Pain
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Comparative Study
Stability of patient adaptation classifications on the multidimensional pain inventory.
This study examined the adaptational classification stability of the multidimensional pain inventory (MPI) in two samples of female fibromyalgia syndrome patients. Retest resulted in one-third of patients being assigned to a different classification. Twenty patients had four repeated MPI assessments over a 10-month period; 85% of them changed classification at least once. ⋯ Examination of the MPI Variable Response Scale and an index of the goodness of fit of the cluster for each patient did not yield sufficient predictive power. The implication of this study is that for a sizable number of chronic pain patients, MPI classifications may not be stable, trait-like characterizations. As such, caution must be applied when treatment is tailored to MPI clusters and when classification change is used as an outcome measure.
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Case Reports Comparative Study
Spinal cord lesion after long-term intrathecal clonidine and bupivacaine treatment for the management of intractable pain.
Long-term intrathecal drug administration using implanted pumps is increasingly used in the treatment of chronic refractory pain [Anderson and Burchiel 1999, Neurosurgery 44 (1999) 289; Krames 2002, Best Pract Res Clin Anaesthesiol 16 (2002) 619; Wallace 2002, Neurology 59 (2002) S18]. Extensive clinical experience over the last 15 years suggests that in selected cases the technique is safe, although infections, system malfunction and drug-related complications have been reported. In most cases, drug-related spinal cord injuries have resulted from the compression of a spinal inflammatory mass or abcess rather than from a direct neurotoxic effect. We report on a case of toxic spinal cord lesion occurring after more than 3 years of uneventful continuous infusion of a mixture of bupivacaine and clonidine.
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This experiment tested whether meaning influences the experience of pain. Thirty-one healthy students participated in a study on evaluations of various stimuli placed against the neck. ⋯ Confirming the hypothesis that tissue-damaging meaning influences the experience of pain, participants who were told that the bar was hot rated it as more painful than participants who were told that it was cold. Damage interpretations mediated the effect of information on pain intensity scores, which supported the theory that tissue-damage is a crucial aspect of meaning to influence the subjective intensity of pain.
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Comparative Study
Evidence that CB-1 and CB-2 cannabinoid receptors mediate antinociception in neuropathic pain in the rat.
The roles of the two cannabinoid receptor subtypes, CB-1 and CB-2, have not been clarified in cannabinoid-mediated analgesia. We investigated the efficacy of the non-selective cannabinoid receptor agonist CP55,940 in the modulation of responses in the rat to both acute pain (tail flick) and neuropathic pain (tactile allodynia following chronic L5/6 spinal nerve ligation). Responses were also assessed in the presence of the CB-1 antagonist SR141716A (SR1) and the CB-2 antagonist SR144528 (SR2). ⋯ CP55,940 on both tail flick antinociception and tactile allodynia (P<0.005). The combination of SR1 and SR2 (i.p.) had an additive effect in decreasing the antinociception induced by CP55,940 on tail flick responses (P<0.005). These results suggest a role for CB-2 receptor-mediated antinociception in both acute and neuropathic pain in addition to centrally located CB-1 mechanisms.
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Comparative Study
Activation of extracellular signal-regulated protein kinase in dorsal horn neurons in the rat neuropathic intermittent claudication model.
Extracellular signal-regulated protein kinase (ERK) is a mitogen-activated protein kinase (MAPK) that mediates several cellular responses to mitogenic and differentiation signals, and activation of ERK in dorsal horn neurons by noxious stimulation is known to contribute to pain hypersensitivity. In order to elucidate the pathophysiological mechanisms of the cauda equina syndrome, secondary to spinal canal stenosis, we evaluated walking dysfunction triggered by forced exercise and activation of ERK in the dorsal horn using a rat model of neuropathic intermittent claudication. Rats in the lumbar canal stenosis (LCS) group showed a shorter running distance from 1 to 14 days after surgery. ⋯ In addition, a prostaglandin E1 analog, OP-1206 alpha-CD, administered orally, improved the walking dysfunction, and further, inhibited activation of ERK following running 7 days after surgery. These findings suggest that intermittent claudication triggered by forced walking might affect the phosphorylation of ERK in the superficial laminae, possibly via transient (partial) ischemia of the spinal cord. ERK activation in the dorsal horn neurons may be involved in the transient pain in the neuropathic intermittent claudication model.