Pain
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Cold allodynia is a common sign of neuropathic pain patients but its underlying mechanisms are still largely unknown, partly because the populations of neurons responding to cold stimuli and their transduction mechanisms have not been fully determined. We report a patient with a small-fiber neuropathy of unknown origin, whose main complaint is cold allodynia. ⋯ These findings provide the first direct evidence in human of abnormal peripheral nociceptor behavior potentially responsible for cold allodynia. The responsiveness of C-nociceptors to menthol suggests an abnormal expression or function of TRPM8 channels in this patient with a small-fiber polyneuropathy.
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Endometriosis is a painful disorder defined by extrauteral endometrial growths whose contribution to pain symptoms is poorly understood. Endometriosis is created in rats by autotransplanting on abdominal arteries pieces of either uterus (ENDO), which form cysts, or fat (shamENDO), which do not form cysts. ENDO, but not shamENDO induces vaginal hyperalgesia. ⋯ The increases in ENDO-induced hyperalgesia produced by the sham-cyst-removal surgery were smaller in proestrus than in other estrous stages. During the other stages (but not during proestrus), sympathetic innervation of the cysts increased. These results suggest that maintenance of ENDO-induced vaginal hyperalgesia requires continued presence of at least some ectopic endometrial tissue, and that surgical treatment that fails to remove ectopic endometrial tissue can exacerbate the hyperalgesia, possibly due in part to an increase in the cysts' sympathetic innervation.
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Randomized Controlled Trial Clinical Trial
Analgesic efficacy of tramadol, pregabalin and ibuprofen in menthol-evoked cold hyperalgesia.
We investigated the analgesic efficacy of single doses of ibuprofen, tramadol and pregabalin in menthol-evoked cold pain in a randomized, placebo-controlled four-way cross-over study in 20 healthy volunteers. Tramadol 100mg significantly reduced menthol-evoked cold hyperalgesia. Effects of ibuprofen 600mg and pregabalin 100mg were not significant. ⋯ Minor side effects also accompanied analgesic effects of pregabalin and ibuprofen in subjects responding to these drugs, mostly fatigue, dizziness and difficulties to concentrate for pregabalin and gastric upset for ibuprofen. Five out of 18 subjects had a 50% reduction of cold hyperalgesia with tramadol, three of these additionally responded to pregabalin, and two with all three drugs. The numbers needed to treat (NNT >or= 50% for tramadol 4.5, for pregabalin 9) largely agree with the reported efficacy of tramadol and of moderate dosages of pregabalin in patients with peripheral or central neuropathic pain suggesting that menthol-evoked cold pain hypersensitivity may represent a valid model for neuropathic pain, particularly cold allodynia.
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Randomized Controlled Trial
Outpatient intravenous ketamine for the treatment of complex regional pain syndrome: a double-blind placebo controlled study.
Complex regional pain syndrome (CRPS) is a severe chronic pain condition that most often develops following trauma. The pathophysiology of CRPS is not known but both clinical and experimental evidence demonstrate the important of the NMDA receptor and glial activation in its induction and maintenance. Ketamine is the most potent clinically available safe NMDA antagonist that has a well established role in the treatment of acute and chronic pain. ⋯ This study showed that intravenous ketamine administered in an outpatient setting resulted in statistically significant (p<0.05) reductions in many pain parameters. It also showed that subjects in our placebo group demonstrated no treatment effect in any parameter. The results of this study warrant a larger randomized placebo controlled trial using higher doses of ketamine and a longer follow-up period.
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Randomized Controlled Trial Clinical Trial
Motor cortex electrical stimulation applied to patients with complex regional pain syndrome.
Motor cortex stimulation (MCS) is useful to treat patients with neuropathic pain syndromes, unresponsive to medical treatment. Complex regional pain syndrome (CRPS) is a segmentary disease treated successfully by spinal cord stimulation (SCS). However, CRPS often affects large body segments difficult to cover by SCS. ⋯ VAS and McGill pain scales diminished significantly (p<0.01) throughout the follow-up, accompanied by disappearance of the sensory (allodynea and hyperalgesia) and sympathetic signs. MCS is effective not only to treat pain, but also improve the sympathetic changes in CPRS. Mechanism of action is actually unclear, but seems to involve sensory input at the level of the spinal cord.