Patient handout

HSV Encephalitis (acute)

PRODUCTION

1. Your condition

This handout is for hsv encephalitis (acute). Your care team identified this based on: fever + altered mental status (acute febrile encephalopathy) → empiric hsv coverage until ruled out (idsa 2008 tunkel pmid 18582201).

Other reasons your team may use this plan: new focal neurological deficit (aphasia / hemiparesis / cranial nerve) with fever — temporal lobe hsv pattern; new-onset seizure with fever / encephalopathy — hsv temporal lobe seizure phenotype (~80% pleds on eeg); acute behavioural change / personality change / psychosis with fever (frontal-temporal involvement).

2. Your medications

Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.

Medication	Starting dose	How	When	What it does
acyclovir	10 mg/kg IV q8h (CrCl-adjusted; ideal body weight if obese) × 14-21 d; pediatric 60 mg/kg/day in 3 divided doses; neonatal HSV 20 mg/kg IV q8h × 21 d (CNS)	IV	q8h	Whitley NEJM 1986 PMID 16983610 — mortality 70% → 28% with acyclovir; time-to-acyclovir = single strongest predictor of outcome; IDSA 2008 PMID 18582201 — empiric for any suspected viral encephalitis; CrCl-based dose to prevent nephrotoxicity
NS 0.9% IV fluids	1.5× maintenance (typically 100-150 mL/h adult)	IV	continuous	Crystalline nephropathy prevention — acyclovir precipitates in renal tubules; aggressive IVF during infusion reduces risk; do NOT use LR (calcium-acyclovir interaction)
valacyclovir	1 g PO TID (when tolerating PO + clinical improvement; not standard for completing acute encephalitis course but used in step-down post-recovery)	PO	TID	NOT first-line acute — IV acyclovir standard for full course; valacyclovir oral may be considered for step-down or in mild disease in select cases (off-label for encephalitis maintenance)

Plan: HSV encephalitis acute Rx — empiric IV acyclovir within 6 h + AED + ICP + foscarnet for resistance + autoimmune overlap (IDSA 2008 Tunkel PMID 18582201; Whitley NEJM 1986 PMID 16983610)

3. When to call your provider

Contact your care team if any of the following happen:

New seizure → ED + EEG + imaging
Biphasic autoimmune relapse → ED + re-admit + autoimmune workup
New focal deficit → ED
Worsening cognitive function despite rehab → neuro-rehab + neuropsych + meds re-eval
Severe depression / suicidality → urgent psych

4. When to seek emergency care

Call 911 or go to the nearest emergency room right away if you have:

Adult with fever + AMS + focal deficit / seizure / new behavioural change — START EMPIRIC IV ACYCLOVIR 10 mg/kg q8h within 6 h; do NOT wait for CSF HSV PCR (IDSA 2008 PMID 18582201; Whitley NEJM 1986 PMID 16983610)(life-threatening)
HSV temporal lobe seizure phenotype — temporal lobe PLEDs on EEG (~80% HSV); status epilepticus complicates ~30%; aphasia / olfactory hallucinations / déjà vu common (Venkatesan IRCNS 2017 PMID 28528537)
Confirmed HSV-1/-2 PCR positive on CSF — complete 21 d IV acyclovir; verify renal + LFT throughout course (Steiner PMID 24839282)
Initial CSF HSV PCR negative + clinical / MRI suspicion → CONTINUE empiric acyclovir + REPEAT LP at day 3-7 (false negatives early <72 h or after recent acyclovir; Steiner PMID 24839282)
Post-HSV anti-NMDAR autoimmune encephalitis — biphasic course 1-6 wk after HSV recovery; psychiatric prodrome + new seizures + movement disorder + autonomic instability; up to 27% of HSV-encephalitis survivors (Armangué Lancet Neurol 2018 PMID 33099399; Graus 2016 PMID 30951513)
Neonatal HSV-2 perinatal (acquired during delivery from genital HSV-2) — disseminated / CNS / SEM (skin-eye-mouth) forms; high-dose acyclovir 20 mg/kg IV q8h × 21 d (CNS); suppressive oral acyclovir 300 mg/m² PO TID × 6 mo post-CNS (CDC + AAP)(life-threatening)
Immunocompromised (HIV / transplant / chemo / steroids) with HSV encephalitis — higher severity, atypical imaging, higher resistance risk (~5%); ID consult; consider foscarnet adjunct
Documented or strongly suspected acyclovir-resistant HSV (no clinical improvement by day 3-5 in immunocompromised; rare in immunocompetent) — thymidine kinase mutant; foscarnet first-line (Sili Antivir Res 2009 PMID 18587392)

5. Follow-up

Neuro-cognitive battery at 3 + 6 + 12 mo (temporal lobe involvement → memory + language + behaviour); seizure follow-up + long-term AED if cortical injury; psych follow-up (depression / behaviour change common); occupational + speech therapy; rehab; return precautions for autoimmune relapse symptoms (new behavioural change, dyskinesia, autonomic instability — re-eval for anti-NMDAR)

6. Sources

Guideline: 2008 IDSA Encephalitis Management Guidelines (Tunkel, Clin Infect Dis 2008;47:303-27) + 2013 International Encephalitis Consortium case definitions (Venkatesan, Clin Infect Dis 2013;57:1114-28) + 2016 Graus autoimmune-encephalitis clinical criteria (Lancet Neurol 2016;15:391-404) + Whitley vidarabine-vs-acyclovir HSE RCT (NEJM 1986;314:144-9) + Armangué post-HSV autoimmune-encephalitis prospective study (Lancet Neurol 2018;17:760-72) + Steiner EFNS viral-meningoencephalitis guideline (Eur J Neurol 2010;17:999-e57) + Lakeman & Whitley CSF-HSV-PCR NIAID CASG (J Infect Dis 1995;171:857-63)