Does a screening trial for spinal cord stimulation in patients with chronic pain of neuropathic origin have clinical utility and cost-effectiveness (TRIAL-STIM)? A randomised controlled trial

Consenting for Spinal Cord Stimulation - the Pitfalls and Solution

PURPOSE OF REVIEW

To discuss the importance of the consenting process for patients undergoing spinal cord stimulation (SCS) therapy and understanding related complications and effects.

RECENT FINDINGS

Litigation for SCS/DRG related complications can be very costly, with the mean average settlement in cases relating to SCS being $303,173 dollars in the USA. According to the US Anaesthesia Closed Claims Project database, 10,546 claims related to pain medicine were made between 1990 and 2013; 43 of which were associated with SCS complications. This article will further explore consenting and complications within the context of SCS. Consenting for SCS is a crucial and very important step which potentially reflect on patients' expectations and outcomes.

Preventing technique-related complications in spinal cord stimulation trials: The Dural Substitute Confetti technique. A retrospective monocentric analysis

BACKGROUND

Spinal Cord Stimulation (SCS) is an established therapy for chronic pain, employing screening trials to identify suitable candidates before implantation. However, complications arising from both technique and medical factors present challenges to this practice. This study introduces the Dural Substitute Confetti technique, which addresses technique-related complications during SCS implantation by preventing scar-induced lead migration or breakage and reducing operating times.

METHODS

We conducted a retrospective analysis on 174 patients treated with SCS trials from 2017 to 2022 at our institution. Of these, 85.1% proceeded to permanent implantation. During trial surgery, synthetic dural substitutes (DS) were used to protect leads, which remained connected to an external pulse generator (EPG) for 20-28 days (mean 21.4 days). Utilizing the DS Confetti technique, leads were easily dissected from the DS during the second surgery and connected to an internal pulse generator (IPG). We compared complications and surgical times before and after the introduction of this technique in 2017.

RESULTS

Following the complete SCS trial, patients experienced over 50% pain relief, with an implant-to-trial ratio of 85.1% and a mean follow-up of 52 months. No technique-related complications occurred during the trial period post-2017, while the pre-2017 group had a 3.9% lead migration rate due to scarring, necessitating re-implantation. The average surgery duration decreased from 54 min pre-2017 to 32 min post-2017. Medical-related complications included infections (2.1%) and wound dehiscence (1.3%).

CONCLUSIONS

The DS Confetti technique prevents scar adhesion formation during screening trials, thereby facilitating and expediting the definitive SCS implantation. Additionally, it may also reduce the risk of lead migration and iatrogenic damage, potentially lowering technique-related complications.

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.

Long-Term Treatment of Chronic Postamputation Pain With Bioelectric Nerve Block: Twelve-Month Results of the Randomized, Double-Blinded, Cross-Over QUEST Study

OBJECTIVE

The multicenter, randomized, double-blinded, active-sham controlled trial (high-freQUEncy nerve block for poST amputation pain [QUEST]) was conducted to show the safety and efficacy of a novel, peripherally placed high-frequency nerve block (HFNB) system in treating chronic postamputation pain (PAP) in patients with lower limb amputations. The primary outcomes from QUEST were reported previously. This study presents the long-term, single-cross-over, secondary outcomes of on-demand HFNB treatment for chronic PAP.

MATERIALS AND METHODS

After the three-month randomized period, subjects in the active-sham group were crossed over to receive therapy for 12 months. Subjects self-administered HFNB therapy as needed and reported their pain (numerical rating scale [NRS]; range, 1-10) before and 30 and 120 minutes after each treatment. Pain medication use was reported throughout the study. Pain-days per week and quality of life (QOL) were assessed using the Brief Pain Inventory (BPI). Adverse events (AEs) were recorded for all subjects implanted for 12 months.

RESULTS

Of 180 subjects implanted in QUEST, 164 (91%) were included in the cross-over period, and 146 (82%) completed follow-up. By month 12, average NRS pain in the combined cohort was reduced by 2.3 ± 2.2 points (95% CI, 1.7-2.8; p < 0.0001) 30 minutes after treatment and 2.9 ± 2.4 points (95% CI, 2.2-3.6; p < 0.0001) 120 minutes after treatment. Mean pain-days per week were significantly reduced (-3.5 ± 2.7 days; p < 0.001), and subject daily opioid use was reduced by 6.7 ± 29.0 morphine equivalent dose from baseline to month 12 (p = 0.013). Mean BPI-interference scores (QOL) improved by 2.7 ± 2.7 points from baseline (p < 0.001). The incidence of nonserious AEs and serious AEs was 72% (130/180) and 42% (76/180), respectively; serious device-related AEs occurred in 15 of 180 subjects (8%).

CONCLUSION

Overall, HFNB delivered directly to the damaged peripheral nerve provided sustained, on-demand relief of acute PAP exacerbations, reduced opioid utilization, and improved QOL for patients with lower limb amputations with chronic PAP.

Spinal Cord Stimulation vs Medical Management for Chronic Back and Leg Pain: A Systematic Review and Network Meta-Analysis

Importance

Chronic back and lower extremity pain is one of the leading causes of disability worldwide. Spinal cord stimulation (SCS) aims to improve symptoms and quality of life.

Objective

To evaluate the efficacy of SCS therapies compared with conventional medical management (CMM).

Data Sources

MEDLINE, Embase, and Cochrane Library were systematically searched from inception to September 2, 2022.

Study Selection

Selected studies were randomized clinical trials comparing SCS therapies with sham (placebo) and/or CMM or standard treatments for adults with chronic back or leg pain who had not previously used SCS.

Data Extraction and Synthesis

Evidence synthesis estimated odds ratios (ORs) and mean differences (MDs) and their associated credible intervals (CrI) through bayesian network meta-analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline for network meta-analyses was followed.

Main Outcomes and Measures

The primary outcomes were pain-related end points, including pain intensity (measured by visual analog scale) and proportion of patients achieving at least 50% pain relief (responder rate) in the back or leg. Quality of life (measured by EQ-5D index score) and functional disability (measured by the Oswestry Disability Index score) were also considered.

Results

A total of 13 studies of 1561 patients were included in the network meta-analysis comparing conventional and novel SCS therapies with CMM across the 6 outcomes of interest at the 6-month follow-up. Both conventional and novel SCS therapies were associated with superior efficacy compared with CMM in responder rates in back (conventional SCS: OR, 3.00; 95% CrI, 1.49 to 6.72; novel SCS: OR, 8.76; 95% CrI, 3.84 to 22.31), pain intensity in back (conventional SCS: MD, -1.17; 95% CrI, -1.64 to -0.70; novel SCS: MD, -2.34; 95% CrI, -2.96 to -1.73), pain intensity in leg (conventional SCS: MD, -2.89; 95% CrI, -4.03 to -1.81; novel SCS: MD, -4.01; 95% CrI, -5.31 to -2.75), and EQ-5D index score (conventional SCS: MD, 0.15; 95% CrI, 0.09 to 0.21; novel SCS: MD, 0.17; 95% CrI, 0.13 to 0.21). For functional disability, conventional SCS was superior to CMM (MD, -7.10; 95% CrI, -10.91 to -3.36). No statistically significant differences were observed for other comparisons.

Conclusions and Relevance

This systematic review and network meta-analysis found that SCS therapies for treatment of chronic pain in back and/or lower extremities were associated with greater improvements in pain compared with CMM. These findings highlight the potential of SCS therapies as an effective and valuable option in chronic pain management.

Hidden influence? Unmasking conflicts of interest from randomized clinical trials on spinal cord stimulation for chronic pain

BACKGROUND

Randomized clinical trials (RCTs) are considered the gold standard for evaluating the efficacy of healthcare interventions. However, conflicts of interest (COIs) can compromise the scientific integrity in these trials. This study characterized COIs in RCTs on spinal cord stimulation for chronic pain, focusing on the prevalence, disclosure, and monetary value of COIs.

METHODS

This cross-sectional study analyzed RCTs published from January 1, 2013 to July 27, 2023. Primary outcomes included the presence, disclosure, and monetary value of COIs, while secondary outcomes assessed the presence of direct/indirect COIs, sponsor access to data, and associations between COIs and select variables, including journal impact factor, publication year, and study outcomes.

RESULTS

Of 38 RCTs, 30 (78.9%) reported COIs. On average, 35.6% of authors per RCT had at least one COI, with a mean of 0.7 COIs per author. The mean annual monetary value of COIs was US$41,157.83 per author per RCT. 29 RCTs (76.3%) had undisclosed COIs, with an average of 24.2% of authors per RCT having undisclosed COIs. Sponsor access to data was reported in 67.6% of RCTs. No associations were observed between the mean percentage of authors with COIs and the monetary value of COIs and select dependent variables (impact factor, publication year, and study outcomes).

CONCLUSIONS

A substantial majority of RCTs reported COIs with many authors having undisclosed conflicts, highlighting the need for stringent COI disclosure guidelines to maintain research integrity. Expanding COI registry systems globally and increasing non-industry funding are crucial steps toward enhancing transparency and reducing biases in medical research.

A sham-controlled, randomized trial of spinal cord stimulation for the treatment of pain in chronic pancreatitis

BACKGROUND

Spinal cord stimulation (SCS) has emerged as a treatment option for patients with chronic pancreatitis (CP) who experience pain that does not respond to standard interventions. However, there is a lack of sham-controlled trials to support its efficacy.

METHODS

This randomized, double-blinded, sham-controlled, cross-over trial enrolled 16 CP patients with insufficient pain relief from standard therapies. Patients underwent high-frequency (1000 Hz) paraesthesia-free SCS or sham for two 10-day stimulation periods, separated by a 3-day washout period. The primary outcome was daily pain intensity registered in a pain diary based on a numeric rating scale (NRS). Secondary outcomes included various questionnaires. Quantitative sensory testing was used to probe the pain system before and after interventions.

RESULTS

The average daily pain score on the NRS at baseline was 5.2 ± 1.9. After SCS, the pain score was 4.2 ± 2.1 compared to 4.3 ± 2.1 in the sham group (mean difference -0.1, 95% CI [-1.4 to 1.1]; P = 0.81). Similarly, no differences were observed between groups for the maximal daily pain score, secondary outcomes or quantitative sensory testing parameters. During an open-label, non-sham-controlled and non-blinded extension of the study, the average daily NRS was 5.2 ± 1.7 at baseline, 3.2 ± 1.8 at 3 months, 2.9 ± 1.9 at 6 months and 3.4 ± 2.2 at 12 months of follow-up (P = 0.001).

CONCLUSION

In this first sham-controlled trial of SCS in painful CP, we did not find evidence of short-term pain relief with paraesthesia-free high-frequency (1000 Hz) stimulation. However, evaluation of the long-term effect by larger sham-controlled trials with long-term follow-up is warranted.

SIGNIFICANCE STATEMENT

In this first sham-controlled trial to apply high-frequency (1000 Hz) spinal cord stimulation in patients with visceral pain due to chronic pancreatitis, we did not find evidence for clinically relevant pain relief. Taken together with potential procedure-related complications, adverse effects and costs associated with spinal cord stimulation, our findings question its use for management of visceral pain.

Identifying SCS Trial Responders Immediately After Postoperative Programming with ECAP Dose-Controlled Closed-Loop Therapy

INTRODUCTION

Drawbacks of fixed-output spinal cord stimulation (SCS) screening trials may lead to compromised trial outcomes and poor predictability of long-term success. Evoked compound action potential (ECAP) dose-controlled closed-loop (CL) SCS allows objective confirmation of therapeutic neural activation and pulse-to-pulse stimulation adjustment. We report on the immediate patient-reported and neurophysiologic treatment response post-physiologic CL-SCS and feasibility of early SCS trial responder prediction.

METHODS

Patient-reported pain relief, functional improvement, and willingness to proceed to permanent implant were compared between the day of the trial procedure (Day 0) and end of trial (EOT) for 132 participants in the ECAP Study undergoing a trial stimulation period. ECAP-based neurophysiologic measurements from Day 0 and EOT were compared between responder groups.

RESULTS

A high positive predictive value (PPV) was achieved with 98.4% (60/61) of patients successful on the Day 0 evaluation also responding at EOT. The false-positive rate (FPR) was 5.6% (1/18). ECAP-based neurophysiologic measures were not different between patients who passed all Day 0 success criteria ("Day 0 successes") and those who did not ("needed longer to evaluate the therapy"). However, at EOT, responders had higher therapeutic usage and dose levels compared to non-responders.

CONCLUSIONS

The high PPV and low FPR of the Day 0 evaluation provide confidence in predicting trial outcomes as early as the day of the procedure. Day 0 trials may be beneficial for reducing patient burden and complication rates associated with extended trials. ECAP dose-controlled CL-SCS therapy may provide objective data and rapid-onset pain relief to improve prognostic ability of SCS trials in predicting outcomes.

TRIAL REGISTRATION

The ECAP Study is registered with ClinicalTrials.gov (NCT04319887).

Multidevice spinal cord stimulation trials: shared decision making in the era of multiple neuromodulation paradigms

Aim: There is a lack of evidence-based standards for matching spinal cord stimulation (SCS) paradigm to individual patients. We aim to determine the feasibility and safety of a new alternative trial strategy, a sequential multidevice trial.Materials & methods: A retrospective analysis was performed on 116 patients who underwent SCS trials, single device or sequential multidevice (tonic and high-frequency), for chronic low back pain to assess feasibility and compare trial-to-implantation rate and explantation rate.Results: Multidevice SCS trials are feasible and safe. There was no statistically significant difference in the trial-to-implantation and explantation rates between the two groups.Conclusion: Multidevice SCS trial, prioritizing patient preference, may serve as an alternative trial strategy to improve long-term success of SCS.

The Neurostimulation Appropriateness Consensus Committee (NACC)®: Recommendations for Spinal Cord Stimulation Long-Term Outcome Optimization and Salvage Therapy

INTRODUCTION

The International Neuromodulation Society (INS) has recognized a need to establish best practices for optimizing implantable devices and salvage when ideal outcomes are not realized. This group has established the Neurostimulation Appropriateness Consensus Committee (NACC)® to offer guidance on matters needed for both our members and the broader community of those affected by neuromodulation devices.

MATERIALS AND METHODS

The executive committee of the INS nominated faculty for this NACC® publication on the basis of expertise, publications, and career work on the issue. In addition, the faculty was chosen in consideration of diversity and inclusion of different career paths and demographic categories. Once chosen, the faculty was asked to grade current evidence and along with expert opinion create consensus recommendations to address the lapses in information on this topic.

RESULTS

The NACC® group established informative and authoritative recommendations on the salvage and optimization of care for those with indwelling devices. The recommendations are based on evidence and expert opinion and will be expected to evolve as new data are generated for each topic.

CONCLUSIONS

NACC® guidance should be considered for any patient with less-than-optimal outcomes with a stimulation device implanted for treating chronic pain. Consideration should be given to these consensus points to salvage a potentially failed device before explant.

Is Response to a Pre-implant Diagnostic Peripheral Nerve Block Associated With Efficacy After Peripheral Nerve Stimulation Implantation? A Ten-Year Enterprise-Wide Analysis

OBJECTIVES

This study aimed to assess whether patient response to targeted diagnostic peripheral nerve block before peripheral nerve stimulator (PNS) device implantation is associated with efficacy after PNS implantation.

MATERIALS AND METHODS

The electronic medical records from the Mayo Clinic Enterprise (three quarternary care medical centers and additional satellite medical centers) were reviewed to identify patients who underwent PNS implantation between January 2014 and January 2023. A primary outcome of interest was to assess whether administration of a preimplant diagnostic peripheral nerve block predicted pain relief at three months and six months after temporary and permanent PNS implantation. Another primary outcome was to investigate whether there was an association between the pain relief from a preimplant diagnostic peripheral nerve block and pain relief after three and six months after temporary or permanent PNS therapy. Linear regression analysis was conducted for outcomes of interest.

RESULTS

Of 193 eligible patients who underwent PNS therapy, a total of 173 patients were included in the final analysis and were stratified into either the temporary PNS cohort (n = 112) or the permanent PNS cohort (n = 61). Overall, 77.5% of all patients (134/173) underwent a preimplant diagnostic peripheral nerve block and reported a mean percentage relief of 70.1 ± 27.0 from the diagnostic block. Of patients in the temporary PNS cohort, there was no difference in postimplant percentage pain relief between patients who received a diagnostic block (n = 93) and control patients (n = 19) at three months (35.4 ± 36.0 vs 49.8 ± 36.1, respectively; β -14.45, 95% CI -32.98 to 4.07, p = 0.125) or at six months (23.3 ± 30.8 vs 45.7 ± 40.0, respectively; β -22.39, 95% CI -46.86 to 2.08, p = 0.072). Of patients in the permanent PNS cohort, there was no difference in postimplant percentage pain relief between patients who received a diagnostic block (n = 41) and control patients (n = 20) at three months (42.4 ± 34.3 vs 43.2 ± 42.4, respectively; β -0.79, 95% CI -23.56 to 21.99, p = 0.945) or at six months (44.3 ± 35.0 vs 38.8 ± 40.9, respectively; β 5.42, 95% CI -20.04 to 30.88, p = 0.669). Pain relief from preimplant diagnostic blocks was associated with postimplant pain relief from temporary PNS at three months (β 0.33, 95% CI 0.04-0.61, p = 0.025). However, pain relief from preimplant diagnostic blocks did not predict postimplant pain relief from temporary PNS at six months, or permanent PNS at three months and six months.

CONCLUSIONS

Administration of a diagnostic block is not associated with superior pain relief at three or six months after PNS implantation to that of an approach without diagnostic block. Pain relief from a diagnostic block may potentially predict short-term pain relief after temporary PNS therapy, although future prospective studies are warranted to evaluate the prognostic utility of diagnostic blocks.

A review of prospective studies regarding percutaneous peripheral nerve stimulation treatment in the management of chronic pain

Conventionally, peripheral nerve stimulation (PNS) for treatment of chronic pain has involved a two-stage process: a short-term (e.g., 7 days) trial and, if significant pain relief is achieved, a permanent PNS system is implanted. A percutaneous PNS treatment is now available where a coiled lead may be implanted for up to 60 days with the goal of producing sustained relief. In the present review, published prospective trials using percutaneous PNS treatment were identified and synthesized. The collected evidence indicates that percutaneous PNS treatment for up to 60 days provides durable clinically significant improvements in pain and pain interference. Similar efficacy across diverse targets and etiologies supports the broad applicability for use within the chronic pain population using this nonopioid technology.

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

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

Neuropathic pain: Evidence based recommendations

Neuropathic pain continues to be a significant problem that lacks effective solutions for every single patient. In 2015, international guidelines (NeuPSIG) were published, while the French recommendations were updated in 2020. The purpose of this minireview is to provide an update on the process of developing evidence-based recommendations and explore potential changes to the current recommendations. Primary treatments for neuropathic pain include selective serotonin-norepinephrine reuptake inhibitors (SNRIs) such as duloxetine and venlafaxine, gabapentin, tricyclic antidepressants, as well as topical lidocaine and transcutaneous electrical nerve stimulation, which are specifically suggested for focal peripheral neuropathic pain. Pregabalin is a first line treatment according to international guidelines but second-line in the more recent French guidelines, due to lower efficacy seen in more recent studies and misuse risk. Additionally, tramadol, combination therapies, and psychotherapy as adjuncts are proposed second line; high-concentration capsaicin patches, and botulinum toxin A are proposed specifically for focal peripheral neuropathic pain. In cases where primary and secondary treatments prove insufficient, third-line options come into play. These include high-frequency repetitive transcranial magnetic stimulation (rTMS) targeting the motor cortex, spinal cord stimulation, and the use of strong opioids when no alternative is available. To ensure optimal management of neuropathic pain in real-life situations, it is imperative to disseminate these recommendations widely and secure the acceptance of practitioners. By doing so, we can bridge the gap between theory and practice, and enhance the overall care and treatment of individuals suffering from neuropathic pain.

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.

Neurophysiological outcomes that sustained clinically significant improvements over 3 years of physiologic ECAP-controlled closed-loop spinal cord stimulation for the treatment of chronic pain

INTRODUCTION

A novel, spinal cord stimulation (SCS) system with a physiologic closed-loop (CL) feedback mechanism controlled by evoked compound action potentials (ECAPs) enables the optimization of physiologic neural dose and the accuracy of the stimulation, not possible with any other commercially available SCS systems. The report of objective spinal cord measurements is essential to increase the transparency and reproducibility of SCS therapy. Here, we report a cohort of the EVOKE double-blind randomized controlled trial treated with CL-SCS for 36 months to evaluate the ECAP dose and accuracy that sustained the durability of clinical improvements.

METHODS

41 patients randomized to CL-SCS remained in their treatment allocation and were followed up through 36 months. Objective neurophysiological data, including measures of spinal cord activation, were analyzed. Pain relief was assessed by determining the proportion of patients with ≥50% and ≥80% reduction in overall back and leg pain.

RESULTS

The performance of the feedback loop resulted in high-dose accuracy by keeping the elicited ECAP within 4µV of the target ECAP set on the system across all timepoints. Percent time stimulating above the ECAP threshold was >98%, and the ECAP dose was ≥19.3µV. Most patients obtained ≥50% reduction (83%) and ≥80% reduction (59%) in overall back and leg pain with a sustained response observed in the rates between 3-month and 36-month follow-up (p=0.083 and p=0.405, respectively).

CONCLUSION

The results suggest that a physiological adherence to supra-ECAP threshold therapy that generates pain inhibition provided by ECAP-controlled CL-SCS leads to durable improvements in pain intensity with no evidence of loss of therapeutic effect through 36-month follow-up.

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

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

1. Lumbosacral radicular pain

INTRODUCTION

Patients suffering lumbosacral radicular pain report radiating pain in one or more lumbar or sacral dermatomes. In the general population, low back pain with leg pain extending below the knee has an annual prevalence that varies from 9.9% to 25%.

METHODS

The literature on the diagnosis and treatment of lumbosacral radicular pain was reviewed and summarized.

RESULTS

Although a patient's history, the pain distribution pattern, and clinical examination may yield a presumptive diagnosis of lumbosacral radicular pain, additional clinical tests may be required. Medical imaging studies can demonstrate or exclude specific underlying pathologies and identify nerve root irritation, while selective diagnostic nerve root blocks can be used to confirm the affected level(s). In subacute lumbosacral radicular pain, transforaminal corticosteroid administration provides short-term pain relief and improves mobility. In chronic lumbosacral radicular pain, pulsed radiofrequency (PRF) treatment adjacent to the spinal ganglion (DRG) can provide pain relief for a longer period in well-selected patients. In cases of refractory pain, epidural adhesiolysis and spinal cord stimulation can be considered in experienced centers.

CONCLUSIONS

The diagnosis of lumbosacral radicular pain is based on a combination of history, clinical examination, and additional investigations. Epidural steroids can be considered for subacute lumbosacral radicular pain. In chronic lumbosacral radicular pain, PRF adjacent to the DRG is recommended. SCS and epidural adhesiolysis can be considered for cases of refractory pain in specialized centers.

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.

Machine Learning in Pain Neuromodulation

This chapter highlights the intersection of pain neuromodulation and machine learning (ML), exploring current limitations in pain management and how ML techniques can address these challenges. Neuromodulation technologies, such as spinal cord stimulation (SCS), have emerged as promising interventions for chronic pain, but limitations such as patient selection have resulted in high rates of failure and costly removal of these devices. ML offers a powerful approach to augment pain management outcomes by leveraging predictive modeling for enhanced patient selection, adaptive algorithms for programming optimization, and identification of objective biomarkers for improved outcome assessment. This chapter discusses various ML applications in pain neuromodulation and how we can expect it to shape the future of the field. While ML holds great promise, challenges such as algorithm transparency, data quality, and generalizability must be addressed to fully realize its potential in revolutionizing pain management.

Real World Characterization of Chronic Pain, Success Rates and Implant Rates: Evidence from a Digital Health Platform of Patients Undergoing Spinal Cord Stimulation Evaluations

Spinal cord stimulation is an effective treatment for those experiencing chronic back and leg pain but requires a temporary evaluation period (SCSeval) before permanent implantation. We present real-world data from 7,000 patients who underwent SCSeval while utilizing a mobile digital health platform for education, feedback, and outcomes collection during their surgical journey. We analyzed preoperative patient demographics, characterized patient pain profiles using the patient-reported outcomes measurement information system-29 surveys, and calculated the rates of conversion from temporary to permanent spinal cord stimulation (SCS) implantation. Between August 1, 2021, and March 2, 2023, 7,000 patients (mean age 59.1, 59.6% female) underwent SCSeval procedures while utilizing a mobile application. Patients commonly experienced aching, sharp, stabbing, tingling, numb, and burning pain. Patients had tried multiple prior therapies and wanted to reduce their use of opioids and pain medications. Overall, 90.1% of the patients had a successful SCSeval, and 80.4% of those converted to permanent implant, with the highest rates among those who underwent SCSeval in a hospital setting. There was a significant improvement in all domains of pain as evaluated by pre and postoperative patient-reported outcomes measurement information system-29 surveys. This study supports the use of digital health technology as part of the SCS journey to improve the patient experience and allow for robust patient-reported outcomes collection. The overall rate of SCSeval to permanent SCS in our study of 72.4% was higher than national rates of 64%, suggesting that an app may allow clinicians to better quantify changes in chronic pain and provide more insight into choosing to implant SCS permanently. PERSPECTIVE: This article presents real-world evidence from a digital health platform for therapy education and outcomes collection from patients undergoing spinal cord stimulation evaluation procedures. Such tools could allow for better pain characterization and allow for more nuanced tracking of patient outcomes among those with chronic pain.

Opinions of Health Care Providers About Neuromodulation for Pain: Results of an Online Survey at the 2nd Joint Congress of the International Neuromodulation Society European Chapters

INTRODUCTION

Neuromodulation for pain has been successfully applied for decades, in that the goals and expectations that patients aim to achieve are clearly described. Nevertheless, the point of view of health care providers is less clear. Therefore, this study aimed to explore the goals, expectations, and definition of success for neuromodulation for pain according to health care providers.

MATERIALS AND METHODS

An online survey was developed and spread at the 2nd Joint Congress of the International Neuromodulation Society (INS) European Chapters in September 2021 in Paris. Respondents were asked 1) to select the goals to treat patients with neuromodulation for pain, 2) to indicate factors that they expect to change according to neuromodulation for pain, and 3) to provide their definition of success of neuromodulation for pain.

RESULTS

We approached 101 respondents, of whom 88 health care providers at least partly completed the survey. Increasing mobility/functionality (26.7%), decreasing pain intensity (24.5%), and decreasing medication use (16.6%) were the most frequently reported goals of neuromodulation. The same top three variables were selected as factors that health care providers expected to change. For the definition of success, quality of life of patients outranked other definitions. Other highly ranked definitions, in descending order, were obtaining pain relief, increasing functionality, and increasing patient satisfaction.

DISCUSSION

Goals and expectations of health care providers are not completely in line with previously explored goals of patients that are related to pain relief and improving walking abilities. Health care providers seem to put a high emphasis on the quality of life of the patient when evaluating the success of neuromodulation, which is not completely aligned with the currently used reimbursement rules that are mainly focusing on pain relief instead of incorporating health-related quality of life.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT05013840.

International Society for the Advancement of Spine Surgery Statement: Restorative Neurostimulation for Chronic Mechanical Low Back Pain Resulting From Neuromuscular Instability

This International Society for the Advancement of Spine Surgery statement has been generated to respond to growing requests for background, supporting literature and evidence, and proper coding for restorative neurostimulation for chronic low back pain. Chronic low back pain describes the diverse experience of a significant proportion of the population. Conservative management of these patients remains the predominant care pathway, but for many patients, symptom relief is poor. The application of new techniques in patients who have exhausted traditional care paradigms should be undertaken with a detailed understanding of the pathology being treated, the mechanisms involved, and the data supporting efficacy. This statement on restorative neurostimulation places this technology in the context of the current understanding of the etiology of mechanical low back pain and the currently available evidence for this technique. In an appropriately selected cohort with a specific subset of chronic low back pain symptoms, this technique may provide benefit to payers and patients.

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 outcomes of single-stage spinal cord stimulation in chronic pain patients: A multicentre, European case series

Background

Spinal cord stimulation (SCS) is effective in treating chronic neuropathic pain. A screening trial is typically conducted prior to implantation to evaluate whether a patient is a good candidate for SCS. However, the need for a screening trial has been debated. We evaluated real-world clinical outcomes in patients who underwent a single-stage procedure to receive SCS therapy (i.e., no screening trial period) (SS-SCS).

Methods

This observational, multicentre, real-world consecutive case series evaluated SS-SCS chronic pain patients. Pain and other functional outcomes were collected as part of standard care by site personnel with no sponsor involvement. Assessments included Numerical rating scale (NRS), Percent Pain Relief (PPR) and EQ-5D-5L (EuroQol 5 Dimensions-5L), recorded prior to SCS and following implantation.

Results

A total of 171 chronic pain patients (mean age: 59.4; 53.2% females) underwent a single-stage procedure (mean last follow-up, 408 days) and were included in the analysis. A 5.0 ​± ​2.1-point improvement in overall pain was reported at 3 months and sustained until the last follow-up post-implantation (p ​< ​0.0001). At last follow-up, 50.3% (86/171) of patients reported an NRS pain score ≤3. Additionally, quality of life also improved (46.1-point change, from 70.2 to 25) at the last follow-up, based on EQ-5D-5L scores.

Conclusions

In routine clinical practice, SS-SCS can provide significant long-term pain relief and improve quality of life in chronic pain patients. Our results suggest that effective long-term outcomes and success may be achieved without a trial period prior to permanent implantation of an SCS system.

Machine Learning in Spinal Cord Stimulation for Chronic Pain

Spinal cord stimulation (SCS) is an effective treatment for chronic neuropathic pain. The success of SCS is dependent on candidate selection, response to trialing, and programming optimization. Owing to the subjective nature of these variables, machine learning (ML) offers a powerful tool to augment these processes. Here we explore what work has been done using data analytics and applications of ML in SCS. In addition, we discuss aspects of SCS which have narrowly been influenced by ML and propose the need for further exploration. ML has demonstrated a potential to complement SCS to an extent ranging from assistance with candidate selection to replacing invasive and costly aspects of the surgery. The clinical application of ML in SCS shows promise for improving patient outcomes, reducing costs of treatment, limiting invasiveness, and resulting in a better quality of life for the patient.

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.

Efficacy of Continuous Intrathecal Infusion Trialing with a Mixture of Fentanyl and Bupivacaine in Chronic Low Back Pain Patients

Intrathecal trialing is used as a screening prognostic measure prior to intrathecal drug delivery system implant. The purpose of this study was to determine the efficacy of a continuous intrathecal infusion of an admixture of bupivacaine and fentanyl in patients with chronic low back pain. Patients with refractory chronic low back pain in the setting of previous lumbar spine surgery and/or chronic vertebral compression fracture(s) were enrolled in a randomized double blind cross-over study comparing saline infusion to infusion of a solution containing bupivacaine combined with low-dose fentanyl over a 14-18 hour period. The primary outcome measure was the change in pain intensity at the end of the screening trial. Patients who experienced significant pain reduction from either infusion relative to baseline pain were offered a permanent implant. In total, 36 patients were enrolled, with 31 patients trialed and 25 implanted. At the end of the screening trial, pain scores, at rest or with activity, decreased appreciably in both groups; however, significantly better improvements occurred in the fentanyl/bupivacaine group compared to saline both with activity and at rest (P = .016 and .006, respectively). Treatment order appeared to affect outcome with saline demonstrating a placebo response. At 12 months following implant, primary and secondary outcome measures continued to be significantly reduced from baseline. Continuous intrathecal delivery of a combination of zlow-dose fentanyl with bupivacaine is superior to saline in screening intrathecal trialing for back pain reduction. With longer term delivery, a sustained reduction of chronic low back pain was also observed.

Spinal Cord Stimulation for Failed Back Surgery Syndrome: to Trial or Not to Trial?

Spinal cord stimulation (SCS) is a recommended therapy to treat failed back surgery syndrome (FBSS). A trial period is practiced to enhance patient selection. However, its fundamental evidence is limited, especially concerning long-term benefit and therapy safety. We compared the long-term (5.3 ± 4.0 years) clinical outcome and therapy safety of a trialed and nontrialed implantation strategy, including multidimensional variables and pain intensity fluctuations over time. A multicenter cohort analysis was performed in 2 comparable groups of FBSS patients. Regarding eligibility, patients had to be treated with SCS for at least 3 months. While the Trial group comprised patients who underwent an SCS implantation after a successful trial, the No-Trial group encompassed patients who underwent complete implantation within 1 session. The primary outcome measures were pain intensity scores and complications. The Trial and No-Trial groups consisted of 194 and 376 patients (N = 570), respectively. A statistically but not clinically significant difference in pain intensity (P = .003; effect = 0.506 (.172-.839)) was found in favor of the Trial group. No interaction between a time dependency effect and pain intensity was noted. Whereas trialed SCS patients were more likely to cease opioid usage (P = .003; OR = .509 (.326-.792)), patients in the No-Trial group endured fewer infections (P = .006; proportion difference = .43 (.007-.083)). Although the clinical relevance of our findings should be proven in future studies, this long-term real-world data study indicates that patient-centered assessments on whether an SCS trial should be performed have to be investigated. According to the current ambiguous evidence, SCS trials should be considered on a case-by-case basis. PERSPECTIVE: The currently available comparative evidence, together with our results, remains ambiguous on which SCS implantation strategy might be deemed superior. An SCS trial should be considered on a case-by-case basis, for which further investigation of its clinical utility in certain patient populations or character traits is warranted.

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

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

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

Background/importance

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

Objective

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

Evidence review

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

Findings

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

Conclusions

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

Spinal cord stimulation for low back pain

BACKGROUND

Spinal cord stimulation (SCS) is a surgical intervention used to treat persistent low back pain. SCS is thought to modulate pain by sending electrical signals via implanted electrodes into the spinal cord. The long term benefits and harms of SCS for people with low back pain are uncertain.

OBJECTIVES

To assess the effects, including benefits and harms, of SCS for people with low back pain.

SEARCH METHODS

On 10 June 2022, we searched CENTRAL, MEDLINE, Embase, and one other database for published trials. We also searched three clinical trials registers for ongoing trials.

SELECTION CRITERIA

We included all randomised controlled trials and cross-over trials comparing SCS with placebo or no treatment for low back pain. The primary comparison was SCS versus placebo, at the longest time point measured in the trials. Major outcomes were mean low back pain intensity, function, health-related quality of life, global assessment of efficacy, withdrawals due to adverse events, adverse events, and serious adverse events. Our primary time point was long-term follow-up (≥ 12 months).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 13 studies with 699 participants: 55% of participants were female; mean age ranged from 47 to 59 years; and all participants had chronic low back pain with mean duration of symptoms ranging from five to 12 years. Ten cross-over trials compared SCS with placebo. Three parallel-group trials assessed the addition of SCS to medical management. Most studies were at risk of performance and detection bias from inadequate blinding and selective reporting bias. The placebo-controlled trials had other important biases, including lack of accounting for period and carryover effects. Two of the three parallel trials assessing SCS as an addition to medical management were at risk of attrition bias, and all three had substantial cross-over to the SCS group for time points beyond six months. In the parallel-group trials, we considered the lack of placebo control to be an important source of bias. None of our included studies evaluated the impact of SCS on mean low back pain intensity in the long term (≥ 12 months). The studies most often assessed outcomes in the immediate term (less than one month). At six months, the only available evidence was from a single cross-over trial (50 participants). There was moderate-certainty evidence that SCS probably does not improve back or leg pain, function, or quality of life compared with placebo. Pain was 61 points (on a 0- to 100-point scale, 0 = no pain) at six months with placebo, and 4 points better (8.2 points better to 0.2 points worse) with SCS. Function was 35.4 points (on a 0- to 100-point scale, 0 = no disability or best function) at six months with placebo, and 1.3 points better (3.9 points better to 1.3 points worse) with SCS. Health-related quality of life was 0.44 points out of 1 (0 to 1 index, 0 = worst quality of life) at six months with placebo, and 0.04 points better (0.16 points better to 0.08 points worse) with SCS. In that same study, nine participants (18%) experienced adverse events and four (8%) required revision surgery. Serious adverse events with SCS included infections, neurological damage, and lead migration requiring repeated surgery. We could not provide effect estimates of the relative risks as events were not reported for the placebo period. In parallel trials assessing SCS as an addition to medical management, it is uncertain whether, in the medium or long term, SCS can reduce low back pain, leg pain, or health-related quality of life, or if it increases the number of people reporting a 50% improvement or better, because the certainty of the evidence was very low. Low-certainty evidence suggests that adding SCS to medical management may slightly improve function and slightly reduce opioid use. In the medium term, mean function (0- to 100-point scale; lower is better) was 16.2 points better with the addition of SCS to medical management compared with medical management alone (95% confidence interval (CI) 19.4 points better to 13.0 points better; I2 = 95%; 3 studies, 430 participants; low-certainty evidence). The number of participants reporting opioid medicine use was 15% lower with the addition of SCS to medical management (95% CI 27% lower to 0% lower; I2 = 0%; 2 studies, 290 participants; low-certainty evidence). Adverse events with SCS were poorly reported but included infection and lead migration. One study found that, at 24 months, 13 of 42 people (31%) receiving SCS required revision surgery. It is uncertain to what extent the addition of SCS to medical management increases the risk of withdrawals due to adverse events, adverse events, or serious adverse events, because the certainty of the evidence was very low.

AUTHORS' CONCLUSIONS

Data in this review do not support the use of SCS to manage low back pain outside a clinical trial. Current evidence suggests SCS probably does not have sustained clinical benefits that would outweigh the costs and risks of this surgical intervention.

Spinal Cord Stimulation-Naïve Patients vs Patients With Failed Previous Experiences With Standard Spinal Cord Stimulation: Two Distinct Entities or One Population?

INTRODUCTION

Nowadays, the success of spinal cord stimulation (SCS) is evaluated separately in patients who have previous experiences with standard SCS and in SCS-naïve patients. Nevertheless, it is yet to be evaluated whether both patient groups are effectively distinct patient groups. Therefore, the aims of this study are twofold: 1) Are there clusters in the data to distinguish between both patient groups? 2) Can we discriminate both patient groups based on routinely collected clinical parameters?

MATERIALS AND METHODS

Baseline data from the Discover study were used, in which 263 patients with persistent spinal pain syndrome type 2 were included (185 neurostimulation-naïve patients and 78 patients with previous SCS experience). Pain intensity scores for low back and leg pain, functional disability, medication use, and health-related quality of life utility scores were used in the analysis. Model-based clustering was performed on standardized data. Discriminant analysis was performed with linear and quadratic discriminant analysis, with leave-one-out cross-validation to evaluate model performance.

RESULTS

Model-based clustering revealed two different clusters in the data. None of the clusters clearly separated SCS-naïve patients from patients with previous SCS experience. Linear discriminant analysis resulted in a leave-one-out cross-validation error rate of 30.0% to discriminate between both patient groups, based on routinely collected clinical parameters.

CONCLUSIONS

Clustering analysis did not result in clusters that separate SCS-naïve patients from patients with previous SCS experience. This may suggest that both patient groups should not be considered as two different patient groups when comparing them on routine clinical parameters, with potentially profound implications for research and clinical settings.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the Discover study is NCT02787265.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Gradation of Clinical Holistic Response as New Composite Outcome to Evaluate Success in Spinal Cord Stimulation Studies for Pain

INTRODUCTION

The most prominent outcome measurement in the field of neuromodulation is pain relief. Nevertheless, the number of studies that rely on composite outcomes has increased. The aims of this study are twofold: (1) to evaluate which measures are important to include in a composite outcome and (2) to develop this new composite outcome to evaluate the degree of being a clinical holistic responder with a corresponding minimal clinical important difference (MCID).

MATERIALS AND METHODS

Data from patients with persistent spinal pain syndrome type 2 treated with High-Dose Spinal Cord Stimulation (HD-SCS) were used. Pain intensity for low back and leg pain, disability, health-related quality of life, medication use, and patient satisfaction were measured at baseline and after 12 months of HD-SCS. Exploratory and Confirmatory Factor Analyses were used to evaluate which measures should be included in the composite outcome. Anchor-based and distribution-based methods were applied to determine the MCID of the newly developed outcome measurement.

RESULTS

A three-factor model was the most appropriate for this data set, in which leg pain intensity, EQ5D VAS, and disability had the largest loading on these factors. A clinical holistic outcome was created with a total score ranging from 0 (=better [no pain, no disability, and perfect health status]) to 300 (=worse [maximal pain, maximal disability, and worst health status]). The MCID value based on an absolute change score from baseline up to 12 months of HD-SCS was 87.97. When calculating with percentage changes, a MCID value of 48.4% was revealed.

CONCLUSIONS

This new composite outcome evaluating the degree of deviation from being a holistic responder is a step toward a meaningful, overall outcome assessment for patients who are treated with SCS. Further studies to evaluate the psychometric properties and the generalizability toward other patient populations still need to be performed.

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.

A Feasibility Study Exploring Measures of Autonomic Function in Patients With Failed Back Surgery Syndrome Undergoing Spinal Cord Stimulation

OBJECTIVES

Failed back surgery syndrome (FBSS) is associated with impaired autonomic tone, characterized by sympathetic prevalence and vagal withdrawal. Although spinal cord stimulation (SCS) alleviates pain in FBSS, there is limited research investigating how SCS affects measures of autonomic function. This was a prospective, open-label, feasibility study exploring measures of autonomic function in patients with FBSS receiving SCS therapy.

MATERIALS AND METHODS

A total of 14 patients with FBSS were recruited for baseline measurements and underwent a trial of 10-kHz SCS. There were three failed trials, resulting in the remaining 11 participants receiving a fully implanted 10-kHz SCS system. One participant requested an explant, resulting in ten participants completing both baseline and follow-up (three to six months after SCS implant) measurements. Autonomic function was assessed using time- and frequency-domain heart rate variability (HRV), baroreceptor reflex sensitivity (BRS), and muscle sympathetic nerve activity (MSNA) using microneurography. Because this was a feasibility study, most of the analysis was descriptive. However, paired t-tests and Wilcoxon signed-rank tests tested for differences between baseline and follow-up.

RESULTS

In the whole (N = 14) and final (N = 10) samples, there was between-participant variation in baseline and follow-up measures. This, combined with a small sample, likely contributed to finding no statistically significant differences in any of the measures between baseline and follow-up. However, plotting baseline and follow-up scores for individual participants revealed that those who showed increases in MSNA frequency, square root of the mean of the squared differences between adjacent RR intervals (RMSSD), percentage of the number of RR intervals >50 ms (pRR50), total power, and up BRS between baseline and follow-up had distinct clustering of baseline values compared with those who showed decreases in these measures.

CONCLUSIONS

Findings from this feasibility study will aid with informing hypotheses for future research. A key aspect that should be considered in future research concerns exploring the role of baseline measures of autonomic function in influencing change in autonomic function with SCS therapy.

Applicability and Validity of an e-Health Tool for the Appropriate Referral and Selection of Patients With Chronic Pain for Spinal Cord Stimulation: Results From a European Retrospective Study

OBJECTIVES

To support rational decision-making on spinal cord stimulation (SCS), a European expert panel developed an educational e-health tool using the RAND/University of California at Los Angeles Appropriateness Method. This retrospective study aimed to determine the applicability and validity of the tool using data from patients for whom SCS had been considered.

MATERIALS AND METHODS

A total of 12 European implant centers retrieved data from 25 to 50 consecutive patients for whom SCS was considered in 2018-2019. For each patient, data were captured on the clinical and psychosocial variables included in the e-health tool, center decisions on SCS, and patient outcomes. Patient outcomes included global perception of effect by the patient and observer, and pain reduction (numeric pain rating scale) at six-month follow-up.

RESULTS

In total, 483 patients were included, of whom 133 received a direct implant, 258 received an implant after a positive trial, 32 had a negative trial, and 60 did not receive SCS for reasons other than a negative trial. The most frequent indication was persistent spinal pain syndrome type 1 and type 2 (74%), followed by neuropathic pain syndromes (13%), complex regional pain syndrome (12%), and ischemic pain syndromes (0.8%). Data on the clinical and psychosocial variables were complete for 95% and 93% of patients, respectively, and missing data did not have a significant impact on the study outcomes. In patients who had received SCS, panel recommendations were significantly associated with patient outcomes (p < 0.001 for all measures). Substantial improvement ranged from 25% if the e-health tool outcome was "not recommended" to 83% if SCS was "strongly recommended". In patients who underwent a trial (N = 290), there was 3% of trial failure when SCS was "strongly recommended" vs 46% when SCS was "not recommended".

CONCLUSIONS

Retrospective application of the e-health tool on patient data showed a strong relationship between the panel recommendations and both SCS trial results and treatment outcomes.

Cross-Country Differences in Pain Medication Before and After Spinal Cord Stimulation: A Pooled Analysis of Individual Patient Data From Two Prospective Studies in the United Kingdom and Belgium

OBJECTIVES

Spinal cord stimulation (SCS) can reduce the need for opioids; however, the influence on the full spectrum of pain medication is less known. The aims of this study were to explore general prescription practices for patients scheduled for SCS, potential differences in prescriptions between Belgium and United Kingdom, and the influence of SCS on pain medication.

MATERIALS AND METHODS

Individual patient data from the TRIAL-STIM study in the United Kingdom and DISCOVER in Belgium were pooled. Medication use was collected before SCS and three months after SCS from 180 chronic pain patients. The Medication Quantification Scale III (MQS) was used to calculate a total score for medication use, as well as subscores for several classes. Differences in prescription practices between United Kingdom and Belgium were evaluated with two-sided Wilcoxon tests. To evaluate differences in medication use after three months of SCS between United Kingdom and Belgium, Tweedie-generalized linear models were calculated.

RESULTS

There was a statistically significant difference (-6.40 [95% CI from -3.40 to -9.10]) between the median total MQS score in United Kingdom and Belgium before SCS. Additionally, a significant difference was found for nonsteroidal anti-inflammatory drugs (NSAIDs) (-3.40 [95% CI -3.40 to -6.80]), neuropathic agents (-2.30 [95% CI -0.40 to -3.80]), and benzodiazepines (1.83e-05 [95% CI 2.64-05 to 7.45-05]) between United Kingdom and Belgium, before SCS. Tweedie-generalized models revealed a statistically significant interaction between country and time for MQS, neuropathic agents, and opioids.

CONCLUSIONS

Our combined analysis revealed differences in prescription practice in patients scheduled for SCS implantation between Belgium and United Kingdom. NSAIDs and neuropathic mood agents are more frequently used in the United Kingdom, presumably due to easier access to repeat prescriptions and over the counter medications. After three months of SCS, a decrease in medication use is observed in both countries, with higher reductions in Belgium, presumably due to strict regulations concerning reimbursement criteria.

Short- and long-term effects of conventional spinal cord stimulation on chronic pain and health perceptions: A longitudinal controlled trial

BACKGROUND

The effectiveness and long-term outcomes of spinal cord stimulation (SCS) are not fully established, especially considering that data from patients who withdrew from the trial are rarely analysed, which may lead to overestimation of SCS efficacy. We evaluated short- and long-term effects of SCS on chronic pain and perceived health, beyond natural variability in these outcomes.

METHODS

In a prospective design, 176 chronic pain patients referred to SCS were evaluated five times (baseline; retest ~6 weeks later; post-SCS trial; 8 and 28 weeks post-permanent implantation). Patients whose SCS trial failed (Temp group) were followed up and compared to those who underwent permanent SCS (Perm group).

RESULTS

Analyses revealed a non-linear (U-shaped) trend significantly different between the two groups. In the Perm group, a significant improvement occurred post-SCS implantation in pain severity, pain interference, health-related quality of life and self-rated health, which was followed by gradual worsening and return to baseline values at end of follow-up. In the Temp group, only minor changes occurred in these outcomes over time. On average, baseline and end of follow-up values in the Perm and Temp groups were similar: ~40% in each group exhibited an increase in pain severity over time and 38% and 33%, respectively, exhibited reductions in pain severity over time.

CONCLUSIONS

Since the greatest improvement in the outcome measures occurred from baseline to post-SCS trial (T1-T3) followed by a gradual decline in the effect, it appears that SCS may not be effective for the majority of chronic pain patients.

SIGNIFICANCE

This longitudinal study evaluated short and long term effects of spinal cord stimulation (SCS) on chronic pain outcome measures, beyond their natural variation in time. Despite significant short term improvements, by the end of the seven months' follow-up, the outcomes in the treatment group (people who received the permanent implantation) were similar to those of the control group (people whose SCS trial failed and did not continue to permanent implantation) suggesting SCS may not be cost-effective for chronic pain patients.

Combining Awake Anesthesia with Minimal Invasive Surgery Optimizes Intraoperative Surgical Spinal Cord Stimulation Lead Placement

Spinal cord stimulation (SCS) is an effective and validated treatment to address chronic refractory neuropathic pain in persistent spinal pain syndrome-type 2 (PSPS-T2) patients. Surgical SCS lead placement is traditionally performed under general anesthesia due to its invasiveness. In parallel, recent works have suggested that awake anesthesia (AA), consisting of target controlled intra-venous anesthesia (TCIVA), could be an interesting tool to optimize lead anatomical placement using patient intra-operative feedback. We hypothesized that combining AA with minimal invasive surgery (MIS) could improve SCS outcomes. The goal of this study was to evaluate SCS lead performance (defined by the area of pain adequately covered by paraesthesia generated via SCS), using an intraoperative objective quantitative mapping tool, and secondarily, to assess pain relief, functional improvement and change in quality of life with a composite score. We analyzed data from a prospective multicenter study (ESTIMET) to compare the outcomes of 115 patients implanted with MIS under AA (MISAA group) or general anesthesia (MISGA group), or by laminectomy under general anesthesia (LGA group). All in all, awake surgery appears to show significantly better performance than general anesthesia in terms of patient pain coverage (65% vs. 34-62%), pain surface (50-76% vs. 50-61%) and pain intensity (65% vs. 35-40%), as well as improved secondary outcomes (quality of life, functional disability and depression). One step further, our results suggest that MISAA combined with intra-operative hypnosis could potentialize patient intraoperative cooperation and could be proposed as a personalized package offered to PSPS-T2 patients eligible for SCS implantation in highly dedicated neuromodulation centers.

Screening trials of spinal cord stimulation for neuropathic pain in England-A budget impact analysis

Screening trials of spinal cord stimulation (SCS) prior to full implantation of a device are recommended by expert guidelines and international regulators. The current study sought to estimate the budget impact of a screening trial of SCS and the costs or savings of discontinuing the use of a screening trial. A budget impact analysis was performed considering a study population that reflects the size and characteristics of a patient population with neuropathic pain in England eligible for SCS. The perspective adopted was that of the NHS with a 5-year time horizon. The base case analysis indicate that a no screening trial strategy would result in cost-savings to the NHS England of £400,000-£500,000 per year. Sensitivity analyses were conducted to evaluate different scenarios. If ≥5% of the eligible neuropathic pain population received a SCS device, cost-savings would be >£2.5 million/year. In contrast, at the lowest assumed cost of a screening trial (£1,950/patient), a screening trial prior to SCS implantation would be cost-saving. The proportion of patients having an unsuccessful screening trial would have to be ≥14.4% for current practice of a screening trial to be cost-saving. The findings from this budget impact analysis support the results of a recent UK multicenter randomized controlled trial (TRIAL-STIM) of a policy for the discontinuation of compulsory SCS screening trials, namely that such a policy would result in considerable cost-savings to healthcare systems.