Dissecting aneurysms of the basilar artery in 2 patients

An uncommon consequence of intracranial vascular disease is the intramural dissection of blood or "dissecting aneurysm". A 69-year-old man with chronic subarachnoid hemorrhage from a posterior fossa mass lesion and a 30-year-old man with migraine and a brain stem stroke illustrate the diverse etiologic, clinical, radiographic, and pathologic characteristics of this unusual lesion.