Aneurysm and Fenestration of the Azygos Anterior Cerebral Artery

—Case Report—

Abstract

A 78-year-old female suffered sudden onset of nausea and headache. Computed tomography demonstrated diffuse subarachnoid hemorrhage. Cerebral angiography demonstrated an aneurysm arising from the right A₁ segment of the azygos anterior cerebral artery, and the hypoplastic left A₁. A right frontotemporal craniotomy was performed to obliterate the aneurysm by neck clipping. Surgical exploration found the fenestration of the right A₁ and showed that the aneurysm had originated from the bifurcation of the fenestrated A₁ and a small perforating artery arising from the fenestration. This unusual combination of an aneurysm associated with a fenestration of the right A₁ and contralateral A₁ hypoplasia may have been caused by local hemodynamic stress.