Herpes simplex encephalitis
From IDWiki
Background
- Infection of the brain parenchyma by HSV, with a predilection for temporal lobes
Microbiology
- More commonly caused by HSV-1 than HSV-2 (which more commonly causes aseptic meningitis)
Pathophysiology
- About one-third are from primary infection while two-thirds are from reactivation of latent infection
Epidemiology
- Causes about 10% of encephalitis cases
Clinical Manifestations
- Fever
- Headache
- Altered level of consciousness
- Personality and behavioural changes
- Focal neuro deficits
- Seizures
- Rapidly progressing and can lead to coma
Differential Diagnosis
- Other causes of encephalitis
Investigations
- Imaging
- CT head usually normal
- MRI head can show T2 signal change in temporal lobes
- Lumbar puncture
- Elevated protein
- Lymphocytosis (10-1000 WBCs)
- Erythrocytes in 80% of cases ("hemorrhagic necrotizing meningoencephalitis")
- Normal or slightly low glucose
- HSV PCR is confirmatory
- If PCR is negative but suspicion remains high, repeat LP in 3 to 7 days
- EEG
- Spikes and slow waves over involved areas
- Periodic lateralized epiieptiform discharges (PLEDs)
- Usually predominately over involved termporal lobe
Management
- May need repeat LP if the first one is negative but suspicion is high
- Acyclovir 10mg/kg q8h IV for 14 days
- Ensure adequate hydration and adjust for renal function
- May do longer 14-21 days in immunocompetent patients due to high risk of relapse
Prognosis
- 15% recover completely
- 20% have severe neurologic sequelae
- Primarily dysnomia and impaired new learning
- Also seizures, neuropsychiatric illnesses
- 28% mortality even with treatment
- Prognosis is worse with those who are older, are sicker at presentation, or have delayed treatment
