Articles: chronic.
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Psychological trauma is typically accompanied by physical pain, and posttraumatic stress disorder (PTSD) often cooccurs with chronic pain. Clinical reports suggest that pain after trauma may be part of re-experiencing symptomatology. Classical conditioning can underlie visual re-experiencing because intrusions can occur as conditioned responses (CRs) to trauma-related cues. ⋯ Our data support that spatiotemporally associating innocuous cues with pain (CS) endows these cues to elicit conditioned pain responses in the absence of noxious stimulation. In this way pain can emerge as a CR with emotional and sensory components. Classical conditioning presents a possible mechanism explaining pain intrusions and, more broadly, pain experienced without a nociceptive input.
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Deficient endogenous pain modulation and increased nociceptive excitability are key features of central sensitization and can be assessed in humans by conditioned pain modulation (CPM, anti-nociceptive) and temporal summation of pain (TSP, pro-nociceptive), respectively. This study aimed to investigate these measures as proxies for central sensitization in subjects with chronic neuropathic pain (NP) after spinal cord injury (SCI). ⋯ Central sensitization encompasses deficient endogenous pain modulation and increased nociceptive excitability. These two mechanisms can be assessed in humans by conditioned pain modulation and temporal summation of pain, respectively. Our data demonstrates a lack of descending pain inhibition only in subjects with severe neuropathic pain which may hint towards central sensitization at spinal and/or supra-spinal levels. Disentangling the mechanisms of endogenous pain modulation and neuronal hyperexcitability might improve mechanism-based treatment of neuropathic pain in subjects with spinal cord injury.
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The pathophysiology of a frozen shoulder (FS) is thought to be related to chronic inflammation. Chronic inflammation may disturb the immune system and consequently the nervous system as part of an overarching system. The aim of this study was to determine the presence of disturbed autonomic nervous system function and altered central pain processing (CPP) in patients with FS. Secondarily, the presence of psychological variables (catastrophizing and hypervigilance) and self-reported associated symptoms of altered CPP in patients with FS were investigated. ⋯ On the basis of the effect sizes, between-group differences in allodynia, hyperalgesia, catastrophizing, and hypervigilance were clinically relevant, but only local allodynia, hyperalgesia, catastrophizing, and hypervigilance were statistically different. Therefore, obvious altered CPP was not present at the group level in patients with FS compared with controls.
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Central sensitization is considered a key mechanism underlying neuropathic pain (NP) after spinal cord injury (SCI). ⋯ We present two surrogate readouts for central sensitization in neuropathic pain following SCI. On the one hand, temporal summation of tonic heat pain is enhanced in subjects with neuropathic pain. On the other hand, pain-autonomic interaction reveals potential advanced measures in chronic pain, as subjects with a high extent of neuropathic pain showed diminished habituation of pain-induced sympathetic measures. A possible implication for clinical practice is constituted by an improved assessment of neuronal hyperexcitability potentially enabling mechanism-based treatment.
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Expectancies for pain and pain relief are central to experimental models of placebo analgesia and nocebo hyperalgesia and are a promising target for clinical intervention in patients with chronic pain. Affective states may play an important role in modulating the degree to which expectancies influence pain, broadening the opportunities for intervention targets. However, findings to date have been mixed and mostly limited to laboratory designs. ⋯ Relatedly, higher morning positive affect predicted greater odds of experiencing a match between pain expectancies and pain experience when the expectation was for low, but not high, pain levels (odds ratio = 1.19, confidence interval: 1.01-1.41, P = 0.03). Negative affect, in contrast, did not significantly influence the assimilation of high pain expectancies with high pain experiences. These findings extend previous experimental studies by showing that the association of daily pain expectancies with pain experience varies as a function of affective state.