Waves of Pain Relief: A Systematic Review of Clinical Trials in Spinal Cord Stimulation Waveforms for the Treatment of Chronic Neuropathic Low Back and Leg Pain

Spinal Cord Stimulation Waveforms for the Treatment of Chronic Pain

PURPOSE OF REVIEW

Since the advent of spinal cord stimulation (SCS), advances in technology have allowed for improvement and treatment of various conditions, especially chronic pain. Additionally, as the system has developed, the ability to provide different stimulation waveforms for patients to treat different conditions has improved. The purpose and objective of the paper is to discuss basics of waveforms and present the most up-to-date literature and research studies on the different types of waveforms that currently exist. During our literature search, we came across over sixty articles that discuss the various waveforms we intend to evaluate.

RECENT FINDINGS

There are several publications on several waveforms used in clinical practice, but to our knowledge, this is the only educational document teaching on waveforms which provides essential knowledge. There is a gap of knowledge related to understanding wave forms and how they work.

1. Lumbosacral radicular pain

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Improved Outcomes and Therapy Longevity after Salvage Using a Novel Spinal Cord Stimulation System for Chronic Pain: Multicenter, Observational, European Case Series

Spinal cord stimulation (SCS) is proven to effectively relieve chronic neuropathic pain. However, some implanted patients may face loss of efficacy (LoE) over time, and conversion to more recent devices may rescue SCS therapy. Recent SCS systems offer novel stimulation capabilities, such as temporal modulation and spatial neural targeting, and can be used to replace previous neurostimulators without changing existing leads. Our multicenter, observational, consecutive case series investigated real-world clinical outcomes in previously implanted SCS patients who were converted to a new implantable pulse generator. Data from 58 patients in seven European centers were analyzed (total follow-up 7.0 years, including 1.4 years after conversion). In the Rescue (LoE) subgroup (n = 51), the responder rate was 58.5% at the last follow-up, and overall pain scores (numerical rating scale) had decreased from 7.3 ± 1.7 with the previous SCS system to 3.5 ± 2.5 (p < 0.0001). Patients who converted for improved battery longevity (n = 7) had their pain scores sustained below 3/10 with their new neurostimulator. Waveform preferences were diverse and patient dependent (34.4% standard rate; 44.8% sub-perception modalities; 20.7% combination therapy). Our results suggest that patients who experience LoE over time may benefit from upgrading to a more versatile SCS system.

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

INTRODUCTION

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

EVIDENCE ACQUISITION

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

EVIDENCE SYNTHESIS

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

CONCLUSIONS

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

Electroacupuncture alleviates neuropathic pain caused by SNL by promoting M2 microglia polarization through PD-L1

As a common clinical disease, neuropathic pain is difficult to be cured with drugs. The occurrence and progression of pain is closely related to the response of spinal microglia. Aspartof the regulation of microglialactivity,PD-L1 playsacriticalrole. Loss of PD-L1 promoted the polarization of M1-like microglia. Increased expression of PD-L1 promoted M2-like polarization. Electroacupuncture has a significant analgesic effect in clinical practice, but its specific mechanism remains to be further explored. In this study, we verified the role of PD-L1 in EA analgesia and the underlying molecular mechanism through spinal nerve ligation (SNL) in rats and lipopolysaccharide (LPS)-treated BV2 microglial cells. Forbehavioralstudiesofrats,mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured, and spinal cord neuros were examined under transmission electron microscopyto determine changes to their myelin structure. The expression levels of PD-L1 and M1/M2-specific markers in rat spinal cord and BV2 microglial cells were measured by enzyme-linked immunosorbent assay, flow cytometry, immunofluorescence staining and Western blot analysis. Our study showed that EA increased the pain threshold, reduced the destruction of myelin structure, promoted the expression of PD-L1 and PD-1, inhibited the MAPK signaling pathway, and promoted the conversion of microglial polarization from the M1 phenotype to the M2 phenotype in SNL rats. PD-L1 knockdown reversed these effects of EA. In addition, PD-L1 knockdown activated the MAPK signaling pathway, promoted microglial polarization to the M1 phenotype, decreased the expression of anti-inflammatory mediators and increased the expression of proinflammatory factors in LPS-stimulated BV2 microglial cells. Our results showed that EA may regulate the excitability of primary afferent neurons through PD-L1 and then inhibit the MAPK signaling pathway to promote the transformation of activated M1 microglia into M2 microglia, reduce inflammatory reactions, and finally achieve analgesic effects. A therapy targeting PD-L1 may be an effective strategy for treating neuropathic pain.

Is Spinal Cord Stimulation Still Effective After One or More Surgical Revisions?

OBJECTIVES

Spinal cord stimulation (SCS) is burdened with surgical complications that may require one or several surgical revision(s), challenging its risk/benefit ratio and cost-effectiveness. Our objective was to evaluate its outcome and efficacy after one or more SCS surgical revisions.

MATERIALS AND METHODS

We identified and retrospectively analyzed 116 patients treated by tonic paresthesia-based SCS who experienced one or more complication(s) requiring at least one surgical revision. Data collected included initial indication, revision indication, number of revisions, and lead design (paddle or percutaneous). Outcome after SCS revision was evaluated by pain intensity decrease (comparing baseline and postrevision Numerical Rating Scale [NRS] scores) and percentage of patients reporting pain relief ≥50%. Outcome was analyzed according to the number of surgical revisions and the revision indications.

RESULTS

Most of the patients (61%) underwent only one revision (mean delay after implantation 44 months). The most frequent causes of revisions were hardware dysfunction (32%), lead migration (23%), and infection (18%). Revision(s) repaired the SCS issue in 87% of the cases. One year after the first revision, 82% of the patients reported pain relief ≥50%, and the mean NRS decrease was 4.0 compared with baseline (p < 0.001). Benefit of SCS revision tended to decrease with the number of revisions but did not differ across revision indications. No serious surgical complications related to the revision occurred, except for three hematomas occurring after repeated revisions.

CONCLUSIONS

Our data suggest that surgical revision of SCS system is safe and led to significant pain relief in most of the cases, provided that the initial indication was good and that the previous stimulation was effective. However, success of SCS revision decreases with the number of revisions.

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

Background/importance

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

Objective

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

Evidence review

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

Findings

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

Conclusions

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

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).

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.

Summary

As new technologies give rise to new perspectives and understanding of pain, new research inspires the development of new technologies

Does Neuromodulation Reduce Chronic Pain Patient Emergency Department Utilization?

BACKGROUND

Chronic pain (CP) affects roughly 100 million adults in the United States. These subjects present disproportionately to the emergency department (ED). Neuromodulation (NM) has been shown to reduce ED visits longitudinally in subjects.

OBJECTIVE

To compare ED utilization rates between subjects with CP with and without NM.

METHODS

Subjects with failed back surgery syndrome, complex regional pain syndrome, or neuropathic pain diagnosis who visited the hospital between January 1, 2019, and December 31, 2019, were included. Subjects were divided into a NM-treated cohort and a non-NM cohort. Demographic information, medications, and pain provider visits were obtained. Pain-related ED visits between 2017 and 2019 were compared.

RESULTS

A total of 2516 subjects were identified; 291 (11.6%) previously underwent NM. The non-NM cohort had significantly higher rate of pain-related ED visits compared with the NM cohort (15.1% vs 10.0%, P = .018). Younger age (odds ratio [OR] = 0.888 [0.843-0.935]), shorter distance to the hospital (OR = 0.807 [0.767-0.849]), lower household income (OR = 0.865 [0.831-0.901]), opioid use (OR = 1.375 [1.291-1.465]), nonopioid use (OR = 1.079 [1.033-1.128]), and non-NM therapy (OR = 1.751 [1.283-2.390]) were significant predictors of ED visits. Opioid use was the only significant predictor (OR = 6.124 [1.417-26.473]) associated with ED visits in the NM cohort.

CONCLUSION

Subjects who underwent NM had fewer visits to the ED when compared with similar subjects who received conventional treatment. Opioid use prompted increased ED utilization in both cohorts. We posit that NM leads to improvement in pain outcomes, integration with multidisciplinary pain specialists, and reduction in severity and frequency of acute pain exacerbations, thereby limiting health care resource utilization.

A Comparison of 1000 Hz to 30 Hz Spinal Cord Stimulation Strategies in Patients with Unilateral Neuropathic Leg Pain Due to Failed Back Surgery Syndrome: A Multicenter, Randomized, Double-Blinded, Crossover Clinical Study (HALO)

INTRODUCTION

Multicenter, randomized, double-blinded crossover study. The Netherlands (ClinicalTrials.gov NCT02112474). We hypothesized that the pain suppressive effects of 1000 Hz and 30 Hz spinal cord stimulation (SCS) strategies are equally effective in patients with chronic, neuropathic, unilateral leg pain after back surgery.

METHODS

Thirty-two patients (18-70 years, minimum leg pain 50 mm on 100 mm visual analog scale (VAS), minimal back pain) were randomized (1:1) to start 1000 Hz or 30 Hz neurostimulation for 9 days. After a 5-day washout, they crossed over, for another 9 days. Primary outcome was pain suppression (mean of VAS scores 4×/day) during the crossover period. The main investigators were blinded to strategy allocation, patients were blinded to the outcome, a blinded assessor analyzed the primary outcome.

RESULTS

The primary outcome was analyzed in 26 patients. There was no period effect (delta 4 mm, p = 0.42, 95% CI [- 5, 13]), allowing direct intrapatient comparison of the treatment effect (delta 1 mm, p = 0.92, 95% CI [- 13, 14]). Ninety-two percent of patients in both periods experienced greater than 34% pain suppression (minimal clinically important difference, MCID). Secondary outcomes (22 patients): pain suppression and improved quality of life were sustained at 12 months; both were statistically significant and clinically relevant. Fifty percent of patients had greater than 80% pain suppression (p < 0.001). At study termination, all events were resolved; no unanticipated events were reported. Medtronic provided a grant for additional study costs.

CONCLUSION

We conclude that our hypothesis regarding the effect of 1000 Hz and 30 Hz stimulation strategies on pain suppression was confirmed. Both stimulation strategies led to a large, sustainable, clinically relevant pain suppression and improvement in quality of life.

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.

New developments for spinal cord stimulation

Spinal cord stimulation (SCS) is a well-established therapy for the treatment of chronic neuropathic pain. Newer SCS waveforms have improved patient outcomes, leading to its increased utilization among many pain conditions. More recently, SCS has been used to treat some symptoms in several movement disorders because of its good profile tolerability and capacity to stimulate local and distant areas of the central nervous system. After the original experimental findings in animal models of Parkinson's disease (PD) in the late 2000s, several studies have reported the beneficial clinical effects of SCS stimulation on gait in PD patients. Additionally, the spinal cord has emerged as a potential therapeutic target to treat essential and orthostatic tremor, some forms of ataxia, and atypical parkinsonisms. In this chapter, we describe the most recent advances in SCS for pain and the rationale and potential mechanism of action of stimulating the spinal cord for treating movement disorders, focusing on its network modulation. We also summarize the main clinical studies performed to date as well as their limitations and future perspectives.

The Effectiveness of Spinal Cord Stimulation for the Treatment of Axial Low Back Pain: A Systematic Review with Narrative Synthesis

OBJECTIVE

Determine the effectiveness of spinal cord stimulation (SCS) for the treatment of axial low back pain (LBP) with or without leg pain.

DESIGN

Systematic review.

SUBJECTS

Persons aged ≥18 with axial LBP with or without accompanying leg pain.

INTERVENTION

Traditional low-frequency, burst, or high-frequency SCS.

COMPARISON

Sham, active standard of care treatment, or none.

OUTCOMES

The primary outcome was ≥50% pain improvement, and the secondary outcome was functional improvement measured six or more months after treatment intervention.

METHODS

Publications in PubMed, MEDLINE, and Cochrane databases were reviewed through September 19, 2019. Randomized or nonrandomized comparative studies and nonrandomized studies without internal controls were included. The Cochrane Risk of Bias Tool and GRADE system were used to assess individual study characteristics and overall quality.

RESULTS

Query identified 262 publications; 17 were suitable for inclusion. For high-frequency SCS, the only level 1 study showed that 79% (95% confidence interval = 70-87%) of patients reported ≥50% pain improvement. For low-frequency SCS, the only level 1 study reported no categorical data for axial LBP-specific outcomes; axial LBP improved by a mean 14 mm on the visual analog scale at six months. Meta-analysis was not performed due to study heterogeneity.

CONCLUSIONS

According to GRADE, there is low-quality evidence that high-frequency SCS compared with low-frequency SCS is effective in patients with axial LBP with concomitant leg pain. There is very low-quality evidence for low-frequency SCS for the treatment of axial LBP in patients with concomitant leg pain. There is insufficient evidence addressing the effectiveness of burst SCS to apply a GRADE rating.

Exploration of High and Low Frequency Options for Subperception Spinal Cord Stimulation Using Neural Dosing Parameter Relationships: The HALO Study

OBJECTIVES

Subperception spinal cord stimulation (SCS) is described mostly utilizing waveforms that require high energy. However, the necessity of these waveforms for effective subperception has not been established. We aimed to explore whether effective subperception pain relief can be achieved using frequencies below 1 kHz.

MATERIALS AND METHODS

Thirty chronic pain patients implanted with SCS were enrolled as part of a multicenter, real-world, consecutive, observational case series. An effective stimulation location was determined using a novel electric field shape designed to preferentially modulate dorsal horn elements. Subsequently, programs at lower frequencies (600, 400, 200, 100, 50, and 10 Hz) were provided with pulse-width and amplitude adjusted to optimize response.

RESULTS

All tested frequencies (1 kHz down to 10 Hz) provided effective subperception relief, yielding a mean of 66-72% reduction in back, leg, and overall pain. It was found that to maintain analgesia, as frequency was decreased, the electrical or "neural" dose had to be adjusted according to parameter relationships described herein. With the reduction of frequency, we observed a net reduction of charge-per-second, which enabled energy savings of 74% (200 Hz) and 97% (10 Hz) relative to 1 kHz. Furthermore, pain reduction was sustained out to one year, with 85% of patients reporting a preference for frequencies of 400 Hz or below.

CONCLUSIONS

We have derived an electric field configuration and, along with previous learnings in the kHz range, a set of neural dosing parameter relationships (10-10,000 Hz), which enable the expansion of effective subperception SCS to low frequency and achieve major energy savings.

The American Society of Pain and Neuroscience (ASPN) Practical Guidelines to Study Design and Scientific Manuscript Preparation in Neuromodulation

Background

Healthcare clinical and even policy decisions are progressively made based on research-based evidence. The process by which the appropriate trials are developed and well-written manuscripts by means of evidence-based medicine recommendations has resulted in unprecedented necessity in evidence-based medicine in neuromodulation.

Methods

The essential considerations in the planning of neuromodulation research are discussed in the light of available scientific literature as well as the authors’ scientific expertise regarding research study design and scientific manuscript preparation.

Conclusion

This article should enable the reader to understand how to appropriately design a clinical research study and prepare scientific manuscripts. The high-quality and well-designed studies, when performed and reported effectively, support evidence-based medicine and foster improved patient outcomes.

A modulator of the low-voltage-activated T-type calcium channel that reverses HIV glycoprotein 120-, paclitaxel-, and spinal nerve ligation-induced peripheral neuropathies

The voltage-gated calcium channels CaV3.1-3.3 constitute the T-type subfamily, whose dysfunctions are associated with epilepsy, psychiatric disorders, and chronic pain. The unique properties of low-voltage-activation, faster inactivation, and slower deactivation of these channels support their role in modulation of cellular excitability and low-threshold firing. Thus, selective T-type calcium channel antagonists are highly sought after. Here, we explored Ugi-azide multicomponent reaction products to identify compounds targeting T-type calcium channel. Of the 46 compounds tested, an analog of benzimidazolonepiperidine-5bk (1-{1-[(R)-{1-[(1S)-1-phenylethyl]-1H-1,2,3,4-tetrazol-5-yl}(thiophen-3-yl)methyl]piperidin-4-yl}-2,3-dihydro-1H-1,3-benzodiazol-2-one) modulated depolarization-induced calcium influx in rat sensory neurons. Modulation of T-type calcium channels by 5bk was further confirmed in whole-cell patch clamp assays in dorsal root ganglion (DRG) neurons, where pharmacological isolation of T-type currents led to a time- and concentration-dependent regulation with a low micromolar IC50. Lack of an acute effect of 5bk argues against a direct action on T-type channels. Genetic knockdown revealed CaV3.2 to be the isoform preferentially modulated by 5bk. High voltage-gated calcium, as well as tetrodotoxin-sensitive and -resistant sodium, channels were unaffected by 5bk. 5bk inhibited spontaneous excitatory postsynaptic currents and depolarization-evoked release of calcitonin gene-related peptide from lumbar spinal cord slices. Notably, 5bk did not bind human mu, delta, or kappa opioid receptors. 5bk reversed mechanical allodynia in rat models of HIV-associated neuropathy, chemotherapy-induced peripheral neuropathy, and spinal nerve ligation-induced neuropathy, without effects on locomotion or anxiety. Thus, 5bk represents a novel T-type modulator that could be used to develop nonaddictive pain therapeutics.

Electroacupuncture improves neuronal plasticity through the A2AR/cAMP/PKA signaling pathway in SNL rats

Improvements in neuronal plasticity are considered to be conducive to recovery from neuropathic pain. Electroacupuncture (EA) is regarded as an effective rehabilitation method for neuropathic pain. However, the effects and potential mechanism associated with EA-induced repair of hyperesthesia are not fully understood. Evidence has suggested that the adenosine A2A receptor (A2AR) and the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway play an important role in improving neuropathic pain. Here, we examined the function of EA in promoting neuronal plasticity in spinal nerve ligation (SNL) rats. The A2AR antagonist SCH58261, A2AR agonist 2-p-(2-carboxyethyl)phenethylamino-50-N-ethylcarboxamido adenosine HCl (CGS21680) and A2AR siRNA were used to confirm the relationship between A2AR and the cAMP/PKA pathway as well as the effects of A2AR on EA-induced improvements in neurobehavioral state and neuronal plasticity. Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), HE staining, Western blotting, RT-PCR, immunofluorescence, enzyme-linked immunosorbent assay, Nissl staining, silver staining, Golgi-Cox staining and transmission electron microscopy were used to evaluate the changes in neurobehavioral performance, protein expression, neuronal structure and dendrites/synapses. The results showed that EA and CGS21680 improved the behavioral performance, neuronal structure and dendritic/synaptic morphology of SNL rats, consistent with higher expression levels of A2AR, cAMP and PKA. In contrast to the positive effects of EA, SCH58261 inhibited dendritic growth and promoted dendritic spine/synaptic remodeling. In addition, the EA-induced improvement in neuronal plasticity was inhibited by SCH58261 and A2AR siRNA, consistent with lower expression levels of A2AR, cAMP and PKA, and worse behavioral performance. These results indicate that EA suppresses SNL-induced neuropathic pain by improving neuronal plasticity via upregulating the A2AR/cAMP/PKA signaling pathway.

Efficacy of different spinal cord stimulation paradigms for the treatment of chronic neuropathic pain (PARS-trial): study protocol for a double-blinded, randomized, and placebo-controlled crossover trial

Background

Spinal cord stimulation (SCS) is an effective method to treat neuropathic pain; however, it is challenging to compare different stimulation modalities in an individual patient, and thus, it is largely unknown which of the many available SCS modalities is most effective. Specifically, electrodes leading out through the skin would have to be consecutively connected to different, incompatible SCS devices and be tested over a time period of several weeks or even months. The risk of wound infections for such a study would be unacceptably high and blinding of the trial difficult. The PARS-trial seizes the capacity of a new type of wireless SCS device, which enables a blinded and systematic intra-patient comparison of different SCS modalities over extended time periods and without increasing wound infection rates.

Methods

The PARS-trial is designed as a double-blinded, randomized, and placebo-controlled multi-center crossover study. It will compare the clinical effectiveness of the three most relevant SCS paradigms in individual patients. The trial will recruit 60 patients suffering from intractable neuropathic pain of the lower extremities, who have been considered for SCS therapy and were already implanted with a wireless SCS device prior to study participation. Over a time period of 35 days, patients will be treated consecutively with three different SCS paradigms (“burst,” “1 kHz,” and “1.499 kHz”) and placebo stimulation. Each SCS paradigm will be applied for 5 days with a washout period of 70 h between stimulation cycles. The primary endpoint of the study is the level of pain self-assessment on the visual analogue scale after 5 days of SCS.

Secondary, exploratory endpoints include self-assessment of pain quality (as determined by painDETECT questionnaire), quality of life (as determined by Quality of Life EQ-5D-5L questionnaire), anxiety perception (as determined by the Hospital Anxiety and Depression Scale), and physical restriction (as determined by the Oswestry Disability Index).

Discussion

Combining paresthesia-free SCS modalities with wireless SCS offers a unique opportunity for a blinded and systematic comparison of different SCS modalities in individual patients. This trial will advance our understanding of the clinical effectiveness of the most relevant SCS paradigms.

Trial registration

German Clinical Trials Register, DRKS00018929. Registered on 14 January 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-020-05013-7.

Finding Optimal Neuromodulation for Chronic Pain: Waves, Bursts, and Beyond

Background

Spinal cord stimulation (SCS) has emerged as state-of-the-art evidence-based treatment for chronic intractable pain related to spinal and peripheral nerve disorders. Traditionally delivered as steady-state, paraesthesia-producing electrical stimulation, newer technology has augmented the SCS option and outcome in the last decade.

Objective

To present an overview of the traditional and newer SCS waveforms.

Materials and Methods

We present a short literature review of SCS waveforms in reference to newer waveforms and describing paraesthesia-free, high frequency, and burst stimulation methods as well as advances in waveform paradigms and programming modalities. Pertinent literature was reviewed, especially in the context of evolution in the waveforms of SCS and stimulation parameters.

Results

Conventional tonic SCS remains one of the most utilized and clinically validated SCS waveforms. Newer waveforms such as burst stimulation, high-frequency stimulation, and the sub-perception SCS have emerged in the last decades with favorable results with no or minimal paraesthesia, including in cases otherwise intractable to conventional tonic SCS. The recent evolution and experience of closed-loop SCS is promising and appealing. The experience and validation of the newer SCS waveforms, however, remain limited but optimistic.

Conclusions

Advances in SCS device technology and waveforms have improved patient outcomes, leading to its increased utilization of SCS for chronic pain. These improvements and the development of closed-loop SCS have been increasingly promising development and foster a clinical translation of improved pain relief as the years of research and clinical study beyond conventional SCS waveform come to fruition.

WITHDRAWN: MiR-216b-5p attenuates chronic constriction injury-induced neuropathic pain in female rats by targeting MAL2 and inactivating Wnt/β-catenin signaling pathway

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Comparison of conventional, burst and high-frequency spinal cord stimulation on pain relief in refractory failed back surgery syndrome patients: study protocol for a prospective randomized double-blinded cross-over trial (MULTIWAVE study)

Background

While the evolution of technology provides new opportunities to manage chronic refractory pain using different waveform modalities of spinal cord stimulation in failed back surgery syndrome (FBSS), there is no randomized controlled trial available to compare the efficacy of these different stimulations waveforms to date. MULTIWAVE is a prospective, randomized, double-blinded, crossover trial study designed to compare the clinical efficacy of tonic conventional stimulation (TCS), burst stimulation (BURST) and high-frequency stimulation (HF) in FBSS patients over a 15-month period in SCS implanted patients.

Methods/design

Twenty-eight patients will be recruited in the Poitiers University Hospital, in Niort and La Rochelle Hospitals in France. Eligible patients with post-operative low back and leg pain with an average visual analog scale (VAS) score ≥ 5 for low back pain are implanted and randomly assigned to one of the six arms (in a 1:1:1:1:1:1 ratio), where they receive a 3-month combination of TCS, BURST and HF including one treatment modality per month and varying the order of the modality received within the six possible combinations. Patients receiving intrathecal drug delivery, peripheral nerve stimulation and back resurgery related to the original back pain complaint and experimental therapies are excluded from this study. Patients included in the spinal cord stimulation group undergo trial stimulation, and they all receive a TCS treatment for 2 months, as the gold standard modality. Thereafter, patients are randomly assigned to one of the six arms for the total duration of 3-month crossover period. Then, patients choose their preferred stimulation modality (TCS, BURST, or HF) for the follow-up period of 12 months. Outcome assessments are performed at baseline (first implant), before randomization (2 months after baseline) and at 1, 2, 3, 6, 9 and 15 months post-randomization. Our primary outcome is the average global VAS of pain over 5-day pain diary period between baseline and after each period of stimulation. Additional outcomes include changes in leg and back pain intensity, functional disability, quality of life, psychological state, paraesthesia intensity perception, patient satisfaction and the number of adverse events.

Discussion

Recruitment began in February 2017 and will continue through 2019.

Trial registration

Clinicaltrials.gov NCT03014583. Registered on 9 January 2017.

Anti-inflammatory protein TSG-6 secreted by bone marrow mesenchymal stem cells attenuates neuropathic pain by inhibiting the TLR2/MyD88/NF-κB signaling pathway in spinal microglia

Background

Neuroinflammation plays a vital role in the development and maintenance of neuropathic pain. Recent evidence has proved that bone marrow mesenchymal stem cells (BMSCs) can inhibit neuropathic pain and possess potent immunomodulatory and immunosuppressive properties via secreting a variety of bioactive molecules, such as TNF-α-stimulated gene 6 protein (TSG-6). However, it is unknown whether BMSCs exert their analgesic effect against neuropathic pain by secreting TSG-6. Therefore, the present study aimed to evaluate the analgesic effects of TSG-6 released from BMSCs on neuropathic pain induced by chronic constriction injury (CCI) in rats and explored the possible underlying mechanisms in vitro and in vivo.

Methods

BMSCs were isolated from rat bone marrow and characterized by flow cytometry and functional differentiation. One day after CCI surgery, about 5 × 10⁶ BMSCs were intrathecally injected into spinal cerebrospinal fluid. Behavioral tests, including mechanical allodynia, thermal hyperalgesia, and motor function, were carried out at 1, 3, 5, 7, 14 days after CCI surgery. Spinal cords were processed for immunohistochemical analysis of the microglial marker Iba-1. The mRNA and protein levels of pro-inflammatory cytokines (IL-1β, TNFα, IL-6) were detected by real-time RT-PCR and ELISA. The activation of the TLR2/MyD88/NF-κB signaling pathway was evaluated by Western blot and immunofluorescence staining. The analgesic effect of exogenous recombinant TSG-6 on CCI-induced mechanical allodynia and heat hyperalgesia was observed by behavioral tests. In the in vitro experiments, primary cultured microglia were stimulated with the TLR2 agonist Pam3CSK4, and then co-cultured with BMSCs or recombinant TSG-6. The protein expression of TLR2, MyD88, p-p65 was evaluated by Western blot. The mRNA and protein levels of IL-1β, TNFα, IL-6 were detected by real-time RT-PCR and ELISA. BMSCs were transfected with the TSG-6-specific shRNA and then intrathecally injected into spinal cerebrospinal fluid in vivo or co-cultured with Pam3CSK4-treated primary microglia in vitro to investigate whether TSG-6 participated in the therapeutic effect of BMSCs on CCI-induced neuropathic pain and neuroinflammation.

Results

We found that CCI-induced mechanical allodynia and heat hyperalgesia were ameliorated by intrathecal injection of BMSCs. Moreover, intrathecal administration of BMSCs inhibited CCI-induced neuroinflammation in spinal cord tissues. The analgesic effect and anti-inflammatory property of BMSCs were attenuated when TSG-6 expression was silenced. We also found that BMSCs inhibited the activation of the TLR2/MyD88/NF-κB pathway in the ipsilateral spinal cord dorsal horn by secreting TSG-6. Meanwhile, we proved that intrathecal injection of exogenous recombinant TSG-6 effectively attenuated CCI-induced neuropathic pain. Furthermore, in vitro experiments showed that BMSCs and TSG-6 downregulated the TLR2/MyD88/NF-κB signaling and reduced the production of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, in primary microglia treated with the specific TLR2 agonist Pam3CSK4.

Conclusions

The present study demonstrated a paracrine mechanism by which intrathecal injection of BMSCs targets the TLR2/MyD88/NF-κB pathway in spinal cord dorsal horn microglia to elicit neuroprotection and sustained neuropathic pain relief via TSG-6 secretion.

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.

Wireless Spinal Cord Stimulation Technology for the Treatment of Neuropathic Pain: A Single-Center Experience

OBJECTIVES

A new wireless spinal cord stimulation (SCS) technology, which was introduced in recent years, promises minimal invasive SCS as well as additional advantages such as a wide range of stimulation paradigms and 3-T magnetic resonance imaging (MRI) conditionality.

MATERIALS AND METHODS

We prospectively evaluated 12 patients suffering from therapy-resistant neuropathic pain, who were implanted with a wireless SCS system from 2017 to 2019. Potential issues pertaining to handling and usability of the SCS device were evaluated from a patients' as well as from a surgeon's perspective.

RESULTS

Mean follow-up was 228.0 days (95% CI, 20.0-518.0 days). We did not record any handling issues nor did we record any relevant local discomfort associated with the implanted SCS device. N = 3/12 patients reported discomfort from wearing the SCS antenna and one patient complained about a short battery life of the controller device. There were no reported incidents during 3-T MRI studies. After an average test period of 51.7 days (95% CI, 11.0-104.0 days), N = 9/12 patients (75%) had reached pain relief of 50% or more with an average pain relief (responders and partial responders) of 67.4% (95% CI, 50.0%-85.0%). On average, patients tested 2.2 different stimulation paradigms, with frequencies ranging from 60 Hz to 10 kHz, but there was no preferred stimulation paradigm.

CONCLUSIONS

Minimal invasive implantation of wireless SCS systems was feasible and safe. The device offered a broader range of stimulation paradigms compared to conventional SCS devices, an allowed for a prolonged testing phase and continuous adjustment of SCS programs.