Pain
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Some patients with myofascial pain from temporomandibular disorders (TMD) report pain in extra-trigeminal body regions. Our aim was to distinguish TMD as regional musculoskeletal pain syndrome (n=23) from a widespread pain syndrome (FMS; n=18) based on patients' tender point scores, pain drawings and quantitative sensory testing (QST) profiles. Referenced to 18 age- and gender-matched healthy subjects significant group differences for cold, pressure and pinprick pain thresholds, suprathreshold pinprick sensitivity and mechanical detection thresholds were found. ⋯ However, sensitive TMD patients had a short pain duration arguing against a transition from TMD to FMS over time. Data rather suggest an overlap in pathophysiology with FMS, e.g. a disturbance of central pain processing, in this subgroup of TMD patients. Those patients could be identified on the basis of their tender point count as an easy practicable screening tool.
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Previous research has demonstrated that the nociceptive flexion reflex (NFR) and pain-related evoked potentials are reduced in amplitude when elicited during the middle of the cardiac cycle. Despite these findings, suggesting a baroreceptor mechanism of antinociception during systole, pain intensity ratings reported in these studies were not modulated across the cardiac cycle. This discrepancy between the neurophysiological correlates of pain and its subjective experience was the focus of the current study that used a mixed block design to assess the effects of natural arterial baroreceptor activity on both the NFR and pain intensity and unpleasantness reports. ⋯ Finally, nociceptive responses did not differ among the R-wave to stimulation intervals for both painful and non-painful intensities. The observed phasic modulation of pain may be explained by a central nervous system alarm/defence reaction triggered by the unpredictability of the potentially damaging stimulation. The absence of systolic attenuation of nociceptive responding is compatible with previous evidence that baroreceptor modulation of the NFR is abolished under conditions of heightened arousal.
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The central processing of peripheral nociceptive messages is highly controlled by the activity of local inhibitory networks in the spinal cord and supraspinal centers. Recently, it has been shown that endogenous 3alpha-reduced neurosteroids (3alphaNS) exert a significant spinal antinociception by potentiating GABA(A) receptor function. Because endogenous 3alphaNS can be produced in many relay structures of the nociceptive system, we tested the potential analgesic efficacy of promoting the production of neurosteroids by using etifoxine (ETX, 50mg/kg i.p.). ⋯ Both the curative and preventive effects of ETX on pain symptoms were mediated by the production of 3alphaNS as demonstrated in animals treated with the enzymatic inhibitor provera (6-medroxyprogesterone acetate; 20mg/kg s.c.). Altogether, this study shows for the first time that promoting 3alphaNS could be a possible therapeutic strategy to treat neuropathic pain symptoms. Since ETX is already available as an anxiolytic, its use in humans, provided that its analgesic properties are confirmed, could be rapidly considered.
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Clinical Trial
Clinical and endocrinological changes after electro-acupuncture treatment in patients with osteoarthritis of the knee.
Neurobiological mechanisms invoking the release of endogenous opioids and depression of stress hormone release are believed to be the basis of acupuncture analgesia. This study compared plasma beta-endorphin and cortisol levels with self assessment scores of intensity of pain, before and after 10 days of electro-acupuncture treatment in patients suffering from chronic pain as a result of osteoarthritis knees. Forty patients of either sex over 40 years with primary osteoarthritis knee were recruited into a single-blinded, sham-controlled study. ⋯ Following electro-acupuncture treatment there was a significant improvement in WOMAC index and VAS (p=0.001), a significant rise in plasma beta-endorphin (p=0.001), and a significant fall in plasma cortisol (p=0.016). In conclusion electro-acupuncture resulted in an improvement in pain, stiffness and disability. Of clinical importance is that an improvement in objective measures of pain and stress/pain associated biomarkers was shown above that of a sham treatment; hence demonstrating acupuncture associated physiological changes beyond that of the placebo effects.
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A prospective controlled intervention cohort study in cancer pain patients (n=50 per group) admitted to radiation oncology wards (62 beds, 3 wards) was conducted in a 1621-bed university hospital. We investigated the effect of an intervention consisting of daily pain assessment using the numeric visual analog scale (NVAS) and pain therapy counseling to clinicians based on a computerized clinical decision support system (CDSS) to correct deviations from pain therapy guidelines. Effects on guideline adherence (primary outcome), pain relief (NVAS) at rest and during physical activity (both groups: cross-sectional assessment on day 5; intervention group: every day assessment), co-analgesic prescription, and acceptance rates of recommendations (secondary outcomes) were assessed. ⋯ From 279 recommendations issued in the intervention 85% were fully accepted by the physicians. Deviations from well-established guidelines are frequent in pain therapy. A multidisciplinary pain management increased adherence to pain management guidelines.