Urgent Workup and Initial Management for Suspected Encephalitis in a 46-Year-Old Woman
Start intravenous aciclovir 10 mg/kg every 8 hours immediately—within 6 hours of presentation—while simultaneously pursuing diagnostic workup, as delays beyond 48 hours significantly worsen outcomes in HSV encephalitis. 1
Immediate Actions (Within 6 Hours)
1. Start Empirical Antiviral Therapy
- Aciclovir 10 mg/kg IV every 8 hours (adjust for renal impairment if present) 1
- Do NOT wait for CSF or imaging results if there will be any delay
- HSV encephalitis reduces mortality from >70% to 20-30% with aciclovir, but outcome worsens dramatically with treatment delays beyond 48 hours 1
2. Urgent Diagnostic Workup
Lumbar Puncture (if no contraindications):
- Perform immediately unless signs of increased intracranial pressure or focal mass lesion suspected
- CSF studies:
Neuroimaging:
- MRI brain with contrast (preferred over CT)
- Look for temporal lobe involvement characteristic of HSV encephalitis
- Can be performed before or after LP, but don't delay aciclovir if imaging takes time 1
Blood Tests:
- Complete blood count
- Comprehensive metabolic panel (baseline renal function critical for aciclovir dosing)
- Blood cultures
- Serum autoantibody panel (NMDAR, LGI1, CASPR2, etc.) 3
- HIV testing
3. Address the Eye Pain
The acute right eye pain requires immediate ophthalmology consultation to evaluate for:
- HSV keratitis/uveitis
- Acute retinal necrosis (can occur with HSV encephalitis) 4
- Optic neuritis (can occur with autoimmune encephalitis) 5
Do not delay systemic aciclovir while awaiting ophthalmology evaluation.
Critical Management Principles
When to Continue Aciclovir
Continue empirical aciclovir unless ALL of the following are met 1:
- CSF HSV PCR negative on two occasions 24-48 hours apart, AND
- MRI not characteristic for HSV encephalitis, AND
- Patient has normal consciousness, AND
- CSF white cell count <5 cells/mm³
Important caveat: A single negative HSV PCR does NOT rule out HSV encephalitis, especially if obtained <72 hours after symptom onset. The CSF can remain PCR-positive for 7-10 days after starting aciclovir, so delayed LP can still confirm diagnosis. 1, 2
Duration of Treatment if HSV Confirmed
- 14-21 days of IV aciclovir (not the original 10-day regimen) 1
- Repeat LP at 14-21 days to confirm CSF HSV PCR negativity 1
- If still positive, continue IV aciclovir with weekly PCR until negative 1
Hydration and Monitoring
- Maintain adequate hydration to prevent aciclovir-induced crystalluria and nephropathy (occurs in up to 20% of patients after 4+ days) 1
- Monitor renal function closely
- Reduce dose in pre-existing renal impairment 1
If Autoimmune Encephalitis Suspected
If infectious workup is negative and autoimmune encephalitis is suspected:
- Start high-dose IV methylprednisolone (1g daily for 3-5 days) once infection ruled out 3
- Consider IVIG or plasma exchange if no improvement
- Do NOT use corticosteroids routinely in HSV encephalitis—evidence is insufficient and may worsen viral replication 1
Common Pitfalls to Avoid
- Stopping aciclovir based on single negative HSV PCR—repeat in 24-48 hours if clinical suspicion remains high
- Delaying aciclovir while awaiting test results—mortality and morbidity increase significantly with delays
- Using only 10 days of treatment—relapse rates are unacceptably high; use 14-21 days minimum
- Starting steroids empirically—can worsen HSV encephalitis; only use after infection definitively ruled out
- Ignoring the eye symptoms—HSV can cause sight-threatening ocular complications requiring specific treatment
Notification
Report suspected encephalitis to public health authorities (Consultant in Communicable Disease Control) 1