Percutaneous 60-day peripheral nerve stimulation implant provides sustained relief of chronic pain following amputation: 12-month follow-up of a randomized, double-blind, placebo-controlled trial

Four-Year Follow-Up from a Prospective, Multicenter Study of Percutaneous 60-Day Peripheral Nerve Stimulation for Chronic Low Back Pain

INTRODUCTION

Chronic low back pain (LBP) is a leading cause of healthcare expenditure and long-term disability associated with complex treatment challenges and the need for progressively invasive interventions. Percutaneous 60-day Peripheral Nerve Stimulation (PNS) is a minimally invasive neurostimulation treatment that has shown efficacy for chronic LBP, providing sustained improvements through 1 year of follow-up after treatment. The present work explores the long-term clinical outcomes of Percutaneous 60-day PNS for chronic LBP approximately 4 years after initial treatment.

METHODS

Follow-up surveys were sent to participants from a prior prospective study who reported clinically meaningful reductions in pain, disability, or pain interference 12 months after Percutaneous 60-day PNS for LBP. The present long-term follow-up survey assessed current levels of LBP, disability, pain interference, and Patient Global Impression of Change (PGIC). Use of medications and other interventions for LBP treatment since completing Percutaneous 60-day PNS was also surveyed.

RESULTS

In total, 23 participants returned completed long-term follow-up surveys. A majority of survey respondents (65%, n = 15/23) reported sustained, clinically meaningful (≥ 30%) relief of back pain compared with baseline an average of 4.7 years after PNS treatment was initiated. On average, these long-term responders reported clinically substantial (≥ 50%) reductions in pain (average 63% reduction), as well as clinically meaningful improvements in disability and quality of life. Furthermore, 70% (n = 16/23) of survey respondents avoided progression to more costly, invasive, and/or destructive LBP pain interventions (i.e., radiofrequency ablation, neurostimulation implant, or lumbar surgery).

CONCLUSIONS

Treatment with Percutaneous 60-day PNS provided clinically meaningful pain relief among a majority of surveyed participants an average of more than 4 years after the short-term treatment. These results demonstrate that Percutaneous 60-day PNS can provide durable outcomes that are often sustained for multiple (4+) years by patients with chronic axial LBP who subsequently avoid the need for more invasive treatment interventions.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the initial study is NCT03179202.

Application of bioelectrical impedance detection techniques: Cells and tissues

Pathological conditions in organisms often arise from various cellular or tissue abnormalities, including dysregulation of cell numbers, infections, aberrant differentiation, and tissue pathologies such as lung tumors and skin tumors. Thus, developing methods for analyzing and identifying these biological abnormalities presents a significant challenge. While traditional bioanalytical methods such as flow cytometry and magnetic resonance imaging are well-established, they suffer from inefficiencies, high costs, complexity, and potential hazards. To address these challenges, bioelectrical impedance detection technology, which leverages the electrical properties of biological cells and tissues to extract relevant biomedical information, has garnered considerable attention in the field of biological detection due to its affordability, convenience, non-invasiveness, and label-free nature. This article first provides a brief introduction to the principles of bioelectrical impedance and related detection techniques, as well as the equivalent circuit models and numerical simulation models developed at the cellular and tissue levels. Next, this article delves into the applications of bioelectrical impedance technology at the cellular level, including recent advancements in cell counting, classification, concentration detection, differentiation, and infection, thereby enriching previous literature reviews from a multicellular perspective. In addition, this article highlights the applications of bioelectrical impedance technology in relevant tissues including muscle, skin, lungs, and so on. Finally, the article explores the future opportunities and challenges of bioelectrical impedance detection and analysis technology, focusing on interdisciplinary research areas and data-driven intelligent analysis, offering researchers broader research directions and perspectives.

Beyond traditional therapies: a network meta-analysis on the treatment efficacy for chronic phantom limb pain

BACKGROUND

Phantom limb pain (PLP) frequently affects individuals with limb amputations. When PLP evolves into its chronic phase, known as chronic PLP, traditional therapies often fall short in providing sufficient relief. The optimal intervention for chronic PLP remains unclear.

OBJECTIVE

The objectives of this network meta-analysis (NMA) were to examine the efficacy of different treatments on pain intensity for patients with chronic PLP.

EVIDENCE REVIEW

We searched Medline, EMBASE, Cochrane CENTRAL, Scopus, and CINAHL EBSCO, focusing on randomized controlled trials (RCTs) that evaluated interventions such as neuromodulation, neural block, pharmacological methods, and alternative treatments. An NMA was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The primary outcome was pain score improvement, and the secondary outcomes were adverse events.

FINDINGS

The NMA, incorporating 12 RCTs, indicated that neuromodulation, specifically repetitive transcranial magnetic stimulation, provided the most substantial pain improvement when compared with placebo/sham groups (mean difference=-2.9 points, 95% CI=-4.62 to -1.18; quality of evidence (QoE): moderate). Pharmacological intervention using morphine was associated with a significant increase in adverse event rate (OR=6.04, 95% CI=2.26 to 16.12; QoE: low).

CONCLUSIONS

The NMA suggests that neuromodulation using repetitive transcranial magnetic stimulation may be associated with significantly larger pain improvement for chronic PLP. However, the paucity of studies, varying patient characteristics across each trial, and absence of long-term results underscore the necessity for more comprehensive, large-scale RCTs.

PROSPERO REGISTRATION NUMBER

CRD42023455949.

A novel single-lead percutaneous approach for multi-nerve peripheral stimulation in upper extremity pain: A case report

Peripheral nerve stimulation (PNS) is an emerging modality for managing painful peripheral neuropathy, offering potential long-term relief when conservative treatments fall short. Conventionally, each PNS lead targets a single nerve, necessitating multiple leads in cases involving pain across multiple nerve distributions. This case report presents a novel approach using a single PNS lead to target multiple peripheral nerves in the upper extremity via an axillary brachial plexus approach. We describe a 47-year-old female with a three-year history of intractable neuropathic pain localized to the ulnar and median nerve distributions, who underwent a temporary PNS trial after failing conventional therapies, including physical therapy, medications, and corticosteroid injections. Under ultrasound guidance, a single PNS lead was placed at the brachial plexus, targeting both ulnar and median nerves. Optimal stimulation thresholds were achieved, and the patient reported 80-100% pain relief throughout the 60-day trial period, with sustained relief for six months post-lead removal. This approach leverages the anatomical proximity of the ulnar, median, and radial nerves at the axilla, enabling multi-nerve targeting with a single lead. The technique offers potential advantages, including reduced procedural complexity, fewer risks, and cost savings, especially in the current landscape of increasing insurance denials for neuromodulation procedures.

[Systematic review of the effectiveness of local anaesthetics in the treatment of neuropathic pain or phantom pain]

BACKGROUND

Chronic pain is still a relevant medical and socioeconomic problem. The treatment focuses not only on pain reduction but also on functional treatment goals. Neuropathic pain includes biological, social and psychological aspects. In September 2023, the updated S3 guidelines for the management of peripheral nerve injuries were published. Multimodal pain management strategies encompassing systemic and local pharmacological, physiotherapeutic and occupational therapeutic interventions, are part of the guidelines. A central question addressed the widely debated treatment option using perineural local anaesthetics.

OBJECTIVE

The aim of the study was to evaluate the effectiveness of local anaesthetic infiltration in the treatment of neuropathic pain following nerve injuries through a systematic literature review and evaluation of the evidence by a meta-analysis.

MATERIAL AND METHODS

After formulating a PICO (patient/population, intervention, comparison and outcomes) question (Infobox 1) within the guideline group, a selective literature analysis of controlled trials in databases (PubMed, Cochrane Central Register of Controlled Trials-CENTRAL) was conducted until 31 July 2023. The literature was assessed by two reviewers and systematic reviews were examined for additional references. The studies were assessed using the Risk of Bias Tool 2.0 of the Cochrane Collaboration for randomized trials and the evidence was classified according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system.

RESULTS

A total of 357 publications were identified in the literature search. After removing duplicates (n = 15) 327 publications were evaluated. The literature analysis showed heterogeneity with respect to the pain localization, local anaesthetics and reported outcomes. In an in-depth literature analysis one relevant study was identified and included in the evaluation of the evidence. This study enrolled and randomized 144 patients between December 2013 and October 2018 and evaluated the effectivity of the continuous infusion of local anaesthetics (lidocaine 2% with epinephrine 2.5 µg/ml as an initial bolus in both study groups followed by an infusion of ropivacaine 0.5% in the intervention group over 6 days) on the intensity of the phantom pain in comparison to the placebo group with a continuous infusion of saline over 6 days. The mean pain intensity and pain-related dysfunctions were reduced in the intervention group after 4 weeks. In the intervention group 25 patients and in the placebo group 40 patients received the crossover treatment after 4 weeks.

CONCLUSION

Infiltration with local anaesthetics represents a potential therapeutic option for neuropathic pain and phantom pain after amputations. A randomized, blinded, placebo-controlled study from 2021 demonstrated lower pain intensity and a reduction in pain-related functional limitations after 4 weeks of continuous perineural local anesthetic infiltration. Further studies are necessary to establish a higher level of evidence regarding the effectiveness of minimally invasive pain treatment with local anaesthetics. In particular, long-term follow-up is necessary to be able to draw conclusions with respect to the analgesic efficacy of infiltration with local anaesthetics.

Cost Savings in Chronic Pain Patients Initiating Peripheral Nerve Stimulation (PNS) with a 60-Day PNS Treatment

INTRODUCTION

This study evaluates the financial impact on healthcare payers when chronic pain patients initiate peripheral nerve stimulation (PNS) with a 60-day percutaneous PNS (60-Day PNS) treatment versus a conventional brief PNS trial (PNS-BT) with possible follow-on of a permanently implanted PNS system (PNS-PI).

METHODS

Centers for Medicare & Medicaid Services (CMS) fee-for-service (FFS) data were analyzed to identify patients with at least 12 months of follow-up (median 26.4 months) who initiated PNS treatment with: (1) 60-Day PNS or (2) PNS-BT. An economic decision tree model assessed the cost to payers in each cohort. Clinical response to 60-Day PNS was estimated by retrospectively reviewing anonymized outcomes from a national real-world database, focusing on patients ≥ 65 years of age who were implanted with a 60-day percutaneous PNS system. For the economic model, a Monte Carlo simulation with 10,000 iterations was used to generate 95% confidence intervals, considering variability in treatment outcome probability and costs.

RESULTS

Based on CMS data, among 60-Day PNS patients, 18% (229/1265) proceeded to a permanently implanted PNS system with a 4% explant rate (10/229). Among PNS-BT patients, 41% (1140/2811) received a permanent implant with a 7% rate of explant (77/1140). Estimated PNS-related weighted average costs for the 60-Day PNS cohort [US$17,344; 95% confidence interval (CI): $16,168-$18,527] were lower than the PNS-BT cohort ($24,392; 95% CI $22,865-$25,941) when considering the percent of patients who advanced to a permanently implanted PNS system. The total cost per successful outcome also favored 60-Day PNS ($25,228 per success for the 60-Day PNS cohort vs. $64,502 per success for the PNS-BT cohort) as a first-line approach in PNS treatment.

CONCLUSIONS

The findings suggest that, when PNS for chronic pain is warranted, initiating PNS with a 60-day treatment is more cost-effective than utilizing a brief conventional trial.

Peripheral Nerve Stimulation and Improved Functional Outcomes in a Prosthetic User: A Case Report

Peripheral nerve stimulation (PNS) is an emerging option for postamputation pain. However, its impact on prosthesis use and comfort remains underexplored. This case report describes a patient whose chronic postamputation pain limited mobility, function, and prosthesis use. After failing conservative therapies, successful treatment was achieved with sciatic PNS which improved pain, prosthesis comfort, and functional outcomes as measured by the Orthotic and Prosthetic Users Survey Lower Extremity Functional Status Measure and Prosthetic Limb Users Survey of Mobility. Although surgical techniques, such as targeted muscle reinnervation, also enhance prosthetic function, PNS offers unique advantages.

Pain Management in Staged Osseointegration Procedures: A Retrospective Study and Foundation for Future Optimization

INTRODUCTION

Osseointegration is an innovative procedure to attach an external prosthetic device directly to the skeleton. The technique has been shown to improve physical function and quality of life relative to conventional socket prosthetic devices. While much of the research in osseointegration has focused on functional outcomes, less is known regarding perioperative pain management. The purpose of this study was to describe perioperative and postoperative pain management approaches received by patients undergoing osseointegration procedures at a tertiary medical center.

MATERIALS AND METHODS

This retrospective study was determined to be exempt from Institutional Review Board review by the Walter Reed National Military Medical Center Department of Research Programs. Perioperative and postoperative pain management approaches received by 41 patients who underwent 76 staged osseointegration procedures from 2016 to 2021 at Walter Reed National Military Medical Center were described.

RESULTS

Pain management approaches included perioperative ketamine (51% stage I, 55% stage II), epidurals (76% stage I, 77% stage II) with a median of 3-4 days across stages, peripheral nerve catheters (27% stage I, 16% stage II), and/or single-shot peripheral nerve block (<10% across stages). The median morphine equivalent dose provided during surgery was 65 mg across both stages, with 56% and 54% of patients also requiring opioid medication in the post-anesthesia care unit. In 11 of 76 (15%) procedures, patients required an increase in the rate or concentration of epidural or peripheral nerve catheter infusion. In six (8%) unique recovery periods, patients experienced a dislodged catheter. In 27 of 76 (36%) unique recovery periods, patients experienced a significant increase in postoperative pain requiring acute pain service intervention in the form of catheter adjustment, intravenous pain medications, and/or the addition of intravenous patient-controlled analgesia. Adequate pain control was achieved with minimal epidural or peripheral nerve catheter trouble-shooting and a bolus for 24 patients (89% requiring intervention). Summed 24-hour pain scores (SPI24) did not vary across stages. SPI24 was positively correlated with opioid doses received. Patients with single, relative to multiple, limb amputations had similar SPI24 values (P > .05).

CONCLUSIONS

Variability in pain management requirements calls forth opportunities to optimize osseointegration analgesia care and future research. As osseointegration becomes more accessible, the need for optimizing pain management through patient-centered research becomes more salient.

Peripheral Nerve Stimulation for Neuropathic Pain Management: A Narrative Review

This narrative review examines the therapeutic efficacy of peripheral nerve stimulation (PNS) in the treatment of neuropathic pain (NP), a type of pain arising from lesions or diseases of the somatosensory system with a global prevalence ranging from 6.90% to 10.00%. Traditional pharmacological interventions often fall short for many persons, highlighting the need for alternative treatments such as PNS, which has demonstrated significant promise with minimal side effects. The review summarizes the effectiveness of PNS in various NP conditions, including trigeminal neuralgia and postherpetic neuralgia, and underscores the need for further research to refine treatment approaches. The mechanism of PNS is discussed, involving the activation of non-nociceptive Aβ fibers and modulation of neurotransmitters, and offering pain relief through both peripheral and central pathways. Despite the proven efficacy of PNS, challenges remain, including the need for randomized controlled trials and the optimization of stimulation parameters. The review concludes that PNS is a promising treatment modality for NP, warranting additional high-quality trials to solidify its role in clinical practice.

Neuromodulation for neuropathic pain

The treatment of neuropathic pain (NeP) often leads to partial or incomplete pain relief, with up to 40 % of patients being pharmaco-resistant. In this chapter the efficacy of neuromodulation techniques in treating NeP is reviewed. It presents a detailed evaluation of the mechanisms of action and evidence supporting the clinical use of the most common approaches like transcutaneous electrical nerve stimulation (TENS), transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), deep brain stimulation (DBS), invasive motor cortex stimulation (iMCS), spinal cord stimulation (SCS), dorsal root ganglion stimulation (DRG-S), and peripheral nerve stimulation (PNS). Current literature suggests that motor cortex rTMS is effective for peripheral and central NeP, and TENS for peripheral NeP. Evidence for tDCS is inconclusive. DBS is reserved for research settings due to heterogeneous results, while iMSC has shown efficacy in a small randomized trial in neuropathic pain due to stroke and brachial plexus avulsion. SCS has moderate evidence for painful diabetic neuropathy and failed back surgery syndrome, but trials were not controlled with sham. DRG-S and PNS have shown positive results for complex regional pain syndrome and post-surgical neuropathic pain, respectively. Adverse effects vary, with non-invasive techniques showing local discomfort, dizziness and headache, and DBS and SCS hardware-related issues. To date, non-invasive techniques have been more extensively studied and some are included in international guidelines, while the evidence level for invasive techniques are less robust, potentially suggesting their use in a case-by-case indication considering patient´s preferences, costs and expected benefits.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Retrospective Evaluation of Bipolar Peripheral Nerve Stimulation for Nociceptive and Neuropathic Pain: A Pilot Study

Purpose

This retrospective review evaluates pain and patient-defined functional goal improvement utilizing bipolar peripheral nerve stimulation (PNS) in chronic neuropathic and nociceptive pain states.

Patients and Methods

Our dataset includes 24 patients who underwent implantation of a permanent peripheral nerve stimulator from January 2018 through December 2022. A total of 29 leads were implanted amongst 24 patients, with 5 patients having leads at 2 different dermatomes. Fifteen leads were placed for primarily neuropathic pain, and 14 leads were placed for nociceptive pain. Inclusion criteria were the following: pain duration greater than 6 months, documented peri-procedural Numerical Pain Rating Scale (NPRS) and greater than 60 days follow-up post implant.

Results

Data was collected and analyzed showing that 89.6% of implants at 6 months follow-up and 70% at 12 months follow-up achieved 50% or greater pain relief. A significant reduction in NPRS scores when comparing pre-procedure pain scores (Median = 7, n = 29) to 6-month follow-up data (Median = 2, n = 29), p<0.001 with a large effect size, r = 0.61. Ninety-three percent of patients reported achieving their personal functional goal. Twelve of the fourteen (86%) leads implanted for primary nociceptive pain and fourteen of the fifteen (93%) leads implanted for neuropathic pain achieved ≥50% relief at 6 months. At twelve months, seven leads in each group provided ≥50% sustained pain relief. Of the 14 patients that were on opioids, 6 discontinued, while another 2 had a reduction in oral morphine milligram equivalents (MME) at the 12-month follow-up.

Conclusion

This retrospective review demonstrates the potential clinical application of PNS in both nociceptive and neuropathic pain states. Further prospective studies are warranted to validate the effectiveness of PNS in the treatment of refractory nociceptive and neuropathic pain states.

Pain intensity and opioid consumption after temporary and permanent peripheral nerve stimulation: a 2-year multicenter analysis

OBJECTIVE

Peripheral nerve stimulation (PNS) is an emerging neuromodulation modality, yet there remains limited data highlighting its long-term effectiveness. The objective of this study was to report real-world data on pain intensity and opioid consumption after temporary and permanent PNS for chronic pain up to 24 months postimplantation.

METHODS

A retrospective study was conducted on all patients who received PNS implants at a multi-centered enterprise between January 1, 2014 and February 24, 2022. The two co-primary outcomes were: (1) change in pain intensity (11-point Numerical Rating Scale) from baseline to 12 months postimplant; and (2) comparison of the change in pain intensity between temporary and permanent PNS cohorts 12 months postimplant.

RESULTS

126 patients were included in this analysis. Pain intensity significantly decreased 12 months postimplant in the overall cohort (mean difference (MD) -3.0 (95% CI -3.5 to -2.4), p<0.0001). No significant difference in this reduction was identified between temporary and permanent PNS cohorts (MD 0.0 (95% CI -1.1 to 1.0), p=1.00) 12 months postimplantation. Pain intensity significantly decreased in the overall, temporary, and permanent cohorts at all secondary time points (3, 6, and 24 months). No change in daily opioid consumption was observed at 6 and 12 months postimplant in the overall cohort.

CONCLUSION

This study found that both temporary and permanent PNS may be effective for reducing pain intensity in patients with chronic pain up to 24 months postimplantation, although no changes in opioid consumption were observed. The decrease in pain intensity was comparable between patients receiving temporary versus permanent implants, highlighting that temporary PNS may achieve long-lasting clinical benefits. However, given the substantial loss to follow-up, further large-scale studies are needed to solidify conclusions about the efficacy of PNS.

Peripheral Nerve Stimulation in Postoperative Analgesia: A Narrative Review

PURPOSE OF REVIEW

Recent research has shown the effectiveness of peripheral nerve stimulators (PNS) in managing chronic pain conditions. Ongoing studies aim to explore its potential application in treating acute postoperative pain states. The purpose of this systematic review is to assess the role of PNS in providing relief for postoperative pain.

RECENT FINDINGS

Clinical studies investigating the use of peripheral nerve stimulators (PNS) for analgesia following various surgeries, such as total knee arthroplasty, anterior cruciate ligament repair, ankle arthroplasty, rotator cuff repair, hallux valgus correction, and extremity amputation, have shown promising results. Lead placement locations include the brachial plexus, sciatic, femoral, tibial, genicular, perineal, sural, radial, median, and ulnar nerves. These studies consistently report clinically significant reductions in pain scores, and some even indicate a decrease in opioid consumption following PNS for postoperative pain. PNS involves the subcutaneous placement of electrode leads to target peripheral nerve(s) followed by delivery of an electric current via an external pulse generator. While the precise mechanism is not fully understood, the theory posits that PNS modulates electrical stimulation, hindering the signaling of nociceptive pain. PNS presents itself as an alternative to opioid therapy, holding promise to address the opioid epidemic by offering a nonpharmacologic approach for both acute and chronic pain states.

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.

Primary 3-Month Outcomes of a Double-Blind Randomized Prospective Study (The QUEST Study) Assessing Effectiveness and Safety of Novel High-Frequency Electric Nerve Block System for Treatment of Post-Amputation Pain

Purpose

This multicenter, randomized, double-blinded, active sham-controlled pivotal study was designed to assess the efficacy and safety of high-frequency nerve block treatment for chronic post-amputation and phantom limb pain.

Patients and Methods

QUEST enrolled 180 unilateral lower-limb amputees with severe post-amputation pain, 170 of whom were implanted with the Altius device, were randomized 1:1 to active-sham or treatment groups and reached the primary endpoint. Responders were those subjects who received ≥50% pain relief 30 min after treatment in ≥50% of their self-initiated treatment sessions within the 3-month randomized period. Differences between the active treatment and sham control groups as well as numerous secondary outcomes were determined.

Results

At 30-min, (primary outcome), 24.7% of the treatment group were responders compared to 7.1% of the control group (p=0.002). At 120-minutes following treatment, responder rates were 46.8% in the Treatment group and 22.2% in the Control group (p=0.001). Improvement in Brief Pain Inventory interference score of 2.3 ± 0.29 was significantly greater in treatment group than the 1.3 ± 0.26-point change in the Control group (p = 0.01). Opioid usage, although not significantly different, trended towards a greater reduction in the treatment group than in the control group. The incidence of adverse events did not differ significantly between the treatment and control groups.

Conclusion

The primary outcomes of the study were met, and the majority of Treatment patients experienced a substantial improvement in PAP (regardless of meeting the study definition of a responder). The significant in PAP was associated with significantly improved QOL metrics, and a trend towards reduced opioid utilization compared to Control. These data indicate that Altius treatment represents a significant therapeutic advancement for lower-limb amputees suffering from chronic PAP.

Literature Review: Mechanism, Indications, and Clinical Efficacy of Peripheral Nerve Stimulators in Lower Extremity Pain

PURPOSE OF REVIEW

Lower extremity pain is deemed by Center for Disease Control and Prevention (CDC) to be a significant source of chronic pain in adults. If not appropriately managed, patients are subjected to risks of prolonged musculoskeletal dysfunction, disruption to quality of life, and elevated healthcare expenditures. Peripheral nerve stimulation (PNS) has shown great potential in recent years demonstrating efficacy in multiple diagnoses ranging from acute post-surgical pain to complex regional pain syndrome (CRPS). This study seeks to delineate efficacy of peripheral neuromodulation in the context of chronic lower extremity pain.

RECENT FINDINGS

Prevailing clinical studies demonstrate evidence levels ranging from II to V (Oxford Centre of Level of Evidence) in lower limb PNS, attaining positive outcomes in pain scores, opioid use, and quality of life measures. Nerves most frequently targeted are the sciatic and femoral nerves with post-amputation pain and CRPS most commonly investigated for efficacy. PNS is a promising therapeutic modality demonstrated to be effective for a variety of nociceptive and neuropathic pain conditions in the lower extremity. PNS offers chronic pain physicians a powerful tool in the multi-modal management of lower limb chronic pain.

Sustained Relief of Complex Regional Pain Syndrome (CRPS) Pain Following a 60-Day Peripheral Nerve Stimulation: A Report of Three Cases

Patients who present to pain clinics with complex regional pain syndrome (CRPS) typically have debilitating pain, including hyperalgesia and allodynia, and additional substantial quality-of-life concerns related to the motor and autonomic-related symptoms of CRPS. Present treatments for CRPS such as neuropathic pain medications and sympathetic blocks are often unsatisfactory for managing symptoms. The present cases highlight the use of a 60-day percutaneous peripheral nerve stimulation (PNS) treatment for three patients with CRPS Type I affecting the foot. In all three patients, the tibial and common peroneal nerves were targeted separately at the popliteal fossa with two percutaneous leads each placed a remote distance (~1 cm) from the target nerve under ultrasound guidance. All three patients reported substantial pain relief and resolution of autonomic symptoms (e.g., swelling, edema, erythema), with sustained relief lasting 8-10 months in two patients, and 34 months (as of this writing) in the third patient. There were no medical complications. These three cases suggest that 60-day PNS is a safe and efficacious treatment for CRPS.

Current Neurostimulation Therapies for Chronic Pain Conditions

PURPOSE OF REVIEW

Neurostimulation treatment options have become more commonly used for chronic pain conditions refractory to these options. In this review, we characterize current neurostimulation therapies for chronic pain conditions and provide an analysis of their effectiveness and clinical adoption. This manuscript will inform clinicians of treatment options for chronic pain.

RECENT FINDINGS

Non-invasive neurostimulation includes transcranial direct current stimulation and repetitive transcranial magnetic stimulation, while more invasive options include spinal cord stimulation (SCS), peripheral nerve stimulation (PNS), dorsal root ganglion stimulation, motor cortex stimulation, and deep brain stimulation. Developments in transcranial direct current stimulation, repetitive transcranial magnetic stimulation, spinal cord stimulation, and peripheral nerve stimulation render these modalities most promising for the alleviating chronic pain. Neurostimulation for chronic pain involves non-invasive and invasive modalities with varying efficacy. Well-designed randomized controlled trials are required to delineate the outcomes of neurostimulatory modalities more precisely.

Current Approaches to Four Challenging Pain Syndromes

During a conference of pain specialists, some of the experts addressed the potential management of four prevalent but difficult painful conditions, namely, chronic postsurgical pain (CPSP), knee osteoarthritis, chest trauma, and facet joint arthropathy. In all cases, the conditions posed challenges in accurate diagnoses as well as safe, effective treatments, especially using locoregional blocks. It is not clear why some surgical patients develop CPSP and others do not, although some risk factors have been identified. More importantly, the transitional phase of pain from acute to chronic deserves greater scrutiny. It appears as if more aggressive and more effective perioperative and postoperative analgesia could help mitigate or possibly prevent CPSP. Knee osteoarthritis is prevalent but is often managed pharmacologically and then with joint replacement; many patients simply live with the condition which can be viewed as a disease of the entire joint. New approaches with intra-articular injections of hyaluronic acid, platelet-rich plasma, and botulinum toxin may provide safe, effective, and durable pain control. Chest trauma can be extremely painful and a source of morbidity, but its management tends to rely on watchful waiting and drug therapy. New approaches to regional nerve blocks can be beneficial and may reduce troublesome symptoms such as the inability to cough or clear the lungs. Facet joint arthropathy is very prevalent among older people but is not completely clarified. It may be the source of intense pain with limited management strategies. The role of nerve blocks in facet joint arthropathy is an important new addition to the armamentarium of pain management, particularly for geriatric patients.

Role of neuromodulation in acute pain settings

Peripheral nerve stimulation (PNS), a type of neuromodulatory technique, is increasingly used to treat chronic pain syndromes. PNS has also recently gained popularity as a viable adjunct analgesic modality in acute pain settings, where the practice primarily relies on using boluses or infusion of local anesthetics for nerve blockade, followed by stimulation to extend the analgesia. There is some early promise in PNS for perioperative analgesic control, but considerable obstacles must be addressed before it can be implemented into standard practice. In this daring discourse, we explore the possibilities and constraints of using the PNS paradigm in acute pain.

Peripheral Nerve Stimulation for Low Back Pain: A Systematic Review

PURPOSE OF REVIEW

Low back pain (LBP) is a prevalent condition that is associated with diminished physical function, poor mental health outcomes, and reduced quality of life. Peripheral nerve stimulation (PNS) is an emerging modality that has been utilized to treat LBP. The primary objective of this systematic review is to appraise the level of evidence on the efficacy of PNS for treatment of LBP.

RECENT FINDINGS

Twenty-nine articles were included in this systematic review, consisting of 828 total participants utilizing PNS as the primary modality for LBP and 173 participants using PNS as salvage or adjunctive therapy for LBP after SCS placement. Different modalities of PNS therapy were reported across studies, including conventional PNS systems stimulating the lumbar medial branch nerves, peripheral nerve field stimulation (PNFS), and restorative neuromuscular stimulation of the multifidus muscles. All studies consistently reported positive modest to moderate improvement in pain intensity with PNS therapy when comparing baseline pain intensity to each study's respective primary follow-up period. There was a very low GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) quality of evidence supporting this finding. Inconsistency was present in some comparative studies that demonstrated no difference between PNS therapy versus control cohorts (sham or SCS therapy alone), which therefore highlighted the potential for placebo effect. This systematic review highlights that PNS, PNFS, and neuromuscular stimulation may provide modest to moderate pain relief in patients with LBP, although evidence is currently limited due to risk of bias, clinical and methodological heterogeneity, and inconsistency in data.

Durable patient-reported outcomes following 60-day percutaneous peripheral nerve stimulation (PNS) of the medial branch nerves

Background

Chronic low back pain (CLBP) is often associated with clinical evidence of central nervous system sensitization and finding a clear source of nociceptive input can be challenging. Conventional therapies targeting peripheral spinal pain structures can fail to address centrally-mediated, underlying causes of pain. Sixty-day percutaneous peripheral nerve stimulation (PNS) applied to the lumbar medial branch nerves is a non-surgical, non-opioid treatment that may restore the balance of peripheral inputs to the central nervous system and reverse maladaptive changes in central pain processing. As a minimally invasive, non-destructive treatment, percutaneous PNS was designed to be used earlier in the treatment continuum than radiofrequency ablation or permanently-implanted neurostimulation systems.

Objective

The objective of this clinical trial was to characterize the durability of responses to medial branch PNS in a prospective multicenter case series study of CLBP patients recalcitrant to multiple non-surgical treatments.

Design

Prospective, multicenter clinical trial.

Population

Adults with CLBP without radicular leg pain who had previously failed multiple types of conventional treatments.

Intervention

Sixty-day percutaneous PNS applied to the lumbar medial branch nerves.

Methods

Percutaneous PNS leads were implanted under image guidance (ultrasound and/or fluoroscopy) and treatment was applied for up to 60 days, after which the leads were removed. Participants were followed through 14 months (12 months after the 2-month PNS treatment). Prospectively-defined endpoints included assessments of pain intensity, disability, pain interference, health-related quality of life, depression, and patient global impression of change.

Results

Treatment of CLBP with 60-day percutaneous PNS treatment produced clinically meaningful improvements in average pain intensity, disability, and/or pain interference for a majority of participants through the entire 14 month follow up period without requiring permanent system implantation. The proportion of participants experiencing clinically meaningful improvement in at least one outcome (pain intensiy, disability, pain interference) with PNS was 91% after 2 months, 79% at 5 months, 73% at 8 months, 75% at 11 months, and 77% at 14 months. There were no serious or unanticipated study-related adverse events.

Conclusion

This prospective multicenter clinical trial demonstrates the clinical utility of percutaneous PNS when applied to the medial branch nerves for the treatment of chronic low back pain recalcitrant to non-surgical treatments. Given the minimally invasive nature of percutaneous PNS and the significant benefits experienced by participants, percutaneous PNS provides a safe and effective first-line neuromodulation treatment for patients with CLBP that may obviate the need for neuroablative procedures or permanent neurostimulation system implantation.

Implantable Peripheral Nerve Stimulation for Peripheral Neuropathic Pain: A Systematic Review of Prospective Studies

Peripheral nerve stimulation (PNS) has been utilized for over 50 years with accumulating evidence of efficacy in a variety of chronic pain conditions. The level and strength of evidence supporting the use of PNS for peripheral neuropathic pain remains unclear. The purpose of this review is to synthesize data from prospective studies on the efficacy of PNS for neuropathic pain as it pertains to pain intensity, neurological deficits/neuropathy (e.g., weakness, sensory deficits, gait/balance), and other secondary outcomes (quality of life, satisfaction, emotional functioning, and adverse events). In compliance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, this review identified articles from MEDLINE(R), EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus. Overall, per the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria, pooled results demonstrate very low quality or low quality of evidence supporting modest to substantial improvement in pain and neurological function after PNS implantation for treatment of peripheral neuropathic pain. PNS for phantom limb pain was the only indication that had moderate level evidence. Future prospective and well-powered studies are warranted to assess the efficacy of PNS for peripheral neuropathic pain.

A scoping review of current non-pharmacological treatment modalities for phantom limb pain in limb amputees

PURPOSE

Phantom limb pain (PLP) is a chronic neuropathic pain condition of a missing limb following amputation. Pain management is multi-modal, including various non-pharmacological therapies. The purpose of this scoping review was to investigate the evidence surrounding current non-pharmacological treatment modalities for PLP and provide insight into their clinical feasibility.

METHOD

A systematic search was conducted using four databases (Medline, Embase, PsychInfo, and CINAHL) following the PRISMA-ScR method. Results from papers meeting the inclusion criteria were charted to summarize findings, demographics, and use of neuroimaging.

RESULTS

A total of 3387 papers were identified, and full texts of 142 eligible papers were assessed. Eleven treatment modalities for PLP were identified with varying levels of evidence. Overall, there were 25 RCTs, 58 case reports, and 59 a combination of pilot, quasi-experimental, observational, and other study designs.

CONCLUSIONS

Currently, the evidence surrounding most treatment modalities is limited and only a fraction of studies are supported by strong evidence. The findings of this review demonstrated a clear need to conduct more rigorous research with diverse study designs to better understand which modalities provide the most benefit and to incorporate neuroimaging to better determine the neural correlates of PLP and mechanisms of various treatments.Implications for RehabilitationPhantom limb pain (PLP) is a prevalent and debilitating condition following amputation and health care professionals should incorporate an evidence-based pain management protocol into their rehabilitation program.There exist a number of different non-pharmacological therapies to address PLP, however the scientific rigor and levels of evidence vary across modalities.Prescription of interventions for PLP should consider individual patient differences, accessibility to the patient, and quite possibly, a multi-modal approach, particularly for those who also experience residual limb pain.Imagery-based therapies provide the highest level of current evidence based on robust and large randomized control trials, are readily accessible, and are thus most recommended for relief of PLP.

Evidence-Based Clinical Guidelines from the American Society of Pain and Neuroscience for the Use of Implantable Peripheral Nerve Stimulation in the Treatment of Chronic Pain

The objective of this peripheral nerve stimulation consensus guideline is to add to the current family of consensus practice guidelines and incorporate a systematic review process. The published literature was searched from relevant electronic databases, including PubMed, Scopus, Cochrane Central Register of Controlled Trials, and Web of Science from database inception to March 29, 2021. Inclusion criteria encompassed studies that described peripheral nerve stimulation in patients in terms of clinical outcomes for various pain conditions, physiological mechanism of action, surgical technique, technique of placement, and adverse events. Twenty randomized controlled trials and 33 prospective observational studies were included in the systematic review process. There is Level I evidence supporting the efficacy of PNS for treatment of chronic migraine headaches via occipital nerve stimulation; chronic hemiplegic shoulder pain via stimulation of nerves innervating the trapezius, supraspinatus, and deltoid muscles; failed back surgery syndrome via subcutaneous peripheral field stimulation; and lower extremity neuropathic and lower extremity post-amputation pain. Evidence from current Level I studies combined with newer technologies facilitating less invasive and easier electrode placement make peripheral nerve stimulation an attractive alternative for managing patients with complex pain disorders. Peripheral nerve stimulation should be used judiciously as an adjunct for chronic and acute postoperative pain following adequate patient screening and positive diagnostic nerve block or stimulation trial.

Neuromodulation Therapy for Chemotherapy-Induced Peripheral Neuropathy: A Systematic Review

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating and painful condition in patients who have received chemotherapy. The role of neuromodulation therapy in treating pain and improving neurological function in CIPN remains unclear and warrants evidence appraisal. In compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we performed a systematic review to assess change in pain intensity and neurological function after implementation of any neuromodulation intervention for CIPN. Neuromodulation interventions consisted of dorsal column spinal cord stimulation (SCS), dorsal root ganglion stimulation (DRG-S), or peripheral nerve stimulation (PNS). In total, 15 studies utilized SCS (16 participants), 7 studies utilized DRG-S (7 participants), and 1 study utilized PNS (50 participants). Per the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) criteria, there was very low-quality GRADE evidence supporting that dorsal column SCS, DRG-S, and PNS are associated with a reduction in pain severity from CIPN. Results on changes in neurological function remained equivocal due to mixed study findings on thermal sensory thresholds and touch sensation or discrimination. Future prospective, well-powered, and comparative studies assessing neuromodulation for CIPN are warranted.

Real-world evidence of sustained improvement following 60-day peripheral nerve stimulation treatment for pain: a cross-sectional follow-up survey

Objective: This study presents real-world data from a cross-sectional follow-up survey of patients who previously received 60-day peripheral nerve stimulation (PNS) treatment for pain. Materials & methods: A survey including validated pain and other related outcome measures was distributed to patients who previously underwent implantation of temporary PNS leads for 60-day PNS treatment. Results: Among survey respondents who were at least 3 months from the start of treatment, most reported sustained clinically significant improvements in pain and/or quality of life, with the length of follow-up at the time of survey completion ranging from 3 to 30 months. Conclusion: These real-world data support recent prospective studies indicating that 60-day percutaneous PNS provides significant and sustained relief across a wide range of pain conditions.

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

Objective

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

Methods

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

Results

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

Conclusion

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

Unveiling the phantom: What neuroimaging has taught us about phantom limb pain

Phantom limb pain (PLP) is a complicated condition with diverse clinical challenges. It consists of pain perception of a previously amputated limb. The exact pain mechanism is disputed and includes mechanisms involving cerebral, peripheral, and spinal origins. Such controversy limits researchers' and clinicians' ability to develop consistent therapeutics or management. Neuroimaging is an essential tool that can address this problem. This review explores diffusion tensor imaging, functional magnetic resonance imaging, electroencephalography, and magnetoencephalography in the context of PLP. These imaging modalities have distinct mechanisms, implications, applications, and limitations. Diffusion tensor imaging can outline structural changes and has surgical applications. Functional magnetic resonance imaging captures functional changes with spatial resolution and has therapeutic applications. Electroencephalography and magnetoencephalography can identify functional changes with a strong temporal resolution. Each imaging technique provides a unique perspective and they can be used in concert to reveal the true nature of PLP. Furthermore, researchers can utilize the respective strengths of each neuroimaging technique to support the development of innovative therapies. PLP exemplifies how neuroimaging and clinical management are intricately connected. This review can assist clinicians and researchers seeking a foundation for applications and understanding the limitations of neuroimaging techniques in the context of PLP.

Sensorimotor effects of plasticity-inducing percutaneous peripheral nerve stimulation protocols

BACKGROUND

Electrical stimulation of skin afferents can induce somatosensory plasticity in humans. Nevertheless, it is unknown if this is possible to do through percutaneous stimulation of a peripheral nerve, which will allow for regional anaesthesia interventions. Furthermore, potentiation protocols applied over mainly non-nociceptive fibers inhibit nociception in rodents, but this has not been tested in humans.

OBJECTIVE

to determine whether a protocol aiming to depress the nociceptive circuit and another aiming to potentiate non-nociceptive circuits produce regional hypoalgesia and changes in motor function, applied through percutaneous peripheral nerve stimulation (pPNS), and to assess which of them is more promising for pain relief, immediately and 24 hours after intervention.

METHODS

PT-cLF protocol aims to depress the nociceptive pathway through Pain Threshold, continuous Low Frequency stimulation and ST-bHF aims to produce potentiation of the non-nociceptive pathway, through Sensory Threshold burst stimulation at High Frequency. All subjects (n=29) went through both protocols and a control condition in a randomized and blinded crossover design.

RESULTS

Compared to control, ST-bHF induced distal hypoalgesia, towards electrical (p=0.04) and mechanical stimuli (p=0.02) and produced mechanical hypoesthesia (p=0.02). Contrarily, hypoalgesia was not observed after PT-cLF (p>0.05) but increased electrical motor threshold (p=0.04), reduced motor recruitment (p=0.03), and the subjects reported feeling reduced strength (p<0.01).

CONCLUSION

This works provides evidence that is possible to induce antinociceptive plasticity in a wide territory using pPNS. Moreover, it demonstrates for the first time in humans that a protocol aiming to produce long-term potentiation applied predominantly over non-nociceptive afferents induces hypoesthesia and hypoalgesia.

Cancer Pain Management-New Therapies

PURPOSE OF REVIEW

Despite the rapid advance in anti-cancer treatment in recent years, the treatment to cancer-related pain remains largely unchanged. One systemic review has shown that approximately 32% of patient with cancer-related pain were undertreated. While in patients responding to strong opioids, long-term use of opioids will lead to many undesired side effects such as constipation, tolerance, and addiction. The goals of this review are to re visit the current algorism of cancer pain management and bring attention to the emerging interventional pain management techniques.

RECENT FINDINGS

Peripheral nerve stimulation (PNS) has been successfully used to treat certain types of chronic non-cancer pain with long-term analgesic effect. PNS has also brought some promising results in treating localized cancer-related pain in a pilot study. More studies are needed to advance the novel and safe treatment of cancer-related pain. Incorporating interventional techniques such as PNS properly can optimize the current treatment strategy and improve outcomes.

Upper-Extremity Peripheral Nerve Stimulators

Chronic pain conditions are some of the most challenging problems upper-extremity surgeons face and often require a multimodal approach including neuromodulation. Peripheral nerve stimulation (PNS) is one of these modalities, delivering electrical stimulation to peripheral axons to modulate the spinal cord and block out nociceptive signals from the extremity. This blockade leads to long-lasting effects in both the peripheral and central nervous systems. Not only does PNS decrease peripheral pain signals but it also decreases the peripheral inflammatory response and assists with central nervous system plasticity for long-term pain control. Although PNS was initially developed in the 1960s, it has been underrepresented in the literature largely due to the advent of spinal cord stimulation and the lack of Food and Drug Administration-approved hardware for PNS. However, for upper-extremity pain, PNS provides notable benefits over spinal cord stimulation devices, as PNS allows for safer, more specific, and often more effective pain control. As clinicians attempt to limit narcotic use, therapies such as PNS have been revisited and are gaining popularity. We present a narrative review of PNS; discuss its mechanism of action, indications, and surgical technique; and provide a summary of the available literature for the upper-extremity surgeon. Peripheral nerve stimulation offers a solution for chronic, debilitating pain recalcitrant to other treatment modalities.

The Neurostimulation Appropriateness Consensus Committee (NACC): Recommendations for Surgical Technique for Spinal Cord Stimulation

INTRODUCTION

The field of neurostimulation for the treatment of chronic pain is a rapidly developing area of medicine. Although neurostimulation therapies have advanced significantly as a result of technologic improvements, surgical planning, device placement, and postoperative care are of equal importance to optimize outcomes. This Neurostimulation Appropriateness Consensus Committee (NACC) project intends to provide evidence-based guidance for these often-overlooked areas of neurostimulation practice.

MATERIALS AND METHODS

Authors were chosen based on their clinical expertise, familiarity with the peer-reviewed literature, research productivity, and contributions to the neuromodulation literature. Section leaders supervised literature searches of MEDLINE, BioMed Central, Current Contents Connect, Embase, International Pharmaceutical Abstracts, Web of Science, Google Scholar, and PubMed from the last NACC publication in 2017 to the present. Identified studies were graded using the United States Preventive Services Task Force criteria for evidence and certainty of net benefit. Recommendations are based on evidence strength and consensus when evidence was scant.

RESULTS

This NACC project provides guidance on preoperative assessment, intraoperative techniques, and postoperative management in the form of consensus points with supportive evidence. These results are based on grade of evidence, strength of consensus, and expert opinion.

CONCLUSIONS

The NACC has given guidance for a surgical plan that encompasses the patient journey from the planning stage through the surgical experience and postoperative care. The overall recommendations are designed to improve efficacy and the safety of patients undergoing these neuromodulation procedures and are intended to apply throughout the international community.

Peripheral Nerve Stimulation: The Evolution in Pain Medicine

Electrical stimulation of peripheral nerves has been utilized for a variety of indications for over five decades [...].

Peripheral Nerve Stimulation for Chronic Pain: A Systematic Review of Effectiveness and Safety

Peripheral nerve stimulation (PNS) was the first application of neuromodulation. Widespread application of PNS was limited by technical concerns. Recent advances now allow the percutaneous placement of leads with ultrasound or fluoroscopic guidance, while the transcutaneous powering of these leads removes the need for leads to cross major joints. This systematic review was written to assess the current status of high-quality evidence supporting the use of PNS for pain conditions treated by interventional pain physicians. The available literature on PNS, limited to conditions treated by interventional pain physicians, was reviewed and the quality assessed. Literature from 1966 to June 2021 was reviewed. The outcome measures were pain relief and functional improvement. One hundred and two studies were identified. Five randomized controlled trials (RCT) and four observational studies, all case series, met the inclusion criteria. One RCT was of high quality and four were of moderate quality; all four case series were of moderate quality. Three of the RCTs and all four case series evaluated peripheral nerve neuropathic pain. Based upon these studies, there is level II evidence supporting the use of PNS to treat refractory peripheral nerve injury. One moderate-quality RCT evaluated tibial nerve stimulation for pelvic pain, providing level III evidence for this indication. One moderate-quality RCT evaluated surgically placed cylindrical leads for cluster headaches, providing level III evidence for this indication. The evidence suggests that approximately two-thirds of patients with peripheral neuropathic pain will have at least 50% sustained pain relief. Adverse events from PNS are generally minor. A major advantage of PNS over spinal cord stimulation is the absence of any risk of central cord injury. The study was limited by the paucity of literature for some indications. No studies dealt with joint-related osteoarthritic pain.

Peripheral nerve stimulation for the management of acute and subacute post-amputation pain: a randomized, controlled feasibility trial

Introduction & aim: Temporary (60-day) percutaneous peripheral nerve stimulation (PNS) has demonstrated effectiveness for the treatment of chronic post-amputation pain, and this pilot study aims to evaluate the feasibility of temporary percutaneous PNS for the treatment of acute post-amputation pain. Patients & methods: Sixteen veterans undergoing lower extremity amputation received PNS and standard medical therapy or standard medical therapy alone. Results: The PNS group reported greater reductions in average phantom limb pain, residual limb pain and daily opioid consumption, and there were fewer participants taking opioids through 3 months post-amputation. Conclusion: This pilot study suggests that PNS is feasible in the acute postoperative period following lower limb amputation and may provide a non-pharmacologic analgesic therapy that lowers pain scores and reduces opioid consumption, and thus warrants further investigation.

Understanding the role of patient preference in the treatment algorithm for chronic low back pain: results from a survey-based study

Aims: Interventional pain treatments range from injections to established radiofrequency ablation techniques and finally neuromodulation. In addition to safety, efficacy and cost dominance, patient preference for type of treatment is important. Methods: Chronic pain patients (n = 129) completed a preference scale to determine which interventional pain management procedures they would prefer from among radiofrequency ablation, temporary (60-day) peripheral nerve stimulation (PNS), conventional PNS and spinal cord stimulation/dorsal root ganglion stimulation. A second survey (n = 347) specific to assessing the preference for radiofrequency ablation or temporary PNS treatment was completed by patients with low back pain. Results: On the basis of mean rank, temporary PNS percutaneously implanted for up to 60 days was the most preferred treatment compared with the other options presented (p = 0.002). Conclusions: Patient preference should be unbiased and considered as an independent variable for physician discussion in treatment options and future research.

Transient electronics: new opportunities for implantable neurotechnology

Neurotechnology includes artificial devices integrated with the neural tissue to mitigate the burden of neurological and mental disorders. This field has significantly expanded its range of applications thanks to the development of flexible, stretchable and injectable electronics. Now, the emergence of green electronics adds a new asset to the neurotechnology toolbox. Transient neurotechnology reduces the side effects of chronic implants and transforms inert devices into bio-active and bio-responsive structures. Ultimately, it holds the potential of bridging together technological devices with modern approaches in regenerative medicine. This review focuses on the rising potential of transient neurotechnology for human benefit, comprehensively summarises recent achievements and highlights feature needs and challenges.

Treatment of chronic axial back pain with 60-day percutaneous medial branch PNS: Primary end point results from a prospective, multicenter study

Background

The objective of this prospective, multicenter study is to characterize responses to percutaneous medial branch peripheral nerve stimulation (PNS) to determine if results from earlier, smaller single‐center studies and reports were generalizable when performed at a larger number and wider variety of centers in patients recalcitrant to nonsurgical treatments.

Materials & Methods

Participants with chronic axial low back pain (LBP) were implanted with percutaneous PNS leads targeting the lumbar medial branch nerves for up to 60 days, after which the leads were removed. Participants were followed long‐term for 12 months after the 2‐month PNS treatment. Data collection is complete for visits through end of treatment with PNS (primary end point) and 6 months after lead removal (8 months after start of treatment), with some participant follow‐up visits thereafter in progress.

Results

Clinically and statistically significant reductions in pain intensity, disability, and pain interference were reported by a majority of participants. Seventy‐three percent of participants were successes for the primary end point, reporting clinically significant (≥30%) reductions in back pain intensity after the 2‐month percutaneous PNS treatment (n = 54/74). Whereas prospective follow‐up is ongoing, among those who had already completed the long‐term follow‐up visits (n = 51), reductions in pain intensity, disability, and pain interference were sustained in a majority of participants through 14 months after the start of treatment.

Conclusion

Given the minimally invasive, nondestructive nature of percutaneous PNS and the significant benefits experienced by participants who were recalcitrant to nonsurgical treatments, percutaneous PNS may provide a promising first‐line neurostimulation treatment option for patients with chronic axial back pain.

Neuromodulation for chronic pain

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

Percutaneous cryoneurolysis for acute pain management: current status and future prospects

Introduction: Conventional nerve blocks utilize local anesthetic drugs to provide pain relief for hours or days following surgery or trauma. However, postoperative and trauma pain can last weeks or months. Ultrasound-guided percutaneous cryoneurolysis is an anesthetic modality that offers substantially longer pain relief compared to local anesthetic-based nerve blocks.Areas covered: In this review, we discuss the history, mechanism of action, and use of ultrasound-guided percutaneous cryoneurolysis by anesthesiologists in the setting of acute pain management.Expert opinion: Ultrasound-guided percutaneous cryoneurolysis offers the potential to provide weeks or months of pain relief following surgery or trauma. Compared to continuous local anesthetic-based peripheral nerve blocks, currently the gold standard for providing long duration postoperative analgesia, cryoneurolysis has benefits that include: 1) longer duration measured in weeks or months rather than days; 2) no external reservoir of local anesthetic to be carried by the patient; 3) no risk of infection; and 4) no risk of catheter dislodgement. However, cryoneurolysis can induce a prolonged motor block in addition to the sensory block, decreasing the appropriate indications to those in which potential sensory and motor deficits are acceptable. Additionally, cryoneurolysis of multiple nerves can have a substantial time requirement relative to conventional nerve blocks.

Mechanism of Action of Peripheral Nerve Stimulation

PURPOSE OF REVIEW

The number of applications for peripheral nerve stimulation (PNS) in the pain management field is ever-growing. With the increasing number of clinical applications for peripheral nerve stimulation, the purpose of this article is to review the mechanism of action surrounding PNS, the recent literature from January 2018 to January 2021, and pertinent clinical outcomes.

RECENT FINDINGS

The authors searched articles identified from PubMed (January 2018-January 2021), Cochrane Central Register of Controlled Trials databases (January 2018-January 2021), and Scopus (January 2018-January 2021) databases, and manually searched references of identified publications. Broad MeSH terms and Boolean operators were queried in each search, including the following terms and their respective synonyms: peripheral nerve stimulation, mechanism of action, biochemical pathway, and pain pathway. 15 consensus articles were selected for in-depth review and inclusion for qualitative analysis. PNS may activate and modulate higher central nervous system (CNS) centers, including the dorsal lateral prefrontal cortex, somatosensory cortex, anterior cingulate cortex, and parahippocampal areas. Neuromodulatory effects from PNS may also extend into the spinal columns. Also, PNS may lead to changes in endogenous neurotransmitters and affect the plasticity of NMDA pathways.

Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

OBJECTIVE

Lumbar radiofrequency ablation is a commonly used intervention for chronic back pain. However, the pain typically returns, and though retreatment may be successful, the procedure involves destruction of the medial branch nerves, which denervates the multifidus. Repeated procedures typically have diminishing returns, which can lead to opioid use, surgery, or implantation of permanent neuromodulation systems. The objective of this report is to demonstrate the potential use of percutaneous peripheral nerve stimulation (PNS) as a minimally invasive, nondestructive, motor-sparing alternative to repeat radiofrequency ablation and more invasive surgical procedures.

DESIGN

Prospective, multicenter trial.

METHODS

Individuals with a return of chronic axial pain after radiofrequency ablation underwent implantation of percutaneous PNS leads targeting the medial branch nerves. Stimulation was delivered for up to 60 days, after which the leads were removed. Participants were followed up to 5 months after the start of PNS. Outcomes included pain intensity, disability, and pain interference.

RESULTS

Highly clinically significant (≥50%) reductions in average pain intensity were reported by a majority of participants (67%, n = 10/15) after 2 months with PNS, and a majority experienced clinically significant improvements in functional outcomes, as measured by disability (87%, n = 13/15) and pain interference (80%, n = 12/15). Five months after PNS, 93% (n = 14/15) reported clinically meaningful improvement in one or more outcome measures, and a majority experienced clinically meaningful improvements in all three outcomes (i.e., pain intensity, disability, and pain interference).

CONCLUSIONS

Percutaneous PNS has the potential to shift the pain management paradigm by providing an effective, nondestructive, motor-sparing neuromodulation treatment.

Peripherally Induced Reconditioning of the Central Nervous System: A Proposed Mechanistic Theory for Sustained Relief of Chronic Pain with Percutaneous Peripheral Nerve Stimulation

Peripheral nerve stimulation (PNS) is an effective tool for the treatment of chronic pain, although its efficacy and utilization have previously been significantly limited by technology. In recent years, purpose-built percutaneous PNS devices have been developed to overcome the limitations of conventional permanently implanted neurostimulation devices. Recent clinical evidence suggests clinically significant and sustained reductions in pain can persist well beyond the PNS treatment period, outcomes that have not previously been observed with conventional permanently implanted neurostimulation devices. This narrative review summarizes mechanistic processes that contribute to chronic pain, and the potential mechanisms by which selective large diameter afferent fiber activation may reverse these changes to induce a prolonged reduction in pain. The interplay of these mechanisms, supported by data in chronic pain states that have been effectively treated with percutaneous PNS, will also be discussed in support of a new theory of pain management in neuromodulation: Peripherally Induced Reconditioning of the Central Nervous System (CNS).