Medial agenesis associated with multiple extracranial peripheral and visceral arterial aneurysms.

Developmental abnormalities consisting of focal absence of the arterial media have been implicated in the formation of the arterial aneurysms commonly observed in the intracranial cerebrovascular system. However, this observation has rarely been associated with visceral or peripheral arterial aneurysm formation. This article describes the experience with two patients having multiple peripheral and visceral arterial aneurysms with histologic findings previously observed only in intracranial, saccular berry aneurysms and in one patient with an isolated common carotid artery aneurysm. The two patients described herein had no clinical or angiographic evidence of cerebrovascular aneurysm formation. Light and electron microscopic histologic studies revealed complete focal absence of the arterial media in the region of aneurysm formation. No clinical or laboratory evidence of associated collagen-vascular disease was demonstrated. The patients were successfully managed with segmental resection and grafting of symptomatic, expanding, or large aneurysms. The necessity for an aggressive search for associated aneurysms as well as the need for long-term follow-up when histologic evidence of medial agenesis is demonstrated in association with arterial aneurysm formation are emphasized.