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Inflammation of the protective membranes (meninges) covering the brain and spinal cord.

  • Bacterial: streptococci; Neisseria; gram negative bacilli, staphylococci; Neisseria meningitides; Haemophilus influenzae; Listeria monocytogenes
  • Lyme (Borrelia burgdorferi)
  • Syphilis – spirochete (Treponema pallidum)
  • Viral: late summer and early fall: enterovirus; arboviruses, West Nile; also Herpes viruses, HIV, mumps, rabies
  • Mycobacterial (MTB and MAI)
  • Fungal: cryptococcal; Coccidioides immitis or Coccidioides posadasii, Cryptococcus neoformans, Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitides
  • Parasitic: Toxoplasma gondii, Taenia solium (cysticercosis)
  • Eosinophilic meningitis: Angiostrongylus cantonensis, baylisascariasis, and gnathostomiasis
  • Drugs: NSAIDs, antimicrobials (e.g., trimethoprim–sulfamethoxazole, amoxicillin, isoniazid), Muromonab-CD3 (Orthoclone OKT3), azathioprine, IVIG, intrathecal methotrexate, intrathecal cystine arabinoside, vaccines, allopurinol
  • Neoplastic: infiltration of the subarachnoid space by cancer cells; can be metastatic or from a primary brain tumor like medulloblastoma
  • Foreign bodies: CSF shunts, external ventriculostomy
  • Systemic illness: sarcoidosis, leptomeningeal cancer, post transplantation lymphoproliferative disorder, systemic lupus erythematosus, Wegener granulomatosis, CNS vasculitis, Behçet disease, Vogt–Koyanagi–Harada syndrome

  • Fever
  • Headache
  • Stiff neck
  • Photophobia
  • Nausea/vomiting
  • Altered mental status
  • Rash/purpura may be present, particularly in meningococcal meningitis
  • Seizures possible

Early recognition, rapid diagnosis, and urgent antimicrobial and adjunctive therapy are paramount; multidisciplinary treatment team should be involved: neurology, infectious diseases, etc.

  • Head CT to evaluate for mass lesion and evaluate signs of elevated intracranial pressure, especially in immunocompromised patients, history of CNS disease, papilledema, change in level of consciousness, focal neurologic deficits
  • SAH is part of the differential and should be excluded by CT
  • Emergent culture sampling – blood and CSF analysis; LP contraindicated if CT signs of elevated ICP, as it may precipitate herniation
  • Presumptive antibiotherapy; if imaging and CSF sampling delayed, presumptive antimicrobial therapy should be given immediately, recognizing this may diminish yield in culture sampling
    • Ceftriaxone 2 mg IV q12 hours or Cefotaxime 2 gm IV q6–8 hours
    • Vancomycin 1 gm IV q12 hours—in light of increasing resistance of streptococci to cephalosporin therapy
    • Ampicillin should be considered in young children, patients over 50, and immunocompromised patients to target Listeria monocytogenes
  • Dexamethasone (0.15 mg/kg q6 hours for 2–4 days, to be initiated before antibiotic therapy) if proven or suspected pneumococcal meningitis
  • Anti-epileptics if seizures are a presenting symptom
  • Anti-fungals: Amphotericin B and Flucytosine in combination
    • Amphotericin B liposomal (Ambisome) 6 mg/kg/day IV for 11–21 days
    • Flucytosine 50–150 mg/kg/day po divided q6 hours
  • Anti-virals: for herpes meningitis/encephalitis
    • Acyclovir 10 mg/kg IV q8 hours (using ideal body weight)
  • Anti-tubercular drugs:
    • Isoniazid 5 mg/kg po/IM daily
    • Rifampin 10 mg/kg po/IV daily
    • Pyrazinamide 20–25 mg/kg po daily
    • Addition of a fourth drug dependent on local resistance patterns
    • Rifater (combination of Isoniazid/Rifampin/pyrazinamide)—weight-based dosing

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CSF Characteristics According to Meningitis Etiology
Opening pressureIncreasedNormalVariableVariable
Glucose (CSF to plasma ratio)Normal to decreasedNormalDecreasedDecreased
ProteinMild to moderate increaseNormal to increasedIncreasedIncreased
Cell differential predominancePMNsLymphocytesLymphocytesLymphocytes
WBC count>1000 per mm...

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