The occipital artery for posterior circulation bypass: microsurgical anatomy

Object The microsurgical anatomy of the occipital artery (OA) was studied to describe the diameter, length, and course of this vessel as it pertains to revascularization procedures of the posterior cerebral circulation. Methods The authors studied 12 OAs in 6 cadaveric heads that had been injected with colored latex. They evaluated the OA's ability to serve as a conduit for extracranial–intracranial (EC–IC) bypass in the posterior circulation. They measured the length of the OA and its diameter at common sites of anastomosis and compared these values with the diameters of the recipient vessels (V 3 and V 4 segments of the vertebral artery, caudal loop of the posterior inferior cerebellar artery [PICA], and anterior inferior cerebellar artery [AICA]). Results The mean thickness of the suboccipital segment of the OA was found to be 1.9 mm. The mean distance of the OA from the external occipital protuberance was found to be 45 mm. The mean length of the suboccipital segment of the OA was 79.3 mm. The mean thickness of the largest trunk of the V 3 segment, the V 4 segment, the caudal loop of the PICA, and the AICA were 3.3 mm, 3.1 mm, 1.2 mm, and 1 mm, respectively. Conclusions The length, diameter, and flow accomodated by the OA make it an ideal choice as a conduit for posterior circulation bypass. The bypass from the OA to the caudal loop of the PICA demonstrates the least difference in vessel diameter, and is therefore best suited for EC–IC bypass procedures in the posterior circulation.