Pain
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Small-fiber neuropathy (SFN) is hallmarked by degeneration of small unmyelinated peripheral nerve fibers in the skin. Traditionally, it has been considered as a pure disorder of the peripheral nervous system. Nevertheless, previous work found that dysfunction of skin nerves led to abnormal recruitment of pain-related regions, suggesting that the brain may be affected in SFN. ⋯ Moreover, the degree of reduction in functional connectivity for the ACC to the amygdala and the precuneus was linearly correlated with the severity of intraepidermal nerve fiber depletion. Our findings suggest that SFN is not a pure peripheral nervous system disorder. The pain-related brain networks tend to break into functionally independent components, with severity linked to the degree of skin nerve degeneration.
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Although emotion regulation modulates the pain experience, inconsistencies have been identified regarding the impact of specific regulation strategies on pain. Our goal was to examine the effects of emotion suppression and cognitive reappraisal on automatic (ie, nonverbal) and cognitively mediated (ie, verbal) pain expressions. Nonclinical participants were randomized into either a suppression (n = 58), reappraisal (n = 51), or monitoring control (n = 42) condition. ⋯ Reappraisal and suppression induction led to reductions in nonverbal and verbal indices of pain. Moreover, self-reported tendencies to use suppression and reappraisal (as measured by the Emotion Regulation Questionnaire) did not interact with experimental condition in the determination of participants' responses. Results suggest that consciously applying emotion regulation strategies during a painful task can moderate both cognitively mediated (e.g., verbal) and automatic (e.g., facial activity) expressions of pain.
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Racial differences in pain responsiveness have been demonstrated in adults. However, it is unclear whether racial differences are also present in youth and whether they extend to experimental pain indices assessing temporal summation of second pain (TSSP). Temporal summation of second pain provides an index of pain sensitivity and may be especially relevant in determining risk for chronic pain. ⋯ Baseline evoked pain ratings were significantly higher in African-American compared with non-Hispanic white youth. These findings suggest that enhanced responsiveness to evoked thermal pain in African Americans is present in adolescence but is unlikely to be related to elevated TSSP. These results may have implications for understanding racial differences in chronic pain experience in adulthood.
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OnabotulinumtoxinA (onabotA) has shown efficacy in chronic migraine (CM). Its mechanism of action, however, remains obscure. We have analysed whether treatment with onabotA is able to induce changes in interictal plasma calcitonin gene-related peptide (CGRP) concentrations, which have been shown to be increased in patients with CM. ⋯ One month after treatment, the CGRP levels did not change in nonresponders (51.89 pg/mL; P not significant), but significantly decreased in responders (52.48 pg/mL; P = 0.003). A number of demographic factors, clinical features, and comorbidities were not different in responders as compared with those of nonresponders. These results confirm that interictal CGRP levels can be of help in predicting the response to onabotA and suggest that the mechanism of action of onabotA in CM is the reversal of sensitization as a result of the inhibition of CGRP release.