Pain
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Evidence from clinic-based studies suggests that the fibromyalgia syndrome (FMS) is associated with impairment in cognitive function though the mechanism is unclear. The aim of this analysis was to determine whether there is a similar association between chronic widespread pain (CWP), a cardinal feature of FMS, and impaired cognition in a community setting. Men (n=3369, 40-79 years) were recruited from population registers in eight centres for participation in the European Male Ageing Study (EMAS). ⋯ There was no association between CWP and the ROCF-copy, ROCF-recall or CTRM scores. CWP is associated with slower psychomotor processing speed among community-dwelling European men. Prospective studies are required to confirm this observation and explore possible mechanisms for the association.
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Clinical Trial
Neuronal mechanisms during repetitive trigemino-nociceptive stimulation in migraine patients.
Habituation deficits in various sensory modalities have been observed in migraine patients in several experimental designs. The underlying neuronal mechanisms are, however, still unknown. Past studies have used electrophysiological measures and focussed on habituation behaviour during one single session. ⋯ These data suggest that several brain areas known to be involved in endogenous pain control show a completely opposite behaviour in migraine patients compared to healthy controls. These brain networks seem not to be disrupted per se in migraine patients but changed activity over time responding to repetitive nociceptive input. The alteration of pain inhibitory circuits may be the underlying mechanism responsible for the dys-functional neuronal filters of sensory input.
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NMDA receptors have an important role in pain facilitation in rostral ventromedial medulla (RVM) and the NR1 subunit is essential for its function. Studies suggest that the NMDA receptors in RVM are critical to modulate both cutaneous and muscle hypersensitivity induced by repeated intramuscular acid injections. We propose that increased expression of the NR1 subunit in the RVM is critical for the full development of hypersensitivity. ⋯ We also downregulated the expression of NR1 in the RVM and measured the hyperalgesia produced by repeated-acid injections. Increasing the expression of NR1 in the RVM reduces cutaneous and muscle withdrawal threshold, and decreasing the expression of NR1 in the RVM increases the muscle withdrawal threshold and prevents the development of hyperalgesia in an animal model of muscle pain. These results suggest that the NR1 subunits in the RVM are critical for modulating NMDA receptor function, which in turn sets the 'tone' of the nervous system's response to noxious stimuli and tissue injury.
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Review Meta Analysis
Do sex differences exist in opioid analgesia? A systematic review and meta-analysis of human experimental and clinical studies.
Although a contribution of sex in opioid efficacy has garnered much attention, the confirmation and direction of any such difference remain elusive. We performed a systematic review of the available literature on sex differences in μ and mixed μ/κ opioid effect on acute and experimental pain. Fifty unique studies (including three unpublished studies) were included in the analyses. ⋯ Female patients had greater μ/κ opioid analgesia (n=7, effect size 0.84; 95% c.i. 0.25-1.43, P=0.005), but no sex-analgesia association was present in experimental studies (n=7). Sex differences exist in morphine-induced analgesia in both experimental pain studies and clinical PCA studies, with greater morphine efficacy in women. The data on non-morphine μ and mixed μ/κ-opioids are less convincing and require further study.
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Randomized Controlled Trial Multicenter Study Clinical Trial
German Randomized Acupuncture Trial for chronic shoulder pain (GRASP) - a pragmatic, controlled, patient-blinded, multi-centre trial in an outpatient care environment.
The German Randomized Acupuncture Trial for chronic shoulder pain (GRASP) comprised 424 outpatients with chronic shoulder pain (CSP) > or =6 weeks and an average pain score of VAS > or =50 mm, who were randomly assigned to receive Chinese acupuncture (verum), sham acupuncture (sham) or conventional conservative orthopaedic treatment (COT). The patients were blinded to the type of acupuncture and treated by 31 office-based orthopaedists trained in acupuncture; all received 15 treatments over 6 weeks. The 50% responder rate for pain was measured on a VAS 3 months after the end of treatment (primary endpoint) and directly after the end of the treatment (secondary endpoint). ⋯ In the ITT (n=424) analysis, percentages of responders for the primary endpoint were verum 65% (95% CI 56-74%) (n=100), sham 24% (95% CI 9-39%) (n=32), and COT 37% (95% CI 24-50%) (n=50); secondary endpoint: verum 68% (95% CI 58-77%) (n=92), sham 40% (95% CI 27-53%) (n=53), and COT 28% (95% CI 14-42%) (n=38). The results are significant for verum over sham and verum over COT (p<0.01) for both the primary and secondary endpoints. The PPP analysis of the primary (n=308) and secondary endpoints (n=360) yields similar responder results for verum over sham and verum over COT (p<0.01). Descriptive statistics showed greater improvement of shoulder mobility (abduction and arm-above-head test) for the verum group versus the control group immediately after treatment and after 3 months. The trial indicates that Chinese acupuncture is an effective alternative to conventional orthopaedic treatment for CSP.