Brain Abscess

Optimal treatment of a brain abscess requires early clinical suspicion, and the diagnosis is usually made by identification of the abscess on contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI). The immediate first step is to reduce the potentially life-threatening brain mass (abscess and surrounding cerebral edema) and secure the diagnosis with culture specimens. This is usually accomplished by reducing the increased intracranial pressure (ICP) through surgical aspiration with or without drainage of the abscess pus. The surgical procedure chosen depends on several factors, including the location and type of abscess, multiplicity, and the medical condition of the patient. In addition, dexamethasone and hyperventilation may be required if brain herniation is imminent. The dexamethasone dose should be reduced as soon as the ICP is reduced because steroid administration may retard abscess capsule formation and decrease antibiotic concentrations within the abscess cavity. Antibiotic therapy should be started as soon as the diagnosis is made. Penicillin G or third-generation cephalosporins plus metronidazole are commonly given to treat both anaerobic and aerobic bacteria. The initial choice of antibiotic will vary on the basis of the suspected source of the brain organisms, which is most often either contiguous spread from a sinus or mastoid infection or hematogenous spread from a pulmonary, gastrointestinal, cardiac, or dental infection. Isolation and determination of the antibiotic sensitivities of the organism from abscess pus allow definitive antibiotic therapy. Patients should be managed in an intensive care unit. Phenytoin is often given to prevent seizures, which could further elevate the ICP. The duration of antimicrobial treatment is 4 to 8 weeks, during which time the patient should be monitored clinically and with repeated neuroimaging studies to ensure abscess resolution.