• Clinical science

Brain abscess

Abstract

A brain abscess is a focal, suppurative lesion that may occur in one or more regions of the brain. It may be caused by the direct spread of sinus, ear, and/or dental infections, inoculation of pathogens following open skull fractures, and/or hematogenous spread from infective foci. During the course of the disease, the infected brain tissue softens and is subsequently encapsulated by granulation tissue. Clinical manifestations include headache, fever, neurological deficits, seizures, nausea, vomiting, and other features of raised intracranial pressure. Given these clinical findings, the main differential diagnosis is primary or metastatic brain tumor. Contrast CT reveals an intraparenchymal lesion with a hypodense center and peripheral ring enhancement. Treatment of brain abscesses involves surgical drainage of the abscess followed by systemic antibiotic therapy.

Etiology

References:[1][1][1][2][3][4]

Pathophysiology

  • Entry of pathogens via contiguous spread, direct inoculation, or hematogenous spread
    • Early cerebritis: infiltration of neutrophils (occurs during the first 3–5 days) and cerebral edema
    • Late; cerebritis (after 2–3 weeks); : necrosis, liquefaction, and infiltration of macrophages
    • Eventually forms a fibrotic capsule around the lesion

References:[5][4][6]

Clinical features

Clinical features depend on the size and location of the lesion.

  • Dull persistent headache
    • A ruptured abscess is associated with a sudden worsening of headache and meningism.
  • Symptoms of raised intracranial pressure (e.g., vomiting, papilledema, altered mental status)
  • Focal neurological deficits
  • Fever
  • Generalized or focal seizures (∼ 30% of cases)

References:[1][2]

Diagnostics

  • Laboratory tests
  • CT/MRI: : intraparenchymal lesions with a central hypodense (necrotic) area and peripheral ring enhancement
  • Biopsy (and drainage): microscopic examination and culture
    • Best confirmatory test; entails either craniotomy for complete excision, or image-guided aspiration; distinguishes an abscess from a tumor
    • Cultures also determine the infective organism and its antibiotic sensitivities. Infections are often multibacterial; tailoring of antibiotic therapy to specific bacterial sensitivities is especially important given the length of treatment.
  • Electroencephalography: striking focal lesions with potential for epileptic seizures

References:[2][7]

Differential diagnoses

Other intracranial lesions with ring enhancement:

The differential diagnoses listed here are not exhaustive.

Treatment

References:[2][5]

Prognosis

  • If treated early: high survival rates and low rates of residual neurological sequelae
  • Multiple, deep, ruptured; , or inadequately treated abscesses have a poor prognosis.[4]
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  • 4. Brook I. Brain Abscess. In: Brain Abscess. New York, NY: WebMD. http://reference.medscape.com/article/212946-overview. Updated October 5, 2015. Accessed February 20, 2017.
  • 5. Williams NS, Bulstrode C, O'Connell PR. Bailey & Love's Short Practice of Surgery. Boca Raton, FL : CRC Press; 2013.
  • 6. Gaillard F et al. Brain abscess. https://radiopaedia.org/articles/brain-abscess-1. Updated January 1, 2017. Accessed February 20, 2017.
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last updated 01/23/2018
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