Distal posterior inferior cerebellar aneurysms--report of 12 cases.

The authors review 12 cases of distal posterior inferior cerebellar artery (PICA) aneurysm. Nine of the aneurysms were discovered after their rupture and three were incidentally detected. Seven (78%) of the nine ruptured aneurysms rebled, leading in four cases to coma and respiratory arrest. Computed tomography revealed intraventricular hematomas, mainly in the fourth ventricle, and a subarachnoid clot at the cisterna magna. In five of the nine cases involving aneurysm rupture, radical surgery was performed. The remaining four, whose clinical status was poor, were treated conservatively and subsequently died. Two patients were rendered partially dependent as a result of perioperative complications. A high incidence of rebleeding is characteristic of ruptured distal PICA aneurysms, and for this reason the prognosis for these patients is rather poor.