Fusiform intracranial aneurysms. Clinicopathologic features.

Seven fusiform aneurysms were found at autopsy in five patients (two males and three females) over a 13-year period. The subjects were between 56 and 65 years of age. The basilar trunk was the most frequent site. Four aneurysms were of giant proportions and contained laminated thrombi. Subarachnoid hemorrhage occurred in four patients. Microscopic examination of the aneurysm walls revealed atheromatous degeneration, focal wall attenuation, mural hemorrhage, rupture, and acute and chronic inflammatory cell infiltration. These findings suggest that rupture is not rare and that atherosclerosis is but one mechanism in the pathogenesis of these lesions.