Supraclinoid internal carotid artery fenestration with an associated aneurysm. Case report.

The case of an aneurysm occurring at the site of fenestration of the supraclinoid portion of the left internal carotid artery (ICA) is reported. A 37-year-old woman presenting with subarachnoid hemorrhage was found to have bilateral ICA aneurysms at the level of the posterior communicating arteries (PCoA's). The patient underwent right-sided craniotomy with uneventful clipping of the right PCoA aneurysm, and attempted clip placement on the contralateral left ICA aneurysm. The follow-up angiogram revealed a residual dome on the left ICA aneurysm, which was noted to originate at the proximal end of a fenestration of the left supraclinoid ICA. This represents the third reported case of fenestration of the intracranial ICA associated with an aneurysm. Intracranial artery fenestrations and their embryological origins are also reviewed.