European journal of pain : EJP
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The 'pain-inhibits-pain' effect stems from neurophysiological mechanisms involving endogenous modulatory systems termed diffuse noxious inhibitory controls (DNIC) or conditioned pain modulation (CPM). Laser-evoked potentials (LEPs) components, the N2/P2 complex, and the N1 wave, reflect the medial and lateral pain pathway, respectively: anatomically, the lateral thalamic nuclei (LT) project mainly to the somatosensory cortex (N1 generator), while the medial thalamic nuclei (MT) are bound to the limbic cortices (N2/P2 generators). ⋯ No reports have described the effect of DNIC on lateral and medial pain pathways. We studied the N1 wave and the N2/P2 complex to detect changes during a CPM protocol. We found a reduction in the amplitude of the N2/P2 complex and no change in the N1 wave. This suggests that the DNIC inhibitory effect on dorsal horns neurons affects only pain transmission via the SRT, whereas the neurons that give rise to the STT are not involved.
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Facial activity during pain is composed of varying combinations of a few elementary facial responses (so-called Action Units). A previous study of experimental pain showed that these varying combinations can be clustered into distinct facial activity patterns of pain. In the present study, we examined whether comparable facial activity patterns can also be identified among people suffering from clinical pain; namely, shoulder pain. ⋯ Similar to experimental pain, facial activity during evoked pain episodes in shoulder pain patients could be clustered into distinct faces of pain. Each cluster was composed of different combinations of single facial responses, namely: narrowed eyes, which is displayed either alone or in combination with opened mouth or wrinkled nose, or furrowed brows and closed eyes. These distinct faces of pain may inform the training of professionals and computers how to best recognize pain based on facial expressions.
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The relationship between habitual physical activity (PA) and experimental pain tolerance has been investigated in small samples of young, healthy and/or single-sex volunteers. We used a large, population-based sample to assess this relationship in men and women with and without chronic pain. ⋯ This study finds that higher level of self-reported leisure-time physical activity is associated with increased cold pressor pain tolerance in a large population-based sample. Though present in both sexes, the association is strongest among men. Despite the robust dose-response relationship between pain tolerance and self-reported activity level, no such relationship was found for accelerometer-measured activity, reflecting a possible discrepancy in the aspect of physical activity measured. Though the study design does not permit causal conclusions, the findings suggest that increasing physical activity may increase pain tolerance in the general population.
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The 'funnel effect' of Fibromyalgia (FM) assumes that as patients access healthcare services, they present greater severity and a more complex clinical situation than individuals with FM from the general population, but the studies comparing patients treated in different levels of healthcare are scarce. The aim of this study was to analyse the 'funnel effect' hypothesis by comparing patients from secondary and tertiary healthcare services. ⋯ The worst clinical and psychological status and poorer quality of life in the patients from tertiary healthcare (chronic pain clinics) in relation to the patients from secondary healthcare (rheumatology practices) must be taken into account to design studies that assess any of these aspects, to a proper analysis and interpretation of the data, and to define the scope of its generalization, as data from different clinical settings are not directly comparable.
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Fibromyalgia is characterized by widespread musculoskeletal pain and often accompanied by cognitive and emotional problems. Adaptation to fibromyalgia may therefore also rely on one's ability to regulate emotional problems. In this study, we examined two indices of emotion regulation, that is, (a) affective instability, involving frequent large fluctuations in self-reported affect, and (b) resting heart rate variability (HRV). ⋯ This study provides novel insight in the link between emotion regulation indices,that is, heart-rate variability and negative affective (NA) instability, in patients with fibromyalgia, and presents evidence for differences in both emotion regulation indices between patients with fibromyalgia and healthy people. Furthermore, results link increased NA instability with increased levels of daily disability in patients with fibromyalgia. Together, these findings offer support for a key role of emotion regulation in fibromyalgia outcomes, providing pathways for clinical practice.