Pain
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparison of the effects of noxious and innocuous counterstimuli on experimentally induced itch and pain.
We have studied experimentally induced itch (using histamine iontophoresis) and pain (using topical mustard oil) in healthy human volunteers, measured using visual analogue scale (VAS) ratings. The effects of the following counterstimuli were evaluated: innocuous vibration; innocuous transcutaneous electrical nerve stimulation (TENS); innocuous warming of skin; noxious heating of skin; noxious chemical skin stimulation (using mustard oil); mildly noxious constant current transdermal electrical stimulation. Innocuous stimuli applied 2 min after histamine or mustard oil challenge produced a modest reduction of itch and pain ratings (20-30%), which did not persist for more than 20 sec when the counterstimuli were removed. ⋯ The differential effects of noxious counterstimuli on itch and pain do not support the suggestion that itch is a subliminal form of pain. Noxious counterstimuli are likely to act via a central rather than peripheral mechanism. The novel finding that a persistent anti-pruritic state can be induced by transdermal constant current may be useful in conditions of clinical itch.
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A model of deafferentation pain is provided by sectioning the sciatic and saphenous nerves in the rat and mouse. This procedure leads to self-mutilation of the denervated hindpaw (autotomy). A noxious stimulus to the denervated area before neurectomy is known to enhance the autotomy. ⋯ The severity of autotomy in neurectomized mice and the duration of acute nociceptive responses induced by the same doses of SP or SOM in intact mice were related. These results suggest that neuropeptides applied to the spinal dorsal horn just before deafferentation induce a state of central neural activation with long-lasting effects on the function of CNS cells. Augmentation of autotomy is a result of this activation which is kept as a 'memory'.
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Randomized Controlled Trial Comparative Study Clinical Trial
Increased pressure pain sensibility in fibromyalgia patients is located deep to the skin but not restricted to muscle tissue.
This study was aimed at comparing pressure pain sensibility in different tissues in fibromyalgia patients. Pressure pain thresholds (PPTs) were assessed in 16 fibromyalgia (FM) patients bilaterally at the bony part of epicondylus lateralis humeri, at the belly of m. extensor carpi ulnaris and at m. brachioradialis where the radial nerve branches pass underneath. Following a double-blind design, either a local anesthetic cream (EMLA) or a control cream was applied to the skin and PPTs were reassessed. ⋯ The PPTs over the bony and the 'pure' muscle sites did not differ. Application of EMLA, compared to control cream, did not change PPTs over any area examined. The results demonstrated that pressure-induced pain sensibility in FM patients is not most pronounced in muscle tissue and does not depend on increased skin sensibility.
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Clinical Trial
Sensitivity of patients with painful temporomandibular disorders to experimentally evoked pain.
Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandibular joint. We determined whether patients with painful TMD are more sensitive to noxious stimuli than age-matched control subjects. Fifty-two TMD patients (16 with muscle pain and 36 with combined muscle and joint pain) and 23 age-matched and gender-matched volunteers participated. ⋯ Furthermore, the submaximal effort tourniquet procedure, which is capable of altering acute orofacial pain (Sigurdsson and Maixner, 1994) did not produce a consistent reduction in orofacial pain associated with TMD. We concluded that TMD patients are more sensitive to noxious stimuli than pain-free controls. These findings provide additional evidence that TMD is a psychophysiological disorder of the central nervous system which modulates emotional, physiological and neuroendocrine responses to emotional and physical stressors.
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Based on behavioral theory, it has been hypothesized that spouse solicitous responses to the pain behaviors of chronic pain patients may contribute to the maintenance of pain behaviors and disability. Self-report data support this hypothesis, but direct observational measures have not been used to study this association. ⋯ Spouse solicitous responses did not predict psychosocial dysfunction or total self-reported pain behaviors. The result support behavioral theory and indicate the need for further study of the association between spouse solicitousness and patient pain behaviors/disability.