Structural Brain Alterations in Individuals Post-COVID-19: A Systematic Review

Although COVID-19 is primarily considered a respiratory pathology, it has been observed to impact other bodily systems, including the nervous system. While several studies have investigated anatomical changes in brain structures, such as volume or thickness post-COVID-19, there are no comprehensive reviews of these changes using imaging techniques for a holistic understanding. The aim of this study was to systematically analyze the literature on brain changes observed through neuroimaging after COVID-19. We conducted a systematic review according to PRISMA guidelines using Web of Science, Scopus, Medline, Pubmed, Sciencedirect, and LitCOVID. We selected studies that included adult patients during or after COVID-19 development, a control group or pre-infection images, and morphometric measurements using neuroimaging. We used the MSQ scale to extract information on sample characteristics, measured anatomical structures, imaging technique, main results, and methodological quality for each study. Out of 1126 identified articles, we included 19 in the review, encompassing 1155 cases and 1284 controls. The results of these studies indicated a lower volume of the olfactory bulb and variable increases or decreases in cortical and limbic structures' volumes and thicknesses. Studies suggest that brain changes occur post-COVID-19, primarily characterized by a smaller olfactory bulb. Additionally, there may be variations in cortical and limbic volumes and thicknesses due to inflammation or neuroplasticity, but these findings are not definitive. These differences may be attributed to methodological, geographical, and temporal variations between studies. Thus, additional studies are required to provide a more comprehensive and quantitative view of the evidence.