Spinal cord stimulation in chronic pain: evidence and theory for mechanisms of action

Review of Guidelines for Implantable Peripheral Nerve Stimulation (PNS) in the Management of Chronic Pain

PURPOSE OF REVIEW

This article assesses the current evidence and guidelines on peripheral nerve stimulation (PNS) and provides recommendations for its use in managing moderate to severe chronic pain.

RECENT FINDINGS

PNS has been utilized for over 50 years in the treatment of chronic pain. However, since 2015, the Food and Drug Administration (FDA) has approved percutaneously implanted PNS leads and neurostimulators, providing a minimally invasive, non-opioid alternative for managing persistent and refractory chronic pain. The American Society of Interventional Pain Physicians (ASIPP) has established evidence-based consensus guidelines for the clinical use of PNS systems in addressing chronic pain. ASIPP guidelines performed extensive evidence synthesis, including systematic reviews, randomized controlled trials (RCTs), and observational studies using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria or certainty of evidence, and qualitative synthesis based on the best available evidence. The evidence level and recommendations showed fair evidence with moderate strength of recommendation for implantable PNS systems following a trial or selective lumbar medial branch stimulation without a trial and for temporary PNS for 60 days. This review offers a comprehensive analysis of peripheral neuropathic pain as a cause of chronic, intractable, function-limiting, and high-impact pain. It discusses the diagnosis of peripheral nerve and neuropathic pain, evidence evaluation and synthesis, medical necessity criteria, patient education, and clinical recommendations. The goal is to enhance patient outcomes by integrating PNS technology into clinical practice.

The Application of Artificial Intelligence to Enhance Spinal Cord Stimulation Efficacy for Chronic Pain Management: Current Evidence and Future Directions

PURPOSE OF REVIEW

Chronic pain significantly impacts quality of life for millions globally, with spinal cord stimulation (SCS) as an established treatment for refractory chronic pain. However, traditional SCS therapies face limitations including inconsistent patient outcomes, challenges in patient selection, and difficulties in sustaining therapeutic efficacy. This review examines how artificial intelligence (AI) can enhance the efficacy and personalization of SCS therapy by optimizing patient selection, refining stimulation parameters, and enabling real-time adaptive adjustments.

RECENT FINDINGS

Recent advances demonstrate that integrating AI with SCS significantly improves patient outcomes through predictive modeling for patient selection and real-time adaptive stimulation. Predictive analytics utilizing machine learning algorithms have successfully identified patient cohorts most likely to benefit from SCS therapy, enhancing response rates and reducing suboptimal outcomes. Closed-loop AI systems incorporating physiological feedback, such as evoked compound action potentials (ECAPs), dynamically optimize stimulation parameters, resulting in sustained pain relief, decreased programming burden, and improved device longevity. Despite these promising results, critical challenges persist, particularly related to data standardization, ethical considerations, and regulatory compliance. AI holds transformative potential for spinal cord stimulation, offering increased precision, personalization, and therapeutic efficiency in managing chronic pain. Although early results are encouraging, comprehensive clinical validation and multidisciplinary collaboration remain essential. Addressing ethical, regulatory, and data management challenges will be critical for widespread adoption of AI-enhanced SCS therapies in routine clinical practice.

Network Meta-analysis of Randomized Controlled Trials Assessing Neuromodulation Therapies for Painful Diabetic Neuropathy

INTRODUCTION

Neuromodulation therapies (including non-invasive and invasive neuromodulation) are being used to treat painful diabetic neuropathy (PDN).

METHODS

A systematic search of the PubMed, Embase, Cochrane Library, Web of Science, and Scopus databases was conducted, from their inception until 1 October 2024, to identify randomized controlled trials (RCTs) on neuromodulation therapies for PDN. Data were collected on pain intensity of various adjunctive therapies for PDN, including transcutaneous electrical nerve stimulation (TENS), percutaneous electrical nerve stimulation, repetitive transcranial magnetic stimulation, pulsed electromagnetic field therapy, spinal cord stimulation (SCS), transcranial direct current stimulation, frequency rhythmic electrical modulation system, mesodiencephalic modulation, and sham.

RESULTS

The data from an aggregate of 12 separate studies, comprising a total sample size of 922 participants, was subject to analysis. All seven neuromodulation therapies exhibited better outcomes in pain intensity compared to the Sham intervention, with TENS achieving the highest ranking, followed by SCS. At the final follow-up time point, statistically significant reductions in pain intensity (vs. Sham) was only observed for SCS.

CONCLUSION

The results of this network meta-analysis should facilitate the development of clinical guidance and enhance the decision-making process for both patients and healthcare professionals, thereby identifying the most appropriate PDN treatment options.

TRIAL REGISTRATION

PROSPERO: CRD42024597208.

Spinal Cord Stimulators Adversely Affect Outcomes in Spinal Deformity Surgery. A Retrospective Case-Control Study

Study DesignRetrospective comparative analysis of prospective cohort.ObjectiveTo examine clinical outcomes of patients with preexisting SCS after adult spinal deformity surgery.MethodsA total of 94 patients with and without a previous history of spinal cord stimulator placement undergoing surgery for ASD with minimum 2-year follow-up. Thirty-three patients with SCS undergoing ASD surgery with minimum 2-year follow-up were compared with a matched cohort of 61 ASD patients without SCS.ResultsDespite similar baseline ODI (56 vs 50, P = .11) and back VAS (6.8 vs 6.6, P = .52), SCS patients did worse at all post-op time intervals. At 6 months, the SCS cohort had higher ODI (48 vs 31, P < .001) and VAS (4.8 vs 3.5, P = .01). This difference persisted at 1 year for ODI (46 vs 30, P < .001) but not for VAS (4.7 vs 4.0, P = .19). At 2 years, ODI remained significantly worse in the SCS cohort (49 vs 38, P = .004). Both cohorts had significant improvement at 2 years compared to baseline (SCS: -1.6 VAS, P < .001, -7 ODI, P = .03; Control: -2.5 VAS, P < .001, -13 ODI, P < .001). Radiographic parameters such as curve magnitude, curve correction, and balance were similar between the 2 groups.ConclusionDespite having substantial improvement after ASD surgery, patients with previous SCS placement did significantly worse in both back VAS and ODI postop compared with controls. They also did not experience a decrease in narcotic use at 2 years despite having similar overall radiographic results and complication rates.

Closed-Loop Spinal Cord Stimulation in Chronic Pain Management: Mechanisms, Clinical Evidence, and Emerging Perspectives

Background: Chronic pain remains a major clinical challenge, which is often resistant to conventional treatments. Spinal cord stimulation has been used for decades to manage refractory pain, traditionally relying on open-loop systems with fixed-output stimulation. However, these systems fail to account for physiological variability, leading to inconsistent pain relief. Closed-loop spinal cord stimulation represents a significant advancement by utilizing evoked compound action potentials to continuously modulate stimulation intensity in real-time, ensuring more stable and effective pain management. Methods: A comprehensive literature review was conducted using PubMed and ClinicalTrials.gov to identify and synthesize relevant published and ongoing studies with a focus on open-loop spinal cord stimulation for managing lower back pain. Results: Clinical trials, including the Avalon and Evoke studies, have demonstrated that closed-loop spinal cord stimulation provides superior pain relief, functional improvement, and reduced opioid dependence compared to traditional open-loop systems. Patients receiving closed-loop stimulation reported significantly higher rates of sustained pain reduction, improved quality of life, and fewer complications related to overstimulation. Emerging studies suggest its potential for conditions beyond back pain, such as neuropathic pain, cancer-related pain, and Raynaud's phenomenon. Furthermore, cost-effectiveness analyses indicate that closed-loop spinal cord stimulation is a more economically viable treatment option compared to conventional medical management and open-loop systems. Conclusions: Closed-loop spinal cord stimulation represents a transformative development in neuromodulation, offering personalized and adaptive pain management that is distinct from open-loop spinal cord stimulation. Further research is warranted to explore its long-term durability, broader applications, and integration with emerging technologies in pain management.

Spinal cord stimulation using time-dynamic pulses achieves longer reversal of allodynia compared to tonic pulses in a rat model of neuropathic pain

Background

Spinal cord stimulation (SCS) utilizing time-dynamic pulses (TDPs) is an emergent field of neuromodulation that continuously and automatically modulates pulse parameters. We previously demonstrated that TDPs delivered for 60 min at paresthesia-free or minimal paresthesia amplitudes significantly reversed allodynia in a rat model of neuropathic pain. Because the anti-allodynic effect was observed to persist post-stimulation, we hypothesized that the anti-nociceptive effects of TDPs may persist longer than those of tonic stimulation.

Methods

We extended SCS stimulation period up to 90 min and investigated the temporal dynamics of SCS-induced analgesia through PWT analysis of the aggregated data from both cohorts.

Results

Both TDPs and tonic stimulation reversed paw withdrawal thresholds (PWT) to near pre-neuropathic levels within 30 min. Most TDPs exhibited significantly slower ramp-up slope (analgesia 'wash-in' rates) as compared to tonic stimulation. All TDPs showed slower wind-down slopes (analgesia 'wash-out' rates) compared to tonic, with pulse width modulation reaching significance. Extending SCS from 60 to 90 min revealed that all TDPs maintained analgesic efficacy longer than tonic stimulation, which showed significant decrease at both 75 and 90 min.

Discussion

Although TDPs and tonic stimulation comparably mitigated allodynia, TDPs exhibited slower rate of wash-out, suggesting longer-lasting analgesic effects and potentially different mechanisms of action.

Spinal cord stimulation induces Neurotrophin-3 to improve diabetic foot disease

Low-extremity ischemic disease is a common complication in diabetic patients, leading to reduced quality of life and potential amputation. This study investigated the therapeutic effect of spinal cord stimulation (SCS) on patients with diabetic foot disease and a rat model of diabetic foot injury. SCS was applied to patients with diabetic foot disease, with clinical assessments performed before and after therapy. Blood levels of NGF, BDNF, and NT-3 were determined by ELISA. A rat model of diabetic foot injury was established to validate NT-3's role in SCS therapy. SCS therapy improved the condition of patients with diabetic ischemic foot disease and promoted wound healing in the rat model. NT-3 levels significantly increased after SCS therapy in both patients and rats. Recombinant NT-3 administration improved wound healing and re-vascularization in the rat model, while NT-3 neutralization abrogated SCS's therapeutic effect. SCS improves the condition of patients with diabetic ischemic foot disease by inducing NT-3 production. Both SCS and NT-3 supplementation show therapeutic potential for ameliorating diabetic foot disease.

Current and Evolving Concepts in the Management of Complex Regional Pain Syndrome: A Narrative Review

Background/Objectives: Complex regional pain syndrome (CRPS) is characterized by severe pain and reduced functionality, which can significantly affect an individual's quality of life. The current treatment of CRPS is challenging. However, recent advances in diagnostic and treatment methods show promise for improving patient outcomes. This review aims to place the question of CRPS in a broader context and highlight the objectives of the research for future directions in the management of CRPS. Methods: This study involved a comprehensive literature review. Results: Research has identified three primary pathophysiological pathways that may explain the clinical variability observed in CRPS: inflammatory mechanisms, vasomotor dysfunction, and maladaptive neuroplasticity. Investigations into these pathways have spurred the development of novel diagnostic and treatment strategies focused on N-Methyl-D-aspartate Receptor Antagonists (NMDA), Toll-like receptor 4 (TLR-4), α1 and α2 adrenoreceptors, as well as the identification of microRNA (miRNA) biomarkers. Treatment methods being explored include immune and glial-modulating agents, intravenous immunoglobulin (IVIG) therapy, plasma exchange therapy, and neuromodulation techniques. Additionally, there is ongoing debate regarding the efficacy of other treatments, such as free radical scavengers, alpha-lipoic acid (ALA), dimethyl fumarate (DMF), adenosine monophosphate-activated protein kinase (AMPK) activators such as metformin, and phosphodiesterase-5 inhibitors such as tadalafil. Conclusions: The controversies surrounding the mechanisms, diagnosis, and treatment of CRPS have prompted researchers to investigate new approaches aimed at enhancing understanding and management of the condition, with the goal of alleviating symptoms and reducing associated disabilities.

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.

Twelve-Month Clinical Trial Results of a Novel, Dorsal Horn Dendrite Stimulation Waveform for Chronic Neuropathic Low Back Pain

OBJECTIVES

The aim of this study was to evaluate the effectiveness and safety of a novel subperception spinal cord stimulation (SCS) waveform paradigm designed to target the dorsal horn dendrites for treating chronic neuropathic low back pain (LBP). The final 12-month results are reported here.

MATERIALS AND METHODS

Twenty-seven participants were implanted with a commercial SCS system. Devices were programmed to deliver the waveform (frequency 100 Hz, pulse width 1000 μsec, T9-T10 disk bipole) at decreasing stimulation perception threshold amplitudes (80%, 60%, then 40%) over a 14-week period. Participants were blinded to the program settings. Participants then received their preferred program for further evaluation at 26 and 52 weeks after activation. Outcome measures included back pain score (visual analogue scale [VAS]), Brief Pain Inventory (BPI), EuroQol 5-Dimension 5-Level (EQ-5D-5L), 36-Item Short Form Health Survey (SF-36), treatment satisfaction, and clinician global impression of change (CGIC).

RESULTS

At 52 weeks (n = 24), the responder rate (≥50% pain relief) was 65.6%, and the high-responder rate (≥80% pain relief) was 56.5%. The mean change from baseline in pain VAS was -43.94 mm (95% CI -57.89, -30.00; p < 0.001) and mean pain relief was 64.69% ± 39.43%. BPI and SF-36 scores remained significantly improved (p ≤ 0.001). EQ-5D-5L index and EuroQoL-VAS further improved, and 87.0% of participants met the minimum clinically important difference for the EQ-5D-5L index. Treatment satisfaction was 83%, and 91% of participants had a CGIC rating of "much improved" or above. No serious study-related adverse events were reported.

CONCLUSIONS

The 12-month trial results show sustained improvements in pain, quality of life, and health-related outcomes. This novel subperception dorsal horn dendrite SCS approach seems a safe and promising treatment option for patients with chronic neuropathic LBP. The open-source availability of this waveform on commercial SCS platforms allows widespread patient access. Further evaluation seems warranted.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is ACTRN12618000647235 (anzctr.org.au).

The Impact of Racial and Low Socioeconomic Status on the Implementation of Spinal Cord Stimulation for Chronic Pain in the United States

OBJECTIVES

This study aims to review the societal, economic, and racial factors that impact the usage of spinal cord stimulation for chronic pain. Our working hypothesis is that patients of ethnic minority groups or of lower socioeconomic status (SES) status may have lower implantation rates and usage of spinal cord stimulation (SCS).

MATERIALS AND METHODS

Our study sourced publications from PubMed, Embase, and Cochrane Library on December 21st, 2023 for SCS for the purposes of pain management. Articles were excluded from the review if the study was not USA based, did not involve SCS for the purpose of pain or did not allow for the subgroup analysis. There were 1028 reports that resulted after the initial search with 184 duplicates which were removed. Six reports met the inclusion and exclusionary criteria and were included in the review.

RESULTS

Several trends were able to be extrapolated from the pooled reviews. Orhurhu et al. found that Black and Hispanic minorities had a higher utilization rate of SCSs than their White and Asian counterparts in the inpatient setting. Jones and Missios et al. found that in the outpatient setting, White and privately insured patients were more likely to utilize SCS. Ovrom et al. observed an increased cost associated with Hispanic ethnicity and inpatient SCS utilization. Wondwossen et al. found that in the US military system White patients were more likely to receive SCS earlier in their care than Black patients. Labaran et al. concluded the Southern US completed more SCS implants, particularly in White patients with Medicare insurance.

CONCLUSIONS

White patients are recipients of SCS earlier and more frequently than minority patients in the outpatient setting. There is mixed evidence regarding inpatient SCS and how household income relates to SCS usage. Insurance type and coverage may be more accurately predictive than simple household income for SCS utilization.

Next generation bioelectronic medicine: making the case for non-invasive closed-loop autonomic neuromodulation

The field of bioelectronic medicine has advanced rapidly from rudimentary electrical therapies to cutting-edge closed-loop systems that integrate real-time physiological monitoring with adaptive neuromodulation. Early innovations, such as cardiac pacemakers and deep brain stimulation, paved the way for these sophisticated technologies. This review traces the historical and technological progression of bioelectronic medicine, culminating in the emerging potential of closed-loop devices for multiple disorders of the brain and body. We emphasize both invasive techniques, such as implantable devices for brain, spinal cord and autonomic regulation, while we introduce new prospects for non-invasive neuromodulation, including focused ultrasound and newly developed autonomic neurography enabling precise detection and titration of inflammatory immune responses. The case for closed-loop non-invasive autonomic neuromodulation (incorporating autonomic neurography and splenic focused ultrasound stimulation) is presented through its applications in conditions such as sepsis and chronic inflammation, illustrating its capacity to revolutionize personalized healthcare. Today, invasive or non-invasive closed-loop systems have yet to be developed that dynamically modulate autonomic nervous system function by responding to real-time physiological and molecular signals; it represents a transformative approach to therapeutic interventions and major opportunity by which the bioelectronic field may advance. Knowledge gaps remain and likely contribute to the lack of available closed loop autonomic neuromodulation systems, namely, (1) significant exogenous and endogenous noise that must be filtered out, (2) potential drift in the signal due to temporal change in disease severity and/or therapy induced neuroplasticity, and (3) confounding effects of exogenous therapies (e.g., concurrent medications that dysregulate autonomic nervous system functions). Leveraging continuous feedback and real-time adjustments may overcome many of these barriers, and these next generation systems have the potential to stand at the forefront of precision medicine, offering new avenues for individualized and adaptive treatment.

Catastrophizing as a Predictor for Pain Perception and Disability Among Patients Undergoing Spinal Cord Stimulation

Background and Objectives: The International Society for Modulation defines persistent spinal pain syndrome type 2 (PSPS-type 2), formerly known as failed back surgery syndrome, as a condition where patients continue to experience pain or develop new pain following spinal surgery intended to alleviate back or lower-limb discomfort. PSPS-type 2 is characterized by pain and significant disability, affecting quality of life. Spinal cord stimulation has proven effective in treating this syndrome, although the role of psychological factors, such as pain catastrophizing and central sensitization, remain unclear. This study seeks to examine the potential connection between psychosocial responses and both functionality and pain perception in patients with persistent spinal pain syndrome type 2 who have undergone spinal cord stimulation treatment. Materials and Methods: A single-site, cross-sectional study was conducted on individuals diagnosed with persistent spinal pain syndrome type 2 who were receiving spinal cord stimulation. Study participants were required to meet specific eligibility criteria and were assessed for disability, pain perception, fear of movement, pain catastrophizing, and central sensitization. The spinal cord stimulation procedure involved the placement of electrodes at vertebral levels T8-T11 for precise pain control, with a particular focus on targeting the dorsal root ganglion to alleviate chronic pain. Results: Thirty-seven patients with persistent spinal pain syndrome type 2 have undergone spinal cord stimulation treatment for 4.68 ± 5.25 years. Clinical assessments indicated a pain perception score of 5.6 ± 1.96, Central Sensitization Inventory score of 42.08 ± 18.39, disability score of 37.62 ± 16.13, fear of movement score of 33.11 ± 8.76, and pain catastrophizing score of 28.43 ± 13.14. Finally, pain catastrophizing was significantly associated with pain perception (β = 0.075 and p = 0.008) and disability (β = 0.90 and p < 0.01). Conclusions: Catastrophizing plays a crucial role in pain perception and disability among patients with persistent spinal pain syndrome type 2 receiving spinal cord stimulation. Integrating psychological interventions may improve clinical outcomes for these patients.

Spinal Cord Stimulation for Low Back Pain: A Systematic Review

PURPOSE OF REVIEW

Chronic low back pain (LBP) is a prevalent and debilitating condition affecting millions worldwide. Among emerging interventions, spinal cord stimulation (SCS) has gained attention as a potential alternative for managing chronic LBP, particularly when alternative approaches fail to provide adequate relief.

RECENT FINDINGS

This systematic review focuses on both residual pain levels and ability to perform daily tasks after treatment with SCS. The present investigation includes a systematic search for studies from PubMed, Google Scholar, and Cochrane, and Embase. Sources were eligible for inclusion in the review if they were published from 2010 to present (May 1, 2024). 8 studies involving a total of 1,172 patients were evaluated. This systematic review demonstrated that SCS is superior to conventional medical management (CMM) for both short and long-term pain relief, functionality, psychological well-being, and opioid dependency. Furthermore, newer SCS approaches, such as high frequency (HF), differential target multiplexed (DTM), and multiphase SCS all demonstrated improved efficacy over traditional SCS for pain relief and functionality scores. Adverse event rates for all trials were low and represent the safety of SCS treatments. The present investigation provides insight into the capabilities of both traditional SCS and HF SCS, DTM SCS, and multiphase SCS as compared to baseline pain and functionality as well as conventional medical management (CMM). This review grants physicians a broader picture of the applicability of SCS, its safety profile, and the opportunities it offers for pain reduction and functionality over CMM.

The mechanisms of electrical neuromodulation

The central and peripheral nervous systems are specialized to conduct electrical currents that underlie behaviour. When this multidimensional electrical system is disrupted by degeneration, damage, or disuse, externally applied electrical currents may act to modulate neural structures and provide therapeutic benefit. The administration of electrical stimulation can exert precise and multi-faceted effects at cellular, circuit and systems levels to restore or enhance the functionality of the central nervous system by providing an access route to target specific cells, fibres of passage, neurotransmitter systems, and/or afferent/efferent communication to enable positive changes in behaviour. Here we examine the neural mechanisms that are thought to underlie the therapeutic effects seen with current neuromodulation technologies. To gain further insights into the mechanisms associated with electrical stimulation, we summarize recent findings from genetic dissection studies conducted in animal models. KEY POINTS: Electricity is everywhere around us and is essential for how our nerves communicate within our bodies. When nerves are damaged or not working properly, using exogenous electricity can help improve their function at distinct levels - inside individual cells, within neural circuits, and across entire systems. This method can be tailored to target specific types of cells, nerve fibres, neurotransmitters and communication pathways, offering significant therapeutic potential. This overview explains how exogenous electricity affects nerve function and its potential benefits, based on research in animal studies. Understanding these effects is important because electrical neuromodulation plays a key role in medical treatments for neurological conditions.

Deciphering pain: molecular mechanisms and neurochemical pathways-challenges and future opportunities

This review delves into the intricate biological underpinnings of pain perception. It encompasses nociceptive signaling pathways, the molecular mechanisms involved, and the subjective experience of discomfort in humans. The initial focus is on nociceptor transduction, where specialized neurons transform noxious stimuli into electrical impulses. Subsequently, the review explores the central nervous system, elucidating how these signals are processed and modulated by critical elements such as ion channels, receptors, and neurotransmitters (e.g., substance P, glutamate, GABA). Shifting gears toward chronic pain, the review examines the concept of neuroplasticity, highlighting its potential to induce maladaptive responses through alterations in neural networks. The burgeoning field of pain genomics, alongside established genetic research, offers valuable insights that could pave the way for a framework of personalized pain management strategies. Finally, the review emphasizes the significance of these molecular insights in facilitating accurate therapeutic interventions. The overarching objective is to establish an integrative framework for precision medicine in pain management by incorporating this information alongside biopsychosocial models. This framework serves to translate the heterogeneous landscape of pain mechanisms into a coherent roadmap for the development of effective therapies.

Management of Post Dural Puncture Headache During Spinal Cord Stimulation Trials: A Review of Current Literature

PURPOSE OF REVIEW

The purpose of this review is to evaluate, discuss and explain the current literature regarding management of post dural puncture headaches (PDPH) during spinal cord stimulation (SCS) trials.

RECENT FINDINGS

Although an epidural blood patch (EBP) remains the gold standard in treatment of PDPH, current literature describes other modalities including various peripheral nerve blocks and pharmacological treatments to reduce PDPH symptoms. PDPH management in SCS centers around conservative treatment and EBP. It has been shown that some practitioners choose prophylactic measures and/or an EBP at the time of the lead placement. Recent literature regarding obstetric anesthesia related PDPH management has included newer potential modalities for addressing symptom improvement that can also be applied to PDPH from SCS trial dural punctures. Due to limited data overall, further studies are needed to effectively provide a guideline on optimal treatment protocols for PDPH after dural puncture in SCS trials.

Quantification of porcine lower thoracic spinal cord morphology with intact dura mater using high-resolution μCT

BACKGROUND AND PURPOSE

Spinal cord stimulation (SCS) is approved by the Food and Drug Administration for treating chronic intractable pain in the back, trunk, or limbs through stimulation of the dorsal column. Numerous studies have used swine as an analog of the human spinal cord to better understand SCS and further improve its efficacy. We performed high-resolution imaging of the porcine spinal cord with intact dura mater using micro-computed tomography (μCT) to construct detailed 3-dimensional (3D) visualizations of the spinal cord and characterize the morphology of the dorsal and ventral rootlets.

METHODS

We obtained spinal cords from Yorkshire/Landrace crossbred swine (N = 7), stained samples with osmium tetroxide, and performed μCT imaging of the T12-T15 levels at isotropic voxel resolutions ranging from 3.3 to 50 μm. We measured the anatomical morphology using the 3D volumes and compared our results to measurements previously collected from swine and human spinal cords via microdissection techniques in prior literature.

RESULTS

While the porcine thoracic-lumbar spinal cord is a popular model for SCS, we highlight multiple notable differences compared to previously published T8-T12 human measurements including rootlet counts (porcine dorsal/ventral: 12.2 ± 2.6, 26.6 ± 3.4; human dorsal/ventral: 5.3 ± 1.3, 4.4 ± 2.4), rootlet angles (porcine ventral-rostral: 161 ± 1°, ventral-caudal: 155 ± 6°, dorsal-rostral: 148 ± 9°, dorsal-caudal: 142 ± 6°; human ventral-rostral: 170 ± 3°, ventral-caudal: 22 ± 10°, dorsal-rostral: 171 ± 3°, dorsal-caudal: 15 ± 7°), and the presence and count of dorsal rootlet bundles.

CONCLUSIONS

Detailed measurements and highlighted differences between human and porcine spinal cords can inform variations in modeling and electrophysiological experiments between the two species. In contrast to other approaches for measuring the spinal cord and rootlet morphology, our method keeps the dura intact, reducing potential artifacts from dissection.

Multimodal functional imaging and clinical correlates of pain regions in chronic low-back pain patients treated with spinal cord stimulation: a pilot study

Objective

Spinal cord stimulation (SCS) is an invasive treatment option for patients suffering from chronic low-back pain (cLBP). It is an effective treatment that has been shown to reduce pain and increase the quality of life in patients. However, the activation of pain processing regions of cLBP patients receiving SCS has not been assessed using objective, quantitative functional imaging techniques. The purpose of the present study was to compare quantitative resting-state (rs)-fMRI and arterial spin labeling (ASL) measures between SCS patients and healthy controls and to correlate clinical measures with quantitative multimodal imaging indices in pain regions.

Methods

Multi-delay 3D GRASE pseudo-continuous ASL and rs-fMRI data were acquired from five patients post-SCS with cLBP and five healthy controls. Three ASL measures and four rs-fMRI measures were derived and normalized into MNI space and smoothed. Averaged values for each measure from a pain atlas were extracted and compared between patients and controls. Clinical pain scores assessing intensity, sensitization, and catastrophizing, as well as others assessing global pain effects (sleep quality, disability, anxiety, and depression), were obtained in patients and correlated with pain regions using linear regression analysis.

Results

Arterial transit time derived from ASL and several rs-fMRI measures were significantly different in patients in regions involved with sensation (primary somatosensory cortex and ventral posterolateral thalamus [VPL]), pain input (posterior short gyrus of the insula [PS]), cognition (dorsolateral prefrontal cortex [DLPC] and posterior cingulate cortex [PCC]), and fear/stress response (hippocampus and hypothalamus). Unidimensional pain rating and sensitization scores were linearly associated with PS, VPL, DLPC, PCC, and/or amygdala activity in cLBP patients.

Conclusion

The present results provide evidence that ASL and rs-fMRI can contrast functional activation in pain regions of cLBP patients receiving SCS and healthy subjects, and they can be associated with clinical pain evaluations as quantitative assessment tools.

Navigating the Neuroimmunomodulation Frontier: Pioneering Approaches and Promising Horizons-A Comprehensive Review

The research in neuroimmunomodulation aims to shed light on the complex relationships that exist between the immune and neurological systems and how they affect the human body. This multidisciplinary field focuses on the way immune responses are influenced by brain activity and how neural function is impacted by immunological signaling. This provides important insights into a range of medical disorders. Targeting both brain and immunological pathways, neuroimmunomodulatory approaches are used in clinical pain management to address chronic pain. Pharmacological therapies aim to modulate neuroimmune interactions and reduce inflammation. Furthermore, bioelectronic techniques like vagus nerve stimulation offer non-invasive control of these systems, while neuromodulation techniques like transcranial magnetic stimulation modify immunological and neuronal responses to reduce pain. Within the context of aging, neuroimmunomodulation analyzes the ways in which immunological and neurological alterations brought on by aging contribute to cognitive decline and neurodegenerative illnesses. Restoring neuroimmune homeostasis through strategies shows promise in reducing age-related cognitive decline. Research into mood disorders focuses on how immunological dysregulation relates to illnesses including anxiety and depression. Immune system fluctuations are increasingly recognized for their impact on brain function, leading to novel treatments that target these interactions. This review emphasizes how interdisciplinary cooperation and continuous research are necessary to better understand the complex relationship between the neurological and immune systems.

Deciphering platinum dissolution in neural stimulation electrodes: Electrochemistry or biology?

Platinum (Pt) is the metal of choice for electrodes in implantable neural prostheses like the cochlear implants, deep brain stimulating devices, and brain-computer interfacing technologies. However, it is well known since the 1970s that Pt dissolution occurs with electrical stimulation. More recent clinical and in vivo studies have shown signs of corrosion in explanted electrode arrays and the presence of Pt-containing particulates in tissue samples. The process of degradation and release of metallic ions and particles can significantly impact on device performance. Moreover, the effects of Pt dissolution products on tissue health and function are still largely unknown. This is due to the highly complex chemistry underlying the dissolution process and the difficulty in decoupling electrical and chemical effects on biological responses. Understanding the mechanisms and effects of Pt dissolution proves challenging as the dissolution process can be influenced by electrical, chemical, physical, and biological factors, all of them highly variable between experimental settings. By evaluating comprehensive findings on Pt dissolution mechanisms reported in the fuel cell field, this review presents a critical analysis of the possible mechanisms that drive Pt dissolution in neural stimulation in vitro and in vivo. Stimulation parameters, such as aggregate charge, charge density, and electrochemical potential can all impact the levels of dissolved Pt. However, chemical factors such as electrolyte types, dissolved gases, and pH can all influence dissolution, confounding the findings of in vitro studies with multiple variables. Biological factors, such as proteins, have been documented to exhibit a mitigating effect on the dissolution process. Other biological factors like cells and fibro-proliferative responses, such as fibrosis and gliosis, impact on electrode properties and are suspected to impact on Pt dissolution. However, the relationship between electrical properties of stimulating electrodes and Pt dissolution remains contentious. Host responses to Pt degradation products are also controversial due to the unknown chemistry of Pt compounds formed and the lack of understanding of Pt distribution in clinical scenarios. The cytotoxicity of Pt produced via electrical stimulation appears similar to Pt-based compounds, including hexachloroplatinates and chemotherapeutic agents like cisplatin. While the levels of Pt produced under clinical and acute stimulation regimes were typically an order of magnitude lower than toxic concentrations observed in vitro, further research is needed to accurately assess the mass balance and type of Pt produced during long-term stimulation and its impact on tissue response. Finally, approaches to mitigating the dissolution process are reviewed. A wide variety of approaches, including stimulation strategies, coating electrode materials, and surface modification techniques to avoid excess charge during stimulation and minimise tissue response, may ultimately support long-term and safe operation of neural stimulating devices.

Improved Selectivity in Eliciting Evoked Electromyography Responses With High-Resolution Spinal Cord Stimulation

BACKGROUND AND OBJECTIVES

As spinal cord stimulation (SCS) offers a therapy for increasing numbers of patients with chronic pain and spinal cord injury, it becomes increasingly important to better understand its somatotopy. In this prospective study, we investigate whether high-resolution SCS (HR-SCS) offers improved selectivity assessed through elicitation of evoked electromyography (EMG) responses as compared with commercial paddle leads.

METHODS

Vertical tripole configurations were used to elicit EMG responses in both types of paddles placed for standard-of-care indications between T6 and T10. In HR-SCS, evoked EMG responses in lower extremity/abdominal muscle groups were monitored at 6 to 8 mediolateral sites. All commercial paddle columns were tested. Percentage change in the maximum root mean square value was calculated at a group level. Heat maps were generated to identify responders for each muscle group. Responders were considered patients who had a >50% change in root mean square over baseline.

RESULTS

We demonstrated significantly greater motor responses across medial and lateral contacts and greater responder rates consistently at the T6 and T9 levels with HR-SCS as compared with commercial paddles in 18 patients. Distal muscle groups (gastrocnemius and tibialis anterior) and proximal muscle groups (biceps femoris and quadriceps) were selectively activated at both levels.

CONCLUSION

We demonstrate that HR-SCS has greater selectivity in eliciting evoked EMG responses in an intraoperative setting. HR-SCS offers recruitment of muscle groups at lateral contacts concurrently with medial contacts. We provide data that HR-SCS may provide higher spatial resolution, which has the potential to allow for personalization of care and treatment of pain syndromes/symptoms which to date have not been effectively treated.

A Scalable, Programmable Neural Stimulator for Enhancing Generalizability in Neural Interface Applications

Each application of neurostimulators requires unique stimulation parameter specifications to achieve effective stimulation. Balancing the current magnitude with stimulation resolution, waveform, size, and channel count is challenging, leading to a loss of generalizability across broad neural interfaces. To address this, this paper proposes a highly scalable, programmable neurostimulator with a System-on-Chip (SOC) capable of 32 channels of independent stimulation. The compliance voltage reaches up to ±22.5 V. A pair of 8-bit current-mode DACs support independent waveforms for source and sink operations and feature a user-selectable dual range for low-current intraparenchymal microstimulation with a resolution of 4.31 μA/bit, as well as high current stimulation for spinal cord and DBS applications with a resolution of 48.00 μA/bit, achieving a wide stimulation range of 12.24 mA while maintaining high-resolution biological stimulation. A dedicated communication protocol enables full programmable control of stimulation waveforms, effectively improving the range of stimulation parameters. In vivo electrophysiological experiments successfully validate the functionality of the proposed stimulator. This flexible stimulator architecture aims to enhance its generality across a wide range of neural interfaces and will provide more diverse and refined stimulation strategies.

Emotional and psychosocial function after dorsal column spinal cord stimulator implantation: a systematic review and meta-analysis

BACKGROUND

The efficacy of spinal cord stimulation (SCS) in chronic pain studies is traditionally assessed by pain scores, which do not reflect the multidimensional nature of pain perception. Despite the evidence of SCS's influence on emotional functioning comprehensive assessments of its effect remain lacking.

OBJECTIVE

To assess changes in emotional and psychosocial functioning in patients who underwent SCS implantation for chronic pain.

EVIDENCE REVIEW

Ovid MEDLINE, EMBASE, PsychINFO, Cochrane CENTRAL and Scopus databases were searched for original peer-reviewed publications reporting emotional functioning after SCS. The primary outcomes were a pooled mean difference (MD) in anxiety, depression, global functioning, mental well-being and pain catastrophizing at 12 months. The Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) was used to determine the quality of evidence.

FINDINGS

Thirty-two studies were included in the primary analysis. Statistically significant improvements were observed in anxiety (MD -2.16; 95% CI -2.84 to -1.49; p<0.001), depression (MD -4.66; 95% CI -6.26 to -3.06; p<0.001), global functioning (MD 20.30; 95% CI 14.69 to 25.90; p<0.001), mental well-being (MD 4.95; 95% CI 3.60 to 6.31; p<0.001), and pain catastrophizing (MD -12.09; 95% CI -14.94 to -9.23; p<0.001). Subgroup analyses revealed differences in Global Assessment of Functioning and mental well-being based on study design and in depression based on waveform paradigm.

CONCLUSION

The results highlight the statistically and clinically significant improvements in emotional and psychosocial outcomes in patients with chronic pain undergoing SCS therapy. However, these results need to be interpreted with caution due to the very low certainty of evidence per the GRADE criteria.

PROSPERO REGISTRATION

CRD42023446326.

Biophysics of Frequency-Dependent Variation in Paresthesia and Pain Relief during Spinal Cord Stimulation

The neurophysiological effects of spinal cord stimulation (SCS) for chronic pain are poorly understood, resulting in inefficient failure-prone programming protocols and inadequate pain relief. Nonetheless, novel stimulation patterns are regularly introduced and adopted clinically. Traditionally, paresthetic sensation is considered necessary for pain relief, although novel paradigms provide analgesia without paresthesia. However, like pain relief, the neurophysiological underpinnings of SCS-induced paresthesia are unknown. Here, we paired biophysical modeling with clinical paresthesia thresholds (of both sexes) to investigate how stimulation frequency affects the neural response to SCS relevant to paresthesia and analgesia. Specifically, we modeled the dorsal column (DC) axonal response, dorsal column nucleus (DCN) synaptic transmission, conduction failure within DC fiber collaterals, and dorsal horn network output. Importantly, we found that high-frequency stimulation reduces DC fiber activation thresholds, which in turn accurately predicts clinical paresthesia perception thresholds. Furthermore, we show that high-frequency SCS produces asynchronous DC fiber spiking and ultimately asynchronous DCN output, offering a plausible biophysical basis for why high-frequency SCS is less comfortable and produces qualitatively different sensation than low-frequency stimulation. Finally, we demonstrate that the model dorsal horn network output is sensitive to SCS-inherent variations in spike timing, which could contribute to heterogeneous pain relief across patients. Importantly, we show that model DC fiber collaterals cannot reliably follow high-frequency stimulation, strongly affecting the network output and typically producing antinociceptive effects at high frequencies. Altogether, these findings clarify how SCS affects the nervous system and provide insight into the biophysics of paresthesia generation and pain relief.

Frequency-Dependent Neural Modulation of Dorsal Horn Neurons by Kilohertz Spinal Cord Stimulation in Rats

Kilohertz high-frequency spinal cord stimulation (kHF-SCS) is a rapidly advancing neuromodulatory technique in the clinical management of chronic pain. However, the precise cellular mechanisms underlying kHF-SCS-induced paresthesia-free pain relief, as well as the neural responses within spinal pain circuits, remain largely unexplored. In this study, using a novel preparation, we investigated the impact of varying kilohertz frequency SCS on dorsal horn neuron activation. Employing calcium imaging on isolated spinal cord slices, we found that extracellular electric fields at kilohertz frequencies (1, 3, 5, 8, and 10 kHz) induce distinct patterns of activation in dorsal horn neurons. Notably, as the frequency of extracellular electric fields increased, there was a clear and significant monotonic escalation in neuronal activity. This phenomenon was observed not only in superficial dorsal horn neurons, but also in those located deeper within the dorsal horn. Our study demonstrates the unique patterns of dorsal horn neuron activation in response to varying kilohertz frequencies of extracellular electric fields, and we contribute to a deeper understanding of how kHF-SCS induces paresthesia-free pain relief. Furthermore, our study highlights the potential for kHF-SCS to modulate sensory information processing within spinal pain circuits. These insights pave the way for future research aimed at optimizing kHF-SCS parameters and refining its therapeutic applications in the clinical management of chronic pain.

A novel CNN-based image segmentation pipeline for individualized feline spinal cord stimulation modeling

Objective. Spinal cord stimulation (SCS) is a well-established treatment for managing certain chronic pain conditions. More recently, it has also garnered attention as a means of modulating neural activity to restore lost autonomic or sensory-motor function. Personalized modeling and treatment planning are critical aspects of safe and effective SCS (Rowald and Amft 2022 Front. Neurorobotics 16 983072, Wagneret al2018 Nature 563 65-71). However, the generation of spine models at the required level of detail and accuracy requires time and labor intensive manual image segmentation by human experts. This study aims to develop a maximally automated segmentation routine capable of producing high-quality anatomical models, even with limited data, to facilitate safe and effective personalized SCS treatment planning.Approach. We developed an automated image segmentation and model generation pipeline based on a novel convolutional neural network (CNN) architecture trained on feline spinal cord magnetic resonance imaging data. The pipeline includes steps for image preprocessing, data augmentation, transfer learning, and cleanup. To assess the relative importance of each step in the pipeline and our choice of CNN architecture, we systematically dropped steps or substituted architectures, quantifying the downstream effects in terms of tissue segmentation quality (Jaccard index and Hausdorff distance) and predicted nerve recruitment (estimated axonal depolarization).Main results. The leave-one-out analysis demonstrated that each pipeline step contributed a small but measurable increment to mean segmentation quality. Surprisingly, minor differences in segmentation accuracy translated to significant deviations (ranging between 4% and 13% for each pipeline step) in predicted nerve recruitment, highlighting the importance of careful workflow design. Additionally, transfer learning techniques enhanced segmentation metric consistency and allowed generalization to a completely different spine region with minimal additional training data.Significance. To our knowledge, this work is the first to assess the downstream impacts of segmentation quality differences on neurostimulation predictions. It highlights the role of each step in the pipeline and paves the way towards fully automated, personalized SCS treatment planning in clinical settings.

Transspinal Focused Ultrasound Suppresses Spinal Reflexes in Healthy Rats

OBJECTIVES

Low-intensity, focused ultrasound (FUS) is an emerging noninvasive neuromodulation approach, with improved spatial and temporal resolution and penetration depth compared to other noninvasive electrical stimulation strategies. FUS has been used to modulate circuits in the brain and the peripheral nervous system, however, its potential to modulate spinal circuits is unclear. In this study, we assessed the effect of trans-spinal FUS (tsFUS) on spinal reflexes in healthy rats.

MATERIALS AND METHODS

tsFUS targeting different spinal segments was delivered for 1 minute, under anesthesia. Monosynaptic H-reflex of the sciatic nerve, polysynaptic flexor reflex of the sural nerve, and withdrawal reflex tested with a hot plate were measured before, during, and after tsFUS.

RESULTS

tsFUS reversibly suppresses the H-reflex in a spinal segment-, acoustic pressure- and pulse-repetition frequency (PRF)-dependent manner. tsFUS with high PRF augments the degree of homosynaptic depression of the H-reflex observed with paired stimuli. It suppresses the windup of components of the flexor reflex associated with slower, C-afferent, but not faster, A- afferent fibers. Finally, it increases the latency of the withdrawal reflex. tsFUS does not elicit neuronal loss in the spinal cord.

CONCLUSIONS

Our study provides evidence that tsFUS reversibly suppresses spinal reflexes and suggests that tsFUS could be a safe and effective strategy for spinal cord neuromodulation in disorders associated with hyperreflexia, including spasticity after spinal cord injury and painful syndromes.

Multi-session transcutaneous spinal cord stimulation prevents chloride homeostasis imbalance and the development of hyperreflexia after spinal cord injury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

Efficacy of spinal cord stimulation as an adjunctive therapy in heart failure: A systematic review

Neuromodulation therapy, like spinal cord stimulation (SCS), benefits individuals with chronic diseases, improving outcomes of patients with heart failure (HF). This systematic review aims to investigate the efficacy of SCS when used as an adjunctive therapy in HF. A systematic analysis of all studies that included SCS therapy in human participants with HF was conducted. After excluding studies not meeting specific criteria, 4 studies involving a total of 125 participants were selected. All participants had heart failure with the New York Heart Association (NYHA) classification ranging from 2.2 ± 0.4 to 3. The primary endpoints for assessment included the impact of SCS in HF-related symptoms, Left ventricular function, VO2 max, and NT-proBNP. All the studies could demonstrate safety and feasibility of SCS therapy, although the outcomes varied. Two studies reported improvement in NYHA classification, MLHFQ and QoL parameters after SCS. Concerning LVEF and VO2 max, only one study indicated positive changes. None of the studies found a significant change of NT-proBNP following SCS therapy. Given methodological variation, discrepancies in the results could be attributed to the diversity of the induction technique. Further studies are needed to develop a solid approach for employing SCS in human patients with HF.

Neuromodulation and Habituation: A Literature Review and Conceptional Analysis of Sustaining Therapeutic Efficacy and Mitigating Habituation

Spinal cord stimulation (SCS) is a therapeutic modality for the treatment of various chronic pain conditions that has rapidly evolved over the past 50 years. Unfortunately, over time, patients implanted with SCS undergo a habituation phenomenon leading to decreased pain relief. Consequently, the discovery of new stimulation waveforms and SCS applications has been shown to prolong efficacy and reduce explantation rates. This article explores various SCS waveforms, their applications, and proposes a graded approach to habituation mitigation. We suspect the neural habituation phenomenon parallels that seen in pharmacology. Consequently, we urge further exploration of the early introduction of these stimulation strategies to abate spinal cord stimulation habituation.

The Efficacy of Neuromodulation Interventions for Chemotherapy-Induced Peripheral Neuropathy: A Systematic Review and Meta-Analysis

Purpose

To determine the efficacy and safety of a neuromodulation intervention regimen in the treatment of chemotherapy-induced peripheral neuropathy (CIPN).

Patients and Methods

Systematic searches were conducted in seven English databases. Randomized controlled trials of all neuromodulation interventions (both invasive and non-invasive) for the treatment of CIPN were selected. Group comparisons of differences between interventions and controls were also made. We divided the outcomes into immediate-term effect (≤3 weeks), short-term effect (3 weeks to ≤3 months), and long-term effect (>3 months).

Results

Sixteen studies and 946 patients with CIPN were included. Among immediate-term effects, neuromodulation interventions were superior to usual care for improving pain (SMD=-0.77, 95% CI -1.07~ 0.47), FACT-Ntx (MD = 5.35, 95% CI 2.84~ 7.87), and QOL (SMD = 0.44, 95% CI 0.09~ 0.79) (moderate certainty); neuromodulation loaded with usual care was superior to usual care for improving pain (SMD=-0.47, 95% CI -0.71 ~ -0.23), and QOL (SMD = 0.40, 95% CI 0.12 ~ 0.69) (moderate certainty). There were no statistically significant differences between the neuromodulation interventions regimen vs usual care in short- and long-term outcomes and neuromodulation vs sham stimulation from any outcome measure. There were mild adverse events such as pain at the site of stimulation and bruising, and no serious adverse events were reported.

Conclusion

Neuromodulation interventions had significant immediate-term efficacy in CIPN but had not been shown to be superior to sham stimulation; short-term and long-term efficacy could not be determined because there were too few original RCTs. Moreover, there are no serious adverse effects of this therapy.

Miniature battery-free epidural cortical stimulators

Miniaturized neuromodulation systems could improve the safety and reduce the invasiveness of bioelectronic neuromodulation. However, as implantable bioelectronic devices are made smaller, it becomes difficult to store enough power for long-term operation in batteries. Here, we present a battery-free epidural cortical stimulator that is only 9 millimeters in width yet can safely receive enough wireless power using magnetoelectric antennas to deliver 14.5-volt stimulation bursts, which enables it to stimulate cortical activity on-demand through the dura. The device has digitally programmable stimulation output and centimeter-scale alignment tolerances when powered by an external transmitter. We demonstrate that this device has enough power and reliability for real-world operation by showing acute motor cortex activation in human patients and reliable chronic motor cortex activation for 30 days in a porcine model. This platform opens the possibility of simple surgical procedures for precise neuromodulation.

Distinct local and global functions of mouse Aβ low-threshold mechanoreceptors in mechanical nociception

The roles of Aβ low-threshold mechanoreceptors (LTMRs) in transmitting mechanical hyperalgesia and in alleviating chronic pain have been of great interest but remain contentious. Here we utilized intersectional genetic tools, optogenetics, and high-speed imaging to specifically examine functions of SplitCre labeled mouse Aβ-LTMRs in this regard. Genetic ablation of SplitCre-Aβ-LTMRs increased mechanical nociception but not thermosensation in both acute and chronic inflammatory pain conditions, indicating a modality-specific role in gating mechanical nociception. Local optogenetic activation of SplitCre-Aβ-LTMRs triggered nociception after tissue inflammation, whereas their broad activation at the dorsal column still alleviated mechanical hypersensitivity of chronic inflammation. Taking all data into consideration, we propose a model, in which Aβ-LTMRs play distinctive local and global roles in transmitting or alleviating mechanical hyperalgesia of chronic pain, respectively. Our model suggests a strategy of global activation plus local inhibition of Aβ-LTMRs for treating mechanical hyperalgesia.

Disease applications of spinal cord stimulation: Chronic nonmalignant pain

Neuropathic pain is a chronic condition representing a significant burden for society. It is estimated 1 out of 10 people over the age of 30 that in the US have been diagnosed with neuropathic pain. Most of the available treatments for neuropathic pain have moderate efficacy over time which limit their use; therefore, other therapeutic approaches are needed for patients. Spinal cord stimulation is an established and cost-effective modality for treating severe chronic pain. In this article we will review the current approved indications for the use of spinal cord stimulation in the US and the novel therapeutic options which are now available using this therapy.

Large-scale real-world data on a multidisciplinary approach to spinal cord stimulation for persistent spinal pain syndromes: first evaluation of the Neuro-Pain® nationwide screening and follow-up interactive register

Introduction

Spinal cord stimulation is a common treatment option for neuropathic pain conditions. Despite its extensive use and multiple technological evolutions, long term efficacy of spinal cord stimulation is debated. Most studies on spinal cord stimulation include a rather limited number of patients and/or follow-ups over a limited period. Therefore, there is an urgent need for real-world, long-term data.

Methods

In 2018, the Belgian government initiated a nationwide secure platform for the follow-up of all new and existing spinal cord stimulation therapies. This is a unique approach used worldwide. Four years after the start of centralized recording, the first global extraction of data was performed.

Results

Herein, we present the findings, detailing the different steps in the centralized procedure, as well as the observed patient and treatment characteristics. Furthermore, we identified dropouts during the screening process, the reasons behind discontinuation, and the evolution of key indicators during the trial period. In addition, we obtained the first insights into the evolution of the clinical impact of permanent implants on the overall functioning and quality of life of patients in the long-term.

Discussion

Although these findings are the results of the first data extraction, some interesting conclusions can be drawn. The long-term outcomes of neuromodulation are complex and subject to many variables. Future data extraction will allow us to identify these confounding factors and the early predictors of success. In addition, we will propose further optimization of the current process.

Exploratory evaluation of spinal cord stimulation with dynamic pulse patterns: a promising approach to improve stimulation sensation, coverage of pain areas, and expected pain relief

Background

The societal burden of chronic pain and the contribution-in-part to the opioid crisis, is a strong motivation to improve and expand non-addictive treatments, including spinal cord stimulation (SCS). For several decades standard SCS has consisted in delivery of tonic pulses with static parameter settings in frequency, pulse width, and amplitude. These static parameters have limited ability to personalize the quality of paresthesia, the dermatomal coverage, and thus may affect SCS efficacy. Further, static settings may contribute to the build-up of tolerance or loss of efficacy of the therapy over time in some patients.

Methods

We conducted an acute exploratory study to evaluate the effects of SCS using time-dynamic pulses as compared to time-static (conventional tonic) stimulation pulses, with the hypotheses that dynamic pulse SCS may enable beneficial tailoring of the sensation and the patient's expectation for better pain relief with SCS. During a single clinic visit, consented subjects undergoing a standard SCS trial had their implanted leads temporarily connected to an investigational external stimulator capable of delivering time-static and six categories of time-dynamic pulse sequences, each characterized by continuously varying a stimulation parameter. Study subjects provided several assessments while blinded to the stimulation pattern, including: drawing of paresthesia maps, descriptions of sensation, and ratings for comfort and helpfulness to pain relief.

Results

Even without optimization of the field location, a majority of subjects rated sensations from dynamic stimulation as better or equal to that of static stimulation for comfortableness and for helpfulness to pain relief. The initial data showed a gender and/or pain dermatomal location related preference to a stimulation pattern. In particular, female subjects and subjects with pain at higher dermatomes tended to rank the sensation from dynamic stimulation better. Dynamic stimulation produced greater pain coverage without optimization; in 70% (9/13) of subjects, maximal pain coverage was achieved with a dynamic stimulation pattern. There was also greater variety in the words used by patients to describe stimulation sensation in the free text and free form verbal descriptions associated with dynamic stimulation.

Conclusions

With the same electrode configuration and comparable parameter settings, acute SCS using dynamic pulses produced more positive ratings, expanded paresthesia coverage, and greater variation in sensation as compared to SCS using static pulses, suggesting that dynamic stimulation has the potential to improve capabilities of SCS for the treatment of chronic pain. Further study is warranted.

Trial Registration

This study was registered at ClinicalTrials.gov under ID NCT02988713, November 2016 (URL: https://clinicaltrials.gov/ct2/show/NCT02988713).

[Neurosurgical treatment of postherpetic neuralgia]

Postherpetic neuralgia is a chronic and debilitating condition that can occur following an episode of herpes zoster (shingles). It is characterized by severe, persistent pain in the area where the shingles rash occurred. While various treatment approaches exist, including medications and non-invasive therapies, some cases of postherpetic neuralgia may require neurosurgical intervention. Neurosurgical treatment options for postherpetic neuralgia aim to alleviate the pain by targeting the affected nerves or neural pathways. One common approach is spinal cord stimulation (SCS). In SCS, electrodes are implanted along the spinal cord, and electrical impulses are delivered to interfere with the transmission of pain signals. This technique can modulate pain perception and significantly reduce the intensity and frequency of postherpetic neuralgia symptoms. Neurosurgical treatment of postherpetic neuralgia is typically considered when conservative measures have failed to provide sufficient relief. However, it is crucial for patients to undergo a comprehensive evaluation and consultation with a neurosurgeon to determine the most appropriate treatment approach based on their specific condition and medical history. The risks, benefits, and potential outcomes of neurosurgical interventions should be carefully discussed between the patient and their healthcare provider to make an informed decision.

Defining the Boundaries of Patient Perception in Spinal Cord Stimulation Programming

OBJECTIVES

Recent developments in spinal cord stimulation (SCS) programming have initiated new modalities of imperceptible stimulation. However, the boundaries of sensory perception are not well defined. The BEnchtop NEuromodulation Following endIng of Trial study aimed to create a map of perceptual threshold responses across a broad range of SCS parameters and programming to inform subperception therapy design.

MATERIALS AND METHODS

This multicenter study was conducted at seven US sites. A total of 43 patients with low back and/or leg pain who completed a percutaneous commercial SCS trial were enrolled. Test stimulation was delivered through trial leads for approximately 90 minutes before removal. SCS parameters, including amplitude, frequency, pulse width (PW), electrode configuration, cycling, and multifrequency stimulation were varied during testing. Paresthesia threshold (PT), comfort level (CL), perceptual coverage area, and paresthesia quality (through patient selection of keywords) were collected. Differences were evaluated with analysis of variance followed by post hoc multiple comparisons using t-tests with Bonferroni correction.

RESULTS

PT was primarily determined by PW and was insensitive to frequency for constant frequency stimulation (range: 20 Hz-10 kHz; F(1284) = 69.58, p < 0.0001). For all tests, CL was approximately 25% higher than PT. The dominant variable that influenced paresthesia quality was frequency. Sensations described as comfortable and tingling were most common for frequencies between 60 Hz and 2.4 kHz; unpleasant sensations were generally more common outside this range. Increasing distance between active electrodes from 7 mm to 14 mm, or cycling the SCS waveform at 1 Hz, decreased PT (p < 0.0001). Finally, PT for a low-frequency stimulus (ie, 60 Hz) was unaffected by mixing with a sub-PT high-frequency stimulus.

CONCLUSIONS

In contrast to previous work investigating narrower ranges, PW primarily influenced PT, independently of frequency. Paresthesia quality was primarily influenced by pulse frequency. These findings advance our understanding of SCS therapy and may be used to improve future novel neuromodulation paradigms.

Spinal Cord Stimulation for Painful Diabetic Neuropathy

Spinal cord stimulation (SCS) technology has been recently approved by the US Food and Drug Administration (FDA) for painful diabetic neuropathy (PDN). The treatment involves surgical implantation of electrodes and a power source that delivers electrical current to the spinal cord. This treatment decreases the perception of pain in many chronic pain conditions, such as PDN. The number of patients with PDN treated with SCS and the amount of data describing their outcomes is expected to increase given four factors: (1) the large number of patients with this diagnosis, (2) the poor results that have been obtained for pain relief with pharmacotherapy and noninvasive non-pharmacotherapy, (3) the results to date with investigational SCS technology, and (4) the recent FDA approval of systems that deliver this treatment. Whereas traditional SCS replaces pain with paresthesias, a new form of SCS, called high-frequency 10-kHz SCS, first used for pain in 2015, can relieve PDN pain without causing paresthesias, although not all patients experience pain relief by SCS. This article describes (1) an overview of SCS technology, (2) the use of SCS for diseases other than diabetes, (3) the use of SCS for PDN, (4) a comparison of high-frequency 10-kHz and traditional SCS for PDN, (5) other SCS technology for PDN, (6) deployment of SCS systems, (7) barriers to the use of SCS for PDN, (8) risks of SCS technology, (9) current recommendations for using SCS for PDN, and (10) future developments in SCS.

Patient profiling and outcome assessment in spinal cord stimulation for chronic back and/or leg pain (the PROSTIM study): a study protocol

Spinal cord stimulation (SCS) is a well-established treatment option in the multidisciplinary approach to chronic back and leg pain. Nevertheless, careful patient selection remains crucial to provide the most optimal treatment and prevent treatment failure. We report the protocol for the PROSTIM study, an ongoing prospective, multicentric and observational clinical study (NCT05349695) that aims to identify different patient clusters and their outcomes after SCS. Patients are recruited in different centers in Europe. Analysis focuses on identifying significant patient clusters based on different health domains and the changes in biopsychosocial variables 6 weeks, 3 and 12 months after implantation. This study is the first to include a biopsychosocial cluster analysis to identify significant patient groups and their response to treatment with SCS.

Spinal cord stimulation may reduce lumbar radiculopathy in the setting of metastatic colon cancer

Cancer pain has a substantial impact on the quality of life and functional capacity with a prevalence of up to 70 % in patients with advanced, metastatic, or terminal disease [1]. The WHO pain ladder has been used in practice to guide cancer pain management. A three-step ladder starts with NSAIDs and non-opioids for mild pain, weak opioids for mild to moderate pain and strong opioids for moderate to severe pain with the use of adjuvant medications such as TCAs and muscle relaxants at any stage for optimization (Fallon et al., Dec 2022) [2] We present a case of a patient with metastatic colon cancer who was admitted for intractable pain crisis and right sided L-5 radiculopathy secondary to epidural metastasis (Figs. 1 and 2). The patient's pain left her bedridden, unable to walk and remained refractory to an escalating intravenous opioid regimen and caudal epidural steroids. The patient subsequently underwent spinal cord stimulation (SCS) trial at level T-7 and achieved >80 % pain relief resulting in a markedly decreased opioid requirement and tremendous recovery of ambulatory function (Fig. 3). After sustained results, a permanent implant was placed at T-8 and patient remains discharged with functional restoration and continued pain improvement (Fig. 4). To our knowledge, this is a novel application of SCS for a refractory pain crisis secondary to a metastatic colon cancer induced radiculopathy presenting with severe functional impairment. As we transition away from opioid use, it is imperative as pain physicians, to investigate the potential of current as an alternative means of cancer pain management: a ubiquitous and challenging clinical conundrum.

Spinal cord stimulation in severe pharmacoresistant restless legs syndrome-two case reports

Restless legs syndrome is a prevalent, sleep-related sensorimotor disorder with relevant impact on the patients' quality of life. For patients suffering from severe, pharmacoresistant restless legs syndrome, few therapeutic options remain to alleviate symptoms. In this case series, two patients with severe, pharmacoresistant restless legs syndrome were treated with epidural spinal cord stimulation and repeatedly assessed with polysomnography, including sleep structure and periodic limb movements as objective biomarkers not subject to placebo effects, during a 6-month follow-up period. One of the patients experienced excellent short- and long-term efficacy on subjective symptom severity (International RLS Study group rating scale 1 vs. 34 points at 3 months) and objective sleep parameters such as sleep architecture and periodic limb movements during sleep, while the second patient only reported short-term benefits from spinal cord stimulation. Ultimately, both patients opted for removal of the device for inefficacy. Based on the complex pathophysiology of restless legs syndrome and presumed mechanism of action of spinal cord stimulation in chronic pain disorders, we provide a detailed hypothesis on the possible modulating effect of spinal cord stimulation on the key symptoms of restless legs syndrome. Apart from describing a new therapeutic option for pharmacoresistant restless legs syndrome, our findings might also provide further insights into the pathophysiology of the syndrome.

Model-based analysis of subthreshold mechanisms of spinal cord stimulation for pain

Objective.Spinal cord stimulation (SCS) is a common treatment for chronic pain. For decades, SCS maximized overlap between stimulation-induced paresthesias and the patient's painful areas. Recently developed SCS paradigms relieve pain at sub-perceptible amplitudes, yet little is known about the neural response to these new waveforms or their analgesic mechanisms of action. Therefore, in this study, we investigated the neural response to multiple forms of paresthesia-free SCS.Approach.We used computational modeling to investigate the neurophysiological effects and the plausibility of commonly proposed mechanisms of three paresthesia-free SCS paradigms: burst, 1 kHz, and 10 kHz SCS. Specifically, in C- and Aβ-fibers, we investigated the effects of different SCS waveforms on spike timing and activation thresholds, as well as how stochastic ion channel gating affects the response of dorsal column axons. Finally, we characterized membrane polarization of superficial dorsal horn neurons.Main results.We found that none of the SCS waveforms activate nor modulate spike timing in C-fibers. Spike timing was modulated in Aβ-fibers only at suprathreshold amplitudes. Ion channel stochasticity had little effect on Aβ-fiber activation thresholds but produced heterogeneous spike timings at suprathreshold amplitudes. Finally, local cells were preferentially polarized in their axon terminals, and the magnitude of this polarization was dependent on cellular morphology and position relative to the stimulation electrodes.Significance.Overall, the mechanisms of action of subparesthetic SCS remain unclear. Our results suggest that no SCS waveforms directly activate C-fibers, and modulation of spike timing is unlikely at subthreshold amplitudes. We conclude that potential subthreshold neuromodulatory effects of SCS on local cells are likely to be presynaptic in nature, as axons are preferentially depolarized during SCS.

Ventral Column Spinal Cord Stimulation for Postlumbar Laminectomy Syndrome

ABSTRACT

Spinal cord stimulation is an increasingly used treatment for a number of chronic pain states. Dorsal column stimulation is historically and currently the anatomical target of choice for most chronic pain conditions, including postlaminectomy syndrome and radicular pain. However, early studies suggested that stimulation of an alternative target, the ventral columns that carry pain fibers in the anterior and lateral spinothalamic tracts, may offer comparable or superior pain relief. A patient undergoing standard-of-care spinal cord stimulation trial had an additional lead placed on the right ventrolateral aspect of the spinal cord. After the usual 7-day trial of dorsal column stimulation, the dorsal leads were removed and ventrolateral column stimulation was applied through the retained ventral lead for a period of 3 days. The Brief Pain Index Short Form and Numeric Rating Scale were recorded for both dorsal and ventral stimulation. Ventrolateral spinal cord stimulation provided comparable outcomes compared with dorsal column stimulation using nonparesthesia-based stimulation. The results suggest further investigation into spinal cord stimulation anatomical placement and mechanism of action is warranted.

Multi-session transcutaneous spinal cord stimulation prevents chloridehomeostasis imbalance and the development of spasticity after spinal cordinjury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

Efficacy of high-frequency spinal cord stimulation for fibromyalgia syndrome in two cases: case reports

BACKGROUND

Reports on the effectiveness of spinal cord stimulation (SCS) for the alleviation of fibromyalgia syndrome (FMS) pain are scarce. We report two cases of effective high-frequency SCS at 1000 Hz against upper- and lower-limb pain in patients with FMS.

CASE PRESENTATION

Two women with widespread pain were diagnosed with FMS and the pain gradually worsened. A 1-week SCS trial was conducted in each patient. In both cases, the patients complained of unpleasant sensations during 10-Hz SCS. However, the pain was alleviated after 1000-Hz stimulation without irritation. Therefore, leads and a generator were implanted, after which they felt almost no pain. Moreover, the dose of the oral medication could be reduced and the patients returned to their daily lives.

CONCLUSION

SCS at 1000 Hz may effectively treat pain associated with FMS. Therefore, performing an SCS trial for patients with FMS with intractable pain might be worthwhile.

Spinal cord stimulation for gait impairment in Parkinson Disease: scoping review and mechanistic considerations

OBJECTIVE

Advanced Parkinson's Disease (PD) is associated with Parkinson's Disease gait impairment (PDg), which increases the risk for falls and is often treatment-refractory. Subthalamic nucleus (STN) and globus pallidus pars interna (GPi) deep brain stimulation (DBS) often fails to improve axial symptoms like PDg. Spinal cord stimulation (SCS) has been suggested to improve PDg. SCS may benefit PDg by disrupting pathologic beta-oscillations and hypersynchrony in cortico-striatal-thalamic circuits to override excessive inhibition of brainstem locomotor regions. SCS may potentially improve locomotion by acting at any of these levels, either alone or in combination.

METHODS

We conducted a comprehensive literature search and scoping review, identifying 106 patients in whom SCS was evaluated for PDg.

RESULTS

Among the identified patients, 63% carried a pain diagnosis. Overall, the most common stimulation location was thoracic (78%), most commonly T9-T10. Burst (sub-perception) was the most common stimulation modality (59%). Prior treatment with DBS was used in 25%. Motor outcomes were assessed by the Unified Parkinson Disease Rating Scale (UPDRS) III-motor, UPDRS, the Timed Up and Go (TUG), and/or 10-/20-meter walking tests.Among these patients, 95 (90%) had PDg amelioration and improved motor outcomes.

CONCLUSIONS

Despite small sample sizes, patient heterogeneity, and unblinded evaluations complicating interpretations of efficacy and safety, SCS may be beneficial for at least a subset of PDg. Further research is required to clarify the role of SCS for PDg and the patients most suitable to benefit from this intervention.