The cause of encephalitis lethargica is unknown. Between 1917 to 1928, an epidemic of encephalitis lethargica spread throughout the world, but no recurrence of the epidemic has since been reported, though isolated cases continue to occur.
The disease is characterized by:
- High fever
- Double vision
- Delayed physical and mental response
In acute cases, patients may enter coma. Patients may also experience:
- Abnormal eye movements
- Upper body weakness
- Muscular pains
- Neck rigidity
- Behavioral changes including psychosis
Postencephalitic Parkinson’s disease may develop after a bout of encephalitis-sometimes as long as a year after the illness.
The course of encephalitis lethargica varies depending upon complications or accompanying disorders.
Treatment for encephalitis lethargica is symptomatic. Levodopa and other antiparkinson drugs often produce dramatic responses.