Abstract
Objective: We aimed to examine the effects of repetitive peripheral nerve magnetic stimulation (rPNMS) on the excitability of the contralateral motor cortex and motor function of the upper limb in healthy subjects.Methods: Forty-six healthy subjects were randomly assigned to either a repetitive peripheral nerve magnetic stimulation group (n = 23) or a sham group (n = 23). The repetitive peripheral nerve magnetic stimulation group received stimulation using magnetic pulses at 20 Hz, which were applied on the median nerve of the non-dominant hand, whereas the sham group underwent the same protocol without the stimulation output. The primary outcome was contralateral transcranial magnetic stimulation (TMS)-induced corticomotor excitability for the abductor pollicis brevis of the stimulated hand in terms of resting motor threshold (rMT), the slope of recruitment curve, and peak amplitude of motor evoked potential (MEP), which were measured at baseline and immediately after each session. The secondary outcomes were motor hand function including dexterity and grip strength of the non-dominant hand assessed at baseline, immediately after stimulation, and 24 h post-stimulation.Results: Compared with the sham stimulation, repetitive peripheral nerve magnetic stimulation increased the peak motor evoked potential amplitude immediately after the intervention. The repetitive peripheral nerve magnetic stimulation also increased the slope of the recruitment curve immediately after intervention and enhanced hand dexterity after 24 h. However, the between-group difference for the changes was not significant. The significant changes in hand dexterity and peak amplitude of motor evoked potential after repetitive peripheral nerve magnetic stimulation were associated with their baseline value.Conclusions: Repetitive peripheral nerve magnetic stimulation may modulate the corticomotor excitability together with a possible lasting improvement in hand dexterity, indicating that it might be helpful for clinical rehabilitation.
Highlights
Repetitive peripheral magnetic stimulation is a safe, non-invasive treatment method for motor impairment and pain in people with neural or musculoskeletal disorders because it can penetrate deeper structures with painless stimulation and can produce muscle contractions and sensory afferents (Beaulieu and Schneider, 2015)
The statistical analysis of all outcomes at baseline with an independent t-test showed that there were no significant differences between the two groups (p > 0.05). repetitive peripheral nerve magnetic stimulation (rPNMS) resulted in a significant increase in peak motor evoked potential (MEP) amplitude than the sham stimulation
Post hoc comparison showed a significant difference in peak MEP amplitude in the rPNMS group (p = 0.002) but not in the sham group (p = 0.762) at post-stimulation compared with baseline (Figure 3)
Summary
Repetitive peripheral magnetic stimulation (rPMS) is a safe, non-invasive treatment method for motor impairment and pain in people with neural or musculoskeletal disorders because it can penetrate deeper structures with painless stimulation and can produce muscle contractions and sensory afferents (Beaulieu and Schneider, 2015). Using neuroimaging tools and transcranial magnetic stimulation (TMS) in stroke, researchers have shown that rPMS on paretic limb muscle can induce the activation of the frontoparietal loops (Struppler et al, 2007; Gallasch et al, 2015) and increase corticomotor excitability (Gallasch et al, 2015; Beaulieu et al, 2017) in the lesioned hemisphere. Such neurophysiological changes can explain the improvement of motor function after rPMS. Understanding the corticomotor effects of rPNMS in healthy subjects might aid in the use of rPNMS as an evidence-based treatment for clinical rehabilitation
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