Encephalitides

Definition

Acute inflammation of the parenchyma secondary to viral infection

Herpes Simplex Virus Encephalitis

  • most common sporadic encephalitis
  • no age, sex, racial, seasonal, or geographical predilection

Neonatal Presentation

  • vertical transmission
  • recognized during the 1st – 3rd week
  • diffuse neurological signs, seizures, hypotonia, diminished responsiveness, poor feeding, irritability, systematic manifestations

Children & Adults

  • predilection for medial temporal and orbital areas
  • neurologic presentation – altered consciousness, seizures
  • neuropsych outcome – memory deficits, social problems; Kluver-Bucy like symptoms
  • less than half of survivors have normal developmental or intellectual outcomes
  • 75-85% show significant personality and behavioral changes
  • 30-50% show motor disorders, seizures

Arboviruses (Arthropod-Borne Viruses)

  • outcome dependent upon age at onset, illness type, clinical course, etc.
  • incubation approximately 4-10 days
  • typically occur from May to October in N. Hemisphere

Eastern Equine Encephalitis (EEE)

  • 153 confirmed cases in the U.S. since 1964
  • most common along Atlantic and Gulf coasts
  • mortality – 30-60%
  • pediatric cases – 50-70%

Western Equine Encephalitis (WEE)

  • 639 confirmed cases in the U.S. since 1964
  • most common in western and central US and Canada
  • mortality – 2-5%
  • disease severity increases with age

California Encephalitis (caused principally by the LaCrosse virus strain)

  • roughly 70 cases per year
  • most common in midwest
  • mortality 1%
  • male>female 2:1
  • typically affects young children (peak 5-10 years)
  • sx: paresis, abnormal EEG’s, seizures (40-50%), status epilepticus (10-15%)
  • neurologic outcomes: residual seizures (20%), EEG abnormalities (33-75%)
  • neuropsych outcomes: typically mild sequelae, unless especially ill at presentation