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A brain abscess is an intracerebral collection of pus. Symptoms may include headache, lethargy, fever, and focal neurologic deficits. Diagnosis is by contrast-enhanced CT or MRI and sometimes culture. Treatment is with antibiotics and usually surgical drainage.

A brain abscess can result from direct extension of cranial infections (eg, osteomyelitis, mastoiditis, sinusitis, subdural empyema), penetrating head wounds (including neurosurgical procedures), hematogenous spread (eg, in bacterial endocarditis, congenital heart disease with right-to-left shunt, IV drug abuse), or unknown causes.

The bacteria involved are usually anaerobic and sometimes mixed, often including anaerobic streptococci or Bacteroides. Staphylococci are common after cranial trauma, neurosurgery, or endocarditis.Enterobacteriaceae are common with an ear source. Fungi (eg, Aspergillus) and protozoa (eg, Toxoplasma gondii, particularly in HIV-infected patients) can cause abscesses.

An abscess forms when an area of cerebral inflammation becomes necrotic and encapsulated by glial cells and fibroblasts. Edema around the abscess may increase intracranial pressure.

Symptoms, Signs, and Diagnosis

Symptoms result from increased intracranial pressure and mass effect. Headache, nausea, vomiting, lethargy, seizures, personality changes, papilledema, and focal neurologic deficits develop over days to weeks. Fever, chills, and leukocytosis may develop before the infection is encapsulated, then subside.

When symptoms suggest an abscess, contrast-enhanced CT or MRI is done. An abscess appears as an edematous mass with ring enhancement, which may be difficult to distinguish from a tumor or occasionally infarction; culture and drainage may be necessary. Lumbar puncture is not done because it may precipitate transtentorial herniation and because CSF findings are nonspecific (see Table 1: Approach to the Neurologic Patient: Cerebrospinal Fluid Abnormalities in Various Disorders).

Brain Abscess (CT Without Contrast)

Brain Abscess (CT With Contrast)

Treatment

All patients receive antibiotics for ≥ 4 to 8 wk. Initial empiric antibiotics include cefotaxime Some Trade Names
CLAFORAN
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2 g IV q 4 h or ceftriaxone Some Trade Names
ROCEPHIN
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2 g IV q 12 h; both are effective against streptococci, Enterobacteriaceae, and most anaerobes but not against Bacteroides fragilis, which requires metronidazole Some Trade Names
FLAGYL
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7.5 mg/kg IV q 6 h. If Staphylococcus aureus is suspected, vancomycin Some Trade Names
VANCOCIN
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1 g q 12 h is used until sensitivity to nafcillin Some Trade Names
UNIPEN
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(2 g q 4 h) is determined. Response to antibiotics is best monitored by serial CT or MRI. Drainage, stereotactic or open, provides optimal therapy and is necessary for most abscesses that are solitary and surgically accessible, particularly those > 2 cm in diameter. Patients with increased intracranial pressure may benefit from a short course of high-dose corticosteroids. Anticonvulsants are sometimes recommended to prevent seizures.

Last full review/revision November 2005

Content last modified November 2005