Brain Abscess

Magnetic resonance imaging (MRI) with contrast administration is the neuroimaging procedure of choice, because MRI is better able to demonstrate an abscess that is in the cerebritis stage than a cranial CT scan. On T1-weighted MRI after the administration of intravenous gadolinium, the abscess appears as a central area of hypointensity with a smooth peripheral enhancing rim. On T2-weighted MRI, the abscess appears as a hyperintense lesion surrounded by a hypointense capsule. A lumbar puncture is contraindicated. Aerobic and anaerobic blood cultures can be obtained, and a careful physical examination may identify the source of infection. Definitive diagnosis is made by CT- or MRI-guided stereotactic aspiration of the abscess for Gram staining and culture. Empiric antimicrobial therapy is typically started before the results of Gram stain and culture are known and is based on the possible causative organism if the source of infection is known. Empiric therapy is modified once the results of Gram stain and bacterial culture and antimicrobial sensitivity testing is known. Corticosteroids are recommended in patients with significant edema but only for a short period of time because they decrease antibiotic penetration into the abscess cavity. Prophylactic antiepileptic medications are recommended because a brain abscess is an epileptogenic focus.

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