Fetal posterior cerebral artery

Last revised by Rohit Sharma on 21 Feb 2024

A fetal (origin of the) posterior cerebral artery is a common variant in the posterior cerebral circulation, estimated to occur in 20-30% of individuals 2.

A fetal posterior communicating artery (PCom) describes a situation whereby the PCom is larger than the P1 segment of the posterior cerebral artery (PCA) and thus, supplies the bulk of the blood to the PCA 4,5. In this setting, the P1 can be small (hypoplastic) or absent. If bilateral, there is bilateral fetal PCom, the basilar artery will be significantly smaller than normal. In cases of non-fetal PCA, the PCom lies superomedial to the oculomotor nerve, whereas, in cases of fetal PCA, it lies superior or superolateral to it.

The significance of fetal PCom is in relation to the pattern of ischemic stroke, given that if a fetal PCom is present, the PCA is essentially part of the anterior circulation. Additionally, a larger PCom with an existing P1 allows for collateral circulation.

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