Pain
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Subcutaneous (s.c.) injection of formalin induces a rapid and prolonged hyperalgesia across widespread areas of the body. This hyperalgesic state involves a brain-to-spinal cord pathway, likely arising from the nucleus raphe magnus. The present study examined whether subsequent activation of spinal cord glia may be critical for the hyperalgesic state to be observed in rats. ⋯ Disruption appeared to be selective, as blockade of only select glial products was effective. That is, up to 120 microg of a functional antagonist of tumor necrosis factor-alpha (TNF binding protein) and 5 microl of an antibody against complement-3 produced no statistically reliable reduction in formalin-induced hyperalgesia. Taken together, the present series of experiments suggest an important role for spinal glial cells in the cascade of events that are initiated by descending signals following s.c. administration of formalin.
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Despite its importance in clinical practice, little research has examined memory for pain in children. This prospective study tried to justify the use of children's pain recall in clinical practice. The purpose of this study was to (a) investigate the accuracy of children's recall of their worst and average pain intensity when controlling for the effects of repeated pain measurement and (b) examine the influence of children's anxiety, age, general memory ability and pain coping strategies on this accuracy. ⋯ The accuracy of children's recalled pain intensities was high and showed little decrement over 1 week. Older children had more accurate recall of their worst pain intensity. Anxiety, general memory ability and pain coping strategies were not related to accuracy of recalled pain intensities.
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Randomized Controlled Trial Clinical Trial
Enhancing sensitivity to facial expression of pain.
Clinicians have long appreciated the information communicated by a patient's facial expression. Advances in the measurement of facial movements, using the Facial Action Coding System (FACS) have allowed for identification of a universal expression of pain, which is primarily encoded in four facial movements. While the FACS provides a rigorous assessment of facial expression, the time required to learn the system and to analyze the facial expression by use of slow motion video recording, makes its use impractical in the clinical setting. ⋯ Analyses indicated that the trained group was significantly more sensitive to subtle facial movements associated with low levels of pain. Relative to the patients' ratings, there was a tendency for raters to underestimate pain particularly when these were at a high level. The findings lend hope to the feasibility of developing a tool which would be clinically useful though this may be more difficult for observers judging more complex facial expressions associated with high levels of pain.
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Patients with reflex sympathetic dystrophy (RSD) often present with pain and disability that cannot be explained on the basis of objective physical findings. This has led some to speculate that RSD may be caused or mediated by non-organic factors. Unfortunately, there have been few studies using standardized measures of mood and illness behavior that have compared patients with RSD to patients with other chronic pain disorders. ⋯ In contrast to previous research using less stringent diagnostic criteria, there was no evidence of higher pain scores or lower levels of psychological distress among patients with RSD. In addition, a validated survey of childhood trauma found that sexual abuse, physical abuse, emotional abuse, and cumulative trauma were evenly distributed among all three diagnostic groups. The burden of proof would appear to be upon those who advocate the non-organic hypothesis to provide credible evidence of psychological involvement in the etiology of RSD.
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Pain symptoms of many disorders are reported to vary with menstrual stage. This study investigated how pain thresholds to electrical stimulation of the skin, subcutis and muscle tissue varied with menstrual stage in normal women and compared these variations with those in women with dysmenorrhea and in healthy men at matched intervals. Thresholds of the three tissues were measured four times during the course of one menstrual cycle at four sites. ⋯ The amount of abdominal muscle hyperalgesia correlated significantly with the amount of spontaneous menstrual pain. Only minor sex differences were observed for pain thresholds of the arm and leg, but there was a unanimous refusal by men, but not by women, to be tested at abdominal sites. These results indicate that menstrual phase, dysmenorrhea status, segmental site, tissue depth and sex all have unique interacting effects on pain thresholds, thus adding more items to the lengthy and still-growing list of biological factors that enter into an individual's judgment of whether or not a stimulus is painful.