The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Repetitive transcranial magnetic stimulation increases the corticospinal inhibition and the brain-derived neurotrophic factor in chronic myofascial pain syndrome: an explanatory double-blinded, randomized, sham-controlled trial.
Chronic myofascial pain syndrome has been related to defective descending inhibitory systems. Twenty-four females aged 19 to 65 years with chronic myofascial pain syndrome were randomized to receive 10 sessions of repetitive transcranial magnetic stimulation (rTMS) (n = 12) at 10 Hz or a sham intervention (n = 12). We tested if pain (quantitative sensory testing), descending inhibitory systems (conditioned pain modulation [quantitative sensory testing + conditioned pain modulation]), cortical excitability (TMS parameters), and the brain-derived neurotrophic factor (BDNF) would be modified. There was a significant interaction (time vs group) regarding the main outcomes of the pain scores as indexed by the visual analog scale on pain (analysis of variance, P < .01). Post hoc analysis showed that compared with placebo-sham, the treatment reduced daily pain scores by -30.21% (95% confidence interval = -39.23 to -21.20) and analgesic use by -44.56 (-57.46 to -31.67). Compared to sham, rTMS enhanced the corticospinal inhibitory system (41.74% reduction in quantitative sensory testing + conditioned pain modulation, P < .05), reduced the intracortical facilitation in 23.94% (P = .03), increased the motor evoked potential in 52.02% (P = .02), and presented 12.38 ng/mL higher serum BDNF (95% confidence interval = 2.32-22.38). No adverse events were observed. rTMS analgesic effects in chronic myofascial pain syndrome were mediated by top-down regulation mechanisms, enhancing the corticospinal inhibitory system possibly via BDNF secretion modulation. ⋯ High-frequency rTMS analgesic effects were mediated by top-down regulation mechanisms enhancing the corticospinal inhibitory, and this effect involved an increase in BDNF secretion.
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Sex differences in pain perception are still poorly understood, but they may be related to the way the brains of men and women respond to the affective dimensions of pain. Using a matched pain intensity paradigm, where pain intensity was kept constant across participants but pain unpleasantness was left free to vary among participants, we studied the relationship between pain unpleasantness and pain-evoked brain activity in healthy men and women separately. Experimental pain was provoked using transcutaneous electrical stimulation of the sural nerve while pain-related brain activity was measured using somatosensory-evoked brain potentials with source localization. Cardiac responses to pain were also measured using electrocardiac recordings. Results revealed that subjective pain unpleasantness was strongly associated with increased perigenual anterior cingulate cortex activity in women, whereas it was strongly associated with decreased ventromedial prefrontal cortex activity in men. Only ventromedial prefrontal cortex deactivations in men were additionally associated with increased autonomic cardiac arousal. These results suggest that in order to deal with pain's objectionable properties, men preferentially deactivate prefrontal suppression regions, leading to the mobilization of threat-control circuits, whereas women recruit well-known emotion-processing areas of the brain. ⋯ This article presents neuroimaging findings demonstrating that subjective pain unpleasantness ratings are associated with different pain-evoked brain responses in men and women, which has potentially important implications regarding sex differences in the risk of developing chronic pain.
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Exercise causes a variety of psychophysical effects (eg, alterations in pain sensation). Tissue injury induces mediator releases in the spinal cord resulting in pain hypersensitivity; however, the contribution of the dorsal root ganglion (DRG) is poorly understood. In this study, we tested if forced treadmill running can attenuate postoperative pain and alter substance P (SP) or proinflammatory cytokine level in the DRG by using a rat model of skin/muscle incision and retraction (SMIR). We evaluated mechanical sensitivity to von Frey stimuli (6 and 15 g) and expression of SP, interleukin-1β, and interleukin-6 in the DRG of sham-operated sedentary rats, SMIR sedentary rats, sham-operated rats with forced treadmill running, and SMIR rats with forced treadmill running. At postoperative day 8, trained rats ran for 5 days per week for 4 weeks on a treadmill 70 minutes/d with an intensity of 18 m/min. On postoperative day 6, SMIR sedentary rats displayed a significant mechanical hypersensitivity that persisted until postoperative day 35. By comparison, SMIR-operated rats, which received forced treadmill running, exhibited a quick recovery from mechanical hypersensitivity. SMIR sedentary rats showed an upregulation of SP, interleukin-1β, and interleukin-6 in the DRG at postoperative days 14 and 28, whereas SMIR-operated rats receiving forced treadmill running reversed this upregulation at postoperative day 28. We concluded that forced treadmill running alleviated persistent postincisional pain caused by SMIR surgery. This appears to be protective against postoperative pain, which probably relates to the downturn in excess SP, interleukin-1β, and interleukin-6 in the DRG. ⋯ Controlling the expression of SP, interleukin-6, and interleukin-1β in the DRG can help manage postoperative pain. This finding could potentially help clinicians and physical therapists who seek to examine how exercise may attenuate postsurgical pain and its mechanism.
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Review Meta Analysis
Self-efficacy and chronic pain outcomes: a meta-analytic review.
A meta-analysis was performed to evaluate overall strengths of relation between self-efficacy (SE) and functioning (pain severity, functional impairment, affective distress) in chronic pain samples, as well as potential moderating effects of sociodemographic characteristics and methodologic factors on these associations. In sum, 86 samples (N = 15,616) fulfilled selection criteria for analysis. SE had negative overall correlations with impairment, affective distress, and pain severity although considerable heterogeneity was observed for all effect sizes. Age, pain duration, SE scale content (SE for functioning despite pain vs SE for pain control vs SE for managing other symptoms such as emotional distress) and type of impairment measure (self-report vs task performance) had significant moderating effects on SE-impairment associations. SE-affective distress relations were moderated by employment status and SE scale content. Finally, moderator analyses of studies having longitudinal designs indicated associations between baseline SE, and each outcome at follow-up remained significant in prospective studies that had statistically controlled for effects of baseline responses on that outcome. Hence, SE is a robust correlate of key outcomes related to chronic pain and a potentially important risk/protective factor that has implications for subsequent functioning in affected groups. ⋯ Meta-analysis indicated that SE has significant overall associations with impairment, affective distress, and pain severity within chronic pain samples and identified several factors that contribute to variability in effect sizes. Findings highlighted SE as a robust correlate and potentially important risk/protective factor for subsequent adjustment in affected groups.
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Review Meta Analysis
Local infiltration analgesia for postoperative pain after hip arthroplasty: a systematic review and meta-analysis.
Postoperative pain after hip arthroplasty (HA) is very common and severe. Currently, use of routine analgesic methods is often accompanied by adverse events (AEs). Local infiltration analgesia (LIA) for controlling pain has been a therapeutic option in many surgical procedures. However, its analgesic efficacy in HA and its safety remain unclear. Data from 9 randomized controlled trials, involving 760 participants, comparing the effect of LIA with that of placebo infiltration or no infiltration on patients undergoing HA were retrieved from an electronic database, and the pain scores, analgesic consumption, and AEs were analyzed. Effects were summarized using weighted mean differences, standardized mean differences, or odds ratio with fixed or random effect models. There was strong evidence of an association between LIA and reduced pain scores at 4 hours at rest (P < .00001) and with motion (P < .00001), 6 hours with motion (P = .02), and 24 hours at rest (P = .01), and decreased analgesic consumption during 0 to 24 hours (P = .001) after HA. These analgesic efficacies for LIA were not accompanied by any increased risk for AEs. However, the current meta-analysis did not reveal any associations between LIA and the reduced pain scores or analgesic consumption at other time points. The results suggest that LIA can be used for controlling pain after HA because of its efficacy in reducing pain scores and thus can reduce analgesic consumption on the first day without increased risk of AEs. ⋯ This is the first pooled database meta-analysis to assess the analgesic effects and safety of LIA in controlling pain after HA. The derived information offers direct evidence that LIA can be used for patients undergoing HA because of its ability to reduce pain scores and analgesic consumption without any additional AEs.