Intradural and extradural dorsal spinal pediatric lesions

Transcription

1 Intradural and extradural dorsal spinal pediatric lesions Poster No.: C-2520 Congress: ECR 2015 Type: Educational Exhibit Authors: L. Riaza, M. Pérez Rubiralta, C. Perez Balagueró, M. Rebollo, E. Inarejos, M. Navallas, J. Muchart ; Esplugues de Llobregat/ ES, L'Hospitalet de Llobregat/ES, Badalona/ES, Esplugues del 5 Llobregat/ES, BARCELONA/ES Keywords: MR, Oncology, Pediatric, Neuroradiology spine, MR-Diffusion/ Perfusion, Contrast agent-intravenous, Education, Perception image, Tissue characterisation, Cancer, Education and training DOI: /ecr2015/C-2520 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 41

2 Learning objectives - To make an anatomic review of the spinal column, and to be emphasized the difference between the intradural and the extradural spaces. - To narrow the differential diagnosis in the different types of dorsal spinal lesions in the pediatric population. - To evaluate the role of radiology, specially the magnetic resonance imaging (MRI) as a diagnostic tool which allows making the correct difference between this lesions and helps to achieve almost certain the diagnosis in some cases. - To realize how the diffusion-weighted image offers more help than other MRI sequences. - To illustrate different practical cases. Background 1) INTRODUCTION to the anatomy of the spinal canal: meninges, spaces and its compartments In establishing the differential diagnosis for a spinal lesion, location is the most important feature. Therefore, below we will detail the anatomy of the spine and its major constituents. The spinal canal is formed by different structures. - There are the MENINGES, three membranes that protect externally the central nervous system and contain the cerebrospinal fluid (CSF). These layers are: o The dura mater: a thick fibrous membrane, which extends from the foramen magnum to the S2, where the dura and the arachnoid join with the filum terminale. o The arachnoid mater: a sheet of connective tissue attached to the dura mater internally and the pia mater externally. Is continued with the roots of the spinal nerves until they leave the intervertebral foramen. Page 2 of 41

3 o The pia mater: a thin fibrous tissue impermeable to fluid, allowing it to enclose cerebrospinal fluid. At the end of the conus the pia mater forms the filum terminale, a fibrous linear structure, surrounded by the dura. - And there are the SPACES between the meninges, which are: o The epidural space: a space which separate the dura mater from the bone. It contains fat, loose connective tissue and blood vessels (venous plexus). Through it passed the nerve roots and vessels. o The subdural space: a virtual space present when dura mater and arachnoid separate because of injury or illness. o The subarachnoid space: the space between the arachnoid and the pia mater, which is attached to the central nervous system tissue. It is filled with cerebrospinal fluid (CSF) and contains glial tissue, nerve fibers and vascular elements. Page 3 of 41

4 Fig. 1 References: Benjamin Cummings, an imprint of Addison Wesley Lognam, Inc Knowledge of the different anatomical compartments is useful for the differential diagnosis of the lesions affecting the spinal canal. In our work we make an anatomical overview of each one of the compartments and a review of the tumoral lesions. The spinal canal is the space that runs through spinal cord and nerve roots. Anatomical boundaries comprise: an anterior wall of the posterior surface of vertebral bodies and intervertebral discs, and the posterior longitudinal ligament (PLL); in their sidewalls, pedicles, lateral masses and facet joints; and in its rear wall, the sheets and yellow ligaments. Due to their localization, the most common presenting symptoms include weakness, back pain and radicular pain. We consider three fundamental spinal anatomical compartments: extradural, intraduralextramedullary and intradural intramedullary. In order to localize each lesion, we use two anatomical landmarks, the dura matter and the spinal cord. Page 4 of 41

5 Fig. 2 References: 2014 CLÍNICA NEUROCRÂNIO & COLUNA & ESPECIALIDADES 2) GENERALITIES of the spinal lesions A spinal lesion may have its origin in any of the above structures. They can grow from: the spinal cord / filum terminale, the nerve roots, the meninges, the intraspinal vessels, the sympathetic nerves, or the vertebrae (Fig. 1). They can be tumoral lesions, both benign or malignant, and primary or secondary, as well as pseudotumoral lesions, cysts, or lesions secondary to infection, both primary in the spine and secondary to dissemination or contiguity. To classify the spinal tumours, they may be referred by the area of the spine in which they occur (cervical, thoracic, lumbar or sacral), and additionally, they can be classified into three main categories according to the their location with respect to the dural sac and spinal cord: extradural; intradural-extramedullary; or intramedullary (see Figure above or Fig. 2). Lesions can occasionally compromise more than one compartment. Page 5 of 41

6 3) Main types of SPINAL TUMORS Depending on their location with respect to the dura mater: (see Fig. 3) - Extradural (60% of all spinal tumors): They originate outside the dural sac. Tumors arise from nerve roots (neurinomas and neurofibromas), vertebrae (most extradural lesions) and/or epidural tissues. Metastases are the most frequent extradural lesions. - Intradural-extramedullary (30%): although most of these lesions are primary, drop metastases can be also observed at this location. - Meningiomas: these tumors develop in the spinal cord's arachnoid membrane. - Schwannomas and neurofibromas: they originate in the nerve roots that extend out from the spinal cord. - Filum terminale ependymomas: they develop at the base of the spinal cord. - Intramedullary (10%): they grow inside the spinal cord, most frequently in the cervical region. Almost all (95%) are malignant. - Ependymomas and astrocytomas: the two most common types in adults and in children respectively. 4) ETIOLOGY and ASSOCIATIONS The cause of most primary spinal tumours is unknown. Some may be attributed to exposure to cancer-causing agents. Some are more common in people with compromised immune systems, whereas others are related to a genetic component and may result from these genetic diseases: - Neurofibromatosis (NF) type 2: Ependymomas, schwannomas and meningiomas - NF type 1: Astrocytomas and neurofibromas - Von Hippel-Lindau (VHL): Hemangioblastomas 5) IMAGING for DIAGNOSIS Page 6 of 41

7 Intradural extramedullary masses can have a number of general morphological features: - solitary vs multiple - they may have a dural tail (especially meningiomas) - the may have a neural exit foraminal (extradural) component (i.e dumbbell appearance). Magnetic resonance imaging (MRI) is the most important diagnostic tool for intraspinal tumours, playing an integral role in their evaluation and improving their anatomic delineation and early diagnosis. The key benefits of MRI over other modalities, is the ability to clearly define the relationship of the mass to the cord, to identify secondary lesions, to identify large feeding/draining vessels and hopefully to give a pre-operative diagnosis. MRI can show the spinal cord, nerve roots, and surrounding areas. The technique-protocol should include: - sagittal and axial unenhanced T1- and T2-weighted images - contrast-enhanced T1-weighted images - diffusion weighted images (DWI) Computed tomography (CT) remains the best modality to assess the osseous structures. CT shows the typical patterns of bone destruction, sclerosis or remodeling. Purely intradural lesions may not be shown. Plain Film Radiography provide information about osseous anatomy: alignment, bone matrix, bone destruction, sclerosis and demineralization. Bone scintigraphy is useful in detecting multiple spinal bone lesions and distant metastases. Angiography is useful in vascular lesions (malformations and tumors). After radiological confirmation of the tumor, the only way to determine whether the tumor is benign or malignant is to examine a small tissue sample (Biopsy). 6) TREATMENT Page 7 of 41

8 - Surgery is the most common treatment, and in most cases the neurological symptoms improve postoperatively. - In patients with metastatic tumors, surgical treatment is primarily palliative (to preserve neurological function, stabilize the spine, or relieve pain). - Nonsurgical treatment options include observation, chemotherapy, and radiation therapy. Watchful waiting with regular MRI monitoring can be an option in asymptomatic and not changing/progressing tumors. At best, palliative treatment may provide the patient with an improved quality of life and prolonged life expectancy. 7) OUTCOME: Outcome depends greatly on: - benign or malignant tumor - primary or metastatic - the histologic grade of tumor - the age - the health of the patient. 8) CLASSIFICATION OF THE MAIN SPINAL LESIONS Page 8 of 41

9 Fig. 3 References: Cristina P. Balaguero Images for this section: Page 9 of 41

10 Fig. 1 Page 10 of 41

11 Fig. 2 Page 11 of 41

12 Fig. 3 Page 12 of 41

13 Findings and procedure details * CASE 1 Fig. 4 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: Extraskeletal Ewing tumor Organized hematoma Page 13 of 41

14 Rhabdomyosarcoma 2. Definitive diagnosis: SPINAL EPIDURAL EXTRASKELETAL EWING SARCOMA - Epidemiology. Extraskeletal Ewing sarcoma is rare in comparison with Ewing sarcoma of bone. Its prevalence is 15-20% and has been rarely reported in a previous site of irradiation. Extraskeletal Ewing sarcoma usually manifests in young patients, with 85% of cases detected between 20 months and 30 years of age. - Location. The most commonly reported locations of extraskeletal Ewing sarcoma include: paravertebral region, lower extremities, chest wall, retroperitoneum, pelvis and hip, and upper extremities. Paravertebral masses can manifest as and intradural extramedullary or extradural mass. - Clinical presentation. The patients often have a large, rapidly growing, solitary, superficial or deep soft-tissue mass measuring 5-10 cm at initial presentation. - Diagnosis. Overall, imaging features of extraskeletal Ewing sarcoma are nonspecific. Radiological manifestations are as a large soft-tissue mass with adjacent bone erosion, cortical thickening, osseous invasion or aggressive periosteal reaction. MRI nonspecific features include a mass with heterogeneous signal intensity similar to that of skeletal muscle on T1-WI and intermediate to high signal intensity on T2-WI. Focal areas of necrosis with low signal intensity on T1-WI and high signal intensity on T2-WI are also frequent. And additional imaging feature that we have recognized at MRI of this tumor is the presence of serpentine high-flow vascular channels, which have low signal intensity with all pulse sequences in 90% of cases. Due to a high degree of cellularity, diffusion restricted signal is often seen. - Differential diagnosis. For the differential with neuroblastoma in imaging of a paraspinal mass, there are tests for urine catecholamine metabolites, which are generally negative for the Ewing sarcoma * CASE 2 Page 14 of 41

15 Fig. 5 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES Page 15 of 41

16 Fig. 6 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: Lymphoma Extraskeletal Ewing tumor (more heterogeneous and enhancing) Dermoid cyst Because of the pelvic mass, a lymphoma was the first diagnostic possibility. 2. Definitive diagnosis: Page 16 of 41

17 BURKITT LYMPHOMA Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that predominantly affects children. - Epidemiology. Burkitt lymphoma is the most common (40%) type of non-hodgkin lymphoma in childhood. Median age of Burkitt lymphoma is 8 years and it has a male predominance. It is less common in adults, accounting for 1-2% of lymphomas. There are geographic differences with Burkitt lymphoma, which is considered endemic in parts of Africa (rates are up to 50 times higher than in the USA), with sporadic cases occurring elsewhere. - Risk factors. HIV/AIDS and post-transplant immunosuppression - Clinical presentation. Due to this tumor affects many organs, this affects it presentation. Extranodal involvement is common at presentation, most often presenting as an abdominal or pelvic mass. Other patients present with widespread disease. - Radiographic appearance & diagnosis. Radiographic features vary widely depending on organ involvement, being the main locations: abdominal, musculoskeletal and head and neck. - Differential diagnosis. The restriction in the diffusion can be a useful tool in the diagnostic imaging of this lesion. Therefore in every case when neuroborreliosis is suspected meningeal lymphoma is an important differential diagnosis * CASE 3 Page 17 of 41

18 Fig. 7 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: A dermoid cyst was suspected 2. Definitive diagnosis: DERMOID CYST Spinal dermoid cysts are uni or multilocular cystic tumours lined by squamous epithelium containing skin appendages (hair follicles, sweat glands, sebaceous glands). 40% are intramedullary 60% extramedullary. Page 18 of 41

19 - Epidemiology. Spinal dermoid cysts are uncommon overall but account for nearly 20% of intradural tumours seen in patients younger than one year of age. They generally present in patients younger than 20 years. Males and females are affected equally. - Associations. May be associated with occult spinal dysraphism. - Location. Spinal dermoid cysts are most often located in the lumbosacral region (60%) and cauda equina (20%). They are rarely found in the cervical or thoracic spine. - Clinical presentation. Spinal dermoid cysts are often asymptomatic and discovered incidentally. If symptomatic, motor disturbances, pain, sensory disturbances and bowel or bladder dysfunction may be present. They may become acutely symptomatic if rupture occurs. - Radiographic appearance & diagnosis. They have variable imaging appearances, but commonly appear as a well-defined mass of CSF density/intensity with fat density/ intensity components. CT imaging: isodense to CSF, often with hypodense components (fat), calcification may be present and minimal enhancement. MR imaging: typical signal characteristics: - T1: hypo (if water content) or hyperintense (due to the presence of fat) - T2: hyperintense - FLAIR: hyperintense compared to surrounding CSF - T1 C+ Gd: no enhancement or mild rim enhancement - DWI: less likely to show diffusion restriction than epidermoid If rupture occurs, multifocal T1 high signal areas (fat) are demonstrated within the subarachnoid space and/or ventricular system. - Differential diagnosis. General imaging differential considerations include: - spinal arachnoid cyst (CSF intensity on all sequences - no restriction on DWI - signal suppression on FLAIR) - spinal epidermoid cyst (not fatty elements - more likely to demonstrate diffusion restriction on DWI - 20 to 40 years old) Page 19 of 41

20 - spinal neurenteric cyst (CSF intensity on all sequences - thoracic and cervical regions most common - usually ventral to the spinal cord - associated vertebral anomalies common). - spinal lipoma (homogeneously hyperintense on T1 and T2 WI - cervical and thoracic regions most common) - spinal teratoma (heterogenous appearance on T1 and T2 WI (fat, soft tissue, fluid, calcium) - heterogenous enhancement of solid portions - rarely diagnosed in patients older than 2 years old) * CASE 4 Fig. 8 Page 20 of 41

21 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: An arachnoid cyst was suspected 2. Definitive diagnosis: ARACHNOID CYST Spinal arachnoid cysts are relatively uncommon and may be either intra-dural (type III meningeal cyst) or extra-dural (type IA meningeal cyst). - Epidemiology. Spinal arachnoid cysts may present at any age. There is no gender predilection. - Clinical presentation. Most spinal arachnoid cysts are asymptomatic and are discovered incidentally. If present, clinical symptoms may include pain, weakness, numbness or bladder/bowel incontinence. Symptoms may be exacerbated with postural changes and the Valsalva maneuver. - Radiographic appearance & diagnosis. MRI: As the cysts follow the intensity of CSF and their walls are generally not visible, they may not be identified unless the cord is displaced. - T1: CSF intensity - T2: CSF intensity, may even be brighter than CSF on account of no signal loss from pulsation/flow 8 - T1 C+ Gd: no contrast enhancement phase-contrast imaging: decreased CSF flow within the cyst 7 - DWI: No evidence of restricted diffusion. - Differential diagnosis. General imaging differential considerations include: Page 21 of 41

22 - herniated ventral cord (focal cord deformity - phase-contrast MRI: absence of CSF flow ventral to the herniated cord and a normal CSF flow pattern dorsal to the cord - can be challenging to distinguish, and myelography may be helpful) - spinal epidermoid cyst (bright on DWI) - spinal dermoid cyst (described above). - spinal hydatid cyst (most commonly extradural (intradural extramedullary lesions are extremely rare) - usually multiloculated - may show minimal enhancement). - spinal cysticercosis (peripheral enhancement - usually multiloculated). Rarely extradural cysts may be considered, although they are usually clearly not within the dura. They include: synovial cyst, ganglion cyst, cysts of ligamentum flavum and cysts originating from the intervertebral discs * CASE 5 Page 22 of 41

23 Fig. 9 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: A lipoma was suspected 2. Definitive diagnosis: INTRADURAL LIPOMA They are typically intradural, subpial, juxtramedullary lesions although they have occasionally been reported as entirely intramedullary lesions. - Epidemiology. Intradural spinal lipomas typically present around the second and third decades of life. Males and females are equally affected. Page 23 of 41

24 - Associations. They are associated with forms of dysraphism. - Clinical presentation. Patients present with neurological deficits secondary to mass effect. The most frequently reported clinical presentation is numbness or spastic weakness in the extremities. Back pain may occur. Radicular pain is uncommon. - Radiographic appearance & diagnosis. CT imaging: the lesion is classically homogeneously of low (fat) attenuation, without solid or enhancing components. MRI: Intradural spinal lipomas are sharply circumscribed masses largely conforming to the dura but distorting the cord. They follow fat signal on all sequences: - T1: hyperintense - T2: hypointense - T1 C+ Gd: no enhancement - Fat-suppressed sequences: hypointense A chemical shift artefact may be seen. - Differential diagnosis. General imaging differential considerations include: - lipomyelomeningocele (an occult spinal dysraphism with palpable mass and a cutaneous stigmata) - lipoma of the terminal filum (fatty infiltration of the filum terminale) - dermoid cyst (described above) * CASE 6 Page 24 of 41

25 Fig. 10 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: An Ewing sarcoma was suspected 2. Definitive diagnosis: SPINAL ESKELETAL EWING SARCOMA Ewing sarcoma is the second most common primary bone tumour of childhood after osteosarcoma. - Epidemiology. Typically occurs in children and adolescents between 10 and 20 years of age (95% between 4 and 25 years of age), and has a slight male predilection. Page 25 of 41

26 - Location. In decreasing order: lower limb: 45% (femur), pelvis: 20%, upper limb: 13%, spine and ribs: 13% (sacrococcygeal) and skull/face: 2%. As far as location within long bones, the tumor is almost always metaphyseal or diaphyseal. - Clinical presentation. Presentation is non-specific with local pain being by far the most common symptom. Occasionally a soft tissue mass may be palpable. Pathological fractures also occur. - Radiographic appearance & diagnosis. The appearance of these tumors is very variable, but usually have clearly aggressive appearance. Common findings include: Permeative, laminated (onion skin) periosteal reaction and less frequent sclerosis. They occasionally demonstrate other appearances, including Codman triangles, spiculated (sunburst) or thick periosteal reaction and even bone expansion or cystic components. Soft tissue calcification is uncommon. MRI - T1: low to intermediate signal - T1 C+ Gd: heterogeneous but prominent enhancement - T2: heterogeneously high signal; may see "hair on end" low signal striations. - Differential diagnosis. General imaging differential considerations include: - other Ewing sarcoma family of tumours (ppnet and Askin tumor) - spinal osteosarcoma - osteomyelitis - metastatic disease * CASE 7 Page 26 of 41

27 Fig. 11 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: A neuroblastoma was suspected 2. Definitive diagnosis: SPINAL NEUROBLASTOMA Neuroblastoma is a tumor of neuroblastic origin and the most common extracranial solid childhood malignancies. It also accounts for ~15% of childhood cancer deaths. - Epidemiology. The tumors typically occur in infants and very young children (mean age of presentation # 22 months; 95% of cases diagnosed before the age of 10 years). Page 27 of 41

28 - Location. Neuroblastomas arise from the sympathetic nervous system. Intra abdominal occurrence is commoner than intra thoracic. Specific sites include: adrenal glands (most common site of origin), retroperitoneum, paravertebral sympathetic chain, posterior mediastinum, neck and pelvis. - Clinical presentation. Abdominal distension / pain, a palpable mass, or other presentations due to mass effect - Radiographic appearance & diagnosis. CT imaging: a typically heterogeneous mass with calcifications and areas of low attenuation due to necrosis. The morphology of is often most helpful, with the mass seen insinuating itself beneath the aorta and lifting it off the vertebral column. It tends to encase vessels and may lead to compression. Lymph node enlargement is often present. MRI: this is superior to all other modalities in assessing the organ of origin. Signal characteristics include: - T1: heterogeneous and iso to hypointense - T2: heterogeneous and hyperintense, cystic/necrotic areas of very high intensity. - T1 C+ Gd: variable and heterogeneous enhancement. - Differential diagnosis. - Spinal ganglioneuroma and ganglioneuroblastoma: often cannot be differentiated from ganglioneuroma based on imaging characteristics. Metastases usually indicate neuroblastoma or ganglioneuroblastoma. The calcification pattern may help, as the tumour calcification in neuroblastomas is more amorphous and rough * CASE 8 Page 28 of 41

29 Fig. 12 References: Radiology, Hospital Universitari Sant Joan de Déu - Esplugues de Llobregat/ES 1. Differential diagnosis: An ependymoma vs medulloblastoma with leptomeningeal metastases 2. Definitive diagnosis: LEPTOMENINGEAL METASTASES (from a CLASSIC MEDULLOBLASTOMA) Page 29 of 41

30 - Epidemiology. The age at presentation depends on tumor type. In the paediatric population, the most common intradural extramedullary neoplasms are leptomeningeal metastases resulting from primary brain tumor. - Location and clinical presentation. As the most commonly affected site is the lumbosacral spine, symptoms and signs include back or radicular pain, weakness, paraesthesia, gait disturbance, cauda equina syndrome and symptoms/signs of meningeal irritation. - Radiographic appearance & diagnosis. MRI - T1: nodular lesions isointense with the spinal cord - T1 C+ Gd: enhancing tumor nodules on the spinal cord or cauda equine - T2: cord edema may be seen with more extensive disease (especially if there is an intramedullary component). - Differential diagnosis. In the nodular form consider: - spinal meningioma (multiple meningiomas most often associated with NF2; dural tail sign) - spinal neurilemmoma/schwannoma (multiple schwannomas often associated with NF2; haemorrhage, vascular changes, cyst formation and fatty degeneration) - spinal neurofibroma (multiple neurofibromes often associated with NF1) - leptomeningeal (pial) lipoma (fat signal intensity; no enhancement). Images for this section: Page 30 of 41

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40 Conclusion Only based on the location of the lesions in the spinal canal, and its performance in the different MRI sequences, we were able to approach the diagnosis of the different lesions under study. Personal information References - Mark D. Murphey, Lien T. Senchak, Pramod K. Mambalam, Chika I. Logie, et al. From the Radiologic Pathology Archives: Ewing Sarcoma Family of Tumors: RadiologicPathologic Correlation. RadioGraphics 2013; 33: Soderlund KA, Smith AB, Rushing EJ et-al. Radiologic-pathologic correlation of pediatric and adolescent spinal neoplasms: Part 2, Intradural extramedullary spinal neoplasms. AJR Am J Roentgenol. 2012;198 (1): Wilkening et al. Unusual presentation of a primary spinal Burkitt's Lymphoma. A J Neurol Neurosurg Psychiatry 2001; 70: David M. Biko. Sudha A. Anupindi. Andrea Hernandez. Childhood Burkitt Lymphoma: Abdominal and Pelvic Imaging Findings. AJR 2009; 192: Koeller KK, Rosenblum RS, Morrison AL. Neoplasms of the spinal cord and filum terminale: radiologic-pathologic correlation. Radiographics. 2000; 20: Wenger M, Zobor N, Markwalder R et-al. Intradural extramedullary arachnoid cyst of the thoracic spine associated with cord compression. J Clin Neurosci. 2007; 14 (7): Brant WE, Helms CA. Fundamentals of Diagnostic Radiology. Lippincott Williams & Wilkins. (2007) ISBN: Page 40 of 41

41 - Ji Honn Shina et al. Spinal Epidural Extraskeletal Ewing Sarcoma: MR Findings in Two Cases. AJNR : Page 41 of 41