Paresthesia-Independence: An Assessment of Technical Factors Related to 10 kHz Paresthesia-Free Spinal Cord Stimulation

Background: Spinal cord stimulation (SCS) has been successfully used to treat chronic intractablepain for over 40 years. Successful clinical application of SCS is presumed to be generally dependenton maximizing paresthesia-pain overlap; critical to achieving this is positioning of the stimulationfield at the physiologic midline. Recently, the necessity of paresthesia for achieving effective reliefin SCS has been challenged by the introduction of 10 kHz paresthesia-free stimulation. In a large,prospective, randomized controlled pivotal trial, HF10 therapy was demonstrated to be statisticallyand clinically superior to paresthesia-based SCS in the treatment of severe chronic low back andleg pain. HF10 therapy, unlike traditional paresthesia-based SCS, requires no paresthesia to beexperienced by the patient, nor does it require paresthesia mapping at any point during leadimplant or post-operative programming.Objectives: To determine if pain relief was related to technical factors of paresthesia, we measuredand analyzed the paresthesia responses of patients successfully using HF10 therapy.Study Design: Prospective, multicenter, non-randomized, non-controlled interventional study.Setting: Outpatient pain clinic at 10 centers across the US and Italy.Methods: Patients with both back and leg pain already implanted with an HF10 therapy devicefor up to 24 months were included in this multicenter study. Patients provided pain scores prior toand after using HF10 therapy. Each patient’s most efficacious HF10 therapy stimulation programwas temporarily modified to a low frequency (LF; 60 Hz), wide pulse width (~470 μs), paresthesiagenerating program. On a human body diagram, patients drew the locations of their chronicintractable pain and, with the modified program activated, all regions where they experienced LFparesthesia. Paresthesia and pain drawings were then analyzed to estimate the correlation of painrelief outcomes to overlap of pain by paresthesia, and the mediolateral distribution of paresthesia(as a surrogate of physiologic midline lead positioning).Results: A total of 61 patients participated across 11 centers. Twenty-eight men and 33 womenwith a mean age of 56 ± 12 years of age participated in the study. The average duration ofimplantable pulse generator (IPG) implant was 19 ± 9 months. The average predominant painscore, as measured on a 0 – 10 visual analog scale (VAS), prior to HF10 therapy was 7.8 ± 1.3 andat time of testing was 2.5 ± 2.1, yielding an average pain relief of 70 ± 24%. For all patients, themean paresthesia coverage of pain was 21 ± 28%, with 43% of patients having zero paresthesiacoverage of pain. Analysis revealed no correlation between percentage of LF paresthesia overlapof predominant pain and HF10 therapy efficacy (P = 0.56). Exact mediolateral positioning ofthe stimulation electrodes was not found to be a statistically significant predictor of pain reliefoutcomes.Limitations: Non-randomized/non-controlled study design; short-term evaluation; certaintechnical factors not investigated.Conclusion: Both paresthesia concordance with pain and precise midline positioning of the stimulation contacts appear to beinconsequential technical factors for successful HF10 therapy application. These results suggest that HF10 therapy is not onlyparesthesia-free, but may be paresthesia-independent.Key words: Spinal cord stimulation, paresthesia, high frequency, 10kHz, pain relief, physiologic midline, paresthesia-free