Persistent primitive trigeminal artery aneurysm.

The trigeminal artery is the most common persistent carotid-basilar anastomotic channel observed in adult life, and its occurrence probably represents a defect in cerebrovascular development. It can be associated with other congenital abnormalities such as cerebral aneurysms, but only rarely do aneurysms of the primitive trigeminal artery itself arise. The authors present a new case of an aneurysm arising directly from the primitive trigeminal artery and discuss its significance and treatment.