Articles: hyperalgesia.
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To look for anatomical and histochemical signs of interaction between sensory and sympathetic nerves in the hyperalgesic skin of patients with complex regional pain syndrome. ⋯ A major difference in distribution or change in histochemical content of cutaneous autonomic or nociceptor fibers is unlikely to underly static mechanical hyperalgesia following a soft-tissue or peripheral nerve injury. The relevance of cutaneous nerve tangles for the pathophysiology of RSD is uncertain.
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Clinical Trial Controlled Clinical Trial
Independent effects of ischaemia and noradrenaline on thermal hyperalgesia in capsaicin-treated skin.
Noradrenaline increases thermal hyperalgesia in skin previously sensitized by capsaicin. The aim of the present study was to determine whether a vasoconstrictor ischaemic effect of noradrenaline increases thermal hyperalgesia. Heat pain thresholds were measured in the capsaicin-treated and untreated skin on the forearms of 13 normal volunteers. ⋯ Thermal hyperalgesia subsided in control sites in the capsaicin-treated skin after cuff pressure was released, but persisted at sites of noradrenaline iontophoresis (in the capsaicin-treated skin, mean heat pain threshold during reactive hyperaemia 45.2 +/- 5.1 degrees C at the noradrenaline site compared with 49.3 +/- 6.0 degrees C at control sites, P < 0.01; in the untreated skin, mean heat pain threshold at the noradrenaline site 46.5 +/- 3.3 degrees C compared with 48.8 +/- 3.0 degrees C at control sites, P < 0.001). Arterial occlusion could increase thermal hyperalgesia in capsaicin-treated skin by preventing the dispersal of nociceptive substances peripherally or through central summation of nociceptive signals. The hyperalgesic effect of noradrenaline is greater than the hyperalgesic effect of ischaemia, suggesting that some mechanism in addition to vasoconstriction contributes to the nociceptive effect of noradrenaline.
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Withdrawal responses to heat and mechanical stimuli applied to the plantar surface of the rat hindpaw were measured before and after an intraplantar injection of capsaicin. In separate groups of rats, capsaicin doses of 1, 10 and 30 micrograms, and the vehicle were given into the center of the plantar surface in a volume of 10 microliters. Withdrawal latency evoked by radiant heat and the frequency of withdrawal evoked by mechanical stimuli (von Frey monofilaments) were obtained from both hindpaws before and after injection. ⋯ Injection of the vehicle did not significantly alter withdrawal responses to heat or mechanical stimuli. These studies demonstrate that intraplantar injection of capsaicin in rats produces hyperalgesia to heat and mechanical stimuli. This model should be useful for correlative behavioral, physiological and pharmacological studies of underlying mechanisms of capsaicin-evoked hyperalgesia.
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The finding in some patients with neuropathic pain that mechanical allodynia (pain evoked by light touch) and hyperalgesia (supranormal pain evoked by painful stimuli) extend beyond the territory of a single nerve or spinal sensory root (extraterritorial pain) often prompts a diagnosis of psychiatric illness. The hypothesis that focal nociceptive input in a single nerve territory can result in allodynia and hyperalgesia in a nerve territory adjacent to the input was investigated in normal human subjects. ⋯ It is concluded that activation of C-nociceptors evokes a state of central sensitization that may manifest itself by the appearance of extraterritorial pain abnormalities.
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Scand J Plast Recons · Sep 1996
Incidence and natural history of touch allodynia after open carpal tunnel release.
Open surgical decompression is believed to be a safe treatment with few complications. However, it was our subjective impression that its morbidity had been underestimated. Fifty one consecutive patients with carpal tunnel syndrome were evaluated prospectively for three years after operation. ⋯ These were confirmed by significantly lowered pressure-pain thresholds over both the thenar and hypothenar eminences (p < 0.005). During the first month after operation all patients were relieved of nocturnal pain, and all clinical signs had disappeared at three months in all 51 patients. Our results confirm that open carpal tunnel decompression has a high success rate, but highlights a previously underestimated morbidity of postoperative allodynia.