encephalitis lethargica

encephalitis lethargica, form of encephalitis that emerged in the early 20th century. An encephalitis lethargica epidemic occurred from 1915 to 1928. The disease was first described medically in 1917, though numerous possible forerunners dating back to the 16th century have been identified.

Encephalitis lethargica has nothing in common with the tropical disease known as sleeping sickness (African trypanosomiasis). It is instead an atypical form of encephalitis which attacks the brain, centering on the gray matter and leaving its victims speechless and unable to move. Its name means, basically, “inflammation of the brain that makes you tired.” Its cause remains a mystery, though research continues and isolated cases still occur. One theory is that it is triggered by an excessive immune response to bacteria. At the time of its emergence, it was thought to be connected with the influenza pandemic of 1918–19, and some later research points to a viral infection. Researchers now suspect that the origins may be toxicological or infectious (viral or bacterial), with the possible implication of autoimmune disorders; some conjecture that the aetiology of the disease may have multiple causes. A BBC documentary of 2004 described encephalitis lethargica as the greatest medical mystery of the 20th century.

The origins of the encephalitis lethargica epidemic can be traced back to 1915, though most cases were reported in the 1920s. It could affect anyone, but it was most common in young people, particularly women, and occurred primarily in the United States and Europe, its transmission tied to wide-scale troop movements during and immediately after World War I. Early symptoms of fever, sore throat, and headache were quickly followed by double vision, tremors, delayed response, then drowsiness and lethargy; many patients became comatose and completely unresponsive. And many of those who survived remained in a coma for months or years.

Those who appeared to make a recovery often went on to develop a form of postencephalitic parkinsonism. In 1969 a newly developed anti-Parkinson’s drug, levodopa (L-DOPA), was used to treat some of the comatose patients. A number made dramatic recoveries, regaining movement and speech after 30 years of unconscious immobility. Most slipped back into coma within days or weeks, however, and could not be roused again. Oliver Sacks was working in the United States at the time, and his book Awakenings (1973), made into a film starring Robin Williams and Robert De Niro in 1990, presents the case histories of these patients.

The epidemic came to an end in 1928, with isolated outbreaks continuing until the mid-1930s. An estimated 1 million people suffered from encephalitis lethargica. As many as half of them died, and hundreds of thousands more were permanently institutionalized, trapped inside akinetic bodies.