Surgery of a high basilar bifurcation aneurysm is one of the most difficult operations because of the location. Aneurysms which are located 1.5cm higher than the posterior clinoid process are difficult to approach by the usual pterional or subtemporal approaches. Our original transzygomatic anteriorsubtemporal approach is useful for aneurysms located up to 2 cm higher than the posterior clinoid process. The patient is placed in a semiprone position with the face turned 60°contralaterally. The skin incision is strated from the external auditory meatus. The zygomatic arch is reflected with the temporal muscle. The bone of the middle fossa is removed. The temporal lobe is retracted upwards after dural incision. The tentorial edge, PCA, fourth nerve and third nerve are recognized first. Then we approach the basilar artery and a highly situated aneurysm. In this report, authors explain this useful approach from an anatomical standpoint.
