Brain abscess

From WikiCNS

Microorganisms introduced into cerebral tissues as a result of trauma, contiguous infection or hematogenous dissemination

1. definitive cause elusive in up to 1/3 of patients
2. common sources sinus infection, mastoid or middle ear infection, periodontal abscess, hematogenous (septic emboli)
   1. hematogenous spread from skin pustules, pulmonary infections, acute diverticulitis, osteomyelitis, dental abscess and infective bacterial endocarditis
   2. right to left heart shunt predisposes to brain abscess with tetralogy of Fallot responsible in 50% of theses cases; long-standing hyoxemia associated with right to left shunt results in polycythemia and increased blood viscosity which then leads to areas of microinfarction in the brain
3. in many series, anaerobic organisms are now the most common cause of brain abscess
   1. most commonly bacteroides and peptostreptococcus
4. in other series aerobic organisms are still more common
   1. most commonly staphylococcus, streptococcus (most common), enterobacteriacae, and haemophilus
   2. most common fungal organism causing brain abscess is aspergillus
5. in infants proteus and citrobacter (Gram neg.) are almost the exclusive causes because IgM does not cross the placenta
6. in children
   1. 0-2 years: GBS, E.Coli, Citrobacter (meningitic spread)
   2. 3-5 years: H.flu, S. pneumo, bacteroides fragilis (otogenic spread)
   3. 5-15 years: staph, S. pneumo, H.flu (sinus spread)
   4. cyanotic heart disease: strep, staph aureus
7. laboratory results are not helpful
8. most common symptom (90%) is headache; just over 50% have fever
9. if abscess is > 3 cm then surgical drainage is indicated; mortality rate from cerebral abscess is 25%
10. patients should be started on triple antibiotic therapy of vancomycin, cefotaxime and metronidazole and adjusted pending culture
    1. antibiotics should be continued 6-8 weeks
11. seizures occur in 50% of patients post-operatively so patients need to be on anticonvulsants for 1-2 years