Pain
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Comparative Study
Investigation of the paradoxical painful sensation ('illusion of pain') produced by a thermal grill.
A paradoxical painful sensation can be elicited by the simultaneous application of innocuous warm and cold stimuli to the skin. In the present study, we analyzed the conditions of production of this unique experimental illusion of pain in 52 healthy volunteers (27 men, 25 women). The stimuli were produced by a thermode composed of six bars whose temperature was controlled by Peltier elements. ⋯ The frequency and intensity of such painful sensations were directly related to the magnitude (i.e. 5-25 degrees C) of the difference of the temperature between the warm and cold bars of the grill. The combination of increasingly colder temperature to a given warm temperature induces similar effects as combining increasingly warmer temperature to a given cold temperature. These results suggest that pain can be the result of a simple addition of non-noxious warm and cold signals.
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Multicenter Study Comparative Study
Comparison of pain syndromes associated with nervous or somatic lesions and development of a new neuropathic pain diagnostic questionnaire (DN4).
Few studies have directly compared the clinical features of neuropathic and non-neuropathic pains. For this purpose, the French Neuropathic Pain Group developed a clinician-administered questionnaire named DN4 consisting of both sensory descriptors and signs related to bedside sensory examination. This questionnaire was used in a prospective study of 160 patients presenting with pain associated with a definite neurological or somatic lesion. ⋯ The analysis of the psychometric properties of the DN4 questionnaire included: face validity, inter-rater reliability, factor analysis and logistic regression to identify the discriminant properties of items or combinations of items for the diagnosis of neuropathic pain. We found that a relatively small number of items are sufficient to discriminate neuropathic pain. The 10-item questionnaire developed in the present study constitutes a new diagnostic instrument, which might be helpful both in clinical research and daily practice.
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Comparative Study
Dot-probe evaluation of selective attentional processing of pain cues in patients with chronic headaches.
Evidence supporting the notion that patients with chronic pain are characterized by attentional biases for sensory and affect pain words, and that such biases are mediated by fear of pain, is mixed. The present investigation was an attempt to replicate and extend initial findings obtained with the dot-probe task. Thirty patients with chronic headache and 19 healthy controls were tested using a dot-probe task including affect pain, sensory pain, and neutral words. ⋯ These results do not provide convincing evidence that patients with chronic headache selectively attend to affect or sensory pain cues when compared to healthy controls. The significant cross-groups associations between anxiety sensitivity and current pain description and indices of selective attention are consistent with the notion that attentional biases may be influenced by fear propensity and current concerns. Implications of the findings and future research directions are discussed.
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The aim of this study was to investigate the relationship between psychosocial work characteristics and neck and upper limb symptoms and to examine to what extent this relationship could be explained by other risk factors. Data were used from a prospective cohort study in a working population, with a follow-up period of 3 years. ⋯ Partly, but not exclusively, these relationships were intermediated by an increased exposure to physical risk factors and increased stress symptoms. Personal characteristics did not considerably influence the main effects of the identified risk factors.
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Comparative Study
Brain processing during mechanical hyperalgesia in complex regional pain syndrome: a functional MRI study.
Complex Regional Pain Syndromes (CRPS) are characterized by a triad of sensory, motor and autonomic dysfunctions of still unknown origin. Pain and mechanical hyperalgesia are hallmarks of CRPS. There are several lines of evidence that central nervous system (CNS) changes are crucial for the development and maintenance of mechanical hyperalgesia. ⋯ The stimulation of the affected limb was painful (mechanical hyperalgesia) and led to a significantly increased activation of the S1 cortex (contralateral), S2 (bilateral), insula (bilateral), associative-somatosensory cortices (contralateral), frontal cortices and parts of the anterior cingulate cortex. The results of our study indicate a complex cortical network activated during pin-prick hyperalgesia in CRPS. The underlying neuronal matrix comprises areas not only involved in nociceptive, but also in cognitive and motor processing.