Ruptured aneurysm of the PICA communicating artery: a case report.

A 47-year-old man presented with a rare aneurysm arising from the posterior inferior cerebellar artery communicating artery (PICA com A), manifesting as subarachnoid with intraventricular hemorrhage. Cerebral angiography showed a defect of the left PICA, and the left PICA region was supplied by a communicating artery formed by the fusion of branches from the right PICA and right vertebral artery. Aneurysms arose in the communicating artery, and a small, unruptured fusiform aneurysm was observed adjacent to a ruptured aneurysm. Trapping was performed for the 2 aneurysms with occipital artery (OA)-PICA bypass. Six cases of aneurysms occurring in this vessel including ours have been reported, and hemodynamic factors and congenital fragility of the arterial wall have been suggested as causative factors. Ours is the first case in which a ruptured aneurysm of this vessel was treated surgically with concurrent vascular reconstruction. If the aneurysm has a shape that is difficult to clip, the affected vessel is difficult to preserve, and collateral blood flow to the affected PICA region is considered insufficient, trapping with OA-PICA bypass is recommended.