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Causes and Incidence Causes include extension of existing cranial infection (e.g., ear infection, sinusitis, mastoiditis, osteomyelitis, periodontal infection); penetrating head wounds; blood-borne transmission from a distant infection (e.g., bacterial endocarditis, abdominal/pelvic infections, bronchiectasis); IV drug abuse; or immunodeficiency. The incidence is highest in individuals with sinusitis or ear or pulmonary infection. The number of abscesses is increasing with the rise in immune-deficiency disorders and IV drug abuse.

Disease Process The brain produces a poorly localized inflammatory response to the invading pathogen. Brain tissue subsequently liquefies and necroses, producing a cystic mass, which is encapsulated by glia and fibroblasts. As this mass enlarges, it increases intracranial pressure, causing signs and symptoms similar to those of a brain tumor.

Symptoms Headache, nausea, vomiting, seizures, altered mental status, nuchal rigidity, low-grade fever; the duration of symptoms varies considerably, from hours to weeks.

Potential Complications The illness is progressive and usually fatal if left untreated. With treatment, the mortality rate is 30%, and more than half of survivors suffer some neurologic sequelae.

Diagnostic Tests

Clinical evaluation

Above manifestations and predisposing conditions

Lumbar puncture

Contraindicated

Computed tomography (CT)/magnetic resonance imaging

Visualization of abscess

Treatments

Surgery

Biopsy; drainage and evacuation of abscess through stereotaxic techniques or craniotomy

Drugs

Intravenous antibiotics as initial choice, depending on suspected organism and probable source of infection; later choices made from culture and sensitivity and Gram's stain results; steroids to reduce brain edema and intracranial pressure; anticonvulsants to control seizure activity

General

Serial-order CT scans to monitor progression; monitoring for hyponatremia, inappropriate antidiuretic hormone secretion; prevention of complications of extended bed rest (i.e., antiembolism stockings, range-of-motion exercises, turning); early, aggressive rehabilitation to prevent or reduce neurologic sequelae