Cerebral abscess (summary)

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This is a basic article for medical students and other non-radiologists

Cerebral abscesses represent focal areas of infection within brain parenchyma, usually containing pus and having a thick capsule. They typically have enhancing walls and can mimic a number of other significant pathologies.

Reference article

This is a summary article; read more in our article on cerebral abscess.

Summary

  • epidemiology
    • may occur at any age
    • risk factors
      • immunocompromise (including HIV, diabetes mellitus)
      • existing infection (eg. middle ear infection, bacteremia)
      • IV drug use
  • presentation
    • fever, headache, and focal neurology may be present
    • signs of raised ICP, focal neurology or seizures should prompt imaging
  • pathophysiology
    • spread of infection to the brain
      • inflammation and irritation of parenchyma
        • thin walled abscess formation
    • source
      • haematogenous spread is the commonest route
        • infection crosses the blood-brain barrier
      • direct infection may occur
        • mastoiditis or sinusitis
        • requires a severe infection and bone destruction
    • microbiology
      • mixed bacteriology
      • sterile cultures in 25-34% of cases
      • gram negative bacteria commoner in pediatrics and immunocompromised patients
      • fungal infection commoner in the immunocompromised
  • investigation
    • blood work to include inflammatory markers and renal function
    • cross-sectional imaging
      • CT with contrast - first line
      • MRI (diffusion-weighted imaging is important)
  • treatment
    • usually require operative management
    • aggresive IV antibiotic therapy

Imaging

  • role of imaging
    • initial diagnosis
    • assessment of any mass-effect, e.g. from surrounding edema
    • assessment of any other lesions
    • aid surgical planning
  • radiographic features
    • CT
      • first line imaging
      • low-density lesion with peripheral enhancement
      • surrounding low-density white-matter edema
    • MRI
      • more sensitive
      • pus is bright on T2 weighted images
      • the wall of the abscess typically lights up after contrasts
      • diffusion restriction within the abscess cavity is helpful to make the diagnosis