The journal of pain : official journal of the American Pain Society
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The nature of the transition from acute to chronic pain still eludes explanation, but chronic pain resulting from surgery provides a natural experiment that invites clinical epidemiological investigation and basic scientific inquiry into the mechanisms of this transition. The primary purpose of this article is to review current knowledge and hypotheses on the transition from acute to persistent postsurgical pain, summarizing literature on clinical epidemiological studies of persistent postsurgical pain development, as well as basic neurophysiological studies targeting mechanisms in the periphery, spinal cord, and brain. The second purpose of this article is to integrate theory, information, and causal reasoning in these areas. ⋯ These propose that chronic pain results from: 1) persistent noxious signaling in the periphery; 2) enduring maladaptive neuroplastic changes at the spinal dorsal horn and/or higher central nervous system structures reflecting a multiplicity of factors, including peripherally released neurotrophic factors and interactions between neurons and microglia; 3) compromised inhibitory modulation of noxious signaling in medullary-spinal pathways; 4) descending facilitatory modulation; and 5) maladaptive brain remodeling in function, structure, and connectivity. The third purpose of this article is to identify barriers to progress and review opportunities for advancing the field. This review reveals a need for a concerted, strategic effort toward integrating clinical epidemiology, basic science research, and current theory about pain mechanisms to hasten progress toward understanding, managing, and preventing persistent postsurgical pain.
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This study reports the results of a researcher-administered survey with 115 patients receiving chronic opioid therapy (>90 days) to obtain information regarding how chronic opioid therapy was started. Chronic opioids were started after surgery (27.0%, 95% confidence interval [CI], 18.5-35.5) or for the treatment of acute injury-related pain (27.0%, 95% CI, 18.5-35.5). Many who initiated opioid therapy after surgery reported postoperative complications (61.3%, 95% CI, 50.8-71.8) and many with injury-related pain reported follow-up corrective surgery (58.1%, 95% CI, 47.5-68.7), which led to the continuation of opioids. ⋯ Patients receiving long-term opioid therapy often transitioned to chronic use after starting opioids for the short-term treatment of postoperative or injury-related pain. It is not evident if a clear decision to continue opioids on a chronic basis was made. This survey provides insight as to how chronic opioid therapy is started, and may suggest opportunities for improved patient selection for opioid therapy.
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The role of various forms of social support (including the mere presence of another person) in pain has been studied in children and younger adults, but parallel studies involving older persons have not been conducted. In this investigation, older adults (N = 100) took part in a series of experimental pain tasks in each of the following conditions: alone, in the presence of a stranger, and in the presence of a family member. Indices of pain (threshold, tolerance, intensity, unpleasantness, facial expressions) and facial expressions of emotion were analyzed. ⋯ In examining sex differences, male participants reported higher pain tolerance and female participants displayed more prominent facial expressions of pain. Moreover, facial expressions of neutral states and happiness were more frequent among female participants, whereas facial expressions of anger were more frequent among male participants. Results show that the presence of others influences the experience and expression of pain in older persons.
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Migraine with aura is a subtype of migraine characterized by transient neurological disturbances that usually precede headache. Cortical spreading depression (CSD) is the likely pathophysiological correlate of the aura phase of migraine, found in common and rare forms of migraine, such as familial hemiplegic migraine. CSD is a depolarization wave that propagates across the cerebral gray matter transiently suppressing neuronal activity. ⋯ In brainstem, CSD with and without treatment, although to a lesser extent, also induced gene expression changes involving genes related to apoptosis. Half of the genes altered in brainstem after CSD were also differentially expressed in the same direction in cortex. No differences in gene expression were identified after CSD as a consequence of the treatments, neither in cortex nor in brainstem.
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Although depression is associated with more clinical pain complaints, psychophysical data sometimes point to hypoalgesic alterations. Studying the more reflex-like facial expression of pain in patients with depression may offer a new perspective. Facial and psychophysical responses to nonpainful and painful heat stimuli were studied in 23 patients with major depressive disorder (MDD) and 23 matched control participants. ⋯ Pain psychophysics was unaltered in MDD patients compared with healthy control participants. In conclusion, the facial expression of pain in MDD patients indicates rather hyper- than hypoalgesia, with enhanced affective pain processing. Moreover, the linkage between subjective and facial responses was much stronger in MDD patients, which may be due to a reduced influence of social display rules, which normally complicate this relationship.