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Encephalitis lethargica
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Encephalitis lethargica

Encephalitis lethargica is an atypical form of encephalitis characterized by high fever, headache, double vision, delayed physical and mental response, and lethargy. In acute cases, patients may enter coma. Patients may also experience abnormal eye movements, upper body weakness, muscular pains, tremors, neck rigidity, and behavioral changes including psychosis.

Between 1917 and 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.

Postencephalitic Parkinson's disease may develop after a bout of encephalitis, sometimes as long as a year after the illness.

The cause of encephalitis lethargica is not yet known for certain, but on the basis of research by British doctors Russell Dale and Andrew Church, the disease is now thought to be due to a massive immune reaction to an infection by the streptococcus-like bacterium, diplococcus.

Treatment for encephalitis lethargica in the early stages is patient stabilisation, which may be very difficult. There is little evidence so far of a consistent effective treatment for the initial stages, though one patient who was given steroids initially has so far made a good recovery. Other patients have been less fortunate, and the disease then becomes progressive, with evidence of brain damage similar to Parkinson's disease. Treament is then symptomatic. Levodopa (L-Dopa) and other antiparkinson drugs often produce dramatic responses. However in most of Sach's patients who were given L-Dopa in the 1960s, the amelioration of the disease was short lived.

The course of encephalitis lethargica varies depending upon complications or accompanying disorders.

The discovery that levodopa could produce some amelioration of the symptoms was described in the book Awakenings by Oliver Sacks, later made into a film starring Robin Williams and Robert De Niro.