Safety and efficacy of spinal cord stimulation for the treatment of chronic pain: a 20-year literature review

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.

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.

Device-Related Complications Associated with Cylindrical Lead Spinal Cord Stimulator Implants: A Comprehensive Review

PURPOSE OF REVIEW

Spinal cord stimulation (SCS) is an increasingly utilized therapy for the treatment of neuropathic pain conditions. Though minimally invasive and reversable, there are several important device-related complications that physicians should be aware of before offering this therapy to patients. The aim of this review is to synthesize recent studies in device-related SCS complications pertaining to cylindrical lead implantation and to discuss etiologies, symptoms and presentations, diagnostic evaluation, clinical implications, and treatment options.

RECENT FINDINGS

Device-related complications are more common than biologic complications. Device-related complications covered in this review include lead migration, lead fracture, lead disconnection, generator failure, loss of charge, generator flipping, hardware related pain, and paresthesia intolerance. The use of SCS continues to be an effective option for neuropathic pain conditions. Consideration of complications prior to moving forward with SCS trials and implantation is a vital part of patient management and device selection. Knowledge of these complications can provide physicians and other healthcare professionals the ability to maximize patient outcomes.

6. Persistent spinal pain syndrome type 2

INTRODUCTION

Persistent Spinal Pain Syndrome (PSPS) refers to chronic axial pain and/or extremity pain. Two subtypes have been defined: PSPS-type 1 is chronic pain without previous spinal surgery and PSPS-type 2 is chronic pain, persisting after spine surgery, and is formerly known as Failed Back Surgery Syndrome (FBSS) or post-laminectomy syndrome. The etiology of PSPS-type 2 can be gleaned using elements from the patient history, physical examination, and additional medical imaging. Origins of persistent pain following spinal surgery may be categorized into an inappropriate procedure (eg a lumbar fusion at an incorrect level or for sacroiliac joint [SIJ] pain); technical failure (eg operation at non-affected levels, retained disk fragment, pseudoarthrosis), biomechanical sequelae of surgery (eg adjacent segment disease or SIJ pain after a fusion to the sacrum, muscle wasting, spinal instability); and complications (eg battered root syndrome, excessive epidural fibrosis, and arachnoiditis), or undetermined.

METHODS

The literature on the diagnosis and treatment of PSPS-type 2 was retrieved and summarized.

RESULTS

There is low-quality evidence for the efficacy of conservative treatments including exercise, rehabilitation, manipulation, and behavioral therapy, and very limited evidence for the pharmacological treatment of PSPS-type 2. Interventional treatments such as pulsed radiofrequency (PRF) of the dorsal root ganglia, epidural adhesiolysis, and spinal endoscopy (epiduroscopy) might be beneficial in patients with PSPS-type 2. Spinal cord stimulation (SCS) has been shown to be an effective treatment for chronic, intractable neuropathic limb pain, and possibly well-selected candidates with axial pain.

CONCLUSIONS

The diagnosis of PSPS-type 2 is based on patient history, clinical examination, and medical imaging. Low-quality evidence exists for conservative interventions. Pulsed radiofrequency, adhesiolysis and SCS have a higher level of evidence with a high safety margin and should be considered as interventional treatment options when conservative treatment fails.

Cervical Spinal Cord Stimulation: A Review

PURPOSE OF REVIEW

This literature review critically examines existing studies on cervical spinal cord stimulation (cSCS) for the treatment of chronic pain. The objective is to evaluate the current evidence, identify knowledge gaps, and collate data to inform clinical decision-making and suggest future research avenues. The review covers indications, contraindications, surgical and anesthetic approaches, trials, efficacy, and complications of cSCS.

RECENT FINDINGS

Recent advancements highlight the evolving role of cSCS in chronic pain management. New neuromodulation techniques involve optimal placement of leads based on the pain's innervation level, maximizing therapeutic outcomes. Contemporary studies underscore the broadening benefits of cSCS, including enhanced functional abilities and sleep quality. However, alongside these innovations come challenges; emerging data bring attention to complications such as hardware issues and infections. Significantly, modern research emphasizes the crucial role of accurate patient selection, factoring in prior therapy responses and comprehensive evaluations. cSCS emerges as a promising tool for chronic pain management, with benefits beyond mere pain relief. As surgical techniques, patient selection criteria, and postoperative care refine, the potential of cSCS expands to benefit a broader patient demographic. However, further comprehensive research is necessary to enhance its application, validate its role earlier in treatment, and ultimately ameliorate the lives of those with chronic pain.

Case report: Dorsal root ganglion stimulator lead fracture

BACKGROUND

One of the unique advances in neuromodulation for chronic pain has been spinal cord stimulators (SCS) and dorsal root ganglion stimulators (DRG-S). These devices have aided in conditions such as neuropathic pain, complex regional pain syndromes, failed back surgery, and peripheral neuropathies. With these benefits, however, complications from implantable stimulators have included lead fractures and migration. The authors reviewed a lead migration, kinking, and subsequent fracture event involving a patient with complex regional pain syndrome (CRPS) II, who was treated with a DRG-S.

CASE PRESENTATION

The case report follows this patient, from their past medical history to assessment of appropriate qualifications for neuromodulation, to successful surgical placement, to follow-up care. The authors further monitored assessment of inefficacy of pain relief, and identification of lead migration and kinking through imaging. In the process of removal, due to lead stress, lead fracturing occurred. After lead removal, the leads were fully replaced, and the patient was followed up and experienced improved pain relief.

CONCLUSION

The case report assesses probable mechanisms of lead fracture and considerations for physicians for future assessment and triage of neuromodulation efficacy.

Pocket pain following spinal cord stimulator generator implantation: A narrative review of this under-reported risk

INTRODUCTION

Spinal cord stimulation (SCS) is a well-established treatment option for chronic pain. Pain over the implantable pulse generator, or pocket pain, is an incompletely understood risk of SCS implantation which may limit the efficacy of treatment and patient quality of life. The goal of this narrative review is to analyze the literature to gain a more thorough understanding of the incidence and risk factors for the development of pocket pain to help guide treatment options and minimize its occurrence in the future.

METHODS

A literature review was conducted investigating the development of pocket pain in patients with SCS for the management of a variety of pain conditions.

RESULTS

In total, 305 articles were included in the original database search and 50 met the criteria for inclusion. The highest level of evidence for papers that specifically investigated pocket pain was level III. Four retrospective, observational analyses included pocket pain as a primary outcome. The remainder of the included studies listed pocket pain as an adverse event of SCS implantation.

CONCLUSIONS

There is a relative dearth of primary literature that examines the incidence, characteristics, and health economic implications of pocket pain in patients with SCS. This highlights the need for large-scale, high-quality prospective or randomized controlled trials examining pocket pain. This may ultimately help prevent and reduce pocket pain leading to improved efficacy of treatment and greater patient quality of life.

1. Lumbosacral radicular pain

INTRODUCTION

Patients suffering lumbosacral radicular pain report radiating pain in one or more lumbar or sacral dermatomes. In the general population, low back pain with leg pain extending below the knee has an annual prevalence that varies from 9.9% to 25%.

METHODS

The literature on the diagnosis and treatment of lumbosacral radicular pain was reviewed and summarized.

RESULTS

Although a patient's history, the pain distribution pattern, and clinical examination may yield a presumptive diagnosis of lumbosacral radicular pain, additional clinical tests may be required. Medical imaging studies can demonstrate or exclude specific underlying pathologies and identify nerve root irritation, while selective diagnostic nerve root blocks can be used to confirm the affected level(s). In subacute lumbosacral radicular pain, transforaminal corticosteroid administration provides short-term pain relief and improves mobility. In chronic lumbosacral radicular pain, pulsed radiofrequency (PRF) treatment adjacent to the spinal ganglion (DRG) can provide pain relief for a longer period in well-selected patients. In cases of refractory pain, epidural adhesiolysis and spinal cord stimulation can be considered in experienced centers.

CONCLUSIONS

The diagnosis of lumbosacral radicular pain is based on a combination of history, clinical examination, and additional investigations. Epidural steroids can be considered for subacute lumbosacral radicular pain. In chronic lumbosacral radicular pain, PRF adjacent to the DRG is recommended. SCS and epidural adhesiolysis can be considered for cases of refractory pain in specialized centers.

Complications of Spinal Cord Stimulators-A Comprehensive Review Article

PURPOSE OF REVIEW

Spinal cord stimulation has been increasing in influence as an option to regulate pain, especially in the chronic pain patient population. However, even with the numerous changes made to this technology since its inception, it is still prone to various complications such as hardware issues, neurological injury/epidural hematoma, infections, and other biological concerns. The purpose of this article is to thoroughly review and evaluate literature pertaining to the complications associated with percutaneous spinal cord stimulation.

RECENT FINDINGS

Lead migration is generally the most common complication of percutaneous spinal cord stimulation; however, recent utilization of various anchoring techniques has been discussed and experienced clinical success in decreasing the prevalence of lead migration and lead fractures. With newer high-frequency systems gaining traction to improve pain management and decrease complications as compared to traditional systems, rechargeable implantable pulse generators have been the preferred power source. However, recent findings may suggest that these rechargeable implantable pulse generators do not significantly increase battery life as much as was proposed. Intraoperative neuromonitoring has seen success in mitigating neurological injury postoperatively and may see more usage in the future through more testing. Though the occurrence of infection and biological complications, including dural puncture and skin erosion, has been less frequent over time, they should still be treated in accordance with established protocols. While many complications can arise following percutaneous spinal cord stimulator implantation, the procedure is less invasive than open implantation and has seen largely positive patient feedback. Hardware complications, the more common issues that can occur, rarely indicate a serious risk and can generally be remedied through reoperation. However, less common cases such as neurological injury, infections, and biological complications require prompt diagnosis to improve the condition of the patient and prevent significant damage.

A Review on Implantable Neuroelectrodes

The efficacy of every neuromodulation modality depends upon the characteristics of the electrodes used to stimulate the chosen target. The geometrical, chemical, mechanical and physical configuration of electrodes used in neurostimulation affects several performance attributes like stimulation efficiency, selectivity, tissue response, etc. The efficiency of stimulation in relation to electrode impedance is influenced by the electrode material and/or its geometry. The nature of the electrode material determines the charge transfer across the electrode-tissue interface, which also relates to neuronal tissue damage. Electrode morphology or configuration pattern can facilitate the modulation of extracellular electric field (field shaping). This enables selective activation of neurons and minimizes side effects. Biocompatibility and biostability of the electrode materials or electrode coating have a role in glial formation and tissue damage. Mechanical and electrochemical stability (corrosion resistance) determines the long-term efficacy of any neuromodulation technique. Here, a review of electrodes typically used for implantable neuromodulation is discussed. Factors affecting the performance of electrodes like stimulation efficiency, selectivity and tissue responses to the electrode-tissue interface are discussed. Technological advancements to improve electrode characteristics are also included.

High-Performing and Capacitive-Matched Triboelectric Implants Driven by Ultrasound

In implantable bioelectronics, which aim for semipermanent use of devices, biosafe energy sources and packaging materials to protect devices are essential elements. However, research so far has been conducted in a direction where they cannot coexist. Here, the development of capacitance-matched triboelectric implants driven is reported by ultrasound under 500 mW cm-2 safe intensity and realize a battery-free, miniatured, and wireless neurostimulator with full titanium (Ti) packaging. The triboelectric implant with high dielectric composite, which has ultralow output impedance, can efficiently deliver sufficient power to generate the stimulation pulse without an energy-storing battery, despite ultrasound attenuation due to the Ti, and has the highest energy transmission efficiency among those reported so far. In vivo study using a rat model demonstrated that the proposed device system is an effective solution for relieving urinary symptoms. These achievements provide a significant step toward permanently implantable devices for controlling human organs and treating various diseases.

History and Future of Spinal Cord Stimulation

Spinal cord stimulation (SCS) is a surgical treatment for chronic neuropathic pain refractory to medical management. An SCS system comprised one or more leads implanted in the epidural space, typically connected to an implantable pulse generator. This review discusses the history, indications, surgical technique, technological advances, and future directions of SCS.

The contralateral oblique fluoroscopic view is associated with a lower incidence of postdural puncture headache in patients undergoing percutaneous spinal cord stimulation

BACKGROUND

Spinal cord stimulation (SCS) is a minimally invasive therapy that is increasingly used to treat refractory neuropathic pain. Although this technique has a low incidence of serious long-term adverse sequelae, the risk of complications such as inadvertent dural puncture remains.

OBJECTIVES

The goal of this article was to determine the impact of the contralateral oblique (CLO) fluoroscopic view incidence of postdural puncture headache (PDPH) during spinal cord stimulator implantation as compared to lateral fluoroscopic view.

METHODS

This was a single academic institution retrospective analysis of electronic medical records spanning an approximate 20-year time period. Operative and postoperative notes were reviewed for details on dural puncture, including technique and spinal level of access, the development of a PDPH, and subsequent management.

RESULTS

Over nearly two decades, a total of 1637 leads inserted resulted in 5 PDPH that were refractory to conservative measures but responded to epidural blood patch without long-term complications. The incidence of PDPH per lead insertion utilizing loss of resistance and lateral fluoroscopic guidance was 0.8% (4/489). However, adoption of CLO guidance was associated with a lower rate of PDPH at 0.08% (1/1148), p < 0.02.

CONCLUSIONS

The incorporation of the CLO view to guide epidural needle placement can decrease the odds of a PDPH during percutaneous SCS procedures. This study further provides real-world data supporting the potential enhanced accuracy of epidural needle placement in order to avoid unintentional puncture or trauma to deeper spinal anatomic structures.

Incidence of Infections, Explantations, and Displacements/Mechanical Complications of Spinal Cord Stimulation During the Past Eight Years

OBJECTIVES

The overall awareness and potential of real-world data have drastically increased in the medical field, with potential implications for postmarket medical device surveillance. The goal of this study was to evaluate real-world data on incidence of infections, explantations, and displacements/mechanical complications of spinal cord stimulation (SCS) during the past eight years and to forecast point estimates for the upcoming three years on the basis of the identified patterns.

MATERIALS AND METHODS

Based on electronic health records from 80 healthcare organizations within the TriNetX data base in the USA, data of 11,934 patients who received SCS as treatment for persistent spinal pain syndrome type 2 (PSPS T2) were extracted. Events of interest were explantations and displacements/mechanical complications of both the lead and implanted pulse generator (IPG), in addition to infection rates from 2015 to 2022. Mann-Kendall tests were performed to detect monotonic trends in the time series. Forecasts were conducted for the upcoming three years for every event of interest.

RESULTS

Statistically significant increasing time trends were revealed for the annual incidence of IPG and lead displacements/mechanical complications in patients with PSPS T2 over the past eight years. These time trends were visible in both male and female patients and in smokers and nonsmokers. For annual incidence of explantations and infections, no significant time effect was observed. In 2025, the incidence of displacements/mechanical complications of the lead (3.07%) is predicted to be the highest, followed by explantations of the IPG (2.67%) and lead (2.02%).

CONCLUSIONS

Based on real world data, device explantation was the most frequent event of interest, with negative peaks in the time series in 2016 and 2020, presumably due to the introduction of rechargeable pulse generators and to the COVID-19 pandemic, respectively.

Long-Term Outcome in Patients With Spinal Cord Stimulation for Failed Back Surgery Syndrome: A 20-Year Audit of a Single Center

STUDY DESIGN

This is a retrospective, observational study.

INTRODUCTION

Spinal cord stimulation (SCS) has found its application in chronic pain treatment, with failed back surgery syndrome (FBSS) as one of the most important indications. However, to date, little is known about the long-term effectiveness of the treatment. The aim of this study is to analyze retrospectively the long-term outcomes of SCS treatment in a single multidisciplinary pain center on predominant radicular pain, using devices of a single manufacturer.

MATERIALS AND METHODS

Patient data on overall patient satisfaction, pain intensity, and adverse events were retrospectively collected in our clinical practice between January 1998 and January 2018, for 191 patients who received a permanent SCS implant. Secondary health measures included the influence of opioid and nicotine use on pain reduction after therapy.

RESULTS

The trial-to-implant ratio was 93.6%. At a mean follow-up of 10.6 years, 78.5% of the patients were satisfied with the treatment outcome, with a significant pain reduction of an average three points on a Numeric Rating Scale. Opioid and nicotine usage did not have a significant link with the pain reduction one year after the treatment. Furthermore, devices had an average battery lifespan of 8.4 years. A total of 248 revisions were recorded. A total of 24 patients (11.7%) acquired an infection; 7 of 204 patients had an infection during the trial period, 2 of 191 patients had an infection in the first postoperative year, and 15 of 191 patients had an infection after the first year. The average time to infection, if not in the first year, was 10.1 years.

CONCLUSIONS

A successful long-term outcome regarding pain relief in patients with predominant radicular pain due to FBSS is established with SCS therapy.

Dorsal root ganglion stimulation for the treatment of chronic pelvic pain: A systematic review

BACKGROUND

Chronic pelvic pain (CPP) is a difficult condition to treat. Due to complex pelvic innervation, dorsal column spinal cord stimulation (SCS) has not been shown to produce the same effect as dorsal root ganglion stimulation (DRGS) given emerging evidence suggesting that applying DRGS may result in favorable outcomes for individuals with CPP. The aim of this systematic review is to investigate the clinical use and effectiveness of DRGS for patients with CPP.

MATERIALS AND METHODS

A systematic review of clinical studies demonstrating the use of DRGS for CPP. Searches were conducted using four electronic databases (PubMed, EMBASE, CINAHL, and Web of Science) across August and September 2022.

RESULTS

A total of nine studies comprising 65 total patients with variable pelvic pain etiologies met the inclusion criteria. The majority of subjects implanted with DRGS reported >50% mean pain reduction at variable times of follow-up. Secondary outcomes reported throughout studies including quality of life (QOL) and pain medication consumption were reported to be significantly improved.

CONCLUSIONS

Dorsal root ganglion stimulation for CPP continues to lack supportive evidence from well-designed, high-quality studies and recommendations from consensus committee experts. However, we present consistent evidence from level IV studies showing success with the use of DRGS for CPP in reducing pain symptoms along with reports of improved QOL through periods as short as 2 months to as long as 3 years. Because the available studies at this time are of low quality with a high risk of bias, we strongly recommend the facilitation of high-quality studies with larger sample sizes in order to better ascertain the utility of DRGS for this specific patient population. At the same time, from a clinical perspective, it may be reasonable and appropriate to evaluate patients for DRGS candidacy on a case-by-case basis, especially those patients who report CPP symptoms that are refractory to noninterventional measures and who may not be ideal candidates for other forms of neuromodulation.

Development of a Modified Bayonet Forceps for Improving Steerability of Paddle Lead Electrodes During Spinal Cord Stimulator Surgery: A Technical Note

BACKGROUND AND OBJECTIVE

Despite recent advancements in spinal cord stimulation (SCS) technology, the surgical instrumentation for placement of SCS paddle leads remains suboptimal. Therefore, we developed a novel instrument to improve the steerability of SCS paddle leads during surgical placement.

METHODS

A review of existing literature was performed to analyze workflow deficiencies in the standard instrumentation of SCS paddle lead placement. After a period of adaptation and iterative feedback with a medical instrument company, a new instrument was developed, tested at benchtop, and successfully incorporated into the surgical routine.

RESULTS

A standard bayonet forceps was modified to include hooked ends and a ribbed surface, providing the surgeon with greater control over the paddle lead. The new instrument also included bilateral metal tubes starting approximately 4 cm proximal from the edge of the forceps. The bilateral metal tubes, through which the SCS paddle lead wires are passed, serve as anchors to keep the wires away from the incision site. In addition, it permitted the paddle lead to assume a bent configuration, reducing its overall size and allowing it to be placed through a smaller incision and laminectomy. The modified bayonet forceps was successfully used intraoperatively for placement of SCS paddle lead electrodes in several surgeries.

CONCLUSION

The proposed modified bayonet forceps increased steerability of the paddle lead, facilitating optimal midline placement. The bent configuration of the device facilitated a more minimally invasive surgical approach. Future studies are needed to validate our single-provider experience and evaluate the impact of this new instrument on operating room efficiency.

The Invasive Management of Pain: Diagnosis and New Treatment Options

Both the diagnosis and treatment of pain are evolving, especially in interventional approaches. Diagnosis of low back pain combines old and new methodologies, in particular, it involves an expanded role for ultrasound. While low back pain is a common complaint, there are many etiologies to the condition which must be explored before a final diagnosis can be made and treatment planned. Tumors and infections are rarely involved in low back pain but should be ruled out in the initial phase itself since failing to address them early can have devastating consequences. Some invasive treatments seem promising in the management of low back pain. Treating musculoskeletal pain with regenerative medicine, such as platelet-rich plasma, holds great promise. Autologous blood products are safe and may help stimulate the body's own responses for regeneration. The so-called "orthobiologics" play a role in sports medicine and the treatment of musculoskeletal pain. Neuromodulation, especially spinal cord stimulation, is undergoing a renaissance with new waveforms, devices, and a greater albeit incomplete understanding of its mechanisms of action. Spinal cord stimulation is not a first-line therapy and not all patients or all back problems respond to this treatment. Nevertheless, the therapy can be safe, effective, and cost-effective with appropriate patient selection. Radiofrequency ablation of nerves in the form of neurotomy can be effective in reducing the pain of osteoarthritis. These procedures, including the newer cooled radiofrequency neurotomy, can restore function, reduce pain, and may potentially have an opioid-sparing effect. Technical expertise in nerve and anatomy is needed for the use of this technique. This review article aims to provide updated information on some invasive intervention techniques in pain management.

Risk factors for surgical site infection in advanced neuromodulation pain procedures: a retrospective study

Aim: To assess the effects of diabetes mellitus (DM) and related variables on surgical site infection (SSI) risk in neuromodulation. Methods: This retrospective study followed patients who underwent neuromodulation procedures for at least 9 months to identify postoperative infections. Demographics, clinical characteristics and surgical outcomes were compared. Results: Of 195 cases included, 5 (2.6%) resulted in SSIs. Median HbA1c was significantly higher for the cases with SSIs (8.2 vs 5.6%; p = 0.0044). The rate of SSI was significantly higher among patients with DM (17.9 vs 0%; p = 0.0005), HbA1c≥7% (37.5 vs 0%; p = 0.0009), and perioperative glucose ≥200 mg/dl (40 vs 2.3%; p = 0.0101). Conclusion: DM, elevated HbA1c and perioperative hyperglycemia may all contribute to increased risk of SSIs with neuromodulation procedures.

Research hotspots and trends on spinal cord stimulation for pain treatment: a two-decade bibliometric analysis

Background

Chronic pain poses a significant social burden. Spinal cord stimulation (SCS) is considered to be the most promising treatment for refractory pain. The aim of this study was to summarize the current research hotspots on SCS for pain treatment during the past two decades and to predict the future research trends by bibliometric analysis.

Methods

The literature over the last two decades (2002-2022) which was related to SCS in pain treatment was obtained from the Web of Science Core Collection. Bibliometric analyses were conducted based on the following aspects: (1) Annual publication and citation trends; (2) Annual publication changes of different publication types; (3) Publications and citations/co-citations of different country/institution/journal/author; (4) Citations/co-citation and citation burst analysis of different literature; and (5) Co-occurrence, cluster, thematic map, trend topics, and citation burst analysis of different keywords. (6) Comparison between the United States and Europe. All analyses were performed on CiteSpace, VOSviewer, and R bibliometrix package.

Results

A total of 1,392 articles were included in this study, with an increasing number of publications and citations year by year. The most highly published type of literature was clinical trial. United States was the country with the most publications and citations; Johns Hopkins University was the institution with the most publications; NEUROMODULATION published the most papers; the most published author was Linderoth B; and the most cited paper was published in the PAIN by Kumar K in 2007. The most frequently occurring keywords were "spinal cord stimulation," "neuropathic pain," and "chronic pain," etc.

Conclusion

The positive effect of SCS on pain treatment has continued to arouse the enthusiasm of researchers in this field. Future research should focus on the development of new technologies, innovative applications, and clinical trials for SCS. This study might facilitate researchers to comprehensively understand the overall perspective, research hotspots, and future development trends in this field, as well as seek collaboration with other researchers.

sPinal coRd stimulatiOn coMpared with lumbar InStrumEntation for low back pain after previous lumbar decompression (PROMISE): a prospective multicentre RCT

INTRODUCTION

Persistent spine pain syndrome type 2 (PSPS2) represents a significant burden to the individual and society. Treatment options include revision surgery, stabilisation surgery of the spine, neuromodulation, analgesics and cognitive behavioural therapy. Nevertheless, structured treatment algorithms are missing as high-level evidence on the various treatments is sparse. The aim of this study is to compare higher frequency neuromodulation with instrumentation surgery in patients suffering from PSPS2.

METHODS AND ANALYSIS

The sPinal coRd stimulatiOn coMpared with lumbar InStrumEntation for low back pain after previous lumbar decompression (PROMISE) trial is a prospective randomised rater blinded multicentre study. Patients suffering from PSPS2 with a functional burden of Oswestry Disability Index (ODI) >20 points are randomised to treatment via spinal cord stimulation or spinal instrumentation. Primary outcome is back-related functional outcome according to the ODI 12 months after treatment. Secondary outcomes include pain perception (visual analogue scale), Short Form-36, EuroQOL5D, the amount of analgesics, the length of periprocedural hospitalisation and adverse events. Follow-up visits are planned at 3 and 12 months after treatment. Patients with previous lumbar instrumentation, symptomatic spinal stenosis, radiographical apparent spinal instability or severe psychiatric or systemic comorbidities are excluded from the study. In order to detect a significant difference of ≥10 points (ODI) with a power of 80%, n=72 patients need to be included. The recruitment period will be 24 months with a subsequent 12 months follow-up. The beginning of enrolment is planned for October 2022.

ETHICS AND DISSEMINATION

The PROMISE trial is the first randomised rater blinded multicentre study comparing the functional effectiveness of spinal instrumentation versus neuromodulation in patients with PSPS2 in order to achieve high-level evidence for these commonly used treatment options in this severely disabling condition. Patient recruitment will be performed at regular outpatient clinic visits. No further (print, social media) publicity is planned. The study is approved by the local ethics committee (LMU Munich, Germany) and will be conducted according to the Declaration of Helsinki.

TRIAL REGISTRATION NUMBER

NCT05466110.

Steering Toward Normative Wide-Dynamic-Range Neuron Activity in Nerve-Injured Rats With Closed-Loop Peripheral Nerve Stimulation

OBJECTIVES

Chronic pain is primarily treated with pharmaceuticals, but the effects remain unsatisfactory. A promising alternative therapy is peripheral nerve stimulation (PNS), but it has been associated with suboptimal efficacy because its modulation mechanisms are not clear and the current therapies are primarily open loop (ie, manually adjusting the stimulation parameters). In this study, we developed a proof-of-concept computational modeling as the first step toward implementing closed-loop PNS in future biological studies. When developing new pain therapies, a useful pain biomarker is the wide-dynamic-range (WDR) neuron activity in the dorsal horn. In healthy animals, the WDR neuron activity occurs in a stereotyped manner; however, this response profile can vary widely after nerve injury to create a chronic pain condition. We hypothesized that if injury-induced changes of neuronal response can be normalized to resemble those of a healthy condition, the pathological aspects of pain may be treated while maintaining protective physiological nociception.

MATERIALS AND METHODS

Using an in vivo electrophysiology data set of WDR neuron recordings obtained in nerve-injured rats and naïve rats, we constructed sets of linear phenomenologic models of WDR firing rate during windup stimulation for both conditions. Then, we applied robust control systems techniques to identify a closed-loop PNS controller, which can drive the dynamics of WDR neuron response in neuropathic pain model into ranges associated with normal physiological pain.

RESULTS

The sets of identified linear models can accurately predict, in silico, nonlinear neural responses to electrical stimulation of the peripheral nerve. In addition, we showed that continuous closed-loop control of PNS can be used to normalize WDR neuron firing responses in three injured cases.

CONCLUSIONS

In this proof-of-concept study, we show how tractable, linear mathematical models of pain-related neurotransmission can be used to inform the development of closed-loop PNS. This new application of robust control to neurotechnology may also be expanded and applied across other neuromodulation applications.

Role of patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain: a comprehensive narrative review

Background/importance

Patient selection for spinal cord stimulation (SCS) therapy is crucial and is traditionally performed with clinical selection followed by a screening trial. The factors influencing patient selection and the importance of trialing have not been systematically evaluated.

Objective

We report a narrative review conducted to synthesize evidence regarding patient selection and the role of SCS trials.

Evidence review

Medline, EMBASE and Cochrane databases were searched for reports (any design) of SCS in adult patients, from their inception until March 30, 2022. Study selection and data extraction were carried out using DistillerSR. Data were organized into tables and narrative summaries, categorized by study design. Importance of patient variables and trialing was considered by looking at their influence on the long-term therapy success.

Findings

Among 7321 citations, 201 reports consisting of 60 systematic reviews, 36 randomized controlled trials (RCTs), 41 observational studies (OSs), 51 registry-based reports, and 13 case reports on complications during trialing were included. Based on RCTs and OSs, the median trial success rate was 72% and 82%, and therapy success was 65% and 61% at 12 months, respectively. Although several psychological and non-psychological determinants have been investigated, studies do not report a consistent approach to patient selection. Among psychological factors, untreated depression was associated with poor long-term outcomes, but the effect of others was inconsistent. Most RCTs except for chronic angina involved trialing and only one RCT compared patient selection with or without trial. The median (range) trial duration was 10 (0–30) and 7 (0–56) days among RCTs and OSs, respectively.

Conclusions

Due to lack of a consistent approach to identify responders for SCS therapy, trialing complements patient selection to exclude patients who do not find the therapy helpful and/or intolerant of the SCS system. However, more rigorous and large studies are necessary to better evaluate its role.

Spinal cord stimulator malfunction as a result of lead fracture: a case report

Spinal cord stimulation is a successful and thoroughly documented procedure in treating chronic refractory pain. Complications are rare and usually mild, but hardware complications such as electrode dysfunction have been shown to be detrimental in treatment efficacy and patient outcome. We report a case in which a patient diagnosed with complex regional pain syndrome underwent spinal cord stimulation for pain management and experienced lead migration and fracture, resulting in loss of paresthesia and increased pain. This case provides useful clinical information on identifying electrode dysfunction in patients with implanted spinal cord stimulators and emphasizes the importance of preventative measures to reduce the risk of similar complications.

Interventional Pain Procedures: A Narrative Review Focusing On Safety and Complications. PART 2 Interventional Procedures For Back Pain

In patients where conservative approaches have failed to relieve from chronic pain, interventional procedures may be an option in well selected patients. In recent years there has been an increase in the use and development of invasive procedures. Concomitantly, there has also been an increase in the complications associated with these procedures. Taken this into consideration, it is important for healthcare providers to take a cautious and vigilant approach, with a focus on patient safety, in order to minimize the risk of adverse events and ensure the best possible outcome for the patient. This may include careful selection of patients for procedures, use of proper techniques and equipment, and close monitoring and follow-up after the procedure. The aim of this narrative review is to summarize the primary complications associated with commonly performed image-guided (fluoroscopy or ultrasound-guided) interventional procedures and provide strategies to reduce the risk of these complications. We conclude that although complications from interventional pain procedures can be mitigated to a certain degree, they cannot be eliminated altogether. In order to avoid adverse events, patient safety should be given considerable attention and physicians should be constantly aware of the possibility of developing complications.

Making a case for endovascular approaches for neural recording and stimulation

There are many electrode types for recording and stimulating neural tissue, most of which necessitate direct contact with the target tissue. These electrodes range from large, scalp electrodes which are used to non-invasively record averaged, low frequency electrical signals from large areas/volumes of the brain, to penetrating microelectrodes which are implanted directly into neural tissue and interface with one or a few neurons. With the exception of scalp electrodes (which provide very low-resolution recordings), each of these electrodes requires a highly invasive, open brain surgical procedure for implantation, which is accompanied by significant risk to the patient. To mitigate this risk, a minimally invasive endovascular approach can be used. Several types of endovascular electrodes have been developed to be delivered into the blood vessels in the brain via a standard catheterization procedure. In this review, the existing body of research on the development and application of endovascular electrodes is presented. The capabilities of each of these endovascular electrodes is compared to commonly used direct-contact electrodes to demonstrate the relative efficacy of the devices. Potential clinical applications of endovascular recording and stimulation and the advantages of endovascular versus direct-contact approaches are presented.

Methods and system for recording human physiological signals from implantable leads during spinal cord stimulation

Objectives

This article presents a method-including hardware configuration, sampling rate, filtering settings, and other data analysis techniques-to measure evoked compound action potentials (ECAPs) during spinal cord stimulation (SCS) in humans with externalized percutaneous electrodes. The goal is to provide a robust and standardized protocol for measuring ECAPs on the non-stimulation contacts and to demonstrate how measured signals depend on hardware and processing decisions.

Methods

Two participants were implanted with percutaneous leads for the treatment of chronic pain with externalized leads during a trial period for stimulation and recording. The leads were connected to a Neuralynx ATLAS system allowing us to simultaneously stimulate and record through selected electrodes. We examined different hardware settings, such as online filters and sampling rate, as well as processing techniques, such as stimulation artifact removal and offline filters, and measured the effects on the ECAPs metrics: the first negative peak (N1) time and peak-valley amplitude.

Results

For accurate measurements of ECAPs, the hardware sampling rate should be least at 8 kHz and should use a high pass filter with a low cutoff frequency, such as 0.1 Hz, to eliminate baseline drift and saturation (railing). Stimulation artifact removal can use a double exponential or a second-order polynomial. The polynomial fit is 6.4 times faster on average in computation time than the double exponential, while the resulting ECAPs' N1 time and peak-valley amplitude are similar between the two. If the baseline raw measurement drifts with stimulation, a median filter with a 100-ms window or a high pass filter with an 80-Hz cutoff frequency preserves the ECAPs.

Conclusions

This work is the first comprehensive analysis of hardware and processing variations on the observed ECAPs from SCS leads. It sets recommendations to properly record and process ECAPs from the non-stimulation contacts on the implantable leads.

Early Experience With a Novel Miniaturized Spinal Cord Stimulation System for the Management of Chronic Intractable Pain of the Back and Legs

INTRODUCTION

A novel, spinal cord stimulation (SCS) system with a battery-free miniaturized implantable pulse generator (IPG) was used in this feasibility study. The system uses an external power source that communicates bidirectionally with the IPG (< 1.5 cm³). Human factors, subject comfort, and effects on low back and leg pain were evaluated in this first-in-human study.

MATERIALS AND METHODS

A prospective, multicenter, open-label clinical trial was initiated to evaluate the safety and performance of a novel miniaturized stimulator in the treatment of chronic, intractable leg and low-back pain. Eligible subjects were recruited for the study and gave consent. Subjects who passed the screening/trial phase (defined as ≥ 50% decrease in pain) continued to the long-term implant phase and were followed up at predefined time points after device activation. Interim clinical and usability outcomes were captured and reported at 90 days.

RESULTS

Results of 22 subjects who chose a novel pulsed stimulation pattern therapy using the battery-free IPG (< 1.5 cm³) are described here. At 90-days follow-up, the average pain reduction was 79% in the leg (n = 22; p < 0.0001) and 76% in the low back (n = 21; p < 0.0001) compared with baseline. Responder rates (≥ 50% pain relief) at 90 days were 86% in leg pain (19/22) and 81% in low-back pain (17/21). Subjects rated the level of comfort of the external wearable power source to be 0.41 ± 0.73 at 90 days on an 11-point rating scale (0 = very comfortable, 10 = very uncomfortable).

DISCUSSION

These interim results from the ongoing study indicate the favorable efficacy and usability of a novel, externally powered, battery-free SCS IPG (< 1.5 cm³) for leg and low-back pain. Study subjects wore the external power source continuously and found it comfortable, and the system provided significant pain relief. These preliminary findings warrant further investigation.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is ACTRN12618001862235.

Review of the Treatments for Central Neuropathic Pain

Central neuropathic pain (CNP) affects millions worldwide, with an estimated prevalence of around 10% globally. Although there are a wide variety of treatment options available, due to the complex and multidimensional nature in which CNP arises and presents symptomatically, many patients still experience painful symptoms. Pharmaceutical, surgical, non-invasive, cognitive and combination treatment options offer a generalized starting point for alleviating symptoms; however, a more customized approach may provide greater benefit. Here, we comment on the current treatment options that exist for CNP and further suggest the need for additional research regarding the use of biomarkers to help individualize treatment options for patients.

The American Society of Pain and Neuroscience (ASPN) Evidence-Based Clinical Guideline of Interventional Treatments for Low Back Pain

Introduction

Painful lumbar spinal disorders represent a leading cause of disability in the US and worldwide. Interventional treatments for lumbar disorders are an effective treatment for the pain and disability from low back pain. Although many established and emerging interventional procedures are currently available, there exists a need for a defined guideline for their appropriateness, effectiveness, and safety.

Objective

The ASPN Back Guideline was developed to provide clinicians the most comprehensive review of interventional treatments for lower back disorders. Clinicians should utilize the ASPN Back Guideline to evaluate the quality of the literature, safety, and efficacy of interventional treatments for lower back disorders.

Methods

The American Society of Pain and Neuroscience (ASPN) identified an educational need for a comprehensive clinical guideline to provide evidence-based recommendations. Experts from the fields of Anesthesiology, Physiatry, Neurology, Neurosurgery, Radiology, and Pain Psychology developed the ASPN Back Guideline. The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Scopus, and meeting abstracts to identify and compile the evidence (per section) for back-related pain. Search words were selected based upon the section represented. Identified peer-reviewed literature was critiqued using United States Preventive Services Task Force (USPSTF) criteria and consensus points are presented.

Results

After a comprehensive review and analysis of the available evidence, the ASPN Back Guideline group was able to rate the literature and provide therapy grades to each of the most commonly available interventional treatments for low back pain.

Conclusion

The ASPN Back Guideline represents the first comprehensive analysis and grading of the existing and emerging interventional treatments available for low back pain. This will be a living document which will be periodically updated to the current standard of care based on the available evidence within peer-reviewed literature.

A Comprehensive Review of Spinal Cord Stimulator Infections

Spinal cord stimulator (SCS) is approved to treat various pain conditions and is commonly seen in the chronic pain patient population. Due to the nature of the device and its location, infections associated with SCS have a particularly high morbidity. According to post-market data and medical device reports, 87% of patients receiving SCS implants were given perioperative antibiotics as the implantable neurostimulator or receiver pocket serve as the most common sites of infection. The most common antibiotics for surgical prophylaxis given are first-generation cephalosporins (cefalexin, cefazolin) at the time of implantation. If deep infection is suspected, imaging in the form of CT scan should be obtained as physical exam is not always sufficient. For infections involving the epidural space, vertebra, or intervertebral discs, MRI is the preferred imaging modality. If meningitis is suspected, a lumbar puncture is recommended. Positive cultures can help guide antibiotic therapy.

Neurosurgical Treatment of Pain

The aim of this review is to draw attention to neurosurgical approaches for treating chronic and opioid-resistant pain. In a first chapter, an up-to-date overview of the main pathophysiological mechanisms of pain has been carried out, with special emphasis on the details in which the surgical treatment is based. In a second part, the principal indications and results of different surgical approaches are reviewed. Cordotomy, Myelotomy, DREZ lesions, Trigeminal Nucleotomy, Mesencephalotomy, and Cingulotomy are revisited. Ablative procedures have a limited role in the management of chronic non-cancer pain, but they continues to help patients with refractory cancer-related pain. Another ablation lesion has been named and excluded, due to lack of current relevance. Peripheral Nerve, Spine Cord, and the principal possibilities of Deep Brain and Motor Cortex Stimulation are also revisited. Regarding electrical neuromodulation, patient selection remains a challenge.

Spinal Cord Stimulation in Special Populations: Best Practices from the American Society of Pain and Neuroscience to Improve Safety and Efficacy

Chronic bleeding disorders, allergy to implants, and chronic infections are all complicating factors when considering neuromodulation therapies. The American Society of Pain and Neuroscience (ASPN) determined a need for clinical guidance in these special patient populations that have increased risk of complications, in order to ensure patient safety and optimal outcomes with device implantation. The purpose of this publication was to review the published literature and explore the unique clinical challenges encountered among several special patient populations with relation to spinal cord stimulation. The executive board of the ASPN appointed a diverse group of well-established physicians to develop best practice guidelines regarding spinal cord stimulation implantation in these special populations. The physicians used the United States Preventive Services Task Force (USPSTF) structured guidelines for grading and level of certainty to make evidence-based recommendations about clinical practice. Where sufficient evidence was lacking to justify a USPSTF ranking, the physicians queried experts in neuromodulation and achieved consensus. These best practices and interventional guideline found the evidence for the use of neuromodulation in specialized patient populations to be relatively modest.

Synergic Effect of Early Administration of Probiotics and Adipose-Derived Mesenchymal Stem Cells on Alleviating Inflammation-Induced Chronic Neuropathic Pain in Rodents

This study investigated the hypothesis that probiotics enhanced the therapeutic effect of adipose-derived mesenchymal stem cells (ADMSCs) on alleviating neuropathic pain (NP) due to chronic constriction injury (CCI) mainly through regulating the microbiota in rats. SD rats (n = 50) were categorized into group 1 (sham-control), group 2 (NP), group 3 (NP + probiotics (i.e., 1.5 billion C.F.U./day/rat, orally 3 h after NP procedure, followed by QOD 30 times)), group 4 (NP + ADMSCs (3.0 × 105 cells) 3 h after CCI procedure, followed by QOD six times (i.e., seven times in total, i.e., mimic a clinical setting of drug use) and group 5 (NP + probiotics + ADMSCs (3.0 × 105 cells)) and euthanized by day 60 after NP induction. By day 28 after NP induction, flow-cytometric analysis showed circulating levels of early (AN-V+/PI−) and late (AN-V+/PI+) apoptotic, and three inflammatory (CD11b-c+, Ly6G+ and MPO+) cells were lowest in group 1 and significantly progressively reduced in groups 2 to 5 (all p < 0.0001). By days 7, 14, 21, 28, and 60 after CCI, the thresholds of thermal paw withdrawal latency (PWL) and mechanical paw withdrawal threshold (PWT) were highest in group 1 and significantly progressively increased in groups 2 to 5 (all p < 0.0001). Numbers of pain-connived cells (Nav1.8+/peripherin+, p-ERK+/peripherin+, p-p38+/peripherin+ and p-p38+/NF200+) and protein expressions of inflammatory (p-NF-κB, IL-1ß, TNF-α and MMP-9), apoptotic (cleaved-caspase-3, cleaved-PARP), oxidative-stress (NOX-1, NOX-2), DNA-damaged (γ-H2AX) and MAPK-family (p-P38, p-JNK, p-ERK1/2) biomarkers as well as the protein levels of Nav.1.3, Nav.1.8, and Nav.1.9 in L4-L5 in dorsal root ganglia displayed an opposite pattern of mechanical PWT among the groups (all p < 0.0001). In conclusion, combined probiotic and ADMSC therapy was superior to merely one for alleviating CCI-induced NP mainly through suppressing inflammation and oxidative stress.

Spinal Cord Stimulation in Chronic Low Back Pain Syndrome: Mechanisms of Modulation, Technical Features and Clinical Application

Chronic low-back pain (CLBP) is a common disease with several negative consequences on the quality of life, work and activity ability and increased costs to the health-care system. When pharmacological, psychological, physical and occupational therapies or surgery fail to reduce CLBP, patients may be a candidate for Spinal Cord Stimulation (SCS). SCS consists of the transcutaneous or surgical implantation of different types of electrodes in the epidural space; electrodes are then connected to an Implanted Pulse Generator (IPG) that generates stimulating currents. Through spinal and supraspinal mechanisms based on the “gate control theory for pain transmission”, SCS reduces symptoms of CLBP in the almost totality of well-selected patients and its effect lasts up to eight years in around 75% of patients. However, the evidence in favor of SCS still remains weak, mainly due to poor trial methodology and design. This narrative review is mainly addressed to those professionals that may encounter patients with CLBP failing conventional treatments. For this reason, we report the mechanisms of pain relief during SCS, the technical features and some clinical considerations about the application of SCS in patients with CLBP.

Successful utilization of high frequency spinal cord stimulation for HIV and chemotherapy induced polyneuropathy

We present a case of a 53-year-old male who presented with functionally limiting bilateral lower extremity neuropathic pain secondary to multiple subtypes of small fiber neuropathy. He had failed management with multiple conservative measures including oral medications, physical therapy and desensitization techniques. He ultimately underwent placement of a spinal cord stimulator and continued to experience 80% improvement of his pain, as well as improved function and quality of life at 5 month follow-up. To our knowledge, this is the first reported case of successful treatment of multiple subtypes of small fiber neuropathy with spinal cord stimulator.

Migration of Epidural Leads During Spinal Cord Stimulator Trials

Objective

Lead migration is the most commonly reported complication of spinal cord stimulation (SCS) procedures and lead migration during trials of SCS can compromise both the success of the trial as well as the efficacy of subsequent implantation. Our objective was to examine the incidence and degree of intra-trial SCS lead migration and our hypothesis was that there would be a higher rate of significant radiographic lead migration during SCS trial than what has been previously published for permanently implanted leads.

Materials and Methods

We retrospectively assessed the radiographic location of SCS leads on final fluoroscopic imaging at the time of trial lead placement compared to thoracic radiographs obtained at the end of the SCS trial to quantify the rate and degree of migration during the trial. Thirty-five patients were included in the study with 69 leads assessed for radiographic degree of migration. The majority of patients were trialed utilizing paresthesia-free systems (57%) and the most common indication was for post-laminectomy syndrome (57%).

Results

In our series of 35 patients, on average there was 28 mm or 1.17 vertebral body levels of migration. No statistically significant correlation was found between fixation technique, physician experience, device manufacturer, patient age, sex, height or BMI and likelihood of significant radiographic migration.

Conclusion

In our study, lead migration appears to be a more significant occurrence during SCS trial than previously reported. Intra-trial migration presents a significant challenge for clinical care and examination of risk factors for migration and techniques for prevention are warranted.

Efficacy of Peripheral Nerve Field Stimulation for the Management of Chronic Low Back Pain and Persistent Spinal Pain Syndrome: A Narrative Review

OBJECTIVES

Various approaches have been developed with a view to treating the back pain component in patients with chronic low back pain (CLBP) and persistent spinal pain syndrome (PSPS). Emerging evidence shows that peripheral nerve field stimulation (PNFS) may be an efficacious therapeutic modality against axial low back pain. Hence, the aim of the review was to evaluate the analgesic efficacy and safety of PNFS, when used alone or as an adjunct to spinal cord stimulation (SCS), for managing CLBP and PSPS.

MATERIALS AND METHODS

A comprehensive search for clinical studies on PNFS and PNFS + SCS used for the management of CLBP and/or PSPS was performed using PubMed, EMBASE, MEDLINE via Proquest, and Web of Science.

RESULTS

A total of 15 studies were included, of which four were randomized controlled trials (RCTs), nine were observational studies, and two were case series. For patients receiving PNFS, a significant decrease in back pain intensity and analgesic consumption, together with a significant improvement in physical functioning, was observed upon implant of the permanent system. Meanwhile, the addition of PNFS to SCS in refractory cases was associated with a significant reduction in back and leg pain, respectively.

CONCLUSIONS

This review suggests that PNFS, when used alone or in combination with SCS, appears to be effective in managing back pain. However, high-quality evidence that supports the long-term analgesic efficacy and safety is still lacking. Hence, RCTs with a larger patient population and of a longer follow-up duration are warranted.

Single Lead Epidural Spinal Cord Stimulation Targeted Trunk Control and Standing in Complete Paraplegia

A 25-year-old male with T3 complete AIS A was implanted with percutaneous spinal cord epidural stimulation (scES; eight contacts each) leads and a Medtronic Prime advance internal pulse generator. The two leads were placed at the midline level to cover the region of the T11–T12 vertebrae. Five days after implantation, X-ray showed complete migration of the left lead outside the epidural space. Two weeks after implantation, reprogramming of the single right lead (20 Hz and 240 µs) after setting the cathode at 0 and the anode at 3 resulted in target activation of the abdominal muscles and allowed for the immediate restoration of trunk control during a seated position, even with upper extremity perturbation. This was followed by achieving immediate standing after setting the single lead at −3 for the cathode and +6 for the anode using stimulation configurations of 20 Hz and 240 µs. The results were confirmed with electromyography (EMG) of the rectus abdominus and lower extremity muscles. Targeted stimulation of the lumbosacral segment using a single lead with a midline approach immediately restored the trunk control and standing in a person with complete paraplegia.

A case series of new radicular pain following the insertion of spinal cord stimulator

Purpose

Although spinal cord stimulation (SCS) is a safe procedure, equipment-related, biological and neurological complications have been observed in previous research, particularly case reports. No reports of new neuropathic pain in the absence of neurological deficit or positive MRI findings have been described. We detail three cases of new-onset radicular pain in the L5/S1 dermatome following insertion of SCS.

Methods

This was a retrospective case series of three patients. Details of clinical background, indications for SCS and events occurring during insertion and further management were recorded.

Results

All three cases were technically difficult and required multiple epidural entry levels, with repeated passage of the electrode into and within the epidural space. All cases involved accessing epidural space T12/L1 and L1/L2. A possible explanation for the new-onset radicular pain could concern oedema to the conus medullaris, resulting from repeated passage of the electrode at the T12/L1 level. Alternative explanations could be direct trauma to transiting nerve roots, neuroplastic changes resulting in peripheral and central sensitisation and immune-mediated nerve injury.

Conclusion

MRI imaging should be analysed prior to the SCS procedure to identify the level of the conus medullaris, with the aim of avoiding repeated passage of electrodes at that level. Unintended neurological adverse events should be discussed with patients during the consent process. Careful patient selection and psychological screening may also help identify patients who may be unlikely to respond to SCS therapy. Further reporting of new radiculopathic pain following SCS insertion is required to strengthen understanding of its potential causes.

Incidence and Risk Factors for Spinal Cord Stimulator Lead Migration With or Without Loss of Efficacy: A Retrospective Review of 91 Consecutive Thoracic Lead Implants

OBJECTIVE

Lead migration after spinal cord stimulator (SCS) implant is a commonly reported complication and the most common reason for revision surgery in cases of loss of efficacy. The primary aims of this study are to describe the incidence and degree of lead migration in the subacute postoperative period after SCS implant and to report potential risk factors for lead migration.

MATERIALS AND METHODS

We performed a retrospective chart review of all patients at a single academic center who received an SCS implant from January 1, 2020, to December 31, 2020. Information on patient (age, sex, weight, and height) and operative factors (device manufacturer, epidural access level and method, and implantable pulse generator location) were extracted from medical records. Intraoperative imaging was compared to subacute follow-up imaging obtained less than 20 days postimplant to measure lead migration distance. Regression models were fitted to determine associations between lead migration distance and potential clinical risk factors.

RESULTS

A total of 91 cases (182 leads) were included in the study. Within 20 days of implantation, 88.5% of leads had migrated (86.3% caudal and 2.2% cephalad). Mean migration distance for leads with caudal migration only was 12.34 ± 12.19 mm based on anteroposterior radiographs and 16.95 ± 15.68 mm on lateral radiographs. There was an association of greater caudal lead migration as patient body mass index increased (β-coefficient 0.07 [95% confidence interval 0.01-0.13], p = 0.031). Within the entire cohort, one patient (1.1%) required lead revision for loss of efficacy.

CONCLUSIONS

In the subacute postoperative period after SCS implant, the majority of SCS leads migrated caudally with an average of two lead contacts. Knowledge of this expected migration and risk factors can better inform implanting physicians intraoperatively when deciding final lead placement location. The finding of high likelihood of caudal lead migration in the subacute postoperative period brings the need for a well-designed prospective study to the forefront of our field. This will allow implanting providers to make well-informed decisions for intraoperative lead placement.

Direct measurement of oxygen reduction reactions at neurostimulation electrodes

Objective. Electric stimulation delivered by implantable electrodes is a key component of neural engineering. While factors affecting long-term stability, safety, and biocompatibility are a topic of continuous investigation, a widely-accepted principle is that charge injection should be reversible, with no net electrochemical products forming. We want to evaluate oxygen reduction reactions (ORR) occurring at different electrode materials when using established materials and stimulation protocols.Approach. As stimulation electrodes, we have tested platinum, gold, tungsten, nichrome, iridium oxide, titanium, titanium nitride, and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). We use cyclic voltammetry and voltage-step amperometry in oxygenated versus inert conditions to establish at which potentials ORR occurs, and the magnitudes of diffusion-limited ORR currents. We also benchmark the areal capacitance of each electrode material. We use amperometric probes (Clark-type electrodes) to quantify the O₂and H₂O₂concentrations in the vicinity of the electrode surface. O₂and H₂O₂concentrations are measured while applying DC current, or various biphasic charge-balanced pulses of amplitude in the range 10-30µC cm^-2/phase. To corroborate experimental measurements, we employ finite element modelling to recreate 3D gradients of O₂and H₂O₂.Main results. All electrode materials support ORR and can create hypoxic conditions near the electrode surface. We find that electrode materials differ significantly in their onset potentials for ORR, and in the extent to which they produce H₂O₂as a by-product. A key result is that typical charge-balanced biphasic pulse protocols do lead to irreversible ORR. Some electrodes induce severely hypoxic conditions, others additionally produce an accumulation of hydrogen peroxide into the mM range.Significance. Our findings highlight faradaic ORR as a critical consideration for neural interface devices and show that the established biphasic/charge-balanced approach does not prevent irreversible changes in O₂concentrations. Hypoxia and H₂O₂can result in different (electro)physiological consequences.

Chronic electrical stimulation of peripheral nerves via deep-red light transduced by an implanted organic photocapacitor

Implantable devices for the wireless modulation of neural tissue need to be designed for reliability, safety and reduced invasiveness. Here we report chronic electrical stimulation of the sciatic nerve in rats by an implanted organic electrolytic photocapacitor that transduces deep-red light into electrical signals. The photocapacitor relies on commercially available semiconducting non-toxic pigments and is integrated in a conformable 0.1-mm³ thin-film cuff. In freely moving rats, fixation of the cuff around the sciatic nerve, 10 mm below the surface of the skin, allowed stimulation (via 50-1,000-μs pulses of deep-red light at wavelengths of 638 nm or 660 nm) of the nerve for over 100 days. The robustness, biocompatibility, low volume and high-performance characteristics of organic electrolytic photocapacitors may facilitate the wireless chronic stimulation of peripheral nerves.

Cervical epidural abscess due to implantation of a spinal cord stimulation lead

Spinal cord stimulation (SCS) for intractable pain syndromes has become a pillar of modern pain management. Common complications include lead migration, implant infection, cerebral spinal fluid leak, and lead fracture. Spinal epidural abscess due to spinal cord stimulator implantation is a very rare occurrence with only two cases reported in the literature so far. We present an illustrative case and discuss the pathophysiology and best clinical management for this very rate entity.

Spatiotemporal Distribution of Electrically Evoked Spinal Compound Action Potentials During Spinal Cord Stimulation

OBJECTIVES

Recent studies using epidural spinal cord stimulation (SCS) have demonstrated restoration of motor function in individuals previously diagnosed with chronic spinal cord injury (SCI). In parallel, the spinal evoked compound action potentials (ECAPs) induced by SCS have been used to gain insight into the mechanisms of SCS-based chronic pain therapy and to titrate closed-loop delivery of stimulation. However, the previous characterization of ECAPs recorded during SCS was performed with one-dimensional, cylindrical electrode leads. Herein, we describe the unique spatiotemporal distribution of ECAPs induced by SCS across the medial-lateral and rostral-caudal axes of the spinal cord, and their relationship to polysynaptic lower-extremity motor activation.

MATERIALS AND METHODS

In each of four sheep, two 24-contact epidural SCS arrays were placed on the lumbosacral spinal cord, spanning the L3 to L6 vertebrae. Spinal ECAPs were recorded during SCS from nonstimulating contacts of the epidural arrays, which were synchronized to bilateral electromyography (EMG) recordings from six back and lower-extremity muscles.

RESULTS

We observed a triphasic P1, N1, P2 peak morphology and propagation in the ECAPs during midline and lateral stimulation. Distinct regions of lateral stimulation resulted in simultaneously increased ECAP and EMG responses compared with stimulation at adjacent lateral contacts. Although EMG responses decreased during repetitive stimulation bursts, spinal ECAP amplitude did not significantly change. Both spinal ECAP responses and EMG responses demonstrated preferential ipsilateral recruitment during lateral stimulation compared with midline stimulation. Furthermore, EMG responses were correlated with stimulation that resulted in increased ECAP amplitude on the ipsilateral side of the electrode array.

CONCLUSIONS

These results suggest that ECAPs can be used to investigate the effects of SCS on spinal sensorimotor networks and to inform stimulation strategies that optimize the clinical benefit of SCS in the context of managing chronic pain and the restoration of sensorimotor function after SCI.

Spinal Cord Stimulation to Treat Unresponsive Cancer Pain: A Possible Solution in Palliative Oncological Therapy

(1) Background: Treatment of cancer-related pain is still challenging, and it can be managed by both medical and interventional therapies. Spinal Cord Stimulation (SCS) is a minimally invasive technique, and its use is rapidly increasing in the treatment of chronic pain. (2) Materials and Methods: Our study aims to perform a review of the pertinent literature about current evidences in cancer pain treatment by Spinal Cord Stimulation. Moreover, we created a database based on case reports or case series (18 studies) in the literature. We analyzed a clinical group of oncological patients affected by intractable pain undergoing SCS implantation, focusing on outcome. (3) Results: The analysis of the 18 included studies in our series has shown a reduction in painful symptoms in 48 out of 56 treated patients (87.51%); also 53 out of 56 patients (96.64%) have shown an improvement in their Quality of Life (QoL). (4) Conclusions: Spinal Cord Stimulation can be considered an efficient method in the treatment of cancer-related pain. However, literature regarding SCS for the treatment of cancer-related pain is largely represented by case reports and small case series, with no effective population studies or Randomized Controlled Trials demonstrating the efficacy and the level of evidence. Further prospective studies are needed.

Mitigating Spinal Cord Stimulator Lead Migration Complications in Minimally Invasive Spine Surgery: Technical Note

Spinal Cord Stimulators (SCS) are a nonpharmacologic chronic pain management treatment modality that is well-validated and cost-effective within the surgeon’s armamentarium. The reported complication rates are between 5.3% to 40%, most commonly secondary to mechanical hardware failure. The most common mechanical complication is lead migration, which necessitates second surgery. The purpose of this technical note is to describe a minimally invasive spine surgery (MISS) implantation technique we believe to be more resilient to lead migration. We present a stepwise technique for SCS implantation with a maxillofacial screw and washer failsafe.

Contralateral and Lateral Views: Analysis of the Technical Aspects of Spinal Cord Stimulator Lead Insertion

Background

Spinal cord stimulation (SCS) is an established treatment modality for neuropathic pain. The critical part of this technique is safe access to the epidural space for lead placement. There have been innovations in radiological views, improving access to the epidural space.

Objectives

This study analyzes the adoption of these technical advantages in daily practice

Methods

We conducted a survey of members in the Spine Intervention Society and American Society of Regional Anesthesia in regard to the practice patterns in SCS therapy. Here we present our findings regarding the use of contralateral oblique (CLO) and lateral views as well direct upper thoracic or cervicothoracic access for SCS lead insertion

Results

A total of 195 unique responses were received between March 20, 2020 and June 26, 2020. Forty-five percent of respondents “always used” the lateral view technique while 15% “always used” CLO view for SCS lead insertion. Overall, sixty-five percent of respondents used the CLO view with varying frequency. Cervical and upper thoracic approach for cervical SCS lead placement is always or often used by 66.8% of the respondents.

Conclusions

A depth view (CLO or lateral) is always used by only 45 - 60% of the respondents and CLO view has been rapidly adopted in clinical practice for SCS lead insertion. Direct cervicothoracic and upper thoracic is the preferred approach for cervical lead placement by the majority.