Vertebrobasilar insufficiency resulting from traumatic atlantoaxial instability: case report.

Vertebrobasilar ischemia revealed atlantoaxial instability in a patient who had cervical spine trauma 2 years previously. Vertigo was elicited by rotation of the head to the right; angiography demonstrated the occlusion of the left vertebral artery in the same position. The patient recovered totally after surgical fusion of the atlantoaxial joint.