Neuropathic pain: quality-of-life impact, costs and cost effectiveness of therapy

ESRRG-controlled downregulation of KCNN1 in primary sensory neurons is required for neuropathic pain

Peripheral nerve injury-induced neuronal hyperactivity in the dorsal root ganglion (DRG) participates in neuropathic pain. The calcium-activated potassium channel subfamily N member 1 (KCNN1) mediates action potential afterhyperpolarization (AHP) and gates neuronal excitability. However, the specific contribution of DRG KCNN1 to neuropathic pain is not yet clear. We report that chronic constriction injury (CCI) of the unilateral sciatic nerve or unilateral ligation of the fourth lumbar nerve produced the downregulation of Kcnn1 mRNA and KCNN1 protein in the injured DRG. This downregulation was partially attributed to a decrease in DRG estrogen-related receptor gamma (ESRRG), a transcription factor, which led to reduced binding to the Kcnn1 promoter. Rescuing this downregulation prevented CCI-induced decreases in total potassium voltage currents and AHP currents, reduced excitability in the injured DRG neurons, and alleviated CCI-induced development and maintenance of nociceptive hypersensitivities, without affecting locomotor function and acute pain. Mimicking the CCI-induced DRG KCNN1 downregulation resulted in augmented responses to mechanical, heat, and cold stimuli in naive mice. Our findings indicate that ESRRG-controlled downregulation of DRG KCNN1 is likely essential for the development and maintenance of neuropathic pain. Thus, KCNN1 may serve as a potential target for managing this disorder.

A phenotypic screening platform for chronic pain therapeutics using all-optical electrophysiology

ABSTRACT

Chronic pain associated with osteoarthritis (OA) remains an intractable problem with few effective treatment options. New approaches are needed to model the disease biology and to drive discovery of therapeutics. We present an in vitro model of OA pain, where dorsal root ganglion (DRG) sensory neurons were sensitized by a defined mixture of disease-relevant inflammatory mediators, here called Sensitizing PAin Reagent Composition or SPARC. Osteoarthritis-SPARC components showed synergistic or additive effects when applied in combination and induced pain phenotypes in vivo. To measure the effect of OA-SPARC on neural firing in a scalable format, we used a custom system for high throughput all-optical electrophysiology. This system enabled light-based membrane voltage recordings from hundreds of neurons in parallel with single cell and single action potential resolution and a throughput of up to 500,000 neurons per day. A computational framework was developed to construct a multiparameter OA-SPARC neuronal phenotype and to quantitatively assess phenotype reversal by candidate pharmacology. We screened ∼3000 approved drugs and mechanistically focused compounds, yielding data from over 1.2 million individual neurons with detailed assessment of functional OA-SPARC phenotype rescue and orthogonal "off-target" effects. Analysis of confirmed hits revealed diverse potential analgesic mechanisms including ion channel modulators and other mechanisms including MEK inhibitors and tyrosine kinase modulators. Our results suggest that the Raf-MEK-ERK axis in DRG neurons may integrate the inputs from multiple upstream inflammatory mediators found in osteoarthritis patient joints, and MAPK pathway activation in DRG neurons may contribute to chronic pain in patients with osteoarthritis.

Cryoneurolysis of the Subcostal Nerve: A Technical Description and Case Report

Cryoneurolysis has been utilized for numerous persistent and intractable painful conditions, including phantom limb pain and postsurgical pain. Although there are reports on the effectiveness of cryoneurolysis in various regions, including the intercostal nerves, the subcostal nerve remains a common culprit of chronic pain for which the literature is scarce. Different modalities are commonly utilized to address subcostal neuropathic pain, such as non-opioid pharmacotherapy, including nonsteroidal anti-inflammatory drugs (NSAIDs) and anticonvulsants, site-specific regional anesthesia, and radiofrequency ablation.However, the analgesia provided by these modalities is often inadequate or short-lived. Cryoneurolysis of the subcostal nerve remains largely unexplored and may provide a promising solution.Here, we present the first technical description of ultrasound and fluoroscopic guided percutaneous cryoneurolysis of the subcostal nerve and the case of a patient with 14 years of lower thoracic rib pain who failed multiple interventions but achieved complete pain resolution at the three-month follow-up through this procedure.

LncRNA Anxa10-203 enhances Mc1r mRNA stability to promote neuropathic pain by recruiting DHX30 in the trigeminal ganglion

BACKGROUND

Trigeminal nerve injury is one of the most serious complications in oral clinics, and the subsequent chronic orofacial pain is a consumptive disease. Increasing evidence demonstrates long non-coding RNAs (lncRNAs) play an important role in the pathological process of neuropathic pain. This study aims to explore the function and mechanism of LncRNA Anxa10-203 in the development of orofacial neuropathic pain.

METHODS

A mouse model of orofacial neuropathic pain was established by chronic constriction injury of the infraorbital nerve (CCI-ION). The Von Frey test was applied to evaluate hypersensitivity of mice. RT-qPCR and/or Western Blot were performed to analyze the expression of Anxa10-203, DHX30, and MC1R. Cellular localization of target genes was verified by immunofluorescence and RNA fluorescence in situ hybridization. RNA pull-down and RNA immunoprecipitation were used to detect the interaction between the target molecules. Electrophysiology was employed to assess the intrinsic excitability of TG neurons (TGNs) in vitro.

RESULTS

Anxa10-203 was upregulated in the TG of CCI-ION mice, and knockdown of Anxa10-203 relieved neuropathic pain. Structurally, Anxa10-203 was located in the cytoplasm of TGNs. Mechanistically, Mc1r expression was positively correlated with Anxa10-203 and was identified as the functional target of Anxa10-203. Besides, Anxa10-203 recruited RNA binding protein DHX30 and formed the Anxa10-203/DHX30 complex to enhance the stability of Mc1r mRNA, resulting in the upregulation of MC1R, which contributed to the enhancement of the intrinsic activity of TGNs in vitro and orofacial neuropathic pain in vivo.

CONCLUSIONS

LncRNA Anxa10-203 in the TG played an important role in orofacial neuropathic pain and mediated mechanical allodynia in CCI-ION mice by binding with DHX30 to upregulate MC1R expression.

Painful Diabetic Neuropathy: The Need for New Approaches

Painful diabetic neuropathy is a common vexing problem for people with diabetes and a costly problem for society. The pathophysiology is not well understood, and no safe and effective mechanistically-based treatment has been identified. Poor glycemic control is a risk factor for painful diabetic neuropathy. Excessive intraneuronal glucose in people with diabetes can be shunted away from physiological glycolysis into multiple pathological pathways associated with neuropathy and pain. The first three treatments that are traditionally offered consist of risk factor reduction, lifestyle modifications, and pharmacological therapy, which includes only three drugs that are approved for this indication by the United States Food and Drug Administration. All of these traditional treatments are often inadequate for relieving neuropathic pain, and thus, new approaches are needed. Modern devices based on neuromodulation technology, which act directly on the nervous system, have been recently cleared by the United States Food and Drug Administration for painful diabetic neuropathy and offer promise as next-in-line therapy when traditional therapies fail.

Comprehensive Bibliometric Analysis of Research Articles on Post-Herpetic Neuralgia and Varicella-Zoster Virus: A 20-Year Review(2003-2022)

Objective

Post-herpetic neuralgia (PHN) is a debilitating condition that has garnered considerable attention from pain physicians due to its association with the or Varicella-Zoster Virus (VZV). In this study, we aimed to conduct a bibliometric analysis to quantitatively assess the research outcomes related to PHN and VZV over the past two decades (2003-2022).

Methods

We conducted a bibliometric analysis by querying the Web of Science database for articles related to PHN published from 2003 to 2022. In this analysis, we collected relevant information from the database including the number of publications, publication year, source, country, institution, and citation data.

Results

A total of 1073 publications were extracted from the database, with 387 articles (36.1%) being authored by individuals from the United States, making it the leading country in terms of article publications. The top ten institutions that made significant contributions to research on PHN and VZV were primarily concentrated within the United States. Notably, the New England Journal of Medicine and Pain claimed the two highest positions in terms of citation count, with 2482 and 1591 citations, respectively. The topics covered in these articles mainly revolved around "Postherpetic Neuralgia", "Herpes Zoster", "Epidemiology", "Vaccine", and "Quality-of-life".

Conclusion

Over the past two decades, there has been a gradual increase in publications on PHN and VZV, demonstrating significant advancements in academic achievements. Vaccines have proven effective in reducing PHN incidence among the elderly, but there is a lack of research on interventional treatments and underlying mechanisms. To elevate evidence-based medicine, researchers should conduct more controlled clinical trials. Additionally, leveraging pathogenesis research findings can lead to the development of better pain relief medications.

Ac4C Enhances the Translation Efficiency of Vegfa mRNA and Mediates Central Sensitization in Spinal Dorsal Horn in Neuropathic Pain

N4-Acetylcytidine (ac4C), a highly conserved post-transcriptional machinery with extensive existence for RNA modification, plays versatile roles in various cellular processes and functions. However, the molecular mechanism by which ac4C modification mediates neuropathic pain remains elusive. Here, it is found that the enhanced ac4C modification promotes the recruitment of polysome in Vegfa mRNA and strengthens the translation efficiency following SNI. Nerve injury increases the expression of NAT10 and the interaction between NAT10 and Vegfa mRNA in the dorsal horn neurons, and the gain and loss of NAT10 function further confirm that NAT10 is involved in the ac4C modification in Vegfa mRNA and pain behavior. Moreover, the ac4C-mediated VEGFA upregulation contributes to the central sensitivity and neuropathic pain induced by SNI or AAV-hSyn-NAT10. Finally, SNI promotes the binding of HNRNPK in Vegfa mRNA and subsequently recruits the NAT10. The enhanced interaction between HNRNPK and NAT10 contributes to the ac4C modification of Vegfa mRNA and neuropathic pain. These findings suggest that the enhanced interaction between HNRNPK and Vegfa mRNA upregulates the ac4C level by recruiting NAT10 and contributes to the central sensitivity and neuropathic pain following SNI. Blocking this cascade may be a novel therapeutic approach in patients with neuropathic pain.

Health-related quality of life and spinal cord stimulation in painful diabetic neuropathy

Peripheral neuropathic pain, including painful diabetic neuropathy (PDN), is associated with marked negative impact on health-related quality of life (HRQoL). The magnitude of reduction of HRQoL experienced by individual PDN patients appears to be strongly associated with their level of pain and disease severity. In spite of the availability of a range of pharmacotherapy, a substantive proportion of PDN patients continue to experience suboptimal HRQoL. Such patients are potential candidates for spinal cord stimulation (SCS) devices. Three randomised controlled trials in over 300 patients with refractory PDN have shown that the addition of SCS to standard of care therapy results in important health gains, including pain reduction and enhancement of HRQoL. Sham-controlled RCTs that enable blinding of patients, clinicians and researchers are needed to confirm the role of SCS in PDN.

Sensory neuron-specific long noncoding RNA in small non-peptidergic dorsal root ganglion neurons selectively impairs nerve injury-induced mechanical hypersensitivity

AIMS

Nerve injury-induced mechanical hypersensitivity is one of major clinical symptoms in neuropathic pain patients. Understanding molecular mechanisms underlying this symptom is crucial for developing effective therapies. The present study was to investigate whether sensory neuron-specific long noncoding RNA (SS-lncRNA) predominantly expressed in small non-peptidergic dorsal root ganglion (DRG) neurons repaired nerve injury-induced mechanical hypersensitivity.

MATERIALS AND METHODS

SS-lncRNA downregulation in the mas-related G protein-coupled receptor member D (Mrgprd)-expressed DRG neurons was rescued and mimicked by crossbreeding MrgprdCreERT2/+ lines with Rosa26SS-lncRNA knock-in mice and SS-lncRNAfl/fl mice, respectively, followed by tamoxifen injection.

KEY FINDINGS

Rescuing SS-lncRNA downregulation in the Mrgprd-expressed DRG neurons significantly reversed the spinal nerve ligation (SNL)-induced reduction of the calcium-activated potassium channel subfamily N member 1 (KCNN1) in these DRG neurons and alleviated the SNL-induced mechanical hypersensitivity, without affecting the SNL-induced heat and cold nociceptive hypersensitivities, on the ipsilateral side. Conversely, mimicking SS-lncRNA downregulation in the Mrgprd-expressed DRG neurons reduced basal KCNN1 expression in these DRG neurons and produced the enhanced response to mechanical stimulation, but not thermal and cold stimuli, on bilateral sides. Mechanistically, SS-lncRNA downregulation caused a reduction in its binding to lysine-specific demethylase 6B (KDM6B) and consequent recruitment of less KDM6B to Kcnn1 promoter and an increase of H3K27me3 enrichment in this promoter in injured DRG.

SIGNIFICANCE

Our findings suggest that SS-lncRNA downregulation in small non-peptidergic sensory neurons is required specifically for nerve injury-induced mechanical hypersensitivity likely through silencing KCNN1 expression caused by KDM6B-gated increase of H3K27me3 enrichment in Kcnn1 promoter in these neurons.

High-frequency spinal cord stimulation (10 kHz) alters sensory function and nerve fiber density in painful diabetic neuropathy: a pilot prospective open-label study

OBJECTIVE

Spinal cord stimulation at 10 kHz has provided effective pain relief and improved function in painful diabetic peripheral neuropathy. This study aims to confirm the clinical outcomes for 10-kHz spinal cord stimulation treatment of painful diabetic peripheral neuropathy and explore its impact on objective quantitative measures of nerve pathology and function.

METHODS

This single-academic center, prospective, open-label, observational study examined the pain relief success of 10-kHz spinal cord stimulation in patients >18 years of age with diabetic peripheral neuropathy. Patients underwent skin biopsies to measure intra-epidermal nerve fiber densities and corneal confocal microscopy measurements before implantation and at the 3-, 6-, and 12-month follow-up visits. Numerical rating scale for pain, visual analog scale, neuropathy pain scale, Short Form-36, and Neuropen (pin prick and monofilament) assessments were also conducted.

RESULTS

Eight patients met the criteria and were enrolled in the study. A successful trial was achieved in 7 subjects, and 6 completed the study. Significant pain relief (P < .001) was achieved at all follow-up visits. Neurological assessments showed reduced numbers of "absent" responses and increased "normal" responses from baseline to 12 months. Both proximal and distal intra-epidermal nerve fiber densities were higher at 12 months than at baseline (P < .01). Confocal microscopy measurements showed a steady increase in nerve density from baseline (188.8% increase at 12 months; P = .029).

CONCLUSIONS

We observed pain relief and improvements in sensory function after stimulation that were accompanied by increases in lower-limb intra-epidermal nerve fiber density and corneal nerve density. Further evaluation with a blinded and controlled study is needed to confirm the preliminary findings in this study.

Deep RNA-seq of male and female murine sensory neuron subtypes after nerve injury

ABSTRACT

Dorsal root ganglia (DRG) neurons have been well described for their role in driving both acute and chronic pain. Although nerve injury is known to cause transcriptional dysregulation, how this differs across neuronal subtypes and the impact of sex is unclear. Here, we study the deep transcriptional profiles of multiple murine DRG populations in early and late pain states while considering sex. We have exploited currently available transgenics to label numerous subpopulations for fluorescent-activated cell sorting and subsequent transcriptomic analysis. Using bulk tissue samples, we are able to circumvent the issues of low transcript coverage and drop-outs seen with single-cell data sets. This increases our power to detect novel and even subtle changes in gene expression within neuronal subtypes and discuss sexual dimorphism at the neuronal subtype level. We have curated this resource into an accessible database for other researchers ( https://livedataoxford.shinyapps.io/drg-directory/ ). We see both stereotyped and unique subtype signatures in injured states after nerve injury at both an early and late timepoint. Although all populations contribute to a general injury signature, subtype enrichment changes can also be seen. Within populations, there is not a strong intersection of sex and injury, but previously unknown sex differences in naïve states-particularly in Aβ-RA + Aδ-low threshold mechanoreceptors-still contribute to differences in injured neurons.

A sensory neuron-specific long non-coding RNA reduces neuropathic pain by rescuing KCNN1 expression

Nerve injury to peripheral somatosensory system causes refractory neuropathic pain. Maladaptive changes of gene expression in primary sensory neurons are considered molecular basis of this disorder. Long non-coding RNAs (lncRNAs) are key regulators of gene transcription; however, their significance in neuropathic pain remains largely elusive.Here, we reported a novel lncRNA, named sensory neuron-specific lncRNA (SS-lncRNA), for its expression exclusively in dorsal root ganglion (DRG) and trigeminal ganglion. SS-lncRNA was predominantly expressed in small DRG neurons and significantly downregulated due to a reduction of early B cell transcription factor 1 in injured DRG after nerve injury. Rescuing this downregulation reversed a decrease of the calcium-activated potassium channel subfamily N member 1 (KCNN1) in injured DRG and alleviated nerve injury-induced nociceptive hypersensitivity. Conversely, DRG downregulation of SS-lncRNA reduced the expression of KCNN1, decreased total potassium currents and afterhyperpolarization currents and increased excitability in DRG neurons and produced neuropathic pain symptoms.Mechanistically, downregulated SS-lncRNA resulted in the reductions of its binding to Kcnn1 promoter and heterogeneous nuclear ribonucleoprotein M (hnRNPM), consequent recruitment of less hnRNPM to the Kcnn1 promoter and silence of Kcnn1 gene transcription in injured DRG.These findings indicate that SS-lncRNA may relieve neuropathic pain through hnRNPM-mediated KCNN1 rescue in injured DRG and offer a novel therapeutic strategy specific for this disorder.

The invisible cost of pain management by the current International Classification of Diseases coding system: a study in a tertiary care inpatient setting

ABSTRACT

The International Classification of Diseases ( ICD ) is applied worldwide for public health data collection among other use cases. However, the current version of the ICD ( ICD-10 ), to which the reimbursement system is linked in many countries, does not represent chronic pain properly. This study aims to compare the ICD-10 with the ICD-11 in hospitalized patients in terms of specificity, clinical utility, and reimbursement for pain management. The medical records of hospitalized patients consulted for pain management at Siriraj Hospital, Thailand, were reviewed, and all pain-related diagnoses were coded into ICD-10 and ICD-11 . The data of 397 patients showed unspecified pain was coded 78% in the ICD-10 and only 0.5% in the ICD-11 version. The difference gap in the proportion of unspecified pain between the 2 versions is wider than in the outpatient setting. The 3 most common codes for ICD-10 were other chronic pain, low back pain, and pain in limb. The 3 most common codes for ICD-11 were chronic cancer pain, chronic peripheral neuropathic pain, and chronic secondary musculoskeletal pain. As in many other countries, no pain-related ICD-10 codes were coded for routine reimbursement. The simulated reimbursement fee remained the same when adding 397 pain-related codings, even if the cost of pain management, such as cost of labor, existed. Compared with the ICD-10 version, the ICD-11 is more specific and makes pain diagnoses more visible. Thus, shifting from ICD-10 to ICD-11 has the potential to improve both the quality of care and the reimbursement for pain management.

DEAD-box helicase 54 regulates microglial inflammatory response in rats with chronic constriction injuries through NF-κB/NLRP3 signaling axis

Neuropathic pain (NP) is caused by damage to or disease of the somatosensory nervous system, but its mechanism is still not fully understood. In this study, DEAD-box helicase 54 (DDX54) was targeted, and its regulatory role was explored in a chronic constriction injury (CCI) rat model. Microglia and HMC3 cells were stimulated with LPS. The interaction between DDX54 and myeloid differentiation factor-88 adapter protein (MYD88) was verified. A CCI of sciatic nerve model in rats was established. Behavioral testing was performed before and after the CCI. The expressions of IL-1β, TNF-α, and IL-6 were upregulated, and those of DDX54, MYD88, NF-κB, and NOD-like receptor 3 (NLRP3) were upregulated in microglia and HMC3 cells after LPS induction. DDX54 knockdown in microglia and HMC3 cells inhibited IL-1β, TNF-α, and IL-6 expressions and downregulated the protein levels of MYD88, p-NF-κB p65 (p-p65), and NLRP3. DDX54 overexpression promoted the stability of MYD88 mRNA. DDX54 binds to the MYD88-3'-untranslated region (UTR). DDX54 interference in rats could alleviate the decrease of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) induced by CCI, inhibit Iba1 expression, and reduce inflammatory factors as well as MYD88 and NF-κB expressions. DDX54 promotes the activation of NF-κB/NLRP3 signaling by regulating MYD88 mRNA stability, thereby affecting inflammatory response and NP progression in CCI rats.NEW & NOTEWORTHY The role of DDX54 protein in LPS-induced microglia and a chronic constriction injury (CCI) rat model was investigated for the first time. DDX54 interference can inhibit microglial activation and reduce the secretion of inflammatory factors. The interaction between DDX54 protein and MYD88 mRNA was explored for the first time. DDX54 promotes NF-κB/NLRP3 signaling activation by regulating MYD88 transcription in a CCI rat model.

Global Research Trends and Hotspots Analysis of the Scientific Production of Amitriptyline: A Bibliometric Approach

Amitriptyline was first introduced as a medication to treat depression. Over time, this substance has been used to treat other conditions, such as gastrointestinal disorders, fibromyalgia, neuropathic pain, and analgesia, among others. However, there are no published studies that provide a broad view of the possible motivations that have led to changes in the use of amitriptyline. In this study, we have identified the landscape of use for amitriptyline based on knowledge mapping of the 100 most-cited articles about this drug. We searched Web of Science Core Collection without time and language restrictions. We obtained 14,446 results, but we only used the 100 most-cited articles that had amitriptyline as the object of study. We collected the following information from each article: authors, country of the corresponding authors, year of publication, citation count, citation density (number of citations per year), and keywords. In addition, we seek to map in the chosen articles study design and research findings. We found that since 1980, the use of amitriptyline has expanded beyond depression, moving to off-label use to treat a variety of diseases and conditions, including post-herpetic neuralgia, neuropathic pain, primary fibrosis, fibromyalgia, and migraine, can be considered a drug with more clinical applicability than its original clinical indication.

Magnetic Peripheral Nerve Stimulation (mPNS) for Chronic Pain

Purpose

To assess magnetic peripheral nerve stimulation (mPNS) for the treatment of chronic or chronic and intractable neuropathic pain with a retrospective review case series.

Patients and methods

Twenty-four patients with predominantly neuropathic post-traumatic or postoperative pain were treated as per protocol and followed for 3 months.

Results

Data were analyzed as an observational, one-armed, convenience sample. Graphical evidence backed up by a mixed model for repeated measures statistical analysis showed a highly significant reduction of pain at one month out from initial treatment with mPNS. At one month, there was a 3.8 average reduction in pre-pain scores using a visual analogue scale (VAS), and that relief was generally durable measured out to three months. Two-thirds of patients, deemed responders, showed an 87% reduction in pain. Opioid reduction was seen in 58.3% of responders as well.

Conclusion

mPNS appears promising for the treatment of chronic or chronic and intractable neuropathic pain for many of the same indications as traditional electrical peripheral nerve stimulation (PNS). No invasive techniques or implants are needed for mPNS.

Ultrasound-controlled cryoneurolysis for peripheral mononeuropathies: a retrospective cohort study

Aim: Cryoneurolysis is a potential therapy for peripheral mononeuropathies, but randomized studies of its effects on the duration of pain reduction are lacking. Methods: This retrospective cohort study evaluated the analgesic effects of cryoneurolysis on patients with refractory peripheral mononeuropathy. We included 24 patients who underwent ultrasound-guided cryoneurolysis between June 2018 and July 2022. The daily maximum pain level was recorded using a numerical rating scale before and 1, 3 and 6 months after the procedure. Results: At 1 month, 54.2% of patients reported pain reduction of at least 30%. This percentage was significantly lower at 3 and 6 months (13.8 and 9.1%, respectively). Conclusion: Our results suggest that repeated cryoneurolysis may be a viable treatment for refractory mononeuropathy. Further investigations are needed.

A Review of Recent Pharmacological Advances in the Management of Diabetes-Associated Peripheral Neuropathy

Diabetic peripheral neuropathy is a common complication of longstanding diabetes mellitus. These neuropathies can present in various forms, and with the increasing prevalence of diabetes mellitus, a subsequent increase in peripheral neuropathy cases has been noted. Peripheral neuropathy has a significant societal and economic burden, with patients requiring concomitant medication and often experiencing a decline in their quality of life. There is currently a wide variety of pharmacological interventions, including serotonin norepinephrine reuptake inhibitors, gapentanoids, sodium channel blockers, and tricyclic antidepressants. These medications will be discussed, as well as their respective efficacies. Recent advances in the treatment of diabetes mellitus with incretin system-modulating drugs, specifically glucagon-like peptide-1 agonists, have been promising, and their potential implication in the treatment of peripheral diabetic neuropathy is discussed in this review.

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.

Mirror peripheral neuropathy and unilateral chronic neuropathic pain: insights from asymmetric neurological patterns in leprosy

ABSTRACT

Leprosy-related multiple mononeuropathy offers a pattern of impairment where neuropathy with and without neuropathic pain (NeP) are present in the same individual, thus allowing to investigate peripheral sensory and innervation in both conditions. This cross-sectional study collected data on clinical and neurological examination, pain assessment questionnaires, quantitative sensory test, and intraepidermal nerve fiber density of patients with leprosy and divided the cohort into 2 groups: with NeP (P+) and without NeP (P-). Furthermore, we assessed mirror body areas in the same NeP individuals with bilateral neuropathy also presenting unilateral NeP. Pain-free patients having unilateral neuropathy were controls. A total of 37 P+ and 22 P- patients were evaluated. Limb areas with NeP had signs of C-fiber dysfunction and hyperesthesia on quantitative sensory testing compared with limb areas having neuropathy without NeP. Skin denervation was found in all patients with leprosy. Comparisons of limbs with and without neuropathy and with and without NeP revealed that higher heat pain thresholds (HPTs) were associated with neuropathic pain areas, whereas less altered HPT was correlated with higher fiber density. Furthermore, a relationship was found between time of leprosy treatment termination and more intense neuropathy, expressed by HPT increasing 0.03°C each month. As expected, interindividual comparisons failed to show differences in intraepidermal nerve fiber density and subepidermal plexus areas between P+ and P- patients ( P = 0.2980, P = 0.9044; respectively). Higher HPT and lower mechanical detection threshold were related to NeP. This study pointed out the relevance of intraindividual comparisons including mirror areas when assessing local changes in peripheral NeP.

Genipin Crosslinks the Extracellular Matrix to Rescue Developmental and Degenerative Defects, and Accelerates Regeneration of Peripheral Neurons

The peripheral nervous system (PNS) is essential for proper body function. A high percentage of the population suffer nerve degeneration or peripheral damage. For example, over 40% of patients with diabetes or undergoing chemotherapy develop peripheral neuropathies. Despite this, there are major gaps in the knowledge of human PNS development and therefore, there are no available treatments. Familial Dysautonomia (FD) is a devastating disorder that specifically affects the PNS making it an ideal model to study PNS dysfunction. FD is caused by a homozygous point mutation in ELP1 leading to developmental and degenerative defects in the sensory and autonomic lineages. We previously employed human pluripotent stem cells (hPSCs) to show that peripheral sensory neurons (SNs) are not generated efficiently and degenerate over time in FD. Here, we conducted a chemical screen to identify compounds able to rescue this SN differentiation inefficiency. We identified that genipin, a compound prescribed in Traditional Chinese Medicine for neurodegenerative disorders, restores neural crest and SN development in FD, both in the hPSC model and in a FD mouse model. Additionally, genipin prevented FD neuronal degeneration, suggesting that it could be offered to patients suffering from PNS neurodegenerative disorders. We found that genipin crosslinks the extracellular matrix, increases the stiffness of the ECM, reorganizes the actin cytoskeleton, and promotes transcription of YAP-dependent genes. Finally, we show that genipin enhances axon regeneration in an in vitro axotomy model in healthy sensory and sympathetic neurons (part of the PNS) and in prefrontal cortical neurons (part of the central nervous system, CNS). Our results suggest genipin can be used as a promising drug candidate for treatment of neurodevelopmental and neurodegenerative diseases, and as a enhancer of neuronal regeneration.

The Similar and Distinct Roles of Satellite Glial Cells and Spinal Astrocytes in Neuropathic Pain

Preclinical studies have identified glial cells as pivotal players in the genesis and maintenance of neuropathic pain after nerve injury associated with diabetes, chemotherapy, major surgeries, and virus infections. Satellite glial cells (SGCs) in the dorsal root and trigeminal ganglia of the peripheral nervous system (PNS) and astrocytes in the central nervous system (CNS) express similar molecular markers and are protective under physiological conditions. They also serve similar functions in the genesis and maintenance of neuropathic pain, downregulating some of their homeostatic functions and driving pro-inflammatory neuro-glial interactions in the PNS and CNS, i.e., "gliopathy". However, the role of SGCs in neuropathic pain is not simply as "peripheral astrocytes". We delineate how these peripheral and central glia participate in neuropathic pain by producing different mediators, engaging different parts of neurons, and becoming active at different stages following nerve injury. Finally, we highlight the recent findings that SGCs are enriched with proteins related to fatty acid metabolism and signaling such as Apo-E, FABP7, and LPAR1. Targeting SGCs and astrocytes may lead to novel therapeutics for the treatment of neuropathic pain.

The Downregulation of Opioid Receptors and Neuropathic Pain

Neuropathic pain (NP) refers to pain caused by primary or secondary damage or dysfunction of the peripheral or central nervous system, which seriously affects the physical and mental health of 7-10% of the general population. The etiology and pathogenesis of NP are complex; as such, NP has been a hot topic in clinical medicine and basic research for a long time, with researchers aiming to find a cure by studying it. Opioids are the most commonly used painkillers in clinical practice but are regarded as third-line drugs for NP in various guidelines due to the low efficacy caused by the imbalance of opioid receptor internalization and their possible side effects. Therefore, this literature review aims to evaluate the role of the downregulation of opioid receptors in the development of NP from the perspective of dorsal root ganglion, spinal cord, and supraspinal regions. We also discuss the reasons for the poor efficacy of opioids, given the commonness of opioid tolerance caused by NP and/or repeated opioid treatments, an angle that has received little attention to date; in-depth understanding might provide a new method for the treatment of NP.

Opioid Dependence and Associated Health Care Utilization and Cost in Traumatic Spinal Cord Injury Population: Analysis Using Marketscan Database

Background

Postinjury pain is a well-known debilitating complication of spinal cord injury (SCI), often resulting in long-term, high-dose opioid use with the potential for dependence. There is a gap in knowledge about the risk of opioid dependence and the associated health care utilization and cost in SCI.

Objectives

To evaluate the association of SCI with postinjury opioid use and dependence and evaluate the effect of this opioid dependence on postinjury health care utilization.

Methods

Using the MarketScan Database, health care utilization claims data were queried to extract 7187 adults with traumatic SCI from 2000 to 2019. Factors associated with post-SCI opioid use and dependence, postinjury health care utilization, and payments were analyzed with generalized linear regression models.

Results

After SCI, individuals were more likely to become opioid users or transition from nondependent to dependent users (negative change: 31%) than become nonusers or transition from dependent to nondependent users (positive change: 14%, p < .0001). Individuals who were opioid-dependent users pre-SCI had more than 30 times greater odds of becoming dependent after versus not (OR 34; 95% CI, 26-43). Dependent users after injury (regardless of prior use status) had 2 times higher utilization payments and 1.2 to 6 times more health care utilization than nonusers.

Conclusion

Opioid use and dependence were associated with high health care utilization and cost after SCI. Pre-SCI opioid users were more likely to remain users post-SCI and were heavier consumers of health care. Pre- and postopioid use history should be considered for treatment decision-making in all individuals with SCI.

Effect of intrathecal NIS-lncRNA antisense oligonucleotides on neuropathic pain caused by nerve trauma, chemotherapy, or diabetes mellitus

BACKGROUND

Blocking increased expression of nerve injury-specific long non-coding RNA (NIS-lncRNA) in injured dorsal root ganglia (DRG) through DRG microinjection of NIS-lncRNA small hairpin interfering RNA or generation of NIS-lncRNA knockdown mice mitigates neuropathic pain. However, these strategies are impractical in the clinic. This study employed a Food and Drug Administration (FDA)-approved antisense oligonucleotides strategy to examine the effect of NIS-lncRNA ASOs on neuropathic pain.

METHODS

Effects of intrathecal injection of NIS-lncRNA antisense oligonucleotides on day 7 or 14 after chronic constriction injury (CCI) of the sciatic nerve, fourth lumbar (L4) spinal nerve ligation, or intraperitoneal injection of paclitaxel or streptozotocin on the expression of DRG NIS-lncRNA and C-C chemokine ligand 2 (CCL2, an NIS-lncRNA downstream target) and nociceptive hypersensitivity were examined. We also assessed whether NIS-lncRNA antisense oligonucleotides produced cellular toxicity.

RESULTS

Intrathecal NIS-lncRNA antisense oligonucleotides attenuated CCI-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and ongoing nociceptive responses, without changing basal or acute nociceptive responses and locomotor function. Intrathecal NIS-lncRNA antisense oligonucleotides also blocked CCI-induced increases in NIS-lncRNA and CCL2 in the ipsilateral L3 and L4 DRG and hyperactivities of neurones and astrocytes in the ipsilateral L3 and L4 spinal cord dorsal horn. Similar results were found in antisense oligonucleotides-treated mice after spinal nerve ligation or intraperitoneal injection of paclitaxel or streptozotocin. Normal morphologic structure and no cell loss were observed in the DRG and spinal cord of antisense oligonucleotides-treated mice.

CONCLUSION

These findings further validate the role of NIS-lncRNA in trauma-, chemotherapy-, or diabetes-induced neuropathic pain and demonstrate potential clinical application of NIS-lncRNA antisense oligonucleotides for neuropathic pain management.

Spinal cord stimulation and return to work of patients with failed back surgery syndrome

OBJECTIVES

Chronic pain has a substantial negative impact on work-related outcomes, which underlines the importance of interventions to reduce the burden. Spinal cord stimulation (SCS) efficiently relieves pain in specific chronic pain syndromes and is recommended for treating failed back surgery syndrome (FBSS) or post-surgical chronic back pain that is refractory to other treatments. To examine the impact of SCS in patients with FBSS on the return to work (RTW), we determined the RTW rate and the factors positively associated with the RTW.

MATERIALS AND METHODS

Among 106 patients with FBSS who benefitted from SCS at a single institution in France between September 1999 and March 2010, we retrospectively included 59 who had stopped work at the time of SCS because of disability or sick leave and evaluated the RTW (rate and predictors, estimating odds ratios [ORs] and 95% confidence intervals [CIs]).

RESULTS

The mean (SD) post-surgery follow-up for the 59 patients (34 men; mean [SD] age 46.9 [7.4] years) was 7.5 (3.6) years (range 5-15). The RTW rate was 30.5%, with a median [IQR] recovery time of 5.5 months [3-8.5]. RTW was improved with functional improvement evolution (OR 1.1, 95% CI [1.01-1.1], p = 0.02) and was reduced with unemployment > 3 years (OR 0.1, 95% CI [0.01-0.7], p = 0.02).

CONCLUSIONS

Our protocol for SCS for patients with FBSS, including a strict selection of patients and a multidisciplinary approach, led to good results, especially for the RTW. RTW should be a therapeutic goal, directly affecting indirect costs related to FBSS.

Small Synthetic Hyaluronan Disaccharide BIS014 Mitigates Neuropathic Pain in Mice

Neuropathic pain (NP) is a challenging condition to treat, as the need for new drugs to treat NP is an unmet goal. We investigated the analgesic potential of a new sulfated disaccharide compound, named BIS014. Oral administration (p.o.) of this compound induced ameliorative effects in formalin-induced nociception and capsaicin-induced secondary mechanical hypersensitivity in mice, but also after partial sciatic nerve transection (spared nerve injury), chemotherapy (paclitaxel)-induced NP, and diabetic neuropathy induced by streptozotocin. Importantly, BIS014, at doses active on neuropathic hypersensitivity (60 mg/kg/p.o.), did not alter exploratory activity or motor coordination (in the rotarod test), unlike a standard dose of gabapentin (40 mg/kg/p.o.) which although inducing antiallodynic effects on the NP models, it also markedly decreased exploration and motor coordination. In docking and molecular dynamic simulation studies, BIS014 interacted with TRPV₁, a receptor involved in pain transmission where it behaved as a partial agonist. Additionally, similar to capsaicin, BIS014 increased cytosolic Ca²⁺ concentration ([Ca²⁺]_c) in neuroblastoma cells expressing TRPV₁ receptors; these elevations were blocked by ruthenium red. BIS014 did not block capsaicin-elicited [Ca²⁺]_c transients, but inhibited the increase in the firing rate of action potentials in bradykinin-sensitized dorsal root ganglion neurons stimulated with capsaicin. Perspective: We report that the oral administration of a new sulfated disaccharide compound, named BIS014, decreases neuropathic pain from diverse etiology in mice. Unlike the comparator gabapentin, BIS014 does not induce sedation. Thus, BIS014 has the potential to become a new efficacious non-sedative oral medication for the treatment of neuropathic pain.

The Identification of Human Translational Biomarkers of Neuropathic Pain and Cross-Species Validation Using an Animal Model

Neuropathic pain is a common chronic condition, which remains poorly understood. Many patients receiving treatment continue to experience severe pain, due to limited diagnostic/treatment management programmes. The development of objective clinical diagnostic/treatment strategies requires identification of robust biomarkers of neuropathic pain. To this end, we looked to identify biomarkers of chronic neuropathic pain by assessing gene expression profiles in an animal model of neuropathic pain, and differential gene expression in patients to determine the potential translatability. We demonstrated cross-species validation of several genes including those identified through bioinformatic analysis by assessing their expression in blood samples from neuropathic pain patients, according to conservative assessments of significance measured using Bonferroni-corrected p-values. These include CASP5 (p = 0.00226), CASP8 (p = 0.00587), CASP9 (p = 2.09 × 10^-9), FPR2 (p = 0.00278), SH3BGRL3 (p = 0.00633), and TMEM88 (p = 0.00038). A ROC analysis revealed several combinations of genes to show high levels of discriminatory power in the comparison of neuropathic pain patients and control participants, of which the combination SH3BGRL3, TMEM88, and CASP9 achieved the highest level (AUROC = 0.923). The CASP9 gene was found to be common in five combinations of three genes revealing the highest levels of discriminatory power. In contrast, the gene combination PLAC8, ROMO1, and A3GALT2 showed the highest levels of discriminatory power in the comparison of neuropathic pain and nociceptive pain (AUROC = 0.919), when patients were grouped by S-LANSS scores. Molecules that demonstrate an active role in neuropathic pain have the potential to be developed into a biological measure for objective diagnostic tests, or as novel drug targets for improved pain management.

CDC Clinical Practice Guideline for Prescribing Opioids for Pain - United States, 2022

This guideline provides recommendations for clinicians providing pain care, including those prescribing opioids, for outpatients aged ≥18 years. It updates the CDC Guideline for Prescribing Opioids for Chronic Pain - United States, 2016 (MMWR Recomm Rep 2016;65[No. RR-1]:1-49) and includes recommendations for managing acute (duration of <1 month), subacute (duration of 1-3 months), and chronic (duration of >3 months) pain. The recommendations do not apply to pain related to sickle cell disease or cancer or to patients receiving palliative or end-of-life care. The guideline addresses the following four areas: 1) determining whether or not to initiate opioids for pain, 2) selecting opioids and determining opioid dosages, 3) deciding duration of initial opioid prescription and conducting follow-up, and 4) assessing risk and addressing potential harms of opioid use. CDC developed the guideline using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework. Recommendations are based on systematic reviews of the scientific evidence and reflect considerations of benefits and harms, patient and clinician values and preferences, and resource allocation. CDC obtained input from the Board of Scientific Counselors of the National Center for Injury Prevention and Control (a federally chartered advisory committee), the public, and peer reviewers. CDC recommends that persons with pain receive appropriate pain treatment, with careful consideration of the benefits and risks of all treatment options in the context of the patient's circumstances. Recommendations should not be applied as inflexible standards of care across patient populations. This clinical practice guideline is intended to improve communication between clinicians and patients about the benefits and risks of pain treatments, including opioid therapy; improve the effectiveness and safety of pain treatment; mitigate pain; improve function and quality of life for patients with pain; and reduce risks associated with opioid pain therapy, including opioid use disorder, overdose, and death.

Effect of Physiotherapeutic Interventions on Biomarkers of Neuropathic Pain: A Systematic Review of Preclinical Literature

The purpose of this systematic review was to evaluate the effects of physiotherapeutic interventions on biomarkers of neuropathic pain in preclinical models of peripheral neuropathic pain (PNP). The search was performed in Pubmed, Web of Science, EMBASE, Cochrane, Cinhal, Psycinfo, Scopus, Medline, and Science Direct. Studies evaluating any type of physiotherapy intervention for PNP (systemic or traumatic) were included. Eighty-one articles were included in this review. The most common PNP model was chronic constriction injury, and the most frequently studied biomarkers were related to neuro-immune processes. Exercise therapy and Electro-acupuncture were the 2 most frequently studied physiotherapy interventions while acupuncture and joint mobilization were less frequently examined. Most physiotherapeutic interventions modulated the expression of biomarkers related to neuropathic pain. Whereas the results seem promising; they have to be considered with caution due to the high risk of bias of included studies and high heterogeneity of the type and anatomical localization of biomarkers reported. The review protocol is registered on PROSPERO (CRD42019142878). PERSPECTIVE: This article presents the current evidence about physiotherapeutic interventions on biomarkers of neuropathic pain in preclinical models of peripheral neuropathic pain. Existing findings are reviewed, and relevant data are provided on the effectiveness of each physiotherapeutic modality, as well as its certainty of evidence and clinical applicability.

Intravenous Lidocaine for Treatment of Chronic Pain: A Retrospective Cohort Study

Introduction

Neuropathic pain is a widespread problem with a big impact on quality of life. The currently used drug regimens are often insufficiently effective or cause - sometimes unacceptable - side effects. Intravenous lidocaine could be an alternative treatment, by blocking spontaneous depolarization and hyperexcitability in upregulated sodium channels in nociceptors. Research so far has shown varying results but the treatment protocols differed a lot and follow-up was usually short. In our hospital, lidocaine infusions have been applied for many years in a unique treatment protocol consisting of a relatively high dose of lidocaine (1000 mg) administered over 25 hours. Our aim is to share information on both the efficacy and safety of this treatment schedule.

Methods

We conducted a retrospective cohort study in all patients who received a lidocaine infusion between January 2014 and January 2018. The standard infusion protocol consists of a total of 1000 mg lidocaine administered intravenously during 25 hours (40 mg/hour). Pain diagnoses were stratified into 15 groups, in agreement with diagnoses used in daily practice. Effectiveness of the treatment was classified as effect or no effect based on the description found in the chart.

Results

We included 282 patients, with a median age of 58 years and 64% of whom were female. Patients with myofascial pain syndrome, peripheral (mono)neuropathy, small fiber neuropathy and vascular disease benefited most. Patients with cancer pain, postherpetic neuralgia, chemotherapy-induced neuropathy and radicular pain showed the least pain improvement. There were no serious adverse events.

Conclusion

In selected patients, lidocaine infusions may be a safe and efficacious treatment for chronic neuropathic pain. More prospective research is needed to further determine the optimal dosing, duration and interval of lidocaine infusion therapy, and to better understand in which specific patient categories this treatment is most beneficial.

Managing Chronic Neuropathic Pain: Recent Advances and New Challenges

Aim. Neuropathic pain affects 7–10% of the population, with most of the patients receiving inadequate and incomplete treatment. Owing to the high financial burden and the poor quality of life of the patients and their caretakers, there is a dire need to address the challenges in diagnosing and treating chronic neuropathic pain. Methods. This literature review was conducted to review novel treatments and related challenges through a systematic search from sources such as PubMed, Google Scholar with the combination of MESH words such as neuropathic pain, management of neuropathic pain. Articles from non-English literature, reports without human subjects, animal studies, and abstracts/posters were excluded. However, human studies and studies published in English were included. Result. This review article discusses novel treatment modalities while acknowledging the challenges medical workers face while encountering neuropathic pain. Despite the recent advances in diagnosis and treatment modalities, several challenges still exist. Hence, there is still a need to explore the various treatment modalities, emphasizing the cause and underlying pathophysiology of neuropathic pain. Conclusion. We recommend integrated multimodal treatment with the current treatment facility, including various medical disciplines. However, a personalized approach would work the best depending on the ’patient’s medical history. Therefore, this article recommends an integrated, cause-specific, cost-effective approach to address this problem of chronic neuropathic pain.

Acceptance of chronic pain in depressed patients with HIV: correlations with activity, functioning, and emotional distress

Chronic pain is highly prevalent among persons with HIV (PWH), as is depression. Both comorbidities might contribute to, as well as be maintained by, avoidance-based coping. A promising alternative to avoidance-based coping is acceptance. Acceptance of pain is associated with improved functioning and quality of life in chronic pain patients, but this relationship has not been substantially explored among PWH. Cross-sectional data from 187 adult outpatients enrolled in a randomized trial for depressed PWH with chronic pain were analyzed. Controlling for pain severity and demographics, the relationships among pain acceptance and indicators of activity, functioning, and emotional distress (i.e., anxiety and anger) were assessed in seven regression models. No significant relationships were found between self-reported physical activity or objective measurement of mean steps/day with pain acceptance. Results revealed an inverse relationship between chronic pain acceptance and pain-related functional interference (by.x = -.52, p < .01) and a positive relationship with self-reported functioning (by.x = 7.80, p < .01). A significant inverse relationship with anxiety symptoms (by.x = -1.79, p < .01) and pain acceptance was also found. Acceptance of chronic pain can facilitate decreased emotional distress, improved well-being, and better functioning and quality of life. Further investigation of chronic pain acceptance among PWH could inform the development of acceptance-based interventions.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Botulinum toxin A for management of refractory concurrent buccal and inferior alveolar nerve post-traumatic neuropathies: a case report

Painful post-traumatic trigeminal neuropathy (PPTTN) can result from iatrogenic injury to one or more branches of the trigeminal nerve during oral surgical procedures such as tooth extractions. Like other chronic neuropathic pain conditions, PPTTN can significantly alter the patient’s quality of life, especially when pharmacological treatment is ineffective or not tolerated. As such, new treatment options have been investigated, including local injections of botulinum toxin type A (BTX-A). A 29-year-old woman presented to our tertiary orofacial pain clinic for evaluation of chronic electric shock-like pain attacks and severe allodynia in the territory of the right inferior alveolar nerve and buccal nerve following right mandibular third molar extraction 3 years prior. Following several failed attempts at classic pharmacological management (including carbamazepine, venlafaxine, duloxetine, pregabalin, clonazepam, and amitriptyline), BTX-A injections were administered in the vicinity of the right mental nerve. This treatment provided significant improvement in the patient’s condition and overall quality of life with no significant adverse effects. Because both neuropathies were significantly improved by remote BTX-A injections, this case report provides preliminary clinical evidence supporting spinopetal transport of BTX-A, as shown in animal models, as an underlying pathophysiological mechanism of BTX-A-mediated analgesia.

Neuropathic Pain Relief after Surgical Neurolysis in Patients with Traumatic Brachial Plexus Injuries: A Preliminary Report

Objective

To evaluate the usefulness of surgical neurolysis for neuropathic pain relief in patients with posttraumatic brachial plexus injury (BPI).

Methods

A prospective, longitudinal, nonrandomized, self-controlled before and after study was performed to evaluate the pain changes according to their intensity using the Visual Analogue Scale (VAS), and the sensory recovery after surgery using the British Medical Research Council (BMRC) scale for sensory recovery. To establish significant changes, a paired T-test was performed, and in order to determine the magnitude of these changes, an effect size was measured. α = 0.05.

Results

Ten patients were included with an average follow-up of 61.9 ± 53.62 months. The main mechanism of injury was vehicular trauma (70%). A significant decrease in pain after the surgical intervention was observed resulting from an average preoperative state according to VAS of 8.4 ± 1.58, to a postoperative state of 3.4 ± 3.27 (59.52%, p = 0.005, Δ = 1.572), added to a mean sensory improvement (25%) from 2.8 ± 1.62 to 3.5 ± 0.97 after surgery according to BMRC, without statistically significant changes (p=0.062), showing a moderate effect size (Δ = 0.413). Almost all patients showed improvement in the continuous and paroxysmal pattern of pain. No postoperative complications were observed. Discussion. These results suggest that in cases of BPI that originates from a compressive syndrome secondary to the posttraumatic fibrosis that surrounds the nerve structures causing strangulation and inducing hypernociception, the use of surgical neurolysis is an appropriate alternative for patients with medically refractory neuropathic pain.

Highly Parallelized, Multicolor Optogenetic Recordings of Cellular Activity for Therapeutic Discovery Applications in Ion Channels and Disease-Associated Excitable Cells

Optogenetic assays provide a flexible, scalable, and information rich approach to probe compound effects for ion channel drug targets in both heterologous expression systems and associated disease relevant cell types. Despite the potential utility and growing adoption of optogenetics, there remains a critical need for compatible platform technologies with the speed, sensitivity, and throughput to enable their application to broader drug screening applications. To address this challenge, we developed the SwarmTM, a custom designed optical instrument for highly parallelized, multicolor measurements in excitable cells, simultaneously recording changes in voltage and calcium activities at high temporal resolution under optical stimulation. The compact design featuring high power LEDs, large numerical aperture optics, and fast photodiode detection enables all-optical individual well readout of 24-wells simultaneously from multi-well plates while maintaining sufficient temporal resolution to probe millisecond response dynamics. The Swarm delivers variable intensity blue-light optogenetic stimulation to enable membrane depolarization and red or lime-light excitation to enable fluorescence detection of the resulting changes in membrane potential or calcium levels, respectively. The Swarm can screen ~10,000 wells/day in 384-well format, probing complex pharmacological interactions via a wide array of stimulation protocols. To evaluate the Swarm screening system, we optimized a series of heterologous optogenetic spiking HEK293 cell assays for several voltage-gated sodium channel subtypes including Nav1.2, Nav1.5, and Nav1.7. The Swarm was able to record pseudo-action potentials stably across all 24 objectives and provided pharmacological characterization of diverse sodium channel blockers. We performed a Nav1.7 screen of 200,000 small molecules in a 384-well plate format with all 560 plates reaching a Z' > 0.5. As a demonstration of the versatility of the Swarm, we also developed an assay measuring cardiac action potential and calcium waveform properties simultaneously under paced conditions using human induced pluripotent stem (iPS) cell-derived cardiomyocytes as an additional counter screen for cardiac toxicity. In summary, the Swarm is a novel high-throughput all-optical system capable of collecting information-dense data from optogenetic assays in both heterologous and iPS cell-derived models, which can be leveraged to drive diverse therapeutic discovery programs for nervous system disorders and other disease areas involving excitable cells.

Prevalence and treatment of neuropathic pain diagnoses among U.S. nursing home residents

ABSTRACT

Neuropathic pain is a common condition experienced by older adults. Prevalence estimates of neuropathic pain and descriptive data of pharmacologic management among nursing home residents are unavailable. We estimated the prevalence of neuropathic pain diagnoses and described the use of pain medications among nursing home residents with possible neuropathic pain. Using the Minimum Data Set 3.0 linked to Medicare claims for residents living in a nursing home on November 30, 2016, we included 473,815 residents. ICD-10 codes were used to identify neuropathic pain diagnoses. Identification of prescription analgesics/adjuvants was based on claims for the supply of medications that overlapped with the index date over a 3-month look-back period. The prevalence of neuropathic pain was 14.6%. Among those with neuropathic pain, 19.7% had diabetic neuropathy, 27.3% had back and neck pain with neuropathic involvement, and 25.1% had hereditary or idiopathic neuropathy. Among residents with neuropathic pain, 49.9% received anticonvulsants, 28.6% received antidepressants, 19.0% received opioids, and 28.2% had no claims for analgesics or adjuvants. Resident characteristics associated with lack of medications included advanced age, dependency in activities of daily living, cognitive impairment, and diagnoses of comorbid conditions. A diagnosis of neuropathic pain is common among nursing home residents, yet many lack pharmacologic treatment for their pain. Future epidemiologic studies can help develop a more standard approach to identifying and managing neuropathic pain among nursing home residents.

A nerve injury-specific long noncoding RNA promotes neuropathic pain by increasing Ccl2 expression

Maladaptive changes of nerve injury-associated genes in dorsal root ganglia (DRGs) are critical for neuropathic pain genesis. Emerging evidence supports the role of long noncoding RNAs (lncRNAs) in regulating gene transcription. Here we identified a conserved lncRNA, named nerve injury-specific lncRNA (NIS-lncRNA) for its upregulation in injured DRGs exclusively in response to nerve injury. This upregulation was triggered by nerve injury-induced increase in DRG ELF1, a transcription factor that bound to the NIS-lncRNA promoter. Blocking this upregulation attenuated nerve injury-induced CCL2 increase in injured DRGs and nociceptive hypersensitivity during the development and maintenance periods of neuropathic pain. Mimicking NIS-lncRNA upregulation elevated CCL2 expression, increased CCL2-mediated excitability in DRG neurons, and produced neuropathic pain symptoms. Mechanistically, NIS-lncRNA recruited more binding of the RNA-interacting protein FUS to the Ccl2 promoter and augmented Ccl2 transcription in injured DRGs. Thus, NIS-lncRNA participates in neuropathic pain likely by promoting FUS-triggered DRG Ccl2 expression and may be a potential target in neuropathic pain management.

Neuroimmune Mechanisms Underlying Neuropathic Pain: The Potential Role of TNF-α-Necroptosis Pathway

The neuroimmune mechanism underlying neuropathic pain has been extensively studied. Tumor necrosis factor-alpha (TNF-α), a key pro-inflammatory cytokine that drives cytokine storm and stimulates a cascade of other cytokines in pain-related pathways, induces and modulates neuropathic pain by facilitating peripheral (primary afferents) and central (spinal cord) sensitization. Functionally, TNF-α controls the balance between cell survival and death by inducing an inflammatory response and two programmed cell death mechanisms (apoptosis and necroptosis). Necroptosis, a novel form of programmed cell death, is receiving increasing attraction and may trigger neuroinflammation to promote neuropathic pain. Chronic pain is often accompanied by adverse pain-associated emotional reactions and cognitive disorders. Overproduction of TNF-α in supraspinal structures such as the anterior cingulate cortex (ACC) and hippocampus plays an important role in pain-associated emotional disorders and memory deficits and also participates in the modulation of pain transduction. At present, studies reporting on the role of the TNF-α–necroptosis pathway in pain-related disorders are lacking. This review indicates the important research prospects of this pathway in pain modulation based on its role in anxiety, depression and memory deficits associated with other neurodegenerative diseases. In addition, we have summarized studies related to the underlying mechanisms of neuropathic pain mediated by TNF-α and discussed the role of the TNF-α–necroptosis pathway in detail, which may represent an avenue for future therapeutic intervention.

The Effect of Preoperative Neuropathic Pain and Nociceptive Pain on Postoperative Pain Intensity in Patients with the Lumbar Degenerative Disease Following Lateral Lumbar Interbody Fusion

OBJECTIVE

The purpose of this study was to analyze whether the type of preoperative pain affects the improvement in postoperative pain intensity in patients with a lumbar degenerative disease (LDD).

METHODS

We retrospectively reviewed 93 patients who underwent lateral lumbar interbody fusion (LLIF) without direct decompression. All patients were evaluated using Numeric Rating Scale (NRS) scores for low back pain (NRS_LBP), leg pain (NRS_LP), and leg numbness (NRS_LN) and imaging data before and after LLIF surgery. Based on the Japanese version of the painDETECT scores, patients were classified into 3 groups: a neuropathic pain (NeP) group, a nociceptive pain (NocP) group, and an intermediate mixed pain group.

RESULTS

The Japanese version of the painDETECT identified NeP in 20.4% of patients with LDD prior to LLIF. Preoperative NRS_LBP, NRS_LP, and NRS_LN scores were higher in the NeP group than those in the NocP group. All types of pain improved after LLIF surgery. The NRS_LBP score 12 months after surgery was higher in the NeP group (3.8 ± 2.8) than that in the NocP group (1.9 ± 2.2) (P = 0.008). Similar results were obtained with NRS_LP (NeP group = 3.1 ± 2.8, NocP group = 1.5 ± 2.0, P = 0.010).

CONCLUSIONS

Although LLIF was useful for relieving all types of preoperative pain in LDD patients, the NRS scores for preoperative pain were higher in the NeP group than those in the NocP group, and the postoperative NRS_LBP and NRS_LP score was significantly higher in the NeP group. Thus, controlling preoperative NeP may improve therapeutic efficacy.

Central Neuropathic Pain Syndromes: Current and Emerging Pharmacological Strategies

Central neuropathic pain is caused by a disease or lesion of the brain or spinal cord. It is difficult to predict which patients will develop central pain syndromes after a central nervous system injury, but depending on the etiology, lifetime prevalence may be greater than 50%. The resulting pain is often highly distressing and difficult to treat, with no specific treatment guidelines currently available. This narrative review discusses mechanisms contributing to central neuropathic pain, and focuses on pharmacological approaches for managing common central neuropathic pain conditions such as central post-stroke pain, spinal cord injury-related pain, and multiple sclerosis-related neuropathic pain. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids have some evidence for efficacy in central neuropathic pain. Medications from other pharmacologic classes may also provide pain relief, but current evidence is limited. Certain non-pharmacologic approaches, neuromodulation in particular, may be helpful in refractory cases. Emerging data suggest that modulating the primary afferent input may open new horizons for the treatment of central neuropathic pain. For most patients, effective treatment will likely require a multimodal therapy approach.

Evaluation of in vitro transdermal permeation, mass spectrometric imaging, and in vivo analgesic effects of pregabalin using a pluronic lecithin organogel formulation in mice

In clinical practice, pregabalin is orally administered for neuropathic pain, but causes severe central nervous system side effects, such as dizziness, which results in dose limitation or discontinuation. To reduce the central side effects of pregabalin, we developed four pregabalin preparations for transdermal application: 0.4% aqueous solution, pluronic lecithin organogel (PLO gel), hydrophilic cream, and lipophilic cream. Transdermal permeabilities of pregabalin among the four formulations were compared in vitro using hairless mouse skin. The longitudinal distribution of pregabalin within the skin was analyzed using mass spectrometric (MS) imaging. Furthermore, the in vivo analgesic effects of the formulations were evaluated using the von Frey filament test in a mouse model of diabetic neuropathy (DN). The PLO gel showed the highest permeability of pregabalin, followed by the aqueous solution, and no permeation was observed in the two cream formulations. The MS imaging analysis showed that pregabalin was distributed up to the dermis in the PLO gel 1 h after application, while the aqueous solution was distributed near the epidermis. A significant analgesic effect (p < .05) was observed 1.5 h after PLO gel application in the DN model mice, but the aqueous solution had no effect. This study indicated for the first time that pregabalin penetrated beyond the skin epidermis up to the dermis, from the PLO gel formulation, and that the application of this formulation exhibited an in vivo analgesic effect in the mouse model of DN.

Characteristics of Persons Seeking Care for Moderate to Severe Pain Due to Chronic Low Back Pain and Osteoarthritis: A Cross-Sectional Study

Purpose

To assess the associations between pain severity or physical (pQoL) and mental (mQoL) health-related quality of life and disability status or health-care utilization among persons living with moderate/severe pain due to chronic low back pain (CLBP) or osteoarthritis (OA), who received treatments in Quebec’s tertiary care pain centers.

Materials and Methods

This retrospective study was carried out using the Quebec Pain Registry (Canada) from 2008 to 2014 and contains data on persons referred to tertiary pain management clinics. Participants were selected if they were diagnosed with CLBP (N = 2663) or OA (N = 139) of more than 3 months duration and of pain intensity ≥5 on the Numeric Rating Scale (0–10) and completed baseline questionnaires.

Results

Less than 5% of persons were hospitalized in the 6 months before their first visit at the pain clinic, and 11.9% and 18.9% of persons with OA and CLBP, respectively, had a pain-related emergency room (ER) visit. Less than 1/5 and more than 1/4 of persons with OA and CLBP were receiving disability benefits, respectively. Persons with CLBP who had visited the ER, those on disability and those receiving disability benefits, reported higher levels of pain severity, interference, and lower levels of mQoL (and pQoL for those on disability or receiving benefits) compared to those who did not consult the ER, those not on disability or not receiving disability benefits, respectively (all p < 0.05). For OA, disability status was the only variable associated with pain interference and QoL (all p < 0.05).

Conclusion

Pain severity, pain interference and mQoL were associated with health-care utilization and disability status in persons with CLBP. These results were globally not found among persons with OA, which might be due to smaller sample size or unique characteristics of this population.

Neuropathic pain after spinal intradural benign tumor surgery: an underestimated complication?

Neuropathic pain presents a burdening and impairing condition which may occasionally occur after spinal tumor surgery. While it has been described in peripheral nerve sheath tumors, data on other intradural tumor patients is sparse. We hereby present a large cohort population undergoing different intradural spinal tumor surgery with assessment of early postoperative and follow-up outcomes, focusing on the occurrence of neuropathic pain. We performed a retrospective monocentric study including all patients treated for intradural spinal tumors between 2009 and 2020. We extracted surgical aspects as well as pre- and postoperative clinical courses from the records. Statistical analysis of potential contributing prognostic factors was performed including matched pair analysis. In total, 360 patients were included for analysis. At a median follow-up of 2 years, 26/360 patients complained of a neuropathic pain syndrome (7.2%) requiring continuous medication. Of these patients only 50% complained preoperatively of pain. Tumor entity did not significantly influence the incidence of postoperative neuropathic pain (p = 0.91). Sacrifice of the tumor carrying nerve root and tumor recurrence also did not increase the risk for this condition. Persistent neuropathic pain requiring continuous treatment occurred in 7.2% of patients undergoing intradural spinal surgery in our cohort. This frequently underestimated postoperative adverse event represents a disabling condition leading to a substantial impairment in the quality of life among the affected patients.

Targeting Chemokines and Chemokine GPCRs to Enhance Strong Opioid Efficacy in Neuropathic Pain

Neuropathic pain (NP) originates from an injury or disease of the somatosensory nervous system. This heterogeneous origin and the possible association with other pathologies make the management of NP a real challenge. To date, there are no satisfactory treatments for this type of chronic pain. Even strong opioids, the gold-standard analgesics for nociceptive and cancer pain, display low efficacy and the paradoxical ability to exacerbate pain sensitivity in NP patients. Mounting evidence suggests that chemokine upregulation may be a common mechanism driving NP pathophysiology and chronic opioid use-related consequences (analgesic tolerance and hyperalgesia). Here, we first review preclinical studies on the role of chemokines and chemokine receptors in the development and maintenance of NP. Second, we examine the change in chemokine expression following chronic opioid use and the crosstalk between chemokine and opioid receptors. Then, we examine the effects of inhibiting specific chemokines or chemokine receptors as a strategy to increase opioid efficacy in NP. We conclude that strong opioids, along with drugs that block specific chemokine/chemokine receptor axis, might be the right compromise for a favorable risk/benefit ratio in NP management.

Tracking the Temporal Footprint Effect of Thermonociception and Denervation on the Brain’s Pain Matrix: fMRI and BOLD Study in Rats

Objective

Pain constitutes an essential alarm for preserving the organism’s integrity. Damage to the nervous system produces a pathological condition known as neuropathic pain.

Purpose

Blood oxygenation level-dependent (BOLD) and functional magnetic resonance imaging (fMRI) have been widely used to map neuroanatomy and the active regions of interest (ROI) of nociceptive processing. Our study explored the brain’s BOLD response in rats after thermal noxious stimulation, immediately after sciatic nerve damage and during 75 minutes after surgical lesion of the sciatic nerve.

Methods

Nine male Wistar rats were tested; the experiments were performed on a 7-Tesla /21-cm Varian Agilent system. This approach allowed, for the first time, to measure in vivo the BOLD changes in brain regions involved with the pain process: cingulated (ACC), somatosensory (S1), and insular cortices (IC), as well as thalamus (Th) and ventral tegmental area (VTA) related with acute thermal pain and during the early stages of sciatic denervation that produce neuropathic pain.

Results

During thermonociception scan, all subjects showed BOLD activation in the ROIs determined as ACC, S1, Th, IC and VTA. After denervation, these regions continued to show activation with a slow decrement in intensity for the duration of the experiment. The results suggest that these brain structures are overactive during the genesis of neuropathic pain.

Conclusion

The study shows for the first time continuous activation of the pain matrix following an acute thermal nociceptive stimulus followed by neuropathic damage. These results have given insight into the early stages of the development of neuropathic pain in vivo.

Cross-Sectional Evaluation of the Economic Burden on Patients Seeking Surgical Treatment for Chronic Nerve Injuries

INTRODUCTION

Little emphasis has been paid toward characterizing the socioeconomic burdens experienced by patients seeking treatment for chronic nerve injuries. The aim of this study was to characterize the direct and indirect costs faced by patients with chronic nerve injuries and their attendant health care utilization.

MATERIALS AND METHODS

A cross-sectional survey was distributed to all patients (N = 767) from a single nerve surgeon's practice treated for chronic nerve injuries in the ambulatory setting between 2014 and 2020. Data collected included demographics, etiology, comorbidities, duration and severity of symptoms, history of prior medical and interventional treatments, work or school time lost due to injury or treatment, money spent on treatment, and health care utilization.

RESULTS

Of the 767 patients, 209 (27.2%) completed the survey. Average age was 48.8 (SD = 19.1) years, 68.9% female and 31.1% male. Patients with chronic nerve injury reported significant direct costs, indirect costs, and health care utilization associated with their nerve injury symptoms. Direct costs consisted of out-of-pocket spending (68.4% had spent >$1000 per year), physician specialists visits (71.3% had seen at least 4 specialists), and prior interventional procedures intended to address symptoms. Indirect costs included lost time from work or school (24.6% had missed more than 12 months). Health care utilization, represented by annual emergency room visits and hospitalizations related to nerve symptoms, was increased relative to the general population. Detailed statistics are presented in the manuscript.

CONCLUSIONS

Chronic nerve injuries may be associated with a notable socioeconomic burden to the patient, including missed work or school, frequent physician visits and procedures, hospital visits, and out-of-pocket costs. Interdisciplinary algorithms recognizing a role for surgical evaluation in patients with chronic neuropathic pain due to underlying nerve injuries would facilitate future research into whether timely surgical intervention may reduce this economic burden.

Cost-utility analysis of transcranial direct current stimulation therapy with and without virtual illusion for neuropathic pain for adults with spinal cord injury in Canada

OBJECTIVE

To undertake a cost-utility analysis comparing virtual illusion (VI) and transcranial direct current stimulation (tDCS) combination therapy, tDCS alone and standard pharmacological care in Ontario, Canada from a societal perspective over a three-month time horizon.

DESIGN

Cost-utility analysis using Markov model methods.

SETTING

Community setting in Ontario, Canada.

PARTICIPANTS

Individuals with spinal cord injury and neuropathic pain (NP) resistant to pharmacological therapy.

INTERVENTIONS

Virtual illusion and transcranial direct current stimulation, transcranial direct current stimulation alone and standard pharmacological therapy.

OUTCOME MEASURES

Incremental costs, quality adjusted life years (QALY) and incremental cost effectiveness ratio.

RESULTS

The incremental cost effectiveness ratio of VI and tDCS therapy cost is $3,396 per QALY (2020 Canadian dollars) when compared to standard care. The incremental cost per QALY of tDCS therapy alone is $33,167. VI and tDCS therapy had lower incremental costs (-$519) and higher incremental QALYs (0.026) compared to tDCS alone. From a public healthcare payer perspective, there is a 74% probability that VI and tDCS therapy and 54% probability that tDCS alone would be cost effective at a $50,000 per QALY willingness-to-pay threshold. Our findings remained relatively robust in various scenario analyses.

CONCLUSION

Our findings suggest that at three-months after therapy, VI and tDCS combination therapy may be more cost effective than tDCS therapy alone. Based on conventional health technology funding thresholds, VI and tDCS combination therapy merits consideration for the treatment of NP in adults with spinal cord injuries.