The surgical anatomy of the anomalous posterior communicating artery

Abstract

We examined the posterior communicating artery (PCoA) and its perforators in different configurations of the Circle of Willis to study the relationship of these arteries to surrounding anatomic structures for a surgical perspective. Twenty-four cerebral hemispheres and five cadavers (10 sides) were examined. The adult configuration was observed in 30%, the fetal in 28%, the transitional in 14%, and the hypoplastic in 28%. The PCoA was always found to be medial to the third nerve. In 12% of sides with the fetal or transitional configurations, the third nerve was either touching the PCoA or the PCoA was overlying it at the level of the brain stem. An infundibular dilatation at the origin of the PCoA was identified in 22% of hemispheres and in 60% of specimens, it was bigger than 3 mm. An infundibular dilatation was always found in the fetal, transitional, and hypoplastic configurations. The number of perforators found arising from the PCoA was 4 to 15. The premamillary artery was always seen as the largest PCoA perforator and arose from the medial wall of the PCoA in 15%. Identifying the presence of a PCoA variant is of surgical relevance. The incidence of infundibular dilatations is higher in transitional, fetal, and hypoplastic configurations. The relationship of the third nerve to PCoA variants must be identified to avoid intraoperative injury. The premamillary artery can arise from the medial wall of the PCoA.