The Evolution of Neuromodulation in the Treatment of Chronic Pain: Forward-Looking Perspectives

The rise of bioelectronic medicine

Bioelectronic Medicine (BEM), which uses implantable electronic medical devices to interface with electrically active tissues, aspires to revolutionize the way we understand and fight disease. By leveraging knowledge from microelectronics, materials science, information technology, neuroscience and medicine, BEM promises to offer novel solutions that address unmet clinical needs and change the concept of therapeutics. This perspective communicates our vision for the future of BEM and presents the necessary steps that need to be taken and the challenges that need to be faced before this new technology can flourish.

The Role and Applications of Artificial Intelligence in the Treatment of Chronic Pain

PURPOSE OF REVIEW

This review aims to explore the interface between artificial intelligence (AI) and chronic pain, seeking to identify areas of focus for enhancing current treatments and yielding novel therapies.

RECENT FINDINGS

In the United States, the prevalence of chronic pain is estimated to be upwards of 40%. Its impact extends to increased healthcare costs, reduced economic productivity, and strain on healthcare resources. Addressing this condition is particularly challenging due to its complexity and the significant variability in how patients respond to treatment. Current options often struggle to provide long-term relief, with their benefits rarely outweighing the risks, such as dependency or other side effects. Currently, AI has impacted four key areas of chronic pain treatment and research: (1) predicting outcomes based on clinical information; (2) extracting features from text, specifically clinical notes; (3) modeling 'omic data to identify meaningful patient subgroups with potential for personalized treatments and improved understanding of disease processes; and (4) disentangling complex neuronal signals responsible for pain, which current therapies attempt to modulate. As AI advances, leveraging state-of-the-art architectures will be essential for improving chronic pain treatment. Current efforts aim to extract meaningful representations from complex data, paving the way for personalized medicine. The identification of unique patient subgroups should reveal targets for tailored chronic pain treatments. Moreover, enhancing current treatment approaches is achievable by gaining a more profound understanding of patient physiology and responses. This can be realized by leveraging AI on the increasing volume of data linked to chronic pain.

Anatomo-physiological basis and applied techniques of electrical neuromodulation in chronic pain

Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies' mechanisms of action, clinical utility, and future perspectives in chronic pain management.

Lower individual alpha frequency in individuals with chronic low back pain and fear of movement

ABSTRACT

Significant progress has been made in linking measures of individual alpha frequency (IAF) and pain. A lower IAF has been associated with chronic neuropathic pain and with an increased sensitivity to pain in healthy young adults. However, the translation of these findings to chronic low back pain (cLBP) are sparse and inconsistent. To address this limitation, we assessed IAFs in a cohort of 70 individuals with cLBP, implemented 3 different IAF calculations, and separated cLBP subjects based on psychological variables. We hypothesized that a higher fear movement in cLBP is associated with a lower IAF at rest. A total of 10 minutes of resting data were collected from 128 electroencephalography channels. Our results offer 3 novel contributions to the literature. First, the high fear group had a significantly lower peak alpha frequency. The high fear group also reported higher pain and higher disability. Second, we calculated individual alpha frequency using 3 different but established methods; the effect of fear on individual alpha frequency was robust across all methods. Third, fear of movement, pain intensity, and disability highly correlated with each other and together significantly predicted IAF. Our findings are the first to show that individuals with cLBP and high fear have a lower peak alpha frequency.

Accessibility and Ease of Use in Neuromodulation Devices

BACKGROUND

The utilization of neuromodulation therapy continues to grow as therapeutic indications expand. These conditions often present with comorbid physical, visual, and auditory impairments. Patients with disabilities in these categories may have difficulty operating their devices. Thus, reviewing the accessibility and inclusive design of neuromodulation devices is imperative to ensure equal access for patients of all ability levels. To date, the literature provides little insight into this topic.

MATERIALS AND METHODS

Manufacturers of Food and Drug Administration-approved neuromodulation devices in the United States completed our electronic survey to assess neuromodulation device features, universal/inclusive design guidelines, and methods used to make the device accessible to patients with disabilities.

RESULTS

We assessed 11 devices from seven manufacturers. Of those, there were six spinal cord, two peripheral nerve, and three deep brain stimulators. Of all respondents, 91% used universal inclusive design guidelines. Of the studied devices, 91% have an interface that uses visual feedback, and 82% have an interface that uses auditory feedback. All surveyed devices were reported to have an interface that requires physical handling.

DISCUSSION

Our study found that most devices incorporate auditory signals, buttons with raised indentations, speech commands, or other useful features to assist those with visual disabilities. Visual interfaces may be sufficient for a patient with hearing impairment to use all the surveyed devices. However, dual sensory impairment presents a significant limitation in all devices surveyed. Furthermore, the biggest barrier to using neuromodulation devices was physical impairment because all surveyed devices require physical handling.

CONCLUSIONS

Manufacturers have awareness of universal inclusive design principles. However, our study was unable to find a device that is accessible to all users regardless of ability. As such, it is critical to involve universal design principles to ensure that inclusive devices are available to improve patient adherence, treatment efficacy, and outcomes.

Wireless Battery-free and Fully Implantable Organ Interfaces

Advances in soft materials, miniaturized electronics, sensors, stimulators, radios, and battery-free power supplies are resulting in a new generation of fully implantable organ interfaces that leverage volumetric reduction and soft mechanics by eliminating electrochemical power storage. This device class offers the ability to provide high-fidelity readouts of physiological processes, enables stimulation, and allows control over organs to realize new therapeutic and diagnostic paradigms. Driven by seamless integration with connected infrastructure, these devices enable personalized digital medicine. Key to advances are carefully designed material, electrophysical, electrochemical, and electromagnetic systems that form implantables with mechanical properties closely matched to the target organ to deliver functionality that supports high-fidelity sensors and stimulators. The elimination of electrochemical power supplies enables control over device operation, anywhere from acute, to lifetimes matching the target subject with physical dimensions that supports imperceptible operation. This review provides a comprehensive overview of the basic building blocks of battery-free organ interfaces and related topics such as implantation, delivery, sterilization, and user acceptance. State of the art examples categorized by organ system and an outlook of interconnection and advanced strategies for computation leveraging the consistent power influx to elevate functionality of this device class over current battery-powered strategies is highlighted.

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).

Neuromodulation Techniques for Headache Management

This narrative review aims to summarize evidence regarding the current utilization and future applications of neuromodulation in patients with headaches, with special attention paid to migraine and chronic cluster headache. A search was conducted in PubMed in August of 2023 to survey the current literature on neuromodulation for the treatment of headache. In total, the search yielded 1989 results, which were further filtered to include only systematic reviews published between 2022 to 2023 to capture the most up-to-date and comprehensive research on this topic. The citation lists of these articles were reviewed to find additional research on neuromodulation and supplement the results presented in this paper with primary literature. Research on the use of neuromodulation for the treatment of headache has predominantly focused on four neuromodulation techniques: peripheral nerve stimulation (PNS), transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), and spinal cord stimulation (SCS). Outcome measures reported in this article include impact on migraine and headache frequency and/or pain intensity, adverse effects of the neuromodulation technique, and associated costs, when available. We found that neuromodulation has developed utility as an alternative treatment for both chronic cluster headaches and migraines, with a reduction in frequency and intensity of headache most elucidated from the articles mentioned in this review.

Practice Trends of Neuromodulation Therapies for Pain and Spasticity in India

BACKGROUND

Neuromodulation has been successfully used globally to address severe refractory chronic pain for over five decades. Compared to the wide acceptance that it enjoys in United States and Europe, it is fairly underutilized in Asia, including India.

OBJECTIVES

We conducted the first systematic nationwide survey to provide an overview of neuromodulation in the past 20 years to investigate the practice trends for severe refractory chronic pain and barriers for the uptake of neuromodulation therapies for pain in India.

DESIGN

A 20-point detailed questionnaire survey was sent out for online completion in August 2020 to practitioners in India involved in interventions for pain. The survey was completed by 112 practitioners (10% return rate). The response data collected were analyzed, tabulated, and presented as percentages.

RESULTS

The average duration of pain practice in India for the majority of respondents was less than a decade. About 70% of practitioners expressed that they manage severe refractory pain without neuromodulation. This survey confirms that neuromodulation is grossly underutilized for pain, comprising only 10% of total neuromodulation implants performed per annum in India. The most common indications were neuropathic pain (45%) and failed back surgery syndrome (42%). The respondents expressed the main barriers to be related to the cost (85%), lack of awareness (68%), and lack of good training (59%). More than 50% of respondents also expressed difficulty of access to neuromodulation therapies for pain and acceptance by patients.

CONCLUSION

The younger generation of pain practitioners in India is becoming more aware and convinced about the role of neuromodulation to alleviate severe pain and suffering. An all-round approach combining improved training, awareness at various levels, more flexible options of newer technology and reimbursement approval can positively influence its use. This can be achieved with the collective efforts of physicians, insurers, industry, and focused academic activities of clinical societies.

Cervical Spinal Cord Stimulation for the Treatment of Headache Disorders: A Systematic Review

OBJECTIVES

Chronic headache remains a major cause of disability and pain worldwide. Although the literature has extensively described pharmacologic options for headache treatment and prophylaxis, there remains a paucity of data on the efficacy of neuromodulation interventions for treatment of headache unresponsive to conventional pharmacologic therapy. The primary aim of this review was to appraise the literature for the efficacy of cervical spinal cord stimulation (cSCS) in treating any intractable chronic headache, including migraine headaches (with or without aura), cluster headache, tension headache, and other types of headaches.

MATERIALS AND METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we performed a systematic review by identifying studies in PubMed, Embase (Scopus), Web of Science, and Cochrane Central Register of Controlled Trials that assessed cSCS to treat chronic headache. Data were synthesized qualitatively, with primary outcomes of headache intensity and frequency. The secondary outcome was adverse effects.

RESULTS

In total, 16 studies comprising 107 patients met the inclusion criteria. Findings were presented based on type of headache, which included migraine headache with or without aura, cluster headache, trigeminal neuropathy, occipital neuralgia, posttraumatic headache, cervicogenic headache, short-lasting unilateral neuralgiform headache with autonomic symptoms, and poststroke facial pain. Per the Grading of Recommendations, Assessment, Development and Evaluations criteria, there was very low-quality evidence that cSCS is associated with a decrease in migraine headache frequency, migraine headache intensity, and trigeminal neuropathy intensity. Placement for cSCS leads ranged from C1 to C4.

CONCLUSIONS

Our review suggests promising data from observational studies that cSCS may be helpful in decreasing frequency and intensity of chronic intractable headache. Future well-powered, randomized controlled trials are needed.

Development of polarization-sensitive optical coherence tomography imaging platform and metrics to quantify electrostimulation-induced peripheral nerve injury in vivo in a small animal model

Significance

Neuromodulation devices are rapidly evolving for the treatment of neurological diseases and conditions. Injury from implantation or long-term use without obvious functional losses is often only detectable through terminal histology. New technologies are needed that assess the peripheral nervous system (PNS) under normal and diseased or injured conditions.

Aim

We aim to demonstrate an imaging and stimulation platform that can elucidate the biological mechanisms and impacts of neurostimulation in the PNS and apply it to the sciatic nerve to extract imaging metrics indicating electrical overstimulation.

Approach

A sciatic nerve injury model in a 15-rat cohort was observed using a newly developed imaging and stimulation platform that can detect electrical overstimulation effects with polarization-sensitive optical coherence tomography. The sciatic nerve was electrically stimulated using a custom-developed nerve holder with embedded electrodes for 1 h, followed by a 1-h recovery period, delivered at above-threshold Shannon model k -values in experimental groups: sham control (SC, n = 5 , 0.0    mA / 0    Hz ), stimulation level 1 (SL1, n = 5 , 3.4    mA / 50    Hz , and k = 2.57 ), and stimulation level 2 (SL2, n = 5 , 6.8    mA / 100    Hz , and k = 3.17 ).

Results

The stimulation and imaging system successfully captured study data across the cohort. When compared to a SC after a 1-week recovery, the fascicle closest to the stimulation lead showed an average change of + 4 % / - 309 % (SL1/SL2) in phase retardation and - 79 % / - 148 % in optical attenuation relative to SC. Analysis of immunohistochemistry (IHC) shows a + 1 % / - 36 % difference in myelin pixel counts and - 13 % / + 29 % difference in axon pixel counts, and an overall increase in cell nuclei pixel count of + 20 % / + 35 % . These metrics were consistent with IHC and hematoxylin/eosin tissue section analysis.

Conclusions

The poststimulation changes observed in our study are manifestations of nerve injury and repair, specifically degeneration and angiogenesis. Optical imaging metrics quantify these processes and may help evaluate the safety and efficacy of neuromodulation devices.

Combination therapy with simultaneous delivery of spinal cord stimulation modalities: COMBO randomized controlled trial

Aim: The Combining Mechanisms for Better Outcomes randomized controlled trial assessed the effectiveness of various spinal cord stimulation (SCS) modalities for chronic pain. Specifically, combination therapy (simultaneous use of customized sub-perception field and paresthesia-based SCS) versus monotherapy (paresthesia-based SCS) was evaluated. Methods: Participants were prospectively enrolled (key inclusion criterion: chronic pain for ≥6 months). Primary end point was the proportion with ≥50% pain reduction without increased opioids at the 3-month follow-up. Patients were followed for 2 years. Results: The primary end point was met (n = 89; p < 0.0001) in 88% of patients in the combination-therapy arm (n = 36/41) and 71% in the monotherapy arm (n = 34/48). Responder rates at 1 and 2 years (with available SCS modalities) were 84% and 85%, respectively. Sustained functional outcomes improvement was observed out to 2 years. Conclusion: SCS-based combination therapy can improve outcomes in patients with chronic pain. Clinical Trial Registration: NCT03689920 (ClinicalTrials.gov), Combining Mechanisms for Better Outcomes (COMBO).

The Association of Psychiatric Comorbidities With Short-Term and Long-Term Outcomes Following Spinal Cord Stimulator Placement

BACKGROUND

Outcomes after spinal cord stimulator (SCS) placement are affected by psychologic comorbidities. It is part of routine practice to do psychologic assessments prior to SCS trials to assess for the presence of maladaptive behavioral patterns. However, few studies have sought to quantify the effect of psychiatric comorbidities on complications, reoperation, and readmission rates. The purpose of this study was to assess the association of psychiatric comorbidities with postprocedural outcomes after SCS implantation.

MATERIALS AND METHODS

Inclusion criteria included SCS placement between 2015 and 2020 (percutaneous approach or an open laminectomy-based approach) using Healthcare Corporation of America National Database. Data on psychiatric comorbidities present at the time of SCS implantation surgery were collected. Outcomes of interest included complication rates (defined as lead migration, fracture, malfunction, battery failure, postoperative pain, infection, dural puncture, or neurological injury), reoperation rates (defined as either revision or explant [ie, removal]), and readmission rates within 30-day and 1-year time after SCS implantation. We measured the association between psychiatric comorbidities and outcomes using multivariable regression and reported odds ratio (OR) and respective 95% confidence intervals.

RESULTS

A total of 12,751 cases were included. The most common psychiatric comorbidities were major depressive disorder (16.1%) and anxiety disorder (13.4%). In unadjusted univariate analysis, patients with any psychiatric comorbidity had heightened rates of any complication (27.1% vs 19.4%), infection (5.9% vs 1.9%), lead displacement (2.2% vs 1.3%), surgical pain (2.1% vs 1.2%), explant (14.7% vs 8.8%), and readmission rates at one year (54.2% vs 33.8%) (all p < 0.001). In multivariable logistic regression, with each additional psychiatric comorbidity, a patient had increased odds of experiencing any complication (OR = 1.5, 95% CI = 1.36-1.57, p < 0.001), requiring a reoperation (OR = 1.5, 95% CI = 1.37-1.6, p < 0.001), and requiring readmission (OR = 1.7, 99% CI = 1.6-1.8, p < 0.001).

CONCLUSIONS

The presence of psychiatric comorbidities was found to be associated with postoperative complication rates, reoperation, and readmission rates after SCS placement. Furthermore, each consecutive increase in psychiatric comorbidity burden was associated with increased odds of complications, reoperation, and readmission. Future studies might consider examining the role of presurgical mental health screening (ie, patient selection, psychologic testing) and treatment in optimizing outcomes for patients with psychiatric comorbidities.

Stimulation holiday rescues analgesia after habituation and loss of efficacy from 10-kilohertz dorsal column spinal cord stimulation

INTRODUCTION

Habituation and loss of efficacy from spinal cord stimulation are commonly reported. This retrospective analysis investigated rescue of analgesia from spinal cord stimulation failure after implementing a strategy called a stimulation holiday, during which spinal cord stimulation is interrupted for a defined period and subsequently restarted.

METHODS

A 6-year review (June 1, 2016-May 13, 2022) from a tertiary care center was conducted on patients who underwent 10 kHz frequency dorsal column spinal cord stimulation for ≥3 months, experienced loss of efficacy (≤30% pain relief or patient self-report of lack of meaningful pain relief), subsequently underwent a stimulation holiday, and then restarted spinal cord stimulation. The primary outcome was comparison of pain relief and responder rate (≥50% relief in pain intensity) before and after stimulation holiday.

RESULTS

Of 212 patients, 40 (18.9%) experienced loss of efficacy at a mean follow-up period of 452.7±326.4 days after stimulator implantation and underwent stimulation holiday. Pain relief was significantly higher 1 month after stimulation holiday (39.4%±28.6%) compared with before stimulation holiday (8.7%±13.0%; mean difference 30.6%, 95% CI 21.9% to 39.3%, paired t-test p<0.001). A significantly higher responder rate (≥50% relief in pain intensity) was identified after stimulation holiday (57.5%) compared with before stimulation holiday (0%; Fisher's exact test p<0.001). Associations of superior pain relief and responder rate remained significant at 3 and 6 months after stimulation holiday.

DISCUSSION

Patients who experience loss of efficacy from spinal cord stimulation habituation could attempt a stimulation holiday rather than abandon therapy. Rescue of analgesia may be achieved after implementing a stimulation holiday and restarting spinal cord stimulation.

Advances in Pain Medicine: a Review of New Technologies

PURPOSE OF REVIEW

This narrative review highlights the interventional musculoskeletal techniques that have evolved in recent years.

RECENT FINDINGS

The recent progress in pain medicine technologies presented here represents the ideal treatment of the pain patient which is to provide personalized care. Advances in pain physiology research and pain management technologies support each other concurrently. As new technologies give rise to new perspectives and understanding of pain, new research inspires the development of new technologies.

Neuromodulation and Hippocampal Neurogenesis in Depression: A Scoping Review

The 'neurogenesis hypothesis of depression' emphasizes the importance of upregulated hippocampal neurogenesis for the efficacy of antidepressant treatment. Neuromodulation is a promising therapeutic method that stimulates neural circuitries to treat neuropsychiatric illnesses. We conducted a scoping review on the neurogenic and antidepressant outcomes of neuromodulation in animal models of depression. PubMed, Web of Science, and PsycInfo were comprehensively searched for full-text English articles from inception to October 5, 2021. Data screening and extraction were conducted independently by two researchers. Seventeen eligible studies were included in this review. The majority of studies used non-invasive neuromodulation (n = 14) and assessed neurogenesis using neural proliferation (n = 16) and differentiation markers (n = 9). Limited reports (n = 2) used neurogenic inhibitors to evaluate the role of neurogenesis on the depressive-like behavioral outcomes. Overall, neuromodulation substantially effectuated both hippocampal cell proliferation and antidepressant-like behavior in animal models of depression, with some providing evidence for enhanced neuronal differentiation and maturation. The proposed neurogenic-related mechanisms mediating the neuromodulation efficacies included neurotrophic processes, anti-apoptotic pathways, and normalization of HPA axis functions. Further research is warranted to explore the role of neuromodulation-induced neurogenic effects on treatment efficacies and to elucidate the underlying molecular mechanisms.

High-Frequency 10-kHz Spinal Cord Stimulation Improves Health-Related Quality of Life in Patients With Refractory Painful Diabetic Neuropathy: 12-Month Results From a Randomized Controlled Trial

Objective

To evaluate high-frequency (10-kHz) spinal cord stimulation (SCS) treatment in refractory painful diabetic neuropathy.

Patients and Methods

A prospective, multicenter randomized controlled trial was conducted between Aug 28, 2017 and March 16, 2021, comparing conventional medical management (CMM) with 10-kHz SCS+CMM. The participants had hemoglobin A1c level of less than or equal to 10% and pain greater than or equal to 5 of 10 cm on visual analog scale, with painful diabetic neuropathy symptoms 12 months or more refractory to gabapentinoids and at least 1 other analgesic class. Assessments included measures of pain, neurologic function, and health-related quality of life (HRQoL) over 12 months with optional crossover at 6 months.

Results

The participants were randomized 1:1 to CMM (n=103) or 10-kHz SCS+CMM (n=113). At 6 months, 77 of 95 (81%) CMM group participants opted for crossover, whereas none of the 10-kHz SCS group participants did so. At 12 months, the mean pain relief from baseline among participants implanted with 10-kHz SCS was 74.3% (95% CI, 70.1-78.5), and 121 of 142 (85%) participants were treatment responders (≥50% pain relief). Treatment with 10-kHz SCS improved HRQoL, including a mean improvement in the EuroQol 5-dimensional questionnaire index score of 0.136 (95% CI, 0.104-0.169). The participants also reported significantly less pain interference with sleep, mood, and daily activities. At 12 months, 131 of 142 (92%) participants were "satisfied" or "very satisfied" with the 10-kHz SCS treatment.

Conclusion

The 10-kHz SCS treatment resulted in substantial pain relief and improvement in overall HRQoL 2.5- to 4.5-fold higher than the minimal clinically important difference. The outcomes were durable over 12 months and support 10-kHz SCS treatment in patients with refractory painful diabetic neuropathy.

Trial registration

clincaltrials.gov Identifier: NCT03228420.

A Novel Spinal Cord Stimulation System with a Battery-Free Micro Implantable Pulse Generator

Spinal cord stimulation (SCS) is effective for the treatment of chronic intractable pain of the trunk and limbs. The mechanism of action may be based, at least in part, upon the gate control theory; however, new waveforms may suggest other mechanisms. Although benefits of the SCS technology generally outweigh the complications associated with SCS, some complications such as infection and skin erosion over the implant can result in device removal. Additional reasons for device removal, such as pocket pain and battery depletion, have driven technological innovations including battery-free implants and device miniaturization. The neurostimulation system described here was specifically designed to address complications commonly associated with implantable batteries and/or larger implantable devices. The benefits of the small size are further augmented by a minimally invasive implant procedure. Usability data show that patients found this novel neurostimulation system to be easy to use and comfortable to wear. What is more, clinical data demonstrate that the use of this system provides statistically significant reduction in pain scores with responder rates (defined as ≥ 50% reduction in pain) of 78% in the low back and 83% in the leg(s). Advances in miniaturization technology arose from the considerable shrinkage of the integrated circuit, with an increase in performance, according to Moore's law (1965). However, commensurate improvements in battery technology have not maintained a similar pace. This has prompted some manufacturers to place the battery outside, against the skin, thereby allowing a massive reduction in the implant volume, with the hopes of fewer device-related complications.

Neuromodulation in the Treatment of Painful Diabetic Neuropathy: A Review of Evidence for Spinal Cord Stimulation

BACKGROUND

Neuropathies, the most common complication of diabetes, manifest in various forms, including entrapments, mononeuropathies or, most frequently, a distal symmetric polyneuropathy. Painful diabetic neuropathy (PDN) in the classic "stocking" distribution is a disease of increasing prevalence worldwide and a condition for which standard medical treatment only provides modest relief. Neuromodulation offers a potential alternative to pharmacotherapies given its demonstrated efficacy in other refractory chronic neuropathic pain syndromes. High-quality evidence from randomized controlled trials (RCTs) is available in these other settings for two approaches to spinal cord stimulation (SCS): (1) conventional low-frequency SCS (LF-SCS), which modulates axonal activity in the dorsal column and is paresthesia-dependent, and (2) high-frequency SCS delivered at 10 kilohertz (10 kHz SCS), which targets neurons in the superficial dorsal horn and is paresthesia-independent.

METHOD

This review examines the evidence for SCS from published RCTs as well as prospective studies exploring the safety and effectiveness of treating PDN with neuromodulation.

RESULTS

Two RCTs enrolling 60 and 36 participants with PDN showed treatment with LF-SCS reduced daytime pain by 45% to 55% for up to two years. An RCT testing 10 kHz SCS versus conventional medical management (CMM) in 216 participants with PDN revealed 76% mean pain relief after six months of stimulation. None of the studies revealed unexpected safety issues in the use of neuromodulation in this patient population.

CONCLUSION

These well-designed RCTs address the unmet need for improved PDN therapies and provide data on the safety, effectiveness, and durability of SCS therapy.

Developing Novel Therapies for Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 7]: Opportunities From Restorative Neurobiology

STUDY DESIGN

Narrative review.

OBJECTIVES

To provide an overview of contemporary therapies for the James Lind Alliance priority setting partnership for degenerative cervical myelopathy (DCM) question: 'Can novel therapies, including stem-cell, gene, pharmacological and neuroprotective therapies, be identified to improve the health and wellbeing of people living with DCM and slow down disease progression?'

METHODS

A review of the literature was conducted to outline the pathophysiology of DCM and present contemporary therapies that may hold therapeutic value in 3 broad categories of neuroprotection, neuroregeneration, and neuromodulation.

RESULTS

Chronic spinal cord compression leads to ischaemia, neuroinflammation, demyelination, and neuronal loss. Surgical intervention may halt progression and improve symptoms, though the majority do not make a full recovery leading to lifelong disability. Neuroprotective agents disrupt deleterious secondary injury pathways, and one agent, Riluzole, has undergone Phase-III investigation in DCM. Although it did not show efficacy on the primary outcome modified Japanese Orthopaedic Association scale, it showed promising results in pain reduction. Regenerative approaches are in the early stage, with one agent, Ibudilast, currently in a phase-III investigation. Neuromodulation approaches aim to therapeutically alter the state of spinal cord excitation by electrical stimulation with a variety of approaches. Case studies using electrical neuromuscular and spinal cord stimulation have shown positive therapeutic utility.

CONCLUSION

There is limited research into interventions in the 3 broad areas of neuroprotection, neuroregeneration, and neuromodulation for DCM. Contemporary and novel therapies for DCM are now a top 10 priority, and whilst research in these areas is limited in DCM, it is hoped that this review will encourage research into this priority.

Non-invasive vagus nerve stimulation modulates trigeminal but not somatosensory perception: functional evidence for a trigemino-vagal system in humans

ABSTRACT

Non-invasive vagus nerve stimulation (nVNS) is effective in several types of headache disorders. We sought to unravel the mechanism of how nVNS exhibits this efficacy. This study used a randomized, single-blind, sham-controlled, crossover-design, and comprised three projects with three independent cohorts of healthy participants. Project I (n=15) was explorative. Six quantitative sensory test (QST) parameters, including mechanical pain threshold (MPT), were measured over the left V1 dermatome and forearm, and compared before and after unilateral nVNS. Projects II (n=20) and III (n=21) were online pre-registered . QST parameters were compared over the left (Project II) or bilateral V1 and V3 dermatomes (Project III), respectively, in addition to the left forearm as a control. A secondary analysis of heart rate variability (HRV) using a historical control group was used to control for systemic effects of nVNS. Verum-nVNS induced trigeminal-specific modulation of pain threshold (i.e., MPT) over the left V1 in Project I, left V1 and V3 in Project II, and bilateral V1 and V3 in Project III. Data pooled from Project II and III demonstrated greater increase of MPT in the V1 vs. V3 dermatome. There were no differences associated with sham-nVNS in any projects. HRV parameters did not change after nVNS. Our results provide functional evidence of a long hypothesized functional trigemino-vagal system in humans and may explain why nVNS is effective in some headache but not in somatic pain disorders. Since unilateral nVNS modulated the trigeminal thresholds bilaterally, this effect is probably indirect through a central top-down mechanism.

A narrative review and future considerations of spinal cord stimulation, dorsal root ganglion stimulation and peripheral nerve stimulation

PURPOSE OF REVIEW

In recent years, neuromodulation has experienced a renaissance. Novel waveforms and anatomic targets show potential improvements in therapy that may signify substantial benefits. New innovations in peripheral nerve stimulation and dorsal root ganglion stimulation have shown prospective evidence and sustainability of results. Sub-perception physiologic bursting, high-frequency stimulation and feedback loop mechanisms provide significant benefits over traditional tonic spinal cords stimulation (SCS) in peer reviewed investigations. We reviewed the themes associated with novel technology in the context of historical stalwart publications.

RECENT FINDINGS

New innovations have led to better nerve targeting, improvements in disease-based treatment, and opioid alternatives for those in chronic pain. In addition, new neural targets from both structural and cellular perspectives have changed the field of Neurostimulation.

SUMMARY

For many years, tonic SCS was representative of neuromodulation, but as this review examines, the progression of the field in the past decade has reshaped patient options.

Status of N-of-1 Trials in Chronic Pain Management: A Narrative Review

N-of-1 trials are randomized controlled clinical trials conducted exclusively on a single patient. The ultimate aim of N-of-1 trials is to optimize a strategy in a particular individual. Chronic pain is a common but refractory clinical problem. Its diverse etiologies and broad variations among patients often lead to the requirement of individualizing medicine. Thus, chronic pain represents a classical condition for N-of-1 clinical trials. Studies have indicated that N-of-1 benefits patients with chronic pain, multiple comorbidities, and uncertain variations during therapies; however, this approach it is not yet adopted as the first choice in pain clinics. To dissect the current status of N-of-1 in chronic pain management, as well as the limitations for its implementation, we herein studied all N-of-1 studies related to chronic pain by searching three major databases (PubMed, ClinicalTrial.gov, Cochrane Library) for publications between 1985 and 2020. Of 35 eligibility papers, 19 were selected for analysis. Results confirmed that N-of-1 trials have solved the refractory cases including osteoarthritis, chronic musculoskeletal pain, and neuropathic pain; however, none of the trials dealt with cancer pain. Longer time and more efforts are needed from investigators when carrying out N-of-1 trials, which inevitably result in implementation difficulties. Of note, all recruited trials were conducted in developed countries. As mobile devices have been introduced and protocols improve, renewed interest in the implementation of N-of-1 trials will occur. Collectively, a previously underestimated conflict between "precision medicine" and "poor implementation" has put N-of-1 in a challenging position for chronic pain management.

Neurodegenerative disorders management: state-of-art and prospects of nano-biotechnology

Neurodegenerative disorders (NDs) are highly prevalent among the aging population. It affects primarily the central nervous system (CNS) but the effects are also observed in the peripheral nervous system. Neural degeneration is a progressive loss of structure and function of neurons, which may ultimately involve cell death. Such patients suffer from debilitating memory loss and altered motor coordination which bring up non-affordable and unavoidable socio-economic burdens. Due to the unavailability of specific therapeutics and diagnostics, the necessity to control or manage NDs raised the demand to investigate and develop efficient alternative approaches. Keeping trends and advancements in view, this report describes both state-of-the-art and challenges in nano-biotechnology-based approaches to manage NDs, toward personalized healthcare management. Sincere efforts are being made to customize nano-theragnostics to control: therapeutic cargo packaging, delivery to the brain, nanomedicine of higher efficacy, deep brain stimulation, implanted stimulation, and managing brain cell functioning. These advancements are useful to design future therapy based on the severity of the patient's neurodegenerative disease. However, we observe a lack of knowledge shared among scientists of a variety of expertise to explore this multi-disciplinary research field for NDs management. Consequently, this review will provide a guideline platform that will be useful in developing novel smart nano-therapies by considering the aspects and advantages of nano-biotechnology to manage NDs in a personalized manner. Nano-biotechnology-based approaches have been proposed as effective and affordable alternatives at the clinical level due to recent advancements in nanotechnology-assisted theragnostics, targeted delivery, higher efficacy, and minimal side effects.

Electrical stimulation in animal models of epilepsy: A review on cellular and electrophysiological aspects

Epilepsy is a debilitating condition, primarily refractory individuals, leading to the search for new efficient therapies. Electrical stimulation is an important method used for years to treat several neurological disorders. Currently, electrical stimulation is used to reduce epileptic crisis in patients and shows promising results. Even though the use of electricity to treat neurological disorders has grown worldwide, there are still many caveats that must be clarified, such as action mechanisms and more efficient stimulation treatment parameters. Thus, this review aimed to explore the comprehension of the main stimulation methods in animal models of epilepsy using rodents to develop new experimental protocols and therapeutic approaches.

Development and Characterization of Novel Conductive Sensing Fibers for In Vivo Nerve Stimulation

Advancements in electrode technologies to both stimulate and record the central nervous system's electrical activities are enabling significant improvements in both the understanding and treatment of different neurological diseases. However, the current neural recording and stimulating electrodes are metallic, requiring invasive and damaging methods to interface with neural tissue. These electrodes may also degrade, resulting in additional invasive procedures. Furthermore, metal electrodes may cause nerve damage due to their inherent rigidity. This paper demonstrates that novel electrically conductive organic fibers (ECFs) can be used for direct nerve stimulation. The ECFs were prepared using a standard polyester material as the structural base, with a carbon nanotube ink applied to the surface as the electrical conductor. We report on three experiments: the first one to characterize the conductive properties of the ECFs; the second one to investigate the fiber cytotoxic properties in vitro; and the third one to demonstrate the utility of the ECF for direct nerve stimulation in an in vivo rodent model.

High Frequency 10 kHz Spinal Cord Stimulation as a First Line Programming Option for Patients With Chronic Pain: A Retrospective Study and Review of the Current Evidence

Introduction Neuromodulation is an evolving and increasingly popular therapy for chronic pain management. Recent data suggest that novel waveforms have demonstrated greater benefit over traditional spinal cord stimulation (SCS). The authors conducted a retrospective review of patients undergoing high-frequency 10 kHz SCS at a single tertiary medical center for the purpose of contributing further evidence to this growing body of data. The literature of high-frequency SCS published to date was also reviewed. Methods A retrospective chart review was performed for patients with chronic pain syndrome, including failed back surgery syndrome and sciatica alone, who underwent high-frequency SCS at 10 kHz. This data was analyzed using R software (R Foundation for Statistical Computing, Vienna, Austria) for statistical analysis. The PubMed database was searched for relevant articles using the search terms "high frequency," "10 kHz," and "spinal cord stimulation." All relevant studies conducted to date were included in this literature review. Results Twenty-one patients had complete follow-up data and were included in this study. Of the 21 patients, 85.7% subjectively reported post-operative pain relief while 71.4% of the total patients reported pain relief by ≥ 50%. There was a statistically significant decrease in mean VAS scores from pre-operative to 12-months post-operative (8.52 vs 4.37, p < 0.001). Additionally, 76.5% of patients subjectively reported improvements in sleep and activities of daily living. Recent studies indicate that high-frequency SCS appears to be a viable option for delivering quality pain relief in patients for chronic regional pain syndrome, failed back surgery syndrome, sciatica, and also pain in the upper cervical region of the spine. Conclusion This article provides evidence both with the authors' own institutional data and from the currently published literature for the efficacy of using high-frequency SCS at 10 kHz as a first-line programming option for patients undergoing SCS.

Real-World Outcomes Using a Spinal Cord Stimulation Device Capable of Combination Therapy for Chronic Pain: A European, Multicenter Experience

Given the differing mechanisms thought to underlie therapeutic sub- and supra-perception-based neurostimulative modalities, Spinal Cord Stimulation (SCS) systems designed for combined delivery of these approaches may help improve analgesic outcomes and quality of life, and reduce treatment failures. This multicenter, observational case-series evaluated 188 patients with chronic back and/or leg pain implanted with an SCS device capable of sequential or simultaneous delivery of sub-perception and supra-perception stimulation programming (i.e., combination therapy) at 16 in Europe. Following implantation, patients were provided with an array of advanced supra-perception programs (e.g., paresthesia-based SCS using multiple independent current sources), and a custom set of sub-perception programs optimized with specific waveforms and/or field shapes. A mean overall pain score of 7.9 ± 1.7 (Standard Deviation (SD)) was reported pre-trial (Baseline). Overall pain was reduced by 4.4 ± 2.8 points (NRS) at 3-months (n = 117) and at 12 months post-implant (n = 90), respectively (p < 0.0001). Substantial quality-of-life (EQ-5D-5L) improvement as assessed at last follow-up was also observed (n = 60). These results suggest that an implanted SCS device capable of combination therapy, while also enabled with patient-specific waveform optimization and stimulation field targeting capabilities, can enable highly effective pain relief and improve quality of life in patients suffering with chronic pain.

Spinal cord stimulation: a real-world data analysis on outcomes and differences between rechargeable and non-rechargeable implantable pulse generators

OBJECTIVE

In this analysis, we examined differences between rechargeable and non-rechargeable spinal cord stimulation (SCS) devices in patients with pain.

METHODS

We conducted a retrospective, longitudinal claims data analysis using a German research database comprising 5 million statutory insured patients (2012-2017). Outcomes of demographics, patient pathways, and health care resource utilization (HCRU) in patients with initial SCS were collected.

RESULTS

Of 150 patients in the database, 73 (49%) received a rechargeable device and 77 (51%) a non-rechargeable device. The average age was 62.5 years (51% female and 49% male patients). A significant decrease over a 3-year follow-up was observed in analgesic prescriptions (-18%), number of patient visits to a physician, and number of patients who were hospitalized. HCRU-related figures for patients with non-rechargeable neurostimulators increased in the last follow-up year whereas the group receiving rechargeable neurostimulators showed a steady decrease.

CONCLUSIONS

SCS seems to be an effective way for patients with chronic pain to decrease pain and improve quality of life. Rechargeable devices seem to be superior to non-rechargeable devices owing to greater longevity and were found to be associated with continuous reduction of pain diagnoses, hospitalization, physician visits, and use of pain medication in our study.

Beta-Endorphin as a Biomarker in the Treatment of Chronic Pain with Non-Invasive Brain Stimulation: A Systematic Scoping Review

A scoping review to synthesize evidence and assess articles describing the use of beta-endorphins as a pain biomarker in chronic pain patients treated with non-invasive brain stimulation techniques was systematically performed with respect to the study quality, the technique employed and the results. Independent reviewers determined if the article met the study criteria at each stage for it to be included. Content analysis was applied and summarized. The results are described in a narrative form grouped by pain condition, type of intervention, stimulation protocol, outcome measures and main results. A total of 67 of 73 references were excluded, and 6 identified studies met the inclusion criteria. The study design, sample size, stimulation type, session protocol and the main findings of each study were extracted. The studies in this scoping review ranged from unsatisfactory to good based on the adopted criteria, with no study achieving an excellent rating. There is limited evidence on the dosage of beta-endorphin in chronic pain conditions during treatment with NIBS. Based on this literature, evidence suggests that BE may not only be useful for acute and persistent pain, but also for a variety of chronic pain states in which opioids are not effective.

Treatment of Painful Diabetic Neuropathy-A Narrative Review of Pharmacological and Interventional Approaches

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus that is associated with a significant decline in quality of life. Like other painful neuropathic conditions, PDN is difficult to manage clinically, and a variety of pharmacological and non-pharmacological options are available for this condition. Recommended pharmacotherapies include anticonvulsive agents, antidepressant drugs, and topical capsaicin; and tapentadol, which combines opioid agonism and norepinephrine reuptake inhibition, has also recently been approved for use. Additionally, several neuromodulation therapies have been successfully used for pain relief in PDN, including intrathecal therapy, transcutaneous electrical nerve stimulation (TENS), and spinal cord stimulation (SCS). Recently, 10 kHz SCS has been shown to provide clinically meaningful pain relief for patients refractory to conventional medical management, with a subset of patients demonstrating improvement in neurological function. This literature review is intended to discuss the dosage and prospective data associated with pain management therapies for PDN.

Deep Brain Stimulation of the Subgenual Cingulate Cortex for the Treatment of Chronic Low Back Pain

OBJECTIVES

Despite converging basic scientific and clinical evidence of the link between chronic pain and depression, existing therapies do not often take advantage of this overlap. Here, we provide a critical review of the literature that highlights the intersection in brain networks between chronic low back pain (CLBP) and depression and discuss findings from previous deep brain stimulation (DBS) studies for pain. Based on a multidimensional model of pain processing and the connectivity of the subgenual cingulate cortex (SCC) with areas that are implicated in both CLBP and depression, we propose a novel approach to the treatment of CLBP using DBS of the SCC.

MATERIALS AND METHODS

A narrative review with literature assessment.

RESULTS

CLBP is associated with a shift away from somatosensory representation toward brain regions that mediate emotional processes. There is a high degree of overlap between these regions and those involved in depression, including the anterior cingulate cortex, medial prefrontal cortex, nucleus accumbens, and amygdala. Whereas targets sites from previous DBS trials for pain were not anatomically positioned to engage these areas and their associated networks, the SCC is structurally connected to all of these regions and as well as others involved in mediating sensory, cognitive, and affective processing in CLBP.

CONCLUSIONS

CLBP and depression share a common underlying brain network interconnected by the SCC. Current data and novel technology provide an optimal opportunity to develop clinically effective trials of SCC DBS for CLBP.

Review of complex regional pain syndrome and the role of the neuroimmune axis

Background

Complex regional pain syndrome (CRPS) is a progressive and painful disease of the extremities that is characterized by continuous pain inconsistent with the initial trauma. CRPS is caused by a multi-mechanism process that involves both the peripheral and central nervous system, with a prominent role of inflammation in CRPS pathophysiology. This review examines what is currently known about the CRPS inflammatory and pain mechanisms, as well as the possible impact of neurostimulation therapies on the neuroimmune axis of CRPS.

Study design

A narrative review of preclinical and clinical studies provided an overview of the pain and inflammatory mechanisms in CRPS and addressed the effect of neurostimulation on immunomodulation.

Methods

A systematic literature search was conducted based on the PRISMA guidelines between September 2015 to September 2020. Data sources included relevant literature identified through searches of PubMed, Embase and the Cochrane Database of Systematic Reviews.

Results

Sixteen preclinical and eight clinical studies were reviewed. Preclinical studies identified different mechanisms of pain development in the acute and chronic CRPS phases. Several preclinical and clinical studies investigating inflammatory mechanisms, autoimmunity, and genetic profiles in CRPS, supported a role of neuroinflammation in the pathophysiology of CRPS. The immunomodulatory effects of neurostimulation therapy is still unclear, despite clinical improvement in the CRPS patients.

Conclusions

Increasing evidence supports a role for inflammation and neuroinflammation in CRPS pathophysiology. Preliminary neurostimulation findings, together with the role of (neuro)inflammation in CRPS, seems to provide a compelling rationale for its use in CRPS pain treatment. The possible immunomodulatory effects of neurostimulation opens new therapeutic possibilities, however further research is needed to gain a better understanding of the working mechanisms.

Regional Techniques and Interventions for Intractable Neuropathic Pain

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Analgesic opioid use disorders in patients with chronic non-cancer pain: A holistic approach for tailored management

Chronic pain is a major public health issue that frequently leads to analgesic opioid prescriptions. These prescriptions could cause addiction issues in high-risk patients with associated comorbidities, especially those of a psychiatric, addictive, and social nature. Pain management in dependent patients is complex and is yet to be established. By combining the views of professionals from various specialties, we conducted an integrative review on this scope. This methodology synthesizes knowledge and results of significant practical studies to provide a narrative overview of the literature. The main results consisted in first proposing definitions that could allow shared vocabulary among health professionals regardless of their specialties. Next, a discussion was conducted around the main strategies for managing prescription opioid dependence, as well as pain in the context of opioid dependence and associated comorbidities. As a conclusion, we proposed to define the contours of holistic management by outlining the main guidelines for creating a multidisciplinary care framework for multi-comorbid patients with chronic pathologies.

Spinal Cord Stimulation for Visceral Pain: Present Approaches and Future Strategies

INTRODUCTION

The introduction of successful neuromodulation strategies for managing chronic visceral pain lag behind what is now treatment of choice in refractory chronic back and extremity pain for many providers in the United States and Europe. Changes in public policy and monetary support to identify nonopioid treatments for chronic pain have sparked interest in alternative options. In this review, we discuss the scope of spinal cord stimulation (SCS) for visceral pain, its limitations, and the potential role for new intradural devices of the type that we are developing in our laboratories, which may be able to overcome existing challenges.

METHODS

A review of the available literature relevant to this topic was performed, with particular focus on the pertinent neuroanatomy and uses of spinal cord stimulation systems in the treatment of malignant and nonmalignant gastrointestinal, genitourinary, and chronic pelvic pain.

RESULTS

To date, there have been multiple off-label reports testing SCS for refractory gastrointestinal and genitourinary conditions. Though some findings have been favorable for these organs and systems, there is insufficient evidence to make this practice routine. The unique configuration and layout of the pelvic pain pathways may not be ideally treated using traditional SCS implantation techniques, and intradural stimulation may be a viable alternative.

CONCLUSIONS

Despite the prevalence of visceral pain, the application of neuromodulation therapies, a standard approach for other painful conditions, has received far too little attention, despite promising outcomes from uncontrolled trials. Detailed descriptions of visceral pain pathways may offer several clues that could be used to implement devices tailored to this unique anatomy.

Neuromodulation Management of Chronic Neuropathic Pain in The Central Nervous system

Neuromodulation is becoming one of the clinical tools for treating chronic neuropathic pain by transmitting controlled physical energy to the pre-identified neural targets in the central nervous system. Its nature of drug-free, non-addictive and improved targeting have attracted increasing attention among neuroscience research and clinical practices. This article provides a brief overview of the neuropathic pain and pharmacological routines for treatment, summarizes both the invasive and non-invasive neuromodulation modalities for pain management, and highlights an emerging brain stimulation technology, transcranial focused ultrasound (tFUS) with a focus on ultrasound transducer devices and the achieved neuromodulation effects and applications on pain management. Practical considerations of spatial guidance for tFUS are discussed for clinical applications. The safety of transcranial ultrasound neuromodulation and its future prospectives on pain management are also discussed.

Biomarker Optimization of Spinal Cord Stimulation Therapies

OBJECTIVES

We are in the process of designing and testing an intradural stimulation device that will shorten the distance between the location of the electrode array and the targeted neural tissue, thus improving the efficacy of electrical current delivery. Identifying a biomarker that accurately reflects the response to this intervention is highly valued because of the potential to optimize interventional parameters or predict a response before it is clinically measurable. In this report, we summarize the findings pertaining to the study of biomarkers so that we and others will have an up-to-date reference that critically evaluates the current approaches and select one or several for testing during the development of our device.

MATERIALS AND METHODS

We have conducted a broad survey of the existing literature to catalogue the biomarkers that could be coupled to intradural spinal cord stimulation. We describe in detail some of the most promising biomarkers, existing limitations, and suitability to managing chronic pain.

RESULTS

Chronic, intractable pain is an all-encompassing condition that is incurable. Many treatments for managing chronic pain are nonspecific in action and intermittently administered; therefore, patients are particularly susceptible to large fluctuations in pain control over the course of a day. The absence of a reliable biomarker challenges assessment of therapeutic efficacy and contributes to either incomplete and inconsistent pain relief or, alternatively, intolerable side effects. Fluctuations in metabolites or inflammatory markers, signals captured during dynamic imaging, and genomics will likely have a role in governing how a device is modulated.

CONCLUSIONS

Efforts to identify one or more biomarkers are well underway with some preliminary evidence supporting their efficacy. This has far-reaching implications, including improved outcomes, fewer adverse events, harmonization of treatment and individuals, performance gains, and cost savings. We anticipate that novel biomarkers will be used widely to manage chronic pain.

Spinal cord stimulation programming: a crash course

The aim of this comprehensive review is to provide an instructional guide for providers regarding the parameters and programming of spinal cord stimulation (SCS) devices. Knowing these fundamentals will aid in providing superior pain relief to patients. SCS has four programmable parameters: contact (electrode) selection, amplitude, pulse width, and frequency. Each parameter needs to be accounted for when assessing which program works for which patient. Traditional open-loop systems allow for different "programs," or combinations of these four parameters, to be pre-set by the provider and medical device representative. These allow for flexibility in the type of stimulation delivered to the patient depending on activity. Patients are also given control over programs and changing the amplitudes of these programs. However, some open-loop systems place the burden of toggling between programs to manage pain control on patients, though this tends to be less in subparesthesia programs. Newer closed-loop systems make it possible for stimulation settings to automatically adjust in response to accelerometry and evoked compound action potential feedback, and therefore have the potential to streamline the patient experience. This article provides practitioners with the basic knowledge of SCS parameters and programming systems. Understanding their use is essential to providing optimal pain relief to patients.

Leptin and Associated Mediators of Immunometabolic Signaling: Novel Molecular Outcome Measures for Neurostimulation to Treat Chronic Pain

Chronic pain is a devastating condition affecting the physical, psychological, and socioeconomic status of the patient. Inflammation and immunometabolism play roles in the pathophysiology of chronic pain disorders. Electrical neuromodulation approaches have shown a meaningful success in otherwise drug-resistant chronic pain conditions, including failed back surgery, neuropathic pain, and migraine. A literature review (PubMed, MEDLINE/OVID, SCOPUS, and manual searches of the bibliographies of known primary and review articles) was performed using the following search terms: chronic pain disorders, systemic inflammation, immunometabolism, prediction, biomarkers, metabolic disorders, and neuromodulation for chronic pain. Experimental studies indicate a relationship between the development and maintenance of chronic pain conditions and a deteriorated immunometabolic state mediated by circulating cytokines, chemokines, and cellular components. A few uncontrolled in-human studies found increased levels of pro-inflammatory cytokines known to drive metabolic disorders in chronic pain patients undergoing neurostimulation therapies. In this narrative review, we summarize the current knowledge and possible relationships of available neurostimulation therapies for chronic pain with mediators of central and peripheral neuroinflammation and immunometabolism on a molecular level. However, to address the needs for predictive factors and biomarkers, large-scale databank driven clinical trials are needed to determine the clinical value of molecular profiling.