Fenestration of intracranial arteries with special attention to associated aneurysms and other anomalies.

PURPOSE To determine the association of intracranial arterial fenestration and aneurysms. METHODS We retrospectively reviewed 5,190 cerebral angiogram reports and identified 37 patients with arterial fenestrations. RESULTS These 37 patients had 38 fenestrated arteries: 16 basilar, 10 vertebral, nine middle cerebral, and three anterior cerebral arteries. Seven of these patients had a total of 13 aneurysms, although only one aneurysm was at the site of a fenestration. The remaining aneurysm patients had fenestrations as unassociated findings. Other anomalies detected were two azygous anterior cerebral arteries, on dural arteriovenous shunt of the cavernous sinus, one extracranial arteriovenous fistula, and one developmental venous anomaly (venous angioma). None of the fenestrations were in the vessels directly involved with these associated lesions. The incidence of aneurysm at the fenestration was 7% (one in 16) for basilar artery fenestrations. Considering all fenestrations, the incidence of aneurysm at the site of fenestration was 3%. CONCLUSION Our data show that the association of a fenestration with an aneurysm at the fenestration site is not different from the typical association of circle of Willis bifurcations with saccular aneurysms.