Abnormal pain modulation in patients with spatially distributed chronic pain: fibromyalgia

Influence of Transcutaneous Electrical Nerve Stimulation (TENS) on Pressure Pain Thresholds and Conditioned Pain Modulation in a Randomized Controlled Trial in Women With Fibromyalgia

Transcutaneous electrical nerve stimulation (TENS) effectively reduces pain in fibromyalgia (FM). The purpose of this study was to examine the influence of TENS use on pressure pain thresholds (PPT) and conditioned pain modulation (CPM) in individuals with FM using data from the Fibromyalgia Activity Study with TENS trial (NCT01888640). Individuals with FM were randomly assigned to receive active TENS, placebo TENS, or no TENS for 4 weeks. A total of 238 females satisfied the per-protocol analysis among the active TENS (n = 76), placebo TENS (n = 68), and no TENS (n = 94) groups. Following 4 weeks of group allocation, the active TENS group continued for an additional 4 weeks of active TENS totaling 8 weeks (n = 66), the placebo and no TENS groups transitioned to receive 4 weeks of active TENS (delayed TENS, n = 161). Assessment of resting pain, movement-evoked pain (MEP), PPT, and CPM occurred prior to and following active, placebo, or no TENS. There were no significant changes in PPT or CPM among the active TENS, placebo TENS, or no TENS groups after 4 weeks. Individuals who reported clinically relevant improvements in MEP (≥30% decrease) demonstrated increases in PPT (P < .001), but not CPM, when compared to MEP non-responders. There were no significant correlations among the change in PPT or CPM compared to MEP and resting pain following active TENS use (active TENS + delayed TENS). PPT and CPM may provide insight to underlying mechanisms contributing to pain; however, these measures may not relate to self-reported pain symptoms. PERSPECTIVE: Pressure pain threshold increased in individuals with clinically relevant improvement (≥30%) in MEP, indicating the clinical relevance of PPT for understanding mechanisms contributing to pain. CPM was not a reliable indicator of treatment response in MEP responders.

Interleukin-18 in chronic pain: Focus on pathogenic mechanisms and potential therapeutic targets

Chronic pain has been proven to be an independent disease, other than an accompanying symptom of certain diseases. Interleukin-18 (IL-18), a pro-inflammatory cytokine with pleiotropic biological effects, participates in immune modulation, inflammatory response, tumor growth, as well as the process of chronic pain. Compelling evidence suggests that IL-18 is upregulated in the occurrence of chronic pain. Antagonism or inhibition of IL-18 expression can alleviate the occurrence and development of chronic pain. And IL-18 is located in microglia, while IL-18R is mostly located in astrocytes in the spinal cord. This indicates that the interaction between microglia and astrocytes mediated by the IL-18/IL-18R axis is involved in the occurrence of chronic pain. In this review, we described the role and mechanism of IL-18 in different types of chronic pain. This review provides strong evidence that IL-18 is a potential therapeutic target in pain management.

The Correlation of Pain, Psychological Aspects, and Sleep in Fibromyalgia: A Cross-Sectional Analysis

Background

This pilot study measures pain perception, somatosensory amplification and its relationship to health anxiety in patients with fibromyalgia (FM) and patients with FM and obstructive sleep apnea (OSA); this study also examines the effects of OSA on pain perception in patients with FM.

Methods

In this pilot study, patients diagnosed with FM or FM and OSA, completed three self-reported questionnaires: Short-Form McGill Pain Questionnaire (SF-MPQ), Somatosensory Amplification Scale (SSAS), and Illness Behavior Questionnaire (IBQ). Sleep study results were analyzed. Scores were summarized using medians and interquartile ranges and are compared using Wilcoxon rank sum tests.

Results

Overall FM (n = 25), female n=23 male n=3 mean age, 57.48 years. OSA n=17 (68%) and 8 (32%) were not. The SF-MPQ Sensory sub-scale scores and the SF-MPQ overall scores differed significantly between patients with and without OSA. The SF-MPQ Sensory sub-scale scores were significantly lower for patients with OSA (p=0.03), as were SF-MPQ overall scores (p=0.04). SSAS overall scores and IBQ overall scores did not differ significantly by OSA diagnosis. Correlations of the different dimensions of IBQ with SSAS and mean number of diagnoses in FM and FM+OSA, mean number of diagnoses in problem list of SSAS ≤30 was 29.5, mean number of diagnoses in SSAS ≥30 was 34.9.

Discussion

Developing a better understanding of the effects of OSA on pain perception in patients with FM is needed for improved health status. More research is needed to see if higher pain perception and SSAS score lead to increased health care utilization and to evaluate the relationship between untreated disordered sleeping and pain perception in patients with FM.

Conclusion

Our findings highlight the need for more research to evaluate the relationship between treated and untreated disordered sleeping, pain perception, somatization and illness behavior in the health status of individuals with FM.

How durable are the effects of cognitive-behavioural therapy‎ in controlling fibromyalgia symptoms? A prospective cohort study

PURPOSE

Cognitive-behavioural therapy (CBT) is widely used for the treatment of fibromyalgia. However, there is no consensus on the durability of its effects on these patients. In this study, we evaluated how durable are the effects of CBT in controlling fibromyalgia symptoms.

METHODS

Forty-eight fibromyalgia patients treated with traditional face-to-face CBT were included. CBT was performed in 20 consecutive group sessions. To evaluate the durability of treatment, the effects of CBT on fibromyalgia symptoms were checked at five time-points: before the CBT, immediately after the CBT, 3 months after the CBT, 6 months after the CBT, and 12 months after the CBT. Outcome measures were the Fibromyalgia impact questionnaire (FIQ) and widespread pain index (WPI).

RESULTS

The mean FIQ score of the patients was 68.3 ± 18.8 before the CBT and 50.5 ± 14.1 1 week after the CBT (p < 0.001). The mean post-CBT FIQ score did not significantly change three and 6 months after the CBT (p = 0.11 and p = 0.09, respectively) while the positive effects of CBT significantly diminished after 12 months (p < 0.001). The mean WPI was 10.4 ± 3.6 before the CBT and 8.6 ± 3.1 1 week after the end of CBT (p < 0.001). The mean WPI of three and 6 months was not statistically different from that immediately after the CBT (p = 0.18 and p = 0.15, respectively), while after 12 months, it significantly worsened (p < 0.001).

CONCLUSION

CBT's beneficial effects for fibromyalgia patients are durable for 6 months. Complementary CBT sessions could be implemented to boost the CBT effect after this period.

Patients with neuropathic pain from lumbosacral radiculopathy demonstrate similar pressure pain thresholds and conditioned pain modulation to those with fibromyalgia

OBJECTIVE

The purpose of the study was to evaluate pain thresholds, impairment of the endogenous pain modulatory system, and self-reported cognitive-emotional and central sensitization-related symptoms among three subject groups: a rarely studied patient cohort with neuropathic pain from lumbosacral radiculopathy (NPLSR), patients with fibromyalgia (FM) and healthy controls (HC).

METHODS

Patient-reported pain-related symptomology was evaluated with psychometricallyvalidated questionnaires. Pressure pain threshold (PPT), heat pain threshold (HPT), and cold pain threshold (CPT) were assessed in the low back and contralateral forearm. Conditioned pain modulation (CPM) was evaluated with a recently introduced methodology that accounts for a standard error of measurement.

RESULTS

Compared to the HC subjects, the FM and NPLSR subjects had significantly lower pain thresholds and more CPM impairment. No significant differences in PPT and CPM were observed between the FM and NPLSR groups. Significant group differences were found in self-reported symptoms of depression, anxiety, stress, and central sensitization. Self-reported symptom severity increased in a stair-step fashion, with the HC group scoring lowest and FM group scoring highest.

CONCLUSION

The NPLSR group manifested CPM dysfunction and pressure hyperalgesia at similar levels to the FM group, indicating that these two chronic pain syndromes, likely based on different pathophysiological mechanisms, in fact share some common pain processing features. However, though both patient groups demonstrated similarities in pain processing, self-reported cognitive-emotional and central sensitization-related symptom severity was significantly higher in the FM cohort, which distinguished them from the chronic NPLSR cohort.

Can the monocyte-to-HDL ratio be used as an inflammation marker in patients with fibromyalgia syndrome?

Background and Aim

The monocyte-to-high-density lipoprotein (HDL) ratio (MHR) may be used as a marker of inflammation and oxidative stress. This study aimed to evaluate the use of MHR and platelet markers in patients with fibromyalgia syndrome (FMS) and demonstrate MHR's relationship with inflammation, the Fibromyalgia Impact Questionnaire (FIQ), and quality of life.

Materials and Methods

Ninety FMS patients and 90 healthy controls, whose clinical and laboratory evaluations were performed simultaneously, were included in the study. The monocyte, platelet, HDL, MHR, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), mean platelet volume (MPV), and platelet distribution width (PDW) values of all patients were evaluated. The quality of life of the participants was assessed using the FIQ and their general health using the health assessment questionnaire (HAQ).

Results

Age, body mass index (BMI), and marital status distribution were similar in both groups. The FMS patients had a mean disease duration of 11.29 ± 2.62 months. The median monocyte, platelet, MPV, visual analog scale (VAS), FIQ, and HAQ values and the mean MHR of the FMS patients were significantly higher than the control group, while the mean HDL level was significantly lower (P < 0.05). There was a weak negative correlation between the MPV and HAQ score and the PDW and HAQ score (rs = -0.225, P = 0.042 and rs = -0.249, P = 0.024, respectively), whereas no correlation was detected between the MHR and the FIQ and HAQ scores in FMS patients. According to the receiver operating characteristic curve analysis, MHR had prediction of FMS (P = 0.002; sensitivity = 0.63, specificity = 0.50, cut-off point ≥8.4).

Conclusions

Our results suggest that the monocyte, platelet, HDL, MHR, and MPV parameters can be used in the evaluation of inflammation in FMS patients.

The Utility of Ultrasound in Evaluating Joint Pain in Systemic Lupus Erythematosus: Looking beyond Fibromyalgia

BACKGROUND

Systemic lupus erythematosus (SLE) is a complex autoimmune condition with varied clinical presentations, and musculoskeletal pain is one of the most commonly associated symptoms. However, fibromyalgia (FM) is a prevalent co-existing condition in SLE patients that can also cause widespread pain, and in patients with both conditions, it is often difficult to distinguish the underlying cause of musculoskeletal pain and provide optimal therapy.

METHODS

A retrospective cohort study was conducted including all adult SLE patients who received musculoskeletal ultrasound (US) examinations for joint pain at the Ohio State University Wexner Medical Center between 1 July 2012, and 30 June 2022. Binary and multiple logistic regression analyses were performed to determine predictors of US-detected inflammatory arthritis as well as improved musculoskeletal pain.

RESULTS

A total of 31 of 72 SLE patients (43.1%) had a co-existing diagnosis of FM. In binary logistic regression, a co-existing diagnosis of FM was not significantly associated with US-detected inflammatory arthritis. In multiple logistic regression analysis, clinically detected synovitis was significantly associated with US-detected inflammatory arthritis (aOR, 142.35, p < 0.01), and there was also a weak association with erythrocyte sedimentation rate (ESR) (aOR 1.04, p = 0.05). In separate multiple logistic regression analysis, US-guided intra-articular steroid injection was the only predictor of improved joint pain at follow-up visit (aOR 18.43, p < 0.001).

CONCLUSIONS

Musculoskeletal US can be an effective modality to detect inflammatory arthritis as well as to guide targeted intra-articular steroid injection to alleviate joint pain in SLE patients with or without FM.

Primary somatosensory cortex and periaqueductal gray functional connectivity as a marker of the dysfunction of the descending pain modulatory system in fibromyalgia

Background

Resting-state functional connectivity (rs-FC) may aid in understanding the link between pain-modulating brain regions and the descending pain modulatory system (DPMS) in fibromyalgia (FM). This study investigated whether the differences in rs-FC of the primary somatosensory cortex in responders and non-responders to the conditioned pain modulation test (CPM-test) are related to pain, sleep quality, central sensitization, and the impact of FM on quality of life.

Methods

This cross-sectional study included 33 females with FM. rs-FC was assessed by functional magnetic resonance imaging. Change in the numerical pain scale during the CPM-test assessed the DPMS function. Subjects were classified either as non-responders (i.e., DPMS dysfunction, n = 13) or responders (n = 20) to CPM-test. A generalized linear model (GLM) and a receiver operating characteristic (ROC) curve analysis were performed to check the accuracy of the rs-FC to differentiate each group.

Results

Non-responders showed a decreased rs-FC between the left somatosensory cortex (S1) and the periaqueductal gray (PAG) (P < 0.001). The GLM analysis revealed that the S1-PAG rs-FC in the left-brain hemisphere was positively correlated with a central sensitization symptom and negatively correlated with sleep quality and pain scores. ROC curve analysis showed that left S1-PAG rs-FC offers a sensitivity and specificity of 85% or higher (area under the curve, 0.78, 95% confidence interval, 0.63-0.94) to discriminate who does/does not respond to the CPM-test.

Conclusions

These results support using the rs-FC patterns in the left S1-PAG as a marker for predicting CPM-test response, which may aid in treatment individualization in FM patients.

Spinal CCK1 Receptors Contribute to Somatic Pain Hypersensitivity Induced by Malocclusion via a Reciprocal Neuron-Glial Signaling Cascade

Recent studies have shown that the incidence of chronic primary pain including temporomandibular disorders (TMD) and fibromyalgia syndrome (FMS) often exhibit comorbidities. We recently reported that central sensitization and descending facilitation system contributed to the development of somatic pain hypersensitivity induced by orofacial inflammation combined with stress. The purpose of this study was to explore whether TMD caused by unilateral anterior crossbite (UAC) can induce somatic pain hypersensitivity, and whether the cholecystokinin (CCK) receptor-mediated descending facilitation system promotes hypersensitivity through neuron-glia cell signaling cascade. UAC evoked thermal and mechanical pain hypersensitivity of the hind paws from day 5 to 70 that peaked at week 4 post UAC. The expression levels of CCK1 receptors, interleukin-18 (IL-18) and IL-18 receptors (IL-18R) were significantly up-regulated in the L4 to L5 spinal dorsal horn at 4 weeks post UAC. Intrathecal injection of CCK1 and IL-18 receptor antagonists blocked somatic pain hypersensitivity. IL-18 mainly co-localized with microglia, while IL-18R mainly co-localized with astrocytes and to a lesser extent with neurons. These findings indicate that the signaling transduction between neurons and glia at the spinal cord level contributes to the descending pain facilitation through CCK1 receptors during the development of the comorbidity of TMD and FMS. PERSPECTIVE: CCK1 receptor-dependent descending facilitation may mediate central mechanisms underlying the development of widespread somatic pain via a reciprocal neuron-glial signaling cascade, providing novel therapeutic targets for the clinical treatment of TMD and FMS comorbidities.

Serial whole-body cryotherapy in fibromyalgia is effective and alters cytokine profiles

Introduction

Whole-body cryotherapy (WBC) has shown to be beneficial in the treatment of fibromyalgia (FM). There is cumulative evidence that cytokines play a crucial role in FM. It’s unknown whether clinical effects of WBC can be demonstrated at the molecular level and how long the effects last.

Methods

We compared effects of serial WBC (6 sessions (− 130 °C in 6 weeks) in FM patients and healthy controls (HC). Primary outcome was the change in pain level (visual analogue scale 0–100 mm) after 6 sessions. Secondary outcomes were a change in disease activity (revised Fibromyalgia Impact Questionnaire) and pain after 3 sessions and 3 months after discontinued therapy and in cytokine levels (interleukin (IL-)1, IL-6, tumor necrosis factor α (TNF-α) and IL-10). The patients’ opinions on the satisfaction, effectiveness and significance of WBC were evaluated.

Results

Twenty-three FM patients and 30 HC were enrolled. WBC resulted in a significant reduction in pain and disease activity after 3 and 6 sessions. No clinical benefit could be measured 3 months after discontinued treatment. Overall, probands were satisfied with WBC and considered WBC to be important and effective. FM patients had significantly different levels of IL-1, IL-6, TNF-α and IL-10 at each reading point compared to HC. Levels of IL-1, IL-6 and IL-10 were significantly altered over time in FM patients. Compared to HC FM patients showed a significantly different response of IL1, − 6 and − 10 to WBC.

Conclusion

Serial WBC is a fast acting and effective treatment for FM. Proven effects of WBC may be explained by changes in cytokines.

Ictal and interictal brain activation in episodic migraine: Neural basis for extent of allodynia

In some patients, migraine attacks are associated with symptoms of allodynia which can be localized (cephalic) or generalized (extracephalic). Using functional neuroimaging and cutaneous thermal stimulation, we aimed to investigate the differences in brain activation of patients with episodic migraine (n = 19) based on their allodynic status defined by changes between ictal and interictal pain tolerance threshold for each subject at the time of imaging. In this prospective imaging study, differences were found in brain activity between the ictal and interictal visits in the brainstem/pons, thalamus, insula, cerebellum and cingulate cortex. Significant differences were also observed in the pattern of activation along the trigeminal pathway to noxious heat stimuli in no allodynia vs. generalized allodynia in the thalamus and the trigeminal nucleus but there were no activation differences in the trigeminal ganglion. The functional magnetic resonance imaging (fMRI) findings provide direct evidence for the view that in migraine patients who are allodynic during the ictal phase of their attacks, the spinal trigeminal nucleus and posterior thalamus become hyper-responsive (sensitized)–to the extent that they mediate cephalic and extracephalic allodynia, respectively. In addition, descending analgesic systems seem as “switched off” in generalized allodynia.

Chronic pain intervention using pulsed shortwave therapy: the relationship between pain demographics and central sensitization inventory

Aim: The central sensitization inventory (CSI) is a validated, patient-reported questionnaire that quantifies symptoms of hypersensitivity disorders such as chronic pain, for which central sensitization (CS) may be the etiology. Objective: To investigate the analgesic effectiveness of ActiPatch and analyze the relationship between baseline CSI scores and demographics of chronic pain sufferers. Methods: Upon completing a 7-day ActiPatch trial, baseline CSI scores along with other assessment measures were obtained via e-mail from 174 chronic pain sufferers. Conclusion: CSI scores were positively correlated with gender (higher for women), baseline visual analog scale scores and pain duration. ActiPatch was found to be effective in reducing baseline pain for all subjects by an average of 4.3 visual analog scale points.

Development and preliminary evaluation of a short self-report measure of generalized pain hypersensitivity

Purpose

Generalized pain hypersensitivity is frequently observed in chronic pain conditions. Currently, identification is based on expert clinical opinion, and in very few cases combined with quantitative sensory testing. The objectives of this study were to develop and evaluate a short self-report measure of generalized pain hypersensitivity: a generalized pain questionnaire (GPQ).

Methods

Items for the GPQ were developed based on a literature review, followed by an interview study with ten rheumatic patients with suspected pain hypersensitivity. We examined the psychometric properties of the preliminary items in a sample of 212 outpatients suffering from either fibromyalgia (FM; n=98) or rheumatoid arthritis (n=114). Additionally, self-reported data were gathered on sociodemographics, fibromyalgia-survey criteria, health status, and neuropathic-like pain features.

Results

Mokken-scale analyses demonstrated a unidimensional seven-item scale with strong homogeneity (H=0.65) and high reliability (r=0.90). Correlations between total GPQ scores and relevant external measures, such as the FM-survey criteria and neuropathic-like pain features, were consistent with a priori expectations, supporting its external construct validity. Furthermore, the GPQ had good accuracy in distinguishing between patients with FM (generally assumed to be the result of central nervous system hypersensitization) and patients with RA (assumed to result mostly in local nociceptive or inflammatory pain), with an area under the receiver-operating characteristic curve of 0.89. A cutoff value >10 had the highest combination of sensitivity (82.7%) and specificity (77.2%).

Conclusion

The GPQ is psychometrically sound and appears promising for measuring the presence and severity of generalized pain hypersensitivity in chronic pain patients.

Potency of descending pain modulatory system is linked with peripheral sensory dysfunction in fibromyalgia: An exploratory study

Fibromyalgia (FM) is characterized by chronic widespread pain whose pathophysiological mechanism is related to central and peripheral nervous system dysfunction. Neuropathy of small nerve fibers has been implicated due to related pain descriptors, psychophysical pain, and neurophysiological testing, as well as skin biopsy studies. Nevertheless, this alteration alone has not been previously associated to the dysfunction in the descending pain modulatory system (DPMS) that is observed in FM. We hypothesize that they associated, thus, we conducted a cross-sectional exploratory study.To explore small fiber dysfunction using quantitative sensory testing (QST) is associated with the DPMS and other surrogates of nociceptive pathways alterations in FM.We run a cross-sectional study and recruited 41 women with FM, and 28 healthy female volunteers. We used the QST to measure the thermal heat threshold (HTT), heat pain threshold (HPT), heat pain tolerance (HPT), heat pain tolerance (HPTo), and conditional pain modulation task (CPM-task). Algometry was used to determine the pain pressure threshold (PPT). Scales to assess catastrophizing, anxiety, depression, and sleep disturbances were also applied. Serum brain-derived neurotrophic factor (BDNF) was measured as a marker of neuroplasticity. We run multivariate linear regression models by group to study their relationships.Samples differed in their psychophysical profile, where FM presented lower sensitivity and pain thresholds. In FM but not in the healthy subjects, regression models revealed that serum BDNF was related to HTT and CPM-Task (Hotelling Trace = 1.80, P < .001, power = 0.94, R = 0.64). HTT was directly related to CPM-Task (B = 0.98, P = .004, partial-η = 0.25), and to HPT (B = 1.61, P = .008, partial η = 0.21), but not to PPT. Meanwhile, BDNF relationship to CPM-Task was inverse (B = -0.04, P = .043, partial-η = 0.12), and to HPT was direct (B = -0.08, P = .03, partial-η = 0.14).These findings high spot that in FM the disinhibition of the DPMS is positively correlated with the dysfunction in peripheral sensory neurons assessed by QST and conversely with serum BDNF.

Assessment and manifestation of central sensitisation across different chronic pain conditions

Different neuroplastic processes can occur along the nociceptive pathways and may be important in the transition from acute to chronic pain and for diagnosis and development of optimal management strategies. The neuroplastic processes may result in gain (sensitisation) or loss (desensitisation) of function in relation to the incoming nociceptive signals. Such processes play important roles in chronic pain, and although the clinical manifestations differ across condition processes, they share some common mechanistic features. The fundamental understanding and quantitative assessment of particularly some of the central sensitisation mechanisms can be translated from preclinical studies into the clinic. The clinical perspectives are implementation of such novel information into diagnostics, mechanistic phenotyping, prevention, personalised treatment, and drug development. The aims of this paper are to introduce and discuss (1) some common fundamental central pain mechanisms, (2) how they may translate into the clinical signs and symptoms across different chronic pain conditions, (3) how to evaluate gain and loss of function using quantitative pain assessment tools, and (4) the implications for optimising prevention and management of pain. The chronic pain conditions selected for the paper are neuropathic pain in general, musculoskeletal pain (chronic low back pain and osteoarthritic pain in particular), and visceral pain (irritable bowel syndrome in particular). The translational mechanisms addressed are local and widespread sensitisation, central summation, and descending pain modulation.

Significance

Central sensitisation is an important manifestation involved in many different chronic pain conditions. Central sensitisation can be different to assess and evaluate as the manifestations vary from pain condition to pain condition. Understanding central sensitisation may promote better profiling and diagnosis of pain patients and development of new regimes for mechanism based therapy. Some of the mechanisms underlying central sensitisation can be translated from animals to humans providing new options in development of therapies and profiling drugs under development.

Pain facilitation and pain inhibition during conditioned pain modulation in fibromyalgia and in healthy controls

Although fibromyalgia (FM) is associated with a deficit in inhibitory conditioned pain modulation (CPM), the discriminative power of CPM procedures is unknown. Moreover, the high intersubject heterogeneity in CPM responses in FM raises the possibility that a sizeable subgroup of these patients may experience pain facilitation during CPM, but the phenomenon has not been explicitly studied. To address these issues, 96 patients with FM and 71 healthy controls were recruited. Thermal stimuli were used to measure pain thresholds. Pain inhibition was elicited using a tonic thermal test (Peltier thermode) administered before and after activation of CPM mechanisms using a cold pressor test. Thermal pain thresholds were lower in patients with FM than in healthy controls. Pain ratings during the cold pressor test were higher in patients with FM, relative to controls. The CPM inhibitory efficacy was lower in patients with FM than in controls. The CPM procedure had good specificity (78.9%) but low sensitivity (45.7%), whereas a composite pain index had good sensitivity (75.0%) and specificity (78.9%). Finally, the rate of patients with FM who reported pain facilitation during the CPM procedure was found to be significantly increased compared with that of controls (41.7% vs 21.2%). The good discriminative power of the composite pain index highlights the need for further validation studies using mechanistically relevant psychophysical procedures in FM. The low sensitivity of the CPM procedure, combined with the large proportion of patients with FM experiencing pain facilitation during CPM, strongly suggests that endogenous pain inhibition mechanisms are deeply impaired in patients with FM, but only in a subgroup of them.

Juvenile Fibromyalgia: Different from the Adult Chronic Pain Syndrome?

While a majority of research has focused on adult fibromyalgia (FM), recent evidence has provided insights into the presence and impact of FM in children and adolescents. Commonly referred as juvenile fibromyalgia (JFM), youths, particularly adolescent girls, present with persistent widespread pain and cardinal symptoms observed in adult FM. A majority of youth with JFM continue to experience symptoms into adulthood, which highlights the importance of early recognition and intervention. Some differences are observed between adult and juvenile-onset FM syndrome with regard to comorbidities (e.g., joint hypermobility is common in JFM). Psychological comorbidities are common but less severe in JFM. Compared to adult FM, approved pharmacological treatments for JFM are lacking, but non-pharmacologic approaches (e.g., cognitive-behavioral therapy and exercise) show promise. A number of conceptual issues still remain including (1) directly comparing similarities and differences in symptoms and (2) identifying shared and unique mechanisms underlying FM in adults and youths.

Stress, Inflammation and Pain: A Potential Role for Monocytes in Fibromyalgia-related Symptom Severity

The possibility that immunological changes might contribute to symptom severity in fibromyalgia (FM) prompted this proof-of-concept study to determine whether differences in monocyte subpopulations might be present in persons with FM compared with healthy controls. Relationships were assessed by comparing specific symptoms in those with FM (n = 20) and patterns of monocyte subpopulations with healthy age-matched and gender-matched controls (n = 20). Within the same time frame, all participants provided a blood sample and completed measures related to pain, fatigue, sleep disturbances, perceived stress, positive and negative affect and depressed mood (and the Fibromyalgia Impact Questionnaire for those with FM). Monocyte subpopulations were assessed using flow cytometry. No differences were observed in total percentages of circulating monocytes between the groups; however, pain was inversely correlated with percentages of circulating classical (r = -0.568, p = 0.011) and intermediate (r = -0.511, p = 0.025) monocytes in the FM group. Stress and pain were highly correlated (r = 0.608, p = 0.004) in the FM group. The emerging pattern of changes in the percentages of circulating monocyte subpopulations concomitant with higher ratings of perceived pain and the correlation between stress and pain found in the FM group warrant further investigation. Copyright © 2015 John Wiley & Sons, Ltd.

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.

Modality and sex differences in pain sensitivity during human endotoxemia

Systemic inflammation can induce pain hypersensitivity in animal and human experimental models, and has been proposed to be central in clinical pain conditions. Women are overrepresented in many chronic pain conditions, but experimental studies on sex differences in pain regulation during systemic inflammation are still scarce. In two randomized and double blind placebo controlled experiments, we used low doses of lipopolysaccharide (LPS) as an experimental model of systemic inflammation. The first study employed 0.8ng/kg LPS in a within-subject design of 8 individuals (1 woman), and the second study 0.6ng/kg LPS in a between-subject design of 52 participants (29 women). We investigated the effect on (a) pressure, heat, and cold pain thresholds, (b) suprathreshold noxious heat and cold sensitivity, and (c) conditioned pain modulation (CPM), and differences between men and women. LPS induced significantly lower pressure pain thresholds as compared to placebo (mean change with the 0.8ng/kg dose being -64±30kPa P=.04; with the 0.6ng/kg dose -58±55kPa, P<.01, compared to before injection), whereas heat and cold pain thresholds remained unaffected (P's>.70). Suprathreshold noxious pain was not affected by LPS in men (P's⩾.15). However, LPS made women rated suprathreshold noxious heat stimuli as more painful (P=.01), and showed a tendency to rate noxious cold pain as more painful (P=.06) as compared to placebo. Furthermore, LPS impaired conditioned pain modulation, a measure of endogenous pain inhibition, but this effect was also restricted to women (P<.01, for men P=.27). Pain sensitivity correlated positively with plasma IL-6 and IL-8 levels. The results show that inflammation more strongly affects deep pain, rather than cutaneous pain, and suggest that women's pain perception and modulation is more sensitive to immune activation than men's.

Dysfunctional endogenous pain modulation in patients with functional dyspepsia

BACKGROUND

Endogenous pain modulation (EPM) is central to the processing of sensory information. Visceral and somatic EPM are abnormal in irritable bowel syndrome, but have not been studied in functional dyspepsia (FD).

METHODS

Visceral EPM was assessed in 34 FD patients and 42 healthy controls. Gastric pain was induced with oral capsaicin and EPM was studied by adding heterotopic thermal foot stimulation or distraction by STROOP test. Somatic EPM was assessed using foot heat stimulation with heterotopic hand electrical stimulation.

KEY RESULTS

Endogenous pain modulation by distraction reduced mean gastric pain by 11.9 on the 0-100 visual analog scale (95% CI: 3.8-20.1) in controls (p = 0.006) and by 2.0 (-6.18 to 10.44) in FD (p = 0.6), with greater EPM in controls than in FD (difference -13.3 [-26.1 to -0.5]; p = 0.04). Endogenous pain modulation by heterotopic foot stimulation reduced gastric pain by 6.5 (-0.7 to 13.6) in controls (p = 0.07) and by 7.1 (-2.29 to 16.47) in FD (p = 0.1), with no significant difference in EPM between controls and FD (-2.0 [-14.5 to 10.5]; p = 0.75). In patients with prominent FD pain, greater pain correlated with decreased visceral EPM by distraction (r = 0.51, p = 0.04). Somatic EPM by heterotopic stimulation significantly decreased foot pain in controls (p = 0.004), but not in FD (p = 0.80).

CONCLUSIONS & INFERENCES

In FD, visceral pain modulation by distraction was dysfunctional compared to controls. Somatic pain modulation was also decreased in FD. These data and the correlation of abnormal pain modulation by distraction with clinical pain in pain-predominant FD suggest a potential pathophysiological significance of abnormal pain modulation in FD.

Sex differences in the stability of conditioned pain modulation (CPM) among patients with chronic pain

OBJECTIVES

To examine the temporal stability of conditioned pain modulation (CPM), formerly termed diffuse noxious inhibitory controls, among a sample of patients with chronic pain. The study also examined the factors that might be responsible for the stability of CPM.

DESIGN, SUBJECTS, AND METHODS

In this test-retest study, patients underwent a series of standardized psychophysical pain-testing procedures designed to assess CPM on two separate occasions (i.e., baseline and follow up). Patients also completed self-report measures of catastrophizing (Pain Catastrophizing Scale [PCS] and negative affect [NA]).

RESULTS

Overall, results provided evidence for the stability of CPM among patients with chronic pain. Results, however, revealed considerable sex differences in the stability of CPM. For women, results revealed a significant test-retest correlation between baseline and follow-up CPM scores. For men, however, the test-retest correlation between baseline and follow-up CPM scores was not significant. Results of a Fisher's Z-test revealed that the stability of CPM was significantly greater for women than for men. Follow-up analyses revealed that the difference between men and women in the stability of CPM could not be accounted for by any demographic (e.g., age) and/or psychological factors (PCS and NA).

CONCLUSIONS

Our findings suggest that CPM paradigms possess sufficient reliability to be incorporated into bedside clinical evaluation of patients with chronic pain, but only among women. The lack of CPM reproducibility/stability observed among men places limits on the potential use of CPM paradigms in clinical settings for the assessment of men's endogenous pain-inhibitory function.

Consumption of fermented milk product with probiotic modulates brain activity

BACKGROUND & AIMS

Changes in gut microbiota have been reported to alter signaling mechanisms, emotional behavior, and visceral nociceptive reflexes in rodents. However, alteration of the intestinal microbiota with antibiotics or probiotics has not been shown to produce these changes in humans. We investigated whether consumption of a fermented milk product with probiotic (FMPP) for 4 weeks by healthy women altered brain intrinsic connectivity or responses to emotional attention tasks.

METHODS

Healthy women with no gastrointestinal or psychiatric symptoms were randomly assigned to groups given FMPP (n = 12), a nonfermented milk product (n = 11, controls), or no intervention (n = 13) twice daily for 4 weeks. The FMPP contained Bifidobacterium animalis subsp Lactis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis subsp Lactis. Participants underwent functional magnetic resonance imaging before and after the intervention to measure brain response to an emotional faces attention task and resting brain activity. Multivariate and region of interest analyses were performed.

RESULTS

FMPP intake was associated with reduced task-related response of a distributed functional network (49% cross-block covariance; P = .004) containing affective, viscerosensory, and somatosensory cortices. Alterations in intrinsic activity of resting brain indicated that ingestion of FMPP was associated with changes in midbrain connectivity, which could explain the observed differences in activity during the task.

CONCLUSIONS

Four-week intake of an FMPP by healthy women affected activity of brain regions that control central processing of emotion and sensation.

Effects of 15 consecutive cryotherapy sessions on the clinical output of fibromyalgic patients

Fibromyalgia is a chronic widespread pain disorder in which, the neurogenic origin of the pain, featured by allodynia and hyperalgesia, results from an imbalance in the levels of neurotransmitters and consequently of the peripheral pro- and anti-inflammatory mediators. Whole body cryotherapy is a peculiar physical therapy known to relieve pain and inflammatory symptoms characteristics of rheumatic diseases, through the regulation of the cytokine expression. The aim of this study was to qualitatively evaluate the effects of cryotherapy on the clinical output of fibromyalgic patients. A total of 100 fibromyalgic patients (age range 17-70 years) were observed; 50 subjects were addressed to cryotherapy, while the second group (n = 50) did not underwent to the cryotherapic treatment. All subjects kept the prescribed pharmacological therapy during the study (analgesic and antioxidants). The referred health status pre- and post-observation was evaluated with the following scales: Visual Analogue Scale, Short Form-36, Global Health Status and Fatigue Severity Scale. Fibromyalgic patients treated with cryotherapy reported a more pronounced improvement of the quality of life, in comparison with the non-cryo treated fibromyalgic subjects, as indicated by the scores of the qualitative indexes and sub-indexes, that are widely recognized tools to assess the overall health status and the effect of the treatments. We speculate that this improvement is due to the known direct effect of cryotherapy on the balance between pro- and anti-inflammatory mediators having a recognized role in the modulation of pain.

Waning of "conditioned pain modulation": a novel expression of subtle pronociception in migraine

OBJECTIVE

To assess the decay of the conditioned pain modulation (CPM) response along repeated applications as a possible expression of subtle pronociception in migraine.

BACKGROUND

One of the most explored mechanisms underlying the pain modulation system is "diffuse noxious inhibitory controls," which is measured psychophysically in the lab by the CPM paradigm. There are contradicting reports on CPM response in migraine, questioning whether migraineurs express pronociceptive pain modulation.

METHODS

Migraineurs (n = 26) and healthy controls (n = 35), all females, underwent 3 stimulation series, consisting of repeated (1) "test-stimulus" (Ts) alone that was given first followed by (2) parallel CPM application (CPM-parallel), and (3) sequential CPM application (CPM-sequential), in which the Ts is delivered during or following the conditioning-stimulus, respectively. In all series, the Ts repeated 4 times (0-3). In the CPM series, repetition "0" consisted of the Ts-alone that was followed by 3 repetitions of the Ts with a conditioning-stimulus application.

RESULTS

Although there was no difference between migraineurs and controls for the first CPM response in each series, we found waning of CPM-parallel efficiency along the series for migraineurs (P = .005 for third vs first CPM), but not for controls. Further, greater CPM waning in the CPM-sequential series was correlated with less reported extent of pain reduction by episodic medication (r = 0.493, P = .028).

CONCLUSIONS

Migraineurs have subtle deficits in endogenous pain modulation which requires a more challenging test protocol than the commonly used single CPM. Waning of CPM response seems to reveal this pronociceptive state. The clinical relevance of the CPM waning effect is highlighted by its association with clinical parameters of migraine.

Comorbidity negatively influences the outcomes of diagnostic tests for musculoskeletal pain in the orofacial region

The aim of this study was to investigate whether diagnostic tests for musculoskeletal pain in the orofacial region [temporomandibular disorder (TMD) pain] are influenced by the presence of comorbid conditions, and to determine whether this influence decreases when the presence of "familiar pain" is used as outcome measure. In total, 117 patients (35 men, 82 women; 75 TMD-pain patients, 42 pain-free patients; mean age ± SD = 42.94 ± 14.17 years) were examined with palpation tests and dynamic/static tests. After each test, they were asked whether any pain was provoked and whether this pain response was familiar or not. For four clinical outcome measures (pain on palpation, familiar pain on palpation, pain on dynamic/static tests, and familiar pain on dynamic/static tests), multiple logistic regression analyses were performed with the presence of TMD pain as the primary predictor and regional (neck/shoulder) pain, widespread pain, depression, and somatization as comorbid factors. Pain on palpation was not associated with the primary predictor but with regional pain [P = 0.02, odds ratio (OR) = 4.59] and somatization (P = 0.011, OR = 8.47), whereas familiar pain on palpation was associated with the primary predictor (P = 0.003, OR = 5.23), but also with widespread pain (P = 0.001, OR = 2.02). Pain on dynamic/static tests was associated with the primary predictor (P < 0.001, OR = 11.08), but also with somatization (P = 0.037, OR = 4.5), whereas familiar pain on dynamic/static tests was only associated with the primary predictor (P < 0.001, OR = 32.37). In conclusion, diagnostic tests are negatively influenced by the presence of comorbidity. This influence decreases when the presence of familiar pain is used as outcome measure.

The role of stimulation parameters on the conditioned pain modulation response

Background and purpose

Conditioned pain modulation (CPM) is a testing paradigm representing features of diffuse noxious inhibitory control. There is large diversity in the paradigms applied to induce CPM, and the consistency in CPM responses assessed by different paradigms is largely unknown. We aimed to characterize and explore the associations between the CPM responses assessed by different paradigms in the same cohort.

Methods

Thirty-three healthy middle-aged subjects underwent six CPM paradigms. The ‘test-stimuli’, consisted of thermal and mechanical modalities, using pain thresholds, suprathreshold pain and temporal summation types of measurements. The ‘conditioning-stimulus’ consisted of a contact heat stimulus applied to the thener of the left hand for 60s at an intensity of 46.5°C.

Results

Large variability was observed among the responses to the different CPM paradigms. Surprisingly, no correlations were found between the various CPM responses.

Conclusions

The variability in the CPM responses may suggest that the capacity of pain modulation is a multifaceted trait, whose expression varies with the application of different CPM paradigms.

Implications

Considering that CPM responses may represent different processes when assessed by different paradigms, we encourage the use of more than one CPM paradigm.

Childhood risk factors for developing fibromyalgia

BACKGROUND

Fibromyalgia is a disease process without an obvious etiology. While some evidence suggests that adverse experiences in childhood contribute to its development, specific evidence has been equivocal.

METHODS

A total of 36 patients with fibromyalgia from the greater New York area were recruited and surveyed using the Centers for Disease Control's Behavioral Risk Factor Surveillance System survey, and questions from the section on adverse childhood experiences were administered. The results were compared to those obtained from over 400,000 people surveyed by the Centers for Disease control each year, and were monitored for statistically significant differences.

RESULTS

A statistically significant difference was noted among the control group, suggesting that individuals reported growing up with someone who was depressed when the respondents were between the ages of 0 and 18 years old. Moreover, respondents reported that they were hit by their parents in some way, were insulted or cursed at by their parents, and had been forced to have sex with someone at least 5 years older than them or with an adult. No correlation was found with the following variables and the development of fibromyalgia: growing up with divorced or separated parents; growing up with someone sentenced to serve time in jail; or having parents that abused each other. Additionally, statistically significant differences were found for the following categories: lack of emotional support; life dissatisfaction; fair or poor health; physical, mental or emotional disability; and being divorced or not married.

DISCUSSION

Using this well-validated survey, it became clear that at least six specific adverse childhood experiences were correlated with the development of fibromyalgia. Data pertaining to disability, quality of life, life satisfaction, number of days of depression, emotional support, and marriage status illustrated the extent of subjective disability that these patients feel every day.

Pharmacotherapy of fibromyalgia

There have been substantial advances in the pharmacotherapy of fibromyalgia (FM), which have occurred in parallel with advances in our understanding of the pathophysiology of FM in the past several years. Consortia of researchers have established a core set of symptom domains, which constitute the condition of FM, including pain, fatigue, sleep and mood disturbance and cognitive dysfunction, which significantly impact a patient's overall well-being and ability to function. Outcome measures, which assess these domains, both singly and in composite format, are showing increasing reliability to discriminate between the treatment and placebo arms in clinical trials of emerging therapies, which are targeting the pathophysiologic mechanisms of FM. Several different medications, including the serotonin and norepinephrine reuptake inhibitors, duloxetine and milnacipran, and the α(2)δ modulator, pregabalin, have been approved by the Food and Drug Administration (FDA) for the management of FM, based on their clinically meaningful and durable effect on pain in monotherapy trials. They also have been shown to beneficially effect patient global impression of change, function and variably other key symptom domains, such as fatigue, sleep disturbance and cognition. Other medicines, although they have not gone through the formal approval process, have also shown efficacy in multiple domains of FM. Although combination trials have generally not yet been performed, the combined use of medicines with complementary mechanisms of action is rational, and, when done with appropriate caution, will likely be shown to be safe and well tolerated. Adjunctive therapy with medicines targeted at specific symptom domains, such as sleep, as well as treatments aimed at common co-morbid conditions, such as irritable bowel syndrome, or disease states, such as rheumatoid arthritis, should be considered for the purpose of reducing the patient's overall symptom burden. Current therapies neither completely treat FM symptoms nor benefit all patients; thus, further research on new therapies with different mechanisms and side-effect profiles is needed.

Toward development of a fibromyalgia responder index and disease activity score: OMERACT module update

Following development of the core domain set for fibromyalgia (FM) in Outcome Measures in Rheumatology Clinical Trials (OMERACT) meetings 7 to 9, the FM working group has progressed toward the development of an FM responder index and a disease activity score based on these domains, utilizing outcome indices of these domains from archived randomized clinical trials in FM. Possible clinical domains that could be included in a responder index and disease activity score include pain, fatigue, sleep disturbance, cognitive dysfunction, mood disturbance, tenderness, stiffness, and functional impairment. Outcome measures for these domains demonstrate good to adequate psychometric properties, although measures of cognitive dysfunction need to be further developed. The approach used in the development of responder indices and disease activity scores for rheumatoid arthritis and ankylosing spondylitis represents heuristic models for our work, but FM is challenging in that there is no clear algorithm of treatment that defines disease activity based on treatment decisions, nor are there objective markers that define thresholds of severity or response to treatment. The process of developing candidate dichotomous responder definitions and continuous quantitative disease activity measures is described, along with participant discussions from OMERACT 10. Final results of this work will be published in a separate report pending completion of analyses.

Strategy-dependent dissociation of the neural correlates involved in pain modulation

BACKGROUND

Cognitive strategies are a set of psychologic behaviors used to modulate one's perception or interpretation of a sensation or situation. Although the effectiveness of each cognitive strategy seems to differ between individuals, they are commonly used clinically to help patients with chronic pain cope with their condition. The neural basis of commonly used cognitive strategies is not well understood. Understanding the neural correlates that underlie these strategies will enhance understanding of the analgesic network of the brain and the cognitive modulation of pain.

METHODS

The current study examines patterns of brain activation during two common cognitive strategies, external focus of attention and reappraisal, in patients with chronic pain using functional magnetic resonance imaging.

RESULTS

Behavioral results revealed interindividual variability in the effectiveness of one strategy versus another in the patients. Functional magnetic resonance imaging revealed distinct patterns of activity when the two strategies were used. During external focus of attention, activity was observed mainly in cortical areas including the postcentral gyrus, inferior parietal lobule, middle occipital gyrus, and precentral gyrus. The use of reappraisal evoked activity in the thalamus and amygdala in addition to cortical regions. Only one area, the postcentral gyrus, was observed to be active during both strategies.

CONCLUSIONS

The results of this study suggest that different cognitive behavioral strategies recruit different brain regions to perform the same task: pain modulation.

An increased response to experimental muscle pain is related to psychological status in women with chronic non-traumatic neck-shoulder pain

Background

Neck-shoulder pain conditions, e.g., chronic trapezius myalgia, have been associated with sensory disturbances such as increased sensitivity to experimentally induced pain. This study investigated pain sensitivity in terms of bilateral pressure pain thresholds over the trapezius and tibialis anterior muscles and pain responses after a unilateral hypertonic saline infusion into the right legs tibialis anterior muscle and related those parameters to intensity and area size of the clinical pain and to psychological factors (sleeping problems, depression, anxiety, catastrophizing and fear-avoidance).

Methods

Nineteen women with chronic non-traumatic neck-shoulder pain but without simultaneous anatomically widespread clinical pain (NSP) and 30 age-matched pain-free female control subjects (CON) participated in the study.

Results

NSP had lower pressure pain thresholds over the trapezius and over the tibialis anterior muscles and experienced hypertonic saline-evoked pain in the tibialis anterior muscle to be significantly more intense and locally more widespread than CON. More intense symptoms of anxiety and depression together with a higher disability level were associated with increased pain responses to experimental pain induction and a larger area size of the clinical neck-shoulder pain at its worst.

Conclusion

These results indicate that central mechanisms e.g., central sensitization and altered descending control, are involved in chronic neck-shoulder pain since sensory hypersensitivity was found in areas distant to the site of clinical pain. Psychological status was found to interact with the perception, intensity, duration and distribution of induced pain (hypertonic saline) together with the spreading of clinical pain. The duration and intensity of pain correlated negatively with pressure pain thresholds.

The science of fibromyalgia

Fibromyalgia (FM) is a common chronic widespread pain disorder. Our understanding of FM has increased substantially in recent years with extensive research suggesting a neurogenic origin for the most prominent symptom of FM, chronic widespread pain. Neurochemical imbalances in the central nervous system are associated with central amplification of pain perception characterized by allodynia (a heightened sensitivity to stimuli that are not normally painful) and hyperalgesia (an increased response to painful stimuli). Despite this increased awareness and understanding, FM remains undiagnosed in an estimated 75% of people with the disorder. Clinicians could more effectively diagnose and manage FM if they better understood its underlying mechanisms. Fibromyalgia is a disorder of pain processing. Evidence suggests that both the ascending and descending pain pathways operate abnormally, resulting in central amplification of pain signals, analogous to the "volume control setting" being turned up too high. Patients with FM also exhibit changes in the levels of neurotransmitters that cause augmented central nervous system pain processing; levels of several neurotransmitters that facilitate pain transmission are elevated in the cerebrospinal fluid and brain, and levels of several neurotransmitters known to inhibit pain transmission are decreased. Pharmacological agents that act centrally in ascending and/or descending pain processing pathways, such as medications with approved indications for FM, are effective in many patients with FM as well as other conditions involving central pain amplification. Research is ongoing to determine the role of analogous central nervous system factors in the other cardinal symptoms of FM, such as fatigue, nonrestorative sleep, and cognitive dysfunction.

Gray matter volumes of pain-related brain areas are decreased in fibromyalgia syndrome

Fibromyalgia (FM) is a chronic, widespread musculoskeletal pain disorder that is very prevalent in the general population (approximately 5%). Accumulating evidence suggests that FM is associated with central pain processing abnormalities, ie, central sensitization. Several previous studies of chronic pain patients, including FM, have shown gray matter atrophy of brain areas associated with sensory and affective pain processing. These findings, however, have not been confirmed in all FM studies. In this study, we investigated gray matter volumes of brain areas associated with pain-related areas of FM patients identified by functional brain imaging. Using voxel-based morphometric (VBM) analysis of magnetic resonance brain images, we compared 19 pain-related brain areas of 14 female FM patients and 11 healthy controls (NC). We found that FM patients had significantly less gray matter volumes than NC in 3 of these brain regions, including the anterior and mid-cingulate, as well as mid-insular cortices. Importantly, FM patients demonstrated neither global gray matter atrophy nor gray matter changes associated with depression, as shown in some studies. Using a more stringent analysis than other VBM studies, we provide evidence for decreased gray matter volumes in a number of pain-related brain areas in FM. Although the mechanisms for these gray matter changes are presently unclear, they may contribute to some of the core features of this chronic disorder including affective disturbances and chronic widespread pain.

PERSPECTIVE

Increasing evidence supports the association of chronic pain with accelerated gray matter atrophy in pain disorders like low back pain, IBS, and FM syndrome. However, cause-effect relationships between chronic pain and decreased gray matter volumes have not been established yet and will require future prospective studies.

Attenuation of experimental pain by vibro-tactile stimulation in patients with chronic local or widespread musculoskeletal pain

Patients with chronic pain syndromes, like fibromyalgia (FM) complain of widespread pain and tenderness, as well as non-refreshing sleep, cognitive dysfunction, and negative mood. Several lines of evidence implicate abnormalities of central pain processing as contributors for chronic pain, including dysfunctional descending pain inhibition. One form of endogenous pain inhibition, diffuse noxious inhibitory controls (DNIC), has been found to be abnormal in some chronic pain patients and evidence exists for deficient spatial summation of pain, specifically in FM. Similar findings have been reported in patients with localized musculoskeletal pain (LMP) disorders, like neck and back pain. Whereas DNIC reduces pain through activation of nociceptive afferents, vibro-tactile pain inhibition involves innocuous A-beta fiber. To assess whether patients with localized or widespread chronic pain disorders have dysfunctional A-beta related pain inhibition we enrolled 28 normal pain-free controls (NC), 29 FM patients, and 19 subjects with neck or back pain. All received 10s sensitivity-adjusted noxious heat stimuli to the forearms as test stimuli. To assess endogenous analgesic mechanisms of study subjects, vibro-tactile conditioning stimuli were simultaneously applied with test stimuli either homotopically or heterotopically. Additionally, the effect of distraction on experimental pain was assessed. Homotopic vibro-tactile stimulation resulted in 40% heat pain reductions in all subject groups. Distraction did not seem to affect experimental pain ratings.

CONCLUSIONS

Vibro-tactile stimulation effectively recruited analgesic mechanisms not only in NC but also in patients with chronic musculoskeletal pain, including FM. Distraction did not seem to contribute to this analgesic effect.

The role of quantitative sensory testing in the evaluation of musculoskeletal pain conditions

Quantitative sensory testing (QST) is a noninvasive method of assessing sensory and pain perception that has been used in the past 30 years primarily for analysis of cutaneous and mucosal perception. In recent years, several published studies have demonstrated that QST may be useful in the analysis of painful musculoskeletal disorders as well. Based on the results of these studies, it can be postulated that QST may be useful in the analysis of the pathogenesis, classification, and differential diagnosis of musculoskeletal disorders. However, due to the diverse ethiopathogenetic basis of these disorders, a broad range of QST test batteries may be necessary to analyze the various musculoskeletal disease entities. This review analyzes published studies on this subject and summarizes current information on altered sensory and pain perception available for some of the most common musculoskeletal disorders. At present, QST remains primarily a research tool but may be useful in differential diagnosis in indicating the presence of central sensitization and for clinical monitoring of disease progression or treatment response.

Mechanisms of fibromyalgia pain

Chronic musculoskeletal pain is highly prevalent in the United States and includes inflammatory and non-inflammatory syndromes, such as low back pain (reported by 59 million Americans in the past 3 months), neck pain (reported by 30.1 million Americans in the past 3 months), clinical osteoarthritis (reported by 27 million Americans in the past 3 months), and fibromyalgia (FM). FM affects between 2% to 4% of the US population or 12 million people. Inflammatory pain conditions commonly reported by patients include rheumatoid arthritis (2.5 million) and gout (3 million), among others. This article will focus primarily on FM, which is a chronic pain condition that predominately affects women.

The current diagnostic criteria for FM include chronic widespread pain for at least 3 months and the presence of widespread mechanical tenderness. A patient with suspected FM must report pain in all four body quadrants and have at least 11 of 18 tender points for a positive diagnosis to be made. Tender points are areas of the body where pressure is applied until pain threshold is achieved. In addition to pain and tenderness, FM patients very frequently describe widespread stiffness and fatigue, disrupted or poor sleep, dyscognition, and mild soft tissue swelling. Patients often also report symptoms of anxiety and depression.