Treatment of Acute Encephalopathy
Start intravenous aciclovir 10 mg/kg every 8 hours immediately when viral encephalitis is suspected, while simultaneously pursuing diagnostic workup to identify the underlying cause. This empiric antiviral therapy should begin within 6 hours of admission, as delays beyond 48 hours significantly worsen outcomes in HSV encephalitis 1.
Initial Management Algorithm
Immediate Actions (First 6 Hours)
Stabilization comes first:
- Secure airway and provide ventilatory support if Glasgow Coma Scale ≤8 or rapidly declining consciousness 1
- Manage raised intracranial pressure and optimize cerebral perfusion pressure
- Correct electrolyte imbalances, particularly hyponatremia 1
- Transfer to ICU or high-dependency unit for close monitoring 1
Start empiric aciclovir immediately if:
- Altered consciousness with fever
- New-onset seizures
- Focal neurological signs
- CSF or imaging findings suggest viral encephalitis 1
Do NOT delay aciclovir for lumbar puncture if:
- Patient is severely ill or rapidly deteriorating
- There will be delays in performing LP
- Strong clinical suspicion exists 2, 1
Diagnostic Workup (Parallel to Treatment)
Lumbar puncture is essential unless contraindicated by:
- Signs of raised intracranial pressure
- Focal mass lesion on imaging
- Coagulopathy 1
Send CSF for:
- HSV PCR (remains positive 7-10 days after starting aciclovir) 2
- Cell count, protein, glucose
- Bacterial culture
- VZV, enterovirus PCR
- Oligoclonal bands 3
Neuroimaging priority:
- MRI brain within 48 hours (90% sensitive for HSV encephalitis) 1
- CT acceptable if MRI unavailable, but less sensitive (only 25% show early changes) 1
- Look for temporal lobe involvement, gyral edema, hemorrhage 1
EEG indicated for:
- Suspected non-convulsive status epilepticus (occurs in 8% of comatose patients) 1
- Distinguishing organic from psychiatric causes 1
- Detecting subtle motor seizures 1
Etiology-Specific Treatment
Viral Encephalitis (Most Common)
HSV Encephalitis:
- Continue aciclovir 10 mg/kg IV every 8 hours for 14-21 days minimum 1
- Repeat LP at 14-21 days to confirm CSF HSV PCR negativity 1
- If CSF remains positive, continue aciclovir with weekly PCR until negative 1
- In children 3 months-12 years, give minimum 21 days before repeat LP 2
- Reduce dose in renal impairment (monitor creatinine; aciclovir causes crystalluria in up to 20% of patients) 2, 1
Dosing specifics:
- Children 3 months-12 years: 500 mg/m² every 8 hours 2
- Children >12 years and adults: 10 mg/kg every 8 hours 2, 1
VZV Encephalitis:
- Aciclovir 10 mg/kg IV every 8 hours for up to 14 days 1
- Consider 15 mg/kg every 8 hours if renal function normal (VZV less sensitive than HSV) 1
- Add corticosteroids (prednisolone 60-80 mg daily for 3-5 days) due to inflammatory component 1
- Prolonged courses needed in immunocompromised patients 1
Enterovirus Encephalitis:
- No specific antiviral treatment recommended 1
- Pleconaril may be considered in severe cases if available (not widely accessible) 1
- IVIG may be useful in severe enterovirus 71 infection 1
Autoimmune Encephalitis
Once infection ruled out by CSF analysis:
First-line therapy (start immediately):
- High-dose IV methylprednisolone (preferred) 3
- OR IVIG if steroids contraindicated 3
- OR plasma exchange (PLEX) if steroids contraindicated 3
Contraindications to steroids:
- Uncontrolled hypertension
- Uncontrolled diabetes
- Active peptic ulcer
- Severe behavioral symptoms that worsen with steroids 3
Choose IVIG first if:
- Agitated patients
- Bleeding disorders 3
Choose PLEX first if:
- Severe hyponatremia
- High thromboembolic risk (cancer, smoking, hypertension, diabetes)
- Associated demyelination 3
For severe presentations (NMDAR encephalitis, new-onset refractory status epilepticus, severe dysautonomia):
- Start combination therapy (steroids + IVIG or steroids + PLEX) from the beginning rather than sequentially 3
If no improvement after first-line therapy:
- Add IVIG or PLEX (whichever not used initially) 3
- If still no improvement 2-4 weeks after combined therapy, start rituximab 3
- Consider experimental therapies (IL-6 inhibitors, bortezomib) for refractory cases 3
Acute Disseminated Encephalomyelitis (ADEM)
High-dose corticosteroids are first-line 4
Alternatives:
Metabolic/Inherited Causes
If suspected inherited metabolic disease:
- Obtain specimens before treatment when possible
- Proceed with disease-specific treatment in parallel with testing 5
- Common causes include urea cycle disorders, organic acidemias, fatty acid oxidation defects, mitochondrial diseases 5
Critical Pitfalls to Avoid
Do not withhold aciclovir waiting for confirmatory testing - HSV encephalitis has 70% mortality without treatment vs. 20-30% with aciclovir 1. The risk-benefit strongly favors empiric treatment.
Do not use presumptive aciclovir for all encephalopathy without clinical suspicion - this is not beneficial and delays identification of other treatable causes 2, 1. However, if there is ANY reasonable suspicion of viral encephalitis, start aciclovir.
Do not stop aciclovir at 10 days - relapse rates are 26-29% in children with courses <14 days 2. Use 14-21 days minimum with repeat LP to confirm viral clearance 1.
Monitor renal function closely - aciclovir causes reversible nephropathy in up to 20% of patients, typically after 4 days of therapy 2, 1. Maintain adequate hydration and adjust dosing for renal impairment.
Do not assume septic encephalopathy without excluding CNS infection - septic encephalopathy is a diagnosis of exclusion found in 50-70% of septic patients, but requires ruling out primary CNS infection first 1.
Do not miss non-convulsive status epilepticus - occurs in 8% of comatose patients with no clinical seizure activity 1. EEG is essential for diagnosis.
Monitoring and Supportive Care
Neurological specialist review within 24 hours of referral 1
Access to:
Transfer to neuroscience unit if:
- Diagnosis not rapidly established
- Patient fails to improve with therapy
- Transfer should occur within 24 hours of request 1
Notify public health authorities - encephalitis due to infection is notifiable 2, 1