Aneurysms of the distal posterior inferior cerebellar artery: experience with three cases and review of the literature.

We report 3 surgically treated aneurysms of the distal posterior inferior cerebellar artery (PICA) and review 36 cases in the literature. More than half of the distal PICA aneurysms arose distal to the choroidal arch. These lesions often arose at a turning point (i.e., a hairpin curve) of an artery instead of at a junction of vessels. Distal PICA aneurysms are likely to be missed and it is necessary to investigate carefully with four-vessel angiography even if computed tomography is done. Eighty-two per cent of the surgically treated 39 patients had good recoveries and 8% had fair results. The mortality rate was 10%. Although clipping of the aneurysm neck is preferable, trapping is useful when neck clipping is impossible in segments distal to the choroidal arch.