Persistent primitive trigeminal artery aneurysm evaluated by MR imaging and angiography.

The primitive trigeminal artery is the most common of the persistent carotid-basilar anastomoses with an angiographic incidence of 0.6%. Fifteen cases of aneurysms of a persistent primitive trigeminal artery have been reported in the literature. A 16th patient is presented in whom an incidental trigeminal artery aneurysm and a thrombosed aneurysm of the vertebrobasilar system are evaluated by magnetic resonance imaging and angiography.