Encephalitis lethargica

Introduction
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By Ravindra Kumar Garg MD

Encephalitis lethargica is also known as or subsumes Epidemic encephalitis and von Economo disease. -ed.

Encephalitis lethargica was a mysterious epidemic disease of the 1920s and 1930s that was better known as the “sleepy” or “sleeping” sickness. It is associated with the subsequent development of postencephalitic parkinsonism, a condition that was popularized in Oliver Sacks’ 1973 book, Awakenings, and the 1990 movie of the same name. Encephalitis lethargica evolved to have many manifestations other than a “lethargic type” including types that were primarily characterized by insomnia and/or movement disorders. Differentiating points from idiopathic Parkinson disease include young age of onset, oculogyric crises, altered sleep-wake cycle, respiratory disturbances, and pyramidal signs. Pathologically, there is diffuse involvement of gray matter of the brain dominantly, the diencephalon, and the mesencephalon. Controversy remains over whether encephalitis lethargica was caused by the influenza virus. No definite treatment is available. Prognosis is variable. In some patients extrapyramidal sequelae persist life-long.

Key points

  • Encephalitis lethargica can only be diagnosed clinically.
  • Oculogyric crises were not associated with acute cases during the epidemic period.
  • Differentiating points from Parkinson disease are young age of onset, oculogyric crises, altered sleep cycle, respiratory disturbances, and pyramidal signs.
  • Recent putative cases have linked the hyperkinetic form of the condition with NMDAR-Ab encephalitis.
  • Although no clear data link encephalitis lethargica with influenza, such a linkage is still supported by some data and some clinicians.

In This Article

Introduction
Historical note and nomenclature
Clinical manifestations
Clinical vignette
Etiology
Pathogenesis and pathophysiology
Epidemiology
Prevention
Differential diagnosis
Diagnostic workup
Prognosis and complications
Management
Pregnancy
References cited
Contributors