Possible Volumetric Changes in the Hippocampus and Olfactory Bulbs After COVID-19: A Stereological MRI Study

COVID-19 affects the olfactory system and the hippocampus, leading to severe olfactory and cognitive impairments. This study aimed to quantify volumetric changes in the olfactory bulbs and hippocampus in patients with COVID-19, and to investigate these differences in relation to loss of smell and taste. This stereological MRI study included 60 COVID-19 (+) participants and 54 non-COVID-19 participants. Using OsiriX software, the volumes of the olfactory bulb and hippocampus were manually measured from 3T MRI images. Compared with controls, participants with loss of smell and taste had smaller olfactory bulb volumes. This decrease was especially noticeable in the left olfactory bulb of female patients. Furthermore, the right hippocampal volume in male patients with loss of smell and taste was significantly decreased. These findings suggest that atrophy of the olfactory bulb and hippocampus may be specific to certain regions and sexes following SARS-CoV-2 infection. Stereological MRI assessments can effectively identify these changes. Prospective longitudinal studies are needed to determine the clinical significance of these changes and their impact on patient management.