- Brain abscess in the immunocompetent host is usually bacterial in origin and a result of spread from a contiguous focus (mastoiditis, sinusitis, dental infection) or from septic emboli from endocarditis or bacteremia or related to trauma or surgery.
- Infection is often polymicrobial, with viridans streptococci, S. aureus, and anaerobes being the most common pathogens; staphylococci and gram-negative bacilli predominate after surgery. In immunocompromised hosts, etiologies include invasive fungal infection, Nocardia, and tuberculosis; in HIV-infected patients, toxoplasmosis is a leading consideration.1
- Diagnosis is radiographic, with ring-enhancing lesions seen on MRI or contrast-enhanced CT scan.
- A microbiologic etiology should be determined by aspiration, biopsy, or at the time of surgery.
- Empiric therapy should cover the most likely pathogens based on the primary infection site. When the source is unknown, a third-generation cephalosporin (ceftriaxone) combined with metronidazole and vancomycin is started in immunocompetent hosts, and it is modified when culture data are available. Cefepime or ceftazidime should be substituted for ceftriaxone after neurosurgical procedures or penetrating head trauma.
- Neurosurgical consultation is imperative for drainage; cultures must be sent to enable pathogen-directed therapy, as a prolonged course of antibiotic therapy is often needed.
- Follow-up imaging to assess improvement determines length of therapy.
- Brouwer MC, Coutinho JM, van de Beek D. Clinical characteristics and outcome of brain abscess: systematic review and meta-analysis. Neurology. 2014;82(9):806-813. [PMID:24477107]
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