Covid-19 patients who lost their sense of smell after infection show brain changes, new study finds.
- A new study reveals that Covid patients who have lost their sense of smell exhibit behavioral, functional and structural brain changes.
- Loss of smell was linked to decreased functional activity during decision-making, loss of white matter integrity, and thinning of the outer layer of the brain in the parietal regions.
- For the team, anosmia could serve as a potential marker of damage caused by the virus to neuronal tissue and as a marker for individuals at risk of brain damage.
While Covid-19 has largely loosened its grip on the world, researchers are still trying to understand one of its most emblematic symptoms: the loss of smell. A Chilean team has made a major discovery on this point. People who have lost their sense of smell after contracting the coronavirus show significant functional and structural brain changes.
Their study was published in the journal Scientific Reports August 17, 2024.
Anosmia and covid: brain changes visible on MRI
For this research, the scientists followed 73 patients who had suffered from a mild to moderate form of Covid-19 and 27 patients infected with other pathogens. Each of them underwent cognitive screening, a decision-making task, functional tests and MRI scans at 15-day intervals. These people, who had an average age of 40.1 years, were recruited 9 months after their diagnosis.
Olfactory tests were also conducted. Among the Covid patients, 29 had a complete loss of the sense and 14 had varying degrees of changes in their sense of smell (decrease in quality). Among these 43 volunteers, six were unable to identify more than four of the six odors presented to them. This suggests a permanent dysfunction of the sense of smell, according to the researchers.
Further analyses revealed that participants whose sense of smell was affected were more impulsive and more likely to make a different choice if the outcome was negative when playing a game. On MRI scans taken during the game, the loss of smell was associated with decreased functional activity during decision-making, loss of white matter integrity, and thinning of the outer layer of the brain in the parietal regions. These areas are known to be responsible for processing sensory input and understanding spatial relationships.
Loss of smell: Spotting those at risk of brain damage
“Only six patients showed indicators of persistent olfactory deficit. Our results are therefore not due to a real deficit”note the authors in their article. For them, it is essential to pay attention to covid patients suffering from anosmia. Indeed, according to the results of their work, this symptom could be a “potential marker of virus damage to neuronal tissue” as well as a “marker of individuals likely to suffer brain damage.”
“Given the significant global incidence of Covid-19, identifying factors that distinguish individuals at risk of developing brain damage is crucial for prioritizing follow-up care.”they conclude. However, they acknowledge that further research is needed.
