Fenestration of the oculomotor nerve by a duplicated posterior cerebral artery and aneurysm

The authors report a case of a posterior cerebral artery aneurysm arising from an aberrant arterial branch that was found to be splitting the oculomotor nerve. This 63-year-old man presented with headaches, and CT imaging revealed subarachnoid hemorrhage primarily within the basilar cisterns. Formal angiography and CT angiography revealed a saccular aneurysm arising from the posterior cerebral artery. Intraoperatively, the third cranial nerve was found to be fenestrated with the artery and aneurysm.