Novel Therapies for the Treatment of Neuropathic Pain: Potential and Pitfalls

Diabetic peripheral neuropathy and neuromodulation techniques: a systematic review of progress and prospects

Neuromodulation for diabetic peripheral neuropathy represents a significant area of interest in the management of chronic pain associated with this condition. Diabetic peripheral neuropathy, a common complication of diabetes, is characterized by nerve damage due to high blood sugar levels that lead to symptoms, such as pain, tingling, and numbness, primarily in the hands and feet. The aim of this systematic review was to evaluate the efficacy of neuromodulatory techniques as potential therapeutic interventions for patients with diabetic peripheral neuropathy, while also examining recent developments in this domain. The investigation encompassed an array of neuromodulation methods, including frequency rhythmic electrical modulated systems, dorsal root ganglion stimulation, and spinal cord stimulation. This systematic review suggests that neuromodulatory techniques may be useful in the treatment of diabetic peripheral neuropathy. Understanding the advantages of these treatments will enable physicians and other healthcare providers to offer additional options for patients with symptoms refractory to standard pharmacologic treatments. Through these efforts, we may improve quality of life and increase functional capacity in patients suffering from complications related to diabetic neuropathy.

Cannabinoids in neuropathic pain treatment: pharmacological insights and clinical outcomes from recent trials

Neuropathic pain, a complex and often devastating condition, poses significant challenges for its effective management. Despite promising research on various cannabis formulations and delivery methods for neuropathic pain, significant gaps remain in our knowledge. While inhaled cannabis shows analgesic effects and alternative delivery methods may improve bioavailability, oral formulations have yielded mixed results, often limited by small sample sizes and placebo effects. Therefore, further research is essential to optimize cannabis formulations, identify responder profiles to tailor treatments effectively, and, most critically, confirm the long-term safety and efficacy of cannabis-based therapies in managing NP. This review article aims to provide a comprehensive analysis of the therapeutic potential of cannabis-based medicines, with a particular focus on cannabinoids. This review, though not systematic, examines 11 clinical studies, specifically Randomised Clinical Trials) published from 2014 to 2024, highlighting the efficacy of numerous cannabis formulations, in alleviating neuropathic pain. Key findings show that cannabinoids can reduce pain perception, improve patient quality of life, and mitigate other symptoms associated with neuropathic pain. The synergistic effects of tetrahydrocannabinol and cannabidiol are discussed, emphasizing their ability to enhance analgesic effects, while potentially reducing the psychoactive side effects of tetrahydrocannabinol. This review emphasizes the importance of the personalized approach to improve therapeutic outcomes. Limitations of the existing research focusing on cannabis for neuropathic pain are limited by heterogeneity, lack of standardization, small sample sizes, and reliance on subjective outcomes, impacting the reliability and generalizability of findings. However, this exhaustive review aims to inform clinicians and researchers about the evolving role of cannabis in contemporary pain management strategies, illustrating the diverse pharmacological profiles of cannabinoids and their potential as adjunct therapies for neuropathic pain management.

Inhibition of SARM1 Reduces Neuropathic Pain in a Spared Nerve Injury Rodent Model

INTRODUCTION/AIMS

The function of the sterile alpha and toll/interleukin receptor motif-containing protein 1 (SARM1) in neuropathic pain development has not yet been established. This protein has a central role in regulating axon degeneration and its depletion delays this process. This study aims to demonstrate the effects of SARM1 deletion on the development of neuropathic pain.

METHODS

Thirty-two wild-type (WT) or SARM1 knockout (KO) rats underwent spared nerve injury (SNI) or sham surgery. Mechanical allodynia was assessed by electronic Von Frey and cold hyperalgesia by the acetone test. Nociception was evaluated at the baseline, Day-1, Day-2, Week-1, Week-2, Week-3, and Week-4 time points. Nerve sections were examined by immunohistochemistry (IHC).

RESULTS

WT Injury rats were more sensitive to pain than WT Sham at all postoperative time points, validating the pain model. Injured SARM1 KO rats only demonstrated a difference in mechanical or cold nociception from KO Sham at Week 3. Injured KO rats demonstrated a clear trend of decreased sensitivity compared to WT Injury nociception, reaching significance at Week 4 (p = 0.044). Injured KO rats showed attenuated sensitivity to cold allodynia relative to WT at Week 2 (p = 0.019). IHC revealed decreased macrophages in spared sural nerves of injured KO animals at 2 and 4 weeks, and the proximal portion of tibial/peroneal nerves at Week 2.

DISCUSSION

This study demonstrates that SARM1 KO rats are less sensitive to mechanical and cold nociception than WT rats in an SNI model with decreased inflammatory response. Given these results, inhibition of SARM1 should be further investigated in the treatment of neuropathic pain.

Moroccan Cannabis sativa essential oil attenuates peripheral neuropathic pain induced by chronic sciatic nerve constriction injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cannabis sativa has been widely used in traditional medicine for its therapeutic properties. However, in Morocco, the ethnobotanical applications of Cannabis sativa, especially its essential oils, are underexplored. This study investigates, for the first time, the effects of Moroccan Cannabis sativa essential oil on peripheral neuropathic pain.

MATERIALS AND METHODS

Peripheral neuropathic pain was induced in mice through sciatic nerve injury. The mice were treated daily with cannabis essential oil for 21 days. Behavioral tests were conducted on days 1, 7, 14, and 21 to evaluate thermal, mechanical, and cold sensitivity. The essential oil's chemical composition was analyzed using gas chromatography-mass spectrometry (GC/MS).

RESULTS

The main constituents of the essential oil were (E)-caryophyllene (41.59%) and α-humulene (14%). Daily treatment with the essential oil significantly reduced pain sensitivity and improved functional and histological recovery over time. These effects are linked to the activity of the dominant terpenoids in the oil.

CONCLUSION

Moroccan Cannabis sativa essential oil shows significant therapeutic potential for managing peripheral neuropathic pain. By enhancing recovery and alleviating pain symptoms, it offers a promising alternative for treating chronic pain caused by nerve injuries.

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.

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.

Emerging Therapeutic Modalities and Pharmacotherapies in Neuropathic Pain Management: A Systematic Review and Meta-Analysis of Parallel Randomized Controlled Trials

Background: Neuropathic pain (NP) is a chronic condition caused by abnormal neuronal excitability in the nervous system. Current treatments for NP are often ineffective or poorly tolerated. Hence, we reviewed the efficacy and safety of novel drugs or devices that target neuronal excitability in NP patients compared with placebo, sham, or usual care interventions. Methods: Six databases were searched for parallel randomized controlled trials (RCTs) reporting novel devices (rTMS, SCS, and TENS) or drugs (EMA401, capsaicin 8% patch, and Sativex) for NP. Data were extracted and quality was assessed using the ROB2 tool. The random-effects inverse variance method was used for analysis. Results: In our review of 30 RCTs with 4251 participants, device-based interventions were found to be more effective in reducing pain scores than control interventions (SMD = -1.27, 95% CI: -1.92 to -0.62). However, high heterogeneity was seen (p < 0.01, I 2 = 91%), attributable to the etiology of NP (R 2 = 58.84%) and year of publication (R 2 = 49.49%). Funding source and type of control comparator were ruled out as cause of heterogeneity. Although drug interventions did not differ from placebo interventions in absolute pain reduction (SMD = -1.21, 95% CI: -3.55 to 1.13), when comparing relative change in pain intensity from baseline, drug interventions were found to be effective (SMD = 0.29, 95% CI: 0.04-0.55). Asymmetry in the funnel plot was visualized, suggesting publication bias. Certainty of evidence was very low according to GRADE assessment. Conclusions: Our review indicates that device-based interventions are more effective than control interventions in reducing pain intensity in NP. Nevertheless, available evidence is limited due to heterogeneity and publication bias, prompting the need for more high-quality RCTs to confirm the efficacy and safety of these interventions.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Black-white hole pattern: an investigation on the automated chronic neuropathic pain detection using EEG signals

Electroencephalography (EEG) signals provide information about the brain activities, this study bridges neuroscience and machine learning by introducing an astronomy-inspired feature extraction model. In this work, we developed a novel feature extraction function, black-white hole pattern (BWHPat) which dynamically selects the most suitable pattern from 14 options. We developed BWHPat in a four-phase feature engineering model, involving multileveled feature extraction, feature selection, classification, and cortex map generation. Textural and statistical features are extracted in the first phase, while tunable q-factor wavelet transform (TQWT) aids in multileveled feature extraction. The second phase employs iterative neighborhood component analysis (INCA) for feature selection, and the k-nearest neighbors (kNN) classifier is applied for classification, yielding channel-specific results. A new cortex map generation model highlights the most active channels using median and intersection functions. Our BWHPat-driven model consistently achieved over 99% classification accuracy across three scenarios using the publicly available EEG pain dataset. Furthermore, a semantic cortex map precisely identifies pain-affected brain regions. This study signifies the contribution to EEG signal classification and neuroscience. The BWHPat pattern establishes a unique link between astronomy and feature extraction, enhancing the understanding of brain activities.

Keratinocyte-Derived Exosomes 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. Exosomes are small extracellular vesicles released from many cell types that mediate cell to cell communication. The role of keratinocyte-derived exosomes (KDEs) 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 KDEs in a well-established high-fat diet (HFD) mouse model of PDN using primary adult mouse keratinocyte cultures. We obtained highly enriched KDEs 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 HFD KDEs compared to KDEs obtained from control mice on a regular diet (RD), including pathways involved in axon guidance and synaptic transmission. Additionally, using an in vivo conditional extracellular vesicle (EV) reporter mouse model, we demonstrated that epidermal-originating GFP-tagged KDEs are retrogradely trafficked into the DRG neuron cell body. Overall, our study presents a potential novel mode of communication between keratinocytes and DRG neurons in the skin, revealing a possible role for KDEs in contributing to the axonal degeneration that underlies neuropathic pain in PDN. Moreover, this study presents potential therapeutic targets in the skin for developing more effective, disease-modifying, and better-tolerated topical interventions for patients suffering from PDN, one of the most common and untreatable peripheral neuropathies.

Exploring the Therapeutic Potential of Mesenchymal Stem Cells-derived conditioned medium: An In-depth Analysis of Pain Alleviation, Spinal CCL2 Levels, and Oxidative Stress

Neuropathic pain, a debilitating condition, remains a significant challenge due to the lack of effective therapeutic solutions. This study aimed to evaluate the potential of mesenchymal stromal cell (MSC)-derived conditioned medium in alleviating neuropathic pain induced by sciatic nerve compression injury in adult male rats. Forty Wistar rats were randomly assigned to four groups: control, nerve injury, nerve injury with intra-neural injection of conditioned medium, and nerve injury with intra-neural injection of culture medium. Following sciatic nerve compression, the respective groups received either 10 µl of conditioned medium from amniotic fluid-derived stem cells or an equal volume of control culture medium. Behavioral tests for cold allodynia, mechanical allodynia, and thermal hyperalgesia were conducted, and the spinal cord was analyzed using Western Blot and oxidative stress assays. The behavioral experiments showed a decrease in mechanical hyperalgesia and cold allodynia in the group receiving conditioned medium compared to the injury group and the control medium group. Western blot data revealed a decrease in the expression of the CCL2 protein and an increase in GAD65. Oxidative stress tests also showed increased levels of SOD and glutathione in conditioned media-treated animals compared to animals with nerve injury. The findings suggest that conditioned medium derived from amniotic fluid-derived stem cells can effectively reduce neuropathic pain, potentially through the provision of supportive factors that mitigate oxidative stress and inflammation in the spinal cord.

Path Analysis Between Family Functioning and Mental Health in People With Neuropathic Pain: Roles of Pain Intensity, Self-Perceived Burden, Pain Catastrophizing, and Functional Status

PURPOSE

This study aimed to explore the pathways between family functioning and mental health in people with neuropathic pain, as well as to discuss the mediating role of pain intensity, self-perceived burden, pain catastrophizing, and functional status.

DESIGN

Cross-sectional design reported using the STROBE guidelines.

METHODS

A total of 277 people with neuropathic pain completed face-to-face questionnaires to evaluate family functioning, pain intensity, pain catastrophizing, self-perceived burden, functional status, and mental health. Structural equation modeling (SEM) was constructed to analyze the pathways between these variables.

RESULTS

The positive total effect between family functioning and mental health was significant and partially mediated by self-perceived burden, pain catastrophizing, and functional status. In addition, better family functioning was associated with higher pain intensity, which worsens self-perceived burden, pain catastrophizing, and functional status, masking 23.68% of the positive effects between family functioning and mental health.

CONCLUSIONS

Better family functioning was associated with better mental health, as explained by reduced self-perceived burden, reduced pain catastrophizing, and improved functional status. However, this benefit may be partially masked by the relationship that better family functioning explains higher pain intensity.

CLINICAL IMPLICATIONS

Nurses' comprehensive assessment and management of neuropathic pain from both the family and individual levels, such as family functioning, pain intensity, self-perceived burden, pain catastrophizing, and functional status, may be beneficial in promoting patients' mental health. In addition, it is necessary to identify why good family functioning is associated with higher pain intensity and intervene in this regard.

Pain intensity and self-perceived burden mediate the relationship between family functioning and pain catastrophizing in patients with neuropathic pain

This cross-sectional study aimed to investigate the relationship between family functioning, pain intensity, self-perceived burden, and pain catastrophizing. Moreover, we also wanted to explore the multiple mediating roles of pain intensity and self-perceived burden. From October 2022 to March 2023, 252 Chinese people with neuropathic pain completed face-to-face questionnaires to assess family functioning, pain intensity, self-perceived burden, and pain catastrophizing. Data analysis was done using descriptive statistics and a structural equation model. The results showed better family functioning was significantly associated with more intense pain, less self-perceived burden, and less pain catastrophizing. Mediation analysis showed that family functioning could indirectly affect pain catastrophizing through pain intensity and self-perceived burden in addition to a direct effect on pain catastrophizing. Moreover, the mediating variable of pain intensity played a masking role. These findings suggest that good family functioning can effectively reduce the self-perceived burden and pain catastrophizing in patients with neuropathic pain. However, family functioning cannot show its maximum effectiveness, and it may be necessary to construct a model of family functioning suitable for patients with neuropathic pain in the future.

The dorsal root ganglion as a target for neurorestoration in neuropathic pain

Neuropathic pain is a severe and chronic condition widely found in the general population. The reason for this is the extensive variety of damage or diseases that can spark this unpleasant constant feeling in patients. During the processing of pain, the dorsal root ganglia constitute an important region where dorsal root ganglion neurons play a crucial role in the transmission and propagation of sensory electrical stimulation. Furthermore, the dorsal root ganglia have recently exhibited a regenerative capacity that should not be neglected in the understanding of the development and resolution of neuropathic pain and in the elucidation of innovative therapies. Here, we will review the complex interplay between cells (satellite glial cells and inflammatory cells) and factors (cytokines, neurotrophic factors and genetic factors) that takes place within the dorsal root ganglia and accounts for the generation of the aberrant excitation of primary sensory neurons occurring in neuropathic pain. More importantly, we will summarize an updated view of the current pharmacologic and nonpharmacologic therapies targeting the dorsal root ganglia for the treatment of neuropathic pain.

Stem cells and pain

Pain can be defined as an unpleasant sensory and emotional experience caused by either actual or potential tissue damage or even resemble that unpleasant experience. For years, science has sought to find treatment alternatives, with minimal side effects, to relieve pain. However, the currently available pharmacological options on the market show significant adverse events. Therefore, the search for a safer and highly efficient analgesic treatment has become a priority. Stem cells (SCs) are non-specialized cells with a high capacity for replication, self-renewal, and a wide range of differentiation possibilities. In this review, we provide evidence that the immune and neuromodulatory properties of SCs can be a valuable tool in the search for ideal treatment strategies for different types of pain. With the advantage of multiple administration routes and dosages, therapies based on SCs for pain relief have demonstrated meaningful results with few downsides. Nonetheless, there are still more questions than answers when it comes to the mechanisms and pathways of pain targeted by SCs. Thus, this is an evolving field that merits further investigation towards the development of SC-based analgesic therapies, and this review will approach all of these aspects.

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.

Ion Channel Genes in Painful Neuropathies

Neuropathic pain (NP) is a typical symptom of peripheral nerve disorders, including painful neuropathy. The biological mechanisms that control ion channels are important for many cell activities and are also therapeutic targets. Disruption of the cellular mechanisms that govern ion channel activity can contribute to pain pathophysiology. The voltage-gated sodium channel (VGSC) is the most researched ion channel in terms of NP; however, VGSC impairment is detected in only <20% of painful neuropathy patients. Here, we discuss the potential role of the other peripheral ion channels involved in sensory signaling (transient receptor potential cation channels), neuronal excitation regulation (potassium channels), involuntary action potential generation (hyperpolarization-activated cyclic nucleotide-gated channels), thermal pain (anoctamins), pH modulation (acid sensing ion channels), and neurotransmitter release (calcium channels) related to pain and their prospective role as therapeutic targets for painful neuropathy.

Neuropathic Pain in the Emergency Setting: Diagnosis and Management

Neuropathic pain, traditionally considered a chronic condition, is increasingly encountered in the emergency department (ED), accounting for approximately 20% of patients presenting with pain. Understanding the physiology and key clinical presentations of neuropathic pain is crucial for ED physicians to provide optimal treatment. While diagnosing neuropathic pain can be challenging, emphasis should be placed on obtaining a comprehensive medical history and conducting a thorough clinical examination. Patients often describe neuropathic pain as a burning or shock-like sensation, leading them to seek care in the ED after ineffective relief from common analgesics such as paracetamol and NSAIDs. Collaboration between emergency medicine specialists, neurologists, and pain management experts can contribute to the development of evidence-based guidelines specifically tailored for the emergency department setting. This article provides a concise overview of the common clinical manifestations of neuropathic pain that may prompt patients to seek emergency care.

Pharmacological Proposal Approach to Managing Chronic Pain Associated with COVID-19

BACKGROUND

Post-COVID syndrome is widespread and chronic pain associated with this syndrome is increasingly being seen in pain clinics. Understanding and managing Chronic Post-COVID Pain (CPCoP) is essential in improving the quality of life of patients. Relevant sections: Identify the types of pain associated with post-COVID syndrome and look for ways to treat them.

RESULTS AND DISCUSSION

Based on our experience, we have identified five groups within CPCoP: (1) chronic pain post-hospitalization in intensive care or long hospitalizations, (2) pain associated with rehabilitation, (3) exacerbation of existing chronic pain pre-COVID-19 infection, (4) central and peripheral neuropathic pain post-COVID-19 infection, (5) chronic pain post vaccination. To fight against misinformation, we created an information capsule for doctors, nurses, and other health workers at a conference via the ECHO* program, delivered 2-3 times a year.

CONCLUSIONS

In pandemic and post-pandemic periods, it is important to determine the sequelae that a disease can leave in the general population, and to understand and treat them. The model proposed may serve as an inspiration to other pain centers to treat the increasing number of patients with CPCoP.

Recent Progress in Gels for Neuropathic Pain

Neuropathic pain is a complex and debilitating condition that affects millions of people worldwide. While several treatment options are available, they often have limited efficacy and are associated with adverse effects. In recent years, gels have emerged as a promising option for the treatment of neuropathic pain. Inclusion of various nanocarriers, such as cubosomes and niosomes, into gels results in pharmaceutical forms with higher drug stability and increased drug penetration into tissues compared to products currently marketed for the treatment of neuropathic pain. Furthermore, these compounds usually provide sustained drug release and are biocompatible and biodegradable, which makes them a safe option for drug delivery. The purpose of this narrative review was to provide a comprehensive analysis of the current state of the field and identify potential directions for future research in the development of effective and safe gels for the treatment of neuropathic pain, ultimately improving the quality of life for patients suffering from neuropathic pain.

Clinical characteristics of ankylosing spondylitis patients depending on neuropathic pain

Introduction

Neuropathic pain (NP) in ankylosing spondylitis (AS) is an important factor that complicates patients' everyday activities and leads to a decrease of life quality. Detection and diagnosis of NP can be facilitated by the use of screening instruments, and the comparative assessment of the sensitivity of different scales is important for improving the diagnosis and personalizing the treatment of AS.The aim of the study was to analyze prevalence of NP in patients with AS and clinical features of AS patients depending on the presence of NP.

Material and methods

We examined 94 patients with NP and 48 patients without pain in AS using the following questionnaires: LANSS, DN4, StEP, BASFI, BASMI, BASDAI, HAQ, ASAS HI/EF and BAS-G.

Results

The prevalence of NP according to LANSS was 51.7% in women and 32.7% in men (p = 0.048); according to DN4 - 58.6% and 32.7%, respectively (p = 0.010). Disease activity and functional disability of the patients were higher in the group of patients with NP than in the group of patients without NP according to the BASDAI, BASFI, BASMI, HAQ, ASAS HI/EF and BAS-G. Significance of differences between groups was at the level of p < 0.01.

Conclusions

The prevalence of NP in AS is alarmingly high. Even with low scores on screening scales, patients showed signs of NP, which may indicate higher prevalence of NP. Neuropathic pain is more associated with the activity of the disease, greater loss of functional capacity and a decrease in indicators of the general state of health, which allows it to be considered as an aggravating factor regarding these manifestations.

Methyl Ferulic Acid Alleviates Neuropathic Pain by Inhibiting Nox4-induced Ferroptosis in Dorsal Root Ganglia Neurons in Rats

Neuropathic pain is a disease that has become one of the major public health problems and a global burden. Nox4-induced oxidative stress can lead to ferroptosis and neuropathic pain. Methyl ferulic acid (MFA) can inhibit the Nox4-induced oxidative stress. This study aimed to estimate whether methyl ferulic acid alleviates neuropathic pain by inhibiting the expression of Nox4 and its induction of ferroptosis. Adult male Sprague-Dawley rats were subjected to spared nerve injury (SNI) model to induce neuropathic pain. After the establishment of the model, methyl ferulic acid was given 14 days by gavage. Nox4 overexpression was induced by microinjection of the AAV-Nox4 vector. All groups measured paw mechanical withdrawal threshold (PMWT), paw thermal withdrawal latency (PTWL), and paw withdrawal cold duration (PWCD). The expression of Nox4, ACSL4, GPX4, and ROS was investigated by Western blot and immunofluorescence staining. The changes in iron content were detected by a tissue iron kit. The morphological changes in mitochondria were observed by transmission electron microscopy. In the SNI group, the paw mechanical withdrawal threshold, the paw withdrawal cold duration decreased, the paw thermal withdrawal latency did not change, the Nox4, ACSL4, ROS, and iron content increased, the GPX4 decreased, and the number of abnormal mitochondria increased. Methyl ferulic acid can increase PMWT and PWCD but does not affect PTWL. Methyl ferulic acid can inhibit Nox4 protein expression. Meanwhile, ferroptosis-related protein ACSL4 expression was decreased, GPX4 expression was increased, ROS, iron content and abnormal mitochondrial number were decreased. By overexpressing Nox4, the PMWT, PWCD, and ferroptosis of rats were more severe than those of the SNI group, but they could be reversed after treatment with methyl ferulic acid. In conclusion, methyl ferulic acid can alleviate neuropathic pain, which is related to Nox4-induced ferroptosis.

Diagnosis and Management of Neuropathic Pain in Spine Diseases

Neuropathic pain is generally defined as a non-physiological pain experience caused by damage to the nervous system. It can occur spontaneously, as a reaction to a given stimulus, or independently of its action, leading to unusual pain sensations usually referred to as firing, burning or throbbing. In the course of spine disorders, pain symptoms commonly occur. According to available epidemiological studies, a neuropathic component of pain is often present in patients with spinal diseases, with a frequency ranging from 36% to 55% of patients. Distinguishing between chronic nociceptive pain and neuropathic pain very often remains a challenge. Consequently, neuropathic pain is often underdiagnosed in patients with spinal diseases. In reference to current guidelines for the treatment of neuropathic pain, gabapentin, serotonin and norepinephrine reuptake inhibitors and tricyclic antidepressants constitute first-line therapeutic agents. However, long-term pharmacologic treatment often leads to developing tolerance and resistance to used medications. Therefore, in recent years, a plethora of therapeutic methods for neuropathic pain have been developed and investigated to improve clinical outcomes. In this review, we briefly summarized current knowledge about the pathophysiology and diagnosis of neuropathic pain. Moreover, we described the most effective treatment approaches for neuropathic pain and discussed their relevance in the treatment of spinal pain.

Effect of Transcutaneous Spinal Direct Current Stimulation in Patients with Painful Polyneuropathy and Influence of Possible Predictors of Efficacy including BDNF Polymorphism: A Randomized, Sham-Controlled Crossover Study

Introduction: The neuromodulating effects of transcutaneous-spinal Direct Current Stimulation (tsDCS) have been reported to block pain signaling. For patients with chronic pain, tsDCS could be a potential treatment option. To approach this, we studied the effect of anodal tsDCS on patients with neuropathic pain approaching an optimal paradigm including the investigation of different outcome predictors. Methods: In this randomized, double-blinded, sham-controlled crossover study we recruited twenty patients with neurophysiologically evaluated neuropathic pain due to polyneuropathy (PNP). Variables (VAS; pain and sleep quality) were reported daily, one week prior to, and one week after the stimulation/sham period. Anodal tsDCS (2.5 mA, 20 min) was given once daily for three days during one week. BDNF-polymorphism, pharmacological treatment, and body mass index (BMI) of all the patients were investigated. Results: Comparing the effects of sham and real stimulation at the group level, there was a tendency towards reduced pain, but no significant effects were found. However, for sleep quality a significant improvement was seen. At the individual level, 30 and 35% of the subjects had a clinically significant improvement of pain level and sleep quality, respectively, the first day after the stimulation. Both effects were reduced over the coming week and these changes were negatively correlated. The BDNF polymorphism Val66Met was carried by 35% of the patients and this group was found to have a lower general level of pain but there was no significant difference in the tsDCS response effect. Neither pharmacologic treatment or BMI influenced the treatment effect. Conclusions: Short-term and sparse anodal thoracic tsDCS reduces pain and improves sleep with large inter-individual differences. Roughly 30% will benefit in a clinically meaningful way. The BDNF genotype seems to influence the level of pain that PNP produces. Individualized and intensified tsDCS may be a treatment option for neuropathic pain due to PNP.

Bibliometric and Visual Analysis of the Scientific Literature on Percutaneous Electrical Nerve Stimulation (PENS) for Pain Treatment

Background: Percutaneous electrical nerve stimulation (PENS) is a minimally invasive peripheral neuromodulation approach implemented against chronic neuropathic and mixed pain. This bibliometric study aims to quantitatively evaluate the output of PENS for pain treatment in the scientific literature. The main purpose is to stimulate research in the field and bridge potential scientific gaps. Methods: Articles were retrieved from the Web of Science (WOS) database. The search key term was “percutaneous electrical nerve stimulation (All Fields) and pain (All Fields)”. Year of publication, journal metrics (impact factor and quartile, Q), title, document type, topic, and citations were extracted. The join-point regression was implemented to assess differences in time points for the publication output. The software tool VOSviewer (version 1.6.17) was used for the visual analysis. Results: One thousand three hundred and eighteen articles were included in the knowledge visualization process. A linear upward trend for annual new publications was found. Almost two-thirds of the documents were published in top-ranked journals (Q1 and Q2). The topic “efficacy” was prevalent (12.81%). Concerning article type, the search strategy yielded 307 clinical investigations (23.3%). Articles were cited 36,610 times with a mean of 42.4 citations per article. Approximately one-half of the articles were cited less than 23 times in a range of 21 years. The semantic network analysis for keywords found eight clusters. The analysis of collaborative efforts among researchers showed five thematic clusters including 102 authors with a minimum of five documents produced in collaborations. Most partnerships involved the United States, England, and Germany. Conclusions: despite the upward trend in the number of publications on the subject and the publication of articles in top-ranked journals, there is a need to increase scientific collaborations between researchers and institutions from different countries.

A Review of the Therapeutic Targeting of SCN9A and Nav1.7 for Pain Relief in Current Human Clinical Trials

Introduction

There is a great need to find alternative treatments for chronic pain which have become a healthcare problem. We discuss current therapeutic targeting Nav1.7.

Areas Covered

Nav1.7 is a sodium ion channel protein that is associated with several human pain genetic syndromes. It has been found that mutations associated with Nav1.7 lead to the loss of the ability to perceive pain in individuals that are otherwise normal. Several therapeutic interventions are presently undergoing preclinical and research using the methodology of damping Nav1.7 expressions as a methodology to decrease the sensation of pain leading to analgesia.

Expert Opinion

It is our strong belief that there is a viable future in the targeting of protein of Nav1.7 for the relief of chronic pain in humans. The review will look at the genomics associated with SCN1A and proteomic of Nav1.7 as a foundation to explain the mechanism of the therapeutic interventions targeting Nav1.7, the human disease that are associated with Nav1.7, and the current development of treatment for chronic pain whether in preclinical or clinical trials targeting Nav1.7 expressions. The development of therapeutic antagonists targeting Nav1.7 could be a viable alternative to the current treatments which have led to the opioid crisis. Therefore, Nav1.7 targeted treatment has a major clinical significance that will have positive consequences as it relates to chronic pain interventions.