Patients with fibromyalgia display less functional connectivity in the brain's pain inhibitory network.

BACKGROUND: There is evidence for augmented processing of pain and impaired endogenous pain inhibition in Fibromyalgia syndrome (FM). In order to fully understand the mechanisms involved in FM pathology, there is a need for closer investigation of endogenous pain modulation. In the present study, we compared the functional connectivity of the descending pain inhibitory network in age-matched FM patients and healthy controls (HC).We performed functional magnetic resonance imaging (fMRI) in 42 subjects; 14 healthy and 28 age-matched FM patients (2 patients per HC), during randomly presented, subjectively calibrated pressure pain stimuli. A seed-based functional connectivity analysis of brain activity was performed. The seed coordinates were based on the findings from our previous study, comparing the fMRI signal during calibrated pressure pain in FM and HC: the rostral anterior cingulate cortex (rACC) and thalamus. RESULTS: FM patients required significantly less pressure (kPa) to reach calibrated pain at 50 mm on a 0-100 visual analogue scale (p < .001, two-tailed). During fMRI scanning, the rACC displayed significantly higher connectivity to the amygdala, hippocampus, and brainstem in healthy controls, compared to FM patients. There were no regions where FM patients showed higher rACC connectivity. Thalamus showed significantly higher connectivity to the orbitofrontal cortex in healthy controls but no regions showed higher thalamic connectivity in FM patients. CONCLUSION: Patients with FM displayed less connectivity within the brain's pain inhibitory network during calibrated pressure pain, compared to healthy controls. The present study provides brain-imaging evidence on how brain regions involved in homeostatic control of pain are less connected in FM patients. It is possible that the dysfunction of the descending pain modulatory network plays an important role in maintenance of FM pain and our results may translate into clinical implications by using the functional connectivity of the pain modulatory network as an objective measure of pain dysregulation.

The interest of gait markers in the identification of subgroups among fibromyalgia patients.

BACKGROUND: Fibromyalgia (FM) is a heterogeneous syndrome and its classification into subgroups calls for broad-based discussion. FM subgrouping, which aims to adapt treatment according to different subgroups, relies in part, on psychological and cognitive dysfunctions. Since motor control of gait is closely related to cognitive function, we hypothesized that gait markers could be of interest in the identification of FM patients' subgroups. This controlled study aimed at characterizing gait disorders in FM, and subgrouping FM patients according to gait markers such as stride frequency (SF), stride regularity (SR), and cranio-caudal power (CCP) which measures kinesia. METHODS: A multicentre, observational open trial enrolled patients with primary FM (44.1 ± 8.1 y), and matched controls (44.1 ± 7.3 y). Outcome measurements and gait analyses were available for 52 pairs. A 3-step statistical analysis was carried out. A preliminary single blind analysis using k-means cluster was performed as an initial validation of gait markers. Then in order to quantify FM patients according to psychometric and gait variables an open descriptive analysis comparing patients and controls were made, and correlations between gait variables and main outcomes were calculated. Finally using cluster analysis, we described subgroups for each gait variable and looked for significant differences in self-reported assessments. RESULTS: SF was the most discriminating gait variable (73% of patients and controls). SF, SR, and CCP were different between patients and controls. There was a non-significant association between SF, FIQ and physical components from Short-Form 36 (p = 0.06). SR was correlated to FIQ (p = 0.01) and catastrophizing (p = 0.05) while CCP was correlated to pain (p = 0.01). The SF cluster identified 3 subgroups with a particular one characterized by normal SF, low pain, high activity and hyperkinesia. The SR cluster identified 2 distinct subgroups: the one with a reduced SR was distinguished by high FIQ, poor coping and altered affective status. CONCLUSION: Gait analysis may provide additional information in the identification of subgroups among fibromyalgia patients. Gait analysis provided relevant information about physical and cognitive status, and pain behavior. Further studies are needed to better understand gait analysis implications in FM.

Anxiety and depressive symptoms in fibromyalgia are related to poor perception of health but not to pain sensitivity or cerebral processing of pain.

OBJECTIVE: Mood disturbance is common among patients with fibromyalgia (FM), but the influence of psychological symptoms on pain processing in this disorder is unknown. We undertook the present study to investigate the differential effect of depressive symptoms, anxiety, and catastrophizing on 1) pain symptoms and subjective ratings of general health status and 2) sensitivity to pain and cerebral processing of pressure pain. METHODS: Eighty-three women (mean ± SD age 43.8 ± 8.1 years) who fulfilled the American College of Rheumatology 1990 criteria for the classification of FM participated in the study. Patients rated pain intensity (100-mm visual analog scale [VAS]), severity of FM (Fibromyalgia Impact Questionnaire), general health status (Short Form 36), depressive symptoms (Beck Depression Inventory), anxiety (State-Trait Anxiety Inventory), and catastrophizing (Coping Strategies Questionnaire). Experimental pain in the thumb was induced using a computer-controlled pressure stimulator. Event-related functional magnetic resonance imaging was performed during administration of painful stimuli representing 50 mm on a pain VAS, as well as nonpainful pressures. RESULTS: A correlation analysis including all self-ratings showed that depressive symptoms, anxiety, and catastrophizing scores were correlated with one another (P < 0.001), but did not correlate with ratings of clinical pain or with sensitivity to pressure pain. However, the subjective rating of general health was correlated with depressive symptoms and anxiety (P < 0.001). Analyses of imaging results using self-rated psychological measures as covariates showed that brain activity during experimental pain was not modulated by depressive symptoms, anxiety, or catastrophizing. CONCLUSION: Negative mood in FM patients can lead to a poor perception of one's physical health (and vice versa) but does not influence performance on assessments of clinical and experimental pain. Our data provide evidence that 2 partially segregated mechanisms are involved in the neural processing of experimental pain and negative affect.

Linguistic validation of six patient-reported outcomes instruments into 12 languages for patients with fibromyalgia.

CONTEXT: The multidimensional nature of the fibromyalgia syndrome means that different instruments need to be used to assess the patients' perception of this constellation of physical and psychological symptoms and their impact on their daily lives. Six questionnaires (Multidimensional Fatigue Inventory MFI, Fibromyalgia Impact Questionnaire FIQ, Multiple Ability Self-report Questionnaire MASQ, State-Trait Anxiety Inventory STAI, Beck Depression Inventory-II BDI-II and Patient Global Impression of Change PGIC) were linguistically validated into 12 languages. METHODS: The standardized cross-cultural adaptation process includes the following steps: forward translation, backward translation, and review of the version by a clinician and comprehension tests on subjects in the target country. RESULTS: Regardless of the instruments and dimensions studied, the same translation and cultural adaptation issues arose: (1) an issue that is strictly related to translation, for example, the word "things" was translated as "something"; (2) literal translation is possible but culturally irrelevant, for example the expression "to walk several blocks", which is a completely abstract concept in Europe, was translated as "to walk for more than one kilometre"; (3) the translation needed to be reformulated or the tense needed to be changed for idiomatic reasons. For example, the present perfect does not exist in German and so the present simple was used in the first version. The imperfect was eventually used with adverbs such as "lately". CONCLUSIONS: Linguistic adaptation was completed according to a recognized and rigorous method allowing for the wide-scale use of these patient-reported outcomes instruments in international studies.

A European multicenter randomized double-blind placebo-controlled monotherapy clinical trial of milnacipran in treatment of fibromyalgia.

OBJECTIVE: This randomized, double-blind, placebo-controlled, multicenter study investigated the efficacy and safety of milnacipran in the treatment of fibromyalgia (FM) in a European population. METHODS: Outpatients diagnosed with FM according to 1990 American College of Rheumatology criteria (N = 884) were randomized to placebo (n = 449) or milnacipran 200 mg/day (n = 435) for 17 weeks (4-week dose escalation, 12-week stable dose, 9-day down-titration), followed by a 2-week posttreatment period. The primary efficacy criterion was a 2-measure composite responder analysis requiring patients to achieve simultaneous improvements in pain (>or= 30% improvement from baseline in visual analog scale, 24-hour morning recall) and a rating of "very much" or "much" improved on the Patient Global Impression of Change scale. If responder analysis was positive, Fibromyalgia Impact Questionnaire (FIQ) was included as an additional key primary efficacy measure. RESULTS: At the end of the stable dose period (Week 16), milnacipran 200 mg/day showed significant improvements from baseline relative to placebo in the 2-measure composite responder criteria (p = 0.0003) and FIQ total score (p = 0.015). Significant improvements were also observed in multiple secondary efficacy endpoints, including Short-Form 36 Health Survey (SF-36) Physical Component Summary (p = 0.025), SF-36 Mental Component Summary (p = 0.007), Multidimensional Fatigue Inventory (p = 0.006), and Multiple Ability Self-Report Questionnaire (p = 0.041). Milnacipran was safe and well tolerated; nausea, hyperhidrosis, and headache were the most common adverse events. CONCLUSION: Milnacipran is an effective and safe treatment for pain and other predominant symptoms of FM. Registered as trial no. NCT00436033.

Functional magnetic resonance imagery (fMRI) in fibromyalgia and the response to milnacipran.

Functional imaging has been used to study response to pain in fibromyalgia patients. Functional magnetic resonance imagery (fMRI) which tracks local changes in blood flow has a higher spatial and temporal resolution than other techniques such as positron emission tomography (PET) or single-photon emission tomography (SPECT). fMRI studies in fibromyalgia patients suggest that similar levels of subjective pain result in similar central nervous system (CNS) activation in both fibromyalgia patients and controls. For a similar stimulus, however, fibromyalgia patients have a greater subjective sensation of pain. This increased sensitivity is accompanied with a decreased activity in brain regions implicated in the descending pain inhibitory pathways. The hypothesis that increased sensitivity to pain is due to decreased activity of the descending inhibitory pathways is supported by results with milnacipran. Fibromyalgia patients treated with the serotonin and noradrenaline reuptake inhibitor, milnacipran, exhibited a reduction in pain sensitivity and a parallel increase in activity in brain regions implicated in the descending pain inhibitory pathways compared to placebo-treated patients.

Evidence of dysfunctional pain inhibition in Fibromyalgia reflected in rACC during provoked pain.

Over the years, many have viewed Fibromyalgia syndrome (FMS) as a so-called "functional disorder" and patients have experienced a concomitant lack of interest and legitimacy from the medical profession. The symptoms have not been explained by peripheral mechanisms alone nor by specific central nervous system mechanisms. In this study, we objectively evaluated the cerebral response to individually calibrated pain provocations of a pain-free body region (thumbnail). The study comprised 16 female FMS patients and 16 individually age-matched controls. Brain activity was measured using functional magnetic resonance imaging (fMRI) during individually calibrated painful pressures representing 50 mm on a visual analogue scale (VAS) ranging from 0 to 100 mm. Patients exhibited higher sensitivity to pain provocation than controls as they required less pressure to evoke equal pain magnitudes (U(A)=48, p<.002). Despite lower pressures applied in patients at VAS 50 mm, the fMRI-analysis revealed no difference in activity in brain regions relating to attention and affect or regions with sensory projections from the stimulated body area. However, in the primary link in the descending pain regulating system (the rostral anterior cingulate cortex) the patients failed to respond to pain provocation. The attenuated response to pain in this brain region is the first demonstration of a specific brain region where the impairment of pain inhibition in FMS patients is expressed. These results validate previous reports of dysfunctional endogenous pain inhibition in FMS and advance the understanding of the central pathophysiologic mechanisms, providing a new direction for the development of successful treatments in FMS.