Articles: pain-threshold.
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Multicenter Study
Brain morphology predicts individual sensitivity to pain: a multicenter machine learning approach.
Sensitivity to pain shows a remarkable interindividual variance that has been reported to both forecast and accompany various clinical pain conditions. Although pain thresholds have been reported to be associated to brain morphology, it is still unclear how well these findings replicate in independent data and whether they are powerful enough to provide reliable pain sensitivity predictions on the individual level. In this study, we constructed a predictive model of pain sensitivity (as measured with pain thresholds) using structural magnetic resonance imaging-based cortical thickness data from a multicentre data set (3 centres and 131 healthy participants). ⋯ Analysis of model coefficients suggests that the most robust cortical thickness predictors of pain sensitivity are the right rostral anterior cingulate gyrus, left parahippocampal gyrus, and left temporal pole. Cortical thickness in these regions was negatively correlated to pain sensitivity. Our results can be considered as a proof-of-concept for the capacity of brain morphology to predict pain sensitivity, paving the way towards future multimodal brain-based biomarkers of pain.
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Referred sensation (RS) as a specific clinical phenomenon has been known for a long time, although the underlying mechanisms remain unclear. The aims of this study were to assess if (1) healthy individuals who experienced RS had a less active endogenous pain system when compared with those who did not; (2) activation of descending pain inhibition mechanisms can modulate RS parameters; and finally, (3) a transient decrease in peripheral afferent input because of a local anesthetic (LA) block in the masseter muscle can modulate RS parameters. To assess these, 50 healthy participants were assessed in 3 different sessions. ⋯ In the second and third sessions, participants had their mechanical sensitivity and RS assessed before and after receiving an injection of 2 mL of LA and isotonic saline into the masseter muscle. The main findings of this study were (1) participants who experienced RS during standardized palpation exhibited increased mechanical sensitivity ( P < 0.05, Tukey post hoc test) and decreased CPM ( P < 0.05, Tukey post hoc test) when compared with those who did not; RS incidence ( P < 0.05, Cochran Q test), frequency ( P < 0.05; Friedman test), intensity ( P < 0.05, Tukey post hoc test), and area ( P < 0.05, Tukey post hoc test) were all significantly reduced when assessed (2) during a painful conditioning stimulus and (3) after LA block. These novel findings highlight that RS in the orofacial region are strongly modified by both peripheral and central nervous system factors.
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Dorsal root ganglia (DRG) neurons have been well described for their role in driving both acute and chronic pain. Although nerve injury is known to cause transcriptional dysregulation, how this differs across neuronal subtypes and the impact of sex is unclear. Here, we study the deep transcriptional profiles of multiple murine DRG populations in early and late pain states while considering sex. ⋯ We see both stereotyped and unique subtype signatures in injured states after nerve injury at both an early and late timepoint. Although all populations contribute to a general injury signature, subtype enrichment changes can also be seen. Within populations, there is not a strong intersection of sex and injury, but previously unknown sex differences in naïve states-particularly in Aβ-RA + Aδ-low threshold mechanoreceptors-still contribute to differences in injured neurons.
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Urologic chronic pelvic pain syndrome (UCPPS) is a complex, debilitating condition in which patients often report nonpelvic pain in addition to localized pelvic pain. Understanding differential predictors of pelvic pain only vs widespread pain may provide novel pathways for intervention. This study leveraged baseline data from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network's Symptom Pattern Study to investigate the impact of childhood sexual and nonsexual violent trauma on pelvic and nonpelvic pain sensitivity among adult patients with UCPPS, as well as potential mediators of this association. ⋯ Path analysis suggested that childhood violent trauma was indirectly associated with pain sensitivity at both sites and that this indirect association was primarily mediated by generalized sensory sensitivity. More experiences of recent trauma also contributed to these indirect effects. The findings suggest that, among participants with UCPPS, childhood violent trauma may be associated with heightened pain sensitivity to the extent that trauma history is associated with a subsequent increase in generalized sensory sensitivity.
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Randomized Controlled Trial
No effect of social interaction on experimental pain sensitivity: a randomized experimental study.
Quantitative sensory testing (QST) is a commonly applied paradigm to investigate pain, which is a subjective experience influenced by a myriad of social and contextual factors. Therefore, it is important to consider the potential sensitivity of QST to the test setting and the social interaction that naturally is a part of it. This may particularly be the case in clinical settings where patients have something at stake. ⋯ All 3 setups consisted of the same pain tests in the same order, including pressure pain threshold and cold pressor tests. We found no statistically significant differences between setups on the primary outcome of conditioned pain modulation nor any secondary QST outcomes. While this study is not without limitations, the results indicate that QST procedures are robust enough not to be influenced by social interaction to an appreciable degree.