2024-11-04 16:18:00
First described in Austria in 1917, encephalitis lethargica claimed countless lives in industrialized countries at the start of the last century, leaving some survivors in a catatonic state. Disappearing as suddenly as she had appeared, she was erased from collective memory. More than a century after this large-scale epidemic outbreak, the causes of the disease are still unknown. But hypotheses exist, notably involving the immune system.
“People have forgotten what life is. They forgot what it means to be alive,” Leonard Lowe says in the film Awakeningby Penny Marshall. Brought back to life after spending 30 years in a comatose state, this patient, played by actor Robert De Niro, believes that we should all remember “what we have, and what we risk losing.”
Inspired by a true story recounted by British doctor and neurologist Oliver Sacks in the book Awakeningsthe film depicts in detail the experience of those affected bylethargic encephalitisalso known as epidemic von Economo-Cruchet encephalitis or “sleeping sickness”.
Far from being rare, this disease affected a million people worldwide, during and after the First World War. Then she disappeared. For a century, a question has remained unanswered: what could have been the cause of this condition which caused countless victims ?
The ordeal of the survivors
Encephalitis lethargica was first described in 1917. Viennaby neurologist Constantin von Economo. If its first symptoms resemble those of the flu, the similarities end there. In the weeks following the onset of the illness, some victims found themselves unable to sleep. Others, conversely, were so sleepy that they could only be awakened during a few minutes to eat.
During this first phase, about half of those affected died. For those who survived, a confusing ordeal then began. After recovering and often returning to work, many convalescents began to notice that their movements were stiffer and slower than before the illness. Also, sometimes their eyes would lock in certain positionsupwards or to the side, for a few seconds or a few hours (oculogyric crises).
Unfortunately for those affected, this new state, far from improving, progressed over time, and many of them ended up finding themselves completely frozen, unable to speak or move, like the character played by Robert De Niro.
But that wasn’t all: many patients also developed language problems, with their speech becoming monotonous or unintelligible. Finally, some presented with mood, perception, or even personality disorders. Patients have seen their thoughts considerably slowed down. Others have had hallucinations or experienced strange delusions. Some seemed to lose all sense of right or wrong. As part of a study that my colleagues and I carried out, we notably met four patients who developed kleptomania (compulsive theft) following the illness.
What hypotheses would explain encephalitis lethargica?
Find the origin of a disease is not always easyas the history of the discovery of the human immunodeficiency virus (HIV, responsible for AIDS) reminds us or that of the demonstration of the causal link between infection by the human papillomavirus virus and cervical cancer of the uterus. The same is true for encephalitis lethargica.
The sudden onset of the disease, then just as abrupt disappearance, led some to speculate that it could have been linked to an infection. Remember that at that time, the Spanish flu epidemic had damaged populations. However, the first cases of encephalitis lethargica had occurred before its outbreak, and none flu virus could not be identified in the brains of people affected by encephalitis lethargica that we were able to autopsy.
To try to identify the origin of the disease, we spent long hours consulting the archives from the National Hospital for Neurology and Neurosurgery and the Institute of Neurology at University College London, meticulously preserved. We were thus able to examine the cases of more than 600 patients suffering from encephalitis lethargica. This research told us that only 32% of them had been affected by something that vaguely resembled the flu in the year before the onset of encephalitis lethargica. In addition, the family circle was only affected in less than 1% of cases. Therefore, the hypothesis of influenza infection is not very convincing – at least if we consider said infection as the sole cause of encephalitis lethargica.
What about the patient environment? The least we can say is that 1917 was a eventful yearthe First World War leading to a considerable mobilization of personnel, weapons and equipment. One could imagine that in this exceptional context, part of the population could have been exposed to new substances. But our study did not highlight any link between the disease and the use of particular products.
More recently, a new theory involving autoimmune mechanisms has been proposed to explain the occurrence of encephalitis lethargica. According to this explanation, the patients’ immune systems attacked their own brains.
We know that such a situation can occur in other contexts. Thus, it is an autoimmune reaction directed against the cells of the pancreas which is at the origin of type 1 diabetes. The production by the body of antibodies directed against the cells of the thyroid gland can also trigger the Graves’ disease. When such dysfunctions affect the brain, the results can be devastating, as in the case of multiple sclerosiswhich also results from autoimmune problems.
Furthermore, a condition called autoimmune encephalitis can also occur when antibodies attack nerve cells in the brain. Our work revealed that almost half of the patients diagnosed as suffering from encephalitis lethargica could in reality have been victims of autoimmune encephalitis, even if the form described then does not correspond to any of the forms of the disease that we know Today.
What could have been the connection with encephalitis lethargica and its many symptoms? This is where the hypothesis of collateral damage caused by infection (by the flu virus or another microorganism) could make sense.
We know that certain autoimmune diseases can be triggered by an infection. The molecular structures carried by certain pathogens can indeed present similarities with those which exist on the surface of our own cells. We understand the interest for the invaders: this disguise allows them to go relatively unnoticed. However, the immune system can still detect them. The problem is that it may then also turn against cells in the body that resemble said invaders…
To conclude, let us focus on one last question: why bother solving an enigma which concerns a pandemic whose last survivor died two decades ago? The answer, this time, is simple: encephalitis lethargica was not the first neurological epidemic of this kind. If we don’t understand it, we won’t be ready to face the next one.
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**Interview with Dr. Jane Thompson, Neurologist and Author of “The Mystery of Encephalitis Lethargica”**
**Editor:** Thank you for joining us, Dr. Thompson. Encephalitis lethargica is often referred to as a forgotten epidemic. Can you provide a brief overview of what this disease is and why it disappeared from public consciousness?
**Dr. Thompson:** Thank you for having me. Encephalitis lethargica was first identified during World War I and affected millions of people, leaving many in a catatonic state. After the initial outbreak, it vanished almost entirely, leading to a lack of awareness. This could be due to the fact that it didn’t resurface in the same way, so it largely faded from medical literature and public memory, until recently.
**Editor:** The causes of encephalitis lethargica remain a mystery over a century later. What are some prominent theories regarding its origins?
**Dr. Thompson:** Several theories have been proposed. Initially, there was speculation about a link to the Spanish flu, but evidence connecting the two is weak. More recently, autoimmune responses have gained attention—suggesting that patients’ immune systems might have unintentionally attacked their own brain cells. This has parallels with other autoimmune diseases.
**Editor:** One of the most haunting portrayals of a survivor is captured in Oliver Sacks’ book and the film “Awakenings.” How do you think these cultural representations influence public understanding of the disease?
**Dr. Thompson:** They play a significant role in humanizing the experience of those affected. The film, particularly, sheds light on the deep emotional and physical toll the disease takes, allowing audiences to connect with the plight of the survivors and perhaps foster greater empathy and awareness for rare medical conditions.
**Editor:** Can you describe some of the long-term effects that survivors of encephalitis lethargica experience, as noted in your studies?
**Dr. Thompson:** Yes, many survivors endure a variety of disabling neuropsychological symptoms. This can include halting speech, muscle rigidity, and cognitive impairments, such as slowed thought processes and personality changes. There are also cases of compulsive behaviors like kleptomania, which highlight the profound changes the brain undergoes post-illness.
**Editor:** Given the ongoing mystery surrounding its cause and treatment, how critical is it for researchers to continue studying encephalitis lethargica today?
**Dr. Thompson:** It is crucial. Understanding this condition not only may help us uncover the fundamental mechanisms behind it but could also shed light on similar neurological disorders. As we learn more about immune reactions and their effects on the brain, we could potentially find better treatments for a range of related diseases.
**Editor:** Thank you, Dr. Thompson, for your insights into this haunting and perplexing disease.
**Dr. Thompson:** Thank you for bringing attention to it. Awareness and research are the first steps towards unlocking the mysteries of encephalitis lethargica.
