De novo intracranial aneurysm formation after Gamma Knife radiosurgery for vestibular schwannoma.

Vascular complications, including vessel occlusion and hemorrhage, can arise after radiosurgery; however, hemorrhage due to a ruptured de novo aneurysm after Gamma Knife radiosurgery (GKS) for tumor is extremely rare. To the authors' knowledge, only a single case of de novo aneurysm formation after GKS for vestibular schwannoma has been previously reported. In this study, they describe their experience with the treatment of a 74-year-old woman with subarachnoid hemorrhage limited to the cerebellopontine cistern, who had undergone GKS for vestibular schwannoma 5 years earlier. Cerebral angiography demonstrated a left distal anterior inferior cerebellar artery aneurysm; coil embolization was attempted and failed. However, self-resolution of the aneurysm was revealed on follow-up angiography.