Spinal Dysraphic Lesion
Bernadette L. Koch, MD
DIFFERENTIAL DIAGNOSIS
Common
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Incomplete Fusion, Posterior Element
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Myelomeningocele
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Lipomyelomeningocele (LMM)
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Lipomyelocele (LM)
Less Common
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Diastematomyelia
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Dorsal Dermal Sinus
Rare but Important
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Meningocele, Dorsal Spinal
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Terminal Myelocystocele
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Segmental Spinal Dysgenesis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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Spina bifida: Incomplete closure of posterior bony elements
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Spina bifida aperta = spina bifida cystica: Protrusion of spinal canal elements through posterior bony defect
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Simple meningocele: Dura and arachnoid, no neural elements
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Myelocele: Midline plaque of neural tissue exposed, flush with skin surface
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Myelomeningocele: Myelocele protrudes above skin surface + expansion of subarachnoid space posterior to placode
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Occult spinal dysraphisms develop beneath intact skin surface
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Meningocele, diastematomyelia, split notochord syndrome, dorsal dermal sinus, fibrolipoma of filum terminale, spinal lipoma, lumbosacral hypogenesis, segmental spinal dysgenesis, myelocystocele
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Helpful Clues for Common Diagnoses
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Incomplete Fusion, Posterior Element
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Key facts: Spina bifida occulta
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Imaging
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Incomplete fusion of spinous process/lamina without underlying neural or dural abnormality
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Lumbosacral > cervical > thoracic
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Myelomeningocele
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Key facts: Open neural tube defect, lacks skin coverage
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Level of dysraphism determines neurological deficit
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Rarely image spine preoperatively
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Postoperative spinal imaging if neurological decline despite adequate treatment of hydrocephalus or if neurologic exam suggests additional underlying lesions
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Imaging
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CSF sac and neural elements protrude through wide osseous dysraphism
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Fetal elongation of low-lying cord, usually in dorsal aspect of canal deep to skin-covered postoperative repair
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Associated abnormalities
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Chiari 2 malformation (≈ 100% )
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Hydrocephalus, kyphoscoliosis, segmentation anomalies, diastematomyelia and dermal sinus, syrinx, intraspinal dermoid/epidermoid, orthopedic abnormalities
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Lipomyelomeningocele (LMM)/Lipomyelocele (LM)
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Key facts: Cutaneous stigmata in up to 50%; hemangioma, dimple, dermal sinus, skin tag, or hairy patch
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Imaging
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LMM = spinal subarachnoid space expanded ventrally → placode, tethered cord, subarachnoid space, and dura extend dorsally through spina bifida
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LM = tethered cord and junction between placode and lipoma within spinal canal, lipoma through bony defect
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Lipoma attached to dorsal aspect of neural placode and contiguous with SQ fat
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Dorsal and ventral nerve roots exit from ventral surface of placode
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± segmentation anomalies, sacral anomalies, syrinx, diastematomyelia, anorectal and GU abnormalities
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Diastematomyelia
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Key facts: Majority between T9 and S1
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Imaging
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Split cord malformation (SCM) = sagittal split into 2 hemicords ± fibrous, osteocartilaginous, or osseous spur
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Pang type 1 SCM = separate dural sac, arachnoid space around each hemicord, separated by fibrous/osseous spur
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Pang type 2 SCM = single dural sac and arachnoid space without spur ± adherent fibrous bands tethering cord
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Nearly all reunite below split
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± thick filum, tethered cord, syringohydromyelia in 1 or both hemicords, myelocele, or MM
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± intersegmental laminar fusion ≈ pathognomonic for diastematomyelia
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Helpful Clues for Less Common Diagnoses
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Dorsal Dermal Sinus
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Key facts
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Midline or rarely paramedian dimple or pinpoint ostium ± pigmented patch, hairy nevus, or cutaneous hemangioma
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Differentiate from simple sacral dimple (< 2.5 cm from anus, extends inferiorly toward coccyx) and pilonidal sinus (low ostium, does not enter spine)
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High suspicion if dimple above intergluteal fold
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Imaging
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↓ curvilinear tract through ↑ SQ fat May end in SQ tissue or extend into canal, terminating in conus medullaris, subarachnoid space, filum terminale, nerve root, fibrous nodule on surface of cord, or dermoid/epidermoid cyst
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Dural “tenting” at dural penetration
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LS > occipital > T > C spine
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± varying degrees of dysraphism; incomplete posterior element fusion → multilevel dysraphism
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± dermoid/epidermoid, abscess, or arachnoiditis
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± cord tethering in lumbosacral lesions
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Helpful Clues for Rare Diagnoses
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Meningocele, Dorsal Spinal
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Key facts: Skin covered
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Imaging
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Meninges protrude through dysraphism into SQ fat
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Cord tethering and syrinx rare
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Terminal Myelocystocele
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Key facts: Large skin-covered mass, usually sacral/coccygeal
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Imaging
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Hydromyelic tethered cord traverses dorsal meningocele, terminates in dilated terminal ventricle
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Segmental Spinal Dysgenesis
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Key facts: Focal dysmorphic/hypoplastic vertebrae, meninges, and spinal cord with normal spine above and below
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Imaging
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Dysplastic vertebrae → severe focal kyphosis
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Thecal sac narrows and then terminates; spinal cord narrows and disappears rostral to thecal sac
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Thecal sac reappears below dysplastic segments
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Spinal cord reappears below reappearance of thecal sac
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Image Gallery