[Bacterial brain abscess]

The most common symptom of brain abscesses are headache, nausea, fever, disturbance of consciousness, focal signs and seizures. CT is the most useful investigation, showing ring-enhancing lesions with perifocal edema. Systemic inflammatory signs, cerebrospinal fluid changes and cerebral enhancement on leukocyte scintigraphy are of limited diagnostic value. In 10-20% of cases, diagnosis can only be established by biopsy. The most frequent organisms are aerobic streptococci, anaerobes, gram-negative bacilli and staphylococci. Metronidazole in combination with a third-generation cephalosporin and--in certain cases--an antistaphylococcal antibiotic should be given for at least 4 weeks. Conservative treatment can give satisfactory results in abscesses less than 2-3 cm in diameter. Medium-sized and deep-seated abscesses are treated by CT-guided stereotactic aspiration. In very large abscesses with the risk of herniation craniotomy and excision are necessary. Mortality is nowadays 5-15% and does not depend on treatment modalities. Prognosis is mainly determined by the patient's level of consciousness on admission.