Cervical flexion myelopathy associated with cervical spina bifida occulta--case report.

A 16-year-old boy presented with segmental muscular atrophy of the bilateral distal upper extremities. Cervical spine x-ray films showed occult spina bifida from C-1 to T-1 associated with an abnormal long club-like bone located parallel to the epidural space between C-5 and C-7. In neck flexion, the cervical spinal cord was stretched and compressed to the posterior aspect of the vertebral body. Moreover, the dorsally placed abnormal bone migrated ventrally, indenting the dorsal portion of the spinal cord. This is quite an unusual case of so-called "flexion myelopathy," aggravated by the abnormal bone located dorsally.