Pain
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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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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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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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Nociceptive impulse activity was recorded extracellularly from single A delta and C primary afferents of the guinea pig's medial articular nerve after induction of an experimental osteoarthritis in the knee joint by partial medial menisectomy and transection of the anterior cruciate ligament (PMM+TACL). Also, the analgesic effects of intra-articular hyaluronan solutions were evaluated. Healthy, PMM+TACL operated, sham-operated (opening of the joint capsule without PMM and TACL surgery) and acutely inflamed (intra-articular kaolin-carrageenan, K-C) animals were used. ⋯ Augmentation of movement-evoked discharges in K-C acutely inflamed knee joints was similar to that observed one week after PMM+TACL. Our results indicate that in the PMM+TACL model of osteoarthritis in guinea pigs, enhancement of nociceptive responses to joint movement was primarily associated to post-surgical inflammation. Intra-articular injection of an elastoviscous hyaluronan solution reduced the augmented nerve activity.