Effects of sub-perception threshold spinal cord stimulation in neuropathic pain: A randomized controlled double-blind crossover study

Background Recent studies suggest that perception of the paraesthesia elicited by spinal cord stimulation (SCS) is not necessarily required for the pain relieving effect. Objective The purpose of the study was to determine the effect of sub‐perception threshold SCS in patients with neuropathic pain. Methods Ten patients with implanted SCS systems underwent continuous sub‐threshold stimulation and no stimulation in a blinded randomized crossover design. Pain scores under these treatment modalities were compared with usual supra‐threshold stimulation. Results Sub‐threshold stimulation elicited significantly lower pain relief than supra‐perception threshold SCS. Mean pain scores were 3.6 [max 6.3, min 1.9, standard deviation (SD) 1.3] under supra‐threshold stimulation, 5.6 (max 9.0, min 2.4, SD 1.9) under sub‐threshold stimulation and 6.4 (max 10.0, min 4.0, SD 2.0) without stimulation. Conclusion Sub‐threshold stimulation under otherwise conventional stimulation parameters has a measurable but not clinically sufficient effect. Thus, the pain relieving effect elicited by SCS is not necessarily linked to the perceptibility of stimulation but may instead be attributed to the intensity of the electric field.