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

Methodological and statistical characteristics of meta-analyses on spinal cord stimulation for chronic pain: a systematic review

BACKGROUND

A growing number of meta-analyses (MA) have investigated the use of spinal cord stimulation (SCS) as a treatment modality for chronic pain. The quality of these MAs has not been assessed by validated appraisal tools.

OBJECTIVE

To examine the methodological characteristics and quality of MAs related to the use of SCS for chronic pain syndromes.

EVIDENCE REVIEW

An online literature search was conducted in Ovid MEDLINE(R), Ovid EMBASE, Ovid Cochrane Database of Systematic Reviews, and Scopus databases (January 1, 2000 through June 30, 2023) to identify MAs that investigated changes in pain intensity, opioid consumption, and/or physical function after SCS for the treatment of chronic pain. MA quality was assessed using A Measurement Tool to Assess Systematic Reviews (AMSTAR-2) critical appraisal tool.

FINDINGS

Twenty-five MAs were appraised in the final analysis. Three were considered "high" quality, three "low" quality, and 19 "critically low" quality, per the AMSTAR-2 criteria. There was no association between the publication year and AMSTAR-2 overall quality (β 0.043; 95% CI -0.008 to 0.095; p=0.097). There was an association between the impact factor and AMSTAR-2 overall quality (β 0.108; 95% CI 0.044 to 0.172; p=0.002), such that studies published in journals with higher impact factors were associated with higher overall quality. There was no association between the effect size and AMSTAR-2 overall quality (β -0.168; 95% CI -0.518 to 0.183; p=0.320).According to our power analysis, three studies were adequately powered (>80%) to reject the null hypothesis, while the remaining studies were underpowered (<80%).

CONCLUSIONS

The study demonstrates a critically low AMSTAR-2 quality for most MAs published on the use of SCS for treating chronic pain. Future MAs should improve study quality by implementing the AMSTAR-2 checklist items.

PROSPERO REGISTRATION NUMBER

CRD42023431155.

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.

Incidence of Lead Tip Fracture and Retention After Percutaneous Lead Implantation for Peripheral Nerve Stimulation With an External Pulse Generator: A Multicenter Comparative Analysis of 456 Lead Implants Across Two Lead Hardware Generations

OBJECTIVES

Lead fracture and retention are potential adverse events that can occur after peripheral nerve stimulator (PNS) lead implantation, although recent technologic advancements in PNS hardware have been implemented to avert this risk. We aim to quantify the current incidence of temporary PNS lead fracture/retention and compare this with rates before changes in lead hardware design of temporary PNS.

MATERIALS AND METHODS

A multicenter, retrospective observational study was conducted for patients implanted with a temporary PNS system (SPR© Therapeutics, Cleveland, OH) between June 1, 2018 and August 1, 2024. Patients were included if they underwent a temporary percutaneous PNS system implantation with planned lead removal at 60 days. Patients were excluded if there was ambiguity regarding the status of the lead tip at time of removal (intact vs fractured) or if there was inadvertent lead removal by the patient during the 60-day treatment. The primary objectives of this study were 1) to quantify the incidence of lead retention with removal of temporary percutaneous PNS and 2) to compare the rates of lead retention in the original lead design (version 1.0) and the revised lead design (version 2.0). Secondary objectives included analysis of lead retention rates based on the following covariates: body mass index (BMI), patient age, location of lead placement, or duration of lead implant.

RESULTS

Within the studied timeframe, 337 patients were implanted with a total of 456 leads. Of 337 patients, 40.4% (n = 136) were implanted with lead version 1.0, and 59.6% (n = 201) were implanted with lead version 2.0. Overall, 7.5% of implanted leads (34/456) were retained, affecting 10.1% of patients. Of 194 implanted version 1.0 leads, 13.4% of leads (n = 26) were retained, whereas of 262 version 2.0 leads, 3.1% (n = 8) were retained (p < 0.001). These results showed a reduction in retained leads per patient from 19.1% with lead version 1.0 to 4.0% with revised lead version 2.0. Covariates including BMI, patient age, location of lead placement, or duration of lead implant did not predict lead retention rates.

CONCLUSIONS

Retention and fracture of temporary PNS leads remain prevalent, affecting 7.5% of all implanted leads, although we also observed a significant decrease in rates (3.1% vs 13.4%) with implementation of the revised lead version 2.0 hardware design.

Peripheral Nerve Stimulation for Pain Management: A Survey of Clinical Practice Patterns

BACKGROUND

Clinical interest in and utilization of peripheral nerve stimulation (PNS) for treating chronic pain has significantly increased in recent years owing to its potential for providing analgesia and improved function and quality of life in comparison with pharmacologic treatments. However, the relative infancy of PNS-specific systems and limited clinical practice guidance likely contribute to significant variation in PNS utilization patterns.

OBJECTIVES

We sought to conduct a survey study to characterize PNS-specific clinical practices and propose the next steps in standardizing key practices for PNS utilization.

MATERIALS AND METHODS

A 19-question survey exploring PNS-relevant clinical parameters was disseminated online to pain physicians in practice. Descriptive statistics were used to summarize results.

RESULTS

A total of 94 responses were collected. Regarding patient selection, most practitioners would apply PNS to treat nociceptive pain from major joint osteoarthritis (77.7%) and chronic low back pain (64.9%), but not for axial neck pain (50.0%). In contrast, most would apply PNS to treat neuropathic pain from peripheral neuralgia (94.7%), pericranial neuralgia (77.7%), and cancer-related neuropathic pain (64.9%). In treating complex regional pain syndrome, most practitioners would apply PNS before all other forms of neuraxial neuromodulation (>50% for each form). Similarly, for treating nonsurgical low back pain, most would apply PNS before neuraxial neuromodulation (>50% for each form) but not before radiofrequency ablation (19.2%). Most routinely performed nerve blocks before PNS, mainly to confirm anatomical coverage (84.0%), and regarded a 50% to 75% interquartile range as the minimum analgesic benefit required before proceeding with PNS. Regarding nerve target selection for treating complex regional pain syndrome of the wrist/hand or ankle/foot, or knee osteoarthritis, we observed a very wide variance of PNS target locations and discrete nerves. Regarding "minor" adverse events, most reported not changing PNS utilization on encountering skin/soft tissue reactions (85.1%), minor infections (76.6%), or lead migration/loss of efficacy (50.0%). In comparison, most reported reducing PNS utilization on encountering skin erosion (58.5%), major infections (58.5%), or lead fractures (41.5%).

CONCLUSIONS

There is significant practice variation regarding the utilization of PNS across numerous key clinical considerations. Future research that explores the reasons driving these differences might help optimize patient selection, target selection, periprocedural management, and ultimately outcomes.

An Algorithmic Overview of Advanced Pain Therapies: A Narrative Review

PURPOSE OF REVIEW

Quickly referenceable, streamlined, algorithmic approaches for advanced pain management are lacking for patients, trainees, non-pain specialists, and interventional specialists. This manuscript aims to address this gap by proposing a comprehensive, evidence-based algorithm for managing neuropathic, nociceptive, and cancer-associated pain. Such an algorithm is crucial for pain medicine education, offering a structured approach for patient care refractory to conservative management.

RECENT FINDINGS

A comprehensive literary review with PubMed and regulatory documents from the United States Food and Drug Administration were searched for a variety of interventions. Pain syndromes were categorized into nociceptive and neuropathic pain, and an algorithm was constructed. Serving as an educational tool for patients, trainees, and non-pain specialists, and as an accessible reference for pain specialists, this algorithm bridges knowledge gaps, promotes interdisciplinary collaboration, and streamlines the learning curve for new practitioners. The strength of this algorithm lies in integrating extensive clinical data, emphasizing the latest clinical evidence, and providing a structured decision-making pathway.

Neuromodulation guide for the non-neuromodulator clinician: What it is and how it can benefit patients?

Neuromodulation is being utilized across a variety of medical subspecialties to treat both painful and non-painful medical conditions. However, publications on neuromodulation topics infrequently occur in journals targeting generalists and medical specialties outside of pain medicine and neurosurgery. This study reviewed implantable neuromodulation devices, their respective Food and Drug Administration-approved indications for use, as well as off-label usage, and the associated potential risks and benefits for each device. PubMed and Medline databases were queried for systematic reviews with or without meta-analyses and randomized controlled trials of implantable neuromodulation devices. The literature review resulted in 106 studies eligible for inclusion, and 67 were included in the final review. In conclusion, as the clinical volume of neuromodulation continues to grow, supporting and educating medical professionals who care for patients that receive implanted neuromodulation devices is paramount. It is likely the use of neuromodulation will continue to expand across all medical subspecialties, and as such, every clinician should have a baseline understanding of this treatment.

Comparative outcomes of microsurgical dorsal root entry zone lesioning (DREZotomy) for intractable neuropathic pain in spinal cord and cauda equina injuries

Treatment of neuropathic pain in patients with spinal cord injury (SCI) and cauda equina injury (CEI) remains challenging. Dorsal root entry zone lesioning (DREZL) or DREZotomy is a viable surgical option for refractory cases. This study aimed to compare DREZL surgical outcomes between patients with SCI and those with CEI and to identify predictors of postoperative pain relief. We retrospectively analyzed 12 patients (6 with SCI and 6 with CEI) with intractable neuropathic pain who underwent DREZL. The data collected were demographic characteristics, pain distribution, and outcomes assessed by numeric pain rating scores. Variables and percentages of pain improvement at 1 year and long-term were statistically compared between the SCI and CEI groups. The demographic characteristics and percentage of patients who experienced pain improvement at 1 year postoperatively did not differ between the groups. Compared with the SCI group, the CEI group presented significantly better long-term pain reduction (p = 0.020) and favorable operative outcomes (p = 0.015). Patients with border zone pain had significantly better long-term pain relief and outcomes than did those with diffuse pain (p = 0.008 and p = 0.010, respectively). Recurrent pain after DREZL occurred in the SCI group but not in the CEI group. DREZL provided superior pain relief in patients with CEI. The presence of border zone pain predicted favorable outcomes. CEI patients or SCI patients with border zone pain are good surgical candidates for DREZL, whereas SCI patients with below-injury diffuse pain are poor candidates.

Implantable Passive Sensors for Biomedical Applications

In recent years, implantable sensors have been extensively researched since they allow localized sensing at an area of interest (e.g., within the vicinity of a surgical site or other implant). They allow unobtrusive and potentially continuous sensing, enabling greater specificity, early warning capabilities, and thus timely clinical intervention. Wireless remote interrogation of the implanted sensor is typically achieved using radio frequency (RF), inductive coupling or ultrasound through an external device. Two categories of implantable sensors are available, namely active and passive. Active sensors offer greater capabilities, such as on-node signal and data processing, multiplexing and multimodal sensing, while also allowing lower detection limits, the possibility to encode patient sensitive information and bidirectional communication. However, they require an energy source to operate. Battery implantation, and maintenance, remains a very important constraint in many implantable applications even though energy can be provided wirelessly through the external device, in some cases. On the other hand, passive sensors offer the possibility of detection without the need for a local energy source or active electronics. They also offer significant advantages in the areas of system complexity, cost and size. In this review, implantable passive sensor technologies will be discussed along with their communication and readout schemes. Materials, detection strategies and clinical applications of passive sensors will be described. Advantages over active sensor technologies will be highlighted, as well as critical aspects related to packaging and biocompatibility.

Mechanism of Action of Temporary Peripheral Nerve Stimulation

PURPOSE OF REVIEW

Peripheral nerve stimulation (PNS) refers to the technique of utilizing electrical stimulation of peripheral nerves to inhibit the transmission of pain signals. PNS is used to treat chronic intractable pain and post-surgical or post-traumatic pain alongside a variety of other pain conditions, including headaches, facial pain, pelvic and urogenital pain, chest wall pain, residual limb or phantom limb pain, and back pain.

RECENT FINDINGS

More recently, PNS has been used temporarily for periods of time less than 60 days to treat acute post-surgical pain. Peripheral nerve stimulation is believed to be effective due to its effects on both central and peripheral pathways. Centrally, it is proposed that the electrical pulses of PNS inhibit alpha-delta and C fibers, which decreases pain signaling in the higher centers of the central nervous system. Peripherally, gate theory is applied as it is theorized that PNS downregulates inflammatory mediators, endorphins, and neurotransmitters associated with pain signaling to decrease the transmission of efferent nociception and reduce pain sensations.

Challenges and Advances in Peripheral Nerve Tissue Engineering Critical Factors Affecting Nerve Regeneration

Peripheral neuropathy is painful and can cause a considerable decline in quality of life. Surgery and autograft are the current approaches and clinical standards for restoring function after nerve damage. However, they usually result in unacceptable clinical results, so we need modern peripheral nerve defect treatment approaches. Tissue engineering techniques have been developed as a promising approach, but there are some considerations for translational application. Clinical application of novel tissue engineering methods is related to combining the appropriate cell and scaffold type to introduce safe and efficient bioscaffolds. Efficient nerve regeneration occurs by mimicking the extracellular matrix and combining topographical, biochemical, mechanical, and conductive signs via different cells, biomolecules, and polymers. In brief, ideal engineered biomaterial scaffolds will have to cover all characteristics of nerve tissue, such as nerve number, myelin, and axon thickness. Nerve regeneration has a highly sensitive response to its surrounding microenvironment. For designing a suitable construct, matching the regenerative potential of the autograft as the golden standard is essential. This review article examines the newest advancements in peripheral nerve tissue engineering. Specifically, the discussion will focus on incorporating innovative cues, biological modification, biomaterials, techniques, and concepts in this area of research.

The Physiologic Basis of Molecular Therapeutics for Peripheral Nerve Injury: A Primer

Peripheral nerve injuries affect a significant number of patients who experience trauma affecting the hand and upper extremity. Improving unsatisfactory outcomes from repair of these injuries remains a clinical challenge despite advancements in microsurgical repair. Imperfections of the nerve regeneration process, including imprecise reinnervation, distal axon degradation, and muscular atrophy, complicate the repair process. However, the capacity for peripheral nerves to regenerate offers an avenue for therapeutic advancement. Regeneration is a temporally and spatially dynamic process coordinated by Schwann cells and neurons among other cell types. Neurotrophic factors are a primary means of controlling cell growth and differentiation in the repair setting. Sustained axon survival and regrowth and consequently functional outcomes of nerve repair in animal models are improved by the administration of neurotrophic factors, including glial cell-derived neurotrophic factor, nerve growth factor, sterile alpha and TIR motif containing 1, and erythropoietin. Targeted and sustained delivery of neurotrophic factors through gelatin-based nerve conduits, multiluminal conduits, and hydrogels have been shown to enhance the innate roles of these factors to promote expedient and accurate peripheral nerve regeneration in animal models. These delivery methods may help address the practical limitations to clinical use of neurotrophic factors, including systemic side effects and the need for carefully timed, precisely localized release schedules. In addition, tacrolimus has also improved peripheral nerve regrowth in animal models and has recently shown promise in addressing human disease. Ultimately, this realm of adjunct pharmacotherapies provides ample promise to improve patient outcomes and advance the field of peripheral nerve repair.

Left Infrapatellar Branch of the Saphenous Peripheral Nerve Stimulation Relieves Refractory Pain Following Total Knee Replacement

Osteoarthritis, the most common joint disease of adults worldwide, is increasing in prevalence due to an increase in aging and rates of obesity in developed countries. Treatment options include physical therapy, pharmacologic management, non-pharmacologic management, and total knee replacement surgery. When conservative measures fail, total knee replacement surgery is pursued. The patient is a 61-year-old woman with a history of severe chronic osteoarthritic knee pain following total left and right knee arthroplasty in 2016 and 2019, respectively, who presents with refractory post-total knee replacement pain. Following her surgeries, the patient was in excruciating 10/10 pain on the numerical rating scale (NRS) and was unable to walk or stand. She underwent revisions which, unfortunately, did not ameliorate her pain. She was later referred to chronic pain management in which a peripheral nerve stimulator (PNS) was offered and implanted. Following her PNS trial, the patient achieved >80% pain relief in her left knee. After the permanent PNS implant, the patient noted she had 100% pain relief (0/10 on the NRS) in her left knee and was able to regain mobility. Here, we discuss a case demonstrating rapid pain relief following the minimally invasive PNS implantation for refractory pain following total knee arthroplasty. Refractory pain following total knee arthroplasty can increase morbidity and mortality as a consequence. Thus, proper management is needed to reduce these adverse outcomes. In patients who have failed conservative medical management, PNS may be an alternative, efficacious treatment option for refractory knee pain. Despite the efficacy in our case, further research is needed to define the optimal patient group that would benefit from PNS for refractory knee pain following total knee arthroplasty.

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.

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Pain in the Context of Sensory Deafferentation

Pain that accompanies deafferentation is one of the most mysterious and misunderstood medical conditions. Prevalence rates for the assorted conditions vary considerably but the most reliable estimates are greater than 50% for strokes involving the somatosensory system, brachial plexus avulsions, spinal cord injury, and limb amputation, with controversy surrounding the mechanistic contributions of deafferentation to ensuing neuropathic pain syndromes. Deafferentation pain has also been described for loss of other body parts (e.g., eyes and breasts) and may contribute to between 10% and upwards of 30% of neuropathic symptoms in peripheral neuropathies. There is no pathognomonic test or sign to identify deafferentation pain, and part of the controversy surrounding it stems from the prodigious challenges in differentiating cause and effect. For example, it is unknown whether cortical reorganization causes pain or is a byproduct of pathoanatomical changes accompanying injury, including pain. Similarly, ascertaining whether deafferentation contributes to neuropathic pain, or whether concomitant injury to nerve fibers transmitting pain and touch sensation leads to a deafferentation-like phenotype can be clinically difficult, although a detailed neurologic examination, functional imaging, and psychophysical tests may provide clues. Due in part to the concurrent morbidities, the physical, psychologic, and by extension socioeconomic costs of disorders associated with deafferentation are higher than for other chronic pain conditions. Treatment is symptom-based, with evidence supporting first-line antineuropathic medications such as gabapentinoids and antidepressants. Studies examining noninvasive neuromodulation and virtual reality have yielded mixed results.

Wireless Battery-free and Fully Implantable Organ Interfaces

Advances in soft materials, miniaturized electronics, sensors, stimulators, radios, and battery-free power supplies are resulting in a new generation of fully implantable organ interfaces that leverage volumetric reduction and soft mechanics by eliminating electrochemical power storage. This device class offers the ability to provide high-fidelity readouts of physiological processes, enables stimulation, and allows control over organs to realize new therapeutic and diagnostic paradigms. Driven by seamless integration with connected infrastructure, these devices enable personalized digital medicine. Key to advances are carefully designed material, electrophysical, electrochemical, and electromagnetic systems that form implantables with mechanical properties closely matched to the target organ to deliver functionality that supports high-fidelity sensors and stimulators. The elimination of electrochemical power supplies enables control over device operation, anywhere from acute, to lifetimes matching the target subject with physical dimensions that supports imperceptible operation. This review provides a comprehensive overview of the basic building blocks of battery-free organ interfaces and related topics such as implantation, delivery, sterilization, and user acceptance. State of the art examples categorized by organ system and an outlook of interconnection and advanced strategies for computation leveraging the consistent power influx to elevate functionality of this device class over current battery-powered strategies is highlighted.

Consensus guidelines on training, diagnosis, treatment and follow-up care of trigeminal nerve injuries

The aim was to present expert-based guidelines on the management of trigeminal nerve injuries. A two-round multidisciplinary Delphi study was conducted amongst international trigeminal nerve injury experts with a set of statements and three summary flowcharts using a nine-point Likert scale (1 = strongly disagree; 9 = strongly agree). An item was deemed appropriate if the median panel score was within the range of 7-9, undecided if the score was 4-6, and inappropriate if the score was 1-3. Consensus was achieved if at least 75% of panelists scored within one range. Eighteen specialists from dental, medical, and surgical specialties participated in both rounds. Consensus was reached on most statements related to training/services (78%) and diagnosis (80%). Statements related to treatment were mainly undecided due to a lack of sufficient evidence for some of the proposed treatments. Nevertheless, the summary treatment flowchart reached consensus with a median score of eight. Recommendations on follow-up and opportunities for future research were discussed. None of the statements were deemed inappropriate. A set of recommendations and accepted flowcharts are presented; these will aid professionals involved in managing patients with trigeminal nerve injuries.

Multifidus dysfunction and restorative neurostimulation: a scoping review

OBJECTIVE

Chronic low back pain (CLBP) is multifactorial in nature, with recent research highlighting the role of multifidus dysfunction in a subset of nonspecific CLBP. This review aimed to provide a foundational reference that elucidates the pathophysiological cascade of multifidus dysfunction, how it contrasts with other CLBP etiologies and the role of restorative neurostimulation.

METHODS

A scoping review of the literature.

RESULTS

In total, 194 articles were included, and findings were presented to highlight emerging principles related to multifidus dysfunction and restorative neurostimulation. Multifidus dysfunction is diagnosed by a history of mechanical, axial, nociceptive CLBP and exam demonstrating functional lumbar instability, which differs from other structural etiologies. Diagnostic images may be used to grade multifidus atrophy and assess other structural pathologies. While various treatments exist for CLBP, restorative neurostimulation distinguishes itself from traditional neurostimulation in a way that treats a different etiology, targets a different anatomical site, and has a distinctive mechanism of action.

CONCLUSIONS

Multifidus dysfunction has been proposed to result from loss of neuromuscular control, which may manifest clinically as muscle inhibition resulting in altered movement patterns. Over time, this cycle may result in potential atrophy, degeneration and CLBP. Restorative neurostimulation, a novel implantable neurostimulator system, stimulates the efferent lumbar medial branch nerve to elicit repetitive multifidus contractions. This intervention aims to interrupt the cycle of dysfunction and normalize multifidus activity incrementally, potentially restoring neuromuscular control. Restorative neurostimulation has been shown to reduce pain and disability in CLBP, improve quality of life and reduce health care expenditures.

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.

Neuromodulation for Peripheral Nerve Regeneration: Systematic Review of Mechanisms and In Vivo Highlights

While denervation can occur with aging, peripheral nerve injuries are debilitating and often leads to a loss of function and neuropathic pain. Although injured peripheral nerves can regenerate and reinnervate their targets, this process is slow and directionless. There is some evidence supporting the use of neuromodulation to enhance the regeneration of peripheral nerves. This systematic review reported on the underlying mechanisms that allow neuromodulation to aid peripheral nerve regeneration and highlighted important in vivo studies that demonstrate its efficacy. Studies were identified from PubMed (inception through September 2022) and the results were synthesized qualitatively. Included studies were required to contain content related to peripheral nerve regeneration and some form of neuromodulation. Studies reporting in vivo highlights were subject to a risk of bias assessment using the Cochrane Risk of Bias tool. The results of 52 studies indicate that neuromodulation enhances natural peripheral nerve regeneration processes, but still requires other interventions (e.g., conduits) to control the direction of reinnervation. Additional human studies are warranted to verify the applicability of animal studies and to determine how neuromodulation can be optimized for the greatest functional restoration.

Editorial for the Special Issue “Chronic Neuropathic Pain Therapy and Anaesthesia”

Chronic neuropathic pain (CNP), a complex and debilitating condition arising from damage or dysfunction of the somatosensory nervous system, affects millions of people worldwide [...]