Definition of "encephalitis lethargica" []

• A viral epidemic encephalitis marked by apathy, paralysis of the extrinsic eye muscle, and extreme muscular weakness. It occurred in various parts of the world between 1915 and 1926. Also called sleeping sickness, sleepy sickness. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.