What is the treatment for encephalitis?

Treatment of Encephalitis

Intravenous acyclovir should be initiated immediately in all patients with suspected encephalitis at a dose of 10 mg/kg every 8 hours for adults and children with normal renal function (20 mg/kg every 8 hours for neonates) for 14-21 days. 1, 2

Initial Management

• Start acyclovir within 6 hours of admission if encephalitis is suspected, even while awaiting diagnostic test results, as early treatment significantly reduces mortality from 70% to 8-30% 1
• For adults and children with normal renal function, administer acyclovir 10 mg/kg intravenously every 8 hours 1
• For neonates, use higher-dose acyclovir at 20 mg/kg intravenously every 8 hours, which has reduced mortality to 5% 1, 2
• Reduce acyclovir dose in patients with pre-existing renal impairment to prevent crystalluria and obstructive nephropathy 1
• If bacterial meningitis is also suspected, add appropriate antibiotics according to meningitis guidelines 1

Treatment Duration and Monitoring

• Continue intravenous acyclovir for 14-21 days in confirmed HSV encephalitis 1, 2
• Consider repeating lumbar puncture at the end of treatment to confirm CSF is negative for HSV by PCR 1
• If CSF remains positive for HSV by PCR after treatment course, continue acyclovir with weekly PCR testing until negative 1
• Monitor renal function throughout treatment, as acyclovir-induced nephropathy can affect up to 20% of patients, typically after 4 days of IV therapy 1

Pathogen-Specific Treatment

Herpes Simplex Virus (HSV)

• Acyclovir is the treatment of choice for HSV encephalitis 1, 3
• Predictors of poor outcome include age >30 years, Glasgow coma score <6, and treatment delay >4 days after symptom onset 1, 2
• Relapse can occur in up to 5% of cases after completion of therapy, especially with shorter treatment courses 1, 4

Cytomegalovirus (CMV)

• For CMV encephalitis, use combination therapy with ganciclovir (5 mg/kg IV every 12h) and foscarnet (60 mg/kg IV every 8h or 90 mg/kg IV every 12h) for 3 weeks 1
• This combination has shown improvement or stabilization in 74% of patients with CMV encephalitis 1

Epstein-Barr Virus (EBV)

• Acyclovir has limited benefit for EBV encephalitis and is not recommended 1
• Corticosteroids may be beneficial in selected patients with EBV-associated neurologic complications 1

Special Considerations

• In resource-limited settings where IV acyclovir is unavailable, oral valacyclovir at 1,000 mg three times daily may achieve adequate CSF concentrations 5
• Patient weight may influence treatment outcome; a recent study suggests that low-weight patients (<79 kg) should receive a minimum acyclovir dosage of 2,550 mg/day (850 mg every 8h) when possible 6
• Immunocompromised patients may require longer courses of therapy and closer monitoring 2

Common Pitfalls to Avoid

• Delaying acyclovir treatment beyond 48 hours after hospital admission significantly worsens outcomes 1, 2
• Premature discontinuation of acyclovir therapy (before 14 days) increases risk of relapse 4
• Empirical use of antimicrobials without thorough diagnostic workup can lead to missed alternative diagnoses 1
• Inadequate hydration during acyclovir treatment increases risk of nephropathy 1