Even mild to moderate infection can cause brain abnormalities
Even mild to moderate infection can cause brain abnormalities

Even mild to moderate infection can cause brain abnormalities

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New research finds long-term consequences of SARS-CoV-2 infection on the brain. By Qi Yang / Getty Images
  • A new study reports that people with a mild to moderate SARS-CoV-2 infection showed greater abnormalities in the brain regions associated with odor on average 4.5 months after a COVID-19 diagnosis than those who did not get the virus.
  • As far as the authors know, this is the first study to assess changes in the brain before and after a SARS-CoV-2 infection, and it therefore accounts for the contribution of pre-existing differences in the brain..
  • Individuals with a previous SARS-CoV-2 infection showed deficits in executive function that were related to the extent of abnormalities in part of the cerebellum.
  • This study serves as a step towards understanding brain changes associated with specific COVID-19 symptoms.

A recent study in Nature found subtle changes in the brain of people with mild to moderate COVID-19 after the first 4 weeks or acute phase of a SARS-CoV-2 infection. The study showed that individuals with SARS-CoV-2 showed greater brain tissue damage and shrinkage of brain areas on average 4.5 months after their COVID-19 diagnosis.

Dr. Maxime Taqueta senior researcher at the University of Oxford, who was not involved in the study, said: “It is well established that [SARS-CoV-2] infection is associated with subsequent risks of neurological and psychiatric problems in some people, including brain fog, loss of taste and smell, depression and psychosis. But why this is happening is largely unknown. ”

“This study begins to shed light on this important issue by showing that brain areas associated with the ‘olfactory center’ of the brain may shrink after COVID-19 in some people.”

The co-author of the study, Professor Naomi AllenChief Researcher at UK Biobank, noted, “[This] is the only study in the world that is able to detect “before versus after” changes in the brain associated with SARS-CoV-2 infection. “

Neurological symptoms are common both during and after acute phase of a SARS-CoV-2 infection. Previous studies that have examined changes in the brain underlying these neurological symptoms have mostly focused on people with acute COVID-19.

The small number of studies assessing brain changes after the acute phase of a SARS-CoV-2 infection lacked access to pre-infection brain image data. As a result, some of the observable differences in these studies could be due to brain anomalies or risk factors that existed before the infection.

Researchers conducted this study to distinguish brain abnormalities related to COVID-19 from those that may occur due to pre-existing risk factors. In addition, the study used several types of brain scans to assess brain changes in many individuals, facilitating the identification of subtle brain abnormalities associated with the SARS-CoV-2 infection.

In this study, the researchers used data from UK Biobanka large database containing medical information, including brain imaging data, from individuals in the United Kingdom.

Specifically, they used image data collected from 785 people using various brain scans before and after the onset of the COVID-19 pandemic. This included 401 participants with a SARS-CoV-2 infection between the two scans and 384 control adults without a COVID-19 diagnosis.

The researchers matched participants in the two groups for age, gender, ethnicity, and duration between the two brain scans. The mean duration between the COVID-19 diagnosis and the second set of brain scans was 141 days.

The researchers used software programs to analyze the raw brain image data and extract quantifiable features, called image-derived phenotypes (IDPs). Each IDP measures a specific brain structure or function, such as the change in brain region activity while performing a task or volume of a specific brain structure.

In this study, the researchers measured changes in over 2,500 internally displaced persons for each individual person.

A loss of odor or odors can be observed in most individuals with a SARS-CoV-2 infection, including after the acute phase. Therefore, the researchers focused on brain regions that are either directly involved in the processing of olfactory information or those associated with olfactory system.

They found a greater reduction in gray matter volume and a greater increase in tissue injury markers in specific brain regions associated with the olfactory system in participants with SARS-CoV-2 compared to controls. The gray matter consists mainly of cell bodies of nerve cells and is involved in information processing.

There was also a greater loss of gray matter all over the brain and an increase in the volume of cerebrospinal fluid in participants with a SARS-CoV-2 infection.

In other words, in addition to changes in brain regions associated with odors, there were global changes in the brains of participants with SARS-CoV-2. In particular, these brain abnormalities could be observed in individuals with mild to moderate COVID-19.

By examining differences in cognitive function, the researchers found that participants with SARS-CoV-2 showed deficits in executive functionwhich includes higher-level cognitive functions such as thinking, reasoning, and decision-making.

In addition, there was an association between a lower performance in the executive function test and atypical brain changes in part of the the cerebellum known to be involved in cognition.

“These results may help explain why some people experience brain symptoms long after the acute infection. The causes of these brain changes, whether they can be prevented or even reversed, as well as whether similar changes have been observed in hospitalized patients, in children and younger adults and in ethnic minority groups, has not yet been determined, ”said Dr. Taquet.

However, the researchers noted that they did not have data on whether participants with a SARS-CoV-2 infection had symptoms of long-term COVID. They were also unable to assess the association between the brain abnormalities and potential long COVID symptoms.

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