The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
High-Definition Transcranial Direct Current Stimulation Enhances Conditioned Pain Modulation in Healthy Volunteers: A Randomised Trial.
Transcranial direct current stimulation (tDCS) is a form of brain stimulation that allows for the selective increase or decrease in the cortical excitability of a targeted region. When applied over the motor cortex it has been shown to induce changes in cortical and subcortical brain regions involved in descending pain inhibition or conditioned pain modulation (CPM). The aim of the current study was to assess whether activation of pain inhibitory pathways via tDCS of the motor cortex facilitates the CPM response. Elevated CPM after active tDCS of the motor cortex was hypothesized. Thirty healthy male volunteers attended 2 experimental sessions separated by 7 days. Both sessions consisted of CPM assessment after 20 minutes of either active or sham (placebo) tDCS over the motor cortex. CPM capacity was assessed via the pain-inhibits-pain protocol; CPM responses were shown to be elevated after active compared with sham tDCS. This report concludes that tDCS of the motor cortex enhances the CPM response in healthy men. This finding supports the potential utility of tDCS interventions in clinical pain treatment. ⋯ The use of noninvasive brain stimulation over the motor cortex was shown to enhance the CPM effect. This finding supports the use of tDCS in the treatment of chronic pain, particularly in sufferers exhibiting maladaptive CPM.
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Central sensitization (CS), nociceptive hyperexcitability known to amplify and maintain clinical pain, has been identified as a leading culprit responsible for maintaining pain in several chronic pain conditions. Recent evidence suggests that it may explain differences in the symptom experience of individuals with sickle cell disease (SCD). Quantitative sensory testing (QST) can be used to examine CS and identify individuals who may have a heightened CS profile. The present study categorized patients with SCD on the basis of QST responses into a high or low CS phenotype and compared these groups according to measures of clinical pain, vaso-occlusive crises, psychosocial factors, and sleep continuity. Eighty-three adult patients with SCD completed QST, questionnaires, and daily sleep and pain diaries over a 3-month period, weekly phone calls for 3 months, and monthly phone calls for 12 months. Patients were divided into CS groups (ie, no/low CS [n = 17] vs high CS [n = 21]), on the basis of thermal and mechanical temporal summation and aftersensations, which were norm-referenced to 47 healthy control subjects. High CS subjects reported more clinical pain, vaso-occlusive crises, catastrophizing, and negative mood, and poorer sleep continuity (Ps < .05) over the 18-month follow-up period. Future analyses should investigate whether psychosocial disturbances and sleep mediate the relationship between CS and pain outcomes. ⋯ In general, SCD patients with greater CS had more clinical pain, more crises, worse sleep, and more psychosocial disturbances compared with the low CS group.
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Patients with depression often report pain. Evidence regarding altered pain sensitivity in depressed patients remains, however, inconclusive. In a large cross-sectional study we investigated the association between depression and pain sensitivity with regard to 2 different dimensions of pain sensitivity, as well as the effect of somatic cofactors, symptom severity, and subtype of depression. In 735 patients with a current episode of major depression and 456 never-depressed control participants pain thresholds (pressure pain thresholds, PPTs) were measured at the index finger pad and self-rated suprathreshold pain intensity ratings were obtained using the Pain Sensitivity Questionnaire (PSQ)-minor subscore, an instrument that assesses pain intensity in daily life situations. Additionally, lifestyle factors, medical, and psychiatric conditions were assessed. Unadjusted, patients with depression had lower PPTs and higher PSQ-minor scores indicating increased pain sensitivity. After adjusting for potential mediators, such as poor sleep quality and physical inactivity, patients did not differ from control participants regarding PPTs, but still had significantly higher PSQ-minor ratings. Among patients with depression, severity of anxiety symptoms predicted higher PSQ-minor scores. In conclusion, we found a differential effect of depression on the 2 pain sensitivity dimensions: Decreased experimentally obtained pain thresholds were explained by depression-associated somatic factors whereas increased self-rated suprathreshold pain intensity ratings were associated with increased anxiety symptoms. ⋯ Because increased pain intensity perception is hypothesized to be a risk factor for the development of chronic pain, our findings may contribute to understanding the high incidence of chronic pain in depressed patients. They also encourage clinicians to consider the role of anxiety in treatment programs for pain in patients with depression.
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High interindividual variability in postoperative opioid consumption is related to genetic and environmental factors. We tested the association between morphine consumption, postoperative pain, and single nucleotide polymorphisms (SNPs) within opioid receptor μ 1 (OPRM1), catechol-O-methyltransferase (COMT), uridine diphosphate glucose-glucuronosyltransferase-2B7, and estrogen receptor (ESR1) gene loci to elucidate genetic prediction of opioid consumption. We analyzed 20 SNPs in 201 unrelated Caucasian patients who underwent abdominal surgery and who were receiving postoperative patient-controlled analgesia-administered morphine. Morphine consumption and pain intensity were dependent variables; age and sex were covariates. A haplotype of 7 SNPs in OPRM1 showed significant additive effects on opioid consumption (P = .007); a linear regression model including age and 9 SNPs in ESR1, OPRM1, and COMT explained the highest proportion of variance of morphine consumption (10.7%; P = .001). The minimal model including 3 SNPs in ESR1, OPRM1, and COMT explained 5% of variance (P = .007). We found a significant interaction between rs4680 in COMT and rs4986936 in ESR1 (P = .007) on opioid consumption. SNPs rs677830 and rs540825 of OPRM1 and rs9340799 of ESR1 were nominally associated with pain Numeric Rating Scale scores. Combinations of genetic variants within OPRM1, COMT, and ESR1 better explain variability in morphine consumption than single genetic variants. Our results contribute to the development of genetic markers and statistical models for future diagnostic tools for opioid consumption/efficacy. ⋯ This article presents the efforts dedicated to detect correlations between the genetic polymorphisms and the clinical morphine effect self-administered by patients using a patient-controlled analgesia pump after major surgery. The clinical effect is expressed in terms of morphine consumption and pain scores. REGISTERED ON CLINICALTRIALS.GOV: NCT01233752.
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Review Meta Analysis
The Efficacy of Motivational Interviewing in adults with Chronic Pain: A Meta-Analysis and Systematic Review.
Motivational interviewing (MI) has become a popular approach for increasing adherence. In this study we investigated whether MI is effective in improving adherence, and pain and physical function for patients with chronic pain. A literature search of randomized controlled trials identified 7 eligible studies with 962 participants with chronic pain. There was a small to moderate overall effect of MI on increased adherence to treatment from baseline to after intervention, but not from baseline to follow-up. Although significant short-term effects of MI were also observed for pain intensity, analyses revealed that this finding might be due to publication bias. There were insufficient studies to examine physical functioning meta-analytically, however, none of the 3 available studies showed that MI resulted in gains in physical function compared with the control group. These results indicate that MI can probably increase short-term adherence to chronic pain treatments, although publication bias cannot be ruled out. Further, it is as yet unclear whether these effects result in improvements in patient function. Although the studies were methodologically strong, they investigated MI in relation to a number of treatments for chronic pain. Future research on the efficacy of MI on adherence to evidence-based self-management interventions for chronic pain is needed. ⋯ MI significantly increased adherence to prescribed chronic pain treatments in the short term, however, effect sizes were small to moderate and publication bias was likely. MI showed some promise in promotion of adherence to pain treatments, but more research is required to confirm its efficacy.