Minimally Invasive Thoracic Spine Surgery 9789811566141, 9789811566158

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Minimally Invasive Thoracic Spine Surgery Sang-Ho Lee Junseok Bae Sang-Hyeop Jeon Editors

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Minimally Invasive Thoracic Spine Surgery

Sang-Ho Lee  •  Junseok Bae Sang-Hyeop Jeon Editors

Minimally Invasive Thoracic Spine Surgery

Editors Sang-Ho Lee Wooridul Hospital Seoul, Korea (Republic of)

Junseok Bae Wooridul Hospital Seoul, Korea (Republic of)

Sang-Hyeop Jeon Wooridul Hospital Busan, Korea (Republic of)

ISBN 978-981-15-6614-1    ISBN 978-981-15-6615-8 (eBook) https://doi.org/10.1007/978-981-15-6615-8 © Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Foreword

Disorders of the thoracic spine are important and have a significant and measurable impact on health-related quality of life. Spinal disorders involving the thoracic spine include congenital and developmental deformity, degenerative disorders, neoplastic disease, infectious and inflammatory disorders, and trauma. Surgical approaches to the thoracic spine are important for decompression of the neural elements, realignment of the spine, and stabilization of the thoracic spine. Surgical approaches to the thoracic spine are challenging and may involve significant morbidity due to the anatomic barriers of the chest wall and mediastinum and the relatively narrow diameter of the spinal canal relative to the spinal cord. Professor Lee and Bae’s textbook Minimally Invasive Thoracic Spine Surgery offers valuable teaching and lessons regarding safe and effective management of spinal disorders involving the thoracic spine using a minimally invasive approach. The thoracic spine is the longest and least mobile region of the spinal column. Optimal management of disorders of the thoracic spine begins with an accurate diagnosis. The spectrum of disorders affecting the thoracic spine includes congenital and developmental deformities, degenerative pathologies, tumor, and infection. The clinical and radiographic evaluation of patients with thoracic disorders is well covered in the textbook and offers important pearls for the clinician reader. Radiographic evaluation of the thoracic spine and spinal canal is important to assess significant cord compression, the presence of ossification of the intervertebral disc, and ligaments including the posterior longitudinal ligament and the interlaminar ligaments. The book includes important information regarding clinical and radiographic evaluation, differential diagnoses, and pathologies that guide an evidence-based approach to management of thoracic disorders. The heart of the textbook involves a comprehensive overview of surgical strategies for the management of specific spinal disorders using a minimally invasive approach. Dorsal, ventral, and lateral approaches to the thoracic spine may be compromised by anatomic barriers of the chest wall and mediastinum and the relatively small diameter of the thoracic spinal canal. The spinal cord is especially susceptible to compromise in many disorders of the thoracic spine due to the relatively narrow anatomy of the thoracic spinal canal and the kyphotic alignment of the thoracic spine region. Surgical approaches to the thoracic spine require knowledge of the anatomy of the thorax, including the lungs and mediastinum, the blood supply to the thoracic spine, and the corridors to safely access the thoracic canal with limited retracv

Foreword

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tion of the spinal cord. The textbook offers important and useful information regarding anesthesia, patient positioning, intraoperative imaging, and postoperative management. Anesthetic considerations that are unified with the thoracic spine include single lung ventilation during anterior and lateral approaches and optimization of intravenous anesthetics to facilitate neural monitoring. The detailed descriptions of minimally invasive surgical approaches to decompression and instrumentation of the thoracic spine are exceptionally instructive and valuable. The sections on specific surgical approaches and techniques are thorough and well written with excellent case examples. The surgical techniques chapters offer tremendous and insightful information to improve the surgical techniques of all readers. Professor Lee and Bae and the contributing authors of the textbook Minimally Invasive Thoracic Spine Surgery have created an important and valuable resource for clinicians and surgeons who treat patients with disorders of the thoracic spine. The textbook is transformational in guiding an evidence-based approach to optimal evaluation and management of disorders of the thoracic spine. Sigurd Berven Department of Orthopaedic Surgery UC San Francisco San Francisco, CA, USA

Foreword

In the last 10 years, the use of minimally invasive surgical techniques has revolutionized spinal care. This is particularly apposite in respect of surgery to the thoracic spine as there are significant potential risks of damage to spinal cord function during most open procedures. Anything that mitigates these risks will enhance patient safety and lessen any fears that the operating surgeon may have of rendering any of their patients paraplegic. Sang-Ho Lee, Junseok Bae, and Sang-Hyeop Jeon now bring to the world literature a comprehensive book which outlines current “state-of-the-art” techniques for the treatment of thoracic pathology. In early chapters, the reader is guided through the essential knowledge required for safe access to the spine. Those learning about minimally invasive surgery for the first time will pick up much valuable information and more experienced practitioners will find that some of the clear recommendations will be of significant benefit to their practice. In the remainder of the text, the authors succinctly describe methods by which the surgeon will cope with common and rare surgical entities, backed up by excellent color illustrations and literature references. Rightly, reflecting the author’s considerable experience, there is an appropriate emphasis on the place of full spinal endoscopy. Important as its place now is and will be in the future, endoscopy is not considered “all inclusive.” There are interesting chapters on trauma and tumor management using other technologies and the reader will be drawn to the methods of regaining an erect and normal posture in those afflicted by painful osteoporosis, post-traumatic vertebral collapse, and other spine deformities. Thoracic spine disorders are responsible for a great deal of misery, and anything that allows safer surgery is to be welcomed. The clear descriptions of the multiplicity of thoracic disorders are without comparison. I am sure that this book will become a reference text for all surgeons wishing to move away from outmoded treatments to the newest innovative procedures in spinal care. J. N. Alastair Gibson Department of Orthopaedic Surgery The Spire Murrayfield Hospital Edinburgh Edinburgh, UK

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Foreword

It is a great pleasure and an honor for me to write a foreword to Prof. Sang-Ho Lee’s textbook Minimally Invasive Thoracic Spine Surgery. This well-structured and organized textbook deals with almost all the techniques available to approach the thoracic spine from any side in less aggressive but highly effective approaches compared with the traditional open techniques. This book is a perfect summary of how quickly spine surgery has evolved during the past few decades. Since Hiiikata and Kambin’s early publications in the mid-1970s dealing with percutaneous lumbar disc treatment, decades of continuous evolution in the field of minimally invasive or, even better, adequately invasive spine surgery have passed. Not only visualization but also special instruments or apparatus has widened the indications for less invasive treatment for degenerative disease, trauma, tumor, infection, or deformities of the spine. The main goal of minimally invasive techniques is to reduce the approach trauma to a minimum while achieving maximal effectivity at the site where the pathology is located, keeping intact the physiological function of as much structures as possible. Although endoscopic or endoscopic assisted techniques are established techniques in almost all surgical fields, it still has to fight to be considered as an alternative to classic approaches in spine surgery. The vast majority of surgeons consider just a small skin incision a minimally invasive step; for those who are not trained in these techniques, this can lead to “less effective” or “failed spinal surgery.” If we just take few minutes to think why this is so, many questions arise in my mind: –– Why are we using extreme expensive instruments like navigation, monitoring, and robotic combined with techniques that are 50 years old and have never been improved or updated? –– Why do most surgeons skip the option of endoscopy when advising their patients about surgical options? –– Why do we always read about how steep the learning curve for endoscopic techniques is but never read similar comments for vertebrectomy or complex instrumentation techniques in spine surgery? –– Why are anterior approaches to the lumbar or thoracic spine so dangerous but cervical and transoral techniques are considered “doable?” –– Why are not minimally invasive procedures part of the curricula during residency? ix

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The listing of questions and possible answers could be endless and probably would never find a consensus. However the most effective, less disruptive, and safest technique should always be the first recommendation to our patients when discussing surgical indication and techniques. Many of the chapters in this book deal with those questions and probably can answer them, serving as a guide for young spine surgeons—not only in practice but also in arousing her/his curiosity and, as many of us did, to start thinking, investigate, and after careful research and tests develop new approaches as well. The peri- and intraoperative high-quality planning, including robotics and navigation when combined with minimally invasive techniques, will push the envelope further forward in the next few years. Probably the fascination of reaching and treating deep-seated spinal diseases using less disruptive but equally effective techniques when compared to classic open procedures, mixed with a big portion of respect, will drive the next generations to spread even more minimally invasive techniques in daily practice. Prof. Sang-Ho Lee’s book is a big step in the right direction. He and his coeditors have to be congratulated for summarizing and updating spine surgeons with the latest minimally invasive approaches to the thoracic spine, thus expanding not only our horizon but also the options we have to help our patients in daily practice. Daniel Rosenthal Neurosurgical Section Hochtaunus Kliniken Bad Homburg, Germany

Preface

Small is beautiful for thoracic spine surgery

The incidence of thoracic spine disease is increasing nowadays by routine screening of cervical-thoracolumbar MRI.  You need more active, positive, and more prompt causal treatment to save your patients from intractable back pain and progressive weakness of legs due to thoracic spine diseases, such as herniated thoracic discs or thoracic stenosis. The available free space of the spinal canal of the thoracic spinal cord is very limited so that during the operation the safe margin for not touching the spinal cord is narrow. That is why a small microscopic or endoscopic surgery as a causal treatment for thoracic spine disease is more efficacious and more successful than a big surgery. Because it is truly minimally invasive and the duration of surgery is quite short, blood transfusion is not required. Because it is safer and has fewer side effects and complications, patients who undergo this less invasive thoracic surgical treatment are more sportive and have more life span than those who undergo maximally invasive surgery. The traditional radical thoracic surgery for neurologic decompression requires extensive resection of the vertebral and rib bones, which leads to fusion surgery to prevent postoperative instability. That is why so many surgeons delay decompression surgery until their patients have profound gait disturbance. However, causal treatment needs earlier thoracic decompression at the stage of unbearable back pain and radiculopathy for prevention of walking difficulty. Because the delay in performing decompression in the thoracic spine eventually causes myelopathy, it might be difficult to get back to normal daily activity. When you are well trained in the discipline of the minimally invasive surgical procedures for the thoracic spine, you can perform thoracic decompression at an early stage before your patients develop leg weakness, paraparesis, and paraplegia. For the safe and successful practice of endoscopic decompression instead of wide-open surgery, you need small bipolar radiofrequency, delicate sidefiring Holmium-YAG laser, and high-speed endoscopic diamond drill. With the help of foraminoplastic thoracic endoscopic decompression, it is possible

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to perform a day surgery for the patient with thoracic disc herniation at the ambulatory surgical center. The authors have put enormous efforts and dedication to guide you, our colleagues, toward endoscopic and microscopic minimally invasive thoracic spine surgery. It is our love and passion to give you hope to save your patients with thoracic back problems. Seoul, Korea Seoul, Korea Busan, Korea

Sang-Ho Lee Junseok Bae Sang-Hyeop Jeon

Acknowledgments

It is such a privilege to publish this textbook with our respected colleagues at Wooridul Spine Hospital. First of all, I want to acknowledge the efforts of my seniors who pioneered the new field. Ever since Dr. Sang-Ho Lee established the first spine center of excellence in 1982, he did not stop expanding the borders of spinal treatment. He is not only a pioneer of endoscopic and minimally invasive spine surgery but also a good teacher and mentor, encouraging his students to do complicated surgeries actively and minimally invasively. Dr. Ho-Yeon Lee was the first director of the thoracic spine surgery team at Wooridul. He has actively performed thoracic endoscopic surgery and published the first paper about it. Dr. Sang-Hyeop Jeon is a senior chest surgeon, leading approach surgeons in Wooridul who have put much effort into the minimally invasive anterior spinal approach. I also sincerely appreciate our contributing authors of this textbook. It is such a great thing that a group of doctors from a single hospital have written this book. It is notable because it integrates the essential know-how of tens of years of advancing thoracic spine surgery and maintained a consistent treatment philosophy for minimally invasive surgery from the beginning to the end of the textbook. I would like to thank Jee-Sun Park and YoonSun Lee for their hard work in preparing and managing the manuscript. I also want to thank Dr. Sang-Ha Shin, Sang Soo Eun, Han Joong Keum, Yong-Soo Choi, Jeong-Hoon Choi, Ju-Wan Seuk, and Shih Min Lee, good friends, and colleague, building an incredible spine team together. Finally, I thank God and thank my beloved family: wife Youngsun, kids, Youmin, Seungmin, and my parents. Without their support, prayer, and patience, this book could not have been published. Junseok Bae

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Contents

Part I Introduction  Anatomical Considerations of the Thoracic Spine��������������������������������   3 Dong-Ju Yun and Sang-Hyeop Jeon  Anesthetic Consideration of the Thoracic Spine Surgery��������������������  13 Jisang Kim, Gyu Dae Shim, and Junseok Bae  Radiologic Evaluation of Thoracic Spinal Disease��������������������������������  21 Wei Chiang Liu  Clinical Presentation of the Thoracic Spinal Compression������������������  43 Won Sok Chang and Junseok Bae  Setup of Operation Room and Patient Position������������������������������������  47 Breno Frota Siqueira, Junseok Bae, and Sang Soo Eun Intraoperative Neuromonitoring During Thoracic Spine Surgery ������������������������������������������������������������������������������������������  55 Sourabh Chachan and Junseok Bae Navigation for Thoracic Spine Surgery ������������������������������������������������  59 Yong Soo Choi, Ji Young Cho, and Ho-Yeon Lee Part II Thoracic Disc Herniation Transforaminal Endoscopic Thoracic Discectomy with Foraminoplasty��������������������������������������������������������������������������������  67 Sang-Ha Shin, Junseok Bae, and Sang-Ho Lee  Transforaminal Endoscopic Thoracic Discectomy for Upper Thoracic Spine������������������������������������������������������������������������������  75 Junseok Bae, Sang-Ha Shin, and Sang-Ho Lee  Transforaminal Endoscopic Thoracic Discectomy for Foraminal Herniation; Rotate to Retract Technique����������������������������������������������  85 Sang Soo Eun and Sang-Ho Lee

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 Transforaminal Endoscopic Thoracic Discectomy for Migrated Herniation������������������������������������������������������������������������������������������������  91 Shin Young Lee and Sang-Ho Lee  Endoscopic System for Transforaminal Approach of Thoracic Spine������������������������������������������������������������������������������������������ 103 Sourabh Chachan, Sang-Ha Shin, and Junseok Bae Mini-Thoracotomy and Microscopic Discectomy Without Fusion ���� 109 Sang Soo Eun, Young Sik Bae, and Sang-Ho Lee Transforaminal Interbody Fusion���������������������������������������������������������� 115 Yong Soo Choi and Sang-Ho Lee Thoracoscopic Discectomy���������������������������������������������������������������������� 125 Sang-Hyeop Jeon and Sang-Ho Lee Posterior Microscopic Discectomy with CO2 Laser������������������������������ 133 Han Joong Keum, Oon-ki Baek, and Sang-Ho Lee  Posterolateral Oblique Paraspinal Approach with Tubular Retractor�������������������������������������������������������������������������������������������������� 141 Jang-Ho Ahn, Ji Young Cho, Ki-Hyoung Moon, and Sang-Ho Lee Part III Ossification of the Ligamentum Flavum Microscopic Decompression�������������������������������������������������������������������� 149 Kiyoung Choi and Chan Shik Shim Endoscopic Decompression of Thoracic OLF �������������������������������������� 161 Eun Soo Park and Sang-Ho Lee Part IV Ossification of the Posterior Longitudinal Ligament  Mini-Thoracotomy and OPLL Resection���������������������������������������������� 175 Seok Jin Ko, Junseok Bae, and Sang-Ho Lee Trans-axillary Approach for Upper Thoracic Spine���������������������������� 187 Hyung Chang Lee and Sang-Hyeop Jeon Modified Oblique Corpectomy for Upper Thoracic Spine������������������ 195 Ji Young Cho and Ho-Yeon Lee  Simultaneous Ventral and Dorsal Decompression of OPLL and OLF������������������������������������������������������������������������������������ 209 Jong Won Yoon and Junseok Bae  Posterolateral Oblique Paraspinal Approach with O-Arm Navigation ������������������������������������������������������������������������������������������������ 221 Ji Young Cho, Won-Chul Choi, and Ho-Yeon Lee  Management of Dural Leak After OPLL Resection���������������������������� 231 Shih Min Lee and Junseok Bae

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Management After Mini-­Thoracotomy Without Chest-Tube�������������� 239 Shin Jae Kim, Young Sik Bae, and Junseok Bae Part V Trauma Vertebroplasty and Kyphoplasty������������������������������������������������������������ 245 Ju-Wan Seuk and Sang-Ho Lee  Minimally Invasive Reconstruction of Vertebral Body in Kümmell’s Disease ���������������������������������������������������������������������������������� 251 Shih Min Lee and Junseok Bae Mini-Thoracotomy Corpectomy������������������������������������������������������������ 259 Hyeong Seok Oh, Sang-Hyeop Jeon, and Won Kyu Choi Thoracoscopic-Assisted Corpectomy and Fusion �������������������������������� 265 Junseok Bae and Sang-Hyeop Jeon Part VI Deformity Minimally Invasive Thoracic Deformity Surgery �������������������������������� 275 Jeong Hoon Choi, Junseok Bae, and Sang-Hyeop Jeon Part VII Tumor and Arachnoid Cyst  Minimally Invasive Resection of Thoracic Arachnoid Cyst: Twist Technique���������������������������������������������������������������������������������������� 285 Sang Soo Eun and Sang-Ho Lee  Minimally Invasive Resection of Thoracic Tumor�������������������������������� 291 Dong Hyun Bae, Sang-Ha Shin, and Sang-Ho Lee Part VIII Interventional Procedures CT and US Guided Intervention in Thoracic Spine ���������������������������� 301 Leesuk Kim and Won Sok Chang Thoracic Neuroplasty������������������������������������������������������������������������������ 305 Chan Hong Park

Part I Introduction

Anatomical Considerations of the Thoracic Spine Dong-Ju Yun and Sang-Hyeop Jeon

Introduction The thoracic spine belongs to the middle segment of the entire spine column between the cervical and the lumbar vertebrae. The thoracic spine consists of the 12 largest vertebral bodies in the spinal column. As a result, the thoracic spine occupies the longest part of the spinal column. It constitutes the longest part but is the most stable of the spinal columns. Thoracic vertebra combines with ribs, and ribs combine with the sternum to form thoracic cages as a whole. The thoracic cage provides stability to the thoracic spine while partially limiting its movement. The curvature of the thoracic spine is kyphotic. The anterior height of vertebral body of the thoracic spine is shorter than the posterior height. This makes natural kyphosis (Fig. 1) [1]. The bone, musculature, vascular, nervous, and ligament anatomy of the thoracic spine will be discussed.

T1

Thoracic spine

T12

Fig. 1  Thoracic spine—kyphotic posture

 uscular Anatomy of the Thoracic M Spine D.-J. Yun (*) Department of Neurosurgery, Busan Wooridul Spine Hospital (WSH), Busan, South Korea e-mail: [email protected] S.-H. Jeon Department of thoracic surgery, Busan Wooridul Spine Hospital, Busan, Korea

The muscles are divided into three layers: superficial, intermediate, and deep. The superficial layer comprises the trapezius and latissimus dorsi muscles connected to the upper extremity in the thoracic spine. The rhomboid major and minor muscles are

© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2021 S.-H. Lee et al. (eds.), Minimally Invasive Thoracic Spine Surgery, https://doi.org/10.1007/978-981-15-6615-8_1

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below this muscle. The intermediate layer consists of the serratus posterior inferior and superior, rhomboid muscles. These muscles are connected to the spinous process and ribs. The deep layer consists of the erector spinae muscles, spinalis, longissimus, iliocostalis, and the underlying intrinsic muscles. Erector spinae bundles are located longitudinally along the entire spine and dorsolaterally in the paraspinal transversospinalis group. The fascial investment of the erector spinae muscles continues laterally, resulting in transversus aponeurosis of the abdominal wall. At the thoracolumbar junction, the quadratus lumborum and intertransversarii muscles are separated by this fascial investment (Fig. 2).

D.-J. Yun and S.-H. Jeon

The thoracic vertebrae are distinguished from the cervical and lumbar spine by their characteristic articulation with the ribs. The typical thoracic vertebral bodies (T2–T8) have four small facets that combine with a total of four ribs, one on the left, one on the right, one above, and one below, respectively. These are known as costal demifacets. The head of each rib articulates with the superior and inferior costal demifacets of the two vertebral bodies, which are known as costocorporeal articulations. The crest of the head of each rib has a ligamentous attachment to the intervertebral disc. For example, the seventh rib articulates with the inferior demifacet of the T6 vertebral body and the superior demifacet of the T7 vertebral body as well as the ligamentous attachment to the Bony Anatomy of T6–T7 intervertebral disc. T9–T12 usually do not have superior and inferior demifacets but only the Thoracic Spine single facets that articulate with the ribs. The T9 The thoracic spine consists of 12 vertebral bod- vertebra may have two demifacets in some cases. ies. Thoracic vertebrae are broadly similar; how- The first, 10th, 11th, and 12th ribs articulate with ever, T1 and T9 to T12 exhibit slightly different a single thoracic vertebra. The single facet of T10, characteristics. Thoracic vertebrae from T2 to T8 T11, and T12 is located on the pedicle. For examare known as typical vertebrae, and T1 and T9 to ple, the 11th rib articulates with the T11 vertebral T12 are known as atypical vertebrae. body (Figs. 3, 5) [4]. Thoracic vertebrae are larger than those comPedicle morphometry of the thoracic spine has prising the cervical spine and smaller than those been reported to exhibit many anatomical variain the lumbar spine. The volume of the vertebral tions [5, 6]. Sagittal and axial angulation of the bodies increases as they descend from T1 to T12 pedicle of the thoracic spine varies with each [2]. Thoracic vertebral bodies appear heart-­ subsequent thoracic level [7]. The pedicle of the shaped when viewed from above. The left-right thoracic spine is angulated in the posterior lateral width of a thoracic vertebral body is larger than fashion in the vertebral body. As T1 descends to the anterior-posterior and the superior-inferior T12, medial angulation of the pedicle decreases. dimensions. The left-right width decreases from The width of the pedicle decreases from T1 to T4 T1 to T3 and then increases from T4 to T12. The and increases from T5 to T12. The height and left-right width is greater than the width of the length of the pedicle gradually increase from T1 superior endplate at the inferior endplate of the to T12 [8]. The pedicle wall is 2–3 times thicker vertebral body. Therefore, in the coronal plane, medially than laterally [9]. the thoracic vertebral bodies are trapezoid in The facet joint of the thoracic spine is oriented shape. In the superior-inferior dimension, the in a more coronal direction. The superior facet posterior aspect of thoracic vertebral bodies is has an articular surface on the dorsal aspect. larger than the anterior aspect. The T1 and T2 Inferior facets, on the other hand, have an articuvertebral bodies are somewhat similar to the cer- lar surface in the ventral aspect. This provides vical vertebral body. The T1 vertebral body has stability against anteroposterior translation. In an uncinate process and superior vertebral notch the lower thoracic spine, the facet changes to a above the pedicle. The T1 vertebral body is rect- more sagittal orientation, which provides stabilangular and not heart shaped. From T9 to T12, ity against rotation. The inferior articular surface the vertebral bodies are somewhat similar to the of the T12 thoracic vertebra is more convex and lumbar vertebral bodies (Figs. 3 and 4) [3, 4]. lateral, similar to the lumbar spine.

Anatomical Considerations of the Thoracic Spine

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Fig. 2 Musculature anatomy of the thoracic spine

Semispinalis capitis muscle Splenius capitis muscle Splenius cervicis muscle Trapezius muscle

Levator scapulae muscle Supraspinatus muscle

Deltoid muscle Infraspinatus fascia over muscle

Rhomboid minor muscle (cut) Serratus posterior superior muscle

Teres minor muscle

Rhomboid major muscle (Cut)

Teres major muscle

Serratus anterior muscle

Latissimus dorsi muscle

Serratus posterior inferior muscle

Thoracolumbar fascia

Erector spinae muscle

External oblique muscle

Internal oblique muscle

Superior nuchal line of skull Posterior tubercle of atlas (C1) Semispinalis capitis muscle Longissimus capitis muscle Splenius capitis and splenius cervicis muscles Serratus posterior superior muscle Iliocostalis muscle Erector spinae muscle

Longissimus muscle Spinalis muscle Serratus posterior inferior muscle Tendon of origin of transversus abdominis muscle

Rectus capitis posterior minor muscle Rectus capitis posterior major muscle Obliquus capitis superior muscle Obliquus capitis inferior muscle Longissimus capitis muscle Semispinalis capitis muscle (cut) Spinalis cervicis muscle Spinous process of C7 vertebra Hook Longissimus cervicis muscle Iliocostalis cervicis muscle Iliocostalis thoracis muscle Spinalis thoracis muscle

Internal oblique muscle

Longissimus thoracis muscle

External oblique muscle (cut)

Iliocostalis lumborum muscle

Iliac crest Spinous process of T12 vertebra Thoracolumbar fascia (posterior layer) (cut)

Transversus abdominis muscle and tendon of origin

D.-J. Yun and S.-H. Jeon

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a

Superior view Spinous process Vertebral canal

Laminae Costal facet

Transverse process 6th Rib

Costotransverse joint

Pedicle

Superior articular facet T6

Costovertebral joint

Superior costal facet Body

b

Lateral view Superior articular process

Superior articular facet Transverse process T6

Costal facet Intervertebral foramen

Superior costal demifacet

Intervertebral disc

Apophyseal joint T7

Spinous process Pedicle Inferior articular process Inferior costal demifacet

Fig. 3  Typical thoracic vertebra. (a) Superior view. (b) Lateral view

The lamina of the thoracic spine is broad, sloping, and overlapping, similar to shingles on a roof. The transverse process of the thoracic spine is relatively long and protrudes posterolaterally from the pedicle and lamina junctions. Except for T11 and T12, the transverse process has a small oval-shaped facet near the tip of the process that articulates with the rib tubercle. This is known as the costotransverse articulation (Fig. 5). The spinous process of the thoracic spine protrudes in

the postero-inferior direction and, in most patients, can be palpitated. The intervertebral foramen of the thoracic spine faces in the lateral orientation. From T1 to T10, the intervertebral foramen is characterized by the head of the closest rib, the articulation between the rib head and the demifacets of the vertebral bodies, ligamentous and capsular attachments with the vertebral bodies, and the interposed intervertebral disc (Fig.  5). The 11th

Anatomical Considerations of the Thoracic Spine

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Mamillary process

Body

Superior articular process and facet Transverse process

Transverse process Spinous process

Body

a

Superior articular process and facet

b

Inferior articular process and facet

Costal facet

T 12 vertebra: lateral view Fig. 4  Atypical thoracic vertebra—T12 vertebral body. (a) Superior view. (b) Lateral view

Fig. 5 Costocorporeal and costotransverse articulation, and ligamentous attachments: (a) Superior view. (b) Superolateral view

Thoracic vertebrae, transverse sectionc superior view

a

Superior articular facet on head of rib

Intraarticular ligament

Radiate ligament of head of rib

Synovial cavities

Superior costotransverse ligament (cut)

Lateral costotransverse ligament

Costotransverse ligament

Posterior longitudinal ligament

b Costotransverse ligament Superior costotransverse ligament

6th

T6

rib

7th

rib

T7

Transverse process Costal facet of the costotransverse joint Superior costotransverse ligament (cut)

T8

Anterior longitudinal ligament Radiate and capsula ligaments of the costocorporeal joint Pair of costal demifacets of the costocorporeal joint

D.-J. Yun and S.-H. Jeon

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and 12th ribs do not play a role in the structure of the T11 and T12 intervertebral foramen. The spinal nerves in the intervertebral foramen account for approximately 50% of the cervical spine, approximately one-third of the lumbar spine, and one-third of the thoracic spine [4].

Thoracic Cage and Ribs

seventh ribs intersect with the sternum and are classified as true ribs. The eighth to tenth ribs are linked through the costal cartilage and classified as false ribs. The 11th and 12th ribs are not associated with the sternum or costal cartilage, but only with corresponding vertebral bodies and are classified as “floating ribs” (Fig. 6).

Neurovascular Structure

The thoracic cage is formed by the sternum and costal cartilages in the anterior, the ribs in the lateral, and thoracic vertebrae in the posterior space. The thoracic ribs start at T1 and articulate through the vertebral body and costal facet. The first to

There are many neurovascular and visceral structures associated with the thoracic spine and ribs in the posterior mediastinal space. The esophagus, trachea, thoracic aorta, vena cava, intercostal

Sternal notch Clavicular notch

Costal notch

1

Sternal angle Manubrium

2 True ribs (1-7)

Body

3

Sternum 4 5 Xiphoid process

6

Costal notch

7 8 False ribs (8-12)

T12 12

9

L1

10 11 Floating ribs (11-12)

Fig. 6  Thoracic cage. Anterior view

Costal cartilages

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artery, vein, nerve, azygos vein, thoracic sympathetic trunk, splanchnic nerve, and thoracic duct are located in the posterior mediastinal space associated with thoracic spine and ribs (Fig. 7).

Fig. 7 Neurovascular and visceral structures associated with thoracic spine. (a) Anterior oblique view. (b) Superior view, mid-thoracic level

a

Between T4 and T7, the aorta is adjacent to the left lateral surface of the thoracic vertebral body. The thoracic aorta moves downward to a more anterior position, and, at the diaphragm

Right Anterior Oblique View

Left common carotid artery

Brachial plexus Anterior scalene

Left subclavian artery

Sympathetic ganglion

Brachiocephalic trunk Trachea

Rami communicantes

Esophagus (cut end)

Vein Posterior Artery intercostal Intercostal nerve Azygos vein

Thoracic duct Descending thoracic aorta

Sympathetic trunk (thoracic)

Esophagus (cut end)

Greater splanchnic nerve

Diaphragm Celiac artery

Lesser splanchnic nerve

Superior mesenteric artery

Inferior vena cava

Stomach

Right crus of diaphragm

b

11 10 9 7

3a3b 3

8

4

6 5

1. Endothoracic fascia 2. Subserous fascia 3. Pleura: 3a. Parietal 3b. Visceral 4. Azygos Vein 5. Esophagus

6. Descending aorta 7. Sympathetic chain 8. Interpleural space 9. Extrapleural compartment 10. Intercostal nerve 11. Posterior primary rami

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level, it is in the prevertebral position. Segmental arteries branching from the posterior surface of the thoracic aorta run horizontally along the thoracic vertebral body. Segmental arteries are bifurcated from the intervertebral foramen to the radiculomedullary and intercostal branches. The artery of Adamkiewicz, an important medullary artery, is primarily located on the left side and is mostly branched between T9 and T11 [10]. The azygos vein rises adjacent to the thoracic spine and drains toward the superior vena cava. The hemiazygos vein rises upward, adjacent to the left lower thoracic spine. The azygos vein drains most of the posterior intercostal veins on the right side of the body. The hemiazygos vein and accessory hemiazygos vein drain most of the posterior intercostal veins on the left side of the body. The chain of paravertebral sympathetic ganglia is located on the right side of the thorax. It descends to the diaphragm, forming the sympathetic trunk and greater splanchnic nerve at the T5 to T9 vertebral level.

Fig. 8 Neurovascular structure related to thoracic vertebrae and ribs

The thoracic duct originates in the abdomen. It rises across the diaphragm and is located between the descending thoracic aorta and the azygos vein in the posterior mediastinal space. Thoracic nerves formed by the combined dorsal and ventral roots consist of 12 pairs. The thoracic spinal nerve has both sensory and motor fibers. Thoracic nerves do not form plexuses but branch into cutaneous branches or send sensory fibers to deeper muscular structures, vessels, periosteum, parietal pleura, peritoneum, and breast tissue. The thoracic nerve sends motor fibers to the thoracic and abdominal walls and serves to transport the preganglionic and postganglionic sympathetic nerve fibers through the sympathetic chain. Thoracic spinal nerves exit the intervertebral foramen and are divided into the dorsal ramus and ventral ramus. The ventral ramus becomes the intercostal nerve and, at the T12 level, becomes the subcostal nerve. The dorsal ramus innervates facet joints (Fig. 8) [4].

Dorsal ramus

Superior costotransverse ligament

Spinal nerve

Ventral ramus Radial ligament Intercostal nerve

Intervertebral disc

White and gray rami communicantes Sympathetic trunk

Posterior intercostal vein Posterior intercostal artery Intervertebral disc

Anatomical Considerations of the Thoracic Spine

References 1. Masharawi Y, Salame K, Mirovsky Y, et al. Vertebral body shape variation in the thoracic and lumbar spine: characterization of its asymmetry and wedging. Clin Anat. 2008;21:46–54. 2. Limthongkul W, Karaikovic EE, Savage JW, et  al. Volumetric analysis of thoracic and lumbar vertebral bodies. Spine J. 2010;10:153–8. 3. Masharawi Y, Salame K, Mirovsky Y, et al. Vertebral body shape variation in the thoracic and lumbar spine: characterization of its asymmetry and wedging. Clin Anat. 2008;21:46–54. 4. Cramer GD, Darby SA.  Clinical anatomy of the spine, spinal cord, and ANS-e-book. Elsevier Health Sciences, 2017.

11 5. Panjabi MM, O’Holleran JD, Crisco JJ 3rd, et  al. Complexity of the thoracic spine pedicle anatomy. Eur Spine J. 1997;6:19–24. 6. Panjabi MM, Takata K, Goel V, et al. Thoracic human vertebrae. Quantitative three-dimensional anatomy. Spine. 1991;16:888–901. 7. McCormack BM, Benzel EC, Adams MS, et  al. Anatomy of the thoracic pedicle. Neurosurgery. 1995;37:303–8. 8. Bak KH OS. Surgical atlas of spine. J Korean Spinal Neurosurg Soc, Koonja 2010:185–190. 9. Kothe R, O’Holleran JD, Liu W, et al. Internal architecture of the thoracic pedicle: an anatomic study. Spine. 1996;21:264–70. 10. Kim DH, Vaccaro AR, Dickman CA, et  al. Surgical anatomy and techniques to the spine e-book: expert consult-online and print. Elsevier Health Sciences, 2013.

Anesthetic Consideration of the Thoracic Spine Surgery Jisang Kim, Gyu Dae Shim, and Junseok Bae

Introduction Thoracic spine surgery varies from a relatively simple procedure like herniated thoracic discectomy to complex surgery like resection of tumor or correction of deformity which accompanies much bleeding. The type of anesthesia for thoracic spine surgery is determined by several factors; approach and length of surgery, patient health, and preference of the patient and surgeon. Regarding the traditional open procedure, thoracic spine surgery by the transthoracic approach requires retraction or collapse of the nondependent lung. The collapse of the nondependent lung is important for visualization of the spine and for minimizing iatrogenic lung injury by various thoracoscopic instruments. During thoracic spinal surgery, several structures are placed at risk for potential injury, including the spinal cord, nerve roots, and all relevant vascular supply to these elements. The use of intraoperative neuromonitoring (IOM) has considerably reduced the rate of neurologic complications after spine surgeries [1–4]. J. Kim · J. Bae (*) Department of Neurosurgery, Wooridul Spine Hospital, Seoul, South Korea e-mail: [email protected]; [email protected] G. D. Shim Department of Anesthesiology, Chungdam Wooridul Spine Hospital, Seoul, South Korea e-mail: [email protected]

In today’s era, when minimally invasive surgery has been incorporated into almost every aspect of managing spine disorders, anesthesiologists must be aware of the various anesthetic techniques for the minimally invasive thoracic spine surgery. Endoscopic procedures present anesthetic considerations that are distinct from traditional open surgeries. Sedation techniques in combination with local anesthesia can not only reduce hospital day, but also improve patient comfort, safety, and satisfaction during surgery. In this chapter, one lung ventilation and IOM for thoracic spine surgery will be discussed, and which are followed by consideration of awakened sedation with local anesthesia.

One Lung Ventilation One lung ventilation (OLV) is essential to perform a thoracoscopy or transthoracic approach. It provides surgical exposure of the thoracic spine by ventilating one lung and letting the other collapse. This is made possible by the use of double lumen tube (DLT), bronchial blocker (BB), or single lumen tube (SLT). Familiarity with the use of these instruments and the physiology of OLV is important for the performance of safe anesthesia. In spite of advantages regarding surgical exposure, OLV is associated with serious respiratory impairment. During OLV, the mismatch of

© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2021 S.-H. Lee et al. (eds.), Minimally Invasive Thoracic Spine Surgery, https://doi.org/10.1007/978-981-15-6615-8_2

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14 Table 1  Contraindications for one lung ventilation Poor candidate for OLV Known or suspected difficult airway Hemodynamic instability Severe hypoxia Cardiac pathology (moderate mitral stenosis, mitral regurgitation) Shortness of breath at rest Moderate-to-severe pulmonary hypertension Cor pulmonale

the occlusion of either of the main bronchi. It has a guidewire in its lumen, the end of which can be hooked over a bronchoscope so the blocker can be inserted under direct vision into the lung that is to be collapsed. It has an inflatable low pressure, high volume cuff at the end of the tube. And a small channel within the blocker may be used to apply suction to the lung and intermittently insufflate oxygen. • Single lumen tubes.

perfusion leads to an increase in shunt and dead space. Hypoxemia is an inevitable adverse consequence of OLV.  Patients who are less likely to tolerate these physiologic changes should not be considered to perform OLV (Table  1). In this respect, patients should be evaluated comprehensively for their primary disease before performing the surgical procedure. Three different methods can be used to achieve OLV: DLTs, BBs, and SLTs advanced into either the right or left main bronchus.

SLTs or endobronchial tubes are advanced into the main bronchus of the dependent lung to selectively ventilate it while permitting the slow collapse of the contralateral lung. This method is hardly used in adult patients in rare cases of emergency surgery or extremely difficult airways. After placing properly one of the tubes described above, OLV is accomplished by ventilating only the dependent lung and exposing the contralateral lung to atmospheric pressure, allowing it to collapse naturally. In general, com• Double lumen tubes. plete deflation of the nondependent lung takes about 15 min. DLTs are tubes with two independent lumens Several physiologic changes occur after initithat can be ventilated independently of each ating OLV. In the lateral decubitus position, the other. The tracheal lumen is designed to termi- blood flow will be the greatest in the dependent nate above the carina, while the bronchial lumen lung due to the effect of gravity, whereas the nonis angled to fit into the appropriate main bron- dependent lung will have higher compliance and chus. The lumens have different openings be easier to ventilate. This compliance will depending on which sided tube is used. A left-­ increase further on the opening of the thoracic sided tube has the endobronchial part down the cavity. When the nondependent lung is deflated, left main bronchus; a right-sided tube down the an intrapulmonary shunt occurs because the venright main bronchus. A left-sided one is com- tilation to one of the lungs is blocked while the monly used irrespective of which side requires perfusion still exists in the nonventilated lung. At the isolation because it is easier to position. first, this is compensated by hypoxic pulmonary Problems with the positioning are the most com- vasoconstriction (HPV), an autoregulatory mechmon cause of ventilatory challenges during anism that increases pulmonary vascular resisOLV. Both auscultation and bronchoscopy should tance in the face of the low partial pressure of be used when a DLT is initially placed and again oxygen in arterial blood (PaO2). This makes after the patient is repositioned (Fig. 1). blood flow redirect from areas of the lung that are not ventilated to those who are well ventilated. • Bronchial blockers. Thus, an excessive drop in PaO2 is prevented. In terms of the anesthetic technique, inhalaA BB is a device that is inserted within an SLT tional agents and direct vasodilators directly and advanced into the left or right main bronchus inhibit HPV. Total intravenous anesthesia (TIVA) to achieve OLV by blocking ventilation distal to with propofol or remifentanil is preferred in OLV

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Fig. 1  A double lumen tube is used to achieve selective, one-sided ventilation of either the right or the left lung

because it presents better oxygenation by less affecting HPV [5]. Interestingly vasoconstrictors such as norepinephrine preferentially constrict the vascular beds in areas of the lung with normal oxygen tensions, which indirectly inhibits HPV.  More recently, dopamine has been shown to have less effect on HPV and the agent of choice if a vasopressor is required. HPV ceases to function, however, when up to 70% of the lung has collapsed due to a lack of normoxic regions in the lung to which blood can be redirected [6]. When full collapse is finally achieved, therefore, significant hypoxia may occur due to both the reduction in pulmonary surface area for gas exchange and the significant V/P mismatch. Hypoxia during OLV is basically due to obligatory shunt through the collapsed lung. With the patient in a lateral decubitus position, further deterioration in PaO2 can occur from impaired ventilation within the dependent lung. Expansion of the dependent lung is restricted by

the weight of the mediastinum, the cephalad displacement of the diaphragm and abdominal organs, decreasing the ventilated lung surface. This leads to diversion of flow to the independent lung, thereby increasing the shunt fraction further. These physiologic alterations emphasize the need to evaluate the cardiopulmonary status of the patient carefully before undertaking a minimally invasive thoracoscopic procedure.

Intraoperative Neuromonitoring There are specific risks to the spinal cord and nerve roots during thoracic spine surgeries. The injuries of neural structure can be made by direct mechanical disruption from surgical maneuvers, thermal injury from coagulation, pressure injury from patient positioning, and ischemia due to local or global hypoperfusion. The role of intraoperative neuromonitoring (IOM) during spine

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surgery is to evaluate the integrity of the spinal cord and nerve roots continuously while patients undergo procedures before the development of irreversible neural injury. Understanding the physiologic effects of various anesthetic agents is important to interpret the changes in IOM noted during spine surgery. The most commonly used IOM modalities include somatosensory evoked potential (SSEP), motor evoked potential (MEP), and electromyography (EMG). Each modality assesses a functionally separate area of the spinal cord, which test is chosen depends on the location of the surgery and the patient’s preexisting injuries and deficits. SSEP, one of the most commonly used modalities, monitors the integrity of sensory pathways from peripheral nerves to the sensory cortex via the dorsal columns. Disruption along any part of this pathway may show abnormal SSEP responses. MEP starts with transcranial motor cortex stimulation and elicits a response from muscles, and thereby assesses the integrity of motor pathways. Changes in MEPs are more sensitive in the detection of postoperative motor deficits [7]. The EMG has two types by the method of elicitation; spontaneous and triggered. Spontaneous EMG records free-running electrical activities from muscles and provides information on the state of the peripheral nerves that innervate that muscle. Triggered EMG, frequently used to determine proper placement of pedicle screw, records direct, intentional stimulation of nerve roots. IOM needs special considerations to choose the anesthetic regimen because the nervous system is suppressed by anesthetics, hypothermia, hypotension, and anemia. False-negative results could lead to unnoticed damage to neural elements and irreversible consequences. False-­ positive results could also produce unnecessary manipulation with its own risk. Most anesthetic agents alter neural function by producing dose-dependent depression at the neurosynaptic and axonal pathways. Although both inhalational and intravenous anesthetics decrease waveform amplitude and increase signal latency, inhalational agents have more effects on the evoked potentials than intravenous agents [8]. Inhalational anesthetic agents act through specific

and nonspecific receptors, and the efficacy of the agent depends on its ability to interact with the cell membrane. The choice and dose of these agents should be adjusted to the modalities. The best regimen for IOM is controversial, but TIVA has proved to be more dependable for signal attainment with patients undergoing IOM [9, 10]. In general, longer pathways with more synapses are more sensitive. MEPs are in general more sensitive to anesthetics than SSEPs. SSEPs appear to have an intermediate dose- or concentration-­dependent sensitivity to anesthetic agents [8]. Inhalational anesthetic agents have dose-dependent effects on SSEPs, leading to an increase in signal latency and a decrease in amplitude. Cortical depression is more markedly noted than subcortical or peripheral responses. The anesthetic technique for SSEP usually involves 0.5–1.0 minimum alveolar concentration of inhalational agents and a narcotic infusion for longer cases. Nitrous oxide, when used alone or in combination with inhalational agents or opioids, increases the latency and reduces SSEP signal amplitude. All intravenous agents including barbiturates, benzodiazepines, propofol, or ketamine have minimal effect and are preferred, with studies reporting a mild increase in latency and decreases in signal amplitude [8, 11]. Standard dose neuromuscular blockers can be used in SSEP. MEPs are generally more sensitive to anesthetic agents than SSEPs. Inhalational agents cause greater depression of MEPs compared with intravenous agents. Inhalational agents should usually be kept to a minimum or not used in MEP. MEP and EMG monitoring are disturbed by muscle relaxants, which inhibit electrical activities across the neuromuscular junctions, affecting the recording of signals as muscle contraction can no longer be produced upon neural stimulation.

Postoperative Continuous Intercostal Nerve Block Thoracotomy-related pain is associated with the pace of recovery as well as a high incidence of pulmonary complications. Postoperative pain relief after spine surgery can be achieved with various

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modalities including continuous infusion of intravenous morphine supplemented with patient-controlled analgesia (PCA). The advantages of PCA are fewer technical problems, and uniform and sustained analgesia with autonomy. But PCA involves disadvantages such as side effects like nausea and vomiting, overdose, or addiction. Continuous infusion of local anesthetics to thoracotomy site for postoperative pain relief has been described as an effective and safe method. At the end of thoracoscopic or transthoracic surgery, a catheter with side holes is advanced into the extrapleural space. The catheter is connected to a pump that automatically and continuously delivers local anesthetics (bupivacaine) to the intercostal nerve. This method results in lower postoperative pain and a decrease of complications such as cardiorespiratory depression by intravenous or epidural analgesia [12, 13].

be prepared to intervene to rescue a patient’s airway from a sedation-induced compromise and convert to general anesthesia. MAC allows for the safe administration of a maximal depth of sedation over that provided during awakened sedation [15]. Comprehensive preoperative patient evaluation is important for a patient undergoing MAC during the minimally invasive endoscopic procedure. Before surgery, the anesthesiologist should review previous medical records of the patient for underlying medical problems; sedation, anesthesia, and surgery history; the history of or sensitivity to anesthesia or sedation; current medications; extremes of age; psychotropic drug use; use of nonpharmaceutical; and family history. Preprocedural laboratory testing is also needed. A preoperative visit should be made by the anesthesiologist responsible for the procedure. The anesthesiologist must evaluate whether the patient is suitable for MAC.  And the patient should receive information relating to the benefits and risks of sedatives and analgesics, preprocedural instruction, and medication usage. Intraoperative monitoring during MAC should be the same as that for general anesthesia. Patients given sedatives or analgesics in unmonitored settings may be at increased risk of complications. It is necessary to monitor ventilation and oxygenation by observation of qualitative clinical signs, capnography, and pulse oximetry as well as hemodynamic measurements including blood pressure, heart rate, and electrocardiography. The patient’s level of consciousness should be assessed by the response of patients, including spoken responses to commands or other forms of bidirectional communication during procedures. After connected to the monitoring equipment, the patient is given 0.5 mg of midazolam intravenously at the start of anesthesia, and continuous infusion of remifentanil is started at the rate of 0.1 μg/kg/min (Fig. 2). Another bolus of 0.5 mg of midazolam is administered just before the incision. Regarding the sedative agent, midazolam is favored than propofol which may reduce blood pressure during the procedure. Midazolam has a greater amnesic effect than propofol and can be reversed by flumazenil in case

Awakened Sedation The endoscopic procedure is a minimally invasive technique that requires a small skin incision and performed under local anesthesia with or without sedation. Awakened sedation allows a patient to undergo painful procedures with less anxiety by inducing decreased levels of consciousness but not requiring intubation as the patient ventilates spontaneously. A combination of a sedative and an opioid analgesic is most commonly used for this purpose. The American Society of Anesthesiologists has defined monitored anesthesia care (MAC) as a specific anesthesia service performed by a qualified anesthesia provider, for a diagnostic or therapeutic procedure [14]. MAC is a distinguishable way of sedation from awakened sedation. During the awakened sedation, the surgeon supervises or personally administers the sedative and/or analgesic medications that can alleviate patient anxiety and limit pain during a diagnostic or therapeutic procedure. In MAC, by contrast, the qualified anesthesiologist is focused exclusively and continuously on the patient for any attendant airway, hemodynamic and physiologic derangements. Further, an anesthesiologist of MAC must

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Fig. 2  An infusion pump is used to deliver remifentanil continuously in awakened sedation

of unintended deep sedation. Supplemental oxygen is administered with a nasal cannula at 5 L/ min. During the procedure, the infusion of remifentanil should be stopped immediately if a decrease in oxygen saturation is noted. After awakened sedation, the patients should be observed and monitored in an appropriately staffed and equipped area until they recover to their baseline level of consciousness and are no longer at increased risk for cardiorespiratory depression. Continuous monitoring of oxygenation is recommended as well until the patients are no longer at risk for hypoxemia. Ventilation and circulation should be checked every 5–15 min until the patients are suitable for discharge. Discharge of the patients should be authorized by the anesthesiologist and surgeon.

References 1. Accadbled F, Henry P, de Gauzy JS, Cahuzac JP. Spinal cord monitoring in scoliosis surgery using an epidural electrode. Results of a prospective, consecutive series of 191 cases. Spine 2006;31(22):2614– 23. Epub 2006/10/19. 2. Fehlings MG, Brodke DS, Norvell DC, Dettori JR.  The evidence for intraoperative neurophysiological monitoring in spine surgery: does it make a difference? Spine 2010;35(9 Suppl):S37–46. Epub 2010/05/07. 3. Kelleher MO, Tan G, Sarjeant R, Fehlings MG.  Predictive value of intraoperative neurophysiological monitoring during cervical spine surgery: a prospective analysis of 1055 consecutive patients. J Neurosurg Spine 2008;8(3):215–21. Epub 2008/03/04. 4. Kundnani VK, Zhu L, Tak H, Wong H.  Multimodal intraoperative neuromonitoring in corrective surgery

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for adolescent idiopathic scoliosis: Evaluation of 354 consecutive cases. Ind J Orthopaed 2010;44(1):64– 72. Epub 2010/02/19. 5. Pilotti L, Torresini G, Crisci R, De Sanctis A, De Sanctis C. Total intravenous anesthesia in thoracotomy with one-lung ventilation. Minerva Anestesiologica. 1999;65(7–8):483–9. Epub 1999/09/10. Anestesia totalmente endovenosa nella toracotomia con ventilazione monopolmonare. 6. Marshall BE, Marshall C.  Continuity of response to hypoxic pulmonary vasoconstriction. J Appl Physiol Respir Environ Exerc Physiol 1980;49(2):189–96. Epub 1980/08/01. 7. Hsu B, Cree AK, Lagopoulos J, Cummine JL. Transcranial motor-evoked potentials combined with response recording through compound muscle action potential as the sole modality of spinal cord monitoring in spinal deformity surgery. Spine 2008;33(10):1100–6. Epub 2008/05/02. 8. Sloan TB, Heyer EJ.  Anesthesia for intraoperative neurophysiologic monitoring of the spinal cord. J Clin Neurophysiol 2002;19(5):430–43. Epub 2002/12/13. 9. Pechstein U, Nadstawek J, Zentner J, Schramm J. Isoflurane plus nitrous oxide versus propofol for recording of motor evoked potentials after high frequency repetitive electrical stimulation. Electroencephalogr Clin Neurophysiol 1998;108(2): 175–81. Epub 1998/05/05. 10. Pelosi L, Stevenson M, Hobbs GJ, Jardine A, Webb JK.  Intraoperative motor evoked potentials to tran-

scranial electrical stimulation during two anaesthetic regimens. Clin Neurophysiol 2001;112(6):1076–87. Epub 2001/05/30. 11. Glover CD, Carling NP.  Neuromonitoring for scoliosis surgery. Anesthesiol Clin 2014;32(1):101–14. Epub 2014/02/05. 12. Hsieh MJ, Wang KC, Liu HP, Gonzalez-Rivas D, Wu CY, Liu YH, et  al. Management of acute postoperative pain with continuous intercostal nerve block after single port video-assisted thoracoscopic anatomic resection. J Thorac Dis 2016;8(12):3563–71. Epub 2017/02/06. 13. Sabanathan S, Smith PJ, Pradhan GN, Hashimi H, Eng JB, Mearns AJ.  Continuous intercostal nerve block for pain relief after thoracotomy. Ann Thorac Surg 1988;46(4):425–6. Epub 1988/10/01. 14. Anesthesiologists ASo. Position on Monitored Anesthesia Care. 2018; Available from https://www. asahq.org/-/media/sites/asahq/files/public/resources/ standards-guidelines/position-on-monitored-anesthesia-care.pdf 15. Anesthesiologists ASo. Distinguishing Monitored Anesthesia Care ("MAC") From Moderate Sedation/ Analgesia (Conscious Sedation). 2018. Available from http://asahq.org/~/media/Sites/ASAHQ/Files/ Public/Resources/standards-guidelines/distinguishing-monitored-anesthesia-care-from-moderate-sedation-analgesia.pdf

Radiologic Evaluation of Thoracic Spinal Disease Wei Chiang Liu

Introduction Spinal disorders constitute one of the most common causes of disability in developed counties. A revolution in the diagnosis and management of spinal disorder, powerful imaging method can be applied in delineate the complicities of pathologic conditions in the spine. The vast majority of spine imaging studies will exclude systemic disease as a cause of back or limb pain and exact targeting of pathologic tissue to minimize normal tissue damage. Physicians should be very careful when relating imaging findings to symptoms because many of the same findings are frequently observed in the asymptomatic patients. Correct interpretation of images is important to determine surgical method and patient prognosis. This chapter reviews the basic imaging technique and specific disease entities of thoracic spine.

Imaging Techniques Plain Radiography Routine radiography is universally available and relatively inexpensive, but they are limited by an W. C. Liu (*) Department of Radiology, Wooridul Spine Hospital, Gangnam-gu, Seoul, South Korea e-mail: [email protected]

inability to allow direct visualization of neural structures and neural compression. In general, simple radiography usually checks the bony structure. On the AP view, the vertebral body appears rectangular, and both sides the pedicle overlaps the vertebrae and is observed symmetrically in a circle. Superior articular process, inferior articular process and lamina are observed on AP view, and outward from the vertebrae shows transverse process. On the lateral view, the pedicle is observed in the back of the upper part of vertebrae and spinous process is observed at the rear. Unlike the cervical spine, the foramen of thoracic spine observed in the inferior aspect of pedicle. Postoperative radiography is essential for tracking and evaluating the location of instruments, and it can be said to be the starting point for all postoperative assessments. Change in the location of a device or failure of a device can usually be found in continuous simple radiography. The goal of spinal fusion is to produce a solid arthrodesis to correction or prevent spinal instability. It usually takes 6–9 months for a routine radiograph to document solid spinal fusion and 3 years to confirm complete remodeling at the fusion site [1].

Computed Tomography CT scanning permits direct visualization of anatomy of bony structures, and provides better

© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2021 S.-H. Lee et al. (eds.), Minimally Invasive Thoracic Spine Surgery, https://doi.org/10.1007/978-981-15-6615-8_3

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v­ isualization of lateral pathologic entities, such as foraminal stenosis. CT can also evaluate the location of instrument, the alignment of vertebra, and complications such as pseudoarthrosis. Disadvantages of CT scanning include sunburst artifact or the effects streak artifacts cause by metal instrument. But using soft tissue algorithm, multiplanar reformatted image, and 3D volume rendering image to minimization of reduction image quality of metal artifact. CT-myelography allows accurate evaluate the degree of central spinal stenosis can in patients who cannot be performed MR image. CT myelography also evaluates CSF leak or pseudomeningocele combined with nerve root injury.

Magnetic Resonance Imaging MRI provides the most anatomic information in vertebral body. These images provide not only bony tissue but also soft tissue in detail. On MR image, the vertebrae show different signals depending on the composition of the bone marrow. Red marrow shows intermediate signal intensity on T1- and T2-weighted image. Fat marrow shows high signal intensity on T1- and T2-weighted images. Normal nucleous pulposus of intervertebral disc shows low signal intensity on T1-weighted image and high signal intensity on T2-weighed image due to sufficient water contents. Degenerated intervertebral disc shows low signal intensity on T2-weighted image due to decreased water content. Annulus of intervertebral disc shows low signal intensity on T1- and T2-weighed image. Axial MR image well delineated central spinal canal. CSF shows low signal intensity on T1-weighed image and high signal intensity on T2-weighed image. Extradural fat tissue shows high signal intensity on both T1and T2-weighted image. Ligamentum flavum and supraspinous ligament show low signal intensity on T1- and T2-weighted images. Interspinous ligament shows variation signal intensity according to fat tissue dystrophic change. MR image is the best way to evaluated central canal of vertebral spine, especially postoperative infection, fluid collection, recurrent interverte-

bral disc herniation, and tumor recurrence. On T2-weighted sagittal image, the three anatomic areas of the central canal, spinal cord, and intervertebral disc should be reviewed carefully. On T1-weighted sagittal image, bone marrow signal abnormality should be carefully reviewed with reference to the signal of the intervertebral disc. Any focal or diffuse low signal intensity of the bone marrow on T1-weighted image could suggest bony pathology. On T2-weighted axial image, the relationship of the posterior margin of the intervertebral disc with the dural sac and nerve root should be carefully defined to identify a herniated disc. On the T1-weighed axial image, the course of the descending nerve root from the dural sac to the neural foramina should be traced, to identify nerve root anomalies such as conjoined nerve root.

Thoracic Disc Herniation Thoracic disc herniation is certainly rare in comparison with either cervical or lumbar disc herniation. The incidence of thoracic disc herniation estimated to be from 1 to 2% of all disc herniation [2, 3]. The thoracic spine had different anatomical features, unlike the lumbar and cervical spine; the thoracic spine also shares articular surfaces with the ribs at each level, which are offer movement with minimal resistance. The attachment of the ribs to the sternum and their articulation with the vertebral body both serve to limit rotation and lateral bending of the thoracic spine [4, 5]. Both the facet and costovertebral joints do add some stability to the entire spinal region as well. The costovertebral joints, however, also limit the overall flexion of the spinal at the thoracic level [6]. Some authors have postulated that a decrease in flexion would be expected to result in an overall decrease in disc disease at the thoracic level. The majority of symptomatic thoracic disc herniation occurs in the mid-thoracic and lower thoracic spine. In the surgical series of Levi et al. reported T6 and T7 were the most common levels of operation [2]. In the large series of Stillerman et  al. reported the T8 through T11 commonly

Radiologic Evaluation of Thoracic Spinal Disease

required intervention [7]. Because lower thoracic level had significantly more advanced disc degeneration and more translational motion than the upper thoracic level [8]. The thoracic herniation has been noted to be central or centrolateral, with a minority of herniation is truly laterally. Many herniated thoracic discs are shown to be calcified at presentation. Despite studies in which calcification is reported to occur in 30–70% of cases of thoracic disc herniation. Calcification is an important consideration, however, because approximately 5–10% of the calcified disc are associated with intradural extension [8, 9]. There is a tendency for a thoracic disc herniation to be multiple in nature and that they are commonly identified in patients in whom herniated disc are present at either the cervical or lumbar levels as well. Thoracic disc herniation at the level of the conus or high cauda equina can mimic lumbar radicular disease [10]. On T1-weighted MR image, herniated disc is seen as intermediate signal intensity and in contiguity with the parent disc, posterior osteophyte shows as low signal intensity similar to the vertebral cortex, while thickened posterior longitudinal ligaments also show low signal intensity on T1-weighted image (Fig. 1).

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fuse idiopathic skeletal hyperostosis (DISH), and Paget disease [14].

Compressive Myelopathy

Extrinsic compression of the spinal cord is the most common cause of myelopathy. Degenerative spondylosis is the most common cause and may be caused by a combination of disc protrusions, osteophyte, ligamentum flavum infolding, and ossification of the posterior longitudinal ligament [15]. On MR imaging, the compressed spinal cord can show normal signal, elevated T2 signal, or in the most severe cases, evidence of cavitation with T1 hypointensity accompanying the T2 hyperintensity. The presence of T1 hypointensity usually indicates more severe clinical deficits and worse postoperative prognosis. The presence of T2 hyperintensity may indicate reversible edema and/or permanent gliosis. Other imaging changes in the spinal cord can be associated with chronic compression. These include myelomalacia; a term referring to permanent spinal cord damage with volume loss, although assessing the caliber of a compressed segment of the spinal cord is not typically possible until after the cord is decompressed. Ischemia due to vascular comSpinal Stenosis pression may cause central gray matter T2 hyperintensity (Fig.  2). Syringohydromyelia may The thoracic spinal cord is approximately 6.5-­ occur in the spinal cord either above or below the mm deep and 8.0-mm wide, whereas the tho- level of compression due to altered cerebrospinal racic spinal canal is approximately 16.8-mm fluid flow dynamics. After decompression, condeep and 17.2-mm wide [6]. Thoracic spinal trast enhancement can be seen in the spinal cord stenosis refers as a group of clinical syndrome on T1 postcontrast image for weeks to month caused by the compression of the thoracic spi- [15, 16]. nal cord that as a result of one or several pathological factors such as degenerative ligamentous hypertrophy and even ossification, disc hernia- Ossification of the Posterior tion, formation of osteophyte at the posterior Longitudinal Ligament edges of vertebrae and developmental spinal stenosis [11, 12]. Thoracic spinal stenosis may Ossification of the posterior longitudinal ligabe defined as narrowing of AP diameter of tho- ment (OPLL) is a hyperostotic condition that racic spinal canal to  40%). The anterior wedge deformity and the central, biconcave deformity can be seen with osteoporotic fractures. However, a posterior wedge deformity or crush fracture raises concern for a neoplastic etiology. Acute fractures may show increased density along the compressed endplate, whereas subacute fractures may show callus formation in addition to increased endplate density. Chronic fractures deformity either from remote trauma or from osteoporotic fracture may show remodeling of marginal osteophyte [61]. MR imaging can be useful in evaluating age indeterminate, occult, and pathologic vertebral fractures. The presence and degree of bone marrow edema suggestive the acuity and severity of the fracture. The bone marrow edema pattern is a typical band like, paralleling the fracture endplate, with some preservation of marrow fat. On MR image, bone marrow in the fractured vertebral body shows low signal intensity on T1-weighted image, high signal intensity on fat-­ suppressed T2-weighed image and contrasted

enhanced T1-weighted image. The presence of a linear low signal intensity line within zone of bone marrow edema can add confidence in the assessment of a fracture (Fig. 6). Absence of bone marrow edema with fatty marrow replacement strongly suggests an old healed compression fractures. Malignant fracture also a cause of compression fracture without an episode of trauma. It should be considered when there is complete bone marrow replacement manifested as T1 hypointensity, involvement of the diffusely entire vertebral body, posterior elements, osseous destruction, surrounding soft tissue component, presence of additional lesions, and involvement of the upper cervical spine (Fig.  7). One finding that seldom occurs with metastasis vertebral compression fractures, and strongly suggests a benign compression, is the fluid sign [40, 62]. The fluid sign can be seen in 40% of osteoporotic vertebral compression fractures with bone marrow edema. If routine MR cannot exclude a malignant fracture, advanced MR such as diffusion-­weighted image can be performed [63–65].

Thoracolumbar Spine Injury The thoracolumbar junction is one of the most commonly injured areas of the spine. This region is particularly vulnerable because of the curvature of the spine from a kyphotic thoracic spinal curvature to lordotic lumbar spinal curvature [66, 67]. And in lumbar spine, there are no ribs to provide additional stability as in the thoracic region. Denis described four basic types of thoracolumbar fracture: (1) compression fracture, (2) burst fracture, (3) Chance fracture, and (4) fracture dislocation [68]. In the same year, McAfee et al. described the similar classification of thoracolumbar injuries base on CT image including wedge compression fracture, stable burst fracture, stable burst fracture, unstable burst fracture, seat belt-type injury, flexion distraction injury, and translation injury [69]. The major difference between the two classification is that McAfee considered some burst fractures stable if they did not have involvement of posterior column, whereas Denis considered all busrt fractures unstable.

Radiologic Evaluation of Thoracic Spinal Disease

a

b

Fig. 6  A 63-year-old male had osteoporotic compression fracture at T12 level. On T1-weighted sagittal image (a) shows preservation of normal fatty marrow on the fracture segment. Bone marrow edema shows mild hypointense signal on T1-weighted image (a), mild hyperintense sig-

a

b

Fig. 7  A 43-year-old male had a malignant fracture due to metastasis. A pathologic fracture typically shows no preservation of normal marrow, marked hypointense signal on T1-weighted image (a). Posterior wall shows con-

31

c

nal on T2-weighted image (b), and high signal intensity on T2-fat saturated image (c). Band-like low signal area suggestive of fracture line that suggests to benign fracture (arrow)

c

vex bulging without fracture line on T1- and T2-weighted image (b). In contrast-enhanced T1 fat-saturated image shows diffuse intense enhancement as well as associated posterior element and distant mass (c) (arrow)

W. C. Liu

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Anterior wedge compression fracture account for 50% of all thoracolumbar fracture [70]. The classic image finding is wedge-shaped vertebral body compression the anterior cortex and sparing posterior columns. The mechanism of injury is an axial loading with or without a flexion component. This fracture occurs in young patients with major trauma or osteoporotic patients with an insufficiency fracture. Lateral compression fracture is characterized by lateral wedge deformity of vertebral body. This fracture occurs most commonly at the thoracolumbar junction followed by the mid-thoracic restriction at T6–T7. The main risk factor is osteoporosis, with many patients complaining of severe and prolonged pain [71]. This fracture usually stable but if have severe compression, the fractures have more than 40% vertebral body compression and more than 30% of angulations; these fractures tend to involve the middle and posterior columns combined with posterior ligament complex injury, they are usually unstable and may require stabilization [68, 72, 73].

a

b

Fig. 8  Bursting Fracture. A 34-year-old male had L1 burst fracture due to fall down. On T1- and T2-weighted sagittal image show loss of height of anterior and posterior vertebral body, retropulsion of fractured segment, and

Burst fracture is typically produced by pure axial loading mechanism, and comminuted fracture of the vertebral body extending through both the superior and the inferior vertebral end plates. The imaging feature of bursting fracture in retropulsion of posterior margin of vertebral into spinal canal or posterior bowing of the posterior vertebral margin. In stable burst fractures, the anterior and middle columns fail, but the posterior elements are intact. An unstable burst fracture is one in which there is also disruption of the posterior column. But clinically, the fracture had more than 50% vertebral body compression, more than 40% of central canal compromise due to retropulsed segment, and more than 25% of kyphotic angle is considered unstable fracture. And regardless of these image findings, if there is any neurologic deficit burst fracture considered as an unstable fracture. Xu et al. described, patients with wider interpedicular distance and larger encroachment of retropulsed fragment in the bony spinal canal were more likely to have dura tear in burst fracture with vertebral laminar fractures [74, 75] (Figs. 8 and 9).

c

epidural hematoma (a, b). On T2-fat saturated image, there is extensive marrow edema without PCL injury (c). On CT image, threes shown comminuted fracture with central canal compromise (d, e)

Radiologic Evaluation of Thoracic Spinal Disease

d

e

Fig. 3.8 (continued)

33

Chance fracture also called seat-belt injury, flexion distraction injury is commonly associated with the use of a lap seat belt in a high-speed motor vehicle accident and caused by compression of the anterior column with distraction of the middle and posterior column. A classic Chance fracture is a horizontal fracture through the spinous process, the lamina, the pedicle, the intervertebral disc space, and posterior longitudinal, supraspinous and intraspinal ligaments. The anterior longitudinal ligament is generally intact. It is an acutely unstable injury and associated with a high rate of abdominal viscera injury [76]. The neurologic deficit is infrequently. A seat belt injury is diagnosed if there is widening of the interspinous distance representing posterior ligamentous complex injury along with horizontal fracture of the pedicle and articular process. MR image was useful diagnosis of PLC injury. The accurate diagnosis of a flexion-distraction injury is important because it can be a cause of delayed neurologic deficits due to progressive kyphosis [77–79] (Fig. 10). Fracture dislocations are the result of complex forces of flexion, rotation, and shearing with failure of all three columns leading to subluxation or dislocation and subsequent extreme instability. There are three subtypes of this injury: flexion-­ rotation, shear, and flexion-distraction. With severe hyperflexion injuries, dislocation occurs anteriorly. With flexion rotation injuries dislocation of the facet joints may occur, with traumatic spondylolisthesis [70]. With severe ­hyperextension injuries, usually from a blow to the back, there is classically posterior element impaction with fracture of the spinous process, lamina, or facet. Instability results from anterior longitudinal ligament injuries, with widening of anterior intervertebral disc space and retrolisthesis [61]. These injuries differ from other thoracolumbar injuries by a higher incidence of neurologic deficit due to spinal cord injury [80– 82]. CT is optimal modality for evaluating the displacement of vertebral body, spinal canal, and facet involvement. Axial CT shows a double rim sign due to vertebral body overlap. MR image

W. C. Liu

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a

b

c

Fig. 9  A 27-year-old female had a bursting fracture due to a fall. T2- and T1-weighed sagittal images show bursting fracture (a, b). On T2-fat saturated sagittal image (c), there shows PLC injury (arrow)

provides information about spinal cord injury, hematoma, the nature, and extent of canal compromise.

Intradural Extramedullary Tumor Lesion in this compartment includes schwannoma, Meningioma, neurofibroma, malignant nerve sheath tumor, hemangiopericytoma, paraganglioma, and metastasis [83]. Schwannoma and meningioma account for 45% of all intraspinal neoplasm. The slow growth of these tumors tends to lead to vague symptoms and signs [84]. Women (between the fourth and fifth decades) account for approximately 80% of patients with spinal meningioma. And most of these lesions are in the thoracic spine [85]. MR image is the modality of choice for defining intradural extramedullary tumor. Typical spinal meningioma is a small, single, discrete, round or oval intradural tumor, although occasionally it may be multiple. Meningioma commonly exhibits microscopic calcification, but gross calcifica-

tion is seldom recognizable on plain radiography. Schwannoma is solitary, well-circumscribed and encapsulated tumor, located eccentrically on peripheral nerves or spinal nerve root. On our series, a tumor located at a thoracic lesion in female and tumor having calcification on CT image and dural tail sign on contrast-enhanced MR proved predictor of meningioma, while tumor with lumbar location, widening of neural foramen, fluid signal intensity on MR T2-weighted image, rim enhancement on contrast MR image proved significant as a predictor of schwannoma [86] (Figs. 11, 12).

Thoracic Arachnoid Cyst Spinal arachnoid cysts are sacs of CSF covered by arachnoid membrane. These cysts can be idiopathic or acquired, usually intradural, but can also rarely be extramural. Secondary arachnoid cysts are usually due to trauma, hemorrhage, inflammation, surgery, or iatrogenic for interventional procedure [87].

Radiologic Evaluation of Thoracic Spinal Disease

a

35

b

c

Fig. 10  Lumbar flexion-distraction injury on CT in a 19-year-old male. The horizontal fracture line extends from the spinous process, through the articular process into the lower posterior corner of the vertebral body (arrow)

Spinal arachnid cyst can be seen in the intradural or extradural location. Intradural arachnoid cyst is usually small, lesion than one or two spine segments, and located in the dorsal aspect of mid-­thoracic level in most cases [88]. The most important finding to suggest intradural arachnoid cyst is a round area with absence of flow artifact inside the dura with cord compression. On CT myelography, there is a filling defect in the arachnoid cyst. Some arachnoid cyst can communicated with subarachnoid space, so in those cases, the diagnosis is diffu-

cult. The most important finding to suggested intradural arachnoid cyst is a round area with abscence of flow artifact inside the dura with cord compression [89] (Fig. 13). Extradural arachnoid cyst is caused by arachnoid herniation through dural defect. Extradural arachnoid cyst commonly located in the thoracolumbar junction. This cyst can become large with adjacent bone erosion and extend to the paraspinal area through neural foramen [90]. CT myelography, the injected contrast is seen in the extradural arachnoid cyst [91] (Fig. 14).

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a

b

c

Fig. 11  A 60-year-old female had thoracic meningioma. On T2-weighted sagittal image show homogeneous hypointense mass at T6 level (a). Post-contrasted

T1-weighed sagittal fat-saturated image shows homogeneous enhancement with dural tail sign (b). On CT axial image, there shows microcalcification on mass lesion (c)

Radiologic Evaluation of Thoracic Spinal Disease

a

37

b

c

Fig. 12  A 37-year-old male had thoracic schwannoma. T2-weighted sagittal image shows a well-defined hyperintense mass at T6–7 level (a). Fat saturated post-contrast T1-weighted image shows diffuse enhancement with

small cystic change within mass (b). A 56-year-old male had schwannoma. On axial contrast-enhanced T1-weighted image shown a dumbbell-shaped mass in the right neural foramen (c)

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a

b

c

d

Fig. 13  A 26-year-old female suffered from upper back pain due to extradural arachnoid cyst. There is a large cystic mass in the posterior epidural space from T11 to L1 level (a). There is no evidence of contrast enhancement on contrast-enhanced MR image (b). Inside the cyst, there is

a patchy low signal (arrow) on T2-weighted axial image, suggestive of CSF flow artifact (c). Because extradural arachnoid cyst is originated from arachnoid herniation through dural defect, there is a CSF flow inside the cyst. There is a bony erosion and extraforaminal extension (d)

Radiologic Evaluation of Thoracic Spinal Disease

a

39

b

c

Fig. 14  A 59-year-old female had intradural arachnoid cyst. There shown an intra-dural cystic mass posterior to the spinal cord at mid-thoracic level (T6–8) (a, b). The

mass compresses the spinal cord. There is a focal absence of CSF flow artifact with cord deformity (c) (arrow) and above lesion shown flow artifact (a) (arrow)

40

Summary We delineated basic imaging finding of thoracic spine combined with radiologic characteristic of thoracic disc herniation, ossification of ligamentum, ossification of posterior longitudinal ­ligament, thoracic spine fracture, and common thoracic benign tumor.

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W. C. Liu 77. Bouliane MJ, Moreau MJ, Mahood J.  Instability resulting from a missed Chance fracture. Can J Surg. 2001 Feb;44(1):61–2. 78. Campbell A, Yen D.  Late neurologic deterioration after nonoperative treatment of a Chance fracture in an adolescent. Can J Surg. 2003 Oct;46(5):383–5. 79. Arkader A, Warner WC Jr, Tolo VT, Sponseller PD, Skaggs DL.  Pediatric Chance fractures: a multicenter perspective. J Pediatr Orthop. 2011 Oct–Nov;31(7):741–4. 80. Gellad FE, Levine AM, Joslyn JN, Edwards CC, Bosse M.  Pure thoracolumbar facet dislocation: clinical features and CT appearance. Radiology. 1986 Nov;161(2):505–8. 81. Denis F.  Spinal instability as defined by the three-­ column spine concept in acute spinal trauma. Clin Orthop Relat Res. 1984 Oct;189:65–76. 82. Manaster BJ, Osborn AG. CT patterns of facet fracture dislocations in the thoracolumbar region. AJR Am J Roentgenol. 1987 Feb;148(2):335–40. 83. Wald JT. Imaging of spine neoplasm. Radiol Clin N Am. 2012 Jul;50(4):749–76. 84. Conti P, Pansini G, Mouchaty H, Capuano C, Conti R.  Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol. 2004 Jan;61(1):34–43; discussion 4. 85. Ledbetter LN, Leever JD.  Imaging of intraspi nal tumors. Radiol Clin N Am. 2019 Mar;57(2): 341–57. 86. Liu WC, Choi G, Lee SH, et  al. Radiological findings of spinal schwannomas and meningiomas: focus on discrimination of two disease entities. Eur Radiol. 2009 Nov;19(11):2707–15. 87. Klekamp J.  A new classification for pathologies of spinal meninges-part 2: primary and secondary intradural arachnoid cysts. Neurosurgery. 2017 Aug;81(2):217–29. 88. Fam MD, Woodroffe RW, Helland L, et  al. Spinal arachnoid cysts in adults: diagnosis and management. A single-center experience. J Neurosurg Spine. 2018 Dec;29(6):711–9. 89. Dietemann JL, Filippi de la Palavesa MM, Kastler B, Warter JM, Buchheit F.  Thoracic intradural arachnoid cyst: possible pitfalls with myelo-CT and MR. Neuroradiology. 1991;33(1):90–1. 90. Morizane K, Fujibayashi S, Otsuki B, et al. Clinical and radiological features of spinal extradural arachnoid cysts: valve-like mechanism involving the nerve root fiber as a possible cause of cyst expansion. J Orthop Sci. 2018 May;23(3):464–9. 91. Kang HS, Lee JW, Kwon JW.  Radiology illustrated spine, 2014, Springer.

Clinical Presentation of the Thoracic Spinal Compression Won Sok Chang and Junseok Bae

Introduction Thoracic disc herniation (TDH) occurs much less frequently than lumbar and cervical disc herniation. Thoracic discs are unique in many respects when compared to the lumbar discs. The thoracic spine is a rigid structure between the mobile cervical and the lumbar regions and its unique stability is the result of the surrounding thoracic ribcage. The thoracic discs are relatively smaller and have well-defined nucleus pulposus and a denser annulus fibrosus [1]. This anatomy makes thoracic disc more stable.

Epidemiology The diagnosis of thoracic disc herniation may be difficult due to the lack of a characteristic clinical presentation. Due to symptomatic obscurity, it is often overlooked in patients suffering from back pain. TDH is generally diagnosed at an average of 15 months after symptom onset. The use of computed tomography (CT) and magnetic resonance imaging (MRI) has resulted in a sigW. S. Chang (*) Department of Anesthesiology, Chungdam Wooridul Spine Hospital, Seoul, South Korea J. Bae Department of Neurosurgery, Wooridul Spine Hospital, Seoul, South Korea e-mail: [email protected]

nificant increase in the detection and diagnosis of this lesion. With improved diagnostic methods of MRI and CT scanning, studies reported the prevalence of thoracic disc herniations as 11.1% to 14.5% [2]. In comparison with asymptomatic thoracic disc herniation, symptomatic thoracic disc herniation is rare, accounting for 0.25 to 0.75% of all disc herniations reported in the literature [3]. Thoracic radicular pain is uncommon compared to lumber or cervical back pain. In fact, only 5% of patients referred to pain clinics present with thoracic back pain. Clinically, thoracic radicular pain is referred to as the upper extremities, thorax and abdomen as neurogenic pain, sensory changes and/or muscular weakness. Patients who complain of thoracic axial pain and/or thoracic radicular pain without a severe neurologic deficit or prominent radiologic abnormality are often treated conservatively. When symptoms are not responsive to conservative treatments including physical therapy or adequate analgesics, the need for surgical treatment emerges. In 75% of thoracic disc herniation patients, the affected level is below T8 and is mostly at T11–T12 [3]. This predominance may be because the lower thoracic level is more mobile and the posterior longitudinal ligament at this level is relatively weaker when compared with other levels. It is more common in males than females, and tends to occur between the fourth and sixth decades of life.

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The majority of cases are central (two-thirds) and the rest are paracentral (one-third). In the vast majority of patients, trauma is often an initiating factor. It is a story of an accidental axial loading such as falling on the hips, a prolonged posture of flexion, incorrect posture, or heavy lifting.

W. S. Chang and J. Bae

ness along with paresthesia and axial pain. A positive Babinski sign, sustained clonus, wide-­ based gait, and spasticity are all signs of myelopathy and indicate marked thoracic cord compression. Often, the presentation is a combination of ataxia, motor deficit in lower limbs, paresthesia, and bowel and bladder symptoms. Guest et  al. described paraplegia resulting from occlusion of the anterior spinal artery by central Clinical Features TDH [7]. Myelopathy is a common clinical manifestation of TDH, which should be treated by Patients with thoracic disc herniation may have a decompression with or without instrumentation. wide variety of symptoms; the most common is Bowel and bladder dysfunction, which are seen continuous or intermittent back pain which is in approximately 15% to 20% of patients with usually described as burning or stabbing [4]. symptomatic TDH can be reported. The presentation of TDH varies depending Although TDH can present with abdominal upon the level involved. Thoracic back pain is a pain and vague symptoms of discomfort, the presenting symptom in most cases. T1/2 disc her- mechanism by which these symptoms occur is niation may mimic a cervical disc herniation and unclear. Intradural nerve roots from the lumbar lead to intrinsic hand weakness and a Horner’s enlargement to conus medullaris follow an orgasyndrome [5]. High thoracic disc herniation (T2– nized pattern with most rostral roots being lateral 5) may be rarer but can mimic cervical disk dis- [8] (Fig. 1). ease and present with symptoms of upper arm Additionally, visceral and somatic afferent pain, radiculopathy, and paresthesia. It is impor- fibers in dorsal columns, spinothalamic and spitant to differentiate between the cervical disc her- nocerebellar tracts, and dorsal and ventral horns niation versus the thoracic disc herniation. have been recognized at different spinal levels Patients with symptomatic thoracic disk her- [9]. Irritation of these tracts with their close assoniation can be divided into three groups including ciation to the dorsal gray column of the spinal axial pain, radicular pain, and myelopathy. cord can cause referred pain and consequently, Axial thoracic pain is usually localized to the further abdominal discomfort. middle to lower thoracic region, but in some cirRohde and Kang proposed that compression cumstances may radiate to the middle to lower of the cord at the site of visceral afferent fibers lumbar area. It is sometimes confused with car- can lead to inflammation and hyper-excitability diac, pulmonary, or abdominal pathology. of visceral neurons [10]. This could possibly Radicular pain is often described as anterior-­ interfere with the descending inhibitory fibers chest band-like discomfort in a dermatomal dis- that modulate noxious input leading to atypical tribution, and is the second type of presentation. presentations of TDH. Foraminal disc herniation in the thoracic spine Also, The Ossification of ligamentum flavum can lead to nerve root compression and severe at the lower thoracic spine causes various neurochest or abdominal discomfort [6]. Therefore, the logical symptoms, sometimes mimicking those clinical presentation may not correlate with the caused by lumbar spinal disease, motor neuron location of the herniation causing these patients disease, or peripheral neuropathy because the to be frequently misdiagnosed by their primary epiconus, conus, and cauda equina are located at physicians and leading to extensive, invasive, and the lower thoracic and thoracolumbar levels and expensive medical and surgical workups. because their localization often varies among Myelopathy is the third category of thoracic individuals. disk lesions and is the most serious symptom. In These atypical symptoms make diagnosis this category, patients will report muscle weak- challenging, which can therefore potentially lead

Clinical Presentation of the Thoracic Spinal Compression

Relation of spinal nerve roots to vertebrae

C1 C2 C3 C4

C1 C2 C3 C4 C5 C6 C7 C8

Cervical nerves

C6 C7 C8

T1 T2

T1 T2

T3 T4 T5 T6 T7

Thoracic nerves

T8 T9 T10

T11 T12

T12

L2

Cauda equina

L3 L4

Filum terminale (pial part)

L4

L5

End of dural/ arachnoid sac

L5 S1

Sacral nerves

Sacral segments

L1

L2 L3

Lumbar segments

T11

L1

Thoracic disc herniation is rare but causes chronic chest pain. In addition to typical thoracic back pain, atypical radiation pain and somatic pain are the main symptoms. To diagnose thoracic disc herniation, clinicians should listen carefully to these symptoms and actively perform physical examination and radiological examination of the thoracic spine.

References

T5 T6 T7

T8 T9

Summary

Thoracic segments

T3 T4

T10

Lumbar nerves

Cervical segments

C5

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S1

S2

S3 S2 S4 S3 S4 S5 S5C0 C0

Filum terminale (pial part) Cocyx

Fig. 1  Diagram of a sagittal section of spinal column showing relation of the spinal cord and the nerves associated with them at each level. Note that lumbar roots begin at lower thoracic spine. Compression at the lower thoracic spine causes radiating pain on lower extremity

to misdiagnosis with progression of the disease. Familiarity with these atypical symptoms will assist providers in making a faster diagnosis and may help eliminate extensive, invasive, and expensive medical and surgical diagnostic workups. TDH could be included in the differential diagnosis of patients with negative gastrointestinal, genitourinary, and cardiopulmonary system basic studies.

1. Singh V, Manchikanti L, Shah RV, et al. Thoraic discography: a focused review. Pain Physician. 2008 Sep–Oct;11(5):631–42. 2. Awwad EE, Martin DS, Smith KR Jr, et  al. Asymptomatic versus symptomatic herniated thoracic discs: their frequency and characteristics as detected by computed tomography after myelography. Neurosurgery. 1991 Feb;28(2):180–6. 3. Arce CA, Dohrmann GJ.  Thoracic disc herniation. Improved diagnosis with computed tomographic scanning and a review of the literature. Surg Neurol. 1985 Apr;23(4):356–61. 4. Wood KB, Garvey TA, Gundry C, et  al. Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individuals. J Bone Joint Surg Am. 1995 Nov;77(11):1631–8. 5. Kalemci O, Naderi S. Thoracic 1-2 disc herniation. J Neurol Sci (Turkish). 2005;22:309–13. 6. Lyu RK, Chang HS, Tang LM, et  al. Thoracic disc herniation mimicking acute lumbar disc disease. Spine (Phila Pa 1976). 1999 Feb 15;24(4):416–8. 7. Guest JD, Griesdale DE, Marotta T. Thoracic disc herniation presenting with transient anterior spinal artery syndrome. Interv Neuroradiol 2000 Dec;6(4):327–31. Epub 2001 May 15. 8. Cho HL, Lee SH, Kim JS.  Thoracic disk herniation manifesting as sciatica-like pain. Neurol Med Chir (Tokyo). 2011;51(1):67–71. 9. Tahmouresie A. Herniated thoracic intervertebral disc. An unusual presentation: case report. Neurosurgery. 1980 Dec;7(6):623–5. 10. Rohde RS, Kang JD.  Thoracic disc herniation presenting with chronic nausea and abdominal pain: a case report. J Bone Joint Surg Am. 2004 Feb;86(2):379–81.

Setup of Operation Room and Patient Position Breno Frota Siqueira, Junseok Bae, and Sang Soo Eun

Introduction A number of approaches have been developed aimed at approaching the thoracic spine with minimal or no manipulation of the dural sac [1–11]. In this chapter, we will discuss the positioning of the operating room and the patient for a better understanding of the reader. There are some positions for certain surgical techniques and locations in the thoracic spine (usually different accesses for high, medium, and low thoracic levels). Generally, the operating room setups are (Fig. 1): 1. Surgeon faces the side of the patient to be operated on. 2. Nurse to surgeon’s right. 3. Table with surgical instrumentals in the nurse’s direct room. 4. Anesthesiologist positioned on the left side of the surgery usually near the patient’s head. 5. C-arm, your monitor, and x-ray technician are positioned in front of the surgeon. B. F. Siqueira · J. Bae (*) Department of Neurosurgery, Wooridul Spine Hospital, Seoul, South Korea e-mail: [email protected] S. S. Eun Department of Orthopedics, Chungdam Wooridul Spine Hospital, Seoul, South Korea

6. Video equipment and its monitor, also positioned in front of the surgeon. An assistant nurse stands next door in the operating room.

 atient Position for Transforaminal P Endoscopic Thoracic Discectomy (TETD) The patient is positioned face down on a radiolucent operating table and on a Wilson frame, with the side to be operated facing the surgeon. The arms are supported on arm boards over the head. As only mild sedation and local anesthesia are used, the extremities, buttocks and shoulders can be prevented from jerking with tape if necessary (Fig. 2). The marking of the level to be operated and the point of entry into the skin is made with the aid of C-arm images in the visualization and axial profile, corroborating the preoperative planning previously measured by computed tomography or magnetic resonance. Using the axial image of the level to be operated on, draw a line from the center of the protrusion through the edge of the facet joint and extending to the skin, joining another line drawn from that point to the midline (spinous process) (Fig. 3). Consider the anatomical shape of rib and watch for lung and aorta. The angulation is approximately 45° and approximately 5–6 cm from the midline (Figs. 4 and 5).

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48 C-ARC X-Ray

Video equipment

X-Ray technician Image processing

Anesthetist

Technician

Surgeon

Suction irrigation equipment

Nurse

Instrument table

Fig. 1  Schematic drawing of operation room with medical staffs

After the patient’s position, the surgeon faces the side to be operated on, the assistant nurse stands on the surgeon’s right side and next to her the table with the instruments. Video tower, C-arm, and laser generator are on the other side of the patient, facing the surgeon (Fig. 6).

 ransthoracic Minimally Invasive T Discectomy After performed general anesthesia, the patient is positioned in lateral decubitus with the side to be operated upward. The neck is supported and held in a neutral position. The upper shoulder and elbow are flexed at 90° and held by an armrest. Hips and knees are flexed and a pillow is placed between the lower limbs. Additional adhesive tapes may be used to stabilize the patient’s position and prevent excessive movement.

One padded roll is placed under the armpit and another between the knees that are semi-­ flexed (Fig. 7). The upper arm is positioned on a Krause support to expose the chest wall (Fig. 8). With C-arm, axial and lateral images are checked to ensure that the patient and spine are perpendicular to the operating table. Intervertebral disc level are marked on the skin. Monitoring of the somatosensory evoked potential and spinal cord motor are installed. The table is folded in slightly to facilitate access to thoracic spine (Fig. 9).

Summary In summary, as shown in this chapter, the operating room layout and patient positioning for the proposed surgery, are of paramount importance to the efficiency of the procedure and its consequent results.

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Fig. 2  Patient position on TETD

Setup of Operation Room and Patient Position

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Fig. 3  Preoperative trajectory is drawn on MRI axial image

Fig. 5  Working channel is inserted with 45° angle

Fig. 4  Skin entry point is drawn with C-arm guidance

Setup of Operation Room and Patient Position Fig. 6  Positions of medical staff during TETD

Fig. 7  Position of patient for transthoracic approach

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Fig. 8  Position patient’s upper arm for exposure of chest wall

Fig. 9  Operation table is folded to expose the thoracic spine to ease the surgery

B. F. Siqueira et al.

Setup of Operation Room and Patient Position

References 1. Daniel H.  Kim, Gun Choi, Sang-Ho Lee, Richard G.  Fessler. Endoscopic Spine Surgery  – 2° Edition – Thieme – 2018. 2. Jin-Sung Kim, Jun Ho Lee, Yong Ahn. Endoscopic procedures on the spine. Springer – 2013. 3. Bae J, Chachan S, Shin SH, Lee SH.  Percutaneous endoscopic thoracic discectomy in the upper and midthoracic spine: a technical note. Neurospine. 2019;16(1):148–53. https://doi.org/10.14245/ ns.1836260.130. 4. Berjano P, Garbossa D, Damilano M, Pejrona R, Bassani R, Doria C. Transthoracic lateral retropleural minimally invasive microdiscectomy for T9-T10 disc herniation. Eur Spine J. 2014;23:1376. 5. Nie HF, Liu KX.  Endoscopic transforaminal thoracic foraminotomy and discectomy for the treatment of thoracic disc herniation. Minim Invasive Surg. 2013;2013:264105. https://doi. org/10.1155/2013/264105. 6. Bouthors C, Benzakour A, Court C.  Surgical treatment of thoracic disc herniation: an overview. Int

53 Orthop 2018 Nov 8 [Epub]. https://doi.org/10.1007/ s00264-018-4224-0. 7. Yen C-P, Uribe JS.  Mini-open lateral retropleural approach for symptomatic thoracic disk herniations. Clin Spine Surg. 2018;31(1):14–21. 8. Paolini S, Tola S, Missori P, et al. Endoscope-assisted resection of calcified thoracic disc herniations. Eur Spine J. 2016;25:200–6. 9. Wagner R, Telfeian AE, Iprenburg M, et  al. Transforaminal endoscopic foraminoplasty and discectomy for the treatment of a thoracic disc herniation. World Neurosurg. 2016;90:194–8. 10. Hsu H-T, Teng M-S, Yang SS, Huang K-F, Wen C-S, Li T-C, Tai P-A. Anterior approach for surgery of thoracolumbar spine: surgical outcomes of series of one self-trained neurosurgeon. Formosan J Surg. 2013;46(5):157–65. 11. Yeung AT, Yeung CA.  Minimally invasive tech niques for the management of lumbar disc herniation. Orthop Clin N Am. 2007;38(3):363–72. https://doi. org/10.1016/j.ocl.2007.04.005.

Intraoperative Neuromonitoring During Thoracic Spine Surgery Sourabh Chachan and Junseok Bae

Introduction

Stagnara Wake-up Test

Thoracic spinal cord has been well established as least tolerant to any kind of compression/ischemia/mechanical manipulation [1–3]. Such is the sensitivity of thoracic spinal cord that despite the utmost surgical carefulness, many patients wake up with neurological deficits after thoracic spinal surgeries [1–3]. The above factors combined with advancements in surgical techniques and spine instrumentation necessitated development of tools and techniques to monitor the physiological wellbeing of spinal cord while operating [1–4].

It was described nearly half a century ago and is still the gold standard [4–8]. It involves pausing the surgery, lowering the anesthesia plane, and asking the patient to move its legs [4–8]. Despite the high sensitivity and specificity, its execution and delayed feedback (the spinal cord damage may become irreversible by the time wake-up test is executed) are its major shortcomings [4–8]. This provided the impetus for the development of more advanced techniques of neurophysiological intraoperative monitoring (IOM) [4–8].

Main Text

 omatosensory Evoked Potential S Monitoring

A number of neuromonitoring techniques are available each with its own unique pros and cons [4–8]. The decision to choose a particular technique depends upon a number of factors including the type of procedure, structures at risk, patient profile and surgeon’s, and monitoring team’s assessment [4–8]. Various techniques of neuromonitoring will be described below.

S. Chachan · J. Bae (*) Department of Neurosurgery, Wooridul Spine Hospital, Seoul, South Korea e-mail: [email protected]; [email protected]

Somatosensory Evoked Potential (SSEP) is the earliest form of electrophysiological monitoring, which assesses the integrity of sensory pathways (dorsal column) [4–8]. It involves stimulation of peripheral nerves (e.g., posterior tibial nerve in the leg, median/ulnar nerve in the arm) while recording from multiple sites that are rostral to the site of surgery [4–8]. The level of surgery determines the choice of stimulation and recording sites, with tibial nerve being the stimulation site of choice, scalp being the recording site of choice and popliteal space being the control recording site in case of thoracic spine surgery [4–8]. A loss

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of amplitude of SSEPs of more than 50% of baseline recordings and/or increased latency of more than 10% are considered as meaningful [4–8]. The usefulness of SSEP lies in its high sensitivity, reproducibility, and continuity [4–8]. The use of SSEP monitoring alone has significantly reduced the rate of neurological complications. Nevertheless, the SSEP monitoring is prone to false negatives, which can be attributed to two factors: differential vascularity of spinal cord and SSEP’s inability to monitor anterior columns [4– 8]. This lead to evolution of motor evoked potential (MEP) monitoring techniques [4–8].

or peripheral nerves [4–9]. This deficiency leads to the evolution of electromyographic (EMG) techniques [4–9].

Electromyographic Monitoring Electromyographic (EMG) activity is recorded from electrodes placed in muscles (same electrodes can be used for recording MEP also) [4–7, 10]. It monitors nerve roots and peripheral nerves, hence monitors the nervous system beyond the capabilities of SSEP and MEP [4–10].

Motor Evoked Potential Monitoring

Surgical Considerations

MEP works by stimulating descending motor pathways (anterolateral column) either at rostral spinal cord or scalp (transcranial magnetic cortical stimulation; most commonly used) and recording from intramuscular needle electrodes placed in multiple muscles in the arms and legs (in case of thoracic spine surgery, only leg muscles, e.g., Tibialis anterior, Abductor hallucis longus are recorded) [4–9]. A 50% increase in stimulus intensity needed to invoke tceMEPs is taken to be a significant change [4–9]. However, for MEP to work, there are certain prerequisites, the foremost of which is absence of neuromuscular blockade, which constraints the choice of anesthetic agents [4–9]. Secondly, each stimulation produces movement of both axial and appendicular movements which requires the surgery to be paused before stimulating [4–9]. Furthermore, a bite block must be used to prevent tongue bite/ mandible/tooth fracture caused by forceful contraction of masseters [4–9]. The use of MEP is further contraindicated in patients with electric implants (e.g., cardiac pacemakers), epilepsy, cortical lesions, skull defects, and increased intracranial pressure [4–9]. However, unlike SSEP monitoring, which requires a turnaround time of ~5 min, MEP information can be updated multiple times during critical portions of the operation [4–9]. Although combined use of SSEP and MEP significantly reduces the number of false negatives, they cannot monitor nerve roots

In the case of thoracic spine surgery, multimodality IOM approach consisting of SSEP, tcMEP, and EMG (Rectus Abdominis) monitoring is advisable [3–14]. While SSEP’s are recorded continuously, tcMEP’s are recorded intermittently: after insertion of pedicle screws, before deformity correction (if any), after the insertion of the concave/ convex rod (in case of deformity cases) and after completion of a spine osteotomy [3–14]. In case of triggered EMG, thresholds