Abscess

• Localised focal necrosis of brain tissue with inflammation, usually caused by bacterial infection.
• Sources of infection:

  • Direct implantation e.g. traumatic inoculation or iatrogenic
  • Local extension from adjacent foci of infection
  • Hematogenous spread e.g. distant source of infection or congenital heart disease with right to left shunt
• Congenital heart disease with right to left shunt causes loss of pulmonary filtration of microorganisms - abscesses in distribution of middle cerebral artery
• Common causative bacteria:

  • Staphylococcus aureus
  • Streptococcus
  • Immunocompromised hosts may develop viral/fungal abscesses
• Risk factors:

  • Right to left cardiac shunts
  • lung is most commonly implicated organ - bronchiectasis, pneumonia, empyema
  • Immunosuppression
• Signs and symptoms:

  • Classic triad - fever, progressive focal neurology and headache
  • Increased ICP - early morning headache and vomiting
  • Mental status change
  • Seizures
  • Papilledema
• Diagnosis:

  • MRI/CT scan with contrast - initial immature lesions difficult to distinguish from space occupying lesions. 4-5 days later formation of capsule around necrotic focus - ring enhancing appearance
  • LP - raised WCC, raised protein and normal glucose
  • Abscess aspirate
• Management:

  • Targeted antibiotic therapy - penetration through abscess wall poor, typically needs surgical management
  • Hyperbaric oxygen therapy
  • Corticosteroids in complicated cases with pituitary insufficiency
  • Surgery - drainage and removal of any foreign material
• Abscess can causes necrosis/ischaemia of pituitary leading to pituitary insufficiency = Addisonian crisis