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Brain Abscess

By

John E. Greenlee

, MD, University of Utah Health

Reviewed/Revised Mar 2022 | Modified Sep 2022
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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 MRI or CT. Treatment is with antibiotics and usually CT-guided stereotactic aspiration or surgical drainage.

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, as may the abscess itself.

Etiology of Brain Abscess

A brain abscess can result from

Symptoms and Signs of Brain Abscess

Symptoms result from increased intracranial pressure, mass effect, and sometimes focal brain injury. Classically, headache, nausea, vomiting, lethargy, seizures, personality changes, papilledema, and focal neurologic deficits develop over days to weeks; however, in some patients, these manifestations are subtle or absent until late in the clinical course.

Fever, chills, and leukocytosis may develop before the infection is encapsulated, but they may be absent at presentation, subside over time, or not develop.

Diagnosis of Brain Abscess

  • Contrast-enhanced MRI or, if unavailable, contrast-enhanced CT

When symptoms suggest an abscess, contrast-enhanced MRI with diffusion-weighted images or, if MRI is unavailable, contrast-enhanced CT is done. A fully developed abscess appears as an edematous mass with ring enhancement, which may be difficult to distinguish from a brain tumor Diagnosis Intracranial tumors may involve the brain or other structures (eg, cranial nerves, meninges). The tumors usually develop during early or middle adulthood but may develop at any age; they are... read more Diagnosis or occasionally infarction Diagnosis Ischemic stroke is sudden neurologic deficits that result from focal cerebral ischemia associated with permanent brain infarction (eg, positive results on diffusion-weighted MRI). Common causes... read more Diagnosis ; CT-guided aspiration, culture, surgical excision, or a combination may be necessary.

Culturing pus aspirated from the abscess can make targeted antibiotic therapy of the abscess possible. However, antibiotics should not be withheld until culture results are available.

Lumbar puncture is not done because it may precipitate transtentorial herniation and because cerebrospinal fluid (CSF) findings are nonspecific (see table Cerebrospinal Fluid Abnormalities in Various Disorders Cerebrospinal Fluid Abnormalities in Various Disorders Cerebrospinal Fluid Abnormalities in Various Disorders ).

Treatment of Brain Abscess

  • Antibiotics (initially cefotaxime or ceftriaxone plus metronidazole for Bacteroides species or plus vancomycin for Staphylococcus aureus based on suspicion, then as guided by culture and susceptibility testing)

  • Usually CT-guided stereotactic aspiration or surgical drainage

  • Sometimes corticosteroids, antiseizure drugs, or both

All patients receive antibiotics for a minimum of 4 to 8 weeks. Initial empiric antibiotics include one of the following:

  • Cefotaxime 2 g IV every 4 hours

  • Ceftriaxone 2 g IV every 12 hours

Both are effective against streptococci, Enterobacteriaceae, and most anaerobes but not against Bacteroides fragilis. If clinicians suspect Bacteroides species (as in chronic sinusitis or otitis), metronidazole 15 mg/kg (loading dose) followed by 7.5 mg/kg IV every 6 hours is also required. If S. aureus is suspected (eg, after cranial trauma or neurosurgery or in endocarditis), vancomycin 1 g every 12 hours is used (with cefotaxime or ceftriaxone) until sensitivity to nafcillin (2 g every 4 hours) is determined. Response to antibiotics is best monitored by serial MRI or CT.

Drainage (CT-guided stereotactic or open) provides optimal therapy and is necessary for most abscesses that are solitary and surgically accessible, particularly those > 2 cm in diameter. If abscesses are < 2 cm in diameter, antibiotics alone may be tried, but abscesses must then be monitored with frequent serial MRI or CT (initially as often as every 2 to 3 days); if abscesses enlarge after being treated with antibiotics, surgical drainage is indicated.

Patients with increased intracranial pressure (assessed by signs and neuroimaging findings) may benefit from a short course of high-dose corticosteroids (dexamethasone 10 mg IV once, then 4 mg IV every 6 hours for 3 or 4 days).

Antiseizure drugs are frequently used to prevent seizures.

Rate of recovery depends on how successful the abscesses are eradicated and the patient's immune status.

If immunocompromised patients (eg, patients with uncontrolled HIV infection) have an abscess due to Toxoplasma gondii or a fungus, they may have to take antibiotics for the rest of their life.

Key Points

  • Brain abscess can result from direct extension (eg, of mastoiditis, osteomyelitis, sinusitis, or subdural empyema), penetrating wounds (including neurosurgery), or hematogenous spread.

  • Headache, nausea, vomiting, lethargy, seizures, personality changes, papilledema, and focal neurologic deficits develop over days to weeks; fever may be absent at presentation.

  • Do contrast-enhanced MRI or, if MRI is unavailable, contrast-enhanced CT.

  • Treat all brain abscesses with antibiotics (usually initially with ceftriaxone or cefotaxime plus metronidazole if clinicians suspect Bacteroides species or plus vancomycin if they suspect S. aureus), typically followed by CT-guided stereotactic aspiration or surgical drainage.

  • If abscesses are < 2 cm in diameter, they may be treated with antibiotics alone but must then be monitored closely with MRI or CT; if abscesses enlarge after being treated with antibiotics, surgical drainage is indicated.

Drugs Mentioned In This Article

Drug Name Select Trade
Claforan
Ceftrisol Plus, Rocephin
Flagyl, Flagyl ER, Flagyl RTU, MetroCream, MetroGel, MetroGel Vaginal, MetroLotion, Noritate, NUVESSA, Nydamax, Rosadan, Rozex, Vandazole, Vitazol
FIRVANQ, Vancocin, Vancocin Powder, VANCOSOL
Nallpen
AK-Dex, Baycadron, Dalalone, Dalalone D.P, Dalalone L.A, Decadron, Decadron-LA, Dexabliss, Dexacort PH Turbinaire, Dexacort Respihaler, DexPak Jr TaperPak, DexPak TaperPak, Dextenza, DEXYCU, DoubleDex, Dxevo, Hemady, HiDex, Maxidex, Ocu-Dex , Ozurdex, ReadySharp Dexamethasone, Simplist Dexamethasone, Solurex, TaperDex, ZCORT, Zema-Pak, ZoDex, ZonaCort 11 Day, ZonaCort 7 Day
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