The posterior communicative artery (PCA) is the main segment of the circle of Willis, which connects two main sources of the anterior and posterior cerebral circulation, namely the internal carotid and basilar arteries. The PCA not only provides an immediate bypass in case of acute arterial insufficiency but also plays a crucial role in the development of the anastomotic leptomeningeal vessels in chronic vascular pathology. The degree of the development of PCAs establishes the range of plasticity of the cerebral circulation and determines the clinical outcomes. The vessels of the posterior part of the circle of Willis were studied on 40 human brains extracted from the cranial cavities during the routine educational dissection. The PCAs were classified as hypoplastic if the outer diameter was less than 1mm, and as fetal if the P1 segment of the posterior cerebral artery was lesser than the diameter of P2 and PCA. The normal PCAs were found only in 10% of the brains with the complete posterior part of the circle. The other 21.25% of PCAs had features of total or partial fetal circulation with prevalent feeding from the internal carotid artery (ICA). The 51.25% of PCAs were hypoplastic on one (32.6%) or both sides. In 3 cases the artery was absent on one side. The results indicate that the effectiveness of the intracranial collateral circulation in American white descents is diminished in half of the study group due to underdevelopment of the PCA, while the fetal peculiarities of this artery in another quarter of subjects indicate the ICA dominance over the whole hemisphere with particular or no contribution from the vertebrobasilar system.

Keywords: Posterior cerebral circulation, Posterior communicative artery, Fetal circulation