Optic nerve contact and compression by the carotid artery in asymptomatic patients.

PURPOSE

To estimate the frequency and clinical correlates of contact and compression of the intracranial optic nerve by the supraclinoid carotid artery in asymptomatic patients.

METHODS

In a retrospective study, we identified asymptomatic patients who had undergone magnetic resonance imaging with sequences that could be used to evaluate the relation between the intracranial optic nerve and the carotid artery. These patients underwent neuroimaging evaluations for reasons unrelated to loss of vision, optic neuropathy, or carotid artery disorders. The relation between the optic nerve and carotid artery was graded in a standardized manner. The effect of a number of clinical covariates on the risk of compression was evaluated using multiple logistic regression.

RESULTS

The frequencies of some of the artery-nerve relationships included contact of one or both optic nerves in 70 (70%) of 100 patients; bilateral compression in 12 (12%) of 100 patients; and unilateral compression with no arterial contact or compression on the opposite side in five (5%) of 100 patients. The estimated odds of compression were significantly increased as the diameter of the carotid artery increased.

CONCLUSIONS

Among asymptomatic patients, supraclinoid carotid artery contact with the intracranial optic nerve occurs frequently. Anatomic compression, on the other hand, especially when unilateral, occurs infrequently. The risk of anatomic compression of the optic nerve is directly proportional to the diameter of the carotid artery.