Perforating branches of the basilar bifurcation.

The perforating branches of the upper basilar artery and of the first (P1) segment of the posterior cerebral artery were studied in 50 fixed brains obtained from human cadavers. No vertical branches arose from the basilar bifurcation. The upper basilar artery gave rise to horizontal branches, which were studied with reference to their angle of origin. Perforating arteries arising from P1 segments were found in all specimens. Rare branches were found to come from the inferior and anterior surfaces of P1 segments. The anatomical patterns of these branches are discussed in the light of previous reports. Preoperative knowledge of some anatomical aspects (the position of the basilar apex, the angle between the right P1 and left P1 segments, and relationships to the dorsum sellae and the mammillary bodies) can help in the selection of a neurosurgical approach and may improve the operative results in the surgical treatment of basilar apex aneurysms.