The Sense of Smell atlas: from creation to the first application for investigating COVID-19-related anosmia with quantitative multimodal-MRI

Motivation: The versatility of MRI allows to study in-vivo brain microstructure, neuroinflammation, iron and myelin properties to understand mechanisms of anosmia. Goal(s): Create an olfactory atlas and analyse 15 quantitative multimodal-MRI metrics to detect pathophysiological changes in COVID-19 related anosmia participants. Approach: The atlas was created starting from anosmia-involved grey matter regions and using tractography to reconstruct anatomically realistic tracts. Region and voxel-wise analyses were applied within the atlas to compare COVID-19 persistent anosmia (COVID-P) with recovered (COVID-R) and healthy controls. Results: COVID-P subjects still present neuroinflammation and axonal degeneration, whereas COVID-R subjects present active compensatory mechanisms including possible remyelination. Impact: For the first time, a comprehensive olfactory circuit atlas with regions and anatomically realistic tracts is presented. This atlas combined with analysis at regions and voxel-wise level on multimodal-MRI maps, lays the foundation for understanding the mechanisms of COVID-19-related anosmia.