Exploring The Neural Network Mechanism Of RTMS Modulating Upper Limb Motor Function Rehabilitation After Stroke Based On Graph Theory Analysis

Objective:To clarify the role of low-frequency repetitive transcranial magnetic stimulation(rTMS)in modulating the topological structure of functional networks,to reveal the neural network mechanism of rTMS in regulating upper limb motor function rehabilitation after stroke,and to provide a theoretical basis for the clinical treatment of rTMS.Methods:Thirty-six patients with upper limb motor dysfunction after stroke were recruited and randomly divided into 18 patients each in the rTMS and control groups according to a 1:1ratio.The rTMS group was treated with low-frequency rTMS and conventional rehabilitation,and the control group was treated with sham rTMS and conventional rehabilitation once a day,5 times a week for 8 weeks.Patients in both groups underwent Fugl-Meyer Motor Function Scale for Upper Extremity(FMA-UE),Modified Barthel Index scale(MBI)evaluation and resting-state functional MRI scan before and 8 weeks after the intervention.The AAL standard brain partitioning template was used to construct a whole-brain functional network for patients with post-stroke motor dysfunction.Based on graph theory analysis,global and nodal topological attributes of the functional network were calculated before and after the intervention in both groups.The changes in global and nodal topological attributes within and between the two groups before and after the intervention were analyzed and their correlation with the improvement of clinical assessment scale scores.Results:Five patients in the control group were dislodged during the study period.Ultimately,18 cases in the rTMS group and 13 cases in the control group were included for analysis.1.After 8 weeks of intervention,the FMA-UE scores and MBI scores of both groups were significantly higher than those before the intervention(P<0.05),and the FMA-UE and MBI scores of the rTMS group were significantly higher than those of the control group(P<0.05).2.The results of the global topological properties of the brain network suggested that the whole brain functional network had small-world network characteristics before and after the intervention in both stroke groups within a sparsity threshold of 0.05-0.50.The 8-week low-frequency rTMS intervention significantly increased the small-world properties in stroke patients compared with the pre-intervention period(P=0.002).Further analysis showed that the network metrics that constitute the small-world properties: the standardized clustering coefficient increased significantly and the standardized characteristic path length decreased significantly after the rTMS intervention(P<0.05).Compared to the control group,global efficiency significantly increased(P=0.014)and characteristic path length significantly decreased(P=0.003)after rTMS intervention,but no significant change in clustering coefficients was observed(P>0.05).3.The results of nodal topological properties of brain networks showed that the nodal degree and nodal efficiency of brain regions in the Sensorimotor Network(precentral gyrus,supplementary motor area,postcentral gyrus,paracentral lobule,caudate nucleus,pallidum,amygdala,superior occipital gyrus,rolandic operculum)and Default Mode Network(precuneus,cuneus,superior parietal gyrus,inferior parietal marginal angular gyrus)were changed in stroke patients after the rTMS group compared with before the intervention(P<0.05).Compared with the control group,the nodal degree of the left precuneus was significantly reduced and the nodal degree of the right caudate nucleus was significantly increased after low-frequency rTMS intervention;the nodal efficiency of the left precentral gyrus,left supplementary motor area,left postcentral gyrus and left paracentral lobule were significantly reduced(P<0.05).4.The correlation analysis showed that the characteristic path length was negatively correlated with FMA-UE score(r=-0.841,P<0.001),and the global efficiency was positively correlated with FMA-UE score(r=0.784,P<0.001).Conclusion:Low-frequency rTMS may increase the small-world properties of functional networks in stroke patients,enhance global information processing efficiency,and modulate the topological properties of nodes in sensorimotor-related brain regions,so as to help restore the balance between functional integration and dissociation in the brain and reshape the network toward a more optimal topology,thereby facilitating upper limb motor function recovery.