Viral Encephalitis Treatment
Immediately initiate intravenous acyclovir 10 mg/kg every 8 hours in all patients with suspected viral encephalitis, even before diagnostic confirmation, as early treatment reduces mortality from 70% to 8-30%. 1, 2, 3
Immediate Empirical Treatment
- Start acyclovir within 6 hours of hospital admission for any patient presenting with altered consciousness, confusion, behavioral changes, new seizures, or focal neurological signs suggestive of encephalitis 2, 4
- Do not delay treatment while awaiting CSF PCR results or MRI findings, as treatment delay beyond 48 hours significantly worsens outcomes 2, 5
- The standard adult dose is 10 mg/kg intravenously every 8 hours for patients with normal renal function 1, 2
- For neonates, use higher-dose acyclovir at 20 mg/kg intravenously every 8 hours, which has reduced mortality to 5% with approximately 40% of survivors developing normally 1, 2
Treatment Duration and Monitoring
- Continue intravenous acyclovir for 14-21 days in confirmed HSV encephalitis 1, 2
- Repeat lumbar puncture at the end of therapy to confirm CSF is negative for HSV by PCR; if positive, continue antiviral therapy 1, 2
- Monitor renal function throughout treatment, as acyclovir-induced nephropathy affects up to 20% of patients, typically after 4 days of IV therapy 2, 5
- Ensure adequate hydration during acyclovir treatment to prevent crystalluria and obstructive nephropathy 2, 5
Dose Adjustments for Special Populations
- Reduce acyclovir dose in patients with pre-existing renal impairment (creatinine clearance <50 mL/min) to prevent nephrotoxicity 2, 3
- Geriatric patients require dose reduction due to age-related changes in renal function and higher plasma concentrations 3
- Immunocompromised patients may require longer courses of therapy (beyond 21 days) and closer monitoring 2, 4
Pathogen-Specific Treatment Considerations
Herpes Simplex Virus (HSV)
- Acyclovir is the definitive treatment of choice for HSV encephalitis, with mortality at 18 months of 25% compared to 59% with older therapies 1, 3
- Predictors of poor outcome include age >30 years, Glasgow coma score <6, and symptom duration >4 days before starting acyclovir 1, 2
- Relapse occurs in approximately 5-8% of cases, particularly when treated with lower doses or shorter durations 1
Varicella-Zoster Virus (VZV)
- Use intravenous acyclovir 10-15 mg/kg three times daily for VZV encephalitis 5, 4
- Consider adding corticosteroids if there is evidence of vasculopathy or stroke 5, 4
Cytomegalovirus (CMV)
- Use combination therapy with ganciclovir (5 mg/kg IV every 12 hours) and foscarnet (60 mg/kg IV every 8 hours or 90 mg/kg IV every 12 hours) for 3 weeks 1, 2, 5
- This combination has shown improvement or stabilization in 74% of patients with CMV encephalitis 1, 2
- Monotherapy with either agent alone has poor outcomes and high therapeutic failure rates 1
Epstein-Barr Virus (EBV)
- Acyclovir has limited benefit for EBV encephalitis and is not routinely recommended 2, 5, 4
- Consider corticosteroids in selected patients with EBV-associated neurologic complications 2
Critical Pitfalls to Avoid
- Delaying acyclovir beyond 48 hours after hospital admission is the single most important modifiable factor that worsens outcomes 2, 5
- Inadequate hydration during acyclovir treatment significantly increases nephropathy risk 2, 5
- Do not withhold empirical acyclovir while pursuing extensive diagnostic workup for alternative diagnoses 2, 5
- Do not stop acyclovir at 10-14 days; the full 14-21 day course is essential to prevent relapse 1, 6
Supportive Care Requirements
- Patients with decreased consciousness require evaluation in intensive care for airway protection, ventilator support, and intracranial pressure management 5, 4
- Monitor for seizures (occur in 38% of HSV encephalitis cases) and treat appropriately 7
- Arrange outpatient follow-up and access to rehabilitation services, as cognitive impairment, behavioral changes, and focal neurological deficits are common sequelae 4