Brain inflammation and cell death found in new study

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New primate research sheds light on the long-term neurocognitive impact of COVID-19. yngsa/Getty Images
  • Cognitive and neurological symptoms are common in people with long COVID, and symptoms can be debilitating for those affected.
  • Although growing evidence suggests that the SARS-CoV-2 virus damages the central nervous system, the underlying mechanisms are not well understood.
  • Now, a new study in primates has shown that SARS-CoV-2 infection causes brain inflammation and even cell death, among other forms of brain damage.

Brain fog is a term that was coined to describe some of the cognitive effects some people may experience during and after SARS-CoV-2 infection.

Long COVID may affect 3 out of 10 people who have COVID-19. More than three-quarters of people with the disease report cognitive or neurological symptoms for months after infection, and many find them debilitating, recent studies show. Some researchers invent the condition “neuro-COVIDto describe this presentation of the disease.

However, despite some recognition of the prevalence of these conditions, treating patients with these symptoms has proven difficult due to a lack of understanding of their cause.

Now, a study published inNature Communication on the effect of SARS-CoV-2 infection on the brain of primates has revealed parallels with studies performed on human autopsies.

Autopsy studies have been performed on human brains of people who died of COVID-19, but the inability to distinguish between damage caused specifically by the virus and other factors is a limitation of this research.

Lead author Dr. Tracey Fischer of Tulane University’s National Center for Primate Research said Medical News Today in an interview that the use of an animal model had allowed the researchers to measure that the damage they observed was solely due to infection with SARS-CoV-2.

She said: “We have additional insight into the pathology of disease in the brain which may be [affecting] people with neurological problems, during the infection, as well as those who experience or continue to experience these neurological problems.

The researchers infected 4 rhesus macaques and 4 African green monkeys with SARS-CoV-2. Two additional animals of each species were selected to serve as age-matched controls. Autopsies of their brains sampled tissue from seven regions, including the frontal, parietal, occipital and temporal lobes, basal ganglia, cerebellum and brainstem.

Neuroinflammation was found to be greater in SARS-CoV-2 infected primates than in controls. The researchers also found significantly more cell death, microhemorrhages, and signs of lack of oxygen in the brain in monkeys infected with SARS-CoV-2.

These findings were consistent with previous studies that had looked at autopsies of human brains from people who died of COVID-19. The findings could be the reason for the neurological and cognitive symptoms of COVID-19 and long COVID, the authors suggested. Dr Fischer said: ‘I believe it’s our body’s response to infection that’s largely to blame for this.

She added: “When we have a big inflammatory event in the body, it affects the brain. And anything [could be] causing this.

“What was really surprising about this is that we saw it in animals that didn’t have severe respiratory disease. [Secondly,] we’ve also seen this increase in the number of microhaemorrhages in the brain – the little bleeds in the brain – and also [in] neuronal cell death.

This latest finding was of most concern, she said, because cell death could result in “a significant deficit for individuals.”

Dr. James Jackson, director of behavioral health at Vanderbilt University’s Critical Care Recovery Center, who was not involved in the research, said the findings add to growing evidence that COVID-19 can cause brain damage.

He advocated moving away from the term “brain fog” to describe neurological or cognitive symptoms following COVID-19. The patients he has spoken to in the support groups he leads, Dr. Jackson explained, have not liked the term. Instead, he explained in an interview with Medical News Today:

“If people start thinking of it as brain damage, and not just ‘brain fog’, they’ll be more inclined to do what we do with people with brain damage. Namely, we refer them to cognitive rehabilitation experts who can help them. […] With mild brain damage, many of these people are much better. […] But people don’t necessarily think of cognitive rehab for “brain fog.” »

– Dr. Jackson

Pointing out that there are millions of survivors with long COVID, he explained that there are not currently enough services to provide cognitive rehabilitation for everyone affected.

“So we need to think about innovative ways to try to improve cognition in these patients, because we’re clearly going to overwhelm the system very quickly if even a small percentage of eligible patients decide to start taking the treatment they need. So that’s a problem,” Dr. Jackson said.

Future research on computerized cognitive programs could be useful in identifying accessible treatments because they are “scalable”, the researcher added.

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