Analgesic and antinociceptive effects of peripheral nerve neurostimulation in an advanced human experimental model

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.

Permanent Peripheral Nerve Stimulator for Complex Regional Pain Syndrome of the Forearm and Hand

A 51-year-old woman with diabetes and depression was referred to the anesthesia pain clinic with a 15-year history of complex regional pain syndrome type I of the right forearm and hand in the radial sensory nerve distribution. There was no recognized antecedent trauma and she had failed both medical treatment and radial sensory nerve decompression surgery. An ultrasound-guided local anesthetic block of the radial nerve in the upper arm resulted in partial and temporary improvement in pain. She subsequently underwent trial of a peripheral nerve stimulator (PNS) followed by permanent PNS implant placement over the radial nerve proper proximal to the elbow. Within the first month of use, she endorsed substantially improved pain and strength in her right hand. These improvements were sustained for more than 1 year. Applications of PNS technology for treatment of extremity complex regional pain syndrome and neuropathic extremity pain in general are reviewed.

Peripheral Nerve Stimulation for the Management of Pediatric Neuropathic Pain

The management of neuropathic pain in children poses an enormous challenge for pediatricians and pain management physicians. Current treatment options include physical therapy and medication management. Peripheral nerve stimulation/neuromodulation is a novel and minimally invasive treatment that can be initiated and monitored in an outpatient setting. This new technology can be a useful tool for treating pain secondary to pediatric neuropathy and chronic refractory pain after conservative management. Our case report describes the use of a peripheral nerve stimulator in the successful management of pediatric neuropathic leg pain.

Current Neurostimulation Therapies for Chronic Pain Conditions

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Peripheral Nerve Stimulator for Chronic Pain From Quadriceps Tendon Rupture: A Case Report

Chronic pain from quadriceps tendon rupture (QTR) presents a significant challenge for both orthopedic surgeons and pain management physicians. Current treatment options include physical therapy and medication management. Patients with refractory pain often end up using opioids and suffer from a prolonged disability that affects the quality of their life. A peripheral nerve stimulator is a novel treatment option for QTR. It is a minimally invasive treatment option that can be used to manage refractory cases in the future. We report a case of successful management of chronic pain in a patient with bilateral QTR with a femoral peripheral nerve stimulator.

Peripheral Nerve Stimulation for Chronic Intractable Neuropathic Pain Following a Brachial Plexus Avulsion Injury: A Case Report

Brachial plexus avulsion injuries result in permanent motor and sensory deficits, leading to debilitating symptoms. We report the case of a 25-year-old man with chronic pain following right-sided C5-T1 nerve root avulsion without evidence of peripheral nerve injury. His pain was recalcitrant to medical and neurosurgical interventions. However, he experienced substantial (>70%) pain relief with peripheral nerve stimulation targeting the median nerve. These results agree with data suggesting collateral sprouting of sensory nerves occurs following a brachial plexus injury. Further study is needed if we are to understand the mechanisms of the peripheral nerve stimulator as a treatment option.

Wireless High-Frequency Peripheral Nerve Stimulation for Chronic Refractory Knee Pain Post-total Knee Replacement

The number of joint replacement surgeries, especially knee replacement surgeries, is rising with the rising geriatric population. Chronic unremitting knee pain post-total knee replacement surgery is a common phenomenon. Usually, the pain responds to conservative measures, including physical therapy and medical management. In some patients, the pain post-knee replacement surgery can be refractory and unremitting. In such scenarios, peripheral nerve stimulation, or neuromodulation, can be an effective option.

Effect of percutaneous electrical stimulation with high-frequency alternating currents at 30 kHz on the sensory-motor system

Background

Unmodulated high-frequency alternating currents (HFAC) are employed for producing peripheral nerves block. HFAC have been applied in humans with frequencies up to 20 kHz, whether transcutaneously, percutaneously, or via surgically-implanted electrodes. The aim of this study was to assess the effect of percutaneous HFAC, applied with ultrasound-guided needles at 30 kHz, on the sensory-motor nerve conduction of healthy volunteers.

Methods

A parallel, double-blind, randomized clinical trial with a placebo control was conducted. Percutaneous HFAC at 30 kHz or sham stimulation was applied via ultrasound-guided needles in 48 healthy volunteers (n = 24 in each group) for 20 min. The assessed outcome variables were pressure pain threshold (PPT), mechanical detection threshold (MDT), maximal finger flexion strength (MFFS), antidromic sensory nerve action potential (SNAP), hand temperature, and subjective sensations by the participants. The measurements were recorded pre-intervention, during the stimulation (at 15 min), immediately post-intervention (at 20 min), and 15 min after the end of treatment.

Results

The PPT increased in the active group compared with sham stimulation, both during the intervention [14.7%; 95% confidence interval (CI): 4.4-25.0], immediately post-intervention (16.9%; 95% CI: -7.2-26.5), and 15 min after the end of the stimulation (14.3%; 95% CI: 4.4-24.3) (p < 0.01). The proportion of participants who reported feelings of numbness and heaviness was significantly higher in the active group (46 and 50%, respectively) than in the sham group (8 and 18%, respectively) (p < 0.05). No intergroup differences were observed in the remaining outcome variables. No unexpected adverse effects derived from the electrical stimulation were reported.

Conclusion

Percutaneous stimulation with HFAC at 30 kHz applied to the median nerve increased the PPT and subjective perception of numbness and heaviness. Future research should evaluate its potential therapeutic effect in people with pain.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT04884932, identifier NCT04884932.

Peripheral Nerve Stimulation for Lower Extremity Pain

Peripheral nerve stimulation (PNS) is rapidly increasing in use. This interventional pain treatment modality involves modulating peripheral nerves for a variety of chronic pain conditions. This review evaluated its use specifically in the context of chronic lower extremity pain. Studies continue to elucidate the utility of PNS and better define indications, contraindications, as well as short- and long-term benefits of the procedure for the lower extremity. While large, prospective evidence is still lacking, the best available evidence suggests that improvements may be seen in pain scores, functionality, and opioid consumption. Overall, evidence synthesis suggests that PNS for the lower extremities may be a viable option for patients with chronic lower extremity pain.

Effect of Percutaneous Electric Stimulation with High-Frequency Alternating Currents on the Sensory-Motor System of Healthy Volunteers: A Double-Blind Randomized Controlled Study

Former studies investigated the application of high-frequency alternating currents (HFAC) in humans for blocking the peripheral nervous system. The present trial aims to assess the effect of HFAC on the motor response, somatosensory thresholds, and peripheral nerve conduction when applied percutaneously using frequencies of 10 kHz and 20 kHz in healthy volunteers. A parallel, placebo-controlled, double-blind, randomized clinical trial was conducted. Ultrasound-guided HFAC at 10 kHz and 20 kHz and sham stimulation were delivered to the median nerve of 60 healthy volunteers for 20 min. The main assessed variables were the maximum isometric flexion strength (MFFS) of the index finger, myotonometry, pressure pain threshold (PPT), mechanical detection threshold (MDT), and sensory nerve action potential (SNAP). A decrease in the MFFS is observed immediately postintervention compared to baseline, both in the 10 kHz group (−8.5%; 95% CI −14.9 to −2.1) and the 20 kHz group (−12.0%; 95% CI −18.3 to −5.6). The between-group comparison of changes in MFFS show a greater reduction of −10.8% (95% CI −19.8 to −1.8) immediately postintervention in the 20 kHz compared to the sham stimulation group. The percutaneous stimulation applying 20 kHz HFAC to the median nerve produces a reversible postintervention reduction in strength with no adverse effects.

Percutaneous Peripheral Nerve Stimulation (Neuromodulation) for Postoperative Pain: A Randomized, Sham-controlled Pilot Study

BACKGROUND

Percutaneous peripheral nerve stimulation is an analgesic technique involving the percutaneous implantation of a lead followed by the delivery of electric current using an external pulse generator. Percutaneous peripheral nerve stimulation has been used extensively for chronic pain, but only uncontrolled series have been published for acute postoperative pain. The current multicenter study was undertaken to (1) determine the feasibility and optimize the protocol for a subsequent clinical trial and (2) estimate the treatment effect of percutaneous peripheral nerve stimulation on postoperative pain and opioid consumption.

METHODS

Preoperatively, an electrical lead was percutaneously implanted to target the sciatic nerve for major foot/ankle surgery (e.g., hallux valgus correction), the femoral nerve for anterior cruciate ligament reconstruction, or the brachial plexus for rotator cuff repair, followed by a single injection of long-acting local anesthetic along the same nerve/plexus. Postoperatively, participants were randomized to 14 days of either electrical stimulation (n = 32) or sham stimulation (n = 34) using an external pulse generator in a double-masked fashion. The dual primary treatment effect outcome measures were (1) cumulative opioid consumption (in oral morphine equivalents) and (2) mean values of the "average" daily pain scores measured on the 0 to 10 Numeric Rating Scale within the first 7 postoperative days.

RESULTS

During the first 7 postoperative days, opioid consumption in participants given active stimulation was a median (interquartile range) of 5 mg (0 to 30) versus 48 mg (25 to 90) in patients given sham treatment (ratio of geometric means, 0.20 [97.5% CI, 0.07 to 0.57]; P < 0.001). During this same period, the average pain intensity in patients given active stimulation was a mean ± SD of 1.1 ± 1.1 versus 3.1 ± 1.7 in those given sham (difference, -1.8 [97.5% CI, -2.6 to -0.9]; P < 0.001).

CONCLUSIONS

Percutaneous peripheral nerve stimulation reduced pain scores and opioid requirements free of systemic side effects during at least the initial week after ambulatory orthopedic surgery.

EDITOR’S PERSPECTIVE

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

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

Cryoneurolysis and Percutaneous Peripheral Nerve Stimulation to Treat Acute Pain

Two regional analgesic modalities currently cleared by the U.S. Food and Drug Administration hold promise to provide postoperative analgesia free of many of the limitations of both opioids and local anesthetic-based techniques. Cryoneurolysis uses exceptionally low temperature to reversibly ablate a peripheral nerve, resulting in temporary analgesia. Where applicable, it offers a unique option given its extended duration of action measured in weeks to months after a single application. Percutaneous peripheral nerve stimulation involves inserting an insulated lead through a needle to lie adjacent to a peripheral nerve. Analgesia is produced by introducing electrical current with an external pulse generator. It is a unique regional analgesic in that it does not induce sensory, motor, or proprioception deficits and is cleared for up to 60 days of use. However, both modalities have limited validation when applied to acute pain, and randomized, controlled trials are required to define both benefits and risks.

Direct Peripheral Nerve Stimulation for the Treatment of Complex Regional Pain Syndrome: A 30-Year Review

INTRODUCTION

Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy (RSD), is a difficult to treat condition characterized by debilitating pain and limitations in functional ability. Neuromodulation, in the form of spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS), have been traditionally used as a treatment for CRPS with variable success.

OBJECTIVE

This chart review describes the use of implantable PNS systems in the treatment of CRPS of the upper and lower extremities spanning nearly three decades.

MATERIALS AND METHODS

A retrospective chart review was performed on 240 patients with PNS implanted between 1990 and 2017 at our institution. Of these, 165 patients were identified who had PNS systems implanted for a diagnosis of CRPS. Patient profile, including baseline characteristics, comorbidities, past/current interventions/medications and targeted nerves, was descriptively summarized through standard summary statistics. Patients' pain scores and opioid consumptions at baseline (preimplant), 1 month, 6 months, and 12 months were collected and compared. Device revisions and explants were summarized, and patient functional outcomes were described.

RESULTS

Pain scores at baseline and at 12-month follow-up were decreased from a mean of 7.4 ± 1.6 to 5.5 ± 2.4 and estimated to be 1.87 (95% CI: [1.29, 2.46], paired t-test p-value <0.001) lower at 12 months. At baseline, 62% of patients were on chronic opioid therapy, compared with 41% at 12 months. Of 126 patients who reported changes in functional status, 64 (51%) reported improvement, 27 (21%) reported worsening, and 35 (28%) did not report any meaningful change. Excluding end-of-life battery replacements, surgical revision occurred in 56 (34%) of patients. Thirteen patients (8%) underwent implantation of a second PNS because of symptomatic expansion outside of the original painful region. Device explant was performed in 32 (19%) of patients. Median length of follow-up was 74 [14, 147] months. Of the 36 patients who continue to follow-up at our institution, 29 (81%) continue to use their PNS.

CONCLUSIONS

We can conclude that PNS is a useful modality to improve function and reduce long-term pain in selected patients suffering from CRPS type I and type II.

Mechanism of Peripheral Nerve Stimulation in Chronic Pain

INTRODUCTION

With the advancement of technology, peripheral nerve stimulation (PNS) has been increasingly used to treat various chronic pain conditions. Its origin is based on the gate control theory postulated by Wall and Melzack in 1965. However, the exact mechanism behind PNS' analgesic effect is largely unknown. In this article, we performed a comprehensive literature review to overview the PNS mechanism of action.

DESIGN

A comprehensive literature review on the mechanism of PNS in chronic pain.

METHODS

Comprehensive review of the available literature on the mechanism of PNS in chronic pain. Data were derived from database searches of PubMed, Scopus, and the Cochrane Library and manual searches of bibliographies and known primary or review articles.

RESULTS

Animal, human, and imaging studies have demonstrated the peripheral and central analgesic mechanisms of PNS by modulating the inflammatory pathways, the autonomic nervous system, the endogenous pain inhibition pathways, and involvement of the cortical and subcortical areas.

CONCLUSIONS

Peripheral nerve stimulation exhibits its neuromodulatory effect both peripherally and centrally. Further understanding of the mechanism of PNS can help guide stimulation approaches and parameters to optimize the use of PNS.

Transcutaneous electrical nerve stimulation is superior than placebo and control for postoperative pain relief

Aim: To determine whether transcutaneous electrical nerve stimulation (TENS) is more efficient than placebo TENS and control groups for pain relief. Design: Randomized, single-blinded, placebo-controlled trial. Setting & participants: A total of 78 adults with postoperative pain, after cholecystectomy, at the University Hospital. They were randomized into active TENS, placebo TENS and control. Intervention: A total of 30-min interventions applied in the first 24 h after the surgery. Outcome: Pain intensity. Results: Pain significantly decreased for both TENS; however, the active TENS was better. A decrease of 2 points or more on the visual analog scale for 53.8% active TENS and 11.5% placebo. Conclusion: There was a greater reduction in pain of important clinical relevance in the active TENS group.

Clinical Trial registration: Brazilian Clinical Trial (REBEC): RBR-6cgx2k.

20-kHz alternating current stimulation: effects on motor and somatosensory thresholds

BACKGROUND

High frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block. Currently, all the studies applying HFAC stimulation in clinical studies, have employed frequencies below 10 kHz. The main aim of this work was to investigate the neuromodulatory effect of transcutaneous 20 kHz stimulation on somatosensory and pain thresholds, and maximal handgrip strength.

METHODS

A randomized, crossover, single-blinded, placebo-controlled trial was conducted following recruitment of fourteen healthy volunteers. Transcutaneous stimulation at 20 kHz and sham stimulation were applied over the ulnar and median nerves of fourteen healthy volunteers for 20 min. Maximal handgrip strength (MHS), mechanical detection threshold (MDT) and pressure pain threshold (PPT) were registered prior to, during (15 min), immediately after the end (20 min), and 10 min following stimulation.

RESULTS

The 20 kHz stimulation showed a lower MHS during the stimulation at the 15 min (30.1 kgs SE 2.8) and at 20 min (31.8 kgs, SE 2.8) when compared to sham stimulation (35.1 kgs, SE 3.4; p < 0.001 and 34.2 kgs, SE 3.4; p = 0.03, respectively). The 20 kHz stimulation resulted in a slight increase in MDT at 15 min (0.25 mN; 0.25-2.00) when compared to the sham stimulation (0.25 mN; 0.25-0.25; p = 0.02), and no effects were showed for PPT.

CONCLUSIONS

High-frequency stimulation at 20 kHz suggests a partial block of nerve activity. Studies in subjects with neurological disorders characterized by nerve hyperactivity are needed to confirm the clinical impact of this non-invasive electrical stimulation technique.

TRIAL REGISTRATION

NCT, NCT02837458. Registered on 12 April 2017.

Ultrasound-guided percutaneous peripheral nerve stimulation: neuromodulation of the suprascapular nerve and brachial plexus for postoperative analgesia following ambulatory rotator cuff repair. A proof-of-concept study

BACKGROUND AND OBJECTIVES

Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain following knee and foot surgery. However, it remains unknown if this analgesic technique may be used in ambulatory patients following upper extremity surgery. The purpose of this proof-of-concept study was to investigate various lead implantation locations and evaluate the feasibility of using percutaneous brachial plexus PNS to treat surgical pain following ambulatory rotator cuff repair in the immediate postoperative period.

METHODS

Preoperatively, an electrical lead (SPR Therapeutics, Cleveland, Ohio) was percutaneously implanted to target the suprascapular nerve or brachial plexus roots or trunks using ultrasound guidance. Postoperatively, subjects received 5 min of either stimulation or sham in a randomized, double-masked fashion followed by a 5 min crossover period, and then continuous stimulation until lead removal postoperative days 14-28.

RESULTS

Leads (n=2) implanted at the suprascapular notch did not appear to provide analgesia, and subsequent leads (n=14) were inserted through the middle scalene muscle and placed to target the brachial plexus. Three subjects withdrew prior to data collection. Within the recovery room, stimulation did not decrease pain scores during the first 40 min of the remaining subjects with brachial plexus leads, regardless of which treatment subjects were randomized to initially. Seven of these 11 subjects required a single-injection interscalene nerve block for rescue analgesia prior to discharge. However, subsequent average resting and dynamic pain scores postoperative days 1-14 had a median of 1 or less on the Numeric Rating Scale, and opioid requirements averaged less than 1 tablet daily with active stimulation. Two leads dislodged during use and four fractured on withdrawal, but no infections, nerve injuries, or adverse sequelae were reported.

CONCLUSIONS

This proof-of-concept study demonstrates that ultrasound-guided percutaneous PNS of the brachial plexus is feasible for ambulatory shoulder surgery, and although analgesia immediately following surgery does not appear to be as potent as local anesthetic-based peripheral nerve blocks, the study suggests that this modality may provide analgesia and decrease opioid requirements in the days following rotator cuff repair. Therefore, it suggests that a subsequent, large, randomized clinical trial with an adequate control group is warranted to further investigate this therapy in the management of surgical pain in the immediate postoperative period. However, multiple technical issues remain to be resolved, such as the optimal lead location, insertion technique, and stimulating protocol, as well as preventing lead dislodgment and fracture.

TRIAL REGISTRATION NUMBER

NCT02898103.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Sciatic Nerve for Postoperative Analgesia Following Ambulatory Foot Surgery, a Proof-of-Concept Study

BACKGROUND AND OBJECTIVES

Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain the day following knee surgery. However, it remains unknown if this analgesic technique may be used in ambulatory subjects following foot procedures beginning within the recovery room immediately following surgery, and with only short series of patients reported to date, the only available data are derived from strictly observational studies. The purposes of this proof-of-concept study were to demonstrate the feasibility of using percutaneous sciatic nerve PNS to treat postoperative pain following ambulatory foot surgery in the immediate postoperative period and provide the first available data from a randomized controlled study design to provide evidence of analgesic effect.

METHODS

Preoperatively, an electrical lead (SPRINT; SPR Therapeutics, Inc, Cleveland, Ohio) was percutaneously inserted posterior to the sciatic nerve between the subgluteal region and bifurcation with ultrasound guidance. Following hallux valgus osteotomy, subjects received 5 minutes of either stimulation or sham in a randomized, double-masked fashion followed by a 5-minute crossover period and then continuous stimulation until lead removal on postoperative days 14 to 28.

RESULTS

During the initial 5-minute treatment period, subjects randomized to stimulation (n = 4) experienced a downward trajectory in their pain over the 5 minutes of treatment, whereas those receiving sham (n = 3) reported no such change until their subsequent 5-minute stimulation crossover. During the subsequent 30 minutes of stimulation, pain scores decreased to 52% of baseline (n = 7). Three subjects (43%) used a continuous popliteal nerve block for rescue analgesia during postoperative days 0 to 3. Overall, resting and dynamic pain scores averaged less than 1 on the numeric rating scale, and opioid use averaged less than 1 tablet daily with active stimulation. One lead dislodged, 2 fractured during use, and 1 fractured during intentional withdrawal.

CONCLUSIONS

This proof-of-concept study demonstrates that percutaneous sciatic nerve PNS is feasible for ambulatory foot surgery and suggests that this modality provides analgesia and decreases opioid requirements following hallux valgus procedures. However, lead dislodgement and fracture are concerns.

CLINICAL TRIAL REGISTRATION

This study was registered at Clinicaltrials.gov, identifier NCT02898103.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Femoral Nerve for Postoperative Analgesia Following Ambulatory Anterior Cruciate Ligament Reconstruction: A Proof of Concept Study

Objectives

The purpose of this prospective proof of concept study was to investigate the feasibility of using percutaneous peripheral nerve stimulation of the femoral nerve to treat pain in the immediate postoperative period following ambulatory anterior cruciate ligament reconstruction with a patellar autograft.

Materials and Methods

Preoperatively, an electrical lead (SPRINT, SPR Therapeutics, Inc., Cleveland, OH, USA) was percutaneously implanted with ultrasound guidance anterior to the femoral nerve caudad to the inguinal crease. Within the recovery room, subjects received 5 min of either stimulation or sham in a randomized, double‐masked fashion followed by a 5‐min crossover period, and then continuous active stimulation until lead removal postoperative Day 14–28. Statistics were not applied to the data due to the small sample size of this feasibility study.

Results

During the initial 5‐min treatment period, subjects randomized to stimulation (n = 5) experienced a slight downward trajectory (decrease of 7%) in their pain over the 5 min of treatment, while those receiving sham (n = 5) reported a slight upward trajectory (increase of 4%) until their subsequent 5‐min stimulation crossover, during which time they also experienced a slight downward trajectory (decrease of 11% from baseline). A majority of subjects (80%) used a continuous adductor canal nerve block for rescue analgesia (in addition to stimulation) during postoperative Days 1–3, after which the median resting and dynamic pain scores remained equal or less than 1.5 on the numeric rating scale, respectively, and the median daily opioid consumption was less than 1.0 tablet.

Conclusions

This proof of concept study demonstrates that percutaneous femoral nerve stimulation is feasible for ambulatory knee surgery; and suggests that this modality may be effective in providing analgesia and decreasing opioid requirements following anterior cruciate ligament reconstruction. clinicaltrials.gov: NCT02898103.

Intensity matters: Therapist-dependent dose of spinal transcutaneous electrical nerve stimulation

The intensity used during transcutaneous electrical nerve stimulation (TENS) in both, clinical practice and research studies, is often based on subjective commands such as “strong but comfortable sensation”. There is no consensus regarding the effectiveness dose of TENS. The objective was to determine the difference in the effect of spinal TENS on soleus H-reflex modulation when applied by two therapists instructed to apply the stimulation at a “strong but comfortable” intensity. Twenty healthy volunteers divided into two groups: Therapist 1 (n = 10) and Therapist 2 (n = 10). Both therapist applied spinal TENS and sham stimulation at the T10–12 spinal level for 40min in random order to each subject, at an intensity designed to produce a “strong but comfortable” sensation. To avoid habituation, the intensity was adjusted every 2min. Soleus H-reflex was recorded before, during, and 10min after TENS by an observer blinded to the stimulus applied. Despite the instruction to apply TENS at a “strong comfortable” level, a significant difference in current density was identified: Therapist 1 (0.67mA/cm², SD 0.54) applied more than Therapist 2 (0.53mA/cm², SD 0.57; p<0.001) at the onset of the intervention. Maximal peak-to-peak H-reflex amplitude was inhibited significantly more 10min following TENS applied by Therapist 1 (-0.15mV, SD 0.16) compared with Therapist 2 (0.04mV, SD 0.16; p = 0.03). Furthermore, current density significantly correlated with the inhibitory effect on peak-to-peak Soleus H-reflex amplitude 10 min after stimulation (Rho = -0.38; p = 0.04). TENS intensity dosage by the therapist based on the subjective perception of the participants alone is unreliable and requires objective standardization. In addition, higher current density TENS produced greater inhibition of the Soleus H-reflex.

Opioidergic effects of transcutaneous electrical nerve stimulation on pain and inflammatory edema in a rat model of ankle sprain

ABSTRACT Although transcutaneous electrical nerve stimulation (TENS) has been proposed to modulate pain and the mechanisms underlying analgesia remain poorly understood, evidence of anti-inflammatory effect is more limited. The purpose of this study was to examine the opioidergic mechanisms of TENS effects in two different frequencies on pain and inflammatory edema in the ankle sprain model in rats. Threshold to mechanical stimulation was utilized to examine the changes produced by intraperitoneal injection of non-selective opioid antagonist naloxone on the antihyperalgesic effect induced by a 20-min period of 2Hz or 100Hz TENS in the ankle sprain model, produced by manually overextending the lateral ligaments. Ankle sprain induced a long-lasting reduction in paw withdrawn latency (PWL) after 30 minutes for up to 24 hours in sham TENS (SH-TENS) treated rats. The reduced PWL after the induction of ankle sprain was restored partially at 0,1,2,3 and 6, but not 24 hours, after the termination of 2 Hz-TENS (LF-TENS). In 100Hz (HF-TENS) the reduction in PWL was shorter than LF-TENS and both LF and HF effects were fully blocked in naloxone-treated rats. LF- and HF-TENS treated rats did not reach the elevation of edema and presented a progressive edema reduction for over 24 hours when compared to SH-TENS group. Both effects were reduced by naloxone. TENS-induced antihyperalgesic and anti-edematous effects observed in ankle sprain model were mediated by the endogenous opioid system.

Peripheral Nerve Stimulation of Brachial Plexus Nerve Roots and Supra-Scapular Nerve for Chronic Refractory Neuropathic Pain of the Upper Limb

OBJECTIVES

We report the outcome of a consecutive series of 26 patients suffering from chronic medically-refractory neuropathic pain of the upper limb (including 16 patients with complex regional pain syndrome), topographically limited, treated by brachial plexus (BP) nerve roots or supra-scapular nerve (SSN) peripheral nerve stimulation (PNS).

MATERIALS AND METHODS

The technique consisted in ultrasound-guided percutaneous implantation of a cylindrical lead (Pisces-Quad, Medtronic) close to the SSN or the cervical nerve roots within the BP, depending on the pain topography. All the patients underwent a positive trial stimulation before lead connection to a subcutaneous stimulator. Chronic bipolar stimulation mean parameters were: frequency 55.5 Hertz, voltage 1.17 Volts. The voltage was set below the threshold inducing muscle contractions or paresthesias.

RESULTS

Two patients were lost immediately after surgery. At last follow-up (mean 27.5 months), the 20 patients still using the stimulation experienced a mean pain relief of 67.1%. Seventeen patients were improved ≥50%, including 12 improved ≥70%. In 11 patients with a follow-up >2 years, the mean pain relief was 68%. At last follow-up, respectively, six out of the nine (67%) patients treated by SSN stimulation and 10 out of 17 patients (59%) treated by BP stimulation were improved ≥50%. At last follow-up, 12 out of 20 patients still using the stimulation were very satisfied, six were satisfied, and two were poorly satisfied. Complications were: stimulation intolerance due to shock-like sensations (three cases), superficial infection (1), lead fractures (2), and migration (1).

CONCLUSION

In this pilot study, SSN or BP roots PNS provided a relatively safe, durable and effective option to control upper limb neuropathic pain.

Laser-Evoked Potentials in Fibromyalgia: The Influence of Greater Occipital Nerve Stimulation on Cerebral Pain Processing

OBJECTIVE

Fibromyalgia causes widespread musculo-skeletal pain in the four quadrants of the body. Greater occipital nerve stimulation has recently shown beneficial effects in fibromyalgia patients on pain, fatigue, and mood disorders. Laser-evoked potentials (LEPs) are used for research to understand the pathophysiological mechanisms of pain and to evaluate the effects of pain treatment. In fibromyalgia patients, LEPs tend to have a higher N2 amplitude, a tendency to shorter latencies, and patients have a lower pain threshold. Greater occipital nerve stimulation might exert a modulation of the medial pain pathways processing the affective motivational components of pain (unpleasantness) as well as the descending pain inhibitory pathways (reducing pain), both of which are contributing to the N2P2 peak.

MATERIALS AND METHODS

To test this hypothesis, the authors performed LEPs in a group of fibromyalgia patients with and without greater occipital nerve stimulation.

RESULTS

Occipital nerve stimulation does not alter the amplitudes of the LEP recordings, although a significant difference in latencies can be seen. More specifically, latencies of the N2P2 increased in the condition after stimulation, and especially at the Pz electrode.

CONCLUSION

Our results suggest Occipital Nerve Stimulation (ONS) induces a modification of the balance between antinociceptive pain inhibitory pathways and pain-provoking pathways.

Effectiveness of High-Frequency Electrical Stimulation Following Sensitization With Capsaicin

Although nonnoxious, high-frequency electrical stimulation applied segmentally (ie, conventional transcutaneous electrical nerve stimulation [TENS]) has been proposed to modulate pain, the mechanisms underlying analgesia remain poorly understood. To further elucidate how TENS modulates pain, we examined evoked responses to noxious thermal stimuli after the induction of sensitization using capsaicin in healthy volunteers. We hypothesized that sensitization caused by capsaicin application would unmask TENS analgesia, which could not be detected in the absence of sensitization. Forty-nine healthy subjects took part in a series of experiments. The experiments comprised the application of topical capsaicin (.075%) on the left hand in the C6 dermatome, varying the location of TENS (segmental, left C6 dermatome, vs extrasegmental, right shoulder), and assessing rating of perception (numeric rating scale: 0-10) and evoked potentials to noxious contact heat stimuli. The extrasegmental site was included as a control condition because previous studies indicate no analgesic effect to remote conventional TENS. Conventional TENS had no significant effect on rating or sensory evoked potentials in subjects untreated with capsaicin. However, segmental TENS applied in conjunction with capsaicin significantly reduced sensation to noxious thermal stimuli following a 60-minute period of sensitization.

PERSPECTIVE

The study indicates that sensitization with capsaicin unmasks the analgesic effect of conventional TENS on perception of noxious contact heat stimuli. Our findings indicate that TENS may be interacting segmentally to modulate distinct aspects of sensitization, which in turn results in analgesia to thermal stimulation.

Chronic post-traumatic neuropathic pain of brachial plexus and upper limb: a new technique of peripheral nerve stimulation

The aim of the study was to evaluate the effect on pain relief in patients with peripheral neuropathic pain after brachial plexus injuries using an implanted peripheral nerve stimulator applied directly to the nerve branch involved into the axillary cavity. Seven patients with post-traumatic brachial plexus lesions or distal peripheral nerve complaining of severe intractable chronic pain were enrolled in a single-centre, open-label trial. Conventional drugs and traditional surgical treatment were not effective. Patients underwent careful neurological evaluation, pain questionnaires and quantitative sensory testing (QST). Surgical treatment consists of a new surgical technique: a quadripolar electrode lead was placed directly on the sensory peripheral branch of the main nerve involved, proximally to the site of lesion, into the axillary cavity. To assess the effect, we performed a complete neuroalgological evaluation and QST battery after 1 week and again after 1, 6 and 12 weeks. All patients at baseline experienced severe pain with severe positive phenomena in the median (5) and/or radial (2) territory. After turning on the neuro-stimulator system, all patients experienced pain relief within a few minutes (>75 % and >95 % in most), with long-lasting pain relief with a reduction in mean Numerical Rating Scale (NRS) of 76.2 % after 6 months and of 71.5 % after 12 months. No significant adverse events occurred. We recommend and encourage this surgical technique for safety reasons; complications such as dislocation of electrocatheters are avoided. The peripheral nerve stimulation is effective and in severe neuropathic pain after post-traumatic nerve injuries of the upper limbs.

Clinical and economic impact of TENS in patients with chronic low back pain: analysis of a nationwide database

This study evaluated patients who were given transcutaneous electrical nerve stimulation (TENS) compared with a matched group without TENS prior to intervention and at 1-year follow-up. Patients who were treated with TENS had significantly fewer hospital and clinic visits, used less diagnostic imaging (31 vs 46 events per 100 patients), had fewer physical therapy visits (94 vs 107), and required less back surgery (7.5 vs 9.2 surgeries) than patients receiving other treatment modalities. Total annual costs for chronic low back pain patients without neurological involvement were lower in TENS patients ($17,957 vs $17,986 for non-TENS), even when the cost of the device was taken into account.

Modulation of laser-evoked potentials and pain perception by transcutaneous electrical nerve stimulation (TENS): a placebo-controlled study in healthy volunteers

OBJECTIVE

To investigate the effects of transcutaneous electrical nerve stimulation (TENS) on brain nociceptive responses (laser-evoked potentials, LEPs) and pain perception.

METHODS

Twenty healthy subjects were included. Nociceptive CO(2)-laser pulses were sequentially delivered to the dorsum of both feet. The amplitude of LEPs and nociceptive thresholds were collected in three consecutive conditions: T1: "sham" TENS (2 Hz/low-intensity) positioned heterotopically, over the left thigh; T2: "active" TENS (120 Hz/low-intensity) applied homotopically, over the left common peroneal nerve; and T3: "sham" TENS (replication of condition T1).

RESULTS

Compared with "sham" TENS, "active" TENS significantly decreased the LEPs amplitude. This effect was observed exclusively when "active" TENS was applied ipsilaterally to the painful stimulus. Nociceptive thresholds increased with sessions in both limbs, but the increase observed during the "active" condition of TENS (T2) exceeded significantly that observed during the condition T3 only on the foot ipsilateral to TENS.

CONCLUSIONS

Compared with a credible placebo TENS, high-frequency TENS induced a significant attenuation of both the acute pain and LEPs induced by noxious stimuli applied on the same dermatome.

SIGNIFICANCE

This modulation of subjective and objective concomitants of pain processing reflects a real neurophysiological TENS-related effect on nociceptive transmission.

Electrical low-frequency stimulation induces central neuroplastic changes of pain processing in man

Electrical low-frequency stimulation (LFS) inhibits pain perception and nociceptive processing as shown by psychophysical and electrophysiological means (long-term depression, LTD). Information regarding central mechanisms involved in LTD induction and maintenance are still missing. This study hypothesizes that electrical LFS induces changes in activation pattern of pain-related brain areas. Thirty-two electrophysiological and psychophysical experiments were performed in 16 healthy volunteers. Painful electrical test stimulation (0.125 Hz, 60 pulses) and conditioning LFS (1 Hz, 1200 pulses) were applied by a concentric electrode to the right hand. Test stimulation series were performed before (Pre) and after LFS (Post) or no stimulation period (Control). Volunteers rated pain perception according to a verbal rating scale (0-100). Somatosensory evoked cortical potentials were recorded with 64-channel electroencephalography. Individual dipole source modeling using CURRY software (Compumedics, Hamburg, Germany) yielded information about dipole location and strength. The strongest decrease in LFS-induced pain perception was shown after LFS (p < 0.01). Topographic distribution of cortical potentials revealed reproducible negative (N1, N2) and positive (P2) components. Dipole magnitude analysis showed a significant difference between Post LFS and Post Control for P2 (p < 0.01). P2 dipole location analysis yielded a significant posterior (p < 0.05) shift following LTD induction. Thus, data reveal central changes of pain processing after LTD induction. These experiments may help judging the potency of LTD as model for electrostimulation in future analgesic therapy.

Pain relief by applying transcutaneous electrical nerve stimulation (TENS) during unsedated colonoscopy: a randomized double-blind placebo-controlled trial

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive alternative to traditional pain treatments. TENS has been studied in the past as a pain reduction modality in colonoscopy with limited success. Reviews and meta-analysis have shown that the inconclusive results of TENS may be due to the lack of randomized controlled trials and the difficulty in defining precise output parameters. The objective of this double-blind randomized placebo-controlled trial was to investigate the pain-relieving effect of a new application of TENS in unsedated screening colonoscopy. Ninety patients undergoing unsedated screening colonoscopy were randomly allocated to one of three groups: a control group (n=30), a group to receive active TENS (n=30), or a group to receive placebo TENS (n=30). A visual analogue scale (VAS) and a five-point Likert scale were used to assess pain 5 min into the procedure and at the end of the procedure. The patient's bloating sensation during colonoscopy and the effect on the duration of the procedure were also evaluated. Throughout the procedure, the active TENS group experienced a VAS pain score reduction ≥50% compared to the placebo TENS group (P<0.001) and the control group (P<0.001). On the five-point Likert scale, there was also a significant reduction in pain score in the active TENS group compared to the placebo TENS and control groups (P=0.009). No significant differences were found between the study groups as to the bloating sensation and the duration of the procedure. We conclude that TENS can be used as a pain relief therapy in unsedated screening colonoscopy.

Long term clinical outcome of peripheral nerve stimulation in patients with chronic peripheral neuropathic pain

BACKGROUND

Chronic neuropathic pain after injury to a peripheral nerve is known to be resistant to treatment. Peripheral nerve stimulation is one of the possible treatment options, which is, however, not performed frequently. In recent years we have witnessed a renewed interest for PNS. The aim of the present study was to evaluate the long-term clinical efficacy of PNS in a group of patients with peripheral neuropathic pain treated with PNS since the 1980s.

METHODS

Of an original series of 11 patients, 5 patients could be invited for clinical examination, detailed assessment of clinical pain and QST examination. The assessments were done both during habitual use of PNS and with the stimulator off.

RESULTS

Average pain intensity and pain unpleasantness ratings as assessed with visual analog and verbal rating scales showed significant beneficial effects of PNS. Quality of life measures (sleep and daily functioning) also showed positive effects. Quantitative Sensory Testing results did not show significant differences in cold pain and heat pain thresholds between the "ON" and "OFF" conditions.

CONCLUSION

In selected patients with peripheral neuropathic pain PNS remains effective even after more than 20 years.