Neural and psychosocial mechanisms of pain sensitivity in fibromyalgia

Percutaneous cryoablation therapy for abdominal wall endometriosis: a systematic review and meta-analysis

OBJECTIVES

Abdominal wall endometriosis (AWE) consists of endometrial tissue between the peritoneum and the abdominal wall. The established treatment involves amenorrheic drugs-not always successful and tolerated-or invasive surgery. In this scenario, minimally invasive techniques such as cryoablation are a potential option. In this study, we primarily aimed to evaluate the efficacy of percutaneous cryoablation in reducing pain scores of AWE patients and analyze their satisfaction with the procedure and its related adverse events.

MATERIALS AND METHODS

MEDLINE, EMBASE, and Cochrane's databases were systematically searched for studies that employed percutaneous cryoablation therapy for AWE and reported any of the outcomes of interest. The primary outcome was the reduction in the visual analog scale (VAS) score after treatment. R Software was used for the statistical analysis. Heterogeneity was assessed using I2 statistics. The Risk Of Bias In Non-Randomized Studies-of Interventions framework assessed potential bias in each selected study.

RESULTS

We included 4 studies, containing 126 patients. All articles were retrospective studies. The difference between the VAS scores before and after treatment was on average 5.97 points (95% CI 5.42-6.52; P <.01; I2 = 0%). The pooled satisfaction rate among patients in the selected studies was 93.1% (95% CI 88.66-97.34; P = .51; I2 = 0%). The pooled prevalence of adverse events was only 5.48% (95% CI 1.71-11.20; P = .58; I2 = 0%). Bias analysis showed an overall moderate risk in all included articles.

CONCLUSION

Our study demonstrated that cryoablation could reduce pain complaints in patients, while presenting a low incidence rate of adverse effects. Randomized clinical trials with a larger number of patients are necessary for greater conclusions.

ADVANCES IN KNOWLEDGE

(1) AWE affects about 3.5% of women. The standard treatment is invasive surgery. (2) This meta-analysis demonstrated that cryoablation can effectively reduce pain scores while presenting a low rate of adverse effects. (3) Cryoablation is a feasible treatment for AWE, furthermore allowing shorter hospital stays and few complications for the patients.

Psychological Factors Modulate Quantitative Sensory Testing Measures in Fibromyalgia Patients: A Systematic Review and Meta-Regression Analysis

OBJECTIVE

Considering the growing evidence that psychological variables might contribute to fibromyalgia syndrome (FMS), our study aims to understand the impact of psychological factors in quantitative sensory testing (QST) in FMS patients by performing a systematic review with meta-analysis.

METHODS

A systematic search was carried out in PubMed/MEDLINE, EMBASE, Web of Science, and PsycINFO databases for records up until January 2024. We included 20 studies ( n = 1623, 16 randomized controlled trials, and 4 nonrandomized controlled trials) with low or moderate risk of bias included.

RESULTS

From nonrandomized evidence, our meta-analysis found a baseline relationship between anxiety, depression, and pain catastrophizing and QST measures in FMS patients. Higher pain catastrophizing levels were associated with less efficient conditioned pain modulation. Higher anxiety and depression were associated with lower pain threshold (PT). Randomized evidence showed a statistically significant increase in PT after fibromyalgia treatments (effect size = 0.29, 95% confidence interval = 0.03-0.56). The effect was not influenced by treatment type. Moreover, we found that only anxiety levels before treatment negatively influenced the PT improvements after treatment.

CONCLUSION

FMS patients with higher anxiety levels at baseline showed a smaller increase in PT after the intervention. Depression factor was not significant in either changes in anxiety or depression. Baseline anxiety levels should be monitored as possible confounders of QST measurements. Understanding how psychological factors and QST are related in FMS patients is critical for improving the syndrome's management and treatment.Protocol Registration: CRD42023429397.

Subgroup characteristics in care workers with low back pain: cluster analysis-based severity of central sensitivity syndromes and low back pain

PURPOSE

This multicentre, collaborative, cross-sectional study aimed to explore the characteristics of subgroups based on central sensitivity syndromes (CSSs) and low back pain (LBP) severity. Furthermore, we investigated the relationship between the classified subgroups and work status among the care workers.

PATIENTS AND METHODS

In 660 care workers, we assessed LBP intensity, pain duration, pain sites, CSS (using the central sensitization inventory-9), psychological factors (using the pain catastrophizing scale and pain self-efficacy questionnaire), and work status (interference, amount of assistance, frequency of assistance, and work environment). We used hierarchical clustering analysis to divide the participants into subgroups based on CSS and LBP severity. We further performed multiple comparison analyzes and adjusted the residuals (chi-square test) to reveal differences between clusters.

RESULTS

Care workers with LBP were divided into four subgroups (Cluster 1: no CSS and mild LBP, Cluster 2: mild CSS and severe LBP, Cluster 3: mild CSS and mild LBP, Cluster 4: severe CSS and moderate LBP). Cluster 4 tended to have a higher number of pain sites, severe pain catastrophizing, and poor pain self-efficacy. In addition, Cluster 4 showed a higher frequency of assistance and an inadequate working environment and equipment. By contrast, Cluster 2 tended to have low pain self-efficacy. In addition, Cluster 2 experienced the highest work-related interference compared with any of the subgroups.

CONCLUSION

Our findings suggested that the severe LBP and severe CSS subgroups had common and different characteristics concerning psychological factors and work status, including interference with work. Our results may help to improve the management of care workers with LBP.

Characterizing clinical progression in patients with musculoskeletal pain by pain severity and central sensitization-related symptoms

Central sensitization-related symptoms (CSS) are associated with the severity and progression of pain. The relationship between the severity of pain/CSS and clinical progresses remains unclear. This multicenter, collaborative, longitudinal study aimed to characterize the clinical outcomes of patients with musculoskeletal pain by classifying subgroups based on the severity of pain/CSS and examining changes in subgroups over time. We measured the pain intensity, CSS, catastrophic thinking, and body perception disturbance in 435 patients with musculoskeletal pain. Reevaluation of patients after one month included 166 patients for pain intensity outcome and 110 for both pain intensity and CSS outcome analysis. We classified the patients into four groups (mild pain/CSS, severe pain/mild CSS, severe pain/CSS, and mild pain/severe CSS groups) and performed multiple comparison analyses to reveal the differences between the CSS severity groups. Additionally, we performed the adjusted residual chi-square to identify the number of patients with pain improvement, group transition, changing pain, and CSS pattern groups at baseline. The most characteristic result was that the mild and severe CSS groups showed worsening pain. Moreover, many of the group transitions were to the same group, with a few transitioning to a group with mild pain/CSS. Our findings suggest that the severity and improvement of CSS influence pain prognosis.

Expanding the notion of mechanism to further understanding of biopsychosocial disorders? Depression and medically-unexplained pain as cases in point

Evidence-Based Medicine has little consideration for mechanisms and philosophers of science and medicine have recently made pleas to increase the place of mechanisms in the medical evidence hierarchy. However, in this debate the notions of mechanisms seem to be limited to 'mechanistic processes' and 'complex-systems mechanisms,' understood as 'componential causal systems'. I believe that this will not do full justice to how mechanisms are used in biological, psychological and social sciences and, consequently, in a more biopsychosocial approach to medicine. Here, I propose, following (Kuorikoski, 2009), to pay more attention to 'abstract forms of interaction' mechanisms. The present work scrutinized review articles on depression and medically unexplained pain, which are considered to be of multifactorial pathogenesis, for their use of mechanisms. In review articles on these disorders there seemed to be a range of uses between more 'abstract forms of interaction' and 'componential causal system' mechanisms. I therefore propose to expand the notions of mechanisms considered in medicine to include that of more 'abstract forms of interaction' to better explain and manage biopsychosocial disorders.

Central metabolites and peripheral parameters associated neuroinflammation in fibromyalgia patients: A preliminary study

To identify central metabolites and peripheral measures associated with neuroinflammation in fibromyalgia (FM), we scanned [11C]-(R)-PK11195 positron emission tomography and magnetic resonance spectroscopy in FM patients. We measured associations between neurometabolite levels measured by magnetic resonance spectroscopy and the extent of neuroinflammation inferred by the distribution volume ratios of [11C]-(R)-PK11195 positron emission tomography in 12 FM patients and 13 healthy controls. We also examined the associations between peripheral parameters, such as creatinine and C-reactive protein, and neuroinflammation. In FM patients, we found negative correlations between neuroinflammation and the creatine (Cr)/total creatine (tCr; Cr + phosphocreatine) ratios in the right (r = -0.708, P = .015) and left thalamus (r = -0.718, P = .008). In FM patients, negative correlations were apparent between neuroinflammation and the glutamate/tCr ratio in the right insula (r = -0.746, P = .005). In FM patients, we found negative correlations between neuroinflammation in the left thalamus (r = -0.601, P = .039) and left insula (r = -0.598, P = .040) and the blood creatinine levels. Additionally, we found significant correlations of other peripheral measures with neuroinflammation in FM patients. Our results suggest that both central metabolites, such as Cr and glutamate, and peripheral creatinine and other parameters are associated with neuroinflammation in patients with FM.

Associations of Central Sensitization-Related Symptoms with Low Back Pain-Related Factors and Work Status in Caregivers

Low back pain (LBP) is associated with psychological factors and central sensitization-related symptoms (CSSs). The relationship between CSSs, LBP-related factors, and work status in caregivers remain unclear. This multicentre, collaborative, cross-sectional study aimed to determine the association between CSS severity, LBP-related factors, and work status in caregivers with LBP. We measured LBP intensity, pain duration, pain sites, CSSs (using the Central Sensitization Inventory-9: CSI-9), psychological factors (using the Pain Catastrophizing and Pain Self-Efficacy scales), and work status (interference, amount of assistance, frequency of assistance, and work environment) in 660 caregivers. CSS severity was categorised as no (CSI-9:0−9), mild (CSI-9:10−19), or moderate/severe (CSI-9:20−36). We further performed multiple comparison analyses and adjusted the residual chi-square to reveal differences between CSS severity groups. Caregivers with more severe CSSs tended to exhibit worse LBP intensity (p < 0.01), widespread pain (p < 0.01), catastrophic thinking (p < 0.01), and pain self-efficacy (p < 0.01), and they also tended to experience work interference (p < 0.01). Caregivers without CSSs tended to receive a smaller amount of assistance with a lower frequency (p < 0.05). The number of participants with an adequate environment and equipment was significantly less in the moderate/severe CSS group (p < 0.01). Thus, our findings may suggest that CSS severity is associated with LBP intensity, widespread pain, psychological factors, and work status in caregivers.

Validation and Cross-Cultural Adaptation of the Spanish Version of the Pain Sensitivity Questionnaire (PSQ-S)

Experimental pain testing requires specific equipment and may be uncomfortable for patients. The Pain Sensitivity Questionnaire (PSQ) was developed to assess pain sensitivity, based on the pain intensity ratings (range: 0–10) of painful situations that occur in daily life. The main objective of this study was to carry out a cross-cultural adaptation and validation of the Spanish version of the PSQ (PSQ-S). A total of 354 subjects (296 healthy and 58 chronic pain patients) filled in the PSQ-S. A subgroup of 116 subjects performed experimental pain testing, including two modalities (cold and pressure), with different measures: pain intensity rating, pressure pain threshold, and tolerance. The validation results showed two factors: PSQ-S-moderate and PSQ-S-minor and, for the total scale and the two factors, an excellent internal consistency (Cronbach’s alpha coefficient > 0.9) and a substantial reliability (Intraclass Correlation Coefficient > 0.8). We obtained strong correlations with all the experimental pain rating parameters, catastrophizing, and depression variables, as well as moderate correlations with anxiety, central sensibilization, and impact on the quality of life. Chronic pain patients received elevated PSQ-S scores compared to healthy controls, and three cut-off values (PSQ-S-total = 7.00, PSQ-S-moderate = 7.57, and PSQ-S-minor = 6.29) based on ROC curve analyses were shown to be able to discriminate between healthy adults and adults with chronic pain. Therefore, PSQ-S may be a simple alternative to experimental pain procedures for clinical and experimental pain research.

Abnormal neurometabolites in fibromyalgia patients: Magnetic resonance spectroscopy study

This study aimed to investigate distinct neurometabolites in the anterior cingulate cortex (ACC), right and left thalamus, and insula of patients with fibromyalgia (FM) compared with healthy controls using proton magnetic resonance spectroscopy (MRS). Levels of N-acetylaspartate (NAA), N-acetylaspartylglutamate (NAAG), total NAA (tNAA = NAA + NAAG), myo-inositol (ml), glutamine (Gln), glutamate (Glu), Glx (Glu + Gln), glycerophosphocholine (GPC), total choline (tCho = GPC + phosphocholine) and glutathione (GSH) levels relative to total creatine (tCr) levels including creatine (Cr) and phosphocreatine (PCr) and relative to Cr levels were determined in the ACC, right and left thalamus, and insula in 12 patients with FM and 13 healthy controls using MRS. In the ACC, NAA/tCr (P = 0.028) and tCho/tCr (P = 0.047) were higher in patients with FM. In the right and left insula, tNAA/tCr (P = 0.019, P = 0.007, respectively) was lower in patients with FM. Patients with FM showed lower levels of ml/Cr (P = 0.037) in the right insula than healthy controls. These findings are paramount to understand decisive pathophysiological mechanisms related to abnormal features in the brain and parasympathetic nervous systems in FM. We suggest that the results presented herein may be essential to understand hidden pathological mechanisms and also life system potential as protective and recovering metabolic strategies in patients with FM.

Central Sensitivity Is Associated with Poor Recovery of Pain: Prediction, Cluster, and Decision Tree Analyses

The process of pain recovery varies and can include the recovery, maintenance, or worsening of symptoms. Many cases of patients with pain show a tendency of recovering as predicted; however, some do not. The characteristics of cases that do not fit the prediction of pain recovery remain unclear. We performed cluster and decision tree analyses to reveal the characteristics in cases that do not fit the prediction of pain recovery. A total of 43 patients with musculoskeletal pain (nonoperative: 22 patients, operative: 13 patients) and central pain (brain disease: 5 patients, spinal cord disease: 3 patients) were included in this longitudinal study. Central sensitivity syndrome (CSS) outcome measures (Central Sensitisation Inventory), pain intensity-related outcome measures (Short-Form McGill Pain Questionnaire-2 (SFMPQ-2)), and cognitive-emotional outcome measures (Hospital Anxiety and Depression Scale and Pain Catastrophising Scale-4) of all patients were assessed at baseline and after 1-2 months. Regression analysis was used to calculate pain recovery prediction values. A hierarchical cluster analysis based on the predicted change of SFMPQ-2 and the observed change of SFMPQ-2 was used to extract subgroups that fit and those that do not fit pain recovery prediction. To extract the characteristics of subgroups that do not fit the prediction of pain recovery, a decision tree analysis was performed. The level of significance was set at 5%. In the results of cluster analysis, patients were classified into three subgroups. Cluster 1 was characterised by worse pain intensity from baseline, cluster 2 by pain, having recovered less and mildly than the predicted value, and Cluster 3 by a marked recovery of pain. In the results of the decision tree analysis, the CSI change was extracted as an indicator related to the classification of all clusters. Our findings suggest that the poor improvement of CSS is characteristic in cases that do not fit the prediction of pain recovery.

Exploring the underlying mechanism of pain-related disability in hypermobile adolescents with chronic musculoskeletal pain

OBJECTIVES

A significant proportion of adolescents with chronic musculoskeletal pain (CMP) experience difficulties in physical functioning, mood and social functioning, contributing to diminished quality of life. Generalized joint hypermobility (GJH) is a risk factor for developing CMP with a striking 35-48% of patients with CMP reporting GJH. In case GJH occurs with one or more musculoskeletal manifestations such as chronic pain, trauma, disturbed proprioception and joint instability, it is referred to as generalized hypermobility spectrum disorder (G-HSD). Similar characteristics have been reported in children and adolescents with the hypermobile Ehlers-Danlos Syndrome (hEDS). In the management of CMP, a biopsychosocial approach is recommended as several studies have confirmed the impact of psychosocial factors in the development and maintenance of CMP. The fear-avoidance model (FAM) is a cognitive-behavioural framework that describes the role of pain-related fear as a determinant of CMP-related disability.

CONTENT

Pubmed was used to identify existing relevant literature focussing on chronic musculoskeletal pain, generalized joint hypermobility, pain-related fear and disability. Relevant articles were cross-referenced to identify articles possibly missed during the primary screening. In this paper the current state of scientific evidence is presented for each individual component of the FAM in hypermobile adolescents with and without CMP. Based on this overview, the FAM is proposed explaining a possible underlying mechanism in the relations between GJH, pain-related fear and disability.

SUMMARY AND OUTLOOK

It is assumed that GJH seems to make you more vulnerable for injury and experiencing more frequent musculoskeletal pain. But in addition, a vulnerability for heightened pain-related fear is proposed as an underlying mechanism explaining the relationship between GJH and disability. Further scientific confirmation of this applied FAM is warranted to further unravel the underlying mechanism.In explaining disability in individuals with G-HSD/hEDS, it is important to focus on both the physical components related to joint hypermobility, in tandem with the psychological components such as pain-related fear, catastrophizing thoughts and generalized anxiety.

Electroacupuncture attenuates chronic fibromyalgia pain through the phosphorylated phosphoinositide 3-kinase signaling pathway in the mouse brain

Objectives

Fibromyalgia (FM) is a central nervous system disorder characterized by widespread mechanical hyperalgesia due to unknown mechanisms. Several inflammatory mediators, such as interleukin-1 (IL-1), IL-6, IL-8, and tumor necrosis factor, are increased in the serum of FM patients. Although medications including pregabalin, duloxetine, and milnacipran are used to treat FM, the results are unsatisfying. In the present study we assessed whether electroacupuncture (EA) can reduce chronic FM pain and then proposed an underlying mechanism for this effect.

Materials and Methods

Chronic FM pain was induced in mice by dual acid saline injection lasting up to 4 weeks.

Results

Chronic FM pain was treated by EA manipulation, but not in the sham operated group. Phosphorylated phosphatidylinositol 3-kinase (pPI3K), protein kinase B, mechanistic target of rapamycin, and nuclear factor kappa-light-chain-enhancer of activated B cells were unaltered in the mouse dorsal root ganglion (DRG) and spinal cord (SC) after inducing FM and administering EA treatment. The pPI3K-associated nociceptive signaling pathway was increased in the thalamus of FM mice, but reversed by EA. Similar results were observed in the mouse somatosensory cortex.

Conclusion

These data suggest that EA has a significant effect on a signaling pathway in brain areas of FM mice. These findings suggest the value of EA for clinical practice.

[Analgesic effects of transcutaneous electrical nerve stimulation (TENS) in patients with fibromyalgia: A systematic review]

OBJECTIVE

To determine whether transcutaneous electrical nerve stimulation (TENS) has an analgesic effect greater than placebo or other treatments in patients with fibromyalgia. Furthermore, it was intended to analyze the optimal application parameters to achieve a greater reduction of pain.

DESIGN

A systematic review.

DATA SOURCE

Randomized clinical trials on the effect of TENS on fibromyalgia in the databases Pubmed, Cochrane and PEDro until November 2016.

SELECTION OF STUDIES

8 studies out of a total of 62 were selected. Controlled clinical trials in which TENS was applied in patients with fibromyalgia were included.

DATA EXTRACTION

Pain was analyzed as the main variable, although other variables such as fatigue, quality of life and impact, range of motion and depression were also included.

RESULTS

6 out of 8 studies obtained a significant decrease of pain. In 2 studies, TENS was applied as complementary treatment to therapeutic exercise with results evidencing a decrease in pain. The rest of the variables studied presented a great variability and conclusive results could not be established.

CONCLUSIONS

Treatment with TENS is effective for reducing pain in people with fibromyalgia. In addition, the inclusion of TENS in therapeutic exercise programs seems to have a greater effect than practicing therapeutic exercise in isolation. However, no efficacy has been demonstrated in other variables different to pain. Further studies are needed to investigate the optimization of the parameters of the TENS and a greater consensus among the variables used.

Role of Asic3, Nav1.7 and Nav1.8 in Electroacupuncture-Induced Analgesia in a Mouse Model of Fibromyalgia Pain

Background

The mechanisms underlying fibromyalgia (FM) pain are not understood. The US Food and Drug Administration has recommended three drugs for treating FM—namely, pregabalin, duloxetine and milnacipran; however, these medications are associated with severe side effects.

Objective

To create a mouse model of FM pain using dual injections of acidic saline to cause mechanical hyperalgesia and test whether ASIC3, Nav1.7 and Nav1.8 are involved in this process and whether electroacupuncture (EA) can reverse these phenomena.

Methods

The FM model was established by injecting acidic saline twice into 40 ICR mice. The mice were assigned to subgroups (n=8 each) treated with different EA frequencies (2, 15 and 50 Hz). ASIC3, Nav1.7 and Nav1.8 expression levels were measured by Western blotting and immunohistochemistry.

Results

Significant mechanical hyperalgesia was induced on day 8 in FM mice, which was reversed by 2, 15 and 50 Hz EA. ASIC3, Nav1.7 and Nav1.8 protein levels increased significantly in both the dorsal root ganglion and in the spinal cord of FM model mice. These changes were further attenuated by 2, 15 and 50 Hz EA.

Conclusion

Reduced nociceptive ASIC3, Nav1.7 and Nav1.8 proteins are involved in the preventive effects of EA against FM, and this series of molecules may represent targets for FM treatment.

High fat diet sensitizes fibromyalgia-like pain behaviors in mice via tumor necrosis factor alpha

Fibromyalgia (FM) and obesity are closely related. However, little is known about how obesity contributes to FM. Importantly, adequate evidence has shown that tumor necrosis factor alpha (TNF-α) plays a critical role in obesity. Thus, we hypothesized that obesity-induced TNF-α release may potentiate FM-associated pain. To test this hypothesis, we investigated the role of TNF-α in the development of FM-like pain in a mouse model of acid saline injection-induced FM. Consistent with previous reports, we showed that repeated acid saline injections induced bilateral mechanical hyperalgesia, and this effect lasted for at least 4 days after acid saline injections. This phenomenon was associated with increased levels of TNF-α in plasma, muscles, and spinal cord. Furthermore, we found that 24 weeks of high fat diet treatment significantly potentiated acid saline-induced bilateral mechanical hyperalgesia. High fat diet-treated mice exhibited robustly increased levels of TNF-α in plasma, muscles, and spinal cord after acid saline injections compared with low fat diet-treated mice. Additionally, using immunofluorescence staining, we found that the number of TNF-α positive cells in dorsal root ganglion (DRG) was increased after acid saline injections, and high fat diet treatment further sensitized this increase. Finally, we reported that acid saline-induced FM-like pain behaviors were abolished in TNFRp55-/- mice, confirming the critical role of TNF-α in the development of FM-like pain. Taken together, our results suggested that high fat diet treatment may sensitize acid saline-induced FM-like pain via increasing TNF-α levels in plasma, muscles, and DRG.

The Role of Chronic Psychosocial Stress in Explaining Racial Differences in Stress Reactivity and Pain Sensitivity

OBJECTIVE

To examine the role of psychosocial factors in mediating the relationship between African American (AA) race and both increased pain sensitivity and blunted stress reactivity.

METHODS

Participants included 133 AA and non-Hispanic white (nHW) individuals (mean [SD] age, 37 [9]) matched for age, sex, and socioeconomic status. Participants underwent mental stress testing (Trier Social Stress Test) while cardiovascular, hemodynamic, and neuroendocrine reactivity were measured. Participants completed questionnaires assessing potential sources of psychosocial stress and were tested for pain responses to cold pain and the temporal summation of heat pulses. Mediation analyses were used to determine the extent to which exposure to psychosocial stress accounted for the observed racial differences in stress reactivity and pain.

RESULTS

Chronic stress exposure and reactivity to mental stress was largely similar among AAs and nHWs; however, AAs exhibited heightened pain to both cold (p = .012) and heat (p = .004). Racial differences in the relationship between stress reactivity and pain were also observed: while greater stress reactivity was associated with decreased pain among nHWs, reactivity was either unrelated to or even positively associated with pain among AAs (e.g., r = -.21 among nHWs and r = .41 among AAs for stroke volume reactivity and cold pressor intensity). Adjusting for minor racial differences in chronic psychosocial stress did not change these findings.

CONCLUSIONS

Accounting for psychosocial factors eliminated racial differences in stress reactivity but not racial differences in sensitivity to experimental pain tasks. Increased exposure to chronic stress may not explain AAs' increased pain sensitivity in laboratory settings.

Effects of electroacupuncture in a mouse model of fibromyalgia: role of N-methyl-D-aspartate receptors and related mechanisms

Objective

N-methyl-D-aspartate receptor (NMDAR) activation and downstream transduction pathways are crucial for pain signalling. Fibromyalgia (FM) is a common pain syndrome of unclear aetiology that is often drug-refractory but may benefit from treatment with electroacupuncture (EA). We examined the contributions of NMDAR signalling to FM pain and EA responses in a mouse model.

Methods

A model of FM was established by acid saline injection in 32 mice and subgroups (n=8 each) were treated with EA (2 Hz, 15 min daily for 4 days) or minimal acupuncture (MA). Expression of NMDAR subunits, calmodulin-dependent protein kinase II (CaMKII), cyclic AMP response element binding protein (pCREB) and their corresponding phospho-activated forms were measured by Western blotting and immunohistochemistry.

Results

Acid saline injection induced significant mechanical hyperalgesia (paw withdrawal threshold 2.18±0.27 g, p<0.05 vs controls), which was reversed by EA (4.23±0.33 g, p<0.05 vs FM group) but not by MA (2.37±0.14 g, p<0.05 vs EA group). Expression levels of phosphorylated N-methyl-D-aspartate receptor (pNR)1 and pNR2B were significantly increased in the dorsal root ganglion of FM model mice (132.21±14.4% and 116.69±3.22% of control values), whereas NR1 and NR2B levels were unchanged (97.31±3.79% and 97.07%±2.27%, respectively). Expression levels of pCaMKIIα and pCREB were also higher in the FM group, and these changes were reversed by EA but not by MA. Similar changes in expression were observed in spinal cord neurons.

Conclusions

Reduced NMDAR−CaMKIIα−pCREB signalling is implicated in the positive effects of EA in FM. NMDAR signalling components may represent promising therapeutic targets for FM treatment.

Myofascial pain and fibromyalgia: two different but overlapping disorders

There is good evidence supporting that people with fibromyalgia syndrome (FMS) exhibit central sensitization. The role of peripheral nociception is under debate in FMS. It seems that widespread pain experienced in FMS is considered multiple regional pains; therefore, several authors proposed that muscles play a relevant role in FMS. Trigger points (TrPs) have long been a contentious issue in relation to FMS. Preliminary evidence reported that the overall spontaneous pain is reproduced by referred pain from active TrPs, suggesting that FMS pain is largely composed of pain arising, at least partially, from TrPs. Finally, there is preliminary evidence suggesting that management of TrPs is able to modulate the CNS and is effective for reducing pain in FMS, although results are conflicting and future studies are clearly needed.

Gray matter abnormalities associated with fibromyalgia: A meta-analysis of voxel-based morphometric studies

OBJECTIVES

Studies employing voxel-based morphometry (VBM) have reported inconsistent findings on the association of gray matter (GM) abnormalities with fibromyalgia. The aim of the present study is to identify the most prominent and replicable GM areas that involved in fibromyalgia.

METHODS

A systematic search of the PubMed database from January 2000 to September 2015 was performed to identify eligible whole-brain VBM studies. Comprehensive meta-analyses to investigate regional GM abnormalities in fibromyalgia were conducted with the Seed-based d Mapping software package.

RESULTS

Seven studies, reporting nine comparisons and including a grand total of 180 fibromyalgia patients and 126 healthy controls, were included in the meta-analyses. In fibromyalgia patients compared with healthy controls, regional GM decreases were consistently found in the bilateral anterior cingulate/paracingulate cortex/medial prefrontal cortex, the bilateral posterior cingulate/paracingulate cortex, the left parahippocampal gyrus/fusiform cortex, and the right parahippocampal gyrus/hippocampus. Regional GM increases were consistently found in the left cerebellum. Meta-regression demonstrated that age was correlated with GM anomalies in fibromyalgia patients.

CONCLUSIONS

The current meta-analysis identified a characteristic pattern of GM alterations within the medial pain system, default mode network, and cerebro-cerebellar circuits, which further supports the concept that fibromyalgia is a symptom complex involving brain areas beyond those implicated in chronic pain.

Muscle Trigger Points and Pressure Pain Sensitivity Maps of the Feet in Women with Fibromyalgia Syndrome

OBJECTIVE : To investigate the presence of trigger points (TrPs) in feet musculature and topographical pressure sensitivity maps of the feet as well as the relationship between TrPs, pressure pain maps, and clinical variables in women with fibromyalgia (FMS). METHODS : Fifty-one FMS women and 24 comparable healthy women participated. TrPs within the flexor hallucis brevis, adductor hallucis, dorsal interossei, extensor digitorum brevis, and quadratus plantae, as well as external and internal gastrocnemius, were explored. Pressure pain thresholds (PPTs) were assessed in a blind manner over seven locations on each foot. Topographical pressure sensitivity maps of the plantar region were generated using the averaged PPT of each location. RESULTS : The prevalence rate of foot pain was 63% (n = 32). The number of active TrPs for each FMS woman with foot pain was 5 ± 1.5 without any latent TrPs. Women with FMS without foot pain and healthy controls had only latent TrPs (2.2 ± 0.8 and 1.5 ± 1.3, respectively). Active TrPs in the flexor hallucis brevis and adductor hallucis muscles were the most prevalent. Topographical pressure pain sensitivity maps revealed that FMS women with foot pain had lower PPT than FMS women without pain and healthy controls, and higher PPT on the calcaneus bone (P < 0.001). CONCLUSIONS : The presence of foot pain in women with FMS is high. The referred pain elicited by active TrPs in the foot muscles reproduced the symptoms in these patients. FMS women suffering foot pain showed higher pressure hypersensitivity in the plantar region than those FMS women without pain.

Post-traumatic stress disorder symptoms may explain poor mental health in patients with fibromyalgia

Symptoms of post-traumatic stress disorder are common in fibromyalgia patients. This study compared post-traumatic stress disorder symptoms in fibromyalgia patients and healthy controls and determined whether patient-control differences in post-traumatic stress disorder symptoms mediated differences in mental health. In all, 30 patients and 30 healthy controls completed questionnaires assessing symptoms of post-traumatic stress disorder and mental health. Fibromyalgia patients had greater symptoms of post-traumatic stress disorder and mental health than controls. Patient-control differences in mental health symptoms were fully or partially mediated by differences in post-traumatic stress disorder symptoms. Healthcare providers should understand the role of trauma as management of trauma symptoms may be one strategy for improving mental health.

The Prevalence and Characteristics of Fibromyalgia in the 2012 National Health Interview Survey

BACKGROUND

Most knowledge of fibromyalgia comes from the clinical setting, where healthcare-seeking behavior and selection issues influence study results. The characteristics of fibromyalgia in the general population have not been studied in detail.

METHODS

We developed and tested surrogate study specific criteria for fibromyalgia in rheumatology practices using variables from the US National Health Interview Survey (NHIS) and the modification (for surveys) of the 2010 American College of Rheumatology (ACR) preliminary fibromyalgia criteria. The surrogate criteria were applied to the 2012 NHIS and identified persons who satisfied criteria from symptom data. The NHIS weighted sample of 8446 persons represents 225.7 million US adults.

RESULTS

Fibromyalgia was identified in 1.75% (95% CI 1.42, 2.07), or 3.94 million persons. However, 73% of identified cases self-reported a physician's diagnosis other than fibromyalgia. Identified cases had high levels of self-reported pain, non-pain symptoms, comorbidity, psychological distress, medical costs, Social Security and work disability. Caseness was associated with gender, education, ethnicity, citizenship and unhealthy behaviors. Demographics, behaviors, and comorbidity were predictive of case status. Examination of the surrogate polysymptomatic distress scale (PSD) of the 2010 ACR criteria found fibromyalgia symptoms extending through the full length of the scale.

CONCLUSIONS

Persons identified with criteria-based fibromyalgia have severe symptoms, but most (73%) have not received a clinical diagnosis of fibromyalgia. The association of fibromyalgia-like symptoms over the full length of the PSD scale with physiological as well as mental stressors suggests PSD may be a universal response variable rather than one restricted to fibromyalgia.