Central Sensitization in Patients with Rheumatoid Arthritis: A Systematic Literature Review

Analysis of the correlation between disease activity score 28 and its ultrasonographic equivalent in rheumatoid arthritis patients

OBJECTIVE

To study the differences between disease activity score 28 (DAS28) index and an ultrasound (US) approach using index echographic disease activity score (ECODAS).

METHODS

This was a cross-sectional study in patients diagnosed with rheumatoid arthritis (RA). Demographic, clinical, and laboratory data were collected. We created a US index (ECODAS) evaluating the joints with synovitis using gray scale US (GSUS) and power Doppler US (PDUS) and calculated the formula of DAS28 index with both variables substituting tender joint for GSUS and swollen joint for PDUS (ECODAS1) and vice versa (ECODAS2).

RESULTS

A total of 58 patients (65.5% women and 34.5% men) were included in the study. There was no significant difference between the 2 US indexes. We obtained a Pearson's correlation coefficient (Pearson's r) of 0.56 (p<0.00001) between DAS28 and ECODAS1 and of 0.57 (p<0.00001) between DAS28 and ECODAS2, respectively. However, for patients with a high disease activity [DAS28>5.1, tender joint count (TJC, high)], the correlation was poor (0.18) and ECODAS indexes were significantly lower (p=0.001). The correlation increased (0.86, p<0.001) when we excluded the tender joints and the joints with GS-positive synovitis in both the scores.

CONCLUSION

US reduces the bias in the evaluation of patients with RA with a high value in DAS28 index. We found a clear difference between DAS and ECODAS when TJC was high. The results suggest that joint tenderness reported by the patient is not a good reflection of inflammation. More studies are needed to find a new combined clinical and sonographic index that would better assess the disease activity in patients with RA.

Association between pain phenotype and disease activity in rheumatoid arthritis patients: a non-interventional, longitudinal cohort study

BACKGROUND

In well-controlled rheumatoid arthritis (RA) without significant joint damage, a substantial proportion of patients complain of persistent pain. Previous studies have identified different pain phenotypes in RA, in which non-nociceptive pain phenotypes are associated with higher concurrent disease activity scores. In this longitudinal study, we explored associations between pain phenotypes and long-term disease activity outcome in RA patients. Secondly, we explored whether pain phenotype is associated with comorbid conditions.

METHODS

One hundred eighty established RA patients were classified with a nociceptive (61%) or a non-nociceptive (39%) pain phenotype, based on their responses to the painDETECT-questionnaire. Two years of clinical follow-up data on disease activity outcomes were collected. Information on comorbid diseases was derived from electronic patient files.

RESULTS

Patients with a non-nociceptive pain phenotype showed higher mean disease activity scores (DAS28, 2.57; 95% CI, 2.37-2.77 vs. 2.11; 95% CI, 1.94-2.27; p < 0.001) and a twofold lower chance of achieving sustained DAS28 remission (OR = 0.49; 95% CI, 0.26-0.92; p = 0.020). Only the tender joint count and patient global health significantly differed between the pain phenotype groups. Patients with a non-nociceptive pain phenotype had more often been diagnosed with concurrent fibromyalgia (9.9% vs. 0.9%; p = 0.007) and other pain-associated comorbid diseases (52.1% vs. 35.8%; p = 0.030) compared with patients with a nociceptive pain phenotype.

CONCLUSION

This longitudinal study showed consistently worse long-term disease activity outcomes in RA patients with a non-nociceptive pain phenotype which appeared to be mainly due to differences in the subjective components of the disease activity score.

TRIAL REGISTRATION

The DREAM cohort study is registered in the Netherlands Trial Register: NTR578.

Altered cerebral pain processing of noxious stimuli from inflamed joints in rheumatoid arthritis: An event-related fMRI study

OBJECTIVE

To our knowledge, this is the first study assessing brain activation in response to painful stimulation over disease-relevant (finger joint) vs. neutral area (thumb nail) in patients suffering from rheumatoid arthritis (RA) compared to healthy controls (HC).

METHOD

Thirty-one RA patients and 23 HC underwent functional magnetic resonance imaging (fMRI) while stimulated with subjectively calibrated painful pressures corresponding to a pain sensation of 50 mm on a 100 mm VAS scale (P50) at disease-affected finger joint and thumbnail (left hand), and corresponding sites in HC.

RESULTS

Compared to controls, RA patients had significantly increased pain sensitivity (lower P50) at the inflamed joints but not at the thumbnail. RA patients exhibited significantly less activation in regions related to pain- and somatosensory processing (S1, M1, anterior insula, S2, SMG and MCC) during painful joint stimulation, compared to HC. No group difference in cerebral pain processing was found for the non-affected thumbnail. Within RA patients, significantly less brain activation was found in response to painful stimulation over disease-affected joint compared to non-affected thumbnail in bilateral S1, bilateral S2, and anterior insula. Further, RA patients exhibited a right-sided dlPFC deactivation, psycho-physiologically interacting (PPI) with the left dlPFC in response to painful stimulation at disease-affected joints.

CONCLUSION

The results indicate normal pain sensitivity and cerebral pain processing in RA for non-affected sites, while the increased sensitivity at inflamed joints indicate peripheral/spinal sensitization. Brain imaging data suggest that disease-relevant pain processing in RA is marked by aberrations and a failed initiation of cortical top-down regulation.

Application of ICD-11 among individuals with chronic pain: A post hoc analysis of the Stanford Self-Management Program

BACKGROUND

Chronic primary pain (CPP) is one of seven diagnostic groups within the proposed classification of chronic pain in ICD-11. Our aims were to apply the proposed ICD-11 criteria in a large cohort of chronic pain patients participating in the Chronic Pain Self-Management Program (CPSMP) and further investigate whether participants with CPP differed from participants with chronic secondary pain (CSP) regarding health, health expenditure and the effect of participating in the CPSMP.

METHODS

A secondary analysis of a randomized, controlled trial on the effect of the CPSMP. Four examiners categorized participants' pain according to ICD-11 using register-based medical diagnoses and patients' self-reported symptoms. Afterwards, differences between CPP and CSP were examined.

RESULTS

Out of 394 participants, 312 were successfully classified into CPP (n = 164) or CSP (n = 148) whereas 76 had a mixed pain condition. Participants with CPP were younger, more likely to be women, and had longer pain duration compared to participants with CSP. Participants with CPP reported worse health-related quality of life on the SF-36 Mental Component Summary and subscales of vitality, social functioning and bodily pain. Participants with CSP had more physical comorbidities and higher total health expenditure. None of the groups benefitted from the CPSMP.

CONCLUSIONS

We successfully applied the new classification of chronic pain in ICD-11 on the basis of ICD-10 medical diagnoses and symptom self-report. Participants with CPP differed significantly from participants with CSP on baseline characteristics, self-reported health measures and total health expenditure. The CPSMP was not effective in any of the groups.

SIGNIFICANCE

The current study applies the proposed new classification of chronic pain in ICD-11 and shares the experiences of the diagnostic rating procedure of individuals with chronic pain. Furthermore, it evaluates the effect of the Stanford Self-Management Program.

The important role of central sensitization in chronic musculoskeletal pain seen in different rheumatic diseases

OBJECTIVE

This study explored the role of central sensitization (CS) pain in patients with various rheumatic diseases using the CS inventory (CSI).

METHODS

A total of 193 patients of mean age 50.72 ± 9.65 years were included; they were divided into four different groups in terms of their rheumatic diseases. Patients with rheumatoid arthritis (RA), spondyloarthropathy (SpA), osteoarthritis (OA), and fibromyalgia syndrome (FMS) were evaluated in tertiary care rheumatology/pain medicine settings. Disease duration and activity, the Bath Ankylosing Spondylitis Disease Activity Index, the Disease Activity Score-28, and pain severity (evaluated using a visual analog scale) were assessed, and the Turkish version of the CSI administered.

RESULTS

CS syndromes were present in almost half the patients (45% of SpA, 41% of RA, 62% of OA, and 94% of FMS patients). We found no significant relationship between disease activity and the CSI-A scores in SpA or RA patients (p = 0.731 and p = 0.390, respectively). As expected, the CSI-A scores were highest in the FMS group (p = 0.000), but were similar in the other groups (p < 0.05). CS-related syndromes (CSI-B conditions) were present at similar frequencies in the RA, SpA, and OA groups, but were less common in the FMS group (p = 0.000).

CONCLUSIONS

The CSI usefully detects CS pain in patients with rheumatic diseases. Treatment of such pain can enhance the quality of daily life in patients with rheumatic diseases.Key Point• Central sensitization pain is common in patients with rheumatic diseases including rheumatoid arthritis, spondyloarthropathies, and osteoarthritis.

Hyperexcitability of the Central Nervous System in Children with Chronic Pain: A Systematic Review

Objective

Hyperexcitability of the central nervous system plays an important role in the development and maintenance of chronic pain in adults. This knowledge has led to improved treatment strategies within this population. In children, however, research on the presence of central hyperexcitability is scarce. To further investigate this topic in children with chronic pain, there is a need for a clear literature overview.

Design

Systematic review.

Methods

The literature search was performed using the electronic databases PubMed and Web of Science. An article was considered eligible if it included children (age two to 12 years) diagnosed with chronic pain. Articles had to report original research outcomes related to central hyperexcitability, and a comparison with a healthy control group was necessary. Characteristics of the study sample, the assessment, and conclusions regarding central hyperexcitability were extracted from each included article.

Results

Twelve case-control studies were included with moderate to good methodological quality (510 children with chronic pain and 670 healthy controls). After summarizing the articles' results on indices of central hyperexcitability, we concluded that secondary hyperalgesia might be present in children with recurrent abdominal pain, juvenile fibromyalgia, and juvenile idiopathic arthritis. Preliminary evidence exists for altered cortical nociceptive processing in children with migraine and recurrent abdominal pain.

Conclusion

Based on the results of this review, central hyperexcitability might be present in in several pediatric chronic pain conditions. Further research on other manifestations of central hyperexcitability (e.g., bottom-up and top-down mechanisms and nociceptive brain changes) is necessary to provide firm evidence about its presence in children with chronic pain.

Pain and Catastrophizing in Patients With Rheumatoid Arthritis: An Observational Cohort Study

BACKGROUND

The aims of this study were to define changes in catastrophizing that occur with initiation of a new disease-modifying antirheumatic drug (DMARD) and to examine the relationship between changes in Clinical Disease Activity Index (CDAI) and changes in catastrophizing.

METHODS

Participants in an ongoing multisite, observational study completed the Pain Catastrophizing Scale (PCS) before and 12 weeks after DMARD initiation. We used multivariable linear regression models to examine the association between changes in CDAI as the exposure and change in pain catastrophizing as the outcome. We also assessed the relationship between changes in each component of CDAI and change in PCS, using multivariable linear regression models.

RESULTS

Among the 165 rheumatoid arthritis patients with data on CDAI at both time points, CDAI decreased from 22 to 11.5 on a 76-point scale (p < 0.0001) after 12 weeks. Pain intensity decreased from a median of 5 to 3 on a 10-point numeric rating scale (p < 0.0001), and catastrophizing decreased, from 16.0 to 12.0 on the 52-point PCS (p = 0.0005). Among the 163 with complete data for the regression analysis, changes in CDAI were positively correlated with changes in catastrophizing (standardized β = 0.19, p = 0.01). Of the components of the CDAI, change in assessor global score was most strongly associated with changes in catastrophizing (standardized β = 0.24, p = 0.003).

CONCLUSIONS

Pain catastrophizing decreases, in conjunction with disease activity, after initiation of a new DMARD. These findings provide support for catastrophizing as a dynamic construct that can be altered with treatment directed at decreasing inflammatory disease activity and pain.

Exploring the transcriptome of resident spinal microglia after collagen antibody-induced arthritis

Supplemental Digital Content is Available in the Text.

Glial inhibitors only reverse mechanical hypersensitivity in male mice subjected to arthritis. No obvious arthritis-related transcriptional difference was identified between male and female spinal microglia.

Recent studies have suggested a sexually dimorphic role of spinal glial cells in the maintenance of mechanical hypersensitivity in rodent models of chronic pain. We have used the collagen antibody–induced arthritis (CAIA) mouse model to examine differences between males and females in the context of spinal regulation of arthritis-induced pain. We have focused on the late phase of this model when joint inflammation has resolved, but mechanical hypersensitivity persists. Although the intensity of substance P, calcitonin gene–related peptide, and galanin immunoreactivity in the spinal cord was not different from controls, the intensity of microglia (Iba-1) and astrocyte (glial fibrillary acidic protein) markers was elevated in both males and females. Intrathecal administration of the glial inhibitors minocycline and pentoxifylline reversed mechanical thresholds in male, but not in female mice. We isolated resident microglia from the lumbar dorsal horns and observed a significantly lower number of microglial cells in females by flow cytometry analysis. However, although genome-wide RNA sequencing results pointed to several transcriptional differences between male and female microglia, no convincing differences were identified between control and CAIA groups. Taken together, these findings suggest that there are subtle sex differences in microglial expression profiles independent of arthritis. Our experiments failed to identify the underlying mRNA correlates of microglial actions in the late phase of the CAIA model. It is likely that transcriptional changes are either subtle and highly localised and therefore difficult to identify with bulk isolation techniques or that other factors, such as changes in protein expression or epigenetic modifications, are at play.

Pressure pain thresholds in adults with patellofemoral pain and patellofemoral joint osteoarthritis: a case-control study

Background and aims

Patellofemoral pain (PFP) and patellofemoral joint osteoarthritis (PFJOA) are common non-self-limiting conditions causing significant pain and disability. The underlying pain pathologies lack consensus with evidence suggesting reduced pressure pain thresholds (PPTs) in adolescent females with PFP and individuals with knee osteoarthritis. A paucity of evidence exists for mixed-sex adults with PFP and PFJOA in isolation. Exploring if pain sensitisation is a dominant feature of PFP and PFJOA may have important implications for the delivery of a patient centred management approach. The primary aim was to measure local and remote PPTs in PFP and PFJOA patients compared to matched controls. Secondary aims were to evaluate the relationship between PPTs and (1) condition severity and (2) knee function.

Methods

13 PFP patients plus 20 matched controls and 15 PFJOA patients plus 34 matched controls were recruited from a UK mixed-sex adult population. Controls were matched on age, sex and activity level. Demographic details, Tegner activity level score, symptom duration, condition severity (Kujala and KOOS-PF scores for PFP and PFJOA, respectively) and knee function (Modified Whatman score rating of five single leg squats) were recorded. PPTs were measured at six sites: five local around the knee, one remote on the contralateral leg. Between-group differences were tested using a two-way mixed model analysis of variance with repeated measures. Strength of association between PPTs and condition severity and knee function were tested using Spearman’s rank order correlation.

Results

No statistically significant difference in PPTs were observed between the PFP patients [F(1,31) = 0.687, p = 0.413, η2 = 0.022] or PFJOA patients [F(1,47) = 0.237, p = 0.629, η2 = 0.005] and controls. Furthermore, no correlation was found between PPTs and condition severity or knee function in PFP or PFJOA (p > 0.05).

Conclusions

Results suggest mechanical pain sensitisation is not a dominant feature of UK mixed-sex adults with PFP or PFJOA.

Implications

PFP and PFJOA remain persistent pain complaints which may not be well explained by objective measures of sensitivity such as PPTs. The findings suggest that peripheral pain processing changes leading to pain sensitisation is not a key feature in PFP or PFJOA. Instead the underlying pain pathway is likely to remain primary nociceptive, possibly with a subgroup of patients who experience pain sensitisation and might benefit from a more targeted management approach.

Achieving Pain Control in Rheumatoid Arthritis with Baricitinib or Adalimumab Plus Methotrexate: Results from the RA-BEAM Trial

The purpose of the study was to assess the proportion of patients who achieve pain relief thresholds, the time needed to reach the thresholds, and the relationship between pain and inflammation among patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate in RA-BEAM (NCT0170358). A randomized, double-blind trial was conducted, comparing baricitinib (N = 487), adalimumab (N = 330), and placebo (N = 488) plus methotrexate. Pain was evaluated by patient’s assessment on a 0–100 mm visual analog scale (VAS). The following were assessed through a 24-week placebo-controlled period: the proportion of patients who achieved ≥30%, ≥50%, and ≥70% pain relief, the time to achieve these pain relief thresholds, remaining pain (VAS ≤ 10 mm, ≤20 mm, or ≤40 mm), and the relationship between inflammation markers and pain relief. Baricitinib-treated patients were more likely (p < 0.05) to achieve ≥30%, ≥50%, and ≥70% pain relief than placebo- and adalimumab-treated patients, as early as Week 1 vs. placebo and at Week 4 vs. adalimumab. A greater proportion of baricitinib-treated patients achieved ≤20 mm or ≤40 mm remaining pain vs. placebo- and adalimumab-treated patients. Baricitinib-treated patients tended to demonstrate consistent pain relief independent of levels of inflammation control. In RA patients with an inadequate response to methotrexate, baricitinib provided greater and more rapid pain relief than adalimumab and placebo. Analyses suggest the relationship between inflammation and pain may be different for baricitinib and adalimumab treatments.

Whether chronic pain is medically explained or not does not moderate the response to cognitive-behavioural therapy

OBJECTIVES

To determine whether pain-related treatment outcomes, following an online Cognitive Behavioural Therapy (CBT) intervention for chronic pain, were moderated by the pain etiology of a medically explained or unexplained origin.

METHODS

Data were available from 471 participants who completed the online pain management program between March 2013 and August 2014. Participants' pain symptoms were classified as being medically explained symptoms (MES: n = 292) or medically unexplained symptoms (MUS: n = 222) via analysis of clinical data. Outcome variables were pain-related disability, average pain intensity, depression and anxiety.

RESULTS

Moderation analyses were non-significant for all dependent variables. Between group differences (CBT and control) were larger for depression in those classified with MES, compared with MUS (MUS: mean change = -3.50 [95% CI = -4.98 to -2.22]; MES: mean change = -5.72 [95% CI = -7.49 to -4.09]). However, between group differences were small for pain intensity (MUS: mean change = -0.03 [95% CI = -0.83 to 0.81]; MES: mean difference = -1.12 [95% CI = -1.84 to 0.40]).

CONCLUSION

The therapeutic outcomes examined in this study associated with an online CBT program do not appear to be altered by whether the participants' pain symptoms are medically explained or unexplained.

Pain Mechanisms and Ultrasonic Inflammatory Activity as Prognostic Factors in Patients With Psoriatic Arthritis: A Prospective Cohort Study

OBJECTIVE

To study the prognostic value of widespread pain and of musculoskeletal ultrasound (US) examination for subsequent treatment outcomes in patients with psoriatic arthritis (PsA).

METHODS

An exploratory prospective cohort study enrolled patients with PsA initiating biologic or conventional synthetic disease-modifying antirheumatic drugs in routine care. Clinical, US, and patient-reported measures were collected at baseline and after 4 months. Widespread nonarthritic pain (WP) was defined as a Widespread Pain Index score of ≥4 with pain in ≥4 of 5 regions. PsA activity by US was defined as color Doppler (yes/no) in selected entheses, joints, or tendons. The main response criteria included the American College of Rheumatology 20% improvement, the Disease Activity in Psoriatic Arthritis 50% improvement, and minimal disease activity. The primary analyses were age- and sex-adjusted logistic regression.

RESULTS

WP was present in 24 of 69 included patients (35%) and was associated with worse patient-reported and composite baseline measures, while US and other objective findings were similar to those in patients without WP. The odds of reaching minimal disease activity after 4 months were significantly greater for patients enrolled without WP (odds ratio 18.43 [95% confidence interval 1.51, 224.41]; P = 0.022), while WP did not impair other response measures. Patients with baseline color Doppler activity (n = 42 [61%]) had a worse objective PsA burden, but their chance of treatment response was comparable to those without color Doppler.

CONCLUSION

More than one-third of patients with PsA presented with WP, which was associated with worse patient-reported scores and failure to achieve minimal disease activity following conventional synthetic or biologic disease-modifying antirheumatic drug therapy. PsA activity by color Doppler US had no influence on subsequent treatment response in this PsA cohort.

Efficacy of Intra-Articular Botulinum Toxin in Osteoarticular Joint Pain: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

This study was conducted with the aim of evaluating the efficacy of intra-articular injections of botulinum toxin type A (BT-A) into the painful joint diseases through a systematic review of the literature and a meta-analysis of controlled randomized trials. Intra-articular therapies (corticosteroids, hyaluronic acid) have limited efficacy and run a risk of toxicity in patients with joint pain. New therapeutic options are needed to treat painful osteoarticular disease.

METHODS

We searched via Pubmed, American College of Rheumatology, and European League Against Rheumatism congresses, and gray literature for the studies reported until June 2016 and addressing the issue of BT intra-articular injections in patients with refractory joint pain. Randomized trials were included. For the meta-analysis, we compared a numeric rating scale (NRS) from 0 to 10 before treatment and at 1 or 2 months and 6 months after in the BT-A and the control groups for each study. We also compared separately low dose and high dose of BT at 1 or 2 months' evaluation.

RESULTS

In a total of 269 selected articles, 8 were analyzed and 6 studies were included in the meta-analysis involving a total of 382 patients. On comparing the NRS rating for 5 trials, at 1 or 2 months irrespective of the dose of BT, 4 trials showed a positive effect of BT compared with the control on the NRS and 1 found no effect; the overall weighted mean difference [95% confidence interval (CI)] was -1.10 (-1.62, -0.58) (P<0.0001, I=63%). Among the 4 trials with a low dose of BT (100 U), comparing NRS at 1 or 2 months, 3 trials showed significant results with a positive effect of BT-A injection compared with the control on the NRS; the fourth study failed to find any effect. The overall weighted mean difference (95% CI) was -0.95 (-0.02, -1.88) (P=0.05, I=67%). In the 2 trials using a high dose of BT (200 U) comparing NRS at 1 or 2 months, there was an almost zero effect of BT, with an overall weighted mean difference (95% CI) of 0.13 (-0.55, 0.81) (P=0.71, I=0%). In the 3 trials comparing NRS at 6 months there was an overall weighted mean difference (95% CI) of -0.57 (-1.98, 0.83) (P=0.42, I=73%).

CONCLUSIONS

BT-A intra-articular injections have short-term benefits with a statistically significant decrease in the NRS pain score of around 1 point in patients with refractory joint pain. A decrease in the pain score was also observed at 6 months but with a nonsignificant result.

Prevalence of chronic widespread pain in a population-based cohort of patients with spondyloarthritis - a cross-sectional study

Background

Chronic pain, regional or widespread, is a frequent and multidimensional symptom in arthritis. There is still limited information on chronic pain in spondyloarthritis, which is important to recognize for adequate diagnosis and treatment. Our objective was to study differences in prevalence of chronic widespread pain in two spondyloarthritis subgroups: ankylosing spondylitis (AS) and undifferentiated spondyloarthritis (USpA).

Methods

A population-based postal survey involving questions on the duration, distribution, and intensity of pain was answered by 940 patients with AS (ICD-10 M45.9) or USpA (ICD-10 M46.1-0, M46.8-9). The patients were categorized as having chronic widespread pain, chronic regional pain, or no chronic pain, and prevalence estimates for the pain groups were calculated, including age- and sex-adjusted prevalence.

Results

The prevalence of chronic widespread pain was 45.3% in AS vs. 49.3% in USpA, and that of chronic regional pain was 17.7% vs. 21.9% (p = 0.033). More women than men reported having chronic widespread pain (54.1% vs. 41.2%, p ≤ 0.001), while the sex distribution for chronic regional pain was equal. Reports of pain intensity were equal in AS and USpA, with no significant difference in pain intensity between women and men who had chronic regional pain or chronic widespread pain. In the multiple logistic regression analysis, chronic widespread pain was associated to female sex, being an ever-smoker, and having a higher body mass index, controlled for SpA subgroup and disease duration.

Conclusions

The prevalence of chronic widespread pain in patients with AS and USpA is high, and with a female predominance, but with no difference in pain intensity between women and men. Chronic pain can complicate the clinical evaluation in patients with SpA, and highlights the need for a thorough clinical examination, including evaluation of inflammation and an accurate pain analysis, to individualize non-pharmacological and pharmacological treatment decisions.

Pain and affective distress in arthritis: relationship to immunity and inflammation

INTRODUCTION

Most arthritides are associated with pain and psychological distress (clinically significant depression and anxiety). Pain and depression are mutually exacerbating; both may continue even when joint involvement appears well controlled. Area covered: There is strong evidence that arthritis-related stress impacts the central nervous system and, together with peripheral inflammatory changes, can cause central sensitization that can lead to chronic pain and worsening of affective distress. Cytokines and chemokines participate both in joint inflammation and in central sensitization. We review evidence of these relationships in five arthritides, namely rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, gout, and in osteoarthritis of the hips and knees. Central sensitization in these conditions results in long-lasting pain and psychological distress. Expert commentary: Chronic pain and depression are important but often neglected in the clinical assessment and treatment of arthritis. The potential role of biologic cytokines and Janus kinase inhibitors in dealing with these symptoms needs further study.

VEGFR2 promotes central endothelial activation and the spread of pain in inflammatory arthritis

Chronic pain can develop in response to conditions such as inflammatory arthritis. The central mechanisms underlying the development and maintenance of chronic pain in humans are not well elucidated although there is evidence for a role of microglia and astrocytes. However in pre-clinical models of pain, including models of inflammatory arthritis, there is a wealth of evidence indicating roles for pathological glial reactivity within the CNS. In the spinal dorsal horn of rats with painful inflammatory arthritis we found both a significant increase in CD11b⁺ microglia-like cells and GFAP⁺ astrocytes associated with blood vessels, and the number of activated blood vessels expressing the adhesion molecule ICAM-1, indicating potential glio-vascular activation. Using pharmacological interventions targeting VEGFR2 in arthritic rats, to inhibit endothelial cell activation, the number of dorsal horn ICAM-1⁺ blood vessels, CD11b⁺ microglia and the development of secondary mechanical allodynia, an indicator of central sensitization, were all prevented. Targeting endothelial VEGFR2 by inducible Tie2-specific VEGFR2 knock-out also prevented secondary allodynia in mice and glio-vascular activation in the dorsal horn in response to inflammatory arthritis. Inhibition of VEGFR2 in vitro significantly blocked ICAM-1-dependent monocyte adhesion to brain microvascular endothelial cells, when stimulated with inflammatory mediators TNF-α and VEGF-A₁₆₅a. Taken together our findings suggest that a novel VEGFR2-mediated spinal cord glio-vascular mechanism may promote peripheral CD11b⁺ circulating cell transmigration into the CNS parenchyma and contribute to the development of chronic pain in inflammatory arthritis. We hypothesise that preventing this glio-vascular activation and circulating cell translocation into the spinal cord could be a new therapeutic strategy for pain caused by rheumatoid arthritis.

Mechanisms for Joint Pain in Rheumatoid Arthritis (RA): from Cytokines to Central Sensitization

PURPOSE OF REVIEW

Pain in rheumatoid arthritis (RA) may be due to different etiologies, ranging from peripheral inflammation to dysregulation of central nervous system (CNS) processing. This review evaluates relevant literature published on RA pain mechanisms in recent years.

RECENT FINDINGS

Despite successes of disease-modifying antirheumatic drugs (DMARDs), pain persists for many RA patients. Studies involving patient-reported outcomes, quantitative sensory testing, and neuroimaging indicate that, in addition to joint inflammation, abnormalities in CNS pain processing may contribute to pain. Some DMARDs (e.g., janus kinus inhibitors) may work via multiple pathways to decrease pain. Adjunctive treatments (e.g., antidepressants, antiepileptics) may also be useful in managing pain in RA patients with well-controlled disease. Both peripheral and central mechanisms play key roles in the expression of pain in RA. To effectively manage pain, physicians need accurate assessment tools to identify the pathways involved in each patient so that treatments may be appropriately targeted.

The subjective components of the Disease Activity Score 28-joints (DAS28) in rheumatoid arthritis patients and coexisting fibromyalgia

To determine the contribution of fibromyalgia (FM) to the subjective components of the Disease Activity Score 28-joints (DAS28) in patients with rheumatoid arthritis (RA), and to analyse the discriminatory performance of the derived DAS28 patient-reported components (DAS28-P) to identify patients with fibromyalgic RA. Consecutive RA patients underwent clinical and clinimetric assessment. The DAS28-P index was derived from the components of the DAS28 scores by rearranging the DAS28-ESR formula. Patients were distinguished by the presence of FM. Student parametric t tests or Mann-Whitney non-parametric U tests were used to determine any between-group differences. Receiver operating characteristic (ROC) curve analysis was used to test the ability of the DAS28-P index to distinguish patients with RA and those with fibromyalgic RA. The study involved 292 RA patients (80.5% females, mean age 63 years) with a mean disease duration of 11.6 ± 8.5 years. Forty-three patients (14.7%) had concomitant FM, and significantly higher tender joint count (p < 0.001), pain numerical rating scale, global health status (p = 0.007), and DAS28 scores (p = 0.006) than those without FM. The DAS28-P values were also significantly higher in the patients with FM (0.68 ± 0.09 vs 0.58 ± 0.06; p < 0.001). The discriminatory power of the DAS28-P was very good (area under the ROC of 0.858, optimal cut-off value of 0.631). The presence of FM strongly influences the DAS28 results. The assessment of patient-reported components to the DAS28 through the DAS28-P can be a useful way to identify patients with fibromyalgic RA.

The course of pain hypersensitivity according to painDETECT in patients with rheumatoid arthritis initiating treatment: results from the prospective FRAME-cohort study

BACKGROUND

Evidence is emerging that pain in rheumatoid arthritis (RA) exists without underlying inflammation. Our objective was to evaluate the prognostic value of pain classification at treatment initiation using the painDETECT questionnaire (PDQ). Outcomes were change in DAS28-CRP and RAMRIS synovitis score.

METHODS

RA patients initiating a disease-modifying anti-rheumatic drug (DMARD) or initiating/ switching a biological agent were included. Follow-up time was 4 months. Clinical examination, imaging (MRI, dynamic contrast-enhanced MRI (DCE-MRI)), and patient-reported outcomes were undertaken. The PDQ was used to differentiate pain mechanisms. Mean change (95% CI) was calculated using ANCOVA. Multivariable regression models were used to determine a prognostic value.

RESULTS

A total of 102 patients were included; 75 were enrolled for MRI. Mean changes in baseline variables were greatest in the high PDQ classification group (> 18), while limited in the intermediate group (13-18). The 12 patients with high baseline PDQ score all changed pain classification group. No prognostic value of PDQ pain classification was found in relation to change of DAS28-CRP, RAMRIS score, or VAS pain. In the unadjusted model, RAMRIS score at baseline was associated with change in DAS28-CRP. The exploratory variables of DCE-MRI did not differ from other inflammatory variables.

CONCLUSIONS

In RA patients a high PDQ score (non-nociceptive pain) at baseline was not associated with worse outcomes, in fact these patients had numerically greater improvement in DAS28-CRP. However, pain classification by PDQ was not independently associated with change in DAS28-CRP, RAMRIS score, or VAS pain in the prognostic models. Furthermore, patients classified with a high baseline PDQ score changed pain classification group. Patients with unclear pain mechanism had reduced numerically treatment response.

TRIAL REGISTRATION

The study was approved by the Regional Ethics Committee of the Capital of Denmark April 18 2013; identification number H-3-2013-049 .

Pain sensitivity at rest and during muscle contraction in persons with rheumatoid arthritis: a substudy within the Physical Activity in Rheumatoid Arthritis 2010 study

Background

We aimed to explore pressure pain sensitivity and the function of segmental and plurisegmental exercise-induced hypoalgesia (EIH) in persons with rheumatoid arthritis (RA) compared with healthy control subjects (HC).

Methods

Forty-six participants with RA (43 female, 3 male) and 20 HC (16 female, 4 male) participated in the study. Pressure pain thresholds, suprathreshold pressure pain at rest, and segmental and plurisegmental EIH during standardised submaximal contractions were assessed by algometry. Assessments of EIH were made by performing algometry alternately at the contracting (30% of the individual maximum) right m. quadriceps and the resting left m. deltoideus.

Results

Participants with RA had higher sensitivity to pressure pain (RA, 318 kPa; HC, 487 kPa; p < 0.001), suprathreshold pressure pain 4/10 (RA, 433 kPa; HC, 638 kPa; p = 0.001) and suprathreshold pressure pain 7/10 (RA, 620 kPa; HC, 851 kPa; p = 0.002) than HC. Segmental EIH (RA, 0.99 vs 1.27; p < 0.001; HC, 0.89 vs 1.10; p = 0.016) and plurisegmental EIH (RA, 0.95 vs 1.36; p < 0.001; HC, 0.87 vs 1.31; p < 0.001) increased significantly during static muscle contraction in both groups alike (p > 0.05).

Conclusions

Our results indicate a generally increased pain sensitivity but normal function of EIH among persons with RA and offer one possible explanation for pain reduction observed in this group of patients following clinical exercise programmes.

Trial registration

ISRCTN registry, ISRCTN25539102. Retrospectively registered on 4 March 2011.

Chronic Pain in Inflammatory Arthritis: Mechanisms, Metrology, and Emerging Targets-A Focus on the JAK-STAT Pathway

Chronic pain is nowadays considered not only the mainstay symptom of rheumatic diseases but also "a disease itself." Pain is a multidimensional phenomenon, and in inflammatory arthritis, it derives from multiple mechanisms, involving both synovitis (release of a great number of cytokines) and peripheral and central pain-processing mechanisms (sensitization). In the last years, the JAK-STAT pathway has been recognized as a pivotal component both in the inflammatory process and in pain amplification in the central nervous system. This paper provides a summary on pain in inflammatory arthritis, from pathogenesis to clinimetric instruments and treatment, with a focus on the JAK-STAT pathway.

Validation of the Japanese version of the Central Sensitization Inventory in patients with musculoskeletal disorders

Background

Many musculoskeletal pain conditions are characterized by hypersensitivity, which is induced by central sensitization (CS). A questionnaire, the Central Sensitization Inventory (CSI), was recently developed to help clinicians identify patients whose presenting symptoms may be related to central sensitivity syndrome (CSS). The aims of the present study were to examine criterion validity and construct validity of the Japanese version of the CSI (CSI-J), and to investigate prevalence rates of CS severity levels in patients with musculoskeletal disorders.

Methods

Translation of the CSI into Japanese was conducted using a forward-backward method. Two hundred and ninety patients with musculoskeletal pain disorders completed the resultant CSI-J. A subset of the patients (n = 158) completed the CSI-J again one week later. The relationships between CSI and clinical symptoms, EuroQol 5-dimension (EQ-5D) and Brief Pain Inventory (BPI), were examined for criterion validity. EQ-5D assesses Health-related QOL and BPI measures pain intensity and pain interference. The psychometric properties were evaluated with analyses of construct validity, factor structure and internal consistency, and subsequently investigate the prevalence rates of CS severity levels.

Results

The CSI-J demonstrated high internal consistency (Cronbach’s α = 0.89) and test-retest reliability was excellent value (ICC = 0.85). The CSI-J was significantly correlated with EQ-5D (r = −0.44), pain intensity (r = 0.42), and pain interference (r = 0.48) (p < 0.01 for all). Ten percent of the participants were above the cutoff “40”. The exploratory factor analysis resulted in 5-factor model.

Conclusions

This study reported that the CSI-J was a useful and psychometrically sound tool to assess CSS in Japanese patients with musculoskeletal disorders. The finding of the prevalence rates of CS severity levels in patients with musculoskeletal disorders may help clinicians to decide strategy of treatment.

Influence of Morphine and Naloxone on Pain Modulation in Rheumatoid Arthritis, Chronic Fatigue Syndrome/Fibromyalgia, and Controls: A Double-Blind, Randomized, Placebo-Controlled, Cross-Over Study

BACKGROUND

Impaired pain inhibitory and enhanced pain facilitatory mechanisms are repeatedly reported in patients with central sensitization pain. However, the exact effects of frequently prescribed opioids on central pain modulation are still unknown.

METHODS

A randomized, double-blind, placebo-controlled cross-over trial was carried out. Ten chronic fatigue syndrome (CFS)/fibromyalgia (FM) patients, 11 rheumatoid arthritis (RA) patients and 20 controls were randomly allocated to the experimental (10 mg morphine or 0.2 mg/mL Naloxone) and placebo (2 mL Aqua) group. Pressure pain thresholds (PPTs) and temporal summation at the Trapezius and Quadriceps were assessed by algometry. Conditioned pain modulation (CPM) efficacy and deep tissue pain pressure were assessed by adding ischemic occlusion at the opposite upper arm.

RESULTS

Deep tissue pain pressure was lower and temporal summation higher in CFS/FM (P = 0.002 respectively P = 0.010) and RA patients (P = 0.011 respectively P = 0.047) compared to controls at baseline. Morphine had only a positive effect on PPTs in both patient groups (P time = 0.034). Accordingly, PPTs increased after placebo (P time = 0.015), and no effects on the other pain parameters were objectified. There were no significant effects of naloxone nor nocebo on PPT, deep tissue pain, temporal summation or CPM in the control group.

CONCLUSIONS

This study revealed anti-hyperalgesia effects of morphine in CFS/FM and RA patients. Nevertheless, these effects were comparable to placebo. Besides, neither morphine nor naloxone influenced deep tissue pain, temporal summation or CPM. Therefore, these results suggest that the opioid system is not dominant in (enhanced) bottom-up sensitization (temporal summation) or (impaired) endogenous pain inhibition (CPM) in patients with CFS/FM or RA.

Association between serum vitamin D levels and neuropathic pain in rheumatoid arthritis patients: A cross-sectional study

AIM

Recent literature suggests that neuropathic pain (NP) and vitamin D deficiency can occur concurrently in patients with rheumatoid arthritis (RA). This study aimed to examine the development of NP in patients with RA and the relationship between NP and vitamin D.

METHODS

We used the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaire to evaluate NP in 93 patients with RA. Demographic and clinical data were obtained from patient files and interviews, and patients' serum vitamin D levels were recorded. Patients were requested to complete both the Short Form-36 survey and the Health Assessment Questionnaire.

RESULTS

Seventy-five of the eligible patients were female (80.6%), and 31 (33.3%) were diagnosed with NP according to the LANSS. There was a negative correlation between vitamin D levels and the LANSS score (P = 0.001). The prevalence of NP was 5.8 times higher among patients with serum vitamin D levels below 20 ng/mL than in patients with vitamin D levels ≥ 30 ng/mL. Based on the area under curve (AUC) values, we found that serum levels of vitamin D were a good predictor of NP diagnoses in patients with RA (AUC = 0.71).

CONCLUSION

We found that vitamin D deficiency was asssociated with increased NP in patients with RA. Although further research is needed to clarify the association between serum vitamin D levels and NP, our study raises awareness of the need to screen for vitamin D deficiency in RA patients with NP.

Short stem total hip arthroplasty: Potential explanations for persistent post-surgical thigh pain

Short stem uncemented femoral implants were developed with the aim of preserving proximal bone stock for future revisions, improving biomechanical reconstruction, aiding insertion through smaller incisions and potentially decreasing or limiting the incidence of thigh pain. Despite all the advantages of short stem designs, it remains unclear whether they are able to limit post-surgical thigh pain. In patients with short stem hip arthroplasty and persistent thigh pain, it is of the utmost importance to understand the potential etiologies of this chronic pain for selecting the appropriate treatment strategy. Therefore, this manuscript explores the hypothetical etiologies of persistent thigh pain in short stem total hip arthroplasty, including both peripheral factors (structural or biomechanical causes) and central factors (involvement of the central nervous system). First, intrinsic causes (e.g. aseptic femoral loosening and prosthetic joint infection) and extrinsic sources (e.g. muscle pathology or spinal pathology) of persistent thigh pain related to hip arthroplasty are explained. In addition, other specific peripheral causes for thigh pain related to the short stem prosthetic reconstruction (e.g. stem malalignment and micro-motion) are unraveled. Second, the etiology of persistent thigh pain after short stem hip arthroplasty is interpreted in a broader concept than the biomechanical approach where peripheral structural injury is believed to be the sole driver of persistent thigh pain. Over the past decades evidence has emerged of the involvement of sensitization of central nervous system nociceptive pathways (i.e. central sensitization) in several chronic pain disorders. In this manuscript it is explained that there might be a relevant role for altered central nociceptive processing in patients with persistent pain after joint arthroplasty or revision surgery. Recognition of a potential role for centrally-mediated changes in pain processing in total hip replacement surgery has important implications for treatment. Comprehensive treatment addressing peripheral factors as well as neurophysiological changes occurring in the nervous system may help to improve outcomes in patients with short stem hip arthroplasty and chronic thigh pain. Working within a biopsychosocial approach in orthopaedic surgery, specifically in relation to total hip arthroplasty, could be very important and may lead to more satisfaction. Further research is warranted.

Pain and pain mechanisms in patients with inflammatory arthritis: A Danish nationwide cross-sectional DANBIO registry survey

Background

Central pain mechanisms may be prominent in subsets of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and other spondyloarthritis (SpA). The painDETECT questionnaire (PDQ) identifies neuropathic pain features, which may act as a proxy for centrally mediated pain.

The objectives were to quantify and characterize pain phenotypes (non-neuropathic vs. neuropathic features) among Danish arthritis patients using the PDQ, and to assess the association with on-going inflammation.

Methods

The PDQ was included onto the DANBIO touch screens at 22 departments of Rheumatology in Denmark for six months. Clinical data and patient reported outcomes were obtained from DANBIO. A PDQ-score >18 indicated neuropathic pain features, 13–18 unclear pain mechanism and <13 non-neuropathic pain.

Results

Pain data (visual analogue scale, VAS) was available for 15,978 patients. 7,054 patients completed the PDQ (RA: 3,826, PsA: 1,180, SpA: 1,093). 52% of all patients and 63% of PDQ-completers had VAS pain score ≥ 30 mm. The distribution of the PDQ classification-groups (<13/ 13-18/ >18) were; RA: 56%/24%/20%. PsA: 45%/ 27%/ 28%. SpA: 55% / 24%/ 21%. More patients with PsA had PDQ score >18 compared to RA and SpA (p<0.001). For PDQ > 18 significantly higher scores were found for all patient reported outcomes and disease activity scores. No clinical difference in CRP or swollen joint count was found. Logistic regression showed increased odds for having VAS pain ≥39 mm (the median) for a PDQ-score >18 compared to <13 (OR = 10.4; 95%CI 8.6–12.5).

Conclusions

More than 50% of the Danish arthritis patients reported clinically significant pain. More than 20% of the PDQ-completers had indication of neuropathic pain features, which was related to a high pain-level. PDQ-score was associated with DAS28-CRP and VAS pain but not with indicators of peripheral inflammation (CRP and SJC). Thus, pain classification by PDQ may assist in mechanism-based pain treatment.

Modern pain neuroscience in clinical practice: applied to post-cancer, paediatric and sports-related pain

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Generalized hypersensitivity in post-cancer, sports-related and pediatric pain.

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Rationale for pain education, stress management and cognition targeted exercises.

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Need to change from a biomedical or psychosocial to an integrated approach.

In the last decade, evidence regarding chronic pain has developed exponentially. Numerous studies show that many chronic pain populations show specific neuroplastic changes in the peripheral and central nervous system. These changes are reflected in clinical manifestations, like a generalized hypersensitivity of the somatosensory system. Besides a hypersensitivity of bottom-up nociceptive transmission, there is also evidence for top-down facilitation of pain due to malfunctioning of the endogenous descending nociceptive modulatory systems. These and other aspects of modern pain neuroscience are starting to be applied within daily clinical practice. However, currently the application of this knowledge is mostly limited to the general adult population with musculoskeletal problems, while evidence is getting stronger that also in other chronic pain populations these neuroplastic processes may contribute to the occurrence and persistence of the pain problem. Therefore, this masterclass article aims at giving an overview of the current modern pain neuroscience knowledge and its potential application in post-cancer, paediatric and sports-related pain problems.

The Reliability of Disease Activity Score in 28 Joints-C-Reactive Protein Might Be Overestimated in a Subgroup of Rheumatoid Arthritis Patients, When the Score Is Solely Based on Subjective Parameters: A Cross-sectional, Exploratory Study

BACKGROUND

Disease Activity Score in 28 Joints (DAS28) is a scoring system to evaluate disease activity and treatment response in rheumatoid arthritis (RA). A DAS28 score of greater than 3.2 is a well-described limit for treatment intensification; however, the reliability of DAS28 might be overestimated.

OBJECTIVE

The aim of this study was to evaluate the reliability of DAS28 in RA, especially focusing on a subgroup of patients with a DAS28 score of greater than 3.2.

METHODS

Data from RA patients registered in the local part of Danish DANBIO Registry were collected in May 2015. Patients were categorized into 2 groups: First, those with DAS28 >3.2 with at least one swollen joint (SJ) or elevated C-reactive protein (CRP) ("objective group"), and second, patients with a DAS28 >3.2 who had no SJ, and CRP values were within the reference range ("subjective group"). Disease Activity Score in 28 Joints, Clinical Disease Activity Index, and Health Assessment Questionnaire scores were calculated for each group. We defined new score, DAS28 subjective, to focus on subjective parameters.

RESULTS

Two hundred thirty patients were included; 198 (86.1%) and 32 (13.9%) patients were in the objective and subjective groups, respectively. Patients in the subjective group had lower mean values of DAS28 (P < 0.001) and Evaluator Global Assessment (P < 0.001) with less common immunoglobulin M rheumatoid factor (P < 0.001) and anti-cyclic citrullinated peptide positivity (P = 0.02) and contrarily higher mean values of tender joints (P = 0.04) and DAS28 based on subjective parameters (P = 0.003) compared with the objective group.

CONCLUSIONS

Rheumatoid arthritis scoring systems should be used cautiously in patients who are considered for treatment intensification. Patients with central sensitization and psychological problems and those with false-positive diagnosis of RA are at high risk of overtreatment.

Rethinking chronic pain in a primary care setting

Chronic pain substantially impacts patient function and quality of life and is a burden to society at large in terms of increased health care utilization and loss of productivity. As a result, there is an increasing recognition of chronic pain as a public health crisis. However, there remains wide variability in clinical practices related to the prevention, assessment, and treatment of chronic pain. Certain fundamental aspects of chronic pain are often neglected including the contribution of the psychological, social, and contextual factors associated with chronic pain. Also commonly overlooked is the importance of understanding the likely neurobiological mechanism(s) of the presenting pain and how they can guide treatment selection. Finally, physicians may not recognize the value of using electronic medical records to systematically capture data on pain and its impact on mood, function, and sleep. Such data can be used to monitor onset and maintenance of treatments effects at the patient level and evaluate costs at the systems level. In this review we explain how these factors play a critical role in the development of a coordinated, evidence-based treatment approach tailored to meet specific needs of the patient. We also discuss some practical approaches and techniques that can be implemented by clinicians in order to enhance the assessment and management of individuals with chronic pain in primary care settings.

Discordance between tender and swollen joint count as well as patient's and evaluator's global assessment may reduce likelihood of remission in patients with rheumatoid arthritis and psoriatic arthritis: data from the prospective multicentre NOR-DMARD study

Objective

To investigate the predictive value of discordance between (1) tender and swollen joint count and (2) patient's and evaluator's global assessment on remission in patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA).

Methods

From the prospective, multicentre Norwegian-Disease-Modifying Antirheumatic Drug study, we included patients with RA and PsA starting first-time tumour necrosis factor inhibitors and DMARD-naïve patients starting methotrexate between 2000 and 2012. The predictive value of ΔTSJ (tender minus swollen joint counts) and ΔPEG (patient's minus evaluator's global assessment) on remission was explored in prespecified logistic regression models adjusted for age, sex, disease duration and smoking.

Results

A total of 2735 patients with RA and 1236 patients with PsA were included (mean (SD) age 55.0 (13.5)/48.3 (12.4) years, median(range) disease duration 0.7 (0.0–58.0)/1.3 (0.0–48.3) years, 69.7/48.4% females). Baseline ΔTSJ/ΔPEG reduced the likelihood of achieving DAS28<2.6, SDAI≤3.3, CDAI≤2.8, ACR/EULAR Boolean and DAPSA<4 remission after 3 and 6 months in RA (OR 0.95–0.97, p<0.001/OR 0.96–0.99, p≤0.01) and PsA (OR 0.91–0.94, p≤0.004/OR 0.89–0.99, p≤0.002), except for ΔPEG and 6-month DAS28 remission in PsA.

Conclusions

Discordance between patient's and physician's evaluation of disease activity reflected through ΔTSJ and partly ΔPEG may reduce likelihood of remission in RA and PsA. The findings are relevant for use of the treat-to-target strategy in individual patients.

Effects of cold mist shower on patients with inflammatory arthritis: a crossover controlled clinical trial

OBJECTIVES

To evaluate the safety and effects of a new home treatment method, a whole-body cold mist treatment, on patients with chronic inflammatory arthritis.

METHOD

Whole-body cold mist shower therapy was given to 121 voluntary patients with chronic inflammatory arthritis in this crossover study during 1-week rehabilitation periods. Pain and sleep quality were assessed by a 10-cm visual analogue scale (VAS). Mental status was assessed by the Depression Scale (DEPS). Body temperature, blood pressure, heart rate, use of occasional pain and sleep medication, and possible side-effects were recorded.

RESULTS

The differences in pain (VAS) between treatment and control periods were significant (2.0 vs. 2.4, p = 0.006, paired t-test) in the last measurement, when assessing the pain of the past week as a whole. A trend could be seen of an increasing difference towards the end of the week. The treatment effect was statistically significant [likelihood ratio test (LRT), p < 0.0001] after controlling for period and sequence effects. There was an indication of better sleep quality (VAS) during the treatment period (2.3 vs. 2.7, p = 0.058 paired t-test) when assessing the past week as a whole. The mean DEPS scores showed no difference between the treatment periods (5.5 vs. 5.0, p = 0.1874 paired t-test, at start, and 4.5 vs. 4.1 p = 0.29 paired t-test, at the end). No significant side-effects were recorded.

CONCLUSIONS

The new whole-body cold treatment method may offer a safe option for self-treatment of pain at home but further study is needed to determine the clinical significance of the effect after longer use.

Mechanisms underlying the hyperalgesic responses triggered by joint activation of TLR4

BACKGROUND

Toll-like receptors (TLRs) including TLR4 and their signal pathways contribute to the pathogenesis of arthritis. Herein, we evaluated the mechanisms underlying the hyperalgesic response caused by TLR4 activation in the tibio-tarsal joint in mice.

METHODS

Joint inflammatory hyperalgesia was induced by intra-articular (ia) injection of LPS (lipopolysaccharide- TLR4 agonist) in C57BL/6, TLR4, TLR2, MyD88, TRIF, TNFR1/2 and IL-1R1 knockout (^-/-) mice. Joint hyperalgesia was evaluated using an electronic von Frey. Neutrophil recruitment was assessed by MPO activity. Joint levels of cytokines were measured by ELISA.

RESULTS

Firstly, it was shown that LPS injected into the joints causes a dose- and time-dependent reduction in the mechanical nociceptive threshold. The TLR4 activation in the joint triggers mechanical hyperalgesia and neutrophil migration, which was abolished in TLR4 ^-/- and MyD88^-/-, but not in TLR2^-/- and TRIF^-/- mice. Besides, joint administration of LPS increased the release of TNF-α, IL-1β, and KC/CXCL1, which were reduced in TLR4^-/- and MyD88^-/-, but not in TRIF^-/- mice. In agreement, the LPS-induced joint nociceptive effect was decreased in TNFR1/2^-/- and IL-1R1^-/- mice or in mice pre-treated with a CXCR1/2 selective antagonist (DF2156A).

CONCLUSIONS

These results suggest that TLR4 activation in the joint produces articular hyperalgesia via MyD88 signaling pathway. Moreover, this pathway is involved in the cascade of events of articular hyperalgesia through mechanisms dependent on cytokines and chemokines production. Thus, TLR4/MyD88 signaling pathway inhibitors might be useful for the treatment of inflammatory joint pain.