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

Background: 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.