The coronavirus does not enter the brain, but it can still damage it

The coronavirus does not enter the brain

A study seems to confirm that the Sars-Cov-2 coronavirus does not penetrate the brain but still causes indirect damage. Researchers have identified a possible mechanism, linked to the immune system, and will investigate whether this is also responsible for the symptoms of long Covid

(photo: Colin Behrens via Pixabay) The coronavirus does not infect the brain directly, i.e. it does not penetrate within the organ, but can indirectly cause brain injury and neurological symptoms. Today a study by Columbia University Irving Medical Center confirms some previous evidence, which we have discussed, on the effects of Covid-19 on the brain, which could in some way also affect those suffering from long Covid associated with symptoms such as mental fog. According to scientists, the mechanism by which the Sars-Cov-2 coronavirus can cause even serious damage to the brain - such as stroke - is to be found in the excessive action of the immune system that causes inflammation and other problems. The study is published in Brain.

The study, even more in-depth

The scientists included in the research 41 patients who died from Covid-19, aged between 38 and 97 years, of about half of whom were intubated, while others unfortunately died shortly after hospitalization. All patients had significant brain inflammation and some had undergone magnetic resonance and CT scan of the brain. The authors then examined the brain tissues by means of autopsies, looking for the presence of the virus in the brain with various tests. In the work they took into account previous research on the subject, increasing the number of patients included in the survey and using a greater number of techniques for local detection of the virus to be sure of being able to exclude its presence.

There is no virus in the brain

The results show that the virus has not affected the brain tissues and is absent in the neurons and cells of the glia, which together with the blood vessels form the system nervous. There are traces of viral RNA probably due to the presence of Sars-Cov-2 in the blood vessels and in the leptomeninges - a part of the meninges - which cover the brain. In addition to the greater extent of tissue considered, the examination included brain areas such as the olfactory bulb, the olfactory control site, widely affected in patients with Covid-19. Some research suggested that the virus could have reached the brain by traveling from the nasal cavity via the olfactory nerve. But this is not the case. "Here, too, we did not find any traces of rna or viral proteins", underlines James E. Goldman, who coordinated the study together with Peter D. Canoll, "although instead we found some in the nasal mucosa and in the olfactory one more in high in the nasal cavity ".

Some doubts

Other studies indicated instead the possible presence of the coronavirus inside the brain. "We believe that this result is the result of a contamination, explains Canoll," since any virus in the brain is contained within the blood vessels ", it being understood that there are viruses that have been shown to enter the brain and directly cause encephalitis and other pathologies.

The immune system is complicit

The fact remains that the patients showed extensive brain lesions, according to the authors, which can be classified into two categories. On the one hand, the researchers found the presence of areas damaged by hypoxia - the lack of oxygen - in the brain. This problem, linked to lung disease and respiratory failure, is caused by stroke or even small blood clots, common in patients with severe Covid-19. The second important manifestation concerns the high amount of microglia, a type of glia cells that are activated and dealt with when it is necessary to provide the nervous system with an immune defense. This process can lead to the loss of some neurons, irreversible damage. "We found clusters of microglia attacking neurons," Canoll points out, "a process called neuronophagy." In the absence of viruses in the brain it is possible that the microglia have been activated by inflammatory cytokines, such as interleukin 6, which in turn is the result of the activation of the immune system in response to coronavirus infection.

The next steps

But not only the most serious cases have manifested brain disorders, but also the average ones often have even persistent neurological symptoms, in those with the so-called long Covid, including fatigue and lack of memory and concentration (the mental fog) which has already been discussed. Researchers are wondering if and how the activation of microglia cells may play a role in causing memory problems and these other symptoms. At present we still don't know.


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Topics

brain Coronavirus Long Covid globalData.fldTopic = "brain, Coronavirus, Long Covid"

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