Skull and Spine Disorders
= SPLIT CORD = MYELOSCHISIS [ diastema, Greek = slit, cleft]
= sagittal division of spinal cord into two hemicords, each containing a central canal, one dorsal horn + one ventral horn
Etiology: congenital malformation as a result of adhesions between ectoderm and endoderm; M÷F = 1÷3
Path:
- 2 hemicords each covered by layer of pia within single subarachnoid space + dural sac (60%); not accompanied by bony spur / fibrous band
- 2 hemicords each with its own pial, subarachnoidal + dural sheath (40%); accompanied by fibrous band (in 25%), cartilaginous / bony spurs (in 75%)
Associated with: myelomeningocele
- hypertrichosis, nevus, lipoma, dimple, hemangioma overlying the spine (2681%)
- muscle wasting, ankle weakness in one leg; clubfoot (50%)
Location: lower thoracic / upper lumbar >upper thoracic >cervical spine
- sagittal cleft in spinal cord resulting in 2 asymmetric hemicords which usually reunite caudal to cleft
- occasionally 2 coni medullaris
- eccentric central canal within both hemicords
- bony spur through center of spinal canal arising from posterior aspect of centra (<50%)
- thickened filum terminale >2 mm (>50%)
- tethered cord (>50%)
- low conus medullaris below L2 level (>75%)
- defect in thecal sac on myelogram
- Vertebrae
- congenital scoliosis (5075%)
- 5% of patients with congenital scoliosis have diastematomyelia
- spina bifida over multiple levels
- anteroposterior narrowing of vertebral bodies
- widening of interpediculate distance
- narrowed disk space with hemivertebra, butterfly vertebra, block vertebra
- fusion + thickening of adjacent laminae (90%)
- fusion to ipsilateral lamina at adjacent levels
- diagonal fusion to contralateral adjacent lamina = intersegmental laminar fusion
Cx: progressive spinal cord dysfunction