Pain
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Three cases are described in which phantom limb pain was successfully treated with ketamine hydrochloride. Possible mechanisms for this observation are suggested.
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Twenty-one patients with post-mastectomy pain syndrome (PMPS) were entered in an open-label trial of topical 0.025% capsaicin treatment (3 daily applications for 2 months). Out of 19 evaluable patients, 2 (10.5%) reported complete disappearance of all symptoms, and 11 (57.9%) had a reduction of pain which was never worse than mild at the end of treatment. ⋯ This is the first independent confirmation of the usefulness of capsaicin in the PMPS, following the recent publication of a randomized, placebo-controlled clinical study showing significant pain relief with 0.075% capsaicin but not with vehicle cream. Further experimental and clinical research on the properties of capsaicin in other painful peripheral neuropathies is desirable.
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A psychophysical study has been carried out in 10 normal human subjects to examine whether conscious perception of pain is necessary for the development of secondary hyperalgesia. Prolonged thermal stimulation of the skin was applied to the subjects at intensities known to evoke discharges in polymodal nociceptors but insufficient to evoke pain sensations. During this stimulation the development of punctate and of stroking hyperalgesia was examined as was the presence of a skin flare indicative of nociceptor activation. ⋯ No difference was observed between the onset of flare and of stroking hyperalgesia. These results show that cutaneous hyperalgesia can be evoked in normal human subjects by prolonged thermal stimulation of the skin at temperatures that are not perceived as painful. The development of a flare in all subjects simultaneously with stroking hyperalgesia but before the perception of pain suggests that activation of nociceptors is necessary for the hyperalgesia to occur.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Clinical Trial
Is TENS purely a placebo effect? A controlled study on chronic low back pain.
Although high-frequency low-intensity transcutaneous electric nerve stimulation (TENS) has been extensively used to relieve low back pain, experimental studies of its effectiveness have yielded contradictory findings mainly due to methodological problems in pain evaluation and placebo control. In the present study, separate visual analog scales (VAS) were used to measure the sensory-discriminative and motivational-affective components of low back pain. Forty-two subjects were randomly assigned to 1 of 3 groups: TENS, placebo-TENS, and no treatment (control). ⋯ This additive effect was not found for placebo-TENS. When evaluated at home, pain intensity was significantly reduced more by TENS than placebo-TENS 1 week after the end of treatment, but not 3 months and 6 months later. At home evaluation of pain unpleasantness in the TENS group was never different from the placebo-TENS group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Recently, it has been reported that loosely constrictive chromic gut ligatures around the sciatic nerve produce behavioral evidence of neuropathic pain in rats. It has been shown that axonal swelling after ligation results in a constriction injury associated with a decrease in the number of both large-diameter myelinated and small-diameter unmyelinated axons, but the mechanism(s) producing spontaneous pain and thermal hyperalgesia remain largely unknown. The present study systematically evaluated potential mechanisms involved in development of the behavioral changes produced by chromic gut ligatures loosely tied around the sciatic nerve. ⋯ These postural changes were most pronounced in the 2-0 and 3-0 chromic gut-treated rats. Chromic gut sutures (4-0, 3-0, or 2-0) tied loosely around the left sciatic nerve also produced a 'dose-dependent' decrease in thermal withdrawal latency that was maximal on postoperative day 3 (25%, 39%, and 41%, respectively). The magnitude of the thermal hyperalgesia declined over time such that a return to baseline was observed by postoperative day 20 in 4-0 and 3-0 chromic gut-treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)