Dissection of the posterior cerebral arteries.

M ost reported arterial dissections involve the carotid and vertebral arteries in the neck. Within the intracranial arteries, dissections most often involve the vertebral and basilar arteries. Intracranial carotid and middle cerebral artery dissections occur much more rarely and seem to develop in younger individuals compared with patients who develop posterior-circulation intracranial dissections. Dissections that involve the posterior cerebral arteries (PCAs) are extremely uncommon and have been very rarely reported. We now describe 3 patients who developed PCA lesions that were most likely dissections. Two patients had acute strokes caused by PCA dissections, and 1 patient had a chronic dissecting aneurysm of the PCA.