Microsurgical anatomy of the hippocampal arteries.

An anatomical study of the vascularization of the hippocampus was performed on 30 hemispheres. There were a total of 140 arteries supplying the hippocampi, for an average of 4.7 arteries per hemisphere (range three to seven arteries). Based on the origin and caliber of the arteries supplying the hippocampus, the hemispheres were divided into five groups: A) in 57% of the hemispheres studied, the origin was mixed and included the anterior choroidal artery (AChA), the main trunk of the posterior cerebral artery (PCA), and the inferior temporal, lateral posterior choroidal, and splenial branches of the PCA; B) in 27%, all of the inferior temporal branches of the PCA predominantly supplied the hippocampus; C) in 10%, the anterior inferior temporal branch of the PCA was the predominant supplier: D) in 3%, the hippocampus was predominantly supplied by arteries originating from the main trunk of the PCA (Uchimura artery); and E) in 3%, the AChA gave origin to the hippocampal vessel. It was found as a result of this study that the PCA directly and by its branches contributes much more to the blood supply of the hippocampal formation than the AChA. The uncal sulcus was found to be an important anastomotic site between the hippocampal branches of the AChA and the hippocampal branches of the PCA. In 26.6% of hemispheres, one of the hippocampal arteries arose from the lateral posterior choroidal artery. The splenial artery made a loop close to the extraventricular part of the hippocampal tail and gave off multiple vessels to this structure in 36.6% of hemispheres. The finding that the AChA passes through the choroid fissure as a trunk and its later division into the lateral plexal and medial perforating branches within the choroid plexus may be of surgical significance.