Cerebral mycotic aneurysm is an uncommon complication of infective endocarditis. In spite of low incidence, mycotic aneurysm is a serious complication because of the high risk of its rupture. Therefore, early diagnosis and management of cerebral mycotic
aneurysm are imperative before the rupture. We experienced a case of asymptomatic cerebral mycotic aneurysm in a 30-year old man with infective endocarditis. He was admitted for splenic and renal infarction due to systemic embolization. The
echocardiography showed severe mitral regurgitation, mitral valve prolapse and vegetation on the mitral valve. Streptococcus mitis was identified from blood cultures. In the course of antibiotics therapy, brain magnetic resonance image and 4-vessel
cerebral angiography were performed, which revealed multiple unruptured cerebral mycotic aneurysms. Considering the high risk of rupture we performed mitral valve replacement with bioprosthesis. On follow-up cerebral angiography after the valve
replacement surgery, one of aneurysms was enlarged, and successfully treated by surgical intervention without complication. We report one case of mycotic aneurysm without neurologic symptom in an infective endocarditis patient, who was treated without
serious sequelae of the aneurysm.