Pain
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Comparative Study
Assessing fear in patients with cervical pain: development and validation of the Pictorial Fear of Activity Scale-Cervical (PFActS-C).
The fear avoidance model (FAM) postulates that fear of pain or reinjury is a risk factor for persistent pain and disability, because it leads to the avoidance of physical activity. Research on the FAM has not yielded consistent results, which may be attributed to the model itself, but could also be a product of the way fear of movement is assessed. Studies of the FAM have measured fear using verbal scales consisting of items that are often vague and have only an indirect relationship with fear. ⋯ Internal consistency (alpha=.98), stability over time (n=44, IntraClass Correlation=.72), and construct validity were all good to excellent. The results indicate that the PFActS-C may be a useful tool for assessing fear of movement in patients with cervical pain. Research is needed to confirm the factor structure of the PFActS-C and to assess the generalizability of the results to other samples with neck pain.
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Comparative Study
Cholinergic mechanisms involved in the pain relieving effect of spinal cord stimulation in a model of neuropathy.
The mechanisms underlying the pain relieving effect of spinal cord stimulation (SCS) on neuropathic pain remain unclear. We have previously demonstrated that suppression of tactile hypersensitivity produced by SCS may be potentiated by i.t. clonidine in a rat model of mononeuropathy. Since the analgesic effect of this drug is mediated mainly via cholinergic mechanisms, a study exploring the possible involvement of the spinal cholinergic system in SCS was undertaken. ⋯ In another group of rats it was found that the response to SCS was completely eliminated by i.t. atropine and a muscarinic M(4) receptor antagonist while a partial attenuation was produced by M(1) and M(2) antagonists. Blocking of nicotinic receptors did not influence the SCS effect. In conclusion, the attenuating effect of SCS on pain related behavior is associated with the activation of the cholinergic system in the dorsal horn and mediated via muscarinic receptors, particularly M(4,) while nicotinic receptors appear not to be involved.
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It is increasingly recognized that pain-induced plasticity may not only provoke sensory gain (hyperalgesia), but also sensory decline, i.e. hypoesthesia and hypoalgesia. We investigated perceptual changes by conditioning electrical stimulation of peptidergic C-nociceptors differing in stimulation frequencies and duty cycles at the left forearm. Four noxious electrical stimulation paradigms (Stim1: 0.5 Hz, continuously; Stim2: 20 Hz, continuously; Stim3: 1s 20 Hz train, 1s break; Stim4: 1s 20 Hz train, 2s break) were applied. ⋯ In summary, we describe here that depending on the applied frequencies and duty cycles, either sensory gain (i.e. hyperalgesia) or sensory decline (i.e. hypoesthesia and hypoalgesia) can be induced. Sensory decline was found to be centrally mediated. Underlying mechanisms may include differential recruitment of inhibitory and facilitating gain control systems leading to homo- and heterosynaptic inhibition or facilitation at the level of the spinal cord or interference of noxious input with tactile processing in the cortex.
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Comparative Study
The spatial characteristics of the painful thermal grill illusion.
Interlaced cold and warm stimuli may induce a paradoxical burning sensation termed the "thermal grill illusion". Studies on the grill illusion have yielded contradictory results regarding its quality and intensity, which in turn led to controversies concerning the underlying mechanism. Some controversies may result from testing the illusion with absolute temperatures thereby disregarding inter-subjects' variation in temperature sensitivity. ⋯ Gender did not affect the PGI. In conclusion, innocuous cold and warm stimuli can spatially summate, both within and between dermatomes and evoke a PGI. Possibly, non-nociceptive channels integrate onto 2nd or 3rd order nociceptive neurons which in turn induce a unique painful burning resulting from the blend of cold and warm sensations.
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Comparative Study
Prevalence and characteristics of opioid use in the US adult population.
This report describes the prevalence of opioid use in the US adult population, overall and in subgroups, the characteristics of opioid use, and concomitant medication use among opioid users. Data were obtained from the Slone Survey, a population-based random-digit dialing survey. One household member was randomly selected to answer a series of questions regarding all medications taken during the previous week. ⋯ Regular opioid users were more likely to use stool softeners/laxatives (9% vs. 2%), proton pump inhibitors (25% vs. 8%), and antidepressants (35% vs. 10%). From this nationally-representative telephone survey, we estimate that over 4.3 million US adults are taking opioids regularly in any given week. Information on the prevalence and characteristics of use is important as opioids are one of the most widely prescribed classes of drugs in the US.