Pain
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The accurate, precise, and consistent assessment of pain is of particular importance in palliative care. The European Palliative Care Research Collaborative is developing a computer-based pain assessment instrument and has been evaluating the content and dimensionality of existing pain questionnaires. The most important dimensions of pain are intensity and interference. ⋯ However, there was strong evidence that the relationship between the intensity and the interference items differs markedly in palliative care patients compared to chronic pain patients. As hypothesized, there was strong correlation between intensity and interference, lending support to the possibility that, for some purposes, these dimensions may be combined to provide a higher-level summary measure of patients' pain experience. We conclude that these dimensions should be kept distinct when assessing patients in general, although for a single type of patient (such as palliative care patients), it may be possible to regard intensity and interference as contributing to an overall measure of pain severity.
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Neuropathic pain is often "spontaneous" or "stimulus-independent." Such pain may result from spontaneous discharge in primary afferent nociceptors in injured peripheral nerves. However, whether axotomized primary afferent nociceptors give rise to pain is unclear. The rostral anterior cingulate cortex (rACC) mediates the negative affective component of inflammatory pain. ⋯ Lesion of the rACC did not block cocaine-induced reward, indicating that rACC blockade did not impair memory encoding or retrieval but did impair spontaneous aversiveness. These data indicate that spontaneous pain arising from injured nerve fibers produces a tonic aversive state that is mediated by the rACC. Identification of the circuits mediating aversiveness of chronic pain should facilitate the development of improved therapies.
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The shared-representation model of empathy suggests that vicarious pain processes rely partly on the activation of brain systems underlying self-pain in the observer. Here, we tested the hypothesis that self-pain may be facilitated by the vicarious priming of neural systems underlying pain perception. Pictures illustrating painful agents applied to the hand or the foot (sensory information), or painful facial expressions (emotional information) were shown to 43 participants to test the effects of vicarious pain on the nociceptive flexion reflex (NFR) of the lower limb and pain intensity and unpleasantness produced by transcutaneous electrical stimulation applied over the sural nerve. ⋯ In contrast, the change in perceived shock-pain intensity was negatively correlated with empathic traits. This dissociation implies that low-level vicarious priming processes underlying pain facilitation may be downregulated at higher pain-processing stages in individuals reporting higher levels of empathy. We speculate that this process contributes to reducing self-other assimilation and is necessary to adopt higher-order empathic responses and altruistic behaviors.
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This study examined processes that contribute to the changing painfulness of a repeatedly presented thermal (heat) stimulus. The 3-second pulses were presented to the side of the hand at a rate of 4/min, too slow to engage wind-up. Over the course of 32 trials, pain intensity (measured by verbal report on a 0-100 scale) first declined and then (in most cases) rose again, indicating adaptation and sensitization, respectively. ⋯ Adaptation and sensitization were comparable in participants with fibromyalgia, temporomandibular disorders, and in healthy controls, indicating that these processes occur before the perceptual amplification that characterizes fibromyalgia and temporomandibular disorders. The ability of vibration to reduce pain has previously been shown to involve segmental inhibition; the finding in the present study that vibratory gating of pain is significantly (inversely) related to the rate of sensitization suggests that the latter also reflects segmental processes. Several lines of evidence thus point to the conclusion that adaptation and sensitization occur at early stages of sensory information processing.