Long-Term effects on cortical excitability and motor recovery induced by repeated muscle vibration in chronic stroke patients

Muscle vibration modifies corticomotor excitability in healthy subjects and reduces muscle tonus in stroke patients. Objective. This study examined whether repeated muscle vibration (rMV) applied over the flexor carpi radialis (FCR) and biceps brachii (BB) can induce long-lasting changes, using transcranial magnetic stimulation (TMS), in patients with chronic stroke. Methods. Thirty hemiparetic patients who offered at least minimal wrist and elbow isometric voluntary contractions were randomly assigned to either an experimental group, which received rMV in addition to physiotherapy (rMV + PT), or a control group that underwent PT alone. The following parameters of the FCR, BB, and extensor digitorum communis (EDC) were measured through TMS before, and 1 hour, 1 week, and 2 weeks after the end of intervention: resting motor threshold (RMT), map area, map volume, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Muscle tonus and motor function were assessed on the same day as TMS. Results. Pre-post analysis revealed a reduction in RMT and an increase in motor map areas occurred in the vibrated muscles only in the rMV + PT group, with an increase in map volumes of all muscles. Moreover, SICI increased in the flexors and decreased in the extensor. These neurophysiological changes lasted for at least 2 weeks after the end of rMV + PT and paralleled the reduction in spasticity and increase in motor function. A significant correlation was found between the degree of spasticity and the amount of intracortical inhibition. Conclusion. rMV with PT may be used as a nonpharmacological intervention in the neurorehabilitation of mild to moderate hemiparesis.