Long-term micro-structure and cerebral blood flow changes in patients recovered from COVID-19 without neurological manifestations

The coronavirus disease 2019 (COVID-19) rapidly progressed to a global pandemic. Although patients totally recover from COVID-19 pneumonia, long-term effects on the brain still need to be explored. Here, two subtypes (mild type-MG and severe type-SG) with no specific neurological manifestations at the acute stage and no obvious lesions on the conventional MRI three months after discharge were recruited. Changes in gray matter morphometry, cerebral blood flow (CBF) and white matter (WM) microstructure were investigated using MRI. The relationship between brain imaging measurements and inflammation markers were further analyzed. Compared with healthy controls, the decrease in cortical thickness/CBF, and the changes in WM microstructure were observed to be more severe in the SG than MG, especially in the frontal and limbic systems. Furthermore, changes in brain microstructure, CBF and tracts parameters were significantly correlated with inflammatory markers. The indirect injury related to inflammatory storm may damage the brain, that led to these interesting observations. There are also other likely potential causes, such as hypoxemia and dysfunction of vascular endothelium, et al. The abnormalities in these brain areas need to be monitored in the process of complete recovery, which could help clinicians to understand the potential neurological sequelae of COVID-19. Key words: COVID-19; Brain MRI; Recovered patients; Inflammatory markers; Cortical thickness; Cerebral blood flow; microstructure; gray matter; white matter; subcortical nucle