Objective: To investigate the changes of subcortical gray matter volume and cortical thickness, andexplorethe correlations between regional abnormalities of cortical thickness and cognitive impairment and the effect of modified Bushenyisui decoction ( BSYSD) on the cognitive function of multiple sclerosis (MS).

Methods: This prospective study was approved by the institutional review board. 92 subjects were recruited, including 46 relapsing-remitting multiple sclerosis (RRMS) patients and 46 healthy controls (HC). Of the 46 patients, 22 patients experienced the treatment of BSYSD for half a year. A conventional three-dimensional T1-weighted sequence were acquired for all participants on a 3.0 tesla magnetic resonance system. Basic information, detailed cognitive scales Montreal Cognitive Assessment (MoCA), symbol digit modalities test (SDMT), immediate memory, delayed recall, and long-term recognition were evaluated. Subcortical gray matter volume and cortical thickness weremeasured by FreeSurfer. The correlations between cortical thickness which MS patients showed reduced with respect to HC and cognitive scales wereanalyzed by Pearson correlation in RRMS patients. The influence of modified BSYSD on MS patients' cognition was analyzed by paired T Test.

Results: MoCA, immediate memory, delayed recall, and long-term delayed recognition in RRMS were significantly decreased than those of HC. Gray matter atrophy measured by FreeSurfer showed mainly in thalamus and hippocampus of RRMS patients. Compared with HC, the cortical thickness of several regions in frontal lobe, parietal lobe, temporal lobe, hippocampal, cingulate gyrus, and fusiform gyrus of RRMS patients were decreased with significant difference. The regions of cortical thickness thinning related to MoCA, immediate memory, delayed recall, and long-term delayed recognition were temporal lobe and fusiform gyrus. Modified BSYSD could improve MoCA, SDMT, immediate memory, delayed recall, and long-term delayed recognition of MS patients, and it could promote the recovery of cognitive function in MS patients.

Conclusions: Gray matter atrophy and cortical thickness thinning were validated in RRMS. Cortical thickness thinning of temporal lobe and fusiform gyrus strongly related to cognitive deficits in RRMS. The modified BSYSD could promote the recovery of cognitive function in MS.