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noun Pathology.
  1. inflammation of the substance of the brain.
  2. Also called encephali·tis le·thar·gi·ca [li-thahr-ji-kuh] /lɪˈθɑr dʒɪ kə/. a form of this condition, caused by a filterable virus and characterized by apathy and abnormal sleepiness; sleeping sickness.

Origin of encephalitis

First recorded in 1835–45; encephal- + -itis
Related formsen·ceph·a·lit·ic [en-sef-uh-lit-ik] /ɛnˌsɛf əˈlɪt ɪk/, adjectivepost·en·ceph·a·lit·ic, adjectivepseu·do·en·ceph·a·lit·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for encephalitis lethargica

encephalitis lethargica

  1. pathol a technical name for sleeping sickness (def. 2)


  1. inflammation of the brain
Derived Formsencephalitic (ˌɛnsɛfəˈlɪtɪk), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for encephalitis lethargica



1843, from medical Latin encephalon (from Greek enkephalos "brain," literally "within the head," from en "in" + kephale "head;" see cephalo-) + -itis.

Online Etymology Dictionary, © 2010 Douglas Harper

encephalitis lethargica in Medicine

encephalitis lethargica

  1. A viral epidemic encephalitis characterized by apathy, paralysis of an eye muscle, and extreme muscular weakness.sleeping sickness von Economo's disease

acute epidemic leukoencephalitis

  1. A usually fatal form of leukoencephalitis that is characterized by acute onset of fever, followed by convulsions, delirium, and coma, and is associated with localized hemorrhaging in the central nervous system.Strümpell's disease
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

encephalitis lethargica in Science


  1. Inflammation of the brain, usually caused by infection with a virus.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

encephalitis lethargica in Culture



An inflammation of the brain. Encephalitis may be caused by a virus or lead poisoning, or it may be a complication of another disease, such as influenza or measles. Encephalitis can cause permanent brain damage or death. It is also possible, however, to recover from it completely.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.