Comparison of Paresthesia Coverage of Patient's Pain: Dorsal Root Ganglion vs. Spinal Cord Stimulation. An ACCURATE Study Sub-Analysis

Comparison of Spinal Cord Stimulation, Dorsal Root Ganglion Stimulation, and Association of Both in Patients With Refractory Chronic Back and/or Lower Limb Neuropathic Pain: A Prospective, Randomized, Double-Blind, Cross-Over Trial (BOOST-DRG Study)

OBJECTIVES

Spinal cord stimulation (SCS) and dorsal root ganglion stimulation (DRGS) have individually shown efficacy in relieving pain in patients with persistent spinal pain syndrome after spinal surgery (PSPS-T2). Combining SCS and DRGS simultaneously, along with Burst stimulation programming, may enhance the responder rate of patients with PSPS-T2.

MATERIAL AND METHODS

This study aimed to compare the pain relief (≥50%) responder rates in SCS, DRGS, and SCS+DGRS (DUAL) through a three-month randomized cross-over trial in patients with PSPS-T2. After the cross-over period, stimulation programming was switched to Burst. Secondary objectives included evaluating the clinical efficacy at three-, four-, six-, and 12-month follow-ups, assessing pain intensity, area of pain, area of paresthesia coverage, quality of life, functional disability, psychologic distress, medication intake, and the Multidimensional Clinical Response Index (MCRI).

RESULTS

The responder rate of pain relief was similar in SCS, DRGS, and DUAL (60%, p = 0.84) at the end of the cross-over period, increasing to 80% with the ability to switch between stimulation possibilities. Burst programming did not provide additional pain relief at the four-month follow-up (p = 0.99). Clinical outcomes significantly improved until 12-month follow-up compared with baseline. Considering a clinically significant increase of 1.05 of the MCRI, all patients were responders at three-, four-, and six- month follow-up, and 80% were responders at 12 months compared with baseline.

CONCLUSIONS

The full option to stimulate different neural structures, separately or simultaneously, led to improved responder rates, allowing patients to personalize treatment. A multidimensional assessment is essential to reveal the full potential benefits of neuromodulation in patients with chronic pain.

An Algorithmic Overview of Advanced Pain Therapies: A Narrative Review

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Open Surgical Implantation of Lumbosacral Dorsal Root Ganglion Stimulators for Chronic Pain: Analysis of Patient Outcomes and Operative Technique

OBJECTIVE

Dorsal root ganglion (DRG) stimulator leads were designed to be placed percutaneously, yet open surgical placement via laminectomy is an option. We present the largest series to date of surgically-placed DRG stimulators and the first series where open surgical implantation was the chosen technique and not a salvage procedure.

METHODS

A retrospective review of a prospective database of DRG implants identified 17 patients who had open lumbosacral DRG lead placement performed by a single surgeon between October 2021 and April 2023. Descriptive statistics, fluoroscopy exposure times, and complications were reported. The window of data collection was 1 month preoperatively to 12 months postoperatively. Phone interviews were conducted to collect information on pain outcomes and patient satisfaction.

RESULTS

We identified 17 patients (12 women, 5 men) who had lumbosacral DRG placement. Phone interviews were conducted for 10/17 patients, with mean follow-up of 11.9 months. 53% reduction in mean pain score was achieved (n = 10, P < 0.001). There were no infections, hematomas, or symptomatic lead migrations. One of 17 experienced a superficial dehiscence and 2 of 17 had an intraoperative repairable durotomy with no postoperative sequelae. Mean fluoroscopy time per lead was 15.4±9.9s (n = 10).

CONCLUSIONS

Open DRG lead placement via laminotomy/laminectomy is reported as a salvage procedure but may have comparable safety and efficacy profile to percutaneous implantation when utilized as the primary implantation method. Before establishing open DRG as an alternative permanent implantation method, more studies are needed to determine whether such benefits as less migration outweigh the risks of a more invasive implantation procedure.

A pilot study of novel ultrahigh-frequency dorsal root ganglia stimulation for chronic lower limb pain: Focusing on safety and feasibility

OBJECTIVES

This single-arm, open-label, single-center observational pilot study assessed the safety and efficacy of ultrahigh-frequency dorsal root ganglia (UHF-DRG) stimulation in patients with chronic leg pain with or without low back pain. Such high-frequency electrostimulation had not been conducted in the human central nervous system previously.

MATERIALS AND METHODS

The primary objective was to evaluate the safety of UHF-DRG stimulation (2 Hz pulses with 50 msec pulse-width and 500 kHz intrapulse sine waves, 5-min duration per stimulation) by identifying incident adverse events (AE) and severe adverse events (SAE) during the trial. The secondary objectives included assessment of pain reduction using a numerical rating score (NRS), presence of paraesthesia, and changes in four pain medications (weak opioids, anticonvulsants, antidepressants, and non-steroid-anti-inflammatory drugs). One DRG lead was implanted for one day then removed, and the patients received maximal three times of UHF stimulation in total.

RESULTS

The study focused on ten cases. Two of them did not complete the study due to difficulty of lead implantation. There was no SAE in this trial. Among the ten cases, AEs occurred in eight, three experienced injection-related local pain and one of them had a post-dural-puncture headache, others had symptoms un-related to implantation procedure or UHF stimulation. The average NRS was reduced from 6.4 ± 1.1 at baseline to 2.9 ± 1.1 on the second-day post-implantation, and it was striking that the NRS was maintained at 3.6 ± 2.8 until 2 days after lead removal. The results showed a trend of lower frequency in medication use for all types of analgesics.

CONCLUSIONS

In this first-in-human pilot study, we discovered that intermittent pulsed UHF-DRG stimulations ameliorated chronic lower limb pain for an extended period in humans. Our finding opens up a new neuromodulatory concept and may initiate a novel paradigm for treating intractable pain.

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

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

The Neurostimulation Appropriateness Consensus Committee (NACC)®: Recommendations for Spinal Cord Stimulation Long-Term Outcome Optimization and Salvage Therapy

INTRODUCTION

The International Neuromodulation Society (INS) has recognized a need to establish best practices for optimizing implantable devices and salvage when ideal outcomes are not realized. This group has established the Neurostimulation Appropriateness Consensus Committee (NACC)® to offer guidance on matters needed for both our members and the broader community of those affected by neuromodulation devices.

MATERIALS AND METHODS

The executive committee of the INS nominated faculty for this NACC® publication on the basis of expertise, publications, and career work on the issue. In addition, the faculty was chosen in consideration of diversity and inclusion of different career paths and demographic categories. Once chosen, the faculty was asked to grade current evidence and along with expert opinion create consensus recommendations to address the lapses in information on this topic.

RESULTS

The NACC® group established informative and authoritative recommendations on the salvage and optimization of care for those with indwelling devices. The recommendations are based on evidence and expert opinion and will be expected to evolve as new data are generated for each topic.

CONCLUSIONS

NACC® guidance should be considered for any patient with less-than-optimal outcomes with a stimulation device implanted for treating chronic pain. Consideration should be given to these consensus points to salvage a potentially failed device before explant.

Research hotspots and trends of spinal cord stimulation for neuropathic pain: a bibliometric analysis from 2004 to 2023

The purpose of this study is to systematically analyze the development trend, research hotspots, and future development direction on the treatment of neuropathic pain (NP) with spinal cord stimulation through bibliometric method. We extracted the literature related to the treatment of NP with spinal cord stimulation from January 2004 to December 2023 from the Web of Science database. As a result, a total of 264 articles were retrieved. By analyzing the annual published articles, authors, countries, institutions, journals, co-cited literature, and keywords, we found that the count of publication in this field has been experiencing an overall growth, and the publications within the past 5 years accounted for 42% of the total output. Experts from the United States and the UK have made significant contributions in this field and established a stable collaborative team, initially establishing an international cooperation network. Pain is the frequently cited journal in this field. The study on spinal cord stimulation therapy for NP especially the study on spinal cord stimulation therapy for back surgery failure syndrome (FBSS) and its potential mechanisms are the research hotspots in this field, while the study on novel paradigms such as high-frequency spinal cord stimulation and spinal cord burst stimulation represents the future development directions. In short, spinal cord stimulation has been an effective treatment method for NP. The novel paradigms of spinal cord stimulation are the key point of future research in this field.

A Narrative Review of the Dorsal Root Ganglia and Spinal Cord Mechanisms of Action of Neuromodulation Therapies in Neuropathic Pain

Neuropathic pain arises from injuries to the nervous system in diseases such as diabetes, infections, toxicity, and traumas. The underlying mechanism of neuropathic pain involves peripheral and central pathological modifications. Peripheral mechanisms entail nerve damage, leading to neuronal hypersensitivity and ectopic action potentials. Central sensitization involves a neuropathological process with increased responsiveness of the nociceptive neurons in the central nervous system (CNS) to their normal or subthreshold input due to persistent stimuli, leading to sustained electrical discharge, synaptic plasticity, and aberrant processing in the CNS. Current treatments, both pharmacological and non-pharmacological, aim to alleviate symptoms but often face challenges due to the complexity of neuropathic pain. Neuromodulation is emerging as an important therapeutic approach for the treatment of neuropathic pain in patients unresponsive to common therapies, by promoting the normalization of neuronal and/or glial activity and by targeting cerebral cortical regions, spinal cord, dorsal root ganglia, and nerve endings. Having a better understanding of the efficacy, adverse events and applicability of neuromodulation through pre-clinical studies is of great importance. Unveiling the mechanisms and characteristics of neuromodulation to manage neuropathic pain is essential to understand how to use it. In the present article, we review the current understanding supporting dorsal root ganglia and spinal cord neuromodulation as a therapeutic approach for neuropathic pain.

Long-term efficacy of spinal cord stimulation for chronic primary neuropathic pain in the contemporary era: a systematic review and meta-analysis

INTRODUCTION

Spinal cord stimulation (SCS) is a modern neuromodulation technique extensively proven to be an effective modality for treatment of chronic neuropathic pain. It has been mainly studied for complex regional pain syndrome (CRPS) and failed back surgery syndrome (FBSS) and recent data almost uniformly establishes its statistically significant positive therapeutic results. It has also been compared with other available treatment modalities across various studies. However, long term data on maintenance of its efficacious potential remains less explored. Few studies have reported data on long follow-up times (>= 12 months) and have compared its efficacy with other treatment options for chronic pain, respectively. Our study pools and analyzes the available data and compares SCS with other treatment options. It also analyzes the efficacy of SCS in long term management of patients with chronic pain.

EVIDENCE ACQUISITION

We reviewed all the data available on MEDLINE, Embase and Cochrane CENTRAL using a search strategy designed to fit our pre-set inclusion and exclusion criteria. Both single-arm and double-arm studies were included. The primary outcome was defined as decrease of visual analogue scale (VAS) by >50% at 6, 12 and/or 24 months after SCS.

EVIDENCE SYNTHESIS

According to the pooled data of double-arm studies, SCS has unanimously proven its superiority over other treatment options at 6 months follow-up; however it fails to prove statistically significant difference in results at longer treatment intervals. Dorsal root ganglion stimulation, a relatively recent technique with the same underlying physiologic mechanisms as SCS, showed far more promising results than SCS. Single-arm studies show around 70% patients experiencing greater than 50% reduction in their VAS scores at 6 and 12 months.

CONCLUSIONS

SCS is a viable option for management of chronic neuropathic pain secondary to FBSS and CRPS. However, data available for its long term efficacy remains scarce and show no further statistically significant results.

Painful Peripheral Neuropathies of the Lower Limbs and/or Lower Extremities Treated with Spinal Cord Stimulation: A Systematic Review with Narrative Synthesis

Introduction

Painful peripheral neuropathy (PPN) is a debilitating condition with varied etiologies. Spinal cord stimulation (SCS) is increasingly used when conservative treatments fail to provide adequate pain relief. Few published reviews have examined SCS outcomes in all forms of PPN.

Methods

We conducted a systematic review of SCS in PPN. The PubMed database was searched up to February 7th, 2022, for peer-reviewed studies of SCS that enrolled PPN patients with pain symptoms in their lower limbs and/or lower extremities. We assessed the quality of randomized controlled trial (RCT) evidence using the Cochrane risk of bias tool. Data were tabulated and presented narratively.

Results

Twenty eligible studies documented SCS treatment in PPN patients, including 10 kHz SCS, traditional low-frequency SCS (t-SCS), dorsal root ganglion stimulation (DRGS), and burst SCS. In total, 451 patients received a permanent implant (10 kHz SCS, n=267; t-SCS, n=147; DRGS, n=25; burst SCS, n=12). Approximately 88% of implanted patients had painful diabetic neuropathy (PDN). Overall, we found clinically meaningful pain relief (≥30%) with all SCS modalities. Among the studies, RCTs supported the use of 10 kHz SCS and t-SCS to treat PDN, with 10 kHz SCS providing a higher reduction in pain (76%) than t-SCS (38-55%). Pain relief with 10 kHz SCS and DRGS in other PPN etiologies ranged from 42-81%. In addition, 66-71% of PDN patients and 38% of nondiabetic PPN patients experienced neurological improvement with 10 kHz SCS.

Conclusion

Our review found clinically meaningful pain relief in PPN patients after SCS treatment. RCT evidence supported the use of 10 kHz SCS and t-SCS in the diabetic neuropathy subpopulation, with more robust pain relief evident with 10 kHz SCS. Outcomes in other PPN etiologies were also promising for 10 kHz SCS. In addition, a majority of PDN patients experienced neurological improvement with 10 kHz SCS, as did a notable subset of nondiabetic PPN patients.

Best Practices for Dorsal Root Ganglion Stimulation for Chronic Pain: Guidelines from the American Society of Pain and Neuroscience

With continued innovations in neuromodulation comes the need for evolving reviews of best practices. Dorsal root ganglion stimulation (DRG-S) has significantly improved the treatment of complex regional pain syndrome (CRPS), and it has broad applicability across a wide range of other conditions. Through funding and organizational leadership by the American Society for Pain and Neuroscience (ASPN), this best practices consensus document has been developed for the selection, implantation, and use of DRG stimulation for the treatment of chronic pain syndromes. This document is composed of a comprehensive narrative literature review that has been performed regarding the role of the DRG in chronic pain and the clinical evidence for DRG-S as a treatment for multiple pain etiologies. Best practice recommendations encompass safety management, implantation techniques, and mitigation of the potential complications reported in the literature. Looking to the future of neuromodulation, DRG-S holds promise as a robust intervention for otherwise intractable pain.

Thoracic dorsal root ganglion stimulation reduces acute myocardial ischemia induced ventricular arrhythmias

Background

Dorsal root ganglion stimulation (DRGS) may serve as a novel neuromodulation strategy to reduce cardiac sympathoexcitation and ventricular excitability.

Objective

In this pre-clinical study, we investigated the effectiveness of DRGS on reducing ventricular arrhythmias and modulating cardiac sympathetic hyperactivity caused by myocardial ischemia.

Methods

Twenty-three Yorkshire pigs were randomized to two groups, which was control LAD ischemia-reperfusion (CONTROL) or LAD ischemia-reperfusion + DRGS (DRGS) group. In the DRGS group (n = 10), high-frequency stimulation (1 kHz) at the second thoracic level (T2) was initiated 30 min before ischemia and continued throughout 1 h of ischemia and 2 h of reperfusion. Cardiac electrophysiological mapping and Ventricular Arrhythmia Score (VAS) were assessed, along with evaluation of cFos expression and apoptosis in the T2 spinal cord and DRG.

Results

DRGS decreased the magnitude of activation recovery interval (ARI) shortening in the ischemic region (CONTROL: -201 ± 9.8 ms, DRGS: -170 ± 9.4 ms, p = 0.0373) and decreased global dispersion of repolarization (DOR) at 30 min of myocardial ischemia (CONTROL: 9546 ± 763 ms2, DRGS: 6491 ± 636 ms2, p = 0.0076). DRGS also decreased ventricular arrhythmias (VAS-CONTROL: 8.9 ± 1.1, DRGS: 6.3 ± 1.0, p = 0.038). Immunohistochemistry studies showed that DRGS decreased % cFos with NeuN expression in the T2 spinal cord (p = 0.048) and the number of apoptotic cells in the DRG (p = 0.0084).

Conclusion

DRGS reduced the burden of myocardial ischemia-induced cardiac sympathoexcitation and has a potential to be a novel treatment option to reduce arrhythmogenesis.

Progress in the efficacy and mechanism of spinal cord stimulation in neuropathological pain

Neuropathic pain (NP) is a long-term recurrent disease caused by somatosensory nervous system injury, with spontaneous pain, hyperalgesia, ectopic pain, and paresthesia as the main clinical manifestations. It adversely affects patients' quality of life. NP treatments often include medication, physical therapy, and invasive therapy; the first two therapies are generally ineffective for some NP patients. These patients sometimes rely on invasive therapy to alleviate pain. Spinal cord stimulation (SCS) is a very effective therapeutic method. SCS is a neuroregulatory method that involves placing the electrodes on the corresponding painful spinal cords. Pain is greatly alleviated after SCS. SCS has been proven to be an effective therapeutic method for the treatment of neurological pain. Furthermore, SCS provides a feasible approach for patients with unsuccessful drug treatment. This paper reviews the relevant literature of spinal cord electrical stimulation, focusing on the mechanism of action, clinical application, clinical efficacy and technical progress of spinal cord electrical stimulation. SCS is widely used in the treatment of NP diseases such as postherpetic neuralgia, back surgery failure syndrome, and phantom limb pain. With advancements in science and technology, tremendous progress has also been made in the spinal cord electrical stimulation method and good momentum has been maintained.

Dorsal Root Ganglion Stimulation for Lower Extremity Neuropathic Pain Syndromes: An Evidence-Based Literature Review

Dorsal root ganglion stimulation (DRG-S) is a form of selective neuromodulation therapy that targets the dorsal root ganglion. DRG-S offers analgesia in a variety of chronic pain conditions and is approved for treatment of complex regional pain syndrome (CRPS) by the US Food and Drug Administration (FDA). There has been increasing utilization of DRG-S to treat various neuropathic pain syndromes of the lower extremity, although evidence remains limited to one randomized controlled trial and 39 observational studies. In this review, we appraised the current evidence for DRG-S in the treatment of lower extremity neuropathic pain using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) criteria. The primary outcome was change in pain intensity after DRG-S compared to baseline. We stratified presentation of results based of type of neuropathy (CRPS, painful diabetic neuropathy, mononeuropathy, polyneuropathy) as well as location of neuropathy (hip, knee, foot). Future powered randomized controlled trials with homogeneous participants are warranted.

Melatonin Moderates the Triangle of Chronic Pain, Sleep Architecture and Immunometabolic Traffic

Preclinical as well as human studies indicate that melatonin is essential for a physiological sleep state, promotes analgesia and is involved in immunometabolic signaling by regulating neuroinflammatory pathways. Experimental and clinical neuromodulation studies for chronic pain treatment suggest that neurostimulation therapies such as spinal cord stimulation, vagus nerve stimulation and dorsal root ganglion stimulation have an impact on circulating inflammatory mediators in blood, cerebrospinal fluid and saliva. Herein, we provide an overview of current literature relevant for the shared pathways of sleep, pain and immunometabolism and elaborate the impact of melatonin on the crossroad of sleep, chronic pain and immunometabolism. Furthermore, we discuss the potential of melatonin as an adjunct to neurostimulation therapies. In this narrative review, we addressed these questions using the following search terms: melatonin, sleep, immunometabolism, obesity, chronic pain, neuromodulation, neurostimulation, neuroinflammation, molecular inflammatory phenotyping. So far, the majority of the published literature is derived from experimental studies and studies specifically assessing these relationships in context to neurostimulation are sparse. Thus, the adjunct potential of melatonin in clinical neurostimulation has not been evaluated under the umbrella of randomized-controlled trials and deserves increased attention as melatonin interacts and shares pathways relevant for noninvasive and invasive neurostimulation therapies.

Management of Refractory Pain After Total Joint Replacement

PURPOSE OF REVIEW

Chronic pain after total joint replacement (TJA), specifically total knee replacement (TKA), is becoming more of a burden on patients, physicians, and the healthcare system as the number of joint replacements performed increases year after year. The management of this type of pain is critical, and therefore, understanding the various modalities physicians can use to help patients with refractory pain after TJA is essential.

RECENT FINDINGS

The modalities by which chronic pain can be successfully managed include genicular nerve radioablation therapy (GN-RFA), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and peripheral subcutaneous field stimulation (PSFS). Meta-analyses and case reports have demonstrated the effectiveness of these treatment options in improving pain and functional outcomes in patients with chronic pain after TKA. The purpose of this paper is to review and synthesize the current literature investigating the different ways that refractory pain is managed after TJA, with the goal being to provide treatment recommendations for providers treating these patients.

Dorsal Root Ganglion (DRG) and Chronic Pain

CONTEXT

Chronic neuropathic pain is a common condition, and up to 11.9% of the population have been reported to suffer from uncontrolled neuropathic pain. Chronic pain leads to significant morbidity, lowered quality of life, and loss of workdays, and thus carries a significant price tag in healthcare costs and lost productivity. dorsal root ganglia (DRG) stimulation has been recently increasingly reported and shows promising results in the alleviation of chronic pain. This paper reviews the background of DRG stimulation, anatomical, and clinical consideration and reviews the clinical evidence to support its use.

EVIDENCE ACQUISITION

The DRG span the length of the spinal cord and house the neurons responsible for sensation from the periphery. They may become irritated by direct compression or local inflammation. Glial cells in the DRG respond to nerve injury, producing inflammatory markers and contribute to the development of chronic pain, even after the resolution of the original insult. While the underlying mechanism is still being explored, recent studies explored the efficacy of DRG stimulation and neuromodulation for chronic pain treatment.

RESULTS

Several reported cases and a small number of randomized trials were published in recent years, describing different methods of DRG stimulation and neuromodulation with promising results. Though evidence quality is mostly low, these results provide evidence to support the utilization of this technique.

CONCLUSIONS

Chronic neuropathic pain is a common condition and carries significant morbidity and impact on the quality of life. Recent evidence supports the use of DRG neuromodulation as an effective technique to control chronic pain. Though studies are still emerging, the evidence appears to support this technique. Further studies, including large randomized trials evaluating DRG modulation versus other interventional and non-interventional techniques, are needed to further elucidate the efficacy of this method. These studies are also likely to inform the patient selection and the course of treatment.

Interventional Modalities to Treat Complex Regional Pain Syndrome

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) is a debilitating pain condition that often requires a multidisciplinary approach including medication, physical therapy, occupational therapy, psychological therapy, and interventional procedures to restore the patient's quality of life. This article reviews the interventional treatments for pain resulting from CRPS.

RECENT FINDINGS

Sympathetic nerve blocks (stellate ganglion and lumbar sympathetic) are the first-line interventional treatment options for patients with CRPS of the upper and lower extremities, respectively. Fluoroscopic techniques for lumbar sympathetic blocks have not significantly changed throughout the years. However, both novel fluoroscopic and ultrasound approaches to stellate ganglion blockade have arisen. In addition, novel neuromodulation therapies to treat CRPS have been developed to include new waveforms with dorsal column stimulation and entirely new nerve targets such as dorsal root ganglion stimulation. This paper will review the latest interventional treatment options available for the treatment of CRPS.

Quantitative sensory phenotyping in chronic neuropathic pain patients treated with unilateral L4-dorsal root ganglion stimulation

Background

In a previous study, we reported that selective dorsal root ganglion stimulation (DRG_STIM) at DRG level L4 promoted a favorable outcome for complex regional pain syndrome (CRPS) patients along with DRG_STIM-related changes of inflammatory biomarkers in blood and saliva. The impact on somatosensation is largely unknown. Herein, we assessed the quantitative sensory profile to quantify L4-DRG_STIM effects in CRPS patients.

Methods

Twelve refractory CRPS patients (4 female; 8 male; mean age 69 ± 9 years) received standardized quantitative sensory testing (QST) protocol at baseline and after 3 months of unilateral L4-DRG_STIM assessing nociceptive and non-nociceptive thermal and mechanical sensitivity of the knee affected by CRPS and the contralateral non-painful knee area.

Results

At baseline, CRPS subjects showed significantly increased thresholds for warmth, tactile and vibration detection (WDT, MDT and VDT) and exaggerated pain summation (WUR). After 3 months of unilateral L4-DRG_STIM all pain parameters exhibited trends towards normalization of sensitivity accumulating to a significant overall normalization for pain sensitivity (effect size: 0.91, p < 0.01), while with the one exception of WDT all non-nociceptive QST parameters remained unchanged. Overall change of non-nociceptive detection was negligible (effect size: 0.25, p > 0.40). Notably, reduction of pain summation (WUR) correlated significantly with pain reduction after 3 months of L4-DRG_STIM.

Conclusions

Selective L4-DRG_STIM lowered ongoing pain in CRPS patients and evoked significant normalization in the pain domain of the somatosensory profile. Thermoreception and mechanoreception remained unchanged. However, larger randomized, sham-controlled trials are highly warranted to shed more light on effects and mechanisms of dorsal root ganglion stimulation on quantitative sensory characteristics.

The study protocol was registered at the 15.11.2016 on German Register for Clinical Trials (DRKS ID 00011267).

https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00011267

Unilateral Dorsal Root Ganglion Stimulation Lead Placement With Resolution of Bilateral Lower Extremity Symptoms in Diabetic Peripheral Neuropathy

Dorsal root ganglion stimulation (DRG-S) is a form of neuromodulation that can target specific dermatomes to obtain better coverage of the distal extremity. Previously proposed mechanisms of action for DRG-S focused on the dorsal root ganglion (DRG) itself, without consideration of orthodromic effects in the dorsal horn and antidromic effects on the nerve root and sympathetic chain. Diabetic peripheral neuropathy (DPN) is an axonal neuropathy that affects around half of all patients with diabetes mellitus, causing severe pain and sensory impairment in the distal extremities. We present a case of a patient with DPN in both feet, in addition to low back pain, who underwent a DRG-S trial with right T12 and S1 leads. The trial was performed unilaterally for seven days, allowing the patient to compare the treated versus the untreated (left) side. Pain, disability, general health status, and quality of life measures improved significantly. In addition to the significant pain relief in the low back and feet, the patient had near resolution of other DPN-related symptoms, including numbness, bluish discoloration, and allodynia of both feet. He also demonstrated functional and psychological benefits with only a single-sided lead. Overall, the placement of unilateral T12 and S1 DRG-S leads resulted in symmetric improvement of DPN symptoms. A possible mechanism of action is antidromic propagation of action potential signaling into the sympathetic chain to a central ganglion and then to the contralateral sympathetic chain. Given the DRG's ability to directly affect afferent sympathetic fibers with low-frequency stimulation, DRG-S may be an effective neuromodulatory treatment for DPN.

A Prospective Analysis of the Use of Intraoperative Neuromonitoring for Mapping the S1 Dorsal Root Ganglion Location to Determine Ideal Lead Positioning and Predict Postoperative Programming

INTRODUCTION

The location of the sacral dorsal root ganglion (DRG) is variable and can range from a location in the canal to the foramen. It is therefore imperative to not only ensure a dorsal placement but also map the location of the DRG.

MATERIALS AND METHODS

This is a prospective analysis of the use of intraoperative neuromonitoring (IONM) being utilized in asleep patients to map the location of the S1 DRG with somatosensory evoked potential (SSEP) and electromyogram (EMG) thresholds, as well as comparing this with postoperative programming. These observations were then correlated with the position of the electrode contacts relative to the sacral border. It was performed in a single center with 12 lead placements in eight patients.

RESULTS

The IONM demonstrated that EMG thresholds decrease or stay the same as you stimulate more distal on the lead. Sensory signals are generated the majority of the time either proximal or on the sacral border. Postoperative programming correlated with the mapped location of the DRG on IONM, which was either posterior or on the sacral border. There was a single lead in which the IONM confirmed DRG location on the distal contact, which was anterior to the sacral border, and also correlated with postoperative programming.

CONCLUSIONS

This prospective analysis further demonstrates the utility and accuracy of IONM. The use of DRG IONM is reliable for confirming dorsal placement along the S1 DRG, mapping its position, and guiding postoperative programming. The S1 DRG is located at the border of the foramen and canal in most, but not all cases.

Synergetic efficacy of simultaneous DRG- and traditional spinal cord stimulation

BACKGROUND

Dorsal root ganglion stimulation has established its role in chronic pain states and is commonly used as an alternative treatment to traditional spinal cord stimulation. Due to its approach, DRG stimulation is preferably used in pain conditions affecting a small area or a distinct nerve root. In selected patients, a combination of both techniques might be useful.

METHODS

We report a series of five patients with chronic pain treated with DRG stimulation and traditional spinal cord stimulation from 2011 to 2018. Pain was reported on the VAS scale at the baseline, before and 12 months after the second procedure.

RESULTS

All patients suffered from back and lower limb pain, four with a FBSS syndrome, one with CRPS. In all but one patient, SCS was implanted first and complemented with a DRG in the course (4-90 months between procedures). An additional stimulation system was implanted because the previous stimulation failed to reach the pain area or because the patient had an altered perception of other pain component after stimulation. All but one patient had a consistent and satisfying therapeutic effect with both systems activated.

CONCLUSION

The combination of dorsal root ganglion and traditional spinal cord stimulation is surgically and technically feasible. In selected patients, the combination of both methods offers an option to alleviate pain states not sufficiently or not efficiently treated with one method alone. The introduction of IPGs combining SCS and DRG stimulation paradigms might be useful to increase acceptance of this option.

Unilateral L4-dorsal root ganglion stimulation evokes pain relief in chronic neuropathic postsurgical knee pain and changes of inflammatory markers: part II whole transcriptome profiling

Background

In our recent clinical trial, increased peripheral concentrations of pro-inflammatory molecular mediators were determined in complex regional pain syndrome (CRPS) patients. After 3 months adjunctive unilateral, selective L4 dorsal root ganglion stimulation (L4-DRG_STIM), significantly decreased serum IL-10 and increased saliva oxytocin levels were assessed along with an improved pain and functional state. The current study extended molecular profiling towards gene expression analysis of genes known to be involved in the gonadotropin releasing hormone receptor and neuroinflammatory (cytokines/chemokines) signaling pathways.

Methods

Blood samples were collected from 12 CRPS patients for whole-transcriptome profiling in order to assay 18,845 inflammation-associated genes from frozen blood at baseline and after 3 months L4-DRG_STIM using PANTHER™ pathway enrichment analysis tool.

Results

Pathway enrichment analyses tools (GOrilla™ and PANTHER™) showed predominant involvement of inflammation mediated by chemokines/cytokines and gonadotropin releasing hormone receptor pathways. Further, screening of differentially regulated genes showed changes in innate immune response related genes. Transcriptomic analysis showed that 21 genes (predominantly immunoinflammatory) were significantly changed after L4-DRG_STIM. Seven genes including TLR1, FFAR2, IL1RAP, ILRN, C5, PKB and IL18 were down regulated and fourteen genes including CXCL2, CCL11, IL36G, CRP, SCGB1A1, IL-17F, TNFRSF4, PLA2G2A, CREB3L3, ADAMTS12, IL1F10, NOX1, CHIA and BDKRB1 were upregulated.

Conclusions

In our sub-group analysis of L4-DRG_STIM treated CRPS patients, we found either upregulated or downregulated genes involved in immunoinflammatory circuits relevant for the pathophysiology of CRPS indicating a possible relation. However, large biobank-based approaches are recommended to establish genetic phenotyping as a quantitative outcome measure in CRPS patients.

Trial registration The study protocol was registered at the 15.11.2016 on German Register for Clinical Trials (DRKS ID 00011267). https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00011267