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 -
Dorsal dermal sinus Diastometamyelia Tight filum terminale Caudal regresion syndrome