Real-World Evidence of Transcutaneous Afferent Patterned Stimulation for Essential Tremor

Abstract

Background: Transcutaneous afferent patterned stimulation (TAPS) is a prescription, wrist-worn device-delivered, non-invasive neuromodulation therapy for treatment of hand tremor in patients with essential tremor (ET). This retrospective post-market surveillance study evaluated real-world effectiveness of TAPS from patients using therapy on-demand for at least 90 days between August 2019 through June 2021.

Methods: Demographics were summarized from TAPS prescriptions received from the patient's healthcare provider. Therapy usage and effectiveness were analyzed from device logs, which included tremor measurements from onboard motion sensors. Tremor history and patient-reported outcomes were assessed from a voluntary survey.

Results: A total of 321 patients (average age 71 years, 32% female) met the criteria for this analysis, 216 of whom had tremor measurements available for analysis and 69 of whom completed the survey. Total usage period ranged from 90 to 663 days, with 28% of patients using the device for over one year. Patients used therapy 5.4 ± 4.5 (mean ± 1 standard deviation) times per week. TAPS reduced tremor power by 71% (geometric mean) across all sessions, with 59% of patients experiencing >50% tremor reduction after their sessions. Eighty-four percent (84%) of patients who returned the voluntary survey reported improvement in at least one of eating, drinking, or writing, and 65% of patients reported improvement in quality of life. Self-reported device-related safety complaints were consistent with adverse events in prior clinical trials.

Discussion: Real-world evidence is consistent with prior clinical trials and confirms TAPS provides safe and effective tremor control for many patients with ET. Future work assessing multi-year safety and effectiveness would be valuable to extend these data.

Keywords: essential tremor; peripheral neuromodulation; real-world evidence; remote sensing; transcutaneous afferent patterned stimulation.

Figure 1

TAPS device and data. (A) The prescription wrist-worn TAPS device was shipped directly to patients and was comprised of a stimulator, band containing TAPS-delivering electrodes, and cloud-connected base station that charged the device and streamed device logs to a centralized database. A user guide included with the device contained instructions for patients on setup, calibration, and usage of TAPS therapy. (B) Study data were derived from the healthcare provider-completed prescription form, device logs automatically generated during therapy home use, and a voluntary survey sent to patients after 90 days of therapy use. (C) For the first 40 sessions and every 7^th session thereafter, the device prompted patients to perform a twenty-second postural hold before and after stimulation and prompted patients to self-rate their tremor improvement after stimulation. Tremor power, computed from postural hold accelerometry data of clean signal quality, was used to characterize tremor severity. Additionally, measurements were classified into patient-specific bands of High, Medium, and Low based on pre-stimulation tremor power.

Figure 2

Effectiveness assessed through longitudinal home-use data. (A) TAPS effectiveness was summarized across all, and High/Medium/Low session groups. Error bars represent geometric mean ×/÷ 1 geometric standard error (equivalent in range to mean ± 1 standard error of log-transformed data). (B) Across all sessions, cumulative distribution of per-patient tremor reductions indicated clinically meaningful improvement for most patients. (C) Patient self-ratings of post-TAPS improvement were similar in distribution to motion-sensor ratings of post-TAPS improvement. (D) Frequency of post-stimulation tremor severity categories were broken down for each pre-stimulation severity group. TAPS improved tremor severity category for most sessions that started High or Medium, and maintained Low tremor for sessions that started Low.

Figure 3

Patient-reported outcomes. (A) Respondents rated effect of TAPS on various activities of daily living, with 84% of respondents indicating improvement in at least one of eating, drinking, or writing, and 65% of respondents indicating improvements in overall quality of life. (B) Survey respondents generally preferred TAPS over medication or surgical management of tremor.