Nontraumatic dissecting aneurysm of the vertebral artery. Case report

A case is described of a nontraumatic dissecting aneurysm of the vertebral artery, which presented as a subarachnoid hemorrhage (SAH). Differentiation from vasospasm and from atherosclerosis is critical. Dissection between the adventitia and media should be noted in the differential diagnosis of SAH when an aneurysm or vascular malformation is not demonstrated angiographically.