Typical consequences of Covid disease include loss of smell and poor memory. Both can also be seen in the brains of those affected, as researchers now report.
One of the most common symptoms of Covid-19 is the loss of the sense of smell, but memory also seems to suffer in many patients following infection. The causes of the symptoms are not yet well understood. A team of researchers has now looked for abnormalities in the brain of Covid 19 patients following the infection – and found changes in areas related to the processing of smells and memory.
In the journal “Nature” Gwenaëlle Douaud and her colleagues report on the investigations. The team analyzed two brain scans taken regarding 38 months apart from 785 volunteers who also underwent cognitive testing. Of the subjects, 401 had been infected with Sars-CoV-2 during the study period, 15 of whom had to be treated in hospital.
The scans showed characteristic changes in the brain of those who tested positive, which might still be detected following some time: That’s how it was gray matter less thick in areas such as the orbital lobe and parahippocampal gyrus than in people who had not contracted Covid-19. The orbital lobe is involved in memory processes, the parahippocampal gyrus in the memory of smells. In addition, damage to the olfactory cortex, in which scent stimuli are processed, was noticed more frequently.
Mild infection is more likely to cause changes in the brain
Patients scored on cognitive tests following the Corona-Infection worse off on average – unlike patients tested as controls following pneumonia. Apparently, a rather mild infection with the Coronavirus for changes in the brain, the researchers conclude; and this does not only affect the supporting cells of the nasal mucosa, which is considered one of the causes of the acute loss of the sense of smell.
The researchers suspect that it is conceivable that the damage caused by the virus might spread to the central nervous system: for example via the olfactory pathway or via inflammatory processes in the nerve ducts. However, it is also possible that the affected brain areas suddenly receive less input due to the damage to the olfactory sensors and gradually shrink due to a lack of activity.
