Treatment of Suspected Viral Meningitis with HSV Features
The most appropriate treatment is D. Intravenous Acyclovir, as this patient's CSF profile with lymphocytic predominance, elevated protein, and low glucose is consistent with HSV meningitis, which requires empiric acyclovir therapy despite the lack of definitive evidence for its efficacy in HSV meningitis (as opposed to HSV encephalitis where benefit is proven). 1
Critical Diagnostic Distinction
The CSF findings presented create diagnostic ambiguity that must be addressed immediately:
- Low CSF glucose (5 mmol/L, approximately 90 mg/dL) is atypical for typical viral meningitis but can occur with HSV-2 meningitis, mumps, and lymphocytic choriomeningitis virus 2
- Elevated protein (700 mg/L) with lymphocytic predominance is consistent with viral meningitis, particularly HSV 1, 3
- This combination specifically suggests HSV-2 meningitis, which characteristically presents with lymphocytic pleocytosis, mildly elevated protein, and normal glucose—though glucose can occasionally be reduced 1
Treatment Algorithm
Immediate Management
Start intravenous acyclovir 10 mg/kg every 8 hours immediately while awaiting confirmatory HSV PCR from CSF 1, 4:
- This dosing applies to patients >12 years of age 1
- For children 3 months-12 years: 500 mg/m² every 8 hours 1
- Dose adjustment required in renal impairment (acyclovir is renally excreted) 5
Duration of Therapy
The treatment duration depends on distinguishing meningitis from encephalitis:
- For HSV meningitis: Acyclovir 10 mg/kg IV every 8 hours until resolution of fever and headache, followed by valacyclovir 1g three times daily to complete a 14-day course 1
- For HSV encephalitis (if any signs of altered mental status, personality changes, or focal neurologic findings): 14-21 days of IV acyclovir 1
Critical Pitfalls and Caveats
The Evidence Paradox
There is a significant evidence gap regarding HSV meningitis treatment:
- The British Infection Association states there is no evidence supporting acyclovir or valacyclovir for HSV meningitis and recommends supportive care only 1, 6
- However, the CDC (2022) recommends acyclovir for HSV-2 meningitis despite acknowledging that "optimal therapies have not been studied" 1
- This discrepancy reflects geographic practice variation, with UK guidelines more conservative and US guidelines more interventional [1 vs 1]
Why Treat Despite Lack of Evidence?
In clinical practice, empiric acyclovir is justified because:
- The risk-benefit ratio favors treatment: HSV meningitis can progress to encephalitis (mortality 70% untreated, reduced to 20-30% with acyclovir) 1
- Low glucose in this case raises concern for more severe disease or potential progression 2
- Acyclovir is relatively safe with main risk being reversible nephropathy (affects up to 20% after 4 days), preventable with adequate hydration 1
- CSF PCR remains positive for 7-10 days even after starting acyclovir, so diagnostic yield is preserved 1
Monitoring Requirements
- Monitor renal function closely during IV acyclovir therapy 1, 5
- Maintain adequate hydration to prevent crystalluria and obstructive nephropathy 1
- Reassess for encephalitis features (personality changes, behavioral changes, altered consciousness) which would mandate full 14-21 day IV course 1
Why Other Options Are Incorrect
A. Ceftriaxone and Vancomycin: These treat bacterial meningitis, but the lymphocytic predominance makes bacterial etiology unlikely; however, antibiotics should be continued until bacterial cultures are negative 1, 6
B. Methylprednisolone: Steroids have no role in viral meningitis treatment and are only indicated for bacterial meningitis (particularly pneumococcal) 1
C. Antifungal therapy: Fungal meningitis typically presents with more profound hypoglycorrhachia and occurs primarily in immunocompromised hosts 1
Special Consideration: Recurrent HSV-2 Meningitis
If this patient develops recurrent episodes: