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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 |
