Fig. (1).

Atlanto-axial rotational instability. The atlas is shown in the rotated position on the axis. The pivot is the eccentrically placed odontoid process. In rotation, the wall of the vertebral foramen of Cl decreases the opening of the spinal canal between Cl and C2. This can potentially cause migraine headaches, C2 nerve root impingement, dizziness, vertebrobasilar insufficiency, 'drop attacks; neck-tongue syndrome, Barré-Liéou syndrome, severe neck pain, and tinnitus.