HF10 therapy promises to substantially impact the management of back and leg pain with broad applicability to patients, physicians, and payers.

A comparative effectiveness trial indicates that dorsal root ganglion stimulation provided a higher rate of treatment success with less postural variation in paresthesia intensity compared to spinal cord stimulation.

ICONOTIDE (FORMERLY SNX-111, Neurex Pharmaceuticals, Menlo Park, Calif) is the synthetic equivalent of-conopeptide MVIIA, a 25-amino-acid polybasic peptide present in the venom of Conus magus, a marine snail. 1 Ziconotide produces potent antinociceptive effects 2 by selectively binding to N-type voltage-sensitive calcium channels 3,4 on neuronal somata, dendrites, dendritic shafts, and axon terminals, thus blocking neurotransmission from primary nociceptive afferents. Ziconotide is the first selective Ntype voltage-sensitive calcium channel blocking agent to be tested in clinical trials. There is no evidence of tolerance to ziconotide 5 or of addictive behavior in animals (Elan Pharmaceuticals Inc, unpublished data), and the drug must be administered intrathecally to maximize antinociceptive effectiveness and minimize sympatholysis. 6

BACKGROUND:Pain relief with spinal cord stimulation (SCS) has focused historically on paresthesias overlapping chronically painful areas. A higher level evidence supports the use of SCS in treating leg pain than supports back pain, as it is difficult to achieve adequate paresthesia coverage, and then pain relief, in the low back region. In comparison, 10-kHz high-frequency (HF10 therapy) SCS therapy does not rely on intraoperative paresthesia mapping and remains paresthesia-free during therapy.OBJECTIVE:To compare long-term results of HF10 therapy and traditional low-frequency SCS.METHODS:A pragmatic randomized, controlled, pivotal trial with 24-month follow-up was conducted across 11 comprehensive pain treatment centers. Subjects had Visual Analog Scale scores of ≥5.0/10.0 cm for both back and leg pain, and were assigned randomly (1:1) to receive HF10 therapy or low-frequency SCS. The primary end point was a responder rate, defined as ≥50% back pain reduction from baseline at 3 months with a secondary end point at 12 months (previously reported). In this article, 24-month secondary results are presented. Non-inferiority was first assessed, and if demonstrated the results were tested for superiority.RESULTS:In the study, 198 subjects were randomized (101 HF10 therapy, 97 traditional SCS). One hundred seventy-one subjects (90 HF10 therapy, 81 traditional SCS) successfully completed a short-term trial and were implanted. Subjects averaged 54.9 ± 12.9 years old, 13.6 ± 11.3 years since diagnosis, 86.6% had back surgery, 88.3% were taking opioid analgesics. At 3 months, 84.5% of implanted HF10 therapy subjects were responders for back pain and 83.1% for leg pain, and 43.8% of traditional SCS subjects were responders for back pain and 55.5% for leg pain (P < .001 for both back and leg pain comparisons, non-inferiority and superiority). At 24 months, more subjects were responders to HF10 therapy than traditional SCS (back pain: 76.5% vs 49.3%; 27.2% difference, 95% CI, 10.1%-41.8%; P < .001 for non-inferiority and superiority; leg pain: 72.9% vs 49.3%; 23.6% difference, 95% CI, 5.9%-38.6%; P < .001 for non-inferiority and P = .003 for superiority). Also at 24 months, back pain decreased to a greater degree with HF10 therapy (66.9% ± 31.8%) than traditional SCS (41.1% ± 36.8%, P < .001 for non-inferiority and superiority). Leg pain also decreased to a greater degree with HF10 therapy (65.1% ± 36.0%) than traditional SCS (46.0% ± 40.4%, P < .001 for non-inferiority and P = .002 for superiority).CONCLUSION:This study demonstrates long-term superiority of HF10 therapy compared with traditional SCS in treating both back and leg pain. The advantages of HF10 therapy are anticipated to impact the management of chronic pain patients substantially.ABBREVIATIONS:IPG, implantable pulse generatorMCID, minimal clinically important differencePI, permanent implantODI, Oswestry Disability IndexSCS, spinal cord stimulationVAS, Visual Analog Scale

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To understand the theoretical effects of pulse width (PW) programming in spinal cord stimulation (SCS), we implemented a mathematical model of electrical fields and neural activation in SCS to gain insight into the effects of PW programming. The computational model was composed of a finite element model for structure and electrical properties, coupled with a nonlinear double-cable axon model to predict nerve excitation for different myelinated fiber sizes. Mathematical modeling suggested that mediolateral lead position may affect chronaxie and rheobase values, as well as predict greater activation of medial dorsal column fibers with increased PW. These modeling results were validated by a companion clinical study. Thus, variable PW programming in SCS appears to have theoretical value, demonstrated by the ability to increase and even ‘steer’ spatial selectivity of dorsal column fiber recruitment. It is concluded that the computational SCS model is a valuable tool to understand basic mechanisms of nerve fiber excitation modulated by stimulation parameters such as PW and electric fields.

BACKGROUND Intractable neck and upper limb pain has historically been challenging to treat with conventional spinal cord stimulation (SCS) being limited by obtaining effective paresthesia coverage. OBJECTIVE To assess the safety and effectiveness of the 10-kHz SCS system, a paresthesia-independent therapy, in the treatment of neck and upper limb pain. METHODS Subjects with chronic, intractable neck and/or upper limb pain of ≥5 cm (on a 0-10 cm visual analog scale [VAS]) were enrolled in 6 US centers following an investigational device exemption from the Food and Drug Administration (FDA) and institutional review board approval. Each subject was implanted with 2 epidural leads spanning C2-C6 vertebral bodies. Subjects with successful trial stimulation were implanted with a Senza® system (Nevro Corp) and included in the evaluation of the primary safety and effectiveness endpoints. RESULTS In the per protocol population, the primary endpoint (≥50% pain relief at 3 mo) was achieved in 86.7% (n = 39/45) subjects. Compared to baseline, subjects reported a significant reduction (P &lt; .001) in their mean (± standard error of the mean) VAS scores at 12-mo assessment for neck pain (7.6 ± 0.2 cm, n = 42 vs 1.5 ± 0.3 cm, n = 37) and upper limb pain (7.1 ± 0.3 cm, n = 24 vs 1.0 ± 0.2 cm, n = 20). At 12-mo assessment, 89.2% of subjects with neck pain and 95.0% with upper limb pain had ≥50% pain relief from baseline, 95.0% reported to be “satisfied/very satisfied” and 30.0% either eliminated or reduced their opioid intake. CONCLUSION In conclusion, 10-kHz SCS can treat intractable neck and upper limb pain with stable long-term outcomes.