Philip Liebson
Chicago, Illinois, United States

Epidemics may come and go, magically disappear, and sometimes recur. An example of this was the “sweating sickness” of sixteenth century Europe. Another example closer to our time was encephalitis lethargica, occurring as an epidemic in the late 1910s and early 1920s followed by only sporadic cases.

Sporadic cases of brainstem encephalitis were described in 1916–17 by Constantin Alexander von Enconomo, a Viennese neurologist and psychiatrist. More cases were observed worldwide in 1919–1920 following the influenza pandemic of 1918–19. It was thought by some that these were due to the influenza virus, but a reevaluation in 2001 of tissue remnants of brain samples from that time showed no evidence of influenza.

The spread of encephalitis lethargica was associated with military activities during World War I, suggesting a commonality with influenza. There is currently a possibility that the disorder was associated with streptococcal infection or was an autoimmune disorder. It has not been entirely disproven that the disorder was due to influenza infection. No further epidemics of this disorder were reported after the early 1920s, but sporadic cases still occur.

The disorder presents in several forms, first described by von Economo. They include a somnolent-ophthalmoplegic form characterized as a sleeping sickness, an amyostatic-akinetic form that resembles parkinsonism or catatonia, and a hyperkinetic form with hallucinations. Von Economo thought the sleep disorder was due to malfunction of the hypothalamus. During the early world-wide epidemic of this encephalitis, the mortality from the somnolent-ophthalmoplegic form was as high as 50%. Treatment was only supportive and included steroids, dopamine agonists, and depending on the presentation.

The appearance and disappearance of epidemics can be mysterious. Could Von Economo’s encephalitis in the sleeping sickness form have been a recrudescence of earlier epidemics of “sleeping sickness” outside of Africa and unrelated to the tsetse fly?

Sources

• Vyas A, De Jesus O. Von Economo Encephalitis. National Library of Medicine Stat Pearls [Internet], 2024.
• Ravenholt RT, Foege WH. 1918 influenza, encephalitis lethargica, parkinsonism. Lancet 1982; 2(8303): 860-4.
• Da Mota Gomes M. Encephalitis lethargica epidemic milestones in early sleep neurobiology researches. Sleep Med 2020; 74:349-56.
• Davis LE, Koster F, Cawthon A. Neurologic aspects of influenza viruses. Handb Clin Neurol. 2014;123:619-45.