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