What is the next step in managing a patient with suspected viral meningitis and a normal Complete Blood Count (CBC)?

Management of Suspected Viral Meningitis with Normal CBC

For a patient with suspected viral meningitis and a normal complete blood count (CBC), the next step should be to perform a lumbar puncture (LP) for cerebrospinal fluid (CSF) analysis to confirm the diagnosis and determine appropriate management. 1

Diagnostic Approach

• A normal CBC does not rule out viral meningitis, as viral infections typically do not cause significant changes in peripheral blood counts compared to bacterial infections 1, 2
• Lumbar puncture is essential for definitive diagnosis of viral meningitis and should be performed promptly 3, 1
• Before performing LP, consider whether the patient has any indications for CT scan prior to LP, including:
  • Immunocompromise
  • History of CNS disease
  • New-onset seizure
  • Papilledema
  • Altered consciousness
  • Focal neurologic deficit 3
• If any of these indications are present, obtain blood cultures and start empiric antimicrobial therapy before sending the patient for CT scan 3

CSF Analysis

• CSF findings in viral meningitis typically include:
  • Lymphocytic pleocytosis (though early viral meningitis may show neutrophil predominance)
  • Normal or mildly elevated protein
  • Normal glucose
  • Normal opening pressure 3, 1
• CSF PCR is the gold standard for confirmation of viral meningitis, testing for:
  • Enterovirus
  • HSV-1
  • HSV-2
  • VZV 1, 4
• CSF lactate levels <3.5 mmol/L support viral rather than bacterial etiology 2

Treatment Approach

• If CSF findings are consistent with viral meningitis:

  • Provide supportive care with analgesia (acetaminophen and NSAIDs) for headache 5, 1
  • Ensure adequate hydration with intravenous or oral fluids 5, 1
  • Discontinue antibiotics once viral diagnosis is confirmed 1
  • Expedite discharge from hospital once diagnosis is confirmed 1

• If CSF findings suggest bacterial meningitis or are equivocal:

  • Start empiric antimicrobial therapy immediately 3
  • For adults, use vancomycin plus either ceftriaxone or cefotaxime 5
  • Consider dexamethasone as adjunctive therapy 3, 5

Special Considerations

• If encephalitis is suspected (altered mental status, seizures, focal neurological deficits):

  • Start intravenous aciclovir (10 mg/kg three times daily) within 6 hours of admission 3, 6
  • Continue aciclovir while awaiting further diagnostic results 3

• For recurrent viral meningitis:

  • Most commonly caused by HSV-2 1
  • Prophylactic aciclovir/valaciclovir is NOT recommended based on clinical trial evidence 1

Follow-up Care

• Assess all patients for potential long-term sequelae before discharge 1
• Common sequelae include headaches (in up to one-third of patients), fatigue, sleep disorders, and emotional difficulties 5, 1
• Consider staged return to work or studies initially 1
• Offer follow-up care as many issues only become apparent after discharge 1

Common Pitfalls to Avoid

• Failing to distinguish between viral meningitis and encephalitis, which requires different management 5
• Delaying antimicrobial therapy while waiting for diagnostic confirmation if bacterial meningitis is suspected 3, 5
• Assuming all headaches in meningitis have the same etiology 5
• Missing altered consciousness, which suggests an alternative diagnosis such as bacterial meningitis or encephalitis 5