Objective: To assess the safety, tolerability, and efficacy of a wrist-worn vibratory stimulator by comparing two active paradigms (Pulsed (AP), Continuous (AC)) to Sham in reducing tremor severity in essential tremor (ET).

Background: ET is a prevalent neurological disorder characterized by involuntary rhythmic tremors primarily affecting the upper limbs, impacting daily activities. Current treatments are limited and there is a need for novel alternatives.

Method: This double-blind, randomized, sham-controlled crossover trial enrolled participants with moderate-to-severe ET (≥2 on The Essential Tremor Rating Assessment Scale [TETRAS] items 4, 6, or 8; ≥3 on Bain & Findley Activities of Daily Living [BF-ADL] items 2, 4, 17, or 21). The AP (low-amplitude) and AC (high-amplitude) stimulations were delivered over ~15 minutes daily and compared to Sham (no-stimulation). Evaluations included self-rated BF-ADL and clinician-rated TETRAS before and during therapy. Primary outcomes were safety and tolerability. Secondary efficacy outcomes were changes in BF-ADL and in TETRAS scores after 3-5 days of usage (cumulative), and responder rates defined by pre-specified improvement thresholds of ≥1 and ≥2 points for BF-ADL (max. score = 16) and ≥1.5 and ≥2.5 points for TETRAS (max. score = 20). Statistical tests were performed on mixed-model estimates adjusting for baseline, randomization, and sequence (fixed effects), with participants as a random effect.

Results: 95% of the 47 randomized participants rated the stimulator as comfortable, and only 11% reported mild/moderate, non-serious, and self-resolving adverse events (AEs). Active stimulation produced significant BF-ADL improvements (Pulsed: 1.93±0.56; Continuous: 1.32±0.57) [Figure 1]. AP significantly outperformed Sham in BF-ADL and TETRAS (p<0.01), but AC outperformed Sham in BF-ADL only (p<0.05) [Figure 2]. For a ≥1-point improvement in BF-ADL, participants were nearly twice as likely to improve with AP (71%) or AC (74%) as with Sham (48%) (p<0.05) [Figure 3]. TETRAS responder rate for ≥1.5-points was higher with AP (50%) vs. Sham (34%) but the difference was not statistically significant (p=0.15) [Figure 4]. Participants’ perception of vibratory stimulation did not predict improvement.

Conclusion: The stimulator was safe, well-tolerated, and reduced tremor severity. AP stimulation provided the greatest benefit over Sham.

Figure 1

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MDS Abstracts - https://www.mdsabstracts.org/abstract/safety-and-efficacy-of-a-wrist-worn-vibratory-stimulator-for-upper-limb-tremor-reduction-in-essential-tremor-ultre-a-randomized-controlled-trial/