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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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.
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Randomized Controlled Trial
Botulinum toxin type A reduces capsaicin-evoked pain and neurogenic vasodilatation in human skin.
The effect of Botulinum Toxin type A (BoNT/A) on pain and neurogenic vasodilatation induced by application to the human skin of thermal stimuli and capsaicin was evaluated in a double blind study. A capsaicin cream (0.5 ml of a 0.075%) was applied to the skin of both forearms of eighteen subjects randomly pretreated with either BoNT/A (Botox) or 0.9% saline (NS). Capsaicin was applied to a skin area either inside (protocol A) or adjacent to the BoNT/A treated area (protocol B). ⋯ In Protocol B, capsaicin-induced pain was unchanged, and capsaicin-induced flare/increase in CBF were reduced only in the area treated with BoNT/A, but not in the BoNT/A untreated area. Results indicate that (i) BoNT/A reduces capsaicin-induced pain and neurogenic vasodilatation without affecting the transmission of thermal and thermal-pain modalities; (ii) reduction in capsaicin-induced pain occurs only if capsaicin is administered into the BoNT/A pretreated area; (iii) reduction in neurogenic vasodilatation by BoNT/A does not contribute to its analgesic action. BoNT/A could be tested for the treatment of conditions characterised by neurogenic inflammation and inflammatory pain.