Characterizing ECAP Detection Thresholds and Therapeutic Spinal Cord Stimulation Dose

Evoked Compound Action Potentials (ECAPs) have been studied for their potential use as a feedback signal for paresthesia-based spinal cord stimulation (SCS) for chronic neuropathic pain. While paresthesia-based SCS therapy is still commonly used, paresthesia-free modalities have emerged over the past decade and are commonly preferred by patients because they avoid persistent stimulation-induced paresthesia. Characterizing the relationship between ECAP detection thresholds and both paresthesia-free and paresthesia-based SCS dosing may assist clinicians in selecting appropriate SCS systems and programming strategies for their patients. We characterized stimulation amplitudes for ECAP detection threshold, perception threshold, and discomfort threshold in patients undergoing a temporary SCS trial for chronic low back and/or leg pain as part of an exploratory clinical study. We found that ECAPs were not detected below most patients' perception threshold (PT) and were absent in all cases below 80% of PT. We also found that mean discomfort was reported across patients at 1.35× the ECAP threshold (ET). This work characterizes the relationships between ECAP, perception, and discomfort thresholds for SCS and characterizes inter-patient and intra-patient variability, clarifying how electrophysiological signals and sensing system capabilities fit into the landscape of SCS therapies.