Paraesthesia may increase attention to pain, study finds

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A study recently published in the journal Neuromodulation has concluded that using spinal cord stimulation devices, paraesthesia are not necessary for pain relief and may actually increase attention to pain.

Until recently, paraesthesia and spinal cord stimulation have come hand-in-hand. That was until the development of paraesthesia-free spinal cord stimulation using high-density parameters. The study investigators, Jennifer Sweet (University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, USA) and others sought to evaluate the relative effectiveness of conventional, subthreshold high-density, and sham stimulation on pain intensity and quality of life.

To conduct the study, Sweet et al screened 15 patients with response to conventional stimulation (60Hz/350μsec) with a one-week trial of subthreshold high-density stimulation (1200Hz/200μsec/amplitude 90% paraesthesia threshold) and enrolled them if there was at least a 50% reduction on visual analogue scale (VAS) for pain. Patients were randomised into two groups and treated with four two-week periods of conventional, subthreshold high-density, and sham stimulation in a randomised crossover design.

The study authors report that four of 15 patients responded to subthreshold high-density stimulation. “Mean VAS during conventional, subthreshold high-density, 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 high-density stimulation versus sham stimulation (p<0.05, Student’s t-test),” they state.

Further, a post hoc analysis revealed that patients reported significantly greater attention to pain during conventional stimulation compared with subthreshold high-density stimulation (p<0.05, Student’s t-test). Sweet et al explain, “All subjects reported a positive impression of change for subthreshold high-density stimulation compared with conventional stimulation, and there was a trend toward greater likelihood for response to subthreshold high-density stimulation in comparison with sham stimulation (p=0.07, Fisher’s exact test).”

Notably, Sweet and colleagues further report that at the end of the trial, all of the patients enrolled elected to continue to receive subthreshold high-density stimulation rather than conventional stimulation.

The study therefore concluded that in fact, “Paraesthesia are not necessary for pain relief using commercially available spinal cord stimulation devices, and may actually increase attention to pain. Subthreshold high-density stimulation represents a viable alternative to conventional stimulation among patients who are confirmed to have a clinical response to it.”