Pain
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Traumatic peripheral nerve injuries are at high risk of neuropathic pain for which novel effective therapies are urgently needed. Preclinical models of neuropathic pain typically involve irreversible ligation and/or nerve transection (neurotmesis). However, translation of findings to the clinic has so far been unsuccessful, raising questions on injury model validity and clinically relevance. ⋯ The partially crushed nerve was characterized by the sparing of small-diameter myelinated axons and intraepidermal nerve fibers, fewer dorsal root ganglia expressing the injury marker activating transcription factor 3, and lower serum levels of neurofilament light chain. By day 30, axons showed signs of reduced myelin thickness. In summary, the escape of small-diameter axons from Wallerian degeneration is likely a determinant of chronic pain pathophysiology distinct from the general response to complete nerve injury.
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Juvenile fibromyalgia (JFM) is a chronic widespread pain condition that primarily affects adolescent girls. Previous studies have found increased sensitivity to noxious pressure in adolescents with JFM. However, the underlying changes in brain systems remain unclear. ⋯ The JFM group showed augmented right primary somatosensory cortex (S1) activation to 4 kg/cm 2 (Z > 3.1, cluster-corrected P < 0.05), and the peak S1 activation magnitudes significantly correlated with the scores on the Widespread Pain Index ( r = 0.35, P = 0.048) with higher activation associated with more widespread pain. We also found that greater primary sensorimotor cortex activation in response to 4 kg/cm 2 mediated the between-group differences in pain intensity ratings ( P < 0.001). In conclusion, we found heightened sensitivity to noxious pressure stimuli and augmented pain-evoked sensorimotor cortex responses in adolescent girls with JFM, which could reflect central sensitization or amplified nociceptive input.
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Randomized Controlled Trial
Placebo effects contribute to brief online mindfulness interventions for chronic pain: results from an online randomized sham-controlled trial.
Mindfulness apps are becoming popular treatments for chronic pain and mental health, despite mixed evidence supporting their efficacy. Furthermore, it is unclear whether improvements in pain are due to mindfulness-specific effects or placebo effects because no trials have compared mindfulness against a sham control. The objective of this study was to compare mindfulness against 2 sham conditions with differing proximity to mindfulness to characterize the relative contributions of mindfulness-specific and nonspecific processes on chronic pain. ⋯ These findings suggest that improvements in chronic pain unpleasantness following a single session of online-delivered mindfulness meditation may be driven by placebo effects. Nonspecific treatment effects including placebo expectancy and pain catastrophizing may drive immediate pain attenuation rather than theorized mindfulness-specific processes themselves. Further research is needed to understand whether mindfulness-specific effects emerge after longer durations of online training.