[A surgically treated case with a ruptured bacterial aneurysm of the middle cerebral arterial bifurcation following occlusion].

A 56-year-old woman with aortic regurgitation (AR) developd a high fever on April 25th, 2003, followed by the sudden onset of left hemiparesis and dysarthria on May 10th, 2003. MRI and MRA showed cerebral infarction due to occlusion of the right proximal portion of the middle cerebral artery. Streptococcus was isolated from arterial blood culture at the time of admission and cardiac examination such as echocardiography revealed active infective endocarditis. Cerebral angiography on the 31st day after the onset of symptoms demonstrated a fusiform-shaped aneurysm at the occluded M2 portion of the middle cerebral artery. Despite administration of antibiotics, a small subcortical hematoma was observed in the right temporal lobe surrounding the aneurysm on the 35th day. The direct surgery of aneurysmal trapping and resection was subsequently performed to prevent rebleeding. The sylvian fissure and perianeurysmal area were strongly adherent to granulation tissue and blood clot. After exposing the aneurysm, the dilated portion of the vessel was successfully trapped and resected. Other than residual left hemiparesis, the postoperative course was uneventful. Histological examination confirmed bacterial aneurysm due to bacterial embolization originating from infective endocarditis (IE). We report a rare case having a ruptured bacterial aneurysm of the middle cerebral arterial bifurcation requiring surgery following occlusion due to bacterial embolization after sepsis and meningitis due to infective endocarditis.