A new study has measured a highly deleterious impact on brain tissues in the comparison between subjects cured of coronavirus and never infected: it is not yet clear what the functional implications are, nor if the damage is reversible.
The Oxford University Clinical Neuroscience Department has published Monday in Nature a study that demonstrates how Covid can have a severely deleterious impact on the brain measurable in loss of gray matter and tissue damage.
The characteristics of the study
The research involved for the first time people undergoing brain scans both before contracting Covid and a few months after: there were 785 subjects whose data is collected by the UK Biobank (an archive of clinical trials from half a million people in Great Britain Brittany).
Each of the participants underwent two brain scans about three years later, plus some cognitive tests Basic. Between the two scans, 401 participants tested positive for coronavirus, all infected between March 2020 and April 2021. The other 384 participants formed the control group because they were not infected, but had similar characteristics to the subjects in the first age group. sex, medical history and socioeconomic status.
The study, which involved people aged 51 to 81, found volume restriction and tissue damage mainly in the brain areas related tosmellbut they are also involved in other functions.
The second brain scan (for the infected) took place on average four and a half months after Covid: these lost more gray matter (in different brain regions) than non-Covid-affected participants.
In particular, between 0.2% and 2% more. They also lost more brain volume overall and showed more tissue damage in some areas. Covid disease had been mild for them. No one was hospitalized (except 15 individuals for whom brain damage appeared to be even greater).
No functional deficits were found
The cause of the brain changes is unclear. The authors mentioned theories including inflammation, the evidence of which has been found in other studies, or “sensory deprivation” for possible loss of the sense of smell. In reality this is only a hypothesis, given that a significant limitation to the study is that the researchers they had no information on symptoms from Covid in the people surveyed, including whether or not they lost their sense of smell.
Net of the marked physical difference in the brain between infected and non-infected and despite the cognitive tests performed, it is not clear what the implications really are of changes in gray matter volume and no cause and effect correlations with this study were demonstrated permanent damage or malfunction of thinking, memory or other brain functions.
The cognitive tests administered, in fact, were not sufficiently thorough to prove significant deficits. The damage was mostly localized on olfactory neurons, other regions (for example related to memory) did not show any functional alteration. The main cognitive assessment in which Covid patients showed a deficit was a type of exercise that connects the dots and involves alternating letters and numbers: Covid patients took longer to complete the task, which may suggest dots weak in focus, processing speed and other skills, but – it should be repeated – it is not a definitive test for evaluation.
What we don’t know
The open questions there are still many: the first, as has been written, is whether there is damage related to the reduction of gray matter, the second is whether this deleterious impact can be partially reversed or if these effects will persistor long term.
For example, differences in brain scans between infected and uninfected people increased with age, a possible indication of better resilience in young people.
Other uninvestigated data concern the viral strains and the effect of vaccination: the influence of Covid on organs could change depending on the variant of coronavirus contracted, since Omicron it has, among the symptoms, a much lower loss of smell, one could hypothesize a lower impact on the brain as well.
Finally, most of the infected patients contracted Covid by April 2021.
Linking this data to the vaccination campaign in Great Britain it is difficult to think that they had been vaccinated, even if it is not known, but it would be interesting, because in some cases of Long Covid vaccination has alleviated the problems
also cognitive, and played a role in balancing the long-term effects of Covid disease.
What do we know about the Covid post
What has long been known is that Covid is not a flu, but one multiorgan and multisystem disease which can damage various parts of the body and can leave important aftermaths. Last year, a poll released by the Centers for Disease Control and Prevention Usa (CDC) found that almost two-thirds of Americans with positive results reported at least un long-term symptom
more than four months after being infected: 55.5% included ‘cognitive dysfunction’, such as difficulty concentrating or memory loss.
Neurological complications have been documented during and after the disease by countless studies: reduced concentration, headaches, sensory disturbances, depression and even psychosis can persist for months after infection, as part of a constellation of symptoms called Long Covid which can also affect young people with mild initial disease.
THE
pathophysiological mechanisms of Long Covid
are not yet fully understood, although the evidence mainly implies immune dysfunction. With millions of people affected by the virus, the complications of the nervous system they pose further challenges to public health which will last for years and which concern the rehabilitation and recovery of functional capacities.
March 8, 2022 (change March 8, 2022 | 13:01)
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