The basilar artery bifurcation: microscopical anatomy.

An anatomical study is performed with the acid of the operating microscope of the basilar artery bifurcation and the posterior portion of the Circle of Willis. The anatomical variations of the superior cerebellar arteries, the P 1 segment of the posterior cerebral arteries and the posterior portion of the posterior communicating arteries are described as well as the anatomical variations of the small branches originating from these arteries: the arteriae interpedunculares profundae, the arteriae thalamo perforantes and the arteriae chorioideae posteriores.