Factor analysis of the reorganization of the brain structures in patients with multiple sclerosis: A positron emission tomography study

The functional reorganization of the human brain cortex and basal ganglia in patients with multiple sclerosis (MS) was studied. Comparative estimation of the local cerebral metabolic rate of glucose (lCM-Rglu) in regions of interest (ROIs) corresponding to the anatomical and functional brain areas was performed. This research was based on the results of positron emission tomography (PET) of healthy volunteers (n = 31) and patients with the relapsing-remitting and progressive types of MS (n = 59 and 39, respectively). Analysis of the factor structure of the obtained patterns of lCMRglu distribution showed similarity to the factor structure of another functional parameter, the regional cerebral blood flow (rCBF); this indicated that the obtained factor solutions mainly reflected the functional organization of the brain. The differences found in the factor structures of the lCMRglu distribution in patients with different types of MS and healthy volunteers allow us to suggest that, despite the normally close anatomical and functional connections between basal ganglia, these structures are functionally separated in MS patients. The bipolarity of the revealed factors possibly reflects different directions of the processes: deafferentation of particular regions caused a relative decrease in the functional activity in the regions directly responsible for the impaired functions, and a compensatory increase in the functional activity in functionally connected regions.