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

Pain, quality of life, and function in chronic intractable leg pain were substantially improved with 10kHz spinal cord stimulation in a multicentre European study

PURPOSE

This prospective, single-arm, multicentre study evaluated the effectiveness of 10 kHz spinal cord stimulation (SCS) in relieving pain and improving function and quality of life in patients with chronic intractable leg pain in routine clinical practice.

METHODS

Patients with leg pain refractory to conservative therapy and scoring ≥ 5 cm on a 10-cm visual analog scale (VAS) were enrolled at 12 centres. Those who achieved ≥ 50% leg pain relief during a temporary trial underwent permanent implantation and were followed for 12 months. Outcomes collected included the proportion of patients who achieved ≥ 50% reduction in leg pain VAS score, health-related quality-of-life (EQ-5D-5 L, functional disability [ODI]), opioid use, sleep quality (PSQ-3), global impression of change (GIC), and patient satisfaction.

RESULTS

Of 121 patients trialed, 118 completed the trial and 95 proceeded to implant. At 3 months, 61/95 (64.2%) of all implanted patients were responders to therapy (≥ 50% VAS reduction), which remained stable at 64.2% through 12 months. EQ-5D-5 L, ODI, and PSQ-3 showed clinically important and sustained improvement over 12 months (repeated measures ANOVA, p < 0.001). Patients also reduced opioid dosage on average (p = 0.022). The safety profile was consistent with previous reports using 10 kHz SCS.

CONCLUSION

This study supports 10 kHz SCS as an effective and safe therapeutic option to reduce pain and disability while improving health-related quality of life in patients with chronic intractable leg pain. 10 kHz SCS appears to be effective in significantly improving the severe disability and poor quality of life experienced by patients with chronic intractable leg pain.

STUDY REGISTERED

ISRCTN Registry - ISRCTN11180496.

Are some people more susceptible to placebos? A systematic review and meta-analysis of inter-individual variability in musculoskeletal pain

Existing data suggest placebo responses to treatments are small, but some people may be more likely to respond. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) on interindividual variability in response to placebo interventions MEDLINE, EMBASE, CINAHL, Web of Science Core Collection, CENTRAL, and SPORTDiscus were searched from inception to September 2023. Trial registry searches, citation tracking, and searches for prior systematic reviews were completed. The PEDro scale assessed study quality. Random effects robust variance estimation estimated the log variability ratio (VR), identifying subgroups with varying responses. Twenty-six studies were included, comprising various musculoskeletal pain conditions. Analysis of pain intensity (VR: 1.06, 95%-confidence interval (CI):[0.97; 1.16], 95%-prediction interval (PI):[0.75; 1.51], p = 0.17, k = 26 studies, N = 52 outcomes, GRADE: low), physical function (VR: 1.14, 95%-CI:[0.97; 1.34], 95%-PI:[0.62; 2.11], p = 0.11, k = 19, N = 40, GRADE: low), and health-related quality of life (VR: 1.14, 95%-CI:[0.91; 1.41], 95%-PI:[0.72; 1.80], p = 0.19, k = 7, N = 13, GRADE: low) outcomes revealed minimal, non-statistically significant variability in placebo response compared to control. However, wide prediction intervals suggest uncertainty regarding individual response patterns. There are likely no distinct subgroups of people who are more likely to respond to placebo interventions in musculoskeletal pain; although the available data limits the certainty of this assessment. Future work should consider individual participant data meta-analyses to better elucidate potential responder subgroups and optimize treatment strategies for musculoskeletal pain. PERSPECTIVE: This study systematically reviewed and analyzed RCTs to assess interindividual variability in placebo responses for musculoskeletal pain. Findings suggest minimal variability in placebo response, with no distinct subgroups more likely to respond. Wide prediction intervals indicate uncertainty, highlighting the need for future individual participant data meta-analyses to better elucidate potential responder subgroups.

Is There a Correlation Between Objective Measurement Tools and Self-Reporting Questionnaires To Evaluate Physical Activity and Health Status in Patients With Persistent Spinal Pain Syndrome Type 2 Before and After Spinal Cord Stimulation? Outcomes of a Feasibility Study

INTRODUCTION

The effect of spinal cord stimulation (SCS) on physical activity in patients with persistent spinal pain syndrome (PSPS) type 2 is commonly evaluated with standardized, validated self-reporting questionnaires. However, questionnaires are susceptible to subjective bias and may not align with objective data.

OBJECTIVE

We investigated the correlation among objective measurement devices, the Oswestry Disability Index (ODI), and patient's health status regarding physical activity in patients with PSPS type 2 receiving SCS.

MATERIALS AND METHODS

Alongside the ODI, we used an activity tracker to objectively measure physical activity and a neurostimulator device to objectively measure body positions at baseline and three-month follow-up. In addition, health status was measured using the positive model of health.

RESULTS

We included 20 patients, of whom 17 completed the three-month follow-up period. At three months follow-up, we found a significant correlation between the activity tracker's steps (r = -0.636, p = 0.006) and distance per day (r = -0.649, p = 0.005) with the ODI and a significant correlation of the neurostimulator's mobile position with the ODI (r = -0.497, p = 0.043). Furthermore, the activity tracker showed a significant increase in strenuous physical activity at three-month follow-up (p = 0.039). We also observed a substantial improvement across the domains of bodily function, social and societal participation, and daily functioning of the positive model of health.

CONCLUSIONS

This study showed significant correlations among objective measurement devices, the ODI, and health status, which could contribute to a more holistic approach to evaluating the effect of SCS. Prospective powered studies with a control group are needed to better understand this area.

CLINICAL TRIAL REGISTRATION

The protocol was registered in the Dutch Trial Register (NTR) on March 13, 2021 under registration number NL 9301 (number NL-OMON21829).

Real-world long-term outcomes of peripheral nerve stimulation: a prospective observational study

AIM

We aimed to evaluate real-world outcomes of peripheral nerve stimulation (PNS) used to treat chronic neuropathic pain (CNP) at a tertiary pain management center.

METHODS

Thirty adults who underwent PNS for CNP between June 2015 and September 2021 completed pain and psychosocial assessments in the 6 months before, and 2-3 years after PNS treatment. Pain intensity was measured using the NIH Patient Reported Outcomes Measurement Information System (PROMIS) Pain Intensity Short From (3A). Psychosocial outcomes including depression, anxiety, and sleep disturbance were also measured.

RESULTS

Prior to receiving PNS, long-term responders reported significantly fewer depressive symptoms compared to non-responders (PROMIS depression t-score 50.3 [10.7] vs 57.9 [8.9]; p-value = 0.05). Eleven participants (36.7%) reported long-term treatment response. There was a significantly greater improvement in pain intensity among responders compared to non-responders who reported increased pain (PROMIS Pain Intensity score -9.0 [-4.2] vs. +3.1[+3.2]; p-value < 0.0001).

CONCLUSIONS

Patients report clinically meaningful long-term pain relief after receiving PNS through both 60-day and permanent implant systems, with significant reductions in pain intensity observed in long-term responders. Long-term responders reported fewer depressive symptoms compared to non-responders prior to receiving therapy, emphasizing the importance of psychological screening and psychological optimization prior to receiving PNS.

Reporting guidelines for randomised controlled trial reports of implantable neurostimulation devices: the CONSORT-iNeurostim extension

Background

The Consolidated Standards of Reporting Trials (CONSORT) statement has improved the quality of reporting of randomised trials. Extensions to the CONSORT statement are often needed to address specific issues of trial reporting, including those relevant to particular types of interventions. Methodological and reporting deficiencies in clinical trials of implantable neurostimulation devices are common. The CONSORT-iNeurostim extension is a new reporting guideline for randomised controlled trials evaluating implantable neurostimulation devices.

Methods

CONSORT-iNeurostim was developed using the EQUATOR methodological framework including a literature review and expert consultation to generate an initial list of candidate items. The candidate items were included in a two-round Delphi survey, discussed at an international consensus meeting (42 stakeholders including healthcare professionals, methodologists, journal editors and industry representatives from the United States, United Kingdom, Netherlands and other countries), and refined through a checklist pilot (18 stakeholders).

Findings

The initial extension item list included 49 candidate items relevant to CONSORT-iNeurostim. We received 132 responses in the first round of the Delphi survey and 99 responses in the second round. Participants suggested an additional 20 candidate items for CONSORT-iNeurostim during the first round of the survey, and those achieving initial consensus were discussed at the consensus meeting. The CONSORT-iNeurostim extension includes 7 new checklist items, including one item for reporting the neurostimulation intervention comprising a separate checklist of 14 items.

Interpretation

The CONSORT-iNeurostim extension will promote increased transparency, clarity, and completeness of trial reports of implantable neurostimulation devices. It will assist journal editors, peer-reviewers, and readers to better interpret the appropriateness and generalisability of the methods used and reported outcomes.

Funding

Abbott, Boston Scientific Corp., Mainstay Medical, Medtronic Ltd, Nevro Corp. and Saluda Medical.

Maximal Analgesic Effect Attained by the Use of Objective Neurophysiological Measurements With Closed-Loop Spinal Cord Stimulation

OBJECTIVES

Spinal cord stimulation (SCS) has been challenged by the lack of neurophysiologic data to guide therapy optimization. Current SCS programming by trial-and-error results in suboptimal and variable therapeutic effects. A novel system with a physiologic closed-loop feedback mechanism using evoked-compound action potentials enables the optimization of physiologic neural dose by consistently and accurately activating spinal cord fibers. We aimed to identify neurophysiologic dose metrics and their ranges that resulted in clinically meaningful treatment responses.

MATERIALS AND METHODS

Subjects from 3 clinical studies (n = 180) with baseline back and leg pain ≥60 mm visual analog scale and physical function in the severe to crippled category were included. Maximal analgesic effect (MAE) was operationally defined as the greatest percent reduction in pain intensity or as the greatest cumulative responder score (minimal clinically important differences [MCIDs]) obtained within the first 3 months of SCS implant. The physiologic metrics that produced the MAE were analyzed.

RESULTS

We showed that a neural dose regimen with a high neural dose accuracy of 2.8μV and dose ratio of 1.4 resulted in a profound clinical benefit to chronic pain patients (MAE of 79 ± 1% for pain reduction and 12.5 ± 0.4 MCIDs). No differences were observed for MAE or neurophysiological dose metrics between the trial phase and post-implant MAE visit.

CONCLUSION

For the first time, an evidence-based neural dose regimen is available for a neurostimulation intervention as a starting point to enable optimization of clinical benefit, monitoring of adherence, and management of the therapy.

Reporting guidelines for protocols of randomised controlled trials of implantable neurostimulation devices: the SPIRIT-iNeurostim extension

Background

The Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) statement has improved the quality of reporting of randomised trial protocols. Extensions to the SPIRIT statement are needed to address specific issues of trial protocol reporting, including those relevant to particular types of interventions. Methodological and reporting deficiencies in protocols of clinical trials of implantable neurostimulation devices are common. The SPIRIT-iNeurostim extension is a new reporting guideline for randomised controlled trial protocols evaluating implantable neurostimulation devices.

Methods

SPIRIT-iNeurostim was developed using the EQUATOR methodological framework including a literature review and expert consultation to generate an initial list of candidate items. The candidate items were included in a two-round Delphi survey, discussed at an international consensus meeting (42 stakeholders including healthcare professionals, methodologists, journal editors and industry representatives from the United States, United Kingdom, Netherlands and other countries), and refined through a checklist pilot (18 stakeholders).

Findings

The initial extension item list included 42 candidate items relevant to SPIRIT-iNeurostim. We received 132 responses in the first round of the Delphi survey and 99 responses in the second round. Participants suggested an additional 14 candidate items for SPIRIT-iNeurostim during the first round of the survey, and those achieving initial consensus were discussed at the consensus meeting. The SPIRIT-iNeurostim extension includes 5 new checklist items, including one item for reporting the neurostimulation intervention comprising a separate checklist of 14 items.

Interpretation

The SPIRIT-iNeurostim extension will help to promote increased transparency, clarity, and completeness of reporting trial protocols evaluating implantable neurostimulation devices. It will assist journal editors, peer-reviewers, and readers to better interpret the appropriateness and generalisability of the methods used for a planned clinical trial.

Funding

Abbott, Boston Scientific Corp., Mainstay Medical, Medtronic Ltd, Nevro Corp., and Saluda Medical.

Durability of Evoked Compound Action Potential (ECAP)-Controlled, Closed-Loop Spinal Cord Stimulation (SCS) in a Real-World European Chronic Pain Population

INTRODUCTION

Closed-loop spinal cord stimulation (CL-SCS) is a recently introduced system that records evoked compound action potentials (ECAPs) from the spinal cord elicited by each stimulation pulse and uses this information to automatically adjust the stimulation strength in real time, known as ECAP-controlled SCS. This innovative system compensates for fluctuations in the distance between the epidural leads and the spinal cord by maintaining the neural response (ECAP) at a predetermined target level. This data collection study was designed to assess the performance of the first CL-SCS system in a real-world setting under normal conditions of use in multiple European centers. The study analyzes and presents clinical outcomes and electrophysiological and device data and compares these findings with those reported in earlier pre-market studies of the same system.

METHODS

This prospective, multicenter, observational study was conducted in 13 European centers and aimed to gather electrophysiological and device data. The study focused on the real-world application of this system in treating chronic pain affecting the trunk and/or limbs, adhering to standard conditions of use. In addition to collecting and analyzing basic demographic information, the study presents data from the inaugural patient cohort permanently implanted at multiple European centers.

RESULTS

A significant decrease in pain intensity was observed for overall back or leg pain scores (verbal numerical rating score [VNRS]) between baseline (mean ± standard error of the mean [SEM]; n = 135; 8.2 ± 0.1), 3 months (n = 93; 2.3 ± 0.2), 6 months (n = 82; 2.5 ± 0.3), and 12 months (n = 76; 2.5 ± 0.3). Comparison of overall pain relief (%) to the AVALON and EVOKE studies showed no significant differences at 3 and 12 months between the real-world data release (RWE; 71.3%; 69.6%) and the AVALON (71.2%; 73.6%) and EVOKE (78.1%; 76.7%) studies. Further investigation was undertaken to objectively characterize the physiological parameters of SCS therapy in this cohort using the metrics of percent time above ECAP threshold (%), dose ratio, and dose accuracy (µV), according to previously described methods. Results showed that a median of 90% (40.7-99.2) of stimuli were above the ECAP threshold, with a dose ratio of 1.3 (1.1-1.4) and dose accuracy of 4.4 µV (0.0-7.1), based on data from 236, 230, and 254 patients, respectively. Thus, across all three metrics, the majority of patients had objective therapy metrics corresponding to the highest levels of pain relief in previously reported studies (usage over threshold > 80%, dose ratio > 1.2, and error < 10 µV).

CONCLUSIONS

In conclusion, this study provides valuable insights into the real-world application of the ECAP-controlled CL-SCS system, highlighting its potential for maintaining effective pain relief and objective neurophysiological therapy metrics at levels seen in randomized control trials, and potential for quantifying patient burden associated with SCS system use via patient-device interaction metrics.

CLINICAL TRIAL REGISTRATION

In the Netherlands, the study is duly registered on the International Clinical Trials Registry Platform (Trial NL7889). In Germany, the study is duly registered as NCT05272137 and in the United Kingdom as ISCRTN27710516 and has been reviewed by the ethics committee in both countries.

Emotional and psychosocial function after dorsal column spinal cord stimulator implantation: a systematic review and meta-analysis

BACKGROUND

The efficacy of spinal cord stimulation (SCS) in chronic pain studies is traditionally assessed by pain scores, which do not reflect the multidimensional nature of pain perception. Despite the evidence of SCS's influence on emotional functioning comprehensive assessments of its effect remain lacking.

OBJECTIVE

To assess changes in emotional and psychosocial functioning in patients who underwent SCS implantation for chronic pain.

EVIDENCE REVIEW

Ovid MEDLINE, EMBASE, PsychINFO, Cochrane CENTRAL and Scopus databases were searched for original peer-reviewed publications reporting emotional functioning after SCS. The primary outcomes were a pooled mean difference (MD) in anxiety, depression, global functioning, mental well-being and pain catastrophizing at 12 months. The Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) was used to determine the quality of evidence.

FINDINGS

Thirty-two studies were included in the primary analysis. Statistically significant improvements were observed in anxiety (MD -2.16; 95% CI -2.84 to -1.49; p<0.001), depression (MD -4.66; 95% CI -6.26 to -3.06; p<0.001), global functioning (MD 20.30; 95% CI 14.69 to 25.90; p<0.001), mental well-being (MD 4.95; 95% CI 3.60 to 6.31; p<0.001), and pain catastrophizing (MD -12.09; 95% CI -14.94 to -9.23; p<0.001). Subgroup analyses revealed differences in Global Assessment of Functioning and mental well-being based on study design and in depression based on waveform paradigm.

CONCLUSION

The results highlight the statistically and clinically significant improvements in emotional and psychosocial outcomes in patients with chronic pain undergoing SCS therapy. However, these results need to be interpreted with caution due to the very low certainty of evidence per the GRADE criteria.

PROSPERO REGISTRATION

CRD42023446326.

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.

Durable multimodal and holistic response for physiologic closed-loop spinal cord stimulation supported by objective evidence from the EVOKE double-blind randomized controlled trial

INTRODUCTION

Chronic pain patients may experience impairments in multiple health-related domains. The design and interpretation of clinical trials of chronic pain interventions, however, remains primarily focused on treatment effects on pain intensity. This study investigates a novel, multidimensional holistic treatment response to evoked compound action potential-controlled closed-loop versus open-loop spinal cord stimulation as well as the degree of neural activation that produced that treatment response.

METHODS

Outcome data for pain intensity, physical function, health-related quality of life, sleep quality and emotional function were derived from individual patient level data from the EVOKE multicenter, participant, investigator, and outcome assessor-blinded, parallel-arm randomized controlled trial with 24 month follow-up. Evaluation of holistic treatment response considered whether the baseline score was worse than normative values and whether minimal clinical important differences were reached in each of the domains that were impaired at baseline. A cumulative responder score was calculated to reflect the total minimal clinical important differences accumulated across all domains. Objective neurophysiological data, including spinal cord activation were measured.

RESULTS

Patients were randomized to closed-loop (n=67) or open-loop (n=67). A greater proportion of patients with closed-loop spinal cord stimulation (49.3% vs 26.9%) were holistic responders at 24-month follow-up, with at least one minimal clinical important difference in all impaired domains (absolute risk difference: 22.4%, 95% CI 6.4% to 38.4%, p=0.012). The cumulative responder score was significantly greater for closed-loop patients at all time points and resulted in the achievement of more than three additional minimal clinical important differences at 24-month follow-up (mean difference 3.4, 95% CI 1.3 to 5.5, p=0.002). Neural activation was three times more accurate in closed-loop spinal cord stimulation (p<0.001 at all time points).

CONCLUSION

The results of this study suggest that closed-loop spinal cord stimulation can provide sustained clinically meaningful improvements in multiple domains and provide holistic improvement in the long-term for patients with chronic refractory pain.

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.

A Definition of Neuromodulation and Classification of Implantable Electrical Modulation for Chronic Pain

OBJECTIVES

Neuromodulation therapies use a variety of treatment modalities (eg, electrical stimulation) to treat chronic pain. These therapies have experienced rapid growth that has coincided with escalating confusion regarding the nomenclature surrounding these neuromodulation technologies. Furthermore, studies are often published without a complete description of the effective stimulation dose, making it impossible to replicate the findings. To improve clinical care and facilitate dissemination among the public, payors, research groups, and regulatory bodies, there is a clear need for a standardization of terms.

APPROACH

We formed an international group of authors comprising basic scientists, anesthesiologists, neurosurgeons, and engineers with expertise in neuromodulation. Because the field of neuromodulation is extensive, we chose to focus on creating a taxonomy and standardized definitions for implantable electrical modulation of chronic pain.

RESULTS

We first present a consensus definition of neuromodulation. We then describe a classification scheme based on the 1) intended use (the site of modulation and its indications) and 2) physical properties (waveforms and dose) of a neuromodulation therapy.

CONCLUSIONS

This framework will help guide future high-quality studies of implantable neuromodulatory treatments and improve reporting of their findings. Standardization with this classification scheme and clear definitions will help physicians, researchers, payors, and patients better understand the applications of implantable electrical modulation for pain and guide informed treatment decisions.

Current and Emerging Technologies to Address the Placebo Response Challenge in CNS Clinical Trials: Promise, Pitfalls, and Pathways Forward

Excessive placebo response rates have long been a major challenge for central nervous system (CNS) drug discovery. As CNS trials progressively shift toward digitalization, decentralization, and novel remote assessment approaches, questions are emerging about whether innovative technologies can help mitigate the placebo response. This article begins with a conceptual framework for understanding placebo response. We then critically evaluate the potential of a range of innovative technologies and associated research designs that might help mitigate the placebo response and enhance detection of treatment signals. These include technologies developed to directly address placebo response; technology-based approaches focused on recruitment, retention, and data collection with potential relevance to placebo response; and novel remote digital phenotyping technologies. Finally, we describe key scientific and regulatory considerations when evaluating and selecting innovative strategies to mitigate placebo response. While a range of technological innovations shows potential for helping to address the placebo response in CNS trials, much work remains to carefully evaluate their risks and benefits.

Factors Predicting Clinically Relevant Pain Relief After Spinal Cord Stimulation for Patients With Chronic Low Back and/or Leg Pain: A Systematic Review With Meta-Analysis and Meta-Regression

RATIONALE

To optimize results with spinal cord stimulation (SCS) for chronic low back pain (CLBP) and/or leg pain, including persistent spinal pain syndrome (PSPS), careful patient selection based on proved predictive factors is essential. Unfortunately, the necessary selection process required to optimize outcomes of SCS remains challenging.

OBJECTIVE

This review aimed to evaluate predictive factors of clinically relevant pain relief after SCS for patients with CLBP and/or radicular leg pain, including PSPS.

MATERIALS AND METHODS

In August 2023, PubMed, Cinahl, Cochrane, and EMBASE were searched to identify studies published between January 2010 and August 2023. Studies reporting the percentage of patients with ≥50% pain relief after SCS in patients with CLBP and leg pain, including PSPS at 12 or 24 months, were included. Meta-analysis was conducted to pool results for back, leg, and general pain relief. Predictive factors for pain relief after 12 months were examined using univariable and multivariable meta-regression.

RESULTS

A total of 27 studies (2220 patients) were included for further analysis. The mean percentages of patients with substantial pain relief were 68% for leg pain, 63% for back pain, and 73% for general pain at 12 months follow-up, and 63% for leg pain, 59% for back pain, and 71% for general pain at 24 months follow-up assessment. The implantation method and baseline Oswestry Disability Index made the multivariable meta-regression model for ≥50% back pain relief. Sex and pain duration made the final model for ≥50% leg pain relief. Variable stimulation and implantation method made the final model for general pain relief.

CONCLUSIONS

This review supports SCS as an effective pain-relieving treatment for CLBP and/or leg pain, and models were developed to predict substantial back and leg pain relief. To provide high-grade evidence for predictive factors, SCS studies of high quality are needed in which standardized factors predictive of SCS success, based on in-patient improvements, are monitored and reported.

Pharmacological and Nonpharmacological Treatments for Painful Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most prevalent chronic complications of diabetes. The lifetime prevalence of DPN is thought to be >50%, and 15%-25% of patients with diabetes experience neuropathic pain, referred to as "painful DPN." Appropriate treatment of painful DPN is important because this pain contributes to a poor quality of life by causing sleep disturbance, anxiety, and depression. The basic principle for the management of painful DPN is to control hyperglycemia and other modifiable risk factors, but these may be insufficient for preventing or improving DPN. Because there is no promising diseasemodifying medication for DPN, the pain itself needs to be managed when treating painful DPN. Drugs for neuropathic pain, such as gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, alpha-lipoic acid, sodium channel blockers, and topical capsaicin, are used for the management of painful DPN. The U.S. Food and Drug Administration (FDA) has approved pregabalin, duloxetine, tapentadol, and the 8% capsaicin patch as drugs for the treatment of painful DPN. Recently, spinal cord stimulation using electrical stimulation is approved by the FDA for the treatment for painful DPN. This review describes the currently available pharmacological and nonpharmacological treatments for painful DPN.

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.

First Report on Real-World Outcomes with Evoked Compound Action Potential (ECAP)-Controlled Closed-Loop Spinal Cord Stimulation for Treatment of Chronic Pain

INTRODUCTION

A novel closed-loop spinal cord stimulation (SCS) system has recently been approved for use which records evoked compound action potentials (ECAPs) from the spinal cord and utilizes these recordings to automatically adjust the stimulation strength in real time. It automatically compensates for fluctuations in distance between the epidural leads and the spinal cord by maintaining the neural response (ECAP) at a determined target level. This data collection was principally designed to evaluate the performance of this first closed-loop SCS system in a 'real-world' setting under normal conditions of use in a single European center.

METHODS

In this prospective, single-center observational data collection, 22 patients were recruited at the outpatient pain clinic of the St. Antonius Hospital. All candidates were suffering from chronic pain in the trunk and/or limbs due to PSPS type 2 (persistent spinal pain syndrome). As standard of care, follow-up visits were completed at 3 months, 6 months, and 12 months post-device activation. Patient-reported outcome data (pain intensity, patient satisfaction) and electrophysiological and device data (ECAP amplitude, conduction velocity, current output, pulse width, frequency, usage), and patient interaction with their controller were collected at baseline and during standard of care follow-up visits.

RESULTS

Significant decreases in pain intensity for overall back or leg pain scores (verbal numerical rating score = VNRS) were observed between baseline [mean ± SEM (standard error of the mean); n = 22; 8.4 ± 0.2)], 3 months (n = 12; 1.9 ± 0.5), 6 months (n = 16; 2.6 ± 0.5), and 12 months (n = 20; 2.0 ± 0.5), with 85.0% of the patients being satisfied at 12 months. Additionally, no significant differences in average pain relief at 3 months and 12 months between the real-world data (77.2%; 76.8%) and the AVALON (71.2%; 73.6%) and EVOKE (78.1%; 76.7%) studies were observed.

CONCLUSIONS

These initial 'real-world' data on ECAP-controlled, closed-loop SCS in a real-world clinical setting appear to be promising, as they provide novel insights of the beneficial effect of ECAP-controlled, closed-loop SCS in a real-world setting. The presented results demonstrate a noteworthy maintenance of pain relief over 12 months and corroborate the outcomes observed in the AVALON prospective, multicenter, single-arm study and the EVOKE double-blind, multicenter, randomized controlled trial.

TRIAL REGISTRATION

The data collection is registered on the International Clinical Trials Registry Platform (Trial NL7889).

Cost-utility Analysis of Evoke Closed-loop Spinal Cord Stimulation for Chronic Back and Leg Pain

OBJECTIVES

The effectiveness of Evoke closed-loop spinal cord stimulation (CL-SCS), a novel modality of neurostimulation, has been demonstrated in a randomized controlled trial (RCT). The objective of this cost-utility analysis was to develop a de novo economic model to estimate the cost-effectiveness of Evoke CL-SCS when compared with open-loop SCS (OL-SCS) for the management of chronic back and leg pain.

METHODS

A decision tree followed by a Markov model was used to estimate the costs and outcomes of Evoke CL-SCS versus OL-SCS over a 15-year time horizon from the UK National Health Service perspective. A "high-responder" health state was included to reflect improved levels of SCS pain reduction recently reported. Results are expressed as incremental cost per quality-adjusted life year (QALY). Deterministic and probabilistic sensitivity analysis (PSA) was conducted to assess uncertainty in the model inputs.

RESULTS

Evoke CL-SCS was estimated to be the dominant treatment strategy at ~5 years postimplant (ie, it generates more QALYs while cost saving compared with OL-SCS). Probabilistic sensitivity analysis showed that Evoke CL-SCS has a 92% likelihood of being cost-effective at a willingness to pay threshold of £20,000/QALY. Results were robust across a wide range of scenario and sensitivity analyses.

DISCUSSION

The results indicate a strong economic case for the use of Evoke CL-SCS in the management of chronic back and leg pain with or without prior spinal surgery with dominance observed at ~5 years.

Real World Clinical Utility of Neurophysiological Measurement Utilizing Closed-Loop Spinal Cord Stimulation in a Chronic Pain Population: The ECAP Study Protocol

Background

Spinal cord stimulation (SCS) is an established chronic pain treatment, but the effectiveness of traditional, open-loop paradigms has been plagued by variable sustainability in a real-world setting. A new approach, utilizing evoked compound action potential (ECAP) controlled closed-loop (CL) SCS, continuously monitors spinal cord activation and automatically adjusts the stimulation amplitude of every pulse, maintaining stimulation at the prescribed ECAP level through this continual feedback mechanism. Recent studies demonstrated the long-term safety and efficacy of ECAP-controlled CL-SCS. Here, we report the design of a prospective, multicenter, single-arm feasibility study to characterize clinical outcomes in a real-world chronic pain population utilizing ECAP-controlled CL-SCS. Objective neurophysiological measurements such as device performance and patient therapy compliance, will be analyzed against baseline biopsychosocial assessments, to explore the clinical utility of these objective physiologic biomarkers in patient phenotyping.

Methods

This study will enroll up to 300 subjects with chronic, intractable trunk and/or limb pain in up to 25 United States investigation sites. Subjects meeting eligibility criteria will undergo a trial procedure and a permanent implant following a successful trial. Neurophysiological measurements (measured in-clinic and continuously during home use) and clinical outcomes including pain, quality-of-life, psychological, emotional, and functional assessments will be collected at baseline, trial end, and up to 24-months post-implantation.

Discussion

Associations between objective neurophysiological data, clinical evaluation and patient-reported outcomes may have important clinical and scientific implications. They may provide novel insights about the chronic pain pathophysiology, its modulation during CL-SCS, and identification of pain phenotypes and/or mechanisms associated with treatment response during SCS trials and long-term therapy. Data from the ECAP study could lead to improvements in diagnosis, assessment, patient identification and management of chronic pain. It could also provide the foundation for development of a new SCS treatment approach customized by the patient's pain phenotype, unique neurophysiology, and disease severity.

Core patient-reported outcome measures for chronic pain patients treated with spinal cord stimulation or dorsal root ganglia stimulation

BACKGROUND

Neurostimulation is a highly effective therapy for the treatment of chronic Intractable pain, however, due to the complexity of pain, measuring a subject's long-term response to the therapy remains difficult. Frequent measurement of patient-reported outcomes (PROs) to reflect multiple aspects of subjects' pain is a crucial step in determining therapy outcomes. However, collecting full-length PROs is burdensome for both patients and clinicians. The objective of this work is to identify the reduced set of questions from multiple validated PROs that can accurately characterize chronic pain patients' responses to neurostimulation therapies.

METHODS

Validated PROs were used to capture pain, physical function and disability, as well as psychometric, satisfaction, and global health metrics. PROs were collected from 509 patients implanted with Spinal Cord Stimulation (SCS) or Dorsal Root Ganglia (DRG) neurostimulators enrolled in the prospective, international, post-market REALITY study (NCT03876054, Registration Date: March 15, 2019). A combination of linear regression, Pearson's correlation, and factor analysis were used to eliminate highly correlated questions and find the minimal meaningful set of questions within the predefined domains of each scale.

RESULTS

The shortened versions of the questionnaires presented almost identical accuracy for classifying the therapy outcomes as compared to the validated full-length versions. In addition, principal component analysis was performed on all the PROs and showed a robust clustering of pain intensity, psychological factors, physical function, and sleep across multiple PROs. A selected set of questions captured from multiple PROs can provide adequate information for measuring neurostimulation therapy outcomes.

CONCLUSIONS

PROs are important subjective measures to evaluate the physiological and psychological aspects of pain. However, these measures are cumbersome to collect. These shorter and more targeted PROs could result in better patient engagement, and enhanced and more frequent data collection processes for digital health platforms that minimize patient burden while increasing therapeutic benefits for chronic pain patients.

Research objectives and general considerations for pragmatic clinical trials of pain treatments: IMMPACT statement

ABSTRACT

Many questions regarding the clinical management of people experiencing pain and related health policy decision-making may best be answered by pragmatic controlled trials. To generate clinically relevant and widely applicable findings, such trials aim to reproduce elements of routine clinical care or are embedded within clinical workflows. In contrast with traditional efficacy trials, pragmatic trials are intended to address a broader set of external validity questions critical for stakeholders (clinicians, healthcare leaders, policymakers, insurers, and patients) in considering the adoption and use of evidence-based treatments in daily clinical care. This article summarizes methodological considerations for pragmatic trials, mainly concerning methods of fundamental importance to the internal validity of trials. The relationship between these methods and common pragmatic trials methods and goals is considered, recognizing that the resulting trial designs are highly dependent on the specific research question under investigation. The basis of this statement was an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) systematic review of methods and a consensus meeting. The meeting was organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership. The consensus process was informed by expert presentations, panel and consensus discussions, and a preparatory systematic review. In the context of pragmatic trials of pain treatments, we present fundamental considerations for the planning phase of pragmatic trials, including the specification of trial objectives, the selection of adequate designs, and methods to enhance internal validity while maintaining the ability to answer pragmatic research questions.

Advances and challenges in neuropathic pain: a narrative review and future directions

Over the past few decades, substantial advances have been made in neuropathic pain clinical research. An updated definition and classification have been agreed. Validated questionnaires have improved the detection and assessment of acute and chronic neuropathic pain; and newer neuropathic pain syndromes associated with COVID-19 have been described. The management of neuropathic pain has moved from empirical to evidence-based medicine. However, appropriately targeting current medications and the successful clinical development of drugs acting on new targets remain challenging. Innovative approaches to improving therapeutic strategies are required. These mainly encompass rational combination therapy, drug repurposing, non-pharmacological approaches (such as neurostimulation techniques), and personalised therapeutic management. This narrative review reports historical and current perspectives regarding the definitions, classification, assessment, and management of neuropathic pain and explores potential avenues for future research.

Holistic Treatment Response: An International Expert Panel Definition and Criteria for a New Paradigm in the Assessment of Clinical Outcomes of Spinal Cord Stimulation

BACKGROUND

Treatment response to spinal cord stimulation (SCS) is focused on the magnitude of effects on pain intensity. However, chronic pain is a multidimensional condition that may affect individuals in different ways and as such it seems reductionist to evaluate treatment response based solely on a unidimensional measure such as pain intensity.

AIM

The aim of this article is to add to a framework started by IMMPACT for assessing the wider health impact of treatment with SCS for people with chronic pain, a "holistic treatment response".

DISCUSSION

Several aspects need consideration in the assessment of a holistic treatment response. SCS device data and how it relates to patient outcomes, is essential to improve the understanding of the different types of SCS, improve patient selection, long-term clinical outcomes, and reproducibility of findings. The outcomes to include in the evaluation of a holistic treatment response need to consider clinical relevance for patients and clinicians. Assessment of the holistic response combines two key concepts of patient assessment: (1) patients level of baseline (pre-treatment) unmet need across a range of health domains; (2) demonstration of patient-relevant improvements in these health domains with treatment. The minimal clinical important difference (MCID) is an established approach to reflect changes after a clinical intervention that are meaningful for the patient and can be used to identify treatment response to each individual domain. A holistic treatment response needs to account for MCIDs in all domains of importance for which the patient presents dysfunctional scores pre-treatment. The number of domains included in a holistic treatment response may vary and should be considered on an individual basis. Physiologic confirmation of therapy delivery and utilisation should be included as part of the evaluation of a holistic treatment response and is essential to advance the field of SCS and increase transparency and reproducibility of the findings.

Device profile of the Evoke physiologic closed-loop spinal cord stimulation system for the treatment of chronic intractable pain: overview of its safety and efficacy

INTRODUCTION

The Evoke® spinal cord stimulation (SCS) device enables the closed-loop feedback of dynamically measured evoked compound action potentials (ECAPs) to adjust stimulation amplitude for every stimulation pulse to maintain the stimulation output level near a targeted ECAP amplitude. No other commercially available SCS device presently uses physiologic feedback from the spinal cord to adjust stimulation. Clinicians should be familiar with the differences in devices and with the latest technologies to provide optimized patient care.

AREAS COVERED

In this device profile, the Evoke system is described and the system capabilities are differentiated from other available SCS devices. A systematic review was conducted based on best practice guidance to identify all available evidence on the safety and efficacy of the Evoke SCS system.

EXPERT OPINION

The Evoke SCS system offers unique capabilities as a means to optimize therapy delivery tailored to each individual patient. Data through 24-months follow-up show statistically significant, clinically meaningful, ample, consistent, and strong evidence of the safety and efficacy of the Evoke system for the treatment of chronic intractable pain.

Objective wearable measures and subjective questionnaires for predicting response to neurostimulation in people with chronic pain

BACKGROUND

Neurostimulation is an effective therapy for treating and management of refractory chronic pain. However, the complex nature of pain and infrequent in-clinic visits, determining subject's long-term response to the therapy remains difficult. Frequent measurement of pain in this population can help with early diagnosis, disease progression monitoring, and evaluating long-term therapeutic efficacy. This paper compares the utilization of the common subjective patient-reported outcomes with objective measures captured through a wearable device for predicting the response to neurostimulation therapy.

METHOD

Data is from the ongoing international prospective post-market REALITY clinical study, which collects long-term patient-reported outcomes from 557 subjects implanted by Spinal Cord Stimulator (SCS) or Dorsal Root Ganglia (DRG) neurostimulators. The REALITY sub-study was designed for collecting additional wearables data on a subset of 20 participants implanted with SCS devices for up to six months post implantation. We first implemented a combination of dimensionality reduction algorithms and correlation analyses to explore the mathematical relationships between objective wearable data and subjective patient-reported outcomes. We then developed machine learning models to predict therapy outcome based on the subject's response to the numerical rating scale (NRS) or patient global impression of change (PGIC).

RESULTS

Principal component analysis showed that psychological aspects of pain were associated with heart rate variability, while movement-related measures were strongly associated with patient-reported outcomes related to physical function and social role participation. Our machine learning models using objective wearable data predicted PGIC and NRS outcomes with high accuracy without subjective data. The prediction accuracy was higher for PGIC compared with the NRS using subjective-only measures primarily driven by the patient satisfaction feature. Similarly, the PGIC questions reflect an overall change since the study onset and could be a better predictor of long-term neurostimulation therapy outcome.

CONCLUSIONS

The significance of this study is to introduce a novel use of wearable data collected from a subset of patients to capture multi-dimensional aspects of pain and compare the prediction power with the subjective data from a larger data set. The discovery of pain digital biomarkers could result in a better understanding of the patient's response to therapy and their general well-being.

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.

Blinding and sham control methods in trials of physical, psychological, and self-management interventions for pain (article I): a systematic review and description of methods

ABSTRACT

Blinding is challenging in randomised controlled trials of physical, psychological, and self-management therapies for pain, mainly because of their complex and participatory nature. To develop standards for the design, implementation, and reporting of control interventions in efficacy and mechanistic trials, a systematic overview of currently used sham interventions and other blinding methods was required. Twelve databases were searched for placebo or sham-controlled randomised clinical trials of physical, psychological, and self-management treatments in a clinical pain population. Screening and data extraction were performed in duplicate, and trial features, description of control methods, and their similarity to the active intervention under investigation were extracted (protocol registration ID: CRD42020206590). The review included 198 unique control interventions, published between 2008 and December 2021. Most trials studied people with chronic pain, and more than half were manual therapy trials. The described control interventions ranged from clearly modelled based on the active treatment to largely dissimilar control interventions. Similarity between control and active interventions was more frequent for certain aspects (eg, duration and frequency of treatments) than others (eg, physical treatment procedures and patient sensory experiences). We also provide an overview of additional, potentially useful methods to enhance blinding, as well as the reporting of processes involved in developing control interventions. A comprehensive picture of prevalent blinding methods is provided, including a detailed assessment of the resemblance between active and control interventions. These findings can inform future developments of control interventions in efficacy and mechanistic trials and best-practice recommendations.

Systematic Review and Network Meta-analysis of Neurostimulation for Painful Diabetic Neuropathy

BACKGROUND

Different waveforms of spinal cord stimulation (SCS) have now been evaluated for the management of painful diabetic neuropathy (PDN). However, no direct or indirect comparison between SCS waveforms has been performed to date.

PURPOSE

To conduct a systematic review and network meta-analysis to evaluate the effectiveness of SCS for PDN.

DATA SOURCES

MEDLINE, CENTRAL, Embase, and WikiStim were searched from inception until December 2021.

STUDY SELECTION

Randomized controlled trials (RCTs) of SCS for PDN were included.

DATA EXTRACTION

Pain intensity, proportion of patients achieving at least a 50% reduction in pain intensity, and health-related quality of life (HRQoL) data were extracted.

DATA SYNTHESIS

Significant reductions in pain intensity were observed for low-frequency SCS (LF-SCS) (mean difference [MD] -3.13 [95% CI -4.19 to -2.08], moderate certainty) and high-frequency SCS (HF-SCS) (MD -5.20 [95% CI -5.77 to -4.63], moderate certainty) compared with conventional medical management (CMM) alone. There was a significantly greater reduction in pain intensity on HF-SCS compared with LF-SCS (MD -2.07 [95% CI -3.26 to -0.87], moderate certainty). Significant differences were observed for LF-SCS and HF-SCS compared with CMM for the outcomes proportion of patients with at least 50% pain reduction and HRQoL (very low to moderate certainty). No significant differences were observed between LF-SCS and HF-SCS (very low to moderate certainty).

LIMITATIONS

Limited number of RCTs and no head-to-head RCTs conducted.

CONCLUSIONS

Our findings confirm the pain relief and HRQoL benefits of the addition of SCS to CMM for patients with PDN. However, in the absence of head-to-head RCT evidence, the relative benefits of HF-SCS compared with LF-SCS for patients with PDN remain uncertain.

Recruitment and retention for chronic pain clinical trials: a narrative review

Opioid misuse is at a crisis level. In response to this epidemic, the National Institutes of Health has funded $945 million in research through the Helping to End Addiction Long-term (HEAL) Pain Management Initiative, including funding to the Vanderbilt Recruitment Innovation Center (RIC) to strategize methods to catalyze participant recruitment. The RIC, recognizing the challenges presented to clinical researchers in recruiting individuals experiencing pain, conducted a review of evidence in the literature on successful participant recruitment methods for chronic pain trials, in preparation for supporting the HEAL Pain trials. Study design as it affects recruitment was reviewed, with issues such as sufficient sample size, impact of placebo, pain symptom instability, and cohort characterization being identified as problems. Potential solutions found in the literature include targeted electronic health record phenotyping, use of alternative study designs, and greater clinician education and involvement. For retention, the literature reports successful strategies that include maintaining a supportive staff, allowing virtual study visits, and providing treatment flexibility within the trial. Community input on study design to identify potential obstacles to recruitment and retention was found to help investigators avoid pitfalls and enhance trust, especially when recruiting underrepresented minority populations. Our report concludes with a description of generalizable resources the RIC has developed or adapted to enhance recruitment and retention in the HEAL Pain studies. These resources include, among others, a Recruitment and Retention Plan Template, a Competing Trials Tool, and MyCap, a mobile research application that interfaces with Research Electronic Data Capture (REDCap).

If the doors of perception were cleansed, would chronic pain be relieved? Evaluating the benefits and risks of psychedelics

Psychedelic substances have played important roles in diverse cultures, and ingesting various plant preparations to evoke altered states of consciousness has been described throughout recorded history. Accounts of the subjective effects of psychedelics typically focus on spiritual and mystical-type experiences, including feelings of unity, sacredness, and transcendence. Over the past two decades, there has been increasing interest in psychedelics as treatments for various medical disorders, including chronic pain. Although concerns about adverse medical and psychological effects contributed to their controlled status, contemporary knowledge of psychedelics suggests that risks are relatively rare when patients are carefully screened, prepared, and supervised. Clinical trial results have provided support for the effectiveness of psychedelics in different psychiatric conditions. However, there are only a small number of generally uncontrolled studies of psychedelics in patients with chronic pain (e.g., cancer pain, phantom limb pain, migraine, and cluster headache). Challenges in evaluating psychedelics as treatments for chronic pain include identifying neurobiologic and psychosocial mechanisms of action and determining which pain conditions to investigate. Truly informative proof-of-concept and confirmatory randomized clinical trials will require careful selection of control groups, efforts to minimize bias from unblinding, and attention to the roles of patient mental set and treatment setting. Perspective: There is considerable promise for the use of psychedelic therapy for pain, but evidence-based recommendations for the design of future studies are needed to ensure that the results of this research are truly informative.

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.

Passive Recharge Burst Spinal Cord Stimulation Provides Sustainable Improvements in Pain and Psychosocial Function: 2-year Results From the TRIUMPH Study

STUDY DESIGN

Prospective, international, multicenter, single-arm, post-market study.

OBJECTIVE

The aim of this study was to assess long-term safety and effectiveness of spinal cord stimulation using a passive recharge burst stimulation design for chronic intractable pain in the trunk and/or limbs. Herein we present 24-month outcomes from the TRIUMPH study (NCT03082261).

SUMMARY OF BACKGROUND DATA

Passive recharge burst spinal cord stimulation (B-SCS) uniquely mimics neuronal burst firing patterns in the nervous system and has been shown to modulate the affective and attentional components of pain processing.

METHODS

After a successful trial period, subjects received a permanent SCS implant and returned for follow-up at 6, 12, 18, and 24 months.

RESULTS

Significant improvements in physical, mental, and emotional functioning observed after 6 months of treatment were maintained at 2 years. Pain catastrophizing scale (PCS) scores dropped below the population norm. Health-related quality of life on EQ-5D improved across all domains and the mean index score was within one standard deviation of norm. Pain reduction (on NRS) was statistically significant (P < 0.001) at all timepoints. Patient reported pain relief, a stated percentage of improvement in pain, was consistent at all timepoints at 60%. Patients reported significant improvements across all measures including activity levels and impact of pain on daily life. At 24 months, 84% of subjects were satisfied and 90% would recommend the procedure. Subjects decreased their chronic pain medication intake for all categories; 38% reduced psychotropic and muscle relaxants, 46% reduced analgesic, anti-convulsant and NSAIDs, and 48% reduced opioid medication. Adverse events occurred at low rates without unanticipated events.

CONCLUSION

Early positive results with B-SCS were maintained long term. Evidence across multiple assessment tools show that B-SCS can alleviate pain intensity, psychological distress, and improve physical function and health-related quality of life.Level of Evidence: 3.

Human Spinal Organoid-on-a-Chip to Model Nociceptive Circuitry for Pain Therapeutics Discovery

The discovery of new pain therapeutics targeting human nociceptive circuitry is an emerging, exciting, and rewarding field. However, current models for evaluating prospective new therapeutics [e.g., animals and two-dimensional (2D) in vitro cultures] fail to fully recapitulate the complexity of human nociceptive neuron and dorsal horn neuron biology, significantly limiting the development of novel pain therapeutics. Here, we report human spinal organoid-on-a-chip devices for modeling the biology and electrophysiology of human nociceptive neurons and dorsal horn interneurons in nociceptive circuitry. Our device can be simply made through the integration of a membrane with a three-dimensional (3D)-printed organoid holder. By combining air-liquid interface culture and spinal organoid protocols, our devices can differentiate human stem cells into human sensori-spinal-cord organoids with dorsal spinal cord interneurons and sensory neurons. By easily transferring from culture well plates to the multiple-electrode array (MEA) system, our device also allows the plug-and-play measurement of organoid activity for testing nociceptive modulators (e.g., mustard oil, capsaicin, velvet ant venom, etc.). Our organoid-on-a-chip devices are cost-efficient, scalable, easy to use, and compatible with conventional well plates, allowing the plug-and-play measurement of spinal organoid electrophysiology. By the integration of human sensory-spinal-cord organoids with our organoid-on-a-chip devices, our method may hold the promising potential to screen and validate novel therapeutics for human pain medicine discovery.

Durability of Clinical and Quality-of-Life Outcomes of Closed-Loop Spinal Cord Stimulation for Chronic Back and Leg Pain: A Secondary Analysis of the Evoke Randomized Clinical Trial

Importance

Chronic pain is debilitating and profoundly affects health-related quality of life. Spinal cord stimulation (SCS) is a well-established therapy for chronic pain; however, SCS has been limited by the inability to directly measure the elicited neural response, precluding confirmation of neural activation and continuous therapy. A novel SCS system measures the evoked compound action potentials (ECAPs) to produce a real-time physiological closed-loop control system.

Objective

To determine whether ECAP-controlled, closed-loop SCS is associated with better outcomes compared with fixed-output, open-loop SCS at 24 months following implant.

Design, Setting, and Participants

The Evoke study was a double-blind, randomized, controlled, parallel arm clinical trial with 36 months of follow-up. Participants were enrolled from February 2017 to 2018, and the study was conducted at 13 US investigation sites. SCS candidates with chronic, intractable back and leg pain refractory to conservative therapy, who consented, were screened. Key eligibility criteria included overall, back, and leg pain visual analog scale score of 60 mm or more; Oswestry Disability Index score of 41 to 80; stable pain medications; and no previous SCS. Analysis took place from October 2020 to April 2021.

Interventions

ECAP-controlled, closed-loop SCS was compared with fixed-output, open-loop SCS.

Main Outcomes and Measures

Reported here are the 24-month outcomes of the trial, which include all randomized patients in the primary and safety analyses. The primary outcome was a reduction of 50% or more in overall back and leg pain assessed at 3 and 12 months (previously published).

Results

Of 134 randomized patients, 65 (48.5%) were female and the mean (SD) age was 55.2 (10.6) years. At 24 months, significantly more closed-loop than open-loop patients were responders (≥50% reduction) in overall pain (53 of 67 [79.1%] in the closed-loop group; 36 of 67 [53.7%] in the open-loop group; difference, 25.4% [95% CI, 10.0%-40.8%]; P = .001). There was no difference in safety profiles between groups (difference in rate of study-related adverse events: 6.0 [95% CI, -7.8 to 19.7]). Improvements were also observed in health-related quality of life, physical and emotional functioning, and sleep, in parallel with opioid reduction or elimination. Objective neurophysiological measurements substantiated the clinical outcomes and provided evidence of activation of inhibitory pain mechanisms.

Conclusions and Relevance

ECAP-controlled, closed-loop SCS, which elicited a more consistent neural response, was associated with sustained superior pain relief at 24 months, consistent with the 3- and 12-month outcomes.

Implanted spinal neuromodulation interventions for chronic pain in adults

BACKGROUND

Implanted spinal neuromodulation (SNMD) techniques are used in the treatment of refractory chronic pain. They involve the implantation of electrodes around the spinal cord (spinal cord stimulation (SCS)) or dorsal root ganglion (dorsal root ganglion stimulation (DRGS)), and a pulse generator unit under the skin. Electrical stimulation is then used with the aim of reducing pain intensity.

OBJECTIVES

To evaluate the efficacy, effectiveness, adverse events, and cost-effectiveness of implanted spinal neuromodulation interventions for people with chronic pain.

SEARCH METHODS

We searched CENTRAL, MEDLINE Ovid, Embase Ovid, Web of Science (ISI), Health Technology Assessments, ClinicalTrials.gov and World Health Organization International Clinical Trials Registry from inception to September 2021 without language restrictions, searched the reference lists of included studies and contacted experts in the field.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing SNMD interventions with placebo (sham) stimulation, no treatment or usual care; or comparing SNMD interventions + another treatment versus that treatment alone. We included participants ≥ 18 years old with non-cancer and non-ischaemic pain of longer than three months duration. Primary outcomes were pain intensity and adverse events. Secondary outcomes were disability, analgesic medication use, health-related quality of life (HRQoL) and health economic outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened database searches to determine inclusion, extracted data and evaluated risk of bias for prespecified results using the Risk of Bias 2.0 tool. Outcomes were evaluated at short- (≤ one month), medium- four to eight months) and long-term (≥12 months). Where possible we conducted meta-analyses. We used the GRADE system to assess the certainty of evidence.

MAIN RESULTS

We included 15 unique published studies that randomised 908 participants, and 20 unique ongoing studies. All studies evaluated SCS. We found no eligible published studies of DRGS and no studies comparing SCS with no treatment or usual care. We rated all results evaluated as being at high risk of bias overall. For all comparisons and outcomes where we found evidence, we graded the certainty of the evidence as low or very low, downgraded due to limitations of studies, imprecision and in some cases, inconsistency. Active stimulation versus placebo SCS versus placebo (sham) Results were only available at short-term follow-up for this comparison. Pain intensity Six studies (N = 164) demonstrated a small effect in favour of SCS at short-term follow-up (0 to 100 scale, higher scores = worse pain, mean difference (MD) -8.73, 95% confidence interval (CI) -15.67 to -1.78, very low certainty). The point estimate falls below our predetermined threshold for a clinically important effect (≥10 points). No studies reported the proportion of participants experiencing 30% or 50% pain relief for this comparison. Adverse events (AEs) The quality and inconsistency of adverse event reporting in these studies precluded formal analysis. Active stimulation + other intervention versus other intervention alone SCS + other intervention versus other intervention alone (open-label studies) Pain intensity Mean difference Three studies (N = 303) demonstrated a potentially clinically important mean difference in favour of SCS of -37.41 at short term (95% CI -46.39 to -28.42, very low certainty), and medium-term follow-up (5 studies, 635 participants, MD -31.22 95% CI -47.34 to -15.10 low-certainty), and no clear evidence for an effect of SCS at long-term follow-up (1 study, 44 participants, MD -7 (95% CI -24.76 to 10.76, very low-certainty). Proportion of participants reporting ≥50% pain relief We found an effect in favour of SCS at short-term (2 studies, N = 249, RR 15.90, 95% CI 6.70 to 37.74, I2 0% ; risk difference (RD) 0.65 (95% CI 0.57 to 0.74, very low certainty), medium term (5 studies, N = 597, RR 7.08, 95 %CI 3.40 to 14.71, I2 = 43%; RD 0.43, 95% CI 0.14 to 0.73, low-certainty evidence), and long term (1 study, N = 87, RR 15.15, 95% CI 2.11 to 108.91 ; RD 0.35, 95% CI 0.2 to 0.49, very low certainty) follow-up. Adverse events (AEs) Device related No studies specifically reported  device-related adverse events at short-term follow-up. At medium-term follow-up, the incidence of lead failure/displacement (3 studies N = 330) ranged from 0.9 to 14% (RD 0.04, 95% CI -0.04 to 0.11, I2 64%, very low certainty). The incidence of infection (4 studies, N = 548) ranged from 3 to 7% (RD 0.04, 95%CI 0.01, 0.07, I2 0%, very low certainty). The incidence of reoperation/reimplantation (4 studies, N =5 48) ranged from 2% to 31% (RD 0.11, 95% CI 0.02 to 0.21, I2 86%, very low certainty). One study (N = 44) reported a 55% incidence of lead failure/displacement (RD 0.55, 95% CI 0.35, 0 to 75, very low certainty), and a 94% incidence of reoperation/reimplantation (RD 0.94, 95% CI 0.80 to 1.07, very low certainty) at five-year follow-up. No studies provided data on infection rates at long-term follow-up. We found reports of some serious adverse events as a result of the intervention. These included autonomic neuropathy, prolonged hospitalisation, prolonged monoparesis, pulmonary oedema, wound infection, device extrusion and one death resulting from subdural haematoma. Other No studies reported the incidence of other adverse events at short-term follow-up. We found no clear evidence of a difference in otherAEs at medium-term (2 studies, N = 278, RD -0.05, 95% CI -0.16 to 0.06, I2 0%) or long term (1 study, N = 100, RD -0.17, 95% CI -0.37 to 0.02) follow-up. Very limited evidence suggested that SCS increases healthcare costs. It was not clear whether SCS was cost-effective.

AUTHORS' CONCLUSIONS

We found very low-certainty evidence that SCS may not provide clinically important benefits on pain intensity compared to placebo stimulation. We found low- to very low-certainty evidence that SNMD interventions may provide clinically important benefits for pain intensity when added to conventional medical management or physical therapy. SCS is associated with complications including infection, electrode lead failure/migration and a need for reoperation/re-implantation. The level of certainty regarding the size of those risks is very low. SNMD may lead to serious adverse events, including death. We found no evidence to support or refute the use of DRGS for chronic pain.

Mechanistically informed non-invasive peripheral nerve stimulation for peripheral neuropathic pain: a randomised double-blind sham-controlled trial

BACKGROUND

Induction of long-term synaptic depression (LTD) is proposed as a treatment mechanism for chronic pain but remains untested in clinical populations. Two interlinked studies; (1) A patient-assessor blinded, randomised, sham-controlled clinical trial and (2) an open-label mechanistic study, sought to examine therapeutic LTD for persons with chronic peripheral nerve injury pain.

METHODS

(1) Patients were randomised using a concealed, computer-generated schedule to either active or sham non-invasive low-frequency nerve stimulation (LFS), for 3 months (minimum 10 min/day). The primary outcome was average pain intensity (0-10 Likert scale) recorded over 1 week, at 3 months, compared between study groups. (2) On trial completion, consenting subjects entered a mechanistic study assessing somatosensory changes in response to LFS.

RESULTS

(1) 76 patients were randomised (38 per group), with 65 (31 active, 34 sham) included in the intention to treat analysis. The primary outcome was not significant, pain scores were 0.3 units lower in active group (95% CI - 1.0, 0.3; p = 0.30) giving an effect size of 0.19 (Cohen's D). Two non-device related serious adverse events were reported. (2) In the mechanistic study (n = 19) primary outcomes of mechanical pain sensitivity (p = 0.006) and dynamic mechanical allodynia (p = 0.043) significantly improved indicating reduced mechanical hyperalgesia.

CONCLUSIONS

Results from the RCT failed to reach significance. Results from the mechanistic study provide new evidence for effective induction of LTD in a clinical population. Taken together results add to mechanistic understanding of LTD and help inform future study design and approaches to treatment. Trial registration ISRCTN53432663.

An implantable restorative-neurostimulator for refractory mechanical chronic low back pain: a randomized sham-controlled clinical trial

ABSTRACT

Chronic low back pain can be caused by impaired control and degeneration of the multifidus muscles and consequent functional instability of the lumbar spine. Available treatment options have limited effectiveness and prognosis is unfavorable. We conducted an international randomized, double-blind, sham-controlled trial at 26 multidisciplinary centers to determine safety and efficacy of an implantable, restorative neurostimulator designed to restore multifidus neuromuscular control and facilitate relief of symptoms (clinicaltrials.gov identifier: NCT02577354). Two hundred four eligible participants with refractory mechanical (musculoskeletal) chronic LBP and a positive prone instability test indicating impaired multifidus control were implanted and randomized to therapeutic (N = 102) or low-level sham (N = 102) stimulation of the medial branch of the dorsal ramus nerve (multifidus nerve supply) for 30 minutes twice daily. The primary endpoint was the comparison of responder proportions (≥30% relief on the LBP visual analogue scale without analgesics increase) at 120 days. After the primary endpoint assessment, participants in the sham-control group switched to therapeutic stimulation and the combined cohort was assessed through 1 year for long-term outcomes and adverse events. The primary endpoint was inconclusive in terms of treatment superiority (57.1% vs 46.6%; difference: 10.4%; 95% confidence interval, -3.3% to 24.1%, P = 0.138). Prespecified secondary outcomes and analyses were consistent with a modest but clinically meaningful treatment benefit at 120 days. Improvements from baseline, which continued to accrue in all outcome measures after conclusion of the double-blind phase, were clinically important at 1 year. The incidence of serious procedure- or device-related adverse events (3.9%) compared favorably with other neuromodulation therapies for chronic pain.

Design and conduct of confirmatory chronic pain clinical trials

The purpose of this article is to provide readers with a basis for understanding the emerging science of clinical trials and to provide a set of practical, evidence-based suggestions for designing and executing confirmatory clinical trials in a manner that minimizes measurement error. The most important step in creating a mindset of quality clinical research is to abandon the antiquated concept that clinical trials are a method for capturing data from clinical practice and shifting to a concept of the clinical trial as a measurement system, consisting of an interconnected set of processes, each of which must be in calibration for the trial to generate an accurate and reliable estimate of the efficacy (and safety) of a given treatment. The status quo of inaccurate, unreliable, and protracted clinical trials is unacceptable and unsustainable. This article gathers aspects of study design and conduct under a single broad umbrella of techniques available to improve the accuracy and reliability of confirmatory clinical trials across traditional domain boundaries.