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Brain abscess

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Aetiology

  • direct entry across bone or dura or haematogenous spread
  • predisposing illnesses and infections:
    • chronic ear or sphenoidal sinus disease (associated with temporal and cerebellar abscesses)
    • paranasal sinus and dental infections (associated with frontal lobe abscesses)
    • suppurative lung disease
    • congenital heart disease
    • cranial trauma
  • organisms depend on aetiology: Staph aureus common in trauma, Streptococci, Bacteroides and gram negatives common in lung disease

Clinical features

  • severe headache
  • vomiting
  • obtundation
  • seizures
  • focal neurological signs
  • neck stiffness often absent

Diagnosis

Depends on:

  • primary source of infection
  • evidence of ­ ICP
  • focal cerebral or cerebellar signs
  • CT/MRI demonstration of abscess (appear as ring enhancing lesions)

NB LP is dangerous and not helpful

Treatment

  • Surgical drainage treatment of choice for most brain abscesses
    • less commonly excision
      • for peripherally placed abscesses which fail to respond to aspiration
    • principles:
      • reduce intracranial pressure by reducing volume of abscess
      • confirm diagnosis and obtain pus for microbiological diagnosis
      • enhance efficacy of antibiotic treatment
      • avoid iatrogenic spread of infection into ventricles
  • Non-surgical management for:
    • neurologically intact patients who are unable to undergo necessary procedure and in whom pathogens can be identified from other specimens, particularly if the abscesses are small

Antibiotics

Penetration

  • penetration of antibotics into brain tissue and intracranial pus differs from penetration into CSF
  • penicillin, ampicillin, cefuroxime, chloramphenicol, co-trimoxazole, ceftazidime and metronidazole have been shown to achieve therapeutic concentrations in intracranial pus

Empirical antibiotics

Infective source Antimicrobial regime
Paranasal sinuses Metronidazole plus cefuroxime or non-Pseudomonal 3rd generation cephalosporin
Teeth Metronidazole plus cefuroxime
Middle ear or sphenoid sinus Ampicillin, metronidazole and either ceftazidime or gentamicin
Penetrating trauma Flucloxacillin or cefuroxime or non-Pseudomonal 3rd generation cephalosporin
Endocarditis or cyanotic congenital heart disease Benzylpenicillin
Other haematogenous spread or cryptogenic Cefuroxime or non-Pseudomonal 3rd generation cephalosporin ± metronidazole

Drug doses

Drug Dose
Ampicillin 2-3g 8 hourly
Benzylpenicillin 1.8-2.4 g 6 hourly
Cefotaxime 2g 6 hourly
Ceftriaxone 3-4 g daily
Cefuroxime 1.5 g 8 hourly
Flucloxacillin 2-3 g 6 hourly
Gentamicin 5 mg/kg daily
Metronidazole 500 mg 8 hourly

Duration of therapy (parenteral)

  • 3-4 weeks if abscess has been excised
  • 4-6 weeks if abscess has been aspirated
  • minimum of 4 weeks if abscess treated with antibiotics alone
    • demonstrate resolution of ring enhancing lesions on CT before stopping antibiotics
  • may be reasonable to switch to oral therapy once C-reactive protein concentration has started to fall, systemic signs of sepsis have resolved and the patient is able to tolerate enteral feeding

Complications

Intraventricular rupture

  • >80% mortality
  • indication for open craniotomy, aggressive debridement of abscess cavity and lavage of ventricular system with saline containing vancomycin and/or gentamicin in concentration of 10mg/l

Prognosis

  • morbidity high
  • mortality 10-20% in most studies

Further reading

The rational use of antibiotics in the treatment of brain abscess. Report by the "Infection in Neurosurgery" working party of the British Society for Antimicrobial Chemotherapy. Br J Neurosurg, 2000; 14(6):525-530


© Charles Gomersall December 1999, March 2005


©Charles Gomersall, February, 2015 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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