1600 John F. Kennedy Blvd.
Suite 1800
Philadelphia, PA 19103-2899

SPINE IMAGING: CASE REVIEW, Second Edition
ISBN-13: 978...
To my parents, who encouraged my interest in
both science and medicine BCB
To my parents, my wife Garnet, and my beautiful...
S ER IE S FO RE WO R D

I have been very gratified by the popularity of the Case Review Series and the
positive feedback t...
PREFACE

The second edition of Spine Imaging: Case Review follows the same format as the
first edition, with each case con...
AKNOWLEDGMENTS

We are especially grateful to Dave Yousem, who offered us the opportunity to write
the second edition of S...
Opening Round
This page intentionally left blank
CASE

1

1. Lumbar spinal stenosis is usually classified anatomically into two types. Name them.
2. What presenting sympto...
A N S W E R S
CASE

1

Spinal Stenosis, Lumbar
1. Central stenosis and lateral stenosis.
2. Neurogenic claudication—pain d...
CASE

2

1. In this patient with elevated erythrocyte sedimentation rate and C-reactive protein level, what is the
most li...
A N S W E R S
CASE

2

Diskitis/Osteomyelitis, Lumbar
1. Diskitis/osteomyelitis at L4–L5 with epidural abscess
or phlegmon...
CASE

3

1. What are these images called, and what is the basis for the variation in CSF intensity?
2. What type of pulse ...
A N S W E R S
CASE

3

CSF Flow Imaging
1. Phase images. The variation in CSF intensity
depends on the size (and sign) of ...
CASE

4

1. List five potential causes of the ‘‘failed back surgery’’ syndrome (FBSS). Which one is most likely
responsibl...
A N S W E R S
CASE

4

Postoperative, Recurrent Disk
Herniation, Lumbar
1. Epidural fibrosis, recurrent or persistent disk...
CASE

5

1. What is the level of the cervical spine injury in this 30-year-old man who was involved in a motor
vehicle acc...
A N S W E R S
CASE

5

Unilateral Facet Dislocation, Cervical
1. C5–C6.
2. With an accompanying fracture.
3. Less likely.
...
CASE

6

1. List three acquired, nondystonic causes of torticollis.
2. What is Grisel syndrome?
3. What is the difference ...
A N S W E R S
CASE

6

Atlantoaxial Rotatory Deformity
1. Atlantoaxial rotatory dislocation, atlantoaxial anterior
subluxa...
CASE

7

1. List five causes of a dense, sclerotic vertebra.
2. List four causes of radiculopathy, cauda equina syndrome, ...
A N S W E R S
CASE

7

Paget Disease, Lumbar
1. Osteoblastic metastasis, Paget disease, lymphoma,
myelosclerosis, and frac...
CASE

8

1. Based on the multisection CT (posterior view), what is the cause of the left-sided, lower cervical
radiculopat...
A N S W E R S
CASE

8

Traumatic Vertebral Artery Occlusion
1. Fracture of the left lateral mass of C6.
2. Transverse fora...
CASE

9

1. What syndrome is illustrated by the T2W image? Name three associated anomalies.
2. What metabolic disorder has...
A N S W E R S
CASE

9

Caudal Regression Syndrome
1. Caudal regression. Sacral dysgenesis, imperforate
anus, and bilateral...
CASE

10

1. Sacral cysts, such as the one shown on the T1W and T2W images, typically arise from which spinal
structures?
...
A N S W E R S
CASE

10

Tarlov Cyst
1. Posterior nerve root sleeves.
2. Extradural.
3. CSF-equivalent signal intensity on ...
CASE

11

1. In this 44-year-old man with chronic low back pain and previous diskectomy at L4–L5, which
intervertebral lev...
A N S W E R S
CASE

11

Anular Tears at Multiple Levels and Recurrent
Disk Herniation, Lumbar
1. Levels L2–L3, L3–L4, L4–L...
CASE

12

1. Based on the axial CT image and the left parasagittal T2W fast-spin-echo MR image, is this 64-year-old
woman ...
A N S W E R S
CASE

12

Schwannoma, Sacral
1. You cannot determine the answer without a biopsy.
Although the imaging findi...
CASE

13

1. The abnormality shown on the postcontrast T1W parasagittal image and on the T2*W GRE (gradientrecalled-echo) ...
A N S W E R S
CASE

13

CASE

14

Lateral Meningocele, Thoracic

Intradural Lipoma, Cervical

1. The abnormality is a late...
CASE

15

1. Is the migration path for lumbar disks that are extruded or sequestered more likely to be midline or
paramedi...
A N S W E R S
CASE

15

Sagittal, Epidural Midline Septum
1. Paramedian, because of the presence of the midline
sagittal s...
CASE

16

1. Based on the T1W left parasagittal image and axial images at the L4 and L4–L5 levels, suggest a
diagnosis and...
A N S W E R S
CASE

16

Herniated Disk Constrained
by Midline Septum
1. The mass is an L4–L5 herniated (extruded) disk wit...
CASE

17

1. List at least three indications for placement of transpedicular screws and rod fixation.
2. What are common c...
A N S W E R S
CASE

17

Loose Transpedicular Screw
1. Dislocation, progressive scoliosis, spondylolysis,
spondylolisthesis...
CASE

18

1. List three inflammatory lesions shown on the postcontrast T1W images of the thoracolumbar spine and
brain.
2....
A N S W E R S
CASE

18

Craniospinal Tuberculosis
1. Vertebral osteomyelitis/diskitis (intraosseous
abscess), meningitis, ...
CASE

19

1. A commonly used nomenclature for characterizing disk herniation on MR imaging studies recognizes
three descri...
A N S W E R S
CASE

19

Disk Herniation (Extrusion), Lumbar
1. Protrusion, extrusion, and sequestration.
2. (a) Extrusion ...
CASE

20

1. List the four most common skeletal sites involved by Paget disease.
2. What are the three phases of Paget dis...
A N S W E R S
CASE

20

Paget Disease, Cervical
1. Skull, spine, pelvis, and proximal long bones.
2. Lytic, mixed, and bla...
CASE

21

1. Which intradural tumor typically involves the dorsal nerve roots?
2. Based on the axial T1W image and on the ...
A N S W E R S
CASE

21

CASE

22

Sarcoidosis, Cauda Equina

Extradural Schwannoma, Cervical

1. Nerve sheath tumor (schwa...
CASE

23

1. Patients with the lesion demonstrated on the fast-spin-echo T2W and the postcontrast T1W images
often present...
A N S W E R S
CASE

23

Retroperitoneal Sarcoma
1. The large mass involves the right psoas muscle,
paravertebral region, a...
CASE

24

1. Name three inflammatory conditions associated with atlantoaxial subluxation.
2. How would you distinguish bet...
A N S W E R S
CASE

24

Adult Rheumatoid Arthritis
1. Rheumatoid arthritis, ankylosing spondylitis,
tonsillitis/pharyngiti...
CASE

25

1. What is the name of this ‘‘Aunt Minnie’’ sign?
2. A classification for the variable appearance of lumbar arac...
A N S W E R S
CASE

25

Arachnoiditis, Lumbar
1. ‘‘Empty thecal sac’’ sign.
2. Pattern 1 is clumping of nerve roots into c...
CASE

26

1. True or False: Lumbar disk herniations rarely regress spontaneously.
2. Are lateral disk herniations more lik...
A N S W E R S
CASE

26

Spontaneous Reduction of Disk Herniation,
Lumbar
1. False.
2. No. There is no correlation between ...
CASE

27

1. Name at least three tissues or substances that produce hyperintensity on T1W images.
2. What is the different...
A N S W E R S
CASE

27

Intradural Lipoma, Conus
1. Fat, melanin, blood (methemoglobin), proteinaceous
collections, mucin,...
CASE

28

1. Name three odontoid anomalies occurring in childhood and adolescence.
2. Do these anomalies produce craniocer...
A N S W E R S
CASE

28

Os Odontoideum
1. Aplasia, hypoplasia, and os odontoideum.
2. Yes.
3. Congenital os odontoideum an...
CASE

29

1. Describe the abnormal findings on the precontrast and postcontrast T1W images.
2. Give a differential diagnos...
A N S W E R S
CASE

29

Tuberculous Meningitis
1. Abnormal, smooth leptomeningeal enhancement of
the distal cord/conus and...
CASE

30

1. Which findings on the axial CT image (C4 level) characterize this type of fracture?
2. Which finding on the r...
A N S W E R S
CASE

30

Fracture-Separation of the Articular Mass
1. Fractures through the right lamina and the right
pedi...
CASE

31

1. Conventional postcontrast T1W axial images were obtained at the levels of L3 (upper left image) and
L4–L5 (lo...
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  1. 1. 1600 John F. Kennedy Blvd. Suite 1800 Philadelphia, PA 19103-2899 SPINE IMAGING: CASE REVIEW, Second Edition ISBN-13: 978-0-323-03124-0 Copyright ! 2008, 2001 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Rights Department: phone: (+1) 215 239 3804 (US) or (+44) 1865 843830 (UK); fax: (+44) 1865 853333; e-mail: healthpermissions@elsevier.com. You may also complete your request on-line via the Elsevier website at http://www.elsevier.com/permissions. NOTICE Knowledge and best practice in this field are constantly changing. As new research and experience broaden our knowledge, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of the practitioner, relying on their own experience and knowledge of the patient, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the Authors assume any liability for any injury and/or damage to persons or property arising out of or related to any use of the material contained in this book. Library of Congress Cataloging-in-Publication Data Bowen, Brian C. Spine imaging : case review / Brian C. Bowen, Alfonso Rivera, Efrat Saraf-Lavi. — 2nd ed. p. ; cm. — (Case review series) Includes bibliographical references and indexes. ISBN 978-0-323-03124-0 1. Spine—Imaging. 2. Spine—Diseases—Diagnosis. I. Rivera, Alfonso, MD. II. Saraf-Lavi, Efrat. III. Title. IV. Series. [DNLM: 1. Spinal Diseases–radiography—Case Reports. 2. Diagnostic imaging—methods—Case Reports. WE 725 B786s 2008] RD768.B656 2008 616.7’30754—dc22 2007015847 Acquisitions Editor: Maria Lorusso Developmental Editor: Colleen McGongial Project Manager: Bryan Hayward Design Direction: Steven Stave Printed in the United States of America. Last digit is the print number: 9 8 7 6 5 4 3 2 1
  2. 2. To my parents, who encouraged my interest in both science and medicine BCB To my parents, my wife Garnet, and my beautiful daughter Allison AR To my wonderful parents for their endless love and support ESL.
  3. 3. S ER IE S FO RE WO R D I have been very gratified by the popularity of the Case Review Series and the positive feedback the authors have received on publication of the first edition volumes. Reviews in journals and word-of-mouth comments have been uniformly favorable. The authors have done an outstanding job in filling the niche of an affordable, easy-to-read, case-based learning tool that supplements the material in THE REQUISITES series. While some students learn best in a noninteractive study-book mode, others need the anxiety or excitement of being quizzed, being put on the hot seat. Recognizing this need, the publisher and I selected the format of the Case Review Series to simulate the Boards experience by showing a limited number of images needed to construct a differential diagnosis and asking a few clinical and imaging questions (the only difference being that the Case Review books give you the correct answer and immediate feedback!). Cases are scaled from relatively easy to very difficult to test the limit of the reader’s knowledge. A brief authors’ commentary, a cross-reference to the companion REQUISITES volume, and an up-to-date literature reference are also provided for each case. Because of the success of the series, we have begun to roll out the second editions of the volumes. The expectation is that the second editions will bring the material to the state-of-the-art, introduce new modalities and new techniques, and provide new and even more graphic examples of pathology. This volume of the Case Review Series, Spine Imaging by Drs. Brian Bowen, Alfonso Rivera, and Efrat Saraf-Lavi, is the latest of the second editions. Once again Dr. Bowen has led the effort to update his edition with new and improved cases and discussions and techniques. For those who will practice neuroradiology in the community or academia, you will have to know spine imaging very well as it constitutes a large volume of our caseload. Fortunately, the authors of this book are world-renowned for their knowledge of spine techniques and spine disease and have given an excellent accounting of their specialty. In addition, residents preparing for the oral Boards will find that this volume is a treasure-trove of quality material that will serve them well in Louisville (or wherever Boards are held in the future) and beyond. I am pleased to present for your viewing pleasure the latest volume of the second editions of the Case Review Series, joining the previous second editions of Head and Neck Imaging by David M. Yousem and Carol da Motta; Genitourinary Imaging by Ronald J. Zagoria, William W. Mayo-Smith, and Julia R. Fielding; Obstetric and Gynecologic Ultrasound by Karen L. Reuter and T. Kemi Babagbemi; Musculoskeletal Imaging by Joseph Yu; and General and Vascular Ultrasound by William D. Middleton. David M. Yousem, MD vii
  4. 4. PREFACE The second edition of Spine Imaging: Case Review follows the same format as the first edition, with each case containing a set of spine images and four related questions on one page, and then on a second page the corresponding answers, literature references, cross-reference to the parent textbook (Neuroradiology: THE REQUISITES, second edition), and a comment on the case imaging findings and teaching points. Cases in the second edition of Spine Imaging differ from those in the first edition in one of three ways: (1) new diagnostic entity with new images and text; (2) similar diagnostic entity with new images and revised text; and (3) same diagnostic entity and images as the first edition, with revised text. Text revisions routinely include updates of literature references and, of course, cross-references to Neuroradiology: THE REQUISITES, second edition. As in the first edition of Spine Imaging, many entities that are discussed in the second edition are covered in more depth than in the parent textbook. Our goal has been to increase the diversity of cases and the information content of each case, thus providing additional insights for all readers but especially those who are preparing for examinations such as the certificate of added qualification (CAQ) and the maintenance of certification (MOC) in neuroradiology. Finally, cases from the first edition of Spine Imaging that are included in the second edition have been selected on the basis of criticisms, comments, and recommendations that the authors have received from residents and fellows at several teaching hospitals over the past 5 years. Brian C. Bowen, MD, PhD Alfonso Rivera, MD Efrat Saraf-Lavi, MD ix
  5. 5. AKNOWLEDGMENTS We are especially grateful to Dave Yousem, who offered us the opportunity to write the second edition of Spine Imaging: Case Review, and to managing editor Maria Lorusso, who guided us through the final stages of the manuscript, seamlessly bringing together the case material contributed by each of us. As occurred in the writing of the first edition, our colleagues in diagnostic neuroradiology—Judy Post, Evelyn Sklar, Steve Falcone, and Rita Bhatia—at the University of Miami pointed our interesting cases to include and generally provided an environment that encouraged dialogue and critical assessment of spinal imaging methods and results during our biweekly division conferences. We continue to benefit from our close working relationship with faculty members in the departments of neurological surgery, neurology, and orthopedic surgery, as well as researchers and clinicians at the interdisciplinary Miami Project to Cure Paralysis. These and other individuals have contributed directly or indirectly to the material in this second edition. In particular, we would like to acknowledge the generosity of Joshua Bemporad, Shimon Maimon, and also John Mathis, who provided several instructive interventional cases. We again single out for special appreciation two individuals in the department of radiology who contributed their expertise during the writing and revising of cases for the second edition of Spine Imaging: Case Review. Pradip Pattany provided us with the perspective of an MR physicist in parts of the text that address image artifacts and the principles underlying various MR techniques. He also contributed the book’s cover figure, which is a ‘‘fiber direction color map’’ of an ex vivo specimen of a human spinal cord. The cross-sectional map was obtained by Diffusion Tensor Imaging at 4.7 Tesla. The bright blue peripheral regions represent highly anisotropic white matter tracts with a head-foot orientation, while the blackish central regions represent the nearly isotropic gray matter. The cord specimen has been rotated so that the dorsal root-entry zones are parallel to the left-right axis (fiber orientation assigned the color red) or the anteroposterior axis (fiber orientation assigned the color green) of the magnet. Color coding of fiber directions facilitates the identification of the different white matter tracts. Robert Quencer, chairman of radiology at the University of Miami and former editor-in-chief of the American Journal of Neuroradiology, provided an additional level of editorial scrutiny. His contributions have resulted in a second edition comprised of cases that are as diverse, informative, and readable as those in the first edition yet more contemporary in educational scope. Brian C. Bowen, MD, PhD Alfonso Rivera, MD Efrat Saraf-Lavi, MD xi
  6. 6. Opening Round
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  8. 8. CASE 1 1. Lumbar spinal stenosis is usually classified anatomically into two types. Name them. 2. What presenting symptom is considered pathognomonic of lumbar spinal stenosis? 3. Which vertebral structures typically appear shortened in patients with congenital narrowing of the lumbar canal? 4. Name at least three degenerative changes of the spine that contribute to neural foraminal stenosis. 3
  9. 9. A N S W E R S CASE 1 Spinal Stenosis, Lumbar 1. Central stenosis and lateral stenosis. 2. Neurogenic claudication—pain developing in the legs on walking. 3. Pedicles. 4. Hypertrophic facet, spondylolisthesis, vertebral body osteophyte, and bulging or herniated disk. References Goh KJ, Khalifa W, Anslow P, et al: The clinical syndrome associated with lumbar spinal stenosis. Eur Neurol 52:242–249, 2004. Hiwatashi A, Danielson B, Moritani T, et al: Axial loading during MR imaging can influence treatment decision for symptomatic spinal stenosis. AJNR Am J Neuroradiol 25:170–174, 2004. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 784–785. Comment In this 50-year-old woman with back pain and L5 radiculopathy, the T1-weighted (T1W) and T2-weighted (T2W) axial images at the L4–L5 level demonstrate severe central stenosis due to degenerative bony and soft tissue changes as well as congenital canal narrowing. Evidence of a congenital component is best shown on axial images that display developmentally shortened pedicles, yet can be inferred from the relative paucity of CSF in the thecal sac over several vertebral levels, with relatively minor spondylotic changes, on the sagittal T2W image. The severity of the stenosis at L4–L5 is best estimated by the loss of epidural fat signal and the marked narrowing of the thecal sac. Because MR imaging depicts these features directly, measurements of the dimensions of the bony canal on CT or radiography are no longer recommended. In this patient, central stenosis is due to a combination of the degenerative bony (hypertrophic facet joints) and soft tissue (hypertrophic ligamentum flavum, bulging annulus) changes as well as underlying congenital canal narrowing. Another indication of the severity of the central stenosis is the lack of CSF signal surrounding the roots of the cauda equina in the thecal sac, thus obscuring the normal tapering of the conus tip and giving the appearance of a mass of clumped roots (as shown here). Lumbar lateral stenosis may be due to lateral recess stenosis (also present at L4–L5) and/or neural foraminal stenosis. The causes of lateral recess stenosis are hypertrophy of the superior articular facet (most common), bulging/herniated disk, and vertebral body osteophyte. In a recent study, 4 patients with moderate to severe lumbar spinal stenosis on routine imaging most often had the following symptoms and signs: numbness (30%), radicular pain (25%), claudication (21%), and motor weakness (18%). Neurogenic claudication was the presenting symptom in only a quarter of patients. Because some patients have symptoms without corresponding imaging abnormalities, several investigators have proposed MR imaging of the lumbar canal in the most symptomatic position. They use axial loading to simulate the upright position and assess the severity of stenosis on images acquired during loading to make treatment decisions. Notes
  10. 10. CASE 2 1. In this patient with elevated erythrocyte sedimentation rate and C-reactive protein level, what is the most likely diagnosis? 2. Does the signal intensity of the L4 and L5 vertebral bodies on the T2W image dissuade you from this diagnosis? 3. What percentage of patients with this diagnosis will have ‘‘typical’’ contrast enhancement of the involved spinal level? 4. List two additional findings on postcontrast images that may aid in diagnosis and assessment of disease extent. 5
  11. 11. A N S W E R S CASE 2 Diskitis/Osteomyelitis, Lumbar 1. Diskitis/osteomyelitis at L4–L5 with epidural abscess or phlegmon. 2. No. Findings of diffuse hypointensity, band-like endplate hypointensity, or diffuse isointensity within the involved vertebral bodies on T2W images were observed in nearly half (44%) of the 39 levels of diskitis/osteomyelitis reported by Modic and colleagues. 3. The same investigators reported that 94% of patients had ‘‘typical’’ contrast enhancement. 4. Epidural and paraspinal enhancing masses (as in this case). Enhancing roots of the cauda equina (meningitis). Reference Dagirmanjian A, Schils J, McHenry M, Modic MT: MR imaging of vertebral osteomyelitis revisited. AJR Am J Roentgenol 167:1539–1543, 1996. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 795–796. Comment The MR images in this case demonstrate the findings that are considered ‘‘typical’’ of diskitis/osteomyelitis: decreased vertebral body signal on T1W images, loss of endplate definition on T1W images, increased disk signal intensity on T2W images, and contrast enhancement of the disk and adjacent vertebral bodies (on fat-saturated, T1W images in this case). Modic and colleagues reported that these findings were each observed with a frequency of approximately 95%. In comparison, increased vertebral body signal on T2W images was observed in only 56% of spinal levels with diskitis/osteomyelitis. Thus, the absence of this finding should not dissuade the observer from making an MR imaging diagnosis of diskitis and osteomyelitis when the typical findings described above are present (as in this case). The variation in signal intensity of the involved vertebral bodies on T2W images has been attributed in part to variability in the ratio of sclerotic bone (as seen on standard radiographs) to edematous marrow. The typical contrast enhancement pattern of the involved disk can vary from thick patchy enhancement to linear enhancement to a ring-like peripheral enhancement that is thick (as in this case) or thin, continuous or discontinuous. The intensity of vertebral body enhancement is variable. Enhancement of epidural and 6 paraspinal associated soft-tissue masses provides additional evidence of infection. Homogeneous enhancement favors phlegmon, and ring enhancement favors mature abscess. Notes
  12. 12. CASE 3 1. What are these images called, and what is the basis for the variation in CSF intensity? 2. What type of pulse sequence is used to obtain such images? 3. What physiologic process is generally thought to be responsible for the signal variation seen here? 4. What is the main use of this technique? Name three lesions that may be better characterized by use of this technique. 7
  13. 13. A N S W E R S CASE 3 CSF Flow Imaging 1. Phase images. The variation in CSF intensity depends on the size (and sign) of the phase shift of excited spins in CSF as they move along a magnetic field gradient. 2. Gradient-echo. 3. Pulsatile forces generated by the cardiovascular system. The arterial pulse transmitted by the cerebrovascular system causes motion of the brain– spinal cord axis and results in displacement of CSF, which in turn is detected as flow of CSF in the spinal canal. 4. To determine whether flow of CSF is blocked. (a) Spinal meningeal cyst, (b) subarachnoid cyst (loculation in the subarachnoid space), and (c) intramedullary cyst (syringohydromyelia). References Haughton VM, Korosec FR, Medow JE, et al: Peak systolic and diastolic CSF velocity in the foramen magnum in adult patients with Chiari I malformations and in normal control participants. AJNR Am J Neuroradiol 24:169–176, 2003. Levy LM: MR imaging of cerebrospinal fluid flow and spinal cord motion in neurologic disorders of the spine. Magn Reson Imaging Clin N Am 7:573–587, 1999. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 276, 436–437. Comment The phase images shown here represent 2 of 14 electrocardiographic-gated images reconstructed from data acquired during each cardiac cycle. With this ‘‘phase contrast’’ technique, the images are obtained in cine mode by pixel-by-pixel computation of the phase difference between two interleaved acquisitions, one being flow compensated and the other having a specific flow encoding. The flow encoding, or flow sensitivity, is usually adjusted by varying the gradient strength or duration. In this case, the flow-encoding gradient is along the superior-inferior (or cephalad-caudad) direction, which is also the read gradient direction. The size of the phase shift resulting from superior-inferior flow is proportional to three factors primarily: (1) the size of the flow-encoding gradient, (2) the magnitude of the CSF velocity in the superior-inferior direction, and (3) the square of echo time (TE). The flow-encoding gradient has been adjusted to give maximum phase shift to CSF 8 moving with a velocity of 8 cm/sec. Caudad flow induces a positive phase shift and is displayed as hyperintense, whereas cephalad flow induces a negative phase shift and appears hypointense relative to nonmoving background tissue (e.g., neck muscles). Regions of CSF with velocities less than 8 cm/sec are either less hyperintense (caudad flow) or less hypointense (cephalad flow). The two images display a biphasic pattern of CSF flow in the cervical region—caudad flow in response to systole (left-hand figure) and cephalad flow in response to diastole (right-hand figure). In the right-hand figure, note that the subarachnoid space posterior to the cord is less hypointense than the subarachnoid space anterior to the cord, which indicates that cephalad CSF flow is slower posteriorly than anteriorly in this patient being evaluated for possible Chiari I malformation. Haughton and colleagues have evaluated the differences in peak systolic and diastolic CSF velocities at the foramen magnum for Chiari I patients and normal controls. Patients with Chiari I had significant elevations of peak systolic velocity. The direction and amplitude of CSF flow vary along the spinal axis because of the effects of wave propagation and expansion/contraction of the epidural venous plexus, so the flow pattern in the lumbar region differs from the pattern in the cervical region. The spinal cord also moves, albeit with a velocity at least 10 times less than that of CSF. Phase, or velocity, images (with appropriate setting of the motion-encoding gradient) can demonstrate both the magnitude and the direction of cord motion. Caudad motion of the cord occurs in early systole, at approximately the same time as the onset of caudad CSF flow. Spinal cord tethering is associated with decreased cord velocities relative to normal. In addition to the longitudinal (superior-inferior) component of cord and CSF motion, a smaller transverse component is present. In the case of postoperative scarring in the cervical canal, loss of transverse motion of the cord at the site of focal cord tethering has been demonstrated in addition to decreased longitudinal velocity. Notes
  14. 14. CASE 4 1. List five potential causes of the ‘‘failed back surgery’’ syndrome (FBSS). Which one is most likely responsible for the syndrome in this patient, based on the T2W and postcontrast T1W images (L4–L5 level) shown here? 2. Are early or delayed (!30 min) postcontrast T1W images better at separating recurrent disk from epidural fibrosis? 3. What percentage of patients undergoing unilateral lumbar laminectomy/diskectomy for disk herniation for the first time are likely to show intervertebral disk space enhancement at the surgical level 3 months after surgery (excluding patients with FBSS)? 4. What is the ‘‘typical pattern’’ of postcontrast enhancement in these patients? 9
  15. 15. A N S W E R S CASE 4 Postoperative, Recurrent Disk Herniation, Lumbar 1. Epidural fibrosis, recurrent or persistent disk herniation, arachnoiditis, spondylolisthesis, and residual bony stenosis; operation at the wrong level is also a valid answer. Recurrent or persistent disk herniation is most likely in this case. 2. Early. 3. 20%. 4. The typical pattern, as seen on postcontrast T1W sagittal images and reported by Ross and colleagues, is ‘‘linear horizontal bands of enhancement paralleling the end plates’’ and converging on the surgical site in the posterior anulus fibrosis. Reference Ross JS: MR imaging of the postoperative lumbar spine. Magn Reson Imaging Clin N Am 7:513–524, 1999. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 788–791. Comment As shown on the fast-spin-echo T2W image, the right ligamentum flavum is disrupted and the anterior aspect of the right lamina has abnormal signal. The right-sided soft tissue mass contiguous with, and isointense to, the intervertebral disk could represent postoperative scar (epidural/peridural fibrosis), recurrent or persistent disk herniation, or a combination of scar plus disk material. On the postcontrast T1W image at the same level, the bulk of the mass does not enhance, compatible with herniation, whereas the thin rim of tissue around the disk does enhance, compatible with mild adjacent scarring. This patient’s symptoms were attributed to recurrent disk herniation. Typically, a physician who is caring for a patient with symptoms of FBSS wants to know if the clinical symptoms (recurrent back pain, radiculopathy, and functional incapacitation) are primarily due to ‘‘scar or disk.’’ The reported accuracy of postcontrast MR imaging in distinguishing between scar and disk in patients at least 6 weeks postsurgery is in the 96% to 100% range. Whether the time elapsed since surgery is months or years, scar consistently enhances on images acquired immediately following injection of contrast material. Because it is avascular, disk does not enhance on these early images. On delayed images (!30 min following injection), disk material may enhance because of the diffusion of the low-molecular-weight contrast material 10 (gadolinium chelate) into the disk from adjacent scar, especially when there is a relatively large volume of scar compared with the volume of the herniation. A secondary sign that favors scar over recurrent/persistent disk is retraction of the thecal sac toward the region of aberrant epidural soft tissue. The presence of mass effect is not helpful, since both epidural scar and disk can produce this finding. Notes
  16. 16. CASE 5 1. What is the level of the cervical spine injury in this 30-year-old man who was involved in a motor vehicle accident 1 month prior to the CT examination? 2. Is the type of injury shown here more likely to occur without or with an accompanying fracture? 3. When fracture is present, is associated spinal cord injury more likely or less likely? 4. What is the frequency of intervertebral disk disruption? 11
  17. 17. A N S W E R S CASE 5 Unilateral Facet Dislocation, Cervical 1. C5–C6. 2. With an accompanying fracture. 3. Less likely. 4. 25%. References Levine AM: Facet fractures and dislocations. In: Levine AM, Eismont FJ, Garfin SR, Zigler JE: Spine Trauma. Philadelphia, WB Saunders, 1998, pp 331–366. Shanmuganathan K, Mirvis SE, Levine AM: Rotational injury of cervical facets: CT analysis of fracture patterns with implications for management and neurologic outcome. AJR Am J Roentgenol 163: 1165–1169, 1994. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 842. Comment The left parasagittal reformatted CT image demonstrates an abrupt transition from a ‘‘lateral view’’ of the C2 to C5 articular pillars to an ‘‘oblique view’’ of the C6 and C7 facet joints and neural foramina. This appearance is due to the rotation of C5 relative to C6, which results from the left C5 facet dislocation. The dislocation is accompanied by a fracture of the superior articular process of C6. The axial and parasagittal images show the anterior displacement of the fracture fragment and the inferior articular process of C5 relative to the fractured C6 facet. Cervical rotational facet injury (RFI) has been proposed as a more encompassing term to describe both pure unilateral facet subluxation/dislocation without a fracture and unilateral subluxation/dislocation with a concurrent facet fracture. Approximately 75% of patients with RFI have concurrent facet fractures. As reported by Shanmuganathan et al, fracture of the inferior facet of the rotated vertebra was observed more frequently than fracture of the superior facet of the subjacent vertebra or fractures of both facets. Other authors have reported that unilateral facet fracture most often involves the superior facet. Facet injuries result from a mixture of forces involving rotation, lateral bending, flexion, and distraction. Facet dislocations without fractures have a significantly higher association with spinal cord injury syndromes than do RFIs with fractures. Additional findings in patients with RFI include fracture-separation of the articular pillar (17%) and avulsion fracture of the posteroinferior aspect of the rotated vertebral body, indicating disk disruption (25%). Notes 12
  18. 18. CASE 6 1. List three acquired, nondystonic causes of torticollis. 2. What is Grisel syndrome? 3. What is the difference between rotatory displacement and rotatory fixation? 4. Which imaging technique is recommended for establishing the diagnosis of atlantoaxial rotatory fixation? 13
  19. 19. A N S W E R S CASE 6 Atlantoaxial Rotatory Deformity 1. Atlantoaxial rotatory dislocation, atlantoaxial anterior subluxation, and C2–C3 rotatory dislocation. 2. Atlantoaxial rotatory deformity resulting from infection (classically nasopharyngeal). 3. In rotatory fixation, the displaced C1–C2 joints are refractory to nonoperative attempts at reduction. 4. CT, with axial images obtained with maximal head rotation to the left and then to the right. Some authors also recommend a CT scan with the head in neutral position. References Currier BL: Atlantoaxial rotatory deformities. In: Levine AM, Eismont FJ, Garfin SR, Zigler JE: Spine Trauma. Philadelphia, WB Saunders, 1998, pp 249– 267. Kowalski HM, Cohen WA, Cooper P, et al: Pitfalls in the CT diagnosis of atlantoaxial rotary subluxation. AJR Am J Roentgenol 149:595–600, 1987. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 842–843. Comment The two CT images represent two sections from the same study, one at the level of C1 (left image) and the other at the level of the C2 body (right image). C1 is rotated clockwise relative to C2 (approximately 458), and no anterior displacement of C1 on C2 can be seen. Atlantoaxial rotatory deformity is a spectrum of disorders. Rotatory deformity may result from infection, trauma, and other conditions, or it may arise spontaneously (as in this case). Atlantoaxial rotatory dislocation generally refers to complete dislocation of the C1–C2 facet joints. Rotational deformity of the C1–C2 joints within the physiologic range of motion has been referred to as atlantoaxial rotatory displacement by Fielding and Hawkins (other authors prefer the term rotary subluxation). In this deformity, the joints are not dislocated. If this condition persists and becomes fixed (refractory to nonoperative management), it is then referred to as atlantoaxial rotatory fixation. Recognizing the importance of transverse ligament integrity in determining the degree of canal compromise that can accompany rotational deformities, Fielding and Hawkins describe four types of rotatory fixation: Type I: Rotatory fixation with no anterior displacement (as shown in this case). The transverse ligament is intact, and the odontoid acts as the pivot. 14 Type II: Rotatory fixation with anterior displacement of 3–5 mm. The transverse ligament is mildly deficient or lax, and one facet acts as the pivot. Type III: Rotatory fixation with anterior displacement of more than 5 mm. The transverse ligament and alar ligaments are deficient. Type IV: Rotatory fixation with posterior displacement (rare—the only case reported by Fielding and Hawkins was in an adult with rheumatoid arthritis and absence of the dens because of erosion). Notes
  20. 20. CASE 7 1. List five causes of a dense, sclerotic vertebra. 2. List four causes of radiculopathy, cauda equina syndrome, and/or myelopathy in patients with Paget disease. 3. What is the most common spinal complication of Paget disease? Does this occur early or late in the disease process? 4. In this patient, is L4 or L5 more likely to be the site of lytic metastasis in the future? 15
  21. 21. A N S W E R S CASE 7 Paget Disease, Lumbar 1. Osteoblastic metastasis, Paget disease, lymphoma, myelosclerosis, and fracture. 2. Vertebral enlargement producing spinal stenosis, ossification of extradural structures producing spinal stenosis, pathologic vertebral fracture, facet arthropathy. 3. Pathologic fracture occurs during the early osteolytic phase of Paget disease. 4. L5, because metastases tend to involve the hypervascular pagetic bone. Reference Poncelet A: The neurologic complications of Paget’s disease. J Bone Miner Res 14(suppl 2):88–91, 1999. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 830. Comment The lateral view of the lumbar spine in this 61-year-old man demonstrates a hyperdense, enlarged L5 vertebral body with a thickened cortex. Cortical thickening results in the appearance of a ‘‘picture frame’’ around the body and thickened pedicles. CT demonstrates the thickened cortex and the coarse trabeculation of cancellous bone, as well as the enlargement of the posterior elements with mild spinal stenosis. The affected facet joints show narrowing of the joint spaces and hypertrophic facets, resulting in moderate pagetic facet arthropathy. Paget disease generally occurs after the age of 50 years. Radiographically, three phases may be seen and may coexist in the same bone: osteolytic (early, active), mixed (intermediate), and osteoblastic (late, inactive). In this case, L5 has features of both mixed and osteoblastic phases. Lymphoma and metastatic prostate cancer tend to have a more uniform increase in bone density and are unlikely to cause vertebral expansion. Monostotic involvement in Paget disease may be mistaken for fibrous dysplasia. Spinal stenosis resulting from enlargement of the vertebral body and/or the neural arch occurs in about 80% of symptomatic patients and 20% of asymptomatic patients. Pagetic facet arthropathy also occurs in about 80% of symptomatic patients. Compression fractures of involved vertebral bodies are usually asymptomatic. Vascular mechanisms (steal of blood supply from cord or nerve roots, or anterior spinal artery compression by pagetoid bone) have also been proposed to account for symptoms. Primary malignant bone tumors are 20 times more likely to develop in individuals with Paget disease than in age-matched controls. Osteosarcoma is the most 16 common histologic type, followed by fibrosarcoma and chondrosarcoma. Sarcomatous transformation is heralded by the development of a lytic lesion, sometimes with cortical breakthrough, pathologic fracture, and/or a soft tissue mass. The differential diagnosis includes lytic or blastic metastases (e.g., breast, prostate, or kidney primary sites) to pagetic bone. Notes
  22. 22. CASE 8 1. Based on the multisection CT (posterior view), what is the cause of the left-sided, lower cervical radiculopathy in this patient following a motor vehicle accident? 2. This lesion likely extends to what other vertebral structure? 3. Is vertebral artery injury a common finding in patients following acute, major cervical spine trauma? Are associated intracranial neurological deficits common? 4. True or False: Eccentric position of the vertebral artery in the transverse foramen is a reliable sign of vertebral artery injury. 17
  23. 23. A N S W E R S CASE 8 Traumatic Vertebral Artery Occlusion 1. Fracture of the left lateral mass of C6. 2. Transverse foramen, resulting in injury to the left vertebral artery. 3. Yes, based on MR angiography and routine MR imaging. No. 4. False. References Friedman D, Flanders A, Thomas C, et al: Vertebral artery injury after acute cervical spine trauma: rate of occurrence as detected by MR angiography and assessment of clinical consequences. AJR Am J Roentgenol 164:443–447, 1995. Sanelli PC, Tong S, Gonzalez RG, et al: Normal variation of vertebral artery on CT angiography and its implications for diagnosis of acquired pathology. J Comput Assist Tomogr 26:462–470, 2002. Veras LM, Pedraza-Gutierrez S, Castellanos J, et al: Vertebral artery occlusion after acute cervical spine trauma. Spine 25:1171–1177, 2000. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 221. Comment Multidetector-row CT scanners allow rapid helical acquisition of image data during iodinated contrast infusion. Axial source images generated from the acquisition are then post-processed, yielding three-dimensional (3D) reconstructions with volume renderings that display both osseous (vertebral) and vascular (cervical carotid and vertebral arteries) structures, as shown in this case. The left C6 lateral mass fracture is shown on the posterior view, while occlusion of the left vertebral artery is suggested by the absence of this structure on the frontal oblique, CT angiographic view (confirmed on the source images). On MR angiography, a significant difference in frequency of vertebral artery nonvisualization (occlusion) between acute cervical spine trauma and control patient groups has been reported. Vascular abnormalities, such as nonvisualization and focal narrowing or focal widening of the vertebral arteries on MRA were common; however, symptoms of vertebrobasilar artery insufficiency or posterior circulation infarction were distinctly uncommon. The use of vertebral artery narrowing or of eccentric position relative to the transverse foramen as evidence of vascular abnormality may lead to Case courtesy of Dr. Diego Nunez. 18 false-positive results. Recent CT angiography (CTA) evaluation of normal young subjects has shown that vertebral artery size and position in the transverse foramina vary markedly. Thus, normal variations must be considered when evaluating CT (and MR) angiograms for vertebral artery injury. Notes
  24. 24. CASE 9 1. What syndrome is illustrated by the T2W image? Name three associated anomalies. 2. What metabolic disorder has been linked to this syndrome? 3. Name two congenital subcutaneous cystic lesions associated with this syndrome. 4. Which MR finding has been used to categorize patients with sacral agenesis into two groups having generally different clinical courses? 19
  25. 25. A N S W E R S CASE 9 Caudal Regression Syndrome 1. Caudal regression. Sacral dysgenesis, imperforate anus, and bilateral renal dysplasia. 2. Maternal diabetes mellitus. 3. Terminal myelocystocele and lipomeningocele. 4. The position of the conus. References Barkovich AJ, Raghavan N, Chuang S, et al: The wedge-shaped cord terminus: a radiographic sign of caudal regression. AJNR Am J Neuroradiol 10: 1223–1231, 1989. Pang D: Sacral agenesis and caudal spinal cord malformations. Neurosurgery 32:755–778, 1993. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 464–465. Comment The T2W image shows a blunted, wedge-shaped conus (shorter ventrally as a result of a deficiency of anterior horn cells) with a thin central canal extending over at least four vertebral segments. The conus ends at about the T12–L1 interspace. Sacral dysgenesis is relatively mild, with sacral segments identified through S4–S5. The distal bony canal and thecal sac are narrowed. Patients with sacral agenesis/dysgenesis have been categorized on the basis of conus position: group 1 (40%) has a high conus terminating cephalic to the L1 inferior endplate, and group 2 (60%) has a low conus terminating caudal to L1. In about 90% of group 1 patients, the conus has a blunted contour (similar to the case shown). This case is atypical, however, in that group 1 patients tend to have a large sacral defect, with the sacrum ending above S1. In group 2 patients, the conus is often elongated as a result of tethering to a thickened filum, lipoma, or myelocystocele. Terminal hydromyelia may be observed in either group. Sacral dysgenesis is relatively mild in group 2 patients; however, their clinical course is more likely to involve neurologic deterioration because of cord tethering. Terminal myelocystoceles and lipomeningoceles are associated with sacral agenesis/dysgenesis in approximately 9% and 6% of cases, respectively. Other anomalies associated with caudal regression include myelomeningocele, diastematomyelia, anterior sacral meningocele, and dermoid. About 16% of patients with the caudal regression syndrome have diabetic mothers, and about 1% of diabetic mothers have offspring with the syndrome. It has been hypothesized that sacral agenesis/dysgenesis may occur as a result of hyperglycemia in a genetically predisposed 20 fetus early in gestation. The insult, like that resulting from various teratogenic agents, may prevent canalization and retrogressive differentiation of the caudal cell mass. Alternatively, the insult may promote excessive retrogression resulting in the sacral deformity and/or anorectal and urogenital malformations. The ventral aspect of the conus may be more affected than the dorsal aspect because the ventrolateral and ventral vascular supply develops earlier, thus allowing enhanced delivery of blood-borne teratogens. Notes
  26. 26. CASE 10 1. Sacral cysts, such as the one shown on the T1W and T2W images, typically arise from which spinal structures? 2. Are the cysts predominantly intradural or extradural? 3. What are the typical signal characteristics on MR imaging? 4. What is the distinctive histopathologic feature of a Tarlov cyst? 21
  27. 27. A N S W E R S CASE 10 Tarlov Cyst 1. Posterior nerve root sleeves. 2. Extradural. 3. CSF-equivalent signal intensity on all pulse sequences. 4. The presence of spinal nerve root fibers within the cyst wall or cavity. References Nabors MW, Pait TG, Byrd EB, et al: Updated assessment and current classification of spinal meningeal cysts. J Neurosurg 68:366–377, 1988. Paulsen RD, Call GA, Murtagh FR: Prevalence and percutaneous drainage of cysts of the sacral nerve root sheath (Tarlov cysts). AJNR AM J Neuroradiol 15: 293–297, 1994. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 806–807. Comment Tarlov, or perineurial, cysts are reported to occur in approximately 4.6% to 9% of the adult population. They may be found at any level along the spinal axis, although they are most often located at S2 and S3. They are usually incidental findings on CT and MR imaging. Approximately one fifth of Tarlov cysts are symptomatic. The symptoms result from nerve root compression and vary depending on their anatomic location. The intraspinal cyst originally described by Tarlov had a wall that was continuous with the arachnoid and dura of the posterior root/ganglion, whereas the cystic cavity itself was located in the space between the endo- and perineurium of the peripheral nerve. Nabors and colleagues classified spinal meningeal cysts into three categories: type I are extradural meningeal cysts without spinal nerve root fibers, type II are extradural meningeal cysts with spinal nerve root fibers (Tarlov cysts), and type III are spinal intradural meningeal cysts. MR is the preferred initial imaging modality owing to its capacity to delineate bone and pedicle erosion, sacral canal widening, and neural foraminal enlargement as well as the relationship of the cyst to the thecal sac. The final diagnosis is based on histopathologic evidence of spinal nerve root fibers within the cyst wall or cavity. Notes 22
  28. 28. CASE 11 1. In this 44-year-old man with chronic low back pain and previous diskectomy at L4–L5, which intervertebral levels have findings on the sagittal T2W fast-spin-echo and postcontrast fat-saturated T1W images that are indicative of degenerative lumbar disk disease? 2. List three of the findings. 3. Define ‘‘intervertebral osteochondrosis.’’ 4. Name three types of anular tears that have been described based on postmortem cryomicrotome anatomic sections. Which type is consistently associated with disk degeneration? 23
  29. 29. A N S W E R S CASE 11 Anular Tears at Multiple Levels and Recurrent Disk Herniation, Lumbar 1. Levels L2–L3, L3–L4, L4–L5, and L5–S1. 2. (a) Diminished disk height, (b) decreased signal in the disk, and (c) radial anular tear. Note the postoperative recurrent disk extrusion at L4–L5. 3. A degenerative process involving the nucleus pulposis, anulus fibrosus, and the adjacent vertebral endplates. In addition to disk space narrowing, endplate changes and a vacuum phenomenon (which were not present in this case) are typically observed. 4. Concentric, horizontal, and radial tears. Radial tears. References Pfirrmann CW, Metzdorf A, Zanetti M, Hodler J, Boos N: Magnetic resonance classification of lumbar intervertebral disc degeneration. Spine 26:1873–1878, 2001. Yu S, Haughton VM, Sether LA, Ho KC, Wagner M: Criteria for classifying normal and degenerated lumbar intervertebral disks. Radiology 170:523–526, 1989. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 769. Comment On the sagittal images, the posterior portion of each disk from L2–L3 to L5–S1 has a slightly hyperintense line or band extending through the normally hypointense anulus fibrosus. The line or band is a radial tear of the anulus. Investigators have shown that the radial tear is consistently associated with gross anatomic (and MR evidence) of disk degeneration, including diminished disk height, shrinkage and disorganization of fibrocartilage in the nucleus pulposus, and replacement of the disk by dense fibrous tissue and cystic spaces. The radial tear, which involves multiple layers of the anulus from the nucleus pulposus to the surface of the disk, allows displacement of the nucleus and hence disk herniation (e.g., L4–L5). Radial anular tear is a necessary but not sufficient condition for herniation. The remaining two types of anular tears, concentric and horizontal tears, have been observed in the majority of adult disks examined by cryomicrotome sectioning, and these types are considered normal findings. Concentric tears represent a delamination of longitudinal anular fibers. Transverse tears represent disruption of the insertion of Sharpey fibers into the ring apophysis, and they are detected as punctate or linear hyperintense foci adjacent to the periphery of the vertebral endplates on T2W images. They typically are smaller than radial tears, which 24 demonstrate a more prominent hyperintense signal and which may enhance on postcontrast T1W images (well seen at L3–L4 and L5–S1 in this case) in both acute and chronic phases. Notes
  30. 30. CASE 12 1. Based on the axial CT image and the left parasagittal T2W fast-spin-echo MR image, is this 64-year-old woman with sciatica more likely to have a malignant or a benign lesion? 2. Name the three most common malignant tumors that ‘‘originate’’ in the sacrum (i.e., cause sacral destruction intrinsically)? 3. The compression or displacement of which presacral structure by the mass may account for the patient’s symptoms? 4. A biopsy of the tumor revealed a cellular neoplasm composed of short intersecting fascicles and whorls of uniform spindle cells lacking hyperchromasia and pleomorphism. There was a low mitotic count and strong, diffuse staining for S100 protein. Your diagnosis? 25
  31. 31. A N S W E R S CASE 12 Schwannoma, Sacral 1. You cannot determine the answer without a biopsy. Although the imaging findings suggest a slowly growing benign lesion, sarcomatous degeneration within a benign lesion cannot be excluded. 2. Chordoma, chondrosarcoma, and metastatic lesions. lesion, and the signal characteristics of the myxoid matrix found in chordoma and chondrosarcoma are lacking. Benign bone lesions such as giant cell tumor, aneurysmal bone cyst, and osteoblastoma occur infrequently in the sacrum, and the latter two typically involve posterior elements. Rarely, sacrococcygeal teratoma and myxopapillary ependymoma occur in the presacral area. 3. The left sacral plexus. 4. Schwannoma. References Dominguez J, Lobato RD, Ramos A, et al: Giant intrasacral schwannomas: report of six cases. Acta Neurochir (Wien) 139:954–959, 1997. Takeyama M, Koshino T, Nakazawa A, et al: Giant intrasacral cellular schwannoma treated with high sacral amputation. Spine 26:E216–219, 2001. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 820–821. Comment This patient has a 20-year history of a pelvic tumor. The CT and MR images demonstrate a heterogeneous mass with smooth, rounded margins; lack of infiltration of adjacent fat; intrinsic regions of cystic change; and extension from the sacrum into the pelvis. On CT, sacral destruction is centered in the region of the left neural foramina, and the eroded bone has sclerotic borders, raising the possibility of a slowly growing nerve sheath tumor. On MR, the solid and cystic components of the tumor have intermediate and high signal intensity, respectively. Gluteal fat, inferoposterior to the mass, is also hyperintense. Spinal schwannomas are relatively uncommon, and less than 1% to 5% occur in the sacrum. Histologically, schwannomas are characterized by alternating Antoni A and Antoni B areas with cellular and hypocellular regions, respectively. They are encapsulated lesions that typically do not compromise motor function but may cause paresthesias or pain owing to pressure. A variant of the conventional schwannoma is the cellular schwannoma, which is composed predominantly of Antoni A areas, lacks Verocay bodies, and is predominantly found in the retroperitoneum, pelvis, and paraspinal area of the mediastinum. Sacral schwannomas are often designated as ‘‘giant’’ because of the enormous size that they may attain, destroying the sacrum and expanding into the pelvis and spinal canal as well as the dorsal muscles and fat. The differential diagnosis for a sacral mass includes malignant and benign lesions. The overall imaging features are not those of a malignant 26 Notes
  32. 32. CASE 13 1. The abnormality shown on the postcontrast T1W parasagittal image and on the T2*W GRE (gradientrecalled-echo) axial image is associated with which of the phakomatoses? 2. What symptoms, if any, result from the abnormality? 3. The abnormality is bilateral in what percentage of patients? 4. What is Lehman syndrome? CASE 14 1. The T1W and STIR (short tau inversion recovery) sagittal images show an intradural mass with both intra- and extramedullary components and signal characteristics of which type of tissue? 2. What is the differential diagnosis for this lesion? 3. Is the lesion more likely to be located in the cervical or thoracic region? 4. On the basis of the hypothesis that intraspinal lipoma is formed by premature disjunction of neuroectoderm from cutaneous ectoderm just before closure of the neural tube, where would you expect to find the dorsal roots? 27
  33. 33. A N S W E R S CASE 13 CASE 14 Lateral Meningocele, Thoracic Intradural Lipoma, Cervical 1. The abnormality is a lateral meningocele, which is associated with neurofibromatosis type 1 (NF-1). 1. Adipose tissue. 2. Most patients are asymptomatic, but some have radicular intercostal pain. 3. 10%. 4. Also called ‘‘lateral meningocele syndrome,’’ it is a syndrome first described by Lehman and colleagues in 1977. Patients do not have neurofibromatosis or Marfan syndrome. Among the findings are multiple lateral meningoceles, wormian bones, malar hypoplasia, down-slanted palpebral fissures, a high narrow palate, and cryptorchidism in males. Other features, such as a hypoplastic posterior arch of the atlas, are variably present. Reference Gripp KW, Scott CI Jr, Hughes HE, et al: Lateral meningocele syndrome: Three new patients and review of the literature. Am J Med Genet 70:229–239, 1997. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 452. Comment This 45-year-old woman has NF-1 and not Lehman syndrome. The parasagittal T1W image demonstrates erosion of the bodies and left pedicles of T4 and T5 with enlargement of the neural foramina. On the axial image at T4–T5, the CSF-equivalent mass extends through the left neural foramen. Lateral thoracic meningocele is a CSF-filled, dura-covered sac that protrudes laterally and anteriorly through an enlarged neural foramen. It is associated with neurofibromatosis in 85% of cases and is bilateral in 10%. The etiology of lateral meningocele includes the following: connective tissue disorder (NF-1, Marfan syndrome, and Ehlers-Danlos syndrome), spinal trauma, and abnormal lengthening of the nerve sleeve. The meningocele is commonly associated with scoliosis (angled or short segment) and protrudes from the convex border of the spinal curve. T5–T6 is the most common level for a lateral meningocele, which tends to be right-sided. Occasionally, traction on the nerve roots may cause tenting of the spinal cord into the meningocele. Motor or sensory symptoms and signs attributable to the lesion are present in less than half the patients, with about 25% complaining of pain. Notes 28 2. Lipoma, teratoma, dermoid. 3. The most frequent location for intradural lipomas is the thoracic region (about 30% of all cases). 4. The dorsal roots are located anterolateral to the cord-lipoma junction and lateral to the ventral roots. Reference Razack N, Jimenez OF, Aldana P, et al: Intramedullary holocord lipoma in an athlete: case report. Neurosurgery 42:394–396, 1998. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 822, 824f. Comment The intradural, and apparently intra- and extramedullary, mass extending from C5 to C7 is hyperintense on the T1W image and hypointense on the STIR image, relative to cord tissue, consistent with a lipoma. While the term intradural is routinely used, it has been noted that these tumors usually have some connection with the dorsal thecal sac and, thus, are not completely intradural. They may appear to be intramedullary, as in this case. In accordance with the hypothesis of premature disjunction, a boundary separates the dorsally placed lipoma from the cord proper, resulting in splaying of the dorsal horns (myeloschisis) and an anterolateral course for the dorsal roots. Hypothetically, the dorsal roots should be distinct from the tumor; however, dorsal roots exiting through the lateral aspect of the lipoma have been observed, and this condition plus the lack of a distinct plane between tumor and spinal cord may preclude complete resection of the tumor. Intradural lipomas comprise approximately 1% of primary intraspinal masses. Most (55%) are discovered in individuals between 10 and 30 years of age. Enlargement of the spinal canal, with erosion of pedicles, lamina, and/or posterior vertebral bodies, is the most commonly associated vertebral abnormality, detected in 53% of cases. When a soft tissue or cystic component is present in addition to the adipose tissue, the differential diagnosis should include dermoid and teratoma. Notes
  34. 34. CASE 15 1. Is the migration path for lumbar disks that are extruded or sequestered more likely to be midline or paramedian in location? Why? 2. Name the attachments of the posterior longitudinal ligament (PLL). 3. Identify the anterior epidural space (AES) in this T1W axial image at the L4 level. List the four major constituents of the AES. 4. Which contains more fatty tissue, the lumbar or the cervical epidural space? 29
  35. 35. A N S W E R S CASE 15 Sagittal, Epidural Midline Septum 1. Paramedian, because of the presence of the midline sagittal septum, which divides the anterior epidural space into left and right compartments (as shown in this case) and constrains the migrating disk to either the left or the right compartment. 2. Anulus fibrosus at the level of the disk space; sagittal septum and lateral membranes at the level of the vertebral body. 3. The AES is the hyperintense region (with two compartments) located between the thecal sac and the posterior surface of the vertebral bodies. The PLL, areolar connective tissue, fat, and a venous network are the major constituents of this region. 4. Lumbar. The cervical epidural space contains predominantly blood vessels and perivascular connective tissue. References Scapinelli R: Anatomical and radiologic studies on the lumbosacral meningo-vertebral ligaments of humans. J Spinal Disord 3:6–15, 1990. Schellinger D, Manz HJ, Vidic B, et al: Disk fragment migration. Radiology 175:831–836, 1990. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 769. Comment As shown on this axial image at the level of the L4 pedicles, a predominantly fat-filled space is located between the posterior surface of the vertebral body and the thecal sac. The hypointense line at the margin of the thecal sac represents the anterior theca and PLL. Perpendicular to this line is a sagittally oriented hypointense band in the midline—the ‘‘sagittal midline septum’’—consisting of lamellae of compact collagen. At its anterior extent the septum merges with another hypointense line, which is the periosteum of the vertebral body. The midline septum thus spans the anterior epidural space from the anterior surface of the thecal sac to the periosteum and divides the space into two compartments. The superior and inferior margins of these compartments are formed by the insertion of the PLL into the anulus fibrosus (i.e., no midline septum is opposite the disk space). The posterior margins of the AES are formed by the PLL and the lateral membranes, which are fibrous bands that stretch laterally from the free edge of the PLL to the lateral wall of the canal. The effect of the midline septum is to direct migrated disk extrusions and fragments into either the left- or the right-sided compartment. The midline 30 septum and lateral membranes are also referred to as lumbosacral meningo-vertebral ligaments and, near the tip of the thecal sac, as the sacrodural ligaments of Trolard and Hofmann. Notes
  36. 36. CASE 16 1. Based on the T1W left parasagittal image and axial images at the L4 and L4–L5 levels, suggest a diagnosis and explanation for the location of the anterior epidural mass. 2. Why is herniated disk preferred to herniated nucleus pulposus when describing herniations? 3. Does a herniated disk have to be sequestered (i.e., be a free fragment) to undergo migration? 4. Give an example of two herniations by the same disk. 31
  37. 37. A N S W E R S CASE 16 Herniated Disk Constrained by Midline Septum 1. The mass is an L4–L5 herniated (extruded) disk with superior migration to the level of the L4 pedicles. It is constrained to the left anterior epidural compartment by the sagittal midline septum. Epidural fat outlines the posterior margin of the migrated disk on the axial image at the level of the L4 pedicles. 2. Herniated disk is preferred because tissues other than the nucleus are common components of displaced disk material. These tissues include cartilage, fragmented apophyseal bone, and fragmented anulus. 3. No. An extruded disk that is not sequestered can undergo migration. Sagittal postcontrast T1W images are useful in determining whether or not the migrated component is sequestered. A sequestered disk often demonstrates enhancing scar tissue separating the sequestration from the parent disk. 4. Herniation through an anular fissure or tear into the anterior epidural space (as shown here), and herniation through a break in an adjacent vertebral body endplate (intravertebral herniation, or Schmorl node). A third herniation, into the prevertebral space, may also occur. References Fardon DF, Milette PC: Nomenclature and classification of lumbar disc pathology: recommendations of the combined task forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. Spine 26:E93– E113, 2001. Schellinger D, Manz HJ, Vidic B, et al: Disk fragment migration. Radiology 175:831–836, 1990. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 769–770. Comment Schellinger and colleagues have reported that when herniated disks (extruded disks, with or without sequestration) migrate either superiorly or inferiorly, the migrated component is found predominantly in either the left or right half of the anterior epidural space in 94% of cases. The migrated component straddles the midline in only 6% of cases. Based on studies of cadaver specimens, the authors concluded that the anterior epidural space opposite the vertebral body is divided into a left and a right compartment by a collagenous, sagittal midline septum 32 (adherent to the posterior longitudinal ligament and the vertebral body periosteum). The migrating disk is thus directed into, and loosely constrained to, either compartment. If the disk is pushed across the midline, the leading edge is smoothly capped by the bowed and potentially detachable midline septum. Schellinger and associates also found no preferred direction of migration (42% superior, 40% inferior, and 18% bidirectional), and moreover, no consensus on migration direction is apparent in the radiology literature. Since 2001, a standardized nomenclature and classification system for imaging features of lumbar disk pathology has been endorsed by several biomedical societies. In this nomenclature, herniated disks may take the form of protrusions or extrusions. A sequestration is a specific form of extrusion in which the displaced disk material has completely lost all continuity with the parent disk. To describe the location of a herniated disk in the axial (horizontal) plane, several terms referring to ‘‘anatomic zones’’ have been proposed. Moving from a central to a lateral direction for a left-sided herniated disk, the location would be identified as ‘‘central,’’ ‘‘left central,’’ ‘‘left subarticular,’’ ‘‘left foraminal,’’ or ‘‘left extraforaminal’’ (synonymous with ‘‘far lateral’’). As in this example, a large herniated disk may span more than one zone. In the sagittal (craniocaudal) plane, anatomic zones, which can be used to describe the extent of migration, are loosely defined as the ‘‘disk level,’’ the ‘‘infrapedicular level,’’ the ‘‘pedicular level,’’ and the ‘‘suprapedicular level.’’ In this case, the disk has migrated to the L4 pedicular level. Notes
  38. 38. CASE 17 1. List at least three indications for placement of transpedicular screws and rod fixation. 2. What are common complications of screw placement? 3. What conventional radiography or CT finding is commonly associated with loosening of a screw within bone? 4. True or False: Multilevel fusions have a higher risk of screw breakage/loosening than do single-level fusions. 33
  39. 39. A N S W E R S CASE 17 Loose Transpedicular Screw 1. Dislocation, progressive scoliosis, spondylolysis, spondylolisthesis, degenerative changes, postlaminectomy pain. 2. Screw breakage/bending, loosening, misplacement, infection, nerve injury. 3. Lucency that surrounds the screw and has a width or thickness greater than 1 mm (regardless of the length). 4. True. References ¨ Pihlajamaki H, Myllynen P, Bostman O: Complications of transpedicular lumbosacral fixation for non-traumatic disorders. J Bone Joint Surg [Br] 79:183–189, 1997. ´ ´ Sanden B, Olerud C, Petren-Mallmin M, et al: The significance of radiolucent zones surrounding pedicle screws. J Bone Joint Surg [Br] 86-B:457–461, 2004. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 788–791. Comment The axial T2W image demonstrates CSF-equivalent hyperintensity, consistent with fluid, in the space surrounding the right L5 transpedicular screw. The corresponding CT images show a lucent zone in the same region. The width of the lucent zone in the transverse plane measured 2.5 mm, consistent with loosening of the screw within its original setting. The complication rate of transpedicular screw placement varies depending on the underlying process. For nontraumatic transpedicular fusions, the complication rate is up to 57% and is generally higher in traumatic cases. The reported rate of screw loosening, regardless of underlying process, ranges from 0.6% to 27%. The rate of screw breakage ranges from 6% to 21%. Less frequent complications than those listed in answer 2 include pedicle fracture and vascular injury. A screw has become loosened when (1) a lucent zone around the screw is detected visually on either CT images or conventional radiographs, and (2) the lucent zone, as measured from the screw surface to the margin of the surrounding bone, is greater than 1 mm in width. The sensitivity of this finding is a relatively low 64%, whereas the specificity is 100%. Notes 34
  40. 40. CASE 18 1. List three inflammatory lesions shown on the postcontrast T1W images of the thoracolumbar spine and brain. 2. Do the findings favor a pyogenic or a granulomatous disease? 3. What primary mechanism produces the findings? 4. What coexisting condition would you expect to find in this 45-year-old woman? 35
  41. 41. A N S W E R S CASE 18 Craniospinal Tuberculosis 1. Vertebral osteomyelitis/diskitis (intraosseous abscess), meningitis, and cerebral (subependymal) granuloma. 2. Granulomatous disease. 3. Hematogenous spread of mycobacteria via the arteries and arterioles to the vertebral endplates, meninges, and brain parenchyma. 4. Acquired immunodeficiency syndrome (AIDS). References Jung NY, Jee WH, Ha KY, et al: Discrimi0nation of tuberculous spondylitis from pyogenic spondylitis on MRI. AJR Am J Roentgenol 182:1405–1410, 2004. Whiteman MLH, Bowen BC, Post MJD, et al: Intracranial infection. In: Atlas SW, Ed: Magnetic Resonance Imaging of the Brain and Spine. 3rd ed. Philadelphia, Lippincott Williams & Wilkins, 2002, pp 1099–1175. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 796–799. Comment The postcontrast images demonstrate a constellation of vertebral, leptomeningeal, and brain parenchymal features that favor granulomatous infection, with pyogenic infection, metastatic disease, and lymphoma being less likely. On the thoracolumbar image, a destructive lesion within T8 extends to the T 7–T8 disk space and exhibits ring enhancement. Axial images (not shown) confirmed epidural extension in the left side of the canal, as well as paraspinal involvement. Leptomeningeal enhancement of the cauda equina is evident at the inferior margin of the spine image. On the brain image, striking enhancement is noted along meningeal surfaces in the prepontine cistern, interpeduncular cistern, suprasellar cistern, and cistern of the lamina terminalis. An enhancing nodule is seen anterior to the splenium in the velum interpositum. Certain imaging features can help distinguish tuberculous from pyogenic spondylitis. Tuberculous spondylitis, which typically affects the lower thoracic spine, is favored in conditions with relatively limited involvement of the disk space in comparison with the vertebral body. In particular, rim enhancement around an intraosseous abscess on postcontrast T1W images (as in this case) is a characteristic of tuberculosis (TB) that is only occasionally demonstrated in other spinal infections. When compared with pyogenic infection, tuberculous spondylitis is more likely to have prominent paraspinal and epidural 36 masses, to demonstrate subligamentous spread to three or more vertebral bodies, and to involve posterior elements. Leptomeningeal and pachymeningeal enhancement involving the intracranial basal cisterns and the cauda equina are consistent with tuberculous meningitis and further support a diagnosis of systemic TB with hematogenous spread to the brain and spine. TB is estimated to be up to 500 times more common in patients with AIDS than in HIV-negative individuals. CNS tuberculosis occurs in 2% to 5% of patients with TB and in 10% of those with AIDS-associated TB. Notes
  42. 42. CASE 19 1. A commonly used nomenclature for characterizing disk herniation on MR imaging studies recognizes three descriptive types. Name them. 2. List some of the reasons that have been given to justify this nomenclature. 3. How common is disk bulge or herniation on MRI of individuals without back pain? 4. Which type corresponds to the findings at L4–L5 on the STIR and T2W images shown here? 37
  43. 43. A N S W E R S CASE 19 Disk Herniation (Extrusion), Lumbar 1. Protrusion, extrusion, and sequestration. 2. (a) Extrusion and sequestration may require a more extensive surgical approach than protrusion; (b) they are a contraindication to percutaneous diskectomy; (c) such categorization may help to differentiate asymptomatic from symptomatic disks. 3. Disk bulges and protrusions are common, occurring, respectively, in 52% and 27% of asymptomatic individuals. Extrusions are uncommon, occurring in only 1%. 4. Extrusion. References Brant-Zawadzki MN, Jensen MC, Obuchowski N, et al: Interobserver and intraobserver variability in interpretation of lumbar disc abnormalities: a comparison of two nomenclatures. Spine 20:1257–1263, 1995. Fardon DF, Milette PC: Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology: Nomenclature and classification of lumbar disc pathology: Recommendations of the Combined Task Forces of the NASS, ASSR, and ASNR. Spine 26: E93–E113, 2001. Jensen MC, Brant-Zawadzki MN, Obuchowski N, et al: Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med 331:69–73, 1994. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 766–773. Comment The sagittal images show a disk herniation at the L4–L5 interspace with caudal extension posterior to the L5 body (the extension beyond the interspace was focal on axial images). The portion of the disk within the canal appears to be (1) connected by a slightly thinner pedicle to the portion of the disk remaining in the L4–L5 interspace and (2) contained posteriorly by a curvilinear low signal intensity believed to represent an intact posterior longitudinal ligament (inseparable from the low signal of dura). This is sometimes called a subligamentous herniation. The herniated portion may or may not have high signal intensity compared with the interspace (parent) portion on T2W images. In general, there are two nomenclature systems for categorizing degenerative disk pathology as displayed on MR imaging. In nomenclature I, disks extending beyond the interspace are categorized as bulging 38 (symmetric, diffuse extension) or herniated (symmetric or asymmetric, focal extension). In nomenclature II, disks extending beyond the interspace are categorized as bulging (symmetric, circumferential extension, i.e., 50–100% of the circumference of the disk space), protruded (asymmetric or symmetric, focal extension, with a roughly conical shape pointing posteriorly, and residual low signal intensity annular fibers), or extruded (as described above for this case, without or with caudad or cephalad extension, with complete rupture of annular fibers). Nomenclature II includes a description of a sequestered disk as an extruded disk with a dissociated fragment (‘‘free fragment’’). Nomenclature II with minor modifications has been endorsed by the major societies representing clinicians and investigators in the area of spine imaging. Notes
  44. 44. CASE 20 1. List the four most common skeletal sites involved by Paget disease. 2. What are the three phases of Paget disease? 3. True or False: Bone scintigraphy will be positive on all three phases. 4. Describe three CT/MR findings that would suggest sarcomatous transformation of Paget disease. 39
  45. 45. A N S W E R S CASE 20 Paget Disease, Cervical 1. Skull, spine, pelvis, and proximal long bones. 2. Lytic, mixed, and blastic phases. 3. True. 4. Mass-like replacement of the bone marrow, cortical destruction, associated soft-tissue mass. Reference Smith SE, Murphey MD, Motamedi K, et al: Radiologic spectrum of Paget disease of bone and its complications with pathologic correlation. Radiographics 22:1191–1216, 2002. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 830, 831f. Comment MR images demonstrate diffuse abnormal low T1 and high T2 signal within the C7 vertebral body, which is mildly enlarged. This finding may be difficult to differentiate from a neoplastic process (eg, blastic metastasis). The key to the diagnosis is the appearance of the spinous process. It demonstrates thickening of the cortex (which is low in signal on both MR sequences) and marked enlargement. The sagittal CT reformatted image demonstrates enlargement of C7 and thickening of the trabecular pattern. Paget disease is due to excessive and anomalous bone remodeling. Common complications include osseous weakening (with secondary deformity and fracture), arthritis, neurologic compromise, and sarcomatous transformation. Polyostotic disease (65–90% of cases) is more common than monostotic disease (10–35% of cases). Common CT findings of uncomplicated Paget disease include bone enlargement, disorganized trabecular thickening, and cortical thickening (as seen in this case). The MR signal intensity pattern is variable. In the early (lytic) phase, the marrow space is heterogeneous in signal on both T1W and T2W images. In the mixed phase, there is preservation of yellow marrow signal. Thus, the marrow follows fat signal intensity in this phase. Speckled enhancement is found on postcontrast images. The mixed phase is by far the most commonly seen. In the blastic phase, low signal intensity usually is found on all sequences. This corresponds to bony sclerosis. All MR sequences must be carefully examined to exclude sarcomatous transformation. Notes 40
  46. 46. CASE 21 1. Which intradural tumor typically involves the dorsal nerve roots? 2. Based on the axial T1W image and on the postcontrast, fat-saturated T1W sagittal image, would you recommend CT myelography, brain CT, brain MR imaging, or MR myelography as the next study? 3. List three ‘‘granulomatous diseases’’ that may produce leptomeningitis with prominent leptomeningeal (spine) and pachymeningeal (intracranial basal cisterns) enhancement patterns. 4. How often do these three diseases coexist? CASE 22 1. Why is this disease unlikely to be lymphoma or metastasis? 2. On the basis of the axial T1W and T2*W images at C6–C7, which root of the right brachial plexus is abnormal? 3. Which muscles border the mass and are greatly displaced by it? 4. Name three tumors that are likely to present with a ‘‘dumbbell’’ appearance on MR or CT. 41
  47. 47. A N S W E R S CASE 21 CASE 22 Sarcoidosis, Cauda Equina Extradural Schwannoma, Cervical 1. Nerve sheath tumor (schwannoma/neurofibroma). 1. The widened right neural foramen implies a chronic condition rather than an aggressive malignancy. 2. Brain MR imaging. 3. Sarcoidosis, tuberculosis, and fungal infection. 4. Patients with sarcoidosis have an increased incidence of tuberculosis (2–5%) as well as of fungal infections—Aspergillus mycetomas, candidiasis, and cryptococcosis. References Christoforidis GA, Spickler EM, Recio MV, et al: MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and response to treatment. AJNR Am J Neuroradiol 20:655–669, 1999. Spencer TS, Campellone JV, Maldonado I, et al: Clinical and magnetic resonance imaging manifestations of neurosarcoidosis. Semin Arthritis Rheum 34:649–661, 2005. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 799–800. Comment The postcontrast, fat-saturated T1W image demonstrates clumping of nerve roots with smooth and nodular enhancement of the cauda equina. These findings are consistent with leptomeningeal disease, for which the differential diagnosis includes drop metastases from cord or brain tumors (e.g., glioblastoma multiforme, ependymoma, medulloblastoma), lymphoma, melanoma, carcinomatous meningitis (e.g., breast or lung primary neoplasm), and infectious/inflammatory disorders, especially those that incite a granulomatous response in the host tissue. The next imaging study should be MR imaging with and without contrast enhancement of the remainder of the neural axis (brain and spine) to look for clues regarding the source of the lumbar leptomeningeal lesions. Myelographic studies would not add to the information available from pre- and postcontrast MR imaging. Neurosarcoidosis has a variety of spinal manifestations, including spinal cord masses, leptomeningitis (e.g., cauda equina syndrome), and/or lumbosacral nerve root masses. In one study, 8 (24%) of 34 patients with neurosarcoidosis had spinal cord and/or nerve root involvement on MR imaging. In general, the percentage of neurosarcoidosis patients with spinal cord lesions is in the range of 6% to 8%, with most lesions found in the cervical region. The most common abnormal MR findings in the brain are (1) leptomeningeal and parenchymal enhancement/thickening in the region of the chiasm, infundibulum, and hypothalamus on postcontrast T1W images, and (2) white matter hyperintensities on T2W images. Notes 42 2. C7. The mass involves the right C7 nerve. Its ventral ramus is the C7 root of the plexus. 3. Anterior and middle scalene muscles, which form two sides of the interscalene triangle. The plexus and the subclavian artery pass through the interscalene triangle. 4. Nerve sheath tumor, meningioma, ganglioneuroma/ neuroblastoma. References Celli P, Trillo G, Ferrante L: Spinal extradural schwannoma. J Neurosurg Spine 2:447–456, 2005. Mautner VF, Tatagiba M, Lindenau M, et al: Spinal tumors in patients with neurofibromatosis type 2: MR imaging study of frequency, multiplicity, and variety. AJR Am J Roentgenol 165:951–955, 1995. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 820–821. Comment The axial images reveal a well-marginated extradural mass with a prolonged T2 relaxation time extending from the right C6–C7 neural foramen to the paraspinal region. An important feature that could be confirmed with a CT scan is the apparently smooth widening of the neural foramen. This finding implies a chronic process favoring a benign neoplasm such as a nerve sheath tumor, hypertrophic neuropathy such as that of DejerineSottas, or a complex meningeal cyst. By carefully tracking the lesion laterally, you may find that it courses between the anterior and middle scalene muscles, as expected for a neural lesion involving the roots of the brachial plexus. Although it is impossible to differentiate schwannoma from neurofibroma by imaging, solitary nerve sheath tumors in the spine are almost always schwannomas. These masses occur in patients without neurofibromatosis (as in this case) and in patients with neurofibromatosis type 2 (often in association with meningiomas and/or ependymomas). When a schwannoma reaches the size of the lesion shown in this case, it is common to find associated hemorrhage, cyst formation, and/or fatty degeneration, resulting in heterogeneous signal intensity and heterogeneous enhancement. Lesions with both intradural and extradural components are usually narrowed at the neural foramen, resulting in a ‘‘dumbbell’’ appearance. Notes
  48. 48. CASE 23 1. Patients with the lesion demonstrated on the fast-spin-echo T2W and the postcontrast T1W images often present with lumbar or lumbosacral plexopathy. Why? 2. What is the differential diagnosis based on the imaging findings? 3. What are the three most common types of retroperitoneal sarcomas? 4. True or False: Poorly differentiated liposarcomas may demonstrate no evidence of fat on either CT or MR imaging. 43
  49. 49. A N S W E R S CASE 23 Retroperitoneal Sarcoma 1. The large mass involves the right psoas muscle, paravertebral region, and L2 vertebra, and it demonstrates epidural extension. The lumbar plexus is formed along the medial margin and within the substance of the psoas muscle from L1 to L5, with the lumbosacral trunk continuing inferiorly to contribute to the sacral plexus. 2. Retroperitoneal sarcoma, lymphoma, metastatic disease, and granulomatous disease or fungal infection. 3. Liposarcoma, leiomyosarcoma, and malignant fibrous histiocytoma. 4. True. References Gupta AK, Cohan RH, Francis IR, et al: CT of recurrent retroperitoneal sarcomas. Am J Roentgenol 174:1025– 1030, 2000. Mendenhall WM, Zlotecki RA, Hochwald SN, et al: Retroperitoneal soft tissue sarcoma. Cancer 104:669– 675, 2005. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 822, 824. Comment Retroperitoneal sarcomas are usually advanced by the time of diagnosis. The treatment is surgical, and macroscopic evidence of clear resection of tumor margins is the best predictor of patient survival. Adjuvant radiation and chemotherapy have no effect on survival. The 5-year survival is 50%. In approximately 20% to 30% of patients the tumor will metastasize outside the abdominal cavity with lung being the most common location. The risk of recurrence has been reported as high as 75% in the first 2 years after surgery. About half of all recurrences occur within the surgical bed, while the remaining half are found elsewhere in the abdominal cavity. Liposarcomas are the most common type of retroperitoneal sarcoma. When liposarcomas with fat-containing regions are resected and then recur, about half of the recurrent tumors show no imaging evidence of fat. Cautious evaluation of potential recurrence versus postoperative scarring is warranted. Notes 44
  50. 50. CASE 24 1. Name three inflammatory conditions associated with atlantoaxial subluxation. 2. How would you distinguish between joint effusion and pannus in patients with rheumatoid arthritis of the craniocervical region? 3. What are the five possible subluxations/dislocations at the C1–C2 level, and which one is the most common? 4. What is the importance of identifying the supradental fat pad? 45
  51. 51. A N S W E R S CASE 24 Adult Rheumatoid Arthritis 1. Rheumatoid arthritis, ankylosing spondylitis, tonsillitis/pharyngitis. 2. Contrast-enhanced T1W spin-echo MR images. 3. Anterior, posterior, lateral, rotary, vertical. Anterior is the most common, and posterior the least common. Vertical subluxation, seen in up to 38% of rheumatoid patients, may result in ‘‘pseudobasilar invagination’’ or ‘‘cranial settling’’—diagnosed when the odontoid tip is located >4.5 mm above McGregor’s line, or by other criteria. 4. In patients with rheumatoid arthritis, loss of supradental fat implies the presence of pannus and/ or thickened ligaments. References Reiter MF, Boden SD: Inflammatory disorders of the cervical spine. Spine 23:2755–2766, 1998. Stiskal MA, Neuhold A, Szolar DH, et al: Rheumatoid arthritis of the craniocervical region by MR imaging: detection and characterization. AJR Am J Roentgenol 165:585–592, 1995. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 442. Comment The preoperative T1W sagittal MR image demonstrates a soft tissue mass with uniform, intermediate signal involving the dens, the widened atlantodental (predental) space, as well as the retrodental and supradental regions. Erosion of the dens, especially its posterior surface, is confirmed on the postoperative reformatted sagittal CT image. The T1W MR image also shows the marked canal stenosis and cord compression resulting from anterior subluxation of C1 on C2. The findings are consistent with an inflammatory process such as pannus formation in a patient with rheumatoid arthritis. The differential diagnosis for a mass involving the odontoid and periodontoid region includes primary bone tumor, chordoma, metastasis, plasmacytoma, lymphoma, or possibly meningioma. The nasopharynx appears normal. Pannus is an inflammatory exudate overlying the lining layer of synovial cells on the inside of a joint; however, histologic findings in rheumatoid patients with inflamed synovium may vary from a fibrinous fluid collection in the joint space to granulation tissue with abundant vessels, angioblasts, inflammatory cells, and soft tissue edema to dense fibrous tissue without proliferating vessels or edema. Contrast-enhanced T1W images of the craniocervical region may differentiate 46 these variations and have been categorized into four groups—joint effusion, hypervascular pannus, hypovascular pannus, and fibrous pannus—on the basis of the enhancement patterns. These patterns have been detected even when plain radiographic studies are negative. Pannus is most commonly found in a retrodental location, as illustrated in this case. The synovium-lined articular capsules and bursae that may exhibit pannus formation are peridental—predental (C1-dens articulation), retrodental (transverse ligament–dens bursa), supradental (bursa)—and zygapophyseal (facet joints) in location. Thickening of the ligaments and dura may also contribute to the mass-like appearance of pannus. Notes
  52. 52. CASE 25 1. What is the name of this ‘‘Aunt Minnie’’ sign? 2. A classification for the variable appearance of lumbar arachnoiditis on CT myelography and MR imaging identifies three patterns. Name them. 3. Under what conditions has central clumping of nerve roots of the cauda equina been found to be reversible? 4. True or False: In the majority of cases, arachnoiditis shows little enhancement on postcontrast MR imaging. 47
  53. 53. A N S W E R S CASE 25 Arachnoiditis, Lumbar 1. ‘‘Empty thecal sac’’ sign. 2. Pattern 1 is clumping of nerve roots into cords and represents central adhesion of the roots within the thecal sac. Pattern 2 is a peripheral displacement of roots (‘‘empty thecal sac’’ sign) and represents adhesion of the nerve roots to the sac. In pattern 3, the thecal sac is filled by a mass, representing the end-stage of the inflammatory response. This mass can cause a ‘‘block’’ to the flow of intrathecal contrast on myelography and produce an irregular ‘‘candle-dripping’’ appearance. 3. Central clumping after lumbar laminectomy has been shown to be reversible, on the basis of serial MR imaging. 4. True. Reference Georgy BA, Snow RD, Hesselink JR: MR imaging of spinal nerve roots: techniques, enhancement patterns and imaging findings. AJR Am J Roentgenol 166:173–179, 1996. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, p 790. Comment Prior to the advent of MR imaging, myelography was the procedure of choice for evaluating the spinal cord and nerve roots. The procedure, though, was considered to be a leading cause of arachnoiditis, especially when lipophilic contrast agents such as Pantopaque were used and intermixed with blood in the subarachnoid space. In current practice, myelography is usually reserved for certain groups of patients: (1) most patients with magnetically sensitive devices, such as cardiac pacemakers; (2) some patients with spinal instrumentation, such as rods, screws, or wires with or without ferromagnetic properties; and (3) some patients with suspected conditions, such as spinal meningeal cyst or CSF leak, who might benefit from identification of contrast material accumulation. In the lower lumbar spine, the nerve roots of the cauda equina normally demonstrate a thin feathery appearance on myelography, CT myelography, and MR imaging. On MR imaging, this appearance is best detected and evaluated with T2W axial images. In patients with arachnoiditis or arachnoidal adhesions due to a variety of causes, the nerve roots may adhere to each other (pattern 1) and/or to the wall of the thecal sac (pattern 2, as in this case), or form a conglomerate 48 mass (pattern 3). The causes of arachnoiditis include infection, subarachnoid hemorrhage (secondary to trauma, surgery, or vascular malformation), and inflammatory diseases (eg, sarcoidosis). Notes
  54. 54. CASE 26 1. True or False: Lumbar disk herniations rarely regress spontaneously. 2. Are lateral disk herniations more likely to spontaneously regress than central disk herniations? 3. True or False: The majority of patients who undergo conservative medical treatment for disk herniation demonstrate worsening of the clinical picture. 4. Are the largest disk herniations the ones that most frequently show a spontaneous decrease in size? 49
  55. 55. A N S W E R S CASE 26 Spontaneous Reduction of Disk Herniation, Lumbar 1. False. 2. No. There is no correlation between the location of a disk herniation and the probability of regression. 3. False. In the study by Bozzao et al, only 8% of the patients demonstrated worsening of the clinical picture. 4. Yes, especially when the disk herniations are larger than 6 mm. Reference Bozzao A, Gallucci M, Masciocchi C, et al: Lumbar disk herniation: MR imaging assessment of natural history in patients treated without surgery. Radiology 185: 135–141, 1992. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 771–772. Comment Axial fast-spin-echo T2W image at L5–S1 from September 2001 demonstrates a central disk herniation. The patient underwent conservative medical treatment. A follow-up study from May 2005 demonstrates spontaneous reduction of disk herniation with a residual bulging disk. In the study cited above, the authors followed 69 patients with back pain and MRI proven lumbar disk herniations. The average follow-up period was 11 months. Sixty-three percent of patients had a size reduction of more than 30%. Nearly half (48%) of all patients showed a reduction of at least 70%. Only 8% of patients demonstrated interval progression of clinical signs and symptoms. Size reduction correlated with symptom improvement. Conservative medical treatment has a reported satisfactory response in over 70% of patients. Similar findings have been reported by other investigators. For this reason, many physicians argue that disk herniation is primarily a medical (nonsurgical) disease. Notes 50
  56. 56. CASE 27 1. Name at least three tissues or substances that produce hyperintensity on T1W images. 2. What is the differential diagnosis for the lesion shown on the T1W image? 3. The tumor shown here is most frequently found in which spinal region: cervical, thoracic, or lumbar? 4. True or False: Chemical shift artifact occurs along the phase-encoding direction. 51
  57. 57. A N S W E R S CASE 27 Intradural Lipoma, Conus 1. Fat, melanin, blood (methemoglobin), proteinaceous collections, mucin, and Pantopaque contrast material. 2. Lipoma, subarachnoid hemorrhage, dermoid, Pantopaque collection, melanotic lesion, neurenteric cyst. 3. The most frequent location for intradural lipomas is the thoracic region (about 30% of all cases). 4. False. It occurs along the frequency-encoding direction. Reference Kamat A, Findlay G: Intramedullary migration of spinal cord lipoma. J Neurol Neurosurg Psychiatry 74:1593– 1594, 2003. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 822, 824. Comment The T1W image demonstrates a hyperintense mass at the level of the conus medullaris. The signal intensity of the lesion is heterogeneous on the T2W image, with distinct chemical shift artifacts along the anterior margin (dark line), center (adjacent bright and dark lines), and posterior margin (bright line) of the lesion. The hyperintensity of the mass is suppressed on the fat-saturated, contrastenhanced T1W image. These findings are consistent with an intradural lipoma. Although the term intradural is routinely used, it has been noted that these tumors usually have some connection with the dorsal thecal sac and, thus, are not completely intradural. They may also appear to be intramedullary. Because the dorsal roots sometimes exit through the lateral aspect of the lipoma, a distinct plane between tumor and spinal cord may not be present, precluding complete resection of the tumor. Cases in which the lipoma appears to encompass the entire cross-section of the cord at some level represent about 3% of all cases of intradural lipoma. Intradural lipomas comprise approximately 1% of primary intraspinal masses. Most (55%) are discovered in individuals between 10 and 30 years of age. Enlargement of the spinal canal, with erosion of pedicles, lamina, and/or posterior vertebral bodies, is the most commonly associated vertebral abnormality, detected in 53% of cases. Spinal cord lipomas may become symptomatic owing to cord compression or cord tethering. They can grow in size when a patient’s body weight increases. Notes 52
  58. 58. CASE 28 1. Name three odontoid anomalies occurring in childhood and adolescence. 2. Do these anomalies produce craniocervical instability? 3. What features may help distinguish congenital os odontoideum from an old odontoid fracture with nonunion? 4. What does the horizontal dark line within C2 on the T1W sagittal image represent? 53
  59. 59. A N S W E R S CASE 28 Os Odontoideum 1. Aplasia, hypoplasia, and os odontoideum. 2. Yes. 3. Congenital os odontoideum and posttraumatic fracture fragment may be indistinguishable if the fracture is old and has smooth sclerotic margins like those of the ossicle. In patients with os odontoideum, though, hypoplasia of the dens is almost always present, and often there is a wide gap between the dens and the ossicle. Hypertrophy of the anterior arch of the C1 (as shown in this case) favors a diagnosis of os odontoideum and may be associated with clefting or absence of the posterior arch of C1. Nevertheless, many investigators believe that os odontoideum is acquired (posttraumatic) rather than congenital/ developmental. 4. The synchondrosis at the odontoid base, called the subdental synchondrosis. References Barnes PD, Kim FM, Crawley C: Developmental anomalies of the craniocervical junction and cervical spine. Magn Reson Imaging Clin N Am 8:651–674, 2000. Smoker WR: MR imaging of the craniovertebral junction. Magn Reson Imaging Clin N Am 8:635–650, 2000. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 845–846. Comment Components of the craniocervical junction are derived from the last occipital sclerotome or proatlas and from the first three cervical sclerotomes. Proposed etiologies for the os odontoideum include congenital (proatlas remnant or hypertrophied ossiculum terminale) and acquired (odontoid fracture) mechanisms. The ossicle may be located near the dens tip (expected location, orthotopic os) or near the basion (anterior lip of foramen magnum, dystopic os) as in this case. The dens is stabilized primarily by attachment of the alar, apical, and transverse (cruciate) ligaments. Hence, odontoid anomalies that affect the integrity of these ligaments can produce craniocervical instability. Odontoid hypoplasia, for example, is often associated with ligamentous deficiency and atlantoaxial or occipitoaxial instability. Determining the nature and degree of instability are more important than establishing the origin of the anomaly. Anterior displacement of the os-atlas complex relative to the body of the axis in the neutral lateral 54 position, as well as increased range of motion (instability) during flexion and extension, can result in cord compression, as shown in this case. Treatment of odontoid anomalies often requires immobilization and traction to achieve reduction, followed by surgical stabilization. An increased incidence of os odontoideum has been reported for congenital conditions such as Down syndrome, Morquio syndrome, Klippel-Feil spectrum of anomalies, and spondyloepiphyseal dysplasia. Notes
  60. 60. CASE 29 1. Describe the abnormal findings on the precontrast and postcontrast T1W images. 2. Give a differential diagnosis based on these findings. 3. Is tuberculous meningitis associated with primary infection more commonly seen in adults or in children? 4. Which imaging study would you suggest next? 55
  61. 61. A N S W E R S CASE 29 Tuberculous Meningitis 1. Abnormal, smooth leptomeningeal enhancement of the distal cord/conus and cauda equina. Cauda equina roots are mildly enlarged. 2. Bacterial, fungal, or viral meningitis; sarcoidosis; metastatic disease (‘‘carcinomatous meningitis’’) due to hematogenous or CSF dissemination; lymphoma ´ or leukemia; Guillain-Barre syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and hereditary motor and sensory neuropathies (HMSN types I and III). 3. Children. 4. MR imaging of the brain, to look for other manifestations of CNS tuberculosis—leptomeningeal enhancement in the basal cisterns, hydrocephalus, and infarction, as well as tuberculomas. References Berenguer J, Moreno S, Laguna F, et al: Tuberculous meningitis in patients infected with the human immunodeficiency virus. N Engl J Med 326:668–672, 1992. Kox LF, Kuijper S, Kolk AH: Early diagnosis of tuberculous meningitis by polymerase chain reaction. Neurology 45(12):2228–2232, 1995. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 304–308, 802, 821–822. Comment Tuberculous meningitis is more frequently seen in children than in adults. It is typically manifested during primary infection (usually from the lungs). Postcontrast intracranial imaging demonstrates meningeal enhancement, which is most prominent at the base of the skull because of a copious exudate in the basal cisterns. Patients frequently develop hydrocephalus, which does not improve after treatment of the mycobacterium. Diagnosis frequently has to be made on a clinical basis. The sensitivity of CSF acid-fast staining is only 9%. The sensitivity of CSF PCR testing is approximately 48%. The growth of the microorganism may take up to 3 months. Culture, therefore, more often serves to confirm the clinical diagnosis. In a study of 2205 tuberculosis patients, Berenguer et al found that patients who also were HIV infected had a five-fold higher risk of tuberculous meningitis than did patients who were not HIV infected (10% vs. 2%, respectively). Nevertheless, the clinical outcome for both groups was the same. 56 CNS tuberculomas can form during primary tuberculosis as a result of hematogenous spread of mycobacteria and seeding of the brain parenchyma and the leptomeninges. The body’s immune response produces a fibrotic capsule that contains the developing tubercles, leading to the formation of a tuberculoma. Tuberculoma and tuberculous meningitis are related pathologic processes that manifest as different clinical conditions. Only 10% of patients with tuberculomas have tuberculous meningitis. Notes
  62. 62. CASE 30 1. Which findings on the axial CT image (C4 level) characterize this type of fracture? 2. Which finding on the right parasagittal T1W MR image is consistent with this type of fracture? 3. What is the probable mechanism of injury? 4. Can this fracture be stabilized by one-level plating? 57
  63. 63. A N S W E R S CASE 30 Fracture-Separation of the Articular Mass 1. Fractures through the right lamina and the right pedicle. 2. ‘‘Horizontalization’’ of the right lateral mass. 3. Extension-rotation. 4. No. References Kotani Y, Abumi K, Ito M, et al: Cervical spine injuries associated with lateral mass and facet joint fractures: new classification and surgical treatment with pedicle screw fixation. Eur Spine J 14:69–77, 2005. Levine AM: Facet fractures and dislocations. In: Levine AM, Eismont FJ, Garfin SR, Zigler JE, Eds: Spine Trauma. Philadelphia, WB Saunders, 1998, pp 331–366. Cross-Reference Neuroradiology: THE REQUISITES, 2nd ed, pp 840–842. Comment As evidenced by the slight rotation of the C4 vertebra on the CT image and by the offset of the facets on the parasagittal MR image, this is a unilateral facet injury. These injuries are categorized as purely ligamentous (ranging from facet subluxation to ‘‘perched facet’’ to facet dislocation), as fractures of only the superior facet or inferior facet, or as fracture-separations of the articular mass with associated displacement. The fractures through the right lamina and the pedicle identify this injury as a fracture-separation of the right lateral mass. This fracture is more often seen as a unilateral injury than a bilateral injury. The mechanism is extension-rotation, as opposed to the flexion-rotation responsible for superior or inferior facet fractures. The fracture-separation creates a free-floating fragment with rotational instability that cannot be stabilized over a single level but rather requires stabilization at both C4–C5 and C3–C4. Typically, treatment is bilateral lateral mass plating from C3 through C5 (two-level plating, C3–C4 and C4–C5). After fracturing, the lateral mass often rotates, and lateral radiographs or a parasagittal MR image (as here) may show ‘‘horizontalization’’ of the lateral mass. Correspondingly, the anteroposterior radiograph shows foreshortening of the lateral mass. In this case, horizontalization and displacement of the right C4 lateral mass have resulted in a perched appearance of the tip of the inferior articular process (here referred to as the inferior facet) of C4 on the superior articular process of C5. Notes 58
  64. 64. CASE 31 1. Conventional postcontrast T1W axial images were obtained at the levels of L3 (upper left image) and L4–L5 (lower left image) in a 62-year-old woman with right lower extremity pain. Name three intradural structures that may produce the unusual findings in this case. 2. What two degenerative conditions are reportedly associated with the intradural postcontrast enhancement shown here? 3. How common is lumbar nerve root enhancement in unoperated, immunocompetent patients? 4. What AIDS-related opportunistic infection is often manifested as lumbosacral nerve root enhancement? 59

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