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

Cervical Spinal Cord Stimulation for Failed Neck Surgery Syndrome

PURPOSE OF REVIEW

Cervical spine pain with or without radicular symptoms is a common condition leading to high utilization of the healthcare system with over 10 million medical visits per year. Many patients undergo surgical interventions and unfortunately are still left with neck and upper extremity pain, sometimes referred to as "Failed Neck Surgery Syndrome." When these options fail, cervical spinal cord stimulation can be a useful tool to decrease pain and suffering as well as reduce prescription medication use.

RECENT FINDINGS

Spinal cord stimulation is a well-established therapy for chronic back and leg pain and is becoming more popular for neck and upper extremity pain. Recent studies have explored cervical spinal cord stimulation with successful outcomes regarding improved pain scores, functional outcomes, and reduction of prescription medication use. Continued research into cervical spinal cord stimulation is essential for maximizing its therapeutic potential for patients with chronic neck and upper extremity pain. This review highlights the importance of cervical spinal cord stimulation as an option for patients with failed neck surgery syndrome.

Spinal Cord Stimulator Inequities Within the US Military Health System

OBJECTIVES

Although studies have described inequities in spinal cord stimulation (SCS) receipt, there is a lack of information to inform system-level changes to support health care equity. This study evaluated whether Black patients exhaust more treatment options than do White patients, before receiving SCS.

MATERIALS AND METHODS

This retrospective cohort study included claims data of Black and non-Latinx White patients who were active-duty service members or military retirees who received a persistent spinal pain syndrome (PSPS) diagnosis associated with back surgery within the US Military Health System, January 2017 to January 2020 (N = 8753). A generalized linear model examined predictors of SCS receipt within two years of diagnosis, including the interaction between race and number of pain-treatment types received.

RESULTS

In the generalized linear model, Black patients (10.3% [8.7%, 12.0%]) were less likely to receive SCS than were White patients (13.6% [12.7%, 14.6%]) The interaction term was significant; White patients who received zero to three different types of treatments were more likely to receive SCS than were Black patients who received zero to three treatments, whereas Black and White patients who received >three treatments had similar likelihoods of receiving a SCS.

CONCLUSIONS

In a health care system with intended universal access, White patients diagnosed with PSPS tried fewer treatment types before receiving SCS, whereas the number of treatment types tried was not significantly related to SCS receipt in Black patients. Overall, Black patients received SCS less often than did White patients. Findings indicate the need for structured referral pathways, provider evaluation on equity metrics, and top-down support.

The deep and the deeper: Spinal cord and deep brain stimulation for neuropathic pain

Neuropathic pain occurs in people experiencing lesion or disease affecting the somatosensorial system. It is present in 7 % of the general population and may not fully respond to first- and second-line treatments in up to 40 % of cases. Neuromodulation approaches are often proposed for those not tolerating or not responding to usual pharmacological management. These approaches can be delivered surgically (invasively) or non-invasively. Invasive neuromodulation techniques were the first to be employed in neuropathic pain. Among them is spinal cord stimulation (SCS), which consists of the implantation of epidural electrodes over the spinal cord. It is recommended in some guidelines for peripheral neuropathic pain. While recent studies have called into question its efficacy, others have provided promising data, driven by advances in techniques, battery capabilities, programming algorithms and software developments. Deep brain stimulation (DBS) is another well-stablished neuromodulation therapy routinely used for movement disorders; however, its role in pain management remains limited to specific research centers. This is not only due to variable results in the literature contesting its efficacy, but also because several different brain targets have been explored in small trials, compromising comparisons between these studies. Structures such as the periaqueductal grey, posterior thalamus, anterior cingulate cortex, ventral striatum/anterior limb of the internal capsule and the insula are the main targets described to date in literature. SCS and DBS present diverse rationales for use, mechanistic backgrounds, and varying levels of support from experimental studies. The present review aims to present their methodological details, main mechanisms of action for analgesia and their place in the current body of evidence in the management of patients with neuropathic pain, as well their particularities, effectiveness, safety and limitations.

The Evolution of Surgical Technique in Spinal Cord Stimulation: A Scoping Review

Since the advent of spinal cord stimulation (SCS), its operative technique has consistently advanced. We performed a scoping review of the literature regarding SCS operative techniques to highlight key advancements. To review, summarize, and highlight key changes in SCS implantation techniques since their inception. The authors performed a MEDLINE search inclusive of articles from 1967 to June 2023 including human and modeling studies written in English examining the role of trialing, intraoperative neuromonitoring, and surgical adaptations. Using the Rayyan platform, two reviewers performed a blinded title screen. Of the 960 articles, 197 were included in the title screen, 107 were included in the abstract review, and ultimately 69 articles met inclusion criteria. We examined the utility of trialing and found that historical controls showed significant efficacy, whereas recent results are more equivocal. We discuss the significant improvement in outcomes with intraoperative neuromonitoring for asleep SCS placement. We highlight technique improvements that led to significant reductions in infection, lead migration, and inadequate pain relief. Physicians implanting SCS systems for chronic pain management must continually refine their surgical techniques to keep up with this rapidly evolving therapy. In addition, through collaborative efforts of neuromodulators and industry, SCS is safer and more effective for patients suffering from chronic pain.

Neurostimulation in the patient with chronic pain: forecasting the future with data from the present - data-driven analysis or just dreams?

Chronic pain involves a structured and individualized development of neurophysiological and biological responses. The final expression in each patient correlates with diverse expressions of mediators and activations of different transmission and modulation pathways, as well as alterations in the structure and function of the brain, all of which develop according to the pain phenotype. Still today, the selection process for the ideal candidate for spinal cord stimulation (SCS) is based on results from test and functional variables analysis as well as pain evaluation. In addition to the difficulties in the initial selection of patients and the predictive analysis of the test phase, which undoubtedly impact on the results in the middle and long term, the rate of explants is one of the most important concerns, in the analysis of suitability of implanted candidates. A potential for useful integration of genome analysis and lymphocyte expression in the daily practice of neurostimulation, for pain management is presented. Structural and functional quantitative information provided by imaging biomarkers will allow establishing a clinical decision support system that improve the effectiveness of the SCS implantation, optimizing human, economic and psychological resources. A correct programming of the neurostimulator, as well as other factors associated with the choice of leads and their position in the epidural space, are the critical factors for the effectiveness of the therapy. Using a model of SCS based on mathematical methods and computational simulation, the effect of different factors of influence on clinical practice studied, as several configurations of electrodes, position of these, and programming of polarities, in order to draw conclusions of clinical utility in neuroestimulation therapy.

Spinal Cord Stimulation for Painful Diabetic Neuropathy

Spinal cord stimulation (SCS) technology has been recently approved by the US Food and Drug Administration (FDA) for painful diabetic neuropathy (PDN). The treatment involves surgical implantation of electrodes and a power source that delivers electrical current to the spinal cord. This treatment decreases the perception of pain in many chronic pain conditions, such as PDN. The number of patients with PDN treated with SCS and the amount of data describing their outcomes is expected to increase given four factors: (1) the large number of patients with this diagnosis, (2) the poor results that have been obtained for pain relief with pharmacotherapy and noninvasive non-pharmacotherapy, (3) the results to date with investigational SCS technology, and (4) the recent FDA approval of systems that deliver this treatment. Whereas traditional SCS replaces pain with paresthesias, a new form of SCS, called high-frequency 10-kHz SCS, first used for pain in 2015, can relieve PDN pain without causing paresthesias, although not all patients experience pain relief by SCS. This article describes (1) an overview of SCS technology, (2) the use of SCS for diseases other than diabetes, (3) the use of SCS for PDN, (4) a comparison of high-frequency 10-kHz and traditional SCS for PDN, (5) other SCS technology for PDN, (6) deployment of SCS systems, (7) barriers to the use of SCS for PDN, (8) risks of SCS technology, (9) current recommendations for using SCS for PDN, and (10) future developments in SCS.

Evidence-based consensus guidelines on patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain

Spinal cord stimulation (SCS) has demonstrated effectiveness for neuropathic pain. Unfortunately, some patients report inadequate long-term pain relief. Patient selection is emphasized for this therapy; however, the prognostic capabilities and deployment strategies of existing selection techniques, including an SCS trial, have been questioned. After approval by the Board of Directors of the American Society of Regional Anesthesia and Pain Medicine, a steering committee was formed to develop evidence-based guidelines for patient selection and the role of an SCS trial. Representatives of professional organizations with clinical expertize were invited to participate as committee members. A comprehensive literature review was carried out by the steering committee, and the results organized into narrative reports, which were circulated to all the committee members. Individual statements and recommendations within each of seven sections were formulated by the steering committee and circulated to members for voting. We used a modified Delphi method wherein drafts were circulated to each member in a blinded fashion for voting. Comments were incorporated in the subsequent revisions, which were recirculated for voting to achieve consensus. Seven sections with a total of 39 recommendations were approved with 100% consensus from all the members. Sections included definitions and terminology of SCS trial; benefits of SCS trial; screening for psychosocial characteristics; patient perceptions on SCS therapy and the use of trial; other patient predictors of SCS therapy; conduct of SCS trials; and evaluation of SCS trials including minimum criteria for success. Recommendations included that SCS trial should be performed before a definitive SCS implant except in anginal pain (grade B). All patients must be screened with an objective validated instrument for psychosocial factors, and this must include depression (grade B). Despite some limitations, a trial helps patient selection and provides patients with an opportunity to experience the therapy. These recommendations are expected to guide practicing physicians and other stakeholders and should not be mistaken as practice standards. Physicians should continue to make their best judgment based on individual patient considerations and preferences.

Role of patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain: a comprehensive narrative review

Background/importance

Patient selection for spinal cord stimulation (SCS) therapy is crucial and is traditionally performed with clinical selection followed by a screening trial. The factors influencing patient selection and the importance of trialing have not been systematically evaluated.

Objective

We report a narrative review conducted to synthesize evidence regarding patient selection and the role of SCS trials.

Evidence review

Medline, EMBASE and Cochrane databases were searched for reports (any design) of SCS in adult patients, from their inception until March 30, 2022. Study selection and data extraction were carried out using DistillerSR. Data were organized into tables and narrative summaries, categorized by study design. Importance of patient variables and trialing was considered by looking at their influence on the long-term therapy success.

Findings

Among 7321 citations, 201 reports consisting of 60 systematic reviews, 36 randomized controlled trials (RCTs), 41 observational studies (OSs), 51 registry-based reports, and 13 case reports on complications during trialing were included. Based on RCTs and OSs, the median trial success rate was 72% and 82%, and therapy success was 65% and 61% at 12 months, respectively. Although several psychological and non-psychological determinants have been investigated, studies do not report a consistent approach to patient selection. Among psychological factors, untreated depression was associated with poor long-term outcomes, but the effect of others was inconsistent. Most RCTs except for chronic angina involved trialing and only one RCT compared patient selection with or without trial. The median (range) trial duration was 10 (0–30) and 7 (0–56) days among RCTs and OSs, respectively.

Conclusions

Due to lack of a consistent approach to identify responders for SCS therapy, trialing complements patient selection to exclude patients who do not find the therapy helpful and/or intolerant of the SCS system. However, more rigorous and large studies are necessary to better evaluate its role.

Does Fibromyalgia Affect the Outcomes of Spinal Cord Stimulation: An 11-Year, Multicenter, Retrospective Matched Cohort Study

BACKGROUND

Fibromyalgia is a prevalent disorder manifesting with widespread musculoskeletal pain and central sensitization, as well as fatigue, sleep issues, psychologic distress, and poor quality of life. Patients with fibromyalgia also may be diagnosed with other painful conditions amenable to treatment with spinal cord stimulation (SCS), although it is unclear how these patients respond to SCS compared with patients without fibromyalgia.

MATERIALS AND METHODS

We performed an 11-year, multicenter, retrospective matched cohort study comparing SCS-treated patients with fibromyalgia and those without fibromyalgia. The primary outcome was comparison in mean calculated percentage pain relief between cohorts at six months after SCS implantation. Secondary outcomes included comparison of patient satisfaction between six and 12 months after SCS implantation, and percentage of patients reporting opioid intake and neuropathic medication intake at six months and 12 months after SCS implantation. Adjusted regression analysis was performed to make comparisons while adjusting for age, sex, body mass index, Charlson comorbidity index, preoperative opioid intake, and preoperative neuropathic medication intake.

RESULTS

Of 90 patients with fibromyalgia who underwent SCS trial, 18 patients (20%) failed their SCS trial and did not proceed toward implantation. Sixty-eight patients with fibromyalgia were matched to 141 patients in the control cohort based on age, sex, Charlson comorbidity index, and the American Society of Anesthesiologists physical status score. At six months after SCS implantation, there was no statistical difference in calculated percentage change in pain intensity between the fibromyalgia cohort (46.6 ± 29.0) and the control cohort (50.9 ± 32.8; β, -18.4; 95% CI, -44.3 to 7.6; p = 0.157). At baseline, a greater percentage of patients in the fibromyalgia cohort reported preoperative opioid intake (51.5% vs 22.7%, p < 0.001) and preoperative neuropathic medication intake (67.6% vs 15.6%, p < 0.001). However, there was no difference between cohorts in the percentage of patients taking opioid or neuropathic medications at six months and 12 months after SCS implantation. Similarly, there was no difference between cohorts in the percentage of patients reporting satisfaction between six and 12 months.

CONCLUSION

Patients with fibromyalgia who received a diagnosis approved for treatment with SCS may expect similar post-SCS-implantation pain relief, overall satisfaction, and analgesic use rate to those of patients without fibromyalgia.

Non-Invasive Treatments for Failed Back Surgery Syndrome: A Systematic Review

STUDY DESIGN

Systematic Review.

OBJECTIVES

The aim of this systematic review is to evaluate the efficacy of non-invasive procedures in relieving chronic pain due to Failed Back Surgery Syndrome (FBSS).

METHODS

Since patients who suffered from FBBS are often non-responders to analgesics, we compared Visual Analogical Scale for low back and leg pain, Oswestry Disability Index, trial success rate, adverse events and complications between conservative treatment groups and control groups.

RESULTS

The included studies were 15. Spinal Cord Stimulation (SCS) was performed in 11 trials; 4 studies assessed the efficacy of different epidural injections; one study evaluated repetitive Transcranial Magnetic Stimulation. All the studies reported back and leg pain relief after treatment with SCS, with a significant superiority in high frequences (HFS) group, compared to low frequences (LFS) group. Moreover, disability decreased with each non-invasive treatment evaluated. Epidural injections of steroids and hyaluronidase have shown controversial results. Adverse events were described in 7 studies: lead migration, hardware-related events, infection and incisional pain were the most reported. Finally, trial success rate showed better outcomes for HFS.

CONCLUSIONS

Our systematic review highlights the efficacy of conservative treatments in FBSS patients, with an improvement in pain scores and a decrease in disability index, especially after SCS with HFS. However, due to the lack of homogeneity among trials and population characteristics, further studies are needed to confirm the effectiveness of non-invasive interventions in patients affected by FBSS.

Case report: The promising application of dynamic functional connectivity analysis on an individual with failed back surgery syndrome

Failed back surgery syndrome (FBSS), a chronic neuropathic pain condition, is a common indication for spinal cord stimulation (SCS). However, the mechanisms of SCS, especially its effects on supraspinal/brain functional connectivity, are still not fully understood. Resting state functional magnetic resonance imaging (rsfMRI) studies have shown characteristics in patients with chronic low back pain (cLBP). In this case study, we performed rsfMRI scanning (3.0 T) on an FBSS patient, who presented with chronic low back and leg pain following her previous lumbar microdiscectomy and had undergone permanent SCS. Appropriate MRI safety measures were undertaken to scan this subject. Seed-based functional connectivity (FC) was performed on the rsfMRI data acquired from the FBSS subject, and then compared to a group of 17 healthy controls. Seeds were identified by an atlas of resting state networks (RSNs), which is composed of 32 regions grouped into 8 networks. Sliding-window method and k-means clustering were used in dynamic FC analysis, which resulted in 4 brain states for each group. Our results demonstrated the safety and feasibility of 3T MRI scanning in a patient with implanted SCS system. Compared to the brain states of healthy controls, the FBSS subject presented very different FC patterns in less frequent brain states. The mean dwell time of brain states showed distinct distributions: the FBSS subject seemed to prefer a single state over the others. Although future studies with large sample sizes are needed to make statistical conclusions, our findings demonstrated the promising application of dynamic FC to provide more granularity with FC changes associated with different brain states in chronic pain.

A Novel Spinal Cord Stimulation System with a Battery-Free Micro Implantable Pulse Generator

Spinal cord stimulation (SCS) is effective for the treatment of chronic intractable pain of the trunk and limbs. The mechanism of action may be based, at least in part, upon the gate control theory; however, new waveforms may suggest other mechanisms. Although benefits of the SCS technology generally outweigh the complications associated with SCS, some complications such as infection and skin erosion over the implant can result in device removal. Additional reasons for device removal, such as pocket pain and battery depletion, have driven technological innovations including battery-free implants and device miniaturization. The neurostimulation system described here was specifically designed to address complications commonly associated with implantable batteries and/or larger implantable devices. The benefits of the small size are further augmented by a minimally invasive implant procedure. Usability data show that patients found this novel neurostimulation system to be easy to use and comfortable to wear. What is more, clinical data demonstrate that the use of this system provides statistically significant reduction in pain scores with responder rates (defined as ≥ 50% reduction in pain) of 78% in the low back and 83% in the leg(s). Advances in miniaturization technology arose from the considerable shrinkage of the integrated circuit, with an increase in performance, according to Moore's law (1965). However, commensurate improvements in battery technology have not maintained a similar pace. This has prompted some manufacturers to place the battery outside, against the skin, thereby allowing a massive reduction in the implant volume, with the hopes of fewer device-related complications.

60-Day PNS Treatment May Improve Identification of Delayed Responders and Delayed Non-Responders to Neurostimulation for Pain Relief

Objective

Conventional neurostimulation typically involves a brief (eg, ≤10-day) trial to assess presumed effectiveness prior to permanent implantation. Low trial conversion rates and high explant rates due to inadequate pain relief highlight the need for improved patient identification strategies. The development of a 60-day percutaneous peripheral nerve stimulation (PNS) system enables evaluation of outcomes following an extended temporary treatment period of up to 60 days, that may obviate or validate the need for permanent implant. The present study provides the first real-world evidence regarding patient response throughout a 60-day PNS treatment period.

Methods

Anonymized data listings were compiled from patients who underwent implantation of temporary percutaneous leads and opted-in to provide real-world data to the device manufacturer during routine interactions with device representatives throughout the 60-day treatment.

Results

Overall, 30% (222/747) of patients were early responders (≥50% pain relief throughout treatment). Another 31% (231/747) of patients initially presented as non-responders but surpassed 50% pain relief by the end of treatment. Conversely, 32% (239/747) of patients were non-responders throughout treatment. An additional 7% (55/747) of patients initially presented as responders but fell below 50% relief by the end of the treatment period.

Conclusion

An extended, 60-day PNS treatment may help identify delayed responders, providing the opportunity for sustained relief and improving access to effective PNS treatment. Compared to a conventionally short trial of ≤10 days, a longer 60-day PNS treatment may also help reduce explant rates by identifying delayed non-responders unlikely to benefit long-term. These scenarios support the importance of an extended 60-day temporary PNS stimulation period to help inform stepwise treatment strategies that may optimize outcomes and cost-effectiveness.

A New Direction for Closed-Loop Spinal Cord Stimulation: Combining Contemporary Therapy Paradigms with Evoked Compound Action Potential Sensing

Spinal cord stimulation (SCS) utilizes the delivery of mild electrical pulses via epidural electrodes placed on the dorsal side of the spinal cord, typically to treat chronic pain. The first clinical use of SCS involved the delivery of paresthesia inducing, low-frequency waveforms to the neural targets corresponding to the painful areas. Contemporary SCS therapies now leverage novel therapeutic pathways to limit paresthesia and deliver superior clinical outcomes. Historically, SCS has largely been delivered with fixed stimulation parameters. This approach, referred to as open-loop (OL) SCS, does not account for the fluctuations in spacing-driven by postural changes and activity-between the electrodes and the cord. These fluctuations result in variability in the delivered dose and the volume of tissue activation (VTA) that manifests with each stimulation pulse. Inconsistent dosing may lead to suboptimal therapeutic efficacy and durability. To address this clinical need, closed-loop (CL) SCS systems have been developed to automatically adjust stimulation parameters to compensate for this variability. The evoked compound action potential (ECAP), a biopotential generated by the synchronous activation of dorsal column fibers, is indicative of the VTA resulting from the stimulation pulse. The ECAP may be utilized as a control signal in CL SCS systems to adjust stimulation parameters to reduce variability in the ECAP, and in turn, variability in the VTA. While investigational CL SCS systems with ECAP sensing have so far focused solely on managing paresthesia-based SCS, such systems must also incorporate the stimulation approaches that now define the contemporary clinical practice of SCS. Accordingly, we describe here a flexible, next-generation framework for neural responsive SCS that blends science-based methodologies for pain management with real-time CL control for biophysical variation. We conclude with a clinical example of such a system and the associated performance characteristics.

Wireless Subcutaneous Trigeminal Nerve Field Stimulation for Refractory Trigeminal Pain: A Single Center Experience

INTRODUCTION

Subcutaneous trigeminal nerve field stimulation (sTNFS) is a neuromodulatory treatment for neuropathic trigeminal pain with the ability to reduce the intensity and frequency of pain attacks. However, hardware issues including lead migration, skin erosion, infection, so-called pocket pain at the site of the implanted neurostimulator are reported. Implantable wireless neurostimulation technology promises not only an even less invasive sTNFS treatment and thinner and more flexible electrodes better suited for facial implants, but also provides further advantages such as lack of an implantable neurostimulator and 3T magnetic resonance imaging compatibility.

MATERIAL AND METHODS

All patients who had received trial stimulation with a partially implantable sTNFS system were analyzed for ICHD-3 (3rd edition of the International Classification of Headache Disorders) diagnosis, success of trial stimulation, pre- and postoperative pain intensity, frequency of attacks, complications, and side-effects of sTNFS.

RESULTS

All patients (N = 3) responded to sTNFS (≥50% pain reduction) during the trial period. According to ICHD-3, N = 2 of the patients were classified with trigeminal neuralgia (TN) with concomitant persistent facial pain and N = 1 patient with multiple sclerosis associated TN. The time of the test period was 44 ± 31.24 days (mean ± SD). The average daily duration of stimulation per patient amounted 2.5 ± 2.2 hours (range 1-5). The pain intensity (defined on a visual analog scale) was reduced by 80% ± 17% (mean ± SD). Reduction or cessation in pain medication was observed in all patients. No surgical complications occurred in the long-term follow-up period of 18.84 ± 6 (mean ± SD) months.

CONCLUSION

The partially implantable sTNFS device seems to be safe, effective, and reliable. Compared to conventional devices, the equipment is not limited to the length of trial stimulation. Furthermore, the daily stimulation duration was much shorter compared to previous reports.

Research design considerations for randomized controlled trials of spinal cord stimulation for pain: Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials/Institute of Neuromodulation/International Neuromodulation Society recommendations

ABSTRACT

Spinal cord stimulation (SCS) is an interventional nonpharmacologic treatment used for chronic pain and other indications. Methods for evaluating the safety and efficacy of SCS have evolved from uncontrolled and retrospective studies to prospective randomized controlled trials (RCTs). Although randomization overcomes certain types of bias, additional challenges to the validity of RCTs of SCS include blinding, choice of control groups, nonspecific effects of treatment variables (eg, paresthesia, device programming and recharging, psychological support, and rehabilitative techniques), and safety considerations. To address these challenges, 3 professional societies (Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials, Institute of Neuromodulation, and International Neuromodulation Society) convened a meeting to develop consensus recommendations on the design, conduct, analysis, and interpretation of RCTs of SCS for chronic pain. This article summarizes the results of this meeting. Highlights of our recommendations include disclosing all funding source and potential conflicts; incorporating mechanistic objectives when possible; avoiding noninferiority designs without internal demonstration of assay sensitivity; achieving and documenting double-blinding whenever possible; documenting investigator and site experience; keeping all information provided to patients balanced with respect to expectation of benefit; disclosing all information provided to patients, including verbal scripts; using placebo/sham controls when possible; capturing a complete set of outcome assessments; accounting for ancillary pharmacologic and nonpharmacologic treatments in a clear manner; providing a complete description of intended and actual programming interactions; making a prospective ascertainment of SCS-specific safety outcomes; training patients and researchers on appropriate expectations, outcome assessments, and other key aspects of study performance; and providing transparent and complete reporting of results according to applicable reporting guidelines.

High-Frequency Spinal Cord Stimulation at 10 kHz for the Treatment of Nonsurgical Refractory Back Pain: Design of a Pragmatic, Multicenter, Randomized Controlled Trial

BACKGROUND

Spinal cord stimulation (SCS) has been shown to provide pain relief for chronic back and leg pain due to failed back surgery syndrome. But many patients with chronic back pain have not had major back surgery or are not good candidates for surgery, and conventional medical management (CMM) provides limited relief. We have termed this condition nonsurgical refractory back pain (NSRBP). Level 1 evidence does not yet exist showing the therapeutic benefit of SCS for NSRBP.

OBJECTIVE

To compare 10-kHz SCS plus CMM (10-kHz SCS + CMM) to CMM alone for treatment of NSRBP in terms of clinical and cost effectiveness.

STUDY DESIGN

Multicenter, randomized controlled trial (RCT), with subjects randomized 1:1 to either 10-kHz SCS + CMM or CMM alone. Optional crossover occurs at 6 months if treatment does not achieve ≥50% pain relief.

METHODS

Patients with NSRBP as defined above may be enrolled if they are ineligible for surgery based on surgical consultation. Subjects randomized to 10-kHz SCS + CMM will receive a permanent implant if sufficient pain relief is achieved in a temporary trial. Both groups will receive CMM per standard of care and will undergo assessments at baseline and at follow-ups to 12 months. Self-report outcomes include pain, disability, sleep, mental health, satisfaction, healthcare utilization, and quality of life.

RESULTS

Enrollment was initiated on September 10, 2018. Prespecified independent interim analysis at 40% of the enrollment target indicated the sample size was sufficient to show superiority of treatment at the primary endpoint; therefore, enrollment was stopped at 211.

CONCLUSIONS

This large multicenter RCT will provide valuable evidence to guide clinical decisions in NSRBP.

Wireless Spinal Cord Stimulation Technology for the Treatment of Neuropathic Pain: A Single-Center Experience

OBJECTIVES

A new wireless spinal cord stimulation (SCS) technology, which was introduced in recent years, promises minimal invasive SCS as well as additional advantages such as a wide range of stimulation paradigms and 3-T magnetic resonance imaging (MRI) conditionality.

MATERIALS AND METHODS

We prospectively evaluated 12 patients suffering from therapy-resistant neuropathic pain, who were implanted with a wireless SCS system from 2017 to 2019. Potential issues pertaining to handling and usability of the SCS device were evaluated from a patients' as well as from a surgeon's perspective.

RESULTS

Mean follow-up was 228.0 days (95% CI, 20.0-518.0 days). We did not record any handling issues nor did we record any relevant local discomfort associated with the implanted SCS device. N = 3/12 patients reported discomfort from wearing the SCS antenna and one patient complained about a short battery life of the controller device. There were no reported incidents during 3-T MRI studies. After an average test period of 51.7 days (95% CI, 11.0-104.0 days), N = 9/12 patients (75%) had reached pain relief of 50% or more with an average pain relief (responders and partial responders) of 67.4% (95% CI, 50.0%-85.0%). On average, patients tested 2.2 different stimulation paradigms, with frequencies ranging from 60 Hz to 10 kHz, but there was no preferred stimulation paradigm.

CONCLUSIONS

Minimal invasive implantation of wireless SCS systems was feasible and safe. The device offered a broader range of stimulation paradigms compared to conventional SCS devices, an allowed for a prolonged testing phase and continuous adjustment of SCS programs.

Cost-Effectiveness Model Shows Superiority of Wireless Spinal Cord Stimulation Implantation Without a Separate Trial

Objective

We evaluated the cost‐effectiveness of wireless spinal cord stimulation (Wireless SCS) with single stage “direct to permanent” implantation vs. screening with temporary electrodes and an external pulse generator followed by implantation of a system for long‐term use (IPG SCS).

Materials and Methods

We created a cost model that takes a 2019 United States (U.S.) payer perspective and is based on IPG SCS cost models for subjects with chronic back and/or leg pain. Our six‐month decision tree includes the screening trial period (success ≥50% relief) and leads to various levels of pain relief with or without complications for IPG SCS and Wireless SCS and without complications for conventional medical management (CMM). Every three months in the follow‐on 15‐year Markov model (with costs and quality‐adjusted life years discounted 3.5% annually), subjects remain stable or transition to deteriorated health or death. Subjects who fail SCS receive CMM. After 60 Markov cycles, a 100,000‐sample simulation reveals the impact of maximum willingness‐to‐pay (WTP) from $10,000 to $100,000 per quality‐adjusted life year on net monetary benefit (NMB). Sensitivity analyses considered the impact of the Wireless SCS screening success rate, Wireless SCS device cost, and IPG SCS device longevity.

Results

Compared with IPG SCS, Wireless SCS offers higher clinical effectiveness at a lower cost and a higher NMB for our WTP thresholds and is, thus, dominant. Wireless SCS is also cost‐effective compared with CMM. Results remain robust with 1) Wireless SCS screening success rates as low as 85% (dominant), 2) the cost of the Wireless SCS devices as high as $55,000 (cost‐effective), and 3) IPG SCS devices lasting 12 years (dominant).

Conclusions

In this model, compared with IPG SCS or with CMM, Wireless SCS is a superior strategy.