Dissecting aneurysm of intracranial vertebral artery: case report and review of literature.

A spontaneous dissecting aneurysm of the intracranial portion of the dominant right vertebral artery presented as massive subarachnoid hemorrhage, excruciating headache, and respiratory arrest in a 57-year-old white man with a history of systemic hypertension. He died on the 3rd day. Postmortem examination revealed a dissecting hemorrhage extending for 2.1 cm along the artery; rupture of the intima, media, and adventitia could be demonstrated. The intramural accumulation of blood in the proximal segments appeared to be related to retrograde dissection within a media weakened by cystic degeneration. Accumulation of pools of mucoid ground substance was also demonstrated in other intracranial and extracranial arteries. Hemodynamic stresses due to arterial hypertension and physical exertion may have played a contributory role in the etiopathogenesis of this uncommon form of cerebrovascular accident. A comprehensive literature review permits a comparison of supratentorial and infratentorial dissecting aneurysms; vertebral and basilar artery dissections are presented in tabular form.