Radiation-induced aneurysm and moyamoya vessels presenting with subarachnoid haemorrhage.

A rare case of a ruptured internal carotid artery (ICA) aneurysm, with ICA stenosis and moyamoya vessels, was diagnosed in a young female patient after radiotherapy for optic glioma. Retrospective analysis revealed that an extraordinarily high dose of radiation (110 Gy) had been delivered to the area around the ICA in two therapeutic sessions. Clipping and wrapping of the aneurysm were performed and the patient made a good recovery. A review of the literature suggested that rupture of radiation-induced aneurysms is a rare event, but may be fatal. Considerable care must therefore be taken when delivering high-dose radiation to cerebral arteries. We suggest that the incidence of radiation-induced moyamoya vessels is higher in younger patients.