Ruptured distal anterior inferior cerebellar artery aneurysm following stereotactic irradiation for vestibular schwannoma: case report.

A 73-year-old woman presented with diffuse subarachnoid hemorrhage from a ruptured fusiform aneurysm directly arising from the right distal anterior inferior cerebellar artery. Six years before admission, she had undergone stereotactic irradiation for right vestibular schwannoma, under a diagnosis based on neuroimaging. The aneurysm was located within the radiation field. We performed trapping and resection of the aneurysm via a right lateral suboccipital craniotomy, and the patient made a good recovery. Histological examination revealed no evidence of elastic lamina in the aneurysm wall, suggesting pseudoaneurysm caused by radiation-induced vascular injury. Aneurysm formation after radiotherapy is relatively rare and often manifests as fatal hemorrhage. Long-term surviving patients who have received intracranial irradiation should undergo sequential follow up for possible vascular involvement.