Agenesis and dysgenesis of the sacrum: neurosurgical implications.

We reviewed 27 patients with congenital anomalies of the sacral spine. There were 16 males and 11 females with a mean follow-up of 81.1 months (range 8-211 months). Fifteen patients had sacral agenesis and 12 had sacral dysgenesis. Fifteen patients had neuroimaging of the spine. Seven patients had conus termination below the L2 vertebral body. Four patients had associated thoracic syringomyelia and 6 patients were identified with caudal or dorsal lipoma. There were only two episodes of neurological deterioration, both in a single patient who had a lipomyelomeningocele, in 182 patient-years of follow-up. Four patients with low lying conus had pre-emptive spinal cord exploration for release of tethering in order to prevent neurological deterioration. Patients with agenesis or dysgenesis of the sacrum should undergo magnetic resonance (MR) imaging of the spine in order to detect spinal cord lesions associated with progressive neurological deterioration. Findings on MR imaging are more likely to correlate with clinical course than findings on skeletal radiography.