The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Neurophysiology of the cortical pain network: revisiting the role of S1 in subjective pain perception via standardized low-resolution brain electromagnetic tomography (sLORETA).
Multiple studies have supported the usefulness of standardized low-resolution brain electromagnetic tomography (sLORETA) in localizing generators of scalp-recorded potentials. The current study implemented sLORETA on pain event-related potentials, primarily aiming at validating this technique for pain research by identifying well-known pain-related regions. Subsequently, we pointed at investigating the still-debated and ambiguous topic of pain intensity coding at these regions, focusing on their relative impact on subjective pain perception. sLORETA revealed significant activations of the bilateral primary somatosensory (SI) and anterior cingulate cortices and of the contralateral operculoinsular and dorsolateral prefrontal (DLPFC) cortices (P < .05 for each). Activity of these regions, excluding DLPFC, correlated with subjective numerical pain scores (P < .05 for each). However, a multivariate regression analysis (R = .80; P = .024) distinguished the contralateral SI as the only region whose activation magnitude significantly predicted the subjective perception of noxious stimuli (P = .020), further substantiated by a reduced regression model (R = .75, P = .008). Based on (1) correspondence of the pain-activated regions identified by sLORETA with the acknowledged imaging-based pain-network and (2) the contralateral SI proving to be the most contributing region in pain intensity coding, we found sLORETA to be an appropriate tool for relevant pain research and further substantiated the role of SI in pain perception. ⋯ Because the literature of pain intensity coding offers inconsistent findings, the current article used a novel tool for revisiting this controversial issue. Results suggest that it is the activation magnitude of SI, which solely establishes the significant correlation with subjective pain ratings, in accordance with the classical clinical thinking, relating SI lesions to diminished perception of pain. Although this study cannot support a causal relation between SI activation magnitude and pain perception, such relation might be insinuated.
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Randomized Controlled Trial
Changes of hypertonic saline-induced masseter muscle pain characteristics, by an infusion of the serotonin receptor type 3 antagonist granisetron.
This study aimed to investigate whether granisetron reduces masseter muscle pain and allodynia induced by hypertonic saline. Fifteen healthy women and 15 age-matched healthy men participated in this randomized, placebo-controlled, double-blinded study. They first received bilateral injections of hypertonic saline into the masseter muscles (internal control). The evoked pain intensity and the pressure-pain threshold (PPT) were recorded during 30 minutes. Granisetron was then injected on one side and placebo (normal saline) on the contralateral side. Two minutes thereafter, the hypertonic saline injections were repeated. Pain and PPT were again recorded. The first injection of hypertonic saline induced pain of similar intensity, duration, and pain area on both sides, but with larger pain area in the women (P = .017). The PPT did not change significantly. The second injection of hypertonic saline induced considerably less pain (62.5%), of shorter duration (44.1%), and of smaller area (77.4%) on the side pretreated with granisetron (P = .005). The PPT was increased on the granisetron side in the men (P = .002). The results of this study show that local injection of a single dose of granisetron attenuates masseter muscle pain induced by hypertonic saline. ⋯ This article presents the changes of hypertonic saline-induced masseter muscle pain characteristics by infusion of granisetron. It appears that the pain-inducing effect in this experimental pain model is partly due to activation of 5-HT3-receptors. Hence, the results indicate that granisetron might offer a new treatment approach for localized myofascial pain.
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Randomized Controlled Trial Multicenter Study
A 14-week, randomized, double-blinded, placebo-controlled monotherapy trial of pregabalin in patients with fibromyalgia.
The purpose of the study was to assess the efficacy and safety of pregabalin monotherapy in patients with fibromyalgia in a randomized, double-blinded, placebo-controlled trial. After 1 week of single-blinded administration of placebo, 750 patients meeting American College of Rheumatology criteria for fibromyalgia were randomly assigned to pregabalin (300 mg/d, 450 mg/d, 600 mg/d) or placebo, administered twice daily for 14 weeks. The primary outcome variable was comparison of end point mean pain scores, derived from daily diary ratings of pain intensity (0 to 10 scale), between each of the pregabalin groups and the placebo group. If positive, additional primary efficacy parameters included the Patient Global Impression of Change (PGIC) and the Fibromyalgia Impact Questionnaire (FIQ) total score. Compared with placebo-treated patients, mean changes in pain scores at the end point in pregabalin-treated patients were significantly greater (P < .001: 300 mg/d, -0.71; 450 mg/d, -0.98; 600 mg/d, -1.00). Compared with placebo, significantly more pregabalin-treated patients reported improvement on PGIC (P < .01 for all 3 pregabalin doses) and significant improvements in total FIQ score for the 450 mg/d (P = .004) and the 600 mg/d (P = .003) doses. Compared with placebo, all 3 doses of pregabalin were associated with significant improvement in sleep. The most commonly reported pregabalin-related adverse events were dizziness and somnolence, which tended to be dose-related. ⋯ This randomized, placebo-controlled trial of 300, 450, and 600 mg/d of pregabalin monotherapy demonstrated that all 3 doses were efficacious for up to 14 weeks for the treatment of fibromyalgia and were well tolerated by most patients. These results provide evidence that pregabalin is an important treatment option for patients with fibromyalgia.
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Randomized Controlled Trial
Acute opioid administration improves work-related exercise performance in patients with chronic back pain.
We studied the impact of acute opioid administration on work-related exercise performance in patients with chronic back pain. A double-blinded, random-order, placebo-controlled, crossover trial was conducted. Subjects were predominantly men (63%), with a mean age of 49 years. Subjects performed a continuous lifting and lowering test to voluntary fatigue at a load equivalent to 33% of their predetermined maximal lifting load twice: Once after receiving a single intravenous dose of 1 mug/kg fentanyl (a narcotic analgesic) and once after saline placebo. Of the 30 subjects undergoing testing, 3 subjects were unable to complete testing due to medication-induced nausea. Subjects lifted on average 29.4 +/- 17.9 kg under the influence of fentanyl versus 25.6 +/- 3.1 kg with placebo (effect size = 0.23). Time to fatigue was higher in the fentanyl group (312 +/- 251.4 vs 231 +/- 199.9 seconds, effect size = 0.40), and these subjects also performed more total work (7004 +/- 5144 vs 4748 +/- 3147 J, effect size = 0.72). Opioid analgesia improves lifting performance in the short term in individuals with chronic back pain. Longer trials of the effectiveness of opioid analgesia as an adjunct to functional restoration programs are recommended. ⋯ This article presents the results of a clinical trial showing that acute opioid administration improves work-related exercise performance in individuals with chronic back pain. Longer trials of the effectiveness of opioid analgesia as an adjunct to functional restoration programs are recommended.
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Randomized Controlled Trial Multicenter Study
Treatment of patients with complex regional pain syndrome type I with mannitol: a prospective, randomized, placebo-controlled, double-blinded study.
To assess the effects of intravenous administration of the free radical scavenger mannitol 10% on complaints associated with complex regional pain syndrome Type I (CRPS I), a randomized, placebo-controlled, double-blinded trial was performed. Forty-one CRPS I patients according to the Bruehl et al diagnostic criteria, were included in 2 outpatient pain clinics of 2 university medical centers and randomly assigned to receive either 10% mannitol iv in 1 L 0.9% NaCL in 4 hours for 5 consecutive days or equal volumes of 0.9% NaCL (placebo). Patients in both groups received physical therapy according to protocol and rescue pain medication if required. Complaints on impairment and disability level and quality of life were assessed up to 9 weeks after baseline, with primary measurement points at 2, 6, and 9 weeks. Monitoring of pain using the visual analogue scale took place continuously during the course of the trial. Except for a significant improvement on a subscale of the Jebsen-Taylor hand function test, no significant differences were found between mannitol and placebo treatment. Changes in both groups in the course of the trial were small and clinically irrelevant on all measurement indices. We conclude that intravenous administration of 10% mannitol is not more effective than placebo in reducing complaints for CRPS I patients and provides no addition to already-established interventions for CRPS I. Whether 10% mannitol can provide beneficial effects for subgroups of CRPS I patients with a pathophysiological profile more closely fitting the presumed mode of action for this intervention remains to be established. ⋯ This article addresses the efficacy of the intravenous administration of the free radical scavenger mannitol for treatment of CRPS type 1. This intervention is not more effective than placebo in reducing complaints for CRPS I patients and provides no addition to already-established interventions for CRPS I.