• Jennifer Sweet, Anish Badjatiya, Daniel Tan, and Jonathan Miller.
• The Neurological Institute, University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
• Neuromodulation. 2016 Apr 1; 19 (3): 260-7.

ObjectiveSpinal cord stimulation (SCS) traditionally is thought to require paresthesia, but there is evidence that paresthesia-free stimulation using high-density (HD) parameters might also be effective. The purpose of this study is to evaluate relative effectiveness of conventional, subthreshold HD, and sham stimulation on pain intensity and quality of life.MethodsFifteen patients with response to conventional stimulation (60 Hz/350 μsec) were screened with a one-week trial of subthreshold HD (1200 Hz/200 μsec/amplitude 90% paresthesia threshold) and enrolled if there was at least 50% reduction on visual analog scale (VAS) for pain. Subjects were randomized into two groups and treated with four two-week periods of conventional, subthreshold HD, and sham stimulation in a randomized crossover design.ResultsFour of 15 patients responded to subthreshold HD stimulation. Mean VAS during conventional, subthreshold HD, and sham stimulation was 5.32 ± 0.63, 2.29 ± 0.41, and 6.31 ± 1.22, respectively. There was a significant difference in pain scores during the blinded crossover study of subthreshold HD vs. sham stimulation (p < 0.05, Student's t-test). Post hoc analysis revealed that subjects reported significantly greater attention to pain during conventional stimulation compared with subthreshold HD stimulation (p < 0.05, Student's t-test). All subjects reported a positive impression of change for subthreshold HD stimulation compared with conventional stimulation, and there was a trend toward greater likelihood for response to subthreshold HD stimulation in comparison with sham stimulation (p = 0.07, Fisher's exact test). At the end of the trial, all subjects elected to continue to receive subthreshold HD stimulation rather than conventional stimulation.ConclusionsParesthesia are not necessary for pain relief using commercially available SCS devices, and may actually increase attention to pain. Subthreshold HD SCS represents a viable alternative to conventional stimulation among patients who are confirmed to have a clinical response to it.© 2015 International Neuromodulation Society.

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