RESUMO
A 67-Year-old male patient was adimitted due to aggravation of long-standing left moter weakness. Past history revealed weakness of left extremity for 20 years caused by CVD attack. On adimission, his mental state was drowsy and brain CT scan showed a round mass mimicking a brain tumor in the frontal horn of right lateral ventricle with asymmetric dilatation of lateral ventricles. After failed carotid angiography due to vascular tortuosity, his mental state was progressively deteriorated and left hemiparesis aggravated. A right external ventricular drainage was done, and 5 days later a craniotomy was performed under the impression of the intraventricular tumor causing obstruction of right foramen of Monro, but a large thrombosed aneurysmal sac was found intraoperatively. Retrial of carotid angiography revealed a large anterior communicating artery aneurysm. After second operation, maningoencephalitis with wound infection was complicated. Twenty days after second operation, clipping of the aneurysmal neck with removal of partially thrombosed aneurysmal sac was performed successfully.