Pain
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Multilevel modeling was used to examine the effects of morning pain intensity and morning positive and negative affect on pain's interference with afternoon work goal pursuit and with evening work goal progress in a community sample of 132 adults who completed a 21-day diary. The moderating effects of pain acceptance and pain catastrophizing on the associations between morning pain intensity and afternoon work goal interference were also tested. Results revealed that the positive relationship between morning pain intensity and pain's interference with work goal pursuit was significantly moderated by pain acceptance, but not by pain catastrophizing. ⋯ Thus, it appears that high pain acceptance significantly attenuates pain's capacity to disrupt work goal pursuit. Moreover, morning positive affect appears to operate as a protective factor. Additional interpretations and potential explanations for some inconsistent outcomes are discussed along with limitations, clinical implications, and suggestions for future studies.
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Elevated nerve growth factor (NGF) in the contralateral dorsal root ganglion (DRG) mediates mirror-image pain after peripheral nerve injury, but the underlying mechanism remains unclear. Using intrathecal injection of NGF antibodies, we found that NGF is required for the development of intra-DRG synapse-like structures made by neurite sprouts of calcitonin gene-related peptide (CGRP(+)) nociceptors and sympathetic axons onto neurite sprouts of Kv4.3(+) nociceptors. ⋯ Furthermore, neutralizing the neurotransmitter norepinephrine or CGRP in the synapse-like structures by antibodies has similar analgesic effect. Thus, elevated NGF after peripheral nerve injury induces neurite sprouting and the formation of synapse-like structures within the contralateral DRG, leading to the development of chronic mirror-image pain.
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Editorial Comment
Mechanism-based therapy of neuropathic pain - a concept in danger?
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The Face, Legs, Activity, Cry and Consolability (FLACC) scale is one of the most widely used behavioural observation pain scales. However, the psychometrics of the scale have not been adequately summarised and evaluated to provide clear recommendations regarding its use. The aim of this study was to rigorously evaluate the reliability, validity, feasibility, and utility of the scale for clinical and research purposes and provide recommendations regarding appropriate use of the scale. ⋯ Limited and conflicting data addressing procedural pain assessment exist. Content validity and scale feasibility have had limited psychometric evaluation. There are insufficient data to support the FLACC scale for use in all circumstances and populations to which is currently applied.
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Randomized Controlled Trial Clinical Trial
Pain relief with lidocaine 5% patch in localized peripheral neuropathic pain in relation to pain phenotype.
In neuropathic pain with irritable nociceptor (IN) phenotype, upregulation of sodium channels on nociceptors is supposed to be an important pain mechanism that may be targeted by topical sodium channel blockade. This randomised, double-blind, phenotype panel, crossover study with 4-week treatment periods of lidocaine 5% patch and placebo was performed to search for phenotype differences in effect. The primary efficacy measure was the total pain intensity on an 11-point numeric rating scale, and the primary objective was to compare the effect of lidocaine in patients with and without IN phenotype as defined by hypersensitivity and preserved small-fibre function determined by quantitative sensory testing. ⋯ For these measures, there was no significant interaction between treatment and phenotype, but there was a significant interaction for pain paroxysms (0.8, 95% CI: 0.4-1.2, P < 0.001) and deep aching pain (0.6, 95% CI: 0.1-1.0, P = 0.013). In conclusion, lidocaine 5% patch had an effect on peripheral neuropathic pain, and it may be most efficacious in patients with IN phenotype. The lack of significant phenotype differences may be caused by too low statistical power.