Red Flags for Recognizing Ruptured Intracranial Mycotic Aneurysms in Clinical Settings

Introduction Intracranial mycotic aneurysms (ICMAs) are rare infection‐related aneurysms of cerebral arteries, most commonly associated with infective endocarditis. These lesions carry a high risk of rupture and mortality, making early recognition and timely diagnosis critical to improving outcomes. However, the clinical and radiological features that should alert clinicians to ruptured ICMAs remain poorly standardized. This case series highlights the clinical and radiological red flags observed in twelve patients with ruptured ICMAs presenting with intracranial hemorrhage, to aid earlier recognition and guide timely management in clinical practice. Materials We conducted a retrospective case series of twelve patients with confirmed ruptured intracranial mycotic aneurysms (ICMAs) between 2013 and 2025. Diagnosis was established using CT angiography and/or digital subtraction angiography in the context of a documented systemic or intracranial infection. Patients with unruptured or non‐infectious aneurysms were excluded. Variables collected included demographics, clinical presentation, infectious source, imaging features (location, multiplicity, hemorrhage pattern), microbiology, and management approaches. Analysis was descriptive. Results Twelve patients with ruptured intracranial mycotic aneurysms were included. The mean age was 33 years (range 12‐53), with a slight female predominance (7/12). Clinical presentations varied from incidental detection to severe headache, focal deficits, seizures, and coma. All patients had intracranial hemorrhage, most commonly subarachnoid hemorrhage (SAH) in 9 patients (75%), intraparenchymal hemorrhage occurred in 5 (42%), and intraventricular hemorrhage in 2 (17%). A mixed pattern of SAH with associated intraparenchymal (IPH) or intraventricular hemorrhage (IVH) was identified in 4 cases (33%). Angiography showed aneurysms predominantly in the distal cortical branches. The distribution of vascular territory involvement was as follows: Middle Cerebral Artery (MCA) territory was involved in 9 patients (75%): with M4 segment involvement in 7 patients and M1 segment involvement in 2 patients. Anterior Cerebral Artery (ACA) territory (A4 segment) was involved in 2 patients (17%). The Posterior Cerebral Artery (PCA) territory was involved in 2 patients (17%). Multiplicity (≥2 aneurysms) was observed in 1 patient (8%), who had six aneurysms (five M4 and one A4). The sizes of the identified aneurysms ranged from 2 mm to 11 mm. Infective endocarditis was the underlying cause in 10 patients. Blood cultures were positive in 8 patients, most commonly Streptococcus species (7) and Enterococcus faecalis (1). Two patients had non‐cardiac infectious sources ( cardiac hydatid cysts, orbital cellulitis with cavernous sinus thrombosis). Treatment included antibiotics in all patients, with surgical or endovascular intervention in selected cases. Conclusion Our case series highlights key red flags for ruptured intracranial mycotic aneurysms, including younger age, distal arterial involvement, multiplicity, mixed hemorrhage patterns (subarachnoid hemorrhage and intraparenchymal hemorrhage), and the presence of an infectious context, most commonly infective endocarditis, but also in rare cases cardiac hydatid cysts and orbital cellulitis. Recognizing these features can facilitate earlier diagnosis, enable more targeted treatment strategies, and ultimately improve patient outcomes.