Mechanisms underlying development of spatially distributed chronic pain (fibromyalgia)

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.

Methodological Considerations for the Temporal Summation of Second Pain

Temporal summation of second pain (TSSP) is a psychophysical indication of a central pain encoding mechanism, potentially enhanced in pathological pain conditions. Low-frequency repetitive stimulation of unmyelinated (C) nociceptors results in a progressive increase of pain intensity when thermal stimulation intensity remains constant. However, when using different methods of nociceptive delivery to the skin, regularity as well as rate of pain enhancement with repetition varies between experiments. Specifically, repetitive ramping up and down from a neutral to a painful temperature has produced weak and inconsistent pain summation. In contrast, repetitive contact of the skin with a preheated probe has generated substantial pain summation. In the present study, TSSP by the intermittent contact with a preheated thermode and constant contact, ramp and hold methods were compared during 10 iterations of stimulation of glabrous skin of the hand or hairy forearm skin, with an onset to onset interval of 3.3 seconds and stimulus interval of .8 seconds. Significantly greater TSSP was observed for intermittent contact stimulation at both sites (P < .001). Differential activation of myelinated and unmyelinated nociceptors by ramping and tapping may account for different rates of temporal summation of heat pain.

PERSPECTIVE

This article presents direct evidence suggesting the constant contact, ramp and hold stimulus may underestimate the level of TSSP. This evidence suggests the re-evaluation of stimulation techniques used for temporal summation tests, especially within clinical models.

Evoked Pressure Pain Sensitivity Is Associated with Differential Analgesic Response to Verum and Sham Acupuncture in Fibromyalgia

OBJECTIVE

Fibromyalgia is a chronic pain condition with few effective treatments. Many fibromyalgia patients seek acupuncture for analgesia; however, its efficacy is limited and not fully understood. This may be due to heterogeneous pathologies among participants in acupuncture clinical trials. We hypothesized that pressure pain tenderness would differentially classify treatment response to verum and sham acupuncture in fibromyalgia patients.

DESIGN

Baseline pressure pain sensitivity at the thumbnail at baseline was used in linear mixed models as a modifier of differential treatment response to sham versus verum acupuncture. Similarly, needle-induced sensation was also analyzed to determine its differential effect of treatment on clinical pain.

METHODS AND PATIENTS

A cohort of 114 fibromyalgia patients received baseline pressure pain testing and were randomized to either verum (N = 59) or sham (N = 55) acupuncture. Participants received treatments from once a week to three times a week, increasing in three-week blocks for a total of 18 treatments. Clinical pain was measured on a 101-point visual analog scale, and needle sensation was measured by questionnaire throughout the trial.

RESULTS

Participants who had higher pain pressure thresholds had greater reduction in clinical pain following verum acupuncture while participants who had lower pain pressure thresholds showed better analgesic response to sham acupuncture. Moreover, patients with lower pressure pain thresholds had exacerbated clinical pain following verum acupuncture. Similar relationships were observed for sensitivity to acupuncture needling.

CONCLUSIONS

These findings suggest that acupuncture efficacy in fibromyalgia may be underestimated and a more personalized treatment for fibromyalgia may also be possible.

D-limonene exhibits superior antihyperalgesic effects in a β-cyclodextrin-complexed form in chronic musculoskeletal pain reducing Fos protein expression on spinal cord in mice

Chronic musculoskeletal pain is one of the main symptoms found in Fibromyalgia with unclear etiology and limited pharmacological treatment. The aim of this study was to complex LIM in β-cyclodextrin (LIM-βCD) and then evaluate its antihyperalgesic effect in an animal model of chronic musculoskeletal pain. Differential scanning calorimetry and scanning electron microscopy was used for the characterization of the inclusion complex. Male Swiss mice were used for experimental procedures where mechanical hyperalgesia, thermal hyperalgesia, muscular strength, Fos immunofluorescence was studied after induction of hyperalgesia. Mechanism of action was also investigated through tail flick test and capsaicin-induced nociception. Endothermic events and morphological changes showed that the slurry complex method was the best method for the complexation. After induction of hyperalgesia, the oral administration of LIM-βCD (50mg/kg) significantly increased the paw withdrawal threshold compared to uncomplexed limonene. Fos immunofluorescence showed that both compounds significantly decreased the number of Fos-positive cells in the dorsal horn. In nociceptive tests, FLU was able to reverse the antinociceptive effect of LIM-βCD. After intraplantar administration of capsaicin, LIM was able to significantly decrease time to lick. LIM-βCD has antihyperalgesic action superior to its uncomplexed form, with possible action in the dorsal horn of the spinal cord. These results suggest the possible applicability of LIM, uncomplexed or complexed with βCD, in conditions such as FM and neuropathic pain, for which there are currently only limited pharmacological options.

Muscle injections with lidocaine improve resting fatigue and pain in patients with chronic fatigue syndrome

OBJECTIVE

Patients with chronic fatigue syndrome (CFS) complain of long-lasting fatigue and pain which are not relieved by rest and worsened by physical exertion. Previous research has implicated metaboreceptors of muscles to play an important role for chronic fatigue and pain. Therefore, we hypothesized that blocking impulse input from deep tissues with intramuscular lidocaine injections would improve not only the pain but also fatigue of CFS patients.

METHODS

In a double-blind, placebo-controlled study, 58 CFS patients received 20 mL of 1% lidocaine (200 mg) or normal saline once into both trapezius and gluteal muscles. Study outcomes included clinical fatigue and pain, depression, and anxiety. In addition, mechanical and heat hyperalgesia were assessed and serum levels of lidocaine were obtained after the injections.

RESULTS

Fatigue ratings of CFS patients decreased significantly more after lidocaine compared to saline injections (p = 0.03). In contrast, muscle injections reduced pain, depression, and anxiety (p < 0.001), but these changes were not statistically different between lidocaine and saline (p > 0.05). Lidocaine injections increased mechanical pain thresholds of CFS patients (p = 0.04) but did not affect their heat hyperalgesia. Importantly, mood changes or lidocaine serum levels did not significantly predict fatigue reductions.

CONCLUSION

These results demonstrate that lidocaine injections reduce clinical fatigue of CFS patients significantly more than placebo, suggesting an important role of peripheral tissues for chronic fatigue. Future investigations will be necessary to evaluate the clinical benefits of such interventions.

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

•

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

•

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

•

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.

Targeting ASIC3 for Relieving Mice Fibromyalgia Pain: Roles of Electroacupuncture, Opioid, and Adenosine

Many scientists are seeking better therapies for treating fibromyalgia (FM) pain. We used a mouse model of FM to determine if ASIC3 and its relevant signaling pathway participated in FM pain. We demonstrated that FM-induced mechanical hyperalgesia was attenuated by electroacupuncture (EA). The decrease in fatigue-induced lower motor function in FM mice was also reversed by EA. These EA-based effects were abolished by the opioid receptor antagonist naloxone and the adenosine A1 receptor antagonist rolofylline. Administration of opioid receptor agonist endomorphin (EM) or adenosine A1 receptor agonist N⁶-cyclopentyladenosine (CPA) has similar results to EA. Similar results were also observed in ASIC3^−/− or ASIC3 antagonist (APETx2) injected mice. Using western blotting, we determined that pPKA, pPI3K, and pERK were increased during a dual acidic injection priming period. Nociceptive receptors, such as ASIC3, Nav1.7, and Nav1.8, were upregulated in the dorsal root ganglion (DRG) and spinal cord (SC) of FM mice. Furthermore, pPKA, pPI3K, and pERK were increased in the central thalamus. These aforementioned mechanisms were completely abolished in ASIC3 knockout mice. Electrophysiological results also indicated that acid potentiated Nav currents through ASIC3 and ERK pathway. Our results highlight the crucial role of ASIC3-mediated mechanisms in the treatment of FM-induced mechanical hyperalgesia.

Controversies and challenges in fibromyalgia: a review and a proposal

Fibromyalgia (FM) is the most commonly encountered chronic widespread pain (CWP) condition in rheumatology. In comparison to inflammatory arthritis (IA), it can seem ill defined with no clear understanding of the pathology and therefore no specific targeted treatment. This inevitably raises controversies and challenges. However, this is an outdated view perpetuated by poor teaching of pain at undergraduate and postgraduate levels, and the perennial problem of advances in relevant cross-speciality knowledge penetrating speciality silos. Research has provided a better understanding of the aetiopathology and FM is now regarded as a centralized pain state. Effective treatment is possible utilizing a multidisciplinary approach combining nonpharmacologic and pharmacologic treatments rooted in a biopsychosocial model. This article will provide a review of the mechanisms, diagnosis and treatment of FM, focus on some ongoing contentious issues and propose a change to the diagnostic terminology.

TauG-guidance of dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia

BACKGROUND

Impaired postural control has been reported in static conditions in chronic fatigue syndrome and fibromyalgia, but postural control in dynamic tasks have not yet been investigated. Thus, we investigated measurements from a force plate to evaluate dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia compared to matched healthy controls.

METHODS

Thirty female participants (10 per group) performed five trials of gait initiation. Center of pressure (CoP) trajectory of the initial weight shift onto the supporting foot in the mediolateral direction (CoPX) was analyzed using General Tau Theory. We investigated the hypothesis that tau of the CoPX motion-gap (τCoPx) is coupled onto an intrinsic tauG-guide (τG) by keeping the relation τCoPx=KτG, where K is a scaling factor that determines the relevant kinematics of a movement.

FINDINGS

Mean K values were 0.57, 0.55, and 0.50 in fibromyalgia, chronic fatigue syndrome, and healthy controls, respectively. Both patient groups showed K values significantly higher than 0.50 (P<0.05), indicating that patients showed poorer dynamic balance control, CoPX colliding with the boundaries of the base of support (K>0.5).

INTERPRETATION

The findings revealed a lower level of dynamic postural control in both fibromyalgia and chronic fatigue syndrome compared to controls.

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.

Current treatments to counter sleep dysfunction as a pathogenic stimulus of fibromyalgia

Fibromyalgia is characterized by chronic widespread pain, fatigue and nonrestorative sleep. Polysomnography showed reduced short-wave sleep and abnormal alpha rhythms during nonrapid eye movement sleep in patients with fibromyalgia. However, sleep dysfunction might be pathogenic in fibromyalgia since myalgia and fatigue could be induced in healthy individuals by disrupting sleep. Poor sleep quality was a major risk factor for the subsequent development of chronic widespread pain in healthy pain-free individuals. Sleep disruption leads to impairment of the descending pain inhibition pathways. Aside from good sleep, hygiene, exercise can promote sleep. Among currently available pharmacological treatments, evidence suggests amitriptyline and pregabalin can improve sleep in fibromyalgia.

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.

Augmented Pain Processing in Primary and Secondary Somatosensory Cortex in Fibromyalgia: A Magnetoencephalography Study Using Intra-Epidermal Electrical Stimulation

The aim of this study was to investigate augmented pain processing in the cortical somatosensory system in patients with fibromyalgia (FM). Cortical evoked responses were recorded in FM (n = 19) and healthy subjects (n = 21) using magnetoencephalography after noxious intra-epidermal electrical stimulation (IES) of the hand dorsum (pain rating 6 on a numeric rating scale, perceptually-equivalent). In addition, healthy subjects were stimulated using the amplitude corresponding to the average stimulus intensity rated 6 in patients with FM (intensity-equivalent). Quantitative sensory testing was performed on the hand dorsum or thenar muscle (neutral site) and over the trapezius muscle (tender point), using IES (thresholds, ratings, temporal summation of pain, stimulus-response curve) and mechanical stimuli (threshold, ratings). Increased amplitude of cortical responses was found in patients with FM as compared to healthy subjects. These included the contralateral primary (S1) and bilateral secondary somatosensory cortices (S2) in response to intensity-equivalent stimuli and the contralateral S1 and S2 in response to perceptually-equivalent stimuli. The amplitude of the contralateral S2 response in patients with FM was positively correlated with average pain intensity over the last week. Quantitative sensory testing results showed that patients with FM were more sensitive to painful IES as well as to mechanical stimulation, regardless of whether the stimulation site was the hand or the trapezius muscle. Interestingly, the slope of the stimulus-response relationship as well as temporal summation of pain in response to IES was not different between groups. Together, these results suggest that the observed pain augmentation in response to IES in patients with FM could be due to sensitization or disinhibition of the cortical somatosensory system. Since the S2 has been shown to play a role in higher-order functions, further studies are needed to clarify the role of augmented S2 response in clinical characteristics of FM.

Sensitization and Interoception as Key Neurological Concepts in Osteopathy and Other Manual Medicines

Historically, approaches used in manual medicine to explain patient reported symptoms have been focused on the so-called exteroceptive paradigm. Arguably, this mindset lacks an appropriate "reading system" able to interpret musculoskeletal disorders from a different perspective, where the properties of the nervous system are embraced into a more holistic and functional-related context. Interestingly, if the underpinning mechanisms of a given treatment scenario/effect are taking into account, the majority of research outcomes focuses on a proprioceptive/exteroceptive explanation, leaving ting aside the additional or even central role of interoception. Currently, to date, the application of theoretical knowledge acquired on the relatively recent neuroscientific concepts and evidence concerning of interoception, sensitization, touch, autonomic functions, inflammation, and pain into a clinical/research manual medicine scenario is lacking, even if theoretically, the impact on the possible etiological mechanisms and treatment effects seems to be important. Here, we propose the conceptual foundations for a new way of interpreting and reading patients' clinical reported outcomes scenario based on interoception and sensitization. We argue that this will provide a foundation to create the ground for future research focusing on the hypotheses that manual therapies, specifically osteopathy, can intercede with sensitization states, at all levels, using interoceptive pathways.

Temporomandibular disorders in fibromyalgia patients: are there different pain onset?

ABSTRACT Objective To identify temporomandibular disorders (TMD) symptoms in two groups of fibromyalgia patients according to the temporal relation between the onset of facial pain (FP) and generalized body pain (GBP). Cross-sectional study design: Fifty-three consecutive women with fibromyalgia and FP were stratified according to the onset of orofacial pain: Group-A (mean age 47.30 ± 14.20 years old), onset of FP preceded GBP; Group-B (mean age 51.33 ± 11.03 years old), the FP started concomitant or after GBP. Clinical assessment Research Diagnostic Criteria for Temporomandibular Disorders and the Visual Analogue Scale. Results Myofascial pain with mouth opening limitation (p = 0.038); right disc displacement with reduction (p = 0.012) and jaw stiffness (p = 0.004) were predominant in Group A. Myofascial pain without mouth opening limitation (p = 0.038) and numbness/burning were more common in Group B. Conclusion All patients had temporomandibular joint symptoms, mainly muscle disorders. The prevalence of myofascial pain with limited mouth opening and right TMJ disc displacement with reduction were higher in Group A.

High Times for Painful Blues: The Endocannabinoid System in Pain-Depression Comorbidity

Depression and pain are two of the most debilitating disorders worldwide and have an estimated cooccurrence of up to 80%. Comorbidity of these disorders is more difficult to treat, associated with significant disability and impaired health-related quality of life than either condition alone, resulting in enormous social and economic cost. Several neural substrates have been identified as potential mediators in the association between depression and pain, including neuroanatomical reorganization, monoamine and neurotrophin depletion, dysregulation of the hypothalamo-pituitary-adrenal axis, and neuroinflammation. However, the past decade has seen mounting evidence supporting a role for the endogenous cannabinoid (endocannabinoid) system in affective and nociceptive processing, and thus, alterations in this system may play a key role in reciprocal interactions between depression and pain. This review will provide an overview of the preclinical evidence supporting an interaction between depression and pain and the evidence supporting a role for the endocannabinoid system in this interaction.

Pain sensitization in people with knee osteoarthritis: a systematic review and meta-analysis

OBJECTIVE

Emerging evidence suggests that pain sensitization plays an important role in pain associated with knee osteoarthritis (OA). This systematic review and meta-analysis examined the evidence for pain sensitization in people with knee OA and the relationship between pain sensitization and symptom severity.

METHODS

A search of electronic databases and reference lists was carried out. All full text observational studies published between 2000 and 2014 with the aim of investigating pain sensitization in humans with knee OA using quantitative sensory testing (QST) measures of hyperalgesia and central hyperexcitability were eligible for inclusion. Meta-analysis of data was carried out using a random effects model, which included results comparing knee OA participants to controls, and results comparing high symptom severity to low symptom severity.

RESULTS

Fifteen studies were identified following screening and quality appraisal. For the meta-analysis, pressure pain threshold (PPT) and heat pain threshold (HPT) means and standard deviations were pooled using random effects models. The point estimate was large for differences in PPTs between knee OA participants and controls [-0.85; confidence interval (CI): -1.1 to -0.6], and moderate for PPT differences between knee OA participants with high symptom severity vs those with low symptom severity (0.51; CI: -0.73 to -0.30). A small point estimate was found for differences in HPTs between knee OA participants and controls (-0.42; CI: -0.87 to 0.02).

CONCLUSION

Evidence from this systematic review and meta-analysis suggests that pain sensitization is present in people with knee OA and may be associated with knee OA symptom severity.

Catechol-O-methyltransferase inhibition alters pain and anxiety-related volitional behaviors through activation of β-adrenergic receptors in the rat

Reduced catechol-O-methyltransferase (COMT) activity resulting from genetic variation or pharmacological depletion results in enhanced pain perception in humans and nociceptive behaviors in animals. Using phasic mechanical and thermal reflex tests (e.g. von Frey, Hargreaves), recent studies show that acute COMT-dependent pain in rats is mediated by β-adrenergic receptors (βARs). In order to more closely mimic the characteristics of human chronic pain conditions associated with prolonged reductions in COMT, the present study sought to determine volitional pain-related and anxiety-like behavioral responses following sustained as well as acute COMT inhibition using an operant 10-45°C thermal place preference task and a light/dark preference test. In addition, we sought to evaluate the effects of sustained COMT inhibition on generalized body pain by measuring tactile sensory thresholds of the abdominal region. Results demonstrated that acute and sustained administration of the COMT inhibitor OR486 increased pain behavior in response to thermal heat. Further, sustained administration of OR486 increased anxiety behavior in response to bright light, as well as abdominal mechanosensation. Finally, all pain-related behaviors were blocked by the non-selective βAR antagonist propranolol. Collectively, these findings provide the first evidence that stimulation of βARs following acute or chronic COMT inhibition drives cognitive-affective behaviors associated with heightened pain that affects multiple body sites.

Comparison of operant escape and reflex tests of nociceptive sensitivity

Testing of reflexes such as flexion/withdrawal or licking/guarding is well established as the standard for evaluating nociceptive sensitivity and its modulation in preclinical investigations of laboratory animals. Concerns about this approach have been dismissed for practical reasons - reflex testing requires no training of the animals; it is simple to instrument; and responses are characterized by observers as latencies or thresholds for evocation. In order to evaluate this method, the present review summarizes a series of experiments in which reflex and operant escape responding are compared in normal animals and following surgical models of neuropathic pain or pharmacological intervention for pain. Particular attention is paid to relationships between reflex and escape responding and information on the pain sensitivity of normal human subjects or patients with pain. Numerous disparities between results for reflex and operant escape measures are described, but the results of operant testing are consistent with evidence from humans. Objective reasons are given for experimenters to choose between these and other methods of evaluating the nociceptive sensitivity of laboratory animals.

Review of overlap between thermoregulation and pain modulation in fibromyalgia

Fibromyalgia (FM) syndrome is characterized by widespread pain that is exacerbated by cold and stress but relieved by warmth. We review the points along thermal and pain pathways where temperature may influence pain. We also present evidence addressing the possibility that brown adipose tissue activity is linked to the pain of FM given that cold initiates thermogenesis in brown adipose tissue through adrenergic activity, whereas warmth suspends thermogenesis. Although females have a higher incidence of FM and more resting thermogenesis, they are less able to recruit brown adipose tissue in response to chronic stress than males. In addition, conditions that are frequently comorbid with FM compromise brown adipose activity making it less responsive to sympathetic stimulation. This results in lower body temperatures, lower metabolic rates, and lower circulating cortisol/corticosterone in response to stress--characteristics of FM. In the periphery, sympathetic nerves to brown adipose also project to surrounding tissues, including tender points characterizing FM. As a result, the musculoskeletal hyperalgesia associated with conditions such as FM may result from referred pain in the adjacent muscle and skin.

Associations between craniomandibular disorders, sociodemographic factors and self-perceived general and oral health in an adult population

OBJECTIVE

The aim of this study was to analyze the relationships between pain in the craniomandibular region and jaw dysfunction, respectively, to sociodemographic factors and self-perceived general and oral health in a middle-aged and elderly population in Västerbotten County, Sweden.

MATERIALS AND METHODS

Six hundred individuals, 35-, 50-, 65- and 75 years old, from inland and 600 individuals from coastal areas were randomly selected in 2002. Of these, 987 individuals completed a questionnaire and 779 participated in a clinical examination. Thirty-five- and 50-year-olds together constituted a middle-aged group and the rest an elderly group.

RESULTS

Among the middle-aged, craniomandibular pain was associated with impaired general health status, signs of temporomandibular disorder (TMD) pain were associated with female gender and living alone, jaw dysfunction symptoms were associated with university degree and chewing with caution; and signs of TMD dysfunction were associated with female gender and living in the more densely populated coastal region. Among the elderly, craniomandibular pain was more common among those living in the inland region, craniomandibular pain and signs of TMD pain were associated with impaired general health status, jaw dysfunction symptoms were associated with higher education level and self-perceived impaired general health and oral health; and signs of TMD dysfunction were associated with female gender and living in the coastal region. Dental status was not associated with craniomandibular pain.

CONCLUSIONS

Socioeconomic factors and impaired general state of health were related to signs and symptoms indicative of CMD. These factors may influence demand for treatment among the affected.

Risk factors associated with incidence and persistence of frequent headaches

OBJECTIVE

Headaches represent a significant public health problem, but the knowledge of factors specifically related to incidence and persistence of headaches is still limited. The aim of this study was to evaluate whether gender, self-reported bruxism and variations in the dental occlusion contribute to onset and persistence of frequent headaches.

MATERIALS AND METHODS

The study population comprised 280 dental students, examined annually in a 2-year prospective study with a questionnaire and a clinical examination of the jaw function. In the analysis subjects were dichotomized into cases with frequent (once a week or more) or without frequent headaches (controls). The 2-year cumulative incidence was based on subjects without frequent headaches at baseline. Cases with 2-year persistent headaches reported such symptoms at all three examinations. Self-reported bruxism and factors in the dental occlusion at baseline were used as independent variables in logistic regression analyses.

RESULTS

The 2-year cumulative incidence of frequent headaches was 21%. Female gender (OR = 2.6; CI = 1.3-5.4), self-reported bruxism (OR = 2.3; CI = 1.2-4.4) and mandibular instability in intercuspal position (OR = 3.2; CI = 1.4-7.5) were associated with incidence of frequent headaches. Persistent headaches during the observation period were present in 12 individuals (4%) and significantly related to mandibular instability in intercuspal position (OR = 6.1; CI = 1.6-22.6).

CONCLUSIONS

The results indicate that female gender, self-reported bruxism and mandibular instability in intercuspal position are of importance in the development of frequent headaches. In management of these patients a multidisciplinary approach including dentists may be important and, thus, advocated.

Cerebral responses to innocuous somatic pressure stimulation following aerobic exercise rehabilitation in chronic pain patients: a functional magnetic resonance imaging study

OBJECTIVE

The purpose of this research was to assess the functional brain activity and perceptual rating of innocuous somatic pressure stimulation before and after exercise rehabilitation in patients with chronic pain.

MATERIALS AND METHODS

Eleven chronic pain patients and eight healthy pain-free controls completed 12 weeks of supervised aerobic exercise intervention. Perceptual rating of standardized somatic pressure stimulation (2 kg) on the right anterior mid-thigh and brain responses during functional magnetic resonance imaging (fMRI) were assessed at pre- and postexercise rehabilitation.

RESULTS

There was a significant difference in the perceptual rating of innocuous somatic pressure stimulation between the chronic pain and control groups (P=0.02) but no difference following exercise rehabilitation. Whole brain voxel-wise analysis with correction for multiple comparisons revealed trends for differences in fMRI responses between the chronic pain and control groups in the superior temporal gyrus (chronic pain > control, corrected P=0.30), thalamus, and caudate (control > chronic, corrected P=0.23). Repeated measures of the regions of interest (5 mm radius) for blood oxygen level-dependent signal response revealed trend differences for superior temporal gyrus (P=0.06), thalamus (P=0.04), and caudate (P=0.21). Group-by-time interactions revealed trend differences in the caudate (P=0.10) and superior temporal gyrus (P=0.29).

CONCLUSION

Augmented perceptual and brain responses to innocuous somatic pressure stimulation were shown in the chronic pain group compared to the control group; however, 12-weeks of exercise rehabilitation did not significantly attenuate these responses.

Widespread pain in temporomandibular disorders

SUMMARY Chronic widespread pain (CWP) represents pain involving several regions of the body. Various psychological and social risk factors such as poor general health status, sleep disturbance, fatigue and high psychological distress have been identified for the development of CWP. Numerous chronic pain conditions are comorbid, resulting in the development of CWP in many of these patients. Temporomandibular disorder is one of the most extensively studied chronic musculoskeletal pain condition in terms of its comorbidity with CWP and fibromyalgia. It has been proposed that these comorbid pain disorders share common denominators, including exposure to certain environmental events, elevated psychological distress, pain amplification and genetic predisposition. Increased awareness of CWP is important for improved diagnoses and more effective pain management. Patients with CWP can be effectively managed in multidisciplinary pain clinics.

Recovery of upper limb muscle function in chronic fatigue syndrome with and without fibromyalgia

BACKGROUND

Chronic fatigue syndrome (CFS) patients frequently complain of muscle fatigue and abnormally slow recovery, especially of the upper limb muscles during and after activities of daily living. Furthermore, disease heterogeneity has not yet been studied in relation to recovery of muscle function in CFS. Here, we examine recovery of upper limb muscle function from a fatiguing exercise in CFS patients with (CFS+FM) and without (CFS-only) comorbid fibromyalgia and compare their results with a matched inactive control group.

DESIGN

In this case-control study, 18 CFS-only patients, 30 CFS+FM patients and 30 healthy inactive controls performed a fatiguing upper limb exercise test with subsequent recovery measures.

RESULTS

There was no significant difference among the three groups for maximal handgrip strength of the non-dominant hand. A significant worse recovery of upper limb muscle function was found in the CFS+FM, but not in de CFS-only group compared with the controls (P < 0·05).

CONCLUSIONS

This study reveals, for the first time, delayed recovery of upper limb muscle function in CFS+FM, but not in CFS-only patients. The results underline that CFS is a heterogeneous disorder suggesting that reducing the heterogeneity of the disorder in future research is important to make progress towards a better understanding and uncovering of mechanisms regarding the nature of divers impairments in these patients.

Characteristics of sensitization associated with chronic pain conditions

OBJECTIVES

To describe and understand varieties and characteristics of sensitization contributing to hyperalgesia in participants with chronic pain conditions.

METHODS

Thermal stimulation was delivered to the face, forearm, and calf of pain-free participants and individuals with irritable bowel syndrome, temporomandibular pain disorder (TMD), and fibromyalgia syndrome (FM). Three-second contacts by a preheated thermode occurred at 30-second intervals in ascending and then in descending series (0.7°C steps).

RESULTS

Thermal pain ratings during ascending series were greater at each site in individuals diagnosed with chronic pain. Intense pain at the time of testing further enhanced the ratings at all sites, but mild or moderate clinical pain did not have this effect. Thermal pain in all participants was greater during descending series compared with the ascending series of arm and leg stimulation. The hypersensitivity during the descending series was comparable in pain-free, FM and TMD participants but was increased in duration for arm or leg stimulation of FM participants.

DISCUSSION

The widespread sensitization for irritable bowel syndrome and TMD participants does not rely on mechanisms of spatial and temporal summation often invoked to explain widespread hyperalgesia associated with chronic pain. Increased sensitivity during descending series of stimulation of an arm or leg but not the face indicates a propensity for sensitization of nociceptive input to the spinal cord. Abnormally prolonged sensitization for FM participants reveals a unique influence of widespread chronic pain referred to deep somatic tissues.

Pain Symptoms in Fibromyalgia Patients with and without Provoked Vulvodynia

Objective. The aim of the study was to compare the pain symptoms of fibromyalgia patients exhibiting (FMS+PVD) and not exhibiting (FMS) comorbidity with provoked vulvodynia. Study Design. The case control study was performed in 39 patients who had been diagnosed with FMS and accepted to undergo gynaecological examination and in 36 healthy women (C). All patients completed standardized questionnaires for pain intensity, pain area, and psychological functioning. The gynaecological examination included vulvar pain pressure reactivity (Q-tip), pelvic tone assessment (Kegel manoeuver), and a semistructured interview collecting detailed information about pelvic symptoms and sexual function. Results. FMS+PVD patients displayed a higher number of associated symptoms than FMS patients. The vulvar excitability was significantly higher in FMS+PVD than in FMS and in both groups than in Controls. Half of FMS+PVD patients were positive to Kegel manoeuver and displayed higher scores in widespread pain intensity, STAI-Y2, and CESD levels than Kegel negative patients. Conclusions. The study reveals that increased vulvar pain excitability may occur in FMS patients independently of the presence of coital pain. Results suggest that coital pain develops in patients with higher FMS symptoms severity due to the cooperative effects of peripheral and central sensitization mechanisms.

Neuropathic sensory symptoms: association with pain and psychological factors

BACKGROUND

A large number of population-based studies of chronic pain have considered neuropathic sensory symptoms to be associated with a high level of pain intensity and negative affectivity. The present study examines the question of whether this association previously found in non-selected samples of chronic pain patients can also be found in chronic pain patients with underlying pathology of neuropathic sensory symptoms.

METHODS

Neuropathic sensory symptoms in 306 patients with chronic pain diagnosed as typical neuropathic pain, radiculopathy, fibromyalgia, or nociceptive back pain were assessed using the Pain DETECT Questionnaire. Two separate cluster analyses were performed to identify subgroups of patients with different levels of self-reported neuropathic sensory symptoms and, furthermore, to identify subgroups of patients with distinct patterns of neuropathic sensory symptoms (adjusted for individual response bias regarding specific symptoms).

RESULTS

ANOVA (analysis of variance) results in typical neuropathic pain, radiculopathy, and fibromyalgia showed no significant differences between the three levels of neuropathic sensory symptoms regarding pain intensity, pain chronicity, pain catastrophizing, pain acceptance, and depressive symptoms. However, in nociceptive back pain patients, significant differences were found for all variables except pain chronicity. When controlling for the response bias of patients in ratings of symptoms, none of the patterns of neuropathic sensory symptoms were associated with pain and psychological factors.

CONCLUSION

Neuropathic sensory symptoms are not closely associated with higher levels of pain intensity and cognitive-emotional evaluations in chronic pain patients with underlying pathology of neuropathic sensory symptoms. The findings are discussed in term of differential response bias in patients with versus without verified neuropathic sensory symptoms by clinical examination, medical tests, or underlying pathology of disease. Our results lend support to the importance of using adjusted scores, thereby eliminating the response bias, when investigating self-reported neuropathic symptoms by patients.

Analgesic and anti-hyperalgesic effects of muscle injections with lidocaine or saline in patients with fibromyalgia syndrome

BACKGROUND

Patients with musculoskeletal pain syndrome including fibromyalgia (FM) complain of chronic pain from deep tissues including muscles. Previous research suggests the relevance of impulse input from deep tissues for clinical FM pain. We hypothesized that blocking abnormal impulse input with intramuscular lidocaine would decrease primary and secondary hyperalgesia and FM patients' clinical pain.

METHODS

We enrolled 62 female patients with FM into a double-blind controlled study of three groups who received 100 or 200 mg of lidocaine or saline injections into both trapezius and gluteal muscles. Study variables included pressure and heat hyperalgesia as well as clinical pain. In addition, placebo factors like patients' anxiety and expectation for pain relief were used as predictors of analgesia.

RESULTS

Primary mechanical hyperalgesia at the shoulders and buttocks decreased significantly more after lidocaine than saline injections (p = 0.004). Similar results were obtained for secondary heat hyperalgesia at the arms (p = 0.04). After muscle injections, clinical FM pain significantly declined by 38% but was not statistically different between lidocaine and saline conditions. Placebo-related analgesic factors (e.g., patients' expectations of pain relief) accounted for 19.9% of the variance of clinical pain after the injections. Injection-related anxiety did not significantly contribute to patient analgesia.

CONCLUSION

These results suggest that muscle injections can reliably reduce clinical FM pain, and that peripheral impulse input is required for the maintenance of mechanical and heat hyperalgesia of patients with FM. Whereas the effects of muscle injections on hyperalgesia were greater for lidocaine than saline, the effects on clinical pain were similar for both injectates.

Excitotoxic injury to thoracolumbar gray matter alters sympathetic activation and thermal pain sensitivity

Studies of humans, monkeys and rodents have implicated combined gray and white matter damage as important for development of chronic pain following spinal cord injury (SCI). Below-level chronic pain and hyperalgesia following injury to the spinal white matter, including the spinothalamic tract (STT), can be enhanced by excitotoxic influences within the gray matter at the site of SCI. Also, excitotoxic injury of thoracic gray matter without interruption of the STT results in below-level heat hyperalgesia. The present study evaluates the possibility that thoracolumbar gray matter injury increases sensitivity to nociceptive heat stimulation by altering spinal sympathetic outflow. Thermal preferences of rats for heat (45 °C) versus cold (15 °C) were evaluated before and after thoracolumbar injections of quisqualic acid (QUIS). A pre-injury preference for heat changed to a post-injury preference for cold. Systemic activation of the sympathetic nervous system by restraint stress decreased the heat preference pre-injury and increased the cold preference post-injury. The heat aversive effect of stress was magnified and prolonged post-injury, compared to pre-injury. Also, peripheral sympathetic activation by nociceptive stimulation was evaluated pre- and post-injury by measuring thermal transfer through a hindpaw during stimulation with 44.5 °C. Skin temperature recordings revealed enhanced sympathetic activation by nociceptive heat stimulation following spinal QUIS injury. However, increased sympathetic activation with peripheral vasoconstriction should enhance cold aversion, in contrast to the observed increase in heat aversion. Thus, peripheral sympathetic vasoconstriction can be ruled out as a mechanism for heat hyperalgesia following excitotoxic gray matter injury.

Facial pain associated with fibromyalgia can be marked by abnormal neuromuscular control: a cross-sectional study

BACKGROUND

Temporomandibular disorder (TMD) development in fibromyalgia syndrome (FMS) is not yet fully understood, but altered neuromuscular control in FMS may play a role in triggering TMD.

OBJECTIVE

The purpose of this study was to verify the association between neuromuscular control and chronic facial pain in groups of patients with FMS and TMD.

DESIGN

A cross-sectional study was conducted.

METHODS

This study involved an analysis of facial pain and electromyographic activity of the masticatory muscles in patients with FMS (n=27) and TMD (n=28). All participants were evaluated according to Research Diagnostic Criteria for Temporomandibular Disorders and surface electromyography (SEMG). Myoelectric signal calculations were performed using the root mean square and median frequency of signals.

RESULTS

The data revealed premature interruption of masticatory muscle contraction in both patient groups, but a significant correlation also was found between higher median frequency values and increased facial pain. This correlation probably was related to FMS because it was not found in patients with TMD only. Facial pain and increased SEMG activity during mandibular rest also were positively correlated.

LIMITATIONS

Temporal conclusions cannot be drawn from the study. Also, the study lacked a comparison group of patients with FMS without TMD as well as a control group of individuals who were healthy.

CONCLUSIONS

Altered neuromuscular control in masticatory muscles may be correlated with perceived facial pain in patients with FMS.

Pain treatment for patients with osteoarthritis and central sensitization

Osteoarthritis is one of the most frequent, disabling, and costly pathologies of modern society. Among the main aims of osteoarthritis management are pain control and functional ability improvement. The exact cause of osteoarthritis pain remains unclear. In addition to the pathological changes in articular structures, changes in central pain processing or central sensitization appear to be involved in osteoarthritis pain. The latter calls for a broader approach to the management of patients with osteoarthritis. Yet, the scientific literature offers scant information addressing the treatment of central sensitization, specifically in patients with osteoarthritis. Interventions such as cognitive-behavioral therapy and neuroscience education potentially target cognitive-emotional sensitization (and descending facilitation), and centrally acting drugs and exercise therapy can improve endogenous analgesia (descending inhibition) in patients with osteoarthritis. Future studies should assess these new treatment avenues.

Peripheral and central mechanisms of fatigue in inflammatory and noninflammatory rheumatic diseases

Fatigue is a common symptom in a large number of medical and psychological disorders, including many rheumatologic illnesses. A frequent question for health care providers is related to whether reported fatigue is "in the mind" or "in the body"-that is, central or peripheral. If fatigue occurs at rest without any exertion, this suggests psychological or central origins. If patients relate their fatigue mostly to physical activities, including exercise, their symptoms can be considered peripheral. However, most syndromes of fatigue seem to depend on both peripheral and central mechanisms. Sometimes, muscle biopsy with histochemistry may be necessary for the appropriate tissue diagnosis, whereas serological tests generally provide little reliable information about the origin of muscle fatigue. Muscle function and peripheral fatigue can be quantified by contractile force and action potential measurements, whereas validated questionnaires are frequently used for assessment of mental fatigue. Fatigue is a hallmark of many rheumatologic conditions, including fibromyalgia, myalgic encephalitis/chronic fatigue syndrome, rheumatoid arthritis, systemic lupus, Sjogren's syndrome, and ankylosing spondylitis. Whereas many studies have focused on disease activity as a correlate to these patients' fatigue, it has become apparent that other factors, including negative affect and pain, are some of the most powerful predictors for fatigue. Conversely, sleep problems, including insomnia, seem to be less important for fatigue. There are several effective treatment strategies available for fatigued patients with rheumatologic disorders, including pharmacological and nonpharmacological therapies.

Excessive peptidergic sensory innervation of cutaneous arteriole-venule shunts (AVS) in the palmar glabrous skin of fibromyalgia patients: implications for widespread deep tissue pain and fatigue

OBJECTIVE

To determine if peripheral neuropathology exists among the innervation of cutaneous arterioles and arteriole-venule shunts (AVS) in fibromyalgia (FM) patients.

SETTING

Cutaneous arterioles and AVS receive a convergence of vasoconstrictive sympathetic innervation, and vasodilatory small-fiber sensory innervation. Given our previous findings of peripheral pathologies in chronic pain conditions, we hypothesized that this vascular location may be a potential site of pathology and/or serotonergic and norepinephrine reuptake inhibitors (SNRI) drug action.

SUBJECTS

Twenty-four female FM patients and nine female healthy control subjects were enrolled for study, with 14 additional female control subjects included from previous studies. AVS were identified in hypothenar skin biopsies from 18/24 FM patient and 14/23 control subjects.

METHODS

Multimolecular immunocytochemistry to assess different types of cutaneous innervation in 3 mm skin biopsies from glabrous hypothenar and trapezius regions.

RESULTS

AVS had significantly increased innervation among FM patients. The excessive innervation consisted of a greater proportion of vasodilatory sensory fibers, compared with vasoconstrictive sympathetic fibers. In contrast, sensory and sympathetic innervation to arterioles remained normal. Importantly, the sensory fibers express α2C receptors, indicating that the sympathetic innervation exerts an inhibitory modulation of sensory activity.

CONCLUSIONS

The excessive sensory innervation to the glabrous skin AVS is a likely source of severe pain and tenderness in the hands of FM patients. Importantly, glabrous AVS regulate blood flow to the skin in humans for thermoregulation and to other tissues such as skeletal muscle during periods of increased metabolic demand. Therefore, blood flow dysregulation as a result of excessive innervation to AVS would likely contribute to the widespread deep pain and fatigue of FM. SNRI compounds may provide partial therapeutic benefit by enhancing the impact of sympathetically mediated inhibitory modulation of the excess sensory innervation.

Painful effects of auditory startle, forehead cooling and psychological stress in patients with fibromyalgia or rheumatoid arthritis

OBJECTIVE

The aim of this study was to determine whether the clinical pain associated with rheumatoid arthritis or fibromyalgia would increase during standard laboratory tasks and, if so, whether these increases were linked with individual differences in psychological distress.

METHODS

Twenty-three patients with fibromyalgia and 16 patients with rheumatoid arthritis rated changes in clinical pain after an acoustic startle stimulus, during painful forehead cooling, and during stressful mental arithmetic. In addition, pain tolerance was assessed during a submaximal effort tourniquet test, and patients provided ratings of distress on a standard Depression, Anxiety and Stress Inventory.

RESULTS

Pain at rest was associated with depression scores in patients with rheumatoid arthritis, and was associated with stress scores in the fibromyalgia group. However, pain tolerance was unrelated to individual differences in psychological distress in either group. In patients with fibromyalgia, clinical pain increased after the acoustic startle stimulus and painful forehead cooling, and increased during stressful mental arithmetic. Arthritic pain also increased during forehead cooling and mental arithmetic in association with indices of psychological distress.

CONCLUSIONS

These findings suggest that processes linked with individual differences in distress aggravate pain in rheumatoid arthritis, whereas some other mechanism (e.g., failure of stress-related pain modulation processes or an aberrant interaction between nociceptive afferent and sympathetic efferent fibers) triggers stress-induced pain in fibromyalgia.

National survey of knowledge, attitude and practice of fibromyalgia among rheumatologists in China

AIM

Fibromyalgia (FM) is a chronic disorder characterized by widespread musculoskeletal pain and fatigue. It is a less frequently diagnosed disease in China, thus Chinese rheumatologists may have lower awareness of FM compared with colleagues in Western countries. The aim of this study is to investigate the perceptions of FM in Chinese rheumatologists and analyze their therapeutic approach in clinical practice.

METHOD

An anonymous questionnaire survey was conducted among a nationwide sample of Chinese rheumatologists at the 15th National Rheumatology Conference in 2010. The 20-question survey included questions regarding background, work experience, perceptions of diagnosis and behaviors of treatment related to FM. Continuing medical education (CME) information was also collected in the survey.

RESULTS

Seven hundred and seven rheumatologists responded to the questionnaire, a response rate of 60%. Less than one-fifth of the respondents were experienced in dealing with FM. Although most of the respondents regarded FM as a distinct pathological entity, nearly 30% of Chinese rheumatologists believed that FM was only a psychological disorder. The respondents recognized some of the FM-related symptoms, but had limited knowledge on the diagnostic criteria. Eighty percent of the respondents declared they had difficulties in treating FM patients. However, nearly all (90.8%) respondents believed that the prognosis of FM patients was usually benign. Our data also showed that most Chinese rheumatologists were eager for CME on FM.

CONCLUSION

The awareness and perception of FM are still low among Chinese rheumatologists. CME on FM is needed for improving the quality of health care in China.