The segmentation of the posterior cerebral artery: a microsurgical anatomic study

There are still different descriptions of the segmentation of the posterior cerebral artery, although there is a radiological and anatomical consensus on the segmentation of the anterior and the middle cerebral artery. This study aims to define the most appropriate localization for origin and end points of the segments through reviewing the segmentation of the posterior cerebral artery. The segments and the cortical branches originating from those segments of the 40 posterior cerebral arteries of 20 cadaver brains were examined under operating microscope. In this research, the P₁, P₂, P₃, P₄, and P₅ classification of the segmentation of the posterior cerebral artery is redefined. This redefinition was made to overcome the complexities of previous definitions. The P₁ segment in this research takes its origin from the basilar tip and ends at the junction with the posterior communicating artery. The average diameter of this segment at the origin was 2.21 mm (0.9–3.3), and the average length was 6.8 mm (3–12). The P₂ segment extends from the junction with the posterior communicating artery to the origin of the lateral temporal trunk. This point usually situates on one level of posterior of the cerebral peduncle. The average diameter of this segment at the origin was 2.32 mm (1.3–3.1), and the average length was 20.1 mm (11–26). The P₃ segment extends from the origin of the lateral temporal trunk to the colliculus where both the posterior cerebral arteries are the nearest to each other (quadrigeminal point) and is located at the anterior-inferior of the splenium. The average diameter of this segment at the origin was 1.85 mm (1.2–2.7), and the average length was 16.39 mm (9–28). The P₄ begins at the quadrigeminal point and ends at the top of the cuneus. The average diameter of this segment at the origin was 1.55 mm (1.1–2.2). While the P₅ segment is named as the terminal branches of the major terminal branches of the posterior cerebral artery, no definite border was found between the P₄ and the P₅ segments. In this study, the segmentation of the posterior cerebral artery, developed by Krayenbühl and Yaşargil, was redefined to be more appropriate for radiological and anatomical purposes.