Localized Subarachnoid Purulence Mimicking Aneurysmal Subarachnoid Hemorrhage: A Case Report.

Subarachnoid purulence is generally formed secondary to the rupture of brain abscesses. Early diagnosis of subarachnoid purulence unrelated to brain abscesses is challenging because of the lack of specific neurological or radiological findings. In this article, we report a case of localized subarachnoid purulence mimicking aneurysmal subarachnoid hemorrhage. A 74-year-old woman with diabetes and a history of rhinosinusitis presented with a sudden deterioration of the level of consciousness, tonic posture, and fever. A head computed tomography (CT) scan revealed a high-density area in the left Sylvian fissure. Subsequent CT angiography revealed an ipsilateral posterior communicating artery aneurysm, suggesting a diagnosis of aneurysmal subarachnoid hemorrhage. Craniotomy for surgical clipping of the presumed ruptured aneurysm revealed a subarachnoid purulence rather than a clot. Antimicrobial agents were administered, and endoscopic sinus surgery was performed to control the infection. Histopathological and microbiological examinations of the sphenoid sinusitis and intracranial specimen revealed Aspergillus, Prevotella intermedia, and Staphylococcus aureus. The functional outcome was poor because of delayed cerebral infarction associated with vascular invasion by the subarachnoid purulence. Localized subarachnoid purulence could be misdiagnosed as aneurysmal subarachnoid hemorrhage, particularly when an incidental aneurysm is detected. Laboratory and physical findings of systemic inflammation, as well as a history of rhinosinusitis, may help physicians add magnetic resonance imaging and lumbar puncture for early and definitive diagnosis of subarachnoid purulence.