Pain
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While a variety of cultural, psychological and physiological factors contribute to variability in both clinical and experimental contexts, the role of genetic factors in human pain sensitivity is increasingly recognized as an important element. This study was performed to evaluate genetic influences on variability in human pain sensitivity associated with gender, ethnicity and temperament. Pain sensitivity in response to experimental painful thermal and cold stimuli was measured with visual analogue scale ratings and temperament dimensions of personality were evaluated. ⋯ Female European Americans with the TRPV1 Val(585) Val allele and males with low harm avoidance showed longer cold withdrawal times based on the classification and regression tree (CART) analysis. CART identified gender, an OPRD1 polymorphism and temperament dimensions of personality as the primary determinants of heat pain sensitivity at 49 degrees C. Our observations demonstrate that gender, ethnicity and temperament contribute to individual variation in thermal and cold pain sensitivity by interactions with TRPV1 and OPRD1 single nucleotide polymorphisms.
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The disinhibition hypothesis of post-stroke central pain (CPSP) suggests that 'the excessive response (dysesthesia/hyperalgesia/allodynia) is accompanied by a em leader loss of sensation' resulting from a lesion of a 'lateral nucleus' of thalamus or of 'cortico-thalamic paths' [Brain 34 (1911) 102]. One recent elaboration of this hypothesis proposes a submodality specific relationship, such that injury to a cool-signaling lateral thalamic pathway disinhibits a nociceptive medial thalamic pathway, thereby producing both burning, cold, ongoing pain and cold allodynia. The current study quantitatively evaluated the sensory loss and sensory abnormalities to discern submodality relationships between these sensory features of CPSP. ⋯ The most dramatic case of cold allodynia occurred in a patient who had a normal detection threshold for cold. Individuals with cold hypoesthesia, strictly contralateral to the cerebro-vascular accident (CVA or stroke), were often characterized by the presence of burning, cold, ongoing pain, and by the absence, not the presence, of cold allodynia. Overall, these results in CPSP suggest that tactile allodynia occurs in disturbances of thermal/pain pathways that spare the tactile-signaling pathways, and that cold hypoesthesia is neither necessary nor sufficient for cold allodynia.
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Electronic diary assessment methods offer the potential to accurately characterize pain and other daily experiences. However, the frequent assessment of experiences over time often results in missing data. It is important to identify systematic reasons for missing data because such a pattern may bias study results and interpretations. ⋯ The most common self-reported reasons for missing interviews were failure to hear the computer alarm (49%) and inconvenient time (21%). Although there was some suggestion that persistent negative mood and stress were associated with missing electronic interviews in a subgroup of patients, on the whole, the patient demographic and clinical characteristics, treatment, and daily fluctuations in pain, activity interference, mood, and stress were not associated significantly with missing daily electronic interviews. The results provide further support for the use of electronic diary methodology in pain research.
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Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have delineated a human pain network in vivo. Despite the recognition of cerebral structures engaged in pain transmission, the cerebral mechanisms involved in pain modulation are still not well understood. Here, we investigated healthy volunteers using fMRI during experimental heat pain and distraction induced by a visual incongruent color-word Stroop task. ⋯ Distraction significantly increased the activation of the cingulo-frontal cortex including the orbitofrontal and perigenual anterior cingulate cortex (ACC), as well as the periaquaeductal gray (PAG) and the posterior thalamus. Covariation analysis revealed functional interaction between these structures during pain stimulation and distraction, but not during pain stimulation per se. According to our results, the cingulo-frontal cortex may exert top-down influences on the PAG and posterior thalamus to gate pain modulation during distraction.
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The aim of this study was to explore gender differences in anticipatory emotional distress, coping strategies, post-operative pain perception, and patient-controlled analgesia (PCA) use among adolescent surgical patients. One hundred and two 12-18-year-old adolescents undergoing surgeries with overnight hospital stay were recruited. Participants completed pre-operative measures of anxiety and anticipated pain. ⋯ Patterns of PCA use did not vary by gender on post-operative days 0 or 1. Findings suggest that adolescent boys' and girls' pain experiences are different in several important respects, although somewhat less divergent than has been reported in samples of adult males and females. Results have implications for the development of targeted intervention strategies to help adolescents cope effectively with acute post-operative pain.