Description

Inflammation of the membranes of the brain or spinal cord, usually caused by viruses or bacteria and, rarely, fungi or parasites

Epidemiology

• Bacterial meningitis
  • Most common agents in children of all ages include Streptococcus pneumoniae and Neisseria meningitidis.
  • Underlying host factors, age, exposure, and geographic location alter incidence and pathogen.
• Viral meningitis
  • Most common agent in all age groups
  • Most common isolated virus are enteroviruses that tend to occur in outbreaks in summer and early fall.
• Fungal meningitis
  • Cryptococcus neoformans is a budding encapsulated yeast-like organism found in soil and avian excreta; associated with immunocompromised patients (especially AIDS), rare cases in healthy children
  • Candida species occurs in immunocompromised patients and ill premature infants.
• Tuberculous meningitis
  • Mycobacterium tuberculosis (TB) meningitis occurs in 0.5% of untreated primary TB infections.
  • Most common in children aged 6 months to 4 years
  • In ∼50% of cases, miliary TB is accompanied by meningitis.

General Prevention

• Haemophilus influenzae type b (Hib) vaccine has significantly reduced the incidence of meningitis and other invasive Hib infections by up to 99%.
• 13-valent S. pneumoniae protein conjugate vaccine (PCV13) for use in all infants given at 2, 4, 6, and 12–15 months of age
• A tetravalent meningococcal vaccine (MCV4) is recommended for all patients ≥11 years of age and select at-risk populations <11 years. A booster dose is recommended for all patients who receive the first dose of the vaccine between 11 and 15 years of age.

Etiology

• Bacterial
  • Cause differs depending on age:
    • <1 month old: group B Streptococcus, gram-negative pathogens (Escherichia coli, Citrobacter koseri, Cronobacter sakazakii, Serratia marcescens, and Salmonella species), Listeria monocytogenes, S. pneumoniae
    • 1–3 months old: group B Streptococcus, E. coli, S. pneumoniae, Hib
    • 3 months to 5 years old: S. pneumoniae, N. meningitidis, Hib
    • >5 years old: S. pneumoniae, N. meningitidis
    • Consider Hib in unvaccinated patients of any age.
• Viral
  • Herpes simplex virus (HSV) in the neonatal population
  • Enteroviruses: ∼70 different strains that include polioviruses, coxsackie A, coxsackie B, and echoviruses. Recently discovered enteroviruses are not placed in these 4 groups but are numbered (e.g., enterovirus 68).
  • Other, less common: arboviruses (e.g., West Nile virus), mumps
• Fungal
  • Fungi most commonly isolated include Candida species, Coccidioides immitis, Cryptococcus neoformans, and Aspergillus species.
• Aseptic meningitis
  • Agents not easily cultured in the viral or microbiology laboratory can cause meningitis and include Borrelia burgdorferi (Lyme disease) and Treponema pallidum (syphilis).
• Tuberculous meningitis
• Unusual pathogens more likely in immunocompromised patients