1919–1930 encephalitis lethargica epidemic

The encephalitis lethargica epidemic lasted from around 1918 to 1930.[1] The cause is still unknown.[2] Though the cause was once attributed to the coinciding Spanish flu epidemic, modern research has disputed this claim.[3] The mortality was as high as 20%[4]

1919–1930 Encephalitis lethargica epidemic
Title page of Encephalitis Lethargica, Economo, 1931
Deaths20% mortality

Background

Encephalitis lethargica is a neurological syndrome that cause lethargy, a “mask like” face, excessive blood in the meninges, and other general neurological symptoms.[5] Officially recognized as its own condition in 1917, it is believed to have exist far longer in human history.[5] It is known to cause post-encephalitic parkinsonism.[3] Despite often being considered a condition of the past, cases still occur.

Timeline

Neurologist Constantin von Economo published a paper in April 1917 on some cases he encountered in the winter months of 1916 and 1917.[3] These patients, despite their various previous diagnoses, had a similar pattern of symptoms. This led him to suggest a novel disease, which he named Encephalitis lethargica.[3] In France, physician René Cruchet was encountering similar patterns, and published his findings within a few days of Constantin von Economo. Following these two reports, many more cases were reported, first in Europe, but quickly spreading around the globe.[3] The epidemic peaked between 1920 and 1929,[1] with an estimated million people diagnosed with Encephalitis lethargica during the epidemic period.[5]

Causes

The causes of encephalitis lethargica are still unknown.[3] Though the connection to the Spanish flu epidemic is often made, the encephalitis outbreak did begin slightly earlier. However, this cannot disprove the claim, simply point out that not all of the existing evidence lines up.[3]

Aftermath

In the aftermath of the epidemic, many cases of post-encephalitic parkinsonism were reported. This condition was distinctive from idiopathic Parkinson's disease, as it occurs in younger patients than typical idiopathic Parkinson's disease, and lacks the "pill-rolling tremor" of idiopathic Parkinson's disease.[3]

References
  1. Dourmashkin, R R (September 1997). "What caused the 1918–30 Epidemic of Encephalitis Lethargica?". Journal of the Royal Society of Medicine. 90 (9): 515–520. doi:10.1177/014107689709000916. ISSN 0141-0768. PMC 1296535. PMID 9370993.
  2. "Encephalitis Lethargica". National Institute of Neurological Disorders and Stroke. Archived from the original on 7 July 2023. Retrieved 7 July 2023.
  3. McCall, Sherman; Henry, James M.; Reid, Ann H.; Taubenberger, Jeffery K. (July 2001). "Influenza RNA not Detected in Archival Brain Tissues from Acute Encephalitis Lethargica Cases or in postencephalitic parkinson Cases". Journal of Neuropathology & Experimental Neurology. 60 (7): 696–704. doi:10.1093/jnen/60.7.696. Archived from the original on 7 July 2023. Retrieved 7 July 2023.
  4. Shorter, Edward (January 2021). "The first psychiatric pandemic: Encephalitis lethargica, 1917-27". Medical Hypotheses. 146: 110420. doi:10.1016/j.mehy.2020.110420. ISSN 1532-2777. Archived from the original on 7 July 2023. Retrieved 7 July 2023.
  5. Hoffman, Leslie A; Vilensky, Joel A (1 August 2017). "Encephalitis lethargica: 100 years after the epidemic". Brain. 140 (8): 2246–2251. doi:10.1093/brain/awx177. Archived from the original on 7 July 2023. Retrieved 7 July 2023.


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