Pain
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Little is known about the pathway from musculoskeletal pain to mobility difficulty among older persons. We examined potential physical and psychological mediators of the pain-disability relationship in the Women's Health and Aging Study (WHAS), a cohort of women aged 65 who had at least mild disability at baseline. Pain was classified according to location and severity (widespread pain; lower extremity pain; other pain; none or mild pain in only one site). ⋯ Pain was not associated with increased risk for becoming unable to walk or climb stairs. The findings suggest that pain is a unique domain as a cause of disablement, independent of the usual pathway to disability via physical impairments. Research is needed to better understand the development of pain-related disability in order to determine optimum approaches to prevent and treat mobility disability in older persons with persistent pain.
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Noxious C-fibre stimulation produces increased sensitivity within the injured area (primary hyperalgesia), and a surrounding zone of secondary hyperalgesia. As significant changes in nociceptive processing occur during development, we compared C-fibre induced primary and secondary hyperalgesia in rat pups aged 3, 10 and 21 postnatal (P) days. Hyperalgesia was measured by electromyography flexion reflex recordings following mustard oil or capsaicin at the site of (primary hyperalgesia), or distant to (secondary hyperalgesia) hindpaw mechanical stimuli. ⋯ These results provide evidence that primary and secondary hyperalgesia are differentially modulated during development. Furthermore, since ERK activation is required for secondary hyperalgesia, phosphoERK expression can be used to map the spatial distribution of neuronal activation in the spinal cord. Understanding changing responses to injury in the developing nervous system is important for clinical paediatric practice, and will enhance our ability to target the most effective site with a developmentally appropriate analgesic regime.
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There is evidence that patients with Complex Regional Pain Syndrome (CRPS) have altered central sensorimotor processing. Sensory input can influence motor output either through indirect pathways or through direct connections from the sensory to motor cortex. The purpose of this study was to investigate sensorimotor interaction via direct connections in patients with CRPS and to compare the results with normal subjects'. ⋯ In seven of the eight CRPS patients EMG responses to TMS were suppressed when paired with median nerve stimulation. Only one CRPS patient's results showed no suppression of EMG responses. These results suggest that the disease mechanisms of CRPS1 do not typically affect the direct neural circuit between sensory and motor cortex and that normal sensorimotor interaction is occurring via this route.