Pain
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Comparative Study
Neonatal pain facial expression: evaluating the primal face of pain.
The primal face of pain (PFP) is postulated to be a common and universal facial expression to pain, hardwired and present at birth. We evaluated its presence by applying a computer-based methodology consisting of "point-pair" comparisons captured from video to measure facial movement in the pain expression by way of change across two images: one image before and one image after a painful stimulus (heel-stick). ⋯ Although facial expression was not identical across or among groups, our analyses showed no particular clustering or unique display by sex, or ethnicity. The clinical significance of this commonality of pain display, and of the origin of its potential individual variation begs further evaluation.
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Comparative Study
Quantitative testing of pain perception in subjects with PTSD--implications for the mechanism of the coexistence between PTSD and chronic pain.
Post-traumatic stress disorder (PTSD) often co-occurs with chronic pain. Neither the underlying mechanism of this comorbidity nor the nature of pain perception among subjects with PTSD is well defined. This study is the first systematic and quantitative evaluation of pain perception and chronic pain in subjects with PTSD. ⋯ These results suggest that subjects with PTSD exhibit an intense and widespread chronic pain and a unique sensory profile of hyposensitivity to pain accompanied by hyper-reactivity to suprathreshold noxious stimuli. These features may be attributed to the manner with which PTSD subjects emotionally interpret and respond to painful stimuli. Alternatively, but not mutually exclusive, the findings may reflect altered sensory processing among these subjects.
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Comparative Study
Effects of mood on pain responses and pain tolerance: an experimental study in chronic back pain patients.
Although chronic pain and depression commonly co-occur, causal relationships have yet to be established. A reciprocal relationship, with depression increasing pain and vice versa, is most frequently suggested, but experimental evidence is needed to validate such a view. The most straightforward approach would be a demonstration that increasing or decreasing depressed mood predictably modifies pain responses. ⋯ Results indicate that the induction of depressed mood resulted in significantly higher pain ratings at rest and lower pain tolerance, whilst induced happy mood resulted in significantly lower pain ratings at rest and greater pain tolerance. Correlations between changes in mood on the one hand and changes in pain response and pain tolerance on the other hand were consistent with these findings. It is concluded that, in chronic back pain patients, experimentally induced negative mood increases self-reported pain and decreases tolerance for a pain-relevant task, with positive mood having the opposite effect.
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Comparative Study
Functional MRI of the brain detects neuropathic pain in experimental spinal cord injury.
Functional magnetic resonance imaging (fMRI) has been used to map cerebral activations related to nociceptive stimuli in rodents. Here, we used fMRI to investigate abnormally increased responses to noxious or innocuous stimuli, in a well-established rat model of chronic neuropathic pain induced by photochemical lumbar spinal cord injury. In this model, a subpopulation of rats exhibits allodynia-like hypersensitivity to mechanical and cold stimulation of the trunk area. ⋯ Identical electrical stimulation, applied on trunks of spinally injured hypersensitive and non-hypersensitive rats, evoked significantly higher responses in SI of the former than the latter. Although levels of fMRI signals in SI of the trunk territory were not significantly different between normal and spinally injured non-hypersensitive rats, the administration of naloxone significantly increased fMRI signals in the non-hypersensitive rats, but not in the normal rats. We conclude that increased activation of contralateral SI is a key feature of behavioural neuropathic pain in spinally injured rats and that fMRI is an effective method to monitor experimental neuropathic pain in small animals.
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Randomized Controlled Trial Comparative Study
Effects of progressive muscle relaxation training on nociceptive flexion reflex threshold in healthy young adults: a randomized trial.
Although prior studies have demonstrated effects of progressive muscle relaxation (PMR) in reducing self-reported pain, no laboratory studies have examined the effects of PMR on objective indicators of descending modulation of nociception. This randomized controlled study utilized the nociceptive flexion reflex (NFR) to evaluate nociceptive responding among 55 college-age men and women (mean age=19.4+/-1.2 years). Participants completed laboratory assessments of NFR threshold and questionnaires evaluating pain and stress. ⋯ Ratings of pain did not change during the study, but PMR participants reported decreased stress following the PMR intervention. This is the first study with a randomized no-treatment control group demonstrating the effect of a brief PMR protocol on descending inhibition of nociception. Results support the efficacy of PMR in reducing nociceptive response and provide further evidence of the utility of behavioral pain management strategies.