Cerebral abscess (summary)

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)
    • IVDU
• 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
    • hematogenous spread is the commonest route ¹
      • 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 ^1,2
    • 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 ¹

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 enhances post contrast
    • diffusion restriction within the abscess cavity is helpful to make the diagnosis