Variability of the division of the cortical branches of the posterior cerebral artery

This article presents a method of analysis of variation in the cortical branching of the posterior cerebral artery (PCA). The method takes account of previous observations and reflects various symptoms of such variation. Of 100 cerebral hemispheres into whose vessels a contrast medium was injected, 94 hemispheres have been qualified for further examination. In six hemispheres, there were anomalies of the PCA, which are not included in the present analysis of division. A general model of the division of the artery has been developed. On the basis of this model, principles of the analysis of the variation have been discussed. The model comprises of three elements. The first is the main trunk. The second is intermediate trunks. The third element may appear in two forms: proper cortical arteries and cortical arterial groups. The main trunk was defined as the vessels arising from the final division of the basilar artery with its end in the place of branching of the most peripheral proper cortical artery, that is, parieto-occipital artery. Intermediate trunks are these parts of the PCA that extend between the main trunk and proper cortical arteries or cortical arterial groups. The identification criterion for the intermediate trunks is its length, which is to be equal to or exceed the sum of the radius of the two vessels, which the intermediate trunk gives off. There have been distinguished primary and secondary intermediate trunks. Proper cortical arteries or cortical arterial groups are parts of the PCA by means of which blood is supplied directly to the cortex. Cortical branches of the PCA of a relatively constant topography and vascularization were termed proper cortical arteries. In some cases, cortical branches are accompanied by small vessels of varying number and size. They were named accessory cortical arteries. Proper cortical arteries together with accompanying accessory cortical arteries have been named cortical arterial groups. The number of the proper cortical arteries is considered to be constant and is six. The theory of combinations has been applied to establish all possible branching variants. There are 16 such variants. Eleven of them (68%) were represented in the analyzed material. In seven hemispheres (7.4%), intermediate trunks were not observed. In 87 hemispheres (92.6%), there were present primary intermediate trunks. In four hemispheres (4.2%), there were found primary and secondary intermediate trunks. Both proper cortical arteries and cortical arterial groups reached the first five cortical areas of the PCA. The last cortical area was reached by a cortical arterial group only. (C) 2004 Wiley-Liss, Inc.