Pain
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Chronic deep brain stimulation (DBS) of the periventricular gray (PVG) has been used for the treatment of chronic central pain for decades. In recent years motor cortex stimulation (MCS) has largely supplanted DBS in the surgical management of intractable neuropathic pain of central origin. However, MCS provides satisfactory pain relief in about 50-75% of cases, a range comparable to that reported for DBS (none of the reports are in placebo-controlled studies and hence the further need for caution in evaluating and comparing these results). ⋯ We have found an interesting and consistent correlation between thalamic electrical activity and chronic pain. This low frequency potential may provide an objective index for quantifying chronic pain, and may hold further clues to the mechanism of action of PVG stimulation. It may be possible to use the presence of these slow FPs and the effect of trial PVG DBS on both the clinical status and the FPs to predict the probable success of future pain control in individual patients.
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Comparative Study
Gender differences in pain characteristics of chronic stable angina and perceived physical limitation in patients with coronary artery disease.
Chronic stable angina pectoris, the chest pain associated with reversible myocardial ischemia has detrimental effects on health-related quality of life, particularly in women. The limited research on gender differences in chronic stable angina suggests that angina may be experienced differently in women and that women report greater functional disability related to angina symptoms. No studies have examined gender differences in chronic stable angina from a multidimensional pain perspective or have included reliable and valid measures of pain that would facilitate comparing chronic angina patients with other chronic pain populations. ⋯ The variables of social status and years diagnosed with CAD significantly interacted with gender in predicting physical limitation suggesting that gender-specific models of physical limitation in angina patients need to be explored. To our knowledge, this is one of the first studies that has assessed chronic anginal pain using a reliable and valid generic pain instrument. More research is needed to better understand the nature of gender differences in functional limitation secondary to anginal pain and the physiologic, cognitive-perceptual and psychosocial mechanisms that lead to angina-related functional disability.
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The primary somatosensory cortex (S1) in adult animals and humans is capable of rapid modification after deafferentation. These plastic changes may account for a loss of tonic control by nociceptive inputs over inhibitory mechanisms within structures of the dorsal column-medial lemniscal system. Most studies, however, have been performed under conditions where deafferentation of C and A delta fibres coexists with large-diameter fibres deafferentation. ⋯ No significant changes in spinal or brainstem potentials were observed. PCC did not affect SEP components obtained by stimulation of the leg ipsilateral to PCC. Our results suggest that nociceptive deafferentation may induce a rapid modulation of cortical neuronal activity along the lemniscal pathway, thus providing the first evidence in humans of short-term cortical plasticity across the spinothalamic and lemniscal systems.
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Complex regional pain syndrome type 1 (CRPS1) often leads to serious activity limitations in everyday life. To date, however, limitations in patients with CRPS1 of an upper limb have not been objectively measured. Therefore, the aim of this study was to determine the long-term impact of upper limb CRPS1 on general mobility and upper limb usage during everyday life, as measured with a novel upper limb-activity monitor (ULAM). ⋯ For upper limb usage outcome measures during sitting, there was a marked difference between CRPS1 patients and controls. Especially patients with dominant side involvement clearly showed less activity of their involved limb during sitting, indicated by significant differences for the mean intensity (P=0.014), percentage (P=0.004), and proportion (P=0.032) of upper limb activity. It is concluded that these ten chronic CRPS1 patients still had limitations in upper limb usage during everyday life, 3.7 years (average) after the causative event.
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Subunit non-selective N-methyl-D-aspartate (NMDA) receptor antagonists reduce injury-induced pain behavior, but generally produce unacceptable side effects. In this study, we examined the antinociceptive and motor effects of cone snail venom-derived peptides, conantokins G and T (conG and conT), which are selective inhibitors of the NR2B or NR2A and NR2B subtypes of the NMDA receptor, respectively. We tested the effects of conG and conT in models of tissue (formalin test), nerve injury (partial sciatic nerve ligation) and inflammation-induced (intraplantar Complete Freund's Adjuvant; CFA) pain in mice. ⋯ Finally, a single dose of conG (100 pmol, i.t.) also reduced CFA-evoked thermal and mechanical allodynia. Taken together, these results demonstrate that conantokins exhibit potent antinociceptive effects in several models of injury-induced pain. The study supports the notion that drugs directed against subtypes of the NMDA receptor, by virtue of their reduced side-effect profile, hold promise as novel therapeutic agents for the control of pain.