A 10-year-old boy on examination was found to have scoliosis and tuft of hairs over skin of lumbar spine. He has weakness and features of lower motor neuron paralysis in both lower limbs. X-ray spine reveals the 2 lumbar veebrae at that level are fused. Most likely diagnosis is

Diastematomyelia (split cord malformation), refers to a type of spinal dysraphism (spina bifida occulta) when there is a longitudinal split in the spinal cord. Diastematomyelia signs and symptoms of tethered cord, although patients with mild type II may be minimally affected or entirely asymptomatic. Presenting symptoms include: leg weakness, low back pain, scoliosis, incontinence Associated anomalies including: meningocoele, neurenteric cyst, dermoid, clubfoot, spinal cord lipoma, haemangioma overlying spine. Type I: duplicated dural sac, with common midline spur (osseous or fibrous) and usually symptomatic Type II: single dural sac containing both hemicords; impairment less marked.