Widespread pain in fibromyalgia is related to a deficit of endogenous pain inhibition
ABSTRACT A deficit of endogenous pain inhibitory systems has been suggested to contribute to some chronic pain conditions, one of them being fibromyalgia. The aim of the investigation was to test whether endogenous pain inhibitory systems were activated by a spatial summation procedure in 30 fibromyalgia, 30 chronic low back pain, and 30 healthy volunteers who participated in a cross-over trial (two sessions). Each session consisted of visual analog scale ratings of pain during the immersion of different surfaces of the arm in circulating noxious cold (12 degrees C) water. The arm was arbitrarily divided into eight segments from the fingertips to the shoulder. One session was ascending (from the fingertips to the shoulder) and the other was descending (from the shoulder to the fingertips); they included eight consecutive 2-min immersions separated by 5-min resting periods. For healthy and low back pain subjects, pain was perceived differently during the ascending and descending sessions (P=0.0001). The descending session resulted in lower pain intensity and unpleasantness. This lowering of the perception curve seems to be due to a full recruitment of inhibitory systems at the beginning of the descending session as opposed to a gradual recruitment during the ascending session. For fibromyalgia subjects, no significant differences were found between the increasing and decreasing sessions (P>0.05). These data support a deficit of endogenous pain inhibitory systems in fibromyalgia but not in chronic low back pain. The treatments proposed to fibromyalgia patients should aim at stimulating the activity of those endogenous systems.
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ABSTRACT: Quantitative sensory testing is widely used in human research to investigate the state of the peripheral and central nervous system contributions in pain processing. It is a valuable tool to help identify central sensitization and may be important in the treatment of low back pain. The aim of this study was to evaluate changes in local and segmental hypersensitivity and endogenous pain inhibition in people with chronic nonspecific low back pain. Thirty patients with chronic low back pain and thirty healthy subjects were studied. Pressure pain thresholds (PPTs) were measured from the lumbar region and over the tibialis anterior muscle (TA). A cold pressor test was used to assess the activation of conditioned pain modulation (CPM), and PPTs in the lumbar region were recorded 30 s after immersion of participant's foot in a bucket with cold water. People with chronic low back pain have significantly lower PPT than controls at both the lumbar region [89.5 kPa (mean difference) 95 % CI 40.9-131.1 kPa] and TA [59.45 kPa (mean difference) 95 % CI 13.49-105.42 kPa]. During CPM, people with chronic low back pain have significantly lower PPT than controls in lumbar region [118.6 kPa (mean difference) 95 % CI 77.9-159.2 kPa]. Women had significantly lower PPTs than men in both lumbar region [101.7 kPa (mean difference) 95 % CI 37.9-165.7 kPa] and over the TA [189.7 kPa (mean difference) 95 % CI 14.2-145.2 kPa]. There was no significant difference in PPTs in men between healthy controls and those with low back pain, suggesting the significant differences are mediated primarily by difference between women.Experimental Brain Research 05/2015; DOI:10.1007/s00221-015-4309-6 · 2.17 Impact Factor
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ABSTRACT: Fibromyalgia is a chronic pain syndrome characterized by widespread pain, fatigue, and memory and mood disturbances. Despite advances in our understanding of the underlying pathophysiology, treatment is often challenging. New research indicates that changes in functional connectivity between brain regions, as can be measured by magnetic resonance imaging (fcMRI) of the resting state, may underlie the pathogenesis of this and other chronic pain states. As such, this parameter may be able to be used to monitor changes in brain function associated with pharmacological treatment, and might also be able to predict treatment response.12/2014; 6. DOI:10.1016/j.nicl.2014.09.007
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ABSTRACT: Background It has been suggested that fibromyalgia (FM) patients show increased sensory processing of nociceptive and non-nociceptive stimuli and also reduced habituation. Although this pattern of increased reactivity has been established for the somatosensory modality, its generalization to other sensory modalities remains controversial.Methods Auditory evoked potentials were obtained using a paired-stimuli paradigm from a sample of 52 FM female patients and 55 healthy women matched for age and socio-economic status. Sensory gating of the P50 component, as indicated by P50 suppression rates to the second identical stimuli, was analysed in relation to clinical indices of FM, including algometry of tender points and a number of self-reported questionnaires.ResultsSensory gating mechanisms in FM patients proved to be normal, robust and as efficient as those recorded in control subjects. There was no correlation between P50 suppression rates and indices of clinical or experimental (threshold or tolerance) pain. In addition, P50 sensory gating was not related to the other main symptoms of FM, including fatigue, sleep dysfunction or co-morbid depression, nor to hypersensitivity to noise or headache.Conclusions The results indicate that FM patients do not present significant deficits in early sensory gating when processing auditory stimuli, and therefore challenge the ‘generalized hypersensitivity’ hypothesis of FM.European journal of pain (London, England) 12/2014; 19(4). DOI:10.1002/ejp.627 · 3.22 Impact Factor