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12.10.12 Meningitis

Sites

  • Leptomeninges
    • Acute meningitis
  • Parenchyma
    • Encephalitis
  • Venticles
    • Ventriculitis


Organisms (Big 3)
  • Meningococcus
    • Neisseria meningitides
      • B > C > A
    • Commonest in all ages except neonates
    • Treat with 3rd gen. cephalosporin (better than Ben Pen due to resistance)
  • HIB
    • Vaccine introduced 1992
    • Now less common
    • 70% of cases are in children <2
    • Chloramphenicol / 3rd gen cephalosporin
  • Pneumococcus
    • Strep. pneumoniae


Atypical organisms

  • Neonates (Little 3)
    • E. coli
    • GBS
    • L. monocytogenes
  • Aseptic
    • TB
    • Viruses
    • Fungal (esp. in immunosuppressed)


Presentation

  • Fever
  • Vomiting
  • Lethargy
  • Quiet; Little spontaneous movement
  • Petechial rash esp. on limbs
  • Neck stiffness
    • Move head quickly forwards + see if it flops onto chest
  • Joint/muscle pain
  • Photophobia
  • Headache
  • Bulging fontanelle


TB meningitis

  • Remember:
    • Maximise CSF tap
    • Do direct microscopy
    • Special culture
  • Treatment
    • Rif
    • Iso
    • Eth
    • Pyraz


Viral meningitis

  • Causes >50% of cases
  • Causes:
    • Echoviruses
    • Coxsackie A + B
    • Polio
    • Mumps
    • Lymphocytic choriomeningitis virus
    • HSV
  • Mostly untreatable
    • But use acyclovir for HSV


Cells

  • WCC
    • Bact: >5000
    • TB <1000
    • Normal: 3
  • Gram stains
    • Big 3
      • N. meningitidis
        • Gram -ve cocci
      • H. influenzae
        • Gram -ve rods
        • Some very short
      • Strep. pneumonia
        • Gram +ve cocci
    • Little 3
      • E. coli
        • Gram -ve rods
      • GBS
        • Gram +ve cocci, chains
      • L. monocytogenes
        • Gram +ve rods


Prophylaxis

  • Rifampicin for Meningococcal / HIB meningitis
    • Or ciprofloxacin in adults


Vaccines

  • NO vaccine against Meningococcus type B (most common strain)
    • Vaccines for A + B
  • Routine immunisation (2, 3, 4 months) for HIB


Other CNS infections

  • Viral encephilitis
    • Uncommon
    • Serious/fatal in some cases
    • Looks clinically like meningitis
    • Organisms:
      • HSV 1+2
      • Enteroviruses
      • Mumps
      • Measles
      • V. zoster
      • EBV
      • CMV
      • Adenovirus
      • Arboviruses
        • Arthropod-borne
      • Rabies
  • Post infectious syndromes
    • Demyelinating syndrome after viral infection
  • Cerebral abscess
    • Very mixed farmyard of bacteria
      • Gram +ves => Penicillins
        • Strep. milleri
        • Beta-haemolytic Strep
        • S. pneumoniae
        • S. aureus
      • Anaerobes => Metronidazole
        • Bacteroides
        • Fusobacterium
        • Veilonella
        • Anaerobic cocci
    • Treat surgically by drainage
  • Slow virus infections
  • Spongiform encephalopathies
  • CNS infections in AIDS


Notes

  • Prevalence greater in winter
  • One of the only illnesses where treatment precedes diagnosis
    • IV/IM Ben Pen
      • 1200 mg >10
      • 600 mg 1-9 yrs
      • 300 mg infants
  • DON'T do an LP if raised ICP!
    • => Coning
  • Xanthochromia in CSF
    • Old bleed
  • Gram -ve look pink
  • Must notify CDC




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