Examining the effects of COVID-19 and prolonged COVID-19 symptoms on structural magnetic resonance imaging measures and cognitive performance

COVID-19 has affected over 775 million people since the beginning of the pandemic. The overall objective of this work was to evaluate the association between COVID-19 and persistent COVID-19 symptoms with structural magnetic resonance imaging (MRI) of the brain and cognitive performance. First, I conducted a systematic review to assess the differences between COVID-19 patients and healthy controls on diffusion MRI measures and brain volumes, in the chronic phase after COVID-19. I found that most of the literature reported widespread lower white matter anisotropy and smaller grey matter volumes in COVID-19 patients compared to controls. Next, in a prospective observational study, I compared quantitative structural MRI measures and cognitive performance between individuals with long-COVID (n = 56) and those who recovered normally from COVID-19 (n = 35). Using diffusion tensor imaging, I found that long-COVID was associated with lower mean diffusivity, but not brain volume or cognitive performance. Finally, I evaluated memory and metamemory performance between individuals with persistent COVID-19-related cognitive symptoms (n = 47) and individuals without persistent cognitive symptoms (n = 87), from the same observational cohort. Memory and metamemory were quantified by applying a signal detection theory framework to a two-alternative forced choice recognition memory task with confidence ratings after every trial. I found no group differences in memory and metamemory performance, but I did find that individuals with persistent cognitive symptoms had higher scores on measures of depression, anxiety, and somatic symptoms than those without persistent cognitive symptoms. Overall, whereas the previous literature suggested that COVID-19 illness was associated with lower white matter anisotropy and smaller grey matter volumes, I found that long-COVID was associated with lower MD, indicating higher white matter anisotropy, and that persistent COVID-19 symptoms were not associated with objective or subjective cognitive abilities. Future research is needed to examine the longitudinal trajectories of persistent COVID-19 symptoms, structural MRI, and cognitive performance.