Functional and structural connectivity abnormalities of default mode network in relapsing-remitting multiple sclerosis: a study combining functional MRI and diffusion tensor imaging

Objective: To investigate the functional and structural changes of connectivity of default mode network (DMN) in relapsing-remitting multiple sclerosis (RRMS) by functional MRI (fMRI) and diffusion tensor imaging (DTI) and to study the relationship between them. Methods: Twenty-seven RRMS patients (clinically diagnosed as RRMS) and 27 healthy volunteers (matched to the patients in age and gender) were selected to participate in this study. All the subjects underwent 3.0 T MR scanning. Softwares such as DPARSF, MICA, TrackVis were used for data post-processing. Medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) of DMN were chosen as ROIs, and functional and structural changes of DMN and the relationship between them were analyzed. Values of r reflecting the functional connectivity and fractional anisotropy (FA) of two groups were obtained. Then statistical analysis was performed by using student t test and Pearson correlation analysis. Results: The DMN space pattern of the RRMS patients was mostly identical to that of controls, but with specific difference in the connectivity strength with respect to that of controls. Particularly, the patient group showed increased DMN connectivity in the mPFC, but decreased connectivity in the inferior parietal lobule(IPL) and PCC. Compared with controls, the r value (0.695 ±0.151 vs. (17% ± 0.085), FA value(0.261 ± 0.012 vs. 0.285 ± 0.017) between mPFC and PCC in RRMS patients were decreased (t = -3.020, -6.206, P < 0.05 ). In addition, functional connectivity (r value) was found to correlate with structural connectivity (FA value) between the PCC and mPFC(r = 0.704, 0.735, P < 0.01). The number of MS lesion, had no correlation with r value or FA value (F > 0.05). Conclusions: The functional connectivity and structural connectivity of DMN change in RRMS patients. The functional connectivity and structural connectivity between mPFC and PCC are both decreased in RRMS patients compared with the controls. The injury of structural connectivity may be the structural basis of the decrease of functional connectivity. (authors)