This study aimed to evaluate the effectiveness and comfort of variable-frequency transcutaneous afferent patterned stimulation (TAPS) for tremor relief in patients with essential tremor (ET).

While TAPS of the median and radial nerves at the wrist has been shown to improve ET symptoms [Isaacson 2020], TAPS with burst or pulse frequency variation (BFV, PFV) may better align with natural variations in tremor frequency and provide improved relief [Schuhmayer 2017].

This prospective, double-blinded, 6-week study enrolled 30 ET patients. Patients performed 2 weeks each of (1) TAPS, (2) BFV of ±1.6Hz around their tremor frequency, and (3) PFV between 50-150Hz, in a random order. Each 2-week period included a telemedicine visit, tremor assessments, and a home-use period where patients performed two therapy sessions daily. Primary endpoints were tremor power improvement ratio (TPIR=power_pre/power_post) as measured via accelerometer during postural hold, and changes in Bain & Findley Activities of Daily Living (BF-ADL) assessed from pre- to post-stimulation.

TPIR (2.3, 3.2, 2.8 for TAPS, BFV, PFV, respectively; p=0.29), BF-ADL improvement (3.7, 4.4, 3.4; p=0.26), and comfort (3.2, 3.2, 3.1 on 5-point scale; p=0.89) were similar across the three patterns. Nevertheless, 80% of patients demonstrated greater median TPIR with BFV or PFV over TAPS, of which 25% had statistically significant TPIR improvements (p<0.05). 66% of patients reported greater BF-ADL improvement and 37% of patients reported an increase in comfort with BFV or PFV over TAPS. Selecting patient-specific best stimulation patterns produced 86% greater median TPIR and 57% greater mean ADL improvement than TAPS alone (p<0.0001).

The results show that at a population level, the effectiveness and comfort between the three patterns are comparable. At a per-patient level, the results highlight the heterogeneity within ET and suggest that specific patterns lead to significantly greater tremor relief and may be an avenue to provide better outcomes in ET.