1/8. hyperalgesia with reduced laser evoked potentials in neuropathic pain.Nociceptive evoked potentials to laser stimuli (LEPs) are able to detect lesions of pain and temperature pathways at peripheral, spinal and supraspinal levels. It is commonly accepted that LEP attenuation correlates with the loss of pain and temperature sensations, while pathological heat-pain hypersensitivity has been associated with increased LEP amplitude. Here we present two patients in whom increased pain sensation (hyperalgesia) to laser stimuli was, on the contrary, associated to delayed, desynchronized and attenuated LEPs. Both patients experienced increased unpleasantness and affective reactions to laser, associated to poor ability to localize the stimulus. In both cases the results may be explained by an overactivation of the 'medial pain system', in one patient due to deafferentation of cortical sensory areas by a capsular lesion, and in the other to imbalance between A-delta and C fiber excitation due to peripheral nerve injury. Our results suggest that LEPs, as currently recorded, reflect the activity of a 'lateral' pain system subserved by rapidly conducting fibers. They may therefore, assess the sensory and cognitive dimensions of pain, but may not index adequately the affective-emotional aspects of pain sensation conveyed by the 'medial' pain system. The dissociation between pain sensation and cortical EPs deserve to be added to the current semiology of LEPs, as the presence of abnormal pain to laser on the background of reduced LEPs substantiates the neuropathic nature of the pain.- - - - - - - - - - ranking = 1keywords = action (Clic here for more details about this article) |
2/8. Analgesic effects of ketamine ointment in patients with complex regional pain syndrome type 1.OBJECTIVE: ketamine hydrochloride (KET), an agent used for general anesthesia, has local anesthetic effects and N-methyl-D-aspartate (NMDA) receptor antagonist action. Because recent studies emphasized the role of peripherally distributed NMDA receptors in processing the nociceptive information, we investigated whether peripheral application of the ointment containing KET is able to attenuate the symptoms of local neuropathic pain. case reports: We applied ointment containing KET (0.25%-1.5%) to the affected area on limbs in 5 patients with complex regional pain syndrome type I (CRPS I) and in 2 patients with type II (CRPS II). One to 2 weeks later, we observed improvement of the report of pain intensity, measured by the visual analog scale, in 4 patients with acute early dystrophic stage of CRPS I. Swelling of the affected limbs subsided as well. No apparent changes were noticed in 1 patient with chronic atrophic stage of CRPS I and in both patients with CRPS II. CONCLUSION: Topical application of KET appears to be beneficial for the patients with acute early dystrophic stage of CRPS I because of either its local anesthetic effect or NMDA receptor antagonist action. patients with chronic atrophic stage of CRPS I and CRPS II patients do not appear to respond to this treatment.- - - - - - - - - - ranking = 2keywords = action (Clic here for more details about this article) |
3/8. Catecholamine-induced excitation of nociceptors in sympathetically maintained pain.Sympathetically maintained pain could either be mediated by ephaptic interactions between sympathetic efferent and afferent nociceptive fibers or by catecholamine-induced activation of nociceptive nerve endings. We report here single fiber recordings from C nociceptors in a patient with sympathetically maintained pain, in whom sympathetic blockade had repeatedly eliminated the ongoing pain in both legs. We classified eight C-fibers as mechano-responsive and six as mechano-insensitive nociceptors according to their mechanical responsiveness and activity-dependent slowing of conduction velocity (latency increase of 0.5 /-1.1 vs. 7.1 /-2.0 ms for 20 pulses at 0.125 Hz). Two C-fibers were activated with a delay of several seconds following strong endogenous sympathetic bursts; they were also excited for about 3 min following the injection of norepinephrine (10 microl, 0.05%) into their innervation territory. In these two fibers, a prolonged activation by injection of low pH solution (phosphate buffer, pH 6.0, 10 microl) and sensitization of their heat response following prostaglandin E2 injection were recorded, evidencing their afferent nature. Moreover, their activity-dependent slowing was typical for mechano-insensitive nociceptors. We conclude that sensitized mechano-insensitive nociceptors can be activated by endogenously released catecholamines and thereby may contribute to sympathetically maintained pain. No evidence for ephaptic interaction between sympathetic efferent and nociceptive afferent fibers was found.- - - - - - - - - - ranking = 2keywords = action (Clic here for more details about this article) |
4/8. hyperalgesia and myoclonus with intrathecal infusion of high-dose morphine.We report the case of a patient who developed myoclonus and hyperalgesia following administration of high-dose subarachnoid morphine. This complication occurred with 40-80 mg/day continuous infusion. The pathophysiology of these side effects is discussed.- - - - - - - - - - ranking = 16796.211326448keywords = myoclonus (Clic here for more details about this article) |
5/8. Disappearance of morphine-induced hyperalgesia after discontinuing or substituting morphine with other opioid agonists.hyperalgesia and allodynia in 4 cancer patients treated with morphine disappeared after discontinuing or substituting morphine with other opioid agonists. The first case describes a young female who developed hyperalgesia and myoclonus during intravenous morphine infusion. The hyperalgesia and myoclonus disappeared when the morphine administration was discontinued and she felt comfortable on small and sporadic oral doses of methadone. The second case describes hyperalgesia occurring after a small dose of sustained-release morphine which disappeared after alternative use of oral ketobemidone. The third case describes hyperalgesia following high doses of intramuscular morphine which disappeared after alternative use of continuous subcutaneous infusion of sufentanil. The fourth case describes a boy developing hyperalgesia after high doses of oral and intramuscular morphine. The hyperalgesia disappeared after discontinuing morphine administration but withdrawal symptoms developed due to too small doses of methadone. Possible mechanisms of morphine-induced hyperalgesia are discussed.- - - - - - - - - - ranking = 6718.4845305791keywords = myoclonus (Clic here for more details about this article) |
6/8. hyperalgesia and myoclonus in terminal cancer patients treated with continuous intravenous morphine.Eight cancer patients in the terminal stages of the disease treated with high doses of intravenous morphine developed hyperalgesia. All cases were retrospectively sampled from three different hospitals in Copenhagen. Five patients developed universal hyperalgesia and hyperesthesia which in 2 cases were accompanied by myoclonus. In 3 patients a pre-existing neuralgia increased to excruciating intensity and in 2 of these cases myoclonus occurred simultaneously. Although only few clinical descriptions of the relationship between hyperalgesia/myoclonus and high doses of morphine are available, experimental support from animal studies indicates that morphine, or its metabolites, plays a causative role for the observed behavioural syndrome. The possible mechanisms are discussed and treatment proposals given suggesting the use of more efficacious opioids with less excitatory potency in these situations.- - - - - - - - - - ranking = 23514.695857027keywords = myoclonus (Clic here for more details about this article) |
7/8. Acute neuropsychiatric findings in a patient receiving fentanyl for cancer pain.A 62-year-old man receiving subcutaneous fentanyl for the management of cancer pain developed generalized central excitation after an overdose of 5000 micrograms of fentanyl. The patient developed acute confusion, restlessness, generalized myoclonus, visual hallucinations, and hyperalgesia and tremors upon tactile stimulation of the arms or legs. These symptoms rapidly disappeared after the administration of 0.2 mg of naloxone. Within an hour the symptoms reappeared and once again, responded immediately after a second injection of 0.2 mg of naloxone. Our findings suggest that fentanyl overdose can occasionally present with general central irritability that responds to naloxone.- - - - - - - - - - ranking = 3359.2422652896keywords = myoclonus (Clic here for more details about this article) |
8/8. Is development of hyperalgesia, allodynia and myoclonus related to morphine metabolism during long-term administration? Six case histories.BACKGROUND: Recently, clinical reports have suggested a relationship between the occurrence of hyperalgesia, allodynia and/or myoclonus and treatment with high doses of morphine in humans. Although few clinical descriptions of these phenomena are available, experimental work supports the notion that high doses of morphine may play a pathogenetic role in the observed behavioural syndrome. methods: Six patients, four with malignant and two with chronic, non-malignant pain conditions, treated with moderate to high doses of oral, continuous intravenous infusion or intrathecal morphine developed hyperalgesia, allodynia and/or myoclonus. When the side-effects occurred, blood or CSF samples were taken and analyzed for contents of morphine, morphine-6-glucuronide (M-6-G) and morphine-3-glucuronide (M-3-G). RESULTS: When comparing the plasma and CSF concentrations from these patients with data from available literature obtained from patients not suffering from these side-effects, it was demonstrated that the values deviated in five patients. In all six patients, the side-effects disappeared after substituting morphine with other opioid agonists or after lowering the daily dose of morphine. CONCLUSION: These results may indicate that elevated concentrations of M-3-G in plasma as well as the plasma and CSF M-3-G/M-6-G ratios may play a pathogenetic role in the development of hyperalgesia, allodynia and myoclonus.- - - - - - - - - - ranking = 23514.695857027keywords = myoclonus (Clic here for more details about this article) |