can identify a medially buckled internal carotid artery at the level of the velopharynx.
Pediatric Head & Neck Emergencies There are a variety of clinical indications for imaging a child in an emergency setting (Table 81.11), however, in most cases it is usually for symptoms of acute upper airway obstruction which is mostly as a result of acute infection or due to foreign body aspiration [46]. Imaging provides answers to the three critical questions in an emergency setting of upper airway obstruction:
1. Is there a mass obstructing in the airway? 2. Is there dynamic narrowing or a vascular compression of the airway? 3. Is there evidence of an infective etiology or associated vocal cord paralysis?
Table 81.11 Classification of Pediatric Emergencies Inflammatory/Infective
Juvenile nasopharyng eal angiofibrom a retinoblasto ma
Foreign body aspiration traumatic; retinal hemorrhages due to child abuse Vascular malformations infantile fibromatosis
It is imperative to choose an imaging technique that can address the above questions as quickly as possible.
Vincent (Ludwig) Angina A rapidly progressive trans-spatial necrotizing cellulitis of the upper neck soft tissues and oral cavity with potential to form multifocal abscesses compromising the airway and further spreading to deep/lower neck spaces and mediastinum. It is most commonly seen as a result of untreated odontogenic infection with patient typically presenting with throat pain and fever. Contrast-enhanced CT is the technique of choice to assess the patency of the airway and to determine the source and extent of the abscesses/inflammatory edema (Fig. 81.41). It also helps in planning surgical approach to decompress the distended superficial and deep neck spaces.
FIGURE 81.41 Vincent angina: Transverse (A) and longitudinal (B) grayscale ultrasound images reveal a well-circumscribed evolving abscess in the submandibular space, abutting the adjacent submandibular gland. Note the finger-like projection from the abscess that extends to the adjacent dentition (arrow) in transverse grayscale ultrasound. Reactive diffuse edema of the overlying mylohyoid muscle (arrow) in the longitudinal ultrasound image. Coronal (C) and axial (D) contrast-enhanced CT images reveal well-circumscribed hypodense fluid collection in the sublingual space (floor of mouth) on both sides (arrows). The axial image is obliquely rotated to reveal its origin from the right side mandibular alveolar arch or third molar tooth with extended fluid collection in right masticator/parapharyngeal space (arrows). (Ultrasound image courtesy: Dr. Ankit Shah, Mumbai, India.)
Acute Tonsillitis and Adenoidal Hypertrophy Enlarged tonsils and adenoid hypertrophy are treatable causes of airway obstruction in children and elective surgical procedures are undertaken for recurrent infections. Peritonsillar cellulitis, if untreated, can result in a tonsillar or peritonsillar abscess with patients typically presenting with fever and odynophagia. This is usually uncommon in children but can occur in an immune compromised patients. Peritonsillar inflammation and abscess may extend to the adjacent parapharyngeal or masticator space. Tonsillar and peritonsillar inflammation and infections occur as a result of beta-hemolytic streptococcal infection. Imaging is usually is not performed for
uncomplicated cases being treated conservatively. Lateral neck soft-tissue radiograph is useful in assessing mass effect on the airway due to adenoidal hypertrophy. USG using an intraoral probe, CECT or CE-MRI is performed to assess unilateral or bilateral involvement and to identify the presence of an abscess. USG-guided abscess drainage may also be undertaken in cooperative patients.
Acute Epiglottitis Epiglottitis is a potentially life-threatening condition in young children with edema of the epiglottis and aryepiglottic folds compromising the airway. Patients usually present with fever, stridor, and dysphagia. Lateral soft-tissue radiograph demonstrates a globular soft-tissue indentation on the air way of the pharynx. The “thumb-sign” (if seen) is a characteristic radiographic feature due to the edematous aryepiglottic folds and effaced glossoepiglottic space (Fig. 81.42). CT is indicated in cases of a diagnostic dilemma, to assist in emergent endoscopic assessment in restoring the airway and to evaluate other emergent neck conditions occurring concomitantly.
FIGURE 81.42 Acute epiglottitis: Lateral soft-tissue radiographs normal view (A) and magnified view (B) of the neck demonstrates the thickening of the epiglottis (arrow in A) represented as the “thumb-print” sign. Note the overdistended hypopharynx (arrow in B). (Courtesy: Dr. Mukund Rahalkar, Pune, India.)
Acute Laryngotracheobronchitis Infants usually present with low-grade fever, barking cough, stridor, hoarseness (elder children), secondary to a viral infection. Frontal soft-tissue radiograph shows widening of the hypopharynx with narrowed glottic region: the “steeple” sign or “inverted V” sign [47]. CT is indicated in cases of a diagnostic dilemma and shows the effaced airway of the larynx, trachea with symmetric straightening of the subglottic airway. CT can also identify foreign body impaction and a normal appearing epiglottis and aryepiglottic folds on cross-sectional imaging rules out possibility of clinical entities with similar presentations. Differential diagnosis: foreign body aspiration, epiglottitis.
Retropharyngeal Abscess
Affected children are usually acutely ill, febrile with neck pain. They have difficulty in swallowing, sore throat, drooling, stridor, and muffled voice. This is typically due to a bacterial infection of tonsils and pharynx, and less commonly, due to penetrating trauma. Patients initially have suppurative adenitis of the lateral retropharyngeal lymph node which may rupture into the retropharyngeal space causing a retropharyngeal abscess. The retropharyngeal space contains a slip of coronally oriented prevertebral fascia—the alar fascia which divides this space into an anteriorly situated true RPS. The alar fascia fuses anteriorly to the visceral fascia effectively cutting off the true RPS from the posteriorly situated “danger space” at approximately T3. The danger space extends inferiorly into the posterior mediastinum to the level of the diaphragm. Hence infections, abscesses, and tumors can extend through the danger space from the neck into the thorax and vice versa [48]. Contrast-enhanced CT is the imaging technique of choice as it defines the full extent of the collection due to the peripherally enhancing wall and pressure effect on the airway. A retropharyngeal abscess may also involve the adjacent vascular structures causing narrowing or pseudoaneurysm of the ICA, thrombosis of thrombophlebitis of the IJV, and mediastinitis (Fig. 81.43). Lateral neck radiographs are also used to demonstrate prevertebral space widening but can be misleading due to neck flexion, and phase of respiration. Plain radiographs also cannot differentiate RPS abscess from RPS edema. However, if CT is not easily available fluoroscopy of the sick child in lateral neck extension and during inspiration can demonstrate widening of the retropharyngeal soft tissues (more than 7 mm at C2 level and more than 14 mm at C6 level or more than half the width of the vertebral body from C1 to C4 levels).
FIGURE 81.43 Retropharyngeal space abscess: Lateral neck softtissue radiograph (A) showing markedly widened prevertebral soft tissues (arrow). STIR sagittal (B) and axial (D–F) and T1W sagittal (C) images reveal a large retropharyngeal abscess (arrows) extending into the thorax along the danger space up to D7 level (arrows).
FIGURE 81.44 Branchiootic syndrome (BOS): Axial (A) and coronal (B) HRCT images of the temporal bone reveal left microtia and EAC atresia (arrows). Ossicular chain is dysmorphic and dysplastic on both sides (arrows) with small sized opacified left middle ear cavity (horizontal white arrows). Coronal reformatted heavily T2W MR sinogram (C) reveals a well-defined sinus tract (oblique arrows) extending from a small skin opening in the left lower neck to the lateral pharyngeal wall. USG examination revealed normal kidneys.
FIGURE 81.45 CHARGE syndrome: Axial HRCT (A) image reveals bilateral cochlear turn abnormalities with cochlear aperture stenosis, hypoplastic vestibules, and absent semicircular canals (arrows). CISS (DRIVE) T2W axial (B and C) and sagittal oblique IAC images (D) reveal bilateral Type 2A cochleovestibular nerve dysplasia with hypoplastic/absent cochlear branch of the eighth nerve bilaterally (angulated arrows in D). Bilateral globe deformities with small colobomas, left microphthalmos (MO), and left retinal detachment (RD) seen in (D). Coronal T2W image (E) reveals bilateral shallow olfactory fossae with hypoplasia/absence of the olfactory bulbs (arrows).
FIGURE 81.46 PHACE syndrome: Postcontrast FS axial MR images (A–C) reveal multiple densely enhancing lesions in the right lip, nasal ala, right periorbital and intraorbital region, and frontal scalp (arrows) indicating multifocal infantile HNF hemangiomatosis evident on clinical photograph (F). MR angiography images (D and E) reveal multiple craniovertebral arterial anomalies: hypoplastic left ICA (oblique double arrow in D and E). Vertebral arteries are hypertrophied (horizontal arrows in D and E) with luminal caliber equal to common carotid arteries.
FIGURE 81.47 Complex odontoma: lateral (A) plain radiograph of a 12-year-old boy with painless swelling in the left jaw. The radiograph and axial CT (B) reveal a well-defined sclerotic lesion (O) in the left mandible with a peripheral radiolucent/hypodense rim (arrows). Postcontrast FS axial MR image (C) shows homogenous enhancement of the peripheral rim of soft tissue (horizontal black arrow) surrounding the complex odontoma.
FIGURE 81.48 Cherubism: Lateral (A) plain radiograph of the mandible in a 13-year-old child show large expansile multicystic multiseptated expansion of the mandible (white arrows). Axial (B), bone CT image reveals asymmetrical expansion of the left mandible with a characteristic soap-bubble appearance (arrows). (Courtesy: Dr. Anand Rahalkar, Pune India.)
Foreign Body Aspiration Children usually present with breathlessness, low-grade fever, cough. A history of foreign body aspiration is available or can be elicited. Frontal and lateral radiographs of neck and thorax are helpful in assessing position of
radio dense foreign bodies but have a low specificity (approximately 17%). Right mainstem bronchus is the most common site for an obstructed lower airway foreign body. Frontal radiographs can show asymmetric lung aeration, increased lucency on the side of obstruction due to hyperinflation with contralateral shift of the mediastinum. Noncontrast ultralow dose CT is useful in identifying radiolucent foreign bodies like fish bones [49].
Acute Suppurative Lymphadenitis Suppurative lymphadenitis is the most common cause of acute painful neck masses in the pediatric age group (age 4–8 years) and is a common sequel of bacterial infections involving the upper respiratory tract with subsequent liquefaction and abscess formation within the draining lymph nodes. Imaging: High-resolution USG provides significant information with an added advantage of guided aspiration/tissue sampling. CT and MRI evaluate mass effect/encasement of adjacent structures and the degree of conglomeration.
Syndromes in Children With Head & Neck Manifestations There is an extensive list of syndromic conditions presenting with clinical abnormalities in the head and neck which have been discussed exhaustively in the medical literature [50,51]. It is important to try and diagnose a specific syndrome based on typical findings (Tables 81.12 and 81.13) to enable identification of multisystemic anomalies. The diagnosis can guide further genetic testing and parental counseling. Table 81.12 Clinico-radiological Manifestations of Commonly Encountered Syndromes A. Syndromes With External Ear Abnormalities, Conductive Hearing Loss; Congenital Sensorineural Hearing Loss; Neck Cysts/Sinuses [50,51]
B. Syndromes With Abnormal Facial Skeleton: PNS, Mandible, Skull Vault
1. Pendred syndrome: Cochlear modiolar and interscalar septum deficiency, dilated
A. Syndromes With External Ear Abnormalities, Conductive Hearing Loss; Congenital Sensorineural Hearing Loss; Neck Cysts/Sinuses [50,51] vestibule/large vestibular aqueduct (LVAS), euthyroid goiter. 2. Branchiootorenal syndrome (BOR): Branchial cleft cyst/fistula, EAC stenosis/atresia, dysplastic ossicles, “unwound cochlea” with offset middle/apical turns, posterior semicircular canal anomaly, LVAS, renal anomalies. Branchiootic syndrome: similar findings except for normal kidneys (Fig. 81.44). 3. Waardenburg syndrome: Aplasia/hypoplasia of the posterior semicircular canal, LVAS, and hypoplastic cochlea/small deficient modiolus. 4. CHARGE: Coloboma, Heart anomaly, Atresia choanae, Retardation: mental & somatic development, Genital hypoplasia, Ear abnormalities (Fig. 81.45). 5. Goldenhar syndrome: microtia/anotia, EAC atresia/stenosis, middle ear hypoplasia and ossicular malformations, oval window atresia & VII nerve hypoplasia. 6. Treacher Collins syndrome: EAC stenosis/atresia, hypoplastic/atretic middle ear, malformed/absent ossicles, oval window stenosis/atresia, facial nerve canal anomalies. 7. Pierre Robin sequence (PRS): Stenotic/atretic EAC, middle ear and mastoid hypoplasia with malformed ossicles, small semicircular canal bone island/anlage
B. Syndromes With Abnormal Facial Skeleton: PNS, Mandible, Skull Vault keratocystic odontogenic tumors. 2. CHARGE: Bony/membranous choanal atresia. 3. Goldenhar syndrome: Mandibular/zygomatic arch hypoplasia, hypoplasia of the muscles of mastication/facial muscles, Klippel–Feil anomaly. 4. Treacher Collins syndrome: Symmetric micrognathia, zygomatic/malar hypoplasia. 5. Pierre Robin sequence (PRS): Bilateral symmetric micrognathia, glossoptosis, and posterior U-shaped cleft palate. 6. McCune–Albright syndrome (MAS): Polyostotic FD, endocrine dysfunction, and cutaneous hyperpigmentation; 7. Cherubism: Familial, bilateral symmetrical expansile fibro-osseous jaw and maxillary involvement.
A. Syndromes With External Ear Abnormalities, Conductive Hearing Loss; Congenital Sensorineural Hearing Loss; Neck Cysts/Sinuses [50,51]
B. Syndromes With Abnormal Facial Skeleton: PNS, Mandible, Skull Vault 8. Crouzons’syndrome and Apert’s syndrome: middle cranial fossa and petrous apex deformities leading to Eustachian tube dysfunction and mastoid—middle ear pathology.
Table 81.13 Clinico-radiological Manifestations of Commonly Encountered Syndromes A. Port-wine Stain, Visible Hemangioma, or Vascular Malformation
B. Orbital Abnormaliti es
1. Sturge–Weber syndrome 2. PHACES syndrome: Posterior fossa structural anomalies, Hemangioma (segmental, infantile type, multiple), Arterial anomalies (agenesis, hypoplasia, and stenosis/occlusion of vessels, aneurysm, the aberrant origin of vessels), Cardiac defects (aortic coarctation/aneurysm/dysplasia, aberrant subclavian artery ± vascular ring, VSD), Eye (persistent hyperplasia primary vitreous, coloboma, morning glory disc anomaly, optic nerve hypoplasia, peripapillary staphyloma, microphthalmia, cataract, sclerocornea), and Sternal/supraumbilical raphe clefts and defects other midline anomalies (Fig. 81.46). A facial hemangioma and either one other major criterion or two minor criteria above must be present to qualify for the diagnosis of PHACES syndrome according to recent consensus statement released in 2009 [52].
1. Neurofibroma tosis-1: Lisch nodules (optic hamartomas), buphthalmos, “empty orbit” due to sphenoid wing dysplasia 2. CHARGE: colobomas 3. Goldenhar
3. syndrome: multiple enchondromas, bone A.Maffucci Port-wine Stain, Visible Hemangioma, or Vascular deformities, and hemangiomas. Malformation
Pediatric Jaw Lesions Mandibular lesions, although uncommon in children, are generally cystic in appearance and benign odontogenic in nature [53] (Box 81.8). Box 81.8
Key Points
◾ Three subtypes: odontogenic, nonodontogenic, and pseudocysts. ◾epithelial, Latest WHO classification categorizes odontogenic lesions as mesenchymal, or mixed lesions based on the tissue of
◾
origin [54]. Differential diagnosis based on: ⚬ Location: Most jaw lesions are typically located in the anterior or posterior mandible, while only a few have a nonspecific location [54]. ⚬ Appearance: 1. Well-circumscribed radiolucent/hypodense lesions. 2. Lesions with mixed or variable appearance/density/signl intensity. 3. Poorly circumscribed radiolucent/hypodense lesions. 4. Radio-opaque/hyperdense lesions. Difficult to make clear distinctions between the various odontogenic lesions because of significant overlap in the radiological features due to transitional appearances. The most common odontogenic lesions include keratocystic odontogenic tumors and dentigerous cysts [53]. Odontomas are classified as compound odontomas, complex odontomas (Fig. 81.47), and ameloblastic fibro-odontoma. Cherubism, a condition histologically identical to a giant cell granuloma, is seen in young children before the age of 5 years, and can be familial or nonfamilial [55] (Fig. 81.48).
◾
Suggested Readings • L Donnelly, Fundamentals of Pediatric Imaging, second ed., NY, Elsevier, New York (2016) 1–7. • AC Merrow, S Hariharan (Eds.), Imaging in Pediatrics, PA, Elsevier, Philadelphia (2018) 2–7. • J-Y Meuwly, D Lepori, N Theumann, P Schnyder, G Etechami, J Hohlfeld, Gudinchet multimodality imaging evaluation of the pediatric neck: techniques and spectrum of findings, RadioGraphics 25 (4) (2005) 931–948. • RT Sataloff, CJ Hartnick (Eds.). Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology, vol. 6. Philadelphia, PA. 2016. • CA Merrow (Ed.), Diagnostic Imaging: Pediatrics, third ed., Elsevier, Philadelphia, PA, 2017. • BL Koch, BE Hamilton, Hudgins, HR Harnsberger (Eds.), Diagnostic Imaging: Head and Neck, third ed., Elsevier, Philadelphia, PA, 2017.
References [1] L Donnelly, Special considerations in pediatric imaging, in: L Donnelly (ed.), Fundamentals of Pediatric Imaging, second ed., NY, Elsevier, New York (2016) 1–7 [2] AC Merrow, Basics of imaging, potential risks of pediatric imaging, in: AC Merrow, S Hariharan (Eds.), Imaging in Pediatrics,
PA, Elsevier, Philadelphia (2018) 2–7 [3] CJ Coté, S Wilson, Guidelines for monitoring and management of pediatric patients before, during, and after sedation for diagnostic and therapeutic procedures American Academy of Pediatrics, Pediatrics 138 (1) (2016) e20161212 [4] R Bhargava, G Hahn, W Hirsch, M Kim, H Mentzel, Ø Olsen, et al., Contrast-enhanced magnetic resonance imaging in pediatric patients: review and recommendations for current practice, Magn Reson Insights 6 (2013) 95–111. [5] SJ Wolf-Magele, L Hirtler, G Heinz, GM Sprinzl, MRI safety with cochlear implants up to three Tesla: experiences by performing an in vitro test, J Otol Rhinol 5 (2016) 4. 10.4172/2324-8785.1000286. [6] M Ditchfield, 3T MRI in pediatrics: challenges and clinical applications, Eur J Radio 68 (2008) 309–319. [7] MB McCarville, PET-CT imaging in pediatric oncology, Cancer Imaging 9 (1) (2009) 35–43. [8] DC Rivard, BD Reading, Pediatric interventional radiology: blurring the lines between specialties, Mo Med 115 (4) (2018) 361– 364. [9] MA LoPresti, JN Sellin, F DeMonte, Developmental considerations in pediatric skull base surgery, J Neurol Surg B Skull Base 79 (1) (2018) 3–12. 10.1055/s-0037-1617449. [10] KL Pricola, DT Lin, BS Bleier, WT Curry, Pediatric skull base malignancies, RT Sataloff, CJ Hartnick (Eds.) Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Medical Inc, Philadelphia, PA, 2016, 705–729. [11] T Chandra, M Maheshwari, TG Kelly, HD Segall, M Agarwal, S Mohan, Imaging of pediatric skull base lesions, Neurographics 5 (2) (2015) 72–84. 10.3174/ng.2150106. [12] EC Tsai, S Santoreneos, JT Rutka, Tumors of the skull base in children: review of tumor types and management strategies, Neurosurg Focus 15 (5) (2002) e1, 12. [13] MP Valencia, M Castillo, Congenital and acquired lesions of the nasal septum: a practical guide for differential diagnosis, Radiographics 28 (1) (2008) 205–223 [14] SA Andreoli, Kazahaya congenital nasal malformations, RT Sataloff, CJ Hartnick (Eds.) Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Medical Inc, Philadelphia, PA, 2016, 347–352. [15] S Vaid, D Shah, S Rawat, R Shukla, Proboscis lateralis with ipsilateral sinonasal and olfactory pathway aplasia, J Pediatr Surg
45 (2) (2010) 453–456. [16] M Parekh, KW Rosbe, Cystic fibrosis-related rhinosinusitis, RT Sataloff, CJ Hartnick (Eds.) Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Medical Inc, Philadelphia, PA, 2016, 342–346. [17] L Sennaroğlu, MD Bajin, Classification and current management of inner ear malformations, Balkan Med J 34 (2017) 397–411. [18] JW Casselman, FE Offeciers, PJ Govaerts, R Kuhweide, H Geldof, T Somers, et al., Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging, Radiology 202 (3) (1997) 773–781. [19] SV Branson, E McClintic, RP Yeatts, Septic cavernous sinus thrombosis associated with orbital cellulitis: a report of 6 cases and review of literature, Ophthalmic Plast Reconstr Surg 35 (3) (2019) 272–280. [20] S Kansara, D Bell, J Johnson, M Zafereo, Head and neck inflammatory pseudotumor: case series and review of the literature, Neuroradiol J 29 (6) (2016) 440–446. [21] PR Sivaperumal, SM Latha, S Narayani, J Scott, Bilateral proptosis in a child: a rare presentation of acute lymphoblastic leukemia, J Ophthalmic Vis Res 13 (4) (2018) 511–513. [22] H Dimaras, K Kimani, EA Dimba, P Gronsdahl, A White, HS Chan, et al., Retinoblastoma, Lancet 379 (9824) (2012) 1436–1446. [23] EB Mota, CR.R Penna, EJ Marchiori, Metastatic dissemination of a neuroblastoma, Pediatrics 189 (2017) 232, –232. [24] J-Y Meuwly, D Lepori, N Theumann, P Schnyder, G Etechami, J Hohlfeld, Gudinchet multimodality imaging evaluation of the pediatric neck: techniques and spectrum of findings, Radiographics 25 (4) (2005) 931–948. [25] M Ibrahim, K Hammoud, M Maheshwari, A Pandya, Congenital cystic lesions of the head and neck, Neuroimaging Clin N Am 21 (3) (2011) 621–639. 10.1016/j.nic.2011.05.006. [26] J Maddalozzo, J Alderfer, V Modi, Posterior hyoid space as related to excision of the thyroglossal duct cyst, Laryngoscope 120 (9) (2010) 1773–1778. [27] BJ Ludwig, J Wang, RN Nadgir, N Saito, I Castro-Aragon, Imaging of cervical lymphadenopathy in children and young adults, AJR Am J Roentgenol 199 (5) (2012) 1105–1113. 10.2214/AJR.12.8629. [28] R Kollipara, L Dinneen, KE Rentas, MR Saettele, SA Patel, DC Rivard, et al., Current classification and terminology of pediatric vascular anomalies, Am J Roentgenol 201 (5) (2013) 1124–1135.
[29] MT Brigger, MJ Cunningham, Pediatric head and neck malignancies, RT Sataloff, CJ Hartnick (Eds.) Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Medical Inc, Philadelphia, PA, 2016, 731–756. [30] RM Ruggeri, F Trimarchi, G Giuffrida, R Certo, E Cama, A Campennì, et al., Autoimmune comorbidities in Hashimoto’s thyroiditis: different patterns of association in adulthood and childhood/adolescence, Eur J Endocrinol 176 (2) (2017) 133–141. [31] DS Babcock, Thyroid disease in the pediatric patient: emphasizing imaging with sonography, Pediatrics 36 (4) (2006) 299–308. [32] O Wongphyat, P Mahachoklertwattana, S Molagool, P Poomthavorn, Acute suppurative thyroiditis in young children, J Paediatr Child Health 48 (3) (2012) E116. [33] DA Zander, WR Smoker, Imaging of ectopic thyroid tissue and thyroglossal duct cysts, Radiographics 34 (1) (2014) 37–50. 10.1148/rg.341135055. [34] JK Hoang, K Williams, F Gaillard, A Dixon, JA Sosa, Parathyroid 4D-CT: multi-institutional international survey of use and trends, Otolaryngol Head Neck Surg 155 (6) (2016) 956–960. [35] ZT Boyd, AR Goud, LH Lowe, L Shao, Pediatric salivary gland imaging, Pediatr Radiol 39 (7) (2009) 710–722. [36] EJ Inarejos Clemente, M Navallas, M Tolend, M Suñol Capella, J Rubio-Palau, A Albert Cazalla, et al., Imaging evaluation of pediatric parotid gland abnormalities, Radiographics 38 (5) (2018) 1552–1575. [37] FM Tucci, R Roma, A Bianchi, GC De Vincentiis, PM Bianchi, Juvenile recurrent parotitis: diagnostic and therapeutic effectiveness of sialography. A retrospective study on 110 children, Int J Pediatr Otorhinolaryngol 124 (2019) 179–184. [38] L Ugga, M Ravanelli, AA Pallottino, D Farina, R Maroldi, Diagnostic work-up in obstructive and inflammatory salivary gland disorders, Acta Otorhinolaryngol Ital 37 (2) (2017) 83–93. [39] RA Ord, ER Carlson, Pediatric salivary gland malignancies, Oral Maxillofac Surg Clin North Am 28 (1) (2016) 83–89. [40] M Prakash, JC Johnny, What’s special in a child’s larynx?, J Pharm Bioallied Sci 7 (1) (2015) S55–S58. [41] L Adewale, Anatomy and assessment of the pediatric airway, Paediatr Anaesth 19 (1) (2009) 1–8. [42] MD D’Eufemia, S Cianci, F Di Meglio, L Di Meglio, L Di Meglio, S Vitale, et al., Congenital high airway obstruction
syndrome (CHAOS): discussing the role and limits of prenatal diagnosis starting from a single-center case series, J Prenat Med 10 (1–2) (2016) 4–7. [43] KE Darras, AT Roston, LK Yewchuk, Imaging acute airway obstruction in infants and children, Radiographics 35 (7) (2015) 2064–2079. [44] B Kimbrell, CM Baldassari, Evaluation of pediatric sleep disorders: from the clinic to the sleep laboratory, Sataloff’s Comprehensive Textbook of Otolaryngology: Head and Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Brothers Medical Publishers, 2016, 820–828. [45] DJ Crockett, CT Wootten, The anatomic basis of velopharyngeal insufficiency, Sataloff’s Comprehensive Textbook Of Otolaryngology: Head And Neck Surgery: Pediatric Otolaryngology vol. 6, Jaypee Brothers Medical Publishers, 2016, 1038–1046. [46] KE Darras, AT Roston, LK Yewchuk, Imaging acute airway obstruction in infants and children, Radiographics 35 (7) (2015) 2064–2079. [47] M Sammer, S Pruthi, Membranous croup (exudative tracheitis or membranous laryngotracheobronchitis), Pediatr Radiol 40 (5) (2010) 781. 10.1007/s00247-009-1397-0. [48] D Donà, A Gastaldi, M Campagna, C Montagnani, G Luisa, S Trapani, et al., Deep neck abscesses in children: an Italian retrospective study, Pediatr Emerg Care 37 (12) (2021) e1358– e136510.1097/PEC.0000000000002037 [49] L Gordon, P Nowik, S Mobini Kesheh, M Lidegran, S Diaz, Diagnosis of foreign body aspiration with ultralow-dose CT using a tin filter: a comparison study, Emerg Radiol 27 (2020) 399– 40410.1007/s10140-020-01764-7 [50] CA Merrow (Eds.) Diagnostic Imaging: Pediatrics, third ed., Elsevier, Philadelphia, PA, 2017. [51] BL Koch, BE Hamilton, Hudgins, HR Harnsberger (Eds.) Diagnostic Imaging: Head and Neck, third ed., Elsevier, Philadelphia, PA, 2017. [52] D Metry, G Heyer, C Hess, M Garzon, A Haggstrom, P Frommelt, et al., Consensus statement on diagnostic criteria for PHACE syndrome, Pediatrics 124 (5) (2009) 1447–1456. [53] BL Dunfee, O Sakai, R Pistey, A Gohel, Radiologic and pathologic characteristics of benign and malignant lesions of the mandible, Radiographics 26 (6) (2006) 1751–1768. [54] L Dinneen, TL Slovis, The mandible, BD Coley (Eds.) Caffey’s Pediatric Diagnostic Imaging, thirteenth ed., Elsevier, Philadelphia,
PA, 2019, 191–201, e1. [55] SJ Theodorou, DJ Theodorou, DJ Sartoris, Imaging characteristics of neoplasms and other lesions of the jawbones: part 1. Odontogenic tumors and tumor-like lesions, Clin Imaging 31 (2) (2007) 114–119.
CHAPTER 82
Pediatric Congenital Heart Disease Jena N. Depetris, Sandeep Hedgire, Nandini M. Meyersohn
Introduction Congenital heart disease (CHD) is perhaps one of the most complex topics within medicine, requiring imaging specialists to have highly subspecialized knowledge and to work within an interdisciplinary team to provide optimal care for these unique patients. There is a wide spectrum of pathologies that fall under the umbrella of CHD, and the goal of this chapter is to educate the reader on how to approach describing complex congenital cardiac anatomy and to identify the characteristic imaging features of these unique pathologies. Moreover, we will focus on the roles, advantages, and disadvantages of various imaging modalities and their diagnostic applications in CHD. The overall incidence of all CHDs combined is approximately 1% of the population, with the most common defects being bicuspid aortic valve (BAV) and mitral valve prolapse [1]. With respect to symptomatic CHD, Table 82.1 summarizes the incidence of the most common pathologies both overall and diagnosed within the first month of life. Table 82.1 Frequency of Symptomatic Congenital Heart Disease for All Groups and Within the First Month of Life Frequency of Symptomatic Congenital Heart Disease Most common congenital anomalies (all ages; bicuspid aortic valve and MVP excluded) Ventricular septal defect (VSD)
3 0 %
Frequency of Symptomatic Congenital Heart Disease Atrial septal defect (ASD)
1 0 %
Tetralogy of Fallot (TOF)
1 0 %
Patent ductus arteriosus (PDA)
1 0 %
Aortic coarctation
7 %
Transposition of great arteries (TGA)
5 %
First month of life (serious clinical problems; high mortality) Hypoplastic left heart syndrome (HLHS)
3 5 %
Transposition of the great arteries (TGA)
2 5 %
Aortic coarctation
2 0 %
Multiple serious defects
1 5 %
Pulmonary atresia/stenosis
1 0 %
Tetralogy of Fallot (TOF) with pulmonic atresia or severe pulmonic stenosis
1 0 %
Adapted from Harisinghani et al. [1].
Normal Fetal Circulation Before discussing the immense complexity of CHD, it is critical to understand the fundamentals of normal fetal and adult circulation. Neonatal circulation (Fig. 82.1) is unique because it is inherently connected to and dependent upon the maternal placenta. Deoxygenated blood from the fetus travels toward the placenta in two umbilical arteries, while oxygenated nutrient-rich blood travels from the placenta through the single umbilical vein toward the right atrium of the fetal heart. From the right atrium, some blood may travel through the tricuspid valve into the right ventricle and the pulmonary artery, mimicking adult circulation patterns. However, since the fetal lungs are underdeveloped and not yet being used for oxygen exchange, the pulmonary arterial system has a relatively high resistance and the majority of the freshly oxygenated blood in the right atrium will be shunted across the foramen ovale, a normal defect in the fetal interatrial septum, into the left atrium, where it can continue through the mitral valve into the left ventricle and out into systemic circulation. Besides the foramen ovale, there is another unique connection normally present in fetal circulation called the ductus arteriosus, which is a connection between the pulmonary arteries and the aorta that also serves to shunt blood away from the developing fetal lungs [2].
FIGURE 82.1 Normal fetal circulation, wherein oxygenated blood travels from the placenta toward the fetus in a single umbilical vein and bypasses the developing fetal lungs through two normal shunts, including the foramen ovale and the ductus arteriosus, deoxygenated blood then travels from the fetus toward the placenta in two umbilical arteries. (Courtesy: Susanne Loomis.)
At the time of birth, a significant shift occurs in the circulation of the newborn child with a sudden drop in pulmonary vascular resistance occurring as the lungs fill with air. Under normal circumstances, this drastic pressure shift results in the closure of both the foramen ovale and ductus arteriosus. These small but important structures may occasionally stay patent in the postnatal period, and in the context of CHD can be vitally important for survival.
Role of Advanced Imaging In a tertiary care setting, the diagnosis of CHD is often made during prenatal or early postnatal life, largely through clinical assessment and echocardiography. Plain chest radiography in early neonatal life can also be useful in the assessment of CHD, as many have classic radiologic signs, which will be discussed in the respective sections for each pathology. Radiography can be used to assess cardiac position and shape, sidedness of the aortic arch, lung volumes, and the presence of pulmonary edema or other signs of fluid overload. However, with continuing advances in the surgical management of CHD resulting in a greater population of adults living with CHD, advanced imaging beyond conventional echocardiography and plain radiography has also become critically important in the pre- and postsurgical evaluation of CHD patients [3,4]. Increased availability and technical advances in multidetector ECG-gated computed tomography (CT) and magnetic resonance imaging (MRI) have rendered these noninvasive modalities valuable complementary tools for anatomic and functional assessment of CHD, particularly as these patients undergo sequentially or staged therapeutic interventions and live long into adulthood. The American College of Radiology (ACR) 2020 Appropriateness Criteria considers both cardiac MRI and cardiac CT more appropriate diagnostic tests in the evaluation of adult congenital heart disease (ACHD) compared with invasive coronary angiography and nuclear scintigraphy [5]. Given the complex anatomy, image acquisition protocols often need to be tailored on an individual patient level to sufficiently answer the diagnostic question while minimizing radiation doses for CT in accordance with the ALARA principle (as low as reasonably achievable) and optimizing scan times for MRI. The following sections will provide an overview of advanced imaging techniques and protocols, as well as their applications for CHD.
Cardiac CT ECG-gated cardiac CT is a versatile imaging technique that allows for precise anatomic delineation, evaluation of vessel/shunt patency, and assessment of cardiac function. A standard image acquisition protocol begins with a precontrast scan, which is particularly helpful in identifying prior surgical repair and cardiac valves, where applicable. This is typically followed by a prospectively or retrospectively ECG-gated arterial phase acquisition and may also be followed by a subsequent delayed phase acquisition. Requirements for a safe and diagnostic quality cardiac CT include adequate renal function (GFR >30) and intravenous access of the appropriate size to achieve a contrast injection rate adequate for optimal contrast opacification of smaller vessels in and around the heart. A normal heart rate and regular cardiac rhythm are ideal for optimizing image quality and minimizing radiation dose. However, utilization of arrhythmia rejection technology, modifications of image acquisition parameters, and
postacquisition image reconstruction can be used for troubleshooting in the setting of rapid or irregular heart rhythms, as are often present in CHD patients. Advantages of cardiac CT include capabilities for isotropic multiplanar image reconstruction, excellent spatial resolution, and improved temporal resolution with advances in scanner technology. Faster image acquisition times compared to MRI allows for imaging of patients with claustrophobia or with non-MRI compatible metallic implants. These advantages come at the expense of radiation exposure, noting that dose reduction strategies and improvements in scanner technology have significantly improved per-scan radiation doses.
Cardiac MRI Cardiac MRI is a highly utilized imaging technique in CHD due to its excellent softtissue resolution, precise anatomic delineation, and dynamic assessment of both qualitative and quantitative cardiac function without the use of ionizing radiation or iodinated contrast media. It remains the technique of choice for estimating myocardial mass and ventricular volumes, calculating ventricular ejection fractions, and detecting the presence of myocardial fibrosis. Furthermore, with the administration of intravenous gadolinium during an MR angiogram, evaluation of vessel, and shunt patency is possible. The combination of these imaging features and functional parameters often drives management decisions for CHD patients, and the 2018 American College of Cardiology/American Heart Association Guidelines for the Management of Adults with Congenital Heart Disease (ACHD) consequently recommends cardiac MR imaging for a variety of CHDs [6]. Recent advances in faster magnetic field gradients, image reconstruction techniques, and newer pulse sequences including 4D flow, T1/T2 mapping, free-breathing acquisitions, arrhythmia rejection technology, and strain imaging have further improved the utility of cardiac MRI in the CHD population. There is no single standard image acquisition protocol for cardiac MRI, as sequence selection is often tailored at the individual patient level for targeted clinical questions. With that said, broadly useful sequences include SSFP cine sequences, “black blood” double inversion recovery sequences, T1/T2 weighted sequences, MR angiography, delayed inversion recovery sequences to evaluate for late gadolinium enhancement (LGE), and velocity-encoded phase-contrast cine sequences. Requirements for a high-quality cardiac MRI include adequate renal function (GFR >30), ability to sustain breath holds, and ability to lay flat for a prolonged period of time. As with cardiac CT, a normal heart rate and regular cardiac rhythm are ideal for optimal image quality. Major limitations of cardiac MRI include long scan times, claustrophobia, and significant image artifacts related to metallic implants from prior surgeries, which are common in CHD patients. Pacemaker-dependent patients have traditionally not been subjected to MRI due to concerns for pacemaker malfunction, however, that practice is
evolving as our understanding of device safety in settings of diagnostic magnetic fields continues to improve.
Choosing Modalities The choice of which technique to utilize in the evaluation of any CHD patient should be based on a balanced multidisciplinary discussion of the risks and benefits among cardiac radiologists, pediatric/adult cardiologists specializing in CHD, interventional cardiologists, electrophysiologists, and cardiac surgeons. Both cardiac CT and cardiac MRI can offer excellent anatomic assessment for CHD patients as previously discussed, but each has its own unique strengths, and therefore the decision, although complex at times, should ultimately be centered around the primary clinical question Table 82.2 summarizes key factors involved in deciding whether to choose CT or MRI for evaluating a CHD patient. Table 82.2 Factors to Consider When Choosing CT Versus MRI as a Diagnostic Technique Factors Favoring Choice of CT
Factors Favoring Choice of MRI
Indwelling metallic implants or devices (particularly if not MRI safe)
Concern for repeated radiation exposure
Claustrophobia
Flow or ventricular volume quantification assessment
Special Considerations Patients with CHD represent a unique population with a number of special considerations that factor into their management. First of all, with continuous improvements in prenatal care and fetal anatomic assessment, the vast majority of CHD diagnoses are made in utero or early in infancy.
Evaluation of a pediatric population from an imaging perspective can be uniquely challenging given concerns about large or repeated radiation doses in early life. Secondly, pediatric patients are often unable to cooperate with breathing instructions during an imaging examination and the use of sedation or general anesthesia may need to be considered to acquire diagnostic images. Depending on the configuration of their congenital anatomy, these patients can be systemically cyanotic and/or hemodynamically unstable, which further complicates the clinical picture when considering the use of general anesthesia. Given these special considerations, decisions on when and how to image these patients should be carefully considered and discussed among the various members of the multidisciplinary care team in conjunction with patients’ families, with full understanding of the risks, benefits, and potential implications.
Segmental Approach to Congenital Heart Disease Due to the inherent complexity of the CHD spectrum, a structured, segmental approach for describing the underlying anatomy is critical, not only for making a correct diagnosis but also for effectively communicating amongst various members of the multidisciplinary care team. The first step is to become familiar with the characteristic morphologic features of the various cardiac chambers so that their position within a congenitally abnormal configuration can be correctly identified (Table 82.3). It is important to note that these characteristics are a guide to identifying the correct morphologic cardiac chambers, however definitive chamber identification may remain uncertain in highly complex cases (Table 82.4). Table 82.3 Morphologic Characteristics of the Cardiac Chambers Cha mber
Morphologic Characteristics
Right atriu m
Coronary sinus drainage
Crista terminalis Pyramidal or trapezoidal shaped atrial appendage
Cha mber
Morphologic Characteristics
Right ventri cle
Moderator band
Septal papillary muscles Muscular infundibulum Tricuspid atrioventricular valve separated from the outflow valve by a muscular infundibulum Left atriu m
Variable atrial appendage morphology (more tubular or finger-like)
Left ventri cle
Smooth upper septal surface
Mitral atrioventricular valve in fibrous continuity with the outflow valve
Table 82.4 Segmental Approach to Congenital Heart Disease
Adapted from Schallert et al. [7].
Following the identification of the morphologic cardiac chambers, a segmental approach is necessary for describing the anatomical configuration of these chambers, as well as inflow and outflow patterns. The widely used Van Praagh approach to the segmental classification of CHD, originally developed in Boston, Massachusetts in the 1960s [7], employs a three-letter notation signifying (1) the visceroatrial situs, (2) the orientation of the ventricular loop, and (3) the conotruncus (or origin and position of the great vessels). An additional important step is to identify the atrioventricular and
ventriculoarterial concordance or discordance, although this is not represented in the three-letter notation system [8]. While this chapter will contain a detailed discussion of the various individual CHDs, a schematic representation of the segmental approach described by Van Praagh is included here for reference (Table 82.5). Table 82.5 Classification Schema of Congenital Heart Disease
Adapted from Harisinghani et al. [1].
Classification of Congenital Heart Disease Cyanotic Congenital Heart Disease Cyanotic CHD represents a complex spectrum of congenital abnormalities that result in varying degrees of cyanosis, which clinically presents as bluish discoloration of the skin (particularly perioral, periorbital, and digital), digital clubbing, end-organ damage, and failure to thrive. Systemic desaturation may occur as a result of blood flow being redirected away from the pulmonary arterial system and preventing adequate oxygenation, or mixing of oxygenated and deoxygenated blood (right-to-left shunting) before exiting into the systemic circulation.
Tetralogy of Fallot (TOF) Embryology and Epidemiology: Tetralogy of Fallot is the most common cyanotic CHD, representing approximately 10% of all CHD [9,10]. The core anatomical defect is a deviation of the outlet ventricular septum during fetal development which results in the classic tetrad of findings: right ventricular outflow tract (RVOT) obstruction, a ventricular septal defect (VSD), an overriding aorta, and right ventricular hypertrophy (Fig. 82.2) [4,9,10].
FIGURE 82.2 Schematic representation of Tetralogy of Fallot, demonstrating the classic tetrad of findings, including right ventricular outflow tract (RVOT) obstruction/hypoplasia, an overriding aorta, a ventricular septal defect (VSD), and right ventricular hypertrophy. (Courtesy: Susanne Loomis.)
TOF is commonly associated with other congenital anomalies, such as a right-sided aortic arch, BAV, or anomalous pulmonary venous return. A minority of patients may present with a concomitant atrial septal defect (ASD), a scenario frequently termed Pentalogy of Fallot [10]. There are also associations between TOF and various genetic syndromes, including DiGeorge syndrome (CATCH 22 microdeletion), VACTERL, and Trisomy 21 [11,12]. Pathophysiology and Clinical Features: The pathophysiology of TOF is centered upon the degree of right ventricular outflow obstruction, which exists on a spectrum from mild obstruction to complete atresia and is the key factor in determining the severity of clinical cyanosis. In fact, patients with only mild RVOT obstruction are often termed “Pink Tetralogy” patients, referencing the relative lack of cyanosis they experience. On the other end of the spectrum, complete pulmonic atresia with a VSD can result in severe cyanosis and global underdevelopment of the native pulmonary vasculature. In these severe cases, abnormal collateral vessels arising from the aorta, known as major aortopulmonary collateral arteries (MAPCAs), may form to redirect blood toward the lungs. Patients with TOF classically present with cyanotic episodes, also called “Tet spells,” relieved by squatting or other maneuvers that increase peripheral systemic vascular resistance, which functionally decreases right-to-left shunting within the heart and increases blood flow into pulmonic circulation. It is important to note that while pulmonic atresia with VSD is considered to be a severe variant of TOF, there is a distinct rare disease entity known as pulmonary atresia with intact ventricular septum (PA/IVS), which will be discussed briefly in a subsequent section. Imaging Features: The radiographic findings of TOF are classically described as a “boot-shaped heart,” the appearance of which is explained by an uplifted cardiac apex due to right ventricular hypertrophy and a concave main pulmonary artery (Fig. 82.3) [9,10]. Underdeveloped pulmonary vasculature (pulmonary oligemia) can also be seen, particularly in patients with severe RVOT obstruction or pulmonary atresia, and approximately one-quarter of TOF patients will have an associated right aortic arch which can also be identified on radiographs [9,10].
FIGURE 82.3 Frontal chest radiograph (A) demonstrating the classic boot-shaped heart (B) of Tetralogy of Fallot, which refers to the uplifted cardiac apex due to right ventricular hypertrophy and a concave main pulmonary artery.
Echocardiography is the primary technique for initial evaluation for TOF, as it allows for direct visualization of the classic anatomic abnormalities, shunt analysis across the VSD using color flow Doppler, and estimation of biventricular function. The inherent limitations of echocardiography include operator dependence and inability to adequately visualize extracardiac structures for associated abnormalities, particularly the peripheral pulmonary arteries and thoracic aorta. Cross-sectional imaging with multidetector ECG-gated CT is useful in delineating the complex cardiac anatomy in these patients (Fig. 82.4) and has the added benefit of allowing for simultaneous assessment of extra-cardiac structures including branch pulmonary arteries, the thoracic aorta, and potential MAPCAs (Fig. 82.5). This can be especially useful in preoperative surgical planning for complex cases and/or preoperative cardiac clearance. Cardiac CT is also an excellent tool in the evaluation of palliative shunt patency and postsurgical complications in surgically corrected TOF patients, which is critical to their ongoing cardiovascular management.
FIGURE 82.4 Oblique coronal (A) and sagittal (B) contrast-enhanced ECG-gated cardiac CT images demonstrate the four characteristic features of Tetralogy of Fallot, including an aorta that overrides the interventricular septum (dotted line), a ventricular septal defect (asterisk), right ventricular outflow obstruction/narrowing (arrowhead), and right ventricular hypertrophy (double-headed arrows). Ao, aorta; LV, left ventricle; PA, pulmonary artery; RV, right ventricle.
FIGURE 82.5 Axial (A) and coronal (B) contrast-enhanced caridac CT demonstrates prominent tortuous collateral vessels (arrows) surrounding the right mainstem bronchus (asterisk) forming aberrant connections between the systemic and pulmonic circulations, known as major aortopulmonary collateral arteries (MAPCAs). MAPCAs are commonly found in patients with severe pulmonary outflow obstruction such as patients with Tetralogy of Fallot.
MR imaging has the unique advantage of providing both detailed anatomical information and quantitative functional data without the use of ionizing radiation. MRI can be used to quantify ventricular volumes using steady-state free precession cine sequences and remains the gold standard for quantification of flow fractions and valvular regurgitation using phase-contrast imaging. For patients with TOF, MRI is important in assessing the pulmonic valve/RVOT, as the degree of residual stenosis and/or pulmonic regurgitation often dictates management. The use of gadolinium-based contrast agents to assess for myocardial fibrosis or scarring is also important for assessing a patient’s risk of ventricular arrhythmia. The key imaging findings are summarized in Table 82.6 and the differential diagnosis of uncorrected TOF is shown in Table 82.7, which includes other cyanotic CHDs such as tricuspid atresia with transposition of the great arteries and double outlet right ventricle (DORV). Table 82.6 Summary of the Key Imaging Features of Tetralogy of Fallot Technique
Imaging Features
Chest radiograph
“Boot-shaped heart” Decreased (underdeveloped) pulmonary vascularity Small or concave pulmonary artery Possible right-sided aortic arch
Cardiac CT/MRI
Overriding aorta Ventricular septal defect Right ventricular outflow tract obstruction/pulmonary atresia Right ventricular hypertrophy Presence of major aortopulmonary collateral arteries (MAPCAs) Main or branch pulmonary artery stenoses Associated abnormalities of the thoracic aorta
Table 82.7 Differential Diagnosis for Uncorrected Tetralogy of Fallot Pentalogy of Fallot (Tetralogy of Fallot + ASD) Tricuspid atresia with ASD ± VSD/PDA ± transposition of the great arteries (TGA)
Double outlet right ventricle (DORV) with pulmonary stenosis
Treatment and Outcomes: The current mainstay of treatment for TOF involves primary surgical repair in infancy, consisting of VSD closure and relief of the right ventricular outflow obstruction in the form of pulmonic valvuloplasty or a transannular patch repair. Although no longer the preferred surgical approach, a transannular patch is occasionally required in settings of severe RVOT obstruction and is known to result in a large area of akinesis in the RVOT. Rarely in extreme cases, palliative shunts such as a Blalock–Thomas–Taussig shunt (subclavian artery to pulmonary artery shunt), Waterston shunt (ascending thoracic aorta to right pulmonary artery shunt), or a Pott shunt (descending thoracic aorta to left pulmonary artery shunt) may be used as a bridge to total surgical repair. The prognosis for patients with TOF is largely dependent on the age at which the abnormality is diagnosed and surgically corrected. While a majority of uncorrected TOF patients will have a life expectancy of less than 10 years, patients who undergo surgical repair early in life are now commonly able to live into adulthood, with the understanding that a degree of residual right ventricular dysfunction is common and reoperation in the future may be unavoidable. Common postsurgical complications for TOF patients in adolescence or adulthood include main or branch pulmonary artery stenoses (Fig. 82.6), RVOT transannular patch aneurysms, and right ventricular volume overload due to significant pulmonic regurgitation [4].
FIGURE 82.6 Axial contrast-enhanced ECG-gated cardiac CT demonstrates focal stenosis (arrow) of the proximal left main pulmonary artery, a frequent postsurgical complication seen in patients with Tetralogy of Fallot. Ao, aorta; PA, pulmonary artery.
Transposition of the Great Arteries Transposition of the Great Arteries (TGA) is a relatively common cyanotic CHD, representing approximately 5–7% of all CHD [9]. The fundamental embryologic defect is abnormal conotruncal septal rotation resulting in ventriculoarterial discordance, and patients most commonly present with progressive cyanosis within the first 24 hours of life. This disease entity can be subdivided into two types based on concurrent morphologic atrioventricular concordance (D-Type) or discordance (L-Type) which will be discussed separately, as their presentation, imaging features, and management are distinct.
Transposition of the Great Arteries, D-Type Embryology and Epidemiology: TGA (D-Type) refers to the presence of ventriculoarterial discordance with atrioventricular concordance, a so called “uncorrected” transposition. In D-TGA, the
morphologic right atrium connects to the morphologic right ventricle through the tricuspid valve with outflow into the aorta, while the morphologic left atrium connects to the morphologic left ventricle through the mitral valve with outflow into the main pulmonary artery (Fig. 82.7). In the D-TGA configuration, the aorta arises anteriorly and to the right of the main pulmonary artery (Fig. 82.8).
FIGURE 82.7 Schematic representation of D-type transposition of the great arteries (D-TGA), demonstrating the aorta arising from the right ventricle and the pulmonary artery arising from the left ventricle. This illustration also includes a patent foramen ovale (PFO) and a patent ductus arteriosus (PDA), at least one of which is required for survival by allowing mixing of oxygenated and deoxygenated blood. (Courtesy: Susanne Loomis.)
FIGURE 82.8 Axial contrast-enhanced ECG-gated cardiac CT demonstrates a patient with D-TGA, wherein the aorta (Ao) arises anteriorly and to the right relative to the pulmonary artery (PA). Note that in this patient, a coronary artery (arrow) is seen arising from the right aspect of the transposed aorta.
While D-TGA most commonly occurs in isolation, it can be associated with other congenital defects, including VSDs, aortic coarctation, and coronary artery anomalies. Extracardiac syndromic associations are rare. Pathophysiology and Clinical Features: In order for patients with this type of congenital abnormality to survive, a shunt between the systemic and pulmonic circuits must be present to allow for mixing of oxygenated blood from the lungs with deoxygenated systemic blood [4,9]. As is typical of cyanotic CHDs, the degree of right-to-left shunting is the key factor in determining the degree of clinical cyanosis. An anatomic shunt is usually present in the form of a patent foramen ovale (PFO) and/or patent ductus arteriosus (PDA) [4].
Imaging Features: The classic radiographic findings of D-TGA are cardiomegaly with an “egg-on a string” appearance and increased pulmonary vasculature (Fig. 82.9), [9]. These findings on plain film radiography refer to the relatively narrow superior mediastinal contour which is a consequence of thymic hypoplasia, the underlying cause of which is unknown, and the orientation of the abnormally rotated transposed great vessels.
FIGURE 82.9 Frontal chest radiograph (A) demonstrating the classic egg on a string appearance (B) of Transposition of the great arteries, which refers to the relatively narrow superior mediastinal contour caused by thymic hypoplasia and the abnormal orientation of the transposed great vessels.
Echocardiography is usually the initial imaging technique, allowing for visualization of the abnormally positioned aorta and pulmonary arteries, as well as characterization of any intracardiac shunts with color flow Doppler. Echocardiography can also be useful in assessment of the AV and outflow valvular morphologies. While visualization of the coronary arteries is often possible, evaluation can become difficult or impossible in the setting of concurrent coronary anomalies, and additional imaging may be necessary for preoperative planning. The known limitations of operator dependence and suboptimal visualization of extra cardiac structures always apply, and advanced imaging does play an important adjunctive role. Cardiac CT can provide additional anatomic and functional detail for problemsolving in particularly complex cases, as well as excellent visualization of the coronary arteries for detection and characterization of anomalies of coronary origins or course, which may be critical for preoperative planning. Cardiac CT is also a valuable tool in the assessment of surgically corrected D-TGA patients, with excellent visualization of the postoperative anatomy (i.e., size of interatrial septal defect, patency of surgical
baffles, etc.) and high sensitivity for the detection of potential postsurgical complications. Cardiac MRI is similarly useful in the assessment of surgically corrected D-TGA patients, with the added capability of quantitatively assessing the flow dynamics across intracardiac shunts, at anastomotic sites, and across the cardiac valves with phasecontrast sequences. The imaging features of D-Type TGA are summarized in Table 82.8. Table 82.8 Summary of the Key Imaging Features of D-Type Transposition of the Great Arteries Technique
Imaging Features
Chest radiograph
“Egg on a string” appearance of the heart Increased pulmonary vascularity Cardiomegaly Thymic hypoplasia
Cardiac CT/MRI
Atrioventricular concordancea Ventriculoarterial discordance Aorta anterior and to the right of the pulmonary artery Patent foramen ovale (PFO) or patent ductus arteriosus (PDA)
a
Note that atrioventricular concordance is the key feature distinguishing D-Type from L-Type transposition of the great arteries.
Treatment and Outcomes: While D-TGA will ultimately require surgical correction, palliative bridging therapies include neonatal prostaglandin therapy for maintaining patency of the ductus arteriosus and balloon atrial septostomy (BAS or Rashkind procedure) for enlarging the ASD to increase the degree of intracardiac shunting. Definitive surgical correction of D-TGA can be performed, usually in the first week of life, through either an atrial switch procedure such as a Mustard or Senning procedure (Fig. 82.10) or an arterial switch operation with coronary reimplantation such as the Jatene procedure (Fig. 82.11).
FIGURE 82.10 Oblique coronal (A) and axial (B) contrast-enhanced ECG-gated cardiac CT demonstrates the postoperative appearance of a patient with D-TGA who underwent an atrial switch operation, in which the pulmonary veins (PV) were baffled to the morphologic right atrium (RA) and the superior vena cava (SVC) and inferior vena cava (IVC) were baffled to the morphologic left atrium (LA). In this postoperative configuration, the right ventricle (RV) functions as the “systemic ventricle” and undergoes hypertrophy over time due to chronic exposure to systemic pressures, as seen in this patient.
FIGURE 82.11 Axial contrast-enhanced ECG-gated cardiac CT demonstrates the postoperative appearance of a patient with D-TGA who underwent an arterial switch operation (Jatene procedure), in which the great arteries are surgically switched and the coronary arteries are reimplanted. This operation creates a characteristic postoperative appearance wherein the pulmonary arteries (PA) appear draped anteriorly over the aorta (Ao).
Current practice patterns favor the arterial switch operation with coronary reimplantation as the treatment of choice for D-TGA, given better long-term outcomes. Postoperative surveillance of surgically corrected D-TGA patients via the arterial switch operation focuses on monitoring for the development of neo-aortic root dilation, aortic regurgitation, left ventricular dysfunction, supravalvular (anastomotic) pulmonic stenosis, and coronary occlusion. By contrast, D-TGA patients who have undergone an atrial baffle switch (Mustard or Senning) procedure are at risk for developing dysfunction of the systemic (morphologic right) ventricle, which is the major source of morbidity and mortality, as well as baffle stenosis.
Transposition of the Great Arteries, L-Type Embryology and Epidemiology: TGA (L-Type), in contrast, refers to the combination of atrioventricular discordance and ventriculoarterial discordance, a so-called “congenitally corrected” transposition. In L-TGA, the anatomic right atrium connects to the morphologic left ventricle via the mitral valve with outflow into the main pulmonary artery, while the anatomic left atrium connects to the morphologic right ventricle via the tricuspid valve with outflow into the aorta (Fig. 82.12). By comparison to the previously discussed subtype, in the L-TGA configuration, the aorta arises anteriorly and to the left of the pulmonary artery.
FIGURE 82.12 Schematic representation of L-Type Transposition of the Great Arteries (L-TGA), demonstrating the anatomic right atrium connecting to the morphologic left ventricle with outflow into the pulmonary artery and the anatomic left atrium connecting to the morphologic right ventricle with outflow into the aorta. (Courtesy: Susanne Loomis.)
L-TGA can be associated with Ebstein anomaly as well as other congenital defects, including VSDs and pulmonic stenosis [1,3]. When these abnormalities are present, cyanosis may occur. Rarely L-TGA can be seen in combination with right ventricular hypoplasia, resulting in single ventricle physiology. Pathophysiology and Clinical Features:
In contrast with D-TGA, patients with L-TGA are not dependent on intracardiac shunting and may be asymptomatic or present in adulthood. In certain patients, however, significant tricuspid insufficiency and systemic ventricular dysfunction can occur, as the morphologic right ventricle faces higher left-sided (systemic) pressures [4]. Imaging Features: With the exception of the atrioventricular discordance, the imaging findings of L-TGA by radiography and echocardiography are often indistinguishable from D-TGA and are summarized in Table 82.9. Table 82.9 Summary of the Key Imaging Features of L-Type Transposition of the Great Arteries Technique
Imaging Features
Chest radiograph
“Egg on a string” appearance of the heart Increased pulmonary vascularity Cardiomegaly Thymic hypoplasia
Cardiac CT/MRI
Atrioventricular discordancea Ventriculoarterial discordance Aorta anterior and to the left of the pulmonary artery Hypertrophy of the morphologic (systemic) right ventricle Tricuspid insufficiency or Ebstein anomaly Ventricular septal defects
a
Note that atrioventricular discordance is the key feature distinguishing L-Type from D-Type transposition of the great arteries.
Echocardiography can be useful evaluating for coexisting VSDs and/or the presence of pulmonic stenosis in these patients. Advanced imaging modalities, such as cardiac CT and cardiac MRI, are again valuable for anatomic delineation (Fig. 82.13) as well as detection of associated abnormalities if a definitive diagnosis cannot be made by echocardiography alone. These modalities are also very powerful tools in evaluating L-TGA patients who undergo simultaneous atrial and arterial switch operations, as baffle patency, anastomotic site stenoses, and coronary reimplantation complications are of particular interest in clinical management.
FIGURE 82.13 Oblique coronal (A), axial (B), and oblique sagittal (C) contrastenhanced ECG-gated cardiac CT images demonstrate a patient with L-TGA. The anatomic right atrium (RA) connects to the morphologic left ventricle (LV) with outflow into the pulmonary artery (PA) while the anatomical left atrium (LA) connects to the morphologic right ventricle (RV) with outflow into the aorta (Ao). Despite the hypertrophy of the ventricular chambers, the morphologic right ventricle can be distinguished by the presence of the moderator band (asterisk).
Treatment and Outcomes: The approach to treating L-TGA differs greatly from that of D-TGA. If significant tricuspid insufficiency or morphologic right (systemic) ventricular dysfunction is present, conventional tricuspid valve replacement may be performed. In rare instances, anatomic repair with a “double switch” procedure may be attempted, combining an atrial baffle with a simultaneous arterial switch operation and coronary artery reimplantation. The goal behind this surgical approach is to correct the anatomic configuration so that the morphologic left ventricle becomes the systemic ventricle. Due to the inverted configuration during development, the left ventricle may need to be preconditioned to tolerate higher systemic pressures, which can be achieved with a pulmonary artery band operation aimed at increasing the pulmonary vascular resistance. L-TGA patients are at risk of developing heart block or atrioventricular reentrant tachycardia, and therefore may additionally require pacemaker placement. Overall L-TGA patients tend to have better outcomes when compared with D-TGA patients. Despite low early postoperative mortality, the long-term outcome for L-TGA patients with conventional repair (tricuspid valve replacement with VSD repair) is poor, largely due to progressive systemic right ventricular dysfunction and heart failure. Limited long-term data are available regarding prognosis after anatomic repair (atrial and arterial switch operations) given its recent introduction into clinical practice. Tricuspid Atresia Embryology and Epidemiology:
Tricuspid atresia is the third most common cyanotic congenital heart defect, accounting for 1–2% of all CHD [10], and is characterized by absence of the tricuspid valve with resulting complete obstruction of right ventricular (systemic venous) inflow (Fig. 82.14). Common associated congenital abnormalities include a PDA and/or VSD, valvular or subvalvular pulmonic stenosis, pulmonary atresia, and aortic arch abnormalities, as well as extracardiac gastrointestinal and skeletal anomalies [1,10].
FIGURE 82.14 Schematic representation of tricuspid atresia, demonstrating complete atresia of the tricusid valve with resulting systemic venous inflow obstruction. This illustration also includes atrial (ASD) and ventricular septal defects (VSD) as well as a patent ductus arteriosus (PDA), some combination of which is required for survival in this “functional single ventricle” congenital abnormality. (Courtesy: Susanne Loomis.)
Pathophysiology and Clinical Features: Tricuspid atresia is considered a “single ventricle defect” and is incompatible with life in isolation. Living patients with this condition always have at least a coexisting ASD or PFO to allow for right-to-left shunting. Patients with this congenital anomaly most commonly present with cyanosis and/or congestive heart failure within the first few days to weeks of life and are often noted to have localized fibrous thickening in the
lower portion of the right atrium (at the expected location of the tricuspid valve) commonly with associated right ventricular hypoplasia. Tricuspid atresia can be broadly subclassified according to the position and morphology of the great arteries, which may be normally configured, transposed in a D-Type TGA configuration, or fused in a truncus arteriosus configuration. Patients with TA and normally related great arteries commonly have a restrictive VSD or pulmonary stenosis/atresia, which obstructs pulmonary blood flow and causes systemic cyanosis. In severe cases, patients will be dependent on a PDA for pulmonary blood flow. In contrast, patients with TA and D-TGA tend to have larger VSDs and thus are more likely to present with symptoms of congestive heart failure due to increased (unrestricted) pulmonary blood flow. These patients are also more likely to have coexisting aortic coarctation or interruption of the aortic arch (IAA), which may complicate the physiology and change the corrective surgical options. Imaging Features: The radiographic appearance of tricuspid atresia varies greatly based on the presence or absence of coexisting congenital abnormalities, and patients may even present with a normal chest radiograph at birth. Frequently, however, at least mild cardiomegaly will be noted due to enlargement of the right atrium and left cardiac chambers. Pulmonary vasculature may be either increased or decreased depending on the presence or absence of pulmonary flow obstruction, and if the great arteries are transposed, the superior mediastinum may appear narrowed. Echocardiography provides direct visualization of the cardiac anatomy, including the atretic tricuspid valve with biatrial enlargement and left ventricular hypertrophy, and a hypoplastic right ventricle. As discussed in other sections, echocardiography is also the first-line technique for assessing associated congenital defects, including TGA, pulmonary stenosis, and intracardiac shunts. The use of contrast-enhanced echocardiography would show the characteristic serial enhancement of the right atrium, left atrium, left ventricle, and finally the right ventricle, reflecting the pattern of intracardiac shunting. Advanced imaging modalities, including cardiac CT and cardiac MRI, can similarly provide excellent anatomic delineation of cardiac and extracardiac structures, quantification of biventricular volume and function, and due to the excellent soft-tissue resolution, replacement of the tricuspid valve by fat extending into the anterior atrioventricular groove can be easily demonstrated. These modalities, especially cardiac MRI if there is no contraindication, now also play a particularly important role in the evaluation of postoperative patients with palliative shunts or Fontan circulation, providing complimentary information when combined with echocardiography or cardiac catheterization. CT and MRI can also be used for routine postoperative surveillance to monitor for the development of anastomotic leaks/stenoses, shunt occlusions, and early branch pulmonary artery stenoses sometimes even before symptoms develop, which may prompt early preventive intervention. Cardiac MRI has the additional advantage of
being able to detect myocardial fibrosis with LGE, which can cause ventricular arrhythmias in these patients. The key imaging features for tricuspid atresia are highlighted in Table 82.10 and the differential diagnosis, summarized in Table 82.11, includes other common cyanotic CHDs, such as TOF and TGA, as well as other tricuspid valve abnormalities, such as Ebstein anomaly. Although there may be significant overlap in the clinical presentation and imaging features of these entities, the key differentiating feature is complete atresia of the tricuspid valve. Table 82.10 Summary of the Key Imaging Features of Tricuspid Atresia Technique
Imaging Features
Chest radiograph
Pulmonary vascularity may be increased or decreased Right atrial enlargement ± left chamber enlargement
Cardiac CT/MRI
Atresia of the tricuspid valve Right atrial enlargement Right ventricular hypoplasia ± pulmonic atresia Patent foramen ovale (PFO) or Atrial septal defect (ASD) Possible D-type transposition of the great arteries or truncus arteriosus
Table 82.11 Differential Diagnosis for Tricuspid Atresia Tetralogy of Fallot (TOF) Transposition of the great arteries (TGA) Ebstein anomaly
Treatment and Outcomes: Typical initial management of TA involves palliative measures to address pulmonary blood flow. In patients with restricted pulmonary blood flow (TA with restrictive VSD and/or pulmonary stenosis/atresia), prostaglandin E1 administration will be used to maintain patency of the ductus arteriosus before surgical intervention. On the other hand, in patients with pulmonary overcirculation (TA with large VSD and D-TGA), pulmonary artery banding may be required to reduce/regulate pulmonary blood flow before surgery.
Definitive surgical palliation of TA and other single ventricle defects has evolved over time into what is now most commonly a three-stage Norwood repair procedure. The first stage in early infancy involves an atrial septostomy to increase intracardiac shunting along with a Blalock–Thomas–Taussig shunt, connecting the right subclavian artery to the right pulmonary artery, to reestablish pulmonary blood flow. The second stage is typically performed around age 6 months and involves conversion to a bidirectional Glenn or Hemi–Fontan shunt, wherein the superior vena cava is connected to the right pulmonary artery to restore systemic venous return from the upper body to the pulmonary circulation. The third and final stage is the Fontan procedure (Fig. 82.15), which is commonly performed after 2 years of age, and establishes a connection between the inferior vena cava and the right pulmonary artery. The ultimate aim of this multistage operation is to separate the left- and right-sided circulations, harnessing the systolic function of the single (in this case morphologic left) ventricle for systemic circulation and creating a systemic venous to pulmonary arterial connection for passive venous return into the pulmonary circulation. This connection is most commonly in the form of a total cavo-pulmonary connection (TCPC), but can alternatively be seen in the form of a right atrium to pulmonary connection (AP).
FIGURE 82.15 Axial (A), coronal (B), sagittal (C) contrast-enhanced ECG-gated cardiac CT demonstrates the postoperative appearance of a patient with tricuspid atresia who has undergone single ventricle palliation with a lateral tunnel Fontan shunt (F), seen on the axial image within the right atrium (RA). The tricuspid valve is atretic (arrow) and there is an underdeveloped nonopacified right ventricle (white asterisk) that does not participate in cardiac output. An atrial septal defect (white circle) allows some blood exchange between the right atrium (RA)/Fontan and the left atrium (LA), while the left ventricle (LV) functions as the “single ventricle” pumping blood into systemic circulation. Coronal (B) and sagittal (C) reformats demonstrate the lateral tunnel Fontan (dotted line) connecting the superior and inferior vena cava to the right pulmonary artery, also known as total cavo-pulmonary connection.
Long-term survival and morbidity data for patients with Fontan circulation are promising, with reported survival rates of nearly 90% at age 30 years and approximately 60% at age 50 years, noting relatively low rates of cardiac
transplantation overall [13]. The most common causes of death in these patients are cardiac failure and presumed arrhythmia-related sudden death. Truncus Arteriosus Embryology and Epidemiology: Truncus arteriosus is a rare cyanotic congenital heart defect, accounting for 1–4% of all CHD [10,14], in which the aorta, pulmonary arteries, and coronary arteries all arise from a common trunk (the truncus arteriosus) that most commonly overrides an associated large VSD (Fig. 82.16). The underlying cause is the failure of septation of the common truncus in the fetus, and arrangement of the cardiac chambers is otherwise anatomically normal in most cases. However, the common truncal valve is often abnormal in its development, with myxomatous valve leaflets arranged in a bicuspid, quadricuspid, or even pentacuspid morphology, often resulting in mixed valvular stenosis and insufficiency.
FIGURE 82.16 Schematic representation of truncus arteriosus, demonstrating a common origin of the aorta and pulmonary artery in the Collett and Edwards Type 1 (most common) configuration overriding a large ventricular septal defect (VSD). (Courtesy: Susanne Loomis.)
Truncus arteriosus is closely associated with right-sided aortic arch with mirror image branching and is commonly seen as part of DiGeorge syndrome (22q11.2 microdeletion) [1,10]. PDA and other anomalies of the aortic arch and branch pulmonary arteries can also be seen in association, some of which have been identified as independent risk factors for surgical mortality, including IAA. Truncus arteriosus can be subdivided into different types depending on the location or takeoff orientation of the pulmonary arteries, and there are multiple historical classification systems used to describe the heterogeneity of the branching pattern (Tables 82.12 and 82.13).
Table 82.12 Collett and Edwards Classification System for Truncus Arteriosus Type 1 (most common)
Short main pulmonary artery from truncus
Type 2
Two separate pulmonary arteries from truncus (posterior origin)
Type 3 (least common)
Two separate pulmonary arteries from truncus (lateral origin)
Type 4 (pseudotrunc us)
Now recognized as Pulmonary Atresia with VSD (severe Tetralogy of Fallot variant)
Table 82.13 Van Praagh Classification System for Truncus Arteriosus T y p e A 1
Origin of the pulmonary trunk from the truncal root
T y p e A 2
Separate origin of the branch pulmonary arteries from the truncal root
T y p e A 3
Absent left, right, or both pulmonary arteries with absent pulmonary artery originating from an arterial duct or collateral artery
T y
Associated with aortic coarctation or interruption of the aortic arch
p e A 4 A
Denotes presence of a ventricular septal defect (VSD)
B
Denotes rare occurrence of intact ventricular septum
Pathophysiology and Clinical Features: The clinical presentation of truncus arteriosus is highly variable and is predominantly dependent upon the morphology of the truncus, the degree of truncal valve regurgitation, and the relative resistances in the pulmonary and systemic vascular systems. Patients will commonly present in early neonatal life with some degree of cyanosis, but may experience shortness of breath and congestive heart failure to a much greater extent due to pulmonary overcirculation. From a physiologic standpoint, there is complete intracardiac mixing of oxygenated pulmonary and deoxygenated systemic venous blood across the VSD, which explains the systemic desaturation. Given that the pulmonary vascular system is frequently lower resistance when compared with the systemic circulation, blood flow within the truncus is preferentially directed into the pulmonary vasculature, causing symptoms of congestive heart failure. Chronically increased pulmonary flow predisposes to early pulmonary vascular obstructive disease. As with many other CHDs, prenatal diagnosis is typically feasible with routine prenatal ultrasound screening. Targeted prenatal screening is commonly pursued in patients with a family history of conotruncal abnormalities, CHD, or DiGeorge syndrome. However, a postnatal presentation of truncus arteriosus is not uncommon. While prenatal diagnosis of truncus arteriosus has not been shown to have a survival benefit, it does allow for family counseling, proper delivery planning, and development of a postnatal care plan. Furthermore, a delay in diagnosis places patients at greater risk of developing progressive coronary steal phenomenon with decreasing pulmonary vascular resistance, as well as significant pulmonary arterial hypertension. Imaging Features: The radiographic findings of truncus arteriosus are similar to many other cyanotic CHDs, and include cardiomegaly, increased pulmonary vascularity, and a narrow superior mediastinum due to concurrent thymic agenesis. An associated right-sided aortic arch is also commonly present. Echocardiography, as the first line technique, allows for definitive diagnosis in a majority of cases, with excellent delineation of the ventricular origin and branching pattern of the common arterial trunk, truncal valvular morphology, and function, associated VSDs, or other intracardiac abnormalities. Advanced imaging modalities, such as cardiac CT and MRI, may be helpful in characterization of truncal anatomy (Fig. 82.17) in complex cases where findings on echocardiography are equivocal, as
well as evaluation of truncal valvular and biventricular function. These modalities are also particularly useful in assessing for postsurgical complications such as RV to PA conduit stenosis, truncal root dilation, or anastomotic pseudoaneurysm formation.
FIGURE 82.17 Coronal (A), sagittal (B), and short-axis (C) MR Angiogram images demonstrate a patient with uncorrected Collett and Edwards Type 1 configuration Truncus Arteriosus. The common truncal root (asterisk) gives rise to both the aorta (Ao) and pulmonary artery (PA) and overrides a large ventricular septal defect (double-headed arrow), thus receiving blood flow from both the right ventricle (RV) and left ventricle (LV). LA, left atrium; RA, right atrium.
The imaging features for truncus arteriosus are highlighted in Table 82.14 and the differential diagnosis is summarized in Table 82.15, which includes other CHDs that allow for pulmonary-systemic mixing, including TGA, aortopulmonary window, and atrioventricular canal defects. Table 82.14 Summary of the Key Imaging Features of Truncus Arteriosus Technique
Imaging Features
Chest radiograph
Increased pulmonary vascularity Cardiomegaly Narrow superior mediastinum/thymic agenesis Possible right-sided aortic arch (with mirror image branching)
Technique
Imaging Features
Cardiac CT/MRI
Common arterial trunk Ventricular septal defect (VSD) Variable truncal valve function (regurgitation)
Table 82.15 Differential Diagnosis for Truncus Arteriosus Transposition of the great arteries (TGA) Aortopulmonary window Atrioventricular canal defect
Treatment and Outcomes: Definitive surgical management for patients with truncus arteriosus involves closure of the VSD, resection of the main/branch pulmonary arteries from the common arterial trunk, and placement of a conduit reestablishing a connection between the right ventricle and the pulmonary arteries, typically early in neonatal life. Although this procedure is one of the more complicated neonatal surgeries, given the reactivity of the pulmonary vascular bed as well as the large ventriculotomy required, modern-day surgical outcomes in most centers are excellent. Truncus arteriosus patients often outgrow their original conduit with time and require reoperation in the future to resize the conduit. Additional potential reoperations or postsurgical interventions may involve the truncal valve or branch pulmonary arteries. Before the era of surgical repair, mortality for truncus arteriosus was exceedingly high with a survival rate of only 15–30% at 1 year [15]. Even in the early days of surgical management where neonatal pulmonary artery banding was initially performed and followed by staged repair later in infancy, mortality was still double what it is with more modern techniques. Currently, despite still having one of the highest early mortality rates among all CHD surgeries, primary repair in the first few weeks of life is the favored approach. Notably, truncal valve manipulation in early life is avoided whenever possible as neonatal valve repair is also associated with an increase in mortality. Long-term outcomes ultimately depend on the adequacy of conduit function in restoring pulmonary arterial flow, pulmonary vascular resistance, and truncal valve competency. Total Anomalous Pulmonary Venous Return (TAPVR) Embryology and Epidemiology:
Total anomalous pulmonary venous return (TAPVR) is a rare cyanotic congenital heart defect in which all the pulmonary veins drain anomalously into the right heart, forming a left-to-right shunt of oxygenated blood back to the lungs (Fig. 82.18). Similar to tricuspid atresia, TAPVR is incompatible with life in isolation, and thus an obligate coexisting right-to-left shunt, commonly in the form of a PFO or an ASD, is required for survival [9].
FIGURE 82.18 Schematic representation of total anomalous pulmonary venous return (TAPVR), supracardiac subtype (Type 1) wherein all the pulmonary veins (PV) drain above the level of the superior vena cava (SVC) into the left innominate vein through a “vertical vein.” This illustration also includes an atrial level shunt in the form of a patent foramen ovale (PFO) or atrial septal defect (ASD), which is necessary for survival in patients with this congenital defect. (Courtesy: Susanne Loomis.)
Surprisingly, despite continued technological advances in prenatal ultrasonography, TAPVR has one of the lowest prenatal detection rates for CHD, with detection as low as 2–10% [16]. The fetal pulmonary veins carry only a small percentage of blood from the developing lungs, and thus visualization by ultrasound can be challenging. If prenatal diagnosis is not made by screening ultrasound, the initial presenting symptoms of TAPVR can be difficult to distinguish from other cyanotic CHDs or neonatal respiratory diseases, including respiratory distress syndrome or persistent pulmonary hypertension. Pathophysiology and Clinical Features: TAPVR can be classified into different subtypes based on the anatomic location of the pulmonary venous drainage (Table 82.16), with the most common morphology being the supracardiac type [9,17]. Physiologically, TAPVR may be classified as obstructive or nonobstructive depending on the degree of obstruction to pulmonary venous flow, which is most commonly seen in infracardiac TAPVR at the level of the diaphragmatic hiatus. Although this congenital heart defect usually occurs in isolation, it can be seen as a component of more complex CHD, particularly in heterotaxy syndromes. Notably, 50% of patients with asplenia will have CHD and the vast majority of those patients will have TAPVR [9]. Table 82.16 Classification System for Total Anomalous Pulmonary Venous Return [9,17] Type I Suprac ardiac (55%)
Pulmonary veins drain at or above the level of the SVC, most commonly draining into the left innominate vein through a vertical vein (gives the classic “snowman” appearance on CXR)
Type II Cardia c (30%)
Pulmonary veins drain into the coronary sinus or right atrium
Type III Infraca rdiac (13%)
Pulmonary veins drain below the level of the diaphragm, most commonly into the hepatic veins or IVC (obstruction at the level of the diaphragm causes pulmonary edema)
Type IV Mixed
A combination of the types described above
Clinical presentation and radiographic findings depend heavily on the position of the venous drainage, the degree of pulmonary venous obstruction, and the degree of intracardiac mixing. Neonates with obstructive infracardiac TAPVR most commonly present with cyanosis in the first hours of life while neonates with nonobstructive supracardiac TAPVR are more likely to present with signs and symptoms of congestive heart failure within the first six weeks of life. Imaging Features: In suspected cases, echocardiography with Doppler is generally able to identify the site of anomalous venous drainage, along with the presence of an atrial level shunt and right heart dilation. The radiographic features, like the clinical symptoms, vary depending on the position of the pulmonary venous drainage. Neonates with obstructive infracardiac TAPVR most commonly demonstrate florid pulmonary edema with pleural effusions on chest radiograph. Conversely, neonates with nonobstructive supracardiac TAPVR often demonstrate the classic “snowman” appearance on chest radiograph due to widening of the superior mediastinum from the dilated right-sided SVC and left-sided vertical vein (Fig. 82.19).
FIGURE 82.19 Frontal chest radiograph (A) demonstrating the classic snowman appearance (B) of supracardiac TAPVR, which is explained by the widening of the superior mediastinum resulting from dilation of the right-sided superior vena cava and total anomalous drainage of the pulmonary veins into a left-sided “vertical vein.”
CT and MRI can provide valuable supplemental information in complex, mixed, or equivocal cases, and are particularly helpful for infracardiac variants which can be
notoriously difficult to image by ultrasound. CT and MRI can also be useful for detecting pulmonary venous stenoses commonly seen in TAPVR repairs. The multiplanar reformatting and three-dimensional volume rendering capabilities of both CT and MRI can be exceptionally helpful for preoperative surgical planning, and cardiac MRI has the added benefit of flow analysis capabilities, allowing for detailed physiologic assessment. Although cardiac MRI is the most common choice for advanced anatomic delineation of a majority of congenital pulmonary vein anomalies, in the setting of obstructed TAPVR, cardiac CT would be a better choice due to the shorter scan time in a more urgent clinical scenario. The key imaging features for TAPVR are highlighted in Table 82.17 and the differential diagnosis is summarized in Table 82.18. Table 82.17 Summary of the Key Imaging Features of Total Anomalous Pulmonary Venous Return Techniqu e
Anomalous (systemic) drainage of all pulmonary veins Patent foramen ovale (PFO) or Atrial septal defect (ASD) Pulmonary vein stenoses
Table 82.18 Differential Diagnosis for Total Anomalous Pulmonary Venous Return Tetralogy of Fallot (TOF) Transposition of the great arteries (TGA) Truncus arteriosus (TA) Respiratory distress syndrome (RDS) Persistent pulmonary hypertension (PPHN)
Treatment and Outcomes:
Definitive surgical repair of TAPVR involves surgical reimplantation of the pulmonary venous drainage into the left atrium. This surgery is performed on an urgent basis for patients with obstructive TAPVR but can be pursued less urgently in nonobstructive TAPVR. Prostaglandin E1 infusion is typically initiated in neonates to maintain patency of the ductus arteriosus as an additional right-to-left shunt before surgical intervention. Additional closure of the ASD may be pursued at a later date. The presence of preoperative pulmonary venous obstruction is associated with increased preoperative morbidity related to the development of pulmonary hypertension and the potential requirement for extracorporeal membrane oxygenation (ECMO). TAPVR found in association with heterotaxy syndromes is associated with the highest rates of postoperative morbidity, with patients often requiring repeated surgical interventions for the postoperative complication of pulmonary venous stenosis/obstruction (Fig. 82.20). Heterotaxy patients with TAPVR also experience postoperative mortality rates up to ∼50% at three years, particularly if they have complex CHD with single ventricle physiology [16]. This is likely due to the fact that in the long term, patients with single ventricle physiology are dependent upon a compliant pulmonary vasculature and normal pulmonary vascular resistance, and TAPVR patients have developmentally abnormal pulmonary vasculature.
FIGURE 82.20 Axial contrast-enhanced ECG-gated cardiac CT demonstrating anastomotic pulmonary vein stenosis (arrows) as a complication of surgical pulmonary venous reimplantation in a patient born with TAPVR. LA, left atrium; LV, left ventricle; PV, pulmonary vein; RA, right atrium; RV, right ventricle..
Hypoplastic Left Heart Syndrome Embryology and Epidemiology: Hypoplastic left heart syndrome (HLHS) is a rare spectrum of cyanotic congenital heart abnormalities representing the fourth most common CHD to present in the first year of life and constituting 1.2–1.5% of all CHDs [1,10,18]. HLHS is characterized by underdevelopment of the left-sided cardiac structures, including the left atrium, mitral valve, left ventricle, aortic valve, and aorta (Fig. 82.21)(1,10). The pathogenesis of this CHD remains poorly understood, but may be attributable to abnormal cardiac partitioning during embryogenesis.
FIGURE 82.21 Schematic representation of hypoplastic left heart syndrome (HLHS), demonstrating underdeveloped of the left-sided heart structures, including mitral stenosis/atresia, hypoplastic left ventricle, aortic stenosis/atresia, and hypoplastic thoracic aora. This illustration also includes an atrial level shunt in the form of a patent foramen ovale (PFO) or atrial septal defect (ASD), as well as a patent ductus arteriosus (PDA), which are necessary for survival in patients with this congenital defect. (Courtesy: Susanne Loomis.)
Approximately 25% of patients with HLHS will exhibit coexisting complex congenital heart defects, such as DORV, and other common associations include aortic coarctation, VSDs, and endocardial fibroelastosis (EFE) [10]. In addition, up to 25% of HLHS patients will exhibit a major extracardiac anomaly or genetic syndromes such as Turner, Noonan, Holt-Oram, or Smith-Lemli-Oplitz [10].
Pathophysiology and Clinical Features: HLHS is the most common of the “single ventricle defects” with a 2:1 male to female ratio [10]. Initial survival is dependent upon both an ASD and a PDA to allow for blood to bypass the underdeveloped left heart and return to systemic circulation [1,10]. Neonates with this congenital defect may be asymptomatic at birth, however, once the PDA closes in the first few days of life, patients will quickly progress to cyanosis, congestive heart failure, and shock if not surgically managed. Imaging Features: Initial neonatal chest radiograph may be normal in patients with HLHS with radiographic abnormalities often developing within the first 2–3 days of life upon closure of the PDA. These features include increased pulmonary vascularity, severe pulmonary edema, and cardiomegaly—particularly dilation of the right-heart structures. Echocardiography is often sufficient for initial diagnosis and preoperative planning, providing a clear visualization of the underdeveloped left-heart structures, identification of any coexisting abnormalities, such as aortic coarctation, and comprehensive noninvasive evaluation of relevant shunts and valvular competency. Preoperative cardiac CT and MRI are usually only necessary in the case of unusually complex cardiac anatomy in the setting of multiple concomitant congenital abnormalities, but will clearly demonstrate the underdeveloped left-sided heart structures (Fig. 82.22). One potential preoperative use for cardiac MRI is for the detection of EFE. In patients with relatively mild left-sided hypoplasia and functioning mitral and aortic valves, the presence or absence of EFE can be a deciding factor in determining whether a single ventricle repair or double ventricle repair is the appropriate course of action.
FIGURE 82.22 Two axial SSFP images at the level of the cardiac chambers (A) and great vessels (B) demonstrate the classic imaging findings of hypoplastic left heart syndrome, including an underdeveloped left ventricle (LV) and small-caliber hypoplastic aorta (Ao). This patient has undergone single ventricle palliation surgery with a lateral tunnel Fontan (F) seen adjacent to the right atrium (RA). Notice the compensatory hypertrophy of the right ventricle (RV), which functions as the single systemic ventricle in this patient, as well as the enlarged pulmonary artery (PA).
Advanced imaging modalities have a more established role in the postoperative monitoring of HLHS patients who have undergone multistaged single ventricle repair (Fig. 82.23), providing useful information related to ventricular function, valvular competency, and overall cardiovascular anatomy. The key imaging features for HLHS are highlighted in Table 82.19 and the differential diagnosis is summarized in Table 82.20.
FIGURE 82.23 Coronal arterial phase (A) and delayed phase (B) MR Angiogram images demonstrate the postsurgical anatomy of a patient with hypoplastic left heart syndrome following single ventricle palliation. This patient has undergone a Norwood procedure, wherein the hypoplastic aorta (Ao) is reconstructed with the pulmonary (PA) to form a neoaorta (NeoAo). In addition, total cavo-pulmonary connection (TCPC) has been achieved in the form of Glenn (G) and Fontan (F) shunts, which connect the superior vena cava and inferior vena cava to the right pulmonary artery (RPA), respectively RA, right atrium; RV, right ventricle.
Table 82.19 Summary of the Key Imaging Features of Hypoplastic Left Heart Syndrome Technique
Imaging Features
Chest radiograph
Increased pulmonary vascularity Severe pulmonary edema Cardiomegaly (enlarged right heart structures) May be normal in the first 1–2 days of life
Technique
Imaging Features
Cardiac CT/MRI
Hypoplastic left ventricle ± hypoplastic aorta Variable degree of aortic stenosis/atresia Variable degree of mitral stenosis/atresia Patent foramen ovale (PFO) or Atrial septal defect (ASD) Patent ductus arteriosus (PDA) Dilated right atrium and right ventricle Increased pulmonary vascularity and pulmonary edema
Treatment and Outcomes: Before the introduction of surgical techniques designed to palliate single ventricle pathologies, HLHS was a universally fatal disease. Today, the two main treatment strategies for surgical management of HLHS include a multistage Norwood repair (described in detail in the tricuspid atresia section) and cardiac transplantation. Despite nontrivial postsurgical and interstage mortality risk, long-term outcomes continue to improve and HLHS patients are now surviving into teenage and adult years. Some HLHS patients will develop end-stage circulatory failure, and cardiac transplantation is the only available option for long-term survival. Ebstein Anomaly Embryology and Epidemiology: Ebstein anomaly refers to a congenital malformation characterized by apical displacement of the septal and posteroinferior tricuspid valve leaflets (Fig. 82.24), representing 0.3–1% of all CHD and accounting for nearly 40% of all congenital tricuspid valve malformations [9,10]. Although most cases of Ebstein anomaly are sporadic, there is a strong documented associated with maternal ingestion of lithium or benzodiazepines during pregnancy [9,10].
FIGURE 82.24 Schematic representation of Ebstein anomaly, demonstrating apical displacement of tricuspid valve leaflets with resulting “atrialization” of the right ventricle. This illustration also includes an atrial level shunt in the form of an atrial septal defect (ASD), which is common in patients with this congenital defect. (Courtesy: Susanne Loomis.)
An associated PFO or ASD is invariably present in Ebstein patients, and associated pulmonic stenosis or atresia is common. Pathophysiology and Clinical Features: The severity of disease in patients with Ebstein anomaly is largely dependent upon the degree of tricuspid leaflet displacement. When the leaflets are significantly displaced toward the cardiac apex, this results in a large volume of right ventricle becoming “atrialized” and leaves little residual functional right ventricular cavity to generate sufficient pulmonary blood flow. In addition, the displacement of the tricuspid valve
leaflets often results in significant tricuspid regurgitation, which increases right atrial pressure and dilatation and promotes right-to-left shunting at the atrial level. The combination of poor pulmonary arterial flow and increased right-to-left shunting explains why Ebstein patients can present as clinically cyanotic. Neonates with severe Ebstein anomaly may also present with symptoms of congestive heart failure due to the elevated right atrial pressures. However, it should be noted that milder forms of Ebstein anomaly may have a less dramatic clinical course and patients may go undiagnosed until adulthood if the right ventricle is able to maintain adequate systolic function and there is minimal tricuspid regurgitation. Imaging Features: The radiographic findings of Ebstein are classically described as an enlarged “boxshaped heart,” the appearance of which is explained by marked right atrial enlargement, dilated and relatively horizontal RVOT, elevated residual right ventricle, and relatively small caliber aorta and main pulmonary artery (Fig. 82.25). Underdeveloped pulmonary vasculature (pulmonary oligemia) can also be seen, particularly in patients with associated pulmonary stenosis or atresia. Notably, Ebstein anomaly is the only cyanotic congenital heart malformation in which the aorta and pulmonary artery are both smaller than normal.
FIGURE 82.25 Frontal chest radiograph (A) demonstrating the classic box-shaped heart appearance (B) of the cardiomediastinal silhouette in Ebstein anomaly, which is explained by the marked right atrial enlargement, dilated and relatively horizontal right ventricular outflow tract, elevated residual right ventricle, and relatively small caliber aorta and main pulmonary artery.
Echocardiography is useful for visualizing the displaced and often dysplastic tricuspid valve leaflets while simultaneously quantifying right ventricular function as well as the degree of tricuspid regurgitation using color flow Doppler. By definition, Ebstein anomaly can be diagnosed when there is greater than 8 mm/m2 body surface area apical displacement of the septal leaflets indexed to patient body surface area [10]. Cross-sectional imaging with multidetector ECG-gated CT is useful in clearly delineating the degree of tricuspid valve leaflet displacement (Fig. 82.26) along with any associated intracardiac or extracardiac abnormalities. Associated findings of congestive heart failure including contrast reflux into the hepatic veins and/or significant right-to-left shunting across an ASD may be seen. Cardiac MRI is useful for noninvasive quantification of right ventricular function and tricuspid regurgitation, particularly in settings where visualization by echocardiography is difficult or findings appear borderline. Patients with Ebstein anomaly are at increased risk for cardiac arrhythmias, which can compromise image quality for both CT and MRI. The key imaging features for Ebstein anomaly are highlighted in Table 82.21 and the differential diagnosis is summarized in Table 82.22, which includes other causes for enlargement of the right-heart structures.
FIGURE 82.26 Four chamber contrast-enhanced ECG-gated cardiac CT demonstrates the abnormally positioned septal tricuspid valve leaflet (arrow) which is apically displaced from the expected annular plane (dotted line), compatible with Ebstein anomaly. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.
Table 82.21 Summary of the Key Imaging Features of Ebstein Anomaly Technique
Imaging Features
Technique
Imaging Features
Chest radiograph
Enlarged “box-shaped heart”–marked right atrial enlargement Decreased pulmonary vascularity
Cardiac CT/MRI
Apically displaced septal and posteroinferior tricuspid valve leaflets Atrialization of the right ventricle PFO or ASD Variable degree of tricuspid regurgitation Small caliber aorta and pulmonary artery
Treatment and Outcomes: Management of Ebstein patients is variable, depending upon the severity of the defect and associated symptoms. Although many patients may be managed nonoperatively, patients with severe defects may require neonatal ECMO for temporization of cyanosis. While some patients can undergo surgical tricuspid valve repair, others with severely displaced and dysplastic tricuspid valves may ultimately require complete tricuspid valve closure with a Blalock–Thomas–Taussig or Bidirectional Glenn shunt to redirect and improve pulmonary blood flow. Given the predisposition to arrhythmias in these patients, pacemakers or catheter ablation therapy can be considered for long-term management [1,10]. Other Rare Cyanotic Congenital Heart Diseases While this section focuses on the most common, high-yield cyanotic CHD pathologies, there are several additional more rare pathologies worth mentioning briefly, should they be encountered in clinical practice. Pulmonary Atresia With Intact Ventricular Septum (PA/IVS): Pulmonary atresia with intact ventricular septum (PA/IVS) accounts for 3% of all CHD with a slight male predominance [14], wherein the development of the pulmonary valve is abnormal and results in complete obstruction of the RVOT. Patients with PA/IVS
frequently have tricuspid regurgitation and a coexisting PFO or ASD, which serves to partially decompress the elevated right ventricular pressures. Other common associations include right ventricular hypoplasia, an underdeveloped or dysplastic (Ebstein anomaly) tricuspid valve, and ventriculocoronary fistulas. PA/IVS is a single ventricle physiology equivalent, and in early neonatal life, the appearance by plain radiograph may be identical to Ebstein anomaly, with massive cardiomegaly predominantly due to right atrial enlargement and decreased pulmonary vasculature. Importantly, if severe tricuspid regurgitation develops in utero, patients may present with intrauterine fetal hydrops or fetal demise. Double Outlet Right Ventricle (DORV): DORV represents less than 1% of all CHD and reflects a type of ventriculoarterial discordance in which both the aorta and pulmonary artery effectively arise from the morphologic right ventricle, resulting in a functional single ventricle physiology (Fig. 82.27) [19]. There is vast morphologic heterogeneity within this particular disease pathology—the great arteries may be normally related to each other or transposed, a coexisting VSD is always present, and superimposed pulmonic stenosis is commonly associated. The unique combination of the various anatomic features determines the symptomatology and clinical course for any given patient, which may range from pulmonary overcirculation to transposition-liked physiology. Similarly, surgical treatment and consequently long-term prognosis for DORV is highly dependent on the morphologic subtype.
FIGURE 82.27 Oblique coronal SSFP image demonstrates a patient with double outlet right ventricle (DORV), wherein the aorta (Ao) and pulmonary arteries (PA) both arise from the morphologic right ventricle (RV). RA, right atrium.
Double Inlet Left Ventricle (DILV): Double Inlet Left Ventricle (DILV) is present when greater than 50% of each atrioventricular connection is contiguous with a dominant left ventricle, and reflects one of the functional single ventricle CHDs. The right ventricle is commonly hypoplastic and if there is ventriculoarterial concordance, a VSD will be present so that blood can shunt left-to-right and exit into the pulmonary arteries for reoxygenation. DILV also represents a heterogeneous spectrum of diseases and is commonly associated with other defects including TGA, pulmonic stenosis/atresia, and aortic
coarctation/obstruction. Similar to other cyanotic CHDs, the presence and severity of pulmonary outflow obstruction is the key factor in determining the degree of cyanosis versus congestive heart failure seen in the clinical presentation. Management is predominantly surgical, most often in the form of staged single ventricle palliation with a Fontan pathway. If there is significant pulmonic stenosis, this may additionally need to be addressed in the form of a Damus–Kaye–Stansel operation.
Acyanotic Congenital Heart Disease Acyanotic CHD similarly represents a wide spectrum of pathologies which, despite the absence of cyanosis, can be clinically significant if severe. This category of CHD is made up of intracardiac left-to-right shunts, obstructive pathologies such as valvular stenoses or HLHS, and a mix of other congenital anomalies. While many of these defects can also be detected with prenatal echocardiography, cardiac CT and MRI again can be valuable adjuncts in delineating anatomy and determining the functional significance of many of these pathologies. This section will contain detailed discussions of the clinical and imaging features of the various acyanotic CHDs, current strategies for management, and the role of advanced imaging in evaluating patients with each pathology. Persistent Fetal Circulation Two normal shunts from fetal circulation, the foramen ovale and ductus arteriosus, may fail to close in the early postnatal period. In patients without other underlying CHD, these findings may be incidentally discovered and asymptomatic. By contrast, in patients with cyanotic CHD, patency of these shunts can be crucial to survival. Patent Foramen Ovale (PFO) Embryology and Pathophysiology: PFO refers to the failure of fusion of the primum and secundum atrial septa, typically resulting in a flap-valve opening in the interatrial septum. This finding is most commonly incidental, reportedly found in approximately 25% of the adult population [20], but has also been identified as a potential source of cryptogenic stroke via paradoxical embolism across the shunt. Imaging Features: PFO is commonly a radiographically occult diagnosis as the degree of shunting across the interatrial septum is usually clinically insignificant. In the setting of high clinical suspicion for PFO, transesophageal echocardiography (TEE) is often the imaging technique of choice for investigation. A TEE “bubble study” involving the intravenous injection of agitated saline during a valsalva maneuver can detect even a small PFO, which is suggested by the early appearance of bubbles within the left atrium.
PFOs are commonly visualized on ECG-gated contrast-enhanced cardiac CT, often appearing as a flap valve or channel-like tunnel in the interatrial septum (Fig. 82.28). This appearance helps distinguish a PFO from an ostium secundum ASD, described in detail in a subsequent section. Cardiac MRI, though not a first-line study for evaluation of PFO, may also be able to demonstrate the defect if large or resulting in significant intracardiac shunting. The imaging features of PFO are summarized in Table 82.23.
FIGURE 82.28 Four-chamber (A) and short-axis (B) contrast-enhanced ECG-gated cardiac CT demonstrates a channel-like tunnel in the interatrial septum with a flap valve appearance on short-axis (arrows), compatible with a small patent foramen ovale. LA, left atrium; RA, right atrium.
Table 82.23 Summary of the Key Imaging Features of Isolated Patent Foramen Ovale Technique
Imaging Features
Chest radiograph
Normal
Cardiac CT/MRI
Channel-like tunnel or flap valve in the interatrial septum Qp/Qs > 1.0 (if clinically significant)
Qp/Qs, pulmonary-systemic flow ratio.
Treatment and Outcomes: PFO frequently requires no treatment, particularly if small and discovered incidentally. In the setting of hemodynamically significant defects or stroke due to suspected paradoxical embolism, both an open surgical approach or percutaneous closure devices can be used for repair. Patent Ductus Arteriosus (PDA) Embryology and Epidemiology: PDA refers to failure of closure of the ductus arteriosus, which is a normal connection between the aorta and pulmonary artery in fetal circulation (Fig. 82.29). Isolated PDA is estimated to account for ∼10% of all congenital heart anomalies (21) and the highest incidence of PDA occurs in premature infants [1].
FIGURE 82.29 Schematic illustration of a patent ductus arteriosus with blood flow shunting left-to-right from the higher pressure aorta into the lower pressure pulmonary arteries. PDA, patent ductus arteriosus. (Courtesy: Susanne Loomis.)
Pathophysiology and Clinical Features:
PDA can be detected on physical examination, classically described as a continuous machine-like systolic and diastolic murmur. While most PDAs are asymptomatic, the physiologic consequences of a PDA may vary depending on the size of the defect and the pressure differential between systemic and pulmonary circulation. Given higher systemic arterial pressures, initially, left-to-right shunting will occur across a PDA. If the degree of shunting is significant, this can result in pulmonary overcirculation and symptoms of congestive heart failure. If uncorrected, long-standing shunting can result in elevated pulmonary arterial pressures and reversal of the shunt to right-to-left, a phenomenon known as Eisenmenger syndrome. Imaging Features: Small isolated PDAs are often radiographically occult, but larger defects may present with increased pulmonary vascularity as well as left atrial and ventricular enlargement on a chest radiograph. Additional radiographic features may vary if a PDA occurs in association with other CHDs, as is commonly the case. The traditional initial noninvasive investigation for suspected PDA is transthoracic echocardiography with color Doppler, which may demonstrate a flow jet through a PDA into the pulmonary artery. Cardiac MRI is an equally effective noninvasive technique for detecting clinically significant PDAs due to its ability to assess detailed vascular anatomy as well as hemodynamic evaluation. Velocity-encoded cine MRI sequences can assess relative flow in the aorta (Qs) and pulmonary arteries (Qp), allowing for the calculation of a pulmonary-systemic shunt fraction (Qp/Qs) which indicates shunt severity. For a PDA, a Qp/Qs ratio > 1.0 suggests the presence of a left-to-right shunt and Qp/Qs > 1.7 suggests shunting significant enough to warrant consideration of surgical repair [21]. While echocardiography and MRI are the imaging tools of choice, cardiac CT may also be useful in evaluating the presence of a PDA (Fig. 82.30), assessing size for consideration of percutaneous closure, and identifying sequela of resulting increased pulmonary arterial pressures, particularly in the setting of complex anatomy due to associated congenital abnormalities. Key imaging features of PDA are summarized in Table 82.24.
FIGURE 82.30 Axial (A) and sagittal (B) contrast-enhanced cardiac CT demonstrates a patent ductus arteriosus (arrows) with densely contrast opacified blood shunting left-to-right from the aorta (Ao) to the pulmonary arteries (PA).
Table 82.24 Summary of the Key Imaging Features of Isolated Patent Ductus Arteriosus Technique
Imaging Features
Chest radiograph
May be normal Increased pulmonary vascularity Enlarged left atrium and left ventricle
Cardiac CT/MRI
Patent connection between aorta and pulmonary arteries Qp/Qs > 1.0 (if clinically significant)
Qp/Qs, pulmonary-systemic flow ratio.
Treatment and Outcomes: In early neonatal life, closure of a PDA can often be achieved with the administration of indomethacin, which inhibits the vasodilator prostaglandin E (PGE) and promotes PDA closure. When this approach is unsuccessful, surgical PDA ligation may be performed with a lateral approach through a left thoracotomy. Depending on the morphology of the PDA, percutaneous catheter closure devices are also available as a minimally invasive option. If a PDA is small and incidentally discovered in adulthood, often no treatment is indicated.
Atrial Septal Defects (ASD) Embryology and Epidemiology: ASDs are a persistent opening or defect in the interatrial septum after birth allowing communication between the left and right atria (Fig. 82.31) and are the most commonly encountered congenital heart abnormality overall [1,22,23]. They may be found in isolation, but are also a very common abnormality found in patients with other complexes CHDs, frequently playing a crucial role in patient survival in numerous cyanotic CHDs.
FIGURE 82.31 Schematic illustration of the interatrial septum demonstrating the location of various types of atrial septal defects (ASDs), including ostium primum, ostium secundum, superior and inferior sinus venosus, and unroofed coronary sinus defects. IVC, inferior vena cava; SVC, superior vena cava. (Courtesy: Susanne Loomis.)
FIGURE 82.32 Four-chamber (A) and short-axis (B) contrast-enhanced ECG-gated cardiac CT demonstrates an ostium primum type atrial septal defect (arrows) with shunting of blood from the left atrium (LA) toward the right atrium (RA).
FIGURE 82.33 Four-chamber (A) and short-axis (B) contrast-enhanced ECG-gated cardiac CT demonstrates an ostium secundum type atrial septal defect (arrows) with shunting of blood from the left atrium (LA) toward the right atrium (RA). Notice the difference in appearance of this atrial septal defect compared with the appearance of a patent foramen ovale, despite being in a similar location.
FIGURE 82.34 Axial (A) contrast-enhanced ECG-gated cardiac CT demonstrates a superior sinus venosus type atrial septal defect (arrows), which occurs along the posterior superior aspect of the interatrial septum where the superior vena cava (SVC) joins the right atrium (RA). An additional axial contrast-enhanced chest CT (B) demonstrates anomalous drainage of the right upper lobe pulmonary vein (asterisk) into the superior vena cava (SVC). Right upper lobe partial anomalous pulmonary venous return (PAPVR) is frequently associated with superior sinus venosus atrial septal defects. LA, left atrium; RA, right atrium.
FIGURE 82.35 Four-chamber (A) and short-axis (B) contrast-enhanced ECG-gated cardiac CT demonstrates an inferior sinus venosus type atrial septal defect (arrows), which occurs along the posterior inferior aspect of the interatrial septum where the inferior vena cava (IVC) joins the right atrium (RA). LA, left atrium; RA, right atrium.
FIGURE 82.36 Oblique axial (A) and sagittal (B) contrast-enhanced ECG-gated cardiac CT demonstrates an unroofed coronary sinus defect (asterisk), which occurs along the margin of where the coronary sinus (CS) abuts the left atrium (LA).
The interatrial septum begins to develop approximately 4 weeks after gestation with atrial septation occurring around the fifth–eighth gestational week [23–25]. The key embryological events of normal atrial septation are summarized below in Table 82.25. Table 82.25 Summary of the Embryological Events Involved in Normal Atrial Septation [23–25] Gesta tional Age
Embryological Event
∼ Week 4
Septum primum (SP) grows from the posterior edge of the common atrium (atrial roof) toward the endocardial cushions at the level of the atrioventricular canal
∼ Week 4–6
Opening develops between the septum primum (SP) and the endocardial cushions, termed the ostium primum (OP)
∼ Week 6
Ostium primum (OP) defect closes as the septum primum fuses with the endocardial cushions, while a second opening simultaneously appears more posteriorly, termed the ostium secundum (OS)
∼ Week 7
A second septum, termed the septum secundum (SS), also grows from the atrial roof toward the endocardial cushions, to the right of the septum primum (SP)
Gesta tional Age
Embryological Event
By week 8
Opening develops in the septum secundum (SS), termed the foramen ovale (FO), which somewhat overlaps with the ostium secundum to form the interatrial connection necessary for shunting of oxygenated blood from the placenta toward systemic circulation, found in normal fetal circulation
Pathophysiology and Clinical Features: Depending on the size, ASDs may remain asymptomatic for years to decades. This is in part due to low atrial pressures, which often means that the degree of interatrial shunting is not clinically significant. Despite the initial lack of clinical symptoms, at least half of adolescents and adults with ASDs will develop symptoms [22]. If an ASD is large and unrepaired for many years, the chronic left-to-right shunting can result in patients presenting with dyspnea, fatigue, atrial fibrillation/flutter, right heart failure, or pulmonary hypertension. As with an uncorrected PDA, the resulting pulmonary hypertension may result in Eisenmenger syndrome, with reversal of the atrial level shunt to become right-to-left. Imaging Features: Similar to a PFO, ASDs are often radiographically occult. If large or longstanding, there may be dilatation of the right heart chambers and pulmonary arterial enlargement. These findings, in combination with a slight rotation of the heart, can make the ascending aorta appear deceivingly small on plain radiograph, though it remains normal in caliber. Transthoracic or TEE is the primary imaging technique of choice for initial diagnosis due to high sensitivity, easy accessibility, and low-cost relative to other imaging modalities. Similar to a PFO workup, a TEE “bubble study” can detect even a small ASD by the early appearance of bubbles within the left atrium. Echocardiography may be limited, however, in its ability to clearly visualize the location and size of the ASD. ASDs are well-visualized on ECG-gated contrast-enhanced cardiac CT, with the appearance depending on the type of ASD (Fig. 82.31). The embryologic origin and imaging features of the various subtypes of ASDs are summarized in Table 82.26. Cardiac CT again provides a more thorough evaluation for coexisting congenital defects, such as anomalous pulmonary venous drainage, and can be particularly useful in assessing the size of the septal defect while also providing information about the surrounding septal rims, which is important for preprocedural planning, especially for percutaneous ASD closure devices. The relevant anatomic septal rims are summarized in Table 82.27.
Table 82.26 Description of Different Types of Atrial Septal Defects Typ e
Location
Embryology
Associations
Osti um pri mu m (15 – 35 %)
Anterior interatrial septum near the atrioventricul ar valves (Fig. 82.32)
Septum primum fails to fuse with endocardial cushions
Associated with Down syndrome (Trisomy 21) Considered the mildest form of the endocardial cushion defect spectrum (discussed separately)
Osti um secu ndu m (60 – 75 %)
Mid interatrial septum near the fossa ovalis (Fig. 82.33)
Excessive resorption of the septum primum or deficient growth of the septum secundum causing a shortened valve of the foramen ovale
Holt–Oram syndrome
Sup erio r sin us ven osu s (4– 11 %)
Posterior superior interatrial septum where the SVC joins the RA (Fig. 82.34)
Thought to result from lack of septation between the pulmonary veins and the SVC or RA
Strongly associated with right upper lobe partial anomalous pulmonary venous return (PAPVR)
Typ e
Location
Embryology
Associations
Infe rior sin us ven osu s (rar e)
Posterior inferior interatrial septum where the IVC joins the RA (Fig. 82.35)
Thought to result from lack of septation between the pulmonary veins and the IVC or RA
Less common than superior sinus venosus defects but also associated with right-sided PAPVR
Unr oofe d cor ona ry sin us (rar e)
Posterior interatrial septum where the coronary sinus contacts the LA (Fig. 82.36)
Lack of septation between the inferior LA and the roof of the coronary sinus
Associated with a persistent leftsided SVC
IVC, inferior vena cava; LA, left atrium; PAPVR, partial anomalous pulmonary venous return; RA, right atrium; SVC, superior vena cava. [1,23,24,26–28].
Table 82.27 Description of Atrial Septal Rims Relevant for Percutaneous Closure Devices [29] Lo cati on
Rims
Definition
Sup eri or
Superior vena cava (SVC) rim
Minimum distance between ASD and the superior vena cava
Superior rim
Rim between the SVC and aortic rim
Lo cati on
Rims
Definition
Ant eri or
Aortic rim
Minimum distance between ASD and the aortic wall
Atrioventricul ar (AV) rim
Minimum distance between ASD and the atrioventricular (tricuspid and mitral) valves
Infe rior
Inferior vena cava (IVC) rim
Minimum distance between ASD and the inferior vena cava
Pos teri or
Posterior rim
Minimum distance between ASD and the posterior atrial wall
ASD, atrial septal defect.
Cardiac MRI is a useful adjunctive imaging technique for quantifying the degree of atrial shunting utilizing velocity encoding sequences, as described in an earlier section about PDA. SSFP cine and spin-echo sequences are often useful for localizing the ASD to set up the shunt quantification sequences appropriately. The imaging features of ASDs are summarized in Table 82.28. Table 82.28 Summary of the Key Imaging Features of Isolated Atrial Septal Defect Technique
Imaging Features
Chest radiograph
May be normal Enlarged pulmonary artery with increased pulmonary vascularity Enlarged right atrium and ventricle No left atrial enlargement (unless Eisenmenger syndrome develops)
Cardiac CT/MRI
Patent connection between the left and right atria Qp/Qs > 1.0 (if clinically significant)
Qp/Qs, pulmonary-systemic flow ratio.
Treatment and Outcomes: Isolated ASDs warrant surgical repair when patients become symptomatic. Depending on the size and location of the defect, this may be accomplished with percutaneous ASD closure device or open surgical closure. Atrioventricular Canal (Endocardial Cushion) Defect Embryology and Epidemiology: Atrioventricular canal defects (also commonly termed endocardial cushion defects) result from abnormal formation or fusion of the endocardial cushions during embryological development [1,9] and account for approximately 2–7% of congenital heart defects [9,27]. This can range from an ostium primum ASD with mild abnormalities of the atrioventricular (tricuspid or mitral) valves to a single common atrioventricular valve with associated atrial and VSDs (Fig. 82.37), allowing for free communication of blood between the right and left heart [1,3,9,22,27].
FIGURE 82.37 Schematic representation of an atrioventricular canal defect (also known as an endocardial cushion defect), demonstrating a common atrioventricular valve with associated atrial septal defect (ASD) and ventricular septal defect (VSD). (Courtesy: Susanne Loomis.)
There is a strong association with Trisomy 21 (Down syndrome)—up to 40% of patients with atrioventricular canal defects have Trisomy 21. [1]. This congenital heart defect may also be seen associated with other genetic disorders as well, including heterotaxy syndromes and Trisomy 18. Pathophysiology and Clinical Features:
While milder spectrum abnormalities may remain asymptomatic or resemble other ASDs in clinical presentation, severe or complete atrioventricular canal defects result in free communication of all four cardiac chambers with significant bidirectional shunting through the atrial and VSDs. These patients may present with florid congestive heart failure and/or pulmonary hypertension in infancy. Imaging Features: Radiographic features of atrioventricular canal defects are often nonspecific and include cardiomegaly with increased pulmonary vascularity. Although rarely performed now given modern advances in cross-sectional imaging, left ventricular angiography was once used for diagnosis and workup of this abnormality. On a lateral oblique view during left ventriculography, this abnormality may result in a “gooseneck sign,” explained by a concave interventricular septum below the mitral valve as well as narrowing and elongation of the left ventricular outflow tract [9]. Atrioventricular canal defects can be accurately diagnosed by echocardiography and will be most visible as a large central defect on a four-chamber view with free communication between the cardiac chambers on color Doppler images. Cardiac CT and cardiac MRI are both excellent modalities for visualizing the atrioventricular defect (Fig. 82.38), can demonstrate the common atrioventricular valve in motion, and are useful adjuncts in determining complete cardiac and extracardiac anatomy in the setting of multiple congenital abnormalities. The imaging features of atrioventricular canal defects are summarized in Table 82.29.
FIGURE 82.38 Four-chamber SSFP image demonstrates a patient with Down syndrome who has a complete atrioventricular canal defect (also known as endocardial cushion defect). Notice in this case that the right atrium (RA) and right ventricle (RV) are larger and more hypertrophied compared to the left atrium (LA) and left ventricle (LV), indicating that there is a right-dominant atrioventricular (AV) valve with more flow entering the right-sided chambers. Given the mobility of the AV valve, the leaflets are often not well seen by imaging, but the absence of the internal cardiac crux (dotted circle) gives a characteristic imaging appearance.
Table 82.29 Summary of the Key Imaging Features of Atrioventricular Canal Defects Technique
Imaging Features
Chest radiograph
Cardiomegaly Increased pulmonary vascularity
Left ventriculograph y
“Gooseneck sign”
Technique
Imaging Features
Cardiac CT/MRI
Common atrioventricular valve—may favor right or left heart Atrial and ventricular septal defects Possible underdevelopment of either side of the heart
Treatment and Outcomes: Treatment for this congenital abnormality is primarily surgical. The surgical approach will depend not only on the severity of the atrioventricular canal defect but also on the presence or absence of unilateral ventricular hypoplasia, which can occur in the setting of an asymmetric common atrioventricular valve favoring one side of the heart. Without two well-developed ventricles, these patients may require some version of single ventricle palliation to survive. Ventricular Septal Defects (VSD) Embryology and Epidemiology VSDs are a persistent opening or defect in the interventricular septum after birth allowing communication between the left and right ventricles (Fig. 82.39) and are the second most common congenital heart abnormality in children, accounting for 20–40% of all congenital heart defects [1,22,24,27]. Embryologically, a VSD may occur due to maldevelopment of the muscular septum, malformation of the endocardial cushions, or abnormal resorption of myocardial tissue in the interventricular septum. Interestingly, up to 75% of isolated VSDs will close spontaneously by age 10 [1].
FIGURE 82.39 Schematic illustration of the interventricular septum demonstrating the location of various types of ventricular septal defects (VSDs), including inlet, perimembranous, supracristal/outlet, and muscular defects. SVC, superior vena cava; IVC, inferior vena cava. (Courtesy: Susanne Loomis.)
FIGURE 82.40 Four-chamber (A) and axial (B) contrast-enhanced ECG-gated cardiac CT images demonstrate a perimembranous ventricular septal defect (arrow), which occurs along the upper membranous portion of the interventricular septum allowing communication between the right ventricle (RV) and left ventricle (LV). This abnormality was detected in adulthood and there is obvious sequela of long-standing left-to-right shunting with elevated right heart pressures, including dilated right atrium (RA) compared with the left atrium (LA), hypertrophy of the right ventricular myometrium (asterisk) and a dilated main pulmonary artery (double-headed arrow). Ao, aorta; PA, pulmonary artery.
FIGURE 82.41 Axial (A) and short-axis (B) contrast-enhanced ECG-gated cardiac CT images demonstrate an apical muscular ventricular septal defect (arrows), which occurs along the lower muscular portion of the interventricular septum allowing communication between the right ventricle (RV) and left ventricle (LV).
The interventricular septum begins to develop around the same time as the interatrial septum, approximately 4 weeks after gestation with ventricular septation occurring
during the fourth–seventh gestational week [27]. Notably, ventricular septation is closely related to the septation of the truncus and conus cordis, which develop into the future ventricular outflow tracts, and thus abnormalities of these processes commonly occur simultaneously [24]. Pathophysiology and Clinical Features: VSDs can be detected on physical examination, classically described as a holosystolic murmur heard best at the left sternal border, due to turbulent flow across the defect. Pathophysiologically, VSDs are similar to ASDs in that they allow for an abnormal intracardiac left-to-right shunt. While small VSDs can be asymptomatic and remain undetected until after birth, ventricular pressures are much higher than atrial pressures, and therefore even relatively small VSDs may present as clinically symptomatic. Large VSDs can result in florid congestive heart failure within 2–3 months of birth [1]. Longstanding uncorrected VSDs can also eventually result in pulmonary arterial hypertension and Eisenmenger syndrome, with reversal of the ventricular level shunt to become right-to-left. Imaging Features: Similar to other types of septal defects, small VSDs are often radiographically occult. If large or longstanding, cardiomegaly may be present, including left atrial dilation, and pulmonary arterial enlargement. VSDs can usually be visualized with a four-chamber view on echocardiography, which remains the primary imaging technique for initial diagnosis as with many other congenital heart defects. Echocardiography may be limited in detecting smaller defects, though the use of color Doppler can increase sensitivity. In particular, echocardiography is less sensitive for the detection of supracristal VSDs, due to the commonly retrosternal location. VSDs are easily visualized on cardiac CT, with the appearance and location depending on the type of VSD (Fig. 82.39). The embryologic origin and imaging features of the various subtypes of VSDs are summarized in Table 82.30. Cardiac CT can also provide shunt quantification and accurate sizing of defects for preprocedural planning before VSD repair. Table 82.30 Description of Different Types of Ventricular Septal Defects Types of ventricular septal defects and imaging features Type
Location
Associations
Types of ventricular septal defects and imaging features Type
Location
Associations
Perimembr anous (70–80%)
Membranous interventricular septum Below the aortic valve and behind the septal leaflet of the tricuspid valve (Fig. 82.40)
Associated with aortic or tricuspid regurgitation due to proximity of the defect to these valve leaflets
Most frequently involves the apical two-thirds of the muscular septum
Inlet or atrioventri cular (5–10%)
Inlet interventricular septum Extends from the tricuspid annulus to the attachments of the tricuspid valve leaflets
Associated with atrioventricular septal defects or anomalous insertion of the chordae tendinae
Outlet or supracrista l (5–8%)
Outlet interventricular septum Above the crista muscle and below the aortic and pulmonic valves
Associated with truncus arteriosus, Tetralogy of Fallot, and double outlet right ventricle Aortic valve prolapse and aortic regurgitation are important complications
LV, left ventricle; RV, right ventricle [1,22,24,27].
Cardiac MRI is useful for localizing defects with SSFP cine and spin-echo sequences as well as quantifying the degree of ventricular shunting utilizing velocity encoding sequences. MRI may be of particular clinical utility in the setting of a supracristal VSD, providing better visualization of the defect and allowing for the diagnosis of common complications of this VSD subtype, including aortic valve prolapse with resultant aortic regurgitation and secondary right ventricular hypertrophy [22]. The imaging features of VSDs are summarized in Table 82.31. Table 82.31 Summary of the Key Imaging Features of the Isolated Ventricular Septal
Defect Technique
Imaging Features
Chest radiograph
May be normal Enlarged pulmonary artery with increased pulmonary vascularity Enlarged right heart + left atrial enlargement
Cardiac CT/MRI
Patent connection between the left and right ventricles Qp/Qs > 1.0 (if clinically significant)
Qp/Qs, pulmonary-systemic flow ratio.
Treatment and Outcomes: Given high rates of spontaneous VSD closure, small defects are typically managed conservatively. In symptomatic patients who develop congestive heart failure or pulmonary hypertension, closure can be considered in the form of a surgical patch or percutaneous closure device, depending on the size and location. Partial Anomalous Pulmonary Venous Return: Described in detail in the Chapter 26 on Diseases of Veins and Lymphatics. Congenital Pulmonary Stenosis Embryology and Epidemiology: Congenital pulmonary stenosis refers to the congenital narrowing of the pulmonary outflow tract which can be subvalvular, valvular, or supravalvular. Valvular pulmonic stenosis is commonly an isolated abnormality and is reported to represent 10% of all CHD [30]. However congenital pulmonary stenosis at any level can be associated with certain genetic syndromes, including Williams syndrome, Noonan syndrome, and TOF [1,30,31]. Pathophysiology and Clinical Features: Congenital pulmonary stenosis is frequently asymptomatic and well-tolerated for many years. Valvular pulmonic stenosis can be detected on physical examination, classically described as a midsystolic crescendo-decrescendo ejection murmur in the second intercostal space along the left sternal border. In cases of severe or long-standing stenosis, patients may present with symptoms of right heart failure and other sequelae of elevated right heart pressures. Congenital pulmonary stenosis can be morphologically classified based on the location of the stenosis, summarized below in Table 82.32.
Table 82.32 Description of Different Types of Congenital Pulmonary Stenosis [30,32] Type
Location
Associations
Suprava lvular (most commo n)
Above the level of the pulmonic valve
Associated with Williams syndrome
Valvular
At the level of the pulmonic valve Dome-shaped (40–60%): Mobile valve with 2–4 raphes and partial commissural fusion; small valve orifice Dysplastic (20–30%): Thickened, dysplastic, immobile cusps without commissural fusion Bicuspid/multicuspid (rare): Abnormal number of pulmonic valve leaflets/cusps
Associated with Noonan syndrome
Subvalv ular
Below the level of the pulmonic valve
Associated with Tetralogy of Fallot
Imaging Features: The radiographic features of congenital pulmonary stenosis are nonspecific, but may include dilated right heart chambers, evidence of right ventricular hypertrophy, or pulmonary arterial enlargement. Occasionally, in patients with vavular pulmonic stenosis, a jet of pulmonary blood flow may be preferentially directed toward the left lung, resulting in asymmetric enlargement of the left pulmonary artery and increased left-sided pulmonary vascularity, a finding known as the Chen sign [32,33]. In the setting of valvular pulmonic stenosis, echocardiography may demonstrate abnormal motion (systolic doming) or dysplastic morphology of the pulmonic valve leaflets. In the setting of subvalvular or supravalvular pulmonary stenosis, color Doppler may aid in diagnosis by demonstrating increased flow velocities across the area of greatest narrowing. In severe cases, echocardiography will also demonstrate sequela of elevated right heart pressures including right heart chamber enlargement and possible right ventricular dysfunction. Advanced cross-sectional imaging modalities including CT and MRI allow for threedimensional visualization of stenotic segments (Fig. 82.42) as well as areas of
poststenotic dilation. Cardiac MRI is useful in assessing the severity stenosis with the use of velocity encoded sequences to evaluate flow volumes, velocities, and pressure gradients across a narrowed segment. The imaging features of congenital pulmonary stenosis are summarized below in Table 82.33.
FIGURE 82.42 Oblique axial (A) and sagittal (B) contrast-enhanced ECG-gated cardiac CT images demonstrate both valvular and supravalvular pulmonic stenosis in a patient with Tetralogy of Fallot. There is focal narrowing at the level of the pulmonic valve (asterisk) followed by a second focal narrowing in the supravalvular proximal main pulmonary artery (star). Ao, aorta; LA, left atrium; PA, pulmonary artery; RV, right ventricle.
Table 82.33 Summary of the Key Imaging Features of Isolated Congenital Pulmonary Stenosis Tech niqu e
Imaging Features
Ches t radio grap h
Enlarged right heart/right ventricular hypertrophy Enlarged main pulmonary artery or left pulmonary artery Possible asymmetric increased left-sided pulmonary vascularity (Chen sign)
Tech niqu e
Imaging Features
Card iac CT/ MRI
Narrowing of the right ventricular outflow tract, pulmonic valve, or supravalvular proximal pulmonary artery +/ poststenotic dilation Abnormal pulmonary valve leaflets (if valvular pulmonary stenosis)
Treatment and Outcomes: Isolated congenital pulmonary stenosis, if severe and symptomatic, may be managed medically or treated with balloon valvuloplasty or valvulotomy to reduce the degree of stenosis. Severely dysplastic valves may alternatively be treated with surgical pulmonary valve replacement. Congenital Aortic Stenosis Embryology and Epidemiology: Congenital aortic stenosis refers to the congenital narrowing of the systemic (aortic) outflow tract. Valvular aortic stenosis is most commonly due to a congenitally BAV, which is the overall most common congenital heart defect [34,35]. While the entity of BAV will be discussed in detail separately, this section will focus broadly on subvalvular, valvular, and supravalvular aortic stenosis. Note that aortic coarctation and other abnormalities of the aortic arch will also be discussed separately. Pathophysiology and Clinical Features: Congenital aortic stenosis is parallel in pathophysiology and clinical presentation to congenital pulmonary stenosis, but affecting the left heart chambers rather than the right. Patients are frequently asymptomatic and valvular aortic stenosis can be detected on physical examination, classically described as a mid-systolic crescendo-decrescendo ejection murmur in the second intercostal space along the right sternal border with radiation to the right neck. In cases of severe or long-standing stenosis, patients may present with symptoms of left heart failure and other sequelae of elevated left heart pressures. Congenital aortic stenosis can also be morphologically classified based on the location of the stenosis, summarized below in Table 82.34. Table 82.34 Description of Different Types of Congenital Aortic Stenosis [1,36]
Type
Locatio n
Subtype
Suprava lvular (least commo n)
Above the level of the aortic valve
Localized: Focal or discrete narrowing of the proximal ascending aorta (also associated with Williams syndrome)
Diffuse: Generalized underdevelopment or small caliber of the ascending aorta Valvular (most commo n)
At the level of the aortic valve
Bicuspid Aortic Valve: Two functional leaflets or cusps of the aortic valve (associated with Turner syndrome and aortic coarctation) Unicommisural Aortic Valve: Single horseshoeshaped valve leaflet
Subvalv ular
Below the level of the aortic valve
Membranous: Discrete fibrous membrane narrowing the left ventricular outflow tract
Hypertrophic: Muscular hypertrophy of the infundibulum narrowing the left ventricular outflow tract
Imaging Features: The radiographic features of congenital aortic stenosis are also nonspecific, but may include dilated left heart chambers and poststenotic dilation of the ascending aorta, often seen only in valvular aortic stenosis. In the setting of valvular aortic stenosis, echocardiography may demonstrate abnormal motion (systolic doming) or abnormal morphology of the aortic valve leaflets. In the setting of subvalvular or supravalvular aortic stenosis, color Doppler may aid in diagnosis by demonstrating increased flow velocities across the area of greatest narrowing. In supravalvular aortic stenosis, the ascending aorta take on an hourglass appearance, which refers to an area of focal severe narrowing with more diffuse narrowing of the adjacent aortic segments [36]. Advanced cross-sectional imaging modalities including CT and MRI allow for threedimensional visualization of stenotic segments (Fig. 82.43) as well as areas of poststenotic dilation and sequela of elevated left heart pressures. Cardiac CT and MRI
may also be helpful in delineating discrete subaortic membranes or evaluating for restricted aortic valve leaflet motion. Calcifications of the aortic valve are easily depicted on cardiac CT, which are commonly seen in valvular aortic stenosis.
FIGURE 82.43 Short-axis (A) image from a contrast-enhanced ECG-gated cardiac CT demonstrates a calcified aortic valve in a patient with valvular aortic stenosis. Coronal (B) image from a contrast-enhanced ECG-gated cardiac CT in a separate patient with demonstrates focal narrowing of the supravalvular proximal ascending aorta (asterisk) with an hourglass appearance, commonly seen in patients with Williams syndrome. Ao, aorta; LV, left ventricle; RA, right atrium.
Cardiac MRI is useful in assessing the severity stenosis with the use of velocity encoded sequences to evaluate flow volumes, velocities, and pressure gradients across the narrowed segment. The imaging features of congenital aortic stenosis are summarized below in Table 82.35. Table 82.35 Summary of the Key Imaging Features of Isolated Congenital Aortic Stenosis Tech niqu e
Imaging Features
Tech niqu e
Imaging Features
Ches t radio grap h
Enlarged left heart/left ventricular hypertrophy Normal pulmonary vascularity Enlarged ascending aorta (valvular subtype only)
Cardi ac CT/ MRI
Narrowing of the left ventricular outflow tract, aortic valve, or supravalvular proximal ascending aorta +/ poststenotic dilation Abnormal aortic valve leaflets (valvular subtype only)
Treatment and Outcomes: Isolated congenital aortic stenosis, if severe and symptomatic, may be managed medically or treated with balloon valvuloplasty or valvulotomy to reduce the degree of stenosis. Severely dysplastic valves may alternatively be treated with aortic valve replacement. Patients with subvalvular or supravalvular aortic stenosis may require alternative surgical intervention, such as resection of a subaortic membrane or reconstruction of the ascending aorta depending on the severity of the defect. Aortic Coarctation Embryology and Epidemiology: Aortic coarctation is a relatively common abnormality representing approximately 4– 8% of all CHDs (37–39) and is defined by congenital narrowing of the aortic lumen, commonly in a juxta ductal location at the aortic isthmus (near the ductus arteriosus). Coarcatation may occur as a sporadic defect or in combination with other congenital defects, most commonly BAV, VSDs, and PDA, and can be seen with increased frequency among patients with Turner syndrome [1,9,37]. Pathophysiology and Clinical Features: Clinical presentation of aortic coarctation depends largely on the degree of luminal aortic narrowing and may present with variable symptomatology. Coarctation may present in neonates as acute heart failure or may be diagnosed in an adult due to hypertension with differential upper and lower extremity blood pressures. Aortic coarctation is classically subdivided into two types, preductal and postductal, based on the location of the narrowing relative to the position of the ductus arteriosus, depicted in Fig. 82.44 and summarized in Table 82.36.
FIGURE 82.44 Schematic illustration of preductal (infantile) and postductal (adult) variants of aortic coarctation. Preductal coarcatation refers to narrowing of the proximal descending thoracic aorta proximal to the level of the ductus arteriosus, which commonly remains patent to allow for right-to-left shunting for compensatory systemic blood flow. Postductal coarctation refers to narrowing of the proximal descending thoracic aorta distal to the level of the ductus arteriosus, which often closes at birth to become the ligamentum arteriosum. (Courtesy: Susanne Loomis.)
Table 82.36 Description of Different Types of Aortic Coarctation [1,9,38,39] Typ e
Location
Features
Typ e
Location
Pred uctal (inf antil e type )
Between left subclavian artery and ductus arteriosus
Post duct al (adu lt type )
At or distal to ductus arteriosus
Features
◾ Ductus arteriosus commonly remains patent ◾ Diffuse narrowing with tubular aortic hypoplasia ◾ More commonly associated with bicuspid aortic valve ◾ Ductus arteriosus often closed (ligamentum arteriosum) ◾ Localized, short segment of narrowing ◾ Extensive collateral vessel formation in the chest wall
Imaging Features: The classic radiographic sign of aortic coarctation is the figure-of-three sign with associated rib notching on a frontal chest radiograph (Fig. 82.45). The figure-of-three sign is explained by the appearance of focal narrowing in the proximal descending thoracic aorta and associated dilation of the left subclavian artery, giving a lobulated contour to the left superior mediastinum that resembles the number three. Rib notching is a phenomenon that occurs as a result of dilated tortuous collateral intercostal arteries which form deep grooves along the inferior margins of the posterior ribs, especially the third–eighth ribs, also known as the Roesler sign [9]. The first two intercostal arteries are supplied by the costocervical trunk instead of the descending thoracic aorta, and are thus spared in this process of rib notching.
FIGURE 82.45 Frontal chest radiograph (A) demonstrating the classic figure-ofthree sign (B) associated with aortic coarctation. There are also several bilateral areas of posterior rib notching (circles) caused by dilated tortuous collateral intercostal vessels.
A corresponding reverse-figure-of-three sign has been described in these patients, which refers to the lobulated contour of the anterior esophagus on a barium swallow due to the impression of the adjacent aortic coarctation, which has the appearance of a backward number three [9]. Due to normal patency of the ductus arteriosus in neonatal life, coarctation can be difficult to diagnose in early neonatal life. Echocardiography may be able to visualize the narrowed segment and quantify and gradient across this segment, however, limited acoustic windows limits the utility of echocardiography in clinical assessment. Cross-sectional imaging modalities, especially CT and MR angiography, are capable of delineating not only the location and anatomy of a coarctation (Fig. 82.46), but can also provide a thorough evaluation of the extent of collateral vessels in the chest and abdomen. The imaging features of aortic coarctation are summarized below in Table 82.37.
FIGURE 82.46 Oblique sagittal SSFP image from an MR Angiogram demonstrates focal aortic coarctation with an associated jet of dephasing artifact (circle) due to turbulent flow across the stenotic segment.
Table 82.37 Summary of the Key Imaging Features of Isolated Aortic Coarctation Technique
Imaging Features
Technique
Imaging Features
Chest radiograph
Figure-of-three sign Posterior rib notching (3rd–8th ribs) Normal pulmonary vascularity
Cardiac CT/MRI
Focal narrowing of the proximal descending thoracic aorta Dilated tortuous collateral intercostal arteries (postductal type) ± Patent ductus arteriosus
Treatment and Outcomes: Treatment of aortic coarctation is primarily surgical, with the timing depending on the severity of clinical symptoms. Neonates with acute heart failure early in life will require intervention more urgently compared with patients who have milder symptoms. Coarctation repair can range from simple balloon angioplasty with stent placement to resection of the narrowed segment and primary end-to-end anastomosis. The left subclavian artery can also be ligated and used as a flap repair across the narrowed segment. Bicuspid Aortic Valve Embryology and Epidemiology: BAV is the most common congenital heart abnormality, found in ∼0.5–2% of the general population [34,35] and refers to an anomaly of the aortic valve wherein there are two functional valve leaflets, or cusps, instead of the normal three. BAV is commonly associated with other CHDs, particularly aortic coarctation, atrial or VSDs, PDA, or HLHS, and is a common feature of the genetic disorder Turner’s syndrome. In addition, coexisting thoracic aortopathy is found in approximately 40% of BAV patients [40]. Pathophysiology and Clinical Features: Patients with BAV often present in the third to fifth decade of life with symptoms of valvular dysfunction, commonly in the form of aortic stenosis or less commonly aortic insufficiency. Given the known associated predilection for developing associated ascending thoracic aortic aneurysms, patients with known BAV may undergo routine imaging surveillance to monitor ascending aortic diameters, as they are at risk for developing aortic complications, such as aortic dissection, earlier in life. The widely used Sievers classification for BAV was proposed in 2007 and subclassifies BAVs based on the pattern of leaflet fusion and the number of raphes, defined as the fusion of two underdeveloped cusps to form a commissure between two
cusps [41]. Table 82.38 summarizes the Sievers classification and Fig. 82.47 provides a visual depiction of various valve morphologies on ECG-gated cardiac CT. Table 82.38 Sievers Classification System for Bicuspid Aortic Valve [41] Type 0
Type 1
Type 2
Number of raphes
0
1
2
Subcategories (cusp fusion patterns)
AP
L-R
L-R
Lateral
R-N
R-N
Morphology
L-N L, left coronary cusp; N, noncoronary cusp; R, right coronary cusp.
Table 82.39 Summary of the Key Imaging Features of Isolated Bicuspid Aortic Valve Technique
Imaging Features
Chest radiograph
Normal chest radiograph Normal pulmonary vascularity
Cardiac CT/MRI
Calcified aortic valve leaflets with bicuspid morphology ± Restricted aortic leaflet motion ± Increased flow velocities across the aortic valve
FIGURE 82.47 Multiple short-axis images from contrast-enhanced ECG-gated cardiac CT in two separate patients demonstrate multiple variants of bicuspid aortic valve morphology during systole. Image (A) demonstrates a Sievers Type 0 bicuspid aortic valve with a classic fish-mouth morphology of the aortic valve orifice. Image (B) demonstrates a Sievers Type 1 bicuspid aortic valve with a single raphe formed by fusion of the right and left coronary cusps. C, coronary cusp; L, left coronary cusp; NC, noncoronary cusp; R, right coronary cusp.
FIGURE 82.48 These images demonstrate multiple different examples of anomalous coronary arteries. Oblique axial (A) and oblique coronal (B) images of an anomalous right coronary artery (red arrow and circle) with an intraarterial, intramural course above the plane of the pulmonic valve (dotted line). Oblique axial (C) and oblique sagittal (D) images of an anomalous right coronary artery (red circle) originating from left coronary artery (red arrow) with a prepulmonic course. Oblique axial (E) and oblique sagittal, 3 chamber view (F) images of an anomalous left circumflex artery (red arrow and circle) with a retroaortic course. Oblique axial (G) and short-axis (H) images of an anomalous left main coronary artery (red arrow) originating from right sinus of Valsalva with a trasseptal course of left anterior descending coronary artery. Ao, aorta; LA, left artery; LV, left ventricle; LVOT, left ventricular outflow tract; PA, pulmonary artery; RA, right atrium; RV, right ventricle.
FIGURE 82.49 Two axial images from a contrast-enhanced ECG-gated cardiac CT demonstrating (A) the left coronary artery arising from the main pulmonary artery (asterisk) and (B) the right coronary artery arising normally from the aorta. Notice that both coronary arteries appear large in caliber with prominent collateral vessels in the myocardium (circled), which is a result of flow reversal in the left coronary artery and shunting physiology within the myocardium. Ao, aorta; L, left coronary artery; PA, pulmonary artery R, right coronary artery.
Imaging Features: Isolated BAV cannot be reliably detected on a chest radiograph, although associated findings such as a thoracic aortic aneurysm or aortic coarctation can be detected radiographically and can suggest the presence of an underlying BAV. Transthoracic echocardiography can easily demonstrate a BAV morphology, best in the parasternal windows, while also providing information regarding valvular function and ascending thoracic aortic diameters. Sonographic features of a BAV include systolic doming of the valve leaflets, possible diastolic leaflet prolapse, and an ellipsoid or “fish mouth” morphology of the valvular orifice in systole. Multiphase acquisition cardiac CT is also highly sensitive for the detection of BAV morphology and provides a larger field of view allowing for detection and assessment of associated aortic abnormalities, such as thoracic aortic aneurysm or aortic coarctation. Early leaflet calcification is a common finding, easily seen on CT, and there will be a similar “fish mouth” valve orifice morphology. Cardiac MRI can easily demonstrate dynamic BAV motion, allowing for assessment, particularly of heavily calcified valves that are not well assessed by echocardiography, as well as quantification of valvular insufficiency and pressure gradients. In addition MRI can provide simultaneous assessment of ascending aortic diameters, and hemodynamic significance of an aortic coarctation when present. The imaging features of BAV are summarized below in Table 82.39. Treatment and Outcomes:
Patients with BAV may develop valvular dysfunction significant enough to warrant surgery in early to midadulthood. In addition, due to the risk of ascending aortic aneurysm and aortic complication, lifetime aortic surveillance is generally advised and The American Association for Thoracic Surgery 2018 consensus BAV guidelines recommend a surgical threshold for ascending aortic repair of 5.5 cm in patients without significant valvular dysfunction and 4.5 cm in patients with valvular dysfunction significant enough to warrant aortic valve repair [42]. Coronary Artery Variants and Anomalies Background: Many complex CHD pathologies are associated with congenital anomalies of the coronary arteries, which represents a wide spectrum of pathologies related to the origin and course of the coronary arteries with varying levels of clinical significance Table 82.40 aims to summarize the most commonly encountered coronary artery anomalies in clinical practice. Table 82.40 Description of Different Types of Anomalous Coronary Arteries [1] Anomalous origin from the aortic root Descripti on
Type/C ourse
Clinical Significance
Left coronary artery arising from the right coronary cusp (Fig. 82.48)
Interart erial (intram ural)
Associated with myocardial infarction and sudden death, requires surgical intervention in the form of coronary artery unroofing
Subpul monic
Often clinically insignificant
Anomalous origin from the aortic root Descripti on
Type/C ourse
Clinical Significance
Right coronary artery arising from the left coronary cusp
Retroao rtic
May become relevant if the patient has aortic valve replacement as sutures along the valve annulus may inadvertently occlude the vessel along its retroaortic course
Prepul monic
Often clinically insignificant. May become relevant in patients undergoing pulmonic valve interventions
Retroao rtic
Also potentially relevant for patients undergoing aortic or mitral valve replacement
Left circumfle x coronary artery arising from the right coronary cusp
Anomalous origin from the pulmonary artery Descripti on
Acrony m
Clinical Significance
Left coronary artery arising from the pulmonar y artery (Fig. 82.49)
ALCAP A (Bland – White– Garlan d syndro me)
Lower pressure in the pulmonary artery causes reversal of blood flow in the anomalous coronary artery and results in global coronary artery enlargement due to shunting from the normal coronary artery to the anomalous artery and possible global myocardial ischemia
Anomalous origin from the aortic root Descripti on
Type/C ourse
Right coronary artery arising from the pulmonar y artery
ARCA PA
Clinical Significance
Pathophysiology and Clinical Features: While the majority of coronary artery anomalies are asymptomatic, several of the above-described anomalies have significant clinical implications. For example, an anomalous left coronary artery arising from the right coronary cusp that takes an interarterial and intramural course is associated with myocardial infarction and sudden cardiac death. This is felt to be related to compression of the proximal left coronary artery as it travels in the wall of the aorta. ALCAPA and ARCAPA are severe coronary anomalies that result in global myocardial ischemia due to reversal of flow within the anomalous coronary artery into the lower pressure pulmonary artery and resulting shunting across the myocardium from the contralateral coronary artery, or “coronary steal.” Patients with these anomalies who present with symptoms early in childhood often die within the first few years of life due to extensive myocardial infarction and congestive heart failure. Imaging Features: Anomalies of the coronary arteries are largely radiographically occult with the exception of nonspecific imaging features related to congestive heart failure. Although echocardiography can often identify abnormal coronary artery origins, cross-sectional imaging modalities such as cardiac CT and MRI are essential adjunctive imaging modalities for delineating coronary artery anomalies. Cardiac CT can provide an excellent assessment of the origins and courses of anomalous coronary arteries utilizing contrast injection rates of 4–5 mL/second to optimize opacification of the coronary arteries. With the use of multiplanar reformatting and three-dimensional reconstruction capabilities, highly detailed evaluation of the coronary arteries can be performed with ease. Cardiac MRI is particularly useful in assessing for signs of myocardial ischemia and/or infarction in patients with coronary artery anomalies. LGE sequences are highly sensitive for the detection of fibrosis or scar, and in combination with quantitative
biventricular functional information, cardiac MRI can provide critical information to guide therapeutic intervention. Treatment and Outcomes: While many coronary anomalies require no intervention, certain high-risk anomalies may be surgically repaired in the form of coronary artery unroofing, coronary artery bypass grafting, or coronary artery reimplantation. It should be noted that familiarity with the postoperative appearance of reimplanted coronary arteries is critical for radiologists to avoid misdiagnosis or misinterpretation for coronary artery aneurysms. Other Rare Acyanotic Congenital Heart Diseases While this section focuses on the most common, high-yield acyanotic CHD pathologies, there are several additional more rare pathologies worth mentioning briefly, should they be encountered in clinical practice. Gerbode Defect: Gerbode defect is a left-to-right communication between the left ventricular outflow tract and the right atrium. This rare entity, which can be congenital or acquired, may be subclassified into direct and indirect defects, where a direct defect represents a deficiency in the atrioventricular aspect of the membranous interventricular septum and an indirect defect describes a membranous VSD with associated perforation of the septal leaflet of the tricuspid valve, allowing for indirect shunting between the left ventricle and right atrium due to tricuspid regurgitation [43]. Similar to other congenital intracardiac shunts, the resulting left-to-right shunt across a Gerbode defect often causes enlargement of the right heart chambers and may present as right-sided congestive heart failure if severe. This rare congenital abnormality can easily be mistaken for a simple membranous VSD, particularly by echocardiography. Distinguishing features include atypical jet direction, persistent shunt flow during diastole, and lack of interventricular septal flattening [43]. Cardiac CT and MRI may prove particularly useful in delineating this defect, allowing for direct visualization of shunt flow into the right atrium (Fig. 82.50).
FIGURE 82.50 Short-axis (A) and oblique coronal (B) contrast-enhanced ECGgated cardiac CT images demonstrate a shunt between the left ventricular outflow tract (LVOT) and the right atrium (RA), consistent with a Gerbode defect (arrows).
Cor Triatriatum: Cor triatriatum is a rare congenital anomaly defined by abnormal septation within the left or right atrium leading to obstruction of venous inflow to the corresponding ventricles. This anomaly exists along a spectrum from a complete imperforate membrane to a highly fenestrated membrane, which determines the degree of ventricular blood flow and thus clinical severity. Associated congenital heart defects are common, including ASDs, PDA, and anomalous pulmonary venous return [44]. The more common left-sided cor triatriatum, also known as cor triatriatum sinistrum, results from abnormal or incomplete incorporation of the pulmonary veins into the left atrium, and clinically mimics mitral stenosis. The more unusual right-sided cor triatriatum, also known as cor triatriatum dextrum, results from abnormal or incomplete incorporation of systemic venous return into the right atrium and clinically
mimics tricuspid stenosis. The key imaging feature, irrespective of technique, is a thin fibrous membrane within one of the atrial chambers, which creates the appearance of a “third atrium” (Fig. 82.51). Clinical symptoms may include congestive heart failure, cyanosis, syncope, or sudden cardiac arrest, and complete cor triatriatum is almost universally fatal within the first two years of life if the membrane is not surgically resected [1,44–46].
FIGURE 82.51 Multiple short-axis images from contrast-enhanced ECG-gated cardiac CTs demonstrate two examples of cor triatriatum with incomplete fibrous septations (arrows) identified within the (A) left atrium, termed cor triatriatum sinistrum and (B) right atrium, termed cor triatriatum dextrum, respectively.
Aortopulmonary Window: Aortopulmonary window is a rare congenital heart defect in which there is a direct communication between the aorta and main (or occasionally right) pulmonary artery. This entity can be distinguished from truncus arteriosus based on the presence of both aortic and pulmonic valves and is commonly associated with other congenital heart defects such as VSDs, PDA, or aortic coarctation [22]. Patients may present with congestive heart failure in early neonatal life and plain radioagraphic features are similar to those seen in PDA [1,22]. Interrupted Aortic Arch: IAA is an uncommon congenital anomaly wherein the ascending and descending thoracic aortas are separated from each other, either by a remnant fibrous band or with complete discontinuity. Common associations include VSDs, PDA, DiGeorge syndrome, and truncus arteriosus [47]. Imaging findings and clinical presentation are
often similar to severe focal aortic coarctation, and this abnormality ultimately requires definitive surgical correction.
Overall Approach to CHD • Due to the complexity of the CHD spectrum, a structured, segmental approach for describing the underlying anatomy is critical for making the correct diagnosis and effectively communicating amongst various members of the multidisciplinary care team. • The choice of imaging technique to utilize in the evaluation of any CHD patient should be based on a balanced multidisciplinary discussion of risks and benefits and a clear understanding of the targeted clinical questions that need to be answered. • While CHD is often diagnosed during prenatal or early postnatal life through clinical assessment and echocardiography, continuing advances in the surgical management of CHD have resulted in a growing population of adult CHD patients. • Advanced imaging modalities such as cardiac CT and MRI may play an important role in the imaging evaluation of the CHD population, thus familiarity with the preoperative and postoperative appearances of various common CHDs is crucial to ensure high-quality patient care and appropriate clinical management. • Clinically, CHD can be subdivided into cyanotic and acyanotic heart diseases. Severity of cyanotic CHDs is dependent upon the amount of pulmonary blood flow and the degree of intracardiac mixing of oxygenated and deoxygenated blood (right-to-left shunting) before exiting into systemic circulation. Acyanotic heart diseases predominantly encompass left to right shunts and obstructive lesions.
Suggested Readings • SV Babu-Narayan, G Giannakoulas, AM Valente, W Li, MA Gatzoulis, Imaging of congenital heart disease in adults, Eur Heart J 37 (15) (2016) 1182–1195. Available from: http://www.ncbi.nlm.nih.gov/pubmed/26424866. • EK Schallert, GH Danton, R Kardon, DA. Young, Describing congenital heart disease by using three-part segmental notation, Radiographics 33 (2) (2013) E33–E46. Available from: https://pubs.rsna.org/doi/10.1148/rg.332125086. • EC Ferguson, R Krishnamurthy, SAA. Oldham, Classic imaging signs of congenital cardiovascular abnormalities, Radiographics 27 (5) (2007) 1323–1334. Available from: https://pubs-rsna-org.ezpprod1.hul.harvard.edu/doi/full/10.1148/rg.275065148. • EJ Zucker, JL Koning, EY. Lee, Cyanotic congenital heart disease: essential primer for the practicing radiologist, Radiol Clin North Am 55 (4) (2017) 693–716. Available from: http://www.ncbi.nlm.nih.gov/pubmed/28601176. • ZJ Wang, GP Reddy, MB Gotway, BM Yeh, CB. Higgins, Cardiovascular shunts: MR imaging evaluation, Radiographics 23 (Suppl 1) (2003) S181–S194. Available from: https://pubs.rsna.org/doi/10.1148/rg.23si035503.
References [1] S Hedgire, Cardiac imaging, MG Harisinghani, JW Chen, R Weissleder (Eds.) Primer of Diagnostic Imaging, 6th ed., Elsevier, 2018, 88–110. [2] EM Merkle, RC Gilkeson, Remnants of fetal circulation: appearance on MDCT in adults, Am J Roentgenol 185 (2) (2005) 541–549, Available from:. https://www.ajronline.org/doi/10.2214/ajr.185.2.01850541. [3] SV Babu-Narayan, G Giannakoulas, AM Valente, W Li, MA Gatzoulis, Imaging of congenital heart disease in adults, Eur Heart J 37 (15) (2016)
1182–1195, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/26424866. [4] SL Partington, AM Valente, Cardiac magnetic resonance in adults with congenital heart disease, Methodist Debakey Cardiovasc J 9 (3) (2013) 156– 162, Available from:. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3782323/. [5] PK Woodard, VB Ho, SR Akers, G Beache, RK.J Brown, KW Cummings, et al., ACR Appropriateness Criteria® known or suspected congenital heart disease in the adult, J Am Coll Radiol 14 (5, Supplement) (2017) S166–S176, Available from:. https://www.sciencedirect.com/science/article/pii/S1546144017302193. [6] KK Stout, CJ Daniels, JA Aboulhosn, B Bozkurt, CS Broberg, JM Colman, et al., 2018 AHA/ACC guideline for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, Circulation 139 (14) (2019) e698–e800, Available from:. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000603. [7] EK Schallert, GH Danton, R Kardon, DA Young, Describing congenital heart disease by using three-part segmental notation, Radiographics 33 (2) (2013) E33–E46, Available from:. https://pubs.rsna.org/doi/10.1148/rg.332125086. [8] C Lapierre, J Déry, R Guérin, L Viremouneix, J Dubois, L Garel, Segmental approach to imaging of congenital heart disease, Radiographics 30 (2) (2010) 397–411, Available from:. https://pubs.rsna.org/doi/full/10.1148/rg.302095112. [9] EC Ferguson, R Krishnamurthy, SA.A Oldham, Classic imaging signs of congenital cardiovascular abnormalities, Radiographics 27 (5) (2007) 1323– 1334, Available from:. https://pubs-rsna-org.ezpprod1.hul.harvard.edu/doi/full/10.1148/rg.275065148. [10] EJ Zucker, JL Koning, EY Lee, Cyanotic congenital heart disease: essential primer for the practicing radiologist, Radiol Clin North Am 55 (4) (2017) 693– 716, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/28601176. [11] G Michielon, B Marino, R Formigari, G Gargiulo, F Picchio, MC Digilio, et al., Genetic syndromes and outcome after surgical correction of tetralogy of fallot, The Ann Thorac Surg 81 (3) (2006) 968–975, Available from:. https://www.sciencedirect.com/science/article/pii/S0003497505017443. [12] L Mercer-Rosa, SM Paridon, MA Fogel, J Rychik, RE Tanel, H Zhao, et al., 22q11.2 deletion status and disease burden in children and adolescents with tetralogy of fallot, Circulation: Cardiovascular Genetics 8 (1) (2015) 74–81, Available from:. https://www.ahajournals.org/doi/10.1161/CIRCGENETICS.114.000819. [13] M Dennis, D Zannino, K du Plessis, A Bullock, PJ.S Disney, DJ Radford, et al., Clinical outcomes in adolescents and adults after the Fontan procedure, J Am Coll Cardiol 71 (9) (2018) 1009–1017, Available from:. http://www.sciencedirect.com/science/article/pii/S0735109718300299.
[14] S Chikkabyrappa, G Mahadevaiah, S Buddhe, T Alsaied, J Tretter, Common arterial trunk: physiology, imaging, and management, Semin Cardiothorac Vasc Anesth 23 (2) (2019) 225–236, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/30596352. [15] S Asagai, K Inai, T Shinohara, H Tomimatsu, T Ishii, H Sugiyama, et al., Long-term outcomes after truncus arteriosus repair: a single-center experience for more than 40 years, Congenital Heart Disease 11 (6) (2016) 672–677, Available from:. https://onlinelibrary.wiley.com/doi/abs/10.1111/chd.12359. [16] S Domadia, SR Kumar, JK Votava-Smith, JD Pruetz, Neonatal outcomes in total anomalous pulmonary venous return: the role of prenatal diagnosis and pulmonary venous obstruction, Pediatr Cardiol 39 (7) (2018) 1346–1354. https://doi.org/10.1007/s00246-018-1901-0. [17] HV Vyas, SB Greenberg, R Krishnamurthy, MR imaging and CT evaluation of congenital pulmonary vein abnormalities in neonates and infants, Radiogr A Rev Publ Radiol Soc North Am Inc 32 (1) (2012) 87–98, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/22236895. [18] DM.E Bardo, DG Frankel, KE Applegate, DJ Murphy, RP Saneto, Hypoplastic left heart syndrome, Radiographics 21 (3) (2001) 705–717, Available from:. https://pubs.rsna.org/doi/10.1148/radiographics.21.3.g01ma09705. [19] D Yim, A Dragulescu, H Ide, M Seed, L Grosse-Wortmann, G van Arsdell, et al., Essential modifiers of double outlet right ventricle: revisit with endocardial surface images and 3-dimensional print models, Circ Cardiovasc Imaging 11 (3) (2018) e006891, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/29855425. [20] YJ Kim, J Hur, CY Shim, HJ Lee, JW Ha, KO Choe, et al., Patent Foramen Ovale: diagnosis with multidetector CT—comparison with transesophageal echocardiography, Radiology 250 (1) (2009) 61–67, Available from:. https://pubs.rsna.org/doi/10.1148/radiol.2501080559. [21] O Goitein, CR Fuhrman, JM Lacomis, Incidental finding on MDCT of patent ductus arteriosus: use of CT and MRI to assess clinical importance, Am J Roentgenol 184 (6) (2005) 1924–1931, Available from:. https://www.ajronline.org/doi/10.2214/ajr.184.6.01841924. [22] ZJ Wang, GP Reddy, MB Gotway, BM Yeh, CB Higgins, Cardiovascular shunts: MR imaging evaluation, Radiographics 23 (Suppl 1) (2003) S181– S194, Available from:. https://pubs.rsna.org/doi/10.1148/rg.23si035503. [23] CA Rojas, A El-Sherief, HM Medina, JH Chung, G Choy, BB Ghoshhajra, et al., Embryology and developmental defects of the interatrial septum, Am J Roentgenol 195 (5) (2010) 1100–1104, Available from:. https://www.ajronline.org/doi/10.2214/AJR.10.4277. [24] S Nicolay, RA Salgado, B Shivalkar, PL Van Herck, C Vrints, PM Parizel, CT imaging features of atrioventricular shunts: what the radiologist must
know, Insights Imaging 7 (1) (2016) 119–129, Available from:. http://www.ncbi.nlm.nih.gov/pubmed/26638005. [25] P Dhanantwari, E Lee, A Krishnan, R Samtani, S Yamada, S Anderson, et al., Human cardiac development in the first trimester, Circulation. 120 (4) (2009) 343–351, Available from:. https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.108.796698. [26] N Naqvi, KP McCarthy, SY Ho, Anatomy of the atrial septum and interatrial communications, J Thorac Dis 10 (Suppl 24) (2018), Available from:. https://jtd.amegroups.com/article/view/19569. [27] JM Barboza, NK Dajani, LG Glenn, TL Angtuaco, Prenatal diagnosis of congenital cardiac anomalies: a practical approach using two basic views, Radiographics. 22 (5) (2002) 1125–1138, Available from:. https://pubs.rsna.org/doi/10.1148/radiographics.22.5.g02se171125. [28] J Plymale, K Kolinski, P Frommelt, P Bartz, J Tweddell, MG Earing, Inferior sinus venosus defects: anatomic features and echocardiographic correlates, Pediatr Cardiol 34 (2) (2013) 322–326. https://doi.org/10.1007/s00246-012-0449-7. [29] Z Amin, Transcatheter closure of secundum atrial septal defects, Catheter Cardiovasc Interv 68 (5) (2006) 778–787, Available from:. https://onlinelibrary.wiley.com/doi/abs/10.1002/ccd.20872. [30] R Ryan, S Abbara, RR Colen, S Arnous, M Quinn, RC Cury, et al., Cardiac valve disease: spectrum of findings on cardiac 64-MDCT, Am J Roentgenol 190 (5) (2008) W294–W303, Available from:. https://www.ajronline.org/doi/10.2214/AJR.07.2936. [31] H Gupta, WW Mayo-Smith, MB Mainiero, DE Dupuy, GF Abbott, Helical CT of pulmonary vascular abnormalities, Am J Roentgenol 178 (2) (2002) 487–492, Available from:. https://www.ajronline.org/doi/10.2214/ajr.178.2.1780487. [32] F Saremi, A Gera, S Yen Ho, ZM Hijazi, D Sánchez-Quintana, CT and MR imaging of the pulmonary valve, Radiographics 34 (1) (2014) 51–71, Available from:. https://pubs.rsna.org/doi/10.1148/rg.341135026. [33] JT.T Chen, AE Robinson, JK Goodrich, RG Lester, Uneven distribution of pulmonary blood flow between left and right lungs in isolated valvular pulmonary stenosis, Am J Roentgenol 107 (2) (1969) 343–350, Available from:. https://www.ajronline.org/doi/10.2214/ajr.107.2.343. [34] SM Ko, MG Song, HK Hwang, Bicuspid aortic valve: spectrum of imaging findings at cardiac MDCT and cardiovascular MRI, Am J Roentgenol 198 (1) (2012) 89–97, Available from:. https://www.ajronline.org/doi/10.2214/AJR.10.6084. [35] CH Ridley, P Vallabhajosyula, JE Bavaria, PA Patel, JT Gutsche, R Shah, et al., The Sievers classification of the bicuspid aortic valve for the perioperative echocardiographer: the importance of valve phenotype for aortic valve repair
in the era of the functional aortic annulus, J Cardiothorac Vasc Anesth 30 (4) (2016) 1142–1151, Available from:. https://www.sciencedirect.com/science/article/pii/S1053077016000720. [36] AS Valente, P Alencar, AN Santos, M Lobo RA de, FA de Mesquita, AG Guimarães, Supravalvular aortic stenosis in adult with anomalies of aortic arch vessels and aortic regurgitation, Rev Bras Cir Cardiovasc. 28 (4) (2013) 545– 549, Available from:. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389441/. [37] K Hanneman, B Newman, F Chan, Congenital variants and anomalies of the aortic arch, Radiographics 37 (1) (2017) 32–51, Available from:. https://pubs.rsna.org/doi/10.1148/rg.2017160033. [38] AD Karaosmanoglu, RD.A Khawaja, MR Onur, MK Kalra, CT and MRI of aortic coarctation: pre- and postsurgical findings, Am J Roentgenol 204 (3) (2015) W224–W233, Available from:. https://www.ajronline.org/doi/10.2214/AJR.14.12529. [39] P Gach, A Dabadie, C Sorensen, E Quarello, B Bonello, H Pico, et al., Multimodality imaging of aortic coarctation: from the fetus to the adolescent, Diagnos Interv Imaging 97 (5) (2016) 581–590, Available from:. https://www.sciencedirect.com/science/article/pii/S2211568416300596. [40] T Liu, M Xie, Q Lv, Y Li, L Fang, L Zhang, et al., Bicuspid aortic valve: an update in morphology, genetics, biomarker, complications, imaging diagnosis and treatment, Front Physiol. 9 (2019) 1921, Available from:. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6363677/. [41] HH Sievers, C Schmidtke, A classification system for the bicuspid aortic valve from 304 surgical specimens, J Thorac Cardiovasc Surg 133 (5) (2007) 1226–1233, Available from:. https://www.sciencedirect.com/science/article/pii/S0022522307002371. [42] MA Borger, PW.M Fedak, EH Stephens, TG Gleason, E Girdauskas, JS Ikonomidis, et al., The American Association for Thoracic Surgery consensus guidelines on bicuspid aortic valve–related aortopathy: full online-only version, J Thorac Cardiovasc Surg 156 (2) (2018) e41–e74, Available from:. https://www.sciencedirect.com/science/article/pii/S002252231831256X. [43] E Saker, GN Bahri, MJ Montalbano, J Johal, RA Graham, GG Tardieu, et al., Gerbode defect: a comprehensive review of its history, anatomy, embryology, pathophysiology, diagnosis, and treatment, J Saudi Heart Assoc 29 (4) (2017) 283–292, Available from:. https://www.sciencedirect.com/science/article/pii/S1016731517300076. [44] H Jolles, DA Henry, SB Rupp, General case of the day. Cor triatriatum, Radiographics 8 (6) (1988) 1227–1231, Available from:. https://pubs.rsna.org/doi/10.1148/radiographics.8.6.3205935. [45] AK Jha, N Makhija, Cor triatriatum: a review, Semin Cardiothorac Vasc Anesth 21 (2) (2017) 178–185. https://doi.org/10.1177/1089253216680495.
[46] JR Dillman, SG Yarram, RJ Hernandez, Imaging of pulmonary venous developmental anomalies, Am J Roentgenol 192 (5) (2009) 1272–1285, Available from:. https://www.ajronline.org/doi/10.2214/AJR.08.1526. [47] L Frank, JR Dillman, V Parish, GC Mueller, EA Kazerooni, A Bell, et al., Cardiovascular MR imaging of conotruncal anomalies, Radiographics 30 (4) (2010) 1069–1094, Available from:. https://pubs.rsna.org/doi/10.1148/rg.304095158.
CHAPTER 83
Pediatric Chest Esther Park, Bojan Kovacina
Introduction Pediatric chest radiology encompasses a vast spectrum of topics ranging from congenital and syndromic abnormalities to acquired diseases. A detailed discussion of this wide-ranging field is beyond the scope of this textbook, and this chapter will instead aim to give a broad overview of pediatric chest radiology. Particular attention will be given to chest radiography, as it is the most commonly used imaging technique for evaluating the respiratory system in children.
Tracheal agenesis is a rare anomaly characterized by complete tracheal agenesis or partial underdevelopment [1,2]. As such, this anomaly manifests clinically as severe respiratory distress immediately upon birth, lack of an audible cry, and failed intubation efforts. It is often associated with polyhydramnios in the antenatal period. Tracheal agenesis can be categorized into three main types [1]:
◾esophagus Type 1. Absent upper trachea. Connection between the lower trachea and ◾esophagus Type 2. Most common. Absent trachea. The main bronchi are connected to the a common bronchus ◾ Type 3. Theviaright and left main bronchi connect to the esophagus separately
Given the connections with the esophagus, intubation of the esophagus consequently improves lung ventilation. Chest radiographic findings include the absence of the tracheal air column, abnormal position of the carina, and absent or decreased lung volumes [1,2]. The diagnosis may be confirmed by chest computed tomography (CT) or broncho-esophagoscopy. Though surgical approaches to maintain airway patency have been proposed, this condition is typically fatal. Tracheal Bronchus A tracheal bronchus is a branching anomaly that occurs when there is a direct tracheal origin of all or part of an upper lobe bronchus (Fig. 83.1) [3,4]. This anomaly most commonly occurs on the right, though it may also occur on the left or even bilaterally [3,4]. A tracheal bronchus may be described as supernumerary or displaced. In the setting of an otherwise normal segmental branching pattern to the upper lobe, the tracheal bronchus is supernumerary. However, if one or more of the normal upper lobe segmental bronchi are absent, the tracheal bronchus is considered to be displaced. Of note, when the entire right upper lobe is supplied by the tracheal bronchus, it is referred to as a bronchus suis. This anomaly is often asymptomatic but may also present with recurrent upper lobe infections or air trapping due to impaired drainage. Unintended blockage of a tracheal bronchus by
a low-lying endotracheal tube may also cause partial or complete upper lobe collapse.
FIGURE 83.1 A 6-year-old male with a supernumerary tracheal bronchus. Coronal MinIP CECT image demonstrates this tracheal bronchus (white block arrow) arising 2 cm proximal to the carina. This had branches to the apical and anterior segments of the right upper lobe. There was otherwise normal segmental branching pattern, with a right upper lobe bronchus originating from the right mainstem bronchus and demonstrating normal trifurcation.
Tracheal Stenosis Congenital tracheal stenosis is a rare anomaly that typically arises due to the presence of complete cartilaginous rings and the absence of the normal posterior membranous portion of the trachea [3]. There is resultant narrowing of the trachea, which can be focal (most common), generalized, or funnel shaped (Fig. 83.2A) [3]. Importantly, there is no associated tracheal wall thickening, which is often seen with acquired causes of tracheal stenosis. This condition manifests early in life with stridor and respiratory distress and has a high mortality rate. It is often associated with other congenital anomalies, such as bronchial or lung agenesis, tracheoesophageal fistula, and pulmonary artery sling (Fig. 83.2B) [3].
FIGURE 83.2 An 8-day-old female with congenital tracheal stenosis. (A) A coronal CECT minimum intensity projection image demonstrates significant narrowing of the trachea distal to the endotracheal tube (luminal diameter of 1 mm). There was also an incidentally noted azygous lobe (asterisk) supplied by a right tracheal bronchus (black solid arrow). (B) Axial CECT demonstrated a pulmonary sling with a left pulmonary artery (white block arrow) originating from the right pulmonary artery and traversing between the trachea and esophagus, an anomaly that has been associated with congenital tracheal stenosis.
Acquired causes of tracheal stenosis are discussed in the dedicated airway section of this textbook. Tracheobronchomalacia This refers to a congenital (primary) or acquired (secondary) weakness of the airways [3,5]. While this condition can arise secondary to a number of conditions, including prior intubation, prior lung surgery, external masses causing compression, and chronic obstructive pulmonary disease, this section will focus on congenital tracheomalacia caused by abnormalities in the cartilaginous matrix. Clinically, tracheomalacia may present with an expiratory wheeze, stridor, or a barking cough. While a wellaccepted standard for the diagnosis of tracheomalacia is bronchoscopy, paired inspiratory-dynamic expiratory CT is a comparable method for evaluating tracheomalacia. On imaging, a greater than 50% decrease in the cross-sectional area of the tracheal lumen in expiration is used to define tracheomalacia in the pediatric population (Fig. 83.3A,B) [5]. Tracheal collapse will also lead to inward bowing of the posterior membranous trachea, giving the appearance of the crescentic “frown” sign. Lateral fluoroscopy may also be used to assess for excessive tracheal collapsibility upon expiration.
FIGURE 83.3 A 71-year-old female with severe tracheomalacia. Dynamic noncontrast axial chest CT images demonstrated severe collapse of the trachea and bilateral main bronchi (the latter not shown) on the expiratory images (arrow in B). (A) In inspiration, the tracheal (arrow in A) diameter was 11 mm. (B) In expiration, there was severe tracheal collapse, and the tracheal diameter reduced to 2 mm.
Tracheoesophageal Fistula The majority of this congenital anomaly occurs in the setting of esophageal atresia and a distal tracheoesophageal fistula [3]. These may present with respiratory distress during initial feeding attempts and inability to pass a feeding tube into the stomach (Fig. 83.4). Less frequently, they can also occur in the setting of a continuous esophagus (H-type), which may present with recurrent infections. An esophagogram can be used to demonstrate the fistulous connection in proximal and H-type tracheoesophageal fistulas. Congenital tracheoesophageal fistulas are strongly associated with other congenital anomalies, including those belonging to the VACTERL (Vertebral defects, Anal atresia, Cardiac defects, Tracheo-Esophageal fistula, Renal anomalies, and Limb abnormalities) constellation (Fig. 83.4) [3].
FIGURE 83.4 A 12-month-old male with a frontal chest radiograph demonstrated a feeding tube in an aerated pouch in the upper chest, consistent with known history of esophageal atresia. There is also a vertebral segmentation anomaly in the lower cervical spine (black block arrow), which is a component of the VACTERL constellation.
Tracheobronchomegaly Also known as Mounier–Kuhn syndrome, this refers to abnormal dilatation of the trachea and main bronchi [6]. It may be associated with tracheal diverticula and corrugated appearance of the central airways, thought to be related to weakening and redundancy of the elastic and muscular walls (Fig. 83.5). CT is a useful technique for diagnosis, particularly as dynamic inspiratory-expiratory imaging can be used to evaluate for possible concomitant tracheobronchomalacia, a condition that
occurs with increased incidence in tracheobronchomegaly patients.
FIGURE 83.5 A 77-year-old male with history of congenital tracheobronchomegaly. A coronal minimum intensity projection CECT image demonstrates diffuse tracheal and central bronchial dilatation with irregular, corrugated appearance.
Accessory Cardiac Bronchus This is a rare anomaly characterized by a supernumerary bronchus that arises from the bronchus intermedius medially [4]. The presence of cartilage in its walls differentiates it from a diverticulum. This anomaly is typically stump-like (Fig. 83.6), though less frequently it may supply a small lobule known as a cardiac lobe. This is typically asymptomatic and incidentally found on imaging. However, it can on rare occasion be associated
with conditions such as chronic infections or inflammation and malignancy.
FIGURE 83.6 A 57-year-old female with an incidentally noted stump-like supernumerary bronchus arising from the bronchus intermedius medially (black block arrow) on this coronal CECT, consistent with an accessory cardiac bronchus.
Bronchial Atresia This is characterized by focal atresia at the lobar, segmental, or subsegmental level, resulting in mucoid impaction distal to the point of interruption and formation of a mucocele (Fig. 83.7) [4,7,8]. In the neonate, the affected segment may be atelectatic or fluid-filled, which gradually becomes air-filled. As collateral air drift increases, the lung distal to the atretic bronchus will become
hyperinflated due to air trapping. There will also be decreased vascularity in the affected lung segments(s). While bronchial atresia can occur in any location of the lungs, the apicoposterior segment of the left upper lobe is the most commonly affected. These imaging findings can be demonstrated by both chest radiography and CT, with the tubular branching mass corresponding to the mucocele often referred to as the “finger in glove” sign.
FIGURE 83.7 A 10-year-old female with bronchial atresia. A coronal CECT image demonstrates increased lucency involving the left upper lobe and lingula representing air trapping, with associated attenuation of pulmonary vascularity. There was also extensive mucus plugging within dilated bronchi distal to the atretic bronchus, one of which is seen on this image (white arrow).
Congenital Bronchiectasis Also known as Williams–Campbell syndrome, this results from partial or complete congenital absence of cartilage in the subsegmental bronchi, typically fourth to sixth order (Fig. 83.8) [9]. The cartilages in the trachea, mainstem bronchi, and segmental bronchi are normal. This leads to diffuse bilateral bronchiectasis and airway collapse during expiration. As such, this presents as recurrent pneumonias and wheezing. Acquired forms of bronchiectasis are discussed in further detail in the dedicated airway section.
FIGURE 83.8 A 49-year-old female with history of congenital bronchiectasis. This coronal chest CT image demonstrates diffuse extensive cylindrical and varicose bronchiectasis with associated bronchial wall thickening and multifocal mucus plugging. The trachea and mainstem bronchi were normal in caliber.
Congenital Lung Abnormalities Pulmonary Underdevelopment Also known as lung agenesis-hypoplasia complex, this describes a spectrum of abnormal lung formation ranging from agenesis to aplasia to hypoplasia [3,7,8]. The cause may be primary or secondary, the latter of which includes in-utero processes that impair development via decreased vascular perfusion or spaceoccupying masses such as diaphragmatic hernias. Of note, pulmonary underdevelopment often occurs with other multisystem congenital abnormalities. Pulmonary agenesis occurs when there is complete absence of the lung, and there are no bronchi or vessels distal to the carina [3,7]. As such, there is mediastinal shift to the affected side and compensatory hyperinflation of the contralateral lung, which crosses the midline (Fig. 83.9). Pulmonary aplasia is also characterized by absent lung tissue and vasculature [3,7]. However, the presence of a rudimentary bronchial stump differentiates pulmonary aplasia from pulmonary agenesis. In the least severe form of this complex, pulmonary hypoplasia, bronchi and pulmonary vessels are present but reduced in number [3,7]. Its appearance on imaging therefore varies depending on the degree of hypoplasia (Fig. 83.10). Transpleural collateral arteries may be seen in pulmonary hypoplasia when the ipsilateral pulmonary artery is small.
FIGURE 83.9 A chest radiograph in a neonate with agenesis of the right lung demonstrates opacification of the right hemithorax and crowding of the right ribs. There is compensatory hyperinflation of the left lung, which crosses the midline.
FIGURE 83.10 (A) A chest radiograph of a hypoplastic right lung demonstrates rightward mediastinal shift. (B, C) Posterior views of VQ scans show reduced ventilation and perfusion in the hypoplastic right lung.
Scimitar Syndrome Also known as a hypogenetic lung syndrome, this refers to a syndrome in which part or all of the right lung is hypoplastic and demonstrates partial or complete anomalous pulmonary venous return [3,7,8]. The anomalous pulmonary vein most frequently drains the affected right lung into the suprahepatic inferior vena cava, though drainage into other systemic circulations, such as the portal vein, azygous vein, right atrium, or coronary sinus has also been described. The anomalous vein takes on the appearance of the scimitar Turkish sword along the right heart border on chest radiography (Fig. 83.11). The affected lung is typically hypovascularized and occasionally coexists with a sequestration receiving a systemic arterial supply. Additional bronchial branching anomalies and lung lobation/segmentation anomalies may also coexist.
FIGURE 83.11 A frontal chest radiograph (A) demonstrates right hemithorax volume loss consistent with pulmonary hypoplasia and a curvilinear opacity along the right heart border (black block arrow) consistent with partial anomalous pulmonary venous return draining a portion of the right lung into an infradiaphragmatic systemic venous circulation. These findings are redemonstrated on a correlative coronal oblique chest CT (B), including the anomalous pulmonary vein (white block arrow). The constellation of findings are consistent with Scimitar syndrome.
Congenital Lobar Overinflation Also known as congenital lobar hyperinflation, this is due to narrowing of a bronchus, which results in air trapping and subsequent progressive overinflation of the affected lobe [3,7,8]. The narrowing can be related to intrinsic weakening or the absence of the bronchial cartilage. Alternatively, it can be due to extrinsic compression by enlarged vessels or masses. The term “congenital lobar emphysema,” which this condition is also sometimes referred to as, is therefore a misnomer as the mechanism does not involve alveolar destruction. Though this condition can affect any lobe, it most frequently affects the left upper lobe and has a slight male predilection. The imaging appearance of this condition varies over time [3,8]. In newborns, retained fetal lung fluid causes this to appear as an increased lobar opacity. As the fluid begins to clear and lung aeration increases, the affected lobe will become hyperexpanded
and hyperlucent, causing shift and displacement of the nearby structures (Fig. 83.12). Symptomatic cases require surgical lobectomy, with conservative/expectant management reserved for those with no or minimal symptoms.
FIGURE 83.12 A 9-year-old male with (A) frontal and (B) lateral chest radiographs demonstrating mildly widened left intercostal spaces compared to the right and an increased retrosternal airspace consistent with left upper lobe hyperinflation. There is also hyperlucency of the left upper lobe with vessel attenuation. Findings are consistent with congenital lobar hyperinflation.
Congenital Pulmonary Airway Malformation Congenital pulmonary airway malformations (CPAM) represent a heterogeneous group of lung masses communicating with an abnormal bronchial tree [3,7,8]. These were previously described as congenital cystic adenomatoid malformations (CCAM) but are now referred to as CPAMs because not all of these malformations contain cystic or adenomatoid components. When large, these can cause neonatal respiratory distress, compression on the adjacent structures, and contralateral mediastinal shift. Though CPAMs are typically unilateral, bilateral involvement has been reported. CPAMs can be divided into five main types [3,7,8].
◾ Type 0: Incompatible with life. All lobes are affected
◾surrounded Type 1: Composed of large cysts (typically 2–10 cm in size) that may be by smaller cysts. During the neonatal period, the cystic portions may appear solid due to the presence of retained fetal lung fluid. However, as the fluid is cleared, this will become air filled (Fig. 83.13) Type 2: Composed of small cysts (typically less than 2 cm in size) (Fig, 83.14) Type 3: Composed of microcysts (less than 0.5 cm in size) and therefore appears solid. May demonstrate mild enhancement and contains adenomatous tissue Type 4: Composed of large, peripheral thin-walled cysts
◾ ◾ ◾
FIGURE 83.13 A chest radiograph (A) and axial chest CT (B) demonstrate a cystic type 1 congenital pulmonary airway malformation in the right lower lobe. There is an air-fluid level (black block arrow) on the chest radiograph due to superimposed infection.
FIGURE 83.14 A 22-month-old male with (A) axial and (B) coronal maximum intensity projection CECT images demonstrating a mixed solid and cystic lesion in right lower lobe (white block arrow). There was a prominent systemic arterial feeding vessel (black block arrow) arising from the celiac axis (origin not shown). This was consistent with a pathology proven type 2 CPAM hybrid lesion with sequestration.
Unlike pulmonary sequestrations, CPAMs demonstrate normal blood supply from the pulmonary arteries and normal pulmonary venous drainage [3,7,8]. While symptomatic CPAMs are universally treated by surgical resection, the treatment of asymptomatic CPAMs is more controversial. However, some argue that asymptomatic CPAMs should also be resected to avoid associated complications such as recurrent infections and a small risk of malignant transformation. Pulmonary Sequestration Pulmonary sequestrations are lung malformations that do not connect with the tracheobronchial tree [3,7,8]. They demonstrate a systemic blood supply, typically from the aorta, though origins from other systemic vessels such as mesenteric, intercostal, and subclavian arteries have also been described. Sequestrations can be classified into extralobar or intralobar types depending on their pleural investment. Of note, sequestrations can also occur as
hybrid lesions in association with other lung anomalies such as CPAMs (Fig. 83.14). Extralobar sequestrations contain abnormal lung tissue that is enveloped by its own pleura separate from the remainder of the normal lung [3,7,8]. It is classically drained by the systemic venous circulation via the azygous or hemiazygos veins, though pulmonary venous drainage can occasionally occur. On imaging, these typically appear as solid masses, though cystic components may also be present when there is a coexistent CPAM. The presence of air in these masses suggests communication with the gastrointestinal tract or superimposed infection. Though extralobar sequestrations can occur anywhere in the thorax, they most often occur in the lower thorax, with a predilection for the left side. Because they are often asymptomatic and have a lower rate of complications, their management is controversial but typically expectant. Intralobar sequestrations consist of abnormal lung tissue that is enveloped by the visceral pleura of the affected lobe and drained by the regional pulmonary veins [3,7,8]. They most often occur in the lower lobes, preferentially on the left side. Unlike extralobar sequestrations, they do not have their own separate pleural lining. Therefore, though intralobar sequestrations have been reported antenatally, not all of these masses are thought to be congenital. Some of these malformations are theorized to be results of recurrently infected or inflamed lung tissue parasitizing its own arterial supply from the aorta. Intralobar sequestrations receive collateral air drift from the adjacent normal lung tissue and therefore will appear aerated on imaging (once retained fetal lung fluid has cleared). The presence of air-fluid levels suggests superimposed infection. Because intralobar sequestrations are at risk for recurrent infections and have a small chance for malignant transformation, they typically undergo elective surgical resection.
A bronchogenic cyst is a foregut malformation resulting from a tracheobronchial branching anomaly [3,7,8,10]. It is lined by respiratory epithelium and is attached to the tracheobronchial tree but does not communicate with the airways. Therefore, the presence of an air-fluid level is abnormal and indicates superimposed infection or prior intervention (such as attempted cyst aspiration). While these cysts can arise anywhere in the thorax, they are most commonly found in the middle mediastinum (particularly in the right paratracheal or subcarinal regions) (Fig. 83.15). They may contain mucoid material, layering milk of calcium, or proteinaceous and hemorrhagic contents, in which case they may demonstrate an attenuation higher than simple water on CT. In these cases, MRI can confirm their cystic nature by demonstrating homogeneous hyperintensity on T2-weighted images and no internal enhancement. Cysts containing simple fluid will be hypointense on T1-weighted images, but complicated cysts may be hyperintense on the same sequence.
FIGURE 83.15 A 29-year-old female with a large, homogeneous thin-walled cystic subcarinal mass on a coronal CECT (white block arrow). There was no internal enhancement or mural nodularity. This was consistent with pathology proven bronchogenic cyst.
Esophageal Duplication Cyst This foregut duplication cyst is lined by gastrointestinal mucosa and typically found in the middle or posterior mediastinum along the paraesophageal region (Fig. 83.16) [10]. Those that contain ectopic gastric mucosa can secrete acid, and these cysts may ulcerate or perforate into the tracheobronchial tree with resultant hemoptysis.
FIGURE 83.16 A 270-day-old male with a round, cystic paraesophageal lesion near the esophageal hiatus on this axial CECT (white arrow). This was consistent with a pathology proven esophageal duplication cyst.
Neurenteric Cyst Neurenteric cysts are another type of foregut duplication cyst that are lined by mixed neural/gastrointestinal lining [10]. They present as posterior mediastinal masses or as intraspinal masses extending into the posterior mediastinum through a vertebral defect. The presence of vertebral anomalies in the setting of an intraspinal cyst is very suggestive of this diagnosis (Fig. 83.17).
FIGURE 83.17 Neurenteric cyst (A) A chest radiograph demonstrates multiple segmentation anomalies of the thoracic vertebral bodies and a large round opacity in the right hemithorax. (B) A coronal T2-weighted spin-echo image demonstrates a hyperintense cystic mass arising from the cervicothoracic spine with consequent compressive atelectasis of the adjacent right upper lobe.
Thymic Cyst This rare cyst may be acquired or arise as a congenital remnant of the thymopharyngeal duct [10]. They may appear as unilocular or multilocular cystic structures in the thymic bed. Complicated thymic cysts may appear solid-like; however, they will be nonenhancing on CT and MRI. Ultrasound can also be used to confirm its cystic nature.
Congenital Diaphragmatic Abnormalities Accessory Diaphragm Also known as duplication of the diaphragm, this rare anomaly almost exclusively occurs on the right side and divides the right hemithorax into two parts [1]. This fibromuscular membrane extends posterosuperiorly from the anterior aspect of the hemidiaphragm toward the posterior chest wall. It exhibits a central hiatus through which vessels and bronchi can traverse, and crowding of these bronchovascular structures may be apparent as
they pass through the hiatus. When this central hiatus is significantly narrowed, it can impair aeration of the trapped lung and cause it to appear mass-like. This anomaly is typically asymptomatic, and surgical intervention is reserved for cases that are complicated by dyspnea or recurrent pneumonias. Congenital Diaphragmatic Hernias Bochdalek hernias are congenital posterolateral hernias that may contain bowel, stomach, kidneys, liver, and/or spleen depending on its location [10,12]. They most frequently occur on the left side and are associated with significant morbidity and mortality due to associated pulmonary hypoplasia. Herniated bowel loops and stomach are also at risk for incarceration and strangulation. The imaging findings are dependent on the contents of the hernia. On radiography, it may initially appear as a posterior mass silhouetting the diaphragm, with associated contralateral mediastinal shift. However, if the hernia contains bowel, it will become air-filled over time as the infant begins to swallow (Fig. 83.18). If the majority of the bowel loops are located in the hernia, the abdomen will appear scaphoid, with paucity of air on abdominal radiographs.
FIGURE 83.18 A 1-day-old male with a frontal chest radiograph demonstrating a left congenital diaphragmatic Bochdalek hernia containing multiple gas-filled bowel loops that fill almost the entire left hemithorax. There is associated mediastinal shift to the right.
Morgagni hernias refer to anterior diaphragmatic hernias occurring through a retrosternal diaphragmatic defect [12]. The majority of these occur on the right side (Fig. 83.19). They are associated with other congenital anomalies, such as congenital heart disease, intestinal malrotation, and Down syndrome.
FIGURE 83.19 A 2-year-old male with a right anterior diaphragmatic Morgagni hernia containing colon (black block arrow), as shown on these frontal (A) and lateral (B) chest radiographs.
Eventration This refers to a focal or diffuse thinning of the diaphragm, most often occurring on the right, with resultant elevation of the affected portion (Fig. 83.20) [12]. This may be congenital (due to failed muscularization of the diaphragm) or develop later in life due to paralysis. While this is often asymptomatic, the diffuse form can cause respiratory insufficiency and require surgical plication.
FIGURE 83.20 A 4-year-old male with abnormal smooth elevation of a portion of the right hemidiaphragm on this frontal chest radiograph, consistent with eventration of the right hemidiaphragm (white block arrow).
Intrathoracic Neoplasms and Masses There are numerous neoplasms and masses that occur in the thorax, which are discussed in detail in their respective chapters of the Respiratory System section. This chapter will therefore focus on intrathoracic neoplasms and masses that are more commonly seen in the pediatric population.
Mediastinal Masses Normal Thymus
The thymus is a normal cause of superior mediastinal widening in the pediatric population and should not be confused as pathology (Fig. 83.21) [10,13]. It is particularly prominent in those under the age of five and can have a triangular shape, particularly on the right, giving rise to the “sail sign.” The thymus gradually involutes over time, but processes such as stress and steroid administration may also cause involution. Thymic rebound hyperplasia after a period of stress can further be a source of confusion and make differentiation of physiologic thymic tissue from pathologic tissue difficult. In such cases, ultrasound or crosssectional imaging, such as MRI, can be helpful by demonstrating the homogeneous appearance of physiologic tissue.
FIGURE 83.21 A 0-day-old with a frontal chest radiograph demonstrating apparent superior mediastinal widening, which represents the normal thymus in a patient of this age. There is also indistinctness of the pulmonary vasculature and diffuse bilateral hazy opacities (black block arrows), consistent with transient tachypnea of the newborn.
Germ Cell Tumor These are anterior mediastinal masses arising from primitive germ cell rests [10,13]. The majority of the germ cell tumors in children are mature teratomas (Fig. 83.22). Immature, malignant teratomas also occur in the pediatric population at a lower frequency and are suggested by their invasive features. Both mature and immature teratomas classically demonstrate fat, fluid, and calcifications on imaging. However, some mature teratomas do not demonstrate fat or calcium, so the lack of these findings does not exclude a teratoma. Though older children tend to be asymptomatic, younger infants with mediastinal germ cell tumors may present with symptoms related to airway compression.
FIGURE 83.22 A 22-year-old female with a pathology proven mature teratoma. Axial CECT demonstrates a mediastinal complex cystic lesion with multiple septations and calcifications. This mass did not demonstrate fat, which emphasizes the important learning point that the absence of fat does not exclude a mature teratoma.
Lymphoma Lymphoma is the most common abnormal anterior mediastinal mass in children [10,13]. The lymphomas that typically occur in the pediatric mediastinum are Hodgkin lymphoma and the lymphoblastic type of non-Hodgkin lymphoma (Fig. 83.23). On imaging, they may present as discrete lymphadenopathy or nodal conglomerates in the anterior mediastinum and/or hila. They are classically noncalcified, unless there is a history of prior treatment. Larger lymphomatous masses may demonstrate
heterogeneous enhancement due to underlying necrosis. When sufficiently large, lymphoma can also displace and compress the adjacent airways and vessels. These features can help differentiate lymphoma from a prominent thymus.
FIGURE 83.23 A 17-year-old male with Hodgkin lymphoma. Axial CECT demonstrated a homogeneous nodal conglomerate manifesting as an anterior mediastinal mass (white arrowhead). Mediastinal blood vessels were seen traversing through this mass (white solid arrow). Conglomerate right hilar lymphadenopathy (white block arrow) and multistation mediastinal lymphadenopathy (not shown) were also seen.
Neurogenic Tumor
Neurogenic tumors, including neuroblastomas, ganglioneuroblastomas, ganglioneuromas, and peripheral nerve sheath tumors, make up the majority of posterior mediastinal masses in children [10,13]. Neuroblastomas are the most malignant of these tumors and can occur anywhere along the sympathetic chain. Approximately 20% of neuroblastomas occur in the mediastinum [13]. These neurogenic tumors appear as solid masses with variable enhancement that may cause adjacent osseous destruction or scalloping (Fig. 83.24) [10,13]. The presence of calcification favors a sympathetic chain tumor, such as a neuroblastoma, over a peripheral nerve sheath tumor. On MRI, sympathetic chain tumors appear as paraspinal, heterogeneously enhancing sausage-shaped structures that are hyperintense on T2-weighted images. They may also demonstrate intraspinal extension with associated widening of the neuroforamina (Fig. 83.24). On the other hand, peripheral nerve sheath tumors classically demonstrate the “target” sign, characterized by a high peripheral signal intensity and intermediate central signal intensity on T2-weighted images.
FIGURE 83.24 A 19-year-old male with neuroblastoma. (A) Axial CECT demonstrates a well-defined paravertebral soft tissue mass that extends into and widens the left T5-T6 neuroforamen (white block arrow). (B) This mass also erodes the adjacent vertebral body (white solid arrow).
Lung Neoplasms
Pleuropulmonary Blastoma Pleuropulmonary blastoma (PPB) is a rare embryonal malignancy composed of primitive mesenchymal tissue that usually occurs before the age of 6 [14,15]. There is an association with other embryonal tumors, such as renal cystic nephroma. The three types of PPB are as follows:
◾CPAM Type I: Multilocular cystic mass that is difficult to differentiate from type I by imaging ◾ Type II: Mixed cystic and solid mass ◾ Type III: Heterogeneously enhancing mass
These masses can cause contralateral mediastinal shift due to mass effect and respiratory distress. They are typically treated by surgical resection ± adjuvant chemoradiotherapy. Recurrent Respiratory Papillomatosis This is characterized by the growth of mucosal papillomas in the airways and is caused by human papilloma virus (HPV) types 6 and 11 acquired during vaginal birth [16]. Though the larynx is most commonly affected, this can spread to the lung parenchyma in a minority of cases and appears as multiple bilateral nodular and cavitary lesions (Fig. 83.25). Post-obstructive atelectasis and bronchiectasis can also be seen. Complications include malignant transformation into squamous cell carcinoma (rare) and secondary infections.
FIGURE 83.25 A 17-year-old male with respiratory papillomatosis. Axial CECT demonstrated (A) multiple bilateral cavitary nodules and (B) polypoid soft tissue lesions along the tracheal wall compatible with tracheal papillomas (white arrow).
Neonatal Chest Meconium Aspiration Syndrome Meconium aspiration syndrome (MAS) occurs due to aspiration of meconium-stained amniotic fluid before or during birth, typically in the setting of a stressor, such as hypoxia [17]. It more frequently affects term or postmature neonates and can be a significant cause of neonatal respiratory distress. The aspirated meconium causes small-airway obstruction and chemical pneumonitis, which on imaging manifests as segmental hyperinflation alternating with hazy or patchy areas of atelectasis, as well as coarse, asymmetric “rope-like” perihilar opacities (Fig. 83.26). Pleural effusions may also be seen. Pneumothorax is a relatively common complication (Fig. 83.26). Additional possible complications include pneumomediastinum, pulmonary interstitial emphysema (PIE), and persistent pulmonary hypertension.
FIGURE 83.26 A chest radiograph demonstrates coarse, rope-like opacities throughout hyperinflated lungs compatible with meconium aspiration syndrome (MAS). Bilateral chest tubes were placed after the patient developed pneumothoraces, relatively common complications of MAS. A persistent right basilar pneumothorax remains (white arrow).
Transient Tachypnea of the Newborn Also known as wet lung disease or transient respiratory distress, transient tachypnea of the newborn (TTN) occurs when there is delayed evacuation of fetal lung fluid [17]. This typically affects neonates born via caesarean section, during which they bypass the natural thoracic compression of vaginal delivery that would have otherwise facilitated fetal lung fluid clearance. Neonates born to
diabetic mothers or those that required anesthesia are also more predisposed to developing this condition. Imaging findings in the first 6–24 h are similar to those found in pulmonary edema, including indistinctness of the pulmonary vasculature, airspace opacification, pleural effusions, and fissural thickening (Fig. 83.27). Lung volumes may be normal or increased. TTN usually takes a benign course that resolves by 2–3 days.
FIGURE 83.27 A 0-day-old female born via caesarean section presenting with respiratory distress. This frontal chest radiograph demonstrates low lung volumes and indistinctness of the pulmonary vasculature, compatible with transient tachypnea of the newborn.
Surfactant Deficiency Disease
Surfactant deficiency disease (SDD) is also known as respiratory distress syndrome and sometimes inaccurately referred to as hyaline membrane disease [17]. This occurs due to surfactant deficiency, which consequently leads to alveolar collapse and decreased lung compliance. As immature type II pneumocytes cannot produce enough surfactant, this is primarily a disease of prematurity. However, primary forms of SDD due to genetic mutations in surfactant and secondary forms of SDD (due to conditions such as MAS or infection that inactivate surfactant) may also occur. On imaging, low lung volumes are seen with bilateral granular opacities representative of the collapsed alveoli accompanied by air bronchograms representing the noncollapsed larger bronchi that are not dependent on surfactant for patency (Fig. 83.28). When severe, the granular opacities become more confluent and result in diffuse lung opacities.
FIGURE 83.28 A 0-day-old premature male born at 26 weeks’ gestation with surfactant deficiency disease. This frontal chest radiograph demonstrates low lung volumes and diffuse bilateral granular opacities, compatible with surfactant deficiency disease.
Persistent Pulmonary Hypertension of the Newborn Also known as persistent fetal circulation, this phenomenon occurs when there is persistent pulmonary hypertension and failure of the fetal shunts to close after birth [18]. Normally, there is high pulmonary vascular resistance in the fetal circulation causing the blood to bypass the lungs. With increased aeration of the lungs after birth, pulmonary vascular resistance normally decreases while systemic vascular resistance simultaneously increases. This leads to increased lung perfusion, as well as reversal of blood flow through fetal shunts (such as the ductus arteriosus) and their eventual closure. However, in conditions that cause hypoxia, such as MAS, SDD, or pulmonary hypoplasia, high pulmonary vascular resistance and pulmonary hypertension
can persist. Chest radiographs are often reflective of the underlying etiology of the persistent pulmonary hypertension but can also be normal.
Neonatal Pneumonia The majority of neonatal pneumonias are caused by bacteria and can have variable appearances that are difficult to distinguish from other neonatal conditions, such as MAS, TTN, and SDD [17,19]. Group B streptococcal (GBS) pneumonia is one of the most common neonatal pneumonias acquired during passage of a colonized vaginal canal, and it can have imaging findings similar to SDD. In GBS pneumonia, the lung volumes are also typically low, and bilateral diffuse granular opacities are seen. However, pleural effusions frequently accompany GBS infections but are uncommon in SDD.
Pulmonary Interstitial Emphysema Pulmonary Interstitial Emphysema (PIE) is a part of the neonatal air leak syndrome, which includes multiple entities in which air collects in spaces outside the tracheobronchial tree (such as pneumomediastinum, pneumothorax, pneumopericardium, pneumoperitoneum, and PIE) [17]. In PIE, elevated alveolar pressures lead to alveolar perforation and leakage of air into the pulmonary interstitium. This typically occurs in premature or low birth weight patients with SDD and on ventilatory support. On chest radiographs, PIE will manifest as bubbly cystic or linear lucencies ranging from single lobar involvement to diffuse bilateral involvement (Fig. 83.29). In more advanced PIE, these cystic lucencies can develop into large cystic masses that can cause mediastinal shift. While PIE is usually asymptomatic, its early recognition can prompt switching from conventional positive pressure to high-frequency ventilation to avoid potential complications such as pneumothorax or pneumomediastinum.
FIGURE 83.29 A 4-day-old intubated male with pulmonary interstitial emphysema. A frontal chest radiograph demonstrates diffuse tubular and linear lucencies throughout both lungs, in keeping with pulmonary interstitial emphysema. There is also a background of diffuse bilateral granular lung opacities consistent with underlying surfactant deficiency disease.
Bronchopulmonary Dysplasia Also known as chronic lung disease of prematurity, bronchopulmonary dysplasia (BPD) is currently defined as oxygen dependency for at least 28 days after birth in those born at less than 32 weeks of gestational age [20]. It is thought to be related to lung injury from long-term mechanical ventilation and oxygen toxicity. Abnormal chest radiograph findings are no longer part of the definition for BPD, and early chest radiographs may be normal. However, over time, diffuse hazy opacifies will develop and eventually may progress into cystic changes, air trapping, and
linear parenchymal bands (Fig. 83.30). These findings may improve with age and clinically have no significant long-term effects. However, some children may experience complications such as exercise intolerance or asthma. Wilson–Mikity syndrome is controversial but refers to the development of BPD despite no or minimal ventilatory support.
FIGURE 83.30 A 76-day-old formerly premature male with diffuse bilateral hazy and coarse lung opacities on this frontal chest radiograph, consistent with bronchopulmonary dysplasia.
Lung Pathologies in the Older Child Foreign Body Aspiration
Foreign body aspiration is a common cause of acute respiratory distress in children, particularly in those younger than 3 years [21,22]. The aspirated foreign body can lodge in multiple locations along the airways, including the trachea. However, the bronchus is the most commonly affected site, with the right mainstem bronchus being favored due to its more vertical orientation. Radiography can easily diagnose this entity when the foreign body is radiopaque [21,22]. However, not all foreign bodies are radiopaque, in which case ancillary findings may be used to suggest the diagnosis. When the foreign body causes complete obstruction, the imaging finding will be postobstructive atelectasis. However, if it causes incomplete obstruction, there may be hyperinflation and air trapping of the affected lung upon expiration (Fig. 83.31). On lateral decubitus radiographs with the affected side down, air trapping will cause the incompletely obstructed lung to appear more hyperlucent compared to the normally deflated adjacent nonobstructed lung. On inspiratory radiographs, the nonobstructed lung will have increased volume compared to the obstructed side, with associated mediastinal shift toward the affected side. However, it should be noted that in approximately one-third of bronchial foreign body cases, the chest radiograph can be normal.
FIGURE 83.31 Foreign body in the right lung. Inspiratory (A) and expiratory (B) chest radiographs demonstrate appropriate loss of volume and increased density in the normal left lung upon expiration. However, the affected right lung remains hyperlucent and overinflated compared to the left upon expiration, compatible with air trapping secondary to a foreign body (not seen in the radiographs).
Bronchiolitis Obliterans This results from bronchiolar inflammation that leads to fibrosis and subsequent stenosis or occlusion of the affected small airways [23,24]. A number of etiologies can serve as the inciting event, including but not limited to a respiratory viral infection, graftversus-host-disease, and lung transplant allograft rejection. Chest radiograph may demonstrate a hyperlucent, underperfused lung that may have normal or decreased volumes. Expiratory air trapping and mosaic attenuation, hyperlucency, decreased pulmonary vasculature, bronchial wall thickening, and bronchiectasis may be seen on CT. Swyer–James–Macleod syndrome refers to a form of postinfectious bronchiolitis obliterans (typically a viral respiratory infection) affecting central larger bronchi. It most often manifests as unilateral involvement on chest radiographs. However, bilateral involvement can also occur.
Viral Pneumonia
Viruses cause more cases of lower respiratory tract infections than bacteria in the pediatric population, so it is important to be familiar with their appearance on imaging [19]. These infections typically affect the small airways and cause peribronchial edema, which often manifest as symmetric peribronchiolar coarse opacities radiating from the hila. Children have smaller airway diameters and incompletely formed collateral ventilation pathways compared to adults. The increased mucus production and reactive peribronchial edema may therefore lead to small airway occlusion, air trapping, and areas of subsegmental atelectasis. This accounts for the hyperlucent and hyperinflated lungs characteristic of viral pneumonias in pediatric patients.
Round Pneumonia Younger children have inadequately formed collateral ventilation pathways, and therefore pneumonias may appear more “round” in younger children (particularly those caused by Streptococcus pneumoniae)(Fig. 83.32) [19]. This should not be confused with a mass, particularly in a child younger than 8 years of age. In the setting of infectious symptoms, a repeat chest radiograph to ensure clearance is the follow-up imaging of choice. A follow-up CT exposes the patient to unnecessary radiation and should be avoided, unless the round opacity is seen in an older child or a child without infectious symptoms.
FIGURE 83.32 A 5-year-old male with multifocal round pneumonia. Front chest radiograph demonstrates a 4 cm rounded opacity in the left lower lung zone (white block arrow) and an additional smaller 2.7 cm rounded opacity in the right perihilar region (white solid arrow). Subsequent chest radiographs demonstrated resolution of these opacities, most consistent with multifocal round pneumonia.
Cystic Fibrosis Cystic fibrosis is a multisystemic autosomal recessive genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein [25]. In the respiratory system, this mutation causes increased viscosity of the mucus secretions resulting in airway obstruction and recurrent infections. Chest imaging demonstrates evidence of air trapping, and in advanced disease, there may be upper lobe predominant bronchiectasis, bronchial wall thickening, and parenchymal
architectural distortion (Fig. 83.33). Mucous plugging can be seen, sometimes giving rise to the finger-in-glove appearance that can also be seen in allergic bronchopulmonary aspergillosis. Chronic inflammation can result in mediastinal/hilar lymphadenopathy and pulmonary hypertension manifesting as pulmonary artery enlargement.
FIGURE 83.33 A 23-year-old male with history of cystic fibrosis. Axial chest CT images (A and B) demonstrate extensive, bilateral upper lobe predominant cylindrical bronchiectasis, bronchial wall thickening, and scattered foci of airway mucous plugging, in keeping with cystic fibrosis. There is diffuse mosaic attenuation in keeping with air-trapping, confirmed with expiratory phase images (B).
Primary Ciliary Dyskinesia This refers to a genetic disorder causing ciliary dysfunction with multisystemic consequences [26]. In the respiratory system, there is impaired clearance of mucous secretions. Imaging findings therefore include middle and lower lung zone predominant bronchiectasis, bronchial wall thickening, mucus plugging, centrilobular nodules, mosaic attenuation, and expiratory air trapping. Approximately half of the patients with primary ciliary dyskinesia also have Kartagener syndrome, which is characterized by a combination of bronchiectasis, sinusitis and/or polyposis, and situs inversus (Fig. 83.34).
FIGURE 83.34 A 14-year-old female with history of primary ciliary dyskinesia (PCD). (A) Axial CECT images demonstrated middle and lower lung zone predominant bronchial wall thickening and bronchiectasis (white arrows) compatible with PCD. (B) Coronal CECT demonstrates dextrocardia and abdominal situs inversus, which are associated with PCD.
Idiopathic Pulmonary Hemosiderosis This is caused by recurrent alveolar capillary hemorrhage and most commonly occurs in children, although cases in adults can also occur [27]. While the pathogenesis is unclear, some have theorized that this may have an autoimmune or allergic etiology given associations with autoimmune disorders (such as celiac disease) and allergies to cow’s milk, respectively. An association with black mold has also been demonstrated. Imaging findings in the acute phase are representative of pulmonary hemorrhage giving rise to perihilar ground glass opacities and/or consolidations (Fig. 83.35). A crazy-paving pattern with interlobular septal thickening may also represent. In the chronic phase, this progresses to lower lobe predominant fibrosis with reticular opacities, traction bronchiectasis and bronchiolectasis, and architectural distortion. In rare cases, this may be complicated by progressive massive fibrosis or hemothorax.
FIGURE 83.35 Idiopathic pulmonary hemosiderosis. A chest radiograph demonstrates patchy and reticulonodular perihilar opacities.
Pulmonary Alveolar Proteinosis This results from accumulation of surfactant and lipoproteinaceous material in the alveoli and terminal bronchioles, which gives rise to the classic crazy-paving pattern of groundglass opacities combined with interlobular/intralobular septal thickening on chest CT [28]. The typical appearance on chest radiographs includes predominantly symmetric and central opacities, with sparing of the apices and costophrenic angles (Fig. 83.36). The appearance can mimic pulmonary edema, though other features often associated with pulmonary edema (such as cardiomegaly or pleural effusions) can be absent. Less frequently, pulmonary alveolar proteinosis (PAP) can also manifest as
extensive consolidations or as multifocal, asymmetric lung opacities.
FIGURE 83.36 Pulmonary alveolar proteinosis. A chest radiograph (A) demonstrates extensive perihilar opacities. A correlative axial chest CT image (B) shows areas of interlobular septal thickening and ground glass opacities in a crazy paving pattern throughout the nondependent lungs and dense consolidations in the dependent lungs.
Most cases of PAP occur in older children or adults and are autoimmune processes in which autoantibodies to granulocyte macrophage colony-stimulating factor (GM-CSF) are produced. GM-CSF is involved in alveolar macrophage signaling, and when this is disrupted, clearance of intraalveolar lipoproteinaceous material is disrupted. Congenital forms of PAP may also arise, although less frequently, due to surfactant deficiency. There are also multiple secondary causes of PAP, including hematologic disorders, toxic inhalation exposure, autoimmune disorders, and other disease processes that interfere with alveolar macrophage function. Treatment is with bronchoalveolar lavage.
Sickle Cell Disease Sickle cell disease is a multisystemic, autosomal recessive hereditary disease that causes abnormal hemoglobin formation [29]. Acute chest syndrome (ACS) is an important pulmonary manifestation of this disease in children and is the leading cause of death in these patients. ACS is characterized by chest pain,
elevated white blood cell count, fever, and new (nonspecific) pulmonary opacities (Fig. 83.37). Whether the etiology of ACS is due to infection or infarction is up to debate, but one of the hypotheses holds that bone infarctions lead to splinting and subsequent atelectasis. Pneumonia is another pulmonary process that occurs more frequently in sickle cell disease, thought to be related to functional asplenia.
FIGURE 83.37 A 12-year-old male with history of sickle cell disease. Frontal chest radiograph demonstrated new scattered patchy and linear opacities in the lungs bilaterally, consistent with acute chest syndrome.
Langerhans Cell Histiocytosis Langerhans cell histiocytosis (LCH) is characterized by proliferation of histiocytes and can involve one site or multiple sites [30]. The most common presentation is osseous lesions, but
other organs including the lung, liver, and spleen can also be involved. While pulmonary LCH can be seen as a single organ disease in adult smokers, this is rare in children. Lung involvement in the pediatric population typically occurs in the setting of multisite disease. Chest imaging findings in LCH vary from normal chest radiographs to extensive cystic disease. The characteristic small nodules and irregular cysts typically have an upper lobe predominance. Spontaneous pneumothorax is a wellknown potential complication of this disease.
Suggested Readings • T Berrocal, C Madrid, S Novo, J Gutiérrez, A Arjonilla, N Gómez-León, Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology, Radiographics 24 (1) (2004) e17. • DR Biyyam, T Chapman, MR Ferguson, G Deutsch, MK Dighe, Congenital lung abnormalities: embryologic features, prenatal diagnosis, and postnatal radiologic-pathologic correlation, Radiographics 30 (6) (2010) 1721–1738. • SH Ranganath, EY Lee, R Restrepo, RL Eisenberg, Mediastinal masses in children, Am J Roentgenol 198 (3) (2012) W197–216. • JP Lichtenberger, DM Biko, BW Carter, MA Pavio, AR Huppmann, EM Chung, Primary lung tumors in children: radiologic-pathologic correlation from the radiologic pathology archives, Radiographics 38 (7) (2018) 2151–2172. • MC Liszewski, EY Lee, Neonatal lung disorders: pattern recognition approach to diagnosis, Am J Roentgenol 210 (5) (2018) 964–975.
References [1] S Ergun, T Tewfik, S Daniel, Tracheal agenesis: a rare but fatal congenital anomaly, Mcgill J Med 13 (1) (2011) 10. [2] JD Geisler, B Smevik, Tracheal agenesis: a report of two cases, J Radiol Case Rep 3 (7) (2009) 11–16. [3] T Berrocal, C Madrid, S Novo, J Gutiérrez, A Arjonilla, N Gómez-León, Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology, Radiographics 24 (1) (2004) e17. [4] B Ghaye, D Szapiro, JM Fanchamps, RF Dondelinger, Congenital bronchial abnormalities revisited,
Radiographics 21 (1) (2001) 105–119. [5] EY Lee, PM Boiselle, Tracheobronchomalacia in infants and children: multidetector CT evaluation, Radiology 252 (1) (2009) 7–22. [6] F Wegner, J Barkhausen, CT of Mounier-Kuhn disease, Radiology 294 (2) (2020) 246. [7] EY Lee, PM Boiselle, RH Cleveland, Multidetector CT evaluation of congenital lung anomalies, Radiology 247 (3) (2008) 632–648. [8] DR Biyyam, T Chapman, MR Ferguson, G Deutsch, MK Dighe, Congenital lung abnormalities: embryologic features, prenatal diagnosis, and postnatal radiologicpathologic correlation, Radiographics 30 (6) (2010) 1721– 1738. [9] HP McAdams, J Erasmus, Chest case of the day. Williams-Campbell syndrome, Am J Roentgenol 165 (1) (1995) 190–191. [10] PG Thacker, MG Mahani, A Heider, EY Lee, Imaging evaluation of mediastinal masses in children and adults: practical diagnostic approach based on a new classification system, J Thorac Imaging 30 (4) (2015) 247–267. [11] A Hidalgo, T Franquet, A Giménez, 16-MDCT and MR angiography of accessory diaphragm, Am J Roentgenol 187 (1) (2006) 149–152. [12] LK Nason, CM Walker, MF McNeeley, W Burivong, CL Fligner, JD Godwin, Imaging of the diaphragm: anatomy and function, Radiographics 32 (2) (2012) E51– E70. [13] SH Ranganath, EY Lee, R Restrepo, RL Eisenberg, Mediastinal masses in children, Am J Roentgenol 198 (3) (2012) W197–W216. [14] LN Naffaa, LF Donnelly, Imaging findings in pleuropulmonary blastoma, Pediatr Radiol 35 (4) (2005) 387–391. [15] JP Lichtenberger, DM Biko, BW Carter, MA Pavio, AR Huppmann, EM Chung, Primary lung tumors in children:
radiologic-pathologic correlation from the radiologic pathology archives, Radiographics 38 (7) (2018) 2151– 2172. [16] JA Worrell, DM O’Donnell, FE Carroll, JA Coleman, Chest case of the day. Respiratory tract papillomatosis, Am J Roentgenol 158 (6) (1992) 1359–1360. [17] MC Liszewski, EY Lee, Neonatal lung disorders: pattern Recognition Approach To Diagnosis, Am J Roentgenol 210 (5) (2018) 964–975. [18] V Sharma, S Berkelhamer, S Lakshminrusimha, Persistent pulmonary hypertension of the newborn, Matern Health Neonatol Perinatol 1 (2015) 14. [19] HK Eslamy, B Newman, Pneumonia in normal and immunocompromised children: an overview and update, Radiol Clin North Am 49 (5) (2011) 895–920. [20] GA Agrons, SE Courtney, JT Stocker, RI Markowitz, From the archives of the AFIP: lung disease in premature neonates: radiologic-pathologic correlation, Radiographics 25 (4) (2005) 1047–1073. [21] BS Pugmire, R Lim, LL Avery, Review of ingested and aspirated foreign bodies in children and their clinical significance for radiologists, Radiographics 35 (5) (2015) 1528–1538. [22] SM Shin, WS Kim, JE Cheon, AY Jung, BJ Youn, IO Kim, et al., CT in children with suspected residual foreign body in airway after bronchoscopy, Am J Roentgenol 192 (6) (2009) 1744–1751. [23] SJ Pipavath, DA Lynch, C Cool, KK Brown, JD Newell, Radiologic and pathologic features of bronchiolitis, Am J Roentgenol 185 (2) (2005) 354–363. [24] AD Moore, JD Godwin, PA Dietrich, JA Verschakelen, WR Henderson, Swyer-James syndrome: CT findings in eight patients, Am J Roentgenol 158 (6) (1992) 1211– 1215. [25] TH Helbich, G Heinz-Peer, D Fleischmann, C Wojnarowski, P Wunderbaldinger, S Huber, et al.,
Evolution of CT findings in patients with cystic fibrosis, Am J Roentgenol 173 (1) (1999) 81–88. [26] MP Kennedy, PG Noone, MW Leigh, MA Zariwala, SL Minnix, MR Knowles, et al., High-resolution CT of patients with primary ciliary dyskinesia, Am J Roentgenol 188 (5) (2007) 1232–1238. [27] L Khorashadi, CC Wu, SL Betancourt, BW Carter, Idiopathic pulmonary haemosiderosis: spectrum of thoracic imaging findings in the adult patient, Clin Radiol 70 (5) (2015) 459–465. [28] AA Frazier, TJ Franks, EO Cooke, TL Mohammed, RD Pugatch, JR Galvin, From the archives of the AFIP: pulmonary alveolar proteinosis, Radiographics 28 (3) (2008) 883–899, quiz 915. [29] GJ Lonergan, DB Cline, SL Abbondanzo, Sickle cell anemia, Radiographics 21 (4) (2001) 971–994. [30] J Zaveri, Q La, G Yarmish, J Neuman, More than just Langerhans cell histiocytosis: a radiologic review of histiocytic disorders, Radiographics 34 (7) (2014) 2008– 2024.
CHAPTER 84
Pediatric Gastrointestinal Tract and Hepatobiliary System Priya Pathak, Hassan Aboughalia, Garvit Khatri, Puneet Bhargava
Normal Embryology The primitive gut is derived from the yolk sac initially as a cylinder of endodermal cells surrounded by mesoderm around the third intrauterine week. It subsequently differentiates into the foregut, midgut, and hindgut. This is followed by series of complex duodenal and colonic rotations, herniation of midgut into the umbilical cord, 270-degree rotation, eventual return to the peritoneal cavity, and fixation by the 12th week, such that the duodenojejunal junction (DJJ) is positioned to the left of the superior mesenteric artery (SMA) and cecum in the right lower quadrant (Fig. 84.1) [1]; this is further discussed in the malrotation section. Complete fixation also leads to the formation of a broad-based mesentery from the DJJ to the cecum. The terminal part of the hindgut, known as the primitive cloaca, is divided into ventral (urogenital sinus) and dorsal parts (rectum and proximal anal canal] by the urorectal septum formed around the seventh week. The cloaca is separated from the amniotic cavity by the cloacal membrane, which ruptures to form the urogenital and anal orifices in perineum at the end of seventh week [2].
FIGURE 84.1 The sequence of normal intestinal rotation.
The liver and pancreas form within the mesentery surrounding the primitive gut, the liver within the ventral mesogastrium or the ventral part of mesentery suspending the stomach, and the pancreas within the dorsal mesogastrium [3]. Hepatic diverticulum is derived from the ventral foregut, forming the liver and intrahepatic ducts from the anterior portion and the gallbladder and extrahepatic ducts from the posterior portion [4]. The pancreas is derived from two foregut endodermal buds. Ventral bud forms the head and uncinate process, and the dorsal bud forms the neck, body, and tail. The ventral bud rotates and unites with dorsal bud with integration of dorsal duct (also known as accessory duct of Santorini) and ventral duct (also known as main duct of Wirsung) around the seventh intrauterine week (Fig. 84.2) [5].
FIGURE 84.2 (A) Formation of the ventral and dorsal pancreatic bud. (B and C) showing development of the bud followed by 180 degree clockwise rotation of the ventral pancreatic duct. (D) The ventral duct unites with the hepatic duct to form the common bide duct and with the dorsal duct to form the main pancreatic duct.
Imaging Techniques
◾through, Radiographs, esophagography, upper gastrointestinal (GI) series, small bowel followcontrast enema, and ultrasonography (USG) are the available modalities for the evaluation of congenital anomalies of the proximal and distal GI tract. Multidetector computed tomography (CT) has a specific role in the evaluation of complicated appendicitis, mesenteric abnormalities, liver neoplasms, and pancreatic disorders. Magnetic resonance imaging (MRI) is predominately indicated for assessment of anorectal malformations and biliary and pancreatic duct anomalies and for characterization of hepatic neoplasms Supine abdominal radiography is the initial examination for evaluation of most patients with bowel disorders, with addition of left lateral decubitus and cross-table views to detect ectopic air in suspected cases. Rectal air is best detected in prone views. Chest radiographs are indicated in cases with suspected esophageal anomalies A fluoroscopic upper GI examination delineates the anatomy of the esophagus, stomach, duodenum, and duodenojejunal junction. It involves monitoring of oral contrast bolus with image acquisition in various sequential, well-centered projections. The overall technique is essentially tailored to the individual patient, clinical manifestations, and preliminary findings. For example, in a patient with malrotation, steps such as imaging the first bolus through the duodenum and DJJ(because the latter gets obscured subsequently by opacification of jejunum), documentation of the DJJ in both frontal and lateral projections, and combining a small bowel follow-through to assess cecal position increase the diagnostic accuracy [1] Contrast can be administered via a bottle, cups, syringes, orogastric, and nasogastric tubes depending on the patient’s age and comfort. Neonates are imaged in a lying-down position. Contrast enema elucidates the anatomy of rectum, colon, and terminal ileum. It involves
◾ ◾
◾
instillation of contrast into the rectum via a catheter and image acquisition in the frontal and lateral projections
In all cases, principles of ALARA (as low as reasonably achievable) should be followed to minimize radiation exposure by adhering to techniques such as intermittent fluoroscopy, last image capture, minimizing patient-image intensifier distance, magnification, and appropriate collimation [6].
Upper Gastrointestinal Tract Anomalies Esophageal Atresia and Tracheoesophageal Fistula A spectrum of congenital anomalies is characterized by malformations of the esophagus and tracheoesophageal separation caused by aberrant folding and separation of the primitive foregut. Approximately 15% to 30% of cases occur as a part of VACTERL syndrome (vertebral anomaly, anorectal malformation, cardiac anomalies, tracheoesophageal fistula, renal anomalies, and limb deformities) [7–9]. Clinical presentations are cyanosis in early neonatal period, apnea, drooling, and respiratory difficulties [9]. The H type may present in young adults with recurrent lung infections [10]. It is classified into the following types [6,8] (Fig. 84.3):
◾ Type A: isolated esophageal atresia ◾ Type B: esophageal atresia with proximal tracheoesophageal fistula ◾ Type C: esophageal atresia with distal tracheoesophageal fistula ◾ D: esophageal atresia with both proximal and distal tracheoesophageal fistulas ◾ Type Type E: tracheoesophageal fistula without esophageal atresia
FIGURE 84.3 The types of tracheoesophageal anomalies.
The diagnosis is usually indicated on antenatal USG by the absence of a gastric bubble and polyhydramnios. Postnatally, it presents with an air-filled and distended esophageal pouch on chest radiography (Figs. 84.4 and 84.5). Attempts to pass a nasoenteric tube leads to curling within the esophageal pouch. The abdomen is gasless in cases without tracheoesophageal fistula and demonstrates bowel gas with tracheoesophageal fistula [8,9].
FIGURE 84.4 Chest radiograph from a 2-day-old boy with esophageal atresia shows a Replogle tube in the proximal esophageal pouch.
FIGURE 84.5 Esophagram from a 1-month-old boy with esophageal atresia (type A) demonstrates a contrast-filled dilated proximal esophageal pouch (white arrow).
H-type fistula is evaluated with an esophagogram as a part of presurgical planning [9]. Nonionic low-osmolality contrast media is used because highosmolar contrast may reach the lungs via the fistula and lead to pulmonary edema. The oblique fistulous tract is delineated in a prone position and with the pull-back technique, which involves placement of nasogastric tube in the stomach followed by stepwise contrast injection as the tube is withdrawn along the esophagus (Fig. 84.6). Postrepair complications are anastomotic leak and strictures, recurrent fistula, tracheomalacia, esophageal dysmotility, and gastroesophageal reflux [9].
FIGURE 84.6 Contrast esophagogram (A) Lateral showing contrast opacification of the esophagus and trachea with delineation of the H shaped tracheo-esoheageal fistula (Type E), and (B) antero-posterior view showing the same findings.
Hypertrophic Pyloric Stenosis Hypertrophic pyloric stenosis refers to thickening and elongation of the pyloric canal caused by abnormal hypertrophy of the pyloric musculature. Resultant failure of pyloric relaxation leads to gastric outlet obstruction. The disease commonly manifests between 2 weeks and 3 months of age with characteristic higher incidence in first-born boys [11]. Clinical presentations include projectile nonbilious vomiting, dehydration, and sometimes a palpable mass in the epigastrium. Implicated risk factors are male sex, prematurity, and postnatal erythromycin exposure, although the exact cause remains unclear [6]. Ultrasonography is the mainstay diagnostic examination. It involves assessment of 1. The pylorus with respect to overall appearance, thickness, and canal length, and 2. Real-time evaluation of gastric peristalsis and egress of contents through the pyloric canal
A high frequency probe is used with the patient placed in a supine position. Oblique positions displace gastric contents and may help in
reduction of air artifacts. The pyloric muscle is visualized as a hypoechoic layer present in between echogenic mucosa and serosa. The hypertrophied pylorus resembles a cervix (cervix sign) (Fig. 84.7). The antral nipple sign refers to a nipplelike protrusion of echogenic pyloric mucosa into the gastric antrum (Fig. 84.8). Upper limits of pylorus measurement can be remembered by “π”—3 mm for muscle thickness and 14 mm for canal length [12,13]. These findings are accompanied by gastric hyperperistalsis and lack of egress of intraluminal contents through the pyloric canal. Pylorospasm is the major differential consideration, which can be excluded by a prolonged or repeat scan [6].
FIGURE 84.7 Longitudinal ultrasound image of the abdomen from a 4week-old boy demonstrates the configuration of the pylorus (P) resembling a cervix (cervix sign) in hypertrophic pyloric stenosis.
FIGURE 84.8 Longitudinal ultrasound image of the abdomen from a 5week-old boy shows hypertrophic pyloric stenosis (A), with a nipplelike projection of pyloric mucosa into the gastric antrum (antral nipple sign) (white arrow) (B).
Findings on upper GI series are passage of a thin stream of contrast through the pylorus (string sign) and shoulder-like extrinsic impression of pylorus on the gastric antrum (shoulder sign) (Fig. 84.9) [12].
Hypertrophic Pyloric Stenosis: Pearls to Remember
◾abnormal Thickening and elongation of the pyloric canal caused by hypertrophy of pyloric musculature ◾incidence Manifests between 2 weeks and 3 months of life with a higher in first-born boys ◾ Cervix and antral nipple signs on USG ◾andUpper limits of pylorus measurement are 3 mm muscle thickness 14 mm canal length ◾ Pylorospasm is the differential consideration
FIGURE 84.9 Upper gastrointestinal study from a 3-week-old boy demonstrates a thin stream of contrast into the duodenum (string sign, white arrowhead) and an extrinsic shoulder-like impression on the gastric antrum from the pyloric muscle (shoulder sign, white arrow) in hypertrophic pyloric stenosis.
Duodenal Obstruction Causes of duodenal obstruction are duodenal atresia, duodenal web and stenosis, annular pancreas, preduodenal portal vein, malrotation, and midgut volvulus. Malrotation is discussed in a separate section.
◾intrauterine Duodenal atresia results from failure of duodenal recanalization during the 9th to 11th weeks. It leads to complete duodenal obstruction presenting with bilious emesis
in newborns. The second portion of duodenum just distal to the ampulla of Vater is the most common site of involvement. Associations are Down syndrome, congenital heart disease, and malrotation [9]. The characteristic finding on abdominal radiography is the doublebubble sign formed by the gas-filled dilated stomach and duodenal bulb, with lack of distal bowel gas (Fig. 84.10). The diagnosis in doubtful cases with equivocal clinical features, lack of a definitive double-bubble sign, or presence of distal bowel gas (secondary to anomalous
Y-shaped bile duct communicating with duodenum on either side of atresia) can be established by an upper GI examination [6,8] Duodenal web or intraluminal diverticulum is characterized by a mucosal membrane or diaphragm in the duodenum, most commonly in the second portion near the ampulla of Vater. Progressive elongation of the membrane secondary to peristalsis produces the characteristic windsock deformity, which presents on upper GI examination as a contrastfilled sac in the duodenum surrounded by a radiolucent line (Fig. 84.11). The windsock deformity can also be visualized on USG if the duodenum is adequately distended and fluid filled. Duodenal web can be associated with malrotation, annular pancreas, and preduodenal portal vein [6,14] Duodenal stenosis involves focal or segmental narrowing of the duodenum secondary to incomplete recanalization and can lead to partial obstruction [6] Annular pancreas results from failure of rotation of the ventral pancreatic bud, forming partial or complete ring of pancreatic tissue around the second portion of duodenum. A complete ring leads to complete duodenal obstruction with double-bubble appearance on radiography; a partial ring can present later in life or remain asymptomatic (Fig. 84.12) [8] Preduodenal portal vein is a rare cause of duodenal compression and obstruction by an abnormal anteriorly located portal vein. The obstruction usually occurs in conjunction with additional duodenal anomalies such as a web [9]
◾ ◾ ◾ ◾
FIGURE 84.10 Abdominal radiograph from a newborn with trisomy 21 and duodenal atresia demonstrates the double bubble sign formed by gas-filled stomach and duodenal bulb.
FIGURE 84.11 Upper gastrointestinal study shows windsock deformity in duodenal web.
FIGURE 84.12 Contrast-enhanced axial computed tomography of the abdomen from a 5-year-old boy shows incidental annular pancreas (white arrow).
Duodenal Obstruction: Pearls to Remember
◾pancreas, Causes are duodenal atresia, duodenal web and stenosis, annular preduodenal portal vein, malrotation, and midgut volvulus. ◾filled The double-bubble sign in duodenal atresia is caused by a gasdilated stomach and duodenal bulb, with a lack of distal bowel gas. ◾ Windsock deformity is present in the duodenal web. ◾ An annular pancreas forms a complete ring, leading to complete duodenal obstruction with double-bubble appearance on radiography. A partial ring can present later in life or remain asymptomatic.
Malrotation and Midgut Volvulus
Embryology and Clinical Presentation Malrotation is a congenital anomaly of abnormal bowel rotation and fixation. The characteristic presentation is bilious emesis in neonates. Other nonspecific symptoms include nonbilious vomiting, diarrhea, signs of septicemia, and shock. It manifests with symptoms of malabsorption and failure to thrive in older children secondary to episodes of self-resolving volvulus. The incidence is slightly higher in males [13,15]. On embryology, sequential steps of intestinal rotation involve extrusion of midgut into the umbilical cord, counterclockwise-wise 270-degree rotation around the SMA, return to the peritoneal cavity, and fixation. Normal fixation is completed around the 12th week with DJJ positioned posterior and to the left of the SMA and cecum in the right lower quadrant, with a broad mesentery connecting them (see Fig. 84.1). Deviation from the normal process leads to malrotation with an abnormally placed duodenojejunal junction (DJJ] failing to crossing the midline, high cecal position, and a shortened mesentery. Additionally, an abnormal position of the right colon with increased cecal mobility initiates hyperfixation attempts, leading to formation of a Ladd band. A Ladd band can lead to bowel obstruction by extrinsic compression. A shortened mesentery predisposes to midgut volvulus and bowel ischemia [12,13,15]. Nonrotation is the absence of bowel rotation with small bowel occupying the right and colon occupying the left abdomen. It is an incidental finding with essentially no risk of midgut volvulus because of a broad mesentery [6]. Imaging Features Upper GI examination is the gold standard. The following criteria should be met to exclude malrotation (Figs. 84.13 and 84.14):
◾ DJJ located lateral to the left vertebral pedicle ◾ present at the level of duodenal bulb ◾ DJJ Proximal jejunum occupying the left upper quadrant
FIGURE 84.13 Upper gastrointestinal study from a 2-month-old boy shows duodenojejunal junction failing to cross the midline (black arrow), with location at a level lower than the duodenal bulb caused by malrotation. Proximal jejunal loops are present in the central and right midabdomen.
FIGURE 84.14 Upper gastrointestinal study in malrotation demonstrates medial position of the duodenojejunal junction (black arrow).
Equivocal findings warrant a small bowel follow-through to confirm cecal position in the right lower quadrant, ensuring sufficient mesenteric length. Midgut volvulus presents with beaking of the contrast column at the level of obstruction (Fig. 84.15), sometimes with associated corkscrew appearance of the duodenum and proximal jejunum [13].
FIGURE 84.15 Upper gastrointestinal study from a 1-month-old girl shows duodenal obstruction with contrast beaking in second portion and no distal passage. Subsequent ultrasonography of the abdomen demonstrates swirling of the mesenteric vessels (whirlpool sign) caused by midgut volvulus.
Normal congenital variants such as duodenum inversum and redundancy, enteric tubes, and bowel overdistension can lead to false-positive results. In duodenal inversum, the third portion of duodenum follows a posterosuperior course before crossing the midline with a normally located DJJ (Fig. 84.16) [6].
FIGURE 84.16 Upper gastrointestinal study from a 3-month-old boy shows the posterosuperior course of the third portion of the duodenum (black arrow) in duodenal inversum.
On USG, malrotation presents with:
◾theReversal of the normal relationship of the SMA to the superior mesenteric vein (SMV) with SMV located to the left of SMA (Fig. 84.17) ◾toVisualization of the SMA and aorta with an intervening duodenum is a sensitive parameter ensure retroperitoneal location of duodenum; there is loss of this relationship in ◾malrotation Midgut volvulus demonstrates duodenal hyperperistalsis with beaking at the transition point and whirlpool sign caused by twisting of the mesenteric vasculature (see Fig. 84.15) [12,13]
FIGURE 84.17 Transverse ultrasound of the abdomen from a 6month-old girl with malrotation demonstrates reversal of the relationship of the superior mesenteric artery (SMA) to the superior mesenteric vein (SMV) with the SMV located to the left of the SMA.
Surgical correction of malrotation (Ladd’s procedure) creates a nonrotation anatomy of the bowel (Fig. 84.18) [12].
FIGURE 84.18 Small bowel follow-through demonstrates nonrotation anatomy with small bowel occupying the right and large bowel occupying the left hemiabdomen.
Malrotation and Midgut Volvulus: Pearls to Remember
◾ Congenital anomaly of abnormal bowel rotation and fixation ◾vertebral Normal duodenal–jejunal junction is present lateral to the left pedicle at the same height as duodenal bulb with proximal jejunum occupying the left upper quadrant.
◾
◾theOnSMV USG, there is reversal of normal SMA–SMV relationship with located to the left of the SMA. ◾duodenum Midgut volvulus demonstrates a corkscrew appearance of the and proximal jejunum on upper GI examination and the whirlpool sign on USG
Lower Gastrointestinal Tract Anomalies Jejunoileal Atresia Pathophysiology and Clinical Presentation Jejunoileal atresia is caused by intrauterine ischemic insult to the developing bowel. The extent of bowel involvement is variable, with focal or multifocal atresia. Neonates present with bilious vomiting in proximal jejunal atresia. Distal jejunal and ileal atresia manifest with abdominal distension and failure to pass meconium [6]. The condition is strongly associated with prematurity and gastroschisis [9]. Imaging Features
◾byAbdominal radiography in proximal jejunal atresia demonstrates the triple bubble formed gas-filled dilated stomach, duodenum, and proximal jejunum, with lack of distal bowel gas. Distal jejunal and ileal atresia presents with low obstruction as multiple dilated loops and air-fluid levels (Fig. 84.19) Upper GI and contrast enema are usually performed in most cases to evaluate for multifocal disease, which can have a mixed radiographic appearance. Atretic segments do not fill with contrast (Fig. 84.20) Microcolon (small caliber colon with normal length] is a characteristic finding on barium enema in ileal atresia caused by functional colonic underutilization. Isolated proximal jejunal atresia is not associated with microcolon because the remainder of the small bowel produces adequate secretions to prevent colonic underutilization Jejunoileal atresia may be complicated by bowel perforation and meconium peritonitis [6,16]
◾ ◾ ◾
FIGURE 84.19 Abdomen radiograph from a 2-day-old boy shows low bowel obstruction with multiple gas-filled distended bowel loop. Subsequent contrast enema demonstrates diffuse microcolon with no passage of contrast beyond the most distal ileal loops caused by ileal atresia. Of note, there is high-riding cecum in the epigastrium (black arrow).
FIGURE 84.20 (A) antero-posterior and (B) lateral/oblique, Contrast enema shows mild degree of microcolon. There is opacification of several normal caliber ileal loops without contrast reaching the dilated air-filled proximal small bowel caused by jejunal atresia.
Meconium Ileus Meconium ileus refers to neonatal bowel obstruction caused by thick and tenacious meconium. The condition is strongly associated with cystic fibrosis (≤90% cases) [6].
◾Soap Abdominal radiography demonstrates low obstruction with multiple gas-filled bowel loops. bubble opacities may be present in the right lower quadrant secondary to admixture of meconium with air ◾diagnostic Contrast enema performed with hyperosmotic agents such as Gastrografin has both and therapeutic effects by causing meconium softening and disimpaction. It demonstrates microcolon with meconium filling defects and contrast reflux into the distal ileum outlining the meconium pellets (Fig. 84.21) [6,16]
FIGURE 84.21 (A) Abdomen radiograph from an 8-day-old boy with meconium ileus shows multiple gas-filled distended bowel loop. (B) Subsequent contrast enema demonstrates diffuse microcolon with several meconium filling defects.
Major complications of meconium ileus are bowel perforation and meconium peritonitis. In meconium peritonitis, there is spillage of bowel contents into the peritoneal cavity caused by perforation, triggering marked inflammatory reaction followed by fibrosis and intraperitoneal calcifications. These calcifications can be detected on radiographs. USG demonstrates intraperitoneal calcifications as echogenic foci (Fig. 84.22), along with loculated intraperitoneal collections, uni- or multilocular pseudocysts with septations and mural calcifications caused by localized perforation. Snowstorm appearance refers to diffusely scattered echogenic material in the peritoneum in generalized meconium peritonitis [16].
FIGURE 84.22 Abdomen radiograph demonstrates multiple calcifications in the right upper abdomen secondary to meconium peritonitis (black arrow)(A), visualized as echogenic foci on ultrasound abdomen (white arrow) (B).
Meconium Ileus: Pearls to Remember
◾meconium Neonatal bowel obstruction caused by thick and impacted ◾ Majority of patients have cystic fibrosis ◾soapOn radiographs, there are multiple gas-filled bowel loops and bubble opacities in the right lower quadrant ◾ Microcolon is seen on contrast enema ◾pseudocyst Meconium peritonitis leads to intraperitoneal calcifications and formation
Hirschsprung Disease Pathophysiology and Clinical Presentation Hirschsprung disease is characterized by functional intestinal obstruction caused by arrested migration of ganglionic cells in the intramuscular and submucosal nerve plexus of the bowel wall. There is resultant failure of relaxation of the aganglionic segment with absent peristalsis. The extent of involvement is variable from isolated anal involvement to aganglionosis of the entire colon, always extending from distal to proximal bowel in the direction opposite to neural crest migration. Short segment disease
involving the rectosigmoid colon is the most common [9]. Clinical presentations are failure to pass meconium in first 24 to 48 hours, bilious vomiting, and abdominal distension in neonates. Older children present with defecation issues and chronic constipation. The condition is strongly associated with Down syndrome. Complications are colonic perforation and enterocolitis [6]. Imaging Features
◾air-fluid Abdominal radiographs demonstrate findings of low obstruction with bowel dilation and levels ◾rectosigmoid Contrast enema is the diagnostic modality of choice. It demonstrates reversal of ratio (ratio 2 hours) attempts after unsuccessful reduction allow for reduction in bowel wall and ileocecal valve edema. Bowel perforation and tension pneumoperitoneum are the major procedural complication [12,46].
FIGURE 84.47 Longitudinal ultrasound from a 6-month-old girl demonstrates ileocolic intussusception (black arrow) (A). It is seen as an oblong soft tissue mass in the central abdomen on radiography (black arrowhead) (B). Subsequent air enema shows the intussusception at hepatic flexure (white arrow) (C), with successful reduction and contrast reflux in the distal ileum (white arrow) (D).
Intussusception: Pearls to Remember
◾ Most common are idiopathic, ileocolic, or ileoileocolic ◾transverse Target or donut sign with bowel-in-bowel appearance is seen on USG. Pseudokidney sign is seen on the longitudinal view ◾enema, Nonsurgical management includes fluoroscopic air enema, liquid and sonographic hydrostatic reduction ◾lesser Air enema is faster and is associated with smaller perforations and peritoneal contamination
Abdominal Wall Defects Omphalocele Normally during development, the fetal bowel loops herniate through the developing anterior abdominal wall into the umbilical cord during the 6th to 10th weeks of gestation (see Fig. 84.1). Interrupted bowel retraction into the abdominal cavity results in omphalocele [47]. Understanding this process explains the characteristic umbilical cord insertion at the apex of the hernia sac and the three-layered membrane composed of peritoneum, Wharton jelly, and amnion covering the defect (Fig. 84.48) [48]. Associated congenital anomalies are frequently noted in cases of omphalocele, the most common of which are cardiac and GI in nature. The condition is associated with a high
risk of underlying genetic abnormalities. In utero detected omphalocele require serial ultrasound monitoring to evaluate the size of the omphalocele and its contents, exclude in utero sac rupture, and determine the route of delivery [49].
FIGURE 84.48 Transverse color Doppler ultrasound image of a 29week-old fetus with omphalocele shows herniation of the liver through a ventral anterior abdominal wall defect. Note the two-vessel cord insertion at the apex of the hernia sac (A). Sagittal T2-weighted magnetic resonance image of the same fetus 3 days later shows the hernia sac containing liver (black arrowhead) and the origin of the cord at anterior inferior aspect of the sac (B). Frontal abdomen radiograph from a different newborn shows a bowel containing omphalocele with no evidence of bowel obstruction or extraluminal air (C).
Gastroschisis Gastroschisis is a paraumbilical ventral body wall defect with secondary midgut herniation into the amniotic cavity. This defect is most commonly to the right of cord insertion, not covered by amniotic membrane, and characteristically smaller than 2 cm (Fig. 84.49). Compared with omphalocele, gastroschisis is rarely associated with congenital abnormalities [50]. Also, underlying genetic abnormalities are uncommon in cases of isolated gastroschisis. Postnatal outcome is mainly dependent on the bowel condition at birth with 95% survival rate in cases of uncomplicated gastroschisis.
FIGURE 84.49 Transverse color Doppler ultrasound image of a 19week-old infant with gastroschisis shows herniation of the small bowel through a paramedian ventral anterior abdominal wall defect (calipers). Note the cord insertion adjacent to the hernia sac.
Exstrophy–Epispadias Spectrum Cloacal Exstrophy Cloacal exstrophy occurs secondary to early breakdown of the cloacal membrane, resulting in a severe abnormality involving the lower half of the body, namely the hindgut, bladder, and genitalia. The associated characteristic elephant trunk appearance represents herniation of the hindgut and bowel between the everted two bladder halves [51]. Cloacal exstrophy is frequently associated with other renal anomalies, including renal agenesis, cystic dysplasia, and ectopia. Associated extrarenal abnormalities include lower extremity defects, ascites, a narrow thorax, and a single umbilical artery. Cloacal exstrophy can also be a part of the Omphalocele, Exstrophy Bladder, Imperforate anus, and Spinal anomalies (OEIS) complex, in which cloacal exstrophy is associated with omphalocele, imperforate anus, and spinal defects. The neonatal prognosis depends on the severity of the defect and associated malformations [52]. Bladder Exstrophy
Bladder exstrophy occurs from incorrect retraction of the cloacal membrane, leading to eversion of the bladder plate. The resultant abnormality involves only the urinary bladder and external genitalia (Fig. 84.50). The normal hindgut differentiates this anomaly from cloacal exstrophy. To differentiate bladder exstrophy from omphalocele, it is important to document the absence of the bladder and the position of the umbilical cord insertion superior to the ventral abdominal wall defect [51].
FIGURE 84.50 Transverse color Doppler ultrasound image of a newborn shows a collapsed anteriorly displaced urinary bladder consistent with bladder exstrophy (A). Frontal radiograph of the pelvis of the same newborn shows widened symphysis pubis, an indirect sign of bladder exstrophy (B).
Epispadias Epispadias is the least severe form of this spectrum and is characterized by an abnormal opening of the urethra secondary to incomplete fusion of the penile tubercles. Prune Belly Syndrome (Eagle-Barrett Syndrome) Prune belly syndrome involves deficiency of the abdominal wall musculature with associated features including hypotonic urinary bladder, urinary tract dilation, and undescended testes (Fig. 84.51). Imaging targets the renal system to evaluate the degree of urinary tract dilation and the extent of associated vesicoureteric reflux. Renal failure develops in up to one-third of affected individuals, requiring transplantation [53].
FIGURE 84.51 (A) Frontal radiograph of a 3-day-old newborn with prune belly syndrome shows bulging flanks. (B & C) Longitudinal grayscale ultrasound images of the right and left kidneys of the same patient shows bilateral collecting system dilation with extension to the peripheral calyces. (D) Frontal radiograph obtained at the end of a voiding cystourethrogram study of the same patient shows an enlarged urinary bladder with trabeculated wall with bilateral vesicoureteric reflux. Assessment of the degree of reflux is difficult because of severe urinary tract dilation and dilution of contrast.
Other Complex Abdominal Wall Defects Pentalogy of Cantrell This syndrome is characterized by five main components [54]: 1. Midline supraumbilical abdominal defect 2. Defect of the lower sternum 3. Deficiency of the diaphragmatic pericardium 4. Deficiency of the anterior diaphragm 5. Cardiac abnormalities
Body Stalk Anomalies This is a lethal condition characterized by malformation of the thorax, abdomen, or both often associated with craniofacial anomalies and limb defects. Cases with predominant limb abnormalities are sometimes called limb body wall defect [55].
Congenital Diaphragmatic Hernia Congenital diaphragmatic hernia (CHD) occurs secondary to an error during diaphragm development and leads to the herniation of the abdominal contents into the chest. The estimated incidence of CDH is 1 per 3000 live births [56]. Chromosomal anomalies are present in up to 35% of CHD cases, and up to 50% of cases are associated with extrapulmonary anomalies, such as intestinal malrotation. Congenital diaphragmatic hernias are classically divided into two types: Bochdalek (posterior] and Morgagni (anterior] subtypes. Bochdalek hernia
is more common accounting for 70% to 90% of cases. It typically occurs on the left side and usually contain the stomach and occasionally bowel. Alternatively, Morgagni hernias typically arises on the right side and usually contain the liver and occasionally gallbladder or bowel [57]. The most important poor prognostic factors are liver herniation and associated congenital anomalies, which are present in up to 40% of cases. Prenatal USG scan can reliably detect the presence of the hernia and its contents. MRI can be an adjunct imaging modality for complex cases. In addition, MRI can better characterize hernia contents and associated congenital anomalies. Delayed lung maturity is the most feared complication in cases of CDH. On USG, the most commonly used predictor for lung hypoplasia is the ratio of the lung area to the head circumference with values less 1 indicating poor survival [58]. Postnatally, CDHs are commonly evaluated with chest radiography to assess for the degree of mediastinal shift and contralateral lung hypoplasia. Fetoscopic endoluminal tracheal occlusion can be pursed in patients younger than 28 weeks’ gestation age, which causes fluid retention within the lung to help maturity. Postnatal surgical repair is the definitive treatment [59].
Disorders of Biliary System, Liver, and Pancreas Biliary Atresia Biliary atresia is thought to arise secondary to an in-utero progressive postinflammatory process with subsequent absent or severely deficient extrahepatic biliary tree. It usually presents in the neonatal period with progressive obstructive jaundice. Death is expected by 2 years of age in untreated cases because of the development of secondary biliary cirrhosis [39]. In 20% of cases, biliary atresia is associated with situs anomalies and is called biliary atresia-splenic malformation syndrome. The gold standard to diagnose biliary atresia is biopsy and intraoperative cholangiogram. Imaging helps establish the diagnosis, especially differentiating it from neonatal hepatitis, and allows establishing to an appropriate plan of management [60]. Imaging is the initial imaging modality of choice in cases of neonatal jaundice.
◾adequate An absent gallbladder or a gallbladder smaller than 15 mm in length on ultrasound despite fasting is 84.8% sensitive and 76.9% specific for biliary atresia. ◾theOntriangular the other hand, a triangular focus of echogenic tissue at the porta hepatis, also known as cord sign, is reported to be 96% accurate, 23.3% to 100% sensitive, and 89% to 100% specific for diagnosing biliary atresia [61].
◾excretion Hepatobiliary scintigraphy can exclude biliary atresia by demonstration of radionuclide into the small bowel (Fig. 84.52) [62,63]. Cases of neonatal hepatitis demonstrate poor hepatic radiotracer uptake and delayed radiotracer excretion into the bowel.
FIGURE 84.52 Transverse grayscale ultrasound from a 5-week-old boy with conjugated hyperbilirubinemia shows absent gallbladder despite adequate fasting in biliary atresia (A). Planar anterior and posterior hepatobiliary iminodiacetic acid scan acquired 24 hours after injection of the radiotracer shows adequate radiotracer uptake in the liver without contrast excretion into the duodenum (B).
Patients with biliary atresia are commonly treated surgically through creating a hepatic portoenterostomy, also known as the Kasai procedure. Cases that develop biliary cirrhosis and end-stage liver disease usually require liver transplantation [64].
Biliary Atresia: Pearls to Remember
◾length An absent gallbladder or a gallbladder smaller than 15 mm in on USG despite adequate fasting ◾ Triangular cord sign at the porta hepatis ◾demonstration Hepatobiliary scintigraphy excludes biliary atresia by of radionuclide excretion into the small bowel
Choledochal Cyst This represents congenital dilation of the bile ducts. Suggested explanations for choledochal cyst formation include abnormal recanalization of the biliary tree and pancreaticobiliary dysfunction. A longer than normal common pancreaticobiliary channel is an implicated variant attributing to this
pancreaticobiliary function; the expected length of the common channel varies with age, with maximum length of 3 mm in infants younger than 1 year old, 5 mm in adolescents, and 10 to 15 mm in adults [65]. Magnetic resonance cholangiopancreatography (MRCP) is the imaging modality of choice to delineate the channel length. Choledochal cyst are either discovered incidentally during imaging or more commonly present with intermittent abdominal pain and features of cholestasis. Another less common presentation is manifestations of renal failure or portal hypertension in patients with Caroli disease [66]. There are five main subtypes of choledochal cysts as follows (Fig. 84.53) [67]:
◾theTypeextrahepatic 1: most common, accounting for 50% to 80% of cases. Focal or fusiform dilation of duct (Figs. 84.54 and 84.55). It has three subtypes: a. Cystic dilation of the entire extrahepatic duct b. Focal fusiform dilation of the extrahepatic duct c. Fusiform dilation of the entire extrahepatic duct Type 2: true diverticulum arising from the extrahepatic duct Type 3: dilation of the intraduodenal portion of the extrahepatic duct, also known as choledochocele (Fig. 84.56) Type 4: multiple extrahepatic biliary cysts. It has two subtypes: a. With intrahepatic biliary cysts. b. Without intrahepatic biliary cysts. Type 5: multiple intrahepatic biliary cysts, also known as Caroli disease (Fig. 84.57)
◾ ◾ ◾ ◾
FIGURE 84.53 Illustration demonstrates the types of choledochal cysts.
FIGURE 84.54 (A) Longitudinal grayscale ultrasound image of the hepatic hilum shows type I choledochal cyst as an abrupt cystic dilation of the Common bile duct (CBD). (B) Color Doppler image.
FIGURE 84.55 Magnetic resonance cholangiopancreatography images show fusiform dilation of the common hepatic and common bile duct in type 1B choledochal cyst (white arrow) (A), with an anomalous biliopancreatic junction (white arrowhead) (B).
FIGURE 84.56 Magnetic resonance cholangiopancreatography image of a 15-year-old young woman with type III choledochal cyst shows dilation of the distal portion of the extrahepatic duct (also known as choledochocele) (black arrow).
FIGURE 84.57 Axial T2 and postcontrast T1-weighted image demonstrates the central dot sign in Caroli disease (white arrow). Also note the associated bilateral polycystic kidneys.
Caroli disease require special attention because it can be complicated by hepatic fibrosis, also called Caroli syndrome. It is important to screen the kidneys in cases of Caroli disease because of increased risk of associated renal disorders such as autosomal recessive polycystic kidney disease and medullary sponge kidney. The “central dot” sign is a specific for Caroli disease, referring to an ectatic intrahepatic biliary duct surrounding an enhancing portal vein (see Fig. 84.57) [68]. MRI can be used to document the communication of a choledochal cyst to the biliary tree, with utilization of dedicated MRCP sequences and hepatobiliary contrast agents [69]. Surgical excision of extrahepatic choledochal cysts is the treatment of choice to avoid associated complications such as pancreatitis, cholangitis, sepsis, and malignancy [70].
Choledochal Cyst: Pearls to Remember
◾subtypes. The Todani classification divides choledochal cyst into five main ◾
◾known Type 5 cyst or Caroli disease complicated by hepatic fibrosis is as called Caroli syndrome. ◾surrounding The central dot sign refers to an ectatic intrahepatic biliary duct an enhancing portal vein in Caroli disease. Cholelithiasis and Acute Cholecystitis Major risk factors for gallstones in the pediatric population include hemolytic anemias, cystic fibrosis, obesity, and parenteral nutrition [71]. Similar to the adult population, USG is the mainstay for biliary stones evaluation (Figs. 84.58 and 84.59). MRCP can be used in equivocal cases and shows calculi as areas of signal void within the biliary tree. In contrast to the adult population, 30% of pediatric cases are acalculous in nature. Cholecystectomy is the treatment of choice for symptomatic gallstone disease and in patients with high-risk comorbidities such as hemolytic anemias [72].
FIGURE 84.58 Longitudinal grayscale ultrasound from a 16-year-old young woman with sickle-cell anemia shows multiple calculi within a distended gallbladder (GB).
FIGURE 84.59 Transverse grayscale ultrasound image from a 12year-old girl with shock of unclear origin demonstrates a grossly thickened gallbladder wall (GB) and pericholecystic fluid in keeping with acalculous cholecystitis.
Hepatic Masses Congenital Hepatic Cysts True congenital hepatic cysts are rare and display a simple cystic appearance Although these are more commonly an isolated finding, they can be seen in the context of syndromes such as autosomal dominant polycystic kidney disease or von Hippel–Lindau syndrome. Those associated with syndromes are more likely to be multiple. On the other hand, acquired cysts may be caused by echinococcal disease, abscesses, or resolving hematomas. Hemangiomas
Liver hemangiomas can occur in two forms, congenital and infantile variants.
◾canThoserapidly observed at their maximum size at birth are termed congenital hemangiomas. They involute early during infancy (rapidly involuting congenital hemangioma) or persist relatively unchanged (noninvoluting congenital hemangioma), previously called hemangioendothelioma] Hepatic hemangiomas that are small or not seen at birth but grow afterward before involution are termed infantile hemangiomas
◾
Compared with congenital hemangiomas, infantile hemangiomas tend to be multiple, exhibit associated skin stigmata, and express a membrane glucose transporter called GLUT1. Also, infantile hemangiomas are more likely to be associated with complications such as high-output cardiac failure secondary to intralesional shunting, platelet consumption, coagulopathy, and anemia [73]. These tumors are important to recognize to avoid confusion with malignant hepatic tumors, given their high vascularity and occasional heterogeneous appearance. In addition to the patient age and the normal alpha-fetoprotein (AFP) levels, imaging can further characterize these tumors. Imaging Features
◾subtypes Imaging features of hepatic hemangiomas vary with the lesion size and number. Both can occur in a focal, multifocal, or diffuse pattern. USG and MRI are the diagnostic modalities of choice ◾vascularity. On ultrasound, both hemangioma subtypes demonstrate variable echogenicity and Doppler A feeding vessel surrounding or within the lesion can be identified (Fig. 84.60). Compared with infantile hemangiomas, congenital hemangiomas are larger lesions, with heterogeneous echogenicity caused by the presence of hemorrhage, necrosis, fibrosis, and calcifications. Congenital hemangiomas may contain large internal vascular channels mimicking an arteriovenous malformation (see Fig. 84.60). Additionally, congenital hemangiomas are more commonly associated with manifestations of high flow dynamic such as enlargement of hepatic veins and tapering of the abdominal aorta below the origin of the celiac artery. USG is indicated for detection, localization, and follow up of these lesions [74] On CT, both lesions demonstrate intense peripheral nodular enhancement in the arterial phase, with progressive fill-in on delayed phase (Fig. 84.61). The enhancement is more uniform in small infantile hemangiomas; large congenital hemangiomas have heterogeneous atypical pattern with lack of complete central fill in. On MRI, infantile hemangiomas are typically T1 hypointense and markedly T2 hyperintense (Fig. 84.62). They may show central cystic areas or a stellate shaped central flow void. Congenial hemangiomas tend to demonstrate more heterogeneous T1 and T2 signal. Calcifications are more commonly present in congenital hemangiomas during their involution [74]
◾
FIGURE 84.60 Longitudinal ultrasound image from a 4-month-old boy demonstrates a congenital hemangioma in the left hepatic lobe. The lesion shows heterogeneous echogenicity, scattered internal cystic areas or vascular channels (white arrows) (A) and marked vascularity on color Doppler mimicking an arteriovenous malformation (B).
FIGURE 84.61 A 3-month-old with multiple infantile hepatic hemangiomas. The lesions demonstrate arterial phase enhancement (white arrow) (A), with gradual centripetal filling in on venous and delayed phases (white arrow) (B) and (C).
FIGURE 84.62 A 15-month-old young girl with multiple hepatic hemangiomas. The lesions are hypointense on axial T1-weighted magnetic resonance imaging and markedly hyperintense on T2weighted imaging (A and B). On sequential postcontrast phases, the lesion shows gradual progressive centripetal enhancement (C–E). (Courtesy: Dr. Vasundhara Smriti, Department of Radiodiagnosis, Tata Memorial Hospital, Mumbai, India.)
The primary differential diagnoses are metastatic neuroblastoma, hepatoblastoma, and mesenchymal hamartoma. The majority of liver hemangiomas are asymptomatic and require no therapy. Patients with symptomatic hemangiomas might be managed medically with propranolol or steroids, but those with more disease may require embolization or resection or rarely liver transplantation in diffuse disease [75]. Mesenchymal Hamartoma This is second most common benign hepatic tumor after hemangioma and is typically diagnosed in children younger than the age of 2 years. It commonly presents with painless abdominal distension and normal AFP levels.
◾appearance The imaging appearance of mesenchymal hamartoma reflect their variable imaging because they can be predominantly cystic or solid. However, the majority of the
cases demonstrate a cystic component (Fig. 84.63), with the presence of multiple cysts imparting a Swiss cheese appearance These cysts vary in their appearance based on their content and typically do not show hemorrhage or calcifications. However, the gelatinous content within the cysts manifests as low-levels echoes on USG, with density slightly higher than that of water on CT. The solid component, on the other hand, can enhance after intravenous contrast administration Despite their benign nature, there is known rare potential for transformation into undifferentiated embryonal sarcoma [76]. Surgical resection is the definitive management as these tumors show rapid growth [77]
◾ ◾
FIGURE 84.63 Longitudinal color Doppler ultrasound image from a 2year-old girl demonstrates mesenchymal hamartoma as a well-defined, avascular multilocular mass with no discrete solid components (A). Coronal T2-weighted imaging (B) and T1-weighted magnetic resonance imaging (C) of the abdomen confirms the multicystic nature of the lesion with no solid components or hemorrhage.
Hepatoblastoma Pathophysiology and Clinical Presentation: This is the most common hepatic malignancy in the pediatric population, primarily affecting children younger than the age of 5 years. A minority of cases occur in the context of trisomy 18, Beckwith-Wiedemann syndrome, and familial adenomatous polyposis syndrome. The most common clinical presentation is with abdominal distension associated with nonspecific symptoms such as anorexia and weight loss. There are two broad histopathologic categories of hepatoblastoma, the epithelial type (more common) and the mixed epithelial and mesenchymal type. More than 90% of the cases of hepatoblastoma exhibit increased serum AFP levels; thus, it can be a useful tumor marker in adjunct to the clinical and imaging findings as well as for treatment response assessment [78,79]. Imaging Features
◾enhancement On CT, hepatoblastomas tend to be well defined with lobulated contours and heterogeneous (Fig. 84.64). Calcifications are present in more than half of these tumors (Fig. 84.65]). The mixed subtype can show the presence of cartilaginous or osseous tissue in the mesenchymal component. Central necrosis and intratumoral hemorrhage may occur MRI better evaluates disease extent and vascular invasion without the risk of radiation; however, there is no consensus on which modality is preferred for hepatoblastoma imaging [78] It is crucial to evaluate the hepatic vasculature to exclude tumor thrombus, which, unlike hepatocellular carcinoma (HCC), is not a contraindication to surgery or even transplant The PRE-Treatment, EXTent of tumor (PRETEXT) classification, last updated in 2017, relies on the contiguous tumor-free liver sections for hepatoblastoma risk stratification and is an important basis for planning management [80]. The classification divides liver into four sections as following: left lateral (segments 2 and 3), left medial (segments 4a and 4b), right anterior (segments 5 and 8), and right posterior (segments 6 and 7). The four PRETEXT stages are as follows:
◾ ◾ ◾
◦ PRETEXT I: 3 contiguous sectors free of tumor ◦ PRETEXT II: 2 contiguous sectors free of tumor ◦ PRETEXT III: 1 sector free of tumor ◦ PRETEXT IV: all sectors involved with tumor
FIGURE 84.64 Virtual unenhanced computed tomography of the abdomen of a 2-year-old girl with hepatoblastoma shows large, multilobulated, heterogeneous mass occupying the near entirety of the right hemiliver with splaying of the right and middle hepatic veins (A). The mass shows heterogeneous postcontrast enhancement (B).
FIGURE 84.65 A and B, Hepatoblastoma with calcification.
Surgical resection can be curative in cases of hepatoblastoma. Neoadjuvant chemotherapy is given in more aggressive cases before surgery
to decrease hepatic tumor burden. On the other hand, patients with nonresectable tumors can benefit from hepatic transplantation. The most common site of metastasis is the lungs (∼10–20% of cases). Metastatic disease to the lung can be treated with either chemotherapy or excision and is not an absolute contraindication for surgery or transplant [81].
Hepatoblastoma: Pearls to Remember
◾ageMostof 5common pediatric hepatic malignancy occurring before the years ◾enhancement Well-defined tumors with lobulated contours and heterogeneous ◾ Calcifications are present in more than half of these tumors. ◾ The PRETEXT classification is used for risk stratification.
Hepatocellular Carcinoma and Fibrolamellar Hepatocellular Carcinoma Pediatric HCC usually affects patients during their second decade of life. Predisposing factors include biliary atresia, glycogen storage disease type 1, α1-antitrypsin deficiency, and Wilson disease. HCCs characteristically demonstrate an elevation in serum AFP levels, whereas AFP elevation is not a feature of fibrolamellar HCC [79]. On imaging, HCC may occur as a solitary mass, multifocal nodules, or diffusely infiltrative lesions, with imaging appearance and enhancement characteristics similar to those of the adult counterpart. Fibrolamellar HCC is a variant of HCC that characteristically occurs without a background liver disease and contains a central scar in 60% to 75% of patients. Classically, the fibrous central scar is hypointense on T2-weighted imaging and does not enhance on delayed contrast phase, in contrast to the vascular central scar associated with focal nodular hyperplasia (Fig. 84.66). In addition, the central scar of fibrolamellar HCC commonly shows calcifications (Fig. 84.67) [82]. Complete surgical resection of HCC offers the best chance at long-term survival, although fewer than 30% of these tumors are resectable in the pediatric population secondary to multifocal disease and metastasis [78,79].
FIGURE 84.66 Axial T2-weighted image from an 18-year-old man shows a central hypointense scar of fibrolamellar carcinoma (white arrow) (A), which does not enhance on delayed phase T1-weighted imaging (black arrow) (B). The patient has associated cardiac cirrhosis caused by single ventricular physiology and Fontan repair.
FIGURE 84.67 Contrast-enhanced coronal CT of the abdomen from a 14-year-old boy with fibrolamellar carcinoma shows focal calcification in the central scar (black arrow).
Undifferentiated Embryonal Sarcoma Undifferentiated embryonal sarcomas are rare aggressive malignant hepatic mesenchymal tumors, with undifferentiated cells accounting for 9% to 13% of the mass. Approximately 90% of the patients are younger than 15 years of age with a slight male predominance. The clinical presentation can be with abdominal pain, palpable mass, lethargy, or weight loss. In contrast to hepatoblastoma, AFP levels are normal with these tumors. The presence of myxoid stroma in the tumors imparts a solid appearance on USG and predominantly fluid attenuation on CT; they often appear cystic on CT (Fig. 84.68). CT may less often show associated solid components, septations, and heterogeneous postcontrast enhancement. On MRI, the tumors are T1 hypointense and T2 hyperintense and may demonstrate occasional areas of hemorrhage (Fig. 84.69). Most common sites of metastasis include the lung,
pleura, peritoneum, and bones. Management is by adjuvant chemotherapy, surgical resection, or liver transplantation [73].
FIGURE 84.68 A 5-year-old child with embryonal sarcoma. Ultrasound image of the liver demonstrates a solid heterogeneous mass in the right hepatic lobe (A). On computed tomography, the mass has a cystic appearance, mimicking a collection or abscess (white arrow) (B).
FIGURE 84.69 Axial T1- (A) and T2-weighted (B) images demonstrate embryonal sarcoma as a large lobulated, heterogeneous cystic mass in the left hepatic lobe (arrow). The mass shows internal T1 hyperintensities indicative of a proteinaceous or hemorrhage component (A).
Pancreatic Masses Pancreatic Pseudocysts
These are the most frequently encountered cystic pancreatic mass, occurring as the sequelae of previous pancreatitis or trauma (Fig. 84.70). An unexplained pseudocyst should raise the suspicion of nonaccidental injury. True epithelial-lined congenital pancreatic cysts are less common and may be associated with von Hippel–Lindau disease, Beckwith-Wiedemann syndrome, or autosomal dominant polycystic kidney disease [83].
FIGURE 84.70 Contrast-enhanced axial computed tomography of the abdomen from a 14-year-old boy with a history of necrotizing pancreatitis shows a large pseudocyst involving the pancreatic tail (white arrow). In addition, there is mild atrophy of the pancreatic body as well.
Solid and Papillary Epithelial Neoplasm This is the most common diagnosed pediatric pancreatic neoplasm. It occurs almost exclusively in female adolescents and is characterized by its welldefined margins and internal heterogeneity attributable to the combination of solid, cystic, and hemorrhagic components (Fig. 84.71). Surgical resection of these tumors is associated with excellent outcome [84]. This is discussed in more detail in Chapter 36.
FIGURE 84.71 Contrast-enhanced axial computed tomography of the abdomen from a 9-year-old girl demonstrates biopsy-proven solid and papillary epithelial neoplasm as a well-defined hypodense mass within the head of pancreas (white arrow).
Pancreatoblastoma Pancreatoblastoma are rare pediatric tumors of the pancreas. Most patients are in the first decade of life with a slight male predominance. BeckwithWiedemann syndrome is a known association. On CT, the tumors are welldefined with lobulated margins and heterogeneous postcontrast enhancement (Fig. 84.72). Multilocular cystic components and calcifications may be seen. There is a high rate of recurrence after surgical excision, although the overall prognosis is better than for adult pancreatic adenocarcinoma [84].
FIGURE 84.72 Contrast-enhanced axial computed tomography of the abdomen from a 5-year-old girl with pancreatoblastoma shows an illdefined infiltrative mass in the pancreatic head and uncinate process (black arrow) with invasion of the adjacent liver, duodenum, and right adrenal gland (A). There is associated nonocclusive portal vein thrombosis (black arrowhead) (B).
Other Pancreatic Tumors These include endocrine functioning and nonfunctioning adenomas of the pancreas. They tend to present during adolescent life and display variable imaging characteristics and sizes at presentation. Other less common tumors include Burkitt lymphoma, which may cause diffuse infiltration and enlargement of the gland. Local invasion by neuroblastoma is common [84].
Burkitt Lymphoma Burkitt lymphoma is an aggressive form of B-cell non-Hodgkin lymphoma. It accounts for up to 30% of the pediatric lymphomas with peak incidence at around the age of 10 years. An important implicated factor in the sporadic cases of Burkitt lymphoma is infection with Epstein-Barr virus, which causes MYC gene mutations. Burkitt lymphoma can be found anywhere but most commonly involves the abdomen, where it presents with symptoms of compression of adjacent organs such as abdominal pain and constipation. Systemic symptoms such as weight loss and fever are less common compared with the other subtypes of lymphoma. Although USG and crosssectional imaging are commonly the initial imaging modalities for local disease evaluation and characterization, PET/CT is the modality of choice for assessment of disease extent and response to therapy. On CT, lymphomatous involvement can present as extranodal soft tissue masses or with extensive bowel wall thickening (Fig. 84.73). There is predilection for involvement of the distal small bowel, cecum, and appendix. Solid organ disease is less common, with the liver being the most common site, where it
manifests as hypoattenuating focal lesions [85]. Burkitt lymphomas are usually markedly sensitive to chemotherapy, which serves as the primary treatment [86].
FIGURE 84.73 Contrast-enhanced axial computed tomography (CT) of the abdomen from a 16-year-old young man with Burkitt lymphoma shows lymphomatous involvement of the distal gastric body and antrum with marked mural thickening (white arrow) (A). Contrast-enhanced coronal CT of the abdomen and pelvis from another patient demonstrates marked mural thickening of the descending colon caused by involvement by Burkitt lymphoma (white arrowhead) (B).
Suggested Readings • EA Dunn, ØE Olsen, TAGM Huisman, The pediatric gastrointestinal tract: what every radiologist needs to know, in: Hodler J, Kubik-Huch R, von Schulthess G (eds.), Diseases of the Abdomen and Pelvis 2018–2021. IDKD Springer Series. Springer, Cham. • SJ Menashe, RS Iyer, MT Parisi, RK Otto, E Weinberger, AL Stanescu, Pediatric abdominal radiographs: common and less common errors, AJR Am J Roentgenol 209 (2) (2017) 417– 429. • AO Adeyiga, EY Lee, RL Eisenberg, Focal hepatic masses in pediatric patients, AJR Am J Roentgenol 199 (2012) 4, W422–W440. • SH Ranganath, EY Lee, RL Eisenberg, Focal cystic abdominal masses in pediatric patients, AJR Am J Roentgenol 199 (2012) 1, W1–W16.
References [1] KE Applegate, JM Anderson, EC Klatte, Intestinal malrotation in children: a problem-solving approach to the upper gastrointestinal series, Radiographics 26 (2006) 1485–1500.
[2] L Alamo, BJ Meyrat, JY Meuwly, RA Meuli, F Gudinchet, Anorectal malformations: finding the pathway out of the labyrinth, Radiographics 33 (2013) 491–551. [3] HK Pannu, M Oliphant, The subperitoneal space and peritoneal cavity: basic concepts, Abdom Imaging 40 (2015) 2710–2722. [4] M Strazzabosco, L Fabris, Development of the bile ducts: essentials for the clinical hepatologist, J Hepatol 56 (2012) 1159– 1170. [5] BM Henry, B Skinningsrud, K Saganiak, PA Pękala, JA Walocha, KA Tomaszewski, Development of the human pancreas and its vasculature: an integrated review covering anatomical, embryological, histological, and molecular aspects, Ann Anat 221 (2019 Jan) 115–124. [6] N Anh-Vu, S ALuana, SP Grace, Neonatal bowel disorders: practical imaging algorithm for trainees and general radiologists, AJR Am J Roentgenol 210 (5) (2018) 976–988. [7] BD Solomon, VACTERL/VATER association, Orphanet J Rare Dis 6 (2011) 56, Published 2011 Aug 16. [8] B Teresa, T Isabel, G Julia, P Consuelo, L .d.e.l. .H.o.y.o María, L Manuel, Congenital anomalies of the upper gastrointestinal tract, Radiographics 19 (4) (1999) 855–872. [9] R Padma, Neonatal gastrointestinal imaging, Eur J Radiol 60 (2006) 171–186. [10] WM Hajjar, A Iftikhar, SA Al Nassar, SM Rahal, Congenital tracheoesophageal fistula: a rare and late presentation in adult patient, Ann Thorac Med 7 (1) (2012) 48–50. 10.4103/18171737.91553. [11] S Costa Dias, S Swinson, H Torrão, et al., Hypertrophic pyloric stenosis: tips and tricks for ultrasound diagnosis, Insights Imaging 3 (3) (2012) 247–250. [12] P Priya, AJ Joel, T Mahesh, Imaging of pediatric gastrointestinal emergencies, Semin Roentgenol 55 (2) (2020) 170–179. [13] T Mahesh, WS Raymond, Pediatric gastrointestinal emergencies, Radiol. (2005). [14] M Roland, The duodenal wind sock sign, Radiology 218 (3) (2001) 749–750. [15] L Lampl, LL Terry, EB Walter, AC Robert, Malrotation and midgut volvulus: a historical review and current controversies in diagnosis and management, Pediatr Radiol 39 (4) (2009 Apr) 359– 366. [16] B Teresa, L Manuel, G Julia, T Isabel, Congenital Anomalies of the small intestine, colon, and rectum, Radiographics 19 (5) (1999)
1219–1236. [17] E Stranzinger, MA DiPietro, DH Teitelbaum, et al., Imaging of total colonic Hirschsprung disease, Pediatr Radiol 38 (2008) 1162. [18] DN Vinocur, EY Lee, RL Eisenberg, Neonatal intestinal obstruction, AJR Am J Roentgenol 198 (1) (2012) W1–W10. [19] A Peña, A Hong, Advances in the management of anorectal malformations, Am J Surg 180 (5) (2000 Nov) 370–376. 10.1016/s0002-9610(00)00491-8. [20] AE Mohamed, FD Lane, HE Kathleen, AL Marc, P Alberto, Postoperative pelvic MRI of anorectal malformations, AJR Am J Roentgenol 191 (5) (2008) 1469–1476. [21] WD Winters, E Weinberger, EI Hatch, Atresia of the colon in neonates: radiographic findings, AJR Am J Roentgenol 159 (1992) 1273–1276. [22] GR Prasad, A Aziz, Abdominal plain radiograph in neonatal intestinal obstruction, J Neonatal Surg 6 (1) (2017) 6. [23] M Epelman, A Daneman, OM Navarro, I Morag, AM Moore, JA Kim, R Faingold, G Taylor, JT Gerstle, Necrotizing enterocolitis: review of state-of-the-art imaging findings with pathologic correlation, Radiographics 27 (2) (2007) 285–305. [24] G Deshpande, S Rao, S Patole, M Bulsara, Updated metaanalysis of probiotics for preventing necrotizing enterocolitis in preterm neonates, Pediatrics 125 (5) (2010) 921–930. [25] J Knell, SM Han, T Jaksic, BP Modi, Current status of necrotizing enterocolitis, Curr Probl Surg [Internet] 56 (1) (2019) 11–38. [26] MC Walsh, RM Kliegman, Necrotizing enterocolitis: treatment based on staging criteria, Pediatr Clin North Am [Internet] 33 (1) (1986 Feb) 179–201. [27] CA Coursey, CL Hollingsworth, C Wriston, C Beam, H Rice, G Bisset, Radiographic predictors of disease severity in neonates and infants with necrotizing enterocolitis, Ajr Am J Roentgenol 193 (5) (2009 nov 1) 1408–1413. [28] G Mostbeck, EJ Adam, MB Nielsen, et al., How to diagnose acute appendicitis: ultrasound first, Insights Imaging 7 (2) (2016) 255–263. [29] RK Jain, M Jain, CL Rajak, S Mukherjee, PP Bhattacharya, MR Shah, Imaging in acute appendicitis. A view, Indian J Radiol Imaging 16 (2006) 523–532. [30] V Simonovský, Normal appendix: is there any significant difference in the maximal mural thickness at US between pediatric and adult populations?, Radiology 224 (2) (2002 Aug) 333–337.
[31] AJ Quigley, S Stafrace, Ultrasound assessment of acute appendicitis in paediatric patients: methodology and pictorial overview of findings seen, Insights Imaging 4 (6) (2013) 741–751. [32] N Pinto Leite, JM Pereira, R Cunha, P Pinto, C Sirlin, CT evaluation of appendicitis and its complications: imaging techniques and key diagnostic findings, AJR Am J Roentgenol 185 (2) (2005 Aug) 406–417. 10.2214/ajr.185.2.01850406. [33] PL Nuno, MP José, C Rui, P Pedro, S Claude, CT evaluation of appendicitis and its complications: imaging techniques and key diagnostic findings, AJR Am J Roentgenol 185 (2) (2005) 406–417. [34] N Simanovsky, N Hiller, Importance of sonographic detection of enlarged abdominal lymph nodes in children, J Ultrasound Med 26 (5) (2007) 581–584. [35] R Helbling, E Conficconi, M Wyttenbach, et al., Acute nonspecific mesenteric lymphadenitis: more than “no need for surgery”, Biomed Res Int 2017 (2017) 9784565. [36] M Macari, J Hines, E Balthazar, A Megibow, Mesenteric adenitis, AJR Am J Roentgenol 178 (4) (2002) 853–858. [37] B Karmazyn, EA Werner, B Rejaie, KE Applegate, Mesenteric lymph nodes in children: what is normal?, Pediatr Radiol 35 (8) (2005 Aug) 774–777, Epub 2005 May 10. [38] AD Levy, CM Hobbs, From the archives of the AFIP, Radiographics [Internet] 24 (2) (2004 Mar 1) 565–587. [39] KM Elsayes, CO Menias, HJ Harvin, IR Francis, Imaging manifestations of Meckel’s diverticulum, AJR Am J Roentgenol [Internet] 189 (1) (2007 Jul 1) 81–88. [40] M Kotecha, R Bellah, AH Pena, C Jaimes, P Mattei, Multimodality imaging manifestations of the Meckel diverticulum in children, Pediatr Radiol 42 (1) (2012 Jan) 95–103. [41] A Daneman, O Navarro, Intussusception, Pediatr Radiol 33 (2003) 79–85. [42] JR Cogley, SC O’Connor, RA Houshyar, K Al Dulaimy, Emergent pediatric US: what every radiologist should know, Radiographics 32 (3) (2012) 651–665. [43] O Navarro, A Daneman, Intussusception, Pediatr Radiol 34 (2004) 305–312. [44] ACR-SPR practice guideline for the performance of pediatric fluoroscopic contrast enema examinations. Resolution 51. Revised 2016 ACR. [45] G Sadigh, KH Zou, SA Razavi, R Khan, KE Applegate, Metaanalysis of air versus liquid enema for intussusception reduction in
children, AJR Am J Roentgenol 205 (5) (2015 Nov) W542–W549. 10.2214/AJR.14.14060. [46] US Torres, E Portela-Oliveira, FD.C.B Braga, H Werner, PA.N Daltro, AS Souza, Delayed repeat enema in the management of intussusception, Pediatr Emer Care 26 (2010) 640–645. [47] US Torres, E Portela-Oliveira, FD.C.B Braga, H Werner, PA.N Daltro, AS Souza, When closure fails: what the radiologist needs to Know about the embryology, anatomy, and prenatal imaging of ventral body wall defects, Semin Ultrasound CT MRI [Internet] 36 (6) (2015) 522–536. [48] JW Revels, SS Wang, A Nasrullah, M Revzin, RS Iyer, G Deutsch, et al., An algorithmic approach to complex fetal abdominal wall defects, AJR Am J Roentgenol [Internet] 214 (1) (2020 Jan 12) 218–231, [cited 2020 Jul 20]. [49] R Pakdaman, PJ Woodward, A Kennedy, Complex abdominal wall defects: appearances at prenatal imaging, Radiographics [Internet] 35 (2) (2015 Mar 12) 636–649, [cited 2020 Jul 20]. [50] T Victoria, S Andronikou, D Bowen, P Laje, DA Weiss, AM Johnson, et al., Fetal anterior abdominal wall defects: prenatal imaging by magnetic resonance imaging, Pediatr Radiol [Internet] 48 (4) (2018) 499–512. [51] NA Chauvin, M Epelman, T Victoria, AM Johnson, Complex genitourinary abnormalities on fetal MRI: imaging findings and approach to diagnosis, AJR Am J Roentgenol [Internet] 199 (2) (2012 Aug) W222–W231, [cited 2019 Feb 9]. [52] JC Carey, B Greenbaum, BD Hall, The OEIS complex (omphalocele, exstrophy, imperforate anus, spinal defects), Birth Defects Orig Artic Ser [Internet] 14 (6B) (1978) 253–263, [cited 2019 Mar 17]. [53] J Garris, H Kangarloo, D Sarti, WF Sample, LE Smith, The ultrasound spectrum of prune-belly syndrome, J Clin Ultrasound [Internet] 8 (2) (1980) 117–120, [cited 2020 Aug 28]. [54] MS Restrepo, A Cerqua, JW Turek, Pentalogy of Cantrell with ectopia cordis totalis, total anomalous pulmonary venous connection, and tetralogy of Fallot: a case report and review of the literature, Congenit Heart Dis [Internet] 9 (4) (2014 Jul) E129– E134, [cited 2019 Feb 10]. [55] MI Van Allen, C Curry, L Gallagher, JF Reynolds, Limb body wall complex: I. Pathogenesis, Am J Med Genet [Internet] 28 (3) (1987 Nov) 529–548, [cited 2019 Feb 10]. [56] L Satyan, V Payam, Congenital diaphragmatic hernia: 25 years of shared knowledge; what about survival?, J Pediatr (Rio J) (2019).
10.1016/j.jped.2019.10.002. [57] GB Chavhan, PS Babyn, RA Cohen, JC Langer, Multimodality imaging of the pediatric diaphragm: anatomy and pathologic conditions, Radiographics 30 (2010) 1797–1817. [58] J Jani, CF.A Peralta, D Van Schoubroeck, J Deprest, KH Nicolaides, Relationship between lung-to-head ratio and lung volume in normal fetuses and fetuses with diaphragmatic hernia, Ultrasound Obstet Gynecol 27 (2006) 545–550. [59] E Snyder, A Baschat, TA.G.M Huisman, A Tekes, Value of fetal MRI in the era of fetal therapy for management of abnormalities involving the chest, abdomen, or pelvis, AJR Am J Roentgenol 210 (2018) 998–1009. [60] Guideline for the evaluation of cholestatic jaundice in infants: Joint recommendations of the North American society for pediatric gastroenterology, hepatology, and nutrition and the European society for pediatric gastroenterology, hepatology, and nutrition, J Pediatr Gastroenterol Nutr 64 (2017) 154–168. [61] LY Zhou, W Wang, QY Shan, BX Liu, YL Zheng, ZF Xu, M Xu, FS Pan, MD Lu, XY Xie, Optimizing the US diagnosis of biliary atresia with a modified triangular cord thickness and gallbladder classification, Radiology 277 (1) (2015 Oct) 181–191. 10.1148/radiol.2015142309. [62] MD Bassett, KF Murray, Biliary atresia: recent progress, J Clin Gastroenterol. NIH Public Access 42 (2008) 720–729. [63] K Kanegawa, Y Akasaka, E Kitamura, S Nishiyama, T Muraji, E Nishijima, et al., Sonographic diagnosis of biliary atresia in pediatric patients using the “triangular cord” sign versus gallbladder length and contraction, AJR Am J Roentgenol. [Internet] 181 (5) (2003 Nov 23) 1387–1390, [cited 2020 Apr 7]. [64] R Superina, JC Magee, ML Brandt, PJ Healey, G Tiao, F Ryckman, et al., The anatomic pattern of biliary atresia identified at time of Kasai hepatoportoenterostomy and early postoperative clearance of jaundice are significant predictors of transplant-free survival, Ann Surg [Internet] 254 (4) (2011 Oct) 577–585, [cited 2020 Apr 7]. [65] H Aboughalia, K Helen, AA.S Dick, et al., Pediatric biliary disorders: multimodality imaging evaluation with clinicopathologic correlation, Clin Imaging 75 (2021 Jan) 34–45. 10.1016/j.clinimag.2021.01.006. [66] M Hukkinen, A Koivusalo, H Lindahl, R Rintala, MP Pakarinen, Increasing occurrence of choledochal malformations in children: a single-center 37-year experience from Finland, Scand J
Gastroenterol 49 (10) (2014 Oct) 1255–1260. 10.3109/00365521.2014.946084. [67] T Todani, Y Watanabe, A Toki, Y Morotomi, Classification of congenital biliary cystic disease: special reference to type Ic IV A cysts with primary ductal stricture, J Hepatobiliary Pancreat Surg [Internet] 10 (5) (2003) 340–344, [cited 2020 Mar 31]. [68] AA Khalefa, M Alrasheed, M .B.i.n Saeedan, Central dot sign. Vol. 41, Abdominal Radiology, Springer, New York, LLC, 2016, 2289–2290. [69] G Brancatelli, MP Federle, V Vilgrain, MP Vullierme, D Marin, R Lagalla, Fibropolycystic liver disease: CT and MR imaging findings, Radiographics 25 (2005) 659–670. [70] H-T Xia, J-H Dong, T Yang, J-P Zeng, B Liang, Extrahepatic cyst excision and partial hepatectomy for Todani type IV-A cysts, Dig Liver Dis [Internet] 46 (11) (2014 Nov 1) 1025–1030, [cited 2020 Apr 11]. [71] B Frybova, J Drabek, J Lochmannova, L Douda, S Hlava, D Zemkova, et al., Cholelithiasis and choledocholithiasis in children; risk factors for development, PLoS One 13 (5) (2018 May 1). [72] AL Franklin, FG Qureshi, EP Nadler, Management of gallstones in the pediatric patient, Acute Cholecystitis, Springer International Publishing, 2015, 197–206. [73] EM Chung, R Cube, RB Lewis, RM Conran, From the archives of the AFIP: pediatric liver masses: radiologic-pathologic correlation part 1. Benign tumors, Radiographics. [Internet] 30 (3) (2010 May 4) 801–826, [cited 2020 Aug 28]. [74] BS Stephanie, Je.s.s.i.c.a K, K-L Debora, HT Benjamin, Hepatic imaging in neonates and young infants: state of the art, Radiology 285 (3) (2017) 763–777. [75] D Lewis, R Vaidya, Hepatic Hemangioma. [Updated 2020 Jun 23], StatPearls [Internet], StatPearls Publishing, Treasure Island (FL), 2020 Jan. [76] Y, G Lauwers, et al., Hepatic undifferentiated (embryonal) sarcoma arising in a mesenchymal hamartoma, Am J Surg Pathol 21 (10) (1997) 1248–1254. [77] R Iyer, T Chapman, Pediatric Imaging: The Essentials, first ed., Lippincott Williams & Wilkins, 2015. [78] PM Masand, Magnetic resonance imaging features of common focal liver lesions in children, Pediatr Radiol 48 (2018) 1234–1244. [79] EM Chung, GE Lattin Jr., R Cube, RB Lewis, C MarichalHernández, R Shawhan, RM Conran, From the archives of the AFIP: pediatric liver masses: radiologic-pathologic correlation part 2. malignant tumors, Radiographics 31 (2) (2011) 483–507.
[80] AJ Towbin, RL Meyers, H Woodley, O Miyazaki, CB Weldon, B Morland, et al., 2017 PRETEXT: radiologic staging system for primary hepatic malignancies of childhood revised for the Paediatric Hepatic International Tumour Trial (PHITT), n.d. [81] RL Meyers, G Tiao, J de Ville de Goyet, R Superina, DC Aronson, Hepatoblastoma state of the art: pre-treatment extent of disease, surgical resection guidelines and the role of liver transplantation, Curr Opin Pediatr 26 (1) (2014 Feb) 29–36. [82] D Ganeshan, J Szklaruk, V Kundra, A Kaseb, A Rashid, KM Elsayes, Imaging features of fibrolamellar hepatocellular carcinoma, AJR Am J Roentgenol 202 (3) (2014 Mar) 544–552. 10.2214/AJR.13.11117. [83] YH Kim, S Saini, D Sahani, PF Hahn, PR Mueller, YH Auh, Imaging diagnosis of cystic pancreatic lesions: pseudocyst versus nonpseudocyst, Radiographics 25 (2005) 671–685. [84] NS Shet, BL Cole, RS Iyer, Imaging of pediatric pancreatic neoplasms with radiologic-histopathologic correlation, AJR Am J Roentgenol 202 (2014) 1337–1348. [85] DM Biko, SA Anupindi, A Hernandez, L Kersun, R Bellah, Childhood Burkitt lymphoma: abdominal and pelvic imaging findings, AJR Am J Roentgenol 192 (5) (2009 May) 1304–1315. 10.2214/AJR.08.1476. [86] K Kalisz, F Alessandrino, R Beck, D Smith, E Kikano, NH Ramaiya, SH Tirumani, An update on Burkitt lymphoma: a review of pathogenesis and multimodality imaging assessment of disease presentation, treatment response, and recurrence, Insights Imaging 10 (1) (2019 May 21) 56.
CHAPTER 85
Pediatric Genitourinary Tract Betty Simon, Anu Eapen, Sridhar Gibikote
Embryology Development of Urinary Tract Kidney
◾undergoes During the early development of human embryo, single layered spherical blastula a process of gastrulation to form the three distinct cell lines (germ layers) namely the ectoderm, mesoderm, and the endoderm, which develops into specific tissues and organs. The parts of the embryonic mesoderm include the paraxial mesoderm, intermediate mesoderm, and the lateral plate mesoderm (Fig. 85.1) Urogenital system develops from the intermediate mesoderm which forms a urogenital ridge on either side of the aorta. The urogenital ridge has two parts—the nephrogenic cord which develops into the urinary tract and gonadal ridge which develops into the genital system There are three stages to the development of adult kidney which occurs in succession and proceeding cranially to caudally in the nephrogenic cord. The three structures that form in succession are the pronephros, mesonephros, and metanephros The paired pronephros which develops in the cranial part of nephrogenic cord completely regresses by 6th–7th week leaving no derivatives in the adult. The pronephros induces the adjacent mesoderm to form the mesonephros The mesonephros develops into the mesonephric tubules and mesonephric duct. The mesonephric tubules also regress. The mesonephric duct, also called the Wolffian duct, extends caudally and opens into the cloaca. This almost completely regresses in females but persists in males to form the epididymis, vas deferens, seminal vesicles, and the ejaculatory duct The metanephros is the third and final excretory organ that develops, replacing the mesonephros as the excretory organ. This is the precursor of the adult kidney. An outpouching arises from the mesonephric duct called the ureteric bud (metanephric diverticulum) and the mesoderm caudal to the mesonephros condenses to form the metanephric blastema. The ureteric bud develops into the ureter, renal pelvis, calyces and collecting ducts, and tubules by multiple divisions. The division starts at around 6 weeks and continues till about week 32 [1] As the branching ureteric bud comes in contact with the metanephric blastema, it forms the nephric vesicle and develops into the nephrons consisting of the Bowman’s capsule,
◾ ◾ ◾ ◾ ◾ ◾
proximal and distal convoluted tubules, and loops of Henle. The metanephric blastema also develops into the interstitium of renal parenchyma. The maturation of nephron continues after birth; however, there is no formation of new nephrons (Fig. 85.2) The underlying lobar structure is the result of this division into calyces. Each renal lobe consists of a calyx and its associated collecting ducts and renal cortex. About 14 lobes are formed initially, which fuse giving rise to a lobulated contour to the kidney As the cells in the cortex continue to multiply postnatally, the contour gradually becomes smooth by around 5 years of age. Fetal lobulations can persist into adulthood in some individuals The developing kidneys initially lie close together in the pelvis. As the fetus grows, they separate from each other and ascend to their final position in the lumbar region by about 8 weeks. As the ascent occurs, there is medial rotation of the kidneys by 90 degrees around the long axis so that the hilum faces anteromedially The vascular supply of the kidney is from the adjoining vessels and so initially, branches from middle sacral artery, then common iliac arteries, inferior mesenteric arteries and finally lateral branches from the aorta supply the kidney. The main renal arteries arise from the aorta usually at the level of L1–2 intervertebral space. Accessory renal arteries are present if the inferior renal arteries fail to regress during the ascent of the kidney. Accessory renal arteries have been found unilaterally in approximately 30% of the population and bilaterally in 10% [2]
◾ ◾ ◾ ◾
FIGURE 85.1 Illustration of stages of early development of human embryo.
FIGURE 85.2 (A) Stages in the development of adult kidney. (B) Illustration of the branching ureteric bud which comes into contact with metanephric blastema to form the nephric vesicle which develops into the nephron.
Bladder and Urethra
◾level The hindgut of the embryo has a dilated caudal end called the cloaca, which is below the of an anterosuperior outpouching from hindgut called the allantois (allantoic diverticulum). The allantois obliterates during development to form a fibrous cord called urachus in the embryo and the median umbilical ligament postnatally. The urorectal septum divides the cloaca into an anterior cavity called urogenital sinus and the anorectal canal posteriorly. The caudal end of urorectal septum forms the perineal body. The cranial part of urogenital sinus (UGS) forms the bladder. The mesonephric ducts which open into the cloaca are incorporated into the wall of the bladder obliquely and to form the vesicoureteric junction (VUJ). The triangular space at the base of the bladder between the two VUJs, called trigone has a mesodermal origin from caudal end of mesonephric ducts whereas the rest of the bladder has an endodermal origin from the hindgut (Fig. 85.3). The caudal part of the UGS is called the definitive UGS and has a pelvic and phallic part. The pelvic part of definitive UGS develops into the urethra in females and prostatic part of urethra in males (Fig. 85.4). Phallic part gives rise to the rest of the urethra except the distal part which is derived from a plate of ectoderm, called urethral plate that grows from the tip of glans penis and canalizes [3].
◾ ◾
FIGURE 85.3 Illustration of embryology of bladder development. (Image courtesy: Dr Praveen)
FIGURE 85.4 Illustration of parts of urogenital sinus. (Image courtesy: Dr Praveen)
Normal Anatomy and Anatomic Variants The anatomy relevant to evaluation of pediatric genitourinary system is discussed here. The kidney after development and normal ascent is located in the retroperitoneum at the level of T12-L3 vertebra. The left kidney can be positioned slightly cranially compared to right and is usually larger by
about 0.5 cm. The size of the kidney varies with age and body habitus. The kidney of a term neonate measures ∼4.5 cm in length. Several studies have assessed renal size, and graphs of renal length plotted against age of the child are available for reference [4]. A cross-sectional observational study by Otiv et al. determined the renal size in normal Indian children by sonography and derived a linear regression equation to calculate renal length based on height and age of the child. The equation obtained for Indian children in this study was as follows: Renal Length = 0.0421 × height + 2.6311; and Renal Length = 0.3055 × age + 5.2533 [5]. A rough guide for renal size according to age is provided in Table 85.1 as adapted from Kecler-Pietrzyk [6–8]. It is useful to remember that ultrasound underestimates and intravenous urogram (IVU) overestimates the size of the kidney [9]. This is because radiographic measurement of renal size varies depending on various technical factors like projection, centering, phase of respiration, etc. On IVU, the contrast media in the renal tubules also results in a slightly higher measurement. Table 85.1 Guide to Renal Size According to Age Age
Size
0–2 months
5 cm (approx. 2 inches)
2–6 months
5.7 cm
6 months to 1 year
6.2 cm (2.5 inches)
1 year to 5 years
7.3 cm (3 inches)
5 years to 10 years
8.5 cm (3.5 inches)
10 years to 15 years
10 cm (approx. 4 inches)
>15 years
Similar to adults (10–14 cm in males, 9–13 cm in females)
Adapted from Kecler-Pietrzyk [6].
The normal sonographic appearance of kidney is different in newborns and infants compared to an adult kidney (Fig. 85.5). The cortical echogenicity is increased due to glomeruli occupying more volume of the cortex in newborns compared to adults. Prominent hypoechoic medullary pyramids are seen as the medulla occupies a larger volume compared to the cortex in infants; the hypoechogenicity could also be relative due to the increased echogenicity of the cortex. The central renal sinus echoes are reduced due to the paucity of fat in this region in a neonate. These findings are usually seen up to 6 months of age [3,10,11]. The renal pelvis measures ∼5 mm in AP diameter.
FIGURE 85.5 Normal sonographic appearance of kidney in a neonate. Note the echogenic cortex, prominent hypoechoic renal pyramids and almost absent central renal sinus echoes.
The kidneys of a newborn may exhibit external indentations at the site of fusion of renal lobules giving rise to a lobulated contour. This can be seen up to 5 years of age and rarely may persist into adulthood [12].
◾between Persistent fetal lobulation can be differentiated from cortical scar due to their location the normal calyces unlike a scar where there is loss of renal parenchyma overlying the calyces (Fig. 85.6) ◾echogenic Junctional parenchymal defect (JPD) is also a similar anatomic variant seen as a thin triangular notch in the parenchyma (Fig. 85.7). This occurs along the line of embryonic parenchymal fusion of lobules [3] and is a result of incomplete fusion and extension of fat into the site of defect. The location and the characteristic triangular
echogenic focus with no focal parenchymal loss helps to differentiate this from a scar. The latter is located overlying the medullary pyramids with focal parenchymal loss and contour abnormality. If the echogenic line reaches up to the hilum, it is called inter-renicular septum (Fig. 85.8) The dromedary hump is a focal bulge in the lateral border of left kidney due to splenic impression; it has the same characteristics as the adjacent cortex and should not be mistaken for a focal lesion Hypertrophied (prominent) column of Bertin is a thick band of renal cortex that projects in between the pyramids centrally towards the renal sinus causing splaying of sinus. It can be either isoechoic or sometimes more echogenic compared to the adjacent cortex, but the renal outline is preserved. This can be mistaken for an intrarenal mass especially if the echogenicity is different (Fig. 85.9). In case of doubt, contrast enhanced computed tomography/magnetic resonance imaging (CT/MRI) will demonstrate density/signal characteristics and enhancement similar to the adjacent cortex, which helps in differentiating this from a focal lesion [13]
◾ ◾
FIGURE 85.6 Persistent fetal lobulation versus parenchymal scar. (A) Sonogram and (B) CT coronal section showing lobulated contour of the kidney with parenchymal indentation in between the calyces. (C) Sonogram and (D) CT coronal section in another patient showing a left lower pole renal parenchymal scar overlying the region of medullary pyramid with loss of and resultant thinning of parenchyma.
FIGURE 85.7 Junctional parenchymal defect. (A) Sonogram of right kidney showing a triangular echogenic notch in the parenchyma at the upper pole. (B) Coronal CT section of the same patient showing the junctional parenchymal defect (arrow).
FIGURE 85.8 Inter-renicular septum. Sonogram through the left kidney in a 5-months-old child showing a linear echogenic focus (arrow) in the upper pole extending up to the hilum.
FIGURE 85.9 Prominent column of Bertin. (A) Ultrasonography of left kidney in a 2-year-old child shows a thick band of cortex (asterisk) causing splaying of the renal sinus which was initially mistaken for an intrarenal mass due to its increased echogenicity. (B & C) CECT scan of the abdomen, axial and coronal images shows hypertrophied parenchyma (arrows) with enhancement similar to the adjacent parenchyma and preserved renal outline in keeping with a prominent column of Bertin. Note the right hydronephrosis on CT.
The renal pelvis can be completely within the renal sinus or partly outside the renal sinus called the extrarenal pelvis. Prominent extrarenal pelvis has to be differentiated from renal pelvis dilatation due to ureteropelvic junction (UPJ) obstruction; the latter usually shows some backpressure changes. Functional imaging like Lasix urography or dynamic renal scintigraphy would be helpful in this differentiation if there is a doubt. Mild ureteral elongation and tortuosity, prominent mid segment of ureter, short kinks, and intraluminal mucosal folds in the proximal ureter are some fetal characteristics which can persist in newborns and infants and should not be mistaken for a pathology [3]. Mucosal folds disappear as the child grows whereas congenital ureteral valves can sometimes cause ureteric obstruction and should be included in the differential diagnosis of ureteric obstruction in children [14]. Another phenomenon in infants which should not be mistaken as pathological is focal bulge of inferolateral wall of urinary bladder, sometimes almost reaching up to the deep inguinal ring. This is called bladder ears, usually seen in infants less than 6 months of age and usually disappears in a fully distended bladder (Fig. 85.10). However, if there is herniation into the inguinal canal, it suggests a persistent processus vaginalis.
FIGURE 85.10 MCU in a 5-year-old child, full bladder image shows bilateral bladder ears (arrows).
Urethra: Certain normal anatomical findings in voiding cystourethrogram of male posterior urethra can mimic disease. A shallow mucosal fold in the anterior wall of prostatic urethra called incisura is a common variant (Fig. 85.11). Thin folds can be seen as a filling defect in the posterior urethra below the level of verumontanum, simulating a posterior urethral valve. These are nonobstructing valves called plicae colliculi and do not cause obstruction or proximal dilatation (Fig. 85.12). Ectasia of posterior urethra is rarely seen as a normal variant without obstruction [15].
FIGURE 85.11 MCU in a 1-year-old child shows incisura—a shallow mucosal fold (arrow) in the anterior wall of prostatic urethra which is a normal variant.
FIGURE 85.12 MCU in a male child showing a thin lucent filling defect (arrow) in the posterior urethra with no features of obstruction— representing a nonobstructing plicae colliculi.
Diagnostic Procedures Knowledge of various imaging techniques available, their techniques, indications, and limitations are of paramount importance in the radiological evaluation of a patient. In particular, for the pediatric age group, each examination has to be justified and chosen based on the age and clinical presentation weighing the risk versus benefit. Imaging techniques have to be optimized to produce images of diagnostic quality in a safe and comfortable environment to allay anxiety while the radiation is kept as low as reasonably achievable. Special attention to create a child-friendly environment like painting on the walls, toys, videos, and immobilization devices for very small children all go a long way in ensuring smooth conduct of examination
of the child. The various imaging techniques available for evaluation of genitourinary tract pathologies in a child is discussed briefly.
Plain Radiograph Plain radiography has limited role in the evaluation of children with suspected genitourinary tract (GUT) pathologies. Abdominal radiographs of kidney, ureter, bladder (KUB) region provide information regarding urinary tract calculi, abnormal air in the GUT, pneumoperitoneum, pneumoretroperitoneum, retained foreign bodies, position of stents and bony abnormalities of spine and pelvis [16]. However, ionizing radiation exposure is a major limitation especially in children with chronic diseases warranting repeated imaging.
Ultrasonography Ultrasonography (USG) is most widely used and is often the initial technique in the evaluation of pediatric GUT pathologies. It has the advantage of being widely available, affordable and lacks ionizing radiation. The technological advances in USG over the years has resulted in significant improvement in image quality. Use of appropriate probes and pediatric settings is important to obtain quality images. Using a linear high frequency probe (up to 12–15 MHz depending on the equipment) is recommended for neonates and focused examination of structures in older children. Low frequency curvilinear probe (frequency of 2.5–7.5 MHz) is useful while scanning older children and for examining structures at a depth. A small foot print sector probe is gaining popularity for scanning through narrow windows like intercostal spaces. The main indications include screening of a neonate with suspected congenital anomalies, antenatally detected hydronephrosis, renal cysts/mass, complicated urinary tract infections (UTI), hematuria, renal/ureteric colic, post void residue (PVR) evaluation, evaluation of internal gonads in disorders of sexual differentiation (DSD), testicular and scrotal pathologies like torsion, tumors, epididymo-orchitis, hydrocele, etc. Contrast enhanced USG using microbubble contrast agents instilled into the bladder has been suggested as a radiation free alternative to look for vesicoureteric reflux (VUR). Some studies have reported almost similar diagnostic accuracy in comparison to voiding cystourethrography (VCUG) for higher grades of VUR. However, the procedure is highly operator dependent [17]. Duplex sonography provides important hemodynamic information using both color and spectral display of blood flow in the organ and vessels. It plays an important role in the evaluation of pyelonephritis, epididymo-
orchitis, testicular and ovarian torsion, evaluation of vasculature in renovascular pathologies and in post renal transplant settings.
Intravenous Urography Intravenous urography enables both morphologic and functional evaluation of the kidney and upper urinary tract. It involves intravenous injection of a low osmolar iodinated contrast media and series of imaging done at specific intervals subsequently. Due to concerns related to radiation exposure and with advent of low dose CT and MR urography, the role of IVU is limited to a few specific indications in certain centers, which include congenital anomalies like UPJ obstruction, evaluation of hydroureteronephrosis, ectopic insertion of ureter, and GU tuberculosis. The protocol for IVU in children varies between centers. In our institution, we avoid tomogram images.
◾dose A scout KUB is initially performed followed by IV contrast which is administered in the of 1 mL/kg body weight ◾ After IV injection of contrast, KUB images are taken at 3, 7, and 15 minutes interval ◾ Delayed images are performed if indicated after evaluation of these initial images ◾ Abdominal compression using a binder is also avoided in children ◾Injection Lasix urogram is performed in patients with suspected congenital UPJ obstruction. Furosemide is given IV at a dose of 1 mg/kg (maximum 20 mg) after the 15minute film and a post Furosemide image is performed 10–12 minutes after diuretic injection (Fig. 85.13) Full bladder and post void images are not routinely performed in a child to avoid unnecessary radiation
◾
FIGURE 85.13 (A) IVU Lasix urogram in a 9-year-old boy with abdominal pain. 20-minute urogram shows horseshoe kidney and hydronephrosis of right-side moiety with disproportionate dilatation of renal pelvis. (B) Lasix urogram demonstrates ballooning of the renal pelvis suggestive of PUJ obstruction.
Micturating/Voiding Cystourethrogram (MCUG/VCUG) Micturating cystourethrogram is the investigation of choice for evaluation of bladder, urethra, and VUR (Fig. 85.14). Retrograde urethrography (RGU) is not routinely performed in children. It is important to remember that overfilling or underfilling of the bladder should be avoided. The normal bladder capacity for age can be calculated using the formula:
Bladder capacity (mL) = [Age in years +2] × 30 mL.
FIGURE 85.14 Normal MCU in an 8-months-old male child. (A) Bladder neck. (B) Verumontanum. (C) Membranous urethra. (D) Bulbar urethra. (E) Penile urethra.
Fluoroscopic screening is done to look for reflux while filling the bladder. To increase the detection rate of VUR, some authors suggest a cyclic VCU approach [18] where the bladder is filled in cycles three times, with the child voiding around the catheter twice and the third time, catheter is removed when the child starts to void. Passive VUR occurs during the bladder-filling phase whereas active reflux occurs during micturition. Lateral and oblique views are essential to avoid missing mild reflux in the distal ureters which can be obscured by a filled bladder on AP films (Fig. 85.15). These views also help in visualization of bladder diverticula (Fig. 85.16). The micturition phase is carefully assessed for voiding dysfunction or structural abnormalities of the urethra like posterior urethral valves (PUV), stricture, fistula or congenital anomalies like duplication.
FIGURE 85.15 MCU in a 5-year-old child with right grade 5 and left grade 1 vesicoureteric reflux. The left grade 1 VUR is obscured by the full bladder on AP film (A) but is clearly demonstrated on the oblique radiograph (arrow in B).
FIGURE 85.16 MCU in a 3-year-old girl with bilateral periureteric diverticuale (Hutch diverticulae).
Genitography Genitography is a fluoroscopic procedure which involves injection of a water-soluble contrast media into the perineal opening to opacify the urethra, bladder, and vagina in a case of persistent urogenital sinus (UGS). In persistent UGS, where there is failure of separation of urinary and genital tracts resulting in a single perineal opening in a female child, genitogram demonstrates the exact site of communication and rectourogenital sinus fistula if present. The length of common channel, its relationship with the bladder and rectum are crucial information that helps in surgical planning. MRI can also provide this information but has its limitations in the neonates
due to poor spatial resolution and need for general anesthesia for the procedure in this age group.
Distal Colonography This examination is performed in a child with diversion loop stoma (hence also called loopography) to assess the distal small or large bowel before reversal of stoma. It evaluates the anatomy, patency and in a child with anorectal malformation, abnormal fistulous tracts (rectourethral/rectovaginal fistula). Water-soluble contrast media is injected into the distal stoma under pressure to opacify the distal bowel. Images are taken in at least two projections to identify any fistulous communication. Lateral and oblique projections are useful to demonstrate the fistula (Fig. 85.17). MCUG is usually performed at the same time in the setting of anorectal malformation. Antibiotic cover may be required because of the risk of infection; however, this practice differs from center to center [19].
FIGURE 85.17 Distal loop colonography in a 4-months-old child with anorectal malformation showing the rectal pouch with rectobulbar urethral fistula (arrow).
Multidetector Computed Tomography (MDCT) The main indications for CT in pediatric uroradiology are in evaluation of masses and trauma. Low dose CT has largely replaced IVU in the evaluation of stone disease. The number of phases is kept to minimum based on the clinical scenario to prevent unnecessary radiation exposure. Single venous phase may be adequate in most cases except in certain special scenarios as discussed ahead. Both arterial and nephrographic phase may be important in prepyeloplasty evaluation of UPJ obstruction to look for crossing vessels as a cause of UPJ obstruction and pre-op surgical planning in neoplasms. Excretory CT urography phase at around 3–7 minutes after the IV injection of contrast helps to assess the ureters, drainage in an obstructed system and in urinary tract trauma. Split bolus technique is a modification in protocol
aimed at reducing the number of images acquired and thus the radiation dose [20]. Either MRI or CT can provide important information when there is suspicion of renal abscess in complicated urinary infection.
Magnetic Resonance Imaging Magnetic resonance imaging (MRI) has emerged in the recent years as an important tool in the evaluation of pediatric genitourinary tract and surpasses other techniques due to its capacity to provide good anatomic delineation, excellent soft tissue contrast, and multiplanar capabilities without ionizing radiation. Moreover, besides morphological evaluation, it can be used for dynamic evaluation and functional assessment by administering intravenous contrast media. The main indications of MRI presently include evaluation of complex genitourinary anomalies and in evaluation of hydronephrosis. It performs better than Tc-99 DMSA scan to differentiate acute pyelonephritis from chronic scarring as parenchymal loss and signal abnormality is demonstrated on MRI. Magnetic resonance urography (MRU) when combined with routine MRI sequences provides useful information in evaluation of hydrouretronephrosis and assessment of ureteric course. MRU can be performed in two ways— static fluid MRU (also known as MR hydrography) and dynamic MRU (also known as excretory MRU). Static Fluid MRU In this technique, the fluid within the urinary tract is considered as a static column and imaged using T2 weighted pulse sequences. It mainly helps identify the level of obstruction. It is also useful in demonstration of the collecting system of an obstructed poorly excreting kidney as it does not involve excretion of contrast (Fig. 85.18).
FIGURE 85.18 Static MR urography in a 3-year-old child. There is left to right crossed fused ectopia with markedly dilated tortous ureter of the crossed ectopic kidney due to distal ureteric stricture (arrow).
Excretory MR Urography This involves injection of gadolinium-based contrast agent and imaging the kidney in excretory phase. Low dose gadolinium-based contrast agent (0.01 mmol/kg) is administered. Diuretic in low dose given (if no contraindication exists) at the beginning of the study enhances the image quality by increasing the dilatation of the urinary tract and helping in
appropriate dilution of gadolinium to avoid artifacts. After the routine T1/T2 and fat suppressed images, post contrast dynamic imaging is performed. The specific sequence for excretory urography phase is a 3D gradient echo sequence. Postprocessing techniques are employed to calculate the function. Parameters like differential renal function, renal transit time, and glomerular filtration rate index can be calculated [21–23]. The need for sedation in young children, relatively higher cost and lack of universal availability hinders the widespread clinical use of MRI. Angiography Main indications for angiography are in the evaluation of renovascular diseases like renal artery stenosis, vascular malformations, other vasculopathies like fibromuscular dysplasia and vasculitis. CT angiography (CTA), due to its spatial resolution, may be preferred in younger children as it avoids the need for anesthesia. Also, intrarenal segmental arteries are better evaluated on CTA. MR angiography has the advantage of being radiation free and can be performed with or without administration of IV contrast. Catheter angiography is mainly performed for therapeutic interventions [24]. Nuclear Medicine The important radionuclide imaging techniques commonly used in evaluation of kidney and urinary tract in children include (3):
The dose of the radiopharmaceutical has to be adjusted according to the size of the child. Cortical Scintigraphy: The radiopharmaceutical used is 99mTc-DMSA (2,3 dimercaptosuccinic acid) which concentrates in the renal parenchyma. It is used to locate functioning renal tissue. A focal lesion in the kidney, scars, or nonfunctioning parenchyma would be seen as focal photopenic areas. It also helps to calculate the split renal function of the kidneys. The scanning should be timed appropriately (3–6 months after the acute infection) if the purpose is to assess for cortical scars as it takes some time for functional recovery after an acute infection (Fig. 85.19).
FIGURE 85.19 Tc99m DMSA scan in a 5-year-old girl with left VUR and recurrent UTI shows mildly impaired tracer uptake in the left renal parenchyma on the early images (left top column) and normal excretion. There is inhomogeneous tracer uptake in the cortex in the left kidney on the delayed images with a photon deficient area in the upper pole suggestive of a scar (black arrow).
Dynamic Renography: The main indication in children is in evaluation of hydronephrosis to quantify the degree of obstruction. Split function of the kidneys can be assessed more accurately than static scintigraphy and a diuretic challenge with furosemide (1 mg/kg) is used to assess washout. Assessment of divided renal function (DRF) and drainage is also useful in follow up of post pyeloplasty patients. A renogram which is a graphic representation of excretion based on a time intensity curve is generated. The shape of the curve, response to diuretic and function compared to contralateral kidney are the parameters that help in assessing significant obstruction (Fig. 85.20). The radiopharmaceuticals commonly in use include 99mTc-DTPA (diethylenetriamine-pentaacetate), 99mTc-MAG3 (mercaptoacetyltriglycine) and 99mTcEC (L-ethylenedicysteine) for dynamic renal imaging.
FIGURE 85.20 Tc 99m EC (L-Ethylenedicysteine) dynamic renal scintigraphy of a 5-months-old child with left PUJ obstruction shows an enlarged left kidney with slow tracer clearance into a dilated pelvicalyceal system (black arrow), delayed drainage and significant holdup on delayed image. Time activity curve shows obstructed drainage in the left kidney (white arrow) and normal drainage in the right kidney.
Nuclear Cystography: Nuclear cystography is performed for the detection and follow up of VUR. It can be done either after direct instillation of radionuclide into the bladder through a catheter or indirectly by filling the bladder after dynamic renography. In comparison to VCUG, there is increased detection of VUR, better detection of higher grades of VUR and reduced radiation dose (Fig. 85.21). The disadvantages compared to VCUG include relatively poor assessment of bladder and urethra due to poor anatomic definition and unrefined grading of VUR on nuclear cystography [25].
FIGURE 85.21 Direct isotope cystography showing right vesicoureteric reflux in the micturition phase (black arrow).
Videourodynamics (VUD) Videourodynamic study is performed in children with neurogenic bladder and complex voiding dysfunction. The bladder and sphincter functions are assessed during the filling, storage, and micturition phases. A graphic recording of the various pressures (bladder pressure, rectal pressure, detrusor pressure), urine flow and electromyography of the sphincter is done along with voiding cystourethrography (VCUG) [3].
Developmental Anomalies of the Kidney and Urinary Tract Renal Agenesis Failure of ureteric bud to come in contact with the metanephric blastema results in failure of induction to form nephric vesicles and hence the development of the kidney. This is often associated with failure of development of the ipsilateral ureter and hemitrigone. In some cases, a blind ending ureter may be seen. Unilateral agenesis has a prevalence of 0.1% of live births and is more commonly seen in males with a male to female ration of 3:1. Agenesis of ipsilateral adrenal gland is seen in 10% of patients with unilateral renal agenesis [3].
The other anomalies associated with renal agenesis include agenesis of ejaculatory duct with resultant seminal vesicle obstruction/cyst, which is called Zinner syndrome. Uterine anomalies like bicornuate uterus with ipsilateral obstruction of hemivagina and renal agenesis constitute the OHVIRA (obstructed hemivagina and ipsilateral renal agenesis). Zinners syndrome has been proposed as a male counterpart of OHVIRA [26,27]. Renal agenesis can be associated with various other syndromes and chromosomal disorders including VACTERL association. This acronym stands for V—vertebral anomalies, A—anorectal malformation, C—cardiac defects, T—tracheal anomalies, E—esophageal anomalies, R—renal and radial ray anomalies, and L—limb anomalies. Another association includes the MURCS, which constitutes Müllerian aplasia, renal agenesis, and cervicothoracic somite dysplasia (Fig. 85.22).
FIGURE 85.22 MURCS (Müllerian aplasia, renal agenesis, and cervicothoracic somite dysplasia) association. (A) Chest radiograph of a 12-year-old girl showing multilevel vertebral segmentation anomalies. (B) On MRI T2 high-resolution sagittal image, the uterus is absent and (C) axial T2 image shows empty left renal fossa.
Bilateral renal agenesis is very rare and incompatible with life. Severe oligohydramnios in this situation results in Potter’s syndrome with abnormal facial features, small chest, and limb abnormalities. Death occurs due to pulmonary hypoplasia.
Supernumerary Kidneys
This is a rare anatomic variant where one or more kidneys are present in addition to the native kidneys. They have separate collecting systems with a complete or partially duplicated ureter. A distinct capsule and separate blood supply helps one to differentiate supernumerary kidney from a Duplex kidney [28]. Embryologically, it occurs due to division of the nephrogenic cord into two metanephric blastemas. The ureteric bud may or may not undergo division.
Abnormalities of Position and Rotation Positional abnormalities occur when the normal migration and ascent of the developing kidney is disrupted.
◾side. Congenital simple ectopia refers to the kidney lying outside of the renal fossa on the same This could be caudal abdominal ectopia when kidney is located below the normal
position of D12-L3 vetebra, pelvic ectopia (if the kidney does not ascend above the pelvic brim) and rarely intrathoracic, if it is associated with a congenital diaphragmatic hernia Sometimes the kidney crosses over to the other side producing crossed renal ectopia, which can be fused or unfused. Lot of other urological abnormalities can be associated with renal ectopia, VUR being the commonest [29] If associated anomalies or syndromes are excluded and if there is a normal contralateral kidney and no hydronephrosis, an ectopic kidney may not require any further investigation Abnormal medial course of the colon occupying the renal fossa (“loop to loop colon” sign) and a lying down (pancake) adrenal gland due to long slender shape of the ipsilateral adrenal gland due to empty renal fossa are observed in renal agenesis/ectopia [30] When the normal medial rotation of kidney does not occur during ascent, it results in a malrotated kidney with the pelvicalyceal system facing anteriorly or laterally (Figs. 85.23 and 85.24)
◾ ◾ ◾ ◾
FIGURE 85.23 Ectopic kidney. Ultrasonography in a 4-year-old child shows an ectopic pelvic kidney and associated malrotation with anteriorly facing renal hilum (arrow).
FIGURE 85.24 Bilateral pelvic kidneys with associated malrotation. IVU of an 11-year-old child, 7 minutes urogram showing bilateral pelvic kidneys (arrows) with associated malrotation.
Abnormalities of Fusion Horseshoe kidney is the commonest renal fusion anomaly with a quoted incidence of 0.25% in the general population [31]. The lower poles are medially aligned and fused in the midline, by a bridge of tissue called isthmus which can be parenchymal or fibrous. The isthmus lies mostly anterior to the aorta and IVC at the level of, and inferior to, inferior mesenteric artery (IMA). IMA prevents the further ascent of the fused kidneys. They are usually asymptomatic but there is an increased incidence
of PUJ obstruction, VUR, ureteric duplication, and Wilm’s tumor reported [32]. The metanephric blastema fuses together very early in the development before rotation begins and hence, an associated malrotation is seen in almost every case. On IVU, the lower calyces of both moieties come close together in the midline as if they are shaking hands with each other (“handholding calyces”) (Fig. 85.25).
FIGURE 85.25 Horseshoe kidney. (A) IVU plain tomogram and (B) 20minute urogram shows medially oriented lower pole of the kidneys and malrotated pelvicalyceal system bilaterally which is anteromedially oriented. Note the calculi in the left side moiety.
Crossed ectopia could be fused (majority, ∼85%) or unfused (∼10%). Very rarely, a solitary crossed ectopia and bilateral crossed ectopia can occur [33]. In crossed ectopia, the ureter crosses over to the normal side with normal insertion into the bladder. Various types of fusion can occur in crossed ectopic kidneys with varying degrees of rotational abnormalities in the ectopic and normal positioned kidney (Figs. 85.26 and 85.27). When normal rotation of both kidneys has happened, the fused kidneys will have renal pelvis facing in opposite direction and the ureters cross one over the other giving rise to a S shaped/sigmoid kidney. When parenchymal fusion occurs along the medial border of the kidneys, it results in pancake/ring/doughnut shaped kidney. When there is extensive fusion along the medial border it forms a disc/shield shape. In a lump kidney, there is substantial fusion between the two kidneys, not necessarily along the medial border [34].
FIGURE 85.26 (A–F) Illustration of different types of fusion in crossed renal ectopia.
FIGURE 85.27 Crossed ectopia. Contrast enhanced CT coronal sections of a 3-year-old male child showing right crossed ectopia with “L” type fusion (black arrow). Associated right PUJ obstruction noted with dilated renal pelvis (white arrow).
Congenital Anomalies of the Pelvicalyceal System and Ureter
Megacalicosis/Polycalicosis Dilatation of calyces in the absence of obstruction with a normal caliber renal pelvis and ureter constitute magacalyces. The calyces have a faceted appearance with absent papillary impression. It can be unilateral or bilateral (Fig. 85.28). Though exact pathogenesis is not clear, underdevelopment of renal medullary pyramids has been suggested as a possible cause for this morphologic appearance of calyces. Often there is also increased number of calyces and calyces have a polygonal appearance when it is called megapolycalycosis. The number of calyces increases to 20–25, where as normal kidney has 10–14 calyces. The interlobar arteries are not displaced/stretched in contrast to hydronephrosis, and the renal cortical thickness is maintained. Function of the kidney is preserved in megapolycalycosis but there is an increased risk of infection and stone formation due to stasis [35,36]. Megacalycosis can sometimes coexist with primary megaureter which is important to recognize and avoid interpreting the calyceal dilatation as due to obstructing primary megaureter. The key would be to assess the renal pelvis morphology, which would be normal in morphology and caliber in congenital primary megaureter whereas it will be dilated in obstruction (Fig. 85.29). If in doubt, renal scintigraphy can be done to assess the ureteric drainage to quantify the degree of obstruction before operative decision is made [36].
FIGURE 85.28 Congenital megacalycosis. (A) Ultrasonogram and (B) IVU 20 minute urogram showing dilated polygonal shaped calyces with normal renal pelvis, ureter and maintained cortical thickness in the right kidney. Stasis calculus is demonstrated in the lower pole calyx (calipers in A).
FIGURE 85.29 Left megapolycalycosis and left megaureter. Threedimensional reconstructed CT image showing increased number of calyces which are enlarged and polygonal shaped, normal caliber renal pelvis and tapered narrowing of the juxtavesical segment of ureter.
Pyelocalyceal Diverticulum Calyceal diverticulum is a congenital outpouching from the renal collecting system lined by transitional epithelium. Stone formation is the most common complication reported in 9.5–50% of patients [37,38].
◾ 1 pyelocalyceal diverticulum communicates with a minor calyx or infundibulum ◾ Type Type 2 communicates with renal pelvis or major calyx
Mean size is around 10 mm, though larger diverticulae measuring a few centimeters can be seen. On USG, an anechoic cyst will be seen indistinguishable from other cortical cysts, unless a mobile calculus is demonstrated within. On IVU, the outpouching from the pelvicalyceal system will show gradual filling-in of contrast. The same finding can be observed in CT urography (Fig. 85.30). Intervention and ablation is required if complicated with infection/calculi.
FIGURE 85.30 Type 1 pyelocalyceal diverticulum. CT axial section, urographic phase shows a cystic lesion in the interpole in close relation to a calyx with contrast extending from the calyx to the cyst in this excretory phase film.
Infundibular and Infundibulopelvic Stenosis This is an extremely rare anomaly where there is congenital narrowing of the infundibulum with resultant hydrocalycosis. Associated stenosis of pelvis can occur resulting in infundibulopelvic stenosis [39]. Infundibular narrowing can be due to intrinsic cause or extrinsic cause like an extrinsic vascular compression. Congenital intrinsic infundibulopelvic stenosis needs to be differentiated from intrinsic stenosis due to acquired causes like
infection, neoplasm or trauma. It can be unilateral or bilateral. It is considered a milder form of disease in the spectrum of obstructive renal dysplasias, the most severe form being infundibulopelvic atresia causing multicystic dysplastic kidney (MCDK) [40].
Ureteropelvic Duplication Anomalies Pathophysiology and Clinical Presentation Duplication of the collecting system is considered as one of the commonest developmental anomalies of the kidney. Reported prevalence of duplex kidneys ranges from 0.3% to 6% [41]. Varying degrees of duplication can occur, ranging from a bifid pelvis to ureters joining at any level along its course and complete duplication of ureters. Complete duplication occurs when two separate ureteric buds arise from the mesonephric duct. In complete duplication, the upper pole moiety ureter inserts medially and at a lower level in the urinary bladder compared to the lower pole moiety ureter. This upper moiety ureter could also have an ectopic insertion and can sometimes be associated with a ureterocele, causing obstruction of the upper pole moiety. The lower pole moiety inserts at a higher and lateral position in the bladder making it prone for VUR. This pattern of ureteric insertion in complete duplication of ureters is called the Weigert Meyer rule (Fig. 85.31).
FIGURE 85.31 Illustration of Weigert Meyer rule in complete duplication.
Duplex kidney could be an incidental finding in many patients. However, some patients present with complications like VUR or obstruction. Ectopic ureteric insertion presents with clinical features related to urinary tract infection, obstruction or dribbling of urine depending on the site of ectopic insertion. Obstruction can be due to various reasons including a ureterocoele or associated UPJ in duplex kidneys. Rarely ureterocele can prolapse into the posterior urethra causing bladder outlet obstruction symptoms. Imaging helps to identify the cause of obstruction, demonstrate VUR if present and delineate the course and site of ectopic ureters in a complicated duplex system [42]. Imaging Features
◾distinct USG can diagnose a duplex collecting system when there is an enlarged kidney with two collecting systems separated by a bridge of normal renal parenchyma. Hydroureteronephrosis with associated polar parenchymal scars and patulous VUJ suggests VUR “Faceless kidney” sign is a CT sign described in duplex kidney. On axial images, a section through the intervening parenchyma between the two collecting systems do not show the normal sinus signature. Since the normal face of the kidney is lacking, it has been termed the “faceless” kidney (Fig. 85.32) An obstructed grossly hydronephrotic upper moiety can cause mass effect on the lower pole moiety with a characteristic “drooping lilly” appearance of lower moiety pelvicalyceal system on IVP (Fig. 85.33) MRU is the technique of choice to clearly delineate the urinary tract anatomy, course of the ectopic ureter and site of ectopic insertion, especially when there is a poorly functioning moiety [42] Isotope studies/dynamic MRU help to assess the function of the two moieties Traditional imaging methods which use ionizing radiation like IVU and CT are largely being replaced by MRU in the evaluation of complicated duplex systems. Scintigraphy helps to assess drainage and split renal function in an obstructed system. Though dynamic MRI can also be used for this assessment, its performance in comparison to scintigraphy needs to be evaluated prospectively [43]
◾ ◾ ◾ ◾ ◾
FIGURE 85.32 (A) Ultrasonogram of duplex kidney showing a bridge of normal renal parenchyma separating the central renal sinus echo (black arrow). (B) Contrast enhanced CT axial section of the patient demonstrating the “faceless” kidney sign (white arrow), where there is absence of the normal sinus signature in this section which passes through the intervening parenchyma between the two collecting systems.
FIGURE 85.33 IVU study, 5 minute pyelogram image (A) shows bilateral duplex collecting system with poorly functioning hydronephrotic right upper pole moiety seen as a rim nephrogram (white arrow). Right upper moiety obstruction is due to an obstructing ureterocele seen as well-defined oval filling defect projecting into the bladder on the 20 minute urogram, black arrow in (B). Mass effect on the right lower moiety by the hydronephrotic right upper moiety producing the characteristic “drooping lilly” appearance, white arrow in (B).
UPJ Obstruction UPJ obstruction is defined as an anatomical or functional obstruction to the flow of urine from renal pelvis into the ureter at the pelviureteric junction. The exact etiology of congenital UPJ obstruction is not clear. An intrinsic mural abnormality is considered more likely than other causes like valves. Secondary UPJ obstruction is a result of strictures due to various causes and tumor. Occasionally, crossing vessels have been implicated in the pathogenesis of UPJ obstruction, and it is important to identify then preoperatively if present to avoid failed pyeloplasty [44]. Both anatomic and functional studies are important in the evaluation of patients with UPJ obstruction. USG can demonstrate a dilated renal pelvis which is out of proportion to calyceal dilatation. Differentiation from a large extrarenal pelvis requires demonstration of functional obstruction. On IVU, long standing UPJ obstruction and gross hydronephrosis produces negative pyelogram on the nephrographic phase (Fig. 85.34). In intermittent UPJ obstruction and doubtful cases, Lasix assisted urography is invaluable to demonstrate a functional obstruction, where hold up and increase in diameter of the pelvis can be demonstrated on diuretic stress after administration of
injection Furosemide. Radioisotope studies can quantitatively assess the differential renal function.
FIGURE 85.34 Negative pyelogram. IVU nephrotomogram image showing “rim nephrogram” also called “negative pyelogram” in a grossly hydronephrotic enlarged left kidney with thinning of renal parenchyma due to UPJ obstruction. A rim of enhancement is seen outlining the lucency produced by the dilated pelvicalyceal system.
Ureterocele Ureterocele refers to the cystic dilatation of terminal ureter in the intravesical intramural segment. They can be either orthotopic or ectopic, the latter occurring at an ectopic site of insertion of ureter. Failure of resorption
and canalization of an embryonic membrane (Chwalla’s membrane) that covers the ureteric orifice in the fetus with obstruction at VUJ and ballooning of the segment just proximal to it has been postulated as one of the causes of ureterocele [45]. On ultrasound, cystic dilatation of the terminal ureter can be demonstrated in continuity with the dilated proximal ureter. Scanning should be done with distended bladder and filling up and collapse of the ureterocele with urine can be demonstrated during a ureteric jet. On MCU, the ureterocele is seen as a filling defect in a contrast filled bladder. On IVU, contrast filled rounded or oval density is seen within the bladder with a surrounding radiolucent halo representing the wall of ureterocele forming the classic “cobra head”/“onion bulb” appearance (Fig. 85.35). If it is a poorly functioning kidney or moiety, a rounded or oval filling defect will be seen in a contrast filled bladder [45,46].
FIGURE 85.35 Ureterocele. (A) Transverse sonogram showing cystic dilatation of left distal ureter projecting into the bladder lumen (arrow) suggestive of an orthotopic ureterocele. (B) IVU 20 minute image of the patient shows contrast filled oval density in continuity with terminal ureter and surrounding radiolucent halo producing the “onion bulb” appearance (arrow).
Primary Megaureter Megaureter is a general term used to denote a dilated ureter, with a caliber of more than or equal to 7 mm in children. This may or may not be associated
with upper tract dilatation. Primary megaureter refers to ureteric dilatation due to congenital abnormalities in the vesicoureteric junction or the juxtavesical segment of the ureter. It can be of three types:
◾ Obstructed ◾ ◾ Refluxing Unobstructed and nonrefluxing
Ureteric dilatation due to other pathologies involving bladder, urethra, etc. is classified as secondary megaureter and can be called hydroureter. In obstructed primary megaureter there is upstream dilatation just proximal to a short narrowed juxtavesical segment. The ureteric orifice is normal. This phenomenon has been likened to achalasia cardia. The cause of the aperistaltic narrowed juxtavesical segment, though not definitely proven, has been attributed to neuromuscular abnormalities in this segment. On imaging, there is a persistently narrowed segment of juxtavesical ureter with dilatation of the distal third of ureter proximal to this. The upper ureter and pelvis are relatively normal in caliber (Fig. 85.36). In a refluxing primary megaureter, the ureter is dilated up to the VUJ with a patulous ureteric orifice. VCUG can demonstrate the VUR if present. In the nonobstructing and nonrefluxing variant, the whole length of ureter is dilated just up to the bladder. In patients with primary megaureter, after reflux is excluded, diuretic renal scintigraphy helps in assessment of function and drainage to decide on the management [45].
FIGURE 85.36 Intravenous urogram shows enlarged and polygonal appearance of the calyces in the left kidney. There is dilatation of the left distal ureter with narrowing of juxtavesical segment giving rise to a bird beak appearance—findings in keeping with congenital primary megaureter with associated megacalycosis.
Retrocaval Ureter Retrocaval/circumcaval ureter is a rare cause of hydronephrosis due to congenital anomaly of the IVC. Due to the persistence of right posterior cardinal vein, it courses anterior to the ureter. There will be varying degrees
of hydroureteronephrosis depending on the degree of obstruction and many are detected in the adult age group as the hydroureteronephrosis is progressive. There are two radiographic patterns identified. In the more common type 1 (low loop) variety IVU demonstrates the classic “fish hook” deformity of the proximal ureter with medial deviation of ureter. In the type 2 (high loop) variety, the medial deviation of ureter occurs at the level of renal pelvis with a sickle shaped appearance and milder degree of hydroureteronephrosis [47] (Figs. 85.37 and 85.38).
FIGURE 85.37 (A) IVU, 45 min urogram image shows right retrocaval ureter, type 1 (low loop variety). The ureter is seen coursing medial to the pedicle at L3-4 vertebral level with proximal hydronephrosis. (B) IVU demonstrating a type 2 retrocaval ureter on the right (high loop variety) with medial deviation of ureter at L2 vertebral level and “sickle shaped” appearance of the renal pelvis.
FIGURE 85.38 Retrocaval ureter. (A) Coronal CT section in the venous phase shows right hydroureteronephrosis. (B) Axial CT urography image of the patient shows right ureter coursing posterior to the IVC (arrow).
Cystic Renal Diseases in Children Unlike in adults, developmental simple cysts are very rare in children and this a diagnosis of exclusion. If a renal cyst is detected for the first time, at least follow up and careful family history should be taken to exclude other underlying conditions. Cystic diseases in children encompass a wide spectrum of hereditary and nonhereditary conditions. Syndromes like Von Hippel Lindau (VHL), tuberous sclerosis, Bardet Biedel syndrome, Meckel Gruber, and some chromosomal anomalies are associated with cysts in the kidney [48].
Multicystic Dysplastic Kidney (MCDK) Multicystic dysplastic kidney is a nonhereditary developmental abnormality in which the kidney is replaced by multiple cysts with no functioning intervening parenchyma. The exact etiology is not clear and postulations include an in utero insult/obstruction resulting in maldevelopment of kidney and replacement by bizarre cysts. Embryologically, it is thought to be due to failure of the ureteric bud to induce the metanephric blastema to form the nephric vesicle and its subsequent development into nephrons. On imaging, cluster of multiple varying sized non communicating cysts are seen replacing the kidney. There is no functioning normal renal parenchyma (Fig. 85.39). Atypically, focal involvement can be seen affecting only a part of the kidney or a single moiety can be involved in a
duplex kidney. Contralateral kidney should be imaged to rule out any associated anomalies [3].
FIGURE 85.39 Multicystic dysplastic kidney. (A, B) USG showing multiple cysts of varying sizes replacing the right kidney with absent normal renal parenchyma. (C) T2W MRI coronal image of another patient showing a right ectopic multicystic dysplastic kidney (arrow).
Autosomal Recessive Polycystic Kidney Disease (ARPKD) Autosomal recessive polycystic kidney disease, also called infantile polycystic kidney disease is a hereditary disorder characterized by cystic dilatation of renal tubules. This occurs due to a genetic abnormality that causes abnormal development of renal and biliary tubules due to alteration in primary cilia. Innumerable tiny cysts 60 years of age, four or more cysts in each kidney was required for diagnosis of ADPKD [54].
Medullary Cystic Kidney Disease/Nephronothisis Medullary cystic kidney disease (MCKD) and nephronothisis also belong to hereditary ciliopathies responsible for renal failure in children. It is a chronic tubulointerstitial nephritis. Though histologically similar, MCKD and nephronothisis is different in terms of inheritance and presentation. On imaging, initially there is increased echogenicity of kidneys with loss of corticomedullary differentiation which progresses to reduction in size with increased echogenicity. The cysts may or may not be visible. If present cysts are located in the medulla and corticomedullary junction with relative sparing of the cortex [48] (Fig. 85.42).
FIGURE 85.42 USG of kidneys in a 4-year-old child with renal tubular acidosis showing loss of corticomedullary differentiation with cysts located predominantly in the medulla and corticomedullary junction suggestive of medullary cystic kidney disease.
Glomerulocystic Kidney Disease (GCKD) It is a rare congenital disorder that affects the Bowman’s capsule. It can be familial or sporadic and predominantly affects children, though adult presentation has been described. All the glomeruli may not be affected and hence varying degrees of renal impairment is observed. On imaging,
typically there is increased echogenicity of renal parenchyma with indistinct corticomedullary differentiation and cysts which are characteristically located peripherally in the cortex and subcapsular location [55].
Medullary Sponge Kidney Medullary sponge kidney is a disorder in which there is dilatation and ectasia of the collecting tubule and ducts. It rarely presents in childhood and usual age of presentation is in the third and fourth decade. It can be bilateral, unilateral or focal in involvement. Calculi with a linear morphology forms within the dilated tubules and patient can have calculuria. The kidneys may be sonologically normal in the early stages, but as the disease progresses there is increased echogenicity of the medulla due to early calculi formation which later progresses to form dense calcification (Fig. 85.43). On IVU, clusters of linear calcific foci can be seen in the region of medulla with contrast collecting around the calculi on the pyelographic phase, called the “growing calculi sign” [56] (Fig. 85.44).
FIGURE 85.43 (A) USG showing echogenic pyramids with posterior shadowing consistent with medullary nephrocalcinosis. IVU (B) Plain scout image shows cluster of linear calcification in the region of medulla bilaterally. The 10 minute pyelogram image shows contrast opacification surrounding the calcification suggestive of medullary nephrocalcinosis due to medullary sponge kidney.
FIGURE 85.44 Growing calculus sign. IVU, scout tomogram (A) shows linear calcification in the right lower pole. (B) 10-minute pyelographic phase shows contrast collecting around the linear calcification—growing calculus sign in a case of focal medullary sponge kidney involving right lower pole.
Infectious and Inflammatory Diseases Urinary Traction Infection (UTI) Urinary traction infections are a common and potentially serious bacterial infection of childhood, and are the most common problem of the genitourinary system in children. Although UTI can be categorized into those involving the upper tract (pyelonephritis, ureteritis) and lower tract (cystitis), differentiating between the two on clinical grounds is less obvious in younger (less than 2 years) children. The rationale for initial imaging of children with UTI is to identify conditions that impair urinary flow, structural and functional anomalies which can increase the risk of recurrence or complications, as well as assess for complications [57–59].
Acute Pyelonephritis (APN) The average prevalence of symptomatic UTI is seen up to as high as 7.5%, of which half the UTIs occur in children younger than 1 year, a group particularly susceptible to renal scarring. Renal scarring occurs in about half the children diagnosed with acute pyelonephritis, and 17–30% of those with significant renal scarring may become hypertensive. Acquired cortical scarring has been linked to renal hypertension, renal insufficiency and in severe cases endstage renal disease.
The pathogenesis behind renal scarring is poorly understood and is believed to be caused by the acute inflammatory response generated to eradicate the infection. The inflammatory response results in chemotaxis, phagocytosis, lysosomal enzyme release, peroxide, and hydroxyl radical production, which result in tubular ischemia, reperfusion injury, and finally fibrosis. Hypertension following fibrosis may take up to 8 years to develop [60]. USG is the technique of first choice; both kidneys should be viewed with the child in the most cooperative position. Although the sensitivity is low, and a normal USG does not rule out APN, multiple findings have been described in APN such as:
◾ Increased renal volume ◾ Areas of increased or heterogeneous echogenicity ◾ Loss of corticomedullary differentiation (CMD) ◾ Thickening of pelvic wall ◾ Hyperechogenicity of renal sinus and perirenal fat [3,61,62] ◾constriction Color or Power Doppler can be used to look for areas of reduced vascularity due to of peripheral arterioles as part of inflammatory response (usually triangular,
peripheral). This can increase the sensitivity of ultrasound [63,64] but requires increased cooperation from the child.
Renal sizes should be noted, which would also serve as the baseline for follow-up (Fig. 85.45)
FIGURE 85.45 Acute Pyelonephritis; Focal lobar nephronia. 5-monthold male with first UTI. USG demonstrates a focal enlargement of the lower pole of the right kidney with internal heterogeneity—(A) predominantly hypoechoic; (B) color Doppler evaluation demonstrates reduced vascularity in this region. (Image courtesy: Dr Ajay Taranath)
Cortical scintigraphy using dimercaptosuccinic acid (DMSA) is the most sensitive test for demonstrating single or multiple areas of lack of uptake of the radiotracer. Acute lesions of pyelonephritis may persist for up to 6 months on scintigraphy, hence permanent scarring can be assessed only if
the DMSA scan is performed at least 6 months after the episode of acute infection. Cortical scintigraphy is thus usually not recommended in an acute setting unless there is need for documentation, as a repeat scan would probably be needed to rule out permanent damage [65]. CT and MRI are sensitive for APN such are focal swelling and hypoperfusion, but are reserved to evaluate potential complications like abscess [66–68].
Vesicoureteric Reflux Pathophysiology and Clinical Presentation VUR is retrograde flow of urine from the bladder to the upper urinary tract. It is found in 30–40% of children with a UTI, with incidence decreasing as the child becomes older. It is considered a major risk factor for pyelonephritis and renal scarring [70]. A grading system for VUR has been developed based on the appearances at MCUG [69] (Figs. 85.46 and 85.47). Patients with high-grade VUR (Grades III–V) are 4–6 times more likely to have scarring than those with low-grade VUR, and 8–10 times more likely than patients without VUR [71]. Similarly, younger patients with high-grade reflux have a greater frequency of new scarring [72].
FIGURE 85.46 VUR grading system based on the appearances at micturating cystourethrography (MCUG). Grade 1: reflux into the ureter alone. Grade II: reflux into the ureter and pelvis. Grade III: reflux into ureter and pelvis with mild dilatation. Grade IV: reflux into ureter and pelvis with moderate dilatation and preservation of the papillae. Grade V: reflux into ureter and pelvis with obliteration of the papillae. Source: G Montini, K Tullus, I Hewitt, Febrile urinary tract infections in children, N Engl J Med 365 (3) (2011 Jul 21) 239–250. doi: 10.1056/NEJMra1007755 . PMID: 21774712.
FIGURE 85.47 MCUG demonstrating different grades of VUR: (A) Right Grade 2, Left Grade 1; (B) Right Grade 2, Left Grade 3; (C) Right Grade 5 with intrarenal reflux, Left Grade 4.
Reflux nephropathy (previously called chronic pyelonephritis) is a term used for renal scarring and loss of nephron mass attributed to VUR or congenital anomalies stemming from chronic high-pressure sterile urine reflux in early childhood [73]. It is the most common cause of hypertension in children [74] and accounts for 7–17% of endstage renal disease (ESRD) cases worldwide [75]. Imaging Features
◾initially Reflux nephropathy is usually asymmetric or unilateral. The classic appearance described on IVU and seen in other techniques is of cortical scarring over clubbed calyces. This is most frequently seen at the renal poles, especially the upper pole, because these are the sites of occurrence of compound calyces which are most susceptible to damage from reflux The relationship of the scarring to underlying abnormal calyces differentiates the condition from vascular scarring and fetal lobulation (when the calyces are normal and, in the case of lobulation, the indentations are between calyces rather than directly over them) Badly affected kidneys grow poorly and are small, with diffuse cortical loss (Fig. 85.48). Focal areas of compensatory parenchymal hypertrophy may occur between the scars and, if prominent, may mimic a tumor (pseudotumor), although their appearance on USG or CT is similar to normal parenchyma. USG, CT, and radionuclide imaging (DMSA) will all demonstrate the areas of scarring
◾ ◾
FIGURE 85.48 Reflux nephropathy. 9-year-old female with recurrent UTI; USG shows the right kidney to plot between the mean and +2 SD for the patient’s age and height. The left kidney is contracted, plots below below –2 SD for the patient’s age and height. Note the undulating contour and parenchymal thinning in keeping with reflux associated nephropathy. (Image courtesy: Dr Ajay Taranath)
The optimal strategy, role, and timing of imaging children with UTI, is an area of debate and has been evolving. Two distinct approaches to imaging exist based on the starting point of the workup. The “top-down” approach starts with DMSA scan to identify cortical defects and tissue inflammation. Those having an abnormal scan will undergo VCUG to diagnose vesicoureteric reflux. The “bottom-up” approach starts with USG to detect pelvicalyceal dilatation, features of obstruction and parenchymal defects,
followed by VCUG and DMSA if required. In both approaches, a normal scan warrants no further studies. Previous AAP guidelines were principally based on data that UTI in children was a marker of anomalies of the urinary tract. Hence, it was targeted at uncovering these abnormalities through prompt VCUG and radionuclide cystography. These guidelines were made at a time when the role of DMSA was poorly understood. Even though VUR is a documented risk factor for renal scarring, recent studies have shown that long term risks of pyelonephritis and renal scarring due to VUR are low [76]. Many recent guidelines suggest less or no imaging after the first uncomplicated UTI for older children and less aggressive imaging after recurrent UTI [77]. USG is an appropriate initial imaging technique of choice, it being noninvasive, relatively inexpensive, having ability to detect anatomical abnormalities and hydronephrosis or hydroureter that suggest obstruction or vesicoureteric reflux, and is thus advocated in many of the current guidelines. (See Table 85.2) [78–83]. Table 85.2 Guidelines for Imaging in Pediatric UTI National Institute for Health and Clinical Excellence (NICE), UK Age 0– 6 months
Uncomplicated first UTI
Outpatient USG
Atypical UTI
Inpatient USG, outpatient DMSA and VCUG
Recurrent UTI Age 6 months to 3 years
Age >3 years
Uncomplicated first UTI
No imaging
Atypical UTI
Inpatient USG, outpatient DMSA scan
Recurrent UTI
Outpatient USG, outpatient DMSA scan
Uncomplicated first UTI
No imaging
Atypical UTI
Inpatient USG
Recurrent UTI
Outpatient USG, outpatient DMSA scan
American Academy of Pediatrics (AAP) Age 0– 24 months
Any febrile UTI
USG
Complex or atypical circumstances
VCUG
Recurrent UTI
Further evaluation
European Association of Urology/European Society of Paediatric urology Any febrile UTI
USG
Suspicion of VUR and/or pyelonephritis
VCUG and/or DMSA scan
ACR appropriateness criteria Age 2 months to ≤6 years
First febrile UTI with good response to treatment
USG (usually appropriate)
Age >6 years
First febrile UTI with good response to treatment
USG (may be appropriate-controversial as VUR is less common in this age group)
Source: J Kaufman, M Temple-Smith, L Sanci, Urinary tract infections in children: an overview of diagnosis and management, BMJ Paediatrics Open 3 (2019) e000487. doi:10.1136/bmjpo-2019-000487 and [87].
Postnatal Evaluation of Antenatally Detected Hydronephrosis Antenatal/prenatal hydronephrosis is diagnosed in approximately 1–2% of all pregnancies. The common causes for antenatal urinary tract obstruction are transient/physiologic, ureteropelvic junction obstruction, vesicoureteral reflux, and posterior urethral valves. The grading of postnatal hydronephrosis has initially been either quantitative using anteroposterior renal pelvis diameter (APRPD) measurement or a semi-quantitative system introduced by the Society for Fetal Urology (SFU) [84]. The APRPD is the largest measurement of the renal pelvis bordered by renal parenchyma in the transverse plane. More recently, the urinary tract dilation (UTD) classification system [85] integrated and simplified the previous systems unifying pre and postnatal imaging, and has been validated and shown to have prognostic value [86]. The UTD classification system uses six ultrasound findings to describe the antenatal and postnatal urinary tract: (1) Anteroposterior renal pelvic diameter (APRPD) (2) Calyceal dilation with distinction between central and peripheral calyces postnatally (3) Renal parenchymal thickness (4) Renal parenchymal appearance (5) Bladder abnormalities (6) Ureteral abnormalities
◾85.49) It accordingly classifies postnatal children into normal, P1, P2, and P3 (most affected) (Fig. and stratifies them into low, intermediate and high-risk groups (Fig. 85.50). They suggest that potentially confusing terms for hydronephrosis like pyelectasis, pelviectasis, and pelvic fullness are to be avoided, and only the term “dilatation” is to be used [85,87]. Scanning in prone position is recommended as it more frequently shows calyceal dilatation, greater size of the APD and almost perfect interobserver agreement. However maintaining consistent same position is the priority when it comes to sequential scans [88] Infants with bilateral antenatal hydronephrosis or a single hydronephrotic kidney should undergo USG on the first or second postnatal day, and infants with unilateral antenatal hydronephrosis should undergo USG after the infant returns to birth weight (after 48 hours of age and within the first two weeks of life) [85,89] Infants with normal findings should undergo a repeat study at 4–6 weeks, as the first week of life ultrasound may not detect all abnormalities of the kidneys or urinary tract due to low urine flow secondary to dehydration and low glomerular filtration rate. Those with isolated mild hydronephrosis (unilateral or bilateral) should be followed with sequential ultrasounds, at 3- and 6-months, followed by 6–12 monthly until resolution; those with worsening hydronephrosis require closer evaluation. Patients with higher grades of hydronephrosis or dilated ureter(s) are screened for underlying obstruction or VUR [90,91]. The imaging algorithm has been summarized in Fig. 85.51
◾ ◾
FIGURE 85.49 Schematic illustration of urinary tract dilation (UTD) classification. Shows a transverse view of (A) mid/interpolar kidney and (B) longitudinal appearances. The green arrows indicate acceptable locations, and the gray arrow shows unacceptable location for measuring the anterior–posterior renal pelvic diameter. NL = normal, P1 = central calyceal dilatation, P2 = peripheral calyceal dilatation with fluid cupping the pyramid, P3 = hyperechoic cystic thinned parenchyma. Source: JS Chow, JL Koning, SJ Back, HT Nguyen, A Phelps, K Darge, Classification of pediatric urinary tract dilation: the new language, Pediatr Radiol 47 (9) (2017 Aug) 1109–1115. doi: 10.1007/s00247017-3883-0 . Epub 2017 Aug 4. PMID: 28779200.
FIGURE 85.50 Urinary tract dilation (UTD) risk stratification—postnatal presentation for UTD P1 (low risk), UTD P2 (intermediate risk), and UTD P3 (high risk). Note: Stratification is based on the most concerning ultrasound finding. For example, if the anterior–posterior renal pelvis diameter (APRPD) is in the UTD P1 range, but there is peripheral calyceal dilation, the classification is UTD P2. Similarly, the presence of parenchymal abnormalities denotes UTD P3 classification, regardless of APRPD measurement. Source: HT Nguyen, CB Benson, B Bromley, et al. Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system), J Pediatr Urol 10 (6) (2014) 982–998.
FIGURE 85.51 Suggested postnatal imaging algorithm of children with antenatally detected hydronephrosis [79,81,82,87].
Congenital Lesions of The Urethra Posterior Urethral Valves
◾cause It is the most common cause of urethral obstruction in male infants, and the commonest of bilateral hydroureteronephrosis and endstage renal disease in children [92–95] ◾prostatic In this condition, there is anomalous development of mucosal folds that obstruct the distal urethra in males. They manifest as bladder outflow obstruction of varying severity, the most extreme producing bilateral hydronephrosis, renal failure, and Potter’s syndrome. The milder forms present with lesser degrees of outflow obstruction and poor urinary stream During the routine second trimester USG, it is seen as bilateral hydroureteronephrosis with a thick walled bladder and keyhole sign in the bladder neck of males, and may account for up to 10% of all prenatally detected hydronephrosis [96–98] Approximately half the patients who are detected postnatally present with UTI [93]. Neonates may present with respiratory distress due to lung hypoplasia, abdominal distension, difficulty in voiding or poor stream. Infants and older boys may present with failure to thrive, urosepsis, poor urinary stream, and straining or grunting while voiding, or other symptoms of voiding dysfunction [15,99] VCUG is the technique of choice; it shows the dilated posterior urethra, membranous filling defect, bladder wall thickening, trabeculations and diverticula, and VUR if present [45,100] (Fig. 85.52)
◾ ◾ ◾
FIGURE 85.52 Posterior urethral valves. 5-month-old boy who presented with burning micturition and elevated serum creatinine; VCUG shows a shelf like filling defect in the dilated posterior urethra, multiple bladder diverticula, and bilateral Grade 5 vesicoureteric reflux.
Müllerian Duct Remnants
The caudal part of the Müllerian duct in the male becomes obliterated (apart from the caudal tip, which persists as the verumontanum). Incomplete obliteration may give rise to cysts between the bladder and the rectum. These may be asymptomatic or present with frequency, infertility, urinary obstructive symptoms or deep perineal pain on micturition or defecation. A cavity communicating with the posterior urethra derived from the caudal Müllerian duct may be seen (prostatic utricle) and is considered the male homolog of the uterus. Again, this may be asymptomatic but may be associated with maldevelopment of the genitalia (hypospadias, cryptorchidism, intersex, etc.) and may lead to urinary tract infection and calculi due to the presence of stagnant urine. These lesions may be demonstrated as cystic structures on CT, MRI, and transrectal ultrasound. Urethrography may demonstrate an extrinsic mass with a Müllerian cyst or a communicating narrow-necked, often irregular, cavity within the prostatic utricle.
Hypospadias In this congenital malformation, the urethra terminates on the ventral surface of the penis abnormally proximally. The meatus is found anywhere from just proximal to its normal site back as far as the perineum in severe cases. There is an association with other urinary tract anomalies and undescended testes. The anatomy is best demonstrated with urethrography but this may be difficult as the meatus is abnormal and usually narrowed, resulting in upstream urethral dilatation, often with secondary infection.
Cowper’s Duct Syringocele Cowper’s glands are paired glands embedded in the urogenital diaphragm and drain via ducts of variable length (from a few millimeters to a few centimeters), which run anteroinferiorly on to the ventral surface of the perineal part of the bulbar urethra. They may be opacified during urethrography in the presence of strictures or inflammation. The ducts to the glands may be congenitally dilated (Cowper’s duct syringocele), usually asymptomatically but on rare occasions associated with urethral obstruction.
Other Congenital Urethral Lesions The urethra is rarely duplicated congenitally, usually in the sagittal plane. The accessory urethra terminates along the shaft of the penis and is usually blind-ending, although if it communicates with the bladder, it is associated with continuous incontinence. Variable narrowing of the urethra may occur, ranging from mild stenosis to complete atresia. The more severe forms are
lethal, associated with obstructive renal failure and Potter’s syndrome unless there is a persistent patent urachus or rectovesical fistula to decompress the system.
Structural Lesions of the Urethral Wall Urethral diverticula: These are rarely congenital, when they are classically saccular and situated in the midpenile urethra. They are associated with high-grade obstruction in children and are difficult to distinguish from urethral valves. Stasis of urine may lead to secondary infection and calculus development. If they become large enough they may elevate the bladder base. They may be demonstrated on urethrography or USG, the latter having the advantage of avoiding radiation.
Congenital Scrotal Disorders Undescended Testicle (Cryptorchidism) Epidemiology and Pathophysiology In the majority of prepubertal males, the testes may normally be retractile into the groin because of the cremasteric muscle reflex. If, however, the testicle is consistently not located within the scrotum, it can be considered undescended. An undescended testicle (UDT) most commonly lies in the inguinal canal (canalicular). Otherwise it may lie higher up along the normal line of descent (abdominal testicle) or in a site away from the normal line of descent (ectopic). Most abdominal testicles lie just proximal to the deep inguinal ring, although they may lie further cranially within the pelvis or retroperitoneum. Ectopic testicles are uncommon and are most often found in the superficial inguinal pouch, occasionally coming to lie in the femoral canal, suprapubic fat pad, the perineum and the opposite scrotum. Failure of descent by the age of 2–3 years is associated with abnormal development of the testicle and this is particularly severe if it continues beyond puberty. Consequently undescended testes may be atrophic with poor spermatogenesis. A small proportion of undescended testes (5%) are not found even at surgical exploration. While some of these may be true agenesis, it is distinctly possible that a number are so severely atrophic that they cannot be located. Testes that remain undescended (especially abdominal testes) in boys above the age of 5 years also suffer from an increased incidence of
malignant neoplasia, up to 40 times normal, usually with the development of seminoma. There is also an increased risk in the contralateral, normally descended testicle. Other associations of undescended testes include abnormalities of Wolffian duct-derived structures, for example seminal vesicle cysts and agenesis [101,102].
Imaging Features
◾quick USG can be regarded as the first-line investigation to locate an undescended testicle, being and able to locate the testicle at its commonest sites (within the inguinal canal or just proximal to it). The testicle may look relatively normal, although the longer it has been undescended the more likely it is to be small, atrophic and echo-poor (Fig. 85.53). If the testicle cannot be identified on ultrasound, a more extensive search may be performed with MRI. This is a better technique than CT as it avoids radiation and the testicle shows a conspicuous high signal on T2-weighted and STIR sequences (Fig. 85.54). Use of DWI with a high b value yields information that complements conventional MRI findings [103]. Testicular phlebography or arteriography have historically been employed in the search for undescended testes. If both ultrasound and MRI are negative, it is unlikely that these angiographic procedures will detect the missing organ.
◾ ◾
FIGURE 85.53 Transverse ultrasound showing an atrophic undescended testicle lying in the inguinal canal.
FIGURE 85.54 Transverse STIR images from MRI examinations of patients with undescended testicles (arrow) in the proximal end of the inguinal canal (A), suprapubic pouch (B) and pelvis (C).
Patent Processus Vaginalis Failure of closure of the processus vaginalis after testicular descent results in a persistent communication between the peritoneal cavity and the scrotum. This may transmit disease processes (for example ascites) or become the site of a hernia. Incomplete closure of the processus may lead to a developmental cyst, usually in the upper scrotum or inguinal region.
The Acute Scrotum Scrotal pain, swelling, and redness of acute onset is a medical emergency [104] and the most common etiologies in children and adolescents include testicular torsion, torsion of the appendix testis, and epididymitis [105]. The technique of choice is high-resolution ultrasound using a linear transducer (∼10 MHz) with color and spectral Doppler, with low pulse repetition frequency (2.5 mm proximal to the radial surface. It has been associated with Kienbocks disease (avascular necrosis of the lunate). A causative role for negative ulnar variance has not been proven, although surgical techniques equalizing the length of the forearm bones do provide symptomatic relief in some patients. Congenital Dislocation of the Radial Head The cardinal feature is nontraumatic dislocation at the radiocapitellar joint, i.e., the longitudinal axis of the radius failing to bisect the capitellum. Congenital dislocation of the radial head may be an isolated abnormality, or seen as part of a genetic syndrome. The main differential for a congenital dislocation of the radial head is an acquired, traumatic dislocation. Distinguishing Features (Fig. 86.20)
FIGURE 86.20 8-year-old boy with inability to pronate elbows. The right radial head is subluxed with a small, abnormally positioned epiphysis, widened metaphysis and partial bony synostosis between the proximal radius and ulna. The proximal ulna metaphysis also appears abnormally broad. The synostosis is in keeping with a “type 2” appearance—that is, just distal to the radial epiphysis and associated with congenital dislocation. This is associated with genetic causes including karyotype abnormalities (e.g., mosaic XXXY).
◾ Small dome-shaped radial head ◾ Hypoplastic capitellum ◾ Prominent ulnar epicondyle ◾ Bowing of the ulna ◾ commonly bilateral ◾ More More commonly posterior dislocation Note, if a traumatic dislocation occurs at birth and is detected late, secondary bony remodeling may have occurred and it may be indistinguishable from a true “congenital” deformity. Associated syndromes include Ehlers-Danlos, Klinefelter, Nail-patella, Klippel-feil, and Apert. Treatment: Often asymptomatic. If there is limitation of movement or pain, ulnar, and radial osteotomies combined with annular ligament reconstruction, or radial head excision may be considered. Supracondylar Process A normal anatomic variant present in approximately 1% of individuals. It is a bony spur projecting from the anteromedial surface of the distal humerus,
approximately 5 cm above the elbow (Fig. 86.21). Considered to be a vestigial remnant, it is sometimes known as an “avian spur.”
FIGURE 86.21 A 13-year-old boy with restriction of elbow movement. The supracondylar spur is not apparent on the AP projection, but well seen on the lateral view in this case (arrow).
Key Facts
◾ Usually an asymptomatic, incidental finding ◾supracondylar May be associated with a fibrous band (Struthers ligament) extending from the process to the medial epicondyle, which can cause median nerve or brachial artery compression [14]
Imaging: Whilst easily seen on an oblique view of the elbow, it may not be apparent on true AP and true lateral views. Treatment: Surgical decompression for symptomatic cases associated with a Struthers ligament. Carpal Coalition
Carpal coalition may occur in isolation, or as part of a syndrome. Isolated carpal coalitions are usually transverse, e.g., lunate-triquetrum and capitatehamate (Fig. 86.22), and can be inherited [15]. In syndromes they may be longitudinal or more extensive [16]. Similar appearances may develop following acquired bony injury. Fusions may be described osseous, fibrous, or cartilaginous.
FIGURE 86.22 Incidental luno-triquetral coalition (arrow) presenting in a young adult (left) and more extensive capito-hamate coalition (arrow) seen in a 10-year-old during a skeletal survey for suspected dysplasia (right).
Key Facts
◾ Isolated ◾
⚬ Inherited as an autosomal dominant Mendelian characteristic ⚬ Most common within the same carpal row, particularly lunate-triquetrum ⚬ More common in females (2:1) ⚬ Regional variation in prevalence. White Caucasian 0.1%, Afro-Caribbean 0.4–0.8% [15] Syndromic ⚬ Coalitions between the proximal and distal rows—particularly if bilateral, were classically thought more likely to indicate a syndromic association [16]. An increasing number of case reports in recent years though have described inter-row fusions in nonsyndromic patients ⚬ Consider Ellis-van Creveld, Holt-Oram, Turner’s, Carpal-tarsal coalition, Otopalatal-digital syndromes
◾ Acquired
⚬ Acquired fusion rather than a primary failure of segmentation ⚬ More likely to be incomplete ⚬ Consider history of prior trauma, infection or inflammatory arthropathy
Pelvis and Lower Limb Hip Pain in Children Hip pain in children is a relatively common presentation, with the likely cause highly dependent on patient age. In preverbal children, specific localization of pain is difficult, and hip pathologies may present as a nonspecific limp, or reluctance to use the limb. Reference to the ACR appropriateness criteria for work-up of a limping child under the age of 5 is suggested [17]. Differentials based on age are considered in Table 86.3. The individual pathologies are considered in more detail in the following sections. Table 86.3 Differential Diagnosis of Hip Pain/Limp in Children Ag e
8 Years of Age
Co m mo n cau ses
Transient synovitis Septic joint/osteomyelitis Referred pain Trauma (including NAI)
Developmental dysplasia of the hipJuvenile idiopathic arthritisTumors Leukemia Metastases (e.g., neuroblastoma) Langerhan’s cell histiocystosis (pelvis more common 6 0
N A
2 a
Immatu re (3 months old)
Defic ient
Round ed
Covers femoral head
5 0 – 5 9
N A
2 c
Stable or unstabl e
Defic ient
Round ed/flat
Covers femoral head
4 3 – 4 9
< 7 7
2 d
Decent ering
Sever ely defici ent
Round ed/flat
Compressed
4 3 – 4 9
> 7 7
3
Disloca ted
Poor
Flat
Displaced upwards and abnormal echogenicity
< 4 3
N A
4
Disloca ted
Poor
Flat
Interposed
< 4 3
N A
Plain Film Is the preferred technique for investigation once the child is over 6 months, but may be useful from 4 months, due to progression of femoral head ossification. Features indicating DDH (Fig. 86.25):
◾ Ossification of the femoral ossific nucleus may be delayed on the dysplastic side ◾ femoral head is displaced upwards and outwards ◾ The The acetabulum is shallow, with an acetabular angle greater than 30 degrees;
This is the angle subtended by a line drawn through the centers of both Ycartilages (Hilgenreiner’s line) and a line parallel to the acetabular roof
FIGURE 86.25 A late presentation of DDH in an 8-month-old boy. The left hip is laterally and superiorly subluxed. There is relatively delayed ossification of the left upper femoral epiphysis. The right hip is normal.
Lines and angles for assessment of DDH on a well-centered plain film are shown:
Hilgenreiner line (dashed)—a horizontal line between triradiate cartilages. Perkin line (dotted)—drawn perpendicular to the Hilgenreiner line, contacting the lateral aspect of the acetabulum. The femoral head (or metaphysis if unossified) should be in the inner lower quadrant. The acetabular angle is measured between the Hilgenreiner line and the roof of the acetabulum, it should be less than 30 degrees.
MRI/CT May be helpful in select cases, for instance for confirming successful reduction of the femoral head postoperatively. Cartilage sensitive MRI sequences facilitate identification of the nonossified femoral head. The two available forms are Double Echo Steady State (DESS, Siemens) and MultiEcho iN Steady-state Acquisition (MENSA, GE). These are gradient echo sequences with a prolonged unbalanced readout gradient which generate combined free-induction-decay and echo-type signals. Treatment For Graf 2a hips, follow-up is undertaken until 3 months of age or hip normalization. For Graf 2b hips and above, splinting with a Pavlik harness is the first-line for treatment and is normally applied for 4–6 weeks. Surgical options are available for cases where the hips are found to be irreducible, or
the Pavlik harness has failed. These range from closed reduction and spica for children under 18 months of age, to open reduction and femoral osteotomy—generally reserved for children over 2 years of age.
Perthes Disease/Avascular Necrosis of the Hip Perthes disease is an idiopathic avascular necrosis of the femoral head. It is more common in boys. Typical age range from 5 to 8 years (although may range from 3 years to 12 years). Most commonly unilateral, but if bilateral typically asymmetric. If symmetry is present, hypothyroidism or multiple epiphyseal dysplasia should be excluded. There is no increased familial incidence, but parents of affected children are often elderly. Many of the affected children have a below-average birth weight and, at presentation, show skeletal growth retardation in the hands. This is especially seen in boys. There is an increased incidence of associated congenital anomalies, including congenital heart disease, pyloric stenosis, hernia, renal anomalies, and undescended testes. Following ischemia, the ossific nucleus of the epiphysis necroses, causing growth arrest. The overlying cartilage, which is supplied by synovial fluid, survives and thickens especially in the nonweight-bearing regions, medially, and laterally. Dense, necrotic bone resorbs and is slowly replaced by vital bone. The predisease shape of the necrotic nucleus does not return to normal and the nucleus ends up flat in whole or in part. Stages of the Disease These occur within each group. There is an initial phase of onset, with widening of the joint space and increased density of all or part of the ossific nucleus, which is followed by collapse of part or all of the nucleus, according to group. Repair removes the fragmented, crushed necrotic bone. Healing shows as an increase in size and re-ossification. Remodeling then occurs and is aided when the femoral head is completely contained within the acetabulum. Uncovering of the lateral margin of the femoral head has a bad prognosis. The metaphyseal lesion leads to an abnormal femoral neck. The most severely involved cases have a broad, short neck, i.e., the neck length/width ratio is lower than normal. Imaging Findings
◾ Radiographs (Fig. 86.26)
⚬ Lateral displacement of the femoral head. Early on, and in the irritable hip syndrome, displacement of the femoral head (Waldenström’s sign) is seen,
◾ MRI
possibly due to effusion or to thickening of the ligamentum teres. Later, the superior part of the joint may also be widened ⚬ Subchondral lucencies/fracturing. This sign is seen early in the disease but is transient. It is best seen in the “frog” lateral view ⚬ Reduction in size of the ossific nucleus of the epiphysis. This is found in some 50% of cases and is due to growth retardation. The medial joint space then seems wider ⚬ Increase in density of the femoral ossific nucleus. This is due to trabecular compression, dystrophic calcification in debris and creeping substitution repair, with laying down of new bone on the pre-existing trabeculation ⚬ As disease progresses, coxa magna may result ⚬ May show marrow edema in early cases ⚬ MRI changes are seen in bone and cartilaginous structures of the femoral head and acetabulum. The ossific nucleus flattens and the normal bright signal related to marrow fat diminishes following loss of the normal circulation. The signal seen from this region varies with the stage of disease and healing, and may range from low early on in the disease to a mixture of high and low when revascularization occurs or if cysts are present. The bone deformity is visualized. Metaphyseal irregularity is seen and an abnormal relationship of the entire head to the acetabulum shown. Dynamic contrast-enhanced MRI may demonstrate reduced perfusion ⚬ MRI also shows thickening of the nonossified cartilage of the femoral head, especially laterally, and of the acetabulum, especially the labrum. The degree of acetabular covering of the developing femoral head, as well as articular congruity is well seen in MRI
FIGURE 86.26 Boy with limp. (A) at 8 years, (B) 8.5 years, and (C) 12 years of age. The natural history of Perthes disease is shown, with initial subchondral lucencies (arrow) progressing to flattening, sclerosis and fragmentation, and later development of a coxa magna with secondary acetabular irregularity.
Differential Diagnosis
◾86.27) Secondary avascular necrosis—underlying predisposing factors need to be sought (Fig. ◾asymptomatic, Meyer’s dysplasia—irregular, variant ossification of the femoral heads which should be normally symmetric, and expected to normalize by approximately 5 years of age ◾ Skeletal dysplasia ⚬ Multiple epiphyseal dysplasia—other epiphyses will be affected ⚬ Mucopolysaccharidosis, particularly Morquio—will show other clinical and radiographic features (described later)
FIGURE 86.27 17-year-old with avascular necrosis of the left hip. There is left femoral head subchondral sclerosis and lucency (block arrow), and fragmentation of the articular surface. There are secondary degenerative changes in the left acetabulum. There has already been a right total hip replacement due to prior right hip avascular necrosis, and there is patchy bony sclerosis and “cod-fish” vertebral shape (open arrow) in keeping with underlying sickle cell disease.
Slipped Upper Femoral Epiphysis (SUFE) SUFE is an idiopathic Salter-Harris type 1 fracture across the proximal femoral growth plate. It is bilateral in a third of cases. More common in boys, obese children, and typically between 12 and 15 years of age. Treatment involves fixation of the femoral head in situ (without relocation).
Avascular necrosis of the femoral epiphysis is a potential complication. Deformity resulting from remodeling of the femoral head can cause a camtype femoroacetabular impingement and early osteoarthritis. This topic is covered in more detail in the Skeletal trauma (pediatric) chapter along with the Salter-Harris classification.
Imaging findings (Fig. 86.28)
FIGURE 86.28 13-year-old boy presenting with left hip pain. AP view demonstrates the line of Klein—drawn along the lateral margin of the femoral neck—failing to intersect with the femoral head on the left side. The metaphyseal overlap sign is also seen—with the normal small triangle of overlap between the posterior acetabular margin and the medial aspect of the proximal femoral metaphysis absent on the left side. The frog-leg lateral projection demonstrates the slipped left upper femoral epiphysis more easily.
◾ Sensitivity on radiographs is much increased in the frog-leg lateral position
◾lineOn ofan Klein, AP radiograph, features may be subtle, including widening of the physis, abnormal and reduced overlap of the medial aspect of the metaphysis with the posterior acetabulum ◾slipped Preoperative dynamic contrast-enhanced MRI can demonstrate altered perfusion within the epiphysis, with subtraction images aiding identification of focal or global devascularization. This can aid prognostication and parental counseling regarding the risk of postoperative avascular necrosis
Distal Femoral Metaphyseal Irregularity Also known as a cortical desmoid or an avulsive cortical irregularity, these are classic “do not touch” abnormalities which are benign and self-limiting. They are seen most often in boys aged 10–15 years, as incidental findings. These focal cortical lucencies in the distal femoral metaphysis are seen at the site of tendon attachments—predominantly the medial head of the gastrocnemius muscle on the posteromedial surface, although the lateral head of gastrocnemius and adductor magnus insertions may also be affected. On MRI, they are low T1 signal, and high T2 signal—although there may be a rim of peripheral low signal sclerosis (Fig. 86.29). The lesions may enhance with gadolinium, and may show uptake on bone scan due to associated inflammation/trauma.
FIGURE 86.29 A distal femoral cortical irregularity at the site of insertion of the medial head of gastrocnemius. (A) On the lateral radiograph, the irregularity appears as a saucer-shaped lucency along the cortical surface (arrow). (B) The lucency can be seen en-face on the AP radiograph (arrow). (C) This corresponds with high signal along the cortex (arrow) on the proton density fat-saturated MRI image, (D) with a thin sclerotic rim (arrow) seen around its margin also on the nonsaturated proton density sequence.
Proximal Focal Femoral Deficiency (PFFD) PFFD is a congenital defect of upper femoral development ranging in severity from mild femoral shortening with coxa vara to complete absence of the proximal third of the femur and no hip joint [21]. Key Facts
◾ Rare entity, affecting approximately 1:50,000 ◾ Bilateral in∼15%, usually asymmetrical ◾ May be associated fibular deficiency (see below) ◾facies Associated sporadic syndromes: femur-fibula-ulna complex, femoral hypoplasia-unusual syndrome
◾ Rarely part of WNT1A associated genetic disorder (Al-Awaadi-Raas-Rothschild syndrome) Imaging Techniques Plain radiographs of pelvis and affected femur. AP radiographs of remaining lower limb bones (a leg length radiograph if able to stand). MRI is useful in preoperative planning. CT is useful for peri and postoperative troubleshooting. Imaging Findings The Paley classification is commonly used to describe the clinical and imaging findings in PFFD (Table 86.5 and Fig. 86.30). Table 86.5 The Paley Classification of Proximal Focal Femoral Deficiency Pale y Type
1
2
3
Esse nce
Intact short femur
Pseudoarthrosis between proximal femur and femoral head
Major deficiency
Imag ing appe aranc e
Short but normally shaped femur (may show varus bowing), may have severe coxa vara, femoral head present.
Blunt proximal end of femur, femoral head may be present or fused to pelvis. Acetabulum present.
Sharp proximal end of femur, deficient femoral head (may be fused to pelvis), poorly formed acetabulum
Pale y Type
1
2
Treat ment
Limb lengthening ± hip reconstruction
Hip reconstruction and limb lengthening
3
1. Hip reconstruction 2. Transfer of knee to hip if reconstruction not possible 3. Amputation and prosthesis in worst cases
FIGURE 86.30 Proximal focal femoral deficiency. (A) Paley type 1 left femur in 17-week-old male; the left femur is short and bowed but has otherwise normal morphology, with a normally formed acetabulum. (B) Paley type 2 right femur in 1-year-old female. The right femur is short with a blunt proximal femoral metaphysis. A femoral capital epiphysis (open black arrow) is present within a normal acetabulum, with a nonossified connection to the metaphysis. (C) Paley type 3 left femur, type 1 right femur in 45-week-old female. The left proximal femur shows a sharp termination (white arrow). The left acetabulum is poorly formed.
Treatment Requires specialist orthopedic management. Depending on imaging findings, reconstruction may be attempted. Successful treatment addresses the deformity and establishes bony continuity of the upper femur, and corrects acetabular dysplasia. Lengthening may be performed later. The surgical results are monitored by radiographs (typically standing “leg lengths” views), supplemented by cross sectional imaging. Alternatively, a prosthetic may be used to restore limb length and function (with or without amputation).
Fibular Deficiency A longitudinal deficiency of the lower limb with hypoplasia of the fibular side elements; sometimes termed fibular hemimelia or postaxial hypoplasia of the lower limb. Key Facts
◾ Typically isolated ◾ Commonest congenital long bone deficiency ◾short Sometimes associated with short femur or proximal focal femoral deficiency, occasionally ulna (femur-fibula-ulna syndrome)
Imaging Technique Plain radiographs including standing leg lengths films to guide surgical treatment. MRI is sometimes helpful to assess knee ligaments. Imaging Findings
◾ Fibula is either partially present (type I) or absent (type II) ◾include: Disorder does not just affect the fibula: other components (Fig. 86.31), variably present, ⚬ Tibial shortening (milder than fibular shortening) ± anteromedial bowing ⚬ Hypoplasia of the lateral femoral condyle leading to genu valgum ⚬ Deficiency of the cruciate ligaments leading to undeveloped tibial spines and knee instability ⚬ Ball-and-socket ankle joint (rounded talar dome with concave tibial plafond) leading to ankle instability ⚬ Tarsal coalition ⚬ Absent lateral rays of the foot
FIGURE 86.31 Fibular hypoplasia of the lower limb. Standing leg lengths radiograph in 9-year-old male. The right fibula is slender, and both the tibia and fibula are short. There is a ball-and-socket morphology of the right ankle joint (white arrow). The right tibial spines are poorly developed (open black arrow), indicating cruciate ligament deficiency. There is hypoplasia of the right lateral femoral condyle (asterisk).
Treatment Nonoperative treatments include shoe raises and bracing. Contralateral epiphysiodesis to reduce limb length discrepancies in mild cases. Limb lengthening procedures for more severe cases. Most severe cases with nonfunctional foot best treated with amputation and prosthesis.
Tibial Dysplasia Longitudinal deficiency of the tibial side of the lower limb. Key Facts
◾ than fibular deficiency ◾ Rarer May be inherited as autosomal dominant trait Imaging Techniques Plain radiographs, with standing leg lengths films when possible. Imaging Findings Different patterns of tibial dysplasia are described by the Jones classification (Table 86.6 and Fig. 86.32) [22]. Table 86.6 Jones Classification of Tibial Dysplasia T y p e
Features
1 a
Absent tibia, absent extensor mechanism, small distal femoral epiphysis
1 b
Delayed ossification of proximal tibia, absent distal tibia, extensor mechanism present, normal distal femur
2
Proximal tibia present at birth, tibia short (Fig. 86.33)
3
Distal tibia present at birth, proximal tibial epiphysis absent
4
Diastasis of distal tibia and fibula (Fig. 86.34)
FIGURE 86.32 The Jones classification of tibial dysplasia.
FIGURE 86.33 Jones type 2 tibial dysplasia. Radiographs of right lower leg and foot in 41-week-old male. The proximal tibia (asterisk) is present but hypoplastic, with absent ossification of the distal tibia. There is ankle deformity. The hallux (arrow) is severely hypoplastic.
FIGURE 86.34 Jones type 4 tibial dysplasia. Radiograph of right lower leg in 6-year-old male. The distal tibia is hypoplastic (asterisk). There is diastasis of the distal tibia and fibula.
Foot malformations including preaxial polydactyly (may be associated with maternal diabetes) and oligodactyly are commonly seen in association.
Genu Varum (Bowed Legs) and Tibial Bowing in Children Bowed legs is a common orthopedic presentation in childhood. Typical causes are described in Table 86.7 and illustrated in Fig. 86.35, along with causes of isolated tibial bowing, illustrated in Figs. 86.36–86.38. Table 86.7 Causes of Bowed Legs and Tibial Bowing in Children
Cause
Clinical Presentatio n
Radiological Features
Management/Out come
Physiological
Normal finding in children between 1 and 2 years of age
Normal growth plates and metaphyses
Should improve by 2 years. Converts to physiological valgus between 3 and 7 years of age, then to a central mechanical axis.
Osteomalacia/r ickets
Usually after first year of life Associated biochemical abnormalitie s (See rickets section)
Varus bowing of femur. Tibial bowing with anteromedial convexity. Rachitic changes usually most marked at knee. Occasionally Looser zones visible, typically in femoral neck
Improves with correction of biochemical defect
Cause
Clinical Presentatio n
Radiological Features
Management/Out come
Blount’s disease
May be unilateral or bilateral Bimodal presentation Infantile: 2– 5 years Commoner in males 50% bilateral Adolescent: >10 years Rare Usually mild Usually unilateral
Varus centered on proximal tibia Fragmentati on and beaking of proximal tibial metaphysis
Conservative treatment with bracing Proximal tibial valgus osteotomy for severe or recalcitrant cases
Focal fibrocartilagin ous dysplasia (Fig. 86.36)
Rare Unilateral bowed tibia Can affect ulna
Focal varus of proximal tibia Fibrocartilag inous band at insertion of pes anserinus on upper medial tibia, produces lucent area with adjacent sclerosis
Usually improves spontaneously Severe or progressive cases may require resection valgus osteotomy
Congenital Typically proceeds to fracture with nonunion and pseudoarthr osis 50% associated with Neurofibro matosis type 1 Occasionall y with other bone lesions, including osteofibrous dysplasia
Bowing ± fracture or pseudoarthro sis
Achieving union can be challenging and require multiple surgeries If these fail, amputation may be required
FIGURE 86.35 Bowed legs in children. (A) Physiological genu varum in 16-month-old male; the metaphyseal appearances are normal. (B) Bowed legs due to x-linked hypophosphatemic rickets in 23 month old female; there is widening and irregularity of the metaphyses at the knees and ankle, more marked on the medial, load bearing sides (white arrows). (C) Blount’s disease in a 7-year-old male; there is irregularity, fragmentation, and beaking of the left proximal medial tibial metaphysis (black arrow), associated with left genu varus. Similar but milder changes on the right.
FIGURE 86.36 Focal fibrocartilaginous dysplasia. (A) AP radiograph and (B) coronal T1 weighted TSE MRI in 15-month-old male with unilateral tibial bowing. There is focal angulation of the upper tibia with irregular ossification of the medial cortex superiorly, and thickening of the cortex inferiorly. MRI shows fibrocartilaginous thickening at the insertion of the pes anserinus (arrow).
FIGURE 86.37 Posteromedial bowing of the tibia. AP and lateral radiographs of lower leg in 38-week-old male with congenital deformity of the tibia, showing posteromedially convex bowing centered on the distal third of the tibia and fibula.
FIGURE 86.38 Anterolateral bowing of tibia with pseudoarthrosis. AP and lateral radiographs of lower leg in 33-week-old female with known type 1 neurofibromatosis. There is anterolaterally convex bowing of tibia and fibula with a pseudoarthrosis (arrows) of the tibia.
A key measure for lower limb bowing is the mechanical axis, a line drawn from the center of the femoral head to the middle of the ankle mortise. A central mechanical axis passes through the center of the knee joint, and is a common treatment target for orthopedic surgeons.
Foot Disorders Correct identification and classification of abnormalities of foot alignment depends on an understanding of normal positioning [23] (Fig. 86.39).
FIGURE 86.39 Weight bearing views demonstrating normal reference angles. As a rule of thumb, the axis of the talus should normally intersect with the navicular and first metatarsal on both the lateral and AP views.
Congenital Talipes Equinovarus Talipes deformity is defined as a congenital abnormality of the foot, which is twisted out of shape. Talipes equinovarus accounts for 75% of these. It has an incidence of around 1–4:1000 live births. It is more common in boys and more commonly unilateral. The condition is multifactorial, contributed to by genetic, environmental, and intrauterine components. If one parent or a sibling had the condition, the chance of recurring in a subsequent pregnancy increases to 1 in 30–35. Clinically, the hindfoot is in equinus and varus, and the forefoot in varus [24] (Fig. 86.40).
FIGURE 86.40 In talipes equinovarus, there is hindfoot varus, hindfoot equinus, and forefoot varus. Note, the axis of the talus runs lateral to the navicular on the AP view.
Note, it is distinct from the more common metatarsus adductus (commonly referred to as “intrauterine packing”); in this condition, the talonavicular angle is normal, but the forefoot is in adduction. Imaging studies are generally not indicated in metatarsus adductus as the natural history in most cases is benign and resolves either spontaneously or with passive stretching.
Imaging Findings
◾onHindfoot equinus (fixed calcaneal plantar flexion with a tibiocalcaneal angle >90 degrees the lateral view) ◾talocalcaneal Hindfoot varus (the axis of the talus is lateral to the 1st metatarsal on the AP view, the ◾ Forefoot varusangle is 90% of children with moderate or severe OI, but only ∼1/3 of those with the mildest forms. Their absence, therefore, does NOT exclude the diagnosis 2) Cleidocranial dysplasia (see below). Wormian bones accompanying large persistent fontanels are a near universal feature of this condition 3) Other genetic causes include Hajdu-Cheney syndrome, hypophosphatasia, Menkes disease, pachydermoperiostosis, Yunis-Varon syndrome and occasionally seen in pyknodysostosis 4) Hypothyroidismmust be excluded in a child with unexplained Wormian bones
Scoliosis This term describes a lateral curvature of the spine. Usually, but not always, there is a primary curve with a compensatory curve above and below, unless
the primary curve is lumbar. It may be idiopathic, due to a structural bone abnormality such as a hemivertebra, or due to a neuromuscular abnormality. Etiologies (see Table 86.8) Table 86.8 Causes of Scoliosis Etiology
Subtype
Notes/Example
Idiopathic
Infantile
More commonly male, levoconvex thoracic
Juvenile
More commonly female, dextroconvex
Adolescent
80% female, 90% dextroconvex thoracic
Vertebral segmentation anomaly
See section below
Spinal dysraphism
Diastematomyelia, Tethered cord
Developm ental
Skeletal dysplasia or dysostosis
Mucopolysaccharidoses, neurofibromatosis
Neuromus cular
Neuropathic
Cerebral palsy
Myopathic
Muscular dystrophy
Osseous or Nonosseous
Osteoid osteoma, spinal tumor
Congenital
Tumourassociated
Idiopathic: This is the most common form of scoliosis (80%) and may be further subdivided into infantile, juvenile, and adolescent based on age at presentation. The infantile form is more common in males, with a left convex thoracic curve, whilst the juvenile and adolescent forms are more common in females with a right convex thoracic curve. In idiopathic scoliosis, no other etiology can be discerned and the diagnosis is made by exclusion. The earlier the onset of disease, the more
marked the curve at the time of spinal skeletal maturity, after which little further deterioration is to be expected. Imaging Radiographs are undertaken for initial assessment [29]. Patient positioning is important. The patient is standing where possible, in a neutral position (fingertips on clavicles) and the pelvis straight—with blocks under the feet if necessary to achieve this. Standard radiographs often require “stitching” to see the full length of the spine on a single image. Some institutes have low dose, full-body bi-planar systems (such as the EOS system), acquiring both AP and lateral images simultaneously at lower dose, with less artifact [30]. The lateral spinal curvature can be measured using the Cobb method (Fig. 86.45): the angle between lines drawn along the respective upper and lower endplates at the margins of the curve. A Cobb angle >10° is used to define scoliosis. Mild curves are 100° [29].
FIGURE 86.45 A dextroconvex thoracic scoliosis with its apex at T9, and a Cobb angle of 47 degrees (lines for angle measurement shown). There is no significant pelvic tilt. The iliac crest apophysis is ossified along 25–50% of its length (Risser stage 2).
Spinal skeletal maturity can be judged by a combination of bone age, and the progression of the iliac wing apophysis development—using the Risser staging. Risser grade 1 is 25% ossification, grade 2 is 50% ossification, grade 3 is 75% ossification, grade 4 is 100% ossification, and grade 5 is fusion of the ossified epiphysis to the iliac wing. MRI allows for evaluation of spinal involvement, particularly in cases with a known or suspected underlying focal abnormality such as a hemivertebra or spinal dysraphism. The role of ultrasound is limited in the initial diagnosis of scoliosis, as the normal progression of vertebral ossification tends to obscure intraspinal views by 3 months of life—before scoliosis would be expected to manifest clinically. Ultrasound has however proved useful as a radiation-free
technique for the evaluation of magnetically controlled growth rods used in the treatment of early onset scoliosis. Scoliosis Reporting Checklist
◾ Patient position—standing/sitting, fingertips on clavicles, pelvic tilt ◾ Number and location of curves (thoracic/lumbar) ◾ Direction of the curve—apex right (dextroconvex) or apex left (levoconvex) ◾ Apex of the scoliosis—most laterally positioned vertebral body (apex) on the AP view ◾ Presence/absence of segmentation anomalies ◾ Cobb angle ◾ Alignment on the lateral view—kyphosis/lordosis; pars defects, gibbus deformities ◾ Special views—bending views and bolster views, and change in Cobb angle ◾ Iliac apophysis development (Risser grading) ◾ of the skeleton—hips, pelvis, ribs ◾ Rest Rest of the radiograph—e.g., lungs, bowel, calculi
Treatment Depends to a large extent on the etiology and severity of the scoliosis. External bracing can be used from early life. Surgery is generally reserved for more severe scoliosis. The more traditional spinal fusions are generally delayed until the end of patient growth, although “growing” rods and vertebral body tethering may be used earlier in adolescence.
Vertebral Segmentation Anomalies These are congenital anomalies of individual or multiple vertebral bodies, typically manifesting as congenital scoliosis. Key Facts
◾ Common malformations present in up to 4% of the population ◾ anomalies in most cases ◾ Other Syndromic associations include
⚬ VACTERAL association (most commonly) ⚬ Oculo-Auriculo-Vertebral syndrome (Goldenhar syndrome), characterized by hemifacial macrosomia ⚬ Alagille syndrome, an autosomal dominant disorder due to mutation in JAG1, manifesting hepatic cholestasis, peripheral pulmonary artery stenosis, characteristic facial dysmorphism and typically a small number of butterfly vertebrae ⚬ If vertebral segmentation anomalies contiguously involve at least 10 vertebral segments, spondylocostal dysostosis or spondylothoracic dysplasia (genetic disorders) should be considered
Imaging Techniques AP and lateral radiographs of the whole spine in the first instance. MRI of spine if there are suspected spinal cord abnormalities. A CT can better define bony anatomy before surgery.
Imaging Findings Individual segmentation anomalies are defined according to the scheme in Table 86.9, illustrated in Figs. 86.46–86.48. Table 86.9 Classification of Vertebral Segmentation Anomalies Etiology
Type
Description
Failure of formatio n
Segmented hemivertebra
Half vertebra body with disc space above and below
Semisegmented hemivertebra (Fig. 86.47)
Half vertebra with disc either above or below
Unsegmented hemivertebra
Half vertebra fused to vertebrae above and below
Block vertebra (Fig. 86.48)
Bars on both sides of vertebral body
Unilateral unsegmented bar
Bar along one side. Likely to progress
Unilateral unsegmented bar with contralateral hemivertebra
Rapid progression
Failure of segment ation
Mixed
FIGURE 86.46 Schematic illustrating main types of vertebral segmentation anomaly.
FIGURE 86.47 Failure of formation: AP lumbar spine radiograph showing left L1 semisegmented hemivertebra (arrow) in 8-year-old female with congenital scoliosis.
FIGURE 86.48 Failure of segmentation: coronal and sagittal CT reformats showing contiguous block vertebrae from L3 to the sacrum (arrows) in a 5-year-old male with congenital lumbar kyphosis.
The overall spinal phenotype can be described as
◾genetic Multiple/Generalized (involving at least 10 contiguous vertebral segments), suggests disorder ◾ Regional (more than one segment involved, but fewer than 10 contiguously) ◾ Single (one segment involved)
Treatment Balanced malformations (e.g., where the effect of one hemivertebra is “cancelled-out” by a nearby contralateral hemivertebra) generally require no intervention. Scoliosis due to segmentation anomalies (“congenital scoliosis”) typically does not respond to conservative measures such as bracing or casting, and progressive or severe deformities require surgical intervention. A single hemivertebra causing scoliosis can be resected. More complex malformations typically require some form of instrumented fusion [31].
Caudal Regression Syndrome A spectrum of congenital defects of the caudal end of the spine, ranging from partially absent coccyx to complete agenesis of the lumbar and sacral spine [32]. Key Facts
◾hyperglycemia, Most cases sporadic. Attributed to an insult before the 4th week of gestation, such as infection, toxins, and ischemia ◾ Some overlap with VACTERAL association ◾ with maternal diabetes in 20% of cases ◾ Associated There may also be cord tethering—in which case neurologic abnormalities tend to be more severe, including neurogenic bladder, more severe cases show lower limb motor ± sensory defects Currarino syndrome, an autosomal dominant disorder due to mutations in MNX1, features partial sacral agenesis, a presacral cystic mass/anterior meningocele and anorectal malformation
◾
Imaging Findings
◾ Mildest cases may show absent coccyx or reduced number of coccygeal segments ◾together Complete sacral agenesis results in abnormal orientation of iliac bones which articulate in midline (Fig. 86.49) ◾bowel Severe cases show bony narrowing of pelvic outlet with associated bladder outlet and obstruction ◾ Characteristic blunted appearance of conus medullaris on ultrasound and MRI (Fig. 86.50) ◾ Associated malformations are common including: ⚬ Vertebral segmentation anomalies ⚬ Diastematomyelia ⚬ Neural tube defects ⚬ Club foot deformities
◾considered Sirenomelia, characterized by fusion of the lower limbs, is no longer part of caudal regression syndrome, although sacral agenesis may be present
FIGURE 86.49 Caudal regression. AP pelvic radiograph in 2-year-old female with complete sacral agenesis. The iliac bones articulate with each other across the midline (arrow). There is bilateral acetabular dysplasia and hip subluxation.
FIGURE 86.50 Caudal regression. Mid-sagittal lumbar spine T2 TSE MRI in 5-year-old female with known partial sacral agenesis. The conus medullaris is normally located but shows a blunted termination (arrow).
Sprengel Deformity This is the most common congenital shoulder anomaly, more common in females (3:1) and most commonly unilateral (70–90%). Key Facts
◾ The scapula is hypoplastic and sits in a high, medially rotated position (Fig. 86.51) ◾ to a failure of scapula descent during the 9th–12th weeks of gestation ◾theDue In 30–50% there is an omovertebral bar connecting between the superior medial aspect of scapula and the cervical spine [33] ◾syndrome”); Associations: cervical block vertebrae (association is sometimes termed “Klippel-Feil congenital scoliosis; upper limb anomalies; diastematomyelia; renal disease
FIGURE 86.51 18-year-old patient with Klippel-Feil syndrome and bilateral Sprengel shoulders with associated omovertebral bone (arrow). Associated cervical spine fusions were also present (not shown).
Imaging Findings Grading of the deformity on radiographs uses the Rigault classification (Table 86.10)—which describes the position of the superomedial angle of the scapula relative to the spine: Table 86.10 Rigault Classification of Sprengel Deformity Rigau lt I
Superomedial angle above T4 but below T2 transverse process
Rigau lt II
Superomedial angle between T2 to C5 transverse process
Rigau lt III
Superomedial angle above C5 transverse process
Treatment Surgical management may be considered for severe cosmetic concerns and moderate to severe functional impairment of the shoulder. It is best
performed from 3 to 8 years of age, with the risk of nerve damage increasing after this [33]. The Woodward, or modified-Green procedures are the most commonly performed, usually with good outcomes. MRI and CT are useful for preoperative planning, to identify an omovertebral connection—which may be fibrotic or cartilaginous rather than bony.
Multifocal Disorders: Infectious, Inflammatory, and Pseudoneoplastic Osteomyelitis and Septic Arthritis in Children The pediatric skeleton can manifest specific patterns of infection, with different vulnerabilities in the immature skeleton due to changing patterns of bone perfusion, development of epiphyses and longitudinal growth. In addition, the clinical features, laboratory tests and imaging findings of bone and joint infections in children are more frequently atypical than in adults making diagnosis challenging. The risk of untreated or undertreated bone and joint infection in children is long-term joint destruction and growth disruption. There is some overlap between osteomyelitis and septic arthritis in young children, due to the capacity for epiphyseal infection to spread into the joint space. Osteomyelitis Difficulties of Symptom-Based and Laboratory Diagnosis: Symptoms may be atypical in >40%, pain can be difficult to localize, and detection is challenging in preverbal and preambulatory children. Although C-reactive protein is almost always elevated (98%), white blood cell counts may be raised in only 30–65%. Isolation of a causative organism can be difficult, with blood cultures positive in 30–75% and tissue sampling/aspiration positive in 50–85% of cases. Kingella kingae, one of the most common pathogens in young children, requires dedicated PCR testing; similarly, TB needs to be suspected in order for specific testing to be carried out.
Patterns of Pediatric Infection
◾andIn neonates and infants, the epiphysis is relatively hyperperfused therefore vulnerable to hematogenous spread of infection. It is
involved in ∼50% of cases of infant osteomyelitis (Fig. 86.52). From the epiphyses, infection may spread directly into the joint space [34]: ⚬ The absence of joint effusion does not exclude epiphyseal infection ⚬ It may be occult on unenhanced MRI sequences ⚬ This may be multifocal, and clinically silent at the time of acute infection, manifesting as joint destruction and growth disruption much later
◾mayCommunity acquired staph. aureus osteomyelitis be aggressive in immunocompetent children, often following innocuous trauma. Previously this aggressive pattern of infection was attributed to methicillin resistant strains with the PantonValentine leucocidin (PVL) gene; although there probably was some sampling bias in earlier studies and this is not always the case. Pyomyositis, septic arthritis and thrombophlebitis/thrombosis may coexist, and disseminated infection may cause multifocal bony involvement and necrotizing pneumonia
FIGURE 86.52 AP pelvic radiograph (A) and coronal STIR MRI image (B) in 22-month-old girl, limping on the right side for the past 3 days. Raised white blood cells and ESR, but normal CRP and afebrile. Intraosseous abscess in the metaphysis of the right proximal femur, involving the growth plate and epiphysis. There is a small right hip joint effusion and pericapsular edema.
Imaging Techniques
◾skeleton, Radiographs may show periosteal reaction or bone destruction, but only in ossified and may be normal in early infection ◾surface Ultrasound may demonstrate associated soft tissue changes, periosteal reaction and cortical irregularity, and is not limited to ossified skeleton. The absence of joint effusion though does not exclude epiphyseal infection ◾ MRI
⚬ A large field of view is recommended initially due to difficult symptom localization ⚬ Acute infection may show increased STIR signal, periosteal elevation, subperiosteal or intraosseous abscess, and associated soft tissue changes ⚬ Gadolinium can be very useful in demonstrating areas of focal abnormal perfusion, and increase the conspicuity of abscesses [35] ⚬ Patchy marrow signal can be normal in the pediatric skeleton, making interpretation more difficult ⚬ Nuclear medicine bone scans may be cold in up to 50% of invasive S. aureus infections in infants
Subacute and Chronic Osteomyelitis: Though several classification systems have been suggested, there is no consensus on classification of ostemyelitis. Generally, osteomyelitis is characterized as acute or chronic based on histopathological findings, rather than duration of infection. Acute osteomyelitis typically presents 2 weeks after bone infection and chronic osteomyelitis 6 or more weeks after bone infection. Some studies describe an additional subacute phase, with 1–3 months of symptoms. The longer timescale allows for the development of single or laminated periostal reactions, and well-circumscribed metaphyseal
lucency in the long bones representing intraosseous abscesses. Given more time, chronic infection can develop, with more established intraosseous abscesses known as a Brodie’s abscess [35]. These contain a sequestrum of necrotic bone, with surrounding thick sclerotic periosteum (involucrum), perforated by cloaca and may have sinus tracts draining to the skin. There may be a lucent channel connecting the abscess to the unfused physeal plate (Fig. 86.53).
FIGURE 86.53 A Brodie’s abscess is seen in the proximal tibial metaphysis of a 10 year old girl, (A) one year after her original presentation with acute osteomyelitis. (B) Sagittal proton density and (C) axial fat saturated proton density MRI sequences show the extension to the open physeal plate (solid arrow), and the cloaca along the medial surface of the tibia, with a little overlying high signal in the soft tissues (open arrow).
Long Term Complications: Delays in diagnosis and treatment may arise in children due to atypical presentation. Severe disseminated neonatal bone and joint infection may only be detected years later when the sequelae of disrupted growth manifest. Premature fusion of growth plates can disrupt longitudinal growth—causing limb length discrepancies. Involvement of articular surfaces can cause joint destruction with early osteoarthritis.
Differential Diagnoses
◾ Chronic recurrent multifocal osteomyelitis (diagnosis of exclusion) ◾ Malignancy—primary bone tumor, leukemia/lymphoma, metastases ◾ Bone infarct ◾ cell histiocytosis ◾ Langerhan’s Caffey’s disease
◾ Fracture Septic Arthritis The hip and knee are most commonly affected sites. Staphylococcus and Streptococcus are the most common pathogens. Early detection is key to preserving joints, and ultrasound can characterize effusions and detect synovial thickening, periosteal reaction and cartilaginous epiphyseal involvement (Fig. 86.54), aiding diagnosis earlier than on radiographs [36,37]. MRI can be invaluable for further assessment. There is significant overlap with osteomyelitis, which may co-exist along with subperiosteal or soft tissue abscess in over 50% of cases. There is a risk of joint damage and growth disruption if inadequately treated (Fig. 86.55).
FIGURE 86.54 A right hip effusion with synovial thickening (arrow) in a 2-year-old girl with right hip pain, fever, and raised inflammatory markers. The presumed diagnosis is therefore septic arthritis until proven otherwise.
FIGURE 86.55 The late sequelae of disseminated meningococcus infection in the neonatal period, with asymmetric involvement at multiple joints.
Pediatric Specific Differential Diagnoses
◾typically Transient synovitis of the hip is a self-limiting, acute inflammation of the synovium most seen in children aged 3–8 years old, more common in males. It is one of the most common causes of pain and limping in this age group ⚬ The child should be afebrile, and otherwise well ⚬ The etiology is not fully understood, but it is commonly seen following viral infection. Some cases may be post-traumatic ⚬ A simple hip effusion (>2 mm) seen on ultrasound, in an afebrile child with joint pain, but normal inflammatory markers is most commonly due to transient synovitis. However, it does not fully exclude septic arthritis: the exact same features may be seen in up to 2.6% of children with a septic hip [37,38] ⚬ Transient synovitis is expected to self-resolve with supportive measures only
Table 86.11 provides a checklist for reporting pediatric bone infection. Table 86.11 Reporting Checklist for Pediatric Bone Infection Reporting Checklist for Pediatric Bone Infection Is infection present? Location of infection, multifocality Presence of drainable collections Associated complications—thrombophlebitis, soft tissue (pyo)myositis, fracture, chronic infection Poor prognostic signs—marrow ischemia, large subperiosteal abscess Recommendations on further investigations—imaging and laboratory tests
Periosteal Reaction in Children The differential diagnosis of periosteal reaction in children can be narrowed by first considering the localization of the periosteal reaction, and the age of the child.
Localization
◾toFocal/unilateral: localized processes such as infection (Fig. 86.56), trauma and tumor need be considered first
◾infection Diffuse/bilateral: more likely due to a systemic process, although prenatal and neonatal are more likely to be disseminated. Metastases may also be multifocal
FIGURE 86.56 3-week-old baby with right hip and leg retracted with no active movement, due to osteomyelitis. Pathological periosteal reaction is demonstrated along the right proximal femur (solid arrows), with a subtle lucency in the medial aspect of the proximal femoral metaphysis
due to an intraosseous abscess (open arrows), shown on radiograph and MRI. There is no joint effusion nor involvement of the epiphysis.
Age
◾ Under 6 months of age: ◾
⚬ Physiological periosteal reaction—normal variant, typically 1–5 months of age, bilateral symmetrical, 40 degree) or thoracolumbar (>30) kyphosis.
Panner
Capitel lum
Children 5–10 years History of throwing Resolves with rest and anti-inflammatories
Kienbo ck
Lunate
20–40 years adults. Repetitive microtrauma, e.g., manual labor Association with negative ulnar variant
LeggCalvePerthes (Perthe s)
Femora l head
Classically boys 4–8 years. Mostly unilateral. If bilateral, asymmetric. Can result in deformity. (see hip section)
Sinding LarsonJohanss on
Inferior pole of patella
Adolescents 10–14 years, particularly jumping/kicking. Point swelling and focal tenderness. Soft tissue changes seen first on ultrasound/MRI. Resolves with supportive management,
Osgood Schlatte r
Tibial tubercl e
Adolescents 10–14 years, particularly jumping/kicking. Bilateral in 25–50%. Point swelling and focal tenderness. Radiographic changes overlap with normal variation. Soft tissues changes on ultrasound/MRI can confirm. Most cases resolve with supportive management.
Name
Affecte d Bone
Features
Blount
Medial compar tment of knee
Bimodal distribution—infantile and adolescent forms. Medial tibial fragmentation, medial meniscal hypertrophy (see leg bowing section)
Sever
Calcan eal apophy sis
Radiographic changes overlap with normal variation. MRI—bone and soft tissue edema, tendon thickening.
Kohler
Navicu lar
Radiographic changes overlap with normal variation—however, tends to be painful and in older children
Freiber g
Head of 2nd/3rd metatar sal
Especially adolescent females, repetitive trauma. Can predispose to early OA.
Rheumatological Disorders Juvenile Idiopathic Arthritis (JIA) JIA encompasses a range of chronic arthritides of childhood onset, characterized by inflammation primarily involving synovial membranes.
Key Facts
◾ rheumatological disorder of childhood ◾ Commonest JIA is currently divided into seven subtypes (see Table 86.13)
Table 86.13 Classification of JIA Subtypes Category
Features
Freq uenc y
Age of Onset
Category
Features
Freq uenc y
Age of Onset
Systemic arthritis
Arthritis with or preceded by fever, with other systemic features, e.g., rash, lymphadenopathy, hepatosplenomegaly, serositis
5– 15%
Any
Oligoarthr itis
Arthritis affecting 1–4 joints during first 6 months of illness.
30– 60%
Early childhood
Rheumatoi d factor positive polyarthrit is
Arthritis involving 5 or more joints in first 6 months, positive rheumatoid factor
3–7%
Late childhood/adoles cence
Rheumatoi d factor negative polyarthrit is
Arthritis involving 5 or more joints in first 6 months, negative rheumatoid factor
10– 25%
Bimodal, pre and post 6 years
Enthesitisrelated arthritis
Arthritis or enthesitis and 2 of: sacro-iliac involvement, HLA B27 antigen, male aged over 6, anterior uveitis (in child or first degree relative), ankylosing spondylitis, inflammatory bowel disease, Reiter’s syndrome
5– 10%
Late childhood/adoles cence
Psoriatic arthritis
Arthritis and psoriasis and 2 of: dactylitis, nail pitting, onycholysis, family history of psoriasis
3– 10%
Bimodal, pre/post 6 years
Category
Features
Freq uenc y
Undifferen tiated arthritis
Arthritis not fulfilling other criteria
10– 20%
Age of Onset
Imaging Techniques and Findings [39,40]: Plain radiographs are typically normal in early JIA, but may be useful in excluding various differential diagnoses, e.g., Perthes disease, skeletal dysplasia, trauma. Erosive changes may be present in established disease. Ultrasound is useful in confirming clinical diagnosis of synovitis, and in complex joints such as the ankle and wrist in particular is useful for distinguishing between tenosynovitis and arthritis. MRI is valuable in demonstration of axial skeletal involvement, particularly in the cervical spine, and for sacroiliitis or enthesitis in the pelvis in suspected enthesitis-related arthritis (Fig. 86.58), and in evaluation of Temporo-Mandibular Joint involvement, which is common. MRI of the appendicular skeleton may allow evaluation for some alternative diagnoses, e.g., pigmented villo-nodular synovitis, intra-articular vascular anomalies. Bone marrow edema is a less useful sign in children than in adults as areas of apparent bone marrow edema are a common incidental finding in healthy children. Similarly, normal developmental pits and subchondral bone irregularity can be mistaken for erosions.
FIGURE 86.58 Enthesitis-related arthritis. Axial and coronal STIR MRI sequences in 13-year-old male with HLA-B27 antigen. There is inflammatory signal change in the right pubic body (white arrow) and in the femoral necks adjacent to both greater trochanters. Minor SI joint inflammation was also shown.
Management: Children with a small number of joints involved may initially be treated with localized joint injections, which may be image guided. Involvement of 5 or more joints is an indication for systemic treatment with a range of diseasemodifying drugs. Juvenile Dermatomyositis (JDM) JDM is a rare autoimmune connective tissue characterized by muscle weakness, elevated serum muscle enzymes and a characteristic skin rash.
Key Facts
◾eyelids Typical rash consists of Gottron’s papules of extensor surfaces and heliotropic rash of the ◾ Affects girls more than boys, typical onset 5–10 years ◾clinical Muscle biopsy usually still performed to establish diagnosis, but not always necessary if and MRI findings typical ◾scleroderma In some cases JDM may overlap with other connective tissue disorders, particularly
Imaging Techniques and Findings: MRI of gluteal and thigh muscles, with STIR sequences most useful. MRI shows muscle edema (Fig. 86.59), which may also involve adjacent fascia and subcutaneous tissues. MRI can also demonstrate muscle wasting and calcinosis in late disease. MRI is more sensitive than muscle enzyme testing [41].
FIGURE 86.59 Juvenile dermatomyositis. Axial STIR MRI of pelvis in 6-year-old male with skin rash and muscle weakness. There is widespread inflammatory signal change within the pelvic musculature, most pronounced in the gluteal muscles; some edema of the deep intermuscular fascia is also shown (arrows).
Plain radiographs and USG can be used to demonstrate areas of calcinosis in late disease. Chronic Nonbacterial Osteomyelitis/Chronic Recurrent Multifocal Osteomyelitis Chronic nonbacterial osteomyelitis is an autoinflammatory disorder characterized by sterile bone lesions. The term chronic recurrent multifocal osteomyelitis (CRMO) is widely used in pediatric medicine; the condition described in adults as SAPHO (synovitis, acnes, pustulosis, hyperostosis, and osteitis) is likely the same disorder, with broadly similar manifestations [42].
Key Facts
◾ Rare in first 5 years of life, typically presents in second decade ◾ female predominance ◾ Slight Typically present with pain and signs of inflammation ◾ Skin disease (typically acne) present in ∼40% of children ◾ ∼40% of cases are monostotic, median number of sites is 3 ◾ Clavicle commonest site of monostotic and polyostotic disease ◾ commonly involved sites include tibiae, femora, vertebrae, foot bones and mandible ◾ Other Synovitis in adjacent joints is common (approximately 50%); sacroileitis/spondyloarthropathy/enthesitis-related arthritis also appear to be associated in a minority of cases
Imaging Techniques: Plain radiographs are typically performed in first instance. Further evaluation with MRI useful in most cases. Screening for additional lesions via whole body MRI or bone scintigraphy can be very helpful, as multifocal involvement at typical sites is strongly supportive of the diagnosis. Imaging Findings: Early appearances may be similar to infectious osteomyelitis with metaphyseal predominance, osteolytic changes on radiographs, inflammatory signal changes on MRI and periosteal reaction. Hyperostosis may develop over time (Fig. 86.60).
FIGURE 86.60 Chronic recurrent multifocal osteomyelitis. (A) Radiographs of right wrist and (B) shoulder in 13-year-old female with long history of recurrent bone pain. There is irregular osteolysis of the distal radial metaphysis reflecting recent inflammation. Transverse bands in the more proximal metaphysis (arrow) reflect prior treatment with intravenous bisphosphonates. The right clavicle shows expansion and hyperostosis in its medial two-thirds, reflecting chronic inflammation.
Management: CRMO may be considered a diagnosis of exclusion. A provisional diagnosis of CRMO may be applied for polyostotic disease in typical sites, especially in the presence of suggestive skin lesions. Other clinical settings, particularly monostotic disease usually require tissue diagnosis to exclude infection or neoplasia. Many patients will receive antibiotics at first presentation owing to overlap with infectious osteomyelitis. Symptomatic
treatment with NSAIDS is helpful. Systemic treatment with steroids, rheumatological disease-modifying drugs and bisphosphonates have been successfully employed. The disease shows a benign course with complete symptomatic remission in approximately 2/3 of affected children, usually over 1–4 years. Langerhans Cell Histiocytosis (LCH) LCH is a disorder of cells of the mononuclear phagocyte system with both neoplastic and immunodysregulatory components which may involve multiple organ systems including bone, skin, reticulo-endothelial system, liver, lungs, and brain (particularly hypothalamic-pituitary axis) [43].
Key Facts
◾ Slightly commoner in females ◾ of childhood cases feature skeletal lesions ◾ 80% Classified as ◾
⚬ Single System Single Site (SS-s); 65% of cases, 80% skeletal ⚬ Single system multi-site (SS-m) ⚬ Multisystem type (MS) MS form commoner in younger children and has worst prognosis
Imaging Technique: Radiographs of index lesion. Skeletal survey (including bilateral limbs, but hands and feet not needed). Ultrasound first line for abdominal involvement and lymph nodes. Imaging Findings (Fig. 86.61):
FIGURE 86.61 Langerhans cell histiocytosis. (A) Radiograph and (B) axial CT of skull in 30-month-old female presenting with a right supraorbital mass. There is purely lytic destruction of the right lateral supraorbital margin. Lateral spinal radiograph (C) from skeletal survey in same child shows a dense, flat vertebral body at T12 (arrow), “vertebra plana.” A left femoral lytic lesion was also shown.
LCH can involve any bone; 50% of lesions involve the axial skeleton. At presentation lesions are lytic, and may have an aggressive appearance. With healing they become better defined.
◾table, Cranial vault lesions produce a lytic lesion that involves the outer table more than the inner producing a “beveled” edge. There is no marginal sclerosis at presentation, this may appear with healing ◾ Skull base lesions may be subtle on radiography
◾ body lesions lead to severe vertebral body collapse (“vertebra plana”) ◾ Vertebral Femoral and humeri are commonest long bone sites Management: SS-s disease may be managed conservatively (depending on site) and has a good prognosis. SS-m and MS disease is usually treated systemically with chemotherapeutic agents, e.g., Vinblastine and prednisolone, with more intensive chemotherapy offered to nonresponders. Bone marrow transplantation has been performed for some intransigent cases [44].
Generalized Skeletal Disorders: Genomic and Chromosomal Overview of Genetic Disorders of the Skeleton Skeletal dysplasias are genetic disorders with major involvement of skeletal tissue. They are both rare and extremely heterogeneous; the commonest disorders affect only approximately 1:20,000 people, and over 450 distinct disorders are recognized. The genetic basis for the great majority of these entities has now been established, and genetic testing is routinely available to confirm diagnosis for most disorders. Nonetheless, radiologists with skeletal dysplasia expertise continue to play a pivotal role in establishing a diagnosis by precise definition of the skeletal phenotype, to allow correct ordering of genetic tests and interpretation of their sometimes ambiguous or uncertain results. Skeletal dysplasias typically present with disproportionate short stature, which may manifest as early as 20-weeks’ gestation or as late as early adolescence. Other clinical pointers to a skeletal dysplasia include facial dysmorphism or a pedigree suggesting a genetic disorder. Early referral of a child with suspected skeletal dysplasia to a clinical geneticist with an interest in these disorders is the most important step. In most cases, a radiographic skeletal survey will be indicated (see below); this should be interpreted by an appropriately qualified individual, typically a pediatric radiologist with musculoskeletal interest. Having established a phenotype and a differential diagnosis, genetic testing will usually be performed. For commoner disorders with a clear phenotype such as achondroplasia this may be testing for a single gene. In most cases, a wider testing strategy using next generation genetic sequencing is undertaken; this may take the form of: testing for a small panel of genes; testing for all genes
known to cause skeletal dysplasia; testing for all genes known to cause human disease (clinical exome); testing for all genes (whole exome sequencing); or testing the whole genome (whole genome sequencing). The results of these genetic tests may give a clear confirmation of diagnosis, but in many cases, the testing reveals multiple gene variants which may or may not be pathogenic; at this point, a further review of the phenotype can help to establish which if any are the cause of the disease.
Imaging Investigations Unlike in nonaccidental injury, where the entire skeleton must be imaged, radiographs for dysplasia diagnosis are more select. Recommended radiographs of:
◾chest, Axial skeleton: skull (two views, to include the mandible), whole spine (AP and lateral), pelvis ◾limb Limbs: unless the disorder is asymmetric, only one side needs to be imaged—whole upper and lower limb, and hand (preferably the nondominant side for bone age). There is much natural variability in foot development, and foot radiographs often are noncontributory, but can be important for some conditions
Terminology The terminology in skeletal dysplasias can be confusing, particularly as there is inconsistent, largely historical naming of some conditions. Table 86.14 provides definitions for some of the more commonly used terms; some of these terms may be combined, e.g., “acromesomelic” means shortening of distal and middle limb segments: Table 86.14 Commonly Used Terms in Skeletal Dysplasia Diagnosis Ter m
Definition
Example/Notes
Dysp lasia
Developmental disorder of chondroosseous tissue— bones and joints
Spondyloepiphyseal dysplasia (due to collagen 2 gene defect)
Ter m
Definition
Example/Notes
Dyso stosi s
Inherited congenital malformation of single (multiple) skeletal elements Typically reflects mutation in genes determining early skeletal patterning (normally 10 ossicles, usually most pronounced around lambda suture ⚬ Present in >80% of type 3 and 4, but only 1/3 of type 1 ⚬ Absence of Wormian bones therefore does not exclude OI Skull base deformity ⚬ Commoner in those with severe short stature, wormian bones and dental involvement (dentinogenesis imperfects) ⚬ Platybasia (cranial base angle of >140 degrees) commoner than basilar invagination (odontoid process entering foramen magnum) Scoliosis ⚬ May relate to ligamentous laxity as well as vertebral body fractures
Management and Prognosis Children with moderate or severe disease or mild disease with recurrent fractures may benefit from cyclical intravenous bisphosphonates, which reduce fracture frequency and allow increased activity. Children with severe disease benefit from intramedullary rod insertion in long bones; growing rods reduce need for rod replacement.
Abnormal Mineralization Hypophosphatasia A bone mineralization disorder resulting from mutations in the gene encoding tissue nonspecific alkaline phosphatase. Key Facts
◾ Usually autosomal recessive (occasional mild dominant forms) ◾inhibitors Alkaline phosphatase degrades pyrophosphate and inorganic phosphates, which are potent of bone mineralization ◾diagnosis, A persistently low serum alkaline phosphatase is an important finding suggesting this and helps to distinguish from rickets ◾manifest Dental involvement common and may be only manifestation of mildest forms; typically with loss of milk teeth with entire root
Imaging Techniques Skeletal survey as primary assessment. Cranial CT to demonstrate craniosynostosis in some cases.
Imaging Findings
◾ Most severe cases manifest in fetus with absent skeletal ossification (“boneless baby”) ◾extent Severe forms show multiple absent bones (often missing ribs, vertebral pedicles, to a lesser vertebral bodies), short, bowed, sometimes bizarrely shaped long bones, very poorly ossified skull vault with “islands” of normal ossification (Fig. 86.89) ◾improvement Some apparently severe cases in prenatal and neonatal period show spontaneous ◾sometimes Moderate cases demonstrate metaphyseal ossification defects that may resemble rickets, metadiaphyseal bone spurs, bowed long bones ◾ Craniosynostosis is common and may be presenting feature
FIGURE 86.89 Severe hypophosphatasia. AP whole body radiograph in 16-week gestation fetus following termination of pregnancy for suspected lethal skeletal dysplasia. The skull is very poorly ossified. There is no ossification of the posterior elements of the spine, and only 4 vertebral bodies are ossified. There is asymmetric shortening and deformity of long bones, with bizarre “chromosome-like” ossification of the left femur (arrow) and both ulnae.
Management The most severe cases (“boneless” or near boneless) are lethal. Prognosis for moderate and severe disease has been transformed by development of new therapeutic agent, asfotase alfa, which restores skeletal integrity and function.
Lysosomal Storage Disorders
A broad range of mostly autosomal recessive disorders resulting from defective lysosomal enzymes. Key Facts
◾other Lysosomes are “cellular recycling centers” which degrade complex polysaccharides and products of metabolism by using specific enzymes ◾accumulation Lysosomal storage disorders result from deficiency of one of these enzymes, leading to of specific waste products (such as glycosaminoglycans) in various tissues including ⚬ The skeleton, resulting in dysostosis multiplex ⚬ Ligaments and tendons, resulting in joint stiffness or laxity ⚬ Skin, resulting in thickening of skin and coarse facial features ⚬ Neural tissue, resulting in developmental delay ⚬ Corneas, resulting in blindness ⚬ Solid organs, resulting in hepatosplenomegaly Examples include ⚬ Mucopolysaccharidosis (MPS) I (Hurler: severe, Scheie: mild) ⚬ MPS II (Hunter): x-linked recessive, moderate, spares eyes ⚬ MPS IV (Morquio): usually severe skeletal features, spares CNS ⚬ MPS VI (Maroteux-Lamy); moderate to severe ⚬ Mucolipidosis type II (I-cell disease); severe, also affects placenta, causing pre and perinatal hypocalcemia and hyperparathyroidism
◾
Imaging Techniques Skeletal survey at first presentation. Cervical spine radiographs with flexion and extension views for some disorders, particularly MPS IV and VI. MRI brain and neural axis for those with neurological features, and to assess for cervical cord compression. Imaging Findings
◾shared In general, lysosomal storage disorders present a constellation of skeletal findings that are between the different conditions, but vary in severity. This constellation is termed “dysostosis multiplex” (Fig. 86.90), and consists of ⚬ Broad, undermodelled tubular bones, particularly anterolateral ribs and medial clavicles ⚬ Areas of bone constriction, particularly posterior ribs, proximal ends of metacarpals and basilar portions of iliac bones ⚬ An elongated “j-shaped” sella turcica, often a scaphocephalic appearance ⚬ A thoracolumbar gibbus (kyphotic) deformity often associated with hypoplasia of L1 or L2 vertebral bodies at apex of kyphosis, and inferior projections of the anterior vertebral bodies in this region. Increased convexity of the vertebral body endplates may also be present Morquio syndrome (MPS type IV, Fig. 86.91) shares some of these features but has distinct spinal appearances with platyspondyly, bone defects at site of vertebral ring apophyses (producing a central “tongue” of the anterior vertebral border), severe odontoid hypoplasia and a severe dysplasia of the upper femoral epiphyses
◾
FIGURE 86.90 Dysostosis multiple in Hurler syndrome; images from skeletal survey in 25 week old male with Hurler syndrome. (A) chest radiograph shows broad ribs and medial clavicles. (B) lateral skull radiograph showing elongated “J-shaped” sella turcica. (C) pelvic radiographs showing shallow acetabula with basilar hypoplasia of the iliac bones (black arrow). (D) left hand radiograph showing proximal tapering of 2nd to 5th metacarpals (white arrows). (E) lateral lumbar spine radiograph shows hypoplasia of the L1 vertebral body (open black arrow) with associated kyphotic (“gibbous”) deformity, leading to inferior hook formation of the L1-L3 vertebral bodies.
FIGURE 86.91 Spinal features in Morquio syndrome; 2-year-old female. (A) Lateral thoracic spine radiograph shows generalized platyspondyly with ossification defects at the sites of ring apophyses, producing an apparent central “tongue” from the anterior vertebral border (arrows). (B) Lateral flexion radiograph shows odontoid hypoplasia with disruption (dashed line) of the spinolaminar line (solid line), indicating atlanto-axial instability.
Management Early bone marrow transplantation in Hurler syndrome can ameliorate neurological impairment, but has little effect on skeletal phenotype. Enzyme replacement therapy is available for many of these disorders. Most children with Morquio syndrome require occipito-cervical stabilization and correction of genu valgum deformities.
Disorganized Development Fibrous Dysplasia Fibrous dysplasia is very variable in appearance, and a great mimic of other bone lesions. There are monostotic and polyostotic forms, and may be associated with changes and premature puberty in McCune-Albright syndrome.
Key Facts
◾ condition is sporadic, usually due to somatic mosaicism in the GNAS gene ◾ The 80% of disease is monostotic
◾may Lesions may progress in number and size until the end of puberty then typically stop. They be reactivated during pregnancy ◾ Bone deformity and pathologic fractures are common ◾ the skull is involved, there may be impingement on foramina ◾andIfCherubism—symmetrical mandibular bony swelling—is considered a separate condition is genetically distinct ◾irregularly In McCune-Albright syndrome there is asymmetric polyostotic fibrous dysplasia, with marginated café-au-lait spots that respect the midline (“coast of Maine”) and endocrine disturbances—most commonly precocious puberty in females, although there may also be hyperthyroidism, acromegaly, Cushing’s and diabetes mellitus and hyperparathyroidism There is a low risk (2.5%) of malignant transformation of lesions to osteosarcoma, fibrosarcoma, chondrosarcoma, and malignant fibrohistiocytoma. Growth hormone treatment and previous radiation exposure increase the risk. Worsening pain and swelling warrant further investigation [49]
◾
Imaging Findings
◾typically Variable appearance of individual lesions, which can be lytic, sclerotic or mixed. Most they are ground-glass, well-defined and mildly expanded (Fig. 86.92) ◾inAlthough any bone may be involved, the ribs, skull, and femur are the most common sites monostotic disease; and the skull, mandible, pelvic bones and femur the most common in polyostotic disease ◾sites Secondary bowing may result in the classic “shepherd’s crook” appearance in the proximal ◾femora There is uptake in the lesions on radionuclide Technicium-99 bone scans—which can be useful to provide a baseline for multifocality of disease once the child is over 5 years of age ◾[47] Appearances are variable and generally nonspecific on MRI, although most enhance to some degree with gadolinium. MRI is the technique of choice if there are suspected aneurysmal bone cysts ◾associated The presence of cortical destruction, osteolysis, increased pathological fractures and associated soft tissue masses are concerning imaging features for malignant transformation. Definitive diagnosis of this may be difficult, as there is histological overlap between fibrous dysplasia lesions and low grade osteosarcoma The variability of fibrous dyplasia lesions means the differential diagnosis for the appearance on imaging is vast, but includes enchondromatosis, extramedullary hematopoiesis, Paget’s disease, extra neurofibromatosis type 1, osteofibrous dysplasia, simple bone cysts, giant cell tumor, and hemangiomas.
FIGURE 86.92 An 8-year-old girl with McCune-Albright syndrome, with bilateral femoral and pelvic foci of fibrous dysplasia. This is complicated by healing osteomyelitis postfracture on the left.
Management: Treatment in fibrous dysplasia is largely supportive—focused on fracture management and reduction of deformity. Although bisphophosphonates can help with bone pain, there is currently no established disease-modifying treatment. All patients require endocrinological evaluation at diagnosis, due to the risk of associated endocrinopathies. In particular, untreated growth hormone excess may exacerbate the progression of fibrous dysplasia lesions. Craniofacial disease requires subspecialist input due to the risk of progressive cranial nerve compression. Ongoing clinical follow-up for patients with fibrous dysplasia is required, with prompt evaluation of any sites of increased pain or swelling—due to the risk of malignant transformation. Multiple Cartilaginous Exostoses (Osteochondromas) Also known as diaphyseal aclasia, or hereditary multiple exostoses. Multiple bony protuberances around the joints, scapulae, and iliac crests with a risk of
malignant degeneration of the cartilaginous cap.
Key Facts
◾ Autosomal dominant, variable expression, with a stronger phenotype in males ◾adulthood Growth of the exostoses slow during adolescence, there should be no new lesions in ◾ resection may be required for lesions causing troublesome local mass effect ◾ Surgical There is a 2% risk of sarcomatous degeneration of the overlying cartilage cap. This most
frequently occurs in the pelvis and proximal femora. Pain and rapid growth are the cardinal features
Imaging Findings
◾flatExostoses may arise from long bone metaphyses and migrate to diaphyses, or arise in some bones—particularly the scapula and iliac crests. They are most commonly seen in the limb ◾lower In the long bones, there is mild broadening of affected metaphyses, with bony which may be sessile or pedunculatedpointing away from the joint ◾protuberances On radiographs, the cortex should be intact and smooth. Irregularity is concerning for transformation ◾malignant The cartilage cap is best demonstrated with MRI, although can also be seen on ultrasound. It should be less than 1.5 mm thick (Fig. 86.93)
FIGURE 86.93 Multiple cartilaginous exostoses in a 16-year-old girl, seen on a radiograph arising from the scapula and proximal humerus (A). The cartilage caps (arrows) can be easily measured on cartilage sensitive MRI sequences (B).
Fibrodysplasia Ossificans Progressiva
Also known as myositis ossificans progressiva, it is characterized by progressive heterotopic ossification of tendons, ligaments, fascia, striated muscle and skin, becoming crippling by early adulthood, with impairment of respiratory function due to thoracic involvement and difficulty eating due to masticator involvement.
Key Facts
◾ First presentation is normally by age 10 ◾ The ossification may be spontaneous, but is exacerbated by even minor trauma ◾ is supportive, and biopsies and surgical procedures should be avoided ◾ Treatment Life expectancy if carefully managed can be up to 40 years
Imaging Findings
◾resulting Short dysplastic hallux, with unusual malformation of the proximal phalanx and metatarsal in a distinctive hallux valgus from birth (Fig. 86.94) ◾appendicular; Heterotopic ossification proceeds cranial to caudal, dorsal to ventral, and axial to although the order may be disrupted by local injuries ◾ The paraspinal muscles, limb girdles and muscles of mastication are preferentially affected ◾ There may be para-articular bony projections, and cervical spinal fusion
FIGURE 86.94 Very extensive heterotopic ossification of the pelvic girdle in a 40-year-old female with fibrodysplasia ossificans progressiva (left). Recognition of the early onset bilateral hallux valgus deformity with variably dysplastic hallux metacarpal and phalanges allows for earlier diagnosis (right).
Enchondromatosis (Ollier Disease) Multiple enchondromas may be present at birth but increase in number and size until puberty. Most cases are due to somatic mosaic mutations of isocitrate dehydrogenase, a Krebs cycle enzyme.
Key Facts
◾ Bone deformity is the main presenting feature ◾pathological Pain may be present during periods of rapid growth, but is otherwise worrisome for fracture or malignant transformation ◾ Bone growth is impaired in affected segments, and limb asymmetry may result ◾including There is an increased risk of chondrosarcoma in later life, and also other malignancies gastrointestinal and gonadal ◾syndrome, If in combination with multiple soft tissue spindle-cell hemangiomas it is termed Maffucci in which there may be a greater risk of malignancy
Imaging Findings
◾bones, Multiple sharply marginated radiolucent defects in the metaphyses of tubular bones and flat with internal calcified matrix elements (Fig. 86.95) ◾ There may be shortening and deformity of the affected bones. ◾phlebolith Unlike other hemangiomas, the spindle-cell hemangiomas of Maffucci syndrome show formation
FIGURE 86.95 10-year-old boy with Ollier’s disease. Enchondromata demonstrated in the right index finger metacarpal, proximal, and middle phalanges. Enchondromas in the hand are the only site where calcified ground-glass matrix may not be seen.
Cleidocranial Dysplasia This disorder results from dominant mutations in RUNX2, an important determinant of osteoblast differentiation, resulting in defective ossification of membranous bone.
Key Facts
◾ Normally manifests at birth, although can be detected in the second trimester ◾ Clavicular hypoplasia to varying degrees, narrow chest, small scapula ◾ teeth can persist, and there can be impaction of supernumerary adult teeth ◾ Deciduous Narrow pelvis and hypoplastic distal phalanges are less commonly seen
Imaging Findings
◾bone, Delayed ossification of the skull, delayed closure of sutures, median cleft in the occipital Wormian bones, small maxilla ◾86.96) Hypoplasia of the clavicles (more commonly middle/lateral), hypoplastic scapulae (Fig. ◾ Delayed ossification and underdevelopment of the pubic bones and inferior ischium ◾phalanx, Pseudoepiphyses of the metacarpal and metatarsal bones, dysplastic little finger middle hypoplastic distal phalangeal tufts, delayed carpal bone ossification
FIGURE 86.96 A 2-month-old baby presented with a palpable clavicular defect. (A) On plain film, there are bilateral mid-clavicular defects, and (B) there is absence of pubic bone ossification (normally expected by 22–24 weeks gestation) in keeping with cleidocranial dysplasia. There is some variability in phenotype, clavicular changes ranging from fairly mild defects seen in this case, to severe hypoplasia with a (C) “bell-shaped” chest.
Craniosynostosis Aperts Dyndrome Aperts syndrome is the commonest of the acrocephalosyndactylies; it comprises brachycephaly due to bicoronal craniosynostosis with central
distal syndactyly of the hands leading to a characteristic “mitten-hand” deformity. Key Facts
◾inAutosomal dominant disorder (frequently due to a new mutation) resulting from mutations FGFR2 ◾ Associated with advanced paternal age ◾ delay present in some children ◾ Developmental Pfeiffer syndrome is a similar disorder with milder hand features but often more severe cranial dysmorphism
Imaging Techniques: Skeletal survey usually not needed as it is a clear clinical diagnosis. Radiographs of hands and feet to define bony anatomy before surgery. Volumetric cranial CT to plan craniosynostosis repair.
Imaging Findings (Fig. 86.97)
FIGURE 86.97 Apert syndrome. (A) Left hand radiograph in 36-weekold female showing “mitten-hand” deformity with central distal bony syndactyly (arrow). (B) Left foot radiograph in same child aged 6 years showing short broad hallux in varus, and soft tissue syndactyly of toes 2–5. (C) Volume rendered image from craniofacial CT in same child at aged 1 year showing bicoronal craniosynostosis.
◾deformity Brachycephaly with bilateral coronal craniosynostosis and resulting harlequin eye ◾ Maxillary hypoplasia ◾phalanx Bony syndactyly of the central distal phalanges in the hands; short radially deviated distal of thumb; carpal synostosis in some
◾variable Cutaneous syndactyly of central toes; broad hallux in varus; metatarsal bony syndactyly in patterns ◾ Glenoid hypoplasia and shoulder instability, occasional elbow anomalies ◾ Cervical spine segmentation anomalies, typically C-6 block vertebra Management: Plastic surgical intervention restores some hand function. Cranial vault expansion to improve cosmesis and in some causes manage raised intracranial pressure. Vertebral Dysostoses
Spondylocostal Dysostoses and Spondylothoracic Dysplasia
Key Facts
◾associated, There are autosomal recessive and dominant forms. Multiple gene mutations have been although most affect the Notch signaling pathway ◾ Due to the genetic heterogeneity, there is broad phenotypic variability ◾ and/or kyphosis is congenital– there may be secondary respiratory impairment ◾ Scoliosis Associated cardiac and genitourinary malformations
Imaging Findings
◾ Normally greater than 10 contiguous vertebral segmentation defects (Fig. 86.98) ◾ Alternating left and right hemivertebrae produce the “pebble beach sign” ◾ The degree of scoliosis depends on the pattern of segmentation defects ◾converge There may be associated rib anomalies—aplasia or fusion, and in some cases ribs may posteriorly (“crab chest”). Respiratory complications are more common in these cases (previously termed “Jarcho-Levin syndrome”)
FIGURE 86.98 Spondylocostal dysostosis. Chest radiograph in 1-yearold female with short trunk. There are contiguous segmentation anomalies of the entire thoracic and lumbar spine, with posterior rib convergence producing the “crab-chest” appearance.
Patellar Dysostoses
Nail-Patella Syndrome
Key Facts
◾ Autosomal dominant, normally presenting in late childhood ◾ Hypoplastic or absent patella, palpable posterior iliac horns, hypoplastic nails ◾ elbow and knee movements ◾ Restricted Nephropathy in approximately 25% in adulthood, which is the major cause of morbidity
Imaging Findings (Fig. 86.99)
FIGURE 86.99 In nail-patella syndrome, there may be joint instability with recurrent dislocations, in addition to patella hypoplasia (A, B). Bilateral iliac horns (arrows) may be present (C).
FIGURE 86.100 Skeletal features in trisomy 21. (A) chest radiograph in 4-week-old female with trisomy 21 post pulmonary artery band procedure for AVSD; there are 11 rib pairs, and the upper ribs are slightly short, producing a slightly “bell-shaped” chest. (B) Pelvic radiograph in 11-year-old male with trisomy 21 and acute leukemia. The iliac bones are markedly flared.
FIGURE 86.101 Turner syndrome; left hand radiograph in 14-year-old female with 45 × 0 karyotype. There is a Madelung deformity of the wrist. The 4th metacarpal is slightly short.
◾ Hypoplastic or absent patella. Hypoplastic lateral femoral condyle ◾ iliac horns ◾ Posterior Hypoplastic radial head and capitellum—occasional radiocapitellar dislocation
Skeletal Findings in Aneuploidies Disorders involving abnormal numbers of chromosomes are termed aneuploidies, and may have wide ranging manifestations, reflecting abnormal imprinting or haploinsufficiency of large numbers of genes. Skeletal findings in some of the commoner disorders are summarized in Table 86.16. Table 86.16 Skeletal Findings in Commoner Chromosomal Aneuploidies Disorder
A disorder of the growth plate, which has been considered synonymous with vitamin D deficiency, it includes a spectrum of conditions that result in prolonged low serum phosphate with or without hyperparathyroidism. Key Facts
◾ In vitamin D deficiency,
◾
⚬ The reduced gut absorption of calcium leads to hypocalcemia ⚬ This in turn leads to secondary hyperparathyroidism, which causes increased phosphate excretion in the urine and subsequent hypophosphatemia ⚬ Hypophosphatemia leads to failure of apoptosis of mature hypertrophic chondrocytes in the growth plate; these then accumulate, causing widening of the growth plate, and fraying and splaying of the metaphysis. This effect is potentiated by a direct action of elevated parathyroid hormone (PTH) on chondrocytes ⚬ Reduced availability of calcium and phosphate leads to diminished mineralization of osteoid during bone turnover, resulting in soft bones which bend (osteomalacia), and sometimes Looser zones (pseudofractures, unmineralized seams of osteoid) ⚬ Prolonged hyperparathyroidism directly leads to loss of bone mass (osteopenia) and bone fragility ⚬ Thus, vitamin D deficient bone disease in children presents as a triad of rickets, osteomalacia, and hyperparathyroidism Causes of rickets are described in Table 86.17
Table 86.17 Causes of Rickets Category PTH dependent (“calcipenic”) rickets 1-alpha hydroxylase deficiency (autosomal recessive disorder) FGF23 dependent (“phosphopenic”) FGF23 is a bone derived hormone which downregulates expression of renal phosphate transporters and inhibits 1-alpha hydroxylase. Excess FGF23 secretion leads to hyperphosphaturia and low serum phosphate. Hyperparathyroidism is usually mild or absent.
Disorder Paraneoplastic rickets (associated with neoplasms of mesenchymal origin, includes linear sebaceous naevus syndrome)
Other
Renal tubular disorders (e.g., Fanconi syndrome) due to renal phosphate wasting
Imaging Techniques Radiographs of one wrist and knee are usually sufficient. Children with xlinked hypophosphatemic rickets require regular renal ultrasound for nephrocalcinosis. Leg length views for bowing deformities are helpful. Imaging Findings (Fig. 86.102) [48]
FIGURE 86.102 Nutritional rickets; 20-month-old male with vitamin d deficiency, hypophosphatemia, and hyperparathyroidism. (A) Chest radiograph shows that the anterior ribs are expanded (“rachitic rosary,” arrows). (B) In the wrist there is splaying and fraying of the distal radial and ulnar metaphyses. There is marked osteopenia.
◾ossification) Widening of the growth plate with splaying (widening) and fraying (irregular, patchy of the metaphyses, most pronounced at sites of rapid growth (e.g., distal ulna); at the costochondral junctions, this produces the “rachitic rosary.” These changes are often milder in FGF23 dependent rickets Bowing of long bones due to osteomalacia, femoral varus bowing and anterolateral bowing of tibiae are typical, and feature in all forms of rickets (Fig. 86.35B) Features of hyperparathyroidism (osteopenia, intracortical and subperiosteal bone resorption, brown tumors, salt and pepper skull) in PTH dependent forms of rickets, less pronounced or absent in FGF23 dependent (“phosphopenic”) forms Fractures common in PTH dependent forms of rickets. Rarer in infants before mobility, although may occur in severe disease. Fractures unusual in FGF23 dependent forms, although Looser zones may occur
◾ ◾ ◾
Management Diagnosis is confirmed by biochemical evaluation, including serum calcium, phosphate, alkaline phosphatase (ALP), PTH and 25-OH Vitamin D levels. These determine subsequent consideration of differential diagnoses.
◾genetic If serum calcium and phosphate are low, but vitamin D levels are normal, testing for forms of rickets are indicated; this includes measurement of renal tubular
reabsorption of phosphate (for hypophosphatemic rickets), 1,25-OH Vitamin D levels (for 1alpha hydroxylase deficiency) as well as genetic sequencing If the alkaline phosphatase level is low (usually elevated in rickets), hypophosphatasia must be considered If sercum calcium, phosphate, and PTH levels are normal, a metaphyseal chondrodysplasia should be considered (e.g., metaphyseal chondrodysplasia type Schmid; note that Jansen metaphyseal chondrodysplasia may present with low serum calcium and phosphate)
◾ ◾
Treatment of vitamin D deficient rickets is with vitamin d supplementation. Restoration of normal serum biochemistry is rapid (within days). The earliest sign of healing rickets radiographically is the reappearance of the “metaphyseal white line” at the zone of provisional calcification, and is apparent within days of restoration of normal biochemistry. Dense metaphyseal bands may subsequently develop. Bowing deformities may take months to remodel.
Metabolic Bone Disease of Prematurity (Osteopenia of Prematurity) The active trans-placental transport of calcium and phosphorus occurs mostly in the third trimester, peaking between weeks 32–36 of gestation. Premature infants miss out on this crucial stage of mineralization. The time of presentation is typically 6–12 weeks after birth [49]. Risk Factors
◾ Placental insufficiency ◾ low (3 mm (Terry Thomas sign) and a scapholunate angle >100°. This is the commonest type of perilunate injury (Fig. 87.106) Stage II injuries involve disruption of the capitolunate joint causing perilunate dislocation. This is recognized on the lateral radiograph as dorsal dislocation of the capitate in relation to the lunate, while the lunate retains normal articulation with the radius (Fig. 87.107) [110] Stage III injury is additional disruption of the lunotriquetral joint and further midcarpal instability Stage IV represents the rarest and most severe injury with lunate dislocation, due to final failure of the dorsal radiocarpal ligament. The normal anatomy of the proximal carpal row is lost, and the lunate is usually seen to abnormally overlap the capitate, hamate and triquetrum on the PA view, also taking on a triangular, rather than a rectangular shape. On the lateral view, the lunate is volarly dislocated and rotated with respect to the distal radius. The capitate maintains its alignment with the distal radius. This is known as the “spilled teacup” sign (Fig. 87.108)
◾ ◾ ◾
FIGURE 87.106 Frontal wrist radiograph demonstrates abnormal widening of the scapholunate interval implying scapholunate dissociation. This is also known as the Terry Thomas or Madonna sign.
FIGURE 87.107 Perilunate dislocation (transscaphoid). (A) Frontal radiograph demonstrates a displaced scaphoid waist fracture (arrow) and an abnormal triangular shape of the lunate with disruption of the carpal arcs as the capitate and lunate/scaphoid overlap. (B) Lateral view shows dorsal subluxation of the capitate (green dots) in relation to the lunate (red dots).
FIGURE 87.108 Lunate dislocation. (A) Frontal radiograph demonstrates an abnormal triangular shape of the lunate with disruption of the carpal arcs. (B) Lateral view shows the lunate (red dots) is volarly dislocated and tilted with respect to the distal radius. The capitate (green dots) remains aligned with the radius. The abnormal appearance of the lunate is likened to a “spilled teacup.”
CT with the capability of multiplanar/3D and volumetric reformats can help delineate these complex injuries and subtle fractures.
Hand Fractures Hand injuries are common and usually present minimal diagnostic difficulty. A few of the more challenging types are discussed below. A Bennett’s fracture is a 2-part fracture-dislocation of the base of the first metacarpal with involvement of the articular surface, usually associated with “dislocation” of the major fragment (Fig. 87.109).
FIGURE 87.109 Lateral thumb radiograph demonstrate a Bennett’s fracture; a base of thumb metacarpal avulsion fracture (volar fragment) that remains articulated with the trapezium due to the intact attachment of the anterior oblique ligament. The remaining thumb metacarpal base is subluxed dorsally.
In contrast a Rolando fracture is a comminuted intra-articular fracture of the thumb metacarpal base (Fig. 87.110), which is more unstable and difficult to reduce.
FIGURE 87.110 Oblique radiograph of the thumb showing a Rolando fracture.
Another significant thumb injury is “skier’s thumb” (or gamekeeper’s thumb) that is avulsion of the ulnar collateral ligament (UCL) at the first metacarpophalangeal joint. This usually results from forceful abduction and hyperextension of this joint and involves avulsion of the proximal phalanx insertion of the ligament. Bony avulsion occurs in approximately 50% [111] (Fig. 87.111). If no bony fragment is evident on the radiograph but clinically there is valgus instability, further investigation with USG or ideally MRI is indicated. MRI is also useful to exclude a Stener lesion (Fig. 87.112); a complication of the injury when the torn UCL is retracted superficial to the adductor aponeurosis that acts as a block to healing and necessitates surgery. Surgery is also indicated for significantly displaced bony fragments or fracture involving >20% of the articular surface.
FIGURE 87.111 Frontal radiograph showing a fracture of the ulnar aspect of the thumb proximal phalanx at the metacarpophalangeal joint in keeping with bony avulsion of the distal UCL insertion.
A “Boxer’s fracture” is the commonest fracture of the metacarpal bones, usually due to punching an object with a clenched fist that causes axial compression along the length of the bone. This is classically a transverse fracture of the fifth (or fourth) metacarpal neck with volar angulation and shortening (Fig. 87.113).
FIGURE 87.112 Coronal T2 fat-saturated sequence of the thumb shows complete avulsion and retraction of the distal attachment of the UCL (red arrow). This is now located superficial to the adductor aponeurosis (yellow arrow) giving a “yo-yo on a string” appearance.
Proximal phalanx (P) and metacarpal (MC) of the thumb are labeled.
FIGURE 87.113 Frontal and oblique radiographs of the hand demonstrate a boxer’s fracture of the little finger metacarpal neck, with volar angulation and shortening.
The Lower Limb Fractures of the Hip Fractures involving the femoral head, femoral neck and the trochanters are commonly known as hip fractures. These fractures are frequently seen in the elderly population secondary to a fall and co-existing low bone mineral density. They are associated with significantly increased morbidity and mortality if not appropriately treated [112]. In the elderly underlying pathology such as metastasis should always be excluded especially in the context of little force. Non-displaced hip fractures can be challenging to identify with plain film, especially in the osteoporotic patient. A faint illdefined linear density across the femoral neck, interruption of trabecular lines, and subtle cortical disruptions may be the only radiological signs. If there is doubt about the presence of a hip fracture, the gold standard for
fracture identification is MRI as CT is not as sensitive, especially in patients with osteopenia. Images will demonstrate a linear band of low signal T1 with associated high T2/STIR signal signifying a fracture line (Fig. 87.114). There may also be a subperiosteal fluid, hematoma and soft tissue edema.
FIGURE 87.114 Fracture of the neck of femur. (A) Pelvic radiograph demonstrating a faint lucent line through the subcapital neck of the left femur (blue arrow). It would be easy to overlook this finding as there is no obvious cortical disruption. The CT (B) does not demonstrate a clear fracture. Noticeable linear signal abnormalities through the neck of femur represents a fracture on the MRI images (C) T1 weighted (red arrow) and (D) T2 weighted (green arrow).
It is important to diagnose and differentiate between intracapsular and extracapsular fractures. Intracapsular fractures are those from the femoral head to the basocervical region of the femoral neck, which is just proximal to the trochanters. Extracapsular fractures are either intertrochanteric (between the greater and lesser trochanter) or subtrochanteric (Figs. 87.115 and 87.116). The majority of the femoral head’s blood supply is from extracapsular medial and lateral circumflex femoral artery branches. A small artery in the ligamentum teres (foveal artery) is not sufficient in isolation to perfuse the femoral head in adults. Any intracapsular neck of femur fractures risk compromising the blood supply to the femoral head with consequent avascular necrosis. Treatment of such fractures usually requires replacement of the femoral head with a metal polymer (Fig. 87.117).
FIGURE 87.115 Image of the proximal femur and hip with annotations of the intracapsular and extracapsular fracture areas.
FIGURE 87.116 Intracapsular neck of femur fractures are subcapital (A), transcervical (B), or basicervical (C). Extracapsular neck of femur fractures include intertrochanteric fractures which can be two-part (D) or comminuted (E and F).
FIGURE 87.117 Preoperative and postoperative radiographs of neck of femur fractures. (A) Displaced intracapsular neck of femur fracture which likely result in avascular necrosis of the femoral head. (B) Patients with such injuries generally require a complete femoral head prosthesis. (C) An extracapsular, neck of femur. fractures generally have a preserved blood supply to the femoral head. (D) Such fractures can be treated with a dynamic hip screw.
Femoral stress fractures arise due to either repeated abnormal mechanical strain onto normal bone (fatigue fractures) or due to normal stresses transmitted to bone of abnormal density (insufficiency fractures). Fatigue fractures most commonly involve the medial cortex of the proximal third of the femur whereas insufficiency fractures involve the lateral cortex of the femur distal to the greater trochanter (Fig 87.118). If a stress fracture is identified on one side the patient is at risk of developing a further stress fracture in the contralateral limb [113].
FIGURE 87.118 Femoral insufficiency fracture. There is thickening and beaking of the lateral cortex of the femoral shaft consistent with an insufficiency type of stress fracture. A fatigue fracture will have similar appearances but involve the medial cortex.
FIGURE 87.119 A transverse fracture through an area of lateral cortical thickening involving the subtrochanteric region of the femur. This is an atypical subtrochanteric femoral stress fracture due to abnormal bone mineral density. These types of fractures are often seen in patients taking bisphosphonate medication.
Subtrochanteric fractures account for 25% of proximal femoral fractures with a bimodal distribution. They are seen in young male adults following high velocity trauma such as road traffic accident and also in elderly female patients whom take bisphosphonate medication for osteoporosis [114,115] (Fig 87.119). Such fractures are uncommon in other circumstances and should be treated with caution as patients may have an underlying bone pathology. Femoral shaft fractures are uncommon injuries and when seen are in the context of significant trauma. If no significant trauma is identified an underlying bone pathology should be suspected. Distal femoral fractures are rare, accounting for 3–6% [116] of femoral fractures with a bimodal distribution as with subtrochanteric fractures. They are frequently comminuted and intra-articular, involving the femoral
condyles and metaphysis (Fig. 87.120). They are frequently seen in the context of high-energy trauma or in the elderly as a result of a fall [117].
FIGURE 87.120 Supracondylar fracture of the femur with comminution and extension to the articular surface.
Fractures of the Knee Fractures around the knee include femoral fractures (see above), patellar fractures, and tibial plateau fractures. Patellar fractures can sometimes be challenging to diagnose in the absence of a clear history of direct trauma to the knee joint and are sometimes missed on AP knee radiographs and a lateral radiograph is important to have to hand in such queries (Fig. 87.121). It is important to differentiate acute fractures from that of normal variants such as bipartite or tripartite patella. Unlike a fracture these normal variants are well corticated. They occur in roughly 2% of the population and involve the superolateral patella in 80%, lateral patella margin in 15% and patella tip in 5% [118]. The absence of any prepatella soft tissue swelling or joint effusion on a lateral radiograph should raise suspicion for the presence of a bipartite patella. Patella dislocations are obvious clinically, however, many patients present post reduction with no evidence of trauma radiologically. MRI can be used to identify the pattern of soft tissue injury that is characteristic of a patella dislocation in such instances or to identify alternative pathology (Figs. 87.122 and 87.123).
FIGURE 87.121 Patella fracture. Lateral knee radiograph demonstrating a comminuted and displaced transverse fracture through the body of the patella. There is also a joint effusion and prepatellar soft tissue swelling evident.
FIGURE 87.122 MRI following a recent patella dislocation. The medial retinaculum should be a thin dark band but it is indistinct as it is torn and edematous (blue arrow). There is extensive patella bone marrow edema along with a fracture involving the medial patella facet (red arrow). There is contralateral femoral condyle marrow edema secondary to patella impaction.
FIGURE 87.123 Quadriceps rupture. The normally low signal band of the quadriceps tendon insertion on the patella has been filled with high signal fluid (blue arrow). The tendon fibers of the quadriceps have retracted. The patella tendon is no longer under tension and slack in appearance (red arrow).
Tibial plateau fractures are synonymous with the presence of a fat–fluid level within the suprapatellar bursa on a lateralradiograph (Fig. 87.124). The extent of injury is often not possible to identify with plain film and it is common to perform a CT to identify the extent of the fracture and also to
identify, the presence of any depressed fragments (Figs. 87.125 and 87.126). Such fractures may be missed in osteopenic bones and subtle signs like a small articular step or the margin of the lateral tibial plateau overhanging the outer edge of the femoral condyle are important to identify. The Schatzker classification system for tibial plateau fractures is widely used by orthopaedic surgeons and subdivides *tibial plateau fractures into six categories based on CT or MRI appearances [119] (Fig. 87.127). The classification system helps to predict the degree of articular surface damage, soft tissue injury, timing of surgery and operative approach. The use of MRI is frequently employed should ligamentous or meniscal injury be queried. Certain fractures such as the Segond (Fig. 87.128) and reverse Segond (Fig. 87.129) fractures are associated with significant ligamentous injury and knee instability.
FIGURE 87.124 A fluid level within the supra-patella bursa seen on this lateral radiograph is due to the presence of both fat and haematoma. This is known as lipohaemarthrosis and is synonymous with an intracapsular fracture of the knee. If not seen on plain radiograph, a CT is indicated.
Fractures of the shaft of the tibia are usually oblique or spiral, although transverse fractures also occur. There is invariably an associated fracture of the fibula, again indicating the association of double injuries with bony “ring” structures. Complications of tibial fractures include a high incidence of open injuries and delayed union, usually the result of high-energy impact forces.
Fractures of the Ankle and Foot The ankle is the most frequently injured joint and fractures are often seen in the context of sporting trauma or axial loading onto a rotated joint. Classification systems play an important role in piecing together the constellation of both bone and ligamentous injury and thus the degree of ankle stability. The Weber classification system focuses on the integrity of the tibiofibular syndesmosis with fractures being classified as
◾ type A (infrasyndesmotic), ◾ B (transsyndesmotic), and ◾ type type C (suprasyndesmotic) [120,121] (Fig. 87.130).
FIGURE 87.125 A fracture to the lateral tibial plateau. (A) Forced knee abduction results in the lateral femoral condyle impacting the lateral tibial plateau resulting in the plateau becoming depressed. (B) CT demonstrates the fracture in greater detail and that the fractures extends to the tibial metaphysis laterally and the tibial spine medially.
FIGURE 87.126 A severe fracture of the tibial plateau. The lateral plateau is depressed, comminuted and has been displaced laterally. There is also a transverse metaphyseal fracture.
FIGURE 87.127 The six subtypes of tibial plateau fractures as described in the Schatzker classification. (A) Type I—Split fracture of the lateral tibial plateau. (B) Type II—Split depression fracture of the lateral tibial plateau. (C) Type III Central depression of the lateral tibial plateau. (D) Type IV—Split fracture involving the medial tibial plateau. (E) Type V—Bicondylar tibial plateau fracture. (F) Type VI—Dissociation between diaphysis and metaphysis.
FIGURE 87.128 Segond fracture with associated soft tissue injury. (A) A small bone avulsion (blue arrow) representing the “lateral capsular sign” on a frontal knee radiograph, also known as a Segond fracture. These fractures are associated with significant soft tissue knee injuries, commonly involving the anterior cruciate ligament and medial meniscus. (B) In this instance the MRI demonstrates that the anterior cruciate ligament is torn (red arrow) as the ACL fibers have been replaced by heterogeneous high signal intensity edema and hematoma.
FIGURE 87.129 Reverse Segond fracture with associated soft tissue injuries. (A) There is an avulsion fracture involving the medial tibial plateau (blue arrow). This type of fracture occurs following valgus stress and external rotation of the knee. (B and C) MRIs demonstrating the associated soft tissue injuries. There is an avulsion of the deep fibers of the medial collateral ligament (red arrow). The normally black band is replaced by high signal intensity at the tibial insertion. The medial meniscus is torn and extruded with intrasubstance abnormal high signal extending through the body of the meniscus (green arrow). The posterior cruciate ligament is also torn as the normally well-defined low signal ligament has been replaced by amorphous mixed signal intensity haematoma (yellow arrow).
FIGURE 87.130 The three patterns of ankle fracture according to the Weber classification system. Type A fractures involve the lateral malleolus distal to the syndesmosis. The medial malleolus is frequently also fractured with the deltoid ligament intact. Type B fractures are trans-syndesmotic and may also have a synchronous medial malleolus fracture or deltoid ligament injury. Type C fractures occur above the level of the syndesmosis. The medial malleolus and deltoid ligament are frequently also injured. If the medial malleolus is injured or the medial clear space widened but no lateral malleolus injury is identified, the proximal fibula should be imaged to exclude a high fibula injury (Maisonneuve fracture).
These fractures are identical to those described by Lauge-Hansen, which concentrates, on the mechanism of trauma in terms of directional force on the ankle joint, those being supination-adduction, supination-external rotation, and pronation-external rotation. On plain film, the medial and lateral clear spaces are crucial review areas as their widening can indicate ankle ligamentous injury. CT can be used to evaluate for the fracture morphology, intra-articular involvement, the presence of any osteochondral defects or intra-articular lose bodies or for the presence of occult talar fractures if suspected however not evident on plain film. MRI is generally reserved for evaluating the pattern of ligamentous and tendinous injury (Figs. 87.131 and 87.132).
FIGURE 87.131 (A) There is soft tissue swelling adjacent to the medial malleolus along with a small avulsion fracture to the fibula tip (blue arrow). (B) The MRI demonstrates the fracture with linear high signal of the fibula tip. The talofibular ligament (green arrow) is strained. (C) Axial MRI showing the posterior calcaneofibular ligament (red arrow) is strained.
FIGURE 87.132 Achilles rupture. (A) Swelling and edema involving the posterior soft tissues of the ankle with an indistinct dorsal fat pad (Kager’s triangle). (B) The MRI demonstrates a full thickness Achilles tendon tear (blue arrow). There is gross swelling, edema, and retraction of the tendon proximal to its insertion along with inflammation of the surrounding soft tissues.
Maisonneuve fractures occur due to forced pronation and external rotation resulting in a combined proximal fibula fracture and unstable ankle injury (Fig. 87.133). This is evident from widening of the medial and lateral clear space with or without the presence of medial malleolus fracture. If suspected a radiograph to visualise the more proximal fibula is indicated. There is often significant concomitant ligamentous injury involving the deltoid ligament and distal tibiofibular syndesmosis.
FIGURE 87.133 Maisonneuve fracture. Forced pronation and external rotation of the ankle has resulted in a fracture to the lateral malleolus (A) and a proximal spiral fibula fracture (B).
Pilon fractures involve high energy axial loading onto ankle joint which drives the talus into the tibial articular surface (tibial plafond). This results in an impacted and comminuted distal tibial fracture extending to the metaphysis (Fig. 87.134). 75% of Pilon fractures are associated with distal fibula fractures [122].Commonly the fracture is in three parts with intact ankle ligaments. These comprise of a medial malleolar fragment with intact deltoid ligament, a posterolateral fragment with intact posterior inferior tibiofibular ligament and an anterolateral fragment with an intact anterior inferior tibiofibular ligament [123].
FIGURE 87.134 Pilon fracture. (A and B) Significant axial loading onto the ankle resulting in the distal tibia to be driven into the talus. The distal tibia fracture extends into the metaphysis. The joint space is narrowed. (C) CT demonstrating the medial malleolus fracture in more detail along with a small talar dome fracture (red arrow).
Tarsal bone fractures are uncommon and account for 2% of all fractures with Calcaneal fractures accounting for 50–60% of these [124]. Calcaneal fractures are a frequent finding in falls from a height, and may be associated with fractures of the thoracolumbar spine. The talus acts as a wedge driving down into the calcaneal body causing depression and widening. Calcaneal fractures can be difficult to appreciate on plain radiograph, flattening of Bohler’s angle may be a helpful sign (Fig. 87.135). CT is particularly useful in the evaluation of calcaneal fractures and in particular to assess for the extent of any intra-articular involvement (Fig. 87.136). A haematoma extending along the sole of the foot (Mondor’s sign) is considered to be pathognomonic of a calcaneal fracture.
FIGURE 87.135 Fracture of the calcaneus. The normal angle formed between the subtalar joint and the upper margin of the tuberosity of the calcaneus should be about 40o. Diminution of this angle should arouse suspicious of a fracture, but this may only be clearly shown in the axial projection. (A) Normal Bohler’s angle measurement. (B) Reduced angle with fracture of the body of calcaneus.
FIGURE 87.136 Fracture of the calcaneus. (A) Fracture through the body of the calcaneus with flattening of Bohler’s angle. (B) 3D reconstruction of the fracture demonstrating extensive comminution.
Fractures of the talus occur due to forced dorsiflexion or plantarflexion with subluxation of the ankle or subtalar joint associated with ankle or subtalar dislocation. Fractures are generally avulsions or fractures through the waist (Fig. 87.137) with avascular necrosis of the proximal fragment being a complication.
FIGURE 87.137 Fracture through the waist (or neck) of the talus, red arrow seen both on plain film (A) and CT (B).
Other notable fractures of the foot include Lisfranc fracture-dislocations. The Lisfranc joint relates to the articulation of the tarsal bones with the metatarsal bases. The strong Lisfranc ligament attaches the medial cuneiform to the base of the 2nd metatarsal and its integrity is paramount to the stability of the Lisfranc joint. Injuries to the Lisfranc ligament manifest as avulsions to the base of the 2nd metatarsal and can be overlooked on plain radiograph [125]. Widening of the interspace between the 1st and 2nd metatarsal bases or malalignment of the 2nd and 3rd tarsometatarsal joints should prompt one to consider a Lisfranc fracture-dislocation. A missed injury results in progressive subluxation of the Lisfranc joints and significant patient disability. CT is crucial in the identification of occult fractures when suspected but not identified on plain film (Fig. 87.138).
FIGURE 87.138 Lisfranc fracture dislocation. (A) Radiograph demonstrating a fracture through the medial cuneiform (red arrow) and widening of the interspace between the base of the 1st and 2nd metatarsals (blue arrow). (B and C) The CT and MRI show that the fractures are more extensive and involve the middle and lateral cuneiforms along with the base of the 3rd and 4th metatarsals.
The 5th metatarsal base should be a review area on all trauma foot radiographs as fractures to the base are common and must be distinguished from an unfused apophysis. Fractures are typically extra-articular and orientated transversally whereas an unfused apophysis is orientated longitudinally parallel to the metatarsal shaft (Figs. 87.139 and 87.140). Fractures involving the proximal diaphysis of the 5th metatarsal, known as a Jones fracture are less common however, they can proceed to delayed union or non-union (Fig. 87.141).
FIGURE 87.139 Base of 5th metatarsal fracture (blue arrow). The fracture orientated transversally with widening of the fracture line laterally.
FIGURE 87.140 Unfused apophysis at the base of the 5th metatarsal. The longitudinal orientation of the bone fragment and lack of paraosseous soft tissue swelling in a pediatric skeleton are consistent with an unfused apophysis.
FIGURE 87.141 Jones’s fracture. A transversely orientated fracture of the proximal 5th metatarsal diaphysis.
Stress fractures of the foot classically involve the 2nd metatarsal and are also known as March fractures due to their occurrence in marching soldiers as a result of repeated mechanical stress on the bone and now often seen in runners along with stress fractures of the tibia where the proximal shaft is commonly involved [113,126]. The fracture can be challenging to identify on initial radiographic imaging with pain and increased uptake on a bone scan being the earliest signs. MRI will be able to demonstrate the presence of bone marrow edema and subperiosteal fluid if the radiograph is normal. Follow up radiographs will demonstrate diaphyseal periosteal reaction and sclerosis confirming the presence of a stress fracture (Fig. 87.142).
FIGURE 87.142 Stress fracture. The 2nd metatarsal diaphysis is a common site for stress fractures in the foot. These fractures are often subtle on the initial radiograph but are more evident on subsequent films when a sclerotic fracture line and periosteal thickening are apparent (blue arrow).
Suggested Readings • TH Berquist, MRI of the Musculoskeletal System, third ed., Lippincott–Raven, Philadelphia, 1996. • K Bohndort, Injuries at the articulating surface of bone, Eur J Radiol 22 (1996) 22–29. • RB Greaney, FH Gerber, RI Laughlin, et al., Distribution and natural history of stress fractures in US marine recruits, Radiology 146 (1983) 339–346.
• JS Fisher, JJ Kazam, D Fufa, RJ Bartolotta, Radiologic evaluation of fracture healing, Skeletal Radiol 48 (2019) 349–361. • JM Kazley, S Banerjee, MM Abousayed, AJ Rosenbaum, Classifications in brief: garden classification of femoral neck fractures, Clin Orthop Relat Res 476 (2) (2018 Feb) 441–445. • RA Marshall, J Mandell, MJ Weaver, M Ferrone, A Sodickson, Imaging features and management of stress, atypical, and pathologic fractures, Radiographics 38 (7) (2018 Nov), doi:10.1148/rg.2018180073. • KE Halliday, NJ Broderick, JM Somers, R Hawkes, Dating fractures in infants, Clin Radiol 66 (11) (2011 Nov) 1049–1054. • F Canavese, A Samba, M Rousset, Pathological fractures in children: diagnosis and treatment options, Orthop Traumatol Surg Res 102 (1, Suppl.) (2016 Feb) S149–S159. • M Paddock, A Sprigg, AC Offiah, Imaging and reporting considerations for suspected physical abuse (non-accidental injury) in infants and young children. Part 1: initial considerations and appendicular skeleton, Clin Radiol 72 (3) (2017 Mar) 179–188. • A Fassier, P Gaucherand, R Kohler, Fractures in children younger than 18 months, Orthop Traumatol Surg Res 99 (1, Suppl.) (2013 Feb) S160–S170. • M Paddock, A Sprigg, AC Offiah, Imaging and reporting considerations for suspected physical abuse (non-accidental injury) in infants and young children. Part 2: axial skeleton and differential diagnoses, Clin Radiol 72 (3) (2017 Mar) 189–201. • R Moverley, N Little, A Gulihar, B Singh, Current concepts in the management of clavicle fractures, J Clin Orthop Trauma, 11 (2020) S25–S30. • SE Sheehan, G Gaviola, A Sacks, R Gordon, LL Shi, SE Smith, Traumatic shoulder injuries: a force mechanism analysis of complex injuries to the shoulder girdle and proximal humerus, Am J Roentgenol 201 (3) (2013 Sep) W409–W424. • AM Ropp, DL Davis, Scapular fractures: what radiologists need to know, Am J Roentgenol 205 (3) (2015 Sep) 491–501. • SE Sheehan, GS Dyer, AD Sodickson, KI Patel, B Khurana, Traumatic elbow injuries: what the orthopedic surgeon wants to know, Radiographics 33 (3) (2013 May) 869–888. • T Pope, H Bloem, J Beltran, W WD Morrison, Acute osseous injury to the wrist, in: Musculoskeletal imaging, second ed., Elsevier Saunders, Philadelphia, PA, 2014, p. 185. • LR Scalcione, LH Gimber, AM Ho, SS Johnston, JE Sheppard, MS Taljanovic, Spectrum of carpal dislocations and fracture-dislocations: imaging and management, Am J Roentgenol (2014) 541–550. • SE Sheehan, JY Shyu, MJ Weaver, AD Sodickson, B Khurana, Proximal femoral fractures: what the orthopedic surgeon wants to know, Radiographics 35 (5) (2015 Sep) 1563–1584. • BK Markhardt, JM Gross, JUV Monu, Schatzker classification of tibial plateau fractures: use of CT and MR imaging improves assessment, Radiographics 29 (2) (2009 Mar) 585–597. • NG Lasanianos, NK Kanakaris, Ankle fractures, in: Trauma and Orthopaedic Classifications: A Comprehensive Overview, Springer-Verlag, London, 2015, pp. 367–370.
References [1] Food and Drug Administration, Guidance Document for Industry and CDRH Staff for the Preparation of Investigational Device Exemptions and Premarket Approval Applications for Bone Growth Stimulator Devices, Office of the Federal Register, National Archives and Records Administration, United States, 1998, 63, 23292-3 FR 23292. [2] H Knipe, A Rezaee, Fracture non-union: radiopaedia reference article. Available from: https://radiopaedia.org/articles/fracture-nonunion-1?lang=gb.
[3] MD Crane, Complex regional pain syndrome, JAAPA 32 (9) (2019) 51–52. 10.1097/01.JAA.0000578792.77298.8a. [4] SE Rand, S Basu, S Khalid, Complex regional pain syndrome: current diagnostic and treatment considerations, Curr Sports Med Rep 18 (9) (2019) 325–329. 10.1249/JSR.0000000000000633. [5] Y Nishida, Y Saito, T Yokota, T Kanda, H Mizusawa, Skeletal muscle MRI in complex regional pain syndrome, Intern Med 48 (4) (2009) 209–212. 10.2169/internalmedicine.48.1611. [6] F Kozin, JS Soin, LM Ryan, GF Carrera, RL Wortmann, Bone scintigraphy in the reflex sympathetic dystrophy syndrome, Radiology 138 (2) (1981) 437–443. 10.1148/radiology.138.2.7455127. [7] KN Shah, J Racine, LC Jones, RK Aaron, Pathophysiology and risk factors for osteonecrosis, Curr Rev Musculoskelet Med 8 (3) (2015 Sep) 201–209. [8] AO Spine Classifications Systems. Available from: https://aospine.aofoundation.org/clinical-library-and-tools/aospineclassification-systems. [9] JY Lee, AR Vaccaro, MR Lim, FC Oner, R John Hulbert, R Hedlund, et al., Thoracolumbar injury classification and severity score: a new paradigm for the treatment of thoracolumbar spine trauma, J Orthop Sci 10 (6) (2005 Nov) 671–675. [10] F Denis, Updated classification of thoracolumbar fractures, Orthop Trans 6 (8) (1982) 41–48. [11] Spinal Injury: Assessment and Initial Management, NICE guideline [NG41], 17 Feb 2016. [12] L Lenchik, LF Rogers, PD Delmas, HK Genant, Diagnosis of osteoporotic vertebral fractures: importance of recognition and description by radiologists, AJR Am J Roentgenol 183 (4) (2004) 949–958. [13] WP Shuman, JV Rogers, ME Sickler, JA Hanson, JP Crutcher, HA King, et al., Thoracolumbar burst fractures: CT dimensions of the spinal canal relative to postsurgical improvement, AJR Am J Roentgenol 145 (2) (1985) 337–341. [14] JM Davis, DP Beall, C Lastine, C Sweet, J Wolff, D Wu, Chance fracture of the upper thoracic spine, AJR Am J Roentgenol 183 (5) (2004) 1475–1478. [15] C Cooper, EM Dennison, HG Leufkens, N Bishop, TI. .v.a.n Staa, Epidemiology of childhood fractures in Britain: a study using the general practice research database, J Bone Miner Res 19 (12) (2004) 1976–1981.
[16] EM Hedström, O Svensson, U Bergström, P Michno, Epidemiology of fractures in children and adolescents, Acta Orthop 81 (1) (2010 Feb 1) 148–153. [17] T Mizuta, WM Benson, BK Foster, LL Morris, Statistical analysis of the incidence of physeal injuries, J Pediatr Orthop 7 (5) (1987 Oct) 518–523. [18] SJ Lombardo, JP Harvey, Fractures of the distal femoral epiphyses: factors influencing prognosis: a review of thirty-four cases, J Bone Joint Surg Am 59 (6) (1977 Sep) 742–751. [19] AM Eid, MA Hafez, Traumatic injuries of the distal femoral physis: retrospective study on 151 cases, Injury 33 (3) (2002 Apr) 251–255. [20] B Patel, M Reed, S Patel, Gender-specific pattern differences of the ossification centers in the pediatric elbow, Pediatr Radiol 39 (3) (2009 Mar) 226–231. [21] JC Cheng, K Wing-Man, WY Shen, H Yurianto, G Xia, JT Lau, et al., A new look at the sequential development of elbowossification centers in children, J Pediatr Orthop 18 (2) (1998 Apr) 161–167. [22] CS Miyazaki, DA Maranho, PM Agnollitto, MH NogueiraBarbosa, Study of secondary ossification centers of the elbow in the brazilian population, Acta Ortop Bras 25 (6) (2017 Dec) 279–282. [23] SJ Goodwin, LJ Irwin, GJ Irwin, Gender differences in the order of appearance of elbow ossification centres, Scott Med J 64 (1) (2019) 2–9. [24] A Peiro, T Mur, J Aracil, F Martos, Fracture-separation of the lower humeral epiphysis in young children, Acta Orthop Scand 52 (3) (1981 Jan) 295–298. [25] EM Manoff, MB Banffy, JJ Winell, Relationship between body mass index and slipped capital femoral epiphysis, J Pediatr Orthop 25 (6) (2005 Dec) 744–746. [26] D Puylaert, A Dimeglio, T Bentahar, Staging puberty in slipped capital femoral epiphysis: importance of the triradiate cartilage, J Pediatr Orthop 24 (2) (2004 Apr) 144–147. [27] MM Witbreuk, BJ van Royen, FJ Van Kemenade, BI Witte, JA van der Sluijs, Incidence and gender differences of slipped capital femoral epiphysis in the Netherlands from 1998–2010 combined with a review of the literature on the epidemiology of SCFE, J Child Orthop 7 (2) (2013 Mar) 99–105. [28] Y Noguchi, T Sakamaki, Multicenter Sutdy Commitee of the Japanese Pediatric Orthopaedic Association. Epidemiology and demographics of slipped capital femoral epiphysis in Japan: a multicenter study by the Japanese Paediatric Orthopaedic
Association, J Orthop Sci Off J Jpn Orthop Assoc 7 (6) (2002) 610– 617. [29] LI Hansson, G Hägglund, G Ordeberg, Slipped capital femoral epiphysis in southern Sweden 1910–1982, Acta Orthop Scand Suppl 226 (1987) 1–67. [30] G Hägglund, LI Hansson, G Ordeberg, Epidemiology of slipped capital femoral epiphysis in southern Sweden, Clin Orthop (191) (1984 Dec) 82–94. [31] EH Dykes, Paediatric trauma, BJA Br J Anaesth 83 (1) (1999 Jul 1) 130–138. [32] Faculty of Clinical Radiology. Paediatric trauma protocols [Internet]. [cited 2014 Oct 4]. Available from: http://www.rcr.ac.uk/publications.aspx? PageID=310&PublicationID=412. [33] EL Willner, HA Jackson, AL Nager, Delayed diagnosis of injuries in pediatric trauma: the role of radiographic ordering practices, Am J Emerg Med 30 (1) (2012 Jan) 115–123. [34] B Kessel, J Dagan, F Swaid, I Ashkenazi, O Olsha, K Peleg, et al., Rib fractures: comparison of associated injuries between pediatric and adult population, Am J Surg 208 (5) (2014 Nov) 831– 834. [35] WF.M Jackson, TN Theologis, CL.M.H Gibbons, S Mathews, G Kambouroglou, Early management of pathological fractures in children, Injury 38 (2) (2007 Feb 1) 194–200. [36] EJ Ortiz, MH Isler, JE Navia, R Canosa, Pathologic fractures in children, Clin Orthop Relat Res 432 (2005 Mar) 116–126. [37] KH Teoh, AC Watts, Y-H Chee, R Reid, DE Porter, Predictive factors for recurrence of simple bone cyst of the proximal humerus, J Orthop Surg Hong Kong 18 (2) (2010 Aug) 215–219. [38] J Labbé, Ambroise Tardieu: the man and his work on child maltreatment a century before Kempe, Child Abuse Negl 29 (4) (2005 Apr 1) 311–324. [39] J Caffey, Multiple fractures in the long bones of infants suffering from chronic subdural hematoma, Am J Roentgenol Radium Ther 56 (2) (1946 Aug) 163–173. [40] CH Kempe, FN Silverman, BF Steele, W Droegemueller, HK Silver, The battered-child syndrome, JAMA 181 (1) (1962 Jul 7) 17–24. [41] PK Kleinman, JM Perez-Rossello, AW Newton, HA Feldman, PL Kleinman, Prevalence of the classic metaphyseal lesion in infants at low versus high risk for abuse, Am J Roentgenol 197 (4) (2011 Oct 1) 1005–1008.
[42] A Tsai, B Coats, PK Kleinman, Biomechanics of the classic metaphyseal lesion: finite element analysis, Pediatr Radiol 47 (12) (2017 Nov 1) 1622–1630. [43] PK Kleinman, SC Marks, B Blackbourne, The metaphyseal lesion in abused infants: a radiologic-histopathologic study, AJR Am J Roentgenol 146 (5) (1986 May) 895–905. [44] RA.C Bilo, SG.F Robben, RR van Rijn, Forensic Aspects of Pediatric Fractures: Differentiating Accidental Trauma from Child Abuse [Internet], Springer-Verlag, Berlin Heidelberg, 2010, [cited 2020 Dec 11]. Available from:. https://www.springer.com/gp/book/ 9783540787150. [45] PK Kleinman, Diagnostic Imaging of Child Abuse, Cambridge University Press, Cambridge, 2015, 755. [46] PK Kleinman, SC Marks, A regional approach to classic metaphyseal lesions in abused infants: the distal tibia, Am J Roentgenol 166 (5) (1996 May 1) 1207–1212. [47] B Karmazyn, MB Marine, MR Wanner, D Sağlam, SG Jennings, RA Hibbard, Establishing signs for acute and healing phases of distal tibial classic metaphyseal lesions, Pediatr Radiol 50 (5) (2020 May 1) 715–725. [48] AM Grayev, DK.B Boal, DM Wallach, LS Segal, Metaphyseal fractures mimicking abuse during treatment for clubfoot, Pediatr Radiol 31 (8) (2001 Aug 1) 559–563. [49] GS Lee, ST Methratta, LD Frasier, Classic metaphyseal lesion of distal tibia following footling breech delivery, Pediatr Radiol 49 (13) (2019) 1840–1842. [50] A O’Connell, VB Donoghue, Can classic metaphyseal lesions follow uncomplicated caesarean section? Pediatr Radiol 37 (5) (2007 May) 488–491. [51] JT Lysack, D Soboleski, Classic metaphyseal lesion following external cephalic version and cesarean section, Pediatr Radiol 33 (6) (2003 Jun 1) 422–424. [52] T Sieswerda-Hoogendoorn, R Rijn, S Robben, Classic metaphyseal lesion following vaginal breech birth, a rare birth trauma, J Forensic Radiol Imaging 2 (1) (2013 Jan 1) 2–4. [53] PA Culotta, LR Burge, AN Bachim, M Donaruma-Kwoh, Are classic metaphyseal lesions pathognomonic for child abuse? Two cases of motor vehicle collision-related extremity CML and a review of the literature, J Forensic Leg Med 74 (2020 Aug 1) 102006. [54] JD Thackeray, J Wannemacher, BH Adler, DM Lindberg, The classic metaphyseal lesion and traumatic injury, Pediatr Radiol 46 (8) (2016 Jul 1) 1128–1133.
[55] NK Pandya, K Baldwin, H Wolfgruber, CW Christian, DS Drummond, HS Hosalkar, Child abuse and orthopaedic injury patterns: analysis at a level I pediatric trauma center, J Pediatr Orthop 29 (6) (2009 Sep) 618–625. [56] AM Kemp, F Dunstan, S Harrison, S Morris, M Mann, K Rolfe, et al., Patterns of skeletal fractures in child abuse: systematic review, BMJ 337 (2008 Oct 2) a1518. [57] NK Pandya, KD Baldwin, H Wolfgruber, DS Drummond, HS Hosalkar, Humerus fractures in the pediatric population: an algorithm to identify abuse, J Pediatr Orthop Part B 19 (6) (2010 Nov) 535–541. [58] K Baldwin, NK Pandya, H Wolfgruber, DS Drummond, HS Hosalkar, Femur fractures in the pediatric population: abuse or accidental trauma?, Clin Orthop 469 (3) (2011 Mar) 798–804. [59] S Llorente Pelayo, J Rodríguez Fernández, MT Leonardo Cabello, M Rubio Lorenzo, MD García Alfaro, C Arbona Jiménez, Current diagnosis and management of toddler’s fracture, An Pediatría Engl Ed 92 (5) (2020 May 1) 262–267. [60] B Bulloch, CJ Schubert, PD Brophy, N Johnson, MH Reed, RA Shapiro, Cause and clinical characteristics of rib fractures in infants, Pediatrics 105 (4) (2000 Apr 1) e48. [61] SC Shelmerdine, D Langan, JC Hutchinson, M Hickson, K Pawley, J Suich, et al., Chest radiographs versus CT for the detection of rib fractures in children (DRIFT): a diagnostic accuracy observational study, Lancet Child Adolesc Health 2 (11) (2018) 802–811. [62] JD Ingram, J Connell, TC Hay, JD Strain, T Mackenzie, Oblique radiographs of the chest in nonaccidental trauma, Emerg Radiol 7 (1) (2000 Mar 1) 42–46. [63] KK Hansen, JS Prince, GW Nixon, Oblique chest views as a routine part of skeletal surveys performed for possible physical abuse: is this practice worthwhile?, Child Abuse Negl 32 (1) (2008 Jan 1) 155–159. [64] A Anilkumar, LJ Fender, NJ Broderick, JM Somers, KE Halliday, The role of the follow-up chest radiograph in suspected non-accidental injury, Pediatr Radiol 36 (3) (2006 Mar 1) 216–218. [65] I Franke, A Pingen, H Schiffmann, M Vogel, D Vlajnic, R Ganschow, et al., Cardiopulmonary resuscitation (CPR)-related posterior rib fractures in neonates and infants following recommended changes in CPR techniques, Child Abuse Negl 38 (7) (2014 Jul) 1267–1274. [66] JA Reyes, GR Somers, GP Taylor, DA Chiasson, Increased incidence of CPR-related rib fractures in infants: is it related to
changes in CPR technique? Resuscitation 82 (5) (2011 May) 545– 548. [67] PS Martin, MD Jones, SA Maguire, PS Theobald, AM Kemp, Increased incidence of CPR-related rib fractures in infants: is it related to changes in CPR technique?, Resuscitation 83 (4) (2012 Apr 1) e109. [68] MR Spevak, PK Kleinman, PL Belanger, C Primack, JM Richmond, Cardiopulmonary resuscitation and rib fractures in infants. A postmortem radiologic-pathologic study, JAMA 272 (8) (1994 Aug 24) 617–618. [69] S Maguire, M Mann, N John, B Ellaway, JR Sibert, AM Kemp, et al., Does cardiopulmonary resuscitation cause rib fractures in children? A systematic review, Child Abuse Negl 30 (7) (2006 Jul) 739–751. [70] KW Feldman, DK Brewer, Child abuse, cardiopulmonary resuscitation, and rib fractures, Pediatrics 73 (3) (1984 Mar) 339– 342. [71] I Prosser, S Maguire, SK Harrison, M Mann, JR Sibert, AM Kemp, How old is this fracture? Radiologic dating of fractures in children: a systematic review, Am J Roentgenol 184 (4) (2005 Apr 1) 1282–1286. [72] KE Halliday, NJ Broderick, JM Somers, R Hawkes, Dating fractures in infants, Clin Radiol 66 (11) (2011 Nov 1) 1049–1054. [73] Subperiosteal new bone and callus formations in neonates with femoral shaft fracture at birth | SpringerLink [Internet]. [cited 2020 Dec 10]. Available from: https://link.springer.com/article/10.1007%2Fs10140-016-1462-6. [74] LI Yeo, MH Reed, Staging of healing of femoral fractures in children, Can Assoc Radiol J 45 (1) (1994 Feb) 16–19. [75] T Hosokawa, Y Yamada, Y Sato, Y Tanami, E Oguma, Subperiosteal new bone and callus formations in neonates with femoral shaft fracture at birth, Emerg Radiol 24 (2) (2017 Apr 1) 143–148. [76] O Islam, D Soboleski, S Symons, LK Davidson, MA Ashworth, P Babyn, Development and duration of radiographic signs of bone healing in children, Am J Roentgenol 175 (1) (2000 Jul 1) 75–78. [77] I Prosser, Z Lawson, A Evans, S Harrison, S Morris, S Maguire, et al., A timetable for the radiologic features of fracture healing in young children, Am J Roentgenol 198 (5) (2012 May 1) 1014– 1020. [78] WA Cumming, Neonatal skeletal fractures. Birth trauma or child abuse?, J Can Assoc Radiol 30 (1) (1979 Mar) 30–33.
[79] CE Shopfner, Periosteal bone growth in normal infants, Am J Roentgenol 97 (1) (1966 May 1) 154–163. [80] B Marti, D Sirinelli, L Maurin, E Carpentier, Wormian bones in a general paediatric population, Diagn Interv Imaging 94 (4) (2013 Apr 1) 428–432. [81] B Cremin, H Goodman, J Spranger, P Beighton, Wormian bones in osteogenesis imperfecta and other disorders, Skeletal Radiol 8 (1) (1982 Mar 1) 35–38. [82] PG Mulugeta, M Jordanov, M Hernanz-Schulman, C Yu, JH Kan, Determination of osteopenia in children on digital radiography compared with a DEXA reference standard, Acad Radiol 18 (6) (2011 Jun) 722–725. [83] J Allgrove, N Shaw, Calcium and Bone Disorders in Children and Adolescents, second ed., 2015, 1. [84] P Arundel, SF Ahmed, J Allgrove, NJ Bishop, CP Burren, B Jacobs, et al., British Paediatric and Adolescent Bone Group’s position statement on vitamin D deficiency, BMJ 345 (2012 Dec 3) e8182. [85] PR Joseph, W Rosenfeld, Clavicular fractures in neonates, Am J Dis Child 1960 144 (2) (1990 Feb) 165–167. [86] ES Ahn, MS Jung, YK Lee, SY Ko, SM Shin, MH Hahn, Neonatal clavicular fracture: recent 10 year study, Pediatr Int 57 (1) (2015) 60–63. [87] HA Choi, YK Lee, SY Ko, SM Shin, Neonatal clavicle fracture in cesarean delivery: incidence and risk factors, J Matern-Fetal Neonatal Med 30 (14) (2017 Jul) 1689–1692. [88] YF Awadef, NI Abdelsalam, SA taha, EA Mohamed, MA Hassan, SS Abouhashim, Risk variables of neonatal clavicular fracture and the role of ultrasound in its diagnosis, Neonatal Pediatr Med [Internet] 4 (2) (2018) 160, [cited 2020 Dec 10]. Available from:. https://www.omicsonline.org/open-access/risk-variables-ofneonatal-clavicular-fracture-and-the-role-of-ultrasound-in-itsdiagnosis-2572-4983-1000160-103275.html. [89] MM Walters, PW Forbes, C Buonomo, PK Kleinman, Healing patterns of clavicular birth injuries as a guide to fracture dating in cases of possible infant abuse, Pediatr Radiol 44 (10) (2014 Oct 1) 1224–1229. [90] A Basha, Z Amarin, F Abu-Hassan, Birth-associated long-bone fractures, Int J Gynecol Obstet 123 (2) (2013 Nov 1) 127–130. [91] N Linder, I Linder, E Fridman, F Kouadio, D Lubin, P Merlob, et al., Birth trauma: risk factors and short-term neonatal outcome, J Matern Fetal Neonatal Med 26 (15) (2013 Oct 1) 1491–1495.
[92] R Kancherla, SR Sankineani, S Naranje, L Rijal, R Kumar, T Ansari, et al., Birth-related femoral fracture in newborns: risk factors and management, J Child Orthop 6 (3) (2012 Jun 1) 177– 180. [93] RR van Rijn, RA.C Bilo, SG.F Robben, Birth-related midposterior rib fractures in neonates: a report of three cases (and a possible fourth case) and a review of the literature, Pediatr Radiol 39 (1) (2009 Jan 1) 30–34. [94] NA Khan, V Lam, A Rickett, F Dickinson, Unforeseen rib fracture findings in infant chest radiographs: evidence of nonaccidental injury or simply a case of birth trauma?, BMJ Case Rep [Internet] (2016 Jun 30), [cited 2020 Dec 12]; 2016. Available from:. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4932391/. [95] MG Levine, J Holroyde, JR Woods, TA Siddiqi, M Scott, M Miodovnik, Birth trauma: incidence and predisposing factors, Obstet Gynecol 63 (6) (1984 Jun) 792–795. [96] R Moverley, N Little, A Gulihar, B Singh, Current concepts in the management of clavicle fractures, J Clin Orthop Trauma. 11 (2020) S25–S30. [97] J Holder, S Kolla, S Lehto, Clavicle fractures: Allman and Neer classification, J Adv Radiol Med Imaging 2 (1) (2017 Jan). [98] SE Sheehan, G Gaviola, A Sacks, R Gordon, LL Shi, SE Smith, Traumatic Shoulder injuries: a force mechanism analysis of complex injuries to the shoulder girdle and proximal humerus, Am J Roentgenol 201 (3) (2013 Sep 23) W409–W424. [99] CS Restrepo, S Martinez, DF Lemos, L Washington, HP McAdams, D Vargas, et al., Imaging appearances of the sternum and sternoclavicular joints, Radiographics 29 (3) (2009 May 1) 839–859. [100] F Alyas, M Curtis, C Speed, A Saifuddin, D Connell, MR imaging appearances of acromioclavicular joint dislocation, Radiographics 28 (2) (2008 Mar) 463–479. [101] AM Ropp, DL Davis, Scapular fractures: what radiologists need to know, Am J Roentgenol 205 (3) (2015 Sep 1) 491–501. [102] CK Sandstrom, SA Kennedy, JA Gross, Acute shoulder trauma: what the surgeon wants to know, Radiographics 35 (2) (2015 Mar 12) 475–492. [103] AL Chen, SA Hunt, RJ Hawkins, JD Zuckerman, Management of bone loss associated with recurrent anterior glenohumeral instability, Am J Sports Med 33 (6) (2005 Jun) 912–925. [104] CM Court-Brown, B Caesar, Epidemiology of adult fractures: a review, Injury 37 (8) (2006 Aug) 691–697.
[105] SE Sheehan, GS Dyer, AD Sodickson, KI Patel, B Khurana, Traumatic elbow injuries: what the orthopedic surgeon wants to know, Radiographics 33 (3) (2013 May 3) 869–888. [106] T Pope, H Bloem, J Beltran, WD Morrison, Acute osseous injury of the elbow and forearm, Musculoskeletal Imaging, second ed., Elsevier Saunders, Philadelphia, PA, 2014, 149. [107] JA Porrino, E Maloney, K Scherer, H Mulcahy, AS Ha, C Allan, Fracture of the distal radius: epidemiology and premanagement radiographic characterization, Am J Roentgenol 203 (3) (2014 Sep 1) 551–559. [108] T Pope, H Bloem, J Beltran, WD Morrison, Chapter 14: acute osseous injury to the wrist, Musculoskeletal Imaging, 2nd ed., Elsevier Saunders, Philadelphia (PA), 2014, 185. [109] R Kaewlai, LL Avery, AV Asrani, HH Abujudeh, R Sacknoff, RA Novelline, Multidetector CT of carpal injuries: anatomy, fractures, and fracture-dislocations, Radiographics 28 (6) (2008 Oct 1) 1771–1784. [110] LR Scalcione, LH Gimber, AM Ho, SS Johnston, JE Sheppard, MS Taljanovic, Spectrum of carpal dislocations and fracturedislocations: imaging and management, Am J Roentgenol (2014) 541–550. [111] MD Weintraub, BG Hansford, SE Stilwill, H Allen, RL Leake, CJ Hanrahan, et al., Avulsion injuries of the hand and wrist, Radiographics 40 (1) (2020 Jan 1) 163–180. [112] SE Sheehan, JY Shyu, MJ Weaver, AD Sodickson, B Khurana, Proximal femoral fractures: what the orthopedic surgeon wants to know, Radiographics 35 (5) (2015 Sep 1) 1563–1584. [113] BJ Tins, M Garton, VN Cassar-Pullicino, PN.M Tyrrell, R Lalam, J Singh, Stress fracture of the pelvis and lower limbs including atypical femoral fractures: a review, Insights Imaging 6 (1) (2015) 97–110. [114] R Esteves, S Pires, Subtrochanteric fractures of the femur: update Paulo Roberto Barbosa de Toledo Lourenc, Rev Bras Ortop 1 (3) (2016) 246–253. [115] A Koh, E Guerado, PV Giannoudis, Atypical femoral fractures related to bisphosphonate treatment, Bone Jt J 99B (3) (2017 Mar 1) 295–302. [116] FW Gwathmey, SM Jones-Quaidoo, D Kahler, S Hurwitz, Q Cui, Distal femoral fractures: current concepts, J Am Acad Orthop Surg 18 (10) (2010) 597–607. [117] M Ehlinger, G Ducrot, P Adam, F Bonnomet, Distal femur fractures. Surgical techniques and a review of the literature, Orthop
Traumatol Surg Res 99, 2013, 353–360. [118] Y Oohashi, T Koshino, Y Oohashi, Clinical features and classification of bipartite or tripartite patella, Knee Surg Sport Traumatol Arthrosc 18 (11) (2010 Nov 29) 1465–1469. [119] BK Markhardt, JM Gross, JU.V Monu, Schatzker classification of tibial plateau fractures: use of CT and MR imaging improves assessment, Radiographics 29 (2) (2009 Mar 1) 585–597. [120] JJ Hermans, A Beumer, TA.W De Jong, GJ Kleinrensink, Anatomy of the distal tibiofibular syndesmosis in adults: a pictorial essay with a multimodality approach, J Anat 217 (6) (2010 Dec) 633–645. [121] NG Lasanianos, NK Kanakaris, Ankle fractures, Trauma and Orthopaedic Classifications: A Comprehensive Overview, SpringerVerlag Ltd, London, 2015, 367–370. [122] YS Lee, SW.S.H Chen, SW.S.H Chen, WC Chen, MJ Lau, TL Hsu, Stabilisation of the fractured fibula plays an important role in the treatment of pilon fractures: a retrospective comparison of fibular fixation methods, Int Orthop 33 (3) (2009 Jun) 695–699. [123] BD Crist, M Khazzam, YM Murtha, JD.R Gregory, Pilon fractures: Advances in surgical management, J Am Acad Orthop Surg 19 (10) (2011) 612–622. [124] T Tosounidis, R Buckley, Calcaneus fractures, Orthopedic Traumatology: An Evidence-Based Approach, Springer, New York, 2013, 359–371. [125] BS Sivakumar, VV.G An, C Oitment, M Myerson, Subtle lisfranc injuries: a topical review and modification of the classification system, Orthopedics 41 (2) (2018 Mar 1) e168–e175. [126] RB Verma, O Sherman, Athletic stress fractures: part I. History, epidemiology, physiology, risk factors, radiography, diagnosis, and treatment, Am J Orthop, 30 (11) (2001) 798–806.
CHAPTER 88
Neuro, Head, and Neck Trauma Curtis Offiah, Mervyn Chong
Introduction Trauma to the head and neck region is a frequent cause of emergency department (ED) attendance with over 2.5 million ED visits for head trauma in the United States in 2014 [1]. The spectrum of potential injuries in this region is vast including osseous, soft tissue, and vascular injury. Imaging plays a major role in the diagnosis of these injuries and knowledge of imaging strategies, typical patterns of injury, radiological findings, and associated complications are vital for the reporting radiologist. Multidetector computed tomography (MDCT) is the primary technique in imaging of acute neuro/head and neck trauma with scanning protocols depending on the traumatic mechanism and briefly described below. For intracranial injury and skull fractures, noncontrast head CT with thin axial slices and multiplanar reformats are standard. For suspected facial bone fractures noncontrast facial CT is first-line (with or without the inclusion of intracranial imaging). Noncontrast CT cervical spine is performed for suspected cervical spine trauma. The indications for CT head examination for head and cervical spine injury in adults in the UK are generally taken from guidance by the National Institute for Health and Clinical Excellence (NICE) [2]. The American College of Radiology (ACR) appropriateness criteria cite the Nexus Criteria and Canadian Cervical Spine rule in their guidance for cervical spine imaging [3]. The ACR appropriateness criteria for imaging in head trauma refer to the use of a validated clinical decision rule as a criterion for imaging, of which the most well-known is the New Orleans Criteria and Canadian CT Head Rule [4]. CT angiography (CTA) of the neck with or without extension to the vertex is utilized in penetrating neck trauma to assess for vascular injury. CTA is
also used in screening for blunt cerebrovascular injury (BCVI). MR angiogram occasionally may be used instead of CT angiogram but may be challenging in intubated and ventilated patients outside major trauma units where specialized adapted magnetic resonance imaging (MRI)-compatible anaesthetic equipment may not be available. Brain MRI is particularly useful as a second-line investigation in neurotrauma where there is a concern for traumatic axonal injury (TAI) and in assisting prognostication. Haem-sensitive sequences such as gradient echo and susceptibility-weighted imaging (SWI) are especially beneficial in demonstrating the hemosiderin staining associated with hemorrhagic TAI, the extent and severity of which is generally under-represented on CT. The use of more specialized MR techniques such as cisternography may be performed in the assessment for cerebrospinal fluid (CSF) leak, a frequent concern in fracture of the skull base. MRI is the imaging technique of choice for assessment of the soft tissues in spinal trauma, demonstrating ligamentous and spinal cord injury, and intraspinal hematoma. MRI is also beneficial in discerning marrow edema of a recent vertebral fracture.
Intracranial Trauma Introduction Intracranial trauma encompasses a number of injury patterns that can be considered as intra-axial or extra-axial injuries. Secondary injuries may also occur including brain herniation, infarction, and hydrocephalus. Intracranial vascular injury represents another important area of consideration.
Imaging Approach Nonenhanced head CT remains the imaging technique of the first choice in suspected traumatic brain injury, and early follow-up due to its speed, accessibility, higher sensitivity for fracture (allowing earlier identification of fracture complications), and no limitation in terms of screening for MRI contraindications such as metallic foreign body [5]. It is generally advised that CT protocols utilize MDCT with axial views acquired from the vertex to the foramen magnum. Liberal use of multiplanar reformats of bone algorithms as well as volume-rendered reconstructions are recommended in the evaluation of pediatric trauma, particularly in the setting of suspected abusive head trauma. When imaging of the facial bones is required the CT acquisition is extended to include the facial bones and/or mandible as required. Facial bone reformats are configured in coronal and
sagittal plane in thin-section (1 mm) aligned to the hard palate, with a bone algorithm applied. Multiplanar facial soft tissue reformats are also performed.
Injury Type and Findings Extradural Hematoma (EDH) These hematomas arise within the extradural space, between the superficial layer of the dura mater, and the inner table of the skull (Figs. 88.1 and 88.2). They may be arterial or venous in origin, classically have a biconvex or “lentiform” contour and are of high density (representing acute clot). A “swirl sign” (Fig. 88.1) is described where there is low density mixed within the hematoma and is suggestive of active hemorrhage [6]. The mass effect from the hematoma typically displaces the lateral ventricles to the contralateral side, there is frequently swelling of the ipsilateral cerebral hemisphere.
FIGURE 88.1 20-year-old male who suffered an alleged punch to the face and resultant accelerated fall striking head on the ground. (A) CT scan demonstrates a large right acute extradural hematoma (white arrow). Note the areas of unclotted blood within the extradural hematoma (black arrow) consistent with active bleeding—the so-called “swirl sign”; there is severe mass effect with midline shift and subfalcine herniation to the left. (B) The bone reconstructions demonstrate a fracture (magnified and highlighted with white arrow) which extended through a right middle meningeal artery branch vascular channel in the squamous temporal bone.
FIGURE 88.2 56-year-old male who fell from standing sustaining head injury. (A) CT scan demonstrating right parietal acute extradural hematoma (long black arrow) with some locules of gas within the hematoma (short black arrows) related to underlying skull base fracture extension. Associated scalp soft tissue hematoma evident (white arrow). (B) Associated comminuted fractures through the right lateral skull base (white arrows) and secondary pneumocephalus (short black arrows).
A pterional extradural hematoma is generally of arterial origin and is caused by injury to the middle meningeal artery by overlying skull fracture (Fig. 88.1B). Venous extradural hematomas may also be seen in fractures that cross a dural venous sinus. Injury to the superior sagittal sinus or sphenoparietal sinus may result in a venous extradural hematoma at the vertex or an anterior temporal pole (anterior middle cranial fossa) extradural hematoma, respectively. Posterior fossa venous EDH may occur with injury to the transverse or sigmoid sinuses or the jugular bulb and is associated with a risk of brainstem and fourth ventricle compression and obstructive hydrocephalus. An identifying feature of EDH is that they do not cross cranial sutures. This is due to the superficial dura being strongly adherent to the inner table of the calvarium at the suture sites [7]. The rare exception to this rule is where the suture itself is involved by a fracture [5]. Extradural hematomas do, however, cross the midline, e.g. when they are overlying the falx cerebri/interhemispheric fissure and superior sagittal sinus (in contrast to subdural hematomas, as later described). The treatment of EDH is with surgical evacuation. In occasional cases, smaller EDHs may potentially be treated with middle meningeal arterial embolization [8]. Anterior temporal EDH specifically, however, has a benign course and does not generally require surgery [9].
Subdural Hematoma (SDH) Subdural hematomas arise between the dura and arachnoid mater. These are characteristically crescentic in shape, moulding to the contour of the underlying cerebral convexity (Fig. 88.3). The vessel of origin is usually a bridging cortical vein as it crosses the dura. There is often associated swelling of the underlying brain parenchyma. In contrast to extradural hematomata, subdural hematomas do cross suture lines. SDHs, however, do not cross dural reflections, such as the falx cerebri or the tentorium [7]. Caution is advised as not all acute subdural hematomas exhibit the classical crescentic morphology (Fig. 88.4).
FIGURE 88.3 73-year-old female with bilateral acute subdural hematomas related to the left (white arrow) and right (black arrows) cerebral hemispheres, larger on the left demonstrated on CT scan. The left subdural hematoma (white arrow) exhibits some mixed density with features suggestive of acute hemorrhage into pre-existing older chronic sudural hematoma but similar appearances can be seen with underlying coagulopathy.
FIGURE 88.4 83-year-old male who sustained a fall striking the left side of the head (short arrow) resulting in contrecoup right cerebral hemispheric convexity subdural hematoma (black arrows) demonstrated on CT scan—note that acute subdural hematoma may not always exhibit the crescentic morphology in their entirety (thick black arrow).
As SDHs mature from acute to chronic, they change in density due to maturation of blood products from hyper- to hypo-dense (Fig. 88.3). While “acute-on-chronic” SDH may result in mixed attenuation characteristics (often from rehemorrhage from internal membranes of granulation tissue), low-density contents can be seen in the hyperacute phase before clot formation, in severe anaemia, in pre-existing coagulopathic states, or in CSF-blood admixture where there is an associated tear in the arachnoid mater. A more useful feature in identifying chronicity of a SDH is the
identification of internal membranes, which tend to enhance if IV contrast is administered. Chronic SDHs may demonstrate calcification [5]. SDH that requires surgery is treated with evacuation by burr hole drainage or craniotomy. Subdural Hygroma These are collections of CSF within the subdural space that occur as the result of a tear in the arachnoid mater (Fig. 88.5). As with all subdural collections, these cause displacement of the vessels within the subarachnoid space, which allows distinction of these from a prominent subarachnoid space. Subdural hygromas may arise within the first 24 hours of trauma, although their mean time of onset is more delayed at 9 days post injury [10].
FIGURE 88.5 28-year-old male hit by a train. CT scan was performed 24 hours later demonstrating bilateral acute subdural hematomas (long thin black arrows) but evolving shallow hygromatous component is evident over the right frontal lobe convexity (short thick black arrow). Note progressive left frontal hematoma (long thin white arrow) and areas of left parietal acute traumatic subarachnoid hemorrhage (thick white arrow).
A chronic subdural hematoma may have a similar appearance as both this and a hygroma will be of CSF density. A potential distinguishing feature is the absence of internal membranes of granulation tissue within the subdural hygroma but more typically, distinction is possible because of the temporal association with recent significant head injury. Definite differentiation is not always possible and indeed a CSF–blood admixture mix of hygroma and hematoma may be present [5,11]. Traumatic Subarachnoid Hemorrhage
This is hemorrhage occurring within the subarachnoid space between the arachnoid and pia mater. In traumatic subarachnoid hemorrhage (SAH), this generally occurs at the coup or contrecoup site relative to the head impact, is of a small volume, and is sulcal in location (Fig. 88.5). When seen as an isolated finding, traumatic SAH is associated with a lower likelihood of clinical deterioration than when hemorrhage in another compartment is also present [12]. Midline traumatic SAH within the perimesencephalic cisterns and interhemispheric fissure on initial head CT has been shown to be associated with an increased incidence of TAI on follow-up imaging [13]. Traumatic SAH within the interpeduncular and perimesencephalic cisterns increases the possibility of associated brainstem injury [13]. Vasospasm may occur as a delayed complication in traumatic SAH but this is much less frequently seen than in aneurysmal SAH [14]. While uncommon, aneurysmal SAH can be present in a patient presenting with traumatic injury and this should be considered, particularly where there is isolated SAH within the basal cisterns [5]. Intraventricular Hemorrhage Traumatic intraventricular hemorrhage may be a primary finding from a ruptured subependymal vein or secondary extension from either intraparenchymal hematoma or redistributed SAH [5]. Intraventricular hemorrhage within the occipital horns may be of small volume and may be overlooked. The presence of IVH on initial CT head imaging has been shown to correlate with an increased risk of TAI [15]. Parenchymal Contusion Parenchymal contusions may be hemorrhagic or nonhemorrhagic. Hemorrhagic contusions appear as focal intracerebral hemorrhages, often with surrounding edema, while nonhemorrhagic contusions are typically of low density and may appear similar to isolated focal cerebral edema. Contusions typically occur at coup and contrecoup sites. The most common locations are at the inferior frontal and (Fig. 88.6) anterior–inferior temporal lobes due to the impact of the parenchyma against the inner table [5]. Hemorrhagic areas may not be identifiable on CT in the very acute stage. MRI has been found to be more sensitive than CT in identifying contusions, especially smaller and nonhemorrhagic contusions [5,16].
FIGURE 88.6 56-year-old female fell and struck the back of the head resulting in contrecoup left subfrontal and right frontal brain parenchymal hemorrhagic contusions (black arrows) demonstrated on CT scan.
While an initial increase in the size of contusions in the first 48 hours postinjury is frequently present and not unexpected (referred to as “blossoming”), [17] interval evolution of unidentified contusions and/or a doubling in contusion volume on follow-up imaging have been found to be associated with worsened clinical outcomes [18]. Traumatic Axonal Injury (TAI) TAI occurs as a result of tractional or shearing forces on axons. The most susceptible regions of the brain are the white matter tracts and areas of
abrupt change in neuroparenchymal density such as the gray–white matter junction. The terms TAI and diffuse axonal injury (DAI) are frequently used interchangeably although DAI is better reserved for multifocal injuries where there are greater than 3 lesions, and TAI for those cases with 3 or fewer lesions [5,19,20]. TAI can be hemorrhagic or nonhemorrhagic. Most commonly they appear as punctate foci of hemorrhage at characteristic locations such as the gray– white matter junction (particularly the frontal lobe), corpus callosum (with predilection for the splenium) (Fig. 88.7A–E), internal capsules, dorsal midbrain and pons.
FIGURE 88.7 28-year-old male who jumped in front of a train. (A) Acute left subdural hemorrhage (long black arrows), right frontal traumatic subarachnoid hemorrhage (short black arrow) and grade 2 traumatic axonal injury in the splenium of the corpus callosum and septum pellucidum (white arrows). (B) Axial susceptibility-weighted image performed several days after neurosurgical left decompressive craniectomy demonstrates grade 1 and grade 2 traumatic axonal injury (long thin white arrows), as well as blossomed left frontal lobe traumatic intraparenchyma hematoma (short thin white arrow) with surrounding edema and areas of parenchymal hemorrhagic contusions (long thin black arrows).31-year-old male driver of a car that collided with a stationary vehicle at high speed. (C) Axial echo-planar b1000 diffusionweighted image demonstrates grade 2 multifocal traumatic axonal injury —high signal lesions consistent with restricted diffusion typical of early traumatic axonal injury MRI appearances and confirmed on ADC image (D). (E) Susceptibility-weighted imaging of the same patient—multiple hypointense foci, again, in keeping with grade 1 and grade 2 hemorrhagic traumatic axonal injury.
MRI is more sensitive than CT for both hemorrhagic and nonhemorrhagic lesions. Hemorrhagic lesions on MRI are best demonstrated using bloodsensitive sequences such as SWI and T2* (GRE) imaging (Fig. 88.7B and E). Restricted diffusion may be present in acute DAI lesions (Fig. 88.7C and D). TAI is graded from 1 to 3 with a higher grade indicating greater injury severity and has potential prognostic implications. Grades 1–3, respectively, refer to involvement of the subcortical white matter, deep brain parenchyma, typically corpus callosum, and brainstem [21].
TAI is associated with a much greater morbidity and mortality than other intracranial injuries. Management is with close monitoring of intracranial pressure and potential craniectomy to avoid herniation [5]. Diffuse Brain Swelling Diffuse swelling of the brain parenchyma may occur post-trauma and is thought to be due to dysfunction of cerebral autoregulation and/or disruption of the blood–brain barrier [22]. Vascular Injury Multiple vascular injuries can occur as a result of head trauma. These include arterial dissections particularly in skull base fracture, pseudoaneurysm (most commonly of the vertebral artery followed by the anterior cerebral artery), active hemorrhage, arterial occlusion, traumatic carotid-cavernous fistula, traumatic dural arteriovenous fistula, and venous thrombosis (particularly where a fracture crosses a dural venous sinus) [5,23,24]. Cervical spine fractures are the subgroup of nonvascular injuries found to have the greatest association with BCVI [25–27]. Vascular injuries are discussed in more depth in a dedicated section “Blunt Cerebrovascular Injury.” Secondary Brain Injury Herniation from a primary brain injury can lead to secondary complications including cerebrovascular infarction, hydrocephalus, and secondary hemorrhage [5,28–30].
◾against Subfalcine herniation (Fig. 88.8) can cause compression of the anterior cerebral artery the falx cerebri leading to anterior cerebral artery territory infarction and may cause lateral ventricular dilatation/entrapment through occlusion of one of the foramina of Monro ◾compression Downward transtentorial herniation (Fig. 88.9A) can cause posterior cerebral artery and posterior cerebral artery territory infarction (Fig. 88.9B and C), as well as
compressive third nerve palsy with ipsilateral pupillary dilatation (the “blown” pupil). More severe and bilateral downward transtentorial herniation can compress small perforating arteries leading to hypothalamic and basal ganglia infarction Severe cerebellar tonsillar herniation may result in posterior inferior cerebellar artery compression and infarction and can also obstruct the fourth ventricular apertures and secondary hydrocephalus Ascending transtentorial herniation can cause effacement of the quadrigeminal cistern, compression of the midbrain, and hydrocephalus from obstruction of the Sylvian aqueduct Duret hemorrhages (Fig. 88.9A) are secondary midbrain hemorrhages due to severe downward transtentorial herniation
◾ ◾ ◾
FIGURE 88.8 60-year-old male who fell from ladder (and was on antiplatelet therapy). The large volume acute right cerebral hemispheric subdural hematoma (short thin black arrows) is causing severe midline shift with subfalcine herniation (broken white arrow) and right descending transtentorial herniation (again, the direction of which is indicated by the broken white arrow). Note displacement and compressive effect on the third ventricle. Traumatic subarachnoid hemorrhage is also evident (long thin black arrow).
FIGURE 88.9 64-year-old male who sustained a fall admitted following discovery several hours after the fall. (A) CT scan demonstrates large traumatic left temporal lobe parenchymal hematoma with some evolving edema around the hematoma and traumatic left subdural hemorrhage and subarachnoid hemorrhage extending over the vermis. The mass effect associated with the left hemispheric traumatic hemorrhage is causing left uncal herniation (descending transtentorial herniation) (thick black arrow) resulting effacement of the left perimesencephalic cistern and compressive effect on the midbrain with some Duret hemorrhage within the left side of the midbrain (small white arrow). (B) CT scan demonstrates early left posterior cerebral artery ischemia with loss of gray–white matter differentiation (white arrows) resulting from herniation syndrome causing effacement of left perimesencephalic cistern and left posterior cerebral artery compromise. Note the large left acute subdural hemorrhage and traumatic subarachnoid hemorrhage. (C) Early postoperative CT scan following neurosurgical evacuation of the acute subdural hemorrhage with further interval establishing demarcation of the left posterior cerebral artery territory ischemic changes (arrows).22year-old male victim of gunshot injuries to the head. (D) CT scan on soft tissue brain algorithm demonstrates gunshot injury entry wound (curved white arrow) and hemorrhagic bullet wound track through the left frontal lobe (black arrow) with associated extra-axial as well as intra-axial hemorrhage and cranial exit wound (curved broken white arrow) in the left temple region. (E) CT scan on bone algorithm better demonstrates the location of the bullet (broken straight arrow) in relation to the penetrating bullet entry wound and associated skull fractures at entry site (curved arrow). (F) CT scanogram confirms the second penetrating bullet injury of the sinonasal-facial region extracranially with second
deformed bullet evident (straight arrow) in addition to the other cranial bullet (curved arrow).
Penetrating Craniocerebral Trauma This is distinct from blunt cranial trauma. This may take the form of sharp force penetrating injury (e.g., from a knife or axe) or projectile penetrating injury, typically from a gunshot or blast injury (with associated in-driven secondary foreign bodies created by the later mechanism). Such penetrating craniocerebral trauma will require noncontrast CT head for imaging assessment and frequently additional CT angiography may be required in obtunded patients or where there is clear evidence of significant hemorrhagic vascular injury on the noncontrast CT head scan or evidence that the penetrating injury has transgressed more than one lobe or more than one hemisphere. Interrogation of the images on bone windows will greatly assist in identifying, e.g., bullet fragments or broken-off blade tips. In addition, the scanogram (scout) images of the CT scan can also be very useful in identifying bullet fragments and potential additional penetrating injuries that may be extracranial (Fig. 88.9D–F).
Key Points for Intracranial Trauma
◾(extradural, Intracranial hemorrhage can be categorized into extra-axial subdural, subarachnoid, and intraventricular) and intraaxial ◾extradural The “swirl” sign is suggestive of active hemorrhage into an hematoma ◾beSubdural hematomas of mixed density should not automatically assumed to be acute-on-chronic ◾when Isolated SAH is less associated with clinical deterioration than accompanied by another intracranial hemorrhage. Perimesencephalic SAH, however, is associated with a higher incidence of TAI and brainstem injury An increase in the size of parenchymal contusions within 48 hours of injury is not unexpected; however, newly identifiable contusions or doubling in contusion volume are associated with poorer clinical outcomes Secondary brain injury relating to mass effect should be assessed for including ACA and PCA territorial infarction relating to subfalcine and downward transtentorial herniation
◾ ◾
Skull Including the Skull Base Calvarial Fractures The calvarium (or skull vault) comprises the frontal and occipital bones and the paired parietal and temporal bones. Calvarial fractures are seen in both blunt and penetrating trauma. Depression of skull fractures increases the risk of meningeal tear and dural vessel injury. Fractures of the skull vault have been classified as linear, stellate, and depressed, with the majority being linear. On occasion, these can cause diagnostic uncertainty when they simulate or are simulated by normal vascular channels. In general, vascular grooves are less lucent and less sharply marginated, and are seen to branch and make curves rather than sharp angles. Fractures traversing a dural venous sinus or the jugular bulb have been shown in approximately two-thirds of cases to be associated with underlying venous injury, either by compressive extra-axial hematoma, and/or thrombosis [31–34]. Sutures should be inspected for diastasis secondary to fracture extension. Basic skull base anatomy is covered in the dedicated skull base chapter.
Introduction to Skull Base Trauma The skull base is fractured in up to 16% of nonpenetrating head injuries [24,35]. This typically occurs in high-velocity trauma such as motor vehicle accidents. Significant complications associated with skull base fractures are listed in Table 88.1 [24]. The radiologist needs to be able to recognize and report these injuries as their presence is a key factor in decision making regarding skull base fracture management. Table 88.1 Major Associated Complications of Skull Base Fractures [24]
◾Anterior skull base (ASB)
⚬Intraorbital injury⚬Sinonasal CSF leak/meningoencephalocele⚬CN I injury⚬Epistaxis from ethmoidal artery injury
⚬Venous injury⚬Vertebrobasilar injury⚬CN IX–XII injury⚬Craniocervical junction and C spine injury Cranial Nerve.
Anterior Skull Base (ASB) Fractures Anterior skull base fractures are most commonly due to blunt direct trauma to the frontal region. The osseous structures at specific risk are the frontal sinus, cribriform plate, fovea ethmoidalis (Fig. 88.10A), lesser wing of sphenoid, and planum sphenoidale.
FIGURE 88.10 31-year-old male driver in high-speed motor vehicle collision—car versus tree. (A) Coronal CT scan image on bone windows shows severe anterior skull base fracture disruption and traumatic dehiscence (white arrows). (B) Coronal CT scan image demonstrates associated severe frontal/ subfrontal brain parenchymal injury associated with the anterior skull base traumatic disruption and associated traumatic cephalocoele (long thin black arrow). Secondary extra-axial pneumocephalus is present (short black arrows). (C) subsequent early MRI brain scan—coronal T2-weighted image demonstrates the extent of traumatic cephalocoele of traumatized subfrontal brain parenchyma (white arrows) present bilaterally but more marked on the left; the patient had developed CSF leak by this time also. The abnormal subfrontal brain parenchymal signal changes consistent with traumatic damage are also evident (black arrows).
The complications most associated with anterior skull base fractures are intraorbital injuries, sinonasal CSF leak, meningoencephalocele (Fig. 88.10A–C), and olfactory nerve injury. Severe epistaxis is also a potential complication due to injury to the anterior or posterior ethmoid arteries within their foramina in the lateral margins of the ethmoid bone [24]. Olfactory Nerve Injury Fracture of the cribriform plate may involve the olfactory grooves within, leading to olfactory nerve injury and anosmia. This is reported in up to 7% of anterior skull base fractures. Approximately 10% of cases spontaneously recover function in the long term [36]. CSF Leak Traumatic CSF leak has been reported in 10–30% of skull base fractures [24,37,38]. This occurs due to skull base fracture with an associated tear of the underlying dura causing CSF from the subarachnoid space to enter the nasal cavity via the paranasal sinuses. The fluid is usually clear, colorless, and contains glucose. The presentation may be delayed by initial edema and hemorrhage or may occur late due to chronic, progressive, dural breach by fracture fragments [24,39]. The most concerning complication in CSF leak is an increased risk of meningitis from intracranial communication with the sinonasal flora. Most CSF leaks resolve spontaneously with conservative bed rest, head elevation, and stool softeners. Some may require lumbar or external ventricular drainage, and persistent leaks are an indication for surgery [24,40]. Radiological features correlating with a persistent leak likely to require surgical repair include defect size >1.5 cm, severe fracture comminution, and meningoencephalocele [24,41]. Frontal Sinus Frontal bone fractures from a direct anterior impact frequently involve the anterior table of the frontal sinus and may extend further to the posterior table. Fracture of the posterior table with an underlying dural tear is associated with a risk of CSF leak and meningitis [24]. When there is fracture of the floor of the frontal sinus the frontal sinus outflow tract/frontal recess should be carefully interrogated for injury. Complications of outflow tract injury include frontal sinus mucocele, osteomyelitis, and intracranial infection including brain abscess [42,43]. Outflow tract injury is also important in determining surgical management. Fractures of the anterior table of the frontal sinus can be repaired with plates and screws if the outflow tract is preserved. In severe injury to the drainage pathway, frontal sinus cranialization is performed and the outflow tract is
removed. In frontal sinus cranialization, the sinus mucosa is removed, preventing the development of mucocele and mucopyocele [43–45].
Central Skull Base (CSB) Fractures Fractures of the central skull base are frequently posterior extensions of anterior skull base fractures, or transverse fractures from lateral high-impact trauma to the temporal, parietal, zygomatic, and/or lateral frontal bones [24].
Complications Intracranial: Since CSB fractures are often due to high-velocity injuries intracranial hemorrhage (especially temporal lobe contusions) and TAI is a common association [24]. Vascular: Fractures of the clivus, orbital apex, petrous ridge, occiput, and occipital condyles are the skull base injuries most commonly associated with BCVI [46]. Anterior Middle Cranial Fossa Epidural Hematoma: The anterior middle cranial fossa extradural hematoma (also referred to as “benign venous epidural hematoma”) is a specific finding related to fracture of the greater wing of sphenoid, due to injury of the sphenoparietal venous sinus, and generally follows a self-limiting course [9]. Carotid-Cavernous Fistula: Post-traumatic carotid-cavernous fistula is a rare but important vascular complication of central skull base trauma. Clinical presentation is with exophthalmos, orbital bruit, chemosis, visual loss, and ophthalmoplegia. There is a risk of blindness, stroke, and death, re-emphasising the importance of CTA in patients with central skull base fractures [24,47]. Cranial Nerve and Sympathetic Chain Injury: Central skull base fractures are associated with cranial nerve injury which may be acute from laceration, or delayed from traction or edema. Fracture involvement of a relevant skull base foramen should raise suspicion for cranial nerve injury [24]. Orbital apex fractures may cause optic (II) nerve injury through entrapment or compressive hematoma [24,48].
Injury to the cavernous sinus can affect cranial nerves III, IV, V1, V2, and/or VI which traverse within the sinus and its lateral wall. An incomplete Horner syndrome (ptosis and meiosis) can arise from injury to the postganglionic sympathetic chain near the ICA, in fractures of the carotid canal or near Meckel’s cave. This syndrome can also occur if damage occurs to the sympathetic chain within the neck adjacent to the carotid space from cervical carotid artery dissection [24]. CSF Leak: CSF leak is less common in central than in anterior skull base fractures. This is more frequently seen in transversely oriented fractures [49]. Clival Involvement: Fracture involvement of the clivus is relatively uncommon, however, is associated with high mortality, (reportedly 24–80%) related to its proximity to the brainstem and risk of significant neurological and vascular injury [50]. Transverse clival fractures are more commonly associated with cranial nerve and internal carotid artery injuries. Longitudinal clival fractures are usually associated with vertebrobasilar arterial injury, brainstem ischemia, and injury to the craniocervical junction. A traumatic VI nerve palsy may occur in clival fractures due to involvement of the Dorello canal, located at the posteromedial part of the petrous apex [24].
Posterior Skull Base (PSB) Fractures Posterior skull base fractures arise most commonly from posterior or posterolateral impact to the occiput and can involve the posterior clivus (basiocciput) [24]. Occipital condyle fractures occur although are relatively uncommon. The most widely used classification system (Anderson and Montesano), divides these into three types dependent on imaging appearance on imaging and probable mechanism of injury [24,51].
◾ Type 1 is condylar impaction with comminution due to an axial load ◾ 2 is a posterior skull base fracture extending in linear fashion into the condyle ◾ Type Type 3 is an avulsion fracture at the attachment site of the alar ligament
Complications
Intracranial and Vascular: Posterior skull base fractures have a reported high incidence of associated intracranial injury, including extradural, subdural, and cerebellar
intraparenchymal hematoma. Of these, extradural hematomas occur with the greatest frequency [24]. Posterior fossa extradural hematomas are generally venous in origin. These can rapidly expand and cause sudden neurological deterioration due to compression of the fourth ventricle and/or brainstem. They are the result of injury to the transverse or sigmoid venous sinus or jugular bulb. Surgical decompression is indicated for large hematomas with mass effect [52]. Fractures extending into the jugular foramen or venous sinuses or can lead to venous thrombosis [53]. On noncontrast CT examination, the venous sinuses should be reviewed for hyperdensity suggestive of clot, and there should be a low threshold for performing a CT venogram [24]. Consideration should be given to vertebrobasilar arterial injury when there is fracture of the clivus at the basiocciput and the occipital condyles. CT angiography and an MRI of the C spine should be performed [24,54].
Cranial Nerve: The lower cranial nerves IX–XII are at risk of injury in fractures of the posterior skull base. Hypoglossal nerve palsy can also occur as a result of internal carotid artery traumatic dissection injury below the skull base.
Key Points for Skull Base Trauma
◾structures A knowledge of skull base anatomy is vital to understand the involved in fractures and potential complications ◾andAnterior skull base fractures carry a potential risk of CSF leak meningitis ◾frontal Frontal sinus fractures involving the posterior table may require sinus cranialization to prevent mucocoele and mucopyocoele ◾fistula There is a particularly high risk of BCVI and carotid-cavernous in central skull base fractures and CT angiography should be performed ◾hematomata Posterior skull base fractures may be associated with extradural and compression of the fourth ventricle and brainstem
Temporal Bone Trauma
Introduction Temporal bone injury is reported in 3–22% of patients with skull fracture. The most common mechanisms include motor vehicle accident, physical assault, and fall [55,56]. The identification of temporal bone trauma and complications is usually made on the unenhanced (noncontrast) CT undertaken for evaluation of general head trauma using a slice thickness of less than 1 mm. The primary sign of temporal bone fracture is the presence of a fracture line. Secondary signs that should raise suspicion include:
◾ of the external auditory canal, mastoid air cells, and middle ear cavity ◾andOpacification Air within the intracranial compartment adjacent to the temporal bone, within the labyrinth the temporomandibular joint
Temporal Bone Fracture Classification Temporal bone fractures have traditionally been classified as transverse, longitudinal, or mixed with respect to the long axis of the petrous temporal bone.
◾10–20% Longitudinal fractures are more common at 50–80% with transverse fracture comprising ◾internal Transverse fractures are more commonly associated with facial nerve injury near the auditory meatus or at the labyrinthine segment ◾injury Longitudinal fractures are less commonly associated with facial nerve injury, and if nerve is present this is often at the geniculate ganglion [55–57]
In more modern practice, violation of the otic capsule has been shown to be of greater clinical relevance than fracture orientation, with better prediction of the complications of sensorineural hearing loss, intracranial, vascular, and facial nerve injury [58–61]. It is recommended that reports include the direction and location of the fracture, and whether or not the otic capsule is involved [55].
Complications Hearing Loss (CHL and SNHL) and Vertigo
Hearing loss: Hearing loss is the most frequent complication of temporal bone trauma and may be conductive, sensorineural, or mixed [55,61]. Causes of traumatic conductive hearing loss (CHL) include perforation of the tympanic membrane (TM), hemotympanum, and ossicular disruption. If
persistent for more than 6 weeks, an ossicular chain injury should be suspected [55,62,63]. Sensorineural hearing loss (SNHL) is due to involvement of the otic capsule or cochlear nerve. Traumatic SNHL may be due to fractures violating the labyrinth or the cochlear nerve within the internal auditory canal (IAC) or intralabyrinth hemorrhage (with or without fracture). Presence of pneumolabyrinth is an important secondary sign of otic capsule-violation (Fig. 88.11A and B) which should be considered to indicate a fracture in the absence of an identifiable line on imaging. Labyrinthitis ossificans is a longer-term complication which may be identifiable on CT (labyrinthine calcification) and MR imaging (loss of normal labyrinthine signal).
FIGURE 88.11 82-year-old female pedestrian struck by car. (A) CT scan demonstrates right otic-involving transverse petrous temporal bone fracture extending through the posterior semicircular canal and vestibule (black arrows). Note the hemotympanum. Also, note right cochlea pneumolabyrinth—small locules of gas in the right cochlear labyrinth secondary to the otic-involving fracture (white arrow). (B) CT scan demonstrates fracture extension through the right lateral semicircular canal and toward the labyrinthine segment of the right facial nerve and geniculate ganglion (long black arrows); pneumolabyrinth is present (short black arrow).
Vertigo: [64]. Axial CT is most useful for evaluation of the labyrinth and fracture of the vestibular structures. Stenvers and Poschl reconstructions (parallel and perpendicular to the long axis of the petrous bone) can help as the posterior and superior semicircular canals are viewed in profile. Ossicular Injury Ossicular injuries (Fig. 88.12A and B) include ossicular joint dislocation and ossicular fracture. Ossicular injuries are more common in longitudinal
fractures than in transverse, and dislocations are more common than fractures.
FIGURE 88.12 72-year-old male pedestrian struck by cyclist. (A) CT scan demonstrates mixed right temporal bone fracture with compete loss of right ossicular integrity—the right incus and malleus are completely absent from normal location (broken white arrow)—compare with normal left side (long thick white arrow). There is hemotympanum (and middle ear cavity perilymph) (long thin black arrow). One of the right petrous temporal bone fracture lines is demonstrated (short white arrow). (B) coronal CT image—the normal left incudo-mallear articulation is evident (short white arrow) compared with absence of the incus and malleus from their normal location on the right (broken white arrow). The right malleus is dislocated, and inferiorly and laterally displaced into the medial bony right external auditory canal and contiguous lateral aspect of the inferior mesotympanum (broken black arrow) compared with the normal location of the left malleus (long thin solid black arrow). The stapes were also dislocated from the oval window (not shown) resulting in a perilymph fistula.
Ossicular Dislocation: The incudostapedial joint is reported to be the most common site of ossicular dislocation [65]. The next most common dislocation is of the incudomalleolar joint (shown as separation of the “ice cream” (head of malleus) and “ice cream cone” (body and short process of incus). Complete incus dislocation is present when there is both incudostapedial and incudomalleolar joint dislocation [64]. Dislocation of the stapedial footplate is rare and may be associated with perilymphatic fistula (PLF) formation at the oval window [65].
Ossicular Fractures: The most frequently fractured ossicle is the incus (especially at the long process), followed by the crura of the stapes. The malleus is the least frequently fractured ossicle [66].
Treatment: TM perforation, hemotympanum, and minor ossicle subluxation often spontaneously resolve and are treated conservatively. If CHL persists beyond 6 months surgical repair of the ossicular chain may be indicated [55,67]. Perilymphatic Fistula PLF occurs due to formation of an abnormal communication between the perilymph and middle ear cavity (Fig. 88.12A and B). Post-traumatic PLF may occur with injury to the oval or round window [68]. Symptoms of persistent vertigo and intermittent SNHL and/or CHL begin within 24–72 hours postinjury. PLF should be considered with fractures through the stapes footplate or round window on CT. Secondary signs in absence of a temporal bone fracture include pneumolabyrinth and unexplained dependent fluid in the middle ear [55,69]. CSF Leak Temporal bone fractures with underlying dural injury are associated with risk of CSF leak and meningitis, particularly if involvement of the tegmen tympani, tegmen mastoideum, or posterior petrous ridge. This can present as otorrhea via the TM or rhinorrhea via eustachian tube drainage (where the TM is intact). CSF leak is more commonly seen in otic capsule-violating fractures than in those where the capsule is spared [55,58,59].
Imaging Findings: Coronal and sagittal reconstructions are best for CT assessment of the tegmen. Reports should include location and size of any defect, orientation of displaced fragments through the defect, and presence of an encephalocele. Factors increasing the risk of persistent CSF leak include widely spaced fracture defect and a bony spicule oriented perpendicularly to the dura. MRI of the temporal bone with high-resolution T2WI and postcontrast T1WI of the temporal bone can be performed to look for the location and size of any encephalocele, and demonstrate dural enhancement as secondary signs of dural tear, CSF leak, and focal meningitis [55,70].
Treatment: Most post-traumatic CSF leaks self-resolve within 7 days with conservative management. If persistent CSF leak beyond day 10 surgical closure may be performed [70]. Facial Nerve Injury and Canal Fractures Due to its long course through the temporal bone, the facial nerve is at risk of injury at multiple points. Identifiable injury is considered relatively uncommon [55,70–72]. Facial nerve palsy is more commonly associated with otic capsuleviolating fractures. Otic capsule-sparing fractures are, however, the more frequent subtype and so the majority of cases are seen in this subgroup [70]. Fractures of the canal are also more common in transverse fractures than longitudinal fractures [73]. The most common sites of injury are the distal labyrinthine segment, at the geniculate ganglion, and the intracanalicular (IAC) segment (Fig. 88.13) [64].
FIGURE 88.13 Temporal bone fracture. 56-year-old male cyclist postmotor vehicle collision. Axial CT of the left temporal bone demonstrates a complex/mixed temporal bone fracture with extension into the left geniculate ganglion.
Compression of the nerve by a fracture fragment may be visible and is important to identify as it is likely to be treatable by early surgical management. High-resolution MRI can demonstrate perineural hematoma, and abnormal enhancement may be seen in scarring or fibrosis [55,74].
Treatment: Optimal management is a controversial topic. Delayed onset palsy has relatively good prognosis without surgery. Surgery may be utilized in complete, immediate paralysis, or cases of progressive loss of function.
Aims of surgery are to evaluate and decompress the facial nerve, and may involve nerve rerouting, re-anastomosis, or sural nerve graft [55]. Vascular Injury A previous series found that 24% of skull base fractures show carotid canal involvement and 11% of fractures were positive for vascular injury [75] and a fracture extending through the carotid canal requires CT angiography to assess for vascular injury [55]. There is a risk of venous injury and CT venogram should be performed in fractures involving the jugular foramen or traversing the sinuses [55].
Key Points for Temporal Bone Trauma
◾andAirwithin within the intracranial compartment near the temporal bone, the labyrinth should raise suspicion for occult temporal bone fracture in the absence of a visualized fracture line ◾fractures Facial nerve injury is more common in transverse temporal bone than longitudinal. Otic capsule-violation are a better predictor of complications than fracture orientation. It is suggested that fracture location, orientation, and otic capsule status are reported The incus is the most commonly fracture ossicle, and the incudostapedial joint is the most common site of dislocation Fractures of the tegmen tympani, tegmen mastoideum, and posterior petrous ridge place the patient at risk of CSF leak and meningitis Fractures of the carotid canal warrant intracranial CT angiography to assess for internal carotid artery injury
◾ ◾ ◾
Facial Trauma—Midface, Orbits, Nasoseptal, and Mandible Introduction Facial fractures can be complex, traversing multiple bones and foramina, potentially daunting for the reporting radiologist. There are, however, several key fracture configurations that commonly occur and have specific clinical and surgical relevance. Knowledge of these can act as a basis for
reporting more straightforward.
complex
fractures
and
make
the
process
more
Midface Fractures Zygomatico–Maxillary Complex (ZMC) Fractures Zygomatico–Maxillary complex or tetrapod fractures are the second most common category of midface fracture (Fig. 88.14) [76]. These were previously incorrectly referred to as “tripod” fractures given the visualization of only three of the four key components on plain radiograph [77].
FIGURE 88.14 36-year-old male victim of alleged assault. CT scan demonstrates right zygomatico–maxillary complex fracture (fractures of the complex annotated with white arrows).
The four core sites are as follows:
◾ Lateral orbital rim ◾ orbital rim ◾ Inferior Zygomatic arch
◾alveolar Zygomaticomaxillary buttress (the lateral vertical facial buttress, extending from the process of the maxilla inferiorly through the body and zygomatic process of maxilla, the zygoma, and lateral orbital wall to the frontozygomatic suture)
Given that part of the lateral orbital wall and floor arise from the zygomatic bone, orbital volume may be increased or decreased as a result of displacement and/or rotation of the ZMC fragment, with the risk of facial asymmetry and enophthalmos [43,78]. Depression of the zygomatic arch can lead to restriction in mouth opening due to compression of the masticatory muscles or impingement of the mandibular coronoid [77,79]. Grading systems such as the Zingg classification have been suggested which increase in severity from incomplete ZMC fractures not involving all four limbs (A), to classic tetrapod (B) through to severe comminution (C). CT fracture grade and surgical findings of fracture instability have been found to correlate [43,80]. Le Fort Fractures Le Fort fractures are craniofacial dissociation injuries. The classically described core component in these is fracture of the pterygoid plates, which form the posterior maxillary buttress and interface between the skull base (sphenoid) and midface [77]. René Le Fort described the classification following cadaveric experiments demonstrating commonly occurring fracture patterns after blunt facial trauma [81]. While many facial fractures do not fit simply into the Le Fort classification, it remains useful as a common descriptive language between radiologists, emergency physicians, and maxillofacial surgeons [43,82]. The individual fracture subtypes traverse several structures, however, use of a single key component can help simplify recognition of the distinction between Le Fort I–III injuries (Figs. 88.1516A) [77,83].
◾extension Le Fort I—Floating Palate—Lateral and medial walls of maxillary sinus with posterior to the piriform aperture. Single key component: nasal piriform aperture (the
anterior bony nasal opening formed superiorly by the nasal bone and laterally and inferiorly by the maxilla). Le Fort II—Floating Maxilla—Pyramidal fractures involving the frontonasal suture, inferior orbital rim/floor, and maxillary sinuses. Single key component: inferior orbital rim. Le Fort III—Floating Face—Frontonasal suture to frontozygomatic suture and zygomatic arch. Often a combination of ZMC and naso-orbito-ethmoidal (NOE) fracture. Single key component: zygomatic arch.
◾ ◾
FIGURE 88.15 Le Fort classification. Frontal volume-rendered reconstructions of a normal CT of the facial bones demonstrating the Le Fort Fracture Classification. The morphology of each fracture type is demonstrated (I = Blue, II = Purple, III = Green). Le Fort type I injuries involve the nasal pyriform aperture, type II injuries involve the inferior orbital rim, and type III injuries involve the lateral orbital wall and zygomatic arch.
Combinations of the Le Fort subtypes can be present on the same side of the face. Le Fort II and III represent severe injuries and a CT angiogram of the neck to vertex is advised to screen for blunt vascular injury.
Nasoseptal Fractures The nasal bones are the most commonly fractured facial bones (Fig. 88.17) [76]. Anatomically the bony nasal structure consists of the two nasal bones, frontal bone and frontal processes of the maxilla.
FIGURE 88.17 Nasal fractures. 35-year-old female following a fall onto face. Axial CT of the facial bones demonstrates displaced fractures of the nasal bones bilaterally with associated external subdermal nasal soft tissue swelling and injury and fracture of the bony nasal septum (not shown) and associated septal mucosal and submucosal gas secondary to intranasal septal mucosal laceration.
Correction of deformity is aimed at restoring a normal nasal pathway and avoiding turbulent flow which can be a risk factor for sinusitis [77,84]. Sinusitis may occur as a complication of fracture fragment displacement into the maxillary sinus.
Naso-Orbito-Ethmoid Fracture (NOE) Extension of proximal nasal bone fractures to the frontal bone, cribriform plate, midface, and orbit gives rise to an NOE-type fracture. Intracranial and orbital injuries are more frequently associated NOE fractures and intracranial imaging is usually warranted (Fig. 88.16B). NOE fractures usually occur in combination with other facial fractures [85].
FIGURE 88.16 59-year-old male who fell on face due to collapse. (A) CT scan showed mixed left and right hemi-Le Fort I, II, and III fractures and left orbital floor fracture—some of the typical fracture line sites of Le Fort fractures are shown (white arrows) but not all. (B) CT scan of the same patient also demonstrates some fracture changes related to left naso-orbito-ethmoidal complex fracture (short white arrow) and right fronto-nasal duct fracture (long white arrows). Right orbital emphysema (black arrow) is shown associated with right medial orbital wall fractures.
The major feature of NOE fracture is that a central NOE fracture fragment is separated along at least four of five fracture lines. These are referred to as “cardinal tracts” and are as follows:
◾ Lateral nose and piriform aperture ◾ Nasomaxillary buttress ◾ Inferior orbital rim/floor ◾ orbital wall ◾ Medial Frontomaxillary suture
The central NOE fragment is the insertion site for the medial canthal tendon, the stability of which is a key factor in operative decision-making. Although the tendon itself is not visible on CT, severe comminution of the medial orbital wall is a useful imaging sign suggesting compromised stability (Fig. 88.18).
FIGURE 88.18 NOE fracture. 65-year-old male following a fall from height. Axial (A) and coronal (B) CT of the facial bones demonstrates severe complex bilateral facial fractures including a bilateral nasoorbito-ethmoid fracture. There is comminution and displacement at the medial NOE fracture component bilaterally. There are also fractures involving the orbital walls, anterior skull base, maxillary sinuses and hard palate.
Other complications associated with NOE fractures are impairment of lacrimal and mucociliary drainage through injury to the nasolacrimal duct, frontonasal duct (frontal recess), and frontal sinuses. The involvement of these influences surgical management and they should be reported [43].
Orbital Fractures Blow-Out Fracture The term “blow-out” fracture is used where there is enlargement of orbital volume due to fracture of the medial orbital wall and/or floor with outward fracture displacement. The medial orbital wall and floor are relatively weaker than the lateral wall and roof and are hence more commonly fractured in primary orbital fractures. The orbital rim itself is usually spared. Primary orbital fractures are associated with higher risk of globe and optic nerve injury than the orbital extension of other local facial fractures. Other risks include enophthalmos from the increased orbital volume, and herniation of soft tissues through fracture defects (Fig. 88.19A and B). Diplopia may occur due to fat and/or muscular herniation and entrapment, and smaller fracture size is a useful predictor (soft tissue entrapment is more commonly associated with small and medium-size orbital floor fractures rather than large defects [86]). Of note, the extra-ocular muscles do not specifically need to be incarcerated for there to be clinical entrapment. The sheaths of these muscles are connected to fibrous septae within the orbital fat and therefore herniation of any soft tissue should be flagged in the report (Fig. 88.19B).
FIGURE 88.19 23-year-old male victim of alleged assault. (A) Coronal CT bone reconstructions demonstrate bilateral “trap-door” orbital floor fractures (arrows) more marked on the left. (B) Coronal CT soft tissue reconstructions demonstrate extraocular fat (long solid white arrow) and inferior rectus muscle herniation (short solid white arrow) and entrapment through the left orbital floor fracture; on the right there is extraocular fat herniation through the right orbital floor fracture (broken white arrow).
Blow-In Fracture
Blow-in fractures where there is orbital volume reduction from fracture fragments prolapsing into the orbit are less common [77]. Orbital Roof Fractures Orbital roof fractures frequently are part of more extensive anterior skull base fractures and may be associated with the risk of intracranial injury, CSF leak, and/or traumatic meningoencephalocele as well as intraorbital subperiosteal hematoma related to the orbital roof (Fig. 88.20). These are discussed further in the intracranial and skull base trauma sections [77].
FIGURE 88.20 59-year-old male who collapsed and “face-planted” on the floor. (A) Coronal CT on bone reconstructions demonstrates multiple fracture associated with mixed Le Fort fractures and extra-axial left frontal pneumocephalus as well as frontal sinus fracture disruption (not shown) and left orbital floor fracture. Left orbital roof fracture line is demonstrated (arrow). (B) Coronal CT soft tissue reconstruction demonstrates extraconal subperisoteal hematoma (white arrow) related to the left orbital roof associated with the orbital roof fracture components.
Orbital Soft Tissue Injuries Soft tissue injuries identified on CT include optic nerve injury, anterior chamber hemorrhage, corneal laceration (with anterior iris prolapse), lens dislocation, globe rupture/open globe injury (Fig. 88.21), retinal detachment (Fig. 88.22), and intraorbital foreign body [87].
FIGURE 88.21 29-year-old male assaulted with a baseball bat. CT scan demonstrates left globe rupture with abnormal ocular morphology and hyperdense intraocular hemorrhage present.
FIGURE 88.22 23-year-old male fell from the fifth storey of a building sustaining severe craniocerebral trauma. CT scan demonstrates left intraocular subretinal hemorrhage (long white arrows) and associated retinal detachment and lens injury—note abnormal attenuation and alignment of lens (short white arrow).
Dental Dental injuries are complex with different healing trajectories. The major traumatic injuries with relevance on imaging include intrusion or extrusion, lateral luxation, fracture of the crown or root, and avulsion (Fig. 88.23A).
FIGURE 88.23 Young adult male driver involved in high speed motor vehicle collision sustaining severe chest injuries and facial injuries. (A) CT scan demonstrates fracture of the right maxillary alveolus (white broken arrow) and associated right central maxillary incisor tooth (UR1) avulsion (straight white arrow) as well as fracture avulsion of the adjacent right maxillary lateral incisor tooth (not shown). Note the extensive soft tissue emphysema (curved white arrows) associated with severe chest injuries (not shown). (B) Sagittal CT reconstruction on bone algorithm of cervical spine assessment confirms the pharyngeal location of the avulsed teeth (arrows) adjacent to the endotracheal tube. Different 37-year-old male driver involved in high-speed motor vehicle collision. (C) CT scan demonstrates markedly displaced symphysis fracture of the mandible (arrow). (D) CT scan demonstrates associated comminuted compound fracture of the region of the left angle of the mandible (white arrow). Note left lateral pterygoid plate fractures (black arrow).
A couple of points relevant to dental injuries on CT are discussed. Alveolar ridge fractures (Fig. 88.23A) are relevant as they are “open” fractures for which antibiotics are indicated. Dental avulsion may warrant assessment on neck and chest imaging for dental aspiration (Fig. 88.23A and B).
Mandible Fractures to the mandible are most commonly bilateral. If there is a fracture of the symphysis or body the usual association is with a fracture of the contralateral angle or subcondylar neck (Fig. 88.23C and B). Fractures at the angle frequently extend to the root of the third molar. Anterior fractures are generally repaired first followed by posterior fractures. Cervical CTA is recommended in condylar fracture dislocations to exclude potentially associated ICA dissection injuries [88].
Key Points for Facial Bones
◾theRotation and displacement of the zygomaticosphenoid suture are most sensitive CT indicators of facial asymmetry and change in orbital volume in ZMC fractures ◾criteria Le Fort II and III fractures form part of the BCVI screening and are an indication for CT angiogram from the neck to vertex ◾examination Nasal fractures should be followed by clinical speculum to assess the septal cartilage for fracture and septal hematoma ◾important The posterior table of the frontal sinus and the frontal recess are structures to assess in NOE fractures ◾occur Muscular entrapment through an orbital blow-out fracture can with intraorbital fat herniation alone. Muscle herniation is not a prerequisite ◾within Any hematoma or bony fragment compressing the optic nerve the canal requires emergency communication to the clinical team for consideration of surgical decompression
Craniocervical Junction, Subaxial Cervical Spine, and Thoracolumbar Spine Trauma Introduction Cervical spine injury is frequent, occurring in 5–10% of blunt polytrauma [89]. MDCT has superseded plain radiography as the initial screening
examination for high-risk patients. Imaging is required where the C-spine cannot be cleared clinically or where indicated by guidelines such as those from the ACR or NICE in the UK. The ACR also recommends CT scan of the C-spine where there is distracting injury or any other positive traumatic finding in the polytrauma patient with obtundation [89]. If a cervical spine injury is present the remainder of the spinal axis should be imaged as further injuries are present in 10–15% [89,90]. A suggested CT protocol is described: appropriately thin-section axial source dataset of 0.75 mm is recommended from which appropriateresolution multiplanar reformats are acquired (ideally, 2 mm or less). Coronal and sagittal reformats are mandatory and scrutiny of the axial source dataset as well as the use of angled/oblique reformats is also advised [91]. MRI is the optimum technique for assessing soft tissue injury including epidural hematoma, ligamentous disruption, and cord injury. MRI may detect CT-occult bony injuries with marrow edema and hemorrhage evident as STIR-hyperintense signal [89,92]. A minimum of sequences recommended includes sagittal T2W, T1W TSE, and STIR sequences with axial T1W TSE and T2W and the T2W isovolumetric coronal sequence [91].
Craniocervical Junction Relevant Anatomy Knowledge of the basic osseous and ligamentous anatomy of the craniocervical junction is crucial to understanding traumatic injury in this region (Fig. 88.24).
FIGURE 88.24 Ligaments at the craniovertebral junction.
The craniocervical junction consists of the atlanto-occipital (C0–C1) and atlanto-axial (C1–C2) joints and encompasses therefore the atlas, axis, and parts of the occipital bone including the occipital condyles, foramen magnum, clivus, and basiocciput. The predominant movements at the atlanto-occipital joint are flexion and extension. Motion at the atlanto-axial joint is predominantly flexion, extension, and axial rotation. The atlanto-axial joint is particularly susceptible to instability secondary to ligamentous injury, more than the atlanto-occipital joint [91]. The paired alar ligaments attach the upper part of the dens to the medial occipital condyles or anterolateral foramen magnum. These in combination with the transverse ligament of the cruciform are the major stabilizers of the craniocervical junction. The cruciform (or cruciate) ligament behind the dens has a cross-like configuration formed by intersecting transverse and vertical parts. The vertical part of the cruciform ligament plays a limited role in craniocervical stability. The transverse ligament of the cruciform is the largest, thickest, and strongest of the craniocervical junction ligaments, arches behind the dens, and attaches to a tubercle on the medial aspect of each lateral mass of the atlas. The tectorial membrane is the superior extension of the posterior longitudinal ligament (PLL). It extends cranially to the clivus and runs posterior to the cruciform ligament. The apical ligament attaches the tip of the dens to the basion and lies between the anterior atlanto-occipital membrane and the cruciform ligament.
The anterior atlanto-occipital membrane is thin and attaches the anterior aspect of the atlas to the anterior rim of the foramen magnum. The posterior atlanto-occipital membrane attaches the posterior arch of atlas to the posterior margin of the foramen magnum and is continuous with the posterior atlantoaxial membrane (and thus the ligamentum flavum). The vertebral arteries pierce the posterior atlanto-occipital membrane before passing through the dura into the posterior fossa. The nuchal ligament is the superior extension of the supraspinous ligament, extending from the C7 spinous process to the inion of the occipital bone [91].
Normal Variants of the Craniocervical Junction: A number of normal developmental variants may mimic fracture including condylus tertius, posterior rachischisis, anterior rachischisis (split atlas), ossiculum terminale, os odontoideum, and calcification of the alar ligament [91]. Blunt Trauma
Basiocciput Fractures: These account for only 2% of cranial fractures but have a high associated mortality due to proximity to the brainstem and frequent neurological and vascular injury. Fractures may be transverse, oblique, or longitudinal [50,91]. Rarely, a retroclival epidural hematoma may occur in association with basiocciput fracture and other craniocervical injury, commonly seen in the pediatric population.
Occipital Condyle Injury: There is a risk of injury to the nearby brainstem, vessels, and lower cranial nerves (IX–XII, a Collet-Sicard is syndrome is present if all are affected). Dissection of the ICA and vertebral arteries, AVF of the PICA arteries and lateral medullary syndrome may occur as sequelae [91]. The Anderson and Montesano is the most widely used classification system.
◾ Type I is an impaction fracture with comminution of the condyle
◾88.25) Type II is linear extension of a larger basiocciput fracture into the occipital condyle (Fig. ◾complete Type III injuries are avulsions which are potentially unstable through partial tear or disruption to the contralateral alar ligament and tectorial membrane, and there is potential for neurologic injury from condylar fragment displacement into the foramen magnum [91,93]
FIGURE 88.25 16-year-old male pedestrian struck by a car. Coronal CT reconstruction on bone algorithm demonstrates type II left occipital condyle fracture component (arrow) of more extensive basiocciput fracture (not shown) of the craniocervical junction.
Atlanto-Occipital Dislocation: Atlanto-occipital dislocation: This is associated with a high risk of death and neurological morbidity and is often part of a fatal injury (Fig. 88.26). It is of greater incidence in pediatric patients likely due to a less concave articular surface of the atlas at the atlanto-occipital articulation and the relative head size compared to the body of the infant. The Traynelis classification describes three types by direction of occipital condylar displacement, relative to the atlas:
◾ Type I is anterior ◾ II is vertical (distraction) ◾ Type Type III is posterior
FIGURE 88.26 31-year-old male cyclist in collision with car. (A) Sagittal CT reconstruction on bone algorithm demonstrates severe atlanto-axial fracture-dissociation mechanism with fracture and distraction-subluxation evident. Note the abnormally widened relationship (white stars) between basion/opisthion and the C1 vertebral fracture elements (long thin arrow) and the C2 odontoid process (peg) and the abnormally widened atlanto-dental interval (curved white arrow). (B) Coronal CT reconstruction on bone algorithm demonstrated the atlanto-occipital distraction (short arrows) and fracture injury as well as atlanto-axial fracture-subluxation (curved arrows). (C) Axial CT reconstruction on soft tissue windows demonstrates large volume prevertebral hematoma (straight solid arrows), the presence of posterior atlanto-occipital hematoma (broken white arrow) associated with the craniocervical junction fracture-distraction injury and the relationship to the spinal cord (curved white arrow).
The Basion–Dens interval and condyle-atlas interval can be used to identify dislocation if they are abnormally increased [91,94]. Further studies of normal measurements of the craniocervical junction traditionally utilized on plain radiograph have been studied on CT. A summary of published findings from studies in the literature is listed in Table 88.2. The abnormal values are sensitive, however, not specific, and identifying a normal value is useful for excluding distraction injury. Table 88.2 Normal Measurements on CT at the Craniocervical Junction [89] Interval
Plain Radiograph Cut-off Value
CT Cut-off Value
Ligaments Involved
BasionDens interval
12 mm
8.5–9.5 mm
Alar ligamentsTe ctorial membrane
Atlanto dental interval
3 mm (men), 2.5 mm (women)
2 mm
Atlantooccipital joint capsules
Alar ligaments Tectorial membrane Atlanto occipita l interval
4 mm (summed) or 2.5 mm (single atlanto-occipital interval)
Powers Ratio: the distance measured from the tip of the basion to the posterior arch of C1 divided by the distance from the opisthion to the anterior arch of C1.
Atlas (C1) Fracture: These comprise 25% of craniocervical injuries. Up to 44% are associated with fracture of the axis, and they are also frequently associated with fractures of the subaxial cervical spine, transverse ligament rupture, and closed head injury (Fig. 88.27) [89,91,95].
FIGURE 88.27 28-year-old male who fell from a height. (A) CT scan demonstrates Jefferson-type fracture of the atlas (C1 vertebra). Widened left lateral atlanto-dental interval in keeping with associated transverse ligament disruption. (B) Axial T2-weighted MR image through craniocervical junction of the same patient—the left side of the transverse atlantal ligament disruption is demonstrated (short white arrow)—compare with the intact right side of the ligament (long white solid arrow). Associated traumatic vascular dissection injury of the right vertebral artery is evident with loss of normal flow void at the level of the C1 lateral mass (long white broken arrow). (C) Sagittal STIR sequence demonstrates large prevertebral soft tissue hematoma (long solid white arrow), posterior atlanto-axial membrane injury (short white arrow), subaxial posterior ligamentous complex injury (curved white arrow) and abnormal marrow edema in keeping with compression injury of the T3 vertebral body on edge of the image (long broken white arrow).
Atlas fractures are typically stable, and neurological injury is rare although potential complications include vertebral artery dissection and lower cranial nerve palsies. Cervical cord and medullary injury are more commonly seen when there are concomitant fractures of the axis or subaxial cervical spine [91,96]. The associated other C-spine fractures and integrity of the transverse ligament are the main factors in determining a need for surgery [89,91]. Atlas fractures are divided into five subtypes by the modified Jefferson classification. The most common patterns are type I and type III. Type II is rare.
◾ Type I fracture involves only the posterior arch ◾ Type II fracture involves only the anterior arch ◾unilateral Type III is the classical Jefferson burst fracture with bilateral posterior arch fractures with or bilateral anterior arch fracture ◾ Type IV is fracture of the lateral mass ◾ Type V is a transverse fracture of the anterior arch [91,95,97] Atlas fractures are predominantly a result of axial loading injuries [23,98]. Transverse ligament injury is a common association. An atlanto-dens interval of >3 mm in adults and >5 mm in children is highly suggestive of transverse ligament disruption and MRI assessment should be performed. “Pseudospread” of the atlas is a normal variant on plain radiograph most commonly seen in children under 7 years of age and is due to the ossified lateral masses of the atlas being projected beyond the ossified articular surface of the axis [91,99].
Axis (C2) Fractures: Injuries to the axis comprise 17–20% of C-spine fractures [89,100]. The three main injury patterns are fractures of the odontoid, axis body, and hangman fracture [91,101].
Odontoid Fracture: This is the most common axis fracture. These are more common in elderly patients which may be due to a greater proportion of force being transmitted to the dens in the spondylotic spine. Fractures of the dens are classified as types I–III by Anderson and D’Alonzo [102].
◾management Type I fractures through the upper part of the dens, are the least common. Nonoperative with collar or halo immobilization leads to a fusion rate near 100% ◾They Type II fractures at the junction of the dens and the body of the axis are the most common. are more susceptible to nonunion (probably due to a relatively poor blood supply at the dens-body junction) and may need surgical fusion
A subtype of Type II fracture is the IIa where “chip” fragments are present at the anterior and posterior aspect of the base of the dens which lead to nonunion, and may require earlier surgical stabilization and fusion [91,103].
◾cancellous Type III (Fig. 88.28) is the next most common and extend through the C2 body into its part. These are potentially unstable although there is healing with immobilization in 88% of cases
FIGURE 88.28 48-year-old male pedestrian struck by a car. Type 3 fracture of the C2 odontoid process (peg) is demonstrated (straight white arrows). There is also a fracture of the left lateral mass of the C2 vertebra (curved white arrow).
Hangman fracture: These are bilateral pars interarticularis fractures of the axis although any part of the axis ring can be involved including lamina, pedicle, or posterior axis body (Fig. 88.29) [89,101]. They comprise 22% of axis fractures and 4% of all cervical fractures [89,104]. The fracture configuration was first described in 1913 in association with judicial hanging, however the “Hangman” name was only given to them in 1965, by which point it referred to the fractures mostly seen post-MVC due to severe, sudden deceleration injury, or after a fall [89,105,106]. If the patient has survived, spinal cord and nerve root injury are reported to be low due to the relative wide calibre of the canal at this level. The majority are treated with immobilization. The most severe distractive flexion injuries with bilateral facet dislocation require surgical stabilization [89,91].
FIGURE 88.29 Hangman fracture. 62-year-old male found on floor. Axial (A) CT images of the cervical spine demonstrate bilateral fractures of the pars interarticularis of C2 with involvement of the foramina transversaria and risk of traumatic vertebral artery injury. Parasagittal image (B) of the same patient demonstrates the appearance of the right C2 pars fracture (contralateral left C2 pars fracture not shown).
Axis Body Fracture: These have a variety of configurations and can include burst injury. They are frequently stable and treated nonsurgically [89].
Ligamentous Injury Without Fracture: This phenomenon occurs in both children and adults and may have longterm sequelae if not identified acutely. Traumatic alar ligament injuries usually occur near the condylar insertion with potential compression or dissection of the vertebral artery and spinal accessory nerve injury [107]. In the absence of a fracture, MRI evidence of injury to the less clinically significant ligaments such as the apical ligaments or effusion associated with the supra-odontoid space may be indicators of associated strain injury of the more important stabilizing ligaments [91].
Traumatic Atlanto-Axial Rotatory Subluxation (AARS) and Fixation:
This is more commonly seen in children and relatively rare in adults [89,91]. Two-thirds of normal rotation of the cervical spine occurs at the atlantoaxial joint. The normal range of rotation at the atlantoaxial joint in adults can be as high as 52° to one side [89,108]. Spasmodic torticollis arising from the sternocleidomastoid contraction should be distinguished clinically from AARS—in torticollis, it is the sternocleidomastoid muscle contralateral to the rotation which is in spasm. In AARS, it is the ipsilateral, lengthened sternocleidomastoid muscle which is in spasm attempting to correct the deformity [91,109].
Subaxial Cervical Spine Subaxial cervical spine fractures generally occur in predictable configurations [110]. A mechanistic approach can be useful in conceptualizing injuries to the subaxial cervical spine. An awareness of these mechanisms and injury patterns allows for a comprehensive assessment of the cervical spine on CT and in particular helps to identify subtle but important abnormalities which might be missed [110,111]. Relevant Anatomy The subaxial cervical spine encompasses the C3–C7 vertebrae and their associated discoligamentous structures. The discoligamentous complex (DLC) comprises the intervertebral discs and spinal ligaments including the anterior longitudinal ligament (ALL), PLL, facet joint capsule, ligamentum flava, interspinous and supraspinous ligaments [110]. A functional spinal unit or spinal motion segment refers to two adjacent vertebrae connected by the DLC. From a biomechanical perspective, this can be divided into anterior and posterior columns.
◾intervertebral The anterior column is anterior to and inclusive of the PLL, comprising the vertebral body, disc, ALL, and PLL ◾posterior The posterior column is posterior to the PLL and consists of the neural arch and the ligamentous complex (PLC)
The vertebral bodies and intervertebral discs transmit the compressive loads on the spine while the ligaments bear the rotational, distractive, and shear forces [110].
General concepts: Compressive traumatic forces generally result in burst or wedge fractures. Distractive force results in ligamentous disruption or dislocation. Rotationshear forces result in combined osseous and ligamentous fracture– dislocation injuries [110].
The following checklist has been suggested as a framework for CT evaluation of the cervical spine (Table 88.3) [110]. On the midsagittal image, bony alignment should be assessed using the anterior and posterior vertebral lines (Fig. 88.30). The posterior vertebral line is considered to be the most reliable and accurate indicator of antero–posterior alignment [110]. Table 88.3 Checklist for Assessment of the Subaxial Cervical Spine [110] Bone
⚬Anterior vs posterior translation ⚬Triangular avulsion at the corners of vertebral end plates Curvatu re
◾ Normal, smooth lordosis or any abnormal focal kyphosis
Alignm ent
◾ Anterior/post erior vertebral lines assessed on sagittal plane
Measur ement
–
–
◾ Spinolaminar and interspinous lines on sagittal plane ◾ Interspinous and articular pillar lines in coronal plane ◾ Interpedicular, interspinous, and interlaminar distances ◾ A difference of more than 2 mm between adjacent segments is considered abnormal, although usage of measurements may be limited by interobserver variability
FIGURE 88.30 Mid-sagittal normal cervical spine CT image demonstrating normal alignment. The anterior spinal line (blue), posterior spinal line (yellow), and spinolaminar line (green) are illustrated. These are useful lines of reference in the identification of anterior or posterior translational and distraction injuries.
Facet joints are best evaluated on parasagittal images and can also be assessed on axial images where they have a “hamburger bun” appearance when normally aligned. Normal facet joint space should be less than 2 mm.
Fractures and Key Injury Patterns Hyperflexion Injury
Compressive Hyperflexion: The compressive force is to the anterosuperior margin of the vertebral body. With increasing force the injuries progress from anterior vertebral body wedging, to development of a vertically oriented fracture line forming a triangular or quadrangular anterior “teardrop” fragment. With further increase in force the posterior disc, PLL, and PLC may fail leading to a highly unstable injury (the flexion teardrop fracture) [110]. The CT features of the flexion teardrop fracture include:
◾plate, Oblique fracture in coronal plane from anterior aspect of superior end plate to inferior end separating a small anterior fragment from the remainder of the vertebral body ◾ Posterior subluxation of the remaining injured vertebral body on the vertebra below ◾ Signs of PLC injury [110]
Vertical Compression/Axial Loading: Energy is absorbed by the vertebral bodies and intervertebral discs with a resultant “burst” (horizontal spread) of fragments. Fragments may be retropulsed into the spinal canal. The loss of vertebral body height is generally symmetrical with minimal kyphosis. A minor vertical compression leads to central cupping of end plates or sagittal/coronal split fracture. A greater force may lead to the typical burst fracture where there is vertebral body height loss and comminution, centrifugal dispersal of fragments, and a fracture line extending to posterior cortex with a retropulsed fragment [110].
Distractive Hyperflexion: In these injuries the center of rotation is considered to be anterior to the vertebral body with the neck in flexion, leading to primary failure of the posterior elements [110,112]. Ligamentous disruption progresses from
posterior to anterior, in sequence from the supraspinous ligament to the interspinous ligament, facet capsules, and ligamentum flavum. If there is an even greater force of injury there may be failure of anterior column ligaments. CT features include the following:
◾ Interspinous widening ◾ Interlaminar widening ◾ Facet joint subluxation or dislocation ◾ Widened posterior disc space ◾ kyphosis ◾ Focal Anterior subluxation of vertebral bodies [113]
Bilateral facet dislocation is the most severe injury of the flexiondistraction spectrum and there is usually a severe associated neurological injury (Fig. 88.31) [114]. PLL disruption is also frequently seen in association, as is traumatic disc herniation with disruption of the posterior annulus. Disc herniation should be confirmed at MRI before stabilization of the facet dislocation. Fracture of the posteroinferior cortex of the vertebral body is often seen. Unilateral facet joint dislocation may occur when the center of rotation is off-midline and is also a highly unstable injury.
FIGURE 88.31 56-year-old male suffered fall from significant height. (A) Sagittal CT reconstruction on bone algorithm demonstrates C7-T1 fracture subluxation (straight arrow) associated with bilateral facet dislocation (“jumped facets”) (not shown). Compression fracture of the T2 superior endplate is also evident (curved arrow). (B) Sagittal CT reconstruction on bone algorithm demonstrates “jumped” right C7-T1 facet joint dislocation (curved arrow) and associated fracture fragment from the right C7 inferior articular facet (straight arrow). Left C7-T1 “jumped” facet was also present (not shown). (C) Sagittal T2-weighted MRI sequence demonstrates the C7-T1 fracture-subluxation (thick solid white arrow) associated with the bilateral facet dislocation at the same level (not shown) and the disrupted ligamentum flavum (black arrow) at the C7-T1 level and the compressive effect caused by the subluxation and associated subligamentous epidural hematoma (broken thin curved white arrow) stripping the posterior longitudinal ligament at the C7-T1 level. Compressive cord signal is present (venous edema) (broken straight white arrows) and there is a small petechial hemorrhagic focus within the affected cord parenchyma (thin curved solid white arrow).
Sagittal plane is best for identifying facet joint dislocations [110]. Normal facet joints show >50% overlap of the articular surfaces. Subluxation of the facet joints is present where there is 2 mm [113]. When the inferior articular process of the cranial vertebra is sat on the tip of the superior articular process of the caudal vertebra this is referred to as a “perched” facet. Further anterior displacement of the inferior articular process of the cranial vertebra constitutes a “locked” or “jumped” facet (Fig. 88.31A and B). Axial images may demonstrate the “reverse hamburger bun” sign [110]. Hyperextension Injury
Hyperextension Compression: In these injuries, the spinal motion segment is extended and there is compression to the posterior column at the neural arch, including fracture of the lateral mass, laminae, or pars interarticularis. If there is bilateral pedicle
or lateral mass fracture traumatic anterior spondylolisthesis may occur. The spinolaminar line may still be intact at the level of the anterolisthesis [110].
Hyperextension Rotation: There is resultant asymmetric, hyperextension compression injury of the posterior column with asymmetric or unilateral fractures of the articular pillars or processes. If there is concomitant fracture of the ipsilateral pedicle and lamina there can be traumatic isolation of the cervical articular pillar with potential rotational instability of the facet above and below [110].
Hyperextension Distraction: In these injuries, the center of rotation is posterior to the vertebral column with the neck in extension. The result is tensile failure of the anterior column. These are mainly ligamentous disruptions progressing from anterior to posterior, starting with ALL. These are common in patients with degenerative or ankylosed spine, including ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis, including with low energy mechanisms [110,115]. On CT, the abnormality may be subtle due to the predominantly ligamentous nature of the injury. Prevertebral soft tissue thickening may be the only apparent feature on CT [110]. Anterior disc space widening is the hallmark feature and is due to rupture of the ALL and anterior annulus [116]. An avulsion of the anterior body may also occur through an intact ALL (the extension teardrop fracture) or there may be fracture of an anterior osteophyte or syndesmophyte. As the hyperextension force increases, there may be a hyperextensiondislocation injury where there is transient posterior dislocation of the cranial vertebra over the caudal vertebra with disruption of the ALL, anterior annulus, disc, posterior annulus, and PLL. This is frequently associated with a major neurological injury, most commonly a central cord syndrome. A high index of suspicion is required, e.g., in patients with lower facial trauma and clinical central cord syndrome [110]. There may again be widening of the anterior disc space and diffuse prevertebral soft tissue swelling. Less commonly seen features on CT include disc vacuum phenomenon, and avulsion of the anteroinferior margin of the involved vertebra. Horizontal fracture through the vertebral body or purely through the fused disc space may occur in the ankylosed spine. MRI is indicated to assess discoligamentous injury and spinal cord compression/injury and should be performed particularly in the elderly or ankylosed spine with minor trauma if there is a neurological deficit.
Rotation Injury: The most commonly utilized sign is malalignment of the spinous process in the coronal plane. On CT, one of the most accurate indicators is asymmetry of the uncinate processes [110,117]. Other useful CT indicators include asymmetric disc space with a rotated vertebral body (in coronal plane) and rotation of fracture fragments.
Thoracolumbar Spinal Trauma Introduction The concepts of thoracolumbar spinal trauma demonstrate some overlap with the cervical spine although the injury configurations vary relating to inherent differences in biomechanics of the injuries sustained (Fig. 88.32).
FIGURE 88.32 Thoracic spinal ligamentous injury. 25-year-old male postfall from height. Sagittal CT (A) demonstrates a three-column fracture involving the T6 vertebra with evidence of flexion-axial loading injury. Subsequent sagittal T2W MRI (B) shows worsening alignment with anterior translation of T5 and T6 and ligamentous disruption including both the posterior longitudinal ligament and ligamentum flavum of the posterior ligamentous complex. There is indentation of the ventral spinal cord by fracture disruption and localized subligamentous epidural hematoma beneath the posterior longitudinal ligament; there is intramedullary spinal cord signal abnormality consistent with cord contusion.
Multiple injury classification systems have been proposed with the most commonly used being the Denis three-column classification in which the vertebral column is divided into anterior, middle, and posterior columns whereby any involvement of the middle column suggests an unstable injury.
◾vertebral The anterior column includes the ALL, anterior annulus, and anterior two-thirds of the body ◾annulus, The middle column includes the posterior one-third of the vertebral body, the posterior and PLL ◾spinous The posterior column includes the posterior elements (pedicles, facets, laminae, and process) and the PLC (ligamentum flavum, interspinous ligament, supraspinous ligament, and facet joint capsules) [111]
Other more recent classifications have been proposed such as the thoracolumbar injury classification and severity score (TLICS), which generates a score based on fracture morphology, ligamentous injury, and neurological involvement to help guide conservative or surgical management [118]. Thoracolumbar Injuries by TLICS Classification The TLICS system classifies injury morphology into compression, translation, and distraction injuries (Tables 88.4 and 88.5). Table 88.4 Thoracolumbar Injury Classification and Severity Score Classification System [118] Injury Category
Point Value
Morphology Compression Burst Translation or rotation Distraction
1 2 3 4
PLC status Intact Injury suspected or indeterminate Injured
0 2 3
Neurological status Intact Nerve root involvement Spinal cord or conus medullaris injury – Incomplete – Complete Cauda equina syndrome
0 2 3 2 3
Table 88.5 Total Thoracolumbar Injury Classification and Severity Score and Treatment Recommendation [118]
TLICS Score
Treatment Recommendation
0–3
Nonsurgical
4
Nonsurgical or surgical
≥5
Surgical
TLICS, thoracolumbar injury classification and severity score.
Compression fractures are demonstrated as a visible loss of vertebral body height or disruption of the endplate. Less severe injuries may involve only the anterior part of the vertebral body. With increasing force, a burst fracture may occur where the posterior vertebral body is involved and there is retropulsion into the spinal canal [118,119]. Translational injuries appear as horizontal displacement or rotation of two vertebral bodies with respect to one another. They are characterized by spinous process rotation, unilateral, or bilateral facet fracture-dislocation, and vertebral body subluxation [118,119]. Distraction injuries appear as dissociation in the vertical axis. The disruption may involve both anterior and posterior ligaments and the vertebrae. A chance-type fracture falls into this category. The chance fracture (Fig. 88.33) was initially described as a specific injury caused by forceful forward flexion, typically sustained by a passenger in a motor vehicle collision (MVC) wearing a lap-seatbelt [119,120]. There is an anterior vertebral body compression fracture with a transverse fracture line extending through the posterior vertebral body into the posterior elements, coupled with posterior element distraction [118,119].
FIGURE 88.33 Chance fracture. 39-year-old motorcyclist postcollision with lamppost. Sagittal CT of the thoracic spine shows a chance fracture extending through the T7/T8 level (A) with characteristic three-column involvement. Subsequent sagittal T2W MRI (B) demonstrates disruption of the T7/T8 intervertebral disc and the posterior ligamentous complex in addition to marrow edema in adjacent vertebral levels secondary to axial loading/compression mechanism of injury.
Disruption of the PLC is inferred on radiograph or CT as widening of the interspinous space, avulsion of the superior, or inferior aspects of contiguous spinous process, facet joint widening, “empty” facet joints, perched or dislocated facet joints, and vertebral body translation or rotation [111,118]. There can be various forms of neuorological injury including nerve root injury, complete spinal cord injury, incomplete cord injury, or cauda equina syndrome. The role of imaging is to detect the presence of cord or nerve root injury and cord or cauda equina compression on MRI [111,118].
MRI Assessment of the Soft Tissues in Spinal Trauma At the authors’ institution, if there has been spinal trauma significant enough to warrant spinal MRI imaging, MRI of the whole spine is generally
performed. Ligamentous Injury The majority of the spinal ligaments appear on MRI as low signal intensity bands on all sequences, with the main exception being the interspinous ligament which is normally of striated low and high-signal on T1W images (due to interspersed fat) [121,122]. A ligamentous tear may be partial or complete. Partial tears are indicated by a high signal area on short TI inversion recovery (STIR) sequences due to edema and hemorrhage combined with some intact, preserved fibers. Complete tears show the absence of intact fibers with associated edema and hemorrhage [121,123]. Other types of injury include an intact ligament being stripped off the bone and combined bony-ligamentous injury [121]. Injuries to the facet joint capsules are shown as widening of the joint and increased fluid signal within the joint space [121,124]. It should be stressed that the ligaments are components of the spinal columns. The PLC forms a core component of the TLICS assessment and from the perspective of the Denis classification, ligamentous injury can upstage a single column bony injury to a two-column injury [121,123]. Acute Traumatic Disc Herniation Traumatic disc herniation is most frequently associated with vertebral fracture-dislocation and hyperextension injury due to injury to the annulus fibrosus and herniation of the nucleus pulposus. There may be disc injury (hematoma) without herniation which appears as asymmetric widening/narrowing of the disc and abnormal signal from edema. There may be compression of the spinal cord by the disc herniation [121,125]. Extramedullary Hemorrhage The most common traumatic extramedullary collection is the epidural hematoma. In the acute phase, epidural hematomatas are isointense to mildly hyperintense on T1W and hyperintense on T2W imaging. Imaging should be extended to capture the full craniocaudal extent of the hematoma. Hemorrhage may also occur within the subdural and subarachnoid spaces. Spinal Cord Injury Spinal cord injury can be hemorrhagic or nonhemorrhagic, both of which may be demonstrated on MRI. Sagittal and axial T2W (Fig. 88.31C) and T2*W (GRE) images are considered to be the most useful with hyperintense intramedullary T2 signal suggestive of cord edema and hypointense signal representing hemorrhage
(best shown on GRE images) [121,126]. There may be expansion of the cord due to edema. Clinical neurological status at presentation is the best predictor of longterm function; however, cord hemorrhage on MRI is particularly important as it is associated with poorer prognosis. Other findings reported to be of prognostic value are the extent of cord hematoma and edema, and spinal cord compression by extra-medullary hematoma [121,127].
Key Points for Spinal Trauma
◾craniocervical Be familiar with the normal alignment and intervals at the junction as injury may be subtle and consequences severe ◾axisIf ashould cervical spine fracture is present the remainder of the spinal be imaged. Further injuries are present in 10–15% ◾craniocervical The transverse atlantal ligament is the primary stabilizer of the junction ◾alignment Ligamentous injury may occur without fracture. Mild malon CT may be the only feature ◾andTheneurological TLICS Classification utilizes morphology, status of the PLC status to help determine stability and the need for surgical treatment of thoracolumbar vertebral injury ◾softMRItissues is the optimum imaging technique for evaluating the spinal including the ligaments and cord, and for compressive intraspinal hematoma
Blunt Cerebrovascular Injury (BCVI) Introduction BCVI refers to nonpenetrating traumatic injury to the cervico-cranial carotid and vertebral arteries. While these are relatively rare injuries, they are associated with a high morbidity and mortality risk from stroke and death if untreated [23,128,129]. The prevalence of BCVI is thought to be 1.0–1.6% in all trauma cases although as the majority of injuries are clinically silent at initial imaging true prevalence is difficult to delineate [23,130].
Mechanisms and Pathophysiology of Injury High-speed MVCs are responsible for more than 50% of BCVI although lower impact mechanisms are also frequently implicated [23]. When BCVI occurs with relatively minor trauma consideration should be given to the possibility of an underlying connective tissue disorder such as Marfan or Ehlers–Danlos syndrome. The type of trauma to the vessel may be a stretching, twisting, or compression injury. The traumatic force results in an intimal arterial injury with intraluminal blood then dissect through the intimal defect. Distal propagation of the dissection can cause flow-limiting stenosis or occlusion. The intimal injury creates a locally prothrombotic environment with the risk of distal embolization and vessel occlusion [23,131–134]. Traumatic pseudoaneurysms are focal outpouchings at a defect in the vessel wall. This may be contained by the adventitia or the surrounding extravascular soft tissues and the sac may compress the source vessel causing stenosis or occlusion. There is also a risk of thrombus within the sac and distal embolization of clot. The most severe subtype of BCVI is arterial transection, in which there is arterial hemorrhage into the adjacent cervical and/or facial soft tissues and massive stroke or exsanguination may occur without emergent treatment. Following transection, traumatic arteriovenous fistula may occur although these are not commonly seen as patients tend not to survive to undergo imaging. Carotico-cavernous fistula may occur in traumatic skull base fracture or rupture of cavernous ICA injury and has been discussed in the skull base section. BCVI also encompasses venous injury, for example, laceration of a vein by bony fragments or external compression. Venous mural injuries include pseudoaneurysm and transection and are more common after penetrating injury than blunt trauma. Extradural hematomas may also lead to compression of venous sinuses and subsequent dural venous sinus thrombosis.
Screening for BCVI Screening for BCVI in modern practice is primarily performed with CT angiogram from the aortic arch to the vertex with reported sensitivity of 66– 98% and specificity of 92–100% [135–139]. Numerous screening criteria have been proposed including by the Eastern Association for Surgery of Trauma and Western Trauma Association/Modified Denver Criteria. The summarized list of imaging risk factors is included in Table 88.6 [23,134].
Table 88.6 Screening Criteria for Blunt Cerebrovascular Injury [23] Screening for BCVI: [23]
◾ Imaging risk factors ⚬Ischemic stroke on imaging ⚬Specific high energy mechanism injuries indicated by: ◾ Le Fort II or III fracture ◾ Skull base fracture with carotid canal involvement ◾ Diffuse axonal injury with GCS ≤ 8 ⚬Cervical spine fracture or subluxation—depends on criteria source ◾ Vertebral body fracture ◾ Transverse foramen fracture ◾ Subluxation or ligamentous injury at any level ◾ Any fracture from C1 to C3 ⚬Near-hanging with anoxia ⚬Clothesline-type injury or seat belt abrasion with swelling/pain and/or altered mental status ⚬Mandible fracture ⚬Complex skull fracture ⚬Scalp degloving ⚬Thoracic vascular injury ⚬Thoracic injury MRI (including MR angiography) is not generally utilized for BCVI screening.
Of note, as a group of nonvascular injuries, cervical spine fractures have the strongest association with BCVI. Of these, injuries of the upper cervical spine, ligamentous disruption, and traumatic subluxation/dislocation show the greatest associated risk [23]. High-grade facial fractures also carry significant risk of BCVI (Fig. 88.34A–C).
FIGURE 88.34 50-year-old male fell from an electric scooter at speed sustaining craniofacial injury including severe facial fractures. (A) CT scan demonstrates traumatic subarachnoid hemorrhage (curved white arrow) and shallow subdural hygroma (broken white arrow) and associated left periorbital soft tissue hematoma (short white arrow). (B) Axial CT angiogram image demonstrates traumatic vascular dissection injury of the right internal carotid artery just below the skull base at the craniocervical junction level with intimal flap and subintimal hematoma and localized dilatation of the vessel (compare to the normal left side). (C) Sagittal oblique reconstructed CT angiogram image demonstrates the longitudinal morphology of the traumatic dissection injury of the right internal carotid artery and its relationship to the skull base—note irregularity and narrowing (straight arrow) in keeping with subintimal hematoma and mural hematoma related to the vessel wall and small subadventitial pseudoaneurysm (curved arrow).
CT venography is the examination of choice where there is suspicion of venous injury. There are no official WTA or EAST recommendations; however, any fracture extension to the dural venous sinuses and/or jugular bulb should raise concern for venous injury.
Appearances on Imaging
◾eccentric Intramural hematoma (IMH) is seen as long segments of mural thickening and may be or circumferential. IMH in the subacute phase on MRI is hyperintense on fatsaturated T1WI (and PDw images). In the acute phase (1–3 days) and chronic (>14 days), IMH tends to be T1-isointense Dissection at cross-sectional imaging shows a linear filling defect within the vessel lumen. A “double lumen” sign with contrast opacification of the false and true lumens is pathognomonic however this may not be seen. On MRI, the false lumen is hyperintense on fat-saturated T1WI Pseudoaneurysms are seen as a focal outpouching through an expansion in the vessel wall (Fig. 88.34B and C) Arterial occlusion in the cervical carotid artery is often seen as a tapering before total occlusion, whereas vertebral occlusion more commonly shows an abrupt cutoff Transection at CTA and DSA shows as an irregular extravasation of contrast surrounding the source vessel. On delayed images, the contrast will disperse AVF can be subtle on CTA. Early venous filling in arterial phase (i.e., arterio-venous shunting) and dilatation of draining veins are the major features (Fig. 88.35). These are more clearly shown on DSA (Fig. 88.35D). Features of caroticocavernous fistula include proptosis, superior ophthalmic vein enlargement, orbital edema, and asymmetric early cavernous sinus opacification in the arterial phase
◾ ◾ ◾ ◾ ◾
◾andHyperdensity within a dural venous sinus on noncontrast CT raises suspicion for thrombus warrants a CT venogram to confirm or exclude a filling defect. Gyral enhancement and prominent intramedullary veins may also be seen due to venous backflow
FIGURE 88.35 39-year-old female pedestrian struck by a car suffered severe mixed Le Fort I, II, and III facial fractures. (A) Coronal CT reconstruction on bone algorithms demonstrates severe mixed Le Fort I, II, and III facial fractures bilaterally. (B) Axial CT angiogram image demonstrates traumatic dissection injury of the left internal carotid artery (straight arrow) just below the skull base with associated subadventitial pseudoaneurysm (curved arrow). Severe midfacial fractures are demonstrated (oval). (C) Axial CT angiogram image more cranially of the same patient also demonstrates traumatic direct left caroticocavernous fistula (straight arrow) with arteriovenous shunting also evident in the contralateral right cavernous sinus (broken arrow) and early mild arteriovenous shunting into the left superior ophthalmic vein (curved arrow) at this time. (D) Lateral digital subtraction catheter angiogram performed a few days later (early phase left internal artery injection run) demonstrates traumatic direct left carotico-cavernous fistula (curved solid black arrow) with arterial phase shunting into the left superior ophthalmic vein (broken straight black arrow) and also into the inferior petrosal sinus (broken curved black arrow). Note other sites of right internal carotid artery traumatic dissection injury just below the skull base (straight solid black arrow) (also demonstrated on CT in (B)).
Pitfalls Atherosclerosis, carotid fibromuscular dysplasia, vasospasm, and vasculitis may mimic BCVI. Vasospasm in particular is common after severe trauma and transient vasospasm may mimic low-grade BCVI. Vasospasm typically resolves over several hours, while BCVI will have a longer duration or persist [23]. Normal vascular variants such as coiled ICAs can mask or mimic small pseudoaneurysms. Congenital hypoplasia may mimic luminal stenosis or occlusion. The vertebral arteries are more commonly hypoplastic than the ICAs, and this is typically uniform throughout the length of the vessel. The skull base, the carotid canal, and at the tortuous V3 segment of the vertebral arteries are locations at which vascular injuries have been found to be more easily overlooked [135,139].
Treatment Treatment of BCVI is with antithrombotic (antiplatelet or anticoagulant) therapy. Low-grade injuries are treated medically unless there is contraindication. Higher grade injury with definite signs of active bleeding or haemodynamic compromise generally warrant surgical or endovascular treatment. Pseudoaneurysms rarely resolve without intervention and early intervention should be considered when lesions are symptomatic or if they grow to a diameter of 1.0–1.5 cm. Follow-up imaging with CTA is frequently used to help determine duration of antithrombotic therapy. A repeat CTA at 7–10 days is advised to assess for progression or resolution of injury [141].
Key Points for BCVI
◾metBeCTawareangiography of the screening criteria for BCVI. If any of these are of the neck and/or intracranial vessels should be performed ◾arterial BCVI encompasses arterial and venous injury. The spectrum of injury includes dissection, intramural hematoma, pseudoaneurysm, complete occlusion, transection, and AV fistula ◾sinus Features of traumatic caroticocavernous fistula include cavernous expansion, asymmetric early venous enhancement in the arterial phase, enlargement of the superior ophthalmic vein and proptosis Vasospasm is common after trauma and may mimic BCVI
◾
Penetrating Neck Trauma Introduction Penetrating neck trauma may be due to projectile mechanisms (including gun and blast injury) or nonprojectile sharp force mechanisms (e.g., knife and other sharp implements). In modern practice MDCT with CT angiography is the standard mode of primary investigation, superseding surgical exploration. CTA allows identification of the wound track and assessment of vascular injury, the upper aerodigestive tract and the cervical spine (Fig. 88.36).
FIGURE 88.36 19-year-old male stabbed to the right suboccipital region. (A) Sagittal oblique MIP CT angiographic image demonstrates stab wound injury to the right vertebral artery (curved arrow) in its V3 segment with subadventitial pseudoaneurysm formation. (B) Coronal MIP CT angiographic image demonstrates right vertebral artery pseudoaneurysm associated with stab injury. Note right suboccipital soft tissue hematoma and loss of perivertebral deep cervical fascia planes (curved white arrow) associated with the stab wound track (compare to contralateral side). (C) Frontal digital subtraction catheter angiogram performed a few days later (selective left vertebral artery injection run) demonstrates subadventitial pseudoaneurysm of the right vertebral artery in its V3 segment (arrow). (D) Lateral digital subtraction catheter angiogram performed a few days later (early phase selective right vertebral artery injection run) demonstrates subadvential pseudoaneurysm (black arrow) of the V3 segment of the right vertebral artery and an associated traumatic arterio-venous fistula (long white arrow) proximal to the pseudoaneurysm shunting into adjacent veins. Note the catheter tip (curved black arrow) and the endo-tracheal tube (curved white arrow).
When describing the site of penetrating neck trauma, three anatomical zones are traditionally described.
◾ Zone 1 extends from sternal notch and clavicles to cricoid cartilage ◾ 2 from cricoid to mandibular angle ◾ Zone Zone 3 from mandibular angle to the skull base
These were originally used to help decide which patients would undergo surgical exploration or initial conservative management in the pre-CTA era; however, it remains useful as a common descriptive language between surgeon and radiologist. It should be noted, however, that injuries frequently traverse multiple zones [141]. Immediate surgical intervention without imaging remains indicated in patients with expanding hematoma, severe external hemorrhage, hypovolaemic shock, airway compromise, and massive subcutaneous emphysema [141–145].
Extracranial Vascular Trauma Extracranial vessel injury is the most common subset of penetrating neck trauma. Arterial injury comprises 15–25%, with 80% of these involving the carotid and up to 43% involving the vertebral arteries [141,142,146]. The associated morbidity and mortality are mainly due to stroke and exsanguination. Vascular injury secondary to penetrating neck trauma is well demonstrated on multidetector CT angiography (MDCTA). Injury subtypes include pseudoaneurysm formation, arteriovenous fistula, vessel transection, intimal injury and flap formation, dissection, active hemorrhage, and partial or complete occlusion of the carotid or vertebral arteries. Venous injury may also occur secondary to penetrating trauma and may be missed on physical examination and can be life-threatening because of potential for exsanguination. Early venous opacification on CTA imaging may assist in assessing for venous irregularities or filling defects suggesting the need for a dedicated CT venogram particularly with craniocerebral penetrating trauma [147]. Careful assessment for the presence of any metallic foreign body is crucial as patients may require MR imaging particularly with injury to the cervical spine or craniocervical junction [141]. Catheter angiography has a role in confirmation and interventional management of injuries identified on CTA [141].
Upper Aerodigestive Tract Oesophageal and Pharyngeal Injury
Penetrating injury to the cervical oesophagus injury is uncommon but identification and a high index of suspicion are crucial in view of the significant risks of mediastinitis, sepsis and death, especially if diagnosis is delayed [141,148]. Water-soluble contrast swallow is reported to be less sensitive for detecting hypopharyngeal injury than oesophageal and for these, flexible nasendoscopy is recommended [141,149]. In penetrating pharyngeal injury, the potential for airway compromise must also be considered [147,150]. Laryngotracheal Injury Laryngotracheal trauma is relatively uncommon; however, it carries a risk of life-threatening airway compromise and a high index of suspicion is also required [141,151]. Extensive subcutaneous emphysema on CT, disproportionate for the local penetrating injury should raise the suspicion for traumatic disruption of the larynx or trachea. Facial Injury Penetrating injury to the face is frequently associated with concomitant intracranial injuries and carries a risk of significant morbidity and mortality. Imaging is normally performed with noncontrast CT head and facial bones although if there is suspected vascular injury MDCTA is indicated. In high energy projectile injuries, fractured fragments of bone and teeth may act as “secondary projectiles” causing further damage [147]. As with pharyngeal and laryngotracheal injury, projectiles entering the oral cavity are at risk of migration and aspiration [141,147,152]. Wooden foreign bodies merit special mention as their density may grossly approximate gas and hence be incorrectly dismissed. The appearance of a geometric focus of “gas” should raise suspicion for a wooden foreign body [141]. Spinal Injury The cervical spine should be carefully interrogated in penetrating neck trauma as both high energy projectile and low energy nonprojectile instruments can cause vertebral fracture and there is a risk of dural breach and spinal cord injury. Reports should include the presence of foreign body and features of dural breach, including intracanalicular gas, bone, or foreign body [151,153].
Key Points for Penetrating Neck Trauma
◾assessment CT angiography is the standard imaging technique for the of penetrating neck trauma ◾
◾compromise Immediate surgical intervention is indicated in airway and severe external hemorrhage ◾ Venous injury should be considered in addition to arterial injury ◾imaging Carefully assess for metallic foreign bodies as spinal MRI may be required ◾pharyngeal A high index of suspicion is required for oesophageal and injury as there is a high associated mortality risk if diagnosis is delayed ◾craniofacial Wooden foreign bodies may be misdiagnosed as “gas” within the soft tissues on CT ◾andGasriskwithin the spinal canal is highly suspicious for a dural breach of spinal cord injury Suggested Readings AD Schweitzer, SN Niogi, CJ Whitlow, AJ Tsiouris, Traumatic brain injury: imaging patterns and complications, Radiographics 39 (6) (2019 Oct) 1571–1595. AM Rutman, JE Vranic, M Mossa-Basha, Imaging and management of blunt cerebrovascular injury, Radiographics 38 (2) (2018 Mar) 542–563. C Offiah, S Twigg, Imaging assessment of penetrating craniocerebral and spinal trauma, Clin Radiol 64 (12) (2009 Dec) 1146–1157. CE Offiah, E Day, The craniocervical junction: embryology, anatomy, biomechanics and imaging in blunt trauma, Insights Imaging 8 (1) (2017 Feb 4) 29–47. C Offiah, E Hall, Imaging assessment of penetrating injury of the neck and face, Insights
Imaging 3 (5) (2012 Oct 4) 419–431. KL Baugnon, PA Hudgins, Skull base fractures and their complications, Neuroimaging Clin N Am 24 (3) (2014 Aug) 439–465, vii–viii. TA Kennedy, GD Avey, LR Gentry, Imaging of temporal bone trauma, Neuroimaging Clin N Am 24 (3) (2014 Aug) 467–486, viii. YY Kurihara, A Fujikawa, N Tachizawa, M Takaya, H Ikeda, J Starkey, Temporal bone trauma: typical CT and MRI appearances and important points for evaluation, Radiographics 40 (4) (2020 Jul) 1148–1162. A Uzelac, AD Gean, Orbital and facial fractures, Neuroimaging Clin N Am 24 (3) (2014 Aug) 407– 424, vii. D Dreizin, AJ Nam, SC Diaconu, MP Bernstein, UK Bodanapally, F Munera, Multidetector CT of midfacial fractures: classification systems, principles of reduction, and common complications, Radiographics 38 (1) (2018 Jan) 248–274. Y Kumar, D Hayashi, Role of magnetic resonance imaging in acute spinal trauma: a pictorial review, BMC Musculoskelet Disord 17 (2016 Dec 22) 310.
References [1] Centers for Disease Control and Prevention – National Center for Injury Prevention and Control. TBI-related Emergency Department (ED) Visits, https://www.cdc.gov/traumaticbraininjury/data/tbi-edvisits.html (accessed February 7, 2021).
[2] National Institute of Health and Care Excellence (NICE). Head Injury: Assessment and Early Management. CG176, https://www.nice.org.uk/Guidance/CG176 (accessed January 31, 2021). [3] O West, D Nunez Jr, C Kirsch, J Aulino, J Broder, R Cassidy, et al., ACR Appropriateness Criteria® Suspected Spine Trauma. American College of Radiology, https://acsearch.acr.org/docs/69359/Narrative/ (accessed February 7, 2021). [4] R Shih, J Burns, AA Ajam, JS Broder, S Chakraborty, A Kendi, et al., ACR Appropriateness Criteria® Head Trauma. American College of Radiology, https://acsearch.acr.org/docs/69481/Narrative/ (accessed February 7, 2021). [5] AD Schweitzer, SN Niogi, CJ Whitlow, AJ Tsiouris, Traumatic brain injury: imaging patterns and complications, Radiographics 39 (6) (2019 Oct). [6] NA Al-Nakshabandi, The swirl sign, Radiology 218 (2) (2001 Feb). [7] H Ellis, Anatomy of head injury, Surgery (Oxford) 30 (3) (2012 Mar). [8] CM.A Peres, JG.M.P Caldas, P Puglia, AF de Andrade, IA.F da Silva, MJ Teixeira, et al., Endovascular management of acute epidural hematomas: clinical experience with 80 cases, J Neurosurg 128 (4) (2018 Apr). [9] AD Gean, NJ Fischbein, DD Purcell, AH Aiken, GT Manley, SI Stiver, Benign anterior temporal epidural hematoma: indolent lesion with a characteristic CT imaging appearance after blunt head trauma, Radiology 257 (1) (2010 Oct). [10] MA Zanini, LA de Lima Resende, AT de Souza Faleiros, RC Gabarra, Traumatic subdural hygromas: proposed pathogenesis based classification, J Trauma 64 (3) (2008 Mar). [11] G Vezina, Assessment of the nature and age of subdural collections in nonaccidental head injury with CT and MRI, Pediatric Radiol 39 (6) (2009 Jun). [12] P Borczuk, J Penn, D Peak, Y Chang, Patients with traumatic subarachnoid hemorrhage are at low risk for deterioration or neurosurgical intervention, J Trauma Acute Care Surg 74 (6) (2013 Jun). [13] D Mata-Mbemba, S Mugikura, A Nakagawa, T Murata, K Ishii, S Kushimoto, et al., Traumatic midline subarachnoid hemorrhage on initial computed tomography as a marker of severe diffuse axonal injury, J Neurosurg 129 (5) (2018 Nov).
[14] A Perrein, L Petry, A Reis, A Baumann, P Mertes, G Audibert, Cerebral vasospasm after traumatic brain injury: an update, Minerva Anestesiol [Internet] 81 (11) (2015 Nov) 1219–1228. http://europepmc.org/abstract/MED/26372114. [15] D Mata-Mbemba, S Mugikura, A Nakagawa, T Murata, Y Kato, Y Tatewaki, et al., Intraventricular hemorrhage on initial computed tomography as marker of diffuse axonal injury after traumatic brain injury, J Neurotrauma 32 (5) (2015 Mar). [16] R Scheid, DV Ott, H Roth, ML Schroeter, DY von Cramon, Comparative magnetic resonance imaging at 1.5 and 3 Tesla for the evaluation of traumatic microbleeds, J Neurotrauma 24 (12) (2007 Dec). [17] H Alahmadi, S Vachhrajani, MD Cusimano, The natural history of brain contusion: an analysis of radiological and clinical progression, J Neurosurg 112 (5) (2010 May). [18] A Chieregato, E Fainardi, AM Morselli-Labate, V Antonelli, C Compagnone, L Targa, et al., Factors associated with neurological outcome and lesion progression in traumatic subarachnoid hemorrhage patients, Neurosurgery 56 (4) (2005 Apr) 671–680. [19] EL Yuh, P Mukherjee, HF Lingsma, JK Yue, AR Ferguson, WA Gordon, et al., Magnetic resonance imaging improves 3-month outcome prediction in mild traumatic brain injury, Ann Neurol 73 (2) (2013 Feb) 224–235. [20] K Paterakis, AH Karantanas, A Komnos, Z Volikas, Outcome of patients with diffuse axonal injury: the significance and prognostic value of MRI in the acute phase, J Trauma Acute Care Surg [Internet] 49 (6) (2000) 1071–1075. https://journals.lww.com/jtrauma/Fulltext/2000/12000/Outcome_of _Patients_with_Diffuse_Axonal_Injury_.16.aspx. [21] KG Moen, V Brezova, T Skandsen, AK Håberg, M Folvik, A Vik, Traumatic axonal injury: the prognostic value of lesion load in corpus callosum, brain stem, and Thalamus in different magnetic resonance imaging sequences, J Neurotrauma 31 (17) (2014 Sep) 1486–1496. [22] C Werner, K Engelhard, Pathophysiology of traumatic brain injury, Br J Anaesth 99 (1) (2007 Jul) 4–9. [23] AM Rutman, JE Vranic, M Mossa-Basha, Imaging and management of blunt cerebrovascular injury, Radiographics 38 (2) (2018 Mar) 542–563. [24] KL Baugnon, PA Hudgins, Skull base fractures and their complications, Neuroimag Clin North Am 24 (3) (2014 Aug). [25] WL Biffl, EE Moore, PJ Offner, KE Brega, RJ Franciose, JP Elliott, et al., Optimizing screening for blunt cerebrovascular
injuries, Am J Surg 178 (6) (1999 Dec) 517–522. [26] RW Franz, PA Willette, MJ Wood, ML Wright, JF Hartman, A systematic review and meta-analysis of diagnostic screening criteria for blunt cerebrovascular injuries, J Am Coll Surg 214 (3) (2012 Mar) 313–327. [27] CC Cothren, EE Moore, WL Biffl, DJ Ciesla, CE Ray, JL Johnson, et al., Cervical spine fracture patterns predictive of blunt vertebral artery injury, J Trauma 55 (5) (2003 Nov) 811–813. [28] PL Johnson, DA Eckard, DP Chason, MA Brecheisen, S Batnitzky, Imaging of acquired cerebral herniations, Neuroimag Clin North Am 12 (2) (2002 May) 217–228. [29] D-H Bae, K-S Choi, H-J Yi, H-J Chun, Y Ko, KH Bak, Cerebral infarction after traumatic brain injury: incidence and risk factors, Korean J Neurotrauma 10 (2) (2014) 35–40. [30] I Tawil, DM Stein, SE Mirvis, TM Scalea, Posttraumatic cerebral infarction: incidence, outcome, and risk factors, J Trauma 64 (4) (2008 Apr) 849–853. [31] Y Fujii, O Tasaki, K Yoshiya, T Shiozaki, H Ogura, Y Kuwagata, et al., Evaluation of posttraumatic venous sinus occlusion with CT venography, J Trauma 66 (4) (2009 Apr) 1002–1006. [32] JE Delgado Almandoz, HR Kelly, PW Schaefer, MH Lev, RG Gonzalez, JM Romero, Prevalence of traumatic dural venous sinus thrombosis in high-risk acute blunt head trauma patients evaluated with multidetector CT venography, Radiology 255 (2) (2010 May) 570–577. [33] SE Slasky, Y Rivaud, M Suberlak, O Tairu, AD Fox, P OhmanStrickland, et al., Venous sinus thrombosis in blunt trauma, J Comput Assist Tomogr 41 (6) (2017) 891–897. [34] MA Rischall, KH Boegel, CS Palmer, B Knoll, AM McKinney, MDCT venographic patterns of dural venous sinus compromise after acute skull fracture, Am J Roentgenol 207 (4) (2016 Oct) 852– 858. [35] S Yilmazlar, E Arslan, H Kocaeli, S Dogan, K Aksoy, E Korfali, et al., Cerebrospinal fluid leakage complicating skull base fractures: analysis of 81 cases, Neurosurg Rev 29 (1) (2006 Jan 4) 64–71. [36] DF Jimenez, S Sundrani, CM Barone, Posttraumatic anosmia in craniofacial trauma, J Craniomaxillofac Trauma 3 (1) (1997) 8–15. [37] S Yilmazlar, E Arslan, H Kocaeli, S Dogan, K Aksoy, E Korfali, et al., Cerebrospinal fluid leakage complicating skull base fractures: analysis of 81 cases, Neurosurg Rev 29 (1) (2006 Jan 4) 64–71. [38] M Wax, H Ramadan, O Ortiz, S Wetmore, Contemporary management of cerebrospinal fluid rhinorrhea, Otolaryngology Head Neck Surg 116 (4) (1997 Apr) 442–449.
[39] RJ Schlosser, WE Bolger, Nasal cerebrospinal fluid leaks: critical review and surgical considerations, Laryngoscope 114 (2) (2004 Feb) 255–265. [40] RB Bell, EJ Dierks, L Homer, BE Potter, Management of cerebrospinal fluid leak associated with craniomaxillofacial trauma, J Oral Maxillofac Surg 62 (6) (2004 Jun) 676–684. [41] M Ziu, JG Savage, DF Jimenez, Diagnosis and treatment of cerebrospinal fluid rhinorrhea following accidental traumatic anterior skull base fractures, Neurosurg Focus 32 (6) (2012 Jun). [42] SA Jain, JV Manchio, J Weinzweig, Role of the sagittal view of computed tomography in evaluation of the nasofrontal ducts in frontal sinus fractures, J Craniofac Surg 21 (6) (2010 Nov) 1670– 1673. [43] D Dreizin, AJ Nam, SC Diaconu, MP Bernstein, UK Bodanapally, F Munera, Multidetector CT of midfacial fractures: classification systems, principles of reduction, and common complications, Radiographics 38 (1) (2018 Jan) 248–274. [44] RB Bell, EJ Dierks, P Brar, JK Potter, BE Potter, A protocol for the management of frontal sinus fractures emphasizing sinus preservation, J Oral Maxillofac Surg 65 (5) (2007 May) 825–839. [45] LA Sivori, R de Leeuw, I Morgan, LL Cunningham, Complications of frontal sinus fractures with emphasis on chronic craniofacial pain and its treatment: a review of 43 cases, J Oral Maxillofac Surg 68 (9) (2010 Sep) 2041–2046. [46] I Feiz-Erfan, EM Horn, N Theodore, JM Zabramski, JD Klopfenstein, GP Lekovic, et al., Incidence and pattern of direct blunt neurovascular injury associated with trauma to the skull base, J Neurosurg 107 (2) (2007 Aug) 364–369. [47] W Liang, Y Xiaofeng, L Weiguo, Q Wusi, S Gang, Z Xuesheng, Traumatic carotid cavernous fistula accompanying basilar skull fracture: a study on the incidence of traumatic carotid cavernous fistula in the patients with basilar skull fracture and the prognostic analysis about traumatic carotid cavernous fistula, J Trauma 63 (5) (2007 Nov) 1014–1020. [48] JT Katzen, R Jarrahy, JB Eby, RA Mathiasen, DR Margulies, HK Shahinian, Craniofacial and skull base trauma, J Trauma 54 (5) (2003 May) 1026–1034. [49] DT Lin, AC Lin, Surgical treatment of traumatic injuries of the cranial base, Otolaryngol Clin North Am 46 (5) (2013 Oct) 749– 757. [50] PG Ochalski, RM Spiro, A Fabio, AB Kassam, DO Okonkwo, Fractures of the clivus, Neurosurgery 65 (6) (2009 Dec 1) 1063– 1069.
[51] JJ Maddox, JA Rodriguez-Feo, GE Maddox, G Gullung, G McGwin, SM Theiss, Nonoperative treatment of occipital condyle fractures, Spine 37 (16) (2012 Jul) E964–E968. [52] S Takeuchi, Y Takasato, K Wada, H Nawashiro, N Otani, H Masaoka, et al., Traumatic posterior fossa subdural hematomas, J Trauma Acute Care Surg 72 (2) (2012 Feb) 480–486. [53] X Zhao, A Rizzo, B Malek, S Fakhry, J Watson, Basilar Skull fracture: a risk factor for transverse/sigmoid venous sinus obstruction, J Neurotrauma 25 (2) (2008 Feb) 104–111. [54] I Feiz-Erfan, EM Horn, N Theodore, JM Zabramski, JD Klopfenstein, GP Lekovic, et al., Incidence and pattern of direct blunt neurovascular injury associated with trauma to the skull base, J Neurosurg 107 (2) (2007 Aug) 364–369. [55] TA Kennedy, GD Avey, LR Gentry, Imaging of temporal bone trauma, Neuroimag Clin North Am 24 (3) (2014 Aug) 467–486. [56] AK Exadaktylos, GM Sclabas, M Nuyens, D Schröder, B Gallitz, P Henning, et al., The clinical correlation of temporal bone fractures and spiral computed tomographic scan: a prospective and consecutive study at a Level I trauma center, J Trauma 55 (4) (2003 Oct) 704–706. [57] BY Ghorayeb, JW Yeakley, Temporal bone fractures, Laryngoscope 102 (2) (1992 Feb) 129–134. [58] R Dahiya, JD Keller, NS Litofsky, PE Bankey, LJ Bonassar, CA Megerian, Temporal bone fractures: otic capsule sparing versus otic capsule violating clinical and radiographic considerations, J Trauma Acute Care Surg [Internet] 47 (6) (1999). https://journals.lww.com/jtrauma/Fulltext/1999/12000/Temporal_B one_Fractures__Otic_Capsule_Sparing.14.aspx. [59] SC Little, BW Kesser, Radiographic classification of temporal bone fractures, Arch Otolaryngol–Head Neck Surg 132 (12) (2006 Dec 1) 1300–1304. [60] SL Ishman, DR Friedland, Temporal bone fractures: traditional classification and clinical relevance, Laryngoscope 114 (10) (2004 Oct) 1734–1741. [61] MA Rafferty, R Mc Conn Walsh, MA Walsh, A comparison of temporal bone fracture classification systems, Clin Otolaryngol 31 (4) (2006 Aug) 287–291. [62] C Wennmo, O Spandow, Fractures of the temporal bone—chain incongruencies, Am J Otolaryngol 14 (1) (1993 Jan) 38–42. [63] OJ Basson, AC van Lierop, Conductive hearing loss after head trauma: review of ossicular pathology, management and outcomes, J Laryngol Otol 123 (2) (2009 Feb 19) 177–181.
[64] YY Kurihara, A Fujikawa, N Tachizawa, M Takaya, H Ikeda, J Starkey, Temporal bone trauma: typical CT and MRI appearances and important points for evaluation, Radiographics 40 (4) (2020 Jul) 1148–1162. [65] O Maillot, A Attyé, E Boyer, O Heck, A Kastler, S Grand, et al., Post traumatic deafness: a pictorial review of CT and MRI findings, Insights Imaging 7 (3) (2016 Jun 16) 341–350. [66] JO Zayas, YZ Feliciano, CR Hadley, AA Gomez, JA Vidal, Temporal bone trauma and the role of multidetector CT in the emergency department, Radiographics 31 (6) (2011 Oct) 1741– 1755. [67] JR Grant, J Arganbright, DR Friedland, Outcomes for conservative management of traumatic conductive hearing loss, Otol Neurotol 29 (3) (2008 Apr) 344–349. [68] V Goodhill, Sudden deafness and round window rupture, Laryngoscope 81 (9) (1971 Sep) 1462–1474. [69] DC Fitzgerald, Head trauma: hearing loss and dizziness, J Trauma 40 (3) (1996 Mar) 488–496. [70] HA Brodie, TC Thompson, Management of complications from 820 temporal bone fractures, Am J Otol 18 (2) (1997) 188–197. [71] JJ Nash, DR Friedland, KJ Boorsma, JS Rhee, Management and outcomes of facial paralysis from intratemporal blunt trauma: A systematic review, Laryngoscope 120 (7) (2010 Jun 18) 1397–1404. [72] S Yetiser, Y Hidir, E Gonul, Facial nerve problems and hearing loss in patients with temporal bone fractures: demographic data, J Trauma 65 (6) (2008 Dec) 1314–1320. [73] PR Lambert, DE Brackmann, Facial paralysis in longitudinal temporal bone fractures, Laryngoscope 94 (8) (1984 Aug) 1022– 1026. [74] T Ulug, S Arif Ulubil, Management of facial paralysis in temporal bone fractures: a prospective study analyzing 11 operated fractures, Am J Otolaryngol 26 (4) (2005 Jul) 230–238. [75] DK Resnick, BR Subach, DW Marion, The significance of carotid canal involvement in basilar cranial fracture, Neurosurgery 40 (6) (1997 Jun) 1177–1181. [76] V Allareddy, V Allareddy, RP Nalliah, Epidemiology of facial fracture injuries, J Oral Maxillofac Surg 69 (10) (2011 Oct) 2613– 2618. [77] A Uzelac, AD Gean, Orbital and facial fractures, Neuroimag Clin North Am 24 (3) (2014 Aug) 407–424. [78] F Roth, J Koshy, J Goldberg, C Soparkar, Pearls of orbital trauma management, Semin Plast Surg 24 (04) (2010 Nov 29) 398–410.
[79] D Dreizin, AJ Nam, N Tirada, MD Levin, DM Stein, UK Bodanapally, et al., Multidetector CT of mandibular fractures, reductions, and complications: a clinically relevant primer for the radiologist, Radiographics 36 (5) (2016 Sep) 1539–1564. [80] M Zingg, K Laedrach, J Chen, K Chowdhury, T Vuillemin, F Sutter, et al., Classification and treatment of zygomatic fractures: a review of 1,025 cases, J Oral Maxillofac Surg 50 (8) (1992 Aug) 778–790. [81] R Le Fort, P Tessier, Experimental study of fractures of the upper jaw, Plast Reconstr Surg 50 (5) (1972 Nov) 497–506. [82] KJ Kelly, PN Manson, CA vander Kolk, BL Markowitz, MC Dunham, TO Rumley, et al., Sequencing Le Fort fracture treatment (organization of treatment for a panfacial fracture), J Craniofac Surg [Internet] 1 (4) (1990) 168–178. https://journals.lww.com/jcraniofacialsurgery/Fulltext/1990/01040/ Sequencing_LeFort_Fracture_Treatment__Organization.3.aspx. [83] JT Rhea, RA Novelline, How to simplify the CT diagnosis of Le Fort fractures, Am J Roentgenol 184 (5) (2005 May) 1700–1705. [84] B Kelley, C Downey, S Stal, Evaluation and reduction of nasal trauma, Semin Plast Surg 24 (4) (2010 Nov 29) 339–347. [85] SE Baril, MK Yoon, Naso-orbito-ethmoidal (NOE) fractures, Int Ophthalmol Clin 53 (4) (2013) 149–155. [86] HA Shah, TZ Shipchandler, AS Sufyan, WR Nunery, HB.H Lee, Use of fracture size and soft tissue herniation on computed tomography to predict diplopia in isolated orbital floor fractures, Am J Otolaryngol 34 (6) (2013 Nov) 695–698. [87] WS Kubal, Imaging of orbital trauma, Radiographics 28 (6) (2008 Oct) 1729–1739. [88] NP Schneidereit, R Simons, S Nicolaou, D Graeb, DR Brown, A Kirkpatrick, et al., Utility of screening for blunt vascular neck injuries with computed tomographic angiography, J Trauma 60 (1) (2006 Jan) 209–215. [89] D Dreizin, M Letzing, CW Sliker, FH Chokshi, U Bodanapally, SE Mirvis, et al., Multidetector CT of blunt cervical spine trauma in adults, Radiographics 34 (7) (2014 Nov) 1842–1865. [90] AR Vaccaro, HS An, S Lin, S Sun, RA Balderston, JM Cotler, Noncontiguous injuries of the spine, Clin Spine Surg [Internet] 5 (3) (1992) 320–329. https://journals.lww.com/jspinaldisorders/Fulltext/1992/09000/Nonc ontiguous_Injuries_of_the_Spine.10.aspx. [91] CE Offiah, E Day, The craniocervical junction: embryology, anatomy, biomechanics and imaging in blunt trauma, Insights Imaging 8 (1) (2017 Feb 4) 29–47.
[92] F Miyanji, JC Furlan, B Aarabi, PM Arnold, MG Fehlings, Acute cervical traumatic spinal cord injury: MR imaging findings correlated with neurologic outcome—prospective study with 100 consecutive patients, Radiology 243 (3) (2007 Jun) 820–827. [93] PA Anderson, PX Montesano, Morphology and treatment of occipital condyle fractures, Spine 13 (7) (1988 Jul) 731–736. [94] M Garrett, G Consiglieri, UK Kakarla, SW Chang, CA Dickman, Occipitoatlantal dislocation, Neurosurgery 66 (suppl_3) (2010 Mar 1) 48–55. [95] UK Kakarla, SW Chang, N Theodore, VK.H Sonntag, atlas fractures, Neurosurgery 66 (suppl_3) (2010 Mar 1) 60–67. [96] TC Ryken, MN Hadley, B Aarabi, SS Dhall, DE Gelb, RJ Hurlbert, et al., Management of acute combination fractures of the atlas and axis in adults, Neurosurgery 72 (suppl_3) (2013 Mar 1) 151–158. [97] G Jefferson, Fracture of the atlas vertebra. Report of four cases, and a review of those previously recorded, Br J Surg 7 (27) (1919) 407–422. [98] EC McKevitt, AW Kirkpatrick, L Vertesi, R Granger, RK Simons, Blunt vascular neck injuries: diagnosis and outcomes of extracranial vessel injury, J Trauma Acute Care Surg [Internet] 53 (3) (2002) 472–476. https://journals.lww.com/jtrauma/Fulltext/2002/ 09000/Blunt_Vascular_Neck_Injuries__Diagnosis_and.13.aspx. [99] R Suss, R Zimmerman, N Leeds, Pseudospread of the atlas: false sign of Jefferson fracture in young children, Am J Roentgenol 140 (6) (1983 Jun) 1079–1082. [100] KA Greene, CA Dickman, FF Marciano, JB Drabier, MN Hadley, VK.H Sonntag, Acute axis fractures, Spine 22 (16) (1997 Aug) 1843–1852. [101] DM Pryputniewicz, MN Hadley, Axis fractures, Neurosurgery 66 (suppl_3) (2010 Mar 1) 68–82. [102] LD Anderson, RT D’Alonzo, Fractures of the odontoid process of the axis, JBJS [Internet] 56 (8) (1974) 1663–1674. https://journals.lww.com/jbjsjournal/Fulltext/1974/56080/Fractures_ of_the_Odontoid_Process_of_the_Axis.17.aspx. [103] MN Hadley, CM Browner, SS Liu, VK Sonntag, New subtype of acute odontoid fractures (type IIA), Neurosurgery 22 (1 Pt 1) (1988 Jan) 67–71. [104] SE Mirvis, JW Young, C Lim, J Greenberg, Hangman’s fracture: radiologic assessment in 27 cases, Radiology 163 (3) (1987 Jun) 713–717.
[105] F Wood-Jones, The ideal lesion produced by judicial hanging, The Lancet 181 (4662) (1913 Jan). [106] RC Schneider, KE Livingston, AJ.E Cave, G Hamilton, “Hangman’s fracture” of the cervical spine, J Neurosurg 22 (2) (1965 Feb) 141–154. [107] RS Tubbs, JD Hallock, V Radcliff, RP Naftel, M Mortazavi, MM Shoja, et al., Ligaments of the craniocervical junction, J Neurosurg: Spine 14 (6) (2011 Jun) 697–709. [108] CJ Roche, SJ King, PH Dangerfield, HM Carty, The Atlantoaxial Joint: physiological range of rotation on MRI and CT, Clin Radiol 57 (2) (2002 Feb) 103–108. [109] JW Fielding, RJ Hawkins, Atlanto-axial rotatory fixation. (Fixed rotatory subluxation of the atlanto-axial joint), JBJS [Internet] 59 (1) (1977) 37–44. https://journals.lww.com/jbjsjournal/Fulltext/1977/ 59010/Atlanto_axial_rotatory_fixation___Fixed_rotatory.5.aspx. [110] SB Raniga, V Menon, KS al Muzahmi, S Butt, MDCT of acute subaxial cervical spine trauma: a mechanism-based approach, Insights Imaging 5 (3) (2014 Jun 21) 321–338. [111] B Khurana, SE Sheehan, A Sodickson, CM Bono, MB Harris, Traumatic thoracolumbar spine injuries: what the spine surgeon wants to know, Radiographics 33 (7) (2013 Nov) 2031–2046. [112] BL Allen, RL Ferguson, TR Lehmann, RP OʼBrien, A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine, Spine 7 (1) (1982) 1–27. [113] AR Vaccaro, RJ Hulbert, AA Patel, C Fisher, M Dvorak, RA Lehman, et al., The subaxial cervical spine injury classification system, Spine 32 (21) (2007 Oct) 2365–2374. [114] AR Vaccaro, L Madigan, ME Schweitzer, AE Flanders, AS Hilibrand, TJ Albert, Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine, Spine 26 (17) (2001 Sep) 1866–1872. [115] MS Taljanovic, TB Hunter, RJ Wisneski, JF Seeger, CJ Friend, SA Schwartz, et al., Imaging characteristics of diffuse idiopathic skeletal hyperostosis with an emphasis on acute spinal fractures: review, Am J Roentgenol 193 (3_supplement) (2009 Sep) S10–S19. [116] SK Rao, C Wasyliw, DB Nunez, Spectrum of imaging findings in hyperextension injuries of the neck, Radiographics 25 (5) (2005 Sep) 1239–1254. [117] F Palmieri, VN Cassar-Pullicino, C Dell’Atti, RK Lalam, BJ Tins, PN.M Tyrrell, et al., Uncovertebral joint injury in cervical facet dislocation: the headphones sign, Eur Radiol 16 (6) (2006 May 16) 1312–1315.
[118] AR Vaccaro, RA Lehman, RJ Hurlbert, PA Anderson, M Harris, R Hedlund, et al., A new classification of thoracolumbar injuries, Spine 30 (20) (2005 Oct) 1239–1254. [119] S Gamanagatti, D Rathinam, K Rangarajan, A Kumar, K Farooque, V Sharma, Imaging evaluation of traumatic thoracolumbar spine injuries: radiological review, World J Radiol 7 (9) (2015) 253–265. [120] GQ Chance, Note on a type of flexion fracture of the spine, Br J Radiol 21 (249) (1948 Sep). [121] Y Kumar, D Hayashi, Role of magnetic resonance imaging in acute spinal trauma: a pictorial review, BMC Musculoskel Disord 17 (1) (2016 Dec 22) 3–10. [122] PF Benedetti, LM Fahr, LR Kuhns, LA Hayman, MR imaging findings in spinal ligamentous injury, Am J Roentgenol 175 (3) (2000 Sep) 661–665. [123] J Warner, K Shanmuganathan, SE Mirvis, D Cerva, Magnetic resonance imaging of ligamentous injury of the cervical spine, Emerg Radiol 3 (1) (1996 Jan) 9–15. [124] MR Terk, M Hume-Neal, M Fraipont, J Ahmadi, PM Colletti, Injury of the posterior ligament complex in patients with acute spinal trauma: evaluation by MR imaging, Am J Roentgenol 168 (6) (1997 Jun) 1481–1486. [125] ES Pratt, DA Green, DM Spengler, Herniated intervertebral discs associated with unstable spinal injuries, Spine 15 (7) (1990 Jul) 662–666. [126] D Kawakyu-O’Connor, R Bordia, R Nicola, Magnetic resonance imaging of spinal emergencies, Magn Reson Imaging Clin N Am 24 (2) (2016 May) 325–344. [127] A Bozzo, J Marcoux, M Radhakrishna, J Pelletier, B Goulet, The role of magnetic resonance imaging in the management of acute spinal cord injury, J Neurotrauma 28 (8) (2011 Aug) 1401– 1411. [128] JD Berne, KS Reuland, DH Villarreal, TM McGovern, SA Rowe, SH Norwood, Sixteen-slice multi-detector computed tomographic angiography improves the accuracy of screening for blunt cerebrovascular injury, J Trauma 60 (6) (2006 Jun) 1204– 1209. [129] NP Schneidereit, R Simons, S Nicolaou, D Graeb, DR Brown, A Kirkpatrick, et al., Utility of screening for blunt vascular neck injuries with computed tomographic angiography, J Trauma 60 (1) (2006 Jan) 209–215. [130] WL Biffl, Ra.y CEJr, EE Moore, RJ Franciose, S Aly, MG Heyrosa, et al., Treatment-related outcomes from blunt
cerebrovascular injuries: importance of routine follow-up arteriography, Ann Surg [Internet] 235 (5) (2002) 699–706. https://journals.lww.com/annalsofsurgery/Fulltext/2002/05000/Treat ment_Related_Outcomes_From_Blunt.12.aspx. [131] EM Paulus, TC Fabian, SA Savage, BL Zarzaur, V Botta, W Dutton, et al., Blunt cerebrovascular injury screening with 64channel multidetector computed tomography, J Trauma Acute Care Surg 76 (2) (2014 Feb) 279–283. [132] DJ Roberts, VP Chaubey, DA Zygun, D Lorenzetti, PD Faris, CG Ball, et al., Diagnostic accuracy of computed tomographic angiography for blunt cerebrovascular injury detection in trauma patients, Ann Surg 257 (4) (2013 Apr) 621–632. [133] AL Eastman, DP Chason, CL Perez, AL McAnulty, JP Minei, Computed tomographic angiography for the diagnosis of blunt cervical vascular injury: is it ready for primetime?, J Trauma 60 (5) (2006 May) 925–929. [134] RW Franz, PA Willette, MJ Wood, ML Wright, JF Hartman, A systematic review and meta-analysis of diagnostic screening criteria for blunt cerebrovascular injuries, J Am Coll Surg 214 (3) (2012 Mar) 313–327. [135] WL Biffl, CC Cothren, EE Moore, R Kozar, C Cocanour, JW Davis, et al., Western trauma association critical decisions in trauma: screening for and treatment of blunt cerebrovascular injuries, J Trauma 67 (6) (2009 Dec) 1150–1153. [136] CC Burlew, WL Biffl, EE Moore, CC Barnett, JL Johnson, DD Bensard, Blunt cerebrovascular injuries, J Trauma Acute Care Surg 72 (2) (2012 Feb) 330–335. [137] CC Cothren, EE Moore, WL Biffl, DJ Ciesla, CE Ray Jr., JL Johnson, et al., Anticoagulation is the gold standard therapy for blunt carotid injuries to reduce stroke rate, Arch Surg 139 (5) (2004 May 5) 540–545. [138] CC Cothren, EE Moore, CE Ray, JL Johnson, JB Moore, JM Burch, Cervical spine fracture patterns mandating screening to rule out blunt cerebrovascular injury, Surgery 141 (1) (2007 Jan) 76–82. [139] WJ Bromberg, BC Collier, LN Diebel, KM Dwyer, MR Holevar, DG Jacobs, et al., Blunt cerebrovascular injury practice management guidelines: the Eastern Association for the Surgery of Trauma, J Trauma Acute Care Surg [Internet] 68 (2) (2010) 471– 477. https://journals.lww.com/jtrauma/Fulltext/2010/02000/Blunt_Cerebr ovascular_Injury_Practice_Management.34.aspx. [140] TC Fabian, SM George Jr., MA Croce, EC Mangiante, GR Voeller, KA Kudsk, Carotid artery trauma: management based on
mechanism of injury, J Trauma Acute Care Surg [Internet] 30 (8) (1990) 953–961. https://journals.lww.com/jtrauma/Fulltext/1990/08000/Carotid_Arte ry_Trauma__Management_Based _on.3.aspx. [141] C Offiah, E Hall, Imaging assessment of penetrating injury of the neck and face, Insights Imaging 3 (5) (2012 Oct 4) 419–431. [142] F Ramadan, R Rutledge, D Oller, P Howell, C Baker, B Keagy, Carotid artery trauma: a review of contemporary trauma center experiences, J Vasc Surg 21 (1) (1995 Jan) 46–55. [143] JP Kuehne, FA Weaver, G Papanicolaou, AE Yellin, Penetrating trauma of the internal carotid artery, Arch Surg 131 (9) (1996 Sep 1) 942–947. [144] F Múnera, S Cohn, LA Rivas, Penetrating injuries of the neck: use of helical computed tomographic angiography, J Trauma 58 (2) (2005 Feb) 413–418. [145] DB Núñez, M Torres-León, F Múnera, Vascular Injuries of the neck and thoracic inlet: helical CT–angiographic correlation, Radiographics 24 (4) (2004 Jul) 1087–1098. [146] RP Gonzalez, M Falimirski, MR Holevar, B Turk, Penetrating zone II neck injury: does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study, J Trauma 54 (1) (2003 Jan) 61–64. [147] C Offiah, S Twigg, Imaging assessment of penetrating craniocerebral and spinal trauma, Clin Radiol 64 (12) (2009 Dec) 1146–1157. [148] N Ahmed, C Massier, J Tassie, J Whalen, R Chung, Diagnosis of penetrating injuries of the pharynx and esophagus in the severely injured patient, J Trauma 67 (1) (2009 Jul) 152–154. [149] SC Bagheri, HA Khan, RB Bell, Penetrating neck injuries, Oral Maxillofac Surg Clin North Am 20 (3) (2008 Aug) 393–414. [150] JM Messmer, MF Fierro, Radiologic forensic investigation of fatal gunshot wounds, Radiographics 6 (3) (1986 May) 457–473. [151] SD Steenburg, CW Sliker, K Shanmuganathan, EL Siegel, Imaging evaluation of penetrating neck injuries, Radiographics 30 (4) (2010 Jul) 869–886. [152] JJ Peterson, LW Bancroft, MJ Kransdorf, Wooden foreign bodies, Am J Roentgenol 178 (3) (2002 Mar) 557–562. [153] SD LeBlang, DB Nuñez, Helical CT of cervical spine and soft tissue injuries of the neck, Radiol Clin North Am 37 (3) (1999 May) 515–532.
CHAPTER 89
Trauma of the Torso Susan Cross
Introduction Trauma is a significant public health problem and remains a leading cause of death and disability worldwide [1]. It is one the commonest causes of death under the age of 40. As such, the impact of fatal and nonfatal injuries on healthcare systems and costs due to loss of work force is huge [2,3]. Nearly one-quarter of global deaths attributable to trauma per year are as a result of road traffic accidents, approximately one-third are as a result of violence (including suicide and homicide) with the remainder of the main causes secondary to falls, drowning, burns, and poisoning [4]. The classic concept of trimodal distribution of trauma deaths was first described over 20 years ago and played an important role in the development of regionalized trauma networks [5]. Despite the advancements in trauma networks, prehospital care, and injury prevention, the first and highest peak of deaths, occurring immediately or within 60 minutes of injury, remains fairly stable at 50–60%. This reflects the devastating nature of injuries to the central nervous and cardiovascular systems [6]. The second peak is the early phase, widely defined as deaths within 24 hours of arrival at a trauma center (excluding immediate deaths) and accounting for 25–30% of all trauma deaths. The cause of death in this group is due to hemorrhage, most commonly from injuries to the liver, heart, or major blood vessels and neurological injury. The late phase which includes deaths occurring days to weeks after the injury is largely attributable to infection and multiorgan failure and accounts for approximately 10% of all deaths. A number of studies have shown the number of deaths in this late phase to have declined dramatically over time [7,8].
Imaging of the chest, abdomen, and pelvis plays a crucial role in the management of the severely injured patient, helping to identify bleeding and infection in the early and late phases, respectively. The aims of this chapter are as follows:
◾andTo understand how best to image the severely injured patient on arrival in the resuscitation room beyond ◾inTotherecognize immediately and potentially life-threatening injuries on x-ray, ultrasonography (USG) form of fast and multidetector CT (MDCT) ◾interventional To identify intrathoracic and intraabdominal injuries that are significant to the trauma surgeons and radiologists, with pearls and pitfalls where appropriate ◾grading To understand the clinical impact of the American Association of Surgery for Trauma (AAST) of intra-abdominal solid organ injuries, upon management of the severely injured patient ◾mesenteric To understand the importance of how the mechanism of injury matters, particular in bowel and injury ◾ To apply what we have covered in the course of the chapter to important clinical scenarios
While evaluation of the neuro spinal axis is outside the scope of this chapter, it is important to appreciate that the presence of acute severe intracranial injury and/or unstable spinal pathology in the multiply injured patient will contribute to decision-making pathway for the trauma team. Therefore, reference will be made to this where appropriate.
Imaging of the Severely Injured Patient When a severely injured patient arrives in the resuscitation room, there are a number of pathways available to them. Their injuries may, e.g., necessitate a trauma laparotomy, urgent neurosurgical review, interventional radiology procedure, orthopaedic intervention, observation and treatment in intensive therapy or high dependency units (ITU/HDU) or the trauma ward; or a combination of these. It may even be, that after a period of observation in the emergency department, the patient is discharged. Instrumental to where the patient goes next will be the hemodynamic status of the patient and the imaging findings. The primary imaging survey consists of a portable anteroposterior (AP) chest radiograph (CXR), AP pelvic radiograph, and USG in the form of focussed assessment with sonography in trauma (FAST). These should be incorporated as an adjunct, into the clinical primary survey, but should not impede definitive investigation (in the form of CT) or definitive treatment [9]. They are of particular value in the hemodynamically unstable patient, where they can help to identify the source of bleeding, particularly if the patient is too unstable to proceed to definitive imaging with CT [10]. For example, in a hemodynamically unstable blunt polytrauma patient with a normal pelvic and chest radiograph but a positive FAST scan, the source of bleeding is most likely to be from the abdominal cavity.
The chest radiograph is useful to screen for immediately life-threatening injuries, e.g., tension pneumothorax (Fig. 89.1) and large hemothorax (Fig. 89.2). It can also evaluate endotracheal tube placement if there has been emergent intubation prehospital (Fig. 89.3). It should be noted that evaluation for potentially lifethreatening mediastinal hematoma from major vessel injury on the supine chest radiograph is challenging. The finding of mediastinal widening on a supine chest radiograph is nonspecific for traumatic injuries, especially for aortic injuries [11]. More discriminating findings include loss of the aortopulmonary contour, abnormality of the aortic arch, and presence of a left apical cap (Figs. 89.3 and 89.4) In up to 7% of cases of traumatic aortic injury (TAI), the chest radiograph may be normal [12]. In reality, those patients with rapid deceleration mechanism of injury and high clinical suspicion of TAI should undergo further evaluation with MDCT to confirm or refute this diagnosis, irrespective of the chest radiograph findings [13].
FIGURE 89.1 Penetrating trauma. Stab wound to left posterior chest wall. AP erect CXR taken in emergency department demonstrates complete paucity of vascular lung markings on the left (asterisk) with complete collapse of left lung. There is mediastinal shift away from this (black arrow), consistent with a leftsided tension pneumothorax. This requires urgent decompression.
FIGURE 89.2 Blunt trauma. Crush injury between lorry and wall. Hemodynamically unstable. Supine AP chest radiograph taken as part of primary survey. This demonstrates complete increased opacification of the right hemithorax due to blood layering posteriorly along the pleural space while patient is in the supine position. Vascular markings still evident in the right lung (compare with Fig. 89.1). There is mediastinal shift away from the opacification. Chest radiograph findings are consistent with a large right hemothorax. This is a potential source of the patient’s hemodynamic compromise.
FIGURE 89.3 Blunt trauma. Cyclist versus taxi. Hemodynamically stable. Intubated at the scene. (A) Supine AP radiograph confirms endotracheal tube (ETT) is too low, the distal tip of which lies within the right main bronchus (black arrow). Note the loss of the normal aortic arch and loss of normal aortopulmonary contour (white block arrow) together with multiple left-sided rib fractures and extensive surgical emphysema within the soft tissues of the chest bilaterally (L>R). (B) Acute traumatic aortic injury was confirmed on subsequent CT, evidenced by intraluminal thrombus at the origin of the descending aorta (white block arrow) with periaortic hematoma with loss of the fat plane around the aorta. This was confirmed as aortic transection at the aortic isthmus and was treated successfully with thoracic endovascular aortic repair (TEVAR).
FIGURE 89.4 Blunt trauma Motorcyclist versus car. Hemodynamically stable in emergency department. (A) Supine AP CXR taken as part of primary survey. ETT in situ appropriately sited. Artefact from tubes and leads extraneous to patient can be distracting. Right-sided intercostal chest drain in situ. Ill-defined air space opacifications in right mid zone in keeping with lung contusions. Note the abnormal contour of aortic arch (black arrow) and loss of the aortopulmonary contour (white arrow). Subsequent CT confirmed aortic transection with large pseudoaneurysm at the aortic isthmus. (B) Erect AP CXR in the same patient at day 13 post-thoracic endovascular aortic repair TEVAR, for comparison. Nasogastric tube in situ. Note the TEVAR stent in situ and now normal aortic arch and aortopulmonary contours.
FIGURE 89.6 Blunt trauma. Male driver MVC (motor vehicle collision). Hemodynamically unstable. AP pelvic radiograph demonstrates complex pelvic fracture pattern resulting in combined lateral compression and vertical shear combined type injury with marked comminution of the right acetabulum extending into the right iliac blade and right pubic rami (white arrows) and disruption to left sacroiliac joint extending into the left iliac blade with displaced fractures of left superior and inferior pubic rami (black arrows). This unstable fracture pattern is susceptible to significant blood loss. Note the pelvic binder is a little high and needs repositioning ideally at the level of the greater trochanters if possible. The patient was hemodynamically unstable and proceeded directly to the theatre for damage control surgery (DCS) and pelvic packing. WBCT was performed post-DCS surgery for complete injury assessment. WBCT, whole body CT.
FIGURE 89.7 Blunt trauma. Pedestrian versus car. Hemodynamically unstable in emergency department. AP pelvic radiograph out of pelvic binder demonstrates an open book pelvic injury resulting from AP compression type injury with pubic symphysis diastasis (white line) and fractures of the sacral ala (black arrows). This fracture pattern is susceptible to significant blood loss.
Mortality in patients with pelvic fractures with hemodynamically instability has been shown to range from 20% to 50% [14–16]. If a blunt polytrauma patient is hemodynamically stable and is proceeding directly to CT for definitive imaging, then a pelvic radiograph will offer little, if any, incremental help in decision making around the next best step in their management [10]. However, a pelvic radiograph confirming unstable pelvic fractures, in a hemodynamically unstable patient, is useful, particularly if they are not able to proceed to MDCT (Fig. 89.5). It will also confirm the adequate placement of the potentially life-saving pelvic binder [17] (Figs. 89.5 and 89.6). All polytrauma patients also require a postbinder pelvic x-ray after resuscitation even in the presence of a “negative” CT because a well-applied pelvic binder can mask a catastrophic pelvic ring injury (Fig. 89.7).
FIGURE 89.5 Blunt trauma. Pedestrian versus truck. Hemodynamically unstable in emergency department. AP pelvic radiograph demonstrates widening of the left sacroiliac joint (block arrow), malalignment of the pubic symphysis (dashed arrow), displaced fractures of the left superior and inferior pubic rami (white arrow). This unstable fracture pattern is susceptible to significant blood loss. The pelvic binder (curved arrow) is an immediate measure to compress the fractured pelvis in an effort to stop the bleeding. It should be positioned at the level of the greater trochanters, as in this case.
Bedside USG in the form of a FAST scan can be useful in the early resuscitative phase, particularly when it is positive in the hemodynamically unstable patient. Typically, the FAST scan involves evaluation of the hepatorenal fossa, splenorenal fossa, and pelvis to assess for free intraperitoneal fluid (blood), and the xyphoid view to assess for hemopericardium (Fig. 89.8). It can also be extended to assess for pneumothorax and hemothorax [18]. It is important to recognize that the FAST scan may not detect clinically significant bleeding within the abdomen, e.g., within the retroperitoneal cavity or within solid or hollow viscus organs [19] (Fig. 89.9). Surgical emphysema and body habitus may also limit interpretation. Therefore a
negative FAST scan, in the trauma patient with a significant mechanism of injury, must be confirmed by either CT or in the case of limited resources, e.g., the mass casualty scenario, by follow-up FAST scan and observation [20].
FIGURE 89.9 Penetrating trauma. Isolated stab wound to epigastric region. FAST scan negative. Patient tachycardic but normal blood pressure. Skin defect from isolated penetrating stab wound to epigastric region (white arrow). Large retroperitoneal hematoma (block arrow). Trauma laparotomy confirmed IVC injury with through and through injury to the SMV. SMV, superior mesenteric vein.
Multidetector CT is now well established as the definitive imaging investigation in the polytrauma patient and its diagnostic accuracy for detecting clinically significant intrathoracic and intraabdominal injuries has been well documented [21–23]. Whole body CT (WBCT) (vertex to pubic symphysis) can provide a rapid and comprehensive overview of injuries and help to direct the order and way in which these injuries should be treated. There are a number of WBCT protocols that are in use, all of which involve the use of intravenous contrast to evaluate the torso [10,24,25]. Acquiring imaging in the portal venous phase maximizes the
detection of intraabdominal solid organ injuries (Figs. 89.10 and 89.11). Arterial phase imaging enables the detection and characterization of solid organ vascular lesions such as pseudoaneurysms and arteriovenous fistulas, which are often not apparent in the portal venous phase [26,27]. In the context of multiple pelvic fractures, it can also facilitate the characterization of active extravasation as being arterial in origin, rather than osseous or venous [28]. This can provide a “roadmap” for the interventional radiologist if angioembolization is appropriate. Selective acquirement of delayed phase imaging will help further characterize injuries of the urinary tract, which is discussed in detail later in the chapter (Fig. 89.12). Active bleeding manifests as amorphous extravasation of contrast that increases in volume on portal venous and delayed phase imaging (Fig. 89.13). When injury to the bladder is suspected, dedicated imaging with CT cystogram, with active distension of the bladder through a Foley catheter is recommended (Fig. 89.14). Recognizing that the trauma population often involves young patients, every effort should be made to decrease the radiation delivered while not compromising the diagnostic capability of the study. One such example of this is the split bolus WBCT technique, favored in our institution for the vast majority of our polytrauma patients, where a single-pass helical acquisition of the chest, abdomen, and pelvis is preceded by two boluses of contrast with saline bolus or time delay between. The result essentially reflects the combination of the arterial and portal venous phases with their benefits as outlined above. Parenchymal and vascular image qualities have been shown to be equal or superior in comparison to nonsplit bolus multiphase trauma CT protocols (Figs. 89.13 and 89.15). Sensitivity and specificity in detecting splenic parenchymal vascular lesions and characterizing pelvic vascular extravasation have yet to be determined [29] (Figs. 89.15 and 89.70).
FIGURE 89.8 Blunt trauma. Selected USG image (scanning in right upper quadrant) confirming anechoic free fluid in hepatorenal fossa (white arrow). FAST positive scan.
FIGURE 89.10 Blunt trauma. Cyclist versus car. Axial CT image in portal venous phase demonstrates homogeneous enhancement of the liver with clear delineation of a linear low attenuation liver laceration, AAST Grade II liver injury, which does not breach the liver capsule (white arrow). The large volume of hemoperitoneum seen in this image in the left upper quadrant (asterisk) was secondary to bowel injury confirmed at laparotomy.
FIGURE 89.11 Blunt trauma. Motorcyclist versus car. Hemodynamically stable axial CT image acquired with single-pass split bolus technique. Note the homogenous enhancement of the liver and the spleen. There is active extravasation from splenic injury into the peritoneal cavity (white arrow) with hemoperitoneum. AAST grade V splenic injury. This was an isolated high-grade splenic injury and the patient remained hemodynamically stable. Decision made to proceed with nonoperative management (NOM) with adjunctive successful angioembolization.
FIGURE 89.12 Blunt trauma. Fall from horse. Hemodynamically stable. Axial CT (soft tissue windows) acquired with split bolus protocol and demonstrates focal linear laceration in lower pole of the left kidney (black arrow) with perirenal hematoma (asterisk). This is at least an AAST grade III injury. We need to decide whether it involves the pelvicalyceal system which would upgrade the injury and potentially alter management. (B and C) The patient was hemodynamically stable and decision was made to perform a delayed phase scan (at 5 minutes) to allow further assessment of the left pelvicalyceal (PC) system and proximal ureter. Selected axial and coronal reformats confirm no urine leak from the PC system or left ureter during this phase, therefore this injury remains classified as AAST grade III.
FIGURE 89.13 Penetrating trauma. Stab wound to lower left posterior chest. Hemodynamically stable in emergency department. Axial CT image (acquired with split bolus protocol) shows surgical emphysema and hematoma in superficial soft tissues of the left chest wall. There is a shallow hemothorax with small focus of active extravasation related to an intercostal vessel (white arrow). Large bore chest drain was inserted was inserted with drainage of approximately 400 mL of blood. (B and C) Patient initially stabilized but then further increase in volume of blood from the left chest drain with drop in systolic blood pressure 5 hours after admission. Repeat dual-phase CT was performed. Arterial phase (B) shows focal of active extravasation has increased in size (white arrow) from the previously noted CT with increase in size of hemothorax (asterisk). Delayed phase at 90 seconds. (C) shows increased amorphous pooling of contrast at this site consistent with active bleeding. Patient proceeded to interventional radiology for coil angioembolization of the ninth intercostal artery.
FIGURE 89.14 Restrained driver. Hemodynamically stable but FAST positive. Coronal reformat from CT cystogram demonstrates focal defect in the dome of the bladder (black arrow) with free intraperitoneal spill of water-soluble contrast. This confirms intraperitoneal bladder rupture which necessitates laparotomy repair (Type). The initial FAST scan was positive due to the free intraperitoneal spill of urine (an important learning point that free fluid in a FAST scan, although most likely, is not always blood).
FIGURE 89.15 Pedestrian versus car. Hemodynamically stable in emergency department. Axial CT image acquired using split bolus protocol with splenic laceration with intralesional focal of vascular injury (white arrows). Small volume of perisplenic hematoma but not active extravasation outside the splenic capsule into the peritoneum. AAST grade IV splenic injury. Patient proceeded to interventional radiology. Discrete pseudoaneurysm not identified on the diagnostic angiogram and patient proceeded to proximal splenic angioembolization with coils.
FIGURE 89.70 Penetrating trauma. Single stab wound to right paravertebral region. Initial responder to fluid resuscitation. Surgical emphysema and hematoma within the right paravertebral musculature (black arrow). Large volume of retroperitoneal hematoma (asterisk) with loss of fat plane around the IVC. The IVC has an irregular contour (white arrow). IVC injury confirmed at laparotomy.
There have been a number of studies and systematic reviews which have assessed the benefits and risks of immediate WBCT scan compared with selective CT in major trauma patients [30–36]. All of these have agreed that there is a time benefit to WBCT scanning; however, while WBCT has been shown to be a predictor of survival in a number of these studies, a consensus has not been reached on overall survival benefit. However, diagnostic accuracy of MDCT together with rapid scan time has meant that many trauma centers incorporate WBCT scanning (vertex to pubic symphysis) into the trauma survey either as a supplement or replacement to conventional imaging in the severely injured patient. It should be noted that as far as possible CT evaluation of the torso should be performed with the arms up, unless prevented from doing so due to fracture or injury. This provides the best quality evaluation of the solid organs by reducing streak artifact from the arms (Fig. 89.16) and also reduces radiation dose by up to
45%, when compared with arms down by sides [37]. Oral contrast is not routinely administered in the emergency setting of blunt abdominal trauma.
FIGURE 89.16 Blunt trauma. (A) Axial CT following IV contrast with arms down. Note the streak artefact from both arms across the upper abdomen which can mask or mimic underlying liver lacerations. (B) Scanogram shows the reason for arm down in this study (angulated fracture of right humeral shaft). (C) Another patient with history of blunt trauma. Arms down with resultant streak artefact across upper abdomen which can mask an underlying liver injury. Note the AAST grade II liver injury in the right lobe of the liver (arrow) and splenic injury with perisplenic hematoma AAST grade III.
There will always be a number of hemodynamically unstable severely injured patients who require immediate life-saving surgery. The decision to proceed to CT with a hemodynamically unstable patient is at the trauma team leaders discretion and should only be performed where there is a well-organized trauma team and appropriate structural requirements to facilitate this safely [38]. Often these patients will proceed to WBCT after immediate life-saving surgery to ensure complete evaluation of the retroperitoneum, mediastinum and neurospinal axis; to further characterize solid organ injuries; to assess for vascular injuries that may require angioembolization or to assess for source of ongoing hemodynamic instability (Figs. 89.17 and 89.18). This is particularly helpful in patients post damage control surgery (DCS) for high velocity penetrating trauma (Fig. 89.19). Of note, it is worth performing a noncontrast CT scan of the abdomen and pelvis in patients who are having WBCT post DCS, as artefact from packing and surgical material can be difficult to distinguish from foci or active extravasation or bone fragments. Alternatively, if the CT scanner has dual energy capabilities then a virtual noncontrast scan can be obtained using the spectral data.
Key Points: Pearls to Remember Incorporation of the chest and pelvic radiographs and FAST scan into the clinical primary survey should enhance and not delay definitive imaging, in the form of MDCT, or definitive treatment
WBCT (vertex to pubic symphysis) can provide a rapid and comprehensive overview of injuries in the polytrauma patient and help to direct the order and way in which these should be treated Appreciate that there is a balance to be struck between time in the scanner, radiation exposure and maintaining diagnostic accuracy, all of which are important in the severely injured patient
FIGURE 89.17 Blunt trauma. One undertrain. Hemodynamically unstable in emergency department patient proceeded directly to theatre for damage control surgery (DCS) with pelvic packing to achieve hemostasis. External pelvic fixator also applied to temporarily stabilize the bony pelvis. Following theatre patient proceeded to CT for WBCT to provide complete assessment of injuries and for assessment for any ongoing bleeding. Selected axial CT images are shown which show extensive pelvic packing material deep within the pelvis (white arrows). Note the effaced catheterized bladder (asterisk) which demonstrates large low attenuation clot within it. It is useful to perform the post DCS WBCT with a noncontrast control scan, in addition to the postcontrast scans, as artefact from packing can be difficult to distinguish from bone fragments or even small foci of active extravasation. If clear visualization of the bladder has not been achieved during initial surgery then CT cystogram can also be performed however, this patient will return to theatre for removal of the packing material within the next 72 hours at which stage direct clinical evaluation can be performed. WBCT, whole body CT.
FIGURE 89.18 Penetrating trauma. Stab wound to right upper quadrant. Hemodynamically unstable in emergency department. Proceeded directly to theatre for DCS. Selected axial CT image following laparostomy with extensive packing material around the liver (white arrow). Note the effaced liver demonstrates large foci of active extravasastion (asterisk) within the large liver laceration (AAST grade III), consistent with ongoing bleeding. Patient proceeded to interventional radiology. Indirect portovenogram was normal. Angiography confirmed active bleeding from the right hepatic artery which was successfully embolized with restoration of hemodynamic stability. It is helpful to perform post DCS WBCT with a noncontrast control scan, in addition to the postcontrast scans, as artefact from packing can be difficult to distinguish from bone fragments or even small foci of active extravasation. Alternatively if using a dualenergy CT scanner, a virtual noncontrast scan can be obtained from the spectral data. DCS, damage control surgery; WBCT, whole body CT.
FIGURE 89.19 High-velocity penetrating trauma. Gunshot wound (GSW) to abdomen. Patient was taken straight to theatre. CT performed post DCS. (A) Coronal reformat of delayed phase CT to characterize the right-sided renal injury noted at surgery. Right sided perirenal hematoma (asterisk) related to lower pole renal laceration. Intact collecting system on the right. AAST grade III renal injury. (B) Axial CT image on bone windows characterizes the musculoskeletal injuries caused by the bullet (black arrows). Note the trajectory of the bullet obliquely from the left side of abdomen to its final resting place in the right retroperitoneal space at the iliopsoas junction (dashed arrow).
Thoracic Trauma Thoracic injury is the third most common cause of trauma, after head and extremity injury, with primary mortality reaching up to 25%. Most thoracic injuries are attributable to a blunt mechanism with motor vehicle collisions contributing to approximately two-thirds of these. Other mechanisms of blunt thoracic injury include falls and blows from blunt objects. Less common is penetrating chest trauma, usually secondary to stabbings or gunshot wounds. It is important to identify thoracic injuries on initial imaging, to recognize that any number of these can coexist in the polytrauma patient and to understand the potential complications that may arise from these injuries in the later phase.
Injuries to the Pleura Pneumothorax
◾fractures Pneumothorax occurs in approximately 30–40% of chest trauma, most commonly, as a result of rib that penetrate the pleural cavity. It can also result from disruption of alveoli due to sudden increased thoracic pressure or rapid deceleration force, with or without rib fractures [22]
◾pleura On an erect chest radiograph, a pneumothorax will be delineated by the sharp line of the visceral beyond which there are no vascular markings. It is important to recognize common mimics of a pneumothorax including artefact from skin folds, oxygen rebreathe masks, and the medial scapula border In total, 10–50% of traumatic pneumothoraces are not identified on chest radiograph in the supine trauma patient but are seen on CT [39]. In the supine position, the air collects in the anterior costophrenic sulcus and may result in the following, often subtle, signs on the radiograph: the “deep sulcus” sign, increased lucency in the lower chest, the “double diaphragm” sign where air outlines the dome and the anterior insertion of the diaphragm (Fig. 89.20). These are termed occult pneumothoraces and are important to identify on CT as these can become clinically symptomatic if the patient is placed on positive mechanical ventilation or requires intubation [40](Fig. 89.21) Although tension pneumothorax is a clinical diagnosis, it can be suggested on chest radiograph and MDCT, when the pneumothorax is associated with the following signs: collapsed ipsilateral lung, mediastinal shift to the contralateral side, widening ipsilateral intercostal spaces, and flattening of the ipsilateral hemidiaphragm (Fig. 89.1) Re-expansion pulmonary edema, although rare, can occur after placement of a chest tube, particularly if there has been a large pneumothorax or hemothorax with rapid lung reinflation [41] (Fig. 89.22)
◾ ◾ ◾
FIGURE 89.20 Blunt trauma. Passenger motor vehicle collision (MVC) chest radiograph (A) confirms adequate positioning of the endotracheal tube (ETT). Illdefined air space opacification in left lower zone medially (white arrow) and subtle increased lucency at the left lower zone (asterisk). (B) Axial CT image on lung windows confirms large left-sided pneumothorax, with air collecting anteriorly in costophrenic sulcus (asterisk). Note the ill-defined coup and contracoup lung contusions in the left upper lobe and medial right lower lobe, respectively (white arrows).
FIGURE 89.21 Blunt trauma. Driver high speed MVC. (A) Supine CXR, performed as part of primary survey, confirms adequate positioning of the endotracheal tube. There is extremely subtle increased lucency in the left lower chest. Minimally displaced fracture of the posterior seventh rib on the right but otherwise no convincing radiographic evidence of pneumothorax on the right. (B) Axial image from CT chest on lung windows confirms presence of shallow bilateral pneumothoraces, slightly larger on the left than the right (asterisk). There is also a shallow left hemothorax, confirmed on soft tissue windows (black arrow).
FIGURE 89.22 Blunt trauma. Fight 10 days earlier with blunt impact to left chest. (A) Erect AP CXR shows large left hemopneumothorax with mediastinal shift to the right. (B) Erect AP CXR on day 4 following insertion of a large-bore intercostal drain when patient is complaining of increasing shortness of breath demonstrates re-expansion of the left lung with multiple air bronchograms within the left lung consistent with re-expansion pulmonary edema. (C) Erect AP CXR on day 15 shows complete resolution of this.
Hemothorax
◾diaphragm, Bleeding into the pleural cavity can come from the pleura, chest wall, lung, mediastinum, or the abdomen, in the case of liver or splenic injuries with concurrent diaphragm rupture. Small volume hemothorax may not be detected on the chest radiograph ◾position, In the erect position, radiographic signs are similar to that of a simple pleural effusion. In the supine blood layers dependently along the posterior pleural space resulting in increased opacification of the hemi thorax (Fig. 89.2). It can also form a rim of increased density at the lateral surface and apex (Figs. 89.23 and 89.24) CT is very sensitive in detecting even a small volume of hemothorax and has the added benefit of using attenuation values to characterize the fluid further. Blood measures 35–70 HU depending on the amount of clot present. Reactive serous effusion can be seen in patients with intraabdominal solid organ injuries and bilious effusion can occur when there is a liver injury associated with diaphragm rupture Once a hemothorax has been identified on CT, it is important to evaluate carefully for any active extravasation, seen as a focus of high density, typically within 10 HU of the nearest large artery. If a delayed phase has been acquired, the focus of high-density persists or increases in size (Fig. 89.13) Thoracotomy is indicated, if there is continued output from the chest tube over a determined period of time. For example, 1 L of blood on intercostal drain insertion, 200 mL/h ongoing drainage for 4 hours or if requiring ongoing transfusion to maintain hemodynamics If, however, CT has delineated active extravasation from an intercostal artery, usually from a fractured rib, one treatment option to consider is transcatheter arterial embolization of the bleeding intercostal artery [42,43] (Figs. 89.13 and 89.23). Retained hemothorax can lead to empyema therefore early diagnosis and treatment are crucial (Fig. 89.24)
◾ ◾ ◾ ◾
FIGURE 89.23 Penetrating trauma. Stab wound to left posterior chest. (A) Erect AP CXR shows large left-sided pleural collection which in context of penetrating trauma to left chest is in keeping with a hemothorax. Note the hemothorax forming a rim of increased density laterally (black arrow). CT confirmed focus of active extravasation into the left pleural space at the 11th intercostal space. Intercostal chest drain was inserted. Patient proceeded to interventional radiology. (B) Selected image from angiogram showing coil angioembolization to left 11th intercostal artery. (C) Erect AP CXR at day 3 following coil embolization and removal of the left intercostal chest drain shows complete resolution of the left hemothorax with only minimal residual atelectasis.
FIGURE 89.24 Penetrating trauma. Stab wounds to left chest. (A) Supine AP CXR on admission in resus bay demonstrates increased opacification of the left hemithorax, with rim of increased density at the lateral surface and apex (black arrows) all consistent with a large left-sided hemothorax. (B) AP erect CXR at day 6 following removal of large-bore chest drain confirms resolution of the large left hemothorax with residual consolidation and atelectasis in left lower lobe and minor surgical emphysema in soft tissues of the left chest wall. USG at this time confirmed minimal residual pleural collection. (C) PA erect CXR at day 14. Patient represents with pyrexia and worsening shortness of breath. CXR confirms left hydropneumothorax with air–fluid level (white arrow). Patient underwent VATs decortication for treatment of large left-sided empyema. (D) AP erect CXR post VATS decortication 4 weeks following injury. There is residual atelectasis and blunting of left costophrenic angle. Patient is now apyrexial with no other respiratory symptoms.
Injury to the Lung Pulmonary Contusions
◾byPulmonary contusions are common and seen in up to 70% of thoracic trauma [41]. They are caused hemorrhage into the alveoli and interstitial spaces resulting from compression and shearing forces osseous structures or pleural adhesions ◾against MDCT is more sensitive than CXR in detecting pulmonary contusions and as such, the radiograph may be normal in the first few hours after penetrating or nonpenetrating trauma. Contusions usually show improvement within 2 days and clear within 3–14 days, in contrast to superimposed aspiration and/or infection which can persist or progress Imaging appearances range from patchy nonsegmental ground glass change to frank consolidation, occasionally sparing a thin rim (1–2 mm) of subpleural lung (demonstrable only on MDCT) (Figs. 89.25 and 89.26) Pulmonary contusions carry a 10–25% mortality risk and persistence of pulmonary contusions after the expected time frame for resolution increases the risk of developing pneumonia and acute respiratory distress syndrome. The development of new airspace opacification more than 24 hours after trauma suggests alternative diagnoses such as aspiration, pneumonia and fat embolism, rather than pulmonary contusion [44]
◾ ◾
FIGURE 89.25 Blunt trauma. Pedestrian versus car. Supine CXR demonstrates multiple air space opacities in right hemithorax (white arrows). (B and C) Corresponding axial CT imaging on lung windows characterizes these much better as lung contusions (white arrow) and lung lacerations (black arrows) respectively. Note also the right hemopneumothorax is much better delineated on the subsequent CT. Multiple right-sided rib fractures are seen on the CXR primarily because a number of them (6th–8th ribs) are displaced. Characterization of rib fractures (including site, number, degree of displacement) should be performed on CT.
FIGURE 89.26 Blunt trauma. Motorcyclist versus car. (A) Supine CXR confirms appropriate siting of ETT (at level of medial clavicles). Right intercostal drain in situ. Ill-defined air space opacifications in right upper and mid zones (white arrows), confirmed on subsequent CT as lung contusions. (B) Axial CT image (lung windows) demonstrates ill-defined ground glass change on the right consistent with lung contusion (white arrow). Note also shallow bilateral hemothoraces (asterisk) and surgical emphysema in right chest wall from recent at scene thoracostomy and subsequent chest drain insertion (not shown).
Pulmonary Lacerations Shearing, compression, and deceleration forces can all result in pulmonary lacerations. The inherent elastic recoil of lung tissue means the normal lung retracts around the laceration leaving thin-walled round or oval spaces filled with air (traumatic pneumatocoele) and/or blood (traumatic hematocoele or pulmonary hematoma) [41,44] (Figs. 89.25, 89.27, and 89.28). These can take months to resolve completely and weeks down the line could be mistaken for a lung nodule if not correlated with previous history and imaging. Potential complications include infection, enlargement of the laceration, and formation of bronchopleural fistula [22].
FIGURE 89.27 Blunt trauma pedestrian versus car. (A) Supine CXR demonstrates multiple displaced right sided rib fractures with diffuse increased opacification throughout right hemithorax consistent with hemothorax layering posteriorly along the pleural space. Further ill-defined nodular air space opacities in the right mid and lower zones are better characterized on the subsequent CT. (B) Axial CT image (lung windows), confirms right-sided hemopneumothorax. The ill-defined air space opacites seen on the x-ray are a combinaton of lung contusion (asterisk) and partially blood-filled lung lacerations (black arrows).
FIGURE 89.28 Blunt trauma pedestrian versus car. (A) Coronal CT reformat, lung windows, on admission, confirms large traumatic lung laceration on the right (asterisk). (B) CXR day 10—the large right lung laceration persists with airfluid level within it (asterisk). Multiple right-sided rib fractures persist. Lung lacerations can persist for weeks to months, therefore it is important to correlate any CXR findings with previous imaging and history.
Injuries to Mediastinal Structures Aorta and Great Vessels
◾80% TAI is the second most common cause of traumatic death (after neurological injury). More than will die before reaching hospital, however, of those that get to hospital, approximately 60–80% will survive [12]. The majority are resultant from highspeed motor vehicle collisions (>30 mph), with a spectrum of injuries from minimal aortic injury to complete transection (Figs. 89.3, 89.29, 89.30, and 89.32). The majority are transverse aortic tears with pseudoaneurysm formation and it is important to recognize that these are not “aortic dissections” as one would see in the nontraumatic population. They can occur anywhere along the aorta but the majority are at the isthmus (85–90%), followed by distal thoracic aorta (5%), abdominal aorta (5%), and aortic root (1%) in order of descending frequency, most often at sites of relative aortic fixation. Abdominal aortic injury can be associated with lower thoracic and lumbar vertebral body fractures (Fig. 89.64) Chest radiograph findings of TAI are sensitive but not specific and described earlier in the chapter. The imaging technique of choice for suspected TAI is MDCT and if the initial MDCT is equivocal then repeat cardiac gated CT is recommended [45,46] Direct signs of aortic injury on MDCT include pseudoaneurysm formation, periaortic hematoma with loss of fat plane around the aorta, abnormal aortic contour, intimal flab and thrombus, active extravasation, and aortic pseudocoarctation (narrowing of the distal thoracic aorta due to hemorrhage) [12] (Figs. 89.3, 89.29, 89.30, and 89.32)
◾ ◾ ◾
◾TAIMediastinal hematoma with preservation of the fat plane around the thoracic aorta will not be from and should prompt further evaluation of the mediastinal structures, in particular the aortic branch vessels (Fig. 89.31). Periarterial hematoma in the superior mediastinum is an important indirect sign of possible brachiocephalic or subclavian injury Multiplanar and volumetric reformats (particularly the sagittal oblique plane) are invaluable to confirm axial findings, characterize the TAI, and determine optimum treatment, particularly as the treatment of choice is more often endovascular stent graft repair [13,46] (Fig. 89.30) Treatment is usually within 24 hours of diagnosis but one must take into account other significant comorbid injuries that may necessitate more urgent treatment. Minimal aortic injures, described as intimal tears less than 10 mm in length, typically follow a nonoperative course and can be followed up with CTA until resolution [45] (Fig. 89.32)
◾ ◾
FIGURE 89.29 Blunt trauma motor vehicle collision at 70 mph. (A) Axial CT image acquired with split bolus protocol (soft tissue windows) demonstrates mediastinal hematoma with loss of the fat plane around the aorta (asterisk). This should alert the reader to potential mediastinal great vessel injury and prompt careful interrogation of the aorta and the major arch vessels. (B) Axial CT image slightly lower confirms acute traumatic aortic injury (white arrow).
FIGURE 89.30 Blunt trauma. Motorcyclist versus car. (A) Axial postcontrast CT acquired using split bolus protocol demonstrates focal traumatic pseudoaneurysm formation at the aortic isthmus consistent with acute TAI (white arrow). Note the periaortic hematoma with loss of fat plane at the aorta (asterisk). (B) Oblique sagittal reformat is useful to delineate the aortic injury further in this region and can help in preoperative planning as distance of the injury from the left subclavian artery is important. (C) Axial image from dedicated CTA of the thoracic aorta 3 months after injury at a similar level confirms resolution of the periaortic hematoma and no endoleak from the thoracic aortic stent.
FIGURE 89.31 Blunt trauma. Motorcyclist versus car. ETT and left-sided intercostal drain in situ. Acute mediastinal hematoma surrounding the left subclavian artery (white arrow). Close interrogation of the aortic arch branch vessels should be performed to ensure no direct signs of vessel injury. Interrogation of the thoracic spine at this level is also warranted. ETT, endotracheal tube.
FIGURE 89.32 Blunt trauma. Pedestrian versus car. (A) Axial CT acquired using split bolus technique confirms focal intimal flap at aortic isthmus consistent with grade 1 acute TAI or minimal aortic injury (white arrow). Decision made to follow up with dedicated CTA at 48 hours. (B) Axial CT image (arterial phase) at 48 hours demonstrates almost complete resolution of the intimal flap tear. Repeat CTA at day 7 was normal.
FIGURE 89.64 Blunt trauma. Fall from 4 m. (A) Axial CT image acquired with split bolus protocol demonstrates segmental edema and hypoenhancement of the splenic flexure (white arrow). This is site of watershed anastomosis between the ascending left colic artery and marginal artery of drummond (Griffiths point) and is the most common location for ischemic colitis. There were no other direct or indirect signs of bowel injury and no clinical peritonism. Patient was non operatively managed with serial observations and follow up CT confirmed resolution of presumed transient ischemia. Patient was discharged after 48 hours.
Tracheobronchial and Esophagus Injuries Laceration or rupture of a major airway is an uncommon result of severe chest trauma, usually in a motor vehicle collision. Fracture of the first three ribs is often present, and mediastinal emphysema and pneumothorax are common. The injury is usually within 2.5 cm of the carina with bronchial laceration being more common than tracheal laceration. If the bronchial sheath is preserved there may be no immediate signs or symptoms, but tracheostenosis or bronchiectasis may occur later. Peristent pneumothorax despite the presence of a chest drain should raise suspicion of possible bronchial injury. CT may be helpful in diagnosis, but bronchoscopy is the best diagnostic method in the acute stage [44]. Blunt esophagus rupture is extremely rare with most esophagus injuries occurring from penetrating trauma. Clinically there is acute mediastinitis; radiographically there are indirect signs including pneumomediastinum, with or without a pneumothorax or hydropneumothorax, which is usually left-sided. The diagnosis should be confirmed by a water-soluble contrast swallow. Injuries to Heart and Pericardium Cardiac injury may result from penetrating or blunt trauma and is rare accounting for less than 10% of all trauma admissions. Penetrating injuries are usually rapidly fatal (mortality of approximately 80% in gunshot wounds and 60% in stab wounds) but may cause tamponade, ventricular aneurysm, or septal defects. Survival is directly related to initial hemodynamic status [47]. Blunt trauma may cause myocardial contusion and infarction and may be associated with transient or more permanent rhythm disturbance. There is no single test to rule blunt cardiac injury in or out but a combination of normal ECG and normal cardiac enzymes has a negative predictive value of 98% for significant blunt cardiac injury [48]. CT has low sensitivity in detecting cardiac injuries but imaging findings include hemo- or pneumo-pericardium, intramural hematoma, and cardiac herniation if pericardial tear (Figs. 89.33 and 89.34). Coronal multiplanar reformats are helpful to identify shallow hemopericardium.
FIGURE 89.33 Penetrating trauma. Self-inflicted stab wounds to praecordial region. Axial CT image following IV contrast demonstrates focal skin defect anteriorly in the midline (white arrow). There is retrosternal hematoma (black arrow) and high attenuation fluid within the pericardium in keeping with hemopericardium (asterisk).
FIGURE 89.34 Blunt trauma. MVC (motor vehicle collision) left-sided impact. (A) Supine AP CXR demonstrates extensive surgical emphysema outlining the pectoral musculature and soft tissues of the chest wall bilaterally. There are multiple displaced left-sided rib fractures. In addition, there is evidence of pneumopericardium (asterisk). (B and C) Axial CT (soft tissue and lung windows) demonstrates pneumopericardium (asterisk). There is also posterior displacement of the heart with clockwise rotation of the left ventricle apex all consistent with traumatic pericardial rupture (arrow).
Injuries to Thoracic Cage Rib Fractures
◾limited Rib fractures are the commonest skeletal injury in blunt chest trauma. The chest radiograph has sensitivity for the detection of rib fractures but can delineate complications from them including significant pneumo- and hemo-thorax (Fig. 89.2). CT is excellent at not only identifying number and location of rib fractures but importantly any associated thoracic injuries. Multiplanar reformats are useful to aid fracture detection, especially if they are undisplaced Fractures of the first three ribs are indicative of high-velocity injury and should prompt careful evaluation of the mediastinal great vessels, in particular the subclavian arteries, while fractures of the lower three ribs may be associated with hepatic, splenic or renal injury [49] (Fig. 89.35) Overall morbidity and mortality increases with the increasing number of fractures, particularly so in the elderly population, therefore early identification and aggressive pain control measures including regional analgesia with percutaneous catheter infusion are crucial [50] Another complication of rib fractures includes a flail segment. Flail chest occurs when there are three or more contiguous ribs with fractures in two or more places. It is usually apparent clinically, the affected part of the chest wall being paradoxically sucked in during inspiration, possibly compromising the underlying lung, and leading to increased requirement for mechanical ventilation At this point, it is important to mention costochondral fractures which commonly occur in high energy trauma, often occur with multiple consecutive rib fractures and also contribute to chest wall instability [51]. These can be more subtle and careful interrogation of the entire rib from costovertebral to costochondral junction with the aid of multiplanar reformats is important Surgical fixation of flail chest injuries has been shown to reduce pulmonary complications, ITU stays and mortality in selected patients [52] (Fig. 89.36). At our institution, there is multidisciplinary team discussion of each case to aid decision making around conservative or surgical management of these patients. Regardless of whether the multiple rib fractures constitute “flail chest,” the importance of early good regional anaesthesia cannot be emphasized enough in these patients
◾ ◾ ◾ ◾ ◾
FIGURE 89.35 Blunt trauma. Fall from height onto wall. Axial CT image following IV contrast demonstrates branching central liver lacerations (bear claw appearance) which extend to the liver capsule posteriorly (white arrow). There is associated hemoperitoneum (asterisk). No active extravasation either within the liver parenchyma or into the peritoneal cavity. AAST Grade IV liver injury. Associated right rib fracture (circle).
FIGURE 89.36 Blunt trauma. Elderly patient fall from standing onto the right side. (A) Semierect AP CXR demonstrates multiple displaced right sided rib fractures with radiological flail segment confirmed on CT. Large bore intercostal drain was placed for the associated pneumothorax. However, despite early and aggressive pain control measures, the patient developed increased respiratory distress. Decision was made to proceed to right-sided surgical fixation on day 4 following the injury with excellent clinical response. (B) CXR following right-sided rib plate fixation.
Sternal Fractures Sternal fractures are most often as a result of direct impact to the chest or deceleration injuries, typically occurring at the body or manubrium. They are most commonly detected using MDCT and sagittal reformats are particularly helpful in detecting the minimally displaced fractures (Fig. 89.37). They may be associated with retrosternal hematoma and if present should prompt careful interrogation of the heart, mediastinal structures and thoracic spine, particularly when as a result of a fall from a height greater than 20 feet [22,48].
FIGURE 89.37 Blunt trauma. Fall from height. Sagittal reformat on bone windows demonstrates minimally displaced fracture through body of sternum. Sternal fractures can be easily overlooked on axial CT imaging and the coronal and in particular sagittal reformats should be reviewed to ensure no injury. Sternal fractures resulting from significant mechanism of blunt trauma should prompt careful review of the heart, mediastinal great vessels, and the spine to ensure no associated injury.
Clavicle Fractures Fractures of the clavicle may be associated with injury to the subclavian vessels or brachial plexus (scapulothoracic dissociation or floating shoulder) and posterior dislocation of the clavicle at the sternoclavicular joint may cause injury to the trachea, oesophagus, great vessels, or nerves of the superior mediastinum. Scapula Fractures Fractures of the scapula are rare and usually as a result of high energy trauma, e.g., fall from height or motor vehicle collisions. Their presence should again prompt careful interrogation for other thoracic injuries, including integrity of the shoulder girdle and adjacent neurovascular bundle. Management is typically conservative unless there is significant displacement.
Injuries to the Diaphragm
◾abdomen. Laceration of the diaphragm may result from penetrating or nonpenetrating trauma to the chest or Ruptures of the left hemidiaphragm are encountered more frequently in clinical practice than ruptures on the right, possibly because of the protective effect of the liver. The typical plain film appearance is of obscuration of the affected hemidiaphragm and increased shadowing in the ipsilateral hemithorax due to herniation of stomach, omentum, bowel, or solid viscera (Fig. 89.38), although such herniation may be delayed A number of direct and indirect CT signs have been described (Figs. 89.39–89.45). In cases of isolated penetrating trauma, injury above and below the diaphragm is an indirect sign of diaphragmatic injury [53] (Fig. 89.43). This is of particular importance on the left as these injuries typically need operative repair (Fig. 89.41). A review of coronal and sagittal reformats on MDCT is essential as more subtle diaphragmatic injuries may not be obvious on the axial imaging (Fig. 89.42)
◾
FIGURE 89.38 Blunt trauma. Restrained driver MVC. AP supine CXR, taken as part of the primary survey, demonstrates loss of left hemidiaphragm with abnormal gas-filled structure in the left hemithorax due to herniation of bowel into left chest (asterisk).
FIGURE 89.39 Blunt trauma. Passenger high-speed MVC. Hemodynamically stable. (A) AP supine CXR taken as part of the primary survey. ETT in situ appropriately sited. There is tracheal deviation to the right and increased shadowing in the lower left hemithorax with complete loss of the left hemidiaphragm. (B) Coronal CT reformat confirms left hemidiaphragm rupture with herniation of splenic flexure and small bowel loops into the left chest. (Indirect sign of diaphragm injury). Patient proceeded to theatre for laparotomy. ETT, endotracheal tube.
FIGURE 89.40 Blunt trauma. Patient crushed between wall and car. Supine AP CXR. ETT in situ appropriately sited. Homogeneous increased opacification of right lower zone with the appearance of marked elevation of the right hemidiaphragm. Coronal reformat of the subsequent CT confirms rupture of the right hemidiaphragm with herniation of the liver into the chest (which explains the appearances seen on the CXR) (asterisk). Intrathoracic herniation of viscera is an indirect sign of diaphragmatic injury. ETT, endotracheal tube.
FIGURE 89.41 Blunt trauma 12 months previously. Patient who had been involved in a MVC 12 months previously. At initial injury patient had sustained a number of rib fractures. The patient represented with clinical evidence of bowel obstruction. Coronal CT reformat demonstrates defect in left hemidiaphragm (white arrow) with herniation of splenic flexure (asterisk) through the defect into the chest with associated bowel obstruction.
FIGURE 89.42 Blunt trauma. Pedestrian versus van. Axial and coronal images demonstrate intrathoracic herniation of left lobe of liver (asterisk) and part of the stomach (white arrow) through defect in the left hemidiaphragm (an indirect sign of diaphragm injury). This case illustrates the importance of evaluation of the multiplanar reformats to fully interrogate the diaphragm.
FIGURE 89.43 Penetrating trauma. Single stab wound to left flank. (A and B) Selected axial CT imaging acquired using split bolus protocol demonstrates moderate left hemothorax (asterisk) and AAST grade I renal injury (white arrow). (C) These contiguous injuries above and below the diaphragm in the context of isolated penetrating trauma to left flank should raise index of suspicion of diaphragmatic injury and prompt careful evaluation of multiplanar reformats (MPRs) (Indirect sign of diaghragmatic injury). Note in this case the sagittal reformats did not reveal the diaphragmatic injury but decision made to proceed to laparotomy to evaluate further given the indirect sign on CT. A 10 cm tear of the left hemidiaphragm was confirmed at laparotomy and repaired.
FIGURE 89.44 Penetrating trauma. Stab wound to left upper quadrant. Hemodynamically stable. (A) Supine CXR, taken as part of primary survey, is essentially normal. In particular the left hemi diaphragm appears intact. (B) Coronal CT reformat confirms focal discontinuity (dashed line) of the left hemidiaphragm with dangling diaphragm sign (white arrow), both direct signs of diaphragm injury. Note the herniation of omentum and bowel through the defect laterally but not above the medial hemidiaphragm which gives the seemingly normal appearance of the left hemidiaphragm on the initial CXR. Patient proceeded to laparotomy for repair of the left hemidiaphragm injury.
FIGURE 89.45 Penetrating trauma. Stab wound to left flank. Focal discontinuity of left hemi diaphragm (white arrow)—a direct sign of diaphragmatic injury Note also the AAST grade II splenic injury adjacent to this (short black arrow).
Abdominal Trauma Introduction Most traumatic abdominal injuries presenting to the emergency department are due to blunt trauma, the majority as a result of road traffic accidents, followed by falls, assault and sports related injuries. The most common cause of penetrating abdominal trauma is a stab wound or gunshot [24]. Initial management of traumatic abdominal injuries will depend on hemodynamic stability and whether there are definitive indications for trauma laparotomy identified either clinically or, more often, on MDCT (e.g., bowel or intraperitoneal bladder injury) (Figs. 89.46–89.48). In the hemodynamically stable blunt trauma patient, management of
solid organ injury has evolved to that of primarily nonoperative management (NOM) with increasing reliance on MDCT for diagnosis and classification of injuries [54]. The most widely accepted grading system for blunt splenic, hepatic and renal injuries is the revised organ injury scale (OIS) of the AAST. Its initial purpose was to provide anatomic description of injury (based on surgical findings) rather than guide clinical pathways [55]. The 1994-AAST revision did not include active contrast extravasation or intraparenchymal vascular injuries, both of which have been shown to be a major factor in failure of NOM of solid organ injuries (Figs. 89.11 and 89.15). A novel CT-based grading system for splenic injury was proposed in 2007 by Marmery et al., which proved to better predict the need for splenic artery embolization (SAE) or operative management (OM) [56]. In 2018, AAST published an OIS update, incorporating CT diagnosed vascular injury and active bleeding into the liver, spleen, and kidney injury grading. This has since been validated in a study by Morell-Hofert et al. in 2020 which showed that the revised 2018 version was superior to the 1994-AAST classification in terms of correlation with primary or secondary OM in blunt splenic and hepatic trauma [57]. As such, timely and accurate CT interpretation of solid organ injuries is crucial to aid management decisions and will be described in the following subsections.
FIGURE 89.46 Blunt trauma. Restrained driver MVC. Hemodynamically labile. Initial responder to resuscitation. Coronal CT reformat acquired with split bolus protocol demonstrates mesenteric hemorrhage with focus of active extravasation
(white arrow). Patient was peritonitic and proceeded directly to laparotomy. Large mesenteric tear was repaired.
There is no consensus on follow up imaging after NOM of solid organ injury. As such decisions around whether to repeat CT is often guided by the patient’s clinical status or deterioration in blood tests [58] (Figs. 89.51 and 89.54). Routine postdischarge scans are often felt unnecessary [59].
FIGURE 89.51 Blunt trauma. Pedestrian versus car. Initial responder, proceeded to CT. (A) Axial CT acquired using split bolus protocol demonstrates large volume hemoperitoneum around liver and spleen (asterisk) with focal active extravasation extending beyond splenic capsule (black arrow). AAST Grade V splenic injury. Complete review of the CT confirmed this to be an isolated high-grade splenic injury with no findings that would necessitate laparotomy. Patient remained hemodynamically stable. Decision made by Trauma Surgeon to proceed with NOM but with adjunct of splenic angioembolization by interventional radiologist. Patient remained on ITU with close monitoring of observations. On day 4, patient was pyrexial with markedly elevated WCC. No signs of active bleeding and hemoglobin was stable. (B) Repeat CT with IV contrast demonstrated organization of the large perisplenic hematoma with foci of gas within the splenic collection (white arrow). The previously noted large hemoperitoneum has resolved. Note the proximal splenic embolization coils in situ. Decision made to proceed to laparotomy for splenectomy. Patient recovered and was commenced on lifelong antibiotic prophylaxis.
FIGURE 89.54 Blunt trauma. Crush injury between van and wall. Hemodynamically stable. (A and B) Selected axial CT images demonstrate multiple ill-defined low attenuation lacerations and hematoma within the substance of the liver (white arrows) with focal intraparenchymal contrast extravasation (black arrow). AAST grade III injury. Given it is isolated high-grade liver injury and patient remained hemodynamically stable, patient proceeded to nonoperative management (NOM). (C and D) Day 5 inflammatory markers rising. Repeat dual-phase CT performed. No intraparenchymal vascular injury on arterial phase. Portovenous phase scan shows evolution of the central liver injury with development of subcapsular biloma (white arrow) and free bile leak into the peritoneum (asterisk). Interval increase in low attenuation fluid within the abdomen and pelvis following high-grade liver injury should raise suspicion for intraperitoneal bile leak. (E and F) Selected scout images from CT scans performed at day 13 and day 46, respectively, demonstrate how protracted the course of these injuries can be. There have been interval percutaneous drainages (white arrows) and placement of a biliary stent endoscopically (black arrow) to encourage resolution of bile leak.
Key Points: Pearls to Remember Changes in the 2018 AAST OIS for spleen, kidney, and liver have implications on management strategies, therefore accurate description and classification of CT is essential The most significant update is the inclusion of vascular injuries to the OIS for the liver, spleen and kidney, specifically with reference to CT imaging findings
Robust collaboration between Diagnostic, Interventional Radiologist and the Trauma Surgeon is essential to timely and optimum management of the Trauma patient
Injury to the Spleen The spleen is the most commonly injured organ in blunt abdominal trauma, accounting for up to 40% of all solid organ injuries. It is essentially a blood reservoir and its thin fibroelastic capsule increases its susceptibility to injury and limits its ability to tamponade intraparenchymal bleeding. Imaging Features
◾splenic Contrast-enhanced MDCT plays a crucial role in the detection of both parenchymal and vascular injuries and CT imaging criteria have now been incorporated into the 2018 AAST OIS [54,55] (Table 89.1) ◾extravasation Imaging in the portal venous phase maximizes the detection of splenic lacerations and foci of active (Figs. 89.11 and 89.48). Complex interconnecting lacerations may combine, resulting in a shattered spleen (Fig. 89.49) ◾from Intrasplenic hematomas appear as more diffuse hypoattenuating regions and must be distinguished the more triangular peripheral nonenhancing regions that are characteristic of splenic infarcts. Subcapsular hematomas may occur alone or in combination with other injuries and result in lowattenuation collections that indent the splenic margin The sinusoidal architecture of the spleen often gives it a heterogenous enhancement pattern in the arterial phase which can mimic or mask parenchymal defects (Fig. 89.50). However, arterial phase imaging enables the detection and characterization of contained splenic vascular lesions such as pseudoaneurysms and arteriovenous fistulas, which are often not apparent in the portal venous phase, but are important predictors of failure of NOM [26,60] (Figs. 89.49 and 89.15) Normal splenic enhancement should exceed that of the liver; however, a number of studies have reported reduced splenic enhancement in trauma even when the spleen itself is not injured. This phenomenon is thought to relate to adrenergic stimulation reducing arterial perfusion to the spleen during hypotension [61] Congenital splenic clefts may be distinguished from lacerations by their superior location and slightly lobulate contour. Further confirmation of a normal variant may be offered by the absence of adjacent perisplenic hematoma and the clarity of the surrounding perisplenic fat Splenic injuries are almost invariably associated with hemoperitoneum (Fig. 89.51). This is initially localized to the left upper quadrant and as the volume increases may extend to other peritoneal compartments. The higher density of blood around the spleen may often indicate the source of hemoperitoneum. This sentinel clot sign may be also utilized to identify other solid-organ origins of intraperitoneal bleeding On occasion, hemoperitoneum may be identified only within the dependent pelvis and, therefore, justifies the extension of the CT examination to include the pelvis. Even in isolated splenic injury blood can track into the anterior pararenal space via the potential space of the splenorenal ligament, which connects the splenic hilum to the left anterior pararenal space
◾ ◾ ◾ ◾ ◾
Table 89.1 Spleen Organ Injury Scale—2018 Revision
A A S T G r a d e
AI S Se ve rit y
Imaging Criteria (CT Findings)
Operative Criteria
Pathologic Criteria
I
2
Subcapsular hematoma 25% devascularizati on
A A S T G r a d e
AI S Se ve rit y
Imaging Criteria (CT Findings)
Operative Criteria
Pathologic Criteria
V
5
Any injury in the presence of splenic vascular injury with active bleeding extending beyond the spleen into the peritoneum Shattered spleen
Hilar vascular injury which devascularizes the spleen Shattered spleen
Hilar vascular injury which devascularizes the spleen Shattered spleen
Vascular injury is defined as a pseudoncuysm or afteriovenous fistula and appears as a focal collection of contrast that decreases in attenuation with delayed imaging. Active bleeding from a vascular injury presents as extra-vascular contrast, focal or diffuse, that increase in size or attenuation in delayed plase. Vascular thrombosis can lead to organ infarction.Grade based on highest grade assessment made on imaging, at operation or on pathologic specimen.
More than one grade of splenic injury may be present and should be classified by the higher grade injury. Advance one grade for multiple injuries up to a grade III.
FIGURE 89.48 Blunt trauma. Cyclist versus car. Hemodynamically stable. Axial CT image acquired using split bolus protocol. Linear low attenuation lesion within the lower pole of the spleen (white arrow). No active extravasation. AAST Grade II splenic injury. If this was an isolated injury treatment and the patient remained hemodynamically stable treatment would be NOM. However, note the hemoperitoneum in Morrison’s pouch (asterisk). This was attributable to small bowel injury (note locule of free extraperitoneal gas, black arrow, a highly specific sign for bowel injury on CT in blunt abdominal trauma). Patient proceeded to theatre for laparotomy for bowel repair but spleen was preserved.
FIGURE 89.49 Blunt trauma. Fall from horse. Hemodynamically stable. (A) Axial CT acquired using split bolus protocol. Widespread hemoperitoneum (asterisk) with multiple lacerations of the spleen (black arrows) with foci of active extravasation extending outside of the splenic capsule (dashed arrow), in keeping with AAST grade V injury. There were no other indications either clinically or on CT to proceed to laparotomy and the patient remained hemodynamically stable. Decision made to proceed with nonoperative management with adjunct of splenic angioembolization. (B) Follow up dual phase CT at day 5 was performed to reassess the high-grade splenic injury. The arterial phase (top image) shows intraparenchymal blush of contrast which washes out on the portovenous phase (bottom image) consistent with focal pseuodaneurysm. Volume of hemoperitoneum reducing and patient remained well. MDT decision to proceed with surveillance CT at 4 weeks. (C) Surveillance dual-phase CT at 4 weeks. Arterial phase shows resolution of the splenic pseudoaneurysm with significant improvement in the splenic lacerations and complete resolution of hemoperitoneum.
FIGURE 89.50 Blunt trauma. Motorcyclist versus car. Axial CT image in arterial phase. The sinusoidal architecture of the spleen often gives it a heterogenous enhancement pattern in the arterial phase which can mimic or mask parenchymal defects. Of note there were no indirect signs of splenic injury, e.g., perisplenic hematoma or adjacent left lower rib fractures. The spleen was normal in this patient.
Management of Splenic Injury The knowledge of the risk of overwhelming sepsis and of susceptibility to coccal infections has led to a desire to preserve splenic function whenever possible and splenic salvage for hemodynamically stable trauma patients has become standard of care [62]. Splenic angioembolization (SAE) is an integral adjunct to NOM. The sensitivity, specificity and accuracy of MDCT have been reported to be as high as 81%, 90%, and 83%, respectively, predicting the need for SAE [56]. A systematic review of 23 studies published in 2017 by Crichton et al., demonstrated that while SAE has been shown to reduce the failure rate of NOM in AAST grade IV and V splenic injuries, it has minimal effect in those with Grade I to III injuries [63] (Fig. 89.49). A study by Zarzaur et al. in 2017 observed that active bleeding outside the splenic capsule (AAST grade V) was a poor prognostic sign, even if the patient undergoes SAE as adjunct to NOM [60] (Fig. 89.51). At present, SAE should be considered for patients in a hemodynamically stable condition with grade IV/V blunt splenic trauma [64] (Figs. 89.15 and 89.48). Follow-up CT can be utilized to monitor the recovery from splenic injury, although the value of such a practice is
contentious and usually dependent on clinical and biochemical parameters and whether there has been adjunct SAE (Fig. 89.51). At present the high accuracy of CT in excluding injury and in documenting the degree of splenic injury and associated other intra-abdominal injuries is undoubted. This information must be coupled with a clinical hemodynamic assessment of the patient’s fluid/ blood requirements, age and concomitant injuries to help guide treatment (Fig. 89.48).
Injury to the Liver and Biliary Tract The liver is the second most frequently injured organ in the abdomen, damage occurring in 20–30% of blunt trauma overall. In patients, hemodynamically stable enough to be examined by MDCT, splenic and hepatic injuries are almost equal in incidence. The relatively large surface area of the liver also makes penetrating trauma a relatively frequent occurrence. The discrepancy in size between the two lobes dictates that right lobe injuries are four times more frequent than those of the left lobe. Injuries to the liver are, in over 50% of cases, accompanied by other injuries. Left lobe injuries are frequently accompanied by splenic (45%) or pancreatic trauma, while those of the right lobe are frequently accompanied by rib (33%) or adrenal injuries (Figs. 89.35 and 89.52).
FIGURE 89.52 Blunt trauma. Pedestrian versus cyclist. Hemodynamically stable. Axial image acquired using split bolus protocol. Liver laceration and intraparenchymal hematoma with no intra or extra parenchymal active extravasation (black arrow) and small volume hemoperitoneum. AAST grade IV injury due to degree of lobar involvement (full extent of injury not shown). Associated with right adrenal hemorrhage (white arrow). Given hemodynamic stability and lack of other injuries that would mandate trauma laparotomy, this injury was managed successfully nonoperatively.
Imaging Features
◾characterization Contrast-enhanced CT remains the best investigative technique for the accurate detection and of hepatic injuries in hemodynamically stable patients ◾correspond The commonest types of injury are low-attenuation defects in linear or stellate patterns that with hepatic lacerations (Fig. 89.10). When these extend to involve the capsule, the volume of hemoperitoneum increases (Figs. 89.52 and 89.53). Multiple radiating lacerations have been described as a “bear claw” appearance (Fig. 89.35) Hematomas are often seen in association with lacerations as more ill-defined areas of low attenuation. Subcapsular hematomas indent the liver margin and are frequently identified in the anterolateral aspect of the right lobe. These injuries do not appear to have the same potential for
◾
delayed rupture as in trauma of the spleen, and in part, the relative infrequency of delayed severe hemorrhage has led to increased confidence in NOM The dual blood supply of the liver protects the liver from traumatic regional infarction unless there has been gross disruption of parenchyma Biliary injury is a rare complication of abdominal trauma, very rarely occurs without concomitant hepatic injury and is often difficult to detect even with multiphase MDCT in the early phase. Such injuries are more common with penetrating injury or iatrogenic procedures and in particular following laparoscopic gallbladder surgery Hematoma in the gallbladder fossa may be another indicator of gallbladder injury; however, the specific sign of gallbladder wall interruption is infrequently identified [65]. The presence of hyperdense blood in the gallbladder may be mimicked by gallbladder debris or hyperattenuating bile. The gallbladder wall thickening or collapsed lumen appearances of trauma may resemble a normally collapsed gallbladder or the features of chronic cholecystitis [66] Hemobilia, due to the communication of the vascular tree with the biliary tree, also usually presents in a delayed fashion with pain, jaundice, and gastrointestinal bleeding. CT may demonstrate the presence of high-attenuation blood in a dilated biliary tree. The use of interventional assessment and selective embolization has reduced the morbidity and mortality of operative intervention
◾ ◾ ◾ ◾
FIGURE 89.53 Blunt trauma. Motorcyclist versus pedestrian. Initial responder, proceeded to CT. (A and B) Selected axial CT images acquired using split bolus protocol demonstrate linear low attenuations within right lobe of the liver in keeping with lacerations. Multiple intraparenchymal foci of active extravasation (white arrows) with further active extravasation extending beyond the liver parenchyma into the peritoneum (black arrow). Note hemoperitoneum in hepatorenal fossa (asterisk). AAST grade IV injury due to active bleeding extending beyond the parenchyma into the peritoneum). Compare this with the splenic injury in Fig. 89.49 where active bleed into the peritoneum would classify it as a Grade V injury with the updated AAST OIS. (C and D) Selected images from hepatic angiogram demonstrates focal active extravasation from right hepatic artery branch (white arrow). Successful coil angioembolization was performed (white circle).
Management of Hepatic Injuries NOM of blunt hepatic injuries is the treatment of choice in hemodynamically stable patients, irrespective of injury grade or patient age [67]. Angioembolization should be considered as an adjunct to this in the hemodynamically stable patient where there is clinical evidence of ongoing bleeding; imaging evidence of arterial bleeding; or suspicion of the ongoing arterial source of bleeding despite operative intervention [64] (Figs. 89.18 and 89.53). Explorative laparotomy should be
considered for those patients that are hemodynamically unstable, regardless of grade of liver injury (Fig. 89.18). There may also be other injuries present that necessitate laparotomy regardless of hemodynamic status or grade of injury (Fig. 89.10). The patient must be appropriately resuscitated and in an environment that permits constant physiological monitoring and ready access to surgery should there be clinical deterioration. The role of CT, therefore, is to identify and characterize the liver injuries, determine the quantity of hemoperitoneum, and exclude the presence of other organ involvement. It is advisable to use the AAST OIS grading scale when reporting CT findings of liver trauma and where possible describe proximity of the injury to hepatic veins and porta hepatis which increase the risk of NOM failure and biliary injury, respectively [68]. The AAST OIS 2018 update now incorporates CT findings and importantly, as with the spleen, vascular injury is now included in the higher grades, which may help to further guide clinical pathways [55,57] (Table 89.2). A difference between the liver and splenic new AAST injury grading is that intraparenchymal bleeding of the liver is Grade III, whereas intraparenchymal bleeding within the spleen is Grade IV. Grade IV liver injury now includes active bleed beyond the parenchyma (Fig. 89.53). The presence of active contrast extravasation or pooling, or of traumatic vascular malformations, are warnings that conservative management alone may fail and should at least prompt either angiographic assessment or follow up imaging to assess for post-traumatic pseudoaneurysm, biloma formation or hemobilia (Fig. 89.54). Table 89.2 Liver Injury Scale—2018 Revision A A S T G r a d e
AI S Se ve rit y
Imaging Criteria (CT Findings)
Operative Criteria
Pathologic Criteria
A A S T G r a d e
AI S Se ve rit y
Imaging Criteria (CT Findings)
Operative Criteria
Pathologic Criteria
I
2
Subcapsular hematoma 3 cm in depth
A A S T G r a d e
AI S Se ve rit y
Imaging Criteria (CT Findings)
Operative Criteria
Pathologic Criteria
I V
4
Parenchymal disruption involving 25– 75% of a hepatic lobe Active bleeding extending beyond the liver parenchyma into the peritoneum
Parenchymal disruption involving 25– 75% of a hepatic lobe
Parenchymal disruption involving 25– 75% of a hepatic lobe
V
5
Parenchymal disruption >75% of hepatic lobe Juxtahepatic venous injury to include retrohepatic vena cava and control major hepatic veins
Parenchymal disruption >75% of hepatic lobe Juxtahepatic venous injury to include retrohepatic vena cava and central major hepatic veins
Parenchymal disruption >75% of hepatic lobe Juxtahepatic venous injury to include retrohepatic vena cava and central major hepatic veins
Vascular injury is defined as a pseudoancurysm or arterioveocus fistula and appears as a focal collection of contrast that decrease in attenuation with delayed imaging. Active bleeding from a vascular injury presents as extra-vascular contrast, focal or diffuse, that increase in size or attenuation in delayed phase. Vascular thrombosis can lead to organ infarction.Grade based on highest grade assessment made on imaging, at operation or on pathologic specimen.More than one grade of liver injury may be present and should be classified by the higher grade of injury.
Advance one grade for multiple injuries up to a grade III.
Complications and Injury Resolution
◾areFollowing hepatic trauma, delayed complications occur in a fifth of patients overall, although these more common in surgically treated patients. The main liver complications are delayed hemorrhage and infective collections. Involvement of the biliary system may result in bilomas, hemobilia, bile peritonitis, and delayed strictures of the extrahepatic biliary tree Unless there are clinical signs or parameters suggesting such complications, there is little value in the routine follow-up of hepatic injuries to monitor resolution. Serial CT following injury to the liver demonstrates that, unless there is persistent hemorrhage, there should be significant reduction of hemoperitoneum within 3–7 days Intraparenchymal lacerations or hematomas initially expand and become more sharply defined as the damaged peripheral parenchyma is resorbed. The attenuation of the focal abnormality often falls owing to clot lysis and water osmosis. The time course of resolution of injuries over weeks or months often exceeds that of comparable splenic injuries, due to the inhibitory effect of stasis of bile products at the injury margins (Fig. 89.54) Injuries may heal completely or result in small cysts or serous collections. Focal intraparenchymal collections developing following hepatic trauma may relate to resolving hematomas, abscesses, or contained bile leaks termed bilomas. Distinguishing one from the other can be difficult, relying largely on the clinical context but often ultimately on diagnostic aspiration Infective abscesses may develop thick enhancing walls and on occasion contain gas bubbles. The latter finding has, however, been described in sterile resolving lacerations. Extension of the infection may result in subcapsular empyemas, which may demonstrate enhancement along their margin Bilomas tend to occur following deep injuries to the central periportal biliary tree. They usually present weeks to months after injury as simple thin-walled cysts with low-attenuation contents. Occasionally, however, septations may develop due to secondary infection or hemorrhage. Their communication with the biliary tree can be confirmed by hepatobiliary scintigraphy. MRI may help distinguish bilomas from hematomas if required [65] Biliary peritoneal leaks may result in biliary peritonitis following secondary infection. The suspicion of such a leak may be raised by the peristence or increase of low attenuation of the peritoneal fluid (0–20 HU compared with >50 HU in hemoperitoneum) after recent trauma, although this is usually confirmed by diagnostic aspiration (Fig. 89.54). A high degree of suspicion by the radiologist, from the index CT findings together with follow up imaging in the days and weeks following the trauma, is integral to diagnosing bile leaks as the signs and symptoms of this delayed complication can be vague and nonspecific Trauma patients with liver injury and free intraperitoneal bile leak have been shown to have prolonged hospital stays and increased requirements for therapeutic procedures [69]. A multitechnique approach to management of post-traumatic bile leaks is often required with percutaneous drainage or endoscopic-surgical intervention often the treatments of choice (Fig. 89.54)
◾ ◾ ◾ ◾ ◾ ◾ ◾
Injury to the Kidneys and Ureters Renal trauma accounts for 8–10% of all abdominal trauma. The vast majority are due to blunt trauma from motor vehicle collisions, assaults, or fall from height. The remainder is largely attributable to stabbings, gunshot, and iatrogenic procedures. Certain anatomical variants predispose to renal injury. These include horseshoe, cross-fused, and pelvic or transplanted kidneys. This susceptibility is due to their relatively anterior location and the potential for compression against the spine. The presence of congenital or acquired cystic disease, hydronephrosis,
and solid vascular lesions (e.g., angiomyolipomas, renal cell carcinomas) also predisposes to injury. Imaging Features
◾injuries. Contrast-enhanced MDCT is the imaging technique of choice for renal trauma and other associated Although it has become clear that CT is an excellent tool for the detection and characterization of renal injuries, more debate has centered on the indications for imaging in suspected renal trauma. In adults with blunt trauma the presence of gross hematuria or the combination of microscopic hematuria and shock (1 cm depth without collecting system rupture or urinary extravasation Any injury in the presence of a kidney vascular injury or active bleeding coetained within Gerota fascia
Renal parenchymal laceration >1 cm depth without collection system rupture or urinary extravasation
Renal parenchymal laceration >1 cm depth without collecting system rupture or urinary extravasation
I V
4
Parenchymal laceration extending into urinary collecting system with urinary extravasation Renal pelvis laceration and/or complete ureteropelvic disruption Segmental renal vein or artery injury Active bleeding beyond Gerota fascia into the retroperitoneum or peritoneum Segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding
Parenchymal laceration extending into urinary collection system with urinary extravasation Renal pelvis laceration and/or complete ureteropelvic disruption Segmental renal vein or artery injury Segemental or complete kidney infarction(s) due to vassel thrombosis without active bleeding
Parenchymal laceration extending into urinary collection system Renal pelvis laceration and/or complete uretropelvic disruption Segmental renal vein or artery injury Segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding
V
5
Main renal artery or vein laceration or avulsion of hilum Devascularized kidney with active bleeding Shuttered kidney with loss of identifiable parenchymal renal aratomy
Main renal artery or vein laceration or avulsion of hilum Devascularized kidney with active bleeding Shuttered kidney with loss of identifiable parenchymal renal anatomy
Main renal artery or vein laceration or avulsion of hilum Devascularized kidney Shuttered kidney with loss of identifiable parenchymal renal anatomy
Vascular injury is defined as a pseudoaneurysm or arteriovenous fistula and appears as a focal collection of contrast that decreases in attenuation with delayed imaging. Active bleeding from a vascular injury presents as extra-vascular contrast, focal or diffuse, that increases in size or attenuation in delayed phase. Vascular thrombosis can lead to organ infraction.
Grade based on highest grade assessment made on imaging, at operation or on pathologic specimen.
More than one grade of kidney injury may be present and should be classified by the higher grade of injury.
Advance one grade for bilateral injuries up to Grade III.
FIGURE 89.55 Blunt trauma. Fall from height. Hemodynamically stable. Axial CT image following IV contrast administration demonstrates small volume of perirenal hematoma anteriorly at the right kidney confined within the perirenal fascia (white arrow). AAST grade II renal injury. This was managed nonoperatively.
FIGURE 89.56 Blunt trauma. Pedestrian versus car. Hemodynamically stable. (A) Axial CT image following IV contrast administration demonstrates focal intraparenchymal contusion and laceration extending to renal capsule medially (white arrow) with perirenal hematoma (asterisk). (B) Delayed phase scan performed at 10 minutes as patient remained hemodynamically stable. Coronal reformat on bone windows delineates leak of contrast from renal pelvis (black arrow) upgrading this to AAST grade IV injury. This was treated with ureteric stent insertion.
FIGURE 89.59 Blunt trauma. Person versus train. (A) Axial CT demonstrates linear low attenuation laceration through the distal body of pancreas (direct sign of pancreatic injury) (white arrow). There is also peripancreatic hematoma with loss of fat plane around the distal pancreas (indirect sign of pancreatic injury). Blunt pancreatic injury is rare and is rarely an isolated injury. (B) Note the lacerations within the spleen (AAST grade III) (black arrows). (C) There are multiple segmental infarcts within the left kidney with hematoma at the left renal pedicle but patent main renal vessels (AAST grade IV) and focal laceration in the right kidney (AAST grade 1).
Management
Consensus has been established that providing the patient is hemodynamically stable and there are no associated injuries requiring treatment, grade I–II injuries can be successfully treated nonoperatively (Fig. 89.55). These injuries are considered minor and constitute the vast majority of renal injuries (75–98%). AAST Grades III–V renal injuries should be promptly recognized and communicated to the Trauma surgeon because they may require angioembolization, endourologic or surgical treatment depending on the nature of the injury that has placed it in this higher grade of injury [70,73] (Fig. 89.56). Devitalized segments were once considered an absolute contraindication to NOM; however, if there are no associated bowel or pancreatic injuries, these have been demonstrated to be treated with similar success nonoperatively. Complete ureteropelvic disruptions are an indication for surgery, although partial tears can be treated by antegrade stenting. Renal pedicle injuries have the worst overall prognosis, with poor operative revascularization rates; however, endovascular stenting may prove a viable alternative. The indications for angiography in renal tract injuries remain predominantly the investigation of delayed or protracted bleeding and the treatment of CT-detected traumatic vascular malformations. Angiography and selective embolization have increased success rates of NOM of higher-grade injuries, with hemostasis successfully achieved in approximately 90%. Angiographic techniques result in a greater preservation of renal parenchyma and are, therefore, the first line of treatment in transplant kidneys.
Injury to the Bladder
◾largely Bladder injury may be the result of blunt or penetrative injuries. The propensity to injury depends on the degree of bladder distension at the time of injury. Hematuria is almost invariably present in bladder injuries and is usually gross in nature. Injuries may be classified as contusions or lacerations that may result in rupture Intraperitoneal ruptures are usually the result of blunt trauma to a distended bladder (Fig. 89.14). By contrast, extraperitoneal ruptures are associated with pelvic fractures in over 95% of cases (Fig. 89.57). Although traditionally these are believed to be due to direct bony penetration, many injuries probably also occur due to shearing injuries of the bladder base. Isolated extraperitoneal injuries are more common (50–85%) than isolated intraperitoneal ruptures (15–45%) or combined injuries (0– 12%) Conventional CT with intravenous contrast may detect contusions of the bladder wall appearing as wall thickening or hyperdense intravesical hematoma (Fig. 89.47). However, CT is poor at depicting bladder lacerations, due to inadequate distension and the absence of intravesical contrast at the time of pelvic scanning. Delayed scanning at 5 minutes is still insensitive due to inadequate vesical distension Cystogram can be performed in those trauma patients who proceed for angiography and angioembolization. However, CT cystography is the technique of choice to delineate bladder injury and indicated in hemodynamically stable patients with frank hematuria and pelvic fractures (Fig. 89.57) Gross hematuria without pelvic fractures and microscopic hematuria with pelvic fractures are relative indications if there is clinical suspicion for bladder injury [74] Foley catheter placement should only be performed after clinical confirmation of urethral continuity. The bladder is drained and approximately 350 mL of dilute (3–5%) water-soluble
◾ ◾ ◾ ◾
iodinated contrast is instilled by gravity drip infusion. This is followed by axial scanning from iliac crests to lesser trochanters of femurs with coronal and sagittal reformats. It is vital to interrogate the urinary bladder in three planes and to adjust the window width and level settings to ensure complete and accurate diagnosis [75] Classification schemes for bladder injury include the AAST classification and the image-based classification which helps to stratify patients in terms of subsequent management. In this, radiologybased classification system there are five types of injury of which Type II (intraperitoneal rupture) and Type V (combined intra- and extra-peritoneal rupture) require surgical repair (Table 89.4) [75,76]
◾
Table 89.4 Imaging-Based Classification of Urinary Bladder Injury Following CT Cystogram Type II and Type V Require Operative Repair Type of Bladder Injury
Pathology
Type I UB (urinary bladder) injury
Urinary bladder contusion
Type II UB injury
Intraperitoneal urinary bladder rupture
Type III UB injury
Interstitial urinary bladder injury (contrast extension into bladder wall but no extension into extra or intraperitoneal spaces)
Type IV UB injury
Extraperitoneal urinary bladder rupture (simple IVa contrast confined to prevesical space; complex IVb contrast may dissect into variety of fascial planes and spaces)
Type V UB injury
Combined intra and extraperitoneal urinary bladder rupture
FIGURE 89.47 Blunt trauma. Pedestrian versus car. Hemodynamically stable. Complaining of abdominal pain. Coronal CT reformat acquired with split bolus protocol demonstrates free fluid within the right lower quadrant (white arrow).
There is no solid organ or bowel injury identified on CT to account for this. However, there is focal bladder wall thickening at dome of bladder (black arrow). A dedicated CT cystogram was not performed as patient was clinically peritonitic and the index of suspicion for intraperitoneal bladder rupture was high based on these CT findings. Patient was taken to theatre for intraperitoneal bladder repair.
FIGURE 89.57 Blunt trauma. Male fall from height. Axial image from CT cystogram confirms contrast extravasation from catheterized bladder into space of retzius (asterisk) and along the pelvic sidewalls, consistent with extraperitoneal bladder rupture. No intraperitoneal spill of contrast. Although in this case, the nature of the bladder injury is obvious, the CT cystogram should be carefully evaluated in all 3 planes to assess for more subtle bladder injuries. The timing of the CT cystogram is dependent on hemodynamic status particularly if there is an unstable pelvic fracture pattern. The more pressing issue of achieving hemostasis should be the first priority. Delineating the nature of the suspected bladder injury is important but can be delayed until the patient is stabilized.
Injury to Pancreas
Injury to the pancreas is relatively uncommon, occurring in less than 2% of blunt abdominal trauma [77]. Such injuries are often the result of compression of the neck and body of pancreas against the spinal column by steering wheels and seat belts in adults and bicycle handlebars in children [78]. These mechanisms of injury result in associated with injuries to the duodenum, spleen, kidneys, or lumbar spine in over 90% of cases. It is these associated injuries that are largely responsible for the increased mortality levels of 10–25% in combined injuries, compared with 3– 10% for isolated injuries. Imaging Features
◾extensive Pancreatic injuries can be subtle or overlooked on initial CT appraisal, particularly when there is multiorgan trauma. Up to 40% of pancreatic injuries may not be visible on CT obtained within 12 hours of trauma and initial clinical and biochemical parameters are often nonspecific and unreliable [77] Direct CT findings include pancreatic swelling or enlargement, laceration, transection, or inhomogenous enhancement (Fig. 89.58). Indirect CT findings include thickening of the anterior pararenal fascia; induration of the peripancreatic fat; extra or intraperitoneal fluid; fluid in the lesser sac; peripancreatic fluid between the splenic vein and pancreas; associated left upper quadrant, hepatobiliary or duodenal injuries (Fig. 89.59) If there is delay in diagnosis, pancreatic injuries often become more apparent owing to the development of localized edema and autodigestion due to pancreatic enzyme leakage. Additional imaging is often required as the injury evolves or to further evaluate for duct integrity in the form of follow up dual-phase CT or MRCP, respectively [77,79] (Fig. 89.58) For equivocal findings about duct integrity on MRCP, ERCP is recommended. Although this is an invasive test, it also has the advantage of facilitating intervention, by means of stent placement, in otherwise well and stable patients
◾ ◾ ◾
FIGURE 89.58 Blunt trauma. Fall from standing onto a low wall. Hemodynamically labile responding to fluids. (A) Axial image from CT acquired using split bolus protocol demonstrates extensive hematoma within and around the head and body of pancreas with foci of active extravasation (black arrows) (direct sign of pancreatic injury). Note also the extensive perihepatic and peri splenic hemoperitoneum (asterisk). Patient proceeded to interventional radiology for diagnostic angiogram but no active bleeding was identified and patient’s hemodynamic status stabilized. (B) Follow-up dual-phase CT performed 48 hours later to further characterize the pancreatic injury. Note the full thickness laceration (a direct sign) through the proximal body of the pancreas (white arrow) with reduction in volume of hemoperitoneum. The full-thickness laceration was not appreciated on the index scan due to the extensive acute hematoma. Note that the laceration is to the left of the SMV making it within the distal pancreas anatomically. This observation is important as it has implications on the nature of the surgery required. Distal pancreatectomy with splenectomy was performed. (C) CT scan performed at 3 weeks following distal pancreatectomy and splenectomy due to increasing inflammatory markers. Postoperative low attenuation collection in surgical bed (asterisk) from stump leak which was drained percutaneously by interventional radiology. SMV, superior mesenteric vein.
Classification and Management of Pancreatic Injuries Pancreatic injuries may be graded using the AAST OIS scale (Table 89.5) [80]. The 2018 update does not include vascular injuries; however, it is still important to report these as it has impact on management (Fig. 89.58). Table 89.5 Pancreas CT Grading C T Gr ad in g
Blunt Pancreatic Injury*
C T Gr ad in g
Blunt Pancreatic Injury*
Gr ad e 1
Minor contusion without duct injury
Gr ad e 2
Major contusion without duct injury or tissue loss
Gr ad e 3
Distal transection or parenchymal injury with duct injury
Gr ad e 4
Proximal transection (to the right of the superior mesenteric vein) or parenchymal injury involving the ampulla
Gr ad e 5
Massive disruption to the pancreatic head
*
Grade based on most accurate assessment of radiology, surgery, or autopsy. Advance one grade for multiple injuries.
Key points to appreciate and comment on:
◾This The proximal pancreas is defined as to the (patients) right of the superior mesenteric vein (SMV). is important as it alters the surgical approach, if warranted ◾morbidity Integrity of the main pancreatic duct. This is important as ductal injury significantly increases and mortality due to development of pancreatic pseudocysts, fistulas and abscesses ◾ All high-grade injuries infer pancreatic duct injury ◾ Advance up to grade III for multiple low-grade injuries
Management depends on grade/severity of injury; location of injury; other concomitant abdominal injuries and time elapsed after injury. If the main pancreatic duct is involved, then surgery is preferred. Interventional radiology has a significant role supporting treatment of complications of traumatic pancreatitis and drainage of postoperative collections (Fig. 89.58).
Injury to Bowel and Mesentery Bowel and mesenteric injuries occur in approximately 5% of blunt abdominal trauma cases and are, therefore, relatively unusual injuries. These injuries often demonstrate subtle or minimal signs on CT imaging and can hence cause interpretative problems [80]. Even when the diagnosis is suspected, several of the described signs of injury have a low diagnostic specificity. Detection of these injuries is of importance as, in contradistinction to the trend to NOM of solid intra-abdominal organ injuries, the optimal treatment for bowel and mesenteric injuries remains early surgical repair. A delay in diagnosis, and hence treatment, increases morbidity and mortality [81]. Deceleration injuries tend to cause shearing forces at the points of fixation of the bowel, such as the retroperitoneal duodenum, the ligament of Treitz, the ileocaecal valve, and any incidental hernias. These forces may precipitate mesenteric tears or bowel wall injuries. Compressive forces tend to cause an increase in intraluminal bowel pressure resulting in direct rupture. Penetrating injuries tend to the affect the colon more due to its relative size and fixation. Blunt trauma injury to the colon is rare. While seatbelts have undoubtedly reduced mortality in car accidents mainly due to a reduction in catastrophic brain injury, their introduction has led to a significant increase in intra-abdominal injuries, with a two- to three-fold increase in intestinal perforations and mesenteric devascularization [80] (Fig. 89.66). The association between abdominal ecchymosis (the “seatbelt” sign) and bowel and mesenteric injury has been well documented (Fig. 89.60). Interruption in mesenteric blood supply can result in bowel ischemia and infarction hours of days later. A similar association is reported between acute lumbar hernias and BMI, likely due to the increased intra-abdominal pressure elicited by rapid deceleration causing herniation of abdominal contents through sites of anatomical weakness in the superior and inferior lumbar triangles [83,84] (Fig. 89.61).
FIGURE 89.60 Blunt trauma. Restrained driver high-speed MVC. Axial CT image with IV contrast demonstrates characteristic seatbelt injury overlying the left iliac blade (white arrow). Mesenteric stranding is seen around the distal descending colon (asterisk). No direct signs of free intraperitoneal air or focal bowel wall discontinuity. Avulsed devascularized descending colon at laparotomy requiring stapled resection.
FIGURE 89.61 Blunt trauma. Restrained driver high speed MVC. Hemodynamically stable. Axial CT image, acquired with split bolus protocol, demonstrates acute right-sided traumatic lumbar hernia (white arrow) with focal stranding and hematoma in the terminal ileal mesentery (asterisk). No free intraperitoneal air on CT. Mesenteric root tear confirmed at laparotomy.
FIGURE 89.66 Blunt trauma. Restrained passenger in high-speed MVC. (A) Axial CT image acquired using split bolus CT protocol demonstrates acute traumatic abdominal wall herniation of devascularized bowel into the subcutaneous tissues anteriorly (white arrow). Note the radiological seat belt sign over the right and left sides of the abdomen (asterisk). Note also direct signs of distal aortic injury of focal narrowing of the vessel with intraluminal thrombus. (B) Coronal reformat confirms the axial CT findings of acute traumatic aortic injury in infrarenal aorta with intimal flap tear (direct sign of vascular injury) best appreciated on coronal reformat. Small bowel resection performed at laparotomy for devascularized segment. Patient proceeded to Interventional Radiology for endovascular stenting of the distal TAI. (C) Acute unstable chance type fracture also present at L3 which required ORIF after laparotomy and endovascular intervention. This case illustrates the importance of multidisciplinary approach to the acute severely injured polytrauma patient.
Imaging Features
◾specific There are a number of signs on CT that help to diagnose bowel and mesenteric injury. The most signs for bowel injury in blunt abdominal trauma include focal bowel wall discontinuity (100%) and extraluminal air (95%) (Figs. 89.48 and 89.62). Detection of pneumoperitoneum is facilitated by the use of lung window settings but it may be present in fewer than 50% of cases at presentation Isolated free intraperitoneal air may be due to pneumothorax, chest tube placement, or diaphragmatic injury [85]. However, when free air is present in combination with other findings such as free intraperitoneal fluid or the seatbelt sign, it is highly predictive of bowel injury (Fig. 89.62). The location of extraluminal air can also help to localize the bowel injury, particularly in the setting of duodenal injury (Fig. 89.62). Oral contrast is not routinely administered in the emergency setting of blunt abdominal trauma therefore the other highly specific sign of oral contrast extravasation is rarely seen in this setting [86] The presence of hyperattenuating peritoneal fluid, particularly in the absence of an identifiable solid organ injury should also cause suspicion, except in the case of small amounts of low attenuation free fluid in the pelvis of women of reproductive age, which may be normal (Fig. 89.63) Other signs of bowel injury include focal bowel thickening due to intramural hematoma (commonest in the second part of the duodenum) (Fig. 89.62) and abnormal bowel wall enhancement (Fig. 89.64). However, the low specificity for significant bowel injury in these signs in isolation does not justify immediate surgical intervention (Fig. 89.64). The presence of diffuse bowel wall thickening and intense enhancement without peritoneal fluid may simply be part of the hypoperfusion–reperfusion complex, commonly known as “shock bowel” and does not necessarily imply bowel rupture Mesenteric injuries may occur in isolation or in combination with bowel perforation. The presence of active vascular contrast extravasation with a large hematoma reflects a patient at high risk for
◾ ◾ ◾ ◾
subsequent bowel ischemia and rupture and is an indication for surgery (Fig. 89.46). However, lesser degrees of hematoma or “misting” of the mesentery do not necessarily indicate a need for surgery and may require follow-up examinations coupled with clinical observation (Figs. 89.65 and 89.67)
FIGURE 89.62 Blunt trauma. Restrained driver high speed MVC. Hemodynamically stable. (A and B) Axial CT images, acquired with split bolus protocol, demonstrate extraluminal free gas (white arrows) and fluid adjacent to duodenum (white asterisk) which is edematous with abnormal enhancement. Further fluid is present in right paracolic gutter (white asterisk). (C) Coronal CT reformat confirms focal bowel wall discontinuity at the third part of duodenum (black arrow). Duodenal rupture confirmed and repaired at laparotomy.
FIGURE 89.63 Blunt trauma. Restrained passenger MVC. Hemodynamically stable. Axial CT ((A) soft tissue and (B) lung windows) demonstrates multiple foci of extraluminal air within the abdomen which is within the retroperitoneum (arrows). There is associated retroperitoneal free fluid (asterisk). This is closely related to the second part of the duodenum which is markedly edematous and CT features are consistent with duodenal perforation. The retroperitoneal extension of fluid and air is explained by the retroperitoneal position of the second part of the duodenum. Of note this patient exhibited vague abdominal signs and was not overtly peritonitic because the pathology was centered on the retroperitoneal space.
FIGURE 89.65 Blunt trauma. Restrained driver high speed MVC. (A) Axial CT image following IV contrast demonstrates subtle small volume of interloop fluid (white arrow). There was no solid organ injury and patient was intubated for concomitant head injury making clinical assessment for peritonism difficult. (B) Axial CT image with IV contrast 48 hours later on background of rising inflammatory markers and increased abdominal distension. Widespread free intraperitoneal air (black arrow) with poorly enhancing distended jejunum (white arrow). Ischemia and necrosis of jejunum and proximal ilium at laparotomy requiring resection.
FIGURE 89.67 Penetrating trauma. Stab wound to left lower quadrant. (A) Axial CT image (with IV contrast) demonstrates skin defect in left lower quadrant (white arrow). Paucity of intraabdominalfat makes interpretation challenging. (B) Axial CT image more inferiorly demonstrates small volume of free intraperitoneal fluid in pelvis only (black arrow). Abdomen was soft and non peritonitic. Patient remained hemodynamically stable. Appreciating that routine laparotomy in hemodynamically stable patients may result in a 35 to 53% rate of non therapeutic laparotomies, decision made to proceed with serial observations. Patient remained well and was discharged 24 hrs later.
Management There is no debate that patients who have sustained blunt or penetrating abdominal trauma, with peritonitis, evisceration or hemodynamic instability should undergo exploratory laparotomy. However, challenges remain in selective NOM of hemodynamically stable nonperitonitic patients with penetrating torso trauma, particularly in low energy penetrating trauma such as stabbings. A triple contrast CT protocol using intravenous, oral, and rectal contrast has been advocated for assessment of these patients, the rationale being that adding enteric contrast allows assessment for extravasation or leakage from bowel, a highly specific sign for bowel perforation [87]. However, although one prospective study of triple contrast CT for detection of bowel injury with surgical correlation showed 100% specificity when extravasation was present on CT, sensitivity of this sign was only 29%. More sensitive signs included direct extension of wound tract to bowel and focal bowel wall thickening. Other signs included mesenteric vascular extravasation, mesenteric fat stranding and interloop fluid [88] (Figs. 89.65–89.67) Interestingly, a recent international survey suggested that enteric contrast is used in a minority of centers for penetrating trauma, thought to be driven by perceived lack of benefit and delays in patient care [89]. A recent systematic review in 2018 evaluated the accuracy of CT for diagnosis of intraabdominal injuries requiring therapeutic laparotomy in stable, nonperitonitic pts with anterior abdominal stab wounds. It showed a high prevalence (8.7%, 95% CI 6.1–12.2%) of injuries requiring laparotomy in patients with a negative CT scan. Almost half (47%, 95% CI 30–
64%) of those injuries involved the small bowel [90]. This finding has to be carefully balanced with the risks associated with nontherapeutic laparotomy. The importance of good clinical-radiological corroboration cannot be underestimated in this cohort of patients. Serial clinical observations, for developing peritonism, in selectively nonoperatively managed cohort of penetrating trauma, with follow up targeted diagnostic studies where necessary, remains a safe approach (Figs. 89.65 and 89.66). Key Points: Pearls to Remember
◾ ◾
Mechanism of injury matters! Interrogate bowel and mesentery closely, particularly if the patient has been restrained occupant of high-speed MVC If mechanism of blunt trauma is severe, look for other markers of significant injury including seat belt sign, traumatic lumbar and abdominal wall hernias and traumatic abdominal aortic injury, which can be overlooked in the context of the multiply injured patient, but will help raise index of suspicion for potential bowel injury Have a high index of suspicion for bowel injury if bowel wall thickening and free intraperitoneal blood in absence of high-grade solid organ injury Challenges remain in selective NOM of hemodynamically stable nonperitonitic patients with penetrating torso trauma, particularly in low energy penetrating trauma such as stabbings. The importance of good clinical-radiological corroboration cannot be underestimated in this cohort of patients. A period of observation, for developing peritonism, in selectively nonoperatively managed cohort of penetrating torso trauma, with follow up targeted diagnostic studies where necessary, remains a safe approach
◾ ◾
Injury to Major Blood Vessels
◾veins Blunt injuries to the inferior vena cava and the aorta are unusual except at the junction of the hepatic with the IVC. At this point, hepatic lacerations may extend directly into the IVC, which is relatively fixated by its opening into the diaphragm ◾even Injuries to the retroperitoneal infrarenal course of these vessels in the abdomen are unusual, and less frequently imaged, as these patients are usually very hemodynamically unstable and have significant associated injuries. Injuries due to penetrating causes are relatively more common (Fig. 89.68) but still very rare unless they are due to gunshot wounds [91]. The mortality of patients surviving initial transfer to hospital with major caval or aortic injuries is very high and even for isolated injuries has been reported as 9% and 20% for caval and aortic injuries, respectively, and up to 75% for combined injuries Contrast-enhanced CT represents an excellent tool for the detection of these injuries. In caval injuries, the lumen of the IVC is often irregular or compressed by retroperitoneal hematoma and active vascular contrast extravasation may be observed. Injuries of the infrarenal IVC have a better prognosis than those of the retrohepatic IVC, due to the tamponading effect of the retroperitoneum (Fig. 89.9). These injuries may initially respond to fluid resuscitation and, therefore, delay presentation. A collapsed IVC, particularly in the absence of pericaval hemorrhage, should alert the careful observer to the possibility of extreme hypovolaemia [92]. This finding is useful in children and young adults, who can initially maintain their blood pressure despite significant volume loss Direct signs of vascular injury tend to be specific but less sensitive and include intimal tears, pseudoaneurysm, focal narrowing, intraluminal thrombus, discrete tear with active extravasation and arteriovenous malformation (Figs. 89.66, 89.69, and 89.72) Indirect signs tend to more sensitive but less specific including perivascular hematoma and variable degrees of end-organ hypoenhancement [93] (Figs. 89.31 and 89.68) In comparison with the thoracic aorta, injury of the abdominal aorta is rare and is well detected by CT. These injuries are usually infrarenal and are often associated with severe lower thoracic and
◾ ◾ ◾ ◾
lumbar vertebral body fractures (Fig. 89.66). The spectrum of CT findings in TAI and its management has been described earlier in the chapter Mortality in patients with pelvic fractures with hemodynamic instability has been shown to range from 20% to 50%. Although the majority of bleeding in pelvic fractures is of venous or bony origin, up to 10% is arterial in origin, which although less common can cause more hemodynamic instability than venous bleeds [64]. The vast majority of this arterial bleeding is from the internal iliac arteries and their subdivisons, most commonly the superior gluteal and inferior pudendal arteries (Fig. 89.70 and 89.71). If hemodynamic status allows it, contrast-enhanced CT is a very useful noninvasive technique at detecting active bleeding sites or vascular abnormalities, with a sensitivity and specificity of approximately 85%. Associated pelvic injuries and hematomas are also simultaneously depicted Indications for pelvic angiography with possible angioembolization include: Patient with pelvic ring fracture who is unstable despite pelvic binder and in whom intra thoracic or intraabdominal sources of bleeding have been excluded [64] Presence of a vascular injury or active extravasation on CT in association with other signs of vascular injury on imaging such as large volume pelvic hematoma, pseudoaneurysm, vasospasm, or vascular “cut off” sign [64] (Figs. 89.72–89.74) When emergency pelvic packing is used as part of DCS, subsequent angioembolization in Interventional Radiology may also be necessary [94]
◾
◾ ⚪ ⚪ ⚪
FIGURE 89.68 Penetrating trauma. Single stab wound to right paraumbilical region. Male patient. (A) Axial CT images demonstrate focal hematoma within deep subcutaneous tissues anteriorly down to the right rectus abdominus. (white arrow) (B) Small volume of high attenuation free fluid in pelvis. CT evidence of peritoneal breach. Patient remained alert, hemodynamically stable and abdomen was soft and not peritonitic. Decision made to serially observe. Peritonism developed 12 hrs later and patient taken for laparotomy. Through and through jejunal injury was repaired.
FIGURE 89.69 Penetrating trauma. (A) Axial CT image from patient with isolated stab wound to right lower quadrant demonstrates focal mesenteric hematoma (white arrow). Indirect sign of bowel or mesenteric injury in penetrating trauma. (B) Axial CT image from a different patient with isolated stab wound to left side of abdomen. Small volume of interloop fluid in pelvis (white arrow). Indirect sign of bowel or mesenteric injury in penetrating trauma.
FIGURE 89.71 Blunt trauma. Motorcyclist versus bollard. Initial responder to fluid resuscitation. Axial CT image acquired with split bolus protocol. There is crescenteric low attenuation around the superior mesenteric artery (white arrow), a direct sign of vessel injury.
FIGURE 89.72 Blunt trauma. Pedestrian versus car. Axial CT image acquired using split bolus protocol demonstrating active extravasation posterior to the comminuted left pubic ramus fracture (white arrow).
FIGURE 89.73 Blunt trauma. Male fall from height. Axial CT image demonstrating active extravasation anterior and posterior to the comminuted left iliac blade fracture (white arrows). Note hematoma tracking retroperitoneally along the left psoas and iliacus muscles (asterisk).
FIGURE 89.74 Blunt trauma. Male fell from height. (A) Selected axial CT images acquired in arterial phase demonstrate patent right internal iliac artery on the right throughout. Initial image shows patent left internal iliac artery then there is an abrupt termination of the vessel (direct sign of vessel injury). Note the displaced fracture though right iliac blade posteriorly extending into the right sacroiliac joint. Note also the abnormally widened left sacroiliac joint with pelvic sidewall hematoma bilaterally. Contrast within the bladder from CT imaging performed at initial receiving hospital. (B) Selected image from pelvic angiogram confirmed complete transection of the right internal iliac artery.
The utilization of angiographic techniques and treatments depends largely on the preplanning for such events. Angiographic suites must be in close proximity to emergency rooms, with 24 hours availability of staff. Although there are everexpanding possibilities for endovascular stenting and the treatment of vascular injuries, the decision to use these techniques relies as much on these factors as on the local expertise and knowledge of trauma surgeons and radiologists.
Summary The reality of trauma imaging is that the severely injured patient often has multiple concurrent injuries. Now that we have described how to diagnose injuries individually, it is important to piece it all together. The case below is an example of a blunt polytrauma patient with selected relevant CT images, a brief summary of
salient findings and how best to proceed in terms of the next stage of management (Fig. 89.75) (Table 89.6). This case, although only one of multiple different scenarios, illustrates the importance of collaborative multidisciplinary approach to managing these patients. Table 89.6 Summary of Salient Findings for the Blunt Polytrauma Patient in Fig. 89.75 Summary of Salient Findings
Management
Traumatic Aortic Injury
Alert Interventional Radiology (TEVAR)
Low grade splenic injury— AAST grade II
NOM (No active extravasation or vascular injury)
Low grade liver injury— AAST grade II
NOM (No active extravasation or vascular injury)
Bowel injury–specific sign of free intraperitoneal air in blunt trauma
Needs laparotomy
Head injury
Possible requirement for intracranial pressure (ICP) bolt but no immediate decompression required
FIGURE 89.75 Blunt trauma. Pedestrian versus car. Hemodynamically unstable. Axial CT image (arterial phase). Markedly displaced fracture of the right iliac blade with intrusion of the fracture into the pelvis demonstrates complete occlusion of the right internal iliac artery (black arrow). A direct sign of vessel injury on CT. Compare with normal opacification of the left internal iliac artery. Note also the extensive hematoma around the bladder anteriorly (asterisk). Patient proceeded to dedicated CT cystogram to evaluate the bladder further after pelvic angio embolization and laparotomy for pelvic packing.
Suggested Readings • The Royal College of Radiologists, Standards of Practice and Guidance for Trauma Radiology in Severely Injured Patients, second ed., The Royal College of Radiologists, London, 2015. • Expert Panel on Major Trauma Imaging, JY Shyu, B Khurana, JA Soto, WL Biffl, MA Camacho, et al., ACR appropriateness criteria® major blunt trauma, J Am Coll Radiol 17 (5S) (2020 May) S160– S174. • RA Kozar, M Crandall, K Shanmuganathan, BL Zarzaur, M Coburn, C Cribari, et al., Organ injury scaling 2018 update: spleen, liver, and kidney, J Trauma Acute Care Surg 85 (6) (2018 Dec) 1119– 1122. doi: 10.1097/TA.0000000000002058. Erratum in: J Trauma Acute Care Surg 87 (2) (2019 Aug) 512. • BJ Baron, R Benabbas, C Kohler, C Biggs, V Roudnitsky, L Paladino, R Sinert, Accuracy of computed tomography in diagnosis of intra-abdominal injuries in stable patients with anterior abdominal stab wounds: a systematic review and meta-analysis, Acad Emerg Med 25 (7) (2018 Jul) 744–757. doi: 10.1111/acem.13380.
• S Chakraverty, K Flood, D Kessel, S McPherson, T Nicholson, CE Ray, et al., CIRSE guidelines: quality improvement guidelines for endovascular treatment of traumatic hemorrhage, Cardiovasc Intervent Radiol 35 (3) (2012 Jun) 472–482.
References [1] T Vos, SS Lim, C Abbafati, KM Abbas, M Abbasi, M Abbasifard, et al., Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019, The Lancet 396 (10258) (2020 Oct) 1204–1222. [2] C Florence, T Simon, T Haegerich, F Luo, C Zhou, Estimated lifetime medical and work-loss costs of fatal injuries—United States, MMWR Morb Mortal Wkly Rep 64 (38) (2013) 1074–1077, 2015 Oct 2. [3] C Florence, T Haegerich, T Simon, C Zhou, F Luo, Estimated lifetime medical and work-loss costs of emergency department–treated nonfatal injuries—United States, 2013, MMWR Morb Mortal Wkly Rep 64 (38) (2015 Oct 2) 1078–1082. [4] Injuries and Violence: The Facts, World Health Organization, Geneva, 2010. [5] DD Trunkey, Trauma. Accidental and intentional injuries account for more years of life lost in the U.S. than cancer and heart disease. Among the prescribed remedies are improved preventive efforts, speedier surgery and further research, Sci Am 249 (2) (1983 Aug) 28–35. [6] J Sobrino, S Shafi, Timing and causes of death after injuries, Bayl Univ Med Cent Proc 26 (2) (2013 Apr) 120–123. [7] D Demetriades, B Kimbrell, A Salim, G Velmahos, P Rhee, C Preston, et al., Trauma deaths in a mature urban trauma system: is “Trimodal” distribution a valid concept?, J Am Coll Surg 201 (3) (2005 Sep) 343–348. [8] M Gunst, V Ghaemmaghami, A Gruszecki, J Urban, H Frankel, S Shafi, Changing epidemiology of trauma deaths leads to a bimodal distribution, Bayl Univ Med Cent Proc 23 (4) (2010 Oct) 349–354. [9] Advanced Trauma Life Support, tenth ed., 2018. [10] Expert Panel on Major Trauma Imaging, JY Shyu, B Khurana, JA Soto, WL Biffl, MA Camacho, et al., ACR appropriateness criteria® major blunt trauma, J Am Coll Radiol JACR 17 (5S) (2020 May) S160–S174. [11] G Vasileiou, S Qian, H Al-ghamdi, D Pace, R Rattan, M Mulder, et al., Blunt trauma: what is behind the widened mediastinum on chest x-ray (CXR)?, J Surg Res 243 (2019 Nov) 23–26. [12] SD Steenburg, JG Ravenel, JS Ikonomidis, C Schönholz, S Reeves, Acute traumatic aortic injury: imaging evaluation and management, Radiology 248 (3) (2008 Sep) 748–762.
[13] D Demetriades, GC Velmahos, TM Scalea, GJ Jurkovich, R KarmyJones, PG Teixeira, et al., Operative repair or endovascular stent graft in blunt traumatic thoracic aortic injuries: results of an American Association for the Surgery of Trauma Multicenter Study, J Trauma 64 (3) (2008 Mar) 561–570, discussion 570–571. [14] D Demetriades, M Karaiskakis, K Toutouzas, K Alo, G Velmahos, L Chan, Pelvic fractures: epidemiology and predictors of associated abdominal injuries and outcomes, J Am Coll Surg 195 (1) (2002 Jul) 1–10. [15] ZB Perkins, GD Maytham, L Koers, P Bates, K Brohi, NR.M Tai, Impact on outcome of a targeted performance improvement programme in haemodynamically unstable patients with a pelvic fracture, Bone Jt J 96-B (8) (2014 Aug) 1090–1097. [16] TW Costantini, R Coimbra, JB Holcomb, JM Podbielski, R Catalano, A Blackburn, et al., Current management of hemorrhage from severe pelvic fractures: results of an American Association for the Surgery of Trauma multi-institutional trial, J Trauma Acute Care Surg 80 (5) (2016 May) 717–723, discussion 723-725. [17] M Marmor, AN El Naga, J Barker, J Matz, S Stergiadou, T Miclau, Management of pelvic ring injury patients with hemodynamic instability, Front Surg 7 (2020) 588845. [18] M Blaivas, M Lyon, S Duggal, A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax, Acad Emerg Med Off J Soc Acad Emerg Med 12 (9) (2005 Sep) 844–849. [19] WC Chiu, BM Cushing, A Rodriguez, SM Ho, SE Mirvis, K Shanmuganathan, et al., Abdominal injuries without hemoperitoneum: a potential limitation of focused abdominal sonography for trauma (FAST), J Trauma 42 (4) (1997 Apr) 617–623, discussion 623–625. [20] D Stengel, J Leisterer, P Ferrada, A Ekkernkamp, S Mutze, A Hoenning, Point-of-care ultrasonography for diagnosing thoracoabdominal injuries in patients with blunt trauma, Cochrane Database Syst Rev 12 (2018 12) CD012669. [21] AK Exadaktylos, G Sclabas, SW Schmid, B Schaller, H Zimmermann, Do we really need routine computed tomographic scanning in the primary evaluation of blunt chest trauma in patients with ‘normal’ chest radiograph?, J Trauma 51 (6) (2001 Dec) 1173–1176. [22] S Peters, V Nicolas, CM Heyer, Multidetector computed tomographyspectrum of blunt chest wall and lung injuries in polytraumatized patients, Clin Radiol 65 (4) (2010 Apr) 333–338. [23] J-F Fang, Y-C Wong, B-C Lin, Y-P Hsu, M-F Chen, Usefulness of multidetector computed tomography for the initial assessment of blunt
abdominal trauma patients, World J Surg 30 (2) (2006 Feb) 176–182. [24] JA Soto, SW Anderson, Multidetector CT of blunt abdominal trauma, Radiology 265 (3) (2012 Dec) 678–693. [25] The Royal College of Radiologists, Standards of Practice and Guidance for Trauma Radiology in Severely Injured Patients, second ed., The Royal College of Radiologists, London, 2015. [26] AR Boscak, K Shanmuganathan, SE Mirvis, TR Fleiter, LA Miller, CW Sliker, et al., Optimizing trauma multidetector CT protocol for blunt splenic injury: need for arterial and portal venous phase scans, Radiology 268 (1) (2013 Jul) 79–88. [27] JW Uyeda, CA LeBedis, DR Penn, JA Soto, SW Anderson, Active hemorrhage and vascular injuries in splenic trauma: utility of the arterial phase in multidetector CT, Radiology 270 (1) (2014 Jan) 99–106. [28] J Uyeda, SW Anderson, J Kertesz, JA Soto, Pelvic CT angiography: application to blunt trauma using 64MDCT, Emerg Radiol 17 (2) (2010 Mar 1) 131–137. [29] C Jeavons, C Hacking, LF Beenen, ML Gunn, A review of split-bolus single-pass CT in the assessment of trauma patients, Emerg Radiol 25 (4) (2018 Aug) 367–374. [30] JC Sierink, TP Saltzherr, JB Reitsma, OM Van Delden, JS.K Luitse, JC Goslings, Systematic review and meta-analysis of immediate total-body computed tomography compared with selective radiological imaging of injured patients, Br J Surg 99 (Suppl 1) (2012 Jan) 52–58. [31] L Jiang, Y Ma, S Jiang, L Ye, Z Zheng, Y Xu, et al., Comparison of whole-body computed tomography vs selective radiological imaging on outcomes in major trauma patients: a meta-analysis, Scand J Trauma Resusc Emerg Med 22 (2014 Sep 2) 54. [32] DA Healy, A Hegarty, I Feeley, M Clarke-Moloney, PA Grace, SR Walsh, Systematic review and meta-analysis of routine total body CT compared with selective CT in trauma patients, Emerg Med J 31 (2) (2014 Feb) 101–108. [33] R van Vugt, DR Kool, J Deunk, MJ.R Edwards, Effects on mortality, treatment, and time management as a result of routine use of total body computed tomography in blunt high-energy trauma patients, J Trauma Acute Care Surg 72 (3) (2012 Mar) 553–559. [34] ND Caputo, C Stahmer, G Lim, K Shah, Whole-body computed tomographic scanning leads to better survival as opposed to selective scanning in trauma patients: a systematic review and meta-analysis, J Trauma Acute Care Surg 77 (4) (2014 Oct) 534–539. [35] A Surendran, A Mori, DK Varma, RL Gruen, Systematic review of the benefits and harms of whole-body computed tomography in the early
management of multitrauma patients: are we getting the whole picture?, J Trauma Acute Care Surg 76 (4) (2014 Apr) 1122–1130. [36] JC Sierink, K Treskes, MJ.R Edwards, BJ.A Beuker, D den Hartog, J Hohmann, et al., Immediate total-body CT scanning versus conventional imaging and selective CT scanning in patients with severe trauma (REACT-2): a randomised controlled trial, Lancet Lond Engl 388 (10045) (2016 Aug 13) 673–683. [37] J Bayer, G Pache, PC Strohm, J Zwingmann, P Blanke, T Baumann, et al., Influence of arm positioning on radiation dose for whole body computed tomography in trauma patients, J Trauma 70 (4) (2011 Apr) 900–905. [38] S Huber-Wagner, P Biberthaler, S Häberle, M Wierer, M Dobritz, E Rummeny, et al., Whole-body CT in haemodynamically unstable severely injured patients—a retrospective, multicentre study, PLoS ONE 8 (7) (2013) e68880. [39] MA de Moya, C Seaver, K Spaniolas, K Inaba, M Nguyen, Y Veltman, et al., Occult pneumothorax in trauma patients: development of an objective scoring system, J Trauma Inj Infect Crit Care 63 (1) (2007 Jul) 13–17. [40] CG Ball, AW Kirkpatrick, KB Laupland, DI Fox, S Nicolaou, IB Anderson, et al., Incidence, risk factors, and outcomes for occult pneumothoraces in victims of major trauma, J Trauma 59 (4) (2005 Oct) 917–924, discussion 924–925. [41] LA Miller, Chest wall, lung, and pleural space trauma, Radiol Clin North Am 44 (2) (2006 Mar) 213–224, viii. [42] N Tamburini, N Carriel, G Cavallesco, L Molins, R Galeotti, R Guzmán, et al., Technical results, clinical efficacy and predictors of outcome of intercostal arteries embolization for hemothorax: a twoinstitutions’ experience, J Thorac Dis 11 (11) (2019 Nov) 4693–4699. [43] A Hagiwara, Y Yanagawa, N Kaneko, A Takasu, K Hatanaka, T Sakamoto, et al., Indications for transcatheter arterial embolization in persistent hemothorax caused by blunt trauma, J Trauma 65 (3) (2008 Sep) 589–594. [44] R Kaewlai, LL Avery, AV Asrani, RA Novelline, Multidetector CT of blunt thoracic trauma, Radiographics 28 (6) (2008 Oct) 1555–1570. [45] ML.D Gunn, BE Lehnert, RS Lungren, CB Narparla, L Mitsumori, JA Gross, et al., Minimal aortic injury of the thoracic aorta: imaging appearances and outcome, Emerg Radiol 21 (3) (2014 Jun) 227–233. [46] N Fox, D Schwartz, JH Salazar, ER Haut, P Dahm, JH Black, et al., Evaluation and management of blunt traumatic aortic injury: a practice management guideline from the Eastern Association for the Surgery of
Trauma, J Trauma Nurs Off J Soc Trauma Nurses 22 (2) (2015 Apr) 99– 110. [47] JA Asensio, J Murray, D Demetriades, J Berne, E Cornwell, G Velmahos, et al., Penetrating cardiac injuries: a prospective study of variables predicting outcomes, J Am Coll Surg 186 (1) (1998 Jan) 24–34. [48] R Yousef, JA Carr, Blunt cardiac trauma: a review of the current knowledge and management, Ann Thorac Surg 98 (3) (2014 Sep) 1134– 1140. [49] CE Murphy, AS Raja, BM Baumann, AJ Medak, MI Langdorf, DK Nishijima, et al., Rib fracture diagnosis in the panscan era, Ann Emerg Med 70 (6) (2017 Dec) 904–909. [50] BT Flagel, FA Luchette, RL Reed, TJ Esposito, KA Davis, JM Santaniello, et al., Half-a-dozen ribs: the breakpoint for mortality, Surgery 138 (4) (2005 Oct) 717–725. [51] MT Nummela, FV Bensch, TT Pyhältö, SK Koskinen, Incidence and imaging findings of costal cartilage fractures in patients with blunt chest trauma: a retrospective review of 1461 consecutive whole-body ct examinations for trauma, Radiology 286 (2) (2018 Feb) 696–704. [52] E Swart, J Laratta, G Slobogean, S Mehta, Operative treatment of rib fractures in flail chest injuries: a meta-analysis and cost-effectiveness analysis, J Orthop Trauma 31 (2) (2017 Feb) 64–70. [53] A Panda, A Kumar, S Gamanagatti, A Patil, S Kumar, A Gupta, Traumatic diaphragmatic injury: a review of CT signs and the difference between blunt and penetrating injury, Diagn Interv Radiol Ank Turk 20 (2) (2014 Apr) 121–128. [54] S Margari, F Garozzo Velloni, M Tonolini, E Colombo, D Artioli, NE Allievi, et al., Emergency CT for assessment and management of blunt traumatic splenic injuries at a Level 1 Trauma Center: 13-year study, Emerg Radiol 25 (5) (2018 Oct) 489–497. [55] RA Kozar, M Crandall, K Shanmuganathan, BL Zarzaur, M Coburn, C Cribari, et al., Organ injury scaling 2018 update: spleen, liver, and kidney, J Trauma Acute Care Surg 85 (6) (2018 Dec) 1119–1122. [56] H Marmery, K Shanmuganathan, MT Alexander, SE Mirvis, Optimization of selection for nonoperative management of blunt splenic injury: comparison of MDCT grading systems, Am J Roentgenol 189 (6) (2007 Dec) 1421–1427. [57] D Morell-Hofert, F Primavesi, M Fodor, E Gassner, V Kranebitter, E Braunwarth, et al., Validation of the revised 2018 AAST-OIS classification and the CT severity index for prediction of operative management and survival in patients with blunt spleen and liver injuries, Eur Radiol 30 (12) (2020 Dec) 6570–6581.
[58] NA Stassen, I Bhullar, JD Cheng, ML Crandall, RS Friese, OD Guillamondegui, et al., Selective nonoperative management of blunt splenic injury: an Eastern Association for the Surgery of Trauma practice management guideline, J Trauma Acute Care Surg 73 (5 Suppl 4) (2012 Nov) S294–S300. [59] M Ilhan, RE Sönmez, A Kut, S Toprak, AF.K Gök, MK Günay, et al., Are radiological modalities really necessary for the long-term follow-up of patients having blunt solid organ injuries? A single center study, World J Emerg Med 10 (3) (2019) 177–181. [60] BL Zarzaur, JA Dunn, B Leininger, M Lauerman, K Shanmuganathan, K Kaups, et al., Natural history of splenic vascular abnormalities after blunt injury: A Western Trauma Association multicenter trial, J Trauma Acute Care Surg 83 (6) (2017 Dec) 999–1005. [61] LL Berland, JA VanDyke, Decreased splenic enhancement on CT in traumatized hypotensive patients, Radiology 156 (2) (1985 Aug) 469–471. [62] MS Patil, SZ Goodin, LK Findeiss, Update: splenic artery embolization in blunt abdominal trauma, Semin Interv Radiol 37 (1) (2020 Mar) 97– 102. [63] JC.I Crichton, K Naidoo, B Yet, SI Brundage, Z Perkins, The role of splenic angioembolization as an adjunct to nonoperative management of blunt splenic injuries: a systematic review and meta-analysis, J Trauma Acute Care Surg 83 (5) (2017 Nov) 934–943. [64] SA Padia, CR Ingraham, JM Moriarty, LR Wilkins, PR Bream, AL Tam, et al., Society of interventional radiology position statement on endovascular intervention for trauma, J Vasc Interv Radiol 31 (3) (2020 Mar), 363-369.e2. [65] K Melamud, CA LeBedis, SW Anderson, JA Soto, Biliary imaging: multimodality approach to imaging of biliary injuries and their complications, Radiographics 34 (3) (2014 May) 613–623. [66] RE Erb, SE Mirvis, K Shanmuganathan, Gallbladder injury secondary to blunt trauma: CT findings, J Comput Assist Tomogr 18 (5) (1994 Oct) 778–784. [67] NA Stassen, I Bhullar, JD Cheng, M Crandall, R Friese, O Guillamondegui, et al., Nonoperative management of blunt hepatic injury: an eastern association for the surgery of trauma practice management guideline, J Trauma Acute Care Surg 73 (5 Suppl 4) (2012 Nov) S288– S293. [68] JA Graves, TN Hanna, KD Herr, Pearls and pitfalls of hepatobiliary and splenic trauma: what every trauma radiologist needs to know, Emerg Radiol 24 (5) (2017 Oct) 557–568.
[69] KW Fleming, BC Lucey, JA Soto, ME Oates, Posttraumatic bile leaks: role of diagnostic imaging and impact on patient outcome, Emerg Radiol 12 (3) (2006 Mar) 103–107. [70] M Hosein, D Paskar, R Kodama, N Ditkofsky, Coming together: a review of the American association for the surgery of trauma’s updated kidney injury scale to facilitate multidisciplinary management, Am J Roentgenol 213 (5) (2019 Nov) 1091–1099. [71] RC Alonso, SB Nacenta, PD Martinez, AS Guerrero, CG Fuentes, Kidney in danger: CT findings of blunt and penetrating renal trauma, Radiogr Rev Publ Radiol Soc N Am Inc 29 (7) (2009 Nov) 2033–2053. [72] S Keihani, BE Putbrese, DM Rogers, DP Patel, GJ Stoddard, JM Hotaling, et al., Optimal timing of delayed excretory phase computed tomography scan for diagnosis of urinary extravasation after high-grade renal trauma, J Trauma Acute Care Surg 86 (2) (2019 Feb) 274–281. [73] RA Santucci, 2015 William Hunter Harridge lecture: how did we go from operating on nearly all injured kidneys to operating on almost none of them?, Am J Surg 211 (3) (2016 Mar) 501–505. [74] Y Mahat, JY Leong, PH Chung, A contemporary review of adult bladder trauma, J Inj Violence Res 11 (2) (2019 Jul) 101–106. [75] G Joshi, EY Kim, TN Hanna, CL Siegel, CO Menias, CT Cystography for suspicion of traumatic urinary bladder injury: indications, technique, findings, and pitfalls in diagnosis: radiographics fundamentals | online presentation, Radiogr Rev Publ Radiol Soc N Am Inc 38 (1) (2018 Feb) 92–93. [76] JP Vaccaro, JM Brody, CT cystography in the evaluation of major bladder trauma, Radiogr Rev Publ Radiol Soc N Am Inc 20 (5) (2000 Oct) 1373–1381. [77] A Kumar, A Panda, S Gamanagatti, Blunt pancreatic trauma: A persistent diagnostic conundrum?, World J Radiol 8 (2) (2016 Feb 28) 159–173. [78] DR Biyyam, S Hwang, MC Patel, DM.E Bardo, SS Bailey, M Youssfi, CT findings of pediatric handlebar injuries, Radiogr Rev Publ Radiol Soc N Am Inc 40 (3) (2020 Jun) 815–826. [79] A Panda, A Kumar, S Gamanagatti, AS Bhalla, R Sharma, S Kumar, et al., Evaluation of diagnostic utility of multidetector computed tomography and magnetic resonance imaging in blunt pancreatic trauma: a prospective study, Acta Radiol Stockh Swed 56 (4) (1987) 387–396, .. [80] EE Moore, TH Cogbill, MA Malangoni, GJ Jurkovich, HR Champion, TA Gennarelli, et al., Organ injury scaling, II: pancreas, duodenum, small bowel, colon, and rectum, J Trauma 30 (11) (1990 Nov) 1427–1429.
[81] W Tilden, M Griffiths, S Cross, Vascular bowel and mesenteric injury in blunt abdominal trauma: a single centre experience, Clin Radiol (2020 Oct 17). [82] M Raza, Y Abbas, V Devi, KV.S Prasad, KN Rizk, PP Nair, Non operative management of abdominal trauma: a 10 years review, World J Emerg Surg 8 (2013) 14. [83] KL Killeen, S Girard, JH DeMeo, K Shanmuganathan, SE Mirvis, Using CT to diagnose traumatic lumbar hernia, Am J Roentgenol 174 (5) (2000 May) 1413–1415. [84] VM Mellnick, C Raptis, C Lonsford, M Lin, D Schuerer, Traumatic lumbar hernias: do patient or hernia characteristics predict bowel or mesenteric injury?, Emerg Radiol 21 (3) (2014 Jun) 239–243. [85] AP Marek, RF Deisler, JB Sutherland, G Punjabi, A Portillo, J Krook, et al., CT scan-detected pneumoperitoneum: an unreliable predictor of intra-abdominal injury in blunt trauma, Injury 45 (1) (2014 Jan) 116–121. [86] CH Lee, B Haaland, A Earnest, CH Tan, Use of positive oral contrast agents in abdominopelvic computed tomography for blunt abdominal injury: meta-analysis and systematic review, Eur Radiol 23 (9) (2013 Sep) 2513–2521. [87] JD Lozano, F Munera, SW Anderson, JA Soto, CO Menias, KM Caban, Penetrating wounds to the torso: evaluation with triple-contrast multidetector CT, Radiogr Rev Publ Radiol Soc N Am Inc 33 (2) (2013 Apr) 341–359. [88] N Saksobhavivat, K Shanmuganathan, AR Boscak, CW Sliker, DM Stein, UK Bodanapally, et al., Diagnostic accuracy of triple-contrast multidetector computed tomography for detection of penetrating gastrointestinal injury: a prospective study, Eur Radiol 26 (11) (2016 Nov) 4107–4120. [89] CJ Ozimok, VM Mellnick, MN Patlas, An international survey to assess use of oral and rectal contrast in CT protocols for penetrating torso trauma, Emerg Radiol 26 (2) (2019 Apr) 117–121. [90] BJ Baron, R Benabbas, C Kohler, C Biggs, V Roudnitsky, L Paladino, et al., Accuracy of computed tomography in diagnosis of intra-abdominal injuries in stable patients with anterior abdominal stab wounds: a systematic review and meta-analysis, Acad Emerg Med Off J Soc Acad Emerg Med 25 (7) (2018 Jul) 744–757. [91] R Tsai, C Raptis, DJ Schuerer, VM Mellnick, CT appearance of traumatic inferior vena cava injury, AJR Am J Roentgenol 207 (4) (2016 Oct) 705–711. [92] J Elst, IE Ghijselings, WP Zuidema, FH Berger, Signs of post-traumatic hypovolemia on abdominal CT and their clinical importance: a systematic review, Eur J Radiol 124 (2020 Mar) 108800.
[93] AH Baghdanian, AS Armetta, AA Baghdanian, CA LeBedis, SW Anderson, JA Soto, CT of major vascular injury in blunt abdominopelvic trauma, Radiogr Rev Publ Radiol Soc N Am Inc 36 (3) (2016 Jun) 872– 890. [94] S Chakraverty, K Flood, D Kessel, S McPherson, T Nicholson, CE Ray, et al., CIRSE guidelines: quality improvement guidelines for endovascular treatment of traumatic hemorrhage, Cardiovasc Intervent Radiol 35 (3) (2012 Jun) 472–482.
CHAPTER 90
Acute Neurological Emergencies Ashok Adams
Introduction The aim of this chapter is to review acute neurological emergencies and approach to imaging. Acute insults to the central nervous system can present in a variety of different ways and this chapter will present the most common clinical scenarios combined with imaging algorithms and differential diagnoses. Imaging of acute trauma and thromboembolic stroke are covered in other chapters and the primary focus of this chapter is on nontraumatic acute neurological emergencies.
Acute Onset Headache Acute onset nontraumatic headaches represent approximately 2– 4% of accident and emergency admissions and secondary causes of headaches are found in a small proportion [1]. This increases in the setting of sudden-onset acute headaches or thunderclap headache that peaks within 60 seconds. The presence of abnormal neurology increases the possibility of a secondary cause for the headache including the presence of Horner’s syndrome, cranial
nerve palsies, visual symptoms and visual aura, systemic symptoms as well as nausea and vomiting [2,3]. An underlying history of immunosuppression or neoplasia should also be sought [4]. Acute onset headache in the peripartum setting is dealt with separately in this chapter. For the radiologist the spectrum of disease processes to consider are myriad and providing an accurate diagnosis or limited differential diagnosis is aided by the clinical information provided that also helps to guide subsequent imaging. An imaging algorithm is provided and, in our institution, a noncontrast computed tomography (CT) head is performed the first line given its accessibility and capability of identifying potential candidates for neurosurgical intervention. In the setting of acute onset headache, this can be supplemented by imaging of the vasculature and targeted at the arterial and/or venous system. If available, arterial or venous vascular imaging can be undertaken at the same time as routine brain CT or magnetic resonance imaging (MRI) of the intracranial compartment (Table 90.1).
◾intracranial In the setting of a confirmed intracranial hemorrhage, imaging of the arterial and venous structures is undertaken ◾vasculitis, If there is concern regarding thromboembolic disease, vascular dissection or imaging of the intra- as well as the extra-cranial vessels is performed
–MR venography (two-dimensional time of flight MRV sensitive to flow perpendicular to plane, contrast-enhanced MRV)
Intracranial Extra-axial Hemorrhage Diffuse subarachnoid hemorrhage (SAH) is observed in the setting of trauma and in the nontrauma setting, this can occur secondary to aneurysmal rupture, arteriovenous malformation, or dural arteriovenous fistula [5]. Nontraumatic aneurysmal rupture in 85% of cases is most likely secondary to a saccular aneurysm rupture [6]. The epicenter of the hemorrhage typically guides the source of the SAH and the most common sites include the anterior communicating artery, posterior communicating artery, middle cerebral artery bifurcation, and basilar artery. Less frequently, the source of the SAH may be the internal carotid artery terminus, superior cerebellar artery, and posterior inferior cerebellar artery. The presence of SAH prompts further evaluation with an intracranial CT angiogram (CTA) to identify the source of hemorrhage and guide subsequent endovascular or surgical therapy if required (Fig. 90.1). It is also of benefit in assessing potential complicating vasospasm (Fig. 90.2). Following CTA imaging this can be supplemented with MR imaging preferably with contrast-enhanced MRI and vessel wall imaging. Vessel wall imaging in particular is of benefit if an underlying vasculopathy is
suspected and in patients with multiple intracranial aneurysms to guide targeted therapy [7,8].
FIGURE 90.1 Axial noncontrast CT demonstrates acute subarachnoid hemorrhage in the right ambient cistern (thin white arrow in A). The CT angiogram (B) and digital subtraction angiogram (DSA) (C) confirmed a ruptured posterior communicating artery aneurysm (thick white arrows) that was successfully treated via an endovascular approach.
FIGURE 90.2 Axial CT head (A) confirms the presence of an extensive subarachnoid hemorrhage secondary to a ruptured anterior communicating artery aneurysm that was successfully treated via and endovascular approach (coil ball demonstrated on the CT angiogram). The CT angiogram (B) demonstrates multifocal irregularity affecting the anterior cerebral arteries (white arrows) compatible with vasospasm.
In a patient with suspected or confirmed sepsis, the development of focal neurological signs or seizures should be viewed as concerning for infarction secondary to septic emboli. Infected mycotic aneurysms can affect the intracranial circulation and although rare, the intracranial compartment is the third most common site of involvement. There should also be a low threshold for vascular imaging, particularly in immunocompromised patients. Mycotic aneurysms more commonly affect the anterior circulation and are typically peripherally located and fusiform in morphology (Fig. 90.3). The evolution of the infective process affecting the vessel wall may lead to rupture of the wall may lead to pseudoaneurysm formation which can be lethal.
FIGURE 90.3 Axial CT head (A) performed in a patient with known infective bacterial endocarditis that presented with a drop in GCS. There is a large parenchymal hematoma with intraventricular extension. The CT angiogram (B) performed postdecompressive craniectomy and clot evacuation demonstrates a focal area of contrast suspicious for a fusiform mycotic aneurysm that was confirmed with a subsequent digital subtraction cerebral angiogram (C) to represent a mycotic aneurysm within a distal M4 segment of right posterior temporal artery (white arrows).
In a patient with confirmed SAH but in whom no aneurysmal source can be identified, the SAH may be secondary to perimesencephalic bleed that is typically venous in origin (Fig. 90.4). These patients have a low risk of rebleeding, vasospasm, and CSF flow impairment, and hydrocephalus with overall better outcomes [9]. The presence of blood anterior to the midbrain/pons, interpeduncular, and prepontine cisterns is characteristic and less likely to extend laterally into the sylvian fissures or demonstrate intraventricular extension. A retro clival hematoma is a rare entity that typically occurs in the posttraumatic setting in children but it can occur spontaneously and can be associated with intraventricular blood. As per a perimesencephalic bleed, the outcomes are favorable [10].
FIGURE 90.4 Axial noncontrast CT (A and B) demonstrating acute subarachnoid hemorrhage within the interpeduncular cistern and prepontine cistern (white arrows). There was a small volume of blood within the suprasellar cistern but no lateral extension into the sylvian fissure. The imaging features were suspicious for a perimesenencephalic hemorrhage, potentially venous in origin with subsequent negative CT angiogram and DSA (not shown). DSA, digital subtraction angiogram.
In the setting of a spontaneous convexity SAH, specific diagnoses to consider include reversible cerebral vasoconstriction syndrome (RCVS), cerebral venous sinus thrombosis (CVST), vasculitis, amyloid angiopathy, and underlying coagulopathy (Table 90.2). It may also reflect hemorrhagic transformation of parenchymal infarction [11]. Table 90.2 Differential Diagnosis Focal Convexity Subarachnoid Hemorrhage Trauma Cerebral venous sinus thrombosis
Patients with CVST typically present with headache which is often the first symptom although the nature of the headache is variable. Focal deficits, seizures, altered consciousness, and papilledema can also occur. The venous thrombosis increases the venous pressure that can impair arterial perfusion that can then result in edema (both vasogenic and cytotoxic) and parenchymal hemorrhage that can be cortical with either subcortical or subarachnoid extension. On a noncontrast CT head, the venous thrombosis can be difficult to identify and the density of the sinus and measurement of the Hounsfield unit can add diagnostic confidence [12]. However, this should be interpreted with caution as it requires correlation with the patients hematocrit level [13,14]. The pattern of parenchymal involvement is dictated by the extent of involvement of the dural venous sinuses, superficial cortical veins and deep internal cerebral veins as well as the collateral drainage pathways (Fig. 90.5). MR imaging is a more sensitive test and can be combined with venographic imaging acquired as either a two-dimensional time of flight (TOF) MR venogram or contrast enhanced MR venogram [15] (Fig. 90.6). The appearance of the sinus thrombosis is dependent on the age of the thrombus and in the acute setting is isointense on T1 and hypointense on T2 thus can be overlooked. The brain parenchymal changes in terms of edema and hemorrhage are well depicted on the T2 weighted, FLAIR, and DW imaging sequences while the thrombus can be identified on either GRE or SWI sequences (Fig. 90.7).
FIGURE 90.5 Axial CT (A) performed in a patient with sudden onset headache. There is abnormal hyperdensity along the pathway of the internal cerebral veins and vein of Galen suspicious for an internal cerebral vein thrombosis (black arrows). On the CT venogram (B), there were confirmed filling defects extending from the internal cerebral veins into the vein of Galen and straight sinus (white arrows).
FIGURE 90.6 (A and B) Axial T2 brain imaging demonstrating abnormal signal in the left transverse sinus that correlates with abnormal hyperintensity on the sagittal T1 weighted imaging (white arrows). The maximum intensity projection from the TOF MRV (C) confirms the lack of flow within the left transverse and sigmoid sinus compatible with venous sinus thrombosis (white arrow). TOF, time of flight.
FIGURE 90.7 Axial MR imaging in a patient with a confirmed extensive superior sagittal thrombosis with involvement of the superficial cortical veins. On the SWI imaging (A) there is a combination of parenchymal susceptibility compatible with microhemorrhages including sulcal convexity subarachnoid hemorrhage (white arrows). The axial FLAIR sequence (B) confirms the presence of edema within the right frontal lobe (black arrow) complicated by cytotoxic edema and cortical infarction on the b1000 image of the DWI (C) [white arrow— corresponding low ADC values (ADC map not shown)].
Diagnosing vasculitis is challenging given the often nonspecific symptoms (e.g., fever, fatigue, night sweats, and weight loss) and it can present with transient ischemic attacks, focal deficits, and thunderclap headaches [16]. The patient may demonstrate no signs of systemic inflammation and cognitive deterioration may be a leading feature. CNS vasculitis is a heterogeneous group of disorders typically classified on the basis of the caliber of the affected vessels. It may affect large, medium-sized, small, and variable-sized blood vessels, and single or multiple organs. In addition, cerebral vasculitis may be due to systemic connective tissue disorders, infection, malignancy, drug use, or radiation therapy. On standard MR imaging sequences, it may be possible to identify areas of ischemia or infarction while contrast-enhanced imaging may depict areas of pathological parenchymal or leptomeningeal enhancement (Fig. 90.8). Angiographic CT or MR imaging typically identified areas of luminal irregularity as a consequence of the pathological changes affecting the vessel wall and typically identified as areas of vascular narrowing and
“beading” of vessels. With improvements in MR imaging techniques associated areas of potential inflammatory change and enhancement can be identified on vessel wall imaging [7].
FIGURE 90.8 Axial FLAIR (A) sequence confirms the presence of abnormal T2 signal hyperintensity within the right anterior striatocapsular region centered on the right caudate head (black arrow) with confirmed restricted diffusion on the DWI imaging (B) [thick white arrow on b1000 image confirms high signal with low ADC value (ADC map not shown)]. There is abnormal enhancement in relation to the MCA perforator vessels and affecting the sylvian branches of the right MCA (thin white arrows) in the postcontrast T1 weighted image (C) in a confirmed case of Varicella-zoster virus vasculitis.
Intra-axial Parenchymal Hemorrhage/Hematoma The presence of an intra-axial parenchymal hemorrhage and hematoma formation is associated with an unfavorable outcome and significant mortality rate of 40% at one month [17]. Headache and vomiting are common but nonspecific symptoms and on a noncontrast CT head, these are readily depicted to guide any potential neurosurgical intervention. Further MR imaging is typically required particularly in normotensive, younger patients
(age 280 in children [25]. Other criteria demonstrable on imaging in addition to transverse sinus stenosis include an empty sella, globe flattening, and prominent subarachnoid spaces. Patients with IIH have a higher incidence of meningoceles and a potential complication of IIH also includes
the development CSF hypotension secondary to a CSF leak [26] (Fig. 90.15).
FIGURE 90.14 Axial noncontrast CT head (A) confirms the presence of bilateral optic nerve head protrusion correlating with bilateral papilledema (thin white arrows). The CT venogram (B) excluded a venous sinus thrombosis but it identified a transverse sinus stenosis (thick white arrow) in this patient with idiopathic intracranial hypertension.
FIGURE 90.15 Axial CT (A) in a patient with idiopathic intracranial hypertension presenting with right-sided nasal discharge. There is opacification within the right sphenoid sinus with multiple arachnoid granulations and potential defect in the lateral wall of the right sphenoid (thin white arrow). The coronal T2 MRI (B) demonstrates a right sided meningoencephalocele (thick white arrow).
Neoplastic Processes A concern in the acute emergency setting in a patient with a newonset headache is the exclusion of a neoplastic process [27]. Unfortunately, primary intrinsic gliomas, and other intracranial tumors as well as the secondary metastatic disease can all potentially present with headache (Fig. 90.16). In the setting of multiple foci of parenchymal hemorrhage, metastatic disease is a consideration, particularly in the setting of melanoma, renal, thyroid, cervical, and choriocarcinoma [28] (Fig. 90.17). Nonhemorrhagic lesions are often identified as areas of parenchymal edema on a noncontrast study that often prompts further evaluation with a contrast-enhanced CT or MRI. Complications of the lesion(s) include mass effect and transcompartmental shift, hydrocephalus, and venous sinus thrombosis. Unique in this setting is the presence of a colloid cyst which,
given its location, can result in obstruction of CSF flow [29]. The MR appearances and signal characteristics are dependent upon cyst composition and it can present with positional headaches (Fig. 90.18). Sudden death can occur from ball valve effect and obstruction of CSF outflow from the third ventricle [30].
FIGURE 90.16 Axial noncontrast CT (A) in a 15-year-old female patient presenting with headaches, double vision, nausea, and vomiting. There is a hyperdense posterior fossa tumor (white arrow) with obstructive hydrocephalus. The coronal T2 weighted sequence (B) confirmed the presence of an intermediate T2 signal tumor (thick white arrow) that demonstrated marked cellularity on the DWI sequence with homogenous enhancement. This was confirmed to be a medulloblastoma.
FIGURE 90.17 Axial FLAIR sequence (A) and an axial gradient recall echo sequence (B) in a patient with a known germ cell tumor. The imaging demonstrates multiple parenchymal lesions (thin white arrows) with evidence of susceptibility on the GRE (thin black arrows) consistent with hemorrhagic parenchymal metastases.
FIGURE 90.18 Axial CT head performed in a patient presenting with headache (A). There is a rounded hyperdense lesion in the third ventricle on the CT consistent with a colloid cyst (thin white arrow). On the axial FLAIR sequence (B), it returns high signal consistent with proteinaceous material.
Pituitary apoplexy (Fig. 90.19) can present with sudden onset headache that is typically retro-orbital in nature, accompanied by nausea and vomiting, visual symptoms, and ophthalmoplegia. It results from hemorrhagic infarction of a pituitary adenoma and can lead to SAH [31].
FIGURE 90.19 Sagittal CT (A) and T1 precontrast MR (B) images in a patient who presented with acute onset headache and opthalmoplegia. There is evidence of pituitary apoplexy and intralesional hemorrhage (white arrows) into a presumed pre-existing pituitary macroadenoma.
Infectious Processes Intracranial sepsis can result from direct spread from sinugenic or otogenic sources or from hematogenous spread. Patients can present with headache with additional features including fever and systemic symptoms. This is covered in detail below in imaging the septic patient.
Comatose Patient Imaging assessment in the patient with a reduced level of consciousness and low GCS presenting to the emergency department typically requires a combination of both CT and MR imaging [32]. Reduced consciousness and altered mental state may be secondary to disruption of the ascending reticular activating system (ARAS) that has an integral role in arousal state and consciousness. The ARAS has connections between the pons and dorsal midbrain with the cortex via the thalamus and
hypothalamus [33]. In addition to disruption of this pathway other widespread cortical and global insults can result in reduced GCS and coma. In the setting of acute trauma the mechanism of trauma is related to the severity of intracranial injuries and in the patient, with altered mental status this can be secondary to a number of factors including diffuse axonal injury, development of cerebral swelling, and edema and trans-compartmental shift that can be related to cerebral edema as well as other intra- and extra-axial hemorrhage [32]. In the nontrauma setting, it is imperative to exclude the possibility of a vertebral or basilar artery thrombosis that may result in brainstem ischemia and infarction as this is potentially reversible with institution of thrombolysis or mechanical thrombectomy to restore perfusion [34] (Fig. 90.20). This is identified as a hyperdensity within the vertebrobasilar circulation and this can be supplemented with CTA or MRA in equivocal cases and for treatment planning purposes. Areas of corresponding infarction within the vertebrobasilar territory aid in subsequent management decisions and potential reperfusion therapies. The presence of midbrain and bilateral thalamic infarcts should prompt consideration of infarction within the artery of percheron [35] (Fig. 90.21).
FIGURE 90.20 Axial CT performed in a patient who presented with a low GCS. There is hyperdensity within the basilar artery (thin white arrow in A) confirmed as a basilar artery thrombosis on CT angiographic imaging (not shown). The subsequent CT head (B) demonstrates persistent thrombus with extensive infarction affecting the brainstem, cerebellum, and right temporal lobe.
FIGURE 90.21 Axial FLAIR image (A) in a patient presenting with acute onset double vision and sensory symptoms with abnormal signal change in the ventromedial aspect of both thalami (thin white arrows) that was confirmed as areas of diffusion restriction on the DWI imaging (B) (thin white arrows on the b1000 image). The features were consistent with infarction within the artery of Percheron territory.
In patients with cardiorespiratory arrest or in cases with a suspected downtime the admission CT may be able to confirm the presence of a global hypoxic brain injury with
◾ global loss of gray–white matter differentiation, ◾ loss of clarity of the basal ganglia, ◾ cerebral swelling and generalized sulcal effacement, ◾ hyperdense cerebellum, and ◾ pseudo-SAH appearance (Fig. 90.22).
FIGURE 90.22 Axial CT head in a patient with an out-ofhospital cardiac arrest. There is cerebral swelling with loss of the gray and white matter differentiation and loss of clarity of the basal ganglia consistent with a hypoxic brain injury.
However, MR is more sensitive and provides more prognostic cases, especially in cases with suspected global hypoxic brain injury and no confirmatory findings on CT [36] (Fig. 90.23). Various patterns of cortical, ganglionic, white matter, and brainstem involvement can be observed [37]. Diffusion-weighted imaging represents the most sensitive imaging sequences with identification of diffusion restriction that may be difficult to appreciate on the conventional T2 and FLAIR imaging sequences (Fig. 90.24). The areas affected reflect areas of brain tissue that have high metabolic demand and thus are more susceptible to the effects of hypoxia.
FIGURE 90.23 Axial CT (A) in a child who sustained neck trauma that was considered within normal limits but an MRI was performed given the mechanism of injury and clinical status. The axial FLAIR (B) and DWI imaging (C) (b1000 imaging shown) demonstrates abnormal signal change within the basal ganglia, internal capsules, occipital lobes, and hippocampi consistent with a hypoxic brain injury.
FIGURE 90.24 Axial FLAIR (A) and DWI (b1000 image (B) and ADC map (C)) in a patient who suffered a cardiac arrest following a road traffic accident. The FLAIR demonstrates subtle abnormal signal change within the caudate nuclei and affecting the cortex and subcortical white matter but this is accentuated and more readily appreciable on the b1000 imaging of the DWI sequences. This correlated with areas of low signal on the corresponding ADC map with features compatible with a global hypoxic brain injury.
A range of systemic abnormalities can induce a comatose state and this includes both metabolic disturbances and exposure to toxins. These can have both acute effects on the CNS while others can have chronic effects and thus the clinical presentation can be more subtle and insidious [38]. In this chapter, we will focus on metabolic disturbances and toxins that demonstrate immediate CNS toxicity and results in an acute presentation to the emergency department. Particular areas of the brain are particularly susceptible to toxic and metabolic insults that include the basal ganglia and cerebral white matter and typically this may occur in a symmetrical distribution. The differential diagnoses to consider in bilateral basal ganglia insults are listed in Table 90.3. Table 90.3 Bilateral Basal Ganglia Abnormalities 1. Vascular Internal cerebral vein thrombosis Artery of percheron infarct/basilar tip syndrome Global hypoxic/hypoperfusion ischemic injury 2. Toxic Carbon monoxide poisoning—globus pallidus necrosis Heroin—basal ganglia, cerebral white matter, and cerebellar involvement Methanol—visual disturbances, putaminal necrosis and white matter demyelination Cyanide poisoning—putaminal and globus pallidus involvement 3. Metabolic Glucose—Hyper glycaemia/Hypoglycaemia Hyperammonaemia/liver failure—globus pallidus changes Wernicke’s encephalopathy Osmotic demyelination
Alcohol (ethanol) is a commonly abused substance that is a potential neurotoxin that easily crosses the blood–brain barrier. It has a variety of acute and chronic effects on the CNS and it is a confounding factory in a significant proportion of emergency department admissions. Acute alcohol poisoning can result in cytotoxic edema affecting the cerebral white matter and thalami and can result in diffuse cerebral swelling [38]. Alcohol may result in Wernicke–Korsakoff syndrome in addition to other nonalcohol related causes of thiamine deficiency. The acute clinical presentation includes the triad of ocular dysfunction, ataxia, and altered mental status and the brain parenchymal areas commonly involved include the mamillary bodies, hypothalamus, medial thalamic nuclei, tectal plate, and periaqueductal gray (Fig. 90.25). These changes are difficult to discern on a noncontrast CT and MR imaging is more sensitive [39].
FIGURE 90.25 Axial T2 (A), FLAIR (B), and DWI (C) (b1000 image) in a patient with chronic alcoholism who presented with diplopia. There is abnormal signal change within the midbrain and periaqueductal gray consistent with Wernicke– Korsakoff syndrome. On the DWI the area of high signal on the b1000 image did not correlate with low signal on the ADC map and was not considered to represent diffusion restriction.
Osmotic demyelination syndrome (ODS) can result from acute electrolyte and osmolality disorders of which hyponatremia and rapid overcorrection are the most common. ODS typically affects the pons (pontine myelinolysis) however, extrapontine myelinolysis also commonly occurs affecting the thalami, basal ganglia, and cerebral white matter in particular [40]. MR imaging and diffusion weighted imaging is the most sensitive sequence in the setting of acute ODS demonstrating restricted diffusion in affected brain areas [39]. Development of hyperintense signal on T2 and FLAIR sequences with the corresponding hypointense signal on T1 weighted sequences develops in the first few days. Acute hepatic encephalopathy results from hyperammonaemia that may be due to hepatic failure or other nonhepatic causes. Ammonia and its principal metabolite glutamine interfere mitochondrial metabolism and energy production and this accounts for the pattern of brain parenchymal involvement and magnetic resonance spectroscopy findings. Patients can present with nonspecific irritability, lethargy and vomiting that may progress to increasing drowsiness, seizures and subsequent coma.
◾sulcal A noncontrast CT may demonstrate diffuse cerebral edema with cerebral effacement. ◾insula, On MR imaging there is abnormal T2 and FLAIR hyperintensity affecting the cingulate gyri, and basal ganglia in particular although more diffuse cortical, thalamic, and white matter involvement may occur (Fig. 90.26). Restricted diffusion is typical and altered glutamate-glutamine peak at short echo times are seen on MRS [41].
FIGURE 90.26 . Axial FLAIR imaging (A and B) in a hepatic encephalopathy with abnormal signal change noted in the right temporal lobe and right insula (with thalamic involvement (white arrows). The bithalamic involvement is accentuated on the DWI sequence (C) (thin white arrows on b1000 imaging).
The brain has significant demand for glucose being a metabolically active organ with no glycogen stores and thus blood glucose levels are tightly regulated. Disruption of glucose levels and either hypoglycaemia or hyperglycaemia has the potential to affect the CNS. Hypoglycaemic encephalopathy results from the direct effect of impaired intracellular metabolism and aerobic oxidation with further indirect effects resulting from the release of excitatory neurotransmitters. The pattern of brain parenchymal involvement includes cortical involvement with a predilection for the parieto-occipital lobes with subsequent cortical laminar necrosis [42]. The basal ganglia, hippocampi and amygdala can also be involved but areas not typically affected include the thalamus, brainstem and cerebellum.
◾caudate On an unenhanced CT head symmetrical hypodensities in the putamina and nuclei can be present with sparing of the thalami. Cortical involvement can be identified as generalized cerebral swelling and sulcal effacement ◾parenchyma MR imaging demonstrates T2 and FLAIR signal hyperintensity in the affected with the development of T1 shortening in areas of cortical laminar necrosis (Fig. 90.27)
FIGURE 90.27 Axial T2 (A) and FLAIR (B) imaging in a patient presenting with low GCS secondary to hypoglycaemia. There was symmetrical abnormal signal change within the caudate nuclei and both putamina (thin black arrows).
The main differential to include would be hypoxic-ischemic encephalopathy given the requirements of oxygen and glucose for aerobic metabolism but HIE may involve the thalami and cerebellum. In the acute emergency setting, hyperglycaemia may result in diabetic ketoacidosis or hyperglycaemic hyperosmolar state (HHS). Hyperglycaemia induced hemichorea and hemiballismus is less common and is evident on imaging as basal ganglia T1 shortening and signal hyperintensity with sparing of the thalamus [43]. These findings are typically unilateral but can be bilateral in nature (Fig. 90.28). The hyperglycaemic state results from
reduced effects of insulin and impaired glucose utilization combined with accelerated glucose production. In diabetic ketoacidosis, this can be identified on imaging as areas of nonspecific vasogenic edema while clinically there is increased ketone production with resultant metabolic acidosis that also precipitates osmotic diuresis and loss of water, and electrolytes (Na+, K+). Correction of the metabolic disturbance can result in osmotic myelinolysis [40]. HHS results in hyperglycaemia with minimal ketone formation with elevated glucose and bicarbonate levels. It typically results in white matter signal hypointensity within the parietal and occipital lobes, The affected cortical regions demonstrate T2/FLAIR signal hyperintensity with restricted diffusion [43].
FIGURE 90.28 Axial T1 (A) and FLAIR (B) imaging in a patient with nonketotic hyperglycaemia presenting with generalized chorea. There was abnormal and symmetrical T1 hyperintensity affecting the putamina with heterogenous signal on the FLAIR (white arrows).
The spectrum of potential toxins that affect the CNS is myriad and, in this chapter, we will focus on the most common presentations to the emergency department. This includes carbon monoxide (CO) poisoning, methanol intoxication, and illicit drug use including cocaine and heroin. CO poisoning may occur due to accidental poisoning or in the setting of attempted suicide. It is a toxic, clear, and odorless gas formed from the incomplete combustion of hydrocarbons that combines with hemoglobin hence it impairs oxygen transportation. The brain parenchymal areas involved include the globus pallida and cerebral white matter [44].
◾suspected CT head imaging is typically normal although CO poisoning should be if there are bilateral pallidal hypodensities ◾T2/FLAIR On MR imaging the globus pallidus necrosis is observed as an area of signal hyperintensity and T1 signal hypointensity with peripheral T2 low signal and T1 shortening (Fig. 90.29)
FIGURE 90.29 Axial CT (A) in a patient with suspected carbon monoxide poisoning who had a CT that confirmed low density within the globus pallida that correlated with abnormal signal hyperintensity on the axial T2 (B) and FLAIR (C) sequences.
The cerebral white matter involvement can be delayed and progresses from demyelination to necrosis. The main differential for the imaging appearances is that of HIE but in the setting of HIE other brain areas including the hippocampi and the other
components of the basal ganglia while the white matter is less often affected. Methanol poisoning can be deliberate or accidental. It is a strong CNS depressant and methanol is metabolized to formaldehyde and formic acid which can result in a metabolic acidosis. Clinical presentation includes visual disturbances and blindness, nonspecific GI symptoms of nausea, and vomiting with coma in severe cases. Changes are observed in the putamina and cerebral white matter. Bilateral putaminal necrosis may hemorrhage with sparing of the globus pallida while cerebral white matter involvement has a predilection for the insula subcortical white matter [44]. In addition to methanol, ethylene glycol poisoning should also be considered in the setting of putaminal necrosis. Cocaine toxicity can result from both direct effects of the drug and its additives. It can be snorted, smoked, or injected but the effects are the same and it has a significant effect on the vasculature. It promotes platelet aggregation hence patients are at increased risk of thromboembolic strokes. Cocaine induces vasospasm and can result in systemic hypertensive crisis that also increases the risk of bleeding from existing aneurysms and vascular malformations. It also accounts for its association with posterior reversible encephalopathy syndrome (PRES) but cocaine use can also result in a vasculitis that also increases the risk of ischemia and infarction (Fig. 90.30).
FIGURE 90.30 Sagittal CTA maximal intensity projection (A) that demonstrated irregularity within the right middle cerebral artery branches (thin white arrow). This was attributed to a cocaine induced vasculopathy with small foci of embolic infarction within the right MCA territory on the DWI sequences (thick white arrows in B and C).
Heroin is another toxin that can result in vasospasm and vasculopathy that results in ischemia that can also be secondary to emboli from impure additives. Heroin inhalation can produce a pattern of leukoencephalopathy affecting the hemispheric white matter, posterior limb of the internal capsule, cerebellar white matter brainstem [38] (Fig. 90.31).
FIGURE 90.31 Axial FLAIR imaging (A and B) in a patient with opioid-induced toxicity with abnormal signal change within both cerebellar hemispheres with involvement of the supratentorial white matter with abnormal signal change within the centrum semiovale (thin black arrows). On the DWI sequences (C and D) this signal change demonstrated restricted diffusion within the splenium of the corpus callosum and centrum semiovale (white arrows on the b100 imaging of the DWI).
Septic Patient The radiologist plays a key role in imaging the patient with suspected intracranial sepsis in terms of potentially identifying the source of infection and the potential complications. If possible, it is important to establish whether the patient is immunocompetent or immunocompromised as this helps with refining potential differential diagnoses. In terms of imaging assessment, this can be broadly subdivided into extra-axial and intra-axial findings but there is frequent overlap with patients having abnormalities in multiple compartments. The extra-axial findings to assess for include extradural collections, subdural collections, and leptomeningeal abnormalities while the intra-axial findings include identification of ring-enhancing lesions and specific assessment of the limbic and ganglionic structures. In our institution, primary assessment is undertaken with a noncontrast CT head supplemented with contrast-enhanced imaging prompted by identification of an intracranial abnormality on the initial CT or in the context of an immunocompromised
patient or high index of suspicion of a meningoencephalitis. CT is of benefit in the acute setting to assess for potential complications including hydrocephalus, assessment of mass effect, and transcompartmental shift and intracranial hemorrhage. Contrastenhanced imaging also enables assessment of both the arterial and venous structures depending on the timing of acquisition and provides an assessment of potential secondary vasculopathy and cerebral venous thrombosis. In the majority of patients in whom there is a high index of suspicion of intracranial sepsis with normal initial CT findings, MR imaging is undertaken as it is inherently more sensitive. The routine imaging protocol includes a combination of T1 and T2 weighted sequences, a FLAIR sequence, diffusion-weighted imaging, and T1 postcontrast imaging either as a volumetric postcontrast sequence to enable multiplanar reformats or a combination of both axial and coronal postcontrast sequences. In our institution, the use of MR spectroscopy is utilized in cases of diagnostic uncertainty and its potential role will also be discussed. Identification of an extra-axial collection on a noncontrast CT head can be difficult, particularly in younger patients with preserved brain volume. However, extra-axial collection identification can be assisted by the administration of intravenous contrast.
◾course Extradural collections and empyema formation typically have a more benign when compared to subdural empyemas [45]. There is dural enhancement
and the collections can extend across midline although they are typically contained by sites of dural attachment to the inner table of the calvarium. Potential sources of infection to be assessed for include the sinonasal compartment, particularly the frontal sinuses, as well as the petromastoid air cells (Fig. 90.32). Extra-dural collections can also occur in the postoperative setting and following direct penetrating trauma. On MR imaging the extra-dural collections can demonstrate restricted diffusion with peripheral enhancement of the collection on the postcontrast imaging but typically do not incite edema within the adjacent brain parenchyma The presence of a subdural collection in the setting of a septic patient typically indicates the presence of a subdural empyema and, as per extradural empyemas, the sinonasal compartment and petromastoid regions should be assessed for potential source of infection (Fig. 90.33). Subdural empyemas can extend over the cerebral convexities and result in local mass effect and can be associated with adjacent leptomeningeal and parenchymal changes. Patients can present with focal deficits and seizures and typically have less favorable outcomes
◾
when compared to extradural empyemas [46]. The subdural empyema demonstrates peripheral enhancement and restricted diffusion on the DWI sequences Involvement of the leptomeninges and associated leptomeningitis can be difficult to identify on CT imaging even with the administration of intravenous contrast. MR imaging is more sensitive in this regard and contrast-enhanced T1 weighted imaging demonstrates abnormal enhancement of the pia-arachnoid which can also identify on FLAIR imaging as sulcal hyperintensity [47]. The presence of pus in the subarachnoid spaces may also demonstrate linear foci of restricted diffusion (Fig. 90.34). There are newer imaging black blood imaging techniques that may improve imaging sensitivity of the vascular complications and vasculitis that can be associated with leptomeningitis and involvement of the perforating arterial vessels and vasculitis can also result in ischemia and infarction [48]. Meningitis can be secondary to bacterial, viral or fungal organisms and may be complicated by CVST, ventriculitis and basal meningitis that increases the risk of impaired CSF flow and hydrocephalus (Fig. 90.35)
◾
FIGURE 90.32 Axial T2 weighted sequence (A) in a patient with frontal sinusitis complicated by an extracalvarial subgaleal abscess (thin white arrow) and within the intracranial compartment a small extradural empyema (thin black arrow). The DWI (B) demonstrates pus with restricted diffusion within the extradural empyema with peripherally enhancing intra- and extra-cranial collections (thick white arrows in C).
FIGURE 90.33 Axial noncontrast CT head (A) in a patient presenting with fever and headache. There is a low density subdural collection (thin white arrow) with peripheral enhancement (thin black arrow in B). This was a suspected subdural empyema secondary to sinusitis (not shown) and the collection demonstrated restricted diffusion on the DWI sequence (thick white arrow on b1000 image (C)).
FIGURE 90.34 MR imaging performed in a patient with infectious meningitis. The axial FLAIR (A) demonstrates altered signal change within the CSF spaces particularly evident in the left parietal region (thin white arrows) that correlated with sulcal restricted diffusion (thick white arrow in B). There is pathological leptomeningeal enhancement (thin black arrow in C).
FIGURE 90.35 Axial T1 postcontrast images (A and B) in a patient with septic shock and low GCS. There are multiple ring-enhancing lesions with abnormal ependymal enhancement secondary to ventriculitis (thin white arrows) with complicating hydrocephalus. The pus within the ventricles and the parenchymal abscesses demonstrate restricted diffusion on the selected b1000 images from the DWI sequence (C and D).
The presence of intra-axial ring-enhancing lesions(s) has a differential that includes the presence of parenchymal abscesses in addition to metastatic deposits, tumefactive demyelination, hematoma, and parenchymal infarction [49]. The development of parenchymal abscess evolves from early to late cerebritis followed by early abscess capsule formation and finally parenchymal abscess with capsule formation. The enhancement pattern is typically smooth in nature as opposed to irregular enhancement that can be seen with neoplastic disease (Fig. 90.36). In addition, the enhancement is typically complete although it is typically thinner in relation to the ventricular side. The abscess contains pus and given its internal viscosity will demonstrate internal restricted diffusion [50]. On T2 and GRE/SWI imaging, there is a peripheral low signal and the pattern of peripheral rim hypointensity can aid lesion characterization and diagnostic confidence [49]. MR spectroscopy within an abscess typically demonstrates elevated lactate (1.3 ppm), acetate (1.92 ppm) and
succinate (2.4 ppm) peaks and presence of amino acids (valine and leucine) [51].
FIGURE 90.36 Axial T2 (A), postcontrast (B), DWI (C), and ADC (D) images demonstrates a rounded lesion within the right cerebellar hemisphere with surrounding signal change and peripheral enhancement (thin white arrows). This was associated with restricted diffusion (thin black arrows) and was confirmed to be a cerebellar abscess.
Patients presenting with suspected encephalitis can present with altered level of consciousness, fever, headache, focal deficits, and seizures. Infectious encephalitis is most often due to Herpes Simplex virus (HSV-1 and HSV-2) [52]. The pattern of intracranial involvement includes the mesial temporal lobe structures and it may be symmetrical or asymmetrical with potential for hemorrhage. Other potential sites of involvement within the limbic system include the insula and inferior frontal lobes, cingulate gyri and thalamus while the ganglionic structures are typically spared [53] (Fig. 90.37). Other viral aetiologies include Japanese encephalitis virus infection that typically affects the hippocampi with sparing of the rest of the temporal lobe [54]. Other sites that can be affected include the thalami, basal ganglia, substantia nigra, pons and cortex. The parenchymal changes are best depicted on MR imaging as T2 and FLAIR signal hyperintensity with associated diffusion restriction. West Nile virus demonstrates a different pattern of CNS involvement that includes the brainstem, thalami, cerebral white matter and anterior horns of the spinal cord [55].
FIGURE 90.37 Axial FLAIR (A and B) imaging in a patient with Herpes simplex encephalitis with abnormal signal change involving the orbitofrontal brain parenchyma, left temporal lobe, left insula, and right cingulate gyrus. The cortical changes affecting the insula demonstrates restricted diffusion on the DWI sequence (thin black arrow in C) with the impression of faint leptomeningeal enhancement on the T1 postcontrast sequence (thin white arrow in D).
Autoimmune encephalitis is included in the differential based on imaging findings and includes both paraneoplastic and nonparaneoplastic aetiologies [56]. Paraneoplastic aetiologies are associated with antibodies that include anti-Hu and anti-CV2. The mesial temporal lobe structures, brainstem, and cerebellum can be affected including the striatum in the setting of anti-CV2 antibodies (Fig. 90.38). Nonparaneoplastic aetiologies include an association with NMDA receptor antibodies and the pattern of brain parenchymal involvement includes cortical T2 signal hyperintensity with variable enhancement and diffusion restriction.
FIGURE 90.38 Combined coronal (A and B) and axial FLAIR (C) imaging in a patient with an autoimmune encephalitis with symmetrical abnormal signal change within both hippocampal formations and mesial temporal lobes.
The presence of basal ganglia abnormalities identified on CT and MR can be secondary to spectrum of aetiologies as described above, but in the setting of the acutely septic patient, there are specific infectious aetiologies that merit consideration. In this setting, knowledge of the patients’ immune status is vital as both cryptococcosis and toxoplasmosis can affect the basal ganglia. Cryptococcus neoformans is a ubiquitous fungus that can infect the CNS and result in either a meningitis, formation of focal lesions or cryptococcomas and result in gelatinous pseudocyst formation through involvement of the perivascular spaces that is typically noted in the basal ganglia, midbrain, dentate nuclei, and subcortical white matter [57]. While cryptococcus infections can occur in both immunocompetent and immunocompromised patients, it is typically encountered in patients with HIV infection with low CD4 counts (approximately 50–100 cells/μL).
◾basal On unenhanced CT imaging the gelatinous pseudocyst formation affecting the ganglia demonstrates low density ◾intensity, On MR imaging, this correlates with areas that are similar to CSF signal low on T1 with high signal on T2 that suppresses on FLAIR imaging (Fig. 90.39)
FIGURE 90.39 Axial FLAIR (A) imaging in a patient with cryptococcal meningitis demonstrating foci of signal hyperintensity within the basal ganglia (thick white arrow) with confirmed abnormal punctate enhancement bilaterally (thin white arrows in B). There was no associated abnormal restricted diffusion on the DWI sequence (C).
Toxoplasma gondii is a ubiquitous intracellular parasite that results in common opportunistic infection. In immunocompromised patients, it can result in an infective process that is typically multifocal with involvement of the basal ganglia, thalami, corticomedullary junction, and cerebellum (Fig. 90.40). On CT, these are identified as hypodense lesions that me demonstrate nodular or ring enhancement while on MR imaging the lesions demonstrate alternating areas of high and low T2 signal change and may demonstrate an eccentric target sign [58]. There is perilesional edema however, they demonstrate reduced relative cerebral blood volume that may help differentiate from other neoplastic entities, lymphoma being the most notable differential diagnosis to consider [59].
FIGURE 90.40 Axial FLAIR (A) sequence in a patient with new-onset right-sided weakness. There is an irregular lesion centered on the left basal ganglia with irregular peripheral enhancement and no significant internal restricted diffusion (white arrows in B (DWI) and C (postcontrast scan)). There is a small lesion in the right frontal lobe (thin black arrow) confirming multifocality. Initially suspected to represent a highgrade intra-axial neoplasm, the patient was confirmed to be immunocompromised and a stereotactic biopsy confirmed cerebral toxoplasmosis.
Aspergillus spp. can result in an angio-invasive fungal CNS infection that may occur secondary to inhaled fungal spores that invade the systemic circulation and as a consequence of hematogenous spread, infect the CNS. Alternatively, it can occur secondary to direct spread from the sinonasal compartment. Patients are typically immunocompromised and on CT imaging of the sinonasal compartment particularly attention to subtle bony changes and inflammatory fat stranding within the fat planes surrounding the sinuses is required given the aggressive angioinvasive nature of the fungal infection and high risk or morbidity and mortality if not identified and treated promptly [60] (Fig. 90.41). Within the intracranial compartment, the fungal infection can result in the formation of multiple abscesses while the angioinvasive nature of the infection can result in mycotic aneurysm formation and high risk of subsequent hemorrhage and ischemia/infarction.
FIGURE 90.41 Axial CT head (A) in a patient with frontal headaches with a known hematological malignancy. There is mucosal thickening and inflammatory change within the paranasal sinuses but there is more concerning abnormal soft tissue and stranding within the right pterygopalatine fossa and retroantral soft tissues (white arrow) confirmed on the axial STIR sequence (B). The findings were compatible with an invasive fungal sinusitis that was confirmed following functional endoscopic sinus surgery.
Pseudomonas is a bacterium that is the main causative organism implicated in a necrotizing otitis externa that affects poorly controlled diabetic patients and the immunocompromised. Assessment of the tissues around the external auditory canal and upper deep fascial neck spaces in addition to the bony integrity of the external auditory canal is required to determine if there is an invasive fungal infection [61]. There is a risk of propagation to involve the posterior and central skull base with risk of potential vascular complications and intracranial extension (Fig. 90.42).
FIGURE 90.42 Axial T2 sequence (A) in a patient with a necrotizing otitis externa complicated by a skull base osteomyelitis with extension of inflammatory phlegmon to involve the upper deep neck spaces (thick white arrows) including the carotid space with an infectious arteritis (thin white arrows) that resulted in small embolic infarcts in the left MCA territory demonstrated on the DWI sequence (B). There was also a left-sided internal jugular vein thrombosis with loss of flow present on the MIP from the MR venogram (C).
Neurocysticercosis caused by the parasitic pork tapeworm Taenia solium is endemic in certain parts of the world and is a common cause of seizures [62]. It can also present with headaches and depending on the pattern of CNS involvement can result in hydrocephalus. The imaging appearances of CNS involvement are dependent on the stage of the life cycle of the parasite.
◾andIn theoccasionally vesicular stage there is no host response and this appears as a small cyst a scolex can be identified as an eccentric T1 hyperintense ◾focus As the parasite dies this initiates a host response and this colloid vesicular stage is often the most symptomatic phase (Fig. 90.43). The cystic lesions
demonstrate nodular or peripheral enhancement and the scolex can be increasingly difficult to identify. Given the immune response there is significant perilesional edema There is progression to the granular nodular phase where the cyst retracts and the edema improves the final nodular calcified phase is represented by calcified lesions with no significant surrounding edema
◾ ◾
FIGURE 90.43 Axial FLAIR sequence (A) demonstrating multiple small lesions with surrounding edema (white arrows) and some of the lesions demonstrated a combination of punctate and ring enhancement (black arrows in B). There are soft tissue calcifications confirmed on the plain radiograph (C) in this patient with neurocysticercosis.
Mycobacterium tuberculosis remains a significant worldwide health problem associated with significant morbidity and mortality [63]. CNS infection with tuberculosis (Tb) typically has a nonspecific clinical presentation with fevers, weight loss, seizures, meningism, and focal deficits dependent upon the pattern of CNS involvement.
◾meningitis Extra-axial involvement and Tb leptomeningitis can result in a florid basal that, given its location, can be complicated by hydrocephalus and
arteritis affecting the basal perforator vessels that can result in areas of infarction (Fig. 90.44) A tuberculous pachymeningitis is a less common pattern of extra-axial involvement Intra-axial involvement is most commonly in the form of tuberculomas that differ from abscesses in the fact that the lesions are associated with a granulomatous inflammatory response and central caseous necrosis. On MR imaging, this is identified as lesions with central low T2 signal with no internal diffusion restriction and elevated lipid and lactate peaks on MR spectroscopy (Fig. 90.45) Tuberculous abscesses are rarer and typically occur in the immunocompromised. The MR signal characteristics are those of a typical abscess with an internal high T2 signal and diffusion restriction with a low T2 peripheral ring and surrounding edema Other patterns of CNS intra-axial involvement and cerebritis and tuberculous rhombencephalitis are less common
◾ ◾ ◾ ◾
FIGURE 90.44 Axial T1 postcontrast imaging (A and B) in a patient with abnormal leptomeningeal enhancement and a confirmed basal meningitis due to Mycobacterium tuberculosis (thin white arrows). The patient had developed right sided symptoms due to a subacute left pontine infarct (thick white arrow in C).
FIGURE 90.45 Axial T2 (A) and T1 postcontrast (B) imaging in a patient with multiple tuberculomata. The lesions demonstrate internal low T2 signal with surrounding high and low signal with peripheral enhancement (thin white arrows). The lesions do not demonstrate restricted diffusion (b1000 image from DWI sequence) (C).
Neurological Emergencies in the Pregnant/Postpartum Patient Acute neurological emergencies in pregnancy can result from exacerbations of pre-existing conditions as well as the development of a new neurological abnormality that is not unique to pregnancy [64]. This chapter will focus on those emergencies that are unique to or encountered with increasing frequency during pregnancy and in the postpartum period. During pregnancy and the postpartum period there are a number of pathophysiological processes that can contribute to the spectrum of clinical presentations [65]. Elevated oestrogen levels result in the increased production of clotting factors and elevated risk of thromboembolic disease. Elevated progesterone levels are associated with increased venous distensibility and vascular leakage while elevated plasma and total blood volume can both contribute to elevated blood pressure. Common symptoms and signs encountered in the pregnant patient include headache, visual symptoms, neurological deficits, and seizures with significant overlap in presentation between different neurological conditions discussed below. In the emergency setting the imaging protocol typically includes a noncontrast CT head as first-line to assess for acute intracranial hemorrhage and parenchymal infarction and in the setting of seizure, to exclude a space occupying lesion. A noncontrast CT head is a low dose procedure with minimal risk to foetus with benefits outweighing the risks in terms of excluding lifethreatening diagnoses for the mother. In a proportion of patients with CVST, identification of hyperdense thrombus and complicating venous infarction or intracranial hemorrhage can establish the diagnosis on the initial noncontrast CT head. However, a normal CT head however does not exclude a number of clinical entities encountered during pregnancy and is supplemented by a CTA for suspected reversible cerebral vasoconstriction syndrome (RCVS) and aneurysmal SAH while CT venogram is performed if there is concern regarding a venous
sinus thrombosis. If available, routine MRI brain with DWI supplemented by MR angiography, MR venography is preferable for exclusion of other entities such as PRES and hypertensive encephalopathy given its superior sensitivity. Pre-eclampsia is graded on the basis of blood pressure and proteinuria progressing to eclampsia in the setting of a grand mal seizure [66]. In this setting, the presence of endothelial dysfunction, capillary leakage and vasogenic edema can result in PRES while vasoconstriction and the resultant elevated blood pressure can result in ischemia and cytotoxic edema that may progress to infarction. RCVS encompasses a spectrum of disorders including callFleming syndrome [67]. The combination of oxidative stresses, endothelial dysfunction and increased sympathetic tone likely contribute to alterations in vascular tone and vasoconstriction thus RCVS may be the end point of a number of different pathological processes [68,69]. During pregnancy, the hormonal effect on the vasculature and alterations in BP, particularly during labor, can further increase in the risk of RCVS. There is a myriad of potential triggers including vasoactive drugs, blood products, certain tumor types, and in the postpartum period [67]. Most commonly, the patient experiences a sudden onset thunderclap headache and other presentations include focal deficits/transient ischemic attacks, encephalopathy and seizures. It is typically a monophasic illness with no new symptoms after 4 weeks. The presence of nonaneurysmal, focal convexity SAH occurs earlier in the process with ischemia/infarction typically occurring as a later complication. On imaging, the noncontrast CT head can be normal but as stated, careful assessment for the presence of sulcal convexity SAH should be sought. CT or catheter angiographic imaging demonstrates the presence of segmental arterial vasoconstriction with identical appearances to vasospasm and primary angiitis that represent the main imaging differential diagnoses [69] (Fig. 90.46).
FIGURE 90.46 DSA lateral image from a right internal carotid artery injection in a patient with RCVS with focal areas of vascular irregularity and luminal narrowing (black arrows). Subsequent DSA imaging performed 3 months later was normal (not shown). DSA, digital subtraction angiogram.
PRES is also considered in the spectrum of disorders associated with abnormalities of vascular tone and endothelial dysfunction. The clinical presentation is with similar symptomatology including headache, visual symptoms, encephalopathy, and seizures. Cerebral edema develops with involvement of the cortical and subcortical white matter with a predilection for the parietal and occipital lobes [70]. It can progress to ischemia and infarction and can be complicated by intracranial hemorrhage although in the majority of cases the vasogenic edema is reversible (Fig. 90.47).
FIGURE 90.47 Axial FLAIR images (A and B) in a patient with hypertensive crisis and visual symptoms. There is abnormal cortical/subcortical signal change with a predilection for the parieto-occipital regions but with additional frontal and temporal lobe involvement (white arrows). This was due to PRES and there was no complicating infarction on the DWI sequence (C) (b1000 imaging shown).
CVST occurs with increased frequency in pregnancy and during the postpartum period as a consequence of the pathophysiological mechanisms outlined above. It is a potential cause of stroke in pregnancy that may also occur in the setting of other conditions including HELPP syndrome, thrombotic thrombocytopenic purpura. The association with vascular dissection in pregnancy is yet to be fully elucidated. Other rarer entities to consider in patients with new focal neurological deficits include amniotic fluid embolism, air embolism and metastases secondary to a choriocarcinoma [64]. In the postpartum period, the presence of nuchal/occipital/postural headaches that resolve on lying flat (worse on standing) raises the possibility of a CSF leak and potential CSF hypotension. The presence of a CSF leak can occur in the setting of spinal anaesthesia (typically 1–7 days postinstrumentation) but it can also occur spontaneously. Intracranial hypotension can be further complicated by the presence of SDH and CVST. The aim of imaging is to confirm the diagnosis, exclude complications and localize potential source of leak with the aim of guiding subsequent blood patch [22].
Visual symptoms in pregnancy may occur in the setting of PRES or ischemic stroke while during early pregnancy, hyperemesis gravidarum can result in thiamine deficiency and Wernicke’s encephalopathy that may present with diplopia and eye movement disorders. The pituitary gland typically enlarges during pregnancy but pituitary apoplexy is rare. Bleeding or impaired blood supply can result in pituitary apoplexy while Sheehan’s syndrome can result in hypopituitarism weeks/months after the postpartum bleed.
Acute Onset Cranial Nerve Deficit(s) In a patient presenting with an acute onset of cranial nerve palsy/palsies, the imaging protocol is guided by the pattern of cranial nerve involvement and suspicion of lesion localization. This requires the radiologist to have an understanding of the anatomy of the cranial nerves from nucleus to target organ (with the exception of the olfactory and optic nerves that have unique anatomy and do not have a CNS nucleus).
◾respect Cranial nerves have an intra-axial component localized to the brainstem with to cranial nerves III-XII and supratentorial brain parenchymal component with cranial nerves I and II ◾course The intracranial but extra-axial component of the cranial nerves refers to their from the CNS to the skull base neural foramina ◾through The extra-axial and extracranial course of the nerves relate to their pathway the extracranial soft tissues and target end organs
While some of the cranial nerves have a purely motor (cranial nerves IV, VI, XI, XII) or sensory function (cranial nerves I, II, VIII), the rest of the cranial nerves have a combination of motor, sensory, and autonomic function. Imaging in the acute setting typically involves a contrastenhanced CT that does provide excellent bony detail of the skull base and neural foramina in addition to intracranial and extracranial soft tissue information that enables significant pathologies in the context of trauma and sepsis to be identified.
However, in most clinical settings this will be followed by MR imaging and tailoring of the MR protocol is essential to depict the anatomical course of the cranial nerves and to highlight potential pathology. The use of T2 weighted imaging of the brain parenchyma enables identification of significant intra-axial pathology that is combined with DWI to assess for areas of potential infarction or inflammatory change. Imaging of the extraaxial and intracranial cisternal course of the cranial nerves can also be assessed on T2 weighted imaging that is best performed with a combination of axial and coronal sequences if a volumetric 3D imaging cannot be acquired. This is augmented by contrastenhanced T1 weighted sequences and pathological cranial nerve enhancement can sometimes be the only radiological abnormality identified (Fig. 90.48). High resolution heavily T2 weighted sequences that accentuate the contrast between CSF and the cranial nerves (e.g., CISS, balanced FFE sequences, DRIVE, 3DTSE) sequences aid assessment of small cranial nerve lesions and potential neurovascular conflicts. The extracranial course of the cranial nerves to be assessed should cover the soft tissues along the path of the nerve and target end organs. This is performed with axial T1, T2, and contrast-enhanced imaging and in our institution the T1 precontrast imaging is performed without contrast to assess the fat planes around the skull base and neural foramina and the marrow signal within the skull base itself. However other protocols that include DIXON sequences can provide both fatsuppressed and nonfat suppressed T1 weighted imaging [71].
FIGURE 90.48 Coronal (A and B) and axial T1 (C) postcontrast imaging in a patient with right-sided retro-orbital pain with asymmetrical right cavernous sinus with asymmetrical thickening of the right oculomotor nerve (thin black arrow) and mandibular division of the right trigeminal nerve (thick white arrow). This was considered to represent a right-sided Tolosa Hunt syndrome and the patient responded to corticosteroid therapy with resolution of the abnormal imaging findings.
In the presence of a single unilateral cranial nerve palsy imaging is targeted at the cranial nerve in question however in the presence of multiple cranial nerve palsies the pattern can guide and limit the differential diagnosis. With unilateral multiple cranial nerve palsies, there are specific sites where multiple cranial nerve palsies can be affected (Table 90.4) (Fig. 90.49). In the presence of multiple and bilateral cranial nerve palsies, this typically implies a more widespread systemic disorder and thus consideration of infectious, granulomatous, and neoplastic pathologies that will typically affect either the brainstem or cisternal courses of the nerves (Fig. 90.50). Table 90.4 Multiple Cranial Nerve Neuropathies 1. Orbital apex/cavernous sinus syndromes Cranial nerves II, III, IV, Vi, VI may be affected
Typically, inflammatory Tolosa-Hunt, IgG4 mediated diseases 2. Petrous apex/cavernous sinus syndrome Cranial nerves III, IV, Vi, VI may be affected Infective process propagating to petrous apex— Gradenigos syndrome 3. Jugular foramen syndromesVernet syndrome affecting cranial nerves IX, X, XICollet Sicard syndrome IX, X, XI, XII Skull base infections (central skull base osteomyelitis) or tumors including glomus lesions and nerve sheath tumors as well as posterior fossa meningiomas
FIGURE 90.49 Axial T2 (A) and T1 postcontrast (B) imaging in this patient with a left jugular foramen syndrome secondary to a left-sided glomus jugulare tumor (white arrows). The soft tissue axial T2 sequences (C and D) confirmed the presence of a left-sided hypoglossal nerve palsy and tongue denervation and left accessory nerve palsy with sternocleidomastoid and trapezius muscle atrophy (thick white arrows). Additional left-sided vocal cord palsy and atrophy of the stylopharyngeus muscle secondary to vagus and glossopharyngeal nerve palsies respectively.
FIGURE 90.50 Axial T1 postcontrast imaging in a patient with carcinomatous meningitis with abnormal leptomeningeal enhancement that is well depicted in relation to the cerebellar folia. Symmetrical and bilateral abnormal cranial nerve enhancement is evident in relation to the oculomotor nerves (thin white arrows in A), facial/vestibulocochlear nerves (thin black arrows in B) and glossopharyngeal/vagal nerve complexes (thick white arrows in C).
Intra-axial pathologies that can present with acute cranial nerve palsies include acute stroke, infective, inflammatory, toxic, and neoplastic aetiologies [72]. Brainstem infarction results from thromboembolic disease affecting the basilar artery or its perforator branch vessels. With regards the extracranial course of the lower cranial nerves:
◾anTheacutepresence of an arterial dissection should be considered in any patient with onset Horner’s syndrome given the relationship of the sympathetic plexus to the internal carotid artery [3] (Fig. 90.51) ◾unilateral In addition, an acute internal carotid artery dissection can result in an acute hypoglossal nerve palsy as the extracranial course of the XII nerve is
intimately related to the carotid sheath and potential disruption of its vascular supply via the vasa vasorum can result in cranial nerve palsy [73] Another specific scenario to consider is the acute onset of an oculomotor nerve palsy particularly if there is involvement of the preganglionic parasympathetic fibers that are present along the superomedial surface of the nerve. This implies potential extrinsic compression on the pathway of the CN III and it is imperative that angiographic imaging is preformed to exclude an internal carotid artery or posterior communicating artery aneurysm [72]
◾
FIGURE 90.51 Axial CT head (A) in a patient with a left sided Horner’s syndrome with an asymmetrical left internal carotid artery (thin white arrow). There is a confirmed left internal carotid artery dissection with luminal irregularity and tapering on the CTA (thin black arrow in B) with intramural hematoma evident on the axial FLAIR sequence (thick white arrow in C).
An acute rhombencephalitis may be infectious in nature and typical organisms to consider include Listeria monocytogenes and viral entities (West Nile virus, Japanese encephalitis) [74]. These typically present with abnormal T2 signal change, potential mass effect/swelling and enhancement that may be parenchymal and/or leptomeningeal with potential DWI changes (Fig. 90.52). The differential for an infectious brainstem encephalitis would include inflammatory aetiologies including neuro-behcets syndrome which is a multisystem, vascular inflammatory disorder [75] (Table 90.5). This is characterized by orogenital ulceration, uveitis, and skin lesions and typically sites of parenchymal involvement in the CNS include pons, midbrain and diencephalon with a higher risk of venous thrombosis (Fig. 90.53). Other acute brainstem inflammatory processes to consider include multiple sclerosis, neuromyelitis optica (NMO) spectrum disorders (assessment of anti-aquaporin 4 and anti-MOG antibodies). NMO in particular has a predilection for the area postrema and periaqueductal gray. Imaging of the entire neuraxis including
brain, orbits and spinal cord can be undertaken to aid diagnosis. Osmotic myelinolysis or central pontine myelinolysis can occur as a result of rapid overcorrection of hyponatremia but it can also result from other insults [76]. While it typically affects the pons other extrapontine sites of involvement are also recognised [40]. Table 90.5 Differential Diagnosis of Rhomboencephalitis 1. Infectious Viral [Enteroviruses, Herpes simplex virus (HSV-1, HSV-2), flaviviruses (West Nile virus, Japanese encephalitic virus) Bacterial (Listeria monocytogenes, Mycobacterium tuberculosis) 2. Inflammatory/autoimmune Neurobehcet’s disease Systemic lupus erythematosus Multiple sclerosis, NMO spectrum disorders 3. Neoplastic/paraneoplastic Lymphoma High grade glioma Paraneoplastic syndromes (small cell lung cancer)
FIGURE 90.52 Axial T2 (A), FLAIR (B), and Sagittal T1 (C) sequences demonstrating abnormal hyperintense signal and swelling centered on the cerebellum (white arrows) secondary to a viral rhombencephalitis (adenovirus). There is distortion of the fourth ventricle with complicating hydrocephalus.
FIGURE 90.53 Axial FLAIR sequence (A and B) in a patient with neurobehcets syndrome with abnormal signal change within the brainstem extending into the superior cerebellar peduncle and into the left optic tract (white arrows). There is superior extension into the diencephalon with pathological enhancement (black arrow in C).
Neoplastic infiltration of the brainstem typically presents with a more insidious onset of cranial nerve palsies however with more aggressive infiltrating tumors this progression can be more rapid. As per other aetiologies, this typically demonstrates abnormal T2
signal change with potential DWI changes and abnormal enhancement. With the associated mass effect this has the potential to obstruct the aqueduct of Sylvius and result in an obstructive hydrocephalus. Cranial nerve involvement of the extra-axial course of the cranial nerves can result from a spectrum of infectious, inflammatory and neoplastic aetiologies.
◾include Specific infectious aetiologies to consider in the setting of a facial nerve palsy Bell’s palsy that is typically related to Herpes simplex virus ◾results Ramsay Hunt syndrome results from varicella zoster virus infection and in sensorineural hearing and external ear vesicles in addition to the facial nerve palsy
Imaging is typically reserved for atypical cases of a facial nerve palsy where the suspected, viral neuritis fails to resolve or in the acute setting where the facial nerve palsy may result from an alternate infectious process. This latter is the case in diabetic and immunocompromised patients where the facial nerve palsy is involved from the direct spread of infection from a necrotizing otitis externa typically due to Pseudomonal infection [61]. As the infection can propagate into the posterior skull base other cranial nerve palsies may ensue including additional arterial and venous complications. In a persistent lower motor neuron palsy, the course of the facial nerve pathway from the pons to the muscles of facial expression including the parotid space is needed to exclude neoplastic processes such as a nerve sheath tumor or perineural spread of disease [77]. As stated in the setting of multiple bilateral cranial nerve palsies, the presence of abnormal leptomeningeal enhancement and cranial nerve enhancement should be sought. This would include infectious processes such as bacterial and tuberculous meningitis, vasculidites including ANCA mediated granulomatous polyangiitis, granulomatous processes such as sarcoidosis and carcinomatous meningitis and lymphoma. These can be difficult to distinguish on the basis of neuroimaging alone and requires correlation with other imaging modalities/body systems and CSF analysis.
Acute Spinal Cord Syndrome In patients with an acute spinal cord syndrome, the suspected localization of the abnormality and targeted imaging is guided by the relevant motor, sensory and autonomic symptoms and signs. The technique of choice is MR imaging with a combination of sagittal T1, T2, STIR sequences with additional axial T1 and T2 weighted sequences acquired in the areas of anatomical interest. Contrast-enhanced imaging is performed in the setting of suspected sepsis, inflammation, or neoplastic disease while highresolution CISS sequences are utilized in specific scenarios including assessment of spinal cord herniation, CSF leaks and potential spinal vascular malformations and arteriovenous fistulae [78,79]. Acute spinal cord syndromes can be broadly subdivided into a complete cord and incomplete cord syndromes.
◾motor, In a complete cord syndrome, a whole cord segment is affected with resultant sensory and autonomic signs below the level of the lesion. This can be secondary to trauma with transection of the cord, an extensive transverse myelitis or due to compression of the cord secondary to neoplastic infective processes and other rarer entities such as spontaneous intraspinal hemorrhage [80] (Fig. 90.54) Incomplete cord syndromes present with specific patterns of motor, sensory, and autonomic features depending on which part of the spinal cord is affected [81]. These patterns include dorsal cord syndromes, ventral cord syndromes, central cord syndromes, brown sequard syndrome, conus medullaris compression, and cauda equina compression
◾
FIGURE 90.54 Sagittal T2 (A) and T1 (B) weighted sequences demonstrating extensive subarachnoid hemorrhage within the spinal canal (white arrows) confirmed on the axial imaging (C). The patient was on anticoagulant therapy.
Dorsal cord syndromes present with disturbances of fine touch, proprioception and vibration sense with sensory ataxia, gait disturbances, and falls. With the increasing size of the lesion, this can extend to involve the autonomic pathways and corticospinal tracts. The differential diagnosis for abnormal signal change within the dorsal columns includes causes of subacute combined degeneration of the cord (SACD) including vitamin B12 deficiency, inflammatory (multiple sclerosis), infectious (tabes dorsalis, AIDS myelopathy), neurodegenerative processes (Freidreich’s ataxia) while extrinsic compression and posterior cord infarcts are less common [82]. In the authors’ institution, the incidence of SACD has increased secondary to abuse of nitrous oxide present in “poppers” that results in impairment of vitamin B12 metabolism [83] (Fig. 90.55).
FIGURE 90.55 Sagittal T2 weighted sequence (A) in a 19year-old patient who used recreational “popper”/nitrous oxide with the suspicion of cord signal change within the dorsal aspect of the cord (thin white arrow) that was confirmed on the axial T2 weighted imaging (B) (thin black arrows).
A ventral cord syndrome presents with motor deficits secondary to disruption of the corticospinal tracts, autonomic disturbances, sensory disturbances secondary to disruption of the spinothalamic tracts. An insult to a hemicord will result in ipsilateral motor signs below the level of the cord while it will result in contralateral impairment of sensory symptoms (relating to pain and temperature sensation). The disruption of the spinothalamic tracts occurs a few segments below the level of the insult as the fibers ascend the cord before they decussate to the contralateral aspect of the cord before ascending to the thalamus. Acute ischemia and infarction (typically arterial in origin) is the most common cause for a ventral cord syndrome but it can also occur secondary to trauma or disc degeneration [84] (Fig. 90.56).
FIGURE 90.56 Sagittal T2 imaging (A) in a patient with a suspected spinal cord infarct that confirms abnormal signal change within the ventral aspect of the thoracic cord confirmed on the axial T2 sequence (white arrows in B).
A central cord syndrome initially results in a sensory disturbances in a cape distribution given decussating spinothalamic tracts in the ventral commissure. Given the somatotopic organization of the cord, this typically involves the upper extremities before the lower extremities. Lower motor neurons signs occur at the level of the insult with upper motor neuron signs present below the affected cord segment. This can occur secondary to injuries and lesions around the central canal. In elderly patients with existing degenerative changes, this can be secondary to hyperextension injuries while in younger patients, it typically occurs secondary to hyperflexion injuries. Syringohydromyelia can be primary/congenital in nature (e.g., basilar invagination, Arnold-Chiari malformations) or secondary to trauma and neoplastic processes. The most common neoplastic disorder to consider include ependymoma, astrocytoma, hemangioblastomas and metastases [85] (Fig. 90.57).
FIGURE 90.57 Sagittal T1 postcontrast (A) and T2 (B) imaging showed an enhancing intra-axial spinal cord tumor and confirmed astrocytoma at the cervicomedullary junction (white arrow in A) with a complicating cord syrinx (black arrow in B).
Brown sequard syndrome results from an insult to the hemicord that produces ipsilateral corticospinal and dorsal column deficits with contralateral spinothalamic tract disturbances [86]. It typically occurs secondary to blunt or penetrating trauma but can also be secondary to inflammatory processes, spinal cord herniation or disc herniation [78]. Conus medullaris compression and cauda equina compression have similar presentations, however, the compression of the conus medullaris also results in upper and lower motor neuron signs. The conus medullaris can be affected by disc herniations, trauma, tumors (e.g., myxopapillary ependymoma), infection, and vascular malformations (spinal dural AVM type I) (Fig. 90.58). The identification of a potential dural arteriovenous fistula is or paramount importance given the potential for curative endovascular or surgical intervention with a progressive course if left untreated that may result in irreversible damage to the spinal cord [87] (Fig. 90.59). Cauda equina syndrome results in a
combination of lower motor neuron deficits, bladder and bowel disturbances and saddle anaesthesia. This is a neurosurgical emergency and commonly occurs secondary to disc herniation (Fig. 90.60) although it may also be secondary to trauma, neoplastic processes (leptomeningeal disease), arachnoiditis (type I–III) and Guillain–Barre syndrome.
FIGURE 90.58 Sagittal (A) and axial (B) T1 postcontrast images demonstrating an enhancing intradural lesion affecting the cauda equina with a more inferior component within the inferior aspect of the thecal sac. The tumor was surgically resected and confirmed to represent a myxopapillary ependymoma.
FIGURE 90.59 Sagittal T2 weighted imaging (A) demonstrating multiple serpiginous flow voids (thin black arrows) compatible with a spinal arteriovenous fistula complicated by edema within the distal cord and conus confirmed on the axial imaging (white arrows in B).
FIGURE 90.60 Sagittal (A) and axial (B) T2 weighted sequences in a patient with cauda equina syndrome secondary to a large L5/S1 disc extrusion (white arrows) that was compressing the thecal sac.
Summary In this chapter, we have provided a general overview of the most common acute neurological emergencies encountered in clinical practice by general radiologists and neuroradiologists. Relevant imaging algorithms have been provided for when these situations arise in clinical practice in addition to the important imaging manifestations to assess for in the emergency setting.
Suggested Readings • A Micieli, W Kingston, An approach to identifying headache patients that require neuroimaging, Front Public Health 7 (2019) 52, doi:10.3389/fpubh.2019.00052. • CA Potter, L Hsu, Emergent neuroimaging in the oncologic and immunosuppressed patient, Neuroimaging Clin N Am 28 (3) (2018) 397–417, doi:10.1016/j.nic.2018.03.004.
• SJ An, TJ Kim, B-W Yoon, Epidemiology, risk factors, and clinical features of intracerebral hemorrhage: an update, J Stroke 19 (1) (2017) 3–10, doi:10.5853/jos.2016.00864. • C Torres, N Zakhari, S Symons, TB Nguyen, Imaging the unconscious “Found Down” patient in the emergency department, Neuroimaging Clin N Am 28 (3) (2018) 435–451, doi:10.1016/j.nic.2018.03.006. • A Krainik, JW Casselman, Imaging evaluation of patients with cranial nerve disorders von Schulthess GK, in: J Hodler, RA Kubik- Huch (eds.), Diseases of the Brain, Head and Neck, Spine 2020–2023, Springer International Publishing, 2020, pp. 143–161, doi:10.1007/978-3-030-38490-6_12. IDKD Springer Series.
References [1] R Davenport, Headache, Practical Neurol 8 (2008) 335– 343. [2] A Micieli, W Kingston, An approach to identifying headache patients that require neuroimaging, Front Public Health 7 (2019) 52. 10.3389/fpubh.2019.00052. [3] A George, AA Haydar, WM Adams, Imaging of Horner’s syndrome, Clin Radiol 63 (5) (2008) 499–505. 10.1016/j.crad.2007.12.006. [4] CA Potter, L Hsu, Emergent neuroimaging in the oncologic and immunosuppressed patient, Neuroimaging Clin N Am 28 (3) (2018) 397–417. 10.1016/j.nic.2018.03.004. [5] E Marcolini, J Hine, Approach to the diagnosis and management of subarachnoid hemorrhage, West J Emerg Med 20 (2) (2019) 203–211. 10.5811/westjem.2019.1.37352. [6] J van Gijn, GJ.E Rinkel, Subarachnoid haemorrhage: diagnosis, causes and management, Brain 124 (2) (2001) 249–278. 10.1093/brain/124.2.249. [7] MD Alexander, C Yuan, A Rutman, et al., Highresolution intracranial vessel wall imaging: imaging beyond the lumen, J Neurol Neurosurg Psychiatry 87 (6) (2016) 589–597. 10.1136/jnnp-2015-312020. [8] P Bhogal, E Navaei, HL.D Makalanda, et al., Intracranial vessel wall MRI, Clin Radiol 71 (3) (2016) 293–303.
10.1016/j.crad.2015.11.012. [9] J Konczalla, J Platz, P Schuss, H Vatter, V Seifert, E Güresir, Non-aneurysmal non-traumatic subarachnoid hemorrhage: patient characteristics, clinical outcome and prognostic factors based on a single-center experience in 125 patients, BMC Neurol 14 (1) (2014) 140. 10.1186/1471-2377-14-140. [10] J Narvid, MR Amans, DL Cooke, et al., Spontaneous retroclival hematoma: a case series, J Neurosurg 124 (3) (2016) 716–719. 10.3171/2015.2.JNS142221. [11] A Khurram, T Kleinig, J Leyden, Clinical associations and causes of convexity subarachnoid hemorrhage, Stroke 45 (4) (2014) 1151–1153. 10.1161/STROKEAHA.113.004298. [12] H Almqvist, M Mazya, A Falk Delgado, A Falk Delgado, Radiological evaluation in patients with clinical suspicion of cerebral venous sinus thrombosis presenting with nontraumatic headache—a retrospective observational study with a validation cohort, BMC Med Imaging 20 (1) (2020) 24. 10.1186/s12880-020-00426-x. [13] DF Black, AE Rad, LA Gray, NG Campeau, DF Kallmes, Cerebral venous sinus density on noncontrast CT correlates with hematocrit, Am J Neuroradiol 32 (7) (2011) 1354–1357. 10.3174/ajnr.A2504. [14] P-J Buyck, SM Zuurbier, C Garcia-Esperon, et al., Diagnostic accuracy of noncontrast CT imaging markers in cerebral venous thrombosis, Neurology 92 (8) (2019) e841–e851. 10.1212/WNL.0000000000006959. [15] V Pai, I Khan, YY Sitoh, B Purohit, Pearls and pitfalls in the magnetic resonance diagnosis of dural sinus thrombosis: a comprehensive guide for the trainee radiologist, J Clin Imaging Sci 10 (2020) 77. 10.25259/JCIS_187_2020. [16] AA.K Abdel Razek, H Alvarez, S Bagg, S Refaat, M Castillo, Imaging spectrum of CNS vasculitis,
Radiographics 34 (4) (2014) 873–894. 10.1148/rg.344135028. [17] SJ An, TJ Kim, B-W Yoon, Epidemiology, risk factors, and clinical features of intracerebral hemorrhage: an update, J Stroke 19 (1) (2017) 3–10. 10.5853/jos.2016.00864. [18] CK Dastur, W Yu, Current management of spontaneous intracerebral haemorrhage, BMJ 2 (1) (2017) 21–29. 10.1136/svn-2016-000047. [19] KM Bond, JC Benson, JK Cutsforth-Gregory, DK Kim, FE Diehn, CM Carr, Spontaneous intracranial hypotension: atypical radiologic appearances, imaging mimickers, and clinical look-alikes, Am J Neuroradiol 41 (8) (2020) 1339–1347. 10.3174/ajnr.A6637. [20] PG Kranz, TP Tanpitukpongse, KR Choudhury, TJ Amrhein, L Gray, Imaging signs in spontaneous intracranial hypotension: prevalence and relationship to CSF pressure, Am J Neuroradiol 37 (7) (2016) 1374–1378. 10.3174/ajnr.A4689. [21] LM Shah, LA McLean, ME Heilbrun, KL Salzman, Intracranial hypotension: improved MRI detection with diagnostic intracranial angles, Am J Roentgenol 200 (2) (2013) 400–407. 10.2214/AJR.12.8611. [22] Farb RI, Nicholson PJ, Peng PW, et al., Spontaneous intracranial hypotension: a systematic imaging approach for CSF leak localization and management based on MRI and digital subtraction myelography, Am J Neuroradiol 40 (4) (2019 Apr) 745–753. doi:10.3174/ajnr.A6016. [23] SP Mollan, KA Markey, JD Benzimra, et al., A practical approach to, diagnosis, assessment and management of idiopathic intracranial hypertension, Pract Neurol 14 (6) (2014) 380–390. 10.1136/practneurol-2014000821. [24] PP Morris, DF Black, J Port, N Campeau, Transverse sinus stenosis is the most sensitive MR imaging correlate of idiopathic intracranial hypertension, Am J Neuroradiol 38 (3) (2017) 471–477. 10.3174/ajnr.A5055.
[25] DI Friedman, DM Jacobson, Diagnostic criteria for idiopathic intracranial hypertension, Neurology 59 (10) (2002) 1492–1495. 10.1212/01.WNL.0000029570.69134.1B. [26] OY Bialer, MP Rueda, BB Bruce, NJ Newman, V Biousse, AM Saindane, Meningoceles in idiopathic intracranial hypertension, Am J Roentgenol 202 (3) (2014) 608–613. 10.2214/AJR.13.10874. [27] S Hadidchi, W Surento, A Lerner, et al., Headache and brain tumor, Neuroimaging Clin N Am 29 (2) (2019) 291– 300. 10.1016/j.nic.2019.01.008. [28] K Fink, J Fink, Imaging of brain metastases, Surg Neurol Int 4 (5) (2013) 209. 10.4103/2152-7806.111298. [29] RC Spears, Colloid cyst headache, Curr Pain Headache Rep 8 (4) (2004) 297–300. 10.1007/s11916-004-0011-2. [30] S Demirci, KH Dogan, Z Erkol, MK Gulmen, Sudden death due to a colloid cyst of the third ventricle: report of three cases with a special sign at autopsy, Forensic Sci Int 189 (1–3) (2009) e33–e36. 10.1016/j.forsciint.2009.04.016. [31] G Barkhoudarian, DF Kelly, Pituitary apoplexy, Neurosurg Clin N Am 30 (4) (2019) 457–463. 10.1016/j.nec.2019.06.001. [32] C Torres, N Zakhari, S Symons, TB Nguyen, Imaging the unconscious “Found Down” patient in the emergency department, Neuroimaging Clin N Am 28 (3) (2018) 435– 451. 10.1016/j.nic.2018.03.006. [33] Ordóñez-Rubiano EG, Johnson J, Enciso-Olivera CO, et al., Reconstruction of the ascending reticular activating system with diffusion tensor tractography in patients with a disorder of consciousness after traumatic brain injury, Cureus 9 (9) (2017 Sep 28) e1723. doi:10.7759/cureus.1723. [34] J Uno, K Kameda, R Otsuji, et al., Mechanical thrombectomy for basilar artery occlusion compared with anterior circulation stroke, World Neurosurg 134 (2020) e469–e475. 10.1016/j.wneu.2019.10.097.
[35] T Pitts-Tucker, J Small, Artery of percheron: an unusual stroke presentation, BMJ Case Rep (2018 Mar 28):bcr-2017-222185, doi:10.1136/bcr-2017-222185. [36] R Wei, C Wang, F He, et al., Prediction of poor outcome after hypoxic-ischemic brain injury by diffusionweighted imaging: a systematic review and meta-analysis. Lazzeri C, ed, PLoS ONE 14 (12) (2019) e0226295. 10.1371/journal.pone.0226295. [37] TJ.E Muttikkal, M Wintermark, MRI patterns of global hypoxic-ischemic injury in adults, J Neuroradiol 40 (3) (2013) 164–171. 10.1016/j.neurad.2012.08.002. [38] AG Osborn, GL Hedlund, KL Salzman, Osborn’s Brain: Imaging, Pathology, and Anatomy, second ed., Elsevier, 2018. [39] S Geibprasert, M Gallucci, T Krings, Alcohol-induced changes in the brain as assessed by MRI and CT, Eur Radiol 20 (6) (2010) 1492–1501. 10.1007/s00330-0091668-z. [40] SA Howard, JA Barletta, RA Klufas, A Saad, U De Girolami, Osmotic demyelination syndrome, Radiographics 29 (3) (2009) 933–938. 10.1148/rg.293085151. [41] A Rovira, J Alonso, J Córdoba, MR imaging findings in hepatic encephalopathy, Am J Neuroradiol 29 (9) (2008) 1612–1621. 10.3174/ajnr.A1139. [42] K-I Chuang, KL.-C Hsieh, C-Y Chen, Hypoglycemic encephalopathy mimicking acute ischemic stroke in clinical presentation and magnetic resonance imaging: a case report, BMC Med Imaging 19 (1) (2019) 11. 10.1186/s12880-019-0310-z. [43] G Bathla, B Policeni, A Agarwal, Neuroimaging in patients with abnormal blood glucose levels, Am J Neuroradiol 35 (5) (2014) 833–840. 10.3174/ajnr.A3486. [44] P Sharma, M Eesa, JN Scott, Toxic and acquired metabolic encephalopathies: MRI appearance, Am J Roentgenol 193 (3) (2009) 879–886. 10.2214/AJR.08.2257.
[45] N Nathoo, JR van Dellen, Cranial extradural empyema in the era of computed tomography: a review of 82 cases, Neurosurgery 44 (4) (1999 Apr) 748–753; discussion 7534, doi:10.1097/00006123-199904000-00033. [46] H French, N Schaefer, G Keijzers, D Barison, S Olson, Intracranial subdural empyema: a 10-year case series, Ochsner J 14 (2) (2014 Summer) 188–194. [47] JG Smirniotopoulos, FM Murphy, EJ Rushing, JH Rees, JW Schroeder, Patterns of contrast enhancement in the brain and meninges, Radiographics 27 (2) (2007) 525– 551. 10.1148/rg.272065155. [48] Guggenberger K, Krafft AJ, Ludwig U, et al., Highresolution compressed-sensing T1 Black-blood MRI: a new multipurpose sequence in vascular neuroimaging? Clin Neuroradiol 31 (1) (2021 Mar) 207–216, doi:10.1007/s00062-019-00867-0. [49] KM Schwartz, BJ Erickson, C Lucchinetti, Pattern of T2 hypointensity associated with ring-enhancing brain lesions can help to differentiate pathology, Neuroradiology 48 (3) (2006) 143–149. 10.1007/s00234-005-0024-5. [50] PF Finelli, EB Foxman, The etiology of ring lesions on diffusion-weighted imaging, Neuroradiol J 27 (3) (2014) 280–287. 10.15274/NRJ-2014-10036. [51] S-H Hsu, M-C Chou, C-W Ko, et al., Proton MR spectroscopy in patients with pyogenic brain abscess: MR spectroscopic imaging versus single-voxel spectroscopy, Eur J Radiol 82 (8) (2013) 1299–1307. 10.1016/j.ejrad.2013.01.032. [52] BP Soares, JM Provenzale, Imaging of herpesvirus infections of the CNS, Am J Roentgenol 206 (1) (2016) 39–48. 10.2214/AJR.15.15314. [53] J Granerod, NW.S Davies, W Mukonoweshuro, A Mehta, K Das, M Lim, et al., Neuroimaging in encephalitis: analysis of imaging findings and interobserver agreement, Clin Radiol 71 (10) (2016) 1050– 1058. 10.1016/j.crad.2016.03.015.
[54] K Jayaraman, R Rangasami, A Chandrasekharan, Magnetic resonance imaging findings in viral encephalitis: a pictorial essay, J Neurosci Rural Pract 9 (4) (2018) 556– 560. 10.4103/jnrp.jnrp_120_18. [55] M Ali, Y Safriel, J Sohi, A Llave, S Weathers, West Nile virus infection: MR imaging findings in the nervous system. Published online 2005:9, AJNR Am J Neuroradiol 26 (2) (2005 Feb) 289–297. [56] BP Kelley, SC Patel, HL Marin, JJ Corrigan, PD Mitsias, B Griffith, Autoimmune encephalitis: pathophysiology and imaging review of an overlooked diagnosis, Am J Neuroradiol 38 (6) (2017) 1070–1078. 10.3174/ajnr.A5086. [57] SB.L Duarte, MM Oshima, JV.A do Mesquita, FB.P do Nascimento, PC de Azevedo, F Reis, Magnetic resonance imaging findings in central nervous system cryptococcosis: comparison between immunocompetent and immunocompromised patients, Radiol Bras 50 (6) (2017) 359–365. 10.1590/0100-3984.2016.0017. [58] GG.S Kumar, A Mahadevan, AS Guruprasad, JM.E Kovoor, P Satishchandra, A Nath, et al., Eccentric target sign in cerebral toxoplasmosis: Neuropathological correlate to the imaging feature, J Magn Reson Imaging 31 (6) (2010) 1469–1472. 10.1002/jmri.22192. [59] EH Dibble, JL Boxerman, GL Baird, JE Donahue, JM Rogg, Toxoplasmosis versus lymphoma: cerebral lesion characterization using DSC-MRI revisited, Clin Neurol Neurosurg 152 (2017) 84–89. 10.1016/j.clineuro.2016.11.023. [60] J Gavito-Higuera, CB Mullins, L Ramos-Duran, H Sandoval, N Akle, R Figueroa, Sinonasal fungal infections and complications: a pictorial review, J Clin Imaging Sci 6 (2016) 23. 10.4103/2156-7514.184010. [61] A Adams, C Offiah, Central skull base osteomyelitis as a complication of necrotizing otitis externa: imaging findings, complications, and challenges of diagnosis, Clin Radiol 67 (10) (2012) e7–e16. 10.1016/j.crad.2012.02.004.
[62] ET Kimura-Hayama, JA Higuera, R Corona-Cedillo, L Chávez-Macías, A Perochena, LY Quiroz-Rojas, et al., Neurocysticercosis: Radiologic-pathologic correlation, Radiographics 30 (6) (2010) 1705–1719. 10.1148/rg.306105522. [63] R Gupta, R Trivedi, S Saksena, Magnetic resonance imaging in central nervous system tuberculosis, Indian J Radiol Imaging 19 (4) (2009) 256. 10.4103/09713026.57205. [64] JA Edlow, LR Caplan, K O’Brien, CD Tibbles, Diagnosis of acute neurological emergencies in pregnant and post-partum women, Lancet Neurol 12 (2) (2013) 175–185. 10.1016/S1474-4422(12)70306-X. [65] M Sanghavi, JD Rutherford, Cardiovascular physiology of pregnancy, Circulation 130 (12) (2014) 1003–1008. 10.1161/CIRCULATIONAHA.114.009029. [66] K Dahiya, M Rathod, MRI brain lesions in eclampsia: a series of 50 cases admitted to HDU of a tertiary care hospital, J Family Reprod Health 12 (1) (2018 Mar) 51– 56. [67] LH Calabrese, DW Dodick, TJ Schwedt, AB Singhal, Narrative review: reversible cerebral vasoconstriction syndromes, Ann Intern Med 146 (1) (2007) 34. 10.7326/0003-4819-146-1-200701020-00007. [68] TR Miller, R Shivashankar, M Mossa-Basha, D Gandhi, Reversible cerebral vasoconstriction syndrome, Part 1: epidemiology, pathogenesis, and clinical course, Am J Neuroradiol 36 (8) (2015) 1392–1399. 10.3174/ajnr.A4214. [69] TR Miller, R Shivashankar, M Mossa-Basha, D Gandhi, Reversible cerebral vasoconstriction syndrome, part 2: diagnostic work-up, imaging evaluation, and differential diagnosis, Am J Neuroradiol 36 (9) (2015) 1580–1588. 10.3174/ajnr.A4215. [70] E Hugonnet, D Da Ines, H Boby, B Claise, V Petitcolin, V Lannareix, et al., Posterior reversible encephalopathy
syndrome (PRES): Features on CT and MR imaging, Diagn Interv Imaging 94 (1) (2013) 45–52. 10.1016/j.diii.2012.02.005. [71] A Krainik, JW Casselman, Imaging evaluation of patients with cranial nerve disorders, von Schulthess GKJ Hodler, RA Kubik-Huch (Eds.) Diseases of the Brain, Head and Neck, Spine 2020–2023, Springer International Publishing, 2020, 143–161. 10.1007/978-3-030-384906_12. IDKD Springer Series. [72] Z Klimaj, JP Klein, G Szatmary, Cranial nerve imaging and pathology, Neurol Clin 38 (1) (2020) 115–147. 10.1016/j.ncl.2019.08.005. [73] W Allingham, V Devakumar, A Herwadkar, M Punter, Hypoglossal nerve palsy due to internal carotid artery dissection, Neurohospitalist 8 (4) (2018 Oct) 199. [74] B Jubelt, C Mihai, TM Li, P Veerapaneni, Rhombencephalitis/brainstem encephalitis, Curr Neurol Neurosci Rep 11 (6) (2011) 543–552. 10.1007/s11910011-0228-5. [75] N Koçer, C Islak, A Siva, et al., CNS involvement in neuro-behçet syndrome: an MR study. Published online 1999:10, AJNR Am J Neuroradiol 20 (6) (1999 Jun–Jul) 1015–1024. [76] KA Ruzek, NG Campeau, GM Miller, Early diagnosis of central pontine myelinolysis with diffusion-weighted imaging. Published online 2004:4, AJNR Am J Neuroradiol 25 (2) (2004 Feb) 210–213. [77] S Chhabda, DS Leger, RK Lingam, Imaging the facial nerve: a contemporary review of anatomy and pathology, Eur J Radiol 126 (2020) 108920. 10.1016/j.ejrad.2020.108920. [78] H Parmar, P Park, B Brahma, D Gandhi, Imaging of idiopathic spinal cord herniation, Radiographics 28 (2) (2008) 511–518. 10.1148/rg.282075030. [79] H Uetani, T Hirai, M Kitajima, et al., Additive value of 3T 3D CISS imaging to conventional MRI for assessing
the abnormal vessels of spinal dural arteriovenous fistulae, Magn Reson Med Sci 17 (3) (2018) 218–222. 10.2463/mrms.mp.2016-0098. [80] J Figueroa, JG DeVine, Spontaneous spinal epidural hematoma: literature review, J Spine Surg 3 (1) (2017) 58– 63. 10.21037/jss.2017.02.04. [81] VK Kunam, V Velayudhan, ZA Chaudhry, M Bobinski, WR.K Smoker, DL Reede, Incomplete cord syndromes: clinical and imaging review, Radiographics 38 (4) (2018) 1201–1222. 10.1148/rg.2018170178. [82] AE Gürsoy, M Kolukısa, G Babacan-Yıldız, A Çelebi, Subacute combined degeneration of the spinal cord due to different etiologies and improvement of MRI findings, Case Rep Neurol Med 2013 (2013) 1–5. 10.1155/2013/159649. [83] S Keddie, A Adams, AR.C Kelso, et al., No laughing matter: subacute degeneration of the spinal cord due to nitrous oxide inhalation, J Neurol 265 (5) (2018) 1089– 1095. 10.1007/s00415-018-8801-3. [84] MI Vargas, J Gariani, R Sztajzel, et al., Spinal cord ischemia: practical imaging tips, pearls, and pitfalls, Am J Neuroradiol 36 (5) (2015) 825–830. 10.3174/ajnr.A4118. [85] J Strahle, KM Muraszko, HJ.L Garton, et al., Syrinx location and size according to etiology: identification of Chiari-associated syrinx, J Neurosurg Pediatr 16 (1) (2015) 21–29. 10.3171/2014.12.PEDS14463. [86] TK Ralot, R Singh, et al., Brown-séquard syndrome as a first presentation of multiple sclerosis, Malays J Med Sci 24 (4) (2017) 106–110. 10.21315/mjms2017.24.4.13. [87] T Krings, S Geibprasert, Spinal dural arteriovenous fistulas, Am J Neuroradiol 30 (4) (2009) 639–648. 10.3174/ajnr.A1485.
CHAPTER 91
Acute Chest Reena Tanna, Janan Jeyatheesan
Radiological Techniques Chest Radiographs Chest radiographs are by far the most common first-line investigation in the acute setting and provide many positive and negative findings to tailor further imaging or immediate management. Careful assessment of a technically good x-ray is key, and subsequently the production of a clear radiology report. Currently, in most centers the x-ray source is a standard portable generator, and the image is captured on a computed radiography detector or a flat-panel digital detector, followed by immediate transfer to a picture archiving and communication system (PACS) [1]. The x-rays of intensive care ward patients need to be examined in the light of full clinical information because many of the pathological processes to which these patients are susceptible produce similar radiographic manifestations. Serial images need to be evaluated for general trends, as day-to-day changes may not be apparent, and special attention needs to be given to monitoring and life-support devices. The injured patient is usually brought to the x-ray department, where, if possible, an erect posteroanterior (PA) x-ray should be taken. A high-kV technique is desirable to see mediastinal detail. If the patient is severely injured, it is necessary to make do with semi-erect or supine radiographs.
Computed Tomography Computed tomography (CT) is the second most common modality when imaging the thorax. These scans vary significantly depending on the
indication including the use of intravenous contrast, patient positioning, inspiration versus expiration, gated scanning, as well as newer techniques such as multispectral or dual-energy CT. The clinical indication and patient factors will dictate the exact protocol of the scan.
Ultrasonography (USG) USG is an excellent method for examining the pleura, diaphragm, and subphrenic areas and has largely been replaced by the concomitant use of “Focussed Assessment with Sonography in Trauma” (FAST scanning) and chest x-rays (CXRs) [2].
Aortography, CT, and Trans-oesophageal USG Aortography, CT, and trans-oesophageal ultrasound may be indicated when vascular injuries are suspected. The best way to assess any scan of the chest is the same as with any form of imaging interpretation. A systematic approach, looking at all areas of the chest wall, pleura, lungs, and mediastinum, as well as any review areas identified by the reader (Fig. 91.1).
FIGURE 91.1 A systematic approach to assessing and reporting acute imaging of the chest, including all systems and review areas.
Nontraumatic Chest Emergencies Chest emergencies in the nontraumatic setting are common presentations to the emergency department and make up a large proportion of the radiologist’s workload. Common clinical presentations are chest pain, shortness of breath, cough, fever, and haemoptysis. It is important to be able to differentiate when certain diagnoses need urgent management to prevent significant morbidity or mortality. The prevalence of chronic lung disease globally in 2017 was estimated to be 545 million people, with almost 4 million associated deaths [3]. Although these chronic conditions are not emergencies in themselves, it is the complications of these diseases that lead patients to attend hospital and where the role of imaging becomes important. Similarly, cardiovascular disease in the British population was recorded at nearly 272,000 in 2018 [4], and the number of deaths globally in 2016 reached an estimated 17.9 million
[5]. These figures give an idea of the importance of detection of the primary condition, but more importantly, the associated morbidity and mortality, some of which can be managed in a timely manner following appropriate image-guided diagnosis. In most instances, a CXR will be enough to diagnose and direct management, however further imaging such as CT, nuclear medicine, or invasive angiography has a role in certain scenarios and is often adopted to gain more detail or a more definitive diagnosis.
Cough/Fever One of the most common presentations in the acute setting is cough and fever. Although a simple lower respiratory tract infection accounts for many of these cases, there are certain differentials that must be considered following appropriate clinical history and examination, for example, atypical infections in the immunosuppressed patient. Pneumonia Airspace opacification or consolidation on a CXR is a classic finding in true pneumonia, and follow-up imaging 4–6 weeks following treatment is the usual advice given to ensure resolution. The appearance, distribution, and development of this consolidation can point the diagnostician toward a specific pathogen. For example, lobar consolidation with bulging fissures should automatically flag Klebsiella as a culprit (Fig. 91.2A and B). In the immunosuppressed patient, patchy perihilar ground-glass changes suggest Pneumocystis pneumonia [6]. Table 91.2 Modified PIOPED II Classification High Probability
◾ ≥2 large segmental perfusion defects ◾ 1 large segmental defect & ≥2 moderate segmental perfusion defects
Intermediate Probability
◾ 1 moderate to 3 small segmental perfusion defects
Very Low Probability
◾ ≤3 small segmental perfusion defects
◾ Corresponding V/Q defect and XR opacity in lower lung OR small pleural effusion ◾ Single moderately matched V/Q defect Normal
◾ No perfusion defects and perfusion outlines normal lung contour
FIGURE 91.2 CXR (A) and CT (B). Consolidation with bulging of the adjacent fissure (arrow), a feature commonly seen in Klebsiella pneumonia.
High-resolution CT may be warranted in patients with unusual presentations or in those high-risk patients with clinical symptoms or refractory infections that do not have any x-ray changes. CT also demonstrates an array of findings dependent on the causative agent, but the most important use is to identify any complications of infections that might pose a risk to the patient’s life. Lung Abscess Lung abscesses can be primary if they arise from the lung due to necrotizing pneumonias, immunodeficiency, or aspiration, or secondary from haematogenic spread or direct invasion from surrounding soft tissues, etc. They are an important entity to pick up on imaging as the mortality rate from untreated abscesses can reach up to 75% [7]. On x-ray, the classic
appearance is of a rounded, thick-walled cavitating lesion, sometimes with an air-fluid level within. Contrast-enhanced CT should be adopted to clearly visualize the margins and any associated vascular or airway complications (Fig. 91.3). Features on CT are similar to radiographs, with thick-walled, discrete cavitating lesions containing fluid, with or without gas. There is often surrounding lung inflammation or atelectasis, and bronchovascular bundles can be seen tracing up to the wall, where they abruptly end. Management options include prolonged antibiotic therapy, and in some instances, surgical drainage [7].
FIGURE 91.3 CXR (A) and axial CT (B). Lung abscess with irregular, thick-walled cavities, and surrounding ground-glass change. Air-fluid levels (arrows) are seen inferiorly on the CXR and dependently on the axial CT.
Empyema Empyema is infected pleural collections, usually developing as a complication of an existing pneumonia, or from any other means of introducing bacteria into the pleural space. This may be iatrogenic following thoracic surgery, from penetrating trauma, extension from a nonpleural infection such as the abdomen, or direct rupture from a lung abscess. Radiographs will demonstrate a pleural collection; however, USG or CT are better modalities to delineate an empyema from a simple effusion and to assess the size, complexity and any associated features that require urgent management [8]. Findings on USG include pleural thickening, septations, and loculated fluid (Fig. 91.4). The echogenicity of blood products will be more echogenic than pus, which will be more echogenic than simple fluid. Immediate drainage can be performed at the same time under direct visualization, which is the most common form of immediate management [9].
FIGURE 91.4 USG static images demonstrating a hypoechoic pleural fluid collection with a thickened pleura overlying the collection, and septations (arrow) in keeping with empyema.
CT with contrast enhancement may show the “split pleura sign,” where there is hyperenhancement of the parietal and visceral pleura (Fig. 91.5), separated by a fluid collection. Gas locules within the collection in the absence of previous instrumentation are indicative of an aerobic organism or may suggest fistulation with the small airways. Septations are easily identified, as well as thoracic wall fat stranding or inflammatory change in the pulmonary tissue [9].
FIGURE 91.5 Axial CT. Pleural collection with hyperenhancing pleura (arrows) known as the “split pleura sign,” indicating empyema. Note the gas locules (arrowhead) within the fluid, another sign of an infected collection.
Empyema is sometimes difficult to differentiate from a lung abscess (Table 91.1), but certain imaging features can help to distinguish between the two [10]. Table 91.1 Imaging Differences to Distinguish Between Pleural Empyema and Pulmonary Abscess Empyema
Lung Abscess
Smoother, thinner walls (“split pleura sign”)
Thick, irregular walls
Empyema
Lung Abscess
Abrupt interruption of bronchovascular bundles
Distortion and compression of bronchovascular bundles and lung parenchyma
Obtuse angle with pleura
Acute angle with pleura
Lentiform shape
Rounded shape, usually with an air-fluid level
Septic Emboli Septic emboli occur when pathogen-laced thrombus fragments detach from an infective source in the body and travel via the bloodstream to the lungs, where they cause microinfarcts and abscesses. This is most commonly seen in intravenous drug users, diabetics, and in patients with infective endocarditis. Complications include lung abscesses, bronchopleural fistulas, pneumothoraces, or fatal sepsis. Small nodular opacification may be seen on CXRs, in a largely peripheral distribution. CT with contrast enhancement demonstrates peripheral, wedge-shaped areas of nodular, and ground-glass change or cavitation. CT can also demonstrate the “feeding vessel sign” (Fig. 91.6) which is an indication of haematogenous spread [11].
FIGURE 91.6 Axial CT bilateral, peripheral areas of consolidation, some showing internal cavitation (arrow) with a “feeding vessel sign” (arrowhead) in keeping with septic emboli.
Pulmonary TB Pulmonary TB should be mentioned in this section, as although the clinical presentation itself is not an “emergency,” imaging plays a vital role in the detection and urgent referral to the appropriate infectious diseases teams to prevent spread. Currently, plain radiography is the only imaging modality in international guidelines for the diagnosis of TB (Fig. 91.7), alongside sputum microscopy for acid-fast bacilli. CT has a role, especially in refractory infections, radiographic occult disease, the assessment of complications and follow-up after management. Signs of active pulmonary TB on radiographs include multifocal, patchy consolidation with an upper lobe predilection with or without lymph node enlargement, miliary nodules, cavitating lesions, and occasional pleural effusions/empyema.
Coronavirus Disease (COVID-19) Coronavirus disease (COVID-19) pneumonia was first presented in December 2019 and escalated within weeks to become a global pandemic. About 754 million cases and 6.83 million deaths of COVID-19 have been reported worldwide as of February 8th, 2023 [12]. There is ongoing research into this disease and whilst a lot is still unknown, it seems that COVID-19 will remain an especially important differential in patients with acute chest symptoms for the foreseeable future. Radiographic features (Fig. 91.8) range from minor illness to more severe cases with complications including adult respiratory distress syndrome (ARDS) and lung fibrosis. Most cases in the acute setting demonstrate bilateral, peripheral, patchy airspace opacification, usually with a slight lower zone distribution [13].
FIGURE 91.8 (A) CXR. Patchy bilateral, mainly peripheral groundglass opacification seen in COVID-19 pneumonia. (B) CT correlate demonstrating patchy ground-glass changes in the absence of mediastinal lymph node enlargement, cardiomegaly, or pleural effusions.
CT is not routinely indicated for uncomplicated cases of COVID-19 as clinical history, radiographic signs, and polymerase chain reaction testing have adequate diagnostic value. However, the complication of COVID-19 pneumonia includes increased thromboembolic potential resulting in pulmonary emboli, significant respiratory compromise leading to ARDS, and long term effects of the infection and mechanical ventilatory support leading to fibrotic lung changes. These are all indications for CT evaluation and will have varying imaging findings [14]. CT findings in uncomplicated COVID-19 pneumonia are similar to those on CXR, with bilateral, patchy, peripheral ground-glass changes. Associated thoracic lymph node enlargement and pleural effusions are not commonly seen [15].
Shortness of Breath Another common presentation in the acute setting is difficulty in breathing, dyspnoea, or shortness of breath. The most common causes are usually those that affect the main airways or lungs themselves, reducing or preventing adequate gas exchange. Acute Exacerbations of Chronic Lung Disease Acute exacerbations of chronic lung disease are a common cause of a sudden deterioration in respiratory function and presentation to the emergency department. Chronic conditions include asthma, chronic obstructive pulmonary disease (COPD) bronchiectasis, fibrotic lung disease, and cystic fibrosis (CF). Although an acute exacerbation is defined slightly differently in these entities, the overall result is the same: a reduction in respiratory function, possible progression of disease, reduced quality of life,
and higher risk of disease-related mortality. It is important to identify these clinically; however, imaging can play a role in the diagnosis and monitoring of these cases [16]. Chest radiographs may show evidence of the underlying chronic condition, such as dilated airways in bronchiectasis or CF, or hyperexpanded lungs in COPD. Acute changes are varied depending on the cause of the exacerbation, but the most common findings include new infective/inflammatory consolidation, bronchial wall thickening, loss of lung volume, or areas of collapse (due to mucus plugging for example) or pleural effusions/edema (Fig. 91.9) [17]. CT is indicated in cases where radiographic findings are equivocal or where there is an unusual presentation, persisting symptoms despite appropriate treatment or when there is concern over associated complications, such as malignant transformation or abscess formation, etc.
FIGURE 91.9 CT and CXR. Imaging features of bronchiectasis with dilatated, thickened airways (arrows) (B and C) and dense consolidation with air bronchograms (A) in acute infective exacerbation. CXR (D) shows “cystic” spaces (arrow) indicating dilated airways.
Pulmonary Edema
Pulmonary edema can also present as acute shortness of breath and is usually cardiogenic in nature, however noncardiogenic pulmonary edema can be seen secondary to inhalation injuries, allergic reactions, acute renal dysfunction, and more severely in ARDS. It is the result of an increase in hydrostatic pressure, pushing fluid into the interstitium, and later into the alveoli [18]. Chest x-ray findings vary depending on the degree of edema but usually demonstrate increased vascular diameter bilaterally with upper lobe diversion, interstitial and interlobular septal thickening (Kerley B lines), and bilateral pleural effusions (Fig. 91.10). With worsening edema, there may be gravity-dependent ground glass changes and a “batwing appearance” representing centrally located alveolar edema [19].
FIGURE 91.10 CXR. Classic radiographic “bat wing” appearance seen in pulmonary edema. (Image courtesy of Dr Zelena Aziz.)
Pleural Effusion
Pleural effusions are commonly associated with pulmonary edema; however, noncardiogenic causes are also common. There is usually at least 200 mL of fluid within the pleural space before a meniscus sign is seen on a PA radiograph, and 500 mL before the meniscus obscures the hemidiaphragm [20]. Acute Interstitial Pneumonitis Acute interstitial pneumonitis is a rapidly progressing, noninfectious interstitial lung disease, the only acute process among the idiopathic interstitial pneumonias. It usually progresses over days or weeks in otherwise healthy individuals, causing nonspecific symptoms of myalgia, pyrexia, and malaise, with rapidly worsening respiratory function and dyspnoea [21]. There is diffuse alveolar damage which has almost identical imaging features to those in ARDS (discussed later). Management when the condition progresses to respiratory failure is usually supportive, with mechanical ventilation and the use of corticosteroids and cyclophosphamide [22] however prognosis is rather poor with more than 70% mortality rate at 3 months. Lung Collapse Anything that blocks the passage of air into the lungs can also lead to shortness of breath or difficulty in breathing. Lung collapse is seen when there is airway obstruction, either intraluminal such as an inhaled foreign body or mucous plugging, or from extrinsic compression such as a lung cancer. On plain radiographs, this will present as an opacity in differing positions dependending on which lobe of the lung is affected [23]. This is described in detail in the Chapter 17 on diseases of airways.
Chest Pain The most common causes of chest pain in the acute setting are pulmonary emboli, myocardial infarction, and acute aortic syndrome (AAS). Various other, less common conditions present with chest pain, which in itself is a rather nonspecific symptom. It is important for referring physicians to have a good idea of the clinical picture and a list of differentials in order of likelihood and clinical urgency, to ensure the correct examination is performed. It is the role of the radiologist to help the physicians if there is any uncertainty, and to direct imaging appropriately to get the best results to help the patient. Pulmonary Embolism
Pulmonary embolism (PE) occurs when thrombus, usually in the deep venous system of the limbs, is left untreated and fragments of thrombus break off, travel via the bloodstream to the right side of the heart and into the pulmonary circulation. These can then become lodged in the pulmonary arteries, depending on their size, causing ischaemia in the supplied lung [24]. Clinical presentation varies depending on the size and distribution of the emboli, from mild dyspnoea, tachycardia, and chest pain to more concerning haemoptysis or cardiac arrest. A chest radiograph is performed in the first instance, acting as an aid to identify any other cause for the patient’s symptoms before following the algorithm in the investigation of PE’s. Biochemical tests such as D-dimer, as well as a scoring system identifies the probability of there being a PE. If the probability is high enough, and the radiograph has not highlighted any significant abnormalities, there are two main imaging pathways that can be taken [25]. A common investigation in those with high probability but clinical stability is a ventilation-perfusion scan (V/Q scan). Approximately 25% of patients with suspected PE having the diagnosis refuted by normal scintigraphy. PE’s obstruct vessels, therefore causing a perfusion defect on a V/Q scan, however it should not affect the ventilation, unless a lung infarct has occurred. This results in a ventilation-perfusion mismatch (Fig. 91.11).
FIGURE 91.11 Single photon emission computed tomography (SPECT) perfusion scan. Perfusion defect in the right upper zone (arrow) with no CT correlate (not shown here), indicating a pulmonary embolus.
The modified Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) criteria are currently used to classify studies by probability (Table 91.2) [26]. An ideal test for PE would provide noninvasive direct visualization of thrombus within pulmonary arteries; CT pulmonary angiography (CTPA) comes close to fulfilling this description. The sensitivities and specificities
for pulmonary emboli detection by CTPA at main, lobar, and segmental levels are almost always reported as greater than 90% [2427]. Newer technologies such as spectral or dual-energy CT have led to improvements in image quality, requiring smaller volumes of intravenous contrast, and reduced beam hardening and streak artefact [28]. The CT signs of PE are now well defined, and the cardinal sign of an intraluminal filling defect, either partially or totally obstructive, remains the central diagnostic criterion for an embolus (Fig. 91.12). There may be features of complications such as interventricular bowing and reflux of contrast into the inferior vena cava, representing a degree of right heart strain. A dilated pulmonary trunk would suggest pulmonary hypertension, seen more commonly with chronic PE’s. Finally, if there is any ischaemia in the lung, CT can demonstrate peripheral, wedge-shaped areas of opacification [29].
FIGURE 91.12 CTPA. Filling defects (arrows) in the right main pulmonary artery and left lower lobar pulmonary artery in keeping with extensive pulmonary emboli.
Myocardial Infarction The clinical management of acute myocardial infarction is a complex matter, depending on the precise mode of presentation and the site and size of the infarct. The CXR is used as a guide to cardiac function and heart failure, but other imaging techniques are not routinely used in the first few days after myocardial infarction unless there are haemodynamic complications. The most common feature identified is the development of pulmonary edema, imaging findings of which have been discussed earlier. Serial radiographs may show pleural effusions which can develop if the left heart failure is prolonged. The presence of pulmonary edema indicates 1-year mortality of 44%. If there is no evidence of heart failure, this indicates a good prognosis with an 8% 1-year mortality. If the serial radiographs taken over the first few days or weeks following myocardial infarction show progressive cardiac enlargement (Fig. 91.13A– C), this is an important adverse prognostic sign that should be further evaluated.
FIGURE 91.13 Sequential CXRs. Increase in the size of the cardiac silhouette on sequential radiographs (A–C) taken weeks apart. The cardiothoracic ratio (CTR) can be calculated on PA radiographs; however, there is an obvious increase in size indicating developing cardiomegaly.
The echocardiogram will usually demonstrate the site, size, and severity of the infarct and will allow an assessment of overall left ventricular function. Trans-oesophageal echocardigram is occasionally helpful in the acute phase but the potential imaging benefits must be seen in the context of the patient’s clinical condition, and therefore this procedure should only be performed when there is a clear clinical management decision to be made. The use of Triple Rule Out CT has been adopted in may centers around the world which has an indication in low to intermediate-risk patients, to assess for significant coronary artery disease, PE, and AAS. A modified CT coronary angiogram is performed, which images from just above the aortic arch to the top of the abdomen, using a split bolus of intravenous contrast,
with ECG gating and the use of beta-blockers and GTN to optimize coronary image quality. TRO CT also has the advantage of being able to pick up any noncardiovascular causes for the patient’s symptoms, for example, any pulmonary infections, pneumothoraces, etc. Acute Pericarditis Acute pericarditis occurs when there is inflammation of the pericardium, usually with an associated effusion and pericardial thickening. It is most commonly due to an infection, usually viral, bacterial, or tuberculous. Less commonly it can be associated with inflammatory disorders such as scleroderma or rheumatoid arthritis, and following an MI, termed “Dressler’s syndrome” [30]. Positional chest pain is the most common presentation, with many experiencing relief when sitting forwards. Chest radiographs have a role in excluding any other causes of chest pain or sepsis and may demonstrate changes to the cardiac contour if there is a significant enough pericardial effusion (“globular heart”) (Fig. 91.14A). On CT, a purulent or loculated pericardial effusion may be seen, however, the presence of pericardial thickening is more specific (Fig. 91.14B). There may be hyperenhancement of the pericardium or areas of calcification in constrictive pericarditis [30].
FIGURE 91.14 (A) CXR. Frontal radiograph demonstrates an enlarged cardiac contour in a patient with pericarditis. (B) Axial CT. Contrastenhanced CT demonstrates a pericardial effusion with irregular thickening of the pericardium (arrow) in a patient with acute pericarditis. Incidental note made of a left pleural collection (star). (C) Axial T2 weighted MRI. High signal pleural (star) and pericardial effusions with a thickened pericardium (arrow) in a patient with acute pericarditis.
MRI is extremely sensitive at detecting even small amounts of fluid within the pericardium and haemopericardium can be distinguished from conventional fluid (Fig. 91.14C). Often in constrictive pericarditis there is disproportionate dilatation of the atrium compared to the ventricles. If assessment of the valves excludes the diagnosis of regurgitation and imaging
of the pericardium shows pathological thickening, then the diagnosis of constrictive pericarditis is likely. Acute Aortic Syndrome Acute aortic syndrome (AAS) is a spectrum of disorders affecting the aortic structure and integrity and is a medical emergency requiring prompt diagnosis and management. The unifying presentation is with sudden onset chest pain and usually a degree of haemodynamic instability. The main complication is aortic rupture, which is rapidly fatal, but this can be avoided with early recognition, accurate diagnosis, and appropriate, timely treatment. CT is the first-choice investigation in the acute setting, whereas MRI is usually reserved for any special circumstances, surveillance or further assessment, for example, haemodynamic assessment. Radiographs have a somewhat limited role, however nonspecific findings such as mediastinal widening may direct the clinical team to investigate further [31]. AAS encompasses the following: intramural haematoma, aortic dissection, penetrating ulcer, and unstable aortic aneurysm [32]. These conditions may all occur independently, or they may also occur together in any combination, to different degrees at different sites. Clinically, it is very difficult to differentiate these conditions, therefore imaging must be performed in a systematic way to enable a radiologist to assess each of these pathologies (Box 91.1). Box 91.1
Acute Aortic Syndrome Imaging Peals Unenhance d
High attenuation crescent indicates mural haematoma
CT is the preferred method of imaging for AAS in the acute setting, with sensitivity and specificity above 98% [33]. ECG-gated or flash scans should be carried out to prevent pulsation artefact, which can degrade image quality and produce false-positive signs of dissection, particularly around the aortic
root. An unenhanced CT should be the first scan performed, to look for a high attenuation crescent shape in the aortic wall, indicative of an intramural haematoma (Fig. 91.15). Depending on their location and size, these may be treated conservatively, or with more aggressive measures such as endovascular repair (EVAR). This is because they can progress to dissection, rupture or aneurysm which all carry poorer prognoses [34].
FIGURE 91.15 Axial CT. Unenhanced gated CT of the aorta demonstrates a high attenuation crescent along the lateral border of the ascending aorta (arrow) indicating an intramural haematoma as part of an acute aortic syndrome.
ECG-gated CT of the whole aorta with intravenous contrast in the angiographic phase is then performed to look at the aortic lumen size and
integrity. Aortic Dissection Aortic dissection is a devastating disease that occurs as a result of degeneration of the thoracic aorta. Despite modern treatment, the mortality from this condition remains high, with death in 25% of patients with a dissection of the ascending aorta within the first 24 hours and a mortality of over 75% within the first month. Aortic dissection in younger patients usually occurs in high-risk groups such as patients with Marfan’s syndrome, Ehlers–Danlos disease or in pregnancy. The most common pattern of dissection involves the right anterior aspect of the ascending aorta and the posterior left lateral aspect of the descending aorta. Dissection in the descending aorta can extend down to the abdominal aorta and may then lead to dissection of the left renal artery with associated ischaemic change. There are two major types of classification: De Bakey and Stanford, described in detail in the chapter “disorder of arteries” (Chapter 25). CT signs of an intimal flap can be identified by demonstration of two lumens within the aorta originating from the point of the dissection tear (Fig. 91.16).
FIGURE 91.16 Coronal CT reformat. Ascending aortic dissection (blue arrow) with lower attenuation contrast filling the false lumen. Medially there is a blush of contrast (blue arrowhead) indicating aortic rupture and haemorrhage into the mediastinum and pericardial space.
Often a differential blood flow within the true and false lumens can be detected by the variable enhancement patterns following the intravenous contrast. Another important consideration is the need to determine whether the dissection extends into any of the great vessels arising from the aortic arch or the aortic valve (Fig. 91.17), which will be vital for the surgeons to know before any intervention.
FIGURE 91.17 Axial CT. Images demonstrate a dissection flap involving the aortic root and extending to the aortic valve, with a crescent of high attenuation seen where the intravenous contrast enhances the false lumen (arrow) at the level of the right coronary artery origin (arrowhead).
Often in aortic dissection the CT will demonstrate periaortic haematoma caused by venous bleeding within the aortic wall. The technique may also demonstrate a pericardial effusion (haemopericardium), related to a tear extension into the aortic root. A dissection can extend into the aortic root leading to the development of aortic regurgitation, or into the origins of either coronary artery, leading to myocardial infarction. It is important to be able to distinguish between the false and true lumens (Table 91.3) so that the surgeons or interventionalists can manage the correct one (Fig. 91.18). This can be challenging if there is a large dissection extending across the whole aorta, however there are several differentiating appearances that can help [35].
FIGURE 91.18 (A) Axial CT. Descending thoracic aorta dissection with “cobweb sign” representing strands of media crossing the false lumen. (B) “Beak sign” represents the acute angle formed by the false lumen in aortic dissection.
Table 91.3 Imaging Features to Distinguish Between the True and False Lumen in Aortic Dissection True Lumen
False Lumen
Smaller
Larger
Continuous with unaffected aorta
Discontinuous from unaffected aorta
Displaced medially
Lateral to or wrapped around the true lumen
Enhances more than false lumen
Slow flow—hypodense to true lumen “Cobweb sign” OR “beak sign”
There are some pitfalls to be avoided in CT diagnosis of dissection.
◾ Linear artefacts across the aortic lumen can mimic an intimal flap. ◾adjacent Leads or metallic lines on the patient’s chest, or more commonly opacification of an venous structure such as the superior vena cava, can generate these artefacts. ◾thatOccasionally periaortic structures can be interpreted as periaortic haematoma; a classic area can give rise to confusion is the presence of fluid in the superior pericardial recess. ◾give Perhaps the most common misinterpretation is caused by tortuosity of the aorta, which can rise to an apparent inward projection of the aortic wall (Box 91.2).
Box 91.2
Reporting a CTA
◾extents Location of tear including the proximal and distal ◾ Aortic size (any evidence of aneurysm) ◾falseWhether the major aortic branches arise from the or true lumen ◾haemopericardium Any associated complications, e.g., or rupture ◾occlusion Signs of end-organ ischaemia or vascular
If further evaluation is required, or in those with contraindications to CT, MRI can be used for initial diagnosis, as well as for follow-up or surveillance (Fig. 91.19). Steady-state free procession MRI allows the possibility of diagnostic images with minimal scanning time in the acute setting. Contrast-enhanced MRI can also be adopted to visualize branching vessels, the presence of penetrating ulcers and any other luminal abnormality [36].
FIGURE 91.19 Sagittal MRI. Multiple dissection flaps (arrows) throughout a tortuous descending thoracic aorta.
Transthoracic echocardiography is limited in the assessment of the aorta. Trans-oesophageal echocardiography, however, can give excellent detail of much of the aorta. Doppler studies will enhance diagnostic accuracy by showing flow in the true and false lumens as well as demonstrating the site of the tear in many cases. Penetrating Atherosclerotic Ulcers Penetrating atherosclerotic ulcers can be seen on CTA as an out-pouching of the aortic wall or into a thickened wall if it has not penetrated through all the intimal layers (Fig. 91.20). These can progress to IMH, dissection or rupture,
and are often managed depending on size, progression and clinical symptoms [37].
FIGURE 91.20 Axial CT. Penetrating aortic ulcer arising from the aortic arch, seen as an outpouching (traced in red) from the aortic wall.
The diagnosis of rupture depends on the identification of haematoma outside the aortic lumen but in close association with the course of the vessel (Fig. 91.21). The haematoma will not usually show contrast enhancement on CT examination unless there is severe bleeding. In some cases where the haematoma cannot be correlated with a bleeding site, the source of the haemorrhage may be periaotic veins or small arteries. There will often be an associated pleural effusion. The presence of a haemopericardium is most likely due to rupture of the aortic root.
FIGURE 91.21 Coronal CT reformats. Gross irregularity of the thoracic aorta at the level of the aortic isthmus (circled), with contrast extravasation and large mediastinal haematoma in keeping with an aortic rupture.
Aortic Aneurysms Another common cause of chest pain is an aortic aneurysm, although chest pain usually arises when there are complications from an aneurysm, such as dissection or rupture. In atherosclerotic and degenerative disease, the arch and descending aorta are commonly involved but in Marfan’s syndrome, it is the aortic root that is most commonly affected. Assessment of any aneurysm must include determination of the site, shape, and size of the lesion as well
as its relationship to aortic branches. The wall must be evaluated to see if there is any associated thrombus formation or dissection. Chest radiographs may demonstrate a widened mediastinum (Fig. 91.22) or abnormal descending aortic contour. However, like with most of these aortic pathologies, CTA is required for diagnosis and evaluation of any associated complications. It is usually stated that risk of spontaneous rupture of an aortic aneurysm rises significantly once the diameter increases beyond 5 cm.
FIGURE 91.22 CT (A) and CXR (B). Descending thoracic aortic aneurysm measuring up to 75 mm in diameter. The aneurysm is clearly seen as an enlarged mediastinal mass on the frontal radiograph.
Mycotic aneurysms are a rare cause of aneurysm of the thoracic aorta, induced by bacteria invading the arterial wall. This type of aneurysm accounts for up to 3% of all thoracic aneurysms and has an extremely poor prognosis since the aneurysm often expands quickly, leading to rupture [38]. Imaging features differ slightly from noninfectious aneurysms and include a saccular aneurysm, sometimes with a lobulated contour (Fig. 91.23). The most specific finding is that of adjacent soft tissue, fat-stranding, fluid or gas locules, all indicating the inflammatory nature [39].
FIGURE 91.23 Axial CT. Saccular, lobulated (traced) mycotic aneurysm arising from the aorta. Commonly seen with adjacent fat stranding or gas locules indicating the infective nature of these ulcers.
Haemoptysis/Haematemesis Another symptom that can be alarming for patients is haemoptysis (the coughing up of blood products), often arising from the lower respiratory tract or alveoli. There is no accepted way of categorizing the severity although more recently, non-massive, massive, and recurrent haemoptysis have taken traction and dictate the management pathway, including that of imaging. There are various causes of haemoptysis, and the more common ones are lung cancer/metastasis, bronchiectasis, infection, trauma, and PE. Clinical and relevant past medical history will aid in formulating a sensible differential and a chest radiograph is often helpful in narrowing the differential. CT chest with contrast (ideally in an aortic arterial phase) and bronchoscopy assist in identifying the site and extent of the problem. Although the treatment pathway is multifactorial, bronchial artery embolization is routinely considered [40,41]. Occasionally distinguishing haemoptysis from haematemesis can be challenging, and upper
gastrointestinal causes of bleeding should be considered in patients that maybe presenting with atypical or copious amount of “haemoptysis.” Arteriovenous Malformations Like the gastrointestinal system, arteriovenous malformations (AVMs) can cause haemoptysis although this is rare. This is a rare congenital condition where a direct arterial–venous connection has developed between small pulmonary arteries and veins in the vast majority of cases (95%), but can occur between the systemic artery and the pulmonary vein. Although there is right-to-left shunt, the condition usually manifest in adulthood. Risk of paradoxical cerebral embolism or abscess is of concern. In one-third of cases these lesions are multiple and in one-third of cases, they form part of a spectrum, hereditary haemorrhagic telectangiectasia (formerly Osler– Weber–Rendu syndrome). On the plain film there are often multiple small soft-tissue lesions that can enlarge rapidly, the differential diagnosis being multiple metastasis (Fig. 91.24A and B). Contrast CT plays an important role in characterizing the lesion, often presenting as an enhancing nodule or mass, highlighting the feeding artery and draining vein which will aid treatment, usually by the interventional radiologist embolizing the feeding artery [42,43]. Very rarely it may calcify, with phleboliths being identified.
FIGURE 91.24 (A) CXR. Asymmetry in the lower zones (circled), with more prominent vascular markings on the right and the appearance of a mass-like structure. (B) Axial CT MIP images correlate with these findings, demonstrating an abnormal network of vessels in the right lower lobe (arrow) with a large feeding artery, multiple collateral vessels, and pulmonary venous drainage in keeping with an AVM. AVM, arteriovenous malformation.
Pulmonary Varix
A pulmonary varix is a rare localized aneurysmal dilatation of the pulmonary vein with no direct arterial input. These lesions are associated with both congenital and acquired heart disease and can develop in isolation. They are usually recognized by the presence of rounded or even lobulated shadows near the hilum, often mimicking a mediastinal mass [44]. Diffuse Pulmonary Haemorrhage Finally, diffuse pulmonary haemorrhage (DPH) can present with haemoptysis and is normally due to a more systemic process causing haemorrhage into the lungs, and sometimes into the alveolar space (termed “diffuse alveolar haemorrhage”) [45]. The most common causes include vasculitides such as granulomatosis with polyangiitis, Goodpasture syndrome, systemic lupus erythematosus and following bone marrow transplant. Less commonly, widespread lung metastases and coagulation disorders can cause DPH. Imaging features on plain radiographs are nonspecific but may show bilateral consolidation. CT features of groundglass changes with areas of more dense consolidation, giving a “crazypaving” pattern appearance are associated with DPH (Fig. 91.25), with interseptal thickening is often seen at a later stage due to intralymphatic accumulation of haemosiderin.
FIGURE 91.25 Axial CT. Diffuse pulmonary haemorrhage is seen as “crazy paving” with regions of consolidation (star), ground glass change (arrowhead), and interseptal thickening (arrow). (Image courtesy of Dr Zelena Aziz.)
Adult Respiratory Distress Syndrome (ARDS) ARDS may be due to various causes (Table 91.4) and presents as acute respiratory failure in patients without previous lung disease, usually following major trauma or shock, who often go onto receive ventilatory support.
The Berlin definition of ARDS requires the acute onset of new or worsening symptoms or an identifiable insult to be within 1 week, with bilateral opacities on chest radiograph (Fig. 91.26) that is unrelated to other pulmonary pathologies. The respiratory failure should not be related to cardiac failure or fluid overload. Depending on the level of oxygenation, it can be categorized into mild, moderate, and severe. Table 91.4 Causes of Adult Respiratory Distress Syndrome Septicaemia
Burns
Fat embolism
Major trauma
Drowning
Disseminate intravascular coagulation
Hypovolaemic shock
Oxygen toxicity
Pancreatitis
COVID-19
FIGURE 91.26 CXR. Bilateral, relatively symmetrical air space opacification with a lower zone predominance, suggestive of ARDS. Incidental pneumomediastinum and surgical emphysema were noted.
◾endothelium Within the first 7 days, the insult causes an exudative/acute phase with damage to the causing increased capillary permeability, influx of protein-rich fluid into the alveoli and interstitial layers resulting in pulmonary edema. This coincides with chest radiograph findings where there is rapid development of bilateral, symmetrical air space opacities, although within the first 24 hours following insult, the imaging can be relatively normal. The intermediate phase (proliferative) between 8 and 14 days demonstrates a more static picture with possible development of diffuse reticulation. Any new opacities in this period may reflect a new infective process or complication. After 15 days, the lungs undergo a late (fibrotic) phase in which the chest radiograph returns to near normal, or a residual fibrotic picture develops.
◾ ◾
CT is increasingly used to further assess the nature of opacification and demonstrates an anteroposterior gradient in the acute phase, where the dependent component of the lungs shows dense consolidation owing to the increased weight of the overlying lung causing passive atelectasis (Fig. 91.27).
FIGURE 91.27 CT. Classic appearances of ARDS with a generalized anteroposterior gradient of ground glass change with more dense consolidation seen dependently. Pneumomediastinum is also seen (asterisk).
Ground glass opacification is noted within the more anterior component of the lung, likely a reflection of the degree of edema in the alveoli and interstitium. Bronchial dilatation can also be seen in the background of ground-glass opacification. CT in the late phase can either show complete resolution or reversal of the pathological distribution that is seen in the acute phase, with fibrosis in the nondependent lung. The reticulation and ground glass opacification in the anterior part is probably due to the barotrauma from mechanical ventilation and the protective effect of the consolidated dependent lung, during the acute period [46,47]. CT is valuable for the detection of complications not clearly delineated by the chest radiograph, particularly loculated pneumothoraces, abscesses, empyema, and mediastinal collections. In addition, CT may aid decisions regarding mode of ventilation support, including recruitment of dependent nonaerated lung by turning the patient prone and in assessing long term sequelae of ARDS on the lungs. Complications include pneumomediastinum (Fig. 91.27), pneumothorax, and subcutaneous emphysema, in addition to pulmonary interstitial emphysema Air may also track into the peritoneum and retroperitoneum. The development of barotrauma is usually related to large tidal volumes, high inflationary pressures and the presence of pre-existing lung disease. Usually,
air leak is initially into the lung interstitium, and although this is frequently difficult to detect, if present is almost always the precursor of pneumothorax and pneumomediastinum.
Summary Imaging of the chest in the acute setting is a challenging task, not only due to the multiple and complex anatomical systems that can be visualized on a single image as well as the endless pathology that can present but also due to the many different imaging modalities and techniques, each with their own benefits and risks. It is up to the clinical team to assess the patient initially and come to some understanding of what the patient may be experiencing, and then to request the appropriate scans. It is the radiologist’s job to ensure that the correct imaging modality is performed, with the correct protocol and parameters to ensure a timely, accurate diagnosis. The radiographers, sonographers, imaging assistants, etc., must all work together to obtain the best possible images for interpretations and diagnosis, a task that can be challenging in itself given the clinical state a lot of these severely injured patients can be in. Finally, interpretation and reporting of the scans must be to a standard where it is clear to the referring physician what the diagnosis or diagnoses are, and in what order of urgency they must be managed. With a systematic approach and thorough understanding of the imaging findings and various pathology that is commonly seen in the acute setting, the radiologist can be one of the most vital people in the management of acutely unwell patients, and with more practice, research and understanding, better imaging can be performed, findings reported, and outcomes can be achieved for the patient.
Suggested Readings • A Kumaresh, M Kumar, B Dev, R Gorantla, SP Venkata, V Thanasekaraan, Back to basics – ‘must know’ classical signs in thoracic radiology, J Clin Image Sci 5 (2015) 43. • The use of imaging in COVID-19—results of a global survey by the International Society of Radiology [48]. • Imaging in acute chest pain—Eur J Radiol [49].
References [1] L Lança, A Silva, Digital imaging systems for plain radiography digital radiography detectors: a technical overview [cited 2021 Jan 5], http://www.springerlink.com/content/j355771202272g70/.
[2] Focused assessment with sonography in trauma (FAST): practice essentials, technique, preparation [Internet] [cited 2021 Jan 5], https://emedicine.medscape.com/article/104363-overview. [3] JB Soriano, PJ Kendrick, KR Paulson, V Gupta, EM Abrams, RA Adedoyin, et al., Prevalence and attributable health burden of chronic respiratory diseases, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017, Lancet Respir Med 8 (6) (2020 Jun 1) 585–596, [Internet] [cited 2021 Jan 19]. http://ghdx.healthdata.org. [4] W Hinton, A McGovern, R Coyle, TS Han, P Sharma, A Correa, et al., Incidence and prevalence of cardiovascular disease in English primary care: A cross-sectional and follow-up study of the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC), BMJ Open 8 (8) (2018 Aug 1) 20282, [Internet] [cited 2021 Jan 19]. http://bmjopen.bmj.com/. [5] Cardiovascular diseases (CVDs) [Internet] [cited 2021 Jan 19], https://www.who.int/en/news-room/factsheets/detail/cardiovascular-diseases-(cvds). [6] B Langevin, M Saleh, Radiological presentation of pneumocystis jiroveci pneumonia mimicking bacterial pneumonia, BMJ Case Rep, 2016, bcr2016215207, [Internet] [cited 2021 Jan 19]. http://group.bmj.com/group/rights-licensing/permissions. [7] I Kuhajda, K Zarogoulidis, K Tsirgogianni, D Tsavlis, I Kioumis, C Kosmidis, et al., Lung abscess-etiology, diagnostic and treatment options, Ann Transl Med, 2015, 183, [Internet] [cited 2021 Jan 19]/pmc/articles/PMC4543327/?report=abstract. [8] Empyema imaging: practice essentials, radiography, computed tomography [Internet] [cited 2021 Jan 19], https://emedicine.medscape.com/article/355892-overview. [9] KR Shen, A Bribriesco, T Crabtree, C Denlinger, J Eby, P Eiken, et al., The American Association for Thoracic Surgery consensus guidelines for the management of empyema, J Thorac Cardiovasc Surg 153 (6) (2017 Jun 1) e129–e146. 10.1016/j.jtcvs.2017.01.030. [Internet] [cited 2021 Jan 19]. [10] DD Stark, MP Federle, PC Goodman, AE Podrasky, WR Webb, Differentiating lung abscess and empyema: radiography and computed tomography (1983) [Internet] [cited 2021 Jan 19, www.ajronline.org [11] CT findings of septic pulmonary embolism in a 28-year-old male intravenous drug user | Eurorad [Internet] [cited 2021 Jan 19], https://www.eurorad.org/case/16404. [12] https://covid19.who.int/.
[13] J Cleverley, J Piper, MM Jones, The role of chest radiography in confirming COVID-19 pneumonia, BMJ (2020) 370. [14] MB Malas, IN Naazie, N Elsayed, A Mathlouthi, R Marmor, B Clary, Thromboembolism risk of COVID-19 is high and associated with a higher risk of mortality: a systematic review and metaanalysis, EClinicalMedicine (2020 Dec 1) 29–30. 10.1016/j.eclinm.2020.100639. [Internet] [cited 2021 Jan 19]. [15] A Bernheim, X Mei, M Huang, Y Yang, ZA Fayad, N Zhang, et al., Chest CT findings in coronavirus disease 2019 (COVID-19): relationship to duration of infection, Radiology, 2020, 685–691. 10.1148/radiol.2020200463. [Internet] [cited 2021 Jan 22]. [16] M Kreuter, V Cottin, The threat in chronic lung diseases: acute exacerbations, Eur Respir Soc, 2017, [Internet] [cited 2021 Jan 20]. http://ow.ly/il2130eDMKl. [17] BA Rangelov, AL Young, J Jacob, AP Cahn, S Lee, FJ Wilson, et al., Thoracic imaging at exacerbation of chronic obstructive pulmonary disease: a systematic review, Int J COPD, 2020, 1751– 1787, [Internet] [cited 2021 Jan 20]/pmc/articles/PMC7385406/? report=abstract. [18] Noncardiogenic pulmonary edema imaging: practice essentials, radiography, computed tomography [Internet] [cited 2021 Jan 20], https://emedicine.medscape.com/article/360932-overview. [19] N Tsuchiya, L Griffin, H Yabuuchi, S Kawanami, J Shinzato, S Murayama, Imaging findings of pulmonary edema: part 1. cardiogenic pulmonary edema and acute respiratory distress syndrome, Acta Radiol, 2020, 184–194, [Internet] [cited 2021 Jan 20]. http://journals.sagepub.com/doi/10.1177/0284185119857433. [20] CC Blackmore, WC Black, RV Dallas, HC Crow, Pleural fluid volume estimation: a chest radiograph prediction rule, Acad Radiol 3 (2) (1996) 103–109, [Internet] [cited 2021 Jan 20]. https://pubmed.ncbi.nlm.nih.gov/8796649/. [21] K Ichikado, M Suga, NL Müller, H Taniguchi, Y Kondoh, M Akira, et al., Acute interstitial pneumonia: comparison of highresolution computed tomography findings between survivors and nonsurvivors, Am J Respir Crit Care Med 165 (11) (2002 Jun 1) 1551–1556, [Internet] [cited 2021 Jan 20]. http://www.atsjournals.org/doi/abs/10.1164/rccm.2106157. [22] A Bonaccorsi, A Cancellieri, M Chilosi, R Trisolini, M Boaron, N Crimi, et al., Acute interstitial pneumonia: report of a series, Eur Respir J 21 (1) (2003 Jan 1) 187–191, [Internet] [cited 2021 Jan 20]. https://erj.ersjournals.com/content/21/1/187.
[23] K Ashizawa, K Hayashi, N Aso, K Minami, Lobar atelectasis: diagnostic pitfalls on chest radiography, British J Radiol 74 (877) (2001 Jan 28) 89–97, [Internet] [cited 2021 Jan 20]. http://www.birpublications.org/doi/10.1259/bjr.74.877.740089. [24] M Riedel, Diagnosing pulmonary embolism, The fellowship of postgraduate medicine, 2004, 309–319, [Internet] [cited 2021 Jan 20]. http://pmj.bmj.com/. [25] Pulmonary embolism | Health topics A to Z | CKS | NICE [Internet] [cited 2021 Jan 20], https://cks.nice.org.uk/topics/pulmonary-embolism/. [26] Modified PIOPED criteria used in clinical practice - PubMed [Internet] [cited 2021 May 26], https://pubmed.ncbi.nlm.nih.gov/7658212/. [27] P Patel, P Patel, M Bhatt, C Braun, H Begum, W Wiercioch, et al., Systematic review and meta-analysis of test accuracy for the diagnosis of suspected pulmonary embolism, Blood Adv, 2020, 4296–4311, [Internet] [cited 2021 Jan 21]. http://ashpublications.org/bloodadvances/articlepdf/4/18/4296/1757997/advancesadv2019001052cr1.pdf. [28] A Otrakji, SR Digumarthy, R .l.o Gullo, EJ Flores, JA.O Shepard, MK Kalra, Dual-energy CT: spectrum of thoracic abnormalities, Radiographics 36 (1) (2016 Jan 1) 38–52, [Internet] [cited 2021 Jan 21],. www.rsna.org/education/search/RG. [29] AJ.E Moore, J Wachsmann, MR Chamarthy, L Panjikaran, Y Tanabe, P Rajiah, Imaging of acute pulmonary embolism: An update, CDT, 2018, 225–243, [Internet] [cited 2021 Jan 21]/pmc/articles/PMC6039809/?report=abstract. [30] MC Olson, HV Posniak, V McDonald, R Wisniewski, R Moncada, Computed tomography and magnetic resonance imaging of the pericardium, Radiographics 9 (4) (1989 Jul 1) 633–649, [Internet] [cited 2021 Jan 21]. https://pubs.rsna.org/doi/abs/10.1148/radiographics.9.4.2756190. [31] T Valente, G Rossi, F Lassandro, G Rea, M Marino, M Muto, et al., MDCT Evaluation of Acute Aortic Syndrome (AAS), BJR, 2016, [Internet] [cited 2021 Jan 22]/pmc/articles/PMC4985458/? report=abstract. [32] CA Nienaber, The role of imaging in acute aortic syndromes, Eur Heart J—Cardiovasc Imag 14 (1) (2013 Jan 1) 15–23, [Internet] [cited 2021 Jan 22]. https://academic.oup.com/ehjcimaging/articlelookup/doi/10.1093/ehjci/jes215. [33] V Vardhanabhuti, E Nicol, G Morgan-Hughes, CA Roobottom, G Roditi, MC.K Hamilton, et al., Recommendations for accurate CT
diagnosis of suspected acute aortic syndrome (AAS)—on behalf of the British Society of Cardiovascular Imaging (BSCI)/British Society of Cardiovascular CT (BSCCT), British J Radiol 89 (1061) (2016) 20150705, [Internet] May 7 [cited 2021 Jan 24]. http://www.birpublications.org/doi/10.1259/bjr.20150705. [34] K Spanos, T Kölbel, AD Giannoukas, Current trends in aortic intramural hematoma management—a shift from conservative to a more aggressive treatment, Ann Cardiothorac Sur 8 (4) (2019) 49799, [Internet] [cited 2021 Jan 24]–49499. https://www.annalscts.com/article/view/16631/html. [35] KK Maddu, W Shuaib, J Telleria, J-O Johnson, F Khosa, Nontraumatic acute aortic emergencies: part 1, acute aortic syndrome, Am J Roentgenol 202 (3) (2014 Mar 20) 656–665, [Internet] [cited 2021 Jan 25]. http://www.ajronline.org/doi/10.2214/AJR.13.11437. [36] TM Grist, GD Rubin, Imaging of Acute Aortic Syndromes, 2019, 207–214, [Internet] [cited 2021 Jan 24]. https://www.ncbi.nlm.nih.gov/books/NBK553865/. [37] NG Baikoussis, EE Apostolakis, Penetrating atherosclerotic ulcer of the thoracic aorta: diagnosis and treatment, Hellenic J Cardiol 51 (2010). [38] H Majeed, F Ahmad, Mycotic aneurysm, StatPearls, 2020, [Internet] [cited 2021 Jan 25]. http://www.ncbi.nlm.nih.gov/pubmed/32809571. [39] TK.M Wang, B Griffin, P Cremer, N Shrestha, S Gordon, G Pettersson, et al., Diagnostic utility of CT and MRI for mycotic aneurysms: a meta-analysis, Am J Roentgenol 215 (5) (2020 Nov 1) 1257–1266, [Internet] [cited 2021 Jan 25]. https://www.ajronline.org/doi/10.2214/AJR.19.22722. [40] KM Olsen, S Manouchehr-pour, EF Donnelly, TS Henry, MF Berry, PM Boiselle, et al., ACR appropriateness criteria® hemoptysis, J Am College Radiol 17 (5) (2020 May 1) S148–S159. 10.1016/j.jacr.2020.01.043. [Internet] [cited 2021 May 26]. [41] N Quigley, S Gagnon, Fo.r.t.i.n. .M Aetiology, Diagnosis and treatment of moderate-to-severe haemoptysis in a North American academic centre, ERJ Open Res 6 (4) (2020 Oct), [Internet] [cited 2021 May 26]00204–2020. https://pubmed.ncbi.nlm.nih.gov/ 33123556/. [42] A Contegiacomo, A del Ciello, R Rella, N Attempati, D Coppolino, AR Larici, et al., Pulmonary arteriovenous malformations: what the interventional radiologist needs to know,
Radiologia Medica 124 (10) (2019 Oct 1) 973–988, [Internet] [cited 2021 May 26]. https://europepmc.org/article/med/31209790. [43] PE Andersen, PM Tørring, S Duvnjak, O Gerke, H Nissen, AD Kjeldsen, Pulmonary arteriovenous malformations: a radiological and clinical investigation of 136 patients with long-term follow-up, Clin Radiol 73 (11) (2018 Nov 1) 951–957, [Internet] [cited 2021 May 26]. https://pubmed.ncbi.nlm.nih.gov/30086858/. [44] D AlNuaimi, R AlKetbi, U AlBastaki, C Pierre-Jerome, E Ahmad Ebrahim, Pulmonary venous varix associated with mitral regurgitation mimicking a mediastinal mass: a case report and review of the literature, Radiol Case Rep 13 (2) (2018 Apr 1) 404– 407, [Internet] [cited 2021 May 26]/pmc/articles/PMC6000197/. [45] SL Primack, RR Miller, NL Muller, Diffuse Pulmonary Hemorrhage: Clinical, Pathologic, and Imaging Features, AJR Am J Roentgenol, 1995, 295–300, [Internet] [cited 2021 May 26]. https://pubmed.ncbi.nlm.nih.gov/7839958/. [46] P Cardinal-Fernandez, JA Lorente, A Ballen-Barragan, G Matute-Bello, Acute respiratory distress syndrome and diffuse alveolar damage new insights on a complex relationship, Ann Am Thorac Soc, 2017, 844–850, [Internet] [cited 2021 May 26]. https://pubmed.ncbi.nlm.nih.gov/28570160/. [47] ND Ferguson, E Fan, L Camporota, M Antonelli, A Anzueto, R Beale, et al., The Berlin definition of ARDS: An expanded rationale, justification, and supplementary material, Intensive Care Med 38 (10) (2012) 1573–1582, [Internet] [cited 2021 May 26]. https://pubmed.ncbi.nlm.nih.gov/22926653/. [48] I Blažić, B Brkljačić, G Frija, The use of imaging in COVID-19 —results of a global survey by the International Society of Radiology, Eur Radiol 31 (3) (2021 Mar 1) 1185–1193. 10.1007/s00330-020-07252-3. [Internet] [cited 2021 Jun 7]. [49] C Fink, Imaging in acute chest pain, Eur J Radiol, 2012, 3661– 3662, [Internet] [cited 2021 Jun 7]. http://www.ejradiology.com/article/S0720048X11006036/fulltext.
The acute abdomen is the assigned diagnosis for acute or rapidly developing abdominal pain for which immediate (usually surgical) intervention/action is required until a specific diagnosis for the cause of the abdominal pain is found [1]. They account for 4–5% of accident and emergency (A&E) presentations [2]. Patients presenting to the A&E department will initially have a careful history taken by the attending physician as well as a meticulous physical examination. Based on these initial findings, the physician will consider imaging examinations to help establish the correct diagnosis. Causes of “the acute abdomen” can be broadly divided into “traumatic” and “nontraumatic.” For the purposes of this chapter, we will only be discussing “nontraumatic” hepatopancreaticobiliary and gastrointestinal causes and their relevant imaging approach. More detailed descriptions are present in the individual chapters. Note that certain pathologies (e.g., pelvic or renal pathologies) are not covered in this chapter; these are covered in detail in other chapters elsewhere in the book. The causes of “the acute abdomen” or acute abdominal pain as such range from the life-threatening to benign self-limiting disorders (Fig. 92.1). The patient will often present with vague abdominal symptoms and signs, making imaging crucial in diagnosis, risk stratification, and for guiding further management.
FIGURE 92.1 Acute abdomen: differential diagnosis by abdominopelvic region.
Conventional x-rays, ultrasonography (USG), and multidetector computed tomography (MDCT) are commonly used in the diagnostic work-up of patients with an acute abdomen.
Chest and Abdominal X-Rays (CXR and AXR) An erect CXR has traditionally been used to exclude subphrenic air and hence a perforated viscus, and a supine abdominal x-ray to exclude bowel obstruction. However, the accuracy of these tests in investigating patients with acute abdominal pain may be as low as 53% [3]. Most patients will go on to have further detailed imaging in the form of an USG or more commonly a contrast-enhanced CT (CECT) which has been found to be much more accurate. However, despite this lack of evidence, patients presenting to the emergency with acute abdominal pain will often have CXR and AXR as part of their work-up.
Ultrasonography
USG is used in the work-up of acute abdominal pain often when the patient is young and/or radiation exposure is an issue (e.g., pregnancy). It is often the first technique of choice when trying to establish or exclude a diagnosis of biliary colic/acute cholecystitis and acute appendicitis in a young patient. USG is also useful at investigating a point of maximal tenderness in the abdomen, hence often yielding the diagnosis versus clinical evaluation of that point of tenderness.
Multidetector Computed Tomography The use of CECT in the evaluation of acute abdominal pain is now common practice and is regarded as the gold standard [4]. Although noncontrast CT may be an alternative [3], contrast administration improves accuracy. The exact CECT protocol used is decided by the reporting radiologist, but there is a consensus that portal venous phase imaging with an approximate delay of 70 seconds is recommended when imaging the abdomen for suspected GI/HPB causes of the abdominal pain [2,5]. Oral or rectal contrast medium (CM) is of little benefit when imaging patients with severe abdominal pain, as it delays the study, and the lack of contrast within the bowel loops does not appear to alter CT accuracy [6].
Magnetic Resonance Imaging (MRI) Despite its lack of ionizing radiation and superior contrast resolution [7], MRI is not widely used in the acute abdominal setting due to the longer time taken. Patient co-operation and lack of motion are also difficult in acutely ill patients. Hence, the use of MRI in evaluating the acute abdomen is typically reserved for pregnant or pediatric patients where the radiation dose is an issue.
Hepatobiliary There is a myriad of hepatobiliary causes for the acute abdomen ranging from acute cholecystitis to a hemorrhagic neoplasm. Imaging is key, as clinical examination and laboratory evaluation alone seldom reveals a specific diagnosis. CECT or USG are used in initial assessment, but the diagnosis may need further clarification with a nonurgent hepatobiliary MRI.
Gallbladder and Billiary System
Inflammation/Infection Acute Cholecystitis One of the most common causes of acute abdomen, 90% of cases are secondary to gallstones [8], the other 10% are due to severe illness or injury (acalculous cholecystitis), the latter having a worse prognosis. Approximately 40% of patients with acute cholecystitis develop complications, discussed ahead pictorially.
Imaging features
◾theUSGsonographic is the technique of choice in initial assessment (Fig. 92.2) and allows assessment for Murphy’s sign, a reliable indicator of acute cholecystitis with a sensitivity of 92% [9]. USG and CT are less accurate for diagnosing acalculous cholecystitis compared with calculous cholecystitis. Gallbladder wall thickening in the presence of gallstones has a positive predictive value of 95% for the diagnosis of acute cholecystitis [9]. It is important to note that gallbladder wall thickening without tenderness may also be seen incidentally in conditions such as hypoalbuminemic states, hepatitis, and liver, renal, or heart failure, presumably due to raised portal or systemic venous pressures. The clinical picture will help differentiate.
Sonographic signs of acute cholecystitis include gallbladder wall thickening (>3 mm) or edema, gallbladder distension (>40 mm), and pericholecystic and perihepatic fluid (Fig. 92.3). Acute cholecystitis on CT is associated with pericholecystic inflammatory fat stranding and fluid; hypo or hyperdense gallstones and gallbladder fossa edema (Fig. 92.4). Complications of acute cholecystitis are better investigated with CT. Emphysematous cholecystitis is a serious complication typically diagnosed on CT by the presence of intraluminal or intramural gas, which could be mistaken for calculi on USG or MRI (Fig. 92.5). It is more commonly seen in diabetics and is usually associated with gasforming organisms such as Clostridium Welchi. Gangrenous cholecystitis can occur in upto 39% of patients with acute calculous cholecystitis [10] and is associated with higher morbidity and mortality than uncomplicated cholecystitis. CECT findings of a poorly enhancing gallbladder wall, striated and reduced mural enhancement, and a pericholecystic abscess have been described with a specificity of approximately 90% in gangrenous cholecystitis [11]. Gangrenous cholecystitis can lead to perforation, usually at the fundus of the gallbladder [12] (Fig. 92.6). The three subtypes of gallbladder perforation include localized perforation, those that result in a cholecystoenteric fistula, and perforation with free intraperitoneal spillage and possibly loculated biloma formation. Despite the increased sensitivity of CT in detecting gallbladder perforation, a mural discontinuity is still only detected in 70% of cases [12].
◾ ◾ ◾ ◾ ◾
FIGURE 92.2 Imaging algorithm for the investigation of RUQ/epigastric pain.
FIGURE 92.3 Dependent echogenic foci within the gallbladder lumen with posterior acoustic shadowing are typical USG appearances for gallstones.
FIGURE 92.4 (A) Isodense gallstone in enhancing, thick-walled gallbladder with surrounding fat stranding in keeping with acute calculous cholecystitis. (B) Axial CT in another patient demonstrates
hyperdense gallstones in the gallbladder with associated pericholecytsic fluid.
FIGURE 92.5 Intraluminal and intramural gas within inflamed gallbladder in keeping with emphysematous cholecystitis.
FIGURE 92.6 Gangrenous cholecystitis with wall which is poorly enhancing and has a perforation at its fundus.
Gallstone Ileus This is diagnosed by the observation of Rigler’s triad, which comprises of pneumobilia, an ectopic gallstone, and bowel obstruction (Fig. 92.7). CT is the technique of choice to demonstrate these signs as well as the cholecystoduodenal fistula and the level of small bowel obstruction. The culprit gallstone is usually larger than 2.5 cm. Bouveret’s syndrome is a rare condition that results from the impaction of a discharged gallstone in the gastroduodenal junction, leading to gastric outlet obstruction.
FIGURE 92.7 Intraluminal air within the gallbladder (arrow in A) in keeping with pneumobilia secondary to choleduodenal fistula as a result of the cholecystitis. Ectopic gallstone in distal ileum (arrow in B) causing proximal small bowel dilatation/obstruction.
Mirizzi Syndrome This results from an impacted gallstone in the neck of the gallbladder or cystic duct causing extrinsic compression of the biliary tree and resultant upstream intrahepatic biliary tree dilatation, in the context of a normal caliber CBD. These features are best demonstrated by magnetic resonance cholangiopancreatography (MRCP) (Fig. 92.8), although CECT can also be informative. A cholecystocholedochal fistula may form due to recurrent inflammation around the impacted gallstone in the cystic duct. Preoperative imaging can be extremely informative in this scenario as its presence and exact anatomy may warn the surgeon to perform an open cholecystectomy.
FIGURE 92.8 Axial T2w (A) and coronal T2w (B) sequences show a large gallstone in the gallbladder neck causing extrinsic compression of the CBD at the hilum and resultant mild upstream biliary dilatation.
Biliary tree obstruction and ascending cholangitis:
◾theBiliary obstruction is highlighted by intrahepatic biliary dilatation with a transition point at site of obstruction. The most common cause of biliary obstruction is choledocholithiasis; other etiologies include benign or malignant biliary strictures and parasitic disease (Table 92.1). Biliary obstruction and its investigation is usually prompted by a clinically jaundiced patient with deranged cholestatic serum liver function tests. Initial assessment with a trans-abdominal USG can reliably detect biliary duct dilatation, where a cut off of 6 mm for a normal caliber common bile duct in a patient with no previous cholecystectomy can be used to evaluate biliary tree dilatation, as well as an intrahepatic bile duct caliber of 2 mm [13]. Trans-abdominal USG is however not as sensitive at detecting CBD stones [14]. CT is also good for demonstrating the biliary tree dilatation and the level of obstruction, but is poor at identifying choledocholithiasis (only 20% stones are high attenuation) [15]. MRCP is the investigation of choice when evaluating the biliary tree in obstructive jaundice. Biliary obstruction secondary to benign and malignant strictures does not necessarily occur acutely, but patients may present to the emergency department with obstructive jaundice and complicating cholangitis. Benign strictures are much less common than malignant ones, are often located at the hepatic hilum, and are usually iatrogenic or postoperative in etiology (e.g., postlaparoscopic cholecystectomy or postliver transplantation). Patients are usually asymptomatic but can occasionally present acutely. Biliary obstruction and subsequent stasis of bile within the biliary tree allows bacteremia to spread up from the duodenum [16] resulting in ascending cholangitis, which has a high mortality and usually requires urgent decompression, either percutaneously or endoscopically. Imaging allows the level of obstruction to be established and helps identify potential complications such as parenchymal abscess and portal vein thrombosis [17]. Ascending cholangitis presents with an obstructed, dilated biliary tree along with smooth ductal wall thickening and enhancement (Fig. 92.9). Associated parenchymal inflammatory changes result in patchy and peribiliary parenchymal enhancement and wedge-shaped
◾ ◾
◾
segments of hypoattenuation on CECT, representing inflamed parenchyma. In acute suppurative cholangitis, purulent dense material may be seen in the dilated biliary tree on CT [12] and will appear low signal relative to liver on T2-weighted MRI and intermediate on T1-weighted MRI [18]. Associated cholangitic abscesses may also be seen [19].
Table 92.1 Causes of Biliary Obstruction Malignant Strictures
Benign Strictures
Cholangiocarcinoma
Primary sclerosing cholangitis
Carcinoma of the gallbladder
IgG4-related disease
Ampullary carcinoma
Mirizzi syndrome
Lymphoma
Recurrent pyogenic cholangitis
Intrabiliary metastasis
HIV cholangiopathy
Sclerosing cholangitis induced by chemotherapy
FIGURE 92.9 Cholangitis with cholangitic abscess formation. Note the enhancement along the CBD wall (arrow).
Liver Acute Hepatitis Acute hepatitis is usually secondary to a systemic infection by a viral agent. Probably the most important role of radiology in these patients is to rule out other diseases. At CT and MR imaging, findings in acute hepatitis are nonspecific and include hepatomegaly (Fig. 92.10) and periportal edema with heterogenous enhancement of the liver parenchyma. Extra-hepatic findings include gallbladder wall edema and ascites.
FIGURE 92.10 (A) Axial CT image demonstrates hepatomegaly in acute hepatitis secondary to hepatic steatosis. (B) Coronal MRCP projection of a different patient with hepatitis demonstrates periportal (arrow) and gall bladder wall edema (dotted arrow). MRCP, magnetic resonance cholangiopancreatography.
◾abdominal PVT can be seen in many conditions including cirrhosis, abdominal tumors, and intrainflammatory processes such as diverticulitis and appendicitis. PVT can be bland or tumoral (Table 92.2). ◾which Chronic PVT can result in the development of numerous periportal collateral vessels, appear as a mass of veins in the porta hepatis. This is known as cavernous transformation and can occur 6–20 days after acute PVT [20]. These cavernomas and varices can cause secondary biliopathy due to the development of an ischemic stricture [21]. PVT occurring secondary to infectious causes such as diverticulitis or appendicitis can present in a nonspecific manner clinically with fever, rigors, leukocytosis, and generalized abdominal pain. CECT becomes the investigation of choice to make the diagnosis. The imaging features include portal venous gas and low attenuation portal vein thrombus on the contrast-enhanced scan (Fig. 92.11). Occasionally acute thrombus can be seen as a hyperattenuating density on a noncontrast CT. Secondary ancillary imaging findings may also include periportal edema and hepatic abscesses [22]. Other causes of portal venous gas include bowel ischemia (most common) due to arterial or venous mesenteric thrombosis or intestinal obstruction [23]. Typically, peripheral branching air at CT helps differentiate portal venous gas from pneumobilia, which is typically more central.
◾ ◾
FIGURE 92.11 Noncontrast (A) and CECT (B) images demonstrate a hyperattenuating nonenhancing bland portal vein thrombus (arrows) with secondary perfusional abnormalities diffusely involving the liver.
Table 92.2 Imaging Features of Tumor Thrombus [18–20] - US: Vascularity on color Doppler - CT: Enhancement and expansion of portal vein on CECT Enhancement and attenuation of thrombus similar to that of the tumor - MRI: Similar SI to that of tumor Restricted diffusion on DWI
Hepatic Vein Thrombosis and Budd–Chiari Syndrome Budd–Chiari syndrome (BCS) results from hepatic venous outflow obstruction at the level of the hepatic veins or at the junction of the IVC and right atrium [24] (Fig. 92.12). BCS can be primary, with an endoluminal
lesion such as a thrombus or web resulting in hepatic venous outflow obstruction, or secondary due to extrinsic compression by an adjacent mass.
FIGURE 92.12 Thrombus in IVC and right hepatic vein (RHV) resulting in heterogenous enhancement of the liver.
Imaging features for BCS vary based on the extent and duration of the disease, but typically on Doppler USG there is absent, turbulent, or reversed flow in the hepatic veins, as well as hepatofugal flow in the portal vein [25]. CECT and CEMR are the investigations of choice in BCS [26]. In the arterial phase, differential contrast enhancement between the central and peripheral liver is usually seen, whereas in the portal venous phase there is washout in the central portion with increased peripheral hepatic parenchymal enhancement, known as the “flip-flop” pattern [27].
Pancreas Acute Pancreatitis Epidemiology Acute pancreatitis is a condition that carries significant morbidity and mortality. It is the commonest pancreatic disease worldwide with no
difference in incidence between genders [29]. The mortality rate ranges from 1 to 60 deaths per 100,000 people/year [29]. Alcohol-related pancreatitis is more prevalent in the Western world and Japan and has risen in parts of Asia. Pathophysiology A trigger such as gallstones or excess ethanol intake results in an insult to pancreatic acinar cells, resulting in the release of digestive enzymes and causing an inflammatory cytokine cascade, which can in severe cases cause a systemic inflammatory response syndrome [30].
Diagnostic Criteria: The revised Atlanta classification requires two or more conditions to be met for the diagnosis of acute pancreatitis:
◾ Abdominal pain ◾ amylase or lipase level >3x upper limit of normal value ◾ Serum Typical imaging findings [31].
Use of Imaging Modalities in Acute Pancreatitis: CECT is the imaging technique of choice for the assessment of acute pancreatitis and its complications (Fig. 92.13). A single portal venous phase is generally sufficient for this purpose, although supplementary arterial phase imaging can be helpful to assess for vascular complications. MRI is a good alternative (especially in cases of renal failure or contrast allergy) (Figs. 92.14 and 92.15). USG is an excellent technique for the detection of gallbladder calculi, besides being quick and inexpensive. The major drawback, however, is that the pancreas/peripancreatic tissues are often obscured by bowel gas [32].
FIGURE 92.13 Imaging algorithm for pancreatitis according to RCR guidelines.
FIGURE 92.14 Acute gallstone pancreatitis. T2W coronal (A) and axial (B) demonstrate edematous body and tail of the pancreas with peripancreatic fluid and fat stranding. A calculus can be seen in the distal CBD (arrow).
FIGURE 92.15 Acute hemorrhagic pancreatitis. Peripancreatic inflammatory stranding surrounding the body and tail of pancreas. The T1-weighted image (A) demonstrates low-signal changes (white arrows) demonstrating interstitial edema. Focal high-signal change is also visible within the gland (black arrow) in keeping with hemorrhagic change. Corresponding area is marked with an arrow on the T2weighted sequence (B).
Imaging can be performed at least 72 hours after the onset of symptoms, which allows time for complications to develop and any pancreatic necrosis to evolve. In the early phase of acute pancreatitis there can often be a mismatch between imaging findings and severity of disease, with a reduced sensitivity for the detection of necrotizing pancreatitis. However, imaging studies may be performed at an earlier stage in the disease to assess for an underlying treatable etiology such as calculi, or pancreatic malignancy [31]. If imaging is performed at least a week after the onset of symptoms, it allows more time for complications to develop and any pancreatic necrosis should be readily demonstrable. Imaging is used in the later stages of the disease course for identification of complications, monitoring of existing collections, and guiding interventional procedures [32]. MRI can be very useful for the identification and follow-up of pancreatitis-related complications, for example, in distinguishing solid from liquid components or debris within collections, when this may be more difficult to ascertain on CT. This can then guide management, for example, drainage or surgery, and may ascertain the reason for the failure of drainage in an acute necrotic collection (ANC) or walledoff necrosis (WON) which has a high proportion of solid material. In this instance, the drain may require upsizing or necrosectomy may be opted for. To apply the relevant nomenclature when reporting imaging studies using the Atlanta classification, it should be noted that the first day of onset of acute pancreatitis coincides with the first day the patient experiences pain and not when they first seek medical help.
Acute pancreatitis is split into early (7 days) phases. Patients whose clinical course terminates within the early phase and who do not present with local complications or features of organ failure are classed as having mild acute pancreatitis with very low mortality rates. Patients with a clinical course lasting beyond 7 days with local complications and transient organ failure lasting 48 hours. Imaging Characteristics of Acute Pancreatitis
◾(IEP) Acute pancreatitis can be divided into two categories: interstitial edematous pancreatitis and necrotizing pancreatitis (Figs. 92.16 and 92.17). In IEP, the pancreatic parenchyma can enhance homogenously or show areas of reduced enhancement, due to interstitial edema. There is often enlargement of the gland and surrounding inflammatory change, small volume free fluid, and occasionally, peripancreatic fluid collections. Necrotizing pancreatitis makes up 5–10% of cases of acute pancreatitis and can be pancreatic only, peripancreatic only, or combined pancreatic and peripancreatic. It is important to note that not all pancreatitis-related collections are solely composed of fluid and may contain nonliquefied components such as fat. The phrase “pancreatic abscess” has fallen out of favor and should no longer be used in reporting terminology. Similarly, “acute pseudocyst” should not be used as a general term to describe any pancreatitis-related collection, because not all are solely composed of fluid. The Atlanta classification groups collections according to time scale (4 weeks being the cut-off) into acute peripancreatic fluid collections (APFC), ANC, pseudocyst, and WON (Fig. 92.18). Collections containing nonliquefied components, whether fat or soft tissue (even if in small quantities), are considered necrotic). An uncommon complication of acute pancreatitis is disconnection of the main pancreatic duct, due to ductal necrosis. The pancreatic segment upstream of the necrosis becomes isolated from the duodenum. A persistent end-fistula results, with continuous leakage of pancreatic secretions into peripancreatic tissues. Recognition of this entity may avoid the need for unnecessary conservative drainage procedures which are unlikely to be effective. The key sign of a disconnected duct is an intraparenchymal focus of necrosis or collection, with a viable segment of parenchyma upstream (Fig. 92.19). The upstream duct may or may not be dilated. A confident diagnosis of disconnected duct requires: (1) necrosis of ≥20 mm of pancreas, (2) viable upstream pancreatic tissue, (3) extravasation of contrast injected into the main pancreatic duct at ERCP [33]. Pancreatitis-related collections can become infected. On imaging, gas within a collection is the only definitive finding suggestive of this. It is also important to exclude fistulous communication with a hollow viscus and any previous intervention (sampling or drainage) (Fig. 92.20). The presence of wall enhancement implies that a collection has matured/organized and is seen in both pseudocysts and WON. Therefore, it is not a reliable marker of infection [44]. Pseudoaneurysms are another important but potentially treatable complication of acute pancreatitis, usually seen in arteries adjacent to the pancreas such as the splenic artery, gastroduodenal artery, or its branches (Fig. 92.20). This is explained in more detail in the section on splenic artery pseudoaneurysm section.
◾ ◾
◾
Key Points: Acute Pancreatitis
◾firstDayday1 ofthethepatient presentation of acute pancreatitis corresponds to the experiences pain. ◾
◾3 Imaging for acute pancreatitis should be performed a minimum of days to over a week after the onset of symptoms, which increases the sensitivity of detection of complications (particularly pancreatic necrosis). The phrases “pancreatic abscess” and “acute pseudocyst” can be misleading and should be avoided. In the early phase ≤4 weeks, pancreatitis-related collections are classified as either APFC or ANC, according to absence/presence of nonliquid components. In the late phase > 4 weeks, pancreatitisrelated collections are classified either as pseudocysts or WON, according to absence/presence of nonliquid components. Disconnected duct is an important, uncommon complication. Identification can obviate the need for ineffective conservative drainage measures. The presence of gas in a collection is the only reliable sign of infection. Other causes should be excluded before this diagnosis, e.g., fistula with a hollow viscus, prior intervention. Wall enhancement is seen in both pseudocyst and WON and is not a reliable indicator of infection.
◾ ◾ ◾ ◾
FIGURE 92.16 Decision tree for reporting according to the revised Atlanta classification. Taken from Radiographics: Revised Atlanta classification for Acute Pancreatitis: A Pictorial Essay (2019).
FIGURE 92.17 (A and B) Axial noncontrast and contrast CT images of acute peripancreatic fluid collection. Two weeks post onset of abdominal pain. Fluid attenuation collection adjacent to the pancreatic head and uncinate process with no discernible wall. (C) Acute necrotic collection. Two days after onset of abdominal pain. A large proportion of the pancreatic parenchyma is replaced by necrotic fluid and there is no discernible wall. There are intervening areas of intact parenchyma.
FIGURE 92.18 (A) Pseudocyst. Four weeks postonset of abdominal pain. Large peripancreatic fluid attenuation collection. There are no solid-appearing components or fat globules. (B) Walled-off necrosis. Study was performed 2 months after initial presentation. Areas of fat density can be seen interspersed amongst the peripancreatic fluid collections, which are well organized with enhancing walls.
FIGURE 92.19 Developing WON. This patient is also at risk of a disconnected pancreatic duct. There are interdigitating areas of intact pancreatic parenchyma. Fat globules are also visible. The collection is beginning to organize with the development of an enhancing wall anteriorly, although this is incomplete toward the tail of pancreas.
FIGURE 92.20 (A) Gas-containing pancreatic peripancreatic collection (solid arrow). Patient with acute pancreatitis presented with signs of sepsis, 2 weeks after start of symptoms. A calcified gall stone is also seen (dotted arrow). (B) Status day 8 of acute pancreatitis in another patient. Axial CECT image reveals hemorrhage into a pseudocyst. A pseudoaneurysm is visible (arrow) and there is dependent contrast material, indicating active bleeding. (C and D) Celiac axis digital subtraction angiogram. The bleeding point is identified in the superior pancreaticoduodenal artery (SPA), arising from the gastroduodenal artery (GDA) (arrow). The second image demonstrates coils placed across the GDA and SPA, achieving homeostasis.
What to Include in the Radiology Report
◾ Necrosis (present or absent)? Location ◾ % of gland involved ◾ Complications? Location(s) ◾ Evidence of disconnected duct? ◾ Fluid-containing collection? Or, nonliquefied component? ◾ Rim-enhancing/walled collection? Any gas? ◾ Subtype of pancreatitis? (IEP or necrotizing) ◾ Name type of collection(s) (according to Atlanta classification) ◾ Mention use of Atlanta classification
Spleen Albeit infrequent, it is important to recognize some key splenic emergencies, especially given that the spleen is a highly vascular organ and prone to severe hemorrhage. As with acute pancreatitis, CT is the primary technique for assessment of splenic emergencies, with USG used in follow-up to assess for evolution and is limited in primary assessment [34,35].
Splenic Infarction Splenic infarction can arise as a result of an interruption to the inflow of blood to the spleen (arterial supply), congestion of the internal splenic circulation, or reduced venous outflow, resulting in indirect impedance to inflow via increased hydrostatic pressure (see Table 92.3) [36–38]. In the early stages of splenic ischemia, the affected area is edematous due to the inflammatory insult, giving rise to poorly demarcated areas of reduced attenuation/hypoechogenicity. With time, the edema evolves into well-
defined wedge-shaped areas of lower hypoattenuation/hypoechogenicity (Fig. 92.21). Chronic changes include volume loss in the affected area and calcification [34,35]. Table 92.3 Causes of Splenic Infarction Inflow Disruption
Intrinsic Splenic Circulatory Disruption
Outflow Disruption
Splenic artery thrombus/embolus Vasculitides
Hemoglobinopathies, for example, sickle cell anemia Lymphoproliferative disorders Vasculitides Hypercoagulable states, for example, factor V Leiden mutation, malignancy
Splenic vein thrombosis Hypercoag ulable states Pancreatiti s Portal hypertensi on
FIGURE 92.21 Splenic infarction (arrow).
Splenic Venous and Arterial Thrombosis Splenic venous thrombosis is a fairly common sequela of pancreatic cancer, and less commonly pancreatitis [34]. Splenic artery thrombosis, on the other hand, is a relatively rare entity. Complete arterial occlusion (Fig. 92.22) can result in infarction of the entire spleen, but preserved capsular enhancement, as the splenic capsule is supplied by the short gastric arteries [39].
FIGURE 92.22 Splenic artery occlusion. Axial precontrast (A), arterial (B), and delayed (C) phase acquisitions. Precontrast phase image demonstrates heavy calcific atheromatous disease of the splenic artery. No splenic artery opacification is evident in the arterial phase, with absence of the typical “zebra” pattern of splenic parenchymal enhancement. The delayed phase image demonstrates lack of splenic enhancement, consistent with ischemic change.
Splenic Artery Aneurysm Most are detected incidentally and are asymptomatic, with a quoted prevalence ranging between 0.2% and 10.4%. The etiology is unclear but associated with hypertension, cirrhosis, portal hypertension, pregnancy, and liver transplant. The rate of rupture is reported at around 2–3% and patients will present with a combination of sudden left upper quadrant abdominal pain, hypovolemic shock and gastrointestinal hemorrhage. Most splenic artery aneurysms are small, often 7 mm) extending from the cecum. The echogenic lining represents the mucosa and the low echogenic band surrounding it is the muscular layer.
FIGURE 92.27 CECT in a young patient with abdominal pain and fever. The appendix is distended and measures >7 mm with radioopaque appendicolith (solid arrow) (A), thickening of its wall and surrounding fluid (B) and (C) small air locule outside the appendix (dashed arrow) in keeping with perforated appendicitis.
Diverticulitis Pathophysiology and Clinical Features Diverticulitis is inflammation of colonic diverticula, which are acquired herniation of mucosa and submucosa through the muscular layers of the colon. The simple outpouching of diverticula through the colonic wall without inflammation is called diverticulosis. Diverticula are small saccular outpouchings of the colon and measure 0.5–1 cm. The pathophysiology of the diverticuli is related to increased pressure in the lumen of the colon with herniation of mucosa and submucosa at the site of vasa recta perforation of the colonic wall which are its weak points. The diverticuli are not composed of whole layers of the colonic wall and are therefore pseudodiverticuli rather than true diverticuli. Fecal impaction at the neck of the diverticulum causes inflammation of the diverticulum and can lead to perforation. The most important cause of increased pressure is a low fiber diet and processed food. Diverticulitis is therefore the most common colonic disease in the Western world [65]. Diverticulitis is more common in patients over 50 years old but can also happen in younger patients. Approximately 30% of patients with diverticulosis will develop diverticulitis. The most common site of diverticulosis and diverticulitis is the sigmoid colon. This is related to its relatively small diameter and the fact that stools reaching this level are dehydrated and harder, which causes increased luminal pressure [66]. Patients with diverticulitis usually present with left lower quadrant colicky abdominal pain and a tender palpable mass. The patient can have fever, altered bowel habits, and elevated leukocyte count on blood tests.
Imaging Features
◾colon Unlike assessment for appendicitis, USG is not the best imaging technique to assess the [67] (Fig. 92.28). However, the radiologist may occasionally see colonic wall thickening and round to oval hyper or hypoechoic foci protruding from the colonic wall, with increased echogenicity of the pericolic fat when there is associated pericolic inflammation. The best imaging technique to assess diverticulitis is CECT, which has been shown to be more than 95% accurate [68]. Additional oral or rectal contrast may be used to increase diagnostic confidence, but is usually not needed to reach the diagnosis. Studies have shown that administration of rectal water-soluble contrast slowly does not expose the patient to increased risk of perforation but yields similar sensitivity and specificity when used on its own compared to MDCT with intravenous and oral contrast [69]. In diverticulosis, the colon is usually thick-walled (4–15 mm thickness) with multiple outpouchings which are air-filled, fluid-filled, or contrast-filled depending on the colonic content. In diverticulitis, the colonic wall is thickened usually over a long segment (>10 cm length), with pericolic fat stranding and engorged pericolonic vessels (Fig. 92.29A and B). Often there is also a small amount of fluid tracking along the mesosigmoid. Occasionally, there is an arrowhead-shaped focal colonic wall thickening due to mural edema at the site of the inflamed diverticula, called the “arrowhead sign” and specific of colonic diverticulitis. In complicated diverticulitis (Fig. 92.29C), the inflammation can be complicated by perforation and pericolic or intra-abdominal abscess, sinus formation, or fistula. Usually, the inflammation is limited to the pericolic area. However, in severe cases, the infection can extend and spread to the venous drainage of the colon with air or thrombus in the portal vein or its tributaries and subsequent liver abscess. Usually, when there is severe diverticulitis with perforation, the omentum acts as a barrier to the spread of infection and covers the site of perforation. Less commonly, when this fails, there is free intra-peritoneal air and diffuse peritonitis [68]. Sometimes inflammatory colon cancer can mimic diverticulitis but usually involves a shorter segment and demonstrates asymmetrical colonic wall thickening. Metastatic lymphadenopathy and distant metastases can help make the diagnosis [65]. Epiploic appendagitis is another differential, but usually presents as a fat density ovoid lesion adjacent to the colon with a thin high-density rim (hyperattenuating rim sign) and often a central hyperdense dot representing a thrombosed vessel (Fig. 92.30). The treatment of acute diverticulitis is usually centered on antibiotics with intravenous fluid and bowel rest and radiological percutaneous drainage if there is an abscess. Surgery is usually delayed and done if there are recurrent episodes of diverticulitis or complicated diverticulitis [70].
◾ ◾ ◾ ◾ ◾ ◾
FIGURE 92.28 Imaging algorithm for appendicitis and diverticulitis.
FIGURE 92.29 Axial (A) and coronal (B) CECT images of an elderly patient presenting with acute abdominal pain. There is thickening of the wall of the descending colon centered around a diverticula with perifocal fat stranding in keeping with acute diverticulitis. (C) Complicated diverticulitis in another patent. CECT image of the pelvis shows a large abscess (asterisk) in close relation to the edematous sigmoid colon with diverticulae (arrow).
FIGURE 92.30 Axial CECT demonstrates an ovoid fat density lesion adjacent to the colon (arrow) with a high-density rim (hyperattenuating rim sign), consistent with epiploic appendagitis.
Inflammatory and Infectious Eneterocolitis
◾chronic. Colitis is a nonspecific term that means inflammation of the colon. It can be acute or The presentation in acute colitis is similar with acute abdominal pain and changes
in bowel habits. We will discuss here only acute colitis and related imaging features. The most common acute causes of colitis are inflammatory (ulcerative colitis and Crohn’s disease) or infectious colitis. The pathophysiology of inflammatory colitis is discussed in detail in the chapter on bowel imaging and is not covered here. The most common presenting symptoms are diarrhea, acute/chronic abdominal pain, weight loss, and fever [71]. Imaging modalities to evaluate Crohn’s disease involve fluoroscopy with oral barium, USG, CECT, and MRI. Fluoroscopy examination is not done in the acute setting and has been largely superseded by CT/MRI, and is not discussed here. USG may help evaluate small bowel loops close to the anterior abdominal wall and the terminal ileum, but provides a limited view, especially in obese patients. The typical imaging findings are mural thickening with submucosal edema and increased vascularity on Doppler. More recently, contrast enhanced USG has been shown to be useful in assess the bowel wall microvascularization, and can be useful in the early diagnosis and follow-up of Crohn’s disease [72]. CECT is usually the investigation performed at presentation. The typical imaging features in the acute flares of Crohn’s are discontinuous asymmetric wall thickening of the small bowel loops and/or colon with avidly enhancing mucosa related to vascular congestion, lowdensity submucosal odema, and soft tissue density of the muscularis propria and serosa giving the appearances of target sign (Fig. 92.31A). There is often associated mesenteric fat stranding, hypertrophy, and enlarged mesenteric lymphnodes [73]. The best imaging technique to assess Crohn’s disease in a nonacute state is MRI with oral and intravenous contrast for better assessment of the small bowel loops (Fig. 92.31B). Imaging features are similar to CT, but MRI is better at evaluating complications which include fistulas, sinuses, and abscesses. Ulcerative colitis involves the mucosa and submucosa but spares the muscularis propria; fistula or sinus tracts are therefore not formed. CT demonstrates a loss of normal colonic haustrations, an enhancing mucosa with a lower density submucosa, and pericolic inflammatory fat stranding [74]. Imaging features of both entities may overlap and therefore the diagnosis is usually confirmed with colonoscopy and biopsy. Treatment includes immunosuppressors and antibiotics in the acute setting. Infectious colitis is usually suspected clinically; imaging does not play a major role in diagnosis. Patients can present with varied symptoms including fever, crampy abdominal pain, and diarrhea. Causes include bacterial, viral, and parasitic infections. A particular condition is Clostridium difficile related colitis (pseudomembranous colitis), related to longterm treatment with broad-spectrum antibiotics with selective overgrowth of the C. difficile bacteria [75]. In atypical or complex presentations, imaging findings could help the clinicians reach a diagnosis. Radiographs and USG have limited utility; CECT has the highest yield. The imaging features are nonspecific and include colonic wall thickening with enhancement of the mucosal and submucosal layers (Fig. 92.32). In severe infection there is rarely inflammatory changes involving the pericolic fat with stranding and enlarged lymphnodes. Imaging can help narrow down the causative agent by identifying the segment of colon involved by the infectious process. E. coli or cytomegalovirus involves the whole colon, Yersinia or Salmonella affect the ascending colon, and Shigella or shistosomiasis more commonly involve the descending colon. Gastroenteritis usually presents with vomiting with or without diarrhea and demonstrates fluid-filled small bowel loops on imaging; bowel thickening, enhancement and associated fat stranding are less common. The diagnosis is usually clinical rather than based on radiology.
◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾
FIGURE 92.31 Axial CECT (A) in a patient with acute abdominal pain and change in bowel habits. CT demonstrates enhancement, mesenteric fat stranding and thickening of the distal and terminal ileum with the typical target sign (arrow). T1 FS CE-MRI (B) in a different patient showing multi-focal bowel wall edema, mucosal enhancement (arrows) and vascular congestion (dotted arrow).
FIGURE 92.32 Axial (A) and coronal (B). MDCT images in an elderly patient with infectious colitis involving the descending colon. There is thickening of the colonic wall with enhancement of the mucosa (white arrows) compared to normal ascending colon (arrowhead). MDCT, multidetector computed tomography.
Ischemic Bowel Pathophysiology and Clinical Presentation Acute intestinal ischemia is a true emergency and a challenging diagnosis with high morbidity and mortality, which can be overlooked by the emergency clinician. The etiology of ischemic bowel can be related to an
arterial obstruction (approximately 60–70%), venous occlusion (5–10%) or decreased mesenteric flow secondary to a low-flow rate like cardiac arrest (20–30%) [76]. The ischemic bowel follows different pathological stages which starts with reversible ischemia and culminates in irreversible infarction, which carries a high mortality rate. The disease is most common in patients above 50 years of age. Patients usually present with severe acute abdominal pain out of proportion with the clinical findings. Other symptomas include nausea, vomiting, and decreased bowel sounds. Imaging Features
◾small Abdominal radiographs are nonspecific and are often normal early on or only demonstrate bowel or colonic distension with air-fluid levels. In advanced infarction, air can be seen tracking into the bowel wall (“pneumatosis intestinalis”) or free air under the diaphragm seen when bowel perforates. USG is of limited use but Doppler can be used to assess the degree of stenosis or obsruction of arterial vessels. The best imaging technique for bowel ischemia is CECT [77]. It demonstrates the clot in the arterial or venous supply as filling defects, and the ischemic changes in the bowel. In arterial and low flow rate ischemic disease, hyperdense mucosa is first seen which is related to submucosal inflammation and hemorrhage (Fig. 92.33). The disease progresses to bowel distension with thinning of the wall and lack of enhancement The ultimate stage is infarction of the wall with air locules tracking into the submucosa and muscularis (pneumatosis intestinalis) and finally perforation of the bowel with air in the peritoneal cavity. In venous infarcion the clot in the mesenteric veins can be seen as a filling defect on the MDCT scan. There are engorged mesenteric vessels, pronounced bowel wall thickening, and dense mucosa from increased back-pressure in the bowel capillaries.
◾ ◾
FIGURE 92.33 Ischemic bowel disease. Axial and coronal reconstructions of arterial phase study showing filling defect in the proximal SMA (solid arrow) with edematous changes in the hepatic flexure and transverse colon (dotted arrows).
Small Bowel Obstruction Versus Ileus
◾question The differentiation between small bowel obstruction and ileus is a commonly encountered in the acute setting as these entities require different management. The radiologist plays a key role in differentiating these entities. Radiographs and USG do not play a significant role, with MDCT being imaging technique of choice. The normal small bowel caliber usually ranges up to 3 cm in diameter. If the small bowel exceeds 3 cm and the patient has abnormal bowel sounds, an obstruction or ileus should be suspected. Ileus is the absence of movement of the bowel with no obstructive lesion. Ileus can be generalized involving the whole small bowel or localized involving a focal area of small bowel. The most common causes are postsurgical, infection and sepsis, metabolic, and post-traumatic. On MDCT there is distension of the bowel with involvement of most of the bowel including the terminal ileum with the absence of focal change in caliber (“transition point”) [78]. In small bowel obstruction there is distension of the bowel which extends up to a segment of bowel that changes suddenly in caliber (“transition point”) (Fig. 92.34) [79], which is the site of the diseased bowel and the cause of the obstruction. The cause of obstruction are varied and most commonly are related to external compression by tumors, peirtoneal fibrous bands, focal segment of bowel inflammation, and fibrosis in the context of Crohn’s disease.
◾ ◾
FIGURE 92.34 CECT in a middle-age man with acute abdominal obstruction. The coronal images (A) demonstrates complete collapse of the terminal ileum (arrowhead) and markedly distended proximal small bowel (dashed arrow). There are two focal areas of sudden narrowing (“transition points”) seen on the axial image (B) in keeping with obstruction (solid arrows). On surgery, the obstruction was caused by a fibrous band crossing two segments of small bowel and causing obstruction (also called closed loop).
Volvulus A volvulus is the pathological torsion of a segment of the colon or small bowel around the axis of its mesentery. It leads to acute obstruction and abdominal pain. The small bowel and colon can be involved, the most common sites being the sigmoid colon and cecum [80]. Abdominal
radiographs are usually performed initially but are less sensitive and specific than MDCT which confirms the diagnosis and identifies complications. On radiographs, there is dilatation of a segment of the colon with loss of haustration. In sigmoid volvulus the dilated colonic segment is in the midline and has an inverted U shape with its upper part directed toward the right hemidiaphragm. In cecal volvulus, there is a dilated segment of the colon in the left abdomen with its tip pointed to the left hemidiaphragm. On MDCT, there is progressive tapering of the afferent and efferent loops of the colon leading to the volvulus which resemble beaks (called “beaking”). The twisting of the colon leads to twisting of the mesentery and accompanying vessels (“whirl sign”). If the colon remains twisted, it can lead to ischemia, infarction and perforation, which can be also assessed with MDCT [81].
Conclusion Imaging plays a crucial role in the management of patients with nontraumatic acute abdominal pain. CECT remains the primary imaging technique and gives invaluable diagnostic information. USG may also serve as an initial diagnostic test, particularly for evaluation of the gallbladder or the abdomen as a whole in pediatric or pregnant patients, when the radiation from CECT is an issue. MRI is becoming used more frequently in select patient populations, but is not always suitable for the acutely unwell patient and has limited variable availability out of normal working hours.
Suggested Readings • J Stoker, A Van Randen, W Laméris, MA Boermeester, Imaging patients with acute abdominal pain, Radiology 253 (2009) 31–46. • NG Ditkofsky, A Singh, L Avery, RA Novelline, The role of emergency MRI in the setting of acute abdominal pain, Emerg Radiol 21 (2014) 615–624. • RM Gore, The acute abdomen. Radiol Clin North Am 53 (6) (2015) 1093–1348.
References 1 RF. Martin, R Rossi, The acute abdomen : an overview and algorithm, Surg Clin North Am (77) (1997) 1227–1243. 2 J Stoker, A Van Randen, W Laméris, MA Boermeester, Imaging patients with acute abdominal pain, Radiology 253 (2009). 3 AB MacKersie, MJ Lane, R Gerhardt, et al., Nontraumatic acute abdominal pain: unenhanced helical CT compared with three- view acute abdominal series, Radiology 237 (1) (2005) 114–122.
4 E Sala, CJ.E Watson, C Beadsmoore, T Groot-Wassink, TR Fanshawe, JC Smith, et al., A randomized, controlled trial of routine early abdominal computed tomography in patients presenting with non-specific acute abdominal pain, Clin Radiol 62 (10) (2007). 5 BA Urban, EK Fishman, Tailored helical CT evaluation of acute abdomen, Radiographics 20 (2000). 6 LN Huynh, BF Coughlin, J Wolfe, F Blank, SY Lee, HA Smithline, Patient encounter time intervals in the evaluation of emergency department patients requiring abdominopelvic CT: oral contrast versus no contrast, Emerg Radiol 10 (6) (2004). 7 NG Ditkofsky, A Singh, L Avery, RA Novelline, The role of emergency MRI in the setting of acute abdominal pain, Emerg Radiol 21 (6) (2014). 8 Y Kimura, T Takada, Y Kawarada, Y Nimura, K Hirata, M Sekimoto, et al., Definitions, pathophysiology, and epidemiology of acute cholangitis and cholecystitis: Tokyo Guidelines, J Hepatobiliary Pancreat Surg (2007). 9 PW Ralls, PM Colletti, SA Lapin, P Chandrasoma, WD Boswell, C Ngo, et al., Real-time sonography in suspected acute cholecystitis. Prospective evaluation of primary and secondary signs, Radiology (1985). 10 SP Fagan, SS Awad, K Rahwan, K Hira, N Aoki, KM.F Itani, et al., Prognostic factors for the development of gangrenous cholecystitis, Am J Surg (2003). 11 GL Bennett, H Rusinek, V Lisi, GM Israel, GA Krinsky, CM Slywotzky, et al., CT findings in acute gangrenous cholecystitis, Am J Roentgenol (2002). 12 OJ O’Connor, MM Maher, Imaging of cholecystitis, American J Roentgenol (2011). 13 K Skoczylas, A Pawełas, Ultrasound imaging of the liver and bile ducts—expectations of a clinician, J Ultrason (2015). 14 PL Cooperberg, D Li, P Wong, Accuracy of common hepatic duct size in the evaluation of extrahepatic biliary obstruction, Radiology (1980). 15 FH Miller, CM Hwang, H Gabriel, LA Goodhartz, AJ Omar, WG Parsons, Contrast-enhanced helical CT of choledocholithiasis, Am J Roentgenol (2003). 16 JY Sung, JW Costerton, EA Shaffer, Defense system in the biliary tract against bacterial infection, Digestive Diseases Sci (1992). 17 OJ O’Connor, S O’Neill, MM Maher, Imaging of biliary tract disease, American J Roentgenol (2011).
18 K Håkansson, O Ekberg, HO Håkansson, P Leander, MR characteristics of acute cholangitis, Acta radiol (2002). 19 J Hoon Lim, K Won Kim, D Choi, Biliary tract and gallbladder, CT and MRI of the Whole Body, 2009. 20 AM De Gaetano, M Lafortune, H Patriquin, A De Franco, B Aubin, K Paradis, Cavernous transformation of the portal vein: patterns of intrahepatic and splanchnic collateral circulation detected with Doppler sonography, Am J Roentgenol (1995). 21 Y Liu, B Hou, R Chen, H Jin, X Zhong, W Ye, et al., Biliary collateral veins and associated biliary abnormalities of portal hypertensive biliopathy in patients with cavernous transformation of portal vein, Clin Imaging (2015). 22 EJ Balthazar, P Gollapudi, Septic thrombophlebitis of the mesenteric and portal veins: CT imaging, J Comput Assist Tomogr (2000). 23 C Sebastià, S Quiroga, E Espin, R Boyé, A Alvarez-Castells, M Armengol, Portomesenteric vein gas: pathologic mechanisms, CT findings, and prognosis, Radiographics (2000). 24 HL.A Janssen, JC Garcia-Pagan, E Elias, G Mentha, A Hadengue, DC Valla, Budd-Chiari syndrome: a review by an expert panel, J Hepatol (2003). 25 P Millener, EG Grant, S Rose, A Duerinckx, VL Schiller, FN Tessler, et al., Color Doppler imaging findings in patients with Budd-Chiari syndrome: correlation with venographic findings, Am J Roentgenol (1993). 26 SA Faraoun, ME.A Boudjella, N Debzi, N Afredj, Y Guerrache, N Benidir, et al., Budd–Chiari syndrome: a prospective analysis of hepatic vein obstruction on ultrasonography, multidetector-row computed tomography and MR imaging, Abdom Imaging (2015). 27 G Brancatelli, V Vilgrain, MP Federle, A Hakime, R Lagalla, R Iannaccone, et al., Budd-Chiari syndrome: spectrum of imaging findings, American J Roentgenol (2007). 28 E Pareja, M Cortes, R Navarro, F Sanjuan, R López, J Mir, Vascular complications after orthotopic liver transplantation: Hepatic artery thrombosis, Transplant Proc (2010). 29 AY Xiao, ML Tan, LM Wu, V Asrani, Global incidence and mortality of pancreatic diseases: a systematic review, meta-analysis, and meta-regression of population-based cohort studies, Lancet Gastroenterol Hepatol 1 (1) (2016). 30 BC Koo, A Chinogureyi, A Shaw, Imaging acute pancreatitis, Br J Radiol 83 (986) (2010) 104–112. 31 BR Foster, KK Jensen, G Bakis, AM Shaaban, FV Coakley, Revised Atlanta classification for acute pancreatitis: a pictorial
essay—erratum, RadioGraphics 39 (3) (2019) 912. 32 T Bollen, Imaging assessment of etiology and severity of acute pancreatitis, Pancreapedia Exocrine Pancreas Knowl Base 1 (2016) 1. 33 K Sandrasegaran, M Tann, SG Jennings, DD Maglinte, SD Peter, S Sherman, et al., Disconnection of the pancreatic duct: an important but overlooked complication of severe acute pancreatitis, Radiographics 27 (5) (2007) 1389–1400. 34 E Unal, MR Onur, E Akpinar, J Ahmadov, M Karcaaltincaba, MN Ozmen, et al., Imaging findings of splenic emergencies: a pictorial review, Insights Imaging 7 (2) (2016) 215–222. 35 A Alabousi, MN Patlas, M Scaglione, L Romano, JA Soto, Crosssectional imaging of nontraumatic emergencies of the spleen, Curr Probl Diagn Radiol 43 (5) (2014) 254–267. 36 F Nehme, K Rowe, A Haris, I Nassif, Spontaneous splenic infarcts in a cirrhotic patient with primary biliary cirrhosis, Case Rep Gastroenterol 11 (1) (2017 Jan) 54–58 37 F Lopez, A Mega, F Schiffman, J Sweeney, Splenic infarction from factor V Leiden mutation [3], Am J Hematol 62 (1) (1999) 62–63. 38 AC.Y Tso, DR Roper, CL Wong, B Bain, DM Layton, Splenic infarction in a patient with sickle cell trait and hereditary spherocytosis, Am J Hematol 86 (8) (2011) 695–696. 39 AJ Taylor, WJ Dodds, SJ Erickson, ET Stewart, CT of acquired abnormalities of the spleen, Am J Roentgenol 157 (6) (1991) 1213– 1219. 40 MA Abbas, WM Stone, RJ Fowl, P Gloviczki, WA Oldenburg, PC Pairolero, et al., Splenic artery aneurysms: two decades experience at Mayo Clinic, Ann Vasc Surg 16 (4) (2002) 442–449. 41 GA Agrawal, PT Johnson, EK Fishman, Splenic Artery Aneurysms and pseudoaneurysms: clinical distinctions and CT appearances, Am J Roentgenol 188 (4) (2007) 992–999. 42 M De Perrot, L Buhler, PA Schneider, G Mentha, P Morel, Do aneurysms and pseudoaneurysms of the splenic artery require different surgical strategy?, Hepatogastroenterology 46 (27) (1999) 2028–2032. 43 R Guillon, JM Garcier, A Abergel, R Mofid, V Garcia, T Chahid, et al., Management of splenic artery aneurysms and false aneurysms with endovascular treatment in 12 patients, Cardiovasc Intervent Radiol 26 (3) (2003) 256–260. 44 SP Dave, ED Reis, A Hossain, PJ Taub, MD Kerstein, LH Hollier, Splenic artery aneurysm in the 1990s, Ann Vasc Surg 14 (3) (2000) 223–229.
45 IH Huang, DA Zuckerman, JB Matthews, Occlusion of a giant splenic artery pseudoaneurysm with percutaneous thrombincollagen injection, J Vasc Surg 40 (3) (2004) 574–577. 46 JW Burke, Pseudoaneurysms complicating pancreatitis: Detection by CT, Radiology 161 (1986) 447–450. 47 K Yamaguchi, S Futagawa, M Ochi, I Sakamoto, K Hayashi, Pancreatic pseudoaneurysm converted from pseudocyst: transcatheter embolization and serial CT assessment, Radiat Med Med Imaging Radiat Oncol 18 (2) (2000) 147–150. 48 JE Roshkow, LM Sanders, Acute splenic sequestration crisis in two adults with sickle cell disease: US, CT, and MR imaging findings, Radiology 177 (3) (1990) 723–725. 49 S Gleich, DA Wolin, H Herbsman, A review of percutaneous drainage in splenic abscess, Surg Gynecol Obstet 167 (3) (1988) 211–216. 50 WS Lee, ST Choi, KK Kim, Splenic abscess: a single institution study and review of the literature, Yonsei Med 52 (2011) 288–292. 51 A Luna, R Ribes, P Caro, L Luna, E Aumente, PR Ros, MRI of focal splenic lesions without and with dynamic gadolinium enhancement, Am J Roentgenol 186 (6) (2006) 1533–1547. 52 GH Mallada, DA Baroja, A Lanas-Gimeno, AL Arbeloa, Peptic ulcer disease, Med (2020). 53 P Guniganti, CH Bradenham, C Raptis, CO Menias, VM Mellnick, CT of gastric emergencies, Radiographics (2015). 54 EK Insko, MS Levine, BA Birnbaum, JE Jacobs, Benign and malignant lesions of the stomach: Evaluation of CT criteria for differentiation, Radiology (2003). 55 KM Horton, EK Fishman, Current role of CT in imaging of the stomach, Radiographics (2003). [56] F Dixon, A Singh, Acute appendicitis, Surgery (Oxf) 38 (2020). 10.1016/j.mpsur.2020.03.015. [57] MM Horrow, DS White, JC Horrow, Differentiation of perforated from nonperforated appendicitis at CT, Radiology 227 (1) (2003 Apr) 46–51. 10.1148/radiol.2272020223. [58] DG Addiss, N Shaffer, BS Fowler, RV Tauxe, The epidemiology of appendicitis and appendectomy in the United States, Am J Epidemiol 132 (5) (1990 Nov) 910–925. 10.1093/oxfordjournals.aje.a115734. [59] AS Doria, R Moineddin, CJ Kellenberger, M Epelman, J Beyene, S Schuh, et al., US or CT for diagnosis of appendicitis in children and adults? A meta-analysis, Radiology 241 (1) (2006 Oct) 83–94. 10.1148/radiol.2411050913.
[60] A van Randen, S Bipat, AH Zwinderman, DT Ubbink, J Stoker, MA Boermeester, Acute appendicitis: meta-analysis of diagnostic performance of CT and graded compression US related to prevalence of disease, Radiology 249 (1) (2008 Oct) 97–106. 10.1148/radiol.2483071652. [61] E Albiston, The role of radiological imaging in the diagnosis of acute appendicitis, Can J Gastroenterol 16 (7) (2002 Jul) 451–463. 10.1155/2002/623213. [62] G Mostbeck, EJ Adam, MB Nielsen, M Claudon, D Clevert, C Nicolau, et al., How to diagnose acute appendicitis: ultrasound first, Insights Imaging 7 (2) (2016 Apr) 255–263. 10.1007/s13244-0160469-6. [63] PJ Pickhardt, EM Lawrence, BD Pooler, RJ Bruce, Diagnostic performance of multidetector computed tomography for suspected acute appendicitis, Ann Intern Med 154 (12) (2011 Jun 21) 789– 796. 10.7326/0003-4819-154-12-201106210-00006. [64] A Bhangu, K Søreide, S Di Saverio, JH Assarsson, FT., Drake, Acute appendicitis: modern understanding of pathogenesis, diagnosis, and management, Lancet 386 (10000) (2015 Sep 26) 1278–1287. 10.1016/S0140-6736(15)00275-5. Erratum in: Lancet 390 (10104) (2017 Oct 14)1736. [65] NS Painter, DP Burkitt, Diverticular disease of the colon: a deficiency disease of Western civilization, Br Med J 2 (5759) (1971 May 22) 450–454. 10.1136/bmj.2.5759.450. [66] JD Feuerstein, KR Falchuk, Diverticulosis and Diverticulitis, Mayo Clin Proc 91 (8) (2016 Aug) 1094–1104. 10.1016/j.mayocp.2016.03.012. [67] JB Puylaert, Ultrasound of colon diverticulitis, Dig Dis 30 (1) (2012) 56–59. 10.1159/000336620. [68] B Sessa, M Galluzzo, S Ianniello, A Pinto, M Trinci, V Miele, Acute Perforated Diverticulitis: Assessment With Multidetector Computed Tomography, Semin Ultrasound CT MR 37 (1) (2016 Feb) 37–48. 10.1053/j.sult.2015.10.003. [69] PM Rao, JT Rhea, RA Novelline, Helical CT of appendicitis and diverticulitis, Radiol Clin North Am 37 (5) (1999 Sep) 895–910. 10.1016/s0033-8389(05)70137-8. [70] T Wilkins, K Embry, R George, Diagnosis and management of acute diverticulitis, Am Fam Physician 87 (9) (2013 May 1) 612– 620. [71] T Gramlich, RE Petras, Pathology of inflammatory bowel disease, Semin Pediatr Surg 16 (3) (2007 Aug) 154–163. 10.1053/j.sempedsurg.2007.04.005.
[72] T Ripollés, MJ Martínez-Pérez, E Blanc, F Delgado, J Vizuete, JM Paredes, et al., Contrast-enhanced ultrasound (CEUS) in Crohn’s disease: technique, image interpretation and clinical applications, Insights Imaging 2 (6) (2011 Dec) 639–652. 10.1007/s13244-011-0124-1. [73] RF Thoeni, JP Cello, CT imaging of colitis, Radiology 240 (3) (2006 Sep) 623–638. 10.1148/radiol.2403050818. [74] P Deepak, DH Bruining, Radiographical evaluation of ulcerative colitis, Gastroenterol Rep (Oxf) 2 (3) (2014 Aug) 169–177. 10.1093/gastro/gou026. [75] I Ramachandran, R Sinha, P Rodgers, Pseudomembranous colitis revisited: spectrum of imaging findings, Clin Radiol 61 (7) (2006 Jul) 535–544. 10.1016/j.crad.2006.03.009. [76] A Theodoropoulou, IE Koutroubakis, Ischemic colitis: clinical practice in diagnosis and treatment, World J Gastroenterol 14 (48) (2008 Dec 28) 7302–7308. 10.3748/wjg.14.7302. [77] C Cruz, HH Abujudeh, RM Nazarian, JH Thrall, Ischemic colitis: spectrum of CT findings, sites of involvement and severity, Emerg Radiol 22 (4) (2015 Aug) 357–365. 10.1007/s10140-0151304-y. [78] EK Paulson, WM Thompson, Review of small-bowel obstruction: the diagnosis and when to worry, Radiology 275 (2) (2015 May) 332–342. 10.1148/radiol.15131519. 79 AC Silva, M Pimenta, LS Guimarães, Small bowel obstruction: what to look for, Radiographics 29 (2) (2009 Mar-Apr) 423–439. 10.1148/rg.292085514. 80 D Gingold, Z Murrell, Management of colonic volvulus, Clin Colon Rectal Surg (2012). 81 CM Peterson, JS Anderson, AK Hara, JW Carenza, CO Menias, Volvulus of the gastrointestinal tract: appearances at multimodality imaging, Radiographics (2009).
CHAPTER 93
Introduction to Interventional Radiology Abhay Kumar Kapoor, Sanjay Baijal
Before the era of interventional radiology (IR), treatments of various disease were compartmentalized mainly into medical and surgical protocols. A large number of patients used to be refused any treatment because they were poor candidates for administration of any kind of anesthesia, or the risks of surgery were deemed too high. This necessitated the need for development of innovative techniques for percutaneous procedures as well as endoscopic procedures. The whole thought process began to use imaging to direct targeted therapies for various organ systems, leading to development of the subspeciality of therapeutic IR. Innovations have been fairly rapid in IR, starting with a new idea, use of existing tools, or development of new ones to meet the challenge and finally gain acceptance in clinical practice. The new procedures are tested against preexisting standard of care treatments with regards to outcome, cost, and safety. There are many diseases that at one point of time were thought to be incurable or had to be dealt with a major surgery with associated morbidity that are now easily managed with a minimally invasive percutaneous approach using image guidance.
History Initial angiograms were performed by surgeons through a direct cutdown [1]. Later, when radiologists started performing angiography, it was only for diagnostic purpose. This practice continued until the mid-1970s with progress to contrast studies in veins and lymphatics to perform presurgical vascular mapping [2].
The major breakthrough in IR dates back to 1953 when Swedish radiologist Sven Ivar Seldinger devised the technique for percutaneous replacement of needle by a catheter [3]. Before this, major complications were associated with vascular procedures because large-bore needles or trocars were used to gain vascular access [4]. With introduction of the Seldinger technique, catheterization became safer, and angiographic procedures were subsequently refined [2]. Charles T. Dotter popularized the use of catheters for various vascular procedures in 1963 and published his case describing dilation of atherosclerotic lesions in femoral artery with serial dilators using Seldinger’s method [5]. During this period in the early 1960s, angiographic techniques were refined and used extensively to diagnose pathologies in all organ systems [6,7]. Use of preshaped catheters came into vogue in this period, allowing pharmacoangiography [8]. With the advent of preshaped catheters, endovascular treatment of gastrointestinal bleeding was started. Initially, this was done for bleeding esophageal varices by selective infusion of vasopressin in the superior mesenteric artery [9]. Following the success in treating varices, patients with arterial and capillary or mucosal bleeding were treated by selectively infusing vasoconstrictor in the supply vessel or with embolic materials [10]. In 1974, German-born physician-scientist Andreas Grüntzig used a balloon catheter to reopen a stenosed femoral artery [11]. Grüntzig and Charles T. Dotter were nominated for the Nobel Prize in Physiology or Medicine in 1978 for balloon angioplasty to treat patients with atherosclerotic vascular disease [11]. The next landmark in IR was with the invention of balloon-expandable vascular stent by Julio Palmaz in 1990. Simultaneously during this period, selective coronary angiographies were also performed, and the technique of F. Mason Sones [12], who performed the first right coronary artery angiogram in 1958, began to be refined by radiologists [13]. However, because most radiologists were not keen on performing cardiac catheterization, the procedure was taken over by cardiologists [14]. Nonvascular interventions rapidly grew in the 1970s with procedures evolving in all organ systems. Percutaneous biliary drainage and nephrostomy were regularly used for various indications. The self-expanding metal stent for biliary use was devised by Cesare Gianturco in 1985 [15] and made a big impact on the treatment of patients with malignant biliary obstruction. The Hybrid Gianturco expandable stent was later devised by Sumit Roy and Sanjay S. Baijal in 1994 [16], and its use in the clinical setting of urethral stricture and Budd-Chiari syndrome was reported in 1995 and 1996, respectively [17,18]. Likewise, drainage of various abscesses percutaneously made a major impact on patient treatment [19,20].
Neurointerventions started in 1927 when the Portuguese physician and neurologist Egas Moniz at the University of Lisbon introduced cerebral angiography by direct puncture of the carotid artery [21]. However, the use of the modality remained limited to diagnostic angiographies until Luessenhop and Spence described endovascular embolization of cerebral arteriovenous malformation in 1960 [22]. Further progress happened in 1970 when Pierre Lasjuanias described the cerebral vascular microanatomy and Fedor Serbinenko developed a technique to treat patients with intracranial aneurysms and carotid cavernous sinus fistulas using detachable balloons [23] The 1980s saw the advent of endovascular stroke management as described by Zeumer and Theron [24,25]. Early 1990 saw the introduction of Gugliemi detachable coils, and by the end of the decade, endovascular coiling was a well-established option used to treat cerebral aneurysms [26]. In the 2000s, advanced techniques such as balloon-assisted coiling, stentassisted coiling, flow diversion, and Onyx embolization made remarkable improvements in the outcomes of neurointerventions [27]. Significant technologic advances in the past two decades in the field of imaging equipment and medical hardware have led to a large increase in the diseases treated by IR. The newer procedures added to the list included transjugular intrahepatic portosystemic shunt (TIPS), uterine artery embolization, stent graft placement, ablative techniques to treat tumors and transarterial therapies (transarterial chemoembolization), transarterial radioembolization, and chemoinfusion to selectively treat primary and metastatic liver tumors [4].
Preprocedure Checklists Before any needle-based procedure, it is very important to evaluate the patient’s coagulation profile. Consensus guidelines regarding periprocedural management for percutaneous image-guided interventions published by the Society of Interventional Radiology (SIR) [28,29] clearly define the various requirements. These guidelines are endorsed by the Canadian Association for Interventional Radiology and the Cardiovascular and Interventional Radiological Society of Europe.
Systemic Disease Evaluation 1. Chronic liver disease (CLD): It is difficult to assess the hemostasis in patients with CLD because the prothrombin time (PT) and international normalized ratio (INR) and partial thromboplastin time evaluate any decrease in procoagulant factors without assessing the effect of concomitant decrease in natural anticoagulants because both are synthesized by the liver [28]. Similarly, although the platelet count is reduced because of multiple factors, the adhesive function of these platelets is actually enhanced [28].
2. Chronic kidney disease (CKD): Higher bleeding rates are associated with CKD because of abnormal platelet–endothelial interaction and anemia. Another important point to be considered is the bioavailability of many anticoagulant agents, including low-molecularweight heparin (LMWH), fondaparinux, and direct oral anticoagulants, requiring prolonged stoppage time before any elective procedure. 3. Cancer: Because patients with cancer are at increased risk of venous and arterial thromboembolism, many of them receive some form of anticoagulation. It is very important to elicit this history and stop the medication before the procedure.
Preprocedure Tests SIR guidelines have discussed the need for laboratory tests depending on the risk category of the procedure. Accordingly, procedures have been categorized into high risk or low risk for bleeding. High-risk procedures have been defined as the ones having a greater than 1.5% rate of bleeding or the bleeding maybe occurring at sites where it will be difficult to diagnose or treat (e.g., lung parenchyma or within the abdomen) [29]. Low-risk procedures are the ones expected to rarely bleed (rate of 29 mm), right ventricular or right atrial enlargement or hypertrophy, PA wall calcification, and leftward bowing of the interventricular septum. BA hypertrophy is seen secondary to interruption of the native PA supply. Parenchymal signs include lower lobe subpleural bandlike, linear, or wedge-shaped opacities that represent the sequelae of pulmonary infarction. Mosaic attenuation is often seen and manifests as sharply demarcated regions of normal lung attenuation alternating with regions of decreased lung attenuation, findings caused by differences in vascular perfusion [132–134]. Fibrosing mediastinitis is a benign but sometimes progressive disorder characterized by infiltrative fibrous tissue in the mediastinum. The two types are nongranulomatous and granulomatous. ⚬ Nongranulomatous fibrosing mediastinitis usually occurs in association with autoimmune disorders or radiation therapy or as a reaction to drugs such as methysergide. ⚬ Granulomatous fibrosing mediastinitis can be caused by infections such as tuberculosis, cryptococcosis, and aspergillosis and as an idiosyncratic reaction to histoplasma antigens.
◾
The most common imaging appearance is a focal soft tissue mass that distorts and narrows adjacent structures. There often is dense or stippled calcification within the mass. Ipsilateral BA dilation is seen when fibrous tissue critically encases and narrows a PA as a physiologic response to decreased blood flow to the lung [135–140].
◾conditions Chronic or acute inflammation: The bronchial circulation often dilates in patients with inflammatory that affect the lungs and airways. It is thought that vasculitis and thrombosis of pulmonary vessels may occur in response to airway or parenchymal inflammation and infection. Angiogenic growth factors such as vascular endothelial growth factor are postulated to promote collateral supply and neovascularity, with proliferation and expansion of the BAs.
The most common inflammatory lung and airway disorders associated with BA dilation include tuberculosis and nontuberculous mycobacterial infections, cystic
fibrosis and other causes of bronchiectasis, mycetoma, and chronic fungal infections. Patients may be asymptomatic or may present with life-threatening hemoptysis resulting from BA hypertrophy, dilation, and eventual rupture. The characteristic CT appearance of mycetoma is a solid round or oval gravitydependent mass within a cavity. There frequently is a crescent of air separating the mass from the cavity wall, a finding termed the “air crescent” sign. In patients who present with hemoptysis and mycetoma, the radiologist should search for hypertrophied BAs to provide a vascular road map for the interventionalist before BA embolization [141–144]. Frequently, necrotic squamous cell cancer is the most common cause of massive hemoptysis in adults older than 40 years with neovascularity, destruction of parenchyma by the tumor, and angioinvasion. CT demonstrates abnormal BA or, rarely, active contrast agent extravasation as the source [145,146].
Bronchial Artery Embolization Technique [147–156] Bronchial artery embolization has become an established procedure in the management of massive and recurrent hemoptysis; its use was first reported in 1973 by Remy et al [147,148]. Angiography Angiography and intervention are performed under either moderate sedation or general anesthesia, as dictated by the clinical presentation and status of the patient. Standard common femoral arterial access predominates, although brachial artery access may be necessary to address extraordinarily difficult NBSA contributions. All arteriography should be performed with either low-osmolar or iso-osmolar nonionic contrast material because high-osmolar contrast has been implicated in transverse myelitis. Prior multiphasic CTA is used to evaluate the number and site of origin of BAs. It is also useful in the detection of NBSA that supply parenchymal lesions. Catheterization: The most commonly used catheters to select the BAs are Cobra, Mikaelson, Simmons, or Judkins right catheters. The usefulness of a microcatheter for selective BAE has been emphasized in many recent articles. This superselective catheterization permits stabilization of the catheter position within the BA and safe positioning in the bronchial circulation beyond the origin of spinal cord branches,
which prevents severe complications. After catheterization of the BA, bronchial angiography is performed with manual injection of contrast medium. Angiographic Findings: Angiographic findings in patients with massive hemoptysis include hypertrophic and tortuous BAs (Fig. 95.35), neovascularity, hypervascularity, and parenchymal blush (Fig. 95.36) shunting into the PA or pulmonary vein, extravasation of contrast medium, and BA aneurysm. Although extravasation of contrast medium is considered a specific sign of bronchial bleeding, this finding is rarely seen, and its reported prevalence ranges from 3.6% to 10.7%. Thus, the determination of which arteries are to be embolized should be based on a combination of CT, bronchoscopic, and angiographic findings with clinical correlation. All angiograms, including intercostal arteriograms, must be carefully scrutinized for opacification of spinal arteries to avoid inadvertent embolization.
FIGURE 95.35 Flush aortogram of the descending thoracic aorta showing hypertrophied right bronchial artery (yellow arrow).
FIGURE 95.36 Selective angiogram of right bronchial artery showing a hypertrophied and torturous bronchial artery with abnormal parenchymal blush (yellow arrow).
Embolic Materials: A variety of embolic materials are used for BAE. Therefore, there is no consensus on which embolic material is best; as of now, absorbable gelatin sponge particles or polyvinyl alcohol (PVA) particles are most widely used because they are inexpensive and easy to handle and can be controlled with regard to embolic size.
◾handle Gelatin sponge: Absorbable gelatin sponge is widely used because it is inexpensive and easy to and has a controllable embolic size. However, disadvantages of absorbable gelatin sponges
are their resolvability and lack of radiopacity. Their use may lead to recanalization of the embolized artery and may sometimes be responsible for recurrent bleeding. PVA: PVA particles are nonabsorbable embolic materials, and particles 350 to 500 μm in diameter are the most frequently used worldwide. Their use may prevent the early recurrence of hemoptysis caused by recanalization of the embolized artery, as might be anticipated with absorbable gelatin sponge. It is essential to avoid the use of embolic materials that can pass through the bronchopulmonary anastomosis. In addition, it is important to avoid using embolic agents that produce distal occlusion to such an extent that normal peripheral branches that supply the bronchi, esophagus, or vasa vasorum of the PA or aorta become occluded, possibly leading to disastrous complications (e.g., bronchial, esophageal, PA, or aortic wall necrosis). To avoid the complications indicated earlier, we recommend the use of polyvinyl alcohol particles with a diameter of 350 to 500 μm for BAE (Fig. 95.37). Microspheres: Microspheres (e.g., Embosphere Microspheres, BioSphere Medical) are composed of cross-linked gelatin and have been used successfully, in particular for the embolization of uterine fibroids. Because of their smoothly spherical shape and hydrophilic nature, they are less prone to clumping and are more uniform in size than their PVA counterpart. In a recent study, BAE with 500to 700-μm microspheres achieved short-term clinical success comparable to PVA particles [152,153,157].
◾
◾
FIGURE 95.37 Cessation of the flow in the right bronchial artery (yellow arrow) after polyvinyl alcohol particle embolization.
In a recent study conducted by Kucukay et al., the technical success rate was 100%. The clinical success rate for preventing massive hemoptysis was 91.9% (160 of 174). There were no procedure-related mortality or morbidities. Minor complications such as chest pain were observed in 9 patients (5.0%). Recurrent hemoptysis (8.1%) was observed within 6 months in 14 patients, 10 of whom were treated with a second embolization session and the remaining 4 with a total of three embolization sessions. The authors concluded that BAE for massive hemoptysis with Embosphere particles 700 to 900 μm in size is a safe and effective
method with high technical and clinical success rates [158]. Long-term results are excellent [153,158].
◾System, Liquid embolic agents: N-butyl-2-cyanoacrylate (NBCA; e.g., TruFill n-BCA Liquid Embolic Johnson & Johnson/DePuy) and ethylene vinyl alcohol polymer (Onyx Liquid Embolic System, eV3 Neurovascular) for BAE have been infrequently reported.
Neurologic complications, probably caused by nontarget embolization of the spinal artery or vertebral artery, are the most dreaded of BAE-related complications. There has been concern that liquid embolic materials, including NBCA, may increase the risk of nontarget embolization. Another issue regarding liquid embolic agents is the possibility of necrosis of tissues, including of the aorta or bronchi. Metallic coils: These achieve a relatively proximal occlusion in the vascular bed. In this patient population with a high rate of rebleeding, this position within the vascular tree may jeopardize further embolic attempts. In addition, as with gelatin sponges, proximal occlusion permits collateral flow, resulting in poor control of hemoptysis. Although not first-line therapy for hemoptysis per se, the presence of pseudoaneurysm in the BAs may represent an ideal situation to be managed by application of metallic coils [158,159].
Outcomes Previous studies have shown that BAE is very effective in controlling acute massive hemoptysis. The initial nonrecurrence rates for BAE have been reported to be 73% to 98%, with a mean follow-up period ranging from 1 day to 1 month. Immediate success rates have increased recently because of the introduction of superselective embolization and the refinement of embolic agents and techniques. However, the long-term success rate of BAE in hemoptysis is unfavorable. Longterm recurrence rates have been reported to be 10% to 52%, with a mean follow-up period ranging from 1 to 46 months. However, the long-term success rate can be improved with repeat BAE. Hemoptysis may recur after successful BAE if the disease process is not controlled with drug therapy or surgery because embolization does not address the underlying disease but rather treats the symptom. In this sense, BAE is a palliative procedure that prepares the patient for elective surgery for localized disease or continued antimicrobial therapy. Causes of recurrences include
◾ Recanalization of embolized vessels ◾ Incomplete embolization ◾ Revascularization by the collateral circulation ◾ Inadequate treatment of the underlying disease
◾ Progression of basic lung disease or NBSA supply Depending on the cause, recurrence rates can be highly variable, and in the setting of infectious (e.g., tuberculosis, aspergillus) or neoplastic (e.g., bronchogenic carcinoma) offenders, one can expect nearly all patients to eventually hemorrhage. Despite technical success, clinical remission is not always achieved. Generally accepted rates of cessation of hemoptysis after technically successful BAE approach 90%. Remobilization is an accepted approach to recurrent hemoptysis; however, surgery remains the definitive treatment for patients with hemoptysis recalcitrant to multiple embolizations and maximum medical therapy [130,159– 161].
Complications Several complications of BAE have been reported in the literature. Chest pain is the most common complication, with a reported prevalence of 24% to 91%. Chest pain is likely related to an ischemic phenomenon caused by embolization and is usually transient. In addition, dysphagia caused by embolization of esophageal branches may be encountered, with a reported prevalence of 0.7% to 18.2%. Dysphagia also regresses spontaneously. Subintimal dissection of the aorta or the BA during BAE is the other minor complication, with a reported prevalence of 1% to 6.3%. There are usually no symptoms or problems related to the subintimal dissection. The most disastrous complication of BAE is spinal cord ischemia caused by inadvertent occlusion of spinal arteries. The prevalence of spinal cord ischemia after BAE is reported to be 1.4% to 6.5%. Other rare complications that have been reported in the literature include aortic and bronchial necrosis, bronchoesophageal fistula, nontarget organ embolization (e.g., ischemic colitis), pulmonary infarction, referred pain to the ipsilateral forehead and orbit, and transient cortical blindness. It is hypothesized that cortical blindness develops because of embolism to the occipital cortex, either via a BA– pulmonary vein shunt or via collateral vessels between the bronchial and vertebral arteries. Pain in the orbit or temporal region ipsilateral to the side of embolization may occur but is thought to be referred pain rather than nontarget embolization in these territories [154,162,163].
Conclusion
Optimal management of patients having different pathologies requires a collaboration among interventional radiologists, clinicians, the critical care team, and anesthesiologists in patient management. Nowadays, the endovascular intervention procedures for various pathologies as discussed in this chapter are effective as well as safer substitutes as compared with surgery.
Suggested Readings • American College of Obstetricians and Gynecologists. ACOG practice bulletin: alternatives to hysterectomy in the management of leiomyomas. Obstet Gynecol 2008;112(2 pt 1):387–400 • Deshmukh SP, Gonsalves CF, Guglielmo FF, Mitchell DG. Role of MR imaging of uterine leiomyomas before and after embolization. RadioGraphics 2012;32(6):E251–E281 • Janette D. Durham, and Lindsay Machan, Pelvic Congestion Syndrome; Semin Intervent Radiol. 2013 Dec; 30(4): 372–380 • Amy Suzanne Thurmond, Fallopian Tube Catheterization; Semin Intervent Radiol. 2008 Dec; 25(4): 425–431.
References [1] D Litmanovich, A Bankier, L Cantin, V Raptopoulos, PM Boiselle, CT and MRI in diseases of the aorta, AJR Am J Roentgenol 193 (4) (2009) 928–940. [2] SS Mao, N Ahmadi, B Shah, et al., Normal thoracic aorta diameter on cardiac computed tomography in healthy asymptomatic adults: impact of age and gender, Acad Radiol 15 (2008) 827–834. [3] LF Tops, DA Wood, V Delgado, et al., Non invasive evaluation of the aortic root with multislice computed tomography, JACC Cardiovasc Imaging 1 (3) (2008) 321–330. [4] R Erbel, V Aboyans, C Boileau, et al., 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases: document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC), Eur Heart J 35 (41) (2014 Nov 1) 2873–2926. [5] C Nienaber, K Eagle, Aortic dissection: new frontiers in diagnosis and management, Circulation 108 (6) (2003) 772–778. [6] LF Hiratzka, GL Bakris, JA Beckman, et al., 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the diagnosis and management of patients with thoracic aortic disease: Executive summary: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice
Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine, Anesth Analg 111 (2) (2010) 279–315. [7] DA Nation, GJ Wang, TEVAR: endovascular repair of the thoracic aorta, Semin Intervent Radiol 32 (3) (2015) 265–271. 10.1055/s-0035-1558824. [8] JB Goldberg, JB Kim, TM Sundt, Current understandings and approach to the management of aortic intramural hematomas, Semin Thorac Cardiovasc Surg 26 (2) (2014) 123–131. [9] CA Nienaber, The role of imaging in acute aortic syndromes, Eur Heart J Cardiovasc Imaging 14 (1) (2013) 15–23. [10] P Chiu, AB Goldstone, JM Schaffer, et al., Endovascular versus open repair of intact descending thoracic aortic aneurysms, J Am Coll Cardiol 73 (6) (2019 Feb 19) 643–651. 10.1016/j.jacc.2018.10.086. PMID: 30765029; PMCID: PMC6675458. [11] NJ Swerdlow, WW Wu, ML Schermerhorn, Open and endovascular management of aortic aneurysms, Circ Res 124 (4) (2019 Feb 15) 647– 661. 10.1161/CIRCRESAHA.118.313186. PMID: 30763206. [12] https://www.nice.org.uk/guidance/conditions-anddiseases/cardiovascular-conditions/aortic-aneurysms. 2022. [13] AC Watkins, A Dalal, JT Lee, et al., Current status of endoluminal treatment of descending thoracic aortic aneurysms, Cardiovasc Intervent Radiol 43 (2020) 1770–1778. 10.1007/s00270-020-02526-1. [14] S Sharma, NN Pandey, M, Sinha, et al., Etiology, diagnosis and management of aortitis, Cardiovasc Intervent Radiol 43 (2020) 1821– 1836. 10.1007/s00270-020-02486-6. [15] HL Gornik, MA Creager, Aortitis. Circulation. 117 (23) (2008) 3039– 3051. [16] A Hata, M Noda, R Moriwaki, F Numano, Angiographic findings of Takayasu arteritis: new classification, Int J Cardiol 54 (Suppl) (1996) S155–S163. [17] S Sharma, S Sharma, K Taneja, AK Gupta, M Rajani, Morphologic mural changes in the aorta revealed by CT in patients with nonspecific aortoarteritis (Takayasu’s arteritis), AJR Am J Roentgenol 167 (5) (1996) 1321–1325. [18] G Keser, H Direskeneli, K Aksu, Management of Takayasu arteritis: a systematic review, Rheumatology (Oxford) 53 (2014) 793–801.
[19] PG Teixeira, K Inaba, G Barmparas, et al., Blunt thoracic aortic injuries: an autopsy study, J Trauma 70 (1) (2011) 197–202. [20] SD Steenburg, JG Ravenel, Acute traumatic thoracic aortic injuries: experience with 64-MDCT, AJR Am J Roentgenol 191 (5) (2008) 1564– 1569. [21] BW Starnes, RS Lundgren, M Gunn, et al., A new classification scheme for treating blunt aortic injury, J Vasc Surg 55 (1) (2012 Jan) 47–54. 10.1016/j.jvs.2011.07.073. Epub 2011 Nov 29. PMID: 22130426. [22] RE Heneghan, S Aarabi, E Quiroga, ML Gunn, N Singh, BW Starnes, Call for a new classification system and treatment strategy in blunt aortic injury, J Vasc Surg 64 (1) (2016 Jul) 171–176. 10.1016/j.jvs.2016.02.047. Epub 2016 Apr 27. PMID: 27131924. [23] G Dhaliwal, D Mukherjee, Peripheral arterial disease: epidemiology, natural history, diagnosis and treatment, Int J Angiol 16 (2) (2007) 36–44. [24] L Norgren, WR Hiatt, JA Dormandy, MR Nehler, KA Harris, FG.R Fowkes, Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II), J Vasc Surg 45 (1) (2007 Jan) S5–67. [25] AT Hirsch, ZJ Haskal, NR Hertzer, CW Bakal, MA Creager, JL Halperin, et al., ACC/AHA 2005 Practice guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease): endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood Institute; Society for Vascular Nursing; TransAtlantic Inter-Society Consensus; and Vascular Disease Foundation, Circulation 113, 2006 Mar 21, e463–e654. [26] FJ Serrano Hernando, A Martín Conejero, Peripheral artery Disease: pathophysiology, diagnosis and treatment, Rev Esp Cardiol 60 (9) (2007 Sep 1) 969–982. [27] D Gerhard-Herman Marie, L Gornik Heather, C Barrett, Barshes NR, MA Corriere, DE Drachman, et al., 2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, Circulation 135 (12) (2017 Mar 21) e686–e725.
[28] D Dhanoa, MO Baerlocher, AJ Benko, JF Benenati, MD Kuo, SR Dariushnia, et al., Position statement on noninvasive imaging of peripheral arterial disease by the Society of Interventional Radiology and the Canadian Interventional Radiology Association, J Vasc Interv Radiol 27 (7) (2016 Jul) 947–951. [29] K Pereira, Treatment strategies for the claudicant, Semin Interv Radiol 35 (05) (2018 Dec) 435–442. [30] SR Bailey, JA Beckman, TD Dao, S Misra, PS Sobieszczyk, CJ White, LS Wann, SR Bailey, T Dao, HD Aronow, R Fazel, HL Gornik, BH Gray, JL Halperin, AT Hirsch, MR Jaff, V Krishnamurthy, SA Parikh, AB Reed, F Shamoun, RE Shugart, EK Yucel, ACC/AHA/SCAI/SIR/SVM 2018 Appropriate Use Criteria for Peripheral Artery Intervention: A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Heart Association, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, and Society for Vascular Medicine, J Am Coll Cardiol 73 (2) (2019 Jan 22) 214–237. [31] MH Shishehbor, MR Jaff, Percutaneous therapies for peripheral artery disease, Circulation 134 (24) (2016 Dec 13) 2008–2027. [32] K Katsanos, G Tepe, D Tsetis, F Fanelli, Standards of practice for superficial femoral and popliteal artery angioplasty and stenting, Cardiovasc Intervent Radiol 37 (3) (2014 Jun) 592–603. [33] DW Losordo, K Rosenfield, A Pieczeck, How does angioplasty work? Serial Analysis at human iliac arteries using intravascular ultrasound, Circulation 77 (1992) 1845. [34] WR Castaneda, K Amplatz, F Laerum, Mechanics of angioplasty: an experimental approach, Radiographics 1 (3) (1981) 1–14. [35] S Giannopoulos, RL Varcoe, M Lichtenberg, J Rundback, M Brodmann, T Zeller, PA Schneider, EJ Armstrong, Balloon angioplasty of infrapopliteal arteries: a systematic review and proposed algorithm for optimal endovascular therapy, J Endovasc Ther 27 (4) (2020 Aug) 547– 564. [36] D Sacks, DL Marinelli, LG Martin, et al., Reporting standards for clinical evaluation of new peripheral arterial revascularization devices, J Vasc Interv Radiol 14 (9, pt 2) (2003) S395–S404. [37] A .D.o.m.i.n.g.u.e.z 3rd, J Bahadorani, R Reeves, E Mahmud, M Patel, Endovascular therapy for critical limb ischemia, Expert Rev Cardiovasc Ther 13 (4) (2015 Apr) 429–444. [38] AR Geronemus, CS Peña, Endovascular treatment of femoral-popliteal disease, Semin Intervent Radiol 26 (4) (2009 Dec) 303–314. [39] F Biancari, T Juvonen, Angiosome-targeted lower limb revascularization for ischemic foot wounds: systematic review and meta-
analysis, Eur J Vasc Endovasc Surg 47 (5) (2014 Jan 31) 517–522. [40] M Cejna, Cutting balloon: review on principles and background of use in peripheral arteries. Cardiovasc Intervent Radiol, 28, 2005 Jul-Aug), 400–408. [41] F Stanek, Laser angioplasty of peripheral arteries: basic principles, current clinical studies, and future directions, Diagn Interv Radiol 25 (5) (2019 Sep) 392–397. [42] K Katsanos, S Spiliopoulos, I Paraskevopoulos, A Diamantopoulos, D Karnabatidis, Systematic review and meta-analysis of randomized controlled trials of paclitaxel-coated balloon angioplasty in the femoropopliteal arteries: role of paclitaxel dose and bioavailability, J Endovasc Ther 23 (2) (2016 Apr) 356–370. [43] J Nordanstig, S James, M Andersson, M Andersson, P Danielsson, P Gillgren, M Delle, J Engström, T Fransson, M Hamoud, A Hilbertson, P Johansson, L Karlsson, B Kragsterman, H Lindgren, K Ludwigs, S Mellander, N Nyman, H Renlund, B Sigvant, P Skoog, J Starck, G Tegler, A Toivola, M Truedson, CM Wahlgren, J Wallinder, A Öjersjö, M Falkenberg, Mortality with paclitaxel-coated devices in peripheral artery disease, N Engl J Med 383 (26) (2020 Dec 24) 2538–2546. [44] M Rigato, M Monami, GP Fadini, Autologous Cell therapy for peripheral arterial disease: systematic review and meta-analysis of randomized, non-randomized, and non-controlled studies, Circ Res (2017 Jan 17). [45] E Frechette, J Deslauriers, Surgical anatomy of the bronchial tree and pulmonary artery, Semin Thorac Cardiovasc Surg 18 (2006) 77–84. [46] A Kandathil, M Chamarthy, Pulmonary vascular anatomy & anatomical variants, Cardiovascr Diagn Ther 8 (3) (2018 Jun) 201. [47] W Kasper, S Konstantinides, A Geibel, et al., Management strategies and determinants of outcome in acute major pulmonary embolism: results of a multicenter registry, J Am Coll Cardiol 30 (1997) 1165–1171. [48] KA Comess, FA DeRook, ML Russell, et al., The incidence of pulmonary embolism in unexplained sudden cardiac arrest with pulseless electrical activity, Am J Med 109 (2000) 351–356. [49] R Koning, A Cribier, L Gerber, et al., A new treatment for severe pulmonary embolism: percutaneous rheolytic thrombectomy, Circulation 96 (1997) 2498. [50] WT Kuo, MA.A.J van den Bosch, LV Hofmann, et al., Catheterdirected embolectomy, fragmentation, and thrombolysis for the treatment of massive pulmonary embolism after failure of systemic thrombolysis, Chest 134 (2008) 250.
[51] T Chechi, S Vecchio, G Spaziani, et al., Rheolytic thrombectomy in patients with massive and submassive acute pulmonary embolism, Catheter Cardiovasc Interv 73 (2009) 506. [52] M Margheri, G Vittori, S Vecchio, et al., Early and long-term clinical results of AngioJet rheolytic thrombectomy 2022. [53] N Nassiri, A Jain, D McPhee, et al., Massive and submassive pulmonary embolism: experience with an algorithm for catheter-directed mechanical thrombectomy, Ann Vasc Surg 26 (2012) 18. [54] L Ferrigno, R Bloch, J Threlkeld, et al., Management of pulmonary embolism with rheolytic thrombectomy, Can Respir J 18 (2011) e52. [55] AJ Brady, T Crake, CM Oakley, Percutaneous catheter fragmentation and distal dispersion of proximal pulmonary embolus, Lancet 338 (1991) 1186. [56] T Schmitz-Rode, U Janssens, SH Duda, et al., Massive pulmonary embolism: percutaneous emergency treatment by pigtail rotation catheter, J Am Coll Cardiol 36 (2000) 375. [57] G Eid-Lidt, J Gaspar, J Sandoval, et al., Combined clot fragmentation and aspiration inpatients with acute pulmonary embolism, Chest 134 (2008) 54. [58] S Müller-Hülsbeck, J Brossmann, T Jahnke, et al., Mechanical thrombectomy of major and massive pulmonary embolism with use of the Amplatz thrombectomy device, Invest Radiol 36 (2001) 317. [59] JA Reekers, HJ Baarslag, MG Koolen, et al., Mechanical thrombectomy for early treatment of massive pulmonary embolism, Cardiovasc Intervent Radiol 26 (2003) 246. [60] RP Engelberger, N Kucher, Catheter-based reperfusion treatment of pulmonary embolism, Circulation 124 (2011) 2139. [61] F Cuculi, R Kobza, M Bergner, P Erne, Usefulness of aspiration of pulmonary emboli and prolonged local thrombolysis to treat pulmonary embolism, Am J Cardiol 110 (2012) 1841. [62] T Schmitz-Rode, RW Günther, JG Pfeffer, et al., Acute massive pulmonary embolism: use of a rotatable pigtail catheter for diagnosis and fragmentation therapy, Radiology 197 (1995) 157. [63] T Schmitz-Rode, U Janssens, HH Schild, et al., Fragmentation of massive pulmonary embolism using a pigtail rotation catheter, Chest 114 (1998) 1427. [64] K Nakazawa, H Tajima, S Murata, et al., Catheter fragmentation of acute massive pulmonary thromboembolism: distal embolisation and pulmonary arterial pressure elevation, Br J Radiol 81 (2008) 848. [65] N Kumar, Y Janjigian, DR Schwartz, Paradoxical worsening of shock after the use of a percutaneous mechanical thrombectomy device in a
postpartum patient with a massive pulmonary embolism, Chest 132 (2007) 677. [66] L Aklog, CS Williams, JG Byrne, SZ Goldhaber, Acute pulmonary embolectomy: a contemporary approach, Circulation 105 (2002) 1416. [67] PD Stein, M Alnas, A Beemath, NR Patel, Outcome of pulmonary embolectomy, Am J Cardiol 99 (2007) 421. [68] ZJ Osborne, P Rossi, J Aucar, et al., Surgical pulmonary embolectomy in a community hospital, Am J Surg 207 (2014) 337. [69] WB Keeling, BG Leshnower, Y Lasajanak, et al., Midterm benefits of surgical pulmonary embolectomy for acute pulmonary embolus on right ventricular function, J Thorac Cardiovasc Surg 152 (2016) 872. [70] P Bloomfield, NA Boon, DP de Bono, Indications for pulmonary embolectomy, Lancet 2 (1988) 329. [71] I Yamada, H Shibuya, O Matsubara, et al., Pulmonary artery disease in Takayasu’s arteritis: angiographic findings, AJR Am J Roentgenol 159 (1992) 263–269. [72] International Study Group for Behcet’s disease. Criteria for diagnosis of Behcet’s disease, Lancet 335 (1990) 1078–1080. [73] J Kreutzer, MJ Landzberg, TJ Preminger, et al., Isolated peripheral pulmonary artery stenoses in the adult, Circulation 93 (1996) 1417–1423. [74] S Tyagi, V Mehta, R Kashyap, UA Kaul, Endovascular stent implantation for severe pulmonary stenosis in aortoarteritis (Takayasu’s arteritis), Catheter Cardiovasc Interv 61 (2004) 281–285. [75] V Cottin, S Dupuis-Girod, G Lesca, JF Cordier, Pulmonary vascular manifestations of hereditary hemorrhagic telangiectasia (Rendu-Osler disease), Respiration 74 (2007) 361. [76] LH. .B.o.s.h.e.r Jr, DA Blake, BR Byrd, An analysis of the pathologic anatomy of pulmonary arteriovenous aneurysms with particular reference to the applicability of local excision, Surgery 45 (1959) 91. [77] JJ Mager, TT Overtoom, H Blauw, et al., Embolotherapy of pulmonary arteriovenous malformations: long-term results in 112 patients, J Vasc Interv Radiol 15 (2004) 451. [78] DE Dines, JB Seward, PE Bernatz, Pulmonary arteriovenous fistulas, Mayo Clin Proc 58 (1983) 176. [79] O Kretschmar, P Ewert, M Yigitbasi, et al., Huge pulmonary arteriovenous fistula: diagnosis and treatment and an unusual complication of embolization, Respir Care 47 (2002) 998. [80] RI White Jr., A Lynch-Nyhan, P Terry, et al., Pulmonary arteriovenous malformations: techniques and long-term outcome of embolotherapy, Radiology 169 (1988) 663.
[81] HH Wong, RP Chan, R Klatt, ME Faughnan, Idiopathic pulmonary arteriovenous malformations: clinical and imaging characteristics, Eur Respir J 38 (2011) 368. [82] RA Pugash, Pulmonary arteriovenous malformations: overview and transcatheter embolotherapy, Can Assoc Radiol J 52 (2001) 92. [83] CS Woodward, RE Pyeritz, JL Chittams, SO Trerotola, Treated pulmonary arteriovenous malformations: patterns of persistence and associated retreatment success, Radiology 269 (2013) 919. [84] AK Abdel Aal, J Eason, S Moawad, et al., Persistent pulmonary arteriovenous malformations: percutaneous embolotherapy, Curr Probl Diagn Radiol 47 (2018) 428. [85] C Kaufman, K Henderson, J Pollak, Clinical significance of pulmonary arteriovenous malformation reperfusion, J Clin Interv Radiol ISVIR 1 (2017) 156. [86] R Ungaro, S Saab, CH Almond, et al., Solitary peripheral pulmonary artery aneurysms. Pathogenesis and surgical treatment, J Thorac Cardiovasc Surg 71 (1976) 566–571. [87] G Ramakrishna, J Sprung, BS Ravi, et al., Impact of pulmonary hypertension on the outcomes of noncardiac surgery: predictors of perioperative morbidity and mortality, J Am Coll Cardiol 45 (2005) 1691– 1699. [88] HS Park, MR Chamarthy, D Lamus, SS Saboo, PD Sutphin, SP Kalva, Pulmonary artery aneurysms: diagnosis & endovascular therapy, Cardiovasc Diagn Ther 8 (3) (2018 Jun) 350. [89] G Drevet, M Conti, J Deslauriers, Surgical anatomy of the tracheobronchial tree, J Thorac Dis 8 (Suppl 2) (2016) S121–S129. 10.3978/j.issn.2072-1439.2016.01.69. [90] N Karabulut, CT assessment of tracheal carinal angle and its determinants, Br J Radiol 78 (933) (2005) 787–790. 10.1259/bjr/75107416. [91] P Lee, AC Mehta, PN Mathur, Management of complications from diagnostic and interventional bronchoscopy, Respirology 14 (7) (2009) 940–953. 10.1111/j.1440-1843.2009.01617.x. [92] S Krawtz, AC Mehta, HP Wiedemann, G DeBoer, KD Schoepf, MZ Tomaszewski, Nd-YAG laser-induced endobronchial burn. Management and long-term follow-up, Chest 95 (4) (1989) 916–918. 10.1378/chest.95.4.916. [93] A Fishman, F Martinez, K Naunheim, et al., A randomized trial comparing lung-volume-reduction surgery with medical therapy for severe
emphysema, N Engl J Med 348 (21) (2003) 2059–2073. 10.1056/NEJMoa030287. [94] N Aljuri, L Freitag, Validation and pilot clinical study of a new bronchoscopic method to measure collateral ventilation before endobronchial lung volume reduction, J Appl Physiol 106 (2009) 774– 783. [95] GJ Criner, F Cordova, AL Sternberg, et al., The National Emphysema Treatment Trial (NETT) Part II: lessons learned about lung volume reduction surgery, Am J Respir Crit Care Med 184 (2011) 881–893. 10.1164/rccm.201103-0455CI27. [96] FC Sciurba, A Ernst, FJ Herth, et al., A randomized study of endobronchial valves for advanced emphysema, N Engl J Med 363 (2010) 1233–1244. 10.1056/NEJMoa0900928. [97] C Davey, Z Zoumot, S Jordan, et al., Bronchoscopic lung volume reduction with endobronchial valves for patients with heterogeneous emphysema and intact interlobar fissures (the BeLieVeR-HIFi study): a randomized controlled trial, Lancet 386 (2015) 1066–1073. 10.1016/S0140-6736(15)60001-0. [98] ID Pavord, NC Thomson, RM Niven, et al., Research in Severe Asthma Trial Study Group Safety of bronchial thermoplasty in patients with severe refractory asthma, Ann Allergy Asthma Immunol 111 (5) (2013) 402–407. [99] NC Thomson, AS Rubin, RM Niven, et al., AIR Trial Study Group Long-term (5 year) safety of bronchial thermoplasty: asthma intervention research (AIR) trial, BMC Pulm Med 11 (2011) 8. [100] ME Wechsler, M Laviolette, AS Rubin, et al., Asthma Intervention Research 2 Trial Study Group Bronchial thermoplasty: long-term safety and effectiveness in patients with severe persistent asthma, J Allergy Clin Immunol 132 (6) (2013) 1295–1302. [101] N Al-Zubaidi, AO Soubani, Advances in diagnostic interventional pulmonology, Avicenna J Med 5 (3) (2015) 57–66. 10.4103/22310770.160229. [102] MS Ali, W Trick, BI Mba, D Mohananey, J Sethi, AI Musani, Radial endobronchial ultrasound for the diagnosis of peripheral pulmonary lesions: a systematic review and meta-analysis, Respirology 22 (3) (2017) 443–453. 10.1111/resp.12980. [103] CE Come, MR Kramer, MT Dransfield, et al., A randomized trial of lung sealant versus medical therapy for advanced emphysema, Eur Respir J 46 (3) (2015) 651–662. 10.1183/09031936.00205614. [104] PL Shah, DJ Slebos, PF Cardoso, et al., Bronchoscopic lung-volume reduction with Exhale airway stents for emphysema (EASE trial):
randomized, sham-controlled, multicentre trial, Lancet 378 (9795) (2011) 997–1005. 10.1016/S0140-6736(11)61050-7. [105] A Valipour, S Fernandez-Bussy, AJ Ing, et al., Bronchial rheoplasty for treatment of chronic bronchitis: 12 month results from a multi-center study [published online ahead of print, 2020 May 14], Am J Respir Crit Care Med 10 (2020). 10.1164/rccm.201908-1546OC. 1164/rccm.2019081546OC. [106] DJ Slebos, PL Shah, FJ.F Herth, et al., Safety and adverse events after targeted lung denervation for symptomatic moderate to severe chronic obstructive pulmonary disease (AIRFLOW). A multicenter randomized controlled clinical trial, Am J Respir Crit Care Med 200 (12) (2019) 1477– 1486. 10.1164/rccm.201903-0624OC. [107] D Gompelmann, PL Shah, A Valipour, FJ.F Herth, Bronchoscopic thermal vapor ablation: best practice recommendations from an expert panel on endoscopic lung volume reduction, Respiration 95 (6) (2018) 392–400. 10.1159/000489815. [108] JF Bruzzi, M Rémy-Jardin, D Delhaye, A Teisseire, C Khalil, J Rémy, Multi–detector row CT of hemoptysis, Radiographics 26 (1) (2006) 3–22. [109] KK Pump, The bronchial arteries and their anastomoses in the human lung, Dis Chest 43 (1963) 245–255, Crossref, Medline, Google Scholar. [110] P Gailloud, S Albayram, DV Heck, KJ Murphy, JH.D Fasel, Superior bronchial artery arising from the left common carotid artery: embryology and clinical considerations, J Vasc Intervent Radiol 13 (8) (2002 Aug) 851–853. [111] W Tanomkiat, K Tanisaro, Radiographic relationship of the origin of the bronchial arteries to the left main bronchus, J Thorac Imaging 18 (1) (2003) 27–33, Crossref, Medline, Google Scholar. [112] S Osiro, C Wear, R Hudson, et al., A friend to the airways: a review of the emerging clinical importance of the bronchial arterial circulation, Surg Radiol Anat 34 (9) (2012) 791–798, Crossref, Medline, Google Scholar. [113] IJ Hartmann, M Remy-Jardin, L Menchini, A Teisseire, C Khalil, J Remy, Ectopic origin of bronchial arteries: assessment with multidetector helical CT angiography, Eur Radiol 17 (8) (2007) 1943–1953, Crossref, Medline, Google Scholar. [114] W Yoon, JK Kim, YH Kim, TW Chung, HK Kang, Bronchial and nonbronchial systemic artery embolization for life-threatening hemoptysis: a comprehensive review, Radiographics 22 (6) (2002) 1395–1409. [115] M Remy-Jardin, N Bouaziz, P Dumont, PY Brillet, J Bruzzi, J Remy, Bronchial and nonbronchial systemic arteries at multi–detector row CT angiography: comparison with conventional angiography, Radiology 233 (3) (2004) 741–749.
[116] C Sancho, E Escalante, J Domínguez, et al., Embolization of bronchial arteries of anomalous origin, Cardiovasc Intervent Radiol 21 (4) (1998) 300–304, Crossref, Medline, Google Scholar. [117] AM Cohen, CF Doershuk, RC Stern, Bronchial artery embolization to control hemoptysis in cystic fibrosis, Radiology 175 (2) (1990) 401–405. [118] M Loukas, M Hanna, J Chen, RS Tubbs, RH Anderson, Extracardiac coronary arterial anastomoses, Clin Anat 24 (2) (2011) 137–142, Crossref, Medline, Google Scholar. [119] JF Aupetit, M Gallet, J Boutarin, Coronary-to-bronchial artery anastomosis complicated with myocardial infarction, Int J Cardiol 18 (1) (1988) 93–97, Crossref, Medline, Google Scholar. [120] Y Morita, K Takase, H Ichikawa, et al., Bronchial artery anatomy: preoperative 3D simulation with multidetector CT, Radiology 255 (3) (2010) 934–943. [121] EW Cauldwell, RG Siekert, et al., The bronchial arteries: an anatomic study of 150 human cadavers, Surg Gynecol Obstet 86 (4) (1948) 395– 412, Medline, Google Scholar. [122] J Ziyawudong, N Kawai, M Sato, et al., Aortic ostia of the bronchial arteries and tracheal bifurcation: MDCT analysis, World J Radiol 4 (1) (2012) 29–35, Medline, Google Scholar. [123] RG Fisher, M Sanchez-Torres, CJ Whigham, JW Thomas, “Lumps” and “bumps” that mimic acute aortic and brachiocephalic vessel injury, Radiographics 17 (4) (1997) 825–834. [124] T Kasai, S Chiba, Macroscopic anatomy of the bronchial arteries, Anat Anz 145 (2) (1979) 166–181, Medline, Google Scholar. [125] AA Liebow, Patterns of origin and distribution of the major bronchial arteries in man, Am J Anat 117 (1965) 19–32, Crossref, Medline, Google Scholar. [126] CM Walker, ML Rosado-de-Christenson, S Martínez-Jiménez, JR Kunin, BC Wible, Bronchial arteries: anatomy, function, hypertrophy, and anomalies, Radiographics 35 (1) (2015 Jan 1) 32–49. [127] KH Do, JM Goo, JG Im, et al., Systemic arterial supply to the lungs in adults: spiral CT findings, Radiographics 21 (2001) 387–402. [128] M Hashimoto, J Heianna, K Okane, J Izumi, J Watarai, Internal mammary artery embolization for hemoptysis, Acta Radiol 40 (1999) 187–190, Crossref, Medline, Google Scholar. [129] D Rosenthal, Spinal cord ischemia after abdominal aortic operation: is it preventable?, J Vasc Surg 30 (1999) 391–399, Crossref, Medline, Google Scholar. [130] R Uflacker, A Kaemmerer, C Neves, PD Picon, Management of massive hemoptysis by bronchial artery embolization, Radiology 146
(1983) 627–634. [131] R Uflacker, A Kaemmerer, PD Picon, et al., Bronchial artery embolization in the management of hemoptysis: technical aspects and long-term results, Radiology 157 (1985) 637–644. [132] M Reñé, J Sans, J Dominguez, C Sancho, J Valldeperas, Unilateral pulmonary artery agenesis presenting with hemoptysis: treatment by embolization of systemic collaterals, Cardiovasc Intervent Radiol 18 (4) (1995) 251–254, Crossref, Medline, Google Scholar. [133] E Castañer, X Gallardo, E Ballesteros, et al., CT diagnosis of chronic pulmonary thromboembolism, Radiographics 29 (1) (2009) 31–50, discussion 50–53. [134] V Pengo, AW Lensing, MH Prins, et al., Incidence of chronic thromboembolic pulmonary hypertension after pulmonary embolism, N Engl J Med 350 (22) (2004) 2257–2264, Crossref, Medline, Google Scholar. [135] IM Lang, Chronic thromboembolic pulmonary hypertension: not so rare after all, N Engl J Med 350 (22) (2004) 2236–2238, Crossref, Medline, Google Scholar44. [136] RT Tan, R Kuzo, LR Goodman, R Siegel, GB Haasler, KW Presberg, Medical College of Wisconsin Lung Transplant Group. Utility of CT scan evaluation for predicting pulmonary hypertension in patients with parenchymal lung disease, Chest 113 (5) (1998) 1250–1256, Crossref, Medline, Google Scholar. [137] I Hasegawa, PM Boiselle, H Hatabu, Bronchial artery dilatation on MDCT scans of patients with acute pulmonary embolism: comparison with chronic or recurrent pulmonary embolism, AJR Am J Roentgenol 182 (1) (2004) 67–72, Crossref, Medline, Google Scholar. [138] MF McNeeley, JH Chung, S Bhalla, JD Godwin, Imaging of granulomatous fibrosing mediastinitis, AJR Am J Roentgenol 199 (2) (2012) 319–327, Crossref, Medline, Google Scholar. [139] SE Rossi, HP McAdams, ML Rosado-de-Christenson, TJ Franks, JR Galvin, Fibrosing mediastinitis, Radiographics 21 (3) (2001) 737–757. [140] EN Arnett, JM Bacos, AM Macher, et al., Fibrosing mediastinitis causing pulmonary arterial hypertension without pulmonary venous hypertension: clinical and necropsy observations, Am J Med 63 (4) (1977) 634–643, Crossref, Medline, Google Scholar. [141] AD Sherrick, LR Brown, GF Harms, JL Myers, The radiographic findings of fibrosing mediastinitis, Chest 106 (2) (1994) 484–489, Crossref, Medline, Google Scholar. [142] CE Denlinger, FG Fernandez, GA Patterson, D Kreisel, Fibrosing mediastinitis associated with complete occlusion of the left main
pulmonary artery, Ann Thorac Surg 87 (1) (2009) 323, Crossref, Medline, Google Scholar. [143] DM McDonald, Angiogenesis and remodeling of airway vasculature in chronic inflammation, Am J Respir Crit Care Med 164 (10) (2001) S39– S45, Crossref, Medline, Google Scholar. [144] DM Hansell, AA Bankier, H MacMahon, TC McLoud, NL Müller, J Remy, Fleischner Society: glossary of terms for thoracic imaging, Radiology 246 (3) (2008) 697–722. [145] JJ Erasmus, HP McAdams, MA Farrell, EF Patz Jr., Pulmonary nontuberculous mycobacterial infection: radiologic manifestations, Radiographics 19 (6) (1999) 1487–1505. [146] T Franquet, NL Müller, A Giménez, P Guembe, J de La Torre, S Bagué, Spectrum of pulmonary aspergillosis: histologic, clinical, and radiologic findings, Radiographics 21 (4) (2001) 825–837. [147] VS Katabathina, CS Restrepo, SL Betancourt Cuellar, RF Riascos, CO Menias, Imaging of oncologic emergencies: what every radiologist should know, Radiographics 33 (6) (2013) 1533–1553. [148] M Remy-Jardin, A Duhamel, V Deken, N Bouaziz, P Dumont, J Remy, Systemic collateral supply in patients with chronic thromboembolic and primary pulmonary hypertension: assessment with multi–detector row helical CT angiography, Radiology 235 (1) (2005) 274–281. [149] J Endrys, N Hayat, G Cherian, Comparison of bronchopulmonary collaterals and collateral blood flow in patients with chronic thromboembolic and primary pulmonary hypertension, Heart 78 (2) (1997) 171–176, Crossref, Medline, Google Scholar. [150] J-P Pelage, Bronchial artery embolization: anatomy and technique, Tech Vasc Interv 10 (4) (2007 Dec) 274–275. [151] S Phillips, MS.T Ruttley, Bronchial artery embolization: the importance of preliminary thoracic aortography, Clin Radiol 55 (2000) 317–319, Crossref, Medline, Google Scholar. [152] N Tanaka, K Yamakado, S Murashima, et al., Superselective bronchial artery embolization for hemoptysis with a coaxial microcatheter system, J Vasc Intervent Radiol 8 (1997) 65–70, Crossref, Medline, Google Scholar. [153] RI., White Jr, Bronchial artery embolotherapy for control of acute hemoptysis: analysis of outcome, Chest 115 (1999) 912–915, Crossref, Medline, Google Scholar. [154] R Ramakantan, VG Bandekar, MS Gandhi, BG Aulakh, HL Deshmukh, Massive hemoptysis due to pulmonary tuberculosis: control with bronchial artery embolization, Radiology 200 (1996) 691–694. [155] EI Hsiao, CM Kirsch, FT Kagawa, JH Wehner, WA Jensen, RB Baxter, Utility of fiberoptic bronchoscopy before bronchial artery
embolization for massive hemoptysis, AJR Am J Roentgenol 177 (2001) 861–867, Crossref, Medline, Google Scholar. [156] DR Sopko, TP Smith, Bronchial artery embolization for hemoptysis, Semin Intervent Radiol 28 (1) (2011 Mar) 48–62. [157] K Pump, Distribution of bronchial arteries in human lung, Chest 62 (1972) 447–451, Crossref, Medline, Google Scholar. [158] F Kucukay, OM Topcuoglu, A Alpar, ÇM Altay, MB Kucukay, NI Ozbulbul, Bronchial artery embolization with large sized (700-900 µm) tris-acryl microspheres (embosphere) for massive hemoptysis: long-term results (clinical research), Cardiovasc Intervent Radiol, 41 (2) (2018 Feb) 225–230. doi:10.1007/s00270-017-1818-7. Epub 2017 Oct 24. PMID: 29067512. [159] S Woo, CJ Yoon, JW Chung, S-G Kang, HJ Jae, H-C Kim, et al., Bronchial artery embolization to control hemoptysis: comparison of nbutyl-2-cyanoacrylate and polyvinyl alcohol particles, Radiology 269 (2) (2013 Nov 1) 594–602. [160] H Lee, CJ Yoon, NJ Seong, CH Jeon, HI Yoon, J Go, Cryptogenic hemoptysis: effectiveness of bronchial artery embolization using n-butyl cyanoacrylate, J Vasc Intervent Radiol 28 (8) (2017 Aug) 1161–1166. [161] K Hayakawa, F Tanaka, T Torizuka, et al., Bronchial artery embolization for hemoptysis: immediate and long-term results, Cardiovasc Intervent Radiol 15 (1992) 154–159, Crossref, Medline, Google Scholar. [162] H Mal, I Rullon, F Mellot, et al., Immediate and long-term results of bronchial artery embolization for life-threatening hemoptysis, Chest 115 (1999) 996–1001, Crossref, Medline, Google Scholar. [163] A Kato, S Kudo, K Matsumoto, et al., Bronchial artery embolization for hemoptysis due to benign diseases: immediate and long-term results, Cardiovasc Intervent Radiol 23 (2000) 351–357, Crossref, Medline, Google Scholar.
CHAPTER 96
Neurointervention Leanne Y. Lin, Zachary Wilseck, Joseph J. Gemmete, Aditya S. Pandey, Neeraj Chaudhary
Introduction As medical and surgical disciplines have rapidly advanced and diversified from their general origins into several specialties and sub- or superspecialties, imaging sciences or clinical radiology have also branched off in tandem and have become more specialized. Similarly, the practice of imageguided minimally invasive procedures is rapidly becoming its own specialty, called interventional radiology. From its general origins, rapid advancement in technology has led to more defined scope of minimally invasive therapeutic options for disease in several different parts of the body. The scope relating to diseases of the brain, spinal cord, osseous vertebrae, head, neck, face, and orbit pathology in adults and children is called neurointerventional radiology (NIR). The scope relating to the rest of the body is termed as vascular/visceral interventional radiology (VIR), which is discussed in separate chapters of this section. As image-guided technology can be generic to VIR and NIR, there is some overlap in these two domains. In this chapter, the seminal developments in the realm of NIR and the therapeutic options available for patients will be summarized. In NIR, vascular procedures range from diagnostic angiography to treatments of aneurysms, stroke, vascular malformations, and tumors. Nonvascular procedures involve mainly spine interventions. The first cerebral angiogram was performed in 1927 by Dr. Egas Moniz using thorotrast (thorium dioxide) via surgical incision and direct carotid puncture [1]. In the 1970s–1980s, there were advances in technologies such as digital subtraction angiography, and early pioneers began using this technique for cerebral angiography [2]. Since then, techniques and available technology have made diagnostic cerebral angiography much safer and to
this day it remains the gold standard in diagnosing cerebrovascular pathologies. Although advances have also been made in noninvasive crosssectional imaging such as CT and MR angiography, they have not superseded selective angiography. Catheter cerebral angiography allows for a more real-time characterization of blood flow and has the best spatial resolution. Fig. 96.1 succinctly displays the milestone developments for NIR.
FIGURE 96.1 Timeline of milestone events in neuro-interventional radiology.
Cerebral Angiography Cerebral angiography is often performed for the evaluation of vascular lesions, intracranial hemorrhage, or vascular supply of tumors before resection. There are no absolute contraindications for catheter angiography, however, relative contraindications include coagulopathy, sensitivity to contrast, and renal insufficiency. Often this is performed under moderate or conscious sedation, however, conditions that make sedation high risk such as hypotension, heart failure, and other causes of clinical instability must be taken into consideration, and evaluation by an independent anesthesia team may be considered. Arterial access can be obtained at the groin via the common femoral artery, wrist via the radial artery, or dorsal aspect of the hand via the deep palmar branch of the radial artery. The modified Seldinger technique would be used to exchange the access needle for a sheath through which catheters can be advanced. A catheter would then be advanced over the wire and
navigated into the cervico–cerebral arteries. A full six-vessel diagnostic angiogram would involve selectively catheterizing the bilateral internal carotid, external carotid, and vertebral arteries (Figs. 96.2–96.4).
FIGURE 96.2 Normal lateral projection external carotid artery digital subtraction angiogram. This view demonstrates the internal maxillary artery (black arrow), occipital artery (white arrow), superficial temporal artery (black arrowheads), and middle meningeal artery (white arrowheads).
FIGURE 96.3 Normal frontal (A) and lateral (B) projection internal carotid artery digital subtraction angiogram. (A) The frontal projection demonstrates the carotid terminus (black arrow) and the proximal anterior (white arrowhead) and middle cerebral (black arrowhead) arteries. (B) The lateral projection best demonstrates the ophthalmic artery (white arrow).
FIGURE 96.4 Frontal (A) and lateral (B) projection vertebral artery digital subtraction angiogram. (A) The frontal projection demonstrates the posterior cerebral arteries (black arrowheads), superior cerebellar arteries (white arrowhead), anterior inferior cerebellar artery (black arrow), and posterior inferior cerebellar artery (white arrow). (B) The lateral projection best demonstrates anomalous course of the posterior inferior cerebellar artery (white arrow) with extracranial origin.
Complications to cerebral angiography are rare in the hands of an experienced operator. The most serious complication would be ischemic stroke, which can be precipitated by thrombus development at the tips of catheters, air embolism, and/or vessel injury. Connecting catheters to a continuous infusion of dilute anticoagulant help prevent thrombus development, and care to keep the lines and rotating hemostatic valves bubble-free avoids air embolism. Performing roadmap imaging to assist with navigation and careful manipulation of wires and catheters will minimize the risk of vessel damage.
Cerebral Aneurysms In its early years in the 1980s, NIR techniques for the treatment of cerebral aneurysms were largely experimental and were performed only for patients who had no other treatment options. This was when Drs. Guido Gulielmi and Fernando Vinuela began their collaboration in developing detachable coils. These coils were first used on a human on March 6, 1990 to treat a direct carotid-cavernous fistula. In the following year, the first aneurysm in a human was treated with coil embolization [3,4]. Subsequently, results of the
International Subarachnoid Hemorrhage Trial (ISAT) were published in 2002, with follow-up results in 2005 and 2009, comparing coil embolization to clipping of ruptured aneurysms. The ISAT demonstrated a relative risk reduction of about 20% in the coil embolization arm and established it as a preferred treatment for ruptured cerebral aneurysms [5–7]. In 1998, the International Study of Unruptured Intracranial Aneurysms investigators prospectively compared clipping vs coil embolization of unruptured aneurysms [8]. Although these data have a strong inherent bias, this remains the best evidence available for unruptured aneurysms, and there is general consensus around treatment of larger-sized aneurysms. Subsequent development of vulnerability scores incorporating clinical characteristics to quantify the rupture risk, e.g., the PHASES (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage, site of aneurysm) score, and unruptured intracranial aneurysm treatment score (Tables 96.1 and 96.2) [9,10]. Extrapolating from the ISAT trial, coil embolization has become a common treatment for unruptured aneurysms as well. Subsequently, developments in compliant balloons and intracranial stents allowed for treatment of wide-neck aneurysms which were previously unsafe for treatment with traditional endovascular coil embolization techniques due to coil herniation and nontarget embolization in the parent vessel. Balloon remodeling allows for coil embolization for securing aneurysm domes without necessitating stent placement, which requires a course of dual antiplatelets. This is a useful technique in the setting of acutely ruptured aneurysms. Stent placement across the neck of an aneurysm provides scaffolding to allow for occlusion of the aneurysm with coils achieving sufficient packing density. Table 96.1 Population, Hypertension, Age, Size of Aneurysm, Earlier Subarachnoid Hemorrhage, Site of Aneurysm (PHASES) Score PHASES Risk Score
Points
Population North American, Non-Finnish European
0
Japanese
3
Finnish
5
Hypertension
PHASES Risk Score
Points
No
0
Yes
1
Age 3 or aspect ratio >1.6
1
Location
Basilar artery bifurcation
5
Vertebral/basilar artery
4
Anterior or posterior communicating artery
1
Other
Aneurysm growth on serial imaging
4
New aneurysm discovered on serial imaging
3
Contralateral stenoocclusive vessel disease
1
Treatment Age-Related risk 80 years
5
Aneurysm Size-Related Risk 20 mm
5
Aneurysm Complexity-Related Risk High
3
Low
0
Intervention-related risk (constant)
5
Total Favors treatment
Favors medical management
Each factor is added up in their respective columns and scores favoring aneurysm repair is compared to score favoring conservative/medical management. A higher score would determine best management. Note: No scores to be given to the black boxes.
Aneurysms that incorporate the origins of a branch increases the risk of their occlusion with aneurysm coils. In these situations, stents may also be placed to protect the patency of the arteries before coil embolization (Fig. 96.5). Occasionally, the branch artery is not large enough or the vessel angulation makes it difficult to place a protective stent (Fig. 96.6). In these cases, open surgical ligation with clipping should be considered.
FIGURE 96.5 Treatment of basilar tip aneurysm (white arrow) with stent-assisted coil embolization. (A) Roadmap imaging with injection of the right vertebral artery for navigation of microcatheters. (B) Digital subtraction angiography demonstrating stenting microcatheter tip in the right posterior cerebral artery (black arrowhead) and second microcatheter within the aneurysm with successful deployment of one coil. (C) Digital subtraction angiography demonstrating occlusion of the basilar tip aneurysm after packing of the aneurysm with coils and stent spanning the right posterior cerebral and basilar arteries. The distal aspect of the stent is visible as a subtraction artifact (black arrow).
FIGURE 96.6 Lateral angiography of middle cerebral artery aneurysm (black arrow) before (A) and after (B) clip ligation. (A) Aneurysm is seen incorporating the anterior temporal artery (white arrowhead) within the neck. Due to the angle of the takeoff of the anterior temporal artery to the parent vessel, the middle cerebral artery, it would be difficult to protect the artery with a stent. (B) After clip ligation, subtle subtraction artifact (black arrowhead) is seen at the clip. The anterior temporal artery (white arrowhead) remains patent.
More recently, the development of flow diverters has allowed for the treatment of large, complex, fusiform aneurysms, and multiple aneurysms in close vicinity of a parent vessel (Fig. 96.7). These have become popular since FDA approval in 2012 and after the results of the Pipeline for Uncoilable or Failed Aneurysms (PUFS) trial demonstrated the utility of these devices in 2013 [11]. These flow diverters are essentially stents with tighter weave of the interstices creating very tiny cell size which allow for a better scaffold for re-endothelialization and thus diversion of blood flow away from the aneurysm. The indications for use of flow diverting stents are increasing and there is gathering evidence that the recurrence rate in flow diverted aneurysms is negligible, albeit 12–18 months to achieve complete occlusion.
FIGURE 96.7 Giant cavernous internal carotid artery aneurysm treated with intravascular flow diverter and coils. (A) Initial angiogram showing irregularly shaped giant aneurysm centered on the cavernous internal carotid artery. (B) Placement of intravascular flow diverter under roadmap guidance to cover the aneurysm. There is an additional microcatheter with tip within the aneurysm (black arrow) which is jailed after placement of the flow diverter. (C) Single-shot radiograph after placement of multiple coils within the aneurysm. The flow diverter traverses the coil mass to keep the parent artery patent.
Acute Ischemic Stroke The establishment of endovascular intervention for the treatment of acute ischemic strokes has occurred more recently. Until the past decade, ischemic stroke was largely medically managed with intravenous tissue plasminogen activator (tPA), which was approved by the FDA in 1995 after the NINDS trial [12]. However, many patients are not eligible for this due to the strict time window (up to 4.5 hours) for the administration of the medication [13]. In the early 2000s, endovascular clot retrieval devices such as the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) and the first penumbra mechanical suction were developed for endovascular treatment of emergent large vessel occlusion in acute ischemic stroke. However, many randomized controlled trials showed no benefit of these endovascular devices compared to intravenous tPA and were only being used in patients who were not eligible for tPA [14,15]. These first-generation thrombectomy devices have largely been replaced with more effective stent-retrievers [16]. In 2015, five randomized controlled trials (MRCLEAN, ESCAPE, EXTEND IA, SWIFTPRIME, and REVASCAT) established level I evidence for benefit from endovascular mechanical thrombectomy in acute ischemic
stroke with occlusion of the internal carotid artery terminus, or first or second portions of the middle cerebral artery, which are defined as large vessel occlusions [17–21]. This is achieved by navigation of an aspiration catheter to the thrombus, and with continuous suction, slowly retracting the catheter until the thrombus is removed. A stent-retriever may also be deployed before suction, usually via a microcatheter which is navigated past the occlusion, such that the thrombus would be trapped between the tines of the stent-retriever and the aspiration catheter. Removing the thrombus allows for immediate reperfusion of the previously occluded vessel and is associated with maximal benefit to the patient (Fig. 96.8).
FIGURE 96.8 Acute right internal carotid terminus thrombus in a patient with left-sided weakness and neglect and National Institute of Health Stroke Scale 9. (A) Digital subtraction angiography of the right internal carotid artery shows abrupt nonopacification of the right internal carotid artery terminus just distal to the origin of the posterior communicating artery (black arrow). (B) After thrombectomy, there is complete reperfusion of the right anterior and middle cerebral artery territories.
Methods of optimal patient selection continue to improve with noninvasive imaging techniques such as CT and MRI used to evaluate perfusion, arterial lumen, and brain parenchyma. Recanalization techniques with stent-retrievers have improved and are achieving 80–90% recanalization rates. Literature has demonstrated overall functional independence in 33–71% of patients after recanalization [17–21]. Perfusionbased imaging by CT or MRI comparing patient’s ischemic penumbra (salvageable brain) to core infarct (nonsalvageable brain) allows for risk stratification of patients for thrombectomy as evidenced by the results of DEFUSE 3 and DAWN trials in 2018. This expanded the eligibility window
for endovascular thrombectomy for large vessel occlusion in acute ischemic stroke up to 24 hours if there is a large ischemic penumbra volume and small core infarct volume [22,23]. These trials established timely neurointervention as a pillar of treatment. Unfortunately, for patients with large core and small ischemic penumbra, recanalization would be contraindicated due to the high risk for subsequent hemorrhage.
Carotid Stenosis Up until the late 2000s, carotid endarterectomy was considered the standard of treatment for symptomatic and asymptomatic extracranial carotid stenosis following the results of the asymptomatic carotid atherosclerosis study and the North American Symptomatic Carotid Endarterectomy Trial (NASCET) [24–26]. The NASCET is still the most commonly referenced method of quantifying carotid stenosis as a percentage of the normal distal vessel lumen, colloquially termed “NASCET criteria” (Fig. 96.9) [26].
FIGURE 96.9 Demonstration of use of the angiography to calculate degree of carotid stenosis popularized by the North American Symptomatic Carotid Endarterectomy Trial (NASCET), colloquially termed “NASCET criteria.” (A) The degree of stenosis is calculated by ([diameter of normal distal vessel] – [minimal luminal diameter of stenosis])/(diameter of normal distal vessel) × 100%, in this case it is (5.24−0.33)/5.24 × 100% = 94%. (B) This stenosis completely resolves after stent placement and angioplasty. The stent spans the internal and common carotid arteries (black arrows).
Randomized trials comparing endarterectomy and carotid stenting have had mixed results, notably the SPACE and EVA-3S studies showing increased incidence of stroke with stent placement [27,28]. However, there have been multiple studies showing no significant difference in outcomes with endarterectomy compared to carotid stenting using various stents and embolic protection devices (CaRESS, ARCHeR, CABERNET, MAVErIC, and CREST) [29–33]. In 2010, the International Carotid Stenting Study, an international, multicenter, open design randomized trial of symptomatic patients with >50% carotid stenosis comparing carotid stenting versus endarterectomy showed there is an increased risk for stroke within 120 days for stenting [34]. However, in 2015, the long-term results of the International Carotid Stenting Study revealed no significant difference in fatal or disabling strokes between stenting compared to endarterectomy. However, nondisabling strokes were more frequent after stenting with no significant difference in functional ability postprocedure as measured by the modified Rankin scale [25]. Currently, both endarterectomy and carotid stenting are
accepted treatments for symptomatic carotid stenosis. The performance of either procedure depends on patient selection based on anatomy, comorbid conditions, and availability of local expertise.
Arteriovenous Malformation An arteriovenous malformation (AVM) is an abnormal tangle of vessels connecting artery and vein without a normal capillary bed. This type of lesion can be present in both the extracranial and intracranial locations. The angiographic appearance of extracranial lesions is graded by the Yakes or Cho-Do classification systems for endovascular treatment (Tables 96.3 and 96.4) and include both direct arteriovenous fistulas (AVFs) and classic AVMs with nidus [36,37]. For intracranial AVMs, the Spetzler–Martin grading system (Table 96.5) is most commonly used to categorize the lesions based on the surgical risk of resection [38]. Table 96.3 Yakes Classification System for Arteriovenous Malformations Type of Arteriov enous Shunt
Suggested Treatment
Type I
Direct arteriovenous fistula
Mechanical occlusion devices
Type IIa
With typical arteriovenous malformation nidus
Transcatheter or percutaneous sclerotherapy
Type IIb
Nidus that shunts into aneurysmal vein
Transcatheter or percutaneous sclerotherapy with/without coil occlusion of outflow veins
Type IIIa
Single outflow vein where vein wall is nidus
Coiling outflow vein
Type of Arteriov enous Shunt
Suggested Treatment
Type IIIb
Vein wall is nidus with multiple outflow veins
Coiling each outflow vein
Type IV
Infiltrative form of arteriovenous malformation
Transcatheter or percutaneous sclerotherapy
Table 96.4 Cho-Do Classification System for Arteriovenous Malformations Type of Arterioveno us Shunt Type I
No more than three separate arteries shunt into single venous drainage
Type II
Multiple (greater than three) arteries shunting into single venous drainage
Type IIIa
Fine multiple shunts are present between arterioles and venules, often appearing as blush on angiography
Type IIIb
Multiple shunts with dilated components, often appear as complex vascular networks on angiography
Table 96.5 Spetzler–Martin Grading System for Intracranial Arteriovenous Malformations
Feature
P o i n t s
Size Small 6 cm
3
Eloquence of Adjacent Brain Noneloquent
0
Eloquent (hypothalamus, thalamus, brain stem, cerebellar peduncles, sensorimotor areas, language areas, and primary visual area)
1
Pattern of Venous Drainage Superficial only
0
Deep component present
1
Grade is calculated for cumulative points from size, eloquence, and venous drainage.
The use of endovascular embolization to treat cerebral AVMs was first described in 1960 using methyl-methacrylate spheres to treat a left middle cerebral AVM [39]. Subsequently, there have been many case series describing the use of catheter-directed embolization as an adjunct to surgical resection of AVM [40–42]. In the era of three-dimensional angiography, cone-beam CT, and the ability to use microselection for further delineation of feeding arteries, the use of NIR is key for both diagnosis and treatment planning of cerebral AVMs (Fig. 96.10). AVMs presenting with hemorrhage are typically treated with a combination of endovascular embolization using liquid embolic, surgical resection, and/or stereotactic radiosurgery (SRS).
FIGURE 96.10 Intracranial Spetzler–Martin grade 4 arteriovenous malformation. (A) Two-dimensional digital subtraction angiography of the left internal carotid artery shows a tangle of vessels (black arrowheads) with early drainage of the thalamostriate tributaries of the internal cerebral vein (black arrow). (B) Three-dimensional reconstruction of rotational angiography with injection of the left internal carotid artery.
Treatment for primary prevention of hemorrhage and other complications in AVM is more controversial. The results of the original ARUBA trial demonstrated superiority of medical therapy over interventions (which included surgery, endovascular treatment, and SRS) [43]. Even with updated long-term follow-up recently published from the ARUBA trial, medical management alone remained superior to medical management plus interventional therapy [44]. Still, a subsequent trial has shown less disabling deficits of intervention compared to the results of the ARUBA trial using a similar cohort of patients, which suggests there is a role of endovascular intervention, SRS, and/or microsurgery for the treatment of unruptured AVMs [45]. Treatment of head and neck AVMs is more commonplace as these lesions tend to be more cosmetically deforming, enlarge over time, and can result in pain, hemorrhage, or rarely high output heart failure [46]. Early case series were described in the 1970s using a gelatin-based embolic for treatment [47]. However, embolization alone does not always control the lesion, and recurrence rates can be as high as 98%, and this is typically used as an adjunct to surgical resection [48]. In more recent series, the use of sclerosant agents to obliterate the endothelium has been described [49]. Sclerosant agents include dehydrated alcohol or bleomycin which can be administered via trans-arterial or percutaneous access. Treatment of head and neck AVMs is typically separated into multiple treatments to minimize toxicity of the sclerosant agents as well as disperse cumulative radiation exposure.
Dural Arteriovenous Fistula Unlike AVMs which are thought to be congenital, dural arteriovenous fistulae (dAVF) usually develop after trauma or other events leading to spontaneous thrombosis of venous channels. Similar to AVMs, dAVF can be diagnosed on noninvasive cross-sectional imaging such as MRI and CT. However, angiography would be required to fully grade lesions utilizing the accepted Cognard or Borden classification system (Tables 96.6 and 96.7), which requires characterization of flow directionality through the venous drainage [50,51]. More aggressive lesions are associated with retrograde dural, cortical, or spinal venous reflux leading to vascular congestion and increased risk of hemorrhage (Fig. 96.11). Table 96.6 Cognard Classification System for Dural Arteriovenous Fistula T y p e s
Description
I
Drain to the dural venous sinus with antegrade flow in the sinus
I I a
Drain to the dural venous sinus with retrograde flow into sinuses only
I I b
Drain to the dural venous sinus with reflux into the cortical veins which drain in antegrade fashion in the venous sinuses
I I a + b
Drain to the dural venous sinus with retrograde flow in the sinus and cortical venous reflux
I I I
Drain to the cortical vein without venous ectasia
T y p e s
Description
I V
Drain into cortical vein with venous ectasia >5 mm
V
Drain into spinal perimedullary veins
Table 96.7 Borden Classification System for Dural Arteriovenous Fistula Ty pes
Description
I
Direct drain into the dural venous sinus or meningeal vein
II
Drain into venous sinus with retrograde drainage into subarachnoid veins
III
Drain into the subarachnoid veins
Su bty pes
Description
A
Simple fistula with direct connection between single meningeal artery and draining vein or sinus
B
Multiple fistulas with complex structure
FIGURE 96.11 Dural arteriovenous fistula fed by branches of the occipital (black arrow) and middle meningeal arteries (black arrowheads), classified Cognard class IV due to ectasia of the draining cortical veins (white arrow). (A) Visualization of the feeding arteries with digital subtraction angiography of the external carotid artery. (B) Subselective microcatheter (white arrowhead) angiography of the occipital artery.
Endovascular treatment of these abnormal connections has become more commonplace. As previously discussed, the first human use of detachable coils was for the treatment of a carotid-cavernous fistula [3]. As illustrated by the Barrow classification for carotid-cavernous fistula (Table 96.8), there are many potential connections between the carotid artery and the cavernous sinus, particularly with an indirect fistula [52]. The standard treatment for such an indirect fistula would be placing embolic material, most commonly coils, to close off the venous side of the fistulous connection. This would involve both arterial and venous access. For a direct, type A, carotidcavernous fistula, often a flow diverting stent is placed within the internal carotid artery at the site of fistula in addition to venous embolization. Table 96.8 Barrow Classification System for Carotid-Cavernous Fistula T y p es
Description
T y p es
Description
D ir ec t
A
Direct shunt from the cavernous portion of the internal carotid artery to the cavernous sinus
In di re ct
B
Dural shunt from meningeal branches of the internal carotid artery and the cavernous sinus
C
Dural shunt from meningeal branches of external carotid artery and the cavernous sinus
D
Dural shunt from meningeal branches from both internal and external carotid arteries and the cavernous sinus
Treatment for dural fistulae at other locations has also primarily been via the endovascular approach. Typical lesions are treated from the arterial side with liquid embolic material pushed forward until sufficient penetration into the nidus and draining vein is visualized. Aggressive lesions may be treated with a combination of arterial and venous approaches, depending on the location of the lesion and accessibility of the vessels. Other approaches for therapy include SRS and or surgical clip ligation [53].
Vein of Galen Malformation A rare arteriovenous malformation in the pediatric population, vein of Galen malformation develops prenatally due to AVF involving the median prosencephalic vein. The term “vein of Galen malformation” itself is a misnomer, as the venous varix is of the median prosencephalic vein, a precursor of the vein of Galen. Often, these are diagnosed prenatally with sonography or in the neonatal period due to patient’s presenting heart failure. There are two main types: choroidal and mural. The choroidal type is fed by multiple choroidal arteries forming a nidus anterior to venous varix. These patients typically present in the neonatal period with high-output heart
failure. In contrast, the mural type has lesser number of more defined fistulous connections within the wall of the venous varix, with patients typically presenting later (as infants) with hydrocephalous [54,55]. Treatment for these malformations is primarily endovascular, with staged embolization using coils and liquid embolics (Fig. 96.12). There are reports of spontaneous thrombosis and resolution of these malformations, however, they are rare, and often patients present with clinical manifestations that require more immediate intervention such as heart failure [54,56].
FIGURE 96.12 Neonate with vein of Galen malformation treated with coil and liquid embolization. (A) Early filling of dilated vein of Galen (black arrowheads) is seen. The pericallosal artery (white arrowheads) appears to be the main feeder. (B) Complete occlusion of fistulous connection causing vein of Galen malformation on follow up angiogram after several stages of coil and liquid embolization, seen as subtraction artifacts (black arrow).
Venous and Lymphatic Malformation Venous and lymphatic malformations are abnormal vessels without clear arterial feeders and/or shunting vessel, and thus most commonly are not high-flow lesions. Compared to AVMs, venous and/or lymphatic malformations are more often managed percutaneously with sclerosant agents (Fig. 96.13), most commonly with dehydrated alcohol, doxycycline, sodium tetradecyl, and/or bleomycin. Sclerotherapy is the first-line management for macrocystic or combined lymphatic malformations, with surgical resection considered only if all the macrocystic components have been treated [57]. Similarly, sclerotherapy is also generally considered safer and more effective for venous malformations and should be considered before resection to improve outcome and lower recurrence rate [58].
FIGURE 96.13 Lymphatic malformation of the right neck treated with sclerotherapy. (A) MRI of the neck shows cystic lesion (white arrows) in the right neck at the level of the submandibular gland. (B) USG guided access with needle (white arrowheads) into the lymphatic malformation. (C) Single shot radiograph of the lymphatic malformation after administration of contrast via pigtail catheter (black arrow) before injecting sclerosing agent.
Often, multiple treatments are required to minimize toxicity and side effects and more effectively treat recurrence. Depending on the location of lesions, image guidance may be required to confirm access to the lesion and ensure adequate treatment of lesions with the sclerosant agents. Additionally, injection of contrast and venography allows for better characterization of flow, particularly of deeper lesions inaccessible to sonography [59,60]. The appearance of these lesions on venography allows for categorization using the Puig classification scheme (Table 96.9) and risk stratification of central embolization of agents [61]. Table 96.9 Puig Classification Scheme for Venous Malformations Ty pes
Description
I
Isolated malformation without peripheral drainage
II
Malformation that drains into normal veins
III
Malformation that drains into dysplastic veins
IV
Presence of venous ectasia
With any of the vascular malformations, the locations of these lesions tend to be variable. Thus, knowledge of head and neck, as well as neurovascular anatomy, is crucial for limiting adverse effects and nontarget treatment.
Tumors Image-guided intervention for tumor treatment encompass endovascular and nonendovascular approaches. The endovascular approach includes selective intra-arterial chemotherapy administration and embolization of tumors. The utilization of an intra-arterial infusion of chemotherapy was first described with direct carotid puncture and infusion in the 1950s [62]. This technique is established in the pediatric intra-ocular retinoblastoma population. The first article describing local chemotherapy to the ophthalmic artery was published in 2004 describing a pseudo-selective technique with balloon occlusion of the ipsilateral internal carotid artery distal to the ophthalmic artery origin and infusing chemotherapy proximally [63]. A later phase I/II study of intra-arterial chemotherapy for salvage therapy in infants with retinoblastoma destined for enucleation used direct infusion into the ophthalmic artery using microcatheters, which has become the preferred technique in delivering intra-arterial chemotherapy (Fig. 96.14) [64]. Overall, this treatment has shown to be safe and effective for intraocular retinoblastoma, and intravenous therapy is reserved for those patients in whom intra-arterial therapy technically fails.
FIGURE 96.14 Access into the ophthalmic artery of a 2-year-old boy with retinoblastoma for intra-arterial chemotherapy administration. (A) Digital subtraction angiography of the internal carotid artery via a 4 French Vertebral catheter shows widely patent ophthalmic artery (black arrow). (B) Digital subtraction angiography of the ophthalmic artery using a 1.2 French Magic (Bard, Covington, GA, USA) microcatheter (black arrowhead at tip) before administration of chemotherapy.
The use of intra-arterial chemotherapy to treat tumors in adults, especially tumors involving brain parenchyma itself, is not well-established. Studies of intra-arterial chemotherapy do show increased intra-tumor drug concentration without significantly increased systemic concentration, however, there are vascular toxicity and neurotoxicity related to these treatments. Advancements in techniques for subselection and monitoring of dosage would be necessary for successful intra-arterial chemotherapy of tumors involving brain parenchyma [65]. Nonmalignant tumor embolization in adults is more often used as a preoperative adjunct to reduce hemorrhagic complications and operative time, with the first such cases published in the late 1970s [66]. The majority of tumors embolized are meningiomas due to the relative predictability of arterial supply from the middle meningeal artery (Fig. 96.15). However, occasionally meningiomas can be supplied by meningeal branches of the internal carotid or vertebral arteries. These arteries are higher risk for strokes during treatment with trans-arterial embolization due to the possibility of reflux of embolic material to the main artery. Often these tumors would be resected without preoperative embolization.
FIGURE 96.15 Endovascular embolization of parietal convexity meningioma before surgical resection. (A) Digital subtraction angiography of the external carotid artery showing supply of the meningioma (white arrowheads) via the middle meningeal artery (black arrowheads). (B) Digital subtraction angiography of via microcatheter of the middle meningeal artery branch supplying the meningioma. (C) Digital subtraction angiography of the external carotid artery showing occlusion of the middle meningeal artery branch supplying the meningioma after particle and coil embolization. Coil construct is seen as a subtraction artifact (black arrow).
Embolization of head and neck tumors should be approached with caution due to possible angiographically occult anastomosis to the intracranial circulation and cranial nerve vasa nervorum [67]. Preoperative embolization can be performed for particularly vascular tumors such as juvenile nasopharyngeal angiofibroma and paragangliomas. Embolization materials generally include particle embolic material and liquid embolic agents, however, occasionally coils can be used to protect adjacent vessels from nontarget embolization [68]. Percutaneous treatment of tumors is used more often in spine intervention, which includes radiofrequency ablation and intrathecal administration of chemotherapy for leptomeningeal disease, which offers local therapy with minimum systemic side effects [69]. Administration of chemotherapy into the thecal sac via lumbar puncture was first described in the 1960s [70–72]. More recently, fluoroscopy-guided lumbar puncture for access has been utilized with increasing frequency, and administration of chemotherapeutic drugs has become common for radiologists [73]. The most common malignancies treated is lymphoproliferative malignant disease of the central nervous system, leptomeningeal spread of breast cancer, and melanoma metastasis, although theoretically this treatment can be applied to any malignancy with leptomeningeal metastasis [69].
Head and Neck Hemorrhage There are many entities that can cause hemorrhage in the head and neck. Often patients who require endovascular intervention present emergently with sentinel hemorrhage and treatments can be lifesaving. Endovascular treatment of epistaxis is often offered after patients have failed endonasal cautery, or if hemorrhage is poorly controlled and endonasal visualization is poor. Often in cases of recurrent epistaxis, angiography would be negative for extravasation, and embolization is performed empirically. This procedure was first described in 1974 with the use of absorbable gelatin particles in the sphenopalatine branch of the internal maxillary artery [74]. More recently, embolization can be carried out with particles, coils, and/or liquid embolics. Carotid artery rupture is a complication of head and neck malignancies that often presents as hemorrhagic shock. Risk factors include prior radiotherapy, infection, delayed wound healing, reconstructive flap necrosis, cutaneous or mucosal fistula, radical resection in close proximity to the carotid sheath, tumor invasion to the carotid sheath, and desiccation secondary to exposure [75]. Early endovascular treatment involves occlusion with balloon, and is often used as a bridge to more durable surgical ligation [76]. However, this ligation essentially sacrifices the artery and can result in permanent neurologic deficits. Covered stent placement can be an alternative to vessel sacrifice, however long-term durability of this treatment is not well established, and patients may be at risk for infection, particularly in setting of cutaneousfistula or adjacent tissue necrosis communicating with the alimentary canal. Endovascular sacrifice of the artery with embolization is an established alternative to surgical ligation in patients with acute hemorrhage [77]. In patients with threatened carotid rupture, prophylactic endovascular embolization of the carotid artery can be considered specially if an enbloc resection is contemplated. This procedure should include a balloon occlusion test, which involves flow arrest by balloon inflation in the internal carotid artery, usually at the petrous segment to avoid reflex bradycardia from carotid sinus stimulation, and neurologic examination. Additionally, collateral flow from contralateral carotid and vertebrobasilar circulation should be documented angiographically during the balloon occlusion. This test allows for candid discussion of risks and benefits of vessel sacrifice in case of hemorrhagic complication [78].
Spinal Vascular Interventions
Spinal angiography is utilized for characterization, treatment, and presurgical evaluation of spinal vascular lesions (Fig. 96.16) and vascular supply to spinal tumors. This is typically performed with a sequential selection of segmental arteries. A reverse curve catheter can be employed in cases of difficult anatomy to maintain access to a certain artery. Often this is performed under general anesthesia, even in the cases of diagnostic angiography, to minimize motion artifact, and optimal visualization of the anterior spinal artery of Adamkiewicz which is often very small.
FIGURE 96.16 46-year-old male with progressive myelopathy found to have spinal dural arteriovenous fistula. (A) MRI STIR sequence showing longitudinally extensive T2 hyperintensity of the thoracic cord with subtle serpiginous flow voids (white arrowheads) along the dorsal aspect of the cord suspicious for vascular malformation. (B) Digital subtraction angiography in the anteroposterior projection showing early draining dural vein (black arrowheads) with injection of the left T11 segmental artery. (C) Surface-rendered 3D reconstruction from cone-beam CT obtained after treatment of the fistula with glue embolization demonstration glue cast in within the fistula.
The first case series of spinal angiography was published in 1967 by Di Chiro et al., which demonstrated the utility of selective spinal angiography in characterizing spinal vascularity [79]. Although there are advances in noninvasive imaging such as contrast-enhanced time-resolved MRA to evaluate spinal vascular lesions, this technique is not widely available and has less spatial and temporal resolution compared to selective spinal angiography [80]. Unfortunately, there is no well-established classification scheme for spinal vascular lesions, with some classification schemes also including vascular neoplastic lesions [81,82]. In general, vascular lesions can be largely classified by compartment: epidural, dural, pial, and intramedullary.
Vertebroplasty and Vertebral Augmentation A point of confusion with spine interventions is the distinction between vertebroplasty and kyphoplasty. Most practitioners agree that vertebroplasty involves the injection of cement into the vertebral body. The term kyphoplasty describes a procedure similar to vertebroplasty with the addition of vertebral body height restoration with various devices such as balloons to reduce kyphosis [83]. A more generalized term that can be used in place of kyphoplasty to describe vertebral body height restoration is “vertebral augmentation.” Unfortunately, these terms have been used almost interchangeably in the literature, and to add to further confusion many trials describing vertebral augmentation often use the term “vertebroplasty.” This point of contention may not be relevant as evidence show no significant outcome difference between vertebroplasty and vertebral augmentation [84,85]. Moreover, height restoration with balloons and other devices inserted within the vertebral body via a percutaneous transpedicular (Fig. 96.17) or para-pedicular approach has not been shown to provide significant clinic benefit when compared to vertebroplasty.
FIGURE 96.17 Vertebroplasty of the lower thoracic vertebral bodies for management of pain after osteoporotic compression fracture. (A and B) Access to the vertebral bodies via transpedicular approach bilaterally at T11 (black arrowheads) and via the left pedicle at T12 with utilization a curved needle (black arrow) to cross midline for administration of cement. (C and D) DynaCT after administration of cement and removal of needles shows satisfactory fill of the vertebral bodies (white arrowheads). The patient had prior vertebroplasties done of the lumbar spine.
The injection of radiopaque bone cement into a diseased vertebral body via percutaneously placed large-caliber needles for the treatment of painful osteoporotic compression fractures was first described in a case series in 1997 [86]. However, two randomized trials published in 2009 from different institutions found no benefit for vertebroplasty over sham procedure in patients with osteoporosis [87,88]. More recently, the VAPOUR trial showed benefit of vertebral augmentation over sham procedure in patients with acute painful vertebral osteoporotic fractures of less than 6 weeks duration [89]. Additional studies and review articles have also tried identifying predictors of favorable outcome for vertebroplasty or vertebral augmentation, suggesting the mixed results of the large randomized trials are due to patient selection and heterogeneity of procedure technique [84,90].
Overall, it is generally accepted to try medical and conservative/noninvasive management of pain secondary to vertebral fracture before any instrumentation including vertebroplasty or vertebral augmentation, and procedural success is largely dependent on patient selection, duration of the patient’s pain, and technique. The consensus opinion supported by a reasonable scientific premise is that severe pain due to osteoporotic fractures of vertebral bodies may be alleviated by vertebroplasty and vertebral augmentation. These results can be sustained by regular physical therapy and reconditioning of paraspinal muscle strength. Alteration of biomechanics by the vertebral augmentation can lead to adjacent level fractures, a risk that is somewhat lower following vertebroplasty without augmentation. Radiofrequency ablation of vertebral bodies with tumor involvement can also be used before vertebroplasty or vertebral augmentation in pathological vertebral body fractures or collapses. For patients with painful osseous metastases that have failed standard treatments such as systemic chemotherapy and radiation therapy, radiofrequency ablation of the tumor can provide pain relief [91]. This technique was expanded to include painful vertebral body metastases with adjunctive vertebroplasty for stability and aid in analgesia [92,93].
Future Directions Since its inception in the late 1990s and early 2000s with a good scientific level of evidence for endovascular treatment of ruptured cerebral aneurysms, the specialty of NIR has become more and more established over the past two decades. Currently, the majority of ruptured and unruptured aneurysms are treated endovascularly. Mechanical thrombectomy is a proven treatment for acute ischemic stroke secondary to large vessel occlusion with eligibility criteria that continue to expand. The trajectory of NIR as a specialty over the next two decades holds promise as newer and more robust minimally invasive techniques gain good scientific evidence for improved outcomes in patients with neurovascular and other neurological pathologies. There is a general anxiety amongst radiologists practicing neurointervention that the field will be taken over by our neurosurgery and neurology colleagues who have established themselves in this practice. However, as diagnostic cerebral angiography is still the gold standard in the diagnosis of many cerebrovascular diseases radiologists play a key role in the field due to the emphasis on the physics of image optimization and the importance of overall radiation dose reduction. As such, most large-volume centers employ all three specialties within the realm of neurointervention. This collaboration is a strength of the field as each specialty brings different
perspectives of treatment and overall enhances patient care. Future directions for this field are only limited by the imagination. Devices are constantly improving, and with continued collaboration between radiology, neurosurgery, and neurology, the possibilities are endless.
Suggested Readings • AY Liu, Update on interventional neuroradiology, Perm J 10 (2006) 42–46. • OA Berkhemer, PS Fransen, D Beumer, et al., A randomized trial of intraarterial treatment for acute ischemic stroke, N Engl J Med 372 (2015) 11–20. • TG Brott, RW Hobson, 2nd, G Howard, et al., Stenting versus endarterectomy for treatment of carotid-artery stenosis, N Engl J Med 363 (2010) 11–23. • TL Rosenberg, JY Suen, GT Richter, Arteriovenous Malformations of the Head and Neck, Otolaryngol Clin North Am 51 (2018) 185–195. • W Clark, P Bird, P Gonski, et al., Safety and efficacy of vertebroplasty for acute painful osteoporotic fractures (VAPOUR): a multicentre, randomised, double-blind, placebocontrolled trial, Lancet 388 (2016) 1408–1416.
References [1] AY Liu, Update on interventional neuroradiology, Perm J 10 (2006) 42–46. [2] DM Pelz, AJ Fox, F Vinuela, Digital subtraction angiography: current clinical applications, Stroke 16 (1985) 528–536. [3] G Guglielmi, F Vinuela, J Dion, et al., Electrothrombosis of saccular aneurysms via endovascular approach. Part 2: preliminary clinical experience, J Neurosurg 75 (1991) 8–14. [4] G Guglielmi, History of the genesis of detachable coils. A review, J Neurosurg 111 (2009) 1–8. [5] A Molyneux, R Kerr, I Stratton, et al., International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial, Lancet 360 (2002) 1267–1274. [6] AJ Molyneux, RS Kerr, LM Yu, et al., International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion, Lancet 366 (2005) 809–817. [7] AJ Molyneux, RS Kerr, J Birks, et al., Risk of recurrent subarachnoid haemorrhage, death, or dependence and standardised mortality ratios after clipping or coiling of an intracranial aneurysm in the International Subarachnoid Aneurysm Trial (ISAT): longterm follow-up, Lancet Neurol 8 (2009) 427–433.
[8] International Study of Unruptured Intracranial Aneurysms I. Unruptured intracranial aneurysms—risk of rupture and risks of surgical intervention, N Engl J Med 339 (1998) 1725–1733. [9] JP Greving, MJ Wermer, RD Brown Jr. et al., Development of the PHASES score for prediction of risk of rupture of intracranial aneurysms: a pooled analysis of six prospective cohort studies, Lancet Neurol 13 (2014) 59–66. [10] N Etminan, RD Brown Jr., K Beseoglu, et al., The unruptured intracranial aneurysm treatment score: a multidisciplinary consensus, Neurology 85 (2015) 881–889. [11] T Becske, DF Kallmes, I Saatci, et al., Pipeline for uncoilable or failed aneurysms: results from a multicenter clinical trial, Radiology 267 (2013) 858–868. [12] National Institute of Neurological D, Stroke rt PASSG, Tissue plasminogen activator for acute ischemic stroke, N Engl J Med 333 (1995) 1581–1587. [13] KR Lees, E Bluhmki, R von Kummer, et al., Time to treatment with intravenous alteplase and outcome in stroke: an updated pooled analysis of ECASS, ATLANTIS, NINDS, and EPITHET trials, Lancet 375 (2010) 1695–1703. [14] WS Smith, G Sung, S Starkman, et al., Safety and efficacy of mechanical embolectomy in acute ischemic stroke: results of the MERCI trial, Stroke 36 (2005) 1432–1438. [15] A Bose, H Henkes, K Alfke, et al., The penumbra system: a mechanical device for the treatment of acute stroke due to thromboembolism, AJNR Am J Neuroradiol 29 (2008) 1409–1413. [16] E Broussalis, E Trinka, W Hitzl, et al., Comparison of stentretriever devices versus the Merci retriever for endovascular treatment of acute stroke, AJNR Am J Neuroradiol 34 (2013) 366– 372. [17] OA Berkhemer, PS Fransen, D Beumer, et al., A randomized trial of intraarterial treatment for acute ischemic stroke, N Engl J Med 372 (2015) 11–20. [18] BC Campbell, PJ Mitchell, TJ Kleinig, et al., Endovascular therapy for ischemic stroke with perfusion-imaging selection, N Engl J Med 372 (2015) 1009–1018. [19] M Goyal, AM Demchuk, BK Menon, et al., Randomized assessment of rapid endovascular treatment of ischemic stroke, N Engl J Med 372 (2015) 1019–1030. [20] TG Jovin, A Chamorro, E Cobo, et al., Thrombectomy within 8 hours after symptom onset in ischemic stroke, N Engl J Med 372 (2015) 2296–2306.
[21] JL Saver, M Goyal, A Bonafe, et al., Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke, N Engl J Med 372 (2015) 2285–2295. [22] GW Albers, MP Marks, S Kemp, et al., Thrombectomy for stroke at 6 to 16 hours with selection by perfusion imaging, N Engl J Med 378 (2018) 708–718. [23] RG Nogueira, AP Jadhav, DC Haussen, et al., Thrombectomy 6 to 24 hours after stroke with a mismatch between deficit and infarct, N Engl J Med 378 (2018) 11–21. [24] Endarterectomy for asymptomatic carotid artery stenosis. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study, JAMA 273 (1995) 1421–1428. [25] GG Ferguson, M Eliasziw, HW Barr, et al., The North American Symptomatic Carotid Endarterectomy Trial: surgical results in 1415 patients, Stroke 30 (1999) 1751–1758. [26] North American Symptomatic Carotid Endarterectomy Trial C, HJ.M Barnett, DW Taylor, et al., Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis, N Engl J Med 325 (1991) 445–453. [27] SC Group, PA Ringleb, J Allenberg, et al., 30 day results from the SPACE trial of stent-protected angioplasty versus carotid endarterectomy in symptomatic patients: a randomised noninferiority trial, Lancet 368 (2006) 1239–1247. [28] JL Mas, G Chatellier, B Beyssen, et al., Endarterectomy versus stenting in patients with symptomatic severe carotid stenosis, N Engl J Med 355 (2006) 1660–1671. [29] RS.C Ca, Carotid revascularization using endarterectomy or stenting systems (CaRESS) phase I clinical trial: 1-year results, J Vasc Surg 42 (2005) 213–219. [30] WA Gray, LN Hopkins, S Yadav, et al., Protected carotid stenting in high-surgical-risk patients: the ARCHeR results, J Vasc Surg 44 (2006) 258–268. [31] LN Hopkins, S Myla, E Grube, et al., Carotid artery revascularization in high surgical risk patients with the NexStent and the Filterwire EX/EZ: 1-year results in the CABERNET trial, Catheter Cardiovasc Interv 71 (2008) 950–960. [32] RT Higashida, JJ Popma, P Apruzzese, et al., Evaluation of the medtronic exponent self-expanding carotid stent system with the medtronic guardwire temporary occlusion and aspiration system in the treatment of carotid stenosis: combined from the MAVErIC (Medtronic AVE Self-expanding CaRotid Stent System with distal protection In the treatment of Carotid stenosis) I and MAVErIC II trials, Stroke 41 (2010) e102–e109.
[33] TG Brott, RW Hobson 2nd., G Howard, et al., Stenting versus endarterectomy for treatment of carotid-artery stenosis, N Engl J Med 363 (2010) 11–23. [34] International Carotid Stenting Study I, J Ederle, J Dobson, et al., Carotid artery stenting compared with endarterectomy in patients with symptomatic carotid stenosis (International Carotid Stenting Study): an interim analysis of a randomised controlled trial, Lancet 375 (2010) 985–997. [35] LH Bonati, J Dobson, RL Featherstone, et al., Long-term outcomes after stenting versus endarterectomy for treatment of symptomatic carotid stenosis: the International Carotid Stenting Study (ICSS) randomised trial, Lancet 385 (2015) 529–538. [36] W Yakes, Yakes’ AVM classification system, J Vascular Interventional Radiol 2 (2015) S224. [37] SK Cho, YS Do, SW Shin, et al., Arteriovenous malformations of the body and extremities: analysis of therapeutic outcomes and approaches according to a modified angiographic classification, J Endovasc Ther 13 (2006) 527–538. [38] RF Spetzler, NA Martin, A proposed grading system for arteriovenous malformations, J Neurosurg 65 (1986) 476–483. [39] AJ Luessenhop, WT Spence, Artificial embolization of cerebral arteries. Report of use in a case of arteriovenous malformation, J Am Med Assoc 172 (1960) 1153–1155. [40] SM Wolpert, BM Stein, Catheter embolization of intracranial arteriovenous malformations as an aid to surgical excision, Neuroradiology 10 (1975) 73–85. [41] WO Bank, CW Kerber, LD Cromwell, Treatment of intracerebral arteriovenous malformations with isobutyl 2-cyanoacrylate: initial clinical experience, Radiology 139 (1981) 609–616. [42] JJ Jafar, AJ Davis, A Berenstein, et al., The effect of embolization with N-butyl cyanoacrylate prior to surgical resection of cerebral arteriovenous malformations, J Neurosurg 78 (1993) 60– 69. [43] JP Mohr, MK Parides, C Stapf, et al., Medical management with or without interventional therapy for unruptured brain arteriovenous malformations (ARUBA): a multicentre, non-blinded, randomised trial, Lancet 383 (2014) 614–621. [44] JP Mohr, JR Overbey, A Hartmann, et al., Medical management with interventional therapy versus medical management alone for unruptured brain arteriovenous malformations (ARUBA): final follow-up of a multicentre, non-blinded, randomised controlled trial, Lancet Neurol 19 (2020) 573–581.
[45] J Wong, A Slomovic, G Ibrahim, et al., Microsurgery for ARUBA Trial (a randomized trial of unruptured brain arteriovenous malformation)-eligible unruptured brain arteriovenous malformations, Stroke 48 (2017) 136–144. [46] MP Kohout, M Hansen, JJ Pribaz, et al., Arteriovenous malformations of the head and neck: natural history and management, Plast Reconstr Surg 102 (1998) 643–654. [47] R Djindjian, J Cophignon, J Theron, et al., Embolization by superselective arteriography from the femoral route in neuroradiology. Review of 60 cases. 1. Technique, indications, complications, Neuroradiology 6 (1973) 20–26. [48] TL Rosenberg, JY Suen, GT Richter, Arteriovenous malformations of the head and neck, Otolaryngol Clin North Am 51 (2018) 185–195. [49] J Pekkola, K Lappalainen, P Vuola, et al., Head and neck arteriovenous malformations: results of ethanol sclerotherapy, AJNR Am J Neuroradiol 34 (2013) 198–204. [50] JA Borden, JK Wu, WA Shucart, A proposed classification for spinal and cranial dural arteriovenous fistulous malformations and implications for treatment, J Neurosurg 82 (1995) 166–179. [51] C Cognard, YP Gobin, L Pierot, et al., Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revised classification of venous drainage, Radiology 194 (1995) 671–680. [52] DL Barrow, RH Spector, IF Braun, et al., Classification and treatment of spontaneous carotid-cavernous sinus fistulas, J Neurosurg 62 (1985) 248–256. [53] H Kiyosue, Y Hori, M Okahara, et al., Treatment of intracranial dural arteriovenous fistulas: current strategies based on location and hemodynamics, and alternative techniques of transcatheter embolization, Radiographics 24 (2004) 1637–1653. [54] PL Lasjaunias, SM Chng, M Sachet, et al., The management of vein of Galen aneurysmal malformations, Neurosurgery 59 (2006) S184–S194, discussion S183-113. [55] J Litvak, MD Yahr, J Ransohoff, Aneurysms of the great vein of Galen and midline cerebral arteriovenous anomalies, J Neurosurg 17 (1960) 945–954. [56] BV Jones, WS Ball, TA Tomsick, et al., Vein of Galen aneurysmal malformation: diagnosis and treatment of 13 children with extended clinical follow-up, AJNR Am J Neuroradiol 23 (2002) 1717–1724.
[57] AK Greene, CA Perlyn, AI Alomari, Management of lymphatic malformations, Clin Plast Surg 38 (2011) 75–82. [58] AK Greene, AI Alomari, Management of venous malformations, Clin Plast Surg 38 (2011) 83–93. [59] L Donnelly, G Bissett 3rd., D Adams, Combined sonographic and fluoroscopic guidance: a modified technique for percutaneous sclerosis of low-flow vascular malformations, Am J Roentgenol 173 (1999) 655–657. [60] DJ Choi, AI Alomari, G Chaudry, et al., Neurointerventional management of low-flow vascular malformations of the head and neck, Neuroimag Clin N Am 19 (2009) 199–218. [61] S Puig, H Aref, V Chigot, et al., Classification of venous malformations in children and implications for sclerotherapy, Pediatr Radiol 33 (2003) 99–103. [62] JD French, PM West, FK Von Amerongen, et al., Effects of intracarotid administration of nitrogen mustard on normal brain and brain tumors, J Neurosurg 9 (1952) 378–389. [63] T Yamane, A Kaneko, M Mohri, The technique of ophthalmic arterial infusion therapy for patients with intraocular retinoblastoma, Int J Clin Oncol 9 (2004) 69–73. [64] DH Abramson, IJ Dunkel, SE Brodie, et al., A phase I/II study of direct intraarterial (ophthalmic artery) chemotherapy with melphalan for intraocular retinoblastoma initial results, Ophthalmology 115 (2008) 1398–1404, e1391. [65] R Huang, J Boltze, S Li, Strategies for improved intra-arterial treatments targeting brain tumors: a systematic review, Front Oncol 10 (2020) 1443. [66] EJ Duffis, CD Gandhi, CJ Prestigiacomo, et al., Head, neck, and brain tumor embolization guidelines, J Neurointerv Surg 4 (2012) 251–255. [67] P Lasjaunias, Nasopharyngeal angiofibromas: hazards of embolization, Radiology 136 (1980) 119–123. [68] A Shah, O Choudhri, H Jung, et al., Preoperative endovascular embolization of meningiomas: update on therapeutic options, Neurosurg Focus 38 (2015) E7. [69] P Beauchesne, Intrathecal chemotherapy for treatment of leptomeningeal dissemination of metastatic tumours, Lancet Oncol 11 (2010) 871–879. [70] JL Soscia, R Dibenedetto, J Crocco, et al., Treatment of “leukemic encephalopathy” with intrathecal amethopterin, Dis Nerv Syst 25 (1964) 308–310.
[71] CB Hyman, JM Bogle, CA Brubaker, et al., Central nervous system involvement by leukemia in children. Ii. Therapy with intrathecal methotrexate, Blood 25 (1965) 13–22. [72] KD Bagshawe, IT Magrath, PR Golding, Intrathecal methotrexate, Lancet 2 (1969) 1258. [73] KA Cauley, Fluoroscopically guided lumbar puncture, Am J Roentgenol 205 (2015) W442–W450. [74] J Sokoloff, I Wickbom, D McDonald, et al., Therapeutic percutaneous embolization in intractable epistaxis, Radiology 111 (1974) 285–287. [75] EM Sanders, KR Davis, CS Whelan, et al., Threatened carotid artery rupture: a complication of radical neck surgery, J Surg Oncol 33 (1986) 190–193. [76] MC Zimmerman, RA Mickel, DJ Kessler, et al., Treatment of impending carotid rupture with detachable balloon embolization, Arch Otolaryngol Head Neck Surg 113 (1987) 1169–1175. [77] Y Oweis, JJ Gemmete, N Chaudhary, et al., Delayed development of brain abscesses following stent-graft placement in a head and neck cancer patient presenting with carotid blowout syndrome, Cardiovasc Intervent Radiol 34 (Suppl 2) (2011) S31– S35. [78] JH Weinberg, A Sweid, D Joffe, et al., Carotid blowout management in the endovascular era, World Neurosurg 141 (2020) e1010–e1016. [79] G Di Chiro, J Doppman, AK Ommaya, Selective arteriography of arteriovenous aneurysms of spinal cord, Radiology 88 (1967) 1065–1077. [80] AM Saindane, SR Boddu, FC Tong, et al., Contrast-enhanced time-resolved MRA for pre-angiographic evaluation of suspected spinal dural arterial venous fistulas, J Neurointerv Surg 7 (2015) 135–140. [81] RF Spetzler, PW Detwiler, HA Riina, et al., Modified classification of spinal cord vascular lesions, J Neurosurg 96 (2002) 145–156. [82] K Takai, Spinal arteriovenous shunts: angioarchitecture and historical changes in classification, Neurol Med Chir (Tokyo) 57 (2017) 356–365. [83] Kyphoplasty, Merriam-Webster. Available from: https://www.merriam-webster.com/medical/kyphoplasty. [84] ID Papanastassiou, FM Phillips, J Van Meirhaeghe, et al., Comparing effects of kyphoplasty, vertebroplasty, and non-surgical
management in a systematic review of randomized and nonrandomized controlled studies, Eur Spine J 21 (2012) 1826–1843. [85] Y Robinson, C Olerud, Vertebroplasty and kyphoplasty: a systematic review of cement augmentation techniques for osteoporotic vertebral compression fractures compared to standard medical therapy, Maturitas 72 (2012) 42–49. [86] ME Jensen, AJ Evans, JM Mathis, et al., Percutaneous polymethylmethacrylate vertebroplasty in the treatment of osteoporotic vertebral body compression fractures: technical aspects, AJNR Am J Neuroradiol 18 (1997) 1897–1904. [87] R Buchbinder, RH Osborne, PR Ebeling, et al., A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures, N Engl J Med 361 (2009) 557–568. [88] DF Kallmes, BA Comstock, PJ Heagerty, et al., A randomized trial of vertebroplasty for osteoporotic spinal fractures, N Engl J Med 361 (2009) 569–579. [89] W Clark, P Bird, P Gonski, et al., Safety and efficacy of vertebroplasty for acute painful osteoporotic fractures (VAPOUR): a multicentre, randomised, double-blind, placebo-controlled trial, Lancet 388 (2016) 1408–1416. [90] JC Jones, JA Miller, DM Sudarshana, et al., Predictors of favorable quality of life outcome following kyphoplasty and vertebroplasty, J Neurosurg Spine 31 (2019) 389–396. [91] MP Goetz, MR Callstrom, JW Charboneau, et al., Percutaneous image-guided radiofrequency ablation of painful metastases involving bone: a multicenter study, J Clin Oncol 22 (2004) 300– 306. [92] TJ Greenwood, A Wallace, MV Friedman, et al., Combined ablation and radiation therapy of spinal metastases: a novel multimodality treatment approach, Pain Physician 18 (2015) 573– 581. [93] W Zhao, ZH Peng, JZ Chen, et al., Thermal effect of percutaneous radiofrequency ablation with a clustered electrode for vertebral tumors: In vitro and vivo experiments and clinical application, J Bone Oncol 12 (2018) 69–77.
CHAPTER 97
Musculoskeletal Interventional Radiology Robin Proctor
Introduction This chapter covers the basic principles and justifications for musculoskeletal interventional procedures with information on methods, indications, contraindications, and the different materials that may be used. More information around the specific application of individual procedures in relation to specific body sites and specific diseases can be found in the relevant chapters covering the relevant area.
Basic Principles of Musculoskeletal Intervention The basic principle for an interventional procedure is to use imaging guidance to accurately access the relevant area percutaneously, that is, without an open procedure and while avoiding contact with adjacent structures that might be damaged. There is a wide range of procedures that may then be performed under image guidance and broadly they may be diagnostic, therapeutic, or a combination of the two. They may not involve any material being injected or removed (e.g., dry needling or cutting a structure), may involve adding material (e.g., local anesthetic, therapeutic agent, or cement), may involve removing material (e.g., drainage, barbotage, or biopsy), or some combination of the above. Most national or regional societies offer guidance and peer support for those who are developing an interest in interventional musculoskeletal
radiology and there are a number of more specialist reference texts available for those seeking more information [1–6].
Preparation for Musculoskeletal Interventional Procedures Although an image-guided percutaneous procedure may spare the patient an operation, it remains invasive and the principles of informed consent still apply. Best practice is for the patient to be informed of the range of options available to them, including the likely outcome of doing nothing, as well as the intended benefits and possible complications from the procedure being proposed. If possible they should be given time to consider this information, for instance by receiving written information in advance or being given access to online guidance and afforded an opportunity to ask questions before the procedure is performed. The exact range of complications that should be quoted must be tailored to the patient and this is particularly relevant in musculoskeletal practice where the needs and aspirations of an elite athlete, a child with a suspected sarcoma, and an older patient with osteoarthritis may be very different. Practical preparation for the procedure is also important. Many potential complications may be avoided by thinking or talking through the procedure in advance ensuring that the necessary staff and equipment are available and that the patient will be appropriately positioned and comfortable enough to remain still for the duration of the procedure. Routine use of checklists has been shown to reduce medical error in relation to surgery. The degree of parallel with surgical practice depends on the procedure and some jurisdictions will enforce similar procedures before interventional radiology procedures [7]. Even when not required by legislation some adoption of similar techniques, such as skin marking to identify the correct side, level, and location can be advantageous.
Range of Technique and Evidence Much of the exact technique for individual musculoskeletal procedures varies from one part of the world to another and from one operator to another. The potential variance between what is ostensibly the same procedure performed by different operators together with the modest volume of some procedures makes research more difficult, and in many areas there is a dearth of high-quality evidence [8–10]. There are sometimes strong and politicized opinions and national and regional guidance varies. Understandably, patients with persistent symptoms
and their doctors are often willing to try procedures where evidence is weak.
Choice of Technique Often there are many possible approaches and more than one technique that could reasonably be considered. Other than suitable equipment and an appropriately trained operator being available, the fundamental requirements are that the patient can be positioned in a comfortable enough position that they can remain still for the duration of the procedure and that sterility can be maintained. For some procedures, a full-sterile field may be required and for others it may be more appropriate for a smaller area to be sterilized and an “aseptic no-touch technique” to be adopted. Just as when radiographic techniques are considered for diagnostic work, the advantages and disadvantages are similar and training, availability, and individual preference may determine which technique is selected. Understanding the procedure and the potential complications are critical to allow for selection of an appropriate technique. For instance, when performing a guided injection to achieve a cervical nerve root block puncture of the vertebral artery is a potentially very serious complication because it may lead to dissection and more so were any particulate injectate to be administered with potential embolic effects to the posterior circulation. Confident location of the tip of the needle away from structures of concern and aspiration before injection to confirm a nonintravascular position are prudent but depending on training some authors advocate precise location [11]while others prefer fluoroscopy because of its dynamic rather than static nature to detect intravascular spread with a test injection of iodinated contrast [12]The relative strengths and weaknesses of each technique are considered as they are described below. Typically ultrasonography (USG), fluoroscopy, or CT are used to guide interventional musculoskeletal procedures, although other approaches using x-rays as an adjunct to landmark techniques are described. USG or fluoroscopy are commonly used to access joints for direct MR arthrography but other than in specialist settings use of MRI to guide musculoskeletal interventions is rare [13]. Aseptic technique is required for interventional procedures and the size of the field and exact technique depends on the procedure. In some scenarios, there will be a large field and all of the field will require to remain sterile but in other procedures, for instance if it is possible to puncture some distance from a guiding probe, then a more limited field or no-touch technique sterilizing only the direct path of the needle may be appropriate.
Ultrasonography
USG is very operator dependent but readily available at the bedside and requires more modestly priced equipment than the alternatives. It does not involve radiation and offers real-time guidance but has limited penetration depth and cannot see beyond certain structures, such as the surface of bowel or bone [14]. Because USG requires line of sight to the area of interest, it is generally less useful for osseous procedures, other than accessing the surface of abnormal bone, or for deep procedures. What may be considered deep will vary from one operator to another and it is safer to remain within one’s competence and change technique in the acute setting of an individual patient while more slowly upskilling is required than to persevere with an unfamiliar situation. USG-guided procedures are particularly useful for tendon-related pathology because the diagnostic procedure may be quickly performed at the same time and other than in the largest patients most appendicular tendons are sufficiently close to the surface for extremely good resolution. As for diagnostic procedures anisotropy is a key consideration and it may be necessary to “heel-toe” (i.e., to indent one side of the probe further into the overlying soft tissues or to use stand-off gel on the other end of the probe) to maintain an approach perpendicular to the tendon to minimize anisotropy which, if unrecognized, might be mistaken for tendinopathy and lead to unnecessary intervention. Similarly, if neovascularity is being assessed to identify the degree of abnormality before intervention then light pressure with additional gel or a stand-off may necessary to minimize the risk that pressure from the operator would compress the tissues and lead to underassessment of the neovascularity. Broadly, there are two techniques to insert a needle when using an USG probe:
◾more “Out of plane” where the needle is inserted perpendicular (transverse) to the beam where vertical penetration following the direction of the beam into the body is usual and where the puncture is adjacent to the probe ◾Fig. “In plane” where the needle is inserted longitudinally along the length of the probe as in 97.1. In longitudinal guidance, the intention is to see a longer length of the needle,
including the tip and to guide it to the intended place. The strongest echo is produced when the beam is perpendicular to an object and having the bevel pointing toward the beam aids visualization of a needle
FIGURE 97.1 USG-guided barbotage of calcific deposit within supraspinatus tendon showing approach of the needle from the right side of the screen. The brightest line near the probe is the needle surface and the multiple parallel lines deep to this within an area of otherwise low signal are reverberation artifact that are strongest when fully in plane with the needle and can aid recognition and tracking of the needle.
For longitudinal guidance to be possible, it is necessary to insert the needle at a shallow enough angle to the probe so that it is possible to see the needle. This may necessitate a track starting with a puncture site several centimeters from the edge of the probe and, particularly for deeper interventions, if a puncture is made too close to the probe then the penetration may be too vertical to enable the needle to be adequately visualized. Angling the probe by rocking it “heel-toeing” the probe can help bring it more perpendicular to the track of the needle and most USG machines will allow a degree of beam steering, which can also be useful to angle the beam to be more perpendicular to the needle. Some manufacturers also offer advanced needle visualization software and special needles offering increased passive or actively echogenicity have also been described. Even with those techniques the strongest echo will be generally be produced when the needle is parallel to the probe (i.e., perpendicular to the beam) and the major learning point is to expect progressive loss of visualization as it is angled deeper and more parallel with the beam. While learning it is necessary to learn to split concentration between the positions of the probe and needle in the operator’s hands, which can be directly observed, and also the findings which can be seen on the screen. The aim with longitudinal tracking of the needle is to maintain visualization of
the tip and it is important to develop an awareness of whether the needle may be out of the plane of the beam which may often give a similar appearance on screen if it is passing obliquely across the beam. Larger needles are easier to see and if the bevel can be identified, then it is possible to be sure the tip is in view. Rapidly “bouncing” the needle along the path can help. Keeping the bevel up can aid visualization; and awareness of machine settings which may help or hinder visualization (such as steer or harmonics) is also helpful. Despite these techniques, it can be challenging to maintain the view of the tip of the needle and if it is necessary to adjust the configuration to maintain view or to find the tip of the needle then in general moving either the probe or the needle is more effective than trying to manipulate them both at the same time. If the position of the needle tip is unknown then moving the needle may be hazardous and moving the probe away from the needle, rocking it toward the path and visually aligning the probe with the path before slowly sweeping the probe across this path is effective to find the needle tip. Needle guides are available for many probes that will hold a needle in the plane of the ultrasound beam and maintain a defined angle of approach. This may be advantageous in some circumstances, but the fixed angle of approach can also become limiting if it is necessary to change angle during the approach, for instance to navigate around a structure on the approach or to avoid an osteophyte or other object near the site of the procedure. Depending on the location, a test injection may be appropriate and when the tip is in view fluid will be seen to flow from the tip. If even a small quantity of air is injected then it creates acoustic shadowing which can hinder further work with USG. There is no substitute for practice, as well as commercially available phantoms many experts have trained by using their own phantoms constructed from commercially available meat.
Fluoroscopy Fluoroscopy may also provide real-time guidance and the image, although importantly not the actual tissue, will be less hindered by overlying structures. Typically, the beam may be angled in each plane and by doing this and performing intermittent exposure the progress of the needle can be monitored. Screening in two planes is one technique to locate the needle tip accurately. An alternative technique is to make an approach along the track of the beam with intermittent exposures after adjusting or advancing the needle. Using this second technique even the longest needle appears as a dot on the screen as the beam is along its length and if it moves out of the line of
the beam then the needle will appear to elongate. It then becomes possible to see the hub and tip of the needle separately and for adjustments to be made to return to the intended track as shown in Fig. 97.2.
FIGURE 97.2 Intraarticular injection into right hip to prepare for MR arthrogram. The needle is 9 cm long but because viewed almost along the length it appears much shorter with the hub slightly lateral to the tip and with iodinated contrast having already passed into the joint and visible lateral to the femoral head.
The need to use radiation and iodinated contrast when confirming position during fluoroscopy may be limiting for some patient populations and locations. It is possible to increase resolution and magnify the image, but this comes with the penalty of increased radiation dose so resolution should be kept at the minimum required to safely perform the procedure. To minimize exposure of the operator it is necessary for them to keep their hands out of the primary beam and this can be facilitated by coning the beam to a smaller anatomical area. When working across the beam the tip of the
needle can be visualized and moved in real time but intermittent screening between adjustments is required when working along the length of the beam. Fluoroscopy may be especially effective in navigating a narrow track in a plane that is more oblique than can be delivered with CT or where there are well-defined bony margins or landmarks, for instance traversing a pedicle to access a vertebral body when performing biopsy or augmentation to the vertebral body.
Computed Tomography (CT) With CT it is possible to see the whole depth of tissue through which an approach is being made and to access deeper structures. CT generally requires a greater amount of radiation than fluoroscopy although with increasingly powerful reconstruction algorithms this dose penalty is diminishing. Once a needle is inserted a series of images are taken centered on a selected gantry position and the track may then be assessed and modified or the needle advanced before further images are taken. Most CT scanners have a biopsy mode where such slices may be repeated as the approach for a procedure is made. If an approach can be made in the plane of the scanner gantry and in an orthogonal plane to the room, then it is much easier for most operators to establish and maintain the intended course (Fig. 97.3).
FIGURE 97.3 CT-guided injection into inferior aspect of left sacroiliac joint. Note the patient is positioned prone for comfort and ease of access and that the needle track is vertical and in the plane of the CT image to make it easier to perform (skin to margin of joint is 9 cm).
The thickness of the needle should be considered when selecting the thickness and number of the images being acquired and when learning it. Depending on local policy and practice, the operator may wear appropriate personal protective equipment and remain within the room or may wear normal clothing and leave the scan room during each acquisition. It is possible to utilize CT fluoroscopy where images are obtained in real time and this may provide benefit in certain cases but it can rapidly increase radiation dose and it also becomes harder for the operator to remain out of the primary beam and to minimize their own dose.
Practical Tips
◾andThethus more at ease and comfortable the patient can be the more likely they are to stay still the easier the procedure is likely to be. Adequate analgesia is important and because certain tissues are better innervated (skin, periosteum) using adequate local analgesia at the puncture site and going through the subcutaneous tissue quickly is likely to minimize discomfort. Syringe exchange: If it is necessary to exchange the syringe to inject more than one substance, for instance to change to inject a therapeutic agent after first confirming position, then it is important to stabilize the needle to prevent displacement. If the size of the target and volume to be delivered permits, then a connecting tube may be helpful and allow the exchange to be performed distant from the needle to minimize the chance of displacement. Secure attachment of syringe and needle is a requirement but if an exchange is planned then this should not be any more firm than necessary to make a seal as straining to undo a stuck connection can make displacement of the needle more likely. Choice of needles: The key considerations are the length and diameter of the needle. Some longer needles are only available as spinal needles and compatibility with other available equipment must be considered. Because of safety measures designed to minimize the risk of inadvertent intrathecal administration of intravenous treatments, there is no universal compatibility between needles, connectors, and syringes.
The wider the needle the easier it will be to make it go in a straight line and to see regardless of the technique but the more difficult it will be to bend and the greater the trauma to tissues it passes through or risk of damage if a structure is contacted unintentionally.
For aspiration, the radius of the needle is the key feature (flow varies with the fourth power of the radius and inversely with the length); hence, the broadest and shortest needle which will safely access the area being aspirated should be selected.
Biopsy needles come in a variety of different configurations. Most soft tissue biopsy needles are spring loaded to take a sample and some can be used to selectively take short or longer samples. The key consideration is an awareness of which piece of tissue will be sampled to enable the core to be obtained from the intended area. When the device is “fired” some will sample along the track which has already been traversed and some will sample the material immediately distal to the position of the tip. Steering the needle: Regardless of the technique used, it is possible to make many needles follow a curved path that may be useful to avoid an obstacle or a hindrance to be minimized if the path to the region of interest is straight.
The shape of the tip of the needle will influence the direction of travel and with a bevel, the tip will tend to move away from the side of the opening as the needle is advanced, “bevel control”. This is more pronounced with thinner needles and some shapes of bevel. The hub of many needles are marked to demonstrate the orientation of the bevel and an operator should become familiar with the orientation of such a marking or make their own mark on the hub so they are confident of the orientation of the needle once it is below the skin surface. The degree of movement in one direction may also be changed by bending the needle, which is also easier with thinner needles but if this is attempted it is imperative that the operator is experienced with the technique and does not apply so much force as to break the needle. Volume of injectate: The amount injected should be considered both in terms of dose of any drugs administered and the total volume. High-volume techniques (e.g., 50 mL paratenon injection around the Achilles) are advocated by some authors and an appropriate diluent, such as saline with a small amount of local anesthetic must be selected as such volumes of many local anesthetics would be toxic. Such high-volume techniques are also contentious and not yet supported by strong evidence [15].
◾ ◾
◾
◾
Individual Procedures Biopsies
Just as in other body systems, a tissue diagnosis may be vital in the diagnosis and treatment of musculoskeletal disease. The basic techniques of fineneedle aspiration for cytology or core biopsy for histopathology are broadly the same as in other techniques; however, certain points should be emphasized as particularly important for musculoskeletal procedures. Particularly, for suspected bone and soft tissue sarcomas and also for other primary bone tumors, the approach for any biopsy may be critical as it may contaminate the track and determine the subsequent operative approach. Consequently, the route of a biopsy should be agreed in advance with the relevant surgeon who would perform resection. Where a lesion is heterogeneous, it may be necessary to agree which element should be biopsied. Broadly, the elements that enhance but which are not vascular structures will be more likely to yield useful tissue rather than necrotic material, although they are often closest to vessels and at greatest risk of bleeding. For some lesions, such as suspected lipomatous tumors, particularly for larger lesions, biopsy may be falsely reassuring as it is not possible to sample the entire lesion and the most relevant component may be missed. For all these reasons, multidisciplinary team working and centralized treatment of such conditions is the norm in many jurisdictions and familiarity with the arrangements in each center is required. Although steering needles is possible through soft tissue and some novel devices for steering through bone do exist, it is more usually the case that the site and angle of penetration into a bone will determine the subsequent track so it must be carefully selected, see for example a bone biopsy in Fig. 97.4. The periosteum is well innervated and more local anesthetic will be required there than in the overlying soft tissues.
FIGURE 97.4 Bone biopsy of suspicious lesion within L2 vertebral body in patient with known breast carcinoma. In this case the lesion is distant from the spinal canal with normal intervening bone but more caution would be required if abnormal tissue extended to the dural surface.
If a procedure is to pass through a bone and out the other side, then it will be necessary to warn the patient that they will feel the penetration through the deep surface of the bone and further local anesthetic is likely to be required at this location as the deep periosteum is traversed. Even when the cortex of a bone has been destroyed some mineralized matrix may remain and depending on the extent it may be necessary to use bone biopsy equipment or it may be possible to sample a section without mineralization using a soft tissue biopsy needle taking care to recognize which section of tissue will be taken when a spring-loaded biopsy device is being used when a soft tissue biopsy is performed. Contraindications to biopsy are similar to those in other body systems
◾orwhere it is not safely possible to obtain tissue without damaging adjacent critical structures, ◾hematoma where there is a risk of making a situation far worse, for instance the risk of epidural from a vertebral lesion could alter whether a procedure was performed depending
on the integrity of the cortex adjacent to the spinal canal and the amount of space around the cord/cauda equina at that level.
The risks from a biopsy procedure are pain, bleeding, introduction of infection, nondiagnostic sample, and damage to other structures. The precise value of each risk and their relative importance will vary by location, lesion being targeted, and the patient’s own values and aspirations.
Aspiration There are a number of areas where diagnostic or therapeutic aspiration may be performed for musculoskeletal procedures, for instance to drain a collection or to establish if it is infected, to perform arthrocentesis, or to target a ganglion or Baker’s cyst. The material being drained should be considered when an appropriate needle is selected: Ganglion contents are typically extremely viscous and aspiration may be difficult if not impossible unless a wide bore (e.g., 16G) needle is used. Similarly, depending on the maturity of hematoma and the viscosity of any collection it may or may not be possible to aspirate to dryness. Where it is not possible to drain material at the initial attempt it may be effective to instill some saline or other fluid to dilute the material of interest and then aspirate the resulting mixture. Table 97.1 lists the typical characteristics of different types of collection. In practice, it remains necessary to send samples of aspirate for appropriate laboratory testing to confirm the diagnosis although awareness of the likely diagnosis may guide selection of equipment and visual analysis of the material at the time of aspiration may help guide immediate management. Table 97.1 Typical Aspirate Findings in Common Conditions Collection /Joint Aspirate
Appearance of Fluid
Viscosity
White Cell Conten t
Crystals
Physiolog ical
Translucent, clear, or straw colored
Synovial fluid— thick Serous fluid— not viscous
Low
Absent
Infected
Cloudy, yellow, green, or brown
Thicker than serous fluid but less viscous than normal synovial fluid
Very high, neutro phil predo minant
Absent
Hemorrha gic
Bloody/pink Varies with age of hematoma and may yellow with developme nt of xanthochro mia
Variable– tends to become less viscous as hematom a matures
Low
Absent
Inflammat ory
Cloudy, yellow although often less so than with infection
Reduced viscosity
High
Present in gout, pseudogout (calcium pyrophosphate deposition disease, CPPD), and hydroxyapatite deposition disease
Some collections that are not infected, such as maturing hematoma, offer a very effective growing medium for bacteria and if intervention is considered then asepsis must be maintained to avoid infecting the collection. Following an aspiration some collections may recur and if left untreated others may hydrodissect and enlarge. In some scenarios, for instance when treating Morel–Lavallée lesions a consideration of the balance between these factors together with consideration of more conservative measures such as compression is necessary before attempting any aspiration.
Guided Injection This may be performed alone or in combination with one or more of the other procedures listed and may be diagnostic or therapeutic and the target intraarticular or extraarticular. Typically a joint or other potential space is targeted, such as a tendon sheath, bursa, epineural space, tissue plane adjacent to a retinaculum or other fascia or paratenon space and material is instilled under guidance. The nature and volume of the material depends on the intended treatment. (More information on common procedures is given next and see also Table 97.2). Table 97.2 Different Substances Commonly Injected During Guided Procedures in Musculoskeletal Radiology Specific Agent Indication Example Agents Complications Local anestheti c agents
To facilitate performing procedures or injection of other material Diagnostic block Short-acting therapeutic block
Lidocaine 1% Other agents may have a longer onset and length of action: Bupivacaine Ropivacaine Levobupivacaine See comparison Table 97.3 with dose information
Cardiorespirat ory and neurological symptoms with toxic dose or injection into wrong cavity (intravascular, intrathecal) Chondrotoxici ty described particularly with bupivacaine
Corticost eroids (also see Table 97.3)
Antiinflammat ory agents used to reduce symptoms in inflammatory processesDecr easing frequency of
Choice of steroid is contentious and licensing varies by jurisdiction. Awareness of the nature of the preparation, expected duration of
Systemic effects: immunosuppre ssion, disordered glucose metabolism, Local effects:
use in treating tendinopathy and chronic injuries but still commonly used
action and relative potency is important, for example particulate (prednisolone (depomedrol), triamcinolone (kenalog)) or dissolved (dexamethasone)
Embolism Post steroid flare Weakening of ligaments and tendons Fat necrosis Chondrotoxici ty
Plateletrich plasma (PRP)
Symptomatic relief and promotion of healing in tendinopathy, chronic tendon, muscle and ligament injuries. Also used in treatment of osteoarthritis and undisplaced labral tears
Prepared by centrifuging the patient’s own blood to yield material with increased concentration of growth factors, cytokines, and platelets. This may be acellular or prepared with varying concentrations of leucocytes. See additional information next
Local irritation Flare or reactive effusion particularly with leucocyte-rich PRP (L-PRP)
Dextrose
Hypertonic dextrose as prolotherapy agent and promoting local tissue healing. Lower molarity dextrose may be used for perineural injection to treat allodynia
Hypertonic for prolotherapy (12.5– 25%) 5% dextrose for perineural injection therapy
Symptoms usually relate to the injection and procedure rather than the dextrose
Hyaluron ic acid
Treatment of osteoarthritis alone or with PRP to increase the concentration of preexisting hyaluronic acid in synovial fluid
Sodium hyaluronate
Generally well-tolerated. Effectiveness not acknowledged by all authorities. May have delayed (several weeks) therapeutic effect
Botulinu m toxin
Treatment of spasticity and muscle contracture
Type A botulinum toxin that causes neuromuscular blockade: blocks cholinergic nerve terminals and decreases release of acetylcholine.
Intended to be long acting and cause paralysis which may affect other muscles if injection site or technique is suboptimal.
Chemical ablation agents
Denervation
Neat ethanol Acetic acid Sodium hydroxide
Intended to damage the location in which they are injected and provide irreversible effect so precise targeting is vital
How to confirm the location is correct: Under USG it is often possible to directly visualize entry to the target area and to watch injectate passing into the intended location. Under fluoroscopy, it is more usual to inject radiopaque contrast and to assess the spread of the contrast from the tip of the needle to confirm location, for instance as intraarticular, or perineural. In CT, it is possible to directly visualize the tip
although some authorities also advocate the use of contrast to demonstrate that the bevel is fully within the intended body cavity. Volume of Injectate Whenever making an injection, the volume of the potential space should be carefully considered together with the necessary volume of any therapeutic material. This may dictate that a smaller volume of nontherapeutic material or shorter connecting tube must be used or that contrast or local anesthetic be mixed with the therapeutic agent. For instance, if a guided injection to the small joints of the hand was performed with local anesthetic and iodinated contrast it would leave very little intraarticular volume for any further therapeutic substance, such as corticosteroid, because the total potential volume of the joint capsule even when fully distended is small. Full distention of joints is also uncomfortable so patients may better tolerate procedures that do not completely fill a joint, unless this is a requirement such as in hydrodilation of the shoulder joint to treat frozen shoulder when rupture of the capsule is often intended.
Dry Needling (Needle Tenotomy) Rather than fully cutting through the tendon, the technique is one of repeatedly passing a needle through an area of pathological tissue, such as tendinosis. This is thought to promote increased tissue response and healing. Increasingly, tendinosis has been demonstrated to be a degenerative process and not principally one of inflammation; hence, treatment with antiinflammatory measures such as steroids and nonsteroidal antiinflammatory drugs has become less popular in favor of other techniques. In some body areas, such as tennis elbow (lateral epicondylitis), there is increasing evidence that while steroids may give short-term relief they do not offer a similar improvement longer term and may lead to a worse eventual outcome than other measures [16]. The indications for dry needling are tendinosis and sometimes, and when under the care of a specialist, typical symptoms in the absence of a visible radiological abnormality. The complications are those of any injection, as well as the potential for increased damage to the tendon although it must be made clear that the tendon is already diseased and therefore not of normal strength otherwise the procedure would not be being considered. True tenotomy and intentionally cutting a tendon or other structure percutaneously is also possible, for instance in performing a full tenotomy of plantaris in selected patients or a release of a finger flexor tendon by cutting an abnormal pulley.
Barbotage Barbotage is indicated to treat deposits of calcium within a tendon, typically the supraspinatus tendon in the rotator cuff (Fig. 97.1). Depending on the consistency of the calcium, it may be possible to aspirate some or all of the calcium or to puncture it many times to break it up and promote a healing response. Typically, this is accompanied by a steroid injection into the subacromial/subdeltoid bursa at the completion of the barbotage. With sufficient local anesthetic, it is usually a well-tolerated procedure with risks similar to those of any guided injection going through a tendon. If the calcium has hardened, then it may not be possible to aspirate much material or it may block the needle and some authors describe multiple needle techniques to flush through the region of interest.
Ablation There are a number of reasons to wish to destroy material, for instance to target a metastasis or primary lesion or to permanently denervate a painful nerve. Several techniques exist that have their own advantages and disadvantages using chemical or thermal agents.
◾ Chemical ablation may be used for denervation, for instance in the context of chronic pain ◾selected Radiofrequency ablation generates heat and may be used as a primary treatment for lesions that would be difficult to access or resect, for example osteoid osteomas ◾treatment Cryoablation using cold rather than heat is also available and has been described for the of musculoskeletal lesions
By their very nature all forms of ablation are potentially destructive and should be considered irreversible specialist procedures.
Augmentation Procedures: Cementoplasty, Vertebroplasty, Kyphoplasty It is possible to percutaneously introduce cement to strengthen bone, relieve pain, and promote fracture healing. This has a range of uses from persistent pain following osteoporotic vertebral fracture, typically after failed conservative management and demonstrating that the fracture is still active on MRI (high signal on fluid sensitive sequences) to treatment of metastatic disease to relieve pain and stabilize the underlying bone.
Choice of Injectate A very large range of materials have been described as being of potential benefit in guided musculoskeletal procedures. This is a developing and
sometimes contentious area where practice and exact protocol varies from jurisdiction to jurisdiction and from institution to institution. Most important is to understand the principles behind the agents being used and to consider their complications. Prolotherapy is the process of injecting material to promote the patient’s own response and achieve healing, for instance using hypertonic dextrose or platelet-rich plasma (PRP). In any procedure, there is always the potential for no therapeutic response and the risks from any such procedure remain: pain, bleeding, and risk of introduction of infection. In addition, there are some specific complications relating to certain injectates as listed in Table 97.2.
◾steroid Choice of steroidsSome reports suggest that the risk of fat necrosis varies with choice of and there are a range of claims about efficacy. There has been a move away from
using corticosteroids for many pathologies, particularly soft tissue pathologies such as lateral epicondylitis because, although short-term outcomes may be favorable, there is evidence of a worse long-term effect.
As with any drug there are absolute contraindications (e.g., uncontrolled infection) and relative contraindications (e.g., poorly controlled diabetes, hypertension, or poor preprocedural condition of the joint). Knowledge of local and general side effects of corticosteroids and of relative potency are important, as well as local protocols as has been previously emphasized.
All steroids give the potential for adrenal suppression and in some patient groups and certain combinations with other drugs this may be markedly potentiated and profound, for example, triamcinolone potentiated by some antiretrovirals (e.g., ritonavir) that can lead to adrenal suppression even after a single dose.
The solubility of steroids varies and the less-soluble steroids intentionally have particles of the active component within the vials even after shaking. The theory of particulate steroids is they are more likely to be locally active for a long time and will be less systemically circulated and absorbed [17]. Embolic effects are, however, a risk with particulate steroids because they would function as a particulate embolic agent if inadvertently injected intravascularly. Consequently, extreme caution of avoiding them all together is recommended around certain sites, cervical neural foraminal injections, in particular, to avoid causing embolic infarctions.
Methylprednisolone acetate or triamcinolone acetonide are popular choices when a particulate preparation is suitable.
Symptoms may transiently worsen after injection—a “post injection flare.” This tends to occur within 1–2 days (sooner than is typical for infection) and typically lasts several days. Such symptoms are common and have been described in up to one-third of patients [18]; hence, appropriate counseling is recommended. The presence of a flare is not associated with either good or bad outcome overall.
Less common but potentially significant local complications of steroids include weakening of the tendons and ligaments and an association with rupture, skin atrophy/depigmentation and fat necrosis. Fat necrosis and skin depigmentation are thought to be less problematic with methylprednisolone than triamcinolone.
There is some evidence of chondrotoxic effect from corticosteroids and they are known to potentiate chondrotoxicity from local anesthetics, at least in vitro, see next under local anesthetics. Platelet-rich plasma (PRP) [19]PRP is now supported by evidence in a number of areas of the body, such as treatment of lateral epicondylitis, osteoarthritis of the knee, patellar tendinopathy, and plantar fasciitis with mixed evidence in a number of other areas. Its use varies internationally but where established it has taken over from corticosteroid for many of these indications.
Injection of PRP begins by harvesting the patient’s own blood in a tube with anticoagulant
◾
and strict asepsis is required. Various proprietary techniques are available which revolve around centrifugation to separate the red blood cells, platelet poor plasma, and the desired PRP. After centrifugation selected layers are harvested to give the intended preparation. This takes between 5 and 20 min and different preparations are possible: those which contain leukocytes are thought to have more proinflammatory properties and to be less favored than leukocyte-poor PRP. The optimal concentration is yet to be established but it has been suggested that it is possible for PRP to be too concentrated.
Some authorities use PRP without prior activation but activation before injection is often thought necessary and may be achieved by physical or chemical methods. The volume depends on the site of injection and is commonly 10 mL for the knee.
There are many active compounds within PRP and the suggested mechanism of action is that platelets are activated (endogenously or before injection) and release various growth factors, which in turn influence cell migration and the overall effect is to promote tissue repair.
Because tissue response is important most practitioners encourage patients to stop nonsteroidal antiinflammatory drugs (NSAIDs) for a period before the procedure and post procedure advice is generally to avoid ice, heat, NSAIDs, and other measures that would usually be intended to reduce tissue response, for at least the first 3 days after the procedure. Local anestheticsLidocaine, ropivacaine, bupivacaine, and levobupivacaine have all been demonstrated to be toxic to human chondrocytes in vitro which appears to be a dose- and time-dependent effect that is potentiated by the addition of corticosteroids. Ropivacaine may be the least chondrotoxic of these local anesthetics [18].
These (and many other available local anesthetics) vary by the useful concentrations, dose, speed of onset, and duration. Table 97.3 shows typical clinically useful concentrations, dose, time of onset, and duration of selected local anesthetics when used in soft tissues but there is a wide range of these factors in clinical use and senior advice should be sought in cases of uncertainty. The maximum safe dose varies according to the site and relative perfusion of the site, as well as overall patient factors, such as percentage body fat—the maximum dose for some anesthetics should be calculated based on lean body mass (e.g., bupivacaine) and for others an allowance may be made for increasing adiposity (e.g., lidocaine). Their effectiveness depends on the degree of innervation and other tissue factors such as pH and degree of buffering such that areas which are infected may be more difficult to anesthetize.
Preparations may be made containing epinephrine which induces vasoconstriction to reduce wash out and hence prolong duration of action. This is useful particularly in the most wellvascularized areas of the body (mouth and face) but should not be used in the extremities to avoid a risk of ischaemia.
◾
Table 97.3 Typical Clinically Useful Concentrations, Dose, Time of Onset and Duration of Selected Local Anesthetics When Used in Soft Tissues [21] Local Anesthetic
Typical Concentration
Dose
Du rati on of On set
Du rati on of Eff ect (So ft Tis
sue ) Lidocaine
1% typical, 2% may be useful in nerve blocks
Adult— max total dose 300 mg
Qu ick >> t1/2(Bio), approximately t1/2 (eff) = t1/2(Bio), and when t1/2 (Bio) >>> t1/2, approximately t1/2(eff) = t1/2.
Musculoskeletal System The bone scan is one of the most common radionuclide imaging procedures performed in nuclear medicine. In general, it is mostly used for whole-body bone surveys in oncology. However, with the advances in instrumentation, there is an increased use in benign bone diseases.
Radiopharmaceuticals The radiopharmaceuticals are either phosphates or diphosphonates. The gamma camera agents for bone scintigraphy SPECT are Tc-99m methylene diphosphonate (Tc-99m MDP), Tc-99m hydroxymethylene diphosphonate (Tc-99m HDP or HMDP), Tc-99m hydroxyethylidene diphosphonate (Tc99m HEDP), and Tc-99m pyrophosphate. The P-O-P bond present in the phosphate-based bone-seeking tracers (pyrophosphate)is less stable in vivo because of the presence of phosphatase enzyme inside the body, which can easily break down the bond. P-C-P bond, however, is resistant to such phosphatase enzyme and is more stable in vivo. Therefore, diphosphonate containing the P-C-P bond is commonly used radiopharmaceutical in bone imaging [2]. The radiotracer uptake in bone is due to ion exchange phenomena. The diphosphonate-based tracers such as Tc-99m MDP and HEDP binding occurs by chemisorption onto the bone matrix’s hydroxyapatite mineral. The radiotracer is primarily excreted through the kidneys.
Radiopharmaceutical Injected Activity [3] Adults receive intravenous (IV) injection of 740–1110 MBq (20–30 mCi). For obese patients, the dose may be increased to 11–13 MBq/kg (300–350 µCi/kg). Children receive 9–11 MBq/kg (250–300 µCi/kg), with a minimum of 20 MBq/kg (0.5 mCi).
Imaging Procedure Patient Preparation
The patient should be well hydrated. After radiotracer administration, the patient should void frequently, and before image acquisition, metallic objects in the area of interest (e.g., pendants, ornaments), should be removed. Imaging In whole-body imaging, anterior and posterior views are imaged. Usually, more than 1.5 million total counts are acquired. The energy window is centered at 140 keV. The window width is 15–20%, and the matrix size is 256 × 1024 or higher. If needed, a special spot view (static image) should be acquired with 500,000 to 1,000,000 counts per image. The three-phase bone scan consists of flow (vascular), blood pool, and a delayed phase. The detector of the gamma camera should be positioned over the area of interest.
◾frame The flow phase is acquired immediately after radiotracer injection for 60 seconds with a rate of 1–3 sec/frame and a matrix size 64 × 64 or higher. ◾tracer The blood pool phase is acquired immediately after the flow phase within 10–20 minutes of administration. The matrix size should be 256 × 256 and counts 3,00,000 per image or time-based acquisition for 5 minutes. ◾counts. The delayed phase is acquired 2–4 hours after tracer injection and approximately 1 million
SPECT acquisition is performed with contoured orbit, 64 × 64 or greater matrix, 3- to 6-degree intervals, and 10–40 sec/stop. Usually, 3D iterative ordered-subsets expectation maximization is ideally 3–5 iterations and 8–10 subsets. CT acquisition parameters in SPECT/CT are 512 × 512 matrix, 80– 130 kV; the intensity–time product depends on the body part being imaged and ranges from 10 to 300 mAs.
Common Indications for Bone Scan
◾ Whole-body survey in oncology to identify bone metastases ◾ Benign bone tumor (e.g., osteoid osteoma) ◾ Osteomyelitis, including malignant otitis externa ◾ fracture or shin splint ◾ Stress Metabolic bone disease ◾ Osteonecrosis ◾ Bone dysplasia (e.g., fibrous dysplasia [FD]) ◾ Loosening and infection of hip and knee prostheses ◾ Unexplained back pain ◾ Unexplained bone pain in the hip, knee, or foot ◾ Bone graft viability ◾ Mandibular condylar hyperplasia ◾ Complex regional pain syndrome ◾ fracture ◾ Nonunion Biodistribution of radiotracer in a bone scan
In general, the normal distribution of radiotracer is homogeneous in the axial and appendicular skeleton (Fig. 98.1). The radiotracer is excreted through the kidneys into the urinary bladder. Some normal variants are commonly seen on the bone scans. For example, “hot skull,” or diffuse increase tracer uptake in the skull, is seen mainly in postmenopausal women or after chemotherapy [4]. Focal increased uptake in the ossifying ischiopubic synchondrosis in children between 4 and 12 years is a normal variant [5].
FIGURE 98.1 Normal bone scan showing homogeneous tracer distribution in the axial and appendicular skeleton. Excretion of tracer is noted through kidneys into the urinary bladder. ANT, anterior; POST, posterior.
Artifacts and Pitfalls on Bone Scan Bone scan artifacts are summarized in Table 98.1 and Fig. 98.2 [4]. Several pitfalls should be avoided while reporting a bone scan. Multiple foci of uptake in consecutive ribs in a linear pattern are typical of fractured ribs and should be correlated with the patient clinical history when presented for
metastatic workup (Fig. 98.3). The unusual extraosseous tracer accumulation might be misinterpreted as bone uptake (Fig. 98.4). An ectopic or transplant kidney can resemble or mimic a pelvic bone uptake on planar images. There may be tracer uptake in the primary breast and lung carcinoma, splenic infarct, calcified hepatic metastases (see Fig. 98.4), ascites, etc. Accurate documentation of a patient’s clinical history is necessary to avoid these pitfalls [4]. Table 98.1 Bone Scan Artifacts Instrum ent Related
◾ Impro per photop eak setting : loss of counts , increa se in scatter , and poor image quality
◾ Photo
multip lier tube defect: photop enic area in the image; usuall y not missed by expert reader
Technical
◾ Injection tracer extravas ation: poor image quality because a lesser amount of radiotrac er reached to the bone; also may lead to lymph node visualiza tion
◾ Arterial
injection : diffuse intense tracer uptake at the site of injection
Patient Related
◾ Patient motion artifact: loss of resolution and blurring of the image Metal artifact (see Fig. 98.2): metal such as jewelry, pacemaker, belt buckle in the region of interest during imaging produces photopenic defect on scan and may be confused as a lytic lesion; therefore, all metallic objects must be removed before scanning if possible and should be documented if they cannot be removed
◾
Treatment Related
◾ Postsurgic al tracer uptake may persist up to months after surgery; hence, treatment history should be recorded during the scan
◾ Radiother apy to a region shows decreased tracer uptake in the bones in the radiation field
FIGURE 98.2 A metal artifact showing a photopenic region in the sternum (arrow) mimicking a lytic lesion. LT, left.
Bone Scan Findings
uptake in the existing lesions even if the lesion is healing); the tracer activity reduces after 4–6 months of flare
Skeletal Metastases Bone is one of the common sites of tumor metastasis. The bone metastases are mostly hematogenous in nature. In general, the hematogenous tumour spread occurs through the normal venous system or Batson’s plexus. The tumor cells enter the red marrow of the medullary bone and get attached to the endothelial surfaces. These cells then multiply and invade the osseous structures to include the cortical bone [6]. The tumor cell induces osteolytic activity by secreting various factors. The ongoing bone resorption induces a reparative response in the adjacent normal bone by the osteoblastic reaction. In general, malignancies that are rapidly growing produce osteolytic lesions. Hence, the metastatic cells can induce osteolytic, osteoblastic, or mixed response in the bone. Metastases from different types of malignancies might be predominantly osteoblastic, osteolytic, or mixed bone metastases (Table 98.2). Prostate and breast cancer cause the majority of bone metastases (i.e., up to 70%) [7]. Table 98.2 Bone Metastasis in Malignancy Producing Different Responses Predominantly Osteoblastic
◾ Prostate cancer ◾ Carcinoid ◾ Small cell lung cancer ◾ Hodgkin lymphoma ◾ Medulloblastoma
◾ Breast cancer ◾ Stomach cancer ◾ Colon cancer ◾ Urinary bladder cancer ◾ Squamous cancers
The radiopharmaceuticals used in bone scans are usually incorporated into the hydroxyapatite crystal matrix in newly formed bone. Hence, a bone scan is ideal for metastasis, which induces osteoblastic reaction. The lytic lesions may be detected when an associated osteoblastic reaction occurs or when the lytic lesion itself is large enough to be seen as a photopenic defect (see Fig. 98.4A). However, the lytic lesions might be missed when there is no associated osteoblastic reaction. The different patterns of metastatic disease on bone scan are described in Table 98.3. SPECT/CT helps in an equivocal focus of uptake to differentiate between benign disease from metastasis (Fig.
98.5). An abnormal pattern of tracer accumulation can also be seen as metastatic superscan with increased ratio of bone to soft tissue (Fig. 98.6). Table 98.3 Metastatic Patterns on Bone Scan Metastasis
◾ Randomly scattered focal uptake ◾ Diffuse heterogeneous uptake in the skeleton with faintly visualized kidney (superscan of malignancy) (Fig. 98.5) A cold defect with peripheral rim uptake (Fig. 98.3A) Photopenic defect in lytic lesion Asymmetric uptake in growth plates of long bones in children in neuroblastoma
◾ ◾ ◾
Benign Uptake Mimicking Metastasis
◾ Multifocal uptake in contiguous ribs could be posttraumatic (Fig. 98.2) ◾ Multifocal uptake may be seen in polyostotic bone dysplasia (Fig. 98.7) ◾ Diffuse uptake in the long bones caused by hypertrophic pulmonary osteoarthropathy (Fig. 98.8) Multifocal uptake in the facet joints or endplate region of the spine could be degenerative changes
◾
FIGURE 98.3 Increased tracer uptake in the linear fashion in continuous ribs (arrows) typical of fracture.
FIGURE 98.4 Whole-body bone scan in a patient with breast cancer shows increased tracer localization in the sternum with a central photopenic region suggestive of a lytic metastasis. There is abnormal activity in the right lower thorax region (arrows in A), which on singlephoton emission computed tomography/computed tomography corresponds to multiple hepatic lesions (arrows in B) suggestive of soft tissue tracer uptake in the metastatic disease.
FIGURE 98.5 A 50-year-old female patient with left breast carcinoma after surgery and chemoradiation. On follow-up, whole-body bone scan (A) shows focal increased uptake in the manubrium (thin arrow), which on single-photon emission computed tomography/computed tomography (SPECT/CT) (B) localizes to the minimally sclerotic lesion (bold arrows) suggestive of solitary bone metastasis. Another tracer nonavid sclerotic lesion is seen on SPECT/CT (thin arrow) suggestive of benign lesion. There is physiological tracer uptake in the ureter overlapping with the vertebra on whole-body bone scan (bold arrow in A), which may be confused with abnormal osteoblastic activity.
FIGURE 98.6 Whole-body bone scan shows heterogeneous increased tracer uptake in the axial and appendicular skeleton and a faintly visualized kidney in a patient with prostate carcinoma consistent with superscan of malignancy and widespread skeletal metastases.
Bone Scan in Benign Bone Diseases Bone scans have been used since the early days in the diagnosis of benign bone diseases. Although the planar bone scans are extremely sensitive in detecting benign conditions, the findings are very nonspecific and noncontributory in diagnosing most such cases. SPECT/CT improves characterization and localization of the uptake seen on planar bone scans. Hence, with the widespread availability of SPECT/CT, bone scans are now routinely used in the management of many benign bone conditions in many nuclear medicine centers. In most patients with shin splints, stress fractures, Paget’s disease, or FD, the diagnosis can be easily made on a planar bone
scan based on the tracer uptake pattern. In unexplained pain in the wrist, back, hip, knee, ankle, or foot, the uptake pattern is nonspecific on planar scans. SPECT/CT helps immensely in these conditions to reach an accurate diagnosis.
Fibrous Dysplasia: Fibrous dysplasia can be monostotic or polyostotic. A whole-body bone scan is performed to differentiate monostotic from polyostotic FD (Fig. 98.7). The tracer uptake in patients with FD is very high. It can be differentiated from Paget’s disease by the patient’s age and tracer uptake pattern on the bone scan. Paget’s disease typically involves the end of the affected bone, whereas FD does not involve the bones’ ends.
FIGURE 98.7 Whole-body bone scan of a patient with suspected fibrous dysplasia (FD) of sphenoid bone shows intense uptake in the sphenoid bone compatible with FD and multifocal uptake in the left scapula and right ribs, which were confirmed on single-photon emission computed tomography/computed tomography to be FD. Hence, the bone scan helps in detecting multifocal involvement.
FIGURE 98.8 In this patient with carcinoma of the lung, whole-body bone scan shows symmetrical linear increased osteoblastic activity in the metaphysis and diaphysis of bilateral femora and tibiae, more prominent in the tibiae (tram-track appearance) suggestive of hypertrophic osteoarthropathy, a paraneoplastic syndrome. There is physiological tracer distribution in rest of the bones with no metastatic involvement.
Osteoid Osteoma: Osteoid osteoma is a benign bone tumor usually present in the adolescent age group, typically as severe night pain that is relieved using salicylate analgesics. It is a cortex-based tumor. In general, results of a three-phase bone scan are positive with focal uptake and double-density sign (i.e., intense tracer accumulation in the central nidus and moderate uptake of tracer in surrounding reactive sclerosis; Fig. 98.9). SPECT/CT is highly
sensitive and specific in the identification of osteoid osteoma, particularly in the spine.
FIGURE 98.9 A 16-year-old male patient with left leg pain at night. A static planar bone scan of the leg shows focal increased uptake in the left mid tibia (arrows in A). This corresponds on single-photon emission computed tomography/computed tomography to a tiny nidus with surrounding reactive sclerosis (arrows in B) suggestive of osteoid osteoma.
Osteomyelitis and Septic Arthritis:
Typical pattern on a three phase bone scan is increased tracer accumulation at the infection site in all three phases. Although the bone scan is highly sensitive with more than 95% sensitivity, the specificity is low. Other conditions also show positive three-phase uptake (e.g., malignancy, stress fracture, and osteoid osteoma) [8]. However, in nonviolated bone with clinical suspicion of osteomyelitis, it detects bone infection with good specificity (Fig. 98.10). False-negative findings may be seen in chronic osteomyelitis and vertebral osteomyelitis. Indium-111 labeled white blood cells, along with marrow imaging, is the radionuclide imaging of choice in infection in violated bone. Septic arthritis, such as osteomyelitis, shows increased tracer accumulation in the involved joints in all three phases.
FIGURE 98.10 Three-phase bone scan in a suspected skull base osteomyelitis shows increased tracer localization at the right-side skull base in the flow and blood pool images with corresponding increased osteoblastic activity (arrow) in the delayed image suggestive of acute osteomyelitis.
Stress and Insufficiency Fracture: Stress fractures are fractures that occur in normal bone because of repetitive activity or overuse. In contrast, insufficiency fracture is caused by normal stress in a pathological or weak bone. Early diagnosis helps in early recovery
and prevention of frank fractures. Bone scan results are positive from the very early or initial phase of stress reaction and are extremely sensitive. Furthermore, because stress reactions may involve multiple sites, the wholebody assessment helps detect additional areas. The uptake is usually focally intense with a shape ranging from oval to fusiform depending on the severity (Fig. 98.11). The first two phases on the bone scan typically show increased hyperemia in a stress fracture. In shin splint or tibial periostitis, there is microavulsion of fibers connecting periosteum to bones. Hence, periostitis is seen as linear tracer uptake, typically in the posteromedial aspect of the tibia involving more than one-third of the tibia. The first two phases of the scan are usually normal.
FIGURE 98.11 A 24-year-old male athlete presented with pain in the left tibia mostly while running. X-ray examination of the left tibia was normal. Three-phase bone scan shows normal flow (A) and blood pool images but increased osteoblastic activity in the left midtibia (B) suggestive of a stress fracture.
Metabolic Bone Disease: Metabolic bone disease caused by primary hyperparathyroidism (PHPT) and renal failure produces a metabolic superscan pattern that shows homogenously increased tracer uptake in the axial and appendicular skeleton with faintly visualized kidneys. Sometimes focal increased tracer uptake is seen in the brown tumors in patients with hyperparathyroidism. Because of hypercalcemia, sometimes there is soft tissue uptake in the lungs, stomach, and kidneys. In patients with rickets, there are changes in endplates of the long bones and beading at costochondral junctions. There may be superscan pattern,
increased uptake in the sternum (tie pattern), pseudofractures, or true fractures. In patients with Paget’s disease, abnormal bone remodeling is seen. A bone scan is useful in confirming the diagnosis and assessing the disease extent. However, most often, it is seen incidentally on a bone scan done for other reasons. The typical scintigraphic pattern is intense florid tracer uptake in the involved bones with a blooming uptake appearance (Fig. 98.12).
FIGURE 98.12 The anterior-view whole-body bone scan image (A) of a patient with prostate cancer showed intense tracer uptake in the right hemipelvis (black arrow in A), which correlated to cortical thickening and trabecular coarsening on CT component of SPECT/CT study (arrow in B and C) suggestive of Paget disease. In addition, on the whole-body study, there is a vertical linear area of increased uptake in the sternum owing to the previous sternotomy (sternal split sign) and uptake in the femoral vessels (red arrow in A) likely owing to calcification. (From: K Agrawal, F Marafi, G Gnanasegaran, H Van der Wall, I Fogelman I, Pitfalls and limitations of radionuclide planar and hybrid bone imaging, Semin Nucl Med 45 (5) (2015) 347–372.)
Osteonecrosis or Avascular Necrosis: The causes of osteonecrosis include trauma, long-term steroid intake, sickle cell disease, and other vascular diseases. During the initial phase, there is a photopenic area in the involved region due to the cut-off of blood supply (Fig. 98.13). Later, there is increased uptake caused by reactive osteoblastic
activity. Magnetic resonance imaging (MRI) is usually the gold standard imaging modality in avascular necrosis. However, the bone scan shows changes quite early during the disease process.
FIGURE 98.13 In a patient with a left femoral neck fracture, wholebody bone scan shows photopenia in the left femoral head (arrow) with increased osteoblastic activity surrounding it suggestive of early avascular necrosis. ANT, anterior; LT, left; POST, posterior.
Complex Regional Pain Syndrome: Complex regional pain syndrome or reflex sympathetic dystrophy is a response to trauma and immobilization. There is variable presentation;
however, typically, there is pain, edema, and muscle wasting. A three-phase bone scan is helpful, and the most specific finding is the periarticular uptake of tracer. Classical increased tracer accumulation in all three phases with periarticular uptake in the delayed phase is seen only in early disease. During the later course of the disease, the blood flow phase may be normal (Fig. 98.14).
Miscellaneous Indications A bone scan is useful in evaluating bone graft viability, and SPECT/CT is usually more specific in such scenarios. (Fig. 98.15). Bone scan is also
extremely sensitive in identification of pain generator in unexplained bone pain in the back (Fig. 98.16), pelvis (Fig. 98.17), knee, and foot (Fig. 98.18) [9–12] Often the fractures are seen early in bone scan comparison with conventional radiographs. Aseptic loosening and hip and knee prostheses infection can be differentiated with high sensitivity on a three-phase bone scan.
FIGURE 98.15 Six months after mandibular bone graft following surgery for a mandibular tumour, the planar bone scan shows mild uptake in the graft (arrows in A). Single-photon emission computed tomography/computed tomography confirms the uptake in the graft suggestive of the viable graft (arrows in B).
FIGURE 98.16 A 55-year-old female patient with low back pain shows heterogeneous tracer uptake in the lower lumbar spine (arrow in A) on whole-body bone scan. Single-photon emission computed tomography/computed tomography of the lumbar region (B) localizes the uptake to anterior listhesis of L4 over L5 with L4 to L5 endplate degenerative changes (arrows) as the cause of pain.
FIGURE 98.17 A 22-year-old male patient with bilateral hip pain. Three-phase bone scan (A) shows minimal tracer accumulation in the bilateral sacroiliac region on blood pool images with corresponding increased osteoblastic activity in the delayed image (arrow in posterior image). Coronal and axial single-photon emission computed tomography/computed tomography image (B) localizes the tracer uptake to irregular endplates with sclerosis suggestive of sacroiliitis.
FIGURE 98.18 A young male patient with right hindfoot pain. Threephase bone scan shows increased tracer localization at the inferior aspect of right calcaneum in the flow and blood pool images (thin arrow) with corresponding increased osteoblastic activity (thick arrow) in the delayed image suggestive of plantar fasciitis as the pain generator. RT, right.
Endocrine System Thyroid Imaging For imaging the thyroid gland, ultrasonography (USG) is the most commonly used modality. However, often functional imaging is needed to either characterize the anatomic abnormality or for confirmation. The nuclear medicine studies in the thyroid gland are mostly based on some hormone synthesis phase in the thyroid gland. Iodine is the most integral part of the thyroid hormone, when taken orally. Iodine is rapidly reduced to iodide in the small intestine and absorbed into the circulation. It is further trapped in the thyroid gland’s follicular cells via sodium iodide symporter. This is usually followed by organification, and iodide is oxidized to iodine by thyroid peroxidase. This binds to tyrosine present on the thyroglobulin, forming triiodothyronine (T3) and thyroxine (T4).
Thyroid-stimulating hormone (TSH) helps in all these trapping processes, organification, and release of thyroid hormones. The thyroid–pituitary feedback mechanism controls the secretion of TSH and thyroid hormones. Monovalent anions such as potassium perchlorate can block the trapping within the thyroid through competitive inhibition. Similarly, organification can be blocked by antithyroid drugs such as carbimazole and methimazole. Radiopharmaceuticals
Iodine-123 and Iodine-131: Radioactive iodine behaves similar to stable iodine and is the ideal radiotracer in providing information related to the thyroid gland. However, the physical characteristics of radioiodine (RAI) iodine-123 (I-123) and iodine-131 (I-131) allow for the preference of one above the other in clinical practice (Table 98.4). The principal gamma energy of I-131 is 364 keV, which is significantly higher than the ideal imaging energy for a gamma camera, leading to poor counts. Furthermore, it has a half-life of 8.04 days and high beta emission, leading to a higher radiation dose to the thyroid gland when used for imaging. I-123 emits photons with an energy of 159 keV and has a physical half-life of 13 hours. Therefore, this is the ideal choice for thyroid imaging with RAI compared with I-131 [13]. Table 98.4 Characteristics of Radiopharmaceuticals Used in Thyroid Scintigraphy [12] Technetiu m-99m (Tc-99m) Pertechnet ate
I-123 Iodide
I-131 Iodide
Use
Imaging the thyroid gland
Imaging the thyroid gland Thyroid uptake
Thyroid uptake Thyroid therapy
Mechanis m of uptake
Trapping similar to iodides
Trapping and organification
Trapping and organification
Technetiu m-99m (Tc-99m) Pertechnet ate
I-123 Iodide
I-131 Iodide
Physical half life
6 hr
13.2 hr
8.04 days
Principal gamma energy
140 keV (ideal for imaging)
159 keV
364 keV
Abundanc e of principal gamma emission (%)
89
83
81
Beta emission
No
No
Yes (606 keV; can be used in therapy)
Advantage s
Low radiation dose Less examinatio n time Easily available Cheaper than radioiodin e
Better image quality when count is low Choice for retrosternal goiter or ectopic thyroid in mediastinum
Not ideal for imaging; used as therapeutic agent because of beta particles
Disadvant ages
Technetiu m-99m (Tc-99m) Pertechnet ate
I-123 Iodide
I-131 Iodide
Poor image quality when the tracer uptake is low
Less readily available Higher radiation compared with technetium-99m agents Long examination time
Poor image quality High radiation burden
Both tracers get absorbed similar to iodine and are trapped in thyroid follicular cells within minutes of oral ingestion. However, a progressive increase in uptake within the thyroid gland occurs between 24 and 48 hours. Because the background clearance is slow, usually scanning or uptake is done at 24 to 48 hours after dose administration. The physiological biodistribution occurs in salivary glands, stomach, choroid plexus, lactating breast tissue, and excretion through kidneys and intestinal route.
Technetium-99m Pertechnetate: Technetium-99m pertechnetate is trapped similar to iodine but is not organified. Hence, imaging must be performed early at 20 minutes after administration because it is not retained in the thyroid. This tracer’s advantages over other tracers are 140-keV photons ideal for imaging, short half-life, no beta particles, and quick imaging. It is also readily available and less expensive than iodine tracers [13]. The only potential disadvantage is low image quality when uptake is low. Therefore, in characterization of retrosternal mass, RAI is used for better image counts. Patient Preparation and Precautions for Thyroid Uptake and Imaging Several drugs and substances interfere with tracer uptake within the thyroid, as mentioned in Table 98.5. The history of these drugs should be taken before the appointment and should be stopped before the thyroid study for the required period if the patient’s medical conditions permit. RAI can cross
the placenta. Therefore, radiation exposure to fetal thyroid can occur after a higher dose of thyroid tracers, and a pregnancy test must be done before tracer administration. Furthermore, because RAI is excreted in breast milk, lactation should be stopped after I-131 iodide administration in lactating mothers and should not be resumed. For I-123 iodide and Tc-99m pertechnetate, breastfeeding should be stopped for 48 hours and 24 hours, respectively. Iodine-rich foods such as sea fish and dairy products can interfere with the radioiodine uptake (RAIU) and should be restricted before the study. Table 98.5 Drugs and Substances That Interfere With Thyroid Uptake [12] Duration of Effects IncreasedUptake Lithium
Thyroid Uptake Although RAI I-123 is preferred, uptake can be performed with I-131 or Tc99m pertechnetate if thyroid imaging is planned along with it. Essentially, a nonimaging sodium iodide (NaI) crystal–based thyroid uptake probe is required for RAIU. The most common indication for RAIU is to differentiate different causes of thyrotoxicosis. Generally, RAIU is increased in patients with Graves’ disease but is decreased in those with thyroiditis. Furthermore, RAIU is used to determine RAI activity (I-131) to be administered to thyrotoxic patients with Graves’ disease and toxic nodular goiter. The drugs interfering with the RAIU should be stopped as mentioned earlier. The patient should be on an empty stomach for approximately 4 hours before RAI intake to ensure good RAI absorption as it is given orally. The RAI dose is 5–10 µCi of I-131 or 50 µCi of I-123 if only RAIU is planned. For scan and uptake, approximately 1–2 mCi of RAI is the preferred dose. The uptake measurement is generally performed 24 hours after administration of RAI; however, some centers measure at 4 hours and others at both 4 and 24 hours [14]. First, the room background activity is measured. Counts are obtained from a known calibrated activity of RAI capsule placed in a neck phantom. This RAI dose is then administered to the patient orally. After 24 hours or the desired time, the patient’s neck counts are obtained with 30-cm distance between the crystal’s face and the anterior neck of the patient. The patient’s body background count is measured as lower thigh counts. Percent RAIU is counted using the following formula:Percent RAIU = Neck Counts (counts per minute [CPM]) – Body Background counts (CPM) × 100Administered RAI counts (CPM) – Room background count (CPM) The uptake can also be measured while a Tc-99m pertechnetate thyroid scan is performed. The advantages are quicker completion of the study within 20–30 minutes. Most of the gamma camera equipment currently available provides software for uptake calculation using Tc-99m pertechnetate. During this, the preinjection and postinjection syringe is imaged, and counts are calculated. The region of interest (ROI) is drawn
over the thyroid on the computer, and the uptake is calculated as follows:Percent uptake at 20 minutes = Preinjection syringe counts – Postinjection syringe counts × 100Total administered activity The normal ranges for percent RAIU are approximately 5–15% at 4 hours and 10–30% at 24 hours. The normal range for percent Tc-99m pertechnetate uptake at 20–30 minutes is 0.3–4.5%. The causes of abnormal RAIU is mentioned in Table 98.6 [14]. Table 98.6 Causes of Increased or Decreased Radioiodine Uptake Increased Uptake
◾ Primary or secondary hypothyroidism ◾ Subacute thyroiditis ◾ Autoimmune thyroiditis ◾ Drug interfering with thyroid uptake ◾ Iodine-containing food or drugs ◾ Congestive heart failure ◾ Renal failure
Thyroid Scintigraphy
Interpretation of Thyroid Scan: A thyroid scan should always be interpreted in the context of clinical history and examination and biochemical and radiologic investigation results. In general, a normal thyroid scan shows diffuse homogenous tracer uptake in both lobes of the thyroid (Fig. 98.19). The uptake localization in the isthmus is variable. The pyramidal lobe is not usually seen in a normal thyroid scan. The salivary glands are routinely visualized on Tc-99m pertechnetate scans.
FIGURE 98.19 Normal thyroid technetium-99m pertechnetate scan shows homogenous tracer uptake in both thyroid lobes and relatively less intense tracer localization in the salivary glands.
Furthermore, Tc-99m pertechnetate scans show higher background uptake than I-123 scans. Sometimes esophageal tracer activity is seen in a normal scan, which is usually just left to the midline. A repeat image of the neck after the patient has swallowed a glass of water helps in differentiating from abnormal uptake. Thyroid enlargement and increased uptake within the gland should be noted. The uptake pattern within the thyroid, whether homogenous or heterogeneous patchy, should be documented. The report should mention any relatively hot or cold regions within the thyroid and any extrathyroidal tracer uptake. In the case of abnormal focal uptake within the gland, the marker image should be taken.
Indications for the Thyroid Scan
◾causes Correlation of thyroid anatomy relative to its function: Mostly it helps in differentiating of thyrotoxicosis such as Graves’ disease and nodular goiter, which helps in determining the therapy dose and differentiate Graves’ disease from thyroiditis ◾ Evaluation of thyroid nodules ◾ Evaluation of congenital hypothyroidism ◾ of retrosternal or mediastinal mass to determine whether it is a thyroid tissue ◾ Evaluation Evaluation of suspected ectopic thyroid tissue Clinical Applications Thyrotoxicosis: Thyroid scans are useful in differentiating the two commonest causes of thyrotoxicosis, Graves’ disease and subacute thyroiditis. Graves’ disease is the cause of thyrotoxicosis in approximately 70–75% of patients. It is an autoimmune disorder in which thyrotropin receptor antibody is produced and has a similar effect to TSH on thyroid follicular cells. Hence, the excessive thyroid hormone is produced independently of thyroid– pituitary feedback. Approximately 30% of patients with Graves’ disease show some signs and symptoms of ophthalmopathy. Generally, it is seen in the female gender. The patient usually presents with signs and symptoms of thyrotoxicosis, goiter or proptosis, and is biochemically thyrotoxic. Subacute thyroiditis could be caused by granulomatous or de Quervain’s thyroiditis, silent thyroiditis, or postpartum thyroiditis. During the initial few months of subacute thyroiditis, a patient usually presents with thyrotoxic signs and symptoms with suppressed TSH level similar to Graves’ disease. In this period, thyroid scan and uptake are useful to differentiate because management is entirely different in these two entities. Imaging in Thyrotoxicosis
◾gland Thyroid scan typically shows diffuse homogenous tracer uptake in the enlarged thyroid and negligible uptake in the salivary gland in those with Graves’ disease (Fig. 98.20). The RAIU is in the range of 40–80% ◾tracer In the thyrotoxic phase of thyroiditis, the scan shows significantly reduced or negligible uptake in the thyroid gland (Fig. 98.21) with decreased RAI uptake. In the recovery phase of thyroiditis, the scan pattern is variable and may show patchy tracer accumulation and uptake within the normal rangeAnother prominent cause of thyrotoxicosis, toxic multinodular goiter (MNG), shows increased percent RAIU, but the scan pattern is different from that in Graves’ disease. In toxic MNG, there is often patchy heterogeneous tracer accumulation with increased tracer accumulation in a hyperfunctioning nodule In autonomously functioning thyroid nodule, there is high accumulation within the nodule with near-complete suppression of uptake in the rest of the thyroid gland, but the percent RAI uptake is usually in the normal rangeIn iodine-induced thyrotoxicosis or Jod-Basedow phenomenon, which occurs because of iodinated contrast media or very high iodine intake, the percent RAIU is generally decreased. Infrequently, the uptake is increased if iodine activates subclinical Graves’ disease or toxic MNG Amiodarone-induced thyrotoxicosis (AIT) type 1 usually occurs in a patient with latent Grave’s disease or multinodular gland. Amiodarone contains high iodine (i.e., ∼37% by
◾ ◾
weight). In preexisting thyroid disorder, excessive iodine leads to increased thyroid hormone biosynthesis. Vascularity is increased on Doppler USG. Percent RAIU is usually in the low normal range but can be high in iodine-deficient regions Contrary to this, AIT type 2 is a destructive process of the thyroid caused by amiodarone’s toxic effect, resulting in the release of thyroid hormones. Typically, percent RAIU is negligible in type 2 AIT. AIT type 2 is more common than type 1
◾
Clinically, it is difficult to differentiate between two different types. A small study showed successful use of Tc99m sestamibi in the differentiation of type 1 and 2 diseases. Tc-99m sestamibi uptake is high in patients with type 1, but uptake is low or absent in those with type 2
◾hormone. Thyrotoxicosis factitia is a condition caused by the ingestion of exogenous thyroid The thyroid scan shows reduced tracer accumulation and percent RAIU ◾Hashimoto’s Hashitoxicosis is a cause of thyrotoxicosis that occurs uncommonly in patients with disease. During this phase of Hashimoto’s disease, there is typically diffuse,
nontender goiter without nodules. The scan findings and percent RAIU are increased similar to Graves’ disease
FIGURE 98.20 In a thyrotoxic patient, technetium-99m pertechnetate thyroid scintigraphy shows enlarged thyroid lobes with homogenously increased tracer uptake in both thyroid lobes (uptake at 20 minutes, 15.8%) suggestive of diffuse toxic goiter. The salivary glands show negligible tracer accumulation.
FIGURE 98.21 In a new-onset thyrotoxic patient with a history of viral fever, technetium-99m pertechnetate thyroid scintigraphy shows negligible tracer uptake in the thyroid gland, increased uptake in the salivary glands, and raised background activity suggestive of subacute thyroiditis.
Hydatidiform mole, choriocarcinoma, and trophoblastic tumors are rare causes of thyrotoxicosis. In struma ovarii, functioning thyroid tissue is seen in benign ovarian teratomas, and thyrotoxicosis is rarely seen. Percent RAIU in the neck is suppressed; however, on the whole-body thyroid scan, ectopic thyroid tissue is visualized in the pelvis. Ectopic Thyroid Tissue: Sometimes because of abnormal descent of the primitive thyroid tissue in the embryonic life, thyroid tissue can be seen at places other than normal anatomic location. The most common site of ectopic thyroid tissue is the lingual area, though it can be seen in the mediastinum, ovary, lungs, adrenal gland, pancreas, gallbladder, and heart. Usually, patients present with anterior neck swelling and features of hypothyroidism, although depending on the site and compression of mass, there can be dysphagia, dyspnea, or dysphonia. Thyroid scintigraphy is always considered as the confirmatory imaging modality for the final diagnosis of functioning ectopic thyroid tissue.
Typically, on thyroid scan, there is focal tracer uptake at the base of the tongue in lingual thyroid with the absence of tracer accumulation in usual thyroid location (Fig. 98.22). However, the ectopic thyroid tissue may coexist along with the normal thyroid gland. Sometimes, a thyroid scan detects multiple ectopias that are missed on anatomic imaging. SPECT/CT can help provide both morphologic and functional imaging information, leading to an accurate diagnosis in a location other than the neck.
FIGURE 98.22 Technetium-99m pertechnetate thyroid scintigraphy shows intense abnormal uptake of tracer in the sublingual region (arrows) suggestive of ectopic functioning thyroid tissue. There is an absence of tracer uptake in the normal thyroid region in the neck. LT, left; RT, right.
Thyroid Nodules: Although the prevalence of thyroid nodules is 3–7% by palpation, the prevalence range is very high by high-resolution USG among randomly selected individuals. The typical clinical dilemma is to differentiate between benign and malignant thyroid nodules. USG is the first-line imaging modality in the thyroid nodules, and fineneedle aspiration (FNA) is the procedure of choice in thyroid nodule assessment. If the thyroid nodule is larger than 1 cm in size, serum TSH is usually performed. If serum TSH is below the normal range, thyroid scintigraphy is indicated. On thyroid scintigraphy, the tracer uptake in the nodule can be (1) greater than the surrounding normal thyroid (hot or hyperfunctioning nodule), (2) equal to the surrounding thyroid (warm or isofunctioning nodule), or (3) less than surrounding thyroid tissue (cold nodule) (Fig. 98.23).
FIGURE 98.23 A 46-year-old female patient with a large nodule in the neck on the left side. Technetium-99m pertechnetate thyroid scintigraphy shows a large photopenic region (arrow) corresponding to the site of a clinically palpable nodule, suggestive of a cold nodule.
A hot nodule is rarely malignant (83%) in an upright position.
FIGURE 98.40 A 4-month-old female baby with a history of frequent vomiting after feeding and recurrent upper respiratory tract infections underwent gastroesophageal reflux study. Serial dynamic images show multiple episodes of tracer movement along the esophagus up to the level of the upper esophagus (black arrows), suggestive of high-grade reflux.
Esophageal Transit Time Scintigraphy Esophageal transit time has been used to evaluate different esophageal motility disorders such as achalasia, scleroderma, systemic lupus, muscular dystrophy, polymyositis, and diffuse esophageal spasm.
Radiopharmaceutical A total of 0.1–0.25 mCi of the radiotracer (Tc-99m sulfur colloid or Tc-99m DTPA) mixed in 10 mL of water is swallowed as a bolus.
Procedure The dynamic acquisition is performed in the posterior view for 30 seconds. Imaging is usually done in a supine position to eliminate the effect of gravity. In some specific conditions, such as scleroderma, imaging in both supine and upright positions is required. The TAC is drawn over the entire esophagus and upper, middle, and lower portions of the esophagus separately. Quantitative parameters obtained for the esophageal transit include the transit time, percentage emptying, and percentage residue in the
esophagus at a defined time point. The transit time is the time from the bolus’ ingestion until 90% of the maximum activity gets cleared.
Interpretation An ETT of more than 15 seconds is usually considered abnormal. Percent emptying has been quantified as maximum counts minus counts at 10 seconds after maximum counts divided by maximum counts before swallow. Percentage emptying greater than 83% is considered normal at 10 seconds of imaging [41,42] (Fig. 98.39). Gastroesophageal Reflux Study or Milk Scan Gastroesophageal reflux disease is a common condition affecting people of all age groups, including neonates and infants. Although reflux is usually physiological in infants and resolves spontaneously by 18 months of age, sometimes it persists beyond then and is pathological. Various investigations are used to confirm the diagnosis, particularly in children. The radionuclide GER study (GER scintigraphy or milk scan) is quantitative, noninvasive, and technically easy to perform.
Procedure In the GER study, the infant or child is administered regular infant feed mixed with Tc-99m SC, usually through a nasogastric tube. In older children and adults, the radiotracer is administered orally integrated with an adequate amount of liquid. The image is obtained on a gamma camera for 30 minutes and a 10- to 15-second frame rate after ingestion. All images are reviewed for any evidence of reflux events. Localizing the mouth using a marker is useful for interpreting the degree of reflux.
Interpretation Simple semiquantitative methods are used to grade the reflux, such as the level and duration of reflux. Combining these two parameters the reflex events can be classified into four grades of reflex:
◾ Grade 1: The low level persists for less than 10 seconds ◾ Grade 2: The low level persists for 10 seconds or more ◾ 3: The high level persists for less than 10 seconds ◾ Grade Grade 4: The high level persists for 10 seconds or more [43] (Fig. 98.40)
Gastrointestinal Bleed Scintigraphy
Scintigraphic imaging of abdominal blood pool imaging is a well-established diagnostic modality useful in detecting active GI bleed.
Radiopharmaceuticals Tc-99m pertechnetate-labeled red blood cells (RBCs) are used. There are three ways of labeling. (Please refer to the nuclear cardiology section.) In addition, a pinch of perchlorate is usually given to the patient for blocking thyroid and stomach uptake of free Tc-99m pertechnetate.
Procedure Anterior view images of the patient’s abdomen and pelvis are acquired in the supine position. After tracer injection, dynamic image acquisition is performed for up to 60–90 minutes with subsequent frequent static images up to 24 hours [44,45]. The dynamic image acquisition must be started as soon as abnormal tracer activity is visualized in the abdomen or pelvis.
Interpretation Gastrointestinal bleed scintigraphy aims to localize the source of bleeding. Generally, the pathological accumulation of tracer increases in intensity on subsequent images and is seen moving along the intestinal anatomy (Fig. 98.41). When the tracer activity appears stationary, other false-positive causes of increased uptake, such as renal or ureteric activity, hemangioma, or accessory spleen, should be considered.
FIGURE 98.41 A 14-year-old girl with a history of melena underwent a gastrointestinal bleed scan. The scan shows focal heterogeneous tracer accumulation in the region of hepatic flexure (H), which moves forward along the transverse colon (T) and splenic flexure (S), suggesting the site of bleed at the hepatic flexure.
Meckel’s Scintigraphy Abdominal scintigraphy with Tc-99m pertechnetate has been used to detect ectopic functioning gastric mucosa.
Radiopharmaceuticals Tc-99m pertechnetate is usually taken up by the gastric mucosa, predominantly by the mucin-producing cells. This property allows for visualization of the ectopic gastric mucosa. Meckel’s diverticulum is the most typical site of the ectopic gastric mucosa.
Procedure Dynamic study for 30 minutes after IV injection of Tc-99m pertechnetate is performed.
Interpretation The typical imaging pattern is a focal intense tracer activity on the abdomen’s right side, in concert with gastric visualization and similar intensity of uptake as in the stomach [46,47]. Besides Meckel’s diverticulum, this investigation is useful in identifying enteric or thoracic duplication cysts containing the ectopic gastric mucosa. It has also been used in evaluating Barret’s esophagus and retained gastric antrum after surgery (Fig. 98.42).
FIGURE 98.42 A 4-year-old male child presented with chronic pain abdomen with intermittent diarrhea and melena. Meckel’s scan shows a focus of increased tracer uptake in right subhepatic region, which appeared in concert with the appearance of the stomach, and increased intensity with time (black arrows), consistent with the presence of functioning ectopic gastric mucosa, in the clinical context suggestive of Meckel’s diverticulum. RT, right.
Hepatobiliary System Hepatobiliary scintigraphy or cholescintigraphy is a clinically useful diagnostic imaging study. However, the indications, methodology, interpretative criteria, and radiopharmaceuticals used have evolved with time. The first clinically useful cholescintigraphic agent was I-123 rose Bengal. However, because of relatively low image quality, 99mTc-labeled radiopharmaceuticals are now used widely.
The first clinically used Tc-99m labeled radiopharmaceutical was hepatobiliary iminodiacetic acid (HIDA), a two-lidocaine analogue attached to Tc-99m by the chelating agent iminodiacetic acid. Several other radiotracers include PIPIDA(para-isopropyl IDA), BIDA(p-butyl acetanilide IDA), EIDA(di-ethyl IDA), DIDA, and DISIDA(diisopropyl IDA). Each of these tracers has different pharmacokinetics. Currently, the most commonly used radiopharmaceutical for cholescintigraphy is Tc-99m mebrofenin (bromo triethyl-IDA) with a high hepatic extraction fraction of 98% and a quick biliary clearance (t1/2 of 17 minutes) [48].
Indications for Cholescintigraphy
◾ Acute cholecystitis ◾ Chronic cholecystitis or chronic gallbladder disease ◾ Biliary obstruction ◾ Sphincter of Oddi dysfunction ◾ Biliary atresia ◾ Biliary leak ◾ Enterogastric bile reflux ◾ Posttransplant complications ◾ diagnosis of hepatic tumors ◾ Differential Choledochal cyst management
Acute Cholecystitis Acute cholecystitis has been one of the most common indications for cholescintigraphy. However, USG has now replaced the role of hepatobiliary scintigraphy because of its wider availability and lack of radiation. The gallbladder is usually visualized within 1 hour after IV radiotracer administration, but nonvisualization of the gallbladder by 1 hour is not diagnostic of acute cholecystitis. Delayed 4-hour imaging or morphine intervention imaging is necessary to diagnose acute cholecystitis. If the gallbladder is still not visualized, then a diagnosis of acute cholecystitis can be made with high accuracy [49–51]. Morphine sulfate is given through the IV route at a dose of 0.04 µg/kg if the gallbladder is not visualized 1 hour after tracer administration. Morphine injection reduces the scan time from 4 hours to 1.5 hours. However, both methods have similar accuracy. Chronic Cholecystitis or Chronic Gallbladder Disease Ultrasonography is the preferred imaging modality in chronic calculous cholecystitis, and the patient is referred for cholecystectomy for cholelithiasis. But when there is suspicion of an acalculous disease or no stones are detected on USG, cholescintigraphy is usually advised for functional assessment of the gallbladder by calculating the gallbladder ejection fraction (GBEF) [52]. If the GBEF is within a normal range,
symptomatic chronic cholecystitis is less likely. The lower range of normal GBEF is shown as 38% in the research [53]. The cholecystagogues that is preferred in this process is sincalide because it has been standardized, and gastric emptying is not an issue. Biliary Obstruction Biliary obstruction can be either of high or low grade and is usually caused by an adjacent tumor, biliary stricture, or cholelithiasis. The clinical presentation depends on the cause of obstruction. The pathophysiology includes reduced bile flow, leading to progressive ductal dilation. However, in the early stages, this ductal dilation may not be appreciable on anatomic imaging such as USG. Functional imaging such as cholescintigraphy can play a significant role in these patients. The usual imaging features of an acute high-grade biliary obstruction show preserved hepatocyte radiotracer extraction without biliary excretion. This is caused by the high backpressure in the bile ducts. Images acquired until 24 hours increase the specificity. Cholescintigraphy has also been used in the management of patients with low-grade biliary obstruction. It has been found that cholescintigraphy has better sensitivity (∼98%) than USG (∼78%) in diagnosing low-grade biliary obstruction [54]. Slow or poor clearance of tracer in the cholescintigraphy is usually its imaging picture. Because the ducts are generally not dilated, it is difficult for anatomic imaging such as USG to diagnose this. Cholescintigraphy, being functional imaging, not only helps in diagnosing the physiological biliary tract obstruction but can also help in checking biliary stent patency when clinically obstruction is suspected. Sphincter of Oddi Dysfunction Postcholecystectomy pain syndrome or sphincter of Oddi dysfunction can present as recurrent colic pain with or without increased liver enzymes, weeks, months, or years after cholecystectomy. The proposed etiopathogenesis is functional obstruction of the biliary duct at the Oddi sphincter level, without any apparent anatomic lesion [55]. Sincalide as a cholecystagogue is used to enhance the bile flow, which increases the pressure on the functionally obstructed sphincter similar to how furosemide enhances urinary excretion from the pelvicalyceal system in suspected renal obstruction. For an objective diagnosis, semiquantitative parameters can also be used during the image analysis. These parameters include the time of first biliary secretion, the percentage common bile duct clearance, and biliary-tobowel transit time. Biliary Atresia
The usual clinical presentation of biliary atresia is neonatal cholestatic jaundice. The progressive inflammatory sclerosis of the intra- and extrahepatic bile ducts often leads to their obliteration and liver failure with time if left untreated. Therefore, a swift diagnosis and intervention are essential within the first few weeks of life. The patient should be primed for at least 5 days before cholescintigraphy. The commonly used priming agents include phenobarbital and ursodeoxycholic acid. These drugs activate the microsomal enzymes of the liver and enhance the bile flow, leading to reduced false-positive results. The cholescintigraphic pattern of biliary atresia is a persistent hepatogram with no bilioenteric transit until 24 hours (Fig. 98.43). With a negative predictive value approaching 100%, visualization of the gallbladder or intestinal tracer activity rules out biliary atresia. In some uncertain cases, SPECT can also be quite helpful [56,57]. Bile Leak Cholescintigraphy has been in clinical practice for a long time in the determination of bile leaks after surgery. Dynamic and subsequent static images until 24 hours are acquired, which help in localization and quantification of the bile leak. Some studies have reported additional value of SPECT/CT scans in evaluating bile leaks, particularly in localizing the leak. It has also been useful in defining the bile collection’s exact location, defining the amount of the bile collection, characterizing large abdominal collections, characterizing suspected contamination, and identifying other miscellaneous conditions (Fig. 98.44) [58].
FIGURE 98.43 A 1.5-month-old male child with persistent jaundice with a raised bilirubin level. Ultrasonography of the abdomen showed a small contracted gallbladder. Hepatobiliary scintigraphy shows no transit of tracer from the liver into common bile duct or gallbladder in initial images or into the bowel loops until the delayed 24-hour image, suggestive of the cholestatic phase of neonatal jaundice or biliary atresia. HIDA, hepatobiliary iminodiacetic acid.
FIGURE 98.44 A 55-year-old male patient with a recent history of laparoscopic cholecystectomy underwent cholescintigraphy to look for bile leak. Dynamic images (A) show preserved hepatocyte function and a patent bilioenteric pathway (the intestinal activity is seen on delayed images as black arrowheads) with bile leak from the porta site (thin arrow) moving into the drain tube (thick arrow) on delayed static images (B). The same findings are confirmed on single-photon emission computed tomography/computed tomography (C).
Choledochal Cyst Evaluation Congenital dilation of bile ducts is called choledochal cysts; however, they are not true cysts. Although they can occur at any site along with the biliary system, the involvement of the extrahepatic bile duct is more common. Occasionally, intrahepatic choledochal cyst (Caroli disease) can also occur, which may be multifocal. Depending on the cysts’ site and shape, they have been divided into different types (types I, II, III, IVA, IVB, and V). USG or CT can usually detect a saccular or fusiform dilation along the bile ducts; however, cholescintigraphy helps to identify whether the cyst is communicating with the biliary tract or not. Posttransplant Complications Hepatobiliary scintigraphy is useful in the management of complications during the post–liver transplant period. Studies have shown that cholescintigraphy can help in differentiating between transplant with and without rejection. However, it cannot distinguish between rejection and
cholestasis if the tracer excretion is normal because both may show similar imaging patterns. Besides, hepatobiliary scintigraphy can also help access the patency of the bilioenteric pathway in the posttransplant patient [59,60]. Differential Diagnosis of Hepatic Tumors Cholescintigraphy alone or in combination with other scintigraphic imaging such as blood pool imaging and sulfur colloid imaging have been used in managing different hepatic space-occupying lesions (SOLs). Focal nodular hyperplasia (FNH) is a benign tumor of the liver that consists of hepatocytes, Kupffer cells, and bile canaliculi. The cholescintigraphic picture of FNH includes include early increased tracer uptake and delayed clearance. In contrast, hepatic adenomas do not show uptake on cholescintigraphy and are hypofunctional even though they consist exclusively of hepatocytes (Table 98.10). Hepatocellular carcinoma demonstrates no uptake within the lesion (cold defect) during the first hour and may show slow progressive fill-in of tracer within the tumor at 2–4 hours with the corresponding clearance of tracer from the adjacent normal hepatic parenchyma [61,62]. Table 98.10 Differentiating Hepatic Adenoma from Focal Nodular Hyperplasia Tracers
Hepatic Adenoma
Focal Nodular Hyperplasia
Tc-99m sulfur colloid
Absent
Normal or increased uptake
Tc-99m HIDA
Do not show uptake and are hypofunctional
Early increased tracer uptake and delayed clearance
Tc-99m sulfur colloid liver scan has also been used for hepatic SOLs. Although practically any SOL within the liver appears as a cold area on Tc99m sulfur colloid scan because of the hyperplastic nature of the FNH containing all the liver elements, it may appear hotter than the surrounding liver tissue. Hepatic adenoma appears photopenic on the Tc-99m sulfur colloid scan. Cavernous hemangioma is the most common benign tumor of the liver. Tc-99m–tagged RBC hepatic blood pool imaging usually shows hypoperfusion and increased blood pool (perfusion–blood pool mismatch) activity in suspected areas of the liver.
Besides characterizing SOLs, a Tc-99m sulfur colloid liver and spleen scan is also used in patients with portal hypertension for distinguishing between noncirrhotic portal fibrosis and cirrhosis. In cirrhosis of the liver, there is a colloid shift (Figs. 98.45 and 98.46). Tc-99m sulfur colloid liver and spleen scan is further used to assess post partial hepatectomy liver status and postsplenectomy patients to look for ectopic or residual spleen.
FIGURE 98.45 A 31-year-old female patient with splenomegaly and features of portal hypertension underwent a liver scan to rule out cirrhosis of the liver. The scan shows preserved trapping function of hepatocyte with no evidence of a colloid shift to the spleen or bone marrow, ruling out cirrhosis. LAO, left anterior oblique; LLAT, left lateral; LPO, left posterior oblique; RAO, right anterior oblique; RLAT, right lateral oblique; RPO, right posterior oblique.
FIGURE 98.46 A 4-year-old male child with features of portal hypertension and splenomegaly underwent a liver scan. The scan shows impaired hepatocyte extraction of radiotracer with a colloid shift to bone marrow and the spleen, suggestive of liver cirrhosis. LAO, left anterior oblique; LLAT, left lateral; LPO, left posterior oblique; RAO, right anterior oblique; RLAT, right lateral oblique; RPO, right posterior oblique.
Neuroimaging Nuclear medicine has established itself as an integral part of neuroimaging and is no longer limited to the research realm. This section discusses the clinical applications of neuromolecular imaging, focusing on SPECT methodologies currently being used in routine clinical care. The following are the common established indications:
1. Seizure focus localization 2. Dementia management 3. Diagnosis of different types of movement disorders 4. Diagnosis of recurrent brain tumors
5. Cerebrovascular diseases management 6. Brain death 7. Normal-pressure hydrocephalus 8. Assessment of ventricular shunt function 9. Detection of cerebrospinal fluid leak Besides the indications already mentioned, nuclear medicine is also being used in few investigational indications, as in psychiatric diseases, head trauma, and neuroinflammation management. The commonly used radionuclides for the purpose are Tc-99m, I-123, Tl-201, and In-111. These radioisotopes, in combination with different molecules, follow different physiologic functions, which help in the diagnosis of many neurologic disorders.
Seizure Focus Localization For decades, neuromolecular imaging has been used in noninvasive localization of the epileptic focus in patients planned for epileptic surgery [63,64]. In neuromolecular imaging, ictal and interictal SPECT help in localizing epileptic focus in patients’ presurgical evaluation. Two perfusion tracers most commonly used for this purpose are Tc-99m-hexamethyl propylene amine oxime (Tc-99m HMPAO) and Tc-99m ethyl cysteinatediethylester (Tc-99m ECD). During the ictal state, the seizure focus demonstrates hyperperfusion, and during the interictal and postictal states, it shows hypoperfusion. Both ictal and interictal studies are performed to localize the culprit focus. When subtraction imaging is done by subtracting the interictal image volume from the ictal image volume, the precise location of the ictal-activated hyperperfusion area can be identified. This computer-generated subtraction imaging of ictal and interictal SPECT, superimposed on MRI, is commonly abbreviated as SISCOM/SISCOS. This ictal activation focus strongly corresponds to the epileptogenic zone (Fig. 98.47). The most challenging issue in performing ictal brain SPECT is the prompt injection of radiotracer as soon as the seizure’s onset because delayed injection leads to inaccurate localisation of the seizure focus.
FIGURE 98.47 A 15-year-old girl with a history of drug-refractory epilepsy underwent ictal and interictal technetium-99m ethyl cysteinatediethylester studies. Ictal images show mildly increased tracer uptake in the right temporoparietal cortex. Interictal images show mild asymmetry in temporoparietal cortex uptake. The same ictal and interictal images were evaluated through subtraction of ictal and interictal SPECT co-registered to MRI (SISCOM), and the subtraction images show focal tracer accumulation in the right temporal cortex, suggestive of the epileptogenic focus.
Dementia Management There are two primary purposes for neuromolecular imaging in dementia; the first is for early diagnosis, and the other is to differentiate the causes of dementia. The brain function or synaptic activity depends on glucose metabolism, which can be correlated with brain perfusion [65]. Brain perfusion has been studied using SPECT perfusion agents (Tc-99m HMPAO,
Tc-99m ECD) for the early diagnosis and management of patients with dementia [65,66]. Many perfusion SPECT studies done to diagnose Alzheimer’s disease (AD) have substantiated a definite hypoperfusion pattern. Usually, the posterior cingulate cortex and precuneus are the earliest to show changes, and hypoperfusion in posterior temporoparietal cortices is seen in late stages. The involvement of frontal cortices is seen only in advanced stages. This hypoperfusion is usually bilateral and often asymmetric. As per various metaanalyses, perfusion SPECT’s sensitivity and specificity in differentiating AD from healthy individuals are about 80% and 85%, respectively. The sensitivity and specificity in differentiating AD from mild cognitive impairment are 64% and 76%, respectively. The characteristic perfusion pattern in dementia with Lewy bodies is hypoperfusion in the occipital lobe and in progressive supranuclear palsy is frontal hypoperfusion [67]. The typical perfusion pattern is seen in behavioral variant frontotemporal dementia, which includes frontal or anterior temporal hypoperfusion (Table 98.11). Although perfusion SPECT has helped diagnose and differentiate different variants of dementia, PET imaging is currently preferred for this purpose. Table 98.11 Perfusion Pattern in Different Types of Dementia Dementia Type
Perfusion Pattern
Alzheimer’s disease
Hypoperfusion in the posterior cingulate cortex and precuneus with posterior temporoparietal and frontal cortices hypoperfusion in late stages
Dementia with Lewy bodies
Occipital hypoperfusion
Behavioral variant frontotempor al dementia
Frontal and/or anterior temporal hypoperfusion
Progressive supranuclear palsy
Frontal hypoperfusion
Movement Disorders Several studies have examined the diagnostic performance of SPECT tracers such as I-123-β-carbomethoxy-3β-4-iodophenyltropane (I-123 β-CIT), I-123 fluoropropyl-CIT, Tc-99m TRODAT-1 (Tropane derivative) or I-123 PE21 (cocaine derivative), I-123 Iodobenzamide (IBZM), and I-123 IBF (IBZM analogue) to distinguish degenerative from non-degenerative parkinsonism with preserved nigrostriatal innervation. They show very high sensitivity and specificity of these agents. SPECT imaging can also help in differentiating between idiopathic Parkinson’s disease (IPD) and atypical parkinsonism [68]. The integrity of the dopaminergic system can be assessed by dopamine transporter (DaT) imaging. A normal DaT scan using I-123 ioflupane rules out dopamine-related pathology (Fig. 98.48). However, other differentials such as essential tremor, vascular parkinsonism, and drug-induced parkinsonism should also be considered. It has been seen that in both IPD and multiple system atrophy (MSA), patients show a reduced DaT tracer uptake in putamen than the caudate nucleus (Fig. 98.49). However, the reduced striatal tracer uptake in the DaT scan is more symmetrical in patients with MSA than with IPD. To make the criteria more objective, few researchers have also suggested that patients with a relative asymmetry of more than 15% favor the diagnosis of IPD, whereas patients with an asymmetry between 5% and 15% favor MSA as the diagnosis. Few studies used I-123 IBF (for D2 receptor) along with I123 β-CIT (DaT scan). It has been found that both IPD and MSA patients show reduced DaT binding, but only those with MSA show reduced tracer uptake in D2 imaging. These results suggest that DAT SPECT may help differentiate IPD from control participants, and D2 receptor imaging can be useful in further differentiating MSA from PD [69]. It is imperative to use multitracer imaging to increase the accuracy of diagnosis.
FIGURE 98.48 Dopamine transporter scan shows normal striatal uptake bilaterally. There is normal background activity. The appearance suggest preservation of the dopaminergic activity within the presynaptic terminals and rules out idiopathic Parkinson’s disease or Parkinson’s plus syndrome.
FIGURE 98.49 Dopamine transporter scan shows markedly reduced tracer uptake in the putamina bilaterally with relatively preserved activity in the caudate nuclei. The appearance suggest the loss of the dopaminergic activity within the presynaptic terminals. Appearance would indicate idiopathic Parkinson’s disease or Parkinson’s plus syndrome.
Brain Tumors Thallium-201 and Tc-99m sestamibi SPECT or SPECT/CT are useful in the evaluation of recurrent brain tumors versus radiation necrosis. However, the factors essential for the uptake of these tracers in the brain tumors are a break in the blood–brain barrier and increased vascularity of the tumors. Besides these, Tc-99m glucoheptonate (GHA) has recently been used in brain tumor management. It is a structural analog of glucose, and a break in
the blood–brain barrier is required for its entry. Whereas the viable tumors show a progressive increase in the GHA uptake, inflammatory cells show rapid clearance. It has been found that Tc-99m GHA SPECT is a more effective imaging modality compared with other mentioned SPECT tracers in detecting recurrent glioma [70,71]. Nonetheless, PET has mostly replaced brain SPECT for this purpose.
Cerebrovascular Diseases Brain perfusion studies using radiopharmaceuticals such as Tc-99m HMPAO and Tc-99m ECD can assess the hemodynamic reserve in patients with cerebrovascular disease. The primary role of SPECT in acute stroke is to select patients for thrombolytic therapy. This is assessed by identifying the potentially salvageable brain parenchyma [72]. The cerebrovascular reserved test (CVR test) is also being used for the evaluation of brain perfusion by using vasodilator agents. SPECT perfusion assesses the cerebrovascular activity in response to a vasodilatory challenge. This is usually done by direct administration of acetazolamide, a carbonic anhydrase inhibitor. The acetazolamide challenge can anticipate the possible cerebrovascular event by evaluating the cerebral perfusion reserve. CVR test is also helpful in managing patients with Moyamoya disease who are planned for therapeutic interventions. A carotid balloon occlusion test is another way of assessing cerebral perfusion reserve, and this evaluates the patency of the collateral circulations in the cerebral vasculature. It can help surgeons to be prepared for any intentional or unintentional sacrifice of the carotid artery during the surgery [73]. Asymmetric perfusion on SPECT imaging may suggest an increased risk of cerebrovascular accidents after internal carotid artery occlusion.
Brain Death Evaluation The diagnosis of brain death can be confirmed by brain death scintigraphy. The commonly used tracers include Tc-99m HMPAO and Tc-99m ECD. Being lipophilic, they can assess the perfusion to the brain and viability of brain cells. The imaging feature characteristic of brain death is the absence of tracer accumulation in the brain. Currently, brain death scintigraphy is used during organ harvesting.
Diagnosis of Normal-Pressure Hydrocephalus
Cisternography has been used for the functional study of cerebrospinal fluid (CSF) dynamics. In this study, the radiopharmaceutical is administered into the CSF spaces and indirectly assess the CSF flow. The radiopharmaceuticals used are In-111 DTPA and Tc-99m DTPA, though In111 DTPA is preferred because of its longer half-life. The tracer is administered into the subarachnoid space through a lumbar puncture. It can help in distinguishing communicating from noncommunicating hydrocephalus. The typical cisternographic picture in communicating hydrocephalus or normal-pressure hydrocephalus is the early tracer uptake in the lateral ventricles (by 6 hours of tracer injection) that persists for 1–2 days.
Assessing Shunt Patency The patency of the shunt can be evaluated by clinical examination of the patient and clinically assessing the subcutaneous CSF reservoir. However, sometimes there may be uncertainty in the diagnosis. In such cases, a radionuclide study with Tc-99m DTPA can add to the diagnosis. The tracer is injected aseptically into the CSF space by a physician who is well aware of the shunt type. Usually, the radiotracer preferred for this purpose is Tc99m DTPA because of its better image quality and lack of delayed imaging.
Detection of Cerebrospinal Fluid Leak Radionuclide imaging is one of the most accurate methods used for detecting CSF leak. The radiotracer Tc-99m DTPA is administered into the CSF space through an aseptic lumbar puncture. Then the nasal pledgets are kept in the anterior and posterior part of each nasal cavity. After about 4 hours, the pledgets are collected, and their radioactivity is measured and compared. The radioactivity of nasal pledgets and blood plasma is compared; if the former is more than two times the latter, then a diagnosis of CSF leak is favored. Besides this, gamma camera imaging with an appropriate projection can also help in localizing the source of CSF leak. Usually, for suspected CSF rhinorrhea, the lateral and anterior projection imaging is acquired, whereas posterior projection is helpful for suspected CSF otorrhea. Other views can also be taken if a clear-cut site of leak is not found. Increased tracer accumulation is seen at the site of the leak on the scintigraphic images. Although both methods can be used for localizing CSF leaks, counting the pledgets always has a higher sensitivity.
Nuclear Cardiology
Nuclear medicine procedures are used to evaluate inducible cardiac ischemia, myocardial viability, ventricular function, and cardiac sympathetic innervation.
Myocardial Perfusion Imaging Myocardial perfusion is evaluated by injecting a radiopharmaceutical that distributes in the myocardium followed by imaging of the heart. The perfusion abnormality is diagnosed as relatively reduced tracer accumulation in the abnormal myocardium compared with that in the adjacent normal myocardium. To increase the sensitivity, different cardiac stress types, such as exercise or pharmacologic stress, are performed during tracer administration. This increases the coronary blood flow compared with resting levels, to render a flow differential between normal and abnormal coronary arteries. These differences can be evaluated visually or quantitatively on myocardial perfusion images. Indications
◾equivalent Evaluation of nonacute chest pain or ischemia ◾ Patients with acute chest pain ◾coronary Risk stratification in known chronic stable artery disease (CAD) ◾surgery Preoperative risk assessment for noncardiac without active cardiac conditions ◾coronary Risk assessment in patients with postacute syndrome ◾ Risk assessment in patients post revascularization ◾ Assessment of myocardial viability or ischemia ◾ Evaluation of ventricular function
Patient Preparation Cardiovascular history and reports of all the relevant investigations, including electrocardiography (ECG), echocardiography, Holter record, etc, done previously should be reviewed. Patients should be clinically assessed for any other cardiac ailments, such as heart failure or valvular diseases.
Patients are instructed to fast for at least 4 hours before the test because this reduces the splanchnic circulation and therefore leads to better imaging because of less tracer activity in the liver and bowel. Patients are also advised to avoid caffeine for at least 24 hours before the test because caffeine can reduce the effect of the pharmacologic agents such as adenosine used for vasodilator stress. If clinically permissible, patients should withhold certain medications such as beta-blockers 24–48 hours before, calcium channel blockers 24 hours before, and long-acting nitrates 24 hours before the procedure because these medications may reduce the sensitivity of stress imaging. Withholding the medications may not be necessary if a perfusion study is planned for risk stratification in patients with known CAD on medical management. Stress Protocols
Physical Stress: Treadmill exercise is the most common form of stress, that is used for myocardial perfusion imaging (MPI). The exercise tolerance, heart rate, blood pressure response, and ST-segment response are assessed during the exercise, which provides additional clinical information useful in decision making. Tracer should be administered intravenously at the peak of the exercise, and exercise should continue for at least 1 minute after the tracer injection for its optimal distribution in the myocardium. For patients undergoing treadmill exercise stress, achieving 85% of the maximum predicted heart rate (calculated as 220 – age in years) is normally considered the cut-off for an optimum exercise level. However, whenever possible, exercise should be symptom limited, and achieving 85% of maximum predicted heart rate is not an indication to terminate the exercise. Similarly, if a patient becomes symptomatic before achieving this, exercise may be terminated.
Pharmacologic Stress: Pharmacologic stress is performed in patients who either cannot do physical exercise or in patients with left bundle branch block or who may not achieve an optimum level of stress through exercise. The commonly used pharmacologic stress agents are:
Adenosine:
Adenosine is a safe vasodilator stress agent. It is administered intravenously at a dose of 0.14 mg/kg/min for 6 minutes, and radiotracer is injected intravenously at 3 minutes of study [74]. Sometimes a short protocol is performed cautiously in patient with relative contraindication in which adenosine is administered for 4 minutes and the radiotracer is injected at 2 minutes. The side effects associated with adenosine are usually transient because of its very short half-life. Most often, side effects subside within 1 minute of termination of the infusion without any intervention. It is contraindicated in patients with second- or third-degree heart block, sick sinus syndrome, and history of bronchospasm.
Regadenoson: This is another vasodilator cardiac stress agent, which activates selectively A2A adenosine receptor and causes coronary vasodilation. The recommended IV dose of regadenoson is 5 mL (0.4 mg regadenoson), which should be injected as a bolus through the peripheral vein in approximately 10 seconds. After 10–20 seconds, the radiotracer is administered [75]. The common side effects associated with regadenoson include dizziness, headache, and flushing. It is safer than adenosine in patients with mild to moderate airway diseases; however, aminophylline may be required for reversal of serious side effects because of its relatively long half-life (∼2–3 minutes).
Dobutamine When vasodilator stress is contraindicated, inotropic agents such as dobutamine can be used for cardiac stress [76]. The pressure products associated with dobutamine stress are usually less than with exercise. The common side effects associated with dobutamine are chest uneasiness, palpitations, hypertension, premature ventricular complexes, and shortness of breath. These side effects of dobutamine mostly subside within minutes after the termination of infusion. Occasionally, beta-blockers such as esmolol or metoprolol may be needed as an antidote to reverse severe side effects. Radiotracers Tc-99m-sestamibi, Tc-99m tetrofosmin, and Tl-201 are the commonly used radiopharmaceuticals in MPI. Tc-99m-sestamibi and Tc-99m tetrofosmin, being lipophilic compounds, enter the myocytes by passive diffusion. After entering the myocytes, they get fixed to the mitochondria in the cell. As a result, they do not undergo redistribution, requiring a second injection for
acquiring rest images. In contrast, Tl-201 gets actively transported into the cardiomyocyte through the sodium–potassium channel. After administration, Tl-201 redistributes between the blood pool and the myocardium, reaching equilibrium at about 3–4 hours. Therefore, with Tl-201, the rest images are acquired at about 3 to 4 hours after the stress images. Currently, Tc-99m– labeled tracers are more frequently used in clinical practice. It has a shorter half-life (6 hours) and gives less radiation dose to the patient than Tl-201, which has a longer half-life (73 hours) and limits the maximal radiotracer dose administered.
Image Acquisition Usually, SPECT/CT with low-dose CT for attenuation correction is used for myocardial imaging. When Tl-201 is used, the study is acquired within 10– 15 minutes after tracer injection at peak stress, and the rest study (redistribution study) is acquired 3–4 hours later. In the case of Tc-99m– labeled tracers, the stress imaging study is acquired 15–60 minutes after the tracer injection (at the time of peak stress), and the rest imaging is acquired 30–60 minutes after rest injection so that the radiotracer gets cleared from the liver. Myocardial SPECT is performed with ECG gating at a frame rate of 8–16 frames per cardiac cycle. A symmetrical 20% energy window is kept around the photopeak energy of Tc-99m (140 keV), and a low-energy high-resolution parallel-hole collimator is used for the imaging. Images are acquired in 64 × 64 matrices with a 180-degree rotation of the detector from the right anterior oblique to the left posterior oblique view. The detectors should be in L-mode with a noncircular body contoured orbit in step-andshoot acquisition mode. Interpretation The myocardial perfusion images should be interpreted systematically. The following aspects should be included while interpreting the SPECT:
1. The presence of significant lung uptake 2. Assessment of the size of the cardiac chambers 3. Perfusion defect in coronary artery territory, extent, severity, and reversibility of defects 4. Results of quantitative perfusion analysis data 5. Parameters obtained from the gated images
Consideration should also be given to clinical hemodynamic data and stress ECG findings during image interpretation. Initial Image Analysis Before assessing the perfusion defect, the cardiac chamber size should be evaluated in both stress and rest mages. Sometimes the left ventricle size may vary between stress and rest images. The cavity size larger on stress compared to rest images is called transient ischemic dilation (TID), which may be associated with multivessel coronary disease. Persistent TID for a long time after completing stress testing is usually associated with a poor prognosis [77,78]. Occasionally in SPECT images, mild diffuse tracer uptake is seen in bilateral lung fields, especially in poststress Tl-201 images. This lung uptake usually is associated with a poor prognosis and is an indirect indication of impaired resting left ventricular function. With Tc-99m–based perfusion agents, there is no clear consensus regarding the significance of lung uptake [79]. The right ventricle is usually not visualized or very faintly visualized in myocardial SPECT images. Quantitatively, the tracer uptake in the right ventricle is approximately 50% of that of the left ventricle. Whereas homogeneous increased right ventricular uptake represents right ventricle hypertrophy, which usually result from pulmonary hypertension. Perfusion Defect Localization The perfusion defect localization can be described using the 17- or 20segment heart model and can be attributed to a specific myocardial wall (apex, septum, anterior, inferior, and lateral wall). These areas can roughly represent one or more coronary arterial territories. For example, inferior and inferoseptal wall perfusion defects may be caused by an obstructed right coronary artery. An inferolateral wall perfusion defect may represent the left circumflex coronary artery territory or first obtuse marginal (OM) territory. Similarly, an anterior wall defect extending into the apex represents left anterior descending coronary artery territory, and an anterolateral defect may represent diagonal branch territory. Perfusion Defect Size and Severity A scoring of 0–4 is usually given in each segment, depending on the severity of the perfusion defect both on stress and rest images. In this grading, 0 is considered normal and 4 as severely reduced perfusion. Semiquantitavely, a perfusion defect involving one or two segments represents small, three or four segments represent medium, and more than 5 segments represent large perfusion defects. The cumulative scores in the stress and rest images are expressed as summed stress and summed rest scores, respectively. The
difference between these two scores is the summed difference score, which is the semiquantitative representation of perfusion defect reversibility, indirectly reflecting the severity of ischemia (Fig. 98.50) [80]. A reversible perfusion defect represents stress induced ischemia (Fig. 98.51), whereas a fixed perfusion defect represents scarred myocardium (Fig. 98.52).
FIGURE 98.50 A 48-year-old male presented with atypical chest pain. Stress myocardial perfusion imaging with adenosine showed normal uptake in both stress and rest images with preserved left ventricular ejection fraction of 55%. The left side shows slices of stress and rest images (left top panel) and summed stress score (SSS) scoring (left bottom panel); the right side shows the extent (top panel) and the gated parameters (right bottom panel).
FIGURE 98.51 A 67-year-old male patient with diabetes and hypertension presented with angina on exertion radiating to the left arm and underwent myocardial perfusion imaging. Images showed reversible perfusion defects mostly involving the mid and basal inferolateral wall, lateral wall, and adjacent inferior wall (arrows in slice images in the left top panel) suggestive of stress-induced reversible ischemia in the left circumflex coronary artery territory with a summed difference score of 12, affecting approximately 24% seen in the left bottom panel The extent image on right panel shows that approximately 24% of the left ventricular myocardium is affected and is 100% reversible (arrowhead).
FIGURE 98.52 A 46-year-old male patient with hypertension and a history of recent myocardial infarction. His stress myocardial perfusion images showed a dilated left ventricular cavity. Also noted was a large area of fixed perfusion defects involving the apex, anterior wall, inferolateral wall, and adjacent inferior wall in slice images on left top panel, suggestive of scarred myocardium.
Many software algorithms help in identifying the epicardial and endocardial edges in the myocardial perfusion study. This can calculate the end-diastolic (ED) and end-systolic (ES) ventricular volumes as well as ventricular ejection fraction. Besides ejection fraction, wall motion abnormality can also be detected on MPI. The wall motion and thickening are usually congruent with certain exceptions, as in patients with left bundle branch block (LBBB). In LBBB, the septal wall moves paradoxically with normal wall thickening. This paradoxical septal movement increases with an increase in heart rate. Hence, in patients with LBBB, vasodilator stress should be preferred over inotropic stress to avoid false-positive perfusion defects (Fig. 98.53).
FIGURE 98.53 A 47-year-old male patient with dyspnea on exertion and known left bundle branch block (LBBB) on electrocardiography underwent adenosine stress Myocardial perfusion imaging. Images showed mild fixed perfusion defect in the septum and apicoseptal region caused by LBBB artifact (arrows).
Myocardial Viability Assessment The irreversible severely hypoperfused area in stress and rest myocardial perfusion imaging usually represents scarred myocardium or myocardial infarction. The differentials include severe chronic ischemic and hibernating myocardium caused by a severely constricted coronary vessel over a long period. Although these myocytes usually do not show any function, they may have maintained cell membranes and enough perfusion just for maintaining their viability. It has been seen that upon coronary revascularization, these patients with severely hypoperfused but hibernating myocardium usually improve in cardiac function and have a reduction in cardiac-related complications. So, infarction must be differentiated from hibernating myocardium. Nuclear cardiology has a significant role in the management of such patients by helping in differentiation between infarcted and hibernating myocardium. Tl-201 has been used for a long time to evaluate viability and hibernating myocardium. Being a potassium analog, it is taken by cells through an intact Na+ -K+ ATPase pump, and the uptake indirectly indicates viable myocardium. There are few protocols using Tl-201 for the assessment of myocardial viability. The most common protocol is a rest redistribution study, in which single Tl-201 injection is administered intravenously when
the patient is at rest; images are obtained at 15 minutes and then at 3–4 hours. In the first study at 15 minutes, Tl-201 uptake in myocardium signifies viable myocardium. In the redistribution study at 3–4 hours, increase in uptake compared with baseline represents hibernating myocardium. Tc-99m sestamibi and Tc-99m tetrofosmin have also been used in some centers for viability assessment because of their better image resolution and less radiation. In this protocol, the patient undergo imaging at resting condition (baseline sestamibi study) and another study post sublingual nitrate administration (nitrate-augmented sestamibi study). Any improvement in perfusion on nitrate augmented sestamibi images reflect hibernating myocardium. Currently, F-18 fluorodeoxyglucose cardiac PET imaging is most commonly used for the assessment of viable myocardium.
Radionuclide Ventriculography Radionuclide ventriculography has long been used for assessment of ventricular function, detection of CAD, and monitoring toxicity of the cardiotoxic drug. There are two ways of doing radionuclide ventriculography, equilibrium radionuclide angiography (ERNA) and firstpass radionuclide angiography (FPRNA) depending on the time of image acquisition [81]. ERNA or MUGA (multigated acquisition) scan requires, an RBC labeling technique, wherein first stannous pyrophosphate or stannous chloride is allowed to create an optimum chemical state inside the RBCs. After 15–20 minutes, Tc-99m pertechnetate is introduced, which enters the RBCs and remains there in the favorable oxidation–reduction environment. The usually administered activity is approximately 800 MBq (20–25 mCi) for adults, and the effective radiation dose received by the patient is approximately 5.6 mSv. There are three methods for RBC labeling, which are in-vivo, modified in vivo–in vitro, and in vitro methods.
◾is The simplest and fastest method of RBC labeling in vivo labeling, which gives the lowest labeling
efficiency of only 80–90%. In this procedure, the stannous agent is administered intravenously 15–20 minutes before Tc-99m pertechnetate. Tc-99m pertechnetate is injected as a bolus during the imaging for FPRNA. Imaging is performed 15–20
minutes after Tc-99m injection in MUGA scan or ERNA. Because of lower labeling efficiency, the background activity is a little higher in other organs such as the stomach and thyroid in this method In the modified in vivo–in vitro method, the reducing agent is administered to the patient. After 20–30 minutes, reduced blood is withdrawn from the patient and kept in a syringe that already contains Tc-99m pertechnetate within it. After the syringe has been gently shaken for 10 minutes, it is administered again to the patient. This method has a labeling efficiency of about 95% The in vitro method of labeling, though tedious and the most complicated procedure, provides the highest labeling efficiency. In this procedure, after withdrawing blood from the patient, it is centrifuged and washed to get the RBC pellets. The washed RBC pellets are then incubated in the stannous agent and Tc-99m pertechnetate, respectively. Then the labeled RBCs are reinjected into the patient. The labeling efficiency is more than 97%
◾
◾
For optimum imaging, it is essential to acquire a minimum of 20,000 counts/minute. This provides sufficient count density in the left ventricle to accurately calculate the left ventricular ejection fraction (LVEF). The best septal view or left anterior oblique (LAO) is the most commonly acquired view for estimating LVEF because it provides the optimum images without any ventricular overlap. Additional images in the anterior and lateral view may be acquired if required (Fig. 98.54). The background-corrected counts in the isolated left ventricle are calculated at the ED and ES phases from the LAO view. The following formula is used to estimate the EF:LVEF =
(Background corrected ED counts − Background counts)/Background corrected ED counts × 100
corrected
ES
FIGURE 98.54 A 40-year-old female patient with carcinoma of the breast taking trastuzumab. For baseline evaluation, a multigated acquisition scan was done, which shows left ventricular ejection fraction of 59% and no regional wall motion abnormality. Besides the systolic and diastolic images, it also shows an amplitude image, phase image, and phase histogram, which can be used for dyssynchrony assessment.
Heart Failure Evaluation Myocardial perfusion study has been an essential part of establishing the etiopathology among newly diagnosed heart failure patients [82]. The literature evidence shows a high negative predictive value of MPI in the detection of CAD among patients with heart failure, and MPI can significantly benefit in better patient management.
Evaluation of Cardiac Dyssynchrony Left ventricular myocardial dyssynchrony can be evaluated through MPI SPECT as well as MUGA scan by using different commercially available software. These programs usually use the phase histogram to assess the global dyssynchrony. This can also be represented visually. The myocardial
dyssynchrony assessment can be done before as well as after the cardiac resynchronization therapy implant [83].
Cardiac Sympathetic Innervation I-123 MIBG cardiac imaging can localize sympathetic denervated myocardium in post-myocardial injury/ischemia situation. I-123 MIBG imaging can risk-stratify and prognosticate heart failure patients with LV dysfunction. Heart failure patients with cardiac sympathetic denervation in the imaging have higher mortality, dysrhythmia, and more likely to have complications related to heart failure. The ADMIRE-HF study showed the benefits of I-123 MIBG imaging in heart failure patients. I-123 MIBG scanning can be used to prognosticate in ischemic as well as non-ischemic heart failure with the prognosis being directly proportional to the myocardial MIBG uptake [84].
Cardiac Amyloidosis Heart failure is the usual presentation of cardiac amyloidosis. Pathologically, cardiac amyloidosis can be primary (amyloid transthyretin [ATTR] type) and secondary (amyloid light chain [AL] type) as a part of systemic plasma cell disease. It has been seen that bone-seeking agents such as radiolabeled MDP, 3,3-diphosphono-1,2-pyrophosphate (DPD), and pyrophosphate tracers show myocardial uptake in patients with TTR-type cardiac amyloidosis and not in those with AL-type amyloidosis. Therefore, positive scintigraphy and absence of monoclonal protein in the serum and urine can help in the noninvasive diagnosis of the ATTR type of cardiac amyloidosis [85].
Lymphoscintigraphy Radionuclide lymphoscintigraphy is a well-established, easy, and commonly performed modality for assessment of the functional status of lymphatics. It is used mostly in two clinical scenarios: for identification of sentinel lymph nodes (SLNs) and for evaluation of lymphedema and lymphatic leaks.
Scintigraphy Evaluation of Sentinel Lymph Nodes Sentinel lymph node biopsy is used in various malignancies for accurate localization SLNs. The scintigraphic method is one of the most important methods in the identification of the sentinel nodes. The commonly used radiotracers include Tc-99m labeled sulfur colloid, nanocolloid, and phytate.
The ideal particle size of the radiopharmaceutical used for this purpose should be approximately 100–200 nm, which does not allow them to enter the capillaries but move along the lymphatic channels and get retained in SLNs. Although various protocols are followed regarding the site of injection, the peritumoral area is the preferred site of tracer injection, especially in breast cancer and malignant melanoma for SLN scintigraphy [86,87]. The usual injection doses are about 500 µCi and 1000 µCi for a single-day and 2-day protocol respectively. After the tracer injection, preoperatively the SLNs can be localized by planar and SPECT/CT imaging. SLNs can also be localized during the surgery through an intraoperative gamma probe. Often, both imaging and probe are used in combination for localizing SLNs in various malignancies.
Scintigraphy Evaluation of Lymphatic Disorders Lymphedema is caused by chronic obstruction of the lymphatic channels. The common symptom is limb swelling, leading to poor quality of life. Lymphoscintigraphy is a reproducible and easily available method for the assessment of lymphedema. Commonly, Tc-99m–labeled SC and nanocolloid are used for this purpose. The typically administered radiotracer dose is approximately 0.5–1 mCi in divided aliquots for each limb [88]. The injection can be made in epifascial and subfascial planes. Usually, the epifascial injection is preferred, in which tracer is injected in the subcutaneous or intradermal planes along the web spaces. Whole-body imaging is performed. In abnormal lymphatic drainage, the imaging shows dermal backflow of tracer, nonvisualization of inguinal or axillary lymph nodes, asymmetrical tracer uptake in the inguinal or axillary lymph nodes, visualization of the popliteal or epitrochlear nodes, and visualization of lesser number of ilioinguinal nodes (less than three). Any of these findings alone or in combination can help in diagnosing lymphatic abnormality or obstruction (Fig. 98.55). Similarly, lymphoscintigraphy is used for scrotal lymphedema and chylothorax evaluation.
FIGURE 98.55 A 10-year-old boy with left lower limb swelling for 1 year with normal venous Doppler results. Lymphoscintigraphy shows dermal backflow in the left leg (arrowheads), popliteal lymph nodes (arrow), and paucity of left ilioinguinal lymph nodes on the left side, suggestive of obstructed lymphatic drainage.
Miscellaneous Investigations There are a few uncommonly performed but important investigations, including peritoneal scintigraphy, evaluation of protein-losing enteropathy, salivary scintigraphy, and dacryoscintigraphy.
◾peritoneal Peritoneal scintigraphy is used to evaluate membrane integrity, pleuroperitoneal
shunt, and shunt patency. The commonly used radiopharmaceuticals in peritoneal scintigraphy are Tc-99m SC and Tc-99m MAA particles because they do not diffuse through the peritoneum. When injected into the peritoneum, these tracers remain distributed inside the peritoneum, and any uptake in the thorax suggests a communication
◾
◾massive Protein-losing enteropathy is associated with loss of protein through the GI tract. This can be caused by a variety of diseases such as lymphangiectasia in the intestine, Crohn’s disease, Ménétrier disease, etc. The radiopharmaceuticals used for these purposes are Tc-99m HSA, In-111 transferrin, and Tc-99m dextran. Tracer accumulation in the abdominal region suggests protein leak from the intestine Salivary scintigraphy is used to evaluate xerostomia or dry mouth caused by salivary gland hypofunction resulting in reduced saliva production. Causes include radiation therapy, chemotherapy, medications, radioactive iodine therapy, and Sjögren’s syndrome. Salivary gland dysfunction can be confirmed by scintigraphy using Tc-99m pertechnetate, which can demonstrate abnormal or normal trapping and poststimulation drainage after administration of lemon juice. Usually 10 mCi of Tc-99m pertechnetate is injected intravenously, and imaging is acquired for 30 minutes with sialagogue is administered orally at 15 minutes Dacryoscintigraphy is occasionally performed to evaluate the drainage of nasolacrimal ducts, most commonly for epiphora, an overflow of tears that can be caused by obstruction by a variety of anatomic abnormalities. A droplet of normal saline with 100 μCi Tc-99m pertechnetate is instilled into
◾
◾
the conjunctiva near the lateral canthus of both the eyes, and serial images are obtained every 15–30 seconds for 15 minutes. It can confirm whether the cause is of obstructive origin The was used for gastric Helicobacter pylori infection for a long time. Although it is a simple, noninvasive, and inexpensive investigation modality, currently it is not being used very often. Its overall accuracy is high. Increasingly, the nonradioactive C-13 is more commonly used instead of the C-14 isotope. This test is based on the ability of H. pylori to break down urea carbon dioxide, which then is absorbed from the stomach and eliminated in the breath. If the urea breath test is positive and the isotope is detected in the breath, it means that H. pylori is present in the stomach
◾
Suggested Readings • GB Saha, Fundamentals of nuclear pharmacy, fifth ed., Springer, New York, NY, 2004. • KJ Donohoe, ML Brown, BD Collier, et al., Society of Nuclear Medicine procedure guideline for bone scintigraphy, Society of Nuclear Medicine website (2003). Accepted June 20. • AT Taylor, DC Brandon, D de Palma, MD Blaufox, E Durand, B Erbas, et al., SNMMI procedure standard/EANM practice guideline for diuretic renal scintigraphy in adults with suspected upper
urinary tract obstruction 1.0, Semin Nucl Med 48 (4) (2018) 377–390. • P Vitali, R Migliaccio, F Agosta, HJ Rosen, MD Geschwind, Neuroimaging in dementia, Semin Neurol 28 (2008) 467–483. • MJ Henzlova, WL Duvall, AJ Einstein, MI Travin, HJ. Verberne, ASNC imaging guidelines for SPECT nuclear cardiology procedures: Stress, protocols, and tracers, J NuclCardiol 23 (3) (2016 Jun) 606–639.
References [1] R Chandra, A Rahmim, Radioactivity: law of decay, half-life, and statistics, Nuclear Medicine Physics. The Basics, eighth ed., Lippincott Williams & Wilkins, a Wolters Kluwer business, Philadelphia, 2018. [2] GB Saha (Eds.) Fundamentals of nuclear pharmacy, , fifth ed., Springer, New York, NY, 2004. [3] KJ Donohoe, ML Brown, BD Collier, et al., Society of Nuclear Medicine procedure guideline for bone scintigraphy. Society of Nuclear Medicine website. Accepted June 20, 2003. [4] K Agrawal, F Marafi, G Gnanasegaran, Van der Wall H, Fogelman I Pitfalls and limitations of radionuclide planar and hybrid bone imaging, Semin Nucl Med 45 (5) (2015) 347–372. [5] LP Connolly, LA Drubach, SA Connolly, et al., Bone, ST Treves (Eds.) Pediatric Nuclear Medicine/PET, , third ed., Springer, New York, NY, 2007. [6] AZ Krasnow, RS Hellman, ME Timins, BD Collier, T Anderson, AT Isitman, Diagnostic bone scanning in oncology, Semin Nucl Med 27 (2) (1997) 107–141. [7] M Cecchini, A Wetterwald, G Pluijm, G Thalmann, Molecular and biological mechanisms of bone metastasis, EAU Update Series 3 (2005) 214–226. [8] W van der Bruggen, CP Bleeker-Rovers, OC Boerman, M Gotthardt, Oyen WJ PET and SPECT in osteomyelitis and
prosthetic bone and joint infections: a systematic review, Semin Nucl Med 40 (1) (2010) 3–15. [9] G Gnanasegaran, T Barwick, K Adamson, et al., Multislice SPECT/CT in benign and malignant bone disease: when the ordinary turns into the extraordinary, Semin Nucl Med 39 (2009) 431–442. [10] SJ Lu, F Ul Hassan, S Vijayanathan, et al., Value of SPECT/CT in the evaluation of knee pain, Clin Nucl Med 38 (2013) 258–260. [11] K Agrawal, G Gnanasegaran, Painful knee prosthesis: is there a role for bone SPECT/CT?, Nucl Med Commun 35 (7) (2014) 782– 785. [12] HK Mohan, G Gnanasegaran, S Vijayanathan, et al., SPECT/CT in imaging foot and ankle pathology—the demise of other coregistration techniques, Semin Nucl Med 40 (2010) 41–45. [13] D Becker, ND Charles, H Dworkin, J Hurley, IR McDougall, D Price, et al., Procedure guideline for thyroid scintigraphy: 1.0. Society of Nuclear Medicine, J Nucl Med 37 (7) (1996) 1264–1266. [14] D Becker, ND Charkes, H Dworkin, J Hurley, IR McDougall, D Price, et al., Procedure guideline for thyroid uptake measurement: 1.0. Society of Nuclear Medicine, J Nucl Med. 37 (7) (1996) 1266– 1268. [15] K Agrawal, AA Esmail, G Gnanasegaran, S Navalkissoor, BR Mittal, I Fogelman, Pitfalls and limitations of radionuclide imaging in endocrinology, Semin Nucl Med 45 (5) (2015) 440–457. [16] HA Ziessman, JP O’Malley, JH Thrall, FH Fahey (Eds.) Nuclear Medicine: The Requisites, fourth ed., Elsevier, Philadelphia, PA, 2014. [17] H Dige-Petersen, S Kroon, S Vadstrup, ML Andersen, NO RoyPoulsen, A comparison of 99Tc and 123I scintigraphy in nodular thyroid disorders, Eur J Nucl Med 3 (1) (1978) 1–4. [18] BR Haugen, EK Alexander, KC Bible, GM Doherty, SJ Mandel, YE Nikiforov, et al., 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer, Thyroid 26 (1) (2016) 1–133. [19] E Bombardieri, F Giammarile, C Aktolun, RP Baum, A Bischof Delaloye, L Maffioli, et al., 131I/123I-metaiodobenzylguanidine (mIBG) scintigraphy: procedure guidelines for tumour imaging, Eur J Nucl Med Mol Imaging 37 (12) (2010) 2436–2446. [20] D Taïeb, HJ Timmers, E Hindié, BA Guillet, HP Neumann, MK Walz, et al., EANM 2012 guidelines for radionuclide imaging of
phaeochromocytoma and paraganglioma, Eur J Nucl Med Mol Imaging 39 (12) (2012) 1977–1995. [21] E Hindié, O Ugur, D Fuster, M O’Doherty, G Grassetto, P Ureña, et al., Parathyroid Task Group of the EANM. 2009 EANM parathyroid guidelines, Eur J Nucl Med Mol Imaging 36 (7) (2009) 1201–1216. [22] BS Greenspan, G Dillehay, C Intenzo, WC Lavely, M O’Doherty, CJ Palestro, et al., SNM practice guideline for parathyroid scintigraphy 4.0, J Nucl Med Technol 40 (2) (2012) 111–118. [23] AT Taylor, DC Brandon, D de Palma, MD Blaufox, E Durand, B Erbas, et al., SNMMI procedure standard/EANM practice guideline for diuretic renal scintigraphy in adults with suspected upper urinary tract obstruction 1.0, Semin Nucl Med 48 (4) (2018) 377– 390. [24] GA Mandell, DF Eggli, DL Gilday, S Heyman, JC Leonard, JH Miller, et al., Procedure guideline for renal cortical scintigraphy in children. Society of Nuclear Medicine, J Nucl Med 38 (10) (1997) 1644–1646. [25] AT Taylor Jr., JW Fletcher, JV. .J.r Nally, MD Blaufox, EV Dubovsky, EJ Fine, et al., Procedure guideline for diagnosis of renovascular hypertension. Society of Nuclear Medicine, J Nucl Med 39 (7) (1998) 1297–1302. [26] GA Mandell, JA Cooper, JC Leonard, M Majd, JH Miller, MT Parisi, et al., Procedure guideline for diuretic renography in children. Society of Nuclear Medicine, J Nucl Med 38 (10) (1997) 1647–1650. [27] GA Mandell, DF Eggli, DL Gilday, S Heyman, JC Leonard, JH Miller, et al., Procedure guideline for radionuclide cystography in children. Society of Nuclear Medicine, J Nucl Med 38 (10) (1997) 1650–1654. [28] BR Mittal, HV Sunil, K Agrawal, Nuclear imaging in pulmonary medicine, SK Jindal (Eds.) Textbook of Pulmonary and Critical Care Medicine, second ed., Jaypee Brothers Medical Publishers, New Delhi, 2007, 346–358. [29] PD Stein, et al., Critical review of ventilation/perfusion lung scans in acute pulmonary embolism, Prog Cardiovasc Dis 37 (1994) 13–24. [30] DF Worsley, et al., Comprehensive analysis of the results of the PIOPED Study. Prospective Investigation of Pulmonary Embolism Diagnosis Study, J Nucl Med 36 (1995) 2380–2387. [31] A Gottschalk, et al., Overview of prospective investigation of pulmonary embolism diagnosis II, Semin Nucl Med 32 (2002) 173– 182.
[32] A Gottschalk, et al., Very low probability interpretation of V/Q lung scans in combination with low probability objective clinical assessment reliability excludes pulmonary embolism, J Nucl Med 48 (2007) 1411–1415. [33] C Wittram, et al., Discordance between CT and angiography in the PIOPED II study, Radiology 244 (2007) 883–889. [34] M Miniati, et al., Perfusion lung scintigraphy for the diagnosis of pulmonary embolism: a reappraisal and review of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis methods, Semin Nucl Med 38 (2008) 450–461. [35] LM Freeman, et al., The current and continuing important role of ventilation-perfusion scintigraphy in evaluating patients with suspected pulmonary embolism, Semin Nucl Med 38 (2008) 432– 440. [36] T Kurose, et al., Functional evaluation of lung by Xe-133 lung ventilation scintigraphy before and after lung volume reduction surgery (LVRS) in patients with pulmonary emphysema, Acta Med Okayama 58 (2004) 7–15. [37] T Win, et al., Ventilation-perfusion scintigraphy to predict postoperative pulmonary function in lung cancer patients undergoing pneumonectomy, AJR 187 (2006) 1260–1265. [38] GH Griffith, GM Owen, S Kirkman, R Shields, Measurement of the rate of gastric emptying using chromium-51, Lancet 1 (1966) 1244. [39] HA Ziessman, FH Fahey, FB Atkins, J Tall, Standardization and quantification of radionuclide solid gastric-emptying studies, J Nucl Med 45 (2004) 760–764. [40] HA Ziessman, A Chander, A Ramos, RL Wahl, JO Clark, The added value of liquid gastric emptying compared to solid emptying alone, J Nucl Med 50 (2009) 726–731. [41] HA Klein, A Wald, Computer analysis of radionuclide esophageal transit studies, J Nucl Med 25 (1984) 957–964. [42] K Tatsch, WA Voderholzer, MJ Weiss, W Schrottle, K Hahn, Reappraisal of quantitative esophageal scintigraphy by optimizing results with ROC analyses, J Nucl Med 37 (1996) 1799–1805. [43] Z Bar-Sever, Scintigraphic evaluation of gastroesophageal reflux and pulmonary aspiration in children, Semin Nucl Med 47 (3) (2017 May) 275–285. [44] IM Gralnek, Z Neeman, LL Strate, Acute lower gastrointestinal bleeding, NEJM 376 (2017) 1054–1063. [45] E Grady, Gastrointestinal bleeding scintigraphy in the early 21st century, J Nucl Med 57 (2016) 252–259.
[46] I Irvine, A Doherty, R Hayes, Bleeding Meckel’s diverticulum: a study of the accuracy of pertechnetate scintigraphy as a diagnostic tool, Eur J Radiol 96 (2017) 27–30. [47] GN Sfakianakis, GM Haase, Abdominal scintigraphy for ectopic gastric mucosa: a retrospective analysis of 143 studies, AJR Am J Roentgenol 138 (1982) 7–12. [48] GT Krishnamurthy, FE Turner, Pharmacokinetics and clinical application of technetium 99m-labeled hepatobiliary agents, Semin Nucl Med 20 (2) (1990) 130–149. [49] HS Weissmann, MS Frank, LH Bernstein, et al., Rapid and accurate diagnosis of acute cholecystitis with 99m Tc-IDA cholescintigraphy, AJR Am J Roentgenol 132 (1979) 523–528. [50] HA Ziessman, Acute cholecystitis, biliary obstruction, and biliary leakage, Semin Nucl Med 33 (2003) 279–296. [51] D Choy, EC Shi, RG McLean, et al., Cholescintigraphy in acute cholecystitis: use of intravenous morphine, Radiology 151 (1984) 203–207. [52] F Raymond, L Lepanto, L Rosenthall, et al., Tc-99m-IDA gallbladder kinetics and response to CCK in chronic cholecystitis, Eur J Nucl Med 14 (1988) 378–381. [53] L Yap, AG Wycherley, AD Morpett, et al., Acalculous biliary pain: cholecystectomy alleviates symptoms in patients with abnormal cholescintigraphy, Gastroenterology 101 (1991) 786–793. [54] RK Zeman, C Lee, MH Jaffe, et al., Hepatobiliary scintigraphy and sonography in early biliary obstruction, Radiology 153 (1984) 793–798. [55] S Sostre, AN Kalloo, EJ Spiegler, et al., A noninvasive test of sphincter of Oddi dysfunction in postcholecystectomy patients: the scintigraphic score, J Nucl Med 33 (1992) 1216–1222. [56] HA Ziessman, JP O’Malley, JH Thrall, FH Fahey, Hepatobiliary system, HA Ziessman, JP O’Malley, JH Thrall, FH Fahey (Eds.) Nuclear Medicine: The Requisites, , fourth ed., Elsevier, Philadelphia, PA, 2014. [57] A Sevilla, R Howman-Giles, H Saleh, et al., Hepatobiliary scintigraphy with SPECT in infancy, Clin Nucl Med 32 (2007) 16– 23. [58] P Sharma, R Kumar, KJ Das, et al., Detection and localization of post-operative and post-traumatic bile leak: hybrid SPECT-CT with 99mTc-Mebrofenin, Abdom Imaging 37 (2012) 803–811. [59] E Oates, DM Achong, Incidence and significance of enterogastric reflux during morphine-augmented cholescintigraphy, Clin Nucl Med 17 (1992) 926–928.
[60] CC Kuni, CM Engeler, RE Nakhleh, et al., Correlation of technetium-99m-DISIDA hepatobiliary studies with biopsies in liver transplant patients, J Nucl Med 32 (1991) 1545–1547. [61] J Kotzerke, R Schwarzrock, O Krischek, H Wiese, H Hundeshagen, Technetium-99m DISIDA hepatobiliary agent in diagnosis of hepatocellular carcinoma, adenoma, and focal nodular hyperplasia, J Nucl Med 30 (7) (1989) 1278–1280. [62] F Pons, F Lomeña, X Calvet, et al., Uptake of technetium-99m DISIDA by bone metastasis from a hepatoma, Clin Nucl Med 13 (4) (1988) 280–282. 10.1097/00003072-198804000-00012. [63] A Kumar, HT Chugani, The role of radionuclide imaging in epilepsy, part 1: sporadic temporal and extratemporal lobe epilepsy, J Nucl Med 54 (10) (2013) 1775Y 1781. 10.2967/jnumed.112.114397. [64] A Kumar, HT Chugani, The role of radionuclide imaging inepilepsy, part 2: epilepsy syndromes, J Nucl Med 54 (11) (2013) 1924Y 1930. 10.2967/jnumed.113.129593. [65] P Vitali, R Migliaccio, F Agosta, HJ Rosen, MD Geschwind, Neuroimaging in dementia, Semin Neurol 28 (2008) 467–483. [66] V Valotassiou, J Papatriantafyllou, N Sifakis, C Tzavara, I Tsougos, E Kapsalaki, et al., Perfusion SPECT studies with mapping of Brodmann areas in differentiating Alzheimer’s disease from frontotemporal degeneration syndromes, Nucl Med Commun 33 (2012) 1267–1276. [67] K Lobotesis, JD Fenwick, A Phipps, A Ryman, A Swann, C Ballard, et al., Occipital hypoperfusion on SPECT in dementia with Lewy bodies but not AD, Neurology 56 (5) (2001) 643–649. 10.1212/WNL.56.5.643. [68] VL Marshall, CB Reininger, M Marquardt, et al., Parkinson’s disease is overdiagnosed clinically at baseline in diagnostically uncertain cases: a 3-year European multicenter study with repeat [123I]FP-CIT SPECT, J Move Disord 24 (4) (2009) 500–508. [69] YJ Kim, M Ichise, JR Ballinger, et al., Combination of dopamine transporter and D2 receptor SPECT in the diagnostic evaluation of PD, MSA, and PSP, J Move Disord 17 (2) (2002) 303–312. [70] T Abraham, J Feng, Evolution of brain imaging instrumentation, Semin Nucl Med 41 (2011) 202–219. [71] DE Tanasescu, RS Wolfstein, AD Waxman, Critical evaluation of Tc-99m glucoheptonateas a brain scanning agent, J Nuci Med 18 (1977) 630. [72] JM Mountz, HG Liu, G Deutsch, Neuroimaging in cerebrovascular disorders: measurement of cerebral physiology
after stroke and assessment of stroke recovery, Semin Nucl Med 33 (2003) 56–76. [73] M Lorberboym, N Pandit, J Machac, et al., Brain perfusion imaging during preoperative temporary balloon occlusion of the internal carotid artery, J Nucl Med 37 (1996) 415–419. [74] MS Verani, JJ Mahmarian, Myocardial perfusion scintigraphy during maximal coronary artery vasodilation with adenosine, Am J Cardiol 67 (14) (1991 May 21) 12D–17D. [75] MJ Henzlova, WL Duvall, AJ Einstein, MI Travin, HJ Verberne, ASNC imaging guidelines for SPECT nuclear cardiology procedures: stress, protocols, and tracers, J Nucl Cardiol 23 (3) (2016 Jun) 606–639. [76] JR Mason, RT Palac, ML Freeman, S Virupannavar, HS Loeb, E Kaplan, et al., Thallium scintigraphy during dobutamine infusion: nonexercise-dependent screening test for coronary disease, Am Heart J 107 (3) (1984) 481–485. [77] EG DePuey, Single-photon emission computed tomography artifacts, BL Zaret, GA Beller (Eds.) Clinical Nuclear Cardiology: State of the Art and Future Directions, third ed., Mosby, Philadelphia, PA, 2005, 82. [78] MG McLaughlin, PG Danias, Transient ischemic dilation: a powerful diagnostic and prognostic finding of stress myocardial perfusion imaging, J Nucl Cardiol 9 (2002) 663–667. [79] JB Gill, TD Ruddy, JB Newell, DM Finkelstein, HW Strauss, CA Boucher, Prognostic importance of thallium uptake by the lungs during exercise in coronary artery disease, N Engl J Med 317 (1987) 1486–1489. [80] DS Berman, A Abidov, X Kang, SW Hayes, JD Friedman, MG Sciammarella, et al., Prognostic validation of a 17-segment score derived from a 20-segment score for myocardial perfusion SPECT interpretation, J Nucl Cardiol 11 (2004) 414–423. [81] B Hesse, TB Lindhardt, W Acampa, C Anagnostopoulos, J Ballinger, JJ Bax, et al., EANM/ESC guidelines for radionuclide imaging of cardiac function, Eur J Nucl Med Mol Imaging 35 (4) (2008) 851–885. [82] P Soman, A Lahiri, JH Mieres, et al., Etiology and pathophysiology of new-onset heart failure: evaluation by myocardial perfusion imaging, J Nucl Cardiol 16 (2009) 82–91. [83] F Tournoux, R Chequer, M Sroussi, et al., Value of mechanical dyssynchrony as assessed by radionuclide ventriculography to predict the cardiac resynchronization therapy response, Eur Heart J Cardiovasc Imaging 17 (2015) 1250–1258.
[84] AF Jacobsen, R Senior, MD Cerqueira, et al., Myocardial iodine123 meta-iodobenzylguanidine imaging and cardiac events in heart failure. Results of the prospective ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) study, J Am Coll Cardiol 55 (2010) 2212–2221. [85] J Gillmore, M Maurer, R Falk, et al., Non-biopsy diagnosis of cardiac transthyretin amyloidosis, Circulation 133 (2016) 2404– 2412. [86] D Krag, et al., Surgical resection and radio localization of the sentinel lymph node in breast cancer using a gamma probe, Surg Oncol 2 (6) (1993) 335–340. [87] J Alex, D Krag, Gamma-probe guided localization of lymph nodes, Surg Oncol 2 (3) (1993) 137–143. [88] A Szuba, WS Shin, HW Strauss, S Rockson, The third circulation: radionuclide lymphoscintigraphy in the evaluation of lymphedema, J Nucl Med 44 (2003) 43–57.
Introduction Functional imaging with positron emission tomography (PET) has grown manifold both in its technical aspect and its uses in medicine. Being a functional imaging modality, it provides information that is significantly different from what we get from conventional anatomic imaging such as radiography, ultrasonography (USG), computed tomography (CT), and magnetic resonance imaging (MRI). This feature of PET has been exploited in different malignancies for the detection of different pathological changes at an early stage of the disease because functional changes usually precede anatomic changes. With the addition of CT to PET (PET/CT), its usefulness has been further enhanced. Although there are different PET radiopharmaceuticals available, the radiopharmaceutical that revolutionized oncology patient management is fluorine-18fluorodeoxyglucose (18F-FDG). Currently, however, FDG PET/CT has also been used for different nononcologic indications such as in infection and inflammation imaging, myocardial viability assessment, and neurodegenerative conditions. The appropriate use criteria (AUC) for FDG PET/CT addresses several clinical scenarios for restaging and response assessment of malignant disease. To improve utilization and guide treatment providers across specialties to use FDG PET, the Society of Nuclear Medicine and Molecular Imaging, the European Association of Nuclear Medicine, and the American Society of Clinical Oncology have collaboratively developed criteria for the appropriate use of this imaging technology. National Comprehensive Cancer Network (NCCN) imaging AUC includes a full complement of imaging AUC in oncology care designed to support clinical decision making based directly on the NCCN guidelines.
Fluorine-18-Fluorodeoxyglucose
Being a glucose analog, FDG enters the cell through the sodium-coupled glucose transporters and glucose transporter facilitators (GLUT) channels [1]. Inside the cells, it gets converted to FDG-6-phosphate by the enzyme hexokinase, but it is not processed further in the metabolic cycle because of the presence of 18F instead of oxygen at the second carbon position. FDG-6-phosphate is not able to move out of the cell unless it gets reconverted to FDG by the enzyme phosphatase as it is not lipophilic. Hence, it gets trapped inside the cells. Therefore, cells that have high glucose affinity or have high GLUT channels on their cell surfaces will have high FDG uptake, and the same can be seen on PET/CT scan. This visual interpretation of FDG uptake is subjective and may vary depending on technical factors. Therefore, to avoid this technical variation, a quantitative parameter such as the standardized uptake value (SUV) is commonly used, which is a semiquantitative indicator of FDG uptake in the tissue. This is calculated as
where MBq = mega-Becquerel and g = grams.
Patient Preparation and Image Acquisition
◾ FDG in the blood can compete with the blood glucose for the GLUT channels because it is a glucose analog. Therefore, blood glucose has to be monitored before FDG injection. A cutoff of 200 mg/dL has been taken as the upper limit for performing FDG PET/CT scan [2] The patient should fast for at least 4 hours before the test. Plain unflavored water may be taken without any added sugar. If the patient is on parenteral nutrition, then glucose- and sugar-containing fluids should be discontinued at least 4 hours before FDG injection [2] The patient must avoid doing strenuous exercise for 24 hours before the study [2] Adequate prehydration is important to ensure optimum background clearance and for radiation safety purposes After the injection, the patient has to sit quietly in a room for at least 1 hour for background clearance and to reduce the FDG uptake in the muscles
◾ ◾ ◾ ◾
◾ The patient should also be kept warm during the whole process to suppress brown fat activity. Sometimes pharmacologic interventions may be required for brown fat activity suppression [2] ◾ When IV contrast agent is administered as part of the diagnostic CT, the renal function should be assessed beforehand ◾ The usual adult dose of administered FDG is 5–12 mCi (0.09–0.14 mCi per kilogram of body weight), and the pediatric dose is 0.10 mCi per kilogram of body weight (minimum, 1.0 mCi) [2,3] ◾ Usually, the patient should be positioned with the arms elevated and alongside the head. However, for head and neck or brain imaging, the arms should be placed down along the torso ◾ Additional specific imaging protocols are also being used depending on the organs involved for better visualization (e.g., puffed cheeks view for [2]
buccal mucosal lesions, a protruded tongue view for tongue lesions, an open mouth view for palate lesions, delayed postdiuretic scan for urinary tract lesions)
Physiological Fluorodeoxyglucose Distribution and Uptake in Benign Lesions Depending on the GLUT expression and glucose demand, the physiological uptake of FDG is seen in various organs (Table 99.1). The brain is an obligate user of glucose, so it shows high physiological FDG uptake. Besides the brain, mild to moderate diffuse FDG uptake is noted in liver, spleen (
![Textbook of Radiology And Imaging [8 ed.]
9780443071096, 9788131259610, 9788131259641, 9788131259597, 9788131259627](https://ebin.pub/img/200x200/textbook-of-radiology-and-imaging-8nbsped-9780443071096-9788131259610-9788131259641-9788131259597-9788131259627.jpg)
![Textbook of Radiology And Imaging [1, 8 ed.]
9788131259634, 8131259633](https://ebin.pub/img/200x200/textbook-of-radiology-and-imaging-1-8nbsped-9788131259634-8131259633.jpg)
![Textbook of Radiology And Imaging [8 ed.]
9780443071096, 9788131259603, 9788131259634, 9788131259597, 9788131259627](https://ebin.pub/img/200x200/textbook-of-radiology-and-imaging-8nbsped-9780443071096-9788131259603-9788131259634-9788131259597-9788131259627.jpg)
![Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging [7th Edition]
0702075248, 9780702075247, 9780702075629, 9780702075612](https://ebin.pub/img/200x200/grainger-amp-allisons-diagnostic-radiology-a-textbook-of-medical-imaging-7th-edition-0702075248-9780702075247-9780702075629-9780702075612.jpg)
![Muller's Imaging of the Chest E-Book : Expert Radiology Series [2 ed.]
9780323531795, 0323531792](https://ebin.pub/img/200x200/mullers-imaging-of-the-chest-e-book-expert-radiology-series-2nbsped-9780323531795-0323531792.jpg)
![Textbook of Radiology And Imaging [2, 8 ed.]
8131259617, 9788131259610](https://ebin.pub/img/200x200/textbook-of-radiology-and-imaging-2-8nbsped-8131259617-9788131259610.jpg)