In a pediatric patient with recent viral upper respiratory tract infection presenting with fever, headache, neck stiffness, and cerebrospinal fluid pleocytosis with 82% lymphocytes, what is the most appropriate initial management: corticosteroids or intravenous acyclovir?

Acyclovir is the Most Appropriate Management

In a pediatric patient presenting with fever, headache, neck stiffness, and CSF showing lymphocytic pleocytosis (82% lymphocytes) following a recent viral URTI, intravenous acyclovir should be initiated immediately—not corticosteroids. This clinical picture is consistent with viral encephalitis, and HSV encephalitis must be presumed and treated empirically until proven otherwise, given its high mortality and morbidity without treatment.

Why Acyclovir Over Corticosteroids

Acyclovir: Evidence-Based First-Line Treatment

The British Paediatric guidelines 1 and IDSA guidelines 2 are unequivocal: children with suspected viral encephalitis should have intravenous acyclovir started within 6 hours of admission when CSF findings suggest viral encephalitis. The CSF profile you describe—elevated WBC with 82% lymphocytes—is classic for viral meningitis/encephalitis and mandates empirical acyclovir therapy.

Key evidence supporting acyclovir:

• Randomized trials demonstrated acyclovir reduces mortality in HSV encephalitis from 70% to 20-30% 1
• Delays beyond 48 hours from hospital admission significantly worsen outcomes 2, 1
• Even if HSV PCR eventually returns negative, early treatment is critical because PCR can be falsely negative if obtained <72 hours after symptom onset 1

Corticosteroids: Not Recommended

Corticosteroids should NOT be used routinely in pediatric viral encephalitis 1. The evidence is clear:

• Only one non-randomized, retrospective study in adults suggested possible benefit, but these results require confirmation before recommendation 2
• British guidelines explicitly state: "corticosteroids should not be used routinely in patients with HSV encephalitis" and note that "data establishing this are needed" 1
• A randomized controlled trial was awaited at the time of guideline publication, but routine use remains unsupported

Practical Management Algorithm

Immediate Actions (Within 6 Hours):

1. Start IV acyclovir empirically 1:

   • Dose for 3 months-12 years: 500 mg/m² every 8 hours
   • Dose for >12 years: 10 mg/kg every 8 hours
   • Adjust dose if renal impairment present 1

2. Ensure adequate hydration to prevent acyclovir-induced nephropathy (occurs in up to 20% of patients) 1

3. Monitor renal function closely during therapy 1

Duration of Treatment:

• Continue acyclovir for 14-21 days if HSV encephalitis is confirmed 1
• For children 3 months-12 years: minimum 21 days due to relapse rates as high as 26-29% with shorter courses 1
• Consider repeat LP at 14-21 days to confirm CSF HSV PCR negativity 1

When to Stop Acyclovir:

Acyclovir can be discontinued if 1:

• Alternative diagnosis is confirmed, OR
• HSV PCR negative on two occasions 24-48 hours apart AND MRI (>72 hours post-symptom onset) not characteristic for HSV, OR
• Single negative HSV PCR >72 hours after symptom onset WITH normal consciousness, normal MRI, AND CSF WBC <5 cells/mm³

Critical Pitfalls to Avoid

1. Don't wait for HSV PCR results before starting acyclovir—early treatment (within 4 days of symptom onset) reduces mortality from 28% to 8% 2

2. Don't stop acyclovir based on a single early negative PCR—PCR can be falsely negative if obtained <72 hours after symptom onset 1

3. Don't use corticosteroids routinely—they are not evidence-based and may mask inadequate response or evolving complications 1

4. Don't forget bacterial coverage initially—if meningitis cannot be excluded, treat according to bacterial meningitis guidelines until bacterial causes are ruled out 1

The Clinical Context

While this patient's recent viral URTI might suggest a post-viral aseptic meningitis (which could be self-limited), the presence of CNS symptoms beyond just meningismus (headache, fever, neck stiffness) suggests encephalitis rather than simple meningitis. HSV encephalitis is the most common identifiable cause of viral encephalitis in industrialized countries 1 and carries devastating consequences without treatment—mortality remains 28% at 18 months even with acyclovir 2.

The risk-benefit calculation strongly favors acyclovir: it's relatively safe (main risk is reversible nephropathy with adequate hydration), while untreated HSV encephalitis is catastrophic. Corticosteroids, conversely, lack evidence of benefit and carry risks including immunosuppression, secondary infection, and potential masking of treatment failure 1, 3.

Answer: B) Acyclovir