Effect of Repetitive Transcranial Magnetic Stimulation on Physical Function and Motor Signs in Parkinson's Disease: A Systematic Review and Meta-Analysis

Background The short-term beneficial effects of repetitive transcranial magnetic stimulation (rTMS) on motor signs in Parkinson's disease (PD) have been addressed by previous meta-analyses while its long-term effects remain undetermined. Although deterioration of walking and upper limb function greatly affects the participation in activities and quality of life of PD sufferers, the effect of rTMS thereon has not been systematically studied. Objective This systematic review aimed to examine the efficacy of rTMS on improving physical function and motor signs over the short- and long-terms in people with PD. Methods Five electronic databases were systematically searched for English language full-text articles using relevant search terms. Only randomized placebo-controlled trials investigating the effects of rTMS in PD were considered. The primary outcomes were walking performance, upper limb function, and unified Parkinson's disease rating scale (UPDRS) section III. Trials with similar outcomes were pooled by calculating Hedges' g using random-effects model. Results Twenty-two trials comprising 555 people with PD were included. Pooled estimates of effect of rTMS indicated significantly improved short-term upper limb function (Hedges' g, 0.40, P = 0.007), short-term (Hedges' g, 0.61, P = 0.03) and long-term walking performance (Hedges' g, 0.89, P = 0.03), short-term (Hedges' g, 0.31, P = 0.003) and long-term (Hedges' g, 0.54, P = 0.003) UPDRS III scores. Subgroup analyses suggest a more prominent effect for M1 stimulation. Meta-regression revealed that a greater number of total stimulation pulses were associated with more UPDRS III improvements over the long-term. Conclusion The pooled evidence suggests that rTMS improves upper limb function in the short-term, walking performance and UPDRS III in the short- and long-terms in PD sufferers. Further studies are required to develop optimal rTMS therapeutic protocols for PD.