Pharmacologic management of neuropathic pain: evidence-based recommendations

Surgical Palliation for Advanced Pancreas Cancer

To provide optimal care in pancreatic ductal adenocarcinoma, involvement of palliative medicine and nutritional support is recommended. Advances in endoscopy have resulted in robust options for biliary and gastrointestinal stenting for relief of obstruction. Notwithstanding, surgical hepaticojejunostomy and gastrojejunostomy remain incontrovertible considerations for biliary obstruction and gastric outlet obstruction, respectively. For PDAC-associated pain, opioid therapy continues to be the mainstay. However, refractory pain may be treated with interventional procedures such as celiac or splanchnic nerve blocks or neurolysis. In patients with PDAC, enteral nutrition can be further complicated by exocrine pancreatic insufficiency, which should be treated with oral pancreatic enzyme supplementation.

Botulinum toxin type A is a potential therapeutic drug for chronic orofacial pain

BACKGROUND

Botulinum toxin type A (BTX-A), produced by the gram-positive anaerobic bacterium Clostridium botulinum, acts by cleaving synaptosome-associated protein-25 (SNAP-25), an essential component of the presynaptic neuronal membrane that is necessary for fusion with the membrane proteins of neurotransmitter-containing vesicles. Recent studies have highlighted the efficacy of BTX-A in treating chronic pain conditions, including lower back pain, chronic neck pain, neuropathic pain, and trigeminal neuralgia, particularly when patients are unresponsive to traditional painkillers. This review focuses on the analgesic effects of BTX-A in various chronic pain conditions, with a particular emphasis on the orofacial region.

HIGHLIGHT

This review focuses on the mechanisms by which BTX-A induces analgesia in patients with inflammatory and temporomandibular joint pain. This review also highlights the fact that BTX-A can effectively manage neuropathic pain and trigeminal neuralgia, which are difficult-to-treat chronic pain conditions. Herein, we present a comprehensive assessment of the central analgesic effects of BTX-A and a discussion of its various applications in clinical dental practice.

CONCLUSION

BTX-A is an approved treatment option for various chronic pain conditions. Although there is evidence of axonal transport of BTX-A from peripheral to central endings in motor neurons, the precise mechanism underlying its pain-modulating effects remains unclear. This review discusses the evidence supporting the effectiveness of BTX-A in controlling chronic pain conditions in the orofacial region. BTX-A is a promising therapeutic agent for treating pain conditions that do not respond to conventional analgesics.

Global hotspots and trends in diabetic peripheral neuropathy research from 2011 to 2023

Diabetic peripheral neuropathy (DPN) is a prevalent disease, and the relevant literature has been increasingly investigated over the past years. Consequently, it is imperative to conduct a scientific and comprehensive DPN research field bibliometric analysis. This study aims to summarize and visualize the literature distribution laws, the research hotspots, and the development trends in DPN using bibliometric methods. We searched all relevant documents published from 2011 to 2023 in the Web of Science Core Collection. Bibliometric analysis and network visualization were performed using VOSviewer, R-bibliometrix, and CiteSpace tools, focusing on countries, institutions, authors, journals, highly cited papers, references, and keywords. This study included a total of 2708 documents. The annual number of publications in the field has notably increased. China, the USA, and the UK take on critical significance in DPN research. The University of Manchester in the UK has the highest number of publications (109). Malik has the most publications (86). Tesfaye literature has been most frequently cited by scholars of DPN research. The Journal of Diabetes and its Complications and Frontiers in Endocrinology have the most publications (45 each). Diabetes Care stands out with the highest impact factor (16.200), number of citations (2516), and H-index (27) among the number of publications top 10 journals. The paper "Colloca, L. et al Neuropathic pain. Nature Reviews Disease Primers. 2017, 3 (1):1-19" has the highest number of citations (1224 times). The most critical co-cited reference is "Tesfaye S, 2010, DIABETES CARE, V33, P2285" (cited 408 times). Keywords like "type 2 diabetes," "diagnosis," "association," "retinopathy," "risk factors," "progression," "corneal confocal microscopy," "nephropathy," "balance," "microvascular complications," "inflammation," "disease," and "insulin resistance" represent the recent research hotspots. The development, research hotspots, and future trends of the global DPN domain from 2011 to 2023 were summarized and visualized in this study. This study can present more insights into the general situation of DPN research and provide a useful reference for clinical decision-making and directions of subsequent research.

Quantitative analysis of nortriptyline's analgesic properties: a comparative systematic review and meta-analysis

OBJECTIVES

This study aims to quantitatively analyse nortriptyline's analgesic potency, safety and tolerability.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

The systematic search was conducted in Scopus, Web of Science and PubMed in February 2023.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Clinical trials evaluating the efficacy of nortriptyline in reducing pain scores (open-label studies and comparisons of nortriptyline with placebo or other analgesics) in different pain types were included.

DATA EXTRACTION AND SYNTHESIS

The data extraction procedure and the screening phases were carried out based on predetermined eligibility criteria. To pool the data, the standardised mean difference (SMD) and standardised mean change (SMC) methods, along with random-effect and fixed-effect meta-analysis, were used. The risk of bias was assessed using the Cochrane Collaboration method, and the Grading of Recommendations Assessment, Development and Evaluation criteria were used to measure the certainty of the results.

RESULTS

14 of the initial 648 studies were eventually imported. Nortriptyline was reported to significantly reduce pain severity in chronic low back pain, painful symptoms in major depressive disorder, neuropathy, chronic pelvic pain and neuropathic corneal pain. However, it was not superior to placebo in fibromyalgia and knee osteoarthritis. In comparison to placebo and various alternative analgesics, the pooled SMD for lowering pain scores was 0.43 (0.23-0.64) and -0.18 (-0.39 to 0.03), respectively. In the pretreatment and post-treatment analyses, the pooled SMC was -1.20 (-1.48 to -0.93). Although constipation and xerostomia were the most commonly reported side effects, all references indicated that the adverse events were well tolerated at the administered dosages.

CONCLUSION

While nortriptyline is effective in some chronic pains, such as neuropathies, it lacks efficacy in some other chronic pains, such as fibromyalgia and osteoarthritis. Nortriptyline is well tolerated when administered in doses intended for its analgesic effects. Moreover, several studies suggested that the analgesic effects of nortriptyline are comparable to those of amitriptyline and gabapentin.

A Review of Remote Monitoring in Neuromodulation for Chronic Pain Management

PURPOSE OF REVIEW

Neuromodulation techniques have emerged as promising strategies for managing chronic pain. These techniques encompass various modalities of nerve stimulation, including Spinal Cord Stimulation (SCS), Dorsal Root Ganglion Stimulation (DRG-S), and Peripheral Nerve Stimulation (PNS). Studies consistently demonstrate significant improvements in pain intensity, quality of life, and reduced opioid usage among patients treated with these modalities. However, neuromodulation presents challenges, such as the need for frequent in-person follow-up visits to ensure proper functionality of the implanted device. Our review explored factors impacting compliance in current neuromodulation users and examined how remote monitoring can mitigate some of these challenges. We also discuss outcomes of recent studies related to remote monitoring of neuromodulation.

RECENT FINDINGS

While remote monitoring capabilities for neuromodulation devices is an emerging development, there are promising results supporting its role in improving outcomes for chronic pain patients. Higher patient satisfaction, improved pain control, and reduced caretaker burdens have been observed with the use of remote monitoring. This review discusses the current challenges with neuromodulation therapy and highlights the role of remote monitoring. As the field continues to evolve, understanding the importance of remote monitoring for neuromodulation is crucial for optimizing pain management outcomes.

Exploring the Role of Community Pharmacists in Pain Management: Enablers and Challenges

Pain is a common complaint, and the consumption of analgesics is prevalent. Community pharmacists, as primary contact points for patients, can play a crucial role in guiding patients toward rational pharmacotherapy or alternative pain management strategies. However, there are no specific educational curricula or standard guidelines to support this role, and the perception of this potential role is not well known. We conducted an anonymous online questionnaire among community pharmacists in Norway to assess their knowledge, perspectives, and willingness to engage in pain care. The survey also explored potential facilitators and barriers, and the use of any current guidelines. Seventy-one community pharmacists participated from various regions in Norway. Findings revealed that community pharmacists felt knowledgeable and willing to engage in pain management but anticipated barriers such as time constraints and a lack of standard guidelines. Participants also highlighted the need for better collaboration with other healthcare professionals and continuous professional development to enhance their role. To optimize the role of community pharmacists in pain management, therefore, integrating them into multidisciplinary healthcare teams, minimizing barriers, and providing continuous education and standard guidelines seem essential. This approach can empower community pharmacists and improve pain management outcomes.

A novel role for microtubule affinity-regulating kinases in neuropathic pain

BACKGROUND AND PURPOSE

Neuropathic pain affects millions of patients, but there are currently few viable therapeutic options available. Microtubule affinity-regulating kinases (MARKs) regulate the dynamics of microtubules and participate in synaptic remodelling. It is unclear whether these changes are involved in the central sensitization of neuropathic pain. This study examined the role of MARK1 or MARK2 in regulating neurosynaptic plasticity induced by neuropathic pain.

EXPERIMENTAL APPROACH

A rat spinal nerve ligation (SNL) model was established to induce neuropathic pain. The role of MARKs in nociceptive regulation was assessed by genetically knocking down MARK1 or MARK2 in amygdala and systemic administration of PCC0105003, a novel small molecule MARK inhibitor. Cognitive function, anxiety-like behaviours and motor coordination capability were also examined in SNL rats. Synaptic remodelling-associated signalling changes were detected with electrophysiological recording, Golgi-Cox staining, western blotting and qRT-PCR.

KEY RESULTS

MARK1 and MARK2 expression levels in amygdala and spinal dorsal horn were elevated in SNL rats. MARK1 or MARK2 knockdown in amygdala and PCC0105003 treatment partially attenuated pain-like behaviours along with improving cognitive deficit, anxiogenic-like behaviours and motor coordination in SNL rats. Inhibition of MARKs signalling reversed synaptic plasticity at the functional and structural levels by suppressing NR2B/GluR1 and EB3/Drebrin signalling pathways both in amygdala and spinal dorsal horn.

CONCLUSION AND IMPLICATIONS

These results suggest that MARKs-mediated synaptic remodelling plays a key role in the pathogenesis of neuropathic pain and that pharmacological inhibitors of MARKs such as PCC0105003 could represent a novel therapeutic strategy for the management of neuropathic pain.

Repetitive transcranial magnetic stimulation in central post-stroke pain: a meta-analysis and systematic review of randomized controlled trials

Background

The rehabilitation of central post-stroke pain (CPSP) is a complex clinical challenge, and repetitive transcranial magnetic stimulation (rTMS) has been widely applied in the research of neurofunctional recovery following stroke. However, there is currently no reliable evidence-based medicine supporting the efficacy of rTMS in central post-stroke pain. This review aims to evaluate the effects of rTMS on central post-stroke pain.

Methods

Following the PRISMA guidelines, we conducted searches on PubMed, Cochrane Library, Embase, Web of Science, CNKI, and Wan Fang Data Knowledge Service Platform. We searched for randomized controlled trials (RCTs) investigating the use of rTMS in treating central post-stroke pain, and conducted screening based on inclusion and exclusion criteria. Characteristics of the included RCTs were extracted. The heterogeneity of the trials was assessed using the I2 statistic. Meta-analysis was performed using Stata 17 software. Bias risk and methodological quality were evaluated using the Cochrane RoB 2 tool and the Pedro scale.

Results

A total of six randomized controlled trials involving 288 patients met our inclusion criteria. In our analysis, rTMS was more effective in treating patients with CPSP compared to the placebo group (SMD=-1.15, 95% CI: -1.69, -0.61, P < 0.001). Furthermore, results from subgroup analysis indicated no statistically significant difference in the improvement of pain for durations exceeding 6 months when comparing rTMS to conventional treatment (SMD=-0.80, 95% CI: -1.63, 0.03, P = 0.059).

Conclusion

TMS can alleviate pain in CPSP patients and improve their motor function, but its effects on depression, anxiety, and MEP-latency are not significant.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, CRD42024497530.

Comparative Study on the Efficacy of Pregabalin Versus Limaprost in Patients With Lumbar Spinal Stenosis: A Prospective, Randomized Controlled Trial

BACKGROUND

Patients with Lumbar Spinal Stenosis (LSS) typically complain of back pain and leg pain. These symptoms reduce the quality of life (QoL) and also cause sleep disturbances. This study compares pregabalin and limaprost's efficacy in LSS for pain, disability, QoL, and sleep, aiming to offer insights for medication selection.

METHODS

This study was designed as a prospective, randomized, single-center, single-blinded, clinical superiority trial targeting patients with LSS. For 6 weeks, 111 patients per group were administered medication following a standard regimen, after which patient-reported outcomes were measured. The primary outcome was the Visual Analogue Scale (VAS) for back and leg pain, and the secondary outcomes included the Oswestry Disability Index (ODI), European Quality of Life 5 Dimensions (EQ-5D), and sleep quality.

RESULTS

After 6 weeks of medication, there were significant improvements over time in the primary outcome, VAS for back pain and leg pain, in both groups, but no significant difference between the 2 groups. Similarly, for the secondary outcomes, ODI and EQ-5D, both groups showed significant improvements, yet there was no significant difference between them. In the subgroup analysis targeting poor sleepers (Pittsburgh sleep quality index, PSQI >5), both groups also exhibited significant improvements in sleep quality, but again, there was no significant difference between the groups.

CONCLUSIONS

Efficacy of pregabalin, limaprost in back and leg pain, ODI, EQ-5D, and sleep quality, but there was no significant difference between the 2 groups. Thus, it is advisable to prescribe based on individual drug responses and potential complications.

Evaluation of tricyclic antidepressant deprescribing in the treatment of diabetic peripheral neuropathy within Federally Qualified Health Centers

BACKGROUND

Tricyclic antidepressants (TCAs) are a treatment option for diabetic peripheral neuropathy (DPN). Existing evidence demonstrates the prolonged use of TCA therapy increases the risk of cognitive decline and dementia, likely due to the anticholinergic effects of these medications. Anticholinergic activity is thought to contribute significantly to the observed increase in cognitive decline and dementia risks associated with long-term TCA use. There is little information available to describe the usage patterns of TCAs in DPN, particularly within underserved populations who receive care at Federally Qualified Health Centers.

OBJECTIVES

The objective of this study was to characterize (1) prescribing patterns of TCAs as a treatment for DPN and (2) evidence of deprescribing attempts in a Federally Qualified Health Center population.

METHODS

A retrospective chart review of electronic medical record data for patients at 2 different Federally Qualified Health Centers was performed. A convenience sample of 100 adults ≥ 18 years of age was stratified into 2 age groups, 18-55 years and 55+ years. All patients had a diagnosis of type 1 or type 2 diabetes mellitus and had been prescribed TCAs in the previous 4 years and had a visit with a primary care provider in the past 12 months.

RESULTS

The study population was comprised of 100 individuals. Seventy-four of 100 were persistent users of TCAs at the time of data collection, and the mean duration of utilization was 54.8 months. In total, 104 TCAs were prescribed across 100 individual patients. Of all 104 prescribed TCAs, 66 (63%) were prescribed at a rate that exceeded thresholds associated with a higher risk of dementia. Black older adults prescribed TCAs were more likely to exceed this dose threshold.

CONCLUSION

Sixty-five percent of patients used TCAs with a strength, frequency, and duration that exceeded risk thresholds for dementia in an older adult population. Interventions preventing use of or deprescribing TCAs in patients with DPN should be conducted for the potential benefits of preventing or delaying cognitive impairment and promoting equitable care.

A Comprehensive Narrative Review of Neuropathic Pain: From Pathophysiology to Surgical Treatment

Neuropathic pain is a challenging condition. Despite the immense progress made in the pathophysiology and treatment of such conditions, so much work still has to be done. New frontiers previously unexplored are now objects of study with exciting results, mainly regarding neuromodulation and optogenetics. This review explores the already known pathophysiology and the clinical and surgical treatment in the light of evidence-based medicine. Additionally, new concepts and insights are discussed, presenting the hope for the development of new paradigms in the treatment of neuropathic pain.

Inhibition of N-type calcium channels by phenoxyaniline and sulfonamide analogues

Building on previous investigations, structural modifications to the neuronal calcium ion channel blocker MONIRO-1 and related compounds were conducted that included replacement of the amide linker with an aniline and isosteric sulfonamide moiety, and the previously used strategy of substitution of the guanidinium group with less hydrophilic amine functionalities. A comprehensive SAR study revealed a number of phenoxyaniline and sulfonamide compounds that were more potent or had similar potency for the CaV2.2 and CaV3.2 channel compared to MONIRO-1 when evaluated in a FLIPR-based intracellular calcium response assay. Cytotoxicity investigations indicated that the sulfonamide analogues were well tolerated by Cos-7 cells at dosages required to inhibit both calcium ion channels. The sulfonamide derivatives were the most promising CaV2.2 inhibitors developed by us to date due, possessing high stability in plasma, low toxicity (estimated therapeutic index > 10), favourable CNS MPO scores (4.0-4.4) and high potency and selectivity, thereby, making this class of compounds suitable candidates for future in vivo studies.

Exploring the mechanisms of kaempferol in neuroprotection: Implications for neurological disorders

Kaempferol, a flavonoid compound found in various fruits, vegetables, and medicinal plants, has garnered increasing attention due to its potential neuroprotective effects in neurological diseases. This research examines the existing literature concerning the involvement of kaempferol in neurological diseases, including stroke, Parkinson's disease, Alzheimer's disease, neuroblastoma/glioblastoma, spinal cord injury, neuropathic pain, and epilepsy. Numerous in vitro and in vivo investigations have illustrated that kaempferol possesses antioxidant, anti-inflammatory, and antiapoptotic properties, contributing to its neuroprotective effects. Kaempferol has been shown to modulate key signaling pathways involved in neurodegeneration and neuroinflammation, such as the PI3K/Akt, MAPK/ERK, and NF-κB pathways. Moreover, kaempferol exhibits potential therapeutic benefits by enhancing neuronal survival, attenuating oxidative stress, enhancing mitochondrial calcium channel activity, reducing neuroinflammation, promoting neurogenesis, and improving cognitive function. The evidence suggests that kaempferol holds promise as a natural compound for the prevention and treatment of neurological diseases. Further research is warranted to elucidate the underlying mechanisms of action, optimize dosage regimens, and evaluate the safety and efficacy of this intervention in human clinical trials, thereby contributing to the advancement of scientific knowledge in this field.

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.

Phylogenetic analysis of mammalian SIP30 sequences indicating accelerated adaptation of functional domain in primates

SIP30, characterized by a coiled-coil functional domain, plays a key role in regulating synaptic vesicle exocytosis and is implicated in neuropathic pain resulting from peripheral nerve injury. Because neuropathic pain is studied in primates (including human), domesticated animals, and rodents, we conducted a phylogenetic analysis of SIP30 in selected species of these three groups of mammals. SIP30 exhibits a high degree of sequence divergence in comparison to its protein binding partners SNAP25 and ZW10, which show broad sequence conservation. Notably, we observed an increased rate of change in the highly conserved coiled-coil domain in the SIP30 protein, specifically within primates. This observation suggests an accelerated adaptation of this functional domain in primate species.

Pharmacological Topical Therapy for Intra-Oral Post Traumatic Trigeminal Neuropathic Pain: A Comprehensive Review

Background: The efficacy of topical treatments in alleviating neuropathic pain is well-established. However, there is a paucity of research on topical interventions designed specifically for intra-oral application, where the tissue composition differs from that of exposed skin. Methods: This comprehensive review endeavors to assess the extant evidence regarding the efficacy of topical treatments in addressing neuropathic pain within the oral cavity. Utilizing combinations of search terms, we conducted a thorough search across standard electronic bibliographic databases-MEDLINE (via PubMed), Embase, Google Scholar, and Up to Date. The variables under scrutiny encompassed topical treatment, local intervention, chronic oral and orofacial pain, and neuropathic pain. All pertinent studies published in the English language between 1992 and 2022 were included in our analysis. Results: Fourteen relevant manuscripts were identified, primarily consisting of expert opinions and case reports. The comprehensive review suggests that topical treatments, especially when applied under a stent, could be effective in mitigating neuropathic pain in the oral area. However, it is crucial to conduct further studies to confirm these preliminary results. The limitations of the reviewed studies, mainly the reliance on expert opinions, small sample sizes, inconsistent study designs, and a lack of long-term follow-up data, highlight the need for more rigorous research. Conclusions: Although initial findings indicate topical treatments may be effective for oral neuropathic pain, the limitations of current studies call for more thorough research. Further comprehensive studies are essential to validate the efficacy of these treatments, standardize procedures, and determine long-term results. This will provide clearer guidance for treating chronic neuropathic pain in the oral cavity.

Nociceptive pain assessed by the PainDETECT questionnaire may predict response to opioid treatment for chronic low back pain

Introduction

The pharmacological management of chronic low back pain (LBP) is complex. The World Health Organisation recommends a laddered approach to pain medication usage. The PainDETECT questionnaire distinguishes between neuropathic pain (NeP), nociceptive pain (NoP), and ambiguous pain. By elucidating the difference in medication efficacy between these groups, clinicians can provide a tailored treatment plan to manage patient's pain. This study aimed to investigate the relationship between pharmacological treatments, pain categorizations, and medication efficacy as reported by patients.

Methods

A secondary retrospective analysis of a prospectively collected database was conducted involving 318 consecutively recruited patients, aged 18 years and above, who completed PainDETECT, medication history and patient reported medication efficacy questionnaires. Medication history was categorized into four lines of treatment: first line (paracetamol ± non-prescribed anti-inflammatories), second line (prescribed anti-inflammatories), third line (anticonvulsants/neuromodulators) and fourth line (opioids). Medication efficacy was measured using a three-point Likert scale: effective (+2), somewhat effective (+1), no effect (0).

Findings

The study included 120, 50, 54 and 94 patients on first line, second line, third line and fourth line treatment, respectively. The NeP group had higher mean numerical rating scale (NRS) compared to NoP group in all four lines of treatment (8.10 ± 1.59 vs. 5.47± 2.27, p < 0.001, 8.64± 1.43 vs. 5.52± 1.86, p < 0.001, 8.00± 1.07 vs. 6.37± 2.39, p < 0.01, and 8.05± 1.73 vs. 7.2± 1.29, p < 0.05). When confounding for severity of LBP as measured by NRS, the distribution of medication efficacy significantly differed amongst the NeP, ambiguous and NoP groups in patients undergoing fourth line pharmacological treatment (r2 = 8.623, p < 0.05). The NoP group exhibited significantly higher medication efficacy compared to the NeP group (U = 14.038, p < 0.05). There was no significant difference in medication efficacy across the pain classifications for first, second- and third-line treatment.

Interpretation

Opioids was the only line of treatment more effective in targeting NoP, as determined by the PainDETECT questionnaire, compared to NeP. This pioneering study illustrates the complex nature of pharmacological management for chronic LBP. It underscores the importance of tailoring pharmacological treatment plans to fit individual pain profiles and expectations instead of adopting a blanket approach to pain management.

Effect of spirocyclopiperazinium salt compound LXM-15 on spinal nerve injury in rats

BACKGROUND

Currently available therapies for neuropathic pain show limited efficacy. This study aimed to investigate the anti-nociceptive effect of the spirocyclopiperazinium salt compound LXM-15 in spinal nerve ligation (SNL) rats and to explore the potential mechanisms.

METHODS

Mechanical allodynia and thermal hyperalgesia tests were used to evaluate the effects of LXM-15 in SNL rats. The expression of CaMKIIα, CREB, JAK2, STAT3, c-fos and TNF-α was detected by western blotting, ELISA or qRT-PCR analysis. Receptor blocking test was performed to explore possible target.

RESULTS

Administration of LXM-15 (1, 0.5, 0.25 mg/kg, i.g.) dose-dependently attenuated mechanical allodynia and thermal hyperalgesia in rats subjected to SNL (p < 0.01, p < 0.05), and the effects were completely blocked by peripheral α7 nicotinic or M4 muscarinic receptor antagonist (p > 0.05). LXM-15 significantly decreased the overexpression of phosphorylated CaMKIIα, CREB, JAK2 and STAT3 proteins and the mRNA levels of TNF-α and c-fos (p < 0.01, p < 05). All of the effects could be blocked by α7 or M4 receptor antagonist. Furthermore, LXM-15 reduced the protein expression of TNF-α and c-fos (p < 0.01, p < 0.05). No significant acute toxicity or abnormal hepatorenal function was observed.

CONCLUSIONS

This is the first study to report that LXM-15 exerts significant anti-nociceptive effect on SNL rats. This effect may occur by activating peripheral α7 nicotinic and M4 muscarinic receptors, further inhibiting the CaMKIIα/CREB and JAK2/STAT3 signalling pathways, and finally inhibiting the expression of TNF-α and c-fos.

SIGNIFICANCE

Existing treatments for neuropathic pain show limited efficacy with severe adverse reactions. This paper is the first to report that LXM-15, a new spirocyclopiperazinium salt compound, exerts a significant anti-nociception in SNL rats without obvious toxicity. The underlying mechanisms include activating peripheral α7 nicotinic and M4 muscarinic receptors, then inhibiting the signalling pathways of CaMKIIα/CREB and JAK2/STAT3 and the expressions of TNF-α and c-fos. This study sheds new light on the development of novel analgesic drugs with fewer side effects.

Emergency radiation therapy in modern-day practice: Now or never, or never again ?

Radiation therapy plays a fundamental role in oncological emergencies such as superior vena cava syndrome (SVCS) and metastatic epidural spinal cord compression (MESCC). These are two examples of critical complications of metastatic cancer in terms of pain and functional impact (respiratory and/or neurological). The aim of this review is to explore the current indications, treatment options and outcomes for emergency radiotherapy regarding to these complications.Regarding SVCS, studies are mostly retrospective and unanimously demonstrated a beneficial effect of radiotherapy on symptom relief. Spinal cord compression remains an indication for urgent radiotherapy, and should be combined with surgery when possible. The innovative stereotactic body radiotherapy (SBRT) showed promising results, however this technique requires small volumes and more time preparation and therefore is often unsuitable for SVCS and MESCC emergencies.This review concluded that radiotherapy has a central role to play within a multimodal approach for SVCS and MESCC treatment. Further prospective studies are needed to confirm the effectiveness of radiation and establish the criteria for selecting patients to benefit from this treatment option.

Transcranial Direct Current Stimulation for Orthopedic Pain: A Systematic Review with Meta-Analysis

(1) Background: Transcranial direct current stimulation (tDCS) appears to alleviate chronic pain via a brain-down mechanism. Although several review studies have examined the effects of tDCS on patients with chronic pain, no systematic review or meta-analysis has comprehensively analyzed the effects of tDCS on chronic orthopedic joint pain in one study. We aim to evaluate the effectiveness of tDCS for pain reduction in chronic orthopedic patients; (2) Methods: A comprehensive search of five electronic databases (Medline, Embase, Web of Science, CINAHL, and Cochrane) was performed. Only randomized controlled trials that compared tDCS with a control intervention were included. Eighteen studies met our inclusion criteria. We identified four categories of chronic orthopedic pain: knee (k = 8), lower back (k = 7), shoulder (k = 2), and orofacial pain (k = 1). Random effect models were utilized, and a sensitivity analysis was conducted in the presence of significant heterogeneity. Studies within each pain condition were further classified according to the number of treatment sessions: 1-5 sessions, 6-10 sessions, and >10 sessions.; (3) Results: Significant reductions in chronic orthopedic joint pain were observed following tDCS compared to controls for knee (g = 0.59, p = 0.005), lower back (g = 1.14, p = 0.005), and shoulder (g = 1.17, p = 0.020). Subgroup analyses showed pain reductions after 6-10 tDCS sessions for knee pain and after 1-5 and >10 sessions for lower back pain; (4) Conclusions: tDCS could be considered a potential stand-alone or supplemental therapy for chronic knee and lower back pain. The effectiveness of tDCS treatment varies depending on the number of treatment sessions. Our findings suggest the importance of implementing individualized treatment plans when considering tDCS for chronic pain conditions.

Headache and Other Pain Syndromes in Multiple Sclerosis: A Narrative Review

Multiple sclerosis is a chronic and progressive neurological disease, with an important socio-economic burden. Over time, an increased incidence of headaches like migraines and tension headaches has been observed among these patients. Headaches have not been considered as multiple sclerosis-related symptoms, even representing a red flag for multiple sclerosis diagnosis. It is uncertain whether the headache-multiple sclerosis association could be explained by the presence of common triggers or a common physiopathological mechanism (involvement of tertiary B-cell follicles). An important differential diagnosis is between multiple sclerosis attacks and migraines with aura, which can also be associated with neurological deficits. Another important aspect is the occurrence or exacerbation of the cephalalgic syndrome after the initiation of therapy for multiple sclerosis (DMTs), or the improvement of headache after the initiation of certain DMT drugs. In addition to headaches, individuals diagnosed with multiple sclerosis often report experiencing diverse pain syndromes, contributing to an additional decline in their overall quality of life. These syndromes are frequently neglected, the focus being on slowing down the progression of neurological deficits. This review aims to evaluate the characteristics of multiple-sclerosis-related headaches (frequency, possible correlation with attacks, and disease-modifying therapies) and the key distinctions in imaging characteristics between demyelinating lesions in multiple sclerosis and those observed in cases of primary headaches.

Allosteric modulation of G protein-coupled receptors as a novel therapeutic strategy in neuropathic pain

Neuropathic pain is a debilitating pathological condition that presents significant therapeutic challenges in clinical practice. Unfortunately, current pharmacological treatments for neuropathic pain lack clinical efficacy and often lead to harmful adverse reactions. As G protein-coupled receptors (GPCRs) are widely distributed throughout the body, including the pain transmission pathway and descending inhibition pathway, the development of novel neuropathic pain treatments based on GPCRs allosteric modulation theory is gaining momentum. Extensive research has shown that allosteric modulators targeting GPCRs on the pain pathway can effectively alleviate symptoms of neuropathic pain while reducing or eliminating adverse effects. This review aims to provide a comprehensive summary of the progress made in GPCRs allosteric modulators in the treatment of neuropathic pain, and discuss the potential benefits and adverse factors of this treatment. We will also concentrate on the development of biased agonists of GPCRs, and based on important examples of biased agonist development in recent years, we will describe universal strategies for designing structure-based biased agonists. It is foreseeable that, with the continuous improvement of GPCRs allosteric modulation and biased agonist theory, effective GPCRs allosteric drugs will eventually be available for the treatment of neuropathic pain with acceptable safety.

A Comparative Study of Effectiveness of Splinting and Splinting Plus Local Corticosteroid Injection in Patients With Carpal Tunnel Syndrome: A Randomized Controlled Trial

Introduction Corticosteroid injection and wrist-hand splint are two of the most commonly used conservative options for the management of carpal tunnel syndrome (CTS). This study compares the effectiveness of splinting and splinting plus local steroid injection in improving clinical and nerve conduction findings of patients with CTS. Methods A total of 44 patients with CTS were randomized into two groups. Group A used a full-time neutral wrist splint and group B was injected with 20 mg of triamcinolone acetonide and was given a full-time neutral wrist splint for 12 weeks. Clinical and nerve conduction findings of the patients were evaluated at baseline, 4 and 12 weeks after interventions. The chi-square test was used to test the association of different study variables. Z-test was used to test the significant difference between the two proportions. The means were compared by t-test. ANOVA was used to compare more than two mean values. Results The mean difference of the Boston Carpal Tunnel Questionnaire and median nerve latency at baseline and 12th week after treatment was significantly higher in group B than in group A (p<0.05). In intragroup comparison, there was significant improvement in the patient satisfaction, and clinical and nerve conduction values between the baseline level and 4 weeks after intervention and between the baseline and 12 weeks after intervention (P < 0.01). However, the inter-group comparisons were not significant. Conclusion Both of the management methods (splinting plus corticosteroid injection and splinting) have significant effects on the improvement of symptoms, and functional and nerve conduction status. It seems that splinting plus corticosteroid injection has a little edge over splinting alone during the follow-up periods.

Neuromuscular complications of the lower extremity after thrombectomy in a patient with superficial femoral artery occlusion: Case series

BACKGROUND

Ischemia reperfusion (IR) injury may result in rhabdomyolysis and compartment syndrome when blood supply returns after thrombectomy for patients with acute limb ischemia.

OBJECTIVE

We highlight the value of early diagnosis and treatment in post-thrombectomy patients with IR injuries in their lower legs.

CASE DESCRIPTION

Two patients received thrombectomy due to left superficial femoral artery occlusion. Both patients complained of left calf pain during ambulation at the 1- and 3-day follow up post-thrombectomy, as well as a heating sensation, swelling, weakness, and sensory changes in the affected leg. For early diagnosis musculoskeletal ultrasounds were performed and in both cases revealed swelling and change of echogenicity in the left calf. To further diagnosis, magnetic resonance imaging of the left leg revealed limb IR-induced muscular injury and rhabdomyolysis, respectively. In both cases, an electrodiagnostic study revealed peripheral nerve injury in the left leg. Medications were provided for neuropathic pain control and early rehabilitation was performed to improve function. In both cases, patients reported during their follow-up that their pain and muscle weakness had improved.

CONCLUSION

When post-thrombectomy calf pain occurs early evaluation and treatment should be performed to identify any potential IR injury.

The Known Biology of Neuropathic Pain and Its Relevance to Pain Management

Patients with neuropathic pain are heterogeneous in pathophysiology, etiology, and clinical presentation. Signs and symptoms are determined by the nature of the injury and factors such as genetics, sex, prior injury, age, culture, and environment. Basic science has provided general information about pain etiology by studying the consequences of peripheral injury in rodent models. This is associated with the release of inflammatory cytokines, chemokines, and growth factors that sensitize sensory nerve endings, alter gene expression, promote post-translational modification of proteins, and alter ion channel function. This leads to spontaneous activity in primary afferent neurons that is crucial for the onset and persistence of pain and the release of secondary mediators such as colony-stimulating factor 1 from primary afferent terminals. These promote the release of tertiary mediators such as brain-derived neurotrophic factor and interleukin-1β from microglia and astrocytes. Tertiary mediators facilitate the transmission of nociceptive information at the spinal, thalamic, and cortical levels. For the most part, these findings have failed to identify new therapeutic approaches. More recent basic science has better mirrored the clinical situation by addressing the pathophysiology associated with specific types of injury, refinement of methodology, and attention to various contributory factors such as sex. Improved quantification of sensory profiles in each patient and their distribution into defined clusters may improve translation between basic science and clinical practice. If such quantification can be traced back to cellular and molecular aspects of pathophysiology, this may lead to personalized medicine approaches that dictate a rational therapeutic approach for each individual.

Targeting the mammalian target of rapamycin pathway in neurological manifestations of Covid-19

The diverse and severe nature of neurological manifestations associated with coronavirus disease 2019 (Covid-19) has garnered increasing attention. Exploring the potential to decrease neurological complications in Covid-19 patients involves targeting the mammalian target of rapamycin (mTOR) pathway as a therapeutic strategy. The mTOR pathway, widely recognised for its central role in essential cellular processes like synthesising proteins, facilitating autophagy, and modulating immune responses, has implications in various neurological disorders. Drawing parallels between these disorders and the observed neurological complications in Covid-19, we present a comprehensive review on the current understanding of mTOR signalling in the context of severe acute respiratory syndrome coronavirus 2 infection and neuroinflammation.

Combination Drug Therapy for the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (NP) is an increasingly prevalent disease and leading cause of disability which is challenging to treat. Several distinct classes of drugs are currently used for the treatment of chronic NP, but each drug targets only narrow components of the underlying pathophysiological mechanisms, bears limited efficacy, and comes with dose-limiting side effects. Multimodal therapies have been increasingly proposed as potential therapeutic approaches to target the multiple mechanisms underlying nociceptive transmission and modulation. However, while preclinical studies with combination therapies showed promise to improve efficacy over monotherapy, clinical trial data on their efficacy in specific populations are lacking and increased risk for adverse effects should be carefully considered. Drug-drug co-crystallization has emerged as an innovative pharmacological approach which can combine two or more different active pharmaceutical ingredients in a single crystal, optimizing pharmacokinetic and physicochemical characteristics of the native molecules, thus potentially capitalizing on the synergistic efficacy between classes of drugs while simplifying adherence and minimizing the risk of side effects by reducing the doses. In this work, we review the current pharmacological options for the treatment of chronic NP, focusing on combination therapies and their ongoing developing programs and highlighting the potential of co-crystals as novel approaches to chronic NP management.

Treating persistent pain after breast cancer: practice gaps and future directions

This paper discusses the growing problem of persisting pain after successful treatment of breast cancer and presents recommendations for improving pain-related outcomes for this group. We discuss the dominant treatment approach for persisting pain post-breast cancer treatment and draw contrasts with contemporary treatment approaches to persistent pain in non-cancer-related populations. We discuss modern application of the biopsychosocial model of pain and the notion of variable sensitivity within the pain system, moment by moment and over time. We present the implications of increasing sensitivity over time for treatment selection and implementation. By drawing on transformative changes in treatment approaches to persistent non-cancer-related pain, we describe the potentially powerful role that an intervention called pain science education, which is now recommended in clinical guidelines for musculoskeletal pain, may play in improving pain and disability outcomes after successful breast cancer treatment. Finally, we present several research recommendations that centre around adaptation of the content and delivery models of contemporary pain science education, to the post-breast cancer context.

Mitochondrial trafficking as a protective mechanism against chemotherapy drug-induced peripheral neuropathy: Identifying the key site of action

AIMS

Chemotherapy induced peripheral neuropathy (CIPN) is a common side effect seen in patients who have undergone most chemotherapy treatments to which there are currently no treatment methods. CIPN has been shown to cause axonal degeneration leading to Peripheral Neuropathy (PN), which can lead to major dosage reduction and may prevent further chemotherapy treatment due to oftentimes debilitating pain. Previously, we have determined the site-specific action of Paclitaxel (PTX), a microtubule targeting agent, as well as the neuroprotective effect of Fluocinolone Acetonide (FA) against Paclitaxel Induced Peripheral Neuropathy (PIPN).

MAIN METHODS

Mitochondrial trafficking analysis was determined for all sample sets, wherein FA showed enhanced anterograde (axonal) mitochondrial trafficking leading to neuroprotective effects for all samples.

KEY FINDINGS

Using this system, we demonstrate that PTX, Monomethyl auristatin E (MMAE), and Vincristine (VCR), are toxic at clinically prescribed levels when treated focally to axons. However, Cisplatin (CDDP) was determined to have a higher toxicity when treated to cell bodies. Although having different targeting mechanisms, the administration of FA was determined to have a significant neuroprotective effect for against all chemotherapy drugs tested.

SIGNIFICANCE

This study identifies key insights regarding site of action and neuroprotective strategies to further development as potential therapeutics against CIPN. FA was treated alongside each chemotherapy drug to identify the neuroprotective effect against CIPN, where FA was found to be neuroprotective for all drugs tested. This study found that treatment with FA led to an enhancement in the anterograde movement of mitochondria based on fluorescent imaging.

The role of evolving concepts and new technologies and approaches in advancing pain research, management, and education since the establishment of the International Association for the Study of Pain

ABSTRACT

The decades since the inauguration of the International Association for the Study of Pain have witnessed major advances in scientific concepts (such as the biopsychosocial model and chronic primary pain as a disease in its own right) and in new technologies and approaches (from molecular biology to brain imaging) that have inspired innovations in pain research. These have guided progress in pain management and education about pain for healthcare professionals, the general public, and administrative agencies.

Neuromodulation Through Magnetic Fields Irradiation with AT-04 Improves Hyperalgesia in a Rat Model of Neuropathic Pain via Descending Pain Modulatory Systems and Opioid Analgesia

Neuromodulation through magnetic fields irradiation with ait® (AT-04), a device that irradiates a mixed alternating magnetic fields (2 kHz and 83.3 MHz), has been shown to have high efficacy for fibromyalgia and low back pain in our previous clinical trials. The aim of this study was to elucidate the underlying analgesic mechanism of the AT-04 using the partial sciatic nerve ligation (PSL) model as an animal model of neuropathic pain. AT-04 was applied to PSL model rats with hyperalgesia and its pain-improving effect was verified by examining mechanical allodynia using the von Frey method. The results demonstrated a significant improvement in hyperalgesia in PSL model rats. We also examined the involvement of descending pain modulatory systems in the analgesic effects of AT-04 using antagonism by serotonin and noradrenergic receptor antagonists. These antagonists significantly reduced the analgesic effect of AT-04 on pain in PSL model rats by approximately 50%. We also measured the amount of serotonin and noradrenaline in the spinal fluid of PSL model rats using microdialysis during AT-04 treatment. Both monoamines were significantly increased by magnetic fields irradiation with AT-04. Furthermore, we evaluated the involvement of opioid analgesia in the analgesic effects of AT-04 using naloxone, the main antagonist of the opioid receptor, and found that it significantly antagonized the effects by approximately 60%. Therefore, the analgesic effects of AT-04 in PSL model rats involve both the endogenous pain modulation systems, including the descending pain modulatory system and the opioid analgesic system.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Impaired Ventrolateral Periaqueductal Gray-Ventral Tegmental area Pathway Contributes to Chronic Pain-Induced Depression-Like Behavior in Mice

Chronic pain conditions within clinical populations are correlated with a high incidence of depression, and researchers have reported their high rate of comorbidity. Clinically, chronic pain worsens the prevalence of depression, and depression increases the risk of chronic pain. Individuals suffering from chronic pain and depression respond poorly to available medications, and the mechanisms underlying the comorbidity of chronic pain and depression remain unknown. We used spinal nerve ligation (SNL) in a mouse model to induce comorbid pain and depression. We combined behavioral tests, electrophysiological recordings, pharmacological manipulation, and chemogenetic approaches to investigate the neurocircuitry mechanisms of comorbid pain and depression. SNL elicited tactile hypersensitivity and depression-like behavior, accompanied by increased and decreased glutamatergic transmission in dorsal horn neurons and midbrain ventrolateral periaqueductal gray (vlPAG) neurons, respectively. Intrathecal injection of lidocaine, a sodium channel blocker, and gabapentin ameliorated SNL-induced tactile hypersensitivity and neuroplastic changes in the dorsal horn but not depression-like behavior and neuroplastic alterations in the vlPAG. Pharmacological lesion of vlPAG glutamatergic neurons induced tactile hypersensitivity and depression-like behavior. Chemogenetic activation of the vlPAG-rostral ventromedial medulla (RVM) pathway ameliorated SNL-induced tactile hypersensitivity but not SNL-elicited depression-like behavior. However, chemogenetic activation of the vlPAG-ventral tegmental area (VTA) pathway alleviated SNL-produced depression-like behavior but not SNL-induced tactile hypersensitivity. Our study demonstrated that the underlying mechanisms of comorbidity in which the vlPAG acts as a gating hub for transferring pain to depression. Tactile hypersensitivity could be attributed to dysfunction of the vlPAG-RVM pathway, while impairment of the vlPAG-VTA pathway contributed to depression-like behavior.

Repetitive transcranial magnetic stimulation in central post-stroke pain: current status and future perspective

Central post-stroke pain (CPSP) is an incapacitating disorder that impacts a substantial proportion of stroke survivors and can diminish their quality of life. Conventional therapies for CPSP, including tricyclic antidepressants, anticonvulsants, and opioids, are frequently ineffective, necessitating the investigation of alternative therapeutic strategies. Repetitive transcranial magnetic stimulation (rTMS) is now recognized as a promising noninvasive pain management method for CPSP. rTMS modulates neural activity through the administration of magnetic pulses to specific cortical regions. Trials analyzing the effects of rTMS on CPSP have generated various outcomes, but the evidence suggests possible analgesic benefits. In CPSP and other neuropathic pain conditions, high-frequency rTMS targeting the primary motor cortex (M1) with figure-eight coils has demonstrated significant pain alleviation. Due to its associaton with analgesic benefits, M1 is the most frequently targeted area. The duration and frequency of rTMS sessions, as well as the stimulation intensity, have been studied in an effort to optimize treatment outcomes. The short-term pain relief effects of rTMS have been observed, but the long-term effects (> 3 months) require further investigation. Aspects such as stimulation frequency, location, and treatment period can influence the efficacy of rTMS and ought to be considered while planning the procedure. Standardized guidelines for using rTMS in CPSP would optimize therapy protocols and improve patient outcomes. This review article provides an up-to-date overview of the incidence, clinical characteristics, outcome of rTMS in CPSP patients, and future perspective in the field.

Neurological Manifestations of Connective Tissue Disorders

Connective tissue disorders (CTD) are a group of disorders affecting the connective tissues. Usually the musculoskeletal and the vascular system is impacted. Along with these systems, the nervous system is also involved in CTD, which leads to various neurological manifestations. The pathophysiology of neurological complications of CTD is caused by various factors and is complicated. Disturbed immune complexes, chronic inflammation, and autoimmunity in which the body attacks its cells are considered to be responsible for the neurological complications of CTD. Additionally, the vascular symptoms that lead to decreased blood flow to the brain are also responsible for the neurological manifestations of CTD in diseases like systemic lupus erythematosus (SLE). In SLE, vessel wall integrity is compromised, which may lead to decreased blood flow leading to neurological complications. CTD can manifest a variety of neurological complications. These neurological complications can be classified into symptoms affecting the peripheral nervous system, central nervous system, and the autonomic nervous system. Some of the common neurological complications of CTD are headaches, seizures, ataxia, neuropathies leading to cranial nerve palsies, myelopathies, tremors, encephalitis, and cerebral infarction. Cranial nerve palsies can disturb sensations, vision, hearing, and mastication. Neuropsychiatric symptoms are also commonly observed in CTD. Cognitive dysfunction can be caused due to neuropsychiatric problems. Some of the cognitive dysfunctions are lack of concentration, memory loss, confusion, and coma. In this review, we will address various neurological manifestations of CTD.

Fully Implantable Neurostimulation System for Long-Term Behavioral Animal Study

Spinal cord stimulation (SCS) is an emerging therapeutic option for patients with neuropathic pain due to spinal cord injury (SCI). Numerous studies on pain relief effects with SCS have been conducted and demonstrated promising results while the mechanisms of analgesic effect during SCS remain unclear. However, an experimental system that enables large-scale long-term animal studies is still an unmet need for those mechanistic studies. This study proposed a fully wireless neurostimulation system that can efficiently support a long-term animal study for neuropathic pain relief. The developed system consists of an implantable stimulator, an animal cage with an external charging coil, and a wireless communication interface. The proposed device has the feature of remotely controlling stimulation parameters via radio-frequency (RF) communication and wirelessly charging via magnetic induction in freely moving rats. Users can program stimulation parameters such as pulse width, intensity, and duration through an interface on a computer. The stimulator was packaged with biocompatible epoxy to ensure long-term durability under in vivo conditions. Animal experiments using SCI rats were conducted to demonstrate the functionality of the device, including long-term usability and therapeutic effects. The developed system can be tailored to individual user needs with commercially available components, thus providing a cost-effective solution for large-scale long-term animal studies on neuropathic pain relief.

A Nutritional Supplement as Adjuvant of Gabapentinoids for Adults with Neuropathic Pain following Spinal Cord Injury and Stroke: Preliminary Results

Gabapentinoids are first choice drugs for central neuropathic pain (CNP) despite limited evidence of efficacy and side effects affecting therapy outcomes. Nutraceuticals could improve their efficacy and tolerability. Our aim is to investigate the effect of NACVAN®, in addition to gabapentinoids, on pain symptomatology in CNP patients. The effect of 6 weeks of treatment of NACVAN® was preliminary observed among 29 adult inpatients with spinal cord injury (SCI) or stroke-related CNP recruited to the experimental group. Pain intensity, neuropathic pain, and quality-of-life were measured at baseline (T0) and after 3 (T1) and 6 weeks (T2). Change in each outcome over time was assessed through a repeated measures analysis of variance or Wilcoxon matched-pairs test. Preliminary results show a significant reduction in pain intensity (T0 → T1, p = 0.021; T0 → T2, p = 0.011; T1 → T2, p = 0.46), neuropathic symptoms (T0 → T1, p = 0.024; T0 → T2, p = 0.003), and evoked pain (T0 → T2, p = 0.048). There were no significant reductions in other neuropathic pain dimensions and in quality-of-life components. No side-effects were detected. NACVAN® could have a beneficial adjuvant effect when used as an add-on to gabapentinoids in patients suffering from CNP due to SCI or stroke, with no adverse effect. Future analysis on a larger sample, compared with a placebo condition, could confirm these preliminary results.

NLR family pyrin domain containing 3 (NLRP3) inflammasomes and peripheral neuropathic pain - Emphasis on microRNAs (miRNAs) as important regulators

Neuropathic pain is caused by the lesion or disease of the somatosensory system and can be initiated and/or maintained by both central and peripheral mechanisms. Nerve injury leads to neuronal damage and apoptosis associated with the release of an array of pathogen- or damage-associated molecular patterns to activate inflammasomes. The activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome contributes to neuropathic pain and may represent a novel target for pain therapeutic development. In the current review, we provide an up-to-date summary of the recent findings on the involvement of NLRP3 inflammasome in modulating neuropathic pain development and maintenance, focusing on peripheral neuropathic conditions. Here we provide a detailed review of the mechanisms whereby NLRP3 inflammasomes contribute to neuropathic pain via (1) neuroinflammation, (2) apoptosis, (3) pyroptosis, (4) proinflammatory cytokine release, (5) mitochondrial dysfunction, and (6) oxidative stress. We then present the current research literature reporting on the antinociceptive effects of several natural products and pharmacological interventions that target activation, expression, and/or regulation of NLRP3 inflammasome. Furthermore, we emphasize the effects of microRNAs as another regulator of NLRP3 inflammasome. In conclusion, we summarize the possible caveats and future perspectives that might provide successful therapeutic approaches against NLRP3 inflammasome for treating or preventing neuropathic pain conditions.

The Usefulness of the Short Form-8 for Chronic Pain in the Orofacial Region: A Prospective Cohort Study

Background and purpose Given that chronic pain has become a major problem in recent years, affecting approximately 30% of the general population, this study used the Japanese version of the Short Form-8 (SF-8) to investigate (1) the quality of life (QOL) of patients with burning mouth syndrome (BMS) or persistent idiopathic facial pain (PIFP) (compared with a Japanese control group) and (2) whether therapeutic intervention improves the QOL and reduces pain (comparison between 0 and 12 weeks) of patients with BMS or PIFP. Materials and methods A total of 63 patients diagnosed with either BMS (n=45) or PIFP (n=18) were included in this study. The diagnostic criteria for BMS and PIFP were established based on the third edition of the International Classification of Headache Disorders. Results Our study results showed that while Physical Component Summary (PCS) in patients with BMS or PIFP improved with treatment, it did not improve to the national standard value (NSV) after 12 weeks of intervention. In contrast, the Mental Component Summary (MCS) improved to the same level as the NSV after 12 weeks of intervention. Conclusions We found that therapeutic intervention improves MCS and reduces pain; however, improving PCS requires time.

Long-Term Safety and Efficacy of Mirogabalin for Central Neuropathic Pain: A Multinational, Phase 3, 52-Week, Open-Label Study in Asia

INTRODUCTION

Central neuropathic pain (CNeP) is difficult to treat and has diverse etiology, including spinal cord injury (CNePSCI), Parkinson's disease (CNePPD), and central post-stroke pain (CPSP). The safety and efficacy of mirogabalin have been demonstrated in short-term trials, including patients with CNePSCI. The objective of our study was to confirm the safety/efficacy of mirogabalin in patients with CNePPD and CPSP, and obtain long-term data for CNePSCI.

METHODS

This 52-week, open-label extension of a previous randomized controlled study was conducted across Japan, Korea, and Taiwan. Patients with CNePSCI, CNePPD, or CPSP received twice daily (BID) 5-10 mg mirogabalin for a 4-week titration period, after which the dosage was maintained for 47 weeks at a maximum of 15 mg BID, followed by a 1-week taper period receiving the same dose but only administered once daily. The primary endpoint was safety, assessed primarily by incidence and severity of treatment-emergent adverse events (TEAEs). Efficacy was assessed in a post hoc analysis of data obtained by the short-form McGill Pain Questionnaire (SF-MPQ).

RESULTS

Of the 210 patients enrolled, 106, 94, and 10 had CNePSCI, CPSP, and CNePPD, respectively. The mean overall age of patients was 62.9 years, and most patients were male and of Japanese ethnicity. TEAEs occurred in 84.8% of patients, the most common being somnolence (16.7%), peripheral edema (12.4%), edema (11.4%), nasopharyngitis (11.0%), and dizziness (7.6%). Most TEAEs were mild. Severe and serious TEAEs occurred in 6.2% and 13.3% of patients, respectively. All patient groups experienced reductions in SF-MPQ visual analog scores for pain: mean ± standard deviation changes from baseline at week 52 were -2.3 ± 21.13 mm (CNePSCI), -17.0 ± 24.99 mm (CPSP), and -17.1 ± 35.32 mm (CNePPD).

CONCLUSION

Mirogabalin was generally safe, well tolerated, and effective for treatment of CNeP in this long-term study.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03901352.

Unravelling Impaired Hypoalgesia at Rest and in Response to Exercise in Patients with Chronic Whiplash-Associated Disorders: Effects of a Single Administration of Selective Serotonin Reuptake Inhibitor versus Selective Norepinephrine Reuptake Inhibitor

(1) Background: Noradrenaline and serotonin have modulatory roles in pain signaling and in exercise-induced hypoalgesia. Patients with chronic whiplash-associated disorders often show impaired exercise-induced hypoalgesia. Therefore, this study aimed to examine the isolated effect of activating serotonergic or noradrenergic descending pathways on hypoalgesia at rest and in response to exercise in patients with chronic WAD by using respectively a single dose of a selective serotonin reuptake inhibitor (SSRI) and a selective norepinephrine reuptake inhibitor (NRI). (2) Methods: Twenty-five people with chronic WAD participated in this double-blind randomized controlled crossover experiment. Serotonin and noradrenaline concentrations were modulated by the oral ingestion of a single dose of citalopram (i.e., SSRI) or atomoxetine (i.e., SNRI). Quantitative sensory testing (including pressure pain thresholds and conditioned pain modulation) was measured before and after exercise in combination with no medication (1), atomoxetine (2), or citalopram (3) at three different test days. (3) Results: Random-intercept linear mixed models analysis was used to analyze pain outcomes (i.e., pain at rest and exercise-induced hypoalgesia) before and after exercise over the three conditions in patients with chronic WAD. No differences in pain at rest were found between the three conditions before exercise. The effect of exercise on pain outcome measures was not influenced by medication intake. The occupational status of the participants had a significant influence on the effect of exercise and medication on pain outcomes (p < 0.05). Patients working full-time had some positive effect of atomoxetine on pain facilitation (p < 0.05). Unemployed patients had some negative effect of citalopram on pain tolerance and experienced exercise-induced hypoalgesia (p < 0.05). (4) Conclusions: A single dose of citalopram or atomoxetine did not result in changes in hypoalgesia at rest and in response to exercise. These results do not support the use of SSRI or selective NRI to overcome impaired hypoalgesia at rest or in response to exercise in people with chronic WAD. Effect of exercise and medication on pain in patients with chronic WAD is influenced by the occupational status.

Effects of Complex Pain Control Programs on Taekwondo Athletes with Recurrent Low Back Pain: A Case Study

Background and Objectives: Practitioners of martial arts such as Taekwondo are likelier to experience back pain during training or competition. As the back pain of taekwondo athletes shows various symptoms depending on the athlete's characteristics, such as technique and movement, a case study was conducted to verify the intervention effect suitable for individual traits. We examined the effects of a complex pain control program on pain, mechanosensitivity, and physical function in a Taekwondo athlete with recurrent low back pain (LBP). Materials and Methods: A Taekwondo athlete with LBP was recruited from D University, Busan. The intervention program was performed for 45 min twice a week for 3 weeks, and the patient was followed up with after 2 weeks. The numerical rating pain scale (NRPS), pain pressure threshold, mechanosensitivity, and Oswestry Disability Index (ODI) scores were measured before and after the intervention. Therapeutic massage and nerve stimulation therapy were performed. Lumbar flexion, extension, and rotation were performed in the movement control exercise group, whereas the sliding technique, a neurodynamic technique of the tibial nerve, was applied in the neurodynamic technique group. This effect was verified by comparing the average measured values before and after the intervention. Results: Pain (NRPS) and mechanosensitivity reduced, range of motion and tactile discrimination abilities improved, and physical function (ODI) improved. The effect of the improved intervention lasted 2 weeks. Conclusions: These results indicate that application of complex pain control programs considering the four aspects of pain mechanisms for 3 weeks can be an effective intervention in Taekwondo athletes with recurrent LBP.

Oxycodone withdrawal induces HDAC1/HDAC2-dependent transcriptional maladaptations in the reward pathway in a mouse model of peripheral nerve injury

The development of physical dependence and addiction disorders due to misuse of opioid analgesics is a major concern with pain therapeutics. We developed a mouse model of oxycodone exposure and subsequent withdrawal in the presence or absence of chronic neuropathic pain. Oxycodone withdrawal alone triggered robust gene expression adaptations in the nucleus accumbens, medial prefrontal cortex and ventral tegmental area, with numerous genes and pathways selectively affected by oxycodone withdrawal in mice with peripheral nerve injury. Pathway analysis predicted that histone deacetylase (HDAC) 1 is a top upstream regulator in opioid withdrawal in nucleus accumbens and medial prefrontal cortex. The novel HDAC1/HDAC2 inhibitor, Regenacy Brain Class I HDAC Inhibitor (RBC1HI), attenuated behavioral manifestations of oxycodone withdrawal, especially in mice with neuropathic pain. These findings suggest that inhibition of HDAC1/HDAC2 may provide an avenue for patients with chronic pain who are dependent on opioids to transition to non-opioid analgesics.

Previous Lumbar Spine Surgery Decreases the Therapeutic Efficacy of Dorsal Root Ganglion Pulsed Radiofrequency in Patients with Chronic Lumbosacral Radicular Pain

Chronic lumbosacral radicular pain (CLRP) as a possible adverse consequence of lumbar spine surgery represents a serious medical challenge. Pulsed radiofrequency of dorsal root ganglion (PRF-DRG) treatment is known to be effective in alleviating CLRP. This retrospective study compares the efficacy of a single CT-guided PRF-DRG procedure in the treatment of unilateral CLRP between patients without (non-PSS) and with (PSS) previous lumbar spine surgery. Non-PSS and PSS groups included 30 and 20 patients, respectively. Outcomes (pain intensity and disability) were evaluated by means of the visual analog scale (VAS) and Oswestry disability index (ODI) immediately after the procedure (VAS), as well as three and six months after the procedure, respectively. Non-PSS group showed a significant (p ˂ 0.001) decrease of VAS (median) at all follow-up intervals (from 6 to 4; 4; 4.5 points, respectively). The PSS group showed a significant yet transient VAS (median) decrease (from 6 to 5 points) immediately after the procedure only (p < 0.001). The decrease of VAS was more pronounced in the non-PSS group after three and six months (p = 0.0054 and 0.011, respectively) in intergroup comparison. A relative decrease of VAS ≥ 50% during follow-up was achieved in 40%; 43.3%; 26.7% (non-PSS), and 25%; 5%; 0% (PSS) of patients. ODI (median) significantly decreased in the non-PSS group (from 21.5 to 18 points) at three and six months (p = 0.014 and 0.021, respectively). In conclusion, previous lumbar spine surgery decreases the therapeutic efficacy of PRF-DRG procedure in CLRP patients.

Efficacy and Safety of SIKD1977 in Combination with Standard Treatment for Postherpetic Neuralgia: Study Protocol for a Double Blind, Placebo-Controlled, Randomized, Multicenter, Phase 2 Clinical Trial

Purpose

Postherpetic neuralgia (PHN) is the most common chronic complication of herpes zoster, associated with poor quality of life and increased patient and healthcare resource expenditure. This randomized controlled trial aims to evaluate the efficacy and safety of SIKD1977 (Sogeonjungtang) in combination with standard treatment and estimate an effective dose for treating PHN.

Patients and Methods

This is a protocol for a randomized, placebo-controlled, double-blind, multicenter trial. A total of 90 eligible participants with PHN will be recruited from three hospitals and randomly allocated to high-dose group, low-dose group, or placebo group in a 1:1:1 ratio. The trial will involve a 6-week oral administration of SIKD1977/placebo, and a 1-week follow-up period. The primary outcome will be the weekly average change in average daily pain score (ADPS) from baseline to the end of treatment. The secondary outcomes will include the weekly average changes in ADPS from baseline to week 2, 4, and 7, differences in Short-Form McGill Pain Questionnaire, Visual analogue scale, 5-level EuroQol-5 dimensions, Patient Global Impression of Change, and consumption of rescue drugs. All adverse events will be assessed during the trial.

Conclusion

This study will provide evidence for the efficacy and safety of SIKD1977, and an effective dose for PHN.

Trial Registration

This protocol has been registered in the Clinical Research Information Service with the identification code KCT0007939.

Telmisartan Is a Promising Agent for Managing Neuropathic Pain and Delaying Opioid Analgesic Tolerance in Rats

Despite the large arsenal of analgesic medications, neuropathic pain (NP) management is not solved yet. Angiotensin II receptor type 1 (AT1) has been identified as a potential target in NP therapy. Here, we investigate the antiallodynic effect of AT1 blockers telmisartan and losartan, and particularly their combination with morphine on rat mononeuropathic pain following acute or chronic oral administration. The impact of telmisartan on morphine analgesic tolerance was also assessed using the rat tail-flick assay. Morphine potency and efficacy in spinal cord samples of treated neuropathic animals were assessed by [35S]GTPγS-binding assay. Finally, the glutamate content of the cerebrospinal fluid (CSF) was measured by capillary electrophoresis. Oral telmisartan or losartan in higher doses showed an acute antiallodynic effect. In the chronic treatment study, the combination of subanalgesic doses of telmisartan and morphine ameliorated allodynia and resulted in a leftward shift in the dose-response curve of morphine in the [35S]GTPγS binding assay and increased CSF glutamate content. Telmisartan delayed morphine analgesic-tolerance development. Our study has identified a promising combination therapy composed of telmisartan and morphine for NP and opioid tolerance. Since telmisartan is an inhibitor of AT1 and activator of PPAR-γ, future studies are needed to analyze the effect of each component.

Mirogabalin for Central Neuropathic Pain After Spinal Cord Injury: A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study in Asia

BACKGROUND AND OBJECTIVES

Patients with spinal cord injury (SCI) commonly experience central neuropathic pain (CNeP), which is challenging to treat. Mirogabalin is effective for peripheral neuropathic pain, but evidence for CNeP is lacking.

METHODS

This randomized, double-blind, placebo-controlled, phase 3 study investigated mirogabalin efficacy and safety for the treatment of CNeP in patients with traumatic SCI. Adult patients from 120 sites throughout Japan, Korea, and Taiwan were randomized (1:1) to receive placebo or mirogabalin (5 mg twice daily [BID] for 1 week, 10 mg BID for 1 week, and 10 or 15 mg BID for 12 weeks). Patients with moderate renal impairment received half the dosage. The primary efficacy endpoint was change from baseline in the weekly average daily pain score (ADPS) at week 14. The secondary endpoints included ADPS responder rates, the Short-Form McGill Pain Questionnaire (SF-MPQ), average daily sleep interference score (ADSIS), and Neuropathic Pain Symptom Inventory (NPSI). Adverse events were monitored for safety.

RESULTS

Each treatment group comprised 150 patients. Mirogabalin elicited a statistical and clinically relevant improvement in change from baseline in the weekly ADPS at week 14 (least-squares mean difference [95% CI] vs placebo -0.71 [-1.08 to -0.34], p = 0.0001). Responder rates at week 14 were higher for mirogabalin than those for placebo (odds ratio [95% CI] 1.91 [1.11-3.27] for the ≥30% responder rate; 2.52 [1.11-5.71] for the ≥50% responder rate). Statistical improvements (i.e., least-squares mean difference [95% CI] vs placebo) were also observed in the SF-MPQ (-2.4 [-3.8 to -1.1]), ADSIS -0.71 (-1.04 to -0.38), and NPSI -7.7 (-11.1 to -4.4) scores. Most treatment-emergent adverse events were mild; no serious adverse drug reactions were reported.

DISCUSSION

Mirogabalin elicited clinically relevant decreases in pain and was well tolerated, suggesting that mirogabalin is a promising treatment for patients with CNeP due to SCI.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov (NCT03901352); first submitted April 3, 2019; first patient enrolled March 14, 2019; available at clinicaltrials.gov/ct2/show/NCT03901352.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that in adult patients with CNeP due to traumatic SCI, mirogabalin, 10 or 15 mg BID, effectively improves weekly ADPS at week 14.

Impact of spinal cord stimulation on sick leave and disability pension in patients with chronic neuropathic pain: a real-world evidence study in Sweden

ABSTRACT

Current research indicates that spinal cord stimulation (SCS) has a positive short-term impact on outcomes, such as quality of life, pain, and productivity in patients with chronic neuropathic pain. However, there is a need for studies on larger population samples. This study used data from Swedish national registers to analyze change and predictors of sick leave and disability pension 2 years before and after SCS treatment. Patients with SCS implanted between 2006 and 2017, and a reference group consisting of 5 individuals matched to each SCS patient without replacement with respect to age, sex, and region of residence, were included. A difference-in-difference approach was used to compare the average change (2 years after treatment vs 2 years before treatment) in net disability days and indirect cost related to disability days for the SCS group, compared with the average change for the reference group. The results showed that SCS treatment in Sweden is associated with a decrease of 21 disability days and consequent decrease in indirect cost of €4127 in working age patients. Large work loss prior to index date was also demonstrated (average 214 days before 1 year), indicating a significant burden on the patient, employers, and the society at large. The number of disability days varied considerably depending on age, sex, socioeconomic variables, and comorbidities; however, the effect of SCS seemed to have little association with patient characteristics. This economic benefit needs to be considered, as well as the clinical outcome, when evaluating the full societal value of SCS.

Lidocaine for Neuropathic Cancer Pain (LiCPain): study protocol for a mixed-methods pilot study

INTRODUCTION

Many patients experience unrelieved neuropathic cancer-related pain. Most current analgesic therapies have psychoactive side effects, lack efficacy data for this indication and have potential medication-related harms. The local anaesthetic lidocaine (lignocaine) has the potential to help manage neuropathic cancer-related pain when administered as an extended, continuous subcutaneous infusion. Data support lidocaine as a promising, safe agent in this setting, warranting further evaluation in robust, randomised controlled trials. This protocol describes the design of a pilot study to evaluate this intervention and explains the pharmacokinetic, efficacy and adverse effects evidence informing the design.

METHODS AND ANALYSIS

A mixed-methods pilot study will determine the feasibility of an international first, definitive phase III trial to evaluate the efficacy and safety of an extended continuous subcutaneous infusion of lidocaine for neuropathic cancer-related pain. This study will comprise: a phase II double-blind randomised controlled parallel-group pilot of subcutaneous infusion of lidocaine hydrochloride 10% w/v (3000 mg/30 mL) or placebo (sodium chloride 0.9%) over 72 hours for neuropathic cancer-related pain, a pharmacokinetic substudy and a qualitative substudy of patients' and carers' experiences. The pilot study will provide important safety data and help inform the methodology of a definitive trial, including testing proposed recruitment strategy, randomisation, outcome measures and patients' acceptability of the methodology, as well as providing a signal of whether this area should be further investigated.

ETHICS AND DISSEMINATION

Participant safety is paramount and standardised assessments for adverse effects are built into the trial protocol. Findings will be published in a peer-reviewed journal and presented at conferences. This study will be considered suitable to progress to a phase III study if there is a completion rate where the CI includes 80% and excludes 60%. The protocol and Patient Information and Consent Form have been approved by Sydney Local Health District (Concord) Human Research Ethics Committee 2019/ETH07984 and University of Technology Sydney ETH17-1820.

TRIAL REGISTRATION NUMBER

ANZCTR ACTRN12617000747325.

Drosophila pain sensitization and modulation unveiled by a novel pain model and analgesic drugs

In mammals, pain is regulated by the combination of an ascending stimulating and descending inhibitory pain pathway. It remains an intriguing question whether such pain pathways are of ancient origin and conserved in invertebrates. Here we report a new Drosophila pain model and use it to elucidate the pain pathways present in flies. The model employs transgenic flies expressing the human capsaicin receptor TRPV1 in sensory nociceptor neurons, which innervate the whole fly body, including the mouth. Upon capsaicin sipping, the flies abruptly displayed pain-related behaviors such as running away, scurrying around, rubbing vigorously, and pulling at their mouth parts, suggesting that capsaicin stimulated nociceptors in the mouth via activating TRPV1. When reared on capsaicin-containing food, the animals died of starvation, demonstrating the degree of pain experienced. This death rate was reduced by treatment both with NSAIDs and gabapentin, analgesics that inhibit the sensitized ascending pain pathway, and with antidepressants, GABAergic agonists, and morphine, analgesics that strengthen the descending inhibitory pathway. Our results suggest Drosophila to possess intricate pain sensitization and modulation mechanisms similar to mammals, and we propose that this simple, non-invasive feeding assay has utility for high-throughput evaluation and screening of analgesic compounds.