Ruptured True Anterior Choroidal Artery Aneurysm in Cisternal Segment.

BACKGROUND Rupture of a true anterior choroidal artery (AChA) aneurysm in the cisternal segment is extremely rare, whereas cases of a distal AChA aneurysm associated with moyamoya disease are increasingly reported. CASE DESCRIPTION A 58-year-old woman presented with a severe headache and vomiting. Computed tomography demonstrated a subarachnoid hemorrhage without intraventricular or intracerebral hemorrhaging. Cerebral angiogram findings revealed a proximal AChA aneurysm mimicking an internal carotid artery aneurysm at the origin of the AChA. Intraoperative findings demonstrated a ruptured aneurysm located on a bend of the proximal AChA in the carotid cistern. Neck clipping of the aneurysm with preservation of the AChA led to a good outcome. CONCLUSIONS A rare case of ruptured true AChA aneurysm in the cisternal segment, unrelated to moyamoya disease, is presented as a cause of subarachnoid hemorrhage.