Intracranial arterial fenestrations: frequency on CT angiography and association with other vascular lesions.

Fenestrations (segmental duplications) of the intracranial arteries are rare anomalies, felt to result from incomplete fusion of primitive embryologic vessels. They have been associated with aneurysms and other vascular lesions. The rate of fenestrations based on published angiographic series has been much lower than that at cadaveric series. The purpose of this study is to determine the frequency of fenestrations and associated vascular lesions at CTA. A total of 504 sequential CTA studies from 2005 to 2006 were retrospectively reviewed for the presence of fenestrations, aneurysms and other vascular lesions. Fenestrations were present in 53 patients (11%). Their frequency was not significantly different in patients referred for aneurysm indications, when compared to those referred for non-aneurysm indications. As expected, there was a much higher frequency of aneurysms in the former group. Associated vascular lesions were relatively uncommon. Aneurysms were present at the fenestration site in three patients, and remote from the fenestration site in eight. One fenestration patient with an associated aneurysm at the fenestration site also had an AVM remote from the fenestration. The frequency of fenestrations in this study was higher than in previously published radiologic studies, suggesting that fenestrations are relatively common, and may be more frequently visualized using cross-sectional imaging. Association with aneurysms and other vascular lesions was relatively uncommon. Our results do not support the theory that fenestrations predispose a patient to aneurysms or vascular malformations remote from the site of the fenestration. Although the association of aneurysms at the site of fenestrations is well documented, our results do not show an overall higher rate of aneurysm formation in patients with fenestrations compared to those without.