Ruptured Intracranial Infectious Aneurysm Mimicking an Expansive Brain Tumor in the Setting of Subacute Infective Endocarditis.

Infective endocarditis (IE) can lead to infectious intracranial aneurysms (IIAs) in a small percentage of cases. These aneurysms may rupture, resulting in intracerebral bleeding that is typically evident on neuroimaging. However, diagnosis becomes challenging when blood cultures and echocardiography are unremarkable, and neuroimaging is misinterpreted as a neoplasm due to overlapping features. We report a rare case of a ruptured IIA initially misdiagnosed as a brain tumor. A 43-year-old man presented with seizures, right-sided hemiparesis, and a 3-month history of fever, malaise, and 15-kg weight loss. Head computed tomography (CT) revealed a left frontal lesion with solid and hemorrhagic components, vasogenic edema, and intraventricular hemorrhage. Brain magnetic resonance imaging showed an enhancing mass-like lesion. Negative pan-cultures, normal echocardiography, and temporary improvement with oral prednisone led to a presumed diagnosis of brain tumor, and the patient was discharged for outpatient follow-up. Three months later, he was readmitted with persistent fever. This time, Streptococcus mutans bacteremia and mitral valve vegetations confirmed IE. Brain CT angiography revealed multiple IIAs. He received intravenous antibiotics. His hospital course was complicated by decompensated heart failure and a myocardial infarction due to obstructive coronary artery disease, requiring mitral valve replacement and coronary artery bypass grafting. He was discharged hemodynamically stable. This case highlights that IIAs can closely mimic brain tumors on imaging. Clinicians should maintain a high index of suspicion for IE in patients with neurological symptoms and systemic signs of infection, even when initial diagnostic studies are inconclusive.