Objective: To develop and clinically validate a responsive deep brain stimulation (R-DBS) paradigm – meaning stimulation would only be delivered when needed – driven by electromyography (EMG).

Background: DBS is an established therapy for patients with essential tremor (ET); however, it is a continuous paradigm (continuous DBS: cDBS) causing shortcomings to the therapeutic window of DBS, the battery life of the implantable neurostimulator (INS), and quality of life for ET patients.

Method: Ten ET patients underwent R-DBS using Nexus-D, a Medtronic telemetry wand that acts as a direct conduit to the INS by modulating stimulation voltage in real-time. Two different R-DBS paradigms were tested: one driven by one EMG (single-sensor) and another driven by two or more EMGs (multi-sensor). The feature controlling stimulation was the power in the participant’s tremor frequency band. Primary outcomes were the Fahn-Tolosa-Marin tremor rating scale (TRS)[1], the total electrical energy delivered (TEED)[2], and objective measures of tremor using hand acceleration contralateral to the implanted lead between R-DBS and cDBS.

Results: Across patients and visits, both R-DBS paradigms had similar outcomes on total and contralateral TRS compared to cDBS (single-sensor R-DBS vs cDBS on contralateral TRS: 3.77±1.99 vs 3.81±2.25; total TRS: 15.15±5.50 vs 14.62±6.34 | multi-sensor R-DBS vs cDBS on contralateral TRS: 3.35±2.00 vs 3.18 vs 2.21; total TRS: 13.71±4.71 vs 13.00±4.29). Furthermore, contralateral hand acceleration in the participant’s tremor frequency band during the TRS was similar across R-DBS paradigms and cDBS (single-sensor R-DBS vs cDBS: 0.135±0.035 vs 0.142±0.038 | multi-sensor R-DBS vs cDBS: 0.142±0.051 vs 0.144±0.040). All measures (total TRS, contralateral TRS, and hand acceleration) were proven statistically equivalent using a two one-sided test for equivalence. Finally, single-sensor R-DBS TEED savings were 59.12±12.90%; whereas multi-sensor R-DBS resulted in 51.29±13.32% TEED savings. Both distributions were significantly different from 0, which is the expected energy savings with cDBS.

Conclusion: Wearable sensor-driven R-DBS provides a statistically equivalent clinical benefit compared to cDBS, while delivering less total electrical energy. Future studies should aim to assess the adverse effects of cDBS to R-DBS in addition to testing R-DBS in naturalistic settings.

References: [1] S. Fahn, E. Tolosa, and C. Marin, Clinical rating scale for tremor. 1988. [2] A. M. Koss et al., “Calculating total electrical energy delivered by deep brain stimulation systems,” Annals of Neurology. 2005.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/wearable-sensor-driven-responsive-deep-brain-stimulation-for-essential-tremor/