Intracranial segmental arterial mediolysis: report of 2 cases and review of the literature.

Extensive nontraumatic subarachnoid hemorrhage is an important cause of unexpected death in young adults. Segmental arterial mediolysis (SAM) represents an uncommon pathologic finding in the intracranial blood vessels associated with this type of hemorrhage. Segmental arterial mediolysis is a pathologic entity with putative vasospastic etiology, which recently has been reported to be associated with Ehlers-Danlos syndrome type 4. We describe 2 additional cases of ruptured intracranial vertebral artery with features of SAM that resulted in fatal subarachnoid hemorrhage. We also review the literature on vessels with features of SAM that are either intracranial or affecting the internal carotid artery with major direct effects (ie, stroke or transient ischemic attack) on the central nervous system.