Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis

Lidocaine Inhibits the Proliferation of Non-Small Cell Lung Cancer and Exerts Anti-Inflammatory Effects Through the TLR-9/MyD88/NF-κB Pathway

Lung cancer represents a significant global health burden, with non-small cell lung cancer (NSCLC) being the most common subtype. The current standard of care for NSCLC has limited efficacy, highlighting the necessity for innovative treatment options. Lidocaine, traditionally recognized as a local anesthetic, has emerged as a compound with potential antitumor and anti-inflammatory capabilities. This study was designed to explore the impact of lidocaine on NSCLC cell proliferation and inflammation, particularly focusing on the Toll-like receptor 9 (TLR)-9/MyD88/NF-κB signaling pathway. A nude mice model of NSCLC was employed, with animals receiving lidocaine at different concentrations. In vitro experiments on A549 cells involved exposure to lidocaine, followed by assessment of cell viability, cytokine expression, and TLR-9 levels using the 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay, enzyme-linked immunosorbent assay, and Quantitative Real-time polymerase chain reaction (qPCR). Protein levels were evaluated via Western blot analysis. Additionally, A549 cells were transfected with a TLR-9-overexpressing lentivirus to dissect the role of TLR-9 in lidocaine's mechanism of action. Treatment with lidocaine led to a significant reduction in tumor dimensions and a decrease in inflammatory marker expression in the NSCLC mouse model. In cellular assays, lidocaine effectively suppressed A549 cell proliferation and the expression of inflammatory cytokines. The overexpression of TLR-9 partially negated the suppressive effects of lidocaine, underscoring the significance of the TLR-9/MyD88/NF-κB pathway in mediating lidocaine's effects. Lidocaine's inhibitory effects on NSCLC cell proliferation and its anti-inflammatory mechanisms are mediated through the TLR-9/MyD88/NF-κB pathway. The study's results offer promising insights into the therapeutic potential of lidocaine in NSCLC and pave the way for future investigations into its application in cancer therapy.

Hippocampal nicotinic acetylcholine receptor signaling mediates the anti-allodynic effect of ketamine and morphine on neuropathic pain

The present study investigated the involvement of hippocampal nicotinic acetylcholine receptors (nAChRs) in the anti-allodynic effect of ketamine/morphine on neuropathic pain in adult male Wistar rats. Morphine or ketamine administration decreased the percentage of maximum possible effect (MPE%), indicating an analgesic effect. The most significant decrease occurred with a 5 mg/kg dose of morphine (average MPE% = 98), while a 0.5 mg/kg dose of ketamine resulted in a high response (average MPE% = 91), using decision trees as a machine learning tool. Combining morphine and ketamine improved neuropathic pain (average MPE% = 91). Intra-CA1 microinjection of mecamylamine (2 μg/rat) with morphine (3 mg/kg) reduced neuropathic pain (average MPE% = 94). Co-administration of lower doses of ketamine (0.1 mg/kg, i.p.) and mecamylamine (0.5 or 1 μg/rat) with morphine (3 mg/kg) led to a considerable reduction in pain (average MPE% = 91). Utilizing the generalized least squares (GLS) model enabled the establishment of a continuous relation between drug dose and MPE% as the outcome of interest. There was a 19.60 higher average MPE% for each mg/kg increase in morphine dose. In contrast, there was a 17.05 higher average MPE% for every 0.1 mg/kg increase in ketamine dose. Each 0.1 mg/kg increase in ketamine dose, when combined with morphine (3 mg/kg), led to a 30.85 higher average MPE%. A tenfold impact of increasing mecamylamine dosage on MPE% was observed when paired with morphine. Thus, hippocampal nAChRs play a significant role in mediating the anti-allodynic effect of ketamine and morphine in neuropathic pain.

Feasibility pilot of a novel coaching intervention to optimize cannabis use for chronic pain management among Veterans

INTRODUCTION

Chronic pain is common among Veterans, some of whom use cannabis for pain. We conducted a feasibility pilot study of a novel coaching intervention to help Veterans optimize use of medical cannabis products for pain management (NCT06320470).

METHODS

The intervention drew from scientific literature, consultation with cannabis experts, Veteran input via a Community Advisory Board, and tenets of motivational interviewing. Participants were Veterans with chronic pain who endorsed current use or interest in using cannabis for pain management. Participants received up to 4 individual coaching sessions via videoconference, spaced approximately 2 weeks apart. We assessed feasibility (adherence, satisfaction, acceptability) and preliminary effects on pain symptoms 14 weeks after baseline. The primary outcome was the Patient Global Impression of Change (PGIC), and exploratory outcomes included domains from the Patient-Reported Outcomes Measurement Information System (PROMIS)-29.

RESULTS

Of 22 enrolled participants, 17 attended 4 coaching sessions, 2 attended 3 sessions, and 2 attended 2 sessions. Among those who completed end of intervention surveys (16/21), 87.5% were very or completely satisfied with the intervention and 81.3% rated coaching as very or extremely helpful. All participants reported improvement on the PGIC, with 63% reporting much or very much improvement. Participants reported statistically significant decreased pain intensity (7.1/10 vs. 5.7/10) and pain interference (T-score 66.3 vs. 61.8), and increased social satisfaction (T-score 41.4 vs. 44.3). Participants noted helpful intervention factors, including co-developing a personalized plan, discussing questions/concerns, and trying different approaches to cannabis-based treatment.

CONCLUSIONS

In this feasibility pilot study of coaching on cannabis use for chronic pain among Veterans, participants were satisfied with the intervention and reported clinically significant improvements in pain symptoms. Our results support evaluating this intervention in a larger, efficacy trial.

Preclinical Insights into the Role of Kir4.1 in Chronic Pain and Depression: Mechanisms and Therapeutic Potential

Chronic pain and mental health disorders, such as depression and anxiety, frequently co-occur and share underlying mechanisms involving neuronal excitability and synaptic transmission. The inwardly rectifying potassium channel 4.1 (Kir4.1), predominantly expressed in glial cells, is crucial for maintaining extracellular potassium and glutamate homeostasis. Dysregulation of Kir4.1 leads to altered neuronal activity, contributing to both chronic pain and mental health disorders. In chronic pain, downregulation of Kir4.1 impairs potassium buffering and glutamate clearance, increasing neuronal excitability and enhancing pain signaling through peripheral and central sensitization. In mental health disorders, impaired Kir4.1 function disrupts neurotrophic factor secretion and neuroinflammatory pathways, leading to mood disturbances. This review primarily summarizes findings from preclinical studies to examine the relationship between Kir4.1 and the pathogenesis of chronic pain and mental health disorders, discussing its molecular structure, expression patterns, and functional roles. Furthermore, we explore therapeutic strategies targeting Kir4.1, including pharmacological modulators and gene therapy approaches, emphasizing its potential as a novel therapeutic target.

Cardiac Autonomic Neuropathy in Diabetes Mellitus: Pathogenesis, Epidemiology, Diagnosis and Clinical Implications: A Narrative Review

Background: Cardiac autonomic neuropathy (CAN) is a serious but sometimes underdiagnosed complications of Diabetes Mellitus (DM). Because of the subtle onset and non-specific symptoms that can be mistaken for other conditions, CAN is frequently underdiagnosed despite the serious consequences that can appear. Its significance as an independent risk factor for cardiovascular events, including arrhythmias, sudden cardiac death, and silent myocardial ischemia, is being demonstrated by recent studies. The objective of this review article is to highlight the reasons why CAN is underdiagnosed and its association with decreased cardiovascular risk and promote clinical awareness. This review article summarizes the epidemiology, influence on the cardiovascular system and diagnostic methods of CAN, and the clinical implications of diabetic neuropathy. This review analyzes available data from papers relevant to the topic of diabetic neuropathy, cardiac autonomic neuropathy, and cardiovascular system implications. Conclusions: CAN is still underdiagnosed despite its clinical impact because routine screening is lacking, and healthcare providers are not aware of it. To improve outcomes for people with DM, it is necessary to introduce standardized diagnostic procedures into clinical practice and increase the knowledge about CAN.

Effects of Spinal Cord Stimulation in Patients with Small Fiber and Associated Comorbidities from Neuropathy After Multiple Etiologies

Objectives: The aim of this study was to evaluate the effects of spinal cord stimulation (SCS) on pain, neuropathic symptoms, and other health-related metrics in patients with chronic painful peripheral neuropathy (PN) from multiple etiologies. Methods: A prospective single center observational longitudinal cohort study assessed SCS efficacy from April 2023 to May 2024, with follow-ups at 2, 4, 6, and 12 months in 19 patients suffering from the painful polyneuropathy of diverse etiologies: diabetic (DPN), idiopathic (CIAP), chemotherapy-induced (CIPN), and others. Patients were implanted with a neurostimulator (WaveWriter AlphaTM, Boston Scientific Corporation, Valencia, CA, USA) and percutaneous leads targeting the lower limbs (T10-T11) and, if necessary, the upper limbs (C4-C7). Stimulation programming was individualized based on patient preference and best response. Assessments were performed before and after implantation and included pain intensity (VAS and DN4), neuropathic pain symptoms (NPSI and SF-MPQ-2), autonomic symptoms (SFN-SIQ and SAS), sensory and small fiber nerve injury (UENS), functionality (GAF), sleep (CPSI), global impression of change (CGI and PGI), and quality of life (EQ-VAS and EQ-5D). Intra-epidermal nerve fiber density (IENFD) via skin biopsy was also performed at baseline (diagnostic) and after 12 months to assess potential small fiber re-growth. Statistical analyses were conducted to determine the evolution of treatment success. Results: To date, 19 patients have undergone implantation and completed follow-up. SCS produced a significant consistent and sustained improvement in pain intensity by 49% in DN4 and 76% in VAS, in neuropathic pain symptoms by 73%, in autonomic symptoms by 26-30%, in the sensorimotor physical exam by 8%, in functionality by 44%, in sleep by 74%, and in quality of life (69% for EQ-VAS and 134% EQ-5D). Both clinicians and patients had a meaningful global impression of change, at 1.1 and 1.3, respectively. Distal intra-epidermal nerve fiber density improved by 22% at 12 months while proximal intra-epidermal nerve fiber density decreased by 18%. Conclusions: SCS is an effective therapy for managing various types of PN.

Prescription of Strong Opioids in Chronic Non-Cancer Pain in the Province of Valladolid (Spain)

Background: Chronic non-cancer pain (CNCP) is one of the leading causes of disability. The use of strong opioids (SOs) in the management of CNCP is increasing, although evidence supporting their use remains limited. Primary care (PC) plays a key role in this context. Objectives: Our objectives were to determine the prevalence and profile of patients using SOs for CNCP in PC consultations in Valladolid in 2022, and to describe the consumption of SO prescribed for CNCP from 2020 to 2023. Methods: We conducted a descriptive and retrospective study using data extracted from the Pharmaceutical Consumption Information System of Castilla y León. Patients in Valladolid with SO use for more than three months due to CNCP were analyzed. Sociodemographic and clinical characteristics of these patients in 2022 were described. The number of defined daily doses (nº DDDs) and costs from 2020 to 2023 were analyzed. Results: A total of 3642 patients were included (0.7% of the population of Valladolid), 71.8% of whom were women. Of the patients, 62.4% were aged 70 or older, 39.8% lived in rural areas, and 9.9% resided in nursing homes. The most frequently prescribed SOs in nº DDDs were fentanyl and tapentadol. The highest consumption in nº DDDs was in patients who lived in nursing homes, were over 70 years old and were resident in rural areas. The number of DDDs from 2020 to 2023 for SOs in DCNO increased by 41%. Conclusions: In total, 0.7% of the population of Valladolid consumes SOs for CNCP, mostly women and people over 70 years old. The consumption of strong opioids in DDDs grew by 41% from 2020 to 2023.

Modulation of morphine antinociceptive and rewarding effect by mirtazapine in an animal model of osteoarthritic pain

People with chronic pain mitigate their suffering by the action of opioids. Adverse reactions aside, opioids are not exempt from potential complications like addiction and abuse, which have posed a global public health problem lately. Finding new therapeutic strategies to improve analgesia and to reduce opioid side effects has become a priority. In this regard, the association of different adjuvant therapies has been postulated. Despite preclinical and clinical evidence supporting the use of antidepressants as analgesics, it is not clear whether they could help reduce the risk of addiction in combination with opioids. To further explore this idea a model of chronic osteoarthritis pain was employed, and a combination of mirtazapine and morphine was used in a chronic regimen in male and female rats. The effects on the development of tactile allodynia, movement-evoked pain, reward, analgesic tolerance, naloxone-induced withdrawal symptoms, impaired locomotor activity and anxiety were evaluated under a 25-day experimental protocol. Additionally, protein expression of μ-opioid receptors and clusterin (related with substance abuse) was evaluated in plasma and in brain structures of the reward system. Chronic morphine caused analgesic tolerance, reward and naloxone-induced withdrawal symptoms. The combination reduced the analgesic tolerance and prevented the development of withdrawal symptoms but showed sex-based differences regarding reward. Increased levels of clusterin in plasma were observed in females treated with morphine, but not with combined therapy. The combination of mirtazapine and morphine could be a promising strategy to improve the management of long-term opioid treatment and its risk of abuse, especially in females.

Reducing medical cannabis use risk among Veterans: A descriptive study

BACKGROUND

Canadian Veterans experiencing chronic pain report concerns about accessing accurate information on the risks associated with medical cannabis (MC) use. The Lower Risk Cannabis Use Guidelines (LRCUG) were developed to equip individuals who use cannabis recreationally with safer-use strategies. Many of the harm reduction recommendations for recreational cannabis use are relevant and important considerations for MC use. The primary objective of our study was to assess Canadian Veterans' awareness of and interest in the LRCUG, and engagement in potential higher-risk MC use behaviours.

METHODS

Canadian Armed Forces Veterans living with chronic pain (N = 582) were recruited online and through the Chronic Pain Centre of Excellence for Canadian Veterans. Participants completed measures on: cannabis use (never, past, current use), sources of cannabis knowledge, mental health, and awareness of and interest in receiving the LRCUG. Chi-Square and post-hoc analyses characterized the sample and assessed for demographic differences based on cannabis use status and awareness of the LRCUG. Engagement in higher-risk MC use behaviours were aligned to LRCUG recommendations, and detailed descriptively.

RESULTS

Veterans who currently use cannabis were more likely to be unemployed (z = 3.62, p < .01), released as a Non-Commissioned Officer (z = -3.83, p < .01), and unable to work due a disability (z = -3.43, p < .01) than Veterans who do not currently use. Less than 30% of Veterans were aware of the LRCUG, with greater awareness among individuals who currently use cannabis (n = 356). Engagement in higher-risk MC use behaviours that contradicted LRCUG recommendations ranged from ~ 9% to ~ 85%. Approximately 9% of Veterans experienced co-morbid mental health concerns, yet their MC use was not for mental health purposes (LRCUG recommendation #7). Additionally, almost 85% of Veterans engaged in daily MC use (LRCUG recommendation #5). The majority of Veterans who currently use cannabis engaged in two or more higher-risk MC use behaviours (60.2%; LRCUG recommendation #12). Almost half of all Veterans received their cannabis information from a healthcare provider or the internet.

CONCLUSIONS

Our study suggests the importance of safer use guidelines tailored for MC use. Development of lower-risk MC use guidelines can support prescribing practitioners and Veterans with information needed for safer and better-informed MC use decisions, tailored to patients' needs and circumstances.

Ketamine Infusion for Complex Regional Pain Syndrome Treatment: A Narrative Review

PURPOSE OF REVIEW

Complex Regional Pain Syndrome (CRPS) is a neuropathic pain disorder characterized by pain disproportionate to the inciting event that is constant for an extended duration. Numerous treatment options for this condition have been explored with unsatisfactory results in many cases. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist typically used as an anesthetic and analgesic, presents a promising potential treatment for CRPS in patients who fail to respond to traditional therapies.

RECENT FINDINGS

Numerous studies report significant improvement in the degree of pain, mobility of extremities, and other parameters after ketamine infusion in patients with CRPS. Although adverse effects were not reported often, some subjects experienced nausea, vomiting, headache or psychotropic or psychomimetic symptoms which could be mitigated with cessation of the drug. Although more research is needed to determine optimal dosing and duration, ketamine seems to be a safe and effective treatment for refractory cases of CRPS.

CONCLUSION

The present investigation summarizes existing knowledge and research surrounding ketamine infusions for CRPS to provide a well-rounded depiction of advantages and disadvantages for physicians who may be considering it for patients with this challenging and complex condition.

mHealth-Augmented Care for Reducing Depression Symptom Severity Among Patients With Chronic Pain: Exploratory, Retrospective Cohort Study

Background

Depression and chronic pain are commonly comorbid, mutually reinforcing, and debilitating. Emerging approaches to mobile behavioral health care (mHealth) promise to improve outcomes for patients with comorbid depression and chronic pain by integrating with existing care models to bolster support and continuity between clinical visits; however, the evidence base supporting the use of mHealth to augment care for this patient population is limited.

Objective

To develop an evidence base that sets the stage for future research, we aimed to explore the associations between changes in depression severity and various integrated care models, with and without mHealth augmentation, among patients with comorbid depression and nonmalignant chronic pain.

Methods

Our team leveraged retrospective, real-world data from 3837 patients with comorbid depression and nonmalignant chronic pain who received integrated behavioral health care (IBH) at a subspecialty pain clinic. We analyzed one IBH-only, non-mHealth cohort (n=2765), an mHealth-augmented cohort (n=844), and a collaborative care (CoCM)+mHealth cohort (n=136), which were supported by the NeuroFlow mHealth platform, and a pre-CoCM mHealth cohort (n=92), which was supported by the mHealth platform for 3 months prior to beginning the chronic pain treatment. We evaluated changes in depression severity between treatment cohorts via longitudinal analyses of both clinician- and mHealth-administered Patient Health Questionnaire-9 (PHQ-9) assessments.

Results

mHealth-augmented integrated care led to significantly greater proportions of patients reaching clinical benchmarks for reduction (725/844, 86% vs 2112/2765, 76%), response (689/844, 82% vs 2027/2765, 73%), and remission (629/844, 75% vs 1919/2765, 69%) compared with integrated care alone. Furthermore, hierarchical regression modeling revealed that patients who received mHealth-augmented psychiatric CoCM experienced the greatest sustained reductions in on-average depression severity compared with other cohorts, irrespective of clinical benchmarks. In addition, patients who engaged with an mHealth platform before entering CoCM experienced a 7.2% reduction in average depression severity before starting CoCM treatment.

Conclusions

Our findings suggest that mHealth platforms have the potential to improve treatment outcomes for patients with comorbid chronic pain and depression by providing remote measurement-based care, tailored interventions, and improved continuity between appointments. Moreover, our study set the stage for further research, including randomized controlled trials to evaluate causal relationships between mHealth engagement and treatment outcomes in integrated care settings.

Intranasal Administration of the Combination of Dextro-Ketamine and Dexmedetomidine for Treatment of Diabetic Neuropathic Pain in Rats

Introduction

Diabetes mellitus (DM) has become a public health problem, which is associated with high morbidity and mortality, due to the chronic complications, such as diabetic neuropathy. Current recommendations for the treatment of neuropathic pain achieve a reduction of 30% in only 30% of cases. Therefore, it is necessary to identify new therapeutic approaches to improve the quality of life of diabetic patients.

Methods

This work evaluated the antinociceptive effect of intranasal administration of the combination of dextro-ketamine (keta), a non-competitive glutamatergic receptor antagonist, and dexmedetomidine (DEX), a selective alpha2-adrenergic agonist, in rats with neuropathic pain induced by streptozotocin-DM.

Results

The thermal hyperalgesia and mechanical allodynia observed in DM model are reduced with the intranasal administration of the combination of keta and DEX (200 + 0.10 μg/kg) after 3 days of treatment. The antinociceptive action could be due to reduction of Ca2+ influx with lower glutamate release and reduced excitability through the activation of alpha2-adrenergic receptors by DEX and reduction of NMDA receptor activation by glutamate with lower excitability due to the antagonism produced by keta. DM induced increased expression of glial fibrillary acid protein (GFAP) and tumor necrosis factor-alpha (TNF-alpha) detected by immunohistochemistry, indicating greater astrocyte activity and intense inflammatory response. Intranasal administration for 10 days of the combination of low doses of keta and DEX promoted an intense decrease in the expression of both GFAP and TNF-alpha, indicating lower activation of astrocytes in the spinal cord and reduced production and release of TNF-alpha, favoring the reduction of inflammation.

Conclusion

Intranasal administration of low doses of keta with DEX could be a new therapeutic approach to reduce neuropathic pain and consequently improve the quality of life of diabetic patients.

Understanding the Physiopathology of Pain Pathways for a Practical Approach of Cancer Pain Management

Pain associated with cancer is often the first symptom reported with major repercussions on patient's quality of life. Mechanical compression, release of algogenic substances by the tumor or the complications of oncologic treatment represent the major causes. Nociceptive and neuropathic pain are both induced by different mediators that give rise to a neuroinflammation creating a peripheral and central sensitization responsible of chronic pain. Understanding the pain pathway may orientate to the most appropriate treatment. Oral medication should be often reevaluated to consider multimodal analgesia including interventional pain procedures with intrathecal therapy and neuromodulation.

A novel approach to completely alleviate peripheral neuropathic pain in human patients: insights from preclinical data

Neuropathic pain is a pervasive health concern worldwide, posing significant challenges to both clinicians and neuroscientists. While acute pain serves as a warning signal for potential tissue damage, neuropathic pain represents a chronic pathological condition resulting from injury or disease affecting sensory pathways of the nervous system. Neuropathic pain is characterized by long-lasting ipsilateral hyperalgesia (increased sensitivity to pain), allodynia (pain sensation in response to stimuli that are not normally painful), and spontaneous unprovoked pain. Current treatments for neuropathic pain are generally inadequate, and prevention remains elusive. In this review, we provide an overview of current treatments, their limitations, and a discussion on the potential of capsaicin and its analog, resiniferatoxin (RTX), for complete alleviation of nerve injury-induced neuropathic pain. In an animal model of neuropathic pain where the fifth lumbar (L5) spinal nerve is unilaterally ligated and cut, resulting in ipsilateral hyperalgesia, allodynia, and spontaneous pain akin to human neuropathic pain. The application of capsaicin or RTX to the adjacent uninjured L3 and L4 nerves completely alleviated and prevented mechanical and thermal hyperalgesia following the L5 nerve injury. The effects of this treatment were specific to unmyelinated fibers (responsible for pain sensation), while thick myelinated nerve fibers (responsible for touch and mechanoreceptor sensations) remained intact. Here, we propose to translate these promising preclinical results into effective therapeutic interventions in humans by direct application of capsaicin or RTX to adjacent uninjured nerves in patients who suffer from neuropathic pain due to peripheral nerve injury, following surgical interventions, diabetic neuropathy, trauma, vertebral disc herniation, nerve entrapment, ischemia, postherpetic lesion, and spinal cord injury.

Clinical Characteristics of Neuropathic Pain and Its Relationship with Cancer in Different Corporal Areas-A Systematic Review

Background: Neuropathic pain (NP) and cancer are caused by nerve damage due to cancer or treatments such as chemotherapy, radiotherapy, and surgery, with a prevalence that can reach up to 40%. Causes of neuropathic cancer pain (NCP) include direct nerve invasion or compression by the tumor, as well as neural toxicity associated with treatments. This type of pain is classified into several categories, such as plexopathy, radiculopathy, and peripheral neuropathies. Methods: Medline, Web of Science, Google Scholar, CINAHL, and LILACS databases were searched until October 2024. Two authors independently performed the search, study selection, and data extraction. Methodological quality was analyzed using the Robins-I tool. Results: The main findings of this review indicate that, depending on the cancer type, neuropathic pain will exhibit different characteristics, as well as identifying which types of cancer have a higher probability of presenting neuropathic pain. Additionally, there is a direct relationship whereby the more advanced the cancer, the greater the likelihood of experiencing neuropathic pain. Finally, although chemotherapy is employed as a cancer treatment, this therapy is quite invasive, and one of its adverse effects is that treated patients have a higher probability of developing neuropathic pain. Conclusions: Neuropathic pain is a condition that adversely affects patients with cancer. A detailed understanding of the relationships and triggers that produce this condition is present in only a small percentage of patients with cancer and is necessary to provide better treatment and gain a more comprehensive understanding of the characteristics of neuropathic pain. The objective of this study is to describe the relationship between different types of cancer or various treatments and the presence of NP.

Quality, topics, and demographic trends of animal systematic reviews - an umbrella review

BACKGROUND

Animal systematic reviews are critical to inform translational research. Despite their growing popularity, there is a notable lack of information on their quality, scope, and geographical distribution over time. Addressing this gap is important to maintain their effectiveness in fostering medical advancements.

OBJECTIVE

This study aimed to assess the quality and demographic trends of animal systematic reviews in neuroscience, including changes over time.

METHODS

We performed an umbrella review of animal systematic reviews, searching Medline and Embase for reviews until January 27, 2023. A data mining method was developed and validated to automatically evaluate the quality of these reviews.

RESULTS

From 18'065 records identified, we included 1'358 animal systematic reviews in our study. These reviews commonly focus on translational research but with notable topical gaps such as schizophrenia, other psychiatric disorders, and brain tumours. They originate from 64 countries, with the United States, China, the UK, Brazil, and Iran being the most prolific. The automated quality assessment indicated high reliability, with F1-scores over 80% for most criteria. Overall, the reviews were of high quality and the quality improved over time. However, many systematic reviews did not report a pre-registered study protocol. Reviews with a pre-registered protocol generally scored higher in quality. No significant differences in quality were observed between countries.

CONCLUSION

Animal systematic reviews in neuroscience are of overall of high quality. Our study highlights specific areas for enhancement such as the recommended pre-publication of study protocols. It also identifies under-represented topics that could benefit from further investigation to inform translational research. Such measures can contribute to the effective translation of animal research findings to clinical applications.

Real-world long-term outcomes of peripheral nerve stimulation: a prospective observational study

AIM

We aimed to evaluate real-world outcomes of peripheral nerve stimulation (PNS) used to treat chronic neuropathic pain (CNP) at a tertiary pain management center.

METHODS

Thirty adults who underwent PNS for CNP between June 2015 and September 2021 completed pain and psychosocial assessments in the 6 months before, and 2-3 years after PNS treatment. Pain intensity was measured using the NIH Patient Reported Outcomes Measurement Information System (PROMIS) Pain Intensity Short From (3A). Psychosocial outcomes including depression, anxiety, and sleep disturbance were also measured.

RESULTS

Prior to receiving PNS, long-term responders reported significantly fewer depressive symptoms compared to non-responders (PROMIS depression t-score 50.3 [10.7] vs 57.9 [8.9]; p-value = 0.05). Eleven participants (36.7%) reported long-term treatment response. There was a significantly greater improvement in pain intensity among responders compared to non-responders who reported increased pain (PROMIS Pain Intensity score -9.0 [-4.2] vs. +3.1[+3.2]; p-value < 0.0001).

CONCLUSIONS

Patients report clinically meaningful long-term pain relief after receiving PNS through both 60-day and permanent implant systems, with significant reductions in pain intensity observed in long-term responders. Long-term responders reported fewer depressive symptoms compared to non-responders prior to receiving therapy, emphasizing the importance of psychological screening and psychological optimization prior to receiving PNS.

Assessment for Diabetic Neuropathy: Treatment and Neurobiological Perspective

Diabetic neuropathy, also known as diabetic peripheral sensorimotor neuropathy (DPN), is a consequential complexity of diabetes, alongside diabetic nephropathy, diabetic cardiomyopathy, and diabetic retinopathy. It is characterized by signs and symptoms of peripheral nerve damage in diabetes patients after ruling out other causes. Approximately 20% of people with diabetes are affected by this painful and severe condition. The development of diabetic neuropathy is influenced by factors such as impaired blood flow to the peripheral nerves and metabolic issues, including increased polyol pathway activation, myo-inositol loss, and nonenzymatic glycation. The present review article provides a brief overview of the pathological changes in diabetic neuropathy and the mechanisms and types of DPN. Various diagnostic tests and biomarkers are available to assess nerve damage and its severity. Pharmacotherapy for neuropathic pain in diabetic neuropathy is complex. This review will explore current treatment options and potential future developments to improve the quality of life for patients suffering from diabetic neuropathy.

Intrathecal Fumagillin Alleviates Chronic Neuropathy-Induced Nociceptive Sensitization and Modulates Spinal Astrocyte-Neuronal Glycolytic and Angiogenic Proteins

Nociceptive sensitization is accompanied by the upregulation of glycolysis in the central nervous system in neuropathic pain. Growing evidence has demonstrated glycolysis and angiogenesis to be related to the inflammatory processes. This study investigated whether fumagillin inhibits neuropathic pain by regulating glycolysis and angiogenesis. Fumagillin was administered through an intrathecal catheter implanted in rats with chronic constriction injury (CCI) of the sciatic nerve. Nociceptive, behavioral, and immunohistochemical analyses were performed to evaluate the effects of the inhibition of spinal glycolysis-related enzymes and angiogenic factors on CCI-induced neuropathic pain. Fumagillin reduced CCI-induced thermal hyperalgesia and mechanical allodynia from postoperative days (POD) 7 to 14. The expression of angiogenic factors, vascular endothelial growth factor (VEGF) and angiopoietin 2 (ANG2), increased in the ipsilateral lumbar spinal cord dorsal horn (SCDH) following CCI. The glycolysis-related enzymes, pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) significantly increased in the ipsilateral lumbar SCDH following CCI on POD 7 and 14 compared to those in the control rats. Double immunofluorescence staining indicated that VEGF and PKM2 were predominantly expressed in the astrocytes, whereas ANG2 and LDHA were predominantly expressed in the neurons. Intrathecal infusion of fumagillin significantly reduced the expression of angiogenic factors and glycolytic enzymes upregulated by CCI. The expression of hypoxia-inducible factor-1α (HIF-1α), a crucial transcription factor that regulates angiogenesis and glycolysis, was also upregulated after CCI and inhibited by fumagillin. We concluded that intrathecal fumagillin may reduce the expression of ANG2 and LDHA in neurons and VEGF and PKM2 in the astrocytes of the SCDH, further attenuating spinal angiogenesis in neuropathy-induced nociceptive sensitization. Hence, fumagillin may play a role in the inhibition of peripheral neuropathy-induced neuropathic pain by modulating glycolysis and angiogenesis.

Real-world healthcare utilization and costs of peripheral nerve stimulation with a micro-IPG system

AIM

To characterize real-world healthcare resource utilization (HCRU) and costs in adults with chronic pain of peripheral nerve origin treated with peripheral nerve stimulation (PNS) using the micro-implantable pulse generator (IPG).

MATERIALS & METHODS

This retrospective observational study (9/1/19-1/31/23) linked patients from the Nalu medical database to the OM1 Real-World Data Cloud (RWDC). Eligible patients received the micro-IPG implant for PNS, were identifiable in both databases, and had ≥ 12 months of RWDC pre/post-implantation claims data. Primary outcomes were all-cause HRCU and medical costs (12 months pre- and post-implantation); secondary outcomes were all-cause pharmacy costs, including opioids, over the same time.

RESULTS

Patients (N = 122) had a higher mean (standard deviation; SD) number of outpatient visits pre-implantation (5.7 [5.4]) than post-implantation (4.9 [5.7]). Mean (SD) total medical costs were 50% lower, from $27,493 ($44,756) to $13,717 ($23,278). Median (first-third quartile [Q1-Q3]) medical costs were 57% lower, from $11,809 ($4,075-$31,788) to $5,094 ($1,815-$13,820). Mean (SD) pharmacy costs (n = 77) were higher post-implantation ($22,470 [$77,203]) than pre-implantation ($20,092 [$64,132]), while median (Q1-Q3) costs were lower (from $2,708 [$222 -11,882] to $2,122 [$50-9,370]). Post-implantation, the proportion of patients using opioids was 31.4% lower.

CONCLUSION

Patients with PNS using the micro-IPG had reduced HCRU, costs, and opioid use.

TangBi Formula for Painful Diabetic Distal Symmetric Polyneuropathy: A Multicenter, Randomized, Double-Blind, Placebo-Controlled and Parallel-Group Trial

OBJECTIVE

To determine whether the use of herbal medicines combined with conventional treatment is more effective than conventional medication alone in improving clinical symptoms in patients with diabetic distal symmetric polyneuropathy (DSPN).

METHODS

This multicenter, placebo-controlled, double-blind, randomized controlled clinical trial recruited patients from 6 clinical centers in mainland China. A total of 188 patients were randomly assigned in a 1:1 ratio to the treatment group (Tangbi Formula plus methylcobalamin) and the control group (placebo plus methylcobalamin). Subjects were reassessed after the 24-week intervention. The primary outcomes were differences in changes in clinical signs and symptoms and changes in the Michigan Diabetic Neuropathy Score (MDNS) between the two groups before and after treatment. Secondary outcomes were changes in nerve conduction velocity (NCV) and single clinical signs and symptoms as measured by the visual-analogue scale (VAS) and Toronto clinical scoring system (TCSS).

RESULTS

Compared with the placebo group, after 24 weeks of treatment, the MDNS score of TangBi Formula group was significantly reduced (p < 0.001). There were no significant changes in NCV results in either group before or after treatment. Compared with baseline, the difference in the change value of VAS score between the two groups after treatment was statistically significant (p = 0.031). A statistically significant difference in the change value of TCSS after treatment compared to baseline was found between the two groups (p = 0.033 at 12 weeks and p = 0.030 at 24 weeks). No severe adverse events due to study participation or study intervention were reported.

CONCLUSIONS AND RELEVANCE

This trial demonstrated that combining Tangbi Formula with basal therapy can be safer and more effective in improving the symptoms of DSPN patients.

Metabotropic Glutamate Receptor 5: A Potential Target for Neuropathic Pain Treatment

Neuropathic pain, a multifaceted and incapacitating disorder, impacts a significant number of individuals globally. Despite thorough investigation, the development of efficacious remedies for neuropathic pain continues to be a formidable task. Recent research has revealed the potential of metabotropic glutamate receptor 5 (mGlu5) as a target for managing neuropathic pain. mGlu5 is a receptor present in the central nervous system that has a vital function in regulating synaptic transmission and the excitability of neurons. This article seeks to investigate the importance of mGlu5 in neuropathic pain pathways, analyze the pharmacological approach of targeting mGlu5 for neuropathic pain treatment, and review the negative allosteric mGlu5 modulators used to target mGlu5. By comprehending the role of mGlu5 in neuropathic pain, we can discover innovative treatment approaches to ease the distress endured by persons afflicted with this incapacitating ailment.

The global and regional burden of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is length-dependent peripheral nerve damage arising as a complication of type 1 or type 2 diabetes in up to 50% of patients. DPN poses a substantial burden on patients, who can experience impaired gait and loss of balance, predisposing them to falls and fractures, and neuropathic pain, which is frequently difficult to treat and reduces quality of life. Advanced DPN can lead to diabetic foot ulcers and non-healing wounds that often necessitate lower-limb amputation. From a socioeconomic perspective, DPN increases both direct health-care costs and indirect costs from loss of productivity owing to neuropathy-related disability. In this Review, we highlight the importance of understanding country-specific and region-specific variations in DPN prevalence to inform public health policy and allocate resources appropriately. We also explore how identification of DPN risk factors can guide treatment and prevention strategies and aid the development of health-care infrastructure for populations at risk. We review evidence that metabolic factors beyond hyperglycaemia contribute to DPN development, necessitating a shift from pure glycaemic control to multi-targeted metabolic control, including weight loss and improvements in lipid profiles.

E-52862-A selective sigma-1 receptor antagonist, in peripheral neuropathic pain: Two randomized, double-blind, phase 2 studies in patients with chronic postsurgical pain and painful diabetic neuropathy

BACKGROUND

We report the efficacy and safety of E-52862-a selective, sigma-1 receptor antagonist-from phase 2, randomized, proof-of-concept studies in patients with moderate-to-severe, neuropathic, chronic postsurgical pain (CPSP) and painful diabetic neuropathy (PDN).

METHODS

Adult patients (CPSP [N = 116]; PDN [N = 163]) were randomized at a 1:1 ratio to 4 weeks of treatment with E-52862 (CPSP [n = 55]; PDN [n = 85]) or placebo (CPSP [n = 61]; PDN [n = 78]) orally once daily. Pain intensity scores were measured using a numerical pain rating scale from 0 (no pain) to 10 (worst pain imaginable). The primary analysis population comprised patients who received study drug with ≥1 baseline and on-treatment observation (full analysis set).

RESULTS

In CPSP, mean baseline average pain was 6.2 for E-52862 vs. 6.5 for placebo. Week 4 mean change from baseline (CFB) for average pain was -1.6 for E-52862 vs. -0.9 for placebo (least squares mean difference [LSMD]: -0.9; p = 0.029). In PDN, mean baseline average pain was 5.3 for E-52862 vs. 5.4 for placebo. Week 4 mean CFB for average pain was -2.2 for E-52862 vs. -2.1 for placebo (LSMD: -0.1; p = 0.766). Treatment-emergent adverse events (TEAEs) were reported in 90.9% of E-52862-treated patients vs. 76.7% of placebo-treated patients in CPSP and 34.1% vs. 26.9% in PDN. Serious TEAEs occurred in CPSP only: E-52862: 5.5%; placebo: 6.7%.

CONCLUSIONS

E-52862 demonstrated superior relief of CPSP vs. placebo after 4 weeks. Reductions in pain intensity were seen in PDN with E-52862; high placebo response rates may have prevented differentiation between treatments. E-52862 had acceptable tolerability in both populations.

SIGNIFICANCE STATEMENT

These proof-of-concept studies validate the mode of action of E-52862, a selective sigma-1 receptor antagonist. In CPSP, E-52862 resulted in clinically meaningful pain relief. In PDN, reductions in pain intensity were seen with E-52862; high placebo response rates may have prevented differentiation between E-52862 and placebo. These findings are clinically relevant given that neuropathic pain is highly incapacitating, lacking effective treatments and representing a significant unmet medical need, and support further development of sigma-1 receptor antagonists for peripheral neuropathic pain.

Anticonvulsant and gabapentinoids pharmacotherapy in the multiple sclerosis prodrome: A population-based matched cohort study

BACKGROUND

Before disease onset, multiple sclerosis (MS) persons fill more prescriptions than controls, including for pain. However, knowledge regarding neuropathic pain-related medications is lacking OBJECTIVE: Compare odds of anticonvulsant/gabapentinoid prescriptions for 4,862 MS-cases versus 22,669 controls, pre-MS onset (defined as first demyelinating disease-related event).

METHODS

Matched-cohort study using administrative data (1996-2013), comparing the odds of anticonvulsant/gabapentinoid prescriptions pre-MS onset using multivariable logistic regression.

RESULTS

Versus controls, MS-cases were more likely to fill prescriptions for anticonvulsants (aOR[adjusted odds ratios] = 3.1,95 % confidence interval[CI]:2.8,3.4), gabapentinoids (aOR = 4.1,95 %CI:3.6,4.6), and gabapentinoids without anticonvulsants (aOR = 3.9,95 %CI:3.4,4.5).

CONCLUSION

MS-cases filled anticonvulsant and gabapentinoid prescriptions more than matched controls pre-MS onset.

Keratinocyte-derived extracellular vesicles in painful diabetic neuropathy

Painful diabetic neuropathy (PDN) is a challenging complication of diabetes with patients experiencing a painful and burning sensation in their extremities. Existing treatments provide limited relief without addressing the underlying mechanisms of the disease. PDN involves the gradual degeneration of nerve fibers in the skin. Keratinocytes, the most abundant epidermal cell type, are closely positioned to cutaneous nerve terminals, suggesting the possibility of bi-directional communication. Extracellular vesicles are lipid-bilayer encapsulated nanovesicles released from many cell types that mediate cell to cell communication. The role of keratinocyte-derived extracellular vesicles (KDEVs) in influencing signaling between the skin and cutaneous nerve terminals and their contribution to the genesis of PDN has not been explored. In this study, we characterized KDEVs in a well-established high-fat diet mouse model of PDN using primary adult mouse keratinocyte cultures. We obtained highly enriched KDEVs through size-exclusion chromatography and then analyzed their molecular cargo using proteomic analysis and small RNA sequencing. We found significant differences in the protein and microRNA content of high-fat diet KDEVs compared to KDEVs obtained from control mice on a regular diet, including pathways involved in axon guidance and synaptic transmission. Additionally, using an in vivo conditional extracellular vesicle reporter mouse model, we demonstrated that epidermal-originating GFP-tagged KDEVs are retrogradely trafficked into the dorsal root ganglion (DRG) neuron cell bodies. This study presents the first comprehensive isolation and molecular characterization of the KDEV protein and microRNA cargo in RD and HFD mice. Our findings suggest a potential novel communication pathway between keratinocytes and DRG neurons in the skin, which could have implications for PDN.

Effects of multiple transcranial magnetic stimulation sessions on pain relief in patients with chronic neuropathic pain: A French cohort study in real-world clinical practice

BACKGROUND

Current clinical trials indicate that repetitive transcranial magnetic stimulation (rTMS) is effective in reducing drug-resistant neuropathic pain (NP). However, there is a lack of studies evaluating the long-term feasibility and clinical efficacy of rTMS in large patient cohorts in real-world conditions.

METHODS

In this retrospective cohort study, we analysed 12 years of clinical data to assess the long-term analgesic effects of 20 Hz rTMS over the primary motor cortex in patients with NP. Subgroup analyses were conducted to identify predictive factors and assess the potential role of epidural motor cortex stimulation (eMCS) as a sustained solution.

RESULTS

In total, 193 patients completed test period of 4 rTMS sessions and 42% of them reported a pain relief (PR) greater than 30%, with concurrent improvement in their most disabling symptom. Iterative rTMS sessions maintained analgesic effects over 10 years in certain patients identified as responders (≥10% PR) without adverse effects. Success probability was higher in patients with central NP compared to peripheral NP (OR = 2.03[1.04;4.00]), and among those with central post-stroke pain, this probability was higher in ischemic versus hemorrhagic strokes (OR = 3.36[1.17;10.05]). PR obtained with iterative rTMS sessions was an excellent predictor of eMCS efficacy.

CONCLUSIONS

While rTMS shows promise as a therapeutic option for some patients with drug-resistant NP, it does not benefit all patients. Efficacy varies by NP aetiology, aiding patient selection. For responders, eMCS may offer a permanent solution. These findings support a tailored approach to rTMS in NP management, while recognizing both its potential and limitations across diverse patient profiles.

SIGNIFICANCE STATEMENT

Multiple rTMS sessions demonstrate long-term efficacy and safety in treating drug-resistant neuropathic pain. Extending session numbers for the test period can enhance responder identification, especially in patients with initial low pain relief. This identification refines patient selection for neurosurgery, reducing non-responders. Central neuropathic pain shows higher success rates than peripheral. For post-stroke central pain, patients with ischemic stroke are more likely to respond than those with hemorrhagic stroke. These results support integrating rTMS into clinical practice for managing neuropathic pain.

Prediction of the response to repetitive transcranial magnetic stimulation of the motor cortex in peripheral neuropathic pain and validation of a new algorithm

CLINICAL TRIAL REGISTRATION

NCT02010281.

Neural networks involved in painful diabetic neuropathy: A systematic review

OBJECTIVES

Diabetic distal symmetric polyneuropathy, affecting up to 50% of adults with diabetes, often leads to painful symptoms; yet current treatments are largely ineffective with standard therapies providing limited relief. The aim of this systematic review is to address the knowledge gap in understanding the neural networks associated with painful diabetic polyneuropathy (P-DPN). By synthesizing evidence from neuroimaging studies, it seeks to identify potential targets for neuromodulation-based treatments, ultimately guiding clinicians and researchers in developing novel, more effective therapeutic interventions for P-DPN.

CONTENT

A comprehensive search following the preferred reporting items for systematic reviews and meta-analysis was conducted across Embase, PsycINFO, and MEDLINE databases to identify relevant neuroimaging studies from 2010 to May 2024. The search focused on studies involving P-DPN and excluded animal research. After the removal of duplicates and irrelevant studies, 18 studies were included and critically appraised for their contributions to understanding the neural correlates of P-DPN.

SUMMARY

The review highlights that P-DPN is associated with alterations in brain networks involved in pain perception, particularly in the primary somatosensory cortex highlighting its role in sensory and pain perception. Regions such as the anterior cingulate cortex and thalamus exhibit altered functional connectivity, with the former showing responses to pain treatment. The review also identified increased connectivity between the cingulate cortex, medial prefrontal cortex, medial temporal region, and insula in individuals with P-DPN, pointing to the involvement of these regions in the emotional and cognitive aspects of pain processing.

OUTLOOK

This review provides a foundational understanding of the neural networks involved in P-DPN, offering potential targets for future neuromodulation therapies. Further research is required to deepen the understanding of these brain alterations and to explore how they can be leveraged for more effective P-DPN treatments.

Effects of Combined Intrathecal Mesenchymal Stem Cells and Schwann Cells Transplantation on Neuropathic Pain in Complete Spinal Cord Injury: A Phase II Randomized Active-Controlled Trial

Neuropathic pain is a debilitating complication following spinal cord injury (SCI). Currently, effective treatments for SCI-induced neuropathic pain are highly lacking. This clinical trial aimed to investigate the efficacy of combined intrathecal injection of Schwann cells (SCs) and bone marrow-derived mesenchymal stem cells (BMSCs) in improving SCI-induced neuropathic pain. This study was a parallel-group, randomized, open-label, active-controlled phase II trial with two arms, including treatment and control groups. Patients with complete SCI-induced neuropathic pain in the treatment group received a single combined intrathecal injection of BMSCs and SCs. Study outcome measures were International SCI Pain Basic Data Set (ISCIPBDS) and World Health Organization (WHO) Quality of Life Assessment Instrument (WHOQOL-BREF). A total of 37 (55.2%) and 30 (44.8%) patients in the treatment and control groups were followed up for 6 months, respectively. Significant reductions in mean scores of interference items in the treatment group, including daily activities (P < 0.001), mood (P < 0.001), and sleep (P < 0.001), were found at 6 months after the injection compared with the control one. Similarly, pain frequency (P = 0.002), mean (P = 0.001), and worst (P = 0.001) numeric rating scale (NRS) pain intensity scores showed significant reductions in the treatment group after 6 months compared with the control one. Based on multiple regression analysis controlled for potential confounders, significant associations between changes in all outcome measures over the study period and the treatment group were found. This clinical trial indicated the efficacy of combined cell therapy in improving the neuropathic pain and quality of life in complete SCI patients. Future investigations should evaluate the effects of combination of this strategy with other existing therapies for SCI-induced neuropathic pain. This clinical trial was also registered prospectively at the Iranian Registry of Clinical Trials (IRCT20200502047277N8).

Management of Refractory Functional Gastrointestinal Disorders: What Role Should Psychiatrists Have?

Currently, it has been stated that psychiatric and psychological problems are equally paramount aspects of the clinical modulation and manifestation of both the central nervous and digestive systems, which could be used to restore balance. The present narrative review aims to provide an elaborate description of the bio-psycho-social facets of refractory functional gastrointestinal disorders, psychiatrists' role, specific psychiatric approach, and the latest psychiatric and psychological perspectives on practical therapeutic management. In this respect, "psyche," "psychiatry," "psychology," "psychiatrist," "psychotropic," and "refractory functional gastrointestinal disorders" (as the keywords) were searched in relevant English publications from January 1, 1950, to March 1, 2024, in the PubMed, Web of Science, Scopus, EMBASE, Cochrane Library, and Google Scholar databases. Eventually, the narrative technique was adopted to reach a compelling story with a high level of cohesion through material synthesis. The current literature recognizes the brain-gut axis modulation as a therapeutic target for refractory functional gastrointestinal disorders and the bio-psycho-social model as an integrated framework to explain disease pathogenesis. The results also reveal some evidence to affirm the benefits of psychotropic medications and psychological therapies in refractory functional gastrointestinal disorders, even when psychiatric symptoms were absent. It seems that psychiatrists are required to pay higher levels of attention to both the assessment and treatment of patients with refractory functional gastrointestinal disorders, accompanied by educating and training practitioners who take care of these patients.

Design of an equilibrative nucleoside transporter subtype 1 inhibitor for pain relief

The current opioid crisis urgently calls for developing non-addictive pain medications. Progress has been slow, highlighting the need to uncover targets with unique mechanisms of action. Extracellular adenosine alleviates pain by activating the adenosine A1 receptor (A1R). However, efforts to develop A1R agonists have faced obstacles. The equilibrative nucleoside transporter subtype 1 (ENT1) plays a crucial role in regulating adenosine levels across cell membranes. We postulate that ENT1 inhibition may enhance extracellular adenosine levels, potentiating endogenous adenosine action at A1R and leading to analgesic effects. Here, we modify the ENT1 inhibitor dilazep based on its complex X-ray structure and show that this modified inhibitor reduces neuropathic and inflammatory pain in animal models while dilazep does not. Notably, our ENT1 inhibitor surpasses gabapentin in analgesic efficacy in a neuropathic pain model. Additionally, our inhibitor exhibits less cardiac side effect than dilazep via systemic administration and shows no side effects via local/intrathecal administration. ENT1 is colocalized with A1R in mouse and human dorsal root ganglia, and the analgesic effect of our inhibitor is linked to A1R. Our studies reveal ENT1 as a therapeutic target for analgesia, highlighting the promise of rationally designed ENT1 inhibitors for non-opioid pain medications.

Research progress in neuropathic pain after spinal cord injury: a bibliometric study from 2013 to 2024

Background

The incidence of neuropathic pain (NP) after spinal cord injury (SCI) is quite high. This pain is clinically challenging to treat and has an debilitating effect on patients. In recent years, NP is a popular topic of research and a number of relevant articles have been published in academic journals. The purpose of this article is to analyze the global research trend of NP after SCI using bibliometric methods.

Methods

The literature was screened from 2013 to 2024 based on the Web of Science core collection (WOSCC). These publications, including annual publications, journals, authors, references, and keywords via CiteSpace, were analyzed in order to help understand the current research direction and hotspots in this field.

Results

A total of 2022 publications were included in the analysis. The results showed that an overall upward trend in the number of publications in the study period. The top five productive journals are Spinal Cord, Journal of Neurotrauma, Pain, Experimental Neurology, and Journal of Spinal Cord Medicine, the journals related to spinal cord or pain. The top five most productive scholars are Armin Curt, Michael G. Fehlings, Wu Junfang, John L. K. Kramer, and Farinaz Nasirinezhad. Keyword bursts showed that signaling pathway, neuroinflammation, neuralgia, spinal cord stimulation, inhibition, and depression have become new research hotspots in the field of NP after SCI.

Conclusion

This study provides a basis for the study of pain after SCI. It summarizes past research on NP following SCI and offers valuable reference data for further exploration of research trends and issues of focus in this field.

Cyperus rotundus Extract and Its Active Metabolite α-Cyperone Alleviates Paclitaxel-Induced Neuropathic Pain via the Modulation of the Norepinephrine Pathway

BACKGROUND

Paclitaxel is a widely used anticancer drug for ovarian, lung, breast, and stomach cancers; however, its clinical use is often limited by the side effects of peripheral neuropathy. This study evaluated the effects of Cyperus rotundus (C. rotundus) extract and its active metabolite, α-cyperone, on paclitaxel-induced neuropathic pain.

METHODS

The oral administration of C. rotundus extract at doses of 500 mg/kg and intraperitoneal administration of α-cyperone at doses of 480 and 800 μg/kg prevented both the development of cold and mechanical pain.

RESULTS

The gene and protein expressions of tyrosine hydroxylase and noradrenergic receptors (α1- and α2-adrenergic), which were upregulated by paclitaxel, were significantly downregulated in the C. rotundus extract-treated group. In the locus coeruleus region of the mouse brain, C. rotundus extract administration also reduced the elevated expression of tyrosine hydroxylase induced by paclitaxel. The concentration of α-cyperone in C. rotundus extract was quantified using high-performance liquid chromatography (HPLC). In the group treated with α-cyperone, at levels corresponding to its content in C. rotundus, both cold and mechanical allodynia were effectively prevented.

CONCLUSIONS

This study suggests that α-cyperone shows potential as a preventive agent for paclitaxel-induced neuropathic pain.

Clinical pharmacist recommendations in daily interdisciplinary ward rounds at a psychiatric hospital: a retrospective pre-post study on drug-related problems focused in somatic comorbidities

Objective

One potential strategy to address inadequate screening for somatic comorbidities among patients with mental disorders is to integrate a clinical pharmacist into the inpatient team for daily interdisciplinary ward rounds. This approach remains under-researched in psychiatric hospitals. This study aimed to evaluate the impact of a clinical pharmacist on drug-related problems (DRPs) during daily ward rounds within an interdisciplinary team in a psychiatric hospital.

Methods

A retrospective observational pre-post study was conducted at the Ormož Psychiatric Hospital in Slovenia, including patients treated between 2019 and 2020, during which clinical pharmacists offered recommendations during daily ward rounds. The primary outcomes assessed the difference in the total number of DRPs observed at the time of hospital discharge compared to previous stage, as well as the recommendations and their continuation rate after three months. The secondary outcomes evaluated adherence to treatment guidelines.

Results

The study included 186 patients (mean age: 58.1 years, SD=17.0). During ward rounds, 280 recommendations related to DRPs were conducted (1.5 recommendations per patient). Regarding the nature of DRPs, 154 (55.0%) were identified as expressed DRPs, while 127 (45.0%) were deemed potential DRPs. Following pharmacist recommendations, 133 (86.4%) of the expressed DRPs were successfully resolved. The majority of DRPs pertained to treatment effectiveness (N=179, 63.9%), followed by unnecessary treatments (N=86, 30.7%) and patient safety (N=15, 5.4%). Initially, the acceptance rate of recommendations was 88.9% (N=249) at discharge, declining to 63.2% (N=177) three months after discharge. The acceptance rate for somatic conditions at discharge was 87.8% (N=122), declining to 59.0% (N=82) three months after discharge. Adherence to treatment guidelines for somatic comorbidities increased (p < 0.05).

Conclusions

The results indicate that this approach led to fewer DRPs, a high rate of acceptance, and better adherence to treatment guidelines. This is the first retrospective pre-post study in the European Union to include this collaboration in daily rounds at psychiatric hospitals, focusing on somatic comorbidities. However, the study also has significant limitations, such as its non-randomized design and short monitoring period, which should be addressed in future research.

Amitriptyline-perphenazine therapy for persistent idiopathic facial pain: translational perspectives from a retrospective study

BACKGROUND

Persistent idiopathic facial pain (PIFP) can be challenging, both in its diagnosis, which appears to be purely exclusionary, and in its treatment, which currently lacks a gold standard. Amitriptyline is considered a first-line therapy, although not always effective. Recent insights into the role of dopamine in facial pain suggest that a novel therapeutic approach could target the dopamine system.

METHODS

This study aimed to retrospectively evaluate the efficacy of treatment with amitriptyline-perphenazine association in patients with severe PIFP. Thirty-one patients were given a regimen dose of amitriptyline-perphenazine at dosages ranging between 10/2 and 20/4 mg and were then retrospectively analyzed. We evaluated the following outcomes, referred to the last week prior to follow-up visits: NRS score for pain intensity (minimum, maximum, and average), the number of attacks, and SF-36 questionnaire for quality of life. Comparisons were made between pre- and post-treatment.

RESULTS

Thirty-one patients over 35 were screened. At baseline, average NRS was 5 ± 0.93 (CI 95%: 4.6-5.3), and the median number of breakthrough episodes over last week was 5 ± 1.57 (CI 95%: 4-6) with a maximum NRS = 9 ± 0.89 (CI 95%: 8-9). After treatment, average NRS was 4.1 ± 0.93 (CI 95%: 3.8-4.5; p < 0.001), maximum NRS was 6.1 ± 1.60 (CI 95%: 5.5-6.6), and the median number of attacks was 4 ± 0.99 (IC 95%: 3-4) (p < 0.001). Regarding SF-36 questionnaire, the most improved parameters were quality of life related to pain (25.89 ± 12.48 vs 31.19 ± 13.44; p < 0.001) and physical function (69.56 ± 17.84 vs 84.17 ± 20.99; p < 0.001).

CONCLUSION

Despite limitations, the pain scores, the frequency of the attacks, and quality of life were found to be significantly improved after treatment. Although results are not broad based given the small sample size, the combination of amitriptyline and perphenazine may be an effective and well-tolerated treatment in patients with PIFP. It is abundantly clear that dopaminergic pathways play a key role in pain modulation, yet the underlying mechanisms have not been fully understood, requiring further investigation.

The Diagnosis and Treatment of Neuropathic Pain

BACKGROUND

The reported prevalence of neuropathic pain in the general population in Germany is from 6.9% to 10%. There are both medical and surgical treatment options.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, with consideration of clinical trials, meta-analyses, and guidelines.

RESULTS

Neuropathic pain is diagnosed when pain of the appropriate character is accompanied by further features such as hypesthesia/anesthesia, allodynia, or hyperalgesia. It is generally treated initially with drugs (antidepressant drugs, anticonvulsant drugs, opioids, topical agents, and others); the number needed to treat (NNT) is between 7 and 8 for gabapentin and 3.6 for amitryptiline, as estimated in meta-analyses. For nerve compression and entrapment syndromes, surgical decompression is a treatment directed against the cause of the problem, which can therefore be curative. Microvascular decompression (MVD) is often used to treat supposed compression syndromes of cranial nerves, above all classic trigeminal neuralgia; according to a meta-analysis, MVD brings about a pain-free state in 92.9% [89.1; 96.8] of patients after 5 months to 5 years of follow-up. Ablative surgical procedures are used for symptom control in patients with refractory and/or cancer-related pain. Further symptomdirected treatment options for medically intractable neuropathic pain include neuromodulatory techniques, which involve minimally invasive electrical stimulation of neural structures, and the chronic intrathecal application of drugs such as opioids and ziconotide.

CONCLUSION

The treatment of neuropathic pain can be either cause-directed or symptom-directed, depending on its origin. Multidisciplinary collaboration can facilitate both the diagnostic evaluation and the selection of the optional modality and timing of treatment.

Compound Probiotics Improve Neuropathic Pain Prognosis in a Murine Model of Chronic Constriction Injury

Purpose

Compound probiotics have been reported to ameliorate imbalances in the intestinal flora that may play a critical role in neuropathic pain. This study aimed to investigate the efficacy of compound probiotic treatment on neuropathic pain.

Methods

Thirty mice were randomly divided into three groups: 1) sham group, 2) mouse with chronic constrictive injury (CCI), and 3) probiotic gavage with CCI (CCI+Prob). The degree of pain and gait recovery was assessed by Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), and mouse footprints. The degree of atrophy of the gastrocnemius muscle was assessed by muscle weight, hematoxylin and eosin (H&E) staining. Gut microbiota were analyzed by 16S ribosomal RNA sequencing (16SrRNA).

Results

Four weeks after surgery, TWL and MWT assessment showed significant increases in the CCI+Prob group compared with the CCI group (P < 0.01). Gait analysis results as well as gastrocnemius muscle weight showed a significant improvement in the CCI+Prob group compared with the CCI group. Measurement of alpha diversity showed a significant increase in the CCI group compared with the sham group, but this increase was attenuated by probiotic intervention in the CCI+Prob group. Although the CCI group had significantly decreased levels of Akkermansia and significantly increased levels of Ruminococcaceae, probiotic treatment reversed these changes.

Conclusion

Compound probiotics treatment can improve the pain and muscle atrophy in mice with CCI-induced neuropathic pain. The improvement of symptoms is associated with changes in the composition of gut microbiota.

Analgesic effect of Dahuang Fuzi Decoction in neuropathic pain through inhibiting TNF-α and PI3K-AKT signaling

Background

Neuropathic pain (NeP) presents considerable challenges in terms of effective management and significantly impacts the quality of life for affected patients. The current treatment options for NeP are limited, highlighting the need for alternative therapeutic approaches. Dahuang Fuzi Decoction (DF), a formula from traditional Chinese medicine, has shown potential in relieving pain symptoms associated with various types of NeP. However, the mechanisms through which DF exerts its effects remain largely unknown.

Methods

In this study, we employed ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) to analyze the chemical composition of DF. A chronic sciatic nerve compression injury (CCI) rat mode was used to assess the analgesic efficacy of DF for NeP. Network pharmacology analysis was performed to identify the potential signaling pathways affected by DF.

Results

DF treatment significantly increased the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in CCI rats, indicating its analgesic effect. Network pharmacology analysis suggested that DF potentially modulated TNF-α and PI3K-AKT signaling pathways. Furthermore, DF treatment decreased the levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) in spinal cord tissues of CCI rats, suggesting an anti-inflammatory effect. Western blot analysis revealed that DF treatment reduced the expression of TNF-α, TNFR1, and phosphorylated forms of PI3K, AKT, IKKα/β, IKBα, and NF-κB in the spinal cord of CCI rats. Immunofluorescence analysis confirmed significant reductions in TNF-α and TNFR1 expression, as well as in AKT and NF-κB phosphorylation within astrocytes following DF administration.

Conclusion

Our findings characterize the chemical constituents of DF and elucidate its underlying mechanism for relieving NeP. The analgesic effect of DF involves the inhibition of TNF-α and PI3K-AKT signaling pathways, providing a potential therapeutic approach for NeP management.

P2X3 and P2X2/3 receptors inhibition produces a consistent analgesic efficacy: A systematic review and meta-analysis of preclinical studies

BACKGROUND

P2X3 and P2X2/3 receptors are promising therapeutic targets for pain treatment and selective inhibitors are under evaluation in ongoing clinical trials. Here we aim to consolidate and quantitatively evaluate the preclinical evidence on P2X3 and P2X2/3 receptors inhibitors for pain treatment.

METHODS

A literature search was conducted in PubMed, Scopus and Web-of-Science on August 5, 2023. Data was extracted and meta-analyzed using a random-effects model to estimate the analgesic efficacy of the intervention; then several subgroup analyses were performed.

RESULTS

67 articles were included. The intervention induced a consistent pain reduction (66.5 [CI95% = 58.5, 74.5]; p < 0.0001), which was highest for visceral pain (114.3), followed by muscle (79.8) and neuropathic pain (71.1), but lower for cancer (64.1), joint (57.5) and inflammatory pain (49.0). Further analysis showed a greater effect for mechanical hypersensitivity (70.4) compared to heat hypersensitivity (64.5) and pain-related behavior (54.1). Sex (male or female) or interspecies (mice or rats) differences were not appreciated (p > 0.05). The most used molecule was A-317491, but other such as gefapixant or eliapixant were also effective (p < 0.0001 for all). The analgesic effect was higher for systemic or peripheral administration than for intrathecal administration. Conversely, intracerebroventricular administration was not analgesic, but potentiated pain.

CONCLUSION

P2X3 and P2X2/3 receptor inhibitors showed a good analgesic efficacy in preclinical studies, which was dependent on the pain etiology, pain outcome measured, the drug used and its route of administration. Further research is needed to assess the clinical utility of these preclinical findings.

PROTOCOL REGISTRATION

PROSPERO ID CRD42023450685.

A clinical approach to the investigation and management of long COVID associated neuropathic pain

COVID-19 has been associated with a wide range of ongoing symptoms following recovery from the acute SARS-CoV-2 infection. Around one in three people with COVID-19 develop neurological symptoms with many reporting neuropathic pain and associated symptoms, including paraesthesia, numbness, and dysesthesia. Whilst the pathophysiology of long COVID-19-associated neuropathic pain remains unclear, it is likely to be multifactorial. Early identification, exclusion of common alternative causes, and a biopsychosocial approach to the management of the symptoms can help in relieving the burden of disease and improving the quality of life for patients.

Peripheral Nerve Stimulation for Neuropathic Pain Management: A Narrative Review

This narrative review examines the therapeutic efficacy of peripheral nerve stimulation (PNS) in the treatment of neuropathic pain (NP), a type of pain arising from lesions or diseases of the somatosensory system with a global prevalence ranging from 6.90% to 10.00%. Traditional pharmacological interventions often fall short for many persons, highlighting the need for alternative treatments such as PNS, which has demonstrated significant promise with minimal side effects. The review summarizes the effectiveness of PNS in various NP conditions, including trigeminal neuralgia and postherpetic neuralgia, and underscores the need for further research to refine treatment approaches. The mechanism of PNS is discussed, involving the activation of non-nociceptive Aβ fibers and modulation of neurotransmitters, and offering pain relief through both peripheral and central pathways. Despite the proven efficacy of PNS, challenges remain, including the need for randomized controlled trials and the optimization of stimulation parameters. The review concludes that PNS is a promising treatment modality for NP, warranting additional high-quality trials to solidify its role in clinical practice.

Human dorsal root ganglia are either preserved or completely lost after deafferentation by brachial plexus injury

BACKGROUND

Plexus injury results in lifelong suffering from flaccid paralysis, sensory loss, and intractable pain. For this clinical problem, regenerative medicine concepts set high expectations. However, it is largely unknown how dorsal root ganglia (DRG) are affected by accidental deafferentation.

METHODS

Here, we phenotyped DRG of a clinically and MRI-characterised cohort of 13 patients with plexus injury. Avulsed DRG were collected during reconstructive nerve surgery. For control, we used DRG from forensic autopsy. The cellular composition of the DRG was analysed in histopathological slices with multicolour high-resolution immunohistochemistry, tile microscopy, and deep-learning-based bioimage analysis. We then sequenced the bulk RNA of corresponding DRG slices.

RESULTS

In about half of the patients we found loss of the typical DRG units consisting of neurones and satellite glial cells. The DRG cells were replaced by mesodermal/connective tissue. In the remaining patients, the cellular units were well preserved. Preoperative plexus MRI neurography was not able to distinguish the two types. Patients with 'neuronal preservation' had less maximum pain than patients with 'neuronal loss'. Arm function improved after nerve reconstruction, but severe pain persisted. Transcriptome analysis of preserved DRGs revealed expression of subtype-specific sensory neurone marker genes, but downregulation of neuronal attributes. Furthermore, they showed signs of ongoing inflammation and connective tissue remodelling.

CONCLUSIONS

Patients with plexus injury separate into two groups with either neuronal preservation or neuronal loss. The former could benefit from anti-inflammatory therapy. For the latter, studies should explore mechanisms of neuronal loss especially for regenerative approaches.

CLINICAL TRIAL REGISTRATION

DRKS00017266.

Maximal Analgesic Effect Attained by the Use of Objective Neurophysiological Measurements With Closed-Loop Spinal Cord Stimulation

OBJECTIVES

Spinal cord stimulation (SCS) has been challenged by the lack of neurophysiologic data to guide therapy optimization. Current SCS programming by trial-and-error results in suboptimal and variable therapeutic effects. A novel system with a physiologic closed-loop feedback mechanism using evoked-compound action potentials enables the optimization of physiologic neural dose by consistently and accurately activating spinal cord fibers. We aimed to identify neurophysiologic dose metrics and their ranges that resulted in clinically meaningful treatment responses.

MATERIALS AND METHODS

Subjects from 3 clinical studies (n = 180) with baseline back and leg pain ≥60 mm visual analog scale and physical function in the severe to crippled category were included. Maximal analgesic effect (MAE) was operationally defined as the greatest percent reduction in pain intensity or as the greatest cumulative responder score (minimal clinically important differences [MCIDs]) obtained within the first 3 months of SCS implant. The physiologic metrics that produced the MAE were analyzed.

RESULTS

We showed that a neural dose regimen with a high neural dose accuracy of 2.8μV and dose ratio of 1.4 resulted in a profound clinical benefit to chronic pain patients (MAE of 79 ± 1% for pain reduction and 12.5 ± 0.4 MCIDs). No differences were observed for MAE or neurophysiological dose metrics between the trial phase and post-implant MAE visit.

CONCLUSION

For the first time, an evidence-based neural dose regimen is available for a neurostimulation intervention as a starting point to enable optimization of clinical benefit, monitoring of adherence, and management of the therapy.

Cross-Species Convergence of Functional Connectivity Changes in Thalamic Pain Across Human Patients and Model Macaques

Thalamic pain can be understood as a network reorganization disorder. This study aimed to investigate functional connectivity (FC) in human patients and a macaque model of thalamic pain. In humans, resting-state FC was compared between patients with thalamic pain and healthy individuals. Furthermore, resting-state FC was compared in macaques, before and after the induction of thalamic pain in the same individuals. FC between the amygdala of the unaffected hemisphere and the brainstem was significantly higher in patients with thalamic pain. More specifically, a significantly higher FC was observed between the basolateral amygdala and the ventral tegmental area, which also significantly predicted the value of a visual analog scale of pain intensity in individual patients. The macaque model of thalamic pain also exhibited a significantly higher FC between the amygdala of the unaffected hemisphere and the brainstem, particularly between the basolateral amygdala and the midbrain. Furthermore, the previously reported significantly higher FC between the amygdala and the mediodorsal nucleus of the thalamus in macaques with thalamic pain was also reproduced in the human patients. Therefore, the present results suggest that the FC changes in the regions associated with emotion, memory, motivation, and reward are part of the underlying mechanisms of thalamic pain onset present in both human patients and model macaques. This cross-species convergence provides new insights into the neurological mechanisms underlying thalamic pain, paving the way for further studies and the development of therapeutic strategies. PERSPECTIVE: This article presents that the FC changes in the regions associated with emotion, motivation, and reward are part of the underlying mechanisms of thalamic pain in humans and macaques.

MiR-200a-3p Attenuates Neuropathic Pain by Suppressing the Bromodomain-Containing Protein 3-Nuclear Factor-κB Pathway

MicroRNAs (miRNAs) have key roles in the pathological processes of neuropathic pain. Here, our aim was to elucidate the function of miR-200a-3p as well as its related regulatory mechanism in neuropathic pain. An animal model of neuropathic pain was established by chronic constriction injury (CCI) induction. The knockdown experiments are performed by injecting a lentiviral construct intrathecally. MiR-200a-3p and bromodomain-containing protein 3 (BRD3) expression in rat spinal cord was determined using RT-qPCR. The mechanical, thermal, and cold responses in animals were assessed at the indicated time after surgery. The levels of inflammatory cytokines in rat spinal cord were measured by ELISA. The changes in NF-κB signaling-related molecules in rat spinal cord were determined using western blot and immunofluorescence. MiR-200a-3p was underexpressed in CCI rats in a time-dependent manner. Overexpression of miR-200a-3p decreased mechanical hyperalgesia and thermal sensitivity to attenuate neuropathic pain in rats. BRD3 was targeted by miR-200a-3p. Additionally, downregulation of BRD3 inhibited neuropathic pain progression. Moreover, overexpression of BRD3 rescued the effect of miR-200a-3p on NF-κB signaling and neuropathic pain in CCI rats. MiR-200a-3p attenuates neuropathic pain via downregulating BRD3 to block NF-κB signaling.

Clinical Predictors of Medication Compliance in Patients With Acute Herpetic Neuralgia

PURPOSE

Pain is one of the most common and harmful symptoms experienced by individuals with acute herpetic neuralgia (AHN). In this population, studies to determine the causes that affect patients taking medications compliance are rare. This study aimed to construct a predictive model for medication compliance of patients with AHN and to verify its performance.

DESIGN AND METHODS

In this prospective study of 398 patients with AHN who were discharged from a tertiary hospital with medications from July 2020 to October 2022, we used logistic regression analysis to explore the predictive factors of medication compliance of patients with AHN and to construct a nomogram. The area under the curve was used to evaluate the predictive effect of the model.

RESULTS

A predictive model of drug compliance of patients with AHN was constructed based on the following four factors: disease duration, pain severity before treatment, medication beliefs, and comorbidity of chronic diseases. The area under the curve of the model was 0.766 (95% confidence interval [0.713, 0.819]), with a maximum Youden's index of 0.431, sensitivity of 0.776, and specificity of 0.655. A linear calibration curve was found with a slope close to 1.

CONCLUSIONS

The prediction model constructed in this study had good predictive performance and provided a reference for early clinical screening of independent factors that affected the medication compliance of patients with AHN.

What is associated with painful polyneuropathy? A cross-sectional analysis of symptoms and signs in patients with painful and painless polyneuropathy

ABSTRACT

It is still unclear how and why some patients develop painful and others painless polyneuropathy. The aim of this study was to identify multiple factors associated with painful polyneuropathies (NeuP). A total of 1181 patients of the multicenter DOLORISK database with painful (probable or definite NeuP) or painless (unlikely NeuP) probable or confirmed neuropathy were investigated clinically, with questionnaires and quantitative sensory testing. Multivariate logistic regression including all variables (demographics, medical history, psychological symptoms, personality items, pain-related worrying, life-style factors, as well as results from clinical examination and quantitative sensory testing) and machine learning was used for the identification of predictors and final risk prediction of painful neuropathy. Multivariate logistic regression demonstrated that severity and idiopathic etiology of neuropathy, presence of chronic pain in family, Patient-Reported Outcomes Measurement Information System Fatigue and Depression T-Score, as well as Pain Catastrophizing Scale total score are the most important features associated with the presence of pain in neuropathy. Machine learning (random forest) identified the same variables. Multivariate logistic regression archived an accuracy above 78%, random forest of 76%; thus, almost 4 out of 5 subjects can be classified correctly. This multicenter analysis shows that pain-related worrying, emotional well-being, and clinical phenotype are factors associated with painful (vs painless) neuropathy. Results may help in the future to identify patients at risk of developing painful neuropathy and identify consequences of pain in longitudinal studies.