COVID-19 can lead to various complications, including neurological complications — sleep disorders, memory and cognitive impairment, and others, as well as post-COVID depression. TSU scientists decided to study whether this is because of changes in the quality and quantity of myelin — a substance that protects the nerve fibers from injury and improves the speed and transmission of electrical nerve signals. The first results showed in which brain structures the nerve sheaths are disrupted. The project is supported by a grant from the Russian National Foundation.
“Several groups of people were recruited for the study at clinical institutions in Tomsk,” said Daria Kamaeva, a project implementer and member of the Laboratory of Neurobiology at the TSU Research Institute of Biology and Biophysics. “The experiment included people who did not have COVID-19 or were asymptomatic; patients whose diagnosis was confirmed by a test, having a mild or moderately severe COVID; and patients who had a severe COVID, including those who required ventilator support.”
The goal was to study the changes of myelin sheaths of nerve fibers in the brain and the relation of these changes to the development of neurological and cognitive complications or post-COVID depression. In order to properly verify this disease, TSU invited psychiatrists from the Mental Health of Tomsk National Research Center for Medicine as well as neurologists and clinical psychologists from Siberian State Medical University participate in the project.
A noninvasive method developed by scientists from the Laboratory of Neurobiology under the supervision of Vasily Yarnykh, a professor at TSU and at the University of Washington, was used to assess myelin. The diagnostic technology is based on brain myelin mapping and enables analyzing fiber sheaths in living subjects. Using special mathematical processing of MRI data, scientists obtain brain images that reflect the amount of myelin similar to the way terrain is reproduced on geographical maps.
Patients with post-COVID depression have the greatest reduction, 3-4% myelin density, compared to healthy individuals, and this was recorded in the hippocampus and amygdala, which are essential in the formation of emotions and memory.
“Myelin damage in these structures is more severe among people with post-COVID depression than in those who suffered from COVID-19 and acquired neurological complications, but not depression,” Daria Kamaeva highlighted.
Furthermore, according to the researchers, the severity of the disease is not a prognostic factor for a particular type of complication. Neurological, cognitive, or affective complications often occur among people who had mild COVID-19.