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Aim: Previous studies of 10 kHz spinal cord stimulation demonstrated its safety and efficacy for treatment of neuropathic pain of the trunk and/or limbs. This study analyzed data from a subset of subjects with painful diabetic neuropathy enrolled in a prospective, multicenter study of peripheral polyneuropathy with various etiologies. Materials & methods: Of the eight subjects that had permanent devices, seven attended the 12-month follow-up assessment. Results & conclusion: At 12 months, 6/7 subjects were treatment responders (≥50% pain relief) and had pain remission (visual analog scale ≤ 3.0 cm). Worsening of neurologic deficits was not reported in any subject. Instead, 5/7 subjects showed improvements in sensory testing and/or reflexes. These results support further investigation of 10 kHz spinal cord stimulation as a safe and effective treatment for intractable painful diabetic neuropathy.

Introduction ACCURATE, a randomized controlled trial comparing dorsal root ganglion (DRG) stimulation to spinal cord stimulation, showed that DRG stimulation is a safe and effective therapy in individuals with lower extremity chronic pain due to complex regional pain syndrome (CRPS) type I or II. Investigators noted that DRG stimulation programming could be adjusted to minimize, or eliminate, the feeling of paresthesia while maintaining adequate pain relief. The present study explores treatment outcomes for DRG subjects who were paresthesia-free vs. those who experienced the sensation of paresthesia, as well as the factors that predicted paresthesia-free analgesia. Methods A retrospective analysis of therapy outcomes was conducted for 61 subjects in the ACCURATE study who received a permanent DRG neurostimulator. Outcomes of subjects who were paresthesia-free were compared to those who experienced paresthesia-present therapy at 1, 3, 6, 9, and 12-month follow-ups. Predictor variables for the presence or absence of paresthesias with DRG stimulation were also explored. Results The percentage of subjects with paresthesia-free pain relief increased from 16.4% at 1-month to 38.3% at 12-months. Paresthesia-free subjects generally had similar or better outcomes for pain severity, pain interference, quality of life, and mood state as subjects with paresthesia-present stimulation. Factors that increased the odds of a subject feeling paresthesia were higher stimulation amplitudes and frequencies, number of implanted leads, and younger age. Conclusions Some DRG subjects achieved effective paresthesia-free analgesia in the ACCURATE trial. This supports the observation that paresthesia is not synonymous with pain relief or required for optimal analgesia with DRG stimulation.

Objective The WHISPER randomized controlled trial (RCT) evaluates safety and clinical effectiveness of subperception spinal cord stimulation (SCS) at ≤1.2 kHz in subjects previously implanted with an SCS system for treatment of chronic, neuropathic pain. Methods WHISPER is a prospective, multicenter RCT with a crossover design sponsored by Boston Scientific, Marlborough, MA (ClinicalTrials.gov: NCT02314000). Eligible subjects were randomized (N = 140) to receive subperception or supraperception for three months and then crossed over to receive the alternative. Upon completion of crossover period, subjects who preferred subperception were followed up to one year. Overall pain, quality-of-life, and other outcomes were collected in the study. The primary endpoint was the overall pain responder rate (≥50% improvement from baseline) with no increase in medications. Secondary endpoints consisted of pain scores, physical disability, quality of life, and treatment preference. Results The study met its primary endpoint and demonstrated noninferiority between supraperception and subperception in a prespecified cohort of 70 randomized subjects (Interim Analysis). Thirty-nine percent of subjects with subperception settings and 29% with supraperception settings had a greater than or equal to 50% reduction in their overall pain scores with no increase in average daily medication at three-months post-activation as compared with baseline. Further assessment of all participating study subjects (N = 140) revealed similar results. Subjects were previously implanted 3.8 ± 2 years and had a disability score (Oswestry Disability Index) of 70.2 ± 11.4 at study start. Of the randomized subjects that completed the End of Period 2 Visit, 93 (66%) preferred subperception SCS and their mean overall pain reduced from 7.3 ± 1.1 (N = 89) at baseline to 4.0 ± 2.1 (N = 80) at 12-months post-activation. Post hoc analysis also demonstrated that multiple options provide superior outcomes, as supported by a 74% increase in the responder rate when subjects could choose their most effective option (47%) compared with supraperception alone (27%). Discussion Subperception SCS at ≤1.2 kHz is safe and effective in subjects with extreme physical disability and previously implanted for chronic pain. Further, by providing study participants with different waveform options, increased pain relief was achieved.

OBJECTIVES This was a sub-analysis of the ACCURATE clinical trial that evaluated the accuracy and necessity of targeting paresthesia coverage of painful areas with dorsal root ganglion (DRG) stimulation vs. tonic spinal cord stimulation (SCS). MATERIALS AND METHODS On diagrams of the torso and lower limbs, subjects marked where they felt pain at baseline and paresthesias at three months postimplant. Seventy-five subjects (41 DRG and 34 SCS) with diagrams of sufficient quality were scanned, digitized, and included in this analysis. Subject completed diagrams were digitized and superimposed with a grid of 1398 squares. Quantification of the percentage of bodily areas affected by pain and stimulation induced paresthesias was performed. RESULTS The percent of painful areas covered by paresthesia was significantly lower for DRG subjects than for SCS subjects (13% vs. 28% of the painful regions, p < 0.05), possibly because significantly more DRG subjects felt no paresthesia during stimulation when compared to SCS subjects (13/41 DRG vs. 3/34 SCS) (p < 0.05). The amount of paresthesia produced outside the painful areas (unrequired paresthesia) was significantly lower in DRG subjects than that of SCS subjects. On average, the percent of unrequired paresthesia was only 20% of the subjects' total painful body surface area in the DRG group compared to 210% in the SCS group (p < 0.01). CONCLUSIONS The results of this ACCURATE study sub-analysis show that DRG stimulation produces paresthesias, on average, that are less frequent, less intense, with a smaller footprint on the body and less dependent on positional changes.