A British study, published July 8, provided a better understanding of the diversity of brain damage that Covid-19 can cause.
She had just left the hospital after being treated for symptoms of Covid-19, such as persistent fever, cough and breathing problems. But a day later, this 55-year-old Briton began hallucinating, seeing monkeys and lions in his house. On top of this, the 50-year-old felt that she was being persecuted and felt compelled to kidnap and put on her coat several times in a row.
This woman is one of 43 patients severely affected by Covid-19 who have experienced neurological complications, which have been studied by British researchers. Their conclusions, published Wednesday, July 8 in the scientific journal Brain, reinforces the belief in the scientific world that the Sars-CoV-2 virus does not just attack the airways. And that this virus can cause serious damage, especially the brain.
A slightly neurotropic virus on the edges
“We had to wait for the virus to migrate from China and come to Europe before scientists in Italy began to warn us of its neurological effects,” recalls Pierre-Marie Lledo, head of the neuroscience department at Institut Pasteur, who leads the working group to study the consequences of the brain of coronavirus, contacted by France24. At the same time, loss of taste and smell was among the first clues to this little-known aspect of the pandemic.
“This study makes it possible to look more clearly at the categories of neurological damage that Sars-CoV-2 can cause,” specifies Pierre-Marie Lledo. And they are many. British researchers have found various types of encephalitis, ADEM (an acute inflammatory disease of the central nervous system that usually affects children), cases of Guillain Barré syndrome (a condition that attacks the nervous system and leads to paralysis) or Stroke (stroke). These complications, which appear to affect only a small minority of infected individuals, can occur up to 6 days before and 14 days after the onset of the more classic symptoms of Covid-19.
These results suggest that Sars-CoV-2 has “a tendency toward neurotropism, that is, it has an appetite for neurons,” states the researcher from the Pasteur Institute. The best known of the neurotropic viruses is rabies, which attacks almost exclusively the neuronal system. However, the current coronavirus remains, above all, a respiratory virus. But one does not hinder the other. “We know that the receptor that allows Sars-CoV-2 to enter cells is found in the airways, but it is also found in cells in other organs, such as the brain or liver,” explains Nicolas Locker, professor of virology at the University of Surrey, contacted by France24. This researcher would not be surprised to know that the coronavirus also has consequences in the liver.
Less severe lung symptoms than the brain
The long history of viruses also proves that these pathogens are not exclusive in their target. The Spanish flu in 1918 left behind patients who later developed brain complications. The Zika virus, which passes through the blood, has been shown to cause brain damage such as microcephaly. Even during previous coronavirus epidemics – SARS 2002 and Mers 2012 – “there were indications of effects on the brain, but not enough to establish a clinical neurological picture”, emphasizes Pierre-Marie Lledo. “It is quite common for a virus to migrate, so it is not surprising that Sars-CoV-2 causes secondary brain damage,” concludes Nicolas Locker.
What seemed more surprising to the British researchers was that for some of the hospitalized patients, “the lung symptoms were relatively weak, while the neurological symptoms were severe,” comments Pierre-Marie Lledo. This is especially the case for a woman in her sixties, who is already suffering for two years from a decrease in brain capacity, which is admitted to the hospital after episodes of hallucinations, visual and speech disorders. In his case, the virus damage to the brain was greater than the respiratory tract.
However, this study does not allow the conclusion that people who are asymptomatic or have only mild symptoms are at risk of developing serious neurological complications. “The researchers looked specifically at what happened in patients who were already very ill,” said Nicolas Locker. Above all, too few cases are considered in this study to enable generalizations.
Chronic neurological consequences?
On the other hand, the fact that some of these patients had developed neurological complications up to two weeks after the onset of symptoms of Covid-19 “suggests that it will be necessary to adjust the monitoring of patients after their discharge from hospital to better take into account to this risk, “estimates the virologist at the University of Surrey.
The study also requires further exploration of the effects of the Sars-CoV-2 virus on the brain, according to the two interviewed specialists. For Nicolas Locker, it should be specifically stated “whether the symptoms of Covid-19 will be more important for people who are likely to develop neurodegenerative diseases”. In other words, should these individuals be included in the vulnerable population along with diabetics or people already suffering from respiratory diseases?
The other fear that this study raises is that “Sars-CoV-2 can have chronic neurological consequences”, emphasizes Pierre-Marie Lledo. The researcher at Institut Pasteur recalls that “for a reason that still avoids us, people seem to have recurring versions of some symptoms of Covid-19”. One of the biggest risks, currently studying at European level, is that the corona virus can trigger chronic fatigue syndrome.