Early Outcomes with a Flexible ECAP Based Closed Loop Using Multiplexed Spinal Cord Stimulation Waveforms-Single-arm Study with In-clinic Randomized Crossover Testing.

Background: Spinal cord stimulation (SCS) systems that deliver fixed amplitudes expose target tissue to varying electrical fields due to the changing lead-to-cord distance accompanying postural shifts and other body movements. Inconsistent stimulation results in periods of overstimulation or under-stimulation perceived by patients as discomfort or potentially inadequate pain relief. CL-SCS may be applied to provide a comfortable level of perception down to imperceptible stimulation, commonly preferred in higher frequency and multiplexed programming. Here we report outcomes from a study evaluating a closed-loop (CL) SCS system that uses spinal evoked compound action potentials to adjust stimulation.

Methods: This ongoing study combines the evaluation of pain-related outcomes (for ≤24 months) with in-clinic randomized, crossover testing of CL performance.

Results: Sixty subjects have been implanted with the CL-SCS system and 54 subjects have completed the 3-month visit. Sixty percent preferred below-perception waveforms for therapy during at-home use. The study successfully met its primary endpoint with 89.3% of subjects in the Primary Analysis Set (n = 28) reporting reduction in overstimulation with CL-SCS relative to OL-SCS at 1-month (p < 0.001; binomial exact test); at 3-months, 86% of subjects with low-back/leg pain (n = 51) and all three with upper limb pain reported ≥50% reduction in pain, relative to baseline.

Conclusions: The data presented here support the performance of a flexible CL-SCS system that can deliver a variety of waveforms, with amplitude programmed to patient comfort and automatically adjusted up to 50 times per second, to improve the consistency of therapy experience.