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Sinusitis and Subdural Empyema: (Left and middle) T1-weighted axial MRIs; (Right) T1-weighted with gadolinium coronal MRI. Note the prominent enhancement in the frontal sinuses, and the collection in the subdural space with surrounding enhancement. Aspiration of the subdural collection demonstrated frankly purulent material, in this case resulting from direct spread from the frontal sinuses. This is a subdural empyema.

Intracranial abscesses can occur in the epidural and subdural space as well as in the brain parenchyma. Infection most often occurs from spread through the blood system, or from direct invasion of an infection from an adjacent structure (e.g., sinusitis, otitis, mastoiditis, etc). Patients most often present subacutely over days to a few weeks with fever, headache, and/or focal neurological signs, including seizures.