[A case of myelopathy due to a peculiar anomaly of the axis].

A very rare case of cervical myelopathy due to an anomaly of the axis was encountered. The patient was a 42-year-old man, in whom motor and sensory disturbance of the four extremities had been in progress during the last two years. Neurological examination revealed myelopathy at the high cervical cord. The operative findings were characterized as follows: The lamina on both sides of the axis was separated at the base of the spinous process. The two bony protrusions from the normally shaped spinous process entered the spinal canal, and was attached to the internal surface of the lamina with connective tissue, and this abnormal bone compressed the cervical cord. Following laminectomy of the axis and excision of the abnormal bone, the symptom and the sign of the myelopathy were remitted. The patient had had no episode of trauma, and it was judged that his aging triggered manifestation of this congenital anomaly. Asymptomatic or mild cases may escape from detection by conventional plain films of the cervical spine, which in fact provided little diagnostic information. Plain and metrizamide CT myelographies are considered to be the most promising diagnostic procedures.