[Ruptured Posterior Inferior Cerebellar Artery Communicating Artery Aneurysm:A Case Report].

The posterior inferior cerebellar artery(PICA)communicating artery is a fine tortuous artery that interconnects the bilateral vermian branches of the distal PICAs. Aneurysms of this anastomotic vessel have been reported in only seven cases(including ours)in the available literature. The PICA communicating artery supplied collateral blood flow to the contralateral vermian territory in all seven cases. A 51-year-old man presented with a rare PICA communicating artery aneurysm(which manifested as a hematoma in the fourth ventricle)and mild subarachnoid hemorrhage at the cerebellomedullary fissure. Angiography revealed a hypoplastic right PICA and a PICA communicating artery from the left PICA that supplied the right vermian territory; the ruptured aneurysm originated from this vessel. Aneurysm trapping is associated with the risk of cerebral infarction of the right vermian territory. We concluded that the distal part of the telovelotonsillar segment could be sacrificed because the right anterior inferior cerebellar artery and the superior cerebellar artery would supply collateral blood flow; therefore, we attempted trapping in this case. A bilateral midline suboccipital approach was used, and we detected a reddish fusiform aneurysm at the top of a hairpin curve of the PICA communicating artery in the uvula of the cerebellar vermis. The aneurysm was trapped and removed without complications. Histopathological evaluation confirmed findings of a true aneurysm. Congenital vulnerability of the arterial wall and hemodynamic stress are considered contributors to PICA communicating artery aneurysms. Preservation of the affected vessel is difficult in patients in whom aneurysmal clipping is challenging. Other vessels tend to establish collateral blood flow to the contralateral vermian territory in such cases. Trapping is a simple and effective therapeutic strategy for these aneurysms.