COVID-19 and the brain: What do we know so far?

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COVID-19 and the brain: What do we know so far?
COVID-19 and the brain: What do we know so far?
Anonim

How does the SARS-CoV-2 virus affect the human brain? Recent studies are coming out with data shedding light on why COVID-19 can be so severe for some people and symptoms can last a long time.

There is a long history of similar viruses affecting the brain. For example, Dr. Gabriel, a professor of neurology at the University of Texas He alth Center in San Antonio, notes that in the influenza pandemic of 1917 and 1918, many of the flu-like illnesses were associated with brain disorders.

These respiratory viruses include H1N1 and SARS-CoV. The SARS-CoV-2 virus that causes COVID-19 is also known to affect the brain and nervous system, the researcher adds. The question is how and to what extent, writes the website www.medicalnewstoday.com.

Effect on brain explains loss of smell

“The main idea of our research is that some of the respiratory viruses have an affinity for the cells of the nervous system”, explains Prof. Sushadri.

She adds that the olfactory cells are very susceptible to viral invasion and are particularly targeted by SARS-CoV-2, and therefore one of the most prominent symptoms of COVID-19 is the loss of the sense of smell”. Olfactory cells are concentrated in the nose. Through them, the virus reaches the corresponding center in the brain, which is located near the hippocampus, the brain area involved in short-term memory.

“The trail of the virus, when it invades the brain, leads almost straight to the hippocampus,” explains Dr. De Erauzkin. - This is thought to be one of the sources of cognitive impairment seen in COVID-19 patients. We suspect that it may be part of the reason for the accelerated cognitive decline over time in susceptible people.”

Relation to Neurological Diseases

In the paper, scientists refer to existing evidence that makes them particularly cautious about the effects of SARS-CoV-2 on the brain. For example, the researchers found that: “Intranasal administration of SARS-CoV-2 in mice resulted in its rapid invasion into the brain. SARS-CoV-1 virus particles can be detected after death in the brain in humans”.

In vitro studies have shown that viral proteins can damage the blood-brain barrier. Headache, decreased taste, and loss of smell occur before the onset of respiratory symptoms in most COVID-19 patients.

Delirium and reduced memory “may be the only symptoms of SARS-CoV-2 infection, even in younger patients. The incidence of delirium in critically ill COVID-19 patients in intensive care units has been reported to be as high as 84%, the authors note.

A new study has found a much higher incidence of delirium and coma in COVID patients than in those with acute respiratory failure. The authors of this study looked at 2,088 cases. They found that about 82% of patients were comatose for an average of 10 days, and 55% had delirium for 3 days.

Average acute brain dysfunction manifesting as coma or delirium lasting 12 days. The authors suggest that strong sedatives and few family visits may play a role.

The study found that patients who received benzodiazepine sedative infusions, which act as a depressant for the nervous system, were 59% more likely to develop delirium.

The study also found that patients who received in-person or virtual family visits were 30% less likely to develop delirium.

Infects neurons 'with devastating consequences'

Other researchers have focused on how the new coronavirus infects neurons and causes damage to brain tissue.

For example, a team led by Akiko Iwasaki, a professor of immunobiology and molecular immunobiology at the Yale School of Medicine in New Haven, used miniature 3D reproductions of organs to analyze how SARS-CoV-2 viruses invade the brain.

The study, which appears in the Journal of Experimental Medicine, showed that the new coronavirus is able to infect neurons in these "laboratory organs" and reproduce by increasing the metabolism of the infected cells.

At the same time, he althy, uninfected neurons nearby die because the oxygen supply has been cut off. The researchers also found that blocking ACE2 receptors prevented viruses from infecting human brains developed in the laboratory.

The scientists also analyzed the effects of SARS-CoV-2 on the brains of mice genetically modified to produce human ACE2 receptors. Here, the virus has changed the vascular structure of the brain or blood vessels.

This can cut off the flow of oxygen to the brain. In addition, mice with infection that had spread to the brain had much more severe disease than others in which it was confined to the lungs.

Once infected, the brain can affect anything

Another study supports the idea that COVID-19's attack on the brain is what makes the disease so severe.

A team of researchers with senior study author Mukesh Kumar, a virologist specializing in emerging infectious diseases and an assistant professor at Georgia State University, Atlanta, infected the nasal passages of mice with the novel coronavirus.

This caused severe disease in the rodents, even after the infection cleared from their lungs.

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