Vibration Selectively Modulates Corticomotor Excitability in Hand Muscles Following Stroke

Background and Purpose. To determine if muscle vibration can elicit selective changes in corticomotor excitability in individuals with chronic stroke. If so, it may prove a useful tool for promoting finger muscle individuation during stroke neurorehabilitation. Methods. The influence of muscle vibration on corticospinal excitability was assessed in six chronic stroke subjects and six age-matched controls. Small amplitude vibration (80 Hz) was applied to the belly of three hand muscles using an electromagnetic vibrator. Motor evoked potentials (MEPs) elicited through transcranial magnetic stimulation were used to quantify corticomotor excitability. Results. Control group results mirrored those reported previously; muscle vibration consistently increased MEPs in the vibrated muscle but decreased excitability in neighboring muscles (p<0.001). Muscle vibration also significantly altered hand muscle corticospinal excitability in all chronic stroke subjects (p<0.001), although the pattern of excitability changes varied greatly across subjects and there were no significant group effects. Nevertheless, reliability measurements across multiple days demonstrated that vibration produced consistent changes within an individual stroke subject (p> 0.2). Conclusions. These results suggest that muscle vibration may be an effective means for selectively altering, and possibly facilitating, hand muscle excitability following stroke but that rehabilitation paradigms incorporating vibration would need to be adjusted on a subject-specific basis.