Saccular aneurysm at the basilar artery fenestration.

The authors describe a 19-year-old patient who was presented with a subarachnoid hemorrhage and was found to have a saccular aneurysm arising at the proximal end of the fenestration of the basilar artery. Previously reported cases are reviewed. Stereoscopic magnification angiography facilitated the analysis of the three-dimensional-anatomical relationship between the aneurysm and its fenestrated parent artery.