The journal of pain : official journal of the American Pain Society
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Review Meta Analysis
Conditioned pain modulation in populations with chronic pain: a systematic review and meta-analysis.
A systematic literature review and meta-analysis were undertaken to determine if conditioned pain modulation is dysfunctional in populations with chronic pain. Studies that used a standardized protocol to evaluate conditioned pain modulation in a chronic pain population and in a healthy control population were selected and reviewed. Thirty studies were included in the final review, encompassing data from 778 patients and 664 control participants. Across all studies there was a large effect size of .78, reflecting reduced conditioned pain modulation in the patient group. Analysis of moderator variables indicated a significant influence of participant gender and age on the effect size. Methodological moderator variables of type of outcome measure, type of test stimulus, type of conditioning stimulus, and the level of conditioning stimulus pain were not significant. A risk of bias assessment indicated that poor blinding of assessors and a lack of control of confounding variables were common. It is concluded that conditioned pain modulation is impaired in populations with chronic pain. Future studies should ensure adequate matching of participant age and gender between patient and control groups, blinding of the assessors obtaining the outcome measures, and more rigorous control for variables known to influence the level of modulation. ⋯ This review compared the efficacy of conditioned pain modulation between chronic pain and healthy populations. The finding of impaired modulation in the chronic pain groups highlights the dysfunction of endogenous pain modulatory mechanisms in this population.
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Spontaneous pain is often discussed in the context of both chronic inflammatory and neuropathic pain conditions, and it has been suggested that spontaneous pain, rather than stimulus-evoked pain, may be the more significant clinical problem. The following issues are discussed here. First, it is suggested that the concept of spontaneous pain makes no sense when the pain is the result of an ongoing inflammatory reaction. Evidence is reviewed that indicates that spontaneous pain is present in patients with neuropathic pain, but perhaps only in a subset of such patients. Second, it is suggested that in the presence of allodynia and hyperalgesia, stimulation from the activities of daily life occurs very many times a day and that these stimulus-evoked pains may summate to give a fluctuating level of daily pain that both patients and investigators mistake for spontaneous pain. ⋯ Which is more important-stimulus-evoked pain or spontaneous pain? This review suggests that to answer the question we will need to distinguish neuropathic spontaneous pain from inflammatory ongoing pain and to differentiate both from summated allodynic and hyperalgesic pains caused by the stimuli of daily life.
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The aim of this study was to investigate the psychometric properties of an abbreviated version of the Tampa Scale for Kinesiophobia (TSK) in a clinical sample of patients with chronic pain. Chronic pain patients (n = 276) seeking treatment at an interdisciplinary treatment center completed self-report questionnaires including the TSK-13, and 2 tests of physical functioning. Four competing models of the TSK were tested using confirmatory factor analysis. Internal consistency was assessed, as were discriminant evidence of construct validity and concurrent criterion-related validity. Incremental validity was assessed with hierarchical multiple regressions controlling for pain severity. The analyses indicated that an 11-item, 2-factor structure best fit the data. The first factor, somatic focus, consisted of 5 items, while the second factor, activity avoidance, was comprised of 6 items. The TSK-11 scales demonstrated acceptable levels of internal consistency, as well as evidence of discriminant, concurrent criterion-related, and incremental validity. Somatic focus uniquely predicted perceived disability while activity avoidance uniquely predicted actual physical performance, controlling for pain severity. The 2-factor structure of the TSK-11 was found to be a brief, reliable, and valid measure of fear of movement/(re)injury for chronic pain patients. We recommend that the TSK-11 be used in future research and in clinical settings. ⋯ In this study, confirmatory factor analysis identified the 2-factor TSK-11 as the best fitting model of TSK factor structure. The TSK-11 is a brief, reliable, and valid measure of fear of movement/(re)injury for chronic pain patients.
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Neonatal pain experiences have been associated with altered processing and perception of pain in later life, but findings tend to vary among studies. We have compared experimental pain tolerance and subjective health complaints in a population-based cohort of adolescents born extremely preterm to that of matched term controls. Subjects performed a standardized cold pressor task (hand in ice water) and completed validated questionnaires regarding current subjective health complaints, including pain issues. Thirty-one (89%) of 35 eligible preterm subjects (mean gestational age 26.8 weeks) and 28 (80%) term controls participated in this follow-up study at mean age 17.8 years. Ten (32%) subjects born preterm versus 17 (61%) born at term reached the ceiling time of 180 seconds immersion time in the ice water, a hazard ratio for early withdrawal of 2.05 (95% confidence interval, 1.72 to 2.44), with males explaining most of the difference. For subjects born preterm, the risk of early withdrawal decreased significantly with more days of mechanical ventilation, more pain events, and more doses of morphine during the newborn period. Subjective pain ratings during the cold pressor task as well as health-related complaints and pain issues reported in the questionnaires were similar in the preterm and term groups. ⋯ Despite reduced tolerance to experimental pain, subjects born preterm scored their pain experiences similarly to those of term controls. Surprisingly, preterm subjects exposed to most painful and invasive neonatal experiences and also to most doses of morphine had a pain response at follow-up most closely resembling that of the control group.
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The multiple bodily pain conditions in temporomandibular disorders (TMD) have been associated with generalized alterations in pain processing. The purpose of this study was to examine the relationship between the presence of widespread body palpation tenderness (WPT) and the likelihood of multiple comorbid pain conditions in TMD patients and controls. This case-control study was conducted in 76 TMD subjects with WPT, 83 TMD subjects without WPT, and 181 non-TMD matched control subjects. The study population was also characterized for clinical pain, experimental pain sensitivity, and related psychological phenotypes. Results showed that: 1) TMD subjects reported an average of 1.7 comorbid pain conditions compared to .3 reported by the control subjects (P < .001); 2) Compared to control subjects, the odds ratio (OR) for multiple comorbid pain conditions is higher for TMD subjects with WPT [OR 8.4 (95% CI 3.1-22.8) for TMD with WPT versus OR 3.3 (95% CI 1.3-8.4) for TMD without WPT]; 3) TMD subjects with WPT presented with reduced pressure pain thresholds (PPTs) in both cranial and extracranial regions compared to TMD subjects without WPT; and 4) TMD subjects with WPT reported increased somatic symptoms. These findings suggest that pain assessment outside of the orofacial region may prove valuable for the classification, diagnosis, and management of TMD patients. ⋯ TMD subjects with WPT experience a greater level of multiple comorbid pain conditions, compared to TMD subjects without WPT and non-TMD controls. Integration of bodily pain assessments can be informative for evaluation, diagnosis, and management of TMD.