Objective: This meta-analytical review aims to compare 1) the effects of non-invasive repetitive transcranial magnetic (rTMS) and transcranial electrical stimulation (tES); and 2) identify optimal stimulation parameters to improve motor and cognitive function in Parkinson’s disease (PD).

Background: There is a growing interest in the use of rTMS and tES as a therapeutic tool to improve motor and cognitive function in people with PD. PD is characterised by a state of increased hyperexcitability and impaired cortical inhibitory circuitry, and the application of rTMS and tES may serve to normalise aberrant neurophysiology that underpin motor and cognitive impairments. However there is no evidence to support 1) the role of tES as an alternative to rTMS in treating motor and cognitive symptoms, and 2) optimal stimulation parameters to produce clinical meaningful outcomes.

Methods: Studies were searched through PubMed, EMBASE, Web of Science, Google Scholar, Scopus, Library of Congress and Cochrane library from inception through to 26th February 2016. Random effects meta-analysis was conducted to assess SMD between NBS (rTMS/tES) and control on motor and cognitive function in PD. The Q and I2 statistic assessed heterogeneity amongst the studies.

Results: 24 rTMS and 9 tES studies (n=33) were included. The Physiotherapy Evidence Database (PEDro) and Cochrane Risk of Bias tool showed high internal validity (7.4/10) and a low risk of bias. Overall, both rTMS (SMD=0.394, CI=0.106-0.683, p=0.007) and tES (SMD=0.611, CI=0.188-1.035, p=0.005) improved motor function but not for measures of cognition. Subgroup analyses revealed that higher doses of stimulation (p=0.005), site of stimulation (motor and pre-frontal cortex, p=0.015) and higher stimulation intensities (p=0.003) were the strongest moderators of improved motor function for rTMS. No significant moderators were identified for TES.

Conclusions: This meta-analysis supports the use rTMS and TES to improve motor function in PD. Higher doses and stimulation intensities produce stronger motor improvements, however safety guidelines for the maximal therapeutic dose has not been established. Evidence for cognitive improvements following NBS remains incongruent and future studies employing more comprehensive neuropsychological testing batteries are warranted.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-non-invasive-electrical-and-magnetic-stimulation-to-improve-motor-and-cognitive-function-in-parkinsons-disease-a-meta-analytical-review/