The journal of pain : official journal of the American Pain Society
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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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Vicarious pain has been shown to enhance observers' nociceptive reactivity and pain perception. We exposed healthy participants to specific parts of facial pain expressions in order to investigate which components are required to induce this modulation. We created 2 classes of stimuli: one containing the most useful information for identification of pain expressions (diagnostic) and one containing the least useful information (antidiagnostic). Twenty-eight normal volunteers received electrical stimulation of the sural nerve immediately after they viewed these stimuli. Subjective ratings (intensity and unpleasantness) as well as the nociceptive flexion reflex (NFR) evoked by the shock were recorded. Results show that diagnostic stimuli lead to higher subjective ratings of shock pain than the antidiagnostic stimuli, but the stimuli classes had no significant impact on the NFR. A control experiment showed that our facial stimuli were given very low valence and arousal ratings compared to stimuli previously used to demonstrate the effect of emotional pictures on pain. Thus, the results are unlikely to be explained by emotions felt by the observer and suggest a vicarious facilitation of supraspinal pain processing induced by key features underlying pain expressions recognition. Results provide further support to the perception-action model of empathy. ⋯ This study demonstrates that visual features that are efficiently used for the recognition of pain expressions are sufficient to induce a vicarious facilitation of self-pain. Supraspinal pain responses were modulated by the informativeness of the areas of the pain expressions that participants viewed prior to the painful stimulations.
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The dominant socioaffective model of empathy has emphasized the overlap between brain mechanisms involved in the encoding and the decoding of internal states. The role of dispositional empathy has been extensively studied in this research, but several other individual factors fundamental to communication processes have been largely ignored. We studied the effects of dispositional expressiveness in chronic back pain patients to determine if the decoding of communicative and noncommunicative information signaling pain in others would be enhanced in individuals displaying a spontaneous propensity to consistently express more pain during a behavioral-observational naturalistic standardized lifting task performed on 2 separate occasions. Blood oxygenation level-dependent signal change was measured in response to pictures showing facial pain expressions and hands/feet in pain-evoking situations in chronic back pain patients and healthy controls. Vicarious brain responses to others' pain were comparable between groups. However, more expressive patients rated others' pain higher and showed stronger vicarious pain responses in the right ventral part of the inferior frontal gyrus, the right insula, and the midbrain. Activity in the right insula correlated positively with both the patients' expressiveness (encoding) and the intensity of the pain perceived in the images (decoding), suggesting that this structure linked the dispositional expressiveness with vicarious pain perception. Importantly, these effects were independent from dispositional empathy and were found with both communicative (facial expression) and noncommunicative (hand and foot) cues. These results suggest that dispositional expressiveness is a self-related factor that facilitates vicarious pain processing and might reflect individual tendencies to rely on social coping strategies. ⋯ This article shows that pain expressivity in chronic pain patients increased the vicarious brain responses and the sensibility to others' pain. These results may help provide empirical support for better defining models of pain communication in chronic pain patients.
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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.