[A case of bacterial aneurysm that occurred in the external carotid artery].

Occurrence of a mycotic aneurysm extracranially is extremely rare. We report our experience with a case of mycotic aneurysm that occurred in the external carotid artery accompanying infectious endocarditis. The case was a 33-year-old male. He visited our hospital with principal complaints of weakness in the lower left side and visual difficulty. Multiple cerebral infarctions were noted in a head MRI. In addition, vegetation was noted on the mitral valve in an echocardiogram, and the patient was admitted to cardiology for infectious endocarditis. Aneurysms were noted in the external carotid artery and the posterior cerebral artery in a cerebral angiogram performed before valve replacement. After administration of antibiotics for 5 weeks, radical surgery was performed for the external carotid artery aneurysm that had remained unchanged. With a satisfactory postoperative course, the patient was able to walk independently after mitral valve replacement and was discharged. We have scoured the literature with regard to mycotic aneurysm occurring extracranially and have studied this case because of this characteristic. When performing cerebral angiography to search for a mycotic aneurysm, the area outside the cranium as well as inside must be closely examined.