Neurophysiological Comparison Among Tonic, High Frequency, and Burst Spinal Cord Stimulation: Novel Insights Into Spinal and Brain Mechanisms of Action

Should we Oppose or Combine Waveforms for Spinal Cord Stimulation in PSPS-T2 Patients? A Prospective Randomized Crossover Trial (MULTIWAVE Study)

Refractory persistent spinal pain syndrome after surgery (PSPS-T2) can be successfully addressed by spinal cord stimulation (SCS). While conventional stimulation generates paresthesia, recent systems enable the delivery of paresthesia-free stimulation. Studies have claimed non-inferiority/superiority of selected paresthesia-free stimulation compared with paresthesia-based stimulation, but the comparative efficacy between different waveforms still needs to be determined in a given patient. We designed a randomized controlled 3-month crossover trial to compare pain relief of paresthesia-based stimulation versus high frequency versus burst in 28 PSPS-T2 patients implanted with multiwave SCS systems. Our secondary objectives were to determine the efficacy of these 3 waveforms on pain surface, quality of life, functional capacity, psychological distress, and validated composite multidimensional clinical response index to provide holistic comparisons at 3-, 6-, 9-, and 15-month post-randomization. The preferred stimulation modality was documented during the follow-up periods. No difference between the waveforms was observed in this study (P = .08). SCS led to significant pain relief, quality of life improvement, improvement of multidimensional clinical response index, and of all other clinical outcomes at all follow-up visits. Forty-four percent of the patients chose to keep the paresthesia-based stimulation modality after the 15-month follow-up period. By giving the possibility to switch and/or to combine several waveforms, the overall rate of SCS responders further increased with 25%. In this study, high frequency or burst do not appear superior to paresthesia-based stimulation, wherefore paresthesia-based stimulation should still be considered as a valid option. However, combining paresthesia-based stimulation with paresthesia-free stimulation, through personalized multiwave therapy, might significantly improve SCS responses. PERSPECTIVE: This article assesses clinical SCS efficacy on pain relief, by comparing paresthesia-based stimulation and paresthesia-free stimulation (including high frequency and burst) modalities in patient presenting with PSPS-T2. Switching and/or combining waveforms contribute to increasing the global SCS responders rate.

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.

Spinal Cord Stimulation for Gait Disorders in Parkinson's Disease and Atypical Parkinsonism: A Systematic Review of Preclinical and Clinical Data

BACKGROUND

Falls in extrapyramidal disorders, particularly Parkinson's disease (PD), multisystem atrophy (MSA), and progressive supranuclear palsy (PSP), are key milestones affecting patients' quality of life, incurring increased morbidity/mortality and high healthcare costs. Unfortunately, gait and balance in parkinsonisms respond poorly to currently available treatments. A serendipitous observation of improved gait and balance in patients with PD receiving spinal cord stimulation (SCS) for back pain kindled an interest in using SCS to treat gait disorders in parkinsonisms.

OBJECTIVES

We reviewed preclinical and clinical studies of SCS to treat gait dysfunction in parkinsonisms, covering its putative mechanisms and efficacies.

MATERIALS AND METHODS

Preclinical studies in animal models of PD and clinical studies in patients with PD, PSP, and MSA who received SCS for gait disorders were included. The main outcome assessed was clinical improvement in gait, together with outcome measures used and possible mechanism of actions.

RESULTS

We identified 500 references, and 45 met the selection criteria and have been included in this study for analysis. Despite positive results in animal models, the outcomes in human studies are inconsistent.

CONCLUSIONS

The lack of blind and statistically powered studies, the heterogeneity in patient selection and study outcomes, and the poor understanding of the underlying mechanisms of action of SCS are some of the limiting factors in the field. Addressing these limitations will allow us to draw more reliable conclusions on the effects of SCS on gait and balance in extrapyramidal disorders.

Modeling Electric Fields in Transcutaneous Spinal Direct Current Stimulation: A Clinical Perspective

Clinical findings suggest that transcutaneous spinal direct current stimulation (tsDCS) can modulate ascending sensitive, descending corticospinal, and segmental pathways in the spinal cord (SC). However, several aspects of the stimulation have not been completely understood, and realistic computational models based on MRI are the gold standard to predict the interaction between tsDCS-induced electric fields and anatomy. Here, we review the electric fields distribution in the SC during tsDCS as predicted by MRI-based realistic models, compare such knowledge with clinical findings, and define the role of computational knowledge in optimizing tsDCS protocols. tsDCS-induced electric fields are predicted to be safe and induce both transient and neuroplastic changes. This could support the possibility to explore new clinical applications, such as spinal cord injury. For the most applied protocol (2-3 mA for 20-30 min, active electrode over T10-T12 and the reference on the right shoulder), similar electric field intensities are generated in both ventral and dorsal horns of the SC at the same height. This was confirmed by human studies, in which both motor and sensitive effects were found. Lastly, electric fields are strongly dependent on anatomy and electrodes' placement. Regardless of the montage, inter-individual hotspots of higher values of electric fields were predicted, which could change when the subjects move from a position to another (e.g., from the supine to the lateral position). These characteristics underlines the need for individualized and patient-tailored MRI-based computational models to optimize the stimulation protocol. A detailed modeling approach of the electric field distribution might contribute to optimizing stimulation protocols, tailoring electrodes' configuration, intensities, and duration to the clinical outcome.

Neurostimulation for Chronic Low Back Pain during Pregnancy: Implications for Child and Mother Safety

Pain therapy for low back pain in pregnancy is a very topical issue. In fact, it is necessary to balance the patient's needs to control pain with the need to manage a pregnancy without negative effects on the fetus. We report a case of a 37-year-old woman with low back pain treated with neurostimulation before pregnancy. She described severe chronic low back pain unresponsive to pharmacologic treatments. We first implanted a subcutaneous stimulator into the patient, and then a definitive stimulator resulting in excellent pain control. The improvement in her quality of life allowed the woman to become pregnant. We decided to stop neurostimulation with the patient during pregnancy. The patient completed her pregnancy without complications and the baby was born healthy. During the pregnancy, the woman took only paracetamol when needed. However, this painful symptomatology, completely anecdotal, is not attributable solely to the previous spine problem but probably also to the changes occurring during pregnancy. At the end of pregnancy, the neurostimulator was reactivated without any discomfort for the patient, who is now pain free. This case report provides a first line of evidence of a possible treatment of low back pain in women intending to become pregnant, with risk-free management for both the patient and the child.

Passive Recharge Burst Spinal Cord Stimulation Provides Sustainable Improvements in Pain and Psychosocial Function: 2-year Results From the TRIUMPH Study

STUDY DESIGN

Prospective, international, multicenter, single-arm, post-market study.

OBJECTIVE

The aim of this study was to assess long-term safety and effectiveness of spinal cord stimulation using a passive recharge burst stimulation design for chronic intractable pain in the trunk and/or limbs. Herein we present 24-month outcomes from the TRIUMPH study (NCT03082261).

SUMMARY OF BACKGROUND DATA

Passive recharge burst spinal cord stimulation (B-SCS) uniquely mimics neuronal burst firing patterns in the nervous system and has been shown to modulate the affective and attentional components of pain processing.

METHODS

After a successful trial period, subjects received a permanent SCS implant and returned for follow-up at 6, 12, 18, and 24 months.

RESULTS

Significant improvements in physical, mental, and emotional functioning observed after 6 months of treatment were maintained at 2 years. Pain catastrophizing scale (PCS) scores dropped below the population norm. Health-related quality of life on EQ-5D improved across all domains and the mean index score was within one standard deviation of norm. Pain reduction (on NRS) was statistically significant (P < 0.001) at all timepoints. Patient reported pain relief, a stated percentage of improvement in pain, was consistent at all timepoints at 60%. Patients reported significant improvements across all measures including activity levels and impact of pain on daily life. At 24 months, 84% of subjects were satisfied and 90% would recommend the procedure. Subjects decreased their chronic pain medication intake for all categories; 38% reduced psychotropic and muscle relaxants, 46% reduced analgesic, anti-convulsant and NSAIDs, and 48% reduced opioid medication. Adverse events occurred at low rates without unanticipated events.

CONCLUSION

Early positive results with B-SCS were maintained long term. Evidence across multiple assessment tools show that B-SCS can alleviate pain intensity, psychological distress, and improve physical function and health-related quality of life.Level of Evidence: 3.

A Call to Action Toward Optimizing the Electrical Dose Received by Neural Targets in Spinal Cord Stimulation Therapy for Neuropathic Pain

Spinal cord stimulation has seen unprecedented growth in new technology in the 50 years since the first subdural implant. As we continue to grow our understanding of spinal cord stimulation and relevant mechanisms of action, novel questions arise as to electrical dosing optimization. Programming adjustment — dose titration — is often a process of trial and error that can be time-consuming and frustrating for both patient and clinician. In this report, we review the current preclinical and clinical knowledge base in order to provide insights that may be helpful in developing more rational approaches to spinal cord stimulation dosing. We also provide key conclusions that may help in directing future research into electrical dosing, given the advent of newer waveforms outside traditional programming parameters.

Modulation of the Somatosensory Evoked Potential by Attention and Spinal Cord Stimulation

Introduction: Spinal Cord Stimulation (SCS) is a last-resort treatment for patients with intractable chronic pain in whom pharmacological and other treatments have failed. Conventional tonic SCS is accompanied by tingling sensations. More recent stimulation protocols like burst SCS are not sensed by the patient while providing similar levels of pain relief. It has been previously reported that conventional tonic SCS can attenuate sensory-discriminative processing in several brain areas, but that burst SCS might have additional effects on the medial, motivational-affective pain system. In this explorative study we assessed the influence of attention on the somatosensory evoked brain responses under conventional tonic SCS as well as burst SCS regime.

Methods: Twelve chronic pain patients with an implanted SCS device had 2-weeks evaluation periods with three different SCS settings (conventional tonic SCS, burst SCS, and sham SCS). At the end of each period, an electro-encephalography (EEG) measurement was done, at which patients received transcutaneous electrical pulses at the tibial nerve to induce somatosensory evoked potentials (SEP). SEP data was acquired while patients were attending the applied pulses and while they were mind wandering. The effects of attention as well as SCS regimes on the SEP were analyzed by comparing amplitudes of early and late latencies at the vertex as well as brain activity at full cortical maps.

Results: Pain relief obtained by the various SCS settings varied largely among patients. Early SEP responses were not significantly affected by attention nor SCS settings (i.e., burst, tonic, and sham). However, late SEP responses (P300) were reduced with tonic and burst SCS: conventional tonic SCS reduced P300 brain activity in the unattended condition, while burst SCS reduced P300 brain activity in both attended and unattended conditions.

Conclusion: Burst spinal cord stimulation for the treatment of chronic pain seems to reduce cortical attention that is or can be directed to somatosensory stimuli to a larger extent than conventional spinal cord stimulation treatment. This is a first step in understanding why in selected chronic pain patients burst SCS is more effective than tonic SCS and how neuroimaging could assist in personalizing SCS treatment.

Exploration of the Supraspinal Hypotheses about Spinal Cord Stimulation and Dorsal Root Ganglion Stimulation: A Systematic Review

Despite the established efficacy and effectiveness of Spinal Cord Stimulation (SCS), there is still no consensus on the supraspinal mechanisms of action of this therapy. The purpose of this study was to systematically review previously raised hypotheses concerning supraspinal mechanisms of action of SCS based on human, animal and computational studies. Searches were conducted using four electronic databases (PubMed, EMBASE, SCOPUS and Web of Science), backward reference searching and consultation with experts. The study protocol was registered prior to initiation of the review process (PROSPERO CRD42020161531). A total of 54 publications were included, 21 of which were animal studies, and 33 were human studies. The supraspinal hypotheses (n = 69) identified from the included studies could be categorized into six groups concerning the proposed supraspinal hypothesis, namely descending pathways (n = 24); ascending medial pathway (n = 13); ascending lateral pathway (n = 10); affective/motivational influences (n = 8); spinal–cerebral (thalamic)-loop (n = 3) and miscellaneous (n = 11). Scientific support is provided for the hypotheses identified. Modulation of the descending nociceptive inhibitory pathways, medial and lateral pathways were the most frequently reported hypotheses about the supraspinal mechanisms of action of SCS. These hypotheses were mainly supported by studies with a high or moderate confidence in the body of evidence.

Management of Chronic and Neuropathic Pain with 10 kHz Spinal Cord Stimulation Technology: Summary of Findings from Preclinical and Clinical Studies

Since the inception of spinal cord stimulation (SCS) in 1967, the technology has evolved dramatically with important advancements in waveforms and frequencies. One such advancement is Nevro’s Senza^® SCS System for HF10, which received Food and Drug and Administration (FDA) approval in 2015. Low-frequency SCS works by activating large-diameter Aβ fibers in the lateral discriminatory pathway (pain location, intensity, quality) at the dorsal column (DC), creating paresthesia-based stimulation at lower-frequencies (30–120 Hz), high-amplitude (3.5–8.5 mA), and longer-duration/pulse-width (100–500 μs). In contrast, high-frequency 10 kHz SCS works with a proposed different mechanism of action that is paresthesia-free with programming at a frequency of 10,000 Hz, low amplitude (1–5 mA), and short-duration/pulse-width (30 μS). This stimulation pattern selectively activates inhibitory interneurons in the dorsal horn (DH) at low stimulation intensities, which do not activate the dorsal column fibers. This ostensibly leads to suppression of hyperexcitable wide dynamic range neurons (WDR), which are sensitized and hyperactive in chronic pain states. It has also been reported to act on the medial pathway (drives attention and pain perception), in addition to the lateral pathways. Other theories include a reversible depolarization blockade, desynchronization of neural signals, membrane integration, glial–neuronal interaction, and induced temporal summation. The body of clinical evidence regarding 10 kHz SCS treatment for chronic back pain and neuropathic pain continues to grow. There is high-quality evidence supporting its use in patients with persistent back and radicular pain, particularly after spinal surgery. High-frequency 10 kHz SCS studies have demonstrated robust statistically and clinically significant superiority in pain control, compared to paresthesia-based SCS, supported by level I clinical evidence. Yet, as the field continues to grow with the technological advancements of multiple waveforms and programming stimulation algorithms, we encourage further research to focus on the ability to modulate pain with precision and efficacy, as the field of neuromodulation continues to adapt to the modern healthcare era.

Multicentre, clinical trial of burst spinal cord stimulation for neck and upper limb pain NU-BURST: a trial protocol

BACKGROUND

Spinal cord stimulation (SCS) is an established therapy for chronic neuropathic pain and most frequently utilised for Failed Back Surgery Syndrome (FBSS). BurstDR™ also known as DeRidder Burst-SCS, a novel waveform, has demonstrated superiority to conventional tonic stimulation of the thoracic spine in FBSS. There are case reports of an improvement in multidimensional pain outcomes using DeRidder Burst-SCS in the cervical spine for chronic neck and cervical radicular pain. The safety and efficacy of cervical DeRidder Burst-SCS stimulation still however remain undetermined.

METHODS/DESIGN

This is a prospective, multicentre feasibility trial evaluating the safety and therapeutic efficacy of DeRidder Burst-SCS stimulation for the treatment of chronic intractable neck pain with or without radiation to the arm, shoulder, and upper back. After baseline evaluation, subjects will undergo an SCS trial using the Abbott Invisible Trial system according to standard clinical procedures. During the trial phase, SCS leads will be implanted in the cervical epidural space. At the end of the SCS trial, subjects experiencing at least 50% pain relief will be considered for permanent implant. Pain intensity, medication usage, and other multidimensional pain outcomes will be collected. The timing of these will be at baseline, end of the SCS trial and at 3-, 6-, and 12-month visits. Incidence of adverse events will be collected throughout the study duration.

DISCUSSION

The results of this feasibility study will validate the efficacy and safety of DeRidder Burst-SCS stimulation in the cervical spine. The results obtained in this study will potentially be used to generate a level 1 evidence-based study with formal statistical hypotheses testing.

TRIAL REGISTRATION

www.clinicaltrials.gov Identifier: NCT03159169.

Advances in the interventional management of neuropathic pain

The management of neuropathic pain, defined as pain as a result of a lesion or disease in the somatosensory nervous system, continues to be researched and explored. As conventional methods demonstrate limited long-term efficacy, there is a significant need to discover therapies that offer both longitudinal and sustained management of this highly prevalent disease, which can be offered through interventional therapies. Tricyclic antidepressants (TCAs), gabapentinoids, lidocaine, serotonin norepinephrine reuptake inhibitors (SNRIs), and capsaicin have been shown to be the most efficacious pharmacologic agents for neuropathic pain relief. With respect to infusion therapies, the use of intravenous (IV) ketamine could be useful for complex regional pain syndrome, fibromyalgia, and traumatic spinal cord injury. Interventional approaches such as lumbar epidurals are a reasonable treatment choice for up to 3 months of pain relief for patients who failed to respond to conservative treatment, with a “B” strength of recommendation and moderate certainty. Neuroablative procedures like pulsed radiofrequency ablation work by delivering electrical field and heat bursts to targeted nerves or tissues without permanently damaging these structures, and have been recently explored for neuropathic pain relief. Alternatively, neuromodulation therapy is now recommended as the fourth line treatment of neuropathic pain after failed pharmacological therapy but prior to low dose opioids. Finally, the intrathecal delivery of various pharmacologic agents, such as quinoxaline-based kappa-opioid receptor agonists, can be utilized for neuropathic pain relief. In this review article, we aim to highlight advances and novel methods of interventional management of neuropathic pain.

Spatial Filtering of Electroencephalography Reduces Artifacts and Enhances Signals Related to Spinal Cord Stimulation (SCS)

OBJECTIVES

How spinal cord stimulation (SCS) in its different modes suppresses pain is poorly understood. Mechanisms of action may reside locally in the spinal cord, but also involve a larger network including subcortical and cortical brain structures. Tonic, burst, and high-frequency modes of SCS can, in principle, entrain distinct temporal activity patterns in this network, but finally have to yield specific effects on pain suppression. Here, we employ high-density electroencephalography (EEG) and recently developed spatial filtering techniques to reduce SCS artifacts and to enhance EEG signals specifically related to neuromodulation by SCS.

MATERIALS AND METHODS

We recorded high-density resting-state EEGs in patients suffering from pain of various etiologies under different modes of SCS. We established a pipeline for the robust spectral analysis of oscillatory brain activity during SCS, which includes spatial filtering for attenuation of pulse artifacts and enhancement of brain activity potentially modulated by SCS.

RESULTS

In sensor regions responsive to SCS, neuromodulation strongly reduced activity in the theta and low alpha range (6-10 Hz) in all SCS modes. Results were consistent in all patients, and in accordance with thalamocortical dysrhythmia hypothesis of pain. Only in the tonic mode showing paresthesia as side effect, SCS also consistently and strongly reduced high-gamma activity (>84 Hz).

CONCLUSIONS

EEG spectral analysis combined with spatial filtering allows for a spatially and temporally specific assessment of SCS-related, neuromodulatory EEG activity, and may help to disentangle therapeutic and side effects of SCS.

Improved Psychosocial and Functional Outcomes and Reduced Opioid Usage Following Burst Spinal Cord Stimulation

Objective

Burst spinal cord stimulation (B‐SCS) has been shown to reduce neuronal firing in the anterior cingulate cortex through selective modulation of the medial pain pathway tract. This pain pathway communicates the affective component of pain processing. The purpose of this study was to assess the effect of B‐SCS on psychosocial functioning and its influence on pain and quality of life.

Materials and Methods

Eligible patients with chronic, intractable pain of the trunk, and/or lower limbs were enrolled. After a successful trial period, subjects received a permanent implant and returned for follow‐up at 6‐ and 12‐months.

Results

In total, 269 patients were enrolled at 22 centers. Trial success rate was 90%. Significant improvements in pain, physical, mental, and emotional functioning were observed from baseline to the 6‐ and 12‐month follow‐up (p < 0.001). Overall, patients had improved quality of life, became more active, and the negative impact of pain on daily life was decreasing. At one year, 81% of subjects were satisfied or very satisfied with their therapy. Subjects showing significant improvements on mental health outcomes reported enhanced pain relief and quality of life scores compared with subjects with continued impaired mental health at follow‐up. At one year, 89% of subjects who were taking opioids at baseline decreased or stayed at the same level of opioid use; 19% stopped taking any opioids. No unanticipated adverse events have been reported.

Conclusions

One‐year outcomes after B‐SCS show improvements across all evaluated psychological measures with the largest impact observed on catastrophizing and depression (the affective component of pain processing). These pain‐related beliefs and behaviors, and not pain intensity, have been shown to put patients at greatest risk of a poor prognosis and quality of life.

Differences in EEG patterns between tonic and high frequency spinal cord stimulation in chronic pain patients

OBJECTIVE

To investigate the differences in neural patterns between spinal cord stimulation (SCS) waveforms (60-Hz tonic vs 10-KHz high frequency stimulation, HFS) and their correlation to stimulation-induced pain relief.

METHODS

We recorded 10-channel electroencephalogram (EEG) in response to stimulation ON and OFF in 9 chronic pain patients (4 women, 5 men) during SCS surgery and examined the intraoperative spatio-spectral EEG features.

RESULTS

We discovered stronger relative alpha power in the somatosensory region and higher trend in alpha/theta peak power ratio in frontal cortex with HFS. We also observed a shift in peak frequency from theta to alpha rhythms in HFS as compared to baseline and tonic stimulation, where slower theta activity was maintained. Further, a positive correlation was found between changes in Oswestry disability index (ODI) scores (from preoperative to postoperative) and HFS-induced alpha/theta peak power ratio in frontal and somatosensory regions.

CONCLUSIONS

Altogether, our findings suggest that dynamic spectral interactions in theta-alpha band and their spatial distributions might be the first intraoperative neural signatures of pain relief induced by HFS in chronic pain.

SIGNIFICANCE

Examining electrophysiological changes intraoperatively has a potential to elucidate response to SCS therapy prior to device selection, reducing the healthcare expenditures associated with failed implants.

Examination and characterisation of burst spinal cord stimulation on cerebrospinal fluid cellular and protein constituents in patient responders with chronic neuropathic pain - A Pilot Study

INTRODUCTION

Patients with neuropathic pain have altered proteomic and neuropeptide constituents in cerebrospinal fluid (CSF) compared to controls. Tonic spinal cord stimulation (SCS) has demonstrated differential expression of neuropeptides in CSF before and after treatment suggesting potential mechanisms of action. Burst-SCS is an evidence-based paraesthesia free waveform utilised for neuropathic pain with a potentially different mechanistic action to tonic SCS. This study examines the dynamic biological changes of CSF at a cellular and proteome level after Burst-SCS.

METHODS

Patients with neuropathic pain selected for SCS had CSF sampled prior to implant of SCS and following 8 weeks of continuous Burst-SCS. Baseline and 8-week pain scores with demographics were recorded. T cell frequencies were analysed by flow cytometry, proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

4 patients (2 females, 2 males) with a mean age of 51 years (+/-SEM 2.74, SD 5.48) achieved a reduction in pain of >50% following 8 weeks of Burst-SCS. Analysis of the CSF proteome indicated a significant alteration in protein expression most related to synapse assembly and immune regulators. There was significantly lower expression of the proteins: growth hormone A1 (PRL), somatostatin (SST), nucleobindin-2 (NUCB2), Calbindin (CALB1), acyl-CoA binding protein (DBI), proSAAS (PCSK1N), endothelin-3 (END3) and cholecystokinin (CCK) after Burst-SCS. The concentrations of secreted chemokines and cytokines and the frequencies of T cells were not significantly changed following Burst-SCS.

CONCLUSION

This study characterised the alteration in the CSF proteome in response to burst SCS in vivo. Functional analysis indicated that the alterations in the CSF proteome is predominately linked to synapse assembly and immune effectors. Individual protein analysis also suggests potential supraspinal mechanisms.

Burst Spinal Cord Stimulation: A Systematic Review and Pooled Analysis of Real-World Evidence and Outcomes Data

Objective

This review provides a comprehensive assessment of the effectiveness of burst spinal cord stimulation (SCS). Ratings of pain intensity (visual analog scale or numeric rating scale) and patient-reported outcomes (PROs) on functional/psychometric domains such as depression (Beck Depression Index), catastrophizing (Pain Catastrophizing Scale), surveillance (Pain Vigilance and Attention Questionnaire), and others are addressed.

Design

Articles were identified and selected from the literature according to prospective, replicable methods. Effectiveness data—pain scores and PRO ratings—were weighted by study sample sizes and pooled. The effects of burst SCS were compared against values at baseline and with tonic SCS. For PROs, published population norms were used for comparison.

Results

Fifteen articles, with a combined sample size of 427, were included. Follow-up ranged from a few hours to two years. A variety of prospective designs were employed, including crossover studies, single-arm cohorts, and a randomized controlled trial, as well as retrospective case reports. The weighted pooled mean pain rating across articles at baseline was 76.7 (±27.4). With tonic SCS, this was reduced to 49.2 (±12.9), and with burst SCS it was further reduced to 36.7 (±11.6), a 12.5-point difference between tonic and burst values. Psychometric analyses of PROs noted preferential improvement with burst SCS. In addition, 65% of subjects stated a preference for burst SCS.

Conclusions

In pooled analyses that incorporated all available published evidence, the improvement over baseline for burst SCS was shown to have a clinically important incremental benefit over tonic SCS. In addition, burst SCS may support resolution of the emotional or cognitive aspects of pain that are mediated by medial thalamo-cortical pathways. This study highlights the value in considering the entire knowledge base in therapeutic assessments as well as adopting a consistent set of outcome variables within neuromodulation. Burst SCS is a valuable intervention, providing both analgesia and psychometric benefits that warrant further thoughtful applications.

All bursts are equal, but some are more equal (to burst firing): burstDR stimulation versus Boston burst stimulation

Introduction: Since the introduction of burst spinal cord stimulation for neuropathic pain, several companies have developed their own version of burst stimulation, which is confusing the marketplace and clinicians of what burst stimulation truly is, the value and utilization of the therapy.Areas covered: We review those two burst stimulation designs and notice important differences. The original burstDR^TM stimulation tries to mimic physiologic burst firing, which involves closely spaced high frequency sodium spikes nested on a calcium mediated plateau. This is realized by generating a train of 5 monophasic spikes of increasing amplitude with passive charge balance after the last spike, in contrast to the other burst designs which involve a version of cycling 4-5 spikes each being individually actively charge balanced spikes.Expert opinion: Based on the neurobiology of burst firing as well as abductive reasoning we like to clarify that burstDR^TM is a true physiologic burst stimulation, and that other versions being called burst stimulation are essentially clustered tonic stimulation. This differentiating terminology will prevent confusion for healthcare providers, regulators, and the marketplace of what burst stimulation is.

Potential Therapeutic Effect of Low Amplitude Burst Spinal Cord Stimulation on Pain

BACKGROUND

The SUNBURST Study, a USA-based controlled cross-over trial demonstrated that burst spinal cord stimulation was superior compared to tonic stimulation in suppressing chronic intractable pain. However, when on burst stimulation, participants preferred lower to higher amplitudes. This led to the hypothesis that lower burst amplitudes will correlate with lower pain scores while higher amplitudes will be associated with higher pain scores.

OBJECTIVE

To investigate correlations between burst amplitude and self-reported pain and different psychosocial measures.

MATERIALS AND METHODS

One hundred participants in the SUNBURST study were randomized to receive burst or tonic stimulation, each for 12 weeks in a cross-over manner. Complete data of 99 participants were used in this secondary analysis. Pearson correlations were conducted at 6-, 12-, 18-, and 24-weeks postactivation to determine the strength of linear relationships between burst amplitude and (1) the average seven-day daily pain Visual Analogue Scale (VAS), (2) the different domains of the Pain Catastrophizing Scale (PCS), (3) the different domains of the SF-36v2 (Quality Metric Incorporated, Lincoln, RI) Health Survey. In addition, correlations between tonic stimulation amplitude and the above-mentioned outcome measures were examined.

RESULTS

Significant positive correlations were identified between burst amplitude and total, "worst," and "trunk" pain for VAS; all domains for PCS; and "Role-Physical," "Bodily Pain," and "General Health" for SF-36v2™ after 12-weeks of burst stimulation.

CONCLUSIONS

In burst spinal cord stimulation, in contrast to tonic stimulation, lower amplitudes are more effective in suppressing pain than high amplitudes.

Fiber Threshold Accommodation as a Mechanism of Burst and High-Frequency Spinal Cord Stimulation

OBJECTIVES

Burst and high-frequency spinal cord stimulation (SCS), in contrast to low-frequency stimulation (LFS, < 200 Hz), reduce neuropathic pain without the side effect of paresthesia, yet it is unknown whether these methods' mechanisms of action (MoA) overlap. We used empirically based computational models of fiber threshold accommodation to examine the three MoA.

MATERIALS AND METHODS

Waveforms used in SCS are composed of cathodic, anodic, and rest phases. Empirical studies of human peripheral sensory nerve fibers show different accommodation effects occurring in each phase. Notably, larger diameter fibers accommodate more than smaller fibers. We augmented our computational axon model to replicate fiber threshold accommodation behavior for diameters from 5 to 15 μm in each phase. We used the model to predict threshold change in variations of burst, high frequency, and LFS.

RESULTS

The accommodation model showed that 1) inversion of larger and smaller diameter fiber thresholds produce a therapeutic window in which smaller fibers fire while larger ones do not and 2) the anodic pulses increase accommodation and perpetuate threshold inversion from burst to burst and between cathodic pulses in burst, high frequency, and variations, resulting in an amplitude "window" in which larger fibers are inactivated while smaller fibers fire. No threshold inversion was found for traditional LFS.

CONCLUSIONS

The model, based on empirical data, predicts that, at clinical amplitudes, burst and high-frequency SCS do not activate large-diameter fibers that produce paresthesia while driving medium-diameter fibers, likely different from LFS, which produce analgesia via different populations of dorsal horn neural circuits.

Effectiveness of tonic and burst motor cortex stimulation in chronic neuropathic pain

Background: Motor cortex stimulation (MCS) is an intracranial, invasive method for treatment of chronic pain. Main indications for MCS are central post stroke pain, neuropathic facial pain, phantom limb pain and brachial plexus or spinal cord injury pain. Spinal cord stimulation (SCS) with burst waveform has been proved to be more effective than tonic mode in chronic pain. Necessity to replace depleted batteries of motor cortex tonic stimulators gave us an opportunity of applying burst stimulation. The objective of the pilot study was to evaluate the effects of burst stimulation applied on motor cortex in patients with chronic pain syndromes as well as comparison to tonic mode. Materials and methods: We have evaluated 6 patients (females N=3, males N=3) belonging to the group of 14 cases (females N=5, males N=9) who had undergone surgical procedure of MCS in years 2005-2017. Selected for the study were 6 patients with thalamic pain N=3, with facial pain N=3 (anaesthesia dolorosa and neuropathic trigeminal neuralgia). The patients were subjected to both modes of stimulation then they chose which one was better in relieving pain: tonic or burst. Pain intensity was assessed with the visual analogue scale (VAS) before the replacement of implanted pulse generator (IPG) and after the stimulation with tonic and burst modes. Results: In the study, 5 out of 6 patients with MCS found burst mode more effective than tonic mode. Baseline VAS score in patients that had at least 3 months depleted battery of tonic IPG was 95 mm. After implantation of a new IPG mean VAS score on tonic stimulation was 72 mm, on burst 53 mm. Conclusions: The most preferred option of MCS in selected group of patients was burst stimulation. This study has shown, that the burst stimulation of cerebral cortex is a promising modality when tonic stimulation is not sufficient in refractory, neuropathic pain.

Cortical Mapping in Conventional and High Dose Spinal Cord Stimulation: An Exploratory Power Spectrum and Functional Connectivity Analysis With Electroencephalography

OBJECTIVES

Spinal cord stimulation (SCS) is considered an effective pain-relieving treatment for patients with Failed Back Surgery Syndrome (FBSS). Despite the clinical effectiveness, it is unknown whether the altered functional connectivity in such patients, as compared to healthy persons, can be influenced by SCS. Therefore, the goal of this study is to evaluate whether brain connectivity assessed by EEG differs between baseline and SCS in patients with FBSS.

MATERIALS AND METHODS

Eight patients with FBSS underwent a resting-state EEG protocol before SCS, 1.5 months and 2.5 months after receiving SCS. At each frequency band, power spectrums were compared for no SCS, conventional (CON) SCS and High Dose (HD) SCS. Functional connectivity, with the aid of eConnectome was also calculated.

RESULTS

Significant differences in the average power density spectrum over the whole scalp were observed between no SCS, CON SCS and HD SCS in delta, theta and beta frequency bands (p < 0.01). The average power spectrum for CON SCS was significantly lower than the average power spectrum for HD SCS. Marked increases in strength of the information flow between electrode pair FC3-TP9 in the beta frequency band (p = 0.006) were found in favor of HD SCS.

CONCLUSIONS

The differences in power spectrum and connectivity between the three conditions lead to the hypothesis that HD SCS differs from CON SCS on average power spectrum, suggesting that HD SCS may have a higher contribution on the excitatory bottom-up pathway.

Mechanism of Action in Burst Spinal Cord Stimulation: Review and Recent Advances

OBJECTIVE

This is a comprehensive, structured review synthesizing and summarizing the current experimental data and knowledge about the mechanisms of action (MOA) underlying spinal cord stimulation with the burst waveform (as defined by De Ridder) in chronic pain treatment.

METHODS

Multiple database queries and article back-searches were conducted to identify the relevant literature and experimental findings for results integration and interpretation. Data from recent peer-reviewed conference presentations were also included for completeness and to ensure that the most up-to-date scientific information was incorporated. Both human and animal data were targeted in the search to provide a translational approach in understanding the clinical relevance of the basic science findings.

RESULTS/CONCLUSIONS

Burst spinal cord stimulation likely provides pain relief via multiple mechanisms at the level of both the spinal cord and the brain. The specific waveforms and temporal patterns of stimulation both play a role in the responses observed. Differential modulation of neurons in the dorsal horn and dorsal column nuclei are the spinal underpinnings of paresthesia-free analgesia. The burst stimulation pattern also produces different patterns of activation within the brain when compared with tonic stimulation. The latter may have implications for not only the somatic components of chronic pain but also the lateral and affective pathway dimensions as well.

A revised psychosocial assessment model for implantable pain devices to improve their evidence basis and consensus with updated pain management guidelines

Although psychosocial evaluations for implantable pain devices have been consensus recommendations since the 1990s, there is an inconsistent support regarding their ability to identify suitable pain device candidates or to predict clinical outcomes. With the emergence of evidence-based practices and the recent release of pain management guidelines emphasizing functional improvements and safety, the disparity between the recommendations for implantable pain device psychosocial evaluations and the evidence supporting them has only grown. In this special report, we describe a revised model for conducting psychosocial evaluations among implantable pain device candidates. This model includes changes to increase the evidence-basis of the psychosocial evaluations, incorporate patient-centered care standards and harmonize the evaluation structure with the most current pain management guidelines.

Neurophysiological Effects of Dorsal Root Ganglion Stimulation (DRGS) in Pain Processing at the Cortical Level

OBJECTIVES

Dorsal root ganglion stimulation (DRGS) has been used successfully against localized neuropathic pain. Nevertheless, the effects of DRGS on pain processing, particularly at the cortical level, remain largely unknown. In this study, we investigated whether positive responses to DRGS treatment would alter patients' laser-evoked potentials (LEP).

METHODS

We prospectively enrolled 12 adult patients with unilateral localized neuropathic pain in the lower limbs or inguinal region and followed them up for six months. LEPs were assessed at baseline, after one month of DRGS, and after six months of DRGS. Clinical assessment included the Numerical Rating Scale (NRS), Brief Pain Inventory (BPI), SF-36, and Beck Depression Inventory (BDI). For each patient, LEP amplitudes and latencies of the N2 and P2 components on the deafferented side were measured and compared to those of the healthy side and correlated with pain intensity, as measured with the NRS.

RESULTS

At the one- and six-month follow-ups, N2-P2 amplitudes were significantly greater and NRS scores were significantly lower compared with baseline (all p's < 0.01). There was a negative correlation between LEP amplitudes and NRS scores (r_s = -0.31, p < 0.10).

CONCLUSIONS

DRGS is able to restore LEPs to normal values in patients with localized neuropathic pain, and LEP alterations are correlated with clinical response in terms of pain intensity.

Treatment of pain post-brachial plexus injury using high-frequency spinal cord stimulation

Purpose

Brachial plexopathy can sometimes cause severe chronic pain. There are many possible treatments for such neuropathic pain, including neuromodulation. However, rigorous scientific evidence on the usefulness of spinal cord stimulation (SCS) is still scarce. Here, we report the use of high-frequency (10 kHz) SCS (HFSCS) in a patient with brachial plexus injury (root avulsion).

Objective

To assess the efficacy of HFSCS in root avulsion and to investigate the putative neurophysiological mechanisms of HFSCS.

Methods

A 32-year-old woman visited our center following an iatrogenic brachial plexus injury. She underwent traditional, paresthesia-inducing, tonic SCS with cervical lead placement. She reported that stimulation-induced paresthesia was uncomfortable, without any pain reduction. After the successful trial of HFSCS, the patient was assessed at 1 month (T1) and 6 months (T6) after HFSCS implantation with pain and quality of life (QoL) scales. Moreover, she underwent a neurophysiological assessment (somatosensory evoked potentials [SEPs], reciprocal inhibition [RI], pain-motor integration [PMI], and the habituation of intraepidermal electrical stimulation-induced evoked potentials [IEPs]) with the stimulator switched on and switched off at T6.

Results

The patient reported 100% paresthesia-free pain relief, a consistent improvement of QoL, and a complete discontinuation of her previous pain treatment at T1 and T6. Moreover, we found suppression of SEPs, restored habituation of IEPs, and strengthening of RI and PMI.

Conclusion

This is the first report to illustrate the usefulness and safety of HFSCS for treating root avulsion in a patient with failed tonic SCS. Our data indicate that HFSCS may either block large-diameter fibers or stimulate medium-/small-diameter fibers, thus inducing analgesia without paresthesia, probably by reducing the activation of the wide-dynamic-range neurons. Moreover, HFSCS seems to modulate spinal inhibitory mechanisms and the descending corticospinal inhibitory output. Thus, HFSCS can be an effective option for treating refractory pain following root avulsion.

Comparison of Tonic vs. Burst Spinal Cord Stimulation During Trial Period

BACKGROUND

Spinal cord stimulation (SCS) is a well-known treatment in patients with failed back surgery syndrome (FBSS). Burst stimulation is a recently developed stimulation modality that seems to be superior to tonic stimulation.

METHODS

This observational multicenter study compared tonic and burst stimulation during a trial period in patients with FBSS or radiculopathy. All the patients enrolled underwent two weeks of tonic stimulation followed by another two weeks of BurstDR stimulation, without randomization. The primary outcome was the reduction of pain in the legs and back. Health-related quality of life (EQ-5D) and the pain catastrophizing scale (PCS) were assessed before and after the trial. Patients were reevaluated after 12 months.

RESULTS

We recruited 23 patients, 57% of whom had FBSS and 43% had radiculopathies. Five patients failed both the tonic and burst stimulation trials. While tonic stimulation reduced leg pain (p < 0.05), the burst mode added an extra pain reduction (ΔNRS 1.2 ± 1.5) (p < 0.01). No significant reduction in back pain was found (p 0.29). Pain on movement was reduced only by BurstDR (p < 0.01). Both stimulation modalities increased EQ-5D and reduced PCS from the baseline (p < 0.0001). At the end of the SCS trial phase, 26% patients chose tonic SCS, while 74% preferred burst. On 12-month follow-up examination, the benefits recorded at the end of the trial were maintained.

CONCLUSIONS

Burst stimulation confers a greater reduction in leg pain intensity at rest and on movement. Reducing axial pain is still a challenge. Further studies are needed in order to provide each patient with the most appropriate stimulation paradigm.

Objective Measures to Characterize the Physiological Effects of Spinal Cord Stimulation in Neuropathic Pain: A Literature Review

OBJECTIVE

The physiological mechanisms behind the therapeutic effects of spinal cord stimulation (SCS) are only partially understood. Our aim was to perform a literature review of studies that used objective measures to characterize mechanisms of action of SCS in neuropathic pain patients.

MATERIALS AND METHODS

We searched the PubMed data base to identify clinical studies that used objective measures to assess the effects of SCS in neuropathic pain. We extracted the study factors (e.g., type of measure, diagnoses, painful area[s], and SCS parameters) and outcomes from the included studies.

RESULTS

We included 67 studies. Of these, 24 studies used neurophysiological measures, 14 studies used functional neuroimaging techniques, three studies used a combination of neurophysiological and functional neuroimaging techniques, 14 studies used quantitative sensory testing, and 12 studies used proteomic, vascular, and/or pedometric measures. Our findings suggest that SCS largely inhibits somatosensory processing and/or spinal nociceptive activity. Our findings also suggest that SCS modulates activity across specific regions of the central nervous system that play a prominent role in the sensory and emotional functions of pain.

CONCLUSIONS

SCS appears to modulate pain via spinal and/or supraspinal mechanisms of action (e.g., pain gating, descending pain inhibition). However, to better understand the mechanisms of action of SCS, we believe that it is necessary to carry out systematic, controlled, and well-powered studies using objective patient measures. To optimize the clinical effectiveness of SCS for neuropathic pain, we also believe that it is necessary to develop and implement patient-specific approaches.