Effects of repetitive peripheral magnetic stimulation for the upper limb after stroke: Meta-analysis of randomized controlled trials

Introduction: Repetitive peripheral magnetic stimulation (rPMS) can stimulate profound neuro-muscular tissues painlessly to evoke action potentials in motor axons and induce muscle contraction for treating neurological conditions. It has been increasingly used in stroke rehabil-itation as an easy-to-administer approach for therapeutic neuromodulation. Objective: We performed this meta-analysis of randomized controlled trials to systematically evaluate the effects of rPMS for the upper limb in patients with stroke, including motor impair-ment, muscle spasticity, muscle strength, and activity limitation outcomes. Methods: The meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. PubMed, EMBASE, Web of Science, Cochrane Library, and Physiotherapy Evidence Database (PEDro) were searched for articles published before June 2022. Forest plots were employed to estimate the pooled results of the included studies, and the I2 statistical analysis was used to identify the source of heterogeneity. Publication bias was examined by Egger's regression tests or visual inspection of the funnel plots. Results: The database searches yielded 1052 potential eligible literature; of them, five randomized controlled trials met the eligible criteria, involving a total of 188 participants. Patients in the rPMS group showed better improvement in motor impairment as measured by the FM-UE (MD: 5.39 [95% CI, 4.26 to 6.52]; P < 0.001; I2 = 0%) compared with the control group. Among the secondary outcomes, no difference was found in the improvement of muscle spasticity (SMD: 0.36 [95% CI,-0.05 to 0.77]; P = 0.08; I2 = 41%). There was a significant difference in the proximal (SMD: 0.58 [95% CI, 0.10 to 1.06]; P = 0.02; I2 = 0%) but not the distal muscle strength (SMD: 1.18 [95% CI,-1.00 to 3.36]; P = 0.29; I2 = 93%). Moreover, the activity limitation outcomes were significantly improved with rPMS intervention (SMD: 0.59 [95% CI, 0.08 to 1.10]; P = 0.02; I2 = 0%). Conclusion: This meta-analysis showed that rPMS might improve upper limb motor impairment, proximal muscle strength, and activity limitation outcomes but not muscle spasticity and distal strength in patients after stroke. Due to the limited number of studies, further randomized clinical trials are still warranted for more accurate interpretation and clinical recommendation.