Diagnosis and treatment of vertebral aneurysms.

The intracranial vertebral artery and its branches are a common site of aneurysms in the posterior fossa. Ninety-four aneurysms in 86 patients were analyzed for their clinical manifestation, diagnosis, and treatment. There were three distinct varieties of aneurysm in this group: 56 (60%) saccular aneurysms, 26 (28%) dissecting aneurysms, and 12 (13%) atherosclerotic fusiform aneurysms. Of the 26 dissecting aneurysms, 81% bled and 24% of these rebled. None of the atherosclerotic fusiform aneurysms bled. Angiographic differentiation between dissecting aneurysms and atherosclerotic fusiform aneurysms was difficult. The dissecting aneurysms were characterized by a "narrowed segment" proximal and/or distal to a "fusiform dilatation" of the affected artery and by the presence of contrast medium in the intramural false lumen until the late phase. Poor postoperative outcome and the lateral medullary syndrome were seen only in dissecting aneurysms. Small atherosclerotic fusiform aneurysms seemed to be benign lesions that do not require any surgical treatment.