The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Pain relief is associated with improvement in motor function in complex regional pain syndrome type 1: secondary analysis of a placebo-controlled study on the effects of ketamine.
There are indications of motor circuit changes in patients with complex regional pain syndrome (CRPS). Nevertheless, although several studies have analyzed motor behavior in CRPS, a relation with pain could not be detected. This might be explained by the use of cross-sectional designs in these studies, in which pain is considered as a trait- rather than a state-dependent variable. We therefore studied the time-dependent relation between pain and motor function in affected arms of 29 CRPS patients during their participation in a placebo-controlled ketamine study. Movement parameters (velocity, frequency, amplitude, and number of arrests) were assessed during a finger tapping task. Linear mixed model analysis of the effects of pain (numerical rating scale score), treatment (ketamine/placebo), and week (1, 3, 6, and 12 weeks after treatment) on the movement parameters revealed that pain intensity was significantly (inversely) related to motor function, irrespective of whether patients had received ketamine or placebo. Movement parameters changed 3-12% per point numerical rating scale change. Because patients were unaware of possible effects of ketamine on motor function, these findings suggest that motor function changes were mediated by, or occurred simultaneously with, changes in pain intensity. By improving motor function, pain relief may offer a window of opportunity for rehabilitation programs in CRPS. ⋯ This article provides evidence for a direct relation between pain and motor function in CRPS, which indicates that pain relief may be an important factor in the treatment of motor disturbances in this condition. These findings may help to advance our understanding of the pathways underlying motor disturbances in CRPS.
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Randomized Controlled Trial
TENS attenuates repetition-induced summation of activity-related pain following experimentally induced muscle soreness.
This study sought to determine whether repetition-induced summation of activity-related pain (RISP) could be demonstrated in healthy individuals in response to experimentally induced musculoskeletal pain. This study also assessed the effects of transcutaneous electrical nerve stimulation on RISP. The relation between the index of RISP and psychological factors such as catastrophizing and fear of pain was also explored. The sample consisted of 56 healthy (35 women, 21 men) participants who underwent 2 testing sessions, separated by 24 hours. In the first session, musculoskeletal pain was induced with a delayed-onset muscle soreness protocol. During the second session, participants were randomly assigned to the transcutaneous electrical nerve stimulation or placebo condition and were asked to rate their pain as they lifted a series of 18 weighted canisters. An index of RISP was derived as the change in pain ratings across repeated lifts. Approximately 25% of participants showed evidence of RISP. Results also revealed that transcutaneous electrical nerve stimulation attenuated the RISP effect. Psychological measures (fear of pain, catastrophizing) were not significantly correlated with the index of RISP, but the index of RISP was significantly correlated with a measure of physical tolerance. Discussion addresses the clinical implications of the findings as well as the potential mechanisms underlying RISP. ⋯ This study showed that RISP could be demonstrated in healthy individuals in response to experimentally induced musculoskeletal pain with delayed-onset muscle soreness. Transcutaneous electrical nerve stimulation led to a significant reduction in RISP.
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Randomized Controlled Trial
An explanatory study evaluating the muscle relaxant effects of intramuscular magnesium sulphate for dystonia in complex regional pain syndrome.
The treatment of dystonia related to complex regional pain syndrome (CRPS) remains unsatisfactory, raising the need of alternative targets for intervention. In dystonia, pathologic muscle changes may occur, which contributes to stiffness. Because magnesium sulphate may act as a muscle relaxant through its actions on the neuromuscular junction and muscle, we performed an explanatory study of the muscle relaxant effect and safety of intramuscular magnesium sulphate (IMMG) in CRPS patients with dystonia. In a double-blind randomized placebo-controlled crossover study, 30 patients were assigned to 3-week treatments of IMMG and placebo. Treatments were separated by a 1-week washout period. The daily dose of IMMG was 1,000 mg in week 1, 1,500 mg in week 2, and 2,000 mg in week 3. The primary outcome measure was the difference in change in Burke-Fahn-Marsden scores after 3 weeks of treatment between both interventions. Secondary outcomes involved severity of dystonia, myoclonus, tremor, and pain, and functional activity. Data of 22 patients available for the explanatory analysis revealed no significant differences between IMMG and placebo treatment in any of the outcomes. In conclusion, we found no indication of efficacy of IMMG in a daily dose of 2,000 mg as a muscle relaxant in CRPS-related dystonia. ⋯ In this double-blind placebo-controlled crossover study there was no evidence found of a muscle relaxant effect of intramuscular magnesium sulphate in dystonia related to CRPS. Consequently, there is insufficient support for new studies evaluating the efficacy of other routes of MG administration in CRPS-related dystonia.
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Randomized Controlled Trial
Timing and gender determine if acute pain impairs working memory performance.
The effects of pain on memory are complex, and little is known about the vulnerability of working memory (WM) performance when individuals complete a WM test while concurrently experiencing pain. Here, we subjected 78 healthy nonsmoking participants to either acute pain or a control condition while we administered a WM test. In this context, we also tested WM 20 minutes after pain in order to determine if timing of pain affected WM performance, and assessed objective and subjective measures of pain. We hypothesized that pain would impair WM performance during pain. Further, women's WM performance would be impaired more than men. Importantly, there was an interaction between gender and condition, with women exposed to pain experiencing impairments during but not after the cold pressor task. Our data imply that timing and gender are critically important in whether acute pain is costly to WM performance. Our findings have interesting clinical, professional, and educational implications, and understanding the influence of pain could help to improve the interpretation of WM tests in these diverse settings. ⋯ Results of this study support the growing body of work that attests to the detrimental effect of pain on WM performance. Further, this study provides new evidence that concurrently experiencing cold pressor pain impairs WM in regularly menstruating women and women taking a contraceptive.
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Randomized Controlled Trial
A trial of a brief group-based form of acceptance and commitment therapy (ACT) for chronic pain in general practice: pilot outcome and process results.
Acceptance and commitment therapy (ACT) is a developing approach for chronic pain. The current study was designed to pilot test a brief, widely inclusive, local access format of ACT in a UK primary care setting. Seventy-three participants (68.5% women) were randomized to either ACT or treatment as usual (TAU). Many of the participants were aged 65 years or older (27.6%), were diagnosed with fibromyalgia (30.2%) and depression (40.3%), and had longstanding pain (median = 10 years). Standard clinical outcome measures included disability, depression, physical functioning, emotional functioning, and rated improvement. Process measures included pain-related and general psychological acceptance. The recruitment target was met within 6 months, and 72.9% of those allocated to ACT completed treatment. Immediately post treatment, relative to TAU, participants in ACT demonstrated lower depression and higher ratings of overall improvement. At a 3-month follow-up, again relative to TAU, those in ACT demonstrated lower disability, less depression, and significantly higher pain acceptance; d = .58, .59, and .64, respectively. Analyses based on intention-to-treat and on treatment "completers," perhaps predictably, revealed more sobering and more encouraging results, respectively. A larger trial of ACT delivered in primary care, in the format employed here, appears feasible with some recommended adjustments in the methods used here (Trial registration: ISRCTN49827391). ⋯ This article presents a pilot randomized controlled trial of ACT for chronic pain in a primary care setting in the United Kingdom. Both positive clinical outcomes and ways to improve future trials are reported.