What is Encephalitis lethargica?

Encephalitis lethargica is an unusual form of encephalitis, also known of as “sleepy sickness.” The condition was first defined in 1917 by Constantin von Economo, a neurologist who described the classic symptoms of speechlessness and loss of motion that the condition causes.

The brain damage seen in encephalitis lethargica can sometimes leave patients in a statue-like state. A worldwide epidemic of the condition occurred between 1915 and 1925 and although no further epidemics have been recorded, isolated cases still sometimes occur.


Some of the symptoms of encephalitis lethargica include:

  • High fever
  • Sore throat
  • Headache
  • Lethargy
  • Double vision
  • Delayed responses, both physically and mentally
  • Sleep inversion
  • Catatonia or unresponsiveness
  • In severe cases, a patient may enter a state resembling coma called akinetic mutism
  • Abnormal eye movements called oculogyric crises
  • Weakness in the upper body
  • Muscle pains
  • Tremors
  • Vocal tic called klazomania
  • Neck rigidity
  • Behavioural changes including psychosis


The exact cause of this condition is not clear. Research has suggested encephalitis lethargica occurs as a result of an immune reaction to strepotococcal infection. Studies have also shown the condition may be autoimmune in origin.


Patients may benefit from the use of corticosteroids in the initial stages. Many of the symptoms seen in encephalitis lethargica are similar to those seen in Parkinson’s disease and anti-parkinson medications such as Levodopa can be effective. The sleeping pill Zolpidem has also been reported as an effective treatment for the condition.

Further Reading

Last Updated: Jun 20, 2019

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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