The journal of pain : official journal of the American Pain Society
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The purpose of this study was to identify neural correlates of pain anticipation in people with nonspecific low back pain (NSLBP) that correlated with pain-related distress and disability, thus providing evidence for mechanisms underlying pain behavior in this population. Thirty NSLBP sufferers, with either high levels of pain behavior or low levels on the basis of Waddell signs, were scanned with functional magnetic resonance imaging while a straight-leg raise (of the side deemed to cause moderate pain in the lower back) was performed. On each trial colored stimuli were presented and used to indicate when the leg definitely would be raised (green; 100% certainty), might be raised (yellow; 50% certainty), or would definitely not be raised (red; 100% certainty). In response to expected versus unexpected pain the group difference in activation between patients with high levels of pain behavior and low levels of pain behavior covaried as a function of anxiety scores in the right insula and pregenual anterior cingulate cortex and as a function of catastrophizing in prefrontal and parietal cortex and hippocampus. The results suggest NSLBP populations with the highest levels of pain-related distress are more likely to attend to and infer threat from innocuous cues, which may contribute to the maintenance of pain behavior associated with some chronic pain states. ⋯ This article shows a likely neural network for exacerbating pain anticipation in NSLBP contributing to high levels of pain behavior in some people. This information could potentially help clinicians and patients to understand how anticipation of pain may contribute to patient pain and disability.
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In this large, sham-controlled, randomized trial, we examined the efficacy of the combination of standard treatment and paraspinous lidocaine injection compared with standard therapy alone in subjects with chronic low back pain. There is little research-based evidence for the routine clinical use of paraspinous lidocaine injection for low back pain. A total of 378 subjects with nonspecific chronic low back pain were randomized to 3 groups: paraspinous lidocaine injection, analgesics, and exercises (group 1, LID-INJ); sham paraspinous lidocaine injection, analgesics, and exercises (group 2, SH-INJ); and analgesics and exercises (group 3, STD-TTR). A blinded rater assessed the study outcomes at 3 time points: baseline, after treatment, and after 3 months of follow-up. There were increased frequency of pain responses and better low back functional scores in the LID-INJ group compared with the SH-INJ and STD-TTR groups. These effects remained at the 3-month follow-up but differed between all 3 groups. There were significant changes in pain threshold immediately after treatment, supporting the effects of this intervention in reducing central sensitization. Paraspinous lidocaine injection therapy is not associated with a higher risk of adverse effects compared with conventional treatment and sham injection. Its effects on hyperalgesia might correlate with changes in central sensitization. ⋯ There are few data to support paraspinous lidocaine injection use in patients with nonspecific chronic low back pain. Our results show that this therapy when combined with standard therapy significantly increases the number of responders versus standard treatment alone. Its effects on hyperalgesia might correlate with a change in central sensitization.
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Review
The Pain Experience of Hispanic Americans: A Critical Literature Review and Conceptual Model.
Although the Hispanic population is a burgeoning ethnic group in the United States, little is known about their pain-related experience. To address this gap, we critically reviewed the existing literature on pain experience and management among Hispanic Americans (HAs). We focused our review on the literature on nonmalignant pain, pain behaviors, and pain treatment seeking among HAs. Pain management experiences were examined from HA patients' and health care providers' perspectives. Our literature search included variations of the term "Hispanic" with "AND pain" in PubMed, Embase, Web of Science, ScienceDirect, and PsycINFO databases. A total of 117 studies met our inclusion criteria. We organized the results into a conceptual model with separate categories for biological and/or psychological and sociocultural and/or systems-level influences on HAs' pain experience, response to pain, and seeking and receiving pain care. We also included information on health care providers' experience of treating HA patients with pain. For each category, we identified future areas of research. We conclude with a discussion of limitations and clinical implications. ⋯ In this critical review of the literature we examined the pain and management experiences of the HA population. We propose a conceptual model, which highlights findings from the existing literature and future areas of research.
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Observational Study
Situational but not dispositional pain catastrophizing correlates with early postoperative pain in pain-free patients before surgery.
Pain catastrophizing may be assessed as a dispositional measure using a previous painful experience as a reference or as a situational measure using an actual ongoing pain as a reference. The latter has shown more robust correlations with pain-related outcomes; the relative influence of dispositional and situational pain catastrophizing remains unknown in relation to populations with no pain before surgery. Forty-two consecutive patients who underwent corrective surgery for funnel chest were asked to complete the Pain Catastrophizing Scale with reference to 1) a previous painful experience (dispositional pain catastrophizing), 2) experimental pain during a 2-minute cold pressor test (situational experimental pain catastrophizing), and 3) clinical pain 3 days after surgery (situational clinical pain catastrophizing) to investigate whether these measures predicted immediate pain intensity and unpleasantness in the early postoperative period. Thirty-four patients were available for analyses. Dispositional pain catastrophizing was unrelated to situational experimental and situational clinical pain catastrophizing and to postoperative pain and unpleasantness (P > .05). In contrast, the 2 situation-specific pain catastrophizing measures were strongly associated (ρ = .59, P = .0002). In analyses adjusted for preoperative anxiety, depression, and cold pressor pain sensitivity, situational experimental and situational clinical pain catastrophizing correlated with postoperative movement-evoked pain (β = 1.36, P = .01 and β = 1.24, P = .02, respectively) and unpleasantness (β = 1.32, P = .01 and β = 1.36, P = .01, respectively). ⋯ Pain catastrophizing should be captured in relation to specific painful events in otherwise healthy patients. Future studies might benefit from assessing situational pain catastrophizing to identify patients at risk for increased postoperative pain to optimize stratified pain treatment.
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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.