Reduced Network Dynamics on Functional MRI Signals Cognitive Impairment in Multiple Sclerosis

Background: Previous studies have demonstrated extensive functional network disturbances in patients with multiple sclerosis (MS), showing a less efficient brain network. Recent studies indicate that the dynamic properties of the brain network show a strong correlation with cognitive function. Purpose: To investigate network dynamics on functional MRI in cognitively impaired patients with MS. Materials and Methods: In secondary analysis of prospectively acquired data, with imaging performed between 2008 and 2012, differences in regional functional network dynamics ( ie, eigenvector centrality dynamics) between cognitively impaired and cognitively preserved participants with MS were investigated. Functional network dynamics were computed on images from functional MRI (3 T) by using a sliding- window approach. Cognitively impaired and preserved groups were compared by using a clusterwise permutation-based method. Results: The study included 96 healthy control subjects and 332 participants with MS ( including 226 women and 106 men;median age, 48.1 years +/- 11.0). Among the 332 participants with MS, 87 were cognitively impaired and 180 had preserved cognitive function; mildly impaired patients ( n = 65) were excluded. The cognitively impaired group included a higher proportion of men compared with the cognitively preserved group ( 35 of 87 [40%] vs 48 of 180 [27%], respectively; P =.02) and had a higher mean age ( 51.1 years vs 46.3 years, respectively; P<.01). The clusterwise permutation- based comparison at P less than .05 showed reduced centrality dynamics in default- mode, frontoparietal, and visual network regions on functional MRI in cognitively impaired participants versus cognitively preserved participants. A subsequent correlation and hierarchical clustering analysis revealed that the default- mode and visual networks normally demonstrate negatively correlated fluctuations in functional importance( r = -0.23 in healthy control subjects), with an almost complete loss of this negative correlation in cognitively impaired participants compared with cognitively preserved participants (r = -0.04 vs r = -0.14; corrected P =.02). Conclusion: As shown on functional MRI, cognitively impaired patients with multiple sclerosis not only demonstrate reduced dynamics in default- mode, frontoparietal, and visual networks, but also show a loss of interplay between default- mode and visual networks. (C) RSNA, 2019