Introduction

Herpes simplex (HSV) encephalitis characteristically affects the temporal lobes - patients may demonstrate temporal lobe signs e.g. aphasia

Epidemiology

  • Incidence: 6.00 cases per 100,000 person-years
  • Peak incidence: 70+ years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Pathophysiology

Pathophysiology
  • HSV-1 responsible for 95% of cases in adults
  • Typically affects temporal and inferior frontal lobes

Clinical features

Investigations

Investigation
  • CSF: lymphocytosis, elevated protein
  • PCR for HSV
  • CT: medial temporal and inferior frontal changes (e.g. petechial haemorrhages) - normal in one-third of patients
  • MRI is better
  • EEG pattern: lateralised periodic discharges at 2 Hz

Management

Intravenous aciclovir

Prognosis

The prognosis is dependent on whether aciclovir is commenced early. If treatment is started promptly the mortality is 10-20%. Left untreated the mortality approaches 80%