Pain
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Impulse frequency and number of recruited central neurons are relevant for pain encoding and temporal as well as spatial summation of pain (SSP). Whereas SSP of heat-induced pain is well characterized, mechanical SSP (MSSP) has been less studied. MSSP may be relevant for chronic pain conditions like fibromyalgia (FM) and play an important role in the pathogenesis of this chronic pain syndrome. ⋯ Furthermore, muscle stimuli elicited more MSSP when separated by 8 cm than 4 cm and this finding was not different between NC and FM subjects. Thus, mechanisms of MSSP were similar for both FM and NC subjects. The important role of MSSP for pain encoding suggests that decreasing pain in some muscle areas by local anesthetics or other means may improve overall clinical pain of FM patients.
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Changes in pain produced by psychological factors (e.g., placebo analgesia) are thought to result from the activity of specific cortical regions. However, subcortical nuclei, including the periaqueductal gray and the rostroventral medulla, also show selective activation when subjects expect pain relief. These brainstem regions send inhibitory projections to the spine and produce diffuse analgesic responses. ⋯ These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice.
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The level and pattern of daily activities performed by persons with chronic pain are regarded as central determinants of their overall physical, social and emotional functioning. Within the chronic pain literature, various approaches to activity are typically considered, including activity avoidance, "pacing", and particular patterns of high rate activity, sometimes referred to as "overuse" or "activity cycling". Of these, activity avoidance has been most studied, while the others remain poorly understood. ⋯ Groups with the most avoidance and disability reported the lowest levels of acceptance of pain. These data suggest that activity patterns are complex and multidimensional, and that avoidance appears to be the overriding process with regard to daily functioning. Moreover, avoidance patterns may be subtle, sometimes resembling healthy coping, and sometimes presenting along side patterns of high activity.
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Depression is a common feature of chronic pain, but there is only limited research into the content of depressed cognitions in pain patients. This study investigated the content of cognition in depressed pain patients, non-depressed pain patients, and two control groups, healthy controls, and osteopaths using a sentence completion task. Participants generated completed sentences to a set of predefined stems that included negative, positive and neutral self-reference, and past, future and world terms. ⋯ We suggest that the focus of depression in chronic pain patients is health related. Pain patients who are not depressed focus on health, but not necessarily in a negative way. The concept of themselves in the future might be a key aspect in depression in pain patients.
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The purpose of this study was to explore gender differences in pain experiences, pain control beliefs, pain coping strategies, and depressive tendency among Chinese elderly with knee osteoarthritis (OA). Participants (N=199) were drawn from a previous convenience sample of outpatients with OA in Taiwan. Results indicated female elders tended to report higher scores on least pain, current pain and overall pain intensity than male elders (all p<0.01). ⋯ In summary, this sample of elders showed gender differences in depressive tendency and some pain experiences but not in pain control beliefs and coping strategies. These results suggest that health care providers should be cautious about using gender differences to explain pain experiences among Chinese elders. In addition, health care providers may decrease these female patients' pain intensity and pain disturbance by treating depressive symptoms.