Supraclinoid Internal Carotid Artery Fenestration with Associated Aneurysm: Case Report and Literature Review

Fenestration of the supraclinoid internal carotid artery (ICA) is extremely rare and may occasionally be associated with saccular aneurysms; nevertheless, the natural history remains unclear. The authors reviewed the cases of fenestration of the supraclinoid ICA and evaluated the clinical characteristics and angioarchitecture with particular focus on the incidence for aneurysm development and rupture. Previously reported 24 cases and 1 new case from our institute were examined for the presence of aneurysms (including size and presence of bleb) leading to subsequent subarachnoid hemorrhage (SAH). Furthermore, 16 cases with sufficient information were classified into one of the three types according to the developmental condition of fenestration and fusion site: Type A (developed fenestration in which the ICA appears to duplicate [two cases]); Type B (hypoplastic fenestration fused to the ICA at the origin of the posterior communicating artery [Pcom] [six cases]); and Type C (hypoplastic fenestration fused to the Pcom itself or appeared to be a duplicated Pcom [eight cases]). In type A, the two cases had an aneurysm (100%), one of which caused SAH (50%). In type B, all six cases had an aneurysm (100%), and one of five led to SAH (20%) (one case lacked information regarding SAH). In type C, five of the eight cases had an aneurysm (62.5%), with no SAH (0%). The result suggested that the extent of development of fenestration and the location of fusion are related to the incidence of aneurysms and risk for rupture.