Synopsis
Recognise encephalitis from altered cognition, focal seizure and behavioural change, start intravenous aciclovir before confirmation, use MRI, EEG and repeat cerebrospinal-fluid PCR correctly, and prevent renal and neurological treatment harm.
- Encephalitis means brain dysfunction with evidence of inflammation; meningism can coexist but altered cognition and focal features are decisive.
- HSV-1 is the most important treatable sporadic cause in adults, often affecting temporal lobes and producing memory, language, behaviour or seizure symptoms.
- Start aciclovir 10 mg/kg intravenously every 8 hours immediately, using protocol weight, hydration and renal adjustment.
Key red flags
New focal seizure, temporal-lobe symptom or personality change with fever is HSV encephalitis until urgently assessed.
Fever, memory failure, dysphasia, personality change, olfactory symptoms or focal seizure strongly supports HSV encephalitis.
Investigation priorities
Detect HSV, VZV and selected viruses while characterising meningeal inflammation.
Management branches
Encephalitis is possible from altered mental status plus fever, seizure or focal findings.
- Stabilise airway, breathing, circulation and glucose, treat convulsive seizure and obtain senior neurology and critical-care review.
- Give intravenous aciclovir immediately with renal-adjusted dosing and continue ceftriaxone when bacterial meningitis remains plausible.
Key medicines
Intravenous aciclovirGive aciclovir 10 mg/kg intravenously every 8 hours using protocol weight, renal adjustment and adequate hydration for suspected HSV encephalitis.
Antiseizure treatmentUse the current emergency benzodiazepine and longer-acting antiseizure protocol for convulsive or electrographic seizures.