Thursday, April 4, 2024

Encephalitis lethargica


Brigo F, Vogrig A. Back to the future: encephalitis lethargica as an autoimmune disorder? Neurol Sci. 2024 Jan;45(1):93-99. doi: 10.1007/s10072-023-07053-8. Epub 2023 Sep 9. PMID: 37688743.


More than 100 years after its emergence, the exact pathophysiological mechanisms underlying encephalitis lethargica (EL) are still elusive and awaiting convincing and complete elucidation. This article summarizes arguments proposed over time to support or refute the hypothesis of EL as an autoimmune neuropsychiatric disorder triggered by an infectious process. It also provides a critical evaluation of modern cases labeled as EL and a comprehensive differential diagnosis of autoimmune neurological conditions that could mimic EL. The evidence supporting the autoimmune nature of historical EL is sparse and not entirely convincing. It is possible that autoimmune mechanisms were involved in the pathogenesis of this disease as an idiosyncratic response to a yet unidentified infectious agent in genetically predisposed individuals. Although there has been an increase in the incidence of presumed autoimmune encephalomyelitis since the peak of EL pandemics, most evidence does not support an underlying autoimmune mechanism. There are significant differences between historical and recent EL cases in terms of clinical symptomatology, epidemiology, and neuropathological features, suggesting that they are different entities with only superficial similarity. The term "encephalitis lethargica," still frequently used in the medical literature, should not be used for cases occurring at present in the sporadic form. Historical EL should be kept apart from recent EL, as they differ in important aspects.

Vyas A, De Jesus O. Von Economo Encephalitis. [Updated 2023 Aug 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from:

Constantin Alexander von Economo, a psychiatrist and neurologist, reported in 1917 about encephalitis lethargica in front of the Vienna Psychiatric Society. Sporadic cases of this brain and brainstem encephalitis were reported in 1916 and 1917, and similar cases were reported around the world between 1919 and 1920. His primary description of the illness that raged in an epidemic in Europe and North America between 1916 and 1927 was named von Economo encephalitis.

A few weeks before, Jean-Rene Cruchet presented his observations to the Paris Medical Society after treating military patients with neuropsychiatric disorders showing unusual neurological signs. Encephalitis lethargica or von Economo encephalitis is also known as sleeping sickness. Originally it was classified into three clinical forms: somnolent-ophthalmoplegic, hyperkinetic, and amyostatic-akinetic. Currently, postencephalitic parkinsonism has a very close relationship with encephalitis lethargica, also called von Economo encephalitis.

Von Economo was nominated for the 1926, 1930, and 1932 Nobel Prize in Physiology or Medicine. Encephalitis lethargica came to light after the book “Awakening” written by an English neurologist, Oliver Sacks. A movie based on the book was released in 1990.

Rosen D. Asleep: the Forgotten Epidemic That Remains One of Medicine's Greatest Mysteries. J Clin Sleep Med. 2010 Jun 15;6(3):299. PMCID: PMC2883045.

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