A prospective controlled study of a wearable rhythmic vibrotactile device for tremor in Parkinson’s disease

Tremor in Parkinson's disease (PD) does not always respond to dopaminergic medication, therefore new treatment strategies are needed. Preliminary evidence has suggested that manipulation of peripheral afferents may reduce tremor amplitude, but existing research is inconclusive and has not been properly controlled. Here, we explored the effects of peripheral vibrotactile stimulation (ViS) on PD tremor using a within-subjects controlled design. Thirty PD patients with clear tremor were included. ViS (open-loop) was applied to the most affected wrist. Four stimulation conditions were compared: tremor frequency (TF), 1.5*TF, 80 Hz stimulation, and sham. We tested the effect of these stimulation conditions on tremor power (measured with accelerometry) during three contexts: rest tremor, rest tremor during cognitive load, and postural tremor. Entrainment between tremor and stimulation was tested using complex phase-locking value (PLV). There were no significant effects on tremor power when ViS was applied. Stimulation effects did not depend on the context in which tremor occurred. PLVs showed that tremor phase was not influenced by ViS. Open-loop ViS does not modulate PD tremor. This study is one of the first controlled large sample studies to investigate how ViS may influence the objective measures of tremor in PD.