What is the initial management approach for a stable, conscious, and oriented patient suspected of having encephalitis?

Approach to Stable, Conscious, Oriented Patient with Suspected Encephalitis

Immediate Actions

Start intravenous aciclovir 10 mg/kg every 8 hours within 6 hours of admission, even if the patient appears stable and oriented, because delays beyond 48 hours significantly worsen outcomes in HSV encephalitis, reducing mortality from 70% to 20-30% with early treatment. 1, 2

Key Initial Steps

• Hospitalize immediately with access to specialized neurological care, as patients with suspected encephalitis are at risk of rapid deterioration, seizures, increased intracranial pressure, and death, even if initially stable 2

• Perform lumbar puncture as soon as possible after admission unless contraindicated by signs of increased intracranial pressure 2, 1

• Do not wait for CSF or imaging results to start aciclovir if there will be any delay, or if clinical suspicion remains high 1, 2

Empiric Aciclovir Treatment Protocol

Dosing

• Adults and adolescents ≥12 years: 10 mg/kg IV every 8 hours 1, 3
• Children 3 months to 12 years: 500 mg/m² (or 10-15 mg/kg) IV every 8 hours 1, 4
• Reduce dose in pre-existing renal impairment to prevent crystalluria and nephropathy 1, 3

When to Start

Aciclovir should be initiated if: 1, 2

• Initial CSF and/or imaging findings suggest viral encephalitis, OR
• Results will not be available within 6 hours, OR
• Clinical suspicion of HSV or VZV encephalitis remains high despite normal initial CSF microscopy or imaging

Critical caveat: Unlike meningococcal septicaemia where minutes matter, in a stable patient with only mild confusion, performing LP before treatment is pragmatic given the wide differential diagnosis 1. However, if there is strong clinical suspicion and potential delay in LP, or if the patient shows any signs of deterioration, start aciclovir immediately 1, 2.

Diagnostic Workup (Concurrent with Treatment)

Essential Investigations

• Lumbar puncture: Cell count, protein, glucose, HSV PCR, VZV PCR, enterovirus PCR 2, 1

  • CSF PCR results should be available within 24-48 hours 2
  • CSF remains PCR-positive for several days after starting aciclovir, so delayed LP can still confirm diagnosis 4

• Neuroimaging: MRI is preferred over CT; CT may be normal even in severe encephalitis 1, 2

  • Perform CT first if MRI unavailable or patient too unstable, then arrange MRI as soon as possible 1

• EEG monitoring: Essential to identify non-convulsive seizures in confused patients 4

Special Considerations

• For travelers from malaria-endemic areas: Perform rapid malaria antigen tests and three thick/thin blood smears; consider empiric antimalarial treatment if cerebral malaria likely and results delayed 2, 5

• If meningitis also suspected: Treat according to bacterial meningitis guidelines with appropriate antibiotics 1

When to Stop Aciclovir

Aciclovir can be stopped in immunocompetent patients if: 1

1. An alternative diagnosis has been made, OR

2. HSV PCR in CSF is negative on two occasions 24-48 hours apart AND MRI is not characteristic for HSV encephalitis, OR

3. HSV PCR in CSF is negative once >72 hours after neurological symptom onset with ALL of the following:

   • Unaltered consciousness
   • Normal MRI (performed >72 hours after symptom onset)
   • CSF white cell count <5 × 10⁶/L

Important pitfall: Do not stop aciclovir based on a single negative CSF PCR if taken <72 hours after symptom onset, as early samples can be falsely negative 1

Duration of Treatment for Confirmed Cases

• HSV encephalitis: Continue IV aciclovir for 14-21 days 1

  • Perform repeat LP at completion to confirm CSF is HSV PCR-negative 1
  • If CSF remains positive, continue aciclovir with weekly PCR monitoring until negative 1
  • Children aged 3 months-12 years may have relapse rates up to 29% and should receive minimum 21 days 1

• VZV encephalitis: 10-15 mg/kg three times daily for up to 14 days 4

  • Add corticosteroids (e.g., prednisolone 60-80 mg daily for 3-5 days) if vasculopathy or stroke-like presentation present 4

Care Environment and Monitoring

• Appropriate care settings: Neurology services, intensive care units, or intermediate care units 2

• Transfer to specialized neurology center within 24 hours if diagnosis not rapidly established or patient fails to improve 2, 4

• Multidisciplinary involvement required: Neurology, infectious disease, virology, neurophysiology, neuroradiology, intensive care 2, 4

• Monitor for complications: Seizures, increased intracranial pressure, aspiration, electrolyte disturbances, renal function (aciclovir can cause crystalluria in up to 20% after 4 days) 2, 4

Common Pitfalls to Avoid

1. Delaying aciclovir while awaiting confirmatory tests - HSV encephalitis outcomes worsen significantly with delays >48 hours 1

2. Stopping aciclovir too early based on single negative PCR - Repeat CSF examination at 24-48 hours if clinical suspicion remains 1

3. Relying on CT scan alone - CT may be normal in severe encephalitis; arrange MRI as soon as possible 1

4. Using routine corticosteroids in HSV encephalitis - Do not use routinely while awaiting RCT results; exception is VZV vasculopathy 1, 4

5. Discharging without definitive diagnosis - All patients require confirmed or suspected diagnosis before discharge, with outpatient follow-up and rehabilitation assessment arranged 2

Notification Requirements

• Report to Consultant in Communicable Disease Control for all patients with suspected infectious encephalitis 1