Spinal Dysraphisms- Congenital Spinal Cord Abnormalities C Herman, J Ponting, I Wu Indiana University School of Medicine Presentation # eEdE-198

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Abstract Purpose: Spinal dysraphisms consist of a very wide range of pathologies and imaging appearances, some of which can be particularly challenging for radiologists and clinicians who primarily deal with adult patients. To simplify these potentially confusing congenital anomalies, spinal dysraphisms can be generally divided into two major categories - open and closed types. This electronic educational presentation will provide an overview of the imaging appearance of both open and closed type spinal dysraphisms. Imaging examples of each type will be provided to reinforce the spectrum of congenital abnormality that can be diagnosed, particularly on MRI. Also, image examples of spinal dysraphisms on fetal MRI will also be provided, which has become an increasing indispensable imaging modality to make early diagnosis of congenital anomalies in utero. Approach/Methods: Imaging studies from patients with congenital abnormalities of the spine and spinal cord are identified from a large tertiary referral center by retrospective case review. Of these, a wide range of cases is selected that represent the appearance of a majority of spinal dysraphisms, including multiple examples of fetal MRIs. From these cases, a PowerPoint presentation is generated focusing on the imaging appearance of each type of congenital abnormality and providing an organized approach to various open, closed and segmentation anomalies. Findings/Discussion: After viewing this presentation, the viewer will have greater familiarity with the appearance of spinal dysraphisms and be better equipped to diagnose these congenital abnormalities based on the organized approach provided. Summary/Conclusion: Congenital spinal cord and spinal abnormalities can be a complex topic for many radiologists. By reviewing this exhibit, the viewer will become more familiar with the appearance of spine dysraphisms, leading to a more organized approach to this spectrum of abnormalities.

Overview of Classification Open spinal dysraphisms Closed spinal dysraphisms With subcutaneous mass Without subcutaneous mass Simple dysraphic states Complex dysraphic states (including segmentation anomalies)

Open Spinal Dysraphisms Types: Myelomenigocele Myelocele Defect in overlying skin causing exposure of neural tissue Neural placode protrudes through a midline skin defect Caused by incomplete closure of the neural tube

Open Spinal Dysraphisms Myelomeningocele Neural placode protrudes above the skin surface Neural tissue, CSF and meninges are displaced Failure of neural tube closure T1 shows wide spinal dysraphism 98% of open dysraphisms Frequently associated with other CNS abnormalities Lumbosacral most common Myelocele Axial T2 Sagittal T2 4-day-old boy with a low lying cord and herniation of the spinal cord, nerve roots and CSF sac dorsally through a spinal dysraphism

Cervicothoracic myelomeningocele Axial T2 Sagittal STIR Sagittal T2 Spinal cord and cerebellar tonsils protruding through a wide posterior spinal dysraphism

Open Spinal Dysraphisms Myelomenigocele Myelocele Neural placode flush with skin Compared to protrusion above the skin as seen in myelomeningoceles Caused by defective closure of the primary neural tube Very rare Less than 2% of open spinal dysraphisms

Closed Spinal Dysraphisms Neural tissue covered by skin With subcutaneous mass: Lipomas with dural defect Meningocele Myelocystocele Without subcutaneous mass: Simple dysraphic states Complex dysraphic states Disorders of midline notochord integration: dorsal fistula and neurenteric cyst Diastatematomyelia Disorders of notochord formation: caudal agenesis Segmental spinal dysgenesis

Closed Spinal Dysraphisms Neural tissue covered by skin With subcutaneous mass: Lipomas with dural defect Meningocele Myelocystocele Without subcutaneous mass: Simple dysraphic states Complex dysraphic states Disorders of midline notochord integration: dorsal fistula and neurenteric cyst Diastatematomyelia Disorders of notochord formation: caudal agenesis Segmental spinal dysgenesis

Closed Spinal Dysraphisms with subcutaneous mass Lipoma with dural defect Disorder of primary neurulation where mesenchymal tissue enters the neural tube and forms fatty tissue (lipoma) Clinically seen as a subcutaneous fatty mass above the intergluteal crease Types: Lipomyelocele Lipomyelomeningocele Meningocele Myelocystocele

Closed Spinal Dysraphisms with subcutaneous mass Lipoma with dural defect Lipomyelocele Low lying spinal cord adheres to a large lipoma that extends through a posterior spinal dysraphism Placode-lipoma complex is contiguous with subcutaneous fat Lipomyelomeningocele Meningocele Myelocystocele Intraspinal lipoma associated with the distal spinal cord (noted to be low lying, extending to the L4 level) and continuous with the subcutaneous fat through a posterior sacral bony defect at the S3 level.

Lipomyelocele Axial T1 images showing an intraspinal lipoma associated with the distal spinal cord that is continuous with the subcutaneous fat through a posterior sacral bony defect at the S3 level.

Closed Spinal Dysraphisms with subcutaneous mass Lipomas with dural defect Lipomyelocele Lipomyelomeningocele Lipomyelocele + myelomeningocele Lipoma associated with the spinal cord and contiguous with subcutaneous fat Protrusion of thecal sac, nerve roots and spinal cord through dysraphic posterior elements Spinal cord is always tethered Meningocele Myelocystocele Sagittal T1

Lipomyelomeningocele Sagittal T1 Axial T1 Axial T1 72-day-old boy with low-lying conus (tethered cord), spinal cord mass with predominately fat signal (lipoma) contiguous with the subcutaneous fat. The mass also has associated CSF and soft tissue signal.

Closed Spinal Dysraphisms with subcutaneous mass Lipomas with dural defect Meningocele Herniation of CSF-filled sac lined by dura and arachnoid through an osseous defect of the posterior spinal elements (spina bifida) Does NOT contain spinal cord Compared to myelomeningocele Lumbar and sacral most common Myelocystocele Sagittal SSFSE Axial SSFSE Fetal MRI showing L5-S1 spinal dysraphism with likely associated meningocele

Fetal MRI: Thoracic Meningocele Sagittal TruFisp Axial Haste Protrusion of a CSF filled sac through a thoracic dysraphism on fetal MRI completed at 32 +4 weeks.

Same patient at 1 day old: Thoracic Meningocele Sagittal T2 Axial T2 Protrusion of a CSF filled sac through a thoracic dysraphism, similar in appearance compared to the fetal MRI.

Closed Spinal Dysraphisms with subcutaneous mass Lipomas with dural defect Meningocele Myelocystocele Dilated central spinal canal (inner cyst) protruding through posterior dysraphic spine into dilated subarachnoid space (outer cyst) in subcutaneous location Caused by incomplete fusion of dorsal neural folds Terminal myelocystocele: herniation of terminal syrinx into posterior meningocele Sagittal T2 8-month-old girl with a tethered spinal cord and myelocystocele.

Closed Spinal Dysraphisms Without subcutaneous mass: Simple dysraphic states Complex dysraphic states

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma filar lipoma tight filum terminale persistent terminal ventricle dermal sinus

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma Lipoma within the dural sac at the dorsal midline Lumbosacral most common Typically present with tethered-cord syndrome: progressive neurologic abnormalities in the setting of traction on low-lying conus filar lipoma tight filum terminale persistent terminal ventricle dermal sinus

Intradural Lipoma Sagittal T1 Sagittal T2 3-month-old boy with a fat signal lesion in the posterior spinal canal compatible with intradural lipoma. The conus is tethered to the lipoma and low-lying.

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma filar lipoma Fibrolipomatous thickening of the filum terminale Hyperintense strip of signal on T1 with thickening of filum Normal variant if no tethered-cord syndrome tight filum terminale persistent terminal ventricle dermal sinus Coronal T1

Filar Lipoma Sagittal T1 Sagittal T1 FS +C 32-month-old girl with hyperintense signal along the filum terminale on T1WI that shows signal drop out on post-contrast fat-saturated T1WI.

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma filar lipoma tight filum terminale Hypertrophy of the filum terminale Can cause tethering and low lying conus (normal above L2-L3) persistent terminal ventricle dermal sinus Sagittal T2 5-year-old girl with thickened filum terminale conus at L2-L3.

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma filar lipoma tight filum terminale persistent terminal ventricle Small ependymal lined cavity in conus located immediately above filum terminale Nonenhancing dilation of the central spinal canal in the conus dermal sinus Axial T2

Closed Spinal Dysraphisms without subcutaneous mass Simple dysraphic states Intradural lipoma filar lipoma tight filum terminale persistent terminal ventricle dermal sinus Epithelial lined fistula connecting the neural tissue or meninges to the skin Can lead to infection Lumbosacral most common Often associated with a spinal dermoid Sagittal T2 Dorsal dermal dermal sinus extending into the thecal sac at the S1-S2 level

T1 T1 C+ T2 T2 10-year-old with a dorsal dermal sinus and associated intramedullary dermoid (characteristic well circumscribed appearance with partial diffusion restriction). DWI ADC T1 C+

Dorsal Dermal Sinus Dorsal dermal sinus tract communicating with an intradural lipoma through a defect in the posterior spine in a 3-month-old boy with a sacral dimple

Closed Spinal Dysraphisms without subcutaneous mass Complex dysraphic states Disorders of midline notochord integration neurenteric cyst diastatematomyelia Disorders of notochord formation caudal agenesis Segmental spinal dysgenesis

Closed Spinal Dysraphisms without subcutaneous mass Complex dysraphic states Disorders of midline notochord integration neurenteric cyst Intraspinal cyst lined by mucin-secreting enteric mucosa Caused by failure of separation of dorsal ectoderm (spinal cord) and ventral endoderm (foregut) Iso- to hyperintense to CSF on T1 depending on mucin content diastatematomyelia Disorders of notochord formation caudal agenesis Segmental spinal dysgenesis Sagittal T1

Neurenteric Cyst: Craniovertebral Junction Sagittal T2 Axial T2 Intradural neurenteric cyst at the craniovertebral junction with a sinus tract extending ventrally

Closed Spinal Dysraphisms without subcutaneous mass Complex dysraphic states Disorders of midline notochord integration neurenteric cyst Diastatematomyelia Separation of spinal cord into two hemicords Usually symmetric with variable length of separation Type 1- individual dural tubes separated by osseous or cartilaginous septum Type 2- single dural tube with two hemicords, sometimes intervening fibrous septum Disorders of notochord formation / secondary neurulation caudal agenesis Segmental spinal dysgenesis Soft Tissue Window Bone window 17-month-old boy with splitting of the thoracic spinal cord by an intervening bony septum (type 1).

Diastatematomyelia: type 2 Axial T1 Axial T2 Axial T1 T7 T7 L3 19-month-old boy with splitting of the spinal cord at the T7 level. The spinal cord rejoins into a single structure at the L3 level and is contained within a single dural sac.

Closed Spinal Dysraphisms without subcutaneous mass Complex dysraphic states Disorders of midline notochord integration neurenteric cyst diastatematomyelia Disorders of notochord formation / secondary neurulation Caudal agenesis Total or partial agenesis of the spinal column Can be associated with anal imperforation, renal and genital anomalies, pulmonary hypoplasia and limb abnormalities Segmental spinal dysgenesis Newborn boy with multiple anomalies including absence of the spine from the mid-thoracic level caudally.

Caudal Agenesis Sagittal T2 Coronal CT 21-year-old woman with abnormal termination of the spinal cord at T10-11 and associated complete absence of the sacrum.

Closed Spinal Dysraphisms without subcutaneous mass Complex dysraphic states Disorders of midline notochord integration neurenteric cyst diastatematomyelia Disorders of notochord formation caudal agenesis Vertebral segmentation anomalies Various appearances CT helpful 17-year-old woman with a fusion anomaly at the lumbosacral junction

Vertebral Segmentation Anomalies 8-year-old girl with scoliosis and a partial sagittal partition segmentation anomaly at T7.

Vertebral Segmentation Anomalies 75-day-old boy with vertebral anomalies including multiple hemivertebrae.

Vertebral Segmentation Anomalies Radiograph Coronal CT 3D reformat CT Coronal T2 T3 butterfly vertebra on multiple imaging modalities.

Summary of Classification Open spinal dysraphisms: defect in skin exposing neural tissue Closed spinal dysraphisms: neural tissue covered by skin With subcutaneous mass Without subcutaneous mass Simple dysraphic states Complex dysraphic states (including segmentation anomalies)

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