What is the recommended treatment for a patient with suspected herpes encephalitis?

Treatment for Suspected Herpes Simplex Encephalitis

Intravenous aciclovir (10 mg/kg every 8 hours) should be started immediately upon suspicion of HSV encephalitis, ideally within 6 hours of admission, without waiting for confirmation of HSV by PCR. 1

Initial Management

• Start IV aciclovir if:

  • Initial CSF and/or imaging findings suggest viral encephalitis
  • Within 6 hours of admission if these results will not be available
  • The patient is very unwell or deteriorating 2, 1
  • Even if first CSF microscopy or imaging is normal but clinical suspicion remains 2

• Standard treatment duration:

  • 14-21 days for adults 1
  • Minimum 21 days for children aged 3 months-12 years (due to higher relapse rates up to 29%) 1

Dosing Considerations

• Adults and children >12 years: 10 mg/kg IV every 8 hours 1, 3

• Children 3 months-12 years: 500 mg/m² IV every 8 hours 1

• Neonates: 20 mg/kg IV every 8 hours 1

• Dose adjustment required in patients with pre-existing renal impairment 2, 1

  • Specific adjustments based on creatinine clearance
  • Reduced dose and extended interval for creatinine clearance <15 mL/min 1

Monitoring During Treatment

• Regular monitoring of renal function is essential:

  • Serum creatinine
  • Blood urea nitrogen (BUN)
  • Creatinine clearance 1

• Increased vigilance after 4 days of therapy when nephropathy risk increases 1

  • Aciclovir can cause crystalluria and obstructive nephropathy in up to 20% of patients receiving IV therapy 1

• Maintain adequate hydration to reduce risk of crystalluria 1

Treatment Evaluation

• Perform repeat lumbar puncture with HSV PCR testing at the end of treatment to confirm resolution of infection 1
• Watch for potential complications:
  • Acute: cerebral edema, status epilepticus 4
  • Chronic: autoimmune encephalitis associated with antibodies to the N-methyl-D-aspartate receptor 4

Important Clinical Considerations

• Poor outcomes are associated with:

  • Advanced age
  • Reduced consciousness (low Glasgow Coma Score)
  • Delays >48 hours between hospital admission and starting treatment 2, 1

• Early initiation of treatment significantly improves outcomes:

  • Reduces mortality from over 70% to less than 20-30% 2, 1
  • Mortality decreases to 8% if therapy starts within 4 days of symptom onset 1

• Relapse rates:

  • Approximately 5% in adults 1, 5
  • Up to 29% in children 1, 6

Common Pitfalls to Avoid

1. Delayed treatment: Do not wait for confirmatory tests before starting aciclovir if HSV encephalitis is suspected 2, 1

2. Inadequate treatment duration: A 10-day course may be insufficient; consider 14-21 days to prevent relapse 1, 5

3. Oral aciclovir substitution: Oral aciclovir does not achieve adequate CSF levels and should not be used for HSV encephalitis 1

4. Inadequate monitoring: Failure to monitor renal function can lead to nephrotoxicity 1

5. Premature treatment cessation: Completing the full course is essential to prevent relapse 1, 5