Most unruptured cerebral aneurysms are asymptomatic and associated with extremely low rates of surgical complications. Therefore, the control of ruptures before clipping the aneurysmal neck should be of considerable prognostic significance. We retrospectively assessed data from 255 consecutive surgical patients with a total of 312 aneurysms treated between September 2006 and June 2019, and selected eight aneurysms that ruptured before clipping. Of the eight intraoperative aneurysm ruptures, four (50%) were anterior communicating artery aneurysms (Acom Ans). The incidence of intraoperative aneurysm rupture was 3.1% of patients and 2.6% of aneurysms. The main contributor to aneurysm rupture was dissection around the aneurysms. The outcomes were favorable in all patients. We considered that the following factors might be involved in the likelihood of an Acom An rupture: the Acom is developmentally fragile, involves several blood vessels, is located deep in the brain, and adheres to the optic chiasma, in addition to the frontal lobe. These considerations indicate that direct surgical manipulation, especially for Acom Ans, can result in intraoperative ruptures and is thus very important for surgeons to bear in mind.
