Low-frequency Spinal Cord Stimulation Research Articles

High frequency spinal cord stimulation for chronic back and leg pain

BackgroundHigh frequency stimulation (HFS) may provide pain relief without the paresthesias typical of traditional low-frequency Spinal cord stimulation (SCS). MethodsA consecutive single-center series of patients was retrospectively reviewed to evaluate safety and efficacy of HF10 therapy. In this 24-month study, 62 patients with variables pathologies (44 patients with back failure surgery syndrome (FBSS), 18 patients with chronic peripheral neuropathic pain in the lower limbs (NeppL) were included to be treated with HF10. Pain outcomes were compared from preoperative baseline and at the conclusion of each study period. Clinical features, outcomes and complications were reviewed. Results62 patients completed this study. All patients had a successful trial before the definitive implantation of a spinal cord stimulator at the low dorsal level. The mean follow-up period was 11 months, ranging from 6 to 24 months. 6 patients showed no change from baseline visual analogue scale (VAS) after permanent implant and 2 had improved during the trial but was aggravated after the permanent implant placement. At 1 month, 63% of implanted HF10 therapy subjects were responders and 77% at 6 months. The average baseline, trial and postoperative Visual Analogue Scale (VAS) was 8.1, 3.6 and 4.2 respectively. When compared to the baseline, the average reduction achieved during the VAS trial was 4.5 points, accounting for a 56% pain reduction. The long-term failure rate was 22%. ConclusionsThis study generated preliminary evidence showing improved VAS current pain scores in absence of paresthesias and increase patient satisfaction with HF10 spinal cord stimulation.

Retrospective Assessment of Salvage to 10 kHz Spinal Cord Stimulation (SCS) in Patients Who Failed Traditional SCS Therapy: RESCUE Study.

Background and ObjectivesA randomized clinical trial demonstrated that 10 kHz SCS (10kHz-SCS) therapy is superior to traditional low-frequency SCS (LF-SCS) at 12- and 24-month clinical follow-ups and led to Food and Drug Administration (FDA) approval of the therapy. The results of the study led our practices to trial 10kHz-SCS in patients who had not maintained pain relief with LF-SCS therapy. Here, we report a large set of data from two clinical sites to assess if 10kHz-SCS is an effective salvage modality when LF-SCS fails.MethodsWe conducted a retrospective chart review of 120 patients across two clinical sites who had LF-SCS implants and were salvaged with 10kHz-SCS.ResultsData were analyzed from 105 patients between 28 and 90 years old (median 60) with chronic pain for 13.6 years. The mean duration of LF-SCS therapy was 4.66±3.9 years. The average Visual Analog Scale (VAS) decreased from 8.30±1.4 (median of 8) cm to 3.32±2.0 (median of 3) cm at 12 months and 3.36±2.0 (median of 3) cm at the most recent clinic visit (p<0.001) following salvage therapy. Pain relief of 50% or more was obtained in 85 out of 105 (81%) patients. Opioid usage decreased from 60.3±77.1 mg to 32.1±44.0 mg MSO4 equivalents (p = 0.001) at 12 months after salvage therapy.ConclusionEighty-one percent of patient cases reviewed, where LF-SCS had failed, achieved >50% pain relief with 10kHz-SCS, and almost all exhibited some clinical improvement. Therefore, 10kHz-SCS should be considered an appropriate option to rescue failed LF-SCS.

14. Nonlinear burst spinal cord stimulation can attenuate pain and catastrophizing in patients with persistent back pain and high psychological distress

BACKGROUND CONTEXT Psychological factors such as depression, anxiety, and poor coping strategies have been shown to predict negative outcomes after lumbar spine surgery and spinal cord stimulation (SCS). Recent studies have shown that nonlinear burst spinal cord stimulation (NLB-SCS), compared with traditional low-frequency tonic SCS, produces a greater effect on brain targets associated with the affective/emotional aspects of pain processing via the modulation of the medial spinothalamocortical pathways. PURPOSE Herein we present outcomes after NLB-SCS in patients with persistent back pain after lumbar spine surgery who are suffering from high psychological distress. STUDY DESIGN/SETTING Subanalysis from a prospective, multicenter, international, single arm study on nonlinear burst spinal cord stimulation. PATIENT SAMPLE Data for this subanalysis were extracted from an ongoing prospective, multicenter, study on NLB-SCS (ClinicalTrials.gov NCT03082261). OUTCOME MEASURES Catastrophizing Scale (PCS), Patient Health Questionnaire Depression scale (PHQ-9), State Trait Anxiety Index (STAI), Numerical Rating Scale (NRS). METHODS One-year outcomes were evaluated in subjects who presented with severe symptoms at baseline on the Pain Catastrophizing Scale (PCS), Patient Health Questionnaire Depression scale (PHQ-9), or State Trait Anxiety Index (STAI). Severity and responder analyses were performed for each measure, based on individually published standards. Severe symptoms were classified as scores of ≥30 on the PCS, ≥10 on the PHQ-9, and ≥40 on the STAI. Responders were classified as subjects who reported below these severity thresholds. Additional outcomes assessed at the 12-month follow-up visit included the Numeric Pain Rating Scale (NRS) and the EuroQol 5-Dimensions (EQ-5D). The minimal clinical important difference (MCID) for the EQ-5D Index is a 0.074 increase. RESULTS At baseline, 107 subjects reported severe symptoms of anxiety (64%), depression (52%), or catastrophizing (37%). Thirty-six percent reported severe symptoms in all three measures. At one-year post-implant, 69% were no longer catastrophizing, 50% were no longer clinically depressed, and 44% responded on STAI. Moreover, quality of life on EQ-5D improved on average from 0.38 before therapy to 0.62 post-therapy. Pain intensity was significantly decreased at 12 months; 77% reported at least 50% pain relief. CONCLUSIONS Our results demonstrate that NLB-SCS is an effective therapy for patients with persistent back pain who are suffering from high psychological distress. Subjects reported improvements across all psychological measures, reaffirming that NLB-SCS modulates the affective/emotional aspects of pain processing. FDA DEVICE/DRUG STATUS Spinal cord stimulation (Approved for this indication)

High-frequency 10 kHz Spinal Cord Stimulation for Chronic Back and Leg Pain: Cost-consequence and Cost-effectiveness Analyses.

There is good evidence that spinal cord stimulation (SCS) is effective for reducing chronic back and leg pain (CBLP). SENZA randomized controlled trial showed high-frequency (10 kHz) stimulation (10 kHz-SCS) is clinically superior to traditional low-frequency SCS (LF-SCS).Undertake cost-consequence and cost-effectiveness analysis of 10 kHz-SCS compared with LF-SCS. A probabilistic decision tree and Markov decision analytic model was used to synthesize data on CBLP outcomes and costs over a 15-year time horizon from a UK National Health Service perspective using data from the SENZA randomized controlled trial and other publications. Results are expressed as incremental cost per quality-adjusted life year (QALY) in 2016 Pounds Sterling. 10 kHz-SCS is cost-saving and cost-effective compared with LF-SCS, with mean cost-savings of £7170 (95% confidence interval: £6767-£7573) and £3552 (95% confidence interval: £3313-£3792) per patient compared with nonrechargeable and rechargeable LF-SCS devices, respectively. 10 kHz-SCS has a 95% likelihood of being cost-effective at a willingness-to-pay threshold of £20,000 per QALY. Our findings were robust across a wide range of sensitivity analyses. There is a strong economic case for choosing 10 kHz-SCS over LF-SCS for CBLP. Furthermore, 10 kHz-SCS has clinical advantages not captured in our analysis, including shorter, and more predictable procedure times.

Does Spinal Cord Stimulation Due to Failed Back Surgery Syndrome Lead to Permanent Occupational Disability?

Spinal cord stimulation (SCS) is a recommended treatment method for patients afflicted by failed back surgery syndrome (FBSS). Although SCS is shown to be clinically effective, not many patients return to work (RTW). The aim of this study is to assess the RTW rate of these patients. We prospectively evaluated 102 patients with FBSS, managed by low frequency SCS at a single institution in Poland. RTW rate was the main endpoint in the study. Additionally, we browsed the first 300 records in Google and extracted the suggested RTW time post-SCS implantation. Mean follow-up was 8.5 years. 79.4% of patients were actively working at the baseline. Fifteen patients were sick leave benefit claimants (15/81; 18.5%) and six were permanently disabled (6/81; 7.4%). In the follow-up, 40 did not change their work status. Only 2 of 21 patients resumed work and the total RTW rate was 9.5%. On the other hand, 38 of 81 patients (46.9%), who actively worked before SCS, gained disability status. Out of entire group, 20.6% (21 of 102) were not working at the baseline and 55.9% (57 of 102) were not working in the follow-up. Neither factor influenced RTW rate. In the second stage of the study, internet data search yielded a mean RTW time of 6.1 weeks. Unlike the well-analyzed effectiveness of SCS, RTW remains an underutilized outcome measure. The RTW rate in our series was the second lowest in the reviewed literature. We demonstrated that half of the patients with an implanted SCS either did not resume their work or left their job.

The Effectiveness of Spinal Cord Stimulation for the Treatment of Axial Low Back Pain: A Systematic Review with Narrative Synthesis.

Determine the effectiveness of spinal cord stimulation (SCS) for the treatment of axial low back pain (LBP) with or without leg pain. Systematic review. Persons aged ≥18 with axial LBP with or without accompanying leg pain. Traditional low-frequency, burst, or high-frequency SCS. Sham, active standard of care treatment, or none. The primary outcome was ≥50% pain improvement, and the secondary outcome was functional improvement measured six or more months after treatment intervention. Publications in PubMed, MEDLINE, and Cochrane databases were reviewed through September 19, 2019. Randomized or nonrandomized comparative studies and nonrandomized studies without internal controls were included. The Cochrane Risk of Bias Tool and GRADE system were used to assess individual study characteristics and overall quality. Query identified 262 publications; 17 were suitable for inclusion. For high-frequency SCS, the only level 1 study showed that 79% (95% confidence interval = 70-87%) of patients reported ≥50% pain improvement. For low-frequency SCS, the only level 1 study reported no categorical data for axial LBP-specific outcomes; axial LBP improved by a mean 14 mm on the visual analog scale at six months. Meta-analysis was not performed due to study heterogeneity. According to GRADE, there is low-quality evidence that high-frequency SCS compared with low-frequency SCS is effective in patients with axial LBP with concomitant leg pain. There is very low-quality evidence for low-frequency SCS for the treatment of axial LBP in patients with concomitant leg pain. There is insufficient evidence addressing the effectiveness of burst SCS to apply a GRADE rating.

Pain relief and improvement in quality of life with 10 kHz SCS therapy: Summary of clinical evidence.

ObjectiveChronic pain is a prevalent condition which has a significant effect on the lives of those it impacts. High‐frequency 10 kHz spinal cord stimulation (10 kHz SCS) has been shown to provide paresthesia‐free pain relief for a wide variety of pain indications. This article summarizes the current and emerging data as they relate to the clinical use of the therapy in various pain syndromes.MethodsA literature search was conducted using the PubMed electronic database using keywords related to 10 kHz SCS. The database was queried from 2013 to May 2019. Articles reporting clinical studies that included human subjects permanently treated with 10 kHz SCS (Senza® system) were included in the review. Recent and relevant conference proceedings known to the authors were also included.ResultsThe selected literature demonstrated significant evidence for the efficacy of 10 kHz SCS in treating chronic back and leg pain (CBLP), including a randomized, controlled trial as well as prospective and retrospective studies. One‐year follow‐up responder rates (pain relief ≥50%) ranged from 60% to 80%. Other studies and case series showed promising outcomes in specific conditions, including nonsurgical refractory back pain, neuropathic limb pain, complex regional pain syndrome, chronic widespread pain, chronic pelvic pain, and intractable headache. Subgroup analyses also pointed toward the potential of 10 kHz SCS being successful when low‐frequency SCS has failed. The vast majority of these studies reported improved quality of life (QOL) metrics and/or reduced opioid consumption.ConclusionsLevel I evidence already exists for the efficacy of 10 kHz SCS in treating CBLP, supported by real‐world clinical experience. Other studies demonstrate the potential of the therapy across a range of chronic pain etiologies, although larger confirmatory studies are recommended. Overall, the literature suggests that the therapy is associated with improved QOL as well as reduced opioid consumption.

High-frequency spinal cord stimulation at 10\u2009kHz for the treatment of painful diabetic neuropathy: design of a multicenter, randomized controlled trial (SENZA-PDN)

BackgroundPainful diabetic neuropathy (PDN), a debilitating and progressive chronic pain condition that significantly impacts quality of life, is one of the common complications seen with long-standing diabetes mellitus. Neither pharmacological treatments nor low-frequency spinal cord stimulation (SCS) has provided significant and long-term pain relief for patients with PDN. This study aims to document the value of 10-kHz SCS in addition to conventional medical management (CMM) compared with CMM alone in patients with refractory PDN.MethodsIn a prospective, multicenter, randomized controlled trial (SENZA-PDN), 216 subjects with PDN will be assigned 1:1 to receive 10-kHz SCS combined with CMM or CMM alone after appropriate institutional review board approvals and followed for 24 months. Key inclusion criteria include (1) symptoms of PDN for at least 12 months, (2) average pain intensity of at least 5 cm—on a 0- to 10-cm visual analog scale (VAS)—in the lower limbs, and (3) an appropriate candidate for SCS. Key exclusion criteria include (1) large or gangrenous ulcers or (2) average pain intensity of at least 3 cm on VAS in the upper limbs or both. Along with pain VAS, neurological assessments, health-related quality of life, sleep quality, and patient satisfaction will be captured. The primary endpoint comparing responder rates (≥50% pain relief) and safety rates between the treatment groups will be assessed at 3 months. Several secondary endpoints will also be reported on.DiscussionEnrollment commenced in 2017 and was completed in 2019. This study will help to determine whether 10-kHz SCS improves clinical outcomes and health-related quality of life and is a cost-effective treatment for PDN that is refractory to CMM.Trial registrationClincalTrials.gov identifier: NCT03228420 (registered 24 July 2017).

Redefining Spinal Cord Stimulation “Trials”: A Randomized Controlled Trial Using Single-Stage Wireless Permanent Implantable Devices

Background“Traditional” spinal cord stimulation (SCS) trials with percutaneous electrodes externalized to a pulse generator (PG) are typically limited in duration due to risk of infection. Newer miniaturized wireless SCS technology eliminates the percutaneous extension (as well as PGs implanted for chronic use), thus facilitating a single‐stage implantation after which the device can remain indefinitely.ObjectiveTo evaluate fully implanted wireless SCS devices during a 30‐day screening trial in subjects with chronic low back pain and leg pain and a history of lumbosacral spine surgery.MethodsIn a randomized controlled trial of single‐stage wireless SCS using a wireless percutaneous system, 99 subjects received either 10 kHz high frequency stimulation (HFS) or lower frequency stimulation (LFS) below 1500 Hz (Bolash R, Creamer M, Rauck R, et al. Wireless high frequency spinal cord stimulation (10 kHz) compared to multi‐waveform low frequency spinal cord stimulation in the management of chronic pain in failed back surgery syndrome subjects: preliminary results of a multicenter, prospective, randomized controlled study. Pain Med 2019, https://doi.org/10.1093/pm/pnz019). In this report, we assess the 30‐day trial success rate (≥50% pain relief from baseline) and complications.ResultsThe overall trial success rate was 88% (87/99): 92% (46/50) for HFS and 84% (41/49) for LFS (NS). The trial success rate in the 64 subjects with predominant low back pain was 92% (59/64) vs. 80% (28/35) in those with leg pain ≥ low back pain (NS). During the screening trial, one infection occurred (1%) and one subject withdrew and was explanted (1%). Electrode migrations were seen on routine follow‐up x‐rays in 10 cases (10%).ConclusionUsing wireless SCS devices that allow for an extended trial period and evaluation of various waveforms, we observed a high rate trial success rate with both HFS and LFS waveforms, with minimal incidence of infection. Long‐term follow‐up will address the cost‐effectiveness and morbidity associated with this technology, which facilitates single‐stage treatment.

Modulation of Spinal Nociceptive Transmission by Sub-Sensory Threshold Spinal Cord Stimulation in Rats After Nerve Injury

High-frequency spinal cord stimulation (SCS) administered below the sensory threshold (subparesthetic) can inhibit pain, but the mechanisms remain obscure. We examined how different SCS paradigms applied at intensities below the threshold of Aβ-fiber activation (sub-sensory threshold) affect spinal nociceptive transmission in rats after an L5 spinal nerve ligation (SNL). Electrophysiology was used to record local field potential (LFP) at L4 spinal cord before, during, and 0-60 min after SCS in SNL rats. LFP was evoked by high-intensity paired-pulse test stimulation (5 mA, 0.2 msec, 400 msec interval) at the sciatic nerve. Epidural SCS was delivered through a miniature electrode placed at T13-L1 and L2-L3 spinal levels. Four patterns of SCS (200 Hz, 1 msec; 500 Hz, 0.5 msec; 1200 Hz; 0.2 msec; 10,000 Hz, 0.024 msec, 30 min, bipolar) were tested at 90% Aβ-threshold as a subthreshold intensity. As a positive control, traditional SCS (50 Hz, 0.2 msec) was tested at 100% Aβ-plateau as a suprathreshold intensity. Traditional suprathreshold SCS at T13-L1 level significantly reduced LFP to C-fiber inputs (C-LFP). Subthreshold SCS of 200 and 500 Hz, but not 1200 or 10,000 Hz, also reduced C-LFP, albeit to a lesser extent than did traditional SCS (n = 7-10/group). When SCS was applied at the L2-L3 level, only traditional SCS and subthreshold SCS of 200 Hz inhibited C-LFP (n = 8-10/group). Traditional suprathreshold SCS acutely inhibits spinal nociceptive transmission. Low-frequency subthreshold SCS with a long pulse width (200 Hz, 1 msec), but not higher-frequency SCS, also attenuates C-LFP.

Low-intensity, Kilohertz Frequency Spinal Cord Stimulation Differently Affects Excitatory and Inhibitory Neurons in the Rodent Superficial Dorsal Horn

Since 1967, spinal cord stimulation (SCS) has been used to manage chronic intractable pain of the trunk and limbs. Compared to traditional high-intensity, low-frequency (<100 Hz) SCS that is thought to produce paresthesia and pain relief by stimulating large myelinated fibers in the dorsal column (DC), low-intensity, high-frequency (10 kHz) SCS has demonstrated long-term pain relief without generation of paresthesia. To understand this paresthesia-free analgesic mechanism of 10 kHz SCS, we examined whether 10 kHz SCS at intensities below sensory thresholds would modulate spinal dorsal horn (DH) neuronal function in a neuron type-dependent manner. By using in vivo and ex vivo electrophysiological approaches, we found that low-intensity (sub-sensory threshold) 10 kHz SCS, but not 1 kHz or 5 kHz SCS, selectively activates inhibitory interneurons in the spinal DH. This study suggests that low-intensity 10 kHz SCS may inhibit pain sensory processing in the spinal DH by activating inhibitory interneurons without activating DC fibers, resulting in paresthesia-free pain relief.

High Frequency (HF10) Spinal Cord Stimulation for Chronic Neuropathic Pain.

Spinal cord stimulation (SCS) is well established treatment. In a prospective randomised controlled trial, novel 10-kHz High-frequency Therapy (HF10 Therapy) was superior to traditional low-frequency SCS for the treatment of chronic back and leg pain. To demonstrate the percutaneous SCS implant technique and discuss the operative nuances. During the stage 1 procedure (permanent trial), two percutaneous electrodes were placed in the midline posterior epidural space spanning T8-T10 segments straddling the T9-10 disc space. The electrodes were anchored to the fascia, tunnelled into the supragluteal incision and connected to the extensions, which were tunnelled out for the external trial. The patient reported 90% pain reduction at follow-up. Thoracic HF10 SCS is effective modality in managing chronic neuropathic pain.

10 kHz spinal cord stimulation for the treatment of chronic back and/or leg pain: Summary of clinical studies.

Chronic pain has a major impact on sufferers and their families. The associated health care costs are substantial. In the context of increasing prevalence, effective treatment options are ever more important. 10 kHz spinal cord stimulation has been shown to effectively provide pain relief, aid in opioid reduction, and improve quality of life in patients with chronic intractable pain. The present review aims to summarize the clinical evidence related to the use of 10 kHz SCS in chronic back and/or leg pain. We searched the PubMed database between 2009 and 2 June 2020 for articles reporting clinical studies that included at least 10 human subjects permanently treated with a 10 kHz SCS system (Senza® system) for chronic back and/or leg pain for a minimum of 3 months. A randomized controlled trial (SENZA-RCT), as well as several prospective and retrospective studies, reported clinical outcomes in subjects with chronic back and leg pain treated with 10 kHz SCS. A high proportion of subjects (60%–80%) reported long-term response to therapy. Pain relief was provided without paresthesia. Other studies showed promising pain relief outcomes in subjects with back pain ineligible for spinal surgery, neuropathic limb pain, and in those with previously failed traditional low-frequency SCS. Most studies reported improved quality of life metrics and/or reduced opioid intake. Level 1 evidence has already been established for the use of 10 kHz SCS in treating chronic back and leg pain, corroborated by real-world, clinical experience. Exploratory studies also show the potential of the therapy in other refractory pain syndromes, although larger studies are desired to validate their findings. Overall, the literature suggests that 10 kHz SCS provides long-term pain relief in a high proportion of patients, along with improved quality of life and reduced opioid consumption.

High-Frequency Spinal Cord Stimulation at T9/10 in Patients With Failed Back Surgery Syndrome

Abstract INTRODUCTION Spinal cord stimulation (SCS) is an effective treatment option for low back pain and radicular leg pain of failed back surgery syndrome (FBSS). In a recent study, high-frequency spinal cord stimulation (HFSCS) was found to be more effective in treating chronic pain than traditional paresthesia-based low-frequency SCS (paresthesia SCS). The purpose of this study is to evaluate the efficacy of paresthesia SCS and HFSCS in improving outcomes. METHODS We retrospectively reviewed the outcomes of patients who underwent paresthesia SCS or HFSCS between September 2016 and January 2019. Paresthesia SCS is generally characterized by programming stimulation parameters such that the patient experiences paresthesia, and the paresthesia topography overlaps the pain topography as much as possible. The patient in HFSCS had a placement of cylindrical lead at levels T9-10. Patients were programmed with the electrode overlying the inferior endplate of T9 (+) and the electrode overlying the superior endplate of T10 (–). RESULTS A total of 14 patients (4 males, 10 females) underwent paresthesia SCS implantation. Mean age was 77.2 ± 9.6 yr. A total of 5 patients (2 males, 3 females) underwent HFSCS implantation. Mean age was 78.2 ± 7.5 yr. Operative time was shorter for the HFSCS group compared to the paresthesia SCS group (53.4 ± 4.8 min vs 82.9 ± 20.3 min, respectively; P &lt; .001). A total of 5 out of 5 patients in the HFSCS group (100%) and 10 out of 14 patients in the paresthesia SCS group (71.4%) achieved the outcome of 50% pain relief (P = .25) CONCLUSION To confirm paresthesia during the procedure in the elderly may be complicated by hearing/language difficulties or by sedative-related confusion. Compared to paresthesia SCS, HFSCS allows for lower operative times and a more efficient and accurate positioning of the electrodes.

The Impact of Electrical Charge Delivery on Inhibition of Mechanical Hypersensitivity in Nerve-Injured Rats by Sub-Sensory Threshold Spinal Cord Stimulation

Spinal cord stimulation (SCS) represents an important neurostimulation therapy for pain. A new ultra-high frequency (10,000 Hz) SCS paradigm has shown improved pain relief without eliciting paresthesia. We aim to determine whether sub-sensory threshold SCS of lower frequencies also can inhibit mechanical hypersensitivity in nerve-injured rats and examine how electric charge delivery of stimulation may affect pain inhibition by different patterns of subthreshold SCS. We used a custom-made quadripolar electrode (Medtronic Inc., Minneapolis, MN, USA) to provide bipolar SCS epidurally at the T10 to T12 vertebral level. According to previous findings, SCS was tested at 40% of the motor threshold, which is considered to be a sub-sensory threshold intensity in rats. Paw withdrawal thresholds to punctate mechanical stimulation were measured before and after SCS in rats that received an L5 spinal nerve ligation. Both 10,000 Hz (10 kHz, 0.024 msec) and lower frequencies (200 Hz, 1 msec; 500 Hz, 0.5 msec; 1200 Hz; 0.2 msec) of subthreshold SCS (120 min) attenuated mechanical hypersensitivity, as indicated by increased paw withdrawal thresholds after stimulation in spinal nerve ligation rats. Pain inhibition from different patterns of subthreshold SCS was not governed by individual stimulation parameters. However, correlation analysis suggests that pain inhibition from 10 kHz subthreshold SCS in individual animals was positively correlated with the electric charges delivered per second (electrical dose). Inhibition of neuropathic mechanical hypersensitivity can be achieved with low-frequency subthreshold SCS by optimizing the electric charge delivery, which may affect the effect of SCS in individual animals.

A review of the Senza System: a novel, high frequency 10kHz (HF10), paresthesia free spinal cord stimulator.

This article reviews Nevro Corporation's(CA, USA)Senza System high-frequency spinal cord stimulator(HF10 SCS). HF10 therapy has been shown to be noninferior to traditional low-frequency spinal cord stimulation (SCS), and in some studies, has been shown to have long-term effects that are superior compared with traditional low-frequency SCS in treating both back and leg pain. In addition, safety profiles for the HF10 SCS system wereequivalent to traditional SCS. HF10 SCS is based on spinal anatomic mapping and does not require intraoperative paresthesia mapping for placement, thereby improving procedural experience for patients and reducing operating room time. HF10 SCS has altered the nature of SCS therapy in a manner that treats more individuals with chronic, refractory leg and back pain than in the past, and is widely used in the USA, Europe and Australia.

High-Frequency Spinal Cord Stimulation at 10 kHz for the Treatment of Complex Regional Pain Syndrome: A Case Series of Patients With or Without Previous Spinal Cord Stimulator Implantation.

High-frequency spinal cord stimulation at 10 kHz (HF10-SCS) has been demonstrated to provide enhanced and durable pain relief in patients with chronic back and radiating leg pain. Patients with pain related to complex regional pain syndrome (CRPS) in the chronic stages are commonly challenging to treat and often receive traditional spinal cord stimulation (SCS). Very little information is currently available about the therapeutic outcomes following application of high-frequency stimulation in this cohort of patients. The purpose of the retrospective case series was to report on the initial experience of HF10-SCS in 13 patients with CRPS, some of whom had been exposed to low-frequency SCS. A temporary trial of HF10-SCS was carried out for 1 week, and those achieving a minimum of 50% pain intensity reduction underwent implantation. Successful responders were those who achieved a 50% decrease in pain intensity on subsequent follow-up. Thirteen patients were trialed, 12 of whom went on to receive a permanent implant. Of the patients receiving permanent implants, the responder rate (50% pain relief) was 67% (95% confidence interval [CI] 0.34 to 0.90), with an average follow-up period of 12.1 ± 4.6 months. Of the 5 patients who had sympathetically independent pain, 3 were responders, and of the 7 patients who had sympathetically mediated pain, 5 were responders. There were no adverse events. This small case series suggests that HF10-SCS may be a viable option for patients with CRPS who have chronic intractable pain, including those who had suboptimal results from traditional SCS.

Long-term efficacy of 1–1.2 kHz subthreshold spinal cord stimulation following failed traditional spinal cord stimulation: a retrospective case series

Background and objectiveWe investigated whether an effective long-term pain relief could be achieved using subthreshold 1–1.2 kHz spinal cord stimulation (SCS) among patients who were initially implanted with traditional paresthesia-based...

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Spinal cord stimulation (SCS) represents an important neurostimulation therapy for pain. A new ultra-high frequency (10,000 Hz) SCS paradigm has shown improved pain relief without eliciting paresthesia. We aim to determine whether sub-sensory threshold SCS of lower frequencies also can inhibit mechanical hypersensitivity in nerve-injured rats and examine how electric charge delivery of stimulation may affect pain inhibition by different patterns of subthreshold SCS.Materials and Methods: We used a custom-made quadripolar electrode (Medtronic Inc., Minneapolis, MN, USA) to provide bipolar SCS epidurally at the T10 to T12 vertebral level. According to previous findings, SCS was tested at 40% of the motor threshold, which is considered to be a sub-sensory threshold intensity in rats. Paw withdrawal thresholds to punctate mechanical stimulation were measured before and after SCS in rats that received an L5 spinal nerve ligation.Results: Both 10,000 Hz (10 kHz, 0.024 msec) and lower frequencies (200 Hz, 1 msec; 500 Hz, 0.5 msec; 1200 Hz; 0.2 msec) of subthreshold SCS (120 min) attenuated mechanical hypersensitivity, as indicated by increased paw withdrawal thresholds after stimulation in spinal nerve ligation rats. Pain inhibition from different patterns of subthreshold SCS was not governed by individual stimulation parameters. However, correlation analysis suggests that pain inhibition from 10 kHz subthreshold SCS in individual animals was positively correlated with the electric charges delivered per second (electrical dose).Conclusions: Inhibition of neuropathic mechanical hypersensitivity can be achieved with low-frequency subthreshold SCS by optimizing the electric charge delivery, which may affect the effect of SCS in individual animals.

Loss of Efficacy to Spinal Cord Stimulator Therapy: Clinical Evidence and Possible Causes

Background: Although spinal cord stimulation (SCS) therapy has been shown to be efficacious in various pain conditions, the ability for SCS therapy to maintain long-term efficacy has been questioned. Objective: The purpose of this study was to investigate whether a loss of efficacy (LOE) phenomenon exists with SCS therapy and to investigate if this phenomenon is more apparent in any specific patient population. Study Design: A retrospective, observation chart review was conducted to evaluate the patient response to SCS therapy over time. Setting: Massachusetts General Hospital, Boston, Massachusetts. Methods: Patients who received a SCS at the Massachusetts General Hospital, between January 1, 2002 and December 31, 2012, were invited to participate. A total of 62 patients were included in this study. Various models were created to analyze pain score changes over time using 2-tailed statistical analysis. Additionally, one-way ANOVA and Pearson’s chi-square tests were used to determine if certain patient characteristics were associated with LOE. Results: Compared to the visual analog scale (VAS) score at one month after device implantation, pain scores increased 1.95 points after 2 years (95% CI: 1.06 to 2.84, P = &lt; 0.001). There were no significant differences in baseline characteristics between the groups of patients who did and did not lose efficacy of their therapy. However, those who experienced LOE had a baseline SCS therapy VAS score 3.09 points lower than those who did not (95% CI: 1.69 to 4.48, P = &lt; 0.001). Limitations: This study had several limitations including the retrospective nature of its design, confounders to VAS scores, small sample size, missing data points, and the evaluation of only conventional, low-frequency SCS therapy. Conclusions: Patients who received a SCS had a significant increase in VAS scores over time. Our data did not show any baseline patient characteristic that helped predict LOE. However, patients who have significant baseline response to therapy may be more likely to experience LOE. Key words: Spinal cord stimulation, chronic pain, retrospective study, low frequency electrical stimulation, efficacy, chronic pain therapy