Aseptic Meningitis

Background

• Aseptic meningitis refers to a clinical syndrome of meningeal inflammation in which common bacterial causes cannot be identified.
• The vast majority of cases are caused by viral infections, with the leader being enteroviruses.
• Additional nonviral causes, by category, include:
  • parasites
  • bacteria that are not readily detected by Gram stain, routine culture, or routine diagnostics
  • fungi (most often in immunocompromised hosts)
  • autoimmune diseases
  • some medications, particularly nonsteroidal anti-inflammatory drugs (NSAIDs)
  • malignancy
• Parameningeal foci, such as brain abscess or epidural abscesses, and partially treated bacterial meningitis may also present similarly.

Evaluation

• Clinical presentation varies with pathogen and host immune status but prominent features include:
  • fever, headache, and photophobia.
  • neck stiffness.
  • nausea/vomiting, diarrhea, rash, or flu-like symptoms.
• Lumbar puncture for cerebrospinal fluid (CSF) analysis is used to confirm diagnosis.
  • Pleocytosis is nearly always present, with cell counts generally ranging from 100 to 1,000 cells/mm³.
  • Polymorphic predominance may be present early but shifts within days to lymphocytic predominance.
  • Increase in protein and decrease in glucose are typically mild, if present.
  • By definition, the Gram stain and culture are negative (though rare cases of concurrent viral/bacterial meningitis exist).
• Establishing an etiology is key to management as some causes will have specific therapy available.

Management

• Treatment is directed at underlying cause, if cause identified and treatment exists.
• Empiric antibiotics may be started initially if there is concern for partially treated bacterial meningitis, the presentation is unclear, or the patient immunocompromised.
• Antibiotics can be stopped in many cases if cerebrospinal fluid (CSF) analysis not consistent with bacterial or fungal infection and CSF and blood cultures are negative.
• When no cause or treatable cause is identified, care is typically supportive, including analgesia for pain, IV fluids, and electrolyte management.