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.

Differences in corneal nerve fiber density and fiber length in patients with painful chronic idiopathic axonal polyneuropathy and diabetic polyneuropathy.

INTRODUCTION/AIMS: Corneal confocal microscopy (CCM) detects small nerve fiber loss and correlates with skin biopsy findings in diabetic neuropathy. In chronic idiopathic axonal polyneuropathy (CIAP) this correlation is unknown. Therefore, we compared CCM and skin biopsy in patients with CIAP to healthy controls, patients with painful diabetic neuropathy (PDN) and diabetics without overt neuropathy (DM). METHODS: Participants with CIAP and suspected small fiber neuropathy (n = 15), PDN (n = 16), DM (n = 15), and healthy controls (n = 16) underwent skin biopsy and CCM testing. Inter-center intraclass correlation coefficients (ICC) were calculated for CCM parameters. RESULTS: Compared with healthy controls, patients with CIAP and PDN had significantly fewer nerve fibers in the skin (IENFD: 5.7 ± 2.3, 3.0 ± 1.8, 3.9 ± 1.5 fibers/mm, all p < .05). Corneal nerve parameters in CIAP (fiber density 23.8 ± 4.9 no./mm2, branch density 16.0 ± 8.8 no./mm2, fiber length 13.1 ± 2.6 mm/mm2) were not different from healthy controls (24.0 ± 6.8 no./mm2, 22.1 ± 9.7 no./mm2, 13.5 ± 3.5 mm/mm2, all p > .05). In patients with PDN, corneal nerve fiber density (17.8 ± 5.7 no./mm2) and fiber length (10.5 ± 2.7 mm/mm2) were reduced compared with healthy controls (p < .05). CCM results did not correlate with IENFD in CIAP patients. Inter-center ICC was 0.77 for fiber density and 0.87 for fiber length. DISCUSSION: In contrast to patients with PDN, corneal nerve parameters were not decreased in patients with CIAP and small nerve fiber damage. Therefore, CCM is not a good biomarker for small nerve fiber loss in CIAP patients.

The Effect of Various Spinal Neurostimulation Paradigms on the Supraspinal Somatosensory Evoked Response: A Systematic Review.

INTRODUCTION: Spinal neurostimulation is a therapy for otherwise intractable chronic pain. Spinal neurostimulation includes stimulation of the spinal cord (SCS), dorsal root ganglion (DRGS), and dorsal root entry zone (DREZS). New paresthesia-free neurostimulation paradigms may rely on different mechanisms of action from those of conventional tonic neurostimulation. The aim of this systematic review is to assess the existing knowledge on the effect of spinal neurostimulation on somatosensory processing in patients with chronic pain. We therefore reviewed the existing literature on the effect of various spinal neurostimulation paradigms on the supraspinal somatosensory evoked response (SER). MATERIALS AND METHODS: Multiple scientific data bases were searched for studies that assessed the effect of spinal neurostimulation on the supraspinal SER, evoked by painful or nonpainful peripheral stimuli in patients with chronic pain. We found 205 studies, of which 24 were included. Demographic data, study design, and study outcome were extracted. RESULTS: Of the 24 included studies, 23 used electroencephalography to assess the SER; one study used magnetoencephalography. Fifteen studies evaluated tonic SCS; six studies (also) evaluated paresthesia-free paradigms; three studies evaluated the effect of tonic DRGS or DREZS. Sixteen studies used nonpainful stimuli to elicit the SER, 14 observed a decreased SER amplitude. Ten studies used painful stimuli to elicit the SER, yielding mixed results. DISCUSSION: The included studies suggest that both paresthesia-based and paresthesia-free spinal neurostimulation paradigms can decrease (part of) the SER elicited by a nonpainful peripheral stimulus. The observed SER amplitude reduction likely is the effect of various spinal and supraspinal mechanisms of spinal neurostimulation that also contribute to pain relief. CONCLUSIONS: Spinal neurostimulation modulates the processing of a peripherally applied nonpainful stimulus. For painful stimuli, the results are not conclusive. It is not yet clear whether paresthesia-free neurostimulation affects the SER differently from paresthesia-based neurostimulation.

Quantitative Sensory Testing in Spinal Cord Stimulation: A Narrative Review.

OBJECTIVES: Quantitative sensory testing (QST) has been used for decades to study sensory abnormalities in multiple conditions in which the somatosensory system is compromised, including pain. It is commonly used in pharmacologic studies on chronic pain but less so in conjunction with neuromodulation. This review aims to assess the utility of QST in spinal cord stimulation (SCS) protocols. MATERIALS AND METHODS: For this narrative review, we searched PubMed for records of studies in which sensory testing has been performed as part of a clinical study on SCS from 1975 onward until October 2023. We focused on studies in which QST has been used to explore the effect of SCS on neuropathic, neuropathic-like, or mixed pain. RESULTS: Our search identified 22 useful studies, all small and exploratory, using heterogeneous methods. Four studies used the full battery of validated German Research Network on Neuropathic Pain QST. There is emerging evidence that assessment dynamic mechanical allodynia (eight studies), and mechanical/thermal temporal summation of pain (eight studies) may have a role in quantifying the response to various SCS waveforms. There also were sporadic reports of improvement of sensory deficits in a proportion of patients with neuropathic pain that warrant further study. CONCLUSIONS: We recommend the adoption of QST into future clinical research protocols, using either the full QST protocol or a less time-demanding short-form QST.

Evaluating Community-Based Intrathecal Baclofen Therapy: Effectiveness, Safety, and Feasibility.

Background: Intrathecal baclofen (ITB) is used for the treatment of intractable spasticity. The burden of traveling for ITB screening and aftercare is problematic for nursing home residents with severe spasticity and seems to result in undertreatment of spasticity. The aim of this study is to evaluate the effectiveness, safety, and feasibility of ITB for nursing home residents treated in their home, describing the selection phase, the initial trial of ITB, and aftercare up to 3 months after implantation of an ITB pump. Methods: This retrospective database study included immobile, adult nursing home residents with severe spasticity, referred to an Ambulatory Care Clinic between 2016 and 2021. When eligible, an ITB trial was performed by ITB experts in the nursing home. If a permanent pump was implanted, dose titration and aftercare were performed on location. Results: A total of 102 patients were referred; 80 underwent an ITB trial on location, and 94% improved significantly on the Modified Ashworth Scale and clonus scale pre-ITB trial versus post-ITB trial, as well as at 3 months post-implantation. There was a low incidence of adverse events, mostly procedure- and drug-related. Conclusions: This study indicates that selection, testing, and aftercare for ITB on location is effective and safe.

Radiofrequency for chronic lumbosacral and cervical pain: Results of a consensus study using the RAND/UCLA appropriateness method.

BACKGROUND: Despite the routine use of radiofrequency (RF) for the treatment of chronic pain in the lumbosacral and cervical region, there remains uncertainty on the most appropriate patient selection criteria. This study aimed to develop appropriateness criteria for RF in relation to relevant patient characteristics, considering RF ablation (RFA) for the treatment of chronic axial pain and pulsed RF (PRF) for the treatment of chronic radicular pain. METHODS: The RAND/UCLA Appropriateness Method (RUAM) was used to explore the opinions of a multidisciplinary European panel on the appropriateness of RFA and PRF for a variety of clinical scenarios. Depending on the type of pain (axial or radicular), the expert panel rated the appropriateness of RFA and PRF for a total of 219 clinical scenarios. RESULTS: For axial pain in the lumbosacral or cervical region, appropriateness of RFA was determined by the dominant pain trigger and location of tenderness on palpation with higher appropriateness scores if these variables were suggestive of the diagnosis of facet or sacroiliac joint pain. Although the opinions on the appropriateness of PRF for lumbosacral and cervical radicular pain were fairly dispersed, there was agreement that PRF is an appropriate option for well-selected patients with radicular pain due to herniated disc or foraminal stenosis, particularly in the absence of motor deficits. The panel outcomes were embedded in an educational e-health tool that also covers the psychosocial aspects of chronic pain, providing integrated recommendations on the appropriate use of (P)RF interventions for the treatment of chronic axial and radicular pain in the lumbosacral and cervical region. CONCLUSIONS: A multidisciplinary European expert panel established patient-specific recommendations that may support the (pre)selection of patients with chronic axial and radicular pain in the lumbosacral and cervical region for either RFA or PRF (accessible via https://rftool.org). Future studies should validate these recommendations by determining their predictive value for the outcomes of (P)RF interventions.

Five-Year Longitudinal Follow-Up of Restorative Neurostimulation Shows Durability of Effectiveness in Patients With Refractory Chronic Low Back Pain Associated With Multifidus Muscle Dysfunction.

BACKGROUND: Adults with refractory, mechanical chronic low back pain associated with impaired neuromuscular control of the lumbar multifidus muscle have few treatment options that provide long-term clinical benefit. This study hypothesized that restorative neurostimulation, a rehabilitative treatment that activates the lumbar multifidus muscles to overcome underlying dysfunction, is safe and provides relevant and durable clinical benefit to patients with this specific etiology. MATERIALS AND METHODS: In this prospective five-year longitudinal follow-up of the ReActiv8-B pivotal trial, participants (N = 204) had activity-limiting, moderate-to-severe, refractory, mechanical chronic low back pain, a positive prone instability test result indicating impaired multifidus muscle control, and no indications for spine surgery. Low back pain intensity (10-cm visual analog scale [VAS]), disability (Oswestry Disability Index), and quality of life (EuroQol's "EQ-5D-5L" index) were compared with baseline and following the intent-to-treat principle, with a supporting mixed-effects model for repeated measures that accounted for missing data. RESULTS: At five years (n = 126), low back pain VAS had improved from 7.3 to 2.4 cm (-4.9; 95% CI, -5.3 to -4.5 cm; p < 0.0001), and 71.8% of participants had a reduction of ≥50%. The Oswestry Disability Index improved from 39.1 to 16.5 (-22.7; 95% CI, -25.4 to -20.8; p < 0.0001), and 61.1% of participants had reduction of ≥20 points. The EQ-5D-5L index improved from 0.585 to 0.807 (0.231; 95% CI, 0.195-0.267; p < 0.0001). Although the mixed-effects model attenuated completed-case results, conclusions and statistical significance were maintained. Of 52 subjects who were on opioids at baseline and had a five-year visit, 46% discontinued, and 23% decreased intake. The safety profile compared favorably with neurostimulator treatments for other types of back pain. No lead migrations were observed. CONCLUSION: Over a five-year period, restorative neurostimulation provided clinically substantial and durable benefits with a favorable safety profile in patients with refractory chronic low back pain associated with multifidus muscle dysfunction. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT02577354; registration date: October 15, 2016; principal investigator: Christopher Gilligan, MD, Brigham and Women's Hospital, Boston, MA, USA. The study was conducted in Australia (Broadmeadow, New South Wales; Noosa Heads, Queensland; Welland, South Australia; Clayton, Victoria), Belgium (Sint-Niklaas; Wilrijk), The Netherlands (Rotterdam), UK (Leeds, London, Middlesbrough), and USA (La Jolla, CA; Santa Monica, CA; Aurora, CO; Carmel, IN; Indianapolis, IN; Kansas City, KS; Boston, MA; Royal Oak, MI; Durham, NC; Winston-Salem, NC; Cleveland, OH; Providence, RI; Spartanburg, SC; Spokane, WA; Charleston, WV).

How Do We Treat Children with Anterior Cutaneous Nerve Entrapment Syndrome and Is the Biopsychosocial Model Also Being Applied? A Scoping Review.

Background: Evidence-based guidelines for managing anterior cutaneous nerve entrapment syndrome (ACNES) in children are absent. The primary aim of this review was to scrutinize the evidence supporting currently used treatment interventions. In accordance with the World Health Organization (WHO) guidelines for managing chronic pain in children, these patients and their families and caregivers should be treated within the context of the biopsychosocial model; pain should not be treated purely as a biomedical problem. Therefore, our second aim was to evaluate whether these interventions are applied within the context of the biopsychosocial model, utilizing an inter- or multidisciplinary approach. Materials and Methods: A scoping review of the literature was conducted to explore treatment strategies for ACNES in children. To ensure a comprehensive overview of published literature on this topic, the search was not restricted based on study type. Two reviewers independently assessed titles and abstracts. After excluding records unrelated to children, full texts were screened for inclusion. Any discrepancies in judgement were resolved through discussion with a third reviewer. Results: Out of 35 relevant titles, 22 were included in this review. Only 4 articles provided information on long-term outcomes. The overall quality of the review was deemed low. The majority of reports did not address treatment or education within the psychological and social domains. A structural qualitative analysis was not feasible due to the substantial heterogeneity of the data. Conclusion: The evidence supporting current treatment strategies in children with ACNES is of low quality. More research is needed to establish an evidence-based treatment algorithm for patients with this challenging pain problem. In line with the WHO recommendation, greater emphasis should be placed on a biopsychosocial approach. The ultimate goal should be the development of a generic treatment algorithm outlining an approach to ACNES applicable to all professionals involved.

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.

4. Painful diabetic polyneuropathy.

INTRODUCTION: Pain as a symptom of diabetic polyneuropathy (DPN) significantly lowers quality of life, increases mortality and is the main reason for patients with diabetes to seek medical attention. The number of people suffering from painful diabetic polyneuropathy (PDPN) has increased significantly over the past decades. METHODS: The literature on the diagnosis and treatment of diabetic polyneuropathy was retrieved and summarized. RESULTS: The etiology of PDPN is complex, with primary damage to peripheral nociceptors and altered spinal and supra-spinal modulation. To achieve better patient outcomes, the mode of diagnosis and treatment of PDPN evolves toward more precise pain-phenotyping and genotyping based on patient-specific characteristics, new diagnostic tools, and prior response to pharmacological treatments. According to the Toronto Diabetic Neuropathy Expert Group, a presumptive diagnosis of "probable PDPN" is sufficient to initiate treatment. Proper control of plasma glucose levels, and prevention of risk factors are essential in the treatment of PDPN. Mechanism-based pharmacological treatment should be initiated as early as possible. If symptomatic pharmacologic treatment fails, spinal cord stimulation (SCS) should be considered. In isolated cases, where symptomatic pharmacologic treatment and SCS are unsuccessful or cannot be used, sympathetic lumbar chain neurolysis and/or radiofrequency ablation (SLCN/SLCRF), dorsal root ganglion stimulation (DRGs) or posterior tibial nerve stimulation (PTNS) may be considered. However, it is recommended that these treatments be applied only in a study setting in a center of expertise. CONCLUSIONS: The diagnosis of PDPN evolves toward pheno-and genotyping and treatment should be mechanism-based.

The efficacy of oral corticoids in treating complex regional pain syndrome: A retrospective cohort study.

OBJECTIVES: There is growing evidence supporting the role of inflammatory mechanisms in complex regional pain syndrome (CRPS). Corticoids, as most effective anti-inflammatory drugs, are widely used in treating inflammation. The aim of this study was to retrospectively assess the efficacy of oral corticoid treatment in CRPS patients. METHODS: Patients treated at the center of pain medicine in the Erasmus University Medical Centre between January 2015 and January 2020 were approached to partake in this study. Medical records were screened for age, gender, medical history, duration of CRPS, and CRPS severity score. Also, treatment effect, dose and duration, pain scores (NRS), and side effects were extracted from medical records. In addition, global perceived effect was completed in patients treated with corticoids. RESULTS: Between January 2015 and January 2020, twenty-nine CRPS patients received corticoids and met the inclusion criteria. One extreme outlier was excluded and treatment effect was unknown for one patient. Average daily dose was 28.9 mg (range 10-30 mg) and the mean treatment duration was 10.5 days (7-21 days). Fourteen patients (51.9%) responded positively to treatment and thirteen (48.1%) did not respond. Side effects were reported in five patients (17.9%). CONCLUSIONS: Corticoid treatment was effective in more than half of the patients. With only mild side effects reported the treatment also appears to be relatively safe. Further research is needed to investigate the efficacy of corticoids in treating (early) CRPS, preferably in an intervention study.

A prospective open label 2-8 year extension of the randomised controlled ICON trial on the long-term efficacy and safety of occipital nerve stimulation in medically intractable chronic cluster headache.

BACKGROUND: We demonstrated in the randomised controlled ICON study that 48-week treatment of medically intractable chronic cluster headache (MICCH) with occipital nerve stimulation (ONS) is safe and effective. In L-ICON we prospectively evaluate its long-term effectiveness and safety. METHODS: ICON participants were enrolled in L-ICON immediately after completing ICON. Therefore, earlier ICON participants could be followed longer than later ones. L-ICON inclusion was stopped after the last ICON participant was enrolled in L-ICON and followed for ≥2 years by completing six-monthly questionnaires on attack frequency, side effects, subjective improvement and whether they would recommend ONS to others. Primary outcome was the change in mean weekly attack frequency 2 years after completion of the ICON study compared to baseline. Missing values for log-transformed attack-frequency were imputed for up to 5 years of follow-up. Descriptive analyses are presented as (pooled) geometric or arithmetic means and 95% confidence intervals. FINDINGS: Of 103 eligible participants, 88 (85%) gave informed consent and 73 (83%) were followed for ≥2 year, 61 (69%) ≥ 3 year, 33 (38%) ≥ 5 years and 3 (3%) ≥ 8.5 years. Mean (±SD) follow-up was 4.2 ± 2.2 years for a total of 370 person years (84% of potentially 442 years). The pooled geometric mean (95% CI) weekly attack frequency remained considerably lower after one (4.2; 2.8-6.3), two (5.1; 3.5-7.6) and five years (4.1; 3.0-5.5) compared to baseline (16.2; 14.4-18.3). Of the 49/88 (56%) ICON ≥50% responders, 35/49 (71%) retained this response and 15/39 (38%) ICON non-responders still became a ≥50% responder for at least half the follow-up period. Most participants (69/88; 78% [0.68-0.86]) reported a subjective improvement from baseline at last follow-up and 70/88 (81% [0.70-0.87]) would recommend ONS to others. Hardware-related surgery was required in 44/88 (50%) participants in 112/122 (92%) events (0.35 person-year-1 [0.28-0.41]). We didn't find predictive factors for effectiveness. INTERPRETATION: ONS is a safe, well-tolerated and long-term effective treatment for MICCH. FUNDING: The Netherlands Organisation for Scientific Research, the Dutch Ministry of Health, the NutsOhra Foundation from the Dutch Health Insurance Companies, and Medtronic.

The effect of recorded music on pain endurance (CRESCENDo) - A randomized controlled trial.

INTRODUCTION: Clarifying the effect of music on pain endurance in an experimental design could aid in how music should be applied during both surgical and non-surgical interventions. This study aims to investigate the effect of music on pain endurance and the involvement of the sympathetic adrenomedullary axis (SAM) and the hypothalamic-pituitary-adrenocortical axis (HPA). MATERIALS AND METHODS: In this randomized controlled trial all participants received increasing electric stimuli through their non-dominant index finger. Participants were randomly assigned to the music group (M) receiving a 20-minute music intervention or control group (C) receiving a 20-minute resting period. The primary outcome was pain endurance, defined as amount milliampere tolerated. Secondary outcomes included anxiety level, SAM-axis based on heart rate variability (HRV) and salivary alpha-amylase, and HPA-axis activity based on salivary cortisol. RESULTS: In the intention-to-treat analysis, the effect of music on pain tolerance did not statistically differ between the M and C group. A significant positive effect of music on pain endurance was noted after excluding participants with a high skin impedance (p = 0.013, CI 0.35; 2.85). Increased HRV was observed in the M-group compared to the C-group for SDNN (B/95%CI:13.80/2.22;25.39, p = 0.022), RMSSD (B/95%CI:15.97/1.64;30.31, p = 0.032), VLF (B/95%CI:212.08/60.49;363.67, p = 0.008) and HF (B/95%CI:821.15/150.78;1491.52, p = 0.0190). No statistical significance was observed in other secondary outcomes. CONCLUSIONS: The effect of the music intervention on pain endurance was not statistically significant in the intention-to-treat analysis. The subgroup analyses revealed an increase in pain endurance in the music group after correcting for skin impedance, which could be attributed to increased parasympathetic activation.

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.

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).

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.

Is there an association between serum soluble interleukin-2 receptor levels and syndrome severity in persistent Complex Regional Pain Syndrome?

OBJECTIVE: A potentially useful biomarker for Complex Regional Pain Syndrome (CRPS) is the serum soluble interleukin-2 receptor (sIL-2R) level, which is a marker for T-cell activation. Elevated serum sIL-2R levels have been described in CRPS patients compared to healthy controls. In T-cell mediated inflammatory diseases such as sarcoidosis and rheumatoid arthritis, the serum sIL-2R levels correlate with disease severity. In this study, we investigate whether an association exists between serum sIL-2R levels in CRPS patients and CRPS severity. METHODS: A cross-sectional cohort study was conducted in a tertiary pain referral center in the Netherlands. Adult CRPS patients diagnosed by the IASP criteria were included between October 2018 until October 2022. The main study parameters were serum sIL-2R levels and the CRPS severity score. RESULTS: Fifty-three CRPS patients were included with a mean syndrome duration of 84 months (Q3 - Q1:180 - 48). The majority had persistent CRPS with a syndrome duration >1 year (n = 52, 98%). The median pain Numerical Rating Score (NRS) was 7 (Q3 - Q1: 8 - 5) and the mean CRPS severity score was 11 (SD ± 2.3). The median serum sIL-2R level was 330 U/mL (Q3 - Q1:451 - 256). No statistically significant correlation was observed between serum sIL-2R levels and the CRPS severity score (rs = 0.15, P = .28). CONCLUSIONS: Our findings suggest that serum sIL-2R levels cannot be used as a biomarker for syndrome severity in persistent CRPS (syndrome duration >1 year). Serial measurements of serum sIL-2R from early CRPS to persistent CRPS are needed to investigate whether serum sIL-2R levels can be used to monitor T-cell mediated inflammatory syndrome activity.

Effectiveness of Infliximab in Patients with Complex Regional Pain Syndrome: A Case Series.

Purpose: Complex regional pain syndrome (CRPS) is a multi-mechanism disease, with an exaggerated inflammatory response as an important underlying mechanism. Auto-inflammation can theoretically be combated by anti-inflammatories, such as TNF-α inhibitors. This study's aim was to assess the effectiveness of intravenous infliximab, a TNF-α inhibitor, in patients with CRPS. Patients and Methods: CRPS patients treated with infliximab between January 2015 and January 2022 were approached to participate in this retrospective study. Medical records were screened for age, gender, medical history, CRPS duration, and CRPS severity score. Additionally, treatment effect, dose and duration, and side effects were extracted from medical records. Patients who still receive infliximab completed a short global perceived effect survey. Results: Eighteen patients received infliximab, and all but two gave consent. Trial treatment with three sessions of 5 mg/kg intravenous infliximab was completed in 15 patients (93.7%). Eleven patients (73.3%) were categorized as responders with a positive treatment effect. Treatment was continued in nine patients, and seven patients are currently treated. Infliximab dose is 5 mg/kg, and frequency is every four to six weeks. Seven patients completed a global perceived effect survey. All patients reported improvement (median 2, IQR 1-2) and treatment satisfaction (median 1, IQR 1-2). One patient described side effects such as itching and rash. Conclusion: Infliximab proved effective in 11 out of 15 CRPS patients. Seven patients are still being treated. Further research is needed on the role of infliximab in the treatment of CRPS and possible predictors of response to treatment.