Diagnostic Imaging of Infants and Children [1st ed.] 0071808396, 9780071808392, 9780071810036

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Diagnostic Imaging of Infants and Children VOLUME

I

Notice Medicine is an ever-changing science. As new research and clinical experience broaden our knowledge, changes in treatment and drug therapy are required. The author and the publisher of this work have checked with sources believed to be reliable in their efforts to provide information that is complete and gener­ ally in accord with the standards accepted at the time of publication. However, in view of the possibility of human error or changes in medical sciences, nei­ ther the author nor the publisher nor any other party who has been involved in the preparation or publication of this work warrants that the information contained herein is in every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the results obtained from use of the information contained in this work. Readers are encouraged to confirm the information contained herein with other sources. For example and in particular, readers are advised to check the product information sheet included in the package of each drug they plan to administer to be certain that the information contained in this work is accurate and that changes have not been made in the recommended dose or in the contraindications for adminis­ tration. This recommendation is of particular importance in connection with new or infrequently used drugs.

Diagnostic Imaging of Infants and Children Robert G. Wells,

MD

Pediatric Diagnostic Imaging, SC PDI Pediatric Teleradiology Milwaukee, Wisconsin Director, Pediatric Imaging

Northwestern Lake Forest Hospital Lake Forest, Illinois Associate Clinical Professor of Radiology and Pediatrics Medical College of Wisconsin Milwaukee, Wisconsin

VOLUME

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To Annie, my loving wife and best friend. To my sons, Jack, Sam, and Joe, who have taught me much more than I will ever teach them. And to Jack Sty, who one day said to me, "Bob, let's write another book . . .

"

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Contents Foreword Preface Acknowledgments

ix xi xiii

.........................................................

...........................................................

..........................................

VOLUME I PART 1

................................

1 Developmental Abnormalities of the Lungs and Diaphragm 2 Neonatal Lung Disease 3 Pulmonary Infection

.........................

................................

Abnormalities, and Systemic Disease 5 Pulmonary Neoplasms and Masses

PART 2

179

219

........................................

...................................................

17 Autoimmune Disorders of the Brain

THE CARDIOVASCULAR .....................................

Heart and Pericardium

...............................

11 Congenital Heart Disease

13 The Vascular System

277 279

................

................................

14 Congenital Abnormalities of the Brain

......

315

403

....................................

THE BRAIN

15 Hydrocephalus

267

...........................

12 Anomalies of the Great Vessels

251

433

485

625

.........

18 Metabolic and Destructive Disorders of the Brain

21 Head Trauma

PART 4

641

................................

20 Intracranial Vascular Abnormalities

683

.........

797

...........

..............................................

THE SPINE

of the Spine

847 887

................................

22 Developmental Abnormalities

889

.................................................

23 Infection, Inflammation, and Degenerative Disorders of the Spine

..........

24 Neoplasms and Masses of the Spine 25 Trauma and Surgery of the Spine

977

........

.............

957

1007

VOLUME II PART 5

THE HEAD AND NECK

26 The Skull and Face

10 Acquired Diseases of the

PART 3

191

.............................................

SYSTEM

75

...........

....................................................

8 The Chest Wall

3

139

........

6 Pulmonary Trauma, Surgery,

7 The Mediastinum

1

45

......................................

4 Chronic Lung Disease, Genetic

9 The Breast

597

·································

19 Intracranial Neoplasms and Masses

THE THORAX

and Toxins

16 Intracranial Infections

27 The Orbit

...........

1043

.....................................

....................................................

28 The Paranasal Sinuses

1045

1091 1137

...............................

29 The Nose, Nasal Cavity, and Nasopharynx

........................................

30 The Neck, Pharynx, and Trachea 31 The Salivary Glands

................

..................................

32 The Thyroid and Parathyroid Glands 33 The Temporal Bone and Ear

1153

1173

1249

........

......................

1261 1293

487

.............................................

575 vii

viii

Contents

PART 6

THE GASTROINTESTINAL SYSTEM

34 The Esophagus 35 The Stomach

1 323

....................................

1325

..........................................

1357

..............................................

50 Urinary Tract Calcifications and Stones

.................................................

51 Urinary System Trauma, Surgery, and Therapy

.................................

36 The Smalllntestine

1379

52 Renal Vascular Abnormalities

37 The Colon

1447

53 The Female Genital System

....................................

...................................................

38 The Omentum, Mesentery, and Peritoneal Cavity

.................................

39 The Anterior Abdominal Wall

1495

....................

1503

40 Abdominal Trauma and

Otherlntraabdominal Emergencies

PART 7

THE HEPATOBILIARY SYSTEM

....................................

41 The Hepatobiliary System PART 8

THE PANCREAS

42 The Pancreas

PART 9

..........

......................

............................................

THE SPLEEN

43 The Spleen

........................

...........................

1629

1631

.......................................

1 653 1655

..................................................

47 Urinary System lnfection

48 Vesicoureteral Reflux

...........

...........................

.................................

49 Neoplasms and Masses of the Urinary System

................................

1715

1741 1759 1777 1785

.......................

PART 11 THE ADRENAL CiLANDS 56 The Adrenal Glands

SYSTEM

...................................

58 Dysostoses and Developmental Deformities

...............................................

59 Metabolic Bone Diseases

Go Systemic Arthritis

1 931

1933

...................................

...................................

57 Skeletal Dysplasias

1925

.........

PART 12 THE M USCULOSKELETAL

.........................

1965

1967

202 9 2073 2113

......................................

61 Hematological and

...........................

of the Extremity Soft Tissues

.....................

65 Musculoskeletal Trauma

2141

.......................

64 Nonneoplastic Abnormalities

Index

2123

.............................

62 Musculoskeletal Infections

..........................

1855 1887

..........................

..................................

63 Musculoskeletal Tumors

................................

46 Diseases of the Renal Parenchyma

Affect Both Genders

1827 1841

...................

55 Genital Abnormalities that

Ischemic Bone Disease

44 Developmental Abnormalities 45 Renal Cysts

1523

1609

PART 10 THE GENITOURINARY

of the Urinary System

1521

1607

.................................................

SYSTEM

1511

54 The Male Genital System

1813

2161

2237

225 9

.............................................................

/-1

Fo rewo rd Diagnostic Imaging of Infants and Children

by Robert Wells

is a must-have text that I am sure you will keep as a con­

stant friend. It is a one-of-a-kind book, written in a style

pathophysiology. For clinicians, this text is a resource for reviewing the advantages and disadvantages of various imaging approaches and for understanding the signifi­

that is concise and informative. Kudos to Dr. Wells for the

cance of imaging findings. The easy-to-read style and the

superlative work.

clear correlation of radiologic findings with disease patho­

This richly illustrated reference covers the gamut of pediatric diseases and injuries. Extensive integration of

physiology and clinical features make it an excellent choice for medical students, residents, and fellows.

clinical considerations and review of disease pathogenesis

This text is a terrific source of information across the

help to make sense of imaging patterns and provide the

entire spectrum of pediatric radiology, and I strongly rec­

radiologist with tools to establish a confident diagnosis.

ommend this book to anyone interested in the subject.

Readers of various backgrounds will find this text use­

ful. Radiologists can pull it off the shelf for a quick review

Richard Towbin, MD

of the imaging findings and differential diagnosis of a con­

Radiologist-in-Chief

dition, with additional material available for those desiring

Phoenix Children's Hospital

a more in-depth review of the clinical presentation and

Phoenix, Arizona

ix

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Preface is designed to be

Because the approach to the individual patient does

an efficient reference source for the practicing radiologist,

not always fit with a disease category system, there are sup­

Diagnostic Imaging of Infants and Children

a learning tool for radiology residents and fellows, and a

plemental features in the text that provide the reader with

cross-specialty resource for all medical providers who care

additional tools. Clinical Presentations sections interject

for children. Technologists in all imaging modalities will

also find it useful. The text is comprehensive, but concise.

discussions of key symptom-based considerations about the differential diagnosis and imaging procedure selec­

Up-to-date descriptions of the clinical features, pathogen­

tion. In addition, differential diagnosis tables are included

esis, and pathology of diseases provide a solid background

where appropriate.

for understanding diagnostic imaging principles. The con­

Radiologists, pediatricians, pediatric specialists, and

tent encompasses essentially all pediatric conditions for

other health care professionals who care for children face

which diagnostic imaging is clinically important.

the ongoing and evermore complex challenge of choosing

The basic organization of the text is by organ system

the most accurate, least invasive, and most cost-effective

and disease category. For each condition, the reader is pre­

diagnostic imaging techniques for the individual patient.

sented with a brief overview of current information about

The balanced approach of this text provides the reader with

the pathogenesis, epidemiology, and clinical presentation.

tools to make informed decisions in everyday practice.

When appropriate, discussion of the disease pathology is correlated with the findings on diagnostic imaging stud­

The information in Diagnostic Imaging of Infants and Children is the result of an exhaustive review of the current

ies. The imaging features with each pertinent imaging

medical literature, blended with the practical knowledge

30

modality are reviewed sequentially. Imbedded "Pathology­

accumulated from nearly

Radiology" tables provide a quick reference for the key

radiologist. My sincere wish is for my fellow radiologists

findings.

years of practice as a pediatric

and clinical colleagues to find this a useful resource as they strive to provide high-quality care to children.

xi

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Acknowledgments This book would not exist without the encouragement,

Wisconsin. The potentially chaotic process of preparing

guidance, and support of Dr. Jack Sty. He has been a men­

thousands of images for use in the book ran with preci­

tor, colleague, and friend throughout my career. His enthu­

sion under the guidance of my dedicated and energetic

siasm for excellence is infectious. My love for teaching and

administrative secretary, Sue Armson. Sue passed too

writing has grown under his influence.

early, but her spirit is part of this book.

My partner, Dr. Brian Lundeen, has been instrumen­

I wish to acknowledge Dr. Jeff Rosengarten and the

tal in helping to maintain our clinical practice as I have

other members of the radiology department at Northwest­

balanced my clinical duties with this time-consuming

ern Lake Forest Hospital. High-quality images from this

project. He has also contributed many of the figures in the

institution are scattered throughout the text. Also, thanks

text and assisted with proofing figure legends. Dr. Smita

to Dr. Darin Brannan and the staff at The Children's Cen­

Bailey, now at Phoenix Children's Hospital, has also pro­

ter in Bethany, Oklahoma.

vided key images. The physician assistants, nurses, and technologists at our outpatient radiology center, Pediatric Diagnos­

The editors and production staff at McGraw-Hill have been supportive and professional. Special thanks to Michael Weitz and Peter Boyle.

tic Imaging, have contributed in various ways, includ­

Finally, the special contribution of my family needs

ing manuscript proofing and acquisition of illustrative

to be recognized. My three sons, Jack, Sam, and Joe, have

images. Special thanks to Darci Grochowski for her assis­

tolerated a father who needed to devote large blocks of

tance with the musculoskeletal chapter.

time to this project. Only my oldest can remember a time

Several dedicated people assisted with photography,

when dad was not working on "the book." They have been

image organization, clinical correlation, and bibliographic

unwavering in their support and encouragement. My dear

research. They include Jessica Mainus-Sohns, Scott Byers,

wife, Annie, is the unnamed coauthor of this book. She

Kevin Cohen, and Monica Godat. Thanks as well to the fi le

has provided encouragement and advice. Her uncondi­

room staff and technologists at the Children's Hospital of

tional support made this book possible.

xiii

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Diagnostic Imaging of Infants and Children VOLUME

I

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CH A PTE R

1

Developmental Abnormalities of the Lungs and Diaphragm

E M B RYOLOCY OF TH E LU NCS AND PULMONARY VESSELS . . . . . . . . . . . . . . . . . . . . . .

3

Anomalous Origi n of the Left Pulmonary Artery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

26

Systemic Arterial S u pply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

26 26

DEVELOPM ENTAL ABNORMALITI ES OF TH E LU NCS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

Pulmonary Agenesis and Aplasia. . . . . . . . . . . . . . . .

4

Anomalous Pulmonary Venous Con nection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P u l monary Hypoplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Anomalous Si ngle Pulmon ary Vei n ...... ......

27

Bronchial Atresia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

Bronchopu l monary Seq uestration . . . . . . . . . . . . . . Extralobar Sequestration . . . . . . . . . . . . . . . . . . . . . . . . . . Intralobar Sequestration . . . . . . . . . . . . . . . . . . . . . . . . . .

9 1o 11

Pulmonary Arteriovenous M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

28

Pulmonary Varix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

30

Congen ital Cystic Adenomatoid M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

COM BI N ED ANOMALI ES OF LU NC AND PULMONARY VESSELS . . . . . . . . . . . . . . . . . . . . . .

30

P u l monary Bronchogenic Cyst . . . . . . . . . . . . . . . . . . . .

19

Hypogenetic Lung Synd rome . . . . . . . . . . . . . . . . . . . . . .

30

Accessory Bronchus . . . . . . . .. . . . . . . . . . . . . . . . . . . . .. . . . . . . .

20 20

32

Accessory Cardiac Bronchus . . . . . . . . . . . . . . . . . . . .

Bridging Bronchus...................................

21 21 21

DEVELOPM ENTAL LYM PHATIC DISORDERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DEVELOPM ENTAL ABNORMALITI ES OF TH E DIAP H RAC M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

33

Congenital Bronchial Stenosis . . . . . . . . . . . . . . . . . . . .

22

Congen ital Diaphragmatic Hernia . . . . . . . . . . . . . .

33

Congen ital Lobar Em physema . . . . . . . . . . . . . . . . . . . .

22

Eventration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

38

H orses hoe Lung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24

Lung H ernias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25

Congen ital Paralysis of the Hemidiaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39

H epatic-Pulmonary Fusion . . . . . . . . . . . . . . . . . . . . . . . . .

39

ANOMALI ES OF PULMONARY VESSELS. . .

25

I nterruption ofthe M a i n Pulmonary Artery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39

25

Tracheal Bronchus.................................... Esophageal Bronchus...............................

EMBRYOLOGY OF THE LUNGS AND PULMONARY VESSELS Fetal lung development can be categorized into the embry­

buds arise from this diverticulum. The developing air­ ways become separated from the esophageal portion of the foregut by ingrowths of adjacent mesoderm that form the tracheoesophageal septum. The lung buds elon­

onic, pseudoglandular, canalicular, and saccular phases.1

gate into primary lung sacs, and the 5 secondary bronchi

Embryonic development begins at 24 to 26 days gesta­

develop as outgrowths of the primary bronchi. This com­

tion when a diverticulum arises from the ventral wall of

pletes the embryonic period, at approximately the end of

the foregut. Over the next 2 days, the right and left lung

the fifth week.

3

4 Part 1 The Thorax The pseudoglandular phase predominantly consists of

syndrome). Developmental arrest occasionally occurs at the

development of the bronchial tree. During this phase, the

segmental level. Segmental bronchial agenesis most often

airways are blind tubules lined with columnar or cuboidal

involves the right upper lobe.8.9

epithelium. The pseudoglandular phase occurs between the fifth and 16th weeks of gestation. Nearly all of the conducting

The pulmonary arteries develop from the sixth aortic arch. The proximal part of the sixth aortic arch becomes the

airways are present by the end of the pseudoglandular phase.

proximal segments of the right and left pulmonary arter­

The canalicular phase represents the early stage of

ies. On the left, the connection with the arch is maintained

development of transitional airways. There is decrease

as the ductus arteriosus. Pulmonary arterial development

in mesenchymal tissue within the developing lungs, and

parallels that of the airways during fetal development.

newly formed capillaries and air spaces approximate one

Postrlatal development results in increase in peripheral ves­

another. The canalicular phase occurs between the qth

sel branching commensurate with alveolar development

week and the 25th to 28th weeks.

until approximately 8 years of age. Anomalies of pulmonary

The saccular (or alveolar) phase relates to develop­

artery development include agenesis, hypoplasia, anoma­

ment of the alveoli. Defined acinar morphology is present

lous systemic connection, and arteriovenous malformation.

by the 28th week of gestation. During the final weeks of

During the embryonic phase of fetal development, pul­

fetal development, there is prolific development of alveoli.

monary venous blood drains from the splanchnic plexus

Alveolar development continues in postrlatal life to approx­

into the primordium of the systemic venous system.

imately the age of 8 years.

Pulmonary venous development begins with caudal and

Tracheal cartilage development predominantly occurs

cranial outpouchings of the sinoatrial regions of the heart.

during the pseudoglandular and canalicular periods. Initial

These extend toward the lung buds. The caudal outpouch­

cartilage development occurs during the seventh to eighth

ing regresses. The cranial portion develops as the common

weeks of gestation. Bronchial cartilage development occurs

pulmonary vein. Eventually, the common pulmonary vein

in a centrifugal direction.

incorporates into the left atrial wall. Residual splanchnic

Anomalies of the lung related to abnormal broncho­

pulmonary connections regress. This leaves

4 independent

pulmonary �ung bud) development include agenesis, bron­

pulmonary veins entering the left atrium. Potential pulmo­

chial atresia, tracheal atresia, some instances of congenital

nary venous anomalies include pulmonary varix, systemic

lobar emphysema, congenital cystic adenomatoid malfor­

connection, and agenesis.

mation, pulmonary bronchogenic cyst, tracheal bronchus,

Congenital lung malformations comprise a heteroge­

and accessory cardiac bronchus. The pathogenesis of bron­

neous and overlapping group of anomalies

chogenic cysts apparently involves abnormal epithelial bud­ ding caused by local defects in the mesenchymal substrate. 2

terminology applied to these lesions is often imprecise.

(Table 1-1).

The

There is overlap of the embryological, pathological, clinical,

The faulty development that results in cystic adenomatoid

and radiological features of these various lesions. A num­

malformation occurs later in gestation, and is character­

ber of classification schemes have been proposed in an

ized by disordered development of the bronchioles and fail­

attempt to provide order to the sometimes confusing array

ure of differentiation of the epithelium into a mature form.

of anomalies. Many investigators consider lung anomalies

This may be related to faulty signaling between the bron­

to represent a spectrum of pulmonary and vascular mal­

chioles and peribronchial mesenchyme during the period

development.10 Bush proposed simplified nomenclature

of active bronchial development, which occurs between the

based on the gross anatomy and imaging appearance. The

fifth and eighth weeks.3 The developmental mechanism

5 major categories in this system consist of a congenitally

of pulmonary sequestration involves both abnormal bron­

enlarged hyperlucent lobe, congenital thoracic malforma­

chial budding (supernumerary budding from the foregut,

tions, a congenitally small lung, absent lung, absent tra­

or pinching off from the developing bronchial tree) and

chea, and absent bronchus." Langston has developed a

failure of normal mesenchymal maturation (persistent sys­

classification system based on the pathologic features and

be caused by any developmental abnormality that results in

system. Langston emphasizes the importance of develop­

lobar air trapping, such as a focal anomaly of airway carti­

mental airway obstruction in the pathogenesis of multiple

lage, intrinsic or extrinsic bronchial obstruction, or abnor­ mal supporting stroma of the alveolar wall.6.7

seemingly unrelated lung malformationsP

temic arterial supply).4·5 Congenital lobar emphysema can

presumed embryogenesis. Table

1-1 is adapted from this

A spectrum of anomalies results from arrested devel­ opment of lung; this is termed the

complex.

agenesis-hypoplasia

The temporal stage of the arrested development

is an important determining factor in the nature of the resultant anomaly. The patterns include agenesis (absence of bronchus and lung), aplasia (absence of lung, but pre­ served bronchus), and hypoplasia

(rudimentary bron­

DEVELOPMENTAL ABNORMALITIES OFTHE LUNCS

Pul monary Agenesis and Aplasia Pulmonary

agenesis i s the complete absence of lung paren­

chus and lung). The agenesis-hypoplasia complex most

chyma, vessels, and bronchial structures in a lung, a lobe,

often involves an entire lung or lobe (hypogenetic lung

or (rarely) both lungs. Pulmonary

aplasia

represents the

Chapter 1 Deve l o p m ental A b n o r m a l ities of the L u n gs a n d D i a p h ragm 5 Table 1-1 . Congenital Lung M alformations

Absent or small lung

Pulmonary hypoplasia Pulmonary agenesis Pulmonary aplasia Bronchogenic cyst I solated bronchial atresia B ronchial atresia with systemic vascu lar connection (intralobar sequestration) Anomalous bronchial connection to the gastroi ntestinal tract Cystic adenomatoid malformation, large cyst type Cystic adenomatoid malformation, small cyst type Extralobar sequestration Laryngea l atresia Solid (adenomatoid) cystic adenomatoid malformation Polyalveolar lobe ·-- ·----- -- ...... ---

_ ...

------------------

---·-· - ·- ·---·------ - ------ ------------------------------------------·

B ronchopul monary malformation

--------- -----------------

-------

-------

Pulmonary hyperplasia and related lesions

· ------- ------

---------- --- - ----- ------

Congenital lobar overinflation Vascular anomalies

-------

------------------------------------

Systemic a rterial con nection to normal l u n g Hypogenetic lung syndrome Anomalous pul monary venous connection I nterru ption of main pulmonary artery Pulmonary arteriovenous malformation Lym phatic cysts Enteric cysts S i m ple parenchymal cysts -----

M iscellaneous cystic lesions

-------

same constellation of findings except that a rudimentary

Severe cardiac anomalies are more common in patients

bronchus is present. Pulmonary agenesis and aplasia

with agenesis of the right lung than with agenesis of the left lung.'3·'4

result from a developmental abnormality at approximately

4

weeks of gestational age. The anomaly usually involves

Symptomatic children with agenesis of a lung often

an entire lung. The left upper lobe is the most common site

have anatomic distortion of the airway and vascular com­

of lobar agenesis/aplasia. The contralateral lung typically

pression. In some patients, there is intrinsic airway ste­

has compensatory enlargement, but is otherwise normal.

nosis. Symptomatic newborns exhibit manifestations of

Morbidity and mortality are greater in those patients with

respiratory distress: tachypnea, cyanosis, and impaired gas

right lung agenesis than in those with involvement of the

exchange.

left lung, presumably as a result of more pronounced medi­

Imaging studies demonstrate shift of normal lung to

astinal shift and concomitant torsion of the great vessels

fill the void created by agenesis or aplasia. There is marked

and major airways.

mediastinal shift and the contralateral lung bulges across

More than 50% of children with pulmonary agenesis or aplasia have coexistent congenital anomalies of the

the midline

( Figure 1-1 ) .

The severity of contralateral

lung herniation varies between patients. If the left lung

cardiovascular, gastrointestinal, skeletal, or genitourinary

is absent, the right cardiomediastinal border sometimes

systems. Patent ductus arteriosus and patent foramen

produces a sharp perpendicular line adjacent to the left

ovale are the most common cardiovascular anomalies in

margin of the sternum as viewed on a frontal radiograph.

these children. The associated skeletal anomalies of the

With agenesis of the right lung, the left cardiomediastinal

limbs and spine tend to be ipsilateral to the lung abnor­

border is shifted to the right of the sternum and the entire

mality. Ipsilateral radial ray defects and hemifacial micro­

cardiac silhouette is contiguous with that of the liver

somia can occur in association with pulmonary agenesis.

The ribs are crowded together on the side of

( Figu re 1-2 ) .

6 Part 1

The

Thorax

A

Figure 1-2 Pulmonary agenesis. There is no aerated right lung on this anteroposterior chest radiograph of a newborn infant. The hyperinflated left lung herniates across the midline

(arrows). There is rightward shift

of the trachea. The outlines of the heart are not visible; the soft­ tissue density of the cardiac structures in the right hemithorax is contiguous with that of the liver. There are right-sided rib deformities and spinal segmentation anomalies.

secondary effects on the airway and mediastinal vessels. The imaging appearance of pulmonary aplasia is identical to that of agenesis except that a rudimentary bronchus is present.'5 ·'6 The radiographic findings of lobar agenesis/aplasia are subtle. Most often, the ipsilateral lung is small and the remaining lobes are hyperinfl.ated. There may be an abnor· mal density in the region of the involved lobe that mim­ ics atelectasis. Agenesis of the right middle lobe and right upper lobe or of the left upper lobe results in a retroster· nal density that parallels the anterior chest wall on lateral radiographs. At times, the radiographic appearance of lobar 8

Figure 1-1 Left pulmonary agenesis. A, B. Anteroposterior and lateral radiographs show a small left hemithorax and leftward shift of the mediastinal structures. The left lung is absent. There is marked leftward displacement of hyperexpanded right lung.

agenesis mimics that of lobar collapse. If the standard radiographic findings are inconclusive, computed tomog­ raphy is diagnostic. MR can be helpful to demonstrate sec­ ondary airway abnormalities, and to define the mediastinal vascular anatomy.'5·16

Pul monary Hypoplasia The definition o f pulmonary hypoplasia i s deficient or

the absent lung. Bronchography and bronchoscopy dem­

incomplete development of the lung, such that there is

onstrate absence of the main bronchus in patients with

decreased size of the lung and a diminished number

agenesis. Cross-sectional imaging with MR or helical CT

of functioning pulmonary units (i.e., cells, airways, and

shows absence of lung parenchyma, bronchial structures,

alveoli). Both lungs are involved in most patients with

and pulmonary and bronchial vessels on the affected

pulmonary hypoplasia. Unilateral or lobar forms also

side. These studies are also valuable for documenting

occur, usually associated with anomalies of the ipsilateral

Chapter 1 Deve l o pmental A b n o r m a l ities of the L u n gs a n d D i a p h ragm

A

B

A An anteroposterior chest radiograph of a newborn with

by polycystic kidney disease, resulting in abdominal distention,

Figure 1-3 Pulmonary hypoplasia.

respiratory distress and abdominal distention shows small­

7

B. An abdominal radiograph shows large flank masses caused

displacement of bowel, and elevation of the diaphragm.

volume lungs, elevation of the diaphragm, and mild cardiomegaly.

pulmonary artery and pulmonary veins. Bilateral pulmo­

newborn, with cyanosis, tachypnea, hypoxia, hypercapnia,

nary hypoplasia typically causes severe, often fatal, neona­ tal respiratory distress.'7 ·18

be rapid progression to death from severe hypoxemia. The

Pulmonary hypoplasia occurs as a primary lesion in

small lungs are difficult to ventilate, and complications of

and acidosis. With severe bilateral involvement, there may

10% to 15% of cases. The more common secondary form is

mechanical ventilation are common; these include pulmo­

associated with one or more other conditions that directly

nary interstitial emphysema, pneumothorax, pneumome­

or indirectly interfere with lung development, usually by

diastinum, and pneumopericardium. Pneumothorax can

compromising the thoracic space available for lung growth.

also develop spontaneously in these infants.

Intrathoracic lesions are most common; these include

The radiographic diagnosis of bilateral pulmonary

congenital diaphragmatic hernia, extralobar sequestra­

hypoplasia is sometimes difficult. Lung aeration can ini­

tion, agenesis of the diaphragm, and a large fetal pleural

tially appear normal on chest radiographs. The small size

effusion or chylothorax. Asphyxiating thoracic dystrophy

of the lungs may not be appreciated until serial radiographs

(Jeune syndrome) is an example of a thoracic cage anomaly

show that the appearance is persistent. The thoracic cage

that compromises fetal lung development. Others include

is usually small and the diaphragm is elevated

short-rib polydactyly syndromes, metatrophic dysplasia,

Unilateral

pulmonary

hypoplasia

( Figure 1 -3) .

appears

radio­

Ellis-van Creveld syndrome, achondrogenesis, and severe

graphically as a small, but well aerated, lung. The ipsilat­

forms of osteogenesis imperfecta. Extrathoracic causes of

eral pulmonary artery is small or absent. Occasionally, an

pulmonary hypoplasia include oligohydramnios (e.g., renal

anomalous draining pulmonary vein is visible (e.g., scimi­

agenesis, severe urinary tract obstruction) and abdomi­

tar syndrome). The hypoplastic lung is oligemic, and blood

nal distention (e.g., ascites, polycystic kidney disease).

flow to the contralateral lung may be increased. The medi­

Diminished pulmonary vascular perfusion as a result of

astinum is deviated toward the side of the hypoplasia; this

a cardiac or vascular anomaly can also lead to pulmonary

is accentuated during inspiration

hypoplasia."'

graphic differential diagnosis includes hypogenetic lung

(Figure 1 -4) .

The radio­

The clinical presentation of pulmonary hypoplasia var­

syndrome, Swyer-James McLeod syndrome, and urlliateral

ies according to the severity of the anomaly. Most often,

absence of the pulmonary artery. Occasionally, there is cys­

there are manifestations of respiratory distress in the

tic distention of the hypoplastic lung (possibly as a result of

8 Part 1 The Thorax

A

B

Figure 1-4 Pulmonary hypoplasia.

obscuration of the right cardiomediastinal border, rightward shill

Anteroposterior and lateral chest radiographs of an asymptomatic

of the mediastinal structures, and lack of appropriate anterior

4-year-old child show diminished size of the right lung, with

extension of the right lung

a developmental defect at the bronchial-alveolar junction),

(arrows) on the lateral view.

Many clinicians also use the term

Potter syndrome

resulting in an appearance that overlaps that of congenital

to refer to similar, but not necessarily lethal, features of

cystic adenomatoid malformation.

infants who are the products of pregnancies in which

The early prenatal detection of clinically significant

there is severe oligohydramnios from causes other than

pulmonary hypoplasia is helpful for parental counsel­

bilateral renal agenesis. A more proper term in this

ing and planning for optimal perinatal management

situation is

Techniques for assessing the fetus with suspected pulmo­

tions account for approximately

nary hypoplasia include various measurements based on

manifestations of the Potter phenotype. These abnor­

Potter phenotype.

These mimicking condi­

8o% of newborns with

sonography and M R I. Sonographic measurements that

malities include cystic renal dysplasia, severe obstructive

can be useful include the ratio of fetal lung area to thoracic

uropathy, autosomal recessive polycystic kidney disease,

area, the ratio of thoracic circumference to abdominal cir­ cumference, and the ratio of lung area to thoracic area.

renal hypoplasia, medullary dysplasia, and Denys-Drash

syndrome. 2 3-25

MR allows estimation of the fetal lung volume, which can be compared to the expected values for the gestational age

Bronchial Atresia

or evaluated as a ratio of lung volume to estimated body weight.'9-2 '

Bronchial atresia is a focal obliteration of a proximal seg­

Potter syndrome refers to a constellation of findings that

mental or subsegmental bronchus. The pathogenesis of

occur with bilateral renal agenesis and other conditions

bronchial atresia is unknown, but apparently involves an

that cause severely diminished urine excretion in utero.

insult to a formed bronchus rather than a primary devel­

The findings include severe pulmonary hypoplasia, oligo­

opmental failure. One potential mechanism is an interrup­

hydramnios, and dysmorphic features. The bilateral pul­

tion of the arterial supply of a developing fetal bronchus,

monary hypoplasia in these infants usually results in death

with subsequent ischemia and scarring or discontinuity

in 3000 livebirths _The newborn with Potter syndrome has

more proximal aspect of the developing bronchus. Despite

soon after birth. Potter syndrome occurs in approximately 1

between the cells at the tip of the bronchial bud and the

characteristic features that include hypertelorism, epican­

the presence of an atretic bronchial segment, the distal

thic folds, low-set ears, a flattened nose, micrognathia, and

branches can develop normally. Typically, the abnormality

limb anomalies; the facial appearance in these children is termed Potter facies. 22

ever, lobar or subsegmental bronchi can also be involved.

involves segmental bronchi at or near their origins; how­

Chapter 1 Deve l o p mental A b n o r m a l ities of the L u n gs a n d D i a p h ragm 9 The most common site is the apical posterior bronchus of

mucous-filled bronchi distal to the obstruction. The appear­

the left upper lobe. Other potential sites include the seg­

ance of the parahilar mass is termed the

mucoid impaction sign. The portion of lung distal to the mass is hyperinflated.

mental bronchi of the right upper lobe, right middle lobe, and right lower lobe.'2 · 2 6

The involved lung is also oligemic, a result of intrapulmo­

At the parahilar margin of the affected portion of the

nary vascular compression and hypoxic vasoconstriction.

lung, a segment of the bronchus immediately distal to

Expiratory CT is particularly useful for demonstrating the

the atresia is dilated and filled with mucous; this is the

hyperinflated portion of involved lung, as well as the central

bronchocele (mucocele) that is a characteristic feature

branching bronchocele that has attenuation characteristics

of bronchial atresia. The cystic, blindly terminating,

of soft tissue or fluid. With MRI, the bronchocele appears

mucus-filled bronchocele does not connect to the main

as a branching structure radiating from the hilum, with

bronchial tree. The more distal bronchi are filled with

high signal intensity on both T1-weighted and T2-weighted images. Lp 8-32

mucous, but otherwise are relatively normal. The alve­ oli in the lobe or segment distal to the atretic bronchus

On prenatal sonography, the portion of lung involved

are ventilated by collateral pathways, and this portion

with bronchial atresia appears enlarged and hyperechoic.

of the lung becomes hyperinflated and noncollapsible.

Enlarged branching central bronchi may be visible.

Occasionally, there is associated microcystic parenchy­

There is sometimes a cystic character. The pathologic anatomy can also be demonstrated with fetal MR. In the

mal maldevelopment. Most patients with bronchial atresia are asymptom­

neonate, bronchial atresia appears as a radiographically

atic. Recurrent lung infections can occur. Other potential

opaque segment or lobe, due to retention of fetal alveolar

clinical findings include dyspnea and manifestations of

fl.uid. 33-35

bronchial asthma. Pectus excavatum is sometimes associ­

The radiographic differential diagnosis of bronchial

ated with bronchial atresia, possibly because of costoster­

atresia includes allergic bronchopulmonary aspergillosis,

nal retraction during the efforts to overcome the airway

cystic bronchiectasis, bronchogenic cyst, and intrapulmo­

obstruction caused by encroachment on normal lung tis­

nary sequestration (bronchial atresia with systemic vascu­

sue by the hyperinflated segments. Spontaneous pneumo­

lar connection). Any acquired lesion that causes proximal

thorax occasionally occurs as a complication of bronchial atresia. 2 7

airway obstruction and focal air trapping can have a radio­ graphic appearance that is similar to that of congenital

Chest radiographs of children with bronchial atresia

bronchial atresia; examples include foreign body, tumor,

show a hyperinflated lobe or segment, and a round or lob­

and inflammatory stricture. CT usually allows accurate

ulated parahilar mass (the bronchocele)

The

exclusion of a hilar mass in these children, and aids in

parahilar mass may appear solid or cystic, and it sometimes

the distinction between mucoid impaction and nodular

(Figure 1 -5 ) .

has a branching character. The mass represents dilated

lesions. Contrast-enhanced spiral CT allows exclusion of an anomalous vascular component, as occurs with sequestration.

Bronchopul monary Sequestration Bronchopulmonary sequestration i s a mass composed of lung tissue that receives its blood supply from an anoma­ lous systemic artery and does not communicate with the bronchial tree via anatomically normal bronchial struc­ tures. Bronchopulmonary sequestration, like hypogenetic lung syndrome, is a combined anomaly of tracheobronchial development and pulmonary vascular development. There are

2 main types: intralobar and extralobar (Table 1 -2 ) . An

intralobar sequestration is within the visceral pleura. The arterial supply is by one or more anomalous systemic arter­

ies, and drainage is usually via the pulmonary veins. An extralobar sequestration is contained in a pleural envelope separate from that of the normal lung, is supplied by one or more anomalous systemic arteries, and can have various pathways of venous drainage.36.37 The typical treatment for bronchopulmonary seques­ trations is surgical resection. The intralobar type usually requires a formal lobectomy.s Because some extralobar

Figure 1-5 Bronchial atresia. The left lung is hyperinflated and oligemic. appears as a small ovoid parahilar mass

A bronchocele

(arrow).

sequestrations

regress

or

disappear

spontaneously,

nonoperative management is appropriate for selected

10 Part 1 Th e Thorax Table 1-2. Bronchopul monary Sequestration: Com parison of l ntralobar and Extralobar Types Differentiati ng I ntralobar

Extra lobar

Age at diagnosis Sex distribution Location

Childhood Equal Basilar: 6o% left, 40% right Systemic Pulmonary (usual ly) Rare

Prenataljinfancy 8o% male g o% left

Extralobar sequestration occurs with a

------

male-to·

sequestration have an associated anomaly, such as con· genital diaphragmatic hernia, diaphragmatic eventration, diaphragmatic paralysis, cystic adenomatoid malforma· tion, bronchogenic cyst, foregut duplication, pericardia! defect, vertebral anomalies, ectopic pancreas, or pectus excavatum. Extralobar sequestration is supradiaphragmatic

Systemic Systemic

- -- - - - - - --

in

90% of patients; usually located between the left lower

lobe and the left hemidiaphragm. Other potential locations include the mediastinum, within the diaphragm, and,

- - - - - - -- - - - - - - - - - ··-- - - · - · -----

Com mon

rarely, below the diaphragm. The arterial supply is from the aorta or a primary branch of the aorta;

15% are supplied

by an artery that arises below the diaphragm. One-fifth of

Rare

Common

4=1

female ratio. More than half of children with extralobar

----- - - -- - · - · - · - · - · - --- - - - -

Other congen ital anomal ies I nfection

bronchopulmonary

foregut malformation. H2

featu res

Arterial su pply Venous d rainage

(esophageal bronchus) with the gastrointestinal tract per· sists; the lesion may then be termed a

these lesions are fed by multiple arteries. The venous drain· age is most often via a systemic vein, typically in the azygos or hemiazygos systems; portal or pulmonary venous con·

asymptomatic patients.38 Transcatheter embolization is an additional nonsurgical therapeutic option that frequently results in complete disappearance of the lesion.39-4 1

nections can also occur.5A3 Extralobar sequestration is typically asymptomatic. Most are detected on routine prenatal sonography or on a chest radiograph obtained of an infant or child for an unrelated indication. A large lesion can cause respira· tory distress in the neonate. The radiographic appearance

Extralobar Sequestration

is easily confused with that of pneumonic consolidation,

An extralobar sequestration results from aberrantly located

and the diagnosis is sometimes first established when CT

mesenchyme that develops apart from the normal lung.

is performed to evaluate a "recurrent" or "nonclearing"

The pathogenesis likely involves abnormal budding of

pneumonia in an older infant or child. In other patients,

the primitive foregut (i.e. , an anomalous or supemumer·

the lesion is detected during the diagnostic workup of an

ary lung bud). Therefore, this is a type of noncommuni·

associated thoracic or cardiac anomaly. Rarely, the lesion

eating bronchopulmonary foregut malformation, as is

produces a symptomatic left-to-right shunt. Congenital ten·

bronchogenic cyst. Although there is no communication

sion hydrothorax caused by torsion of a sequestration has

with the tracheobronchial tree, bronchial atresia is not the

been reported.44·45

primary embryonic event in this anomaly. Persistence of

Extralobar sequestration can be detected prenatally

primitive splanchnic arteries that supply the foregut dur·

with sonography or MR as a solid well-defined triangular

ing fetal development leads to systemic arterial supply of

mass in the lower aspect of the thorax, usually on the left.

the sequestration. The mass contains dilated bronchioles,

The complex character of the lesion results in a hyperechoic

alveoli and subpleural lymphatic vessels. The original con·

appearance on sonography. The differential diagnosis

nection with the foregut disappears or regresses to form

includes various other congenital lung lesions

a fibrous pedicle. Occasionally, a patent communication

With MR. the lesion produces greater signal intensity than

(Table 1 ·3) .

Table 1-3. Echogenic Lu ng Masses on Prenatal Sonography48 Lesion

Sonogra p h i c a p peara n ce

Congenital cystic adenomatoid malformation B ronchopul monary seq uestration B ronchogenic cyst

Cystic and solid; someti mes spontaneous resol ution Solid, ± small cysts; sometimes spontaneous resol ution U n i locu lar cyst; two-thi rds in middle or posterior med iastin u m, one-thi rd in lung I ntrathoracic extension of bowel or viscera M ediasti nal mass Enlarged, hyperechoic lobe or segment

Congenital diaphragmatic hernia Thoracic neuroblastoma Tracheal or bronch ial atresia

--- ·

· - - - · - · - - - · - - - - - - - - -- - - -- - - - -

·----- - · - - - · - · - · - · · · · - · · · · · · · -- - ·

------

Chapter 1 Deve l o p m ental A b n o r m a l ities of the L u n gs a n d D i a p h ragm 1 1 lung o n T2-weighted images . Cystic areas are sometimes visible. If a systemic feeding artery can be visualized, this finding is helpful in confirming the diagnosis. In 6% to 10% of cases, a pleural effusion accompanies the lesion; this may be a result of dilated subpleural lymphatics or torsion around the connecting vasculature. Rarely, a large pleural effusion leads to compression of the vena cava and heart, causing fetal hydrops ; this can be treated with in utero drainage. Partial or complete spontaneous regres­ sion of extralobar sequestrations is common during fetal life; approximately three-quarters of these lesions undergo relative decrease in size in utero. The fetus with suspected sequestration should be carefully evaluated for potential accompanying anomalies.3 4 ·46·47 In the neonate, the sonographic appearance of an extralobar sequestration is that of an echogenic mass, usu­ ally located adjacent to the diaphragm. The degree of sono­ graphic heterogeneity of the lesion varies between patients. Rarely, small hyperechoic foci are present because of collat­

eral air drift. An additional rare pattern is that of multiple,

small, fluid-fille d cysts. Sonography of the affected neonate sometimes allows visualization of an anomalous supply­ ing artery arising from the aorta. An attempt should also be made to demonstrate the pattern of venous drainage. Enlargement of the azygos and hemiazygos vessels can occur in these infants .

Intralobar Sequestration Intralobar sequestration is a form of bronchial atresia in which there is systemic arterial supply to the involved por­ tion of the lung. Langston terms this as

with systemic vascular connection.

bronchial atresia

The blood supply of an

intralobar sequestration is from the thoracic or abdomi­ nal segments of the aorta in 75% of instances, and other thoracic systemic vessels in 25%. Potential supplying arter­ ies include the celiac, splenic, intercostal, subclavian, and coronary arteries . Venous drainage is often through the pulmonary veins. As with isolated bronchial atresia, paren­ chymal maldevelopment similar to the small cyst type of cystic adenomatoid malformation can occur with intralobar sequestration.'2·5'-54 As compared to the extralobar type, intralobar seques­ tration usually presents later in childhood. Most patients have manifestations of recurrent or persistent pulmonary infection. Infection is much more common with intralobar sequestration than with the extralobar type. Hemoptysis may occur. Rarely, there are signs of congestive failure because of shunting through the lesion. Hemothorax caused by infarction of an intralobar sequestration has been reported. An intralobar sequestration is usually visualized on standard chest radiographs as a soft-tissue density lung mass with smooth or lobulated margins. It is most often located in the basilar portion of the lower lobe

( Figure 1 -6) .

Other potential imaging findings include bronchiectasis,

Extralobar Pu l monary Sequestration Pathology

Dysplastic lung No bronch ial tree com m u n ication Persistent s planchnic arteries

Rad iology

Soft-tissue mass Airless

atelectasis, mediastinal shift, and prominence of the ipsi­ lateral pulmonary hilum. In some patients, suggestive findings of a sequestration are recurrent lower-lobe pneu­ monias or the presence of a rounded consolidation that does not clear completely with antibiotic therapy. 5 '· 55 The computed tomographic appearance of intralo­ bar sequestration is variable. Potential findings include a

Systemic arterial su pply

homogeneous soft-tissue mass, a cystic lesion containing air or fluid, focal emphysema with surrounding solid tis­ sue, or a hypervascular focus of lung tissue

(Figure 1 -7) .

Calcifications are occasionally present. The anomalous sys­ The pathologic anatomy of extralobar sequestration i s optimally demonstrated with helical CT or M R I . The hall­ mark feature is at least one large systemic artery supplying the lung "mass . " With CT, the lesion is typically homoge­ neous ; occasionally, there are internal cysts. The margins are relatively well defined, and may be lobulated. Adjacent atelectatic lung sometimes obscures the borders , however.

temic vascular supply and the pathway of venous drainage are demonstrable with helical CT, MR angiography, or cath­ eter angiography

( Figure 1 -8) .

The characteristic venous

drainage of an intralobar sequestration is via pulmonary veins rather than systemic veins; however, this finding alone does not provide accurate distinction from an extralo­ bar sequestration. 5 '· 54-57

No air is present within the mass unless there is superim­ posed infection or a connection with the gastrointestinal system.42 ·49 In those unusual instances of sequestration in which

Congen ital Cystic Adenomatoid Malformation

there is a patent communication with the gastrointestinal

Congenital cystic adenomatoid malformation

system, air bronchograms may be visible within the lesion.

tal pulmonary airway malformation)

(congeni­

is a complex devel­

CT shows the communication as an air-filled tubular struc­

opmental lesion composed of cystic and solid dysplastic

ture extending toward the esophagus. An upper GI contrast

pulmonary tis sue. The lesion has hamartomatous char­

study usually allows definitive demonstration of an esopha­

acteristics pathologically. It consists of immature lung

geal bronchus.5°

tissue, with proliferation of bronchioles that form cysts

12 Part 1 The Thorax components of congenital cystic adenomatoid malfor­ mation suggests that there is an arrest or disruption of normal branching morphogenesis, which causes an over­ growth of respiratory epithelium. The solid adenomatoid form apparently is embryologically distinct from the more common cystic variety.3 · 5 8 .s9 Congenital cystic adenomatoid malformation accounts for approximately

25% of all congenital lung abnormali­

ties. The prevalence is slightly higher in males than in females . There is equal frequency of occurrence in both lungs. There is a slight predilection for location in the upper lobes; it is uncommon in the right middle lobe. Congenital cystic adenomatoid malformation can occur in association with a pulmonary sequestration; this is sometimes termed a hybrid lesion.6o-6 2 Congenital cystic adenomatoid mal­ formation can also be associated with congenital bronchial atresia. 63 Congenital cystic adenomatoid malformation is classi­ cally divided into

A

3

types, based on the gross and micro­

scopic features) Although there is substantial overlap in the clinical and pathological features of cystic adenomatoid malformation in individual patients, there is utility in con­ sidering the

3

basic types as separate entities . Type I �arge

cyst type) is most common, accounting for approximately

70% of cases. This lesion contains one or more cysts that 2 em in diameter. The cysts communicate with

are at least

adjacent airways, and have some pathologic features of dilated bronchi. There are often adjacent smaller cysts and solid components. Type II (small cyst type) cystic adeno­ matoid malformation contains numerous cysts between

0.5 and 2 em diameter. The cysts are lined by cuboidal to columnar epithelium, and histologically resemble dilated terminal and respiratory bronchioles . This lesion some­ times occurs as a secondary phenomenon because of a localized embryonic airway obstruction; that is, bronchial atresia. The rare type I I I cystic adenomatoid malformation (solid type) is a grossly solid-appearing lesion that contains tiny cysts 8

Figure 1-6 I ntralobar sequestration. A, B. Posteroanterior and lateral chest radiographs show a homogeneous soft tissue-density mass in the posterior basal portion of the left lung. Air bronchograms are lacking. The patient had no symptoms of pneumonia, and follow-up radiographs (not shown) demonstrated persistence of the opacity.

( 66 Chest radiographs of unilateral diaphragmatic paraly­ sis usually show elevation of the involved hemidiaphragm. Sonography and fluoroscopy show elevation of the affected hemidiaphragm and paradoxical motion during respira­ tion. Phrenic nerve paralysis related to birth injury often resolves spontaneously during the first few months of life. Persistent abnormality can be treated surgically with plication of the hemidiaphragm. Autologous nerve trans­ plantation is an additional therapeutic option for select patients.'67-'6 9

6. Raynor AC, Capp M P , Sealy WC. Lobar emphysema of infancy. Diagnosis, treatment, and etiological aspects. Ann Thorae Surg. 1967;4(4):374-385. 7· Schwartz D S , Reyes-Mugica M , Keller M S . Imaging o f surgical diseases of the newborn chest. Intrapleural mass lesions.

Radial Clin North Am. 1999:37(6) :1067-1078, v. 8. Ghaye B , Szapiro D, Fanchamps J-M, Dondelinger RF. Congenital bronchial abnormalities revisited. Radiographies. 2001;21(1) :105-119 . 9· Keslar P, Newman B, Oh KS. Radiographic manifestations of anomalies of the lung. Radiol Clin North Am. 1991;29(2): 255-270. 10. Panicek DM, Heitzman ER, Randall PA, et al. The continuum of pulmonary developmental anomalies. Radiographies. 1987;7(4):747-'772. 11. Bush A. Congenital lung disease: a plea for clear thinking and clear nomenclatnre. Pediatr Pulmonol. 2001;32(4) :328-337· 12. Langston C. New concepts in the pathology of congenital lung malformations. Semin Pediatr Surg. 2oop2(1):17-37· 13- Cunningham ML, Mann N. Pulmonary agenesis: a predictor of ipsilateral malformations. Am 1 Med Genet. 1997;70(4): 391-398. 14· Berrocal T, Madrid C, Novo S , e t a l . Congenital anomalies o f

Hepatic-Pul monary Fusion

the tracheobronchial tree, lung, a n d mediastinum: embryology,

Hepatic-pulmonary fusion is a rare anomaly in which supradiaphragmatic hepatic tissue is fused to a hypoplas­ tic right lung through a diaphragmatic defect. Radiographs of patients with hepatic-pulmonary fusion show displace­ ment of the liver into the right hemithorax. The mediasti­ nal structures either remain at the midline, or are shifted to the right. This appearance, while not pathognomonic, is in contradistinction to the contralateral shift that typi­ cally occurs with congenital diaphragmatic hernia, and serves to raise the possibility of this diagnosis. The radio­ graphic appearance is usually indistinguishable from that of primary right lung hypoplasia with an intact hemidia­ phragm. Further evaluation can be performed with M R, which confirms the displacement of liver into the chest. MR shows dysplastic atelectatic lung adherent to the liver as a band of enhancing tissue along the dome of the liver, with venous drainage into the inferior vena cava.'7°·'7'

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Radiology. 2004;232(3) :767-772. 20. Vintzileos AM, Campbell W A , Rodis J F , et al. Comparison of six different ultrasonographic methods for predicting lethal fetal pulmonary hypoplasia.

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2. Stovin PG. Early lung development. Thorax. 1985;40(6): 401-404. 3· Stocker JT, Madewell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum.

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Bioi Neonate. 1998;74(5) :323-336. 157. Sokol ) . Bohn D, Lacro RV, et al. Fetal pulmonary artery

Pediatr

Surg. 1999;34(11) :1740-1742. 156. Thebaud B , Mercier J C , Dinh-Xuan AT. Congenital diaphragmatic hernia. A cause of persistent pulmonary

Pediatr Surg. 1998;33 (4): 6 02-605.

168. Zifko U , Hartmann M , Girsch W, et a!. Diaphragmatic paresis in newborns due to phrenic nerve injury. Neuropediatrics. 199s;z6(5):281-284. 169. Langer JC, Filler RM, Coles ) . Edmonds JF. Plication of the diaphragm for infants and young children with phrenic nerve palsy. ]

Pediatr Surg. 1988;23(8) :74 9--751.

170. Keller RL, Aaroz PA, Hawgood S , Higgins CB. M R imaging of hepatic pulmonary fusion in neonates. AJR Am] Roentgenol. 2003;180(2) :438-440. 171. Slovis TL , Farmer DL, Berdon WE, et al. Hepatic pulmonary fusion in neonates. A]R Am] Roentgenol. 2000;174(1) : 22 9-233·

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CH A P T E R

2

Neonatal Lung Disease

TRANSI ENT TACHYP N EA OF TH E N EWBORN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

45

PULMONARY I NTERSTITIAL G LYCOG ENOSIS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

64

RESPI RATORY DISTRESS SYNDRO M E . . .

48

CH RONIC PNEUMONITIS OF I N FANCY . . .

65

N E U RO E N DOCRI N E CELL HYPERPLASIA OF I N FANCY . . . . . . . . . . . . . . . . . . . . . . .

65

65

BRONCHOPU LMONARY DYSPLASIA (CH RO N I C LU NG DISEASE OF I N FANCY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

52

I M MATURE LUNG SYNDRO M E . . . . . . . . . . . . . . . . .

56

CONGEN ITAL SU RFACTANT P ROTEI N B DEFICI E NCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I NTERSTITIAL PULMONARY FIBROSIS. . . .

57

N EONATAL P N E U M O N IA . . . . . . . . . . . . . . . . . . . . . . . . . . . .

65

G roup B Streptococcus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

66

Chlamydia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

66

Listeria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

Varicella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

Syp h i l i s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

Congen ital Tu bercu losis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

M ECO N I U M ASPI RATION SYNDRO M E. . . . .

58

PERSISTENT PU LMONARY HYPERTENSION OF T H E N EWBORN . . . . . .

59

CONGEN ITAL ALVEOLAR CAP I L LARY DYSP LASIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6o

PULMONARY H E M ORRHAG E . . . . . . . . . . . . . . . . . . . .

6o

ASPI RATION P N EU M O N ITIS. . . . . . . . . . . . . . . . . . . . . .

A I R LEAK IN N EO NATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

61

Pneu mothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

ERYT H ROBLASTOSIS FETALIS . . . . . . . . . . . . . . . . . .

62

Pneumomediasti n u m and Pneumopericard i u m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

I N FANT OF A DIABETIC MOT H E R . . . . . . . . . . .

62

Pul monary I nterstitial E m p hysema . . . . . . . . . . . .

70

N EONATAL POLYCYTH E M IA . . . . . . . . . . . . . . . . . . . . . .

63

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

71

T RANSIENT TACHYPNEA OF T HE NEWBORN

with an increased risk for transient tachypnea include pro­ longed labor, cesarean section, narcotic depression, mater­ nal asthma, and maternal diabetes. 2·3 Typically, the infant is

The clinical syndrome of transient tachypnea of the new­

clinically normal immediately after delivery, but becomes

born (TIN) is caused by persistence of fetal lung fluid in

tachypneic over the next few hours. Despite the signs of

the neonate. Other terms for this syndrome include

mild to moderate respiratory distress, there is usually nor­

wet lung disease, transient respiratory distress of the newborn, and neonatal retained fluid syndrome. Transient tachypnea is the

mal oxygenation. As the name indicates,

TIN is typically a

self-limited process.

most common of the various causes of respiratory distress

In the fetus , lung fluid is produced by type I I pneu­

2-1 ) .' Factors that are associated

mocytes . This fluid is cleared from the neonatal lung by

in term newborns

(Table

45

46 Part

1

T h e Thorax

Table 2-1 . Causes ofTachypnea in the N eonate

Respi ratory

Transient tachypnea of the newborn Pneumothorax ' Tracheal obstruction Phrenic nerve i nj u ry Pu l monary lym phangiectasia Pneumonia !···· . M econ i u m aspiration syndrome Cardiac Congen ital heart disease Paroxysmal tachycardia Central nervous Trau majbirth asphyxia system Oversedation N a rcotic withdrawal · Hypervolemia M etabolic ' Hypoxiajacidosis Hypoglycemia Hypocalcem ia M aternal diabetes Hematological Polycythemia Severe anemia ·

In most affected infants, the tachypnea peaks between

6 and 3 6 hours after birth and then slowly returns to nor­

mal by the third or fourth day. Pneumothorax can compli­ cate the clinical course

(Figure

2-1 ) . Physical examination

may reveal an overexpanded chest; the lungs are typically clear to auscultation. Unlike respiratory distress syndrome, there are no substantial abnormalities on blood gas analy­ sis or blood pH assesment. 6 Some infants with transient tachypnea follow a more prolonged course than described above, and sometimes

i···

A capillary resorption, lymphatic resorption, and expulsion via the airways. The pathophysiology of transient tachy­ pnea involves compromised clearance of fetal lung fluid.4 The association with cesarean section delivery presum­ ably relates to the lack of normal physiological expulsion of fluid from the lungs by the extrinsic compression that occurs during vaginal delivery. These infants may also have a diminished catecholamine surge - a result of lack of exposure to all stages of labor. There is evidence that dimin­

ished �-adrenergic responsiveness may be a factor in some affected neonates. Proper function of the �-adrenergic response system is important for the successful transition of the neonate from fetal life to breathing air. Other condi­ tions that result in diminished clearance of lung fluid in the newborn are hypoalbuminemia, elevated pulmonary venous pressure, diminished respiratory drive (sedation), endothelial cell damage (oxygen toxicity), and bronchial obstruction. 5 The clinical findings in neonates with transient tachy­ pnea include a rapid respiratory rate, mild retractions, and expiratory grunting. Occasionally, there is mild cya­ nosis that is promptly relieved by supplemental oxygen administration. The tachypnea develops within the first

B

Figure 2-1 Transient tachypnea of the newborn. A. An anteroposterior radiograph at 5 hours of age shows faint prominence of interstitial lung markings. Heart size is in the upper limits of normal.

B.

A radiograph obtained the next day,

several hours of life. The respiratory rate is usually nor­

after onset of increased respiratory distress, demonstrates a right

mal for the first hour, with gradual subsequent increase.

tension pneumothorax.

Chapter 2 N eo n atal L u n g D i sease require supplemental oxygen. Some of these infants have evidence of global myocardial dysfunction on echocardiog­ raphy. In severely affected infants, echocardiography shows signs of pulmonary hypertension and biventricular myo­ cardial dysfunction. With classic mild TIN, there is mini­ mal left ventricular overload. Complete clinical recovery is to be expected regardless of the echocardiographic pattern.7 Chest radiographs of neonates with TIN show promi­ nent and ill-defined pulmonary vascular markings, edema­ tous interlobar and interlobular septa, and small pleural effusions (usually with small fluid collections in the coste­ phrenic sulci and interlobar fissures) (Figu re 2-2) . Engorged lymphatics account for at least some of the interstitial opac­ ities. These findings involve both lungs, but frequently are more pronounced on the right. Mild hyperinflation is usu­ ally present. Alveolar opacification is occasionally present early in the course. The heart is normal or only minimally enlarged; the presence of cardiomegaly portends a pro­ longed clinical course.8.9

A

47

Transient Tachypnea of the Newborn Pathology

Rad i o l ogy

Engorged lym phatics

Septal thickening Pleural effusions Prominent i nterstitial markings Hyperi nflation (and tachypnea)

Retained fetal lung fluid I nh ibited gas exchange

There are several important considerations in the radiographic differential diagnosis of TTN . Conditions that can potentially mimic transient tachypnea on the initial chest radiograph include mild respiratory distress syndrome, congestive heart failure, neonatal polycythe­ mia, total anomalous pulmonary venous connection, and primary pulmonary lymphangiectasia. Correlation of the

B

Figure 2-2 Transient tachypnea of the newborn; three different infants. A. This 8-hour-old infant with moderate tachypnea has mild hyperinflation and subtle prominence of peribronchial markings. The heart is in the upper limits of normal in size.

B. This markedly tachypneic 12 -hour-old infant has severe hyperinflation, diffuse interstitial opacities, and a small, right pleural effusion. Dilated lymphatics contribute to the perihilar opacities. C. There is no substantial hyperinflation in this 2-hour­ old infant. Faint alveolar opacification accompanies prominent peribronchial markings and indistinct pulmonary vessels . There

c

is a trace of fluid in the minor fissure.

48 Part 1 T h e Thorax findings on serial radiographs with the clinical factors allows a correct diagnosis in most instances . When present, the observation o f hyperinflation i s helpful i n differentiating transient tachypnea from early or mild respiratory distress syndrome. Respiratory dis­ tress syndrome is typically associated with generalized underaeration of the lungs, in the absence of mechanical ventilation. Because of the slow clearance of pulmonary fluid by premature infants, imaging during the first 2 hours of life of an infant with mild respiratory distress syndrome shows diffuse alveolar fluid and normal lung volumes. A more radiographically distinct pattern of hypoaeration and granular parenchymal lung densities usually is present by 4 to 6 hours of age. Occasionally, infants with transient tachypnea do not have evidence of hyperaeration, and additional serial radiographs are necessary to demonstrate the clearance of the lung fluid. A lack of hyperaeration is usually because of a superim­ posed abnormality that causes respiratory depression, such as sedation, hypoxia, hypothermia, or central ner­ vous system pathology. Because mild cardiomegaly can be one of the radio­ graphic features of TIN, the appearance can be confused with that of congestive heart failure. The neonate with congenital heart disease of sufficient severity to result in pulmonary vascular congestion and edema usually has distinct cardiomegaly, while transient tachypnea results in borderline or minimal cardiac enlargement in combi­ nation with prominent linear vascular markings radiating from the hila. Infants with transient tachypnea also have normal blood gas values and improve promptly with oxy­ gen therapy.

RESPIRATORY DISTRESS SYNDROME Neonatal respiratory distress syndrome (RDS) is a pul­ monary abnormality of premature infants in which there is poor aeration of alveoli, predominantly a result of sur­ factant deficiency. Other terms for this disorder include hyaline membrane disease and surfactant deficiency disease. Surfactant deficiency is the most common serious pulmo­ nary abnormality of premature infants. The prevalence of RDS is inversely proportional to the gestational age and birth weight. Between 6o% and 8o% of infants born at less than 28 weeks of gestational age develop R D S , whereas only 15% to 30% of those born between 32 and 36 weeks of gestational age are affected. Additional risk factors for this complication in premature infants include precipitous delivery, asphyxia, maternal diabetes, multifetal pregnan­ cies, cold stress, and a history of RDS in siblings . Males are affected more frequently than females. Genetic altera­ tions in surfactant proteins (S P-A, SP-B) influence the risk for RDS .10 The primary factor in the pathophysiology of RDS is deficiency of surfactant. Pulmonary surfactant reduces the surface tension of the alveolar air-liquid interface.U This

serves to provide mechanical stability of the alveoli and pre­ vent atelectasis. Synthesis of surfactant takes place within alveolar epithelial type II cells. The largest component of surfactant (>so%) is the surface tension reducing agent dipalrnitoyl phosphatidylcholine. The other components include unsaturated phosphatidylcholines, phosphatidyl­ glycerol, cholesterol, and protein; the functions of these components in surfactant are unknown. The metabolism of surfactant is under hormonal control, and appears to involve interplay between �-adrenergic agonists, cyclic ade­ nosine monophosphate, and prostaglandins. In neonatal RDS, the produced surfactant is abnormal with respect to its chemical and physical properties.l2 The high alveolar surface tension that occurs in neo­ nates with deficient surfactant results in a propensity for collapse of small air spaces at end-expiration. Additional factors include the small size of the respiratory units and the compliant chest wall of the ill premature infant. The alveoli within the atelectatic lung are perfused but not ven­ tilated, resulting in hypoxia. Small tidal volumes, increased physiological dead space and poor lung compliance result in hypercarbia. Hypercarbia, hypoxia, and acidosis cause pulmonary arterial vasoconstriction and secondary right­ to-left shunting through the foramen ovale and ductus arteriosus. The diminished pulmonary blood flow leads to ischemic injury of alveolar cells, including the surfactant­ producing type I I pneumocytes. This process results in the accumulation of proteinaceous material within the alveolar spaces. Epithelial cell damage related to high oxygen con­ centrations in ventilated lungs is an additional factor that interferes with surfactant synthesis. The clinical presentation of RDS typically occurs within minutes ofbirth, with tachypnea, grunting, retrac­ tions, and nasal flaring. Cyanosis and dyspnea are pro­ gressive and respond poorly to oxygen administration. The severity of the clinical manifestations typically peaks at approximately 3 days, after which there is gradual improvement. The risk for mortality during the acute phase of the illness is primarily related to complications from air leaks, pulmonary hemorrhage, and intracranial hemorrhage.

Respiratory Distress Syndrome Pathology

Rad iology

Alveolar atelectasis Collapsed alveoli, i nterstitial flu id, bronchiolar distention

Underaeration Fi ne, reticular and granu lar l u n g opacities

Radiographic manifestations of RD S are usually pres­ ent on images of the symptomatic neonate obtained soon after birth. Rarely, initial radiographs are normal and the characteristic radiographic findings do not develop until

Chapter 2 N e o n atal L u n g D i sease 49 several hours later. This disorder is essentially excluded when a symptomatic neonate has a normal chest radio­ graph obtained beyond 8 hours of life. Radiographs of the neonate with RDS typically show fine reticular and granu­ lar lung opacities, and global underaeration (Figures 2-3 and 2-4) . In some infants, there is a ground-glass pattern of lung opacification. The abnormality involves the entire lung, but is frequently more prominent at the bases. This

radiographic pattern is predominantly a result of alveo­ lar atelectasis. Air bronchograms may be lacking in the early stages of the process (grade 1 disease) . At this stage, the alveolar atelectasis preferentially involves the poste­ rior (dependent) portions of the lungs. With progression, the reticular and granular opacities become more promi­ nent, because of coalescence of smaller atelectatic areas, and scattered air bronchograms become visible (grade 2

A

B

c

0

Figure 2-3 Respiratory distress syndrome; radiographs of multiple infants. A. First day of life; 2 6 weeks' gestation. There are diffuse fine granular opacities and mild underaeration. B. Second day of life; 26 weeks' gestation. There is marked pulmonary underaeration

despite mechanical ventilation. C. Second day of life; 27 weeks'

gestation. There are diffuse ground glass and granular opacities. Pulmonary underaeration is asynunetric.

D. Second day of life;

28 weeks' gestation. There are diffuse fine opacities in mildly underinflated lungs. Air bronchograms are present centrally.

so Part 1 The Th orax

A

Figure 2-4 Respiratory distress syndrome. An enlarged image of a 1-day-old infant's chest radiograph shows the characteristic fine reticulonodular pattern.

disease) . Progressive increase in opacification occurs in the anterior aspects of the lrmgs , resulting in obscuration of the cardiac silhouette. Because many of the larger bronchi are located in the mid and anterior aspects of the lrmgs, air bronchograms are more pronormced during this phase (grade 3 disease) . In severely affected infants , the lrmgs are poorly inflated, diffusely opacified, and contain prominent air bronchograms (grade 4 disease) . Therapy for children with mild manifestations of R D S consists of supportive care. Acidosis, hypoxia, hypotension, and hypothermia are managed medically. Supplemental oxygen is administered. Infants with severe R D S , and those who develop complications , usu­ ally require assisted mechanical ventilation. Exogenous surfactant administration and antenatal corticosteroid therapy have a maj or impact on improving survival and morbidity in R D S .'3 Therapy influences the radiographic findings in children with R D S . With tracheal intubation and posi­ tive pressure ventilation, the lungs become hyperin­ flated. The granular parenchymal lrmg opacities become less apparent, and peripheral air bronchograms become more pronormced. Radiographic improvement occurs in the great maj ority of infants treated with exogenous sur­ factant ( Figure 2-5) . In some instances, the radiographic clearing is asymmetric or nonuniform. Improvement is

B

Figure 2-5 Respiratory distress syndrome; surfactant therapy. A. There are typical diffuse granular lung opacities in this !·day­ old premature infant. B. After intubation and surfactant therapy, substantial interval clearing has occurred on this image obtained 2

days later.

sometimes more rapid in the right lung, possibly as a consequence of facilitation of surfactant delivery to the right lung because of the orientation of the right main bronchus ( Figure 2-6) . Unilateral improvement in lung aeration can lead to contralateral mediastinal shift. However, asymmetry of lung opacities in these children can also result from a pneumothorax or pneumomedi­ astinum related to mechanical ventilation. Pulmonary hemorrhage is a rare complication of surfactant therapy. Infants with pulmonary hemorrhage typically have acute respiratory decompensation, blood-tinged tracheal secre­ tions, and abrupt onset of dense airspace consolidation on radiographs .'4 Potential complications in children with R D S include those related to the disease itself and those related to medi­ cal treatment. These infants are at risk for fluid overload, pulmonary edema, patent ductus arteriosus, pulmonary

Chapter 2 N eo n atal L u n g D i sease 51

Figure 2-7 Respiratory distress syndrome and patent ductus arteriosus. Figure 2-6 Respiratory distress syndrome; surfactant therapy.

This 10-day-old premature infant has diffuse pulmonary edema.

An image obtained several hours after introduction of surfactant via the endotracheal tube shows an asymmetric response, presumably because of preferential passage of the medication into the right main bronchus.

hemorrhage, superimposed infection, and barotrauma. With the exception of barotrauma, the radiographic find­ ings with the other entities are often nonspecific and dif­ ficult to differentiate from lung opacification because of the underlying surfactant deficiency. A common clue to the presence of a complicating condition is failure of radio­ graphic improvement by the third or fourth day of life. Excessive right-to-left shunting through a patent ductus arteriosus occurs in some infants with RD S . The delayed closure of the ductus is related to hypoxia, acido­ sis, elevated pulmonary pressure, systemic hypotension, and local release of prostaglandins. Left-to-right shunt­ ing through a patent ductus can occur as the acute phase of RDS resolves and the pulmonary vascular resistance decreases. This left-to-right shunting can lead to left ven­ tricular volume overload and pulmonary edema ( Figure 2-7) . Spontaneous closure of the ductus frequently occurs in response to supportive medical therapy. Pharmacological closure can be induced by the use of indomethacin, which inhibits prostaglandin synthesis. Patients who fail medical therapy are candidates for surgical closure. Air leaks caused by positive-pressure ventilation and oxygen therapy can occur in infants with RDS. Rupture at the level of the terminal bronchioles and terminal air sacs leads to leakage of air into the intralobar septa, producing pulmo­ nary interstitial emphysema. The radiographic indicator of this complication is the presence of fi ne linear interstitial lucencies, which may involve a single lobe, one lung, or both lungs (Figu re 2-8) . With increased distention, air-filled cysts

Figure 2-8 Pulmonary interstitial emphysema. There are linear air collections in the interstitium.

52 Part 1 The Thorax

Figure 2-9 Air leak complicating respiratory distress syndrome.

cocci in gastric or tracheal aspirates , a history of mater­ nal colonization, the identification of streptococcal anti­ gen within the urine, and marked neutropenia. Transient tachypnea is distinguished from RDS by its short and mild clinical course, responsiveness to supplemental oxygen administration, and pulmonary overaeration on chest radiographs . Congenital alveolar proteinosis may have a clinical and radiographic appearance that is indis­ tinguishable from that of severe RDS. Diffuse pulmonary hemorrhage can mimic the radiographic appearance of RD S ; this diagnosis should be considered if there are pleural effusions. Pulmonary hemorrhage can also occur as a complication of surfactant therapy for R D S . There is often clinical evidence of hemorrhage in these infants ­ that is, frothy blood-tinged fluid in the endotracheal tube. Infants of diabetic mothers , particularly those with severe hypoglycemia, sometimes have radiographic findings similar to those of RD S , with bilateral reticular densities; helpful differentiating features include cardiomegaly and hepatosplenomegaly. Pulmonary lymphangiectasia that presents in the newborn usually results in diffuse ground-glass opacities and bilateral pleural effusions .

There is extensive pneumomediastinum, with extension into the neck and peritoneal space. The lungs are poorly inflated and are diffus ely opacified because of the underlying surfactant deficiency.

may become visible. The lungs are hyperinfl.ated. Air leak can also result in pneumomediastinum, pneumothorax, or pneumopericardium (Figures 2-9 and 2-10) . Group B streptococcal sepsis is a n important consid­ eration in the differential diagnosis of RD S . Indicators of this diagnosis include the presence of Gram-positive

Figure 2-10 Tension pneumothorax. There are bilateral pneumothoraces in this 3-day-old with respiratory distress syndrome. Chest cavity expansion and lung volume loss indicate high pressure in the air-filled pleural spaces.

BRONCHOPULMONARY DYSPLASIA (CHRONIC LUNG D ISEASE OF INFANCY) Bronchopulmonary dysplasia (BPD) is a distinct clini­ cal entity that occurs as a therapy-related complication in infants who are undergoing treatment for respira­ tory failure. The features include pulmonary fibrosis, nonuniform aeration, and respiratory insufficiency. Bronchopulmonary dysplasia can be defined as the triad of oxygen dependence, characteristic radiographic findings, and respiratory symptoms that persist beyond 28 days of life in an infant who suffered respiratory failure in the perinatal period. An alternative clinical definition is oxy­ gen dependency in a premature infant at an age greater than 36 weeks after conception. More recently introduced terms for B P D are chronic lung disease of infancy and chronic lung disease of prematurity. The pathological fea­ tures of B P D include manifestations of alveolar maldevel­ opment, with or without areas of pulmonary fibrosis.•s-•7 Although most commonly associated with RDS (respi­ ratory distress syndrome) , B P D can also occur with other conditions that are treated with supplemental oxygen therapy and mechanical ventilation, including meconium aspiration syndrome, immature lung syndrome, congeni­ tal heart disease, and neonatal pneumonia. Risk factors for BPD include low gestational age, male sex, patent ductus arteriosus, radiographic evidence of pulmonary intersti­ tial emphysema, elevated pulmonary artery pressure, and high peak expiratory pressure. Because of advancements in therapy for premature infants, B P D is now uncommon in infants with a gestational age of greater than 30 weeks or a birthweight of greater than 1200 g.

Chapter 2 N e o n atal L u n g D i sease 53 The pathophysiology of B P D involves the response of immature lungs to oxygen toxicity and barotrauma from positive-pressure ventilation. Highly concentrated oxygen is toxic to the pulmonary capillaries and alveo­ lar cells, with tissue injury occurring through the forma­ tion of reactive oxygen intermediates and peroxidation of membrane lipids. Premature infants , who have severely reduced antioxidant defenses, are particularly sensitive to the toxic effects of oxygen. The cellular damage leads to abnormal microvascular permeability, pulmonary edema, and acute necrotizing tracheobronchitis . These effects are intensified by positive-pressure ventilation, which forces oxygen into unventilated acini. Direct lung injury also occurs in the form of barotrauma at the level of the acini and small airways. Inflammation caused by prenatal andjor postnatal infections or antenatal expo­ sure to proinflammatory cytokines in amniotic fluid is a likely contributing factor in most patients . With modern therapeutic techniques, oxygen toxicity and barotrauma have diminished importance in the pathophysiology of B P D . Many of these children apparently have an aberrant response of the immature lung to early air breathing that causes inhibition of acinar and vascular growth.18-2o The lung is affected in a nonuniform fashion in B P D . Local bronchiolar obstruction protects some acini from barotrauma and exposure to concentrated oxygen. These initially protected acini may later become normal when recanalization of the bronchiolar lumen allows aeration, or they may become hyperexpanded. Those acini that are exposed to high pressures and concentrated oxygen typi­ cally go on to develop persistent interstitial fibrosis in the alveolar septa; some of these acini become completely obliterated and permanently nonfunctional. Acini that are distal to partially obstructed bronchioles sustain dam­ age of intermediate severity. Surfactant therapy, however, results in a more uniform pattern of acinar ventilation.

Bronchopulmonary Dysplasia Pathology

Rad i o l ogy

B ronchial/bronchiolar hyperplasia Alveolar coalescence Fi brosis M icroatelectasis

Hyperi nflation Focal hyperlucendes Linear opacities

Northway et al described 4 radiographic stages of B P D . During stage I (2 to 3 days of age) , chest radio­ graphs show manifestations of severe R D S , with diffuse granular lung opacities and prominent central air bron­ chograms . The lungs are underinflated. Stage II occurs between 4 and 10 days of age; the lungs become densely consolidated, with a coarse reticulonodular pattern. Stage I I I occurs over the next 10 days, and is characterized by

Figure 2-11 Bronchopulmonary dysplasia. This 2-month-old infant had respiratory distress syndrome as a neonate. The lungs are hyperinflated. There are multiple air-filled cysts with intervening coarse linear and peribronchial opacities.

the onset of hyperinflation and the appearance of numer­ ous air-filled cysts of various sizes. Stage IV occurs at 20 to 30 days of age and is characterized by diffuse emphysema, with interspersed strand-like densities and areas of atelectasis (Figure 2-1 1 ) . Cardiomegaly and cor pulmonale may develop during this stage. Because of advances in therapy, the classic progressive stages of B P D described by Northway et al are rarely identi­ fied in current practice.21 Unlike the classic pathophysiol­ ogy that involved barotrauma and oxygen toxicity, current forms of the condition are predominantly related to imma­ turity, perinatal infection and inflammation, persistent patency of the ductus arteriosus, and disrupted alveolar and capillary development. The most common radiographic finding is the persistence of fine, diffuse, granular opacities in a ventilated infant who fails to exhibit the expected clini­ cal signs of improvement by the third or fourth day of life. Respiratory distress persists in conjunction with hypoxia, hypercarbia, and oxygen dependence. Interstitial emphy­ sema may be noted on radiographs. There is gradual pro­ gression on serial radiographs to a pattern characterized by hyperinflation and numerous small round air filled cys­ tic areas alternating with irre gular opacities ( Figure 2-1 2) . This corresponds to Northway stage IV; however, the find­ ings are usually more symmetrical and the cystic areas are smaller and more uniform than with classic stage IV B P D . Other potential radiographic patterns o f late-phase B P D include generalized overaeration with coarse interstitial

54 Part 1 The Thorax

Figure 2-12 Bronchopulmonary dysplasia. This 6-week-old infant born at a gestational age of 24 weeks has coarse diffuse irregular pulmonary opacities, cystic air collections, and hyperinflation.

opacities and diffuse fine infiltrates without emphysema (Figure 2-13) . The histological features during the pro­ gression from RD S to BPD consist of progressive alveolar coalescence, microatelectasis, interstitial edema, coarse focal basement membrane thickening, and bronchial and bronchiolar mucosal metaplasia and hyperplasia.

Figure 2-13 Bronchopulmonary dysplasia. This 13-week old infant was born at a gestational age of

25 weeks. A radiograph obtained at the time of discharge shows hyperinflation and diffuse coarse interstitial opacities.

The treatment of BPD includes fluid restriction, diuretic therapy, steroid therapy (early in the course) , main­ tenance of adequate oxygenation, nutritional support, and prompt detection and treatment of infection. 22 The most common fatal complications of B P D are right-sided heart failure and viral necrotizing bronchiolitis. Most infants with B P D undergo a slow clinical recovery during the first year of life. Survivors of neonatal BPD often exhibit mani­ festations of chronic pulmonary dysfunction during child­ hood, such as recurrent episodes of coughing, wheezing, dyspnea, and pneumonia. Cardiovascular sequelae can also occur, including pulmonary hypertension, systemic hypertension, left ventricular hypertrophy, and exercise intolerance. 23 A variety of strategies are used to diminish the risk for the development of B P D in premature infants. The treatment of maternal infection, administration of prenatal glucocorticoids, and postnatal surfactant replace­ ment therapy improve survival of preterm infants, but the effectiveness of these interventions in preventing progression to B P D is unclear. Techniques that appear to be effective in mitigating the severity of B P D include the administration of retinol (vitamin A) , the use of high-fre­ quency oscillatory ventilation, early aggressive nutrition, the treatment of a patent ductus arteriosus , and admin­ istration of glucocorticoids. The routine use of gluco­ corticoids is discouraged, however, because of potential neurodevelopmental side effects.22•24 Chest radiographs usually show gradual improve­ ment during the first few years of life in children who survive B P D as infants . The radiographic findings of B P D in the postneonatal period include hyperinflation, focal hyperlucencies , and linear scars ( Figu re 2-14) . Generalized pulmonary interstitial thickening i s a less common finding. The late CT manifestations of B P D include extensive areas o f reduced lung attenuation (the size and number of vessels are reduced) , widespread bronchial wall thickening, and a decreased bronchus-to­ pulmonary-artery ratio (the airways appear of reduced diameter) (Figu re 2-1 5) . Bronchiectasis does not occur. Linear opacities and bullae are sometimes present. A mosaic pattern can occur. Triangular subpleural opacities , with the apices directed centrally, have been described; these may be contiguous with well-defined linear opacities ( Figu re 2-1 6) . Most older children and adults with a history of B P D have residual pulmonary abnormalities identifiable on CT. 25-2 8 Lobar hyperinflation can occur as a complication of B P D . This is termed acquired lobar emphysema or persistent acquired lobar overinjlation. The pathogenesis is multifac­ torial, and includes the effects of barotrauma and oxygen toxicity. An additional factor may be repeated trauma to the bronchial walls by suction catheters , resulting in luminal narrowing by granulation tissue and distal air trapping. The importance of this latter mechanism is supported by the observed predilection for involvement of the right lower and right middle lobes.

Chapter 2 N e o n atal L u n g D i sease 55

A B

Figure 2-14 Bronchopulmonary dysplasia. A. Age 2 months. There are coarse diffuse lung opacities and central areas of scarring. The lungs are hyperinflated.

B.

Age 5 months. There is increased severity of hyperinflation.

Atelectasis and scarring produce parahilar patchy densities.

C. Age 3 years. The lungs are mildly hyperinflated and there are coarse central interstitial opacities and subsegmental areas of

c

A

Figure 2-1 5 Bronchopulmonary dysplasia.

atelectasis f scarring.

....

B

There are multiple areas of lung that have reduced attenuation and reduced vascularity. linear areas of fibrosis are present as well.

56 Part 1 The Thorax immature lung syndrome than in those with RD S . The overall prognosis of immature lung syndrome is poor. The pathophysiology of immature lung syndrome is incompletely understood. Despite the extreme prematurity that is usually associated with this disorder, surfactant is present. This may be a result of the stimulation of early pro­ duction of surfactant in response to fetal stress. The pres­ ence of surfactant likely accounts for the typical delay in the clinical onset of respiratory distress. The surfactant, how­ ever, may be of insufficient quantity or quality to maintain alveolar ventilation. Other possible pathophysiological fac­ tors include fluid overload and thoracic cage insufficiency.

I mmature Lung Syndrome

Figure 2-1 6 Chronic lung disease of infancy (bronchopulmonary dysplasia) . CT of a toddler with a history of prematurity shows triangular subpleural opacities in the right lower lobe that are contiguous with linear opacities.

Acquired lobar emphysema is usually associated with severe neonatal respiratory distress that required prolonged ventilatory support and high peak inspiratory pressures. The time course for the initial development of lobar hyper­ inflation ranges from a few weeks to several months of age. Radiographs show lobar hyperinflation, atelectasis in adjacent lung, and mediastinal shift. The clinical course of acquired lobar emphysema ranges from complete sponta­ neous resolution to persistent severe hyperinflation requir­ ing surgical resection. Successful treatment of severe early onset lobar overaeration with selective intubation and high frequency oscillatory ventilation of the unaffected lung has been reported_> 9-33

Pathology

Rad i o l ogy

Alveolar col lapse, alveolar fluid

Fluffy parahilar opacities

During the early asymptomatic phase of immature lung syndrome , chest radiographs are normal except for pulmonary hypoaeration. The appearance of ill-defined, fluffy parahilar opacities correlates with the develop­ ment of symptomatic respiratory distress ( Figu re 2-1 7) . Unlike RD S , air bronchograms are absent o r minimal ( Figu re 2-1 8) . The radiographic findings usually are relatively stable for 1 to 2 months, after which there is slow dearing of the parenchymal opacities. Air-block

IMMATURE LUNG SYNDROME Immature lung syndrome (chronic pulmonary insufficiency of prematurity) is a respiratory disorder of the newborn that occurs in very small premature infants (birth weight 1 oo days) Cryptogenic organizing pneumonia (BOOP bronchiolitis obliterans organizing 1-.. - -- - -pneumonia) - - -- - - - - - - ------Rad iation fibrosis Lym phoid i nterstitial pneumonitis

I I

During the first few weeks after bone marrow trans­ plantation, patients are severely neutropenic and are sus­ ceptible to pulmonary infections. The most common infecting organisms include various bacteria, Candida, Aspergillus, respiratory syncytial virus, and herpes simplex virus. Opportunistic pathogens account for the majority of serious pulmonary infections in bone marrow transplant patients, with Cytomegalovirus and Aspergillus species being the two most common. Fungi cause the majority of pulmo­ nary infections during the first month after bone marrow transplantation, after which viruses are more common. Recipients of allogeneic transplants have a higher prob­ ability of developing Cytomegalovirus pneumonitis than do those receiving autologous or syngeneic transplants. 5° The most common CT finding in patients with Cytomegalovirus pneumonia is mixed alveolar and intersti­ tial disease. Most often, alveolar disease is the dominant imaging feature. Multiple small nodules can also occur with this infection, but are less common than the consoli­ dative pattern. Invasive Aspergillus infection typically causes nodules, masses, or both. Bone marrow transplantation patients are also at increased risk for bacterial pneumonias, particularly in association with the complications of venoocclusive dis­ ease and chronic graft-versus-host disease. During the first few months after bone marrow transplantation, hos­ pital-acquired Gram-negative bacteria such as Pseudomonas

aeruginosa, Klebsiella pneumoniae, and Enterobacter cloacae are the most common responsible pathogens. Subsequently, community-acquired Gram-positive bacteria predominate, particularly Streptococcus pneumoniaeY As described in "Drugs and Toxins" above, chemother­ apy and bone marrow transplantation can cause noninfec­ tious interstitial or airspace pneumonitis, hypersensitivity pneumonitis, and pulmonary fibrosis (Figure 6-28) . The most common radiographic findings are diffuse reticular or reticulonodular opacities. Children with more severe involvement have diffuse ill-defined airspace consolidation. When alveolar damage predominates, high-resolution CT shows ground-glass opacities. Progression to fibrosis can result in persistent interstitial opacities. Idiopathic pneumonia syndrome (idiopathic interstitial pneumonitis) is a noninfectious diffuse alveolar lung injury that can occur 30 to 180 days after stem cell transplanta­ tion. The pathophysiology is multifactorial: toxic effects of myeloablative conditioning, immunological cell-mediated injury, inflammatory cytokines , and prior pulmonary infec­ tions. The clinical manifestations and radiographic fea­ tures mimic those of infectious pneumonia: dry cough, fever, dyspnea, hypoxemia, and nonlobar infiltrates. High­ resolution CT usually shows airspace consolidation that predominates in the basal regions. Other potential patterns are multifocal reticular opacities, ill-defined nodules , and the crazy-paving pattern. Fatal respiratory failure can occur in these patients. Graft-versus-host disease is an immune reaction in which donor T lymphocytes recognize the recipient's tissue as foreign. Pulmonary involvement (interstitial opacities or nodules) is rare with the acute form of graft-versus-host disease. The lung is affected more frequently with the chronic form, usually as bronchiolitis obliterans (mosaic perfusion, air trapping, and bronchial dilation) or crypto­ genic organizing pneumonia (ground-glass opacities and patchy consolidation) . Diffuse pulmonary calcification is a rare complication of bone marrow transplantation. This can occur as a result of abnormal calcium metabolism or calcium deposition in damaged pulmonary tissue. The major clinical manifesta­ tions are dyspnea and a chronic nonproductive cough. The calcification most often occurs in areas of parenchymal con­ solidation and can appear on chest radiographs as persis­ tent lung opacification. Individual foci of calcification may not be visible on standard radiography. High-resolution CT is diagnosticY

PULMONARY EMBOLISM

Th romboembolism Pulmonary thromboembolism in children most often occurs in association with a predisposing condition, such as deep venous thrombosis, oncological disease, trauma, a central venous catheter, congenital heart disease, a hyperco­ agulable state, or recent surgery. Children with pulmonary

210 Part 1 The Thorax

8

A

Figure 6--28 Noninfectious pneumonitis.

This n-year-old child is 4 months status post bone marrow

transplantation for acute myelogenous leukemia. He presented

with cough and nocturnal hypoxia.

A, B. CT shows

ground-glass

thromboembolism may be asymptomatic or exhibit non­ specific clinical manifestations such as dyspnea, tachy­ pnea, and pleuritic chest pain.53-55 If pulmonary thromboembolism does not result in lung infarction, chest radiographs are usually normal. Occasionally, the affected portion of the lung is oligemic. Enlargement of the ipsilateral pulmonary artery can occur. With infarction, pulmonary consolidation occurs. Although uncommon, a somewhat characteristic cone-shaped pleu­ ral based pattern of consolidation is sometimes present. A small pleural effusion is common in patients with pulmo­ nary infarction. Dynamic contrast-enhanced CT allows visualization of an embolus as a filling defect within a pulmonary artery (Figure 6-29) - Peripheral to the embolism, there may be consolidation that has diminished contrast enhancement due to the embolic vascular obstruction. The sensitivity of helical CT for the diagnosis of pulmonary embolism is greater than 90%. Pulmonary embolism can also be diag­ nosed with angiography or ventilation-perfusion scintigra­ phy. The imaging evaluation for the source of pulmonary embolism can be performed with sonography, venography, or contrast-enhanced CT.5 6-59 The clinical and radiographic differentiation between patients with chronic or recurrent pulmonary thromboem­ bolism and those with acute pulmonary embolism is essen­ tial. as the therapeutic approaches are quite different for these two groups. Computed tomographic signs of chronic pulmonary embolism include a crescent-shaped throm­ bus adhering to the arterial wall, a thrombus containing

opacities, patchy peripheral consolidation, and atelectasis, with most prominent involvement in the left lower lobe.

A lung

biopsy demonstrated interstitial fibrosis, intraalveolar edema, alveolar macrophages, and mild acute bronchiolar-alveolitis.

calcifications, a centrally recanalized thrombus, bands, webs, poststenotic dilation, and a mosaic perfusion pat­ tern. CT signs of pulmonary hypertension in these patients include enlargement of the main pulmonary artery, vas­ cular tortuosity, and enlargement of the right ventricle. In some patients with chronic embolism, dilated bronchial

Figure 6--29 Pulmonary thromboembolism. (arrow) in the left pulmonary artery on this contrast-enhanced CT image.

There is a large filling defect

Chapter 6 P u l mo n a ry Tra u m a , S u rgery, a n d Toxi n s 21 1 arteries are visible on CT; this finding does not occur with acute pulmonary embolism. Normal bronchial arteries are

usually too small to be visualized on CT. Go

Fat Embolism Pulmonary fat embolism can occur following bone marrow infarcts in sickle cell patients and in trauma patients with fractures. Fat droplets originating from the marrow pass into the venous system and lodge in capillaries ofthe lungs, brain, and other organs. The clinical manifestations include dyspnea, cyanosis, cough, fever, tachycardia, central ner­ vous system abnormalities, and skin petechiae. The symp­ toms usually do not develop until 1 to

2 days after the injury.

Radiographs are normal in many patients with labora­ tory evidence of fat embolism. With more severe involve­ ment,

radiographs

typically

show

extensive

airspace

consolidation as a result of alveolar hemorrhage and edema. The findings are usually similar to those of acute respira­ tory distress syndrome. The peripheral aspects of the lungs

A

are often most markedly involved. Pleural effusion does not occur or is small. Some patients have a predominantly interstitial pattern of lung opacification. The CT findings of fat embolism are also variable: areas of consolidation, interlobular septal thickening, ground-glass opacities , and/ or nodules

(Figure 6-30). 6 1

Septic Embolization Septic embolization of the lung occurs from a distant s ource of infection, such as an infected venous cath­ eter, pacemaker lead, vascular graft, or prosthetic heart valve . This complication may also occur in children with osteomyelitis. Pulmonary septic embolism is a common

B

complication of Lemierre syndrome (septic thrombo­ phlebitis of the internal j ugular vein caused by bacterial pharyngitis) . The radiographic features

of septic

embolization

typically consist of multiple nodular or peripheral wedge­ shaped opacities. Cavitation can occur; this is optimally detected with CT

(Figu re 6-31 ) .

CT sometimes shows the

nodule or focal consolidation to be located at the tip of a pul­ monary vessel; this is the "feeding vessel sign." However, high-resolution CT images usually show the apparent feed­ ing vessel to course around the nodule. In instances where a vessel actually communicates with the nodule, it usually is a pulmonary vein. Imaging evaluation of the neck is indi­ cated for most patients with suspected septic embolization to assess for an underlying septic thrombophlebitis of the internal jugular vein.6 2

c

Figure 6-30 Fat embolism.

A A posteroanterior chest radiograph of a teenage boy with

CHYLOT HORAX Chylothorax indicates the abnormal accumulation oflymph in the pleural space. Chylothorax occurs as a primary dis­ ease in neonates and as an iatrogenic or traumatic condi­ tion in older infants and children. Inadvertent surgical

dyspnea 2 days after a femur fracture shows mixed airspace opacities and multiple ill-defined nodules bilaterally.

B, C.

Contrast-enhanced CT images demonstrate bilateral interstitial opacities, patchy areas of consolidation, and ill-defined nodules. There is a focus of peripheral airspace consolidation in the left lower lobe.

212 Part 1 The Thorax

Figure 6---3 2 Primary chylothorax. A chest radiograph of an infant with respiratory distress shows homogeneous opacification of the left hemithorax. There is rightward mediastinal shift.

Figure 6---3 1 Septic embolization. A coronal CT image of a child with lower-extremity osteomyelitis shows a cavitary nodule in the peripheral aspect of the left lower lobe.

laceration of the thoracic duct is a relatively common iatro­ genic cause of chylothorax. Oozing of chyle can also occur from smaller transected lymphatic vessels. Other second­ ary mechanisms of chylothorax include elevated thoracic duct pressure due to venous thrombosis (small infants are most susceptible) , lymphatic duct disruption because of blunt chest trauma, and extravasation of chyle caused by a mediastinal tumor or infection.63-66 Primary chylothorax is the most common cause of a large pleural fluid collection in a newborn. Primary neona­ tal chylothorax may be a result of temporary overdistention and resultant rupture of the thoracic duct during deliv­ ery in association with elevated central venous pressures . Leakage of chyle can occur into one or both pleural spaces. There is also a developmental form of primary chylothorax in which multiple lymphatic fistulae lead to oozing of chyle into the pleural spaces. A large chylothorax in the fetus can cause pulmonary hypoplasia. The neonate with chylotho­ rax often presents with signs of respiratory distress shortly after birth. Chest radiographs of chylothorax show homogeneous pleural fluid (Figure 6-32) . With a large fluid collection,

there is contralateral shift of the mediastinal structures. Chylous ascites may also be present. Primary chylothorax is more frequent on the right ( Figure 6-33) . Thoracentesis in patients with chylothorax yields opalescent fluid because of

Figure 6---3 3 Primary chylothorax. There is a large amount of right pleural fluid on this chest radiograph of a newborn girl with respiratory distress. The mediastinal structures are shifted to the left.

Chapter 6 P u l mo n a ry Tra u m a , S u rgery, a n d Tox i n s 213 the high lipid content. In neonates, prior to the initiation of feedings, the fluid may be dear. Repeated thoracenteses can be used to treat chy­ lothorax, but most patients benefit from thoracostomy tube placement. Most lymphatic leaks eventually seal in response to tube drainage and dietary treatment. Octreotide therapy is used at some centers . If there is excessive pro­ tein loss in the drained fluid, total parenteral nutrition may be necessary.

PNEUMOTHORAX Pneumothorax refers to air within the chest cavity that is extrinsic to the lung and mediastinum. The ter­ minology of pneumothorax describes the location of the air, the mechanism of the air leak, and the presence of coexistent fluid (Table 6-3) . The two major categories of pneumothorax are primary (idiopathic) and secondary. A primary spontaneous pneumothorax occurs in the absence of trauma, thoracic medical procedure, or under­ lying pulmonary disease. Air leaks caused by blebs and bullae in otherwise normal individuals are included in the primary category. An iatrogenic pneumothorax is a secondary lesion that is a result of an invasive medical procedure such as central venous catheter placement or lung biopsy. A secondary spontaneous pneumothorax occurs without trauma or intervention in an individual with an underlying lung disease such as pneumonia or cystic fibrosis. I n young infants , pneumothorax is usually the result of alveolar rupture associated with pulmonary overinfla­ tion. Unilateral idiopathic pneumothorax occurs in 1% to 2% of all newborn infants; symptoms are usually lacking. Birth - related pneumothorax is more common in larger infants and in males. The development of pneumothorax postrlatally is usually associated with an underlying lung disease such as respiratory distress syndrome or meco­ nium aspiration, and is particularly common in infants receiving assisted ventilation. In infants with respiratory distres s syndrome, the greatest risk for pneumothorax is during the first 3 days of life and again during the recov­ ery phase (sometimes associated with improper manage­ ment of assisted ventilation) . Other potential etiologies of secondary neonatal pneumothorax include lobar emphy­ sema, rupture of a pneumonic cyst, trauma, pulmonary hypoplasia, pneumonia, and aspiration pneumonitis (ball-valve airway obstruction) . In older children, spontaneous pneumothorax is usu­ ally caused by rupture of a bulla or bleb (Figu re 6-34) . A bulla i s a sharply demarcated air-fill e d subpleural lung cyst that is greater than 1 to 2 em in diameter, while a bleb is a smaller air filled thin-walled structure that may be located on the lung surface or entirely within the pleura. These air- fill e d cysts apparently result from rupture of an alveolus and subsequent dissection of air into the inter­ stitium deep to the visceral pleura. Blebs and bullae are most common at the lung apices because of the presence

Table 6-3. Terminology of Pneumothorax Type

Feat u res

Pri mary pneu mothorax

No pulmonary d isease, trau ma, or i ntervention Primary pneumothorax Caused by pulmonary disease, trau ma, or i ntervention N o trauma or invasive medical proced u re N o pulmonary d isease, trau ma, or i ntervention Caused by pul monary disease; no trauma or i ntervention Caused by medical proced u re Caused by b l u nt or penetrati ng thoracic i njury Pressure above atmospheric Fluid and gas in pleural cavity Puru lent fl uid and gas i n pleural cavity Free chyle and air i n pleural cavity Blood and air in pleural cavity Gas between endothoracic fascia­ pleural layer and chest wal l

I diopath ic pneumothorax Secondary pneumothorax -

--

-

-----

-

- - - - - - --

-

Spontaneous pneu mothorax

- - - - - - - - - - - - - - - - - - - ---- - ---- -

Pri mary spontaneous pneumothorax Secondary spontaneous pneumothorax

-------

� - - � - - � · - - - - � - - - - - � - - - · - - - - � - - � - -- --�- - -

I atrogenic pneu mothorax -

-

Traumatic pneu mothorax - - -

-------

- - - - - - - - -- - - - - ---

Tension pneumothorax Hydropneumothorax -- - - - - - - - - - - - - - - - - - - - - - - - -

Pyopneumothorax

Chylopneumothorax Hemopneu mothorax Extrapleural pneumothorax

o f relatively large alveoli in this region and higher intra­ thoracic pressure than elsewhere in the lungs. Secondary spontaneous pneumothorax in older children is related to an underlying condition, such as interstitial fibrosis, emphysema, infection, developmental lesion, or neo­ plasm. The traumatic form of secondary pneumothorax occurs as a consequence of penetrating trauma, blunt trauma, or medical procedures (e.g., subclavian puncture, lung biopsy) . Chest radiographs of patients with spontaneous pneumothorax should be inspected for evidence of bul­ lae. These are thin-walled air fill e d structures , usually

214

Part

1

The Thorax

Figure 6-35 Apical blebs and bullae. There are multiple thin-walled air-filled cysts at the lung apices of this 15-year-old boy with a spontaneous left pneumothorax.

A

B

Figure 6-34 Spontaneous pneu mothorax.

This 13-year-old boy complained of sudden onset ri ght chest pain.

A. There is a large pneumothorax and partial collapse of the right lung. B. A CT performed after thoracostomy tube placement shows multiple blebs and bullae at the lung apices.

located at the lung apex (Figu re 6-35) . They are most eas­ ily visualized when outlined by air in the pleural space. CT provides much greater sensitivity for the detection of blebs and bullae in comparison to standard chest radio­ graphs (Figure 6-36) . Thin, soft- tissue attenuation lines in otherwise normal-appearing lung at the apices are com­ mon findings on axial CT images of normal patients. Differentiation from true blebs or bullae is based on the lack of distention with air. These "apical lines" often have branching, rather than spherical, morphology. Coronal reformatted images are helpful in confirming the pres­ ence of blebs and bullae, as normal apical lines do not

appear spherical on this projection. In addition to blebs and bullae, CT of patients with spontaneous pneumo­ thorax may show foci of pulmonary overaeration termed emphysema-like changes. This finding is identified in up to 81% of adult patients with spontaneous pneumothorax (nonsmokers) . 67·68 CT can be useful to select those patients with spon­ taneous pneumothorax who may benefit from preventive surgical treatment. However, the presence of bullae does not necessarily indicate that spontaneous pneumothorax will be recurrent. The risk of recurrence may correlate with the number of blebs, severity of emphysema-like changes, and size and number ofbullae; however, this has not as yet been clearly established in the literature. 6 9--7' In the absence preventive surgical therapy, the esti­ mated frequency of recurrence of a primary spontane­ ous pneumothorax is 20% to so%, while the frequency of recurrence of a secondary spontaneous pneumothorax is approximately 40%. The risk for eventual development of a contralateral pneumothorax is 5% to 4%; the risk increases to approximately 30% if there is radiographic evidence of bullae. In teenagers, the risk for recurrence of a spontaneous pneumothorax is 41% without bullae and 6o% with bullae.72 Conservative treatment is sufficient for most patients with spontaneous pneumothorax. The administration of oxygen accelerates the resorption of air from the pleural space. The rate of resorption of a pneumothorax is 3 to 4 times greater with the administration of oxygen than when breathing room air. A larger pneumothorax can be treated with thoracentesis or thoracostomy tube place­ ment. The maj or indications for percutaneous aspiration or tube thoracostomy in patients with pneumothorax are dyspnea, significant chest pain, enlargement of the air collection on sequential radiographs , and a pneumotho­ rax volume greater than 25% of that of the chest cavity.

Chapter 6 P u l mo n a ry Tra u m a , S u rgery, a n d Tox i n s

Figure 6-36 Spontaneous pneumothorax; apical bulla. (arrow) projecting from the surface

There is an oval-shaped bulla

of the left lung apex on this coronal reformatted

21 5

There is a small pneumothorax. A pleural thoracostomy tube is present lateral to the bulla.

Cf image.

Refractory or recurrent pneumothorax can be treated with chemical pleurodesis . Surgical options to help prevent recurrence include bullectomy and thoracoscopic stapling of apical blebs .

PULMONARY EDEMA Pulmonary edema refers to the excessive accumulation of clear fluid in the lung tissues. In many cases, pulmonary edema is due to elevated pulmonary microvascular pres­ sure (hydrostatic pulmonary edema) , as occurs with vari· ous cardiac abnormalities (cardiogenic pulmonary edema) or pulmonary venous obstruction. Pulmonary edema can also result from elevated capillary permeability despite normal microvascular pressure; many of these patients meet the criteria of acute respiratory distress syndrome. There are several conditions in which pulmonary edema develops because of combined elevation in pulmonary microvascular pressure and elevation of capillary perme­ ability. Pulmonary edema can also occur from systemic fluid overload. Cardiogenic pulmonary edema is a result of elevated pulmonary venous pressure, usually related to diseases of the left side of the heart. Elevated pressure within the left atrium and pulmonary veins can be caused by left ventricular dysfunction (e.g., cardiomyopathy) or obstruction of the left atrial outflow (e.g., mitral valve ste­ nosis) . Dyspnea is the dominant clinical manifestation of cardiogenic pulmonary edema. The early radiographic manifestations include increased pulmonary vascular size, indistinct vascular margins , bronchial wall thick­ ening, thickening of fissures, and septal edema (Kerley lines) . With progression, fluid accumulates in the alveoli,

resulting in acinar opacities that may become confluent. Alveolar (airspace) edema is typically most prominent in the central portions of the lungs . Acute pulmonary edema can occur i n association with elevated intracranial pressure, head trauma, or seizures; this is termed neurogenic pulmonary edema. This likely involves elevations of both pulmonary microvascular pres­ sure and capillary permeability. The radiographic pattern for these patients usually consists of homogeneous bilat­ eral airspace consolidation. Occasionally, the opacities are heterogeneous, asymmetric, or unilateral. The radio­ graphic findings are sometimes altered by superimposed aspiration of secretions or gastric contents. Pulmonary edema can occur in association with acute glomerulonephritis, most often developing in response to elevation of pulmonary microvascular pres­ sure and increased capillary permeability. This disorder is characterized by systemic hypertension, renal fail­ ure, periorbital edema, peripheral edema, and the pres­ ence of blood, protein, and red cell casts in the urine. Radiographs show pulmonary vascular congestion, sep­ tal edema , cardiomegaly, and chest wall edema ( Figu re 6-37) . A diffuse pulmonary edema pattern can occur as well (Figu re 6-38) . Pleural effusions in these patients are absent or small. Nephrotic syndrome is a constellation of clinical find­ ings that can occur as a result of a variety of renal disor­ ders. The features include proteinuria, hypoalbuminemia, and soft-tissue edema. In contradistinction to acute glo­ merulonephritis , radiographic studies of children with nephrotic syndrome show a normal to small-size heart, large pleural effusions, and minimal if any fluid in the lung parenchyma.

21 6 Part 1 The Thorax

Figure 6--3 8 Acute glomerulonephritis.

A

There is marked cardiomegaly. Pulmonary edema is present,

with greater involvement of the right lung. There are no significant pleural fluid accumulations.

in response to rapid reexpansion on a collapsed lung after evacuation of a large pneumothorax or pleural effusion.

R E F E R E N C ES 1. Wagner RB, Crawford WO Jr, Schimpf PP. Classification of parenchymal injuries of the lung. Radiology. 1988;167(1) :77-82. 2. Greene R. Lung alterations in thoracic trauma. 1 Thorae Imaging. 1987;2(3) :1-n. 3 · Zinck S E , Primack S L. Radiographic and CT findings in blunt chest trauma. 1 Thorae Imaging. 2ooo;15(2) :87-9 6. 4· Gaebler C , Mueller M , Schramm W, et a!. Tracheobronchial ruptures in children. Am 1 Emerg Med. 1996;14(3) :279-284. B

Figure 6--3 7 Acute glomerulonephritis. A, B. Anteroposterior and lateral chest radiographs show interstitial and septal fluid. There is only a trace of pleural fluid.

5· Shady K, Siegel MJ, Glazer HS. CT of focal pulmonary masses in childhood. Radiographies. 1992;12(3):505-514· 6. Eren S, Bald AE, Dikici B , et a!. Foreign body aspiration in children: experience of n6o cases. Ann Trop Paediatr. 2003;23 (1) :31-37· 7· Metrangelo S, Monetti C, Meneghini L, et a!. Eight years' experience with foreign-body aspiration in children: what is really important for a timely diagnosis? 1 Pediatr Surg.

Pulmonary edema can occur in association with airway obstruction. In the presence of acute airway obstruc­ tion, such as occurs with severe croup or epiglottitis, respi­ ratory effort against the obstruction causes diminished intrathoracic pressure that induces fluid to pass from the intravascular space into the interstitial tissues of the lung. Pulmonary edema can also occur because of sudden alterations in intrathoracic pressure created by relief of airway obstruction (e.g. , after endotracheal intubation) or

1999;34(8) :1229-1231. 8. Franquet T, Gimenez A, Roson N , et a!. Aspiration diseases: findings, pitfalls, and differential diagnosis. Radiographies. 2000;20(3):673-6 85. 9· Kosucu P, Ahmetoglu A, Koramaz I , et a!. Low-dose M DCT and virtual bronchoscopy in pediatric patients with foreign body aspiration. A1R Am 1 Roentgenol. 2004;183 (6):177!-1777·

10. Applegate KE, Dardinger JT, Lieber M L, et a!. Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies. Pediatr Radio/. 2001;31(12):836-84o.

Chapter 6 P u l mo n a ry Tra u m a , S u rgery, a n d Toxi n s 11. Kelly JP, Webb WR, Moulder PV, et al. Management of airway trauma. 1: tracheobronchial injuries. Ann Thorac Surg. 1985;4o(6): w-ss s 1 2 . Cay A , lmamoglu M, Sarihan H, e t a l . Tracheobronchial rupture due to blunt trauma in children: report of two cases. Eur] Pediatr Surg. 2002;12(6) :419-422. 13- Wiot J F . The radiologic manifestations of blunt chest trauma. JAMA. 1975:231(5 ) : soo-so3. 14· Barmada H , Gibbons JR. Tracheobronchial injury in blunt and penetrating chest trauma. Chest. 1994;106 (1) :74-78. 15. Ikeda M, Himi K, Yamauchi Y, et a!. Use of digital subtraction fluoroscopy to diagnose radiolucent aspirated foreign bodies in infants and children. Int ] Pediatr Otorhinolaryngol. 2001;61(3) :233-242. 16. Manson D, Babyn P S , Palder S , Bergman K. CT of blunt chest trauma in children. Pediatr Radio!. 1993 ;23 (1):1-5. 17. Konen E, Yellin A, Greenberg I, et a!. Complications of tracheal and thoracic surgery: the role of multisection helical CT and computerized reformations. Clin Radiol. 2003;s8(s) :341-350. 18. Truemper E, Reyes de la Rocha S , Atkinson SD. Clinical characteristics, pathophysiology, and management of hydrocarbon ingestion: case report and review of the literature. Pediatr Emerg Care. 1987;3(3) :187-193· 19. Betancourt S L, Martinez-Jimenez S , Rossi S E , et al. Lipoid pneumonia: spectrum of clinical and radiologic manifestations. AJR Am] Roentgenol. 2010;194 (1) :103-109· 20. Szpilman D. Near-drowning and drowning classification: a proposal to stratify mortality based on the analysis of 1,831 cases. Chest. 1997;112 (3) : 6 6 o-665. 21. Adeyemi SD, Stephens CA. Traumatic diaphragmatic hernia in children . Can ] Surg. 1981;24(4) :355-357· 22. West K, Weber TR, Grosfeld J L. Traumatic diaphragmatic hernia in childhood. ] Pediatr Surg. 1981;16 (3):392-3 9 5 . 23- Worthy S A , Kang E Y, Hartman T E , e t a l . Diaphragmatic rupture: CT findings in 11 patients. Radiology. 199 5:194 (3): 88s-888. 24. Nchimi A, Szapiro D, Ghaye B, et al. Helical CT of blunt diaphragmatic rupture. AJR Am J Roentgenol. 2oop84 (1) :24-30. 25. Bergin D, Ennis R, Keogh C, et a!. The "dependent viscera" sign in CT diagnosis of blunt traumatic diaphragmatic rupture. AJR Am J Roentgenol. 2001;177(5):1137-1140. 26. Tonz M , von Segesser LK, Mihaljevic T, et a!. Clinical implications of phrenic nerve injury after pediatric cardiac surgery. J Pediatr Surg. 1996;31(9):1265-1267. 27. Mok Q, Ross-Russell R, Mulvey D, et al. Phrenic nerve injury in infants and children undergoing cardiac surgery. Br Heart ]. 1991:6s(s):287-2 92. 28. Commare MC, Kurstjens S P , Barois A. Diaphragmatic paralysis in children: a review of 11 cases. Pediatr Pulmonol. 1994;18(3) :187-193· 29. Oh KS, Newman B , Bender TM, Bowen A. Radiologic evaluation of the diaphragm. Radio! Clin North Am. 1988;26(2):355-364. 30. Beal DD, Conner G H . Respiratory tract injury: a guide to management following thermal and smoke injury. Laryngoscope. 197o;8o (1):25-35· 31. Avecillas J F , Freire AX , Arroliga A C . Clinical epidemiology of acute lung injury and acute respiratory distress syndrome:

217

incidence, diagnosis, and outcomes. Clin Chest Med. 2oo6;27(4):549-557; abstract vii.

32. Erasmus J J , McAdams H P , Rossi S E . Drug-induced lung injury. Semin Roentgenol. 2002;37(1):72-81. 33- Erasmus JJ, McAdams HP, Rossi SE. High-resolution CT of drug-induced lung disease. Radio! Clin North Am. 2002;4o (1) : 61-J2. 34· Ellis S J , Cleverley JR, Muller NL. Drug-induced lung disease: high-resolution CT findings. AJR Am] Roentgenol. 2000;175(4) :1019-1024. 35· Hirschmann JV, Pipavath SN, Godwin JD. Hypersensitivity pneumonitis: a historical, clinical, and radiologic review. Radiographies. 2009;29 (7) :1921-1938. 36. Tobias ME, Plit M . Bronchiolitis obliterans organizing pneumonia with migratory infiltrates: a late complication of radiation therapy. AJR Am] Roentgenol. 199p6o(1):205-206. 37· Epler GR. Bronchiolitis obliterans organizing pneumonia. Semin Respir Infect. 199s;to(2): 65-'77· 38. Schlesinger AE, Braverman RM, DiPietro MA. Pictorial essay. Neonates and umbilical venous catheters: normal appearance, anomalous positions, complications, and potential aid to diagnosis. AJR Am J Roentgenol. 2oop8o(4) :1147-1153· 39· Narla LD, Hom M, Lofland GK, Moskowitz WB. Evaluation of umbilical catheter and tube placement in premature infants . Radiographics. 1991;11(5):849-86J. 4o. Nicotra J J , Mahboubi S , Kramer SS. Three-dimensional imaging of the pediatric airway. Int ] Pediatr Otorhinolaryngol. 1997;41(3):299-305. 41. Jaffe RB. Balloon dilation of congenital and acquired stenosis of the trachea and bronchi. Radiology. 1997;2o3(2) :4o5-409. 42. Gotway MB, Dawn S K, Sellami D, et al. Acute rejection following lung transplantation: limitations in accuracy of thin ­ section CT for diagnosis. Radiology. 2001;221(1) :207-212. 43· Bankier AA, Van Muylem A, Knoop C, et a!. Bronchiolitis obliterans syndrome in heart-lung transplant recipients: diagnosis with expiratory cr. Radiology. 2001;218 (2):533-539·

44· Konen E, Gutierrez C, Chaparro C, et a!. Bronchiolitis obliterans syndrome in lung transplant recipients: can thin-section cr findings predict disease before its clinical appearance? Radiology. 2004;231(2):467-473· 45· deMello DE, Lin Z. Pulmonary alveolar proteinosis: a review. Pediatr Pathol Mol Med. 2oo1;2o(s) :413-432. 46. Frenckner B , Radell P. Respiratory failure and extra corporeal membrane oxygenation. Semin Pediatr Surg. 2008;17(1) : 34-41. 47· Barnacle AM , Smith LC, Hiorns MP. The role of imaging during extracorporeal membrane oxygenation in pediatric respiratory failure. AJR Am] Roentgenol. 2oo6;18 6 (1) :58-66. 48. Franquet T, Muller NL, Lee KS, et al. High-resolution CT and pathologic findings of noninfectious pulmonary complications after hematopoietic stem cell transplantation. A] R Am] Roentgenol. 2005;184(2):629-637· 49· Levine D S , Navarro OM, Chaudry G, et al. Imaging the complications of bone marrow transplantation in children. Radiographies. 20D7;27(2):3 o7-324. so. LeUIIg AN, Gosselin MV, Napper CH, et a!. Pulmonary infections after bone marrow transplantation: clinical and radiographic findings. Radiology. 1999;210(3) : 6 9 9-710.

218 Part 1 The Thorax 51. Lossos IS, Breuer R, Or R, et al. Bacterial pneumonia in recipients of bone marrow transplantation. A five-year prospective study. Transplantation. 1 9 9 5 ; 6 0 (7 ) : 672-678. 52. Guermazi A, Esperou H , Selimi F, Gluckman E. Imaging of diffuse metastatic and dystrophic pulmonary calcification in children after haematopoietic stem cell transplantation. Br J

Radial. 2005;78(932) 7o 8-713. 53- Baird J S , Killinger J S , Kalkbrenner KJ, et al. Massive pulmonary embolism in children. ] Pediatr. 2010;15 6 (1) : 148-151-

54· Biss TI, Brandao LR, Kaltr WH, et al. Clinical features and outcome of pulmonary embolism in children. Br J Haematol. 2oo8;142 (5):8o8-818. 55 · Babyn PS, Gahunia HK, Massicotte P . Pulmonary thromboembolism in children. Pediatr Radial. 2005;35(3) : 258-274 5 6 . Lee EY. Zurakowski D, Diperna S, et al. Parenchymal and

pleural abnormalities in children with and without pulmonary embolism at M DCT pulmonary angiography. Pediatr Radial. 2010 A0(2):173-181. 57· Kritsaneepaiboon S, Lee EY. Zurakowski D , et al. M DCT pulmonary angiography evaluation of pulmonary embolism in children. AJR Am] Roentgenol. 2 0 0 9 ;192(5) :1246-1252.

58. Gelfand M J , Gruppo RA, Nasser M P . Ventilation-perfusion scintigraphy in children and adolescents is associated with a low rate of indeterminate studies. Clin Nucl Med. 2oo8;33 ( 9 ) : 6 o 6-6o9. 5 9 · Eng J , Krishnan JA, Segal J B , et al. Accuracy of CT in the diagnosis of pulmonary embolism: a systematic literature review. AJR Am] Roentgenol. 2004;183 (6):1819-1827. 6 o . Cohen MC, Drut R, Garcia C, Kaschula RO. Mesenchymal

hamartoma of the chest wall: a cooperative study with review of the literature. Pediatr Pathol. 1992;12 (4) :525-534. 61. Arakawa H , Kurihara Y, Nakajima Y. Pulmonary fat embolism syndrome: CT findings in six patients. ] Comput Assist Tomogr. 2000;24 (1) : 24-2 9-

62. Dodd J D , Souza CA, Muller NL. High-resolution M DCT of pulmonary septic embolism: evaluation of the feeding vessel sign. AJR Am ] Roentgenol. 2oo6;187(3 ) : 623-6 2 9 . 63. Carey B E . Neonatal chylothorax. Neonatal Netw. 2001;20(2): 53-55· 64. Soto-Martinez M , Massie J . Chylothorax: diagnosis and management in children. Paediatr Respir Rev. 2009;10 (4) : 199-20765. Ergaz Z, Bar-Oz B, Yatsiv I. Arad I. Congenital chylothorax: clinical course and prognostic significance. Pediatr Pulmonol. 2009;44(8) :8o6-8u. 66. Milonakis M , Chatzis AC, Giarmopoulos NM, et al. Etiology and management of chylothorax following pediatric heart surgery. ] Card Surg. 2 0 0 9 ; 24 (4) :36 9-373 · 67. Guimaraes CV, Donnelly LF, Warner BW. CT findings for blebs and bullae in children with spontaneous pneumothorax and comparison with findings in normal age-matched controls. Pediatr Radial. 2007;37(9) : 879-884. 68. Chaudhary AK, Sellars ME, Wallis C, et al. Primary spontaneous pneumothorax in children: the role of CT in guiding management. Clin Radial. 2 o o 5 ; 6 o (4) : 5 o8-5n.

6 9 . Lesur 0, Delorme N , Fromaget J M , et al. Computed tomography in the etiologic assessment of idiopathic

spontaneous pneumothorax. Chest. 1990;98(2):341-347· 70. Nathan N, Guilbert J, Larroquet M, et al. Efficacy of blebs detection for preventive surgery in children's idiopathic spontaneous pneumothorax. World ] Surg. 2010;34 (1) : 185-18 9 . 7 1 . Smit H J , Golding RP, Schramel FM, e t a l . Lung density measurements in spontaneous pneumothorax demonstrate airtrapping. Chest. 20o4;12 5 ( 6 ) :2o83-2090. 72. Poenaru D, Yazbeck S , Murphy S . Primary spontaneous pneumothorax in children. ] Pediatr Surg. 1994;29 (9) : u83-u85.

CH A P T E R

7

The Mediastinum

DEVELO P M ENTAL ABNORMALITI ES . . . . . .

21 9

Lipoblastoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

232

Thym us . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 9

Lym p hoblastic (T-Cell) Lym p homa . . . . . . . . . . . . .

232

Neu renteric Cyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

221

N o n lymphoblastic Lym phoma . . . . . . . . . . . . . . . . . . . .

233

Bronchogenic Cyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

221

H odgkin Lym phoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

234

E nteric Cyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

224

N e u rogen ic Tu mors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23 9

Neuroblastoma, Ganglioneuroblastoma,

N EOPLASMS AND MASSES . . . . . . . . . . . . . . . . . . . . . . . .

224

Ganglioneuroma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23 9

Anatomic Com partments . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

224

Neurofibroma, S chwannoma . . . . . . . . . . . . . . . . . . .

241

C l i n ical Presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

225

H emangioma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

241

Lym p h atic M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

242

Langerhans Cel l H i stiocytosis . . . . . . . . . . . . . . . . . . . . .

242

Pericard ia! Cyst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

244

I N FECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

244

M EDIASTI NAL TRAUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

245

P N E U M O M EDIASTI N U M . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

245

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

247

Stridor or Respiratory Distress Because of a Mediastinal Lesion . . . . . . . . . . . . . . . . . . . . . . . .

225

Superior Vena Cava Syndrome . . . . . . . . . . . . . . . . .

227

Germ Cel l Tu mors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Teratoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intrapericardial Teratoma . . . . . . . . . . . . . . . . . . . . . . . . . Malignant Germ Cell Tumors . . . . . . . . . . . . . . . . . .

227 228 229 229

Thymic Enlargement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymic Cyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

230

Thymolipoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

232

230 230

DEVELOPMENTAL ABNORMALIT IES

is predominantly composed of epithelial cells (especially

Thym us

plasma cells, eosinophils, histiocytes, and chromaffin cells.

The function of the thymus is to produce T lymphocytes , which are crucial components o f cell-mediated immunity. The primordia of the thymus develop from the third pha­ ryngeal pouches during the fifth to sixth gestational weeks. The paired primordia then migrate medially and caudally where they meet at the midline by the eighth embryonic week. Connective tissue extends between the lobes , but the thymic tissue itself is not completely fused. Each lobe of the thymus maintains a thin fibrous connection to the adjacent inferior lobe of the thyroid gland. Incomplete or excessive migration of the thymic primordia can lead to ectopic or aberrant locations of thymic tissue. Prior to puberty, the predominant constituents of the thymic cortex are lymphocytes . The central medulla

Hassall corpuscles) . Other tissue components include Although the thymus is at its greatest size relative to over­ all body mass during infancy, there is continued growth of the gland during childhood such that its maximum size occurs around the age of puberty. Soon after the onset of puberty, growth slows, and the interlobular septa of the thy­ mus become thicker. Around the age of 15 years, gradual involution begins, with infiltration of the gland by fatty tissue and progressive decrease in the number of cortical lymphocytes . In young children, the thymus has a quadrilateral shape and convex lateral margins. There is a triangular or a bilobed configuration in older children, with the left lobe more prominent than the right. There is consider­ able variability in position, size, and configuration of the

21 9

220

Part 1 Th e Thorax

B

A

Figure 7-1 Normal thymus. A An anteroposterior chest radiograph of a

a normal thymus. Lordotic patient positioning accentuates 6-month-old

superimposition of the thymus on the heart contour. B. The

infant shows a prominent mediastinal silhouette caused by

lateral view confirms normal heart size.

normal thymus . In children, the thymus usually abuts

to confirm that a density proj ecting over the lung actually

the sternum, and there is no plane of delineation between

represents the thymus rather than lung pathology.

the thymus and the sternum on lateral radiographs. The

A homogeneous composition and well-defined mar­

thymus may obscure the heart on frontal radiographs of

gins are important characteristics of the normal thymus on

infants, and correlation with a lateral view is essential for

cross-sectional imaging studies. After puberty, the thymus

accurately assessing cardiac size

Occasionally,

becomes slightly heterogeneous because of infiltration

a normal thymus mimics an anterior mediastinal mass or

with fat. A lack of compression or displacement of adjacent

(Figure 7-1 ) .

lung consolidation. On standard chest radiographs, the sail

structures is an additional important imaging feature of

sign and thymic wave sign suggest that a mediastinal soft­

the normal thymus . On sonography, the normal thymus is

tissue density is actually caused by the thymus

( Figure 7-2) .

homogeneous aside from scattered echogenic strands; it is

Frontal oblique radiographs are useful for selected patients

slightly hypoechoic in comparison to the thyroid gland. On

A

B

Figure 7-2 Normal thymus. A An anteroposterior radiograph of a 2-month-old infant shows the "sail wave sign" (arrow) is visible on this radiograph of a 28-day-old infant.

sign"

(arrow)

appearance of a normal thymus. B. The "thymic

Chapter 7 The M e d i asti n u m unenhanced CT, the attenuation of the thymus is approxi­ mately equal to or slightly greater than that of adjacent normal chest wall muscle. On T1-weighted MR images, the normal thymus is slightly hyperintense to other soft-tissue structures in young children; the signal intensity increases with age as a consequence of fat deposition. The thymus is usually slightly hypointense to fat on T2-weighted images, and is hyperintense on fat-suppression T2-weighted images! Variations in thymic size in response to systemic stresses of infants are common. Rapid involution can occur in response to chemotherapy, steroid therapy, bums, sepsis, heart surgery, respiratory distress syndrome, and a variety of other severe systemic diseases. Endogenous cor­ ticosteroid production apparently mediates this process. With resolution of the underlying condition, the thymus regenerates and sometimes attains a slightly larger size than existed prior to the initial event. This is termed rebound growth or rebound hyperplasia. This regeneration occurs in both the cortex and medulla of the thymus. Rebound thy­ mic enlargement sometimes results in an atypical shape of the structure. Some degree of gallium uptake is common in patients with rebound thymic enlargement, complicat­ ing the differentiation from residual or recurrent tumor in children with lymphoma. Thyromegaly can occur in chil­ dren with Beckwith-Wiedemann syndrome. There is also a rare idiopathic condition termed giant thymic hyperplasia or massive true thymic hyperplasia, which is apparently caused by endocrine dysregulation.2-5 In addition to rare forms of hyperplasia, developmen­ tal abnormalities of the thymus include aplasia, hypopla­ sia, congenital cyst, ectopic location, and aberrant location. Aplasia and hypoplasia of the thymus result in diminished T-cell-related immune function, and are often associ­ ated with immunological deficiency syndromes such as DiGeorge syndrome, ataxia-telangiectasia, severe combined immunodeficiency syndrome, and Nezelof disease. In chil­ dren with DiGeorge syndrome (more properly, 22qn dele­ tion syndrome) , the severity of T-cell deficiency correlates with the morphology of the thymus. Severe immune defi­ ciency occurs in individuals with thymic aplasia (approxi­ mately 20% of patients with DiGeorge syndrome) . Absence of normal thymic tissue is a universal finding in children with severe combined immunodeficiency syndrome. 6 Anomalies of thymic position are classified as ectopic or aberrant locations. Aberrant thymus refers to the pres­ ence of thymic tissue anywhere along the normal pathway of embryological descent of the gland. An ectopic thymus is located in any position except along the normal path­ way of descent. Anomalous thymic tissue can be located in the neck, superior mediastinum, or posterior medias­ tinum. The abnormally located tissue may or may not be contiguous with the main mass of the thymus. However, ectopic thymic tissue in the mediastinum usually is contig­ uous with the normally positioned thymus at some point. Posterior mediastinal ectopic thymus is usually located between the superior vena cava and the trachea. Thymic

221

tissue is considered to be in an abnormally cephalad posi­ tion if it is above the left brachiocephalic vein. The term cervical thymus refers to anomalous herniation of the thy­ mus into the lower portion of the neck. In most children, however, cervical thymus should be considered a develop­ mental variation rather than symptom-producing pathol­ ogy. Protrusion of the thymus into the anterior chest wall can occur in association with a congenital defect of the sternum.'·7 The diagnosis of ectopic or aberrant thymus should be considered when cross-sectional imaging studies show a cervical or mediastinal mass that has similar or identical imaging characteristics to the normal thymus; i.e., similar echogenicity on sonography, attenuation on CT, and signal intensity on MRI ( Figure 7-3) . A connection to the ortho­ topic thymus is sometimes present (Figure 7-4) . Ectopic thy­ mus in the mediastinum usually produces little or no mass effect on adjacent structures. Aberrant or ectopic tissue in the neck is usually lateral or anterolateral in location and may cause mild mass effect on adjacent structures, depend­ ing on the size and location of the lesion. The lesion occa­ sionally mimics a thyroid tumor. A cervical mass as a result of aberrant or ectopic thymus is sometimes cystic. Surgical excision is generally recommended for isolated anomalous thymic tissue in the neck because of rare reports of malig­ nant degeneration.8-to

Neurenteric Cyst Neurenteric cyst is a developmental lesion that results from delayed closure of the connection from the yolk sac to the amniotic cavity. This anterior paraspinal cyst contains both neural and G I elements. A stalk extends from the cyst to the meninges via a vertebral defect. Spinal cord anomalies are common in these children, such as syringohydromyelia and tethered cord. Additional vertebral anomalies are also common. There is additional discussion of neurenteric cyst in Chapter 22. The diagnosis of a neurenteric cyst should be con­ sidered when radiographs show a posterior mediastinal mass adjacent to vertebral anomalies. MR imaging usually affords a specific diagnosis. CT allows optimal evaluation of the vertebral anomalies. With sonography, a neurenteric cyst appears as a well-defined anechoic lesion with thin walls. Higher echogenicity occurs if there is blood, protein­ aceous fluid, or mucus within the lesion.

Bronchogenic Cyst Bronchogenic cyst is a developmental lesion that results from anomalous budding of the ventral diverticulum of the foregut, with isolation of the resultant cyst from the normal airway. Because of this developmental pathophysi­ ology, most mediastinal bronchogenic cysts are located near the carina. The cyst sometimes shares a common wall with the adjacent airway or is attached by a fibrous stalk. Communication with the airway does not occur, however,

222

Part 1 The Thorax

A

B

Figure 7-3 Ectopic thym us.

A Sonography of a palpable mass adjacent to the right hemimandible shows an oval hypoechoic solid lesion B,

(arrows) .

C . The lesion (arrows) also has a homogeneous appearance

on T1-weighted (A) and fat-suppressed T2-weighted

MR images.

The orthotopic thymus is normal.

except as an occasional secondary phenomenon related to infection or instrumentation. Mediastinal broncho­ genic cysts may be clinically silent or produce symptoms related to airway compression or esophageal compression. Infection of a bronchogenic cyst within the mediastinum is much less common than with those located in the lungs . Bronchogenic cysts are lined with pseudostratified colum­ nar respiratory epithelium. The walls usually contain car­ tilage, smooth muscle, and mucous gland tissue. The cyst may contain serous fluid or thick mucoid material.U-'3

c

Bronchogenic cyst is the most common cystic mass of the mediastinum in children. Approximately two-thirds of bronchogenic cysts are located within the mediastinum, and one-third within the lung parenchyma. The lesion is most often in the middle mediastinum, although poste­ rior mediastinal locations are also common (Figure 7-5) . Standard radiographs usually show a well-defined, solitary mediastinal or hilar mass. Rapid increase in size or accu­ mulation of gas within the cyst may be visible if the lesion becomes infected. Esophagography demonstrates extrinsic

Chapter 7 The M e d i asti n u m

8

A

Figure 7-4 Aberrant thymus.

base of the neck anterior to the trachea. B. A sagittal short

This 9-year-old boy had a palpable mass adjacent to the left lobe

tau inversion recovery ( STI R) image shows connection to the

of the thyroid. A. An axial fat-suppressed Tz-weighted image

orthotopic thymus via a thin stalk

shows a small homogeneous soft-tissue mass

(arrow)

(arrow) .

at the

8

A

Figure 7-5 Bronchogenic cyst.

223

c

B,

C. The cystic paraspinal mass is homogeneously hyperintense

A. An oval soft-tissue density mass (arrow) causes extrinsic

on Tz-weighted

impression on the posterior-right lateral aspect of the esophagus .

the axial image.

MR

images. A thin capsule

(arrow)

is visible on

224

Part 1 The Thorax

A

Figure 7-6 Bronchogenic cyst. A There is a large middle mediastinal cyst on this contrast­ enhanced

B

pneumonias. B. A reformatted coronal image demonstrates the proximity to the carina and main bronchi.

CT image of a teenage girl with recurrent

compression or deviation of the esophagus in about half of patients with a mediastinal bronchogenic cyst.l4·15 Cross-sectional imaging with CT, M R, or sonography serves to document the fluid composition of a mediasti­ nal bronchogenic cyst. Most often, the contents of the cyst have characteristics of clear fluid, although debris or pro­ teinaceous fluid sometimes alters the appearance, particu­ larly on M RI (i.e., increased signal intensity on T1-weighted images) . The contents of the cyst do not enhance with intra­ venous contrast (Figure 7-6) . Rarely, CT demonstrates high attenuation within the cyst because of milk of calcium. The borders of a bronchogenic cyst are well-defined and smooth or lobulated. Calcification of the wall is rare. The wall may enhance with intravenous contrast. Most mediastinal bronchogenic cysts are not detect­ able with prenatal sonography. When this lesion is visible, it usually appears as a unilocular fluid-filled cyst in the middle or posterior mediastinum. The differential diag­ nosis in this situation includes other cystic mediastinal lesions, such as esophageal duplication cyst and neuren­ teric cyst.I 6 ·17 The treatment of bronchogenic cyst is surgical resec­ tion. Even small asymptomatic lesions may become symp­ tomatic later in childhood or adulthood. Malignant degeneration (rhabdomyosarcoma) has been reported within bronchogenic cysts.18·19

Enteric Cyst Approximately 10% to 15% of enteric duplications occur in the posterior mediastinum. This is a cystic or

tubular structure that has smooth muscle walls and G I tract mucosa. Ectopic gastric mucosa is present in about half of these lesions. Communication with the esopha­ geal lumen is rare. Many mediastinal enteric duplica­ tions are asymptomatic; potential clinical manifestations include airway obstruction, cough, dysphagia, and pain. Approximately two-thirds of thoracic enteric duplication cysts are located on the right side. Occasionally, a duplica­ tion traverses the diaphragm, resulting in both thoracic and abdominal components . A mediastinal enteric duplication cyst is demon­ strated on esophagography as an extrinsic mass ; occasion­ ally, there are characteristics of an intraluminal lesion. CT or MRI serves to document the cystic character of the mass and to assess compression or displacement of adj a­ cent mediastinal structures. The lesion produces attenu­ ation values of water or soft tissue on CT, and there is no enhancement (Figu re 7-7) . The cyst has high T2 sig­ nal intensity on MR images. Most often, the lesion is round or oval; a tubular duplication cyst is uncommon. In those cysts with ectopic gastric mucosa, uptake of technetium- 9 9 m pertechnetate can be demonstrated scintigraphically. 2 0

NEOPLASMS AND MASSES

Anatomic Compartments The mediastinum is defined as the central portion of the thorax that lies between the pleural cavities, the diaphragm, and the thoracic inlet. Division of the mediastinum into

Chapter 7 The M e d i asti n u m

A

Figure 7-7 Enteric duplication cyst.

225

B

A, B. Axial and coronal contrast-enhanced cr images of a s-month-old child show a cystic mass (arrows) adjacent to the left side of the air-filled esophagus.

anterior, middle, and posterior compartments is arbitrary, as there are no fascial separations between these areas. The anterior mediastinum is the portion anterior to the heart, ascending aorta, and brachiocephalic vessels on a lateral chest radiograph. The anterior mediastinum contains the thymus, adipose tissue, and lymph nodes. The middle mediastinum consists of the structures contained within the pericardium, and includes the heart, the ascending and transverse portions of the aortic arch, the brachiocephalic vessels, the vena cava, the main pulmonary artery and prox­ imal aspects of the right and left pulmonary arteries, the right and left pulmonary veins, the trachea, the main bron­ chi, and lymph nodes. The posterior mediastinum extends from the thoracic vertebral margin to the heart and trachea, and contains the descending thoracic aorta, esophagus, azygos veins, autonomic ganglia and nerves, thoracic duct, and lymph nodes. 2 1 The majority of mediastinal masses in young infants are located in the posterior mediastinum. Posterior medi­ astinal masses include neurogenic tumors, neurenteric cyst, and enteric duplication cyst (Table 7-1 ) . The most com­ mon mediastinal mass in older children is lymphadenopa­ thy caused by lymphoma or leukemia; this is usually most prominent in the middle compartment of the mediasti­ num (Table 7-2) . Adenopathy related to metastatic disease or inflammatory conditions is usually most prominent in the right paratracheal region of the middle mediastinum. With massive adenopathy, there may be extension from the middle mediastinum into the anterior mediastinum. The differential diagnosis of an anterior mediastinal mass in a child includes thymoma, teratoma, dermoid cyst, hem­ angioma, lymphatic malformation, and tumors of thyroid

origin (Table 7-3) . The most common cysts of the mediasti­ num in children are bronchogenic cyst and enteric duplica­ tions (Table 7-4) . A bronchogenic cyst is most often located in the middle mediastinum, but posterior locations also occur. Duplications are usually in the posterior mediasti­ num, with a predilection for the right side. 22•2 3

Clinical Presentations Stridor or Respiratory Distress Because ofa Mediastinal Lesion Extrinsic tracheobronchial compression in children occurs because of great vessel anomalies and mediasti­ nal masses (Table 7-5) . The most common symptomatic vascular ring in infants is the double aortic arch. The components of the aortic arch completely encircle the esophagus and trachea, and cause narrowing of both of these structures. Symptomatic tracheal narrowing can also result from a right aortic arch with a left ligamentum arteriosum. Some degree of focal intrathoracic tracheal abnormality nearly always occurs in children with pulmo­ nary artery sling. This anomaly consists of a left pulmo­ nary artery origin from the right pulmonary artery, with the left pulmonary artery passing over the right main bronchus and between the trachea and esophagus, caus­ ing compression of the right upper lobe bronchus and/ or trachea. Associated tracheal stenosis caused by abnor­ mal development of the tracheal cartilage or localized tracheomalacia is common in children with pulmonary sling. Other vascular abnormalities that can cause tra­ cheobronchial compression include right aortic arch with

226

Part 1 T h e Th o ra x

Table 7-1 . Posterior Mediastinal Masses in Children

Neoplasm

. Gangl ion tumor (neuroblastoma) Nerve root tumor (neu rofibroma) 1 Paraganglioma (pheochromocytoma) Hemangioma Lym phoma . Lipoma Rhabdomyosarcoma Vertebral tumor Metastasis Lipoblastoma Abscess Loculated empyema Vertebral osteomyel itisjdiscitis Sarcoidosis Aortic aneu rysm E nteric cyst Neurenteric Cyst Sequestration B ronchogenic cyst Anterior meningocele · Hematoma Bochdalek hernia Retroperitoneal neoplasm Pancreatic pseudocyst •

---

I nflammation

Vascu lar Developmental

Trauma Other

•

Table 7-2. M iddle Mediastinal Masses in Children

Neoplastic lymphadenopathy

I nflammatory lymphadenopathy Developmental l B ronchogenic cyst - - - - - - - - - ---- --- ! E n ���i � �; ;t ' Sequestration I Lym phatic malformation : Ane ��� Vascu lar lesion --- -Right aortic arch - - - -- -- - � 0 � �� : - ao � � � � � � -- ---- -- - - -- - - - - --Other Card iac neoplasm - ---

-

-

-

- --

·

- --·-------

'

!

Table 7-3. Anterior Mediastinal M asses in Children

Thym us

N ormal thymus - - T- cel l lym phoma H odgkin lym phoma Thymoma Thymic cyst Lymphoma M etastases Sarcoidosis Germ cell tumor Dermoid cyst - Thyromegaly N eoplasm Aortic aneurysm Dilated s u perior vena cava Pericardia! cyst Card iac neoplasm -Lymphatic malformation B ronchogenic cyst Sequestration Hemangioma Lipoma Sternal mass Lipoblastoma -

Lymph nodes

Teratoid lesions Thyroid

Cardiovascu lar

------

Other

- - - - - --

---

-

---- - - - - -

anomalous left subclavian artery, origin of the innomi­ nate artery to the left of the midline, and enlarged or dis­ placed vessels following cardiac surgery. 24-26 Mediastinal malignant tumors, such as lymphoma, are often quite large and rapidly growing at the time of clini­ cal presentation. They are also frequently associated with deviation and narrowing of the airway. Therefore, patients with these masses are at significant risk for cardiopulmo­ nary complications when general anesthesia is admin­ istered. Careful evaluation of the airway on preoperative imaging studies is essential for these patients. The peak expiratory flow rate and the tracheal cross - section area are useful markers to identify children at high risk for anes­ thetic complications. General anesthesia is particularly dangerous if the peak expiratory flow rate is less than so% of the predicted value and the tracheal cross sectional area is narrowed greater than so%. 27

Lym phoma Leu kemia

-

-

---

- -

-

-

-

- - ----

-----

- - - -

- -

-

-

-

- --

-

-

--

- - - - - ---------

---

-

-

-

-

-

---

-

- --

- - -- -

-

-

-

-

-

--

- ---

Chapter 7

The M ed i asti n u m

227

Table 7-4. Cystic Mediastinal M asses in Children I magi ng featu res

Type of cyst

B ronchogenic cyst

Duplication cyst Pericardia( cyst Thymic cyst

. . . . . . . . . . . . . . . . . . . . ...

Meningocele Teratoma Lym phatic malformation Pancreatic pseudocyst Abscess

Homogenous; th i n wall; often near carina Thicker wall; near esophagus Wel l - defined wall; i n cardiophrenic angle I n thym us; may be m u ltilocu lar Paraspinal; vertebral defect Soft tissue com ponent; ± fat, calci u m Septations; debris i n cysts Posterior mediasti n u m ; splayed cru ra Thick wall; debris; gas .... . . . ............ ........

. . .

A

. . ... .. .

Superior Vena Cava Syndrome Superior vena cava syndrome is caused by intraluminal occlusion or extrinsic compression of the superior vena cava. The most common mechanism is catheter-related thrombosis, often related to malposition of a central venous catheter. Other potential etiologies of symptomatic superior vena cava obstruction include compression by a mediastinal neoplasm, absces s , or hematoma. The rare syndrome of fibrosing mediastinitis is an additional cause.

B

Figure 7-8 Superior vena cava syndrome. A. There is a large mediastinal mass in this teenager with Hodgkin lymphoma. The tumor encases the aortic arch. There is no visualization of the superior vena cava. Multiple dilated collateral vessels are present in the mediastinum, paraspinal

The dominant clinical characteristic of superior vena cava

region, and anterior chest wall . B. Venography with bilateral

syndrome is edema of the face, neck, upper extremities,

upper-extremity contrast injections confirms occlusion of the

and upper portion ofthe thorax. Dilated chest wall veins are usually visible.> 8 · 2 9

superior vena cava.

Standard chest radiographs of children with superior vena cava syndrome may show enlargement of the azygos

A specific diagnosis is usually provided by venogra­ phy, contrast-enhanced CT, or MR (Figure 7-8) . Systemic vein.

anticoagulation and catheter directed thrombolysis are

useful treatments for patients with acute superior vena cava syndrome. Imaging evaluation for an underlying ste­ nosis is often useful after recanalization.3°

Germ Cel l Tu mors Table 7-5. Causes of Extrinsic Tracheobronchial Compression

Double aortic arch Pul monary artery sling Right aortic arch with anomalous left s u bclavian Postsu rgical com pression B ronchogenic cyst Esophageal dupl ication cyst M ed iasti nal neoplasm

The mediastinum is the third most common site of germ cell tumors, following sacrococcygeal and gonadal loca­ tions. Most mediastinal germ cell tumors are located in the anterior mediastinum, sometimes arising in the thymus . Teratoma i s the most common, accounting for approxi­ mately

8o% of these lesions. Germinoma, embryonal

carcinoma, yolk sac tumor, choriocarcinoma, and mixed germ cell tumor are other primary germ cell tumors of the mediastinum. Malignant germ cell tumors often cause elevations of serum �-human chorionic gonadotropin and a-fetoprotein. Teratomas occur with an equal frequency in boys and girls, but malignant germ cell tumors are much more common in males)'-34

228

Part 1 The Thorax

Mediastinal germ cell tumors apparently arise from multipotent germ cells that fail to migrate properly dur­ ing embryogenesis. The primitive germ cells normally descend along the midline from the yolk sack endoderm to the gonads. It is also possible that some of these tumors arise from myoid cells within the thymus. These germ cells retain the ability to proliferate and differentiate into embry­ onic or extraembryonic tissue.

Teratoma Teratoma is a benign developmental neoplasm that con­ tains tissues that either represent more than one of the embryonic germ layers or are foreign to the site of the lesion. Approximately 10% of all teratomas arise in the mediastinum. Many of these lesions are asymptomatic. If the mass is of sufficient size to compress the airway,

patients may experience cough, wheezing, dyspnea, chest pain, or shortness of breath. Manifestations of supe­ rior vena cava obstruction can occur with a large mass. Hemoptysis has been reported in infants with mediastinal teratoma.35 ·36 Teratoma is an encapsulated mass that typically con­ tains a mixture of tissue types , including cystic and solid areas ( Figure 7-9) . Attempted tissue differentiation and organ formation may result in the presence of skin, hair, teeth, cartilage, bone, bronchial tissue, or intestinal tissue. On diagnostic imaging studies, the margins of a teratoma are usually well-defined, and may be rounded or lobu­ lated. The mass is usually predominantly located within the anterior compartment of the mediastinum. Most contain one or more cysts with thick well-defined walls. Fat-fluid levels can occur, and there may be calcifications within the walls. The presence of fat and calcification or

B

A

Figure 7-9 Mediastinal teratoma. A. There is a large soft-tissue density mass arising from the left side of the mediastinum and bulging into the left chest cavity. The margins are well-defined. The heart and great vessels appear normal. B. An unenhanced calcifications mass.

(arrows)

CT image demonstrates multiple

in this encapsulated anterior mediastinal

C. The cystic components remain hypoattenuating on

this contrast-enhanced image. There is no invasion of adjacent structures .

c

Chapter 7 The M ed i asti n u m

229

ossification within the mass is highly specific for the diag­ nosis of teratoma. 37

Intrapericardial Teratoma Intrapericardial teratoma is a rare lesion that presents in the neonatal period with congestive cardiac failure as a consequence of mass effect on the great vessels. This lesion is located within the pericardium adjacent to the bases of the great vessels. Neonates with intrapericardial teratoma have a markedly enlarged cardiac silhouette on chest radiographs , and there are often indications of congestive heart failure. Cross-sectional imaging with sonography, CT, or MRI shows a mass in the superior aspect of the pericardium, with a heterogeneous tissue composition.3 8

Malignant Germ Cell Tumors Malignant germ cell tumors of the mediastinum are uncommon. In teenagers and young adults, this tumor is more common in males. The frequency is approximately equal between boys and girls in younger children. There are a variety of histological types , including germinoma, embryonal carcinoma, yolk sac tumor, choriocarcinoma, mixed germ cell tumor, and polyembryoma. The evalua­ tion of serum tumor markers is helpful in the diagnosis and followup monitoring of these lesions; at least 90% of nonseminomatous malignant germ cell tumors elaborate a-fetoprotein andfor �-human chorionic gonadotropin. Endodermal sinus tumor results in elevated a-fetoprotein; choriocarcinoma elaborates �-human chorionic gonadotro­ pin; embryonal carcinoma and polyembryoma elaborate both a-fetoprotein and �-human chorionic gonadotropin; neither of these tumor markers is usually elevated in the presence of germinoma. 3'·3 4·J 6 ,J 9 A malignant germ cell tumor is usually a large, unen­ capsulated mass that contains hemorrhage, necrosis, and cysts . There is usually a nonspecific appearance on chest radiographs: a lobulated unilateral mediastinal mass. CT and MR imaging may show evidence of invasion of adj a­ cent structures and violation of tissue planes. The large cysts and well-formed calcifications that are common in benign teratomas are typically lacking in malignant germ cell tumors. However, hemorrhage and necrosis are fre­ quent findings. Cysts with irregular thick walls are some­ times present. Other potential findings are pleural effusion and pulmonary nodules (Figure 7·1 0) . 32 ·4° Seminoma is a malignant germ cell tumor that occurs nearly exclusively in males. Although most seminomas of the mediastinum are primary lesions , seminoma can also occur at this location as a metastatic lesion from a testicular primary. The peak prevalence of mediastinal seminoma is from the second to fourth decades of life. The most com­ mon presenting complaints are a result of tumor compres­ sion of the trachea or superior vena cava. Patients may report chest pain, dyspnea, cough, and weight loss. The

A

B

Figure 7-10 Mediastinal germinoma.

A, B. There is a large mediastinal mass that extends into the right chest cavity. The lesion contains areas of necrosis. The heart and great vessels are compressed. Metastatic tumor deposits are present in the right pleural space.

a-fetoprotein is never elevated with pure seminoma, and �-human chorionic gonadotropin is elevated in a minority of patients. The prognosis for appropriately treated medi­ astinal seminoma is excellent; the 5-year survival rate is greater than 90%. The imaging features of seminoma are similar to those of other malignant germ cell tumors . Cross-sectional imaging studies typically demonstrate a bulky, lobular anterior mediastinal mass; this lesion only rarely arises in the posterior mediastinum. Cysts are occasionally pres­ ent. The tumor matrix tends to be more homogeneous than other malignant germ cell tumors. Calcifications are rare. Contrast enhancement is minimal. Local struc­ tures may be encased or invaded. The most common sites of metastasis are regional lymph nodes and the skeletal system. 4'

230

Part 1 Th e Thorax

Thym ic Enlargement The differential diagnosis of enlargement of the thymus includes a variety of developmental, neoplastic, and idio­ pathic conditions. Enlargement of an otherwise normal thyroid thymus can occur as a rebound phenomenon after stress-related atrophy, or as an idiopathic process. Masses that can be located within the thymus include thymoma, cysts , hemangioma, lymphatic malformation, hematoma, and thymic carcinoma. The thymus is a common site of involvement with lymphoma and leukemia. Infiltration of the thymus can occur with Langerhans cell histiocytosis, particularly in young infants. Infiltration and enlargement of the thymus can be part of Castleman disease. Cystic lesions of the thymus include primary epithelial cysts, cys­ tic teratoma, and Hodgkin disease. Enlargement of the thymus can occur in children with autoimmune diseases . This is termed lymphoid follicular hyperplasia ofthe thymus. The hyperplasia only occurs in the medulla. Lymphoid follicular hyperplasia of the thymus is common in children with HIV infection.

Thymic Cyst Most thymic cysts are developmental lesions , possibly rep­ resenting remnants of the third pharyngeal pouch. The mass has an epithelial lining. Developmental (congenital) thymic cyst accounts for less than 1% of pediatric medias­ tinal masses. Thymic cysts can be located anywhere along the course of embryonic thymic descent, from the level of the mandible to the diaphragm. Those that arise in the neck or at the thoracic inlet can cause symptoms because of mass effect (e.g. , airway compression) . Some present as an otherwise asymptomatic palpable mass. Occasionally, a large mediastinal thymic cyst bulges through the thoracic inlet into the base of the neck.4 2 ·43 On standard radiographs, a thymic cyst has the non­ specific appearance of a homogeneous mass, sometimes accompanied by airway deviation. Imaging with sonog­ raphy, CT, or M R documents the cystic composition (Figu re 7-1 1 ) . The contents usually have imaging charac­ teristics of clear fluid; hemorrhage occasionally alters the appearance. The lesion is most often unilocular. A cervical thymic cyst is nearly always located at least partially in the carotid sheath.44-45 Acquired thymic cysts can occur due to infection, trauma, neoplasm, radiation therapy, or thoracic surgery. 4 6 Thymic cysts have been reported in children with aplastic anemia. Multilocular thymic cyst occurs in association with immune mediated systemic disorders and certain tumors, such as Hodgkin disease and germinoma. Multilocular cysts may result from induction of cystic changes in ducts by reactive lymphoid hyperplasia.47 Approximately 1% of children with H IV infection develop multilocular thymic cysts; sonography, CT, and MR show a cystic anterior medi­ astinal mass, without airway compression, containing multiple septations that are no more than a few millime­ ters in thickness. The septa undergo mild homogeneous

Figure 7-1 1 Thymic cyst. Contrast-enhanced Cf of a 17-year-old boy shows a unilocular cyst in the anterior mediastinum.

contrast enhancement on CT and M R. 4 8 Benign thymic cysts have been reported in children following mediastinal radiation therapy for treatment of Hodgkin disease. On CT, these cysts are well-circumscribed and the fluid has attenuation values similar to those of water; this appear­ ance aids in the differentiation from the irregular, thick walls that are typically present in cystic or necrotic areas of tumor.49

Thymoma Thymoma is a primary tumor of the thymus that accounts for less than 5% of mediastinal masses in children. Most are benign; approximately 15% of thymomas are classified as invasive. These tumors can be further classified patho­ logically according to the proportion of epithelial and lym­ phoid cells. Most often, these two cell types are present in roughly equal amounts; this is termed biphasic thymoma. In others, there is a predominance of either lymphocytes or epithelial cells; spindle cell types also have been described. Those thymomas that undergo extracapsular extension lack histological features of malignancy and do not metas­ tasize; therefore, the term invasive thymoma is more appro­ priate than malignant thymoma. Various pathological and clinicopathological classification systems have been pro­ posed for thymomas to reflect the prognosis and degree of invasiveness.5° Most thymomas in children arise sporadically in oth­ erwise normal patients. Occasionally, they occur in asso­ ciation with myasthenia gravis or various other systemic conditions such as red cell aplasia, hypogarnmaglobu­ linemia, or an endocrine disorder. Approximately 15% of adult patients with myasthenia gravis have thymoma, but the association between the two conditions is much weaker in children. Myasthenia gravis is an autoimmune

Chapter 7 The M e d i asti n u m neurological disorder. Despite the association with thy­ moma, the most common thymic abnormality in patients with myasthenia gravis is follicular thymic hyperplasia; imaging studies of these patients show a normal appear­ ance of the thymus or mild thymic enlargement. Many individuals with thymoma are asymptomatic. The lesion may be detected as an incidental finding on an imaging study performed for an unrelated indication. Signs and symptoms can result from compression of adja­ cent structures such as the trachea, esophagus, or recur­ rent laryngeal nerve. Rarely, venous compression causes manifestations of superior vena cava syndrome. Other potential effects are cough, dyspnea, cyanosis, spontaneous pneumothorax, and pleuropericardial effusion. There is no significant gender predilection for thymoma in adults and older children. In children younger than age 10 years, this tumor is more common in males. Young children appear to have a propensity for the invasive form of thymoma.5 '· 52 Most thymomas are slow-growing completely encap­ sulated tumors. The lesion deforms the surface of the thy­ mus. Radiographs usually show a well-defined mediastinal mass that protrudes into one hemithorax (Figure 7-12) . The size of the lesion at the time of diagnosis varies greatly between patients. Calcifications can sometimes (approxi­ mately 25% of the time) be visualized, often with an egg­ shell pattern. The presence or absence of calcification is not helpful in differentiating the benign versus invasive types. Thymoma most often has a homogeneous appearance on

Figure 7-1 2 Thymoma. posteroanterior chest radiograph of a 14-year-old girl shows a large mediastinal soft-tissue mass that extends into the left hemithorax. The lesion is homogeneous and has slighdy lobulated margins. A

231

Figure 7-13 Thymoma. This left-sided mediastinal mass has well-defined margins and a homogeneous character on cr.

CT (Figure 7-1 3) . Continuity with the thymus is usually apparent. Enhancement is homogeneous for most of these lesions; necrosis, cysts, and hemorrhage are more com­ mon with the invasive type. On MR, thymoma is usually isointense to muscle on T1-weighted images and produces high signal intensity on T2-weighted images. 53 Invasive thymoma grows through the tumor capsule into the surrounding mediastinal tissues. The most frequent site oflocal invasion is the pleura. Invasion ofthe lung, medi­ astinal blood vessels, pericardium, and heart can also occur. Growth through the diaphragm has also been reported. Pleural tumor implants can occur; distant metastases to liver, bone, lymph nodes, kidneys, or brain are rare. Chest radio­ graphs generally do not allow distinction between the benign and invasive types of thymoma. An irregular interface with the adjacent lung is sometimes visible with the invasive type. Rarely, there are findings of pleural involvement. Cross­ sectional imaging with CT or M RI is more sensitive for demonstrating invasion of adjacent structures; however, an apparent absence of invasion is not entirely accurate in pre­ dicting the pathological features of the mass or subsequent biological behavior. Findings that indicate a more aggressive lesion and a poorer prognosis include a lobulated or irregu­ lar contour and mediastinal fat invasion. Assessment of the patency of adjacent vessels is an essential component of the diagnostic imaging workup of these patients.54·55 Thymic carcinoma is histologically distinct from inva­ sive thymoma. This term refers to a group of aggressive epithelial malignancies that arise within the thymus. This lesion is quite rare in children. Thymic carcinoma lacks a capsule, and the tumor contains areas of necrosis and hem­ orrhage. Regional and distant metastases are common. Diagnostic imaging studies show a heterogeneous locally aggressive anterior mediastinal mass. Invasion of adjacent great vessels can occur.

232

Part 1 The Th orax

Other rare primary malignant neoplasms of the thy­ mus include carcinoid tumor and thymic sarcoma. Carcinoid tumor of the thymus may present with manifestations of Cushing syndrome. Diagnostic imaging studies of thymic carcinoid show a large, lobulated, locally invasive anterior mediastinal mass. Hemorrhage and necrosis are common within the lesion. Local metastatic lymphadenopathy may be visible. 56

Thymolipoma Thymolipoma is a rare benign mesenchymal neoplasm. It most likely represents a type of hamartoma. A thymoli­ poma can present at any age, but is most often identified in older children and young adults. There is a rare association with Graves disease, myasthenia gravis, and aplastic ane­ mia. There is no gender predilection. This tumor is usually asymptomatic. Most are detected on imaging studies per­ formed for an unrelated clinical indication. Thymolipoma consists of an admixture of mature fat and irregular solid thymic tissue. The proportion of these two components varies greatly between tumors. The adi­ pose tissue consists of mature adipocytes, while the thymic tissue is composed of a mixture oflymphocytes and epithe­ lial cells. Thymo.fibrolipoma is a rare variant that is clinically and radiographically indistinguishable from classic thymo­ lipoma. This lesion contains abundant collagenous tissue, as well as mature fat and thymic tissue.2'·57, 58 Diagnostic imaging studies depict thymolipoma as a fat-containing anterior mediastinal mass. The mass either occupies the expected location of the thymus or is con­ tiguous with adjacent normal thymus. On standard radio­ graphs , the lesion may be indistinguishable from a normal thymus, although the fatty composition is sometimes sug­ gested by diminished radiopacity. CT and M RI provide the most characteristic findings, with the mass having mani­ festations of fatty and solid components organized in a haphazard pattern. The imaging differential diagnosis of thymolipoma includes teratoma and lipoma.

Lipoblastoma Lipoblastoma i s a benign mesenchymal tumor that arises from embryonal white fat. At the time of diagnosis , approxi­ mately 90% of patients with lipoblastoma are younger than 3 years of age. There is a male predominance. Lipoblastoma can develop at many locations throughout the body. Potential areas of thoracic origin are the mediastinum and chest wall. Imaging studies indicate the predominantly fatty composition (Figure 7-14) . On CT and MR, the lesion usually has a well- defined capsule; internal septations are common. Lipoblastomatosis is a histologically similar lesion that lacks a capsule and is diffusely infiltrating. 59-6'

Lym phoblastic (T-Cell) Lym phoma The mediastinum i s the most common site o forigin oflym­ phoblastic (T-cell) non-Hodgkin lymphoma. Mediastinal

A

B

Figure 7-14 Lipoblastoma.

A. There is a well-defined left upper mediastinal mass (arrow) . The density is slightly less fuan tllat of adjacent soft tissues. B . CT confirms fue fatty composition (arrow) .

involvement with the other subtypes of non-Hodgkin lym­ phoma usually occurs in the form of disseminated disease with lymphadenopathy or thymic infiltration. The medi­ astinal mass associated with lymphoblastic non - Hodgkin lymphoma is frequently quite large, and rapid growth may result in precipitous respiratory distress as a result of air­ way compression. Other potential clinical manifestations include superior vena cava syndrome, dysphagia, and car­ diac tamponade. 62 Pleural effusion is common in patients with lympho­ blastic lymphoma. A prompt diagnosis can often be estab­ lished by analysis of aspirated pleural fluid, thus obviating the need for open biopsy and general anesthesia, which are risky in these patients with airway compromise. Because

Chapter 7 The M e d i asti n u m

A

Figure 7-1 5 Lymphoblastic lymphoma. A. A posteroanterior chest radiograph of a 7-year-old child who presented with cough and respiratory distress shows a large anterior mediastinal mass (arrows) and a right pleural effusion.

lymphoblastic lymphoma is a rapidly growing tumor that affects the airway, the diagnostic workup and initiation of therapy should occur in an urgent fashion when radio­ graphs demonstrate a bulky mediastinal mass. Rarely, lym­ phoblastic non-Hodgkin lymphoma presents with a pleural effusion and no radiographically visible mediastinal mass. Dissemination of disease can lead to involvement of the central nervous system, bone marrow, kidneys, or gonads . Chest radiographs of most children with lymphoblastic non-Hodgkin lymphoma show a large, lobulated anterior mediastinal mass, often with at least a small pleural effusion (Figure 7·1 5) . The trachea is displaced and narrowed. On CT and M R, the mass is usually homogeneous, with relatively well-defined borders (Figure 7-1 6) . Tracheobronchial com­ pression is present in at least 8o% of patients. There may be spread to hilar or mediastinal lymph nodes. Imaging should also be performed of the abdomen, neck, skeletal system, and central nervous system to evaluate for dissemi­ nated disease (Figure 7-17) . 63

233

B

B. A lateral view obtained after thoracentesis demonstrates posterior displacement and narrowing of the trachea (arrow) and main bronchi.

and non-Burkitt subtypes. Undifferentiated non-Hodgkin lymphomas typically arise within the abdomen; medias­ tinal involvement with dis seminated disease can occur in the form of lymphadenopathy or spinal lesions. The mediastinum is an occasional site of origin of large cell

N o n lymphoblastic Lymphoma More than half o f all mediastinal neoplasms i n children are malignant lymphomas. Approximately two-thirds are non-Hodgkin lymphomas and one-third are Hodgkin lymphomas. As described above, most mediastinal non­ Hodgkin lymphomas in children are lymphoblastic lymphomas. Nonlymphoblastic lymphomas of mediasti­ nal origin are rare. Undifferentiated non-Hodgkin lym­ phoma usually derives from B cells, and includes Burkitt

Figure 7-1 6 Lymphoblastic lymphoma. A contrast-enhanced CT image of a 6-year-old boy shows a large homogenous mediastinal mass that displaces adjacent vessels. There is an associated right pleural effusion. Small enhancing pleural metastases are also present.

234

Part 1 The Th orax

A

B

c

Figure 7-17 Lymphoblastic lymphoma.

This 9-year-old boy presented with a history of a persistent dry cough for 1 month. A A radiograph on the day of admission shows a large anterior mediastinal mass. There is tracheal narrowing. The course of the peripherally inserted central

(histiocytic) non-Hodgkin lymphoma ( Figure 7-1 8) . Most of these tumors arise from B cells. 6 3 , 64

Hodgkin Lym phoma Thoracic involvement is common in patients with Hodgkin lymphoma (Hodgkin disease) . Thoracic involvement can occur in the form of mediastinal lymph node enlargement, thymic enlargement, pulmonary disease, chest wall inva­ sion, or skeletal disease. This neoplasm typically arises

catheter indicates superior vena cava displacement. No pleural effusion is present in this patient. B. The mass is homogeneous on this contrast-enhanced CT image. C. There are multiple metastatic deposits (low attenuation nodules) in the kidneys.

within lymph nodes and spreads via the lymphatic sys­ tem. The most common sites of origin are the neck and mediastinum. Spread of disease tends to occur in a con­ tiguous fashion via lymphatics, with sequential involve­ ment of cervical, anterior mediastinal, paratracheal, and hilar lymph nodes. Eventually, the disease may spread to involve the pulmonary parenchyma. The most commonly involved lymph nodes in the abdomen are periaortic and celiac axis nodes; mesenteric lymph node involvement is rare. Hematogenous spread also occurs in some patients,

Chapter 7 The M e d i asti n u m

A

B

c

Figure 7-1 8 Large cell non-Hodgkin lymphoma. A, B. Chest radiographs demonstrate a middle mediastinal mass (arrows) . Narrowing and posterior displacement of the inferior

potentially involving the lung, liver, spleen, bone marrow, bone, or central nervous system. Infiltration of the thymus occurs in 25% to 30% of patients with Hodgkin lymphoma. Approximately 85% of children with Hodgkin lymphoma have mediastinal lymph node involvement. Between 10% and 15% of children with Hodgkin lymphoma have pulmonary parenchymal involve­ ment at the time of diagnosis or at some point during therapy. Isolated pulmonary disease is exceedingly rare. The most commonly utilized staging system for Hodgkin lymphoma is based on the diagnostic imaging pattern of disease distribution (Table 7-6) . 6 5-67 The peak incidence of Hodgkin lymphoma in pedi­ atric patients occurs during adolescence. This neoplasm occurs with a male predominance in patients who present when they are younger than 10 years of age, whereas the gender incidence is equal in adolescent patients. Hodgkin lymphoma is rare in children younger than age 5 years. Involvement of the lung in patients with Hodgkin disease is most often associated with the nodular sclerosing histo­ logical subtype.

aspect of the trachea are visible on the lateral view. C. The lesion (arrow) has a homogeneous appearance on contrast­ enhanced CT.

Table 7-6. An n Arbor Staging Classification for Hodgkin Lymphoma Stage

II

Ill IV

Criteria

I nvolvement of a single lym ph node region, lymphoid structure, or extralym phatic site I nvolvement of �z lym ph node regions on the same side ofthe diaphragm; or localized contiguous i nvolvement of one extranodal organ or site and lymph node region on the same side of the diaphragm I nvolvement of lymph node regions o n both sides of the diaphragm Diffuse or disseminated i nvolvement of�1 extra nodal organs or tissues

235

236

Part 1 The Thorax

The most common presenting clinical feature of Hodgkin lymphoma is palpable cervical or supraclavicular lymphadenopathy. The mass is typically painless and firm. Pathologically enlarged lymph nodes in the inguinal or axil­ lary regions are uncommon. Palpable hepatosplenomegaly is rare at the time of clinical presentation. Intrathoracic disease may result in clinical manifestations of airway obstruction, pleural effusion, or pericardia! effusion. Other common clinical findings at presentation include fatigue, weight loss, fever, pruritus, and night sweats. Mediastinal lymph node enlargement is the most common imaging finding in children with Hodgkin lymphoma. This usually predominates in the anterior and middle mediastinal compartments. Cross-sectional imaging may show discrete lymph node enlargement or a mass that is composed of multiple lymph nodes and/ or an enlarged thymus (Figure 7-1 9) . The mass may have lobulated borders and contain cystic areas because of necrosis or hemorrhage ( Figu re 7-20) . Displacement and compression of adj acent mediastinal vascular structures and the airway are common; tracheobronchial compres­ sion is present in about half of patients . Cross-sectional imaging studies sometimes show evidence of extension of mediastinal disease into adj acent structures . Invasion can occur into the esophagus, vena cava, pericardium, or chest wall. After radiation therapy, there may be delayed development of dystrophic calcification within mediasti­ nal lymph nodes. 68

A

Figure 7-1 9 Hodgkin lymphoma. A A coronal contrast-enhanced Tl-weighted M R image shows a multinodular anterior mediastinal mass that is contiguous with

Thymic involvement in children with Hodgkin lym­ phoma is most common with the nodular sclerosis sub­ type. Coexistent mediastinal lymphadenopathy is usually present. The abnormal thymus appears enlarged, nodular, and lobulated on cross-sectional imaging studies. Adjacent structures are displaced. Prominent gallium uptake and fl.uorodeoxyglucose positron emission tomography (FOG­ P ET) activity are common. The most common radiographic pattern of pulmonary involvement with Hodgkin lymphoma consists of mul­ tiple, irregularly marginated pulmonary nodules. There is usually coexistent hilar or mediastinal lymphadenopathy. Isolated nodules are present in some patients. Central necrosis within nodules is typical, and contrast-enhanced CT may show diminished attenuation or frank cavitation. Adjacent nodules sometimes coalesce to form a relatively homogeneous parenchymal lung mass, which may sub­ sequently undergo necrosis. Coalescent disease occasion­ ally produces a radiographic pattern of lobar or segmental consolidation. Interstitial opacification occasionally occurs, with a miliary or reticulonodular pattern; this results from interstitial tumor deposits or venous or lymphatic obstruc­ tion due to hilar adenopathy. A third pattern oflung involve­ ment is lobar or segmental consolidation that can mimic a pneumonia. Each of the above-described imaging patterns of lung involvement can occur in isolation or combina­ tion (Figure 7-21) . Pleural or subpleural nodules or plaques can sometimes be identified on CT. Pleural effusion is an

8

supraclavicular and cervical lymphadenopathy. A retrocrural mass is visible as well (arrow) . B. Vertebral metastases are demonstrated on this T2-weighted image.

Chapter 7 The M e d i asti n u m

237

B

Figure 7-20 Hodgkin lymphoma.

c

A, B. Axial and coronal contrast-enhanced cr images demonstrate a conglomerate mediastinal mass composed oflymph nodes and the thymus. The margins are lobulated. Contrast enhancement is heterogeneous because of intermixed areas of necrosis. There is displacement of the great vessels. C. Fluorodeoxyglucose positron emission tomographyfCT imaging shows the mediastinal and supraclavicular disease to be fluorodeoxyglucose-avid.

occasional finding, either at the time of presentation or during therapy. Effusions in these patients are usually due to lymphatic obstruction. 6 8 . 6 9 Involvement of the soft tissues or osseous structures of the chest wall may be identified on diagnostic imag­ ing studies of patients with Hodgkin lymphoma, but this complication is uncommon. Chest wall involvement most often occurs by direct extension of tumor from the mediastinum or lungs. Osseous lesions can also occur as a result of hematogenous metastasis. CT, M R , and FDG­ P ET are useful for detecting chest wall involvement in these patients . 7 ° Gallium scintigraphy has traditionally been part of the standard workup of Hodgkin lymphoma, although newer techniques such as FDG-PET and whole body MRI are replacing this method in many institutions. This is usually

performed with total body planar imaging and single­ photon emission computed tomography imaging of the neck, chest, and abdomen. If gallium imaging is planned for followup evaluations, it is essential to perform a base­ line examination to determine if the tumor is gallium-avid. For those patients with gallium-avid Hodgkin lymphoma, scintigraphy is a highly sensitive technique for detecting disease (Figure 7-22) .71 FDG-PET is highly sensitive and specific for disease detection in the initial staging and restaging of Hodgkin lymphoma, particularly when performed with the hybrid PETfCT technique. PET provides a survey of the entire body for active disease, and the information complements that of conventional imaging studies. Active Hodgkin lym­ phoma has elevated FDG uptake that resolves after success­ ful oncotherapy (Figure 7-23) . F DG-PET/CT is particularly

238

Part 1 The Th orax

A

Figure 7-21 Hodgkin lymphoma. A. There is marked mediastinal widening in this 14-year-old boy. Multiple ill-defined nodules and areas of consolidation are present in the right lung. B. CT confirms a large mediastinal

Figure 7-22 Hodgkin lymphoma. There is markedly gallium-avid disease in the mediastinum and neck.

B

mass and associated nodular opacities in the right lung. Interstitial markings are prominent in the right upper lobe, likely caused by lymphatic obstruction.

useful for the detection of disease in normal-size lymph nodes and in extranodal sites such as liver, spleen, bone, and skin. Although the optimal role for PET in the care of Hodgkin lymphoma patients is a subject of active investi­ gation, this technique is now recommended for staging of most lymphoma patients. 7°·72-7 6 Following treatment of a mediastinal Hodgkin lym­ phoma, residual soft-tissue fullness because of inflam­ matory, fibrous, or necrotic tissue can mimic residual or recurrent disease. The characteristics of the mass on radiographs and CT lack specificity for determin­ ing benign versus malignant tissue, although stability of the findings on serial examinations is a suggestive finding of a benign process. The presence of calcifica­ tion suggests bland fibrosis. 77 With MRI, fibrosis usu­ ally produces lower signal intensity than active neoplasm on Tz-weighted images, although radiation fibrosis can have signal intensity that is indistinguishable from that of neoplasm. Gallium-67 scintigraphy, particularly when performed with the single-photon emission computed tomography technique, is quite helpful for determining the presence or absence of residual neoplasm in those tumors that are confirmed to be gallium-avid prior to the initiation of therapy. Scintigraphy with thallium-201 is an alternative to gallium. 78 FDG-PET is also useful in this situation, as the rate of glycolysis in neoplastic tissue is typically elevated in comparison to that of normal tissue. FDG-PET provides a higher degree of accuracy than stan­ dard scintigraphic techniques in evaluating the mediasti­ num for residual or recurrent lymphoma. 79 , 8 o Rebound enlargement of the thymus or thymic hyper­ plasia can also mimic recurrent disease in patients treated for Hodgkin lymphoma. This enlargement of the thymus typically occurs between 4 and 10 months after comple­ tion of chemotherapy, but sometimes develops soon after

Chapter 7 The M ed i asti n u m

23 9

·"' \ �,- � )/ I

A

B

Figure 7-23 Hodgkin lymphoma.

c

completion of therapy or even during therapy. Lack of associated lymphadenopathy is a useful, but not definitive, finding on CT in these patients. With M R imaging, nor­ mal thymus typically produces homogeneous signal inten­ sity, while lymphomatous infiltration is usually associated with heterogeneity. However, calcification and scarring in the thymus can also occur as sequelae of therapy. Gallium scintigraphy or FDG-PET imaging is helpful in differentiat­ ing rebound enlargement/hyperplasia from active disease within the thymus ifthe activity is normal. However, prom­ inent thymic uptake can occur in the absence of neoplasm; the temporal pattern of thymic uptake and the presence or absence of disease at other sites are important consider­ ations in the interpretation.7 °

Neurogenic Tu mors Neuroblastoma, Ganglioneuroblastoma, Ganglioneuroma Neurogenic tumors of sympathetic nervous system origin are the most common causes of mediastinal masses in infants and young children. These lesions nearly always are

This 18-year-old girl presented with enlargirlg cervical lymph nodes, weight loss, and night sweats. A. A fused FDG-PETfCT image shows marked uptake in the anterior mediastinum. There is also abnormal paraspinal soft-tissue thickening. B. A sagittal image obtained to the left of the midline demonstrates the multinodular anterior mediastinal lesion superior to the normal myocardial uptake. Abnormal uptake in enlarged cervical lymph nodes is also present. C. A followup P ET/CT examination after completion of therapy shows normal uptake in a normal-size thymus and resolution of lyrnphadenopathy.

located in the posterior compartment of the mediastinum; at least 95% of posterior mediastinal neoplasms in children are neurogenic tumors. Neuroblastoma is the most com­ mon mediastinal neurogenic tumor, followed by ganglia­ neuroblastoma and ganglioneuroma. All of these lesions arise from ganglion cells in the paravertebral sympathetic chain. 22 ,81,8 2 Ten percent to 15% of neuroblastomas arise in the tho­ rax. Mediastinal neuroblastomas carry a more favorable prognosis than those arising in the abdomen, and tend to occur at a younger age. Thoracic neuroblastomas usu­ ally present during the first 5 years of life, most commonly during infancy. These lesions sometimes undergo spon­ taneous maturation or regression, particularly in infants. Intraspinal extradural extension is common with thoracic neuroblastoma. The lesion may also extend directly into mediastinal lymph nodes or cross the diaphragm into the abdomen via the retrocrural space. Disseminated disease is uncommon with mediastinal neuroblastoma; potential sites of hematogenous spread include the bone marrow, lung, and pleura. Ganglioneuroblastoma is a malignant neoplasm that shares characteristics of benign ganglioneuroma and

240

Part 1 The Thorax

A

Figure 7-24 Neuroblastoma. A A frontal chest radiograph of an 11-month-old child demonstrates a left paraspinal soft-tissue density mass (arrows) . Note preservation of the thymic silhouette. There is widening

malignant neuroblastoma. This tumor is much less com­ mon than neuroblastoma. The usual age range for this neo­ plasm is from infancy through early childhood. Ganglioneuroma is a mature, benign neoplasm. Ganglioneuroma is the second most common neurogenic mediastinal tumor, after neuroblastoma. Approximately 40% of ganglioneuromas arise in the thorax. Although patients at any age can be affected, this neoplasm usually occurs in adolescents and older children. Neurogenic tumors of the mediastinum are some­ times clinically silent (approximately half of patients) , and are detected on imaging studies performed for an unre­ lated indication. Some patients exhibit clinical manifes­ tations related to mass effect on adjacent organs, such as pain, cough, or dyspnea. A mass in the apex of the thorax can cause Homer syndrome. Because thoracic neurogenic tumors are located in the paraspinal region, the lesion may extend into the spinal canal via 1 or more neural foram­ ina. Intraspinal extension can cause symptoms of spinal cord or nerve root compression, including radicular pain, lower extremity weakness, bladder or rectal sphincter dys­ function, or paraplegia. Approximately 5o% of children with myoclonic encephalopathy of infancy (opsoclonus­ myoclonus cerebellar ataxia syndrome) have a thoracic paraspinal neuroblastoma. Children with a malignant neu­ rogenic tumor may have nonspecific systemic signs and symptoms, such as fever, weight loss, irritability, malaise, and anemia. On chest radiographs , a thoracic neurogenic tumor usually appears as a paraspinal mass, with a sharp

8

of the left third intercostal space and the posterior aspect of the third rib is thinned. B. The lateral view confirms the posterior location of the mass (arrow) .

pleural-pulmonary interface (Figu re 7-24) . The mass is often oriented along the vertical axis of the thorax, corresponding to the plane of the sympathetic chain. Calcification within the mass is common, and may appear sand-like, curvilinear, or globular. There some­ times are manifestations of erosion of adj acent skeletal structures (ribs or spine); enlargement of one or more neural foramina is common. CT is the most sensitive technique for detecting calcification within the mass, and for assessing osseous changes . M RI is often use­ ful in these patients for detecting and characterizing extension into the spinal canal ( Figu re 7-25) . MRI also allows evaluation of the thoracic vertebrae for meta­ static disease. Extraosseous uptake of radiopharmaceu­ tical is often visible within thoracic neurogenic tumors on skeletal scintigraphy ( Figu re 7-26) . Accumulation of '23iodine-metaiodobenzylguanidine occurs in most neu­ roectodermally derived neoplasms such as neuroblas­ toma (Figu re 7-27) .83 Unless metastatic disease is identified, diagnostic imaging studies do not allow reliable distinction between benign and malignant neurogenic tumors of the medias­ tinum. Ganglioneuroma almost invariably has smooth margins with no evidence of invasion, whereas the borders of a neuroblastoma may be either smooth or indistinct (Figu re 7-28) . Ganglioneuroma tends to have homoge­ neous attenuation on CT and minimal contrast enhance­ ment, while neuroblastoma often has a heterogeneous pattern of contrast enhancement. Areas of frarlk necrosis or hemorrhage are sometimes present in neuroblastoma

Chapter 7 The M e d i asti n u m

Figure 7-25 Neuroblastoma. A contrast-enhanced MR image of a s-year-old child shows a left paraspinal mass that extends into an enlarged neural foramen.

241

A

( Figure 7-29) . Neuroblastoma usually results in a greater degree of osseous defonnity and erosion than does ganglio­ neuroma. Infiltration of adjacent structures is also more common. Ganglioneuroblastoma has similar imaging fea­ tures as neuroblastoma; the frequency of calcification may be somewhat less (Figure 7-30) .

Neurofibroma, Schwannoma Neurofibroma and schwannoma (neurilemmoma) are neurogenic tumors that arise from the peripheral nervous system. In the mediastinum, these usually develop in asso­ ciation with a nerve root. Neurofibroma is much more common than schwannoma. Both of these lesions most often occur in individuals with neurofibromatosis type 1. The most common location is the upper portion of the pos­ terior mediastinum. In patients with neurofibromatosis, multiple lesions are often present. 84 , 85 Diagnostic imaging studies of neurofibroma and schwannoma usually show a smooth or lobulated soft­ tissue mass. CT and MR imaging may show a dumb­ bell configuration, with intraspinal and extraspinal components. On unenhanced CT, these lesions are usu­ ally homogeneous and of slightly lower attenuation than muscle. There is minimal enhancement with intravenous contrast. The lesion is hyperintense on T2-weighted M R images (Figure 7-31 ) . Occasionally, there i s a target appear­ ance, with intermediate signal intensity centrally and high signal intensity in the periphery. This is apparently a result of packed nerve sheath cells and fibrous tissue in the central aspect of the tumor and myxoid degeneration peripherally. Plexiform neurofibroma also can arise in the thorax. This type of neurofibroma has an infiltrative growth pat­ tern, and may extend from the posterior into the middle

B

Figure 7-26 Neuroblastoma.

A. Contrast-enhanced CT shows an infiltrative paraspinal mass. There are hypoattenuating areas of necrosis. The margin of the mass is lobulated. B . The mediastinal primary accumulates radiopharmaceutical (arrow) on skeletal scintigraphy. There is extensive skeletal metastasis, including lesions in the orbital walls, skull, spine, and extremities .

mediastinal compartments . Chest wall involvement is common. Plexiform neurofibromas are most effectively depicted with fat-suppressed T2-weighted M R images.8 6

Hemangioma Infantile hemangiomas can occur anywhere within the mediastinum, but approximately 3 of 4 arise in the ante­ rior compartment. Symptoms, if any, are usually related to

242

Part 1 The Thorax

A

8

Figure 7-27 Neuroblastoma.

avid accumulation of 12 3iodine-metaiodobenzylguanidine within the lesion (arrow) on this posterior view.

mass effect on adjacent structures , such as the airway. A posterior mediastinal hemangioma may have an intraspi­ nal component.87

Prominent arteries and veins may also be present. Standard radiographs show a nonspecific mass. Some degree of infil­ tration of adjacent structures is common. There may be chylous pleural or pericardia! effusions. Occasionally, there are lytic lesions in adjacent skeletal structures . CT and M R show multiple cysts. Fluid-fluid levels are sometimes vis­ ible on MR.'5

A. An unenhanced coronal CT image shows a large left posterior mediastinal mass that contains calcifications (arrow) . B. There is

Lymphatic M alformation Lymphatic malformation �ymphangioma) is a develop­ mental lesion that consists of an abnormal proliferation of lymph vessels. Most localized lymphatic malformations of the thorax occur in the mediastinum. Symptoms can occur in those patients with airway compression. Histological examination shows dilated lymph vessels and cysts.

A

Figure 7-28 Ganglioneuroma. A, B. Axial and coronal contrast-enhanced CT images of an asymptomatic 8-year-old boy show a homogeneous, minimally

Langerhans Cel l H istiocytosis Potential mediastinal pathology in patients with Langerhans cell histiocytosis includes lymphadenopathy,

B

enhancing right paraspinal mass. The margins are smooth and the interface with the lung is sharp.

Chapter 7 The M e d i asti n u m

B

Figure 7-29 Neuroblastoma. This 10-month-old infant presented with neurological symptoms caused by spinal cord compression. A The mediastinal mass has large, irregular calcifications. There are low-attenuation areas of necrosis or hemorrhage. B. A large hemorrhagic focus (arrow) produces high signal intensity on this T1-weighted MR image. C. The viable portions of the tumor enhance with intravenous gadolinium. There is a large intraspinal component.

c

A

Figure 7-30 Ganglioneuroblastoma.

B

A, B. This posterior paraspinal mass (arrows) has a homogenous character on these enhanced CT images. Infiltration between ribs is visible on the sagittal image.

243

244

Part

1

The Thorax

Figure 7-32 Langerhans cel l histiocytosis. There are multiple irregular calcifications in an enlarged thymus in this 2-year-old child with multiorgan disease.

Figure 7-31 Neurofibroma. A T2-weighted image of a 12-year-old boy with neurofibromatosis type 1 shows large bilateral hyperintense mediastinal masses. Adjacent mediastinal structures are displaced. There are mul­ tiple encased vessels on the left.

pneumomediastinum, and thymic infiltration. Most patients with mediastinal lesions have coexistent pul­ monary disease. The enlarged thymus that can occur in these patients usually maintains smooth lobulated mar­ gins. Punctate or serpentine calcifications within the thy­ mus are occasionally visible on CT ( Figure 7-32) . Cysts are sometimes present. Focal fatty replacement can result in foci that are hypoattenuating on CT and produce high signal intensity on T1-weighted MR images. 88 . 8 9

Pericardia! Cyst A pericardia! cyst is a rare benign mesothelial-lined cyst that is usually located at the cardiophrenic angle. Only 10% of these cysts communicate with the pericardium. Imaging studies show a round cyst with well-defined walls.9°·9'

INFECTI ON Acute infections of the mediastinum in children are most often complications of cardiac or esophageal surgery. Sometimes there is spread of infection from postthora­ cotomy sternal osteomyelitis or an infected sternal wire. Acute mediastinitis can also occur as a consequence of esophageal rupture during endoscopy, esophageal stric­ ture dilation procedures, or placement of an enteric tube. Spontaneous perforation of the esophagus is an additional

mechanism; in this instance, the tear is usually vertical and located in the inferior aspect of the esophagus. Mediastinal infection can occur as a consequence of spread of infec­ tion from the spine (osteomyelitis) , chest wall, or neck. The clinical manifestations of acute mediastinitis include fever and chest pain. Standard radiographs may show widening of the mediastinum in the child with acute mediastinitis. An abscess of sufficient size produces the appearance of a localized mass, with displacement of adjacent structures . Pneumomediastinum, pleural effusion, andjor pneumo­ thorax may be present if there is an esophageal perforation. Esophagography serves to demonstrate an esophageal leak for these patients. Potential CT findings of acute mediastinitis include extraluminal gas, obliteration of fat planes, mediasti­ nal or pleural fluid accumulations, and thickening of the esophageal wall. However, all of these findings are com­ mon following uncomplicated cardiac or mediastinal sur­ gery. Postoperative accumulations of blood can mimic the appearance of an abscess, and percutaneous aspiration may be required for differentiation when there is a high clinical suspicion. An established abscess frequently has wall enhancement with IV contrast. Orally administered contrast material can be used to document an esophageal perforation with CT.92-93 Mediastinal lymphadenitis can occur with various infections, such as infectious mononucleosis and tubercu­ losis . Coexistent lung involvement is common with many of these infections. Cervical or retroperitoneal lymphade­ nopathy is also common. A mediastinal mass can occasionally occur in chil­ dren with histoplasmosis in the form of a granuloma

Chapter 7 The

M e d i a sti n u m

245

(histoplasmoma) . This may lead to obstruction of the air­

CT: dis section, intimal tear, contrast extravasation, pseu­

way, vena cava, or esophagus. Granulomatous middle

doaneurysm, and luminal narrowing. 98-too

mediastinal lymphadenopathy is common in patients with tuberculosis or sarcoidosis.94 Fibrosing mediastinitis is a rare condition that is usu­

PNEUMOMEDIAST INUM

ally associated with histoplasmosis or tuberculosis. The

Pneumomediastinum (mediastinal emphysema) refers to

pathological

gas in the mediastinal space . Pneumomediastinum most

characteristics

of fibrosing

mediastinitis

include chronic inflammation and fibrosis of the mediasti­

often occurs as a result of a known precipitating condi­

nal soft tissues, either focally or diffusely. Progressive fibro­

tion or event that leads to sudden elevation of intraalve­

sis can lead to compres sion of mediastinal vessels , airways,

olar pressure. The most common etiologies in children

and the esophagus. I maging studies show a focal mediasti­

are asthma and mechanical ventilation. Other potential

nal soft tissue mass or diffuse mediastinal widening. When

causes include a forceful Valsalva maneuver (e.g. , weight­

the condition is caused by histoplasmosis or tuberculosis,

lifting) , airway obstruction (e.g. , foreign body) , vomiting,

calcifications may be visible within the soft-tissue mass

blunt thoracic or abdominal trauma, and a sudden drop

of focal fibrosing mediastinitis or in adjacent mediastinal

in atmospheric pressure (e.g. , rapid ascent of a diver) . The

allows characterization of the mass and demonstration of

tinum via the perivascular and peribronchial interstitial

lymph nodes; calcification is rare in the diffuse form. cr

air from the ruptured alveolus extends into the medias­

effects on the airway and maj or vessels. The fibrous nature

spaces. There is often extension from the mediastinum

of the abnormality is indicated on T2-weighted MR images

into the neck, soft tis sues of the chest wall, and retroperi­

by relatively low signal intensity. 95

toneum. Associated pneumopericardium is a potential complication, particularly in neonates . With a large air leak, there can also be extension from the mediastinum

MED IAST I NAL TRAUMA

into the peritoneum or pleural space. Pneumothorax

Mediastinal hemorrhage in trauma patients most often

ruptured alveolus through the visceral pleura. Other eti­

can also result from peripheral migration of air from a

arises from small vessels. However, the most important

ologies of pneumomediastinum include thoracic surgery,

mediastinal vascular injury from a therapeutic standpoint

penetrating trauma, tracheal rupture, esophageal perfora­

is aortic rupture. The most common site of aortic injury is

tion, pneumoperitoneumjpneumoretroperitoneum, and neck traumajsurgery.10'·1 02

at the level on the aortic isthmus, immediately distal to the origin of the left subclavian artery. In those patients who

The clinical features of pneumomediastinum vary

survive long enough to reach the hospital, the adventitia at

with the size of the air collection, the age of the patient and

the site of injury is usually intact.

the presence of associated pathology. A small pneumome­

Various manifestations of thoracic aortic injury can

diastinum is often asymptomatic. Many patients report

be identified on standard radiographs . Mediastinal hem­

retrosternal pain, sometimes with radiation to the shoul­

orrhage from any source results in mediastinal widening

ders and arms. Dyspnea may be present. Subcutaneous

and an indistinct contour of the aortic arch. Other potential

emphysema is often clinically apparent. Rarely, a large

findings include rightward displacement of a nasogastric

pneumomediastinum causes symptomatic compromise

tube, rightward deviation of the trachea, inferior displace­

of cardiac output (obstructive shock) as a consequence of

ment of the left mainstem bronchus, a left apical cap, and

pulmonary venous compres sion.

thickening of the right paratracheal stripe. Coexistent

Radiographs and CT of patients with pneumomedi­

hemothorax is common, particularly with mediastinal

astinum show lucencies in the mediastinum that outline

hemorrhage caused by aortic rupture. Significant aortic

mediastinal structures such as the thymus , aorta and pul­

injury is unlikely in the presence of a normal upright chest

monary artery ( Figu res

radiograph.96,97

tion, there is lateral displacement of the pleura that appears

7-33 and 7-34) .

On the frontal proj ec­

CT, particularly with the helical technique, is highly

as a thin linear structure parallel to the heart border. On the

sensitive and specific for the diagnosis and characteriza­

lateral view, the retrosternal region is usually the site of the

tion ofinjuries ofthe thoracic aorta. Potential findings with

largest air accumulation

CT include periaortic hematoma , localized narrowing,

pneumomediastinum is visible only on the lateral view.

( Figure 7-35) .

Occasionally, a small

contour abnormality of the aortic wall, intimal flap, pseu­

Radiographs often show coexistent air collections tracking

doaneurysm, and contrast extravasation. A technically

along tissue planes in the neck and chest wall. Occasionally,

adequate helical CT provides nearly

wo%

accuracy for

there is extrapleural extension posteriorly at the lung apex

the exclusion of thoracic aortic inj ury. Transcatheter angi­

or along the diaphragm. When standard radiographs are

ography is indicated if CT is abnormal but nonspecific/

equivocal for the diagnosis of a concomitant pneumotho­

inconclusive, or if further definition of the abnormal­

rax, decubitus views or CT are often helpful. Air within the

ity is required for presurgical planning. Potential find­

peribronchial and perivascular spaces of the lung is occa­

ings with aortography are similar to those described for

sionally visible on Cf.103

Part 1 The Thorax

246

Figure 7-33 Pneumomediastinum. A n axi al C T image shows air outlining the trachea, esophagus and vessels in the mediastinum. The displaced pleura appears as a thin linear interface between the lung and the mediastinal air. There is a small area of subcutaneous emphysema on the right.

Figure 7-34 Pneumomediastinum.

Mediastinal air causes displacement of the thymus ( lower arrow). There are linear air collections ( upper arrow) extending from the mediastinum into the neck. Subcutaneous emphysema is present at the base of the neck on the right. The cause of the air leak in this child was left main bronchus obstruction by a foreign body.

A

B

Figure 7-35 Pneumomediastinum.

( upper arrows) . B. The lateral view shows the greatest volume of

This 13-year-old boy experienced sudden onset of retrosternal chest pain while participating in a soccer match. A. On the posteroanterior view, mediastinal air displaces the parietal pleura (lower 3 arrows) . Air outlines the aortic knob. Streaks of air extend from the upper mediastinum into the neck

air to be in the anterior mediastinum. The presence of air causes a sharp interface with the anterior borders of the heart and ascending aorta (arrows) . There is a thin stripe of air adjacent to the anterior tracheal wall.

Chapter 7 The M ed i asti n u m

R E F E R E N C ES 1. Siegel M J , Glazer H S , Wiener J l , Molina PL. Normal and abnormal thymus in childhood: MR imaging. Radiology. 1989;172 (2):3 67-37! . 2. Woywodt A, Verhaart S, Kiss A. Massive true thymic hyperplasia. Eur J Pediatr Surg. 199 9 ; 9 (5 ) :331-333. 3 · Dimitriou G, Greenough A, Rafferty G, et al. Respiratory distress in a neonate with an enlarged thymus. Eur] Pediatr. 2000;15 9 (4) :237-238.

4· Gow KW, Kobrynski L, Abramowsky C, Lloyd D . Massive

benign thymic hyperplasia in a six-month-old girl: case report. Am Surg. 2003;6 9 (8) :717-?1 9 ·

5 · linegar A G , Odell J A , Fennell WM, e t al. Massive thymic hyperplasia. Ann Thorac Surg. 1993;55(5) :1197-1201. 6 . Yin EZ, Frush DP, Donnelly LF, Buckley RH. Primary immunodeficiency disorders in pediatric patients: clinical features and imaging findings. A]R Am] Roentgenol. 2001;176 (6) :1541-1552. 7· Saggese D, Ceroni Compadretti G, Cartaroni C. Cervical ectopic thymus : a case report and review of the literature. Int ]

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51. Liang X, Lovell MA, Capocelli K.E, et a!. Thymoma in children: report of 2 cases and review of the literature. Pediatr Dev Pathol. 201o;13 (3):zoz-zo8. 52. Spigland N, Di Lorenzo M , Youssef S , e t a l . Malignant thymoma in children: a zo-year review. J Pediatr Surg. 199o;zs (11) :t143-1146. 53- Tomiyama N , Honda 0, Tsubamoto M , et al. Anterior

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62. Rizvi M A , Evens AM, Tallman M S , et a!. T-cell non-Hodgkin lymphoma. Blood. zoo6;Io7(4) :125 5-1264. 63. Harnrick-Turner J E , Saif M F , Powers C I , et al. Imaging of childhood non-Hodgkin lymphoma: assessment by histologic subtype. Radiographies. 1994;14 (1) :u-z8.

64. Piira T, Perkins SL, Anderson JR, et a!. Primary mediastinal large cell lymphoma in children: a report from the Childrens Cancer Group. Pediatr Pathol Lab Med.

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CH A PTE R

8

The Chest Wall

CLI N ICAL PRESENTATIONS: CH EST PAI N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

251

DEVELOPM ENTAL ABNORMALITI ES . . . . . .

252

Sternal Anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

252

CH EST WALL N EOPLASMS AND MASSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

258

Normal Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

252

Pectus Excavatum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

252

M esenchymal Ham artoma . . . . . . . . . . . . . . . . . . . . . . . . . .

259

Pectus Carinatum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

253

Lipoblastoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

261

Fi brous Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

263

..............

265

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

266

Anomalies of Fusion and O ssification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

255

Rib Anomal ies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

256

Poland Anomaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

257

CLINICAL PRESENTAT IONS: CHEST PAIN

As phyxiati ng Thoracic Dystrophy (J eune synd rome) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

M al ignant Chest Wal l N eoplasms

257

child with sickle cell disease is a n important clinical indi­ cator of

acute chest syndrome. Chest pain in children with pulmonary embolism may be accompanied by cough, dys­

A variety o f cardiac, pulmonary, and esophageal lesions

pnea, or hemoptysis, and sometimes includes a pleuritic

can result in chest pain.

component.

Pericarditis causes severe subster­

nal chest pain that is exacerbated by movement or respira­

Esophageal pathology can produce symptoms local­

tion. Patients sometimes report that the pain diminishes

ized to the thorax. The pain associated with

when assuming an upright position and leaning forward.

tends to be localized to the retrostemal region and has a

Tachyarrhythmias can compromise myocardial

esophagitis

blood flow

burning character. Because gastroesophageal reflux is the

and result in ischemic pain, often in association with

usual underlying cause, assuming the supine position may

lightheadedness, syncope , or palpitations. The pain asso­

worsen the pain. An

ciated with

stantial retrostemal pain.

aortic dissection

varies according to the site

of the lesion. Dissection in the ascending aorta causes

esophageal foreign body may cause

sub­

Chest pain in children without a known underlying

anterior chest pain. Dissection in the upper portion of

cardiac or pulmonary abnormality is usually

the arch or descending aorta causes pain that radiates to

in origin; for example, rib fracture, muscle strain, contu­

the back.

sion, or costochondritis . Pain in these patients is usually less

musculoskeletal

Pulmonary conditions are important considerations

severe than pain associated with substantial intrathoracic

in the differential diagnosis of chest pain in children.

pathology. The chest wall pain may be localized and non­

Spontaneous pneumothorax causes acute onset of unilateral

radiating, and is often exacerbated by exercise or palpation. '

chest pain. The pain is often difficult to localize and may be accompanied by dyspnea. Pain caused by pleural

tion (pleuritic pain)

Costochondritis is

an inflammatory proces s of one or

irrita­

more of the costochondral cartilages that causes localized

is typically exacerbated during inspira­

tenderness and pain of the anterior chest wall at the cos­

tion; physical examination may demonstrate a pleural rub.

tochondral andjor costosternal articulations . Most cases

Pleural irritation can occur as a result of a viral infection

in children are idiopathic. Others are a result of trauma,

or as a complication of bacterial pneumonia. Chest pain

exercise, or irritation because of forceful coughing. Some

is part of the constellation of symptoms in many chil­

patients have an underlying systemic condition, such

dren with

as an autoimmune disorder, chronic renal failure, or

pneumonia.

The acute onset of chest pain in a

252

Part

1 The

Thorax

thyroid disease. In most patients , there is no appreciable

Ossification is usually radiographically visible in the

soft-tis sue swelling on physical examination. Diagno stic

manubrium and sternal body at birth. Xiphoid ossification

imaging studies are often normal. CT sometimes shows

occurs during the first year of life. Fusion of the paired

cartilaginous irregularity/enlargement, local soft-tis sue

ossification centers in the body progresses in a superior­

swelling, and resorption of adjacent bone. Signal alter­

to-inferior pattern, and is usually complete by

ation in the inflamed cartilage is sometimes visible on

of age. Fusion between these segments progresses during

1

to 2 years

in an inferior-to-superior pattern. The manu­

M R I . The pain tends to be unilateral, and most frequently

childhood

is localized in the region of the fourth through sixth cos­

brium, sternal body, and the xiphoid ossification centers

tochondral junctions . The onset of pain is insidious for

usually remain separate throughout childhood. The pat­ tern of sternal ossification center development and fusion

most patients .2·3

Tietze syndrome refers to unilateral pain and swelling of

varies considerably between individuals . 9

the anterior chest wall in the region of the second and third costochondral junctions , with normal overlying skin. This is an idiopathic condition that often follows an intermit­ tent course for several months. Radiographs are normal. Potential M RI findings include enlargement and thicken­ ing of cartilage at the symptomatic site, increased signal intensities of affected cartilage on T2-weighted and short tau inversion recovery (STIR) images , and bone marrow edema in the adjacent subchondral bone.4

Precordial catch

(Texidor twinge) is a clinical syndrome

characterized by the sudden onset of severe or shooting chest pain that is usually localized over the cardiac apex and lasts for no more than a few minutes . The pain is worsened by deep inspiration. The symptoms are recurrent. This is a common cause of chest pain in children and adolescents. The etiology of this syndrome is unknown. Radiographic studies are normal.5

Slipping rib syndrome

results from inadequate or dam­

aged medial fibrous attachments of the anterior margins of the eighth, ninth, or tenth ribs that allow a cartilage tip to slip superiorly and impinge on the intervening intercostal nerve. Slippage of the rib is associated with sudden onset of pain, and tenderness at the site may persist for a few days. Moving the ribs at physical examination reproduces

Pectus Excavatum Pectus excavatum is a congenital anomaly in which there is inward depression of the sternum and deformities of the adjacent ribs. The pattern and severity of sternal and rib deformities vary greatly between patients. In some patients, the entire sternum, including the manubrium, is depressed; in other patients, the deformity is confined to the inferior aspect of the sternum. Rotational deformity of the sternum (sternal torsion) , usually to the right, often accompanies pectus excavatum. In some patients with ster­ nal rotation, the associated rib deformities are asymmetric (Figu re 8-1 ) . 10•11 Most patients with pectus excavatum are asymptom­ atic, aside from the cosmetic deformity. Severe deformity, however, can result in cardiorespiratory symptoms. Pectus excavatum is more common in males . The frequency of this condition in the general population is approximately

1%,

although most patients have only mild sternal deformity. Pectus excavatum can occur in association with idiopathic scoliosis, Marfan syndrome, homocystinuria, neurofibro­ matosis type

1 (5o%

of patients) , osteogenesis imperfecta,

the pain. The diagnosis can be confirmed with real-time sonographic evaluation of the costal cartilage during pro­ vocative maneuvers.G-8

DEVELOPMENTAL ABNORMALIT IES

Sternal Anomal ies Normal Development The sternum develops from 2 longitudinal bands of meso­ blastic tissue that are separate from the ribs. These bands eventually fuse. The developing ribs migrate medially and fuse with the sternal tissue. Cartilaginous centers form within this mesoblastic tissue. The manubrium (and

in

many individuals , the first sternal segment) have single cartilaginous centers; there are paired centers for the other sternal segments . The earliest sonographic visualization of the fetal sternum with two to three ossification centers is at

19 weeks'

gestational age. The fifth ossification center is

first visible at 2 9 weeks' gestation.

Figure 8--1 Pectus excavatum. An axial CT image of a 17-year-old boy with severe pectus excava­ turn shows posterior deviation of the sternum. The sternum has a tipped configuration, and there is asymmetry of the associated anterior chest wall deformity. The heart is shifted to the left.

Chapter 8 The Chest Wa l l

A

Figure 8-2 Pectus excavatum.

A An axial T2-weighted M R image of a 4-year-old child

with neurofibromatosis type 1 demonstrates severe pectus excavatum deformity (Haller index = 9 . 2 ) . There is also torsion of the sternum. The heart is deviated to the left and there is

Turner syndrome, Ehlers-Danlos syndrome, and myotonic muscular dystrophy (Figure 8-2) . Frontal chest radiographs o f children with pectus excavatum show steep inferior sloping of the anterior aspects of the ribs as a consequence of the sternal defor­ mity. With moderate to severe pectus excavatum, there is alteration in the appearance of the heart on frontal chest radiographs that can lead to a mistaken diagnosis of cardiac or pulmonary pathology. The sternal deformity causes the heart to shift to the left and rotate on its verti­ cal axis, resulting in a straight left-heart border and the appearance of mild cardiomegaly. The right-heart border is obscured by the depressed sternum and there is often increased density along the right-heart border; this can mimic the appearance of atelectasis or consolidation in the right middle lobe (Figure 8-3) . The lateral radiograph is diagnostic: the depressed sternum projects posterior to the anterior rib margins ( Figure 8-4) . There are rare patients who develop air trapping in the left lung because of bronchomalacia of the left main bronchus in associa­ tion with pectus excavatum. CT evaluation accurately assesses the severity of pec­ tus excavatum and determines the effects on intrathoracic structures . Three-dimensional CT images are sometimes useful for planning of surgical repair ( Figure 8-s) . The Haller index quantifies the severity of pectus excavatum. This is the ratio of the transverse diameter of the thoracic cavity to the distance between the sternum and spinal column measured on an axial image at the level of most severe deformity (Figure 8-6) . In normal patients, the mean Haller index is 2 . 5 6 (0.35 standard deviation [SD]). An index of greater than 3.25 indicates moderate to severe pectus deformity,'>

253

B

compression of the right atrium. B . A sagittal fat-suppressed T2-weighted image shows posterior deviation of the inferior aspect of the sternum and anterior deviation of the superior aspect. The hyperintense tissue in the mediastinum and anterior chest wall represents a plexiform neurofibroma.

The traditional surgical method for pectus excava­ tum repair was first described by R.avitch. This consists of resection of deformed cartilages and correction of the ster­ nal angulation by a wedge osteotomy in the upper sternal cortex. Various modifications of this technique have been developed over time. The most commonly utilized tech­ nique for the treatment of moderate to severe pectus exca­ vatum in current practice is the insertion of a curved metal bar (Nuss bar) dorsal to the sternum. Stabilizer bars are positioned along the outer margins of the retrosternal bar. The bar is usually removed after about 2 years. Preoperative CT allows measurements for accurate Nuss bar sizing. Common radiographic findings in the perioperative period include pleural fluid accumulation, pneumothorax, pneu­ momediastinum, and atelectasis. Potential long-term com­ plications include bar migration and separation from a stabilizer bar. Reactive changes in the ribs adjacent to the stabilizer bars are normal.'3-' 6

Pectus Carinatum Pectus carinatum (pigeon breast) is an idiopathic congeni­ tal deformity in which there is abnormal anterior protru­ sion of the sternum. The deformity is typically confined to the inferior third of the sternum. Pectus carinatum is approximately 10 times less common than pectus excava­ tum. The male-to-female ratio is 4:1. In approximately half of patients with pectus carinatum, there is an association with congenital heart disease (often cyanotic) . Syndromes associated with pectus carinatum include Marfan syn­ drome, homocystinuria, spondyloepiphyseal dysplasia, prune-belly syndrome, Morquio syndrome, osteogenesis imperfecta, and Noonan syndrome.'7 ·' 8

254

Part 1 The Th orax

A

B

Figure 8-3 Pectus excavatum.

A, B, C. Chest radiographs of 3 children with pectus excavatum deformities of varying severity. Each child has obscuration of the right-heart border, leftward deviation of the heart, and variable straightening of the left-heart border. The anterior portions of the ribs angle inferiorly.

Lateral chest radiographs of children with pectus cari­ natum show protrusion of a portion of the sternum ante­ rior to the anterior rib ends ( Figure 8-7) . This most often involves the inferior third of the sternum ( Figure 8-8) . In some patients, there is posterior angulation of the xiphoid process. The costal cartilages adjacent to the sternal anom­ aly are deformed. The type of pectus carinatum in which there is symmetric protrusion of the body of the sternum and costal cartilages is sometimes termed chon.drogladiolar

c

protuberance or keel chest diformity. A less-common type of pectus carinatum consists of protrusion of the manubrium. There is also a mixed type of pectus carinatum in which there is rotation ofthe sternum, with depression ofthe costal cartilages and sternum on one side, and protrusion of these structures on the contralateral side. CT imaging is useful for selected patients to plan operative intervention or moni­ tor the deformity during conservative therapy. The Haller index serves to quantify the severity of the deformity. '9

Chapter 8 The Chest Wa l l

255

Figure 8-5 Pectus excavatum. A right anterior oblique three-dimensional CT image of a 15-year­ old boy shows posterior deviation of the inferior portion of the sternum. The anterior aspects of the ribs turn inferiorly and posteriorly. The costal cartilages curve posteriorly to meet the sternum.

congenital heart disease (particularly cyanotic varieties) often have early fusion of the ossification centers in the sternal body and early fusion between the manubrium and body. In some individuals , this early fusion leads to pectus carinatum.

Figure 8-4 Pectus excavatum. A lateral chest radiograph of a 15-year-old boy shows posterior deviation of the inferior aspect of the sternum and the adjacent soft tissues (arrow) .

There is a spectrum of potential anomalies related to defective fusion of the longitudinal cartilaginous bars from which the sternum develops. Deficient fusion may result in a longitudinal fissure , either partial or complete

(Figure 8-1 0) .

Isolated partial fissures are most common,

and are usually located at the superior aspect of the ster­ num. Defective fusion of the superior aspect of the ster­

Anomalies of Fusion and Ossification

num can result in a V-shaped deft and lateral deviation of the medial ends of the clavicles. A large superior sternal

The most common developmental variation of the sternum

defect is sometimes associated with pulmonary hernia­

is the presence of multiple manubrial ossification centers

tion or ectopia cordis. Intrinsic abnormalities in the heart

in approximately 15% of otherwise

are uncommon in these patients with a superior defect.

(Figure 8-g) .

This occurs

normal children, and in at least 8 5% of children with Down

However, clinically significant intracardiac anomalies are

syndrome. Delayed sternal ossification occurs in about

common in patients with ectopia cordis accompanied by an

w% of infants with congenital heart disease. Patients with

inferior sternal defect. The combination of ectopia cordis, a

256

Part 1 The Th orax

A

B

Figure 8-6 Hailer index. A An axial CT image of a 1o-year-old child with mild pectus excavatum deformity demonstrates a Haller index of 2.93 (23.12/7.89 em) . B. A 12-year-old child with a more severe form of pectus excavatum has a Haller index of 4.11 (26.13/6.35 em) .

sternal defect, congenital heart disease, and defects in the abdominal wall, diaphragm, and pericardium is termed the pentalogy of Cantrell. 2 0 There are various additional sternal anomalies, most of which are clinically insignificant. Accessory supraster­ nal bones are due to ossification of persistent episternal cartilage. A notched or cleft appearance of the xiphoid process is a common developmental variation of no clini­ cal significance. Incomplete fusion of the embryonic car­ tilaginous sternal bars can also lead to a sternal foramen, usually at the junction of the third and fourth segments of the body.

Rib Anomal ies Rib anomalies include accessory (cervical) ribs, fusion anomalies, bifid ribs, and a diminished number of ribs

Figure 8-7 Pectus carinatum. A lateral radiograph of a 16-year-old patient shows anterior pro­ trusion of the inferior aspect of the sternum.

(Figu re 8-1 1 ) . Most of these anomalies are of no clinical sig­ nificance. Large cervical ribs occasionally compress adj a­ cent structures. A bifid rib results in a palpable lump on the chest wall, which is sometimes mistaken for a neoplasm (Figure 8-1 2) . Isolated rib synostoses most often involve the first and second ribs, and are asymptomatic. Intrathoracic rib is a rare malformation in which an anomalous rib fol­ lows an oblique inferior course within the chest cavity, compressing and displacing lung ( Figure 8-13) . Although most patients with only 11 pairs of ribs are otherwise

Chapter 8 The Chest Wa l l

257

there are multiple segmentation anomalies in the tho­ racic and lumbar spine, including hemivertebra and ver­ tebral fusions.

Poland Anomaly Poland anomaly refers to absence or hypoplasia of compo­ nents within one side of the chest wall and the ipsilateral upper extremity. This sporadic disorder occurs in approxi­ mately 1 in 32,ooo livebirths. Theories as to the pathogen­ esis include abnormal migration of embryonic tissues, hypoplasia of the subclavian artery, and fetal injury. Various patterns of deformity occur in these patients. Most prac­ titioners consider absence of the pectoralis major muscle to be a prerequisite for true Poland anomaly. About half of these patients also have hypoplasia and for syndactyly of the ipsilateral hand. Other potential findings ipsilateral to the deformity include hypoplasia/aplasia of the pectoralis minor andjor serratus anterior muscles, absent axillary hair, diminished subcutaneous fat, breast hypoplasia or aplasia, athelia, rib deformities, undergrowth of the clavicle or scapula, upper extremity defects, and Sprengel defor­ mity. Vertebral or renal anomalies can occur. Approximately three-fourths of instances of Poland anomaly involve the right side. It is three times more common in boys than in girls. 22-24 Chest radiographs of patients with Poland anomaly typically show diminished density of one side of the thorax because of diminished soft-tissue bulk (Figure 8-14) . This can lead to a mistaken diagnosis of a unilateral hyperlucent lung. Observation of asymmetry of the axillary soft-tissue thickness is often helpful (Figure 8 1 5) . Osseous abnor­ malities are present in a minority of patients with Poland anomaly. Potential radiographic findings in patients with associated osseous deformities include: ipsilateral rib cage and sternal depression, with contralateral sternal and rib protrusion; ipsilateral rib hypoplasia without other defor­ mities; and rib aplasia, with depression of adjacent ribs and sternal rotation. Ribs 2 through 4 are most often involved in these patients. -

Figure 8-8 Pectus carinatum.

There is marked anterior deviation of the inferior aspect of the sternum in this 15-year-old boy.

normal, this finding occurs in association with various syndromes, including asphyxiating thoracic dystrophy, tri­ somy 18, trisomy 21, carnptomelic dysplasia, and cleidocra­ nial dysplasia. 21 Rib anomalies are associated with various other skel­ etal disorders. Rib deformities are common in patients with severe thoracic scoliosis. Rib deformities are an important component of many bone dysplasias. The ribs are wide in patients with storage diseases. Thin osteope­ nic ribs are present in children with osteogenesis imper­ fecta. Generalized rib hypoplasia occurs in asphyxiating thoracic dysplasia and various short-rib polydactyly syn­ dromes . Mild rib undergrowth occurs in many of the skeletal dysplasias that affect the metaphyses and epiphy­ ses. Rib fusion anomalies occur in patients with spon­ dylocostal dysostosis (Jarcho-Levin syndrome) . The ribs in these children may have a fan-shaped appearance and

Asphyxiati ng Thoracic Dystrophy (Jeune synd rome} Asphyxiating thoracic dystrophy (Jeune syndrome) is an autosomal recessive dysplasia in which failure of normal chest wall development in utero causes a narrow thorax, small chest cavity, and bilateral pulmonary hypoplasia. There is a wide spectrum of severity of the chest wall undergrowth and of the resultant respiratory compromise, although most patients have substantial neonatal respira­ tory distress. Nearly all patients with J eune syndrome have brachydactyly. Other potential associated anomalies in these patients include hepatic fibrosis with bile duct prolif­ eration, cystic liver disease, situs inversus , pancreatic cysts , abdominal muscular deficiency, lobulated tongue, nail

258

Part 1 The Thorax

A

Figure 8-9 Sternal ossification defects. A. B. A lateral radiograph and a sagittal CT image show a thin cleft (long arrows) between separate ossification centers in the

hypoplasia, polydactyly, dental malformations, and abnor­ malities of retinal pigmentation. Patients who survive the neonatal period develop progressive renal disease.2P6 A characteristic radiological feature of asphyxiating tho­ racic dystrophy is a very narrow thorax, with horizontal ribs that have bulbous anterior ends. The pelvis is small. The iliac bones are short and flared. There is a trident appearance of the acetabula. Spurs arise from the inferolateral aspects of the sciatic notches. There is early ossification ofthe proximal femoral epiphyses. Potential findings in the hands include cone-shaped epiphyses, short metacarpals and phalanges,

B

manubrium. The CT image shows the apparent defect in the inferior aspect of the sternal body (short arrows) to be unossified cartilage.

and syndactyly. A handlebar deformity ofthe clavicle is com­ mon. Craniosynostosis is occasionally present.

CHEST WALL NEOPLASMS AND MASSES The differential diagnosis of pediatric chest wall masses includes various developmental lesions, benign tumors, and malignancies (Table 8-1 ) . Many palpable lesions of the chest wall in children are nonneoplastic anoma­ lies such as bifid rib or costal cartilage deformity. An

Chapter 8 The Chest Wall

259

Table &-1 . Primary Chest Wall M asses in Children

Benign bone lesions

·

Mal ignant bone neoplasms Benign soft-tissue masses

Mal ignant soft-tissue neoplasms

·

Osteochondroma Fi brous dysplasia Aneurysmal bone cyst Chondroma Chondroblastoma Langerhans cel l histiocytosis Ewi ng sarcoma Osteosarcoma Chondrosarcoma Hemangioma Lym phatic malformation Venous m alformation Lipoma M esenchymal hamartoma Lipoblastoma Teratoma Plexiform neurofibroma Askin tumor Neuroblastoma Rhabdomyosarcoma Lym phoma Leiomyosarcoma M esenchymal sarcoma

Figure 8-1 0 Sternal fusion anomaly. A coronal CT image of a 3-year-old child shows persistent separa­ tion of the paired ossification centers in the body of the sternum.

composed predominantly of chondroid tissue with large endothelium-lined blood spaces and immature mesen­ chyme with osteoclastic giant cells and osteoid. 27 The lesion arises from a rib , usually from the central portion. Occasionally, more than one distinct lesion arises from one or more ribs; this may lead to a mistaken diagnosis of malignancy. Mesenchymal hamartoma affects adj a­ cent structures by compression, but there is no invasion;

osteochondroma can cause a slowly enlarging mass. Benign soft-tissue lesions of the chest wall include vas­ cular malformations, mesenchymal hamartoma, lipoma, lipoblastoma, and plexiform neurofibroma ( Figure 8-1 6) . Primary malignancies include bone tumors, Askin tumor, and rhabdomyosarcoma.

M esenchymal Hamartoma Mesenchymal hamartoma o f the chest wall is a rare benign tumor derived from skeletal elements. This lesion occurs in infants and young children. It is not consid­ ered a true neoplasm. The composition of mesenchymal hamartoma is a mixture of proliferating mature elements of bone, cartilage, and fibroblasts. There are also hemor­ rhagic cavities that represent secondary aneurysmal bone cysts. Histological examination shows the mass to be

Figure 8-11 Cervical ribs. There are bilateral cervical ribs arising from C7 in this I4·year­ old child.

260

Part 1 The Thorax

A

Figure 8-12 Bifid rib. There is a bifid configuration of the anterior aspect of the right fourth rib (arrows) in this 15-month-old boy evaluated for a palpable mass.

metastasis does not occur. Other terms that have been used for this lesion include infantile cartilaginous ham­ artoma, mesenchymoma, osteochondrosarcoma, benign chondroblastoma, chondromatous hamartoma, and infan­ tile osteochondroma. The clinical presentation of mesenchymal hamartoma of the chest wall can occur at any time throughout child­ hood, but it is most often identified during infancy and can be present at birth. Detection of this lesion with prenatal ultrasound has been reported? 8 ·29 Intrathoracic extension is common, and many patients present with respiratory symptoms, such as tachypnea, cough or fever, that lead to chest radiography and incidental discovery of the mass. In rare instances, the respiratory compromise caused by a large mesenchymal hamartoma in a newborn is life threat­ ening. Other patients present with a visible or palpable chest wall mass or deformity. A posterior location is most common.3°·3' Radiographs of mesenchymal hamartoma of the chest wall show a large expansile rib lesion with cortical irregu­ larity and erosion. The extraosseous soft-tissue mass is extrapleural. The adjacent ribs may be markedly deformed and displaced. Most often, multiple continuous ribs are involved. Matrix mineralization typically has a chondroid

B

Figure 8-1 3 I ntrathoracic rib.

A. An anomalous supernumerary rib arises at the base of the left fourth rib and courses inferiorly (arrows) . B. CT confirms that the rib (arrow) is within the thoracic cavity. There is localized elevation of the pleura.

pattern, with arcs and rings; amorphous mineralization (osteoid pattern) is less common.3' CT shows a large rib mass with a heterogenous soft­ tissue component that contains mixed skeletal elements. Mineralization is nearly always present, and is demon­ strated with greater sensitivity by CT than with standard radiographs. When present, secondary aneurysmal bone cysts appear as cavities with fluid levels. CT documents the degree of intrathoracic extension; the lesion typically remains extrapleuralY With MR, the complex composition of mesenchymal hamartoma produces a heterogenous pattern. The lesion

Chapter 8 The Chest Wa l l

261

A

Figure 8-1 5 Poland anomaly. There is a hyperlucent appearance of the right lung because of a paucity of ipsilateral chest wall soft tissue.

possible with percutaneous needle biopsy in correlation with the imaging features. The differential diagnosis of mesenchymal hamartoma includes both malignant and benign chest wall lesions, such as Ewing sarcoma, primitive neuroectodermal tumor, metastasis, fibrous dysplasia, Langerhans cell histiocyto­

B

sis, and hemangioma. Matrix mineralization, hemorrhagic

Figure 8-14 Poland anomaly. The parents of this otherwise healthy Jo-year-old girl reported "indentation" of the left anterior chest wall. A. There is subtle hyperlucency of the left lung and asymmetry of the axillary soft tissues. The ribs are normal. B. CT confirms underdevelopment of the left anterior chest wall muscles.

cysts, and extrapleural extension without pleural effusion are helpful differential imaging findings .

Lipoblastoma Lipoblastoma i s a benign soft-tissue tumor that predomi­ nantly occurs in infants and young children. In the tho­ rax, the most common sites of origin are the chest wall and

is predominantly of intermediate signal intensity on

mediastinum. This tumor is composed of fibrovascular

Tl-weighted images. High-signal-intensity blood within

septa, adipose tissue, and myxoid stroma. Approximately

aneurysmal bone cysts is a useful identifying feature of this

90% of lipoblastomas are diagnosed in children younger

lesion. Hemorrhagic and cystic components lack contrast

than

enhancement. Mesenchymal hamartoma is heterogenous

12 months. Seventy percent of lipoblastomas occur in the

on T2-weighted images. Fluid levels may be present in cys­

extremities, with most of the remainder located in the

tic areas.3'·32

mediastinum, retroperitoneum, or paraspinal areas. Two

Surgical resection is required for mesenchymal ham­

3

years of age; 9% are identified before the age of

subtypes are recognized. A well-defined mass is termed whereas a deep unencapsulated infiltrative

artoma when there are significant secondary pulmonary or

lipoblastoma,

cardiac effects, or if there is unacceptable physical deformity.

lesion is termed

lipoblastomatosis.33-34

Small lesions may be observed, as spontaneous regression

The radiographic appearance of a lipoblastoma is

has been reported. Hemorrhagic complications can occur

that of a well-defined soft-tissue mass. The fatty composi­

with surgical biopsy or resection. An accurate diagnosis is

tion sometimes results in a hypodense character. CT and

262

Part

1

The Thorax

B

A

C

Figure 8-1 6 Benign chest wall masses.

A A fat-suppressed T2-weighted M R image of a child with neurofibromatosis type 1 shows an infiltrative hyperintense neurofibroma of the right anterior chest wall and mediastinum. B. A venous malformation in a 4-year-old child with a palpable right chest wall lesion appears as a dumbbell-shaped hyperintense

Figure 8-17 Lipoblastoma. There is a predominantly fat-attenuation mass in the right chest wall (arrows) . Areas of higher-atten­ uation soft tissue are present within the lesion.

D

mass on this fat-suppressed T2-weighted MR image. C. There are fluid-fluid levels in this lymphatic malformation in a 2-year­ old child (T2-weighted MR). D. Histological examination of this heterogenous right chest wall mass in a 7-year-old patient demon­ strated a mixed lymphatic-venous malformation (fat-suppressed T2-weighted MR).

Chapter 8 The Chest Wa l l

263

A

c

Figure 8-1 8 Fibrous hamartoma of infancy.

This n-month-old boy presented with a rapidly growing soft­ tissue mass deep to the left scapula. A, B. The lesion (arrow) is hyperintense on both T1-weighted (A) and T2-weighted (B) spin­ echo images as a result of adipose tissue. There are hypointense

M RI indicate a predominantly fatty composition, with intermixed fibrous tissue that undergoes some degree of contrast enhancement (Figure 8-1 7) . On CT, there is stranding of fat within the lesion. M R demonstrates intratumoral streaks and whorls caused by the fibrovas­ cular network.

D

septa. C. The fibrous components are slightly hyperintense to the fatty components on this fat-suppressed T2-weighted sequence. D. Moderate contrast enhancement occurs, greatest in the fibrous septa, on this fat-suppressed T1-weighted image.

Fibrous Lesions A variety of fibrous lesions can involve the chest wall, including fibromatosis (desmoid tumor or aggressive fibromatosis) , infantile myofibromatosis, juvenile hya­ line fibromatosis , fibrous hamartoma, and fibrosarcoma.

264

Part 1 The Thorax

A

B

c

This 18-year-old girl presented with cough and left-sided chest pain. A, B. Posteroanterior and lateral radiographs show a large mass iri the upper aspect of the left thoracic cavity. C. The lesion

has a heterogeneous character on this contrast-enhanced cr image. The tumor extends into the chest wall between several ribs. At surgery, this primitive neuroectodermal tumor infiltrated the chest wall and left upper lobe.

Fibromatosis in the pediatric age group predomiriantly affects adolescents. Chest wall involvement with fibromato­ sis most often occurs in the region of the shoulder. CT and M RI typically show an infiltrative soft-tissue mass. With M R imagirig, the identification of low signal intensity on both T1-weighted and T2-weighted sequences may provide a due to the fibrous composition of the tumor.

Fibrous hamartoma of infancy is a rare, benign soft­ tissue tumor that most often occurs within the first 2 years of life. There is a male predilection (p) . This lesion can arise anywhere in the body, but the most common locations are the axilla , shoulder, upper arm, inguinal region, and chest wall. It is usually located iri the subcutaneous tissue. Although a benign lesion, fibrous hamartoma can be quite

Figure 8-1 9 Askin tumor.

Chapter 8 The Chest Wa l l large at the time of clinical presentation. The major tissue components are mature adipose tissue and intersecting trabeculae of fibrous tissue. Histological evaluation dem­ onstrates clusters of loosely spaced primitive spindle cells. Radiographs show a nonspecific soft-tissue lesion, without calcification. The lesion is hyperechoic on sonography. MRI and CT show a lobulated mass that contains fat. On MR, the fibrous septa are often somewhat hyperintense to the tumor matrix on fat-suppressed T2-weighted sequences. Most often, there is moderately intense contrast enhance­ ment (Figure 8 1 8) . 3 5 -

Malignant Chest Wal l Neoplasms Askin tumor is a malignant tumor that arises in the soft tis­ sues of the chest wall or the peripheral aspect of the lung. This neoplasm is composed of undifferentiated small round cells, likely of neural crest origin. Askin tumor is part of the Ewing sarcoma family of neoplasms, which includes peripheral primitive neuroectodermal tumor and

Ewing sarcoma of bone or soft tissue. Askin tumor is also termed primitive neuroectodermal tumor of the chest wall. This rare tumor occurs predominantly in children and young adults . It is more common in females. Askin tumor accounts for at least half of primary malignant chest wall neoplasms in children. J6-38 Imaging studies of Askin tumor typically show an infiltrative mass, often extending into the visceral pleura andfor paraspinal soft tissues. Lung invasion can occur, and in some patients , the site of origin is unclear ( Figure 8-1 9). Areas of necrosis are common within the lesion; calcification is occasionally present. The mar­ gins of the lesion are poorly defined in many patients. Rib destruction in the region of the tumor is common ( Figu re 8-20) . Pneumothorax and pleural effusion may occur. The skeletal system is the most common site of metastatic disease. After neoplasms of the Ewing sarcoma family, rhab­ domyosarcoma is next most common primary malig­ nancy of the chest wall. Other potential primary malignant

B

A

Figure 8-20 Askin tu mor. A A chest radiograph shows a large right extrapulmonary thoracic mass. The adjacent ribs are irregular, but the lesion does not appear to arise from a rib. B. The mass contains areas of necrosis or hemorrhage that are hypoattenuating on this contrast-enhanced CT image. There are enlarged right hilar lymph nodes. C. A bone window view demonstrates irregular rib demineralization and reactive new bone formation.

265

c

266

Part 1 The Thorax

chest wall lesions include lymphoma, malignant periph­ eral nerve sheath tumor, mesenchymal sarcoma, and bone tumors such as osteosarcoma, Ewing sarcoma, and chondrosarcoma.

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2 0 0 9;44(12):2287-2 2 9 0 . 1 4 · !ida H . Surgical repair o f pectus excavatum. Gen Thorac Cardiovasc Surg. 2010 ; 5 8 ( 2 ) : 5 5-61. 15. Sidden CR, Katz ME, Swoveland BC, Nuss D . Radiologic considerations in patients undergoing the Nuss procedure for correction of pectus excavatum. Pediatr Radial. 2001;

31(6) :429-434· 16. Lancaster L, Mcilhenny J , Rodgers B , Alford B . Radiographic findings after pectus excavatum repair. Pediatr Radial. 1995;

2 5 ( 6 ) :452-454· 17. Goretsky MJ, Kelly RE Jr, Croitoru D, Nuss D . Chest wall anomalies: pectus excavatum and pectus carinatum. Adolesc

Med Clin. 2004;15 (3) A 5 5-471. 18. Robicsek F, Cook JW, Daugherty H K, Selle JG. Pectus carinatum. ] Thorac Cardiovasc Surg. 1979 ;78 (1) : 5 2-61.

33· Ko S F , Shieh C S , Shih TY, et al. Mediastinal lipoblastoma with

intraspinal extension: MRI demonstration. Magn Reson Imaging.

1998;16 (4) :445-448 . 3 4 · Samuel M , Moore I E , Burge D M . Thoracic wall lipoblastoma: a case report and review of histopathology and cytogenetics. Eur J

Pediatr Surg. 2ooo;10 (1) :53-57· 3 5 · Sotelo-Avila C, Bale P M . Subdermal fibrous hamartoma of infancy: pathology of 40 cases and differential diagnosis. Pediatr

Pathol. 1994;14 (1) :39-52. 3 6 . Fink M , Salisbury J , Gishen P . Askin tumor: three case histories and a review of the literature. Eur] Radial. 1992;14(3) :178-18 0.

37· Bourque M D , Di Lorenzo M , Collin P P , et al. Malignant small­ cell tumor of the thoracopulmonary region: "Askin tumor".

J Pediatr Surg. 1989;24(10) :1079-10833 8 . Shamberger RC, Grier H E . Ewing's sarcoma/primitive neuroectodermal tumor of the chest wall. Semin Pediatr Surg.

2001;10 (3):153-160.

CH A P T E R

9

The B reast

NORMAL DEVELOPM ENT . . . . . . . . . . . . . . . . . . . . . . . . . . .

267

N EOPLASMS OF TH E BREAST . . . . . . . . . . . . . . . . . . .

271

Fi broadenoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

271

DEVELOPM ENTAL ABNORMALITI ES . . . . . .

269

Prem atu re Breast Development . . . . . . . . . . . . . . . . . .

269

Lactational Adenoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

274

Accessory Breast Tiss ue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

269

J uven i le Pap i l lomatosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

274

.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

270

H a martoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

274

Gynecomastia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

270

Phyl lodes Tu mor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

274

J uven i le Hypertrophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

270

I N FECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

274

BREAST CYSTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

270

TRAUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

275

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

275

Amastia

NORMAL DEVELOPMENT Paired ectodermal primitive

mammary

breast bud produces a single mound of tissue that includes streaks

(milk

streaks) form along the ventral surface of the embryo dur­ ing the fifth week of gestation. These extend from the axilla to the inguinal region. The mammary ridges arise in the thorax from these streaks and there is progressive differen­ tiation into breast parenchyma during fetal development. The other portions of the mammary streaks normally regress; incomplete involution of embryonic breast tissue can result in accessory or ectopic breast tissue anywhere along the primitive mammary streaks. The prepubertal breast is a rudimentary organ that con­ sists of simple branched ducts surrounded by a connective tissue stroma. With the onset of puberty, the ducts elongate, divide, and form terminal duct lobular units. Lobular differ­ entiation begins in the peripheral regions of the breast and progresses centrally. At the end of pubertal development, the breast consists of a ductal system lined by epithelial cells and

breast tissue and the nipple. The breast bud is demonstrated sonographically as a retroareolar nodule that is hypoechoic relative to adjacent fat and contains low-level echoes. Often, there is a central star-shaped or linear hypoechoic area that correlates histologically with simple branched ducts. During Tanner stage

3,

enlargement and elevation of

the entire breast occur. As with stage

2,

the breast tissue

and nipple form a single mound of tis sue. Development of glandular tissue occurs during this stage. The glandular tis­ sue is relatively hyperechoic on sonography. A central ret­ roareolar spider-shaped hypoechoic region is often visible, representing the ductal system. Tanner stage

4

is transient and does not occur in

all individuals . A secondary mound develops , with the nipple and areola proj ecting anterior to the breast tissue. Sonography shows a prominent hypoechoic nodule in the retroareolar region, surrounded by hyperechoic periareolar fibroglandular tissue .

ending in terminal duct lobular units. Normal breast devel­ opment is classified into a 5-stage Tanner grading system. 1

breast contour, with regression of the areola to form a

bertal breast may show

The hypoechoic central nodule visible in the earlier Tanner

Tanner stage 1 is prepubertal. Sonography of the prepu­

thin ill-defined retroareolar tissue

that is slightly hypoechoic or hyperechoic with respect to adjacent subcutaneous fat

(Figure 9-1 ) .

At the beginning o f puberty, the breast bud develops; this is Tanner stage

2.

Initially, there is a subareolar lump

that is appreciable by palpation only. Enlargement of the

Tanner stage 5 indicates development of a mature smooth contour with the remainder of the breast tissue. stages is no longer visible with sonography. The breast pre­ dominantly consists of hyperechoic glandular tissue.2 Newborns sometimes have mild enlargement of the breast buds as a result of hormonal stimulation; this is

268 Part

1

The Thorax

Figure 9-1 Normal prepubertal breast u ltrasound. Sonography of a 7-year-old girl shows normal breast tissue as a small hypoechoic area (arrows) within the subcutaneous adipose tissue. The deeper hypoechoic structure is the pectoralis muscle.

termed transient gynecomastia of the newborn. This occurs in males and females. Some degree of ductal development can also occur, leading to nipple secretion (termed witch's milk) . Sonographic examination of these infants shows promi­ nent subareolar ducts, which can be symmetric or asym­ metric (Figure 9-2) . Spontaneous resolution occurs over the next weeks to months, and sonography shows regression of the ducts to age-appropriate morphology. Resolution may take longer in breastfed infants because of estrogenic sub­ stances in human milk. The initial development of the breast bud is termed thelarche. The typical age range of thelarche is 8 to 13 years , with a mean of 9.8 years. The ductal system of the breast bud proliferates and enlarges, resulting in a lump deep to the nipple; that is, Tanner stage 2. Occasionally, this process occurs asymmetrically, and sonography may be requested to determine if there is a mass or cyst ( Figure 9·3) - The appear­ ance at this stage is identical to that demonstrated in males with gynecomastia: a hypoechoic subareolar "nodule." The breast tissue appears hypoechoic because the ducts are

B

c

Figure 9-2 Transient gynecomastia of the newborn.

D

A-D. Sonographic images of the right and left breasts of a 30-day-old male (A, B) and a 25-day-old female (C, D) with breast enlargement and nipple discharge show prominent breast tissue with dilated ducts.

Chapter 9 The B reast 269

A

Figure 9-3 Asymmetrical breast development at thelarche.

The parents of this 8-year-old girl reported a "lump in the right breast." A. Sonography of the right breast shows a pubertal

predominantly end-on to the transducer. Manual rotation of the breast tissue while angling the transducer helps con­ firm the solid nature of the structure, which now appears moderately echogenic and contains thin hypoechoic ducts. It is essential that this nodule not be removed surgically, as this would lead to iatrogenic amastia. Spontaneous resolu­ tion of breast bud asymmetry occurs in nearly all affected children.

DEVELOPMENTAL ABNORMALIT IES

Prematu re Breast Development Premature thelarche indicates abnormally early breast devel­ opment. Because thelarche tends to occur earlier in girls of black African descent than in others, the most com­ monly utilized clinical definition of premature thelarche is the onset of breast development prior to 7 years of age in blacks and 8 years in whites. Premature thelarche can be unilateral or bilateral, and may occur as an isolated abnor­ mality or in association with central precocious puberty.3-5 The most common cause of premature thelarche appears to be subtle overfunction of the pituitary-ovarian axis. Menarche in these patients occurs at the usual age. I solated premature thelarche generally occurs between 1 and 3 years of age and is nonprogressive. Sonography is useful for selected children with pre­ mature breast development to document that the palpable "lump" represents normal breast tissue (Figure 9-4) . In addition, sonographic evaluation of the uterus and ovaries can aid in the differentiation between isolated premature thelarche and central precocious puberty. A radiographic bone age assessment is usually indicated for patients with clinical findings suspicious for precocious puberty.

B

pattern of developing breast tissue. The cursor measurement at the base of the breast tissue is 2 . 2 em. B. The breast bud on the left is smaller, with a diameter of 1 . 2 em.

Accessory Breast Tissue Accessory breast tissue refers to normal breast tissue in an ectopic location. Because the ectopic breast tissue typically occurs in conjunction with a normal ipsilateral breast, this represents polymastia, or multiple breasts . Accessory breast tissue can occur anywhere along the courses of the embryonic primitive mammary streaks, from the axillae to the inguinal regions. The most com­ mon location is the axilla; the vulva is the next most common site. The accessory breast tissue may occur as a very small asymptomatic focus of parenchyma to a more developed structure with a nipple and areola. The most common clinical manifestation of supernumerary breast

Figure 9-4 Premature thelarche. There is abnormally advanced development of otherwise normal­ appearing breast tissue ( cursors ) on this sonographic image of a s-year-old girl.

270 Part 1 The Thorax tissue is the isolated presence of a supernumerary (acces­ sory) nipple; this is termed polythelia. 6 The clinical presentation of accessory parenchymal breast tissue often occurs during thelarche, when hor­ monal stimulation causes the tissue to enlarge. Discomfort and swelling may occur; the symptoms are exacerbated by pregnancy, during which milk secretion may be observed. When ectopic parenchymal tissue is present without a nip­ ple or areola, the clinical diagnosis is more difficult. The anomaly is sometimes mistaken for a lipoma, lymphatic malformation, or adenopathy.7 The typical sonographic appearance of accessory breast tissue is that ofmoderately echogenic tissue that has a sim­ ilar character to the normal breast. The tissue may contain varying proportions of glandular, fatty, and fibrous tissue. Ifthe accessory breast lacks a pathway for drainage through an accessory nipple, secretory response during hormonal stimulation (particularly during pregnancy) can lead to sonographically detectable duct ectasia or a galactocele.8 Accessory breast tissue is demonstrated with M R imaging a s a poorly demarcated mass that contains tis­ sue of mixed single intensity on T1-weighted images. Fat­ suppressed T2-weighted images show moderately high signal intensity within the parenchyma and interspersed hypointense areas of fat. The amount of fatty tissue within the lesion varies between patients. As with normal breast tissue, there is a moderate degree of contrast enhancement of accessory breast tissue.9

Although gynecomastia is physiological in the great majority of affected boys, various pathological condi­ tions can cause mammary tissue enlargement, including Klinefelter syndrome, testicular insufficiency, and andro­ gen receptor defects. Other rare causes of gynecomastia include Sertoli or Leydig cell tumors of the testis, femi­ nizing adrenal cortical tumors, gonadotropin-secreting tumors (hepatoblastoma, fibrolamellar carcinoma, chorio­ carcinoma) , prolactinoma, liver disease, and neurofibroma­ tosis type 1. Drugs that can lead to gynecomastia include digitalis , isoniazid, tricyclic antidepressants , cimetidine, and marijuana. Athletes or bodybuilders who consume nutritional supplements (e.g. , dehydroepiandrosterone [DH EA]) or anabolic steroids can develop gynecomastia.5·12 When the clinical diagnosis is in doubt, sonography serves to confirm that the palpable mass in a boy with sus­ pected gynecomastia is breast tissue ( Figure 9-5) . These sonographic findings are identical to those of a girl with pre­ mature thelarche. The breast tissue is usually hypoechoic relative to adjacent subcutaneous fat, and is located in the subareolar region (Figure 9-6) . The echogenicity increases when transducer angulation provides interrogation at an oblique or perpendicular angle to the majority of the ducts.2·'3 Pseudogynecomastia can occur in obese boys . There is breast prominence as a result of excessive adipose tissue, but no mammary tissue enlargement. Sonography con­ firms lack of breast bud enlargements

Amastia

J uvenile Hypertrophy

Amastia refers to developmental absence of the breast. Individuals with this rare anomaly often have additional manifestations of Poland syndrome (urillateral pectoralis muscle aplasia, undergrowth/hypoplasia ofipsilateral chest wall and upper-extremity structures) . Athelia (absence of the nipple) accompanies amastia in many patients. There are rare instances of bilateral amastia associated with ecto­ dermal dysplasia.'0

Juvenile hypertrophy is excessive and rapid breast develop­ ment that usually occurs shortly after menarche or �ess commonly) during pregnancy. Although most often bilat­ erally symmetric, asymmetric or urillateral involvement can occur. Imaging is generally not required. Sonography shows dense breast tissue, with no discrete mass.2

Gynecomastia Gynecomastia refers to excessive development ofthe breast in a male. In children, the peak frequencies are in the neo­ natal period and during adolescence. Neonatal gynecomas­ tia in infants of both genders is a result of the effects of maternal estrogens. This transient gynecomastia of the new­ born is a self-limited abnormality that usually resolves by about 12 months of age. Breast tissue enlargement in other­ wise normal adolescent boys is termed physiological pubertal gynecomastia. This most often occurs approximately 1 year after the onset of puberty; the peak age frequency is 13 to 14 years. Some degree of gynecomastia occurs in 6o% to 75% ofhealthy boys. Spontaneous resolution occurs within 1 to 2 years. Physiological pubertal gynecomastia is caused by an increase in free testosterone, which is metabolized to estradiol by the enzyme aromatase. Excessive body fat facilitates this conversion.u

BREAST CYSTS Most breast cysts arise from the lobular acini, either because of obstruction of the draining duct or an imbal­ ance between the rate of fluid production and resorption. The most common type of breast cyst in adolescent girls is the retroareolar cyst (Montgomery cyst) . Retroareolar cysts are caused by obstruction of the glands of Montgomery, which are sebaceous glands associated with the terminal portions of the lactiferous ducts. Breast cysts can be single or multiple, and unilocular or septated. The lesion is firm to palpation, mobile, and usually non tender (unless infected) . Sonography shows the mass to be anechoic, unless there is superimposed infection or hemorrhage ( Figure 9-7) . Internal septations are sometimes visible. An infected cyst has internal debris and a thickened wall."� A galactocele is a milk-filled cystic dilation of terminal ducts and ductules. This most commonly develops dur­ ing or soon after lactation. The cause is an obstructed milk

Chapter 9 The B reast 271

A

Figure 9-5 U nilateral gynecomastia.

This 12-year-old boy had a palpable left retroareolar nodule. A. A longitudinal sonographic image of the left breast shows prominent hypoechoic mammary tissue (arrows) , measuring

B

1.4 em in diameter and 0 . 5 em in depth. B. Breast tissue on the

right (arrows) is normal for age, measuring o . 6 em in diameter and o.z em in depth.

duct. Rarely, a galactocele can develop in an infant of either

Mammary duct ectasia

most commonly occurs in the

gender because of maternal hormones in breast milk.

subareolar region, but can involve any portion of the breast.

This lesion can also occur in adolescent boys. Sonography

The clinical findings range from a complete lack of symp­

shows a cystic (unilocular or multilocular) or branching

toms to a painful mas s .

hypoechoic tubular structure. Early in the course, the con­

mon. Secondary bacterial infection can occur. Sonography

A bloody nipple discharge is com­

tents are nearly anechoic or have diffuse low-level echoes.

shows one or more tubular, sometimes branching, fluid­

With time, the contents often become more echogenic and

filled structures . The contents are anechoic if clear, or vari­ ably echogenic if there is debris. '7· •8

sometimes sonographically mimic a solid lesion. Doppler studies, however, show no vessels within the "mas s . " Also,

Multiple cysts of varying sizes and dilated ducts are

color Doppler examination during transducer ballottement

common sonographic features of .fibrocystic

of the cyst demonstrates motion of particles within the cav­ ity. A fat-fluid level is sometimes visible on MR.'3·'5 ·' 6

breasts . In addition, there are often multiple echogenic foci

changes of the

because of fibrous tis sue. Fibrous involvement without sub­ stantial cystic change can also occur; this is termed fibrous

mastopathy.

In the pediatric population, clinical manifesta­

tions of fibrocystic changes can occur in late adolescence, with cyclical breast tenderness. Palpation demonstrates a nodular character. 2

NEOPLASMS OF THE BREAST The great majority of breast masses in children and adoles­ cents are benign. The most common solid tumor is fibro­ adenoma. Galactoceles and other cysts are also common. Sonography is the imaging procedure of choice for evalua­ tion of most pediatric breast masses

(Table 9-1 ) .

MR serves

a complementary role for selected patients.

Fibroadenoma Figure 9-6 Gynecomastia. Enlarged breast tissue in this 1o-year-old boy appears hypoechoic (arrows) relative to adjacent adipose tissue on this transverse sonographic image. The deeper linear stripes are the pectoralis muscle.

Fibroadenoma is the most common neoplasm o f the breast in children. This benign fibroepithelial tumor accounts for more than half of solid breast masses in girls during the

2 decades of life. The mean age at diagnosis is 15 to 17 years . The typical clinical presentation is that of a slowly

first

272

Part

1

T h e Th orax

A

B

c

Figure 9-7 Retroareolar cysts. A-C. Sonography of retroareolar cysts in three different teenage girls. These uninfected cysts have thin walls, and lack internal debris. Note prominent acoustic enhancement of the large cyst in A.

enlarging painless lump. Clinical examination identifies a mobile, rubbery, nontender breast mass. More than 1 lesion is present in 10% to 15% of patients) Most fibroad­ enomas stop growing after reaching approximately 3 em in diameter. The lesion may undergo rapid growth during pregnancy. A fibroadenoma that is greater than 5 em ill diameter is termed a giant fibroadenoma.'9 Approximately 5% to 10% of adolescents with a fibro­ adenoma have a highly cellular variant termed a juvenile fibroadenoma. Juvenile fibroadenoma frequently under­ goes rapid growth. In the United States, this type of fibro­ adenoma most often occurs in African American girls. Multiple or bilateral lesions are present in 10% to 25% of patients. The most common sonographic appearance of a fibro­ adenoma is that of a sharply marginated, oval, solid mass, with the long axis parallel to the skin surface. There is a macrolobulated contour in some instances. When present, lobulations should number fewer than 4, have gentle con­ tours, and be well-circumscribed (Figure 9-8) . Often, a thirl, well-defined echogenic pseudocapsule is visible. The lesion is usually homogenous or mildly heterogenous. Thin fluid­ filled clefts are sometimes present. A fibroadenoma is typically hypoechoic relative to glandular breast tissue and approximately isoechoic to fat lobules (Figure 9-9) . Some appear nearly anechoic. Focal echogenic calcifications are occasionally present. Most fibroadenomas produce slight acoustic enhancement. Approximately two-thirds of fibro­ adenomas are avascular on Doppler examination, while one-third contairl central vessels. Durillg pregnancy and lactation, a fibroadenoma may have imagirlg marlifesta­ tions of growth, infarction, large cysts, promillent ducts, and secretory hyperplasia.'6 ·20•2' As with ultrasound, MR demonstrates a fibroadenoma as an oval solid mass, with smooth or macrolobulated mar­ gins. Although most often hyperilltense on T2-weighted sequences, there is variability ill the signal characteris­ tics between patients. Internal septations are present ill a minority of these lesions. Most undergo slow enhancement and delayed washout.22 Most fibroadenomas spontaneously regress after a period of slow growth. It is uncommon for a fibroade­ noma to grow after the age of 35 years. After menopause, the lesion usually involutes and often calcifies . Malignant transformation of fibroadenomas either does not occur or is exceedingly rare. Therefore, the usual approach for girls with clinical and imaging findings of an uncom­ plicated typical fibroadenoma consists of clinical and sonographic followup. Percutaneous biopsy is an option for diagnostic confirmation. Surgical excision is usually reserved for rapidly growing or significantly symptomatic lesions.23 A subtype of fibroadenoma is the complex fibro­ adenoma, which accounts for approximately one-third of these lesions. The complex fibroadenoma contains cysts larger than 3 mm, sclerosing adenosis, epithelial

Chapter 9 The B reast

273

Table g-1 . Sonography of Breast M asses in Children

Benign

M ass

Sonography

Fi broadenoma

Well-circumscribed, homogeneous, long axis parallel to the chest wal l I l l - defined mass, m u ltiple s m a l l peripheral cysts Wel l - circumscribed , homogeneous, long axis parallel to the chest wal l Wel l-defined, smooth - walled, solid, hypoechoic nodu le; or cystic lesion with solid com ponents Sol id, variable echotexture, 1-2 em Solid, circumscribed, hypoechoic Wel l - circumscribed Peripheral, solid, oval, hilar notch Sol id, ± i nfiltrative Anechoic with wel l - defined wall; ± i ncreased echogenicity because of debris Wel l - circumscribed , macrolobulated , heterogeneous, cysts or fluid -filled clefts I rregular margi ns, heterogeneous, long axis perpendicular to the chest wal l I rregular or lobulated, heterogeneous Variable

, J uvenile papillomatosis Lactational adenoma I ntraductal papilloma G ranular cel l tumor Pseudoangiomatous stromal hyperplasia Hamartoma , l ntramammary lym ph node ' I nfantile hemangioma Cyst Mal ignant

Phyllodes tumor Carcinoma ' Metastatic disease Angiosarcom a

Figure g-8 Fibroadenoma.

Figure 9-9 Fibroadenoma.

Breast sonography of a 15-year-old girl with a palpable lump demonstrates an oval hypoechoic mass with slightly lobulated borders. There is a thir1 echogenic capsule.

This small mass (arrow) is hypoechoic relative to normal breast tissue (B). The lesion is oval and wider than it is tall.

274

Part

1

The Thorax

calcifications, and capillary apocrine changes . This lesion cannot be differentiated from standard fibroadenoma with imaging studies. Diagnosis is by percutaneous core biopsy or surgical excision. The complex fibroadenoma is associated with an increased risk for subsequent devel­ opment of breast cancer. 4 However, the cancer in these patients arises in breast tissue rather than in a fibroad­ enoma; therefore management is usually identical to that of other fibroadenomas.

Lactational Adenoma Lactational Oactating) adenoma is a benign lesion that can develop late during pregnancy or during lactation. This is a true adenoma, with cellular epithelial proliferation. The typical sonographic appearance is that of a hypoechoic mass with well-defined margins. There may be smooth lobula­ tions along the border. The lesion has a homogeneous echotexture. Posterior acoustic enhancement is common. Occasionally, there are small hyperechoic foci that represent fat in milk produced by the tumor. Fibrous bands traversing the lesion are sometimes present. When oval, the long axis of the lesion is parallel to the chest wall. Lactational adeno­ mas typically regress after delivery or cessation oflactation.24

J uven ile Papillomatosis Juvenile papillomatosis of the breast is a benign local­ ized proliferative disorder that occurs in adolescents and young women. The clinical presentation is that of a well­ defined mass at the periphery of the breast. Pathologically, the lesion consists of a dense fibrous stroma that contains multiple small cysts . The cysts are easily demonstrated with sonography. The margins usually are somewhat ill-defined. The small internal cysts are hyperintense on Tz-weighted M R images. The solid components enhance prominently on MR images obtained with intravenous gadolinium. 2 •25

Hamartoma Hamartoma o f the breast i s a rare benign tumor. In the pediatric population, most of these lesions occur in adoles­ cents. There is an association with Cowden syndrome in some patients. The tumor consists of densely packed lob­ ules in a fibrous stroma. The sonographic appearance is similar to that of fibroadenoma: a homogeneous soft-tissue mass with well-defined margins.

Phyllodes Tu mor Phyllodes tumor (cystosarcoma phyllodes) is a malignant fibroepithelial neoplasm. Although this lesion accounts for only approximately 1% of breast masses in children and adolescents, it is the most common primary malignant tumor of the breast in the pediatric age group. The clini­ cal presentation is similar to that of juvenile fibroadenoma, with a rapidly growing painless rubbery mass. The imaging

appearance is also similar to that of fibroadenoma. With sonography, the margins are often well-circumscribed, with or without macrolobulations. The lesion is round or oval. The echotexture tends to be more heterogeneous than is typical for fibroadenoma. Anechoic cysts or clefts are commonly present.2'·2 6

INFECTION Mastitis can result from obstruction of a mammary duct, infection of a retroareolar cyst, or cellulitis or skin disrup­ tion of the nipple or surrounding soft tissue. Breast infec­ tions can occur in children of any age, including infants of both genders and prepubertal girls. Breast infection in a lactating female is termed puerperal mastitis. Puerperal mastitis typically occurs in a subareolar location, while non­ puerperal mastitis can occur at this location or peripherally. Staphylococcus aureus is the most common infecting organ­ ism, followed by Streptococcus species. The clinical findings include induration, erythema, and tenderness. The mass may be fluctuant if there is an abscess.27 Sonography is useful to determine if a breast infection includes the presence of an abscess that requires drain­ age. Mastitis usually has the appearance of a complex or solid mass, although echogenic soft-tissue edema may be the only finding during the early phase of the infec­ tion. Sonographic differentiation between ducts, lobules, fat, and fibrous tissue is diminished. If there is ductal obstruction, the dilated ducts may have the appearance of hypoechoic tubular structures with thickened walls . An infected retroareolar cyst has a thick hyperemic wall, with or without luminal debris ( Figure 9-1 0) . Sonography of a breast abscess shows a cystic mass with irregular thick­ ened walls. There may be internal septations or debris. Doppler examination shows hyperemia at the periphery, but no flow within the abscess. Sonographically guided aspiration is therapeutic for many patients with a breast abscess.'7·28 Infection of breast tissue in the neonatal period, that is, neonatal mastitis, is an uncommon condition that occurs exclusively in term infants. This condition is twice as frequent in females as males. Most affected infants are younger than 5 weeks of age. The maj or clinical findings are erythema, swelling, warmth, and nipple discharge; the clinical manifestations are subtle in some patients. Sonography demonstrates regional soft-tis sue swelling and hyperechogenicity of the subcutaneous tissues adja­ cent to the breast bud. The beast bud is often enlarged relative to the contralateral breast and there is altered echogenicity. 29·3° Mammary duct ectasia refers to dilation of the mam­ mary ducts in association with inflammation and periduc­ tal fibrosis. This can occur in boys and girls of any age. Affected patients present with a nipple discharge, often bloody. Unilateral breast involvement is typical. Sonography shows dilated mammary ducts that are oriented radially around the nipple.'2·3'

Chapter 9 The B reast

A

Figure 9-1 0 I nfected retroareolar cyst.

This 13-year-old girl presented with swelling md redness in the region of a palpable right retroareolar lump lateral to the nipple. A Sonography demonstrates a small thick-walled cyst (arrow)

T RAUMA Hematomas ofthe breast usually are a result ofa sports injury or medical procedure. Sonography demonstrates a complex mass, usually cystic. An acute hematoma is hyperechoic. There is progressive decrease in echogenicity with timeY Fat necrosis is a potential sequela of breast trauma. This most often presents as a painless lump that develops temporally remote to the traumatic event. The sonographic features vary substantially between patients: solid, com· plex with mural nodules, complex with echogenic bands, or anechoic. The margins can be sharp or ill-defined. Calcifications are present in some of these lesions . The most characteristic sonographic pattern is that of a mass that contains echogenic internal bands that shift in orienta­ tion with changes in patient position.33

275

B

adjacent to the nipple. There are low-level internal echoes caused by debris. B. A color Doppler image indicates hyperemia of the cyst wall.

7· Scanlan KA, Propeck P A Accessory breast tissue in an unusual location. AJR Am J Roentgeno!. 1996;166(z):339-340.

8. Yang WT, Suen M , Metreweli C. Mammographic, sonographic and histopathological correlation of benign axillary masses.

C!in Radio!. 1997;5z(z) :130-135· 9· Laor T, Collins M H , Emery KH, et al. MRI appearance of accessory breast tissue: a diagnostic consideration for an axillary mass in a peripubertal or pubertal girl. AJR Am] Roentgeno!. 2.004;183 (6):1779-1781.

10. Perlyn C, Edmiston J , Tunnessen WW Jr. Picture of the month. Unilateral amastia (Poland syndrome) . Arch Pediatr Ado!esc Med. 199 9;153 (1:�.) :1305-1306. n.

Greydanus D E , Parks D S , Farrell EG. Breast disorders in children and adolescents. Pediatr C!in North Am. 1989;36 (3) : 6 01-638.

12.. Weinstein S P , Conant E F , Ore! SG, et a!. Spectrum of U S findings in pediatric and adolescent patients with palpable breast masses. Radiographies. zooo;zo(6) :

R E F E R E N C ES 1. Simmons P S . Diagnostic considerations in breast disorders of children and adolescents. Obstet Gyneco! C!in North Am. 1992.;19 (1) :91-102. . z. Chung EM, Cube R, Hall G J , e t al. From the archives o f the AFIP: breast masses in children and adolescents: radiologic­ pathologic correlation. Radiographies. zoo9;z9(3):907-931.

3- Knorr D, Bidlingmaier F. Gynaecomastia in male adolescents. C!in Endocrino! Metab. 1975;4(1) :157-171.

4· West KW, Rescorla FJ, Scherer LR 3rd, Grosfeld JL. Diagnosis and treatment of 5yn1ptomatic breast masses in the pediatric

population. ] Pediatr Surg. 199s:3o (z):18z-186; discussion 186-187.

1613-162.1. 13- Welch ST, Babcock D S , Ballard ET. Sonography of pediatric male breast masses: gynecomastia and beyond. Pediatr Radio!. Z004;34 (1z):952.-957·

14· Huneeus A Schilling A Horvath E, Pinochet M, Carrasco 0. Retroareolar cysts in the adolescent. ] Pediatr Ado!esc Gynecol. zoop6 (1) :45-49 ·

15. Perez-Boscollo A C , Dutra RA, Borges L G , e t a l . Galactocele: a n unusual cause o f breast enlargement in children. J Pediatr Surg. zoo9;44(7) :e1--e3 . 1 6 . S abate JM, Clotet M , Torrubia S , et a!. Radiologic evaluation of breast disorders related to pregnancy and lactation.

Radiographies. 2007;Z7(Suppl 1) : S101-S12.4.

5 · Garcia CJ, Espinoza A, Dinamarca V, et al. Breast US in children and adolescents. Radiographies. zooo;zo(6): 16o5-161z.

17· Nicholson BT, Harvey JA, Cohen MA. Nipple-areolar complex:

6. Merlob P. Congenital malformations and developmental changes of the breast: a neonatological view. ] Pediatr Endocrino! Metab. zoop 6 (4) :471-485.

18. Bayrak I K, Yalin T, Nural MS, Ceyhan M . Mammary duct ectasia

normal anatomy and benign and malignant processes.

Radiographies. zoo9;29(z):5o9-52.3in infant breast with bloody nipple discharge: sonographic findings. J C!in Ultrasound. zoo8;3 6 (4):z29-230.

276 Part 1 The Thorax 19. Gobbi D, Dall'Igna P, Alaggio R, et al. Giant fibroadenoma of the breast in adolescents: report of 2 cases. J Pediatr Surg. 2 0 0 9 ;44 (2):e39-e41. 2 0 . Dupont WD, Page DL, Pari F F , et al. Long-term risk of breast cancer in women with fibroadenoma. N Engl ] Med. 1994;331(1) :10-15.

21. Kronemer KA, Rhee K, Siegel MJ, et al. Gray scale sonography of breast masses in adolescent girls. J Ultrasound Med. 2001;2 0 ( 5 ) : 4 91-49 6 ; quiz 4 9 8 .

2 2 . Hochman M G , Ore! S G , Powell CM, e t a l . Fibroadenomas: MR imaging appearances with radiologic-histopathologic correlation. Radiology. 1997;20 4 (1) :123-129. 23- Pacinda S J , Ramzy I . Fine-needle aspiration of breast masses. A review of its role in diagnosis and management in adolescent patients. ] Adolesc Health. 1998;23 (1) :3-6.

2 4 . Yang WT, Suen M , Metreweli C. Lactating adenoma of the

breast: antepartum and postpartum sonographic and color Doppler imaging appearances with histopathologic correlation.

J Ultrasound Med. 1997;16 (2) :14 5-147. 2 5 . Kersschot EA, Hermans M E , Pauwels C, et al. Juvenile papillomatosis of the breast: sonographic appearance.

Radiology. 1988;16 9 (3 ) : 631-633.

2 6 . Pistolese CA. Tanga I , Cossu E , et al. A phyllodes tumor in a child. ] Pediatr Adolesc Gynecol. 2009;22(3) :e21-e24. 27. Greydanus DE, Matytsina L, Gains M . Breast disorders in children and adolescents. Prim Care. 2 0 0 6 ;33(2) : 455-5 ° 2 · 2 8 . Kamal RM, Hamed ST, Salem D S . Classification of inflammatory breast disorders and step by step diagnosis. Breast]. 2 0 0 9 ;15 (4J :367-38o . 2 9 . Efrat M, Mogilner JG, Iujtman M, et al. Neonatal mastitis­ diagnosis and treatment. Isr] Med Sci. 1995;31(9) :558-5 6 0 . 3 0 . Borders H , Mychaliska G , Gebarski K S . Sonographic features of neonatal mastitis and breast abscess. Pediatr Radial. 2009;3 9 ( 9 ) : 9 5 5-958. 31. Imamoglu M, Cay A, Reis A, et al. Bloody nipple discharge in children: possible etiologies and selection of appropriate therapy. Pediatr Surg Int. 2 o o 6 ; 2 2 (2 ) :158-16 3 . 3 2 . Greydanus DE, Patel D R, Baxter T L . The breast a n d sports: issues for the clinician. Adolesc Med. 1998;9(3):533-5 5 0 , vi-vii.

33· Taboada JL, Stephens TW, Krishnamurthy S , et al. The many faces of fat necrosis in the breast. A] R Am J Roentgenol. 2009;19 2 ( 3 ) : 815-825.

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CH A P T E R

10

Acquired Diseases of t he Hea rt and Perica rdium

DISEASES OF TH E MYOCARD I U M A N D EN DOCARDI U M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

Sickle Cel l Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

300

Myocard ial I ron Deposition . . . . . . . . . . . . . . . . . . . . . . . . .

300

Myocard ial Calcification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

301 301

Term inology of M yocard ial and Endocardial Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

279

I d iopath ic Dilated Card iomyopathy . . . . . . . . . . . .

281

ACQU I RED PERICARDIAL DISEASE . . . . . . . . .

Endocardial Fibroelastosis .. . . . . . .. .. . . . .. .. . . . . .. . . .

282

Pericard ia! Effusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

301

H ypertrophic Card iomyopathy . . . . . . . . . . . . . . . . . . . .

283

Pericard itis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I d iopath ic Restrictive Card iomyopathy . . . . . .

284 284

Infectious Pericarditis .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Idiopathic Acute Pericarditis . . . . . . . . . . . . . . . . . . . . Miscellaneous Forms of Pericarditis . . . . . . . . Constrictive Pericarditis . . . . . . . . . . . . . . .. . . . . . . . .. . .

301 301 302 302 303

Endomyocardial Fibrosis . . . . . . . . . . . . . . . . . . . . . . . . . . loffler E ndocard itis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

286

N oncom paction Card iomyopathy . . . . . . . . . . . . . . .

286

Arrhythmogenic Right Ventricular Dysplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

286

Myocard itis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

289

Pericard ia! Cyst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

304

I nfective Endocard itis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

290

Rhabdomyoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

305

H IV and AI DS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

292

Fi broma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

306

Kawasaki Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

292

Teratoma . .. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . .. . . . . . . .. . . . . . . .

306

Rheu m atic Fever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

294

M yxom a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

307

295 Mitral Insufficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 Mitral Stenosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 Aortic Insufficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

U�ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

30

Rheu m atic H eart Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sarcoidosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

297

I nfant o f a Diabetic M other . . . . . . . . . . . . . . . . . . . . . . . . .

297

G lycogen Storage Disease Type I I (Po m pe Disease) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

298

M itochondrial Respiratory Chain Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

299

DISEASES OF THE MYOCARDIUM AND ENDOCARDIUM

Term i nology of Myocardial and Endocardial Diseases The myocardium is the middle layer ofthe heart wall and is predominantly composed of cardiac muscle. A spectrum of

N EOPLASMS AND MASSES OF TH E H EART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

.

lym p h atic M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

307

I nfl a m m atory Pseudotu mor . . . . . . . . . . . . . . . . . . . . . . . .

307

Ectopic Thyroid . . . . . . . . . .. . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .

308

Pri mary M a l ignancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

309

M etastatic Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

309

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . 309

acquired, developmental, and idiopathic disorders causes acute or chronic forms of cardiac disease with myocardial involvement. Inflammatory disease of the myocardium, termed myocarditis, includes infectious and autoimmune disorders. In contradistinction to the adult age group, myo­ cardial ischemia is rare in children. Causes of myocardial ischemia in children include vasculitis (e.g., Kawasaki dis­ ease), thromboembolism, cardiac surgery, and coronary 279

280 Part 2 The Ca rd i ovascu l a r System artery anomalies. Imaging techniques that evaluate myo­ cardial perfusion and viability include stress echocardiog­ raphy, coronary angiography, single-photon emission computed tomography ( S P E CT) scintigraphy, positron emission tomography, and perfusion M R I .' The term cardiomyopathy is nonspecific in that it applies to any disorder that involves the cardiac muscle. There are various classification schemes for cardiomyopathy. Primary, or idiopathic, cardiomyopathy refers to heart muscle disease of unknown cause or related to a genetic abnormality (e.g. , arrhythmogenic right ventricular dysplasia) , whereas the secondary form has a lmown underlying cause (e.g., infective myocarditis, chronic hypertension, or vasculitis) or is asso­ ciated with a systemic disorder (e.g., muscular dystrophy) . Some practitioners reserve the term cardiomyopathy for those conditions in which there is a structural or functional abnormality of the myocardium that is not associated with coronary artery disease, hypertension, valvar heart disease, congenital heart disease, or pulmonary vascular disease. Cardiomyopathy can also be divided into acute and chronic forms . The World Health Organization classi­ fies chronic cardiomyopathies into dilated, hypertrophic, and restrictive categories . Dilated cardiomyopathy is the most common variety; this is characterized by impaired

systolic function and poor ventricular contractility. Dilated cardiomyopathy is most often caused by infective myo­ carditis or exposure to myocardial toxins. Ventricular wall thickening in the less common hypertrophic form of car­ diomyopathy can cause systolic outflow obstruction or impaired diastolic filling. Hypertrophic cardiomyopathy frequently has a genetic basis. Restrictive cardiomyopathy is the least-common variety. Grossly impaired ventricular filling causes poor diastolic function. Restrictive cardiomy­ opathy can be idiopathic or caused by disorders that lead to cellular infiltration of the myocardium, such as glycogen storage disease. The endocardium is the endothelial lining membrane of the heart and the underlying connective tissue bed. Because the cardiac valves are predominantly endocardial structures, valvar dysfunction is a common manifesta­ tion of endocardial diseases . Endocardial involvement is an important component of many diseases that also affect the myocardium. The most common acquired endocardial disease is endocarditis, which is inflammation of the endo­ cardium. Endocarditis is most often caused by infection, but noninfectious varieties such as rheumatic fever are also common (Table 1 0-1 ) .

Table 1 o-1 . Myocardial and Endocardial Diseases of Children P ri m a ry

Secon dary

Dilated

I nfectious I nflammatory

. I diopath ic dilated cardiomyopathy I Endocardial fibroelastosis Hypertrophic , Idiopathic hypertrophic cardiomyopathy Restrictive Idiopath ic restrictive cardiomyopathy Endomyocardial fibrosis 1 Loffler disease � Arrhythmogenic Arrhythmogen ic right ventricu lar right ventricu lar dysplasia cardiomyopathy ' N axos disease

---------

-

Myocard itis Rheumatic fever 1 Rheumatic heart d isease Collagen vascular I Polyarteritis nodosa disease I Systemic l u pus erythematosus Dermatomyositis Scleroderma M ixed con nective tissue disease I nfiltrative G lycogen storage disease l Sarcoidosis I 1 M ucopolysaccharidosis i Neuromuscular disease i Friedrich ataxia Progressive m uscu lar dystrophy M itochond rial Barth syndrome d isorders Kearns - Sayre syndrome Other I ron deposition ' I Hypertensive cardiomyopathy

J

I I ji

Chapter 1 0 Acq u i red D i seases of the H e a rt a n d Pericard i u m 281

A

Figure 1o-1 Dilated cardiomyopathy.

B

A, B. Anteroposterior and lateral radiographs of an u-month-old infant show marked cardiomegaly and mild pulmonary edema. There is superimposed central atelectasis.

I diopathic Dilated Cardiomyopathy Idiopathic dilated cardiomyopathy occurs because of struc­ tural and functional abnormalities of the myocytes, possi­ bly related to an immunological abnormality. Histological examination shows interstitial fibrosis within the myocar­ dium and hypertrophy of myofibrils. This is most often a sporadic disorder, although unusual familial cases have been reported. There is generalized cardiac dilation, fre­ quently accompanied by some degree of hypertrophy. These changes cause impaired systolic function of both ventricles. More than half of patients with idiopathic dilated cardiomyopathy present before the age of 2 years.2 Manifestations of heart failure usually constitute the initial clinical presentation of idiopathic dilated cardiomy­ opathy. Idiopathic dilated cardiomyopathy is among the most common causes of congestive heart failure in young children. Patients may exhibit tachypnea, tachycardia, and fatigue. Some patients present because of the effects of car­ diac dysrhythrnias. The prominent end-systolic ventricular volumes in patients with dilated cardiomyopathy make these children susceptible to intracardiac thrombosis, which can lead to pulmonary and systemic emboli. Chest radiographs ofchildren with dilated cardiomyop­ athy typically show substantial cardiomegaly (Figure 1 0-1 ) . Pulmonary venous congestion and pulmonary edema are common (Figure 1 0-2) . Echocardiography shows dilation to be most pronounced in the left atrium and left ven­ tricle (Figure 1 0-3) . There is global left ventricular (LV)

dysfunction; the ejection fraction is diminished. These patients may have mitral regurgitation. Intracavitary thrombi are sometimes visualized during sonographic

Figure 1o-2 Dilated cardiomyopathy. An anteroposterior radiograph of a 15-month-old child demonstrates cardiomegaly and prominence of interstitial lung markings.

282 Part 2 The Ca rd iovascu l a r System

A

8

Figure 1o-3 Idiopathic dilated cardiomyopathy. A, B. Anteroposterior and lateral chest radiographs of an 18-month-old boy with a 2-week history of increasing fatigue show moderately severe cardiomegaly. There is slight prominence of pulmonary vascular markings. C. Dilation of the left ventricle (arrows) is evident on this apical view echocardiographic image obtained during systole. The left ventricular ejection fraction was 20%.

evaluations. M R imaging is an alternative technique to measure the ejection fraction and delineate regional wall motion abnormalities in patients with dilated cardiomy· opathy. MR also documents the pattern of associated myo­ cardial thickening.3·4

Idiopathic Dilated Cardiomyopathy Pathology

Rad iology

Myocard ial damage Atrial and ventricu lar dilation Poor cardiac output

Cardiomegaly Pu l monary vascular congestion Pu l monary edema

c

Endocardial Fibroelastosis Endocardial fibroelastosis refers t o severe, diffuse, thick­ ening of the ventricular endocardium. Endocardial fibro­ elastosis can occur as a primary idiopathic cardiac lesion or, more frequently, in association with a congenital heart disease. Primary endocardial fibroelastosis is further classi­ fied into dilated (most common) and contracted (restrictive) types. Endocardial fibroelastosis is characterized patho­ logically by diffuse endocardial thickening and clinically by manifestations of myocardial dysfunction. Histological examination shows invasion of the endocardial and suben­ docardial regions by fibroelastic tissue. There is hyperpla­ sia of collagen, smooth muscle, and elastic fibers within the endocardium.s A common mechanism of endocardial fibroelastosis is myocardial damage that causes persistently increased

Chapter

10

Acq u i red D i seases of the H e a rt a n d Pericard i u m 283

ventricular wall tension and secondary mitral regurgita­

are dilated. In patients with congestive heart failure, pulmo­

tion. In patients with endocardial fibroelastosis as a result

nary vascular congestion and pulmonary edema are present.

of a congenital heart lesion, the pathophysiology usually

Echocardiography confirms the pattern of cardiac

includes ventricular hypertrophy, disrupted myocardial

chamber dilation in patients with endocardial fibroelasto­

oxygen supply, and resultant endocardial thickening. A viral

sis. Left ventricular function is poor and the ej ection frac­

etiology (e.g., mumps) is suggested in some instances of of

tion is reduced. There is abnormal mitral valve motion;

this condition.G Although generally occurring as a sporadic

mitral regurgitation is common. The endocardial thick­

disorder, familial cases account for up to

10%

of children

ening can sometimes be demonstrated with echocardiog­

with endocardial fibroelastosis. The frequency of this dis­

4%.

raphy as prominent echogenicity along the endocardial surface of the left ventricle. '3 Cine MR and catheter angio­

Reported inheritance patterns of familial endocardial fibro­

cardiography of endocardial fibroelastosis demonstrate a

elastosis include X-linked recessive, autosomal dominant, and autosomal recessive varieties . 2 ·7-9

poorly functioning dilated left ventricle. LP5

order in siblings of an affected child is approximately

In patients with dilated primary endocardial fibroelas­ tosis, there is marked enlargement of the heart. The left atrium and left ventricle are disproportionately dilated. There is diffuse thickening of the LV endocardium; thick­ ening is most pronounced in the outflow tract. The papil­ lary muscles and cordae tendineae are involved, preventing appropriate mitral valve closure. Endocardial thickening is also present, to varying degrees, in the left atrium, right

Endocardial Fibroelastosis Rad iology

Pathology

E ndocardial thickening Card iomegaly Pulmonary vascular congestion Poor LV fu nction Pulmonary edema M itral insufficiency

ventricle, and right atrium. The ventricular wall thick­ nesses are usually normal. The secondary form of dilated endocardial fibroelasto­ sis can occur in association with aortic stenosis, aortic atre­ sia, aortic coarctation, ventricular septal defect, anomalous origin of the left coronary artery from the pulmonary artery, carnitine deficiency, various myocardial injuries, and several metabolic disorders. The endocardial thickening often has a more focal character in patients with the secondary form. The contracted type of primary endocardial fibroelas­ tosis is rare. While the endocardium of the left ventricle is thickened, this chamber is normal in size or is hypoplastic. The atria and the right ventricle are dilated and the myocar­ dium of the right ventricle is hypertrophied. The secondary form of contracted endocardial fibroelastosis most often occurs in association with hypoplastic left heart syndrome.10 The most common clinical presentation of endocar­ dial fibroelastosis is that of unexplained heart failure in an infant or young child. Common symptoms include dys­ pnea, tachypnea, irritability, and mild cyanosis. Congestive heart failure is progressive, and can lead to death within weeks of the initial presentation. Patients with endocardial fibroelastosis usually present during infancy, most often during the first

6 months of life (8o%) . The prevalence of

primary endocardial fibroelastosis has diminished mark­ edly in recent years .11•12 The radiographic features of endocardial fibroelastosis include marked cardiomegaly and manifestations of con­ gestive heart failure. In some patients, substantial cardiac enlargement is present from birth; while in others, the heart initially appears normal and enlargement occurs during the first several weeks or few months of life. Dilation of the left ventricle and left atrium usually predominates . Left-lower­ lobe atelectasis because of enlargement of the left atrium is common. With the rare contracted form, the left ventricle is small or normal in size, while the other cardiac chambers

Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is an uncommon genetic disease that causes myocardial hypertrophy. The myocar­ dium in these patients is thickened and hypercontractile. There is variation

in the hereditary pattern and genetic

alterations , indicating that hypertrophic cardiomyopathy represents a group of related disorders . Most often, there is an autosomal dominant pattern of inheritance, with vari­ able penetrance. Approximately

45%

of cases represent

new mutations. Mutations in various chromosomes have been reported in patients with hypertrophic cardiomyopa­ thy, typically leading to abnormal sarcomere proteins. The mutations cause abnormal myocyte stresses and impaired function that eventually lead to hypertrophy and fibrosis. Histological examination of the thickened myocardium in patients with hypertrophic cardiomyopathy shows abnor­ mally short and thick myofibrils in a disordered pattern. The peak age range for the presentation of pediatric hypertrophic cardiomyopathy is

5

estimated prevalence in children is

through 15 years. The p,ooo,ooo. There are

various systemic disorders that sometimes occur in asso­ ciation with hypertrophic cardiomyopathy, usually with a clinical presentation during irlfancy. These include Noonan syndrome, Beckwith-Wiedemann syndrome, glycogen stor­ age disease type I IA, defects of fatty acid oxidation (e.g., carnitine deficiency) and mitochondrial diseases. ' 6-2 o The pattern of myocardial thickening in hypertrophic cardiomyopathy varies In approximately

70%

substantially between

patients.

of patients , the myocardial thick­

ening is asymmetric, with predominant involvement of the septum. In

25%

of patients, the septal hypertrophy is

asymmetric. When the upper portion of the septum is pre­ dominantly involved, obstruction of the LV outflow tract can cause sudden death. Right ventricular hypertrophy

284 Part 2 The Ca rd iovascu l a r System

occurs in 15% to 20% of patients. Atrial wall hypertrophy is an occasional finding. Left atrial dilation is common. Hypertrophic cardiomyopathy causes impaired relax­ ation of the ventricular myocardium during diastole. Manifestations of congestive heart failure can occur despite a normal or elevated ejection fraction. Some patients have findings of myocardial ischemia despite patent coronary arteries. The initial clinical presentation of hypertrophic cardiomyopathy in children is most frequently a result of a murmur in an otherwise healthy patient. Many cases are discovered because of a positive family history. Common symptoms include exertional dyspnea (9o% of symptom­ atic patients) , angina and syncope. Auscultation dem­ onstrates a harsh midsystolic murmur. With substantial cardiac involvement, marlifestations of congestive heart failure may develop. In general, this disorder follows a more rapid and severe course when presenting during infancy than in older children. The overall risk for sudden cardiac death in children with hypertrophic cardiomyopa­ thy is approximately 6%; most deaths are a result of myo­ cardial ischemia or an arrhythmia. Nearly all children with hypertrophic cardiomyopathy have radiographically demonstrable cardiomegaly, usu­ ally of moderate severity. Cardiac enlargement is predom­ inantly caused by LV hypertrophy and left atrial dilation. Pulmonary vascular congestion and pulmonary edema are unusual in these patients, unless there is severe progres­ sive disease. Echocardiography is usually diagnostic in patients with suspected hypertrophic cardiomyopathy. Myocardial wall thickening is easily demonstrated with this technique ( Figure 1 0-4) . Asymmetrical septal hypertrophy is indicated by a septal thickness-to-posterior wall thickness ratio of at least 1.3. Myocardial thickening is indicated when the LV wall thickness is equal to or greater than 1.3 em. In those patients with LV outflow obstruction, color Doppler shows turbulent flow through a dynamic subaortic stenosis. Mitral insufficiency is common in these patients. Mild aor­ tic regurgitation is present in approximately one-third of patients with hypertrophic cardiomyopathy. 2 1•22 Thallium-201 SPECT scintigraphy of patients with hypertrophic cardiomyopathy shows myocardial thicken­ ing. The LV cavity is usually small. Reversible perfusion defects sometimes occur, most often in patients with a history of syncope; this finding is a risk factor for sudden death. The detection of ischemia is complicated by the occurrence of inhomogeneous hypertrophy?P4 Dynamic imaging of the heart with gated blood pool scintigraphy shows the LV cavity to be relatively small during diastole and markedly diminished in size during systole. Cardiac MR of patients with hypertrophic cardio­ myopathy provides important anatomic and functional information. Cross-sectional MR images demonstrate the distribution and severity of myocardial wall thickening (Figure 1 0-5) . MR is superior to echocardiography for the detection of apical LV hypertrophy. As with gated scintigra­ phy, cine MR shows lack of appropriate diastolic ventricular

relaxation and filling. Forceful contraction during systole nearly obliterates the LV cavity. Most often, the degree of wall thickening at the hypertrophic site diminishes some­ what during systole and thickening becomes more pro­ nounced at the nonhypertrophic sites. In those patients with LV outflow tract obstruction, cine MR angiography demonstrates the dynamic nature of the narrowed outflow tract. The regional character of myocardial involvement in patients with hypertrophic cardiomyopathy can be assessed with "myocardial tagging" MR. Delayed contrast enhance­ ment, usually with a patchy character, within the abnormal myocardium can occur as a result of fibrosis. 2 5-2 9 Hypertrophic Cardiomyopathy Pathology

Rad iology

Myocardial thickening

N M , M R, Echo: LV wall thickening - Card iomegaly Pu l monary vascular congestion

- - ---------

- - -

-

---

-

--

-

I m paired diastolic relaxation Elevated left atrial pressure Left ventricular outflow obstruction

NM,

- - -- - - - - - - - - - - - -

-----

-

-----

n u clear m e d i c i n e ; E c h o , echoca rdiography.

I diopathic Restrictive Cardiomyopathy Restrictive cardiomyopathy is the least common of the pri­ mary cardiomyopathies. This disorder is characterized by markedly reduced diastolic ventricular compliance. The ventricular chambers are usually normal in size or mildly dilated. Histological examination shows fibrosis through­ out the deep layers of the myocardium and within the endocardium. The clinical marlifestations are similar to those of constrictive pericarditis, with peripheral edema, jugular venous engorgement, and ascites.3°·3' Chest radiographs of children with idiopathic restric­ tive cardiomyopathy show normal heart size or mild car­ diomegaly. Echocardiography and cine MR sometimes demonstrate reduced ventricular contraction, although systolic contraction is normal in many patients. Dynamic imaging shows subnormal ventricular filling during dias­ tole. Compromised ventricular filling causes some degree of atrial enlargement. In contrast to constrictive pericar­ ditis, ventricular septal motion is not paradoxic. Likewise, M R shows no evidence of pericardia! thickening (i.e., the pericardium is 1 .5 em)

" Fever p l u s at l e a s t 4 o f criteria 2 t o

-----------

6.

Fewer t h a n

4 of the add itio n a l

criteria a re accepta b l e w h e n coro n a ry a rtery d i sease i s docum ented with i m agi n g stud ies.''

There are 3 phases of the clinical course of Kawasaki disease. High fever, often greater than 3 9 · 5°C (103°F) , is invariable present during the acute phase; this phase lasts for 1 to 2 weeks. The development of a polymorphous rash in conjunction with, or soon after, the onset of fever is also characteristic. The rash most often is morbilliform or con­ sists of irregular nonpruritic erythematous plaques. The rash generally begins to fade spontaneously within a week. Perineal erythema and subsequent desquamation can occur. In some patients, there is peripheral edema, with induration of the hands and feet. The subacute phase of Kawasaki disease begins 1 to 3 weeks after the initial presentation. Fever, rash, and lymphadenopathy resolve during the subacute phase. Thrombocytosis occurs during this phase; normalization of the platelet count is one of the indicators for completion of the subacute phase. The convalescent phase begins dur­ ing the third or fourth week of illness, with disappearance of overt clinical signs of the disease. Laboratory indicators of inflammation normalize during this period. Cardiovascular involvement is a major factor in the morbidity and mortality of Kawasaki disease. Vasculitis in these patients predominantly involves the walls of small and medium-size arteries, although the aorta can also be affected. Many ofthe cardiac manifestations, however, are a result of a microvasculitis. During the acute phase, approxi­ mately 30% of patients have pericarditis and a pericardia} effusion; in rare instances, this can lead to cardiac tampon­ ade. Myocarditis is also common in patients with Kawasaki disease; the presence of myocarditis is suggested clinically by tachycardia. Arrhythmias, congestive heart failure, and manifestations of cardiac valve disease can occur. Up to 30% of patients have some degree of mitral regurgitation because of valvulitis or papillary muscle ischemia. Vasculitis of the coronary arteries is a characteristic and serious manifestation of Kawasaki disease, accounting

Chapter 1 0 Acq u i red D i seases of the H e a rt a n d Pericard i u m

293

for most of the fatalities and long-term disabilities that can occur in these children. Vasculitis sometimes causes generalized weakening of the arterial wall, manifested by coronary artery ectasia. More often, there are focal areas of necrosis within the arterial wall, leading to aneurysm formation, thrombosis, and stenoses. The coronary artery aneurysms that occur in children with Kawasaki disease are classified as small giant

(>8

(7o%) are benign. In

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

.. ................. ..

neoplasms in children are rare; most

decreasing order of frequency, the most common lesions are rhabdomyoma, fibroma, myxoma, hemangioma, and teratoma. Primary malignant cardiac tumors in children are exceedingly rare. Potential clinical manifestations of an

Pericardia! Cyst

intracardiac tumor include an unexplained heart murmur,

Pericardia! cyst is a congenital lesion that apparently occurs

congestive heart failure, and cardiac rhythm disturbance.

when a small portion of the pericardium pinches off during

Potential systemic manifestations include fever, anemia

embryonic development. These lesions do not communi­

70%

and weight loss . The electrocardiogram may be normal or

cate with the pericardia! cavity. Approximately

indicate nonspecific alterations .

cardia! cysts are located in the right cardiophrenic angle,

Chest radiographs are frequently normal in children

2 0% in the left cardiophrenic angle, and 10%

of peri­

in other loca­

with cardiac tumors. If the lesion substantially affects car·

tions. Those located superiorly can be confused with a thy­

diac function, manifestations of congestive heart failure

mic or bronchogenic cyst.

can be present. With a large tumor, asymmetrical enlarge­

With MR, a pericardia! cyst usually produces low sig­

ment of the heart silhouette is common. Radiographically

nal intensity on T1-weighted images and high signal on

visible calcifications are sometimes present in rhabdo·

T2-weighted images. Blood or protein alters these charac­

myoma, teratoma, and lipoma. Cross-sectional imaging

teristics. I mages obtained perpendicular to the cyst show

with CT or M R is an important part of the evaluation of

the characteristic low-signal-intensity appearance of peri­ cardium in the wall of the cyst.' 6 1

cardiac tumors. These studies provide information about the composition, location, and invasiveness of the lesion.

A congenital or acquired diverticulum of the pericar­

Many cardiac tumors in children are amenable to surgical

dium can lead to a cystic mass that mimics a pericardia!

resection. De bulking of a large lesion can also be useful to relieve obstruction.' 5 3-t6o

cyst. Careful inspection of images shows communication of a diverticulum with the pericardia! cavity at some point.

Chapter 10 Acq u i red D i seases of the H e a rt a n d Pericard i u m 305 In addition, the size of the lesion may vary with changes in body position.

Rhabdomyoma Rhabdomyoma is the most common primary cardiac tumor of infants and young children. More than two-thirds of patients with this lesion are younger than

3 years of age.

Multiple lesions are present in most patients (approxi­ mately 90%) . Rhabdomyomas most frequently arise within the ventricular septum or adjacent portions of the ventric­ ular walls . The atria and papillary muscles are occasional sites of origin. A diffuse nodular pattern of cardiac involve­ ment can also occur.'62 Pathologically, a rhabdomyoma is a well-circumscribed, nonencapsulated nodule located within the myocardium. A large lesion often proj ects into a cardiac chamber. This benign tumor is predominantly composed of altered car­ diac myocytes .

Histological examination

shows large,

round, vacuolated cells. Protoplasmic strands extend out­

A

ward from the centrally located nucleus, resulting in a "spider cell" appearance. The cells of rhabdomyoma are fill e d with a mucopolysaccharide that is histochemically distinct from that in mucopolysaccharidosis. The tumors usually arise deep within the myocardium. The pathogenesis of cardiac rhabdomyoma is uncer­ tain. Rhabdomyoma is most likely a hamartoma, rather than a true neoplasm. Tuberous sclerosis is present in approximately

so% to 90% of children with cardiac rhab­ 30% to so% of

domyoma.162•163 Conversely, approximately

patients with tuberous sclerosis develop cardiac rhabdo­ myoma. Cardiac rhabdomyoma is also associated with the basal cell nevus syndrome. Common presenting features of cardiac rhabdomy­ oma include a murmur, signs of heart failure, and mani­ festations of cardiac ischemia. The clinical manifestations depend on the size, number, and location of the lesions . Small nodules may be asymptomatic. Larger nodules that proj ect into the cardiac chambers can interfere with valve function or directly block the inflow or outflow of blood. Diffuse nodular myocardial involvement can result in heart failure and death. Cardiac rhabdomyomas often affect the cardiac conduction system and produce arrhyth­

8

Figure 1o-2o Cardiac rhabdomyomas.

A. An echocardiogram image of a newborn infant with tuberous sclerosis shows multiple homogeneous hyperechoic myocardial lesions. B. A T2-weighted MR image shows a hyperintense mass (arrow) that projects into the left ventricle.

mias . Severe arrhythmias can result in sudden death of these patients. Partial or complete spontaneous regression of rhabdomyomas occurs in more than half of affected patients . Regression is most common with small lesions

with lobulated margins

and in those occurring in younger patients. B ecause of this ,

confined to the myocardium (intramural) or proj ect into

surgery is usually reserved for those patients with hemody­ namic compromise or refractory dysrhythmias.' 64 ·'6 5

the adjacent cardiac chamber (intracavitary) . Cardiac rhab­

Chest radiographs of the child with cardiac rhabdomy­

ally as multiple round moderately echogenic myocardial

oma are frequently normal. If there are large lesions, the car­

masses. If there is hemodynamic compromise due to the

(Figu re 1 0·20) . The lesions may be

domyoma is often detectable with prenatal ultrasound, usu­

diac silhouette may be prominent and irregular. Radiographic

mass (i. e . , fetal dysrhythmia or ventricular outflow obstruc­

signs of pulmonary vascular congestion can accompany

tion) , manifestations of hydrops may be present.' 66 ,, 6 7

those lesions that cause substantial hemodynamic effects.

Rhabdomyoma is usually isointense or slightly hyper­

Echocardiography typically demonstrates cardiac rhab­

intense to normal myocardium on T1-weighted images ,

domyoma as a homogeneous , moderately echogenic mass

and isointense or hyperintense on T2-weighted images .

306 Part 2

The

Ca rd i ovascu l a r System

Cine M R imaging is useful for detecting ventricular inflow

fibrous consistency is reflected on T2 -weighted images

or outflow obstruction. Rhabdomyomas may alter regional

by a homogeneous hypointense appearance. The margins

wall motion. Quantitative studies can be performed to

with the adjacent myocardium vary from sharply defined

determine if there is substantial functional impairment. In

to infiltrative. Calcifications are present in some patients.

those patients with LV outflow obstruction, the ventricular wall thickness is sometimes increased.167,,6 8

because of the fibrous consistency. In some patients, there

Cardiac fibromas tend to have little contrast enhancement is greater enhancement in the periphery than in the central aspect of the tumor, likely related to poor vascularization of the central fibrous tissue. Cine MR may demonstrate

Cardiac Rhabdomyoma

restricted ventricular wall motion in the region of the

Pathology

Rad iology

Benign, well circumscribed Com posed of cardiac myocytes

Homogeneous, lobulated M R: s i m i lar signal intensity to myocard i u m

tumor. Some patients have an accompanying pericardial effusion.'53 · 1 6 9-'7'

Cardiac Fibroma Pathology

F1 broblasts w1th 1 n collagen

Fibroma Fibroma i s the second most common cardiac tumor in chil­ dren, after rhabdomyoma. Approximately

90%

of cardiac

fibromas occur in children. Approximately half of these lesions are diagnosed during the first year of life ; many are discovered in utero with prenatal ultrasound. There is no gender predilection. Patients with Godin syndrome (basal cell nevus syndrome) have an increased frequency of

[

Rad iology

T2 M R: homogeneous,

I hypointense

�

Benign solitary neoplasm Arises from ventricular wal l 1

------ -

M i n imal enhancement Solitary Myocardial mass

----

cardiac fibroma. The predominant features of Godin syn­ drome include basal cell carcinomas, odontogenic kerato­ sis of the mandible, skeletal anomalies , and neoplasms of various organ systems . The clinical manifestations o f cardiac fibroma are caused by mass effect and involvement of the conduction system. A large lesion may compromise ventricular volume. A fibroma located along the outflow tract of the right or left ventricle can produce symptomatic obstruction. Valvular obstruction can also occur. Manifestations of congestive failure can occur if there is significantly impaired cardiac function. Sudden death in children with cardiac fibroma can result from supraventricular arrhythmias and ventricu­ lar tachycardia. Approximately one-third of patients have no symptoms prior to incidental discovery of the mass . Nearly all cardiac fibromas arise within the myocardial wall of a ventricle. The LV wall and the interventricular septum are the most common sites , followed by the RV wall. Fibroma is usually a solitary lesion. The gross appear­ ance consists of a rounded, firm, well-circumscribed mass that is unencapsulated. This is a benign neoplasm that is characterized histologically by mature fibroblasts intermin­ gled with cardiac muscle fibers and strands of collagen. Occasionally, dystrophic calcification is present. Cardiac fibromas usually contain no substantial necrosis, hemor­ rhage, or cysts . Malignant degeneration does not occur. Most cardiac fibromas are large at the time of diag­

nosis , measuring a few to several ern in diameter. On T1-weighted MR images , fibromas typically are hypoin­ tense or isointense to normal myocardium. The dense

Teratoma Teratoma is a very rare pediatric cardiac tumor. A s with other heart tumors, the clinical manifestations can include conduction disturbances and valvar obstruction. Because teratomas tend to be large lesions , many of these infants present with manifestations of congestive heart failure. Other potential findings include cyanosis, heart murmur, and failure to thrive. Most cardiac teratomas are located within the pericardial sac, often arising near the bases of the great arteries .

An intrapericardial teratoma is nearly

always associated with a pericardial effusion. The fluid col­ lection is often massive and may cause cardiac tamponade. Effusion and tamponade in the fetus with pericardial tera­

toma can lead to fetal demise.'72 ·'73

Cardiac teratoma is frequently visible on chest radio­ graphs as a large mass that forms part of the cardiac sil­ houette. The cardiopericardial silhouette also may be prominent because of an associated pericardial effusion. Echocardiography, CT, and M R document the location and structural characteristics of the mass, as well as the effects on adjacent structures . Most often, the majority of the mass is located peripheral to the myocardium and compresses the adjacent portion of the heart; there are, however, uncom­ mon instances in which the lesion projects into a cardiac chamber. As with teratomas in other locations, cardiac tera­

tomas most often consist of multiple cysts and interposed irregular solid tissue. Fat and calcium are occasionally present. '64·'74

Chapter 10 Acq u i red D i seases of the H e a rt a n d Pericard i u m 307

Myxoma

Lipoma

Myxoma is a rare cardiac tumor i n children. Most pediat­

Cardiac lipoma is a benign lesion that can present a t any

ric cases occur in adolescents . This lesion is slightly more

age . The tumor is composed of mature fat cells. Other

common in girls. About two-thirds of pediatric myxomas

adipose-containing tumors that can arise in the heart

arise in the left atrium, typically near the fossa ovalis; most

include lipoblastoma and fibrolipoma; a cardiac teratoma

of the remainder arise in the right atrium. The lesion usu­

may contain fat in combination with other tissue types.

ally is within the cardiac chamber of origin and connects

Lipoma most often arises in a subendocardial location; an

to the wall by a narrow stalk. Myxomas are gelatinous

intramural location is less common. This soft, noninvasive

tumors made up of tissue that has similarities to primi­

lesion can grow to a large size without causing symptoms .

tive mesenchyme. An amorphous matrix contains spindle

Myocardial lipomas can proj ect into the cardiac chambers

cells associated with thin-walled capillaries . Myxomas typi­

and result in obstruction or valve dysfunction. Lipomas can

cally are morphologically heterogeneous, containing cysts ,

also arise in an epicardial location, where they may even­

necrosis, hemorrhage, and (occasionally) calcification. The

tually cause cardiac compression or lung displacement

pathophysiology of cardiac myxoma may involve trapping

(sometimes presenting with dyspnea) .

of embryonic rests during the septation phase of cardiac

Cardiac lipoma is usually an encapsulated, homo­

development. There is great variation between patients

geneous fatty tumor. Those that arise from the epicar­

with regard to tumor size, ranging from 1 em to a mass that

dial surface typically spread into the pericardia! space,

nearly fill s a cardiac chamber. '75

while those arising from the endocardium tend to form

The clinical martifestations of cardiac myxoma usu­

a broad-based pedunculated mass that extends into a car­

ally are a result of atrioventricular valve obstruction andfor

diac chamber. There is substantial individual variation in

tumor embolization. As most of these lesions arise in the

the echogenicity of cardiac lipomas on echocardiography.

left atrium, a common clinical presentation is that of mitral

Intracavitary lipoma tends to be homogeneous and hyper­

valve obstruction with pulmonary artery hypertension and

echoic, while those located in the pericardia! space range

congestive heart failure. Mitral insufficiency can also occur.

from completely hypoechoic to completely echogenic.

Acute symptoms can result from a ball-valve effect when a

Intracavitary lipomas are usually less mobile than are

myxoma prolapses through the mitral or tricuspid valve;

myxomas. The fatty composition of lipoma produces low

this can precipitate syncopal episodes or sudden death.

attenuation on CT and homogeneous hyperintensity on

Other potential clinical manifestations include fever, ane­

T1-weighted MR images. Fat-suppressed MR images serve

mia, weight loss, and elevation of the erythrocyte sedimen­

to confirm the fatty tissue. There is no substantial contrast

tation rate. Systemic or pulmonary embolization of tumor

enhancement.'57·'7°·'78-t8o

fragments occurs in about half of patients. Multiple cardiac myxomas can occur in patients with the Carney complex; other components of this autosomal dominant condition include hyperpigmented skin lesions and various neo­ plasms, such as pituitary adenoma and fibroadenoma of the breast.164,,76,t77 The classic diagnostic imaging appearance of a car­ diac myxoma is that of an intracavitary soft-tissue mass that attaches to the wall with a stalk. The sonographic echotex­ ture of the lesion varies considerably between patients, ranging from homogeneous to heterogeneous and necrotic. Echocardiography and cine MR may show prolapse of the neoplasm into a valvar orifice. Myxoma is hyperintense on T2-weighted M R images; hypointense foci reflect the presence of hemosiderin or calcification. Myxoma usually produces lower signal intensity than adjacent normal myocardium on gradient refocused echo images, due to areas ofhemorrhage, hemosiderin and calcification. Contrast enhancement of the mass on T1-weighted MR images is helpful in differentiat­ ing myxoma from intracardiac thrombus; the enhancement pattern is usually somewhat heterogeneous

(Figure 10-21) .

The gelatinous nature o f cardiac myxoma results in hetero­ geneous low attenuation on CT; calcifrations are sometimes

Lym phatic M alformation Cardiac lymphatic malformation Oymphangioma) is an exceedingly rare lesion. Most reported cases have occurred in newborns or young children. Potential clinical manifesta­ tions include arrhythmias , palpitations, and manifestations of cardiac compression. Most cardiac lymphatic malforma­ tions are predominantly located in the pericardia! space; a chylous pericardia! effusion can accompany the lesion. ,s,,,s2

As with lymphatic malformations elsewhere, the sono­ graphic appearance is largely determined by the sizes of the contained cysts. Most often, the mass has an obvi­ ous cystic composition when viewed with echocardiogra­ phy. The cysts vary from hypointense to hyperintense on T1-weighted MR images . The lesion is generally hyperin­ tense on T2-weighted images. The diagnostic imaging appearance of a predominantly cystic lymphatic malforma­ tion in the pericardia! space may overlap that of a complex pericardia! effusion or a cardiac teratoma.'7°·'8'

I nflam matory Pseudotu mor

present. The stalk of a myxoma is sometimes too thin to be

Inflammatory pseudotumor (plasma cell granuloma) o f the

specifically visualized with CT and M R; however, a narrow

heart is a very rare primary tumor that can occur in chil­

base of attachment is usually discernible.'7°

dren. Inflammatory pseudotumor is an idiopathic lesion

308 Part 2 The Ca rd iovascu l a r System

B

A

Figure 1o-21 Cardiac myxoma. A. A 4-chamber echocardiographic image shows an oval, slightly heterogeneous mass (arrow) within the right ventricle. B. On fat-suppressed Tz-weighted M R, the lesion (arrow) is predominantly hyperintense. C. There is a heterogeneous pattern of enhancement (arrows) on this delayed Tl-weighted image after gadolinium administration. Pathological evaluation of the mass demonstrated dense fibrous tissue at the periphery, a gelatinous myxoid stroma, and areas of hemorrhage.

that is generally considered to represent a low-grade neo­ plasm. It is composed of fibroblasts in association with an

c

hyperintense on Tz-weighted images. The enhancement pattern is usually heterogeneous. '8J-t8 5

inflammatory reaction. On gross examination, the lesion appears as a solid encapsulated mass with a fibrous stroma. Reported cardiac sites of origin include the atrial and ven­

Ectopic Thyroid

tricular walls , the pulmonary and tricuspid valves , the sep­

Ectopic thyroid of the heart (struma cordis) is a rare cause

tum, and the superior vena cava. The lesion may grow into

of a cardiac mass . In the embryo, the primitive thyroid

a heart chamber or into the pericardia! space. Most of the reported cardiac inflammatory pseudotu­

gland is in dose proximity to the bulbous cordis. Ectopic thyroid of the heart apparently is a result of failure of nor­

mors have been intracavitary; therefore this lesion some­

mal separation of these tissues, resulting in a residual

times mimics a thrombus or myxoma. The lesion may have

island of thyroid tissue that grows in this ectopic location.

a somewhat heterogeneous character on echocardiography.

Greater than 9 0 % of cardiac ectopic thyroid tissue is in

The mass is isointense to slightly hypointense relative

the right heart. The mass is often located within the inter­

to normal myocardium on T1-weighted MR images. It is

ventricular septum. Most often, the lesion is discovered

Chapter 10 Acq u i red D i seases of the H e a rt a n d Perica rd i u m 309 incidentally. Occasionally, there are manifestations of ven· tricular outflow tract obstruction or arrhythmias. Cardiac MR demonstrates a well-defined mass of intermediate sig­ nal intensity. ' 86· ' 87

Primary M al ignancy Primary malignant cardiac tumors in children are exceed­ ingly rare. The most common primary cardiac malignancy in children is rhabdomyosarcoma. Other reported lesions include myxosarcoma of the left atrium, intracardiac hemangiosarcoma, small cell sarcoma, leiomyosarcoma, angiosarcoma, fibrosarcoma, and malignant germ cell tumor. Most often, these lesions have infiltrative margins on imaging studies ; however, small malignant tumors can have similar features to the benign lesions described above.'88

M etastatic Disease Metastatic disease to the heart is rare in children. The most common malignancy to secondarily involve the heart in young children is lymphoma. Older children with osteo­ sarcoma or chondrosarcoma can have cardiac involvement, usually in the form of direct extension into the pericar­ dium and myocardium from adjacent disease. The right atrium can be involved with tumor thrombus in patients with Wilms tumor, a result of extension via the renal vein and inferior vena cava. Actual tumor thrombus invasion into the wall of the atrium is rare, however. Children with neuroblastoma can develop cardiac involvement because of direct tumor extension.1 8 9·'9° Myocardial metastases sometime lead to conduction disturbances . Cardiac function abnormalities are unusual, except with mas sive tumor infiltration or extension of a mass into a cardiac chamber. Extensive tumor in the pericardium or pericardia! effusion because of metastatic neoplasm can lead to clinical manifestations of cardiac tam­ ponade. Echocardiography and MR are the most important diagnostic imaging techniques for the evaluation of chil­ dren with suspected cardiac metastasis.

R E F E R E N C ES 1. Prakash A, Powell A), Krishnamurthy R, Geva T. Magnetic resonance imaging evaluation of myocardial perfusion and viability in congenital and acquired pediatric heart disease. Am f Cardia!. 2004;93{5): 657-6 6!. 2. Ross RS, Bulkley BH, Hutchins GM, et al. Idiopathic familial myocardiopathy in three generations: a clinical and pathologic study. Am Heart f. 1978;96(2):170-178. 3- Soler R, Rodriguez E, Remuinan C, Bello M J , Diaz A. Magnetic resonance imaging of primary cardiomyopathies. J Comput Assist Tomogr. 2003;27{5) 724-'734· 4· Gaudio C, Tanzilli G, Mazzarotto P, et al. Comparison of left ventricular ejection fraction by magnetic resonance imaging and radionuclide ventriculography in idiopathic dilated cardiomyopathy. Am J Cardia!. 1991;67(5) :411-415.

5· Stehbens WE, Delalmnt B, Zuccollo )M. The histopathology of endocardial sclerosis. Cardiovasc Pathol. 2ooo;9{3) :I6J-173· 6. Ni ), Bowles NE, Kim YH, et al. Viral infection of the myocardium in endocardial fibroelastosis. Molecular evidence for the role of mumps virus as an etiologic agent. Circulation. 1997:95 {1) :133-13 9 · 7· Westwood M , Harris R , Burn J L, Barson A J . Heredity in primary endocardial fibroelastosis. Br Heart f. 197s:37{Io) :J077-1084. 8. Schryer MJ, Karnaucl!ow PN. Endocardial fibroelastosis; etiologic and pathogenetic considerations in children. Am Heart J. 1974:88(5):557-5 6 5 .

9 · Mitchell SC, Froehlicl! LA, Banas J S Jr, Gilkeson MR. An epidemiologic assessment of primary endocardial fibroelastosis. Am f Cardia!. 1966;18(6) :859-8 6 6 . 10. Horigome H. The contracted type of endocardial fibroelastosis. Clin Cardia!. 1999;22{4):309. 11. Matitiau A, Perez-Atayde A, Sanders SP, et al. Infantile dilated cardiomyopathy. Relation of outcome to left ventricular mechanics, hemodynamics, and histology at the time of presentation. Circulation. 1994;9o{3):13I0-1318. 12. !no T, Benson LN, Freedom RM, Rowe RD. Natural history and prognostic risk factors in endocardial fibroelastosis. Am J Cardia!. 1988;62(7) A31-434·

13- Mahle WT, Weinberg PM, Rychik ). Can echocardiography predict the presence or absence of endocardial fibroelastosis in infants 8o%) , is the ostium secundum defect. This is usually a large lesion and is located near the fossa ovalis. A margin of atrium sep­ arates the defect from the atrioventricular valves. Associated cardiac anomalies are present in less than 10% of patients with an ostium secundum defect. The most common asso­ ciated conditions are partial anomalous pulmonary venous connection, persistent left superior vena cava, and prolapse of the mitral valve. The ostium primum type of ASD is located in the inferior atrial septum caudal to the fossa ovalis. The patho­ physiology involves failure of fusion of the septum pri­ mum to the septum intermedium. The ostium primum type accounts for approximately 10% of ASDs. The ostium primum defect is a component of the spectrum of abnor­ malities that occur with endocardial cushion defect; that is, atrioventricular septal defect. Cleft mitral valve and mitral insufficiency often occur in association with an ostium pri­ mum ASD. A superior sinus venosus AS D is located above the fossa ovalis, adjacent to the entrance of the superior vena cava. There is deficiency in the sinus venosus septum that in normal individuals separates the sinus venosus portion of the right atrium from the right pulmonary veins and sys­ temic veins; that is, deficiency of the common wall between the superior vena cava and the right upper pulmonary vein. This type accounts for 5% to 10% of ASDs. The superior vena cava may straddle the defect, such that systemic blood is directed into both atria. In approximately 90% ofpatients with a sinus venosus defect, there is anomalous pulmonary venous drainage. In addition, the proximity and orientation of the right pulmonary veins to the defect result in prefer­ ential flow of pulmonary venous return through the defect into the right atrium, while blood from the left pulmonary veins courses toward the left atrium. Defects of the posterior inferior portion of the atrial septum are rare. This lesion is usually associated with absence of the wall between the coronary sinus and the left atrium; that is, coronary sinus septal defect. A persistent left superior vena cava empties into the left atrium. Defects can also occur at the junction of the inferior vena cava with

the right atrium (inferior sinus venosus septal defect) , as well as posterior to the fossa ovalis. A patent foramen ovale is an additional potential cause ofatrial-level shunting. Failure of appropriate closure of the foramen ovale in the neonate can occur as a consequence of an anatomic abnormality of the valve mechanism or abnormal atrial pressure relationships. In some instances, the valve is too short to completely cover the foramen ovale. In others, there is enlargement of the foramen ovale, a result of elevated left atrial pressure and volume, as occurs with patent ductus arteriosus, VSD, or left ventricular out­ flow obstruction. If the cause of the elevated left atrial pres­ sure is relieved in these infants, shunting at the atrial level diminishes or disappears completely. With some congeni­ tal heart defects, patency of the foramen ovale after birth occurs because of elevated right-heart pressures. Right-to­ left shunting through a patent foramen ovale is essential for survival prior to surgical repair with some types of congeni­ tal heart disease. Examples include tricuspid atresia, mitral atresia, total anomalous pulmonary venous connection, and some forms of transposition. In newborns who fail to undergo normal decrease in pulmonary vascular resistance after birth, pulmonary hypertension causes elevated right atrial pressure and persistent right-to-left shunting across an anatomically normal foramen ovale. In normal infants, functional closure of the foramen ovale occurs soon after birth. There is anatomical clo­ sure of the septum primum and septum secundum by approximately 1 year of age. However, the foramen ovale is probe-patent in greater than 25% of normal adults. Minor left-to-right shunting through a patent foramen ovale is present in 10% to 15% of asymptomatic children and adults evaluated with Doppler or contrast echocardiography. Detection of a patent foramen ovale is also possible utilizing contrast-enhanced dynamic MRI. The small shunt associ­ ated with a patent foramen ovale is usually of no hemody­ namic significance. There is, however, a weak association with migraine headaches, transient ischemic events, and stroke. The risk for a neurological event is greater in those individuals with a large shunt or an associated atrial septal aneurysm. 27 Fetal cardiac hemodynamics are normal despite the presence of an ASD, as right-to-left shunting normally occurs across the patent foramen ovale. However, failure of appropriate closure of the atrial septal communication after birth in response to elevation of the left atrial pres­ sure leads to a left-to-right shunt. The left atrium does not enlarge despite the prominent blood flow, as it is decom­ pressed by the communication with the right atrium. In general, right ventricular hypertrophy does not occur in patients with an ASD, unless there is pulmonary vascular hypertension. With a large ASD, the pressures in both atrial chambers are equal; therefore, ventricular compliance is a major determinant of the magnitude of the shunt. Because the right ventricular wall is thinner than the left and the right ventricle is more distensible, more blood tends to

330

Part 2 T h e Ca rd iovascu l a r System

empty into the right ventricle, thereby facilitating left-to­

are prominent. In some patients, the vessels are ill defined because of interstitial fluid. In those patients with cardio­

right shunting. Infants with an isolated A S D are frequently asymp­

megaly, chamber enlargement consists of the right atrium

tomatic. If cardiac failure occurs during infancy, it is usu­

and right ventricle

ally precipitated by coexistent cardiac defects or another

forms of pretricuspid left-to-right shunts. The left atrium

(Figure 1 1 -9) . This pattern occurs with all

complication. In infants with pulmonary hypertension

does not dilate in patients with an A S D . Tills is an impor­

and an atrial septal communication, right-to-left shunting

tant differentiating feature from other left-to-right shunts,

can result in clinically evident cyanosis. Tbis is particularly

such as V S D or patent ductus arteriosus.

common in preterm infants with congenital or acquired

Right ventricular enlargement in patients with an

lung disease. Children with an isolated A S D occasionally

ASD causes uplifting of the cardiac apex that is often

exhibit manifestations of failure to thrive. Exercise intol­

visible on frontal radiographs . Clockwise rotation of the

erance may develop, but often not until adolescence. A S D

heart causes the right ventricle to form the left cardiac

is the most common congenital heart lesion t o first clini­

border. The left upper heart border is straight or convex

cally present during the adult years . In general, blood flow

because of prominence of the right ventricular outflow

through an A S D does not produce a murmur. However,

tract. The main pulmonary artery is prominent and the

prominent flow across the right ventricular outflow tract

aortic arch is normal in size. On lateral radiographs , right

and pulmonary valve in these patients often produces a

ventricular prominence fills the inferior retrosternal space

A loud first heart sound

( Figure 1 1 -1 o) . Enlargement of the right ventricular outflow

precedes the murmur. The second heart sound is widely

tract is best visualized on the right anterior oblique view.

split and fixed.

A lateral esophagram view sometimes shows indentation

long systolic ejection murmur.

As with other left-to-right shunts, the shunt caused

1.5:1

or displacement of the esophagus by the left atrium; this is

in order to produce radio­

a result of displacement of the normal size left atrium by

graphically detectable alterations in the pulmonary vascu­

the enlarged right atrium. In patients with a sinus veno­

by an AS D must be at least

lar pattern. Most patients with a small secundum defect

sus defect, an abnormal horizontal orientation of the right

have normal chest radiographs. With a moderate or large

upper pulmonary vein is occasionally visible on frontal

shunt, both the central and peripheral pulmonary vessels

radiographs.

A

B

Figure 11-9 Sinus venosus atrial septal defect and partial anomalous pulmonary venous return. A, B. Anteroposterior and lateral chest radiographs of an asymptomatic child with a murmur demonstrate mild cardiomegaly and pulmonary vascular prominence. There is no left atrial enlargement.

Chapter 11 Congenital H e a rt D i sease 331

A

B

Figure 1 1-10 Atrial septal defect. A An anteroposterior radiograph of a 2-year-old child with a systolic ejection murmur shows cardiomegaly and pulmonary vascular prominence. The main pulmonary artery segment of

at the atrial level. Transesophageal echocardiography can

Atrial Septal Defect Phys iology

Left-to-right s h u nt

the left cardiomediastinal border is prominent. The aortic knob is normal. B. Pulmonary vascular prominence is also evident on the lateral view. Right ventricular enlargement causes fullness of the anterior aspect of the heart.

Rad iol ogy

Active pulmonary vascu lar : prominence : Prominent main pul monary : artery : Enlargement of right heart

I ncreased volume and pressure i n right atriu m , right ventricle Left atriu m decompressed ' N ormal-size left atri u m i nto right atriu m

provide the detailed measurements required for treatment with a transcatheter septal ocduder. 2 8 Echocardiography is the primary imaging technique for children with an A S D . For selected patients, M R I pro­ vides supplemental information concerning the morphol­ ogy of the defect and the magnitude of the shunt. M RI is an alternative to transesophageal echocardiography for obtain­ ing the detailed measurements of A S D that are required in planning for the placement of a transcatheter occlusion device. With M R, axial, long axis, and short axis views are all helpful for demonstrating an A S D and for evaluating the right ventricle

(Figure 1 1 -1 1) . In evaluating the atria with

M RI , it is important to recognize that lack ofvisualization of the atrial septum in the region of the fossa ovalis is normal. The atrial septum i s visualized with echocardiography

The normal fossa ovalis has gradually tapered borders .

An

on the subcostal 4-chamber, apical, and subcostal short

A S D can be differentiated from a normal fossa ovalis by the

axis views . Most A S D s are easily demonstrated with echo­

abrupt termination at the septum in the presence of a true

cardiography, although accurate asses sment of the size is

defect. Dynamic imaging with a gradient-echo technique

sometimes difficult. In the presence of an A S D , there is

allows documentation of shunt flow. The spatial orienta­

usually enlargement of the right atrium, while the left atrial

tion, size, and shape of an ASD change during the cardiac

size is normal. Echocardiographic manifestations of right

cycle. Phase-shift velocity mapping of flow within the pul­

ventricular volume overload include an increased diastolic

monary artery and aorta provides information regarding

dimension of the ventricular chamber and abnormal ante­

the magnitude of the left-to-right shunt. On dynamic con­

rior motion of the interventricular septum during systole.

trast-enhanced imaging, right-to-left shunting at the atrial

Color Doppler evaluation shows left-to-right blood flow

level results in the appearance of contrast in the left atrium

332 Part 2 The Card iovasc u l a r System

Figure 1 1-1 1 Secundum atrial septal defect. An axial T1-weighted image of an n-month-old child shows a large atrial septal defect (large arrow) . There is a small residual segment of the septum prirnum (sma!! arrow) . The right atrium (RA) is markedly dilated. The right (RV) and left ventricular (LV) chambers are also prominent. (LA, left atrium.)

prior to the pulmonary veins. Imaging during the Valsalva maneuver accentuates shunting. M RI is particularly use­ ful for demonstrating the pathological anatomy in patients with a sinus venosus defect and partial anomalous pulmo­ nary venous connection (Figu re 1 1 ·1 2) . 22 •2 5 - 27.2 9-32 The therapeutic approach to ASDs is tailored accord­ ing to the size of the defect, the clinical manifestations , and the presence or absence of associated lesions. Generally, repair during childhood is appropriate for an ASD that causes shunting of at least so%, thereby preventing the onset of pulmonary vascular disease. Treatment is usually not required for an asymptomatic ASD in an infant, as up to half of these defects dose spontaneously. The surgical technique involves either direct suture closure of the defect or the placement of a patch composed of pericardium or synthetic material. Some ASDs are amenable to treatment with transcatheter closure devices (Figure 1 1 -1 3) .

Endocardial Cushion Defect (Atrioventricular Septal Defect) Endocardial cushion defect encompasses a spectrum of cardiac anomalies that result from maldevelopment of the embryonic endocardial cushion structures. Synonyms for endocardial cushion defect include atrioventricular sep­ tal defect and atrioventricular canal defect. Most of these patients have a defect that involves portions of both the atrial and the ventricular septa, as well as various abnor­ malities of the mitral and tricuspid valves . Endocardial cushion defect accounts for 4% to 5% of congenital heart lesions. The gender incidence is equal. Endocardial cush­ ion defect is the most common cardiac anomaly in patients with trisomy 21.

The endocardial cushions are 2 masses of tissue, one dorsal and the other ventral, that grow into the embryonic atrioventricular canal and fuse to form the atrioventricu­ lar septum. Development of the atrial septum divides the embryonic single atrium into 2 chambers. The primitive single ventricle separates into 2 parts by way of fusion of the membranous portion of the ventricular septum, the endocardial cushions, and the bulbus cordis. The muscular portion of the ventricular septum grows cephalad to meet with the 2 ridges of the bulbus cordis. The endocardial cushions develop concomitantly and eventually fuse with the bulbar ridges and muscular portion of the septum. The final stage of ventricular separation occurs by growth of the fibrous tissue of the membranous portion of the interven­ tricular septum. Maldevelopment of the endocardial cushions results in a spectrum of malformations (Table 1 1 -8) . Structures that derive from the endocardial cushions include the lower atrial septum (the septum primum) , the upper ventricu­ lar septum (membranous septum) , the anterior leaflet of the mitral valve, and a septal leaflet of the tricuspid valve. Failure of normal growth of the endocardial cushions results in a low intraatrial communication inferior to the free margin of the septum primum. In most patients, there is also a defect in the uppermost portion of the ventricular septum, thereby creating an atrioventricular canal. If there is complete lack of endocardial cushion fusion, a common atrioventricular valve orifice results, with a continuous common leaflet that passes through the septal defect from one ventricle to the other. At the other end of the spectrum, partially deficient fusion produces a deft in the anterior leaflet of the mitral valve. The most common type of endocardial cushion defect is complete atrioventricular canal. There is a single contig­ uous defect in the lower portion of the atrial septum and the adjacent portion of the upper ventricular septum. The atrioventricular valve development is always abnormal in these patients. There are bridging leaflets that pass through the septal defect because of fusion of portions of the septal leaflets of the developing mitral and tricuspid valves . The single atrioventricular valve of complete atrioventricular canal is composed of s leaflets, 2 of which are entirely con­ tained in the right ventricle, 1 ofwhich is entirely contained in the left ventricle, and the other 2 are bridging. With partial atrioventricular canal, there are 2 atrio­ ventricular valves and 2 valve rings. The anterior mitral leaflet is cleft and attaches to the crest of the incompletely developed ventricular septum. The most common form of incomplete atrioventricular canal is termed ostium primum defect; in these patients, the anterior leaflet of the mitral valve is divided equally. The intermediate type of endocar­ dial cushion defect is characterized by the presence of a limb of atrioventricular valve tissue that bridges common anterior and posterior leaflets . In all patients with endocardial cushion defect, the left ventricular outflow tract is narrowed and elongated. There is concavity of the interventricular septum below the mitral

Chapter 11 Congenital H e a rt D i sease 333

A

B

Figure 1 1-1 2 Sinus venosus defect and partial anomalous pulmo­ nary venous connection. A, B. Axial and sagittal ECG-triggered study-state free precession cine MR images of a q-year-old patient with exertional chest pain and a heart murmur show a wide defect (arrows) in the tissue that separates the posterior wall of the superior vena cava and the

valve, producing a shortened left ventricular inflow tract. These features result in an angiographic appearance lik­

c

anterior wall of the right upper pulmonary vein at its insertion with the left atrium. C. Anomalous drainage of the right upper pulmonary vein (arrow) to the superior vena cava is visible on this oblique coronal image. LA, left atrium; RA, right atrium; RP A, right pulmonary artery; RPV, right upper pulmonary vein; SVC, superior vena cava.

There are

5 potential hemodynamic alterations of an

endocardial cushion defect: left-to-right atrial shunt; left­

ened to that of a goose neck. This morphology is a result

to-right ventricular shunt; left-to-right shunt from the left

of the attachment of the anterior mitral valve leaflet to the

ventricle to the right atrium; mitral regurgitation; and pul­

crest of the incompletely developed ventricular septum.

monary hypertension. In patients with partial atrioventric­

Other features shared by all forms of endocardial cushion

ular canal, the hemodynamics are similar to those of A S D

defect include normal development of the inferolateral leaf

with mitral regurgitation. If the A S D is large, the elevated

lets of the mitral and tricuspid valves and inferior displace­

pressure related to mitral valve incompetence is mainly

ment of the septal portions of the atrioventricular valve

transmitted to the right side ofthe heart. If the A S D is small,

annulus.33

the left atrium and left ventricle enlarge approximately in

334 Part 2 The Card iovasc u l a r System

Figure 11-1 3 Device closure of secundum atrial septal defect. A lateral chest radiograph of a 17-year-old girl shows an Arnplatz septal closure device in place (arrow) .

proportion t o the severity o f the mitral regurgitation. With complete atrioventricular canal, all 4 cardiac chambers communicate. Because the right ventricle is more compli­ ant than the left, prominent left-to-right shunting causes volume overload of the right atrium, right ventricle, and pulmonary circulation.3 4 The clinical manifestations of endocardial cushion defect vary with the specific anatomy and the presence or

absence of associated lesions . In those patients with an isolated ostium primum defect and only minimal insuf ficiency of the mitral valve, the clinical course is similar to that of an ostium secundum ASD: few or no symptoms during childhood and progression to heart failure and arrhythmias during adult life. When there is substantial mitral valve insufficiency in association with an ostium primum defect, the onset of symptomatic congestive heart failure is earlier in life. At the other end of the clinical spectrum of endocardial cushion defect are patients with complete atrioventricular canal (complete atrioventricular septal defect) . This is usually accompanied by the onset of severe heart failure early dur­ ing infancy. These children have manifestations of failure to thrive and frequently suffer recurrent respiratory infections. If the lesion is not corrected, pulmonary hypertension devel­ ops during childhood. Approximately 70% of infants with complete atrioventricular canal have trisomy 21. 3 5 In keeping with the spectrum of hemodynamic conse­ quences of endocardial cushion defect, there is variability in the radiographic findings. An ostium primum defect with little or no mitral regurgitation results in cardiomegaly caused by a large volume left-to-right shunt. Enlargement involves the right ventricle, right atrium, main pulmonary artery, and central pulmonary arteries; the size of the left atrium is normal. An ostium primum defect that is accompanied by sub­ stantial mitral regurgitation also leads to right ventricular enlargement and pulmonary vascular prominence because of a large volume left-to-right shunt. However, mitral valve dysfunction causes increased strain on the left ventricle, and this chamber enlarges as well. The left atrium may also be prominent. In addition to pulmonary vascular promi­ nence related to increased volume from the left-to-right shunt, left-heart failure often results in pulmonary venous distention and indistinct vascular margins. Complete atrioventricular canal is associated with sub­ stantial cardiomegaly. There is disproportionate enlarge­ ment of the right atrium. The main pulmonary artery segment is prominent and the aorta is small ( Figures 1 1 ·14 and 1 1 - 1 5) .

Table n-8. Endocardial Cushion Defects

Partial atrioventricular canal

Com plete atrioventricular canal

i Osti u m pri m u m defect Osti u m pri m u m defect, cleft m itral valve Com mon atri u m , atrioventricular ; valve deform ity Anterior m itral valve leaflet cleft Anterior tricuspid valve leaflet cleft Atrioventricu lar canal VS D

Endocardial Cushion Defect Pathology

Rad iology

' Right ventricular enlargement Right atrial enlargement Pulmonary vascu lar prominence ± M itral regurgitation : Left ventricular enlargement Left atrial enlargement Pu l monary venous distention M arked right-heart enlargement Complete atrioventricular canal Left-to-right shunt

Chapter 1 1 Congenital H e a rt D i sease 335

Figure 1 1-14 Endocardial cushion defect. An anteroposterior chest radiograph of an infant demonstrates cardiomegaly and pulmonary vascular prominence. The aortic arch is inconspicuous.

A

Figure 1 1-1 5 Complete atrioventricular canal. A, B. Anteroposterior and lateral chest radiographs of a 4-month­ old child with trisomy 21 demonstrate cardiomegaly, pulmonary vascular prominence, enlargement of the main pulmonary

In patients with an ostium prirnum ASD, echocar­ diography shows the lower portion of the atrial septum to be absent. The apical and subcostal views usually pro­ vide optimal visualization of the deft anterior mitral valve leaflet. The right atrium and right ventricle are enlarged. Paradoxic motion of the interventricular septum indi­ cates the presence of right ventricular volume overload. Echocardiography of the complete form of atrioventricular canal shows a large central defect that involves the lower portion of the atrial septum and the upper portion of the ventricular septum. There is lack of complete separation of the mitral and tricuspid valves, and a bridging leaflet spans the defect. Images in the plane of the aortic root show the classic gooseneck deformity of the left ventricular outflow tract. With angiocardiography, the gooseneck deformity of the left ventricular outflow tract in patients with endocardial cushion defect is visible on the frontal view ( Figu re 1 1 -1 6) . The best projection for visualization o fthe anomalous valve apparatus is the hepatodavicular view. This projection shows the atrial septum in profile. Blood sampling from right-heart catheterization demonstrates abnormally high oxygen saturation because of shunting. Pulmonary artery systolic pressure is at or near systemic pressure in patients with complete atrioventricular canal.36 M R examination of patients with endocardial cush­ ion defect shows absence of portions of the atrial and ven­ tricular septa (Figure 1 1 -1 7) . Visualization of the cleft septal leaflet of the mitral valve that is a feature of incomplete atrioventricular canal often is not possible with M R . With

B

artery, and an inconspicuous aortic arch. Right-heart border prominence on the frontal view is predominately a result of enlargement of the right atrium.

336 Part 2 The Ca rd iovascu l a r System

A

Figure 1 1-1 6 Endocardial cushion defect. A. Left ventriculography shows a narrow, elongated, and elevated character of the outflow tract, producing the "gooseneck"

B deformity (arrow). B. The mitral valve contour is irregular and there is a prominent notch in the anterior leaflet (arrow).

complete atrioventricular canal, there is a common atrio­ ventricular valve orifice, with contiguous valve leaflets. M R shows secondary signs o f volume overload i n the right car­ diac chambers in patients with endocardial cushion defect. Coronal images may demonstrate the classic gooseneck deformity of the left ventricular outflow tract. Dynamic first-pass contrast agent signal-time studies show rapid recirculation and shunting. Volumetric and phase contrast cine methods allow quantification of shunting by compar­ ing the pulmonary artery flow to the aortic flow.37·3 8

Patent Ductus Arteriosus

Figure 1 1-17 Endocardial cushion defect. An axial MR image shows a large septal defect. There is communication between the ventricles and the right atrium.

Persistent ductus arteriosus i s the second most common congenital heart defect in full-term infants, after VSD. In most patients, a patent ductus arteriosus causes left-to-right shunting. This lesion often occurs as an isolated anomaly. The most common associated cardiac lesion is a restric­ tive VSD. With some cardiac anomalies, a patent ductus arteriosus provides a pathway for lifesaving blood flow into the pulmonary arteries (e.g., pulmonary atresia with intact ventricular septum) .

Chapter 1 1 Co ngenital H e a rt D i sease In the fetus, the ductus arteriosus permits right ventric­ ular blood to bypass the nonaerated lungs. Approximately 6o% of fetal right ventricular output is diverted through the ductus into the aorta. At the time of delivery, expansion of the lungs causes most of the pulmonary artery blood flow to be redirected into the low resistance pulmonary vas­ cular system. A decrease in circulating prostaglandins and an increase in arterial oxygen tension stimulate smooth muscle contraction and closure of the ductus. During the first few hours of life, there is usually small volume right­ to-left or bidirectional shunting through the ductus arte­ riosus . With progressive decrease in pulmonary vascular resistance, mild left-to-right shunting occurs. Functional closure of the ductus normally occurs by 12 to 24 hours of age. Structural obliteration occurs by 2 weeks in 35% of infants, by 3 months in 95% of infants, and by 1 year in 99% of infants. The fibrosed ductus arteriosus constitutes the ligamentum arteriosum.39·4° Patent ductus arteriosus accounts for 5% to w% of congenital heart lesions. The male-to-female ratio is approximately 1:2. The prevalence is about 1 in 16oo term livebirths. Maternal rubella virus infection during the first trimester is a risk factor for patent ductus arteriosus. Patent ductus arteriosus is more common in preterm infants than in those born at term, with a prevalence of 20% to 30% in this group. The prevalence rises with earlier gestational age and lower birth weight; approximately 75% of infants of 28 to 30 weeks' gestation have patent ductus arteriosus. Patent ductus arteriosus is much more common in pre­ term infants with respiratory distress syndrome than in those without.4'·42 Patent ductus arteriosus in the preterm infant can cause retrograde blood flow in the descending aorta dur­ ing diastole, leading to diminished systemic flow and a pre­ disposition to end-organ ischemia. Therefore, this lesion can contribute to morbidity from necrotizing enterocoli­ tis, abnormal cerebral perfusion, respiratory distress syn­ drome, and chronic lung disease. In term infants and older children, a small patent ductus arteriosus is sometimes hemodynamically insignificant and associated with no symptoms. A large patent ductus with no other congenital heart lesions causes a left-to-right shunt. If left ventricular volume overload ensues, there is progressive congestive heart failure. As with other large left-to-right shunts, an untreated hemodynamically significant patent ductus arte­ riosus can lead to the eventual development of pulmonary arteriolar hypertension and Eisenmenger physiology. Older patients with patent ductus arteriosus are at increased risk for infective endocarditis. The clinical marlifestations of a patent ductus arterio­ sus predominantly relate to the size of the ductus, the pul­ monary vascular resistance, and the presence or absence of additional cardiovascular anomalies. The narrow lumen of a small ductus restricts the volume of left-to-right shunt­ ing, and the child may be asymptomatic. These lesions are most often discovered incidentally at the time of auscul­ tation, typically as a continuous "machinery" murmur. A

337

moderate-sized patent ductus arteriosus often is associated with progressive increase in left-to-right shunting during the first few months of life, as the pulmonary vascular resistance falls. Common clinical manifestations in these patients include failure to thrive, recurrent upper respira­ tory tract infections, and exertional fatigue. A large ductus usually causes left ventricular decompensation during the first few weeks of life, producing tachypnea, tachycardia, poor feeding, and hepatomegaly. Preterm infants with pat­ ent ductus arteriosus often exhibit manifestations of con­ gestive cardiac failure, as the incompletely developed left ventricle is unable to manage the volume overload. Physical examination often demonstrates prominent peripheral pulses and an active precordium. As with the clinical findings, the conspicuity of the radiographic features of patent ductus arteriosus is roughly proportional to the degree of left-to-right shunting and the size of the ductus. The chest radiograph of a child who has a small patent ductus arteriosus is usually normal. As with other left-to-right shunts, a shunt magnitude of at least L S :1 is generally required for radiographic detection. A moder­ ate-size patent ductus results in slight prominence of the main pulmonary artery and the central pulmonary vessels, with a normal-size heart. Potential findings with a large patent ductus include dilation of the left atrium and left ventricle, prominent pulmonary vascular markings, and enlargement of the main pulmonary artery (Figu re 1 1 -18) . Because the shunted blood also courses through the aor­ tic arch, this structure eventually enlarges as well; when present, this finding helps in the differentiation of patent

Figure 1 1-18 Patent ductus arteriosus. Cardiomegaly and pulmonary vascular prominence are present in this 1-month-old infant with a large patent ductus arteriosus. There is left upper mediastinal fulln ess as a result of dilation of the main pulmonary artery and the ascending aorta.

338 Part 2 The Card iovasc u l a r System

A

Figure 1 1-1 9 Patent ductus arteriosus.

B

Posteroanterior and lateral radiographs of a 2-year-old child show pulmonary vascular prominence and enlargement of the main pulmonary artery, aortic arch, and left atrium.

ductus arteriosus from an intracardiac left-to-right shunt ( Figure 1 1 -1 9) . Likewise, dilation of the left atrium helps to differentiate this lesion from an ASD. In those patients with congestive cardiac failure, the puhnonary vascular markings are indistinct and there are fluffy parenchymal opacities due to pulmonary edema. Although the shunt does not directly involve the right ventricle, long-term increase in puhnonary artery pressure eventually causes right ventricular hypertrophy.

Patent Ductus Arteriosus Physiology

Left-to-right s h u nt

Left ventricle volume overload

Rad iol ogy

Active p u l monary vascu lar prominence . Enlarged main pulmonary artery Enlarged left ventricle and left atriu m Enlarged aortic arch : Congestive fai l u re

Occasionally, a patent ductus arteriosus is radiograph· ically visible as a small mass along the left upper mediasti­ num, adj acent to the aortic arch. A similar appearance can occur with a ductus diverticulum, which is a funnel-shaped

widening of the aortic origin of a ductus that is occluded at the pulmonary end. Aneurysm formation is an additional rare ductus anomaly; aneurysms can rupture or become infected. Calcification of the ligamentum arteriosum is an occasional incidental finding on imaging studies of infants and children. Although this can persist into adult­ hood, the calcification most often disappears with age. Echocardiography readily demonstrates a patent duc­ tus arteriosus in most affected patients . Occasionally, the long and tortuous patent ductus of a premature infant is less conspicuous . Doppler studies demonstrate the direc­ tion of flow through the ductus. Ratios of the left atrial diameter to that of the aortic root provide an indication of the hemodynamic significance of left-to-right shunt­ ing in patients with patent ductus arteriosus . In normal infants , this ratio is between 0 . 9 and 1.0. A ratio of greater than 1.2:1 is generally considered clinically significant in the premature infant with a patent ductus. With more substantial left-to-right shunting at the ductus, this ratio is 1.4 or greater. Echocardiography occasionally demon­ strates minimal flow through a ductus arteriosus in a patient with no symptoms and no evidence of cardiovas­ cular or pulmonary consequences; this is termed a silent ductus.43-45 Aortography is not required for the routine diagnostic evaluation of a patent ductus arteriosus. This study shows a patent ductus as a tubular structure that connects the anterior wall of the aorta to the proximal portion of the puhnonary artery, paralleling the course of the aortic arch (Figu re 1 1 -20) . Often, the aortic end of the ductus is larger than the pulmonary end. An isolated patent ductus usually does not opacify with pulmonary angiography, as the shunt

Chapter 11 Congen ital H e a rt D i sease

Figure 11-20 Patent ductus arteriosus. An anteroposterior angiographic image shows contrast injected into the aortic arch passing through a large ductus arteriosus (arrow) into the pulmonary arteries.

is entirely in the left-to-right direction. However, unopaci­ fied aortic blood streaming through the ductus causes dilu­ tion of contrast along the superior aspect of the opacified

A

Figure 11-21 Patent ductus arteriosus occlusion device.

339

pulmonary artery. In patients with patent ductus arteriosus in combination with aortic arch obstruction, right-to-left shunting occurs through the ductus, and contrast from the pulmonary artery opacifies the aorta. MR demonstrates a patent ductus arteriosus as a tubu­ lar structure coursing between the proximal aspect of the descending aorta (the aortic isthmus) and the distal portion of the main pulmonary artery or the proximal aspect of the left pulmonary artery. Most often, optimal viewing of the ductus is on axial or right anterior oblique images. Patent ductus arteriosus is sometimes difficult to visualize with MR because of the short length of the lesion, the turbu­ lent blood flow, and the presence of large adjacent vessels. Turbulent flow within the adjacent portions of the pulmo­ nary artery or aorta may provide a clue to the presence of a patent ductus. Secondary findings of a patent ductus arteri­ osus on MR include dilation of the left atrium and left ven­ tricle, pulmonary vascular prominence, and enlargement of the aortic arch.4 6 In premature infants , indomethacin administration effectively facilitates closure of the ductus arteriosus; indo­ methacin is an inhibitor of prostaglandin synthetase. 4MB Indomethacin therapy is of limited usefulness, however, in full -term infants . Most patients with patent ductus arte­ riosus who are not candidates for, or fail, medical therapy undergo surgical ligation.49 Various transcatheter occlu­ sion devices are also available ( Figure 1 1 -21 ) . There is a small risk for a hemodynamically significant residual shunt after deployment of these devices.5°

8

A, B. Anteroposterior and lateral chest radiographs show an Arnplatz closure device in the ductus arteriosus.

340 Part 2 The Card i ovascu l a r System

Partial Anomalous Pul monary Venous Connection Partial anomalous pulmonary venous connection refers to the insertion of 1 or more pulmonary veins into the right atrium or a systemic vein. Hemodynamically, this is a left­ to-right shunt, with fully oxygenated blood recirculated through the lung via the right heart. Patients with partial anomalous pulmonary venous connection are acyanotic. The prevalence of this anomaly is less than 1% oflivebirths. Partial anomalous pulmonary venous connection is frequently associated with a superior sinus venosus ASD or, less commonly, an ostium secundum defect. Approximately 10% of patients with A S D have coexistent partial anomalous pulmonary venous connection. Approximately 8o% of par­ tial anomalous venous connections involve veins from the right lung. Anomalous drainage from both lungs is rare. Potential sites of anomalous pulmonary venous con­ nection from the right lung include the superior vena cava (common) , right atrium (common) , inferior vena cava, coronary sinus, azygos vein (rare) , ductus arteriosus (rare) , and portal vein (rare) . Connection of a right pulmonary vein to the inferior vena cava immediately below the dia­ phragm, in association with a hypoplastic ipsilateral lung and small right pulmonary artery, represents scimitar syn­ drome (hypogenetic lung syndrome) . Connection of all of the right pulmonary veins to the right atrium in associa­ tion with an ASD is common in children with polysplenia. Potential sites of anomalous connection of left pulmonary veins include a persistent left superior vena cava, the left brachiocephalic vein, the left subclavian vein, the coronary sinus, and the inferior vena cava (rare)Y · 52 Because only a portion of pulmonary venous return shunts into the right heart in patients with partial anomalous pulmonary venous connection, many individuals with this anomaly are asymptomatic. Those who are symptomatic usu­ ally have clinical marlifestations that are identical to those of an ASD. In fact, many symptomatic patients have a coexistent ASD. The most common complaint is exercise intolerance. Symptoms often do not occur until adolescence or adult­ hood. Some patients have recurrent pneumonias. Failure of proper diagnosis and treatment of partial anomalous pulmo­ nary venous connection can lead to congestive heart failure, atrial arrhythmias, and pulmonary vascular disease in adult­ hood. Cyanosis only occurs if there is progression to pulmo­ nary artery hypertension. Auscultation demonstrates systolic murmurs because of increased blood flow across the tricus­ pid valve and right ventricular outflow tract. The radiographic features of partial anomalous pul­ monary venous connection vary with the size of the shunt and the presence or absence of associated anomalies. Occasionally, a somewhat prominent pulmonary vein is vis­ ible following an anomalous course. This finding is most common when an entire lung drains anomalously. If there is a high-volume shunt, radiographs may demonstrate pul­ monary vascular prominence and mild to moderate cardio­ megaly (enlargement of the right atrium and right ventricle) .

Figure 11-22 Partial anomalous pulmonary venous connection (scimitar syndrome).

A frontal chest radiograph of an asymptomatic child with a heart murmur shows an anomalous right pulmonary vein (arrow) along the right-heart border. The vessel is wider inferiorly than superiorly, resulting in a resemblance to a scimitar sword.

In patients with scimitar syndrome, the anomalous pulmonary vein courses obliquely along the inferior aspect of the right lung toward the medial aspect of the diaphragm (Figu re 1 1 -22) . Pulmonary hypoplasia results in rightward deviation of the heart and elevation of the right hemidia­ phragm ( Figure 1 1 -23) . The right pulmonary artery is small and the hypoplastic lung may appear oligemic. The pul­ monary vessels in the contralateral lung are often slightly prominent. The shunt volume determines the heart size. 53 Standard echocardiography is sometimes equivo­ cal for determining the number or sites of anomalous pulmonary veins in patients with partial anomalous pul­ monary venous connection; consequently, cardioangiog­ raphy is often used. Less-invasive techniques such as transesophageal echocardiography, helical CT, and car­ diac M R can also be helpful ( Figures 1 1 -24 and 1 1 -25) . M R also allows quantification o f the right-to-left shunting and differential lung perfusion. The major pulmonary veins are usually best visualized on axial and short axis views . The vessels between the anomalous connection and the right atrium are usually enlarged, for example, promi­ nence of the superior vena cava as a result of anomalous pulmonary venous connection with the brachiocephalic vein. 54·55

Chapter

A

c

Figure 11-23 Scimitar syndrome.

A A posteroanterior chest radiograph of a 7-year-old boy with a history of fatigability shows a small right lung with an anomalous pulmonary vein (arrow) coursing along the inferior aspect. The pulmonary artery branches are small on the right, and slightly prominent on the left. B. The lateral view confirms the small volume of the right lung (arrow indicates

11

Co ngenital H e a rt D i sease

341

B

D

anterior margin oflung) . C, D . Coronal contrast-enhanced MR images show 2 anomalous right pulmonary veins (small arrows) draining into the inferior vena cava near its insertion into the right atrium. The right main pulmonary artery (large arrow) is small. The right lung hypoplasia results in elevation of the right hernidiaphragm and rightward extension of the upper mediastinal margin.

342

Part

2

The Card iovascu l a r System

8

A

Figure 11-24 Partial anomalous pulmonary venous connection. A. A chest radiograph of an 8-year-old child shows enlargement of the lower aspect of the superior vena cava (arrow) . Additional findings include pulmonary vascular prominence bilaterally, enlargement of the main pulmonary artery, and slight right heart prominence. B. A cine cardiac MR image shows a dilated anomalous right pulmonary vein (arrow) that drains nearly the entire right lung. C. A more anterior image demonstrates dilation of the superior vena cava (arrow) beginning at the level of the anomalous connection.

Partial Anomalous Pulmonary Venous Con nection Pathology

Anomalous pul monary vei n Left-to-right s h u nt

Sci m itar synd rome

Rad iology

. ± Abnormal vei n cou rse; prominent vein _ M i ld cardiomegaly M i ld pul monary vascular prominence Small right l u ng

c

Sinus ofValsalva Aneurysm and Fistu la Sinus of Valsalva fistula is a left-to-right shunt that occurs because of rupture of a sinus of Valsalva aneurysm. A sinus of Valsalva aneurysm is a localized dilation of one of the aortic sinuses of Valsalva. The lesion can be con­ genital or acquired. Congenital sinus of Valsalva aneu­ rysm accounts for less than 3% of congenital heart disease. These patients often have additional cardiac defects, such as VSD. Alteration in valve cusp function because of a sinus of Valsalva aneurysm can cause aortic insufficiency. At least 8o% of sinus of Valsalva aneurysms involve the

Chapter 11 Co ngenital H e a rt D i sease

343

Table n-g. M ost Com mon Forms of Acyanotic Congenital Heart Disease With I ncreased Pul monary Venous Vasculature Acya n otic, p u l m on ary ven o u s prom i n en ce

Stenosis of pul monary veins Cor triatriatum Congenital m itral stenosis Supravalvar stenosis of the left atriu m Left-heart fai l u re

ventricle and lack a communication that provides a path­ way for right-to-left shunting (Table 1 1 -9) . The obstruction can occur at the confluence of pulmonary veins, within the left atrium, or at the mitral valve. Obstructive lesions of the left ventricle or aortic arch can cause pulmonary venous congestion if there is progression to left ventricular failure (Table 1 1 -1 0) . Although usually acyanotic at the time of pre­ sentation, the lesions discussed in this section can cause cyanosis when there is superimposed pulmonary edema. Lesions that cause elevation of pulmonary venous pressure lead to redistribution of blood flow into the upper portions of the lungs, with enlargement of the upper lobe pulmonary veins. The pulmonary response to chronic eleva­ tion of pulmonary venous pressure predominantly consists Figure 11-25 Partial anomalous pulmonary venous connection. This right anterior oblique contrast-enhanced maximum­ intensity projection MR image shows anomalous connection of the right upper pulmonary vein (arrow) into the superior vena cava (SVC) . AA, Ascending aorta; RA, right atrium.

Table 1 1-1 0. Left-Sided Obstructive Lesions

Pulmonary vei ns Left atriu m

right coronary sinus. Most sinus ofValsalva aneurysms are asymptomatic. However, rupture into the right ventricle (75%) or right atrium is common late in childhood, result­ ing in a fistula and a symptomatic left-to-right shunt.56.57 Chest radiographs of patients with a sinus of Valsalva aneurysm are normal. After rupture of the lesion, nonspe· cific signs of a left-to-right shunt develop: cardiomegaly, prominent pulmonary vascularity, and congestive failure. Echocardiography demonstrates a left-to-right shunt and aortic valvular insufficiency.

ACYANOT IC, INCREASED PULMONARY VENOUS VASCULATURE Cardiac anomalies that result in pulmonary venous disten­ tion without cyanosis predominantly consistent of those that obstruct the flow of blood from the lungs into the left

Lesion

S ite of obstructio n

M itral valve

Congen ital stenosis Postoperative strictu re ' Cor triatriatu m Supravalvar ring Atrial tumor (e.g., myxoma) Congen ital atresia Congen ital stenosis Parach ute m itral valve Hypoplastic left ventricle Diffuse su baortic stenosis Focal su baortic stenosis Valvar aortic stenosis Supravalvar aortic stenosis Coarctation of the arch I nterru ption of the aortic arch

·

Left ventricle

Aortic valve Aortic arch

344

Part 2 The Card iovascu l a r System

of thickening of the intima and media of the pulmonary veins. Communications between pulmonary veins and the bronchial venous system progressively enlarge, sometimes precipitating hemoptysis. Elevation of pulmonary capillary pressure causes fluid, serum, and erythrocytes to move into the alveolar spaces; that is, pulmonary edema. Dilation of pulmonary lymphatic channels ensues. Pulmonary arterial pressure also increases and, eventually, right ventricular hypertrophy ensues.

Congen ital M itral Stenosis Mitral valve disease in pediatric patients most often occurs as an acquired phenomenon, a result of conditions such as rheumatic heart disease, infective endocarditis, and cardiomyopathy. Congenital stenosis of the mitral valve occurs in 2 basic forms: hypoplasia and a developmental lesion termed parachute mitral valve, in which the cordae tendineae from both valve leaflets converge into a single bulky papillary muscle. With hypoplasia of the mitral valve, the margins of the valve leaflets are thickened and rolled, the cordae tendineae are short and thickened, the papil­ lary muscles are underdeveloped, and the valve leaflets are fused. 5 8 Congenital mitral stenosis often occurs in associa­ tion with other anomalies , such as coarctation of aorta, valvar aortic stenosis, V S D , tetralogy of Fallot, and endo­ cardial fibroelastosis. A form of parachute mitral valve is often associated with the Shone complex (coarctation of aorta, subaortic stenosis , supravalvar mitral ring, and para­ chute mitral valve). In those patients with hypoplasia of all components of the mitral valve apparatus including the annulus, the resultant outflow obstruction causes manifes­ tations of hypoplastic left heart syndrome. 5 9-6• The major hemodynamic effects of congenital mitral valve stenosis occur during diastole. With a substantial gra­ dient, pressures are elevated in structures proximal to the mitral valve, including the left atrium and pulmonary veins. The severity of symptoms relate to the degree of obstruc­ tion and the presence of coexistent anomalies . With severe stenosis, diminished cardiac output causes manifestations of congestive heart failure. In other patients, the maj or clinical manifestation is exercise intolerance. Pulmonary venous congestion in infants and young children with con­ genital mitral stenosis results in a propensity for recurrent respiratory infections. Elevation ofleft atrial pressure in patients with congen­ ital mitral stenosis often produces radiographically demon­ strable left atrial enlargement. The pulmonary vascular pattern relates to the severity of obstruction, ranging from redistribution of flow into the upper lobes to frank pulmo­ nary edema. The left atrial enlargement is disproportionate to the degree of pulmonary vascular prominence. Overall cardiac size is normal or only minimally prominent, unless there is right ventricular decompensation. Echocardiography of congenital mitral stenosis shows thickened mitral leaflets with poor diastolic motion. The

left atrium is dilated. There may be diastolic fluttering of the mitral valve leaflets. With the classical form of para­ chute mitral valve, there is a single papillary muscle in the left ventricle into which all cordae tendineae insert. There are also transitional forms in which there are partially or completely fused papillary muscles. 62 Angiocardiography of congenital mitral stenosis shows varying degrees of valve leaflet thickening, as well as shortening and thickening of the cordae tendineae. The left ventricle is relatively small. During the levo phase of pulmonary angiography, enlargement of the left atrium is visible. As with other imaging techniques, MR shows a thick­ ened, often crescent shaped, mitral valve. The left atrium is enlarged. There is thickening of the right ventricular myo­ cardium. Central pulmonary vessels are prominent. The lungs often appear somewhat hyperintense on T2-weighted images because of prominent interstitial fluid.

Congenital M itral Stenosis Pathology

Radiology

M itral obstruction Elevated pul monary venous pressure Righ t ventricu lar hypertrophy

Enlarged left atriu m Pulmonary venous distention Normal heart s ize M R, echocardiography: thick right ventricle wal l

Supravalvar Stenosis of the Left Atriu m Supravalvar stenosis of the left atrium i s a rare anomaly that shares hemodynamic, clinical, and radiographic fea­ tures with congenital mitral stenosis. This is a circumfer­ ential ring of connective tissue that is attached to the base of the atrial surfaces of the mitral valve leaflets. Most often, this lesion is nonobstructive and asymptomatic. In some patients , there is hemodynamically significant obstruction to blood flow from the left atrium into the left ventricle. This obstruction can result in symptomatic pulmonary venous congestion. 63-65 Supravalvar stenosis of the left atrium is most often associated with other anomalies. This is a common com­ ponent of Shone syndrome (subaortic stenosis, coarcta­ tion of aorta, parachute mitral valve, and supravalvar left atrial ring) . Other reported associations include tetralogy of Fallot, VSD, and corrected transposition of the great vessels. The radiographic findings of an obstructive supraval­ var stenosing ring of the left atrium are identical to those of congenital mitral stenosis: pulmonary venous congestion and left atrial enlargement. The presence of a coexistent

Chapter 11 Co ngenital H e a rt D i sease cardiovascular anomaly can substantially alter the radio­ graphic pattern. Echocardiography is diagnostic.

Cor Triatriatu m Cor triatriatum, or triatrial heart, refers to division of 1 of the atria into 2 chambers. The most common form is cor triatriatum sinister, in which a membrane partially divides the left atrium into a posterior-superior chamber that receives the 4 pulmonary veins and an anterior-inferior chamber that empties into the left ventricle. Cor triatriatum sinister accounts for approximately 0.1% of congenital car­ diac malformations. This lesion is caused by faulty incorpo­ ration of the embryonic pulmonary venous confluence into the left atrium. Each of the pulmonary veins connects into the pulmonary venous confluence, which persists as an accessory chamber. The accessory chamber communicates through one or more orifices with the left atrium (or, rarely, the right atrium) . The anatomy of the connection with the atrium occurs in 3 forms: (a) a fibromuscular diaphragm partially divides the left atrium from the accessory cham­ ber; (b) a constriction between the atrium and the chamber produces an hourglass deformity, or (c) a tubular channel connects the atrium and the accessory chamber.66 Most often, cor triatriatum sinister occurs as an iso­ lated anomaly. Potential associated cardiovascular anoma­ lies include partial anomalous venous connection, VSD, ASD, atrioventricular canal, and coarctation of the aorta. Uncommon associations with cor triatriatum include tetralogy of Fallot, Ebstein malformation, hypoplastic left heart syndrome, and asplenia. The hemodynamic consequences and resultant clinical manifestations of cor triatriatum sinister primarily relate to the severity of obstruction at the level of the connec­ tion between the accessory chamber and the left atrium. Pulmonary venous pressure is elevated. Patients may suf­ fer tachypnea, chronic cough, and recurrent pneumonia; the features often suggest pulmonary rather than cardiac pathology. Affected infants may be irritable and suffer fail­ ure to thrive. Episodes of pulmonary edema and congestive cardiac failure can occur. The major radiographic feature of cor triatriatum sinis­ ter is that of pulmonary venous congestion. In infants, the imaging findings can mimic those of respiratory distress syndrome; however, air bronchograms are usually lacking and the onset of the radiographic abnormality is delayed for at least 24 hours. With mild obstruction, there is only minimal vascular prominence or pulmonary vascular redistribution. In contradistinction to mitral stenosis, the left atrium is smaller than normal. The enlarged accessory chamber may or may not cause radiographic alterations. Although right ventricular hypertrophy is a feature of cor triatriatum, this is usually not radiographically demonstra­ ble. Heart size is typically normal except in those patients with decompensation. Rarely, there is a double density along the right cardiac border because of the prominent accessory chamber.

345

The major echocardiographic feature of cor triatria­ tum sinister is the presence of a membrane or narrowing between a posterior-superior chamber that receives the pulmonary veins and the adjacent left atrium. In some patients, the lesion appears as a membrane stretchirlg across the left atrium. The membrane moves toward the mitral valve during diastole and away from the mitral valve with systole. The left atrial diaphragm of cor triatriatum is demonstrated on angiocardiography with either pulmo­ nary artery or left atrial inj ections. The diaphragm is best visualized on frontal or right anterior oblique views. With pulmonary angiography, there is prolonged transit of con­ trast through the lungs and there is prolonged opacification of the accessory chamber. With M RI , the anatomy of the connection between the accessory chamber of cor triatriatum sinister and the adja­ cent left atrium is often best visualized with axial images. The accessory chamber is posterior and superior to the true left atrium. The membrane dividing the 2 chambers bulges into the left atrial cavity. When there is severe obstruction, there may be high signal intensity in the proximal cham­ ber on T1-weighted images. T2-weighted images show increased water content of the lungs because of interstitial edema.67

Cor Triatriatum Sinister Pathology

Rad iology

Persistent pul monary venous confluence Obstruction at left atriu m com m u n ication

Right-heart border double density (u ncom mon) Passive pulmonary congestion Pulmonary edema Left atriu m diaphragm on echocardiography, angiocardiography, and M R

Diaphragm between accessory chamber and left atri u m

Cor triatriatum dexter refers to partial membranous division of the right atrium into 2 chambers. This is less common than the left atrial form of cor triatriatum. The pathogenesis of cor triatriatum dexter likely involves per­ sistence of the right valve of the sinus venosus during embryonic development. The clinical manifestations of cor triatriatum dexter vary with the degree of partitioning of the right atrium. Many patients are asymptomatic through­ out life. A large membrane can cause right-sided heart failure and elevated central venous pressure. Associated symptomatic cardiac defects, such as ASD, are sometimes present. Echocardiography and cardiac MRI demonstrate the thin right atrial membrane. The lesion is usually best visualized on transverse images.6 8

346 Part 2 The Card iovascu l a r System Table 1 1 -1 1 . Cardiac Anomalies Associated With Cyanosis and Active Pulmonary Vascular Prominence Cya nos is and active p u l mo n a ry vascu l a r p ro m i n en ce

D-transposition of the great vessels L-transposition of the great vessels Persistent tru ncus arteriosus Double-outlet right ventricle Single ventricle, without pul monary outflow obstruction Total anomalous pulmonary venous connection Double-outlet left ventricle Single atriu m Tricuspid atresia with transposition ofthe great vessels Pu l monary arteriovenous fistu la

------ -

CYANOT IC, INCREASED PULMONARY ARTERIAL VASCULATURE There are multiple cardiovascular anomalies that cause cyanosis and radiographic evidence of active (arterial) pulmonary vascular prominence (Table 1 1 -1 1) . This pat­ tern indicates the presence of a bidirectional shunt. A right-to-left shunt causes cyanosis, while a left-to-right shunt results in increased pulmonary arterial flow. Cardiac anomalies with bidirectional shunts are termed admixture lesions. The admixture of systemic and pulmonary venous returns can occur at any level of the heart or great vessels (i.e., the pulmonary veins, the atria, the ventricles, or the great vessels) . With the exception of transposition of the great vessels, there is an inverse relationship between the volume of pulmonary blood flow and the degree of cya­ nosis in children with admixture lesions: greater volumes of pulmonary flow are associated with lesser degrees of cyanosis.

D-Transposition of the G reat Arteries D-transposition of the great arteries is the most com­ mon cyanotic congenital heart anomaly to present during the first day of life. The prefix D indicates that the aorta is located to the right of the pulmonary artery. The great arteries are transposed, the atria are normal, the ventricles are normally related, and the atrioventricular connections are normal. Therefore, the ventriculoarterial connec­ tions are discordant and the atrioventricular connections are concordant. The aorta (including the coronary arter­ ies) originates from the morphological right ventricle and the pulmonary artery arises from the morphological left ventricle. This anatomy results in parallel pulmonary and systemic circuits: systemic venous blood enters the right atrium, passes into the right ventricle, and is ejected into

the aorta, while venous return from the lungs empties into the left atrium, passes into the left ventricle, and is ejected into the pulmonary artery. D-transposition is incompat­ ible with life unless there is an associated communica­ tion between the 2 circulations. Potential communications include a patent foramen ovale, ASD, VSD, patent ductus arteriosus, systemic collateral arteries to the lung, or any combination of these pathways. There are 3 major classifications of D-transposition: (a) D-transposition ofthe great arteries with an intact ventricu­ lar septum. This anomaly may or may not be accompanied by left ventricular outflow obstruction (i.e., subpulmonic stenosis) . (b) D-transposition with a VSD and no left ven­ tricular outflow tract obstruction. (c) D-transposition of the great arteries in association with a VSD and a variable degree ofleft ventricular outflow tract obstruction (complex transposition) . Severe subpulmonic stenosis or pulmonic atresia in these infants results in relatively equal pressures in the ventricles. D-transposition accounts for approximately 10% of congenital heart disease in children. Additional cardiac defects occur in somewhat less than half of these patients. The most common associated anomalies are VSD (often in combination with pulmonary stenosis) and lesions of the aortic arch. Other cardiac anomalies that sometimes occur in association with D-transposition include tricus­ pid atresia, atrioventricular canal. ASD, double-outlet right ventricle (Taussig-Bing anomaly) , subvalvar aortic steno­ sis, pulmonary stenosis, pulmonary atresia, interrupted aortic arch, coarctation, and patent ductus arteriosus. A right aortic arch is present in only 4% of children with D-transposition and an intact ventricular septum. A right arch is present in 10% of those with a VSD in the absence of substantial pulmonic stenosis. There is a strong asso­ ciation (particularly in patients with dextrocardia) between single ventricle, D-transposition of the great vessels, and pulmonary stenosis or pulmonary atresia. Extracardiac congenital anomalies occur in only approximately 10% of children with D-transposition. There is an association with maternal diabetes. In utero, the hemodynamics of the fetus with D-transposition of the great arteries are nearly normal, as blood returning from the systemic and pulmonary veins passes into the atria and ventricles in a normal manner. Blood from the right ventricle passes into the ascending aorta and subsequently into the systemic arteries and pla­ centa. Blood from the left ventricle enters the pulmonary artery, but most diverts through the ductus arteriosus into the descending aorta because ofhigh pulmonary resistance. There are 2 minor variations from normal fetal circulation: (a) poorly saturated blood from the superior vena cava is preferentially shunted to the cerebral circulation rather than through the ductus arteriosus, and (b) more highly saturated blood from the inferior vena cava is shunted to the lung. The newborn with D-transposition of the great arter­ ies is dependent on mixing between the pulmonary and

Chapter 1 1 Congen ital H e a rt D i sease

347

systemic circulations for survival. For a brief period after birth, the ductus arteriosus and foramen ovale suffice for mixing. However, progressive decrease in pulmonary vascu­ lar resistance facilitates shunting of hypoxemic blood from the aorta to the pulmonary artery through the ductus arte­ riosus. There is obligatory shunting of pulmonary venous return from the left atrium to the right atrium. Therefore, there is a bidirectional shunt that mitigates severe cyanosis, with blood flowing from the aorta to the pulmonary artery and from the left atrium to the right atrium. As the ductus arteriosus begins to dose in the newborn with D-transposition of the great arteries, the obligatory shunting from the aorta to the pulmonary artery is progres­ sively eliminated. When the ductus doses, the only site of admixture is via the foramen ovale, unless there is a defect in the ventricular septum. However, the increasing pulmo­ nary venous return tends to dose the foramen ovale. In infants with an intact ventricular septum, the bidirectional shunting at the atrial level is usually inadequate to prevent the onset of severe systemic hypoxemia. Hypoxemia is less severe in those infants with a VSD, particularly when the defect is large; the ventricular communication permits mixing of the 2 circulations at the ventricular level. Infants with transposition of the great vessels present with cyanosis and tachypnea. A murmur is usually lacking, unless there is an associated VSD, patent ductus arteriosus, or pulmonary stenosis. Cyanosis is clinically evident dur­ ing the first hour of life in more than half of infants with D-transposition and an intact ventricular septum; cyanosis develops during the first day of life in more than 90%. In

some patients, however, associated cardiac lesions provide a pathway for mixing between the pulmonary and systemic circulations (at least temporarily) , such that the infant is only mildly cyanotic or only develops cyanosis at times of stress. The critically cyanotic neonate with D-transposition often benefits from an urgent balloon atrial septostomy. Prior to definitive surgical correction, infants with D-transposition are at elevated risk for neurological complications.69 Chest radiographs ofthe newborn with D-transposition may be normal initially, particularly if the ventricular sep­ tum is intact. Mild to moderate cardiomegaly develops in most of these infants during the first several days of life, but up to one-third have a more delayed onset of cardio­ megaly (Figu re 1 1 -26) . Most infants with D-transposition have prominent pulmonary vasculature due to increased flow within the lungs. This finding is most pronounced in those infants with a large VSD. However, up to one-half of neonates with D-transposition have normal pulmonary vascularity for the first few days oflife. Infants with normal vascular markings tend to have more pronounced hypox­ emia clinically. Because of the orientation of the transposed main pulmonary artery, the right pulmonary artery tends to align with the ventricular outflow tract, often resulting in greater vascular prominence in the right lung than in the left lung. In infants with elevated left atrial pressure, pas­ sive pulmonary congestion may occur. Because of the abnormal medial and posterior position of the pulmonary trunk in infants with D-transposition, the normal convex pulmonary artery bulge along the left upper-heart border is lacking on frontal chest radiographs.

A

B

Figure 11-26 D-transposition and small VSD.

A A chest radiograph of a cyanotic newborn on the first day of life shows mild cardiomegaly and a normal pulmonary vascular

pattern. B. Cardiomegaly has increased by day 8 of life. There is also pulmonary vascular prominence.

348 Part 2 The Card iovascu l a r System

Figure 11-27 0-transposition and moderate-size VSO. A chest radiograph of an 8-day-old premature infant shows a narrow cardiac waist and moderate cardiomegaly. There is mild pulmonary vascular prominence, greater in the right lung than in the left lung.

This causes a narrow appearance of the cardiac waist (Figure 1 1 -27) . In addition, the aortic knob is poorly visual­ ized because of malposition of the arch. The small size of the thymus in these stressed infants also contributes to a narrow appearance of the upper portion of the mediasti­ num. The left cardiac border has a smooth, convex contour extending toward the apex. The enlarged right ventricle forms the cardiac apex. There is displacement of the apex to the left and inferiorly. A slightly enlarged right atrium forms the right-heart border. The distinctive shape pro­ duced by the narrow cardiac waist, right atrial enlargement, and left ventricular dilation is likened to that of an egg on a string (Figure n -28) .33 ·7°

D-Transposition of the Great Arteries Pathology

Malposition arch and main p u l monary artery

Rad i o l ogy ·

·

Prominent right atriu m a n d left ventricle S h u nting Preferential right pulmonary artery flow Bidirectional shunt

N arrow cardiac waist Aorta anterior to main pul monary artery Oval cardiac shape Prominent pulmonary vascularity Asymmetric vascu larity Cardiomegaly

Figure 1 1-28 0-transposition of the great arteries. An anteroposterior chest radiograph of a cyanotic infant shows cardiomegaly and pulmonary vascular prominence. There is a narrow cardiac waist. The main pulmonary artery is not visible, and the aortic knob is inconspicuous. The thymus is small. The oval-shaped heart "suspended" from a narrow mediastinum results in the "egg on a string" appearance.

Echocardiography of patients with D-transposition of the great arteries shows that the aorta is anterior to the pulmonary artery and the pulmonary artery is positioned posteriorly. The aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. The myocardium of the right ventricle is thickened. Most often, the right atrium and right ventricle are considerably larger than the left atrium and left ventricle. If the left ventricle is larger than the right ventricle in a patient with trans­ position, there is usually an associated anomaly such as pulmonic stenosis, patent ductus arteriosus , VSD, or per­ sistent pulmonary artery hypertension. As with echocardiography, the anterior location of the aorta with respect to the pulmonary artery is a key diag­ nostic feature of D-transposition of the great arteries on evaluation with angiocardiography, M R, or CT. The main pulmonary artery is posterior to and to the left ofthe ascend­ ing aorta. The large trabeculated right ventricle empties into a smooth-walled infundibulum and transposed aortic

Chapter 1 1 Congenital Heart D i sease 349

B

A

Figure 1 1-29 D-transposition. A A lateral angiocardiographic image with injection into

ascending aorta. B. The anteroposterior projection shows filling of the main pulmonary artery from the left ventricle.

the right ventricle shows filling of the anteriorly positioned

root. The left ventricle is usually normal in size or mildly

chronic nature of the ostial stenosis may allow collateral

enlarged; this chamber empties into the pulmonary artery

ves sel formation and prevent the onset of readily identifi­

Careful evaluation of the pulmonary valve

able clinical manifestations . There is a long-term risk for

(Figure 1 1 -29) .

region for evidence of stenosis is an essential component of

enlargement of the neoaortic root and the development of

the examination. Hemodynamic evaluation shows higher

aortic regurgitation after an arterial switch operation. M R

oxygen saturation of blood within the pulmonary artery

and nuclear medicine studies play a role i n the long-term

than in the aorta. If the ventricular septum is intact, the left

surveillance of patients who have undergone arterial switch

ventricular systolic pressure is approximately equal to that

surgery. These techniques allow the noninvasive assess­

of the right ventricle in the immediate newborn period, but

ment of myocardial viability, myocardial perfusion, and

left ventricular pressure falls over the next few days unless

coronary artery anatomy. MR is particularly useful for the

there is a left ventricular outflow tract obstruction. Accurate

evaluation of the branch pulmonary artery anatomy.73-77

characterization of coronary artery anatomy is important preoperatively for patients who will undergo an arterial

switch procedure.7'

Without treatment, 30% ofinfants with D-transposition die within the first week of life and

90% die within the

L-Transposition of the G reat Arteries L-transposition of the great arteries is caused by anoma­ lous leftward looping of the primitive cardiac tube during

first year. However, current therapeutic techniques result

embryogenesis. This results in displacement of the ana­

in long-term survival of more than 90% of patients with this anomaly.7 2 Arterial switch surgery is the treatment

tomic right ventricle posteriorly and to the left; this cham­ ber serves as the arterial ventricle. There is displacement

of choice for most patients with transposition of the great

of the anatomic left ventricle anteriorly and to the right,

arteries . The great arteries are transected above their

to become the venous ventricle. Therefore, there is ven­

valves and reanastomosed to their counterparts. The coro­

tricular

nary arteries are transferred to the systemic great vessel.

displaced posteriorly and to the right, while the aorta is dis­

Myocardial ischemia or infarction can occur during the

placed anteriorly and to the left. The prefix

perioperative period, because of the necessary reimplan­

the aorta is to the left of the pulmonary artery.

tation of the coronary arteries . Delayed abnormalities

in

myocardial perfusion can also occur in these patients. The

inversion.

The origin of the pulmonary artery is

L indicates that

Unlike D -transposition, L-transposition results in nor­ mal hemodynamics . In

95% of patients, there is atrial and

350 Part 2 The Card i ovasc u l a r System visceral situs solitus. Systemic venous return enters a nor­ mally positioned right atrium and is directed through the mitral valve into the anatomic left ventricle. The pulmonary artery arises from this venous ventricle; therefore, unoxy­ genated blood circulates through the lungs. Pulmonary venous return of oxygenated blood empties into a nor­ mally positioned left atrium and then passes through the tricuspid valve into the anatomic right ventricle. The aorta arises from the infundibulum of this arterial ventricle, thereby supplying the systemic circulation with oxygenated blood. Patients with isolated L-transposition are acyanotic. Because of the hemodynamic pattern of L-transposition, an alternate term for this anomaly is

corrected transposition.

The position of the cardiac conduction system is reversed in patients with L-transposition of the great ves­ sels . Therefore, the interventricular septum depolarizes from right-to-left, rather than the normal pattern of left-to­ right. In addition, the abnormal cardiac rotation results in elongation of the bundle of His, resulting in the potential for fiber disruption and heart block. Although isolated L-transposition of the great arter­ ies is usually asymptomatic, most patients have

1

or more

associated cardiac lesions that cause varying degrees of cardiovascular dysfunction. The most common associated anomalies are tricuspid (left atrioventricular) valve insuf­ ficiency, V S D , and pulmonary stenosis. The frequency of V S D in these patients is nearly 8o%. The defect is usually large and located in the membranous septum. Pulmonary stenosis in patients with L-transposition can be valvar or subvalvar (fibrous ring, myxomatous soft tissue thickening,

Figure 11-30 L-transposition, without associated anomalies. A posteroanterior chest radiograph shows normal heart size and normal pulmonary vascularity. The normal main pulmonary artery segment of the cardiomediastinal contour is lacking. There is a bulge along the left upper cardiac border (arrow) because of the ascending aorta and right ventricular outflow tract.

or a fibromuscular tunnel) . Tricuspid insufficiency occurs in approximately 3 0 % of patients . Less common cardiac lesions in patients with L-transposition include A S D , pat­ ent ductus arteriosus, coarctation of the aorta, aortic insuf­

anteriorly. If there is substantial pulmonic stenosis, the

ficiency, valvar aortic stenosis, mitral atresia, and tricuspid

wall of the left-sided ventricle is concentrically thickened.

atresia.

Tricuspid insufficiency, when present, results in dilation of

The radiographic features of L-transposition of the

the left atrium; left atrial enlargement is sometimes pro­

great arteries are frequently subtle. The left upper cardiac

nounced. I n some cases, the valve configuration mimics

border may have a squared off bulge because of leftward

the appearance of Ebstein malformation; however, the cir­

deviation of the right ventricular outflow tract and ascend­ ing aorta

(Figure 1 1 -30) .

Because the aorta originates and

ascends along the upper left cardiac border, this portion of

cumference of the tricuspid valve is not enlarged as it is with Ebstein malformation. Angiocardiography and

MR show the ventricles in

the mediastinal silhouette is slightly convex. The pulmo­

children with L-transposition to be positioned side-by-side,

nary artery arises medially and does not contribute to the

with the ventricular septum oriented in an anterior-poste­

cardiac border on the frontal proj ection. The superior vena

rior direction. The right-sided (venous) ventricle has the

cava usually forms the upper right cardiac border. Because

smooth-walled triangular configuration of a left ventricle.

V S D and tricuspid insufficiency are common, left atrial

The venous ventricle, when viewed on the lateral proj ec­

enlargement may be present. The patient-specific pulmo­

tion, is anterior and the pulmonary artery arises from this

nary vascular pattern is determined by the presence of, and type of, associated cardiac lesions.7 8

ventricle near the midline posterior to the origin of the

Echocardiography of patients with

aorta. The left-sided (arterial) ventricle has the trabeculated

L-transposition

morphology of a normal right ventricle. The ascending

shows the pulmonary artery to be located posterior and

aorta arises anteriorly from this ventricle. The position of

medial to the aorta. The short axis view confirms bifurca­

the aorta is anterior and to the left of the origin of the pul­

( Figure 1 1 -31 ) .

tion of this vessel into right and left pulmonary branches.

monary artery

The left-sided (arterial) ventricle has the morphology of a

the atrioventricular valve from the semilunar valve. There

An infundibulum separates

right ventricle, in that it is coarsely trabeculated and has

is inversion of the coronary arterial pattern in all patients

an infundibular chamber that is located on the left and

with L-transposition.

Chapter 1 1 Congenital H e a rt D i sease

A

351

8

Figure 1 1-31 L-transposition. A A coronal cine flash M R image of a 2-year-old boy shows origin of the aorta from a left-sided ventricle. B. An image obtained more posteriorly demonstrates the pulmonary artery arising near the midline. C. The ascending aorta is anterior and to the left of the pulmonary artery. A, Aorta; P, pulmonary artery.

c

L-Transposition of the Great Arteries Pathology

Rad iology

Leftward orientation of right ventricu lar outflow tract and ascending aorta ± VS D, tricuspid insufficiency Ventricular inversion

B u l ge along the left upper cardiac border Left atrial enlargement Trabeculated left-sided ventricle

Ventricular I nversion Without Transposition Ventricular inversion without transposition (also termed clinical transposition) is a rare anomaly in which there are discordant atrioventricular connections and concordant ventriculoarterial relationships. Ventricular inversion indi­ cates that the ventricle receiving systemic venous blood has anatomic features of a left ventricle, while the ventricle receiving pulmonary venous return has anatomic features of a right ventricle. However, because of a lack of great vessel transposition, the systemic venous (anatomic left) ventricle gives rise to the aorta and the ventricle receiving

352 Part 2 The Card i ovasc u l a r System pulmonary return (anatomic right) gives rise to the pulmo­

regurgitation in approximately one-fourth of patients.

nary artery. The circulation in these children is hemody­

Hemodynamically sigrlificant trurlcal valve stenosis occurs

namically identical to that of D-transposition of the great arteries . Affected neonates are profoundly cyanotic.79· 8 o

in approximately one-third of patients. A right aortic arch with mirror image branching occurs

Infants with ventricular inversion without transposi­

in approximately one-third of children with trurlcus arterio­

1 mandatory site of admixture, such as a

sus. Other arch anomalies, such as interruption or hypopla­

tion have at least

patent ductus arteriosus or septal defect. Pulmonary ste­

sia, are uncommon in these patients. An ostium secundum

nosis occurs in some patients . The clinical features are

A S D is present in approximately

identical to those of D-transposition of the great vessels .

sistent truncus arteriosus, an aberrant right subclavian

The radiographic findings are also similar t o those o f trans­

artery in

position. Angiocardiography and cross-sectional imaging

into the coronary sinus in

15% of patients with per­

5%, a persistent left superior vena cava that drains 5%, and mild tricuspid stenosis

5%. Other potential cardiac anomalies in these patients

studies show a smooth, left ventricular configuration of

in

the venous ventricle; the aorta arises from this chamber.

include patent ductus arteriosus, unilateral absence of a

Unlike D-transposition, the aorta is located posterior to the

pulmonary artery, and coronary ostial anomalies (single

main pulmonary artery. The ventricle that gives rise to the

coronary artery, high posterior origin of the left coronary

pulmonary artery has the trabeculated configuration of a

artery, and ostial stenosis) . As mentioned above, trurlcal

right ventricle; this ventricle forms the upper left cardiac

valve insufficiency and stenosis are relatively common.

border and is located to the left of the ventricle that supplies the aorta. 81

of patients with trurlcus arteriosus ; these include skeletal

Extracardiac anomalies occur in approximately one-fourth deformities, renal anomalies, and intestinal malrotation. Approximately

Persistent Tru ncus Arteriosus

9% of patients with DiGeorge syndrome

have trurlcus arteriosus ; one-third of DiGeorge syndrome

Persistent truncus arteriosus is a n uncommon anomaly in

patients with a hypoplastic aortic arch have this anomaly. 83

which a single arterial vessel, the trurlcus , exits the heart

The clinical presentation of persistent truncus arterio­

3

sus typically occurs during the first month of life. Truncus

and encompasses a large V S D . This vessel gives rise to

arterial circulations: systemic, pulmonary, and coronary.

arteriosus is an admixture lesion, as mixing of oxygenated

The truncal root straddles the ventricular septum approxi­

and unsaturated blood occurs within the truncus as well

6o% of patients with trurlcus arteriosus;

as in the region of the V S D . The severity of hypoxemia is

of the remainder, dominant right ventricular overriding

inversely related to the volume of pulmonary blood flow,

mately equally in

occurs somewhat more frequently. Embryologically, trun­

which is in turn determined by the pulmonary vascular

cus arteriosus is caused by failure of appropriate septation

resistance. At birth, there is relatively high pulmonary vas­

of the conotrurlcus between the sixth and seventh weeks of

cular resistance, resulting in restricted blood flow to the

1% of con­

lungs and prominent cyanosis . As the pulmonary vascular

gestation. This anomaly accounts for less than

genital cardiac anomalies. The prevalence is approximately

1 in n,ooo livebirths.82,83

resistance falls in the neonate, the severity of cyanosis usu­ ally diminishes with increasing pulmonary blood volume.

4

types based

The excessive pulmonary blood flow leads to left ventricu­

on the origin of the pulmonary arteries. Truncus arteriosus

lar enlargement and congestive heart failure. Hypoxemia

Truncus arteriosus is categorized into

65% of cases, has a short

exacerbates poor cardiac function. The pulmonary vascula­

main pulmonary artery that arises from the left posterolat­

ture is exposed to near systemic arterial pressures, rapidly

type I , which accounts for so% to

eral wall of the truncus. Truncus arteriosus type II accounts

leading to secondary pulmonary vascular disease. The large

30% of cases; this is characterized by separate origins of 2 pulmonary arteries, arising in dose

V S D in these patients is associated with systolic pressures

for approximately

that are nearly equal in both ventricles. Rarely, stenosis

proximity to each other from the back wall of the trurlcus .

at the origins of the pulmonary arteries causes restricted

5% to 10% of cases; in these patients ,

pulmonary flow and prominent cyanosis. Auscultation of

independent pulmonary arteries arise from the sidewalls

the patient with truncus arteriosus typically demonstrates

Type I I I accounts for

2

2

independent

a prominent second heart sound. If the truncal valve is ste­

pulmonary arteries arise from the descending aorta; this

notic, there is a systolic ejection murmur. A diastolic mur­ mur can occur if there is trurlcal valve insufficiency. 8 5

of the trurlcus. With the rare type IV lesion,

physiologically resembles tetralogy of Fallot with pulmo­ nary atresia and systemic collateral supply to the lungs . 84 Often, there is abnormal thickening of the leaflets of

The radiographic findings in children with persistent trurlcus arteriosus are often nonspecific and sometimes

the valve serving a trurlcus arteriosus. An abnormal num­

mimic those of D-transposition. The diagnosis is suggested

6o% of

when chest radiographs show a right aortic arch (present

ber of leaflets can also be present. Approximately

30% of patients) in conjunction with

patients with persistent truncus arteriosus have a tricuspid

in approximately

30% have a quadricuspid valve, 7% have a bicuspid valve, and the remaining 3% have 5 or more valve cusps.

markedly increased pulmonary vascularity and a concave pulmonary outflow tract

Truncal valve regurgitation is present in approximately half

enlargement in these patients causes clockwise rotation

of patients with trurlcus arteriosus , with moderate to severe

of the heart and midline displacement of the trurlcus, the

valve,

( Figure 1 1 -32) .

Because right-heart

Chapter 1 1 Congenital H e a rt D i sease 353

A

8

Figure 11-32 Persistent tru ncus arteriosus type I.

A, B. Anteroposterior and lateral chest radiographs of an infant wi th tachypnea, tachycardia, and mild cyanosis demonstrate cardiomegaly, a prominent right aortic arch, and pulmonary vascular congestion.

dilated ascending aorta is frequently not discernible radio­ graphically. However, the remainder of the aortic arch is also prominent. In those patients with a right aortic arch, this structure usually appears prominent radiographically. The normal main pulmonary artery segment of the cardiac silhouette typically is lacking or abnormal in patients with truncus arteriosus. However, the left pulmonary artery can simulate a normal-appearing pulmonary artery seg­ ment. Occasionally, the left pulmonary artery is visible in an abnormally high location. The "hilar comma sign" that occurs in some patients with truncus arteriosus type

II

refers t o a distinct curved appearance o f the left main pul­ monary artery within the left upper lobe. Most children with persistent truncus arteriosus have cardiomegaly of at least moderate severity

( Figure 1 1 -33) .

Cardiomegaly in these patients i s a result o f enlargement of all 4 chambers. Pulmonary vascular prominence is usu­ ally substantial. If there is pulmonary vascular asymmetry between the lungs, the possibility of unilateral absence of the pulmonary artery should be considered. Asymmetric pulmonary blood flow can also result from a streaming phenomenon or stenosis of the orifice of a pulmonary artery. When there is discrepancy, the left lung usually has diminished flow relative to the right.

Figure 1 1-33 Persistent truncus arteriosus type I I . A n anteroposterior chest radiograph o f a 17-day-old infant shows cardiomegaly and mild pulmonary vascular prominence. The enlarged aortic arch is left-sided.

354 Part 2 The Card iovasc u l a r System Persistent Tru ncus Arteriosus Pathology

Rad iology

Single truncal vessel

Absent pu l monary a rtery segment Pu l monary vascu lar prominence Right aortic arch Fou r chamber cardiomegaly

Pulmonary su pply from tru ncus Right aortic arch (30%) S h u nting, valvar insufficiency

Echocardiography of children with persistent truncus arteriosus shows a single enlarged truncal vessel overrid­ ing a large VSD. The anterior border of the aortic root is located anterior to the plane ofthe interventricular septum. There is continuity between the posterior aortic wall and the anterior leaflet of the mitral valve. The outflow tract of the right ventricle is absent. The anterior wall of the right ventricle is markedly thickened. It is sometimes difficult to echocardiographically differentiate truncus arteriosus from severe tetralogy of Fallot or pulmonary atresia with a VSD. Angiocardiography of truncus arteriosus shows a large single vessel that gives rise to the pulmonary arteries, the aortic arch, and coronary arteries (Figu re 1 1 -34) . The trun­ cal vessel has a large single valve. The left anterior oblique projection with 20-degree caudal angulation facilitates the identification of the proximal pulmonary vessels. The right ventricular infundibulum is absent; this finding aids in the differentiation from tetralogy of Fallot with pulmonary atresia. MR is a noninvasive technique for demonstrating the pathological anatomy in patients with persistent truncus arteriosus. The enlarged truncal vessel overrides a VSD. Imaging in various planes may be required to accurately demonstrate the sites of origin of the pulmonary arter­ ies. Cine MR images demonstrate associated truncal valve regurgitation or stenosis.67 The typical primary repair procedure for persistent truncus arteriosus is closure of the VSD and placement of a valve conduit between the right ventricle and the pulmonary arteries. This is termed the Rastelli procedure. Postoperatively, valve dysfunction can occur, sometimes suggested by the presence of calcification. Stenosis or thrombosis can develop within the conduit.

Dou ble-outlet Right Ventricle Double-outlet right ventricle refers to a group of trans­ position complexes in which both great arteries arise from the morphological right ventricle. There are bilateral muscular infundibula in these patients and

Figure 11-34 Persistent truncus arteriosus type I. A left anterior oblique image obtained after injection o f the aortic arch (AA) shows a dilated pulmonary artery (PA) arising from the posterior-left lateral aspect of the truncus.

atrioventricular-semilunar valve continuity is lacking. Nearly all patients with double-outlet right ventricle have a V S D . The defect is classified according to the relationship of the VSD to the aortic and pulmonary valves: (a) subaor­ tic (approximately half of patients) , (b) subpulmonic, (c) doubly committed (adjacent to both the pulmonary and aortic valves) , or (d) noncommitted (remote to the pul­ monary and aortic valves) . Pulmonary stenosis (usually a combination of infundibular and valvar) occurs in approxi­ mately 75% of patients with double-outlet right ventricle, and is particularly common in association with a subaortic location of the VSD.8 6 ,87 There is substantial variation between patients with double-outlet right ventricle as to the relationships of the

Chapter 1 1 Co ngenital H e a rt D i sease 355 great arteries to each other and to the ventricles . The rela­ tionship is defined by the locations of the aorta and pul­ monary artery at the level of the semilunar valves . The presence of a V S D sometimes interferes with a clear defini­ tion of the sites of origin of the great arteries ; as a general rule, double-outlet right ventricle is indicated when more than

1.5 of the semilunar valves arise from a single ven­

tricle. The aorta can be normally positioned with respect to the pulmonary artery, or inversely positioned. With inverse positioning, the aorta is located anterior to the main pul­ monary artery, on either the right (more common) or left. Incomplete forms of inverse positioning also occur. The most common relationship is a side-by-side orientation, with the aorta positioned to the right of the main pulmo­ nary artery and the semilunar valves located in approxi­ mately the same transverse plane. The

Taussig-Bing anomaly is

a variant of double-outlet

right ventricle. The characteristics of this anomaly are com­ plete transposition of the aorta, partial transposition of the pulmonary artery, and a subpulmonic V S D . The pulmo­ nary artery arises from both the right and left ventricles, bridging a large VSD that is in a high supracristal anterior

Figure 1 1-35 Double-outlet right ventricle and pulmonary atresia_ A radiograph of a cyanotic newborn infant shows markedly diminished pulmonary vascularity. The normal main pulmonary artery segment of the mediastinal contour is lacking. There is a right-sided aortic arch. These radiographic features are similar to those of tetralogy of Fallot.

location. The pulmonary artery is located to the left of, and slightly posterior to, the aorta. The hemodynamic conse­ quences of Taussig- Bing anomaly are similar to those of complete transposition with a V S D . Double-outlet right ventricle accounts for approxi­

The radiographic findings in children with double­ outlet right ventricle are usually nonspecific. The predomi­

2% of congenital heart anomalies. The male­ 2:1. Most patients with

nant features include generalized cardiomegaly (often of

to-female ratio is approximately

moderate severity) and pulmonary vascular prominence.

double-outlet right ventricle do not have other congenital

The main pulmonary artery is enlarged. The radiographic

mately

anomalies. This cardiac lesion is common, however, in

appearance resembles that of a simple V S D . If there is

infants with trisomy

substantial pulmonary stenosis, the radiographic features

13. Coarctation and interruption of the

aortic arch occur with an increased frequency in patients

resemble those of tetralogy of Fallot: mild cardiomegaly

with double-outlet right ventricle. Other cardiac anomalies

with a right ventricular configuration, a concave main pul­

that can occur

monary artery segment, and diminished pulmonary blood

in these patients include subaortic stenosis,

A S D , anomalous coronary arteries, and endocardial cush­

flow

ion defect.

of the aortic arch, there is early onset of congestive failure

(Figure 1 1 -35) . In patients with an obstructive lesion

The clinical manifestations of double-outlet right

in infancy. Radiographs show cardiomegaly, pulmonary

ventricle vary somewhat according to the patient-specific

vascular prominence, and pulmonary edema. The Taussig­

nature of the anomaly. Most often, the findings are simi­

Bing variant results in cardiomegaly and prominent pul­

lar to those of an uncomplicated V S D , as there is a large

monary vascularity. The appearance may resemble that

left-to-right shunt. In classic double-outlet right ventricle,

of D-transposition; however, the pulmonary artery is not

although both great arteries arise from the right ventricle,

located directly behind the aorta and, therefore, the cardiac

oxygenated blood is shunted from the left ventricle to the

waist does not appear as narrow as it does in patients with

right ventricle and subsequently into the systemic circu­

transposition.

lation via the transposed aorta. Because of mixing of oxy­

A key feature of double-outlet right ventricle on echo­

genated and nonoxygenated blood in the right ventricle,

cardiography is a side-by-side orientation of the great ves­

these patients are mildly cyanotic. When the V S D is sub­

sels , most often with the aorta located anterior and to the

pulmonic, cyanosis tends to be more pronounced and the

right of the pulmonary artery. This is often best demon­

findings may mimic those of transposition of the great ves­

strated on the short axis view. The parasternal long axis

sels. An associated left-sided obstructive lesion (e.g. , coarc­

view demonstrates the origin of the aorta from the right

tation, subaortic stenosis or interruption of aortic arch)

ventricle. Commitment of the V S D can usually be dem­

can exacerbate manifestations of congestive heart failure.

onstrated with echocardiography; that is, adjacent to the

In patients with substantial pulmonic stenosis, the clini­

aorta, the pulmonary artery, both vessels, or neither vessel.

cal findings simulate those of tetralogy of Fallot, with pro­

In patients with pulmonary stenosis, the valve leaflets are

nounced cyanosis .

thickened and the valve has a domed configuration.

356 Part 2 The Card iovasc u l a r System

A

Figure 11-36 Double-outlet right ventricle with subaortic VSD and pulmonary stenosis. This 3-month-old female with 22qn deletion syndrome had progressive cyanosis. A, B. Cardioangiography in the left anterior

The diagnosis of double-outlet right ventricle is estab­ lished with angiocardiography by demonstrating that at

B

oblique (A) and lateral (B) projections with injection into the right ventricle shows opacification of the aorta and pulmonary artery, with contrast passing through a VSD.

Double-outlet Right Ventricle

least half of each great vessel arises from the morphological

Path ology

right ventricle

Left-to-right shunting

(Figure 1 1 -36) . The left anterior oblique pro­

j ection shows the relationship of the pulmonary artery to the septum. With classic double-outlet right ventricle, the pulmonary artery is positioned anterior to the

VSD. With

Taussig-Bing anomaly, the pulmonary artery overrides the

VSD. 88 MRI provides accurate depiction of the complex ven­

tricular and great vessel anatomy in patients with double outlet right ventricle. As with other imaging techniques , the diagnosis is established b y observing a t least partial origin of the aorta and pulmonary artery from the right ventricle. Three-dimensional depiction of great vessel orientation and caliber is sometimes useful for operative

planning. 8 9--9•

Rad i o l ogy

. Cardiomegaly ' Enlarged main pulmonary artery Pulmonary vascular : prominence Abnormal great vessel N arrow cardiac waist orientation ± Pul monary stenosis Oligemic l u ngs . Small main pulmonary artery : Cardiomegaly ± Aortic arch obstruction : Congestive heart fai l u re .

... ...

...

...

... ...

.

.

.

·

·

Infants with double-outlet right ventricle and hemo­ dynamically significant pulmonary obstruction sometimes require temporizing treatment with balloon atrial septos­ tomy and surgical creation of a systemic-to-pulmonary artery shunt. The definitive repair consists of closure of the

VSD and the establishment of physiological blood flow

Total Anomalous Pu l monary Venous Con n ection

from the appropriate cardiac chambers to the great arteries

Total anomalous pulmonary venous connection (total

by placement of internal and external conduits.

anomalous pulmonary venous return) refers to complete

Chapter 11 Congenital H e a rt D i sease 357 lack of pulmonary venous drainage into the left atrium.

D-transposition of the great vessels, pulmonary atresia,

Embryologically, this anomaly is the result of persistence

coarctation of the aorta, and anomalies of the systemic

of pulmonary venous connection to the primitive systemic

veins. There is a strong association between total anoma­

venous circulation. Most commonly, there is connection to

lous pulmonary venous connection and heterotaxy syn·

the left common cardinal venous system, resulting in pul­

drome with asplenia.

monary venous return into the left innominate vein (35%)

Because all of the blood from the pulmonary venous

or the coronary sinus (2o%) . Other potential pathways

circulation in patients with total anomalous pulmonary

include the superior vena cava or azygos vein (10%) , the

venous connection enters the right atrium, there is an

vitelline system, the ductus venosus, the portal vein, and

obligatory right-to-left shunt at the atrial level. This can

the right atrium. Occasionally, drainage occurs by more

occur through either a patent foramen ovale or a true A S D .

1 pathway. There are 4

anatomic types of total anoma­

Systemic and pulmonary venous blood that enters the right

lous pulmonary venous connection: type I, supracardiac

atrium can exit into the right ventricle and pulmonary artery

(5o%) ; type I I , cardiac (3o%); type I I I , infracardiac or infra­

or through the A S D into the left atrium, left ventricle, and

than

diaphragmatic (15%) ; and type IV, anomalous connection

aorta. The ventricular compliance largely determines the

at 2 or more levels (5%) . Most often, all of the pulmonary

magnitude of the shunt. Because right ventricular compli·

veins converge into a common chamber or sinus before

ance is less than that of the left ventricle, flow preferen­

entering the right atrium or a systemic vein.

tially occurs into the right ventricle. Other determinants

The most common variety of total anomalous pulmo­

of shunting include pulmonary vascular resistance, the

nary venous connection is a type I lesion in which pulmo­

presence or absence of pulmonary venous obstruction, the

nary venous blood enters a persistent left superior vena

size of the interatrial communication, and the presence or

cava (the vertical vein) , and drains through the innominate

absence of a patent ductus arteriosus .

vein and right superior vena cava into the right atrium.

Cyanosis is present in most infants with total anoma­

The next most common pathway is via the coronary sinus .

lous pulmonary venous connection. The severity of cyano­

Hemodynamically significant obstruction is lacking with most type I and type

II

sis is inversely related to the volume of pulmonary blood

total anomalous pulmonary venous

flow. Patients with pulmonary venous obstruction usually

connections. Obstruction occasionally occurs as a conse·

have severe cyanosis, hepatomegaly, and severe dyspnea.

quence of compression of the persistent left superior vena

Considering patients with all types of total anomalous pul­

cava by the left main bronchus. Obstruction can also occur

monary venous connection, hemodynamically significant

at the insertion into the brachiocephalic vein or superior

obstruction is present in slightly more than half. If there is

vena cava. Obstruction can occur with type II lesions if the

high pulmonary blood flow and good mixing, cyanosis is

pulmonary veins converge into a short common vertical

mild. Cardiac decompensation eventually leads to conges­

vein prior to entry into the coronary sinus .

tive heart failure, clinically manifested by tachypnea, dys­

The infracardiac (type III) form of total anomalous

pnea, and feeding difficulties. Increased blood flow across

pulmonary venous connection is caused by a persistent

the pulmonary and tricuspid valves may cause a systolic

communication of the common pulmonary vein with the

ejection murmur and a mid diastolic murmur.

vitelline venous system. The pulmonary veins j oin poste·

In infants with total anomalous pulmonary venous

rior to the left atrium and form a common vertical descend­

return in the absence of obstruction, chest radiographs

ing vein that courses inferiorly through the esophageal

show pulmonary vascular prominence as a result of the

hiatus to enter the portal venous system, either directly

combined systemic and pulmonary return to the right

or through the ductus venosus . B ecause the hepatic capil·

atrium.

lary bed is interposed between the portal vein and the right

increased volume in the right atrium and right ventricle.

atrium, there is severe pulmonary venous obstruction in

The main pulmonary artery segment is prominent. The

these patients. Occasionally, the vertical vein connects to

left atrium is normal in size. These radiographic features

Moderately

severe

cardiomegaly results

from

the hepatic veins or inferior vena cava; obstruction is less

closely resemble those of an isolated A S D ; the hemody­

severe in these patients.

namic features of blood flow are also similar with these

There are anomalous venous connections at 2 or more

2 lesions .

levels in children with type IV total anomalous pulmonary

If the common pulmonary vein drains into the left bra­

venous connection. Most often, the vertical vein drains into

chiocephalic vein (i.e . , the most common form of type I

the innominate vein and the anomalous vein(s) from the

total anomalous pulmonary venous connection) , the com­

right lung empty into either the right atrium or the coro­

bination of pulmonary and systemic flow causes dilation

nary sinus. Additional cardiac malformations are usually

of the brachiocephalic vein, left superior vena cava, and

present in these children.

right superior vena cava

Approximately one-third of patients with total anom­ alous

pulmonary venous

connection

have

associated

(Figure 1 1 -37) .

The appearance

on frontal radiographs is likened to that of a snowman or figure-of-eight. There is widening of the upper portion of

major cardiovascular malformations. The most common

the mediastinum (the head of the snowman) because of

associated lesions are single ventricle, truncus arteriosus,

the enlarged veins , and the borders are convex. In infants ,

358 Part 2 The Card i ovasc u l a r System

A

B

silhouette. Pulmonary vascular prominence is lacking in this patient because of coexistent pulmonary atresia. The aortic

arch is on the right. B. An anteroposterior angiographic image shows the confluence of pulmonary veins draining via a large anomalous vein (arrow) into the brachiocephalic veins. SVC, Superior vena cava.

the thymus can obscure these prominent veins, or they can mimic the appearance of the thymus. The lateral projec­ tion frequently shows a straight anterior mediastinal den­ sity that represents the dilated right superior vena cava and the left superior vena cava anterior to the trachea. In those patients with connection to the right superior vena cava, mediastinal widening is confined to the right side.33 The cardiac (type I I) form of total anomalous pulmo­ nary venous connection is typically associated with radio­ graphic findings that are indistinguishable from those of an AS D . The major features are cardiomegaly and pul­ monary vascular prominence. The anomalous pulmonary veins are usually not directly visible. If the connection is to the coronary sinus , the dilated coronary sinus results in an indentation on the contrast opacified esophagus as viewed in the lateral projection. This indentation is lower and smaller than the impression caused by the normal left atrium. Infants with total anomalous pulmonary venous con­ nection and obstruction have pulmonary venous conges­ tion and pulmonary edema ( Figure 1 1 -38) . In many patients, dilated intralobular lymphatics are visible. The heart is nor­ mal in size or only mildly enlarged (Figure 1 1 -39) . Pleural effusions may be present in infants with severe obstruction (Figure 1 1 -40) . The thymus is usually small in these stressed infants . Nearly all children with type III total anomalous pulmonary venous connection have hemodynamically

A radiograph of a 4-week-old cyanotic infant shows marked pulmonary edema. The lungs are hyperinfiated. Heart size is normal and the thymus is small. This patient has total anomalous pulmonary venous connection type I, with an obstructed vertical vein.

Figure 1 1-37 Total anomalous venous connection type I. A. There i s a "snowman" configuration o f the cardiomediastinal

Figure 1 1-38 Total anomalous pulmonary venous connection.

Chapter 1 1 Co ngenital H e a rt D i sease 359

Figure 11-39 Total anomalous venous con nection. This 1-day-old infant with profound cyanosis as a consequence of type I total anomalous pulmonary venous return has pulmonary vascular prominence and interstitial pulmonary edema. Heart size is normal.

significant obstruction, sometimes leading to severe con· gestive heart failure in the neonatal period. The manifesta­ tions of obstruction dominate the radiographic findings in these infants.

Echocardiography usually provides documentation of the anomalous vasculature in children with total anoma­ lous pulmonary venous connection. In most patients, the venous confluence of the common pulmonary vein is dem­ onstrated posterior to the left atrium. There are manifes­ tations of right ventricular diastolic volume overload. The right ventricle is enlarged and there is paradoxical motion of the interventricular septum (in the absence of obstruc­ tion) . The left atrium is small. In the presence of pulmo­ nary venous obstruction, Doppler shows continuous flow without phasic variation.92·93 MR and CT angiography of patients with total anom­ alous pulmonary venous connection shows lack of pul­ monary veins entering the left atrium. Most often, the common pulmonary vein appears as a structure dorsal or cephalad to the left atrium. Images in multiple planes are helpful to detect and characterize narrowed veins. If there is stenosis, sluggish flow within the pulmonary vein(s) may lead to high signal intensity on T1-weighted MR images. Phase-contrast MR evaluation demonstrates the direction of blood flow and thus provides a physiological method of distinguishing the vertical vein of anomalous pulmonary venous return from normal flow in a left superior vena cava.67o9 4-96

Total Anomalous Pulmonary Venous Connection Pathology

Rad iology

Systemic and pul monary venous return to the right atriu m Atrial septal com m u nication

Pulmonary vascular promi nence

± Drainage into the left s u perior vena cava ± Pul monary venous obstruction

Figure 11-40 Total anomalous pulmonary venous return. This 6-hour-old infant with obstructed supracardiac total anomalous pulmonary venous return had oxygen saturations ofless than so% despite supportive measures. Radiographic evaluation shows severe pulmonary edema and normal heart size. There is a ri ght pleural effusion; the left effusion has been drained.

Enlarged main pulmonary a rtery ' Cardiomegaly (moderate) Snowman heart _

, Congestive heart fai l u re M i n imal or no ca rdiomegaly

·

There is a variant of total anomalous pulmonary venous connection in which the common pulmonary vein is atretic; that is, atresia of the common pulmonary vein. The pulmonary veins in these infants form a venous conflu­ ence near the left atrium, but there is no connection of this structure to either atrium or to systemic veins. The only exit pathway for blood from the pulmonary venous system is through intrapulmonary connections with the bronchial venous system. The severe pulmonary venous obstruction in these infants results in marked elevation of pulmonary arterial and right ventricular systolic pressures. Right-to­ left shunting at the atrial level is the only source of blood

360 Part 2 The Card i ovascu l a r System flow into the left side of the heart. These infants are pro­ foundly cyanotic.97·9 8 The radiographic features of atresia of the common pulmonary vein are identical to those of total anomalous pulmonary venous connection with obstruction. Because there is no increase in the volume of blood within the heart, cardiomegaly is not a feature unless right ventricular decompensation develops. There is right ventricular hyper­ trophy from pulmonary hypertension, but this is usually not discernible on radiographs. Pulmonary venous conges­ tion in the neonate produces a diffuse granular pattern on chest radiographs that is similar or identical to that of respi­ ratory distress syndrome.8'·99

Dou ble-outlet Left Ventricle Double-outlet left ventricle refers to at least partial origin of both great vessels from the anatomic left ventricle, in association with a VSD. Great vessel orientation varies between patients. Most commonly, the aorta is located to the right of the pulmonary artery. Subpulmonic andjor subaortic stenosis can occur. Double-outlet left ventricle is an exceedingly rare anomaly. In those patients without pul­ monic obstruction, the clinical features are similar to those of other types of transposition. The presence of substantial pulmonic obstruction produces features similar to those of tetralogy of Fallot. The radiographic features of double-outlet left ventri­ cle are nonspecific. In those patients without pulmonary stenosis, the pulmonary blood flow is prominent and there is moderate cardiomegaly. If there is hemodynamically sig­ nificant pulmonary stenosis, the pulmonary vascular pat­ tern is diminished and heart size is normal. Echocardiography and angiocardiography of patients with double-outlet left ventricle show origins of the aorta and pulmonary artery from the left ventricle. There is nor­ mal aortic-mitral valve continuity. A VSD is present.

Si ngle Ventricle Single ventricle is an admixture lesion that produces cya­ nosis and, unless there is substantial pulmonary outflow obstruction, radiographic increase in pulmonary vascular­ ity. This anomaly refers to a heart that contains one ventric­ ular chamber that receives blood from both the mitral and tricuspid valves or a common atrioventricular valve. Other terms for this lesion include univentricular heart, common ventricle, and cor triloculare biatriatum. Transposition of the great vessels is sometimes associated with single ventricle. Pulmonic and systemic outflow obstructions are common. Single ventricle occurs in approximately 1 in 6 5 0 0 live­ births. This anomaly is slightly more common in males. Single ventricle with pulmonary atresia is common in patients with asplenia. Systemic and pulmonary venous drainage into a single ventricle heart occurs through 2 separate atrioventricular valves or through a common valve. In rare patients with 2

atrioventricular valves, 1 valve is completely obstructed by an imperforate membrane. There are 4 possible arrange­ ments of the atrial chambers in these patients: (a) normal orientation, (b) mirror image orientation (situs inversus) , (c) right atrial isomerism, and (d) left atrial isomerism. Single ventricle is subdivided anatomically accord­ ing to ventricular morphology into 3 groups: hearts with dominant left, dominant right, or indeterminate ventricu­ lar morphology. The apical component of a morphological right ventricle contains coarse trabeculae, while that of a left ventricle has a fine crisscross trabecular pattern and a smooth septal surface. In addition to the ventricular mor­ phology, important anatomic variations of single ventricle are the patterns of atrioventricular connection and ventric­ uloarterial connection (Table 1 1 -12) . The most common type of single ventricle (75%) is double-inlet left ventricle or single left ventricle, with the nondominant right ventricle located anteriorly, on either the right or the left. The left ventricle gives rise to one or both of the great arteries. When the dominant chamber

Table 1 1-12. Terminology of Single Ventricle Heart

Atrioventricu lar connection

Dou ble-inlet left ventricle

Dou ble-inlet right ventricle U niventricu lar atrioventricular connection Biventricu lar atrioventricular connection with VS D Ventricu loarterial Concordant connection

Discordant

Double outlet

Si ngle outlet

Fine trabeculations at apex Prominent trabecu lations I ndeterm inate morphology ----

U n i l ateral ventricu lar trabecu lation

Pul monary from right ventricle Aorta from left ventricle Pul monary from left ventricle Aorta from right ventricle Pul monary and aorta from right ventricle, left ventricle, or indeterm inate From right ventricle, left ventricle, or indeterm inate

Chapter 11 Co ngenital H e a rt D i sease 361 of a single ventricle possesses an apical trabecular com­

In those patients with single ventricle and aortic out­

ponent, the lesion is termed a double-inlet right ventricle

flow obstruction, the most common outflow anomaly is

or single right ventricle; this accounts for approximately

severe coarctation or interruption of the aortic arch. These

20% of single ventricles. The nondominant left ventricle is

infants usually have clinical manifestations of cardiac

located posteriorly. The left ventricular portion has neither

decompensation soon after birth. When coarctation is pres­

inlet nor outlet components. In those instances in which

ent, the femoral pulses diminish after closure of the ductus

patients with asplenia) , the lesion is termed single ventricle

preserved lower-extremity pulses despite the presence of

only 1 ventricular component is demonstrated (common in

arteriosus . While the ductus is patent, shunting results in

with morphologically indeterminate myocardium. A fourth

severe aortic arch obstruction. Some patients with single

variation is that of a heart in which a single ventricle has

ventricle have obstruction of the left atrioventricular valve.

the trabecular pattern of a right ventricle on one side and

If the atrial septum is largely intact, this results in obstruc­

the trabecular pattern of a left ventricle on the other side,

tion to pulmonary venous return and clinical manifesta­

with a small rim of apical ventricular septum between the

tions of pulmonary venous hypertension.

2;

this is a form ofbiventricular atrioventricular connection

As with the clinical manifestations, the severity of pulmonary outflow obstruction influences the radio­

with a large V S D . The connections of the great arteries i n patients with

graphic features of single ventricle. Those patients lacking

single ventricle are also classified according to the trabecu­

pulmonary stenosis have markedly enlarged pulmonary

lar morphology of the ventricle. The ventriculoatrial connec­

arteries and prominent cardiomegaly

tions are concordant when the pulmonary

connects

pulmonary stenosis, the pulmonary vasculature is nor­

to the trabeculated (morphological right) portion of the ven­

mal or diminished and cardiomegaly is lacking or is mild.

trunk

(Figure 1 1 -41 ) . With

tricle and the aorta connects to the morphological left ven­

Pulmonary atresia in these patients is associated with

tricular chamber, regardless of the sizes of these chambers.

markedly decreased vascularity. If the great vessel rela­

Discordant connection refers to the reverse of this connec­

tionships are normal , the findings in infants with single

tion pattern; this can occur either as a D-transposition or

ventricle and severe pulmonary outflow obstruction are

L-transposition. In

9 0%

of patients with double-inlet left

similar to those of tetralogy of Fallot. In those patients

ventricle, there is associated transposition of the great ves­

with D-transposition of the great vessels, the radiographic

sels. An additional variation of single ventricle is double

findings

outlet from either the main or the rudimentary ventricular

D-transposition: cardiomegaly and a narrow cardiac waist.

are

indistinguishable

from

other

forms

of

chamber. Single outlet can also occur. Pulmonary or aor­

Likewise, L-transposition is associated with similar find­

tic outflow obstruction is common in patients with single

ings whether or not a single ventricle is present; there is

ventricle.

often a bulge along the left upper-heart border because of

The clinical features of single ventricle are largely determined by associated obstructions to inflow and out­ flow from the ventricular chamber. The most common findings are cyanosis and congestive heart failure. The severity of cyanosis depends on the presence and sever­ ity of pulmonary outflow obstruction. Approximately

6o%

of patients with single ventricle have pulmonary stenosis, and

5%

have pulmonary atresia. If pulmonary stenosis is

severe, the neonate develops marked cyanosis as the duc­ tus arteriosus closes. Infants with pulmonary atresia either have no murmur or have a continuous murmur because of a patent ductus arteriosus. Less-severe pulmonary stenosis results in an ej ection systolic murmur. In newborns with single ventricle and no pulmonary stenosis, the onset of clinical manifestations is often delayed for a few days until diminished pulmonary vas­ cular resistance allows excessive pulmonary blood flow. As pulmonary vascular congestion develop s , these neo­ nates develop tachypnea, subcostal retraction, poor feed­ ing and hepatomegaly. The findings resemble those of a large left-to-right shunt at the ventricular level. Cyanosis may become less prominent as pulmonary vascular resis­ tance falls . If there is good mixing within the ventricu­ lar cavity and no substantial pulmonic stenosis, oxygen saturation in the aorta is usually in the range of 8o% to

9 0% .100

Figure 11-41 Single ventricle. This infant has double-inlet left ventricle, with D-transposition and severe coarctation of the aorta. Substantial cardiomegaly is present. There is pulmonary vascular prominence on this chest radiograph, since pulmonary outflow tract obstruction is lacking.

362 Part 2 The Card iovascu l a r System

Figure 11-42 Si ngle ventricle. An anteroposterior radiograph of a cyanotic infant with double-inlet left ventricle, right atrioventricular valve atresia, L-transposition, nonrestrictive ASD, large patent ductus arteriosus (with right-to-left shunting) , and distal transverse arch hypoplasia. There is no pulmonary outflow tract obstruction in this infant, and the radiograph shows pulmonary vascular prominence as well as interstitial edema. There is cardiomegaly. The left upper-heart border is prominent because of the L-transposition.

the anomalous left-sided aorta (Figure 1 1 -42) . In patients with single ventricle and obstructed pulmonary venous return, radiographs show pulmonary venous congestion and pulmonary edema.'o ' ·'o2

Single Ventricle Associated anomaly

Without p u l monary stenosis

Pathology

Rad iology

' Single ventricular ; cham ber, mixing i of systemic and : p u l monary return ' Diminished flow : i nto pul monary • artery

' Cardiomegaly . Active congestion

...

' Normal or ' d i m i n ished , p u l monary ' vascularity ; N arrow cardiac D-transposition ; Altered great ' vessel orientation · waist L-transposition : Anomalous left ' Left u pper heart ' a rch border bulge

With p u l monary stenosis

. . . . ..

··· ···· ···

...

.

....

·

Echocardiography of single ventricle demonstrates absence of the ventricular septum. Likewise, there is no septum separating the atrioventricular valves. The rudi­ mentary second chamber that is present in most of these hearts may be difficult to identify with echocardiography. In those patients with trabeculated right ventricular mor­ phology, the rudimentary left ventricular chamber is usu­ ally located directly posterior or posterior and to the right of the main ventricular cavity. With echocardiography, the atrioventricular valves are considered to be overriding when the tensor apparatus arises from the main cham­ ber. A straddling valve has at least a portion of the tensor apparatus arising from the rudimentary chamber. Doppler studies are useful for demonstrating atrioventricular and ventriculoarterial valvar obstruction or insufficiency. Angiocardiography or cardiac MR of infants with single ventricle confirms the ventricular anatomy. Various projections may be required to demonstrate the hypoplastic ventricular chamber, when present. In patients with asso­ ciated transposition, accurate detection of coronary artery anatomy is important for operative planning. Pressure mea­ surements are useful for quantifying inflow and outflow gradients. The timing of angiocardiography is determined by the need for intervention. Critically ill newborns may require balloon atriotomy or pulmonary artery banding.

Si ngle Atriu m Single atrium (common atrium) is a rare anomaly in which the atrial chamber exists as a single cavity, with or without a rudimentary septum. A contiguous VSD is lack­ ing. Pulmonary vascular resistance and relative ventricu­ lar compliances largely determine the hemodynamics of shunting at the atrial level in these children. Most often, the predominant shunt is left-to-right, and cyanosis is absent or is minimal. With time, pulmonary vascular disease may develop, leading to increasing degrees of right-to-left shunting. Cyanosis in children with single atrium may be accentuated with exercise.'03 Single atrium is often complicated by mitral insuffi­ ciency; tricuspid insufficiency is less common. About half of children with single atrium have a persistent left supe­ rior vena cava, which can insert into the coronary sinus or directly to the left side of the common atrium. Single atrium can occur in association with polysplenia. Left-to-right shunting at the atrial level in patients with single atrium results in prominent pulmonary arte­ rial vasculature on chest radiographs. The main pulmonary artery segment of the mediastinal contour is prominent as a result of the increased pulmonary flow. Cardiomegaly is present, predominantly involving the right ventricle. Left atrial enlargement is lacking as there is usually no substan­ tial elevation of atrial pressure in these patients. With time, radiographic manifestations of pulmonary hypertension can develop in children with single atrium; the major find­ ing is prominent central vessels and peripheral vascular pruning.

Chapter 1 1 Congen ital H e a rt D i sease

363

Single Atri u m Rad iology

Pathology

Left-to-right shunt

' Active congestion Right-heart enlargement Prominent main p u l monary artery Normal atrial pressure Lack of left atri u m enlargement

CYANOT IC, INCREASED PULMONARY VENOUS VASCULATURE Cardiac anomalies that cause cyanosis in association with radiographic evidence of pulmonary venous congestion (as opposed to active, or arterial, congestion) have a right-to-left shunt in conjunction with an anatomic obstruction of pul­ monary venous return

(Table

1 1 -1 3) . Obstruction to pulmo­

nary venous return can occur at the level of the pulmonary veins (e.g., total anomalous pulmonary venous connection with obstruction) , the mitral valve (e.g. , mitral atresia) , or the left ventricle (e.g., hypoplastic left ventricle syndrome) . The location of the right-to-left shunt varies with the spe­ cific features of the anomaly.

Hypoplastic Left H ea rt Syndrome Hypoplastic left heart syndrome comprises ( H L H S ) a spec­ trum of cardiac malformations characterized by a diminu­

Figure 11-43 Hypoplastic left heart syndrome and double-outlet right ventricle. This infant appeared normal at delivery, but developed cyanosis the next day. The left ventricle is hypoplastic as a consequence of mitral valve atresia. The aorta and pulmonary artery arise from the right ventricle. The aortic valve and aortic arch are hypoplastic. Marked dilation of the right ventricle and right atrium accounts for the finding of cardiomegaly on this radiograph. The left atrium is small. The atrial septal defect is restrictive, resulting in pulmonary venous congestion.

tive left ventricle and normally related great vessels . The cardiac pathology includes hypoplasia or atresia of the aor­ tic andjor mitral valves, and hypoplasia of the left ventricle and ascending aorta. Hypoplastic left heart syndrome is the fourth most common cardiac malformation to present during the first year of life , behind V S D , D -transposition, and tetralogy of Fallot.'04 Hypoplastic left heart syndrome accounts for approximately

8%

of symptomatic congeni­

tal heart disease in infants . The prevalence is approxi­ mately 0 . 2 per woo livebirths. The male-to-female ratio is 2 :1 . 1 0 5, 1 06 Patients

with

hypoplastic

left

heart

syndrome

often have complex cardiac anomalies . Cardiovascular

malformations that sometimes occur in association with hypoplastic left heart syndrome include coarctation of the aorta, double-outlet right ventricle, endocardial fibroelas­ tosis , anomalous systemic and pulmonary venous con­ nections, abnormalities of aortic arch branching, and V S D (Figu re 1 1 -43) .10? Coarctation of the aorta proximal to the ductus arteriosus occurs in approximately

so% of patients.

Approximately one-quarter of infants with hypoplastic left heart syndrome have underlying genetic abnormalities or major extracardiac anomalies. 1 0 8 The principal anatomic feature of hypoplastic left heart syndrome is a diminutive left ventricle. The aortic valve is

Table 1 1-13. Cardiac Anomalies That Cause Cyanosis and Passive Pulmonary Venous Congestion

Total anomalous pulmonary venous connection with obstruction M itral atresia Hypoplastic left heart syndrome Aortic atresia Atresia of the com mon pul monary vei n

usually atretic, but occasionally there is a severely stenotic aortic valve. With atresia of the aortic valve, the ascend­ ing aorta is markedly hypoplastic and the only blood fl ow through this segment is retrograde into the coronary arter­ ies. The diminutive ascending aorta in these patients is termed a

common coronary artery.10 9

Systemic perfusion

in patients with hypoplastic left heart syndrome occurs predominantly or exclusively via the ductus arteriosus . Maintenance of patency of the ductus arteriosus (with intravenous prostaglandin be performed is essential.

EJ

until palliative surgery can

364 Part 2 The Card iovascu l a r System As with the aortic valve, the mitral valve is atretic or markedly stenotic in patients with hypoplastic left heart syndrome. With combined aortic and mitral valve atresia, only a thin rudimentary left ventricle is present. If flow into the developing left ventricle occurs via stenotic aortic or mitral valves , some ventricular development will occur.

However, the wall is hypertrophied and there is endocardial

fibroelastosis of the endocardial surface. In patients with hypoplastic left heart syndrome, pul­ monary venous blood entering the left atrium cannot empty into the left ventricle, and instead passes through an inter­ atrial communication into the right atrium. The increased volume of recirculating blood causes enlargement of the right atrium, right ventricle, and pulmonary arteries. There is hypertrophy of the right ventricular wall. The left atrium is hypoplastic, and the endocardium is thickened. The anat­ omy of the atrial septum is variable. Most often, an A S D at the fossa ovalis allows communication between the atria. If the atrial communication is restrictive, herniation of the septum primum through the ostium secundum may occur.

Figure 1 1-44 Hypoplastic left heart syndrome.

In addition to the interatrial communication, pathways

This 3-day-old cyanotic infant has atresia of the mitral and aortic valves, a restrictive ASD, and a large patent ductus arteriosus. Cardiomegaly is accompanied by pulmonary vascular congestion and edema.

for pulmonary venous return that are sometimes present include a venous channel between the left subclavian vein and the left atrium or a left upper-lobe pulmonary vein (the

levoatrial cardinal vein) ,

communication between the left

atrium and the coronary sinus, and anomalous pulmonary venous connection. Approximately half of newborns with hypoplastic left heart syndrome present within the first 9 0 % present within the first

2

days of life, and

2 weeks . The clinical manifes­

to these infants include transcatheter A S D creation and emergent staged surgical repair."0 The diagnosis of hypoplastic left heart syndrome is

tations vary according to the patient-specific hemodynamic

sometimes possible prenatally with sonography, although

effects and the presence of any associated cardiovascular

the findings are frequently not apparent or are missed. The

lesions. All of these patients receive pulmonary, systemic, and coronary blood flow exclusively from the right heart.

B ecause systemic perfusion and oxygenation are normal in utero, infants with hypoplastic left heart syndrome usually

identification of diastolic flow reversal in a narrow ascend­ ing aorta is essentially pathognomonic. m Ventricular size

discrepancy is best demonstrated on a 4-chamber view, but may not be apparent prior to

22

weeks' gestation.'05

appear normal at birth. Tachypnea and dyspnea develop

The most common findings on standard radiographs

soon after birth as pulmonary vascular resistance falls and

of newborns with hypoplastic left heart syndrome are

pulmonary blood flow increases. Cyanosis is not a promi­

cardiomegaly and pulmonary venous distention. There

nent early feature. Congestive heart failure, tachypnea, and

is often a mixed pattern of prominent pulmonary arter­

hepatomegaly are usually present by

1 to 2

days of age. As

ies and veins. The size of the interatrial communication is

the ductus arteriosus closes, there is compromise of sys­

the major determinate of the radiographic pulmonary vas­

temic perfusion that results in clinical manifestations of

cular pattern. Pulmonary venous congestion is common

progressive cyanosis and acidosis. Without appropriate

since the interatrial communication is usually restrictive

medical therapy and effective palliative surgery, virtually all

(Figures 1 1 -44

affected neonates die within days or weeks .

pulmonary vascular pattern is normal or increased arte­

The size of the interatrial communication is an impor­

and

1 1 -45) .

With a nonrestrictive A S D , the

rial flow is present. In these patients, the radiographic

tant determining factor in the clinical course of a neonate

appearance can be indistinguishable from other forms

with hypoplastic left heart syndrome. A nonrestrictive A S D

of congenital heart disease with a left-to-right shunt

allows a large volume left-to-right shunt; pulmonary venous congestion is not a major feature. A small communication

(Figure 1 1 -46) .

The severity of the left ventricular inflow

and outflow obstructions (e.g., valvar stenosis vs . atresia)

with restricted flow results in severe congestive heart fail­

also affects the pulmonary vascular pattern

ure; this is the most common pattern. Neonates with hypo­

Although cardiomegaly i s usually present, some infants

plastic left heart syndrome and intact atrial septum (and

with hypoplastic left heart syndrome have a normal size

thus lacking an effective pathway for emptying of the left

heart or even a small heart. The major determinants of

(Figure 1 1 -47) .

atrium) are critically ill as newborns, and suffer profound

radiographic heart size and shape are the size of the left

hypoxemia and acidosis. Potential therapeutic approaches

ventricle and whether it forms the cardiac apex, the degree

Chapter 11 Co ngenital H e a rt D i sease 365

Figure 11-47 Hypoplastic left heart syndrome.

Figure 11-45 Hypoplastic left heart syndrome. lbis cyanotic infant has aortic atresia, mitral hypoplasia, an intact ventricular septum, a restrictive ASD, a patent ductus arteriosus, and severe hypoplasia of the ascending aorta. A radiograph obtained at 7 days of age shows cardiomegaly and pulmonary edema.

Figure 11-46 Hypoplastic left heart syndrome. lbis 7-day-old infant has atresia of the mitral and aortic valves. Cardiomegaly is caused by dilation of the right ventricle and right atrium. There is a large patent ductus arteriosus. The secundum atrial septal defect is nonrestrictive; therefore, there is pulmonary vascular prominence without substantial venous distention or pulmonary edema.

lbis 2-day-old infant has mitral and aortic stenosis, patent ductus arteriosus, moderately severe left ventricular hypoplasia, and a restrictive atrial septal defect. There is mild central interstitial edema, without pulmonary vascular prominence.

of right atrial dilation, and the severity of ascending aortic hypoplasia. The most important echocardiographic feature of hypoplastic left heart syndrome is a diminutive left ven­ tricle. If both the aortic and mitral valves are atretic, the left ventricular chamber exists only as a slit-like cavity in the myocardium, and there is a single atrioventricular valve. The right ventricle is enlarged and the wall is thickened. The left atrium is usually small, and there is a variable degree of dilation of the right atrium. The ascending aorta is diminutive.112 •113 Short-axis cine MRI provides accurate depiction of ventricular volume in infants with hypoplastic left heart syndrome. This information is important preoperatively for deciding between a biventricular repair and univentric­ ular palliation. M R is also helpful in selected hypoplastic left heart patients with suspected left ventricular endo­ cardial fibroelastosis. Delayed-enhancement myocardial imaging provides precise localization of the fibrotic tissue for preoperative planning.''4 Presurgical medical management of neonates with hypoplastic left heart syndrome includes intravenous administration of prostaglandin E, to maintain patency of the ductus arteriosus. Because the main pulmonary artery supplies both the systemic and pulmonary vascular ter­ ritories, the relative distribution of blood flow is in large part determined by the relative resistances of these terri­ tories. If there is severe congestive heart failure because of a restrictive interatrial communication, hypoventilation is initiated to increase C0 2 tension and maintain elevated

366 Part 2 The Card i ovascu l a r System pulmonary vascular resistance. Intravenous administration of nitroprusside can be helpful to decrease systemic vascu­ lar resistance and encourage systemic perfusion. Medical intervention to maintain appropriate balance between pulmonary and systemic vascular resistance is also essen­ tial postoperatively to achieve a balanced circulation with matched pulmonary and systemic flow. The surgical approach to infants with hypoplastic left heart syndrome typically consists of 3 stages that comprise the modified Norwood procedure. The initial procedure is the creation of a neoaorta from the main pulmonary artery, the descending aorta, and the aortic arch. The neo­ aorta receives blood from the right ventricle via the pul­ monic valve. The ductus arteriosus is excised. Perfusion of the lungs is via a shunt from the innominate artery to the main pulmonary artery; creation of a right ventricle-to-pul­ monary artery shunt is an alternative technique. Excision of the atrial septum helps to prevent pulmonary venous hypertension. Chest radiographs after this procedure may show decrease in cardiac size in comparison to the preop­ erative appearance. The right atrium remains prominent. There should be improvement or resolution of pulmonary venous congestion. Radiographic monitoring of the pul­ monary vascular pattern is helpful in tailoring medical management. The second stage surgical repair of hypoplastic left heart syndrome is performed when pulmonary artery resis­ tance decreases to normal levels, usually at 3 to 6 months of age. A bidirectional cavopulmonary shunt is created, with an end-to-side anastomosis of the superior vena cava to the right pulmonary artery. The shunt from the innominate artery to the pulmonary artery that was created during the first-stage procedure is taken down. This procedure serves to partially separate the pulmonary and systemic circula­ tions, and decreases the volume of blood delivered to the atria and right ventricle. Chest radiographs after the sec­ ond-stage procedure typically show a normal size heart and normal pulmonary vasculature. The third stage of surgical palliation of hypoplastic left heart syndrome is the modified Fontan procedure. A tun­ nel is created within the right atrium into the right pulmo­ nary artery. This completes separation of the systemic and pulmonary circulations, with blood from both the superior vena cava and inferior vena cava passing directly into the pulmonary arteries. Heart size usually does not change sig­ nificantly after the third-stage procedure, but most patients develop pulmonary edema that may be persistent, because of the increased volume of pulmonary blood flow. Chronic pleural effusions are common. MRI and CT angiography are occasionally helpful in evaluating hypoplastic left heart syndrome patients follow­ ing palliative surgery. The reconstructed great vessel anat­ omy and intracardiac anatomy are well demonstrated by these noninvasive techniques . Important findings include the size of the interatrial communication, the patency and caliber of the systemic-to-pulmonary artery shunt, and the size of the central and branch pulmonary arteries.U5·116

M itral Atresia With I ntact Aortic Valve Mitral atresia most often occurs in conjunction with aortic atresia or severe aortic stenosis, as a form ofhypoplastic left heart syndrome. Mitral atresia with an intact aortic root is much less common. Outflow from the left atrium in these patients is into a markedly enlarged right atrium. Blood flows through an enlarged tricuspid valve into a hypertro­ phied right ventricle. In approximately three-fourths of patients, there is a VSD that communicates with a small or hypoplastic left ventricle. In those patients with an intact ventricular septum, there is no identifiable left ventricle. Various outflow patterns can occur in patients with mitral atresia, including normally related great vessels, transposed great vessels, double-outlet right ventricle, and single ven­ triculoarterial outlet (e.g., truncus arteriosus) . A right aor­ tic arch occurs in some patients. Various forms of outflow obstruction can occur.''7·118 Mitral atresia is an admixture lesion, as the entire pul­ monary venous return passes into the right atrium where it mixes with the entire systemic venous return. The severity of arterial desaturation is inversely related to the volume of pulmonary blood flow. A greater degree of cyanosis is present when there is pulmonary stenosis. Cyanosis is most severe in those patients with restricted flow from the left atrium. Alternate pathways of drainage may be present in this situation, such as an anomalous pulmonary venous connection. Most patients with mitral atresia and an intact aortic valve present with cyanosis that develops during the first week of life. Manifestations of congestive cardiac failure are common, including tachypnea and hepatomegaly. The radiographic features are nonspecific. The right atrium and right ventricle are enlarged. If there is left atrial outflow obstruction, pulmonary venous congestion is pronounced. In other patients, the major radiographic alterations reflect associated anomalies, such as transposition or single ventricle.

NORMAL PULMONARY VASCULATURE Congenital cardiovascular lesions that usually are associ­ ated with normal pulmonary vascularity on chest radio­ graphs include congenital aortic stenosis, coarctation of the aorta, interruption of the aortic arch, and pulmonary stenosis. With high-grade left-heart obstruction or left ven­ tricular decompensation, these lesions can cause pulmo­ nary venous congestion.

Congen ital Aortic Stenosis Aortic stenosis refers to obstructive narrowing at or adja­ cent to the aortic valve. This spectrum of lesions ranges from an asymptomatic bicuspid valve to aortic atresia. Subcategories include valvar, subvalvar, and supravalvar forms of aortic stenosis. Congenital valvar aortic stenosis accounts for approximately 70% of cases of aortic stenosis.

Chapter 1 1 Congenital H e a rt D i sease 367 Supravalvar aortic stenosis is the least common type. As a group, the various forms of aortic stenosis account for approximately s% of congenital heart disease. The aortic valve begins to develop near the end of ges­ tation month 2, as the truncus arteriosus divides into the embryonic aorta and pulmonary arteries. The valve is pro­ duced by proliferation from 3 tubercles in the lumen of the aorta that grow toward the center of the vessel. Subsequent resorption of some of this tissue leads to the eventual thin character of the valve and gives rise to the sinuses of the valve.

Valvar Aortic Stenosis The classification ofvalvar aortic stenosis is according to the number of valve cusps: unicuspid, bicuspid, tricuspid, and quadricuspid. Approximately 8o% to 85% of congenitally stenotic aortic valves are bicuspid. The typical morphol­ ogy is 1 large cusp and 1 small cusp, with an eccentric fish­ mouth orifice between them. Those bicuspid valves that are stenotic have some degree of commissural fusion. Bicuspid aortic valve is the most common congenital cardiac malfor­ mation, occurring in approximately 2% of the population. The great majority of these individuals are asymptomatic or do not develop clinical manifestations until adult life (calcific aortic stenosis or infective endocarditis) . Most patients with coarctation of the aorta have a bicuspid aortic valve, although the valve is not always stenotic. A unicuspid valve most often occurs as a thick cusp with an eccentric, teardrop-shaped orifice. Obstruction of a unicuspid valve is caused by lack of normal mobility of the thick valve, as well as a small orifice size caused by commissural fusion. Unicuspid aortic valve is commonly associated with hypo­ plastic left heart and endocardial fibroelastosis. "9 ·' 20 A stenotic aortic valve requires increased work by the left ventricle to maintain sufficient pressure in the aorta. This leads to left ventricular hypertrophy, the sever­ ity of which varies greatly between patients . With severe stenosis, the left ventricle sometimes fails to develop appropriately in utero and is quite small; this is a form of hypoplastic left heart syndrome. In others, the left ven­ tricle is normal in size or dilated. There is compromised endocardial and subendocardial perfusion as a result of the high intracavitary pressure within the left ventricle, thickening of the myocardium, low diastolic blood pres­ sure in the aorta (and coronary arteries ) , and the short duration of diastole (because of tachycardia) . This can lead to subendocardial ischemia, necrosis, and fibrosis in patients with severe aortic stenosis. The result in some infants with critical aortic stenosis is a secondary form of endocardial fibroelastosis, in which the left ventricu­ lar endocardium is thickened and covered with a layer of fibrous and elastic tissue. Papillary muscle involvement can lead to substantial mitral regurgitation. In patients with less-severe forms of congenital aor­ tic stenosis, there is no significant compromise of cardiac output. There is compensatory left ventricular hypertrophy.

As the child grows, however, enlargement of the valve ori­ fice usually fails to keep pace with the requirements for increased cardiac output. Hemodynamic decompensation eventually occurs. Congenital valvar aortic stenosis is more common in boys than in girls; the gender ratio is approximately 4:1. The clinical manifestations and age at presentation relate to the severity of obstruction and the presence or absence of an associated anomaly, such as coarctation of the aorta or hypoplastic left ventricle. Associated cardiovascular anoma­ lies are present in approximately 20% of patients with con­ genital valvar aortic stenosis. In the newborn with severe aortic stenosis, the clinical presentation typically is perinatal. However, a delayed clini­ cal onset can occur, even with critical aortic stenosis. The major findings are those of congestive heart failure in con­ junction with a systolic murmur. Potential marlifestations include respiratory distress, tachypnea, and poor feeding. If the cardiac output is greatly reduced, the systolic murmur may be soft or absent and the findings can minlic those of septic shock. These infants may have cool mottled extremi­ ties and diminished peripheral pulses. Those children with milder forms of congenital aor­ tic stenosis usually develop normally and are asymptom­ atic. The diagnosis of aortic valve disease in these patients is most frequently based on an incidentally discovered murmur. The potential symptoms in these older children include fatigue, exertional dyspnea, angina pectoris, and syncope. Patients with aortic stenosis are at elevated risk for the development of infective endocarditis. Older patients with untreated aortic valvar stenosis are also at risk for sud­ den death. The radiographic findings of critical aortic stenosis in the infant include marked cardiomegaly and pulmonary venous congestion. There may be small pleural effusions . Hyperinflation is common. The radiographic appearance is essentially identical to that of severe coarctation of the aorta. Many infants with decompensated aortic stenosis have intermediate findings, with mild-to-moderate cardio­ megaly and pulmonary edema ( Figure 1 1 -48) . In infants with compensated aortic stenosis, the pulmonary vascular pattern is normal and heart size is normal or only mini­ mally prominent.•2t,t22 In older children with aortic stenosis , left ventricular hypertrophy often results in a rounded appearance of the cardiac apex on frontal radiographs. On the lateral view, the left heart bulges toward the inferior vena cava shadow. The left atrium is enlarged. Poststenotic dilation of the ascending aorta is visible radiographically in about half of patients with aortic stenosis. There is prominence of the right upper cardiomediastinal border on frontal and left anterior oblique views; dilation is most prominent along the anterior and lateral portions of the aortic walls. Valvar calcifications, which are common in adults with congenital aortic valve lesions, are unusual in the pediatric age group. With the onset of aortic insufficiency or cardiac decompensation in the older child with aortic stenosis,

368 Part 2 The Card iovascu l a r System morphology. Coronal and sagittal images may demonstrate valve cusp thickening. Cine M R shows signal loss because of high flow velocity and turbulence in the aortic root (Figu re 1 1 -50) . Valvar regurgitation results in a signal void in the left ventricle during diastole ( Figure 1 1 -51 ) . Various MR measurements of cardiac morphology and function are pertinent in patients with aortic stenosis : ventricular func­ tion, ventricular wall thickness, regurgitant fraction, valve area, and transvalvar pressure.

Valvar Aortic Stenosis C l i n i cal

Rad iology

Pathology

Figure 11-48 Decompensated aortic stenosis. An anteroposterior radiograph of a 3-week-old infant with tachypnea and a murmur shows moderate cardiomegaly and diffuse interstitial fluid. The radiographic findings are not diagnostically specific.

cardiomegaly becomes more pronounced. The cardiac silhouette in these patients frequently has a rounded and elongated left border, with displacement inferior to the apex of the left hemidiaphragm. With severe decompensa­ tion, pulmonary vascular congestion occurs. Echocardiography of congenital valvar aortic stenosis shows thickening and a domed appearance of the valve. Most valves with congenital structural abnormalities have an eccentric pattern of closure. There is hypertrophy of the left ventricle. In patients with decompensation, the ventricle is dilated (Figure 1 1 -49) . Left atrial enlargement and mitral regurgitation are common. Doppler evaluation allows quantification of the gradient across the stenotic valve. The angiocardiographic examination of the infant with suspected aortic valvar stenosis usually is performed with contrast injection into the left ventricle via catheterization through the foramen ovale. The major findings include a domed appearance of the valve, leaflet thickening, post­ stenotic dilation of the ascending aorta, and left ventricu­ lar hypertrophy. Contrast injection of the ascending aorta allows detection of aortic insufficiency, as well as associated lesions such as coarctation and patent ductus arteriosus. M RI is useful for the evaluation of selected patients with valvar aortic stenosis. Poststenotic dilation in the ascending aorta is well documented by this technique. Axial images provide optimal visualization of bicuspid

Left ventricle hypertrophy Cardiac decompensation Asym ptomatic . Left ventricle - hypertrophy i nfant Left ventricle Older child - hypertrophy Poststenotic dilation

Cardiomegaly Pulmonary venous congestion

Sym ptomatic i nfant

N ormal or mild , cardiomegaly Rounded cardiac - apex Prominence of the right u pper card iomediasti nal border _

Transcatheter balloon valvuloplasty is the treatment of choice for most patients with valvar aortic stenosis. However, patients with annular hypoplasia, substantial aortic insufficiency, or calcific aortic stenosis are poor candidates for this procedure and usually require surgi­ cal therapy. A pressure gradient of more than so mm H g is a n indication for the treatment o f the asymptomatic patient. In appropriately selected children, valvoplasty results in hemodynamically satisfactory, but temporary, relief of aortic obstruction. Mild aortic insufficiency is common after this procedure, however. Among the more substantial risks of valvuloplasty are severe aortic insuf­ ficiency, emboli, and arrhythmias. Restenosis is common in patients with aortic stenosis who have been treated either surgically or with balloon valvuloplasty (approxi­ mately 40% of patients treated with balloon valvuloplasty require repeat treatment within 10 years) . In patients with restenosis, balloon valvuloplasty frequently provides pal­ liation and allows delay in surgical valve replacement until the patient has matured.

Supravalvar Aortic Stenosis Supravalvar aortic stenosis involves the proximal portion of the ascending aorta and, therefore, is a form of coarc­ tation. However, this lesion is included in the congenital

Chapter 11 Congenital Heart D i sease 369

A

B

Figure 1 1-49 Critical valvar aortic stenosis.

c

aortic stenosis spectrum because of shared clinical and pathophysiological features. The most common type of supravalvar aortic stenosis (65%) consists of localized nar­ rowing just above the level of the coronary arteries and the superior annular margin of the sinuses of Valsalva, often with an hourglass configuration. Diffuse narrowing of the ascending aorta occurs in 20% to 30% of patients with supravalvar aortic stenosis. The least-common form (approximately 10%) is a constricting diaphragm in the supravalvar region.123 Supravalvar aortic stenosis is less common than the valvar and subvalvar types. Supravalvar aortic stenosis

A. A chest radiograph of a 3-day-old infant with a history of cyanosis and respiratory distress at birth shows marked cardiomegaly and mild pulmonary edema. B. There is turbulent flow across the stenotic aortic valve on this color Doppler image. The left ventricle is dilated. C. There is regurgitant flow into the left atrium.

frequently occurs as part of a generalized process that involves other vessels, such as the pulmonary arteries. Supravalvar aortic stenosis can occur sporadically, but about one-third of cases are associated with Williams syndrome. There are also unusual familial cases of supravalvar aortic stenosis that do not have the other features ofWilliarns syn­ drome; this type is transmitted as an autosomal dominant disorder with variable expression. Potential clinical manifestations of supravalvar aortic stenosis include dyspnea, syncope, angina, and findings of left-heart failure. A prominent systolic ejection murmur is present on auscultation, best heard at the base of the heart.

370

Part 2 The Card iovascu l a r System

Figure 11-50 Valvar aortic stenosis. A systolic cine MR image of a child with a bicuspid aortic valve shows a high velocity jet of blood through the stenotic valve.

The aortic closure sound is often accentuated. In patients with coexistent peripheral pulmonic stenosis, there may be a continuous murmur that is best appreciated with auscul­ tation along the lateral aspect of the chest. In most patients with supravalvar aortic stenosis, peripheral pulses are more prominent in the right arm than the left, and the right arm blood pressure is approximately 15 mm Hg higher than that of the left arm . The radiographic findings in children with supraval­ var aortic stenosis are similar to those of valvar aortic ste­ nosis. However, poststenotic dilation of the aortic arch is usually lacking, even with focal supravalvar stenosis. In some patients, the ascending aorta appears small on chest radiographs. Because the aorta is small, the right main­ stem bronchus is more dearly visualized on the frontal radiograph than usual. As with other forms of aortic steno­ sis, the heart has a rounded left ventricular configuration because of myocardial hypertrophy. If cardiac decompensa­ tion occurs, radiographs show cardiomegaly and manifes­ tations of congestive heart failure. Echocardiography of supravalvar aortic stenosis dem­ onstrates narrowing of the ascending aorta, either focal or diffuse. There is concentric left ventricular hypertro­ phy. Doppler evaluation provides an estimate of the pres­ sure gradient across the narrowed segment of the aorta. Evaluation for pulmonary stenosis is an important compo· nent of the echocardiographic examination. Angiocardiography demonstrates the length and character of narrowing in patients with supravalvar aortic stenosis (Figure 1 1 -52) . Aortic regurgitation is present in approximately zo% of these patients. Potential additional findings include aortic coarctation and brachiocephalic ves­ sel stenosis. Careful evaluation ofthe pulmonary arteries is an essential component of the examination. Stenoses of the brachiocephalic vessel origins are common with the diffuse type of supravalvar aortic stenosis. MR studies of children with supravalvar aortic stenosis show the severity and nature of the aortic narrowing, as well as the degree of associated left ventricular hypertro­ phy. When the narrowing is focal, it is located just above the sinus of Valsalva. As with other stenotic lesions, MR flow studies provide an estimate of the pressure gradient. Cine MR frequently demonstrates turbulence in the region of the stenosis. Aortic regurgitation can also be detected. Three-dimensional images are often useful for evaluating associated stenotic lesions in the pulmonary arteries.

Supravalvar Aortic Stenosis

Figure 11-51 Bicuspid aortic valve with valvar regurgitation. A cine M R image obtained during diastole shows a low signal intensity regurgitant jet (arrow) through the aortic valve. There is dilation of the left ventricle and ascending aorta.

Pathology

Rad iology

Focal or d iffuse supravalvar narrowing Left ventricu lar hypertrophy

Small ascending aorta Rou nded , slightly promi nent heart

Chapter

11

Congenital H e a rt D i sease

371

Williams syndrome is caused by the deletion of con­ tiguous genetic material from a specific region in the

7 (7q11.23). This region includes 28 genes. Among the gene deletions in

long arm of chromosome approximately

patients with Williams syndrome are

G TF2IRD1,

and

LIMK1.

Loss of the

CLIP2, ELN, GTF2I, ELN (elastin) gene

appears to be the most important factor in vascular connec­ tive tissue pathology in these patients. Deletion of the gene for LIM kinase apparently causes the impaired visuospa­ tial constructive cognition that is typical of Williams syn­ drome. The estimated prevalence of Williams syndrome is

1 in 7500 to 1 in 2o,ooo livebirths .U4 Symptomatic cardiovascular disease is present in about half of children with Williams syndrome. Most patients with cardiac abnormalities have clinical manifestations in

75% of Williams syn­

the neonatal period. Approximately

drome patients with cardiovascular disease have supraval­ var aortic stenosis and approximately

40% have pulmonary

artery stenosis or pulmonary artery hypoplasia. Other less­ common findings include aortic or mitral valve lesions and multiple obstructive cardiovascular lesions . Vasculopathy of the carotid, vertebral, or cerebral arteries in these patients can lead to stroke. Coronary artery lesions can cause myo­ cardial infarction. Renal artery stenosis can also occur. ' 2 5

Figure 11-52 Supravalvar aortic stenosis. An angiocardiogram demonstrates an hourglass type of supravalvar aortic narrowing (arrows) in a child with Williams syndrome. The narrowed segment is immediately above the sinuses of Valsalva.

Subvalvar Aortic Stenosis Subvalvar aortic stenosis occurs in

2 major forms : hyper­

trophic muscular subaortic stenosis and discrete subaor­ tic stenosis. Hypertrophic muscular subaortic stenosis (diffuse subaortic stenosis) refers to any form of left ven­ tricular outflow tract obstruction caused by left ventricular hypertrophy. Discrete subaortic stenosis essentially refers

Williams Syndrome Williams syndrome (idiopathic infantile hypercalcemia; subaortic stenosis syndrome; Williams-Beuren syndrome)

to all other causes of subvalvar narrowing.

Hypertrophic Muscular Subaortic Stenosis

is a rare genetic disorder that is characterized by supraval­

Muscular subaortic stenosis can occur as an idiopathic pri­

vular aortic stenosis, multiple peripheral pulmonary artery

mary disorder or in association with various cardiac and

stenoses, characteristic facies, mental deficiency (abnormal

systemic disorders. The idiopathic form is most common.

gyral development) , short stature, failure to thrive, den­

This is a form of hypertrophic cardiomyopathy. Other

tal malformations, and transient infantile hypercalcemia.

terms applied to idiopathic muscular subaortic stenosis,

Other potential manifestations include bladder diverticula,

include idiopathic hypertrophic subaortic stenosis, hypertro­ phic obstructive cardiomyopathy, diffuse subaortic stenosis, and asymmetric septal hypertrophy. This disorder is transmitted

inguinal hernia, and rectal prolapse. The facial appearance ofWilliams syndrome is likened to that of an elf depressed nasal bridge, hypoplastic mandible, prominent maxilla,

as an autosomal dominant trait with variable penetrance.

short upturned nose, prominence of the philtrum (the

Various specific mutations have been identified in these

vertical groove in the midportion of the upper lip) , hyper­

patients ; approximately half involve a gene on chromo­ some 14 · ' 2 6,12 7 Nearly any condition that causes hypertrophy of the left

telorism, and low-set ears . Most infants with Williams syndrome have hypercalce­ mia at the time of diagnosis; spontaneous resolution occurs

ventricle can lead to muscular subaortic stenosis . The ven­

by 18 to

tricular hypertrophy that occurs in response to valvar aortic

24 months of age . However, calcium levels are nor­

mal in some children with Williams syndrome despite the

stenosis can produce hemodynamically significant outflow

presence of nephrocalcinosis and soft-tissue calcifications

tract narrowing. Various forms of cardiomyopathy can also

that suggest prior episodes of substantial hypercalcemia.

cause outflow tract obstruction, including glycogen storage

There are also some patients with classic phenotypic fea­

disease, Turner syndrome, and infant of a diabetic mother.

tures of Williams syndrome who have no findings to indi­

Noonan syndrome is sometimes associated with eccentric

cate current or previous hypercalcemia.

subaortic hypertrophy.

372

Part

2

The Card iovasc u l a r System

In most patients with muscular subaortic stenosis, there is disproportionate hypertrophy of the interven­

to aortic insufficiency. Increased cardiac workload causes concentric left ventricular hypertrophy.

tricular septum. The anterior leaflet of the mitral valve is

There are no reliable clinical features to differenti­

thickened. The subaortic obstruction in these patients is

ate discrete subvalvar aortic stenosis from valvar stenosis.

dynamic: contraction of the hypertrophied septum and

During childhood, most of these patients are asymptom­

anterior motion of the septal leaflet of the mitral valve

atic or have mild symptoms. The clinical presentation is

combine to produce outflow tract obstruction during sys­

sometimes related to a coexistent cardiac lesion, the most

tole. Many patients are asymptomatic, particularly dur­

common of which is V S D . Subvalvar aortic stenosis occa­

ing childhood. Progression to heart failure is unusual.

sionally occurs in patients with atrioventricular canal or

Some patients develop clinical manifestations related to

single ventricle. The Shone complex refers to discrete

arrhythmias. Idiopathic hypertrophic cardiomyopathy is

subvalvar aortic stenosis in conjunction with a parachute

an important potential cause of sudden cardiac death in

mitral valve, a stenosing ring

children.'28

coarctation of the aorta. Discrete subvalvar aortic stenosis

Chest radiographs of patients with muscular subaor­ tic stenosis may be normal or show manifestations of left

occurs with a

within the left atrium, and

6:1 male-to-female ratio.

Chest radiographs of young children with subvalvar

ventricular hypertrophy. The heart often has a somewhat

aortic stenosis are usually normal or show manifesta­

rounded configuration. With more severe, hemodynami­

tions of an associated cardiac anomaly. Older children

cally significant forms of subaortic stenosis, cardiomegaly

have nonspecific left ventricular hypertrophy. Poststenotic

occurs. The features are nonspecific, however, and are

dilation of the ascending aorta is an occasional finding.

identical to those of cardiomyopathy. If cardiac decompen­

Echocardiography, MR, and angiocardiography demon­

sation occurs, manifestations of congestive heart failure are

strate the localized area of narrowing in the subaortic por­

present.

tion of the left ventricle. There may be systolic preclosure

Echocardiography

of muscular

subaortic

stenosis

shows ventricular thickening, most prominent in the sep­

of the aortic valve. Mitral or aortic regurgitation can occur as well.

tum. There is abnormal positioning of the anterior mitral valve leaflet during systole. Abnormal mitral valve motion can also be demonstrated with angiocardiography or M R: systolic anterior motion of the anterior leaflet against the ventricular septum, resulting in outflow obstruction. Other angiocardiographic findings

in these patients

include

asymmetric septal hypertrophy, mitral regurgitation, and left ventricular hypertrophy.

Discrete Subvalvar Aortic Stenosis Pathology

Rad iology

Focal subvalvar narrowing

X-ray: ± ascending aorta dilation Echocardiography, M R: focal

�-���� � Rounded, slightly prominent j heart

- - - - - - - - - - - -- ·

M uscu lar Su baortic Stenosis Rad iology

Pathology

Septal thickening Outflow tract obstruction

I -----------X-ray: left ventricle hypertrophy ! ± Cardiomegaly i Echocardiography, M R: septal I thickening

Left ventricle hypertrophy

1

-- - -- - - -------

Congen ital Pul monary Stenosis Pulmonary Valve Stenosis With Intact Ventricular Septum The initial formation of the pulmonary valve is during the eighth week of gestation, occurring concomitantly with

Discrete Subvalvar Aortic Stenosis Discrete subvalvar aortic stenosis accounts for approxi­ mately

w%

of cases of congenital aortic stenosis. This

formation of the truncus arteriosus and aortic valve. Three tubercles arise in the lumen of the pulmonary artery and grow toward the center of the vessel. Tissue resorption causes subsequent thinning of the tubercles . Tissue resorp­

thin membranous diaphragm, a fibro­

tion also gives rise to the valve sinuses. Slightly before the

muscular ring, or (uncommonly) a broad fibromuscular

initial development of the pulmonary valve, the infundibu­

constriction. The clinical and hemodynamic effects of dis­

lum of the right ventricle arises from the proximal aspect of

crete subvalvar aortic stenosis are similar to those of val­

the bulbus cordis. Differentiation of the aortic arch occurs

lesion occurs as a

var aortic stenosis. Poststenotic dilation of the ascending

simultaneously. The sixth arch gives rise to the distal por­

aorta is common. The high velocity j et streaming from the

tion of the pulmonary artery. This vessel connects distally

stenotic area eventually damages the aortic valve, leading

to peripheral pulmonary arteries that develop from the

Chapter 11 Co ngenital H e a rt D i sease 373 pulmonary vascular plexus. The proximal communication is with the main pulmonary artery. There is a spectrum of developmental anomalies of the pulmonary valve. Most common (accounting for approxi­ mately 95% of all cases of valvar pulmonary stenosis) , is the presence of 3 partially fused leaflets that form a dome­ shaped valve with a small central orifice. In other patients, there is a 2-leaflet pulmonary valve, with partial fusion at the commissures. There is also a familial form of congeni­ tal dysplastic pulmonary valvar stenosis characterized by marked thickening of the cusps without fusion. The thick­ ening is a result of disorganized myxomatous tissue. The thickened valve cusps are immobile, resulting in obstruc­ tion despite a lack of fusion between the cusps. Dysplastic thickening of the valve cusps can also occur in patients without a family history. This valve morphology is pres­ ent in most patients with Noonan syndrome, although the clinical severity of pulmonary stenosis is usually mild in these children. Valvar pulmonary stenosis is sometimes accompanied by deficient development of the right ventricle and tricus­ pid valve, apparently as a secondary phenomenon. If severe obstruction of the pulmonary valve occurs early in gesta­ tion, the majority of venous return is diverted across the foramen ovale (and ejected by the left lateral ventricle) , thereby increasing the likelihood of hypoplasia of the right ventricle and tricuspid valve. With mild valvar obstruction or obstruction that develops later during gestation, the right ventricle and tricuspid valve are normal or only mini­ mally affected. In the newborn with pulmonic stenosis and an intact ventricular septum, the alterations in cardiac hemodynam­ ics largely depend on the severity of the obstruction and on the integrity of the right ventricle, tricuspid valve, and pul­ monary arteries. With moderate to severe valvar obstruc­ tion, the resultant right ventricular hypertension leads to tricuspid regurgitation, elevated right atrial pressures, and shunting into the left atrium. These patients are cyanotic; some or most of the pulmonary arterial fl ow is via a patent ductus arteriosus. This clinical situation is termed critical pulmonic stenosis. The features of critical pulmonic stenosis are similar to those of pulmonic atresia. These infants may develop severe cyanosis and cardiac collapse as the ductus arteriosus closes. In most neonates with pulmonic stenosis and an intact ventricular septum, the stenotic pulmonary valve allows sufficient antegrade pulmonary blood flow despite closure of the ductus arteriosus. If there is a patent inter­ atrial communication, there is no substantial right-to-left atrial shunting. Right ventricular hypertrophy occurs, however, as a consequence of the chronically increased pressure load. With the more-severe forms of pulmonary valvar obstruction, right ventricular decompensation may eventually occur, with manifestations of right-sided cardiac failure developing within a few months after birth. Clinical manifestations of right ventricular failure include rapid onset ofhepatomegaly and prominent pulsatile neck veins.

Right-to-left shunting through a previously asymptomatic interatrial communication leads to the development of cyanosis . Patients with more mild forms of pulmonic stenosis are usually asymptomatic, with the lesion detected because of a murmur. The murmur of pulmonic stenosis is an ejec­ tion systolic murmur that is best heard at the upper left sternal border. The murmur has a crescendo-decrescendo character. The intensity of the murmur diminishes during the Valsalva maneuver. Although some children with mild to moderate pulmonary valvar stenosis remain clinically stable over long periods , others have progressive disease as a result of failure of adequate enlargement of the valve orifice during growth and development. In addition, sec­ ondary right ventricular hypertrophy can sometimes exac­ erbate outflow obstruction.129 An important radiographic feature ofvalvar pulmonary stenosis with an intact ventricular septum is prominence of the main pulmonary artery. This is the result of postste­ notic dilation related to turbulent high velocity flow distal to the stenosis. The proximal portion of the left pulmonary artery is sometimes enlarged as well. This finding is pres­ ent in the majority of older children with valvar stenosis, but is unusual in infants and young children. Poststenotic dilation does not occur in patients with a dysplastic pulmo­ nary valve, since this form of pulmonic stenosis does not cause an ejection jet. Heart size is normal in most patients with valvar pul­ monic stenosis. The apex is rounded and slightly uplifted because of right ventricular hypertrophy. The right atrial border may be somewhat prominent, particularly in those patients with tricuspid insufficiency. In the absence of right-to-left atrial shunting, the peripheral pulmonary vas­ cularity is normal. The pulmonary vascularity is decreased if there is a right-to-left shunt. Echocardiography and angiocardiography of patients with pulmonary stenosis typically demonstrate a domed configuration of the valve. There is restricted systolic motion of the valve. Poststenotic dilation of the main pul­ monary artery is typical. Thickening of the right ventricular wall is common. Unless there is cardiac decompensation, the volume of the right ventricular cavity is usually normal. In some patients, there is dynamic infundibular narrowing during systole. Findings in patients with a dysplastic valve include marked thickening of the cusps, poor mobility of the valve, a small annulus, and (in some patients) a hypo­ plastic main pulmonary artery. As with other imaging studies, M RI of patients with pulmonary stenosis shows poststenotic dilation of the main pulmonary artery and left pulmonary artery. Cine studies demonstrate turbulent flow at and beyond the valve. MR usually allows characterization ofvalve morphol­ ogy with regard to thickening or asymmetry. The major findings with angiocardiography include a thickened irreg­ ular pulmonary valve, a domed configuration of the valve, poststenotic dilation, right ventricular hypertrophy, and infundibular narrowing during systole.'3°

374 Part 2 The Ca rd iovascu l a r System Pulmonary Stenosis With I ntact Ventricular Septum Pathology

Rad iology

Poststenotic di lation Promi nent main pul monary artery Right ventricu lar Uplifted cardiac apex hypertrophy No s h u nting Normal p u l monary vascu larity

Isolated Infondibular Pulmonary Stenosis The most common instance of infundibular pulmonic obstruction occurs as a component of tetralogy of Fallot, in which a VSD is the dominant feature. Isolated infundibular pulmonary stenosis is a rare anomaly that lacks a coexistent VSD. The hemodynamic consequences and clinical mani­ festations of isolated infundibular narrowing are identi­ cal to those of valvar pulmonary stenosis. Radiographs of children with this anomaly are often normal. Substantial chamber dilation is not a feature of this lesion. The pulmo­ nary vasculature is normal or diminished, depending on the severity of the obstruction. Poststenotic dilation of the pulmonary artery does not occur. Cardiac MRI examination shows right ventricular hypertrophy and persistent narrow­ ing of the infundibulum.

A

Subinfondibular Pulmonary Stenosis Stenotic lesions in the body of the right ventricle are rare. These can occur as isolated lesions or in association with a VSD. Potential causes include hypertrophy of the inter­ ventricular septum, anomalous muscle bundles, and mem­ branes arising from the tricuspid valve or right atrium. With marked stenosis, a double-chamber right ventricle occurs; this term is most appropriate for stenosis caused by anomalous muscle bundles. The radiographic appearance of subinfundibular pul­ monary stenosis is similar to that of infundibular pulmo­ nary stenosis. Heart size is usually normal or minimally prominent. The pulmonary vascular pattern is usually nor­ mal, unless there is an associated VS D . A VSD distal to the obstruction is common in patients with anomalous right ventricular muscle bundles (Figure 1 1 -53) . Poststenotic dilation of the main pulmonary artery does not occur. Cross-sectional imaging studies show the subinfundibular narrowing. In patients with thickening of the ventricular septum, encroachment may occur on both the right ven­ tricular outflow tract and the left ventricular outflow tract.

Pulmonary Artery Stenosis Stenoses can occur at any point within the pulmonary arterial system. Obstructing lesions can be single or mul­ tiple, and localized or diffuse. There are long hypoplastic segments in some patients, as in children with Alagille syndrome.

B

Figure 1 1-53 Subinfu ndibular pulmonary stenosis caused by anomalous right ventricular muscle bundles. This is a 6-month-old infant with an asymptomatic murmur. A, B. Anteroposterior and lateral chest radiographs show mild cardiomegaly, with right-heart prominence. There is mild pulmonary vascular prominence because of a superimposed ventricular septal defect. The radiographic features are nonspecific.

Chapter 11 Congen ital H e a rt D i sease Supravalvar pulmonic stenosis most often occurs as a constricting ring. This lesion can occur in association with rubella syndrome. Rubella syndrome can also result in peripheral pulmonary arterial stenosis. The clinical findings in patients with supravalvar pulmonic stenosis are similar to those of subvalvar pulmonic stenosis. The diagnosis is usually established by echocardiography or angiocardiography. Stenosis or hypoplasia of a major branch pulmonary artery is often associated with hypoplasia of the portion of the lung supplied by that vessel. Chest radiographs frequently demonstrate an oligemic appearance of the involved lung, and the ipsilateral central pulmonary vascu­ lar structures are noticeably small. Occasionally, a branch pulmonary artery stenosis leads to radiographically demon­ strable poststenotic dilation. Differential lung perfusion in these patients can be accurately quantified with lung per­ fusion scintigraphy. Assessment of the stenotic lesions is with angiocardiography, CT angiography or M R I .

CYANOT IC, DECREASED PULMONARY VASCULAT URE Most of the cardiac lesions that cause cyanosis and decreased pulmonary vascularity involve obstruction of the right heart in conjunction with a right-to-left shunt. Right-side obstructions without a shunt are typically acya­ notic and have normal pulmonary vascularity. Right-sided obstructions occur from the level of the systemic veins to the pulmonary arteries (Table 1 1 -14) .

Tetralogy of Fallot Tetralogy of Fallot refers to the combination of an overrid­ ing aorta, VSD, pulmonary stenosis (or atresia) , and hyper­ trophy of the right ventricle. Tetralogy of Fallot is the most common cyanotic congenital heart disease, and accounts for approximately 10% of all congenital heart defects. The fre­ quency oftetralogy of Fallot in siblings of an affected patient is 2. 5%. Approximately 4% of the offspring of patients with tetralogy of Fallot have this anomaly. Extracardiac malfor­ mations that occasionally occur in association with tetral­ ogy of Fallot include cleft lip and palate, hypospadias, and skeletal anomalies. Tetralogy of Fallot can occur in a variety of malformation associations, including Apert, Goldenhar, Klippel-Feil, and DiGeorge syndromes, phenylketonuria, and the VACTERL and CHARGE associations. The common denominator of tetralogy of Fallot is conal maldevelopment, with anterior and leftward displace­ ment of the infundibular septum.131 There is hypoplasia of the right ventricular infundibulum, which causes superior and upward displacement of the crista supraventricularis, thereby narrowing the right ventricular outflow tract. The aorta is overriding and there is a perimembranous VSD. The size of the proximal aorta increases with the severity of the pulmonary arterial stenosis. The VSD is large and nonrestrictive.

375

Table 1 1 -14. Right-Sided Obstructive Lesions S ite of obstruction

Systemic vei ns

Ca rd i ovascu l a r lesion 1

Stenosis 1 Compress io �--- - - --- - -- ----- - - -­ Th rombosis Tu mor ·-· -----�g: · ;;.·;;� � ;) ·-Atrial tumor (e I - - - - - - -Thrombus Stenosis .....

Right atri um Tricuspid valve Right ventricle

.

· - - - - - -· -

-

-

--

-

..

Congenital hypoplasia Valvar pul monic stenosis Pu l monary atresia Subvalvar stenosis Right ventricular m uscle bands

Pulmonary arteries Peripheral p u l monic stenosis

Classic tetralogy of Fallot includes right ventricular outflow tract obstruction. Concomitant pulmonary valvar stenosis is present in approximately 90% of patients; the valve is bicuspid in approximately 6o%. In approximately 7% of patients with tetralogy of Fallot, there is pulmonary atresia. Obstruction can also occur within the proximal por­ tions of the pulmonary arteries; hypoplasia of one or both branches is an occasional finding. Approximately 5% of patients with tetralogy of Fallot have complete absence of the pulmonary valve leaflets, resulting in severe pulmonary regurgitation. Absence of the pulmonary valve can lead to aneurysmal dilation of the main pulmonary artery, which, in tum, causes compression of the main bronchi. A mirror image aortic arch occurs in approximately 25% of children with tetralogy of Fallot. This finding occurs more frequently in children with pulmonary atresia or high-grade stenosis. A right aortic arch accompanies tetral­ ogy of Fallot with pulmonary atresia in approximately half of patients. The aorta in these patients typically descends on the right and crosses to the left prior to passing through the diaphragm. Other potential associated cardiovascular lesions in patients with tetralogy ofFallot include ASD (10% of patients) , left superior vena cava that connects to the coronary sinus (5%) , and coronary artery anomalies (5%) . Rare associated anomalies include tricuspid insufficiency, double aortic arch, Ebstein malformation, partial anoma­ lous pulmonary venous connection, and mitral stenosis.

376 Part 2 The Card iovascu l a r System A maj or consequence of right ventricular outflow obstruction and an aorta that overrides a VS D is a right-to­ left shunt that produces cyanosis. The severity of right ven­ tricular outflow tract obstruction is the maj or determinant of the degree of cyanosis. Most often, cyanosis is relatively mild at birth and worsens gradually with age as the increas­ ing hypertrophy of the right ventricular infundibulum causes progressive increase in obstruction. When there is mild obstruction, the predominant shunt across the V S D may initially b e left-to-right. The maj or clinical manifesta­ tions in this situation are those of congestive heart failure; the onset of cyanosis is delayed until later in infancy. These patients frequently have characteristic "cyanotic spells . " These are episodes o f profound systemic hypoxemia pre­ cipitated by decreased pulmonary blood flow and increased right-to-left shunting across the V S D . The right ventricular outflow tract obstruction of tetralogy of Fallot causes a sys­ tolic murmur of moderate intensity. The murmur disap­ pears during cyanotic spells. Patients with tetralogy of Fallot and pulmonary valve atresia are dependent on a patent ductus arteriosus or systemic aortopulmonary collateral vessels for pulmonary blood flow. These patients have cyanosis at or soon after birth. The severity of cyanosis is largely dependent on the volume of blood flowing between the aorta and pulmonary circulation through collateral pathways. Occasionally, well­

Figure 1 1-54 Tetralogy of Fallot. There is an upturned cardiac apex in this cyanotic infant, producing a classic "boot-shaped" appearance. Additional findings include diminished pulmonary vascularity, a concave middle segment of the left-heart border, lack of a normal main pulmonary artery segment, and a right aortic arch. The lungs are hyperinflated.

developed collateral pathways lead to pulmonary overcircu­ lation and congestive heart failure. Chest radiographs typically show normal heart size in patients with tetralogy of Fallot. The shape of the heart, however, is abnormal. The cardiac apex is elevated and rounded because of right ventricular hypertrophy; an upturned apex is the most consistent radiographic finding of tetralogy of Fallot

(Figure 1 1 -54) .

The ascending aorta is

prominent and the pulmonary artery segment of the heart silhouette is concave. The right ventricular infundibulum often forms a slight bulge along the left upper heart bor­ der. The middle portion of the left heart border tends to be somewhat concave. The heart shape is frequently described

Tetralogy of Fallot Pathology

Rad iology

Right ventricu lar outflow obstruction Right-to-left s h u nt Right ventricle enlargement, rotation of the heart Small infundibulum

D i m i nished pul monary vascularity

as being boot shaped; more specifically, the shape is that of a wooden shoe (in French,

coeur en sabot) .

Most often, tetral­

ogy of Fallot results in diminished pulmonary vascularity

Right aortic arch (2 5%)

Boot-shaped heart Straight, upper-left cardiac border Right aortic arch

on chest radiographs. Both hilar and peripheral pulmonary vessels are small. Mild to moderate pulmonary overaeration is common. As noted above, the aortic arch is sometimes located on the right in children with tetralogy of Fallot.33 In patients with tetralogy of Fallot accompanied by pulmonary atresia or severe pulmonary stenosis, large

Echocardiography of tetralogy of Fallot shows the ventricular septum to be deficient below the aortic valve

(Figu re 1 1 -55) .

The anterior margin of the aorta projects

anterior to the interventricular septum and the dilated

systemic collateral vessels may alter the radiographic

ascending aorta overrides the V S D . The pulmonary valve

appearance. These collateral vessels frequently appear as

annulus is usually narrowed; valve leaflet thickening or a

fine reticular densities that lack the progressive peripheral

bicuspid valve may be present. The right ventricular wall

decrease in caliber that occurs with normal vessels . In addi­

is thickened. Doppler evaluation demonstrates the direc­

tion, the pattern produced by collateral vessels is usually

tion and magnitude of shunting through the V S D . Doppler

nonuniform, with some areas having engorged tortuous

studies may also demonstrate left-to-right shunting via a

vessels and others devoid of vascular markings. In some

ductus arteriosus or systemic collateral vessels.

patients , large collateral vessels cause impressions on the contrast opacified esophagus .

Although not required for most patients, M RI accu­ rately demonstrates the pathological anatomy of tetralogy

Chapter 1 1 Co ngenital H e a rt D i sease 377

Figure 1 1-55 Tetralogy of Fallot. Echocardiography demonstrates a perimembranous ventricular septal defect (arrow) . A, Ascending aorta; LV, left ventricle; RV, right ventricle.

A

Figure 11-56 Tetralogy of Fal lot and pulmonary atresia.

A. The aorta (A) overrides a VSD on this oblique sagittal MR image of a cyanotic 14-day-old infant. There is right ventricular

of Fallot. There is thickening of the right ventricular wall. Sagittal or oblique views show the overriding aorta and VSD (Figure 1 1 -56) . The major role for M RI in children with tetralogy of Fallot is for the detection of pulmonary artery abnormalities and the delineation of bronchial or other systemic collaterals. The main pulmonary artery and the proximal portions of the right and left pulmonary arteries are sometimes difficult to adequately evaluate with echo­ cardiography; these structures are well visualized on axial MR images, allowing accurate characterization of stenoses. In patients with absent pulmonary valve and aneurysmal dilation of the main pulmonary artery, M R or helical CT can be used to assess the character and severity of bron­ chial compression.132-136 Right ventriculography of patients with tetralogy of Fallot demonstrates: (a) concomitant opacification of the pulmonary artery (unless there is pulmonary atresia) and aorta; (b) narrowing of the infundibulum that is most pronounced during systole; (c) a small pulmonary annu­ lus; (d) stenosis of the pulmonary valve (90% of patients) ; (e) right ventricular hypertrophy and prominent trabecu­ lations; (f) pulmonary arterial stenoses (not present in all patients) ; (g) a subaortic VSD; and (h) overriding of the

B

hypertrophy. B. Collateral vessels (arrows) from the descending thoracic aorta supply the pulmonary circulation.

378 Part 2

The

Ca rd iovascu l a r System

A

8

Figure 11-57 Tetralogy of Fallot.

Lateral projection images of a right ventriculogram (A) . The image obtained during systole shows marked infundibular narrowing (arrow) . There is faint opacification of the aorta as a consequence of shunting of a small amount of contrast across

aorta

(Figure 1 1 -57) .

a perimembranous ventricular septal defect. B. During diastole, the severity of infundibular narrowing diminishes. There is a small pulmonary valve anulus (small arrow) . Contrast passes into the left ventricle via the VSD (large arrow) .

Injection of the left ventricle shows

M RI i s helpful for the evaluation o f selected patients

shunting across the perimembranous V S D and overriding

who have undergone surgical repair of tetralogy of Fallot. A

of the aorta

(Figure 1 1 -58) .

Aortography serves to accurately

assess pulmonary collateral supply

(Figu re 1 1 -59) .

residual V S D is demonstrated on M R as a signal void in the region of the patch. The presence and severity of pulmo­

The primary goal o f surgical therapy i n patients with

nary regurgitation can be assessed with velocity-encoded

tetralogy of Fallot is the provision of adequate pulmonary

cine M R . In patients with long-standing pulmonary regur­

circulation. In some patients, the repair is carried out in

gitation, M R shows right ventricular dilation and wall

a staged manner, with the initial treatment consisting of a

thickening. Flow volumes and wall motion abnormalities

systemic-to-pulmonary shunt (e.g., Blalock-Taussig shunt) .

can be assessed with cine MR. MR is particularly helpful

Definitive repair of tetralogy of Fallot includes placement of

for the characterization of pulmonary artery abnormalities

a transannular patch at the right ventricular outflow tract

in patients with tetralogy of Fallot, such as stenosis, occlu­ sion, or aneurysm formation. '3 8-14 2

and closure of the VS D with a pericardia! patch. Systemic­ to-pulmonary artery shunts are ligated or treated with transcatheter embolization. Potential complications of surgical repair of tetralogy of Fallot include residual V S D , outflow patch aneurysm,

Pul monary Atresia With Ventricu lar Septal Defect

and residual pulmonary insufficiency. Most patients have

Pulmonary atresia with V S D accounts for approximately

some degree of pulmonary valve incompetence, which is

2% of congenital heart disease. The clinical features and

associated with an elevated risk for arrhythmias and sud­

hemodynamics are similar to those of tetralogy of Fallot.

den death. Dilation of the right ventricle can result in

The anatomic alterations consist of a large perimembra­

reduced exercise capacity. Uncommonly, progression of

nous or infundibular V S D , main pulmonary artery atresia,

pulmonary regurgitation leads to deterioration of right ven­

underdevelopment of the right ventricular outflow tract,

tricular function and congestive heart failure. The presence

and overriding of the aorta. The length of the atretic seg­

of substantial pulmonary stenosis may be an exacerbating

ment of the pulmonary artery is variable between patients.

factor. These complications do not typically become mani­

This anomaly can occur in children with velocardiofacial

fest for many years after the original surgical repair. Some

syndrome or DiGeorge syndrome.

patients eventually need pulmonary valve replacement; this

Radiographs of infants with pulmonary atresia with

generally leads to reduced right ventricular dilation and improvement in systolic function.'3P3 7

V S D demonstrate mild cardiomegaly and absence of the main pulmonary artery segment

(Figure 1 1 -60) .

Cardiac

Chapter 1 1 Congenital H e a rt D i sease 379

A

Figure 11-58 Tetralogy of Fallot. A An anteroposterior right ventriculogram image shows a dilated right ventricle with prominent trabeculations. The infundibulum (arrow) is narrow. There is faint opacification of

enlargement is predominantly caused by dilation of the right ventricle and, to a lesser extent, the right atrium. The pulmonary vascular pattern varies between patients accord· ing to the nature of collateral flow. The pulmonary vascular pattern is asymmetric in some children with this anomaly. Approximately 5o% of individuals with pulmonary atresia and VSD have a dilated right-sided aortic arch. CT angiog­ raphy and MR angiography can be useful in these patients for delineating the intracardiac anatomy and the pulmo­ nary vascular supply.

Pul monary Atresia With I ntact Ventricu lar Septu m Pulmonary atresia with intact ventricular septum accounts for approximately 1% of all congenital heart anomalies. The prevalence is approximately 4 · 5 per 1oo,ooo live­ births. Although this is a rare lesion, it accounts for about one-quarter of infants who present with signs of cya­ notic heart disease on the first day of life. This anomaly is associated with a high mortality rate. Pulmonary atre­ sia with intact ventricular septum occurs with a slight male predominance. The pathogenesis of this lesion is unknown. '4 3·44 Pulmonary atresia with intact ventricular septum is nearly always accompanied by situs solitus and concor­ dant atrioventricular and ventriculoatrial connections.

B

a right aortic arch. B. Contrast injected into the left ventricle fills both ventricles because of a VSD subjacent to the overriding aorta.

There is no physiological communication between the right ventricle and the pulmonary arteries ; pulmonary perfusion is via the ductus arteriosus. An atrial commu­ nication (septal defect or patent foramen ovale) must be present for propagation of systemic venous return, both in utero and after birth. Most often, pulmonary artery development is essentially normal, except for proximal tapering of the main pulmonary artery adjacent to the atretic valve. There are myocardial abnormalities in most patients with pulmonary atresia and intact ventricular septum. The most common abnormalities of the right ventricle are hypertrophy and diminutive chamber size, although there is considerable variation between patients with regard to the size of this chamber. Up to 10% of patients with severe tricuspid valve regurgitation have a dilated right ventricle that has a very thin wall. Ischemia and fibrosis can further compromise the right ventricular myocardium in patients with pulmonary atresia and intact ventricular septum. Left ventricular abnormalities in these patients are related to volume overload, chronic ischemia, and mitral valve abnormalities. There is a spectrum of tricuspid valve dys­ plasia in patients with pulmonary atresia and intact ven­ tricular septum, ranging from severe stenosis to severe regurgitation. '45·'4 6 Coronary artery anomalies are present in about half of patients with pulmonary atresia and intact ventricular

380 Part 2 The Card iovascu l a r System

B A

Figure 11-59 Tetralogy of Fallot with left pulmonary artery atresia. A An anteroposterior radiograph of a cyanotic newborn shows an uplifted cardiac apex, absence of the pulmonary artery silhouette, a right arch, oligemic lungs, and hyperinflation. B. A right ventriculogram performed at 10 days of age demonstrates concomitant opacification of the aorta and pulmonary artery. The infundibulum is narrow (arrow) . There is no filling of the left pulmonary artery. C . An aortogram shows filling of the left pulmonary artery via a ductus arteriosus (arrow) that arises from the left brachiocephalic artery. There is a right arch with mirror image branching.

septum. Fistulas between the right ventricle and the coro­ nary arteries can occur when there is a thick-walled high­ pressure right ventricle. These patients sometimes have stenotic coronary artery lesions near the fistulas. In some patients with myocardial thickening, there are blind-ending fissures in the ventricular wall that fill during systole but do not communicate with the coronary arteries. Rarely, the proximal aortocoronary connections are completely absent and all coronary perfusion is supplied from the right ven­ tricular cavity via fistulas. Infants born with pulmonary atresia and intact ventric­ ular septum depend on retrograde flow through the duc­ tus arteriosus for pulmonary blood flow. Systemic venous return is dependent on right-to-left shunting at the atrial level. Therefore, all of these children are cyanotic. The sys­ temic oxygen saturation is predominantly determined by the volume of pulmonary blood flow. Closure of the duc­ tus arteriosus leads to acidosis, profound hypoxemia, and

c

hemodynamic collapse. Prostaglandin E infusion allows temporizing maintenance of ductal patency. Auscultation demonstrates a systolic murmur caused by flow through the ductus. In some patients, a pansystolic murmur is present due to tricuspid regurgitation. The radiographic features of pulmonary atresia with intact ventricular septum vary greatly between patients. At least some degree of right atrial prominence is usually present. In those children lacking tricuspid regurgitation, overall heart size is normal or only mildly prominent; the right ventricle is diminutive and the right atrium is only mildly enlarged. Substantial tricuspid regurgitation results in enlargement of the right ventricle and right atrium. Severe tricuspid regurgitation leads to massive cardiomeg­ aly, predominantly a result of dilation of the right atrium and right ventricle. Even those children who have normal cardiac size at birth usually have progressive and rapid car­ diac enlargement.

Chapter 1 1 Co ngenital H e a rt D i sease 381 Pul monary Atresia With I ntact Ventricular Septum Rad iology

Pathology

Figure n-6o Pulmonary atresia with ventricular septal defect. A chest radiograph of a 1-year-old child demonstrates cardiomegaly, uplifting of the cardiac apex, absence of the main pulmonary artery segment, and a right-sided aortic arch. There are asymmetric, generally decreased, pulmonary vascular markings.

The left cardiac border in patients with pulmonary atresia and intact ventricular septum usually has a rounded configuration due to volume overload of the left ventricle. The amount of flow through the ductus arteriosus deter­ mines the pulmonary vascular pattern. Diminished vascu­ larity is present in most infants , but others have a normal pulmonary vascular pattern. The pulmonary artery seg­ ment of the cardiomediastinal border is always concave. The left atrium is normal in size or only mildly enlarged because of diminished pulmonary venous return. The aor­ tic arch is nearly always on the left side in patients with pulmonary atresia and intact ventricular septum; when a right arch accompanies pulmonary atresia, a V S D is usu­ ally present. Echocardiography in the short axis view shows the imperforate pulmonary valve membrane in infants with pulmonary atresia and intact ventricular septum. There is lack of antegrade pulmonary blood flow on Doppler stud­ ies. There is retrograde flow through the ductus arteriosus to supply the pulmonary artery. The distal portions of the

Pulmonary atresia Tricuspid valve dysplasia Hypoplastic right ventricle, with thick wall Left ventricu lar vol ume overload, ischemia AS D, patent ductus a rteriosus Pulmonary atresia Severe tricuspid valve dysplasia with insufficiency Dilated right ventricle, with thin wall Dilated right atriu m Left ventricu lar vol ume overload, ischemia AS D, patent ductus a rteriosus Pulmonary atresia Restrictive AS D Tricuspid regu rgitation

, N ormal heart size i n itially, progress ive : cardiomegaly ! Right atrial , enlargement ; Diminished p u l monary vasculature !

! Right �e�tricular

: enlargement i Right atrial , enlargement ' Marked cardiomegaly : Diminished pul monary : vasculature i····

Right atrial : enlargement Diminished pul monary . vasculatu re

•

The maj or findings of puhnonary atresia with an intact ventricular septum on angiocardiography and MR include atresia of the pulmonary valve, a competent tricuspid valve, and right ventricular hypertrophy. As described above, the size of the right ventricle varies between patients; most often, the chamber is small. Angiocardiography sometimes demonstrates retrograde filling of the coronary arteries from right ventricular sinusoids . Surgical

intervention in children with puhnonary

atresia and intact ventricular septum serves to augment pulmonary blood flow and encourage development of the right ventricle by establishing continuity between the right ventricle and the pulmonary artery. The procedures include construction of a systemic-to-pulmonary artery anastomo­ sis. The surgical approach is tailored with consideration of the severity of right ventricular hypoplasia and tricuspid regurgitation. A recently introduced option for the treat­ ment or palliation of infants with this anomaly is radio­ frequency-assisted perforation and balloon dilation of the atretic valve .48·49

main right and left pulmonary arteries are usually normal in size. Cross-sectional images, as well as Doppler analysis, confirm absence of a VSD. The size of the right ventricle and the anatomy of the tricuspid valve are important prog­

Tricuspid Atresia Tricuspid atresia refers to absence of the tricuspid valve

nostic and presurgical factors on echocardiography. Also,

and the inflow portion of the right ventricle. This anomaly

the adequacy of the interatrial communication should be

occurs in approximately 1 in 18 ,ooo livebirths and accounts

assessed.47

for approximately

1% of congenital heart disease. Although

382 Part 2 The Ca rd iovascu l a r System a rare lesion, tricuspid atresia is an important cause of cya­

decreased pulmonary vascularity. Heart size ranges from

nosis and death in the neonatal period. Approximately 20%

normal to moderately prominent. Some degree of right

of children with tricuspid atresia have extracardiac anoma­

atrial enlargement is typical; a very prominent right atrium

lies, most often involving the GI or musculoskeletal sys­

can occur if there is a restrictive A S D . The prominent right

tems. Tricuspid atresia occurs in association with trisomy

atrium results in a large convexity along the right-heart bor­

21, asplenia, cat-eye syndrome, and Christmas disease.'5°

der. Moderate dilation of the left atrium is common. On

Tricuspid atresia is urliformly associated with other

the frontal proj ection, the left-heart border usually has a

cardiac anomalies . In all forms , however, the tricuspid valve

rounded contour because of enlargement and hypertrophy

is absent and the inflow portion of the right ventricle is

of the left ventricle. The pulmonary artery segment of the

hypoplastic. There is no communication between the right

heart border is usually flat or concave. In tricuspid atre­

atrium and the right ventricle. The right ventricle is hypo­

sia patients with pulmonary atresia and normally related

plastic and the conus is usually the only identifiable por­

great vessels, flow through the ductus causes slight dila­

tion. If the ventricular septum is intact, the right ventricle

tion of the ascending aorta. Pulmonary vascular congestion

is rudimentary or completely absent. In this circumstance,

is present in those patients who have a patent pulmonary

the pulmonary valve and pulmonary trurlk are atretic and

valve and large septal defects in the atrium and ventricle

there is an obligatory interatrial communication. If there is

(Figure 1 1 -61 ) . 9

a large V S D , right ventricular development is more com­ plete, the right ventricular sinus is present, and the pulmo­

The radiographic features

of tricuspid atresia in

patients with transposition also vary with the degree of pul­

nary arteries are enlarged. The only outlet from the right

monary outflow obstruction. Hemodynamically significant

atrium is via an ostium secundum ASD. A left-sided mitral

pulmonary obstruction is less common in these patients;

valve provides communication between the morphological

therefore, the pulmonary vascular pattern is often normal

left atrium and left ventricle. The left ventricle is dilated

or increased. There is no visible pulmonary artery segment

as it receives the entire systemic and pulmonary venous

of the cardiomediastinal contour, and the upper mediasti­

return.' 5'

num may appear narrowed. The heart is enlarged because

The great vessels are normally related in

70% to 8o%

of dilation of the left ventricle, left atrium, and right atrium.

of children with tricuspid atresia. D-transposition is pres­ ent in approximately

20% to 30%. Approximately 3% of

patients with tricuspid atresia have L-transposition of the great arteries . These anomalies are further characterized into

Tricuspid Atresia

3 subtypes: (a) intact ventricular septum and pulmo­

nary atresia, (b) a small V S D and pulmonary stenosis , and

Path ology

Rad i o l ogy

(c) a large ventricular septal detect without pulmonary ste­

Left ventricu lar vol ume overload Elevated right atrial pressure Pulmonary stenosis or atresia I ntact septum or small VS D (Patent pul monic valve, large VS D)

Cardiomegaly, rou nded left­ heart border Right atrial bulge along the right-heart border Small main pulmonary artery D i m i n ished pul monary vascularity (N ormal or increased pul monary vascu larity)

nosis. Only approximately

5% of patients with tricuspid

atresia have a right-sided aortic arch.'52 About half of infants with tricuspid atresia present dur­ ing the first day of life with cyanosis and a heart murmur. The diagnosis is made within

2 months of life in 85% of

patients . Cyanosis is present in most of these children, and is particularly prominent in those with pulmonary atresia or valvar pulmonary stenosis. Infants with severe pulmo­ nary outflow obstruction are dependent on patency of the ductus arteriosus for blood flow to the lungs . Closure of the ductus leads to profound hypoxemia and acidosis. Death ensues unless there is prompt therapeutic intervention.

- - - -- - -- -

Those patients with unobstructed pulmonary blood flow and a large V S D may present with manifestations of con­ gestive heart failure. This clinical feature occurs in approxi­

Echocardiography of tricuspid atresia shows no com­

mately 10% of patients, and is more common in those with

munication between the right atrium and the right ven­

transposition. The onset of clinically apparent heart failure

tricle. There may be a small impression at the site of the

and pulmonary edema correlates with progressive decrease

atretic tricuspid valve. There is an echogenic band, pro­

in pulmonary vascular resistance that allows greater pul­

duced by the fibrofatty tissue of the atrioventricular groove,

monary blood flow.

between the muscular floor of the right atrium and the

An important determinant of the radiographic appear­

ventricular mass. Echocardiography provides information

ance of tricuspid atresia is the presence or absence of,

concerning the size of the associated A S D and the flow

and severity of, pulmonary outflow obstruction. The most

characteristics at the interatrial communication. The flow

common form of tricuspid atresia has normally related

characteristics through the pulmonary valve and ductus are also evaluated. '5 3·'54

great vessels and pulmonary stenosis; therefore, there is

Chapter 1 1 Co ngenital H e a rt D i sease 383

A

Figure 1 1-61 Tricuspid atresia with a patent pulmonary valve, normally related great vessels, a large ASD, and a large VSD. A, B. There is cardiomegaly, with prominence of the right atrium. Left atrial enlargement causes elevation of the left main

With angiocardiography, injection into the right atrium of the patient with tricuspid atresia shows lack of filling of the right ventricle. There is prompt opacification of the left atrium. Because of slow fl ow, contrast often refluxes into the hepatic veins and inferior vena cava. Left ventriculog­ raphy allows assessment of an associated VSD. Contrast shunted through the VSD opacifies the hypoplastic right ventricle. As with other imaging techniques, the characteristic M RI finding of tricuspid atresia is absence of a right atrio­ ventricular connection. Most often, axial images show a solid bar of fat and muscle interposed between the right atrium and ventricle (within the atrioventricular groove) . Occasionally, there is an imperforate tricuspid valve, appearing as a fibrous band. Cine images show no flow at the expected location of the tricuspid valve. The size of the right ventricle in patients with tricuspid atresia varies according to the characteristics of the VSD and pulmonary outflow obstruction. The VSD is considered to be restric­ tive if its diameter is less than the diameter of the pul­ monary annulus in a patient with normally related great arteries, or less than the diameter of the aortic annulus in a patient with D-transposition. For accurate measurement of the VSD, the imaging plane should be perpendicular.155 The initial surgical approach for tricuspid atresia in infants with pulmonary stenosis or atresia usually consists of the creation of a systemic-to-pulmonary artery shunt. Those with increased pulmonary flow can be treated with

B

bronchus on the frontal view. There is a rounded left-heart border. Pulmonary vascular congestion is present. Clinically, this z-month-old child had congestive failure and was acyanotic.

pulmonary artery banding. At about 1 year of age, a Fontan procedure is usually performed. Systemic venous blood is thereby rerouted to the pulmonary circulation, bypassing the right ventricle. Success of this procedure requires a rela­ tively low mean pulmonary artery pressure and low pulmo­ nary vascular resistance. MR examinations are sometimes helpful postoperatively to evaluate the integrity of the shunt and to detect complications.156

Ebstei n Anomaly Ebstein anomaly is an uncommon congenital heart defect that is due to anomalous development of the tricuspid valve. This lesion accounts for approximately 0.5% to 1.0% of patients with congenital heart disease. There is a strong association with maternal oral lithium therapy during pregnancy. Ebstein anomaly is an important diag­ nostic consideration for a cyanotic newborn with massive cardiomegaly. 9 The major pathological feature of Ebstein anomaly is dysplasia of the tricuspid valve. The anterior leaflet is usually attached at the normal location, but it is often enlarged and malformed. The distal leaflet may attach to portions of the right ventricular apex, abnormally placed chordae, or a moderator band. The tricuspid valve annu­ lus is enlarged and is sometimes displaced inferiorly. There is displacement of the tricuspid valve leaflets into the right ventricle.

384 Part 2 The Card iovascu l a r System The anomalous tricuspid valve of Ebstein anomaly causes division of the right ventricle into 2 components: a dilated, thin-walled proximal portion and a more distal com­ ponent that has diminished pumping capacity. Substantial dysfunction of the right ventricle occurs, although there is a spectrum of severity among patients. The outflow tract typically performs the majority of right ventricular pump­ ing function. The degrees ofleaflet displacement and right ventricle enlargement also vary widely between patients. The pulmonary trunk is usually normal or small.'5M8 Left ventricular function in patients with Ebstein anomaly is usually normal. Bulging of the ventricular sep­ tum as a result of the increased volume of the right side of the heart, however, can cause diminished diastolic volume of the left ventricle. A patent foramen ovale or secundum ASD is present in most patients with Ebstein anomaly. Other potential associated cardiac lesions include pulmo­ nary stenosis or atresia, VSD, mitral stenosis, tetralogy of Fallot, and corrected or partial transposition of the great vessels.'59 The tricuspid valve leaflets are derived from both the right ventricular myocardium and the atrioventricular endocardial cushions. The anterior leaflet develops first, arising from the mesenchyme surrounding the atrioven­ tricular orifice. The posterior and septal leaflets develop later through the formation of a diverticulum and under­ mining of the myocardium. Ebstein anomaly may be a result of failure of proper undermining of the myocardium, leaving the septal and posterior valve leaflets and the distal portion of the anterior valve leaflet either low within the right ventricle or adherent to the right ventricular walls. The different timing and mechanisms of formation of the tricuspid valve leaflets likely explain the variation in sever­ ity of involvement of the leaflets.'58,,6o In keeping with the spectrum of anatomic abnor­ malities of Ebstein anomaly, there is substantial variation between patients with regard to the clinical manifesta­ tions. Severely affected infants may succumb to congestive heart failure. Individuals with a mild form of the anom­ aly may be asymptomatic. Common signs and symptoms include fatigue, dyspnea, cyanosis, a systolic murmur of tricuspid regurgitation, and a fixed split second heart sound. Arrhythmias and conduction disturbances occur in approximately 20% to 40% of patients; the most common conduction abnormalities are Wolff-Parkinson-White syn­ drome and right bundle-branch block.'6' In utero, the incompetent tricuspid valve results in diversion of systemic venous return through the foramen ovale into the left heart. The tricuspid regurgitation can cause fetal heart failure. After birth, the severity of right­ to-left shunting at the atrial level is the major determi­ nant of the degree of cyanosis and hypoxemia. Elevation of right atrial pressure is a result of any combination of tricuspid stenosis, tricuspid insufficiency, pulmonary vas­ cular resistance, decreased right ventricular compliance, and a restrictive interatrial communication. In the neona­ tal period, high pulmonary vascular resistance increases

right ventricular afterload, thereby exacerbating tricuspid regurgitation. Some hypoxic infants with Ebstein anomaly are dependent on the patent ductus arteriosus for pul­ monary blood flow; ductal closure initiates worsening of hypoxemia. In those infants with restrictive flow through the interatrial communication, right-heart failure and hep­ atomegaly are prominent features . Infants with less-severe tricuspid stenosis and regurgitation have less-prominent right-to-left shunting and cyanosis. The decrease in pul­ monary vascular resistance that occurs after birth leads to diminished right ventricular afterload and decreased sever­ ity of tricuspid regurgitation. This results in improvement in arterial oxygen saturation and lessening of congestive heart failure. The radiographic findings of Ebstein anomaly range from normal to massive cardiomegaly (Figure 1 1 -62) . The most common pattern includes diminished pulmonary vascularity and moderate to severe cardiomegaly. Heart enlargement is predominantly a result of dilation of the right atrium and right ventricle; right atrial enlargement is the most consistent radiographic feature of Ebstein anom­ aly. There is often a bulge along the upper left cardiac bor­ der because of elevation of the right ventricle and dilation of the right ventricular outflow tract. The main pulmonary artery segment of the cardiac contour is absent, and the aortic knob is small. This combination of findings often results in a squared or boxlike appearance of the cardiac sil­ houette. Left atrial enlargement is not a feature of Ebstein

Figure n-62 Ebstein anomaly. There is massive cardiomegaly on this chest radiograph of a cyanotic infant. The aorta is inconspicuous. There is diminished pulmonary vascularity.

Chapter 11 Co ngenital H e a rt D i sease 385 anomaly. Ebstein anomaly is the only cyanotic cardiac mal­

the heart. Each atrium, therefore, appears to empty into the

formation in which both the aorta and the pulmonary trunk

contralateral ventricle. Most patients with crisscross heart

are smaller than normal.33

have hypoplasia of the tricuspid valve and right ventricle, a V S D , pulmonary stenosis, and abnormal ventriculoatrial alignments (either great vessel transposition or double­ outlet right ventricle) . Consequently, cyanosis during the

Ebstein Anomaly

neonatal period is typical. Cris scross heart accounts for less

Pathology

Rad iology

Tricuspid regu rgitation Tricuspid stenos is Enlarged right ventricle outflow tract Right-to-left shunt

M arked right atrial dilation Right ventricu lar enlargement Box-like heart

.. ... - .. .... - - - - - -- ·

D i m i n i shed pul monary vascularity

than

0 .1% of congenital heart defects .

The diagnosis of cris scross heart is by echocardiogra­ phy, catheter angiography, or M R. The right ventricle is superior to the left ventricle. There is a horizontal orien­ tation of the ventricular septum. The tricuspid orifice is small. A narrow elongated right ventricular inflow tract crosses from right to left between the infundibulum and the right atrium. Flow from the left atrium to the left ventricle is in a posterior to anterior direction. In most patients, visceroatrial situs is normal and atrioventricular connections are concordant. Dextrocardia is an occasional

E chocardiography of Ebstein anomaly shows left­

finding. i 6s, t 66

ward and inferior displacement of the septal and po ste­ rior leaflets of the tricuspid valve . This is best visualized on the parasternal short axis view and the apical 4-cham­

CORONARY ARTERY ANOMALIES

ber view. The proximal attachment of the anterior leaflet

Anomalies of the coronary arteries include variation in the

of the tricuspid valve is usually normal, but the leaflet is enlarged and has a sail-like configuration. Observation of the position of the atrioventricular groove allows esti­ mation of the severity of displacement of the septal and po sterior leaflets. There is usually diminished mobility of the septal leaflet.1 6 2 MRI of Ebstein anomaly shows the normal proximal attachment and faulty distal attachment of the anterior tri­ cuspid leaflet. The septal and posterior tricuspid leaflets are either not visible or are displaced. The anomalus valve results in an anatomically atrialized chamber of the right ventricle. There is enlargement of the right atrium. The pumping outflow tract of the right ventricle is markedly dilated and the compressed trabecular portion is small. The aorta and pulmonary artery are smaller than normal. Cine MR serves to quantifY the chamber size and ej ection frac­ tion of the right ventricle.16J.164 The surgical approach to Ebstein anomaly is tai­ lored according to the patient-specific morbid anatomy. Surgical techniques for these patients include plication of the enlarged right ventricle and creation of a monocuspid valve, creation of a bileaflet valve with displaced leaflet reat­ tachment, restoration of the mobility of adherent leaflets, or prosthetic valve placement. The important variables that require preoperative documentation include leaflet size and location, annulus and atrial size, and right ventricular function.

Crisscross H eart Crisscross heart is a rare anomaly in which there is cross­ ing of the long axes of the atrioventricular valves , rather than the normal parallel orientation. The ventricles appear twisted about their long axes, with fixation at the base of

number of vessels, congenital fistula, variation in vessel size, anomalous origin, and anomalous course Congenital

(Table 1 1 -1 5) .

coronary artery anomalies are present in

Table 1 1-1 5. Coronary Artery Anomalies

Variation in n u m ber

Single coronary artery Dupl ication ' Separate origin of right con a I branch �Separate origins of left circumflex and left anterior descending a rteries Coronary a rtery atresia Variation in size Congenital ectasia or aneurysm Segmental hypoplasia ic� ng; nital stenosis Congenital ostial stenosis - - -Congenital fistula -:1 Myocard ial bridgi ng Anomalous cou rse Coronary crossing ---- - ----�,- --Anomalous From pul monary artery origi n From aorta From systemic a rtery From opposite or noncoronary sinus From opposite coronary a rtery •

- - - - · -- - - - - -----

- -- --

- - �--- --

·

386 Part 2 The Card iovascu l a r System approximately 1% of the population. The clinical spectrum ranges from "malignant" anomalies that cause symptoms during infancy or carry a substantial risk for myocardial ischemia and sudden death later in life to "benign" anoma­ lies that are generally of no clinical consequence. The most important hemodynamically significant coronary artery anomalies are anomalous origin of a coronary artery from the pulmonary artery, an anomalous course of a coronary artery between the pulmonary artery and the aorta, coro­ nary artery origin from an opposite or noncoronary sinus of Valsalva, myocardial bridging, and congenital coronary artery fistula. The most common clinical consequence of a coro­ nary artery anomaly is fixed or episodic myocardial isch­ emia. Sudden death is a common initial presentation of an ectopic coronary artery origin. Many patients , how­ ever, have various preceding clinical manifestations of the anomaly, such as chest pain or syncope. Coronary artery anomalies account for approximately 20% of car­ diovascular deaths in athletes. Approximately 6o% of individuals with an anomalous left coronary artery aris­ ing from the right sinus die before the age of 2 0 years , usually in conjunction with vigorous exercise. Some coro­ nary artery anomalies have clinical consequences other than myocardial ischemia; for example, volume overload or bacterial endocarditis because of a coronary fistula. Coronary MR angiography and multidetector CT angi­ ography are the most useful noninvasive imaging tech­ niques for the detection and characterization of coronary artery anomalies .167-17°

Ischemia and hypoperfusion in the distribution of a left coronary artery that has an anomalous origin can lead to a myocardial infarct. Manifestations of myocardial failure most often become clinically evident between 2 weeks and 6 months of age. Approximately 90% of untreated infants die in the first year of life. The initial clinical features may be nonspecific: tachypnea, increased respiratory rate, and poor feeding. Some patients are inconsolable and have pal­ lor and sweating. Auscultation may demonstrate a mitral insufficiency murmur. Some patients with anomalous ori­ gin of the left coronary artery have sufficiently developed collateral vessels to allow relatively normal left-heart func­ tion. Symptoms in these patients sometimes do not occur until adolescence or adulthood. Most infants with anomalous origin ofthe left coronary artery have marked cardiomegaly on chest radiographs as a result of left-heart failure. There is enlargement ofboth the left ventricle and left atrium. Pulmonary vascular conges­ tion and pulmonary edema are often present. Pneumonia is a common complication. The radiographic features are similar or identical to those of infants with myocarditis, endocardial fibroelastosis, or cardiomyopathy.

Anomalous Origin of the Left Coronary Artery From the Pul monary Artery Pathology

'

Rad iology

D i m i nished left coronary Cardiomegaly artery pressure --.Left ventricu lar ischem ia Pulmonary vascular congest1on Pulmonary edema .----

Anomalous Origin of the Left Coronary Artery From the Pu l monary Artery Anomalous origin of the left coronary artery from the pul­ monary artery (Bland-Garland-White syndrome) is a rare congenital malformation. This lesion accounts for 0.25% to 0.5% of congenital heart disease. The prevalence is approximately 1 in 30o,ooo livebirths. Anomalous origin of the left coronary artery from the pulmonary artery is associated with myocardial ischemia and sudden death in childhood. Anomalous origin of the coronary artery usually is an isolated lesion. Cardiovascular abnormalities that are occasionally associated with this anomaly include patent ductus arteriosus, VSD, trurlcus arteriosus, and tetralogy of Fallot.'7l-l73 In the fetus, pressures and oxygen saturations are similar in the aorta and pulmonary arteries. Therefore, there is no substantial compromise in left-heart perfusion and oxygenation via the anomalous left coronary artery. When pulmonary arterial pressure diminishes after birth, the pressure within the left coronary artery drops precip­ itously. The right coronary artery has a normal origin in these patients, and blood flows from the higher-pressure right coronary artery system into the left coronary artery via collateral pathways. Therefore, a small volume left-to-right shunt occurs.

·

----

Echocardiography o f patients with anomalous origin of the left coronary artery shows marked left ventricular and left atrial enlargement. The right coronary artery is promi­ nent. There is diminished contractility of the left ventricle. Mitral insufficiency is common; this is most likely related to dilation of the valve ring or papillary muscle infarction. Most patients have poor left ventricular myocardial contrac­ tility, similar to the findings of dilated cardiomyopathy.'74 Aortography and CT angiography of anomalous origin of the left coronary artery show absent left coronary artery filling on initial images and late visualization because of col­ lateral filling via the right coronary artery. There is enlarge­ ment of the right coronary artery. Pulmonary angiography usually allows direct visualization of the left coronary artery arising from the pulmonary artery. If there is retrograde flow in the left coronary artery because of shunting from the right coronary artery, a jet of unopacified blood extends into the pulmonary artery at the orifice of the anomalous vessel. As with echocardiography, the other features of this anomaly include left ventricular dilation, poor left ventricu­ lar function, and mitral insufficiency.

Chapter 11 Co ngenital H e a rt D i sease 387 artery arises from the ascending aorta above the sinus of

Anomalous Origin of the Left Coronary Artery From the Aorta

Valsalva.'74·'79-' 8'

There are rare instances in which the left coronary artery

H igh Takeoff of a Coronary Artery

arises from an anomalous site in the aorta. The most com­ mon site is the right sinus ofValsalva. There are 4 common pathways of a left coronary artery in this situation: between the aorta and the pulmonary artery (interarterial) , ret­ roaortic, prepulmonic, and septal. An interarterial course is present in up to 75% of these patients ; this anatomy is associated with a high risk for angina pectoris, syncope, or sudden death. The diagnosis of anomalous origin of the left coro­ nary artery should be suspected in an adolescent or young adult who has exercise-related ischemic symptoms and a positive stres s electrocardiogram. Some patients suffer sudden death despite experiencing no prior symptoms. The cause of ischemia in these patients can be compres­ sion of an intramural segment of the coronary artery and/ or compression because of an anomalous course of the vessel between the aorta and the main pulmonary artery. In addition to compression, anomalous coronary arteries are susceptible to angulation and stretching or kinking during exercise. The diagnosis of anomalous aortic ori­ gin of the left coronary artery is established with echo­ cardiography, coronary arteriography, CT angiography, or M R.'7s-q8 Anomalous origin of the left coronary artery can also occur from the noncoronary (posterior) sinus. This varia­ tion usually is of no clinical significance when occurring in an otherwise normal heart. This anomaly is sometimes associated with transposition of the great arteries .

Origin of either the right coronary artery or the left coronary artery from an abnormally high location in the aorta usu­ ally is of no clinical consequence. The definition is origin of the vessel at a point above the junctional zone between the sinus ofValsalva and the tubular part of the ascending aorta.

Myocard ial Bridging of a Coronary Artery Myocardial bridging of a coronary artery is a developmen­ tal variation, with a prevalence of up to 86% at autopsy. This refers to passage of a portion of an epicardial coronary artery through the myocardium. Myocardial bridges most often involve the left anterior descending artery (usually in the middle segment) . Bridging of smaller left ventricular branches can also occur. There is compression of the ves­ sel during systole; the effect is greatest with deep bridges . Because most coronary flow occurs during diastole, myo­ cardial bridging is usually of no clinical consequence. However, there are rare instances of ischemia, angina, acute heart failure, arrhythmia, or sudden death. Symptoms may relate to diastolic compression of the vessel. Patients with hypertrophic cardiomyopathy are at particular risk for symptoms, a result of accentuated compression by the thickened myocardium. Multidetector row CT angiography is the procedure of choice for the detection of myocardial bridging. Comparison of images obtained during systole and diastole is essential for the diagnosis.182-184

Si ngle Coronary Artery

Anomalous Origin of the Right Coronary Artery

With the single coronary artery anomaly, a single vessel

Anomalous origin of the right coronary artery from the

patients with single coronary artery have an associated car­

supplies the entire myocardium. Approximately 40% of

pulmonary artery is a rare, clinically benign entity. This

diac anomaly, such as transposition of the great vessels,

anomaly generally is not associated with myocardial dys­

truncus arteriosus, tetralogy of Fallot, bicuspid aortic valve,

function, as the portions of the right ventricular myocar­

or coronary arterial fistula. The prevalence of this anomaly

dium that are supplied by this vessel have low intramural

is approximately o . o4%.'73·1ss

tension and the pulmonary arterial pressure transmitted

Single coronary artery comprises a spectrum that

through the anomalous vessel is sufficient for adequate

ranges from an asymptomatic normal variation to substan­

perfusion. These patients generally do not suffer manifes­

tial perfusion deficiency that is associated with angina pec­

tations of myocardial ischemia.

toris, myocardial infarction, or sudden death. The origin

Anomalous origin of the right coronary artery from the

of a single coronary artery is above either the right aortic

left sinus ofValsalva or proximal aspect of the left coronary

cusp or left aortic cusp. Because of the anomalous proxi­

artery sometimes is accompanied by symptomatic narrow­

mal portion of the vessel, at least some branches must fol­

ing. The initial course of the right coronary artery in these

low abnormal courses to reach their distributions within

patients is between the aortic root and the pulmonary trunk

the myocardium. In those instances in which an impor­

(i. e . , interarterial) , resulting in the potential for compres­

tant vessel follows an anomalous course between the pul­

sion. Up to 3 0 % of untreated patients with this anomaly

monary artery and aorta, compression can cause serious

suffer sudden cardiac death. The vessel sometimes has an

hemodynamic consequences . Even in those patients with­

acute angle near the orifice. In addition, there is often an

out compression or stenosis, the presence of a single coro­

anomalous slit-like ostium that is susceptible to narrow­

nary artery can interfere with cardiac surgery.

ing as the aorta dilates during exercise. Myocardial bridg­

Chest radiographs of patients with single coronary

ing can occur in these patients. Rarely, the right coronary

artery are normal, unless there is myocardial ischemia

388 Part 2 The Ca rd iovascu l a r System and congestive heart failure. The anomalous vessel can be evaluated with echocardiography and, most accurately, with angiography. MR angiography and CT angiography are noninvasive options for visualizing coronary artery anatomy in older children and adults.

Coronary Artery Anomalies Associated With Congen ital Heart Disease A variety of coronary artery anomalies occur in associa­ tion with other cardiac malformations. The coronary artery lesions sometimes complicate the hemodynamic effects of the underlying malformation. More often, the coronary artery abnormality is asymptomatic, but can complicate surgery. The left anterior descending artery originates from the right aortic sinus or the right coronary artery in approxi­ mately 10% of patients with tetralogy of Fallot. The ante­ rior descending artery in these patients usually courses across the right ventricular infundibulum. In addition, the coronary artery branches along the anterior wall of the right ventricle tend to enlarge in response to the right ventricular hypertrophy that is a part of tetralogy of Fallot. Approximately 25% of patients with tetralogy of Fallot have a major coronary artery branch that crosses the infundibu­ lum. In 2% of patients with tetralogy of Fallot, there is a single coronary artery.m There are 2 common patterns of coronary artery anat­ omy in patients with D-transposition of the great vessels. In 65% of these patients, the left coronary artery arises from the left sinus ofValsalva and the right arises from the poste­ rior sinus. The less-common pattern consists oforigin ofthe right coronary artery and the left circumflex coronary artery from the posterior sinus (either from a single ostium or from separate ostia) and origin of the left anterior descend­ ing artery from the left sinus, with passage of the circumflex artery posterior to the pulmonary artery. In D-transposition, the right aortic sinus is the noncoronary sinus.'8 6 In patients with L-transposition ofthe great vessels, the right coronary artery usually arises above the right aortic sinus and gives rise to the anterior descending branch. It then courses inferiorly in the right atrioventricular groove. The left coronary artery arises from the left coronary sinus and predominantly supplies the distribution of the circum­ flex artery. The anterior sinus is the noncoronary sinus in patients with L-transposition. Coronary artery anomalies are common in patients with truncus arteriosus. Approximately 15% of these patients have a single coronary artery. Other potential abnormalities include a high posterior location of the left coronary artery ostium, ostial stenosis, an angular takeoff, pulmonary origin of the circumflex artery, and left anterior descending origin of the right coronary artery.

Coronary Artery Fistu la Congenital coronary arteriovenous fistula i s a n anomalous connection of a coronary artery to a cardiac chamber, the

coronary sinus, a pulmonary vessel, or the superior vena cava. Any heart chamber and any or multiple coronary arteries can be involved. There is right coronary involve­ ment in approximately 6o% of patients. Most often, there is communication with the right ventricle (45% of fistulas) . Communication with the right atrium is also common (25% of fistulas) ; blood empties either directly into the atrium or via the coronary sinus. Approximately 15% of fis­ tulas communicate with a pulmonary artery. At least 90% of congenital coronary artery fistulas communicate with the right circulation, thereby producing a left-to-right shunt. Other anomalous sites of coronary artery communication are rare; these include the left atrium, the left ventricle, and the superior vena cava. Connection to a left-sided cardiac chamber causes symptoms similar to those of aortic insuf ficiency, sometimes including myocardial ischemia due to a hemodynamic steal phenomenon.'7° Many patients with a coronary artery fistula are asymp­ tomatic. Rarely, a large shunt causes manifestations of heart failure. The symptoms can mimic those of a patent ductus arteriosus, arteriovenous malformation of the tho­ rax or lung, or a VSD with atrioventricular valve regurgi­ tation. Auscultation demonstrates a continuous murmur that is best heard along the lower left sternal border. The murmur is maximal during diastole. Treatment is surgical; occasional patients have an anomaly that is amenable to transcatheter coil embolization. Chest radiographs of patients with coronary artery fis­ tula are usually normal, unless a large left-to-right shunt produces pulmonary vascular prominence and cardiomeg­ aly. Occasionally, the presence of 1 or more aneurysmally dilated anomalous vessels results in abnormal soft-tissue bulges along the margin of the cardiac silhouette. In most patients, echocardiography accurately demonstrates the anomalous vessels. Examination with angiocardiography, CT angiography, or MR provides detailed anatomic depic­ tion. The drainage site(s) of the fistula can be single or mul­ tiple communications, or a network of small vessels.'87,,88 Myocardial sinusoids are congenital communications between a coronary artery and a ventricular chamber. In otherwise normal individuals, sinusoids are nonfunction­ ing and clinically insignificant. In patients with aortic or pulmonary atresia, retrograde flow of blood from the high­ pressure ventricular cavity into the coronary arteries can occur via enlarged sinusoids.

Congen ital Coronary Artery Aneu rysm The definition o f a coronary artery aneurysm i s a segment of vessel with a diameter more than 1. 5 times that of the normal adjacent segment. Congenital coronary artery aneurysms are exceedingly rare. Most coronary artery aneurysms in children are acquired lesions caused by Kawasaki disease, infection, or trauma. The major clinical importance of a congenital coronary artery aneurysm is the potential for rupture or thrombosis. Congenital coronary artery aneurysms can be multiple, saccular, or fusiform.

Chapter n Congenital H e a rt D i sease 389 Occasionally, the lesion is quite large. Aneurysms are opti­ mally evaluated with angiography; however, detection and characterization are sometimes adequate with echocardiog­ raphy or M R.'8 9

I diopathic I nfantile Arterial Calcification Idiopathic infantile arterial calcification (Stryker disease) is a rare congenital vascular disease. This is a systemic disorder, in which there is deposition of calcific material in the walls of medium-sized systemic arteries. There is a propensity for prominent involvement of the coronary arteries. Cerebrovascular involvement is rare. The calcium deposition and intimal hyperplasia lead to progressive coronary artery occlusion. Patients develop manifesta­ tions of myocardial ischemia. Because this is a progres­ sive process, myocardial fibrosis and mitral insufficiency can occur.'9° As the name implies, the clinical onset of idiopathic infantile arterial calcification is usually early in infancy. These infants presumably suffer angina pectoris that is exacerbated by activity, such as feeding. The potential clini­ cal findings include tachycardia, respiratory distress, irrita­ bility, and a mitral insufficiency murmur. Serum calcium levels are usually normal. Most affected patients die during infancy. Medical treatment with the pyrophosphate analog etidronate disodium may be beneficial. The coronary artery calcifications of idiopathic infan­ tile arterial calcification may or may not be visible on standard chest radiographs . Unenhanced helical CT is the most sensitive imaging technique for the detection of coronary artery cacifications. The calcifications result in acoustic shadowing on sonography; prenatal detec­ tion of this condition has been reported. The appearance of the heart ranges from normal to severe cardiomegaly, depending on the severity of ischemia and myocardial damage. The appearance of the heart is often similar to that of anomalous origin of the left coronary artery from the pulmonary artery. The left ventricle and left atrium are enlarged. Findings of congestive failure are sometimes present.191-193

pulmonary veins and has a smaller, narrower appendage is termed the pulmonary, or left, atrium. The position of the cardiac apex is categorized inde­ pendent of the atrial and visceral situs. The normal left- �f­ midline position is levocardia. A midline apex is mesocardia. Rightward orientation of the apex is dextrocardia. These terms do not indicate the orientations of the cardiac cham­ bers. The term dextroposition refers to displacement of the heart into the right hemithorax because of extracardiac pathology, such as hypoplastic right lung. The positions of the liver, spleen, stomach, and other asymmetric organs determine the visceral situs. Pulmonary situs is deter­ mined by the lobar pattern, bronchial anatomy, and pulmo­ nary arterial branching pattern. Ectopia cordis indicates a location of the heart at least partially outside of the thoracic cavity.'94-196 Situs solitus is the normal arrangement of the atria, lung, and abdominal viscera. The systemic atrium is on the right and the pulmonary atrium is on the left, as is the bilobed lung. In normal individuals, the cardiac apex is directed to the left; that is, levocardia. The prevalence of congenital heart disease in patients with situs solitus and levocardia is less than 1% (Table 1 1 -1 6) . Situs inversus i s the mirror image o f normal, with the liver on the left, the stomach on the right, and the trilobed lung on the left. The systemic atrium is on the left. The pul­ monary atrium is on the right. Most often, the cardiac apex is to the right of the midline (i.e., dextrocardia) . Situs inver­ sus is present in o.o1% of the population. The prevalence of congenital heart disease in individuals with situs inversus and dextrocardia (i.e., situs inversus totalis ) is approximately 3% to s%. Situs ambiguous, also termed heterotaxy, indicates devi­ ation from the orderly arrangement of situs solitus or situs inversus. This may involve duplication of, absence of, or abnormal positioning of structures that are normally urillat­ eral. The term isomerism indicates the presence of abnormal mirror image sets of structures that normally are asym­ metric, such as the lungs and atria. With left isomerism,

Table 1 1-1 6. Correlation of Situs and Cardiac Position with Prevalence of Congenital Heart Disease

CARDIAC MALPOSIT ION

Term inology of Cardiac Mal position Cardiac malposition encompases any form of abnormal positioning of the heart, or discordance between the loca­ tion of the heart and the other thoracic structures or the abdominal viscera. Situs is a term that refers to the position of normally asymmetric organs, such as the lungs, atria, liver, spleen, and stomach. With regard to the heart, the atrial anatomy is the most important determinant of situs. The atrium that receives blood from the inferior vena cava and has a broad-based appendage is termed the systemic, or right, atrium. The atrium that receives blood from the

Co ngen ital Visceral situs

Ca rd iac position

heart d i sease

Sol itus Solitus l nversus l nversus Ambiguous, polysplenia Ambiguous, asplenia

Levocard ia Dextrocardia Levocardia Dextrocard-ia Variable

gs% >g s% 3% to s % -g o% to 95% -

------------ >g 8% -

Variable

390 Part 2 The Card i ovascu l a r System right-sided structures have characteristics of those nor­ mally present on the left; this is sometimes termed bilateral left-sidedness. Right isomerism indicates the bilateral pres­ ence of right-sided anatomy; for example, bilateral bilobed lungs and absence of splenic tissue. Congenital heart dis­ ease is present in at least 90% of patients with heterotaxy. The terms concordance and discordance also have util­ ity in the description of cardiac and visceral malpositions. Concordance indicates that the systemic atrium, the infe­ rior vena cava, and the major lobe of the liver are located on the same side of the body, while the pulmonary atrium, the descending portion of the aorta, and stomach are located on the contralateral side. Concordance is present in patients with situs solitus and situs inversus. Most cardiac malpo­ sitions are concordant. Discordance occurs in association with situs ambiguous. Abnormal positioning of the cardiac apex, such as dextrocardia, does not necessarily indicate discordance.

inferior vena cava and the liver are on the right, while the pulmonary atrium, descending aorta, and stomach are on the left. In contradistinction to the infrequent occurrence of cardiac anomalies in patients with dextrocardia and situs inversus, situs solitus with dextrocardia is associated with congenital heart disease in at least 95% of patients. The most common lesion, occurring in about half of these patients, is L-transposition of the great arteries. There are usually additional anomalies as well, such as pulmonary stenosis, VSD, or left-sided atrioventricular valvular insuffi­ ciency. Dextrocardia patients without transposition usually have complex cardiac malformations; most result in cyano­ sis. Pulmonary stenosis is common, usually in conjunction with anomalies of the atrial or ventricular septa. Radiographic examinations of patients with dextrocar­ dia and situs inversus show a mirror-image pattern. The cardiac apex is directed to the right, the liver is on the left, and the stomach is on the right ( Figure 1 1 -63) . There is a

Levocard ia Normal individuals have situs solitus and levocardia. However, levocardia in an individual with situs inversus or situs ambiguous is nearly always associated with a major cardiac anomaly. The aortic arch is usually located on the right. The most common cardiac lesions in patients with levocardia and situs ambiguous are complex lesions that are associated with cyanosis. These include pulmonary ste­ nosis or atresia, transposition complexes, atrioventricular canal, and VSD.

Dextrocardia Dextrocardia with situs inversus indicates mirror image anatomy of the viscera and thoracic structures. Cardiac concordance is usually maintained. Approximately 20% of patients with situs inversus have primary ciliary dyski­ nesia (Kartagener syndrome) . Primary ciliary dyskinesia is a genetic abnormality that results in deficient ciliary func­ tion, resulting in compromised mucociliary transport. In addition to situs inversus, the major clinical manifestations are bronchiectasis, nasal polyposis, and chronic sinusitis. The genes for situs inversus and ciliary formation appar­ ently are closely linked. About half of patients with dys­ motile cilia syndrome have situs solitus and half have situs inversus.'97 The prevalence of congenital heart disease in patients with dextrocardia and situs inversus is 3% to 5%. Many of the associated cardiac lesions involve atrioventricular dis­ cordance. Common lesions include transposition of great arteries, pulmonary stenosis or atresia, double-outlet right ventricle, and VS D. The aortic arch is located on the right side in approximately 8o% of patients with dextrocardia and situs inversus. With dextrocardia and situs solitus ( isolated dextrocar­ dia) , the cardiac apex points to the right, but the visceral and atrial orientations are normal. The systemic atrium,

Figure n-63 Dextrocardia and situs inversus. This cyanotic newborn has transposition of the great vessels, VSD, and pulmonary stenosis. The liver is on the left and the stomach on the right. There is a left aortic arch. The lungs are oligemic.

Chapter 1 1 Co ngenital H e a rt D i sease 391 minor fissure in the left lung. Sonography shows a normal spleen in the right upper quadrant. In patients with situs solitus and dextrocardia, the visceral organs are in normal positions and there is isolated rightward positioning of the heart. Most often, the aortic arch is located on the right. The radiographic appearance of the heart is altered by the associated cardiac malformations that are usually present in these patients.

M esocardia Mesocardia indicates a midline orientation of the car­ diac apex. Mesocardia is present in approximately 1% of autopsy evaluations of congenital heart disease patients. However, most patients with mesocardia have no other anomalies, and the cardiac position can be considered a developmental variation. Tall, slender adolescents fre­ quently have a midline position of the heart on chest radiographs. In contradistinction, the cyanotic newborn with mesocardia and a murmur is likely to have a serious cardiac malformation.

Heterotaxy Heterotaxy (situs ambiguous) is associated with a very high likelihood of a major cardiac malformation. Although there is considerable variation between patients with regard to the expression ofheterotaxy, it is frequently helpful to consider 2 major categories : heterotaxy with asplenia and heterotaxy with polysplenia. Cardiac lesions in patients with asplenia are more frequent and more severe than in patients with polysplenia. Individuals with asplenia have the additional burden of an elevated lifetime risk for sepsis. Intestinal malrotation is common in patients with heterotaxy syndrome. The most common forms are non­ rotation and reverse rotation. Some forms of malrotation impart an elevated risk for midgut volvulus. Bowel obstruc­ tion in patients with heterotaxy can also result from intes­ tinal atresia, annular pancreas, or preduodenal portal vein. Those patients with microgastria may have severe gastro­ esophageal reflux and failure to thrive.'9 8,'99

The inferior vena cava in patients with asplenia may empty into either atrium. Anomalies of pulmonary venous connection are common, most often occurring as total anomalous pulmonary venous connection. The anomalous veins can drain into the superior vena cava or the portal venous system. Various, usually severe, cardiac malfor­ mations occur in patients with asplenia. These typically include pulmonary atresia or severe pulmonary stenosis; therefore, cyanosis is common. The most frequent combi­ nation of cardiac lesions in patients with asplenia consists of complete atrioventricular canal or single ventricle with D-transposition of the great arteries and pulmonary steno­ sis or atresia. The findings on standard chest radiographs often allow a suggestive diagnosis of asplenia and heterotaxy. The most common initial clues are an abnormal trans­ verse orientation of the liver andjor malposition of the gas-filled stomach ( Figure 1 1 -64) . The identification of bilateral minor fissures is confirmatory. The associated congenital heart disease usually causes diminished pul­ monary vascularity. With most of these lesions, heart size is normal or only mildly prominent. The orientation of the cardiac apex is variable, but mesocardia is common in these patients. The anatomy of the abdominal viscera in the neonate with suspected heterotaxy and asplenia can be evaluated with sonography (Figure n -65) . There is no visible splenic tissue in either the left upper quadrant or right upper quad­ rant. Because hypoplastic or malposition splenic tissue can be missed with sonography, the most accurate technique for determining the presence or absence of the spleen is scintigraphy with heat-damaged labeled erythrocytes. Because many patients with heterotaxy have intestinal malrotation, contrast studies of the bowel are indicated for most patients.'94 ·'96·200

Asplenia

Right isomerism Asplenia Heterotaxy with asplenia indicates the presence of right isomerism; this is also termed bilateral right-sidedness. When the spleen is absent, there is nearly always a right­ sided developmental pattern of the lungs; that is, each has 3 lobes and an eparterial upper lobe bronchus. There is considerable variation in the anatomy ofthe abdominal vis­ cera in patients with asplenia. Most often, the liver has an abnormal horizontal midline position. The stomach may be located on the left or right, or at the midline; in some patients there is microgastria. The vena cava is usually intact and tends to be located on the same side as the abdominal aorta. Fusion of the adrenal glands (i.e., horseshoe adrenal gland) can occur in individuals with asplenia.'94

Radiology

Pathology

i

Bilateral m i nor fiss u res

:- ----- - - - - - - - - - - - - - - - - - - - - 1 Transverse l iver

I

Cyanotic congen ital Cardiomegaly -- ---= : _ ...:. - - -- heart disease 1 1 N orma 1 or d 1 m 1 n 1. s h e d pu 1 monary 1 vascularity --

__ _

Polysplenia Heterotaxy with polysplenia indicates left isomerism, or bilateral left-sidedness. Multiple spleens are located in a normal position or ectopically. The lungs in these patients have a left-sided developmental pattern, with 2 lobes. The bronchial and pulmonary arterial branching patterns also

392

Part

2

The Card iovascu l a r System

A

B

Figure n-64 Heterotaxy and asplenia. A An anteroposterior radiograph of a newborn with double­ outlet right ventricle shows cardiomegaly, pulmonary vascular prominence, and an abnormal transverse configuration of the liver. A minor fissure is visible on the left. The right-sided

minor fissure is not discernible on this image. B. A transverse sonographic image confirms the transverse orientation of the liver. There is no visible spleen. The aorta is at the midline and the vena cava is on the right. The hypoplastic stomach (echogenic focus) is at the midline.

have a left-sided configuration. There are bilateral pulmo­ nary atria. The liver morphology varies between patients, but a transverse central orientation is common. The stom­ ach may be small or malpositioned. Interruption of the inferior vena cava with azygous or herniazygos continu­ ation occurs in about so% of patients with polysplenia. Other potential findings in these patients include intes­ tinal malrotation, biliary atresia, and a congenitally short pancreas. Congenital heart disease occurs in 90% to 95% of indi­ viduals with heterotaxy and polysplenia. In comparison to asplenia, the cardiac malformations associated with poly­ splenia tend to be less severe. In addition, most of these lesions do not cause cyanosis in the affected neonate. Heart disease in infants with polysplenia frequently results in symptoms of congestive heart failure as a consequence of a left-to-right shunt. Some patients with polysplenia have no heart disease or have relatively minor lesions. Polysplenia is more common in females. The most common cardiac malformations in children with polysplenia are defects in the atrial or ventricular septa. Partial anomalous pulmonary venous return and atrioventricular canal are also common. In some patients, there are left-sided obstructive lesions. In 30% to 40% of patients with polysplenia, bilateral superior vena cavae con­ nect directly to their respective atria.

A transverse sonographic image of a 2-day-old infant with congenital heart disease shows symmetric morphology of the liver and no visible spleen. There is fusion of the adrenal glands (Ad) . As is typical of asplenia, the isthmus of the horseshoe adrenal passes anterior to the aorta (Ao). The inferior vena cava (IV C) is to the left of the midline and the stomach (S) is on the right.

Figure n-65 Asplenia.

Chapter 11 Congen ital H e a rt D i sease 393 cross-sectional imaging studies by absence of the intrahe­ patic segment and the presence of

1

or more prominent

azygos vessels passing adjacent to the spine.' 94· 2 00

Polysplenia Pathology

Rad iology

Left isomerism Heterotaxy I nterru ption of i nferior vena cava Polysplenia Acyanotic congen ital heart disease

N o m inor fissu res Transverse liver Enlarged azygos M u ltiple splen ules Cardiomegaly, vascular congestion

Figure n-66 Heterotaxy and polysplenia. An anteroposterior chest radiograph shows dextrocardia, a right aortic arch, and prominent pulmonary vasculature. There is no visible minor fissure.

Ectopia Cordis Ectopia cordis i s rare congenital abnormality i n which the heart is located partially or completely outside of the tho­ racic cavity. The underlying cause likely is failure of proper

Chest radiographs of patients with polysplenia show

fusion of the lateral embryonic folds during the fourth ges­

a bilateral left bronchial branching pattern. Neither lung

tational week. The prevalence is approximately

contains a minor fissure

lion livebirths. There are

(Figure 1 1 -66) .

The cardiac apex

5

6 per 1 mil­

types of ectopia cordis. (a) With

may be directed to the left or right, but mesocardia is rare.

the cervical type, the heart extends into the neck. The ster­

The typical cardiac lesions associated with polysplenia are

num is usually intact. (b) There is usually a split in the upper

usually accompanied by little or no cardiac enlargement. Pulmonary vascular prominence is conunon. An abnor­ mal midline position of the liver is frequently visible on chest or abdominal radiographs. The location of the stom­

portion of the sternum in patients with the cervicothoracic type. (c) The thoracic type refers to anterior deviation of the heart through a split or absent sternum. (d) There is usually an inferiorly split sternum in patients with the thoracoab­

ach may also be abnormal. Chest radiographs sometimes

dominal form of ectopia cordis. (e) Extension of the heart

show enlargement of the azygous vein in those patients

inferiorly through a diaphragmatic defect is the abdominal

with interruption of the inferior vena cava. In older patients

type. The thoracic and thoracoabdominal types are the most

with this anomaly, the normal inferior vena cava shadow is

common forms of ectopia cordis

absent on lateral chest radiographs .

ogy of Cantrell

Although sonography i s the usual technique for the evaluation of the infant with suspected polysplenia, the

( Figure 1 1 -67) . The pental­

refers to thoracoabdominal ectopia cordis

accompanied by a bifid sternum, a diaphragmatic defect, a diaphragmatic pericardia! defect, an anterior abdominal

pathological anatomy can also be demonstrated with CT

wall defect, and intracardiac anomalies. The most conunon

or MR. Polysplenia most often results in a group of mul­

intracardiac anomalies in patients with ectopia cordis are

tiple splenules , which may be located in the left upper quadrant, right upper quadrant, or both. The splenic tissue

septal defects of the atria and ventricles, tetralogy of Fallot, and ventricular diverticulum. 20 1

is typically ipsilateral to the stomach and may be located adjacent to the greater curvature. In the appropriate clinical situation, the presence of 1 or more clefts in an otherwise normal-appearing spleen is consistent with the diagnosis.

As with asplenia, the liver frequently (but not invariably)

MISCELLANEOUS ANOMALIES

Cardiac Diverticu l u m

has a transverse configuration and is at a midline loca­

A congenital cardiac diverticulum i s an outpouching of

tion. Careful evaluation of the biliary tract is important in

the ventricular wall. This rare anomaly most often involves

patients with polysplenia, because of the association with

the left ventricle; a congenital diverticulum of the right

biliary atresia. The abdominal aorta usually is located on

ventricle is exceedingly rare . Occasionally, there is a coex­

the side opposite to the stomach in patients with polysple­

istent cardiac anomaly. There are usually no substantial

nia. Interruption of the inferior vena cava is indicated on

hemodynamic consequences, unless the diverticulum is

394 Part 2 The Card iovascu l a r System cardioscintigraphy, angiography, CT angiography, or M R. Most often, the neck of the diverticulum is relatively nar­ row, although a large lesion can be broad-based and have the appearance of an aneurysm. A congenital fibrous diverticulum of the left ventricle is typically located at the base of the heart, most often aris­ ing posterolaterally. The connection with the ventricular cavity is usually narrow. Calcium deposits are occasionally present in the wall. Most affected patients are of African descent.

Anomalous Systemic Connection to the Left Atriu m Anomalous systemic venous connection to the left atrium is most often caused by a persistent left-sided superior vena cava that drains into the left atrium. Structures that uncom­ monly or rarely form anomalous connections to the left atrium include a right-sided superior vena cava, the infe­ rior vena cava, the coronary sinus, the azygos vein, and a hepatic vein. Total anomalous systemic venous connection to the left atrium is quite rare. Anomalous systemic venous

Figure n-67 Ectopia cordis. An anteroposterior chest radiograph shows an abnormal inferior and rightward location of the heart in this newborn with thoracoabdominal ectopia cordis and tetralogy of Fallot. The interface with air results in a sharp character of the cardiac borders.

connections to the left atrium result in a right-to-left shunt. If the shunt is substantial, the patient is cyanotic. 20 5> 2 °6

Congen ital Defects ofthe Pericard i u m Congenital defects of the pericardium comprise a spec­ trum that ranges from an isolated small defect to com­ plete absence of the pericardium. I n about three-fourths

quite large. Rare instances of rupture of a congenital diver­

of patients, there is absence of the entire left side of the

ticulum have been reported. The wall of a diverticulum is

pericardium. Most other defects are small. Total absence

either fibrous or muscular. A muscular congenital ventric­

of the pericardium and absence of the entire right side of

ular diverticulum may contract during systole or undergo

the pericardium are quite rare. Potential associated con­

systolic expansion (dyskinesis ) . An aneurysm caused by a

genital anomalies include diaphragmatic hernia, pulmo­

myocardial infarction, which can mimic a congenital diver­

nary sequestration, bronchogenic cyst, and various cardiac

ticulum, is usually broad-based and akinetic.

malformations (tricuspid insufficiency, A S D , tetralogy of Fallot, and mitral stenosis ) .20 7

A congenital diverticulum arising from the apex of the left ventricle is usually muscular and has a long and narrow

Most patients with a congenital defect of the pericar­

configuration. These lesions are frequently accompanied by

dium are asymptomatic. Herniation of all or portions of the

additional cardiac anomalies, dextroposition of the heart,

heart through the defect occasionally produces symptoms

and an anterior thoracoabdominal defect (a midline ante­

related to myocardial ischemia (usually related to coronary

rior upper abdominal wall defect, deficiency of the inferior

artery compression or great vessel torsion) . Potential clini­

aspect of the sternum, a defect in the anterior portion of the

cal manifestations in these patients include chest pain, car­

diaphragm, and a defect in the diaphragmatic portion of

diac arrhythmias , syncope, and sudden death. The chest

the pericardium) . The most common cardiac anomalies in

pain may be paroxysmal and is often described as " stab­

these patients include V S D , A S D , truncus arteriosus, tetral­

bing. " The patient sometimes reports diminished pain

ogy of Fallot, and tricuspid atresia. Approximately

with postural changes .

Go%

of

these patients have an omphalocele or hiatal hernia.2 ° 2-204

Because congenital absence of the pericardium most

Congenital diverticula are only visible radiographically

often involves the left side, the typical radiographic find­

when they are quite large. A congenital diverticulum of

ings include prominence of the pulmonary artery segment

the left ventricle associated with a thoracoabdominal wall

andjor left atrial appendage on the frontal view. B ecause

defect may be visible on standard radiographs as an inferior

the pericardium is lacking, there is abnormally sharp

thoracic or upper abdominal mass at the midline. The car­

visualization of the aorta and main pulmonary artery (i. e . ,

diac contour shifts toward the right during inspiration as a

a "tongue" o f aerated lung interposed between the main

result of defective support of the heart. A ventricular diver­

pulmonary artery and aorta) . Occasionally, there is inter­

ticulum is more accurately assessed with echocardiography,

position of a portion of the left lung between the inferior

Chapter 11 Co ngenital H e a rt D i sease 395

PALLIATIVE SHUNTS

Figure n-68 Congenital absence ofthe pericardium. An anteroposterior chest radiograph shows prominence of the main pulmonary artery, a deep sulcus between the aorta and the main pulmonary artery, and leftward displacement of the heart.

aspect of the heart and the left diaphragmatic border. Frequently, there is shift and rotation of the heart toward the left (Figure 1 1 -68) . Herniation of the left atrial append­ age through a small defect can result in a localized mass along the left cardiac border. 208 M RI demonstrates the normal pericardium as a low signal (fibrous) linear structure that surrounds the heart. The adjacent epicardial fat produces high signal on T1-weighted images and the myocardium is of intermedi­ ate signal. A disruption in the normal low signal-intensity line of the pericardium suggests a defect. With complete absence of the left pericardium, the heart is displaced to the left. Coronal images show lateral bulging of the pulmo­ nary artery, and a sharply defined angle between the main pulmonary artery and the left ventricle. The apex of the left ventricle is in the left costophrenic sulcus.209· 2 '0

Palliative surgical procedures for congenital heart disease patients serve to provide symptomatic relief, while leav­ ing the main pathophysiology uncorrected. The 4 primary palliative procedures are aorticopulmonary shunts, cava­ pulmonary shunts, pulmonary artery banding, and atrial septectomy. The various shunt procedures serve to direct blood flow to the pulmonary circulation from either sys­ temic arteries or the vena cava (Table 1 1 -1 7 ) . 2u The classic Blalock-Taussig shunt is a direct end-to-side anastomosis of the transected subclavian artery to the pul­ monary artery. The procedure is performed in the hemitho­ rax contralateral to the aortic arch. Because the subclavian artery is sacrificed, ipsilateral upper extremity ischemia or growth disturbance can occur. Most Blalock-Taussig shunts are now performed with a modified technique, in which a prosthetic graft is interposed between the subclavian and pulmonary arteries. With this technique, the shunt is pre­ cisely sized and there is preservation of arterial flow into the ipsilateral arm. Approximately 10% of patients have suf ficient leakage of serum through the fabric of the graft to cause a seroma or prolonged chest tube drainage. The Potts shunt is an anastomosis between the descending thoracic aorta and the left pulmonary artery. The approach is through a left thoracotomy. The Waterston shunt is an anastomosis between the ascending aorta and the right pulmonary artery via a right thoracotomy. The Cooley shunt is an intrapericardial connection between

Table 1 1-17. Palliative Shu nts S h u nt

Co n n ectio n

Classic Blalock-Taussig

End-to-side su bclavian to p u l monary artery Descending aorta to left p u l monary artery Ascending aorta to right p u l monary artery Ascending aorta to right p u l monary artery S u bclavian artery to pul monary artery; synthetic graft Ascending aorta to main p u l monary artery; synthetic graft S u perior vena cava to right p u l monary artery Right ventricle to pul monary artery; synthetic graft I nferior vena cava to pul monary artery tun nel

Potts Waterston Cooley Mod ifi e d Blalock­ Taussig Central s h u nt

Congenital Pericardia! Defect Pathology

Small focal defect Absence of left pericard i u m

Rad iology

; ± Herniated cardiac structure • (e.g., atrial appendage) , Sharp visualization of the aorta and ' · pul monary artery i· Leftward shift of the heart

G lenn Sano Fontan

396 Part 2 The Card i ovascu l a r System the ascending aorta and the right pulmonary artery. These 3 procedures have largely been abandoned in favor of the modified Blalock-Taussig shunt. The bidirectional Glenn shunt is a technique for direct­ ing systemic venous blood into the pulmonary arterial sys­ tem. This is an end-to-side anastomosis of the superior vena cava to the right pulmonary artery. Venous blood from the upper portion of the body passes through this connec­ tion into the lungs. The right pulmonary artery remains connected to the left pulmonary artery. Inferior vena cava drainage enters the heart without change. The Fontan procedure shunts blood from the inferior vena cava into the pulmonary arteries , bypassing the heart. Typically, this is performed as a second-stage procedure following a Glenn shunt. There are 3 basic techniques for the Fontan procedure: (a) an atrial-pulmonary connection, (b) an intraatrial cavopulmonary tunnel, and (c) an extra­ cardiac cavopulmonary tunnel. MR is an important adjunct to echocardiography for evaluation of surgically created shunts. In some patients, angled imaging planes delineate the entire course of the shunt. Gradient-refocused echo pulse sequences are some­ times helpful to improve the MR conspicuity of the shunt. M RI approaches 100% sensitivity for documenting patency of a palliative shunt, but the sensitivity for focal stenoses is limited (predominantly because of the tortuous course of many shunts that compromises visualization on cross-sec­ tional images) . In patients with a pulmonary artery band, MR velocity mapping is a noninvasive technique to quan­ tify pulmonary blood flow. 6, 212

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1972;50(5) :778-'792. 205. de Leval M R. Ritter DG, McGoon DC, Danielson G K.

coronary artery fistula to left superior vena cava and right

Anomalous systemic venous connection. Surgical

atrium with compression ofleft pulmonary vein simulating cor

considerations. Mayo Clin Proc. 1975;5o(10) :599-6IO.

triatriatum---ill agnostic value of magnetic resonance imaging.

Eur J Cardiothorac Surg. 1994;8(2) : 97-99 .

188. Boxer RA , LaCorte MA, Singh S , e t al. Noninvasive diagnosis of congenital left coronary artery to right ventricle fistula

by nuclear magnetic resonance imaging. Pediatr Cardiol.

1989;10(1) :45-47· 189. Meinert D, Mohammed Z. M RI of congenital coronary artery aneurysm. Br J Radio!. 2000;73(867) :322-324. 190. Moran )) . Idiopathic arterial calcification of infancy: a clinicopathologic study. Pathol Annu. 197po :393-417.

401

2o6. Raghib G, Ruttenberg HD, Anderson RC, et al. Termination of left superior vena cava in left atrium, atrial septal defect, and absence of coronary sinus; a developmental complex.

Circulation. 196 5;31:9 06-918. 207. Faridah Y, )ulsrud PR. Congenital absence of pericardium revisited. Int ] Cardiovasc Imaging. 2002;18(1) : 67-73208. Gatzoulis MA. Munk MD, Merchant N, et al. Isolated congenital absence ofthe pericardium: clinical presentation, diagnosis, and management. Ann Thorac Surg.

2ooo;6 9 (4) :1209-1215.

191. Saigal G, Azouz E M . The spectrum of radiologic findings in idiopathic arterial calcification of infancy: pictorial essay. Can Assoc Radio! ]. 2oo4;55(2):I02-107.

209. Gutierrez FR, Shackelford G D , McKnight RC, et al. Diagnosis

192. Pao DG, DeAngelis GA. Lovell MA, et al. Idiopathic arterial

210. Schiavone WA. O' Donnell )K. Congenital absence of

of congenital absence of left pericardium by MR imaging.

] Comput Assist Tomogr. 1985; 9(3):55J-5 53-

calcification of infancy: sonographic and magnetic resonance

the left portion of parietal pericardium demonstrated

findings with pathologic correlation. Pediatr Radio!.

by nuclear magnetic resonance imaging. Am J Cardiol.

1998;28(4):256-25 9 . 1 9 3 . Bellah R D . Zawodniak L , Librizzi R ) , Harris M C . Idiopathic arterial calcification of infancy: prenatal and postnatal effects of therapy in an infant. J Pediatr. 1992;121(6):930-933.

194. Applegate KE, Goske M ) . Pierce G , Murphy D. Situs revisited: imaging of the heterotaxy syndrome. Radiographies. 1999;19 (4 ) :837-852; discussion 853-854.

1985;55 (11) :143 9-1440.

211. Ohye RG, Sleeper LA, Malwny L, et al. Comparison of shunt types in the Norwood procedure for single-ventricle lesions.

N Eng! ] Med. 2010;3 62(21) :198o-19 92. 212. Katz M E , Glazer H S , Siegel M J , e t a l . Mediastinal vessels: postoperative evaluation with M R imaging. Radiology. 1986;161(3 ) : 647-65!.

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CH A P T E R

12

Anoma l ies of the Great Vesse ls

ANOMALI ES OF TH E AORTA . . . . . . . . . . . . . . . . . . . . . .

403

Aneurysm of the Ductus Arteriosus . . . . . . . . . . .

41 6

Term inology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

403

Ductus Diverticu l u m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 6

Vascu lar Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

403

Congen ital Coarctation of the Aorta . . . . . . . . . . .

41 7

Double Aortic Arch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 Left Aortic Arch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

407

Anomalous Right Subclavian Artery . . . . . . . . 407 Left Circumflex Aortic Arch . . . . . . . . . . . . . . . . . . . . . 408 Right Aortic Arch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409

Right Aortic Arch With an Aberrant Left Subclavian Artery .. .. .. . . . . 409 Right Aortic Arch With Mirror-image Branching . . . . . . . . . . . . . . . . . . . . . . 41 0 Right Aortic Arch With Isolated Left Subclavian Artery . . . . . . . . . . . . 41 3 Right Aortic Arch With Left Descending Aorta . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 4 Cervical Aortic Arch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

414

M id l i n e Descending Aorta . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 5

Anomalous Brach iocephalic Artery. . . . . . . . . . . . .

41 5

ANOMALIES OF THE AORTA

Term inology The aorta consists of thoracic and abdominal compo­ nents . There are 5 segments of the thoracic aorta. The aor­ tic root is a short segment that includes the aortic valve, the annulus, and the sinuses of Valsalva. The ascending aorta extends from the root to the origin of the right bra­ chiocephalic artery. The proximal aortic arch is the seg­ ment from the origin of the right brachiocephalic artery to the left subclavian artery. The posterior aortic arch (the aortic isthmus) extends from the origin of the left subcla­ vian artery to the ligamentum arteriosum. This portion of the arch is often slightly narrower than the descend­ ing aorta. The descending thoracic aorta begins at the ligamentum arteriosum and ends at the diaphragm. The proximal aspect of the descending aorta is sometimes slightly prominent relative to the adjacent segments. Mild

Isthmic Coarctation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 9 Localized Coarctation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 Interrupted Aortic Arch. . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 Pseudocoarctation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 Middle Aortic Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . 426

ANOMALI ES OF TH E PULMONARY ARTERI ES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

427

Absent Proxi mal Pulmonary Artery. . . . . . . . . . . . .

427

Anomalous Origi n of Left Pulmonary Artery From the Right Pu l monary Artery. . . . . . . . . . . 427 Anomalous Origi n of One Pul monary Artery From the Ascending Aorta . . . . . . . . . . .

429

Aortopulmonary Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

429

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

430

localized bulging of the posterior aortic arch or the supe­ rior aspect of the descending aorta is termed the aortic spindle. The abdominal aorta consists of suprarenal and infrarenal segments.

Vascular Rings The most common vascular rings are double aortic arch and right aortic arch with an aberrant left subclavian artery. Unusual arch anomalies that can cause a complete vascular ring include circumflex aorta, right aortic arch with mirror image branching and a left-sided ligamentum arteriosum, and left aortic arch with an aberrant right subclavian artery and a right-sided ligamentum arteriosum (Table 1 2-1 ) . ' The most important determinants of the clinical pre­ sentation of a vascular ring are the severity of tracheal com­ pression and the occurrence of associated anomalies such as a congenital heart lesion. Some patients present in the

404

Part 2 The Ca rd iovascu l a r System

Table 1 2-1 . Vascu lar Rings

Double aortic a rch

Bilateral patent arches Atretic left arch Atretic right arch (rare) Left aortic Aberrant right s u bclavian, right arch l igamentu m Circu mflex left arch, right ligamentu m Right aortic Aberrant left subclavian, left l igamentu m arch Circu mflex right arch, left ligamentu m M i rror image branchi ng, left ligamentu m to aorta --.,. Cervical ; Contralateral ligamentu m aortic a rch

- --

-

neonatal period with life-threatening respiratory distress. At the other end of the spectrum are patients who remain asymptomatic into adulthood, with the lesion discovered incidentally. Symptoms are present during infancy in most patients with double aortic arch or right aortic arch with a left ductus arteriosus. Pulmonary artery sling (origin of the left pulmonary artery from the right pulmonary artery) is another great vessel anomaly that, although not a vascular ring, is usually symptomatic during infancy. The most common clinical manifestations of a vas­ cular ring are stridor and wheezing. The stridor is most severe during inspiration. Severely affected infants tend to hold their neck hyperextended. Physical activity may exacerbate the respiratory symptoms . These patients are prone to recurrent lower respiratory tract infections. Dysphagia is a less consistent finding in patients with an arch anomaly. Infants with a tight vascular ring may have poor feeding, fatigability, or episodes of aspiration. Older patients occasionally present with food impaction in the esophagus at the site of the vascular compression.' The imaging evaluation of the child with a suspected arch anomaly generally consists of standard chest radio­ graphs , esophagography, and MR or CT. The location of the aortic arch can usually be demonstrated on properly positioned frontal chest radiographs . The arch appears as a soft-tissue density aortic knob that causes slight indentation on the tracheal air column. The presence of a vascular ring is suggested on chest radiographs by abnormal narrowing of the inferior aspect of the trachea, anterior bowing of the trachea as viewed on the lateral proj ection, and thickening of the retrotracheal soft tis· sues. Esophagography provides important anatomic information with regard to compression of the esopha­ gus by components of the aorta, anomalous great vessels, and the ductus arteriosus or ligamentum arteriosum. A vascular ring is indicated by abnormal esophageal

compression in association with tracheal narrowing. M R o r C T provides specific depiction o f the pathological vas­ cular anatomy.'-3

Dou ble Aortic Arch Double aortic arch is the most common symptomatic vas­ cular ring. This anomaly is a result of embryological per­ sistence of both the left and right fourth aortic arches. The ascending aorta divides anterior to the trachea into right and left limbs that encircle the trachea and esophagus. The ascending portion of the arch is anterior to the trachea, and the descending portion courses posterior to the esophagus. Vascular structures thereby encircle the esophagus and trachea. The clinical manifestations of double aortic arch predominantly relate to tracheal obstruction and associated tracheomalacia. There are no significant hemodynamic sequelae. In approximately 75% of patients with double aortic arch, the right arch is dominant and the descending aorta is on the left. The right arch in this situation usually extends more superiorly than the left arch. The larger right arch curves behind the esophagus to join the smaller left arch and form a left-sided descending aorta. A dominant left arch with a right descending aorta occurs in approximately 20% of patients with a double arch. The arches are approxi­ mately equal in size in approximately 5% of patients. The ductus arteriosus in patients with double aortic arch is most often left-sided. The ductus/ligamentum is not an integral component of the vascular ring, however.' In some patients with double aortic arch, there is regression of at least a portion of the left-sided arch (dou­ ble aortic arch with partial atresia of the left arch). The seg­ ments remain in fibrous continuity, thereby maintaining an anatomic vascular ring. The descending aorta in these patients is frequently on the right. A portion of the left aortic arch sometimes persists and forms a diverticulum that gives rise to the left common carotid artery and left subclavian artery. An additional potential variation is left arch atresia between the left common carotid and left sub­ clavian arteries, resulting in origins of the left common carotid artery from the ascending aorta and the left subcla­ vian artery from an aortic diverticulum. Atresia of the right side of a double arch can occur, but is rare. The severity of symptoms in patients with double aor­ tic arch is variable, with the age at presentation largely determined by the degree of tracheal narrowing. Those patients who are symptomatic as infants most often present with wheezing, stridor, and respiratory distress, which are sometimes severe. Apnea and cyanosis may occur. Older children may present with wheezing, stridor, chronic cough, dyspnea, and recurrent pneumonia. The cough in children with double aortic arch has a harsh, brassy character ("seal bark" ) . Dysphagia is not a major characteristic in the clinical presentation of double aortic

Chapter

A

Figure 1 2-1 Double aortic arch.

B

A A lateral airway image of a 12-month-old child with stridor shows tracheal narrowing at the level of the aortic arch. There is slight anterior displacement of the trachea along the inferior aspect of the narrowed segment. The encircling vessels produce

arch. Approximately 20% of patients with double aortic arch have associated cardiac anomalies , most often cya­ notic. The most commonly associated lesions are tetralogy of Fallot and ventricular septal defect. Other associations include common arterial trunk, tricuspid atresia, and D-transposition of the great arteries . Approximately 15% of patients with double aortic arch have a chromosome band 22qu deletion. There is a weak association between double aortic arch and the VACTERL (vertebral, vascu­ lar, anal, cardiac, tracheoesophageal, renal, limb) and CHARGE (coloboma, heart anomaly, choana! atresia, retardation, genital, ear) syndromes.'·2

12

A n o m a l i es of the G reat Ves s e l s 405

slight soft-tissue fullness (arrows) . B. A sagittal reformatted CT angiography image shows the air-filled trachea and esophagus compressed between the anterior and posterior components of the vascular ring (arrows) .

Frontal and lateral chest radiographs o f patients with double aortic arch usually show narrowing of the tra­ chea just above the level of the carina. Tracheal obstruc­ tion sometimes leads to symmetric hyperinflation. On the lateral view, there is anterior bowing of the mid to distal portion of the thoracic segment of the trachea and at least some degree of narrowing. Lateral radiographs may also show prominence of the retrotracheal soft tissues because of the anomalus vessel (Figure 1 2-1 ) . On the frontal view, bilateral soft-tissue densities represent the aortic arches, with the bulge on the right usually larger than that on the left ( Figure 1 2-2 ) . In other patients, the nondominant

406 Part 2 The Ca rd iovascu l a r System

A

Figure 1 2-2 Double aortic arch. A. There is soft-tissue density fullness adjacent to the inferior aspect of the trachea, which is greater on the right than the left (upper arrow) . This segment of the trachea is poorly visualized

(usually the left) arch is too small to produce a radiographic density. In this situation, the radiographic appearance may mimic that of a right-sided arch with a left descend­ ing aorta. However, if substantial tracheal narrowing is observed, the finding should be considered suspicious for a vascular ring.2 Esophagography of patients with double aortic arch shows prominent bilateral and posterior esophageal inden­ tations . On the frontal view, the indentations sometimes have the appearance of a reverse S: the upper curve of the S is produced by the large right arch, while the lower curve is a result of the smaller left arch. The prominent posterior indentation of the esophagus viewed on a lateral or steep oblique projection represents the retroesophageal component of the arch. This indentation is more promi­ nent and more horizontal than that of an anomalous right subclavian artery with a left aortic arch. The presence of a complete ring is confirmed by visualization of concomitant tracheal narrowing anteriorly (Figure 1 2·3) .4· 5 M RI or contrast-enhanced CT provides excellent depiction of the pathological vascular anatomy in patients with double aortic arch, and demonstrates the effects on the airway (Figure 1 2-4) . On axial images just superior to the arch, the subclavian and carotid arteries produce a characteristic appearance, with these 4 vessels evenly

8

because of anterior-posterior narrowing. The descending aorta is on the right (lower arrow) . B. The lateral view shows narrowing and anterior displacement of the trachea (arrow) .

spaced around the trachea; this is termed the 4 artery sign.3 This finding is not, however, specific to double aortic arch, as it also occurs with other arch anomalies that have inde­ pendent origins of these 4 vessels. In patients with partial atresia of the left arch, CT and MR show lack of patency of the atretic segment. As described above, the patterns of origin for the left common carotid artery and left sub­ clavian artery are variable in these patients, depending on the site of atresia.

Double Aortic Arch Path ological a n atomy

Rad iology

Right

Right arch

Posterior

Descending aorta

Left

Left arch

Anterior

Ascend ing aorta

Right esophageal indentation Horizontal posterior esophageal i ndentation; anterior tracheal bowing Left esophagea l indentation Tracheal compression ,.

Chapter 12 A n o m a l ies of the G reat Ves s e l s 407

Figure 1 2-3 Double aortic arch. A An anteroposterior esophagrarn image shows focal narrowing of both sides of the esophagus. The impression on the ri ght (large arrow) is somewhat larger and more cephalad than the impression on the left. The trachea is also narrowed.

Left Aortic Arch Anomalous Right Subclavian Artery A left aortic arch with an anomalous origin of the right subclavian artery (aberrant right subclavian artery; arteria lusoria) is the most common malformation of the great vessels . The prevalence of this anomaly in the general population is approximately 0.5%. The configuration of the aortic arch is normal. The anomalous right subclavian artery arises as the last branch of the arch and courses obliquely from left to right across the midline dorsal to the esophagus . Rarely, the anomalous subclavian artery courses between the trachea and the esophagus; these patients usually have coexistent cardiac anomalies. An anomalous right subclavian artery in conjunction with a normal left aortic arch is nearly always asymptom­ atic, and can be considered an inconsequential develop­ mental variation. There may be rare instances in which this anomaly is associated with mild dysphagia in adults (dysphagia lusoria) . There also are rare instances in

B

The descending thoracic aorta is on the left (small arrows) . B. On the lateral view, there is a prominent posterior indentation on the esophageal contrast column (arrow) . The trachea is narrow.

which the combination of an aberrant right subclavian artery and a tortuous right common carotid artery causes tracheal compression in children. An anomalous right subclavian artery sometimes occurs in those tetralogy of Fallot patients who have a left aortic arch. When an anomalous right subclavian artery occurs in patients with coarctation of the aorta, it often arises distal to the site of the coarctation. This results in an elevated blood pres­ sure in the left upper extremity and decreased blood pres­ sure in the right upper extremity. The blood pres sure in the lower extremities is similar to that of the right upper extremity in these patients. Anomalous right subclavian artery with a left aor­ tic arch is most often detected as an incidental finding during esophagography performed for another purpose. On the frontal view, the subclavian artery produces a characteristic oblique esophageal indentation that is lower on the left and higher on the right. This indenta­ tion often parallels the course of the left main bronchus and is located 2 to 3 em above the bronchus. The lateral view shows a posterior indentation on the esophagus

408 Part 2 The Ca rd iovas cu l a r System

Left Circumflex Aortic Arch Left circumflex aortic arch is an extremely rare anomaly in which the aorta ascends to the left of the trachea, crosses dorsal to the esophagus, and descends to the right of the spine. If the ductus arteriosus/ligamentum arteriosum is right-sided, a vascular ring results. The components of the vascular ring in this situation are the left-sided segment of the aortic arch (on the left) , the dorsal retroesophageal por­ tion of the arch (posteriorly) , the ductus arteriosus (on the right) , and the pulmonary artery (anteriorly) . The anoma­ lous right subclavian artery that is usually present in these patients does not form part of the ring. However, if there is a diverticulum of Kommerell (at the aortic origin of the vessel) , this can contribute to compression of the airway. The maj or importance of an anomalous right subclavian artery in patients with left circumflex aortic arch relates to its association with a right-sided ductus arteriosus_7-9 The embryological basis for left circumflex aortic arch likely involves preservation of the proximal left fourth arch, persistence of a segment of the right sixth arch (right-sided ductus arteriosus) , and persistence of the dis­ tal portion of the right fourth arch (the right dorsal arch) . The distal portion of the right dorsal aortic arch may per­ sist in these patients as the diverticulum of Kommerell, from which the right subclavian artery arises. The presence of, and severity of, symptoms in patients with left circumflex aortic arch relate to the specific anat­ omy and the completeness of the vascular ring. Those

Figure 1 2-4 Double aortic arch.

A posterior view of a cr angiography volume rendering shows the ascending aorta to branch into 2 approximately equal size aortic arches that give rise to the 4 brachiocephalic vessels. The aortic arches join posteriorly to form a normal appearing descending aorta.

patients with a right-sided ductus or ligamentum arteria­ sum have a complete ring, and may have feeding difficul­ ties and respiratory distress as infants . The distal portion of the trachea is displaced to the left and the right main bronchus may be compressed.

A hypoplastic right lung

sometimes accompanies this anomaly. If the ductus is located on the left, the ring is incomplete; these patients

(Figure 1 2-5) .

This anomaly is differentiated from a vas­

cular ring or other more significant arch anomaly by the lack of substantial lateral esophageal impressions , the mild degree of the posterior es ophageal impres sion, the characteristic oblique course, and the lack of associated tracheal narrowing.

CT and M R demonstrate the vascu­

lar anatomy in patients with anomalous right subclavian artery, and serve in selected patients to exclude the pres­ ence of a vascular ring

(Figure 1 2-6) . 6

may be asymptomatic or suffer mild dysphagia as a con­ sequence of compres sion of the esophagus by the retro­ esophageal segment of the aortic arch. The characterizing features of left circumflex aortic arch on chest radiographs are a descending aorta on the right side of the spine and the aortic knob located to the left of the trachea. The right lung is small in many of these patients . The retroesophageal segment of the aorta pro­ duces a large posterior indentation on the esophagus that is readily demonstrable with esophagography. Frequently, the esophageal impression follows an oblique course, from

Anomalous Right Subclavian Artery, Left Aortic Arch Pathological a n atomy

Right Posterior Left Anterior

Normal Anomalous subclavian Normal arch Normal

a more cephalad location on the left to a caudad orientation on the right. There is some degree of rightward displace­

Rad iol ogy

ment of the trachea and esophagus , as well.

N o i ndentation Oblique mild esophageal i ndentation Normal left arch N o tracheal i ndentation

horizontal segment of the aortic arch to pass posterior to

MR shows the

the trachea and esophagus, with the descending portion coursing inferiorly to the right of the midline. Although the ligamentum arteriosum usually cannot be visualized on

MR, the presence of an aberrant right subclavian artery

(arising as the last arch vessel) indicates that the ductus is on the right and that a complete ring is present.10

Chapter 1 2 Ano m a l i es of the G reat Vess e l s 409

A

B

Figure 1 2-5 Anomalous right subclavian artery. A An anteroposterior esophagrarn image shows an oblique impression on the contrast column (arrow), paralleling the left

main bronchus. B. The extrinsic esophageal impression is posterior on the lateral view. There is no tracheal narrowing on either projection.

Left Circu mflex Aortic Arch With Right Ductus

Right Aortic Arch

Pathological a n atomy

Posterior

Right ductus/ l igamentu m , descend ing aorta Descend ing aorta Aortic arch

Left Anterior

Ascending aorta Pulmonary artery

Right

Rad iology

Descend ing aorta to the right of the m idline Posterior esophageal i ndentation Left aortic knob Tracheal compression

Right Aortic Arch With an Aberrant Left Subclavian Artery Right aortic arch with an aberrant left subclavian artery is one of the more common forms of vascular ring. The aor­ tic arch ascends anterior and to the right of the trachea, then courses posterior to the esophagus, and descends to the left of the spine or at the midline . The first branch of the arch is the left common carotid artery, followed by the right common carotid artery and then the right sub­ clavian artery. The left subclavian artery arises anoma­ lously from the descending portion of the aorta. In many

41 0 Part 2 The Ca rd iovascu l a r System

Figure 1 2-6 Anomalous right subclavian artery. The right subclavian artery (arrow) is the last vessel to arise from the aortic arch on this posterior projection of a three-dimensional CT image.

patients, the ongm and proximal segment of the left subclavian artery are enlarged; this is termed the diver­ ticulum of Kommerell. Embryologically, this represents the posterior portion of the otherwise obliterated left aortic arch. The ductus arteriosus in patients with this anom­ aly nearly always arises from the descending aorta, the left aortic diverticulum, or the proximal aspect of the left subclavian artery. The ductus communicates with the left pulmonary artery. Although the anomalous left subcla­ vian artery does cause some degree of compression along the posterior wall of the esophagus, it is the ductus arte­ riosus or ligamentum arteriosum that actually completes the vascular ring of this anomaly.' The vascular ring produced by a right aortic arch with an aberrant left subclavian artery and a left ligamentum arteriosum is relatively loose, and many of these patients are asymptomatic. Those patients who are symptomatic tend to have milder manifestations than those patients with a double aortic arch. Potential findings of tracheal or esophageal narrowing include wheezing, stridor, cough, and recurrent respiratory infection. Older children may complain of dysphagia alone. Standard chest radiographs of children with right aortic arch and aberrant left subclavian artery show the position of the arch as a right-sided indentation in the tracheal air column. The aortic knob is usually located somewhat higher than is typical for a normal left aortic knob. Occasionally, there is a round density along the left upper mediastinum, slightly below the level of the aortic knob; this represents the diverticulum of Kommerell or a

portion of the descending aorta. The lateral chest radio­ graph frequently shows anterior bowing andjor narrow­ ing of the inferior aspect of the trachea. 2 Esophagography of patients with right aortic arch and an anomalous left subclavian artery demonstrates a pronounced posterior indentation on the esophagus, best visualized on the lateral projection ( Figure 1 2-7) . The ligamentum arteriosum, diverticulum of Kommerell, and aberrant left subclavian artery all contribute to this poste­ rior indentation. On the frontal view, there is an impres­ sion along the right side of the esophagus because of the right aortic arch. The presence of a ring is indicated by an indentation along the left side of the esophagus at approximately the same level. The left-sided indentation is a result of the diverticulum of Kommerell, the aberrant left subclavian artery, and/or the ligamentum arteriosum. This constellation of findings often produces a "reverse S" configuration, similar to that of double aortic arch. The lat­ eral esophageal indentations tend to be less pronounced with this anomaly than with double aortic arch. Also, tra­ cheal narrowing is mild or absent in most patients with a right arch and aberrant left subclavian artery." MR and CT provide a definitive diagnosis of right aor­ tic arch with aberrant left subclavian artery. The right-sided location of the arch is easily appreciated on cross-sectional imaging studies (Figure 1 2-8) . A key finding is the anoma­ lous origin of the left subclavian artery as the last branch of the arch. When present, the diverticulum of Kommerell appears as an outpouching from the arch at the origin of the left subclavian artery ( Figure 1 2-9) . The ligamentum arteriosum is not visible on M R or CT; if the ductus arte­ riosus is patent, it can sometimes be demonstrated on M R angiography o r contrast-enhanced CT. M R and C T gener­ ally provide accurate characterization of the tracheobron­ chial compression in these patients (Figure 1 2-10) . ' 2 ·' 3

Right Aortic Arch With Aberrant Left Su bclavian Artery Pathological a n atomy

Rad iol ogy

Right

Right esophageal indentation, right aortic knob Horizontal posterior esophageal i ndentation Left esophageal i ndentation

Right arch

Posterior Aberrant s u bclavian, aortic d iverticu l u m , ductus/ligamentu m Left Aberrant s u bclavian, aortic d iverticulum, d uctus/ligamentu m Anterior Ascending aorta, Tracheal com pression p u l monary artery

Right Aortic Arch With Mirror-image Branching Right aortic arch with mirror-image branching is a rel­ atively common anomaly in which the aorta ascends

Chapter 1 2 A n o m a l ies of the G reat Vess e l s

A

Figure 1 2-7 Right aortic arch and an anomalous left subclavian artery. A. An anteroposterior esophagram image shows focal esophageal narrowing (arrow) caused by right· and left-sided extrinsic impressions. There is slight leftward deviation of the

A

41 1

8

trachea because of a right aortic arch. B. A diverticulum of Kommerell appears as a soft-tissue density (arrow) that causes deviation and narrowing of the esophagus on this lateral view. Note that there is no substantial tracheal narrowing.

B

Figure 1 2-8 Right aortic arch and anomalous left subclavian artery. A, B. Axial CT images demonstrate a right aortic arch ( A) and diverticulum of Kommerell (arrow). There is no significant tracheal narrowing.

41 2 Part 2 The Ca rd i ovascu l a r System

A

Figure 1 2--9 Right aortic arch with aberrant left subclavian artery. A. A left lateral view of a three-dimensional maximum-intensity projection MR examination shows the left subclavian artery (arrow) as the last branch vessel of a right aortic arcll. The first vessel is the left common carotid artery, followed by the right

anterior to the trachea, courses over the right main bron­ chus, and descends to the right of the vertebral column. The first branch of the arch is the left brachiocephalic artery, which courses to the left of and anterior to the trachea. The right common carotid and the right subcla­ vian arteries constitute the second and third branches of the arch. In most patients, the descending thoracic aorta crosses over the spine and exits the thorax through the aortic hiatus in a normal left-sided location. The ductus arteriosus in patients with right aortic arch and mirror­ image branching is most often located on the left, usually arising from the left brachiocephalic artery near its origin and connecting to the left pulmonary artery. Occasionally, there is a right-sided ductus; there are rare instances of bilateral duct ductus arteriosi. Rarely, a left-sided liga­ mentum arteriosum extends from the descending aorta to the left pulmonary artery, thereby forming a complete vascular ring. The other forms of right aortic arch with mirror-image branching do not constitute complete rings.' Approximately 95% of patients with right aortic arch and mirror-image branching have congenital heart

8

common carotid artery and right subclavian artery. B. There is a large diverticulum of Kommerell (arrow) at the origin of the aberrant left subclavian vessel on this posterior view. The aortic arcll is on the right side.

disease. Most of the associated lesions are cyanotic. This arch anomaly occurs in approximately 25% of patients with tetralogy of Fallot, 35% of those with truncus arte­ riosus, and 20% of individuals with double-outlet right ventricle. Other less-common associations include tri­ cuspid atresia and transposition of the great arteries with pulmonary valvular stenosis. This aortic arch configura­ tion is present in the great majority of individuals with situs inversus and mirror-image dextrocardia. Of those patients without associated intracardiac anomalies, most either have a vascular ring formed by a ductus extending from the descending aorta to the left pulmonary artery or have anomalies of the proximal aspect of the left pulmo­ nary artery. Some of these patients have a chromosome 22qn deletion.'-4-' 6 Chest radiographs of patients with right aortic arch and mirror-image branching show leftward deviation of the trachea. There may be minimal impression on the contrast-filled esophagus , without substantial narrowing. MR or CT shows a right-sided aortic arch and great vessel orientation that is the mirror image of a normal left arch ( Figure 1 2·1 1 ) . '7

Chapter 1 2 A n o m a l ies of the G reat Vess e l s 413 With the rare form of aortic arch and mirror-image branching in which a vascular ring is formed by a left ductus or ligamentum that extends from the descend­ ing aorta to the left pulmonary artery, esophagography shows a pronounced right-sided impression (the right aortic arch) , a posterior impression (the anomalous duc­ tus or ligamentum) , and a small left-sided impression (the left pulmonary artery) that is slightly inferior to the arch impression. MR of these patients shows the right­ sided aortic arch, as well as the great vessel anatomy. Although the ligamentum arteriosum is not directly visu­ alized on M R, the presence of an anomalous ligamentum is suggested if there is a diverticulum arising from the proximal aspect of the descending aorta. M R may also show anterior displacement of the trachea adjacent to the diverticulum.' 8-20 A

Right Aortic Arch With M i rror-image Branching and Ductus from Aorta to Left Pul monary Artery Pathological a n atomy

Right Posterior Left Anterior

8

Figure 1 2-10 Right aortic arch with aberrant left subclavian artery.

There is focal tracheal narrowing as it passes between the right pulmonary artery ( RPA) and a diverticulum of Kommerell (D).

Right Aortic Arch With M irror-image Branching Pathological a n atomy

Rad iology

Right

Right esophageal and tracheal i ndentation Normal Normal Normal ± Cardiomegaly, without vascular congestion

Right arch

Posterior Normal Left N ormal Anterior Normal Cyanotic congenital heart disease

Rad iol ogy

Right arch

Right esophageal and tracheal i ndentation Left ductus/ Posterior esophageal ligamentu m i m pression Left pul monary Small left esophageal i ndentation artery Pulmonary arteries Tracheal compression

Right Aortic Arch With Isolated Left Subclavian Artery Right aortic arch with an isolated left subclavian artery is a rare anomaly in which the left subclavian artery does not directly connect to the aorta or the brachiocephalic artery. In utero, blood flow to the left subclavian artery is via a left ductus arteriosus . When the ductus closes in the neonate, antegrade flow ceases in the proximal aspect of the subclavian artery. Blood then fl ows in a retrograde manner from the ipsilateral vertebral artery to supply the subclavian artery and the left upper extremity; this represents a congenital subclavian steal syndrome. This anomaly sometimes occurs in association with tetralogy of Fallot.'5 Right aortic arch with isolated left subclavian artery is not a vascular ring and does not cause respiratory symptoms or swallowing dysfunction. The maj or clini­ cal manifestations are a result of the poor arterial sup­ ply to the left upper extremity. These patients sometimes develop ischemic changes in the left arm or hand. Clinical examination shows diminished pulses.

414

Part 2 The Ca rd i ovascu l a r System Right Aortic Arch With Isolated Left Su bclavian Artery Pathology

Rad iology

Right arch

M i ld tracheal and esophageal indentation M R, CT: absent proximal segment of subclavian Angiography, Doppler: retrograde flow in left vertebral

Left su bclavian not con nected to aorta S u bclavian steal

Right Aortic Arch With Left Descending Aorta Right aortic arch with a left descending aorta (right circumflex aortic arch) is a mirror image of a left aor­ tic arch with a right descending aorta. The aortic arch ascends on the right, courses across the midline dorsal to the esophagus, and descends on the left. In many of these patients, there is an aberrant left subclavian artery, sometimes arising from an aortic diverticulum. The left subclavian artery may be stenotic at its origin. In those patients with an aberrant left subclavian artery, the ductus arteriosusjligamentum arteriosum is located on the left and completes a vascular ring. Esophagography shows a right-sided impression produced by the right aortic arch and a prominent obliquely oriented posterior impres­ sion because of the retroesophageal segment of the aorta. When present, the aortic diverticulum and aberrant sub­ clavian artery contribute to the esophageal impression. The presence of a ring is indicated by an impression along the left side of the esophagus. Figure 1 2-1 1 Right arch with mirror-image branching. An anterior projection image from a three-dimensional rendering of a cardiac MR study of a child with a repaired tetralogy of Fallot shows a right aortic arch with a brachiocephalic vessel arrangement that is a mirror image to normal.

The diagnosis of right aortic arch with isolated left subclavian artery is suggested when radiographs show a right-sided aortic arch in a patient with clinical signs of poor left upper-extremity perfusion. MR or CT angi­ ography confirms absence of the proximal segment of the left subclavian artery. Retrograde flow in the left ver­ tebral artery can be documented with Doppler sonogra­ phy, transcatheter angiography, or phase-contrast M R I . Aortography shows failure o f opacification o f the left sub­ clavian and vertebral arteries on the initial images , and delayed visualization as contrast-opacified blood courses in a retrograde manner from the left vertebral artery. Additional neck and chest vessels may supply collateral blood flow to the left upper extremity. 21•22

Cervical Aortic Arch Cervical aortic arch is a rare anomaly in which there is abnormal extension of the aorta into the neck. Great ves­ sel anomalies typically accompany this lesion: (a) there is a separate origin of the carotid artery contralateral to the side of the aortic arch, and (b) the descending tho­ racic aorta passes dorsal to the esophagus, crossing to the side opposite to the aortic arch. The arch can be either right-sided or left-sided, but the former is more common. In some patients, the ductus arteriosusjligamentum arteriosum originates from the descending aorta on the side contralateral to the arch, thereby producing a vascu­ lar ring. Most patients with a cervical aortic arch are asymp­ tomatic. Feeding difficulties andjor respiratory symp­ toms (e.g., stridor) sometimes occur, particularly when there is a vascular ring. Physical examination demon­ strates a pulsatile mass at the base of the neck, some­ times with a thrill. In infants, extrinsic compression of the mass causes reduction of lower-extremity pulses, as well as diminished pulses in the upper extremity contra­ lateral to the arch.

Chapter 1 2 A n o m a l ies of the G reat Vess e l s 41 5

Figure 1 2-13 Midline descending aorta. Figure 1 2-12 Cervical aortic arch. A reformatted sagittal image to the right of the midline shows a tortuous right aortic arch that extends into the neck.

The major findings of cervical aortic arch on frontal chest radiographs are superior mediastinal widening, dis­ placement ofthe trachea from the side ofthe arch, and loca­ tion of the descending aorta contralateral to the arch. The frontal view of an esophagram shows lateral displacement of the esophagus, while the lateral view demonstrates a large, round, posterior indentation where the aorta crosses the midline. A definitive diagnosis is established with CT or MR (Figure 1 2-1 2 ) .

Cervical Aortic Arch

Pathology Extension of arch i nto neck Mass effect from arch Descending aorta crosses midline

Rad iology U pper med iastinal widening Right or left deviation of trachea and esophagus Oblique i m p ression on posterior aspect of esophagus

M id l i ne Descending Aorta Midline descending aorta is an uncommon anomaly in which the upper portion of the descending aorta is

Axial contrast-enhanced CT of an 11-month-old child with a right-sided aortic arch shows the descending aorta (arrow) immediately anterior to the thoracic spine. There is compression of the left main bronchus. AA, Ascending aorta; S VC, superior vena cava.

anterior to the vertebral bodies rather than in a right or left paravertebral location. It can occur as an isolated lesion, in association with other aortic anomalies (double aortic arch, right aortic arch with anomalous left subcla­ vian artery, or right aortic arch with left-sided descending aorta) , or as a secondary phenomenon in patients with mediastinal deviation caused by a hypoplastic right lung. The anomalous position of the descending aorta can cause compression of the inferior aspect of the trachea and the main bronchi. Stridor and respiratory symptoms are common. The diagnosis is straightforward on CT or MR ( Figure 1 2-13 ) .23

Anomalous Brachiocephalic Artery Anomalous brachiocephalic artery refers to an origin of this vessel to the left of the midline . In crossing to the right, the vessel causes some degree of anterior compres­ sion of the trachea. This anatomic variation usually is of no clinical consequence. There are rare instances in which the anomaly causes or contributes to symptomatic tracheal compression in infants . Evaluation with CT or MR shows a normal order of brachiocephalic vessel ori­ gins from the arch . However, the brachiocephalic artery arises to the left of the midline and crosses immediately anterior to the trachea ( Figure 1 2-14 ) . Sagittal images show variable compression of the trachea. CT virtual

41 6 Part 2 The Ca rd iovascu l a r System

B

A

Figure 1 2-14 Anomalous brach iocephalic artery. A. B. Contrast-enhanced Cf images of a 9-month-old infant with inspiratory stridor show the brachiocephalic artery (arrows) to pass anterior to the trachea. There is mild localized narrowing of the adjacent portion of the trachea. C. A lateral chest radiograph obtained at 2 months of age demonstrates tracheal narrowing as a result of tracheomalacia. The narrowing is most pronounced in the region of the anomalous vessel (arrow) .

tracheobronchoscopy provides three-dimensional depic· tion of associated airway narrowing.'·24

Aneu rysm ofthe Ductus Arteriosus The prevalence of congenital aneurysm of the ductus arteriosus is approximately 1. 5%.25 Secondary aneurysms caused by infection or trauma can also occur. The diag­ nosis of a congenital aneurysm is usually established early during infancy. There is an increased frequency of ductus arteriosus aneurysm in patients with connec­ tive tissue diseases such as Marfan syndrome. Other associated conditions include trisomy 21, trisomy 13 , and Smith-Lemli-Opitz syndrome. Many patients are asymp· tomatic; however, severe complications can occur, includ­ ing extension of thrombus into the pulmonary arteries, systemic thromboembolism, and spontaneous rupture of the lesion.

c

On chest radiographs, an aneurysm of the ductus arte­ riosus often produces a mass or abnormal fullness along the left upper mediastinal border between the main pul· monary artery and the left aortic arch. There is deviation of the trachea. Confirmation of the diagnosis is usually possible with echocardiography. MR and CT angiography are alternative techniques. Thrombus within the lesion often leads to increased signal intensity on Tl-weighted M R images (Figure 1 2-1 5) . Th e aneurysm usually i s fusiform. Communication with the aorta is typical; the pulmonary end is narrow or occluded (Figu re 1 2-16) . > 6,27

Ductus Diverticu l u m A ductus diverticulum i s a remnant of the aortic portion of the ductus arteriosus. The pulmonary end of the ductus closes appropriately, but a variable length of the aortic end remains patent. On imaging studies, a ductus diverticulum

Chapter 12 Anom a l i es of the G reat Vess e l s 41 7

Figure 1 2-1 5 Aneurysm of the ductus arteriosus. A thrombosed ductus aneurysm (arrows) appears as a mass adjacent to the aorta on this Tl-weighted MR image.

appears as a convex bulge along the anterior-inferior sur­ face of the isthmic portion of the arch (posterior aortic arch) (Figure 1 2-17) . Typically, there are smooth uninterrupted margins and gently sloping shoulders. A larger diverticu­ lum has a funnel shape.2 8

Figure 1 2-1 6 Ductus arteriosus aneurysm. A sagittal oblique contrast-enhanced M R angiography image shows a small aneurysm (arrow) along the undersurface of the aortic arch. There is no visible thrombus. The acute angles at the junction with the aorta and the rounded walls differentiate this small aneurysm from a simple ductus diverticulum.

Congen ital Coarctation of the Aorta The aortic arch develops between gestation weeks 5 and 7 as 6 paired vessels that emerge from the distal portion of the embryonic truncus arteriosus. The right fourth arch contributes to development of the right subclavian artery. The left fourth arch becomes the definitive aortic arch and connects with the left dorsal aorta. The portion of the aorta near the insertion of the ductus arteriosus is prone to abnormal development that results in narrowing; that is, coarctation. The typical cause of the narrowing is deformity of the aortic media and intima, with posterior infolding of the lumen. The narrowing may occur proxi­ mal to, adjacent to, or distal to the insertion of the ductus arteriosus. The narrowing can involve a short or long seg­ ment of the arch, and be symmetric or asymmetric. The most common location of coarctation is at the junction of the aortic arch and descending aorta opposite the site of insertion of the ductus arteriosus . Cystic medial necrosis is common at the site of aortic coarctation. Intimal thick­ ening and elastic tissue disruption often develop in the poststenotic segment.

Categorization of congenital coarctation of the aorta is generally on the basis ofthe anatomy and the hemodynamic characteristics (Table 1 2-2) . Coarctation can be localized or diffuse. The most common type is a short-segment stenosis (i.e., localized coarctation) in the region of the attachment of the ductus arteriosus; this is termedjuxtaductal, postductal, or adult-type coarctation. Narrowing of the aortic isthmus, termed isthmic or preductal coarctation, usually involves a relatively long segment of the arch (i.e., tubular hypoplasia) , combined with a superimposed focal short-segment con­ striction proximal to the ductus arteriosus. Additional less­ common forms of coarctation include atresia of the aortic arch and interruption of the aortic arch. Supravalvular steno­ sis of the ascending aorta occurs in patients with Williams syndrome. Kinking of the aortic arch without obstruction is termed pseudocoarctation. Abdominal coarctation can occur as a focal or long segment stenosis. Coarctation of the aortic arch accounts for 5% to 10% of congenital heart disease. There is a 2:1 male-to-female

41 8 Part 2 The Ca rd i ovascu l a r System

Figure 1 2-17 Ductus diverticulum. A left posterior oblique volume rendering C T image shows a smooth bulge (arrow) at the junction of the posterior aortic arch and descending aorta.

ratio. Various cardiac anomalies are common in these patients, including ventricular septal defect (33% of patients) , patent ductus arteriosus (65% of patients) , bicuspid aortic valve (5o% o f patients) , atrial septal defect, transposition of the great vessels, mitral valve disease,

Table 1 2-2. Types of Congenital Coarctation of the Aorta S ite

Arch, proxi mal to the d uctus

Type

; Hypoplasia Atresia I nterru ption ' Focal j uxtaductal or postd uctal coarctation ' Pseudocoarctation __

Arch, adjacent to ductus

·

Arch, kinking without obstruction Thoracic aorta Abdom inal aorta

; Thoracic coarctation ' Abdom inal coarctation

endocardial fibroelastosis, atrioventricular canal, and common ventricle. Cerebral aneurysms occur with a greater frequency in patients with coarctation of aorta than in the general population. Coarctation is associated with various syndromes and chromosomal anomalies , including Turner syndrome ( 2 o % t o 35% o f patients with Turner syndrome have coarctation) and Shone complex. Noncardiac malformations that occur with increased fre­ quency in children with coarctation include tracheoesoph­ ageal fistula, clubfoot, hypospadias, and ocular anomalies . Echocardiography of patients with coarctation of the aortic arch serves to document the morphology of the nar­ rowed aorta and to evaluate the blood flow characteristics. The suprasternal notch projection is most useful. Doppler evaluation shows turbulent flow. There is alteration of the amplitude and wave pattern within the aorta distal to the coarctation. Evaluation of the arch for associated anoma­ lies is an essential component of the echocardiographic examination. 29 MR is an excellent technique for the evaluation of coarctation of aorta, particularly in older children. The parasagittal oblique ("candy cane") proj ection provides visualization of the entire aortic arch ( Figure 12-18) . Because of tortuosity, however, careful inspection of the arch in various proj ections is usually required. Cine M R images show turbulent blood flow i n the region o f the narrowed lumen. There is often a j et-like signal void extending distal to the stenosis. A bicuspid aortic valve is frequently present; the resultant turbulent flow may pro­ duce systolic signal loss in the ascending aorta on cine MR images. Accurate definition of the location and mor­ phology of the left subclavian artery is an important part of the examination, as this vessel is often used in surgical repair procedures for coarctation. Blood flow volume and velocity in the region of a coarctation can be measured noninvasively with velocity-encoded cine sequences . As with echocardiography, the peak j et velocity correlates with the severity of obstruction. With a long-standing coarctation, there is progressive dilation of collateral ves­ sels , including the internal thoracic (internal mammary) and intercostal arteries ( Figure 1 2-19) . 3°-3 8 MR also serves an important role in the followup of patients who have undergone surgical repair of a coarc­ tation. MR is more accurate than echocardiography in these patients for the measurement of luminal caliber at the repair site . The most common complications are recoarctation, pseudoaneurysm, and true aneurysm. The hemodynamic significance of recurrent or residual narrowing at the site of a repaired coarctation can be estimated by observing the status of collateral vessels; collaterals are best demonstrated on contrast-enhanced images or phase-contrast MR angiography. The dynamics of flow in the repaired aorta can be measured by velocity­ encoded cine M R.3° ·39-42 Aneurysm formation after patch angioplasty for aortic coarctation is a relatively frequent and potentially lethal complication. Although several mechanisms of

Chapter 12 A n o m a l i es of the G reat Vessels

Figure 1 2-18 Preductal localized coarctation. An oblique "candy cane" M R angiography image of the arch shows a short-segment circumferential narrowing (arrow) just beyond the left subclavian artery. There is mild poststenotic dilation.

aneurysm formation are possible, an important factor in many patients is flow acceleration in a hypoplastic trans­ verse aortic arch that exerts strain on the distal portion of the arch. This can lead to expansion of the patch and aneurysm formation.4H4 A postoperative pseudoaneurysm is caused by a transintimal leak, usually at the margin of a graft. Pseudoaneurysm can also occur in children treated with percutaneous angioplasty or stent placement. The site of the leak can sometimes be demonstrated with cine M R as a jet of flowing blood.45-47

Isthmic Coarctation Hypoplasia of the aortic arch most commonly occurs in the isthmus, which is the segment of the arch between the origin of the left subclavian artery and the insertion ofthe ductus arteriosus. In more than half of these patients,

41 9

there is tubular hypoplasia of the transverse portion of the aortic arch. Arterial flow into the brachiocephalic ves­ sels via the ascending portion of the arch is preserved. There is often a coexistent localized coarctation adjacent to the ductus arteriosus; the ductus is usually patent. Aortic arch atresia is the most severe manifestation of aortic arch hypoplasia. Hypoplasia or atresia of the aortic arch is usually accompanied by a maj or congenital car­ diac anomaly, such as a large ventricular septal defect, double-outlet right ventricle, endocardial cushion defect, Taussig- Bing anomaly, or tricuspid atresia with aortopul­ monary transposition. Many of the associated conditions cause diversion of blood flow from the aortic arch during fetal development, presumably causing or contributing to hypoplasia of the arch. Most patients with isthmic coarctation have an asso­ ciated large ventricular septal defect, which provides a pathway for blood flow into the right heart and sub­ sequently into the thoracic aorta via the patent ductus arteriosus. In utero, isthmic coarctation has little hemo­ dynamic consequence because there is little flow (approx­ imately 10% of cardiac output) across this segment of the arch even in the normal fetus . The brachiocephalic ves­ sels are primarily supplied by the ascending aorta and the thoracic aorta is supplied by the ductus. In fact, this fetal physiology is reflected in normal full-term infants by an aortic isthmus that is about three-fourths the diameter of the descending aorta; the calibers slowly equalize over the next 6 months. In the newborn with isthmic coarcta­ tion, constriction of the ductus arteriosus and decrease in pulmonary vascular resistance lead to increased reliance on perfusion via the ascending aorta. The aortic obstruc· tion causes left ventricular afterload. Because most of these infants have a ventricular septal defect, marked left­ to-right shunting occurs. Coarctation syndrome refers to the common clinical findings in infants with severe hypoplasia of the aortic arch. Many of these infants have associated cardiac anom­ alies that cause elevation of the right ventricular pressure, thereby contributing to right-to-left flow through the duc­ tus arteriosus . Infants with coarctation syndrome may appear normal immediately after birth , but constriction of the ductus arteriosus and progressive decrease in pul­ monary vascular resistance rapidly lead to respiratory dis­ tress and signs of cardiac failure. The findings can mimic those of severe aortic stenosis or overwhelming sepsis. Cardiogenic shock, metabolic acidemia, and oliguria may occur. Prior to the onset of overt left ventricular failure, these infants may appear irritable and debilitated, with a weak cry, tachypnea, and failure to thrive. The upper­ extremity pulses are preserved, while those in the lower extremities are weak or absent. Prostaglandin E, infusion in infants with severe coarctation serves as a temporizing measure to maintain patency of the ductus and preserve lower-body perfusion. The clinical manifestations of less-severe forms of isthmic coarctation tend to be subtler, particularly while

420 Part 2 The Ca rd iovas cu l a r System

A

Figure 1 2-1 9 Localized coarctation. A There is severe focal narrowing of the aorta (arrow) just beyond the origin of the left subclavian artery on this M R angiography image o f a z-year-old.

the ductus arteriosus remains patent. Maintenance of a fetal pattern of perfusion mitigates severe symp· toms in these infants, with perfusion of the brachio· cephalic vessels via the left heart and perfusion of the lower portion of the body via a patent ductus arteriosus . Infants with isthmic coarctation who have a patent due· tus arteriosus , a ventricular septal defect, and pulmonary artery hypertension usually have normal or mildly dimin· ished lower-extremity blood pressures. Most infants with coarctation and an intact ventricular septum have major blood pressure gradients between the arms and legs. However, those with severe heart failure may have similar, but subnormal, pressures in the upper and lower extremities . Infants with moderate to severe isthmic coarctation often have generalized cardiomegaly on chest radiographs (Figure 1 2-20) . Chamber enlargement usually includes the left ventricle, right ventricle, and left atrium. Most patients have a ventricular septal defect that results in prominent pulmonary vascularity because of left-to-right shunting. Left ventricular volume overload is associated

8

B. An anterior three-dimensional image shows marked enlarge­ ment of the internal thoracic arteries (arrows) , which provide collateral flow to the lower portion of the body.

with pulmonary venous hypertension and pulmonary edema. Coarctation syndrome is the most common cause of pulmonary venous hypertension in infants during the second and third weeks of life. The radiographic findings in infants with coarctation generally do not allow a spe­ cific diagnosis. Patients with coarctation of the aorta who have less­ severe disease and present later in childhood may have radiographic signs of left ventricular hypertrophy and poststenotic dilation of the descending aorta. Overall heart size is often normal or only minimally prominent ( Figure 1 2-21 ) . The hypertrophied left ventricle has a rounded contour. The pulmonary vascular pattern is nor­ mal. The pulmonary artery segment of the cardiac border is small because of rotation of the heart. Rib notching is sometimes visible on radiographs of older children with uncorrected coarctation. The radiographic appear­ ances of the aortic knob and descending aorta vary with the nature of the anomaly. Echocardiography, MR, and angiocardiography provide detailed depiction of the arch anatomy ( Figure 1 2·22) .

Chapter 12 A n o m a l ies of the G reat Ves s e l s 421

Figure 1 2-20 Isthmic coarctation of the aorta. An anteroposterior chest radiograph of an infant with severe coarctation shows marked cardiomegaly, pulmonary edema, and pulmonary vascular prominence.

Isth mic Coarctation Pathology

Rad iology

N arrowed aortic arch Elevated left ventricular afterload Left�o-right s h u nting

Cardiomegaly Pulmonary edema Pulmonary vascu lar prominence Prominence of the descend i ng aorta

Poststenotic di lation

Localized Coarctation Localized coarctation most often occurs just beyond the origin of the left subclavian artery or adjacent to the duc­ tus arteriosum (Figure 1 2-23) . Classification of the anomaly is according to the relationship with the ductus arteriosus: preductal, juxtaductal, or postductal. Major intracardiac anomalies are not as common with the localized form of coarctation as with isthmic coarctation. Bicuspid aortic valve is common, however. Other potential cardiovascular anomalies in these patients include aberrant subclavian artery origins, ventricular septal defect, patent ductus arte· riosus, and parachute mitral valve. There is a strong asso· dation of localized coarctation with Turner syndrome.

Juxtaductal short-segment coarctation typically causes no major hemodynamic abnormality in the fetus. In utero and prior to ductus closure in the neonate, the patent duc­ tus mitigates aortic narrowing, as the constriction is usu­ ally located along the lateral wall of the aorta across from the ductus. In addition, constriction of the ductus arterio­ sus in the neonate usually begins along the portion arising from the pulmonary artery. Therefore, despite the proximal closure, the patent distal portion of the ductus contributes to the aortic lumen. Postnatal closure of the ductus arterio­ sus in these infants sometimes leads to an abrupt increase in afterload of the left ventricle. The increased workload of the heart causes congestive heart failure. The limited abil· ity of the neonatal myocardium to respond to the increased workload exacerbates the effects of ductus closure. The major determinants of the resultant clinical manifestations are the severity of the aortic narrowing and the nature of any associated cardiac anomalies. In children with mild forms of localized coarctation, the clinical presentation can be mild or delayed until later in childhood. Some older children with this anomaly present with complaints of leg pain or weakness, often induced by strenuous exercise. Physical examination demonstrates systolic hypertension in the right arm or both arms, with reduced pressure in the lower extremi· ties. In patients with prominent collateral vessels, systolic or continuous murmurs are sometimes audible along the thorax with auscultation. As with the isthmic form, the radiographic manifes­ tations of localized coarctation vary with the severity of obstruction, the status of the ductus arteriosus, and the presence or absence of associated cardiac anomalies . In general, the radiographic manifestations of this type of coarctation in infants are relatively mild. Cardiomegaly may or may not be present on chest radiographs. Localized coarctation can cause a figure-of.three con­ figuration on frontal chest radiographs, best visualized in older children. The proximal portion of the 3 is formed by the distal aspect of aortic arch and the dilated proximal aspect of the left subclavian artery. The distal component of the 3 is formed by poststenotic dilation ofthe aorta immedi­ ately beyond the coarctation (Figure 1 2-24) . The coarctation produces a notch at the center of the 3· Similar findings are often present on the anteroposterior and left anterior oblique views of esophagography. The esophagram pat­ tern is the "reverse 3 " or "E" sign, with the portions of the aorta proximal and distal to the coarctation producing impressions in the left lateral margin of the barium filled esophagus (Figure 1 2-25) . In older patients who develop rib notching as a result of dilated collateral intercostal arter­ ies, radiographs show defects with sclerotic margins along the inferior aspects of multiple ribs. This finding is most frequent in the posterior segments of ribs 3 through 8. As with other arch anomalies, accurate characterization of a localized coarctation requires angiography, echocardiogra­ phy, or MRI (see Figures 12-18 and 12-19).

422 Part 2 The Ca rd iovascu l a r System

B

A

c

Figure 1 2-21 I sthmic coarctation of the aorta. A, B. Anteroposterior and lateral radiographs of a 3-month-old infant show the heart size in the upper limits of normal. There is a rounded contour of the left-heart border. Central pulmonary vessels are slightly prominent. There is no pulmonary edema.

D

C. An oblique MR angiography image (gradient-echo fast imaging employing steady-state acquisition) demonstrates tubular hypoplasia of the distal portion of the arch ( arrow) . D. A short axis view of the heart shows left ventricular hypertrophy.

Chapter 12 A n o m a l i es of the G reat Vessels 423

Figure 1 2-24 Coarctation of the aorta. A frontal chest radiograph shows bulges in the aortic contour

(arrows)

caused by prestenotic and poststenotic dilation. The

notch at the site of the coarctation between these segments

Figure 1 2-22 Isthmic coarctation of the aorta. An oblique aortogram image shows tubular hypoplasia of the

forms the center of the "3 sign . " Rib notching is also present.

aortic arch from just beyond the innominate artery origin to the level of the ductus. There is no contrast opacification of the left subclavian artery. The right internal mammary artery is enlarged.

Figure 1 2-25 Coarctation ofthe aorta. (arrow) in the aortic contour on this frontal

There is a notch

Figure 1 2-23 J uxtaductal short-segment coarctation.

radiograph. The fullness superior to the notch represents the

A left ventriculogram shows focal concentric narrowing of the

aortic arch proximal to the coarctation, and the inferior bulge is

distal arch

(arrow) . There is

descending aorta.

poststenotic dilation of the adjacent

caused by poststenotic dilation. There are corresponding impressions on the barium filled esophagus.

424 Part 2

The

Ca rd i ovascu l a r System

Interrupted Aortic Arch Interrupted aortic arch is an extreme form of aortic coarcta­ tion in which there is complete discontinuity of a segment of the aortic arch. Unlike aortic arch atresia, there is no bridging fibrous remnant. The most widely used classifica­ tion system for this anomaly was developed by Celoria and Patton.4 8 Type A refers to interruption distal to the origin of the left subclavian artery

(4o% to 45% of patients) ; type B ,

interruption between the left carotid and the left subclavian arteries

(55% to 50% of patients) ; and type C, interruption

proximal to the origin of the left common carotid artery (5% of patients) . The right subclavian artery in these children sometimes arises anomalously from the descending aorta or the right pulmonary artery.49·5° Interrupted aortic arch accounts for approximately

1% of all congenital heart diseases that are clinically mani­ fest in the newborn. The prevalence is approximately 1 in so,ooo livebirths. Patent ductus arteriosus is present in at least 95% of these infants, ventricular septal defect in 8o%, and subaortic stenosis in more than 50%. Almost any other cardiac anomaly can occur in association with interruption of the aortic arch; the most frequent include aortic steno­ sis, double-outlet right ventricle, truncus arteriosus, trans­ position of the great arteries , aortopulmonary window, and single ventricle.49·5'·5 2 The pathophysiology of interrupted aortic arch is iden­ tical to that ofaortic arch atresia. A patent ductus arteriosus and a ventricular septal defect provide a pathway for sys­

Figure 1 2-26 I nterrupted aortic arch. A chest radiograph of an infant with respiratory distress shows cardiomegaly and mild pulmonary vascular congestion. There is fullness of the main pulmonary artery segment of the mediastinal contour. The trachea is straight; the normal aortic knob impression is lacking.

temic perfusion. Infants with interrupted aortic arch are acyanotic. Signs and symptoms of congestive heart failure develop as the pulmonary vascular resistance falls soon after birth: tachypnea, respiratory distress, tachycardia,

Echocardiography of interruption of the aortic arch

and hepatomegaly. As the ductus arteriosus closes, signs

most often shows a straight, vertically oriented ascending

of hypoperfusion of the lower portion of the body develop;

aorta that continues directly into

the lower extremities may appear mottled. Prostaglandin

vessels. The normal rounded configuration of the arch is

1 or more brachiocephalic

E, infusion can be used to maintain patency of the ductus

lacking. The enlarged patent ductus arteriosus extends

arteriosus as a temporizing measure. Assessment of pulse

from the pulmonary artery to the descending thoracic aorta.

strengths in the upper extremities, neck, and lower extrem­

The curved nature of the prominent ductus can mimic the

ities provides clues about the location of the coarctation.

configuration of an aortic arch. The precise location of the

Factors that tend to be associated with life-threatening dis­

arch discontinuity can usually be ascertained by careful

ease in the neonatal period include absence of a ventricular

scanning in the long axis. Doppler evaluation demonstrates

septal defect, a coexistent complex cardiac anomaly, and

the direction of flow within the arch, the descending aorta,

severe aortic stenosis .53

and the brachiocephalic vessels. There may be retrograde

Chest radiographs of infants with interrupted aortic

diastolic flow in the descending aorta due to diastolic run­

arch usually show moderate to marked cardiomegaly and

off into the pulmonary artery via the ductus arteriosus .

pulmonary vascular congestion. Because most of these

Subclavian steal physiology occurs in some patients with

infants have a ventricular septal defect that produces a left­

interruption of the aortic arch.54·55

to-right shunt, shunt vascularity is often visible, particu­

Definitive anatomical evaluation of interruption of

larly in older infants. The main pulmonary artery segment

the aortic arch requires conventional angiography, CT

is prominent. Because a normal aortic knob is lacking,

angiography, or MR. The ductus arteriosus is a route for

the trachea as viewed on a frontal radiograph often has an

catheter access to the descending aorta in these children.

abnormally straight vertical configuration

(Figure 1 2-26) .

Aortography with injection through the ductus shows no

Rib notching i s uncommon, a s these infants typically pres­

brachiocephalic artery opacification with type A arch inter­

ent early and receive prompt treatment. When present, rib

ruption, left subclavian artery opacification with type B (or

notching is bilateral, right-sided, or left-sided, depending

both subclavian arteries if the right subclavian arises anom­

on the site of the arch obstruction.

alously) , and opacification of the left subclavian and left

Chapter 12 A n o m a l i es of the G reat Vessels 425 carotid arteries with type C. Left ventriculography demon­ strates a straight configuration of the ascending aorta and direct continuation into the brachiocephalic vessels.56·57 Noninvasive angiographic imaging with CT or M R often provides sufficient characterization o fthe arch defect for surgical planning. The major flow into the descend­ ing aorta in patients with interruption of the aortic arch is via the main pulmonary artery and the ductus arterio­ sus. These structures often line up with the distal aspect of the arch such that there is the appearance of a complete arch on sagittal images. This finding is an important clue to the correct diagnosis, as a normal aortic arch should never follow this straight midline course. The brachioce­ phalic vessels sometimes have a V configuration on coronal images. Because of diminished distal supply, the ascend­ ing arch is often smaller than normal in patients with arch interruption.5°·5 8

I nterruption of the Aortic Arch Pathology

Absence of a segment of the arch Left-to-right cardiac shunt

Rad iology

! Lack of normal tracheal i m pression Lack of normal aortic knob i Cardiomegaly ! Pu l monary vascu lar congestion Figure 1 2-27 Pseudocoarctation.

The prognosis for children with interrupted aortic arch varies between patients. Five-year survival for those with a repaired uncomplicated lesion is greater than 8o%. Poor outcomes are more frequent when there is an associated complex cardiac anomaly. The operative approach to inter­ ruption of aortic arch usually consists of direct anastomo­ sis, patch augmentation, or conduit interposition. If there is a substantial intracardiac shunt, pulmonary artery band­ ing is sometimes useful for palliation prior to definitive repair.49·53

Pseudocoarctation Pseudocoarctation of the aortic arch is a rare congenital anomaly in which there is elongation of the aortic arch and secondary kinking or buckling near the attachment of the ligamentum arteriosum. There is no hemodynamically sig­ nificant stenosis. Pseudocoarctation is usually asymptom­ atic. Pulses and blood pressure measurements are equal in the arms and legs. Occasionally, turbulent flow causes a murmur. Lesions that sometimes occur in association with pseudocoarctation include bicuspid aortic valve, pat­ ent ductus arteriosus, and subaortic stenosis . Occasionally, a clinically significant aneurysm develops adjacent to the buckled segment of the aorta.

A left anterior oblique M R image shows elongation and buckling of the aortic arch. There is mild enlargement of the aorta distal to the kinked segment.

The appearance of pseudocoarctation on standard chest radiographs is frequently similar to that of coarcta­ tion. The elongated arch projects somewhat high and to the left on the frontal view. There may be an irregular or kinked appearance of the arch, visible on either the frontal or the lateral view. Rib notching is absent. MR and helical CT show an elongated arch that buckles at the level of the ligamentum (Figure 1 2-27) . Turbulent flow causes a variable degree of dilation of the aorta distal to the kink. There are no enlarged collateral vessels. Transcatheter angiography and pressure evaluations are indicated for selected patients to rule out hemodynamic alterations.37·59·6 o

Pseudocoarctation Pathology

Radiology

Elongated arch Kinking of the arch Non obstructive

Elevated aortic knob I rregu lar or buckled character No pressure gradient

426 Part 2 The Ca rd iovas cu l a r System Table 1 2-3. Differential Diagnosis of a N arrowed Abdomi nal Aorta in a Child

M iddle aortic syndrome Takayasu disease Idiopathic infanti le a rterial calcification Neu rofibromatosis type 1 G ranu lomatous disease M ucopolysaccharidosis Prenatal or neonatal viral infection Rad iation therapy Arterial fibrous dysplasia Wil l iams syndrome

Middle Aortic Syndrome Middle aortic syndrome is a rare idiopathic vasculopathy of the midthoracic through abdominal portions of the aorta. The pathophysiology may involve a developmen­ tal anomaly in the fusion and maturation of the paired embryonic dorsal aortas. Similar patterns of aortic steno­ sis can occur in association with Takayasu arteritis , neu­ rofibromatosis type 1, arterial fibrous dysplasia, Williams syndrome, mucopolysaccharidosis, radiation therapy, and congenital infections (Table 1 2-3) . Some clinicians consider the term middle aortic syndrome to include both congenital and acquired forms of abdominal aortic narrowing. The idiopathic form of middle aortic syndrome most often presents during the second decade oflife. Hypertension is common. Other potential clinical manifestations include headache, fatigability, weak or absent lower-extremity pulses, and lower-extremity claudication.61 The pathological anatomy of middle aortic syndrome is effectively demonstrated with catheter angiography, CT angiography, or M R ( Figure 1 2-28) . The imaging appear­ ance of middle aortic syndrome is that of segmental abdominal or thoracoabdominal aortic stenosis, often with a smooth tapered character (Figure 1 2-29) . There may be a short spindle-shaped stenosis, or a long hypo­ plastic segment. Renal arterial stenoses are present in more than 6o% of patients . There can also be narrowing of splanchnic arteries . There is no active mural inflam­ mation with idiopathic middle aortic syndrome; conse­ quently, abnormal vessel wall enhancement is lacking on CT and M R. The most prominent collateral pathway in patients with middle aortic syndrome is usually the subclavian arteries to the internal thoracic arteries to the superior epigastric arteries to the inferior epigastric arteries to the external iliac arteries . If there is substantial obstruction at the origins of the celiac and superior mesenteric arteries,

Figure 1 2-28 M iddle aortic syndrome. Contrast-enhanced M R angiography of a 5-week-old infant with hypertension and poor lower-extremity pulses demonstrates a markedly narrowed segment of the abdominal aorta (arrow) . The right kidney (RK) fails to enhance. LK, Left kidney.

Figure 1 2-29 M iddle aortic syndrome. An abdominal aortogram shows segmental narrowing of the abdominal aorta below the celiac and superior mesenteric artery origins. There are multiple dilated collateral vessels.

Chapter 1 2 A n o m a l i es of the G reat Ves s e l s 427 the typical collateral pathway is the inferior mesenteric

or

artery to the superior mesenteric artery, from which pan­

monary segment of the pulmonary artery. If the ductus

MR. These studies confirm absence of the extrapul­

creaticoduodenal vessels fill the celiac trunk. The maj or

arteriosus is patent, it usually arises from the base of the

collateral pathway for a severe renal artery stenosis is via

ipsilateral brachiocephalic artery and connects to the intra­

lower intercostal arteries to lumbar arteries that fill the

pulmonary portion of the pulmonary artery. If the ductus is

renal arteries by way of ureteral, adrenal, and gonadal

closed, systemic-to-pulmonary collateral vessels may be vis­

ves sels . The radiographic features of middle aortic syn­

ible. Pulmonary wedge inj ections can be used to visualize

drome overlap those of late-phase Takayasu arteritis ,

the hypoplastic intrapulmonary vessels in potential surgi­ cal candidates .63·6 5 ·66

although ves sel wall enhancement on C T o r M R favors the later diagno sis. Histopathological exclusion of ves­ sel inflammation confirms the diagnosis of middle aortic syndrome.5 9 ·6 2

Anomalous Origin of left Pu l monary Artery From the Right Pu l monary Artery Anomalous origin of the left pulmonary artery from the

ANOMALIES OF THE PULMONARY ARTERIES

Absent Proximal Pu l monary Artery Absence of the extra pulmonary segment of a pulmonary

right pulmonary artery, also termed

pulmonary sling,

is an

uncommon lesion that is associated with clinically signifi­ cant airway compromise. The embryogenesis apparently relates to failure of embryonic left pulmonary arteries to connect with the sixth aortic arch. The pathological anat­ omy of this malformation consists of a normal sized left

artery is thought to be a result of abnormal involution

pulmonary artery that arises from the right pulmonary

of the proximal aspect of the sixth aortic arch during

artery, passes to the right of the trachea above the right

embryonic development. The intrapulmonary pulmo­

mainstem bronchus, and then courses between the trachea and esophagus toward the left lung. 67 , 6 8

nary arteries arise from the lung buds , and are relatively normal during fetal life in these patients . The distal

The anomalous left pulmonary artery compresses the

aspect of the sixth aortic arch (which forms the ductus

inferior aspect of the trachea and the main bronchi. The air­

arteriosus) maintains connection to the intrapulmonary

way obstruction is usually most pronounced on the right.

pulmonary artery, and the blood supply to the affected

Most patients with this anomaly exhibit clinical manifes­

lung is via the ductus arteriosus . Closure of this commu­

tations early in life; two-thirds present by

nication after birth leads to regression and hypoplasia of

Potential clinical findings include stridor, wheezing, cyano­

1

month of age.

the intrapulmonary pulmonary arteries . There is progres­

sis, and recurrent pneumonia. These patients are at risk

sive decrease in perfusion of the affected lung. The main

for obstructive apnea. Unlike infants with a vascular ring,

pulmonary artery, which is derived from the truncoaortic

dysphagia is not a component of anomalous left pulmonary

sac, is intact. 63

artery since the esophagus is not encircled.

Absence of the pulmonary artery can be unilateral or

Ass ociated congenital anomalies occur in more than

bilateral (rare) , and isolated or associated with other car­

half of patients with anomalous origin of the left pul­

diovascular abnormalities. Associated conditions include

monary artery. Common respiratory system anomalies

right-sided aortic arch, septal defect, truncus arteriosus,

in these children include cartilage rings (the "ring-sling

and tetralogy of Fallot.64 Stenoses of the contralateral main

complex" ) , tracheomalacia, bronchus sui s , and abnor­

pulmonary artery andjor peripheral pulmonary arteries

mal pulmonary lobation . Congenital heart defects that

can occur. Early detection of this anomaly is desirable, as

can occur in ass ociation with anomalous left pulmonary

surgical correction is more effective prior to regression of

artery include persistence of the left superior vena cava,

the intrapulmonary pulmonary arteries. Affected infants often present with cyanosis. In some

atrial septal defect, patent ductus arteriosus, and ventric­

ular septal defect. 6 9 ,7°

infants, the predominant findings are because of an asso­

Chest radiographs of children with anomalous origin

ciated cardiovascular anomaly. Older patients may exhibit

of the left pulmonary artery show hyperinflation. In some

dyspnea on

patients , hyperinflation is more pronounced on one side

exertion,

recurrent pulmonary infections ,

hemoptysis, o r signs o f pulmonary hypertension. Some

(usually the right) . The distal tracheal air column is indis­

patients are asymptomatic.

tinct on the frontal view if it is substantially narrowed.

The classic radiological findings in patients with uni­

The lateral view shows narrowirlg and anterior deviation

lateral absence of a pulmonary artery are diminished vas­

of the inferior aspect of the trachea. A lateral esophagram

cular markings in a hyperlucent lung and lack of a visible

image is usually diagnostic: an oval pulsatile soft-tissue

ipsilateral pulmonary artery. In infants , the vascular mark­

mass produces an impression along the anterior wall of the

ings may be near normal if the ductus arteriosus is patent.

esophagus and anterior deviationjnarrowirlg of the infe­

Nuclear medicine studies show absence of perfusion to the

rior segment of the trachea

affected lung, and normal washout on ventilation images.

anatomy is accurately characterized with M R or CT angiog­

A definitive diagnosis can be made with angiography, CT,

raphy

(Figure 1 2-31 ) .

(Figure 1 2-30) . The pathological

428 Part 2 The Ca rd iovascu l a r System

A

Figure 1 2-30 Anomalous origi n of the left pulmonary artery from the right pulmonary artery. A An anteroposterior chest radiograph shows hyperinflation, which is greater on the left.

A

Figure 12-31 Anomalous origin of the left pulmonary artery from the right pulmonary artery (pulmonary sling). A, B. Sequential axial contrast-enhanced CT images of an infant with stridor show the anomalous left pulmonary artery (arrows)

B

B . The anomalous left pulmonary artery produces a soft­ tissue density "mass" between the trachea and barium-filled esophagus. The adjacent portion of the trachea is markedly narrowed (arrow) .

looping around the narrowed trachea. The right pulmonary artery (RPA) is prominent because it supplies both lungs.

Chapter 12 A n o m a l ies of the G reat Ves s e l s 429 Left Pulmonary Artery Origin From the Right Pul monary Artery Pathology

Rad iology

Com pression of i nferior Pu l monary overaeration trachea and main bronchi by anomalous left p u l monary artery Left pul monary artery Anterior indentation of passes between the trachea esophagus; posterior and esophagus i ndentation of trachea

Anomalous Origi n of One Pu l monary Artery From the Ascending Aorta Anomalous origin of one pulmonary artery from the ascending aorta (hemitruncus arteriosus) refers to a sin­ gle large systemic artery that extends into the pulmonary hilus and joins the pulmonary artery; the ipsilateral pulmo­ nary artery at the pulmonary trunk is absent. This is a rare anomaly, accounting for less than 1% of congenital heart lesions_ A patent ductus arteriosus usually connects to the normal pulmonary artery. Potential associated cardiovas­ cular lesions in these patients include ventricular septal defect, atrial septal defect, tetralogy of Fallot, and coarcta­ tion of the aorta.7>.72 An anomalous pulmonary artery arising from the ascending aorta is typically contralateral to the side of the aortic arch. Therefore, the anomalous vessel is most often on the right. Those that occur on the left are usually asso­ ciated with tetralogy of Fallot (with either a left or a right arch) . The orifice of the anomalous vessel is usually large and arises just above the aortic valve. The normally connected lung in patients with anom­ alous origin of a pulmonary artery receives twice-normal blood flow because the entire systemic venous return passes through the normal pulmonary artery. This large volume of blood flow delays the normal decrease in pul­ monary vascular resistance that occurs in the newborn. Blood flow into the anomalously connected lung varies with the pulmonary vascular resistance. Most patients have clinical manifestations of pulmonary hypertension and a large left-to-right shunt. Infants may have severe congestive heart failure. Other findings can include fail­ ure to thrive and respiratory distress. Cyanosis in these infants occurs as a result of pulmonary disease rather than to a right-to-left shunt. Chest radiographs of patients with an anomalous ori­ gin of a pulmonary artery show cardiomegaly caused by left­ to-right shunting and pulmonary hypertension. In some cases, pulmonary vascular markings are prominent in the lung with anomalous connection and normal in the con­ tralateral lung. However, because the normally connected lung receives the entire right heart output, and because

there is often a patent ductus arteriosus on this side, this lung may also have increased pulmonary vascularity. There is enlargement of the left atrium because of the left-to-right shunt. Eventually, pulmonary vascular disease develops, resulting in tapering of peripheral pulmonary vessels and decrease in size of the left atrium.

Anomalous Origin of a Pulmonary Artery From the Aorta Path ology

Rad i o l ogy

Left-to-right shunt I ncreased flow i n contralateral l u n g U nilateral systemic pressure pul monary flow

Cardiomegaly Pulmonary vascular prominence Asym metric pulmonary vascularity

Cross-sectional imaging studies of unilateral origin of a pulmonary artery from the ascending aorta are usu­ ally diagnostic. The large anomalous vessel arises from the proximal aspect of the aortic arch, usually posterolat­ erally. Most often, the main pulmonary artery is normal, and continues as the left pulmonary artery. Differential lung perfusion in these patients can be quantified with scintigraphy or M R.73--7 5

Aortopu l monary Wi ndow Aortopulmonary window (aorticopulmonary septal defect) refers to a congenital communication between the proximal aspect of the aorta and the adjacent main pulmonary artery in the presence of normal aortic and pulmonary valves . This anomaly is closely related embry­ ologically and hemodynamically to the congenital anom­ aly of origin of 1 pulmonary artery from the ascending aorta. Aortopulmonary window is apparently caused by failure of normal separation of the truncus arteriosus into the aorta and pulmonary artery. Aortopulmonary window accounts for approximately 0.2% of congenital heart disease. Up to 5o% of patients with aortopulmo­ nary window have an associated cardiac lesion, such as patent ductus arteriosus, interruption of the aortic arch, ventricular septal defect, or tetralogy of Fallot -76-7 8 Aorticopulmonary window occurs as a single defect in the wall of the aorta, beginning immediately above the semilunar valves on the left side. This results in a direct communication between the aorta and pulmonary artery. The hemodynamic effects of aortopulmonary window are similar to those of patent ductus arteriosus , ventricular septal defect, and truncus arteriosus. Generally, there is a high-pressure left-to-right shunt. Patients with this lesion are acyanotic. Tachypnea and tachycardia are com­ mon. The magnitude of the left-to-right shunt relates to

430 Part 2 The Ca rd i ovascu l a r System the size of the defect and the pulmonary vascular resis­ tance. A large shunt can result in congestive heart fail­ ure during infancy. Other nonspecific symptoms can also occur, such as failure to thrive and recurrent pneumonias. Untreated, a large shunt eventually leads to pulmonary vascular disease. Chest radiographs of patients with aortopulmonary window show nonspecific cardiomegaly and pulmonary vascular prominence. There is enlargement of the left atrium. The ascending aorta and main pulmonary artery are prominent. Echocardiography usually provides a defini­ tive diagnosis. The semilunar valves are normal, thereby differentiating this anomaly from truncus arteriosus.

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Chapter 1 2 A n o m a l ies of the G reat Vess e l s 431 31. Godart F. Labrot G, Devos P. et al. Coarctation of the aorta: comparison of aortic dimensions between conventional M R imaging, 3 D M R angiography, and conventional angiography. Eur Radio!. 20o2;12 (8):2034-2039· 32. Nyman R, Hallberg M, Sunnegardh J , et al. Magnetic resonance imaging and angiography for the assessment of coarctation of the aorta. Acta Radio!. 1989;3o(S) A81-485. 33· Choe YH, Kim YM , Han BK. et al. M R imaging in the morphologic diagnosis of congenital heart disease. Radiographies. 19 97;17(2) :403-422. 34· Mohiaddin RH, Kilner PJ, Rees S , Longmore DB. Magnetic resonance volume flow and jet velocity mapping in aortic coarctation. J Am Coll Cardiol. 1993;22(5) :1515-1521. 35· Bank ER, Aisen AM, Rocchini AP, Hernandez RJ . Coarctation of the aorta in children undergoing angioplasty: pretreatment and posttreatment MR imaging. Radiology. 1987;162 (1 Pt 1) :235-240. 36. Didier D , Saint-Martin C, Lapierre C, et al. Coarctation of the aorta: pre and postoperative evaluation with MRI and M R angiography; correlation with echocardiography and surgery. Int J Cardiovasc Imaging. 2oo6;22 (3-4):457-475 · 37· Mirowitz SA, Lee J K, Gutierrez FR. et al. "Pseudocoarctation" of the aorta: pitfall on cine MR imaging. J Comput Assist Tomogr. 1990;14(5) 753--755· 38. Secchi F , Iozzelli A, Papini GD, et al. M R imaging of aortic coarctation. Radiol Med. 2009 ;114 (4):524-537· 3 9 · Holmqvist C, Stahlberg F. Hanseus K, et al. Collateral flow in coarctation of the aorta with magnetic resonance velocity mapping: correlation to morphological imaging of collateral vessels. J Magn Reson Imaging. 2002;15 (1) :39-46. 40. Julsrud PR, Breen J F , Felmlee J P , et al. Coarctation of the aorta: collateral flow assessment with phase-contrast MR angiography. AJR Am ] Roentgenol. 19 97;16 9(6): 1735-174241- Rees S, Somerville J, Ward C, et al. Coarctation of the aorta: MR imaging in late postoperative assessment. Radiology. 1989;J73 (2) A 9 9-S02. 42. Muhler EG, Neuerburg JM, Ruben A, et al. Evaluation of aortic coarctation after surgical repair: role of magnetic resonance imaging and Doppler ultrasound. Br Heart ]. 1993;7o(3):285-29o. 43· Bogaert J, Dymarkowski S, Budts W, et al. Graft dilation after redo surgery for aneurysm formation following patch angioplasty for aortic coarctation. Eur] Cardiothorac Surg. 2001;19(3) :274-27844· Parks WJ. N go TD. Plauth WH Jr, et al. Incidence of aneurysm formation after Dacron patch aortoplasty repair for coarctation of the aorta: long-term results and assessment utilizing magnetic resonance angiography with three-dimensional surface rendering. J Am Coll Cardiol. 1995;26(1) : 266-27J. 45· Riquelme C, Laissy JP, Menegazzo D, et al. MR imaging of coarctation of the aorta and its postoperative complications in adults: assessment with spin-echo and cine-MR imaging. Magn Reson Imaging. 1999;17(1) :37-46. 46. Pedra C A . Pilla CB, Braga S L , e t al. Management of a large pseudoaneurysm secondary to balloon dilation for native coarctation of the aorta with coil occlusion after stent implantation in a child. Catheter Cardiovasc Interv. 2002;5 6(2):2 62-266.

47- Liang CD, Ko S F , Tiao M M . False aneurysm and mediastinal hematoma: complications of simultaneous transcatheter therapy for coarctation of the aorta and patent ductus arteriosus in an infant. ] Invasive Cardiol. 200J;13 (10) 710--712. 48. Celoria GC, Patton RB. Congenital absence of the aortic arch. Am Heart ]. 1959;58A o7-413 . 49· Serraf A, Lacour-Gayet F, Robotin M, et al. Repair of interrupted aortic arch: a ten-year experience. ] Tho rae Cardiovasc Surg. 199 6;n2(5) :nso-n6o. so. Dillman JR, Yarram SG, D'Amico AR, Hernandez RJ. Interrupted aortic arch: spectrum of MRI findings. A] R Am J Roentgenol. 2oo8;19o(6) :1467-1474· 51. Freedman H K. Congenital absence of the aortic arch. Arch Pathol. 1961;72:375-377. 52. Fournier P. Zaidi Z H . Congenital absence of the aortic arch. Am Heart ]. 196o;s9:148-152. 53· OosterhofT, Azakie A, Freedom RM, et al. Associated factors and trends in outcomes of interrupted aortic arch. Ann Thorae Surg. 2oo4;78(5):1696-17o2. 54· Williams RV, Ritter S , Minich LL, et al. Doppler evidence of subclavian steal in neonates with interrupted aortic arch using transthoracic echocardiography. Am ] Cardiol. 2ooo;85(12): 1501-1503; A1so8. 55· Morera JA, Celano V, Roland J M , et al. A rare form of isolated interrupted aortic arch: the value of two-dimensional echocardiography in the precatheterization evaluation. Pediatr Cardiol. 198J;4(4) :289-2 92. 56. Roche KJ, Krinsky G , Lee VS, et al. Interrupted aortic arch: diagnosis with gadolinium-enhanced 3D M RA. ] Comput Assist Tomogr. 1999;23(2) :197-202. 57· Cinar A, Haliloglu M , Karagoz T, et al. Interrupted aortic arch in a neonate: multidetector CT diagnosis. Pediatr Radio!. 2004;34 (11) :901-9 03s8. Yang DH, Goo HW, Seo DM, et al. Multislice CT angiography of interrupted aortic arch. Pediatr Radio!. 2oo8;38(1) :89-100. 5 9 · Sebastia C, Quiroga S , Boye R, et al. Aortic stenosis: spectrum of diseases depicted at multisection CT. Radiographies. 2003; 23 Spec No:S79-S91. 6o. Taneja K, Kawlra S , Sharma S , Rajani M. Pseudocoarctation of the aorta: complementary findings on plain film radiography, CT, DSA, and M RA. Cardiovasc Intervent Radio!. 1998;21(5):439-441.

61. Delis KT, Gloviczki P. Middle aortic syndrome: from presentation to contemporary open surgical and endovascular treatment. Perspect Vase Surg Endovasc Ther. 200S;I7(3):187-203; discussion 204-205, author reply 205-206.

62. O'Neill JA Jr, Berkowitz H , Fellows KJ, Harmon CM. Midaortic syndrome and hypertension in childhood. ] Pediatr Surg. 1995;30(2) :164-171; discussion 171-172. 63. Apostolopoulou SC, Kelekis NL, Brountzos EN, et al. "Absent" pulmonary artery in one adult and five pediatric patients: imaging, embryology, and therapeutic implications. AJR Am J Roentgenol. 2002;179 (5) :1253-126o. 64. Kucera V, Fiser B , Tuma S , Hucin B . Unilateral absence of pulmonary artery: a report on 19 selected clinical cases. Thorac Cardiovasc Surg. 1982;30(3) :152-158. 65. Grum CM, Yarnal J R, Cook SA, et al. Unilateral hyperlucent lung. Non-invasive diagnosis of pulmonary artery agenesis. Angiology. 19 81;32(3) : 194-207.

432 Part 2 The Ca rd iovascu l a r System 6 6 . Currarino G , Williams B . Causes of congenital unilateral pulmonary hypoplasia: a study of 33 cases. Pediatr Radio!. 198s;t5 (1) :15-24. 67. Dodge-Khatami A, Tulevski, I I , Hitchcock JF, et al. Vascular rings and pulmonary arterial sling: from respiratory collapse to surgical cure, with emphasis on judicious imaging in the hi-tech era. Cardiol Young. 2002;12(2):9 6-104. 68. Dohlemann C, Mantel K, Vogl TJ , et al. Pulmonary sling: morphological findings. Pre- and postoperative course. Eur 1 Pediatr. 199P54 (1) :2-4 . 6 9 . Berdon WE, Baker DH, Wung JT, et al. Complete cartilage-ring tracheal stenosis associated with anomalous left pulmonary artery: the ring-sling complex. Radiology. 1984;152(1) :57-64. 70. Gikonyo B M , Jue KL, Edwards J E . Pulmonary vascular sling: report of seven cases and review of the literature. Pediatr Cardiol. 1989;10(2) :81-8 9 . 71. Prifti E , Bonacchi M , Murzi B , e t al. Anomalous origin o f the right pulmonary artery from the ascending aorta. 1 Card Surg. 2004;19(2) :103-112. 72. Kutsche LM , Van Mierop LH. Anomalous origin of a pulmonary artery from the ascending aorta: associated anomalies and pathogenesis. Am 1 Cardiol. 1988; 61(1o) :85o-856.

73· Lo RN, Mok C K, Leung M P , et al. Cross-sectional and pulsed Doppler echocardiographic features of anomalous origin of right pulmonary artery from the ascending aorta. Am 1 Cardiol. 1987;60 (10) :921-924. 74· Lin MH, Shen CT, Wang NK, et al. Magnetic resonance imaging of anomalous origin of the right pulmonary artery from the ascending aorta in association with ventricular septal defect. Am Heart 1· 1996;132 (5) :1073-1074· 75· Long WA, Perry JR, Henry GW. Radionuclide diagnosis of anomalous origin of the right pulmonary artery from the ascending aorta (so-called hernitruncus) . Int 1 Cardiol. 1985;8(4):492-4 9 6 . 76. Kutsche L M , Van Mierop LH. Anatomy and pathogenesis of aorticopulmonary septal defect. Am 1 Cardiol. 1987;5 9(5): 443-447· 77· Blieden LC, Moller J H . Aorticopulmonary septal defect. An experience with 17 patients. Br Heart ]. 1974;3 6 (7): 63o-635· 78. Mert M , Paker T, Akcevin A. et al. Diagnosis, management, and results of treatment for aortopulmonary window. Cardiol Young. 2oo4;4 (5):5o6 -5n.

CH A P T E R

13

The Vascular S ystem

NON I N FECTIOUS VASCU LITIS . . . . . . . . . . . . . . . . . .

434

Takayasu Arteritis (Occlusive Throm boarth ropathy) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

434

Polyarteritis N odosa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 5

NON I N FLAM MATORY ARTERIOPATH I ES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 5

I d iopath ic I nfa ntile Arterial Calcification . . . .

43 5

N e u rofi bromatosis Type 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 6

Arterial Fi brous Dysplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 6

Arteria l Tortuosity Syndrome . . . . . . . . . . . . . . . . . . . . . . .

437

M oyamoya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

437

Median Arcuate Ligament Synd rome . . . . . . . . .

437

CON N ECTIVE TISSU E DISORDERS . . . . . . . . . .

437

M arfan Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

437

Arteriovenous Fistu la . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

454

Venous M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

455

Capillary M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

458

Lym p h atic M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

459

General ized Cystic Lym p h angiomatos is . . . .

462

Combined Vascular M alformations . . . . . . . . . . . .

462

Angiodysplasias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

463

Hereditary Hemorrhagic Tela ngiectasia. . . . . 464

Pulmonary Involvement in Hereditary Hemorrhagic Telangiectasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 Liver Involvement in Hereditary Hemorrhagic Telangiectasia . . . . . . . . . . . . . . . . 465 Central Nervous System Involvement in Hereditary Hemorrhagic Telangiectasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6 6 Varicocele . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

466

VASCU LAR TRAU MA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

466

General Concepts ofVascular Tra u m a . . . . . . .

466

441

Chest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

468

DISSECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444

Abdomen and Pelvis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

470

N eck. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

470

I ntracran i al . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

472

ARTERIAL TH RO M BOSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

472

POPLITEAL ARTERY ENTRAPM ENT SYNDRO M E . . . . . . . . . . . . . . . . . . . . . . . .

473

VENOUS DISEASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

474

Venous Anomal ies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

474

Ehlers- Dan los Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 Loeys-Dietz Syndrome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A N E U RYSMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VASCU LAR MALFORMATIONS AND VASCU LAR N EOPLASMS . . . . . . . . . . . . . . . . . . .

441

445

H em angioma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

Infantile Hemangioma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 Rapidly Involuting Congenital Hemangioma . . . . . . . . . . . . . . . . . . . . 451 Noninvoluting Congenital Hemangioma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 52 Kaposiform Hemangioendothelioma . . . . . . . . .

452

Tufted Angioma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

452

Hemangiopericytoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

452

Arteriovenous M alformation . . . . . . . . . . . . . . . . . . . . . . .

453

Persistent Left Superior Vena Cava . . . . . . . . . . 474 Right Superior Vena Cava Anomalies . . . . . . 474 Congenital Interruption of the Inferior Vena Cava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474 .

433

434 Part 2

The Cardiovascu lar System

Su perior Vena Cava Obstruction . . . . . . . . . . . . . . . . .

474

I nferior Vena Cava Obstruction . . . . . . . . . . . . . . . . . . .

475

Lower-Extremity Deep Venous Thro m bosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

475

M ay-Thu rner Synd rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

478

NONINFECT IOUS VASCULITIS The term vasculitis refers to inflammation ofblood vessels. There are various classification schemes for noninfectious vasculitis, based on the sizes of the blood vessels typically involved and the pathology of the lesions (Table 1 3-1 ) . Takayasu disease i s the most important large vessel vas­ culitis in children. Kawasaki disease, polyarteritis nodosa, and primary central nervous system (CNS) vasculitis of childhood are vasculitides that primarily involve medium­ size vessels. Examples of small vessel vasculitis include Henoch- Schonlein purpura, Wegener granulomatosis, Churg-Strauss syndrome, and microscopic polyangiitis. There is considerable variation in the organ systems most prominently affected by the various vasculitides. Constitutional symptoms , fever, and skin lesions are com­ mon with these disorders .'

Takayasu Arteritis (Occlusive Thromboarth ropathy) Takayasu arteritis (Takayasu disease) is a rare idiopathic chronic inflammatory arteritis that causes thrombosis, ste­ nosis, dilation, and aneurysm formation in the puhnonary arteries, aorta, and major aortic branch vessels. Although

Pri mary Axil losu bclavian Venous Thro m bosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

479

Central Venous Catheter- Related Central Venous Stenosis . . . . . . . . . . . . . . . . . . . . . . . . . .

479

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

480

.

the pathogenesis is incompletely understood, Takayasu arteritis apparently is an autoimmune process. There is granulomatous inflammation of the involved vessel, a result of the deposition of autoimmune complexes in areas of vessel wall permeability. The inflammation damages the adventitia and media, and leads to subsequent reactive pro­ liferation of the intima and adventitia. Ultimately, there is progression to concentric mural thickening and calcifica­ tion; all layers of the arterial wall are involved. The aortic arch and its branches are the most common locations of symptomatic disease in patients with Takayasu arteritis. Other potential sites of involvement include the descend­ ing thoracic aorta, abdominal aorta, renal arteries, and splanchnic arteries.2 The clinical manifestations of Takayasu arteritis are predominantly caused by vascular stenoses. Symptomatic aneurysms can also occur. The clinical onset of Takayasu arteritis in children is usually during the second decade of life; 90% of patients are younger than 30 years at the time of presentation. The onset may be insidious or, less commonly, fulminant. Potential early symptoms in chil­ dren include dyspnea and hemoptysis. Hypertension is common, usually as a result of renovascular steno­ sis. Carotid artery involvement can result in syncope or other neurological symptoms . Aortic regurgitation can

Table 1 3-1 . Noninfectious Vasculitides Vascu l itis

Vessel s ize

Areas of p redo m i nant i nvolvement

Takayasu arteritis Large Aorta, major aortic branches, pulmonary arteries M ed i u m Polyarteritis nodosa Skin > kidneys > �--�-� � - - - - - - - - - - - - - ------··------- --- ----- ---S m ; I I ·--- -----L :- � :-;; n > G l > kidney, spl::�..: - ��!-� ---C� � : $;;�� � � � d �� � -----Lu ng, kidney, skin, orbit, joints, pericard i u m , C N S Wegener gra n u lomatosis Small Small Henoch - Schon lein pu rpura Ski n , joi nts, G l , kid ney M icroscopic polyangiitis Small ------ - - Kidney, l u n g M u ltisystem, cardiac, gal l bladder, lym ph nodes M ed i u m Kawasaki disease M outh, skin, gen italia, orbit, joi nts, th rombosis Small Behs;et d isease L_u_n-'g· � lmo_'2:_rr _capi ������- - ------ - ---------- -· -S_m_a_II CNS M ed i u m Primary C N S vasculitis of childhood

-------- -----

-

-

-

-

-

--

------

---

- - - - - --- - -

- - - - - - - ---

_

_

-

___ _

_

------

Chapter 13 The Vascu l a r System 435

A

Figure 13-1 Takayasu disease.

B

A. An anterior contrast-enhanced MR angiography study of a 10-year-old child shows marked narrowing (arrow) of the inferior

occur in patients with a dilated aortic root. Patients with Takayasu arteritis are at risk for osteoporosis, either as a complication of the disease or as a side effect of ther­ apy. Takayasu arteritis most often occurs in young adult women. This disorder is most prevalent in individuals of Asian descent.3 CT is useful for demonstrating mural thickening and calcification within the aorta, pulmonary arter­ ies, and maj or aortic branch vessels in patients with Takayasu arteritis . The thickened vascular wall may enhance prominently with IV contrast. M R can show mural thickening and adherent thrombi, but visual­ ization of calcifications is poor with this technique. As with CT, prominent contrast enhancement is often present within the thickened aortic wall; this is an indicator of active disease. The inflamed aortic wall is hyperintense on fat-suppressed T2-weighted sequences during the active stage of the dis ease ( Figu re 1 3-1 ) . The most common angiographic finding in patients with Takayasu arteritis is the presence of one or more long stenotic vascular lesions andjor large ves s el occlusions ( Figu re 1 3-2) . There may be vessel wall irregularity and poststenotic dilation. Ectatic vessels or true aneu­ rysms are present in a substantial minority of patients . Doppler sonography shows elevated flow velocity at the site of a stenosis and dampened velocity distally. An aortic aneurysm in a patient with Takayasu arteritis usually has a visibly thickened wall on cross-sectional imaging with CT or M R.4-7

Polyarteritis Nodosa Polyarteritis nodosa is an idiopathic focal segmental necrotizing vasculitis. The necrotizing vasculitis results

aspect of the abdominal aorta and the adjacent portions of the common iliac arteries. B. There is prominent signal in the aortic wall (arrow) on this T2-weighted fat-suppressed image.

in aneurysm or pseudoaneurysm formation, typically at the bifurcation of a medium-sized artery. The most commonly affected vessels are the renal and mesenteric arteries. The vascular pathology can lead to ischemia or hemorrhage that is detectable with cross-sectional imag­ ing examinations. Affected organs include the kidneys, liver, spleen, pancreas , and intestine. Angiography shows multiple small aneurysms at bifurcations and small vessel irregularity. 8 , 9

NONINFLAMMATORY ARTERIOPATH I ES

I diopathic I nfanti le Arterial Calcification Idiopathic infantile arterial calcification is a rare autoso­ mal recessive disorder in which there is deposition of cal­ cium (hydroxyapatite) in the elastic fibers of the walls of large- and medium-size systemic and pulmonary arteries. Associated intimal proliferation leads to vessel narrowing. The descending aorta and the coronary arteries are the most common areas of clinically significant involvement. There is typically little or no involvement of intracranial vessels. Many affected patients die during the first few months oflife because of cardiac failure, although the clini­ cal severity of disease is variable and medical intervention can alter the course. Fetal involvement can lead to nonim­ mune hydrops and polyhydramnios. Infants with this dis­ order may exhibit manifestations of myocardial ischemia, hypertension, visceral infarction, periarticular swelling, developmental delay, and seizures.10 Potential prenatal sonographic findings of idiopathic infantile arterial calcification include polyhydramnios,

436 Part 2 The Ca rd iovascu l a r System

A

B

Figure 13-2 Takayasu arteritis. A. B. Anterior and left lateral volume rendering images of a contrast-enhanced MR study of a 13-year-old child show occlusion

pericardia! fluid, and echogenic calcifications in the walls of the coronary arteries , aorta, and pulmonary arteries. In infancy, radiographs may show calcifications in vessel walls and periarticular soft tissues. On CT, axial images of the aorta sometimes demonstrate a target pattern caused by hypoattenuating thickened intima between the contrast-enhanced lumen and the calcified media. Intimal plaques are often visible on sonography. M R angiography i s useful for characterization o f stenoses.11-13

Neu rofibromatosis Type

1

Neurofibromatosis type 1 (NF-1) is a multisystem disorder in which there are dysplasias of mesodermal and neuroec­ todermal tissues. Vascular involvement is uncommon, but can lead to serious clinical alterations. Potential vascular manifestations of NF-1 include arterial stenoses and aneu­ rysms. Common sites of involvement are the renal arteries, splanchnic vessels, abdominal aorta, central cerebral arter­ ies, coronary arteries, and subclavian arteries . Approximately 1% of individuals with NF -1 have hypertension as a result of coarctation of the aorta, pheochromocytoma, or renal artery

of the superior mesenteric and right renal arteries. The celiac, left renal, and inferior mesenteric vessels are patent.

stenosis. Renal artery stenosis is the most common vascu­ lar lesion in patients with NF-1. There are two basic categories of vascular stenosis in NF-1.14 The first consists of encasement of larger vessels such as the aorta, carotid arteries, and main renal arter­ ies by neurofibromatous or ganglioneurofibromatous tis­ sue. This abnormal perivascular tissue can elicit intimal proliferation, thinning of the media, and fragmentation of elastic tissue, with progression to a stenosis or aneurysm. The second type of vascular lesion in NF-1 is a small ves­ sel mesodermal dysplasia that causes vascular stenoses. In the kidneys, multiple small intrarenal branches may be involved. Visceral stenoses are usually, but not invariably, accompanied by aortic narrowing. This has the appearance oflong smoothly tapered narrowing of the abdominal aorta.

Arterial Fibrous Dysplasia Arterial fibrous dysplasia (fibromuscular dysplasia) is a developmental abnormality of the fibrous, muscular, and elastic tissues of the involved vessel. Pathological classifi­ cation is according to the predominantly affected layers:

Chapter 13 The Vascu l a r System 437 intimal fibroplasia, medial fibroplasia, perimedial fibro­ plasia, medial hyperplasia, and adventitial dysplasia. The renal arteries are the most common sites of arterial fibrous dysplasia,

although there occasionally is concomitant

involvement of other vessels (e.g. , the aortic arch, extremity arteries , or splanchnic arteries ) . Chapter

52

has additional

discussion of vascular fibrous dysplasia.

Arterial Tortuosity Synd rome Arterial tortuosity syndrome is a rare autosomal reces­ sive disorder in which elongation, tortuosity, stenoses, and aneurysms occur in large and medium-size arteries. Vascular dissection and pulmonary artery stenosis are common. Patients with this disorder have mutations in the

SLC2A1 o

gene, which encodes for the facilitative glucose 10 (G LUTw) .'5·' 6

transporter

M oyamoya Moyamoya disease is an idiopathic vasculopathy of central intracranial arteries . Progressive narrowing of cerebral ves­ sels leads to various neurological complications. There is secondary enlargement of numerous collateral vessels in the central aspect of the brain. Moyamoya syndrome refers to similar cerebrovascular alterations occurring in associa­ tion with a systemic disease or known insult, such as sickle cell disease,

NF-1, cranial irradiation, PHAC E S (posterior

fossa malformations, facial hemangiomas , arterial anoma­ lies, cardiac anomalies and aortic coarctation, eye anoma­ lies, and sternal defting andfor supraumbilical raphe) syndrome, or Down syndrome. Chapter 20 has additional discussion of moyamoya.

Figure 13-3 Median arcuate ligament syndrome.

M edian Arcuate Ligament Syndrome Median arcuate ligament syndrome refers t o stenosis o fthe celiac artery as a result of extrinsic compression of the vessel

A sagittal contrast-enhanced CT image of a 15-year-old girl shows marked narrowing of the celiac artery (arrow) near its origin. Note inferior deviation at the stenotic site, a result of compression by the median arcuate ligament.

by the median arcuate ligament of the diaphragmatic crura. With time, fibrosis of the vessel wall leads to an intrinsic stenosis. Most individuals with imaging evidence of celiac artery narrowing are asymptomatic. Symptomatic patients

Normalization of the vessel caliber and flow characteristics

may suffer weight loss and report postprandial abdominal

during deep inspiration militates against significant fibrotic

pain, nausea, or diarrhea. The nonspecific nature of the

stenosis, suggesting that a simple median arcuate ligament

symptoms is frequently problematic in the management of

release procedure would likely be effective in improving

these patients. Median arcuate ligament syndrome is more

flow. In some patients, there is enlargement of the gastro­

common in females than males.

duodenal artery as a collateral pathway. End-expiratory infe­

Imaging studies of median arcuate ligament syndrome

rior deviation and narrowing of the celiac artery has been

demonstrate inferior deviation and narrowing of the proxi­

reported to be common in asymptomatic adults undergoing MR studies for unrelated indications. >7-2 0

mal aspect of the celiac artery, best demonstrated on sag­ ittal images in the plane of the aorta

(Figure 1 3-3) .

There

is exacerbation of the stenosis during expiration. Doppler sonography shows elevation of the flow velocity at the site of stenosis during expiration and normalization during inspi­ ration. There is dampened systolic flow distal to a moderate­ to-severe narrowing

CONNECTIVE T ISSUE DISORDERS

M arfan Syndrome

With severe involvement,

Marfan syndrome is a generalized connective tissue disease

flow through the celiac artery ceases during expiration.

that primarily involves elastic tissue . This is an autosomal

(Figure 13-4) .

438 Part 2 The Ca rd iovascu l a r System

A

B

Figure 1 3-4 Median arcuate ligament syndrome. A. CT shows focal narrowing near the origin of the celiac artery. There is mild post-stenotic dilation. (The apparent defect in the superior mesenteric artery is artifactual.) B. Doppler evaluation of the celiac artery during inspiration shows normal flow. C. Interrogation of the vessel beyond the stenosis during expiration shows dampening of systolic flow.

c

dominant condition with high penetrance, predominantly caused by mutations in the fibrillin-1 ( FBN1) gene. These patients lack normal fibrillin, a glycoprotein that is the main constituent of the microfibrils of the extracellular matrix. Fibrillin is crucial for normal elastin function. The cardiovascular manifestations of this disorder are predom inantly a result of a lack of normal tensile strength of the supportirlg tissue of the aorta and other major blood ves­ sels as well as the cardiac valves. Abnormal tissue growth factor signaling is an additional pathogenic factor. Potential cardiovascular manifestations of Marfan syndrome include aortic valve disease, aortic root dilation, aortic aneurysm, aortic dissection, mitral valve prolapse, and pulmonary artery dilation (Table 1 3-2) . About half of individuals with Marfan syndrome have clinical evidence of cardiovascular disease during childhood or adolescence. The most common finding is a murmur caused by mitral regurgitation. Aortic regurgitation can also occur, but is more common in adults. Aortic regurgitation in infants with Marfan syndrome is predominantly restricted to males. Chapter 57 has additional discussion of the genetic and clinical factors of Marfan syndrome.>'-24 Histological examination of the ascending aorta in patients with Marfan syndrome shows disruption and ·

disorganization of the elastic media, with separation of fibers by mucoid material. Aortic involvement usually begins in the sinuses ofValsalva (Figure 1 3-5) . There is pro­ gressive dilation of the ascending aorta. Small linear tears occur in the intima immediately above the aortic valve. These usually heal spontaneously, but there is a potential for progression to a dissecting aneurysm. Dilation of the aortic root causes aortic valve regurgitation. There also can be thinning or fenestration of the aortic valve leaflets. Mitral valve abnormalities are common in these patients,

Table 13-2. Cardiovascular Manifestations of M arfan Syndrome

An nu loaortic ectasia Aortic aneurysm Aortic regurgitation Aortic dissection Pulmonary artery di lation M itral valve prolapse

Chapter 13 The Vascu l a r System 439

Figure 1 3-5 Marfan d isease; aortic root dilation and aneurysm of the aortic arch. A gated M R image obtained during systole shows marked sinus of Valsalva dilation (arrows) . There is also dilation of the entire arch and of the visualized portions of the innominate and left common carotid arteries.

A

Figure 13-6 Marfan syndrome. A The frontal view shows prominence of the ascending aorta (right-sided arrow) . Dilation and tortuosity of the distal portion of the arch produce a soft-tissue density along the upper left

leading to regurgitation. The combination of aortic and mitral valve disease can precipitate marked left ventricular volume overload. Involvement of a coronary artery ostium in a patient with an aortic dissection can lead to myocardial infarction. Potential fatal cardiovascular complications in individuals with Marfan syndrome include severe valvar incompetence, aortic dissection, and rupture of an aortic aneurysm. Conduction abnormalities and severe ventricu­ lar dysrhythmias can occur. Chest radiographs of individuals with Marfan syn­ drome often show a narrow anteroposterior diameter of the thorax. Scoliosis and pectus excavaturn are common. Sinus of Valsalva dilation is usually not visible on stan­ dard radiographs. Dilation of the ascending aorta some­ times results in fullness that obliterates the retrosternal airspace on the lateral view. Increasing dilation of the arch leads to fullness of the upper right-heart border on the frontal proj ection. Aneurysmal dilation and tortuos­ ity can also produce radiographic fullness of the remain­ der of the arch andfor the descending aorta ( Figure 1 3-6) . The presence o f cardiomegaly suggests substantial aortic insufficiency. Abnormalities of the aorta in patients with Marfan syndrome are effectively detected and characterized with M R or dynamic contrast-enhanced CT ( Figu re 1 3-7) . Annuloaortic ectasia has a characteristic appearance. There is loss of visualization of the normal sinotubular ridge. The aortic root (annulus, sinuses of Valsalva, and sinotubular

B

side of the mediastinum. Heart size is normal. B. On the lateral view, the dilated ascending aorta bulges into the retrostemal region (arrows) .

440

Part 2 The Ca rd iovascu l a r System

A

Figure 13-7 Sinus ofValsalva aneurysm.

B

A, B. Axial and sagittal M R images demonstrate dilation of the sinuses of Valsalva (arrows) .

junction) and proximal ascending aorta are dilated. There usually is abrupt change to normal caliber proximal to the upper aspect of the arch. Surgical therapy is generally indicated when the sinus of Valsalva aneurysm is equal to or greater than 5 · 5 em in diameter (�5 . 0 em in a child) or when the diameter is at least twice that of the uninvolved distal portion of the thoracic aorta. Aneurysms can also occur in any other portion of the thoracoabdominal aorta (Figure 1 3-8) . Concomitant involvement of major branch vessels is common.25 Sinus of Valsalva aneurysms and mitral valve dis­ ease with a floppy valve are frequent findings on echo· cardiography and angiocardiography in patients with Marfan syndrome. Prolapse most often involves the mitral valve, but aortic or tricuspid prolapse can occur as well. There is usually aortic arch dilation, although severe aortic lesions often do not occur until later in life. Echocardiography allows monitoring of aortic and pulmonary artery calibers and cardiac valve function. Marfan syndrome patients sometimes develop an inter­ atrial septal aneurysm.26·27 Electrocardiographically gated cardiac CT and M R are useful for evaluating aortic valve function in selected patients with Marfan syndrome. B ecause of dilation of the sinus of Valsalva, the cusps of the aortic valve appear tethered on midsystolic-phase images, rather than hav­ ing normal arched configurations . There is a triangular coaptation defect on end-diastolic images, resulting in valvular insufficiency. An aortic dissection results from an intimal tear that allows blood to enter the medial layer of the aorta. The possibility of an aortic dissection should be considered when sequential chest radiographs show progressive

enlargement of the aorta. Characteristic features of dissec­ tion on CT and MR are an intimal flap and a false lumen ( Figures 1 3-9 to 1 3-1 1 ) . However, one or both of these find­ ings are often absent despite the presence of dissection. Important secondary findings of dissection on cross-sec­ tional imaging evaluations include mediastinal or pericar­ dia! hematoma, dot in the false lumen, and ischemia in organs supplied by branch arteries . The most common surgical treatment for an aneu­ rysm of the aortic root in a Marfan syndrome patient is insertion of a composite valve graft (prosthetic valve with a synthetic graft) . In some institutions, the native aortic valve is left in place. An aortic root homograft with a valve can also be used; this procedure is most often carried out in the setting of prosthetic valve endocarditis and aortic root inflammatory destruction. Pseudoaneurysm forma­ tion is an important potential complication following aor­ tic root surgery. The pseudoaneurysm most often occurs at the anastomotic site. MR demonstrates a localized area adjacent to the graft that has a signal void on spin-echo M RI because of flowing blood. Cine gradient-recalled echo MR shows bright signal because of flowing blood within the cavity of the pseudoaneurysm. An infectious pseudoa­ neurysm can occur in the presence of endocarditis; this has a similar appearance to that of a noninfected pseu­ doaneurysm. Extraluminal fluid collections that do not have features of flowing blood on MR include abscess and hematoma. 2 8-3•

Eh lers-Dan los Synd rome Ehlers-Danlos syndrome encompasses a heterogeneous group of connective tissue disorders that result in deficient

Chapter 1 3 The Vascu l a r System heterozygous mutations of the type

COLJA1

441

gene encoding for

I I I procollagen. The maj or consequence of the procol­

lagen abnormality is excessive tissue fragility. Patients with deficient or abnormal procollagen

I I I are

prone to various vascular lesions, including catastrophic ves sel rupture. The typical clinical features include

thin (8o% of patients) ; excessive bruising; a thin "pinched" nose and prominent eyes (3o% of patients) ; translucent skin

j oint hypermobility; spontaneous rupture o f the bowel; transient intestinal obstruction; obstetrical complications; and manifestations of arterial fragility. The prevalence of

vascular Ehlers- Danlos syndrome is 1 per 25,ooo livebirths .

The long-term prognosis is poor; approximately

8o% o f

these patients develop a life-threatening complication by age

40 years .32·33 The most common vascular consequences of vascu­

lar Ehlers-Danlos syndrome are vessel ruptures and solid organ infarcts within the abdomen, thorax, and brain. Vascular ruptures are often spontaneous or follow minor trauma or interventional procedures . Vascular rupture can occur in vessels without a preexisting aneurysm or dissec­ tion. On imaging evaluation, most patients with vascular Ehlers-Danlos syndrome have vascular lesions at multiple sites. Aneurysms are most common, followed by dissec­ tions and vascular ectasia. The most common sites are the abdominal visceral arteries , iliac arteries, aorta, and the lower extremity, carotid, vertebral, subclavian, pulmo­ nary, and cerebral arteries. Noninvasive vascular imaging techniques are preferable for these patients because of the elevated risk for complications with arterial puncture and catheterization.

Loeys-Dietz syndrome Loeys- Dietz syndrome is a rare disorder characterized by arterial tortuosity, aneurysms, and hypertelorism. Bifid uvula or deft palate can occur. Scoliosis and foot deformi­ ties are common. This autosomal dominant disorder is a result of mutations in transforming growth factor (TG F ) - � receptors I

(TGFBR1)

and

I I ( TGFBR2) genes . Individuals

with Loeys- Dietz syndrome have a high risk for aortic dis­ section or aortic rupture. Some patients have findings that overlap those of vascular E hlers-Danlos syndrome or

Figure 13-8 M arfan syndrome; aortic aneurysms. A sagittal reformatted contrast-enhanced CT image of a 9 -year­ old child with Marfan syndrome shows fusiform aneurysms of the aortic arch, upper thoracic aorta, and the abdominal aorta.

Marfan syndrome. The intracranial vessels are tortuous , and intracranial aneurysms can develop. Carotid or ver­ tebrobasilar dissections can also lead to central nervous system symptoms.%35

ANEURYSMS integrity of the supporting structures of the body. Common

Aneurysms of the aorta are rare in children. These lesions

features of these disorders include hyperextensible skin,

are most often associated with Marfan syndrome, Ehlers­

hypermobile j oints , easy bruisability, and dystrophic scar­

Danlos syndrome, Loeys- Dietz syndrome, Turner syn­

(type IV) of Ehlers­

drome, Noonan syndrome, bicuspid aortic valve, Takayasu

Danlos syndrome are at risk for catastrophic bleeding from

arteritis , bacterial endocarditis, or repaired aortic coarcta­

weakened maj or arteries . Vascular Ehlers- Danlos syn­

tion. Trauma and infection can also lead to large vessel

drome is an autosomal dominant disorder that is caused by

aneurysms. Mycotic aneurysm of the aorta is a potential

ring. Patients with the

vascular type

442

Part 2 The Ca rd i ovascu l a r System

A

B

Figure 13-9 Marfan syndrome; aortic dissection. This 16-year-old boy with known Marfan syndrome presented with tachycardia and a new aortic insufficiency murmur. Axial A, B, and coronal C contrast-enhanced CT images show an intimal flap (arrows) and annuloaortic ectasia.

complication of an indwelling arterial catheter in the new­ born. The ductus arteriosus is a potential site of a congeni­ tal aneurysm. Aneurysmal dilation of the pulmonary artery can occur in association with pulmonary hypertension or in neonates with tetralogy of Fallot and absence of the pul­ monary valve. Multiple large pulmonary artery aneurysms can occur in children with Behc;:et syndrome. Aneurysms and pseudoaneurysms of small and mid-size vessels in children are most often mycotic, traumatic, or related to a systemic vasculitis. In the abdomen and pelvis, aneurysms can occur in the aorta, mesenteric vessels, renal arteries , or small branch vessels within an organ (Table 1 3-3) . Aneurysms of the main

c

Table 13-3. Arterial Aneurysms of Abdominal Organs i n Children

Mycotic Systemic vascu l itis Fibromuscular dysplasia Con nective tissue disease Trauma (pseudoaneu rysm)

Sepsis Pancreatitis

M a rfan syndrome Ehlers-Danlos

Chapter 13 The Vascu l a r System 443 and conventional angiography (Figure 13-1 2) . Transcatheter angiography is usually required for accurate characteriza­ tion of small vessel meurysms. Noninvasive techniques are usually sufficient for evaluation of aneurysms of large md mid-size vessels. On MR, gradient-echo pulse sequences complement standard spin-echo images by demonstrating

Figure 13-10 Marfan syndrome; aortic dissection. A CT image of a 1o-year-old girl with Marfan syndrome and acute onset of chest pain shows a clilated thoracic aorta with an intimal flap (arrow) . There is greater contrast enhancement in the true lumen than in the false lumen.

renal artery can occur in children with NF-1, infectious arte­ ritis, renal artery stenosis, or Kawasaki disease. Vasculitis is the most common cause of small vessel renal meurysms. Aneurysms of the cerebral vasculature are most often con­ genital, mycotic, or traumatic Mycotic pulmonary artery pseudoaneurysm is a rare lesion that is usually associated with lung infection. The most common cause is erosion from adjacent cavitary tuberculosis; this is termed a Rasmussen aneurysm. This lesion can also develop adjacent to a pyogenic lung abscess or in patients with aspergillosis. Noninfectious causes of pulmonary pseudoaneurysm include trauma, iatrogenic (e.g., thoracostomy tube or angioplasty) , vasculitis, and neoplasm. The radiographic appearance of a pulmonary artery pseudoaneurysm is that of a round or lobulated lung mass. Diagnostic imaging techniques for the detection and characterization of meurysms include sonography, CT, MR.

A

B

Figure 1 3-1 2 Aortic pseudoaneurysm. Figure 1 3-1 1 Marfan syndrome; aortic dissection. The intimal flap appears as a thin band coursing between the true and false lumens on this T1-weighted MR image.

A. A pseudoaneurysm of the ascending aorta appears as an oval mass (arrow) on this Tl-weighted MR image. Slow blood flow within the lesion results in greater signal intensity than in the adjacent aorta. B. The lesion (arrow) fills with contrast on this arch aortogram image.

444

Part 2 The Ca rd iovas cu l a r System

A

Figure 13-13 Aneurysm.

B

A. A sagittal contrast-enhanced CT image of a child with Marfan syndrome shows a wide-mouthed aneurysm (A) of the distal

the blood flow characteristics in the region of the lesion. CT angiography also demonstrates the flow characteristics, thrombus within the lesion, and effects on adjacent struc· tures (Figure 1 3-13) . Sonography provides similar informa­ tion for accessible lesions (Figure 1 3-14) . Sonography is particularly helpful for characterization of posttraumatic pseudoaneurysms in the extremities; pulsed Doppler examination typically shows to-and-fro blood flow within the neck of the lesion.36

DISSECTION Patients with Marfan syndrome, Ehlers-Danlos syndrome, Loeys-Dietz syndrome, Turner syndrome (Table 13-4) , sys­ temic lupus erythematosus, and aortitis are susceptible to the development of aortic dissection, particularly in con­ junction with hypertension. Dissection can also occur fol­ lowing blunt trauma to the chest or abdomen (see "Vascular Trauma" below) . Dissection is a potential complication of cardiac surgical procedures. Clinical manifestations of

Table 1 3-4. Cardiovascular Disease in Patients with Tu rner Syndrome

Coarctation of the aorta B icuspid aortic valve Aortic dissection Hypertension

arch/proximal descending aorta. B. The lesion compresses the left main bronchus. There are bilateral pleural fluid collections caused by hemorrhage.

acute dissection include chest pain, back pain, hypoten­ sion, loss of pulses, mesenteric ischemia, and hyperten­ sion. Cardiac tamponade can occur as a consequence of the accumulation of blood in the pericardial space.37·3 8 The initiating event of an aortic dissection is a tear within the intima, leading to separation of the layers of the aortic wall and the formation of 2 lumina, 1 true and 1 false. There is propagation of the dissection from the site of the tear; distal propagation is most common. Blood from the false lumen can reenter the true lumen at any point along the course of the dis section. The most com­ mon sites of origin of dissections are the proximal aspect of the ascending aorta and the distal arch just beyond to the origin of the left subclavian artery. According to the Stanford classification, dissections involving the ascend­ ing aorta are type A (regardless of the distal extent) and all others are type B . Techniques for the diagnosis and characterization of aortic dissection include CT, MR, transesophageal echo­ cardiography, and conventional angiography. Catheter aortography is rarely required because of the availabil­ ity of highly sensitive and specific noninvasive imaging techniques. Potential findings on standard radiographs include mediastinal widening, cardiac silhouette enlarge­ ment, and a double contour of the aortic arch. Thrombus is occasionally present in the false lumen, producing high attenuation on unenhanced CT images and high signal intensity on T1-weighted MR sequences. The most important finding on contrast-enhanced CT and M RI is the presence of a thin intimal flap that separates the true lumen from the false lumen (see Figures 13-9 and 13-11) . There are sometimes thin linear residual ribbons of media

Chapter 13 The Vascu l a r System 445

A

B

Figure 1 3-14 Mycotic pseudoaneurysm.

c

within the false lumen; that is, the "cobweb sign." There are often varying flow characteristics in the true and false lumens (see Figure 13-10) . The false lumen frequently compresses the true lumen. Potential complications of aortic dissection include branch-vessel obstruction and rupture into the pericardium, the left pleural space, or the mediastinum.39·4°

VASCULAR MALFORMATIONS AND VASCULAR NEOPLASMS The nomenclature and classification of congenital vas­ cular and lymphatic lesions has undergone considerable evolution. In 1982, Mulliken and Glowacki proposed the

This septic infant had a pulsatile mass in the left side of the pelvis. A. Doppler ultrasound shows arterial flow in a round mass. B. A reconstructed CT image demonstrates marked contrast enhancement of the lesion and apparent connection to the left common iliac artery. C. A T1-weighted MR image confirms connection of the pseudoaneurysm to the common iliac artery by a narrow neck (arrow).

most widely accepted and most clinically useful system. 4' They developed a biological classification system that separates vascular anomalies into 2 major categories: vas­ cular neoplasms and vascular malformations . Vascular neoplasms, such as hemangioma, are characterized by cellular proliferation, cellular hyperplasia, and rapid growth; the suffix "-oma" should only be used for lesions with these characteristics . In contradistinction, vascular malformations are nonproliferating lesions caused by dysmorphogenesis. 42-44 The development of blood vessels occurs by 2 gen­ eral mechanisms : vasculogenesis and angiogenesis. Vasculogenesis is the formation of new blood vessels by differentiation of precursor mesenchymal cells into endo­ thelial cells. As opposed to this in situ formation of new

446 Part 2 The Ca rd iovas cu l a r System blood vessels , angiogenesis is the formation of capillaries

are syndromes in which vascular malformations occur in

as extensions from preexisting blood vessels. As the endo­

association with specific patterns of involvement of adj a­

thelial lining of developing blood vessels matures , smooth

cent structures (e.g., limb hypertrophy) .

muscle cell precursors migrate to form the muscular lay­

Vascular malformations can be categorized with imag­

2

ers of the blood vessel walls. Vessel differentiation leads

ing studies into

to the formation of veins, arteries , and capillaries . The lym­

High-flow lesions contain substantial arterial components

main types: high flow and low flow.

phatic system develops as an extension from the embryonic

(e.g., an arteriovenous malformation) . Low-flow lesions

venous system. Vascular malformations are congenital

have little or no arterial component (e.g. , a venous mal­

lesions that result from developmental errors at 1 or more stages of vasculogenesis and for angiogenesis .4 5 ,4 6

formation) . MR is the most useful imaging technique for demonstrating the location of a vascular lesion and for

Vascular malformations tend to grow commensu­

detecting involvement of adjacent structures. This can be

rately with the patient. When greater expansion occurs, it

supplemented with M R angiography or M R venography to

is because of enlargement of the blood-filled components

ascertain the flow characteristics. The simplest technique

rather than because of cellular proliferation. Vascular mal­

to evaluate the nature of blood flow within these lesions ,

formations can be subclassified according to the predomi­

however, is Doppler sonography. Blood flow velocity is

nant vascular component and the hemodynamic features .

accurately determined with sonography, and the compress­

Arteriovenous malformations and arteriovenous fistulae

ibility of vessels and cysts can be evaluated. Angiography

are high-flow malformations . Capillary malformations

remains the gold standard technique for the imaging eval­

and venous malformations are slow-flow vascular malfor­

uation of vascular malformations. However, noninvasive

mations. Lymphatic malformations

(previously termed

techniques have largely supplanted angiography as a pri­

are also slow-flow lesions. Mixed lesions

mary diagnostic technique for this indication. Angiography

lymphangiomas)

can occur, and the terminology can be adapted to indicate

serves an important role during catheter-directed therapeu­

the predominant components, such as "lymphaticovenous

tic interventions .47

malformation" or "capillary-venous malformation. " All of the congenital vascular malformations can be consid­ ered variations of a single embryological anomaly, with categorization based on the pattern of embryological dif. ferentiation. In some patients , vascular malformations or vascular neoplasms occur in conjunction with additional developmental abnormalities

(Table 1 3-5) .

Angiodysplasias

Hemangioma Infantile Hemangioma Infantile hemangioma is a benign developmental neo­ plasm composed of fibrous connective tissue and multiple

Table 1 3-5. Syndromic Vascular Malformations and Vascu lar N eoplasms

Kl ippei-Trenaunay synd rome Parkes-Weber synd rome Servelle-Martorell syndrome von H ippei-Lindau synd rome

Lim b hypertrophy, dilated vei ns, cutaneous hemangiomatous nevi ... Li m b hypertrophy, combi ned vascular malformations, a rteriovenous fi stulas Li m b enlargement, vascular anomalies, local ized skeletal hypoplasia Angiomatosis, hemangioblastoma, pheoch romocytoma, pancreatic cysts, renal cell carci noma -- -- -- - -----------Stu rge-Weber synd rome Facial capillary malformations, leptomeni ngeal capillary and venous malformations M u ltiple enchondromas, hemangiomas, lym phatic malformations M affucci syndrome Hereditary hemorrhagic Telangiectasias and arteriovenous malformations i n the skin, G I mucosa, telangiectasia viscera, l u ngs, and brain ------ - - - - - - --------Proteus synd rome Vascular malformations, l i pomas, li pomatosis, asym metric l i m bs, partial gigantism ofthe hands or feet, and verrucous nevus CLOVE syndrome Congenital l i pomatous overgrowth, vascular malformations, and epidermal nevi Bannayan-Ri ley-Ruvalcaba Vascu lar malformations, l i pomas, macrocephaly, Hashimoto thyroid itis, and G l polyps syndrome �------ -- ------- ---Posterior fossa malformations, hemangiomas, arterial anomal ies, cardiac anomalies PHACES syndrome and aortic coarctation, eye abnormalities, and a sternal cleft or suprapubic raphe Blue rubber bleb nevus syndrome Cutaneous (rubbery blebs) and G l venous malformations -

... ... ... _ ... _ _ _ _

- - ----------

--·-

- - · · - - - - - - - - - - -- - · · - -

-

---

---

----· ·-- · -

--------

- ------ -- ----· ------ � � .

. � � -- -- ------ -------- -- ------ -- ------ ------ ---

------ ---- ------- - ---- - --·

------·-------

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --

Chapter 13 The Vascu l a r System 447 vascular channels that are lined with a single layer of endo­ thelium. Infantile hemangioma is the most common vascu­ lar tumor. The overall prevalence in infants is greater than 4%. Twenty percent of patients have multifocal lesions. At least one infantile hemangioma is present in approximately 10% of white infants by 1 year of age. There is an association with prematurity, low birth weight, female gender, and cho­ rionic villus sampling. The female-to-male ratio is 2.5-4:1.46 Infantile hemangioma is a complex mixture of cell types, including endothelial cells, pericytes, dendritic cells, and mast cells. Infantile hemangiomas undergo char­ acteristic growth patterns, consisting of an initial phase of proliferation and rapid growth during the first year of life and subsequent slow involution over the next several years. During the proliferating phase, there is endothelial hyperplasia and the lesion contains a large number of mast cells. Elevated levels of the angiogenic proteins basic fibro­ blast growth factor and vascular endothelial growth fac­ tor are detectable within proliferating hemangiomas. The endothelial cells of a proliferating hemangioma express proteins that are also present in the placenta, including GLUT1. GLUT1 is an important histochemical marker for infantile hemangioma. Histological evaluation of involut­ ing hemangiomas shows evidence of endothelial apop­ tosis, diminished angiogenesis, decreased size, fibrosis, and fat deposition. The tissue inhibitor metalloproteinase, which suppresses new blood vessel formation, appears to be involved in involution. Infantile hemangioma is dis­ tinct from noninvoluting vascular tumors in adults and older children that are sometimes labeled as hemangiomas because of clinical andfor histological similarities (e.g., cav­ ernous hemangioma) .4'·45 ·46,48 Although infantile hemangioma is a developmental lesion, it often is not identifiable at birth. Approximately one-third of patients present in the perinatal period with a pale cutaneous spot, a macular stain, or a pseudoecchy­ mosis. The mass itself first becomes apparent sometime over the next few weeks or months, as the lesion enlarges. Nearly all patients present during the first year of life. Enlargement of the lesion (the proliferation stage) occurs for at least several months before the onset of regression. Small hemangiomas usually grow rapidly for a few weeks to a few months. Larger hemangiomas tend to grow for a longer period; rarely, there is continued growth during the second year of life. The involution stage varies from months to years. After involution, there is a variably sized end-stage fibrofatty residuum. Classic infantile hemangioma is absent or quite small at birth. There are unusual instances of true "congenital" hemangiomas, with initiation of the proliferation phase during fetal life and the presence of a fully developed tumor at birth. These variants include rapidly involuting congenital hemangioma (RICH) and noninvoluting con­ genital hemangioma (NICH) (discussed in subsequent sections) .49 Infantile hemangiomas can arise in nearly any loca­ tion throughout the body, with the skin representing the

most common site . Approximately 6o% of infantile hem­ angiomas occur in the head and neck region. Potential deeper sites of origin include the liver, trachea, orbit, and GI tract. Hemangiomas with a cutaneous component are readily diagnosed clinically. The lesion is red, raised, and irregular. Deeper lesions may have normal overly­ ing skin, although the presence of skin hemangiomas elsewhere is a clue to the diagnosis. Cutaneous lesions can ulcerate and bleed. The size, location, and hemody­ namic effects of the lesion determine the potential com­ plications. Orbital hemangiomas can cause proptosis and visual disturbance. Approximately 3 0 % of facial heman­ giomas lead to childhood facial disfigurement. Subglottic hemangiomas cause stridor and hoarseness. Extensive hepatic hemangiomas can cause high-output cardiac fail­ ure in young infants . A variety of developmental anomalies can occur in association with infantile hemangiomas. Head and neck hemangiomas (most commonly segmental hemangiomas of the face) sometimes occur in association with other anomalies as part of the PHAC E S syndrome. PHAC E S syndrome includes posterior fossa malformations, hem­ angiomas, arterial anomalies, cardiac anomalies and aortic coarctation, eye abnormalities, and a sternal cleft or supra­ pubic raphe. The hemangiomas in PHACES syndrome patients tend to be large, plaque-like lesions of the face. The appearance can be mistaken for the port-wine stain that occurs with Sturge-Weber syndrome. The potential posterior fossa malformations in children with PHAC E S syndrome include cerebellar hypoplasia, Dandy-Walker malformation, and cerebellar cortical dysplasia with fea­ tures of polymicrogyria ( Figure 1 3-1 5) . Arterial anomalies that can occur in these children include unilateral or bilat­ eral carotid artery aplasia or hypoplasia, kinking or tortu­ osity of the carotid arteries, vertebral artery hypoplasia, and persistence of the trigeminal artery ( Figure 1 3-1 6) . The eye lesions include glaucoma, cataracts, microphthalmos, optic nerve hypoplasia, and exophthalmos caused by an orbital hemangioma. PHAC E S syndrome may represent a phakomatosis with a broad phenotypic spectrum. A devel­ opmental field defect that occurs during early gestation is postulated. The female-to-male ratio for patients with PHAC E S syndrome is 9 :1.S 0-52 Many infantile hemangiomas do not require diagnos­ tic imaging evaluation. Imaging studies are useful, how­ ever, to establish the diagnosis of a deep hemangioma or to delineate involvement of adjacent structures . Sonography, CT, M RI, angiography, and scintigraphy all provide charac­ terizing information; imaging modality selection is based on the specific patient circumstance. In general, imaging of the spinal cord is indicated when there is a cutaneous hemangioma adjacent to the spine. Imaging of the liver and brain may be appropriate for children with multiple (5 or more) cutaneous hemangiomas. Sonography shows an infantile hemangioma as a solid mass. Although large lesions insinuate along adj a­ cent structures, the margins are usually relatively well

448 Part 2 The Ca rd i ovascu l a r System

A

B

Figure 13-1 5 PHACES syndrome. A. A Tz-weighted fat-suppressed image of an infant with right­ sided proptosis and a clinically evident right facial hemangioma

shows a large intraorbital hyperintense mass (arrow) that contains multiple flow voids. B. A coronal image through the posterior fossa demonstrates right cerebellar hypoplasia.

circumscribed with both small and large hemangiomas. Doppler examination during the proliferation phase shows venous flow within the lesion, as well as high­ velocity low-resistance arterial flow. There can be pul­ satile flow in draining veins as a result of arteriovenous shunting. Color Doppler images show prominent perfu­ sion during the proliferation phase, even if individual

vessels are too small to be visualized on standard images ( Figure 1 3-17) . The vascularity of the lesion progressively diminishes during the involuting phase. A large high­ flow hemangioma of the liver is sometimes detectable with prenatal sonography; initiation of maternal cortico­ steroid therapy may diminish the hemodynamic conse­ quences for the neonate.53-54

A

Figure 13-1 6 PHACES syndrome.

B

This u-year-old boy had a large left facial hemangioma as an infant that spontaneously regressed. A, B . M R angiography images show marked tortuosity of the carotid and vertebral

arteries. The left carotid vessels are small and there is a segment of marked tortuosity in the left internal carotid. The intracranial arteries are normal.

Chapter 13 The Va scu l a r System 449

A

Figure 13-17 I nfantile hemangioma.

A. Sonography of a clinically evident sacral hemangioma in a 4-week-old infant shows a solid lesion (arrow) in the skin. B. This

The solid nature of an infantile hemangioma can also be documented with CT. The lesion has similar attenu­ ation characteristics as normal muscle on unenhanced images. Prominent contrast enhancement is typical. Some hemangiomas have a very homogeneous high­ attenuation appearance on contrast-enhanced images , whereas others appear more heterogeneous. Some, but not all, have prominent vessels coursing through the mass. In areas such as the face, CT is useful for evaluat­ ing bony expansion adjacent to the mass. For many children with a suspected infantile heman­ gioma, MR is the most useful and comprehensive imag­ ing technique. The degree of involvement of adj acent soft-tissue structures is well documented by M R. Fat­ suppressed Tz-weighted images often provide the greatest differentiation from adjacent normal structures. A prolif­ erating hemangioma is visualized as a solid, lobulated tumor that produces moderately high signal intensity on Tz-weighted images, and is roughly isointense to other soft-tissue structures on T1-weighted images. Some hem­ angiomas have prominent vascular fl. ow voids within the tumor matrix ( Figure 1 3-18) . The major arteries and veins adj acent to the lesion are usually normal. A large lesion in the proliferation phase sometimes has enlarged feed­ ing arteries and draining veins ( Figure 1 3-1 9) . As with CT, contrast enhancement is usually intense, but var­ ies somewhat between patients . During the involution phase, the increasing fibrous and fatty composition of the lesion results in a relative increase in signal inten­ sity on T!-weighted images ; the mass often appears het­ erogeneous on Tz-weighted images. Vascular structures diminish in prominence during involution. In any infant with a plaque-like facial hemangioma, the examination should include cross-sectional M RI of the brain as well as M R angiography of the neck and head to asses for associated lesions .

B

proliferating hemangioma has prominent blood flow on color Doppler evaluation.

Scintigraphy with radionuclide-labeled red blood cells (blood pool imaging) can be used as a confirmatory test for the diagnosis of infantile hemangioma. The vascular nature of the lesion is indicated on this study by rapid, intense, and persistent accumulation of labeled red cells.

Figure 1 3-1 8 I nfantile hemangioma. There are multiple flow voids within this left-sided facial hemangioma in a 4-month-old infant. The lesion is hyperintense on this fat-suppressed T2-weighted sequence. The outer surface is lobulated.

450 Part 2 The Ca rd iovascu l a r System Although only rarely indicated as a primary diagnostic study for patients with a suspected infantile hemangioma, angiography is an essential tool for endovascular therapeu­ tic procedures . During the proliferating phase, an infan­ tile hemangioma appears as a lobular mass with intense, persistent staining

( Figure 1 3-20) .

The mass sometimes

has the appearance of multiple lobules that are separated by ill-defined zones of diminished vascularity. The supply­ ing arteries are usually only minimally enlarged, as are the draining veins. Angiographic evidence of arteriovenous shunting is lacking with most of these lesions.

I nfantile Hemangioma Pathology

Rad i o l ogy !

Fibrous connective tissue Solid mass M u ltiple vascular channels : Promi nent contrast ! enhancement , Avid uptake on labelled ' red cell scan . Doppler: high-velocity low­ Promi nent vascularity ' resistance arterial flow , M R: flow voids '

A

.

...

'

'

Most infantile hemangiomas d o not require specific therapy. Parents need to be reassured that the initial increase in size during the proliferation phase is to be expected, and that eventual spontaneous reduction will occur. Pulsed-dye laser therapy can be used to treat lesions with substantial ulceration. Medical, surgical, or endovascular therapies are sometimes indicated to treat hemangiomas that are associated with obstruction or distortion of an important structure, or those rare lesions that cause sufficient shunt­ ing to produce heart failure. The most commonly used medical therapy is intralesional or systemic corticosteroids. Interferon-a therapy is a second-line medical option, but carries the risk of spastic diplegia as a complication (occur­ ring in approximately 5% of patients) . Systemic vincristine therapy is also effective. Some hemangiomas are in loca­ tions that are amenable to surgical resection or debulk­ ing. Transcatheter particulate embolotherapy is effective in reducing the vascularity of a high-flow hemangioma that is causing cardiac failure. Embolization is also an option for B

reducing the size a hemangioma that is interfering with the function of an important adjacent structure; intraarte­

Figure 13-1 9 I nfantile hemangioma.

rial injection of corticosteroid can be performed as part of

A This large right neck mass enhances prominently with intravenous contrast on a fat-suppressed Tl-weighted image. A few flow voids are present within the lesion. B. Slightly enlarged feeding arteries from the right external carotid artery and branches of the thyrocervical trunk are visible on this time­ of-flight MR angiography image.

the procedure.55 The distinction between a hemangioma and a venous malformation

or

lymphatic

malformation

is

usually

straightforward on cross-sectional imaging studies, as a hemangioma is a solid mass without cysts or large blood­ filled spaces. Infantile vascular neoplasms with features

Chapter

A

Figure 13-20 I nfantile hemangioma. A A lateral thoracic aortogram image of a 1-year-old child shows a hypervascular mass (arrow) supplied by slightly prominent

that sometimes overlap those of infantile hemangioma include kaposiform hemangioendothelioma, tufted angi­ oma, and hemangiopericytoma. Malignant neoplasms occasionally have imaging features that overlap those of hemangioma. Biopsy is required for children with clinical or imaging features suggesting an aggressive lesion.

Rapidly Involuting Congenital Hemangioma RICH is a recently recognized vascular lesion in which the tumor is fully developed at birth and undergoes rapid involu­ tion. This is distinct to the pattern of infantile hemangioma, in which there is increase in size for at least the first several months oflife, prior to spontaneous regression. Involution of RICH progresses rapidly over the early months of life, and complete resolution occurs at less than 1 year of age in most patients. Physical examination demonstrates a firm mass or plaque that is red or purple with a pale or blanched halo. A surface telangiectasia may be present. After invo­ lution, some patients have residual soft-tissue atrophy. A large RICH can cause high-output cardiac failure.

13

The Va scu l a r System

451

8

intercostal arteries. B. There is intense staining of the lesion on the venous phase image.

The pathological features of RICH are distinct from those of infantile hemangioma. Histological examination shows lobules of capillaries within a densely fibrotic stroma that contains hemosiderin deposits. There is focal lobular thrombosis and sclerosis. Multiple thin-walled vessels are usually present. Intermingling of the neovasculature with normal tissue elements (as occurs with infantile heman­ gioma) is lacking. Also distinctive from infantile heman­ gioma is a lack of immunoreactivity for GLUT1 and LeY)6,57 Sonographic examination of RICH shows a well­ circumscribed mass that is predominantly located in the subcutaneous fat. The lesion is diffusely vascular. A mixture of vessels with arterial and venous flow characteristics is typical. The echo character varies between patients. The lesion enhances intensely on CT and MR (see Figure 2 6-35 in Chapter 2 6 ) . There is marked hyperintensity on T2-weighted M R sequences. Fat-suppressed T2-weighted images provide optimal differentiation from adjacent soft tissues. The mass may appear homogeneous or somewhat heterogeneous on MR images. With a large mass, there are usually prominent flow voids because of dilated draining

452 Part 2 The Ca rd i ovascu l a r System veins. The flow voids predominate along the peripheral aspect of the lesion. The flow voids tend to be much larger than those associated with infantile hemangioma.57·5 8 Angiography of RICH shows heterogeneous paren­ chymal staining, large and irregular feeding arteries in a disorganized pattern, arterial aneurysms, direct arterio­ venous shunts, and intravascular thrombi. Large drain­ ing veins predominate at the periphery of the lesion. The angiographic appearance sometimes mimics that of an arteriovenous malformation or a congenital infantile fibrosarcoma. 59

Noninvoluting Congenital Hemangioma N I C H refers to a rare cutaneous vascular lesion that, unlike classic infantile hemangioma or RICH, does not regress spontaneously. This lesion may represent a variant of RICH. A NICH is a solitary cutaneous lesion that usually measures a few to several centimeters in diameter. The lesion is clinically evident at birth, and continues to grow approximately in proportion to the adjacent normal struc­ tures. Histological examination shows lobular collections of small thin-walled vessels and a large central vessel. Doppler ultrasound demonstrates high-velocity flow. The mass usu­ ally appears homogeneous on cross-sectional imaging studies, and undergoes prominent uniform enhancement. The imaging features of NICH generally do not allow dis­ tinction from classic hemangioma of infancy.6 o

Kaposiform Hemangioendothelioma Kaposiform hemangioendothelioma is a rare benign vas­ cular tumor that is distinct from infantile hemangioma and has no association with Kaposi sarcoma. The lesion is characterized histologically by the presence of infiltrat­ ing nodules and sheets of spindle cells. This aggressive benign neoplasm often undergoes rapid enlargement. The cutaneous component is clinically obvious, with marked edema, induration, and purpura. There is a poorly defined ecchymotic margin. The lesion is often painful. Kaposiform hemangioendothelioma is a lesion of infancy, with the diagnosis made at birth in approxi­ mately half of patients. Unlike infantile hemangioma, kaposiform hemangioendothelioma does not have a gen­ der predilection. Common sites of involvement include the extremities, head and neck region, mediastinum, ret­ roperitoneum, and pelvis. Kaposiform hemangioendothe­ lioma is often (at least so% of patients) complicated by Kasabach-Merritt syndrome (as is tufted angioma) . This potentially life-threatening thrombocytopenia results from platelet trapping within the vascular tumor. The architec­ tural features of these lesions cause turbulent blood flow and platelet activation.52·6'-63 M RI is the most useful imaging technique for infants with kaposiform hemangioendothelioma. This aggres­ sive vascular neoplasm has poorly defined, infiltrative margins. Fibrosis, blood products, and vessels result in a

heterogeneous character (Figure 1 3-21 ) . Signal voids as a result of hemosiderin deposits are common. The majority of the lesion is moderately hyperintense on T2-weighted images. There is diffuse contrast enhancement of the mass. Erosion of adjacent bony structures can occur; this is best demonstrated with CT. Imaging studies performed after therapeutic interventions typically show diminished size of the mass, but there are usually residual enhancing foci of viable tumor. The aggressive growth characteristics ofkaposiform hemangioendothelioma sometimes result in imaging features that overlap those of a malignancy. 64 Because of the large and aggressive nature of kapo­ siform hemangioendothelioma, therapy is almost always required. Variable clinical results have been achieved in treating these patients with systemic corticosteroids, interferon-a, and systemic chemotherapy. Radiation ther­ apy has also been utilized for some patients. Spontaneous regression is not a feature of this tumor. Metastasis does not occur. 65 , 66 Kaposiform hemangioendothelioma complicated by Kasabach-Merritt syndrome is fatal in nearly 1 in 4 patients. Heparinization is contraindicated for these children, as it can lead to accelerated tumor growth and subcutane­ ous hemorrhage. Platelet infusion can also precipitate rapid expansion of the mass. Treatment of children with Kasabach-Merritt syndrome generally consists of support­ ive care and immediate institution of therapies aimed at diminishing the size of the tumor. Transcatheter emboliza­ tion is helpful for some patients.63.67.6 8

Tufted Angioma Tufted angioma is a rare cutaneous vascular tumor that is characterized clinically by slowly spreading erythematous macules and plaques , sometimes including nodular forma­ tions. The name is derived from the histological appear­ ance, which includes small circumscribed angiomatous tufts and lobules scattered ir1 the dermis. Tufted angioma is predominantly a lesion of children. The tumor is vis­ ible at birth in some patients. The neck and upper trunk are the most common sites of involvement. Slow exten­ sion into the adjacent skin is typical. Extensive lesions can cause Kasabach-Merritt syndrome. Because this is a cuta­ neous lesion, diagnostic imaging studies are generally not required. Tufted angioma is sometimes termed angioblas­

toma ofNakagawa. 6 9-7'

Hemangiopericytoma Hemangiopericytoma i s a rare soft-tissue neoplasm that arises from endothelial pericytes. In keeping with the vascu­ lar origin, this tumor can arise anywhere in the body. Some hemangiopericytomas have malignant characteristics. Hemangiopericytomas arising in children younger than 1 year of age typically follow a more benign clinical course than those arising in older children or adults. Histological examination shows endothelial proliferation within these

Chapter 13 The Vascu l a r System 453

A

Figure 13-21 Kaposiform hemangioendothelioma. A There is a large infiltrative mass of the right side of the neck

B

and face on this fat-suppressed T2-weighted image of an infant. There is a heterogenous character. Infantile hemangiomas

usually have a more homogenous composition and produce greater signal intensity on T2-weighted sequences. B. The lesion undergoes moderate enhancement on this fat-suppressed T1-weighted image obtained with IV contrast.

lesions . Approximately one-third of hemangiopericytomas

which consists of a tangle of small, tortuous, dysplastic ves­

in children are congenital. Congenital hemangiopericy­

sels . There are dilated arteries extending into the nidus and

toma may undergo a phase of rapid initial growth in the

dilated veins draining from the nidus, but the enlargement

young infant; spontaneous regression similar to that of infantile hemangioma occasionally occurs.7 2

of these vessels is secondary to the shunting at the nidus.

The imaging appearance of hemangiopericytoma is

malformations can present at any age during childhood;

Even though they are congenital lesions, arteriovenous

that of a well-circumscribed soft-tissue mas s . Calcifications

some do not become apparent until adulthood. Potential

are occasionally present. Although any portion of the body

presenting symptoms include cutaneous changes, a pal­

can be involved, the most common locations are the thigh

pable mass , pain, or manifestations of effects on adj a­

and the pelvic retroperitoneum. The congenital variety

cent structures . Superficial lesions can ulcerate or bleed.

often arises within the subcutaneous tis sues. These aggres­

Arteriovenous malformations in the extremities cause

sive lesions sometimes cause erosion of adjacent bone.

hemodynamic alterations that sometimes lead to soft tis­

M R.

sue and osseous overgrowth. Arteriovenous malformations

Conventional angiography shows a dense tumor stain and

tend to slowly increase in size with time. Sudden enlarge­

There is marked contrast enhancement on CT and small vessel arteriovenous shunting.73

Arteriovenous M alformation

ment can be triggered by pregnancy, puberty, hormonal

therapy, trauma, or surgery.4 6

An arteriovenous malformation is visualized on ultra­ sound as a poorly defined, complex pulsatile mass . Doppler

Arteriovenous malformations are congenital high-flow

evaluation shows high-velocity low-resistance flow within

vascular anomalies. Abnormal connections between arter­

the supplying arteries. Arteriovenous shunting is indicated

ies and veins are present within the "nidus" of the lesion,

by an arterialized waveform in the draining veins.54

454

Part 2 The Ca rd iovascu l a r System CT shows an arteriovenous malformation as a rapidly

of feeding vessels is counterproductive in that an intact

enhancing complex mas s . CT and standard radiographs

nidus rapidly recruits other vessels and subsequent access

are helpful for selected patients to assess trophic or erosive

to the nidus will be more complicated. Complete surgical

excision of the nidus is often curative, but is difficult or

changes in adjacent osseous structures . As with other congenital vascular lesions , M RI is usu­

impossible to achieve in many patients because of a large

ally the most useful technique to characterize the size of

size of the lesion or involvement of important normal

the arteriovenous malformation and the effects on adjacent

structures. Transcatheter particle or glue embolization of

structures. The lesion appears as a network of enlarged ser·

the nidus serves to diminish the size of the lesion and pro­

piginous feeding and draining vessels . The nidus may or

vide symptomatic relief. Ablation of the nidus with ethanol is also effective.7 5-'77

may not be specifically visualized. Soft-tissue thickening is sometimes present; this is caused by edema or fibrofatty changes induced by the lesion. The malformation itselfhas no soft-tissue component.74 The nidus of an arteriovenous malformation is opti­

Arteriovenous Fistu la An arteriovenous fistula can be congenital or acquired as

mally demonstrated with angiography. The nidus consists

a consequence of trauma, surgery, or percutaneous inter­

of a network of small, tortuous vessels. There are enlarged

vention.

supplying arteries

and draining veins. Arteriovenous

direct connections between feeding arteries and draining

shunting results in rapid flow through the lesion and ear­

veins; the nidus that characterizes an arteriovenous mal­

lier opacification of veins draining the malformation than

formation is lacking. A large arteriovenous fistula can

those draining normal adjacent soft tissues Relatively

high-volume

contrast

(Figure 1 3-22) .

inj ections

are

often

An arteriovenous fistula consists of one or more

cause clinically significant elevation in cardiac output; this is an extracardiac left-to-right shunt. Techniques for dem­

required, and rapid image acquisition sequences should be

onstrating the pathological anatomy of an arteriovenous

performed.

fistula include CT angiography, M R angiography, and con­

Surgical and endovascular therapy of an arteriovenous

ventional angiography

(Figure 1 3-23) .

Doppler evaluation

malformation should be directed toward elimination of the

demonstrates arterialization of flow in the enlarged drain­

nidus . Surgical ligation or transcatheter embolic occlusion

ing vein (s) . Accurate delineation of the precise site of the

B

A

c

Figure 13-22 Arteriovenous malformation. This 12-year-old girl has a vascular malformation of the right inferior lip. A. A color Doppler image of the nidus shows a collection of tortuous vessels. B-D. Sequential images of a left

D

external carotid arteriogram show an intense blush in the nidus. Enlarged facial artery branches supply the lesion. Multiple enlarged draining veins begin to fill with contrast during the early arterial phase.

Chapter

A

B

c

D

Figure 13-23 Iatrogenic arteriovenous fistula.

This 1-year-old child developed arm pain and swelling after removal of a peripherally inserted central catheter (PICC) . A A longitudinal color Doppler image of the antecubital fossa shows turbulent flow (arrow) at the site of an arteriovenous communication. B. A transverse image in the upper arm shows

arterial-venous communication is essential in planning therapy. The vein adjacent to the communication is dilated

13

The Va scu l a r System 455

arterial flow in the dilated brachial vein (blue) . C. An arteriogram shows a prominent brachial artery (A) and tortuous early filling veins at the site of the fistula (arrow) . There are prominent draining veins M extending up the arm. D. The arteriovenous communication (arrow) is visible on an oblique view.

Temporary enlargement with

dependent position­

ing or the Valsalva maneuver is a characteristic feature of

and often tortuous . Cure can be achieved with surgical liga­

venous malformations. Elevation of the affected portion of

tionfresection or transcatheter coil embolization.

the body or extrinsic compression of the lesion results in a diminished size. The rapidity at which blood empties dur­

Venous M alformation Venous malformation is a congenital vascular malfor­

ing these maneuvers varies substantially between vascular malformations; the pattern of venous drainage is the most important factor. Physical examination demonstrates a

mation that is composed of dysplastic venous channels.

spongy mass that is compressible on palpation. There may

Venous malformations are sometimes erroneously labeled

be a blue or purplish discoloration of the skin. Swelling

with the term cavernous hemangioma, which is a misnomer.

and pain are common, particularly when the affected

Venous malformation is not a neoplasm, and the dysplas­

portion of the body has been in a dependent position for

tic vessels grow at the same rate as the patient. If there is

a prolonged period. More substantial pain and swelling

disproportionate enlargement of the lesion, it is predomi­

can occur acutely in these patients because of episodes of

nately caused by increased distention of the blood-filled

thrombosis.4 6,74

spaces rather than cellular proliferation. Most, but not all ,

There are various familial and syndromic forms of

venous malformations increase in size slowly throughout

venous malformation. The blue rubber bleb nevus syn­

the patient's life. This is particularly true for those lesions

drome

located in dependent portions of the body.

soft, rubbery blebs) and GI venous malformations that

includes

cutaneous

(compressible,

deep-blue,

456 Part 2 The Ca rd iovascu l a r System frequently lead to anemia as a result of recurrent G I hem­ orrhages. Venous anomalies, including venous malfor­ mations, can occur in children with Maffucci syndrome. Intracranial venous anomalies sometimes occur concomi­ tantly with venous malformations of the scalp or face. Klippel-Trenaunay syndrome is a developmental vascular abnormality of the extremities; most commonly, there is a triad of cutaneous capillary malformations, dilated superfi­ cial veins or venous malformations, and overgrowth of the limb (local gigantism) . With sonography, a venous malformation appears as a collection of irregular vessels and blood filled spaces. The lesion can have a sponge-like character. Some venous malformations have relatively well-circumscribed mar­ gins, whereas others are infiltrative. The lesion may be difficult to identify if it is collapsed; placing the involved portion of the body in a dependent location for a few minutes often facilitates visualization. Use of a tourni­ quet can be helpful if the lesion is in an extremity. Most often, the mass diminishes in size during the applica­ tion of gentle pressure with the ultrasound transducer. The cystic components of a lymphatic malformation, in contradistinction, do not empty with palpation. Venous malformations of the trunk or head and neck often dis­ tend when the patient performs the Valsalva maneuver. Doppler studies of a venous malformation show stag­ nant blood and slow venous flow. There is no arteriove­ nous shunting. Echogenic areas caused by thrombus or phleboliths are sometimes present.54 The identification of calcified phleboliths with CT or radiography is a characterizing feature of venous malfor­ mations. Phleboliths appear as laminated round densities ( Figure 1 3-24) . The lesion enhances with contrast material on CT. Typically, there is slow heterogeneous enhancement on initial images, and delayed images show a more homo­ geneous pattern of enhancement. CT may be helpful to define the effects of the lesion on adjacent structures, such as the airway. MRI is generally the most specific technique for documenting the size and character of venous malforma­ tions, and for detecting involvement of adjacent struc­ tures . The lesion is hyperintense on T2-weighted images. Fat-suppressed T2 sequences are usually most satisfac­ tory for defining the extent of the lesion ( Figure 1 3-25) . Those venous malformations that are infiltrative tend to insinuate along tissue planes. Muscle involvement can have a markedly infiltrative character. Atrophy of infil­ trated muscles is common. Large lesions cause displace­ ment of adj acent structures . With a head and neck lesion, clinically significant narrowing of the airway or maj or blood vessels is uncommon. Venous malformations enhance on MRI images obtained with IV contrast. The enhancement pattern tends to the more homogeneous on delayed images than on those obtained immediately after contrast administra­ tion (Figure 1 3-26) . MR angiography is useful for selected patients to rule out an arteriovenous component. The

Figure 1 3-24 Venous malformation; phleboliths.

There are multiple round calcifications in the forearm of this 8-year-old child with a venous malformation. Mass effect from the long-standing infiltrative soft-tissue mass has resulted in lucencies and slight deformity of the radial diaphysis.

Chapter

13

The Vascu l a r System 457

A

B

Figure 1 3-26 Venous malformations.

Figure 13-25 Venous malformation. This venous malformation of the forearm is markedly hyperintense relative to normal soft tissues and bone on this coronal short tau inversion recovery (STIR) image.

A A sagittal short tau inversion recovery (STIR) image shows multiple irregular fluid-filled structures in the retropharyngeal soft tissues (arrow) . There is an additional lesion in the posterior aspect of the neck (arrow) . The venous malformations infiltrate the tissues and cause only minimal mass effect. B. The lesions enhance with intravenous contrast, although some of the larger components of the superficial malformation have not yet fill e d with contrast-enhanced blood on this early image.

458 Part 2 The Ca rd i ovascu l a r System arteries supplying a venous malformation typically are

dysplastic, draining veins. Other venous malformations,

normal in size. Pulse sequences sensitive for venous

particularly those that appear well-circumscribed on cross­

velocity blood flow can be performed, but are generally

sectional imaging studies, drain quite slowly, and the

not necessary and may be unrewarding because of stag­

injected contrast may persist within the lesion for several

nant blood within these lesions . D oppler ultrasound is

minutes .

usually a simpler and faster technique for evaluating the flow characteristics.

M R venography is sometimes help­

ful for defining the anatomy of the major draining veins of a venous malformation, as part of planning for surgery or sclerotherapy. Angiography is not part of the standard workup of venous malformations. When performed, angiography shows normal-appearing supplying arteries. There may be

Venous Malformation Rad iology

Pathology

Dysplastic venous channels

an early blush within the lesion if there is a capillary com­ ponent. Slow, and usually incomplete, opacification of the veins and sinusoidal spaces of the venous malformation is sometimes present. Direct puncture venography pro­ vides the most satisfactory angiographic characterization of venous malformations

(Figure 1 3-27) . Optimal filling is

. Tortuous blood-fil led spaces . Fat-suppressed T2: marked ly hyperintense Little or no flow on Doppler, or M R venography Ph leboliths ·

Stagnant blood ······· ····

········ ·

· · ······

Calcified thrombi

.

·

......... .

achieved with the application of a tourniquet or direct exter­ nal compression of the maj or draining veins . The rapidity of venous drainage varies greatly between these lesions . Some empty relatively quickly into prominent, sometimes

The therapeutic approach t o the patient with a venous malformation must be carefully tailored. Important factors that need to be considered include the size and location of the lesion, the effects on adjacent structures, the growth history, the effectivenes s of prior conservative treatments, and patient and family preferences. Elastic compressive garments are effective for many venous malformations of the extremities . Aspirin reduces the incidence of painful thrombotic episodes. Surgical resection and percutaneous sclerotherapy represent more aggressive therapies that can be helpful for selected patients . 47

Capillary M alformation A capillary malformation is a thin vascular lesion that is composed of dilated capillaries in the superficial dermis or, less commonly, the leptomeninges . The pathophysiology appears to be distinct from that of other vascular malfor­ mations; a loss of primary autonomic-origin nerves in the vicinity of the lesion apparently causes progressive vascular ectasia by a failure of blood flow regulation in the affected portion of the dermis.78 Clinically, a capillary malforma­ tion appears as a pink or red cutaneous birthmark, most often located in the head and neck region. The port-wine stain that occurs

in patients with Sturge-Weber syndrome

is an example of a capillary malformation. As the child increases in age, these lesions tend to become darker and undergo fibrovascular overgrowth. The adjacent soft tis­ sues and osseous structures may become thickened.46 Capillary malformations are superficial lesions that do not require diagnostic imaging evaluation. However,

Figure 13-27 Venous malformation.

they can occur as components of various syndromes, and

Direct puncture venography performed in preparation for sclerotherapy of a venous malformation of the hand shows a collection of multiple tortuous irregular veins.

lying structures. Capillary malformations are common

can signal the presence of important pathology in under­ in patients with hereditary hemorrhagic telangiectasia.

Chapter 13 The Vascu l a r System 459

Patients with Sturge-Weber syndrome have facial capillary malformations as well as venous and capillary malforma­ tions of the leptomeninges. However, the great majority (98%) of patients with facial port-wine stains do not have Sturge-Weber syndrome. Spinal dysraphism and calvarial cephaloceles sometimes have an overlying cutaneous cap­ illary malformation. Extensive cutaneous capillary malfor­ mations are a component of the macrocephaly-capillary malformation syndrome.46,74

Lymphatic M alformation Congenital lymphatic malformation is a developmental lesion composed of dilated lymphatic spaces. Because this is not a true neoplasm, the commonly applied terminology oflymphangioma is a misnomer. A lymphatic malformation consists of endothelial-lined lymphatic channels of vari­ ous sizes that are filled with proteinaceous fluid. Studies using tritiated thymidine have shown that the endothelial cells that line the channels have turnover rates of normal mature cells, supporting the classification as a develop­ mental anomaly rather than a true neoplasm.4'·79 Categorization oflymphatic malformations is into mac­ rocystic, microcystic, and mixed subtypes. Traditionally, a lymphatic malformation comprised of very large cysts is termed a cystic hygroma. Some of these malformations have a mixed character that includes dilated vascular channels fill ed with slowly flowing blood; these are best termed lym­ phaticovenous malformations. The initial phase of development of the lymphatic sys­ tem consists of the formation of endothelial-lined struc­ tures that arise from the embryonic jugular veins and unite to form plexuses. These go on to develop into paired jugular sacs. The jugular sacs progressively enlarge, and each maintains a single communication with the ipsilateral internal jugular vein. Extensions occur into the soft tissues and between muscles, ultimately forming lymph vessels that permeate all the tissues, coursing adjacent to blood vessels. There are multiple potential pathogenic mechanisms for the formation of lymphatic malformations. Loss of communication with the venous system may result in iso­ lation of a group oflymphatic channels. This mechanism is favored to explain the large lymphatic malformations that occur in the head and neck. Another potential mechanism is sequestration of lymphatic tissue early in embryogene­ sis, thereby resulting in failure of communication with nor­ mal central lymphatics. A third theory postulates abnormal budding of embryonic lymphatic structures, leading to loss of connections with the lymphatic primordia. The resul­ tant lymphatic cysts grow in an uncontrolled disorderly manner. 80 The typical natural history of a lymphatic malforma­ tion is that of slow progressive growth. This is a congeni­ tal lesion and is present at the time of birth, although it may remain clinically occult for a number of months or

years. The clinical presentation sometimes results from sudden enlargement caused by hemorrhage or infection. Hemorrhage, either spontaneous or because of minor trauma, is common in lymphatic malformations. Some of these lesions come to clinical attention because of mass effect on adjacent structures, such as proptosis caused by an enlarging intraorbital mass. Mediastinal or cervi­ cal lymphatic malformations can cause symptomatic air­ way obstruction. Lymphatic malformations located in the extremities commonly are associated with soft-tissue over­ growth and skeletal growth deformities. A microcystic lymphatic malformation frequently has the characteristics of a solid mass, and is firm to palpation. The macrocystic variety tends to have a spongy character on palpation. When in an accessible location, the lesion often transilluminates. Infection of a lymphatic malformation is common. Some patients note transient increase in size of the lesion during upper respiratory infections. Lymphatic malformations occur as components of various syndromes. Nearly three-fourths of lymphatic malformations that cause untoward effects on the fetus are associated with Turner syndrome. Approximately 6o% of patients with Turner syndrome have 1 or more lym­ phatic malformations. Prenatal sonography of a fetus with Turner syndrome typically shows prominent hypoechoic thickening in the nuchal region because of the presence of subcutaneous fluid that accumulates because of hypo­ plastic dermal lymphatic vessels. Lymphatic malforma­ tions also occur with an elevated prevalence in patients with Noonan syndrome, trisomy 21, trisomy 13 , and tri­ somy 18. Gorham-Stout syndrome refers to diffuse skel­ etal and soft tissue lymphatic malformations that result in progressive osteolysis. Pathologically, a lymphatic malformation is a thirl­ walled cystic mass. There is considerable variation of cyst size between patients, as well as variation within a single lesion. The cysts represent dilated lymphatic spaces lined by attenuated endothelial cells. Individual cysts may con­ tain chylous, serous, or hemorrhagic fluid, or a mixture of different components. The supporting stroma of the lesion is composed ofcollagen. Lymphocytes and lymphoid aggre­ gates are often present within the stroma. Histopathology demonstrates irregular vascular channels with thin walls, attenuated endothelial layers, and interrupted basement membranes. Pericytes are absent. There is loose fibrous stroma, with collections of lymphocytes and few smooth muscle cells. The cystic character of a macrocystic lymphatic mal­ formation is effectively documented with sonography ( Figure 1 3-28) . Debris or blood products frequently result in elevation of echogenicity within some of the cysts ( Figu re 1 3-29) . Differing echogenicity in adjacent cysts is characteristic. Small arteries and veins are visible within the cyst walls on Doppler studies. Arteriovenous shunt­ ing is lacking in pure lymphatic malformations. In those lymphatic malformations composed of cysts too small to

460 Part 2 The Ca rd iovascu l a r System

A

B

Figure 13-28 Lymphatic malformation. This 1-year-old child was evaluated for soft-tissue fullness in the left upper arm. A, B. Sonography demonstrates a multiloculated cystic mass. One of the loculations is moderately echogenic as a result of hemorrhage or debris (arrow) . C. The cysts in the arm and axilla are hyperintense on this fat-suppressed T2-weighted MR image.

be resolved sonographically, the appearance is that of a hyperechoic solid mass.43 . 5 4 Macroscopic cysts within a lymphatic malformation typically have higher attenuation than dear fluid on CT because of proteinaceous fluid andjor blood products. Fluid-fluid levels are sometimes visible; when present, this is a helpful characterizing feature. The solid components of the lesion undergo a variable degree of contrast enhance­ ment. In many instances, the septations within the mass are too thin to be visualized with CT. Sonography often pro­ vides a more specific appearance, with a network of thin septations that divide the mass into cysts of varying sizes. A microcystic lymphatic malformation appears on CT has a moderately enhancing heterogeneous mass; the CT appearance in this situation may be nonspecific. Imaging of an infected lymphangioma typically shows thickening of septations, as well as edema and prominent enhancement in the adjacent soft tissues.

c

M RI is often the most useful and specific imag­ ing technique for the evaluation of a suspected lym­ phatic malformation. As with other imaging studies , the appearance i s influenced b y the sizes and contents of the cystic components. Both macrocystic and micro­ cystic lymphatic malformations are hyperintense on T2-weighted images . Fat-suppression sequences aid in the distinction from adjacent soft tissues. As with CT, individual cysts within the same lesion frequently have slightly different signal characteristics . Elevated signal intensity is often present within cysts on T1-weighted images because of protein or blood products. Fluid-fluid levels may be present ( Figu re 1 3-30) . These helpful char­ acterizing features are relatively specific for the diagno­ sis of lymphatic malformation. The solid components of a lymphatic malformation enhance with IV contrast. The MR findings of a microcystic lymphatic malformation are less specific, but this technique does allow accurate

Chapter 13 The Vascu l a r System 461

8

A

Figure 1 3-29 Lymphatic malformation. A. A longitudinal sonographic image of the inguinal-femoral region of a 16-month-old boy shows 2 adjacent cysts ( arrows) that contain echogenic debris. Factors that favor a cystic composition despite prominent echogenicity include acoustic enhancement and lack of perfusion on Doppler (not shown) . B. A fluid---13

mm in adults) , splenomegaly, gastroesopha­

geal varices, other portosystemic collaterals, and ascites.

orrhage, tion

obstruction,

(Table 1 3-6) .

and arteriovenous communica­

Arteries and veins can be transected,

Chapter 1 3 The Vascu l a r System 467

A

B

Figure 1 3-32 Varicocele. A. A transverse image of the left hemiscrotum shows multiple prominent vessels adjacent to the testis. B. Color Doppler confirms vascular flow. Pulsed wave evaluation (not shown) confirmed venous flow characteristics in these vessels. C. An image obtained during the Valsalva maneuver shows distention of the veins and transient increase in flow velocity.

c

lacerated, overstretched, or contused. The clinical mani­ festations of vascular injuries are related to hemorrhage from the damaged vessel, diminished flow, andfor distal embolization. 1 2 1 • 1 22

Table 13-6. Spectrum of Vascular Trauma

H emorrhage Obstruction

Other

, Transection Ru ptu red pseudoaneurys m Th rombosis Dissection Embolization Spasm Com pression I ntra m u ral hematoma Traumatic arteriovenous fistu la

Transection or laceration of a vessel is most often related to a penetrating injury. The usual management of patients with life-threatening hemorrhage or a rapidly expand­ ing hematoma is immediate surgical exploration without preoperative imaging studies. In clinically stable patients who have suffered penetrating trauma, imaging studies are often useful for the detection and characterization of arte­ rial injuries. Angiography and sonography are the imag­ ing techniques most often utilized for this indication. The imaging findings in these patients range from complete occlusion of the vessel to minimal irregularity of the wall. A localized intimal flap may project into the vessel lumen. An adjacent hematoma often causes extrinsic compression or deviation of the vessel. An arterial dissection is a hematoma within the vessel wall. Dissection is usually a result of stretching of a seg­ ment of a vessel or a direct blow to the artery. Most, but not all, dissections are associated with an intimal defect. Two pathophysiological mechanisms of traumatic dissec­ tion are possible: (a) a tear in the intima that allows the accumulation of blood, which usually clots, within the

468 Part 2 The Ca rd iovas cu l a r System vessel wall, and (b) an intramural hematoma that rup­ tures through the intima to produce a communication with the lumen. The intramural hematoma of a traumatic dissection is usually located in the media. If the hema­ toma extends between the media and adventitia, the outer wall of the vessel frequently becomes dilated; this is a dis­ secting aneurysm. If the vessel ruptures completely and the walls of the perivascular hematoma cavity consist of clot­ ted blood and the perivascular soft tissues, the lesion is termed a pseudoaneurysm. The pathological anatomy of a trauma-related arterial dissection includes a narrowed or completely occluded lumen caused by inner displacement of the intima. Most often, there is an intramural hematoma peripheral to the intimal layer, and outward bulging of the adventitial layer results in enlargement of the overall diameter of the ves­ sel. Perivascular blood leakage and a pseudoaneurysm can occur as part of this process, usually located near the distal portion of the dissection. In some instances, blood flow occurs in both the true and false lumens of a dis­ section, resulting in 2 channels separated by a thin layer of intima. If only a small segment of intima is displaced into the lumen, the lesion is termed an intimal flap. Direct signs of arterial injury on sonography include partial or complete transection of the arterial wall and dis­ section. Indirect signs include spasm, thrombosis, and wall thickening.'23 Dissection is effectively evaluated with sonography if the lesion is in a vessel that is not obscured by bone or other structures. Obstruction caused by a dissec­ tion results in diminished forward flow. If there is severe obstruction, diastolic reversal of flow during diastole can occur in the portion of the vessel proximal to the dissection. The diminished antegrade flow results in dampened spec­ tral waveforms. The appearance of the displaced intima of the dissection on sonography is a thin linear echogenic structure in the lumen. Echogenic thrombus in the false lumen is sometimes visible. CT angiography of patients with an acute dissection most often shows eccentric narrowing of the contrast­ enhanced lumen. The intramural hematoma causes enlargement of the overall vessel diameter in the region of the dissection. A nonocclusive dissection or intimal flap appears as a thin filling defect in the vessel lumen. Thrombus produces larger filling defects. Other potential CT findings include mural thickening and pseudoaneurysm. With MR angiography, flowing blood in the nar­ rowed lumen at a dissection has high signal intensity. High signal from the intramural hematoma can mimic the appearance of flow-related enhancement. The hema­ toma is usually best demonstrated on T1-weighted fat­ suppressed sequences, and appears as a crescentic area of increased signal that is associated with expansion of the vessel wall and narrowing of the lumen; flowing blood in the lumen is hypointense. If there is flow in both the true and false lumens, a "double-lumen sign" occurs . Axial images usually provide optimal depiction of the severity of overall vessel enlargement. With complete

or high-grade obstruction, MR angiography may over­ estimate the length of the occlusion, as flow in the pat­ ent lumen proximal to the obstruction may be too slow to produce flow enhancement. Gadolinium-enhanced images are sometimes helpful for accurate documenta­ tion of the anatomy of a dissection or intimal flap. Because the false lumen of a dissection is usually fill e d with clotted or stagnant blood, angiography typi­ cally shows tapered narrowing of the contrast-opacified true lumen. The degree of narrowing varies between patients, and can range from minimal irregularity of the inner wall of the vessel to complete occlusion. An inti­ mal flap appears as a thin intraluminal membrane. The flap is most often located at the proximal aspect of the dissection. A longer elevation of the intima with a patent false lumen produces a double-lumen appearance. Other potential angiographic findings in patients with dissec­ tion include slow flow through the vessel, aneurysmal dilation, and evidence of distal emboli. A pseudoaneurysm is common after penetrating injury. This results from confined perivascular hemorrhage arising from a disruption of the vessel wall. The imaging appearance of a pseudoaneurysm is that of a focal widening or outpouching of the vessel, often containing thrombus. The abnormal vessel contour is effectively demonstrated with sonography or CT. The aneurysm may or may not fill with contrast, depending on the degree of thrombosis. M R angiography i s unreliable for the detection o f pseudoaneu­ rysms because of the lack of, or turbulent nature of, flow within the lesion. Conventional axial MR images should be inspected for vessel contour abnormalities in trauma patients. The angiographic visualization of an injured vessel is sometimes complicated by adjacent normal vessels that obscure the abnormality. In some patients, an important clue to the location of the involved vessel is the demon­ stration of intermittent opacification. This refers to inter­ mittent visualization and nonvisualization of a vessel on sequential rapid sequence angiographic images as a result of altered flow during the cardiac cycle. When this sign is present, it facilitates identification of a small branch ves­ sel involved in posttraumatic hemorrhage, and is useful for directing embolization. Intermittent opacification typically occurs in association with contrast material extravasation or a false aneurysm.'24·'25

Chest Rupture of the thoracic aorta is a common cause of death in patients suffering blunt chest trauma. Thoracic aorta inju­ ries are common in fatal vehicular trauma. Those patients who survive long enough to be evaluated in the hospital usually have an injury that is contained by an intact adventi­ tia. There is a substantial risk of mortality in these patients absent prompt diagnosis and management. Most pediatric aortic injury victims are passengers in, or are struck by, a motor vehicle. '26

Chapter Aortic injury caused by blunt chest trauma most often results from horizontal shear forces that occur during high-speed deceleration. The ascending and descending portions of the arch are relatively mobile in comparison to the transverse portion that is fixed by the brachiocephalic vessels. Other potential mechanisms include shearing forces related to compression, and "pinching" of the aorta between the spine and the anterior bony thorax.'27 The most common site (approximately 8o %) of aortic disruptions in patients who are evaluated with diagnos­ tic imaging studies is in the region of the aortic isth­ mus. Injuries can also occur elsewhere in the aortic arch. Injuries in the thoracic aorta beyond the arch are less com­ mon. Brachiocephalic vessel inj uries can occur alone or in combination with aortic injuries . Complete laceration of aorta is the most common traumatic lesion in autopsy series , but tears of the intima and media with an intact adventitia are most common in those patients who survive long enough to undergo imaging evaluation. The medias­ tinal hemorrhage that occurs in these patients, therefore, is predominantly a result of rupture of smaller arteries and veins. Rarely, a complete aortic tear is contained by peri­ aortic tissue, producing an acute pseudoaneurysm.' 2 8-t3 o The possibility of aortic injury should be considered in all patients who have experienced high-speed rapid decel­ eration trauma or severe nonpenetrating thoracic impact trauma, as there may be no external signs of the injury. Potential clinical findings include chest pain, mid-scapular pain, and shortness ofbreath. A lack of symptoms does not guarantee the absence of a potentially fatal aortic injury, however. There is a difference in pulse amplitude between upper and lower extremities in some patients. Standard chest radiographs serve as the primary screening method for mediastinal hemorrhage in patients suffering blunt thoracic trauma. The most common radiographic finding is widening of the medi­ astinum. In adults , a transverse distance of equal to or greater than 8 em from the left side of the aortic arch to the right margin of the mediastinum is considered abnormal. Other potential radiographic findings include obscuration of the aortic knob and descending aorta, rightward displacement of a nasogastric tube, rightward deviation of the trachea, inferior displacement of the left mainstem bronchus, a left apical cap, and thickening of the right paratracheal stripe. It should be noted that most patients with hemomediastinum do not have an aortic injury, and approximately 7% of patients with aortic rup­ ture do not have abnormalities on chest radiographs. In those patients with an aortic injury, the volume of medi­ astinal hemorrhage does not directly correlate with the severity of aortic pathology.'3' Thoracic aortography is the gold standard technique for the detection and characterization of aortic injuries. Potential angiographic findings include one or more tran­ section lines involving the intima and media, a subadven­ titial contrast collection (false aneurysm) , intimal flap, and dissection. Occasionally, there is an impression on the

13

The Va scu l a r System 469

contrast-opacified aortic lumen as a consequence of an intramural hematoma. If there is no evidence of a lacera­ tion, an intramural hematoma often does not require surgi­ cal intervention. A transfemoral approach is the generally preferred access technique for aortography. If pelvic injury precludes femoral artery access, utilization of the right axillary artery is appropriate. Because of the potential for exacerbating the injury, extreme care is essential during catheter and guidewire manipulation. A J guidewire is preferable. If there is resistance to passage of the guidewire and catheter, no attempt should be made to force the catheter; contrast material should not be injected in this situation. If there is any doubt as to the feasibility of safe injection of contrast material, the angiographic study should be abandoned and replaced by CT or M R. Patients with thoracic aortic injury frequently are in a hyperdynamic cardiovascular state, and this should be con­ sidered when selecting the contrast injection parameters and image acquisition rate for angiography. In adults, Go to 70 mL are injected at rates of up to 40 mL per second. The image acquisition rate should be between 4 and 6 images per second. Standard images are obtained in 45-degree right posterior oblique and 45-degree left posterior oblique projections. The evaluation includes the entire thoracic aorta and the brachiocephalic arteries. The right posterior oblique images should be obtained initially; the examina­ tion can usually be terminated at this time if there are posi­ tive findings. Helical CT angiography is a reasonable alternative to angiography for many patients with suspected aortic injury, particularly when performed with a multidetector machine. However, the reported false negative rate for the diagnosis of aortic rupture with standard contrast­ enhanced CT is as high as 17% .'32 Most false-negative CT examinations in these patients are because of suboptimal images related to patient motion, bolus mistiming, car­ diac motion, or hardware artifacts. A technically adequate helical CT provides nearly 100% accuracy in the exclu­ sion of thoracic aortic injury (if a negative examination is judged to show no direct or indirect evidence of aortic injury) .'33 The American College of Radiology guidelines now recommend helical CT angiography as the preferred examination for most patients with suspected aortic injury. Potential findings with helical CT include periaor­ tic hematoma, localized narrowing, contour abnormality of the aortic wall, intimal flap, pseudoaneurysm, and con­ trast extravasation. Aortic injury is unlikely when CT dem­ onstrates a mediastinal hematoma without other findings of vascular injury. In those patients who have a contrain­ dication to intravenous contrast, CT without contrast can be useful to evaluate for a mediastinal hematoma.'34-tJ 6 The pathological anatomy of aortic injury can be effec­ tively demonstrated with M RI . However, this technique is inappropriate for acute trauma patients, particularly when there is hemodynamic instability. M RI can be useful for the evaluation of chronic traumatic aortic pseudoaneurysms.

470 Part 2 The Ca rd i ovascu l a r System The treatment of patients with suspected aortic injury includes the early administration of P-blockers. Most patients with documented aortic injuries undergo emergent surgery. Nonoperative treatment is appropriate for some injuries, such as minimal intimal abnormality or a small noncommunicating intramural hematoma. Endovascular stent graft placement is an option for selected patients with thoracic aortic injuries.'37·'38 Cardiac injuries can occur in children suffering blunt thoracic trauma. The most common injury to the heart is a cardiac contusion. Other potential injuries include trau­ matic ventricular septal defect, cardiac pseudoaneurysm, and coronary artery occlusion or aneurysm.'39

Abdomen and Pelvis The renal arteries are susceptible to damage from blunt abdominal trauma or severe deceleration mechanisms. Stretching or avulsion of the renal artery can occur as the mobile kidney moves relative to the fixed aorta. Potential renal arterial injuries include intimal disruption, dissec­ tion, main renal artery avulsion, branch vessel transection, false aneurysm, and arteriovenous fistula. CT is sufficient for the detection of many renal vascular injuries. Absent or diminished contrast enhancement ofthe renal parenchyma is an important indicator of possible renal arterial injury. CT angiography, MR angiography, and conventional angi­ ography provide detailed assessment of arterial injuries. Chapter 51 has additional discussion of renal injuries.l4° Most liver and spleen injuries involve relatively small intraparenchymal vessels. Active contrast extravasation on CT is an important indicator of a clinically significant vas­ cular injury. Avulsion or thrombosis of the main hepatic artery or splenic artery is rare. Tearing of the intrahepatic segment of the inferior vena cava can occur with deep liver lacerations caused by blunt trauma.'3 6 Trauma patients with unstable pelvic fractures often have associated disruption of pelvic arteries and veins. For those patients with clinical evidence of traumatic pel­ vic hemorrhage, the strategy for treatment and diagnostic evaluation depends on the clinical stability of the patient and the availability of resources. Unstable patients often proceed immediately to surgery. Others can be evaluated with contrast-enhanced CT. Emergent angiography and embolization are most appropriate for patients with active hemorrhage from the internal iliac artery.'4'·'42

N eck Cervical vascular injuries present challenges both in diag­ nosis and management. These injuries may be clinically silent, and are probably underdiagnosed. Patients with cer­ vical vascular injuries are at substantial risk for death or major permanent neurological deficits.l43-l44 Penetrating injuries of the neck that extend deep to the platysma muscle result in carotid or vertebral artery inju­ ries in approximately 20% to 35% of patients. Penetrating injuries occur from gunshot wounds, stab wounds, and

other lacerations. Potential vascular injuries in these patients include pseudoaneurysm, arteriovenous fistula, vessel transection, intimal flap, dissection, and occlusion. Stab wounds account for 20% to 40% of cervical vascular injuries in reports that include pediatric and adult patients. The typical arterial injury in these patients is a tangential laceration or complete transection. Penetrating injuries of the neck are classified as occur­ ring within three anatomic zones. Zone 1 is inferior to the cricoid cartilage. Zone 2 is between the cricoid cartilage and the angle of the mandible, and zone 3 is superior to the angle of the mandible. Zone 1 and 3 injuries are more difficult to assess clinically than those in zone 2, and imag­ ing studies are more often required. The clinical presenta­ tion ofvascular injury caused by penetrating trauma ranges from an otherwise asymptomatic innocuous-appearing wound to exsanguinating hemorrhage. Injuries to the pharynx, esophagus, and jugular veins are common in these patients. Tracheal injury is rare. The carotid arteries are involved in approximately 8o% of neck vessel injuries caused by penetrating wounds; the vertebral arteries are partially protected by the cervical spine. Vascular neck injuries with blunt trauma are rare, but are potentially devastating. The prevalence in children is unknown. For individuals of all ages, cervical vascular injury is estimated to occur in less than 1% of instances of blunt trauma to the neck. Many of these patients are asymptom­ atic or have delayed manifestations of the vascular injury. Cervical vascular injury caused by blunt trauma carries a mortality rate of approximately 20%, and a permanent neurological sequelae rate of greater than 50%. The most common arterial injuries in patients suffering blunt trauma are occlusion, intimal flap, and dissection. Vertebral artery injuries are more common than carotid injuries with blunt trauma. The vertebral arteries are susceptible to direct injury from a transverse foramen fracture, and to indirect injury from stretching across adjacent bones with facet dislocation or with whiplash, twisting, or hyperflexion of the neck. The most common imaging findings of cervical vascu­ lar injury with both penetrating and blunt mechanisms are occlusion and stenosis. Occlusion and stenosis can occur from a variety of mechanisms, such as dissection, throm­ bosis, transection, and extrinsic compression. Complete occlusion is detected with a high sensitivity by all vascular imaging techniques. Doppler sonography shows no flow at the site of occlusion, and echogenic thrombus may be vis­ ible. Proximal to the occlusion, there is a high impedance waveform, and absent or reversed diastolic flow. CT angi­ ography shows lack of enhancement of the occluded seg­ ment. On standard MR images, there is a lack of a flow void in the involved vessel, and thrombus may be identified as material of elevated signal intensity within the lumen. M R angiography shows lack o f flow-related signal. I t i s impor­ tant to recognize that the diminished flow velocity within the patent vessel distal and proximal to the occlusion may result in overestimation of the length of the occluded seg­ ment. Contrast-enhanced MR angiography may increase

Chapter 13 The Vascu l a r System 471 the diagnostic accuracy by allowing the differentiation of a true occlusion from patent segments of the vessel with slow flow.145 The imaging findings in the presence of a trauma­ related stenosis overlap those of complete obstruction. Doppler sonography of the vessel proximal to the steno­ sis shows high impedance. If the stenotic segment is in a location that can be evaluated with ultrasound, Doppler shows increased flow velocity at the narrowed portion of the vessel. CT angiography is the best noninvasive tech­ nique to accurately characterize a high-grade stenosis, as the contrast allows visualization of the remaining patent lumen ("string sign"). Contrast-enhanced M R angiography provides similar information. Traumatic intimal flaps and dissections are usually caused by blunt injuries, and are rare with penetrating mechanisms. The impact is most often to the neck, but cervical vascular injuries can also occur with thoracic or cranial trauma. The mechanism often involves hyperexten­ sion of the neck with rotation, hyperflexion, or whiplash. Motor vehicle-related injury is the overall most common cause of traumatic neck vessel dissection in patients of all ages. Dissection can result from chiropractic manipula­ tion. Dissection can also occur with athletic activities that involve abrupt turning or extension of the neck. The verte­ bral arteries are most susceptible to stretching injury in the C1-C2 region. Basilar skull fractures can be accompanied by dissection of the petrous portions of the carotid arter­ ies. Most carotid artery dissections involve both the cervical and petrous portions; 20% are localized to the cervical seg­ ment only, and 10% to the petrous segment only. In young children, intraoral trauma as a consequence of a fall while carrying an object in the mouth is the most common cause of traumatic carotid artery dissection. Spontaneous dissec­ tions are rare in children; the risk is elevated in patients with a connective tissue disease or fibromuscular dysplasia.146 Patients with trauma-related cervical vascular dissec­ tion often have nonspecific clinical findings, and some patients are asymptomatic. Potential findings include neurological symptoms from embolism or hypoperfusion (stroke, transient ischemic attack) , incomplete Horner syn­ drome (oculosympathetic paresis with preserved ipsilateral facial sweating) , neck bruit, headache, and neck pain. Neck pain sometimes follows the course of the carotid artery (car­ otodynia) . The clinical manifestations of the vascular injury are often masked by those of other injuries, such as direct head trauma. In addition, the onset of symptoms from neck vessel dissection can be delayed. In general, noninva­ sive evaluation of the neck vessels (CT angiography, sonog­ raphy, or MR angiography) is appropriate for blunt trauma patients in the following situations: neurological symptoms that are not accounted for by direct injury to the brain or spinal cord, suspicious findings on physical examination of the neck, a basilar skull fracture with mental status abnor­ malities, or evidence of a delayed infarct.'47-'4 9 Sonography is effective for the detection of dissection in those portions of the carotid and vertebral arteries that

are not obscured by bone or other structures . The common carotid arteries and the proximal aspects of the internal carotid arteries in particular are amenable to sonographic evaluation. A vascular abnormality beyond the reach of the transducer can also be surmised if diminished antegrade flow results in dampened spectral waveforms. CT angiography is an excellent noninvasive tech­ nique to screen trauma patients for possible injuries of the neck vessels. Axial images typically show the contrast enhanced lumen to be eccentrically narrowed at the site. The overall vessel diameter in the region of the dissection is usually enlarged because of an intramural hematoma. An intimal flap is visualized as a thin filling defect in the vessel lumen. CT is particularly well suited for the detec­ tion of a pseudoaneurysm. CT angiography is superior to sonography for the depiction of abnormalities in the intraosseous segments of the carotid and vertebral arter­ ies , and avoids some of the flow-related artifacts of M R angiography. MRI for the evaluation of a trauma patient with neu­ rological symptoms should include M R angiography sequences as well as conventional axial images of the neck to detect neck vessel abnormalities. Obstruction or high­ grade stenosis is detected with a high sensitivity utilizing MR angiography; however, subtle arterial wall abnormali­ ties may be difficult to differentiate from artifactual irregu­ larity. An inconclusive exam must be supplemented with additional imaging such as angiography, as even minor abnormalities of a major neck artery can lead to serious neurological consequences. Angiography is the gold standard technique for the detection of trauma-related pathology of the neck vessels. In general, the examination should include evaluation of the aortic arch, the carotid and vertebral arteries, and the intracranial vessels. The potential findings include abnor­ mal flow characteristics of a vessel, obstruction, stenosis, intimal flap, dissection, aneurysm, and distal embolism. Pseudoaneurysm is common after a penetrating injury of the neck, and nearly always involves the carotid artery. This lesion is clinically silent in many patients. The pseudo­ aneurysm sometimes produces a palpable mass, depending on the size and location. Neurological symptoms occur in a substantial minority of patients, a result of distal migration of thrombus or vascular occlusion. Imaging studies show a pseudoaneurysm as a focal widening or outpouching of the vessel. Although angiography provides the greatest imag­ ing detail of the vessel lumen and the cavity of the pseu­ doaneurysm, sonography and CT show the relationship to adjacent structures in the neck and the thickness of clot within the lesion. Treatment approaches for cervical vascular injuries are varied, and somewhat controversial. Complete occlusion of an artery can be treated with anticoagulation, thromboly­ sis, or surgical repair or bypass. Because collateral flow via other neck vessels is often sufficient, definitive endovas­ cular embolization to prevent distal thrombus migration is one treatment option. Nonocclusive dissection is often

472 Part 2 The Ca rd iovascu l a r System treated with anticoagulation and observation alone; many heal spontaneously.

empties slowly, and has an irregular contour. Unlike most congenital aneurysms , the traumatic variety does not have a neck, and is not usually located at a branching

I ntracranial Intracranial vascular injuries are less common than are

point in the vessel. A large lesion can be visualized on CT or M R

(Figure 1 3-33) .

I n addition to the carotid-cavernous fistula described

those of the neck. A similar pathological spectrum of inju­

above, traumatic arteriovenous fistulae can involve other

ries occurs in these vessels . Intracranial arterial injuries

ves sels in the neck and head. Most are a result of penetrat­

can occur with closed head trauma or penetrating injuries.

ing injuries , but blunt trauma is responsible for a sub­

Most traumatic intracranial dissections occur in the supraclinoid segments of the carotid arteries, the middle

stantial minority of these lesions

(Figure 1 3-34) .

Potential

clinical manifestations of a traumatic arteriovenous fistula

cerebral arteries , or the vertebrobasilar arteries . Intracranial

include pain, a palpable mass, a bruit, pulsatile tinnitus, and

dissection can occur with either penetrating or blunt trauma

venous distention. Neurological manifestations can occur

mechanisms. Spontaneous intracranial dissections are rare

as a consequence of intracranial hemorrhage, shunting of

in children. The supraclinoid segments ofthe internal carotid

blood away from the brain and cord, intracranial venous

arteries are prone to stretching during acceleration/decelera­

hypertension, or cord compres sion from enlarged veins.

tion events, as the vessels are tethered at the anterior clinoid processes and are mobile beyond this point. Stretching and/ or a sudden increase in blood pressure because of trauma or

ARTERIAL THROMBOSIS

exertion may cause enlargement of, and dissection of blood

Arterial thrombosis in children is typically associated with

into, the normal small gaps in the honeycomb structure of

a predisposing factor, such as an indwelling arterial cath­

the internal elastic lamina. The intramural hematoma of an

eter, hypercoagulable state, trauma, or arterial stenosis.

intracranial dissection is usually located between the inter­

I nfants with an umbilical arterial catheter have a risk of

nal elastica and media, as compared to a location within

about

the media of most cervical dissections. However, the media

nal aorta or common iliac vein . Potential clinical manifes­

25%

for the formation of thrombus in the abdomi­

and adventitia of intracranial arteries are relatively thin, and

tations of aortoiliac thrombosis in neonates include signs

there is a greater risk of aneurysmal dilation or rupture if

of diminished lower extremity perfusion and hematuria

the hematoma extends into the outer layers of the vessel. '5°

or hypertension due to renal artery involvement. However,

Traumatic intracranial aneurysms are quite rare. Most

signs and symptoms are lacking in many infants with

are pseudoaneurysms in which there is complete disrup­

umbilical catheter-related thrombosis. Complete sponta­

tion of the vessel wall; the cavity of the aneurysm represents

neous resolution of thrombosis occurs in most affected

excavation of a hematoma. Closed head trauma is the most

infants ; removal of the umbilical catheter speeds this

common precipitating event, with vascular injury produced

process. Thrombosis in some infants , however, leads to

by shearing forces, compression against an unyielding

permanent stenosis or occlusion. Potential long-term

structure (bone, falx, tentorium) , or tearing at the site of a

sequelae include hypertension and diminished lower­

fracture. Other mechanisms include penetrating injury and

extremity growth. 1 5 2 • 1 53

surgical procedures. The most commonly involved vessels

The appropriate position of an umbilical artery cath­

are the internal carotid arteries, the major carotid branch

eter is with the tip either superior or inferior to the maj or

vessels, and the vertebrobasilar vessels . Traumatic aneu­

visceral branches of the abdominal aorta. In general, tip

rysms of the cavernous segments of the internal carotid

positions between

arteries are nearly always associated with a basal skull frac­

positions between

T6 and Tw are acceptable, as are tip L3 and L5 . An umbilical artery cath­

ture. Traumatic aneurysms can also arise from peripheral

eter follows a distinctive inferior loop as it courses from

cerebral vessels and the middle meningeal arteries .'5'

the umbilicus to the internal iliac artery, before ascending

Rupture of a traumatic intracranial aneurysm is associ­

to the left of the midline in the abdomen (see Chapter

6).

ated with a high mortality rate. Rupture often does not occur

The maj or risk o f umbilical artery catheter malposition is

until days or weeks after the injury; consequently, the lesion

thrombosis of a mesenteric vessel.'54

may initially be clinically silent. Some patients complain of

Sonography is the imaging modality of choice for

An aneurysm of the intracranial portion of the

evaluation of the neonate with suspected aortoiliac throm­

headaches.

internal carotid artery because of a basal skull fracture can

bosis, although overlying intestinal gas can interfere with

produce a characteristic triad that includes the fracture, ipsi­

the examination. Most often, the thrombus appears as

lateral visual impairment, and epistaxis. This type of aneu­

echogenic material in the lumen. The character of the clot

rysm can also rupture into the cavernous sinus to produce a

varies between patients, and ranges from distention and

carotid-cavernous fistula. Clinical manifestations ofthis com­

complete occlusion of the lumen, to nonocclusive localized

plication include proptosis, abducens and oculomotor nerve

clot adherent to the vessel wall, to thin linear intraluminal

palsies, facial numbness, a pulsatile bruit, and headache. Angiography is the most sensitive technique for the

material. On Doppler studies , collateral vessels have con­ stant forward flow during diastole because of downstream

detection and characterization of a traumatic intracra­

vasodilation; the normal triphasic high-resistance flow pat­

nial aneurysm. The aneurysm cavity typically fills and

tern is lacking.'55

Chapter 1 3 The Vascu l a r System

A

c

Figure 13-33 Traumatic intracranial pseudoaneurysm.

This 2 -year-old child was struck in the head by a falling television. A. There is a basilar skull fracture (arrows) of the body and right greater wing of the sphenoid bone and the petrous portion of the left temporal bone. B. Two days later, an unenhanced CT shows an oval suprasellar lesion surrounded

POPLITEAL ARTERY ENTRAPMENT SYNDROME Popliteal artery entrapment syndrome is the most com­ mon cause of lower-extremity claudication in young athletic individuals . This refers to a developmental abnor­ mality in which the popliteal artery courses between the medial head of the gastrocnemius muscle and the femur, rather than in a normal location lateral to the muscle.

473

B

D

by high-attenuation subarachnoid blood. C. Imaging with IV contrast confirms that this is a result of an aneurysm. D. An anterior three-dimensional volume-rendering shows the aneurysm to arise from the left internal carotid artery. (Images courtesy Dr. Smita Bailey, Phoenix Children's Hospital.)

Chronic vascular microtraurna because of the compres­ sion can lead to thrombosis, stenosis, or aneurysm for­ mation. Occasionally, there are manifestations of acute lower-leg ischemia as a consequence of thrombosis or embolism. Arteriography with the leg in neutral position is often normal in patients with popliteal artery entrapment syn­ drome, unless there is stenosis, thrombosis, or aneurysm. Stenosis caused by compression by the gastrocnemius

474

Part 2 The Ca rd iovascu l a r System approximately 30% of these patients, the left innominate vein is present. These developmental variables influence the dynamics of blood flow, and are important in determin­ ing the severity of right-to-left shunting when there is an anomalous connection to the left atrium. Rarely, a right superior vena cava drains anomalously into the left atrium in conjunction with a normal draining (via the coronary sinus) left superior vena cava.'5 9-' 6 ' A left superior vena cava usually is not detectable on standard chest radiographs unless traversed by an IV cath­ eter. In this situation, the catheter descends lateral to the aortic arch, courses obliquely across the midportion of the heart, and enters the right atrium. Occasionally, there is slight focal prominence of the left upper mediastinal con­ tour, just above the aortic knob. Imaging with CT or M R shows a n enlarged coronary sinus . There i s preferential flow though the anomalous vessel if IV contrast is injected via the left arm ( Figure 1 3 -35) .' 62

Right Superior Vena Cava Anomalies Figure 13-34 Traumatic arteriovenous fistula. This 8-year-old child suffered severe multisystem trauma in a motor vehicle incident. A lateral image from a vertebral an giogram shows an atrioventricular fistula from the basilar artery.

muscle is present on arteriographic images obtained with the ankle in active dorsiflexion or plantarflexion. M RI allows accurate depiction of the relationship between the popliteal artery and the gastrocnemius muscle in these patients. The differential diagnosis of lower extremity clau­ dication in a teenager includes popliteal artery entrapment syndrome, arterial compression by a mass (e.g., osteochon­ droma) , cystic adventitial disease, fibromuscular dysplasia, and arteritis.'s 6 ,ts7

VENOUS DISEASE

Rare isolated anomalies of the right superior vena cava include absence, congenital aneurysmal dilation, and anomalous insertion. Anomalous insertion of the left bra­ chiocephalic vein into the right superior vena cava inferior to the azygous vein is an occasional finding in children with congenital heart disease. The anomalous vein crosses the midline dorsal to the ascending aorta.

Congenital Interruption ofthe Inferior Vena Cava Interruption of the inferior vena cava with azygous con­ tinuation occurs in approximately half of patients with polysplenia. This anomaly occurs only rarely in otherwise normal individuals. On standard radiographs, there is dila­ tion of the azygous vein as it enters the superior vena cava. Cross-sectional imaging shows lack of the intrahepatic segment of the inferior vena cava, and enlargement of the azygous vein.

Venous Anomalies

Su perior Vena Cava Obstruction

Persistent Left Superior Vena Cava

Superior vena cava syndrome i s caused b y extrinsic com­ pression or intraluminal occlusion ofthe superior vena cava. The most common mechanism is catheter-related thrombo­ sis, often related to malposition of a central venous catheter. Another potential cause of vena cava occlusion is compres­ sion by a mediastinal neoplasm, abscess, or hematoma. The clinical syndrome consists of edema of the face, neck, upper extremities, and upper portion of the thorax. Dilated chest wall veins are usually visible. The pericardiophrenic veins serve as important collateral pathways, and become distended in response to superior vena cava obstruction. The pericardiophrenic veins may be single or multiple, and drain into the left superior intercostal vein or the brachioce­ phalic veins opposite the jugular vein insertions. Inferiorly, they anastomose with the inferior phrenic veins, which drain into the inferior vena cava or renal vein.'63

Persistent left superior vena cava occurs in approximately 0.3% of individuals without heart disease, and in 4.3% of individuals with congenital heart disease.'s8 A left-sided superior vena cava represents a persistent left anterior car­ dinal vein. The persistent left superior vena cava most often drains through the oblique vein of Marshall, dorsal to the left atrium, and into the coronary sinus of the right atrium. In approximately 8% of patients with a left superior vena cava, drainage occurs into the left atrium; this results in a right-to-left shunt. With a large shunt, cyanosis occurs. 99rn'fc-MAA scintigraphy provides documentation of the degree of right-to-left shunting in these patients. A right superior vena cava is present in 8o% to 90% of individuals with a persistent left superior vena cava. In

Chapter 13 The Vascu l a r System 475

Figure 1 3-36 I nferior vena cava thrombosis.

Figure 13-35 Left superior vena cava. There is dense opacification of a persistent left superior vena cava on this coronal reformatted CT image. The contrast injection was via a left arm vein.

Standard chest radiographs of children with superior vena cava syndrome may show enlargement of the azy­ gos vein. Underlying pathology in the mediastinum may produce widening. A specific diagnosis can be achieved with venography, contrast enhanced CT, or MR. Superior vena cava syndrome as a result of acute thrombosis can be treated with catheter directed thrombolysis. In some instances, an underlying stenosis is identified on venogra­ phy after recanalization; treatment with angioplasty in this situation may improve venous blood flow and decrease the risk for recurrent thrombosis .

I nferior Vena Cava Obstruction Occlusion o f the inferior vena cava can b e caused by extrinsic compression or intraluminal thrombus. The most common cause of thrombosis is the presence of a catheter. Other causes of thrombosis include dehydration, trauma, sepsis, and thrombophilic disorders. Although there is effective collateralization in children who suffer vena cava occlusion, various long-term and acute compli­ cations can occur. These include pulmonary embolism, renal vein thrombosis, lower extremity edema, hepatic vein thrombosis, and chronic lower-extremity venous hypertension. Neoplasms , most commonly Wilms tumor, can extend into the vena cava as tumor thrombus . The azygos and hemiazygous systems are important collateral pathways for blood flow in the presence of inferior vena cava obstruction.'55·' 64

A longitudinal sonographic image of a 6-month-old infant with congenital heart disease shows echogenic thrombus completely filling the intrahepatic portion of the inferior vena cava (arrows) . The superior aspect of the cava in the region of hepatic vein inflow is patent.

Sonography of thrombotic inferior vena cava obstruc­ tion usually allows visualization of the intraluminal clot, if there is no intervening intestinal air ( Figure 1 3-36) . Doppler studies, particularly i n infants , provide a n accu­ rate assessment of flow or the lack thereof in the pres­ ence of thrombosis or extrinsic narrowing. Doppler evaluation of patent veins below the obstruction shows dampening of normal waveforms. Vena cava obstruction is also effectively diagnosed with CT and M R . These tech­ niques are particularly useful in older patients with an intraabdominal or retroperitoneal mass . Contrast venog­ raphy is the gold standard test for the depiction of the luminal integrity of the vena cava and its major tributar­ ies . Dilated paraspinal collateral vessels fill with contrast if there is substantial vena cava stenosis or occlusion.

Lower- Extrem ity Deep Venous Th rombosis Deep venous thrombosis and pulmonary embolism con­ stitute the 2 clinically important manifestations of venous thromboembolic disease. In the pediatric age group the annual incidence is approximately 5 per 1oo,ooo children. '6 5 The pathophysiology of deep venous thrombosis most often involves the formation ofvenous thrombi along valve cusps within the soleal sinuses. Typically, the precipitat­ ing event is endothelial injury, which allows exposure of the subendothelium to platelets that bind to the vein wall. Subsequently, there is adhesion of fibrin, erythrocytes, and leukocytes, thereby creating a thrombus. Slowing or turbu­ lence of blood flow may contribute to endothelial damage and thrombus formation. After approximately 1 week, the thrombus becomes increasingly adherent to the vein wall.

476 Part 2 The Ca rd i ovascu l a r System Fibroblast infiltration and neovascularization of the throm­ bus lead to scarring and venous valve damage. Although eventual recanalization usually occurs, some degree of per­ manent damage to the vein is typical. Hypercoagulability is an important precipitating or exacerbating factor in some patients with venous throm­ bosis. The possibility of an inherited hypercoagulable condition should be considered in any child who devel­ ops extensive venous thrombosis or thromboembolism. A positive family history of venous thromboembolic dis­ ease is also an important indicator in these patients. The most common inherited cause of hypercoagulability in the United States is factor V Leiden mutation; this is pres­ ent in nearly 5% of the white American population. This mutation is rare among individuals of Asian or African descent. Antithrombin deficiency, protein C deficiency, and protein S deficiency are additional causes of hyper­ coagulability, but are much less common. Homozygous homocystinuria and dysfibrinogenemia are rare causes of hypercoagulability.'66 The factor V Leiden mutation causes resistance to acti­ vated protein C, thereby leading to increased conversion of prothrombin to thrombin. The risk for thromboembolic disease in patients who are homozygous for this mutation is 50 to 100 times that of the general population; heterozy­ gotes have 4 to 10 times the risk. Other factors that place individuals at elevated risk for venous thrombosis include trauma, surgery, prolonged immobilization, malignancy, myeloproliferative disorders, the use of oral contraceptives, and pregnancy. Antiphospholipid syndrome refers to vascular throm­ bosis in association with the presence of 1 of 3 antiphospho­ lipid antibodies . These antibodies are lupus anticoagulant, anticardiolipin, and anti-j3-glycoprotein I. Up to half of patients with antiphospholipid syndrome suffer at least 1 episode of venous thrombosis. Other potential clinical manifestations include arterial thrombosis, cardiac isch­ emia, renal vein thrombosis , and hematological abnor­ malities such as thrombocytopenia. The prevalence of antiphospholipid antibodies increases with patient age.' 67 Deep venous thrombosis of the lower extremities typi­ cally begins in the deep calfveins and propagates superiorly. It is associated with symptomatic pulmonary embolism in approximately one-third of untreated patients. The usual clinical findings include pain, swelling, and warmth of the affected lower extremity. The pain may be exacerbated by dorsiflexion of the foot (the Homan sign) . A positive D-dimer assay is a sensitive, but nonspecific, marker for venous thrombosis. In most patients with deep venous thrombosis, the clinical findings are nonspecific, and the differential diagnosis includes various other lesions such as cellulitis, lymphedema, and venous insufficiency. The most important acute complication of deep venous thrombosis is pulmonary embolism, although approxi­ mately one-half of patients with proven pulmonary embo­ lism do not have detectable deep venous thrombosis with sonography.'68 The major long-term sequela of deep venous

thrombosis is chronic venous insufficiency, which occurs in approximately 90% of these patients. Chronic venous insufficiency may lead to the "postthrombotic syndrome" : chronic limb pain, edema, skin hyperpigmentation, claudi­ cation, and venous stasis ulcers. Postthrombotic syndrome is rare in children, but can occur as an adult manifestation of venous disease that began in childhood. Sonography is usually the initial imaging study for the evaluation of a patient with suspected deep venous thrombosis. A noncompressible, thrombus-filled vein on sonography is diagnostic of venous thrombosis. There is temporal variation in the echogenicity of the clot. Acute thrombosis is often hypoechoic; lack of compressibility and absence of flow on Doppler are crucial findings for proper diagnosis ( Figu re 1 3-37) . Within a few days, the clot becomes moderately hyperechoic (Figure 1 3-38) . Contrast venography is generally considered the gold standard for the diagnosis of deep venous thrombosis, but is not com­ monly performed because of the availability ofless-invasive diagnostic techniques. The American College of Radiology Practice Guide­ lines recommend that the sonographic evaluation for deep venous thrombosis include duplex color and spec­ tral Doppler studies, with compression and augmentation maneuverers. The major veins of the leg are sequentially imaged in transverse orientation and inspected for echo­ genic thrombus. With real-time observation, the transducer is utilized to intermittently compress the underlying vein. With pressure applied, the walls of a normal vein coapt, thereby showing that no clot is present. Longitudinal images of the vein using color and spectral Doppler evalu­ ations are then used to evaluate the blood flow characteris­ tics (Figu re 1 3-39) .'6 9 The evaluation of respiratory phasicity and augmenta­ tion on Doppler studies provides indirect assessment of adjacent vein segments that are not in the field of view. Venous occlusion cranial to the level of Doppler evalu­ ation is suggested by a lack of normal respiratory pha­ sicity. Assessment of flow augmentation is performed by squeezing the leg (e.g. , the calf or distal thigh) at a level below the area of Doppler observation. If the tran­ sient increased venous flow is transmitted to the level of evaluation, it suggests that no occlusive thrombus exists between the level of compression and the transducer. The augmentation portion of the examination is usually of limited usefulness as it rarely detects clot that has not already been demonstrated by standard images and com­ pression images.'7° CT venography is an additional option for the detec­ tion of deep venous thrombosis, and can be performed in conjunction with CT pulmonary angiography.'7' For the combined study, standard CT pulmonary angiography is performed followed by 5- or 10-mm axial CT images obtained at 4-cm intervals from the diaphragm to the ankles . Imaging should be delayed at least 2 minutes after the intravenous inj ection; most investigators con­ sider a 3- to 3 .5-minute delay to be optimal. Contiguous

Chapter

13

The Vascu l a r System 477

A

B

Figure 13-37 Deep venous thrombosis. A. Transverse images without and with compression show distention of the common femoral vein with faintly echogenic thrombus (arrow) . B. There is no detectable blood flow with color

c

Doppler. Note the hypoechoic appearance of the acute thrombus. C. A color Doppler image shows lack of flow in the popliteal vein (arrow) . The adjacent artery has normal Doppler signal.

helical acquisition is an option, but results in a higher

warfarin. Low-molecular-weight heparin is frequently used

radiation expo sure than the discontinuous axial tech­

in lieu of unfractionated heparin. Anticoagulation with

nique. The combined CT venography and CT pulmonary

oral warfarin is usually continued for at least 3 months.

angiography examination has high sensitivity for the

Longer therapy may be indicated in certain clinical situa­

detection o f l ower-extremity venous thrombosis and pro­

tions, such as the presence of a nonreversible risk factor

vides superior evaluation of abdominal and pelvic veins

or recurrent disease. Anticoagulation therapy is effective

in comparison to sonography.'72 The technique offers

in preventing recurrence of deep venous thrombosis,

advantages over sonography in obese patients or those

but it does not directly promote clot lysis and is relatively

with severe pain or swelling.

ineffective in preventing the future development of post­

Treatment goals in patients with acute deep venous

thrombotic syndrome. There are various treatment tech­

thrombosis include mitigation of acute symptoms, preven­

niques that involve clot lysis or direct thrombus removal,

tion of pulmonary embolization, prevention of thrombus

with the goals of speeding symptom resolution, diminish­

propagation and recurrence, and the prompt restoration of

ing the near-term risk for pulmonary embolism, preserv­

venous patency to help prevent long-term manifestations

ing venous valve function, and decreasing the likelihood

of venous insufficiency. The current standard of care indi­

or severity of chronic venous insufficiency. These meth­

cates the use of heparin, usually supplemented with oral

ods

include

surgical

thrombectomy,

catheter-directed

478 Part 2 The Ca rd iovascu l a r System

Patients with excessive extrinsic compression ofan iliac vein may be at an increased risk for deep venous thrombosis.

The most common form of iliac vein narrowing is com­ pression of the left iliac vein against the fifth lumbar ver­ tebra by the right iliac artery as it crosses anteriorly; this is termed May-Thurner syndrome or Cockett syndrome. The involved segment of the vein wall may develop intimal hypertrophy with time, resulting in a propensity for throm­ bosis. However, compression of the left common iliac vein by the right common iliac artery is common in asymptom­ atic individuals , and the risk associated with substantial compression for the eventual development of symptoms is unknown. This is borne out by a study of asymptomatic adults undergoing helical CT for other indications, dem­ onstrating greater than so% compression in approximately 25% of the patients.'75-'77 Patients with symptomatic left iliac vein compression are usually female. Symptoms typically develop during the second through fourth decades of life, often in association with prolonged immobilization or pregnancy. Most com­ monly, patients report persistent left-leg edema, with or without other clinical signs of unilateral lower-extremity venous hypertension. The clinical presentation is often related to acute deep venous thrombosis in the iliac vein. These patients do not necessarily suffer extension of thrombosis into the leg veins, and therefore lower-extrem­ ity sonography may be normal or show Doppler manifes­ tations of upstream obstruction. A specific diagnosis is achieved with helical CT or MR venography. There is focal narrowing of the proximal aspect of the left common iliac vein at the level of the right common iliac artery. When present, thrombus is identified as intraluminal material. Typically, there are dilated pelvic and lower abdominal col­ lateral veins because of chronic obstruction. Treatment

A

B

Figure 13-38 Subacute venous thrombosis.

There is a mixed echogenic pattern of clot in the greater saphenous vein in this patient with 3 days of symptoms. The vessel did not collapse with compression, and there was no visible flow on color Doppler (not shown).

thrombolysis (e.g., alteplase) , and percutaneous mechani­ cal thrombectomy.'7J.l74

M ay-Th u rner Syndrome

Figure 1 3-39 Normal duplex Doppler evaluation of the femoral vein. A. The transverse image without compression shows a normal hypoechoic appearance of the vein ( arrow) . The vessel ( arrow)

collapses appropriately with compression. The adjacent femoral artery remains patent. B. A longitudinal image with Doppler interrogation of the femoral vein shows normal respiratory phasicity and augmentation.

Chapter 13 The Vascu l a r System 479 consists of catheter directed thrombolysis (when there is substantial thrombosis) and endovascular stenting.'78

Primary Axillosu bclavian Venous Throm bosis Primary thrombosis of the subclavian andfor axillary veins is distinct from thrombosis associated with venous cath­ eters, trauma, or instrumentation. Primary thrombosis at this site is also termed effort thrombosis or Paget-Schroetter syndrome. Most patients are young adults or teenagers who develop acute symptoms after strenuous upper extremity exercise. Symptoms include upper-extremity pain, swell­ ing, weakness, and limitation of motion. The pathophysiology of primary axillosubclavian thrombosis involves venous compression in the upper por­ tion of the thorax. The most common site of thrombosis is in the medial aspect of the subclavian vein, where the vessel is compressed as it passes between the clavicle and the subclavius muscle anteriorly and the scalenus muscle posteriorly, or between the costocoracoid ligament and the first rib. The axillary vein can be compressed between the pectoralis muscle and the anterior rig cage. Some cases appear to be related to hyperabduction of the arm , leading to stretching of the vessel and endothelial injury. Primary subclavian vein thrombosis can also result from extrinsic compression by anomalous structures such as a cervical rib, aberrant transverse cervical artery, persistent axillopec­ toral muscle, or anteriorly positioned phrenic nerve. '79 This is termed thoracic outlet compression syndrome. Venography is usually the best method to diagnose axillosubclavian thrombosis. This allows an unequivocal diagnosis, and also provides venous access and a roadmap for therapy. Sonography and CT venography represent alternative diagnostic methods . Because these patients present acutely, imaging studies show findings of fresh thrombosis. Collateral pathways are poorly developed. The length of the clot and the severity of obstruction vary between patients. The standard therapy for acute primary thrombosis of the axillary or subclavian veins is thrombolysis. '8 o This can be accomplished via peripheral IV infusion or, more effectively, by catheter-directed thrombolysis. Any residual stenosis after restoration of venous patency can be treated with transluminal angioplasty. An underlying extrinsic compression of the vein is sometimes best detected with venography performed with the arm elevated. Surgical resection of the first rib or the proximal aspect of the clavi­ cle is often recommended for these patients, particularly if venography shows evidence of extrinsic compression. '8' ·1 8 2 Anticoagulation can be maintained after successful thrombolysis until surgery is performed. Urschel and Razzuk have reported that the best long-term results are achieved with an early diagnosis (less than 1 month), expe­ ditious thrombolytic therapy, and prompt first rib resec­ tion.'8 3 Other surgical therapies that are occasionally used for these patients include patch angioplasty and venous bypass.

Central Venous Catheter- Related Central Venous Stenosis The most common cause of central venous thrombosis and stenosis is the presence of a central venous catheter. Various factors, some of which are preventable, increase the risk for this complication. Improper tip position is probably the most common preventable risk factor; the tip is optimally oriented away from the sidewall and located at the junction of the superior vena cava and the right atrium. The use of an internal jugular entry site has a lower throm­ bosis risk than does a subclavian site. The risk is dimin­ ished by selecting a catheter with as small a diameter as possible, and with as few lumens as possible. Some studies show a lower complication rate for central venous catheters placed by interventional radiological techniques than with surgical cut-downs. Standard radiographs serve to assess catheter posi­ tion. The detection of thrombus or a stenosis requires venography or sonography (Figure 1 3-40) . Thrombus appears as a filling defect in the vessel, whereas fibrotic stenosis usually has a tapered character. Catheter-related central venous thrombosis and stenosis can be treated with catheter-directed thrombolysis and transluminal angioplasty. Therapy is indicated for symptomatic indi­ viduals and those patients with an expected need for long­ term or repeated access (chronic total parenteral nutrition or hemodialysis).

Figure 1 3-40 Catheter-related venous thrombosis. A right arm venogram shows thrombosis of the medial aspect of the right subclavian vein (arrow) adjacent to a hemodialysis catheter that enters via the internal jugular vein.

480 Part 2 The Ca rd iovas cu l a r System Neonates can suffer a variety of complications related to umbilical venous catheters. Optimal positioning of an umbilical venous catheter is such that the tip is located at the junction of the inferior vena cava and the right atrium. On a properly positioned anteroposterior radiograph, the catheter projects just to the right of the spine and has a slight bend as it courses through the umbilical vein. Malposition of the catheter into a portal vein is indicated by an abrupt angulation of the catheter within the liver, usually with the tip directed medially or laterally. Extension into a portal vein can be confirmed with sonography. Malposition in a portal vein carries the risk of thrombosis. Malposition of an umbilical venous catheter in the pulmonary arteries or heart can lead to arrhythmias, thrombosis, perforation, and cardiac tamponade. A catheter that has been advanced too far will frequently cross the atrial septum into the left atrium or a pulmonary vein; potential pulmonary com­ plications in this situation include thrombosis, pulmo­ nary edema, and pulmonary infarction. Catheter-related thrombosis in the inferior vena cava can lead to renal vein thrombosis.'84-t8 6

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180. Kreienberg PB, Chang B B , Darling RC 3rd, et al. Long-term results in patients treated with thrombolysis, thoracic inlet decompression, and subclavian vein stenting for Paget­ Schroetter syndrome. ] Vase Surg. 2001;33 (2 suppl) : S10o-S105.

161. Pretorius PM, Gleeson FV. Case 74: Right-sided superior vena cava draining into left atrium in a patient with persistent left­ sided superior vena cava. Radiology. 2oo4;232 (3) :73 0-734·

181. Kunkel J M , Machleder H I . Treatment of Paget-Schroetter syndrome. A staged, multidisciplinary approach. Arch Surg. 1989;124 (10):1153-1157: discussion 1157-1158.

162. Demos TC, Posniak HV, Pierce KL, et al. Venous anomalies of the thorax. AJR Am] Roentgenol. 2004;I82(5) :113 9-1150.

182. Machleder H I . Effort thrombosis of the axillosubclavian vein: a disabling vascular disorder. Compr Ther. 19 91;17(5) :18-24.

163. Lawler LP, Cor! FM, Fishman EK. Multi-detector row and volume-rendered CT of the normal and accessory fbw pathways of the thoracic systemic and pulmonary veins. Radiographies. 2002;22 Spec No: S45-S 6o.

183 . Urschel HC Jr, Razzuk MA. Paget-Schroetter syndrome: what is the best management? Ann Thorac Surg. 2ooo;69(6): 1663-16 68; discussion 1668-16 69.

164. Hausler M , Hubner D, Delliaas T, Muhler EG. Long term complications of inferior vena cava thrombosis. Arch Dis Child. 2o01;85(3):228-233I65. White RH. The epidemiology of venous thromboembolism. Circulation. 2oopo7(23 suppl 1) : I4-I8. 166. Seligsohn U, Lubetsky A. Genetic susceptibility to venous thrombosis. N Eng! J Med. 2001;344 (!6):1222-1231. 167. Levine JS, Branch DW, Rauch J . The antiphospholipid syndrome. N Eng! ] Med. 2002;346(10)752-763-

184. Narla LD, Hom M, Lofland GK, Moskowitz WB. Evaluation of umbilical catheter and tube placement in premature infants. Radiographies. 19 91;11(5) : 849-863. 185. Kim J H , Lee YS, Kim S H , et al. Does umbilical vein catheterization lead to portal venous thrombosis? Prospective US evaluation in 100 neonates. Radiology. 2001;219 (3) : 645-Gso. 186. Bjorklund LJ, Malmgren N, Lindroth M . Pulmonary complications of umbilical venous catheters. Pediatr Radio!. 1995:25 (2) :149-152.

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CH A P T E R

14

Congen ital Abnormalities of the Bra in

NORMAL DEVELOPM ENT . . . . . . . . . . . . . . . . . . . . . . . . . . .

488

N eu rofi bromatosis Type 2. . . . . . . . . . . . . . . . . . . . . . . . . . . .

522

DISORDERS OF DORSAL I N DUCTION . . . .

493

N e u rofi bromatosis Type 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

524

Anencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

493

Tu berous Sclerosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

524

Exencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

Stu rge-Weber Synd rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

525

Chiari M alformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

von H i ppei-Lindau Disease . . . . . . . . . . . . . . . . . . . . . . . . .

530

Chiari I Malformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 Chiari II Malformation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 Chiari III Malformation . . . . . . . . . . . . . . . . . . . . . . . . . . . 501

Ataxia-Telangiectasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

531

N e u rocuta neous M elanosis . . . . . . . . . . . . . . . . . . . . . . . .

533

Epidermal N evus Synd rome . . . . . . . . . . . . . . . . . . . . . . . .

534

.

DISORDERS OF VENTRAL I N DUCTION . .

502

Holoprosencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

502

l nconti nentia Pigmenti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

535

Alobar Holoprosencephaly . . . . . . . . . . . . . . . . . . . . . . . 505 Sernilobar Holoprosencephaly . . . . . . . . . . . . . . . . . 505 Lobar Holoprosencephaly .. .. . . . . .. . . .. .. .. .. .. . . 5 0 6 Middle Interhemispheric Variant of Holoprosencephaly . . . . . . . . . . . . . 5 0 6

Hypomelanosis of lto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

535

Chediak- H igas h i Syndrome . . . . . . . . . . . . . . . . . . . . . . . . .

53 6

Septooptic Dysplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DISORDERS OF CELLU LAR M IC RATION (CORTICAL MALFORMATIO NS) . . . . . . . . . . . . . . . .

53 6

Lissencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53 6 537

514

Classical Lissencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lissencephaly Caused by LIS1 Mutations . . . . . . . . . . . . . . . . . . . . . . . . . Lissencephaly Caused by DCX Mutations . . . . . . . . . . . . . . . . . . . . . . . .

514

X-Linked

507

Arh i nencep haly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

508

Dysgenesis of the Corpus Callos u m . . . . . . . . . . .

508

Callosal Dysgenesis with an Interhemispheric Cyst . . . . . . . . . . . . . . . . . . . . . . . . . Callosal Dysgenesis with Lipoma . . . . . . . . . . . . . Aicardi Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hereditary Spastic Paraplegia with Thin Corpus Callosum . . . . . . . . . . . . . . . . . . . . . . . .

513

51 5

DISORDERS OF N E U RONAL PROLI FERATION AND DI FFERENTIATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 5

M icrocephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 5

M icrocephaly with S i m p l ified Gyral Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 6

M egalencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 6

H e m i megalencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 6

DISORDERS OF H ISTOC E N ESIS . . . . . . . . . . . . . . .

51 9

General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 9

Neu rofi bromatosis Type 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 9

Lissencephaly with Absent Corpus Callosum . . . . . . . . . . . . . . . . . . . . . Lissencephaly Caused by RELN Mutations (Norman-Roberts Syndrome) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Congenital Muscular Dystrophies with Cobblestone Lissencephaly . . . . . . . . . . Fukuyama Congenital Muscular Dystrophy . . . . . . . . . . . . . . . . . . . . . Walker-Warburg Syndrome . . . . . . . . . . . . . . . Cerebroocularmuscular Syndrome . . .

537 537 538

538 53 9 540 540 540

G ray M atter H eterotopia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

541

Subependymal Heterotopia. . . . . . . . . . . . . . . . . . . . . . Subcortical Heterotopia . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcortical Band Heterotopia . . . . . . . . . . . . . . . . . .

541 542

Polymicrogyria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymicrogyria Syndromes .. . . . . . . . . . . . . . . . . . . . .

543

541 543

488 Part 3 The B ra i n

Schizencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

544

Blake Pouch Cyst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

551

Focal Cortical Dysplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

546

Cerebellar Hypoplasia

..................................

552

Cerebellar Dysplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

553

J o u bert Synd rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

555

Rhom bencephalosynapsis . . . . . . . . . . . . . . . . . . . . . . . . . . .

556

Focal Cortical Dysplasia with Balloon Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Focal Cortical Dysplasia Without Balloon Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

546 547

CLI N ICAL PRESENTATIONS: TH E CH I LD WITH SEIZU RES . . . . . . . . . . . . . . . . . . . . . .

547

Sym ptom atic Generalized Epi lepsy . . . . . . . . . . . .

547

...........................................

548

Partial-Onset Epilepsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

548

Epi lepsia Partial is Conti n u a . . . . . . . . . . . . . . . . . . . . . . . . .

548

M esial Tem poral Sclerosis . . . . . . . . . . . . . . . . . . . . . . . . . . .

548

Vagus Nerve Sti m u l ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

549

I nfantile Spasms

ANOMALI ES OF TH E PITUITARY GLAND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

556

Pituitary G land Hypoplasia/Aplasia . . . . . . . . . . .

557

Pituitary G l a n d Duplication . . . . . . . . . . . . . . . . . . . . . . . . .

559

Em pty Sel la Tu rcica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

559

BRAI N MALFORMATIONS ACQU I RED IN UTERO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydranencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

559

559

Preoperative Bra i n Fu nction Localization . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

549

Porencephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

563

Febrile Seizu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

550

M oebius Syndrome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 64

POSTERIOR FOSSA ANOMALI ES. . . . . . . . . . . . . .

550

CONGEN ITAL N EOPLASMS . . . . . . . . . . . . . . . . . . . . . . . .

565

Dandy-Wal ker M alformation . . . . . . . . . . . . . . . . . . . . . . .

550

M ega Cisterna M agna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

551

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

565

The spectrum of congenital brain malformations is complex and classification schemes are imperfect. Neuroimaging evaluations provide extensive informa­ tion concerning abnormal brain morphology and cellular organization. Correlation of this information with well­ established concepts of normal embryological and fetal neural development provides a conceptual framework for a greater understanding of brain anomalies . The most frequently utilized neuroimaging classification scheme for congenital malformations of the brain recognizes 4 major types that correlate to stages of development: (1) dorsal induction (primary neurulation) , (2 ) ventral induction (telencephalization) , (3) neuronal prolifera­ tion, differentiation, and histogenesis, and (4) neuronal migration. It is important to recognize, however, that this system is an oversimplification of a heterogeneous and complex group of disorders .

NORMAL DEVELOPMENT At about 16 days' gestational age, the embryo consists of a 3-layered disc. Cells from the primitive node migrate between the endoderm and ectoderm cranially and form the notochordal process, the structure around which the

vertebral column forms. The notochordal process fuses with endoderm and reaches the oropharyngeal membrane by day 18. There is concomitant thickening of ectodermal cells that overlie the notochord, thereby forming the neural plate. On day 18, neural plate cells along the dorsal aspect of the notochordal process invaginate, forming the neural groove. Cells lateral to the groove thicken and give rise to the neural folds. The neural folds move medially and close over the neural groove, forming the neural tube. Closure of the neural tube begins in the cervical region and proceeds toward both ends of the embryo. The brain ventricular system and the spinal cord central canal develop from the lumen of this tube. The walls of the neural tube eventually thicken to form the brain and the spinal cord. Dorsal induc­ tion refers to the sequence of embryological events in the dorsal aspect of the embryo that culminate in formation of the neural tube. Neurulation is the process of neural tube closure. Primary neurulation encompasses initial closure of the neural tube from the anterior neuropore to the upper lum­ bar segments. Secondary neurulation refers to the events that produce closure of the more caudal segments. Various congenital anomalies result from failure of appropriate neural tube closure during the third and fourth weeks

Chapter 14 Congenital Abnorm a l ities of the B ra i n 489 of development. Deficient neurulation encompasses a spectrum of malformations that includes anencephaly, exencephaly, encephalocele, and Chiari I I malformation. Craniorachischisis is total failure of neurulation: central nervous system (CNS) tissue exists only as a neural plate that is devoid of dorsal osseous or dermal covering. Ventral induction refers to the series of events after neurulation that lead to the formation of 2 separate cere­ bral hemispheres (i.e., diverticulation) . Luminal epithelial cells secrete a watery liquid into the dosed neural tube. The cephalic end becomes somewhat distended with fluid and forms the primary brain vesicles: the prosencephalon, mesencephalon, and rhombencephalon. The prosencepha­ lon (forebrain) consists of 2 secondary vesicles: the telen­ cephalon and the diencephalon. The telencephalon gives rise to the cerebral hemispheres, putamina, caudate nuclei, retinae, and optic nerves. The diencephalon gives rise to the thalami, hypothalami, globi pallidi, pineal gland, and neurohypophysis. The rhombencephalon (hindbrain) par­ tially divides into the metencephalon, which forms the cer­ ebellum, and the myelencephalon, which forms the pons and medulla. Developmental disturbances during the ventral induc­ tion stage can lead to the various forms of holoprosen­ cephaly, septooptic dysplasia, pituitary anomalies, absence of the septum pellucidum, and olfactory aplasia. The pre­ chordal mesenchyme that induces diverticulation of the primitive forebrain into paired cerebral vesicles also stimu­ lates formation of the premaxillary facial structures from overlying ectoderm. Therefore, craniofacial anomalies often occur in association with intracranial disturbances of diverticulation. Embryogenesis of the major posterior fossa struc­ tures occurs simultaneous to the ventral induction stage of cerebral development. The 2 maj or divisions of the rhombencephalon are the metencephalon and the more caudally located myelencephalon. The walls of the met­ encephalon form the pons and the cerebellum; the fluid­ filled cavity forms the superior portion of the fourth ventricle. The myelencephalon gives rise to the medulla and the inferior portion of the fourth ventricle. Anomalies of posterior fossa development include Dandy-Walker malformation, Joubert syndrome, rhombencephalosyn­ apsis, cerebellar hypoplasia, vermian hypoplasia, and mega cisterna magna. Development of the cerebral cortex occurs in 3 over­ lapping stages. During the first stage (approximately weeks 5 to 18) , stem cells proliferate into neuroblasts and glial cells in the ventricular and subventricular germi­ nal zones that line the cerebral cavity of the forebrain; this is the proliferation stage. After the initial mitotic division of these neurons, neuronal migration from the germinal matrix occurs during the second, or migration, phase (weeks 6 to 22). This neuronal migration occurs in a radial fashion toward the pial surface. Successive generations of neurons pass one another within the

cortical plate. The third phase, or organization stage, rep­ resents organization of cells in the cortex into 6 layers . Synaptogenesis and apoptosis occur during this phase. Sulcation refers to the process by which the surface of the brain develops a convolutional pattern of gyri and sulci. Sulcation involves neuronal migration, glial cell proli£:. eration, neuronal growth and differentiation, and influx of afferent fibers . ' Anomalies that predominantly involve disordered neuronal proliferation, histogenesis, and differentiation include primary megalencephaly, hemimegalencephaly, primary micrencephaly, neurocutaneous syndromes, and primary aqueductal stenosis. Abnormalities of neuronal migration and sulcation include schizencephaly, lissen­ cephaly, and gray matter heterotopias. Abnormal cortical organization can lead to polymicrogyria or schizencephaly. Although not pure migrational anomalies, disorders of the corpus callosum apparently occur at a similar time during development. Commissural fibers that form the corpus cal­ losum develop between weeks 8 and 17 of gestation; altera­ tions in this process result in hypoplasia or aplasia of the corpus callosum. Brain myelination begins during the fourth and fifth months of gestation and continues throughout child­ hood. The period of most active myelin synthesis is during the first 8 postnatal months. The temporal sequences of myelination vary in different brain regions and structures . In general, the pattern of myelination reflects the evolv­ ing functional capacity of the CNS. The spinal cord, brain­ stem, central cerebellar white matter, and posterior limbs of the internal capsules are the initial areas of myelination. Peripheral cerebral white matter is the last area to become myelinated. There are myriad congenital and acquired abnormalities ofbrain myelin. Sonography and M RI provide accurate depiction of brain development in the fetus and infant. M RI is the superior technique for assessing brain composition and structure, particularly with the implementation of diffu­ sion-tensor techniques.2 The brain of the fetus and pre­ mature infant is lissencephalic, with a smooth surface and lack of white matter interdigitation (Figu res 14-1 and 14-2) . At 26 weeks' gestation, the white matter i s hypointense to gray matter on T1-weighted images and hyperintense on T2-weighted images. Decrease in water content because of myelin formation results in conversion to hyperintensity on T1-weighted images and hypointensity on T2-weighted images (Figure 14-3) . MRI provides accurate assessment of this orderly process (Table 14-1 and Figure 14-4) . Most nor­ mal children have M R evidence of near-complete myelina­ tion by approximately 2 years of age. Persistence of high T2 signal intensity because of incomplete myelination until the fourth birthday is common in the peritrigonal white matter (the terminal zone) and the frontotemporal subcortical white matter (Figure 14-5) . Occasionally, mild T2 hyperintensity in the terminal zone persists into early adolescence.M

490 Part

3

The B r a i n

Table 1 4-1 . Normal Brain Myelination Age in m onths0

-------

T1

Stru ct u re

Su perior cerebel lar pedu ncles Posterior l i m b internal ca psule, posterior aspect M iddle cerebellar ped uncles Posterior l i m b internal ca psule, anterior aspect Cerebe l l u m Anterior l i m b i nternal capsule Splen i u m of corpus cal losum Genu of corpus callos u m Occipital white matter Frontal white matter

. . . .

... ... ....

·······

.

.. .

. . . . .. . . . . . . . .

(28 GA) (36 GA) 0

o-1 o-3 1-3 3-4 s-6 4-7 s-n

T2

(28 GA) (4o GA) o-2 4-7 . . . . . . . . . . . . . . . .. .

. . . . . ..

3-5 s-n 4-6 7-8 1 2-14 1 6-1 8

0A pproxi m ate ages of conve rsion of s i g n a l i nten s i ty fo r T1 -weighted and T2-weighted seq u e n ces in vario u s b r a i n struct u res. Fetal ages a re in weeks of gestat i o n a l age (GA) . Postnatal ages are i n months.

Figure 14-1 Normal 31 -week fetus. An axial T2-weighted fetal M R image shows the normal lissencephalic character of the developing fetal brain.

As described above, the ventricular system develops from the lumen of the primitive neural tube. Early dur­ ing brain development, a vascular layer of the pia mat­ ter is located outside of the ependymal roof of the fourth ventricle. This fuses with the ependyma to form the tela choroidea, which subsequently invaginates into the fourth ventricle and develops into the choroid plexus of the fourth ventricle. A similar process occurs within the roof of the third ventricle and in the medial walls of the lateral ven­ tricles. Thereby, there is formation of four choroid plex­ uses. These secrete cerebrospinal fluid into the embryonic ventricular system. The thin roof of the fourth ventricle ruptures during the second trimester to give rise to the foramina of Luschka and the foramen of Magendie. Normal developmental variations ofthe ventricular sys­ tem include the cavum septum pellucidum, cavum vergae, and cavum velum interpositum. The cavum septum pellu­ cidum is a fluid filled space within the membrane that sepa­ rates the lateral ventricles (Figure 1 4-6) . A cavum septum pellucidum is present in nearly all newborns; subsequent complete fusion occurs in approximately 8o% of individu­ als. Fusion of the septal lamellae occurs from posterior to anterior. A cavum vergae represents extension of a cavum septum pellucidum posterior to the columns of the for­ nix. This normal variation occurs in approximately 33% of newborns and spontaneously disappears in approximately 99% of individuals. Rarely, a cavum septum pellucidum or cavum vergae serves as a site of origin of an intraventricu­ lar arachnoid cyst. Because there is posterior-to-anterior

Figure 14-2 Premature infant. A transverse head ultrasound image of a newborn 25-week­ gestati.on infant shows a smooth brain surface that lacks gyral development. The sylvian fissures are shallow. This is a normal appearance for this stage of development.

Chapter

A

c

Figure 14-3 Normal brain development.

Midline Tl-weighted MR images of 4 infants at different ages. A Six days. The corpus callosum is thin and unmyelinated. The early stage of myelination in the cord and brainstem (except the ventral pons) results in subtle hyperintensity. Note hyperintensity of both the anterior and posterior lobes of the

14

Co ngenital A b n o r m a l ities of the B ra i n

491

B

D

pituitary. B. Three months. There is increased myelination of the ventral pons, cerebellar vermis, and dorsal aspect of the corpus callosum. C. Eight months. The brainstem and vermis now have an adult pattern. The corpus callosum is myelinated but is still somewhat thin. D. Eighteen months. The corpus callosum has mature morphology and myelination.

492 Part 3 The B ra i n

A

c

Figure 14-4 Normal brain myelination. T2-weighted images in children of different ages. A Six days. Beginning myelination in the posterior limbs of the internal capsules (arrow) is hypointense. The adjacent thalamic nuclei are also hypointense. B. Two months. There is additional myelination of the posterior aspects of the posterior limbs. The basal ganglia and thalami are hypointense relative to

B

D

the unmyelinated cerebral white matter. C. Seven months. The entire posterior limbs are myelinated. There is faint hypointensity in the anterior limbs. D. Twelve months. There is myelination of the anterior and posterior limbs of the internal capsules (arrows) and the genu and splenium of the corpus callosum. Hyperintensity of the cerebral white matter is less pronounced.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 493 fusion of the septal lamellae, a cavum septum pellucidum invariably accompanies a cavum vergae; that is, a cavum septum pellucidum et vergae (Figure 14-7) . The cavum veli interpositi (cavum velum interpositum) is an anterior exten­ sion of pia-arachnoid from the quadrigeminal plate cistern. This fluid-filled structure is inferior to the body of the for­ nix, contains the internal cerebral veins, and can extend as far forward as the columns of the fornix ( Figure 14-8) . In contradistinction to an arachnoid cyst, cavum veli interpos­ iti does not cause substantial mass effect.5

D ISORDERS OF DORSAL INDUCTION

Anencephaly Anencephaly is a severe fatal defect of neuraxis develop­ ment. Major portions of the cranium and CNS fail to develop or are destroyed during the first trimester. The calvarial defect involves the frontal, parietal, and occipi­ tal bones, often with extension into the cervical spine. The forebrain is absent. Most often, the entire cerebrum consists of a small nonfunctioning fibrotic mass of neu­ ral tissue. Concomitant malformations of the cerebellum, brainstem, optic nerves, and spinal cord are often pres­ ent. Anomalies of other organ systems are also common. Anencephaly leads to spontaneous abortion, stillbirth, or Figure 14-5 Terminal zone white matter. There is mild bilateral peritrigonal white matter hyperintensity (arrows) on this T2-weighted image of a normal 4-year-old child.

Figure 14-6 Cavum septum pell ucidum.

Figure 14-7 Cavum septum pellucidu m et vergae.

The cavum is between the frontal horns o n this coronal sonographic image of a 1-day-old infant.

There is a thin midline fluid collection (arrows) between the leaves of the septum pellucidum on this T2-weighted MR image.

494 Part 3 The B ra i n tissue are sometimes visible floating in the amniotic fluid. Polyhydramnios is present in about half of these pregnan­ cies. a-Fetoprotein levels are elevated in maternal serum and amniotic fluid.7-9

Exencephaly Exencephaly is a rare neural tube defect in which a large portion of the brain is located outside of the skull. Early fetal manifestations of exencephaly on sonography some­ times progress to those of anencephaly later in gestation, a result of necrosis of neural tissue that is exposed to amni­ otic fluid. This anomaly usually results in fetal death. Skull radiographs of the neonate with exencephaly demonstrate absence of the membranous portions of the bony calvaria. There is also variable deficiency of the skull base. There is a disorganized mass of cerebral tissue. '0•11

Chiari M alformations

Figure 14-8 Cavum veli interpositi. There is an oval fluid collection (arrow) anterior to the quadrigeminal plate cistern. The internal cerebral veins course along the lateral aspects of the cavum.

neonatal death. The prevalence is 1.2 per 1o,ooo births and up to 1 per woo pregnancies.6 There are 3 types of anencephaly: meroanencephaly, holoanencephaly, and craniorachischisis. Meroanencephaly is characterized by rudimentary brain tissue and partial for­ mation of the cranium. Abnormal tissue, called the area cerebrovasculosa, protrudes through a median cranial defect. The area cerebrovasculosa consists of abnormal spongy vascular tissue admixed with glial tissue. It ranges from a thin membrane to a large pseudoencephalic mass that simulates cerebral tissue. Holoanencephaly is the most common type of anencephaly. The brain is completely absent. Craniorachischisis is the most severe type of anen­ cephaly, with defects in the head and spine. The area cere­ brovasculosa and area medullovasculosa (vascular mass of rudimentary spinal cord at the site of a bony defect) fill cra­ nial and spinal column defects. Standard radiographs of the newborn infant with anen­ cephaly demonstrate severe microcephaly and absence of large portions ofthe membranous calvaria. Facial anomalies may also be present. Prenatal ultrasound shows absence of the normal fetal skull and brain above the level of the orbits (Figure 14-9) . Occasionally, there is echogenic angioma­ tous stroma (area cerebrovasculosa) at the expected site of the cerebrum. During the first trimester, sonography may demonstrate relatively intact cerebral hemispheres with absent membranous calvaria. Echogenic particles of neural

The Chiari malformations are a group of congenital hind­ brain anomalies that involve the posterior fossa and cranio­ cervical junction. The various types of Chiari malformation are clinically and pathophysiologically distinct (Table 14-2) . Each likely involves failure o f normal dorsal induction. These anomalies are named after Hans Chiari, a patholo­ gist at the University of Prague, who described types I to I I I o fthese malformations i n 1891. Chiari malformation type I I i s also termed Amold-Chiari malformation, i n recognition

Table 1 4-2. C hiari M alformations C h i a ri malformati o n s

M ajor featu res

_

II

Ill IV 0

Caudal extension of the cerebellar tonsils Occi pitaljcraniocervical deformities Syringohydromyelia is com mon Scol iosis is common Caudal descent of vermis and medulla Spinal dysraphism Hyd rocephal u s Associated CNS anomalies are common Herniation of portions of the cerebel l u m and brainstem i nto a sac at the craniocervical junction Aplasia or marked hypoplasia of cerebel l u m and tentori u m "Crowded " posterior fossa; no tonsillar herniation Syringomyelia is com mon

Chapter 14 Congenital Abnorm a l ities of the B ra i n 495 of Chiari

I malformation and a "crowded" posterior fossa,

but no caudal displacement of the cerebellar tonsils.1 2-'4

Chiari I Malformation Chiari

I malformation consists of downward displacement

of the cerebellar tonsils through the foramen magnum into the cervical spinal canal, unrelated to acquired intracranial pathology. There also is variable inferior displacement ofthe brainstem. The cerebellar tonsils are elongated and often have a peg-like or pointed shape. The tonsillar morphol­ ogy is often asymmetric. Symptoms in these patients can result from alteration in cerebrospinal fluid flow dynamics in the region of the foramen magnum or from compres­

A

sion of neural structures . Fibrous adhesions that develop between the dura, arachnoid, and tonsils can obstruct the fourth ventricular outlet foramina. A constricting band of dura at the level of the foramen magnum and arch of the atlas is common in patients with Chiari

I malformation.

Occasionally, there is flattening or buckling of the medulla. Congenital malformations of the supratentorial structures are rare in patients with Chiari

I malformation.'5

O sseous deformities of the occipital region and craniocervical junction occur in approximately half of patients with Chiari

I malformation. The volume of the

posterior fossa tends to be somewhat small; this may be the primary etiological factor for the tonsillar ectopia in many individuals (i. e . , a developmental disorder of the paraxial mesoderm) . Flattening and elevation of the squamous portion of the occipital bone are often present, resulting in a shallow posterior fossa. The tentorium may

8

have a steep orientation

Figure 14--9 Anencephaly. A There is lack of normal cranial development (C) on this longitudinal prenatal ultrasound image. The arrows mark the spine and the arrowheads indicate the base of the head. B. An anteroposterior radiograph of the stillborn infant shows lack of the membranous calvaria. Facial bones are present.

(Figu re 14-10) .

Other potential

findings include platybasia, basilar impression, Klippel­ Feil deformity, a concave clivus, atlantoaxial assimilation, and atlanto-occipital fusion. Syringohydromyelia occurs in

so% to 75% of individuals with Chiari I malformation;

the cervical region is the most common location. S coliosis is present in nearly

90% of individuals with Chiari I mal­

formation. Single curves and convex left curves are more of the German pathologist Julius Arnold. The type type

IV and

common in these patients than in those with idiopathic scoliosis.'6-1 8 The estimated prevalence of Chiari

o malformations are later additions.

Chiari I malformation consists of downward hernia­ tion of the cerebellar tonsils into the cervical spinal canal.

the general population is approximately

I malformation in o.s%. Many indi­

viduals with this anomaly are asymptomatic, however.

This type of Chiari malformation clinically occult at birth

Potential clinical manifestations include headaches , nystag­

in nearly all affected patients. Chiari

mus , motor deficits, sensory deficits, and manifestations of

I I malformation occurs

in association with myelodysplasia. There are numerous

syringohydromyelia

developmental abnormalities of the brain and skull in

clinically evident deformity and back pain. There is con­

these patients, including caudal extension of vermis and

siderable variation in the nature and severity of the clini­

medulla into the cervical spinal canal. Chiari

cal consequences of Chiari

I I I malfor­

mation refers to a low occipital or high cervical encephalo­

(Figu re 14-1 1 ) .

Scoliosis may result in

I malformation; the severity of

tonsillar ectopia is a weak indicator of symptomatology. In

or aplasia of the cerebellum and tentorium. Most investi­

12 mm is usually symp­ 30% of individuals with displace­ ments between 5 and 10 mm are asymptomatic. Patients

gators exclude this anomaly from the Chiari malformation

with a small posterior fossa volume are prone to develop

cele in combination with anomalies of the brainstem and cerebellum. Chiari

IV malformation refers to hypoplasia

general, herniation of greater than

tomatic. Approximately

spectrum since there is no hindbrain herniation. Some cli­

symptoms. Prominent retroflexion of the dens is often

nicians apply the term Chiari

associated with syringohydromyelia. There is a moderate

o to patients with symptoms

496 Part 3 The B ra i n

Figure 14-1 1 Chiari I malformation. Figure 14-1 0 Chiari I malformation. A sagittal T2-weighted MR image of a 1-year-old child shows herniation of a thin tongue of the cerebellum (arrow) into the cervical spinal canal. The posterior fossa volume is small. There is a vertical configuration of the tentorium. The superior aspect of the odontoid process is somewhat small.

female predilection of Chiari I malformation. Occasional cases are familial.'9 MR is the imaging study of choice for the diagno­ sis and characterization of Chiari I malformation. The maj or findings are tonsillar herniation, obliteration of the retrocerebellar subarachnoid spaces, and cranial base dysplasia (Figu re 14-12) . The generally accepted imaging criterion for the diagnosis of Chiari I malformation is herniation of 1 or both cerebellar tonsils 5 mm or more below the foramen magnum (measuring from the opis­ thion-basion line) in a patient without a predisposing factor such as myelodysplasia , hydrocephalus , intracra­ nial mass , or prior craniocervical junction surgery. Also included in the diagnosis are patients with herniation of both tonsils 3 to 5 mm inferior to the foramen mag­ num if there are accompanying features such as syrin­ gohydromyelia or cervicomedullary kinking. In most patients with Chiari I malformation, there is a short and flat clivus, sometimes associated with C1 assimilation (Figure 1 4-13) . There is often retroflexion of the odontoid process , which can cause compression of the medulla (Figure 1 4-14) . Occasionally, there is compression of neu­ ral structures by an elongated clivus; the superior aspect of the odontoid process is often absent in these patients.

This 14-year-old girl presented with headaches precipitated by coughirlg. She also noted increasing clumsiness over the past several months. There is caudal extension of the cerebellar tonsils below the neural arch of C1. The foramen magnum ( arrows) is enlarged. There is slight impression on the medulla by the odontoid (artifact from orthodontic hardware distorts the anterior spinal structures) . Septated syringohydromyelia is present in the cervical cord.

Substantial compression can lead to abnormal signal ele­ vation in the cord, medulla, or herniated cerebellar ton­ sils because of edema or gliosis. In those patients with fourth ventricular outlet obstruction, there is ventriculo­ megaly ( Figu re 1 4·1 5) . ' 8 .2 o· 2 ' Tonsillar ectopia and the small size of the posterior fossa in patients with Chiari I malformation alter the cerebrospinal fluid flow patterns at the foramen mag­ num and in the superior aspect of the cervical subarach­ noid space, leading to diminished cerebrospinal fluid (CSF) flow volume and elevated C S F flow velocity. Phase­ contrast flow sequences with MR are useful in selected patients to assess these flow patterns . The potential find­ ings include lack of detectable flow at the craniocervical junction, flow j ets, regions with predominantly unidirec­ tional flow, synchronous bidirectional fl ow, and pulsatile systolic tonsillar descent. Abnormal C S F fl ow patterns in a patient with Chiari I malformation correlate with the likelihood of symptomatic disease and syringohydro­ myelia. MR flow evaluation, therefore, can be helpful in selecting patients who will likely benefit from surgical therapy. 22-24

Chapter 14 Congenital Abnorm a l ities of the B r a i n 497

Figure 14-1 2 Chiari I malformation. A sagittal T2-weighted image of a 14-year-old patient with scoliosis shows caudal extension of the cerebellar tonsils below the C1 neural arch. There is associated distortion of the upper cervical cord. The medulla extends inferior to the enlarged foramen magnum and is compressed by a slightly retroflexed odontoid process.

Chiari II Malformation Chiari II malformation is a complex CNS deformity that occurs in association with myelodysplasia. Essentially all patients with myelomeningocele have Chiari II malforma­ tion. There is variable involvement of the posterior fossa structures, spine, skull, and spinal column. The most con­ sistent features are a small posterior fossa, tentorial dys­ plasia, and hydrocephalus . The primary pathophysiological event in Chiari II malformation is localized failure of neu­ ral tube closure because of deficient expression of crucial neuronal surface molecules in the developing neural tube. Cerebrospinal fluid escapes through the neural tube defect, resulting in reduced pressure in the brain vesicles, which in tum interferes with normal intracranial mesenchymal development; for example, a small posterior fossa and dysgenesis of the falx. As the cerebellum and brainstem grow in the abnormally small posterior fossa, alterations occur in hindbrain morphology, including inferior exten­ sion through the foramen magnum into the cervical spinal canal. The prevalence of Chiari II malformation is approxi­ mately 0-44 per woo livebirths. 25 The major clinical symptoms of Chiari II malfor­ mation relate to hydrocephalus and myelodysplasia. Manifestations ofbrainstem or lower cranial nerve dysfunc­ tion can also occur; for example, nystagmus, dysphagia,

Figure 14-1 3 Chiari I malformation. There is marked caudal extension of the cerebellar tonsils as viewed on this T1-weighted sagittal M R image. The clivus is short and the inferior aspect of the occipital bone is flattened (arrow) . The posterior fossa volume is small. There is retroflexion of the odontoid.

vocal cord paralysis, or apneic spells. Clinically significant hydrocephalus is present at the time of birth in more than half of infants with Chiari II malformation. Most others develop hydrocephalus over the next several days or weeks. However, signs and symptoms of hydrocephalus are often absent in the perinatal period. Macrocephaly is often lack­ ing, and head circumference measurements are unreliable for predicting the development ofhydrocephalus. The early diagnosis of hydrocephalus in infants with Chiari II mal­ formation frequently requires direct imaging, usually with sonography. 2 6 Skull

The membranous potion of the skull in young infants with Chiari II malformation sometimes has a mesodermal dys­ plasia termed Liickenschadel, craniolacunia, or lacunar skull. Radiography and CT show a "soap bubble" pattern of focal calvarial thinning , with oval areas of lucency sur­ rounded by sclerotic bands (Figure 14-1 6) . The findings are most prominent in the parietal and frontal bones. Craniolacunia is a developmental abnormality that is unre­ lated to increased intracranial pressure or hydrocephalus. Spontaneous resolution occurs by the end of the first year of life. 27

498 Part 3 The B ra i n

Figure 14-14 Chiari I malformation. A sagittal MR image of an 18-year-old patient shows caudal herniation of the cerebellum and medulla through an enlarged foramen magnum. There is retroflexion of the odontoid process. The clivus is short.

Figure 14-1 5 Chiari I malformation; fourth ventricular outlet obstruction. A sagittal T2-weighted MR image shows herniation of cerebellar tissue to the C5 leveL There is dilation of the fourth ventricle.

A

Figure 14-1 6 Chiari I I malformation; craniolacu nia.

B

CT of a 1-week-old infant with myelomeningocele shows multiple focal areas of calvarial thinning.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 499

A

B

Figure 14-1 7 Chiari I I malformation.

c

Flattening or scalloping of the posteromedial portions ofthe petrous pyramids is common in infants with Chiari I I malformation. Scalloping of the clivus occasionally occurs. These bony changes apparently result from compression of osseous structures by the cerebellum and brainstem. Pressure effects also produce enlargement of the foramen magnum. 2 8 Dura

Dural abnormalities in patients with Chiari II malfor­ mation include an abnormally low attachment of the

A. An axial T1-weighted image of a 16-year-old boy shows the cerebellum bulging through the splayed tentorial incisura (arrows). There is anterior extension of the cerebellum adjacent to the brainstem. B. A sagittal image at the midline demonstrates a vertical orientation of the tentorium (arrow) . The medulla and cerebellar vermis extend from the small posterior fossa into the cervical spinal canal. The rostrum of the corpus callosum is deficient. C. A contrast -enhanced image to the right of the midline shows extension of the superior sagittal sinus (arrow) to the inferior occipital region where it merges with the vertically oriented straight sinus.

tentorium, enlargement of the tentorial incisura, and fenestration or hypoplasia of the falx cerebri. Attachment of the tentorium in these patients ranges from a near­ normal position to a location adjacent to the foramen magnum. A low attachment contributes to the small vol­ ume of the posterior fossa. The transverse sinuses and torcula help to define the position of the tentorial attach­ ment on imaging studies ( Figure 1 4-1 7) . On axial cross­ sectional imaging studies , the enlarged incisura often appears heart-shaped.

500 Part 3 The B ra i n Cerebellum

Brainstem

Involvement of the cerebellum in patients with Chiari I I malformation i s important clinically and radiographically. The volume of the posterior fossa is small and the cerebel­ lum is variably hypoplastic. The cerebellar folia are some­ times absent. There is displacement of the inferior aspect of the cerebellar vermis through the foramen magnum into the cervical spinal canal (Figure 14-1 8) . This "tail" or "peg" of cerebellar tissue extends a variable distance along the dorsal aspect of the cervical spinal canal. Occasionally, thin cerebellar tissue reaches the inferior aspect of the cer­ vical spine or the upper aspect of the thoracic spine. The descended vermian tissue is usually gliotic and poorly vascularized. Caudal descent of the tonsils occasionally occurs. Upward protrusion of the cerebellar hemispheres and vermis through the enlarged incisura produces the appearance of a "pseudotumor" of the tentorium or a "tow­ ering" cerebellum on cross-sectional imaging. The cerebel­ lum sometimes grows anteriorly and partially surrounds the brainstem (Figure 14-1 9) . Occasionally, there is inferior extension of the posteromedial aspect of the cerebrum through the enlarged incisura.2 9-31

In addition to caudal extension ofthe inferior cerebellar ver­ mis, Chiari II malformation usually includes inferior dis­ placement of the brainstem into the cervical spinal canal. The brainstem has an elongated configuration and the pontomedullary junction is less distinct than normal. The medulla buckles backward, creating a characteristic "cervi­ comedullary kink" on sagittal MR images; this is present in approximately 70% of patients with Chiari II malforma­ tion. Stretching of the inferior cranial nerves is common. The pons occasionally has a flattened appearance, usually in association with concavity of the clivus. The mesence­ phalic tectum has a beak-shaped configuration on axial CT and MR images (Figure 14-20) . On sagittal images, there is posteroinferior stretching of the quadrigeminal plate. Syringobulbia is an occasional complication of Chiari I I malformationY Ventricles

The fourth ventricle has an elongated and narrowed con­ figuration in individuals with Chiari II malformation. Occasionally, a trapped (isolated) fourth ventricle occurs as a consequence of aqueductal obstruction in conjunction with obstruction of the outflow foramina or basilar cisterns. Another potential complication is posteroinferior hernia­ tion of the fourth ventricle dorsal to the medulla and infe­ rior to the vermis ("encysted fourth ventricle") . Deformities of the cerebral aqueduct are common; aqueductal stenosis or atresia is present in 50% to 75% of patients. A variable degree of enlargement of the lateral ventricles occurs in nearly all patients with Chiari I I malformation, often with a colpocephalic pattern. The frontal horns point anteroin­ feriorly. Substantial enlargement of the third ventricle is uncommon. The massa intermedia is prominent. The sep­ tum pellucidum is absent in approximately 40% of indi­ viduals with Chiari II malformation; there is a fenestrated appearance in 35% ( Figure 14-21 ) . Cerebrum

Figure 14-1 8 Chiari I I malformation. A sagittal T2-weighted image of a 15·day-old infant shows a small posterior fossa, marked enlargement of the foramen magnum, and inferior displacement of the medulla and cerebellar vermis into the cervical spinal canal. There is heterogenous signal in the dysplastic cerebellar tissue. The inferior tentorial attachment is near the foramen magnum. There is syringohydromyelia in the thoracic spine.

The cerebral tissue in patients with Chiari I I malformation is histologically normal. However, there is a contracted, closely folded pattern of the gyri. After shunting, the medial aspects of the occipital lobes often have multiple small gyri with normal gray matter thickness; this is termed stenogy­ ria. The interhemispheric fissure of patients with Chiari II malformation has an irregular, serrated appearance. Gyri cross the midline and interdigitate through a hypoplastic or fenestrated falx (Figure 14-22) . Abnormal development of the corpus callosum occurs in at least 75% of patients with Chiari II malformation. The most common pattern is absence of the rostrum and absence or hypoplasia of the splenium. Enlargement of the caudate heads and massa intermedia is common (Figure 14-23) . Gray matter hetero­ topias occasionally occur.33

Chapter 1 4 Co ngenital A b n o r m a l ities of the B ra i n

A

501

B

Figure 14-1 9 Chiari I I malformation.

c

Chiari III Malformation The Chiari III malformation is exceedingly rare. This term describes a low occipital or high cervical encephalocele in combination with multiple anomalies of the brainstem and cerebellum. Portions of the cerebellum and occipital lobes

A A sagittal T2-weighted M R image of a 33-day-old infant with a myelomeningocele and shunted hydrocephalus demonstrates extension of the medulla and dysplastic cerebellar tissue into the cervical spinal canal. The fourth ventricle is narrow. The inferior aspect of the tectum (arrow) is beaked posteriorly. The corpus callosum is thin . There is scalloping of the clivus. B. Superior protrusion of the cerebellum through the tentorial incisura (arrows) is visible on this coronal image. C. The compressed cerebellum bulges anteriorly and partially surrounds the brainstem.

extend through the calvarial defect, sometimes in conjunc­ tion with part of the brainstem. The herniated tissue is gliotic and necrotic; heterotopias may be present. Other potential findings include petrous and clivus scalloping, dysgenesis of the corpus callosum, cerebellar tonsillar her­ niation, hydrocephalus, and syringohydromyelia.H-36

502 Part 3 The B ra i n

DISORDERS OF VENTRAL INDUCTION

Holoprosencephaly

Figure 14-20 Chiari I I malformation. There is a beaked appearance of the tectum (arrow).

A

Figure 14-21 Chiari I I malformation.

A, B. Coronal ultrasound images of a newborn with myelomeningocele and macrocephaly show dilation of the lateral

Holoprosencephaly is a rare disorder of organogenesis, in which there is failure of normal lateral cleavage into distinct cerebral hemispheres, as well as deficient trans­ verse cleavage into a diencephalon and telencephalon. The developmental pathogenesis likely involves defective devel­ opment of the notochordal plate early in embryogenesis, thereby causing a lack of normal lateral migration of the telencephalic and optic vesicles . There is failure of normal division of the forebrain (i.e. , the prosencephalon) between weeks 5 and 6 of embryogenesis, resulting in a complex facial and craniocerebral anomaly of variable severity. The term holoprosencephaly derives from this lack of division of the prosencephalon. The estimated prevalence of holoprosencephaly is between 1 in 5000 and 1 in 16,ooo livebirths. Because many pregnancies with a holoprosencephalic fetus end with spontaneous or elective abortion, the fetal prevalence may be as high as 1 in 250. Holoprosencephaly accounts for at least half of all instances of ventriculomegaly detected on prenatal sonography. Although often an isolated anomaly, holoprosencephaly sometimes occurs in association with various chromosomal syndromes, including trisomy 13, trisomy 15, and trisomy 18. The clinical severity of holo­ prosencephaly ranges from mild to severe. Common marrifestations include apneic episodes during infancy, sei­ zures, and neurological dysfunction. Holoprosencephaly often is associated with combined anterior and posterior

B

ventricles and absence of the septum pellucidum. There is mild prominence of the third ventricle.

Chapter 14 Co ngenital Abnormal ities of the B ra i n 503

Figure 14-22 Chiari I I malformation. There is marked interdigitation of gyri at the midline on this axial CT image of a near-old child with spina bifida.

A

Figure 14-23 Chiari I I malformation. A An axial T1-weighted image of a 10-year-old child shows a markedly enlarged massa intermedia (arrows) extending between the thalami. B. The massa intermedia (arrow) appears as a round

pituitary hormone defects; diabetes insipidus is common in these patients. Poiki.lothermia may occur as a result of hypothalamic hypoplasia. Cardiac, skeletal, genitourinary, and GI anomalies are common with the severe forms of holoprosencephaly. 37 Holoprosencephaly comprises a spectrum of anoma­ lies, with 4 generally recognized subtypes: alobar, sernilo­ bar, lobar, and syntelencephaly (middle-hemisphere variant) (Table 1 4-3) . Not all patients, however, have features that fit precisely into one of these categories. The alobar and lobar forms represent the most severe and least severe types, respectively. In all forms of holoprosencephaly, the sep­ tum pellucidurn and the olfactory bulbs are absent and the sylvian fissures are poorly developed. The posterior fossa structures are usually normal. Most patients with holopros­ encephaly are normocephalic or microcephalic; approxi­ mately 10% have macrocephaly. Facial dysmorphism, such as hypotelorism and midline facial clefts, often occurs in the more severe forms of holoprosencephaly. J S There is an anterior-to-posterior gradient in the severity ofholoprosencephaly. The corpus callosum is an important marker of brain development in these patients. In general, the severity of brain maldevelopment inversely relates to the degree of corpus callosum development. In the severe forms of the disorder, that is, alobar holoprosencephaly, the

8

structure in the third ventricle on this T2-weighted sagittal image. Additional findings include a fourth ventricle cyst, caudal descent of the cerebellum and brainstem, and scalloping of the clivus.

504 Part 3 The B ra i n Table 1 4-3- Patterns of Brain M alformation in the 4 Types of Holoprosencephaly Structu re

Alobar

Semilobar

Lo bar

Syntelencephaly

Septum pel l ucidu m Rostru m corpus callos u m Body corpus callosum Splen i u m corpus ca llosum I nterhem ispheric fiss u re Falx Frontal horns Third ventricle Site offusion

Absent Absent Absent Absent Absent Absent Absent Absent Cerebrum

Absent Absent Absent Present Partial Partial Rudimentary Variable Variable

Absent ± ± Present Partial Partial Sq uared Present I nferior frontal

Absent Present Absent Present Partial Partial Present Present Parietal { Posterior frontal

......

.. .

... .

.......

..

...

· · · · · · · ···

····-···

· · ···· ···

···

..

···

..

........

corpus callosum is absent. With the lobar and sernilobar forms, the posterior aspect of the corpus callosum is intact (Figure 14-24) . With syntelencephaly, the callosal genu and splenium are present, and a portion of the callosal body is absent. Barkovich et al propose a grading system for the sever­ ity ofholoprosencephaly based on the "sylvian angle." With

A

Figure 14-24 Semilobar holoprosencephaly. A. Only the splenium (arrow) of the corpus callosum is present on this sagittal T1-weighted image. Heterotopic gray matter and fused central gray matter structures surround the anterior aspects of the malformed lateral and third ventricles. B. On the

. ...

.... ...

. .. . . . .

holoprosencephaly, there is anterior and medial displace­ ment of the sylvian fissures; in severe cases, there are no identifiable sylvian fissures. The sylvian angle is defined as the angle between lines that extend tangential to the sylvian fissures ( Figure 14-25) . Normal measurements are 12 degrees to 18 degrees. The sylvian angles are largest with the severe forms of holoprosencephaly. 3 9

B

axial image, there is fusion of the frontal lobes. The anterior interhemispheric fissure is absent. The fissure is normal posteriorly. There is dilation of the posterior aspect of the fused lateral ventricles, with a batwir!g configuration.

Chapter 14 Co ngenital Abnormal ities of the B ra i n

505

Figure 14-25 Holoprosencephaly.

The sylvian angle measures 40 degrees in this child with semilobar holoprosencephaly. The sylvian fissures (arrows) are located more anteriorly than normal and there is deficient frontal lobe development. The anterior interhemispheric fissure is absent and there is a common thin gyrus at the midline anteriorly, with fusion of gray matter and white matter structures at the base of this gyrus. There is relatively normal differentiation of the thalami. The occipital lobes are normal in appearance.

Figure 14-26 Alobar holoprosencephaly. There is a crescentic monoventricle that communicates with a large dorsal cyst. A thin layer of dysplastic cortex is present peripherally. The interhemispheric fissure is absent.

holoprosencephaly demonstrates deft palate, microphthal­ mia or anophthalmia, trigonocephaly, micrognathia, and absence of the nasal septum. Skull radiographs show a small anterior cranial fossa, superior arching of the orbits,

Alobar Holoprosencephaly Alobar holoprosencephaly is the most severe form of this anomaly. There is absence of a distinct third ventricle on neuroirnaging studies; the thalami are fused (i. e . , fused

and severe hypotelorism.

Semilobar Holoprosencephaly

diencephalon) . There is no interhemispheric fissure, and

Sernilobar holoprosencephaly consists of incomplete sepa­

the falx cerebri is absent or markedly hypoplastic. The cere­

ration of the prosencephalon into cerebral lobes. The sever­

brum consists of a thin rim of tissue, which is usually most

ity of the brain dysmorphism that occurs in the sernilobar

A crescent­

type of holoprosencephaly is intermediate between that of

shaped or horseshoe-shaped single ventricle (monoven­

the alobar and lobar types. Individual patients may have

prominent in the frontal and occipital regions .

tride) occupies most of the intracranial cavity. The fused

features that overlap the descriptions of these 3 types.

diencephalon indents the inferior aspect ofthe ventricle. In

There is more cerebral tissue with the semilobar than the

some patients , the roof of the monoventride balloons out

alobar type. The thickness of the cerebral cortex is often

to form a large dorsal midline cyst; these children are often

normal. There are usually small gyri in the anterior aspect

(Figure 14-26) . There is a single midline

of the cerebrum. The sulci in the abnormal cortex are often

macrocephalic

"azygous" anterior cerebral artery. The internal cerebral

shallow

veins, straight sinus , and superior sagittal sinus are absent.

the anterior/inferior aspect of the cerebrum appears as a

(Figure 14-27) . Occasionally, the cerebral tissue in

Many infants with alobar holoprosencephaly are still­

mushroom-shaped mass. Subcortical heterotopic gray mat­

born or die in infancy. Physical examination typically shows

ter that crosses the midline in the anterior aspect of the

severe midline facial anomalies. Hypotelorism in these

cerebrum can occur in association with semilobar holo­

infants results from absence or hypoplasia of the premaxil­

prosencephaly

lary portion of the face; a severe form results in cyclopia.

(Figure 14-28) . A single ventricle i s present with semilobar holo­

MRI of the facial structures in patients with alobar

prosencephaly, but there is rudimentary formation of the

CT and

506 Part 3 The B ra i n

Figure 14-28 Semilobar holoprosencephaly.

Figure 14-27 Severe semilobar holoprosencephaly. A coronal T1-weighted image demonstrates a large monoventricle. There are rudimentary sylvian fissures. The sulci are shallow. The interhemispheric fissure is lacking.

frontal and temporal horns. The posterior aspect of the monoventride is usually somewhat dilated, and some­ times has a batwing character (see Figure 14-24) - In some patients, the monoventride communicates with a dorsal cyst (Figure 14-29) . There is at least partial formation of the posterior aspect of the interhemispheric fissure. The poste­ rior portion of the falx is usually present, but it may deviate from the midline. There is a variable degree of third ventricular develop­ ment in patients with semilobar holoprosencephaly. There is also a spectrum of deep gray matter separation, ranging from fusion into a common mass to near-complete separa­ tion of the thalami and basal ganglia. The temporal horns are rudimentary, and hippocampal gyrus formation is gen­ erally incomplete. As with all forms of holoprosencephaly, the septum pellucidum is absent and the lateral ventricles are fused. The splenium of the corpus callosum is present in patients with semilobar holoprosencephaly. Important markers for assessing the severity of semilobar holoprosen­ cephaly include the degree of corpus callosum formation, the anterior extent of interhemispheric fissure formation, and the severity of central gray matter fusion. In most chil­ dren with semilobar holoprosencephaly, the facial struc­ tures are normal; mild facial anomalies (deft lip or deft palate) occasionally occur.

A coronal T2-weighted MR image shows heterotopic gray matter (arrow) superior to the rudimentary lateral ventricles and triangular-shaped third ventricle. The gyri at the base of the short interhemispheric fissure are thick and dysmorphic.

Lobar Holoprosencephaly Lobar holoprosencephaly is the least-severe type. There is usually a small area of midline cerebral fusion along the inferior aspect of the frontal lobes. There is at least partial formation of the interhemispheric fissure and falx cerebri; however, the anterior aspect of the falx is usually dysplastic. The septum pellucidum is absent. The hippocampal for­ mations are nearly normal. There is less distortion of tem­ poral hom and third ventricular morphology than with the alobar and semilobar forms. Moderate ventriculomegaly is typical. The frontal horns typically have a "squared off' appearance. The sylvian fissures are absent or small, and the frontal lobes are often hypoplastic. The corpus callo­ sum may or may not be present. Lobar holoprosencephaly is distinguished from septooptic dysplasia by visualization of a normal falx cerebri in the latter. The facial bones are normal in patients with lobar holoprosencephaly.

Middle Interhemispheric Variant of Holoprosencephaly The middle interhemispheric variant of holoprosenceph­ aly, also termed syntelencephaly, refers to fusion of the parietal lobes and posterior aspects of the frontal lobes . There appears to be an association with a mutation in the ZIC2 gene, which is important for neural tube closure and embryonic roof plate differentiation. Neuroimaging

Chapter 14 Co ngenital A b n o r m a l ities of the B ra i n 507

A

Figure 14-29 Severe semilobar holoprosencephaly. A A coronal ultrasound image shows fusion of central gray matter structures into a midline mass (arrow) . There is no

B

The frontal lobe white matter is fused deep to a foreshortened interhemispheric fissure. B. There is a dorsal cyst (arrow) on this image of the posterior aspect of the brain.

separation of the malformed lateral ventricles at this level.

evaluation demonstrates continuity of the mid portions of the cerebral hemispheres and a common ventricle. The interhemispheric fissure is absent at the site of fusion, but intact between the occipital lobes and the anterior aspects of the frontal lobes. There is often abnormal connection of the sylvian fissures across the midline over the vertex. The body of the corpus callosum is absent, while the genu and splenium are preserved. The basal portions of the frontal lobes are normal in appearance. The basal ganglia are nor­ mal. Heterotopic gray matter or dysplastic cerebral cortex is common. 4 °-42

Septooptic Dysplasia Septooptic dysplasia (SOD) consists of hypoplasia of the optic nerves and absence of the septum pellucidum. Hormonal deficiencies and a variety of forebrain defects can occur in these patients. Although SOD is generally spo­ radic, there are unusual familial cases. The pathogenesis is likely multifactorial, involving contributions from environ­ mental factors as well as abnormalities of crucial develop­ mental genes such as HESX1, SOX2, SOXJ.43 .44 Nystagmus andjor diminished visual acuity are some­ times present in patients with SOD. Ophthalmological examination shows hypoplasia of the optic discs. Endocrine deficiencies related to pituitary or hypothalamic dysfunction occur in about two-thirds of patients with SOD. These chil­ dren may exhibit manifestations of growth hormone defi­ ciency, hypogonadotropic hypogonadism, central diabetes

insipidus, hypothyroidism, or adrenal insufficiency. Of those patients with an endocrinopathy, more than halfhave anterior pituitary hormone deficiency and approximately 10% have diabetes insipidus. Deficiencies of adrenocortico­ tropic hormone and gonadotrophin can also occur; these may lead to neonatal hypoglycemia or genital anomalies. Endocrinopathy occasionally occurs in patients with optic nerve hypoplasia (unilateral or bilateral) despite the pres­ ence of an intact septum pellucidum.4 5 ·4 6

Septooptic Dysplasia Struct u re

I magi n g fi n d i n g

Septum pell ucidu m Optic nerves, chiasm, tracts Frontal horns

Aplasia or hypoplasia Small Box-like

Neuroirnaging studies of patients with SOD show hypo­ plasia or aplasia of the septum pellucidum ( Figure 14-30) . This i s associated with "box-like" frontal horns o n coronal images. Sagittal MR images show low positions of the for­ nices. The optic nerves, chiasm, and optic tracts usually appear small; however, normal imaging morphology of these structures does not exclude the diagnosis. Optic nerve

508 Part 3 The B ra i n

Figure 14-30 Septooptic dysplasia. A coronal T1-weighted MR image of a 4-month-old child shows a common lateral ventricle as a result of absence of the septum pellucidum. The optic chiasm is small.

hypoplasia in patients with S O D is usually bilateral. Some patients with S O D have absence of the septum pellucidum in association with cerebral white matter hypoplasia and normal cerebral cortex. Others have disorders of neuronal organization, such as schizencephaly and gray matter het· erotopia; this is termed SOD-plus (Figure 14-31 ) . Posterior pituitary ectopia or absence of the pituitary stalk occasion· ally occurs in association with SOD. Other reported mor· phological abnormalities of the brain in these patients include cerebellar hypoplasia, dysgenesis of the corpus cal­ losum, aplasia of the fornix, and empty sella turcica.47-5°

Arh inencephaly Arhinencephaly is a rare anomaly in which there is deficient development of components of the olfactory system (i.e., olfactory aplasia) . Although occasionally isolated, arhinen­ cephaly usually occurs in association with other cranial and facial anomalies, such as holoprosencephaly, dysgenesis of the corpus callosum, cleft palate, ocularjorbital deformi· ties, ventral forebrain anomalies, and hypoplasia or aplasia of the nose (arhinia) . Patients with bilateral arhinencephaly lack olfactory sensation (anosmia). Coronal MR images show absence or hypoplasia of the olfactory bulbs and olfac­ tory tracts (Figure 14-32) . The olfactory sulcus is absent. The gyrus rectus and orbital gyrus form a common gyrus. M R and C T examinations are also important for the detection of associated intracranial and facial anomalies. 5'

Kallmann syndrome is a hereditary anomaly in which aplasia or hypoplasia of components of the olfactory sys­ tem occurs in patients with hypogonadism and anosmia or hyponosmia. This is a localized neuronal migration anomaly of cells from the embryonic olfactory placode into the forebrain. Proper migration of these cells is required for development of the olfactory system. In addi­ tion, cells from the olfactory placode normally migrate to the hypothalamus where they differentiate into luteiniz­ ing hormone-releasing hormone cells that control adeno· hypophyseal release of follicle-stimulating hormone and luteinizing hormone. KALI or FGR..l mutations are respon­ sible for most instances of Kallrnann syndromeY High-resolution coronal M R images of patients with Kallmann syndrome show small or absent olfactory sulci and absent olfactory bulbs. The olfactory tracts are usually hypoplastic. In some patients, there are small irregular "nodules" ventral to the frontal lobes, apparently represent­ ing dysplastic tissue caused by deficient neuronal migra­ tion. In patients with severe functional impairment of the hypothalamus, the pituitary gland is small. Kallmann syn· drome is sometimes associated with renal anomalies or facial anomalies, such as cleft palate, dental agenesis, and mandibular deformities.53·54

Dysgenesis of the Corpus Callos u m Dysgenesis o f the corpus callosum i s a common devel­ opmental lesion of the brain. This anomaly ranges from a small posterior callosal defect to complete agenesis. In general usage, the term dysgenesis refers to the spectrum of developmental lesions of the corpus callosum. Agenesis indicates complete absence and hypoplasia indicates par· tial failure of development; the misnomer "partial agen­ esis of the corpus callosum" refers to the latter instance. Interference with normal development of the corpus cal­ losum can occur as a consequence of hereditary factors, chromosomal disorders (8, 9, 13, and 18 ) , fetal exposure to exogenous teratogens (e.g., alcohol) , and metabolic dis­ orders (e.g., peroxisomal disorders and nonketotic hyper­ glycinemia) . The estimated prevalence of agenesis of the corpus callosum in the general population is 0.2% to 0.7%. A population-based study from California demonstrated a prevalence of 1.8 per 10 ,000 livebirths.55·56 Most patients with callosal agenesis suffer neuro­ developmental manifestations of the anomaly, although there is substantial individual variation in severity. More than 8o% of children with agenesis of the corpus callo­ sum have clinically detectable neurological manifestations such as macrocephaly, epilepsy, developmental delay, and various forms of neurological disability. Many patients with callosal agenesis or hypoplasia have additional CNS anomalies or a genetic syndrome; for example, holopros­ encephaly, intracranial lipoma, interhemispheric cyst, migrational disorders, cephalocele, craniofacial anomalies, Toriello-Carey syndrome, Aicardi syndrome, Chiari I I mal­ formation, orofacial-digital syndrome, Rubinstein-Taybi

Chapter

A

14

Congenital Abnormal ities of the B ra i n

509

8

Figure 14-31 Septooptic dysplasia-plus.

c

A. A coronal M R image shows absence of the septum pellucidum. The optic chiasm is small. B. The optic nerves are hypoplastic. C. There is closed-lip schizencephaly in the right parietal lobe. Irregular gray matter (arrow) lines the thin cleft.

syndrome, Dandy-Walker malformation, and frontonasal dysplasia. 57-6' The initial phase of corpus callosum development is at approximately the seventh week of gestation, with the formation of callosal precursors along the ventral aspect of the embryonic commissural plate and cortical fibers. The callosal precursors secrete the chemoattractant axonin-1 to guide the developing axons across the midline, thereby causing each region of the hemispheric fibers to connect to the contralateral side through the corpus callosum. The corpus callosum develops in a sequential fashion: the genu develops first, then the body, the splenium, and lastly the rostrum. Normally, the corpus callosum is structurally complete by the 2oth week of gestation. The corpus callo­ sum is the largest of the cerebral commissures; the anterior

commissure and the hippocampal commissure also derive from the embryonic commissural plate. True agenesis of the corpus callosum usually is the result of failure of formation of the commissural plate. Deficiencies of the other cerebral comrnissures sometimes accompany dysgenesis of the corpus callosum. Because of the developmental sequence of the corpus callosum, partial deficiencies most often involve the portions that are formed later during embryogenesis; that is, the rostrum, splenium, and posterior portion of the body. Exceptions to this pattern include some forms of holoprosencephaly and focal cere­ bral lesions that interfere with embryonic axonal migration across the midline. Also, acquired destructive abnormali­ ties of the corpus callosum in the fetus or child can involve any portion of the structure. With agenesis of the corpus

510

Part 3 The B r a i n

A

B

Figure 14-32 Arhinencephaly. A, B. T2-weighted coronal MR images of a 6-year-old child with anosmia show bilateral gyrus rectus and orbital gyrus fusion (arrow) ; the olfactory sulcus is absent. The olfactory tracts and olfactory bulbs are absent bilaterally. C. An image of a normal child shows the olfactory bulbs (large arrows) at the cribriform plates, surrounded by cerebrospinal fluid. There is normal gyrus rectus, orbital gyrus, and olfactory sulcus development (small arrows) .

callosum, hemispheric axons fail to cross the midline and instead course longitudinally to form paramedian bundles along the medial borders of the lateral ventricles; that is, the bundles of Probst. The normal corpus callosum appears on neuroimag­ ing studies as a C-shaped midline structure. The rostrum is the small anterior inferior portion. The anterior curved por­ tion is in the genu. The body is the longest portion of the structure; the isthmus is an area of slight thinning in the dorsal aspect of the body. The slightly expanded posterior aspect of the corpus callosum is the splenium. The hippo­ campal commissure crosses between the bodies of the for­ nices, adjacent to the splenium. The anterior commissure is located in the anterior wall of the third ventricle. Prenatal detection of corpus callosum anomalies is possible with sonography and MR. The corpus callosum in the normal fetus reaches adult form by 18 to 20 weeks' ges­ tation. Coronal and midline sagittal images are most use­ ful for depicting the integrity of the fetal corpus callosum. Supplemental imaging findings of hypoplasia or agenesis

c

include enlarged atria and occipital horns, teardrop config­ urations of the lateral ventricles, absence of the cavum sep­ tum pellucidum, superior extension of the third ventricle, and radiating medial sulci. 6 2, 63

Agenesis of the Corpus Callosum Struct u re

I m agi n g fi n d i n g

Corpus callosum Lateral ventricles

Absent Separated and parallel lateral ventricular bodies Enlarged atria and occi pital horns

In infants and older children with agenesis of the corpus callosum, the lateral ventricles have a separated and parallel appearance on axial images because of the

Chapter 14 Congenital Abnorm a l ities of the B ra i n 51 1

A

8

Figure 14-33 Agenesis of the corpus callosum.

demonstrates the typical separated and parallel configurations of the bodies of the lateral ventricles.

A. An axial Tl-weighted M R image shows colpocephaly and separation of the frontal horns. B. A more superior image

interposed bundles of Probst. The third ventricle extends

fibers in patients with corpus callosal anomalies . With

superiorly between the lateral ventricles , into the inter­

agenesis of the corpus callosum, hemispheric cortex fibers

hemispheric fissure . Colpocephaly is usually present; that

fail to cross the midline and instead form the paramedian

is, enlargement of the atria and occipital horns. The medial

Probst bundles. The Probst bundles are longitudinally

borders of the frontal horns are somewhat concave because

oriented fibers adjacent to the medial walls of the lateral

( Figu re 14-33) .

ventricles. There is fusion of the Probst bundles with the

of indentation by the bundles of Probst

Coronal and sagittal images provide optimal evaluation of

rudimentary cingulum and dysplastic fornices. In patients

the corpus callosum and are essential for the detection and

with hypoplasia of the corpus callosum, diffusion-tensor

With

MR shows extensive fiber connections through the intact

hypoplasia, the most common imaging pattern is absence

portion of the corpus callosum. The white matter fibers

characterization of callosal hypoplasia

(Figure 14-34) .

of the rostrum, inferior aspect of the genu, the splenium,

from the parietooccipital regions form a back-to-front

and a variable segment of the posterior aspect of the body.

bundle and enter into the remaining portion of the genu.

With agenesis , sagittal images often show a "cartwheel"

Frontal lobe fibers also j oin the connection through the

or "sunburst" appearance of the interhemispheric sulcal

partially formed corpus callosum; these form an H -shaped configuration of hemispheric fibers on axial views. 66

markings, as a result of lack of inversion of the cingulate Normal cingulate sulci are

There are various acquired causes of thinning of the

lacking. Hypoplasia of the hippocampi is associated with

corpus callosum that should not be mistaken for dysgen­

gyri

(Figures 14-35

and

14-36) .

enlargement of the temporal horns

(Figure 14-37) .

Reduced

esis. Focal or diffuse thinning because of neonatal hem·

cerebral hemispheric white matter volume and malfor­

orrhage, head trauma, ischemia, or hydrocephalus is most

A variable degree of thinning often occurs in

mations of cortical development are common additional

common.

neuroimaging findings in patients with dysgenesis of the corpus callosum. 6 4, 6 5

association with various developmental brain lesions, such as Chiari II malformation. Focal thinning of the corpus

Diffusion-tensor MR and MR fiber tractography can

callosum is common in children with hereditary spastic

demonstrate the abnormal orientation of white matter

paraplegia.

512

Part

3

The B r a i n

Figure 14-35 Agenesis on the corpus callosum. A T1-weighted image at the midline shows complete absence of the corpus callosum. The cingulate sulcus is absent, and the cerebral sulci radiate to the margin of the third ventricle.

Figure 14-34 Agenesis o ft h e corpus callosum. There is no visible corpus callosum on this coronal sonographic image. There are prominent bundles of Probst (arrows) adjacent to laterally displaced ventricles.

Figure 14-37 Agenesis of the corpus callosum. Figure 14-36 Agenesis ofthe corpus callosum. The cerebral sulci extend toward the third ventricle (TV) , with no intervening corpus callosum, on this midline sagittal sonographic image.

A coronal T1-weighted M R image of a 10-month-old infant shows superior extension of the third ventricle into the interhemispheric fissure; the wall of the ventricle is too small to be visualized. The bundles of Probst (arrows) cause lateral and inferior displacement of the frontal horns. The temporal horns are prominent.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 513

A

B

Figure 14-38 Callosal dysgenesis with interhemispheric diverticulum.

c

Callosal Dysgenesis with an Interhemispheric Cyst Complete or partial absence of the corpus callosum some­ times occurs in association with a large midline ventricular diverticulum or interhemispheric cyst(s) . Hydrocephalus is common with both forms of this disorder. The latter form often has multiloculated cysts and is sometimes associated with subcortical heterotopia, subependymal heterotopia,

A. A T1-weighted sagittal M R image o f a 1-year-old child with macrocephaly and hydrocephalus shows a large midline fluid collection. Only the genu and anterior aspect of the body of the corpus callosum are present. B. The diverticulum extends along the left side of the interhemispheric fissure. It is contiguous with the lateral ventricles and third ventricle. C. The dilated left lateral ventricle widely communicates with the diverticulum.

or polyrnicrogyria. Some of these patients have manifesta­ tions of Aicardi syndrome. 6 7 ·68 Imaging studies of callosal dysgenesis with an inter­ hemispheric diverticulum demonstrate a large interhemi­ spheric fluid collection that widely communicates with the dilated third andfor lateral ventricles (Figure 14-38) . The findings are similar with the cystic form of this anomaly except that thin walls separate the cysts from the ventricles .

514 Part 3 The B r a i n

A

Figure 14-39 Callosal agenesis with an interhemispheric cyst. A There are multiple midline cysts on this enhanced T1-weighted image. The corpus callosum is absent. B. A coronal fluid-attenuated

B

inversion recovery (FlAIR) image shows one of the cysts to extend superiorly along the left side of the interhemispheric fissure. There is dilation of the right lateral ventricle.

The cysts may be slightly hyperintense to clear C S F on T1-weighted M R images and hyperintense on T2-weighted images, as a result of proteinaceous fluid or subacute hem­ orrhage. The cysts usually bulge superiorly along one or both sides of the interhemispheric fissure (Figure 14-3 9) . 6 9

Callosal Dysgenesis with Lipoma Hypoplasia of the corpus callosum is often present in patients with a lipoma of the adjacent portion of the inter­ hemispheric fissure. Interhemispheric fissure lipoma in association with callosal dysgenesis occurs with a frequency of approximately 1 per qoo live births. Closure defects such as encephalocele are common in these patients. Cutaneous lipomas may also be present. Lipomas are hypoattenuating on CT and hyperintense on T1-weighted MR (Figure 14-40) . There i s considerable variation between patients i n the size and morphology of interhemispheric lipomas and the sever­ ity ofassociated callosal dysgenesis (Figure 14-41 ) . Substantial corpus callosum deficiency is common with a large round or oval lipoma. The corpus callosum often is nearly normal in patients with a thin curvilinear lipoma along the splenium. Occasionally, there is intraventricular extension of an inter­ hemispheric lipoma via the choroid plexus?0 ·71

Aicardi Syndrome Aicardi syndrome is a rare X-linked syndrome that only occurs in females. The causative mutation is apparently lethal for male embryos. The major clinical features of Aicardi syndrome include chorioretinal lacunae (wo%

Figure 14-40 Callosal dysgenesis with interhemispheric lipoma. A T1-weighted M R image of a 2-year-old child shows a large interhemispheric lipoma and absence of the corpus callosum.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 51 5

Figure 14-41 Callosal dysgenesis with interhemispheric lipoma. There is a small lipoma (arrow) of the anterior interhemispheric fissure in this child with agenesis of the corpus callosum. The lipoma is hyperintense on this Tl-weighted MR image.

of patients) , dysgenesis of the corpus callosum (wo% of patients; agenesis in 72% and hypoplasia in 28%), infantile spasms, cerebral cortical heterotopias (s o%) , cortical dys­ plasia, and costovertebral defects (39%) . The callosal anom­ aly in these patients frequently includes interhemispheric cysts. Other potential neuroimaging findings in patients with Aicardi syndrome include cerebellar hypoplasia, cho­ roid plexus papilloma, posterior fossa cyst, microphthal­ mia, and polyrnicrogyria .72-'74

volume. The usual clinical definition is an occipital-frontal head circumference that is greater than 2 standard devia­ tions below the normal mean adjusted for age and gender. Some clinicians use a cutoff measurement of 3 standard deviations. The most common causes of microcephaly are severe postnatal brain destruction, metabolic brain disease, and neurosurgical procedures that substantially diminish the volume of brain or ventricular fluid. Various forms of brain hypoplasia can also lead to congenital microcephaly. Potential mechanisms for brain hypoplasia include mater­ nal alcoholism, fetal irradiation, intrauterine infection, maternal undernutrition, and various chromosomal disor­ ders (Table 14-4) . There are hundreds of genetic disorders that can cause microcephaly.7 6 m Primary microcephaly includes conditions in which fail­ ure of brain development is caused by a genetic abnormal­ ity. Secondary microcephaly indicates the involvement of an extrinsic insult that interferes with brain development or causes brain damage. Microcephaly that occurs in utero can be primary or secondary. The term isolated microcephaly indicates a lack of associated anomalies. These classifica­ tion schemes are imprecise, and not all children have find­ ings that allow accurate differentiation between primary versus secondary mechanisms.

Table 1 4-4. Causes of M icrocephaly: Partial List

Acq u ired

Hereditary Spastic Paraplegia with Thin Corpus Callosum Hereditary spastic paraplegia comprises a clinically and genetically heterogeneous group of neurodegenerative dis­ orders. A subtype of autosomal recessive hereditary spastic paraplegia is associated with thinning of the corpus callo­ sum. The thinning apparently represents atrophy rather than hypoplasia. The major clinical features include progressive spastic paraplegia, dementia, muscle rigidity, and cerebellar ataxia. The clinical onset is usually during the second decade of life. MR shows a thin, but otherwise intact, corpus cal­ losum. Thinning is most prominent in the anterior portion. White matter signal abnormality may also be present. 75

DISORDERS OF NEURONAL PROLIFERATION AND D l FFERENTIAT ION

M icrocephaly Microcephaly is a nonspecific term for an abnormally small head. Microencephaly refers to subnormal brain

Genetic

Hypoxic-ischemic encephalopathy Status post shunting of hyd rocephalus . I ntrauterine infection Fetal teratogen exposure (e.g., alcohol) · M aternal phenylketonuria · Poorly control led maternal diabetes Fetal irradiation Autosomal recessive m icrocephaly M icrocephaly with s i m pl ified gyral pattern Autosomal domi nant m icrocephaly . X-l i n ked microcephaly · Trisomies 1 3, 1 8, 21 4P Deletion syndrome · Wil l iams syndrome Lissencephaly de Lange syndrome . .Cornelia . . . S m ith-Lemli-Opitz syndrome Lym phedema, m icrocephaly, chorioretinopathy syndrome ...

. . . ...... . ........... ... ....... ..........

... . .

.

516 Part 3 The B r a i n Autosomal recessive primary microcephaly is a spec­

trum of disorders in which there is subnormal size of the C N S , particularly the cerebral cortex. In some of these

patients, the brain architecture is normal aside from being small. Others , including those described below with a simplified gyral pattern, have focal or generalized brain anomalies. The phenotype includes a receding forehead and a normal-size face. The responsible genes appar­ ently regulate mitosis of progenitor cells in the neuroepi­ thelium that lines the cerebral ventricles. There are also rare autosomal dominant and microcephaly.78,7 9

X-linked forms of primary

of brain pathology. The pathogenesis may involve over­ production of neurons because of a derangement in neu­ ral proliferation. Megalencephaly occurs as a primary isolated

condition

(idiopathic

anatomic

megalenceph­

aly) , a primary developmental lesion in association with another disorder, or as a secondary phenomenon caused by a metabolic disorder. The isolated form can occur as a familial or sporadic lesion. Primary megalencephaly can syndrome, achondroplasia, neurocutaneous syndromes , and various endocrine disorders . Metabolic disorders that can cause secondary megalencephaly include leukodys­

Microcephaly with simplified gyral pattern (oligogyric microcephaly) refers to a spectrum of genetic brain anoma­ lies in which the gyri are shallow and diminished in num­ ber and there is substantial microcephaly. The thickened cortex of lissencephaly is lacking. The pathophysiology apparently involves subnormal neuronal and glial pro­ liferation in the germinal zones and increased apoptosis (programed cell death) . Tertiary sulci fail to form. There is thinning of the cerebral white matter. Severe forms may lead to neonatal death; survivors have developmental delay, intellectual disability, and neurological deficits . Seizures are common.8 0-82 B arkovich and others divide microcephaly with simpli­

6 groups according to the clinical and neuroimaging features . Group 1 infants are the prod­

fied gyral pattern into

ucts of normal pregnancies and have uneventful deliveries .

MR demonstrates microcephaly, a paucity of gyri, shallow sulci, normal cortical thickness, and normal myelination.

2 often have a history of a breech presenta­

tion, develop seizures during the first few days of life, and exhibit limb spasticity and abnormal reflexes as neonates . M R shows a paucity o f gyri, shallow sulci, delayed myelina­ tion, and preserved cerebral cortical thickness . Group 3 con­ sists of term infants who exhibit spasticity, seizures , and lack of normal reflexes . The abnormalities of the gyri and sulci are more pronounced than in the group

2

Megalencephaly refers t o abnormal enlargement o f the entire brain in association with clinical manifestations

be a feature of Beckwith-Wiedemann syndrome, Sotos

M icrocephaly with Simplified Gyral Pattern

Infants in group

M egalencephaly

1

trophies, mucopolysaccharidoses, sphingolipidoses, and gangliosidoses.83-8 5 Megalencephaly typically leads to macrocephaly; that is, an occipitofrontal head circumference greater than the 98th percentile. However, most children with macro­ cephaly do not have megalencephaly. Other causes of head enlargement include hydrocephalus, extraaxial fluid collec­ tions, neoplasm, and calvarial thickening. Macrocephaly is a component of the

capillary malformation syndrome

macrocephaly­

(macrocephaly-cutis mar­

morata telangiectasia congenita) . Cranial prominence in these children is usually a result of brain overgrowth as well as hydrocephalus . The megalencephaly is sometimes asymmetric. Inferior herniation of the cerebellar tonsils occurs in approximately

70% of children with this syn­

drome, apparently because of progressive enlargement of the cerebellum. There is delay in white matter myelination. Focal cortical dysplasia and polyrnicrogyria are common. The typical locations of polyrnicrogyria in children with macrocephaly-capillary malformation syndrome are the perisylvian and insular regions

(Figure 14-42) .

The corpus

callosum often has a thickened character. Other findings of this syndrome include somatic overgrowth, hemihyperpla­ sia, extensive cutaneous capillary malformation, polydac­ tyly, syndactyly, and frontal bossing.8 6 ,87

and group

patients . Additional potential neuroimaging findings

include subependymal heterotopias and arachnoid cysts .

Hemi megalencephaly

4 have clinically obvious abnormalities as

Hemimegalencephaly refers to hamartomatous overgrowth

neonates : abnormal reflexes, seizures , nystagmus, thumb

of one cerebral hemisphere or some of its lobes . The histo­

deformities , and hypertonia. The M R appearance is identi­

pathological features include immature-appearing neurons,

5 and group 6 have lissencephaly. Clinical findings in group 5 include severe

architecture, as well as marrifestations of incomplete cellu­

microcephaly,

lar maturation. The involved hemisphere is hypertrophied

Infants in group

cal to that of group

1.

Infants in group

hypotonia,

abnormal

reflexes,

seizures ,

astrogliosis, and balloon cells. There is disorganized tissue

and severe developmental delay. M R shows prominent

and dysplastic, and contains areas of polymicrogyria, gray

subarachnoid spaces , severe microencephaly, markedly

matter heterotopia, pachygyria, and white matter gliosis.

deficient gyral formation, deficient white matter, and corti­

The anomaly can be focal, lobar, or hemispheric; bilateral

cal thinning. There is severe neurological impairment of

cerebral megalencephaly is quite rare. The pathophysiology

in group 6. MR shows agyria and cortical thicken­

of hemimegalencephaly apparently involves aberrant cell

ing; agenesis of the corpus callosum and cerebellar hypo­

proliferation; a secondary disturbance of neuronal migra­

plasia are common.

tion during the first trimester contributes to the disorderly

infants

Chapter

14

Congenital Abnorm a l ities of the B ra i n

517

8

A

Figure 14-42 M acrocephaly-capillary malformation syndrome.

c

A. A sagittal T1-weighted image at 2 months of age shows a prominent head size relative to the face. There is mild inferior herniation of the cerebellar tonsils. B. Craniofacial disproportion is more pronounced at age 4 years. The tonsillar herniation has increased. The corpus callosum is thick. C. An axial T2-weighted image shows ventriculomegaly and bilateral insular polyrnicrogyria.

tissue architecture. Hemimegalencephaly likely represents a spectrum of disorders that lead to similar pathophysiolog­ ical changes in the brain. Involvement of the right cerebral hemisphere is more common than the left.88-9 o Common clinical manifestations of hemimegalen­ cephaly consist of the triad of contralateral hemipare­ sis, psychomotor retardation, and intractable seizures that develop soon after birth. Most often, there is clini­ cally evident macrocephaly during infancy. In some patients, there is ipsilateral hemihypertrophy of all or a portion of the body. Slightly less than half of patients

with hemimegalencephaly have an associated syndrome. Hemimegalencephaly is common in patients with epider­ mal nevus syndrome. Other associated syndromes include tuberous sclerosis, Proteus syndrome, neurofibromatosis type 1, congenital infection (Cytomegalovirus, toxoplas­ mosis) , hypomelanosis of Ito, Klippel-Trenaunay-Weber syndrome, and encephalocraniocutaneous lipomatosis. Individuals with idiopathic hemihyperplasia sometimes have craniofacial and brain asymmetry. 9 ' ·9 2 M RI or CT imaging of hemimegalencephaly demon­ strates enlargement ofall or a large portion one hemisphere.

518 Part 3 The B r a i n

A

B

Figure 14-43 Hemimegalencephaly. A, B, C. CT demonstrates an enlarged and dysplastic right cerebral hemisphere. The ipsilateral cortical gray matter is thick, there is deficient sulcus formation, and there is prominent white matter.

The contralateral hemisphere is usually somewhat smaller than normal; that is, contralateral hemimicrencephaly. In most patients, there is proportionate enlargement of the ipsilateral lateral ventricle. The frontal hom usually has a thin irregular character, and tapers superiorly and ante­ riorly. The appearance of the ipsilateral cortex is variable.

c

Most often, the cortex is grossly dysplastic, with cortical thickening and deficient sulci ( Figure 14-43) . There may be enlarged and irregular deep gray matter and white matter structures. The border between the cortex and the subja­ cent white matter is usually indistinct or obliterated. The deeper white matter may be heterogeneously hyperintense

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 519

A

Figure 14-44 Hemimegalencephaly.

A, B. Axial T2-weighted MR images show global enlargement of the left cerebral hemisphere. The ipsilateral gyri are broad. There

on T2-weighted MR images and hypoattenuating on CT; this is due to gliosis, neuronal dysplasia, and heterotopia ( Figure 14-44) . Occasionally, there is enlargement ofthe ipsi­ lateral cerebellar hemisphere and brainstem. Other poten­ tial findings include ipsilateral olfactory nerve enlargement and cerebral vascular dilation. Fluorodeoxyglucose positron emission tomography imaging indicates glucose hypome­ tabolism in the ipsilateral hemisphere. Proton MR spec­ troscopy demonstrates diminished glutamate and N-acetyl aspartate (NAA) peaks.9 J-98

DISORDERS OF HISTOGENESIS

General Considerations The neurophakomatoses (also termed phakomatoses or neu­ rocutaneous syndromes) comprise a clinically heterogeneous group of congenital disorders that have the common patho­ physiological mechanism of anomalous development of neuroectodermal derivatives (Table 14-5) . There is variable involvement of the nervous system, skin, and eyes. Visceral organs can also be involved. The most clinically important phakomatoses are neurofibromatosis type 1, neurofibroma­ tosis type 2, tuberous sclerosis, Sturge-Weber syndrome, von Hippel-Lindau syndrome, and ataxia-telangiectasia. The most common phakomatosis is neurofibromatosis typ e 1. 99 ,100

B

are areas of white matter hyperintensity. The left lateral ventricle is mildly enlarged.

Neu rofibromatosis Type

1

Neurofibromatosis type 1 (NF-1) is a multisystem disorder that predominantly results in CNS lesions, skin lesions , and focal areas of mesodermal dysplasia. The hallmark lesion of this disorder is the peripheral neurofibroma. N F-1 is an autosomal dominant genetic disorder that is caused by a mutation of chromosome 17. The penetrance is high, but the expressivity is variable. Approximately half of cases are a result of new mutations. The N F-1 tumor-suppressor gene encodes the protein neurofibromin. Among other functions, such as tumor suppression, this protein is apparently required for normal myelination by Schwarm cells. The prevalence of NF-1 is 1 in 3000 individuals . 99·101 Neurofibromatosis type 1 has great variability in clini­ cal expression. Some patients have very mild manifesta­ tions, whereas others are severely affected. At least 95% of N F-1 patients have cutaneous involvement. The characteris­ tic skin lesions of neurofibromatosis type 1 include cafe-au­ lait spots (with smooth outlines) , freckling, and cutaneous neurofibromas. The cafe-au-lait spots are usually detectable during the first year of life. Cutaneous neurofibromas and iris Lisch nodules most often become evident during the second and third decades of life. Children with NF-1 have 200 to 500 times the normal risk of developing leukemia compared to the general population. Table 14-6 outlines the diagnostic criteria for NF-1. 102

520 Part 3 The B ra i n Table 1 4-5. The Neurophakomatoses

Neurofibromatosis type 1 Neurofibromatosis type 2 Tuberous sclerosis - Stu rge-Weber synd rome von H ippei-Lindau disease

Neurofibromas, optic glioma, focal skeletal dysplasia Schwan nomas (acoustic neu romas) Hamartomatous lesions in m u ltiple organ systems Angiomatosis ofthe leptomeni nges, face, and choroid of the eyes Reti nal angiomas, CNS hemangioblastoma, cysts/neoplasms of abdominal organs, epididymal cystadenomas M ucocutaneous and ocu lar telangiectasias, cerebellar atrophy Cutaneous pigmented nevi, deposits of melanin i n the leptomeni nges and brain Epidermal nevi, dysplasiasfdeform ities of the CNS, eyes, skin, skeleton, and heart Skin eruptions, retinal vascular lesions, dental anomalies, mu ltifocaljdiffuse brain atrophy Skin lesions, m usculoskeletal deform ities, ± brain anomal ies Abnormal pigmentation of skin and hair, i m munodeficiency, brain atrophy, wh ite matter lesions Posterior fossa malformations, hemangiomas, arterial anomal ies, ca rd iac anomalies, aortic coarctation, eye abnormalities, sternal cleft or su prapubic raphe

--- ·

----

-

-------

-

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-----·-- - - --- - - --...

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-

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- --- - -------- - --- - -- - - -- -- - --

-- - - -

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-- - -

Ataxia-telangiectasia Neurocutaneous melanosis Epidermal nevus syndrome l ncontinentia pigmenti Hypomelanosis of Ito Chediak- H igashi syndrome

· - - - - · · - - - · - - - - - - · · - - - · · - - - - -- - - · - · - - · - - - · - · · - · · - · - - - - · · - - · · - - · · - - - · · - · · · · - - · · - · - - - - - - - - - - - - - - --

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PHACES syndrome

Clinical andjor diagnostic imaging manifestations of CNS involvement are present in most patients (Table 14-7) . Approximately 5 o % o f children with N F-1 have learning disabilities. Other potential CNS manifestations include headaches, seizures, deafness, macrocephaly, visual impairment, and stroke. Neuroimaging evidence of CNS involvement is present in approximately 20% of patients; the potential abnormalities include optic pathway glioma, brainstem glioma, hydrocephalus, and focal areas of non­ neoplastic glial dysplasia. Patients with N F-1 have a slightly elevated risk for gliomas of the cerebellar hemispheres and cerebrum. Most intracranial neoplasms in these patients are low-grade pilocytic astrocytomas. Macrocephaly is

common in patients with N F-1; some of these individu­ als have hydrocephalus or increased cerebral white mat· ter volume and an enlarged corpus callosum. Vascular dysplasia (present in approximately 2.5% of children with

Table 14-7. Central Nervous System Manifestations of N F-1

Dysplastic wh ite matter lesions Dysplastic central gray matter lesions Optic pathway glioma Astrocytoma (brai nstem, tectum, cerebel l u m) Plexiform neurofibroma (orbit, skull base) Dural ectasia (optic sheath, internal auditory canal) Vascu lar stenosis Cerebral aneu rysm Sphenoid wing dysplasia M acrocephaly Aqueductal stenosis Scoliosis Posterior vertebral body scalloping - - - - - - - - - - Spinal nerve sheath tumors (neurofibroma) Spinal d u ral dysplasia Meni ngocele Spinal cord astrocytoma

- ----

Table 1 4-6. M ajor Diagnostic Criteria for N F-1°

�6 Cafe-au-lait spots; �o. s em i n a prepu bertal child or �1 .5 em i n a postpu bertal i ndivid ual Axillary or inguinal freckling �2 Cutaneous neu rofibromas �1 Plexiform neu rofibroma �2 Lisch nod ules Optic glioma A characteristic s keletal lesion (pseudarth rosis, sphenoid wing hypoplasia, severe kyphoscoliosis) Fi rst-degree rel ative with N F-1 'At least 2 of t h e s e c r i t e r i a a re req u i red fo r d i agnos i s .

-

-- -

-

- - - - - - - - - - - - - -- -- -- -- --- - ---------

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- - - · - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - · -----

--------

-

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Chapter 14 Co ngenital Abnorm a l ities of the B ra i n 521 NF-1) can result in cerebrovascular stenosis or aneurysm. Orbital abnormalities that can occur in patients with NF-1 include plexiform neurofibroma, optic nerve glioma, sphe­ noid wing dysplasia, buphthalmos, retinal phakomas, and Lisch nodules. The presence of bilateral optic gliomas is pathognomonic of NF-1. Skeletal system abnormalities are common. In the skull, sphenoid wing dysplasia is the most frequent finding.102•103 Small foci of high signal intensity on T2-weighted and fluid-attenuated inversion recovery ( F LAIR) images within the brain are common on MR studies of children with N F-1 (Figure 14-45) . Terms applied to these lesions include neurofibromatosis bright obj ects , focal areas of signal intensity, hamartomas , and myelin vacuolization. These are most often located in the brainstem (pons) , internal capsules, cerebellar white matter, and splenium of the corpus callosum. These white matter lesions do not enhance with contrast and have little or no mass effect. They are usually not visible on TI-weighted images, but occasionally appear hyperintense or hypointense on these sequences. Typically, these lesions begin to appear

at approximately 3 years of age and tend to diminish in size after approximately 10 years of age. The pathogen­ esis likely involves a focal myelin dysplasia related to defi­ ciency of neurofibromin. Histological evaluation of these lesions on autopsy series shows myelin vacuolization. There is an increase of apparent diffusion coefficients on diffusion-weighted images. Proton spectroscopy can help in the differentiation between these nonneoplastic lesions and gliomas in patients with NF-1. Typically, a glioma results in elevation of choline and myoinositol, as well as markedly diminished NAA. The benign white matter lesions usually have elevated choline, diminished creatine, and normal NAA. 104-w 6 In addition to the typical white matter lesions described above, children with NF-1 sometimes have non­ neoplastic central gray matter abnormalities on MR. Most common, are foci within the globi pallidi that are hyper­ intense on T2-weighted images and slightly hyperintense on T1-weighted images (Figure 1 4-46) . The lesions are usually bilateral. Contrast enhancement is usually identi­ cal to that of adjacent brain. Proton spectroscopy of the

Figure 14-45 Neurofibromatosis type 1; white matter lesions.

Figure 14-46 Neurofibromatosis type 1; globus pallidus lesions.

There are multiple hyperintense foci in the cerebellar white matter and pons on this T2-weighted image of a 7-year-old child with NF-1.

There is bilateral globus pallidus hyperintensity on this FLAIR image of a 10-year-old child with N F-1. There is no appreciable mass effect.

522

Part 3 The B ra i n

thalami and basal ganglia i s abnormal i n most patients with these lesions. In young children, the predominant finding is elevation of choline and normal NAA, whereas teenagers and adults may have normal choline and reduced NAA. 107 · 10 8 The vascular dysplasia of NF-1 predominantly consists of intimal proliferation that leads to stenosis of a large or medium-sized artery. In the head and neck region, the carotid arteries and proximal aspects of the cerebral arter­ ies are the most commonly involved vessels. There is usu­ ally slow progression of the stenosis, thereby allowing collateralization. There are occasional patients with a cere­ bral aneurysm or arteriovenous fistula. The potential clini­ cal manifestations of vascular dysplasia include paralysis, headaches, seizures, and intellectual impairment. Because the process typically involves medium and large vessels, CT angiography or M R angiography is usually sufficient for the diagnostic evaluation (Figure 14-47) . A moyamoya pattern, with dilated lenticulostriate arteries, is common in these patients.'0 9·110 Optic pathway glioma is the most common CNS tumor in patients with NF-1, with a prevalence of approxi­ mately 15%. Most are low-grade lesions that arise in the optic nerves and produce only mild symptoms such as visual impairment. Gliomas of the optic chiasm or optic tracts carry a more guarded prognosis. Involvement of the optic chiasm and hypothalamus can cause precocious puberty. Extension of an optic pathway glioma beyond the lateral geniculate bodies into the optic radiations is a rare occurrence that indicates a biologically aggressive lesion. T1-weighted M R images of children with suspected optic pathway glioma best demonstrate the morphology of the optic nerves, chiasm, and optic tracts. These lesions produce a variable degree of hyperintensity on FLAI R images. Aggressive lesions, with extension into the brain via the hypothalamus or optic radiations, are hyperintense on FLAIR and T2-weighted images, and usually enhance intensely. In addition to tumors of the optic pathway, patients with NF-1 have a moderately increased propensity for CNS gliomas at other sites (Figure 14-48) . Juvenile pilocytic astrocytomas are most common. Although any site in the neuraxis can be involved, the brainstem is particularly com­ mon. Most brainstem gliomas in children with NF-1 arise in the medulla or mesencephalon. These are usually biologi­ cally low-grade tumors. A glioma of the tectum can cause hydrocephalus. Most gliomas are moderately hyperintense on T2-weighted images and undergo a variable degree of contrast enhancement.m

Neu rofibromatosis Type 2 Neurofibromatosis type 2 (NF-2) is an autosomal domi­ nant phacomatosis that is clinically and genetically distinct from N F-1. The major features are acoustic neu­ romas (usually bilateral) , schwannomas of other cra­ nial nerves, meningiomas, spinal neurofibromas, and

A

B

Figure 14-47 Neurofibromatosis type 1 ; vascular dysplasia.

A An anterior time-of-flight MR angiography image of a

10-year-old boy shows absence of flow in the left internal carotid artery. The left middle cerebral artery fills by retrograde collateral flow via the At segment of the left anterior cerebral artery. B. This child also has a large orbitaljfacial plexiform neurofibroma.

ependymomas. The cause of this disorder is a mutation in the NF2 gene on chromosome 2 2 , which encodes neu­ rofibroin-2 ; other terms for this enzyme are merlin and schwannomin. Neurofibroin-2 is apparently involved in cellular interactions with structures in the extracellular matrix. The estimated prevalence of NF-2 is 1 per s o , o o o individuals. 99 ·112

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 523 Table 14-8. Diagnostic Criteria for Neu rofibromatosis-2

Bilateral vestibular schwan nomas, or U nilateral vesti bular A first-degree relative with N F-2, and schwannoma before the . age of 30 years, or Any 2 of: meni ngioma, glioma, schwannoma, juvenile posterior subcapsu lar lenticular opacity

before 10 years of age. In families with a history of early onset NF-2, a normal cranial MR in the late teen years indi­ cates a decreased likelihood for the eventual development of the clinical manifestations of NF-2. A normal MR at 30 years of age makes the diagnosis of NF-2 unlikely, except in families with a history oflate-onset disease. Annual cranial MR is useful as a screening tool for patients with known N F-2. Both schwarmomas and meningiomas enhance intensely with intravenous contrast (Figure 14-49) . 114

Figure 14-48 Neurofibromatosis type 1 ; ganglioglioma. MRI of this 12-year-old girl was performed for routine followup of an optic nerve glioma that was diagnosed at age 4 years. There is a round mass in the mesial aspect of the left cerebral hemisphere that is hyperintense on this FLAIR image. Perilesional edema is present. Histological evaluation indicated a ganglioglioma.

Table 14-8 shows the updated National Institutes of Health Consensus Development Conference criteria for the diagnosis of NF-2."3 At least 95% of individuals with NF-2 eventually develop acoustic neuromas (vestibular schwannomas), many by adolescence. The lesions are often bilateral. Schwannomas can also arise in other cranial nerves and spinal nerves; there is a predilection for the sen­ sory nerves and roots. Cutaneous schwannomas in these patients most often develop during the first decade of life. Cranial nerve schwannomas tend to arise during the sec­ ond decade or later. Patients with NF-2 also have a predis­ position for neoplastic and dysplastic glial lesions, although gliomas are less common than schwarmomas and menin­ giomas. Approximately 8o% of gliomas in these patients are intramedullary spinal or cauda equina lesions and 10% involve the medulla; most of these tumors are ependymo­ mas. Retinal hamartomas and epiretinal membranes occur in 9% to 22% of patients with NF-2. Peripheral tumors in NF-2 are usually schwannomas.U3 ·1'4 Although NF-2 is a genetic disorder, the diagnosis is not established until adulthood in more than 8o% of patients. Only 10% of patients with NF-2 become symptomatic

Figure 14-49 Neurofibromatosis type 2. There are intensely enhancing bilateral vestibular schwannomas ( upper arrows) on this contrast-enhanced T1-weighted coronal image of a child with NF-2. The lesions fill the internal auditory canals and extend into the cerebellopontine angle cisterns. There is an additional schwannoma adjacent to the superior aspect of the medulla (lower arrow) .

524 Part 3 The B ra i n

Neu rofibromatosis Type 3 Neurofibromatosis type 3 (NF-3) shares some features of N F-1 and NF-2, and is sometimes termed as a mixed cen­ tral and peripheral type. This disorder may, in fact, repre­ sent a variation of NF-1. Cafe-au-lait spots, freckling, and cutaneous neurofibromas occur as in classical NF-1, but the skin lesions are usually few in number. Optic gliomas do not occur. The predominant CNS manifestations of N F-3 include bilateral acoustic neuromas, meningiomas of the posterior fossa or cervical spine, and spinal or paraspinal neurofibromas. Most patients with N F-3 develop symp­ tomatic tumors during the second or third decades of life. Unlike typical N F-1 and NF-2, patients with NF-3 frequently suffer rapid deterioration related to the presence of mul­ tiple CNS neoplasms.U5

Tu berous Sclerosis Tuberous sclerosis complex is an autosomal dominant neu­ rocutaneous disorder with variable expression. There is widespread occurrence ofhamartomatous lesions in multi­ ple organ systems. CNS involvement is universal, although symptom severity is quite variable. The major brain lesions in these patients include subependymal hamartomas, parenchymal hamartomas (cortical and subcortical tubers) , white matter lesions, and subependymal giant-cell astrocy­ tomas. There are two causative genes for tuberous sclerosis: TSC1 on chromosome band 9q}4 and TSC2 on chromo­ some band 16p13 .3. These genes encode for hamartin and tuberin, which are tumor-suppressor proteins and may par­ ticipate in the regulation of cell proliferation and differen­ tiation. These mutations are lacking in approximately 15% of patients with tuberous sclerosis; these individuals usu­ ally have milder neurological involvement. The estimated prevalence of tuberous sclerosis is 1 in 6ooo to w,ooo live­ births. Approximately 75% of cases are sporadic.u6-n9 Tuberous sclerosis is a disorder of cell migration, prolif­ eration, and differentiation. The abnormal neuroepithelial cells in patients with tuberous sclerosis are part of an abnor­ mal cellular line of neuroblasts that often fail to undergo clear neuronal or glial differentiation. Incomplete or dis­ ordered migration of dysgenetic neuroastrocytes during brain development results in islets of heterotopic dysplastic cells that have histological characteristics of both neurons and glial cells. More differentiated cells tend to migrate to the cortical plate, where they comprise clusters of dysplas­ tic cortex; that is, "tubers." These cortical and subcortical tubers consist of a heterogenous population of giant cells, cells with both glial and neuronal characteristics, and primi­ tive poorly differentiated cells. The histological features are similar to those of focal cortical dysplasia. The myelin sheaths in these lesions are deficient and disordered. There is also a fibrillary gliotic reaction in the subcortical tubers. Other dysplastic cells fail to migrate from the sub­ ependymal regions, where they form subependymal hamartomas and subependymal giant cell astrocytomas. Subependymal giant cell astrocytoma (giant cell tumor) differs clinically and radiographically from subependymal

hamartoma by a larger size, a more rapid growth pattern, and the potential for obstructive hydrocephalus. However, these two lesions are histologically indistinguishable. Degeneration into a higher-grade neoplasm is rare. The third site of dysplastic cells in patients with tuberous scle­ rosis is along curvilineal tracts in the cerebral white matter; that is, "migration tracts."'20·'2' Epilepsy is the most common neurological feature of tuberous sclerosis, occurring in approximately 8o% of patients. Infantile spasms occur in 20% to 30% of patients. Electroencephalography may demonstrate hypsarrhythmia (abnormal interictal high amplitude waves and a back­ ground of irregular spikes) . At the time of clinical onset, partial motor seizures are common. Subtle partial seizures may be present in the early neonatal period and sometimes precede the onset ofinfantile spasms. Seizures in older chil­ dren are frequently severe and intractable. Approximately 45% of patients with tuberous sclerosis have intellectual disability. The severity of the neurological symptoms cor­ relates with the number and location of parenchymal ham­ artomas on imaging studies. Subependymal hamartomas are generally asymptomatic.'22-'24 Tuberous sclerosis is a multiorgan system disorder (Table 14-9) . Cutaneous lesions such as shagreen patches, hypomelanotic macules, and facial angiofibroma are readily

Table 1 4-g. Spectru m of Pathology in Tuberous Sclerosis O rga n system

F i n d i ngs

Neurological

Cortical tu bers S u bependymal hamartomas Su bcortical glioneuronal hamartomas S u bependymal giant cell astrocytoma Chordoma Angiomyolipoma Renal cysts Retinal hamartoma Rhabdomyoma (infancy) Hypomelanotic macules (infancyfearly childhood) Shagreen patches Facial angiofibromas (late childhood) U ngual fibroma (after puberty) Lym phangiomyomatosis (adu lts) Hepatomegaly Angiomyolipoma - ----- ·

Renal Ocu lar Cardiac Cutaneous

Pulmonary Hepatobiliary

I

-----

I

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 525 diagnosed with clinical evaluation. Diagnostic imaging evaluations are important for the detection of other non­ CNS lesions such as renal cysts, renal angiomyolipomas, and cardiac rhabdomyomas. There are rare instances of vascular dysplasias, particularly intracranial aneurysms, occurring in association with tuberous sclerosis. There are several case reports of chordomas occurring in patients with tuberous sclerosis."9 ·'2 5 Subependymal hamartomas are visible on neuroimag­ ing studies in essentially all children with tuberous scle­ rosis. Calcifications are frequently present within the nodules on CT evaluation. The degree of calcification tends to increase somewhat during childhood, and the lesions are usually more conspicuous in older children (Figure 14-50) . In the myelinated brain, subependymal nodules are approximately isointense to white matter on T1-weighted MR images. They appear as small, somewhat irregular, oval or round masses projecting into the lateral ventricles. Densely calcified nodules are hypointense on T2-weighted images. There is a variable degree of contrast enhancement of most subependymal hamartomas on CT and MR.'2 6 ·'27 In the myelinated brain, parenchymal hamartomas (subcortical tubers) are isoattenuating-to-slightly hypoat­ tenuating relative to adjacent normal brain on CT (Figu re 14-51 ) . Calcifications are common, however. With MRI, parenchymal hamartomas are slightly hypointense on Tl-weighted images and variably hyperintense to myelin­ ated brain on T2-weighted images. FLAI R sequences pro­ vide improved contrast between the lesions and adjacent myelinated white matter in older children and adults. Most tubers are subcortical; the signal intensity in the adjacent cortical gray matter is normal ( Figure 14-52) . The interface between the tuber and the subjacent cerebral white mat­ ter is ill defined. Tubers with microscopic calcification are sometimes hyperintense on T1-weighted images. There is a variable degree of contrast enhancement. The MR spec­ troscopy features include slightly diminished NAA, normal to slightly elevated choline, and increased myo-inositol. The number of cortical tubers is quite variable between patients, ranging from a single lesion to 25 or 3 0 . Cerebellar tubers occur in approximately 10% of patients. The M R signal characteristics of the white matter lesions of tuberous sclerosis are identical to those of cor­ tical tubers (Figure 1 4-53) . The lesions are usually most conspicuous on F LAIR sequences. There are four distinct morphological patterns : (1) straight or curvilinear bands extending radially from the ventricle through the cere­ bral mantle toward the cortex, (2) wedge-shaped lesions, (3) nonspecific conglomerate foci, and (4) cerebellar radial bands. Dystrophic calcifications of sufficient size are hypointense on MR images ( Figure 14-54) . Diffusion­ weighted imaging sometimes shows signal abnormality (increased apparent diffusion coefficient) in the white matter of patients with tuberous sclerosis despite normal findings on conventional MR images. On CT, the white matter lesions of tuberous sclerosis are nonenhancing low-attenuation foci or bands that sometimes contain calcification. 1 2 8-'3 °

Subependymal giant cell astrocytoma appears on imaging studies as a large contrast-enhancing subependymal nod­ ule, often adjacent to the foramen of Monro ( Figure 14-55) . A size o f equal t o o r greater than 10 m m i s a reasonable, although somewhat arbitrary, threshold for the diagno­ sis. However, a nodule of any size that causes ventricular obstruction is considered to be a giant cell tumor. The rate of growfu of subependymal giant cell tumors varies sub­ stantially between patients, ranging from 1 mm per year to 1 mm per month. The typical location is near the foramen of Monro. Weak differentiating signs between giant cell tumor and subependymal hamartoma are a greater degree of contrast enhancement and incomplete calcification in the former. Imaging manifestations of tuberous sclerosis are usually present even in young infants with this disorder. Subependymal hamartomas appear on sonography as small echogenic foci projecting into the lateral ventricles. Cortical tubers are also echogenic relative to normal brain. In infants, subependymal hamartomas often lack calcifica­ tion, and therefore are difficult to detect with CT. Cortical and subcortical tubers in the infantile brain appear on CT as hypoattenuating areas within widened gyri. Subependymal hamartomas, cortical tubers, subcortical tubers, and linear white matter lesions in infants younger than 3 months old are hyperintense relative to adjacent brain on T1-weighted images and hypointense on T2-weighted images; this is opposite to the signal intensity pattern that occurs in older patients (Figure 14-56) . The lack of peripheral myelination in young infants increases the conspicuity of white matter lesions on MR and CT; these tend to become less apparent as myelination progresses. However, purely intracortical tubers are more difficult to detect in infants than in older children. Brain abnormalities are sometimes demonstrable with neuroimaging studies in the fetus with tuberous sclerosis. Sonography may show ventricular enlargement or defi­ cient gyral development. Sonographic abnormalities have been detected as early as 14 weeks gestation. Fetal MR may show hyperintense subependymal and cortical nodules on T1-weighted images. However, the prenatal imaging find­ ings are often not specific to the diagnosis of tuberous scle­ rosis , and the lack of prenatal brain abnormalities does not reliably exclude the diagnosis. When present, the identifi­ cation of cardiac rhabdomyomas is confirmatory.'3'-'33

Stu rge-Weber Synd rome Sturge-Weber syndrome (encephalotrigerninal angioma­ tosis) is an uncommon neurocutaneous syndrome that includes angiomatosis of the leptomeninges, face, and choroid of the eyes. The leptomeningeal vascular malfor­ mations of Sturge-Weber syndrome consist of simple vas­ cular structures situated along the space between the pia mater and the arachnoid membrane. The primary CNS defect in Sturge-Weber syndrome may occur early during lamination, when there is normally a connection between the developing cortical veins (cerebral circulation) and the superior sagittal sinus (dural and calvarial circulation) .

526 Part 3 The B ra i n

A

c

Figure 14-50 Tuberous sclerosis; CT findings in four different patients. A This 1-year-old infant has small faintly calcified subependymal hamartomas and multiple ill-defined hypoattenuating parenchymal hamartomas. B. There is a group of densely calcified subependymal nodules in this 4-year-old. C. There

B

D

are faint calcifications in subcortical tubers (arrow), as well as small calcified subependymal lesions. The skull is thickened in this 19-year-old patient who has been treated for seizures since infancy. D. Two subcortical tubers have large dense calcifications in this 14-year-old child. Typical subependymal hamartomas are also present.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 527 medullary and subependymal veins, and enlargement of the choroid plexus. The abnormalities are most often unilateral and ipsilateral to the cutaneous lesions. Calcifications are located in the cortex underlying the leptomeningeal vascular malformations, and are most common in the parietal and occipital lobes. The calcifications are usually gyriform and curvilinear. Occasionally, they are more extensive, with fron­ tal lobe or bilateral involvement. Calcifications are uncom­ mon prior to the age of 2 years. There are enlarged deep medullary and subependymal veins ipsilateral to the corti­ cal lesions. These are a result of slow flow or thrombosis in the superficial venous system and the resultant shunt­ ing of blood through deep medullary veins. Choroid plexus enlargement is common in the ipsilateral lateral ventricle. Potential ocular lesions in patients with Sturge-Weber syn­ drome include buphthalmos and scleral or choroidal venous angiomas. 138

Sturge-Weber Syndrome Path ology

Figure 14-51 Tuberous sclerosis; subcortical tubers. An unenhanced CT image of a 4-year-old child shows hypoattenuating lesions in the parietal lobes.

Failure of maintenance of this communication during the differentiation and separation of these 2 areas of circula­ tion leads to impairment of the venous outflow from the cerebral cortex. The poor venous drainage in turn causes metabolic insufficiency in the adjacent cerebral cortex. The cerebral cortex underlying the areas ofleptomeningeal vas­ cular malformation progressively becomes dysfunctional, atrophic, and calcified. Unlike other neurocutaneous syn­ dromes, there is no association between Sturge-Weber syn­ drome and intracranial neoplasia.'H-137 The major clinical features of Sturge-Weber syndrome include facial nevus flammeus (cutaneous capillary mal­ formation or port-wine stain) , seizures, and developmental delay. Some patients suffer hemiparesis and hemianopia. The facial nevus is most often unilateral and located in the midportion of the face; some patients with ocular or CNS manifestations of Sturge-Weber syndrome lack a facial nevus, however. Approximately 90% of patients develop infantile spasms during the first year of life. Subsequently, focal or generalized seizures occur. Epilepsy in these patients can be intractable. Spontaneous intracranial hem­ orrhage, usually subarachnoid, is a rare complication of Sturge-Weber syndrome. Most children with this disorder suffer compromised cognitive development. The prevalence of Sturge-Weber syndrome is at least 1 per so,ooo livebirths. There is no substantial gender or racial predilection. Characteristic pathological features of Sturge-Weber syndrome include cerebral atrophy, enlargement of the

U n i lateral cerebral atrophy

Rad iology

X-ray: u n i lateral skull : th icken ing ' M R, CT: u n i l ateral cerebral · volume loss Cerebral calcifications : Serpiginous cortical ' calcifications I m paired venous ' Enlarged med u l lary and outflow from cerebru m subependymal veins ' Enlarged choroid plexus Pial angiomatosis ' Leptomeni ngeal enhancement ·

The hallmark finding of Sturge-Weber syndrome on skull radiographs is the presence of serpiginous cortical calcifications; this is the "tram-track sign" ( Figure 14-57) . In adults and older children, secondary changes can occur in the skull overlying the involved cortex: a thickened diploic space, ipsilateral frontal sinus enlargement, and enlarge­ ment of mastoid air cells with elevated petrous ridges. On CT, the cortical calcifications of Sturge-Weber syndrome appear as gyriform, curvilinear, parallel densities. The cal­ cifications are located in areas of cortical atrophy. The most common sites of calcification are the parietooccipital cortex and the choroid plexus. Microcalcifications can lead to dif­ fuse high attenuation of superficial and deep white matter. Contrast-enhanced CT demonstrates enlarged deep med­ ullary and subependymal veins. There is often gyriform enhancement because of pial angiomatosis. With long­ standing disease, CT and radiography show ipsilateral cal­ varial thickening. 1 2 9·139

528 Part 3 The B ra i n

A

B

Figure 14-52 Tuberous sclerosis; subcortical tubers. A A T1-weighted image shows hypointense subcortical white matter lesions in the frontal lobes. There is an isointense giant cell astrocytoma adjacent to the right foramen of Monro. B. The lesions are hyperintense on this Tz-weighted image. The overlying cortical gray matter is normal. Additional smaller tubers are visible elsewhere in the brain. The astrocytoma has a slightly heterogeneous character. C. The tubers are hyperintense on this FLAIR image.

MR frequently shows more extensive abnormalities in patients with Sturge-Weber syndrome than does CT. The most characteristic finding is leptomeningeal enhance­ ment, which is apparently a result of leakage of contrast medium through the anomalous pial vessels. Enhancement is not universally present, however; the absence of this

c

characteristic finding does not preclude the diagnosis. The enlarged ipsilateral deep medullary and subependy­ mal veins also enhance with IV contrast (Figure 1 4-58) . Choroid plexus enlargement i s common i n the ipsilateral lateral ventricle (Figure 14-59) . Calcifications appear as areas of decreased signal intensity on proton-density and

Chapter

Figure 14-53 Tuberous sclerosis; white matter lesion. There is a region of heterogeneous hyperintense signal abnormality in the deep right parietal white matter on this T2-weighted image. Subcortical tubers are present in the temporal lobes bilaterally.

Tz-weighted MR images ; long echo time gradient-recalled images are most sensitive for the detection of calcification. With long-standing disease, local atrophy develops in the involved portion of the brain. Findings of Sturge-Weber syndrome on MR angi­ ography include a paucity of superficial cortical veins, diminished flow in the superior sagittal sinuses, and enlargement/tortuosity of the subependymal and medul­ lary veins. Perfusion MR demonstrates hypoperfusion of the cortex underlying the leptomeningeal angiomatosis. M R spectroscopy in the early phases of Sturge-Weber syn­ drome shows mild elevation of choline. With neuronal loss, there is decrease in N-acetyl aspartate in the affected portions of the brain. MR of the orbits may demonstrate enlargement of a globe because of buphthalmos ; other potential findings include choroidal detachment and sub­ acute ocular hemorrhage.1 00 ·14°-142 99mTc HMPAO (hexamethylpropylenearnine oxime) imaging is sometimes a useful supplement to CT and M R in Sturge-Weber syndrome when it i s clinically important to assess the full extent of the disease (e.g., prior to surgery) . This technique is sensitive for the detection of areas ofhypo­ perfusion, which represent ischemic regions that can act as epileptogenic foci and often appear normal on standard CT or MR images. The most common finding on perfu­ sion imaging consists of focal regions of decreased uptake.

14

Co ngenital A b n o r m a l ities of the B ra i n

529

Figure 14-54 Tuberous sclerosis; white matter lesions. There are multiple hypointense cerebral white matter calcifications on this FLAIR image of an n-year-old child. Irregular foci of white matter hyperintensity are present as well. There is a hyperintense subcortical tuber in the left temporal lobe.

Figure 14-55 Tuberous sclerosis; subependymal giant cel l astrocytoma. There is an intensely enhancing subependymal mass (arrow) projecting into the left lateral ventricle on this coronal MR image obtained with IV gadolinium. The lesion obstructs the foramen of Monro, resulting in mild unilateral hydrocephalus. There are multiple hypointense cortical tubers (small arrows) .

530 Part 3 The B ra i n

A

c

Figure 14-56 Tuberous sclerosis; M R manifestations in a 2-day­ old infant. A. There are subependyrnal hamartomas that are hyperintense on this T1-weighted image. Small white matter lesions are

Occasionally, there is widespread decrease in perfusion without focal defects. Dynamic MR perfusion imaging is an alternative technique for demonstrating areas ofbrain hypo­ perfusion. The pattern typically is that of impaired venous drainage, with diminished arterial perfusion occurring latter in the disease process. Glucose hypometabolism in affected portions of the brain can be defined with fluorodeoxyglu­ cose positron emission tomography (FDG-PET) .143-148

8

D

present in the frontal lobes. B. The subependyrnal lesions are hypointense on this T2-weighted sequence. C, D. T1-weighted images show hyperintense subcortical tubers (arrows), as well as multiple linear and punctate white matter lesions.

von H ippei- Li ndau Disease von Hippel-Lindau disease is an autosomal dominant phakomatosis that leads to retinal angiomas, hemangio­ blastomas of the cerebellum and spinal cord, cysts and neoplasms of the solid abdominal viscera, and epididymal cystadenomas. The responsible tumor-suppressor gene is located on chromosome 3p25-p26 and encodes for pVH L,

Chapter 14 Congenital Abnorm a l ities of the B ra i n 531

A

Figure 14-57 Sturge-Weber syndrome. A. A lateral skull radiograph shows serpiginous intracranial calcifications in the parietal region. B. There is extensive left

which is involved in transcription elongation. There is no gender predilection. The prevalence is approximately 1 in 3 5 , 0 0 0 to s o , o o o individuals. The clinical presenta­ tion is usually in early adulthood or in the teenage years. About half of patients with von Hippel-Lindau disease have ocular angiomas , often multiple or bilateral. C N S hemangioblastoma also occurs i n about half of patients; this lesion is the most common cause of death in von Hippel-Lindau disease. Up to 40% of patients with von Hippel-Lindau disease develop renal cell carcinoma by the fourth decade of life. This disorder is also associated with pheochromocytoma. '4 9-151 Approximately half ofhemangioblastomas in patients with von Hippel-Lindau disease arise in the spinal cord and half in the brain (38% in the cerebellum, 10% in the brainstem, and 2% in the cerebrum) . Intracranial heman· gioblastomas in patients with von Hippel-Lindau disease are often cystic. Typically, there is a tumor nodule in the wall of a large cyst. Approximately 20% to 40% of these tumors are solid, many ofwhich develop cysts with time. A cerebellar hemangioblastoma is most often located in the superficial aspect of a hemisphere. Supratentorial lesions are usually smaller and predominately solid. On neuro­ imaging studies, the wall of a cystic hemangioblastoma is well defined. The solid components are hypervascular and undergo prominent contrast enhancement. Tubular flow voids may be visible on MR (Figure 14-60) . Conventional angiography shows filling of irregular tumor vessels in the early arterial phase and a subsequent intense tumor blush.' 2 9·1 52 Individuals with von Hippel-Lindau disease are prone to the development of cystadenoma of the endolymphatic

B

parietal leptomeningeal thickening and enhancement on this T1-weighted MR image obtained after IV gadolinium administration. The underlying brain is locally atrophic.

sac. The overall prevalence of this tumor in patients with von Hippel- Lindau disease is approximately 7%. The major clinical manifestations are sudden onset of hearing loss, vestibulopathy, aural fullness, and tinnitus. The tumor is located along the posterior aspect of the petrous pyra­ mid at the site of the vestibular aqueduct. Evaluation with CT may show bone destruction. The mass has a hetero­ geneous character on both Tl-weighted and T2-weighted MR images. The lesion may contain hyperintense foci on Tl-weighted images . With a large tumor, vascular flow voids may be present. There is usually prominent contrast enhancement of the mass . '53·15 4

Ataxia-Telangiectasia Ataxia-telangiectasia is an autosomal recessive neurocu­ taneous disorder that involves the C N S , skin, respiratory tract, and immune system. The maj or C N S manifesta­ tion is degeneration of the cerebellar cortex because of selective loss of Purkinje and granular cells, particu­ larly in the vermis . Additional potential findings include dilated cerebellar and spinal leptomeningeal veins, with perivascular necrosis, dentate and olivary nuclei atro­ phy, posterior column degeneration, and perivascular hemorrhage/hemosiderosis in the cerebral white matter. The responsible gene for ataxia-telangiectasia (ATM) is located on chromosome nq22-23 . The protein product of the ATM gene is a homologue of phosphatidylinosi­ tol 3 -kinase; this is the catalytic subunit of an enzyme involved in transmitting signals from the cell surface to the nucleus. The ATM protein also plays an important role in the detection and repair of DNA damage. The

532

Part 3 The B r a i n

A

8

c

Figure 14-58 Sturge-Weber syndrome. A A contrast-enhanced T1-weighted image of a 22-monthold child with a right facial port·wine stain shows abnormal leptomeningeal enhancement in the anterior aspect of the right hemisphere. Enhancing medullary veins extend through the white matter. There are flow voids in enlarged right subependymal veins. B. The right choroid plexus is prominent.

0

C . Subcortical calcifications in the right frontal lobe are visible on this unenhanced CT image. D. One year later, leptomeningeal enhancement has diminished. There are again prominent enhancing medullary veins on the right. Atrophy in the anterior aspect of the right hemisphere has progressed. There is now diploic space expansion in the adjacent portion of the skull.

Chapter 14 Congenital Ab n o r m a l ities of the B ra i n

A

533

B

Figure 14-59 Sturge-Weber syndrome.

A, B. Contrast-enhanced T1-weighted MR images show mild pial enhancement in the left parieto-ocdpital region (arrows) . There is prominent enhancement of the enlarged left choroid plexus.

prevalence of ataxia-telangiectasia is approximately

1

per

Cerebellar cortical atrophy i s the dominant neuro­ imaging finding of ataxia-telangiectasia. Atrophy is most

4 o , o o o livebirth s .'55-•57 Mucocutaneous telangiectasias appear in the skin of patients with ataxia-telangiectasia early in childhood. Ocular telangiectasias are also common. Deficient cellu­

pronounced in the vermis and the lateral aspects of the cerebellum early irl the course of the disease. With pro­

gression, there is concomitant enlargement of the fourth

lar and humeral immunity leads to recurrent pulmonary

ventricle and the posterior fossa subarachnoid spaces.

infections ,

bronchiectasis .

The cerebellar folia are thin and the sulci are promirlent.

Other features include a predisposition t o malignancies

Parenchymal brain telangiectasias can lead to hemorrhage.

sometimes

complicated

by

(acute lymphocytic leukemia, Hodgkin lymphoma, and non-Hodgkin lymphoma) , premature aging, and radiation

In older patients with ataxia-telangiectasia, there may be

multiple small foci of hemosiderin deposition irl the cere­

sensitivity. There is premature loss of hair. Infants with

bral white matter; optimal detection is with T2 *-weighted

ataxia-telangiectasia are neurologically normal. Progressive

gradient echo MR images

ataxia and choreoathetosis usually begin by the age of 2 years. Oculomotor disturbances are common. Survival beyond the teenage years is uncommon.

Neurocutaneous M elanosis Neurocutaneous melanosis is a rare phakomatosis irl

which there are

1

or more large cutaneous pigmented nevi

and abnormal accumulations of melanocytes irl the lepto­

Ataxia-Telangiectasia

menirlges and brain. The pathogenesis apparently involves

Pathology

Rad iology

Cerebellar degeneration B rain telangiectasias

Cerebellar atrophy

Deficient i m m u n ity

(Figure 14-61 ) . '5 8-•Go

Small foci of hemorrhage or hemosiderosis Recu rrent pneumonia

an abnormality of growth factors that control the distribu­ tion and proliferation of melanocytes . In approximately two-thirds of patients, there is a very large cutaneous mela­ nocyte nevus, usually in the dorsal lumbosacral region. Others have multiple small nevi dorsal to the spine or in the head and neck region. Some patients never develop symptoms related to C N S involvement. Most affected indi­ viduals , however, have manifestations of CNS disease that

534

Part 3 The B r a i n

A

B

Figure 14-60 von Hippei-Lindau d isease; hemangioblastoma. A, B. There is a hyperintense solid mass (arrow) of the right cerebellar hemisphere and brainstem on these T2-wei ghted MR images. Flow voids are present in multiple enlarged vessels in the tumor. There is hydrocephalus due to obstruction of the fourth ventricle. C. A lateral arterial phase angiographic image shows neovascularity and prominent tumor blush of this vascular lesion.

begin early in childhood. There may be seizures or signs of increased intracranial pressure or hydrocephalus. Some patients suffer intellectual impairment. lntraparenchymal and leptomeningeal deposits of melanin in patients with neurocutaneous melanosis appear slightly hyperintense on T1-weighted MR images. These are also hyperintense on FLAIR images. The deposits are usually focal and measure up to a few millimeters in diam­ eter. The most common intracranial sites are the anterior temporal lobes, thalami, cerebellar nuclei, cerebellar white matter, and brainstem. Cerebellar and brainstem hypopla­ sia/atrophy may be present. Neuroimaging findings that suggest degeneration into a CNS malignant melanoma

c

include progressive growth of a lesion, mass effect, perile­ sional edema, and central necrosis. Leptomeningeal spread of tumor can occur. 'Gt-1 6 3

Epidermal N evus Synd rome Epidermal nevus syndrome is a neurocutaneous disorder in which epidermal nevi occur in association with various dysplasias and deformities of the CNS, eyes, skin, skele­ ton, and heart. The skin lesions are usually located on the scalp, face, andfor neck. Epidermal nevi are hamartomas of embryonal ectodermal origin. This sporadic disorder likely involves mosaicism of an autosomal lethal mutation.

Chapter

A

Figure 14-61 Ataxia telangiectasia. A A sagittal T1-weighted image of a 19-year-old patient demonstrates marked cerebellar atrophy. B. There are multiple

14

Congenital Abnorm a l ities of the B ra i n

535

B

small hypointense foci in the cerebral white matter on this gradient echo sequence because of hemosiderin deposition.

Diagnosis during childhood is uncommon. Approximately 40% of patients have clinical manifestations of neuro­ logical impairment. Seizures, sometimes intractable, are present in most patients. Other potential neurological manifestations include cranial nerve paresis, hemiparesis, and cortical blindness. •64 Approximately half of individuals with epidermal nevus syndrome have CNS involvement. Brain lesions that can occur in these patients include hemimegalencephaly, heterotopias, focal cortical malformations, cortical atrophy (often unilateral) , dysgenesis ofthe corpus callosum, Dandy­ Walker malformation, hydrocephalus, porencephaly, and various neoplasms. Unilateral hemimegalencephaly, which is the most common intracranial abnormality in patients with epidermal nevus syndrome, is typically ipsilateral to the skin lesions. The most common neuroimaging find­ ings are unilateral hemimegalencephaly, ventriculomegaly, and ipsilateral hyperintensity of cerebral white matter on Tz-weighted M R images. Ipsilateral cerebral white matter thinning and calcifications can occur. The most common skeletal abnormalities in these patients are radiolucent lesions, typically well-defined, in the calvaria, mandible, and long bones. Extremity hemihypertrophy has been reported. Other associations include kyphosis, scoliosis , syndactyly, and vitamin D-resistant rickets.' 6 5-•67

eruptions that develop early in infancy. Retinal vascular abnormalities are common. Approximately two-thirds of patients have dental anomalies, such as delayed eruption or malformed teeth. CNS involvement apparently results from small vessel disease. Potential clinical findings include sei­ zures, mental retardation, ataxia, quadriplegia, stroke, and progressive microcephaly. Nearly all patients with inconti­ nentia pigmenti are female; affected males usually die in utero. The responsible mutation in most patients is NEMO (nuclear factor-kappa-B essential modulator) at chromo­ some Xqz8.t68 In the absence of clinical manifestations of CNS involvement, neuroimaging studies of patients with incon­ tinentia pigmenti are normal. Those with symptoms may have MR signal alterations of the brain and focal atrophy of the cerebrum, cerebellum, or corpus callosum. The find­ ings are often asymmetric; brain involvement tends to be most prominent contralateral to the side of the predomi­ nant clinical symptoms. Regions of brain involvement typi­ cally are hyperintense on Tz-weighted MR images, usually including cortex and the subjacent white matter. Similar findings can occur in the cerebellum. There is usually pro­ gressive thinning of gray matter and white matter in the involved portions of the brain, accompanied by ex vacuo ventriculomegaly. •6 9 .•7 o

l nconti nentia Pigmenti

Hypomelanosis of Ito

Incontinentia pigmenti is a rare X-linked dominant phaco­ matosis that involves the CNS in 30% to so% of patients. The skin lesions consist of linear vesicular or bullous

Hypomelanosis oflto (incontinentia pigmenti achromians) is a heterogeneous group of neurocutaneous disorders in which there are hypopigmented skin lesions with irregular

536 Part 3 The B ra i n borders, patches, whorls, and streaks. Various other skin lesions can also occur, such as cafe-au-lait spots, nevus marrnorata, angiomatous nevi, and alopecia. Potential musculoskeletal anomalies include spinal deformities, hemihypertrophy, rib deformities, and foot deformities. About half of patients have seizures. Mental retardation can occur. The neuroimaging findings of hypomelanosis of Ito are nonspecific. Reported intracranial pathology in these patients includes cerebellar hypoplasia/atrophy, hemimegalencephaly, lissencephaly, dysgenesis of the cor­ pus callosum, polyrnicrogyria, heterotopia, white matter lesions, and enlarged perivascular spaces. The intracranial structures are normal in many patients, however.'7'·'72

Chediak-H igashi Syndrome Chediak-Higashi syndrome is a rare autosomal recessive disorder that is caused by a mutation in the LYST gene, which encodes a lysosomal transport regulator. The major clinical manifestation is abnormal pigmentation of the skin and hair caused by the accumulation of giant melano­ somes and failure of transport of melanin granules to epi­ dermal cells. This mutation also causes immunodeficiency, which may be fatal without successful bone marrow trans­ plantation. CNS involvement can lead to seizures, mental retardation, and cerebellar signs. The imaging findings are nonspecific, with prominent subarachnoid spaces, ventric­ ulomegaly, and hyperintense foci within the white matter on T2-weighted MR images.'7J.l74

DISORDERS OFCELLULAR MICRAT ION (CORTICAL MALFORMATIONS)

Lissencephaly Lissencephaly is a developmental abnormality of the brain in which there is deficient gyral and sulcal development. The pathophysiology involves arrested neuronal migration; that is, deficient migration of postrnitotic neurons from the ventricular zone to the cortical plate during embryogenesis (12th to 24th weeks of gestation) . The term agyria refers to "complete" lissencephaly, with a smooth brain surface because offailure ofgyral formation. Pachygyria, or "incom­ plete" lissencephaly, indicates the presence of a diminished number of gyri and abnormally broad gyri. Abnormal corti­ cal thickening is present in both forms oflissencephaly; this finding is more pronounced with agyria then pachygyria. Subcortical band heterotopia is a related disorder of neuro­ nal migration in which there is a circumferential band of heterotopic neurons separated from the overlying cortex by a thin layer of white matter. The sulci are often shallow with band heterotopia, but the cortical thickness is normal and the number of gyri is normal. Mutations of various genes involved in the complex process of neuronal migration are associated with lissencephaly; some of the genes identified to date include LIS1, PAFAH1 B1, DCX, RELN, ARX, 14-3-]t:,

Table 1 4-1 0. Classification of lissencephaly

m utation Type I isolated lissencephaly M iller-Dieker nd� � - ---OCX (doublecorti n) m utation � - - - -·- - - - -· - · - - - - -· - .. - · - · --- ·- - - - -· --Type I isolated lissencephaly without a known genetic defect Cobblestone lissencephaly I Walker-Warburg , syndrome •·F u k�;;�� ���g;�lt;i m uscular dystrophy Cerebroocularm u scular syndrome X-li n ked lissencephaly with absent corpus callosum · · ··-- N-�-; �; � R- b;�� -- - -- - -- - Lissencephaly wit h �;r;b� j � ; � � syndrome hypoplasia M icrolissencephaly Classical l issencephaly (type I )

LIS1

________

l:_y

I

--

_ __

T

POMT1, POMGnT1, FCMD, and FKRP. Some instances of lissencephaly may result from fetal viral infections or fetal brain ischemia.'75 ·'7 6 Lissencephaly represents a pathophysiological and clinical spectrum. The current consensus recognizes 5 major types of lissencephaly and several subtypes (Table 14-10) . Children with classical lissencephaly have agyria or pachygyria. This is also termed type I lissenceph­ aly. Cobblestone lissencephaly refers to a nodular form of lissencephaly in patients with congenital muscular dystro­ phy. Histologically, there is a disorganized, nonlayered cor­ tex. The major subtypes of cobblestone lissencephaly are Walker-Warburg syndrome, Fukuyama congenital muscu­ lar dystrophy, and cerebroocularrnuscular syndrome (mus­ cle-eye-brain disease) .'77 ·'7 8 Children with the classic form of lissencephaly and no associated anomalies have isolated lissencephaly sequence; this is usually caused by deletion or mutation of LIS1 . More than 25 dysmorphology syndromes that include lissenceph­ aly are recognized. Miller-Dieker syndrome represents severe type I lissencephaly in association with characteristic facial anomalies (prominent forehead, short nose, upturned nares, bitemporal hollowing, widely spaced eyes, micro­ gnathia, and low-set ears) and postrlatal growth deficiency; these patients have deletions in 17Pl3 -3· Norman-Roberts syndrome patients have lissencephaly and severe cerebel­ lar hypoplasia. The Norman-Roberts phenotype includes a short sloping forehead, microcrania, widely set eyes, and a broad nasal bridge. Walker-Warburg syndrome refers to cobblestone lissencephaly occurring in combination with

Chapter 14 Co ngenital Abnorm a l ities of the B ra i n hydrocephalus, hypoplasia of the cerebellar vermis, severe congenital eye malformations (e.g. , persistent hyperplastic primary vitreous) , and congenital muscular dystropy.'77 ·17 9

Classical Lissencephaly Classical lissencephaly comprises a spectrum of severity that ranges from diffuse agyria to mixed agyria and pachy­ gyria to pachygyria only. The cerebral cortex consists of an abnormally thick dysplastic cortex: a thin dysplastic outer layer of neurons, a thick inner layer of ectopic neurons, and an interposed "cell sparse zone" of white matter. The thick inner layer may represent young neurons that failed to migrate peripherally during fetal development. The cell sparse zone is thicker and more hypocellular in patients with agyria than with pachygyria. In addition, the organiza­ tion of the cortex into layers is more deficient with agyria than with pachygyria.1,18o Most children with classical lissencephaly suffer sei­ zures and global developmental delay. As infants, they may have hypotonia and motor abnormalities. In general, there is a correlation between the extent of brain involvement and the clinical severity. Complete lissencephaly is usually associated with medically refractory epilepsy that begins during infancy. Infants with lissencephaly may suffer infan­ tile spasms. Common findings on physical examination include microcephaly and a wide flat face. Children with Miller-Dieker syndrome have a tall prominent forehead, narrowing at the temples, hypertelorism, upward slanting palpebral fissures, low-set ears, a short nose with anteverted nares, micrognathia, and a long, wide, and thick upper lip.181 The most common diagnostic imaging appearance of severe classical lissencephaly (i.e., agyria) is that of a smooth brain surface, devoid of sulci. There is lack of normal white matter interdigitation. The white matter is often undermyelinated. Shallow, vertically oriented sylvian fissures in the patient with agyria produce a figure-of-8 appearance on axial images. Most patients have ventricu­ lomegaly, although the severity is variable. Dilation of the lateral ventricles is sometimes most prominent in the pos­ terior portions. On high-quality MR images, the cell sparse zone is often visible as a thin band of white matter subja­ cent to the outer cortical layer of gray matter and peripheral to the thick zone of ectopic neurons . This band is hyper­ intense to gray matter on T2-weighted images in infants (Figure 14-62) . After myelination, it appears hypointense on T2-weighted images and hyperintense on T1-weighted sequences. Other potential findings are dysgenesis of the corpus callosum and absence of the claustrum and extreme capsule. The imaging appearance of pachygyria is that of broad, thick, and fiat gyri, and shallow sulci ( Figure 14-63) . There is deficient opercularization, resulting in prominence of the sylvian cisterns and abnormally vertical orientations. Brain myelination is usually deficient or delayed. Pachygyria can be focal, multifocal, or diffuse; some patients have coexistent pachygyria and agyria. Cortical thickening is an important

537

imaging feature ofpachygyria, although the severity ofthick­ ening is usually less than in agyria. As with severe lissen­ cephaly, the cell sparse zone is often visible on high-quality MR images. This is an important differentiating feature from polymicrogyria. In addition, the gray matter-white matter junction is smooth and well-defined in regions of pachygy­ ria; polyrnicrogyria results in an irregular gray-white junc­ tion. Some instances of subcortical band heterotopia have a similar appearance to pachygyria. However, the cortex in patients with band heterotopia is normal aside from shallow sulci. There is a layer of normal white matter between the band of heterotopic gray matter and the cortex. l76 The diagnosis of lissencephaly with prenatal neuro­ imaging is often challenging, in part because of the rela­ tively smooth appearance of the normal-developing fetal brain. In the normal fetus, the parietooccipital and calca­ rine fissures are visible with sonography between 18 and 21 weeks of gestation and with MR between 18 and 23 weeks. The cingulate sulcus is visible with sonography at 23 to 25 weeks and with MR at 24 to 2 9 weeks. Convexity sulci appear at 23 to 28 weeks on sonography and 26 to 29 weeks on MR. Imaging findings of fetal lissencephaly include an abnormally smooth brain surface, a shallow sylvian fissure, ventriculomegaly, and prominence of the subarachnoid spaces. Manifestations of associated anomalies are also important; e.g., encephalocele, microcephaly, and posterior fossa abnormalities.17 6 Lissencephaly Caused by

LIS1

Mutations

Mutations of the LIS1 gene on chromosome 17 are relatively common causes oflissencephaly. The encoded protein may play a role in migration of neuronal cell nuclei. Individuals with this mutation usually have classical (type I) lissenceph­ aly. There is some degree ofvariation between patients with regard to the clinical severity and imaging findings. Nearly all patients with isolated classical lissencephaly sequence have a LIS1 mutation or absence of the gene. Patients with Miller-Dieker syndrome usually have deletions of LIS1, YWHAE, CRK, and other genes. Most often, imaging stud­ ies of children with LIS1 abnormalities demonstrate a com­ bination of agyria and pachygyria. Agyria is most common in the parietal and occipital regions, while the frontal and temporal lobes often have a pachygyric pattern. Cerebellar hypoplasia, usually mild, is common.18o,l8 2 Lissencephaly Caused by

DCX Mutations

Mutations ofthe DCXgene (also termed XLIS) at Xq22.3-q23 result in similar clinical and imaging findings as LIS1 mutations. The encoded protein apparently is involved in the assembly of microtubules within migrating neurons. As an X-linked disorder, most of these patients are boys. Heterozygous females with this mutation (e.g., mothers of affected boys) usually have mild forms of lissenceph­ aly or, most frequently, band heterotopia. Neuroimaging studies of children with lissencephaly due to DCX muta­ tions may demonstrate complete or incomplete forms of

538 Part 3 The B r a i n

A

B

Figure 14-62 Classical lissencephaly. Till s 12-month-old infant with medically refractory epilepsy has a smooth cerebral surface with complete lack of gyral formation and lack of white matter interdigitation. A. The shallow vertically oriented Sylvian fissures result in a figure-of-8 appearance on this axial T1-weighted image. B, C . T2-weighted images show the dysplastic cortex as a thin slightly hypointense peripheral layer (arrow in B) . The cell sparse zone is an irregular hyperintense band (arrow in q of unmyelinated white matter. Between the cell sparse layer and the myelinated deep white matter is a thick intermediate intensity band of ectopic neurons {small arrows in B) .

c

lissencephaly; the latter is more common. There is a ten­ dency for more severe involvement in the frontal lobes. Cerebellar hypoplasia can occur. '75 .18 o

X- Linked

Lissencephaly with Absent Corpus Callosum

X-linked lissencephaly with absent corpus callosum is a distinct clinical syndrome. This is apparently caused by a mutation of the ARX gene at Xp22.13 . These infants have intractable seizures, hypotonia, severe psychomotor retardation, growth failure, and hypoplastic external geni­ talia. There is progressive microcephaly during infancy. Imaging studies show absence of the corpus callosum, posterior agyria, and anterior pachygyria. Cortical thicken­ ing tends to be less pronounced than in most other forms

of lissencephaly. There is usually disorganized develop­ ment of the basal ganglia. The cerebral white matter is gli­ otic. Female siblings of boys with this disorder often have mental retardation, epilepsy, and dysgenesis of the corpus callosum.'8p84

Lissencephaly Caused by RELN Mutations (Norman-Roberts Syndrome) Mutations of the RELN gene on chromosome 7 result in a clinically severe form of lissencephaly, termed Norman­ Roberts syndrome. This is an autosomal recessive disorder. Absence of the protein product of this gene (reelin) leads to failure of migration of young neurons to the outer lay­ ers of the developing cortex. There are 6 cortical layers, but their order of orientation is abnormal (layer 6 subjacent to

Chapter 14 Co ngenital A b n o r m a l ities of the B ra i n 539 lirnitans. The coexistence of brain and muscle abnor­ malities apparently relates to deficiency of proteins (e.g., merosin) that are involved in muscle contraction and also participate in neural development. The 3 major disorders in which cobblestone lissencephaly and ocular anomalies occur in combination with congenital muscular dystrophy are Fukuyama congenital muscular dystrophy, Walker­ Warburg syndrome, and cerebroocularmuscular syndrome (muscle-eye-brain disease) . MDC1C muscular dystrophy caused by abnormalities of the FKRP gene is an additional cobblestone lissencephaly syndrome. '87-t89 The hallmark neuroimaging feature of the congeni­ tal muscular dystrophies is cobblestone lissencephaly (Table 14-1 1) . Cobblestone lissencephaly consists of disor­ ganized cortex of variable thickness that lacks a layered

Table 1 4-1 1 . Cranial M R Findings in the Congenital M uscular Dystrophies M R fi n d i n gs

D i sord e r

Fu kuyama congenital m uscular dystrophy

Tem porooccipital cobblestone . cortex Cerebral wh ite matter dysmyelinationj • hypomyeli nation Cerebellar and frontal polym icrogyria · Subcortical cerebellar cysts . Hypoplasia of pons and cerebellar vermis Hydrocephal u s (variable) Cerebroocularmuscular Diffuse cerebral cobblestone cortex syndrome Cerebellar polym icrogyria !··· . Absence of septu m pel l ucid u m · Hypoplasia o f pons and cerebellar verm is ' Subcortical cerebellar cysts · Hydrocephal u s · Delayed myelination Severe d iffuse cerebral Wal ker-Warburg syndrome cobblestone cortex Cerebraljcerebellar hypomyeli nation · Cerebellar hypoplasia and · dysplasia . Pontine hypoplasia Severe hydrocephalus ·

Figure 14-63 Diffuse pachygyria. There is a thickened appearance of the cortex on this Tl-weighted image. The sulci are shallow and the gyri are broad. There is a sharp interface between the dysplastic cortical gray matter and the subjacent white matter.

·

1, 5 subjacent to 6, etc.). The usual imaging appearance is that of generalized pachygyria. There is moderately severe cortical thickening. Unlike other forms of lissencephaly, a peripheral cell sparse zone is lacking. The cerebellum is lissencephalic and markedly hypoplastic. The brainstem is also small. In general, cerebellar hypoplasia in these patients is more severe than the hypoplasia that sometimes occurs in patients with LIS1 and DCX mutations. '8P8 6

Congenital Muscular Dystrophies with Cobblestone Lissencephaly Congenital muscular dystrophies include various disor­ ders that result in hypotonia that is clinically manifest in the newborn. These infants have generalized muscle weak­ ness. Joint contractures, CNS anomalies, and ocular abnor­ malities are common. Potential neuroimaging findings include regions of pachygyria, polymicrogyria, leukodys­ trophy, cerebellar subcortical cysts , cerebellar hypoplasia, hydrocephalus, and pontine hypoplasia with fused col­ liculi. Lissencephaly in these patients involves "overmi­ gration" of neuroblasts and glia through the external glial

·

· ·

540 Part 3 The B ra i n structure. There are conglomerate clusters o f gray matter, some of which extend into relatively thin subjacent white matter. The leptomeninges are thickened. Neuroimaging evaluation demonstrates shallow sulci and cortical dyspla­ sia. The cortex is thick and irregular, often with features of both agyria and polyrnicrogyria. Deficient white matter myelination is common. Fukuyama Congenital Muscular Dystrophy

Fukuyama congenital muscular dystrophy is an autoso­ mal recessive disorder caused by a mutation of the FCMD (fukitin) gene on chromosome 9· In addition to altera­ tions of muscle (i.e., muscular dystrophy) , this disorder is associated with various CNS abnormalities, such as corti­ cal dysplasia. There are 3 patterns of cerebral cortical dys­ plasia in these patients: type 1 is verrucous dysplasia that usually occurs along the medial surfaces of the occipital lobes ; type 2 is nonlayered polymicrogyria that is usually most pronounced in the frontal and parietal lobes ; type 3 is cobblestone lissencephaly that involves the lateral surfaces of the occipital and temporal lobes . There is polymicrogy­ ria in the cerebellum. The major clinical manifestations of Fukuyama congenital muscular dystrophy are muscular hypotonia and severe developmental delay. Various ocu­ lar abnormalities also occur. Fukuyama congenital mus­ cular dystrophy is most common in children of Japanese ancestry.' 9 ° The major MR features of Fukuyama congenital mus­ cular dystrophy are diffuse central cerebral dysmyelinationf hypomyelination, cerebellar polymicrogyria, frontal/pari­ etal polymicrogyria, variable hypoplasia of the pons and cer­ ebellar vermis, and temporalfoccipital cobblestone cortex. The frontal and parietal polyrnicrogyria appears on MR as irregularity along the cortical surface and at the gray-white matter junction. The cobblestone lissencephaly typically appears as areas of thickened cortex that have a smooth outer surface and somewhat irregular inner surface. Abnormal increased signal within the cerebral white matter is com­ mon in these patients, particularly during infancy and early childhood. Abnormal cortical vessels are sometimes visible in areas of cortical thickening. Nonspecific prominence of the ventricles and subarachnoid spaces is common. Many patients with Fukuyama congenital muscular dystrophy have dysplastic folia and subcortical cysts in the dorsal midportion of the cerebrum. Infants and young children with this disorder have delay in myelination; myelination in these patients usually begins in the peripheral portion of the white matter and progresses centrally.18 9 ·191 Walker-Warburg Syndrome

Walker-Warburg syndrome refers to cobblestone lissen­ cephaly occurring in combination with hydrocephalus, hypoplasia of the cerebellar vermis , severe congenital eye malformations, and congenital muscular dystropy. This syndrome is also termed the HARD±E sy ndro me: hydro­ cephalus, agyria, and retinal dysplasia, with or without

encephalocele. Potential orbital malformations in these patients include persistent hyperplastic primary vitreous, retinal dysplasia, anterior chamber mesenchymal dysgen­ esis, congenital glaucoma, and optic nerve hypoplasia. A posterior cephalocele occurs in some patients. This disor­ der is in the spectrum of congenital muscular dystrophies; affected children have hypotonia of variable severity. Other clinical findings include severe psychomotor impairment and progressive macrocephaly. Cleft lip or genital anom­ alies occur in some patients. Most affected children die during the first few years of life. The responsible gene for Walker-Warburg syndrome is POMT1 at 9q34.1.1 9 2 Neuroimaging studies of Walker-Warburg syndrome demonstrate diffuse cortical thickening and lack of sulci. There is irregularity at the gray matter-white matter junc­ tion, resulting in a cobblestone appearance. There is severe hypomyelination. In infants, there is elevated diffusion in the cerebral white matter on MR examination; signal intensity in the lissencephalic cortex is normal on diffu­ sion-weighted images. Most patients with Walker-Warburg syndrome (>9o%) have hydrocephalus, usually as a result of aqueductal stenosis (Figure 14-64) . Dysgenesis of the cor­ pus callosum is common. In some patients, there is hypo­ plasia of the pons and fusion of the superior and inferior colliculi, resulting in a dorsal kink at the mesencephalic­ pontine junction (Z-shaped brainstem or notched pons). The cerebellum may also be hypoplastic. Manifestations of ocular anomalies are usually discernible on cross-sectional imaging studies of these patients as well. An occipital encephalocele is occasionally present. l9 3-195 Cerebroocularmuscular Syndrome

Cerebroocularmuscular syndrome (muscle-eye-brain dis­ ease; cerebroocular dysplasia with muscular dystrophy) is a rare congenital muscular dystrophy. Many of these patients have mutations in 0-linked mannose �-1,2-N­ acetylglucosarninyltransferase. The responsible gene is POMGnT1 at 1p32 . There is abnormal cortical development in these patients. Affected infants are hypotonic and visually impaired. Spasticity eventually occurs. Seizures and severe intellectual impairment are typical. In general, the clini­ cal features and neuroimaging findings are intermediate between those of the other two major congenital muscular dystrophies that affect brain development, Walker-Warburg syndrome and Fukuyama congenital muscular dystrophy.196 Neuroimaging studies of patients with cerebroocu­ larmuscular syndrome show diffuse thickening of the cerebral cortex and irregularity at the gray-white matter junction; that is, cobblestone lissencephaly. The findings are often most prominent in the frontal lobes. Other find­ ings include ventriculomegaly, wide sylvian fissures, pon­ tine or pontocerebellar hypoplasia, cystic cerebellar cortical dysplasia, and dysplasia of the corpus callosum. There is delayed brain myelination; myelination initially occurs in the subcortical region and progresses centrally. Some patients have hydrocephalus. 197-199

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 541

A

Figure 14-64 Walker-Warburg syndrome.

B

A CT of an infant with macrocephaly shows severe hydrocephalus. The cortex is smooth and lacks normal sulci.

G ray M atter Heterotopia Gray matter heterotopia are collections of nerve cells in abnormal locations extrinsic to the cortex. The pathogen­ esis involves arrested radial migration of neurons. These "masses" of gray matter are functional. The most common clinical manifestation is epilepsy. Gray matter heteroto­ pia can be isolated or occur in association with additional CNS anomalies. The lesions can occur at various locations. Heterotopias can have a nodular, laminar, or transcerebral morphology. Sporadic and familial forms occur.'·200

Subependymal Heterotopia Subependymal (periventricular) heterotopia are neuro­ nal rests along the walls of the lateral ventricles. This form of gray matter heterotopia is most often a sporadic disorder. Other brain anomalies are present in some of these patients, such as agenesis of the corpus callosum, hydrocephalus , cephalocele, or Chiari II malformation. Autosomal recessive and X-linked familial forms (e.g., mutations of the FLN1 gene) also occur. The most common pattern of subependymal heterotopia consists of a few to several small bilateral lesions, usually along the trigones, temporal horns, and occipital horns . Other patients have extensive nodular heterotopia along the lengths of the lateral ventricles; this pattern is often associated with the X-linked form. X-linked bilateral periventricular nodular heterotopia causes focal epilepsy in females and prenatal death in males.201-203 The clinical consequences of subependymal heteroto­ pia roughly correlate with the extent of brain involvement. Children with a small number of lesions tend to have mild symptoms; these patients usually have a sporadic form of the disorder. Focal epilepsy occurs in approximately 90%

B . There are manifestations of hyperplastic primary vitreous in the right eye on this enhanced CT image.

of patients with subependymal heterotopia. Mixed partial complex or tonic-donie seizures may develop during the second decade oflife. Children with associated brain anom­ alies usually have more severe symptoms. Some patients with extensive heterotopia and associated brain anomalies suffer profound mental deficiency. 204·205 On MR, the nodules of subependymal heterotopia are typically isointense to normal gray matter on all imaging sequences. Calcification, cystic degeneration, and hyper­ enhancement do not occur. The lesions are usually ovoid, with the long axis parallel to the ventricular wall. The nod­ ules often bulge into the ventricular cavity to some extent (Figure 14-65) . Uncommonly, extensive subependymal het­ erotopia form an irregular band of gray matter along the ventricular wall (Figure 14-66) . This usually has the appear­ ance of multiple adjacent nodules, but rarely has a linear configuration. As described above, MR may demonstrate additional brain anomalies in patients with subependymal heterotopia. Females with the X-linked form often have hypoplasia of the cerebellar vermis. Interictal scintigraphy with FDG-PET or HMPAO-single-photon emission com­ puted tomography (SPECT) demonstrates activity within the heterotopic gray similar to that of normal cortex. 20 6 · 207 An important differential consideration of nodular subependymal heterotopia is tuberous sclerosis. The sub­ ependymal hamartomas of tuberous sclerosis, however, usually have a long axis that is perpendicular to the ven­ tricular wall, typically are not isointense to gray matter, may be calcified, and undergo contrast enhancement.

Subcortical Heterotopia Subcortical heterotopia are ectopic neuronal rests located anywhere from the periventricular white matter to the cor­ tical gray-white matter junction. The clinical consequences

542 Part 3

The

B ra i n

Figure 14-66 Subependymal heterotopia.

Figure 14-65 Subependymal heterotopia. A T2-weighted M R image of a 4-month-old infant with seizures shows multiple nodules of gray matter (arrows) along the walls of the slightly dilated lateral ventricles.

Multiple nodules (arrows) isointense to gray matter line the ventricular walls on this T1-weighted coronal image.

include seizures , motor disturbances , and intellectual

are consistently isointense with gray matter on all imaging

impairment. The size, number, and location of lesions

sequences (including enhanced images) , lack surrounding

correlate with the clinical severity. A large lesion often is

edema, and lack true mass effect. Proton spectroscopy of heterotopia is normal. 2 08· 2 0 9

associated with contralateral hemiparesis. Patients with minimal involvement may have a seizure disorder without additional neurological compromise. The onset of epilepsy in patients with subcortical heterotopia is usually during

Subcortical Band Heterotopia Subcortical band heterotopia (double cortex syndrome; sub­

the first or second decades oflife . The spectrum of imaging patterns of subcortical het­

cortical laminar heterotopia) refers to an anomalous layer

erotopia includes multiple nodules , curvilinear ribbons of

of heterotopic neurons deep to the cortex. More than

cortex extending into the white matter, deep nodular foci

of patients with band heterotopia are female. Subcortical

with curvilinear areas more peripherally that contact the

band heterotopia is the typical intracranial finding in

cortex, and a linear band of gray matter extending from

females who are heterozygous for mutations of the XLIS

90%

the cortex to the ventricular surface (transmantle heteroto­

(or D CX) gene. There are rare male patients with missense

pia) . The clinical manifestations of the disorder are similar

mutations of both the LIS1 and XLIS genes. Mutations

70% of

of other genes apparently are causative in some patients.

patients have dysgenesis of the corpus callosum. Dysplasia

for each of the imaging patterns. Approximately

Patients with subcortical band heterotopia have intellectual impairment and epilepsy of variable severity and type. 2 10-212

of the ipsilateral basal ganglia or thalamus is also common. The cortex overlying the heterotopia is usually thin and has

The neuroimaging appearance of band heterotopia is

shallow sulci. There is diminished white matter volume in

that of a homogeneous band or layer of gray matter situ­

the ipsilateral hemisphere. With the curvilinear form of

ated between the lateral ventricles and the cerebral cortex There is white matter central and periph­

heterotopia, there are deep infoldings from the overlying

(Figure 14-67) .

cortex toward the malformation.

eral to this band. Occasionally, there are hyperintense foci

Neuroimaging features that are helpful in the differ­

within the cerebral white matter. Band heterotopia can be

entiation of subcortical heterotopia from schizencephaly

complete or partial. Bands restricted to the frontal lobes are

include absence of a fluid-filled cleft and lack of ventricular

most common with DCX mutations , while bands restricted

tenting. Unlike most neoplasms , subcortical heterotopia

to the posterior aspect of the cerebrum tend to occur with

Chapter 14 Co ngenital A b n o r m a l ities of the B ra i n 543

Figure 14-67 Band heterotopia. An axial T2-weighted M R image of a 6-year-old female demonstrates a layer of anomalous gray matter between the relatively normal hypointense subcortical and periventricular white matter.

LIS1 mutations. Occasionally, the temporal lobes con­ tain 2 layers of heterotopia. Gyral formation is normal or mildly "simplified." The sulci in the overlying cortex are sometimes shallow. Normal thickness of the cortex and the presence of normal subcortical white matter help to dif­ ferentiate this anomaly from pachygyria. FDG-PET shows equal or greater uptake within the band relative to normal cortex.

Polym icrogyria Polymicrogyria is a disorder of cortical organization in which the cortex contains multiple abnormally small con­ volutions and a diminished number of sulci. The pathogen­ esis apparently involves abnormalities during the cortical organization and late neuronal migration stages of cerebral development. Histologically, there is alteration of the nor­ mal 6-layered lamination of the cortex. There is etiologi­ cal heterogeneity of polymicrogyria; predisposing factors include prenatal cytomegalovirus infection, fetal cerebral ischemia, and various genetic disorders (e.g., 22qn and 1p3 6 deletions) . Polymicrogyria occurs in some patients with Zellweger, Aicardi, and Walker-Warburg syndromes. There is substantial variation between patients with regard to the histological features, clinical presentations, and

neuroimaging appearances. Polymicrogyria can be urrilat­ eral (approximately 40% of patients) or bilateral, isolated or associated with other anomalies, and symptomatic or asymptomatic. 1 • 213 The clinical presentation of polymicrogyria relates to the extent of the abnormality, the location, and the presence of additional anomalies. The most common clinical con­ sequence is a seizure disorder. Patients with mild involve­ ment may be asymptomatic. Unilateral polymicrogyria can lead to contralateral hemiparesis. Bilateral frontal involve­ ment is often associated with developmental delay, intel­ lectual deficiency, speech impairment, and mild spastic quadriparesis. The cortex surrounding the sylvian fissures is a relatively common site of polymicrogyria (approxi­ mately 8 o%) . When bilateral, perisylvian polymicrogyria can lead to dysarthria, facial diplegia, and pseudobulbar palsy. The frontal lobes are involved in approximately 70% of patients with polymicrogyria, and the parietal lobes in approximately 6 o%?L4 MR generally allows a definitive diagnosis of poly­ microgyria. Thin-section images obtained in the coronal plane are particularly valuable. The most common imaging appearance is that of cortical thickening, numerous poorly developed sulci, and irregularity at the gray-white matter junction. Prior to myelination of the adjacent white mat­ ter, the involved cortex appears thin on T2-weighted MR images. The apparent thickness of the cortex is greater after myelination, because of blending of peripheral gliotic white matter with the adjacent dysplastic gray matter. Both the inner and outer margins of the cortex are irregular and "bumpy" in most patients (Figure 14-68) . Occasionally the outer cortical surface appears relatively smooth, particu­ larly on thick MR and CT slices. In some patients, there is infolding of polymicrogyric cortex. 215 Regions of polymicrogyria are usually isointense to normal gray matter on all M RI sequences. The tis­ sue has a normal spectrum on proton MR spectroscopy. Approximately one-quarter of patients have abnormal increased signal intensity on T2-weighted images in sub­ jacent white matter. Anomalous cortical veins are present in areas of polymicrogyria in about half of patients. There is prominence of perivascular spaces adjacent to the dys­ plastic cortex in approximately 30% of patients. Fractional anisotropy values are diminished in the subcortical white matter on diffusion tensor M R. 2 09· 216 ·217

Polymicrogyria Syndromes Bilateral frontal polymicrogyria refers to symmetric brain involvement extending from the frontal poles to the precen­ tral gyrus posteriorly and to the frontal opercula inferiorly. The major clinical manifestations of this polymicrogyria syndrome include developmental delay, seizures, and spas­ tic hemiparesis or quadriparesis. 218· 219 Bilateral frontoparietal polymicrogyria includes sym­ metrical involvement of the frontoparietal regions of the cerebrum. In addition, there are abnormalities within

544

Part 3 The B ra i n Kabuki syndrome, Ehlers-Danlos syndrome, trisomy 13, congenital constriction band syndrome, and esophageal malformations. 222-224 Bilateral generalized polymicrogyria usually is most severe in the perisylvian regions. These patients often have enlarged ventricles and generalized white matter thin­ ning. The clinical manifestations include seizures , devel­ opmental delay, and spastic hemiparesis or quadriparesis. Additional anomalies are present in some patients with this form of polymicrogyria; for example, limb defects, macrocephaly, low-set ears, and macrosomia! 25

Sch izencephaly

Figure 14-68 Polymicrogyria. A coronal Tz-weighted M R image of a 2-month-old infant demonstrates slight thickening and an irregular bumpy surface of the right insular cortex (arrows) . There is also an irregular gray-white matter junction.

the subjacent white matter and atrophy/hypoplasia of the brainstem and cerebellum. Ventriculomegaly is common. This pattern results in some degree of imaging overlap with the cobblestone lissencephaly syndromes. The most common clinical features include disconjugate gaze, global developmental delay, pyramidal signs, cerebellar signs. and seizures. The pathogenesis involves mutations of the GPR56 gene.22 0•221 Bilateral perisylvian polymicrogyria (bilateral opercular polymicrogyria; congenital bilateral perisylvian syndrome) is the most common form of bilateral polyrnicrogyria. On MR. the opercula are dysplastic and the sylvian fissures are poorly developed and wide. The multiple small gyri are often best viewed on thin section sagittal or parasagittal views. The usual clinical manifestations include pseudo· bulbar palsy, pyramidal signs, and seizures. Some patients have feeding problems and dysarthria. Epilepsy, frequently intractable, occurs in more than 85% ofthese patients. Both sporadic and familial (often X-linked) forms of bilateral perisylvian polyrnicrogyria occur. Anomalies associated with this disorder include dysgenesis of the septum pellu· cidum, pituitary hypoplasia with ectopic neurohypophysis,

Schizencephaly is a rare CNS malformation in which a gray matter-lined lateral cerebral cleft extends from the pial sur­ face of the brain to the ependyma of the lateral ventricle. There are 2 main forms of schizencephaly. With type 1 (closed-lip) schizencephaly, the walls of the cleft appose one another. Type 2 (open-lip) schizencephaly has sepa­ rated walls and filling of the cleft with C S F . The open-lip variety accounts for approximately 8o% of these lesions. Unilateral and bilateral lesions occur with approximately equal frequency. Associated facial anomalies are usually lacking in infants with schizencephaly. 22 6· 227 Schizencephaly is a primary malformation that is most often a result of a neuronal migrational anomaly. A het­ erozygous mutation of the EMX2 gene on chromosome w q2 6 is associated with some familial cases of schizen· cephaly. Intrauterine insults such as cytomegalovirus infection, maternal drug abuse, and abdominal trauma are additional identified risk factors. Irrespective of the underlying insults, schizencephaly results from abnormal neuroblast migration during the third to fi fth gestational months. 1 ,22 8 , 22 9 Common clinical manifestations of schizencephaly include seizures, developmental delay, and motor impair­ ment. The open-lip form of schizencephaly typically imparts more severe neurological impairment than the closed-lip variety. Bilateral lesions are more clinically sig· nificant than unilateral lesions. Patients with a small uni­ lateral closed-lip cleft may be normal except for seizures. Children with bilateral schizencephaly and intractable sei­ zures tend to have substantial impairment. Blindness may occur in patients with bilateral clefts. 2 3° · 23 1

Schizencephaly

Pathology Focal neu ronal migration anomaly Transmantle cleft Dysplastic gray matter l i nes the cleft

Radiology Cerebral cleft from surface to lateral ventricle H eterotopic gray matter along cleft ! Tented ventricle at cleft

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 545

A

Figure 14-69 Bilateral open-lip schizencephaly.

B

A, B. There are bilateral fluid-filled cerebral clefts in this 8-month-old infant with seizures (f1-weighted images). Thick gray matter lines the clefts. The septum pellucidurn is intact.

M RI is more sensitive than CT for the detection of schizencephaly and the potential associated brain lesions. This shows a collapsed or fluid-filled cerebral cleft that extends from the pial surface to the wall of the lateral ventri­ cle. Heterotopic gray matter lines the cleft. The gray matter is dysplastic and often has a somewhat irregular charac­ ter ( Figure 14-69) . Occasionally, heterotopic gray matter extends into the subependymal portion of the lateral ventri­ cle. The cortex adjacent to the cleft may have an abnormal gyral pattern, including radiation of sulci into the cleft. At the insertion of a thin cleft, there is usually a tented config­ uration of the ventricle (ventricular dimple) ( Figure 14-70) . This i s a useful characterizing feature in patients with closed-lip schizencephaly, and aids in the differentiation from transmantle heterotopia. With a large open-lip vari­ ety of schizencephaly, there is often prominence of the adjacent subarachnoid space and localized calvarial expan­ sion (Figure 14-71 ) . A thin membrane is sometimes visible at the cortical surface separating the fluid-filled cleft from the adjacent convexity subarachnoid space. The features of open-lip schizencephaly are often demonstrable with sonography in young infants (Figu re 14-72) . 226 Various additional brain anomalies are common in patients with schizencephaly. The septum pelluddum is absent in approximately two-thirds of patients. Many patients have optic nerve hypoplasia. There is absence or focal thinning ofthe corpus callosum in approximately 30% of patients. White matter thinning ipsilateral to the cleft is common. Polymicrogyria, either adjacent to or remote from a schizencephalic cleft, is present in approximately

Figure 14-70 Closed-lip schizencephaly. There is a thin gray matter-lined deft (arrow) in the right cerebral hemisphere on this Ti-weighted image. Note tenting of the ventricle at the connection with the cleft.

546 Part 3 The B ra i n

Figure 14-72 Open-lip schizencephaly. A coronal sonographic image shows a large fluid-filled defect in the right cerebral hemisphere. The septum pellucidum is absent.

Figure 14-71 Bilateral open-lip schizencephaly. This child has large gray matter-lined cerebral defects that communicate with the lateral ventricles. The skull is expanded.

two-thirds of patients. Heterotopic gray matter can occur adjacent to the cleft or at remote locations. There is an association with frontal lobe dysplasia or inferior fusion. Developmental venous anomalies are common in individu­ als with schizencephaly. 227 ·232 · 233

Focal Cortical Dysplasia Focal cortical dysplasia is a localized area of anomalous cor­ tical structure, with histological findings that include corti­ cal dyslarnination and abnormal giant neurons. There are various neuropathological classification schemes for this spectrum of cerebral anomalies. Patients with focal cortical dysplasia typically present early in childhood with intrac­ table partial epilepsy. Focal cortical dysplasia is a common neuropathological diagnosis in children undergoing corti­ cal resections for refractory epilepsy. 234-23 6 Potential MR findings of focal cortical dysplasia include localized cortical thickening (see Figure 19-U5) , indistinct­ ness at the gray matter-white matter junction, cortical hyperintensity on heavily T1-weighted images (e.g., magneti­ zation-prepared rapid acquisition gradient-echo sequences) , and abnormal hyperintensity on T2-weighted images. Ipsilateral hippocampal sclerosis sometimes accompanies focal cortical dysplasia of the temporal lobe. MR spectros­ copy is often helpful for the differentiation of focal cortical

dysplasia from a low-grade neoplasm. Brain tumors usually have diminished NAA, elevated choline-containing com­ pounds (Cho) , diminished NAAto-Cho ratios, and dimin­ ished NAAto-creatine-phosphocreatine ratios. Focal cortical dysplasia often is associated with only mild decrease in NAA and normal or mildly diminished NAA-to-creatinine and NAA-to-Cho ratios.237·23 8 Diffusion-tensor imaging allows noninvasive evalu­ ation of the integrity of the white matter adjacent to the abnormal cortex in children with suspected cortical dyspla­ sia. There are manifestations of decreased fractional anisot­ ropy in the region of the corticomedullary junction of the dysplastic brain as well as in fiber connections between the deep white matter and the dysplastic cortex. Dysplastic white matter may have an aberrant course on diffusion­ tensor imaging. 66 •23 9

Focal Cortical Dysplasia with Balloon Cells Focal cortical dysplasia with balloon cells is a localized mal­ formation of the cortex and adjacent white matter. Other terms for this disorder include focal transmantle cortical dys­ plasia and Taylor type offocal cortical dysplasia. The major his­ tological manifestation is alteration in the normal orderly lamination of the cortex at the site. There are also abnormal cells interspersed between normal neurons ; these include dysplastic neurons and balloon cells. Changes in the adja­ cent white matter include astroglial proliferation and defi­ cient myelination. Most patients present during childhood with partial epilepsy. Additional neurological manifesta­ tions may be present if the area of involvement is large.

Chapter 14 Co ngenital Abnormal ities of the B ra i n 547 MRI of focal transmantle cortical dysplasia shows focal cerebral cortical thickening, heterogenous eleva­ tion of T2 signal intensity in the subjacent white matter, and indistinctness of the gray-white matter junction. The white matter signal abnormality may extend to the ven­ tricular margin, sometimes with a linear, curvilinear, or wedge-shaped character. The involved gray matter can be isointense or hyperintense relative to normal gray matter on T2-weighted images. In young infants, the white mat­ ter abnormality is hyperintense on T1-weighted images and faintly hypointense on T2-weighted images. M R spectros­ copy of focal transmantle cortical dysplasia shows a subnor­ mal NAA-creatine ratio and elevation of myo-inositol. 239-241

Focal Cortical Dysplasia Without Balloon Cells Focal cortical dysplasia without balloon cells is a localized lamination abnormality of the cerebral cortex, usually in association with abnormal neurons. B alloon cells are lack­ ing. The major clinical manifestation is partial seizures. The typical MR finding of this anomaly is localized cortical thinning and T2 hyperintensity, in association with thin­ ning of the subjacent white matter. There is blurring of the gray-white matter junction at this site. The imaging find­ ings can be quite subtle, requiring careful inspection of thin section images.239·242

CLINICAL PRESENTAT IONS: THE CHI LD WITH SEI ZURES Epilepsy is a disorder of recurrent unprovoked seizures. Nonepileptic, or simple acute, seizures are those provoked by an acute CNS abnormality, such as infection, tumor, trauma, or ischemia. The prevalence of epilepsy in chil­ dren is approximately 4 per 1000; the cumulative risk dur­ ing childhood is approximately 10 per 1000. Epilepsy is a chronic endogenous functional disorder of the brain. In many instances, there are no discernible structural abnor­ malities of the brain; however, various congenital and acquired brain lesions can facilitate the expression of epi­ lepsy (Table 14-1 2) . Factors that are important in the clas­ sification of epilepsies include the age at presentation, the electroencephalographic patterns, the cause (idiopathic, symptomatic, or cryptogenic) , the prognosis, and the response to treatrnent.243 Neuroimaging studies of the child with epilepsy serve to detect a causal disease or malformation, evaluate effects of the disease on the brain (e. g., atrophy) , and aid in the localization of an epileptogenic focus for surgical therapy. In general, MR is the technique of choice for those chil­ dren with epilepsy who require neuroimaging evaluation. MR spectroscopy, M R perfusion imaging, diffusion tensor imaging, nuclear medicine studies (FDG-PET and SPECT) , and functional M R serve complementary roles in selected patients. Most children with idiopathic epilepsy have no detect­ able brain abnormalities on MRI. In patients with status

Table 1 4-1 2. Structural Causes of Refractory Epilepsy

Developmental tu mors

Ganglioglioma Dysembryoplastic neu roepithelial tumor Desmoplastic i nfantile gangliogl ioma Pleomorphic xanthoastrocytoma Gangliocytoma ; Hypothalamic hamartoma ' Focal cortical dysplasia Tu berous sclerosis , Hemi megalencephaly G ray matter heterotopia Sch izencephaly Polymicrogyria Stu rge-Weber syndrome Cavernous malformation Destructive brain lesions N eoplasms --- - - - - - - - -- -- - - -

Non neoplastic developmental lesions

Acq u ired brain lesions

- - - - - -- - - - - ------------

epilepticus, edema and subsequent selective neuronal necrosis occasionally lead to MR signal abnormality (i.e., restricted diffusion and increased signal on T2-weighted images) in the epileptogenic cortex and in the ipsilateral pulvinar, ipsilateral thalamus, and contralateral cerebel­ lum. In patients with tonicjclonic seizures or status epi­ lepticus, MR studies performed during the periictal period may demonstrate transient restricted diffusion and T2 pro­ longation in the involved cortical gyrus or subcortical white matter. This likely is the result of increased neuronal activ­ ity and the associated metabolic and vascular responses. Additional potential M R findings include effacement of gyri at the epileptogenic focus, local vascular dilation, and faint contrast enhancement.244·245

Sym ptomatic Generalized Epilepsy Symptomatic generalized epilepsy refers to patients with generalized seizures or spreading of partial seizures. The term symptomatic indicates that the patient has a demon­ strable underlying lesion of the brain, most of which are visible on M RI . Nearly any form of cerebral malformation may be present in children with symptomatic generalized epilepsy, including cortical maldevelopment, holopros­ encephaly, commissural agenesis, and pachygyria. Other potentially associated conditions include metabolic dis­ eases, hydrocephalus, and neuroectodermal syndromes (e.g., tuberous sclerosis) .

548 Part 3 The B ra i n

I nfanti le Spasms Infantile spasms (West syndrome) is a malignant symp­ tomatic generalized epilepsy syndrome with a clinical onset during the first year oflife. This disorder represents a response ofthe infantile brain to any of various CN S insults. In approximately 15% of patients with infantile spasms, the disorder is "cryptogenic" (i.e., no demonstrable cause on clinical and imaging evaluations). The remaining 85% of patients have a "symptomatic" form, caused by a known prenatal factor (e.g., infection) or brain malformation. Potential neuroimaging findings in these patients include commissural agenesis, agyria, pachygyria, and hemimega­ lencephaly. The combination of infantile spasms, com­ missural dysgenesis (including dysgenesis of the corpus callosum) , chorioretinal lacunae, and cortical malforma­ tions constitutes Aicardi syndrome. Infantile spasms occur in up to one-quarter of patients with tuberous sclerosis. 24 6

Partial-Onset Epilepsy Partial-onset epilepsy refers to forms of epilepsy in which the seizure pattern indicates involvement of a specific func­ tional area of the cortex. Surgical excision of the epilepto­ genic focus is potentially curative for these patients. The clinical features, electroencephalogram (EEG) findings, and results of neuroimaging investigations all are impor­ tant in seizure focus localization. Included in this category are seizure disorders related to cortical dysplasias, hemi­ megalencephaly, dysplastic glioneuronal tumors, hetero­ topia, agyria-pachygyria, micropolygyria, schizencephaly, hamartomas, and cerebral scars.

acids that cause prolonged neuronal depolarization and the entry of cytotoxic amounts of calcium. This process even­ tually leads to localized brain sclerosis. The occurrence of prolonged temporal lobe seizures is a major risk factor for the development of mesial temporal sclerosis. 247-24 9 The seizures that adolescents with mesial temporal sclerosis experience tend to include auras that involve a motionless stare, visceral sensation, oral alimentary autom­ atism, and loss of awareness. Affected infants and young children usually do not have identifiable auras, and may have long duration (>1 minute) seizures with prominent convulsive activity. In addition, seizures of temporal lobe origin in infants can have a generalized pattern; for exam­ ple, infantile spasms or generalized tonic seizures. Mesial temporal sclerosis is rare in infants; temporal lobe seizures in this age group are more often a result of a brain dyspla­ sia, migrational disorder, hamartoma, or low-grade tumor such as ganglioglioma. 25 ° Standard M RI shows mesial temporal sclerosis as thin­ ning of the hippocampus, often with alteration in signal intensity. High-resolution T1-weighted images generally provide the best assessment of hippocampal volume; the contralateral hippocampus serves as a comparative standard. Atrophy may also involve the subjacent subiculum. Gliosis, when present, results in hyperintensity on Tz-weighted images. In some patients, there is signal alteration in the hippocampus, without volume loss (Figure 14-73) . M R

Epi lepsia Partialis Conti n u a Epilepsia partialis continua refers to continuously repeated partial-onset seizures. This is the most common seizure pattern in patients with Rasmussen encephalitis, which is a progressive unilateral cerebral degenerative disease that is an important cause of intractable epilepsy in children. Epilepsia partialis continua is not specific to this diagno­ sis, however, and can occur in association with various infectious, neoplastic, inflammatory, and idiopathic brain conditions.

M esial Tem poral Sclerosis Mesial temporal sclerosis i s a structural abnormality i n the hippocampus that is associated with temporal lobe epilepsy or partial complex epilepsy. This is the most common neu­ roimaging finding in adolescents with seizures of temporal lobe origin. By definition, there is loss of at least half the neurons in the hippocampus, with or without associated gliosis. The pathogenesis is likely multifactorial, and may involve a combination of environmental and hereditary fac­ tors; prolonged febrile seizures in childhood appear to play a role in many patients. Therefore, mesial temporal scle­ rosis is not only a cause of seizures, but is also a result of seizures. Seizures result in the release of excitatory amino

Figure 14-73 Mesial temporal sclerosis. A coronal T2-weighted M R image of a teenager with temporal lobe epilepsy shows hyperintensity of the left hippocampus ( arrow).

Chapter 14 Congenital Abnorm a l ities of the B ra i n 549

A

8

Figure 14-74 Mesial temporal sclerosis.

c

spectroscopy may demonstrate metabolic abnormalities in the hippocampus. FDG-PET imaging shows diminished glucose metabolism in the epileptogenic temporal lobe dur­ ing the interictal state (identified in approximately 8o% of patients) (Figu re 14-74) . The demonstration of a hypometa­ bolic temporal lobe in these patients is a favorable indica­ tor for the likely effectiveness of surgical therapy. Anterior temporal lobe resection leads to complete seizure control in at least 8o% of these patients. Medical therapy alone is effective in fewer than so% of patients with mesial tempo­ ral sderosis.25'

Vagus N erve Sti m u lation Stimulation of the vagus nerve is helpful for seizure control in some children with drug-resistant epilepsy. A subcutane­ ous pulse generator connects to ribbon electrodes wrapped

Tiris 16-year-old boy has a history of partial complex epilepsy since age 9 years. During his seizures, he stares blankly and has automatisms. A. The right hippocampus (arrow) is smaller than the left as viewed on this thin­ section T1-weighted image. B. The right hippocampus (arrow) is hyperintense on a T2-weighted image. C. An interictal FDG-PET image shows hypometabolism in the right temporal lobe.

around the left vagus nerve. The antiepileptic action appar­ ently relates to effects on the brainstem reticular activat­ ing system. Potential adverse effects of this device include cough, vocal cord paralysis, chest pain, infection, nausea, and paresthesia. Radiographic evaluation serves to confirm electrode integrity. 252

Preoperative Brain Fu nction Localization The localization o f language-critical areas i n the brain is important for operative planning prior to surgery for sei­ zure disorders or neoplasm resection. The procedure most often used to assess language lateralization is the Wada test (also termed the intracarotid sodium amobarbital proce­ dure) , which involves the injection of amobarbital sodium into the carotid arteries. Before and after the intraarterial

550 Part 3 The B ra i n inj ection o f amobarbital sodium, the patient undergoes neuropsychological testing and

EEG monitoring.

Functional M R I is an alternative method for evaluating language lateralization, visual cortex function, and other cerebral activities . This technique is particularly useful for the preoperative evaluation of patients with neurological lesions in dose proximity to regions of vital cerebral func­ tion. The most commonly employed functional MR tech­ nique is based on the blood oxygenation level--dependent contrast effect. Signal alterations occur with changes in the ratio between the oxygenated and deoxygenated forms of hemoglobin in blood. Alternative functional MR tech­ niques include echoplanar imaging and signal targeting with alternating radiofrequency and flow-sensitive alternat­ ing inversion recovery.2 5 3

Febrile Seizu res Febrile seizures refer to those that occur in patients with

Dandy-Walker Malformation The

Dandy-Walker

malformation

(Dandy-Walker

syn­

drome) encompasses the triad of agenesis or hypoplasia of the cerebellar vermis , cystic dilation of the fourth ven­ tricle, and enlargement of the posterior fossa with supe­ rior displacement of the dural sinuses and tentorium. The pathogenesis apparently involves anomalous development of the inferior vermis and fourth ventricle. The posterior fossa cyst of the Dandy-Walker malformation has

3

lay­

ers : an inner ependymal layer that is contiguous with the ependyma of the fourth ventricle, a middle layer of neuro­ glial tissue that apparently represents residual embryonic cerebellar tissue, and an outer pial layer. The prevalence of this malformation is approximately

1 per 2 5 , 0 0 0 live­ 1% to 4%

births. Dandy-Walker malformation accounts for of cases of hydrocephalus .2 5 7-2 5 9

In infants prior to cranial suture closure, macroceph­ aly (often with a dolichocephalic configuration) is the most

fever and no other identifiable cause. By definition, these

common presenting feature of Dandy-Walker malforma­

patients do not have in intracranial infection, an underly­

tion. There may be bulging of the fontanelle. Older chil­

ing seizure disorder, or systemic metabolic abnormality.

dren may have manifestations of delayed psychomotor

5% of children experience a febrile seizure at some point during their lives. The peak age range is 6 months to 6 years . Febrile seizures can be simple or complex.

development. Increased intracranial pressure can lead to headaches and vomiting. Focal neurological findings are

Neuroimaging evaluation is only indicated if there is a clin­

cephalus is present by the first few months of life in most

Up to

uncommon in these children. Clinically significant hydro­

ical suspicion for a nonfebrile etiology or a complication

infants with Dandy-Walker malformation, but usually

such as elevated intracranial pressure.

is not present at birth. Approximately half of individuals

MRI within 2 days of a prolonged febrile seizure some­ times demonstrates manifestations of vasogenic edema

with Dandy-Walker malformation have normal intellectual development. 2 58

in the hippocampus, with hyperintensity on T2-weighted

Various C N S anomalies occur in association with

images and diffusion-weighted images. Typically, this

Dandy-Walker malformation. The most frequently associ­

resolves without sequelae on followup studies. In those

ated lesions are dysgenesis of the corpus callosum (most

unusual instances in which a prolonged febrile seizure is

common is absence of all but the genu) , occipital encepha­

followed by encephalopathy, M R performed a few days after

locele or meningocele, and aqueductal stenosis. Other

onset may demonstrate restricted diffusion and T2 -image

potential associated anomalies include holoprosencephaly,

hyperintensity in the subcortical cerebral white matter.

medullary pyramid absence , anomalies of the cerebel­

The most common areas of involvement are the frontal

lar folia, choroid plexus cyst, diverticular cyst of the third

lobes and anterior aspects of the parietal lobes , with spar­

ventricle, hypothalamic fusion, hemimegalencephaly, mal­

ing of the perirolandic regions. The diffusion abnormality

formation of the inferior olivary nuclei, anomalous gyral

usually disappears within several days to a few weeks, but

formation, and neurocutaneous melanosis. Approximately

long-term manifestations of local encephalomalacia are common.2 5 4· 2 55

have one or more non-CN S anomalies . Cardiac anomalies,

one-quarter of patients with Dandy-Walker malformation such as ventricular septal defect, patent ductus arteriosus,

POSTERIOR FOSSA ANOMALIES

tetralogy of Fallot, and arterial septal defect, are common. Anomalies of the facial bones (e.g., cleft palate) , skeleton

GI system (e.g. ,

The maj or cystic malformations of the posterior fossa

(e.g., syndactyly, Klippel-Feil syndrome) ,

include classic Dandy-Walker malformation, variations of

Meckel diverticulum, tracheoesophageal fistula, biliary

the Dandy-Walker anatomy, mega cisterna magna, arach­

atresia) , and genitourinary system (e.g., cryptorchidism,

noid cyst, and persistent Blake pouch. Anatomic, patho­

polycystic kidney, hypospadias) can occur as well.2 5 9·2 6o

physiologic, and histological distinction between many of

The neuroimaging features of classic Dandy-Walker

these malformations is imprecise. The important noncystic

malformation include an enlarged posterior fossa with a

malformations include Joubert syndrome, rhombencepha­

high tentorium, a small (approximately three-quarters of

losynapsis, and various forms of cerebellar hypoplasia.

patients) or absent cerebellar vermis, and a markedly dilated

Additional important posterior fossa anomalies are the

fourth ventricle

various Chiari malformations described earlier in this chapter. 2 5 6

forms the roof of the dilated fourth ventricle. This "cyst"

(Figures 14-75 and 14-76) . A thin membrane

causes anterior-superior rotation of any residual malformed

Chapter 14 Congenital Abnorm a l ities of the B ra i n 551 As noted above, many patients have posterior fossa cystic malformations with features intermediate between those of classic Dandy-Walker malformation and those of other anomalies. For instance, mild cerebellar hypoplasia sometimes accompanies a Blake pouch cyst. Prominence of the cisterna magna and fourth ventricle can occur in patients who have cerebellar hypoplasia, but lack other manifestations of classic Dandy-Walker malformation. Therefore, it is important to recognize that cystic malfor­ mations of the posterior fossa encompass a spectrum, and that categorization of malformations within this spectrum is imprecise. The term Dandy-Walker complex includes classic Dandy-Walker malformation, mega cisterna magna, intermediate anomalies (i.e., Dandy-Walker variant) , and Blake pouch cyst. Posterior fossa arachnoid cyst is usu­ ally considered a separate entity. A retrocerebellar arach­ noid cyst does not communicate with the fourth ventricle, causes anterior cerebellar displacement, and often leads to occipital bone thinning and expansion (Figure 14-79) . 2 63

M ega Cisterna M agna

Figure 14-75 Dandy-Walker malformation. An axial CT image of a 2-month-old infant shows an enlarged fourth ventricle that opens into a dorsal posterior fossa "cyst." The vermis is absent. There is dilation of the lateral and third ventricles.

superior vermis (Figures 14-77 and 14-78) . There is variable anterior displacement and compression of the brainstem. Hypoplasia of the cerebellum is a consistent feature, but the severity varies considerably between patients; involvement of the hemispheres is sometimes asymmetric. The torcula and transverse sinuses are in abnormally high positions. There is widening of the tentorial incisura. Normal lobula­ tion of the vermis and lack of supratentorial anomalies are imaging indictors of a favorable neurological prognosis for patients with Dandy-Walker malformation.2 6 '· 2 6 2

Mega cisterna magna refers to enlargement of the poste­ rior fossa in association with a prominent cisterna magna. The cerebellar vermis and the fourth ventricle are normal. There is no association with hydrocephalus. In the absence of other posterior fossa pathology, a mega cisterna magna is of no clinical consequence. Secondary enlargement of the cisterna magna is frequent in patients with an atrophic or hypoplastic cerebellum. 2 6 4 The neuroimaging appearance of mega cisterna magna consists of a prominent dorsal posterior fossa subarach­ noid space in conjunction with normal cerebellar anatomy (Figure 14-8o) . There is sometimes slight dorsal bulging/ thinning of the occipital bones. The normal cisterna magna thickness is less than 9 mrn, as measured in the midsagittal plane from the posterior margin of the foramen magnum to the adjacent portion of the vermis. Thin dural folds are sometimes present within a mega cisterna magna, but are typically lacking in other forms of Dandy-Walker complex (Figure 14-81 ) . Manifestations of mass effect on the cerebel­ lum in conjunction with prominent dorsal extraaxial fluid raise the possibility of an arachnoid cyst or Blake pouch cyst. 5

Blake Pouch Cyst Dandy-Walker M alformation

Hypoplastic/aplastic verm is Cystic dilation of fou rth ventricle Enlarged posterior fossa U pward displacement of tentoriu m , torcular ± Hyd rocephalus/macrocephaly Thi n n i ngjbulging of occiput

·· · · · · · · · · · · · · · · ·· · · · · · · · · · · · · · ·· · · · · · · · ·

... .

. .... . .

............................

..... . ..

..

· · · ·· · · · · ·· · · ··· · · ·· · · · · · · · · · · · · ·

. . .... ............. ... ..

..

. . ........ ........... . . . . .

... . ..

· · · · · · · · · · ·· · · · · · · · ···· · ··-

.. . .............

Blake pouch is a transient embryonic structure that nor­ mally regresses during the fifth to eighth gestational weeks. Persistence of this structure results in a retrocere bellar cyst that communicates with the fourth ventricle via an enlarged foramen of Magendie. Imaging studies show a midline posterior fossa cyst, dilation of the fourth ventricle, hydro­ cephalus, and separation of the cerebellar hemispheres. The cerebellar vermis is sometimes hypoplastic. The diagnostic imaging appearance of a Blake pouch cyst sometimes does not allow accurate distinction from an arachnoid cyst. The imaging findings can also overlap

Part 3 The B r a i n

552

A

8

Figure 14-76 Dandy-Walker malformation.

Axial M R images of 3 children. A. An enlarged arrow-shaped fourth ventricle cormnunicates with a retrocerebellar fluid collection. There is posterior bulging of the occipital portion of the skull. B. This child has moderate cerebellar hypoplasia as well as a large retrocerebellar cyst. There is hydrocephalus. C. There is mild dilation of the fourth ventricle in this patient. Fluid outlines hypoplastic cerebellar hemispheres.

those of Dandy-Walker malformation. The appearance of the fourth ventricular choroid plexus varies between these conditions, however. There is displacement of the choroid plexus into the superior wall of a Blake pouch cyst. With a retrocerebellar arachnoid cyst, the choroid plexus should be in a normal location. The fourth ventricular choroid plexus is usually absent in patients with Dandy-Walker malformation. 2 57,264 ,26 5

c

Cerebellar Hypoplasia Cerebellar hypoplasia without a posterior fossa cystic mal­ formation can be focal, asymmetric, or diffuse. In keep­ ing with this morphological heterogeneity, the pathogenic mechanisms are disparate. The anomaly can be sporadic or genetic. In some patients, there is true deficiency in cer­ ebellar development. A congenitally small cerebellum can

Chapter 14 Congenital Abnorm a l ities of the B ra i n 553

Figure 14-77 Dandy-Walker malformation. A midline longitudinal sonographic image of a newborn shows a large posterior fossa "cyst" (arrow) that communicates with the fourth ventricle. There is minimal residual ecl10genic vermis superior and posterior to the fourth ventricle. The oval fluid-filled supratentorial structure is a dilated cavum septum pellucidurn.

hypoplasia, Marinesco-Sj ogren syndrome, carbohydrate­ deficient glycoprotein syndrome, and autosomal recessive lissencephaly with cerebellar hypoplasia. Chapter 18 dis­ cusses the causes of cerebellar atrophy. The major clinical features of cerebellar hypoplasia are speech delay, ataxia, hypotonia, abnormal ocular move­ ments , microcephaly, and autistic features ( Figure 14-82) . Neuroimaging studies most often demonstrate a uniformly small cerebellum, usually accompanied by a hypoplastic pons ( Figure 14-83) . The relative severity of involvement of the hemispheres and vermis is variable. Isolated hypopla­ sia of a cerebellar hemisphere can also occur ( Figure 14-84) . Differentiation between cerebellar hypoplasia and cerebel­ lar atrophy is sometimes difficult. With hypoplasia, the relative sizes of the folia and fissures are usually normal despite the small size of the cerebellum. Atrophy results in enlargement of the fissures and shrinkage of the folia. 18 p66,267 Vermian agenesis or hypogenesis is a component of Dandy-Walker malformation, as described above. In some patients, vermian hypoplasia occurs without the other fea­ tures of Dandy-Walker malformation. "Isolated" vermian hypoplasia refers to a congenitally small vermis, with nor­ mal cerebellar hemispheres, a normal-size posterior fossa, and no significant posterior fossa cyst.

Cerebellar Dysplasia

also result from an acquired prenatal insult. Genetic dis­ orders that involve hypoplasia of the cerebellum (without a posterior fossa cyst) include pontocerebellar hypoplasia types 1 and 2, X-linked nonprogressive congenital cerebellar

Various patterns of cerebellar dysplasia can occur. These sometimes accompany malformations of the cerebrum. Imaging studies of cerebellar dysplasia show abnormal cortical architecture. The findings can be unilateral or

A

B

Figure 14-78 Dandy-Walker malformation.

Midline sagittal T1-weighted M R images of 2 children. A There is elevation of the tentorium and an enlarged fluid-filled posterior fossa. The hypoplastic vermis (arrow) is displaced posteriorly

and superiorly. The soft tissue dorsal to the medulla ( inferior to the arrow) is the medial margin of the cerebellar hemisphere. B. The posterior fossa "cyst" is smaller in this patient. The enlarged fourth ventricle displaces the vermis (arrow) .

Part 3 The B r a i n

554

A

Figure 14-79 Retrocerebellar arachnoid cyst. A An axial CT image of a 4-year-old child shows a large posterior fossa fluid collection that causes anterior displacement of

A

Figure 14-80 Mega cisterna magna. A, B. There is prominence of the retrocerebellar subarachnoid space on these T1-weighted images of a 7-year-old child.

B

the cerebellum. There is no communication with the fourth ventricle. B. The elevated tentorium separates the occipital lobes.

B

The cerebellum is normal. There is slight thinning of the occipital bone.

Chapter 14 Congenital Abnorm a l ities of the B ra i n 555 bilateral, and may or may not have accompanying cerebel­ lar hypoplasia (Figure 14-85) .

Jou bert Syndrome

Figure 14--81 Mega cisterna magna. An axial T2-weighted image shows prominent retrocerebellar fluid on the left. There is focal thinning of the occipital bone. (arrows) pass through the fluid.

Thin dural folds

A

Figure 14--82 Severe cerebellar hypoplasia.

This 15-year-old girl has mild ataxia, poor extraocular muscle control, swallowing difficulty, dysarthria, and cognitive delay.

Joubert syndrome is an autosomal recessive posterior fossa malformation that consists of vermian hypoplasia in con­ junction with structural and functional abnormalities of the midline brainstem structures. The alterations include dysplastic and heterotopic cerebellar nuclei, anomalous inferior olivary nuclei, and derangement of the cerebellar­ brainstem connections and cerebellar-cortical connections. The typical clinical findings in infants with Joubert syn­ drome include hypotonia, developmental delay, abnormal respiratory patterns, and abnormal eye movements. On axial cross-sectional CT and MR images, there is a characteristic "molar tooth" appearance at the level of the pontomesencephalic junction in patients with Joubert syndrome. This finding is a result of a narrow midbrain isthmus and relatively large, horizontally oriented supe­ rior cerebellar peduncles. Narrowing of the anteroposterior dimension of the midbrain is most prominent at the mid­ line. Sagittal images demonstrate a markedly hypoplastic vermis in an abnormally high position. The midbrain is narrow at the midline. A midline cleft in the vermis may be visible on coronal and axial images. The fourth ventricle is usually prominent (Figu re 14-86) . 66.26 8 ,26 9

8 A, B. Sagittal and axial T1-weighted MR images show near­ complete absence of the cerebellum, secondary enlargement of the cisterna magna and fourth ventricle, and a small pons.

556 Part 3 The B r a i n

A

Figure 14-83 Cerebellar hypoplasia. A. An axial M R image of a 2-year-old child with developmental delay and hypotonia shows markedly deficient cerebellar hemispheres (arrow) and a small pons. B. A midline sagittal

Posterior fossa findings identical or similar to those of Joubert syndrome can occur with various other dis­ orders. Reported associated malformations in patients with Joubert-like neuroimaging features include polydac­ tyly, ocular lesions (coloboma or retinal dysplasia) , renal anomalies (multicystic dysplastic kidney or juvenile neph­ ronophthisis), hepatic pathology (cysts or fibrosis) , and hypothalamic anomalies. 27 °

Rhombencephalosynapsis Rhombencephalosynapsis is a rare congenital anomaly that consists of vermian agenesis, fusion of the cerebel­ lar hemispheres, and apposition or fusion of the dentate nuclei. Most of these patients have associated supratento­ rial brain anomalies, usually resulting in severe motor and intellectual developmental delay. In occasional patients, the findings are limited to the posterior fossa and the clinical manifestations are less severe. All affected patients have ataxia and other signs of cerebellar dysfunction. Some patients suffer major psychiatric disorders, such as obses­ sive oral self-mutilation. Imaging studies show lack of separation of the cerebel­ lum into distinct hemispheres . The cerebellar white matter and dentate nuclei form a continuous band that surrounds the lateral and posterior aspects of the fourth ventricle, with no intervening vermis. The fourth ventricle is elongated in the anterior-posterior dimension and narrowed in the

B

image demonstrates a small posterior fossa, with inferior extension of the occipital lobes. Hypoplasia of the vermis is less pronounced than that of the hemispheres.

medial-lateral dimension (Figure 1 4-87) . This sometimes results in a characteristic "keyhole" shape of the fourth ventricle on axial images (Figure 14-88) . Other potential posterior fossa deformities in these patients include fusion of the quadrigeminal plate to the middle and superior cer­ ebellar peduncles and hypoplastic olivary nuclei. Common supratentorial lesions in patients with rhombencephalo­ synapsis include anomalies of the corpus callosum, fusion of the thalami, tectum, and fornices, hypoplasia of the chi­ asm, temporal lobes, andfor anterior commissure, a cleft in the parietooccipital region, frontal or occipital enceph­ alocele, and subcortical or periventricular heterotopia. Ventriculomegaly is common. 271•2 7 2

ANOMALIES OF THE PITUITARY CLAND The pituitary gland arises from 2 sites: (1) from an ectoder­ mal outpocket of the stomodeum (Rathke pouch) and (2 ) from a downward extension of the diencephalon. Pituitary gland anomalies result from deficient or abnormal develop­ ment of either or both of these components. The dominant clinical feature of most developmental lesions of the pitu­ itary gland and hypothalamus is growth failure. Pituitary anomalies are often associated with malformations of other midline or paramedian structures, such as the optic chi­ asm, septum pellucidum, skull base, and palate.

Chapter

A

14

Co ngenital Abnorm a l ities of the B ra i n

557

8

Figure 14-84 Unilateral cerebellar hypoplasia. A-C. T2-weighted MR images of a 2-year-old child

c

Pitu itary G land Hypoplasia/Aplasia Congenital deficiency of growth hormone or of other ade­ nohypophyseal and neurohypophyseal hormones can occur as a consequence of pituitary gland hypoplasia or aplasia. Some instances of a congenitally small, poorly functioning pituitary gland are due to rupture of the pituitary infun­ dibulum during delivery (a history of breech presentation is common) or a perinatal ischemic event. True pituitary aplasia usually results in death during the perinatal period.

with a history of ataxia and sei=es show absence of the right cerebellar hemisphere aside from a small superior component (arrow) . The vermis is present. The left cerebellar hemisphere is normal in appearance, and bulges slightly across the midline.

Other forms of congenital pituitary gland deficiency often present with manifestations of growth hormone deficiency (i.e., pituitary dwarfism) . Children with pituitary gland hypoplasia/aplasia often have associated craniofacial or brain anomalies; anomalies of other organ systems are sometimes present as well.273 There is a spectrum of pituitary gland morphology on MR evaluation of infants with congenital growth hormone deficiency. Those patients with normal-appearing pituitary glands tend to have only mild biochemical abnormalities.

558 Part 3 The B r a i n

8

A

Figure 14--85 Cerebellar dysplasia and hypoplasia. Axial Tt-weighted (A) and T2-weighted (B, C) images of a 25-day-old infant show a globally small cerebellum that lacks normal folia. There is a focus of heterotopic gray matter (arrows) in the inferior aspect of the left cerebellar hemisphere. Images of the supratentorial structures were normal.

c

Individuals with a small anterior lobe and normal appear­ ances of the stalk and posterior lobe usually have interme­ diate clinical manifestations. Children with more severe alterations in the pituitary gland often have multiple pitu­ itary hormone deficiencies. The most common neuroim­ aging pattern in these more severely affected children is that of a small sella turcica, small anterior pituitary gland, absence of the normal high signal intensity posterior pitu­ itary gland (on Tt-weighted MR), absence or hypoplasia of

the inferior aspect of the pituitary stalk, and an anomalous high signal focus in the superior aspect of the pituitary stalk near the median eminence (Figure 14-89) . 274 The characteristic hyperintense focus in the pituitary stalk that is common in patients with pituitary gland hypo­ plasia/aplasia is often termed an ectopic neurohypophysis. However, this apparently represents accumulation of neu­ rosecretory vesicles at the site of stalk discontinuity rather than an abnormally located true posterior pituitary gland.

Chapter 14 Co ngenital A b n o r m a l ities of the B ra i n 559 nerves. Pituitary duplication is a component of the median cleft-lip syndrome (frontonasal dysplasia) ; other features of this syndrome include hypertelorism, midfacial cleft­ ing, a broad nasal root, a low frontal hairline, agenesis of the corpus callosum, and cranium bifidum occultum frontale. 277-2 83 Coronal M RI is usually the best technique for demon­ strating duplication of the pituitary gland. The duplicated infundibula course along the lateral margins of the supra­ sellar cistern and merge with small duplicated pituitary glands that also are situated more laterally than normal. There is no visible pituitary gland on midline sagittal images. The sella is shallow. A "bar" of thickened tissue is often visible along the floor of the third ventricle on sagit­ tal and coronal images (Figu re 14-90) . This bar is isoin­ tense to gray matter and apparently represents tissue that would normally migrate laterally to form hypothalamic nuclei.

Em pty Sella Tu rcica

Figure 14-86 Joubert syndrome. An axial CT image of a 9-year-old child with developmental delay shows a "molar tooth" configuration of the midbrain and superior cerebellar peduncles. The fourth ventricle is enlarged.

This focus sometimes has a nodular configuration, and should not be misinterpreted as a suprasellar or hypotha­ lamic neoplasm. The small size of the anterior pituitary gland that is common in patients with pituitary stalk dis­ continuity may be a secondary phenomenon due to depri· vation of hypothalamic-stimulating factors and lack of normal blood supply. 27 s.>76

Pitu itary G land Duplication Duplication o f the pituitary gland is a rare anomaly. This sometimes occurs in conjunction with hypothalamic duplication. Nearly all of these patients have additional craniofacial anomalies, such as hypertelorism, congenital pharyngeal tumors, cleft palate, facial clefting, olfactory anomalies, choanal atresia, or dysgenesis of the corpus cal· losum. Developmental brain lesions that can occur in asso­ ciation with pituitary gland duplication include cerebellar hypoplasia, migrational defects, hydrocephalus, vascular anomalies (e.g., basilar artery duplication) , and absence of the corpus callosum, anterior commissure, septum pel­ lucidum, anterior falx, massa intermedia, and olfactory

"Empty sella turcica" refers to a flattened pituitary gland in association with enlargement of the diaphragmatic hia­ tus. The diaphragma sella is thin. The deficiency of the dia­ phragma allows herniation of the suprasellar cistern into the sella. The resultant exposure to C S F pulsation com­ presses the pituitary gland and causes enlargement of the sella turcica. Most often, empty sella is of no clinical signifi­ cance. Rarely, there is headache, endocrinopathy, or visual field loss; the term "empty sella syndrome" refers to those patients with symptoms. Empty sella can occur in associa· tion with intracranial hypertension or nevoid basal cell car­ cinoma syndrome. On imaging studies, the pituitary gland in patients with empty sella appears flat, sometimes with only a thin rim of tissue along the floor of an enlarged sella. The pituitary stalk is intact and is in a normal position; this finding is important for the distinction from a space-occu· pying cyst (Figure 14-91 ) . 2 84, 2 85

BRAIN MALFORMATIONS ACQUIRED IN UTERO

Hyd ranencephaly Hydranencephaly is a congenital destructive CNS disor· der in which most of the cerebrum is absent and replaced by C S F . The thin remaining peripheral brain tissue forms a membrane that is composed of an outer layer of lepto· meningeal tissue and an inner layer of remnants of cere­ bral cortex and white matter. The fluid-filled cavity within the brain exists as a large monoventricle or cyst; formed lateral ventricles are lacking. The cyst usually communi­ cates with the third ventricle. Obstructive hydrocepha­ lus of variable severity is sometimes present, because of obstruction of the aqueduct. The thalami are usually pre­ served, and the posterior fossa structures are normal or minimally involved.

560 Part 3 The B ra i n

A

B

Figure 14-87 Rhombencephalosynapsis. A-C. Axial T2-weighted images of a 22-month-old boy show vermian agenesis and complete fusion of the cerebellar hemispheres. The fused cerebellar white matter is best visualized in B. There is a narrow fourth ventricle in A. with posterior tapering.

The pathogenesis of hydranencephaly involves a pre­ natal event that causes massive destruction and subsequent resorption of fetal cerebral tissue (i.e., liquefactive necro­ sis) . Therefore, this lesion probably represents a severe form of porencephaly. The precise mechanism of injury is unknown in most instances; different factors likely are involved in individual cases. Bilateral carotid artery occlu­ sion appears to be the most common cause. Intrauterine infection apparently plays a role in many patients; for example, toxoplasmosis or Cytomegalovirus infection.

c

Neonates with hydranencephaly may initially appear clinically normal, since cerebellar and brainstem functions are relatively preserved. Neurological findings become apparent within a few weeks after birth, however. Spasticity and myoclonic seizures are common. Hydrocephalus leads to macrocephaly in some of these children, whereas lack of brain growth causes microcephaly in others. There is absent or markedly suppressed brain activity on electroen­ cephalography. Many children with hydranencephaly die during infancy.28 6

Chapter 14 Co ngenital A b n o rm a l ities of the B ra i n 561

B

A

Figure 14--88 Rhombencephalosynapsis.

A Vermian agenesis results in a "keyhole" configuration of the fourth ventricle on this axial T2-weighted image. B. There is fusion of the thalami.

Neuroirnaging studies of the infant with hyclranen­ cephaly demonstrate replacement of the cerebral hemi­ spheres by C S F , with only a thin peripheral rim of brain tissue (Figure 14-92) . The thalami are usually present

A

Figure 14--89 Pituitary hypoplasia. A, B. Sagittal and coronal T1-weighted M R images of a 38-day-old infant with congenital growth hormone deficiency show a small

(Figure 14-93) . Occasionally, there is somewhat greater formation of the inferior aspects of the frontal lobes and the inferior-medial portions of the temporal lobes. The falx cerebri is usually present ( Figu re 14-94) . The cerebellum is

B

pituitary gland. There is a nodular hyperintense focus at the base of the infundibulum (arrows) ; i.e., "ectopic neurohypophysis." The remainder of the stalk is absent.

562 Part 3 The B ra i n

A

Figure 14-90 Duplication of the pituitary gland.

A A coronal MR image shows 2 pituitary glands (arrows) and 2 pituitary stalks. B. A normal sella turcica is lacking on this

B

midline sagittal image. There is a thick bar of tissue (arrow) along the floor of the third ventricle.

normal or slightly small, but otherwise intact. The brain­ stem is variably hypoplastic. 2 87,2 88

Hyd ranencephaly Struct u re

Cerebrum Thalami Falx cerebri Cerebel l u m B rainstem

Figure 14-91 Empty sella turcica. The anterior pituitary gland has a flattened configuration and there is prominent fluid in the sella on this sagittal T1-weighted image of a 14-year-old boy with headaches. The pituitary stalk is normal.

I m agi ng fi n d i n g

Replaced by fl u id Thi n peripheral ri m of tissue : Present, u nfused Present , N ormal or small Small

Hydranencephaly i s sometimes difficult t o distin­ guish from severe hydrocephalus, although the treatment approach is similar for both: diversionary shunting ifthere is macrocephaly. In most instances , MR provides suffi­ cient differentiating information. Neuroimaging studies of severe hydrocephalus demonstrate a definite mantle of cerebral tissue surrounding the dilated ventricles; the membrane surrounding hydranencephaly is quite thin. The differentiation ofhydranencephaly from severe alobar holoprosencephaly is usually straightforward: in the latter

Chapter

14

Co ngenital A b n o r m a l ities of the B ra i n 563

A

Figure 14-93 Hydranencephaly. The posterior fossa structures are normal. The thalami are preserved as well. Fluid occupies the remainder of the supratentorial space. The peripheral rim of brain tissue in this infant is too thin to visualize on CT.

condition, the falx cerebri is absent, the thalami are fused, cerebral tissue inferior to the midline cyst is preserved, and a rudimentary third ventricle is usually identifiable.

Porencephaly

8

Figure 14-92 Fetal hydranencephaly. A, B. T2-weighted images obtained coronal and sagittal to the fetal head show fluid occupying the majority of the cranial vault (arrows) and absence of most cerebral tissue. The brainstem and cerebellum are hypoplastic. The falx cerebri is visible on the coronal image. There is partial formation of the central gray matter structures of the cerebrum. There are small areas of cerebrum in the inferior aspect of the right temporal lobe and in the posterior parietal-occipital region. The fetus is in a cephalic presentation, with the face directed anteriorly.

In the general sense, the term porencephaly refers to any nonneoplastic fluid-filled cavity in the brain. Various types of porencephaly are recognized based on the pre­ sumed etiological factors, morphology, and patient age. Encephaloclastic porencephaly refers to a smooth-walled, congenital cystic brain lesion that lacks substantial sur­ rounding glial reaction. This type is usually a result oflocal­ ized brain destruction during the first half of gestation; for example, hemorrhage or stroke. A brain cyst that results from an insult later in fetal life or acquired after birth (e.g. , caused by neonatal asphyxia or a cerebrovascular accident) is more properly termed cystic encephalomalacia. This type is associated with glial reaction. Porencephaly can also be divided into communicating and noncommunicating types, to reflect the presence or absence of connection with the ventricular system. Amygdalar-hippocarnpal atrophy

564 Part 3 The B ra i n

A

8

Figure 14--94 Hydranencephaly. This 1-week-old infant had seizures and macrocephaly. A. A coronal sonographic image shows fluid occupying nearly the entire supratentorial space. There is minimal irregular brain tissue adjacent to the tentorium. A falx cerebri is present. B, C. Sagittal and coronal Tz-weighted MR images confirm replacement of the cerebrum by fluid. Minimal temporal and occipital lobe tissue is present inferiorly. The cerebellum and brainstem are small, but otherwise intact.

often coexists with congenital porencephaly in patients with seizures. Neuroirnaging studies demonstrate encephaloclastic porencephaly as a smooth-walled cavity. Most often, the cyst has a wide communication with the ventricular system (Figure 14-95) . The fluid within the cavity is isointense to C S F on all M RI sequences . Sonography and MR are also useful for the antenatal detection of porencephaly. 2 89 .2 9 ° With cystic encephalomalacia, manifestations of glio­ sis are usually demonstrable adjacent to the cyst. The wall of the cyst is often irregular and septations may be pres­ ent. The gliosis in the adjacent brain produces areas of

c

high signal intensity on T2-weighted images. T1-weighted sequences often provide the best demonstration of glial septa in the cavity. Sonography is also quite sensitive for identifying the numerous glial septa that commonly occur in cystic encephalomalacia. The cyst may or may not com­ municate with the ventricular system.

M oebiu s Syndrome Moebius syndrome is an extremely rare developmen­ tal condition of the facial nerves. The classic clinical features relate to involvement of the sixth and seventh

Chapter

Figure 14-95 Porencephaly. A coronal FLAIR image of a 6-year-old child shows a large porencephalic cyst on the left that communicates with the lateral ventricle.

cranial nerves, with paralysis of the face and eye muscles. Abnormalities of other cranial nerves are common as well. Infants with Moebius syndrome have a weak suck. There is an inability to move the eyes horizontally to fol­ low an obj ect. Facial expression is lacking and the eyes are crossed. Other potential findings include central respi­ ratory dysfunction, delayed walking (muscle weakness) , and speech impediments. The underlying pathology is facial nerve underdevelopment, pos sibly related to a pre­ natal brainstem insult. Neuroimaging of patients with Moebius syndrome occasionally shows tegmental calcifi­ cations in the brainstem and/ or brainstem hypoplasia. 2 9 1

CONGENITAL NEOPLASMS Approximately 10% of fetal tumors are intracranial. Teratoma is the most common primary intracranial neo­ plasm of the fetus. This lesion accounts for about half of prenatally diagnosed C N S tumors. Other intracranial tumors that can arise in the fetus include astrocytoma, lipoma, choroid plexus papilloma, craniopharyngioma, and primitive neuroectodermal tumor. The most com­ mon sites of origin of congenital intracranial neoplasms are the suprasellar region, pineal gland, and cerebral hemispheres . Unlike brain tumors in infants and chil­ dren, infratentorial neoplasms are uncommon in the fetus .2 9 2

14

Co ngenital A b n o r m a l ities of the B ra i n 565

Most CNS tumors of the fetus are discovered inciden­ tally on prenatal ultrasound. Occasionally, there is palpable enlargement of the uterine fundus as a result of polyhy­ dramnios. The usual mechanism of polyhydramnios in this situation is depressed fetal swallowing due to hypo­ thalamic dysfunction. Uterine enlargement can also result from hydrocephalus caused by obstruction of ventricular system outflow by the mass or from increased C S F pro­ duction (e.g., choroid plexus papilloma) . Congenital brain tumors sometimes grow quite rapidly. Most are diagnosed during the third trimester. With the exception of lipoma and choroid plexus papilloma, congenital brain tumors are associated with a very high fetal mortality rate. 2 9 3 Both sonography and M R are useful for the prena­ tal detection and characterization of congenital brain tumors. Macrocephaly and hydrocephalus are commonly present. An intracranial teratoma typically appears as a large complex mass that contains cystic and solid compo­ nents . Calcifications may be present. Most teratomas arise at the midline. An astrocytoma is usually a solid mass located in the cerebral hemisphere or thalamus. A cranio­ pharyngioma is a heterogeneous suprasellar mass that is often calcified; this lesion cannot be reliably differentiated from a teratoma. A fetal choroid plexus papilloma appears as a lobular intraventricular mass with well-defined mar­ gins. There is hydrocephalus. With sonography, a choroid plexus papilloma is hyperechoic. A congenital intracra­ nial lipoma is a well-defined mass either at the midline or in the central aspect of a cerebral hemisphere. Those arising in the midline are often associated with dysgen­ esis of the corpus callosum. Lipomas are hyperechoic on sonography. 2 94 ·2 9 5

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243. Guerrini R, Carrozza R. Epileptogenic brain malformations: clinical presentation, malformative patterns and indications for genetic testing. Seizure. 2001;10 (7) :532-543; quiz 544-537. 244. Raybaud C, Shroff M , Rutka JT, Chuang S H . Imaging surgical epilepsy in children. Childs Nerv Syst. 2oo6;22 (8):786-8o9.

245. Kim )A, Chung ) 1 , Yoon P H , et al. Transient M R signal changes in patients with generalized tonicoclonic seizure or status epilepticus: periictal diffusion-weighted imaging. A1NR Am 1 Neuroradiol. 2001;22 (6) :1149-116o. 246. Fukuyarna Y. History of clinical identification of West syndrome-in quest after the classic. Brain Dev. 2001;23(8): 779-'787. 247. liu Z, Mikati M , Holmes GL. Mesial temporal sclerosis: pathogenesis and significance. Pediatr Neurol. 1995;12 (1) :5-16. 248. Lewis DV. Febrile convulsions and mesial temporal sclerosis. Curr Opin Neurol. 1999;12(2) :197-201.

261. Boddaert N, Klein 0, Ferguson N, et al. Intellectual prognosis of the Dandy-Walker malformation in children: the importance of vermian lobulation. Neuroradiology. 200J;45 (5):320-324. 262. Hanigan WC, Wright R, Wright S . Magnetic resonance imaging of the Dandy-Walker malformation. Pediatr NeurosGi. 198p2 (3) :151-156. 263. Barkovich AJ, Kjos BO, Norman D, Edwards MS. Revised classification of posterior fossa cysts and cystlike malformations based on the results of multiplanar M R imaging. A1R Am 1 Roentgenol. 1989;153(6) :1289-1300. 264. Tortori-Donati P, Fondelli M P , Rossi A, Carini S . Cystic malformations of the posterior cranial fossa originating from a defect of the posterior membranous area. Mega cisterna magna and persisting Blake's pouch: two separate entities . Childs Nerv Syst. 1996;12(6) :3 03-308. 265. Calabro F, Arcuri T, Jinkins JR. Blake's pouch cyst: an entity within the Dandy-Walker continuum. Neuroradiology. 2000;42(4):2 90-295· 266. Wassmer E, Davies P, Whitehouse WP, Green S H . Clinical spectrum associated with cerebellar hypoplasia. Pediatr Neurol. 2oop8(5) :347-351· 267. Uhl M , Pawlik H, Laubenberger ) . et al. M R findings in pontocerebellar hypoplasia. Pediatr Radiol. 1998;28(7) :547-5 51·

249. Ng YT, McGregor AL, Duane DC, et al. Childhood mesial temporal sclerosis. 1 Child Neurol. 2006;21(6):512-517.

268. Alorainy IA. Sabir S , Seidahmed MZ, et al. Brain stem and cerebellar findings in Joubert syndrome. 1 Comput Assist Tomogr. 2oo6;3o (1) :u6-121.

250. Bourgeois BF. Temporal lobe epilepsy in infants and children. Brain Dev. 1998;20(3) :135-141.

269. Quisling RG, Barkovich A). Maria BL. Magnetic resonance imaging features and classification of central nervous system malformations in Joubert syndrome. 1 Child Neurol. 199 9;14(10):628-635; discussion 66 9-672.

251. Lee S K, Lee D S , Yeo JS, et al. FDG-PET images quantified by probabilistic atlas of brain and surgical prognosis of temporal lobe epilepsy. Epilepsia. 2oo2;43 (9):1032-1038. 252. Benifia M , Rutka )T, Logan W, Donner E). Vagal nerve stimulation for refractory epilepsy in children: indications and experience at The Hospital for Sick Children. Childs Nerv Syst. 2oo6;22(8) :1o18-1o26.

270. Chance PF, Cavalier L, Satran D, e t a l . Clinical nosologic and genetic aspects of Joubert and related syndromes. 1 Child Neurol. 1999;14(10) : 6 6 o-666; discussion 669-672. 271. Silit E, Mutlu H , Ozturk T. A rare cerebellar malformation: rhombencephalosynapsis. 1 Neuroradiol. 2002;29(3): 208-210.

253. Benson RR, FitzGerald DB, LeSueur LL, et al. Language dominance determined by whole brain functional MRI in patients with brain lesions. Neurology. 1999;52(4) :798-809.

272. Toelle SP, Yalcinkaya C, Kocer N, et al. Rhombencephalosynapsis: clinical findings and neuroimaging in 9 children. Neuropediatrics. 2002;33 (4) :209-214.

254. Scott RC, King MD, Gadian DG, et a!. Prolonged febrile seizures are associated with hippocampal vasogenic edema and developmental manges. Epilepsia. 2oo6;47(9) :1493-1498.

273. Simon D, Hadjiathanasiou C, Garel C, et al. Phenotypic variability in children with growth hormone deficiency associated with posterior pituitary ectopia. Clin Endocrinol (Oxf} . 2006;64(4) :416-422.

255. Takanashi ) , Oba H, Barkovich A), et al. Diffusion M RI abnormalities after prolonged febrile seizures with encephalopathy. Neurology. 2oo6;66 (9) :1304-13o 9 ; discussion 1291. 256. Niesen CE. Malformations of the posterior fossa: current perspectives. Semin Pediatr Neurol. 2002; 9 (4):320-334· 257. Nelson M D Jr, Maher K. Gilles FH. A different approaciJ to cysts of the posterior fossa. Pediatr Radiol. 2004;34 (9): 720-732. 258. Hirsch JF, Pierre· Kahn A. Renier D, et a!. The Dandy­ Walker malformation. A review of 40 cases. 1 Neurosurg. 1984;61(3):515-522.

274. Maghnie M, Triulzi F, Larizza D, et al. Hypothalamic-pituitary dwarfism: comparison between MR imaging and CT findings. Pediatr Radiol. 1990;2o(4):229-235· 275. Maintz D, Benz-Bohm G, Gindele A, et al. Posterior pituitary ectopia: another hint toward a genetic etiology. A1NR Am 1 Neuroradiol. 2ooo;21(6) :m6-m8 . 276. Denton ER, Powrie ) K, Ayers AB, Sonksen P H . Posterior pituitary ectopia and hypopituitarism-magnetic resonance appearances of four cases and a review of the literature. Br 1 Radiol. 1996;69 (821) A02-406.

259. Pascual-Castroviejo I, Velez A, Pascual-Pascual SI, et al. Dandy-Walker malformation: analysis of 38 cases. Childs Nerv Syst. 1991;7(2): 88-97-

277. Lees M M , Hodgkins P, Reardon W, et al. Frontonasal dysplasia with optic disc anomalies and other midline craniofacial defects: a report of six cases. Clin Dysmorphol. 1998;7(3) :157-162.

260. Has R, Ermis H, Yuksel A. et al. Dandy-Walker malformation: a review of 78 cases diagnosed by prenatal sonography. Fetal Diagn Ther. 2004;19 (4) :342-347-

278. Slavotinek A, Parisi M , Heike C, et al. Craniofacial defects of blastogenesis: duplication of pituitary with cleft palate and orophgaryngeal tumors. Am 1 Med Genet. 2005:135 (1) :13-20.

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281. Harnon-Kerautret M, Ares G S , Demondion X, et al. Duplication of the pituitary gland in a newborn with median cleft face syndrome and nasal teratoma. Pediatr Radial. 1998;28(5):290-2 92. 282. Ryals BD, Brown DC, Levin SW. Duplication of the pituitary gland as shown by MR. AJNR Am J Neuroradiol. 1993;14(1) : 137-13 9·

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CH A P T E R

15

H ydrocephalus

M ECHANISMS OF HYDROCEPHALUS. . . .

575

CLI N ICAL FEATURES OF HYDROCEPHALUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

576

I MACi i NCi OF HYDROCE PHALUS . . . . . . . . . . . . . .

576

SPECI FIC TYPES OF HYDROCEPHALUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

578

Hyd rocephalus Due to Excessive Cerebrospinal Fluid Formation . . . . . . . . . . . . . . .

578

Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

585

Chiari I I Malformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

585

Dandy-Walker Malformation . . . . . . . . . . . . . . . . . . . .

586

FETAL VENTRICULOM ECiALY . . . . . . . . . . . . . . . . . . . .

586

B E N I Ci N E N LARCi E M ENT OF SU BARACH NOI D SPACES. . . . . . . . . . . . . . . . . . . . . . . . . . . .

586

EX VACUO VENTRICU LOM ECiALY . . . . . . . . . . . .

587

TREAT M E NT OF HYDROCEPHALUS . . . . . . . .

587

Central N ervous System S h u nt Eval u ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

587

.

I ntraventricular Obstruction ( N oncom m u n icati ng Hyd rocep halus) . . .

578

Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

578

Foramen of Monro Obstruction . . . . . . . . . . . . . . .

579

Aqueductal Stenosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

579

Ventriculopleural Shunt

Fourth Ventricle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

581

Trapped Fourth Ventricle . . . . . . . . . . . . . . . . . . . . . . . . .

581

Ventriculocardiac Shunt

Outlet Obstruction o f the

Extraventricular Obstruction (Co m m u n icati ng Hyd rocephalus) . . . . . . . . . .

583

Meningitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

584

Meningeal Metastasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

584

Venous Obstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

585

MECHANI SMS OF HYDROCEPHALUS Hydrocephalus refers to abnormal dilation of the ven­ tricular system in association with narrowing of the subarachnoid spaces. Elevation of the intraventricular pres sure may or may not be present. Hydrocephalus is not synonymous with ventriculomegaly.

Most forms

of hydrocephalus are due to an imbalance between the formation and absorption of cerebrospinal fluid, that is, inadequate passage of cerebrospinal fluid (CSF) from its point of production within the ventricular system to its point of absorption into the systemic circulation. The excess intraventricular C S F that results from this imbal­ ance in turn causes an increase in intracranial pres­ sure . The degree and pattern of enlargement of the C S F pathways and the amount o f damage t o central nervous

Ventriculoperitoneal Shunt Complications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

589 591

Complications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

593

T h i rd Ventricu lostomy Evaluation . . . . . . . . . . . . . . .

593

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

595

system ( C N S ) structures depend o n both the severity and the pathogenesis of the hydrocephalus. t-3

An important site of C S F absorption is into the sagittal sinus via the arachnoid villi, that is, the pacchionian granula­ tions. Absorption of C S F at the pacchionian granulations is passive. The valve system of the arachnoid villi has an open­ ing pressure of approximately

5 mm of mercury. Above this

opening pressure, the rate of fluid absorption is directly pro­ portional to the intracranial pressure. Equilibrium between C S F production and absorption occurs at approximately mm of mercury

10 (14 em water) . Capillaries throughout the

C N S also contribute substantially to C S F absorption. In par­ ticular, there is relatively free bidirectional mixing of C S F with fluid i n the interstitium o f the brain. 4 Approximately

6o% of C S F production is via the cho­

roid plexus, with the remainder by other mechanisms such

575

576 Part 3

The

B ra i n

a s parenchymal capillaries and the ependyma. The rate of

pressure. Also important are the rate ofincrease of pressure

C S F production in the brain is relatively constant in most

and the presence or absence of associated structural abnor­

individuals ; overproduction of C S F is not the cause of

malities. Hydrocephalus that develops prior to the age of

hydrocephalus in the great maj ority of cases (choroid plexus

2

papilloma is an important exception) . Acute hydrocephalus

mation and aqueductal stenosis account for approximately

years generally leads to macrocephaly. Chiari II malfor­

is generally due to pathology that blocks the flow of C S F

8o% of cases ofhydrocephalus in this age group. Other rel­

o r results i n impaired resorption o f fluid. Typically, this

atively common causes ofhydrocephalus in infants include

is related to blockage of flow in the ventricular system, in

intrauterine infection, perinatal hemorrhage, and neonatal

the basal cisternae, or in the subarachnoid space along the

meningitis . Rare etiologies include midline tumor, choroid

cerebral convexities. Diminished absorption can also result

plexus papilloma, arachnoid cyst, and C N S arteriovenous

from abnormalities of the arachnoid villi. Ventriculomegaly

malformation.

due to mechanical obstruction of C S F drainage pathways

In infants with hydrocephalus, the head circumference

causes brain expansion, compression of cortical veins,

increases at an abnormal rate, that is, the macrocephaly

secondary venous congestion, impaired brain capillary

is progressive. The head circumference in infants with

absorption of C S F , and elevated intracranial pressure. This

idiopathic "benign" macrocephaly usually follows an age

sequence of events may exacerbate hydrocephalus and

appropriate rate of growth.

cause symptomatic reduction in cerebral oxygenation.

head and a thin skull often accompany long-term infantile

Acute obstructive hydrocephalus causes elevation of

A disproportionately large fore­

hydrocephalus . Other potential clinical findings include

intraventricular pressure, ventricular enlargement, and

widening of the cranial sutures, bulging of the anterior fon­

brain expansion. Compression of cortical veins by the

tanelle, and dilation of the scalp veins. Ocular disturbances

expanding brain leads to intracranial venous congestion and

that can occur in these patients include paralysis of upward

elevation of the intracranial pressure that counteracts ven­

gaze (Parinaud syndrome) , nystagmus, proptosis , and a

tricular expansion. As the intracranial pressure increases

diminished pupillary light reflux. Spasticity of the lower

in the patient with hydrocephalus, there is increased C S F

extremities is common.

absorption through th e arachnoid membrane and the

Hydrocephalus that first develops later in childhood

stroma of the choroid plexus. Fluid may also egress through

is usually due to aqueductal stenosis or a posterior fossa

the extracellular spaces of the cortical mantle, that is, tran­

tumor. The most important determinants of the clinical

sependymal C S F flow that appears as periventricular edema

features in these patients are the severity of hydrocephalus

on CT and MR examinations. These compensatory absorp­

and the nature of any underlying primary lesion. A com­

tive pathways establish a new equilibrium between the pro­

mon presentation is that of early morning headaches that

duction and absorption of C S F at an elevated pressure.

improve in the upright position. Vomiting, particularly in

Transependymal flow of C S F through the white mat­

the morning, is another frequent clinical sign of increased

ter in the patient with hydrocephalus leads to neuronal

intracranial pressure. This presentation sometimes leads

and astrocytic swelling in the gray matter, and atrophic

to a mistaken diagnosis of G I tract pathology.

changes in the nerve fibers of the cerebral hemispheres.

Papilledema and strabismus are common findings of

The cilia that normally cover the ependymal surface of the

hydrocephalus at presentation. In the lower extremities ,

ventricular system may disappear in the presence of sub­

spasticity and cerebellar signs are the predominant mani­

stantial long-standing hydrocephalus . Marked elevation of

festations. Endocrine abnormalities may result from com­

the intraventricular pressure can cause reduction of cere­

pression of the hypothalamic-pituitary axis by the enlarged

bral blood flow; this reduction is most pronounced in the

anterior recesses of the third ventricle; potential manifes­

distribution of the anterior cerebral arteries . Compromised

tations include short stature, gigantism, menstrual irregu­

blood flow can in

larities , hypothyroidism, and diabetes insipidus.

turn lead to ischemic injury of the basal

forebrain and medial cerebral hemispheres. In the chronic phase of communicating hydrocephalus, compensatory absorption pathways result in a CSF pressure that is normal or only mildly increased. Because the com­

IMACINC OF HYDROCEPHALUS The mainstay imaging technique for the diagnosis and

pressed intracranial arteries have diminished compliance,

characterization of hydrocephalus is CT. Sonography is

there is abnormal increased pulse pressure in the brain cap­

valuable for the detection and monitoring of hydrocepha­

illaries. This, in

lus in young infants . MR provides optimal depiction of the

turn increases the intraventricular pulse ,

pressure and thereby serves to maintain and exacerbate ven­

pathological anatomy in patients with hydrocephalus. M R

triculomegaly even if the mean C S F pressure is normal.4

i s also a n option t o C T for followup o f patients with known hydrocephalus , thereby avoiding repeated exposure to ion­

CLINICAL FEATURES OF HYDROCEPHALUS

izing radiation.s,6 Cross-sectional imaging studies

of hydrocephalus

show dilation of the ventricular system proximal to the

Several factors influence the clinical manifestations of

obstruction. Differentiation from ex vacuo ventriculo­

hydrocephalus, including the age of the patient at the time

megaly is crucial. Features that favor true hydrocepha­

of onset and the duration of the increased intracranial

lus include effacement of cortical sulci, enlargement of

Chapter 15

H yd rocep h a l u s

577

the temporal horns in conjunction with prominence of the remainder of the lateral ventricles , inferior displace­ ment of the floor of the third ventricle, and dilation of the anterior andjor posterior recesses of the third ventricle (in those patients with obstruction beyond the level of the third ventricle)

( Figure 1 5-1) .

Clinically, there is mac­

rocephaly in most patients with hydrocephalus. Evidence of transependyrnal flow of C S F (periventricular edema) , when present, confirms elevation of intraventricular pres­ sure

( Figure 1 5-2) .

Fluid-attenuated inversion recovery

( F LA I R) MR images are most sensitive for this finding. CT images may show periventricular hypoattenuation

(Figure 1 5-3 ) .

Periventricular edema sometimes causes

hyperechogenicity in the periventricular white matter on sonography.7-9 Two-dimensional cine phase-contrast MRI provides information about C S F flow dynamics. This can be useful for selected patients to document

an

obstruction, such as at the

cerebral aqueduct or foramen magnum. This technique is also useful for assessing patency of a third ventriculostomy. Image acquisition is performed parallel andjor perpendic­

Figure 1 5-1 Hydrocephalus. A midline sagittal image of a child with aqueductal stenosis shows dilation of the third ventricle (arrows) .

ular to the expected direction of flow. C S F that is flowing downward appears white and upward flow is in black.'0•11 S kull radiographs of infants with hydrocephalus show nonspecific macrocephaly. There often is widening of the cranial sutures . With chronic hydrocephalus in older chil­ dren, there occasionally is a "beaten silver" or "hammered silver" appearance of the skull.

A

Figure 1 5-2 Hydrocephalus.

A. A Tz-weighted spin echo M R image shows dilation of the lateral ventricles, effacement of cortical sulci, and periventricular edema (arrow) . B. The periventricular edema (arrow) is

B

hyperintense on this coronal FLAIR image. There is dilation of the third ventricle and the temporal horns, as well as the bodies of the lateral ventricles.

578 Part 3 The B ra i n Table 1 5-1 . Causes of Noncommunicating Hydrocephalus

I ntrinsic causes

Extri nsic causes

Figure 1 5-3 Hydrocephalus. An unenhanced CT image shows ventriculomegaly and periventricular edema.

SPECIFIC TYPES OF HYDROCEPHALUS There are 2 maj or types of hydrocephalus: that due to over· production of C S F and that due to obstruction to the flow of, or the inadequate absorption of, fluid. Overproduction of CSF is rare; the major cause is papilloma or carci­ noma of the choroid plexus. The great majority of cases of hydrocephalus are due to obstruction of normal C S F flow or inadequate absorption. There are 2 subcategories of this type: (1) communicating hydrocephalus, in which there is an extraventricular (beyond the foramina of Luschka and Magendie) obstruction to flow or diminished absorption, and (2) noncommunicating (or obstructive) hydrocepha· lus, which is caused by intraventricular obstruction, most often at the aqueduct of Sylvius. Other common sites of obstruction include the foramina of Monro and the fourth ventricular outlet foramina.12

Hyd rocephal us Due to Excessive Cerebrospinal Fluid Formation Choroid plexus papilloma and carcinoma can cause hydro­ cephalus by way of C S F overproduction and for mechanical ventricular outflow obstruction. Occasionally, a papilloma

Congenital stenosis or atresia I ntraventricular cyst H emorrhage : Ad hesions (infection, hemorrhage) N eoplasm N eoplasm Vascu lar malformation B rain edema H emorrhage B rain malformation I nfection

on a pedicle leads to manifestations ofintermittent obstruc­ tion. Imaging evaluation of a choroid plexus tumor shows a prominently enhancing, lobulated intraventricular mass. Parenchymal invasion can occur, particularly with carci­ noma. These tumors are most often located in the lateral ventricle near the trigone. Diffuse villous hyperplasia is a rare developmental lesion, in which there is generalized choroid plexus enlarge­ ment without a localized mass. Overproduction of C S F causes communicating hydrocephalus i n these patients.'J

I ntraventricu lar Obstruction (N oncom m u n icating Hyd rocephal us) Noncommunicating hydrocephalus (i.e., intraventricular obstructive hydrocephalus) can result from obstruction in any portion of the ventricular system, from the foramina of Monro to the foramina of Magendie and Luschka. The cause of the obstruction may be congenital or acquired, and the obstruction can be intrinsic or extrinsic to the ventricu­ lar system (Table 1 5-1 ) . CT, sonography, and MR all serve important roles for the detection and characterization of obstructive hydrocephalus. Because of the potential for even small neoplasms to cause obstructive hydrocephalus, MR is often useful for evaluation of patients who have clini­ cal and CT findings suggestive ofidiopathic hydrocephalus.

Tumors Various neoplasms and congenital cysts can cause ven­ tricular obstruction at the level of the foramina of Monro. Midline parenchymal brain lesions tend to obstruct both foramina, whereas unilateral or asymmetric tumors more often cause unilateral obstruction. Intraventricular tumors or cysts (e.g., intraventricular arachnoid cyst and colloid

Chapter 1 5 Hyd roce p h a l u s 579

A

Figure 1 5-4 Arachnoid cyst of the quadrigeminal plate cistern.

A. B. Sagittal and axial T1-weighted MR images of a 2-month-old child with macrocephaly show obstructive hydrocephalus due to a very large cyst (arrows) of the quadrigeminal plate cistern. The

cyst of the third ventricle) can also obstruct the foramen of Monro. Suprasellar masses can displace the floor of the third ventricle superiorly and cause extrinsic obstruction of the foramina of Monro and third ventricle. In children with tuberous sclerosis , a subependymal nodule or giant cell astrocytoma that originates adjacent to the foramen of Monro can grow medially to obstruct the foramen. A second potential site of neoplastic ventricular system obstruction is at the aqueduct of Sylvius. Pineal tumors that can cause extrinsic aqueductal obstruction in children include germ cell tumors (germinoma, endodermal sinus tumor, and teratoma) , pineocytoma, and pineoblastoma. Gliomas and hamartomas of the tectum are uncommon tumors that, even when quite small, can produce obstruc­ tive hydrocephalus by compression of the aqueduct; these lesions are often subtle on neuroimaging studies. A vein of Galen aneurysm is a nonneoplastic lesion that can pres­ ent with signs of hydrocephalus due to compression of the aqueduct. A large arachnoid cyst of the quadrigeminal plate cistern can compress the tectum and obstruct the aqueduct (Figure 1 5-4) . Obstruction due to a pineal cyst is rare. At the level of the fourth ventricle, various poste­ rior fossa masses can cause obstructive hydrocephalus (Figure 1 5-5) . Posterior fossa tumors may obstruct the fourth ventricle or aqueduct by way of invasion or extrin­ sic compression. Hydrocephalus is relatively common with

B

cyst compresses the dorsal aspect of the brainstem and causes inferior displacement of the cerebellum. The cerebral aqueduct is not visible.

ependymal and cerebellar tumors (e.g., medulloblastoma and ependymoma) ; this complication is less frequent with intrinsic brainstem tumors.

Foramen of Monro Obstruction Hydrocephalus due to obstruction of the foramen of Monro can occur as a developmental lesion (e.g., congenital atre­ sia or stenosis of the foramen) or due to a mass of the anterior aspect of the third ventricle or adjacent portion of the lateral ventricle (e.g., hypothalamic glioma, colloid cyst of the third ventricle, craniopharyngioma, suprasellar germinoma, or giant cell astrocytoma) . Imaging studies show unilateral or bilateral dilation of the lateral ventricles, without third ventricular enlargement (Figure 1 5-6) . With long-standing obstruction in an infant, such as occurs with congenital stenosis of the foramen of Monro, there often is enlargement of the ipsilateral hernicranium.

Aqueductal Stenosis Intrinsic aqueductal stenosis accounts for 15% to zo% of cases of pediatric hydrocephalus. The prevalence is approximately 1 in 1000 live births. Both developmental and acquired forms of aqueductal stenosis occur; the latter are less common. Acquired stenosis is usually due to fibrillary gliosis related to prior hemorrhage or infection. Aqueductal

580 Part 3 The B ra i n

A

Figure 1 s-s Acute hydrocephalus due to a cerebellar juvenile pilocytic astrocytoma. This 4-year-old child presented with a 10-day history of headache, nausea, and vomiting. A. Contrast-enhanced sagittal MR shows an enhancing cystic and solid mass of the cerebellum. There

A

Figure 1 5-6 Unilateral congenital foramen of Monro obstruction. A, B. Axial and coronal M R images of a 1-day-old infant with macrocephaly show marked dilation of the right lateral ventricle.

B

is compression of the fourth ventricle. The cerebral aqueduct is prominent. B. There is mild dilation of the lateral and third ventricles on this coronal FLAIR image. Minimal periventricular edema is present.

B

There is no periventricular edema. The enlarged lateral ventricle bulges across the midline. The third ventricle and left lateral ventricle are normal in size.

Chapter 15 Hyd roce p h a l u s 581

A

Figure 1 5-7 Aqueductal stenosis. A An axial Tl-weighted MR image of a newborn with macrocephaly shows severe dilation of the lateral ventricles. The 3rd ventricle (arrow) is blind-ending and there is no visible

stenosis occurs in so% to 75% of individuals with Chiari I I malformation. A rare X-linked form o f congenital aqueduc­ tal stenosis has been described.l4-'6 Intrinsic obstruction of the aqueduct is due to a mem­ brane, focal or long-segment stenosis, or forking (replace­ ment of the aqueduct by multiple narrow channels) . Focal stenosis most often occurs at the level of the superior col­ liculi or at the intercollicular sulcus. Forking and stenosis of the aqueduct are frequently accompanied by fusion of the quadrigeminal bodies, fusion of the third nerve nuclei, and molding or beaking of the tectum. In some patients, the shape of the molded tectum is congruent with that of the medial aspects of the dilated adjacent temporal lobes. Neuroimaging studies suggest the diagnosis of aque­ ductal stenosis when there is dilation of the lateral and third ventricles in association with a normal or small fourth ventricle. M R provides the most detailed characterization of the morbid anatomy (Figure 1 5-7) . Contrast-enhanced images are helpful to exclude a small neoplasm. Normal C S F pulsation in the region of the aqueduct is lacking on T2-weighted and cine phase-contrast MR sequences. In patients with severe hydrocephalus due to aqueductal ste­ nosis, rupture ofthe septum pellucidurn can occur. Stenosis of the proximal portion of the aqueduct, either at the level of the superior colliculus or at the entrance of the aqueduct immediately inferior to the posterior commissure, usually leads to severe hydrocephalus. Stenosis of the more distal

B

aqueduct in the midbrain. There is a somewhat beaked character of the tectum. B. 3 mm thick Tl-weighted sagittal images also failed to demonstrate a patent aqueduct. On this midline image, the superior aspect of the fourth ventricle ( arrow) is blind-ending.

portions of the aqueduct tends to be associated with mild or moderate severity hydrocephalus. In these patients, imaging studies show dilation of the proximal aspect of the aqueduct and posterior displacement of the quadrigeminal plate ( Figure 1 5-8) .'7

Outlet Obstruction ofthe Fourth Ventricle Intraventricular obstructive hydrocephalus is occasionally due to an obstruction of the fourth ventricular foramina of Magendie and Luschka. The cause of the obstruction can be developmental (e.g., Chiari I malformation) , mechanical (e.g., posterior fossa tumor) , or postinfl.ammatory. Imaging studies usually show dilatation of the entire ventricular system, and disproportionate enlargement of the fourth ventricle ( Figure 1 5-9) . Syringohydromyelia may occur in patients with outlet foramina occlusion when the opening into the central canal is patent.

Trapped Fourth Ventricle Trapped, or isolated, fourth ventricle results from con­ comitant obstruction of the aqueduct of Sylvius and the fourth ventricular outflow foramina. Continued C S F pro­ duction by the fourth ventricular choroid plexus in these patients leads to progressive cystic dilatation of the fourth ventricle. This condition is usually due to mechanical or

582 Part 3 The B ra i n

A

Figure 1 5-8 Aqueductal stenosis.

B

This 3-year-old boy presented with a history of progressive ataxia for 6 weeks and headaches for 4 days. A. A sagittal T1-weighted MR image shows dilation of the third ventricle (3) and a normal fourth ventricle. The superior aspect of the aqueduct is

dilated; no fluid is visible in the mid to inferior aspect (arrow) . There is splaying of the midbrain. The quadrigeminal plate is displaced and thinned. B. Normal C S F pulsation is lacking in the aqueduct. Note normal signal loss due to pulsation at the foramen magnum.

A

B

Figure 1 5-9 Chiari I malformation; obstructive hydrocephalus.

A. Herniation of the cerebellar tonsils to the C4 level is visible on this T1-weighted sagittal M R image. There is ventriculomegaly,

including dilation of the fourth ventricle and aqueduct. B . An axial T2-weighted image shows ventriculomegaly and periventricular edema.

Chapter 1 5

H yd rocep h a l u s

583

inflammatory abnormalities . The most common associa­ tion is prior intraventricular hemorrhage related to prema­ turity. Postinflammatory scarring due to prior shunting or meningitis is an additional potential cause.'8 On neuroimaging studies, a trapped fourth ventricle appears as a large, round or pear-shaped, midline cystic structure in the posterior fossa

(Figu re 1 5-10) .

The dilated

ventricle causes anterior displacement of the brainstem and posterior displacement of the cerebellar vermis. There is also dilation of the lateral and third ventricles; however, the fourth ventricular dilation is usually disproportionate. Enlargement of the fourth ventricle persists despite surgi­ cal decompression of the lateral ventricles. As with other lesions that distort and compress the cervicomedullary junction, trapped fourth ventricle can lead to syringomyelia

(Figure 1 5-1 1 ) . '9

Extraventricu lar Obstruction (Co m m u n icati ng Hyd rocephal us) Approximately

30% of children with hydrocephalus have a

communicating form, that is, extraventricular obstructive hydrocephalus. After passing through the outlet foram­ ina of the fourth ventricle, C S F normally enters the cis­

Figure 1 5-10 Trapped fourth ventricle.

terna magna and basal cisternae and then flows into the

An axial CT image demonstrates marked dilation of the fourth ventricle. There is also dilation of the lateral ventricles in this newly diagnosed patient prior to shunting.

can impede this drainage pathway include meningeal

A

Figure 1 5-11 Trapped fourth ventricle. A A sagittal MRI image of a 5-year-old child with shunted hydrocephalus shows marked dilation of the fourth ventricle. There is displacement of the cerebellum and brainstem. The

cerebral and cerebellar subarachnoid spaces. Factors that

B

inferior aspect of the fourth ventricle bulges below the foramen magnum. B. There is associated syringohydromyelia of the cervical spinal cord.

584 Part 3

The

B ra i n

Table 1 5-2. Causes o fComm u nicating Hydrocephalus

Obliterative arach noiditis (posthemorrhagic or inflammatory) Leu kemiajlymphoma Langerhans cell histiocytosis Venous obstruction Subarach noid tumor i m plants

thickening, adhesions in the subarachnoid spaces, and elevated venous pressure in the arachnoid villi. The basal cisternae, the tentorial hiatus, the spaces surrounding the cerebral hemispheres , and the arachnoid granulations are potential sites of extraventricular obstruction. Communicating

hydrocephalus

can

occur

as

a

sequela to bleeding (e.g., germinal matrix hemorrhage in a premature newborn) , infection, or granulomatous meningitis

(Table 1 5-2) .

Meningeal cellular infiltration

due to leukemia, lymphoma, or Langerhans cell his­ tiocytosis can also obstruct the subarachnoid spaces . There are rare instances in which communicating hydro· cephalus occurs in association with superior vena cava obstruction, presumably due to interference with C S F absorption by elevated venous pres sures . A n additional

Figure 1 5-12 Hydrocephalus due to acute bacterial meningitis. An unenhanced CT image shows mild ventriculomegaly and bilateral subdural effusions.

proposed mechanism of communicating hydrocephalus is diminished absorption of C S F by C N S capillaries, due to intracranial hemodynamic alterations caused by arteri­

the neuroimaging pattern of hydrocephalus in these

opathy or arachnoiditis (i. e . , "restricted arterial pressure hydrocephalus" ) . 4

patients is usually that of global ventriculomegaly. Mild ventricular dilatation during the acute phase of meningitis does not necessarily portend permanent obstructive hydrocephalus . Followup imaging after resolu­

Meningitis Meningitis

causes

alteration

of C S F

flow

dynamics,

although clinically evident hydrocephalus is uncommon in these patients. Purulent material accumulates in the subarachnoid spaces during the acute phases of bacterial meningitis, thereby impeding extraventricular C S F flow. In addition, inflammation of the arachnoid granulations interferes with C S F absorption. These abnormalities usu­ ally resolve as the inflammatory process decreases during treatment. However, fibrosis in the subarachnoid spaces

tion of the infection is required to determine the likelihood of long·term hydrocephalus . During acute meningitis, contrast-enhanced MR often shows localized or diffuse meningeal enhancement; this finding is

occasionally

demonstrable on contrast-enhanced CT as well. Small subdural fluid collections are common in these patients

( Figure 1 5-1 2) ?' · 22

Meningeal Metastasis

can lead to long-term obstructive sequela. Bacterial menin­

Neoplastic disease that involves the subarachnoid spaces

gitis tends to produce arachnoiditis in the cerebral cortical

and meninges can lead to extraventricular obstruction of

region, whereas granulomatous infections of the meninges

C S F flow. The

(e. g . , tuberculous meningitis) more often cause oblitera­

(e.g., medulloblastoma and ependymoma) and hematoge­

tion of the cisternae. 2 0

2 major mechanisms are C S F tumor seeding

nous neoplastic infiltration of the meninges (e. g . , leukemia

With prompt treatment of bacterial meningitis, clini­ cally significant hydrocephalus is uncommon. The like­

and lymphoma) . Clinically evident hydrocephalus is most common in those patients with extensive disease.

in these

CT and M RI evaluations of patients with communi­

patients roughly correlates with the duration and severity

cating hydrocephalus due to meningeal metastasis show

of the infection. Poor outcomes tend to be associated with

variable degrees of ventriculomegaly. The involved menin­

lihood for the development of hydrocephalus

delayed initiation of therapy. B ecause the manifestations

ges are thickened and undergo prominent enhancement.

of meningeal infection are predominantly extraventricular,

There is often obliteration of some or all of the cisternae.

Chapter 1 5 Hyd roce p h a l u s 585 With seeding via the C S F , enhancing tumor nodules can be present anywhere in the subarachnoid spaces or ven­ tricular system. In general, MR is more sensitive than other imaging techniques for demonstrating neoplastic menin­ geal abnormalities .

Venous Obstruction Hydrocephalus can occur in patients with venous out­ flow obstruction in the neck or head. This presumably results from alteration of C S F absorption dynamics at the arachnoid villi due to elevation of the intracranial venous pressure. Infants and young children are particularly susceptible to the development of hydrocephalus by this mechanism; patients older than 3 years of age who have venous outflow obstruction are more likely to develop pseu­ dotumor cerebri. This age-related variation may relate to relatively greater brain parenchymal pliability and calvarial expandability in infants, thereby allowing greater ventricu­ lar dilatation in response to pressure elevations. In older children and adults, the myelinated brain parenchyma is less pliable, and fused sutures prevent calvarial expansion; therefore, intracranial venous hypertension leads to pseu­ dotumor cerebri without ventriculomegaly.

Hemorrhage Hydrocephalus is a frequent complication of intraventricu­ lar hemorrhage in infants. This complication is particularly common in premature infants who are born before gesta­ tion week 32. In the first few days after the hemorrhage, clotted blood may cause obstruction both within the ven­ tricular system and in the subarachnoid space. Therefore,

A

Figure 1 5-13 Chiari I I malformation; hydrocephalus.

A, B. Transverse (A) and longitudinal (B) sonographic images of a neonate with meningomyelocele show marked dilation of the lateral ventricles and mild prominence of the third ventricle (3) .

there is a combination of noncommunicating and commu­ nicating hydrocephalus. Hydrocephalus that occurs dur­ ing this acute phase may spontaneously resolve or persist indefinitely. Following infantile intraventricular hemorrhage, a variable degree of scarring and fibrosis develops in the sub­ arachnoid spaces within several days of the initial bleed. This adhesive arachnoiditis tends to be most prominent in the region of the cisterna magna. If there is substantial fibrosis within the subarachnoid spaces, a subacute form of communicating hydrocephalus may develop. The devel­ opment of subacute hydrocephalus after germinal matrix hemorrhage in a premature infant is associated with a poor functional prognosis. In full-term neonates, subarachnoid hemorrhage is most often due to birth trauma. The mechanisms by which hemorrhage causes acute and subacute hydrocephalus in these infants are similar to those in premature infants. There is a greater likelihood for spontaneous resolution of hydrocephalus in this age group, however. Hemorrhage into the subdural space is a potential cause of hydrocephalus in children of all ages. Hydrocephalus by this mechanism is usually of mild or moderate sever­ ity. Imaging studies show ventricular dilatation, subdural fluid, and slight enlargement of the subarachnoid space adjacent to the subdural hematoma.

Chiari II Malformation The Chiari II malformation is the most common cause of hydrocephalus in children, accounting for approxi­ mately 40% of cases ( Figure 1 5-13) . The pathophysiology

B

There is no identiliable fourth ventricle on the longitudinal image. Absence of the septum pelluddum, as demonstrated on the transverse image, is common in patients with Chiari I I malformation.

586 Part 3 The B ra i n o f hydrocephalus in these children i s multifactorial. The outlet foramina of the fourth ventricle in children with Chiari I I malformation usually empty into the cervical spinal canal. The connection between the spinal and intra­ cranial subarachnoid spaces is deficient in these patients due to "plugging" of the foramen magnum by displaced cerebellum and brainstem. Because of the limited capacity for C S F absorption in the spinal canal, the poor communi­ cation with the intracranial subarachnoid spaces presum­ ably leads to hydrocephalus. In most cases, there does not appear to be significant obstruction in the ventricles or at the fourth ventricular foramina. Intrinsic aqueductal steno­ sis contributes to hydrocephalus in more than half of chil­ dren with Chiari II malformation.

Dandy-Walker Malformation Hydrocephalus occurs in about three-quarters of patients with Dandy-Walker malformation ( Figure 1 5-14) . Ventriculomegaly i s usually not present at birth in these children, however. The mechanism of hydrocephalus in most patients with Dandy-Walker malformation is unknown. One proposed factor is an increased susceptibil­ ity to subarachnoid hemorrhage from episodes of minor trauma. Subarachnoid hemorrhage (either from a single large bleed or from multiple small bleeds) may impede absorption of C S F and thereby result in communicating hydrocephalus. A less common mechanism is an anatomic obstruction at the level of the aqueduct.

Figure 1 5-14 Hydrocephalus with Dandy-Walker malformation. A coronal sonographic image shows markedly dilated lateral ventricles, as well as the classic Dandy-Walker pattern of a dilated fourth ventricle opening into a posterior fossa "cyst."

FETAL VENTRICULOMECiALY Ventriculomegaly is the most common fetal CNS abnor­ mality demonstrated on prenatal sonography. Fetal ven­ triculomegaly is defined as an atrial width of greater than 10 mm as measured at the posterior margin of the glomus of the choroid plexus on an axial image at the level of the thalami. 2 3 Associated CNS anomalies are common in fetuses with ventriculomegaly; those with isolated prenatal ventriculomegaly usually have a better outcome than those with other anomalies. Potential coexistent CNS lesions include dysgenesis of the corpus callosum, Dandy Walker malformation, neural tube defects, holoprosencephaly, and cortical malformations. MRI is particularly well suited for the detection of associated CNS lesions in fetuses with ventriculomegaly. Obstruction can occur due to intraventricular hemorrhage arising from the germinal matrix, appearing as foci ofhyper­ intensity on T1-weighted images. Periventricular white mat­ ter injury results in foci of periventricular T2 hyperintensity, defects in the germinal matrix, irregularity of the ventricu­ lar margin, or larger areas of signal abnormality in the white matter and cortex. The subset of fetuses with mild isolated ventriculomegaly (atrial width of 10 to 15 mm) and no addi­ tional sonographic findings most often go on to have no or mild neurodevelopmental abnormalities. 24·2 5

BENIGN ENLARGEMENT OF SUBARACHNOI D SPACES Mild enlargement of the subarachnoid spaces in the frontal and parietal regions of otherwise normal infants is a com­ mon occurrence. This finding in an infant with normal ven­ tricular size and no evidence of neurological dysfunction should be considered a variation of normal. Synonymous terms for this finding include "benign extraaxial fluid col­ lections of infancy" and "benign enlargement of the sub­ arachnoid spaces. " Terms that have been used in the past include "external hydrocephalus" and "benign subdural effusions of infancy" (the fluid is not in the subdural space, however) . The mechanism apparently involves normal­ pressure communicating hydrocephalus due to immaturity of the pacchionian granulations. Clinically, infants with benign enlargement of the subarachnoid spaces often have macrocephaly or rapid increase in head circumference. The rate of head growth usually stabilizes during the second year of life, and head circumference measurements eventually return to normal. Neuroimaging studies such as CT demonstrate a prominent amount of subarachnoid fluid surrounding the convexities , particularly in the frontal and parietal regions ( Figure 1 5-1 5) . There i s often mild prominence o f the ventricles . Unlike subdural collections, the extraaxial fluid extends into the sulci. In addition, normal cortical veins course through the subarachnoid fluid. Occasionally, the findings on CT do not allow unequiv­ ocal distinction from nonhemic subdural fluid collections;

Chapter 1 5 Hyd roce p h a l u s 587

Figure 1 5-1 6 Benign enlargement of the subarachnoid spaces. Figure 1 5-15 Benign enlargement of the subarachnoid spaces. A T2-weighted MR image of a 9-month-old infant with macrocephaly shows prominent extraaxial fluid anteriorly. The signal intensity of the fluid is that of clear C SF . Flow voids from cortical veins are present in this expanded subarachnoid space. The fluid extends into normal sulci. There is borderline prominence of the ventricles.

MR examination is definitive. Subdural fluid nearly always produces higher signal intensity than clear C S F on at least 1 MR sequence (proton-density and FLAI R images are par­ ticularly useful) . Sonography also is useful to demonstrate the subarachnoid location of the fluid. On images obtained with a high frequency transducer, the fluid often appears slightly echogenic (Figure 1 5-1 6) . Color Doppler sonography can be helpful to document normal cortical veins crossing the prominent subarachnoid spaces (Figure 1 5-17) . Although not necessary for most patients, followup neuroimaging studies typically show spontaneous resolution of the promi­ nent subarachnoid spaces by the age of 2 to 3 years. 26 ·27

EX VACUO VENTRICULOMECALY Ventriculomegaly that occurs because of parenchymal brain volume loss (e.g., atrophy or surgery) does not rep­ resent true hydrocephalus. The intraventricular pressure is normal. There is usually accompanying expansion of the subarachnoid space adjacent to the involved portion of brain (Figure 1 5-18) .

A coronal sonographic image shows slightly echogenic fluid in prominent frontal subarachnoid spaces. The fluid in the anterior interhemispheric fissure extends into sulci.

TREATMENT OF HYDROCEPHALUS Most children with ventriculomegaly who have clinical marlifestations of elevated intracranial pressure undergo surgical treatment. The therapeutic options include third ventriculostomy and C S F shunting. Ventriculoperitoneal shunting is the most common procedure. Ventriculopleural and ventriculoatrial (ventriculocardiac) shunts usually are reserved for patients who fail a standard ventriculoperito­ neal shunt. Regulation of shunt flow is by way of a 1-way valve that is designed to open at a threshold ("opening") pressure. Low-, medium-, and high-pressure designations correspond to 5, 10, and 15 mm H20 pressure. Some shunts are externally programmable.

Central N ervous System Sh u nt Evaluation Imaging studies play an essential role in the evaluation of CNS shunt integrity and patency. Standard radiographs are useful for assessing continuity and positioning of the shunt. Cranial CT or M R is useful for assessing the posi­ tion of the ventriculostomy catheter and for documenting ventricular size. Needle puncture of the shunt reservoir allows determination of the pressure and collection of a C S F sample for laboratory analysis.

588 Part 3 The B ra i n

A

Figure 1 5-18 Ex vacuo ventriculomegaly. A T2-weighted MR image a 2-year-old child with a history of perinatal asphyxia shows prominence of the lateral ventricles in conjunction with expansion of the subarachnoid spaces and parenchymal brain thinning.

B

c

Figure 1 5-17 Benign enlargement of the subarachnoid spaces. This s-month-old infant presented with macrocephaly. A, B. Coronal and midline sagittal color Doppler sonographic images show vessels coursing through prominent subarachnoid spaces. C. Bridging cortical veins in the convexity subarachnoid spaces are also visible on this unenhanced CT image.

Complications and malfunctions of CNS shunts are common. The risk for mechanical shunt failure is great­ est during the first several months after placement. Infants are also at greater risk for shunt failure than are older chil­ dren and adults. The overall failure rate (including infec­ tions) for CNS shunt catheters is approximately 40% per year. Mechanical failure occurs in approximately 30% of patients per year. The most frequent form of shunt malfunction is luminal obstruction, without mechanical shunt disrup­ tion. A radionudide shunt study is the mainstay imaging technique for assessing shunt patency and the adequacy of fluid absorption. Injection of iodinated contrast under fluoroscopic observation is useful for selected patients. With both techniques , the shunt reservoir is punctured, the C S F pressure measured, a specimen collected, and the ease of fluid aspiration assessed. During injection of radiopharmaceutical, the distal limb of the shunt should be compressed (or the on-off valve depressed into the off position) . Anterior and lateral images are then obtained of the head. The valve, if present, is returned to the "on"

Chapter 1 5 Hyd roce p h a l u s 589

....

.

.'

• • I

. 1·.

.. �

I

.

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A

8

radiopharmaceutical in the lateral ventricles, shunt reservoir, and distal limb. B. A posterior image of the abdomen at 25 minutes

•

t

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... .

o

•' : '

-

0

:

'-.' • : •' ,• J � .· I .· . .....

. I •. · �·

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Figure 1 5-19 Normal ventriculoperitoneal shunt. A A lateral image of the head and thorax shows

•

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'-' ' ' : /)f '·

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demonstrates dispersion of tracer in the peritoneal cavity. There is faint activity in the bladder. C. At 6 o minutes, most remaining activity is in the kidneys and bladder.

position, and images are obtained of the neck, thorax, and abdomen to follow the distal passage of tracer. If spontane­ ous distal passage does not occur, the patient should sit up or ambulate for a few minutes before additional imag­ ing. With persistent stasis, pumping of the reservoir may force the labeled C S F distally. With ventriculoperitoneal shunts, delayed images of the abdomen allow assessment of intraperitoneal dispersion, absorption, and renal excre­ tion (Figure 1 5-1 9) . 2 8-33

Ventriculoperitoneal Shunt Complications Potential mechanical malfunctions of ventriculoperito­ neal shunt catheters include malposition, disconnec­ tion, occlusion, and migration (Figures 1 5-20 and 1 5-21 } (Table 1 5-3) . Ideally, CSF bathes the drainage holes of the ventriculostomy catheter. Poor drainage can occur if the catheter is buried in the brain parenchyma or in contact with the choroid plexus or ependyma. Iatrogenic or pre­ existing intraventricular hemorrhage can impede shunt function. Ventricular system loculations and foramen of Monro obstruction are relatively common complicating factors . Obstruction can also occur at the distal open­ ing of a ventriculoperitoneal shunt, due to peritoneal adhesions or other mechanical factors ( Figure 1 5-22) . Intraperitoneal pseudocyst formation at the tip can pre­ vent adequate C S F absorption. Less common complications include migration of the tip of the shunt into the subphrenic space, intrathoracic region, or scrotum. Perforation of a viscus by a ventricu­ loperitoneal shunt is a rare serious complication. Rarely, there is malposition of the catheter at the time of insertion into the preperitoneal space or the anterior abdominal wall (Figu re 1 5-23) . 2 8 ·32 · 33

Figure 1 5-20 Ventriculoperitoneal shunt disconnection. An oblique radiograph shows separation of the distal limb from the valve device (arrows).

590 Part 3 The

Brain Table 1 5-3. Ventriculoperitoneal S h u nt Complications

Malposition Occl usion by choroid plexus Catheter fractu re M igration Discon nection Kinking Tract calcification Over-sh u nting I nfection CSF pseudocyst Periton itis Bowel perforation

A

B

Figure 1 5-21 Ventriculoperitoneal shunt catheter disconnection.

A. The distal limb of the shunt catheter is absent on this lateral skull radiograph. The arrow marks the level of the valvef reservoir device. B. The disconnected catheter has migrated into the peritoneal cavity.

A peritoneal pseudocyst is a potential complication of ventriculoperitoneal shunts. The cyst adjacent to the shunt tip can develop over a broad time range, from within a few weeks of catheter placement to many years later. The cyst has a thin wall that is composed of fibrous tissue without

an epithelial lining. The cyst contains C S F and a variable amount of debris. The pseudocyst can either move freely within the peritoneal cavity or become adherent to adjacent structures. The pathophysiology of pseudocyst formation is unclear in most patients, although subclinical infection is hypothesized to be a common cause. The clinical manifestations of a C S F peritoneal pseudocyst relate to shunt dysfunction (e.g., intracranial pressure elevation) , bowel obstruction, or torsion of the pseudocyst. Children most often exhibit manifestations of elevated intracranial pressure and abdominal pain, whereas adults more often suffer abdominal complaints . Abdominal radiographs may show soft tissue-density fullness and displacement of bowel loops in the region of the distal portion of the shunt catheter ( Figu re 1 5-2.4 ) . Sonography and CT show a clear fluid collection through which the catheter passes ( Figu re 1 5-25) . Septations are sometimes present ( Figure 1 5-26) . A scintigraphic shunt study usually demonstrates slow distal passage of radio­ pharmaceutical through the shunt catheter, eventual accu· mulation within the peritoneal loculation, and delayed or absent renal excretion. The treatment of an uninfected pseudocyst consists of drainage of the cyst and reposition­ ing of the shunt tip. If infection is present, the intraperi· toneal portion of the shunt tube is typically removed and the pseudocyst is drained; percutaneous techniques can be utilized for drainage of an infected pseudocyst once the shunt has been removed. 3 4 Overdrainage of C S F is an important potential com­ plication of CNS shunts . Excessive drainage of fluid in a patient with substantial ventriculomegaly can lead to subdural hemorrhage or a subdural hygroma. Overdrainage in an infant can cause cranial collapse and overlapping of sutures, with the potential for subsequent

Chapter 1 5 Hyd roce p h a l u s

591

. .·

16 0

�

0

70%) , particularly when the tumor arises in the temporal lobe. Imaging studies of pleomorphic xanthoastrocytoma most often show a well-circumscribed peripheral cerebral

B

enhancing tumor (arrow) on the T1-weighted image obtained after gadolinium injection is much smaller, suggesting that much of the T2 signal abnormality is due to peritumoral edema.

mass. Pathological examination frequently demonstrates extension into the leptomeninges, usually without dural invasion. Adjacent calvarial erosion is occasionally pres­ ent. About half of these lesions contain 1 or more macro­ scopic cysts. Cystic tumors may have an avidly enhancing mural nodule (Figure 1 9-9) . The solid components of a pleomorphic xanthoastrocytoma usually appear simi­ lar to normal gray matter on CT and Tl-weighted M R sequences . Fluid-attenuated inversion recovery ( F LAIR) and spin echo T2-weighted images usually show only minimal tumor hyperintensity relative to normal brain. Typically, there is only minimal perilesional edema. Prominent contrast enhancement occurs within the solid portions (Figure 1 9-10) . 8 , 9

Su bependymal G iant Cel l Astrocytoma Subependymal giant cell astrocytoma (giant cell tumor) is a mixed glioneuronal neoplasm that occurs in children with tuberous sclerosis. This is the most common cerebral neoplasm in tuberous sclerosis patients, with a prevalence of s% to 15%. It accounts for approximately q% of brain tumors in all pediatric patients.10 It is presumed to arise from a subependymal hamartoma and is nearly always

688 Part 3 The B ra i n

A

B

Figure 1 9-3 Pilocytic astrocytoma of the thalamus. This n-year-old male with papilledema presented with a 2-week history of headaches and intermittent nausea, vomiting, and diplopia. A. Unenhanced CT shows a cystic mass of the left thalamus, with a solid mural nodule. There is obstructive hydrocephalus. Peritumoral edema produces hypoattenuation in the left basal ganglia and adjacent white matter. B. A coronal FLAIR MR image shows peritumoral and periventricular edema. The mural nodule is slightly hyperintense. C. There is intense contrast enhancement of the mural nodule on this T1-weighted image obtained with IV gadolinium.

located adjacent to the foramen of Monro. Subependymal giant cell astrocytoma rarely occurs in patients without clinical manifestations of tuberous sclerosis; in most or all of these instances, the apparent absence of tuberous scle­ rosis is due to an insufficient period of time having elapsed before the clinical signs become manifest or is related to variable gene expression."·'2 Although subependymal giant cell astrocytoma some­ times occurs in adults, the mean age at presentation is u years. Symptoms specifically related to the presence of the lesion are frequently lacking, and the mass is typically

c

found during routine brain imaging for known tuberous sclerosis. In occasional patients, ventricular obstruction by the lesion leads to signs and symptoms of hydrocephalus (headache) . Hemiparesis is an uncommon manifestation of this tumor. There appears to be an increased prevalence of cardiac rhabdomyoma in tuberous sclerosis patients with subependymal giant cell astrocytoma in comparison to those with subependymoma nodules only.'o--'4 The histogenesis of subependymal giant cell astrocy­ toma is unclear, with evidence supporting both neuronal and astrocytic lineage. This tumor has a mixed glioneuronal

Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 689

A

Figure 1 9-4 Pilocytic astrocytoma. A A coronal FLAIR image of a 9-year-old child shows a large cystic lesion in the right parietal lobe. There is a multinodular intraluminal component medially (arrow) . There is extensive

pattern histologically. There is a low proliferative index; malignant histological features are rare. It is classified as a WHO grade I neoplasm. The mass grows slowly and exhib­ its benign biological behavior. Occasionally, there is degen­ eration into a higher grade infiltrating neoplasm.'2 Neuroimaging studies show a subependymal giant cell astrocytoma as a nodular intraventricular mass. Although nearly always located near the foramen of Monro, it can develop anywhere along the ependymal surface. The lesion typically has slightly lower attenua­ tion than normal brain on unenhanced CT.'S Calcification within the lesion is common. Increased attenuation due to recent hemorrhage is occasionally present. With M R I , subependymal giant cell astrocytoma is slightly hypoin­ tense to brain on T1-weighted images and hyperintense on T2-weighted images. The presence of calcification or hemorrhage may alter this appearance. In addition, the relative intensities with respect to normal brain are often different in neonates because of the high water content of the brain at this age; the lesion may appear slightly hyper­ intense on T1-weighted images and slightly hypointense on T2-weighted images. Intense contrast enhancement is visible on both CT and M RI of subependymal giant cell astrocytomas (Figure 1 9-11 ) .10•16-t9 The hallmark neuroimaging appearance of a subepen­ dymal giant cell astrocytoma is that of an intensely enhanc­ ing subependymal mass in the region of the foramen of

B

hyperintense perilesional edema. B. The medial solid component enhances intensely with IV gadolinium on this T1-weighted sequence. The margins of the tumor cyst are well-defined.

Monro in a child with tuberous sclerosis, with progressive enlargement on sequential studies. Accurate differentia­ tion of this lesion from a benign subependymal hamar­ toma is not always possible. A giant cell tumor typically has a greater degree of contrast enhancement, but a subepen­ dymal hamartoma may also undergo some enhancement, particularly on M RI . A subependymal astrocytoma is usu­ ally a larger lesion than a hamartoma; lesions greater than or equal to 10 mm in diameter are usually astrocytomas. Hamartomas typically are stable in size on sequential neu­ roimaging studies. Although astrocytomas progressively enlarge, the rate of growth varies considerably between patients.20 There is controversy about the optimal management of children with subependymoma giant cell astrocytoma. A rapidly growing or infiltrative lesion, or a tumor that causes a new focal neurological deficit, is usually treated surgically. If there is hydrocephalus due to a stable or slowly grow­ ing lesion, either surgical resection of the mass or simple diversionary ventricular shunting represent reasonable treatment options. Radiation therapy is not effective for the treatment of this lesion.' o ·2'·22

Oligodendroglioma Oligodendroglioma is a glial neoplasm that is uncom­ mon in the pediatric age group. This lesion accounts for

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Figure 1 9-5 Diffuse astrocytoma. This is an 8-year-old girl with right hemiparesis, aphasia, and seizures. A, B. T2-weighted images show hyperintensity in a large region of the left cerebral hemisphere, without a definable mass. There is rightward shift of midline structures. C. The contrast enhancement characteristics of the brain are normal. Stereotactic biopsy demonstrated a high-grade astrocytoma.

c

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 691

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Figure 19-6 Gemistocytic astrocytoma_

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approximately 1% of pediatric brain tumors. About six per­ cent of oligodendrogliomas occur in children, with a peak age of 6 to 12 years. There is a male predilection. More than half of these lesions arise in the frontal lobes. Other supratentorial sites, in decreasing order of frequency, are the temporal, parietal, and occipital lobes. Additional potential sites for primary oligodendroglioma include the

A. There is a large hypointense area in the right frontoparietal region on this T1-weighted MR image. Mild mass effect is present. B. This infiltrative tumor is hyperintense on a FLAIR sequence. C . Most of the lesion is isointense on this contrast­ enhanced T!-weighted image. There are 2 foci of enhancement within the tumor. Gemistocytic astrocytoma is a form of diffuse astrocytoma. This patient presented with seizures.

cerebellum, brainstem, spinal cord, ventricular system, lep­ tomeninges, retina, and optic nerves.23 Most oligodendrogliomas are low-grade neoplasms ; that is , well-differentiated. This slowly growing neoplasm typically is associated with a protracted symptomatic period prior to diagnosis. The less common anaplastic variety usu­ ally has a much shorter clinical course. The most common

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Figure 1 9-7 Glioblastoma multiforme. A A Tz-weighted M R image demonstrates a large heterogeneous central right cerebral mass, with extensive perilesional edema. There is a cystic component laterally. Hydrocephalus is present.

Figure 1g-8 Anaplastic astrocytoma. The spectrum suggests a high-grade lesion, with elevation of choline (Cho), and diminished N-acetyl aspartate (NAA) and creatine (Cr) .

B

There are focal areas of edema in the left cerebral hemisphere. B. The solid portion of the tumor enhances intensely with IV gadolinium. The margins are lobulated.

presenting symptom is a seizure disorder, likely related to the propensity for the neoplasm to involve the cortical gray matter. Other potential findings include headache, visual alterations, mental status change, nausea, ataxia, and weakness. Oligodendrogliomas presumably arise from oligoden­ drocytes, which are neuroglial cells that are predominantly located in the white matter of the C N S . Oligodendroglioma is usually a soft, fleshy mass. Histologically, there are sheets of uniformly dense cells. Calcifications, either microscopic or macroscopic, are present in approximately 90% of these lesions. Mucoid degeneration and leptomeningeal infiltra­ tion can occur. A well-differentiated oligodendroglioma is a WHO grade II lesion; the anaplastic variety is WHO grade III. Neuroimaging studies typically show an oligoden­ droglioma as an oval cortical or subcortical mass. Most often, the margins are well defined and lobulated; occa­ sionally, the mass blends imperceptibly with the adjacent brain parenchyma. Calcification is visible on CT in at least half of these lesions; this is the most common neo­ plasm of the cerebral hemisphere in children to calcify. The calcification may be nodular, shell-like, or linear. In some instances, the calcification has a gyriform pattern. The soft tissue components of the mass are most often hypoattenuating to normal brain, but an isoattenuating or hyperattenuating character occurs in zo% to 30% of these

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 693

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Figure 19-9 Pleomorphic xanthoastrocytoma. This 15·year-old boy presented with seizures. A A solid tumor nodule (arrow) nearly fills a cyst in the right parietal lobe. The nodule is slightly hyperintense relative to normal cortical gray

lesions. Rarely, a small isoattenuating oligodendroglioma is occult on CT. This slowly growing neoplasm some· times causes erosion of the inner table of the calvaria (Figure 1 9-1 2) . Contrast enhancement on CT is absent or minimal, and is more common with higher-grade tumors (Figure 1 9-13) .24

Oligodendroglioma Pathology

Calcification M ucoid, cystic degeneration Well-differentiated glial tumor

Rad iology

: CT: calcification ' M R: heterogeneity . Heterogeneity; cysts ; Li m ited or absent ' enhancement

M RI of oligodendroglioma shows a mass that is pre­ dominantly hypointense on T1-weighted images and hyperintense on T2-weighted images (Figure 1 9-14) . Heterogeneity i s a characteristic feature o f this tumor (Figure 1 9-1 5) . Large calcifications, when present, are

B

matter. The cyst fluid has higher signal intensity. There is minimal perilesional edema medial to the tumor. B. The tumor nodule enhances intensely with IV contrast.

hypointense on both sequences. Microscopic calcifications may lead to regions ofT1 hyperintensity or nonspecific het­ erogeneity. Cysts can occur with this tumor. Peritumoral vasogenic edema is usually absent or minimal, particularly with a low-grade lesion. Some oligodendrogliomas are infiltrative and have ill-defined margins. Contrast enhance­ ment on MR ranges from none to moderate in intensity. As with CT, prominent MR contrast enhancement suggests aggressive biological behavior ( Figure 1 9-1 6) . The enhance­ ment pattern often has a lacy or heterogeneous character. Most oligodendrogliomas are hypermetabolic to normal brain on positron emission tomographic (PET) imaging.25

Prim itive Neu roectodermal Tu mor PNET is a malignant embryonal tumor that accounts for less than s% of supratentorial neoplasms in children. The most common CNS location of this lesion is the cer­ ebellum (medulloblastoma) . Other potential sites of ori· gin include the pineal gland (pineoblastoma) , cerebrum, spinal cord, and retina (retinoblastoma) ; the brainstem is a rare site. Histologically, PNET consists of primitive neu­ roepithelial cells. There is considerable variation between patients with regard to the cellular composition of PNETs; ependymal, melanocytic, mesenchymal, oligodendroglia!,

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Figure 1 9-1 0 Pleomorphic xanthoastrocytoma. A A small cyst (arrow) is visible in the right temporal lobe on

this T1-weighted image. B. There are 3 small cysts surrounding

and photoreceptor differentiation can ocrur. These highly proliferative neoplasms tend to metastasize along the lep­ tomeninges. Neuroblastoma, medulloblastoma, and pineo­ blastoma arise from similar primitive cells and represent additional members of this family of embryonal neoplasms (Table 1 9-3) . PNET has also been termed "primary cerebral neuroblastoma. " 2 6

Table 1 9-3. Supratentorial Embryonal Tu mors

Prim itive neu roectodermal tumor M edul loepithelioma Neuroblastoma M elanotic neu roectodermal tumor of infancy Atypical teratoidjrhabdoid tumor

B

a small mass (arrow) that is slightly hyperintense relative to normal brain on this T2-weighted coronal image. Minimal high signal intensity edema surrounds the lesion.

Supratentorial PNET most often ocrurs as a large hemispheric mass of heterogeneous composition. Most of these lesions arise in children under the age of 10 years. The most common presenting clinical manifestations are macrocephaly, seizures, and neurological signs of elevated intracranial pressure. The rerurrence rate of this highly malignant neoplasm following surgical resection is approx­ imately 40%. Potential pathways of metastasis include sub­ arachnoid seeding and hematogenous spread to the lungs, liver, or bone marrow. PNET is a highly cellular tumor. At least 90% of the lesion consists of undifferentiated cells. The neuroimaging features of PNET are quite variable. These tumors are usu­ ally large at the time of diagnosis (Figure 1 9-17) . The tumor margins are well defined in many patients, but others have a lesion with an infiltrative character. Perilesional edema is variable. The cerebral white matter is usually the region of greatest involvement. Intraventricular extension can ocrur.

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 695

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D

Figure 1 9-1 0 (Continued) C. The mass and perilesional edema are moderately hyperintense on this FLAIR image.

D.

The tumor enhances intensely with IV

gadolinium.

Most PN ETs are heterogeneous, due to the presence of calcification, cysts, necrosis , or hemorrhage (Figure 1 9-18) . Nonnecrotic portions undergo moderate contrast enhance­ ment. The signal intensity of the solid components of the mass on Tz-weighted MR images tends to be lower than in most other brain tumors, due to the high nuclear-to­ cytoplasmic ratio of the primitive cells that make up the neoplasm (Figure 1 9-1 9) . Some of these tumors are isoin­ tense to gray matter. Likewise, the lesion may be somewhat hyperattenuating to normal white matter on unenhanced CT. M R shows the solid components to have reduced dif­ fusion, whereas cystic areas have increased diffusion. Necrosis and hemorrhage produce high signal intensity on FLAIR sequences, whereas clear cysts are hypointense. M R spectroscopy typically demonstrates high Cho 1 Cr and Cho 1 NAA ratios and elevation of glycine-rnl (3-56 ppm) . 27·2 8

M ed u lloepithel ioma Medulloepithelioma is a rare highly malignant embryo­ nal tumor composed of epithelial elements. Most of these lesions arise in the supratentorial compartment, in either the suprasellar region or the cerebral hemispheres. Origin within the brainstem or cerebellum is also possible. Presentation usually occurs during infancy; nearly all of these lesions occur in children under the age of 5 years . Most patients have manifestations ofintracranial hyperten­ sion and suffer severe neurological deficits. The prognosis is poor in the absence of complete resection. Medulloepithelioma usually is isoattenuating or hypoattenuating to normal brain on unenhanced CT. The lesion is hypointense or isointense to brain on T1-weighted MR images. There is homogeneous hyperintensity on

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Figure 1 9-1 1 Subependymal giant cell astrocytoma. A A T2-weighted M R image of a 6-year-old child with tuberous sclerosis shows a 13 mm in diameter subependymal mass (large arrow) adjacent to the foramen of Momo. There is mild dilation of the ipsilateral lateral ventricle. Multiple parenchymal hamartomas are also present; the largest on this image is in the right occipital lobe (small arrow) . B, C. The astrocytoma is isointense to brain on this T1-weighted sequence (B) and undergoes intense contrast enhancement (C). The cortical tubers are hypointense on both images.

B

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Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 697

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Figure 1 9-1 2 Oligodendroglioma. A Contrast-enhanced Cf shows a low attenuation lesion in the

B

lesion does not enhance. B. There is thinning of the adjacent portion of the skull (arrow) .

left cerebral hemisphere, with minimal mass effect. Most of the

T2-weighted images; intratumoral hemorrhage results in heterogeneity in some patients. There are usually well­ defined tumor margins. The contrast enhancement charac­ teristics on CT and MR are variable; many of these tumors lack substantial enhancement. 29·3°

Atypical Teratoid/Rhabdoid Tu mor

Figure 1 9-13 Oligodendroglioma. There is no appreciable contrast enhancement of this hypoattenuating left parietal low grade oligodendroglioma.

Atypical teratoid/rhabdoid tumor is a rare embryonal tumor that is pathologically and clinically similar to PNET. Approximately 3 0 % of atypical teratoid/rhabdoid tumors are supratentorial, with most of these in the cere­ bral hemispheres or pineal region. Three-quarters of these lesions present in children younger than 3 years of age. There is a male predominance. The clinical pre­ sentation usually relates to intracranial hypertension. Common findings include cranial nerve signs, nausea and vomiting, headache, and seizures . This is a highly aggressive neoplasm; most patients succumb within 1 year of the diagnosis .3'·32 Neuroirnaging studies of supratentorial atypical tera­ toid/rhabdoid tumor demonstrate a predominantly solid mass that contains regions of necrosis ( Figure 1 9-20) . The solid components are isoattenuating-to-hyperatten­ uating relative to gray matter on CT and approximately isointense to gray matter on MR. Foci of necrosis and

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Figure 1 9-14 Oligodendroglioma. A. Unenhanced CT of a 6-year-old boy demonstrates a hypoattenuating left occipital lesion that contains irregular calcification. B. The lesion is hyperintense and slightly

calcification produce a heterogeneous appearance in most of these tumors. Cysts are sometimes present. There is prominent contrast enhancement of the solid components (Figure 1 9-21 ) . Metastatic disease at the time of diagnosis is common.33.34

D

heterogeneous on FLAIR M R. C. There are well-defined margins on this SE Tz-weighted image. There is no peritumoral edema. D. Irregular contrast enhancement is present on this T1-weighted image.

G anglioglioma Ganglioglioma i s a rare lesion that accounts for less than 3% of pediatric CNS tumors. This neuronal-glial (glioneural) neoplasm contains varying amounts of atypical ganglion

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 699

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Figure 1 9-1 5 Oligodendroglioma. A. There is a somewhat heterogeneous character of this left parietal lesion on T1· weighted MR. B. The tumor is hyperintense

cells and neoplastic glial cells. There is histological overlap with gangliocytoma. Pediatric glioneural neoplasms com­ prise a spectrum of CNS lesions (Table 1 9-4) . The histologi­ cal grade and the clinical behavior of gangliogliomas vary between patients, although most are low grade. Ganglioglioma can arise anywhere within the C N S ; most are within the brain. The temporal lobe i s the over­ all most common location, followed by the parietal and frontal lobes. Posterior fossa locations can also occur. Approximately 95% of patients with ganglioglioma have seizures; most common are temporomesial and tempo­ rolateral locations. Ganglioglioma accounts for approxi­ mately 40% of epilepsy-associated tumors. Removal of the lesion usually leads to improved seizure control. Although

Table 1 9-4. Glioneural N eoplasms

Glioneural tumors Ganglioglioma M edul loepithelioma M edul loblastoma Des moplastic i nfantile gangliogl ioma Dysembryoplastic neu roepithelial tumor G l ioneural tumor with neuropil rosettes M ixed glioblastoma-cerebral neuroblastoma Papillary glioneuronal tumor

B

on T2-weighted imaging. The mass involves white matter and central gray matter.

ganglioglioma usually follows a benign pattern of growth, there is a propensity for hemorrhage that can produce acute catastrophic symptoms.3 5·36 The most characteristic imaging appearance of a gan­ glioglioma is that of a cystic mass with a mural nodule, although a completely solid composition can also occur (Figure 1 9·22) . A cystic component is visible with imaging in approximately 8o% of gangliomas in children under the age of 10 years ( Figure 1 9-23) . There can be a single cyst or multiple small cysts. There is evidence of calcification of the solid portion on CT evaluation in approximately 30%. The solid component often appears heterogeneous on MRI (Figure 1 9·24) · Most often, the solid portion predomi­ nantly has relatively low signal intensity on T1-weighted MR images and high signal on T2-weighted images (Figu re 1 9-25) . Although most gangliogliomas enhance with IV contrast, the enhancement pattern is not consistent between lesions. Because this is a slow growing tumor, a peripheral ganglioglioma sometimes causes scalloped ero­ sion of the adjacent portion of the inner table of the skull. There is a high Cho peak relative to the Cr and NAA peaks on MR spectroscopy. P ET imaging ('8f.fl.uorodeoxyglucose positron emission tomography) of ganglioglioma shows heterogeneous metabolic activity, including areas of hyper­ metabolism. Gangliogliomas have intense uptake on 20'TI scintigraphy.37-39

Gangliocytoma Gangliocytoma (ganglioneuroma) includes a spectrum of CNS tumors in which neuronal cells are the sole neoplastic constituents, although there is an accompanying network

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Figure 1 9-1 6 Oligodendroglioma. A. Unenhanced CT shows a large densely calcified right cerebellar mass. There is obstructive hydrocephalus. B. The

D

lesion is heterogeneous on T1 MR. There are faintly hyperintense areas due to microscopic calcification. C, D. There is marked contrast enhancement of this anaplastic oligodendroglioma.

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses

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of nonneoplastic glial cells. The presence of anaplastic glial cells in ganglioglioma serves as the histopathological dif­ ferentiating feature from gangliocytoma. Gangliocytomas most often arise in the cerebrum; other potential sites include the cerebellum, hypothalamus, pineal region, and pituitary. Fewer than to% arise in the spinal cord. Gangliocytoma is a rare lesion, accounting for fewer than 3% of pediatric brain tumors. The location of the mass

determines the clinical manifestations. Most patients suffer seizures. Hydrocephalus can occur. The biological behavior is usually benign, with slow growth. Gangliocytoma of the cerebellum in patients with UJ.ermitte-Duclos disease is a slowly growing hamartomatous lesion.3 6 The imaging features of gangliocytoma are varied, and often nonspecific. Differentiation from ganglioglioma is not possible. Gangliocytoma is an encapsulated tumor

A

B

Figure 1 9-1 7 Primitive neuroectodermal tumor.

c

A, B. Tt-weighted (A) and T2-weighted (B) MR images of a 1-year-old child show a large heterogeneous left cerebral mass. There are cysts, areas of hemorrhage, and extensive perilesional edema. C. This PNET in a 3-year-old child contains multiple large necrotic cysts. The solid portion of the tumor undergoes prominent contrast enhancement. The margin s are well-defined.

702 Part 3 The B ra i n

Figure 1 9-1 8 Primitive neuroectodermal tumor. This bifrontal cerebral neoplasm contains cysts and areas of hemorrhage. Most of the tumor is slightly hypoattenuating to brain on this unenhanced CT image.

that contains varying proportions of Schwann cells, colla­ gen fibers, and myxoid stroma. MR most often shows low signal intensity on T1-weighted images and high signal on Tz-weighted images. Those lesions with a prominent fibrous composition and minimal myxoid stroma produce intermediate or low signal intensity on Tz-weighted images. Cystic areas are common. Typically, there is mild contrast enhancement; enhancement may be lacking on early images and gradually increases on subsequent images. CT may show calcification. Some lesions are hyperattenuating on unenhanced CT images.4°-42

Desmoplastic I nfantile Cangl ioglioma Desmoplastic infantile ganglioglioma is a rare mixed neuronal-glial tumor that has aggressive histological fea­ tures, but a benign clinical course. Desmoplastic astrocy­ toma of infancy is a variant lesion. Desmoplastic infantile ganglioglioma is typically very large at the time of diag­ nosis, and is predominantly cystic. In the desmoplastic solid component, histological examination demonstrates fibroblasts, astrocytic cells, and ganglionic cells. There are spindle-shaped neoplastic cells that contain elongated

pleomorphic nuclei. The presence of ganglionic cells may lead to histological features that overlap those of a classic ganglioglioma.4M4 Desmoplastic infantile ganglioglioma is a supratento­ rial lesion. The usual sites of origin, in decreasing order of frequency, are parietal, frontal, and temporal. There is usually a short duration of symptoms prior to diagnosis. Physical examination shows macrocephaly and tense bulg­ ing fontanelles. Partial complex seizures may occur. Most patients present during the first several months of life. The treatment of desmoplastic infantile ganglioglioma is surgical excision. In many patients, the lesion is amenable to complete removal, which is associated with a favorable prognosis.4°·45 Neuroimaging studies show desmoplastic infan­ tile ganglioglioma as a large, cystic, peripheral cerebral hemispheric mass. The cystic composition is readily apparent with sonography. The fluid component does not enhance on CT examination, and has attenuation val­ ues that are similar to those of cerebrospinal fluid ( C S F) . The superficial solid component i s o f equal or slightly greater attenuation as normal gray matter on CT and is isointense on standard T1-weighted and Tz-weighted MR sequences; these features are helpful in the differ­ entiation from a cystic astrocytoma. The solid compo­ nent is often heterogeneous on Tz-weighted M R images, whereas the cystic component is typically homogeneous and has the characteristics of clear fluid. The solid por­ tion of the mass enhances intensely with IV contrast on M R . The solid component is peripherally located, and the tumor enhancement has characteristic extension to the leptomeninges. 4 6 ,47

Dysembryoplastic Neuroepithelial Tu mor D N ET is a benign mixed neuronal-glial tumor of the C N S that is a n important cause o f medically refractory partial seizures in children and young adults . Typically, there is no neurological deficit. Most affected pediatric patients present during adolescence. The histopathological fea­ tures raise the possibility that this lesion is a malforma­ tion rather than a true neoplasm. DNET is composed of heterogeneous cellular components that are located in a myxoid or mucinous interstitial matrix. There is fre­ quently a background of cortical dysplasia adjacent to the lesion. Most DNETs arise in the cerebral cortex, with the tem­ poral lobes accounting for approximately 6o% and the frontal lobes 30%. Although uncommon, posterior fossa and deep cerebral origins can occur. Imaging studies typi­ cally demonstrate a well-demarcated cortical lesion that extends into the subcortical white matter. The mesial cortex is a common site of origin. The myxoid matrix and multinodular architecture of DNET cause a multicystic appearance on M R images in most patients. There is only minimal mass effect. The mass has low attenuation on CT. Calcifications are present

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses

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Figure 1 9-1 9 Primitive neuroectodermal tumor.

c

This 2-year-old girl presented with a history of vomiting and right sided weakness. A. The majority of the left cerebral neoplasm has signal intensity intermediate between CSF and brain parenchyma on this T2-weighted image. The lesion is somewhat heterogeneous. There are well-defined margins. B. The mass is hypointense to brain on T1-weighted imaging. C. There is mild-to-moderate, heterogeneous contrast enhancement.

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Figure 1 9-20 Atypical teratoidfrhabdoid tumor. A An axial MR image shows a large left temporal lobe mass, with midline shift and hydrocephalus. The lesion is

in about one-third of these lesions. Bone remodeling of the adjacent portion of the skull is common. The mass is hypointense to normal gray matter on T1-weighted MR images and markedly hyperintense on Tz-weighted images. Adjacent vasogenic edema is typically lacking. The mass may have a multilobulated or gyriform character. Contrast enhancement is either absent or of mild inten­ sity. PET imaging shows similar metabolic activity within the tumor as in normal brain. The multicystic character of DNET helps in the differentiation from ganglioglioma and glioneuronal malformations .4°·48·49

Papillary G lioneuronal Tu mor Papillary glioneuronal tumor is a rare glioneural tumor of the brain that occurs in individuals of all ages. The lesion is usually asymptomatic or associated with mild clinical manifestations such as headache. The tumor usu­ ally arises adj acent to the lateral ventricle; the temporal lobe is the most common location. Histologically, there is a mixed neuronal-glial cell composition. CT or M R I of papillary glioneuronal tumor typically demonstrates a cys­ tic cerebral mass with well-defined borders . The margins enhance with contrast. Septations are sometimes pres­ ent. Occasionally, there is an enhancing mural nodule. Individuals with this low-grade lesion typically have an excellent prognosis.5°-52

B

heterogeneous and approximately isointense to brain on this T2-weighted sequence. B. There is intense contrast enhancement of this solid mass.

Ependymoma Ependymoma is a relatively common glial neoplasm of the CNS. This lesion accounts for 6% to 12% of brain tumors in children. Approximately 30% of intracranial ependymo­ mas arise in a supratentorial location. In decreasing order frequency, the sites of origin of a cerebral ependymoma are the frontal, parietal, and temporal lobes. As is com­ mon with posterior fossa ependymomas, some of those in the supratentorial region arise within the ependyma of the lateral or third ventricles and produce an intraventricular mass. More often, however, the mass is completely extra­ ventricular, arising from embryonic rests of ependymal tis­ sue trapped within the developing cerebral hemispheres. Supratentorial ependymoma and infratentorial ependy­ moma are histologically identical.53·54 The clinical presentation of a supratentorial epen­ dymoma is often nonspecific. Headaches, seizures, and focal neurological signs are common. Manifestations of hydrocephalus may occur, particularly with an interven­ tricular tumor. Clinical examination may demonstrate hemiparesis, hyperreflexia, and visual field abnormalities. The peak age range is between 1 and 5 years. The overall s -year progression-free rate for children with ependymoma is approximately so%. The prognosis is slightly better for supratentorial lesions than for those of the posterior fossa. Cerebrospinal fluid dissemination is also less common

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Figure 1 9-21 Atypical teratoid/rhabdoid tumor.

c

A. A FLAIR image of a 13-month-old child shows a large heterogeneous left cerebral mass. B. There is also a heterogeneous appearance on this spin echo T2 sequence. There is a cyst along the posterior aspect. C. The solid components, including the cyst wall, enhance with IV gadolinium.

705

706 Part 3 The B ra i n with supratentorial ependymomas, a s most arise i n an extraventricular location.55 The typical neuroimaging appearance of supratento­ rial ependymoma is that of a heterogeneous, calcified, peri­ ventricular, off-midline mass ( Figure 1 9-26) . Supratentorial ependymomas tend to contain large cystic components (Figure 1 9-27) ; cysts are more common in supratento­ rial ependymomas than in those of the posterior fossa. ( Supratentorial ependymomas without substantial cystic components or calcification are often indistinguishable on imaging studies from astrocytoma.) The mass is usu­ ally located in the cerebral parenchyma, most often in the cerebral white matter. An intraventricular ependymoma typically is a well-circumscribed mass that fill s the ventric­ ular lumen and sometimes extends into the adjacent brain parenchyma.5 6

Supratentorial Ependymoma Rad i o l ogy

Pathology

Glial neoplasm

Calcification Cysts H emorrhage

A

•

CT: isojhyperatten uati ng ' T1 M R: isofhypointense ' T2 M R: isojhyperintense CT: calcification • M R: hypo intense foci H eterogeneity; cysts ; H eterogeneity ·

The soft tissue component of an ependymoma is usu­ ally isoattenuating or slightly hyperattenuating to brain on unenhanced CT. Calcifications, when present, are often multiple; the pattern of calcification ranges from small round densities to large confluent foci. There is a variable degree of enhancement of the solid components of the lesion. The character of a supratentorial ependymoma is frequently heterogeneous on M R, due to the presence of cysts, calcification, and hemorrhage ( Figure 1 9-28) . The solid components are hypointense or isointense to normal gray matter on T1-weighted images and isointense or mildly hyperintense on T2-weighted images. The viable soft-tissue components enhance with IV contrast.57 · 5 8

Germ i noma Germinoma occasionally arises i n the deep cerebral gray matter structures . This is the third most common intracra­ nial location of this tumor, after the pineal and suprasellar regions . Germinoma at this location occurs with a strong male predilection and most commonly arises in older chil­ dren and teenagers. Other types of germ cell tumor can also arise in the thalami and basal ganglia, but are much less common than germinoma.

B

Figure 1 9-22 Ganglioglioma.

A, B. This is a cystic cerebral mass, with a large mural nodule. The cystic component is hyperintense on the T2-weighted image (A) and hypointense on the contrast-enhanced T1-weighted sagittal sequence ( B ) . The solid component is heterogeneous, and undergoes moderately intense contrast enhancement. There are small low signal intensity foci of calcification on the T2-weighted image.

Chapter

A

Figure 1 9-23 Ganglioglioma. A There is a large partially cystic mass of the left cerebral hemisphere, with extensive perilesional edema. The solid

A small germinoma of the basal ganglia or thalamus may have a subtle appearance on unenhanced neuro­ imaging studies. The solid component is isoattenuating or slightly hyperattenuating to normal tissue on CT, and isointense to slightly hyperintense to normal gray matter on T1-weighted and Tz-weighted MR sequences. Larger germinomas frequently are heterogeneous, due to necrosis and cysts. There is prominent contrast enhancement of the solid components of a gerrninoma.59

INTRAVENTRICULAR NEOPLASMS

I ntraventricular Tu mors: Differential Diagnosis The tissues in and around the ventricular system that can give rise to intraventricular neoplasms include the ependyma, subependymal plate, septum pellucidum, and choroid plexus . The ependyma and subependymal plate are composed of glial cells that can lead to formation of ependymoma, subependymoma, subependymal giant cell astrocytoma, and central neurocytoma. The choroid plexus can be the site of origin of choroid plexus papilloma, cho­ roid plexus carcinoma, and metastatic disease. Neoplasms that on rare occasions are located within the ventricular system include oligodendroglioma, pilocytic astrocy­ toma, glioblastoma multiforme, lymphoma, medulloblas­ toma, PNET, meningioma, and teratoma. An accurate

19

I ntracra n i a l N eo p l a s m s a n d M asses 707

B

component of the lesion is slightly hyperintense to normal brain on this Tz-weighted sequence. B. There is marked contrast enhancement of the cyst wall and the solid tumor.

diagnosis of the common neoplastic and nonneoplastic intraventricular masses in children is usually possible by correlating the clinical and imaging findings. Table 1 9-5 shows the major differentiating features between these lesions; the neoplasms are listed in decreasing order of frequency.11• 6 0· 6 1 Some intraventricular tumors achieve a relatively large size before the onset of symptoms . The clinical manifes­ tations may relate to compression/invasion of an adjacent structure or to sequelae of elevated intracranial pressure. A lesion in the third ventricle can also result in findings of hypothalamic compression, such as diabetes insipidus, weight gain, or hypersomnia. Compression of the tectum by a tumor in the posterior aspect of the third ventricle may lead to Parinaud syndrome. Neoplasms of the trigone can cause posterior temporal lobe seizures. Hydrocephalus due to forarninal obstruction by an intraventricular mass can lead to macrocrania or other manifestations of elevated intracranial pressure. 62

Colloid Cyst Colloid cyst (paraphyseal cyst) is a congenital mucin-con­ taining epithelial-lined intraventricular cyst. More than 90% arise in the anterosuperior aspect of the third ven­ tricle and bulge into the foramen of Monro. Other poten­ tial sites include the lateral ventricles, cerebellum, and

708 Part 3 The

Brain

Table l !r-5· I ntraventricular Tu mors in Children N eo p l a s m jmass0

Location

C l i n ical fi n d i n gs

I magi ng fi n d i ngs

Ependymoma

Fou rth ventricle lateraljth i rd ventricle Lateral ventricle >4th ventricle

Hyd rocephalus, ataxia, cranial nerve dysfunction, nausea/ vom iting; mean age 6 years Hyd rocephalus; infants and young ch ildren

H eterogeneous; ± Ca++, extends th rough outlet foramina

»

Choroid plexus papil loma Subependymal giant cell astrocytoma

----

Choroid plexus carci noma

Lateral ventricle, Tu berous sclerosis; any age adjacent to foramen of Monro Lateral ventricle Hydrocephalus; infants and young ch ildren >4th ventricle

Colloid cyst

3 rd ventricle

Central neu rocytoma Cran iopharyngioma Su bependymoma

Lateral ventricle Thi rd ventricle 4th ventricle > lateral ventricle

Choroid plexus angioma Xanthogranuloma

Lateral ventricle

Stu rge-Weber syndrome

Lateral ventricle

Asym ptomatic or hyd rocephalus

---

Hyd rocephal us

Enhancing, lobulated, i ntraventricular mass; hydrocephalus I ntensely enhancing subependymal nodular mass; 2':1 0 m m in size Lobulated, enhanci ng, heterogeneous mass; extraventricular extension; m i ld hyd rocephal u s Oval cyst; often bright on CT and T1 M R Wel l circu mscri bed, lobulated Complex, cysts, Ca++ Well circumscri bed , lobulated; usually no extraventricular extension U nilateral ventriculomegaly; ipsilateral cortical lesions Oval ventricular wall mass

- - · - - - - - - - - - --

,_ __________ _ _ __ _ _ _ _ ____ __

Hyd rocephalus; young adu lts Hyd rocephalus Nonspecifi c ; rare i n children

-- -----

-------

0 n e o p l a s m s a r e i n d ecrea s i n g order o f freq u e n cy,

extraaxial spaces. This lesion accounts for 15% to 20% of intraventricular masses. Despite the developmental origin of colloid cyst, the typical age at detection is early or mid­ dle adulthood; children account for less than 10% of cases. There is no substantial gender predilection. Some colloid cysts are asymptomatic and discovered incidentally on imaging studies performed for an unrelated indication. Symptoms usually relate to obstructive hydro­ cephalus (e.g. , headache) . In some patients, headaches are positional. Rarely, acute obstruction causes a precipitous presentation. In addition to headache, patients with colloid cyst may have nausea, visual changes, memory loss, or gait disturbance. Surgical excision is the usual treatment for a symptomatic lesion.63 Colloid cyst derives from embryonic endoderm. Mucinous secretions and desquamated epithelial cells fill the lumen. The outer wall is a thin fibrous capsule and the inner lining is a single layer of columnar cells. On unenhanced CT, the lesion is slightly hyperattenuating to brain in about two-thirds of patients and is isoatten­ uating in one-third. Calcification and manifestations of hemorrhage are rare. The CT finding of a hyperattenu­ ating round or oval third ventricular mass is essentially

pathognomonic. Findings of obstructive hydrocephalus are common. Contrast enhanced images occasionally show slight capsular enhancement; the cyst contents do not enhance. 64

Col loid Cyst Pathol ogy

Rad iol ogy

I ntraventricular cyst with Wel l-defined thi n wal l thi n fibrous capsule ' N onenhancing contents Contains mucin and B right on CT and T1 M R epithelial cel ls

The cholesterol concentration within a colloid cyst is the major determinant of the MR signal characteristics. About two-thirds of colloid cysts are hyperintense to brain on T1-weighted images and about one-third are isointense (Figure 1 9-29) . Most are isointense to CSF on T2-weighted images, but there is considerable variation between patients.

Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 709

A

Figure 1 9-24 Ganglioglioma. A. T1-weighted MR shows a predominantly hypointense lesion of the left parietal lobe. There are irre gul ar foci of hyperintensity

B

the mass is also heterogeneous on this T2-weighted sequence. The peripheral aspect is hyperintense. There is no macroscopic cystic component.

within the lesion, due to calcification. B. The central portion of

There is a heterogeneous character in about one-quarter of these lesions. Occasionally, a fluid-fluid level is present. There is no restricted diffusion. As with CT, MR shows no enhancement of the lesion or minimal enhancement con­ fined to the capsule (Figure 1 9-30) . Spectroscopy demon­ strates a prominent peak in the region of 2 . 0 ppm due to the mucinous material; there is also a small lactate peak. 65 , 66

Choroid Plexus Tu mors Choroid plexus papilloma and carcinoma arise from the neuroepithelial tissue of the choroid plexus. Approximately 8o% of choroid plexus tumors are papillomas. The pap­ illoma is a benign, slow-growing neoplasm that carries a WHO grade I designation. The less common choroid plexus carcinoma is a WH 0 grade III neoplasm. Choroid plexus tumors account for 1% to 4% of pediatric brain tumors and 10% to 20% ofbrain tumors in children during the first year of life. "·36·6' Choroid plexus tumors can arise anywhere that cho­ roid plexus tissue exists , including the lateral ventricles, third ventricle, and fourth ventricle. There is no choroid plexus within the cerebral aqueduct or the temporal horns. The greatest volume of choroid plexus tissue is within the atria of the lateral ventricles . Approximately 5o% of choroid

plexus tumors arise within the lateral ventricles, 40% in the fourth ventricle, and 5% in the third ventricle. Up to s% of these lesions are multicentric. Rarely, this tumor arises from choroid plexus tissue in the cerebellopontine angle. There are rare instances of choroid plexus tumors in other extraventricular locations, presumably arising from an embryonic rest of choroid plexus tissue. Choroid plexus tumors of the lateral ventricles most often present during the first decade oflife, whereas those in the fourth ventricle have similar diagnostic incidences in children and adults. Choroid plexus tumors of the fourth ventricle are more common in males, but this gender predilection is absent for those that arise in the lateral ventricles. The predominant clinical manifestations of choroid plexus tumors are due to hydrocephalus. Increased produc­ tion of cerebrospinal fluid by the tumor is the typical cause ofhydrocephalus in these patients. Additional potential fac­ tors are ventricular obstruction by the mass and impairment of arachnoid granulation C S F absorption due to the release of blood or proteinaceous material from the tumor. 67 , 68 A variety of other, less common, clinical findings can occur, including focal neurological deficits, cranial nerve palsies, and seizures. 6 9 A lateral ventricular choroid plexus tumor that has a pedicle may move within the ventricle, lead­ ing to clinical manifestations of intermittent ventricular

710

Part 3 The B ra i n

A

8

Figure 1 9-25 Ganglioglioma.

c

obstruction (e.g., bobble-head doll syndrome) . 67 ·7° Choroid plexus tumors can occur in patients with Li-Fraumeni syn­ drome and Aicardi syndrome.71 ·72 The gross pathological appearance of a choroid plexus tumor is that of a soft, well-circumscribed cauliflower-like mass, with prominent peripheral lobulations . A vascu­ lar pedicle connects the mass to the choroid plexus. Both papillomas and carcinomas may contain cysts or areas of hemorrhage. Necrosis and parenchymal invasion are characteristics of carcinoma. On histological examination, choroid plexus papilloma usually appears similar to nor­ mal choroid plexus tissue. Findings with a choroid plexus carcinoma include invasion of adjacent normal tissue,

This 12-year-old patient presented with seizures. A. The left occipital lobe mass is hypointense on this Tl-weighted image. There is a small lower signal intensity cyst (arrow) along the left anterior portion of the tumor. B. The solid component and the cyst are hyperintense on T2-weighted imaging. There is minimal perilesional edema. C. The mass undergoes moderately intense contrast enhancement.

hypercellularity, and prominent mitotic activity. Rarely, a choroid plexus tumor has histological features that do not allow definitive characterization as a papilloma or carci­ noma; this is termed an atypical choroid plexus papilloma. Both choroid plexus papillomas and carcinomas can seed cells into the cerebrospinal fluid, but growth of metastatic deposits is much more common with carcinoma.U The diagnosis of a choroid plexus tumor with neuro­ imaging studies is usually straightforward. There are imag­ ing features that help to distinguish between papillomas and carcinomas, but the imaging findings alone are not pathognomonic.67,68 A papilloma usually appears on CT as a lobulated intraventricular mass that is of similar or

Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 71 1

Figure 1 9-26 Ependymoma.

A

This left temporal lobe ependymoma is densely calcified. There is extensive perilesional edema.

slightly greater attenuation than normal brain. Calcification is present in about one-fourth of these lesions. Prominent, homogeneous contrast enhancement occurs. 67,73 The lobulated character of a papilloma is easily visual­ ized on MRI. On T1-weighted images, a papilloma is usu­ ally homogeneous and isointense-to-hypointense relative to gray matter. The central aspect of a papilloma is often hypointense compared to gray matter on T2-weighted images; this hypointensity often has a branching pattern (Figure 1 9-31) . Foci ofhemorrhage or calcification within the lesion may produce some heterogeneity. Flow voids from prominent vessels are commonly visible. Choroidal artery enlargement may be demonstrable. Contrast enhance­ ment is intense and uniform (Figure 1 9-32) . Choroid plexus tumors that arise in the region of the trigone sometimes appear to engulf rather than invade the choroid plexus glo­ mus.74 Extension may occur from 1 ventricle to another, and a papilloma arising within the fourth ventricle can grow through the foramen of Luschka.7 5 Sonography of a choroid plexus papilloma in an infant shows a lobulated echogenic intraventricular mass. Doppler evaluation may demonstrate bidirectional vascular flow within the lesion.76m Choroid plexus carcinoma typically has imaging fea­ tures of a more aggressive lesion than does papilloma,

B

Figure 1 9-27 Ependymoma.

A An unenhanced CT image shows a cerebral mass that

contains amorphus calcifications and large cysts. B. The solid components undergo prominent contrast enhancement.

Part 3 The B r a i n

712

A

Figure 1 9-28 Ependymoma. A A T2-weighted M R image of a 23-month-old child shows a heterogeneous left cerebral mass. A temporizing drainage

A

8

catheter is present in a collapsed cystic component. B. The multiple small cysts in the mass result in hypointense foci on this contrast-enhanced image.

8

Figure 1 9-29 Colloid cyst of the third ventricle. A, B. Sagittal and coronal T1-wei ghted MR images show a small hyperintense cyst (arrows) in the superior aspect of the third ventricle. There is no associated ventriculomegaly.

Chapter

A

8

19

I ntracra n i a l N eo p l a s m s a n d M asses

Figure 1 9-30 Colloid cyst of the third ventricle. A. There is a round hyperintense cyst {arrow) in the third

this coronal Tl-weighted sequence obtained after

ventricle on this midline sagittal fat-suppressed T2-weighted

brain. There is obstructive dilation of the lateral ventricles.

713

IV gadolinium

administration. The cyst contents are slightly hypointense to

MR image. B. There is enhancement of the cyst wall (arrow) on

A

Figure 1 9-31 Choroid plexus papilloma. A. This intraventricular mass {arrow) is slightly hyperintense on the

FlAIR sequence. The margins are lobulated and there B. The mass is hypointense

is a vascular flow void medially.

8

relative to

CSF on this T2-weighted spin ecllo image. There are

characteristic branclling hypointense regions centrally. This benign lesion does not invade adjacent parencllyma.

714 Part 3 The B ra i n

A

B

Figure 1 9-32 Choroid plexus papilloma. Contrast-enhanced T1-weighted MR images in 3 patients. A. There is only mild ventricular prominence associated with this small lesion in the right lateral ventricle. B. This small lesion causes severe ventriculomegaly. C. Ventricular dilation is predominantly ipsilateral to this large choroid plexus papilloma of the lateral ventricle, and there is left-to-right midline shift. There is a parenchymal cyst lateral to the mass.

although there are unusual instances in which a papilloma grows through the ependyma and incites edema in the adjacent white matter (Figure 1 9-33) . Features that favor the diagnosis of a carcinoma include extraventricular extension into the brain parenchyma, a heterogeneous composition, vasogenic edema in adjacent cerebral white matter, and rela· tively mild hydrocephalus (hydrocephalus tends to be more

c

pronounced with papilloma) (Figure 1 9-34) . Occasionally, a large choroid plexus carcinoma invades the brain paren­ chyma to an extent that the ventricular origin of the tumor cannot be determined with certainty on imaging studies. On both CT and MRI, choroid plexus carcinoma typically has an irregular contour and prominent, but somewhat heterogeneous, contrast enhancement. Cysts,

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 71 5

A

Figure 1 9-33 Choroid plexus papilloma. A. A coronal FLAIR image shows extensive edema adjacent to this large left ventricular tumor. There is only mild ventriculomegaly. B. An axial Tt-weighted image obtained with

hemorrhage, and necrosis are common, producing a mix· ture of regions of high and low signal intensity on both T1-weighted and T2-weighted MR images. 6 7 t8 f-FDG PET imaging of choroid plexus carcinoma demonstrates promi­ nent metabolic activity consistent with increased glycolysis. MR spectroscopy of choroid plexus tumors shows a promi· nent Cho peak and suppression of the NAA and Cr peaks (Figure 1 9-35) . Elevation of lactate is sometimes present, particularly with carcinoma.78 Surgical resection is the treatment for both choroid plexus papilloma and carcinoma. Imaging definition of the major vascular supply is sometimes helpful for pre­ surgical planning in children with choroid plexus tumors. This is usually accomplished with MR angiography. The anterior, lateral-posterior, and medial-posterior choroidal arteries usually supply those tumors located in the lateral ventricle. Choroidal branches of the posterior inferior cer­ ebellar artery usually supply choroid plexus tumors aris· ing in the fourth ventricle. Preoperative embolization with transcatheter or stereotactic techniques has been utilized at some centers to facilitate the safety and efficacy of sur· gical resection. The prognosis for children following suc­ cessful resection of a choroid plexus papilloma is excellent. The s·year survival rate for children with a diagnosis of choroid plexus carcinoma is 26% to so%. 68 . 6 9.79 Congenital choroid plexus cysts are nonneoplastic devel­ opmental lesions that result from invagination of neuro­ epithelium into the choroid plexus stroma. In the fetus, choroid plexus cysts often spontaneously disappear later

B

IV gadolinium shows the typical lobulated margins and intense enhancement of a choroid plexus tumor. Despite multiple imaging features suggestive of a carcinoma, histological examination demonstrated a WHO grade I papilloma.

in gestation. There is an association of large or multiple fetal choroid plexus cysts with chromosomal abnormalities such as trisomy 18 and trisomy 21. A choroid plexus cyst is an occasional, usually incidental, finding on neuroimaging studies of infants and children. Rarely, the lesion is large enough to cause intraventricular obstructive hydrocepha­ lus. The cyst contents are anechoic on sonography and have similar characteristics as clear fluid on CT and MR. The fluid sometimes has restricted diffusion. 6• Dij]Use villous hyperplasia is a rare developmental lesion in which there is generalized choroid plexus enlargement without a localized mass. There is overproduction of cere· brospinal fluid that leads to ventriculomegaly. 8 o

Su bependymoma Subependymoma is a glial tumor that usually arises from the subependymal glial layer that surrounds the ventricles. This lesion nearly always grows into the adjacent ventricle; there are rare instances of location within the brain paren­ chyma, cerebellopontine angle, or spinal cord. Most occur in the fourth ventricle, with the lateral ventricle being the next most common site. Subependymoma is an uncom­ mon lesion in adults, and is rare in children; approximately 8o% occur in patients older than 15 years . This tumor is more common in males."·58 . 8 t,8 2 Symptoms in patients with subependymoma depend on the location and size of the tumor. The clinical findings are often nonspecific. Most subependymomas are small

716 Part 3 The B ra i n

A

B

Figure 1 9-34 Choroid plexus carcinoma. A Unenhanced CT shows a large hyperattenuating mass arising from the right lateral ventricle. There are foci of calcification within the mass. The margins of the lesion are lobulated. There is right-to-left midline shift. B. There is extensive perilesional edema in the right cerebral hemisphere, as well as periventricular edema along the margins of the dilated left lateral ventricle. The tumor has a heterogeneous rnaracter on this T2·weighted image. C. There is intense contrast enhancement of this lobulated tumor.

c

Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 717 are sometimes visible on CT and MR. The enhance­ ment characteristics vary considerable between patients, although those lesions that do enhance typically have a het· erogeneous pattern, especially on M R. Hydrocephalus is common. n.•s .s 7 . s 8.81, 84,85

Central Neu rocytoma

Figure 1 9-35 Choroid plexus carcinoma. There is a prominent choline peak, no discernible creatine peak, depression of N-acetylaspartate, and elevation of lactate in this malignant choroid plexus tumor.

( 5 6

Chordoma Intracranial chordoma arises i n the clivus. This i s an exceedingly rare lesion. Chordomas occur with an increased frequency in patients with tuberous sclerosis. Imaging studies demonstrate a large destructive mass, often with extension into the posterior fossa as well as the sphenoid sinuses and nasopharynx. On CT, there

may be spicules of bone visible within the tumor. The MR signal characteristics and enhancement pattern vary between patients; the mass is usually somewhat het­ erogeneous and undergoes only minimal enhancement ( Figure 1 9·1 1 6) .257·258

I nflammatory Pseudotu mor Inflammatory pseudotumor (plasma cell granuloma) is a benign inflammatory mass of unknown etiology. Although most frequently located in the lungs, this lesion can arise nearly anywhere throughout the body. The most com­ mon intracranial site of origin is the dura mater; however,

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 783

A

B

c

Figure 1 9-1 1 4 Lipoma and agenesis ofthe corpus callosum. A An axial CT image of a 2-year-old child shows a low attenuation mass in the interhemispheric region and right frontal lobe. There is thin calcification along the anterior margin.

B. The lipoma is hyperintense on this Tl-weighted MR image. There is a small intraventricular component (arrow) . C. A midline Tl-weighted image shows the hyperintense lipoma and absence of the corpus callosum.

parenchymal brain or interventricular origins also occur. Nearly half of CNS inflammatory pseudoturnors occur in the pediatric age group. The clinical manifestations are nonspecific; potential findings include headache, seizures, and cranial neuropathy. 25 9· 2 6°

pseudoturnor arising in the choroid plexus can mimic the appearance of a papilloma.

Inflammatory pseudotumor contains polyclonal plasma cells, fibrosis, myofibroblasts, and large histio­ cytes. The mass is usually hyperattenuating to brain on unenhanced CT. Characteristically, the lesion is hypoin­ tense to normal brain on T2-weighted MR images. There is usually homogeneous contrast enhancement. A dural or peripheral lesion may lead to calvarial erosion or scle­ rosis. Inflammatory pseudotumor of the dura has similar imaging characteristics as meningioma. An inflammatory

Patients with retinoblastoma, particularly the hereditary form, are at risk for the development of an intracranial PNET. The classic association is the so-called trilateral retinoblastoma, in which a pineal region PNET occurs in a patient with bilateral retinoblastomas (Figu re 1 9-1 1 7) . The ocular lesions may precede the intracranial abnormality. Occasionally, the ocular tumor is unilateral. Less common sites for the intracranial lesion include the parasellar and suprasellar re gi ons. 2 61-2 63

Reti noblastoma

784 Part 3 The B ra i n

8

A

Figure 1 9-1 1 5 Lipoma. A A midline sagittal Tl-weighted M R image of a 6-year­ old child with a seizure disorder shows hyperintense fatty tissue (arrow) in the interhemispheric fissure, wrapping around the superior aspect of the corpus callosum. B. The lipoma (arrow) is hypoattenuating on CT. C. This patient also has focal cortical dysplasia remote to the lipoma, with thickened cortical gray matter (arrow) on this T2-weighted coronal image.

c

Lym phoma and Leu kemia

Granulocytic s arcoma ( chloroma) is a mass com­

Involvement a t sites other than the hemopoietic organs

posed

and skeleton is uncommon at the time of presentation of

including myeloblasts , promyelocytes , and myelocytes .

of primitive precursors

of granulocytic cell s ,

leukemia or lymphoma. Mild prominence of the ventricu­

Granulocytic sarcoma is most often associated with

lar system and cerebral sulci occurs in some children with

myelogenous

leukemia, even prior to therapy.

can also occur with other myeloproliferative disorders.

CNS involvement with

leukemia,

although

this

complication

leukemia and lymphoma, however, most often occurs as a

Granulocytic sarcoma may be present at the time of the

relapse after therapy. The

original diagnosis, or develop during the course of the

CNS is a " sanctuary site," along

with the testes and kidneys. Infiltration with leukemic or

disease.

lymphomatous cells in these patients can occur in the cal­

is very uncommon . These lesions are often contiguous

varial bone marrow, dura, or leptomeninges. Involvement

with a meningeal surface. The mass tends to be slightly

may be diffuse or focal. Imaging with

hyperattenuating on unenhanced

CT or MR shows

abnormal increased meningeal enhancement.

A granulocytic sarcoma of the brain parenchyma

stantial contrast enhancement. 2 6 4

CT and undergoes sub­

Chapter 19 I ntracra n i a l N eo p l a s m s a n d M asses 785

Figure 1 9-1 1 6 Chordoma. A midline Tl-weighted M R image of a child with tuberous sclerosis demonstrates a large mass arising from the clivus and causing marked displacement of the brainstem.

Figure 1 9-1 1 7 Trilateral retinoblastoma. A contrast-enhanced T1-weighted M R image of a patient with hereditary retinoblastoma shows a solid mass of the pineal gland.

The C N S is the occasional site of complications related to the systemic manifestations of leukemia or lymphoma, as well as the effects of therapy. Leukocytosis, thrombocytopenia, sepsis, or coagulopathy can lead to intracranial hemorrhage or cerebral vascular thrombo­ sis. Massive brain hemorrhage is an important potential cause of death in patients with some forms of leukemia ( Figu re 1 9-1 1 8) . Potential side effects of radiation ther­ apy and chemotherapy in these patients include white matter edema, white matter destruction, vasculopathy, mineralizing microangiopathy (dystrophic calcifications in the basal ganglia and subcortical white matter) , and capillary telangiectasias. Mild prominence of the ven­ tricles and subarachnoid spaces is common in patients with leukemia; this may be due to the primary disease or the effects of therapy. This finding sometimes resolves during remission and after completion of therapy; therefore, caution should be exercised in assigning an imaging diagnosis of "atrophy. " Subtle deterioration in gray-white matter differentiation is also common during therapy. 2 6 p 66 Inrmunosuppressor medication (e.g. , cyclosporine) for a myeloproliferative disorder is 1 of the causes of posterior reversible encephalopathy syndrome (reversible posterior leukoencephalopathy syndrome; PRE S ) . The potential clinical features include seizures, headache, nausea, visual disturbance, and coma. Neuroimaging studies show sub­ cortical edema, predominantly in the occipital lobes and the posterior aspects of the temporal and parietal lobes. In severe cases, the cerebellum, basal ganglia, and brainstem are involved. Diffusion-weighted images are most useful for evaluating these patients. In the (reversible) early phase, there is increased diffusion. If the process is prolonged, cytotoxic edema (restricted diffusion) and subsequent encephalomalacia may develop due to vasospasm-induced ischemia. 2 67 Inununosuppression is a consequence of both the underlying disease and the medical therapy in patients with myeloproliferative disorders . Fungal disease is the most important consequence, particularly involving Candida and Aspergillus organisms. Hematogenous dissemination of Aspergillus to the CNS can produce an infectious vascu­ lopathy (infarction or hemorrhage) or focal fungal enceph­ alitis. Contiguous spread from the paranasal sinuses can also occur. There are varied imaging patterns of invasive CNS aspergillosis: foci of edema in the cortex or subcorti­ cal regions (low attenuation on CT and hyperintensity on T2 M R) , ring-enhancing cerebral lesions, and meningeal infl.anunatory enhancement. Candida infections of the CNS can lead to ring-enhancing rnicroabscesses or mani­ festations of vasculitis (mycotic aneurysm, hemorrhage, or infarction) . >6 8

Hemophagocytic Lyrn phohistiocytosis The C N S is a relatively common site of involvement in patients with hemophagocytic lyrnphohistiocytosis.

786 Part 3 The

Brain Table 1 9-1 1 . Hereditary Central N ervous System Tu mor Syndromes Syn d ro m e

Neurofibroma, peri pheral nerve sheath tumor, optic pathway glioma Neurofibromatosis Schwan noma, type 2 meni ngioma, ependymoma Tu berous sclerosis G iant cel l astrocytoma, hamartomatous tu bers Von H i ppei-Li ndau Hemangioblastoma syndrome Tu rcot Syndrome Astrocytoma, med u l loblastoma, ependymoma Basal cell nevus Medul loblastoma syndrome Ru bi nstei n-Taybi Medul loblastoma, syndrome meni ngioma, oligodendroglioma Astrocytoma, Li-Fraumeni syndrome med u l loblastoma, choroid plexus tumors Cerebellar Cowden disease hamartoma, meni ngioma, venous angioma Bannayan-Zonana Spinal l i poma, vascular syndrome malformations Pal l i ster-Hall Hypothalamic syndrome hamartoma Neurofibromatosis type 1

Figure 1 9-1 1 8 Leukemia. This 13-year-old girl undergoing chemotherapy for acute myelogenous leukemia has multifocal parenchymal hemorrhage, intraventricular hemorrhage, and hydrocephalus.

During the acute phase, the most common finding on M RI is the presence of multiple foci of signal abnormal­ ity in the cerebellum and periventricular cerebral white matter. These are hyperintense on T2-weighted images and undergo variable contrast enhancement. Mild mani­ festations of local mass effect are sometimes present. There may be subsequent progression to focal encepha­ lomalacia and generalized cerebral atrophy.

HEREDITARY CENTRAL NERVOUS SYSTEM TUMOR SYNDROMES The hereditary CNS tumor syndromes comprise a varied group of conditions (Table 1 9-1 1 ) . Most are due to muta­ tions of tumor suppressor genes. 2 69

Basal Cel l N evus Syndrome Basal cell nevus syndrome (Gorlin syndrome; nevoid basal cell carcinoma syndrome) is a hereditary, autosomal

Associ ated t u m o rs

I n heritance

AD

AD AD

AD

AD AD AD

AD

AD AD

dominant syndrome caused b y a germline defect i n the PTCH1 gene located at chromosome 9q22-3. These patients have multiple basal cell carcinomas, odontogenic kerato­ cysts of the mandible and maxilla (often multiple) , deft lip or palate, pitted palms, and various neoplasms or ham­ artomas. Patients with basal cell nevus syndrome are at increased risk for medulloblastoma. Up to 2% of pediatric patients with medulloblastoma have basal cell nevus syn­ drome; the association is as high as 10% in medulloblas­ toma patients younger than the age of 2 years. Meningioma

Chapter 1 9 I ntracra n i a l N eo p l a s m s a n d M asses 787

B

A

c

A,

B. Unenhanced axial CT images show dense irre gul ar calcification within the falx cerebri. C. There is a keratocyst in

the alveolar ridge of the maxilla (arrow) . A thin sclerotic margin surrounds the low-attenuation keratocyst.

occasionally occurs in association with basal cell nevus syn· drome. Myriad additional CNS abnormalities can occur in patients with this syndrome: neuronal migration disor· ders, hemimegalencephaly, cerebral atrophy, hydrocepha· lus, widening of the insula, and white matter hypoplasia in association with focal calvarial thickening. Associated skel­ etal anomalies include bifid ribs, deformities of the digits, vertebral anomalies, prognathism, and frontal bossing. Calcification and thickening of the dura matter are common neuroimaging findings in children with basal

cell nevus syndrome ( Figure 1 9-1 1 9) . In decreasing order of frequency, potential sites of calcification include the falx cerebri, the diaphragma sella, the tentorium, and the petroclinoid ligaments. Mandibular and maxillary kera­ tocysts appear as sharply marginated expansile lesions with CT attenuation values similar to or slightly greater than those of water (Figure 1 9-1 20) . On MR, the cyst con­ tents are often heterogeneous. The contents are hyperin­ tense on T2-weighted images and variable on T1-weighted images. 27°-272

Figure 1 9-1 1 9 Basal cell nevus syndrome.

788 Part 3 The B ra i n

B

A

c

Figure 1 9-1 20 Basal cell nevus syndrome. A There is calcification along the falx cerebri (arrow) on this unenhanced axial Cf image. B , keratocysts appear as homogeneous expansile lesions (arrows) .

Rubinstei n-Taybi Syndrome Rubinstein-Taybi syndrome is a congenital disorder characterized by abnormal facies, microcephaly, broad thumbs , enlarged toes , and intellectual impairment. The most commonly identified genetic defect is agerrnline mutation in 1 allele of the CREB BP gene, which encodes a transcriptional coactivator for many cyclic adenosine monophosphate-regulated genes. Other genetic defects include mutations in EPJOO and deletions in band 16p13 . C N S neoplasms that can occur in these patients include medulloblastoma, meningioma, and oligodendroglioma. Cranial MR features of Rubinstein-Taybi syndrome

C.

Bilateral maxillary odontogenic

include bilateral rolandic cortical clefts and white matter thinning. 2 73

Li-Frau meni Syndrome Li-Fraumeni syndrome is a n autosomal dominant heredi­ tary tumor syndrome. The most common associated genetic abnormality is a mutation of the tumor suppressor gene TPSJ· Many of these patients develop malignancies as children or young adults. Common associated neo­ plasms include sarcomas, acute leukemia, breast cancer, and adrenal cortical carcinoma. CNS lesions that occur with an increased frequency in patients with Li-Fraumeni

Chapter 19 I ntracra n i a l N eo p l a s m s and M asses 789 syndrome include astrocytoma, medulloblastoma, and cho­ roid plexus tumors. 2 74

13- Nishio S, Morioka T, Suzuki S, et al. Subependymal giant cell

Cowden Disease

14· Menor F, Marti-Bonmati L, Mulas F, et al. Neuroimaging in

Cowden disease (multiple hamartoma-neoplasia syn­ drome) is a rare autosomal dominant systemic disorder that includes hamartomas of multiple organs (includ­ ing the cerebellum and skin) , various developmental anomalies (e.g. , macrocephaly) , intracranial venous malformation s , and an elevated risk for meningiomas and various malignancies (breast, colon, and thyroid) . The cerebellar lesion that occurs in these patients is a dysplastic gangliocytoma; that is, Lhermitte-Duclos dis­ ease. Approximately 85% of individuals with Cowden disease have a mutation of the tumor suppressor gene PTEN. 2 7 P76

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276. Lok C, Viseux V. Avril M F , et a!. Brain magnetic resonance imaging in patients with Cowden syndrome. Medicine (Baltimore) . 2005;84 (2) :129-136 .

CH A P T E R

20

Intracranial Vascula r Abnormalities

DEVELO P M ENTAL VARIATIONS A N D VASCU LAR ANOMALI ES . . . . . . . . . . . . . . . . . . . .

798

Arterial Agenesis, Aplasia, and Hypoplasia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

798

Anomalous Vessel Origi ns and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

798

I ntracranial Venous Developmental Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

799

VASCU LAR MALFORMATIONS . . . . . . . . . . . . . . . . . .

799

C l i n ical Presentations: N o ntra u m atic Acute I ntracranial H emorrhage . . . . . . . . . . . . . .

799

Arteriovenous M alformation . . . . . . . . . . . . . . . . . . . . . . . 8oo Arteriovenous Fistu la . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

801

Dural arteriovenous Fistula . . . . . . . . . . . . . . . . . . . . . . Vertebral Arteriovenous Fistula . . . . . . . . . . .. .. . Carotid-cavernous Fistula . . . . . . . . . . . . . . . . . . . . . . . . .

801 803

Vei n of Galen M alformation . . . . . . . . . . . . . . . . . . . . . . . .

803

803

Hypoxic- I schemic Encephalopathy . . . . . . . . . . . .

81 7

I schemia and N ontra u m atic Hemorrhage in Prematu re I nfants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

81 9

CERVICOCEREBRAL ARTERIAL DISSECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

827

VASCULITIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

827

I nfectious Vascu l itis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

827

.............................. Primary Central Nervous System Vasculitis of Childhood . . . . . . . . . . . . . . . . . . . . . . . .

828

Germinal Matrix Hemorrhage . . . . . . . . . . . . . . . . . 81 9 Periventricular Hemorrhagic Infarction . . . 822 Periventricular Leukomalacia . . . . . . . . . . . . . . . . . . . 822 Clinical Presentations: Cerebral Palsy . .. . . 826 Severe Hypoxic-ischemic Injury in the Premature Infant. . . . . . . . . . . . . . . . . . . . . . . 826

N o n i nfectious Vascu l itis

828

804

NON I N FLAM MATORY VASCU LOPATHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M oyamoya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

828

Cavernous M alformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8o6

Sickle Cel l Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

831

Capillary Telangiectasia . . . . . . . . .. .. .. . . . . . . . .. .. .. . . . . .

8o6

SI NOVENOUS TH ROM BOSIS. . . . . . . . . . . . . . . . . . . . .

832

C l i n ical Presentations: Trigeminal N e u ralgia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

807

HYPERTENSIVE ENCEPHALOPATHY . . . . .

834

A N E U RYSMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

807

Congen ital Aneu rysms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

809

POSTERIOR REVERSI BLE ENCEPHALOPATHY SYNDRO M E . . . . . . . . . . . . .

835

Mycotic Aneurysms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

809

BENIGN I NTRACRAN IAL HYPERTENSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83 6

M IG RAI N E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83 6

CLIN ICAL PRESENTATIONS: H EADACH E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

837

EXTRACO RPOREAL M EM BRAN E OXYG E NATION . . . . . . . . . . . . . . . . . . . . . .

838

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83 9

Venous Angioma ( Developmental Venous Anomaly) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Trau m atic Aneurys ms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809 I magi ng Eval u ation of I ntracranial Aneurysms . . . . . . . . . . . . . . . . . . . . . . . . . . .

81 0

ISCH E M IC BRAI N I NJ U RY. . . . . . . . . . . . . . . . . . . . . . . . . . . .

81 1

C l i n ical Presentations: Stroke . . . . . . . . . . . . . . . . . . . . . .

81 1

Arterial I nfarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

81 2

Venous I nfarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

81 6

828

797

798 Part 3 The B ra i n

DEVELOPMENTAL VARIAT IONS AND VASCULAR ANOMALIES

Arterial Agenesis, Aplasia, and Hypoplasia Developmental abnormalities that result in absence or narrowing of intracranial vascular structures are com­ mon. However, collateral pathways prevent functional brain alterations in most individuals with these anomalies. Agenesis refers to complete failure of embryological devel­ opment. Aplasia indicates lack of development despite the presence of a precursor. Hypoplasia is incomplete develop­ ment. Agenesis and aplasia of vascular structures usually cannot be differentiated radiographically or clinically, and the 2 terms are generally used interchangeably. Agenesis or hypoplasia of an internal carotid artery occurs in less than 0. 01% of the population. There is a p left-sided predominance. The anomaly is most often uni­ lateral. Absence of the internal carotid artery is usually an isolated lesion, but can also occur in association with other cervicocerebral vascular anomalies, as in patients with PHACES (posterior fossa malformations, hemangiomas, arterial anomalies, cardiac anomalies and aortic coarctation, eye abnormalities, and a sternal cleft or suprapubic raphe) syndrome (see Figure I3·I6). Most patients are asymptom­ atic or have nonspecific complaints, such as headache. Rare potential clinical manifestations include transient ischemic attacks, hemiplegia, and congenital Homer syndrome. Patients with absence of an internal carotid artery are at increased risk for cerebral aneurysms, although these are usually not evident until adult life.'·2 There are 3 basic patterns of collateralization in patients with congenital absence or substantial hypoplasia of a carotid artery; the developmental stage at which the insult occurs determines the specific pattern. (I) By far the most common pattern of collateralization is by way of the circle of Willis. Typically, the contralateral internal carotid artery provides flow to the anterior cerebral artery via a prominent anterior communicating artery. An enlarged posterior communicating artery supplies flow to the mid­ dle cerebral artery ipsilateral to the absent carotid artery. (2) If the embryonic insult occurred prior to completion of the circle of Willis, primitive pathways of collateral circula­ tion prevail. This most often consists of an intercavernous communication between the ipsilateral carotid siphon and the cavernous segment of the contralateral internal carotid artery. (3) Rarely, collateral flow occurs into a reconstituted internal carotid artery via skull base collaterals from the external carotid artery system. Potential pathways for arterial supply to the ophthalmic artery in patients with absence of the internal carotid artery are external carotid branches , a residual hypoplastic segment of the internal carotid artery, and various anomalous origins of the oph­ thalmic artery (e.g., from the posterior communicating, middle meningeal, or anterior cerebral arteryp-6 Techniques for the diagnosis of congenital absence of the internal carotid artery include angiography, CT

Figure 2o-1 Azygous anterior cerebral artery. MRA shows a single midline anterior cerebral artery (arrow) supplied by normal right and left Al segments.

angiography (CTA) , and M R angiography (MRA) . The pres­ ence of the developing internal carotid artery is a prereq­ uisite for formation of the carotid canal (5 to 6 weeks of gestation) . Therefore, an absent carotid canal on CT or M R confirms the diagnosis o f internal carotid artery agenesis, as opposed to an acquired occlusion. Likewise, a diminu­ tive carotid canal is confirmatory of the diagnosis of hypo­ plasia rather than acquired narrowing.7 Agenesis, hypoplasia, and duplication anomalies of smaller intracranial arteries are common anomalies that usually are of no clinical significance other than poten­ tial limitations in collateral flow in patients with acquired pathology. Aplasia or hypoplasia of the AI segment of the anterior cerebral artery is the most common anom­ aly, occurring in approximately 10% of the population. Duplication of the anterior communicating artery is also common. An azygous anterior cerebral artery refers to a single trunk supplied by the right and left AI segments (Figure 20-1 ) ; this rare anomaly occurs in many children with holoprosencephaly. Hypoplasia of the distal aspect of the basilar artery occurs in some individuals with a fetal origin of the posterior cerebral artery.

Anomalous Vessel Origi ns and Con nections Fetal origin of the posterior cerebral artery occurs i n approxi­ mately 10% of the population. This is due to persistence of the embryonic pattern of circulation. Imaging stud­ ies show origin of the posterior cerebral artery from the

Chapter 20 I ntracra n i a l Va scu l a r A b n o r m a l ities

799

A rare persistent carotid-vertebrobasilar anastomosis is the

proatlantal intersegmental artery.

This vessel originates

from the internal carotid artery or external carotid artery, courses between the occiput and atlas, and connects to the horizontal portion of the vertebral artery near the foramen magnum. The

persistent otic artery

arises from the petrous seg­

ment of the internal carotid artery, extends through the internal auditory canal, and j oins the caudal aspect of the basilar artery. One or both vertebral arteries are hypo­ plastic or absent in some individuals with this very rare anomaly.

I ntracranial Venous Developmental Variations Asymmetry o f the venous sinuses o f the posterior fossa is common.

An absent or hypoplastic transverse sinus is the

most common venous sinus "anomaly." The ipsilateral sig­ moid sinus and internal jugular vein are usually small as well in these patients . A dominant right transverse sinus is most common. A small or absent transverse sinus can

Figure 2o-2 Fetal origin of the posterior cerebral artery. An oblique M RA image shows the right posterior cerebral artery (large arrow) to arise from the internal carotid artery. The left PCA (small arrow) arises from the basilar artery.

mimic the findings of venous sinus thrombosis on M R venography. Careful inspection of cross-sectional images is essential to differentiate a clot-filled sinus from a hypoplas­ tic or absent sinus .11 The persistent

occipital sinus is

an uncommon anomaly

that is due to persistence of a fetal venous pathway between internal carotid artery

(Figure 20-2) .

The ipsilateral P1 seg­

ment is hypoplastic or absent. This anomaly is usually of no clinical significance except in adults with atheroscle­ rotic disease.8 Persistent embryonic circulatory patterns can lead to various anomalous communications between the carotid arteries and the vertebral or basilar arteries . These occur in up to

1% of the population. Most common is a persis­

tentprimitive trigeminal artery, which connects the proximal intracavernous portion of the internal carotid artery to the distal third of the basilar artery. The ipsilateral vertebral and

the torcula and internal jugular veins. The occipital sinus is a midline vessel dorsal to the cerebellum, contained within the leaves of the dura. In some instances , there are

2

ves­

sels or a network of vessels . The straight sinus and sagittal sinus drain into the persistent occipital sinus at the torcula. At the foramen magnum, the sinus either continues as a single vessel to 1 internal jugular vein or splits into

2 vessels

that drain bilaterally. The transverse sinuses are usually small or absent. Recognition of this anomaly is important

for patients who will be undergoing posterior fossa decom­ pression surgery.' 2

posterior communicating arteries are sometimes hypoplas­ tic in individuals with this anomaly. There is a variant of this anomaly in which the persistent trigeminal artery connects with the superior or posterior inferior cerebellar arteries. Potential associated lesions include intracranial aneurysm (posterior communicating artery or the primitive trigemi­

VASCULAR MALFORMAT IONS

Clin ical Presentations: N ontraumatic Acute I ntracran ial Hemorrhage

nal artery) , arteriovenous malformation (AVM ) , moyamoya disease, and additional intracranial arterial anomalies .9 ·10

is in important cause of morbidity and mortality in chil­

The second most common persistent carotid-vertebra­

dren. The brain parenchyma is the most common site of

Spontaneous, or nontraumatic, intracranial hemorrhage

This

spontaneous intracranial hemorrhage. Subarachnoid or

vessel arises from the internal carotid artery at the C1-C3

intraventricular hemorrhage can occur by way of exten­

basilar anastomosis is the

primitive hypoglossal artery.

level of the neck, courses through the hypoglossal canal,

sion from a parenchymal focus or, less commonly, as the

and connects to the basilar artery just beyond its origin.

primary site of bleeding. Nontraumatic pediatric intrapa­

Potential associated conditions include aneurysm at the

renchymal hemorrhage occurs at a rate of approximately

junction of the vessel with the basilar artery, persistent

0.7 per 1oo,ooo children per year. Common nontraumatic

primitive trigeminal artery, glossopharyngeal neuralgia, and hypoglossal nerve paralysis .

AVM , cavernous malformation, mycotic aneurysm, venous

causes of intraparenchymal hemorrhage in children are

8oo Part 3

The

B ra i n

Table 2o-1 . Causes of Atraumatic Su barach noid Hemorrhage

Ruptu red aneu rysm (so%) Arteriovenous malformation (25%) Idiopathic ----,.- - - - - - -- Systemic disease Leukemia Idiopath ic th rom bocytopenic pu , _r��_:: _ , Hemoph ilia Hemorrhagic disease of the newborn Brain tumor Stroke _

_ _

------ - - · · · - - - - - - - --------

reveal a source of hemorrhage and there is a strong clinical suspicion of an AVM or aneurysm, conventional catheter angiography is usually indicated.

Arteriovenous M alformation An AVM is a congenital nonneoplastic lesion composed of dysplastic thin-walled vessels fed by dilated arteries and drained by enlarged veins . A normal intervening capillary network is lacking. Usually, the dysplastic vessels comprise a "mass" ; this is the nidus of the lesion. The pathogenesis involves a localized failure of appropriate differentiation of primitive arteriovenous connections early in embryogen­ esis. Absence of normal capillaries between arteries and veins leads to high velocity blood flow through the nidus. Enlargement of a congenital arteriovenous malformation may occur by way of progressive dilation of the involved vessels, recruitment of collateral vessels, proliferation of new abnormal vessels, and destruction of adjacent paren­ chyma. The vascular supply of a cerebral arteriovenous malformation is through pial arteries, dural arteries, or

sinus thrombosis, neoplasm, vasculopathy, and coagu­

both. 2 7

lopathy. The major clinical manifestations of spontaneous

The most common location of an intracranial arte­

intraparenchymal hemorrhage relate to elevated intracra­

riovenous malformation in a child is in the subpial space;

nial pressure : depressed level of consciousness, headache,

dural-based lesions and deep cerebral lesions are less

irritability, and vomiting. Focal neurological symptoms and seizures are also common. '3-17

common. Approximately

Spontaneous hemorrhage into the subarachnoid space

97% of nontraumatic sub­ arachnoid hemorrhages occur in patients older than 18 years. The most common causes are aneurysm (5o%) and AVM (25%) (Table 20-1 ) . Fewer than 2% of children with a is rare in children. Greater than

90% of supratentorial arterio­

venous malformations are superficial. Superficial lesions often have a triangular shape, with a peripheral base and a central apex. Deep lesions can arise in the thalami or basal ganglia. Eighty percent to

90% of intracranial arte­

riovenous malformations are supratentorial. Multifocal lesions are uncommon. The predominant blood supply of

lmown aneurysm suffer intracranial hemorrhage prior to

pediatric intracranial arteriovenous malformations is from

the age of 19 years. The risk for hemorrhage is even lower

the middle cerebral arteries in

for small lesions ; the estimated rate of rupture of aneu­

arteries in

rysms smaller than

5 mm is 0.55% per year. Spontaneous

hemorrhage into the subarachnoid space usually leads to a sudden onset of intense headache and neurological defects of variable severity.'8-26

55%. the posterior cerebral 29%, the anterior cerebral arteries in 8.5%, and the internal carotid arteries in 7- s%. 26 , 2 8

Wyburn-Mason syndrome

(Bonnet- Dechaume-Blanc

syndrome) is an uncommon phacomatosis in which intra­ cranial arteriovenous malformations (usually multifocal)

In term infants , the most common cause of sponta­

occur in association with facial nevi and retinal vascular

neous intracranial hemorrhage is sinovenous thrombosis .

malformations. Multiple arteriovenous malformations of

Straight sinus thrombosis is an important potential cause

the central nervous system (CNS) can also occur in patients

of thalamic hemorrhage in the term infant. Thrombosis of

with hereditary hemorrhagic telangiectasia; most of these lesions are pial. 2 9 ·3°

the superior sagittal sinus can lead to parasagittal hemor­ rhage. Spontaneous choroid plexus hemorrhage, usually

Although these are congenital lesions , most (approxi­

minor, can lead to intraventricular dot. Hemorrhage due to

mately

an AVM or intracranial neoplasm is rare in this age group.

ered until adult life. A neonate with a large arteriovenous

In some patients with intracranial hemorrhage, there is no

malformation sometimes has manifestations of hemody­

clinically or radiographically demonstrable cause. In the acute setting, CT is the imaging technique of

8o%) arteriovenous malformations are not discov­

namic deterioration due to massive shunting. A high-flow lesion can also cause clinical marrifestations of intracra­

choice for evaluation of the child with suspected intracra­

nial venous hypertension. Older children may suffer sei­

nial hemorrhage.

zures (usually generalized) . Seizures occur in up to

An underlying vascular malformation or

70% of

aneurysm is occasionally visible; contrast-enhanced images

patients with an intracranial arteriovenous malformation,

or CT angiography may provide more specific information

and are the presenting marrifestations in approximately

in these patients. M R and M RA are essential components

15%. Many patients are asymptomatic until suffering

for the evaluation of clinically stable patients with spon­

spontaneous hemorrhage; an arteriovenous malformation

taneous intracranial hemorrhage. If these studies fail to

is the most common cause of spontaneous intracranial

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 801 h emorrhage in children. Hemorrhage usually arises from the venous side of the l esion, and can occur into the cere­ bral parenchyma (most common) , the sub arachnoid space, or the ventricular system. After the initial presenting event, the annual rate o f sub sequent hemorrhage is approxi­ mately 2%. C hronic or recurrent headache is another potential pre­ senting manifestation intracrania l vascular malformations, occurring in approximately 5% of cases. Uncommonly, chronic vascular steal andjor venous hypertension com­ promise brain development and function, leading to pro­ gressive neurological defi cits; imaging studies may show enceph al omal acia and calcifications. Some infants with an intracranial vascular malformation develop macrocra­ nia, particularly if th ere is prominent dural venous drain­ age of the lesion. Occasiona lly, ob structive hydrocephalus occurs. 22 • 2 3 On unenhanced CT, an intracranial arteriovenous mal ­ formation usually appears as a heterogeneous area ofs lightly increased attenuation within the brain parenchyma. Small dystrophic calcifications are sometimes present. There may b e adjacent hypoattenuation due to encephal omal acia or gliosis. The nidus of the lesion enhances intensely with IV contrast. There are prominent contrast-enhancing arteries and veins adj acent to the ni dus. Peripheral lesions often have a triangular or cone-shape d confi guration, whereas deep malformations often are rounde d . There is usually lit­ tl e mass effect. High-pressure fl ow through the lesion can l ead to the formation of an aneurysm within the nidus, in a feeding artery, or in a draining vein. Unenhance d CT after hemorrhage from an intra­ cranial arteriovenous malformation most often shows a parenchymal hematoma. There may al so b e bl oo d in th e sub arachnoi d space or the ventricular system. The h em­ orrhage sometimes partially or compl etely ob scures the underlying malformation. Spontaneous h emorrh age can al so lead to thromb osis of th e malformation. Sequential CT imaging performe d after intracerebral hemorrhage s hows progressive resolution of the hematoma and the devel op­ ment of localized encephalomal acia; dystrophic cal cifica­ tions may devel op. The rapidly fl owing bloo d within an arteriovenous lf ma ormation results in a hypointense appearance on MR (i.e., flow voids) . C lassically, the nidus appears as a tangle of serpiginous flow void s ( Figure 20-3) . Hypointense sup­ plying arteries and draining veins extend from the periph­ ery o f the ni dus. Sub acute hemorrhage is hyperintense on T1-weighted images. Hemosi derin from prior hemorrhages may lead to foci within or adjacent to the malformation that are hypointense on T2- and T2*- weighte d images. Gliosis is hyperintense on T2-weighted sequences and FlAIR (fluid attenuate d inversion recovery) images.3'·3 2 M RA and CT angiography provide supplemental information about th e angioarchitecture of an intracra­ nial arteriovenous malformation. Differentiation of arter­ ies from veins is often difficult, as both have rapid fl ow. Conventional angiography provides the greatest anatomic

detail and allows accurate characterization of flow dynam­ ics through the lesion. Rapid sequence image acquisition is essential because of th e rapid blood fl ow. Multipl e pro­ j ections or rotational angiography may b e nee de d to accu­ rately characterize the path ol ogical anatomy. Arteriovenous shunting is a hallmark angiographic feature of an arterio­ venous malformation. The supplying arteries and drain­ ing veins are dilated and tortuous. The nidus consists o f a tangle o f small irregular vessel s. When present, an asso­ ciate d aneurysm appears as a contrast-opacifie d pouch . Occasionally, the aneurysm is remote to the actual malfor­ mation. Arteriovenous malformations o f the dura usually do not have a discrete nidus, but rath er consist of multiple rnicrofistulae; that is, a developmental arteriovenous fi stula (AVF) . 2'·33·34

Arteriovenous Fistu la A n AVF is a large-calib er arteriovenous connection without an intervening capillary bed . Th e distinguis hing feature from an arteriovenous malformation is the lack of a vascu­ lar nidus. The connections of an AVF can b e single or mul ­ tiple. AVFs can be developmental (idiopathic) or acquired . The most common types of intracranial AVFs are dural , vertebral , an d carotid-cavernous.

Dural Arteriovenous Fistula A dural AVF is a direct shunt located insi de th e dural layer. Some dural AVFs are acquire d lesions that arise as a con­ sequence of dural sinus thromb osis, trauma, or surgery. In chi ldren, h owever, th e i diopathic variety is most common. I diopathic congenital dural malformations ten d to b e large high - flow lesions that can clinically mimic vein o f Galen malformation. Potential fee ding arteries are meningeal vessel s (most common) , cerebral arteries, internal carotid arteries, and external caroti d artery b ranches. The potential clinical manifestations o f dural AVFs include h eadache, macrocephaly, distende d scalp veins, pul satil e tinnitus, proptosis, chemosis, and manifestations relate d to intra­ cranial hypertension. A l arge congenital lesion in an infant can lead to cardiac failure. Th ose AVFs with retrograde cortica l venous drainage o ften cause neuro logical manifes­ tations . Cortical venous drainage an d aneurysmal venous dil ation indicate either ob struction of the involved venous sinus or pressure e levation due to l arge volume bl oo d fl ow.Js-3 8 Dural AVFs can usually b e detecte d with MRA. Potential findings include multiple curvilinear or no dular vascular structures adjacent to a sinus wall , as well as high signal intensity areas of turbulent high-velocity fl ow within th e venous sinus. Contrast-enh anced digital subtraction M RA documents early filling of the involved venous sinus. Angiograp hy usually demonstrates multiple enlarged men­ ingeal arteries that converge on a venous sinus. Transcranial sonography of the neonate with a congenital dural AVF typically s hows marke d enlargement of the venous sinuses

802 Part 3 The B ra i n

A

c

B

D

Figure 2o-3 Cerebral arteriovenous malformation. A Tl-weighted M R image of a 14-year-old child with recent onset headaches shows a superficial "mass" (arrow) composed of multiple flow voids. The lesion has a triangular shape, with the peripheral aspect wider than the central aspect. B. A sagittal T1-weighted image demonstrates hyperintense blood products (arrow) at the inferior-lateral margin of the lesion. C. The nidus of the malformation enhances intensely with intravenous gado­ linium. D, E. Anterior and lateral MRA images confirm that the nidus consists of a tangle of vessels with arterial flow (arrow) . The predominant feeding arteries arise from the right middle cerebral and posterior cerebral arteries. There is also supply from the right pericallosal artery. A.

E

Chapter 20 I ntracra n i a l Va scu l a r A b n o r m a l ities 803 distal to the lesion. Unlike vein of Galen malformation, the cerebral vessels in these infants are often normal in size or minimally enlarged. Older children with a large dural AVF often have hydrocephalus and imaging manifestations of parenchymal ischemia, such as white matter thinning and gliosis.J 8

Vertebral Arteriovenous Fistula Vertebral AVFs can be congenital, iatrogenic, or posttrau­ matic. There is a connection, usually solitary, between the vertebral artery and markedly dilated draining veins in the paravertebral plexus. The most common clinical manifes· tations are neck pain and a bruit. Neurological findings occasionally occur due to vascular steal from the intracra· nial circulation. Imaging studies demonstrate enlargement of the vertebral artery proximal to the fistula and direct communication with multiple enlarged tortuous draining veins.3 9

Carotid-cavernous Fistula An AVF between an internal carotid artery and the cav· ernous sinus is usually an acquired lesion due to trauma. Although quite rare, developmental dural AVFs from a meningeal artery can also occur at this site. Potential clin­ ical manifestations of a carotid-cavernous fistula include headache, bruit, proptosis , and diplopia. Neuroimaging studies show 1 or more prominent supplying arter· ies and marked enlargement of the involved cavernous sinus. There is also dilation of veins that communicate with the involved venous sinus, including the superior ophthalmic vein. Shunting of blood through intercavern· ous connections often leads to concomitant enlargement of the contralateral cavernous sinus and its tributary veins.4°

prosencephalic vein. The clinical presentation of the cho­ roidal type typically is in the newborn period and includes manifestations of congestive heart failure. The mural type of vein of Galen aneurysmal malformation involves fewer fistulae than with the choroidal type. Feeding vessels from the collicular arteries, the posterior choroidal arter­ ies, or the pericallosal arcade drain into the wall of the dilated median prosencephalic vein. These patients usu· ally present as infants with macrocephaly and failure to thrive, often accompanied by some degree of congestive heart failure. The vein of Galen aneurysmal dilation refers to a deep midline arteriovenous malformation that drains into the vein of Galen ( Figure 20-4) . Enlargement of the vein of Galen in these patients is in part due to restric­ tion of outflow. Common supplying vessels include len­ ticulostriates, thalamoperforators, trans-sylvian branches of the middle cerebral arteries , and perforators from the anterior cerebral arteries. Patients with the vein of Galen aneurysmal dilation usually present beyond infancy with seizures, neurological deficits, or manifestations of intra­ cranial hemorrhage; congestive heart failure is rare in these children. More than 90% of vein of Galen malformations are detected prenatally or during the neonatal period. There

Vei n of Galen M alformation Vein of Galen malformation is a developmental cerebro­ vascular lesion in which midline arteriovenous commu­ nications feed enlarged deep venous structures of the galenic venous system. This term encompasses a spec· trum of anomalies. Most often, the pathogenesis consists of developmental AVFs between deep choroidal arter· ies and the median prosencephalic vein of Markowski. The arteriovenous communications can be in the form of 1 or more large direct fistulae or multiple smaller connections.4•-5 ° There are various classification schemes for vein of Galen malformations . The vein of Galen aneurysmal malformation refers to a direct AVF into the embryonic median prosencephalic vein. There is lack of embry­ onic development of a true vein of Galen. The choroi­ dal type of this malformation is most common. This is a complex lesion, with arterial supply from choroidal, pericallosal, thalamoperforator, and transmesencephalic arteries that communicate with tributaries of the median

Figure 2o-4 Vein of Galen aneurysmal dilation. A contrast-enhanced CT image shows multiple dilated and tortuous vessels in a right thalamic AVM. Drainage through the vein of Galen and straight sinus results in marked dilation of these structures.

804 Part 3 are

3

The

B ra i n

clinical classifications o f vein o f Galen malformation:

(1) the neonate with a prominent intracranial bruit and congestive heart failure (about one-third of patients) ; (2) an infant presenting with macrocephaly, prominent scalp veins, or seizures; and

(3 )

an older child presenting with

headaches or manifestations of subarachnoid hemorrhage. Occasionally, spontaneous thrombosis results in an acute presentation. With a large shunt, cerebral venous hyperten­ sion and ischemia lead to brain damage. Ventriculomegaly in children with vein of Galen malformation often has a multifactorial pathogenesis; potential causes include com­ pression of the aqueduct, intracranial venous hyperten­ sion, and brain atrophy.42·45·5' The prenatal sonographic appearance of vein of Galen malformation is that of a "cyst" or prominent vascular struc­ ture at the midline dorsal to the thalamus and midbrain. The appearance can mimic that of other developmental cys­ tic lesions such as porencephaly or arachnoid cyst. Doppler evaluation confirms blood flow through the lesion. The neck vessels may appear prominent. With a large lesion, there may be sonographic manifestations of heart failure. The dilated "vein of Galen" usually is not sonographically

MR can also be help­ ful to document the pathological vascular anatomy and

visible until the third trimester. Fetal associated alterations in the brainY CT angiography and

MRA are the most useful non­

invasive imaging techniques for demonstrating the mor­ bid vascular anatomy of a vein of Galen malformation. Conventional transcatheter angiography is reserved for

Figure 2o-s Vein of Galen aneurysmal malformation. Rapidly flowing blood in the varix produces a flow void on this T1-wei ghted MR image. The posterior extension of the varix is more superior than expected for a dilated straight sinus. The anterior aspect of the varix compresses the tectum. The basilar artery is dilated and tortuous.

therapeutic embolization procedures . The most commonly utilized angiographic classification for vein of Galen mal­ formation recognizes

4 types. The type 1 lesion involves 1

or a few feeding arteries from the pericallosal and poste­

draining veins. Chronic ischemia may lead to parenchymal

rior cerebral arteries. The type 2 lesion is somewhat more

hypoattenuating foci of encephalomalacia. Occasionally,

complex, with additional feeders from thalamoperfora­

hemorrhage or dystrophic calcification results in foci

tors. The type

of high attenuation.43·54·55

3

lesion has feeding ves sels from the peri­

callosal, posterior cerebral, thalamoperforator, and basilar arteries ; lenticulostriate and sylvian arteries can also be involved. The type

4 lesion is an arteriovenous malfor­

mation of the thalamus or midbrain, with secondary dila­

The rapidly flowing blood in the varix of a vein of Galen malformation is predominantly hypointense on sequences

(Figure 20-5) . A

MR

somewhat heterogeneous char­

acter is common, reflecting turbulent flow andfor intralu­

tion of an otherwise normal vein of Galen; that is, vein of

minal dot. There may be pulsation artifact associated with

Galen aneurysmal dilation. In some patients with vein of

the mas s . The feeding arteries appear as linear flow voids

Galen malformation, there are abnormalities in the maj or

adjacent to the varix. The mass causes displacement of

draining veins , such as duplication of the straight sinus ,

the tectum; hydrocephalus is common. There may also be

an accessory straight sinus , or stenosis of the straight

prominence of subarachnoid fluid surrounding the cere­

sinus. If there is hemodynamically significant resistance

bral convexities, due to elevated intracranial venous pres­

to drainage through the venous sinuses of the posterior

sure and diminished cerebrospinal fluid (CSF) resorption.

fossa, redistribution into anterior vessels may lead to mas­

Parenchymal foci of acute ischemia are hyperintense on

sive enlargement of facial veins .53

diffusion-weighted images ; in the subacute phase, these

Standard CT and

MR examinations demonstrate a vein

of Galen malformation as a large mass at the midline in the

become hyperintense on standard T2-weighted images and hypointense on T1-weighted images.

region of the quadrigeminal plate cistern. The varix may have a spherical or tubular shape. On unenhanced CT, the blood-filled "aneurysm" usually appears slightly hyperat­ tenuating to normal brain. Foci of thrombosis may alter

Venous Angioma (Developmental Venous Anomaly)

the attenuation characteristics . There is intense contrast

A venous angioma is a relatively common developmen­

enhancement of the lesion, the feeding arteries, and the

tal lesion composed of radially oriented dilated veins that

Chapter 20 I ntracra n i a l Va scu l a r A b n o r m a l ities converge in a single enlarged transcortical draining vein. The brain tissue between the venous channels is normal. The term "angioma" is a misnomer, as this lesion is not a neoplasm. Developmental venous anomaly is a more accu­ rate term for this localized venous malformation. The thin-walled anomalous veins are usually medullary or sub­ cortical. There is no arteriovenous shunting. Most venous angiomas are asymptomatic. Potential clinical manifesta­ tions include headache, seizure, and focal neurological deficit. Hemorrhage is rare. Multiple venous angiomas can occur in patients with the blue rubber bleb nevus syndrome. 27·5 6-58 A specific imaging diagnosis of venous angioma is usually possible with M R (preferably performed with IV contrast) , contrast-enhanced CT, or cerebral angiography. The key feature is a tuft of small vessels that converge into a single enlarged transcortical draining vein (Figure 20-6) . Th e collection o f dilated anomalous veins has been likened to a medusa head (caput medusa) . In most instances, the lesion is not visible on unenhanced CT; rarely there is a focus of dystrophic calcification ( Figure 20-7) . Identification

A

Figure 2o-7 Venous angioma. A. Unenhanced Cf of a 17-year-old boy with headaches shows a small focus of calcification (arrow) in the right frontal lobe. The adjacent parenchyma appears normal. B. A contrast-enhanced

8os

Figure 2o-6 Venous angioma. A lateral image from the venous phase of a cerebral angiogram shows a network of thin veins (arrows) that empty into an enlarged draining vein.

B

T1-weighted MR image is diagnostic, demonstrating a tuft of radially oriented veins (large arrow) that converge into a single prominent draining vein (small arrow) .

8o6 Part 3 The B ra i n

Figure 2o-8 Venous angioma. The draining vein (arrow) of a right cerebellar venous angioma produces a flow void on this TI·weighted image. The thin vessels in the lesion itself are faindy visible as hyperintense structures than converge on the draining vein.

of the draining vein is an important clue to the diagnosis on unenhanced MR images. Because the velocity of blood flow within the lesion is low, the signal intensity on unen· hanced MR is variable (Figu re 2o-8) . 32 · 59 . 6 o Venous angiomas occur throughout the brain; periven­ tricular or deep locations are more common than superfi­ cial, and supratentorial locations are more common than infratentorial. Drainage can occur into superficial cortical veins or sinuses, into deep periventricular veins, or into both. The draining vein communicates with the superfi­ cial venous system in approximately 70% of cases. There is occasionally a stenosis of the draining vein as it enters the dural sinus. Stenosis can lead to localized venous hypertension, draining vein thrombosis , and hemorrhagic complications.

Cavernous M alformation Cavernous malformation is a form of cerebral vascular mal­ formation. As this is not a neoplasm, the synonymous terms cavernous angi oma, cavernoma, and cavernous h emangi oma are inaccurate. Pathologically, a cavernous malformation is a discrete well-circumscribed cerebral mass with distinct lobulations. Most are 0.5 to 3 em in diameter. The supply­ ing arteries are of normal size and there is no nidus. Blood flow through the lesion is relatively slow. The lesion con· sists of endothelial-lined, blood-filled sinusoidal chambers that are separated by fibrous or collagenous tissue; there is no intervening normal brain tissue. Repeated small hem­ orrhages lead to adjacent gliosis , microcalcification, and small cysts that contain blood breakdown products. Most cavernous malformations are supratentorial. Occasionally,

multiple lesions are present; about half of patients with the autosomal dominant familial form of cavernous malforma· tion have multiple foci. Approximately 75% of patients with familial cerebral cavernous malformation have mutations in the CCM2, KRIT1, or PDCD10 genes.27. 6 t-6 s Most clinical manifestations a cavernous malforma­ tion relate to acute hemorrhage or seizures. Occasionally, there are focal neurological deficits; these are relatively common presenting features in young children. Chronic or recurrent headache occurs in some patients. Some cav­ ernous malformations are entirely asymptomatic; approxi­ mately 25% of individuals with this lesion experience no symptoms throughout their lifetimes. Even asymptomatic lesions have histological evidence of prior hemorrhagic episodes. The incidence of spontaneous clinically apparent hemorrhage of an untreated cavernous malformation is probably less than 1% per year. In general, deep (i.e., brain­ stem and central gray matter) lesions have a higher risk for hemorrhage and neurological deficits then do superficial supratentorial lesions. When feasible, surgical resection is the treatment of choice for cavernous malformation. 6 2, 6 3 Examination with unenhanced CT shows a cavernous malformation as a well-circumscribed irregular nodule of mixed attenuation. At least a portion of the mass is slightly hyperattenuating to brain. There is mild contrast enhance­ ment. Intraparenchymal edema and hemorrhage some­ times obscure the lesion. One or more prior hemorrhagic events may lead to encephalomalacia, calcification, or cysts. On MR, an uncomplicated cavernous malformation appears as a small mass with well-defined, lobulated bor­ ders. Varying signal characteristics are typical. Blood prod­ ucts may result in hyperintensity within portions of the lesion on TI·weighted images ( Figure 20-9) . There is usu­ ally gadolinium contrast enhancement. On T2-weighted or T2*-weighted sequences, hemosiderin within glial cells and macrophages at the periphery of the lesion causes marked hypointensity (Figure 20-10) . The remainder of the lesion and any surrounding gliosis are hyperintense on T2-weighted and FLAIR images (Figure 20-1 1 ) . Enlarged feeding arteries and draining veins are lacking. Circulation through a cavernous malformation is quite slow, and arte­ riovenous shunting does not occur. Cavernous malforma· tions are often not visible on conventional angiography. Occasionally, there is a faint capillary blush or sedimenta­ tion of contrast within the lesion. 66-68

Capillary Telangiectasia A capillary telangiectasia is a collection of dilated capillaries intermixed with normal brain parenchyma. Hemorrhage from these lesions is rare. Many are asymptomatic. The most common location is the pons. There are often coex­ istent cavernous angiomas in patients with capillary telan­ giectasias. Most capillary telangiectasias of the brain are small and solitary; there are rare large or diffuse forms. On M R evaluation, capillary telangiectasias are small, homogeneously enhancing, hypointense-to-isointense on

Chapter 20 I ntracra n i a l Va scu l a r A b n o r m a l ities 807

A

Figure 2--9 Cavernous malformation. The central aspect of the lesion is hyperintense (arrow) on this unenhanced T1-weighted image, due to the presence of blood

A.

Tl-weighted images, and isointense-to-slightly hyperin­ tense on proton density and T2-weighted images. There is marked signal loss on gradient echo sequences, apparently due to deoxygenated blood within the dilated capillaries. The hemosiderin rim that is typical of cavernous angioma is lacking. There is usually mild-to-moderate contrast enhancement, often with slightly irregular borders. 6 9 ,7°

Clinical Presentations: Trigeminal Neuralgia Posterior fossa vascular abnormalities are occasionally implicated in trigeminal neuralgia. Trigeminal neuralgia is a craniofacial pain syndrome that rarely occurs in children. Approximately 1% of instances of trigeminal neuralgia have onset in patients younger than 20 years. These patients experience episodic unilateral facial pain in the distribution of the trigeminal nerve, most commonly in the maxillary and mandibular distributions. Grimacing during episodes of pain gives rise to the term tic douloureux that describes this condition.?' Trigeminal neuralgia occurs in idiopathic and sec­ ondary forms. Deficits of trigeminal function are some· times identifiable clinically in patients with the secondary form. Some instances of idiopathic trigeminal neuralgia are caused by compression of the nerve near its origin from the brainstem by an anomalous loop of the anterior

8

products. B. Hemosiderin results in marked hypointensity on the T2-weighted sequence.

inferior cerebellar artery. Other potential causes include multiple sclerosis, neoplasm, vascular malformation, and petrous sinusitis. Children presenting with this disorder generally should be evaluated with MRI. Careful evalu­ ation of the course of the trigeminal nerve for a tumor or anomalous vessel is essential. Potential sites of nerve impingement include the posterior fossa, Meckel cave, the cavernous sinus, the skull base, and the pterygopalatine fossa. Symptoms due to trigeminal nerve damage can also occur following head or facial trauma, surgery, or a dental procedure.72 ·73

ANEURYSMS Cerebral aneurysms are rare in children. The 3 major types of cerebral aneurysms are congenital, mycotic, and traumatic. The morphological classification of aneurysms is into saccular, fusiform, and dissecting forms. Most con­ genital intracranial aneurysms are isolated. Cerebral aneu­ rysms occasionally occur in association with a predisposing systemic disease, such as autosomal dominant polycystic kidney disease, coarctation of aorta, fibromuscular dyspla­ sia, Ehlers-Danlos syndrome, Marfan syndrome, or tuber­ ous sclerosis. Aneurysms sometimes occur due to local hemodynamic alterations caused by a vascular anomaly, such as persistent fetal patterns or vestigial remnants.

8o8 Part 3 The B ra i n

A

Figure 2o-1o Familial cavernous malformations. This asymptomatic s-year-old girl was evaluated due to a history of cavernous malformations in her mother and maternal aunt. A. There are innumerable hypointense foci in the brain on this

A

Figure 2o-n Cavernous malformation. A. The lesion (arrow) has a heterogenous character on this coronal FLAIR sequence. There is a peripheral hypointense

8

Tz*-weighted gradient echo sequence. B. The lesions are only faintly visible on a spin echo Tz-weighted image. The larger left frontal lobe focus (arrow) has a mixed character on this sequence.

8

rim, due to hemosiderin. B. Blood breakdown products result in marked hypointensity on this axial Tz*-weighted gradient echo image.

Chapter 20 I ntracra n i a l Va s c u l a r Abnormal ities Other associations include moyamoya, H IV infection, and hematological disorders (e.g. , sickle cell disease) . Between 1.3% and 1.9% of cerebral aneurysms are diag­ nosed in patients less than 20 years of age. There is a male predilection. Approximately 40% of pediatric aneurysms are located in a middle cerebral artery and 25% in the pos­ terior circulation. Many congenital cerebral aneurysms in the pediatric age group (particularly in infancy) are giant, that is, greater than 2.5 em in size. Most pediatric aneurysms are symptomatic at the time of diagnosis. There is a bimodal distribution of present­ ing age: The first peak is in infants less than 6 months of age and a second peak occurs from 8 years of age to ado­ lescence. The most common clinical presentation of all types of intracranial aneurysms is due to hemorrhage; in decreasing order of frequency, hemorrhage is subarach­ noid (>8o%) , intraparenchymal, andfor intraventricular. Other common presenting features relate to mass effect, hydrocephalus, or seizures (seizures are uncommon, however, with an unruptured aneurysm) . Enlargement of an aneurysm can produce focal neurological findings by way of cranial nerve compression or parenchymal com­ pression. Hydrocephalus or other manifestations of mass effect are relatively common in association with a giant aneurysm.20·74·7 5

Congen ital Aneu rysms The most common type of intracranial aneurysm in child­ hood is a congenital saccular aneurysm. The lesion is usu­ ally due to a developmental defect in the tunica media and tunica elastica of the arterial wall. The intima bulges through the defect; only adventitia covers the aneurysm peripherally. The imaging features of cerebral aneurysms that occur in association with a predisposing systemic con­ dition are similar to those of true congenital aneurysms. The most common site of a pediatric congenital intra­ cranial aneurysm is the middle cerebral artery. Sites that are more common in children than in adults include the proximal aspects of the anterior and middle cerebral arter­ ies and the vertebrobasilar system. The circle of Willis is a less common site of origin in children than in adults. Approximately 30% to 35% of congenital aneurysms arise at the internal carotid bifurcations; this site is most com­ mon in older children and adolescents . In infants and young children, 30% to 40% of cerebral aneurysms occur in the posterior circulation. Only approximately 5% of children with a congenital intracranial aneurysm have multiple lesions . Aneurysms larger than 2 . 5 em account for 16% to 29% of pediatric cases; this is a much higher frequency than in adults. Forty to fifty percent of pediat­ ric congenital intracranial aneurysms are in the 1 to 2 . 5 e m size range. About half o f giant aneurysms i n children occur in the anterior circulation and half in the posterior circulation.7 6 Most congenital intracranial aneurysms are clinically silent until the lesion ruptures. Rupture of a congenital

8og

intracranial aneurysm accounts for approximately 5o% of atraurnatic subarachnoid hemorrhages (Table 20-1) . An unruptured aneurysm occasionally produces neurologi­ cal symptoms due to mechanisms such as mass effect on the second and third cranial nerves or cerebral ischemia resulting from aneurysm thrombosis and embolization. Brairl compression by a giant aneurysm can cause focal neurological signs. Common clinical manifestations of aneurysm-related subarachnoid hemorrhage include sud­ den onset of headache, vomiting, seizures, coma, paresis, cranial nerve palsy, fever, and meningismus. Occasionally, headache occurs as a warning sign of impending major hemorrhage. Headache is uncommon in young children and infants with an aneurysm.77·78 The size and location of a congenital intracranial aneu­ rysm affect the risk for rupture. Smaller lesions and those located in the anterior circulation are less likely to rupture than larger aneurysms and those in the posterior circula­ tion. Management options of an ur1ruptured aneurysm include surgical clipping, endovascular coiling, and obser­ vation without intervention (for a small lesion) .79

Mycotic Aneu rysms Most infectious (mycotic) aneurysms i n children are due to bacterial rather than fungal or protozoan infections . The most common underlying pathology is embolization from bacterial endocarditis. A second type of infectious aneu­ rysm involves direct extension from an adjacent focus, such as meningitis, osteomyelitis, paranasal sinus infection, or cavernous sinus septic thrombophlebitis. This type of aneu­ rysm most often arises from a large artery at the base of the brain. A third form of infectious aneurysm occurs in the absence of a detectable inflammatory lesion elsewhere in the body. The most common organisms involved in bacte­ rial intracerebral aneurysms in children are alpha strepto­ coccus, staphylococcus, Pseudomonas, and Haemophilus species. 8 o ,s, Subarachnoid hemorrhage is the most common pre­ senting symptomatic feature of a mycotic aneurysm in childhood. Seizures, intraparenchymal hemorrhage, or neurological alterations related to mass effect or ischemia can also occur. A mycotic aneurysm within the cavernous sinus typically causes various orbital manifestations, such as proptosis, ophthalmoplegia, and venous engorgement.

Trau m atic Aneu rysms A traumatic intracranial aneurysm can result from a direct penetrating injury or a closed head injury in which there is accelerationfdeceleration-induced shear. The former can be located anywhere along the direct path of the penetrat­ ing injury. Aneurysms related to closed head injury tend to occur in the vascular suspensory regions of the brairl or areas of vascular contiguity with dural margins. Examples include the anterior cerebral arteries along the falx, the

81 0 Part 3 The B ra i n posterior cerebral arteries adjacent to the free edge o f the tentorium, and the middle cerebral arteries adjacent to the sphenoid ridges. Peripheral cortical vessels can be damaged at the edge of a skull fracture. The most common traumatic intracranial aneurysms involve the internal carotid arter­ ies; these are classified as cavernous, supradinoid (rare) , and petrous types. Traumatic aneurysms of the anterior cerebral arteries are most often distal to the AJ. segments. Traumatic aneurysms of the middle cerebral arteries typi· cally occur at or just distal to a bifurcation. In the posterior circulation, the most common location of a traumatic aneu­ rysm is adjacent to the vertebrobasilar confl.uence.82. 83 Traumatic intracranial aneurysms are true or false. A true aneurysm has an intact layer of adventitia in the wall. A false traumatic aneurysm (i.e., pseudoaneurysm) represents fibrous organization around a communicating perivascular hematoma. Direct penetrating injuries or neu­ rosurgical procedures are the most common causes of false aneurysms. Blunt head trauma and penetrating injuries can also lead to a traumatic aneurysmal AVF. A dissecting aneurysm is a form of true aneurysm; this represents an outpouching beyond the vessel lumen due to a tear in the intima and internal elastic lamina, with dissection of blood subintimally. 84

A

Figure 2o-12 Carotid siphon aneurysm in a child with Marfan syndrome. Contrast·enhanced CT shows the lesion as a homogenously enhancing mass (arrow) . B. There is enhancement of the aneurysm wall (arrows) on this T1-weighted

A.

Intracranial hemorrhage is the most common present­ ing feature of a traumatic cerebral aneurysm. Less com­ mon findings in these patients include recurrent epistaxis, cranial nerve palsy, and manifestations of hydrocephalus. Some patients are asymptomatic. Occasionally, there is a substantial delay between the initiating traumatic event and the onset of clinical manifestations of a traumatic cere­ bral aneurysm. 85

I magi ng Evaluation of I ntracranial Aneu rysms Because subarachnoid hemorrhage is the most common presenting feature of an intracranial aneurysm, CT is usually the initial imaging study performed. If large, the aneurysm itself may be visible as a mass , and occasion­ ally mimics the appearance of a neoplasm. In the situa­ tion of acute intracranial hemorrhage, the lesion is often a least partially filled with dotted blood. The patent por­ tion of the aneurysm enhances intensely with IV contrast (Figure 20·1 2) . Other potential CT findings include an intracerebral hematoma, intraventricular or subarachnoid hemorrhage, and hydrocephalus. The hemorrhage associ­ ated with a cerebral aneurysm sometimes localizes to the basilar cisterns. A partially thrombosed giant aneurysm

8

gadolinium-enhanced MR image. The patent potion of the lesion enhances with contrast, whereas the dot-filled inferior aspect is relatively hypointense. The aneurysm displaces the adjacent left temporal lobe.

Chapter 20 I ntracra n i a l Va s c u l a r Abnormal ities 81 1 may appear as a ring-enhancing mass. CT angiography generally provides excellent depiction of the morbid anat­ omy of a patent cerebral aneurysm. In neonates and young infants, a large cerebral aneurysm is often demonstrable with sonography. 25· 86 On standard M R images, a patent aneurysm appears as an oval or round flow void adjacent to a vessel. Thrombus within the lumen produces greater signal intensity; the specific character varies with the age of the clot. Artifacts from turbulent flow are sometimes present within a giant aneurysm. There is usually intense homogeneous con­ trast enhancement of a patent cerebral aneurysm. The enhancement pattern typically is ringlike when the aneu­ rysm is thrombosed. MRA provides supplemental infor­ mation and is an important screening tool for high-risk patients. Contrast-enhanced MRA may improve sensi v­ ity for the detection of a small lesion or an aneurysm w1th slow flow. A thrombosed aneurysm usually is not visible on M RA.87 Conventional catheter cerebral angiography remains the gold standard for the detection and characteriza­ tion of intracranial aneurysms . The typical angiographic appearance of an intracranial aneurysm is a saccular out­ pouching from an arterial wall, often at the bifurcation of a vessel (Figure 20-13) . Accurate demonstration of the anatomy at the neck of the lesion often requires multiple projections. Giant aneurysms can be fusiform or saccu­ lar; accurate depiction of the communication with the source artery is essential for therapeutic planning. A dis­ secting aneurysm appears as an elongated, ovoid, or sac­ cular contrast collection that extends beyond the vessel lumen.88 Focal arterial spasm or aneurysm thrombosis some­ times prevents contrast opacification of a ruptured aneu­ rysm. Angiography in this situation is often normal or demonstrates subtle irregularity of the vessel wall. These hemodynamic alterations also interfere with visualization on MRA and CT angiography. Follow-up evaluation in a few weeks may allow detection of the aneurysm due to recanalization of the lumen. When multiple aneurysms are present, angiographic clues to the source of subarachnoid hemorrhage include large aneurysm size, a small diverticu­ lum near the apex of the aneurysm, and an irregular con­ tour of the aneurysm wall.89 Arterial vasospasm is a potential sequela of aneurysm­ related subarachnoid hemorrhage that can lead to cere­ bral ischemia (Figure 20-14) , although overt stroke due to vasospasm in children is uncommon. The severity of vaso­ spasm roughly correlates with the volume of blood in the basal cisterns. Typically, vasospasm related to subarachnoid hemorrhage peaks a few-to-several days after the initial event Transcranial Doppler of children with vasospasm shows elevation of middle cerebral artery velocities; this technique allows sequential monitoring of these patients. Central cerebral arterial narrowing and irregularity due to spasm can be demonstrated with M RA, CTA, or conven­ tional angiography.

�

I SCH EMIC BRAIN INJURY

Clinical Presentations: Stroke The term stroke refers to acute occlusion or rupture of a cerebral artery or vein, resulting in focal cerebral damage and neurological deficits that persist for at least 24 hours. Strokes are ischemic, hemorrhagic, or both. Ischemic strokes, or brain infarctions, are arterial or venous. Thromboembolic occlusion of a cerebral artery is the usual cause of an arterial infarction. Venous strokes are due to sinovenous thrombosis. The 2 major mechanisms of hem­ orrhagic strokes are bleeding into acutely ischemic brain tissue and rupture of an intracranial artery.9° Each year, over half a million individuals in United States suffer a stroke. The incidence of stroke is approxi­ mately 3 per w o , o o o children per year. About half of pediatric strokes are hemorrhagic. About three-quarters of pediatric strokes are arterial and one-quarter venous. Potential predisposing conditions for pediatric stroke include sickle cell disease, cardiac lesions, cerebral vascular malformations , hematological disorders, neurocutaneous syndromes (e.g., neurofibromatosis) , various chromo­ somal abnormalities (e.g., Down syndrome) , primary vas­ culopathies (e.g., moyarnoya) , trauma (e.g., carotid or vertebral dissection) , and headjneck infections. Up to half of children with stroke have no known underlying condition. 9'-9 4 Most strokes cause localized brain ischemia. Multiple factors influence the clinical and neuroimaging manifesta­ tions of the insult. These include the volume and location of brain tissue involved, the rapidity of onset of ischemia, the severity of ischemia, the time course, the age of the patient, the adequacy of collateral circulation, the presence of preexisting brain pathology, and the institution of thera­ peutic intervention. Brain hypoxia/ischemia can be focal or global, acute or chronic, and episodic or recurrent . w1th . The typical clinical presentation of stroke vanes patient age. Infants who have suffered a stroke in utero may present with early onset of hand dominance or other signs of unilateral weakness. Strokes in the perinatal period often lead to seizures , with subacute development of hemiparesis . Older children with stroke usually have similar presentations as do adults , with an acute onset of a focal neurological deficit, dysarthria, andfor apha­ sia; seizures may or may not occur. In addition to stroke, the differential diagnosis of acute hemiplegia in a child includes Todd paralysis (transient hemiparesis follow­ ing a seizure) and complicated migraine. Over half of children with stroke suffer lifelong cognitive or motor disabilities. 9 5 ·96 Hemorrhagic stroke often has a precipitous clinical presentation, with neurological alterations due to local­ ized brain compression and elevated intracranial pressure. Common manifestations include impaired mental status, severe headache, bradycardia, and emesis. In general, the survival rate is worse with hemorrhagic strokes than with ischemic strokes.

81 2 Part 3 The B ra i n

A

B

Figure 2o-13 M iddle cerebral artery aneurysm. Liquid blood within the lesion (arrow) is slightly

A.

hyperattenuating relative to brain on this unenhanced CT image. There is a small focus of hyperattenuating clot in the posterior aspect of the aneurysm. B. Because of slow flow within the aneurysm cavity, it is only faintly visible (arrow) on this time-of-flight MRA image. C. The aneurysm (arrows) fills with contrast on this angled AP image from a conventional cerebral angiogram.

Arterial I nfarction Arterial infarction of the brain is an important cause of CNS damage in children of all ages. Major cerebral infarc­ tion in the newborn occurs with an estimated prevalence of 1 in 4000 births. The clinical manifestations of perinatal or

c

neonatal brain infarction are often nonspecific. Common findings include seizures, hypotonia, and lethargy. Some neonatal strokes are clinically silent. Fetal stroke may lead to early hand preference in infancy or unilateral weakness. Older infants and children with arterial infarction usually experience an acute neurological event, similar to the adult

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 813

B

A

c

Figure 2o-14 Ruptured congenital saccular aneurysm. A. An unenhanced cr image of a s-week-old infant shows intraparenchymal and subarachnoid hemorrhage on the right. The oval blood-filled aneurysm (arrow) adjacent to the hematoma is isoattenuating to brain. B. Flowing blood in the aneurysm (arrow) causes elevated signal intensity on this T1-weighted image. Blood is present in the dependent portion of the dilated

D

left lateral ventricle. C. A diffusion-weighted image demonstrates manifestations of ischemia throughout a large portion of the right cerebral hemisphere. D. An anterior-superior view of a CTA image shows the bilobed enhancing aneurysm to be located adjacent to the right middle cerebral artery (RMCA) , which was the vessel of origin. ACA anterior cerebral artery. =

814 Part 3 The B ra i n presentation. The key factors in the long-term prognosis

of vessels . Petechial hemorrhage, laminar necrosis , and

are the volume of brain involved, the location in the brain,

increased contrast enhancement on neuroimaging studies

the adequacy of collateral circulation, and the age of the

may be present at this stage. In the subacute phase, edema

patient at the time of the event. Other factors being equal,

diminishes and macrophages process the necrotic tissue,

functional recovery is much better in young infants follow­

resulting in encephalomalacia and gliosis . Eventually, there

ing a stroke than in older children.97-99

is restoration of the blood-brain barrier.

Potential causes of cerebral infarction include emboli

During the first several hours after the onset of symp­

(often cardiogenic) , sickle cell disease, prior varicella infec­

toms from an acute infarction, CT is usually normal.

tion, coagulation disorders, congenital vascular malforma­

Occasionally, there is abnormal increased attenuation

tions, aneurysm, vasculopathy (e.g., moyamoya, vascular

within an intracranial artery, usually the proximal segment

fibrous dysplasia, and PHACES syndrome) , metabolic dis­

of the middle cerebral artery, due to slow blood flow or the

orders

(e.g., M E LA S syndrome, organic aciduria, and

presence of a thrombus; this is termed the "hyperdense

lysosomal storage disorders) , trauma (e.g., child abuse,

vessel sign . " The " M CA dot sign" refers to hyperattenuat­

penetrating neck injuries, and vascular dissection) , vasculi­

ing thromboembolism within a branch of the middle cere­

tis, maternal drug use (fetal stroke) , meningitis, and intra­

bral artery in the sylvian fissure.

cranial or neck neoplasm. Many infarcts are idiopathic.

Between

6 and 12 hours after the event, there is usu­

Perivascular space inflammation in patients with meningi­

ally sufficient edema to produce alterations in the attenu­

tis can cause a vasculitis that progresses to venous throm­

ation characteristics of the ischemic brain on CT. Subtle

bosis or arterial thrombosis . The most common causes of

findings that reflect the presence of cytotoxic edema during

ischemic stroke in the pediatric population as a whole are

the early phase of an ischemic stroke include indistinctness

sickle cell disease and vasculopathy. An epidemiological

of the gray matter-white matter junction, loss of the usual

study in the central Maryland and Washington, DC area

slightly higher attenuation of the insular cortex just super­

reported an incidence of o . 6 per

for ischemic stroke in individuals less than

1oo,ooo children per year 15 years of age.

bon sign" ) , and loss of the normal attenuation differences

For individuals with sickle cell disease, the incidence was

between the globus pallidus and putamen with respect to

28o per 1oo,ooo children per year.16>9J,100

ficial to the external and extreme capsules (the "insular rib­

adjacent white matter. With ischemia in the distribution of

Ischemic vascular accidents most often occur in the

the middle cerebral artery, local mass effect may produce

middle cerebral artery territory. This is particularly true for

effacement of sulci or narrowing of the sylvian fissure. Loss

children who suffer strokes due to thromboembolism, such

of the normal high attenuation appearance of the basal

as those with right-to-left shunts or thrombogenic pathol­

ganglia (due to cytotoxic edema) as an early CT manifesta­

ogy in the left heart. The basal ganglia are also susceptible

tion of cerebral infarction is termed the "disappearing basal

to ischemic injury because the blood supply derives from

ganglia sign . " (Changes in basal ganglia attenuation, usu­

small end arteries. The blood supply of the basal ganglia

ally bilateral, can also occur with a variety of other insults,

consists of the medial lenticulostriate arteries (which sup­

including global brain hypoperfusion, poisoning [e.g. ,

ply the head of the caudate nucleus and a portion of the

methanol, cyanide] , severe hypoglycemia, lactic acidosis,

anterior limb of the internal capsule) and the lateral len­

Leigh disease, and mitochondrial myopathy.) Patients with

ticulostriate arteries (which supply the lentiform nucleus

identifiable parenchymal brain abnormalities on CT within

and parts of the caudate nucleus and internal capsule) .

3

The medial lenticulostriate arteries arise from the Al seg­

strokes and worse outcomes than those with normal CT

ment of the anterior cerebral artery. The recurrent artery

examinations during this early period.1o1-1o3

hours of the onset of symptoms tend to have more severe

of Heubner is an important branch of the medial lenticu­

In the subacute phase of an arterial infarct, the involved

lostriate arteries; this vessel can arise from the A1 or A2

portion of the brain is hypoattenuating on CT. Classic cor­

segments of the anterior cerebral artery. The lateral lenticu­

tical infarcts are often wedge-shaped and involve both cor­

lostriate arteries arise from the superior portion of the M1

tical gray matter and the underlying white matter. Mass

segment of the middle cerebral artery.

effect from edema usually diminishes in severity after 5 to 7 days. Within several days of the injury, petechial hem­

Unlike most tissues that can mobilize energy stores from fat and glycogen, the brain does not have an energy

orrhage or microcalcification in the cortex may develop,

buffer for protection when challenged with ischemia.

resulting in a laminar necrosis pattern (high attenuation

Ischemia causes cell membrane pump failure and a resul­

along the cortical surface) . There is also prominent con­

tant cascade of fluid shifts that ultimately leads to cell death.

trast enhancement at the site of an arterial infarct during

The ischemic threshold occurs at about one-fourth of nor­

the subacute phase. The greatest risk for frarlk hemor­

mal blood flow.

rhagic transformation of an infarct is between the fourth

An orderly sequence of events occurs at the

tissue level of the brain in response to ischemia. The ini­

and seventh days after the stroke .

tial consequence is cytotoxic edema due to cell membrane

M RI provides greater sensitivity and specificity than

pump failure. Vasogenic edema develops subsequently.

CT for the imaging evaluation of acute brain infarction.

By approximately

5 to 7 days after the initial insult, there

is loss of integrity of the blood-brain barrier due to injury

Diffusion-weighted

MR

of ischemia as early as

images

20

to

30

reflect manifestations

minutes after the insult.

Chapter 20 I ntracra n i a l Va s c u l a r Abnormal ities 81 5 An early physiological consequence of ischemia is failure of cell membrane sodium-potassium pumps. This leads to influx of water into cells from the interstitium; that is, cytotoxic edema. This intracellular water has diminished diffusion in comparison to normal extracellular interstitial water. This is predominantly due to interaction of the water molecules with intracellular structures. Additional factors that serve to restrict water molecule motion are compres­ sion and increased tortuosity of the extracellular spaces (due to cellular swelling) , as well as elevated intracellular viscosity. Because of the relatively high water content of brain in young infants, careful inspection of apparent dif­ fusion coefficient (ADC) map images is essential to detect subtle or early edema. "Pseudonormalization" of diffu­ sion-weighted images often occurs between 7 and 14 days after the insult, as the cell walls in the area of infarction break down and diffusion increases. However, standard T2-weighted and FLAIR images are usually abnormal by this time. 104·'0 5 Arterial infarction usually progresses to vasogenic edema, which alters the T2 relaxation time. Conventional T2-weighted MR images generally become abnormal within a few to several hours of the event in older children, but may appear normal for the first few days in young infants. Potential MR findings of arterial infarction include signal abnormality due to edema, mass effect, and absent or diminished vascular flow voids in the area of the stroke. With ischemia in the middle cerebral artery territory, the MR corollary of the insular ribbon sign of CT is elevated T2 signal intensity within the insular cortex. Elevated signal within the lentiform nuclei is also common. Slow blood flow may result in exaggerated intravascular contrast enhance­ ment on MR. Leptomeningeal enhancement adjacent to an infarct is an early phenomenon that becomes less pro­ nounced over the next few days. Consequences of ischemic damage to the blood-brain barrier include petechial surface hemorrhages , prominent parenchymal contrast enhance­ ment, and (occasionally) calcium deposition; that is, lami­ nar necrosis. Gyral surface enhancement is first apparent approximately 3 days after the injury; it peaks at approxi­ mately 3 weeks , and usually disappears by 3 months.106 Because of the high water content of normal white matter in neonates and young infants, the neuroimaging manifestations of edema due to brain ischemia are some­ times subtle. On sonographic examination, a stroke may appear as a region of increased echogenicity with poorly defined margins. Hemorrhagic components, when pres­ ent, result in intermixed foci of greater echogenicity. Doppler evaluation may confirm regional hypoperfusion or a vascular lesion. As in older patients, diffusion-weighted MR images and calculated ADC images are sensitive for the cytotoxic edema of an acute stroke in the neonate. The typical appearance of vasogenic edema in a young infant on standard M R sequences is isointensity of the involved gray matter relative to the adjacent unmyelinated white matter. FLAIR images are of limited usefulness in young infants with edema. Likewise, the typical CT findings of

acute cerebral infarction are diminished attenuation of the involved gray matter structures, with or without manifesta­ tions of regional brain swelling. As in older patients, a cor­ tical laminar necrosis pattern may develop subsequently. There are CT and MR techniques that serve to detect hypoperfused brain that is not infarcted but is at risk for infarction if blood flow does not improve. The most com­ mon MR method for assessment of cerebral perfusion is a contrast-enhanced dynamic susceptibility bolus technique. This quantifies the signal intensity increase on rapidly acquired scans as a bolus of intravenous contrast material passes through the brain. Hemodynamic parameters quan­ tified by this technique include relative cerebral blood flow, relative cerebral blood volume, mean transit time, bolus arrival time, and flow heterogeneity. The CT technique for measurement of brain perfusion involves rapid image acquisition that dynamically depicts the effects of a bolus of intravenous contrast material at a single location or at several contiguous intracranial locations.'07 In general, children who have suffered an arterial infarction should be evaluated with M RA to assess the cer­ vicocerebral vessels (Figure 20-1 5) . CT angiography is useful in selected patients to study the cervical vessels; for exam­ ple, stroke in a patient with neck trauma. Transcatheter angiography is the gold standard technique, but is required in only a small number of patients; potential indications for this technique include equivocal findings on M RA or clinical features that suggest small vessel disease. Stroke patients with an associated cervicocerebral arterial abnor­ mality are at increased risk for a recurrent stroke. 108 Neuroimaging studies may demonstrate various long­ term sequelae ofischemic events, including lacunae, demy­ elination, loss of white matter volume, encephalomalacia, leukoencephalopathy, and porencephaly. Ischemic destruc­ tion ofbrain tissue in the fetus or severely premature infant generally leads to the formation of a cavity that has smooth walls and minimal adjacent glial reaction; that is, poren­ cephaly. On neuroimaging studies, porencephaly appears as a smooth-walled cavity, usually contiguous with the ven­ tricular system. Occasionally, there is dysplastic gray mat­ ter along the cyst margin. ' 09 Term infants and older children develop astroglial proliferation at the site of injury; that is, encephalomala­ cia. Cystic degeneration in these patients represents cystic encephalomalacia. Encephalomalacia is hypoattenuating on CT, hyperintense on T2-weighted M R, and echogenic on sonography. Cystic encephalomalacia appears as 1 or more fluid-filled cavities, often with irregular contours, sur­ rounded by gliotic thinned brain tissue (Figure 20-1 6) . A lacuna is a form of cystic encephalomalacia that appears as a shelled-out focus, usually in white matter, that is isointense and isoattenuating to water. Leukoencephalopathy refers to postischemic demyelination; this appears as large diffuse areas of high signal intensity on T2-weighted images and hypoattenuation on CT, usually with concomitant white matter thinning. Wallerian degeneration of axons and their myelin sheaths appears as ipsilateral brainstem atrophy.

81 6 Part 3 The B ra i n

A

B

Figure 2o-1 5 Arterial infarction. This 17-year-old male with a patent foramen ovale had sudden onset of right-sided hemiparesis 3 hours prior to the MRI. A. A coronal FLAIR image shows subtle enlargement of the left caudate nucleus (arrow) , but normal signal intensity. B. There is restricted diffusion in the left basal ganglia, resulting in marked hypointensity on this ADC map image. C. An anterior M RA image shows complete occlusion o f the proximal aspect o f the left middle cerebral artery (arrow) .

Catheter-directed or systemic thrombolysis is a treat­ ment option for carefully selected patients with an acute arterial infarction. This carries the potential benefit of rapid restoration of blood flow to ischemic tissue. If recanaliza­ tion occurs quickly enough, the ischemic brain tissue may recover. However, thrombolysis carries the risk of reper­ fusion hemorrhage as well as systemic complications. Thrombolysis is only useful if instituted within a few hours after the ischemic event. A hemorrhagic component must be excluded (usually with CT) prior to the initiation of thrombolytic therapy. no

c

Venous I nfarction Venous infarction is an important cause of acute CNS pathology in children, particularly young infants . The patho­ genesis involves cerebral sinovenous thrombosis in nearly all cases. Conversely, approximately 40% of instances of sinovenous thrombosis result in infarction. Common clini­ cal manifestations of venous infarction include seizures and focal or diffuse neurological signs, such as headache, visual impairment, or hemiparesis. Venous infarctions are often hemorrhagic.

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 817

A

8

Figure 2o-1 6 Encephalomalacia. This 7-year-old child suffered a severe ischemic event as a newborn. A, B. There is bifrontal and left parietooccipital cystic encephaloma­ lacia. Gliotic and thinned white matter is hyperintense on these FLAIR images.

The most common neuroimaging appearance of venous infarction is a mixture of edema and hemorrhage in the cortex and subcortical white matter. There is a patchy character with ill-defined margins. Diffusion-weighted MR images are sensitive for demonstration of the edema, although the appearance is variable, as both cytotoxic edema and vasogenic edema can be present ( Figure 20-1 7) . Hemorrhage, when present, can b e petechial o r multifo­ cal. Venous infarction is an important nontraumatic cause of intracranial hemorrhage in infants and young children that can at times resemble the neuroimaging appearance of intentional injury. The demonstration of clot within a cerebral vein or venous sinus is a key diagnostic feature of venous infarction. There is additional discussion of venous infarction in the Sinovenous Thrombosis section below.m

Hypoxic-I schemic Encephalopathy Hypoxic-ischemic encephalopathy is a global disturbance of brain perfusion or oxygenation. Cerebral hypoperfu­ sion is the dominant factor in most patients. With resus­ citation and subsequent reintroduction of oxygen to the affected tissues, various cytotoxic events may occur; that is, secondary reperfusion injury. Potential causes of hypoxic­ ischemic encephalopathy in children include severe neona­ tal asphyxia, cardiac arrest, prolonged severe hypotension, drowning, and carbon monoxide inhalation. Infants expe­ riencing severe inertial forces due to intentional trauma often develop neuroimaging manifestations of regional or global brain hypoxia/ischemia.

Figure 2o-17 Venous infarction. A diffusion-weighted image of a patient with sagittal sinus thrombosis shows multiple areas of restricted diffusion in the cortex and subjacent white matter.

81 8 Part 3 The B ra i n Most neonates with hypoxic-ischemic encephalopathy are term infants (gestation > 37 weeks) . The pathogenesis in this age group usually relates to an intrapartum or early antepartum event. A severe brief insult can occur with placental abruption, uterine rupture, or cord prolapse. Perinatal asphyxia (i.e., critical impairment of the intra­ partum gas exchange) affects 3 to 5 infants per 1000 live births, with encephalopathy occurring in 25% and death in approximately 30%. Neonatal hypoxic-ischemic encepha­ lopathy is usually associated with signs of distress before delivery. Neurological manifestations, often nonspecific in character, usually develop during the first 24 hours after delivery. Common findings include a decreased level of con­ sciousness and seizures. It is important to recognize that the clinical and diagnostic imaging features of other condi­ tions, such as hypoglycemia, kernicterus, and many inborn errors of metabolism, overlap those of hypoxic-ischemic encephalopathy. Potential long-term neurological sequelae of perinatal hypoxic-ischemic encephalopathy include cere­ bral palsy, intellectual impairment, and epilepsy.U 2-115 The pathophysiological effects of brain ischemia vary with the age of the individual. In preterm infants, germi­ nal matrix hemorrhage and periventricular white matter edema are the most common manifestations of a moder­ ately severe global hypoxic/ischemic insult. Involvement of periventricular white matter can lead to leukomalacia of varying severity. With severe hypoxia, there is involvement of the gray matter nuclei and the brainstem. In term infants, hypoxiajischemia tends to involve watershed areas between cerebral arterial territories. Moderate decrease in blood flow in term infants often produces a "border-zone" injury, with involvement of the parasagittal regions between the major vascular territories of the cerebral arteries. Occasionally, there is an "expanded border-zone" pattern, with diffuse cortical involvement and relative sparing of insular and perirolandic cortex and the deep gray matter. With a severe global insult of acute onset in a term infant, there is selective injury to the regions of the brain that have the highest metabolic requirements: central gray matter structures (i.e., the lentiform nuclei and thalami) , the posterior limbs of the internal capsules, portions of the brainstem and cerebellar vermis, the hippo­ campal formations, and the perirolandic cortex. Older infants and children also may suffer watershed brain injuries following a hypoxic-ischemic insult of mod­ erate severity, whereas an episode of marked global isch­ emia usually involves the cortex and basal ganglia diffusely. In the cortex, the third, fifth, and sixth layers are most sus­ ceptible to ischemic injury; that is, cortical laminar necro­ sis. At all ages, a severe prolonged anoxic insult can lead to diffuse brain damage. n6 The neuroimaging principles of hypoxic-ischemic encephalopathy in children are similar to those described above for arterial infarction. CT images are often nor­ mal during the first several hours after the insult. Subtle early findings that are sometimes present include the insular ribbon sign, gray matter-white matter junction

indistinctness, and diminished attenuation of the basal ganglia as described above. Reduced attenuation of the basal ganglia is an important CT finding of severe hypoxia in a term infant. Imaging over the next few days demon­ strates compression of the ventricles, sulci, and cisterns due to brain swelling, and hypoattenuation of the brain due to edema. There is often relative sparing of the posterior fossa structures, except in patients who have experienced severe prolonged ischemia. With ischemia of mild-to-mod­ erate severity, the areas of greatest edema include the basal ganglia and intervascular border zones between major vascular territories. During the acute-to-subacute phase, severe ischemia sometimes results in hyperattenuation of cerebral white matter relative to cortex; this is the "reversal sign." Gyriform hyperattenuation due to cortical laminar necrosis may develop several days after the insult.117 As with arterial infarction, MRI provides superior sen­ sitivity for the detection of hypoxic-ischemic encephalopa­ thy. There is usually restricted diffusion within the affected portions of the brain within 24 hours after the ischemic event; this finding usually persists for 5 to 6 days. Careful evaluation of ADC map images is important to detect subtle restriction of diffusion in the immature brain of the young infant. Pseudonormalization of the ADC map images may occur at approximately 1 week after the event. Decreased fractional anisotropy on MRI provides even greater sensi­ tivity than standard diffusion images for hypoxic-ischemic insults of mild or moderate severity; this is likely due to breakdown of white matter organization. Elevation of lac­ tate on proton spectroscopy is an additional indicator of severe ischemic injury that may be apparent during the first 24 hours. Short echo time spectroscopy demonstrates elevation of glutamate and glutamine. Within a few days of the event, standard MR sequences show marrifestations of brain swelling and cytotoxic edema. Common early find­ ings on these images include effacement of sulci and cis­ terns, subtle T2-image hyperintensity in the insular cortex and basal ganglia, and indistinctrless of gray matter-white matter interfaces. In the subacute phase, cortical laminar necrosis may lead to gyral hyperintensity on T1-weighted images.7 6,n8 ,n9 In the term infant suffering an acute, severe, global hypoxic event, the typical MR findings consist of ele­ vated signal intensity in the basal ganglia and thalami on T1-weighted images, lack of normal prominent signal inten­ sity on T1-weighted images in the posterior limbs of the internal capsules, and signal alteration in all of these struc­ tures on diffusion-weighted and ADC map images. Term infants with severe hypoxia often have manifestations of global brain edema. Others have bilateral parasagittal corti­ cal gray matter and subcortical white matter edemajnecro­ sis. With prolonged hypoxia of moderate severity, such as occurs with a protracted delivery, imaging studies usually show predominant involvement of the cortex. Central gray matter structure alterations are usually less pronounced in these infants than in those who have experienced severe total hypoxia.' 20

Chapter 20 I ntracra n i a l Va s c u l a r Abnormal ities 81 9 MRI provides important prognostic information for term infants who have suffered acute cerebral hypoxia/ ischemia. Cerebral edema does not necessarily portend a poor long-term outcome. However, concomitant involve­ ment of cortical gray matter and deep basal ganglia is an important early indicator of a poor outcome, particularly when there is substantial internal capsule abnormality. Signal alterations within the corticospinal tracts of the cerebral peduncles ("pre-Wallerian degeneration") on ADC map images during the acute phase of the injury indicate a high likelihood of subsequent motor impair­ ment. Indicators of a poor neurological outcome on proton spectroscopy include decreased absolute N-acetylaspartate (NAA) , choline (Cho), and creatine (Cr) concentrations, as well as reduced NAA ratios and elevated lactate ratios . There is elevation of lactate and GLx-a peaks. Elevated lactate/choline ratios in the basal ganglia and thalami also are associated with a poor prognosis. 7 6 By 2 to 3 weeks after the injury, neuroimaging stud­ ies provide prognostic information concerning the likely long-term sequelae of hypoxic-ischemic encephalopathy. Continued evolution of the process occurs for at least a few months. With severe insults , there is progressive global brain atrophy. In some children, there is relative sparing of the brainstem, cerebellum, central gray matter structures, and perirolandic regions. Focal encephaloma­ lacia, gliosis, and dystrophic calcification can also occur (Figure 20-1 8) . Children suffering less severe ischemia sometimes have mild ventriculomegaly as the only long­ term neuroimaging manifestation of prior hypoxic-isch­ emic encephalopathy. Conditions that are included with hypoxic-ischemic encephalopathy in the differential diagnosis of seizures or other C N S alterations in term infants include bilirubin encephalopathy (kernicterus) , prolonged hypoglycemia, inborn errors of metabolism, herpes simplex encepha­ litis, and intentional trauma. On MR examination, the acute phase of bilirubin encephalopathy typically involves the globi pallidi, with relative sparing of the thalami. Severe perinatal hypoglycemia can cause diffuse white matter signal alterations, often with greatest involvement in the occipital and parietal lobes . Urea-cycle disorders can cause the onset around day 2 or 3 of life of various neurological findings and MR signal abnormalities that predominate in the lentiform nuclei and the insular and perirolandic regions; there is sparing of the thalami. In newborns with nonketotic hyperglycinemia, diffusion­ weighted MR images may demonstrate signal abnormal­ ity in the posterior limbs of the internal capsules , the dorsal aspect of the brainstem, and the cerebral pedun­ cles. Brain edema due to herpes simplex encephalitis may be regional or multifocal; the clinical and radiographic onset usually does not occur until 1 to 2 weeks after birth. Maple syrup urine disease in the newborn can cause marked restriction of diffusion and T2 prolongation dif­ fusely or in the regions of the brain that are myelinated or myelinating."G

I schemia and Nontraumatic Hemorrhage in Prematu re I nfants Hypoxic-ischemic and nontraumatic hemorrhagic brain injuries are relatively common in premature infants . The pathogenesis of nontraumatic encephalopathies in prema­ ture newborns is often multifactorial; however, localized or diffuse brain ischemia and cerebrovascular hemodynamic instability are key factors with most of these events. There are usually various precipitating or complicating condi­ tions, such as lung immaturity, patent ductus arteriosus, obstetrical complications, sepsis , mechanical ventilation, pneumothorax, anemia, or hypoglycemia. Potential conse­ quences of hypoxic-ischemic events in premature infants include germinal matrix hemorrhage, periventricular hem­ orrhagic infarction, periventricular leukomalacia (PVL) , arterial infarction, and cerebral edema. The long-term neu­ rological impairments that can result from these insults include cerebral palsy, cognitive delay, severe hearing loss, and bilateral blindness. Both sonography and M R have high predictive abilities for subsequent neurological abnor­ malities in very low birth weight infants, but MR has much greater sensitivity. ' 2'-' 2 5

Germinal Matrix Hemorrhage Germinal matrix hemorrhage is an important potential complication of prematurity. The primary cause is altera­ tion in cerebral blood flow within the microvasculature of the immature germinal matrix. The germinal matrix is the site of neuronal and glial proliferation in the developing brain. There are relatively large and irregular vessels within the capillary bed of the germinal matrix. The blood-brain barrier is deficient. The pathophysiology of germinal matrix hemorrhage in premature infants is multifactorial; a lim­ ited capacity for cerebral vascular autoregulation in the pre­ mature infant is an important component. Hypoxia leads to vascular dilation and congestion of the germinal matrix vessels, resulting in a propensity for rupture. Increases in systemic blood pressure or impairment of cerebral venous drainage potentiate germinal matrix hemorrhage. This mechanism of hypoperfusion and subsequent reperfusion of weakened capillaries can also result in hemorrhage in other portions of the brain, including the choroid plexus. There is an inverse relationship between gestational age and the prevalence of germinal matrix hemorrhage. Very low birth weight is also an important risk fac­ tor. Approximately 20% to 40% of neonates of less than 34 weeks gestational age and less than 15 00 g birth weight suffer this complication. Hemorrhage occurs in 50% to 6o% of newborns weighing less than 1000 g. Germinal matrix hemorrhage is uncommon in premature infants of older gestational age and is rare in term infants. The first 3 to 4 postnatal days comprise the risk period for germinal matrix hemorrhage. Over half of these hemorrhages occur during the first several postnatal hours. Less than 5% of hemorrhages occur after the fifth postnatal day. About half

820 Part 3 The B ra i n

A

Figure 2o-18 Hypoxic-ischemic encephalopathy. This n-month-old child suffered a suffocation injury. A. CT performed 20 hours after the event shows diffuse brain white matter edema, with prominent cerebellar involvement. B. CT 7 days after the injury shows resolution of edema and normalization of the cerebellar appearance. There are early manifestations of cerebral volume loss, with prominence of the ventricles and subarachnoid spaces. C. Six months later, areas of encephalomalacia are visible in the cerebellar hemispheres. There is faint dystrophic calcification as well.

of infants with germinal matrix hemorrhage suffer exten­ sion of the hemorrhage (i.e., increase in the grade) and the development of parenchymal injury. Risk factors for delayed onset hemorrhage include respiratory distress syn­ drome, vigorous resuscitation, hypoxemia, hypercapnia, acidosis, seizures, and pneumothoraxP6-l28

B

c

The germinal matrix of the cerebrum is located along the lateral walls of the lateral ventricles. The period of greatest germinal zone activity, and the period of greatest propensity for hemorrhage, is between 8 and 28 weeks gestation. Spontaneous involution of the germinal matrix begins near the end of the second trimester, and germinal

Chapter 20 I ntracra n i a l Vas c u l a r A b n o r m a l ities 821 sequelae. (2 ) Grade II hemorrhage involves the germinal matrix and ventricle, without ventriculomegaly. Grade I and II hemorrhages are the most common types; many of these infants have no clinical manifestations of CNS bleeding. Fewer than 10% of infants with grade I I lesions suffer permanent neurological sequelae. (3) Grade I I I refers t o ventricular distention with hemorrhage o f sub­ ependymal origin. About half of infants with this pattern develop long-term neurological complications. The intra­ ventricular component of grade II and I I I lesions consists of either free blood or bulging of a subependymal hema­ toma into the ventricle. (4) Grade IV indicates intraparen­ chymal hemorrhage, with or without ventriculomegaly; most of these patients suffer permanent brain injuries. A grade IV lesion was originally envisioned to represent extension of subependymal hemorrhage into the paren­ chyma. However, most intraparenchymal hemorrhages in premature infants actually represent hemorrhagic venous infarctions due to compression of subependymal veins by a large subependymal hemorrhage.134-137 The sonographic appearance of acute subependymal hemorrhage is that of a homogeneous echogenic focus in the caudate nucleus adjacent to the wall of the lateral ventricle (Figu re 20- 1 9) . This can occur as an isolated oval area of hemorrhage or more extensive bleeding along the wall of the ventricle. The most frequent site is at the caudothalamic groove. Differentiation from normal choroid plexus, which is also hyperechoic, is straightforward when the hemorrhage is anterior to the foramen of Monro. Elsewhere, hemorrhage may appear as focal or diffuse thickening of the choroid plexus. The normal choroid plexus of the lateral ventricle pro­ gressively tapers as it extends anteriorly from the tri­ gone; it descends between the head of the caudate and

matrix hemorrhage is uncommon after 34 weeks gesta­ tion. The germinal matrix adjacent to the caudate heads is the last area to involute; therefore, this is a common site of hemorrhage. Hemorrhage can also occur in the germi­ nal zone of the cerebellum; this is located in the external granular layer. Potential neuropathological sequelae of germinal matrix hemorrhage include germinal matrix destruction, periventricular hemorrhagic infarction, hydrocephalus, and porencephaly. Sequelae that have multifactorial ori­ gins include PVL and ventriculomegaly. Between 25% and so% of preterm infants with germinal matrix hem­ orrhage and concomitant bleeding in the parenchyma develop posthemorrhagic hydrocephalus. Even infants with a history of uncomplicated germinal matrix hemor­ rhage may have somewhat diminished cortical gray matter volume. 12 9 ·13° In the acute phase of intraventricular hemorrhage, some degree of ventriculomegaly can occur due to disten­ tion ofthe ventricles with blood. There may also be blockage of the C S F drainage pathways by hemorrhagic particulate matter. This form of ventriculomegaly is often self-limited or responsive to medical management. In other patients, arachnoid or ependymal adhesions can lead to hydro­ cephalus (neonatal posthemorrhagic hydrocephalus) that necessitates surgical diversion. Trapped fourth ventricle can occur. Parenchymal brain injury in premature infants can also lead to varying degrees of ex vacuo hydrocephalus, without obstruction.13l-l33 The most commonly utilized system for grading ger­ minal matrix hemorrhage recognizes 4 degrees of sever­ ity. (1) Grade I is hemorrhage confined to the germinal matrix, with little or no intraventricular or intraparenchy­ mal extension. There are usually no long-term clinical

A

Figure 2o-1 9 Germinal matrix hemorrhage; grade I . A . A coronal sonographic image of a 4-day-old premature infant shows bilateral echogenic germinal matrix hemorrhages (arrows)

B

adjacent to the frontal horns. B. The hemorrhage extends anterior to the caudothalarnic groove on this longitudinal image. (T = thalamus; F = frontal lobe.)

822 Part 3 The B ra i n the thalamus along the roof o f the third ventricle. The choroid plexus is not present within the frontal horn or occipital horn. '3 8 Intraventricular hemorrhage appears on sonogra­ phy as echogenic material within the ventricular system. This may fill only a portion of the ventricle or completely obscure the lumen. The echogenic clot is often isoechoic to the choroid plexus; power Doppler evaluation can help differentiate the avascular clot from the perfused choroid plexus. In some patients , there is a well-defined mar­ gin to the hematoma within the ventricular cavity due to displaced, but intact, ependyma. Free intraventricular blood may form a fluid-fluid level in the dependent por­ tion of the ventricle, particularly in the subacute phase. Chemical ventriculitis due to the effects of intraventricu­ lar hemorrhage can lead to thickening and elevated echo­ genicity of the ependyma, usually visible 2 to 3 days after the event. Accumulation of blood in the cisterna magna is associated with an increased risk for posthemorrhagic hydrocephalus.'39·'4° On CT, acute germinal matrix hemorrhage appears as a round or ovoid periventricular hyperattenuating focus. During the first few days, the hemorrhage is isoin­ tense or slightly hypointense on T1-weighted MR images and hypointense on T2-weighted images. The hematoma becomes hyperintense on T1-weighted M R images within a few days of the hemorrhage and remains hypointense on T2 images for about the first week. Foci of hemorrhage are markedly hypointense on gradient echo (gradient-refocused echo; GRE) M R images; this is a particularly sensitive tech­ nique for the demonstration of small hemorrhages in the choroid plexus and posterior fossa."�' Cerebellar germinal matrix hemorrhage appears on imaging studies as 1 or more foci of blood within the cer­ ebellar parenchyma. These tend to be peripheral, in contra­ distinction to the periventricular pattern of supratentorial bleeds. Cerebellar germinal zone hemorrhages are poorly demonstrated with sonography, unless the hematoma is large; imaging via the posterior fontanelle or mastoid fon­ tanelle substantially improves the sensitivity of this exami­ nation. CT and MRI studies are diagnostic.'4 2 With aging of a subependymal hematoma, the echo­ genicity diminishes on sonography and the attenuation decreases on CT. On MR, the hematoma gradually con­ verts from a hypointense to a hyperintense character on T2-weighted images after the first week. The center of the clot may eventually liquefY, resulting in the neuroimaging appearance of a periventricular of subependymal cyst that contains fluid of similar character as C S F . Most often, there is eventual complete resorption of the cyst and adjacent maturing clot, with no residual neuroimaging abnormality. MRI temporally remote to neonatal intraventricular hem­ orrhage may demonstrate hypointensity within the cho­ roid plexus and ependyma on T2-weighted images, due to hemosiderin deposition. With a grade IV hemorrhage, cys­ tic degeneration may progress to porencephaly. Extensive germinal zone hemorrhage in the cerebellum can lead to

atrophy; hydrocephalus does not occur as a consequence of isolated cerebellar hemorrhages.

Periventricular Hemorrhagic Infarction As described above, the most common cause of intrapa­ renchymal hemorrhage in premature infants (i.e., grade IV hemorrhage) is venous infarction. The pathophysiology apparently involves compression of subependymal veins by a large subependymal hematoma. The parenchymal brain injury caused by hemorrhagic infarction in association with germinal matrix hemorrhage often leads to spastic hemipa­ resis . Cerebral palsy is uncommon in these children.'3 P3 6 Periventricular hemorrhagic infarction occurs in the deep white matter adjacent to the lateral ventricle. Most of these infarcts are in the parietal or occipital lobes. The hemorrhage is unilateral or asymmetrical. Typically, edema (nonhemorrhagic venous infarction) surrounds 1 or more parenchymal hematomas. Sonography usually demon­ strates an echogenic parenchymal focus that may appear globular or fan-shaped ( Figure 20-20} . In some patients, the periphery is more echogenic than the center. CT dem­ onstrates a periventricular hematoma, with mass effect and surrounding edema. The acute hematoma is hypointense on T2-weighted MR images and the adjacent edema is hyperintense. Follow-up imaging studies over the next few months usually demonstrate liquefaction of the hematoma and necrotic brain, with eventual formation of a porence­ phalic cyst (Figure 20-21 ) .143-145

Periventricular Leukomalacia PVL (white matter injury of prematurity) is a nonhemor­ rhagic hypoxic-ischemic or inflammatory injury of white matter in premature infants. The pathological alterations consist of focal necrosis of all cellular elements in the deep periventricular white matter (focal PVL) or diffuse injury of the oligodendroglia! precursors (diffuse PVL) . The patho­ genesis is multifactorial. Premature infants are susceptible to this complication because ofthe immature vasculature in the periventricular watershed, limited intracranial vascular autoregulation, and the vulnerability oflate oligodendrocyte progenitors to hypoxic-ischemic injury. A hypoxic-ischemic event is a common cause of PVL. However, various other insults to the fetal or premature brain (e.g., infection, meta­ bolic disease, or maternal chorioarnnionitis) can result in identical pathological alterations. Commonly associated medical conditions in these premature infants include respiratory distress syndrome, septicemia, asphyxia during delivery, antepartum placental abruption, twin pregnancy, and hypocapnia. 14 6.147 The risk for PVL in premature infants inversely corre­ lates with gestational age. The overall prevalence in preterm infants may be as high as so%; however, PVL of sufficient severity for detection with sonography is present in only approximately 10% of premature infants. Hypoxic brain injury in premature infants of sufficient severity to cause

Chapter 20 I ntracra n i a l Vascu l a r A b n o r m a l ities 823

A

B

Figure 2o-2o Periventricular hemorrhagic infarction. A, B. Coronal (A) and right parasagittal (B) sonographic images of a 4-day-old infant show echogenic hemorrhage ( arrows) in the right frontal and parietal lobes. There is also clot in the right lateral ventricle.

PVL is the most common cause of cerebral palsy in this patient population. Cerebral palsy is a nonprogressive disor­ der of motor function of various causes. Because the lower extremity axons are located medial to the upper extremity axons, they are more often injured by periventricular white matter insults; therefore, motor function compromise (i.e., spastic diplegia or quadriplegia) in patients with PVL tends to be more prominent in the lower extremities. Involvement of the optic radiations frequently leads to visual impairment.148 The pathological consequences of the initial white matter insult in patients with PVL are infarctive edema, followed by coagulation necrosis and subsequent phagocy­ tosis of the necrotic tissue. There is often petechial hem­ orrhage associated with the necrosis. In the more severe forms of PVL, cavitation occurs; that is, cystic PVL. These cavities usually appear between 2 and 5 weeks after the insult; the rapidity of formation and the sizes of the cavi­ ties roughly correlate with the severity of the insult. The cavities eventually diminish in size, resulting in white mat­ ter volume thinning and ex vacuo ventriculomegaly. PVL can involve nearly any portion of the cerebral white matter of the premature infant. The regions most commonly and most severely affected include the arterial border zones in the regions of the optic radiations (adjacent to the trigones of the lateral ventricles) and the central-medial aspects of the frontal lobes. The characteristic sonographic appearance of PVL is periventricular white matter hyperechogenicity that pro­ gresses to a heterogeneous cavitary stage within a few to several weeks after the injury. The initial increased echo­ genicity of the periventricular white matter is not specific to PVL, as it can also occur in patients with transient edema

or (if subtle) as a normal variation. The hyperechogenicity in the early phase of PVL often is equal or greater to that of the choroid plexus; this is the "periventricular flare." There is loss of the normal tissue homogeneity within the periventricular flare and the margins are indistinct (Figure 20·22) .'49-151 The sonographic characteristics of periventricular white matter injury roughly correlate with the clinical severity and prognosis. The most commonly utilized sono­ graphic classification system recognizes 3 grades. Grade I indicates noncavitary periventricular hyperechogenicity; that is, prolonged periventricular flare. Grade I I lesions develop small frontoparietal cavities. Grade I I I lesions progress to extensive irregular cavitation of the occipital and frontoparietal white matter. The cysts of PVL may be single or multiple, but are usually bilateral and relatively symmetrical. They are usually irregular, and parallel the ventricular border in the deep white matter ( Figure 20-23) . The cysts may subsequently enlarge o r resolve. There is residual gliosis and white matter thinning.' 52 The sensitivity of sonography for the detection of acute white matter injuries in premature infants is limited. A definitive sonographic diagnosis requires demonstration of a cavitary stage and subsequent white matter volume loss. However, many white matter injuries in premature infants do not progress to cavitation (i.e., resolving flares) . Also, some neonates who develop classic PVL have normal cranial ultrasound examinations initially. With true PVL, periventricular hyperechogenicity should be visible within 2 weeks of the injury.' 53 Although not commonly utilized for evaluation of premature infants, M R provides greater sensitivity than

824 Part 3 The B ra i n

A

c

Figure 2o-21 Evolution of periventricular hemorrhagic infarction. A· D. Sequential sonographic images of a right hemispheric hemorrhage at 3 (A) , 6 (B), 16 (C), and 25 (D) days after the event show conversion to a heterogeneous pattern due to clot

B

D

liquefaction and gliosis. On the day 6 image (B), there is a large focus of liquefaction (arrow) . There are smaller cystic areas (arrows) on the day 16 image (C) .

Chapter 20 I ntracra n i a l Vascu l a r A b n o r m a l ities 825

Figure 2o-22 Periventricular leukomalacia. There is marked white matter hyperechogenicity on this coronal sonographic image of a premature infant. The white matter has a coarse appearance.

A

sonography for the detection of PVL. The earliest manifes­ tation is multifocal or regional white matter hyperintensity on T1-weighted images. T2-weighted images may be nor­ mal or demonstrate subtle alterations in signal intensity. Hemorrhagic foci are hypointense on T2-weighted and gra­ dient-recalled echo (GRE) images . Reduced diffusion of the periventricular white matter on ADC map images appears to be the most sensitive technique for the early detection of white matter injury in premature infants. Diffusion tensor imaging demonstrates stable or decreased anisotropy on sequential studies. The early proton spectroscopy findings include lactate elevation and diminished NAA. 154-t56 The cavitary stage of PVL results in a heterogeneous appearance of the involved white matter on CT and MR. Larger cavities appear as small irregular cysts that are hypoattenuating on CT and hypointense on T1-weighted MR images. On M R, the cavities may be located adjacent to or within regions of T1 hyperintensity. The cavities dimin­ ish in size and often disappear over the next few to several weeks. The neuroimaging appearance of this "end-stage PVL" includes white matter thinning, enlargement and irregularity of the lateral ventricles, and deep extension of cerebral sulci. Small periventricular cysts may or may not be present (Figure 20-2.4) . T2-weighted MR images at this stage demonstrate abnormal periventricular white matter hyperintensity, usually most pronounced in the peritrigo­ nal regions.' 57 In patients with PVL and spastic quadriplegia or diplegia, diffusion-tensor MR shows severe atrophy of the periventricular fibers. The corticospinal tract is usually normal. The number of sensory fibers is diminished in

B

Figure 2o-23 Cystic periventricular leukomalacia. A, B. Coronal and sagittal sonographic images show irregular white matter cysts in the frontal and parietal lobes. There is hyperecho­ genicity throughout the cerebral white matter due to microcysts and gliosis.

826 Part 3 The B ra i n

A

B

Figure 2o-24 Periventricular leukomalacia. This zo-year-old patient has relatively mild clinical manifestations of cerebral palsy. A. Multiple small periventricular cysts (arrows)

are visible on this T1-weighted MR image. B. A coronal FLAIR image shows minimal hyperintense gliosis surrounding the cysts.

comparison to normal children of similar age. The con­ necting fibers between the thalamus and the parietal cor­ tex (the posterior thalamic radiations) are absent. Single photon emission computed tomography (SPECT) imaging has been utilized to demonstrate thalamic hypoperfusion in patients with PVL, suggesting that the spasticity of cere­ bral palsy may involve dysfunction ofthe inhibitory stimuli from the thalamus . There is often thinning of the corpus callosum, due to degeneration of transcallosal axons. The periventricular white matter is thin; however, the sever­ ity of spasticity does not correlate well with the degree of white matter thinning. In patients with hemiplegic cere­ bral palsy, the affected corticospinal tract is atrophied. ' 58-t6l

2 per 1000 live births. Many affected patients have a history of prematurity. Neuroimaging, preferably MR, is indicated at the time of diagnosis for most children with cerebral palsy to guide the prognosis and detect potentially treatable CNS abnormalities .'6 2

Clinical Presentations: Cerebral Palsy Cerebral palsy is a clinical syndrome of aberrant control of movement and posture due to a CNS lesion or dysfunction. By definition, the clinical onset is early during childhood; a recognized progressive or degenerative brain disease is lacking. In most affected patients, the diagnosis is estab­ lished prior to the age of 2 years. The underlying CNS insult can occur prenatally (infection, stroke, toxemia) , perinatally (hypoxic-ischemic encephalopathy, kernicterus, trauma) , or postnatally (infection, trauma, hydrocephalus) . Cerebral palsy is a descriptive term that encompasses a spectrum of etiologies and clinical presentations; all patients have motor deficits. The worldwide incidence is approximately

Severe Hypoxic-ischemic Injury in the Premature Infant Severe hypoxic-ischemic insults , such as cardiac arrest or prolonged asphyxia, prominently affect the most mature and metabolically active portions of the brain. In the fetus and premature infant, the regions of the brain most sus­ ceptible to severe hypoxic-ischemic insults include the deep gray matter nuclei and brainstem nuclei. Imaging studies demonstrate manifestations of edema, and some­ times hemorrhage, in the affected areas of the brain. The most common sonographic finding is hyperechogenicity in the basal ganglia and thalami, often not visible until a few days after the event. The CT finding of hypoattenua­ tion in the structures may also be somewhat delayed. The earliest MR finding is alteration of ADC values in the cen­ tral gray matter structures. Hyperintensity develops on T1-weighted images within a few days of the injury and on T2-weighted images by the end of the fi rst week. MR may also demonstrate abnormal signal within the brainstem. There is variable involvement of the peripheral cerebral structures.'6J.l64

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 827

CERVI COCEREBRAL ARTERIAL DISSECTION Arterial dissection is an important cause of acute brain ischemia in children. The initiating event is an intimal tear. This leads to formation of an intramural hematoma that splits the media. The dissection narrows the true lumen of the artery. CNS manifestations of cervicocerebral arterial dissection result from diminished perfusion distal to the narrowed artery or, more commonly, a secondary throm­ boembolic event. Head and neck dissections most com­ monly arise within the extracranial portions of the internal carotid arteries or in the vertebral arteries, although intra­ cranial dissections can also occur. At least half of verte­ bral artery dissections occur at the C1-C2 level. There is a male predominance of both traumatic and nontraumatic dissections.1 65 Vertebral artery dissection is an important cause of posterior fossa strokes in children. Vertebral artery dissec­ tion can occur spontaneously, but is most often associated with blunt trauma or a sporting activity that involves abrupt turning or extension of the neck. Patients may report neck pain and a variety of neurological marlliestations: ataxia, headache, vomiting, eye signs, and paresis or paralysis of l or more extremities. Vertebral artery dissection can result in cerebellar or brainstem infarction. Carotid artery dissection and anterior circulation infarction can occur with trauma or vigorous physical activity, in association with a pharyn­ geal infection, and in patients with a vasculopathy such as Marfan syndrome or arterial fibrous dysplasia.166-l69 Sonography is an effective technique for the detection of dissection in the carotid arteries inferior to the skull base. The displaced intima appears as a thin echogenic septum in the arterial lumen. Echogenic dotted blood may fill the false lumen. Doppler analysis determines the flow charac­ teristics of both the false and true lumens. There is usually a dampened waveform on Doppler analysis proximal to an obstructing dissection; this is an important sonographic finding when the dissection is distal to the field of view. Most vertebral artery dissections occur above the C2 level. Intracranial extension is relatively uncommon. Because of this high level, sonography is of limited value for the detec­ tion of vertebral dissections. M RA and CT angiography allow evaluation of the carotid and vertebral vessels throughout their courses, and are therefore the best noninvasive imaging techniques for patients with possible cervicocerebral arterial thrombosis or dissection. The intramural hematoma of a dissection is sometimes visible in cross-sectional MR images. With incomplete occlusion, T1-weighted images show a narrow eccentric signal void adjacent to a semilunar signal hyper­ intensity. The signal void represents the narrowed residual lumen surrounded by the hyperintense mural hematoma. 2D time of flight MRA shows abrupt termination when there is a completely occluded vessel. This can also be effectively demonstrated with CT angiography. The char­ acteristic angiographic appearance of an arterial dissection

is that of a double lumen due to a raised intimal flap or a long-segment of tapered narrowing due to a thrombosed false lumen. 4 o,qo

VASCULIT IS Vasculitis encompasses various infectious and inflamma­ tory conditions of blood vessels. CNS vasculitis most often occurs in association with a systemic vasculitis, systemic disease, infectious disease, drug abuse, or radiation ther­ apy. Inflammation of cerebral vessels in these patients can lead to stenosis or occlusion. There is also a rare primary form of vasculitis, termed primary (or isolated) CNS vas­ culitis of childhood. The term vasculitis does not include the noninflammatory vasculopathies, such as sickle cell disease and moyamoya.171•172

I nfectious Vascul itis Intracranial infectious arteritis most often occurs as a complication of bacterial or tuberculous mening1t1s. Brain injury is either due to direct angioinvasion by the microbe or collateral vascular injury caused by the host inflammatory response. An additional potential factor is interruption of arterial blood flow due to vasospasm or an extrinsic vascular compression within the meninges. Infarctions in the lenticulostriate distributions are most common in these patients. Cerebral infarction occurs in up to one-quarter of children with bacterial meningitis, appearing as hypoattenuating regions on CT and hyper­ intense areas on F LAIR and diffusion-weighted M R sequences . Occasionally, there are associated parenchy­ mal microhemorrhages that produce small hypointense foci on T2*-weighted GRE M R images. In children with C N S vasculitis due to tuberculous meningitis, basal gan­ glia infarctions are common. Viral pathogens that are rare causes of cerebral vasculitis include varicella-zoster, West Nile virus, enterovirus, and H IV. The most common forms of mycotic arteritis are actinomycosis, aspergillosis, and coccidiomycosis. These patients may suffer embolic or occlusive cerebral infarc­ tions. Most patients with mycotic arteritis are irnmuno­ compromised. Infection with Actinomyces can directly involve the vessel walls, sometimes resulted in complete occlusion. Small vessel involvement may lead to multiple hemorrhagic infarctions. Evolution of an infarct into an abscess can occur.173 Varicella-zoster infection in children (chickenpox) can rarely lead to cerebrovascular stenotic lesions and isch­ emic stroke; that is, postvaricella angiopathy or varicella vasculopathy. These patients are also at risk for an auto­ immune cerebellitis. The ischemic changes due to vari­ cella vasculopathy most often occur in the basal ganglia or internal capsule; peripheral ischemia tends to localize to the anterior cerebral territories. The peak risk for stroke in patients with chickenpox is within several months of the clinical onset of the viral infection. The pathogenesis of

828 Part 3 The B ra i n varicella vasrulopathy may involve intraneuronal migration of virus along the trigeminal nerve to the cerebral arter­ ies. Hemiparesis is common in children suffering vari­ cella-associated strokes. There is a relatively high risk for recurrent arterial ischemic strokes and transient ischemic attacks. However, spontaneous regression of stenosis can occur, with concomitant reduction in the risk for additional events.100 ·'74·'75

Noninfectious Vasculitis Noninfectious CNS vasrulitis is rare in children. Vasculitides that can involve the brain include Henoch­ Schonlein purpura, Wegener granulomatosis, polyarteri­ tis nodosa, poststreptococcal glomerulonephritis, Behc;:et disease, and systemic lupus erythematosus. Medications and illicit drugs (cocaine) are additional rare potential causes of noninfectious vasculitis. The usual neuroimag­ ing appearance of CNS vasculitis is that of multiple focal areas of edema, sometimes with petechial hemorrhage. Diffusion-weighted MR images may show manifestations ofinflammation (perivasrular vasogenic edema) andfor tis­ sue ischemia (restricted diffusion) . The cortical gray-white matter junction of the cerebrum is the most common site. There is usually prominent contrast enhancement due to breakdown of the blood-brain barrier. 17 6-t7 8 Small vessel disease in children with Wegener granu­ lomatosis occasionally results in neurological symptoms . This is most commonly in the form of peripheral and cranial neuropathies. The uncommon CNS manifesta­ tions include ophthalmoplegia, seizures, stroke, and cerebritis. C N S involvement can occur in the form of cerebral vasculitis, granulomas, or extension of sinonasal granulomas.'79

are urlilateral and in the anterior cirrulation. Infratentorial involvement is uncommon. Intraparenchymal or subarach­ noid hemorrhage occasionally is present at the time of pre­ sentation, apparently due to aneurysm or vessel rupture. The most common finding of primary CNS vasculitis with noninvasive or conventional angiography is 1 or more areas of stenosis in the anterior circulation. The most com­ monly involved vessels are the M1 segment of the middle cerebral artery (5o%) , A1 segment of the anterior cerebral artery (2o%) , and the internal carotid artery. Multiple ipsi­ lateral stenoses are common; bilateral lesions occur in approximately 2o% of patients. Individual stenotic lesions are usually less than 1 em in length. Complete vessel occlu­ sion, aneurysm formation, and a beaded pattern of steno­ ses are uncommon findings. 183

NONINFLAMMATORY VASCULOPATHY

M oyamoya Moyamoya is a noninflammatory vasculopathy of central intracranial arteries. There is progressive stenosis of the supraclinoid portions of the carotid arteries, the compo­ nents of the circle of Willis, and the proximal portions of the anterior and middle cerebral arteries. This leads to the formation of extensive small collateral vessels at the base of the brain. The 3 basic collateral pathways include basal vessels from perforators, leptomeningeal collateral vessels from the posterior cerebral arteries , and transdural collat­ eral vessels from the external carotid arteries. Collateral vessels coursing through the basal ganglia to provide blood supply to more distal portions of the parenchyma produce a hazy or cloudy appearance on angiography; the term moyamoya is synonymous with "puff of smoke." True moy­ amoya disease is idiopathic; this is also termed idiopathic

Primary Central Nervous System Vasculitis of Childhood

progressive arteriopathy of childhood. Moyamoya syndrome

Primary C N S vasculitis of childhood (isolated angiitis of the CNS) refers to an idiopathic inflammatory vasculopa­ thy confined to the C N S . The maj or histological change in affected intracranial vessels is granulomatous or lym­ phocytic infiltration of the vessel wall. The diagnosis usually rests on the combination of compatible clini­ cal features and characteristic imaging features ; brain biopsy is rarely performed. The typical clinical presenta­ tion is that of an acquired focal or diffuse neurological deficit. By definition, there is no history of another condi­ tion or discernible cause of vasculopathy, such as infec­ tion, sickle cell disease, systemic vasculitis, migraine, or moyamoya. ' 8 o-t82 Neuroimaging studies of primary CNS vasrulitis at the time of presentation typically show multiple small parenchymal ischemic lesions . The most common areas of involvement are within the lentirulostriate distribution. There is involvement of at least 1 deep gray matter structure in more than 90% of patients. Most commonly, the lesions

(or "moyamoya-like vasculopathy") is the most appropriate terminology for patients with moyamoya vasculopathy in association with an underlying condition such as sickle cell disease. 184 ·'8 5 Most instances of moyamoya apparently involve inter­ play between predisposing congenital factors and envi­ ronmental triggers. Approximately 10% of patients with moyamoya appear to have a familial form. Moyamoya syndrome in children can occur in association with neuro­ fibromatosis type 1, Down syndrome, previous cranial irra­ diation, sickle cell disease, PHAC E S syndrome, congenital heart disease, and hypomelanosis of ! to. Patients with neu­ rofibromatosis type 1 appear to be partirularly susceptible to circle of Willis vasrulopathy following radiation therapy for an optic tract glioma. Head and neck infections may play a role in the pathogenesis of some instances of moy­ amoya disease.'86-'88 The age at presentation ofmoyamoya follows a bimodal distribution, with peaks at the ages of 5 and 34 years. Most

Chapter 20 I ntracra n i a l Va scu l a r A b n o r m a l ities 829 symptoms relate to brain isch emia. Approximately 6% of stro kes in children are due to moyamoya. Symptoms range from transient isch emic attack s to overt stroke. Headach e is common. Approximately 8o% o f patients h ave extremity weakn ess or paralysis as an initial fi nding. Transient isch ­ emic attacks in th ese children are sometimes precipitated by crying. coughing, or straining. Intracranial hemorrh age occasionally occurs in moyamoya patients due to rupture o f collatera l vessel s at th e base o f th e brain or in th e ven­ tricular system. Th e h emorrh age involves th e basal ganglia in approximately 40% o f instances, the ventricul ar system in 35%. and th e th al amus in w%. Moyamoya is progres­ sive in nearly all patients; h owever, th ere is consid erable variability in th e natural history o f th e disease. Medical th erapy pre dominantly consists o f th e administration o f antipl atelet agents, anticoagulants, and calcium ch annel blockers. Surgical cerebral revascularization procedures are appropriate for some patients.18 9.19° Neuroimaging studies of moyamoya patients with acute neurological symptoms o ften demonstrate findings of an isch emic stroke in conjunction with circl e of Willis vasculopathy (Figure 20-25) . Many patients h ave small areas of enceph al omalacia due to prior infarcts; th ese tend to be most numerous in cortical watershe d zones. Invo lvement of th e basal ganglia and periventricular white matter is al so common. In some instances, th e dil ate d coll ateral vessel s

A

Figure 2o-25 Moyamoya syndrome. A. B. Diffusion-weighted and ADC map images of a 12-year-old child with Down syndrome and acute right hemiparesis show a

are visible on standard CT and M R images. Contrast­ enhance d images may exhibit gyra l enhancement and a central vascular blus h due to th e collateral vessel s. Prominent l eptomeningeal enh ancement in patients with moyamoya (th e ivy sign) represents engorgement o f th e fine collateral vascul ar network over th e pial surface. There may al so be high signal intensity on FLAIR images in the leptomeninges. Standard M R images demonstrate dimin­ ishe d flow voids in the intracranial portions of th e carotid arteries and in the major branch vessel s of th e circle o f Willis. Aneurysm formation can occur. M RA demonstrates th e specific central vessel pathology. Conventional cerebral angiography is defi nitive, and is particularly h elpful for pre­ operative planning (Figure 20-26) .191•19 2 Suzuki and Takaku describe d 6 angiographic stages of moyamoya in childhood . (1) Early, often bilateral . ste­ noses o f th e suprasellar portions of th e carotid arteries. (2 ) The initial phase of coll ateral vessel formation at the b ase of th e brairl. (3) E nl argement of the coll ateral vessel s and marke d stenoses of the anterior and middle cerebral arteries; this is the stage at which most patients become symptomatic. (4) The entire circle of Willis an d the pos­ terior cerebral arteries are severely stenotic or completely occlude d . Basal coll ateral s decrease in size and extracranial collateral networks began to form. (5) Progressive enlarge­ ment of extracranial collateral vessels; occlusion of the

8

large area of restricted diffusion in the left cerebral hemisphere due to an acute ischemic stroke.

830 Part 3 The B ra i n

c

E

Figure zo-25 (Continued) C. A vertex MRA view shows a narrowed and occluded left internal carotid artery (arrow) , and nonvisualization of the left posterior communicating artery, the Al segment of the left anterior cerebral artery, and the M1 segment of the left middle cerebral artery. D. The left lateral view of the MRA demonstrates lack of flow in both carotid siphons. There are dilated collateral

D

F

vessels above the posterior communicating and posterior cerebral arteries. E. A lateral mgiographic image shows the left internal carotid artery to end at the level of the ophthalmic artery. There are small collateral vessels extending intracrmially. F. A lateral vertebral injection image shows supply of the anterior and middle cerebral territories via the right posterior communicating artery and multiple smaller collateral vessels.

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 831

A

Figure 2o-26 Moyamoya disease. A, B. Lateral (A) and AP (B) images of a right internal carotid/ cerebral angiogram show complete occlusion of the supraclinoid portion of the internal carotid artery. There is a central "blush"

posterior cerebral arteries. (6) Complete disappearance of the basal moyamoya collaterals; complete occlusion of the internal carotid arteries. The most common extracra· nial sources of collateral flow are the anterior branch of the middle meningeal artery and the maxillary artery. The ophthalmic arteries also commonly provide collateral fl ow. Occasionally, there are collaterals from the superficial tern· poral and occipital arteries.'9 3·'94 Cerebral perfusion studies are sometimes helpful for assessing disease progression in patients with moyam­ oya syndrome. This information can be useful for surgi­ cal planning. Sequential cerebral blood flow studies with SPECT, positron emission tomography (PET) , or xenon· enhanced CT show progressive decrease in normal fron­ tal lobe perfusion and increased occipital perfusion; the degree of this perfusion shift correlates with the severity of disease. There are progressive decreases in regional cere· bral blood flow, regional cerebral metabolic rate, and oxy­ gen concentration.'95-'97 Surgical therapy often plays a role in the management of moyamoya patients, as the disease is progressive and medical therapy is of limited benefit. The most commonly employed direct revascularization, or bypass, procedure consists of anastomosis of the superficial temporal artery to the middle cerebral artery. Superficial temporal artery­ to-anterior cerebral artery bypass is also occasionally pos· sible. Many revascularization procedures, however, are "indirect. These take advantage of the propensity for the ischemic brain of moyamoya syndrome patients to attract collateral blood flow from any available source. Most of n

B

due to telangiectatic basal collaterals ( arrows) . The ophthalmic artery also provides collateral perfusion. On the lateral view (obtained at a later phase than the AP), distal cerebral vessels fill via collateral flow.

these procedures consist of suturing the intact superficial temporal artery into a linear dural opening (encephalodu­ roarteriosynangiosis) or directly to the pial surface (pial synangiosis) . Potential complications of revascularization procedures include stroke and subdural hematoma.'98·'99

Sickle Cel l Disease Cervicocerebral vasculopathy is an important source ofmor· bidity in children with sickle cell disease. Approximately 20% of children with sickle cell disease develop paren­ chymal brain abnormalities such as infarction, ischemia, or atrophy. Imaging manifestations of vasculopathy are present in more than half of children with hemoglobin (Hgb) SS disease. Intimal proliferation causes carotid and cerebral vascular narrowing, predominantly in the internal carotid and middle cerebral arteries . Acute occlusion of small vessels can occur due to sludging of sickled erythro­ cytes. The anemia in these children adds to the potential for watershed infarction. 2oo-2o2 Silent infarcts are common in individuals with sickle cell disease; neuroimaging manifestations of prior ischemic events are present in approximately 13% of sickle cell patients who have no history of a prior clini­ cally evident stroke. These children may have diminished cognitive function. Other patients exhibit manifestations of an acute stroke, with sudden onset of a focal neurologi­ cal deficit. Sickle cell vasculopathy occasionally leads to the devel­ opment of an intracranial aneurysm (sometimes multiple) ;

832 Part 3 The B ra i n subarachnoid hemorrhage due to rupture o f a n aneurysm causes acute onset of headache and meningismus. Other risk factors for hemorrhagic stroke in sickle cell patients include hypertension, recent transfusion, and corticoste­ roid therapy. Approximately 3% of individuals with Hgb S S disease have a hemorrhagic stroke by the age of 20 years . The neuroimaging diagnosis of an acute stroke in a child with sickle cell disease is identical to that of other patients. Diffusion-weighted MR demonstrates cytotoxic edema soon after the event, with subsequent vasogenic edema that is hypoattenuating on CT and hyperintense on T2-weighted MR. Common neuroimaging findings in sickle cell patients with cognitive delay due to prior silent strokes include generalized atrophy and multifocal encephalomalacia. The clinically silent lesions most often involve the deep white matter. Patients with a history of prior clinically overt cerebrovascular accidents more com­ monly have encephalomalacia that involves both the deep white matter and the cortex. Occasionally, prominent cen­ tral cerebral collateral vessels are visible on standard MR sequences, with a moyamoya pattern. M RA ofpatients with sickle cell vasculopathy may demonstrate occlusions, ste­ noses, prominent collateral vessels, vessel tortuosity, and aneurysms. 76 ,2oo,2o3-2o 5 Transcranial Doppler sonography serves as a noninva­ sive screening and monitoring tool for sickle cell disease patients with suspected vasculopathy. Time averaged mean cerebral blood velocity (TAMV) values of at least 200 cmfs within the middle cranial arteries are abnormal, and indi­ cate a substantial risk for stroke. TAMV values of qo to 199 cmfs indicate an intermediate stroke risk. Transfusion therapy is an important tool for stroke prevention in chil­ dren with sickle cell disease_> o 6-2o 8 Children with sickle cell trait (Hgb AS) occasionally develop cerebral vasculopathy, although the neuroimaging findings tend to be mild, and the clinical significance of the findings is unclear. MR of these children may demonstrate cerebrovascular tortuosity or, less commonly, abnormally hyperintensity in the cerebral white matter on T2-weighted or FLAIR images. The occurrence of vasculopathy corre­ lates with the proportion of Hgb S (the key risk factor) , rather than sickle cell trait per se?09-2 11

Sl NOVENOUS THROMBOSIS Intracranial sinovenous thrombosis i s in important potential cause of stroke and other acute neurological abnormalities in infants and children. The Canadian Pediatric Ischemic Stroke Registry determined an incidence of o . 67 cases per 1oo,ooo children per year. Forty-three percent of patients in this report were less than 3 months of age. Most patients with sinovenous thrombosis have an identifiable risk fac­ tor, such as head and neck infection, meningitis, acute systemic illness, nephrotic syndrome, malignancy, cardiac disease, trauma, or hematological disorder. Common pre­ disposing conditions in neonates include dehydration, sep­ sis, and other perinatal complications.76

Figure 2o-27 Sagittal sinus thrombosis. Hyperintense thrombus fills the superior sagittal sinus (arrows) on this unenhanced Tl-weighted MR image of a child with 2 days of symptoms.

Various focal or diffuse neurological signs can occur in children with sinovenous thrombosis . In older chil­ dren, diffuse neurological alterations are most common, including headache or diminished level of consciousness. Focal neurological signs, such as hemiparesis, cranial nerve palsy, or visual impairment, are also more frequent in older children than in neonates. Seizure is a common manifestation of sinovenous thrombosis. In the Canadian study, 71% of neonates and 48% of nonneonates with his condition had seizures . Approximately 40% of chil­ dren with sinovenous thrombosis suffer venous brain infarction; approximately 70% of these infarctions are hemorrhagic. The key diagnostic finding on neuroimaging studies of patients with sinovenous thrombosis is visualization of dot within a venous structure. Thrombus is echogenic on sonography and hyperattenuating on CT. The M R appear­ ance varies with the age of the clot: acute thrombus is generally isointense to brain on T1-weighted images and hypointense on T2-weighted images, whereas subacute dot is hyperintense on both sequences (Figu re 20-27) . Acute dot is hypointense on GRE M R sequences ( Figu re 20-28) . A thrombosed venous sinus may appear hyperintense on diffusion-weighted MR images. In decreasing order of fre­ quency, the common sites of sinovenous thrombosis are the superior sagittal sinus, transverse and sigmoid sinuses, straight sinus , internal cerebral veins, jugular veins, and cortical veins.

Chapter 20 I ntracra n i a l Vas c u l a r A b n o r m a l ities 833

A

B

c

Figure 2o-28 Cortical venous thrombosis. This 14-year-old with acute lymphoblastic leukemia developed left-sided hemiparesis, facial droop, and slurred speech on day 27 of induction chemotherapy with medications that included PEG-asparaginase. A. Unenhanced CT shows hyperattenuating thrombus in a cortical vein (arrows) on the

right. There is subtle edema in the adj acent portion of the brain. B. A F LAIR MR image 4 days later shows a peripheral region of edema due to venous infarction. C . Thrombus in the occluded cortical vein (arrows) is hypointense on this gradient­ recalled image.

Techniques to demonstrate lack of flow in the throm­ bosed vessel include Doppler sonography, contrast­ enhanced CT, conventional angiography, time-of-flight MR venography, and contrast-enhanced MR venography ( Figure 20-29) . On contrast-enhanced studies, there is often prominent enhancement surrounding a throm­ bosed venous sinus, resulting in the "empty delta sign" (Figure 20-30 and Figure 20-31 ) . With long-term occlusion, there may be thickening and prominent enhancement of the tentorium and falx due to vascularization of organized thrombus and slow flow in dural collaterals.

Acute venous sinus occlusion can lead to cytotoxic or vasogenic edema in the portion of the brain drained by the occluded vessel, particularly when there is propagation of dot into tributary cortical veins. This may progress to true infarction; however, there is a greater potential for rever­ sal of parenchymal abnormalities in venous occlusions than with arterial ischemia. As noted above, hemorrhage is common in venous infarcts. The typical MR appearance of parenchymal involvement with venous thrombosis is a poorly defined region of T2 hyperintensity centered in the subcortical white matter, sometimes with a heterogeneous

834 Part 3 The B ra i n

Figure 2o-29 Venous sinus thrombosis. There is lack of visualization of nearly all the venous sinuses on this lateral image of a contrast-enhanced M R venogram. There is flow in the right sigmoid sinus and right internal jugular vein. There are dilated superficial and deep cortical veins.

character due to intermixed hemorrhage. The appearance on diffusion-weighted images is variable, as both cytotoxic edema and vasogenic edema are typically present. Areas of the brain that have restricted diffusion often progress to tis­ sue loss. Areas with increased diffusion (vasogenic edema) may undergo resolution without tissue loss. Clot is usually visible in sinovenous structures adjacent to the edematous

Figure 2o-31 Sagittal sinus thrombosis. An axial contrast-enhanced CT image shows a filling defect within the superior sagittal sinus (arrow) . There is contrast enhancement along the dural margins of the sinus.

brain. Deep venous thrombosis (i.e., of the straight sinus, vein of Galen, or internal cerebral veins) can lead to edema or true infarction within the thalami. On CT, venous infarcts usually appear as poorly defined areas of hypoattenuation. There may be intermixed pete­ chial hemorrhage or a larger hematoma with mass effect. Careful assessment of the imaging findings is essential to prevent misinterpretation of venous sinus thrombosis and hemorrhagic infarction as an interhemispheric subdural hematoma with associated brain injury from child abuse. 21 2 I sola ted cortical venous thrombosis or birth-related ven­ ular injury in a newborn occasionally causes a small infarc­ tion, with associated hemorrhage into the parenchyma and subpial space. Affected infants are usually born at term and have an unremarkable postpartum period until developing seizures at a few days of life. Imaging studies show a small peripheral focus of hemorrhage and surrounding edema. The edema is hyperintense on T2-weighted images and diffusion-weighted images. Progression to focal encepha­ lomalacia is typical. 213

HYPERTENSIVE ENCEPHALOPATHY

Figure 2o-30 Sagittal sinus thrombosis. There is prominent contrast enhancement at the margins of the thrombosed superior sagittal sinus (arrow) on this T1-weighted axial MR image. The clot appears as a nonenhancing filling defect that is approximately isointense to brain.

Hypertensive encephalopathy is a clinical syndrome of transient neurological symptoms in association with a malignant hypertensive state. The pathophysiology likely involves hyperperfusion of the brain and breakdown of the blood-brain barrier, thereby resulting in hydrostatic leakage of fluid across the brain capillaries. If there is persistent substantial elevation of the systemic blood pressure, arte­ riolar damage occurs. Progressive vascular damage leads to cerebrovascular vasodilatation, cerebral edema, intraparen­ chymal hemorrhage, and various neurological deficits. 2LP15

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 835

A

8

Figure 2o-32 Hypertensive encephalopathy. A, B. Coronal FLAIR images of a 13-year-old female with severe hypertension show multiple areas of edema in cortical gray matter and subcortical white matter.

The neurological manifestations of hypertensive encephalopathy are usually nonspecific. Common findings include headache, visual disturbances, altered mentation, seizures, nausea, and vomiting. The onset of symptoms usually is within 2 days of the initiation of the hyperten­ sive state. The neurological findings are often transient and migratory. Funduscopic examination may show papill­ edema, hemorrhage, and exudates. Hypertensive enceph­ alopathy can occur in association with hemolytic uremic syndrome, renal failure, thrombotic thrombocytopenic purpura, chemotherapy, and toxemia of pregnancy. 21 6 Neuroimaging studies of patients with hypertensive encephalopathy demonstrate areas of edema, with or with· out associated hemorrhage. Because the edema is predomi· nantly vasogenic, the apparent diffusion coefficient values are increased in the involved areas. The typical regions of involvement include the cerebral cortex and subcorti­ cal white matter, the external capsules, and the basal gan­ glia (Figure 20-32) . Cerebral lesions are often multifocal. Hemorrhage, when present, can be petechial (most com· mon) or in the form of a larger hematoma. In patients with hemolytic uremic syndrome, there is a predilection for basal ganglia involvement. 217 ·2 18

POSTERIOR REVERSIBLE ENCEPHALOPAT H Y SYNDROME Posterior reversible encephalopathy syndrome (PRE S ; reversible posterior leukoencephalopathy syndrome) i s an acquired idiopathic disorder in which vasogenic edema

occurs bilaterally in the posterior aspect of the cerebrum. Potential underlying clinical conditions include systemic hypertension, hypercalcemic crisis, hemolytic-uremic syndrome, Henoch- Schonlein purpura, eclampsia, renal failure, thrombocytopenic syndromes, and exposure to immunosuppressive, chemotherapeutic (e.g., cyclosporine A and L-asparaginase) , or neurotoxic medications. The pathophysiology likely involves alterations in cerebral blood flow (abnormal cerebral blood flow autoregulation) andfor vascular endothelial dysfunction. There is local breakdown of the blood-brain barrier, with extravasation of fluid that may contain blood or macromolecules. In some patients, PRES is a manifestation of hypertensive encephalopathy. A predilection for involvement of the posterior circulation and watershed zones may relate to relatively sparse vasomotor sympathetic innervation in these regions. The hypertension need not be severe; rapid-onset or fluctuating hypertension is a risk factor. Patients with PRES often have seizures, visual disturbances, headache, and altered mental status. 2 19-221 The imaging hallmark of PRES is bilateral regions of brain edema (see Figure 18-28). The classic distribution is parietooccipital although other patterns do not exclude the diagnosis. In many patients, there is concomitant involve· ment of the posterior aspects of the frontal lobes. There is a predilection for localization of edema in the cortex and sub· cortical white matter. The edema can be regional or mul­ tifocal, but is usually relatively symmetric. Children with PRES often have involvement of the anterior border-zone regions between the anterior and middle cerebral artery territories. Less common sites include the temporal lobes, thalami, brainstem, basal ganglia, and cerebellum.

836 Part 3 The B ra i n

A

B

Figure 20-33 Posterior reversible encephalopathy syndrome. A. An axial FLAIR image of an 8-year-old child with seizures and hypertension shows bilateral areas of edema within cortical

gray matter and adjacent white matter. B. An ADC map image shows high signal intensity in the involved white matter, due to vasogenic edema.

Because the edema in PRES is predominantly vasa­ genic, MR findings of restricted diffusion are usually mini­ mal or lacking, and most lesions have elevated ADC values (Figure 20-33) . This imaging pattern helps in the differentia­ tion from an acute ischemic event. Contrast enhancement is usually minimal or absent. Small foci of hemorrhage are occasionally present. Proton MR spectroscopy reveals ele­ vation of choline and decrease in NAA. CT demonstrates hypoattenuating white matter. With appropriate treatment of the underlying condition, the neuroimaging abnormalities often resolve completely on follow-up imaging evaluations. Occasionally, there is progression to ischemia and overt infarction. Foci of restricted diffusion on MRI frequently undergo subsequent conversion to encephalomalacia. 222-22 5

pathogenic factors include increased resistance to C S F out­ flow, vasogenic brain edema, and increase in intracranial blood volume. The incidence of benign intracranial hyper­ tension in children is estimated to be 0.4 to 2.2 per 1oo,ooo child-years exposure. There is a female preponderance after the age of puberty, often in association with obesity. 22 6 ·227 Common clinical features of benign intracranial hypertension include daily diffuse or frontal headaches, pulsatile tinnitus, and pain in the neck, shoulders, arms, or legs . Compression of the optic nerves in patients with chronic elevation of intracranial pressure can lead to irre­ versible visual loss. The ophthalmic manifestations include papilledema, transient visual obscuration, enlarged blind spots (on visual field testing) , strabismus, and sixth nerve palsy. Substantial compromise of visual acuity often does not occur until late in the disease, but there can be progres­ sion to extensive visual field loss. Therefore, early recogni­ tion of this condition is crucial to allow early institution of vision-saving therapy. In general, the upper limit of normal intracranial pressure in adults and older children is 15 mm Hg (2o em H 2 0 ) . In young children, the normal range is 3 to 8 mm Hg. The normal range for infants is approximately 1.5 to 6 mm Hg. Transient increases occur with coughing, the Valsalva maneuver, and agitation. (Conversion for mm HG to ern water or C S F : 1 mm HG 1.35 em H 2 0 ) . 22 8 The medical treatment for benign intracranial hyper­ tension typically consists of serial lumbar punctures and

BENIGN INT RACRANIAL HYPERTENSION Benign intracranial hypertension (pseudoturnor cerebri; idiopathic intracranial hypertension) refers to elevation of intracerebral pressure in the absence of a mass or other detectable structural brain abnormality. There is no discern­ ible cause in many patients, whereas others have underlying cerebral venous sinus thrombosis or a toxic or mechani­ cal insult. Benign intracranial hypertension occasionally occurs in children following renal transplantation. Potential

=

Chapter 20 I ntracra n i a l Vas c u l a r A b n o r m a l ities 837 the administration of a carbonic anhydrase inhibitor (acetazolamide) . Weight reduction for obese patients is generally recommended. The role of diuretics and corti­ costeroids is uncertain. Spontaneous resolution occurs in some patients even without specific treatment. If conserva­ tive therapy fails, surgical CSF diversion (shunting) or optic nerve sheath fenestration can be helpful.22 9 Neuroimaging studies , particularly M R, are important for evaluation of the child with suspected benign intracra­ nial hypertension to detect underlying pathology such as sinovenous thrombosis or an intracranial mass. In most patients, however, imaging studies are normal or show nonspecific diminished size of the ventricular system. Occasionally, there is distention of the optic nerve sheaths. Bilateral transverse sinus stenoses are common in patients with benign intracranial hypertension; it is uncertain if this is a cause or effect of increased intracranial pressure. It is important to recognize that unilateral transverse sinus atresia or hypoplasia is a common developmental variation that has no correlation with intracranial hypertension.2'2

MIGRAINE Migraine is the most common cause of severe headache. In adolescents, the prevalence of migraines is approximately 7% for girls and 4% for boys. By the age of 15 years , up to 10% of children have experienced a migraine headache. 23° ·23' The 2 major forms of migraine are those with (clas­ sic migraine) and without (common migraine) an aura. An aura is a complex of neurological symptoms that occurs just before or at the onset of a migraine headache, typically a transient visual, sensory, language, or motor disturbance. Typically, migraine headache is unilateral and throbbing. Photophobia and for phonophobia are common. Abdominal pain, nausea, or vomiting sometimes occurs. The patho­ genesis of migraine apparently involves spreading cortical depression, possibly hypothalamic in origin. MR and CT studies are usually normal in patients with migraine. Neuroimaging studies of patients with presumed migraines primarily serve to exclude mimicking condi­ tions. Neuroimaging is usually indicated for patients with symptoms of "complicated migraine"; that is, those with focal neurological findings or other atypical presentations. Nonspecific hyperintense focal white matter lesions on T2-weighted MR images are more common in patients with migraine then in otherwise normal individuals. 23 2 •233 Hemiplegic migraine is an uncommon disorder in which the patient experiences recurrent episodes of migraine associated with focal weakness. The weakness preferentially involves the upper limbs. Additional poten­ tial findings during episodes include aphasia, lethargy, confusion, visual changes, ataxia, fever, seizures, and loss of consciousness. The clinical onset is during childhood for most affected individuals. Familial and sporadic forms are recognized. The familial form has autosomal domi­ nant inheritance. Mutations in the CACNA1A and ATP1.A2 genes are implicated. 23 4

Neuroimaging studies are occasionally abnormal in patients with hemiplegic migraine. There is diminished cerebral blood flow in the involved occipital lobe prior to the onset of aural symptoms. This hypoperfusion slowly spreads anteriorly in the affected hemisphere. There is a subsequent phase of hyperperfusion, during which M R evaluation sometimes demonstrates diffuse unilateral cor­ tical gray matter thickening. The involved gray matter usu­ ally is slightly hyperintense on T2-weighted images, due to edema. The affected region of cortex does not correspond to a single vascular territory. There is no abnormal contrast enhancement. The affected region of the brain sometimes has restricted diffusion. FDG-PET (2-[fluorine-18]fluoro2-deoxy-d-glucose positron emission tomography) images show glucose hypometabolism. All of the neuroimaging findings ofhemiplegic migraine typically resolve spontane­ ously, without permanent sequelae. 23 5- 23 6

CLINICAL PRESENTATIONS: HEADACHE Headache is common in children, occurring in about three-quarters of girls and half of boys. There is an exten­ sive differential diagnosis for this symptom (Table 20-2) .

Table 2o-2. Differential Diagnosis of Headache in Children

Primary

U ncompl icated migraine Chronic �aily headach : :.. Com plicated m igraine Cluster headache/trigeminal autonomic cephalalgia . Tension-type headache Secondary Posttraumatic headache Seizu re-related headache Sinus d i sease � --M edication side effect Pseudotu mor cerebri Brain tumor I ntracranial vascu lar lesion I ntracranial i nfection ----Febrile i l lness ------- - - - - - - - - - - - ----- ----: Trigeminal neu ralgia Cranial neuralgias and central causes of facial l Optic neu ritis pain Tolosa- H unt syndrome Ophthal moplegic "m igrai ne" _ _ _ __

838 Part 3 The B ra i n Th e International Headache Society maintains a website with information about the current classification scheme: http:/ fihs-classification.orgfen.237 Tension headache is a common cause of minor self-limited headaches . Migraine is the most common cause of severe headache (see above) . Neuroimaging studies are not required for most children with typical uncomplicated headaches . However, care­ ful clinical evaluation is essential since headache is an important presenting feature of many clinically significant intracranial lesions for which a prompt imaging diagnosis facilitates appropriate therapy.231•23&-24° The presence of focal neurological findings or atypical symptoms generally mandates a neuroimaging evaluation for the child with severe or recurrent headache. Atypical symptoms include focal neurological signs , headaches that awaken the child from sleep, headaches of increasing sever­ ity, and headaches that are unusually intense, prolonged, or incapacitating. For most intracranial pathology, MR is the most sensitive imaging technique. CT is an alternative method, and is generally preferred to MR for patients with a history of recent trauma or other indication of a possible acute intracranial hemorrhage. M RA or CTA are useful for patients with a suspected vascular lesion. Brain tumor. Headache is a common presenting symp­ tom of brain tumors. Headaches due to a brain tumor tend to be most pronounced in the morning and gradually improve during the day. Coughing, exercise, bending, or kneeling may exacerbate the headache. Some patients have nausea and vomiting. Nearly all children with headaches due to a brain tumor have additional clinical findings such as ataxia, abnormal reflexes, papilledema, nystagmus, cra­ nial nerve abnormalities, or altered sensation. Sinogenic headache. Headaches are common in individ­ uals with sinus disease. Most common is a pressure sensa­ tion over the sinuses or behind the eyes. The symptoms may increase with movement of the head. Most, but not all, patients with sinogenic headache have additional clini­ cal findings of sinus disease; for example, congestion and nasal drainage. Severe or persistent headache in a patient with acute sinusitis can be an indication of a complication such as intraorbital or intracranial extension. Trauma. Nearly all patients with acute intracranial hemorrhage due to trauma have headache. The acutely injured patient with a neurologic deficit requires urgent head CT. Indications for neuroimaging of patients with headache following minor head trauma include vomiting, positive neurological signs, and headache of increasing fre­ quency, severity, or duration. Chronic headache is a poten­ tial sequela that can occur even following relatively minor trauma. Posttraumatic headache tends to decrease in fre­ quency and severity with time, but can persist for months or years. Some patients have additional symptoms such as dizziness, insomnia, and difficulty with concentration. A concussion is a specific symptom complex of head injury in which the patient experiences an immediate and transient posttraumatic impairment of neurological func­ tions, with or without loss of consciousness at the time of

the event. Headache, vision disturbance, and loss of equilib­ rium are common. Postconcussion syndrome refers to per­ sistence or delayed onset of symptoms such as headache, dizziness, noise sensitivity, difficulty with concentration, alterations in memory, irritability, anxiety, and fatigue.24' Intracranial hemorrhage; dissection. Nontraumatic intra­ cranial hemorrhage can present with a severe headache of sudden onset; that is, "thunderclap headache." Potential etiologies include an aneurysm or arteriovenous malfor­ mation. Dissection of a carotid or vertebral artery can lead to a sudden-onset severe headache that is unilateral. Other potential causes of a thunderclap headache include cere­ bral venous thrombosis, unruptured aneurysm, CNS angi­ itis, and pituitary apoplexy. Ophthalmoplegic migraine refers to recurrent episodes of headache accompanied by paresis of cranial nerves I I I , IV, o r VI . This may represent a recurrent demyelinating neuropathy, and is no longer considered a migraine variant. The duration of symptoms during these episodes varies substantially between patients: hours, weeks, or months. The onset is usually during childhood. Prominent contrast enhancement of the involved cranial nerve is occasionally visible on MR.242

EXTRACORPOREAL MEMBRANE OXYGENAT ION The brain is an important and common site of complica­ tions in children undergoing extracorporeal membrane oxygenation (ECMO) . This is a supportive technique for infants with potentially reversible severe respiratory fail­ ure due to conditions such as meconium aspiration, con­ genital diaphragmatic hernia, sepsis, cardiac surgery, or persistent pulmonary hypertension. ECMO is occasionally utilized in older children with cardiac disease, overwhelm­ ing sepsis , or multiorgan failure. Various intracranial complications can occur in patients undergoing ECMO; causative factors include the underlying systemic illness, surgical cannulation of the common carotid artery and jugular vein, hemodynamic alterations, systemic heparin­ ization, and/ or platelet consumption. 243 Up to half of infants treated with ECMO develop clini­ cal or imaging manifestations of intracranial complica­ tions, and 10% to 20% suffer severe complications. The most common severe complications are primary hemor­ rhage (4o%) , ischemia without hemorrhage (4o%) , and combined hemorrhage and ischemia (2o%) . At least one­ third of intracranial hemorrhages in these children are located within the brain parenchyma. Most hemorrhages occur during the first 3 to 5 days of therapy. Sonography plays a crucial role for the detection of CNS complica­ tions in children during ECMO therapy. Widening of the C S F-filled interhemispheric fissure is a common clinically insignificant sonographic finding during ECM0.244 Removal of desaturated venous blood during ECMO therapy occurs via a venous canula that extends into the

Chapter 20 I ntracra n i a l Vascu l a r Abnormal ities 839 right atrium. On standard chest radiographs, the tip should be approximately at the level of the posterior aspects of the eighth and ninth ribs. The tip of the arterial canula should be in the brachiocephalic artery, near the origin of the right common carotid artery, thereby facilitating deliv­ ery of oxygenated blood to the aorta without obstructing the lumen of the arch. With venovenous ECMO, the tip of the double lumen cannula should be in the right atrium, with the opening of the arterial lumen directed toward the tricuspid valve.

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844 Part 3 The B ra i n 192. Fujiwara H, Momoshima S , Kuribayashi S. Leptomeningeal high signal intensity (ivy sign) on fluid-attenuated inversion· recovery (FLAIR) MR images in moyamoya disease. Eur] Radio!. 2005;55{2):224-230. 193. Suzuki ) , Takaku A, Kodama N, Sato S . An attempt to treat cerebrovascular 'Moyamoya' disease in children. Childs brain. 197P{4) :193-206. 194. Satoh S , Shibuya H , Matsushima Y, Suzuki S . Analysis of the angiographic findings in cases of childhood moyamoya disease. Neuroradiology. 1988;30 {2) :m-n9. 195. So Y, Lee HY, Kim S K, et al. Prediction of the clinical outcome of pediatric moyamoya disease with postoperative basal/acetazolamide stress brain perfusion S PEer after revascularization surgery. Stroke. 2005;36 (7):1485-1489.

196. Saito N , Nakagawara J , Nakamura H, Teramoto A Assessment of cerebral hemodynamics in childhood moyamoya disease using a quantitative and a semiquantitative I M P·SPECT study. Ann Nucl Med. 2004;18 (4) :323-331· 197. Miller JH, Khonsary A, Raffel C. The scintigraphic appearance of childhood moyamoya disease on cerebral perfusion imaging. Pediatr Radio!. 1996;26 (12) :833-838. 198. Houkin K, Kuroda S , Nakayama N . Cerebral revascularization for moyamoya disease in children. Neurosurg Clin N Am. 2001;12 {3):575-584. ix. 199. Fung LW, Thompson D, Ganesan V. Revascularisation surgery for paediatric moyamoya: a review of the literature. Childs Nerv Syst. 2oop1{5):358-3 64. 200. Steen RG, Xiong X, Langston )W, Helton K) . Brain injury in children with sickle cell disease: prevalence and etiology. Ann Neurol. 2003;54{5):5 64-572. 201. Ohene-Frempong K, Weiner SJ, Sleeper LA, et al. Cerebrovascular accidents in sickle cell disease: rates and risk factors. Blood. 1 1998;91{1) :288-294· 202. Strouse )), Hulbert M L, DeBaun MR, et al. Primary hemorrhagic stroke in children with sickle cell disease is associated with recent transfusion and use of corticosteroids. Pediatrics. zoo6;n8{5) :1916-1924.

211. Shroff M , deVeber G. Sinovenous thrombosis in children. Neuroimaging Clin N Am. 2oop3 {1) :u5-138. 212. Leach ) L, Fortuna RB, Jones BV, Gaskill-Shipley M F . Imaging of cerebral venous thrombosis: current techniques, spectrum of findings, and diagnostic pitfalls. Radiographies. 2oo6; 26 suppl 1:S19-41. 213. Huang AH, Robertson RL. Spontaneous superficial parenchymal and leptomeningeal hemorrhage in term neonates. AJNR Am J Neuroradiol. 2004;25{3):46 9-475 · 214. )ones B, Egelhoff ), Patterson R. Hypertensive encephalopathy in children. AJNR Am J Neuroradiol. 1997;18 (1) :101-106. 215. Wright RR, Mathews KD. Hypertensive encephalopathy in childhood. J Child Neurology. 1996 ;11{3) :193-196. 216. Cooney MJ, Bradley W G , Symko SC, e t a l . Hypertensive encephalopathy: complication in children treated for myeloproliferative disorders-report of three cases. Radiology. 2ooo;214{3) :711--'716. 217. Schwartz RB, Jones K M , Kalina P, e t al. Hypertensive encephalopathy: findings on CT, MR imaging, and SPEer imaging in 14 cases. A]R Am] Roentgeno/. 1992 ;159 {2) :379-383. 218. Weingarten K, Barbut D, Filippi C, Zimmerman RD. Acute hypertensive encephalopathy: findings on spin-echo and gradient-echo MR imaging. AJR Am J Roentgenol. 1994; 162(3) : 6 6 5-670. 219. Pavlakis SG, Frank Y, Chusid R. Hypertensive encephalopathy, reversible occipitoparietal encephalopathy, or reversible posterior leukoencephalopathy: three names for an old syndrome. J Child Neuro!. 1999;14{5):277-281. 220. Hinchey ), Chaves C, Appignani B , et al. A reversible posterior leukoencephalopathy syndrome. N Eng! ] Med. 1996;334(8) :494-500. 221. Ishikura K, Ikeda M , Hamasaki Y, et al. Posterior reversible encephalopathy syndrome in children: its high prevalence and more extensive imaging findings. Am ] Kidney Dis. 2oo6;48(2) :231-238.

203. el Gammal T, Adams R), Nichols FT. et al. M R and er investigation of cerebrovascular disease in sickle cell patients. AJNR Am J Neuroradiol. 1986;7{6) :1043-1049·

222. Covarrubias D), Luetrner PH, Campeau NG. Posterior reversible encephalopathy syndrome: prognostic utility of quantitative diffusion-weighted MR images. AJNR Am J Neuroradiol. 2oo2;23{6) :1o38-I048.

204. Moser FG, Miller ST, Bello ) A , e t a l . The spectrum o f brain MR abnormalities in sickle cell disease: a report from the Cooperative Study of Sickle Cell Disease. AJNR Am J Neuroradiol. 1996;17{5) :965-972.

223- Kinoshita T, Moritani T, Shrier DA, et al. Diffusion-weighted MR imaging of posterior reversible leukoencephalopathy syndrome: a pictorial essay. Clin Imaging. 2003;27{5) : 3°7-315·

205. Steen RG, Emudianughe T, Hankins GM, et al. Brain imaging findings in pediatric patients with sickle cell disease. Radiology. 2oo3;228{1) :216-225.

224. Keyserling HF, Provenzale )M. Atypical imaging findings in a near-fatal case of posterior reversible encephalopathy syndrome in a child. AJR Am] Roentgenol. 2oo7;188 {1) :219-221.

206. Adams RJ . TCD in sickle cell disease: an important and useful test. Pediatr Radio!. 2005;35{3) :229-234. 207. Lowe LH, Bulas Dl. Transcranial Doppler imaging in children: sickle cell screening and beyond. Pediatr Radio!. 2005;35 {1) :54-65.

225. McKinney AM, Short ), Truwit CL, et al. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. AJR Am J Roentgenol. 2007;189 {4):904-912.

208. Adams RJ. Lessons from the Stroke Prevention Trial in Sickle Cell Anemia (STOP) study. ] Child Neurol. 2ooo;15 {5): 344-349·

226. Francis PJ, Haywood S , Rigden S , et al. Benign intracranial hypertension in children following renal transplantation. Pediatr Nephrol. 2oop8{12):1265-126 9 .

209. Steen RG, Hankins GM, Xiong X, et al. Prospective brain imaging evaluation of children with sickle cell trait: initial observations. Radiology. 2003;228(1) :2o8-215.

227. Gordon K . Pediatric pseudotunJor cerebri: descriptive epidemiology. Can J Neurol Sci. 1997;24{3):219-221.

210. Sebire G, Tabarki B, Saunders DE, et al. Cerebral venous sinus thrombosis in children: risk factors, presentation, diagnosis and outcome. Brain. 2oop28{pt 3) :477-489.

228. Radhakrishnan K, Ahlskog )E, Garrity JA, Kurland LT. Idiopathic intracranial hypertension. Mayo Clin Proc. 1994;69 (2) :169-180. 229. Johnson LN, Krohel G B , Madsen RW, March GA, Jr. The role of weight loss and acetazolamide in the treatment of

Chapter 20 I ntracra n i a l Vascu l a r A b n o r m a l ities 845 idiopathic intracranial hypertension (pseudoturnor cerebri) .

237. I H S Classification ICHD-11: International Headache Society.

Ophthalmology. 1998;105(12):2313-2317.

238. linet M S , Stewart WF, Celentano DD, et a!. An epidemiologic study of headache among adolescents and young adults. ]AMA. 1989;261(15 ) :22U-2216.

230. Chu M L, Shinnar S . Headaches in children younger than 7 years of age. Arch Neurol. 1992;49 (1) :79-82. 231. Abu-Arafeh I , Razak S , Sivaraman B, Graham C. Prevalence of headache and migraine in children and adolescents: a systematic review of population-based studies. Dev Med Child Neurol. 2010;52 (12) :w88-1097· 232. Singer H S . Migraine headaches in children. Pediatr Rev. 1994;15(3) :94-101; quiz 101. 233- Lewis DW, Dorbad D. The utility of neuroimaging in the evaluation of children with migraine or chronic daily headache who have normal neurological examinations. Headache. 2ooo;4o(8):629-632. 234· Politi M , Papanagiotou P, Grunwald IQ, Reith W. Case 125: hemiplegic migraine. Radiology. 2007;245(2) :6oo-6o3235· Jacob A, Mahavish K, Bowden A, et a!. Imaging abnormalities in sporadic hemiplegic migraine on conventional MRI, diffusion and perfusion MRI and M RS . Cephalalgia. 2oo6;26 (8) :1oo4-1009. 236. Butteriss D), Ramesh V, Birchall D. Serial MRI in a case of familial hemiplegic migraine. Neuroradiology. 2003;45 (5): 300-303-

239. Abend N S , Younkin D, Lewis DW. Secondary headaches in children and adolescents. Semin Pediatr Neurol. 20JO;J7(2) :123-133· 240. Brenner M , Oakley C, Lewis D W. Unusual headache syndromes in children. Curr Pain Headache Rep. 2007;11(5):383-389. 241. Ryan LM, Warden DL. Post concussion syndrome. Int Rev Psychiatry. 2003;15 (4) :310-316. 242. Bharucha DX, Campbell TB, Valencia I , et a!. MRI findings in pediatric ophthalmoplegic migraine: a case report and literature review. Pediatr Neurol. 2007;37(1) :59-63. 243- Barnacle AM, Smith LC, Hiorns MP. The role of imaging during extracorporeal membrane oxygenation in pediatric respiratory failure. AJR Am] Roentgenol. 2006;18 6 (1) : 58-6 6. 244. Khan AM, Shabarek FM, Zwischenberger ) B , et a!. Utility of daily head ultrasonography for infants on extracorporeal membrane oxygenation. ] Pediatr Surg. 1998;33(8): 1229-1232.

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CH A P T E R

21

Head Trauma

SKU LL FRACTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

847

I NTENTIONAL TRAU MA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

864

Li near Sku l l Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

847

Pathogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

865

Depressed Skull Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

848

Sku l l and Sca l p I nj u ries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

866

Basilar Sku l l Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

848

Subdural Hemorrhage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

867

Cranial Bu rst Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

850

Epid u ral Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

868

EXTRAAXIAL H E MORRHAG E . . . . . . . . . . . . . . . . . . . . .

850

Su barach noid Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . .

868

Epid u ral Hematoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

850

l ntraparenchymal Hemorrhage . . . . . . . . . . . . . . . . . . .

868

Subdural Hematoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

852

Parenchymal Brain I nj u ries . . . . . . . . . . . . . . . . . . . . . . . . .

868

Su barach noid Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . .

854

N o n hemic S u bd u ral Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . .

870

PARENCHYMAL I NJ U RY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

854

Specificity of N e u roi magi ng for I ntentional Trau ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

874

Concussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

855

I nj u ry Dati ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

876

Contusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

855

Shear I nj u ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

856

B I RTH TRAU MA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

879

Diffuse Bra i n Swel l i ng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

857

Subperiosteal H emorrhage (Cep halhematoma) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

879

Edema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

858

Caput Succedaneum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

88o

Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

858

Su bgaleal Hemorrhage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

881

Penetrati ng Brain I nj u ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

858

Su bgaleal Hyd roma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

881

Cerebral Hern iation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

859

Skull Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

881

Vascu lar I nj u ries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 o

I ntracranial Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

881

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

884

LONC-TERM SEQU ELAE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

86o

Encephalomalacia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 o Hyd rocephalus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

864

Leptomeni ngeal Cyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

864

Traumatic brain injury is a leading cause of death and dis­ ability in children. In the United States, approximately 3000 children and adolescents (o to 16 years of age) die from traumatic brain injury each year. There are approxi­ mately 40o,ooo hospital emergency department visits and 2 9 , o o o hospitalizations each year for pediatric head trauma.'-4

SKULL FRACTURE

Linear Sku ll Fractu re About three-quarters of skull fractures in children are lin­ ear. Approximately 75% of these fractures occur in the pari­ etal bones, 15% in the occipital bones, and 5% in the frontal

848 Part 3 The B ra i n

Figure 21-1 Linear skull fracture. A lateral radiograph of a 18-month-old child shows a linear parietal skull fracture (arrows) . The fracture stops at the coronal suture.

bones. Most linear skull fractures do not cross sutures (Figure 21-1 ) ; extension across a suture usually indicates a high force injury, such as a motor vehicle incident or child abuse. Traumatic suture separation (diastases) is a rare form of a linear skull fracture. An isolated, linear, nondia· static skull fracture most often occurs without accompany­ ing brain injury. A small venous epidural hematoma is the most common intracranial sequela. A subperiosteal hema­ toma is a common extracranial complication of a skull frac­ ture. Identification of a crescentic subperiosteal hematoma is an important clue on axial CT images for an underlying fracture.2

Depressed Sku l l Fractu re A depressed skull fracture involves displacement of the injured portion of the skull intracranially. These fractures sometimes require surgical intervention. Many depressed skull fractures are compound; brain injury is more common in association with compound depressed skull fractures than with simple fractures. Depressed fractures are more frequent in older children than in infants. Common mecha· nisms include a fall (4o%) , motor vehicle incident (zo%) , and birth injury (15%).Most often, the mechanism involves a focal blow or other application of force to the head.5 A ping-pong ball fracture is a depressed fracture that is unique to newborns and young infants. There is indenta­ tion of a portion of the thin pliable skull, without disconti­ nuity of the bone (Figure 21 -2) . A true depressedfracture has a break ofthe inner or outer cortical table and inward displace­ ment of 1 edge of the bone relative to the other, but without displacement of an isolated fragment (Figure 21-3) . The .flat depressedfracture refers to displacement of one or more sep· arated fragments of bone intracranially (Figure 21 -4) ; this

Figure 21-2 Ping-pong ball fracture. CT of a 2-week-old infant following a fall shows inward buckling of a portion of the left parietal bone (arrow) . There is no lucent fracture line or fragment separation.

is the least common of the depressed skull fractures. CT provides the most accurate characterization of depressed skull fractures. This allows quantification of diastasis and depression, as well as the detection of intracranial hemor· rhage, brain injury, pneurnocephalus, extracranial compli· cations, and foreign material (Figure 21 -5) . Accumulation of low attenuation fluid in the region of the fracture suggests the presence of a dural tear.6

Basilar Sku ll Fractu re Basilar skull fractures are uncommon in children. The petrous portion of the temporal bone is the most frequent site of a pediatric basilar skull fracture. At least 8o% of petrous bone fractures are longitudinal, extending from the external auditory canal anteromedially toward the fora· men ovale; facial nerve injury occurs in approximately 15% of these patients (Figu re 21-6) . Transverse petrous fractures usually extend from the jugular foramen toward the fora­ men lacerum or foramen spinosurn; facial nerve injury occurs in about half of these patients. Basilar skull frac­ tures involving the anterior cranial fossa are less common than are those of the petrous bone; these fractures may involve the walls of the ethmoid sinuses, orbits, and sphe­ noid sinuses (Figu re 21-7) . Potential clinical manifestations o f a basilar skull frac­ ture include hemotyrnpanurn, ecchymosis over the mas­ toid (Battle sign) , periorbital ecchymosis (raccoon sign) , cerebrospinal fluid (CSF) otorrhea, C S F rhinorrhea, and facial nerve injury. Up to half of patients with a basilar skull fracture suffer a C S F leak; many of these leaks resolve

Chapter 21 H ead Tra u m a 849

A

8

Figure 21-3 True depressed sku ll fracture. A. Overlapping of the fracture margins results in a dense band (arrow) on this lateral radiograph. B. CT confirms the presence of a fracture, with inward displacement of the anterior component.

Figure 21-4 Flat depressed skull fracture. Two intracranially displaced fragments of the parietal bone are visible on this axial CT image.

Figure 21-5 True depressed fracture. An axial CT image shows a mildly depressed fracture and an accompanying subperiosteal hematoma (arrow) .

8so

Part 3 The B ra i n spontaneously. C S F leaks sometimes occur due to fracture involvement of the eustachian tube, paranasal sinuses, or mastoid. Diagnostic studies that are useful for evaluation of the patient with a suspected posttraumatic C S F leak include high resolution CT, CT cistemography, radionu­ clide cistemography, and MR cistemography.7 ·8

Cranial B u rst Fracture

Figure 21� Basilar skull fracture. A longitudinal fracture (arrows) extends through the petrous portion of the left temporal bone, foramen ovale, and greater wing of the sphenoid bone.

Cranial burst fracture is an uncommon severe calvarial injury that is unique to infants . This consists of extrusion of cerebral tissue outside the calvaria via a dural laceration and widely diastatic skull fracture. The scalp is intact. The potential clinical manifestations include seizures, contra­ lateral hemiparesis, a depressed level of consciousness, and hemorrhagic shock. Prompt diagnosis and surgical repair are essential to prevent a growing skull fracture and addi­ tional cortical injury. In the subacute phase, clinical exami· nation may demonstrate a scalp mass, sometimes pulsatile. Skull radiographs of the infant with a cranial burst fracture demonstrate a widely diastatic fracture, usually at least 4 mm wide. There is nonspecific scalp swelling. Over the course of several weeks, the fracture margins widen due to resorption, that is, a "growing skull fracture. " An associated scalp mass is also present in the chronic phase. CT demonstrates similar findings . Although the dural tear is usually not visible on CT, herniation of cerebral tissue through the defect is sometimes identifiable on CT at the time of initial evaluation. In some patients, however, MR is required to establish the diagnosis in the acute phase. The key features are a defect in the dura and subgaleal cerebral extrusion. 9

EXTRAAXIAL H EMORRHACE

Epid u ral Hematoma

Figure 21-7 Basilar skull fracture. A transverse fracture through the sphenoid bone involves the sphenoid sinus (arrow) and right orbital wall . There is pneumocephalus.

An epidural hematoma is located between the inner table of the skull and the periosteal layer of the dura. Epidural hematomas are typically due to an impact injury; an adj a­ cent skull fracture is present in most of these patients. Most epidural hematomas in children are small and result from disruption of a meningeal vein or oozing of blood from the diploic space. Laceration of the middle menin­ geal artery is relatively uncommon in young children, as there is incomplete development of the surrounding bony canal. The temporal and parietal regions are the most com· mon locations of an epidural hematoma. Fewer than w% of epidural hematomas are located in the posterior fossa. The clinical presentation of a child with an epidural hematoma is variable. Most often, there is a history of an impact head injury, with or without loss of consciousness. Focal neurologic alterations are usually lacking. A large expanding epidural hematoma can lead to neurological deterioration or coma, sometimes following a lucid interval. Most children with an epidural hematoma have an excellent long-term clinical outcome. Generalized brain injury is an uncommon sequela of the impact mechanism associated

Chapter 21 H ead Tra u m a 851

A

B

Figure 21-8 Epidural hematomas in 3 children. This biconvex extraaxial blood collection has a predominantly isoattenuating character due to tlle presence of hyperacute hemorrhage. There is an adjacent skull fracture. B. This right frontal hematoma has tlle typical biconvex configuration tllat is characteristic of an epidural location. C. There is marked mass effect associated witll this left parietal epidural hematoma.

A.

c

with most epidural hematomas; occasionally, there is a con­ tusion or other localized injury. The most important danger of an epidural hematoma is mass effect on the brain. A large hematoma can cause fatal brain herniation, but this compli­ cation is unusual in children. Small epidural hematomas resolve without surgical therapy. Even children with a large epidural hematoma generally have an excellent long-term outcome if there is prompt surgical evacuation.10•11

An epidural hematoma appears on cross-sectional imaging studies as a biconvex (lens-shaped) blood collec­ tion adjacent to the inner table ( Figure 21 -8) . With a small epidural blood collection, accurate distinction from a sub­ dural hematoma is not always possible on neuroimaging studies. However, a small extraaxial blood accumulation in subjacent to a skull fracture is usually in the epidural space. Active bleeding in a large hyperacute epidural

852 Part 3 The B ra i n hematomas. Small subdural hemorrhages are common in newborns , usually due to delivery-related tearing of a venous sinus or cortical vein. The accumulation of blood in the subdural space is common in children undergoing intracranial surgical procedures.

A large subdural hematoma can lead to various neu­ rological signs and symptoms, many of which are non­ specific. Potential findings include seizures , irritability, lethargy, vomiting, and macrocephaly. With severe trauma, such as in abused children, a small subdural hematoma is an important marker for potentially significant associated brain injury that is not a direct effect of the subdural blood. In older children, a large subdural hematoma can lead to manifestations of mass effect and elevated intracranial pressure: pupillary asymmetry, hemiparesis, depressed consciousness, irregular respiration, and increased sys­ temic blood pressure. The maj or determinant of the long­ term prognosis for children with a subdural hematoma is the severity of associated brain injury. There are usu­ ally no long-term sequelae of small birth-related subdural hematomas. The presence of subdural hemorrhage in an abused child suggests a poor or guarded prognosis because of a strong association with coexistent parenchymal brain injuries . The cross-sectional imaging appearance o f a convex­ ity subdural hematoma is that of a crescentic extraaxial accumulation of blood

( Figure 21-10) . Extension into the

Figure 21--9 Epidural hematoma. The dura appears as a thin hypointense band (arrow) at the inner margin of the epidural blood collection on this T2-weighted M R image. The epidural collection has a heterogenous character, due to a mixture of fluid and clotted blood.

CT MR. B ecause of firm dural attachments , an epidural

hematoma can lead to a heterogeneous character on or

hematoma usually does not cross sutures or the midline. On

M R, the displaced dura appears as a thin low signal

intensity membrane along the inner margin of the hema­ toma

(Figu re 21 -9) . In those patients with an underlying

skull fracture, there is often an accompanying epicranial hematoma. Imaging studies occasionally show evidence of a contusion in the brain parenchyma adjacent to the epi­ dural hematoma or in a contrecoup location.

Subd u ral Hematoma A subdural hematoma is a n accumulation o f blood i n the potential space between the meningeal layer of the dura and the arachnoid. Subdural hematomas can occur along the convexities, in the interhemispheric fissure (parafal­ cial) , peripherally in the posterior fossa, or along the tento­ rium. The typical cause is tearing of one or more bridging cortical veins, usually due to a high-force inertial mecha­

Figure 21-10 Convexity subdural hematoma.

nism. In children, child abuse and motor vehicle incidents

An axial CT image of a 13-year-old boy shows a crescentic hematoma on the right.

are the most frequent traumatic etiologies of subdural

Chapter 21 H ead Tra u m a 853

Figure 21-1 1 Convexity subdural hematomas. Coronal CT of a 6-month-old child shows a large left parietal hyperattenuating blood collection that is confined medially by the falx cerebri. The brain is displaced. There is no extension of blood into sulci. A much smaller subdural hematoma is present on the right.

interhemispheric subdural space is common. Because the tentorium is approximately parallel to the plane of axial CT imaging, tentorial subdural hemorrhage may produce only subtle increased attenuation on these images; coro­ nal images are usually diagnostic. Unlike epidural hema­ tomas, subdural hematomas freely cross sutures. Dural attachments at the falx cerebri and at the tentorium confine subdural hematomas, however ( Figu re 21 -1 1 ) . An acute sub­ dural hematoma is usually homogeneously hyperattenuat­ ing on CT. Occasionally, there is a mixed pattern due to extravasation of C S F via an arachnoid tear. A rare cause of heterogeneous attenuation of a hyperacute large subdural hematoma is active bleeding.12 MR is highly sensitive and specific for the diagnosis of subdural hemorrhage. The multiplanar capabilities of MR are particularly useful for the detection of small sub­ dural blood collections within the tentorium or interhemi­ spheric fissure (Figure 2 1 - 1 2 ) . The arachnoid membrane confines a subdural collection such that there is no exten­ sion into sulci. The MR signal characteristics of intracra­ nial hemorrhage vary with the time since the injury; there is additional discussion on this topic in the Intentional Trauma section later in this chapter. During the acute phase of the injury, hemorrhage is usually hyperintense on T1-weighted images and markedly hypointense on gra­ dient echo sequences.13 In infants, sonography shows an acute convexity subdu­ ral hematoma as a relatively homogeneous echogenic extra­ axial fluid collection. In contradistinction to prominence of

Figure 21-1 2 Posterior interhemispheric subdural hematoma. A 9-day-old infant with sei=es has a thin blood collection (arrow) that is hyperintense on this T1-weighted image. There is no blood on the right side of the falx.

the subarachnoid space, there are few or no cortical veins coursing through the fluid. As the hematoma ages, a thick­ ened inner membrane may be visible with sonography. Liquefaction of a large hematoma may result in progressive decrease in the internal echogenicity with time.l4·15 Many subdural hematomas in children are relatively small and do not require surgical evacuation. These small lesions often disappear spontaneously over the course of several days to a few weeks. A larger subdural hematoma undergoes a sequential process ofclot lysis, hematoma orga­ nization, and neomembrane formation. Within a few days of the injury, there is leukocyte infiltration into the hema­ toma from the adjacent meninges. Neovascularization and collagen production begin soon thereafter. The connective tissue organizes into an outer membrane within a few days of the injury. A thinner inner membrane forms gradually over a few weeks. A chronic subdural hematoma is a san­ guinous or serosanguineous fluid collection encapsulated by inner and outer fibrous membranes. The sources of the fluid are clot liquefaction and oozing of serum or blood from proliferating capillaries. During the subacute phase, the CT attenuation of a subdural hematoma diminishes until it becomes isoattenu­ ating and then hypoattenuating to brain. The fluid within a chronic subdural hematoma is hypoattenuating to normal brain on CT. MR of a chronic subdural typically shows sig­ nal intensity intermediate between that of brain and C S F o n T1-weighted images, and hyperintensity t o clear C S F on proton density-weighted images. Alterations in the imaging

854 Part 3 The B ra i n characteristics can occur due t o recurrent small hemor­ rhages or the accumulation of proteinaceous fluid. The cap­ sule of a chronic subdural hematoma is relatively vascular and enhances with intravenous contrast. Chronic subdural hematomas often contain septations. As noted in the dis­ cussion of intentional trauma later in this chapter, most low attenuation subdural fluid collections in children do not occur by way of this classic "chronic subdural" mechanism. The fluid usually appears within a few days of the injury, suggesting that it represents meningeal extravasation of serum or accumulation of C S F via an arachnoid laceration.

Su barach noid H emorrhage Subarachnoid hemorrhage is common in severe head inju­ ries, although small amounts of blood in the subarachnoid spaces may be subtle or undetectable on imaging studies. In addition, small hemorrhages in the subarachnoid space often dear rapidly. Subarachnoid hemorrhage may result from shearing of bridging veins due to rotational forces or tearing of vessels in response to direct contact forces. The blood accumulates subjacent to the arachnoid membrane. The CT appearance ofacute subarachnoid hemorrhage is that of high-attenuation material within the sulci and cis­ terns (Figure 21-13) . Accumulation in the interhemispheric fissure is common. Blood in the subarachnoid spaces may not be visible on standard MR sequences. Acute sub­ arachnoid hemorrhage is hyperintense on fluid-attenuated inversion recovery ( FLAIR) images. There is often an accompanying hemorrhagic contusion.

PARENCHYMAL INJURY

Figure 21-13 Subarachnoid hemorrhage. A CT image of a 14-year-old boy who was hit by an automobile shows high attenuation blood (arrows) in the cisterns, sylvian fissures, and anterior interhemispheric fissure.

Parenchymal injuries of the brain comprise a spectrum of focal and diffuse abnormalities (Table 21-1 ) . Traumatic brain injury results in a combination of cytotoxic injury and

Table 21-1 . Classification of Parenchymal Brain I njuries Parenchym a l bra i n i nj u r i es

Focal

Diffuse

' Contusion

Adjacent to a sku ll fractu re Fracture contusion At the s ite of an external i mpact Cou p contusion Contrecou p contu sion Opposite the point of i mpact Caused by rotational or translational deceleration Gliding contusion : I ntracerebral hematoma ' Penetrating injury M issile i nj u ry Nonmissile i nj u ry ··-·· ! ' Concussion • Diffuse axonal i nj u ry Diffuse brain swel ling ' Hypoxiafischem ia

Chapter 21 H ead Tra u m a 855 extracellular vasogenic edema soon after the event, followed by the accumulation of extracellular fluid. Eventually, atrophy/encephalomalacia develops. Affected areas of the brain have early imaging findings identical to those of ischemic insults, with restricted diffusion as the initial manifestation. Diffusion-weighted images allow detection of contusions and shear injuries earlier than conventional T2-weighted sequences. Trauma-related restricted diffu­ sion sometimes resolves with no residual findings on any imaging sequence.'6 ·'7

Concussion The Committee of Head Injury Nomenclature of the Congress of Neurological Surgeons defines concussion as "a clinical syndrome characterized by immediate and transient posttraumatic impairment of neural functions, such as alteration of consciousness, disturbance of vision or equilibrium due to brain stem involvement. Although loss of consciousness is common with a concussion, this is not specifically required to meet the criteria. In addi­ tion, the presence or absence of loss of consciousness is not predictive of the clinical manifestations following a concussion. A concussion results from acceleration, deceleration, and rotational forces that accompany a blow to the head. The pathogenesis of concussion likely involves disruption ofthe autoregulatory functions that balance cellular glucose demands with cerebral blood flow. Accelerated glycolysis and increased lactate production may then ensue. Relative ischemia and the local metabolic abnormality presumably cause disturbances in neurological function. In general, there are no specific findings of concussion on standard neuroimaging examinations. Experimental studies utiliz­ ing functional M RI have demonstrated brain alterations related to concussion despite normal brain structure on conventional MR images.'8-2' Postconcussion syndrome refers to symptoms that last for weeks or months after a concussion. Headache and dizziness are early symptoms that tend to persist in these patients. Signs and symptoms that often develop days or weeks after the injury include noise sensitivity, altera­ tions in concentration and memory, irritability, anxiety, and fatigue. Nausea and drowsiness are common early symp­ toms of concussion that usually resolve rapidly.22 n

Contusion A brain contusion is a localized area of microscopic disruption of brain cellular architecture that results in increased local water content. There may or may not be associated hemorrhage. Most contusions involve the cerebrum, with tearing in the cortical layers and subcor­ tical white matter. Brain contusion can occur due to an impact injury or a rotational force. A fracture contusion is an impact-related injury to the brain that results from forces generated by a fracture. These are usually located

Figure 21-14 Contusions. A diffusion-weighted image shows multiple peripheral areas of brain edema in this trauma patient.

over the convexities or adjacent to the base of the tem­ poral bone. A coup contusion is located at the site of an impact, with or without a skull fracture. A contrecoup con­ tusion is directly opposite the point of impact; the mecha­ nism involves motion of the brain and impact against the contralateral inner table. A gliding contusion refers to the consequences of motion of the brain with respect to the surrounding support structures and along the irregular bony services of the skull in reaction to an external rota­ tional force. Imaging studies show a contusion as a peripheral focus of brain edema that is hypoattenuating on CT and hyperintense on T2-weighted M R, with or without mani­ festations of intermixed hemorrhage. The lesion often has a patchy, ill-defined character. In the acute setting, diffu­ sion-weighted or F LAI R M R is the most sensitive imaging technique for the demonstration of a contusion. The earli­ est neuroimaging finding of a nonhemorrhagic contusion is hyperintensity on diffusion-weighted MR images, begin­ ning within several hours after the injury (Figure 21-14) . Many contusions are purely hypoattenuating o n CT. A hemorrhagic contusion contains intermixed areas ofhyperat­ tenuating blood ( Figures 21 -1 5 and 21-1 6) . Petechial hem­ orrhage occasionally occurs as a delayed phenomenon in a previously nonhemorrhagic contusion. Edema, mass effect, and imaging conspicuity generally increase during the first few days after the insult, and then gradually dimin­ ish over time. There is usually progression to localized encephalomalacia. 23-2 5

856 Part 3 The B ra i n

Shear I nj u ry

Figure 21-15 Hemorrhagic contusion. CT of a child who suffered a blow to the head shows a focal area of intermixed hemorrhage and edema on the left. There is rightward midline shift.

A

Figure 21-1 6 Hemorrhagic contusion. A. An axial CT image obtained 2 hours after an impact injury shows a subtle hyperattenuating focus (arrow) in the right parietal

Shearing injuries are traumatic alterations in axons, deep white matter, and callosal commissural tissue. Although the pathogenesis is likely multifactorial, the predomi­ nant mechanism for most patients is rapid acceleration­ deceleration of the brain, resulting in axial stretching and disruption of nerve fiber tracts. The unmyelinated pliable immature brain apparently is particularly susceptible to distortion in response to shearing stress. The most com­ mon form of shear injury is diffuse or focal axonal injury. The classic pattern of diffuse axonal injury is that of diffuse damage to axons located at the gray-white matter interface of the cerebral hemispheres, the dorsolateral aspect of the rostral brainstem, and the corpus callosum. The rare mac­ roscopic shear injury is a white matter tear or contusion tear. Shear injuries are common in infants subjected to inten­ tional trauma. Axonal injury refers to microscopic damage to axons due to inertial (acceleration/deceleration) forces. This is a common cause of prolonged coma in head injury patients. Despite the profound neurological consequences of the injury, CT often is normal or shows only subtle manifesta­ tions of multifocal edema and hemorrhage. There may be multiple petechial hemorrhages in the deep white matter and central cerebral structures. Intraventricular hemor­ rhage or focal subarachnoid hemorrhage within the pre­ pontine cistern is also common in these patients. MR provides greater sensitivitythan CT for the detection of multiple areas of edema due to axonal injury. The typical appearance is that of 1 or more small foci of hyperintensity

B

lobe subjacent to a skull fracture. B. The attenuation of the hemorrhage has increased on this image obtained the next day. A hypoattenuating ring of edema surrounds the hemorrhagic focus.

Chapter 21 H ead Tra u m a 857 on FLAIR and T2-weighted sequences. Petechial hemor­ rhages, when present, appear as small hypointense foci on T2*-weighted (gradient-echo; GRE) images (Figure 21-17) . Signal alterations due t o microhemorrhages can persist for years after the event, due to hemosiderin in macrophages. The most common locations of shear injuries are the cor­ pus callosum (particularly the splenium) , dorsolateral aspect of the brainstem, and cerebral gray-white matter junction. Diffusion imaging (elevated signal intensity) and diffusion tensor imaging (reduced anisotropy) are sensi­ tive for the early detection of axonal injury ( Figure 21 -1 8) . Shearing injuries result i n decreased N-acetyl-L-aspartate (NAA) and increased lactate on M R spectroscopy.24·26·27 A gross white matter tear (contusion tear) is a rare form of shear injury that can occur in a young infant who has experienced a severe head injury. The appearance on neuroimaging studies is that of a linear hematoma in the subcortical white matter, most often in the frontal or pari­ etal lobe. In the subacute phase, CT demonstrates a well­ defined low attenuation linear or oval hypoattenuating focus, sometimes with layering blood products. The cav­ ity is hypointense to brain on T1-weighted MR images and hyperintense on T2-weighted images.

Diffu se Brain Swelling Diffuse brain swelling i s a potentially reversible reactive phenomenon that occurs in some patients following head injury. Children are particularly susceptible to this compli­ cation. The pathophysiology is apparently multifactorial.

A

Figure 21-1 7 Shear injury. A gradient-echo Tz*-weighted MR image of a 2-year-old child who suffered a whiplash injury shows multiple small hypointense foci of hemorrhage.

B

Figure 21-18 Shear injury. A, B. Tl-weighted (A) and diffusion-weighted (B) MR images demonstrate a small focus of edema in the splenium of the corpus callosum in a child who suffered a whiplash injury.

858 Part 3 The B ra i n There i s increase in the cerebral blood volume, without substantial increase in extracellular fluid. The resultant elevation of intracranial pressure can be life threatening. CT and MR examinations in these patients may be normal or show subtle manifestations of increased brain volume, such as compression of sulci and cisterns. The attenuation of the brain on CT and the signal intensity of the brain on MR (including diffusion images) are normal. If there is subsequent cellular brain damage, imaging studies show manifestations of true vasogenic edema, with hypoattenua­ tion on CT and high signal intensity on T2-weighted M R. 2 8

Edema Trauma-related brain edema, either focal or diffuse, is relatively common in children who experience severe acceleration-deceleration injuries. This complication is par­ ticularly common in infants . Edema can occur as a direct consequence of head trauma or in response to hypoxia. Hypoxia in these patients can result from posttraumatic apnea or traumatic involvement of other organ systems. An additional potential mechanism for brain edema in trauma patients is impedance of venous return due to thoracic trauma or resuscitative chest compressions . Substantial brain edema can lead to elevated intracranial pressure and brain herniation, thereby further compromising brain per­ fusion. Cerebral edema can cause compressive occlusion of the posterior cerebral arteries at the level of the incisura of the tentorium, with subsequent posterior cerebral artery infarctions. The identification of brain edema in a head trauma patient indicates a guarded prognosis. 2 9 The CT appearance of brain edema is abnormally diminished attenuation of the brain parenchyma. There is loss of distinction between gray and white matter. Mass effect produces sulcal effacement and compression of cis­ terns. There may be midline shift or evidence of hernia­ tion. Most often, the lateral and third ventricles collapse in response to the elevated intracranial pressure; however, compression of C S F drainage pathways can result in nor­ mal sized or enlarged ventricles. On CT, manifestations of edema may be subtle or absent on images obtained soon after the traumatic event; followup examinations are usu­ ally diagnostic. Edema in infants often spares the posterior fossa structures; this may produce a "bright cerebellum sign" on CT (Figure 21-1 9) . Sonography o f infants with brain edema typically shows manifestations of brain expansion: effacement of the sulci, obliterated convexity subarachnoid spaces, and narrowed lateral ventricles. Alterations in the parenchyma are often subtle. The edematous brain parenchyma is often hyperechoic. With diffuse edema, there is a heterogeneous character of the parenchyma and poor sonographic defini­ tion of structures. M R is exquisitely sensitive for the detection of brain edema. Diffusion-weighted M R sequences accurately depict cytotoxic edema soon after the injury. Early in the course, diffusion-weighted images demonstrate increased

signal intensity (decreased on apparent diffusion coefficient images) . Subsequent conversion to vasogenic edema pro­ duces high signal intensity on FLAIR and T2-weighted MR images. Damaged, edematous brain has decreased NAA levels and elevated lactate levels on MR spectroscopy. 3°

Hemorrhage A parenchymal hematoma is a discrete collection of blood within the brain parenchyma that causes local mass effect. A hemorrhagic contusion, in contradistinction, consists of blood that is intermixed with edematous brain paren­ chyma. Most hemorrhagic contusions contact the surface of the brain, whereas intracerebral hematomas tend to be deeper. Some parenchymal hematomas represent coales­ cence of hemorrhagic contusions, whereas others are due to direct injury of deep cerebral vessels. Shear injuries can also be hemorrhagic. An intracerebral hematoma may occur due to dosed head trauma or a penetrating injury. The CT appearance of a parenchymal hematoma is that of a hyperattenuating collection of blood, usually with surrounding edema and manifestations of mass effect (Figure 21 -20) . A fluid-fluid level is sometimes present (Figu re 21 -21 ) . The blood dot liquefies and decreases in attenuation in the weeks after the injury, usually leading to cystic encephalomalacia. A hemorrhagic contusion is an ill­ defined focus of mixed hypoattenuating edema and hyper­ attenuating blood. The mass effect due to a hemorrhagic contusion predominantly relates to the severity of edema rather than the hemorrhage. Progression to focal encepha­ lomalacia is often less pronounced with a contusion than with a hematoma)' Various systemic disorders are associated with spontaneous, that is, nontraumatic, parenchymal brain hemorrhage in children. Nonstructural causes include thrombocytopenia (e.g. , idiopathic thrombocytopenic pur­ pura) , hemophilia, vitamin K deficiency, disseminated intravascular coagulation, sickle cell disease, and thera­ peutic anticoagulation. Potential structural causes of spon­ taneous intracranial hemorrhage include a neurosurgical procedure, vascular malformation, brain infarction, brain neoplasm, vasculopathy (e.g., systemic lupus erythemato­ sus), dural sinus thrombosis, and intracranial infection_32-34

Penetrati ng Brain I nj u ry Penetrating brain injuries are relatively uncommon in children, but engender unique clinical and neuroimag­ ing considerations. A peiforating injury refers to an open­ head injury in which the wound enters the calvaria on 1 side and exits on the other. A penetrating injury refers to a missile or stab wound to the head that does not exit the cranial vault (Figure 21 -22) . The primary brain injury mech­ anisms related to perforating and penetrating open-head trauma include energy translation, tissue cavitation, and dissemination of shock waves. Secondary mechanisms of injury include hypoxia, hypotension, elevated intracranial

Chapter 21 H ead Tra u m a 859

A

c

pressure, and release of damaging chemicals. Imaging studies following penetrating brain injury may demonstrate intracranial hemorrhage, brain edema, pneurnocephalus, or foreign material. Intracranial infection is an important potential delayed complication of these injuries. Vascular injuries, such as a pseudoaneurysm, can also occur)5-J7

Cerebral Herniation Cerebral herniation refers to mechanical displacement of the brain from 1 cranial compartment to another, often

B

Figure 21-1 9 Cerebral edema. A. CT of a 4-month-old infant shows diffuse parenchymal hypoattenuation, lack of gray-white differentiation, and effacement of cerebral sulci. B. A coronal reformatted image shows the cerebrum to be hypoattenuating relative to the normal cerebellum. C. There is a heterogeneous hyperechoic appearance of the brain on sonography.

leading to vascular compression or interference with C S F drainage. Herniation i s a common cause o f posttraumatic cerebral infarction. Herniation can occur due to severe brain edema, an intraparenchymal mass or hematoma, or an expanding extraaxial lesion such as an epidural hema­ toma. The major types of cerebral herniation include sub­ falcine, transtentorial (descending, ascending) , tonsillar, and transalar (descending, ascending) .38 Subfalcine herniation of the frontal lobe can lead to obstruction of the contralateral foramen of Monro and ipsi­ lateral anterior cerebral artery compression. Descending

86o Part 3 The B ra i n

Figure 21-20 Parenchymal hematoma. A thin rim of hypoattenuating edema surrounds a large right cerebral hematoma. The hematoma causes right-to-left midline shift. Blood is also present in the lateral and third ventricles.

Figure 21-21 Parenchymal hematoma. This 10-year-old boy suffered blunt head trauma in a car-versus· bike incident. The acute intracerebral hematoma has separated into 3 distinct layers. The sulci, cisterns, and ventricles are collapsed due to generalized brain edemafswelling.

transtentorial herniation refers to displacement of a por­ tion of the supratentorial brain through the incisura into the posterior fossa. The imaging findings include widening of the ipsilateral ambient and prepontine cisterns, narrow· ing of the contralateral cisterns, and contralateral temporal hom widening. Uncal herniation is a specific type of descending trans· tentorial herniation, in which there is medial displacement of the uncus and parahippocampal gyrus of the temporal lobe. Uncal herniation results in effacement of the ipsilat· eral aspect of the suprasellar cistern, enlargement of the ipsilateral cerebellopontine angle cistern (early) , complete obliteration of the basal cisterns (late) , and compression of the anterior choroidal, posterior communicating and poste· rior cerebral arteries (Figu re 21 -23) . Ascending transtentorial herniation i s a n uncommon condition in which there is upward displacement of the vermis and cerebellar hemispheres through the tentorial incisura. Tonsillar herniation refers to inferior extension of the cerebellar tonsils through the foramen magnum in response to posterior fossa mass effect. Descending transalar (trans sphenoidal) herniation represents posterior displacement of the frontal lobe over the greater sphenoid

ala. Ascending transalar herniation consists of upward dis­ placement of the temporal lobe, sylvian fissure, and middle cerebral artery over the sphenoid ridge.

Vascular I nj u ries Vascular injuries and vascular complications ofhead trauma include arterial dissection, vascular transection, aneurysm, arterial or venous thrombosis, stroke due to vascular com­ pression, dural sinus laceration, and traumatic arterio­ venous fistula. Some of these occur as delayed sequelae. CT and MR techniques generally are diagnostic; selected patients require catheter angiography (Figu re 21-24) .

LONG-TERM SEQUELAE

Encephalomalacia Trauma-related damage to the brain parenchyma leads to macrophage migration, processing of necrotic tissue, and eventual gliosis. Encephalomalacia represents the end­ result of this process, that is, gliosis and focal loss of neu­ ronal tissue. With severe damage, a fluid-filled cavity may

Chapter 21 H ead Trau m a 861

A

8

c

D

Figure 21-22 Penetrating injury. A-C. A lateral digital scout image and 2 axial CT images of a 15-year-old girl show a screwdriver enterirlg the left temporal

bone and extending through the brain into the posterior fossa. D. An image obtained after removal of the object shows hemorrhage and edema along the tract of the injury.

form at the site; this is cystic encephalomalacia. Depending on the volume of tissue involved, encephalomalacia ranges from microscopic foci of gliosis to extensive confluent areas of gross parenchymal loss or generalized atrophy ( Figure 21 ·25) - Localized encephalomalacia occasional serves as a seizure focus. Encephalomalacia appears as a low attenuation, non­ enhancing area on CT. The gliotic brain is hypointense on T1-weighted MR images and moderately hyperin­ tense on T2-weighted sequences. Occasionally, there are

hypointense foci on T2-weighted images due to dystrophic calcification or hemosiderin deposition. The cystic form of encephalomalacia consists of a parenchymal fluid collec­ tion that is approximately isoattenuating to C S F on CT, with variable surrounding gliotic tissue that is hypoattenuating to normal brain (Figure 21 -26) . Septations may be present. Occasionally, the cavity communicates with an adjacent ventricle. On M R, cystic encephalomalacia appears as 1 or more fluid-filled cavities within the parenchyma. The fluid produces similar signal intensity as dear CS F.39

862 Part 3 The B ra i n

A

B

c

Figure 21-23 U ncal herniation. A, B. Coronal and axial Cf images of a 19-month-old victim of intentional trauma show displacement of the uncus (arrows) into the left side of the suprasellar cistern. There is a mixed­ attenuation convexity subdural hematoma on the left, as well as hyperattenuating blood in the interhemispheric and tentorial subdural spaces. The left lateral ventricle is collapsed and the

D

contralateral temporal hom is slightly prominent. There is effacement of the contralateral ambient cistern. C. Rightward shift of the brainstem results in widening of the ipsilateral portion of the prepontine cistern. There is edema in the left temporal lobe. D. There is edema in the left occipital lobe due to compression of the left posterior cerebral artery.

Chapter 21 H ead Tra u m a 863

E

Figure 21-23 (Continued) E. Manifestations of the left posterior cerebral artery territory stroke are more pronounced on an image obtained 2 days later. Areas of edema are also present in the frontal lobes.

Figure 21-24 Traumatic pseudoaneurysm. A coronal contrast-enhanced CT image of a 2-year-old child following a head injury shows a large aneurysm arising from the left carotid siphon.

Figure 21-25 Cystic encephalomalacia. This 2-year-old child suffered an inflicted head injury 8 months earlier. An axial CT image shows replacement of the brain parenchyma by multiple cysts.

Figure 21-26 Encephalomalacia.

CT of a 4-year-old child, 1 year after a severe head injury shows multiple areas of cystic encephalomalacia. Left cerebral hemisphere atrophy results in prominent sulci, parenchymal volume loss, and leftward midline shift. There is mild ex vacuo hydrocephalus.

864 Part 3 The B ra i n

A

Figure 21-27 Post-traumatic hydrocephalus. A. CT of a 14-month-old child abuse victim shows multiple areas of edema in the cerebrum. There are small subdural fluid collections. B. Despite a lack of documented intraventricular hemorrhage at the time of the injury, CT performed 4 months

Hyd rocephalus Hydrocephalus i s common a s a delayed sequela o f sub­ stantial head trauma in children. This can occur as ex vacuo hydrocephalus due to cerebral atrophy, or obstruc­ tion of C S F drainage pathways caused by posthemorrhagic inflammation and adhesions. With atrophy-related ven­ triculomegaly, neuroimaging studies usually demonstrate parenchymal thinning, prominent sulci, and expanded subarachnoid or subdural spaces. In most instances, there is a stable or diminished head circumference. True post­ traumatic hydrocephalus generally results in ventricu­ lomegaly accompanied by relatively small subarachnoid spaces (Figure 21 -27) . In infants and young children with hydrocephalus, the cranial sutures may widen and physi­ cal examination demonstrates an enlarging head circum­ ference. Radionuclide cisternography is helpful in selected patients to assess the dynamics of intracranial C S F flow.

Leptomen ingeal Cyst Leptomeningeal cyst refers to herniation of meninges at the site of a skull fracture. This is the most common form of a growing skull .fracture. Leptomeningeal cyst is an uncom­ mon occurrence in children. The pathophysiology involves a diastatic skull fracture accompanied by laceration of the underlying dura. Herniation of meninges through the

8

later for evaluation of progressive macrocephaly demonstrates dilation of the lateral and third ventricles due to acquired aqueductal stenosis. A thin fibrous band is visible in the third ventricle. There is effacement of the sulci and cisterns .

dural defect prevents normal healing of the dura and bone. Pulsations of C S F within the herniated meningeal sac cause progressive enlargement of the fracture and increase in the size of the cyst. These patients may have a soft pal­ pable mass or intermittent swelling at the fracture site, usually first apparent several weeks after the initial injury. Skull radiographs of leptomeningeal cyst demonstrate a diastatic skull fracture with ill-defined, beveled, or scle­ rotic margins. The cyst itself is sometimes identifiable as an extracranial mass. The diagnosis can be confirmed with CT or MR, which shows a fluid-fille d leptomeningeal cyst that communicates with the intracranial subarachnoid space (Figu re 21 -28) . The other 2 forms of growing skull fractures involve herniation ofbrain or a porencephalic cyst through a widened fracture.4 ° ·41

INTENT IONAL TRAUMA Intracranial injury is a common and potentially devastating occurrence in physically abused children. Child abuse is the most common cause of serious head trauma in infants. Intracranial irljury is the most common cause of death in abused children. Most serious intracranial injuries related to child abuse occur in the infant and toddler age group. Boys are more commonly affected than are girls. The mean age at the time of diagnosis is 6 to 8 months.

Chapter 21 H ead Tra u m a 865 intracranial injuries due to child abuse every year. The inci­ dence of inflicted traumatic brain injury in children under the age of 1 is approximately 30 per 10o,ooo children per year. About one-quarter of these children die from their head injuries. Common consequences of intentional head trauma in children who survive the initial event include visual impairment, motor impairment (e.g., cerebral palsy), and various cognitive impairments. 4 2 ·43 Common presenting clinical findings for children suffering intentional head injury include apnea, seizures, vomiting, irritability, and lethargy. The signs and symptoms often are nonspecific, and may not directly indicate head trauma or intracranial pathology. Most often, caregivers report no history of trauma. Others may blame the injuries on low-impact trauma or cardiopulmonary resuscitation. Inconsistent or changing histories also are indicators ofpos­ sible intentional trauma. Although victims of intentional head injury may not be brought to medical attention until sometime after the injury, the onset of symptoms nearly always occurs immediately after the abusive event.44>4 5 A

B

Figure 21-28 Leptomeningeal cyst. Coronal CT images show subarachnoid fluid extending into a diastatic skull fracture. The adjacent cortex also bulges into the defect.

A, B.

The estimated incidence of child maltreatment in United States is more than 8oo,ooo children per year (12 per 1000 children per year). Approximately 18% of these children suffer physical abuse (i.e. , intentional trauma, inflicted injury, or nonaccidental trauma). The fatality rate for child maltreatment (neglect or physical abuse) is approximately 2 children per 1oo,ooo population per year; 81% of these children are age 3 or under. Approximately 13 00 to 16oo American children suffer clinically substantial

Pathogenesis There are 2 basic mechanical forces involved in head trauma: translational and rotational. A direct impact of the head produces a translational force that affects the soft tis­ sues and skull at the site of the impact, and causes variable additional transmission of force to the underlying intracra­ nial structures. Translational force is the dominant feature when the head strikes a rigid object or an object strikes the head. This is the typical mechanism responsible for most unintentional head injuries. Translational force is impor­ tant in some, but not all, instances of intentional trauma. Potential consequences of substantial translational force include scalp contusion, subgaleal hemorrhage, skull frac­ ture, epidural hematoma, subarachnoid hemorrhage, and cerebral contusion. Rotational forces result from sudden acceleration or deceleration of the head. Whiplash mechanisms result in the application of rotational forces to the skull, meninges, and brain. Substantial rotational force also occurs with motion of the head in response to an impact injury. Severe manual shaking of an infant is the classical rotational mechanism of intentional brain injury, that is, "shaken baby syndrome." Importantly, many infants subjected to severe shaking injuries also experience 1 or more epi­ sodes of head impact and severe deceleration when thrown against a wall, the floor, or another object. Severe rotational forces can lead to differential motion of structures that have different consistencies, such as brain with respect to skull or white matter with respect to gray matter. Bridging veins that extend between the brain surface and the dural sinuses are susceptible to tearing by this mechanism. Similarly, stretching and injury of axons that extend between the superficial and deep regions of the brain may occur. The major consequences of injuries in which rotational forces predominate include subdural hemorrhage, brain edema,

866 Part 3 The B ra i n brain shear injury, nonhemic subdural fluid accumulation, and craniocervical junction injuries . In addition to mechanical forces, various other mechanisms can lead to brain injuries in abused chil­ dren. Nonhemorrhagic hypoxic-ischemic injury appears to account for most of the severe brain damage and visual disturbances that occur with intentional head trauma. Strangulation, suffocation, or cardiorespiratory alterations can cause intracranial hypoxic-ischemic insults. Seizures or apnea related to the initial brain or cervical cord injury can also cause hypoxia that exacerbates the intracranial pathology.

Sku l l and Scalp I nj u ries Cranial impact injuries in children suffering intentional trauma typically lead to extracranial hemorrhage or soft tis­ sue edema that is visible on imaging studies; CT and MR are most sensitive. Most often, there is nonspecific extracranial soft tissue prominence. This finding should prompt careful evaluation for an underlying skull fracture. However, lack of detectable soft tissue swelling adjacent to a skull fracture does not rule out an acute injury. Occasionally, cross-sec­ tional imaging studies demonstrate a subgaleal hematoma caused by an impact injury or hair pulling.46 Skull fractures are present in approximately 10% of all physically abused children and approximately 30% of those less than 2 years of age. Forty percent to 50% of children with inflicted intracranial injuries have a skull fracture. Skull fractures are, however, also common in children expe­ riencing unintentional head trauma. In general, the iden­ tification of a skull fracture in a child simply indicates that head trauma of at least moderate severity has occurred. The nature and location of the fracture provide some indication of the mechanism. Skull fractures result from contact inju­ ries, either with an object striking the skull or the skull strik­ ing a stationary object. In general, the larger the surface area of the object and the softer the composition, the less likely a fracture will occur. High velocity impact injuries of the head with a soft object, such as a mattress, can lead to severe intracranial injuries without an associated skull fracture. Standard radiography is the preferred imaging tech­ nique for children with a suspected skull fracture, although CT is often indicated as well in order to detect intracranial injuries. A linear fracture parallel to the imaging plane may be undetectable or subtle on axial CT images. A simple lin­ ear parietal bone fracture is the most common type of skull fracture in children suffering either intentional or uninten­ tional head trauma. Imaging features that indicate trauma of severe magnitude or an unusual mechanism (e.g., impact with a sharp object) include multiple or complex fractures, fracture depression, fracture diastases (>3 mm) , and crossing of a suture (Figure 21 -29) . Fractures with any of these characteristics are generally not compatible with a short distance fall.47-49 Observation of widened cranial sutures on skull radiographs of infants can be an important indicator of

B

Figure 21-29 I ntentional trauma; skull fractures. B. Lateral radiographs of a 2-month-old infant show multiple skull fractures, some of which are diastatic and cross suture lines. There is also widening of the cranial sutures. A,

intracranial pathology. This finding, however, is nonspe­ cific, as it can occur with various nontraumatic conditions such as brain tumors and hydrocephalus. In addition, there is considerable individual variation in suture width between normal children. Abused children with large chronic sub­ dural hematomas or hygromas often have macrocephaly and widened sutures ( Figure 21 -30) . Extraaxial blood and brain swelling are the most common causes of widened sutures with an acute injury (Figure 21 -31 ) .

Chapter 21 H ead Tra u m a 867

Figure 21-30 I ntentional trauma; widened sutures. There is a subtle parietal skull fracture on this lateral radiograph of a 10-week-old infant. The sutures are wide. cr (not shown) confirmed the presence of large subdural fluid collections.

Figure 21-32 I nterhemispheric subdural hematoma. There is a linear high attenuation hematoma in the right interhemispheric subdural space on this axial CT image.

S u bd u ral Hemorrhage Hemorrhage is the most common intracranial imaging manifestation of intentional head trauma; the typical site of bleeding in these patients is the subdural space. In fact,

Figure 21-31 I ntentional trau ma; widened sutures. A lateral skull radiograph of a 9-month-old infant shows macrocephaly and widening of the cranial sutures. CT (not shown) demonstrated acute subdural hematomas and diffuse brain edema.

acute subdural hemorrhage in an infant or young child without an appropriate history of a predisposing medical condition or procedure, recent vaginal delivery, or severe accidental injury is the most common neuroirnaging fea­ ture to suggest a diagnosis of intentional traumatic brain injury. The most common location of subdural hemor­ rhage due to intentional trauma is in the posterior inter· hemispheric fissure. The subdural hemorrhage in these infants is usually ofinsufficient volume to cause secondary brain injury. However, even small subdural hemorrhages in abused children usually are accompanied by neuroradio­ logical or clinical indications of substantial parenchymal brain injury.47 On axial CT or MR images, an interhemispheric (para­ falcine) subdural hematoma appears as a linear or triangu­ lar blood collection that has a flat medial border where it contacts the falx ( Figure 21 -32) . The lateral margin is usu­ ally convex. Because the falx separates the subdural spaces at the midline, interhemispheric subdural hematomas can be unilateral or asymmetric. There is usually some degree of extension of an interhemispheric subdural hematoma into the adjacent pericerebral subdural space. A posterior interhemispheric fissure subdural hematoma often is con­ tiguous with a subdural blood collection along the surface of the tentorium. The tentorial blood dot may be difficult to visualize on axial images; coronal or sagittal images are diagnostic (Figure 21 -33) . A convexity (or pericerebral) subdural hematoma typically appears on neuroimaging studies as a crescentic blood collection. In children suffering an inflicted injury,

868 Part 3 The B ra i n (Figu re 21 -34) . Alternatively, supplemental evaluation with MR usually allows a confident diagnosis . Intracranial hem­ orrhage is usually hyperintense on T1-weighted MR images and markedly hypointense on gradient-echo sequences (Figu re 21-35) .

Epid u ral Hemorrhage A large epidural hematoma is a relatively uncommon find­ ing with intentional trauma. This lesion is usually asso­ ciated with a skull fracture. As in children experiencing unintentional head trauma, most epidural hematomas in patients with child abuse are small hematomas of venous origin. CT and MR demonstrate a lenticular blood collec· tion along the convexity.

Su barach noid Hemorrhage

Figure 21-33 Subdural hematoma. A reformatted coronal CT image of a 4-month-old victim of intentional injury shows high attenuation clotted blood in the tentorial and interhemispheric subdural spaces (arrows) .

convexity subdural hematomas vary from small isolated foci to large hemorrhages that require surgical drain­ age. A small localized convexity subdural hematoma may have a similar imaging appearance as an epidural hema­ toma; most small epidural hematomas are subjacent to a skull fracture, however. A paramedian convexity subdural hematoma often is contiguous with an interhemispheric component. The presence of even a very small subdural hematoma indicates that substantial head injury has occurred. In some instances , this is the only clinical or radiological feature to raise the possibility of intentional trauma. Radiologists must carefully inspect all neuroimaging studies of infants and young children for this finding, even when there is no history of head trauma. Differentiation of a small inter­ hemispheric subdural hematoma from the normal falx cerebri is difficult in some patients. In addition, normal flowing blood within the venous sinuses produces slightly higher attenuation values than immature brain on CT, potentially leading to a mistaken diagnosis of hemorrhage. A hematoma usually has a thicker and more irregular con­ figuration than the normal falx. In some instances, the hematoma is only along 1 side of the falx. Extension of the hematoma into the convexity or tentorial subdural space, when present, is a helpful confirmatory finding. With equivocal findings, a repeat CT examination in 12 to 24 hours nearly always demonstrates a change in the appear­ ance of the hematoma that confirms the diagnosis, that is, increase in the size or attenuation values of the hematoma

Subarachnoid hemorrhage due to intentional head injury may occur from shearing of bridging veins or contact injuries of surface vessels . There is often a concomitant brain contusion. CT demonstrates high attenuation blood within the cisterns and cerebral sulci. There is often accu­ mulation of blood within the interhemispheric fissure. Differentiation from an interhemispheric subdural hema· toma is based on extension of the blood central to the margin of the falx, a more frequent anterior location, and symmetric involvement of both sides of the falx.

I ntraparenchymal Hemorrhage Intraparenchymal hemorrhage in abused infants usually occurs as a hematoma or hemorrhagic contusion caused by a direct impact injury. Additional potential mechanisms include rotational shear injuries and hemorrhagic conver­ sion of brain ischemia. A hemorrhagic contusion appears as an ill-defined focus of mixed high and low attenuation on CT. A parenchymal hematoma causes mass effect on adjacent structures; there is often perilesional edema.

Parenchymal Brain I nj u ries Probably the most common parenchymal brain manifesta­ tion of intentional trauma is edema. The presence of sub­ stantial edema on neuroimaging studies is an important indicator of a poor prognosis. Edema can be a manifesta­ tion of the primary injury or a consequence ofhypoxia (e.g., posttraumatic apnea, suffocation, or strangulation) . Brain edema in association with intentional trauma can be focal, multifocal, or diffuse. Potential causes of edema in these children include apnea, cerebrovascular vasoconstriction, shear injury, and neck vessel injury. There is often relative sparing of the posterior fossa structures and central cere­ bral gray matter structures . CT demonstrates diminished attenuation in the edem­ atous portion of the brain, often accompanied by poor gray-white matter distinction and sulcal effacement. The findings may be subtle or absent early in the course, but

Chapter 21 H ead Tra u m a 869

A

c

B

D

Figure 21-34 CT of posterior i nterhemispheric hematoma. The normal falx in this 2-year-old child is thin and slightly hyperattenuating; there is no hemorrhage. B. A right-sided posterior interhemispheric fissure subdural hematoma in a 16-month-old boy is thicker and of higher attenuation than the falx. There is no blood on the left. C. There is subtle bilateral posterior interhemispheric hemorrhage in this 3-month-old infant on an image obtained approximately 4 hours after the injury. D. CT of the infant in (C) two days later shows the hematomas to be thicker and of higher attenuation. Normal flowing blood in the torcula is hypoattenuating relative to the clot. E. CT of a s-month-old infant 2 days after head trauma shows a small high attenuation hematoma in the posterior interhemispheric fissure.

A.

E

are visible on CT examinations within a few days of the event. Relative sparring of the cerebellum and brain stem may produce the bright cerebellum sign or reversal sign on CT. Occasionally, neuroimaging studies obtained soon after head trauma demonstrate increased brain volume without

overt manifestations of edema. This "brain swelling" may result from compromised cerebrovascular vasoregulation or elevated venous return pressure. When performed soon after the traumatic episode, diffusion-weighted MR is a sensitive imaging technique

870 Part 3 The B ra i n While axonal injury is a common finding in autopsy evaluations of physically abused children, imaging evi­ dence of a focal shear injury is uncommon. Shear injuries usually result from a mechanism that involves severe accel­ eration-deceleration forces . Most shear injuries occur at the gray-white matter junction. These lesions often are not visible on CT imaging unless there is a substantial hemor­ rhagic component. There is often a background of diffuse edema. Nonhemorrhagic shear injuries are hyperintense on FLAI R and diffusion MR sequences. Associated hemor­ rhage, when present, produces a mixed appearance on MR, including hyperintense foci on T1-weighted images. The magnetic susceptibility-induced static field inhomogene­ ities that arise from paramagnetic blood breakdown prod­ ucts in petechial hemorrhages result in T2* shortening. Therefore, foci of intracranial hemorrhage are hypointense on gradient-echo sequences. 53

N on hemic S u bd u ral Fluid

Figure 21-35 I nterhemispheric subdural hematoma. A right interhemispheric subdural hematoma is markedly hypointense on this axial gradient-echo MR sequence.

for the detection of brain injuries in abused children (Figure 21 -36) . Areas of restricted diffusion are present in most children suffering inflicted brain injuries. Diffusion­ weighted images frequently demonstrate more severe edematous brain alterations than would be expected based on the CT features of the injury. In addition, diffusion­ weighted images often show more extensive abnormalities than are visible on conventional MR. Diffusion-weighted images are particularly useful in infants , as the nor­ mal immature white matter is relatively intense on T2-weighted images, whereas restricted diffusion due to cytotoxic lesions contrasts markedly with the increased dif­ fusion pattern of normal immature white matter. Diffusion tensor imaging also may demonstrate brain injuries that are not identifiable by other methods. The presence of ele­ vated lactate on MR spectroscopy is an indicator or a poor clinical outcome. 5 °-52 As described above, a cerebral contusion can occur due to a direct contact force. Contusions may be hemorrhagic or nonhemorrhagic. The damaged tissue is edematous. CT demonstrates an ill-defined superficial area of diminished attenuation of brain parenchyma. The area is hyperintense on T2-weighted MR images. When hemorrhage is present, it usually has a petechial character, resulting in heteroge­ neous foci of high attenuation on CT and high signal inten­ sity on T1-weighted MR images.

The accumulation o f nonhernic fluid i n the subdural spaces is common in infants and young children subjected to severe intentional head injuries. This fluid can accumu­ late via a dural tear (i.e., hygroma) , clot liquefaction, or leak­ age of serum from meninges or subdural membranes (i.e., posttraumatic subdural effusion) . Except for those due to clot liquefaction, these fluid accumulations can occur in the absence of preceding or coexistent subdural hemor­ rhage (Figure 21 -37) . Traumatic nonhernic subdural fluid collections most often arise within a few to several days of the traumatic event, and may subsequently enlarge, persist indefinitely, or spontaneously resolve. Those that persist (i.e., "chronic subdural hematomas") usually achieve maxi­ mum size within a few weeks of the injury. It is important to recognize, however, that a low attenuation subdural fluid collection of at least several millimeters in thickness can develop during the first week after the injury. During this time, there can be coexistent high attenuation intracranial hemorrhage. Care must be exercised not to confuse this appearance with "acute and chronic subdurals" that are due to more than 1 episode of trauma. 54 Cross-sectional neuroimaging studies demonstrate fluid in the subdural space as linear or crescentic extraaxial material that displaces cortical veins and effaces adjacent sulci. Because the attenuation characteristics of nonhemic fluid are similar to those of C S F , differentiation from prom­ inent subarachnoid spaces (e.g., atrophy or benign enlarge­ ment of the subarachnoid spaces) is sometimes difficult on CT. Because of the strong association with intentional trauma, equivocal findings on CT require additional investi­ gation. Administration of IV contrast is sometimes helpful to detect cortical vein displacement. In infants , sonogra­ phy may provide additional characterization of the fluid and depiction of cortical veins. For most patients, however, MR is the definitive technique if other imaging studies are equivocal. Posttraumatic nonhernic fluid in the subdural space nearly always produces higher signal intensity than

Chapter 21 H ead Tra u m a 871

A

8

Figure 21-36 I ntentional trauma, brain edema. A CT image of an umesponsive 2-month·old infant shows marked hypoattenuation of the cerebrum, with relative sparing of the thalami, occipital lobes, and cerebellum. There is low attenuation fluid in the convexity subdural spaces. B , C. The edematous brain is hyperintense on a diffusion-weighted image (B) and hypointense on an ADC image (C) .

A.

c

C S F on proton-density and FLAIR images. There is usually a sharp demarcation at the interface between the subdural and subarachnoid spaces. M R (T1-weighted and gradient echo sequences) is also sensitive for the detection of small associated intracranial hemorrhages (Figure 21 -38) . Delayed images following IV gadolinium administration may dem­ onstrate accumulation of contrast in a traumatic subdural effusion; this does not occur with a hygroma ( Figure 21 -39) . Patients with chronic subdural fluid collections are susceptible to small hemorrhages or interment oozing of blood into the expanded subdural space. This hemorrhage may occur spontaneously or following minor trauma.

However, these spontaneous hemorrhages are generally asymptomatic or associated with signs and symptoms related to mass effect from the expanded subdural space. Symptomatic acute subdural hemorrhage in conjunc­ tion with a chronic nonhemic subdural fluid collection usually indicates that multiple episodes of head trauma have occurred, and strongly correlates with a diagnosis of child abuse. The spontaneous hemorrhages that occur in patients with chronic nonhemic subdural collections are usually small and located along the convexities; hemor­ rhage in the posterior interhemispheric fissure suggests substantial acute trauma.47

872 Part 3 The B ra i n

A

Figure 21-37 Nonhemic subdural fluid. This n-month-old infant suffered a severe acceleration/ deceleration head injury. A. A Cf performed 5 hours after the injury is normal. No areas of intracranial hemorrhage were visible on this or subsequent CT examinations. B. Small low attenuation subdural fluid collections are present on this image obtained 32 hours after the injury. C. Large subdural fluid collections indistinguishable from "chronic subdural hematomas" are present on this MR image obtained on day +

B

c

A

c

E

B

D

Figure 21-38 Non hemic subdural fluid. This 3-month-old infant presented with macrocephaly and irritability. A skeletal survey performed after the CT showed multiple extremity and rib fractures. A. CT shows large low attenuation convexity fluid collections. The flattened adjacent brain surface suggests that the fluid is subdural. In some areas, an interface between the subdural and subarachnoid spaces is visible (short arrows) . There is an acute subdural hematoma posteriorly (long arrow) . B. The subdural fluid is hyperintense relative to the subjacent subarachnoid fluid on this T2-weighted image. C. On a FLAIR sequence, there is a sharp demarcation between the black CSF and the white subdural fluid. D. Small foci of recent hemorrhage within the large nonhernic subdural fluid are hypointense on this gradient echo image. E. Small acute subdural hemorrhages (arrow) are hyperintense on a sagittal T1-weighted image.

874 Part 3

The

B ra i n

A

Figure 21-39 Traumatic subdural effusion. A. A T1-weighted M R image of an infant several days after head trauma shows a left subdural fluid collection (arrow) that has signal intensity intermediate between that of brain and dear

B

CSF. B. A T1-weighted imaged obtained 30 minutes after IV gadolinium administration shows prominent enhancement of the fluid.

examination, resemble the neuroimaging appearance of

Specificity of Neuroimagi ng for I ntentional Trauma

a subdural hematoma. Secondary bland or hemorrhagic venous infarctions in these patients can result in cortical

An accurate diagnosis o f intentional head injury requires

abnormalities on imaging studies . A congenital intracra­

careful correlation of key clinical factors with the findings

nial vascular malformation is an important consideration

6o%

in the differential diagnosis of spontaneous intraparenchy­

from technically adequate neuroimaging studies . In

to 70% of cases, the caregiver reports no history of trauma.

mal, intraventricular, or subarachnoid hemorrhage; subdu­

Others relate a history of a low impact mechanism, such as

ral hemorrhage in these patients is rare. The differential

a short distance fall. The presence of subdural hemorrhage

diagnosis of a nonhemorrhagic subdural fluid collection in

or parenchymal brain injury (other than a small contusion) in an infant or young child without an appropriate history

a child includes surgery, trauma, a meningeal inflamma­

tory process, and brain volume loss (atrophy) .5 6

is highly suspicious for a diagnosis of intentional trauma.55

Various neuroimaging patterns are highly specific

There are important considerations in the differential

for intentional trauma in infants and young children who

diagnosis that are nearly always discernible on clinical and

have no evidence of a nontraumatic etiology and lack of

radiographic investigations ; systematic exclusion of these

a history of a severe urlintentional injury. Acute intracra­

conditions is an important component in the accurate diag­

nial hemorrhage accompanied by a large nonhemorrhagic

nosis of intentional trauma. Small posterior fossa subdural

(i.e., low attenuation on CT) subdural fluid collection

hemorrhages are common in neonates following vaginal

in a child with acute symptoms is nearly always due to

delivery. Metabolic disorders occasionally cause acute or

intentional trauma

chronic subdural hematomas; the most important of these

convexity subdural space or posterior interhemispheric

1, and

subdural space is the most common fi nding in abused

conditions are Menkes disease, glutaric aciduria type

( Figure 21 -41 ) .

A hematoma within the

Hermansky-Pudlak syndrome. Children with hemophilia

children with head injury. The presence of intracranial

or other serious coagulopathies occasionally develop intra­

hemorrhage without a concomitant skull fracture is also

Table 21 -2

cranial hemorrhage following relatively minor trauma.

a suspicious finding.

Intracranial sinovenous thrombosis can cause hemorrhagic

for estimating the probability of intentional trauma based

(Figure 21 -40) .

on the CT findings alone , regardless of the history and

venous infarctions that resemble contusions

High attenuation intravascular blood dot can, o n cursory

clinical findings . 57

provides a prediction rule

Chapter 21 H ead Tra u m a 875

A

Figure 21-40 Sinovenous thrombosis. A. An unenhanced CT image shows multiple areas of parenchymal hemorrhage and adjacent edema in the left cerebral hemisphere. The superior sagittal sinus is hyperattenuating.

A

B

Figure 21-41 I ntentional trau ma. The presence of acute subdural hemorrhage in conjunction with large low attenuation convexity subdural fluid collections (i.e., acute and chronic subdural pattern) at the time of presentation

B

B. The torcula and straight sinus are distended with hyperintense clot on this Tl-weighted MR image. There are multiple thrombosed deep cerebral veins as well.

has a strong correlation with intentional trauma. The imaging findings are particularly suspicious when there is posterior interhemispheric bleeding remote to the convexity fluid.

876 Part 3 The B ra i n Table 21-2. Prediction Rule for I ntentional Trauma i n I nfants Less Than 3 Years of Age, Based o n the C T Findi ngs Alone Co nvexity

SDH

N o n o n h e m i c fl u i d

Probabi l ity of

Non h e m i c

Posterior

s u b d u ra l fl u i d

i nterh e m i s p heric

No

Yes

No

Yes

No

SDH

Sku l l fractu re

Yes

No

No

No

Yes

Yes

Yes

Yes

No

Yes

No

Yes

No

Yes

No

No

Yes

No

Yes

Yes

No

No

No

--

·--·---

No

No Yes

-

---

--

-----·-

- - ······-------

- - ·-- - · - ··----

-

----

- -- - - ----�- -

--

- - - - - - - - - ·----

Yes

99 97 97 9- 3 93

-

---·----

..___ _. _ _ _ _ _ _ _ ____ _

i ntentio n a l tra u m a (%)

-

----

- - - ---

go

78 76 75 45

- - - -- - -

Yes

Yes

No

Yes

No

No

No

Yes

- - - - - - --

S D H = s u bd u ra l hemorrhage. (Sens itivity 85%; s pecificity 83%)

of manifestations oflaminar necrosis, and the radiographic features of skull fractures (Table 21 -3) . The accuracy of imaging techniques for estimating the date of an injury var­ ies with the timing of the first examination, the availability of sequential examinations, and the nature of the injury. Because most patients present for medical attention soon after the injury, there is often sufficient diagnostic imaging data to provide useful information about the likely timing of the injury.

I nj u ry Dati ng Estimation of the timing of an intracranial injury based on the neuroimaging findings is often a crucial component of the medicolegal investigation of suspected intentional trauma. Factors that can be useful for injury dating include CT attenuation and MR signal intensity of intracranial blood clots, the characteristics of brain edema, the appear­ ance of nonhemic subdural fluid accumulations, the onset

Table 21-3. Neuroimaging Findi ngs Useful for I nj u ry Dating* I magi ng featu re

B l ood CT atte n u ation

1 -3 days

i

ii

i

i/i so

J_

i

i

i

i -

i

i

Nonhemic s u b d u ral fl u i d

-

----

- - - - - - - - - - - - - - · ----- - ----

S u bd u ral membrane e n h a ncement Edema M R d iffusion signal

i

Lactate o n M RS

+

- - - - - - - - - - - - - - - - - -----

Edema CT

·------ -----

- - - · - - - - - - - - - - - - - - - - - - - -- - - ------

Edema T2 M R

--

J_ --

------

- -----

-

-

i

- -

---

-+

- - -- ---

+

wk

-----

-- -

-

wk

++

++

+

+

----·--·-·

i

J_ -- - - - -

--

------ · -- · - - - - - - - - - - - - -- - -- - -

+

J_

++

-

------

-- - - -· - - - -- - - - - --· - - -

++

+

La m i n a r necros is

-�.:.:!:���-�_a�-� �-------------------------------------Fracture Sharp S h a rp Sharp

---

''itJ.t� = atte n uation

>1-2

6-J o

Meningeal cysts of the spine include arachnoid cysts, meningoceles, and spinal nerve root diverticula (Tarlov cysts) . Arachnoid cysts can be intradural or extradural (also termed occult intrasacral meningocele) . Most are con­ genital in origin, although acquired arachnoid loculations have a similar appearance. An extradural meningeal cyst is herniation of arachnoid through an acquired or congeni­ tal dural defect. A Tarlov cyst is a meningeal dilation of a posterior spinal nerve root sheath (accumulation of fluid between the perineurium and endoneurium) , usually in the sacrum; this lesion is rare in children. Many meningeal cysts are asymptomatic. Potential clinical manifestations include pain and weakness, sometimes accentuated in the upright position. Other potential findings include radicu­ lopathy, paraparesis, quadriparesis, spasticity, paresthesias, and sphincter dysfunction. A meningocele is a CSF-filled protrusion of meninges through a bony defect. Lateral or ventrolateral meningoceles can occur in patients with neu­ rofibromatosis type 1. Radiography and standard CT are usually normal in the presence of a meningeal cyst. A large lesion can cause localized expansion ofthe spinal canal. An extradural lesion sometimes is associated with widening of the interpedicu­ lar distance. A perineural (Tarlov) cyst can cause enlarge­ ment of the involved neural foramen. Extradural meningeal cysts also can result in enlargement of one or more neu­ ral foramina (Figure 24-1 2) . Most meningeal cysts contain fluid that is isointense to C S F on M RI sequences, includ­ ing diffusion-weighted images. Care should be exercised

' .

. ."

.. .

. -

"' -

.

.

"' ,

. ....�.

A

Figure 24-12 Meningeal cyst. A This asymptomatic arachnoid cyst (arrow) bulges through the right Tu-neural foramen. The lesion is homogeneously

,.

Arteriovenous M alformation Intraspinal arteriovenous malformation is a potentially devastating developmental lesion. Although a congenital lesion, the clinical presentation can occur at any age. Often, there is sudden onset of symptoms in association with intense physical activity or the Valsalva maneuver. Potential clinical findings include back pain, lower extremity motor abnormalities, and sphincter dysfunction. Young children with a spinal arteriovenous malformation may have lower extremity weakness, poor development, and progressive spasticity. About one-third of patients with spinal cord a arteriovenous malformation have an associated angiodys­ plasia, such as port wine angiomas or Klippel-Trenaunay syndrome. Cobb syndrome is a rare abnormality that is char­ acterized by the combination of a vascular skin nevus and an angioma or arteriovenous malformation in the spinal canal at the same metamere)'

� .. . ..

_,

B

hyperintense on this Tz-weighted image. B . Smooth erosion of the adjacent aspects of the pedicle, pars interarticularis and vertebral body is visible on this Ti-weighted sagittal image.

990

Par q The S p i ne

A

Figure 24-13 Sacral meningeal cyst (arachnoid cyst). A, B. Sagittal and axial MR images of a 10-year-old girl with

8

(arrows) . Adjacent nerve roots are displaced. There is slight bony expansion. The cyst contents are isointense to C S F .

radiculopathy show an oval cyst in the sacral spinal canal

About half of intraspinal arteriovenous malforma­ tions occur in the thoracolumbar region, although any portion of the cord can be involved. Potential radiographic findings include vertebral body scalloping, pedicle ero­ sion, focal vertebral canal widening, and kyphoscoliosis. M R shows multiple serpiginous signal voids within the intramedullary nidus, as well as in supplying and drain­ ing vessels (Figure 24-1 5) . Hyperintense foci interspersed between regions of low signal are sometimes present on TI-weighted images, due to hemorrhage within the cord. Areas of hemosiderin deposition may also be pres­ ent (low signal intensity) . Prominent contrast enhance­ ment is typical. The anomalous arterial anatomy can be further evaluated with M R angiography or conventional angiography.

Meni ngioma Spinal meningiomas are relatively common in adults, but account for only 4% of pediatric spinal neoplasms. This tumor can occur in individuals with neurofibromatosis type 2. Most spinal meningiomas are intradural and extramedullary. Meningioma of the spine is usually an encapsulated lesion that is attached to the dura; the spi­ nal cord is displaced but not invaded. The clinical mani­ festations typically relate to spinal cord or nerve root compression. Meningiomas typically have signal intensity that is isointense or slightly hypointense to the normal spi­ nal cord on T1-weighted images. The lesion is slightly hyperintense on T2-weighted images. There is intense

homogeneous contrast enhancement. A dural tail may be present with this lesion. Although rare , meningioma is part of the differential diagnosis of a dumbbell shaped spinal tumorY

I ntrad u ral Li poma Intradural lipoma is a developmental mass that often is associated with congenital spinal cord abnormalities. The spectrum of lipomas within the dural sac includes intra­ dural lipoma, terminal lipoma, and fibrolipoma of the filum terminale (see Chapter 22 for discussion of these lesions ) .

EXTRADURAL MASSES Extradural spinal neoplasms can arise from the vertebrae, fat, vessels, lymph nodes, or extramedullary neural ele­ ments . Benign lesions include osteochondroma, osteoid osteoma, and aneurysmal bone cyst. Malignant tumors include osteosarcoma, Ewing sarcoma, chordoma, and metastatic disease.

Vertebral Col u m n M asses Neoplasms and nonneoplastic masses that can arise within the pediatric spinal column include osteoblastoma, osteoid osteoma, osteochondroma, aneurysmal bone cyst, fibrous dysplasia, Langerhans cell histiocytosis, chordoma, giant cell tumor, osteosarcoma, and Ewing sarcoma. There is additional discussion of these lesions in Chapter 63. Ewing

Chapter 24 N eo p l a s m s a n d M a sses of the S p i n e 991

Figure 24-1 5 Spinal arteriovenous malformation. A T2-weighted image demonstrates multiple serpiginous flow voids in the subarachnoid space. Expansion and distortion of the cord are present at the nidus of the malformation

(arrow) .

Figure 24-14 Arachnoid cyst. This intradural extramedullary mass appears as an oval filling defect (arrows) on myelography.

sarcoma is the most common primary malignant lesion of the vertebral column. The marrow spaces of the vertebrae are common sites of metastasis from various tumors. The spinal column can be involved in patients with Langerhans cell histocytosis and leukemia.33 The clinical manifestations of vertebral column neo­ plasms vary with the location, size, and aggressiveness of the lesion. Patients may present with pain, a palpable mass, or torticollis. Other potential findings include radicular pain, paresthesia, weakness, and bladder dysfunction.

Aneu rysmal Bone Cyst An aneurysmal bone cyst is a destructive, expansile lesion that contains chronic blood products. In the spine, there

992

Part 4 The S p i n e

A

B

Figure 24-1 6 Osteoid osteoma. A. There is a focus of intense tracer uptake {arrow) in the

left side of T12 on this posterior delayed bone scintigraphy image. B. An unenhanced CT image demonstrates a small oval

soft tissue-attenuation nidus {arrow) in the posterior elements, with minimal extension through a cortical defect. There is adjacent reactive sclerosis.

is a predilection for involvement of the posterior elements. The lesion weakens the involved bone; pathological frac­ ture is common. In the spine, pathological fracture can result in spinal cord compression. Imaging studies show an aneurysmal bone cyst as an expansile, lytic lesion. On MRI and CT, it is multiloculated and there are hetero­ geneous fluid-fluid levels within the loculations due to hemorrhage and sedimentation. Enhancement is usually heterogeneous.

Osteoid Osteoma and Osteoblastoma Approximately 1 0 % o f osteoid osteomas and 40% of osteoblastomas arise in the spine. Both of these are osteoid-producing benign neoplasms. These neoplasms can cause painful scoliosis . Osteoblastoma can lead to manifestations ofcord or nerve root compression. Imaging studies of osteoid osteoma show a small hypervascular nidus and surrounding reactive sclerosis. CT is often required to demonstrate the small nidus ( Figure 24-1 6) . A n osteoblastoma i s a n expansile lucent lesion that con­ tains a variable quantity of dense, amorphous bone or stippled, ringlike calcifications ( Figure 24-1 7) . By defi­ nition, the nidus of an osteoblastoma is at least 1 em in diameter. Approximately 85% of spinal osteoblastomas are confined to or have involvement of the posterior ele­ ments. Ninety percent of osteoid osteomas arise in the posterior elements. Osteoid osteoma and osteoblastoma avidly accumulate bone-seeking radiopharmaceuticals on blood pool and delayed images ( Figu re 24-18) .

Figure 24-17 Osteoblastoma. A CT myelogram image demonstrates an expansile lesion of C2 (arrow). There is a heterogeneous low attenuation character of the matrix. The margins are relatively well defined.

Chapter 24 N eo p l a s m s a n d M asses of the S p i n e 993

A

Figure 24-18 Osteoblastoma.

8

A A posterior blood pool phase image of bone scintigraphy shows uptake in the left side of L3 (arrow) . B. There is avid accumulation of radiopharmaceutical on the delayed image.

Vertebral Osteochondroma The spinal column i s a n uncommon site o f osteochondro­ mas. Most are small and asymptomatic. However, spinal cord compression or nerve root impingement can occur. These lesions can arise from any portion of the vertebra, although there is a predilection for the posterior elements. The cervical spine is the most common site of symptomatic osteochondromas. They can occur as solitary tumors or as part of multiple osteochondromatosis (hereditary multiple exostoses) . CT is the optimal technique for defining the bony anatomy (Figure 24-1 9) , whereas M R is the superior method for viewing the cartilage cap and assessing mass effect on adjacent soft tissues .34-37

Vertebral M etastasis Replacement of normal vertebral marrow by meta­ static disease produces hypointensity on T1-weighted MR images and hyperintensity on T2-weighted images. Short tau inversion recovery ( STI R) or fat-suppressed T2-weighted images are essential to differentiate the abnormal T2 signal from normal marrow fat. Metastatic tissue usually undergoes prominent contrast enhance­ ment. Extraosseous soft tissue extension can occur

Figure 24-1 9 Vertebral osteochondroma. An axial CT image of a child with hereditary multiple exostoses shows a broad-based osteochondroma (arrow) arising from the neural arch of C3 and projecting into the spinal canal.

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Chordoma Chordoma i s a rare malignant tumor that arises from rem­ nants of the fetal notochord. Potential locations include the sacrum, clivus, and upper aspect of the cervical spine. The notochordal origin is reflected by a midline location of the tumor, with sparing of the posterior elements. This lesion can also arise in the musculature of the perivertebral space, presumably from extraosseous notochordal rests . Chordomas contain physaliferous cells; these are clear cells with intracy­ toplasmic vacuoles and abundant mucin. This slowly grow­ ing tumor tends to encase and compress adjacent neural structures. Common symptoms of cervical spine chordoma are weakness and pain in the neck and shoulders.39-4' Imaging studies show a chordoma as a lytic destruc­ tive lesion. The mass typically produces low to interme­ diate signal on T1-weighted images and is hyperintense on T2-weighted images . There is heterogeneous contrast enhancement. Calcifications are present in a majority of these lesions, typically with an amorphous character. The lesion is destructive and locally aggressive. There may be a prominent exophytic soft tissue component. In the spine, the mass may invade adjacent vertebral bodies and spread into the epidural and paraspinal spaces.

Sacrococcygeal Germ Cel l Tu mors Germ cell tumors include mature and immature teratomas and malignant germ cell tumors. Teratoma is the second most common congenital neoplasm, after hemangioma. The sacrococcygeal region is the most common site of tera­ toma; approximately

70% of teratomas arise in this region.

The prevalence of sacrococcygeal teratoma is approximately

1 in 4o,ooo live-births. There is a 4:1 female preponderance. Anomalies in other organ systems are present in approxi­ mately

15% of infants with sacrococcygeal teratoma. The

Figure 24-20 Vertebral metastasis.

genitourinary system is most commonly involved; potential

A STIR image of a 4-year-old child with Wilms tumor shows hyperintense vertebral body lesions and extensive intraspinal extension.

findings include obstructive uropathy, urethral atresia, renal dysplasia, urinary ascites , hydrocolpos, and cryptorchidism. Atresia or stenosis of the rectum can occur. Children with sacrococcygeal teratoma have an elevated incidence of devel­ opmental dysplasia of the hips and clubfoot deformities . 4243

Evidence of permeative bone destruction

Teratoma is a benign germ cell neoplasm that contains

is often present on radiographs and CT. Pediatric tumors

tissues that either derive from more than 1 of the embryonic

(Figure 24-20) .

that can result in blastic vertebral metastases include

germ layers or are foreign to the site of the lesion. Many

medulloblastoma, neuroblastoma , and Ewing sarcoma.

teratomas have tissues from all

Lytic metastases with other tumors sometimes convert to

are tissues of varying degrees of maturation and organiza­

sclerotic foci during chemotherapy.38

tion; cells with embryonal, fetal, and adult characteristics

A vertebra weakened by metastatic disease is at ele­

3

germinal layers. There

are often contained in a single tumor. Differentiation of

vated risk for a pathological fracture. At times, differen­

ectodermal elements can produce teeth, squamous epithe­

tiation between an osteoporotic vertebral fracture and

lium, and neural tissue. Mesodermal elements can produce

a pathological fracture due to metastasis is difficult. An

bone, cartilage, and muscle. Differentiation of endodermal

osteoporotic fracture most often consists of anterior wedg­

elements leads to gastrointestinal epithelium, respiratory

ing of the vertebral body, and there is usually normal sig­

epithelium, and mucous glands. Nongonadal teratomas

nal within the posterior elements on M R. An osteoporotic

apparently arise from primordial germ cells that are "mis­

compression fracture sometimes has the appearance of a

placed" during embryonic development.

well-defined band of abnormal signal extending across the

Teratoma is classified histologically into mature and

vertebral body, with preservation of adj acent normal mar­

immature types . The rate of recurrence following surgi­

row signaL

cal therapy is somewhat greater for the immature type.

Chapter 24 N eo p l a s m s a n d M a sses of the S p i n e 995 Malignant germ cell tumors of the sacrococcygeal region include yolk sac tumor and embryonal carcinoma; the term "malignant teratoma" is a misnomer. Teratocarcinoma is a very rare lesion in which there is malignant degenera­ tion of tissue elements within a benign teratoma, leading to a tumor such as a neuroblastoma. As with germ cell tumors in other locations , those arising in the sacrococ­ cygeal region sometimes produce a-fetoprotein. Most often, a sacrococcygeal teratoma has a large exter­ nal component that leads to a prompt perinatal diagnosis. Those that are completely or predominantly intrapelvic, however, may not be clinically obvious. Approximately s% of sacrococcygeal teratomas are first detected beyond the age of 2 years . Sacrococcygeal germ cell tumors that are detected in the newborn period are rarely malignant. The frequency of malignancy increases with the age at diagnosis, however. Overall, approximately IS% to 30% of all sacrococcygeal germ cell tumors are malignant. Sacrococcygeal germ cell tumors arise from the ante­ rior portion of the coccyx. Most often, the lesion extends

A

Figure 24-21 Malignant sacrococcygeal germ cell tumor (yolk sac). A. A sagittal T2-weighted fat·suppressed MR image of a 3-year­ old boy evaluated for a "small bump over the sacrum" shows a large presacral mass that has only a small external component (arrows) . The mass is predorninandy solid and has a somewhat heterogeneous composition. There is extension into the sacral

posteriorly and inferiorly to produce a clinically obvious external mass. Intrapelvic extension can occur concomi­ tantly or in isolation. A classification system for sacrococ­ cygeal teratoma has been developed by the Surgery Section of American Academy of Pediatrics. A type I tumor is almost entirely external. Type II has internal and external compo­ nents, with more than so% of the lesion external. A type I I I lesion also has a dumbbell configuration, but more then so% is internal. A type IV teratoma is entirely internal (presacral) . The likelihood of malignant histology increases with the degree of presacral involvement ( Figure 24-21 ) . The type IV lesion has the greatest frequency of malignant histology, and tends to be diagnosed later in infancy than the other types. Male gender is a risk factor for malignancy in these patients as well. Purely cystic sacrococcygeal germ cell tumors are nearly always benign, whereas purely solid lesions are associated with the greatest risk of malignancy; those with mixed cystic and solid composition are usually benign. Substantial calcification or ossification is unusual in a malignant germ cell tumor.

B

spinal canal. B. The lesion undergoes moderately intense contrast enhancement. There is a nonenhancing cyst inferiorly. Factors that favor a malignant lesion include presentation beyond infancy, male gender, predominantly presacral morphology, and solid composition.

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Although some fetuses with sacrococcygeal teratoma proceed to term with relatively uneventful pregnancies, these lesions often lead to clinically important complications. The fetal mortality rate in association with sacrococcygeal tera­ toma is nearly

so% when the tumor is discovered prior to 30

weeks of gestation.44 This lesion may cause in utero death, stillbirth, or a variety of obstetrical complications such as premature delivery, dystocia, intratumoral hemorrhage, or tumor avulsion. The earliest clinical sign of fetal sacrococ­ cygeal teratoma is an increase in uterine fundal height, due to a large teratoma andjor polyhydramnios. Fetal complica­ tions can result from compression of adjacent structures, such as the urinary tract or bowel. Arteriovenous shunting within the lesion can lead to high output cardiac failure and fetal hydrops. Other potential prenatal complications include polyhydramnios, oligohydramnios (due to urinary tract obstruction) , preterm labor, preeclampsia, and maternal fluid retention with hemodilution (mirror syndrome) .45-47 Prenatal sonography typically shows a sacrococcygeal teratoma as a large mass that extends externally from the base of the spine. Most often, the lesion has a heteroge­ neous character that includes cystic and solid components. Approximately 15% of sacrococcygeal teratomas are purely cystic.48 Doppler evaluation oftumorvascularity is an impor­ tant component of the prenatal examination. High fl ow and arteriovenous shunting are more often associated with a poor prognosis. A predominantly cystic lesion, even iflarge, is associated with a good prognosis.

An attempt should be

made to determine if there is an internal component of the tumor; this most often is located between the sacrum and the rectum. Rarely, intraspinal extension occurs. If sonog­ raphy is inconclusive, fetal MR provides greater imaging detail of the spinal canal and presacral space. 49 Tumor calcification or ossification is visible on standard radiographs in about half of infants with sacrococcygeal tera­ toma. Fat can result in subtle hypodense areas. Radiographs of the newborn with a large lesion sometimes show air collections due to tumor rupture during delivery. In those infants with substantial presacral disease, there may be

Figure 24-22 Sacrococcygeal teratoma. Small calcifications and subtle lucent areas of fat are visible in the sacrococcygeal mass on this lateral radiograph of a newborn infant. The sacrum is radiographically normal.

signs of displacement of adjacent structures. Contrast stud­ ies of the urinary tract and bowel are sometimes useful to characterize secondary involvement. Although these tumors arise from the coccyx, radiographic abnormalities of the sacrum and coccyx are usually not discernible

( Figure 24-22) .

A s with prenatal studies, sonography o f the newborn with teratoma allows tissue characterization and assess­ ment of the affects on adjacent structures. Those teratomas that are cystic usually have a multiloculated character, but some consist of a single or a few dominant cysts. Debris or fluid-fluid levels are sometimes present. The echogenicity often varies among individual cysts. Solid components of

Sacrococcygeal Teratoma Path ology

Rad iology

Coccygeal origin Tu mor cysts ± H emorrhage, protein

External andjor presacral mass M u ltiple variably-sized cysts Variable attenuation/signal i ntensity Flu id-fluid levels Foci of fat attenuation/signal i ntensity Foci of Ca++

the lesion are usually heterogeneous. Bone, teeth, and cal­ cifications may produce acoustic shadowing. Those lesions that are predominantly solid sometimes contain areas of necrosis or hemorrhage. The sonographic evaluation of the infant with a suspected sacrococcygeal tumor should include assessment of the kidrleys, bowel, and spine.

Ad i pose tissue Calcification/ ossification

.

.

Chapter 24 N eo p l a s m s a n d M asses of the S p i n e

A

Figure 24-23 Sacrococcygeal teratoma.

8

997

A A sagittal T2-weighted image of a 2-day-old infant shows a large predominantly cystic pelvic and abdominal mass. The cystic components of the tumor are hyperintense and the solid components are isointense. This teratoma has type I I I

morphology. There is extension of a small cyst into the sacral spinal canal {arrow) . B. The tumor cysts are hypointense on this T1-weighted fat-suppressed image obtained with intravenous gadolinium. There is anterior displacement of the contrast­ opacified urinary bladder.

Most teratomas have a heterogeneous tissue composi­ tion on CT, including cysts, fat, and calcium. Fluid-fluid levels are often present within cysts . Gas collections within 1 or more cysts can occur following the trauma associated with delivery. Osseous destruction or intraspi­ nal invasion (best demonstrated with reformatted coronal or sagittal images) is suggestive of malignant histology. MR is also an excellent imaging technique for the detec­ tion of presacral and intraspinal extension in infants with sacrococcygeal germ cell tumors ( Figure 24-23) . The mass is usually heterogeneous (Figure 24-24) . Foci of high signal intensity in T1-weighted images may occur due to adipose tissue, subacute hemorrhage, or cystic proteinaceous fluid. Bone and calcifications produce sig­ nal voids . Flow voids due to prominent vessels are some­ times present. Currarino syndrome is a specific malformation complex that sometimes includes a sacrococcygeal teratoma. This

is a clinical triad of (1) a low anorectal malformation such as congenital anorectal stenosis, (2 ) a curvilinear anterior sacral defect, and (3) a presacral mass ( Figure 24-25) . The presacral mass may be a teratoma, meningocele, enteric cyst, or a combination of lesions. Currarino syndrome often occurs as a familial disorder, although the expression varies among family members. The presacral mass that occurs in children with Currarino syndrome is often small and clinically occult. The radiographic finding of an anterior sacral defect in a child with a low anorectal malformation is in important clue to the diagnosis. Most often, the sacrum has a cres­ centic or sickle-shaped character. The associated presacral mass is located immediately adjacent to the osseous sacral defect. The teratomas that occur in children with Currarino syndrome are type IV presacral lesions. Despite the pre­ sacral location, these germ cell tumors are nearly always benign.

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Part 4 The S p i n e

A

Figure 24-24 Sacrococcygeal teratoma. A sagittal T2-weighted MR image documents a heterogenous composition of this lesion, including multiple hyperintense cysts. There are multiple small cysts in the portion of the mass adjacent to the coccyx (arrow) . There is no displacement of the rectum (R) or other evidence of presacral extension.

Hemangioma Vertebral hemangioma i s a benign vascular lesion that is relatively common in adults. This lesion apparently rep· resents an intraosseous venous malformation; therefore, the term "hemangioma" is incorrect. This lesion is distinct from the common congenital hemangiomas that occur in infants ; infantile hemangioma only rarely involves the spine. Most vertebral hemangiomas in adults and ado· lescents are asymptomatic. The lesion is solitary in about two-thirds of patients. Approximately

6o% of these lesions

occur in the thoracic portion of the spine. Histologically, vertebral hemangioma consists of prominent intraosse· ous endothelium-lined cavities that contain slowly flowing blood. There is often fatty infiltration of the adjacent mar­ row. Secondary trabeculae are thickened.so Vertebral hemangioma is a lesion of the vertebral body, although extension into the neural arch sometimes occurs.

B

Figure 24-25 Currarino syndrome.

A An anteroposterior radiograph of an infant with anorectal

atresia shows a sickle-shaped sacrum. B. A small asymptomatic presacral teratoma (arrows) is visible on this coronal MR image. An oval cyst in the tumor is slightly hyperintense to the solid components.

Chapter 24 N eo p l a s m s a n d M asses of the S p i n e 999 Standard radiographs typically show parallel linear scle­ rotic bands in the involved vertebral body. CT shows irreg­ ular destruction of the central aspect of the vertebral body, with sclerosis and thickening of the remaining trabeculae. Classically, there is a "corduroy" appearance due to promi­ nent vertical trabeculae and interspersed fat. The lesion is typically somewhat hyperintense on both T1-weighted (due to adipose tissue) and T2-weighted MR images. Prominent contrast enhancement occurs with both CT and MR. Extraosseous extension occasionally occurs, potentially leading to cord compression. 5 '

Langerhans Cell H istiocytosis Langerhans cell histiocytosis (LCH) is a proliferative dis­ order that can affect multiple organ systems. The skeletal lesions ofLCH are focal granulomas that contain histiocytes

A

Figure 24-26 Langerhans cell histiocytosis; vertebra plana. A, B. AP and lateral lumbar spine radiographs show marked collapse of the 4 vertebral body. As is typical of LCH , the loss

and eosinophils. The vertebral body is the most common site of spinal involvement, occasionally with extension into the posterior elements. Isolated involvement of the posterior elements is uncommon. The thoracic region is the most common site of vertebral LCH, followed by the lumbar and cervical regions . The lesions can be solitary or multiple; a radiographic skeletal survey is helpful for con­ firming the diagnosis in a patient with a vertebral lesion. Some children with vertebral LCH are asymptomatic. Back pain, often mild, can occur. Symptoms are occasionally related to a pathologic fracture. 5 2-54 The classic imaging feature of vertebral LCH is vertebra plana, that is, wafer-like collapse of the body (Figure 24-26) . There is preservation of the adjacent discs. The discs are often expanded due to the loss of height of the vertebral body (Figure 24-27) . Earlier in the course of the disease, imaging studies show small irregular

B

of height is less pronounced posteriorly. The adjacent disc spaces are normal. There are mixed lucent and sclerotic alterations in the L3 vertebral body as well.

1 000

Part 4 The S p i n e

Figure 24-27 Langerhans cell histiocytosis; vertebra plana. A sagittal T2-weighted M R image shows marked flattening of the Tu vertebral body (arrow) . Preservation of the discs is characteristic; the hyperintense discs are slightly widened due the vertebral body collapse.

radiolucencies in the centrum. Subsequent collapse of the body is often insidious . The extraosseous soft tissue component of vertebral body LC H tends to be relatively small. This tis sue can extend into the spinal canal or a neural foramen. Paraspinal soft tissue prominence adj a­ cent to a thoracic spine focus of LC H is sometimes visible on

frontal

radiographs

(Figure 24-28) .

LC H of the poste­

rior elements usually appears on imaging studies as a geo­ graphic lytic lesion. The character of bone destruction is

M R is often superior (Figure 24-29) . The soft tissue component enhances with IV contrast on CT

best demonstrated with CT, whereas

for depicting the soft tissue component and M R . 55

Figure 24-28 Langerhans cell histiocytosis. An anteroposterior radiograph of a teenager with vague back pain shows 2 partially collapsed vertebral bodies (arrows) . There is slight para spinal soft tissue prominence to the left of the T9 lesion.

Chapter 24 N e o p l a s m s a n d M asses of the S p i n e

1 001

paraspinal neoplasms associated with intraspinal exten­ sion are neurogenic tumors, such as neural crest tumors (e.g., neuroblastoma) and neurofibroma (see earlier discus­ sion of intradural neurofibroma) . Other potential lesions include rhabdomyosarcoma, peripheral primitive neuroec­ todermal tumor, leukemic chloroma, and extramedullary hematopoiesis.

Neural Crest Tu mors The neural crest tumors include neuroblastoma, ganglia­ neuroblastoma, and ganglioneuroma. These lesions typi­ cally arise from the adrenal gland or sympathetic ganglia. Paraspinal sites of origin are the next most common after the adrenal glands. The

3

pathological types comprise a

spectrum that ranges from the frankly malignant neuro­ A

blastoma to the benign ganglioneuroma, with ganglia­ neuroblastoma representing an uncommon intermediate form. Neuroblastoma most often occurs in infants and young children, whereas ganglioneuromas typically are not discovered until the second or third decades of life. Ganglioneuroblastoma most often presents in young children. Intraspinal extension of a paravertebral neural crest tumor most often occurs via

1 or more neural foramina.

The intraspinal component typically is confined to the extradural space. Although the involved neural foramina are enlarged, more extensive bone destruction is usually lacking. Neurological signs and symptoms occur when there is compression of the spinal cord or nerve roots . A mass in the apex of the thorax can cause Horner syndrome. In infants , the initial presenting findings may include irri­ tability, constipation, and pain with limb motion. Potential findings in older children include motor signs , back pain, and sphincter dysfunction . Muscle weakness can progress B

Figure 24-29 langerhans cell histiocytosis. This 22-month-old girl presented with a 3-week history of progressive torticollis and neck pain. A. Contrast-enhanced CT (bone window) shows a lytic lesion (arrow) of the left side of C 2 . Adjacent soft tissue fullness is present. There is no appreciable new bone formation or matrix calcification. B. The enhancing soft tissue component of the lesion ( arrows) is better visualized on this T!-weighted MR image. There is a small extradural component in the left side of the spinal canal.

to complete paraplegia or quadriplegia over a period of hours to days . Approximately

s o%

of children with myo­

clonic encephalopathy of infancy (opsoclonus-myoclonus cerebellar ataxia syndrome) have a thoracic paraspinal neuroblastoma. The

3

types of paraspinal neural crest tumors have

similar imaging appearances , unles s manifestations of metastatic disease are present. Osseous and lymphatic metastasis are common with neuroblastoma. Identical patterns of spread can occur with ganglioneuroblastoma. The paraspinal mass is usually discernible on standard radiographs; concomitant neural foramina! enlargement is strongly suggestive of this diagnosis. If there is a large intraspinal component, radiographs may show focal wid­ ening of the spinal canal, thinning of the pedicles and

PARASPINAL TUMORS The paraspinal soft tissues consist of muscles , peripheral nerves, and connective tissue that can give rise to vari­

lamina, and posterior vertebral body scalloping. Thoracic neural crest tumors often are accompanied by erosion and thinning of posterior ribs. The osseous effects of a paraspinal neural crest tumor

CT. CT myelography is an MR for definition of the intraspinal extent.

ous neoplasms . Intraspinal extension of these lesions can

are best demonstrated with

lead to neurological manifestations. The most common

alternative to

1 002

Part 4 The S p i ne for these children to detect bone metastasis; the combina­ tion of "hot" and "cold" vertebral lesions is characteristic of metastatic neuroblastoma. MR is generally the optimal imaging technique for the characterization of intraspinal extension of a para­ spinal neural crest tumor (Figure 24-31 ). Most often, the mass is approximately isointense to nervous tis­ sue on Tl-weighted images and mildly hyperintense on T2-weighted images. Calcification may lead to signal voids. The contrast enhancement pattern is usually somewhat heterogeneous . Intraspinal extension through 1 or more neural foramina may result in dumbbell morphology. The spinal cord and nerve roots in the region of the tumor are usually displaced, but not frankly invaded; the lesion typically remains extradural. With marked compression, the involved segment of cord may appear deformed and edematous.

Peri pheral Pri m itive Neu roectodermal Tu mor

Figure 24-30 Neuroblastoma. A posterior image of a child with neuroblastoma demonstrates avid accumulation of'23MIBG in vertebral, pelvic, and proximal femoral metastases.

Peripheral primitive neuroectodermal tumor can arise nearly anywhere in the body, including the meninges and paraspinal soft tissues. These small round cell tumors often have a heterogeneous composition, including cysts and necrosis. The viable solid portions are usually isoatten­ uating to slightly hyperattenuating relative to normal spinal cord on CT. On M R, the solid components are isointense to slightly hypointense on T1-weighted images and isoin­ tense to slightly hyperintense on T2-weighted images. The degree and pattern of contrast enhancement vary some­ what between patients. A peripheral primitive neuroecto­ dermal tumor that arises from the meninges may appear as an entirely intraspinal extradural mass, with or without bone destruction. Those that arise in the paraspinal region commonly extend into the spinal canal via 1 or more neu­ ral foramina, resulting in a dumbbell configuration. The imaging appearance is often similar or identical to that of a paraspinal neural crest tumor; calcification is not common with this lesion, however.

Hamartoma hamartoma is a malformation that consists o f a mixture of normal tissues in an abnormal location. Spinal ham­ artomas are composed of mesodermal elements such as muscle, fat, cartilage, and bone. These are dorsal skin­ covered lesions that occur in the midline of the midtho­ racic, thoracolumbar, and lumbar regions. Associated cutaneous angiomas may be present. Radiographs show spina bifida in more than so% of these patients and wid­ ening of the spinal canal in approximately 8o%. The char­ acteristics of the mass on CT and M R are determined by the tissue composition; osseous elements are visible in approximately so%.

A

Calcification is commonly present within all 3 forms of neural crest tumors , and can also occur in metastatic lymphadenopathy. Involvement of the vertebral column with metastatic disease in patients with neuroblastoma and ganglioneuroblastoma may result in vertebral body destruction, sometimes with extension of an extraosse­ ous soft tissue mass into the spinal canal. Most neural crest tumors avidly accumulate bone-seeking radiophar­ maceutical and ' 2 3M J B G (metaiodobenzylguanidine) (Figure 24-30) . Skeletal scintigraphy is typically indicated

Chapter 24 N eo p l a s m s a n d M asses of the S p i n e 1 003

A

B

Figure 24-31 Neuroblastoma.

A A gadolinium-enhanced fat-suppressed T1-weighted M R image of a n u-month-old child with acute onset of lower extremity weakness shows a large left thoracic paraspinal mass, with intraspinal extension via an enlarged neural foramen. There is marked displacement and partial

EPIDURAL MASSES

The MR appearance of epidural lipomatosis is diffuse prominence of the epidural fat, with compression and

Extramed u l lary Hematopoiesis

displacement of the thecal sac and spinal cord. On axial

Extramedullary hematopoiesis is a rare cause of epidural and paravertebral (thoracic) masses. Patients with this complication have a long-standing chronic anemia, such as thalassemia. Paravertebral lesions in these patients are usually asymptomatic, and are discovered inciden­ tally on imaging studies.

c

encasement of the cord. B . A T2-weighted sagittal image shows involvement of 2 upper thoracic neural foramina and widening of adjacent intercostal spaces . C. Extensive intraspinal disease is visible on this gadolinium-enhanced T1-weighted sagittal sequence.

Epidural involvement can

progre ss to symptomatic cord compres sion. MR shows homogeneous thickened epidural

soft tis sue,

images, the epidural fat may assume a convex character at the margin of the dura. With severe circumferential lipo­ matosis, the compressed lumbar thecal sac sometimes has a Y-shaped appearance on axial images

(Figure 24-32) .

S calloping o f vertebral bodies i s a rare associated finding. Occasionally, there is increased signal intensity in the com­ pressed cord on T2-weighted images. 56-5 8

some­

times with a nodular character. There is intense contrast enhancement.

Epid u ral Leu kemic Deposits Leukemic involvement of the spine most often occurs in the form of marrow infiltration. However, leukemic depos­

Epid u ral Lipomatosis

its can also occur in the spinal epidural space. Focal soft

S pinal epidural lipomatosis consists of diffuse over­

myelogenous leukemia are termed granulocytic sarcomas

growth of nonencapsulated adipose tissue in the epi­

or chloromas . Epidural leukemic deposits can lead to clini­

dural space. This is a rare abnormality in children, and

cal manifestations of meningeal irritation. Occasionally,

tissue deposits of leukemia cells in patients with acute

can occur in obese individuals and those receiving long­

there are findings of spinal cord compression or nerve root

term steroid therapy. The idiopathic form is very rare .

involvement. Pathologically, epidural leukemic deposits

The potential clinical manifestations include back pain,

occur as

paresthesias, and progressive paraplegia. The clinical

lesions are best detected on contrast-enhanced M R; promi­

1 or more masses, or as diffuse infiltration. The

manifestations of the myelopathy usually predominate

nent homogeneous enhancement is typical. The epidural

in the thoracic region, as this is the narrowest portion of

lesions are usually approximately isointense to neural tis­

the spinal canal.

sue on unenhanced MR sequences .

1 004

Part 4 The S p i n e

B

Figure 24-32 Epidural lipomatosis. A. A T1-weighted sagittal MR image of a child undergoing

A

treatment for acute myeloid leukemia shows prominent epidural fat, particularly in the lumbosacral region where there are early manifestations of vertebral body scalloping. B. The compressed thecal sac has a Y-shape on this axial image at the lumbosacral junction.

R E F E R E N C ES 1. )allo GI, Freed D, Epstein F. Intramedullary spinal cord tumors in children. Childs Nerv Syst. 2oop9 ( 9 ) : 641-649 · 2. Steinbok P, Cochrane DD, Poskitt K. Intramedullary spinal cord tumors in children. Neurosurg Clin N Am. 1992;3 (4): 931-945 . 3 - Constantini S , Houten ) , Miller D C , e t al. Intramedullary spinal cord tumors in children under the age of 3 years. ] Neurosurg. 1996;85 (6) :1036-1043 . 4· Muraszko K, Youkilis A. Intramedullary spinal tumors of disordered embryogenesis. ] Neurooncol. 2ooo;47(3):271-281.

7· Auguste KI. Gupta N. Pediatric intramedullary spinal cord tumors. Neurosurg Clin N Am. 2006 ;17(1) :51-61. 8. Nadkarni TD, Rekate H L. Pediatric intramedullary spinal cord tumors. Critical review of the literature. Childs Nerv Syst. 1999;15 (1) :17-28. 9 · Baleriaux DL. Spinal cord tumors. Bur Radio!. 1999;9(7): 1252-1258. 10. Grabb PA, Kelly DR, Fulmer B B , Palmer C . Radiation-induced glioma of the spinal cord. Pediatr Neurosurg. 1996;25 (4): 2 J4-219.

5· Epstein F). Spinal cord tumors in children. J Neurosurg. 1995; 82 (3) :516-517.

n. Chelcun )L, Pope RS. Spinal cord astrocytomas: rare but life­ threatening tumors in children. JAAPA. 2009;22(6): 37-41·

6. Zelcer S, Keene D, Bartels U, et al. Spinal cord tumors in children under the age of 3 years: a retrospective Canadian review. Childs Nerv Syst. 2on;27 (7) :1089-10 94 ·

12. Rossitch E )r, Zeidman SM. Burger PC, et al. Clinical and pathological malysis of spinal cord astrocytomas in children. Neurosurgery. 199 0;27(2) :193-196.

Chapter 24 N eo p l a s m s a n d M asses of the S p i n e 13- Koeller KK, Rosenblum RS, Morrison AL. Neoplasms of the spinal cord and filum terrninale: radiologic-pathologic correlation. Radiographies. 2ooo;2o(6) :t721-1749 ·

1 005

32. Yoshiura T, Shrier DA, Pilcher WH, Rubio A. Cervical spinal meningioma with unusual MR contrast enhancement. A]NR Am J Neuroradiol. 1998;19 (6) :1040-1042.

14· Kulkarni AV, Armstrong DC, Drake J M . M R characteristics of malignant spinal cord astrocytomas in children. Can ] Neural Sci. 1999;26(4):290-2 93·

33· Fenoy A ) . Greenlee ) D , Menezes AH, e t a l . Primary bone tumors of the spine in children. ] Neurosurg. 2oo6;105(4 suppl) : 252-260.

15. Larson D B , Hedlund GL. Non-enhancing pilocytic astrocytoma of the spinal cord. Pediatr Radial. 2oo6;36 (12):1312-I315.

34· Tian Y, Yuan W, Chen H , Shen X. Spinal cord compression secondary to a thoracic vertebral osteochondroma. J Neurosurg. 2ou;15 (3) :252-257-

16. Benesch M , Weber-Mzell D , Gerber NU, et al. Ependymoma of the spinal cord in children and adolescents: a retrospective series from the H IT database. J Neurosurg Pediatr.

2010;6(2) :137-144· 17. Kahan H, Sklar EM, Post M ) . Bruce ) H . MR characteristics of histopathologic subtypes of spinal ependymoma. AJNR Am J Neuroradiol. 1996;t7(I) :143-150. 18. Fountas KN, Karampelas I. Nikolakakos LG, et al. Primary spinal cord oligodendroglioma: case report and review of the literature. Childs Nerv Syst. 2oos ;2t(2):t71-175·

35. Gunay C, Atalar H, Yildiz Y, Saglik Y. Spinal osteochondroma: a report on six patients and a review of the literature. Arch Orthop Trauma Surg. 2oiO;I30(12) :1459-1465. 36. Srikantha U, Bhagavatula ID, Satyanarayana S , e t al. Spinal osteochondroma: spectrum of a rare disease. J Neurosurg. 2oo8;8(6) :561-566. 37· Lotfinia I , Vahedi P, Tubbs RS, e t a l . Neurological manifestations, imaging characteristics, and surgical outcome of intraspinal osteochondroma. ] Neurosurg. 2010;12 (5) :474-489.

19. Patel U, Pinto RS, Miller DC, et al. MR of spinal cord ganglioglioma. AJNR Am] Neuroradiol. 1998;t9 (5) : 879-887.

38. Guillevin R, Vallee JN, Lafitte F , et al. Spine metastasis imaging: review of the literature. ] Neuroradiol. 2007;34(5):311-321.

20. Park S H , Chi )G, Cho B K, Wang KC. Spinal cord ganglioglioma in childhood. Pathol Res Pract. 199P89(2) :t89-19 6.

3 9 · Wippold F) 2nd, Koeller KK, Smimiotopoulos )G. Clinical and imaging features of cervical chordoma. A] R Am J Roentgenol. 1999;172 (5) :1423-1426.

21. Chu BC, Terae S , Hida K. e t a l . M R findings i n spinal hemangioblastoma: correlation with symptoms and with angiographic and surgical findings. AJNR Am J Neuroradiol.

200I;22 (I) :2o 6-217. 22. Baker KB, Moran C), Wippold F) 2nd, et al. MR imaging of spinal hemangioblastoma. AJR Am] Roentgenol. 2ooo; 174 (2):377-3 82. 23- Bekar A, Cordan T, Evrensel T, Tolunay S . A case of primary spinal intramedullary lymphoma. Surg Neural. 2001;55(5): 26!-264. 24. Caruso PA, Patel M R, joseph ) . Rachlin ) . Primary intramedullary lymphoma of the spinal cord mimicking cervical spondylotic myelopathy. AJR Am J Roentgenol. 199 8;t7J(2) :

52 6-527-

40. Zacay G, Eyal A, Shacked I, et al. Chordoma of the cervical spine. Ann Otol Rhinal Laryngol. 2ooo;109 (4):438-440. 41. Uauger ) , Palmer ) , Amores S , et al. Primary Tumors of the Sacrum: Diagnostic Imaging. AJR Am] Roentgenol. 2000 2000;174(2) :417-424. 42. Parkes SE, Muir KR, Southern L, et al. Neonatal tumours: a thirty-year population-based study. Med Pediatr Oneal. 1994;22 (5):3o9-317. 43· Rao S , Azmy A, Carachi R. Neonatal tumours: a single-centre experience. Pediatr Surg Int. 2oo2;18(s-6):3o6-309. 44· Garmel S H , Crombleholme TM, Semple )P, Bhan I . Prenatal diagnosis and management of fetal tumors. Semin Perinatal. 1994;18(4):3so-365.

25. Khong PL, Goh WH, Wong VC, et al. M R imaging of spinal tumors in children with neurofibromatosis 1. AJR Am J Roentgenol. 2oop8o (2) :413-417.

45· Bond S ) . Harrison MR, Schmidt KG , e t al. Death due t o high­ output cardiac failure in fetal sacrococcygeal teratoma. ] Pediatr Surg. 1990;25(12) :1287-1291.

26. Acosta FL )r, Quinones-Hinojosa A, Schmidt M H , Weinstein

46. Chisholm CA. Heider AL, Kuller )A, et al. Prenatal diagnosis and perinatal management of fetal sacrococcygeal teratoma. Am ] Perinatal. 1999;16(2) :89-92.

PR. Diagnosis and management of sacral Tarlov cysts. Case report and review of the literature. Neurosurg Focus.

2oop5 (2) : E15. 27. Davis SW, Levy LM, LeBihan D), et al. Sacral meningeal cysts: evaluation with MR imaging. Radiology. 1993;187(2): 445-448. 28. Chang IC, Chou MC, Bell WR, Lin Z l . Spinal cord compression caused by extradural arachnoid cysts. Clinical examples and review. Pediatr Neurosurg. 2004;40(2)70-'74·

29. Nabors MW, Pait TG, Byrd EB, et al. Updated assessment and current classification of spinal meningeal cysts. J Neurosurg. 1988;68(3) :366-377· 30. Khosla A, Wippold F) 2nd. CT myelography and MR imaging of extramedullary cysts of the spinal canal in adult and pediatric patients. AJR Am J Roentgenol. 2002;I78(1) :201-207.

31. Soeda A, Sakai N, Iihara K. Nagata I. Cobb syrtdrome in an infant: treatment with endovascular embolization and corticosteroid therapy: case report. Neurosurgery. 2003;52(3) : 711-715; discussion 714-715.

47· Vidaeff AC, Pschirrer ER, Mastrobattista J M , et al. Mirror syrtdrome. A case report. ] Reprod Med. 2002;47(9) :770-774· 48. Coleman BG, Adzick N S , Crombleholme TM , et al. Fetal therapy: state of the art. J Ultrasound Med. 2002;21(11) :1257-1288. 49· Woodward P). Sohaey R, Kennedy A, Koeller KK. From the archives of the AFIP: a comprehensive review of fetal tumors with pathologic correlation. Radiographies. 2005;25 (1) :

215-242. 50. Baudrez V, Galant C, Vande Berg BC. Benign vertebral hemangioma: MR-histological correlation. Skeletal Radial. 2001;3o (8) :442-446. 51. Ross ) S , Masaryk T) . Modic MT, e t al. Vertebral hemangiomas: MR imaging. Radiology. 1987;165 (1):16s-169. 52. Brown CW, Jarvis )G, Letts M , Carpenter B . Treatment and outcome of vertebral Langerhans cell histiocytosis at the Children's Hospital of Eastern Ontario. Can ] Surg. 2005 ;48(3) :

230-236.

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53 - Garg S , Mehta S , Dormans J P . Langerhans cell histiocytosis of the spine in children. Long-term follow-up. ] Bone joint Surg Am. 2004;86-A(8):174D-175 0 . 5 4 · Levine SE, Dormans JP, Meyer J S , Corcorart TA. Lmgerhans' cell histiocytosis of the spine in children. Clin Orthop Relat Res. 199 6 (323):288-29} 55· Azouz EM, Saigal G, Rodriguez MM, Podda A. Langerhans' cell histiocytosis: pathology, imaging and treatment of skeletal involvement. Pediatr Radio!. 200s;J5 (2) :103-115. 56. Munoz A, Barkovich JA, Mateos F, Simon R. Symptomatic epidural lipomatosis of the spinal cord in a child: M R

demonstration o f spinal cord injury. Pediatr Radio!. 2002; 32(12) :865-868. 57· Roy-Camille R, Maze! C, Husson J L, Saillmt G. Symptomatic spinal epidural lipomatosis induced by a long·term steroid treatment. Review of the literature and report of two additional cases. Spine. 1991;16 (12) :1365-1371· 58. Hogg JP, Shank T, Gingold M, et al. Childhood presentation of idiopathic epidural lipomatosis: a case report with magnetic resonance imaging and pathologic confirmation. J Child Neural. 1996; n (3):236-240 .

CH A P T E R

25

Trauma and Surgery of the Sp ine

CERVICAL SPI N E TRAU MA . . . . . . . . . . . . . . . . . . . . . . . . . . 1 007

Chance Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 02 6

Radiographic Signs of I nj u ry . . . . . . . . . . . . . . . . . . . . . . . 1 008

Fracture Dislocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 027

Atlantoocci pital Dislocation . . . . . . . . . . . . . . . . . . . . . . . . . 1 01 0 Atlas Fractures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 01 1

Spinous Process and Tra nsverse Process Fractures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 027

Axis Fractu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 01 1

Acute Spondylolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 02 9

Atlantoaxial Rotatory Fixation . . .. .. .. . . . . . . . . . . . . . 1 01 1

Spondylolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 02 9

Atlantoaxial and Atlantooccipital I n stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 01 3

Spondylolisthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 032

M id and Lower Cervical Spine Fractures . . . 1 01 5

Schmorl N ode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 037

Spinal Cord and N erve Root I nj u ries . . . . . . . . . . 1 020 Spinal Cord Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 020

SU RC E RY AND I NTERVENTIONS . . . . . . . . . . . . . 1 037

Brachial Plexus Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 021

Spinal Cord I nfarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 037

THORACIC AND LU M BAR SPI N E TRAUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 023

Lu m bar Puncture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 03 8

Vertebral Com pression Fractu res . . . . . . . . . . . . . . . 1 024 .

Apophyseal Ring Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 024 Bu rst Fractu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 02 6

CERVICAL SPINE T RAUMA About half of vertebral fractures and substantial ligamen­ tous injuries of the spine in children occur in the cervical region. However, serious cervical spine injuries in children are rare. This relates in part to the resilient nature of liga­ ments and bones in children. In addition, young children are infrequently exposed to high-force injury mechanisms. In infants and young children, child abuse and birth trauma are the most common mechanisms of cervical spine trauma. Birth-related injuries of the spine and spinal cord most often are associated with a traumatic breech delivery. These injuries are usually in the lower cervical or upper thoracic region, and often result from traction forces. Spine injuries suffered during cephalic delivery tend to occur in the upper cervical region, and typically involve rotational forces. In older children and teenagers with spine injuries, common mechanisms include diving, sports injuries, and

Disc Hern i ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 035

Epid u ral Anesthesia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 03 9 Baclofen Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 03 9

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 040

motor vehicle incidents. The prevalence of pediatric cer­ vical spine injuries increases with age. In older patients, the mid and inferior aspects of the cervical spine are most commonly involved, whereas infants and young children tend to suffer injuries at the C3 level or higher. Because the pediatric spine has greater elasticity than the spinal cord (which is fixed by nerve roots) , trauma-related neu­ rological injuries can occur in the absence of fractures or malalignment.•-3 Cervical spine injuries range from mild ligamentous injuries to severe fracture-dislocations, with or without spinal cord involvement. The 5 major mechanisms con­ sist of flexion, extension, lateral flexion, rotation, and axial compression. With excessive flexion, compressive force is applied to the anterior aspect of the vertebra, and distrac­ tion force posteriorly; this can lead to an anterior verte­ bral body fracture and posterior ligamentous disruption. Extension injuries subject the vertebrae to compressive 100]

1 008 Part 4 The S p i n e forces dorsally and distracting forces anteriorly; fractures of the articular facets , pillars, and posterior elements may occur, as well as vertebral body avulsion injuries . Lateral flexion mechanisms can lead to vertebral compression injuries , fractures of the transverse or uncinate processes, and contralateral avulsion of the brachial plexus. Rotation injuries can cause locked facet, rotatory subluxation, or rotatory fixation; there are usually concomitant flexion or extension injuries . Burst-type fractures can result from axial compression forces. The most common cervical spine fractures in children occur in the vertebral bodies ; more than half involve the C 6 o r C 7 vertebral bodies . Neural arch fractures o f the cervical spine are uncommon in children. The most common site is the articular pillar, especially at the C6 level. These frac­ tures are difficult to detect on standard radiographs; CT is diagnostic. Other neural arch fractures are less common. Laminar fractures tend to occur at the C5 and C6 levels . Most spinous process fractures involve C 6 o r C7- Fractures of the pedicles tend to occur at the C2 level. Transverse pro­ cess fractures are rare in the cervical spine; the C7 level is the most frequent site of this injury. Approximately 5 % to

10% of pediatric cervical spine An additional

fractures involve the dens, usually at the base. 5 % to

10% of fractures involve the body or neural arch of

the axis. Fractures of the atlas account for approximately 5 % of pediatric cervical spine fractures ; these are usually burst or focal arch fractures . The upper cervical spine can also be involved with atlantoaxial dislocation or atlantooc­ cipital dislocation injuries .

Curvature The normal cervical spine assumes a mild lordotic curve in the neutral position, as viewed on a lateral radiograph. The cervical spine should be straight on the frontal view. Deviation from this appearance raises the pos sibility of muscle spasm or osseous or ligamentous injury. On the lateral proj ection, neck muscle spasm leads to straighten­ ing of the cervical spine or mild kyphosis . Unlike adults and teenagers, however, isolated lack of lordosis is com­ mon in normal children. The apex of spasm-related kypho­ sis is usually located at the C2-C3 level. Localized kyphosis at other levels may be an indicator of dorsal ligamentous injury. On the frontal projection, muscle spasm leads to scoliosis or torticollis .

Prevertebral Soft Tissues Proper evaluation of a lateral neck radiograph of the child who has suffered trauma requires careful assessment of the paravertebral soft tissues. On a properly positioned lat­ eral neck radiograph without swallowing artifact, the ret­ ropharyngeal space (posterior pharyngeal wall at C2-C3 to the anterior margin of the vertebra) should be 7 mm or less and the upper retrotracheal space (distance between the trachea and the vertebra at C4-C5) should be

14 mm or less.

The prevertebral soft tissues at the C6-C7 level should be 21 mm or less . As a rule, the width of the normal prevertebral soft tissue space below the level of the glottis is less than twice the anterior-posterior diameter of the adjacent verte­ bral body. The width of the normal retropharyngeal space is less than the anteroposterior diameter of the second cervi­

Radiographic Signs of I nj u ry

cal vertebra.

Selection of the optimal diagnostic imaging approach to

presence of hemorrhage or edema, and therefore is an

the child with suspected cervical spine trauma requires consideration of the specific situation. These concepts are reviewed in the American College

of Radiology

Appropriateness Criteria (www. acr.orgjac) . For adults and most older children with acute cervical spine trauma, heli­

cal CT is the procedure of choice. In many institutions, a three view radiographic examination is the usual evalua­ tion method for young children (AP , lateral, and open­ mouth frontal views) ; CT is reserved for those patients who require additional characterization of a known fracture and those for whom there is a high clinical suspicion of a radio­ graphically occult inj ury. MR is sensitive for demonstrating marrow edema due to a vertebral injury and for detect­ ing ligamentous injuries. M R is the technique of choice for patients with suspected cord injury, nerve root injury, or intraspinal hemorrhage. Flexion and extension lateral

Prevertebral soft tis sue widening can indicate the important indicator of possible osseous or ligamentous injury of the cervical spine. However, this finding is often lacking in the presence of a mild compression fracture or a nondisplaced fracture of the den s . The most common cause of prevertebral soft tissue thickening is artifact due to swallowing or neck flexion . Findings that suggest patient swallowing during image acquisition include air in the esophagus, distortion of the hypopharynx, and elevation of the glottis. Ancillary findings that are some­ times helpful for identifying change s due to a true cer­ vical spine injury include anterior displacement of the airway and anterior displacement of the prevertebral fat stripe.

Predental Space

radiographs andjor fluoroscopy are of benefit for selected

Widening of the predental space (atlas-dens interval) is an

patients to detect ligamentous injuries , although MR has

important radiographic indicator of potential ligamentous

greater sensitivity for this indication. Flexion and exten­

or osseous injuries in this region. This is defined as the dis­

sion radiographs should only be performed if the patient

tance from the anterior aspect of the dens to the posterior­

is responsive and able to report pain during positioning

inferior margin of the anterior arch of the atlas. In adults,

maneuvers .

the predental space measures 2 . 5 mm or less . However,

Chapter 25 Tra u m a a n d S u rgery of the S p i n e 1 009 the measured distance on a lateral radiograph is up to 4 - 5 m m i n normal children. O n CT, the predental space should measure less than 2 . 6 mm. Variations of up to 3 mm can occur between flexion and extension in children. In gen­ eral, pathological widening of the predental space suggests disruption of the transverse ligament that bridges C1 and the dens. Disruption of this ligament is uncommon, how­ ever, even with a fracture of the dens; most instances of pre­ dental space widening are artifactual or related to chronic abnormalities such as Down syndrome, rheumatoid arthri­ tis, or dens hypoplasia.4

Alignment Abnormal vertebral body alignment as viewed on a lateral cervical spine radiograph can occur in the presence of a fracture or ligamentous injury. Most often, there is ante­ rior displacement of a vertebral body with respect to the next most inferior vertebra. This type of malalignment is usually associated with a flexion injury or, less commonly, a rotatory or extension injury. Posterior displacement of a cervical vertebral body with respect to the subjacent verte­ bra occasionally occurs during the acute phase of an exten­ sion injury. Lateral vertebral body displacement can occur in the presence of a fracture-dislocation.

A

Figure 25-1 Type I I odontoid fracture. This 4-year-old child suffered a hyperflexion injury when he was struck in the head by a truck tailgate. A. A lateral radiograph shows anterior displacement of the odontoid process and wid­ ening of the synchondrosis. The C2 spinous process projects

B

The appearance of anterior vertebral body displace­ ment in the upper portion of the pediatric cervical spine must be interpreted with caution, because mild dis­ placement occurs as a normal finding. This physiologic displacement can involve the upper 4 vertebral bodies or C2 on C3 only. The physiologic nature of the displacement is obvious when multiple vertebral bodies are involved. Isolated anterior displacement of C2 on C3 is more easily confused with true pathology such as a neural arch frac­ ture of C2. Assessment of the posterior element alignment and the prevertebral soft tissues is helpful in differentiat­ ing physiological versus pathological localized cervical ver­ tebral body displacement. Assessment of the posterior cervical line is often use­ ful for evaluating apparent localized anterior subluxation of C2 on C3. This line extends from the anterior aspect of the cortex of the spinous process of C1 to the same point on C3 (see Chapter 2 2 ) . With physiologic subluxation, the anterior cortex of the C2 spinous process is within 2 mm of the posterior cervical line. Injuries that cause excessive deviation of the C2 spinous process from the posterior cervical line include odontoid fractures, atlan­ toaxial subluxation due to a transverse atlantal ligament disruption, C2 neural arch fractures, and C2-C3 disloca­ tion (Figure 25-1 ) .

posterior to the posterior cervical line due to anterior displace­ ment of C1. There is prevertebral soft tissue prominence (arrows) . B. A sagittal CT image confirms a fracture through the synchon­ drosis of the odontoid. There are small fracture fragments adja­ cent the base of the displaced odontoid.

1010 Part 4 The S p i n e

Disc Spaces Alterations in disc space height can occasionally occur with cervical spine trauma. Disc space narrowing usually is related to a flexion or rotation injury, whereas pathologic disc space widening is associated with an extension injury. Normally, the intravertebral disc spaces are of equal height throughout the cervical spine. Disc space widening or nar­ rowing is best appreciated on a properly positioned lateral radiograph or a reformatted CT image. MR may show sig­ nal abnormality within the injured disc.

Apophyseal joints The lateral cervical spine radiograph of a child who has experienced trauma should be carefully evaluated for align­ ment of the apophyseal joints. An abrupt discrepancy in apophyseal joint alignment is suggestive of a locked facet due to rotatory subluxation. The involved apophyseal joint may also appear widened or narrowed. Apophyseal joint dislocation is usually related to a flexion mechanism.

Spinous Processes Alignment of the spinous processes should be carefully evaluated on both the frontal and lateral cervical spine views. Posterior spinal ligament disruption with a hyper­ flexion injury typically leads to widening of the interspi­ nous distance at the involved site. The widening increases on flexion views. It is important to recognize that there is substantial variation in the interspinous distance at C1-C2 in normal individuals. Focal deviation of spinous process alignment on the frontal view can indicate the presence of an underlying vertebral arch fracture or unilateral locked facet. With uriilateral locked facet, the superior spinous process is displaced toward the side of locking.

Atlantooccipital Dislocation Atlantooccipital dislocation (occipitoatlantal dissociation) is a rare injury that is due to stretching or disruption of the tectorial membrane and the alar ligaments. This injury is usually associated with a deceleration mechanism in which the head moves forward and the torso is restrained. Atlantooccipital dislocation is usually fatal, due to associated damage to the brainstem and cervical spinal cord. Vascular injuries and damage to cranial nerves and upper cervical spinal nerves can also occur. Infants and young children are relatively susceptible to this injury due to their small occipi­ tal condyles and horizontally oriented atlantooccipital joints. Radiographs of patients with atlantooccipital disloca­ tion show malalignment and widening at the craniocervical junction (Figure 25-2) . Because there is usually no associ­ ated fracture, the imaging diagnosis requires visualiza­ tion of malalignment. In some instances, the findings on standard radiographs are subtle. Sagittal and coronal refor­ matted CT images best demonstrate the pathological anat­ omy. Occasionally, there is an associated occipital condyle

Figure 25-2 Atlantooccipital dislocation. A lateral radiograph of a teenager involved in a motor vehicle crash shows marked distraction of C1 from the skull. There is also atlantoaxial separation. Marked retropharyngeal soft tissue prominence is present.

fracture. Complete dislocation is more common than par­ tial. Dislocation is further classified as anterior, posterior (rare) , and purely distracted forms. The most common pat­ tern is concomitant anterior and distracted. On lateral cervical spine radiographs, various mea­ surements can be utilized to evaluate atlantooccipital align­ ment. (1) The distance between the occipital condyles and the condylar surfaces of the atlas should be 5 mm or less (