Background and Aims:
Spinal cord stimulation (SCS) is a well-established treatment for chronic pain. Advancements in SCS systems have focused on eliminating paresthesias, but long-term success rates remain suboptimal. Variability in spinal cord (SC) activation with open-loop (OL) systems results in unpredictable inhibition of pain processing pathways and may limit the efficacy of SCS. We report the first randomized, double-blind, pivotal study of SCS and the first therapy to measure real-time in vivo SC neurophysiology using Evoked Compound Action Potentials (ECAPs). This study provides comparative efficacy and safety of closed-loop (CL) feedback stimulation compared with OL stimulation.

Methods:
134 subjects were randomized into OL or CL. Subjects and the clinical staff were blinded to the treatment assignment. A pain assessment and other patient-reported outcome measures per IMMPACT were collected. ECAPs were collected in both groups to compare the magnitude of SC activation and percentage of time within the therapeutic window.

Results: 
The primary composite endpoint demonstrated superior results in overall pain responders (P=0.005) for CL-SCS (82.3%) compared to OL-SCS (60.3%). In addition, all pre-specified hierarchical endpoints demonstrated better outcomes in the CL group, with back pain reduction (P=0.015) and back pain responders (P=0.003) demonstrating superiority. The magnitude of SC activation was 7 times greater for CL-SCS, and CL subjects spend 50% more time within the therapeutic window. In both groups, subjects showed improvements across secondary outcomes.

Conclusions:
ECAP-controlled CL-SCS has demonstrated superior overall pain relief compared with OL-SCS. The study has just completed the primary outcome data analysis.

RANDOMIZED, DOUBLE-BLIND TRIAL COMPARING EVOKED COMPOUND ACTION POTENTIAL (ECAP)-CONTROLLED CLOSED-LOOP SPINAL CORD STIMULATION (SCS) TO CONVENTIONAL, OPEN-LOOP SCS