Unilateral infundibular origin of a fetal posterior communicating artery, associated with an unruptured fusiform aneurysm of the terminal segment of internal carotid artery. A case report

Fetal-type posterior communicating artery (PComA) is considered when it serves as a dominant source of blood supply to the distal segment of the posterior cerebral artery (PCA) instead of being supplied as usual from the basilar arterial system. The infundibular origin of the PComA from the internal carotid artery (ICA) is a commonly observed anatomical variant, which has important implications for cerebrovascular dynamics. Infundibular dilatation may be complicated by a saccular aneurysm. Nevertheless, we present for the first time a case of infundibular origin of a right PComA of a fetal type, associated with a fusiform aneurysm of the terminal segment of the ICA. We hypothesize that the infundibular origin of PComA occurred due to the persistence of the fetal pattern of PComA and that it was a predisposing factor for the development of a fusiform aneurysm at the terminal segment of ICA. We recommend follow-up MRI for infundibula because of the high risk of their evolution into true aneurysms.