Longitudinal analysis of anatomical and diffusion changes by magnetic resonance imaging in patients with multiple sclerosis.

Abstract

Multiple Sclerosis (MS) is a neurodegenerative disease whose main affected area is the central nervous system. The regions most affected by this disease are usually the motor and sensory regions. The study of the effects of MS has become increasingly relevant given that the prevalence of this pathology has been increasing in recent decades. Based on this, this work aimed to search for a relationship between cortical anatomical changes and changes in brain structural connectivity in subjects with MS. During this research, the study of changes was divided into two aspects: cortical anatomical changes and changes in brain structural connectivity. First, the anatomical study was applied over two databases. The first had only anatomical images, where each subject has 3 time points, separately by 12 month each one. The second has anatomical and diffusion data, where each subject has 2 time points, separated by 3 years. The software for the longitudinal analysis was FreeSurfer. Then, to determine the anatomical changes, we used the generalized linear model (GLM). On the other hand, diffusion magnetic resonance imaging (dMRI) was used to study changes in brain structural connectivity. This study was carried out by analyzing the dMRI metrics of the brain fibers tracts. These metrics were obtained from the generalized q-sampling imaging (GQI) model. To examine the changes in the diffusion metrics obtained we employed a generalized equation model (GEE). Finally, we determined the relationship between the regions presenting significant changes at the cortical level and the brain fibers showing substantial differences across time. The regions that suffered significant anatomical changes at the cortical level are the pre and post-central regions and the superior temporal region, among others. In addition, there were changes in the parietal and occipital region, but these were much smaller compared to the previous ones. Concerning brain structural connectivity, the brain fibers that presented the significant changes are associated with the cortical regions highlighted in the anatomical analysis. From these results, the short brain fiber connecting the superior frontal and the pre-central region of the left hemisphere stands out since it was the only one that showed significant differences in all dMRI metrics. The values of the dMRI metrics did not match with the literature, our interpretation was that the treatments given to the subjects might be effective. We arrived at this conclusion by analyzing the relationship between the change in the Expanded Disability Status Scale (EDSS) value and the dMRI metrics. The analysis revealed there was an improvement in the EDSS value. However, due to the size of the database, it’s recommended that other kind of analyses be conducted to further support this conclusion.