A large anomalous anterior choroidal artery associated with internal carotid artery-posterior communicating artery aneurysm. Case report.

A case of a large anomalous anterior choroidal artery (AchA) associated with internal carotid artery-posterior communicating artery aneurysm is reported. At surgery, the large anomalous AchA mimicked the PcomA. Therefore, we initially mistook the large anomalous AchA for the PcomA, and the ICA-PcomA aneurysm for the dorsal ICA aneurysm arising at a location of other than an arterial division. This is a rare case of an anomaly of the AchA with an associated aneurysm found at surgery. Anatomical and surgical considerations are made.