Young patient with an internal carotid artery occlusion resulting in acute MCA and PCA territory infarcts due to a fetal origin of posterior cerebral artery.

Typically the PCA is part of the posterior circulation, so an internal carotid artery occulsion should not result in a PCA territory infarct. However, upto 30% of individuals have a fetal origin of the PCA, in so doing getting the majority of the blood supply from the anterior circulation derived PCOM artery.