In addition to hypoplasia or aplasia of the P1 segment of the posterior cerebral artery (PCA), rare variations of PCA include fenestration, early bifurcation, duplication of PCA, and hyperplastic anterior choroidal artery (AchA). One study found the prevalence of PCA fenestration, early bifurcation, duplication, and hyperplastic AChA to be 0.34%, 0.34%, 0.05%, and 0.55%, respectively [1]. Hyperplastic AchA, accessory PCA, and replaced PCA refer to the same variation, which depends on the part of the PCA territory that they supply [1-3]. Accessory PCA describes hyperplastic AchA that supplies a part of the PCA territory, and replaced PCA refers to hyperplastic AchA that supplies to all branches [1].
The three-dimensional study of the circle of Willis in 28-year-old woman with migraine revealed that both PCAs and superior cerebellar arteries originated normally from the basilar artery (Fig. 1). The right AchA was hyperplastic and covered areas of the parieto-occipital and calcarine branches. The left AchA was not visualized. In contrast to left side, there was no right posterior communicating artery. Our patient had an accessory PCA that supplied a portion of the PCA territory. It is essential to understand the anatomic variants of cerebral arteries when planning surgical or endovascular treatment.
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