Randomized Placebo-/Sham-Controlled Trials of Spinal Cord Stimulation: A Systematic Review and Methodological Appraisal

ECAP-controlled closed-loop versus open-loop SCS for the treatment of chronic pain: 36-month results of the EVOKE blinded randomized clinical trial

INTRODUCTION

The evidence for spinal cord stimulation (SCS) has been criticized for the absence of blinded, parallel randomized controlled trials (RCTs) and limited evaluations of the long-term effects of SCS in RCTs. The aim of this study was to determine whether evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS) is associated with better outcomes when compared with fixed-output, open-loop SCS (OL-SCS) 36 months following implant.

METHODS

The EVOKE study was a multicenter, participant-blinded, investigator-blinded, and outcome assessor-blinded, randomized, controlled, parallel-arm clinical trial that compared ECAP-controlled CL-SCS with fixed-output OL-SCS. Participants with chronic, intractable back and leg pain refractory to conservative therapy were enrolled between January 2017 and February 2018, with follow-up through 36 months. The primary outcome was a reduction of at least 50% in overall back and leg pain. Holistic treatment response, a composite outcome including pain intensity, physical and emotional functioning, sleep, and health-related quality of life, and objective neural activation was also assessed.

RESULTS

At 36 months, more CL-SCS than OL-SCS participants reported ≥50% reduction (CL-SCS=77.6%, OL-SCS=49.3%; difference: 28.4%, 95% CI 12.8% to 43.9%, p<0.001) and ≥80% reduction (CL-SCS=49.3%, OL-SCS=31.3%; difference: 17.9, 95% CI 1.6% to 34.2%, p=0.032) in overall back and leg pain intensity. Clinically meaningful improvements from baseline were observed at 36 months in both CL-SCS and OL-SCS groups in all other patient-reported outcomes with greater levels of improvement with CL-SCS. A greater proportion of patients with CL-SCS were holistic treatment responders at 36-month follow-up (44.8% vs 28.4%), with a greater cumulative responder score for CL-SCS patients. Greater neural activation and accuracy were observed with CL-SCS. There were no differences between CL-SCS and OL-SCS groups in adverse events. No explants due to loss of efficacy were observed in the CL-SCS group.

CONCLUSION

This long-term evaluation with objective measurement of SCS therapy demonstrated that ECAP-controlled CL-SCS resulted in sustained, durable pain relief and superior holistic treatment response through 36 months. Greater neural activation and increased accuracy of therapy delivery were observed with ECAP-controlled CL-SCS than OL-SCS.

TRIAL REGISTRATION NUMBER

NCT02924129.

Does industry funding and study location impact findings from randomized controlled trials of spinal cord stimulation? A systematic review and meta-analysis

BACKGROUND/IMPORTANCE

Concerns have been raised that effects observed in studies of spinal cord stimulation (SCS) funded by industry have not been replicated in non-industry-funded studies and that findings may differ based on geographical location where the study was conducted.

OBJECTIVE

To investigate the impact of industry funding and geographical location on pain intensity, function, health-related quality of life and adverse events reported in randomized controlled trials (RCTs) of SCS.

EVIDENCE REVIEW

Systematic review conducted using MEDLINE, CENTRAL, EMBASE and WikiStim databases until September 2022. Parallel-group RCTs evaluating SCS for patients with neuropathic pain were included. Results of studies were combined in random-effects meta-analysis using the generic-inverse variance method. Subgroup meta-analyses were conducted according to funding source and study location. Risk of bias was assessed using Cochrane RoB 2.0 tool.

FINDINGS

Twenty-nine reports of 17 RCTs (1823 participants) were included. For the comparison of SCS with usual care, test for subgroup differences indicate no significant differences (p=0.48, moderate certainty evidence) in pain intensity score at 6 months for studies with no funding or funding not disclosed (pooled mean difference (MD) -1.96 (95% CI -3.23 to -0.69; 95% prediction interval (PI) not estimable, I2=0%, τ2=0)), industry funding (pooled MD -2.70 (95% CI -4.29 to -1.11; 95% PI -8.75 to 3.35, I2=97%, τ2=2.96) or non-industry funding (MD -3.09 (95% CI -4.47 to -1.72); 95% PI, I2 and τ2 not applicable). Studies with industry funding for the comparison of high-frequency SCS (HF-SCS) with low-frequency SCS (LF-SCS) showed statistically significant advantages for HF-SCS compared to LF-SCS while studies with no funding showed no differences between HF-SCS and LF-SCS (low certainty evidence).

CONCLUSION

All outcomes of SCS versus usual care were not significantly different between studies funded by industry and those independent from industry. Pain intensity score and change in pain intensity from baseline for comparisons of HF-SCS to LF-SCS seem to be impacted by industry funding.

Spinal cord stimulation for the symptomatic treatment of rigidity and painful spasm in a case of stiff person syndrome

BACKGROUND

Stiff person syndrome (SPS) is a rare neuroimmunological disorder characterized by rigidity and painful spasm primarily affecting the truncal and paraspinal musculature due to autoimmune-mediated neuronal hyperexcitability. Spinal cord stimulation (SCS) is an approved therapy for managing painful neuropathic conditions, including diabetic peripheral neuropathy and refractory angina pectoris. We describe the novel use of SCS for the treatment of spasm and rigidity in a 49-year-old man with seropositive stiff person syndrome (SPS). The patient was treated with intravenous immunoglobulin (IVIG) and oral medications over a 13-month period with minimal improvement, prompting consideration of SCS. To our knowledge, this is the first report of the successful use of SCS in SPS with the demonstration of multifaceted clinical improvement.

METHODS

Following a successful temporary SCS trial, permanent implantation was performed. Spasm/stiffness (Distribution of Stiffness Index; Heightened Sensitivity Scale; Penn Spasm Frequency Scale, PSFS), disability (Oswestry Disability Index, ODI; Pain Disability Index, PDI), depression (Patient Health Questionnaire-9, PHQ-9), sleep (Pittsburgh Sleep Quality Index, PSQI), fatigue (Fatigue Severity Scale, FSS), pain (Numerical Pain Rating Scale, NPRS), quality of life (EuroQoL 5 Dimension 5 Level, EQ-5D-5L), and medication usage were assessed at baseline, 6-month, and 10-month postimplantation.

RESULTS

ODI, PHQ-9, FSS, NPRS, PSQI, and EQ-5D-5L scores showed a notable change from baseline and surpassed the defined minimal clinically important difference (MCID) at 6-month and 10-month follow-up. Oral medication dosages were reduced.

CONCLUSIONS

The novel use of SCS therapy in seropositive SPS resulted in functional improvement and attenuation of symptoms. We present possible mechanisms by which SCS may produce clinical response in patients with SPS and aim to demonstrate proof-of-concept for a future comprehensive pilot study evaluating SCS-mediated response in SPS.

Sham controls in device trials for chronic pain - tricky in practice-a review article

Background

Chronic pain affects one in four people and this figure is likely to increase further in line with an ageing population. Efforts to evaluate nonpharmacological interventions to support this patient population have become a priority for pain research. For device trials, the use of a sham control can add to the scientific validity and quality of a study. However, only a small proportion of pain trials include a sham control, and many are of poor quality. To facilitate the conduct of high-quality trials there is a need for a comprehensive overview to guide researchers within this area. The objective of this review was to synthesise the published data to address this need.

Methods

We identified studies that considered the evaluation, design, and conduct of sham-controlled trials in chronic pain by searching MEDLINE, CINAHL and Science Direct to November 2022. Studies that included sufficient content to inform the conduct/design of future research were included. An inductive thematic analysis approach was used to identify themes that require consideration when conducting sham-controlled trials. These are presented as a narrative review.

Results

37 articles were included. Identified themes related to the type of sham device, sham design, bias, study population and ethics.

Conclusions

To conduct good quality research the challenges surrounding the use of sham interventions need to be better considered. We highlight salient issues and provide recommendations for the conduct and reporting of sham-controlled device trials in chronic pain.

Dorsal root ganglion stimulation for the treatment of chronic pelvic pain: A systematic review

BACKGROUND

Chronic pelvic pain (CPP) is a difficult condition to treat. Due to complex pelvic innervation, dorsal column spinal cord stimulation (SCS) has not been shown to produce the same effect as dorsal root ganglion stimulation (DRGS) given emerging evidence suggesting that applying DRGS may result in favorable outcomes for individuals with CPP. The aim of this systematic review is to investigate the clinical use and effectiveness of DRGS for patients with CPP.

MATERIALS AND METHODS

A systematic review of clinical studies demonstrating the use of DRGS for CPP. Searches were conducted using four electronic databases (PubMed, EMBASE, CINAHL, and Web of Science) across August and September 2022.

RESULTS

A total of nine studies comprising 65 total patients with variable pelvic pain etiologies met the inclusion criteria. The majority of subjects implanted with DRGS reported >50% mean pain reduction at variable times of follow-up. Secondary outcomes reported throughout studies including quality of life (QOL) and pain medication consumption were reported to be significantly improved.

CONCLUSIONS

Dorsal root ganglion stimulation for CPP continues to lack supportive evidence from well-designed, high-quality studies and recommendations from consensus committee experts. However, we present consistent evidence from level IV studies showing success with the use of DRGS for CPP in reducing pain symptoms along with reports of improved QOL through periods as short as 2 months to as long as 3 years. Because the available studies at this time are of low quality with a high risk of bias, we strongly recommend the facilitation of high-quality studies with larger sample sizes in order to better ascertain the utility of DRGS for this specific patient population. At the same time, from a clinical perspective, it may be reasonable and appropriate to evaluate patients for DRGS candidacy on a case-by-case basis, especially those patients who report CPP symptoms that are refractory to noninterventional measures and who may not be ideal candidates for other forms of neuromodulation.

Spinal cord stimulation for refractory pericarditis: a case report and a review of the mechanism of action

Background and objectives

In recent years, spinal cord stimulation (SCS) has emerged as a promising management option for chronic pain of multiple etiologies. While its effectiveness has been strongly suggested in many patients, the exact mechanism of action of SCS is incompletely understood. This article reviews the leading mechanisms underlying the analgesic and cardiovascular effects of SCS and reports its novel benefits in a case of recurrent pericarditis.

Literature review

Throughout history, the analgesic properties of SCS were thought to arise via stimulation of the spinothalamic tract. Although this mechanism has been thoroughly reported, new research and patient outcomes from SCS have revealed various additional properties that cannot be fully explained by this mechanism alone. Evidence suggests that SCS enhances calcitonin gene-related peptide release and modulates inflammatory cytokine secretion, sympathetic tone, and inhibitory neurotransmitter secretion. These distinct mechanisms likely collectively contribute to the therapeutic effects of SCS on the cardiovascular system and pain management.

Case report

We report the case of a 48-year-old male patient with recurrent pericarditis, characterized by refractory angina-like pain and reduced left ventricular ejection fraction (LVEF). After 1 year of having a spinal cord stimulator implanted, the patient is free from pain and narcotics, with a reduction of 428 mg equivalent dose of morphine. The patient's LVEF increased from 40% to 45% without changes to his previous medical treatment. This is the first reported case of refractory pericarditis managed with spinal cord stimulation.

Conclusion

Recognizing the improved pain management, reduced narcotic usage, and improved LVEF in our patient following SCS is critical to paving the way toward a complete understanding of the mechanism of action of SCS. This case reveals the therapeutic potential of SCS for cardiovascular pathologies other than refractory angina pectoris.

Spinal Cord Stimulation for Gait Disorders in Parkinson's Disease

BACKGROUND

Spinal cord stimulation (SCS) is a therapeutic procedure widely used in the management of refractory chronic pain. Evidence from case reports and small descriptive studies has emerged suggesting a role for SCS in patients with gait dysfunction, such as freezing of gait (FoG) and postural imbalance. These are severely debilitating symptoms of advanced Parkinson's disease (PD).

OBJECTIVE

To establish the current evidence base for the potential application of SCS on gait and balance dysfunction in PD patients.

METHODS

Three online databases were screened for relevant manuscripts. Two separate searches and four different search strategies were applied to yield relevant results. The main parameters of interest were postural and gait symptoms; secondary outcomes were Quality of Life (QoL) and adverse effects.

RESULTS

Nineteen studies fulfilled the inclusion criteria. Motor improvements using section III of the Unified Parkinson's Disease Rating Score (UPDRS-III) were available in 13 studies. Measurements to assess FoG reported the following improvements: FoG questionnaires (in 1/19 studies); generalized freezing parameters (2); and walkway/wireless accelerometer measurements (2). Parameters of postural imbalance and falling improved as follows: BBS (1); posture sagittal vertical axis (1); and generalized data on postural instability (8). Two studies reported on adverse effects. QoL was shown to improve as follows: EQ-5D (2); ADL (1); SF-36 (1); BDI-II (1); PDQ-8 (1); HDRS (1); and VAS (5).

CONCLUSION

SCS may have a therapeutic potential in advanced PD patients suffering from postural and gait-related symptoms. The existing evidence suggests that SCS positively affects patients' QoL with an acceptable safety profile in this patient population.

Does a Screening Trial for Spinal Cord Stimulation in Patients With Chronic Pain of Neuropathic Origin Have Clinical Utility (TRIAL-STIM)? 36-Month Results From a Randomized Controlled Trial

BACKGROUND

Screening trials before full implantation of a spinal cord stimulation device are recommended by clinical guidelines and regulators, although there is limited evidence for their use. The TRIAL-STIM study showed that a screening trial strategy does not provide superior patient pain outcome at 6-month follow-up compared with not doing a screening trial and that it was not cost-effective.

OBJECTIVE

To report the long-term follow-up results of the TRIAL-STIM study.

METHODS

The primary outcome of this pragmatic randomized controlled trial was pain intensity as measured on a numerical rating scale (NRS) and secondary outcomes were the proportion of patients achieving at least 50% and 30% pain relief at 6 months, health-related quality of life, and complication rates.

RESULTS

Thirty patients allocated to the "Trial Group" (TG) and 36 patients allocated to the "No Trial Group" (NTG) completed outcome assessment at 36-month follow-up. Although there was a reduction in NRS pain and improvements in utility scores from baseline to 36 months in both groups, there was no difference in the primary outcome of pain intensity NRS between TG and NTG (adjusted mean difference: -0.60, 95% CI: -1.83 to 0.63), EuroQol-5 Dimension utility values (adjusted mean difference: -0.02, 95% CI: -0.13 to 0.10), or proportion of pain responders (33% TG vs 31% NTG). No differences were observed between the groups for the likelihood of spinal cord stimulation device explant or reporting an adverse advent up to 36-month follow-up.

CONCLUSION

The long-term results show no patient outcome benefit in undertaking an SCS screening trial.

Effect of Spinal Cord Burst Stimulation vs Placebo Stimulation on Disability in Patients With Chronic Radicular Pain After Lumbar Spine Surgery: A Randomized Clinical Trial

IMPORTANCE

The use of spinal cord stimulation for chronic pain after lumbar spine surgery is increasing, yet rigorous evidence of its efficacy is lacking.

OBJECTIVE

To investigate the efficacy of spinal cord burst stimulation, which involves the placement of an implantable pulse generator connected to electrodes with leads that travel into the epidural space posterior to the spinal cord dorsal columns, in patients with chronic radiculopathy after surgery for degenerative lumbar spine disorders.

DESIGN, SETTING, AND PARTICIPANTS

This placebo-controlled, crossover, randomized clinical trial in 50 patients was conducted at St Olavs University Hospital in Norway, with study enrollment from September 5, 2018, through April 28, 2021. The date of final follow-up was May 20, 2022.

INTERVENTIONS

Patients underwent two 3-month periods with spinal cord burst stimulation and two 3-month periods with placebo stimulation in a randomized order. Burst stimulation consisted of closely spaced, high-frequency electrical stimuli delivered to the spinal cord. The stimulus consisted of a 40-Hz burst mode of constant-current stimuli with 4 spikes per burst and an amplitude corresponding to 50% to 70% of the paresthesia perception threshold.

MAIN OUTCOMES AND MEASURES

The primary outcome was difference in change from baseline in the self-reported Oswestry Disability Index (ODI; range, 0 points [no disability] to 100 points [maximum disability]; the minimal clinically important difference was 10 points) score between periods with burst stimulation and placebo stimulation. The secondary outcomes were leg and back pain, quality of life, physical activity levels, and adverse events.

RESULTS

Among 50 patients who were randomized (mean age, 52.2 [SD, 9.9] years; 27 [54%] were women), 47 (94%) had at least 1 follow-up ODI score and 42 (84%) completed all stimulation randomization periods and ODI measurements. The mean ODI score at baseline was 44.7 points and the mean changes in ODI score were -10.6 points for the burst stimulation periods and -9.3 points for the placebo stimulation periods, resulting in a mean between-group difference of -1.3 points (95% CI, -3.9 to 1.3 points; P = .32). None of the prespecified secondary outcomes showed a significant difference. Nine patients (18%) experienced adverse events, including 4 (8%) who required surgical revision of the implanted system.

CONCLUSIONS AND RELEVANCE

Among patients with chronic radicular pain after lumbar spine surgery, spinal cord burst stimulation, compared with placebo stimulation, after placement of a spinal cord stimulator resulted in no significant difference in the change from baseline in self-reported back pain-related disability.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03546738.

Spinal Cord Stimulation in Chronic Low Back Pain Syndrome: Mechanisms of Modulation, Technical Features and Clinical Application

Chronic low-back pain (CLBP) is a common disease with several negative consequences on the quality of life, work and activity ability and increased costs to the health-care system. When pharmacological, psychological, physical and occupational therapies or surgery fail to reduce CLBP, patients may be a candidate for Spinal Cord Stimulation (SCS). SCS consists of the transcutaneous or surgical implantation of different types of electrodes in the epidural space; electrodes are then connected to an Implanted Pulse Generator (IPG) that generates stimulating currents. Through spinal and supraspinal mechanisms based on the “gate control theory for pain transmission”, SCS reduces symptoms of CLBP in the almost totality of well-selected patients and its effect lasts up to eight years in around 75% of patients. However, the evidence in favor of SCS still remains weak, mainly due to poor trial methodology and design. This narrative review is mainly addressed to those professionals that may encounter patients with CLBP failing conventional treatments. For this reason, we report the mechanisms of pain relief during SCS, the technical features and some clinical considerations about the application of SCS in patients with CLBP.

Patient Selection for Spinal Cord Stimulation in Treatment of Pain: Sequential Decision-Making Model - A Narrative Review

Despite the well-known efficacy of spinal cord stimulation (SCS) in chronic pain management, patient selection in clinical practice remains challenging. The aim of this review is to provide an overview of the factors that can influence the process of patient selection for SCS treatment. A sequential decision-making model is presented within a tier system that operates in clinical practice. The first level incorporates the underlying disease as a primary indication for SCS, country-related reimbursement rules, and SCS screening-trial criteria in combination with underlying psychological factors as initial selection criteria in evaluating patient eligibility for SCS. The second tier is aligned with the individualized approach within precision pain medicine, whereby individual goals and expectations and the potential need for preoperative optimizations are emphasized. Additionally, this tier relies on results from prediction models to provide an estimate of the efficacy of SCS in the long term. In the third tier, selection bias, MRI compatibility, and ethical beliefs are included, together with recent technological innovations, superiority of specific stimulation paradigms, and new feedback systems that could indirectly influence the decision-making of the physician. Both patients and physicians should be aware of the different aspects that influence patient selection in relation to SCS for pain management to make an independent decision on whether or not to initiate a treatment trajectory with SCS.

The Added Value of Intraoperative Hypnosis during Spinal Cord Stimulation Lead Implantation under Awake Anesthesia in Patients Presenting with Refractory Chronic Pain

To improve pain relief for refractory pain condition, spinal cord stimulation (SCS) needs to target the dedicated neuronal fibers within the dorsal columns. Intraoperative feedback from the patient can optimize lead placement but requires “awake surgery”, allowing interaction between patient and surgeon. This can produce negative effects like anxiety and stress. To better manage these aspects, we propose to combine intraoperative hypnosis with awake anesthesia. Seventy-four patients (35 females, 22–80 years) presenting with chronic refractory pain, were offered intraoperative hypnosis during awake SCS lead implantation. Interactive conversational hypnosis was used as well as interactive touch, which was enhanced during painful moments during the lead intraoperative programming. All patients participated actively during the intraoperative testing which helped to optimize the lead positioning. They kept an extremely positive memory of the surgery and of the hypnotic experience, despite some painful moments. Pain could be reduced in these patients by using interactions and touch, which works on Gate Control modulation. Positive memory was reinforced by congratulations to create self-confidence and to induce positive expectations, which could reinforce the Diffuse Noxious Inhibitory Controls at the spinal level. Cooperation was improved because the patient was actively participating and thus, much more alert when feedback was required. Combining intraoperative hypnosis with awake anesthesia appears helpful for SCS lead implantation. It enhances patient cooperation, allows optimization of lead positioning, and leads to better pain control, positive and resourceful memory.

The Challenge of Converting "Failed Spinal Cord Stimulation Syndrome" Back to Clinical Success, Using SCS Reprogramming as Salvage Therapy, through Neurostimulation Adapters Combined with 3D-Computerized Pain Mapping Assessment: A Real Life Retrospective Study

While paresthesia-based Spinal Cord Stimulation (SCS) has been proven effective as treatment for chronic neuropathic pain, its initial benefits may lead to the development of "Failed SCS Syndrome' (FSCSS) defined as decrease over time related to Loss of Efficacy (LoE) with or without Loss of Coverage (LoC). Development of technologies associating new paresthesia-free stimulation waveforms and implanted pulse generator adapters provide opportunities to manage patients with LoE. The main goal of our study was to investigate salvage procedures, through neurostimulation adapters, in patients already implanted with SCS and experiencing LoE. We retrospectively analyzed a cohort of patients who were offered new SCS programs/waveforms through an implanted adapter between 2018 and 2021. Patients were evaluated before and at 1-, 3-, 6- and 12-month follow-ups. Outcomes included pain intensity rating with a Visual Analog Scale (VAS), pain/coverage mappings and stimulation preferences. Last follow-up evaluations (N = 27) showed significant improvement in VAS (p = 0.0001), ODI (p = 0.021) and quality of life (p = 0.023). In the 11/27 patients with LoC, SCS efficacy on pain intensity (36.89%) was accompanied via paresthesia coverage recovery (55.57%) and pain surface decrease (47.01%). At 12-month follow-up, 81.3% preferred to keep tonic stimulation in their waveform portfolio. SCS conversion using adapters appears promising as a salvage solution, with an emphasis on paresthesia recapturing enabled via spatial retargeting. In light of these results, adapters could be integrated in SCS rescue algorithms or should be considered in SCS rescue.

Association of Spinal Cord Stimulator Implantation With Persistent Opioid Use in Patients With Postlaminectomy Syndrome

IMPORTANCE

The results of studies evaluating spinal cord stimulation (SCS) for postlaminectomy syndrome (PLS) have yielded mixed results. This has led to an increased emphasis on objective outcome measures such as opioid prescribing.

OBJECTIVE

To determine the association between SCS and long-term opioid therapy (LOT) for PLS.

DESIGN, SETTING, AND PARTICIPANTS

In this cohort study, adults with PLS were identified using the TriNetx Diamond Network and separated based on whether they underwent SCS. Patients were stratified according to baseline opioid use (opioid-naive or receiving LOT) and subsequent opioid therapy over the 12-month period ranging from 3 to 15 months post-SCS implantation or post-PLS index date. Statistical analysis was performed from June to December 2021.

EXPOSURE

SCS.

MAIN OUTCOMES AND MEASURES

The main outcome was cessation of opioid use among patients receiving LOT or abstinence from opioids among opioid-naive patients. Opioid-naive patients were defined as those receiving at most 2 opioid prescriptions per year, and patients on LOT were those receiving at least 6 opioid prescriptions per year.

RESULTS

Among 552 937 eligible patients treated between December 2015 and May 2021, 26 179 with PLS received an SCS implant. The median (IQR) patient age was 60 (51-69) years; 305 802 patients (55.3%) were female. Among those reporting racial identify (37.0% [204 758 patients]), 9.3% (18 971 patients) were African American, 0.3% (648 patients) were Asian, and 90.4% (185 139 patients) were White. Compared with those who did not receive an SCS, individuals who received an SCS were more likely to be using opioids preimplantation (mean [SD] prescriptions: 4.3 [8.5] vs 4.1 [9.3]; P < .001) but less likely to be using opioids after SCS implantation (mean [SD] prescriptions: 3.8 [8.2] vs 4.0 [9.4]; P = .006). In the 12-month study period, similar proportions in the SCS and no-SCS groups receiving baseline LOT remained on LOT (70.3% [n = 74 585] vs 69.2% [n = 3882], respectively; P = .10). In opioid-naive patients, SCS was associated with a small decreased likelihood of patients subsequently receiving LOT (7.6% vs 7.0%; difference, -0.6% [95% CI, -1.0% to -0.2%]; P = .003). In multivariable analysis, SCS was associated with an increased likelihood of not being on opioids in both opioid-naive (adjusted odds ratio [OR], 0.90 [95% CI, 0.85-0.96]; P < .001) and LOT patients (adjusted OR, 0.93 [95% CI, 0.88-0.99]; P = .02). White patients were significantly more likely to be diagnosed with PLS (ie, underwent surgery) (90.4% vs 85.2%; difference, 5.2% [95% CI, 5.1%-5.4%]; P < .001) and receive an SCS (93.7% vs 90.3%; difference, 3.4% [95% CI, 2.9% to 4.0%]; P < .001) than patients of other racial identities.

CONCLUSIONS AND RELEVANCE

These findings suggest that under real-life conditions, SCS was associated with small, clinically questionable associations with opioid discontinuation and not starting opioids in the context of PLS.

Comparison of Spinal Cord Stimulation vs. Dorsal Root Ganglion Stimulation vs. Association of Both in Patients with Refractory Chronic Back and/or Lower Limb Neuropathic Pain: An International, Prospective, Randomized, Double-Blinded, Crossover Trial (BOOST-DRG Study)

While spinal cord stimulation (SCS) is a well-established therapy to address refractory persistent spinal pain syndrome after spinal surgery (PSPS-T2), its lack of spatial selectivity and reported discomfort due to positional effects can be considered as significant limitations. As alternatives, new waveforms, such as burst stimulation and different spatial neural targets, such as dorsal root ganglion stimulation (DRGS), have shown promising results. Comparisons between DRGS and standard SCS, or their combination, have never been studied on the same patients. "BOOST DRG" is the first prospective, randomized, double-blinded, crossover study to compare SCS vs. DRGS vs. SCS+DRGS. Sixty-six PSPS-T2 patients will be recruited internationally in three centers. Before crossing over, patients will receive each stimulation modality for 1 month, using tonic conventional stimulation. After 3 months, stimulation will consist in switching to burst for 1 month, and patients will choose which modality/waveform they receive and will then be reassessed at 6 and 12 months. In addition to our primary outcome based on pain rating, this study is designed to assess quality of life, functional disability, psychological distress, pain surface coverage, global impression of change, medication quantification, adverse events, brain functional imaging and electroencephalography, with the objective being to provide a multidimensional insight based on composite pain assessment.

The Added Value of Subcutaneous Peripheral Nerve Field Stimulation Combined with SCS, as Salvage Therapy, for Refractory Low Back Pain Component in Persistent Spinal Pain Syndrome Implanted Patients: A Randomized Controlled Study (CUMPNS Study) Based on 3D-Mapping Composite Pain Assessment

While Spinal Cord Stimulation (SCS) provides satisfaction to almost 2/3 of Persistent Spinal Pain Syndrome-Type 2 (PSPS-T2) patients implanted for refractory chronic back and/or leg pain, when not adequately addressed the back pain component, leaves patients in a therapeutic cul-de-sac. Peripheral Nerve field Stimulation (PNfS) has shown interesting results addressing back pain in the same population. Far from placing these two techniques in opposition, we suggest that these approaches could be combined to better treat PSPS-T2 patients. We designed a RCT (CUMPNS), with a 12-month follow-up, to assess the potential added value of PNfS, as a salvage therapy, in PSPS-T2 patients experiencing a "Failed SCS Syndrome" in the back pain component. Fourteen patients were included in this study and randomized into 2 groups ("SCS + PNfS" group/n = 6 vs. "SCS only" group/n = 8). The primary objective of the study was to compare the percentage of back pain surface decrease after 3 months, using a computerized interface to obtain quantitative pain mappings, combined with multi-dimensional SCS outcomes. Back pain surface decreased significantly greater for the "SCS + PNfS" group (80.2% ± 21.3%) compared to the "SCS only" group (13.2% ± 94.8%) (p = 0.012), highlighting the clinical interest of SCS + PNfS, in cases where SCS fails to address back pain.

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.

Neuromodulation for chronic pain

Neuromodulation is an expanding area of pain medicine that incorporates an array of non-invasive, minimally invasive, and surgical electrical therapies. In this Series paper, we focus on spinal cord stimulation (SCS) therapies discussed within the framework of other invasive, minimally invasive, and non-invasive neuromodulation therapies. These therapies include deep brain and motor cortex stimulation, peripheral nerve stimulation, and the non-invasive treatments of repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation. SCS methods with electrical variables that differ from traditional SCS have been approved. Although methods devoid of paraesthesias (eg, high frequency) should theoretically allow for placebo-controlled trials, few have been done. There is low-to-moderate quality evidence that SCS is superior to reoperation or conventional medical management for failed back surgery syndrome, and conflicting evidence as to the superiority of traditional SCS over sham stimulation or between different SCS modalities. Peripheral nerve stimulation technologies have also undergone rapid development and become less invasive, including many that are placed percutaneously. There is low-to-moderate quality evidence that peripheral nerve stimulation is effective for neuropathic pain in an extremity, low quality evidence that it is effective for back pain with or without leg pain, and conflicting evidence that it can prevent migraines. In the USA and many areas in Europe, deep brain and motor cortex stimulation are not approved for chronic pain, but are used off-label for refractory cases. Overall, there is mixed evidence supporting brain stimulation, with most sham-controlled trials yielding negative findings. Regarding non-invasive modalities, there is moderate quality evidence that repetitive transcranial magnetic stimulation does not provide meaningful benefit for chronic pain in general, but conflicting evidence regarding pain relief for neuropathic pain and headaches. For transcranial direct current stimulation, there is low-quality evidence supporting its benefit for chronic pain, but conflicting evidence regarding a small treatment effect for neuropathic pain and headaches. For transcutaneous electrical nerve stimulation, there is low-quality evidence that it is superior to sham or no treatment for neuropathic pain, but conflicting evidence for non-neuropathic pain. Future research should focus on better evaluating the short-term and long-term effectiveness of all neuromodulation modalities and whether they decrease health-care use, and on refining selection criteria and treatment variables.

Auricular Vagus Neuromodulation-A Systematic Review on Quality of Evidence and Clinical Effects

Background: The auricular branch of the vagus nerve runs superficially, which makes it a favorable target for non-invasive stimulation techniques to modulate vagal activity. For this reason, there have been many early-stage clinical trials on a diverse range of conditions. These trials often report conflicting results for the same indication. Methods: Using the Cochrane Risk of Bias tool we conducted a systematic review of auricular vagus nerve stimulation (aVNS) randomized controlled trials (RCTs) to identify the factors that led to these conflicting results. The majority of aVNS studies were assessed as having "some" or "high" risk of bias, which makes it difficult to interpret their results in a broader context. Results: There is evidence of a modest decrease in heart rate during higher stimulation dosages, sometimes at above the level of sensory discomfort. Findings on heart rate variability conflict between studies and are hindered by trial design, including inappropriate washout periods, and multiple methods used to quantify heart rate variability. There is early-stage evidence to suggest aVNS may reduce circulating levels and endotoxin-induced levels of inflammatory markers. Studies on epilepsy reached primary endpoints similar to previous RCTs testing implantable vagus nerve stimulation therapy. Preliminary evidence shows that aVNS ameliorated pathological pain but not evoked pain. Discussion: Based on results of the Cochrane analysis we list common improvements for the reporting of results, which can be implemented immediately to improve the quality of evidence. In the long term, existing data from aVNS studies and salient lessons from drug development highlight the need for direct measures of local neural target engagement. Direct measures of neural activity around the electrode will provide data for the optimization of electrode design, placement, and stimulation waveform parameters to improve on-target engagement and minimize off-target activation. Furthermore, direct measures of target engagement, along with consistent evaluation of blinding success, must be used to improve the design of controls-a major source of concern identified in the Cochrane analysis. The need for direct measures of neural target engagement and consistent evaluation of blinding success is applicable to the development of other paresthesia-inducing neuromodulation therapies and their control designs.

The American Society of Pain and Neuroscience (ASPN) Practical Guidelines to Study Design and Scientific Manuscript Preparation in Neuromodulation

Background

Healthcare clinical and even policy decisions are progressively made based on research-based evidence. The process by which the appropriate trials are developed and well-written manuscripts by means of evidence-based medicine recommendations has resulted in unprecedented necessity in evidence-based medicine in neuromodulation.

Methods

The essential considerations in the planning of neuromodulation research are discussed in the light of available scientific literature as well as the authors’ scientific expertise regarding research study design and scientific manuscript preparation.

Conclusion

This article should enable the reader to understand how to appropriately design a clinical research study and prepare scientific manuscripts. The high-quality and well-designed studies, when performed and reported effectively, support evidence-based medicine and foster improved patient outcomes.

Spinal cord stimulation in the treatment of peripheral vascular disease: a systematic review - revival of a promising therapeutic option?

INTRODUCTION

Peripheral vascular disease (PVD) is caused by a blood circulation disorder of the arteries and Critical Limb Ischemia (CLI) is the advanced state of PVD. For patients with surgically non-reconstructable CLI, Spinal Cord Stimulation (SCS) appears to be an alternative therapeutic option.

OBJECTIVE

The aim of our study was to investigate the efficacy of SCS in non-reconstructable CLI compared with the conservative treatment and re-appraise the existing literature in light of the recent advances in neuromodulation.

METHODS

We conducted a systematic review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, using electronic databases and reference lists for article retrieval.

RESULTS

A total of 404 records were identified and finally 6 randomised controlled trials (RCTs), a Cochrane review and a meta-analysis were included in our systematic review. The studies assessed the efficacy of tonic SCS in the treatment of patients with non-reconstructable CLI compared with the conservative treatment. There is moderate to high quality evidence suggesting, that tonic SCS has beneficial effects for patients suffering from non-reconstructable CLI in terms of limb salvage, pain relief, clinical improvement and quality of life. The contradictory conclusions of the two meta-analyses regarding the efficacy of SCS for limb salvage at 12 months refer rather to the magnitude of the beneficial effect than to the effect itself. So far, the current literature provides evidence about the traditional tonic SCS but there is a lack of studies investigating the efficacy of new waveforms in the treatment of non-reconstructable CLI.

CONCLUSION

SCS represents an alternative for PVD patients with non-reconstructable CLI and the existing literature provides encouraging clinical results, that should not be neglected. Instead, they should be re-appraised in light of the recent advances in neuromodulation with the emergence of novel waveform technologies and neuromodulation targets.

Efficacy of different spinal cord stimulation paradigms for the treatment of chronic neuropathic pain (PARS-trial): study protocol for a double-blinded, randomized, and placebo-controlled crossover trial

Background

Spinal cord stimulation (SCS) is an effective method to treat neuropathic pain; however, it is challenging to compare different stimulation modalities in an individual patient, and thus, it is largely unknown which of the many available SCS modalities is most effective. Specifically, electrodes leading out through the skin would have to be consecutively connected to different, incompatible SCS devices and be tested over a time period of several weeks or even months. The risk of wound infections for such a study would be unacceptably high and blinding of the trial difficult. The PARS-trial seizes the capacity of a new type of wireless SCS device, which enables a blinded and systematic intra-patient comparison of different SCS modalities over extended time periods and without increasing wound infection rates.

Methods

The PARS-trial is designed as a double-blinded, randomized, and placebo-controlled multi-center crossover study. It will compare the clinical effectiveness of the three most relevant SCS paradigms in individual patients. The trial will recruit 60 patients suffering from intractable neuropathic pain of the lower extremities, who have been considered for SCS therapy and were already implanted with a wireless SCS device prior to study participation. Over a time period of 35 days, patients will be treated consecutively with three different SCS paradigms (“burst,” “1 kHz,” and “1.499 kHz”) and placebo stimulation. Each SCS paradigm will be applied for 5 days with a washout period of 70 h between stimulation cycles. The primary endpoint of the study is the level of pain self-assessment on the visual analogue scale after 5 days of SCS.

Secondary, exploratory endpoints include self-assessment of pain quality (as determined by painDETECT questionnaire), quality of life (as determined by Quality of Life EQ-5D-5L questionnaire), anxiety perception (as determined by the Hospital Anxiety and Depression Scale), and physical restriction (as determined by the Oswestry Disability Index).

Discussion

Combining paresthesia-free SCS modalities with wireless SCS offers a unique opportunity for a blinded and systematic comparison of different SCS modalities in individual patients. This trial will advance our understanding of the clinical effectiveness of the most relevant SCS paradigms.

Trial registration

German Clinical Trials Register, DRKS00018929. Registered on 14 January 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-020-05013-7.

Analgesic Efficacy of "Burst" and Tonic (500 Hz) Spinal Cord Stimulation Patterns: A Randomized Placebo-Controlled Crossover Study

OBJECTIVES

The aim of this study was to compare the efficacy in reducing pain intensity in adult subjects suffering from chronic back and leg pain of burst (BST) and tonic sub-threshold stimulation at 500 Hz (T500) vs. sham stimulation delivered by a spinal cord stimulation (SCS) device capable of automated postural adjustment of current intensity.

MATERIALS AND METHODS

A multicentre randomized double-blind, three-period, three-treatment, crossover study was undertaken at two centers in the United Kingdom. Patients who had achieved stable pain relief with a conventional SCS capable of automated postural adjustment of current intensity were randomized to sequences of BST, T500, and sham SCS with treatment order balanced across the six possible sequences. A current leakage was programmed into the implantable pulse generator (IPG) in the sham period. The primary outcome was patient reported pain intensity using a visual analog scale (VAS).

RESULTS

Nineteen patients were enrolled and randomized. The mean reduction in pain with T500 was statistically significantly greater than that observed with either sham (25%; 95% CI, 8%-38%; p = 0.008) or BST (28%; 95% CI, 13%-41%; p = 0.002). There were no statistically significant differences in pain VAS for BST versus Sham (5%; 95% CI, -13% to 27%; p = 0.59). Exploratory sub-group analyses by study site and sex were also conducted for the T500 vs. sham and BST versus sham comparisons.

CONCLUSIONS

The findings suggest a superior outcome versus sham from T500 stimulation over BST stimulation and a practical equivalence between BST and sham in a group of subjects with leg and back pain habituated to tonic SCS and having achieved a stable status with stimulation.

Spinal cord stimulation therapy for gait dysfunction in progressive supranuclear palsy patients

BACKGROUND

There are no effective symptomatic treatments for progressive supranuclear palsy (PSP). Recent studies report benefits of spinal cord stimulation (SCS) for freezing of gait (FOG) and gait disorders in Parkinson's disease and atypical Parkinsonism patients. This is the first study to report therapeutic effects of SCS in Richardson's syndrome PSP (PSP-RS) patients.

METHODS

Epidural SCS was implanted in three female PSP-RS participants (3.2 ± 1.3 years with disease). Six programs (300-400 µs/30-130 Hz) were randomly tested at suprathreshold intensity on separate days. The setting that best improved gait/FOG was used daily by each participant in the study. Protokinetics walkway captured spatiotemporal gait measures and FOG episodes (turning on the spot and while walking) and clinical scales including FOG questionnaire, UPDRS-III (OFF-/ON-L-dopa), and participant-perceived global impression of change (GISC) were collected at pre-SCS, and 3, 6, 12 months post-SCS.

RESULTS

Participant #1 demonstrated the highest GISC score (6.5/10) with a consistent reduction of FOGs by 43.8%, UPDRS-III score (- 5 points), and improved step length and stride velocity (33.6%) while maintaining a L-dopa response of ~ 12% over the 12 months. Participant #2, walking FOG frequency and turning duration was reduced by 39.0% (OFF-L-dopa), and ON-L-dopa UPDRS-III score worsened (+ 5 points) at 12 months. Participant #3, FOG frequency reduced by 75% up to 6 months rating a GISC 3/10 score, however disease severity worsened at 12 months. Ambulatory gait parameters universally improved by 29.6% in all participants.

CONCLUSION

The results support the benefit of SCS for FOG and gait symptoms in PSP-RS and suggests early SCS intervention for dopaminergic-resistant gait should be considered.

Sub-Perception and Supra-Perception Spinal Cord Stimulation in Chronic Pain Syndrome: A Randomized, Semi-Double-Blind, Crossover, Placebo-Controlled Trial

BACKGROUND

The introduction of modern sub-perception modalities has improved the efficacy of spinal cord stimulation (SCS) in refractory pain syndromes of the trunk and lower limbs. The objective of this study was to evaluate the effectiveness of low and high frequency SCS among patients with chronic pain.

MATERIAL AND METHODS

A randomised, semi-double-blind, placebo controlled, four period (4 × 2 weeks) crossover trial was conducted from August 2018 to January 2020. Eighteen patients with SCS due to failed back surgery syndrome and/or complex regional pain syndrome were randomised to four treatment arms without washout periods: (1) low frequency (40-60 Hz), (2) 1 kHz, (3) clustered tonic, and (4) sham SCS (i.e., placebo). The primary outcome was pain scores measured by visual analogue scale (VAS) preoperatively and during subsequent treatment arms.

RESULTS

Pain scores (VAS) reported during the preoperative period was M (SD) = 8.13 (0.99). There was a 50% reduction in pain reported in the low frequency tonic treatment group (M (SD) = 4.18 (1.76)), a 37% reduction in the 1 kHz treatment group (M (SD) = 5.17 (1.4)), a 34% reduction in the clustered tonic settings group (M (SD) = 5.27 (1.33)), and a 34% reduction in the sham stimulation group (M (SD) = 5.42 (1.22)). The reduction in pain from the preoperative period to the treatment period was significant in each treatment group (p < 0.001). Overall, these reductions were of comparable magnitude between treatments. However, the modality most preferred by patients was low frequency (55% or 10 patients).

CONCLUSIONS

The pain-relieving effects of SCS reached significance and were comparable across all modes of stimulation including sham. Sub-perception stimulation was not superior to supra-perception. SCS was characterised by a high degree of placebo effect. No evidence of carryover effect was observed between subsequent treatments. Contemporary neuromodulation procedures should be tailored to the individual preferences of patients.

Systematic Review of Research Methods and Reporting Quality of Randomized Clinical Trials of Spinal Cord Stimulation for Pain

This systematic review assessed design characteristics and reporting quality of published randomized clinical trials of spinal cord stimulation (SCS) for treatment of pain in adults and adolescents. The study protocol was registered with PROSPERO (CRD42018090412). Relevant articles were identified by searching the following databases through December 31, 2018: MEDLINE, Embase, WikiStim, The Cochrane Database of Systematic Reviews, and The Cochrane Central Register of Controlled Trials. Forty-six studies were included. Eighty-seven percent of articles identified a pain-related primary outcome. Secondary outcomes included physical functioning, health-related quality of life, and reductions in opioid use. Nineteen of the 46 studies prespecified adverse events as an outcome, with 4 assessing them as a primary outcome. Eleven studies stated that they blinded participants. Of these, only 5 were assessed as being adequately blinded. The number of participants enrolled was generally low (median 38) and study durations were short (median 12 weeks), particularly in studies of angina. Fifteen studies employed an intention-to-treat analysis, of which only seven specified a method to accommodate missing data. Review of these studies identified deficiencies in both reporting and methodology. The review's findings suggest areas for improving the design of future studies and increasing transparency of reporting. PERSPECTIVE: This article presents a systematic review of research methods and reporting quality of randomized clinical trials of SCS for the treatment of various pain complaints. The review identifies deficiencies in both methodology and reporting, which may inform the design of future studies and improve reporting standards.