From lethargic encephalitis to Covid-19 – April 16, 2021 – Luciano Melo

In late 1916, Viennese neurologist Constantin von Economo found that several patients were suffering from a number of previously unusual symptoms: fever, excessive sleepiness, and inability to move their eyes. Everyone was static for many hours. Some survivors have progressive disease that is very similar to Parkinson’s disease. Realizing that he was facing a different situation, Von Economo called it lethargic encephalitis. Historical records show that the outbreak identified by the neurologist occurred in Romania in 1915 and conquered the world in 1920.

Lethargic encephalitis was timely with two other scourges of humanity: World War I and the Spanish flu. The war conflict caused an intense flow of cross-border combatants, which facilitated the spread of pandemics.

Again, it is not certain whether there was a link between the Spanish flu and lethargic encephalitis. It has been speculated that both conditions were caused by the same virus. Another theory is that the flu virus would help an unidentified, opportunistic virus attack. However, the patterns of spread and epicentres were very different, which separates the two pandemics. And to this day we do not know the cause of lethargic encephalitis.

This mysterious pandemic left a historical baggage that exemplifies a disease that can spread across continents and cause progressive neurological disorders. Even if the infectious agent is no longer present in the individual.

Can we experience something similar triggered by the current pandemic? Question that hangs over us like a medieval fog. Because the survivors of Covid-19 often point to emerging difficulties in recognizing priorities, understanding the sequences between the steps of a process and remembering. These problems are not exclusively limited to those who have suffered from severe forms of the disease.

These mental changes often persist after the infection heals. The new coronavirus can affect thinking in traditional ways known to medicine. For example, by impairing organs such as the lungs or kidneys. For the inadequacy of an organic system impoverishes knowledge when it is severe.

In addition, Sars-CoV-2 sometimes causes cerebral ischemia, which affects the intellect. However, many survivors with reasoning problems did not have ischemia and their thoughtless organs are already functioning properly. Hence, the new coronavirus has to work in a different way to affect the intellect.

There are other uncertainties about the interaction between Sars-CoV-2 and the brain. Would the disturbances resulting from this relationship be progressive, irreversible, or temporary? Clinical experience to date suggests recovery, but caution should be exercised. Disaster or realism aside, bad news may emerge pointing to another phase of the epidemic, this time with an increasing number of intellectual consequences in the population, just like the type of lethargic encephalitis.

These concerns were the motto of neurologist Jonas Hosp from the University of Freiburg to investigate how Covid-19 affects brain activity. His conclusions, recently reprinted in Brain magazine, shed some light on the subject.

The researcher found that there is a pattern of brain dysfunction caused by Covid-19 in which only certain parts of the brain do not function properly. These areas are responsible for our ability to elaborate, organize, sort, and remember. This very distinctive marking should not be the result of a number of factors, such as: B. fatigue, side effects of medication and breathing disorders. But from a characteristic attack on the brain.

The autopsy in one of the patients examined by Hosp showed activation of the brain defense cells and no permanent damage. This indicates that Sars-CoV-2 is indirectly affecting the brain through inflammation.

Now this microorganism is a major cause of inflammation that will eventually win over the brain and persist even after the virus is no longer in that organ. Intellectual disturbances do not appear to be due to the virus’ direct destructive action against the brain.

Apparently it won’t be this time around that we will have a late wave of progressive cognitive outcomes.


1-Hosp YES, Dressing A, cognitive impairment and altered cerebral glucose metabolism in the subacute stage of COVID-19. Brain. 2021 April 3: awab009. doi: 10.1093 / brain / awab009. Epub before printing. PMID: 33822001.

2- Leslie A. Hoffman, Joel A. Vilensky, Encephalitis lethargica: 100 years after the epidemic, Brain, Volume 140, Issue 8, August 2017, pages 2246–2251,

3- Blazhenets G, Schröter N, Slow but obvious recovery from neocortical dysfunction and cognitive impairment in a number of chronic COVID-19 patients. J Nucl Med. 2021 Mar 31: jnumed.121.262128. doi: 10.2967 / jnumed.121.262128. Epub before printing. PMID: 33789937.

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