Cerebral abscess (summary)

Dr Derek Smith et al.

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.

  • epidemiology
    • may occur at any age
    • risk factors
      • systemic infection
      • remote abscess
      • IV drug abuse
  • presentation
    • neurological symptoms rather than signs of infection
    • 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 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 paediatrics 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
      • MRI (diffusion-weighted imaging is important)
  • treatment
    • usually require operative management
    • intensive IV antibiotic therapy 1
  • initial diagnosis
  • assessment of any mass-effect, e.g. from surrounding oedema
  • assessment of any other lesions
  • aid surgical planning

CT will be the first line investigation in most cases, since patients will present with focal neurology, evidence of raised ICP, headache. However, like most neuropathology, MRI is the most sensitive and specific method for investigation 3.

CT

Whenever a mass is demonstrated at CT, it is useful to give contrast to demonstrate the post-contrast enhancement pattern. Typically, the wall of the abscess enhances with low-attenuation, non-enhancing centre (pus) and surrounding low-attenuation throughout the white matter (oedema).

MRI

MRI more clearly demonstrates the mass-lesion. The central pus and surrounding oedema is full of water and therefore bright on T2. The wall classically enhances following Gadolinium.

However, these findings are not specific to abscess. Demonstrating diffusion restriction within the abscess is key to making the diagnosis.

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Cases and figures

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    Case 1: non-contrast CT with hyperdense rim with surrounding oedema
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    Case 1: contrast showing ring-enhancing lesion
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    Case 2: T2 MRI images with high signal (consistent with fluid)
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    Case 3: left sided abscess with contrast enhancement
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    Case 4: fungal abscesses
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