Peripheral Nerve Stimulation: A Review of Techniques and Clinical Efficacy

Effects and mechanisms of synchronous virtual reality action observation and electrical stimulation on upper extremity motor function and activities of daily living in patients with stroke: a protocol for a randomized controlled trial

Background

Existing rehabilitation techniques are not satisfactory in improving motor function after stroke, resulting in heavy social burdens. With discovery of mirror neuron system (MNS), action observation (AO) has become a promising strategy to promote motor learning in rehabilitation. Based on MNS theory and virtual reality (VR) technology, we designed an innovative rehabilitative approach: synchronous 360° VR video AO (VRAO) and neuromuscular electrical stimulation (NMES). We hypothesized that VRAO+NMES could enhance MNS activation, thus to improve upper limb motor function and activities of daily living in stroke survivors.

Methods

To explore the efficacy and mechanism of VRAO+NMES, we designed this single center, evaluator blinded, prospective, two arm parallel group randomized controlled trial with 1:1 allocation ratio. The experiment group will receive VRAO+NMES, while the control group will receive VR landscape observation combined with NMES. The Fugl-Meyer Assessment for Upper Extremity is the primary outcome of this study, Brunstrom Recovery Stages for Upper Extremity, Manual Muscle Test, Range of Motion, Modified Barthel Index, and Functional Independence Measure are the secondary outcomes. In addition, functional near-infrared spectroscopy (fNIRS) and surface electromyography (sEMG) will be used to evaluate the activation of MNS brain regions and related muscles, respectively.

Discussion

Applying VR in AO therapy (AOT) has become popular, another study direction to improve AOT is to combine it with peripheral stimulations simultaneously. Due to its full immersive characteristic and multi-sensory input, 360° videos based VRAO+NMES could improve the motivation and engagement level of participants. In addition, fNIRS and sEMG test results may act as good biomarkers to predict rehabilitation outcomes, helping select suitable candidates for this new intervention.

Conclusion

The results of this study will provide evidence for the feasibility and potential clinical efficacy of VRAO+NMES in stroke rehabilitation, thus to promote the clinical applicability and generalize its use in hospital, community, and home rehabilitation settings.

Clinical trial registration

https://www.chictr.org.cn/showproj.html?proj=178276, Identifier [ChiCTR2200063552].

Peripheral superior cluneal nerve stimulation for intractable low back pain: Combined fluoroscopy and ultrasound technique, A case series

Background

Chronic low back pain (CLBP) is a common and debilitating condition often difficult to diagnose, with entrapment of the superior cluneal nerves (SCN) being a overlooked cause. Cluneal neuralgia (CN) arises from injury to the SCN and can significantly impact patients' quality of life.

Objectives

This case series aims to evaluate the effectiveness of the Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) for treating cluneal neuralgia, utilizing both fluoroscopic and ultrasound guidance for accurate nerve localization.

Methods

A retrospective review was conducted on six nonconsecutive patients who underwent Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) implantation for cluneal nerve entrapment at MetroHealth System between August 2021 and January 2024. Patient selection focused on individuals with cluneal neuralgia refractory to conservative treatments. Data collection included demographics, pain characteristics, opioid usage, and follow-up evaluations at 30, 60, 90 days, and 2 years post-procedure. Outcomes were assessed using the Numerical Rating Scale (NRS) for pain. Dividing the NRS score by the maximum score (10) and multiplying by 100 expresses pain intensity as a percentage.

Results

Among the six nonconsecutive patients (83 % female, mean age 60 years), the mean pain score prior to implantation was 7.1. At follow-up, five patients reported over 50 % improvement in pain and functional status. Three patients with prior opioid use had varying outcomes regarding opioid consumption post-procedure.

Conclusion

The Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) demonstrates promise as an effective treatment for cluneal neuralgia, leading to reductions in pain and improvements in daily living activities. Further studies are warranted to validate these findings.

Genitofemoral Neuromodulation as a Novel Pain Management Solution for Patients with Chronic Testicular Pain: A Proof-of-Concept Study

Introduction

Severe chronic testicular pain that has failed medical therapy and physiotherapy poses a treatment dilemma. This study presents a proof of concept for the use of genitofemoral neuromodulation (GFM) as a potential pain management solution for patients with persistent testicular pain unresponsive to conservative and surgical management.

Methods

Patients with chronic testicular pain refractory to conventional treatments were selected for GFM. A total of three patients were included in this proof-of-concept study. Demographic information, prior medical and surgical interventions, and pre- and post-operative pain scores using the Numerical Rating Pain Scale were collected. All patients must have had temporary relief from pain with a spermatic cord block.

Results

Patient 1 (75 years old) had a history of opioid medication use, physiotherapy, radiofrequency ablation, and nerve block. His pain score reduced from 10/10 to 4/10 six months post-operatively. Patient 2 (59 years old) had a history of opioid, nortriptyline, baclofen medication use, and physiotherapy. His pain score reduced from 9/10 to 2/10 six months post-operatively. Patient 3 (36 years old) had a history of opioid medication use and physiotherapy, and bilateral orchidectomy for pain relief. His pain score reduced from 8/10 to 6/10 six months post-operatively.

Conclusion

This study suggests that GFM is effective in reduce pain scores and could be a viable option for patients with chronic testicular pain refractory to traditional interventions. Further research is essential to establish the long-term efficacy and safety of GFM in this cohort.

A Body-Temperature-Triggered In Situ Softening Peripheral Nerve Electrode for Chronic Robust Neuromodulation

Implantable peripheral nerve electrodes are crucial for monitoring health and alleviating symptoms of chronic diseases. Advanced compliant electrodes have been developed because of their biomechanical compatibility. However, these mechanically tissue-like electrodes suffer from unmanageable operating forces, leading to high risks of nerve injury and fragile electrode-tissue interfaces. Here, a peripheral nerve electrode is developed that simultaneously fulfills the criteria of body temperature softening and tissue-like modulus (less than 0.8 MPa at 37 °C) after implantation. The central core is altered from the tri-arm crosslinker to the star-branched monomer to kill two birds (close the translation temperature to 37 °C and decrease the modulus after implantation) with one stone. Furthermore, the decreased interfacial impedance (325.1 ± 46.9 Ω at 1 kHz) and increased charge storage capacity (111.2 ± 5.8 mC cm-2) are achieved by an in situ electrografted conductive polymer on the strain-insensitive conductive network of Au nanotubes. The electrodes are readily wrapped around nerves and applied for long-term stimulation in vivo with minimal inflammation. Neuromodulation experiments demonstrate their potential clinical utility, including vagus nerve stimulation in rats to suppress seizures and alleviation of cardiac remodeling in a canine model of myocardial infarction.

Real-world healthcare utilization and costs of peripheral nerve stimulation with a micro-IPG system

AIM

To characterize real-world healthcare resource utilization (HCRU) and costs in adults with chronic pain of peripheral nerve origin treated with peripheral nerve stimulation (PNS) using the micro-implantable pulse generator (IPG).

MATERIALS & METHODS

This retrospective observational study (9/1/19-1/31/23) linked patients from the Nalu medical database to the OM1 Real-World Data Cloud (RWDC). Eligible patients received the micro-IPG implant for PNS, were identifiable in both databases, and had ≥ 12 months of RWDC pre/post-implantation claims data. Primary outcomes were all-cause HRCU and medical costs (12 months pre- and post-implantation); secondary outcomes were all-cause pharmacy costs, including opioids, over the same time.

RESULTS

Patients (N = 122) had a higher mean (standard deviation; SD) number of outpatient visits pre-implantation (5.7 [5.4]) than post-implantation (4.9 [5.7]). Mean (SD) total medical costs were 50% lower, from $27,493 ($44,756) to $13,717 ($23,278). Median (first-third quartile [Q1-Q3]) medical costs were 57% lower, from $11,809 ($4,075-$31,788) to $5,094 ($1,815-$13,820). Mean (SD) pharmacy costs (n = 77) were higher post-implantation ($22,470 [$77,203]) than pre-implantation ($20,092 [$64,132]), while median (Q1-Q3) costs were lower (from $2,708 [$222 -11,882] to $2,122 [$50-9,370]). Post-implantation, the proportion of patients using opioids was 31.4% lower.

CONCLUSION

Patients with PNS using the micro-IPG had reduced HCRU, costs, and opioid use.

A Pressure-Sensitive, Repositionable Bioadhesive for Instant, Atraumatic Surgical Application on Internal Organs

Pressure-sensitive adhesives are widely utilized due to their instant and reversible adhesion to various dry substrates. Though offering intuitive and robust attachment of medical devices on skin, currently available clinical pressure-sensitive adhesives do not attach to internal organs, mainly due to the presence of interfacial water on the tissue surface that acts as a barrier to adhesion. In this work, a pressure-sensitive, repositionable bioadhesive (PSB) that adheres to internal organs by synergistically combining the characteristic viscoelastic properties of pressure-sensitive adhesives and the interfacial behavior of hydrogel bioadhesives, is introduced. Composed of a viscoelastic copolymer, the PSB absorbs interfacial water to enable instant adhesion on wet internal organs, such as the heart and lungs, and removal after use without causing any tissue damage. The PSB's capabilities in diverse on-demand surgical and analytical scenarios including tissue stabilization of soft organs and the integration of bioelectronic devices in rat and porcine models, are demonstrated.

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.

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.

Needle infiltration assisted explantation technique for peripheral nerve stimulator leads

INTRODUCTION

Peripheral nerve stimulation is a neuromodulation modality that is increasing used to treat chronic pain. The permanent peripheral nerve stimulator systems, while easy to implant, are designed to stay in place and scar at the implantation site. There is a paucity of literature on explantation techniques for peripheral nerve stimulators.

METHODS

In this report, we describe a needle infiltration assisted technique for lead explantation. This novel technique is minimally invasive, cost-effective, and utilizes a combination of fluoroscopy and ultrasound imaging. We describe the successful use of this technique in 3 cases without any adverse events.

CONCLUSION

There are many situations which might require a permanent peripheral nerve stimulator to be explanted such as infection, lead erosion, patient request, or need for the patient to undergo magnetic resonance imaging. In these scenarios, we propose a novel needle infiltration assisted technique of explantation that is safe, effective, and easy to replicate.

Real-world evidence of durable multi-dimensional improvement after 60-day peripheral nerve stimulation treatment used for shoulder pain

Aim: This real-world analysis aims to quantify improvements in multiple health domains in patients who received 60-day peripheral nerve stimulation (PNS) for shoulder pain.Materials & methods: Patients reported percent pain relief and Patient Global Impression of Change in quality of life, physical function and sleep at the end of treatment (EOT), 3 months, and 6 months.Results: Of 768 patients, 80.7% were responders in at least one domain at EOT. In a subset who were followed up, a cumulative 75% continued to respond in at least one domain through 6 months (85% [n = 140/165] at 3 months and 88% [n = 53/60] at 6 months).Conclusion: 60-day PNS used for shoulder pain produced multi-dimensional improvements across health domains at EOT and through 6 months.

Computational Modeling of Dorsal Root Ganglion Stimulation: Understanding Pain Suppression Mechanisms

This study aims to advance our mechanistic understanding of electrical stimulation of dorsal root ganglia (DRG) for treating chronic pain. While DRG stimulation has shown moderate clinical success in managing certain types of chronic pain, the underlying neural mechanism remains inconclusive, hindering the further development of the technology to treat a broader range of chronic pain symptoms and benefit a larger patient population. In this study, we conducted computational simulations in the NEURON simulation environment to assess the neuromodulatory effect of DRG stimulation on action potential transmission in Aδ-fiber and C-fiber sensory afferents. Our simulation incorporates Markov-type state models to capture the subtle gating characteristics of voltage-gated sodium channel subtypes, especially NaV1.6, the anatomical distribution of which was revealed by our immunohistological staining on sparsely labeled afferents. Our simulation results indicate that DRG stimulation causes a significant increase in intra-axonal Na+ concentration and a reduction in K+ concentration, collectively disrupting the transaxonal ionic gradients. This disruption resulted in activitydependent conduction slowing, leading to the eventual conduction block in both Aδ- and C-fiber afferents. This research marks a crucial step forward in unraveling the intricate mechanisms underlying DRG stimulation, presenting a framework for the further development of innovative pain modulation strategies that target the DRG.

NerveTracker: a Python-based software toolkit for visualizing and tracking groups of nerve fibers in serial block-face microscopy with ultraviolet surface excitation images

Significance

Information about the spatial organization of fibers within a nerve is crucial to our understanding of nerve anatomy and its response to neuromodulation therapies. A serial block-face microscopy method [three-dimensional microscopy with ultraviolet surface excitation (3D-MUSE)] has been developed to image nerves over extended depths ex vivo. To routinely visualize and track nerve fibers in these datasets, a dedicated and customizable software tool is required.

Aim

Our objective was to develop custom software that includes image processing and visualization methods to perform microscopic tractography along the length of a peripheral nerve sample.

Approach

We modified common computer vision algorithms (optic flow and structure tensor) to track groups of peripheral nerve fibers along the length of the nerve. Interactive streamline visualization and manual editing tools are provided. Optionally, deep learning segmentation of fascicles (fiber bundles) can be applied to constrain the tracts from inadvertently crossing into the epineurium. As an example, we performed tractography on vagus and tibial nerve datasets and assessed accuracy by comparing the resulting nerve tracts with segmentations of fascicles as they split and merge with each other in the nerve sample stack.

Results

We found that a normalized Dice overlap (Dice norm ) metric had a mean value above 0.75 across several millimeters along the nerve. We also found that the tractograms were robust to changes in certain image properties (e.g., downsampling in-plane and out-of-plane), which resulted in only a 2% to 9% change to the meanDice norm values. In a vagus nerve sample, tractography allowed us to readily identify that subsets of fibers from four distinct fascicles merge into a single fascicle as we move ∼ 5    mm along the nerve's length.

Conclusions

Overall, we demonstrated the feasibility of performing automated microscopic tractography on 3D-MUSE datasets of peripheral nerves. The software should be applicable to other imaging approaches. The code is available at https://github.com/ckolluru/NerveTracker.

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.

Remotely Controlled Electrochemical Degradation of Metallic Implants

Biodegradable medical implants promise to benefit patients by eliminating risks and discomfort associated with permanent implantation or surgical removal. The time until full resorption is largely determined by the implant's material composition, geometric design, and surface properties. Implants with a fixed residence time, however, cannot account for the needs of individual patients, thereby imposing limits on personalization. Here, an active Fe-based implant system is reported whose biodegradation is controlled remotely and in situ. This is achieved by incorporating a galvanic cell within the implant. An external and wireless signal is used to activate the on-board electronic circuit that controls the corrosion current between the implant body and an integrated counter electrode. This configuration leads to the accelerated degradation of the implant and allows to harvest electrochemical energy that is naturally released by corrosion. In this study, the electrochemical properties of the Fe-30Mn-1C/Pt galvanic cell model system is first investigated and high-resolution X-ray microcomputed tomography is used to evaluate the galvanic degradation of stent structures. Subsequently, a centimeter-sized active implant prototype is assembled with conventional electronic components and the remotely controlled corrosion is tested in vitro. Furthermore, strategies toward the miniaturization and full biodegradability of this system are presented.

The Relevance of Implanted Percutaneous Electrical Nerve Stimulation in Orthopedics Surgery: A Systematic Review

Background: Percutaneous peripheral nerve stimulation (PNS) is a form of neuromodulation that involves the transmission of electrical energy via metal contacts known as leads or electrodes. PNS has gained popularity in orthopedic surgery as several studies have supported its use as a pain control device for patients suffering from pain due to orthopedic pathologies involving the knee, shoulder, and foot. The purpose of this systematic review is to summarize the literature involving peripheral nerve stimulation in orthopedic surgery. The existing body of literature provides support for further research regarding the use of PNS in the management of knee pain, hip pain, shoulder pain, foot pain, and orthopedic trauma. Notably, the evidence for its efficacy in addressing knee and shoulder pain is present. Methods: This study was conducted following PRISMA guidelines. Seven hundred and forty-five unique entries were identified. Two blinded reviewers assessed each article by title and abstract to determine its relevance and categorized them as "include", "exclude", and "maybe". After a preliminary review was completed, reviewers were unblinded and a third reviewer retrieved articles labeled as "maybe" and those with conflicting labels to determine their relevance. Twenty-eight articles were included, and seven hundred and seventeen articles were excluded. Articles discussing the use of PNS in the field of orthopedic surgery in patients > 18 years of age after 2010 were included. Exclusion criteria included neuropathic pain, phantom limb pain, amputation, non-musculoskeletal related pathology, non-orthopedic surgery related pathology, spinal cord stimulator, no reported outcomes, review articles, abstracts only, non-human subjects. Results: A total of 16 studies analyzing 69 patients were included. All studies were either case series or case reports. Most articles involved the application of PNS in the knee (8) and shoulder (6) joint. Few articles discussed its application in the foot and orthopedic trauma. All studies demonstrated that PNS was effective in reducing pain. Discussion: Peripheral nerve stimulation can be effective in managing postoperative or chronic pain in patients suffering from orthopedic pathology. This systematic review is limited by the scarcity of robust studies with substantial sample sizes and extended follow up periods in the existing literature.

Enhancement of Motor Learning and Corticospinal Excitability: The Role of Electroacupuncture and Motor Training in Healthy Volunteers

BACKGROUND This study embarked on an innovative exploration to elucidate the effects of integrating electroacupuncture (EA) with motor training (MT) on enhancing corticospinal excitability and motor learning. Central to this investigation is the interplay between homeostatic and non-homeostatic metaplasticity processes, providing insights into how these combined interventions may influence neural plasticity and motor skill acquisition. MATERIAL AND METHODS The investigation enrolled 20 healthy volunteers, subjecting them to 4 distinct interventions to parse out the individual and combined effects of EA and MT. These interventions were EA alone, MT alone, EA-priming followed by MT, and MT-priming followed by EA. The assessment of changes in primary motor cortex (M1) excitability was conducted through motor-evoked potentials (MEPs), while the grooved pegboard test (GPT) was used to evaluate alterations in motor performance. RESULTS The findings revealed that EA and MT independently contributed to enhanced M1 excitability and motor performance. However, the additional priming with EA or MT did not yield further modulation in MEPs amplitudes. Notably, EA-priming was associated with improved GPT completion times, underscoring its potential in facilitating motor learning. CONCLUSIONS The study underscores that while EA and MT individually augment motor cortex excitability and performance, their synergistic application does not further enhance or inhibit cortical excitability. This points to the involvement of non-homeostatic metaplasticity mechanisms. Nonetheless, EA emerges as a critical tool in preventing M1 overstimulation, thereby continuously fostering motor learning. The findings call for further research into the strategic application of EA, whether in isolation or with MT, within clinical settings to optimize rehabilitation outcomes.

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.

Peripheral Nerve Stimulation of the Shoulder: A Technical Primer

Scapulalgia or shoulder pain accounts for 16% of all musculoskeletal complaints in the healthy adult population and becomes more common as we age. When this pain exceeds 3 months in duration, it is deemed to be chronic, and typically treated in an escalating manner. Spanning a continuum of conservative and non-conservative measures, chronic shoulder pain treatments range from rest and physical therapy to surgery. Since each patient presents with a unique spectrum of symptoms a customized treatment plan is often required. Over the lifetime of many of these patients, a variety of treatment options are required. One of these treatment options, peripheral nerve stimulation (PNS), is a minimally invasive procedure in which an electrical impulse is delivered through a percutaneously implanted, small caliber electrode to a peripheral nerve proximal to the lesion which interferes with the pain signals. Over the past several years, significant growth of PNS in the treatment of chronic neuropathic pain has been observed. However, the procedural techniques have not been well described. The foundation of long-term, minimally invasive percutaneous PNS in patients with chronic shoulder pain, and procedural techniques for stimulating the suprascapular and axillary nerves using fluoroscopy or ultrasonography will be described in this report.

Peripheral direct current reduces naturally evoked nociceptive activity at the spinal cord in rodent models of pain

Objective.Electrical neuromodulation is an established non-pharmacological treatment for chronic pain. However, existing devices using pulsatile stimulation typically inhibit pain pathways indirectly and are not suitable for all types of chronic pain. Direct current (DC) stimulation is a recently developed technology which affects small-diameter fibres more strongly than pulsatile stimulation. Since nociceptors are predominantly small-diameter Aδand C fibres, we investigated if this property could be applied to preferentially reduce nociceptive signalling.Approach.We applied a DC waveform to the sciatic nerve in rats of both sexes and recorded multi-unit spinal activity evoked at the hindpaw using various natural stimuli corresponding to different sensory modalities rather than broad-spectrum electrical stimulus. To determine if DC neuromodulation is effective across different types of chronic pain, tests were performed in models of neuropathic and inflammatory pain.Main results.We found that in both pain models tested, DC application reduced responses evoked by noxious stimuli, as well as tactile-evoked responses which we suggest may be involved in allodynia. Different spinal activity of different modalities were reduced in naïve animals compared to the pain models, indicating that physiological changes such as those mediated by disease states could play a larger role than previously thought in determining neuromodulation outcomes.Significance.Our findings support the continued development of DC neuromodulation as a method for reduction of nociceptive signalling, and suggests that it may be effective at treating a broader range of aberrant pain conditions than existing devices.

Peripheral Nerve Stimulation for the Treatment of Superior Cluneal Neuralgia: A Cadaver Demonstration of a Novel Technique for Lead Placement

Superior cluneal neuralgia (SCN) is a distinct cause of lower back and/or leg pain related to pathology of the superior cluneal nerve. When assessing a patient with low back pain (LBP), superior cluneal neuralgia is frequently misdiagnosed. The pathophysiology of SCN ranges from myofascial compression brought on by aberrant muscle tone to direct iatrogenic injury or trauma. In this technical report we will discuss the anatomy of superior cluneal nerve, superior cluneal neuralgia, current treatment modalities, and a novel approach to peripheral nerve stimulation (PNS) lead placement via a cadaver demonstration for SCN.

Use of Temporary Percutaneous Peripheral Nerve Stimulation in an Oncologic Population: A Retrospective Review

OBJECTIVES

Patients with an underlying cancer diagnosis may experience pain from many sources. Temporary, percutaneous peripheral nerve stimulation (PNS) is a minimally invasive procedure that can control pain in those who have failed conservative management. The purpose of this retrospective review is to show the use of PNS in managing pain in the oncologic setting.

MATERIALS AND METHODS

Temporary, percutaneous PNS was placed under fluoroscopic or ultrasound guidance for 15 patients at a cancer pain facility. Cases were grouped by subtypes of cancer pain (ie, tumor-related, treatment-related, cancer-associated conditions, and cancer-independent). Before PNS, patients were refractory to medical management or previous interventional treatments. Patients were observed with routine clinic visits to monitor pain levels via visual analog scale (VAS) and quality-of-life measures. PNS was removed after the indicated 60-day treatment period.

RESULTS

This retrospective review presents ten successful cases of oncologic-related pain treated with PNS. Patients with subtypes of pain that were tumor related, from cancer-associated conditions, and cancer independent all experienced a similar degree of pain relief. However, patients with cancer-treatment-related pain experienced the least analgesia from PNS. We also present six cases in which PNS did not provide adequate pain relief.

CONCLUSION

PNS is an emerging technology in neuromodulation that may be useful in managing pain, especially in the oncologic population. Patients with cancer-related and non-cancer-related pain localized to a specific nerve distribution should be considered appropriate candidates for PNS. Further research is needed to optimize patient selection and indications for PNS in the population with cancer.

Dual-neuromodulation strategy in pain management of herpes zoster ophthalmicus: retrospective cohort study and literature review

BACKGROUND

Effective pain control of herpes zoster ophthalmicus (HZO) is not only essential to attenuate the clinical symptoms but to reduce the risk of postherpetic neuralgia development. Recently, neuromodulation therapy has been one promising option for neuropathic pain and increasingly applied in management of zoster-related pain. One key factor of neuromodulation treatment is the therapeutic site for the impaired nerves. In this study we aim to investigate one novel dual-neuromodulation strategy, targeting the level of the peripheral branch and trigeminal ganglion, in the pain management of HZO.

METHODS

Dual neuromodulation strategy combining short-term peripheral nerve stimulation (PNS) with pulsed radiofrequency (PRF) of trigeminal ganglion was compared with single PNS treatment for HZO-related pain. Clinical recordings of patients were retrospectively reviewed. The primary outcome was the pain severity, assessed by the visual analogue scale (VAS) before and after neuromodulation therapy.

RESULTS

PNS achieved significant relief of pain with or without PRF treatment before discharge, which provided enduring therapeutic effect up to 12-month follow-up. The mean reduction of VAS was 6.7 ± 1.4 in dual modulation therapy (n = 13) at last follow-up and 5.4 ± 1.5 in PNS subgroup (n = 20), respectively. Moreover, dual modulation strategy provided better control of pain compared with PNS therapy alone at each time point.

CONCLUSION

It is feasible and effective to combine the PNS and PRF in pain management of HZO. This novel dual modulation strategy of trigeminal pathway may provide additional therapeutic effects of pain symptoms in HZO population.

Fascicle-Selective Ultrasound-Powered Bidirectional Wireless Peripheral Nerve Interface IC

This paper presents an innovative, minimally invasive, battery-free, wireless, peripheral nervous system (PNS) neural interface, which seamlessly integrates a millimeter-scale, fascicle-selective integrated circuit (IC) with extraneural recording and stimulating channels. The system also incorporates a wearable interrogator equipped with integrated machine-learning capabilities. This PNS interface is specifically tailored for adaptive neuromodulation therapy, targeting individuals with paralysis, amputation, or chronic medical conditions. By employing a neural pathway classifier and temporal interference stimulation, the proposed interface achieves precise deep fascicle selectivity for recording and stimulation without the need for nerve penetration or compression. Ultrasonic energy harvesters facilitate wireless power harvesting and data reception, enhancing the usability of the system. Key circuit performance metrics encompass a 2.2 μVrms input-referred noise, 14-bit ENOB, and a 173 dB Schreier figure of merit (FOM) for the neural analog-to-digital converter (ADC). Additionally, the ultra-low-power radio-frequency (RF) transmitter boasts a remarkable 1.38 pJ/bit energy efficiency. In vivo experiments conducted on rat sciatic nerves provide compelling evidence of the interface's ability to selectively stimulate and record neural fascicles. The proposed PNS neural interface offers alternative treatment options for diagnosing and treating neurological disorders, as well as restoring or repairing neural functions, improving the quality of life for patients with neurological and sensory deficits.

Peripheral nerve stimulation for chronic knee pain following total knee arthroplasty: a systematic review

Chronic knee pain following total knee arthroplasty (TKA) affects a subset of patients that is refractory to pharmacological and non-pharmacological modalities. Peripheral nerve stimulation (PNS) has been used in patients with chronic knee pain following TKA and has shown some efficacy. Methods: Comprehensive search of Ovid Medline, Elsevier Embase, Cochrane Central Register of Controlled Trials, CINAHL Plus with Full Text, Scopus, SPORTDiscus with Full Text and the Web of Science platform. From inception to August 2022, for studies using PNS to treat chronic knee pain following TKA. Primary outcomes included pain scores, functional status and medication usage. Results: Nine studies were extrapolated with all demonstrating effectiveness of PNS for patients with chronic knee pain following TKA. Discussion: PNS for chronic knee pain following TKA has been shown to be an efficacious treatment modality. The level of evidence is low and more research is needed to assess its safety and effectiveness.

Current Evidence for Biological Biomarkers and Mechanisms Underlying Acute to Chronic Pain Transition across the Pediatric Age Spectrum

Chronic pain is highly prevalent in the pediatric population. Many factors are involved in the transition from acute to chronic pain. Currently, there are conceptual models proposed, but they lack a mechanistically sound integrated theory considering the stages of child development. Objective biomarkers are critically needed for the diagnosis, risk stratification, and prognosis of the pathological stages of pain chronification. In this article, we summarize the current evidence on mechanisms and biomarkers of acute to chronic pain transitions in infants and children through the developmental lens. The goal is to identify gaps and outline future directions for basic and clinical research toward a developmentally informed theory of pain chronification in the pediatric population. At the outset, the importance of objective biomarkers for chronification of pain in children is outlined, followed by a summary of the current evidence on the mechanisms of acute to chronic pain transition in adults, in order to contrast with the developmental mechanisms of pain chronification in the pediatric population. Evidence is presented to show that chronic pain may have its origin from insults early in life, which prime the child for the development of chronic pain in later life. Furthermore, available genetic, epigenetic, psychophysical, electrophysiological, neuroimaging, neuroimmune, and sex mechanisms are described in infants and older children. In conclusion, future directions are discussed with a focus on research gaps, translational and clinical implications. Utilization of developmental mechanisms framework to inform clinical decision-making and strategies for prevention and management of acute to chronic pain transitions in children, is highlighted.

A review of combined neuromodulation and physical therapy interventions for enhanced neurorehabilitation

Rehabilitation approaches for individuals with neurologic conditions have increasingly shifted toward promoting neuroplasticity for enhanced recovery and restoration of function. This review focuses on exercise strategies and non-invasive neuromodulation techniques that target neuroplasticity, including transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and peripheral nerve stimulation (PNS). We have chosen to focus on non-invasive neuromodulation techniques due to their greater potential for integration into routine clinical practice. We explore and discuss the application of these interventional strategies in four neurological conditions that are frequently encountered in rehabilitation settings: Parkinson's Disease (PD), Traumatic Brain Injury (TBI), stroke, and Spinal Cord Injury (SCI). Additionally, we discuss the potential benefits of combining non-invasive neuromodulation with rehabilitation, which has shown promise in accelerating recovery. Our review identifies studies that demonstrate enhanced recovery through combined exercise and non-invasive neuromodulation in the selected patient populations. We primarily focus on the motor aspects of rehabilitation, but also briefly address non-motor impacts of these conditions. Additionally, we identify the gaps in current literature and barriers to implementation of combined approaches into clinical practice. We highlight areas needing further research and suggest avenues for future investigation, aiming to enhance the personalization of the unique neuroplastic responses associated with each condition. This review serves as a resource for rehabilitation professionals and researchers seeking a comprehensive understanding of neuroplastic exercise interventions and non-invasive neuromodulation techniques tailored for specific diseases and diagnoses.

Neurotechnology for Pain

Neurotechnologies for treating pain rely on electrical stimulation of the central or peripheral nervous system to disrupt or block pain signaling and have been commercialized to treat a variety of pain conditions. While their adoption is accelerating, neurotechnologies are still frequently viewed as a last resort, after many other treatment options have been explored. We review the pain conditions commonly treated with electrical stimulation, as well as the specific neurotechnologies used for treating those conditions. We identify barriers to adoption, including a limited understanding of mechanisms of action, inconsistent efficacy across patients, and challenges related to selectivity of stimulation and off-target side effects. We describe design improvements that have recently been implemented, as well as some cutting-edge technologies that may address the limitations of existing neurotechnologies. Addressing these challenges will accelerate adoption and change neurotechnologies from last-line to first-line treatments for people living with chronic pain.

A Case Report of Three Patients Who Underwent Temporary Peripheral Nerve Stimulation for Treatment of Knee Pain Secondary to Osteoarthritis

Knee osteoarthritis affects millions of people worldwide. There remains a role for novel therapies to manage pain for patients who are unable or unwilling to undergo knee arthroplasty. A peripheral nerve stimulator (PNS) may be beneficial in this population. We present a case report of three patients who received temporary femoral or saphenous PNS and were either unwilling or unable to undergo knee arthroplasty. Two of the three patients reported significantly reduced pain and improved functioning. Our case report demonstrates that temporary PNS may offer a safe and effective treatment for chronic knee pain secondary to knee osteoarthritis.

Acute and chronic pain management in sport medicine: an expert opinion looking at an alternative mechanism-based approach to the pharmacological treatment

In the last decades there has been a huge increase in people who practice sports requesting an increase of the performance. Consequently, also incidence of acute and chronic pain is highly increased in this population of "healthy" people. Pain represents not only a signal of a lesion occurred during the sportive activity, but also (and almost) an unbalance of posture or an overuse of specific articulations or muscles, that has to be resolved not only with a correct physiotherapeutic approach, but also with a careful diagnosis of the complex mechanisms that sustain the pain. Furthermore, many drugs, commonly used in patients with acute pain, can cause side effects in people who practice sports, or they cannot be used as classified in the doping list. Hence, the pain therapist assumes a pivotal role in the management of pain in people who practice sports, for his skills in pain diagnosis, and for the possibility to introduce new mechanism-based therapies. In the last decade, these new therapies, such as regenerative medicine and peripheral neuromodulation, have demonstrated their effectiveness not only to reduce pain, but also to facilitate the healing process and the faster return to the sportive activity. In this expert opinion we summarize the most recent data to support this approach, focalizing not only on how to treat specific pain syndromes but also on how pain therapist could drive, through a careful diagnosis of the pain mechanism, to a new simultaneous mechanism-based disease modifying approach in people with pain practicing sport.

Calcium imaging and analysis of the jugular-nodose ganglia enables identification of distinct vagal sensory neuron subsets

Objective.Sensory nerves of the peripheral nervous system (PNS) transmit afferent signals from the body to the brain. These peripheral nerves are composed of distinct subsets of fibers and associated cell bodies, which reside in peripheral ganglia distributed throughout the viscera and along the spinal cord. The vagus nerve (cranial nerve X) is a complex polymodal nerve that transmits a wide array of sensory information, including signals related to mechanical, chemical, and noxious stimuli. To understand how stimuli applied to the vagus nerve are encoded by vagal sensory neurons in the jugular-nodose ganglia, we developed a framework for micro-endoscopic calcium imaging and analysis.Approach.We developed novel methods forin vivoimaging of the intact jugular-nodose ganglion using a miniature microscope (Miniscope) in transgenic mice with the genetically-encoded calcium indicator GCaMP6f. We adapted the Python-based analysis package Calcium Imaging Analysis (CaImAn) to process the resulting one-photon fluorescence data into calcium transients for subsequent analysis. Random forest classification was then used to identify specific types of neuronal responders.Results.We demonstrate that recordings from the jugular-nodose ganglia can be accomplished through careful surgical dissection and ganglia stabilization. Using a customized acquisition and analysis pipeline, we show that subsets of vagal sensory neurons respond to different chemical stimuli applied to the vagus nerve. Successful classification of the responses with a random forest model indicates that certain calcium transient features, such as amplitude and duration, are important for encoding these stimuli by sensory neurons.Significance.This experimental approach presents a new framework for investigating how individual vagal sensory neurons encode various stimuli on the vagus nerve. Our surgical and analytical approach can be applied to other PNS ganglia in rodents and other small animal species to elucidate previously unexplored roles for peripheral neurons in a diverse set of physiological functions.

Efficacy of Peripheral Nerve Stimulation with a High Frequency Electromagnetic Coupled (HF-EMC) Powered Implanted Receiver in Treating Different Pain Targets/Neuralgias

Introduction

Chronic pain is a significant global public health problem. Peripheral nerve stimulation (PNS) has been gaining popularity in recent years as it is effective, safe and less invasive than surgery for the treatment of chronic pain. The authors aimed to document and share a collection of patient-reported pain scores before and after implanting a percutaneous PNS lead/s with an external wireless generator at various target nerves.

Methods

The authors designed a retrospective study, reviewing electronic medical records. Statistical analysis was performed using SPSS 26; p-value ≤ 0.05 was considered significant.

Results

The mean baseline pain scores of 57 patients have reduced significantly after the procedure at different follow-up durations. Target nerves included genicular nerves, superior cluneal nerves, posterior tibial nerve ± sural nerve, middle cluneal nerves, radial and ulnar nerves and right common peroneal nerve. In the one-month follow-up group, mean pain score was reduced from 7.44 ± 1.48 pre-procedure to 1.6 ± 1.49, from 7.42 ± 1.5 pre-procedure to 1.6 ± 1.5 7.42 at 3 months, from 7.52 ± 1.5 to 1.72 ± 1.57 at 6 months, from 7.41 ± 1.53 to 1.7 ± 1.55 at 9 months, from 7.41 ± 1.58 to 1.76 ± 1.63 at 12 months, from 7.38 ± 1.59 to 1.69 ± 1.56 at 15 months and from 7.5 ± 1.7 to 1.45 ± 1.57 at 24 months (p ≤ 0.001). Patients also reported significant reduction in morphine milliequivalent, pre-procedure MME 47.75 ± 452.5 to 37.92 ± 43.51 at 6 months (p = 0.002, N = 57), pre-procedure MME 42.72 ± 43.19 to 30.38 ± 41.62 at 12 months (p = 0.003, N = 42), and pre-procedure MME 41.2 ± 46.12 to 21.19 ± 40.88 at 24 months (p ≤ 0.001, N = 27). The only complications occurred post procedure with 2 patients receiving an explant and 1 patient receiving a lead migration.

Conclusion

PNS has been shown to be safe and effective in treating chronic pain at different sites with sustained pain relief for up to 24 months. This study is unique in providing long-term follow-up data.

Peripheral Nerve Stimulation in Painful Conditions of the Upper Extremity-An Overview

Our objective is to present a brief history of the evolution of peripheral nerve stimulation, the current understanding of peripheral nerve stimulation mechanisms in chronic pain, peripheral nerve stimulation applications in upper extremity chronic pain conditions, and complications of peripheral nerve stimulation. The evolution of peripheral nerve stimulation from the early ages to the current status has been facilitated by discoveries in neurobehavioral mechanisms of pain, advances in technology and percutaneous lead development, and the availability of high-quality portable ultrasound units. Peripheral nerve stimulation application in managing upper extremity pain of amputated limbs, post-stroke shoulder pain, complex regional pain syndrome (CRPS), and median, ulnar, and radial neuropathies are discussed. Finally, we describe complications of peripheral nerve stimulation. The availability of ultrasound-guided peripheral nerve stimulation techniques and superior peripheral nerve stimulation technology have opened up new and minimally invasive treatment options for chronic intractable neuropathic pain of the upper extremity. Additionally, the ability to place peripheral nerve stimulation leads percutaneously without open peripheral nerve surgery expands the pool of implanting physicians, while simultaneously decreasing the risks and complications that are associated with open surgery.

A comprehensive review of intraarticular knee injection therapy, geniculate injections, and peripheral nerve stimulation for knee pain in clinical practice

The knee is the most common joint in adults associated with morbidity. Many pathologies are associated with knee damage, such as gout or rheumathoid arthritis, but the primary condition is osteoarthritis (OA). Not only can osteoarthritis cause significant pain, but it also can result in signficant disability as well. Treatment for this condition varies, starting off with oral analgesics and physical therapy to surgical total knee replacmenet. In the gamut of this various treatments, a conservative approach has included intra articular steroid injections. With time, researchers and clinicians determined that other components injected to the knee may additionally provide relief of this condition. In this investigation, we describe different types of knee injections such as platelet-rich plasma (PRP), hyaluronic acid, stem cells, and prolotherapy. Additionally, we describe the role of geniculate knee injections, radiofrequency, and periopheral nerve stimulation. These treatments should be considered for patients with knee pain refractory to conservative therapies.

Peripheral Nerve Stimulation for Chronic Shoulder Pain Due to Rotator Cuff Pathology

Chronic shoulder pain affects millions of patients each year. Various conditions can result in shoulder pain ranging from rotator cuff injury, subacromial impingement, post-surgical pain, bursitis, adhesive capsulitis, and osteoarthritis. Typically, rotator cuff pathology is diagnosed by physical exam maneuvers along with advanced imaging modalities. Initial treatment for rotator cuff injury typically consists of physical therapy, NSAIDs, and possible injections depending on the extent of the injury. If conservative measures fail or the injury is too substantial, surgery is typically the appropriate treatment for healthy patients. For patients who are not surgical candidates or refuse surgery, peripheral nerve stimulation (PNS) can be considered. With the use of PNS, the suprascapular and axillary nerves can be targeted to provide pain relief for a variety of chronic shoulder pain issues. We describe the use of PNS in 2 patients with significant rotator cuff pathology who were not surgical candidates.

Peripheral Nerve Stimulation for Treatment of Cluneal Neuropathy Case Study

Chronic low back pain is a prevalent and sometimes debilitating condition. This case report describes a 69-year-old female presenting with axial spine pain. The pain was inadequately controlled by opioids as she was treated unsuccessfully with hydrocodone and remained to have the pain between 7/10 and 10/10. Peripheral neural stimulation (PNS) was trialed and then used to control her pain. PNS is a device-based treatment option that appears effective in a subset of patients. It has been effectively used to treat many different chronic pain syndromes. The patient responded well to the treatment, with her pain intensity going down to between 2/10 and 5/10 on the same scale. She was able to discontinue her use of opioids. PNS can be a safe and effective treatment in patients who have not responded well to pharmacologic analgesia.

Outcomes after minimally invasive and surgical management of suprascapular nerve entrapment: A systematic review

BACKGROUND

The prevalence of suprascapular neuropathy is higher than previously estimated. Recent literature highlights a myriad of treatment options for patients ranging from conservative treatment and minimally invasive options to surgical management. However, there are no comprehensive review articles comparing these treatment modalities.

OBJECTIVE

The purpose of this review article is to summarize the current state of knowledge on suprascapular nerve entrapment and to compare minimally invasive treatments to surgical treatments.

METHODS

The literature search was performed in Mendeley. Search fields were varied redundant. All articles were screened by title and abstract and a preliminary decision to include an article was made. A full-text screening was performed on the selected articles. Any question regarding the inclusion of an article was discussed by 3 authors until an agreement was reached.

RESULTS

Recent studies have further elucidated the pathoanatomy and described several risk factors for entrapment ranging. Four studies met our inclusion criteria regarding peripheral nerve stimulation with good pain and clinical outcomes. Two studies met our inclusion criteria regarding pulsed radiofrequency and showed promising pain and clinical outcomes. One study met our inclusion criteria regarding transcutaneous electrical nerve stimulation and showed good results that were equivalent to pulsed radiofrequency. Surgical treatment has shifted to become nearly all arthroscopic and surgical outcomes remain higher than minimally invasive treatments.

CONCLUSIONS

Many recently elucidated anatomical factors predispose to entrapment. A history of overhead sports or known rotator cuff disease can heighten a clinician's suspicion. Entrapment at the suprascapular notch is more common overall, yet young athletes may be predisposed to isolated spinoglenoid notch entrapment. Pulsed radiofrequency, peripheral nerve stimulation, and transcutaneous electrical nerve stimulation may be effective in treating patients with suprascapular nerve entrapment. Arthroscopic treatment remains the gold-standard in patients with refractory entrapment symptoms.

Neurostimulation as a Method of Treatment and a Preventive Measure in Canine Drug-Resistant Epilepsy: Current State and Future Prospects

Modulation of neuronal activity for seizure control using various methods of neurostimulation is a rapidly developing field in epileptology, especially in treatment of refractory epilepsy. Promising results in human clinical practice, such as diminished seizure burden, reduced incidence of sudden unexplained death in epilepsy, and improved quality of life has brought neurostimulation into the focus of veterinary medicine as a therapeutic option. This article provides a comprehensive review of available neurostimulation methods for seizure management in drug-resistant epilepsy in canine patients. Recent progress in non-invasive modalities, such as repetitive transcranial magnetic stimulation and transcutaneous vagus nerve stimulation is highlighted. We further discuss potential future advances and their plausible application as means for preventing epileptogenesis in dogs.

The analgesic effect of localized vibration: a systematic review. Part 1: the neurophysiological basis

INTRODUCTION

The analgesic action of localized vibration (LV), which is used in rehabilitation medicine to treat various clinical conditions, is usually attributed to spinal gate control, but is actually more complex. The aim of this review is: 1) to provide neurophysiological insights into the mechanisms underlying the ways in which afferent activity set up by LV induces analgesia through interactions with the nociceptive system throughout the nervous system; 2) to give a broader vision of the different effects induced by LV, some of them still related to basic science speculation.

EVIDENCE ACQUISITION

The Medline, EMBASE, AMED, Cochrane Library, CINAHL, Web of Science and ROAD databases were searched for animal and human neurophysiological and neurohormonal studies related to the direct effects of LV on nociceptive transmission and pain perception and were supplemented by published books and theses.

EVIDENCE SYNTHESIS

The spinal gate control mechanism through Aβ-fibers activation seems to be the most effective antinociceptive system activated by LV at frequencies between 100 and 250 Hz (high-frequency LV [HF-LV]) when applied in the same segment as the pain. A gating effect can be obtained also when it is applied contralaterally to the painful site or to adjacent dermatomes. Kinesthetic illusions of movement induced by HF-LV may induce a stronger analgesic effect. Activation of C-mechanoreceptors induced by a massage-like LV of low frequency and low intensity may interfere with pain through the activation of the limbic system. This action does not involve any gating mechanism. Frequency is more important than intensity as different frequencies induce activity in different cortical and cerebellar areas; these activations may be related to plastic cortical changes tentatively reversing pain-related maladaptive disorganization. Distraction/shift of attention or cortisol-mediated stress-induced analgesia are not involved in LV analgesic action in humans for both LF and HF. The release of opioidergic neuropeptides (analgesia not reversed by naloxone) as well as a reduction in substance P in the CSF does not seem to play a major role in the HF-LV action. Decrease in calcitonin and TRPV1 expression in the trigeminal ganglia in animals has been induced by HF-LV but the role of LF-LV is not completely deciphered. Both high and low LV induce the release of oxytocin, which may induce antinociceptive responses in animals and contribute to controlling pain in humans.

CONCLUSIONS

Although many aspects of LV-induced pain alleviation deserve more in-depth basic and translational studies, there are sound neurophysiological reasons for using LV in the therapeutic armamentarium of pain control. Laboratory animal and human data indicate that LV relieves pain not only by acting on the spinal gate, but also at higher levels of the nervous system.

Advances in targeting central sensitization and brain plasticity in chronic pain

Maladaptation in sensory neural plasticity of nociceptive pathways is associated with various types of chronic pain through central sensitization and remodeling of brain connectivity. Within this context, extensive research has been conducted to evaluate the mechanisms and efficacy of certain non-pharmacological pain treatment modalities. These include neurostimulation, virtual reality, cognitive therapy and rehabilitation. Here, we summarize the involved mechanisms and review novel findings in relation to nociceptive desensitization and modulation of plasticity for the management of intractable chronic pain and prevention of acute-to-chronic pain transition.

Measuring Spinal Cord Potentials and Cortico-Spinal Interactions After Wrist Movements Induced by Neuromuscular Electrical Stimulation

Electroencephalographic (EEG) correlates of movement have been studied extensively over many years. In the present work, we focus on investigating neural correlates that originate from the spine and study their connectivity to corresponding signals from the sensorimotor cortex using multivariate autoregressive (MVAR) models. To study cortico-spinal interactions, we simultaneously measured spinal cord potentials (SCPs) and somatosensory evoked potentials (SEPs) of wrist movements elicited by neuromuscular electrical stimulation. We identified directional connections between spine and cortex during both the extension and flexion of the wrist using only non-invasive recording techniques. Our connectivity estimation results are in alignment with various studies investigating correlates of movement, i.e., we found the contralateral side of the sensorimotor cortex to be the main sink of information as well as the spine to be the main source of it. Both types of movement could also be clearly identified in the time-domain signals.

Application of Hybrid Electrically Conductive Hydrogels Promotes Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) occurs frequently, and the prognosis is unsatisfactory. As the gold standard of treatment, autologous nerve grafting has several disadvantages, such as lack of donors and complications. The use of functional biomaterials to simulate the natural microenvironment of the nervous system and the combination of different biomaterials are considered to be encouraging alternative methods for effective tissue regeneration and functional restoration of injured nerves. Considering the inherent presence of an electric field in the nervous system, electrically conductive biomaterials have been used to promote nerve regeneration. Due to their singular physical properties, hydrogels can provide a three-dimensional hydrated network that can be integrated into diverse sizes and shapes and stimulate the natural functions of nerve tissue. Therefore, conductive hydrogels have become the most effective biological material to simulate human nervous tissue's biological and electrical characteristics. The principal merits of conductive hydrogels include their physical properties and their electrical peculiarities sufficient to effectively transmit electrical signals to cells. This review summarizes the recent applications of conductive hydrogels to enhance peripheral nerve regeneration.