Hari Verdhman, 9 yrs old child, presents with scoliosis, hairy tuft in the skin of the back and neurological deficit. Plain X- rays reveal multiple vertebral anomalies & a vertical bony spur overlying lumbar spine on AP view. The most probable diagnosis is -
Diastometamyelia 

Is division of the spinal cord into two halves by projection of a fibrocartilaginous or bony septum (spur)
The defect involves lumbar vertebrae (L1 to L3) in 50% of cases.
Abnormalities of vertebral bodies include fusion defects, kyphoscoliosis, spina bifida and myelomeningo coele.
Midline abnormality of the skin provides a clue.
Initial features may occur from infancy to young adulthood.
Neurological signs are thought to result from flexion and extension movements of the cord which produce traction and additional trauma by the septum.
Treatment of the symptomatic patients is excision of the bony spur or septum.
Dorsal dermal sinus
Diastometamyelia
Tight filum terminale
Caudal regresion syndrome