Proximal ligation of large distal posterior inferior cerebellar artery aneurysm.

A 41-year-old male presented with vertigo, nausea, and vomiting suggesting a space-occupying lesion of the posterior fossa. Computed tomography (CT) and left vertebral angiography revealed a large distal posterior inferior cerebellar artery (PICA) aneurysm. Operation revealed the fusiform aneurysm was partially embedded in the medulla, preventing neck clipping or trapping of the aneurysm. Therefore, proximal ligation of the PICA was performed. The symptoms caused by the mass effect improved, and the aneurysm was not visualized by CT or angiography. Ligation of the PICA proximal to the choroidal point is not necessarily safe. In our case, ligation was distal to the tonsillomedullary segment from which the perforating arteries mainly arose, so the postoperative course was good without new neurological deficits. Proximal ligation is an effective treatment for distal PICA aneurysms manifesting as mass effect if other interventions are not possible.