https://www.cidrap.umn.edu/covid-19/covid-related-loss-smell-tied-changes-brain
COVID-related loss of smell tied to changes in the brain
Mary Van Beusekom, MS
Today at 4:27 p.m.
COVID-19
Researchers in Chile conducted cognitive screening, performance on a decision-making task, functional testing, and magnetic resonance imaging (MRI) results with 73 patients after mild to moderate COVID-19 infection and 27 COVID-naïve patients with infections from other pathogens. Two follow-up sessions were conducted 15 days apart.
The patients were recruited from public and private hospitals in Santiago an average of 9 months after diagnosis from February 2020 to May 2023. The average age was 40.1 years. The team used loss of smell and need for hospitalization as proxies for potential markers of neurologic involvement and disease severity, respectively.
The results were published late last week in Scientific Reports.
"Given the significant global incidence of COVID-19, identifying factors that can distinguish individuals at risk of developing brain alterations is crucial for prioritizing follow-up care," the study authors wrote.
Role of loss of smell as marker
Twenty-two of 73 COVID-19 patients (30.1%) reported having differing degrees of attention and memory problems. Seven patients said they had headaches, six reported fatigue, and four had a persistently impaired sense of smell lasting, on average, 1.3 months. Of these patients, 68% experienced a total loss of smell, while the rest had an altered sense of smell.
Given the significant global incidence of COVID-19, identifying factors that can distinguish individuals at risk of developing brain alterations is crucial for prioritizing follow-up care.
In addition to self-reported changes in smell, 6 of 43 patients who lost their sense of smell during the acute infection could identify at most four of six odors on olfactory testing, suggesting persistent dysfunction.
The COVID and non-COVID groups were similar in age and cognitive performance, but patients with a loss of smell showed more impulsivity and were more likely to make different a choice given a negative result when performing a behavioral task (game), while those who were hospitalized displayed less strategic thinking and made the same wrong choice repeatedly.
On MRI conducted during the game, 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 cerebrum in the parietal regions (responsible for processing sensory input, understanding spatial relationships, and how to navigate).
"Only six patients present indicators of persistent olfactory deficit; thus, our results are not due to actual deficit," the study authors wrote. "Hence, anosmia could serve as both a potential marker of virus-induced damage to neuronal tissues and a marker for individuals susceptible to brain damage."
Research is needed into the extent that loss of smell reflects COVID-related brain damage, whether it is a marker of patient susceptibility to different neuropathologic mechanisms, the mechanism of the link between loss of smell and brain changes, and treatment targets, the researchers concluded.
COVID-related loss of smell tied to changes in the brain
Mary Van Beusekom, MS
Today at 4:27 p.m.
COVID-19
A new study of 73 adults recovering from COVID-19 finds that those who lost their sense of smell showed behavioral, functional, and structural brain changes.Researchers in Chile conducted cognitive screening, performance on a decision-making task, functional testing, and magnetic resonance imaging (MRI) results with 73 patients after mild to moderate COVID-19 infection and 27 COVID-naïve patients with infections from other pathogens. Two follow-up sessions were conducted 15 days apart.
The patients were recruited from public and private hospitals in Santiago an average of 9 months after diagnosis from February 2020 to May 2023. The average age was 40.1 years. The team used loss of smell and need for hospitalization as proxies for potential markers of neurologic involvement and disease severity, respectively.
The results were published late last week in Scientific Reports.
"Given the significant global incidence of COVID-19, identifying factors that can distinguish individuals at risk of developing brain alterations is crucial for prioritizing follow-up care," the study authors wrote.
Role of loss of smell as marker
Twenty-two of 73 COVID-19 patients (30.1%) reported having differing degrees of attention and memory problems. Seven patients said they had headaches, six reported fatigue, and four had a persistently impaired sense of smell lasting, on average, 1.3 months. Of these patients, 68% experienced a total loss of smell, while the rest had an altered sense of smell.
Given the significant global incidence of COVID-19, identifying factors that can distinguish individuals at risk of developing brain alterations is crucial for prioritizing follow-up care.
In addition to self-reported changes in smell, 6 of 43 patients who lost their sense of smell during the acute infection could identify at most four of six odors on olfactory testing, suggesting persistent dysfunction.
The COVID and non-COVID groups were similar in age and cognitive performance, but patients with a loss of smell showed more impulsivity and were more likely to make different a choice given a negative result when performing a behavioral task (game), while those who were hospitalized displayed less strategic thinking and made the same wrong choice repeatedly.
On MRI conducted during the game, 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 cerebrum in the parietal regions (responsible for processing sensory input, understanding spatial relationships, and how to navigate).
"Only six patients present indicators of persistent olfactory deficit; thus, our results are not due to actual deficit," the study authors wrote. "Hence, anosmia could serve as both a potential marker of virus-induced damage to neuronal tissues and a marker for individuals susceptible to brain damage."
Research is needed into the extent that loss of smell reflects COVID-related brain damage, whether it is a marker of patient susceptibility to different neuropathologic mechanisms, the mechanism of the link between loss of smell and brain changes, and treatment targets, the researchers concluded.