BACKGROUND: Intracranial infected aneurysms (IIAs), also known as mycotic aneurysms, complicate infective endocarditis (IE) in around 2-4% of cases. IIAs can spontaneously rupture and present with intracerebral bleeding, which is usually straightforwardly recognized in brain imaging. This case documents a rare presentation of a ruptured IIA initially misdiagnosed as a brain neoplasm due to clearly suggestive radiologic features.

CASE PRESENTATION: A 43-year-old male with history of cocaine and tobacco consumption and treated tuberculosis was admitted for tonic-clonic seizures and right hemiparesis along with a 3-month history of persistent fever, malaise, and 15-kg weight loss. A head computed tomography (CT) showed a left frontal lesion having both solid and central hemorrhagic content along with surrounding vasogenic edema and intraventricular hemorrhage. In the magnetic resonance imaging, the brain lesion was expansive and showed contrast enhancement. The workup showed elevated inflammatory markers and glomerulonephritis but was otherwise unremarkable for infectious, autoimmune, or oncological etiologies. At present, the primary suspicion was a brain tumor based on the characteristic radiologic features, the otherwise unremarkable workup including negative pan-cultures and transthoracic echocardiogram (TTE), and the maintenance of afebrile status following oral prednisone for vasogenic edema. He was discharged for outpatient follow-up. Around 3 months later, he was readmitted for persistent fever; a new TTE showed mitral valve vegetations and blood cultures grew Streptococcus mutans, confirming IE. A brain CT angiography confirmed multiple IIAs. He received intravenous ceftriaxone and vancomycin. Besides, the hospital course was complicated by decompensated heart failure and myocardial infarction with an obstructive coronary artery that required mitral valve and coronary artery bypass graft surgery, respectively. He was discharged hemodynamically stable.

DISCUSSION: IIAs represent an embolic complication of IE caused by septic arterial emboli that travels to the vasa vasorum of cerebral arteries and triggers a local inflammation and dilation of the arterial wall. Ruptured IIAs present with intracranial hemorrhage in brain imaging studies. However, this case and other around two-to-four cases documented that ruptured IIAs can rarely mimic intra-axial masses, leading to misdiagnosis. For example, similarities between IIAs and glioblastoma multiforme were reported, as both conditions can enhance contrast in imaging. It is unclear if this presentation is extremely rare or is underreported. This case documents a ruptured IIA presenting radiologically as a brain cerebral neoplasm. As a final reminder, clinicians should be aware of this unique presentation to maintain a high index of suspicion for IIAs despite unremarkable blood cultures and echocardiography.