EFNS guidelines on neurostimulation therapy for neuropathic pain

The Preventive Effect of Decorin on Epidural Fibrosis and Epidural Adhesions After Laminectomy

Laminectomy is commonly performed to treat degenerative spinal diseases by reducing compression on the spinal cord and nerve roots. The postoperative epidural fibrosis and epidural adhesions may result in failed back surgery syndrome, which is characterized by the symptoms of lower back pain or leg pain. There is currently no satisfactory treatment for this complication. The pathological processes of epidural fibrosis and epidural adhesions are relevant to the proliferation of fibroblasts, transdifferentiation of fibroblasts into myofibroblasts, and the excessive deposition of extracellular matrix (ECM) protein. According to reports, transforming growth factor-β1 (TGF-β1) played a vital role in the development of fibrosis by promoting aforementioned processes. Decorin, an endogenous proteoglycan and natural inhibitor of TGF-β1, has exhibited prominent anti-fibrosis activity in various scar formation and fibrosis models of many organs. However, the preventive effect of decorin on epidural fibrosis and epidural adhesions requires further investigation. Here, we investigated the therapeutic effects and potential mechanisms of decorin on epidural fibrosis and epidural adhesions. Our results indicated that decorin could significantly suppress the TGF-β1-induced proliferation, transdifferentiation, and extracellular matrix production in primary fibroblasts. Furthermore, Smad2/3 signaling pathway had been demonstrated to be involved in the preventive effect of decorin. Moreover, administration of decorin in vivo could notably inhibit epidural fibrosis and epidural adhesions after laminectomy. To date, there is no approved therapy to target TGF-β1 for the treatment of epidural fibrosis and epidural adhesions after laminectomy. Our research proved the anti-fibrosis effect of decorin, which may provide an effective and promising treatment for epidural fibrosis and epidural adhesions.

Top 100 Most-Cited Papers in Neuropathic Pain From 2000 to 2020: A Bibliometric Study

Background: Neuropathic pain research has grown impressively in the past two decades, as evidenced by improvements in research quality and increments in the number of research papers. In views of this situation, the use of quantitative measurements to analyze and characterize existing research has become imperative. The aim of this research is to identify and analyze the 100 most-cited papers in neuropathic pain research.

Methods: Neuropathic pain-related articles published between 2000 and 2020 were screened from Web of Science (WOS) by using the following subject terms: TI = (Neuralgia$ OR Neurodynia$ OR “Neuropathic pain” OR sciatica OR “Nerve pain$”). The publications were ranked in a descending order on the basis of citation counts, and the top 100 most-cited neuropathic pain papers were determined. Subsequently, we conducted a bibliometric study to determine the authors, journals, countries, and institutions that contributed the most to the top 100 neuropathic pain lists; describe the keywords and hotspots of the top 100 most-cited papers; and explore the factors associated with successful citations.

Results: The top 100 most-cited papers were published from 2000 to 2017, and 2003 had the largest number of published papers (n = 16). The mean number of citations per paper was 480.72, with a range of 262–1,569. Forty-four kinds of journals contributed to the top 100 most-cited papers, which were predominantly published in “Pain” (n = 23). The USA was determined to be the leader of neuropathic pain research in terms of quality and quantity.

Conclusion: This study provides a comprehensive list of the most influential papers on neuropathic pain and demonstrates the important advances in this field to help understand academic concerns and the directions of technological innovations in neuropathic pain worldwide.

Comparing pregabalin and gabapentin for persistent neuropathic pain: A protocol for a pilot N-of-1 trial series

Background

Evidence-based management of neuropathic pain is commonly ineffective due to the large variability in response between cases. Patients often have to trial several drugs before finding one that provides adequate relief, leading to increased costs and worsened outcomes. There is thus a need for tools to guide and streamline prescribing decisions in neuropathic pain. N-of-1 trials provide a potentially precise and economical method of selecting between multiple interventions in an individual patient, and merit a feasibility assessment for use in clinical pain practice.

Aims

We aim to evaluate the feasibility of N-of-1 trials to compare pregabalin and gabapentin for individual presentations of neuropathic pain.

Methods

This is a double-blinded multiple crossover study, with recruitment from existing patients at an outpatient pain clinic in New South Wales, Australia. Participants will undergo three 4-week treatment pairs, comprising 2 weeks of pregabalin (150–600 mg/day) and 2 weeks of gabapentin (900–3600 mg/day), in an individually randomised order. Intervention doses will be derived from participants’ existing treatment dose. Medications will be taken orally three times daily. The primary outcome will be pain intensity; measures will be self-reported daily in patient diaries. After completing all three cycles, participants and their physicians will be presented with the results of the trial to form an informed decision about their treatment.

Discussion

As a stable yet debilitating condition, neuropathic pain is especially amenable to an N-of-1 study design. A successful trial would represent a significant quality of life improvement for the patient, possibly extending over the course of their lifetime.

Spinal Cord Stimulation and Treatment of Peripheral or Central Neuropathic Pain: Mechanisms and Clinical Application

Spinal cord stimulation (SCS) as an evidence-based interventional treatment has been used and approved for clinical use in a variety of pathological states including peripheral neuropathic pain; however, until now, it has not been used for the treatment of spinal cord injury- (SCI-) induced central neuropathic pain. This paper reviews the underlying mechanisms of SCS-induced analgesia and its clinical application in the management of peripheral and central neuropathic pain. Evidence from recent research publications indicates that nociceptive processing at peripheral and central sensory systems is thought to be modulated by SCS through (i) inhibition of the ascending nociceptive transmission by the release of analgesic neurotransmitters such as GABA and endocannabinoids at the spinal dorsal horn; (ii) facilitation of the descending inhibition by release of noradrenalin, dopamine, and serotonin acting on their receptors in the spinal cord; and (iii) activation of a variety of supraspinal brain areas related to pain perception and emotion. These insights into the mechanisms have resulted in the clinically approved use of SCS in peripheral neuropathic pain states like Complex Regional Pain Syndrome (CRPS) and Failed Back Surgery Syndrome (FBSS). However, the mechanisms underlying SCS-induced pain relief in central neuropathic pain are only partly understood, and more research is needed before this therapy can be implemented in SCI patients with central neuropathic pain.

Efficacy of electroacupuncture in patients with failed back surgery syndrome: study protocol for a randomized controlled trial

BACKGROUND

Persistent pain following back surgery called failed back surgery syndrome remains a major treatment challenge. The aim of this study is to evaluate the efficacy and safety of electroacupuncture on relieving back pain in FBSS patients.

METHODS/DESIGN

This is a randomized, single-blind, single-site, placebo-controlled trial. A total of 144 eligible FBSS patients will be randomly assigned to the electroacupuncture, manual acupuncture, or sham acupuncture group in a 1:1:1 ratio. Each group will receive 2 treatment sessions per week for 12 weeks. The primary outcome will be low back pain intensity based on the 11-point numerical rating scale (NRS). The secondary outcomes include Oswestry Disability Index (ODI) questionnaire, Beck Depression Inventory-II (BDI-II), Pittsburgh Sleep Quality Index (PSQI), and analgesic consumption. All clinical outcomes will be collected at baseline, during the treatment phase (at 8 and 12 weeks), and at the 16-, 24- and 36-week follow-ups. All data will be analyzed based on the intention-to-treat principle and adverse events will be assessed during the trial.

DISCUSSION

This pilot randomized controlled trial will evaluate the efficacy of electroacupuncture for treating failed back surgery syndrome. The outcomes will determine whether electroacupuncture is efficacious in relieving low back pain as well as improving the quality of life in failed back surgery syndrome patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2000040144 . Registered on 22 November 2020.

Does TENS Reduce the Intensity of Acute and Chronic Pain? A Comprehensive Appraisal of the Characteristics and Outcomes of 169 Reviews and 49 Meta-Analyses

Background and Objectives: Uncertainty about the clinical efficacy of transcutaneous electric nerve stimulation (TENS) to alleviate pain spans half a century. There has been no attempt to synthesise the entire body of systematic review evidence. The aim of this comprehensive review was to critically appraise the characteristics and outcomes of systematic reviews evaluating the clinical efficacy of TENS for any type of acute and chronic pain in adults. Materials and Methods: We searched electronic databases for full reports of systematic reviews of studies, overviews of systematic reviews, and hybrid reviews that evaluated the efficacy of TENS for any type of clinical pain in adults. We screened reports against eligibility criteria and extracted data related to the characteristics and outcomes of the review, including effect size estimates. We conducted a descriptive analysis of extracted data. Results: We included 169 reviews consisting of eight overviews, seven hybrid reviews and 154 systematic reviews with 49 meta-analyses. A tally of authors' conclusions found a tendency toward benefits from TENS in 69/169 reviews, no benefits in 13/169 reviews, and inconclusive evidence in 87/169 reviews. Only three meta-analyses pooled sufficient data to have confidence in the effect size estimate (i.e., pooled analysis of >500 events). Lower pain intensity was found during TENS compared with control for chronic musculoskeletal pain and labour pain, and lower analgesic consumption was found post-surgery during TENS. The appraisal revealed repeated shortcomings in RCTs that have hindered confident judgements about efficacy, resulting in stagnation of evidence. Conclusions: Our appraisal reveals examples of meta-analyses with 'sufficient data' demonstrating benefit. There were no examples of meta-analyses with 'sufficient data' demonstrating no benefit. Therefore, we recommend that TENS should be considered as a treatment option. The considerable quantity of reviews with 'insufficient data' and meaningless findings have clouded the issue of efficacy. We offer solutions to these issues going forward.

Spinal cord stimulation for neuropathic pain

Spinal cord stimulation (SCS) is used for more than 40years to treat localized chronic medically refractory neuropathic pain involving limb(s) and trunk. The most frequent indications remain complex regional pain syndrome (CRPS) failed back surgery syndrome (FBSS), and peripheral neuropathy. Stimulation-induced paresthesias, perceived by the patient, prevent blinded evaluation and increase the placebo effect, decreasing the credibility of the tonic SCS efficacy. Retrospective studies reported that about 50% of the patients are improved more than 50% at short-term, but long-term improvement is less. Several comparative randomized trials (RCT) are now available. In CRPS, a RCT demonstrated the superiority of SCS plus physiotherapy compared to physiotherapy alone. In FBSS, two RCTs have shown that SCS was superior to reoperation and conventional medical treatment, (CMM) respectively. New stimulation waveforms, namely burst, high frequency (10KHz) stimulation and close-loop SCS, have been proposed recently to avoid the perception of paresthesias and/or increase the pain relief. RCTs in FBSS have suggested that these new SCS modalities were as least as efficient than conventional tonic SCS and perhaps slightly superior. Two RCTs confirmed SCS efficacy in painful diabetic neuropathy in comparison with CMM. Complications are frequent (hardware dysfunction or migration, superficial infection) but exceptionally serious. Consequently, the risk/benefit ratio is favorable to SCS, considering that chronic pain patients undergoing this procedure are usually resistant to all the other therapies.

Motor cortex stimulation for chronic neuropathic pain: results of a double-blind randomized study

Motor cortex stimulation (MCS) via surgically implanted electrodes has been used as an off-label treatment for chronic neuropathic pain (cNeP) but its efficacy has not been fully established. We aimed to objectively study the efficacy of MCS and characterize potential predictors of response. In this randomised, double-blind, sham-controlled, single centre trial, we recruited 18 cNeP patients who did not adequately respond to conventional treatment and had a numerical rating pain scale (NRS) score ≥ 6. Patients were initially assigned to receive three months of active ("on") or sham ("off") stimulation in a double-blind cross-over phase. This was followed by a 3-month single-blind phase, and 6 months of open-label follow-up. A meaningful response in our trial was defined as a ≥ 30% or 2-point reduction in NRS scores during active stimulation. Using Bayesian statistics, we found a 41.4% probability of response towards "on" vs. "off" MCS. The probability of improvement during active stimulation (double-blind, single-blind and open label phases) compared to baseline was of 47.2-68.5%. 39% of patients were long-term responders, 71.4% of whom had facial pain, phantom limb pain, or complex regional pain syndrome. In contrast, 72.7% of non-responders had either post-stroke pain or pain associated with brachial plexus avulsion. 39% of patients had a substantial post-operative analgesic effect after electrode insertion in the absence of stimulation. Individuals with diagnoses associated with a good postoperative outcome or those who developed an insertional effect had a near 100% probability of response to MCS. In summary, we found that approximately 40% of patients responded to MCS, particularly those who developed an insertional effect or had specific clinical conditions that seemed to predict an appropriate postoperative response.

Benefit of spinal cord stimulation for patients with central poststroke pain: a retrospective multicenter study

OBJECTIVE

Spinal cord stimulation (SCS) has been considered an ineffective procedure for patients with central poststroke pain (CPSP). However, recent case series that included small numbers of patients reported the possible efficacy of SCS as a treatment of CPSP. This multicenter retrospective study aimed to examine the outcomes of using SCS to treat patients with CPSP and to explore factors related to outcomes.

METHODS

The authors reviewed the medical records of patients with CPSP who underwent SCS to collect data regarding their background, surgical information, and outcomes of SCS at trial stimulation and last follow-up after long-term implantation in six study centers. Outcomes were evaluated with a pain score for intensity (range 0-10) and the Patient Global Impression of Changes (PGIC) scale. Factors associated with outcomes were explored with univariable and multivariable analyses.

RESULTS

The authors collected data from a total of 166 patients (mean age 63.4 years; mean pain score at baseline 8.2). Of these patients, 163 underwent trial stimulation. The mean pain score decreased by 42.0%, 104 (64%) patients had ≥ 30% decrease in pain score, and 96 (59%) reported much or very much improved condition on the PGIC scale at trial stimulation. Moreover, 106 (64%) patients underwent long-term implantation of SCS devices. The mean decrease in pain score was 41.4%, 63 (59%) patients continued to show ≥ 30% decrease in pain score at last follow-up, and 60 (56%) reported much or very much improved condition on the PGIC scale at last follow-up (median [range] follow-up period 24 [24-63] months). Eleven device-related complications and 10 permanent explantations were observed. Univariable and multivariable analyses suggested that young age, less sensory disturbance, implantation of cervical leads, treatment of upper-limb pain, and extensive treated regions were associated with satisfactory outcomes at last follow-up after long-term implantation.

CONCLUSIONS

These findings indicate that SCS may modestly benefit patients with CPSP. SCS has therapeutic potential for patients with intractable CPSP owing to the lower invasiveness of the SCS procedure and refractory nature of CPSP. Nevertheless, trial stimulation is necessary because of the high initial failure rate.

Focused Ultrasound (FUS) for Chronic Pain Management: Approved and Potential Applications

Chronic pain is one of the leading causes of disability and disease burden worldwide, accounting for a prevalence between 6.9% and 10% in the general population. Pharmacotherapy alone results ineffective in about 70-60% of patients in terms of a satisfactory degree of pain relief. Focused ultrasound is a promising tool for chronic pain management, being approved for thalamotomy in chronic neuropathic pain and for bone metastases-related pain treatment. FUS is a noninvasive technique for neuromodulation and for tissue ablation that can be applied to several tissues. Transcranial FUS (tFUS) can lead to opposite biological effects, depending on stimulation parameters: from reversible neural activity facilitation or suppression (low-intensity, low-frequency ultrasound, LILFUS) to irreversible tissue ablation (high-intensity focused ultrasounds, HIFU). HIFU is approved for thalamotomy in neuropathic pain at the central nervous system level and for the treatment of facet joint osteoarthritis at the peripheral level. Potential applications include HIFU at the spinal cord level for selected cases of refractory chronic neuropathic pain, knee osteoarthritis, sacroiliac joint disease, intervertebral disc nucleolysis, phantom limb, and ablation of peripheral nerves. FUS at nonablative dosage, LILFUS, has potential reversible and tissue-selective effects. FUS applications at nonablative doses currently are at a research stage. The main potential applications include targeted drug and gene delivery through the Blood-Brain Barrier, assessment of pain thresholds and study of pain, and reversible peripheral nerve conduction block. The aim of the present review is to describe the approved and potential applications of the focused ultrasound technology in the field of chronic pain management.

Thalamic deep brain stimulation for post-traumatic neuropathic limb pain: Efficacy at five years' follow-up and effective volume of activated brain tissue

Chronic neuropathic pain affects 7%-10% of the population. Deep brain stimulation (DBS) has shown variable but promising results in its treatment. This study prospectively assessed the long-term effectiveness of DBS in a series of patients with chronic neuropathic pain, correlating clinical results with neuroimaging. Sixteen patients received 5 years' post-surgical follow-up in a single center. Six had phantom limb pain after amputation and 10 had deafferentation pain after traumatic brachial plexus injury. Patient-reported outcome measures were completed before and after surgery, using VAS, UWNPS, BPI and SF-36 scores. Neuroimaging evaluated electrode location and effective volumes of activated tissue (VAT). Two subgroups were created based on the percentage of VAT superimposed upon the ventroposterolateral thalamic nucleus (eVAT), and clinical outcomes were compared. Analgesic effect was assessed at 5 years and compared to preoperative pain, with an improvement on VAS of 76.4% (p=0.0001), on UW-NPS of 35.2% (p=0.3582), on BPI of 65.1% (p=0.0505) and on SF-36 of 5% (p=0.7406). Eight patients with higher eVAT showed improvement on VAS of 67.5% (p=0.0017) while the remaining patients, with lower eVAT, improved by 50.6% (p=0.03607). DBS remained effective in improving chronic neuropathic pain after 5 years. While VPL-targeting contributes to success, analgesia is also obtained by stimulating surrounding posterior ventrobasal thalamic structures and related spinothalamocortical tracts.

Pre-motor versus motor cerebral cortex neuromodulation for chronic neuropathic pain

Electrical stimulation of the cerebral cortex (ESCC) has been used to treat intractable neuropathic pain for nearly two decades, however, no standardized approach for this technique has been developed. In order to optimize targeting and validate the effect of ESCC before placing the permanent grid, we introduced initial assessment with trial stimulation, using a temporary grid of subdural electrodes. In this retrospective study we evaluate the role of electrode location on cerebral cortex in control of neuropathic pain and the role of trial stimulation in target-optimization for ESCC. Location of the temporary grid electrodes and location of permanent electrodes were evaluated in correlation with the long-term efficacy of ESCC. The results of this study demonstrate that the long-term effect of subdural pre-motor cortex stimulation is at least the same or higher compare to effect of subdural motor or combined pre-motor and motor cortex stimulation. These results also demonstrate that the initial trial stimulation helps to optimize permanent electrode positions in relation to the optimal functional target that is critical in cases when brain shift is expected. Proposed methodology and novel results open a new direction for development of neuromodulation techniques to control chronic neuropathic pain.

Enhancing analgesic spinal cord stimulation for chronic pain with personalized immersive virtual reality

ABSTRACT

Spinal cord stimulation (SCS) is an approved treatment for truncal and limb neuropathic pain. However, pain relief is often suboptimal and SCS efficacy may reduce over time, requiring sometimes the addition of other pain therapies, stimulator revision, or even explantation. We designed and tested a new procedure by combining SCS with immersive virtual reality (VR) to enable analgesia in patients with chronic leg pain. We coupled SCS and VR by linking SCS-induced paresthesia with personalized visual bodily feedback that was provided by VR and matched to the spatiotemporal patterns of SCS-induced paresthesia. In this cross-sectional prospective interventional study, 15 patients with severe chronic pain and an SCS implant underwent congruent SCS-VR (personalized visual feedback of the perceived SCS-induced paresthesia displayed on the patient's virtual body) and 2 control conditions (incongruent SCS-VR and VR alone). We demonstrate the efficacy of neuromodulation-enhanced VR for the treatment of chronic pain by showing that congruent SCS-VR reduced pain ratings on average by 44%. Spinal cord stimulation-VR analgesia was stronger than that in both control conditions (enabling stronger analgesic effects than incongruent SCS-VR analgesia or VR alone) and kept increasing over successive stimulations, revealing the selectivity and consistency of the observed effects. We also show that analgesia persists after congruent SCS-VR had stopped, indicating carry over effects and underlining its therapeutic potential. Linking latest VR technology with recent insights from the neuroscience of body perception and SCS neuromodulation, our personalized new SCS-VR platform highlights the impact of immersive digiceutical therapies for chronic pain.Registration: clinicaltrials.gov, Identifier: NCT02970006.

Successful application of burst spinal cord stimulation for refractory upper limb pain: a case series

Spinal cord stimulation (SCS) has been used to treat sustained pain that is intractable despite various types of treatment. However, conventional tonic waveform SCS has not shown promising outcomes for spinal cord injury (SCI) or postamputation pain. The pain signal mechanisms of burst waveforms are different to those of conventional tonic waveforms, but few reports have presented the therapeutic potential of burst waveforms for the abovementioned indications. This current case report describes two patients with refractory upper limb pain after SCI and upper limb amputation that were treated with burst waveform SCS. While the patients could not obtain sufficient therapeutic effect with conventional tonic waveforms, the burst waveforms provided better pain reduction with less discomfort. However, further studies are necessary to better clarify the mechanisms and efficacy of burst waveform SCS in patients with intractable pain.

What Are the Results and the Prognostic Factors of Motor Cortex Stimulation in Patients with Facial Pain? A Systematic Review of the Literature

INTRODUCTION

Facial pain (FP) is a type of neuropathic pain which recognizes both central and peripheral causes. It can be difficult to treat because it can often become resistant to pharmacological treatments. Motor Cortex Stimulation (MCS) has been used in selected cases, but the correct indications of MCS in FP have not been fully established. Here we systematically reviewed the literature regarding MCS in FP analysing the results of this technique and studying the possible role of different factors in the prognosis of these patients.

METHODS

A literature search was performed through different databases (PubMed, Scopus, and Embase) according to PRISMA guidelines using the following terms in any possible combination: "facial pain" or "trigeminal" or "anaesthesia dolorosa" and "motor cortex stimulation."

RESULTS

111 articles were reviewed, and 12 studies were included in the present analysis for a total of 108 patients. Overall, at latest follow-up (FU), 70.83% of patients responded to MCS. The preoperative VAS significantly decreased at the latest FU (8.83 ± 1.17 and 4.31 ± 2.05, respectively; p < 0.0001). Younger age (p = 0.0478) and a peripheral FP syndrome (p = 0.0006) positively affected the definitive implantation rate on univariate analysis. Younger age emerged as a factor strongly associated to a higher probability to go to a definitive MCS implant on multivariate analysis (p = 0.0415).

CONCLUSION

Our results evidenced the effectiveness of MCS in treating FP. Moreover, the younger age emerged as a positive prognostic factor for definitive implantation. Further studies with longer FU are needed to better evaluate the long-term results of MCS.

Exercise and Neuropathic Pain: A General Overview of Preclinical and Clinical Research

Neuropathic pain is a disease of the somatosensory system that is characterized by tingling, burning, and/or shooting pain. Medication is often the primary treatment, but it can be costly, thus there is an interest in understanding alternative low-cost treatments such as exercise. The following review includes an overview of the preclinical and clinical literature examining the influence of exercise on neuropathic pain. Preclinical studies support the hypothesis that exercise reduces hyperalgesia and allodynia in animal models of neuropathic pain. In human research, observational studies suggest that those who are more physically active have lower risk of developing neuropathic pain compared to those who are less active. Exercise studies suggest aerobic exercise training (e.g., 16 weeks); a combination of aerobic and resistance exercise training (e.g., 10–12 weeks); or high-intensity interval training (e.g., 15 weeks) reduces aspects of neuropathic pain such as worst pain over the past month, pain over the past 24 h, pain scores, or pain interference. However, not all measures of pain improve following exercise training (e.g., current pain, heat pain threshold). Potential mechanisms and future directions are also discussed to aid in the goal of understanding the role of exercise in the management of neuropathic pain. Future research using standardized methods to further understanding of the dose of exercise needed to manage neuropathic pain is warranted.

Burst spinal cord stimulation for central neuropathic pain: Two case reports

INTRODUCTION

Central neuropathic pain can result from any type of injury to the central nervous system. Treatment of central neuropathic pain is very challenging. Recently, a novel stimulation paradigm, called burst stimulation, has been presented as an excellent alternative in a group of patients with intractable central neuropathic pain. We report 2 cases where burst spinal cord stimulation (SCS) was applied in patients with neuropathic pain due to spinal cord injury (SCI) or traumatic brain injury.

PATIENT CONCERNS

A 52-year-old man who underwent posterolateral fusion surgery for a T12 bursting fracture after a fall 11 years prior developed disabling pain in the anterolateral part of his right thigh. His neuropathic pain following SCI was refractory to various treatment modalities. A 65-year-old man had complained of intractable, cold, throbbing, and shooting pain mainly in his left lower limb during rehabilitation since undergoing a craniotomy 9 years prior for multiple brain injuries caused by a motorcycle accident.

DIAGNOSIS

Both of these 2 cases were diagnosed with central neuropathic pain syndrome caused by SCI or traumatic brain injury.

INTERVENTIONS

Burst SCS were proposed to alleviate the significant refractory pains that were resistant to various medications and stimulation was delivered to the patient in an alternating pattern between traditional tonic and burst waveforms.

CONCLUSION

The efficacy of burst SCS in central neuropathic pain is desirable considering the severity of pain in such patients, the refractory nature of their pain, and the paucity of alternative therapeutic options.

A randomized controlled trial of 5 daily sessions and continuous trial of 4 weekly sessions of repetitive transcranial magnetic stimulation for neuropathic pain

Supplemental Digital Content is Available in the Text.

Five daily sessions of repetitive transcranial magnetic stimulation with stimulus conditions were ineffective in neuropathic pain relief. Long-term administration should be investigated for clinical use of repetitive transcranial magnetic stimulation in neuropathic pain.

We conducted a multicenter, randomized, patient- and assessor-blinded, sham-controlled trial to investigate the efficacy of repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) in patients with neuropathic pain (NP). Patients were randomly assigned to receive 5 daily sessions of active or sham rTMS of M1 corresponding to the part of the body experiencing the worst pain (500 pulses per session at 5 Hz). Responders were invited to enroll in an open-label continuous trial involving 4 weekly sessions of active rTMS. The primary outcome was a mean decrease in a visual analogue scale of pain intensity (scaled 0-100 mm) measured daily during the daily sessions in an intention-to-treat population. Secondary outcomes were other pain scores, quality-of-life measures, and depression score. One hundred forty-four patients were assigned to the active or sham stimulation groups. The primary outcome, mean visual analogue scale decreases, was not significantly different (P = 0.58) between the active stimulation group (mean, 8.0) and the sham group (9.2) during the daily sessions. The secondary outcomes were not significantly different between 2 groups. The patients enrolled in the continuous weekly rTMS achieved more pain relief in the active stimulation group compared with the sham (P < 0.01). No serious adverse events were observed. Five daily sessions of rTMS with stimulus conditions used in this trial were ineffective in short-term pain relief in the whole study population with various NP. Long-term administration to the responders should be investigated for the clinical use of rTMS on NP in the future trials.

Effects of dose titration on adherence and treatment duration of pregabalin among patients with neuropathic pain: A MarketScan database study

OBJECTIVE

To examine pregabalin dose titration and its impact on treatment adherence and duration in patients with neuropathic pain (NeP).

METHODS

MarketScan database (2009-2014) was used to extract a cohort of incident adult pregabalin users with NeP who had at least 12 months of follow-up data. Any dose augmentation within 45 days following the first pregabalin claim was defined as dose titration. Adherence (measured by medication possession ratio/MPR) and persistence (measured as the duration of continuous treatment) were compared between the cohorts with and without dose titration. Logistic regressions and Cox proportional hazards models were used to identify the factors associated with adherence (MPR ≥ 0.8) and predictors of time to discontinuation.

RESULTS

Among the 5,186 patients in the analysis, only 18% of patients had dose titration. Patients who had dose titration were approximately 2.6 times as likely to be adherent (MPR ≥ 0.8) (odds ratio = 2.59, P < 0.001) than those who did not have dose titration. Kaplan-Meier analysis shows that the time to discontinuation or switch was significantly longer among patients who had dose titration (4.99 vs. 4.04 months, P = 0.009).

CONCLUSIONS

Dose titration was associated with improved treatment adherence and persistence among NeP patients receiving pregabalin. The findings will provide valuable evidence to increase physician awareness of dose recommendations in the prescribing information and to educate patients on the importance of titration and adherence.

Randomized Prospective Study in Patients With Complex Regional Pain Syndrome of the Upper Limb With High-Frequency Spinal Cord Stimulation (10-kHz) and Low-Frequency Spinal Cord Stimulation

OBJECTIVE

The objective of this prospective randomized study of cases and controls was to evaluate the efficacy of treatment with low-frequency spinal cord stimulation (LF-SCS) and 10 kHz spinal cord stimulation (10-kHz SCS) in patients diagnosed with complex regional pain syndrome type I (CRPS) with upper limb involvement.

MATERIALS AND METHODS

Fifty patients were randomized to receive conventional treatment or SCS with a commercially available low-frequency or 10-kHz system. Patients were assessed at 1, 3, 6, and 12 months. The primary endpoint was at 12-months post permanent implantation of the SCS devices. Outcome measures assessed included: Numerical Rating Scale (NRS), 12-Item Short-Format Health Survey (SF-12), Oswestry Disability Index (ODI), Study Sleep Scale medical outcomes (MOS-SS), Douleur Neuropathique 4 questions pain questionnaire (DN4), Patient Global Impression Scale on the impact of treatment improvement (PGI-I), Clinician Global Impression Scale on the impact of improving the patient (CGI-I).

RESULTS

Forty-one patients were finally included in the analysis, 19 patients in the conventional treatment group, 12 in the LF-SCS group, and 10 in the 10-kHz SCS group. At the primary endpoint, patients treated with LF-SCS presented improvements in the NRS and DN4 outcomes around 2.4 and 1.5 times above the minimal clinically important difference (MCID) thresholds. At the primary endpoint, patients treated with 10-kHz SCS presented improvements in the NRS and DN4 outcomes around 2 and 1.4 times above the MCID thresholds.

CONCLUSIONS

Patients experienced considerable improvement after SCS. The results show that LF-SCS has very good results when compared with conventional treatment. The results obtained with 10-kHz SCS are encouraging, with the advantages of the absence of paresthesia making it an alternative in the treatment of CRPS.

Short-Term Suppression of Somatosensory Evoked Potentials and Perceived Sensations in Healthy Subjects Following TENS

Transcutaneous electrical nerve stimulation (TENS) has been reported to alleviate pain in chronic pain patients. Currently, there is limited knowledge how TENS affects can cause cortical neuromodulation and lead to modulation of non-painful and painful sensations. Our aim was therefore to investigate the effect of conventional, high-frequency TENS on cortical activation and perceived sensations in healthy subjects. We recorded somatosensory evoked potentials (SEPs) and perceived sensations following high-frequency TENS (100 Hz) in 40 healthy subjects (sham and intervention group). The effect of TENS was examined up to an hour after the intervention phase, and results revealed significant cortical inhibition. We found that the magnitude of N100, P200 waves, and theta and alpha band power was significantly suppressed following the TENS intervention. These changes were associated with a simultaneous reduction in the perceived intensity and the size of the area where the sensation was felt. Although phantom limb pain relief previously has been associated with an inhibition of cortical activity, the efficacy of the present TENS intervention to induce such cortical inhibition and cause pain relief should be verified in a future clinical trial.

Neuropathic Pain and Rehabilitation: A Systematic Review of International Guidelines

Background: Neuropathic pain is an injury or disease of the central and/or peripheral somatosensory nervous system, and it has a significant impact on quality of life, especially since it is often refractory to treatment. Rehabilitative intervention is considered in various guidelines on neuropathic pain treatment, although not in an organic nor detailed way. The aim of this systematic review was to analyze the most indicated therapeutic strategies, providing rehabilitative recommendations in the management of neuropathic pain. Methods: A systematic review was performed according to PRISMA guidelines. The scientific search, carried out until July 2020, considered guidelines in English language of the last thirteen years. Results: Six guidelines were analyzed, from which emerges that a multidisciplinary approach, comprehensive of pharmacologic and nonpharmacologic interventions, should drive neuropathic pain management. A relevant role in non-pharmacological intervention is played by rehabilitation, through an adequate tailored rehabilitation program and physical therapies. Conclusion: This analysis highlights the importance of rehabilitation but also the lack of evidence on various rehabilitative practices. Arises hence the need for further studies in this field to better define a rehabilitative treatment strategy.

Regional Techniques and Interventions for Intractable Neuropathic Pain

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10 kHz Spinal Cord Stimulation for the Treatment of Failed Back Surgery Syndrome with Predominant Leg Pain: Results from a Prospective Study in Patients from the Dutch Healthcare System

INTRODUCTION

Persistent back/and or leg pain is a common outcome after spinal surgery (otherwise known as failed back surgery syndrome [FBSS]). Studies have shown that spinal cord stimulation (SCS) at 10 kHz provides effective analgesia in FBSS patients with both back and leg pain symptoms and in those with predominant back pain. This study is the first to evaluate the therapy in FBSS patients with predominant leg pain.

METHODS

The safety and efficacy of 10 kHz SCS was evaluated in an uncontrolled, open-label, prospective study of FBSS patients with predominant leg pain in the Netherlands. Follow-ups were performed at 1, 3, 6, and 12 months post implantation.

RESULTS

Sixty out of 68 patients (88%) experienced sufficient pain relief during a stimulation trial. Of these, 58 proceeded to permanent implantation of a 10 kHz SCS system. After 12 months of treatment, 80% of patients experienced ≥ 50% reduction in baseline leg pain, and a similar proportion (76%) experienced ≥ 50% reduction in baseline back pain. At least two-thirds of patients were also leg pain and back pain remitters (visual analog scale [VAS] ≤ 2.5 cm). The therapy was also associated with a general improvement in patients' quality of life, as measured by secondary outcomes including disability, perception of health improvement, mental well-being, and satisfaction. A positive impact on opioid consumption was also observed.

CONCLUSIONS

Consistent with previous findings, 10 kHz SCS for the treatment of FBSS patients with predominant radicular symptoms is safe and effective and is associated with improved quality of life.

Somatosensory Thalamic Activity Modulation by Posterior Insular Stimulation: Cues to Clinical Application Based on Comparison of Frequencies in a Cat Model

BACKGROUND

The posterior insula (PI) has been proposed as a potential neurostimulation target for neuropathic pain relief as it represents a key-structure in pain processing. However, currently available data remain inconclusive as to efficient stimulation parameters.

OBJECTIVE

As frequency was shown to be the most correlated parameter to pain relief, this study aims to evaluate the potential modulatory effects of low frequency (LF-IS, 50 Hz) and high-frequency (HF-IS, 150 Hz) posterior insular stimulation on the activity of somatosensory thalamic nuclei.

MATERIALS AND METHODS

Epidural bipolar electrodes were placed over the PI of healthy adult cats, and extracellular single-unit activities of nociceptive (NS), nonnociceptive (NN), and wide dynamic range (WDR) thalamic cells were recorded within the ventral posterolateral nucleus and the medial division of the thalamic posterior complex. Mean discharge frequency and burst firing mode were analyzed before and after either LF-IS or HF-IS.

RESULTS

LF-IS showed a significant thalamic modulatory effects increasing the firing rate of NN cells (p ≤ 0.03) and decreasing the burst firing of NS cells (p ≤ 0.03), independently of the thalamic nucleus. Conversely, HF-IS did not induce any change in firing properties of the three recorded cell types.

CONCLUSION

These data indicate that 50 Hz IS could be a better candidate to control neuropathic pain.

Picosecond Pulse Electrical Field Suppressing Spike Firing in Hippocampal CA1 in Rat In Vivo

Picosecond pulse electrical fields (psPEFs), due to their high temporal-resolution accuracy and localization, were viewed as a potential targeted and noninvasive method for neuromodulation. However, few studies have reported psPEFs regulating neuronal activity in vivo. In this paper, a preliminary study on psPEFs regulating action potentials in hippocampus CA1 of rats in vivo was carried out. By analyzing the neuronal spike firing rate in hippocampus CA1 pre- and post-psPEF stimulation, effects of frequency, duration, and dosimetry of psPEFs were studied. The psPEF used in this study had a pulse width of 500 ps and a field strength of 1 kV/mm, established by 1 kV picosecond voltage pulses. Results showed that the psPEF suppressed spike firing in hippocampal CA1 neurons. The suppression effect was found to be significant except for 10 s, 10 Hz. For short-duration stimulation (10 s), the inhibition rate of spike firing increased with frequency. At longer stimulation durations (1 and 2 min), the inhibition rate increased and decreased alternately as the frequency increased. Despite this, the inhibition rate at high frequencies (5 and 10 kHz) was significantly larger than that at 10 and 100 Hz. A cumulative effect of psPEF on spike firing inhibition was found at low frequencies (10 and 100 Hz), which was saturated when frequency reached 500 Hz or higher. This paper conducts a study on psPEF regulating spike firing in hippocampal CA1 in vivo for the first time and guides subsequent study on psPEF achieving noninvasive neuromodulation. © 2020 Bioelectromagnetics Society.

Honokiol protects against epidural fibrosis by inhibiting fibroblast proliferation and extracellular matrix overproduction in rats post‑laminectomy

Epidural fibrosis (EF)‑induced failed back surgery syndrome (FBSS) in patients post‑laminectomy remains a medical challenge. Although the scarring mechanisms remain unclear, the majority of aetiological studies have reported fibroblast dysfunction. Honokiol, the major bioactive constituent of the magnolia tree, exerts a variety of pharmacological effects, including anti‑proliferative and anti‑fibrotic effects, on various cell types. The present study investigated whether honokiol attenuates EF progression. In vitro, it was found that honokiol inhibited excessive fibroblast proliferation induced by transforming growth factor‑β1 (TGF‑β1) and the synthesis of extracellular matrix (ECM) components, including fibronectin and type I collagen, in a dose‑dependent manner. These effects were attributed to the ability of honokiol to suppress the activity of connective tissue growth factor (CTGF), which is indispensable for the progression of fibrosis. Mechanistically, honokiol attenuated the TGF‑β1‑induced activation of the Smad2/3 and mitogen‑activated protein kinase (MAPK) signalling pathways in fibroblasts. In vivo, honokiol reduced the proliferation of fibroblasts and the synthesis of ECM components, thus ameliorating EF in a rat model post‑laminectomy. Taken together, these preclinical findings suggest that honokiol deserves further consideration as a candidate therapeutic agent for EF.

A novel controlled release tetrandrine-loaded PDLLA film: evaluation of drug release and anti-adhesion effects in vitro and in vivo

To investigate the drug release and anti-adhesion effects of a TET (tetrandrine)-loaded PDLLA (poly-dl-lactide) film. Detection of TET release in vitro was carried out by high-performance liquid chromatography (HPLC) every 2 days following immersion of the tetrandrine-loaded PDLLA film in simulated body fluid until the TET content of the eluate could not be detected. For the in vivo test, TET-loaded PDLLA films were implanted into animal laminectomy models and positive and blank control groups were also set up. Postoperative serum tests, and macroscopic and histological analyses at 1, 4, 8, and 12 weeks, were used to assess the effects of the film. Statistical analyses were performed by one-way ANOVA. The drug release of the tetrandrine-loaded PDLLA film in vitro showed two phases with a second release peak. Ultimately, the duration of continuous delivery was up to 66 days and the cumulative delivery rate was up to 93.18%. Scores for the proliferation of epidural scars or adhesion of the dura mater in the test group were much lower than those for the two control groups. Histological analysis revealed the test group had fewer inflammatory cells and fibroblasts, as well as fewer extracellular collagen fibers, and a lower histology score than those of the two control groups at all time points. Tetrandrine-loaded PDLLA film is a novel controlled drug release and anti-adhesion material in vitro and in vivo.

Neuromodulation Management of Chronic Neuropathic Pain in The Central Nervous system

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

Peripheral Nerve Stimulation of the Brachial Plexus for Chronic Refractory CRPS Pain of the Upper Limb: Description of a New Technique and Case Series

OBJECTIVE

Upper limb complex regional pain syndrome is an important cause of chronic pain, and its treatment is challenging. In this pilot case series, we preliminarily evaluated the feasibility, effectiveness, and safety of a new technique for brachial plexus neuromodulation in the treatment of this disease in patients refractory to conservative treatment.

METHODS

Between 2017 and 2018, 14 patients considered to be refractory to optimized conservative treatment were recruited to this study. In the first stage, patients were trialed for seven days with a new technique of implant of the brachial plexus. Patients with ≥50% pain relief in visual analog scale (VAS) score received a definitive implantation in the second stage. Follow-ups were conducted at pre-implant and 12 months using the Neuropathic Pain Scale, SF-32, and the visual analogic scale for pain.

RESULTS

After the initial trial, 10 patients had a pain reduction of ≥50% and received a permanent implant. At 12-month follow-up, VAS, Neuropathic Pain Scale, SF-12 physical and mental scores improved by 57.4% +/- 10% (P = 0.005), 60.2% +/- 12.9% (P = 0.006), and 21.9% +/- 5.9% (P = 0.015), respectively.

CONCLUSIONS

Our data suggest that this new technique of brachial plexus stimulation may have long-term utility in the treatment of painful upper limb complex regional pain syndrome. New more detailed comprehensive studies should be carried out to confirm our findings in a larger population and to further refine the clinical implementation of this technique.

Repetitive Transcranial Magnetic Stimulation for Chronic Prostatitis/Chronic Pelvic Pain Syndrome: A Prospective Pilot Study

Purpose

To evaluate the feasibility, efficacy, and safety of repetitive transcranial magnetic stimulation (rTMS) in patients with treatment-resistant chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS).

Methods

Eleven patients with CP/CPPS were enrolled in this prospective clinical study. rTMS was performed for 5 consecutive days in 20-minute sessions. Patients were evaluated at baseline, after treatment, and at 1, 4, 8, and 12 weeks after the last session with questionnaires concerning pain (numerical rating scale [NRS], the National Institutes of Health Chronic Prostatitis Symptom Index [NIH-CPSI], and the Short Form-36 [SF-36]), urinary symptoms (NIH-CPSI, Danish Prostatic Symptom Score [DAN-PSS-1]), quality of life (NIH-CPSI, SF-36), and psychometrics (Beck Depression Index [BDI]). Telephone-based interviews were used to evaluate side effects, subjective response, and changes in drug consumption.

Results

All patients completed the planned treatment and follow-up according to protocol. No patients experienced serious side effects or significant pain increase during or after treatment. Mild transient tension headache responsive to oral pain medication was reported by 2 patients. Decreased pain was observed on the NRS after treatment and at 1 and 8 weeks (P=0.019, P=0.006, P=0.042, respectively) and on the NIH-CPSI pain domain at 1 week (P=0.04). Improvement in lower urinary tract symptoms was observed after treatment in the NIH-CPSI urinary domain (P=0.02) but not with the DANPSS-1. No significant changes in the BDI were observed. Nine patients reported a positive overall subjective response (82%) and 6 patients (55%) were able to reduce pain medication. Higher age was associated with lower NRS scores after treatment (R=0.605, P=0.048) and at 8 weeks (R=0.659, P=0.028).

Conclusions

rTMS for patients with CP/CPPS seemed to be well tolerated, at least moderately effective in pain reduction, and might be of interest in patients with chronic pelvic pain resistant to conventional treatment. These findings remain to be confirmed by a randomized trial.

Electrical Thalamic Stimulation in the Anterior Part of the Ventral Posterolateral Nucleus for the Treatment of Patients With Central Poststroke Pain

OBJECTIVES

The effects of thalamic stimulation of the anterior part of the ventral posterolateral nucleus (VPLa) for central poststroke pain (CPSP) and the pain-related electrophysiological characteristics of this structure were investigated.

MATERIALS AND METHODS

Nine patients with CPSP manifesting as hemibody pain were enrolled. Stereotactic thalamic VPLa stimulation was implemented, and intraoperative electrophysiological studies on hyperactive and unstable discharges (HUDs) and responses to sensory and electrical stimulation were performed in the sensory thalamus. A preoperative somatosensory-evoked potential (SEP) study was carried out in all nine patients and in eight other patients with localized pain.

RESULTS

The patients were classified into two groups: a HUD-dominant group (group H, n = 5) and a sensory response-dominant group (group R, n = 4). HUDs were frequently encountered in the thalamic VPLa in the former group. The total number of HUDs and the number along the trajectory to the VPLa in group H were significantly larger than those in group R. The improvements on the pain numeric rating scale in group H were significantly higher than those in group R two years after surgery. The amplitude ratio of the SEP N20s in the ipsilateral to the contralateral side of CVD lesion in the study group was significantly lower than in the localized pain group.

CONCLUSIONS

Adequate and stable pain relief with thalamic VPLa stimulation is obtainable in patients with CPSP who exhibit hyperactivity and electrical instability along the trajectory to this nucleus. Both responders and nonresponders were found to have severe dysfunction of the lemniscal system.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Opioids and Spinal Cord Stimulators: Pre- and Postoperative Opioid Use Patterns and Predictors of Prolonged Postoperative Opioid Use

Objective

The aim of the study was to compare trends and differences in preoperative and prolonged postoperative opioid use following spinal cord stimulator (SCS) implantation and to determine factors associated with prolonged postoperative opioid use.

Methods

A database of private-payer insurance records was queried to identify patients who underwent a primary paddle lead SCS placement via a laminectomy (CPT-C3655) from 2008–2015. Our resulting cohort was stratified into those with prolonged postoperative opioid use, opioid use between 3- and 6-month postoperation, and those without. Multivariate logistic regression was used to determine the effect preoperative opioid use and other factors of interest had on prolonged postoperative opioid use. Subgroup analysis was performed on preoperative opioid users to further quantify the effect of differing magnitudes of preoperative opioid use.

Results

A total of 2,374 patients who underwent SCS placement were identified. Of all patients, 1,890 patients (79.6%) were identified as having prolonged narcotic use. Annual rates of preoperative (p = 0.023) and prolonged postoperative narcotic use (p < 0.001) decreased over the study period. Significant independent predictors of prolonged postoperative opioid use were age < 65 years (odds ratio [OR], 1.52; p = 0.004), male sex (OR, 1.33; p = 0.037), preoperative anxiolytic (OR, 1.55; p = 0.004) and muscle relaxant (OR, 1.42; p = 0.033), and narcotic use (OR, 15.04; p < 0.001). Increased number of preoperative narcotic prescriptions correlated with increased odds of prolonged postoperative use.

Conclusion

Patients with greater number of preoperative opioid prescriptions may not attain the same benefit from SCSs as patients with less opioid use. The most significant predictor of prolonged narcotic use was preoperative opioid use.

Transcranial Magnetic Stimulation for Pain, Headache, and Comorbid Depression: INS-NANS Expert Consensus Panel Review and Recommendation

BACKGROUND

While transcranial magnetic stimulation (TMS) has been studied for the treatment of psychiatric disorders, emerging evidence supports its use for pain and headache by stimulating either motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC). However, its clinical implementation is hindered due to a lack of consensus in the quality of clinical evidence and treatment recommendation/guideline(s). Thus, working collaboratively, this multinational multidisciplinary expert panel aims to: 1) assess and rate the existing outcome evidence of TMS in various pain/headache conditions; 2) provide TMS treatment recommendation/guidelines for the evaluated conditions and comorbid depression; and 3) assess the cost-effectiveness and technical issues relevant to the long-term clinical implementation of TMS for pain and headache.

METHODS

Seven task groups were formed under the guidance of a 5-member steering committee with four task groups assessing the utilization of TMS in the treatment of Neuropathic Pain (NP), Acute Pain, Primary Headache Disorders, and Posttraumatic Brain Injury related Headaches (PTBI-HA), and remaining three assessing the treatment for both pain and comorbid depression, and the cost-effectiveness and technological issues relevant to the treatment.

RESULTS

The panel rated the overall level of evidence and recommendability for clinical implementation of TMS as: 1) high and extremely/strongly for both NP and PTBI-HA respectively; 2) moderate for postoperative pain and migraine prevention, and recommendable for migraine prevention. While the use of TMS for treating both pain and depression in one setting is clinically and financially sound, more studies are required to fully assess the long-term benefit of the treatment for the two highly comorbid conditions, especially with neuronavigation.

CONCLUSIONS

After extensive literature review, the panel provided recommendations and treatment guidelines for TMS in managing neuropathic pain and headaches. In addition, the panel also recommended more outcome and cost-effectiveness studies to assess the feasibility of the long-term clinical implementation of the treatment.

Spinal cord stimulation for the treatment of chronic pelvic pain after Tarlov cyst surgery in a 66-year-old woman: A case report

Tarlov cysts are extradural meningeal cysts with collections of cerebrospinal fluid within the nerve sheath. These cysts are uncommon but tend to present more often in women. Symptomatic Tarlov cysts can lead to a variety of neurologic symptoms and painful conditions, including chronic pelvic pain. There is no consensus regarding the best treatment for symptomatic cysts. Surgical management has high rates of complication, including chronic pain, but better long-term results for symptom and cyst resolution. We describe a patient who developed worsening pelvic pain and lumbar radiculopathy after surgical management of her Tarlov cysts. Medication failed to relieve the pain, as did a variety of other procedures, before the patient ultimately received significant pain relief from high-frequency spinal cord stimulation. This case may provide guidance for physicians when managing patients suffering from symptomatic Tarlov cysts, or worsening pain symptoms after surgical management of these cysts.

Remote Analgesic Effects Of Conventional Transcutaneous Electrical Nerve Stimulation: A Scientific And Clinical Review With A Focus On Chronic Pain

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) is a safe, noninvasive treatment for chronic pain that can be self-administered. Conventional TENS involves stimulation of peripheral sensory nerves at a strong, non-painful level. Following the original gate-control theory of pain, stimulation is typically near the target pain. As another option, remote stimulation may also be effective and offers potential advantages.

OBJECTIVE

This narrative review examines mechanisms underlying the remote analgesic effects of conventional TENS and appraises the clinical evidence.

METHODS

A literature search for English-language articles was performed on PubMed. Keywords included terms related to the location of TENS . Citations from primary references and textbooks were examined for additional articles.

RESULTS

Over 30 studies reported remote analgesic effects of conventional TENS. The evidence included studies using animal models of pain, experimental pain in humans, and clinical studies in subjects with chronic pain. Three types of remote analgesia were identified: at the contralateral homologous site, at sites distant from stimulation but innervated by overlapping spinal segments, and at unrelated extrasegmental sites.

CONCLUSION

There is scientific and clinical evidence that conventional TENS has remote analgesic effects. This may occur through modulation of pain processing at the level of the dorsal horn, in brainstem centers mediating descending inhibition, and within the pain matrix. A broadening of perspectives on how conventional TENS produces analgesia may encourage researchers, clinicians, and medical-device manufacturers to develop novel ways of using this safe, cost-effective neuromodulation technique for chronic pain.

Therapeutic Approaches for Peripheral and Central Neuropathic Pain

Neuropathic pain is a chronic secondary pain condition, which is a consequence of peripheral or central nervous (somatosensory) system lesions or diseases. It is a devastating condition, which affects around 7% of the general population. Numerous etiological factors contribute to the development of chronic neuropathic pain. It can originate from the peripheral part of the nervous system such as in the case of trigeminal or postherpetic neuralgia, peripheral nerve injury, painful polyneuropathies, or radiculopathies. Central chronic neuropathic pain can develop as a result of spinal cord or brain injury, stroke, or multiple sclerosis. As first-line pharmacological treatment options, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids are recommended. In trigeminal neuralgia, carbamazepine and oxcarbazepine are the first-choice drugs. In drug-refractory cases, interventional, physical, and psychological therapies are available. This review was structured based on a PubMed search of papers published in the field from 2010 until May 2019.

Prospective case series on the use of peripheral nerve stimulation for focal mononeuropathy treatment

Aim: This case series looks at outcomes in 39 patients implanted using the Bioness Stimrouter system on various isolated mononeuropathies. Patients & methods: A case series of 39 patients with a total of 42 implants were enrolled starting August 2017 at various pain management centers. Results: Of 39 patients studied, 78% of the participants noticed an improvement in their pain. There was a 71% reduction in pain scores with the average preprocedure score of 8 improving to 2 post-implant. Participants noted on average a 72% improvement in activity with the greatest observed in the brachial plexus (80%) and suprascapular nerve (80%) and smallest in the intercostal nerve (40%). Approximately 89% of those implanted with a peripheral nerve stimulator experienced a greater than 50% reduction in opioid consumption. Conclusion: Peripheral nerve stimulators are a new, minimally invasive neuromodulation modality that shows promising early results in our 39-patient case series.

Neurostimulation methods in the treatment of chronic pain

The goal of this narrative review was to give an up-to-date overview of the peripheral and central neurostimulation methods that can be used to treat chronic pain. Special focus has been given to three pain conditions: neuropathic pain, nociplastic pain and primary headaches. Both non-invasive and invasive techniques are briefly presented together with their pain relief potentials. For non-invasive stimulation techniques, data concerning transcutaneous electrical nerve stimulation (TENS), transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), remote electrical neuromodulation (REN) and vagus nerve stimulation (VNS) are provided. Concerning invasive stimulation techniques, occipital nerve stimulation (ONS), vagus nerve stimulation (VNS), epidural motor cortex stimulation (EMCS), spinal cord stimulation (SCS) and deep brain stimulation (DBS) are presented. The action mode of all these techniques is only partly understood but can be very different from one technique to the other. Patients' selection is still a challenge. Recent consensus-based guidelines for clinical practice are presented when available. The development of closed-loop devices could be of interest in the future, although the clinical benefit over open loop is not proven yet.

Alterations in grey matter density and functional connectivity in trigeminal neuropathic pain and trigeminal neuralgia: A systematic review and meta-analysis

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Activation likelihood estimation (ALE) shows to be a verified method to meta-analyze heterogeneous imaging results.

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From a broad variety of key regions, structural and functional changes were repeatedly found in the thalamus, the cingulate cortex and the middle frontal gyrus in TN/TNP patients.

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Future research should focus on these regions of interest in order to improve diagnostic imaging in TN/TNP.

Background

Various studies reported changes in grey matter volumes and modifications in functional connectivity of cortical and subcortical structures in patients suffering from trigeminal neuralgia (TN) and trigeminal neuropathic pain (TNP). This study meta-analyzed the concordant structural and functional changes in foci and provide further understanding of the anatomy and biology of TN/TNP.

Methods

Relevant articles on magnetic resonance imaging (MRI) and functional MRI in TN/TNP, published before August 2018, were searched for on PubMed and Embase. Following exclusion of unsuitable studies, a meta-analysis was performed using activation likelihood estimation (ALE).

Results

In total, 322 paper were identified, 11 of which could be included based on the predefined inclusion and exclusion criteria. Eight papers, totaling 279 subjects, discussing structural changes and four papers, totaling 102 subjects, discussing functional changes were included (i.e., one paper investigated both structural and functional alterations). ALE analysis showed that in TN/TNP, grey matter decreases are found in the thalamus, (anterior) cingulate gyrus, bilateral striatum, the superior-, middle- and transverse temporal gyrus, subcallosal gyrus, the bilateral insular cortex, the pre- and postcental gyrus, the middle frontal gyrus bilaterally and the anterior cerebellar lobe. Grey matter increases were seen in the periaqueductal grey (PAG). Increased resting state functional organization was found within the bilateral middle- and superior frontal gyri, the (posterior) cingulate cortex and the thalamus/pulvinar.

Conclusions

Structural and functional changes meta-analyzed in this paper may contribute to elucidating the central pathophysiological mechanisms involved in TN/TNP. These results may be used as biomarkers to predict the response to medication and, ideally, in the future to offer personalized treatments.