A case of infectious intracranial aneurysm that formed and ruptured within a few days after occlusion of the proximal middle cerebral artery by infective endocarditis.

Background: Embolic cerebral infarction and infectious intracranial aneurysms (IIAs) are well-known central nervous system complications of infective endocarditis (IE). In this report, we describe a rare case of cerebral infarction caused by the occlusion of the M2 inferior trunk due to IE, followed by the rapid formation and rupture of IIA. Case Description: A 66-year-old woman was admitted to the hospital with a diagnosis of IE and embolic cerebral infarction after being brought to the emergency department with a 2-day history of fever and difficulty walking. After admission, she was immediately started on antibiotic therapy. Three days later, the patient suddenly became unconscious, and a head computed tomography (CT) scan showed massive cerebral hemorrhage and subarachnoid hemorrhage. Contrast-enhanced CT showed a 13-mm large aneurysm in the left middle cerebral artery (MCA) bifurcation. An emergency craniotomy was performed, and intraoperative findings revealed a pseudoaneurysm at the origin of the M2 superior trunk. Clipping was considered difficult, so trapping and internal decompression were performed. The patient died on the 11th day after surgery due to the worsening of her general condition. The pathology of the excised aneurysm was consistent with a pseudoaneurysm. Conclusion: IE may cause occlusion of the proximal MCA and rapid formation and rupture of IIA. It should be noted that the location of IIA may be a short distance away from the occlusion site.