The Prevalence and Impact of Chronic Pain with Neuropathic Pain Symptoms in the General Population

The efficacy of attentional distraction and sensory monitoring in chronic pain patients: A meta-analysis

Attentional strategies, such as distraction and sensory monitoring, are often offered to reduce pain and pain-related distress. However, evidence for their efficacy in chronic pain patients is equivocal. We report a meta-analysis on the efficacy of distraction and sensory monitoring in chronic pain patients, and explore possible methodological and theoretical moderators. The scientific literature was searched for relevant articles, which were coded for methodological quality and several theoretical and methodological moderator variables. Only 10 articles fulfilled the search criteria. Eight studies allowed us to compare distraction with a control condition, two studies to compare sensory monitoring with a control condition, and four studies to compare the effect of distraction with the effect of sensory monitoring. Overall, results indicate that distraction did not differ from control in altering pain experience (k=8; Hedges' g=0.10, ns) and distress (k=2; Hedges' g=0.549). Sensory monitoring did also not alter pain experience (k=2; Hedges' g=-0.21, ns) and distress (k=1; Hedges' g=-0.191, ns). We found no evidence to support the superiority of distraction or sensory monitoring in altering pain compared to control conditions. We offer guidance for future theory-driven research to investigate distraction and sensory monitoring in this largely unexplored field, albeit one replete with methodological difficulties.

Antinociception induced by a novel α2A adrenergic receptor agonist in rodents acute and chronic pain models

The mechanisms and antinociceptive effects of a novel α_2A adrenoceptor agonist, 3-(2-chloro-6-fluorobenzil)-imidazolinide-2,4-dione (PT-31) were investigated using animal models of acute and chronic pain. The effects of PT-31 on pain responses were examined using hot plate and formalin tests in mice and spinal nerve ligation (SNL)-induced hyperalgesia in rats. The effects of antagonists acting on α adrenoceptor were assessed to investigate the interaction of these pathways upon PT-31 induced antinociception. PT-31 effects on motor activity/skills and on hemodynamic parameters were also evaluated. PT-31 had dose-dependent antinociception effects on hot-plate and formalin-injection induced pain responses. Thermal hyperalgesia and mechanical allodynia were reduced following a 7 d treatment with PT-31 (1, 5, and 10mg/kg/d, p.o.), and those effects were attenuated by yohimbine (5mg/kg), atropine (2mg/kg), L-nitro arginine methyl ester (L-NAME; 30mg/kg), or naloxone (2mg/kg). In contrast to clonidine, PT-31 did not have locomotor or hemodynamic effects in rats. The present results suggest that PT-31 represents a candidate for pain treatment with advantages over clonidine, namely no locomotor or hemodynamic impairments.

Promoted Interaction of C/EBPα with Demethylated Cxcr3 Gene Promoter Contributes to Neuropathic Pain in Mice

DNA methylation has been implicated in the pathogenesis of chronic pain. However, the specific genes regulated by DNA methylation under neuropathic pain condition remain largely unknown. Here we investigated how chemokine receptor CXCR3 is regulated by DNA methylation and how it contributes to neuropathic pain induced by spinal nerve ligation (SNL) in mice. SNL increased Cxcr3 mRNA and protein expression in the neurons of the spinal cord. Meanwhile, the CpG (5'-cytosine-phosphate-guanine-3') island in the Cxcr3 gene promoter region was demethylated, and the expression of DNA methyltransferase 3b (DNMT3b) was decreased. SNL also increased the binding of CCAAT (cytidine-cytidine-adenosine-adenosine-thymidine)/enhancer binding protein α (C/EBPα) with Cxcr3 promoter and decreased the binding of DNMT3b with Cxcr3 promoter in the spinal cord. C/EBPα expression was increased in spinal neurons after SNL, and inhibition of C/EBPα by intrathecal small interfering RNA attenuated SNL-induced pain hypersensitivity and reduced Cxcr3 expression. Furthermore, SNL-induced mechanical allodynia and heat hyperalgesia were markedly reduced in Cxcr3^-/- mice. Spinal inhibition of Cxcr3 by shRNA or CXCR3 antagonist also attenuated established neuropathic pain. Moreover, CXCL10, the ligand of CXCR3, was increased in spinal neurons and astrocytes after SNL. Superfusing spinal cord slices with CXCL10 enhanced spontaneous EPSCs and potentiated NMDA-induced and AMPA-induced currents of lamina II neurons. Finally, intrathecal injection of CXCL10 induced CXCR3-dependent pain hypersensitivity in naive mice. Collectively, our results demonstrated that CXCR3, increased by DNA demethylation and the enhanced interaction with C/EBPα, can be activated by CXCL10 to facilitate excitatory synaptic transmission and contribute to the maintenance of neuropathic pain.

SIGNIFICANCE STATEMENT

Peripheral nerve injury induces changes of gene expression in the spinal cord that may contribute to the pathogenesis of neuropathic pain. CXCR3 is a chemokine receptor. Whether it is involved in neuropathic pain and how it is regulated after nerve injury remain largely unknown. Our study demonstrates that spinal nerve ligation downregulates the expression of DNMT3b, which may cause demethylation of Cxcr3 gene promoter and facilitate the binding of CCAAT/enhancer binding protein α with Cxcr3 promoter and further increase CXCR3 expression in spinal neurons. The upregulated CXCR3 may contribute to neuropathic pain by facilitating central sensitization. Our study reveals an epigenetic mechanism underlying CXCR3 expression and also suggests that targeting the expression or activation of CXCR3 signaling may offer new therapeutics for neuropathic pain.

The suffering of chronic pain patients on a wait list: Are they amenable to narrative therapy?

Background: Chronic pain affects one in five Canadians. People with chronic pain frequently experience loss in their lives related to work, relationships, and their independence. They may be referred to a chronic pain program, which aims to strengthen coping through medical intervention and self-management skills. Data suggest that, even when individuals begin their pain program, many feel overwhelmed and do not continue.

Aims: The aim of this study was to conduct a needs assessment to explore the acceptability and feasibility of developing a psychosocial intervention, narrative therapy (NT), to address loss for chronic pain patients on the wait list of a chronic pain program.

Methods: Two focus groups were conducted with ten patients who had experienced being on a wait list for a provincial chronic pain management program (CPMP). Transcribed interviews were subjected to thematic and interpretive analysis.

Results: Two major themes emerged from the analysis: loss of identity and sharing a story of chronic pain. All patients were enthusiastic toward an NT intervention, although individual preferences differed regarding mode of delivery.

Conclusions: Loss is a significant part of the chronic pain experience. NT seems to be an acceptable intervention to address loss for patients on the wait list for a chronic pain program.

Identification of Key Gene Modules of Neuropathic Pain by Co-Expression Analysis

Neuropathic pain (NP) is a substantial clinical problem causing great injury to people word-widely. Although gene expression analyses had been performed previously, the mechanisms underlying the etiology and development of NP are still poorly understood. To understand the function genes involved in the etiology and development of NP, we built the co-expression modules and performed function enrichment analysis for neuropathic pain. In the present study, from a public microarray data set (GSE69901) from NCBI, gene co-expression modules were contributed with the help of WGCNA for 12 neuropathic pain samples and 13 control samples, respectively. And functional enrichment analyses were followed by DAVID database. Firstly, we established 21 co-expression modules and 19 co-expression modules out of 5,000 high-express genes in NP and control samples, respectively. Then, it showed great difference in interaction relationships of total genes and hub-genes between pairwise modules, which indicated the high confidence of gene co-expression modules. Finally, functional enrichment analysis of the top five co-expression modules in NP exhibited great differences and significant enrichment in transcription regulation of RNA polymerase II promoter and ubiquitin mediated proteolysis pathway. RNA polymerase II promoter and ubiquitin-mediated proteolysis pathway played important role in etiology and development of NP. Anyhow, our findings provided the framework of gene co-expression modules of NP and furthered the understanding of these modules from functional aspect. J. Cell. Biochem. 118: 4436-4443, 2017. © 2017 Wiley Periodicals, Inc.

Vitamin D (FokI) Receptor Gene Polymorphism is associated with Vitamin D Deficiency and Chronic Musculoskeletal Pain. A meta-analysis

Background: Musculoskeletal pain is the most common chronic pain experienced by older adults. The aim of this study is to explore the associations between vitamin D (FOKI) receptor gene polymorphism (VDR) and vitamin D deficiency (VDD) and chronic musculoskeletal pain. Methods: Cross-sectional studies published in English from January 2000 to January 2015which reported prevalence of chronic pain (CP) and chronic musculoskeletal pain (CMP) were included in this systematic review and meta-analysis. A heat map was used to visualize and observe the correlation between VDR and CMP, CP and VDD. Results: 20 studies (N = 216,365) were included in the analysis, which showed an overall pooled prevalence estimate of CMP and CP as 30.6 per 100 (95 % CI: 30.59, 30.69) and 27.9 per 100 (95 % CI: 27.68, 28.24) respectively. The heat map clustering analysis visualizes the similarity between CP and CMP. Moreover, a direct correlation was observed between the three disease conditions (namely CMP, CP, and VDD) and FokI VDR polymorphism (FF). Spearman's correlation analyses with adjusted r² revealed that there is a statistically significant interaction effect of the FF genotype and VDD on CMP (r² = 0.19, p = 0.03), a marginally significant interaction effect of the ff genotype and VDD on CMP (r² = 0.11, p = 0.08). VDD was also associated with increased CMP (r² = 0.19, p = 0.028). The pooled estimates of the prevalence of CMP in this review were found to be high. Conclusion: FokI VDR gene polymorphism (FF) plays an important role in the relationship between VDD and CMP.

Flow cytometry analysis of inflammatory cells isolated from the sciatic nerve and DRG after chronic constriction injury in mice

BACKGROUND

Cellular responses to nerve injury play a central role in the pathogenesis of neuropathic pain. However, the analysis of site specific cellular responses to nerve injury and neuropathic pain is limited to immunohistochemistry staining with numerous limitations.

NEW METHODS

We proposed to apply flow cytometry to overcome some of the limitations and developed two protocols for isolation of cells from small specimens of the sciatic nerve and dorsal root ganglion (DRG) in mice. RESULTS AND COMPARASION WITH EXISTING: methods We found that both the non-enzymatic and enzymatic approaches were highly effective in harvesting a sufficient number of cells for flow cytometry analysis in normal and pathological conditions. The total number of cells in the injury site of the sciatic and its DRGs increased significantly 14days after chronic constriction injury (CCI) of the sciatic nerve, compared to sham surgery control or the contralateral control. The enzymatic approach yielded a significantly higher total number of cells and CD45 negative cells, suggesting that this approach allows for harvest of more resident cells, compared to the non-enzymatic method. The percentage of CD45⁺/CD11b⁺ cells was significantly increased in the sciatic nerve but not in the DRG. These results were consistent with both protocols.

CONCLUSIONS

We thus offer two simple and effective protocols that allow for application of flow cytometry to the investigation of cellular and molecular mechanisms of neuropathic pain.

Neuropathic Pain Assessment with the PainDETECT Questionnaire: Cross-Cultural Adaptation and Psychometric Evaluation to Hindi

OBJECTIVE

The contribution of neuropathic pain (NeP) in chronic pain conditions is increasingly emphasized with the development of multiple questionnaire-based measurement scales. The painDETECT questionnaire (PDQ) is a frequently used self-reported outcome measure to assess NeP in patients with chronic pain conditions in research and regular clinical practice. The aim of the study was to translate and cross-culturally adapt the PDQ into Hindi (Hi-PDQ) for use in India and to investigate its psychometric properties.

METHODS

PainDETECT questionnaire translation into the Hindi language was carried out according to standard guidelines. Patients suffering from chronic pain attending a pain clinic were recruited. Patients completed the Hi-PDQ at baseline and were retested was conducted after 3 days Exploratory factor analysis (EFA) was carried out to assess the factor structure of the Hi-PDQ. Measurement properties, including floor and ceiling effects, discriminative validity, and psychometric properties, were also assessed.

RESULTS

A total of 160 patients with chronic pain were recruited, including 80 in each NeP and non-NeP group. The retest was completed in 82 patients. Mean Hi-PDQ scores were significantly higher in the NeP group compared with the non-NeP group (20.7 [SD 5.9] vs. 9.9 [SD 5.9]; P < 0.01). EFA revealed a 2-factor structure explaining 56.9% variance. The Hi-PDQ was found to have adequate internal consistency (Cronbach's alpha = 0.83), test-retest reliability (intraclass correlation coefficient = 0.94), and excellent discriminant validity (area under the curve = 0.88), with an optimal cutoff value of > 18 (sensitivity and specificity of 82.5% and 91.2%, respectively).

CONCLUSION

The PDQ was successfully translated into the Hindi language. The Hi-PDQ showed good discriminative validity and psychometric properties. The Hi-PDQ is a reliable instrument to assess NeP in chronic pain conditions.

Chronic Pain Features Relate to Quality of Life More than Physiopathology: A Cross-Sectional Evaluation in Pain Clinics

OBJECTIVE

To compare the impact of chronic pain physiopathology on health-related quality of life (HR-QoL), considering the influence of pain features and psychosocial adjustment (intensity, interference, psychological comorbidities, and sleep quality).

DESIGN

A cross-sectional study involving 1,025 noncancer patients with predominantly neuropathic, nociceptive, or mixed chronic pain conditions was conducted in 88 pain clinics within Spain. The EuroQol-5 Dimensions instrument (EQ-5D) was used to measure HR-QoL. The Brief Pain Inventory (BPI), Hospital Anxiety and Depression Scale (HADS), and sleep scale developed for the MOS study (MOS-SQ) were used to measure pain features and psychosocial adjustment. Multivariate analyses were used to model HR-QoL measures.

RESULTS

All patients reported very low HR-QoL. The mean EQ-5D index scores were 0.33, 0.36, and 0.37 in the mixed, neuropathic, and nociceptive pain groups, respectively. The differences did not reach statistical significance (P = 0.057). Patients with nociceptive pain had less pain (least pain intensity score: 4.7 vs. 5.2 in the other groups; P = 0.006), less interference with daily activities (BPI average interference score: 6.3 vs. 6.6 and 6.7 in the neuropathic and mixed pain groups, respectively; P = 0.013), less anxiety (HADS score: 8.5 vs. 9.6 and 9.7 in the same respective groups; P = 0.001), and fewer sleep problems (MOS-SQ sleep problems index: 46.8 vs. 52.2 and 50.2 in the same respective groups; P = 0.005). In the adjusted analyses, HR-QoL measures were explained by pain intensity, anxiety, and sleep quality, but not by physiopathological pain type.

CONCLUSIONS

Pain features, particularly intensity, have a greater impact than pain physiopathology on HR-QoL. Distinct physiopathological mechanisms give rise to different pain features that, in turn, may mediate the HR-QoL of patients with chronic pain. This could be used to improve pain management strategies.

The prevalence and impact of chronic neuropathic pain on daily and social life: A nationwide study in a Japanese population

BACKGROUND

This study marks the first epidemiological evaluation of the prevalence and burden of chronic neuropathic pain (NeP) in an Asian population. The objective of this nationwide cross-sectional study was to identify the characteristics of individuals with NeP, detect the NeP features that affect their quality of life (QOL), and demonstrate the negative effects of NeP on social and daily living as well as comorbidities including depression, anxiety and sleep disorders.

METHODS

We mailed a cross-sectional, population-based epidemiological survey to a random nationwide sample of 10,000 Japanese adults over 20 years old.

RESULTS

The response rate was 54.4% (2445 men, 2992 women; mean age, 53.4 years). Prevalence of chronic pain was 16.6%, and prevalence of NeP was 3.2% as detected by the PainDETECT. Participants with NeP showed significantly lower quality of life according to scores on the EuroQol-5 Dimensions scale (p < 0.001), higher levels of psychological distress on the Kessler 6-item psychological distress scale (p < 0.001), poorer sleep quality (p < 0.001), and more workdays lost (p < 0.001) than did participants without NeP. Linear regression modelling showed that widespread pain, thermal hyperalgesia and pressure-induced pain had strong associations with lower QOL, with regression coefficients of -0.046 (p < 0.001), -0.038 (p < 0.001), and -0.040 (p < 0.001), respectively.

CONCLUSIONS

This study is the first to report the prevalence of NeP in an Asian population using a validated questionnaire. This study provides compelling evidence that chronic NeP is more strongly associated with poorer QOL, mental health and social well-being than CP without a neuropathic component.

SIGNIFICANCE

This population-based nationwide epidemiological study revealed the prevalence, characteristics, and negative effects of chronic pain with neuropathic components in Asian society. The prevalence of neuropathic pain was 3.2% with PainDETECT.

The effect of sinomenine in diabetic neuropathic pain mediated by the P2X3 receptor in dorsal root ganglia

Type 2 diabetes mellitus (T2DM) accounts for more than 90% of all cases of diabetes mellitus (DM). Diabetic neuropathic pain (DNP) is a common complication of T2DM. Sinomenine is a natural bioactive component extracted from the Sinomenium acutum and has anti-inflammatory effects. The aim of our study was to investigate the effects of sinomenine on DNP mediated by the P2X₃ receptor in dorsal root ganglia (DRG). The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in T2DM rats were lower than those of control rats. MWT and TWL in T2DM rats treated with sinomenine were higher compared with those in T2DM rats. The expression levels of the P2X₃ protein and mRNA in T2DM rat DRG were higher compared with those of the control, while those in T2DM rats treated with sinomenine were significantly lower compared with those of the T2DM rats. Sinomenine significantly inhibited P2X₃ agonist ATP-activated currents in HEK293 cells transfected with the P2X₃ receptor. Sinomenine decreased the phosphorylation and activation of P38MAPK in T2DM DRG. Therefore, sinomenine treatment may suppress the up-regulated expression and activation of the P2X₃ receptor and relieve the hyperalgesia potentiated by the activation of P38MAPK in T2DM rats.

Regenerative peripheral neuropathic pain: novel pathological pain, new therapeutic dimension

After peripheral nerve damage, injured or stressed primary sensory neurons (PSNs) transmitting pathological pain (pathopain) sensitize central nervous system (CNS) neural circuits and determine behavioral phenotypes of peripheral neuropathic pain (PNP). Therefore, phenotypic profiling of pathopain-transmitting PSNs is vital for probing and discovering PNP conditions. Following peripheral nerve injuries (PNIs), PNP might be potentially transmitted by distinct classes of damaged or stressed PSNs, such as axotomized PSNs without regeneration (axotomy-non-regenerative neurons), axotomized PSNs with accurate regeneration (axotomy-regenerative neurons), and spared intact PSNs adjacent to axotomized neurons (axotomy-spared neurons). Both axotomy-non-regenerative neurons and axotomy-spared neurons have been definitely shown to participate in specific PNP transmission. However, whether axotomy-regenerative neurons could transmit PNP with unique features has remained unclear. Recent studies in rodent models of axonotmesis have clearly demonstrated that axotomy-regenerative neurons alone transmit persistent pathological pain with unique behavioral phenotypes. In this review, we exclusively review this novel category of PNP, reasonably term it ‘regenerative peripheral neuropathic pain’, and finally discuss its potential clinical significance as a new therapeutic dimension for PNIs beyond nerve regeneration.

Assessment of the effectiveness and safety of Ethosuximide in the Treatment of non-Diabetic Peripheral Neuropathic Pain: EDONOT-protocol of a randomised, parallel, controlled, double-blinded and multicentre clinical trial

INTRODUCTION

Currently available analgesics are ineffective in 30-50% of patients suffering from neuropathic pain and often induce deleterious side effects. T-type calcium channel blockers (mibefradil, ethosuximide, NNC 55-0396) are of great interest for the development of new symptomatic treatments of neuropathic pain, due to their various effects on pain perception. Interestingly, ethosuximide, which has already been approved for treating epilepsy, is available on the European market for clinical use. Despite numerous preclinical data demonstrating an antinociceptive effect of ethosuximide in various animal models of neuropathic pain, no clinical studies have been published to date on the analgesic efficacy of ethosuximide in patients with neuropathic pain.

METHODS AND ANALYSIS

The Ethosuximide in the Treatment of non-Diabetic Peripheral Neuropathic Pain (EDONOT) trial is a randomised, parallel, controlled, double-blinded, multicentre clinical study. It is the first clinical trial to evaluate the efficacy and safety of ethosuximide in the treatment of non-diabetic peripheral neuropathic pain. Adult patients exhibiting peripheral neuropathic pain (Numeric Rating Scale (NRS) ≥4 and Douleur Neuropathique 4 (DN4)≥4) for at least 3 months and under stable analgesic treatment for at least 1 month will be included. Patients (n=220) will be randomly assigned to receive either ethosuximide or control treatment for 6 weeks following a 1 week run-in period. The primary end point is the intensity of neuropathic pain, assessed by NRS (0-10) before and after 6 weeks of treatment. The secondary end points are safety (adverse events are collected during the study: daily by the patient on the logbook and during planned phone calls by investigators), the intensity and features of neuropathic pain (assessed by Brief Pain Inventory (BPI) and Neuropathic Pain Symptom Inventory (NPSI) questionnaires) and health-related quality of life (assessed by Medical Outcome Study Short Form 12 (MOS SF-12) and Leeds questionnaires).

ETHICS AND COMMUNICATION

The study was approved by an independent ethics committee (CPP Sud-Est VI, France, IRB00008526) and registered by the French competent authority (Agence nationale de sécurité du médicament (ANSM)).

TRIAL REGISTRATION NUMBER

NCT02100046, Recruiting.

The epidemiology of chronic pain in Libya: a cross-sectional telephone survey

Background

Chronic pain is a public health problem although there is a paucity of prevalence data from countries in the Middle East and North Africa. The aim of this study was to estimate the prevalence of chronic pain and neuropathic pain in a sample of the general adult population in Libya.

Methods

A cross-sectional telephone survey was conducted before the onset of the Libyan Civil War (February 2011) on a sample of self-declared Libyans who had a landline telephone and were at least 18 years of age. Random sampling of household telephone number dialling was undertaken in three major cities and interviews conducted using an Arabic version of the Structured Telephone Interviews Questionnaire on Chronic Pain previously used to collect data in Europe. In addition, an Arabic version of S-LANSS was used. 1212 individuals were interviewed (response rate = 95.1 %, mean age = 37.8 ± 13.9 years, female = 54.6 %).

Results

The prevalence of chronic pain ≥ 3 months was 19.6 % (95 % CI 14.6 % to 24.6 %) with a mean ± SD duration of pain of 6 · 5 ± 5 · 7 years and a higher prevalence for women. The prevalence of neuropathic pain in the respondents reporting chronic pain was 19 · 7 % (95 % CI 14 · 6-24 · 7), equivalent to 3 · 9 % (95 % CI 2 · 8 to 5 · 0 %) of the general adult population. Only, 71 (29 · 8 %) of respondents reported that their pain was being adequately controlled.

Conclusions

The prevalence of chronic pain in the general adult population of Libya was approximately 20 % and comparable with Europe and North America. This suggests that chronic pain is a public health problem in Libya. Risk factors are being a woman, advanced age and unemployment. There is a need for improved health policies in Libya to ensure that patients with chronic pain receive effective management.

Utility of DN4 questionnaire in assessment of neuropathic pain and its clinical correlations in Turkish patients with diabetes mellitus

AIM

We aimed to assess the utility of DN4 questionnaire (Douleur Neuropathique en 4 questions) to define the frequency and severity of neuropathic pain (NP) and also its clinical correlation to daily clinical practice.

METHODS

We included 1357 patients with diabetes (56.5% women, 90.4% type 2 diabetes) who were followed up in our diabetes outpatient clinic. Presence of NP was evaluated by performing simultaneous DN4 questionnaires and physical examination. Those who had a DN4 score ≥4 were considered to have NP.

RESULTS

The mean age was 58.2±12.1 years, mean duration was 12.5±7.5; (min-max: 1-45) years, mean HbA1c level was 7.8±1.6% (min-max: 5-16.2%), (61.7±6.0mmol/mol; min-max: 31.1-153.6mmol/mol). Three hundred thirteen patients (23%) were diagnosed with NP using the DN4 tool. Male gender (p=0.01), receiving antihypertensive treatment (p=0.01), presence of retinopathy (p<0.001), cardiovascular disease (CVD) (p=0.01) and previously diagnosed neuropathy (p<0.001) were significantly associated with higher NP scores. Those who had increased DN4 scores were more likely to be on oral hypoglycemic agents (OHA)+insulin combinations (p<0.001), had longer diabetes duration (p<0.001) and higher HbA1c levels (p=0.001). Logistic regression model revealed that diabetes duration (OR: 1.02, 95% CI: 1.00-1.04, p=0.007), elevated HbA1c levels (1.11, 1.02-1.21, 0.015), presence of retinopathy (1.41, 1.20-1.64, <0.001), management with at least one OHA (1.47; 1.12-1.92; 0.004) or any insulin regimen (1.62; 1.16-2.27; 0.005) (compared with diet only-regimens) were significantly associated with NP.

CONCLUSION

Utilization of DN4 questionnaire in daily clinical practice is an effective tool in the identification of pain related with peripheral diabetic polyneuropathy.

Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology

The electronics surrounding us in our daily lives rely almost exclusively on electrons as the dominant charge carrier. In stark contrast, biological systems rarely use electrons but rather use ions and molecules of varying size. Due to the unique combination of both electronic and ionic/molecular conductivity in conducting and semiconducting organic polymers and small molecules, these materials have emerged in recent decades as excellent tools for translating signals between these two realms and, therefore, providing a means to effectively interface biology with conventional electronics-thus, the field of organic bioelectronics. Today, organic bioelectronics defines a generic platform with unprecedented biological recording and regulation tools and is maturing toward applications ranging from life sciences to the clinic. In this Review, we introduce the field, from its early breakthroughs to its current results and future challenges.

Study protocol for a pilot, randomised, double-blinded, placebo controlled trial of perineural local anaesthetics and steroids for chronic post-traumatic neuropathic pain in the ankle and foot: the PREPLANS study

INTRODUCTION

Peripheral neuropathic pain (PNP) associated with trauma is often refractory to treatment. Administration of local anaesthetics (LA) and steroids around injured nerves has been proposed as an option for patients unresponsive to conventional treatments for refractory PNP following trauma. There is insufficient evidence to support a large, potentially expensive, full-scale randomised controlled trial (RCT) that involves comparison of effects of perineural steroids and LA against LA or saline injections on analgesia, physical and psychological functioning, and quality of life. There is also a lack of data that would allow estimation of analgesic efficacy or sample size for the full-scale RCT. The objective of this pilot RCT is to yield information to support planning of a full-scale RCT in this population.

METHODS AND ANALYSIS

30 participants with post-traumatic PNP in the ankle and foot of moderate-to-severe intensity and duration of more than 3 months will be enrolled in this pilot RCT. Participants will be randomised to receive three ultrasound-guided perineural injections of 0.9% saline, 0.25% bupivacaine (a long-acting LA) or a combination of 0.25% bupivacaine and a steroid (methylprednisolone 16 mg per nerve) at weekly intervals. The primary objectives are to determine the feasibility and sample size of a full-scale RCT in this population. The secondary objectives are to evaluate the effect of study interventions on analgesia, persistence of neuropathic pain, psychological and physical function, quality of life and participants' global impression of change at 1 and 3 months after the interventions. In addition, adverse effects associated with perineural injections and with systemic absorption of steroids will also be recorded.

ETHICS AND DISSEMINATION

The protocol was approved by the University Health Network Research Ethics Board (UHN REB number 15-9584-A). The results will be disseminated in peer-reviewed journals and at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT02680548; Pre-results.

Brain morphological alternation in chronic pain patients with neuropathic characteristics

Background

Neuropathic characteristics are highly involved in the development of chronic pain both physically and psychologically. However, little is known about the relationship between neuropathic characteristics and brain morphological alteration.

Objectives

The aim of this study is to investigate the mechanisms of chronic pain development by examining the above-mentioned relationships by voxel-based morphometry in patients with chronic pain.

Methods

First, we assessed neuropathic characteristics using the painDETECT Questionnaire in 12 chronic pain patients. Second, to assess the gray matter volume changes by voxel-based morphometry, we conducted magnetic resonance imaging of the brain. We applied multiregression analysis of these two assessment methods.

Results

There were significant positive correlations between painDETECT Questionnaire scores and the gray matter volume in the bilateral anterior cingulate cortex and right posterior cingulate cortex.

Conclusions

Our findings suggest that neuropathic characteristics strongly affect the brain regions related to modulation of pain in patients with chronic pain and, therefore, contribute to the severity of chronic pain.

Chronic Stress Is Associated with Pain Precipitation and Elevation in DeltaFosb Expression

A number of acute or repeated stimuli can induce expression of DeltaFosB (ΔFosB), a transcription factor derived from the fosB gene (an osteosarcoma viral oncogene) via alternative splicing. ΔFosB protein is currently viewed as a ‘molecular switch’ to repeated stimuli that gradually converts acute responses into relatively stable adaptations underlying long-term neural and behavioral plasticity. ΔFosB has received extensive attention in drug addition, depression, and stress adaptation, but changes in ΔFosB protein expression during pain is not fully understood. In this study we explored ΔFosB expression in the medial prefrontal cortex (mPFC) of rats experiencing chronic or acute stress-induced pain. Our data reveal that chronic pain induced by neonatal colorectal distension, chronic constriction injury (CCI) of the sciatic nerve, or maternal separation was associated with an increase in ΔfosB protein expression in mPFC, but acute application of acetic acid or zymosan did not alter the ΔFosB protein expression. ΔFosB expression in the rat visual cortex, a non pain-related brain region, did not change in response to (CCI) of the sciatic nerve and acetic acid treatment. In conclusion, our results indicate that ΔFosB protein expression is significantly elevated in rats that have experienced chronic pain and stress, but not acute pain. The ΔFosB protein may serve as an important transcription factor for chronic stress-induced pain. Further research is needed to improve the understanding of both the upstream signaling leading to ΔFosB protein expression as well as the regulation of ΔFosB gene expression in cortical neurons.

An Epidemiological Study of Neuropathic Pain Symptoms in Canadian Adults

The reported prevalence of neuropathic pain ranges from 6.9% to 10%; however the only Canadian study reported 17.9%. The objective of this study was to describe the epidemiology of neuropathic pain in Canada. A cross-sectional survey was conducted in a random sample of Canadian adults. The response rate was 21.1% (1504/7134). Likely or possible neuropathic pain was defined using a neuropathic pain-related diagnosis and a positive outcome on the Self-Report Leeds Assessment of Neuropathic Symptoms and Signs pain scale (S-LANSS) or the Douleur Neuropathique 4 (DN4) Questions. The prevalence of likely neuropathic pain was 1.9% (S-LANSS) and 3.4% (DN4) and that of possible neuropathic pain was 5.8% (S-LANSS) and 8.1% (DN4). Neuropathic pain was highest in economically disadvantaged males. There is a significant burden of neuropathic pain in Canada. The low response rate and a slightly older and less educated sample than the Canadian population may have led to an overestimate of neuropathic pain. Population prevalence varies by screening tool used, indicating more work is needed to develop reliable measures. Population level screening targeted towards high risk groups should improve the sensitivity and specificity of screening, while clinical examination of those with positive screening results will further refine the estimate of prevalence.

Inhibition of the kinase WNK1/HSN2 ameliorates neuropathic pain by restoring GABA inhibition

HSN2is a nervous system predominant exon of the gene encoding the kinase WNK1 and is mutated in an autosomal recessive, inherited form of congenital pain insensitivity. The HSN2-containing splice variant is referred to as WNK1/HSN2. We created a knockout mouse specifically lacking theHsn2exon ofWnk1 Although these mice had normal spinal neuron and peripheral sensory neuron morphology and distribution, the mice were less susceptible to hypersensitivity to cold and mechanical stimuli after peripheral nerve injury. In contrast, thermal and mechanical nociceptive responses were similar to control mice in an inflammation-induced pain model. In the nerve injury model of neuropathic pain, WNK1/HSN2 contributed to a maladaptive decrease in the activity of the K(+)-Cl(-)cotransporter KCC2 by increasing its inhibitory phosphorylation at Thr(906)and Thr(1007), resulting in an associated loss of GABA (γ-aminobutyric acid)-mediated inhibition of spinal pain-transmitting nerves. Electrophysiological analysis showed that WNK1/HSN2 shifted the concentration of Cl(-)such that GABA signaling resulted in a less hyperpolarized state (increased neuronal activity) rather than a more hyperpolarized state (decreased neuronal activity) in mouse spinal nerves. Pharmacologically antagonizing WNK activity reduced cold allodynia and mechanical hyperalgesia, decreased KCC2 Thr(906)and Thr(1007)phosphorylation, and restored GABA-mediated inhibition (hyperpolarization) of injured spinal cord lamina II neurons. These data provide mechanistic insight into, and a compelling therapeutic target for treating, neuropathic pain after nerve injury.

Post-translational modifications of voltage-gated sodium channels in chronic pain syndromes

In the peripheral sensory nervous system the neuronal expression of voltage-gated sodium channels (Navs) is very important for the transmission of nociceptive information since they give rise to the upstroke of the action potential (AP). Navs are composed of nine different isoforms with distinct biophysical properties. Studying the mutations associated with the increase or absence of pain sensitivity in humans, as well as other expression studies, have highlighted Nav1.7, Nav1.8, and Nav1.9 as being the most important contributors to the control of nociceptive neuronal electrogenesis. Modulating their expression and/or function can impact the shape of the AP and consequently modify nociceptive transmission, a process that is observed in persistent pain conditions. Post-translational modification (PTM) of Navs is a well-known process that modifies their expression and function. In chronic pain syndromes, the release of inflammatory molecules into the direct environment of dorsal root ganglia (DRG) sensory neurons leads to an abnormal activation of enzymes that induce Navs PTM. The addition of small molecules, i.e., peptides, phosphoryl groups, ubiquitin moieties and/or carbohydrates, can modify the function of Navs in two different ways: via direct physical interference with Nav gating, or via the control of Nav trafficking. Both mechanisms have a profound impact on neuronal excitability. In this review we will discuss the role of Protein Kinase A, B, and C, Mitogen Activated Protein Kinases and Ca++/Calmodulin-dependent Kinase II in peripheral chronic pain syndromes. We will also discuss more recent findings that the ubiquitination of Nav1.7 by Nedd4-2 and the effect of methylglyoxal on Nav1.8 are also implicated in the development of experimental neuropathic pain. We will address the potential roles of other PTMs in chronic pain and highlight the need for further investigation of PTMs of Navs in order to develop new pharmacological tools to alleviate pain.

Effects of insular stimulation on thermal nociception

BACKGROUND

Electrical stimulation used for brain mapping in the postero-superior insula can evoke pain. The effects of prolonged high frequency insular stimulation on pain thresholds are unknown.

OBJECTIVE/HYPOTHESIS

Prolonged high frequency insular stimulation, by virtue of its inhibitory properties on networks, could decrease thermal nociception.

METHODS

Epileptic subjects had electrodes implanted in the insular cortex for the purpose of epileptic focus resection. Thermal and pressure nociceptive thresholds were tested bilaterally on the forearm on two consecutive days. Randomly assigned double-blind high frequency (150 Hz) insular stimulation took place for 10 min before pain testing either on the first day or on the second day.

RESULTS

Six subjects (three females; mean age of 35 years) were included. Insular stimulation increased heat pain threshold on the ipsilateral (p = 0.003; n = 6) and contralateral sides (p = 0.047; n = 6). Differences in cold pain threshold did not reach statistical significance (ipsilateral: p = 0.341, contralateral: p = 0.143; n = 6), but one subject had a profound decrease in both heat and cold pain responses. Pressure pain threshold was not modified by insular stimulation (ipsilateral: p = 0.1123; contralateral: p = 0.1192; n = 6). Two of the three subjects who had a postero-superior operculo-insulectomy developed central pain with contralateral thermal nociceptive deficit.

CONCLUSIONS

High frequency inhibitory postero-superior insular stimulation may have the potential to decrease thermal nociception. Together with previous studies, our data support the notion that the integrity of this brain region is necessary for thermal but not pressure nociceptive processing.

Use of neuropathic pain questionnaires in predicting persistent postoperative neuropathic pain following lumbar discectomy for radiculopathy

OBJECT Failed-back surgery syndrome has been historically used to describe extremity neuropathic pain in lumbar disease despite structurally corrective spinal surgery. It is unclear whether specific preoperative pain characteristics can help determine which patients may be susceptible to such postoperative disabling symptoms. METHODS This prospective study analyzed surgical microdiscectomy patients treated for lumbar, degenerative, painful radiculopathy. Clinical parameters included general demographics, preoperative and postoperative clinical examination status, self-reported pain and disability scores, and neuropathic pain scores. The screening tests for neuropathic pain were the Douleur Neuropathique 4 and Leeds Assessment of Neuropathic Symptoms and Signs, with correlation tested for ordinal score and screen positivity. Multiple logistic regression analysis was used to define predictors of postoperative symptomatology. RESULTS Twelve percent of the 250 patients with radiculopathy who underwent microdiscectomy experienced persistent postoperative neuropathic pain (PPNP) with only modest, if any, relief of leg pain. The condition was highly associated with abnormal preoperative screen results for neuropathic pain, but not sex, smoking status, or preoperative pain severity (α = 0.05). Good correlation was seen between the 2 screening tests used in this study for both absolute ordinal score (Spearman ρ = 0.84; p < 0.001) and the threshold for terming the patient as having neuropathic pain features (Spearman ρ = 0.48; p < 0.001). Younger age at treatment also correlated with a higher likelihood of developing PPNP (p = 0.03). CONCLUSIONS This population exhibited a low overall frequency of PPNP. Higher neuropathic pain screening scores correlated strongly with likelihood of significant postoperative leg pain. Further work is required to develop more accurate prognostication tools for radiculopathy patients undergoing structural spinal surgery.

Diagnostic Accuracy of the Slump Test for Identifying Neuropathic Pain in the Lower Limb

STUDY DESIGN

Diagnostic accuracy study with nonconsecutive enrollment.

OBJECTIVES

To assess the diagnostic accuracy of the slump test for neuropathic pain (NeP) in those with low to moderate levels of chronic low back pain (LBP), and to determine whether accuracy of the slump test improves by adding anatomical or qualitative pain descriptors.

BACKGROUND

Neuropathic pain has been linked with poor outcomes, likely due to inadequate diagnosis, which precludes treatment specific for NeP. Current diagnostic approaches are time consuming or lack accuracy.

METHODS

A convenience sample of 21 individuals with LBP, with or without radiating leg pain, was recruited. A standardized neurosensory examination was used to determine the reference diagnosis for NeP. Afterward, the slump test was administered to all participants. Reports of pain location and quality produced during the slump test were recorded.

RESULTS

The neurosensory examination designated 11 of the 21 participants with LBP/sciatica as having NeP. The slump test displayed high sensitivity (0.91), moderate specificity (0.70), a positive likelihood ratio of 3.03, and a negative likelihood ratio of 0.13. Adding the criterion of pain below the knee significantly increased specificity to 1.00 (positive likelihood ratio = 11.9). Pain-quality descriptors did not improve diagnostic accuracy.

CONCLUSION

The slump test was highly sensitive in identifying NeP within the study sample. Adding a pain-location criterion improved specificity. Combining the diagnostic outcomes was very effective in identifying all those without NeP and half of those with NeP. Limitations arising from the small and narrow spectrum of participants with LBP/sciatica sampled within the study prevent application of the findings to a wider population.

LEVEL OF EVIDENCE

Diagnosis, level 4-.

Interleukin-17A Acts to Maintain Neuropathic Pain Through Activation of CaMKII/CREB Signaling in Spinal Neurons

Immunity and neuroinflammation play major roles in neuropathic pain. Spinal interleukin (IL)-17A, as a mediator connecting innate and adaptive immunity, has been shown to be an important cytokine in neuroinflammation and acute neuropathic pain. However, the effects and underlying mechanisms of spinal IL-17A in the maintenance of neuropathic pain remain unknown. This study was designed to investigate whether spinal IL-17A acted to maintain neuropathic pain and to elucidate the underlying mechanisms in IL-17A knockout or wild-type (WT) mice following L4 spinal nerve ligation (L4 SNL). WT mice were treated with anti-IL-17A neutralized monoclonal antibody (mAb) or recombinant IL-17A (rIL-17A). We showed that IL-17A levels were significantly increased 1, 3, 7, and 14 days after SNL in spinal cord. Double immunofluorescence staining showed that astrocytes were the major cellular source of spinal IL-17A. IL-17A knockout or anti-IL-17A mAb treatment significantly ameliorated hyperalgesia 7 days after SNL, which was associated with a significant reduction of p-CaMKII and p-CREB levels in spinal cord, whereas rIL-17A treatment conferred the opposite effects. Furthermore, we showed that blocking CaMKII with KN93 significantly reduced SNL- or rIL-17A-induced hyperalgesia and p-CREB expression. Our in vitro data showed that KN93 also significantly inhibited rIL-17A-induced CREB activation in primary cultured spinal neurons. Taken together, our study indicates that astrocytic IL-17A plays important roles in the maintenance of neuropathic pain through CaMKII/CREB signaling pathway in spinal cord, and thus targeting IL-17A may offer an attractive strategy for the treatment of chronic persistent neuropathic pain.

Therapy using implanted organic bioelectronics

Many drugs provide their therapeutic action only at specific sites in the body, but are administered in ways that cause the drug's spread throughout the organism. This can lead to serious side effects. Local delivery from an implanted device may avoid these issues, especially if the delivery rate can be tuned according to the need of the patient. We turned to electronically and ionically conducting polymers to design a device that could be implanted and used for local electrically controlled delivery of therapeutics. The conducting polymers in our device allow electronic pulses to be transduced into biological signals, in the form of ionic and molecular fluxes, which provide a way of interfacing biology with electronics. Devices based on conducting polymers and polyelectrolytes have been demonstrated in controlled substance delivery to neural tissue, biosensing, and neural recording and stimulation. While providing proof of principle of bioelectronic integration, such demonstrations have been performed in vitro or in anesthetized animals. Here, we demonstrate the efficacy of an implantable organic electronic delivery device for the treatment of neuropathic pain in an animal model. Devices were implanted onto the spinal cord of rats, and 2 days after implantation, local delivery of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) was initiated. Highly localized delivery resulted in a significant decrease in pain response with low dosage and no observable side effects. This demonstration of organic bioelectronics-based therapy in awake animals illustrates a viable alternative to existing pain treatments, paving the way for future implantable bioelectronic therapeutics.

Cancer treatment-related neuropathic pain: proof of concept study with menthol--a TRPM8 agonist

PURPOSE

Effective treatment of neuropathic pain without unacceptable side effects is challenging. Cancer sufferers increasingly live with long-term treatment-related neuropathic pain, resulting from chemotherapy-induced peripheral neuropathy (CIPN) or surgical scars. This proof-of-concept study aimed to determine whether preclinical evidence for TRPM8 ion channels in sensory neurons as a novel analgesic target could be translated to clinical benefit in patients with neuropathic pain, using the TRPM8 activator menthol.

PATIENTS AND METHODS

Patients with problematic treatment-related neuropathic pain underwent a baseline assessment using validated questionnaires, psychophysical testing, and objective functional measures. The painful area was treated with topical 1 % menthol cream twice daily. Assessments were repeated at 4-6 weeks. The primary outcome was the change in Brief Pain Inventory total scores at 4-6 weeks. Secondary outcomes included changes in function, mood and skin sensation.

RESULTS

Fifty-one patients (female/male, 32/19) were recruited with a median age of 61 (ranging from 20 to 89). The commonest aetiology was CIPN (35/51), followed by scar pain (10/51). Thirty-eight were evaluable on the primary outcome. Eighty-two per cent (31/38) had an improvement in total Brief Pain Inventory scores (median, 47 (interquartile range, 30 to 64) to 34 (6 to 59), P < 0.001). Improvements in mood (P = 0.0004), catastrophising (P = 0.001), walking ability (P = 0.008) and sensation (P < 0.01) were also observed.

CONCLUSION

This proof-of-concept study indicates that topical menthol has potential as a novel analgesic therapy for cancer treatment-related neuropathic pain. Improvements in patient-rated measures are supported by changes in objective measures of physical function and sensation. Further systematic evaluation of efficacy is required.

Anti-inflammatory T-cell shift in neuropathic pain

Background

The classification of pain into nociceptive and neuropathic pain is based on characteristic symptoms and different pathophysiological mechanisms. In a recent investigation, we found a disrupted TH17/Treg balance in patients suffering from chronic unspecific low back pain (CLBP). These patients did not show any signs of neuropathy. There is evidence for a considerable impact of the immune system also in neuropathic pain. However, the role of the adaptive immune system is still unclear. In the present study, we investigated systemic T-cell subset responses and T-cell related cytokine profiles in patients with chronic neuropathic pain.

Methods

We analyzed T-cell subsets, mRNA expression and T-cell-related cytokine profiles in 26 patients suffering from neuropathic pain in comparison to 26 healthy controls. Using multicolor flow cytometry (FACS), we quantified the number of T helper cells 1 (TH1), TH2, TH17 and regulatory T-cells (Tregs). Forkhead-Box-Protein 3 (FoxP3), Transforming growth factor-β (TGF-β) and RAR-related orphan receptor-γT (ROR-γT) mRNA expression was determined by quantitative real-time PCR (qPCR) and levels of pain-related cytokines were measured by Human Cytokine Multiplex Immunoassay (Macrophage inflammatory protein-1α (MIP-1α), Tumor necrosis factor-α (TNF-α), Interferon-γ (IFN-γ), Interleukin (IL) -4, IL-6, IL-10, IL-17, and IL-23).

Results

We found a TH17/Treg imbalance with significantly increased anti-inflammatory Tregs and decreased pro-inflammatory TH17 cells in patients with neuropathic pain as compared to healthy controls. These results were confirmed on mRNA level: Treg-related FoxP3 and TGF-β mRNA expression was elevated, whereas expression of TH17-related RORγT was reduced. Cytokine analyses revealed only marginal changes.

Conclusions

Our investigation revealed a clear shift of T-cell subsets towards anti-inflammation in patients with neuropathic pain. Interestingly, this is quite similar to our previous findings in CLBP patients, but even more pronounced. Therefore, it remains to be elucidated in future investigations whether the immune changes represent an underlying pathophysiological mechanism or an epiphenomenon induced by ongoing pain and stress.

German Clinical Trial Register (DRKS)

Trial registration number: DRKS00005954

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0225-0) contains supplementary material, which is available to authorized users.

Exploring the lived experience of adults using prescription opioids to manage chronic noncancer pain

BACKGROUND

Chronic noncancer pain (CNCP) and prescription opioid use is a highly complex and growing health care issue in Canada. Many quantitative research studies have investigated the effectiveness of opioids for chronic pain; however, gaps remain in the literature regarding the personal experience of using opioids and their impact on those experiencing CNCP.

OBJECTIVE

To explore the lived experience of adults using prescription opioids to manage CNCP, focusing on how opioid medication affected their daily lives.

METHODS

In-depth qualitative interviews were conducted with nine adults between 40 and 68 years of age who were using prescription opioids daily for CNCP. Interviews were audiorecorded and transcribed, and subsequently analyzed using interpretive phenomenological analysis.

RESULTS

Six major themes identified positive and negative aspects of opioid use associated with social, physical, emotional and psychological dimensions of pain management. These themes included the process of decision making, and physical and psychosocial consequences of using opioids including pharmacological side effects, feeling stigmatized, guilt, fears, ambivalence, self-protection and acceptance.

CONCLUSION

Although there were many negative aspects to using opioids daily, the positive effects outweighed the negative for most participants and most of the negative aspects were socioculturally induced rather than caused by the drug itself. The present study highlighted the complexities involved in using prescription opioids daily for management of CNCP for individuals living with pain.

Transient receptor potential ion channels in primary sensory neurons as targets for novel analgesics

The last decade has witnessed an explosion in novel findings relating to the molecules involved in mediating the sensation of pain in humans. Transient receptor potential (TRP) ion channels emerged as the greatest group of molecules involved in the transduction of various physical stimuli into neuronal signals in primary sensory neurons, as well as, in the development of pain. Here, we review the role of TRP ion channels in primary sensory neurons in the development of pain associated with peripheral pathologies and possible strategies to translate preclinical data into the development of effective new analgesics. Based on available evidence, we argue that nociception-related TRP channels on primary sensory neurons provide highly valuable targets for the development of novel analgesics and that, in order to reduce possible undesirable side effects, novel analgesics should prevent the translocation from the cytoplasm to the cell membrane and the sensitization of the channels rather than blocking the channel pore or binding sites for exogenous or endogenous activators.

Building a diagnostic algorithm on localized neuropathic pain (LNP) and targeted topical treatment: focus on 5% lidocaine-medicated plaster

Within the broad definition of neuropathic pain, the refinement of clinical diagnostic procedures has led to the introduction of the concept of localized neuropathic pain (LNP). It is characterized by consistent and circumscribed area(s) of maximum pain, which are associated with negative or positive sensory signs and/or spontaneous symptoms typical of neuropathic pain. This description outlines the clinical features (currently lacking in guidelines and treatment recommendations) in patients for whom topical targeted treatment with 5% lidocaine-medicated plaster is suggested as first-line therapy. Few epidemiologic data are present in the literature but it is generally estimated that about 60% of neuropathic pain conditions are localized, and therefore identifiable as LNP. A mandatory clinical criterion for the diagnosis of LNP is that signs and symptoms must be present in a clearly identified and defined area(s). Cartographic recordings can help to define each area and to assess variations. The diagnosis of LNP relies on careful neurological examination more than on pain questionnaires, but it is recognized that they can be extremely useful for recording the symptom profiles and establishing a more targeted treatment. The most widely studied frequent/relevant clinical presentations of LNP are postherpetic neuralgia, diabetic neuropathy, and neuropathic postoperative pain. They successfully respond to treatment with 5% lidocaine-medicated plaster with equal if not better pain control but with fewer side effects versus conventional systemic treatments. Generally, the more localized the pain (ie, the area of an A4 sheet of paper) the better the results of topical treatment. This paper proposes an easy-to-understand algorithm to identify patients with LNP and to guide targeted topical treatments with 5% lidocaine medicated plaster.

Epidemiology of neuropathic pain

Epidemiology is an essential clinical tool in designing and evaluating management and prevention strategies, and is particularly relevant to neuropathic pain. Despite its relevance to neuropathic pain however, there is a paucity of accurate information on its prevalence, distribution and determinants, for several reasons. In many ways, it is appropriate to study neuropathic pain merely as a symptom or a pain mechanism rather than a specific disease. However, the different causes display sufficient similarities in their clinical and personal impact, and in their response to treatment, to make it worthwhile to consider neuropathic pain as a distinct condition. There are, however, important specific disease-based factors that need to be considered separately. Older estimates of the prevalence of neuropathic pain (based on specific diagnoses) tend to be lower (1-2%) than newer estimates that are based on questionnaires examining classic symptoms (6-8%). Further methodological research is needed to clarify these. Associated poor general health is a feature of all neuropathic pain, similar to other severe chronic diseases.

Neuromodulatory treatments for chronic pain: efficacy and mechanisms

Chronic pain is common, and the available treatments do not provide adequate relief for most patients. Neuromodulatory interventions that modify brain processes underlying the experience of pain have the potential to provide substantial relief for some of these patients. The purpose of this Review is to summarize the state of knowledge regarding the efficacy and mechanisms of noninvasive neuromodulatory treatments for chronic pain. The findings provide support for the efficacy and positive side-effect profile of hypnosis, and limited evidence for the potential efficacy of meditation training, noninvasive electrical stimulation procedures, and neurofeedback procedures. Mechanisms research indicates that hypnosis influences multiple neurophysiological processes involved in the experience of pain. Evidence also indicates that mindfulness meditation has both immediate and long-term effects on cortical structures and activity involved in attention, emotional responding and pain. Less is known about the mechanisms of other neuromodulatory treatments. On the basis of the data discussed in this Review, training in the use of self-hypnosis might be considered a viable 'first-line' approach to treat chronic pain. More-definitive research regarding the benefits and costs of meditation training, noninvasive brain stimulation and neurofeedback is needed before these treatments can be recommended for the treatment of chronic pain.

Impact of neuropathic pain at the population level

BACKGROUND

One of the chief complaints of individuals who frequent the Family Health Units is chronic pain which, in Salvador, affects over 40% of the population. However, little is known about the type of pain and its impact on quality of life (QoL) at population level. The aim of the study is to evaluate the impact of neuropathic pain on QoL in a community.

METHODS

A descriptive cross-sectional study was conducted from March to October 2012, in a Family Health Unit, Salvador, Bahia, Brazil. The DN-4 (type of pain), body map (location), VAS (intensity) and SF-36 (QoL) instruments were applied. The Chi-square (univariate analysis) and logistic regression (multivariate) tests were used, with IC 95% and P < 0.05.

RESULTS

In a sample of 191 individuals with chronic pain, predominantly women (86.4%), single (48.7%), nonwhite (93.2%), low educational (46.6%) and low economic (100%) level. The most affected locations of the body were knees, lumbar region and head. In 60.2% of interviewees, neuropathic pain, of high intensity (VAS = 7.09 ± 3.0) predominated, with duration of 8.53 ± 8.8 years and mean QoL was reduced in 47.13%.

CONCLUSIONS

Intense pain in the dorsal region and type of neuropathy are independent predictors for greater compromise of QoL.

Pregabalin: latest safety evidence and clinical implications for the management of neuropathic pain

Used mainly for the management of neuropathic pain, pregabalin is a gabapentinoid or anticonvulsant that was initially developed as an antiepileptic agent. After more than a decade of experience with pregabalin, experience and studies have shown that the adverse effect profile of pregabalin is well tolerated for the management of neuropathic pain and other conditions. Its use is associated with benign central nervous system and systemic adverse effects, and there are very limited metabolic, idiosyncratic or known teratogenic adverse effects. Along with its efficacy in particular neuropathic pain conditions, pregabalin's safety led it to be one of the first pharmacotherapies considered for the management of neuropathic pain. This review discusses the use of pregabalin as well as its potential adverse effects, including the most commonly noted features of sedation, dizziness, peripheral edema and dry mouth. Although other adverse effects may occur, these appear to be uncommon. The review also discusses the clinical implications of pregabalin's use for the clinician.

Transcranial Direct Current Stimulation in Neuropathic Pain

Neuropathic pain (NP) is one of the most common problems contributing to suffering and disability worldwide. Unfortunately, NP is also largely refractory to treatments, with a large number of patients continuing to report significant pain even when they are receiving recommended medications and physical therapy. Thus, there remains an urgent need for additional effective treatments. In recent years, nonpharmacologic brain stimulation techniques have emerged as potential therapeutic options. Many of these techniques and procedures – such as transcranial magnetic stimulation, spinal cord stimulation, deep brain stimulation, and motor cortical stimulation – have very limited availability, particularly in developing countries. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation procedure that has shown promise for effectively treating NP, and also has the potential to be widely available. This review describes tDCS and the tDCS procedures and principles that may be helpful for treating NP. The findings indicate that the analgesic benefits of tDCS can occur both during stimulation and beyond the time of stimulation. The mechanisms of cortical modulation by tDCS may involve various activities in neuronal networks such as increasing glutamine and glutamate under the stimulating electrode, effects on the μ-opioid receptor, and restoration of the defective intracortical inhibition. Additional research is needed to determine (1) the factors that may moderate the efficacy of tDCS, (2) the dose (e.g. number and frequency of treatment sessions) that results in the largest benefits and (3) the long-term effects of tDCS treatment.

Neuropathic pain in the general population: a systematic review of epidemiological studies

Most patients with neuropathic pain symptoms present and are managed in primary care, with only a minority being referred for specialist clinical assessment and diagnoses. Previous reviews have focused mainly on specific neuropathic pain conditions based in specialist settings. This is the first systematic review of epidemiological studies of neuropathic pain in the general population. Electronic databases were searched from January 1966 to December 2012, and studies were included where the main focus was on neuropathic pain prevalence and/or incidence, either as part of a specific neuropathic pain-related condition or as a global entity in the general population. We excluded studies in which data were extracted from pain or other specialist clinics or focusing on specific population subgroups. Twenty-one articles were identified and underwent quality assessment and data extraction. Included studies differed in 3 main ways: method of data retrieval, case ascertainment tool used, and presentation of prevalence/incidence rates. This heterogeneity precluded any meta-analysis. We categorised comparable incidence and prevalence rates into 2 main subgroups: (1) chronic pain with neuropathic characteristics (range 3-17%), and (2) neuropathic pain associated with a specific condition, including postherpetic neuralgia (3.9-42.0/100,000 person-years [PY]), trigeminal neuralgia (12.6-28.9/100,000 PY), painful diabetic peripheral neuropathy (15.3-72.3/100,000 PY), glossopharyngeal neuralgia (0.2-0.4/100,000 PY). These differences highlight the importance of a standardised approach for identifying neuropathic pain in future epidemiological studies. A best estimate of population prevalence of pain with neuropathic characteristics is likely to lie between 6.9% and 10%.

A systematic review of the effectiveness of knowledge translation interventions for chronic noncancer pain management

BACKGROUND

Reliable evidence detailing effective treatments and management practices for chronic noncancer pain exists. However, little is known about which knowledge translation (KT) interventions lead to the uptake of this evidence in practice.

OBJECTIVES

To conduct a systematic review of the effectiveness of KT interventions for chronic noncancer pain management.

METHODS

Comprehensive searches of electronic databases, the gray literature and manual searches of journals were undertaken. Randomized controlled trials, controlled clinical trials and controlled before-and-after studies of KT interventions were included. Data regarding interventions and primary outcomes were categorized using a standard taxonomy; a risk-of-bias approach was adopted for study quality. A narrative synthesis of study results was conducted.

RESULTS

More than 8500 titles and abstracts were screened, with 230 full-text articles reviewed for eligibility. Nineteen studies were included, of which only a small proportion were judged to be at low risk of bias. Interactive KT education for health care providers has a positive effect on patients' function, but its benefits for other health provider- and patient-related outcomes are inconsistent. Interactive education for patients leads to improvements in knowledge and function. Little research evidence supports the effectiveness of structural changes in health systems and quality improvement processes or coordination of care.

CONCLUSIONS

KT interventions incorporating interactive education in chronic noncancer pain led to positive effects on patients' function and knowledge about pain. Future studies should provide implementation details and use consistent theoretical frameworks to better estimate the effectiveness of such interventions.

LDL receptor-related protein-1: a regulator of inflammation in atherosclerosis, cancer, and injury to the nervous system

Low-density lipoprotein receptor-related protein-1 (LRP1) is an endocytic receptor for numerous proteins that are both structurally and functionally diverse. In some cell types, LRP1-mediated endocytosis is coupled to activation of cell signaling. LRP1 also regulates the composition of the plasma membrane and may, thereby, indirectly regulate the activity of other cell-signaling receptors. Given the scope of LRP1 ligands and its multifunctional nature, it is not surprising that numerous biological activities have been attributed to this receptor. LRP1 gene deletion is embryonic-lethal in mice. However, elegant studies using Cre-LoxP recombination have helped elucidate the function of LRP1 in mature normal and pathological tissues. One major theme that has emerged is the role of LRP1 as a regulator of inflammation. In this review, we will describe evidence for LRP1 as a regulator of inflammation in atherosclerosis, cancer, and injury to the nervous system.