Pain
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Comparative Study
Rapid deterioration of pain sensory-discriminative information in short-term memory.
The assessment of pain and analgesic efficacy sometimes relies on the retrospective evaluation of pain felt in the immediate, recent or distant past, yet we have a very limited understanding of the processes involved in the encoding, maintenance and intentional retrieval of pain. We examine the properties of the short-term memory of thermal and pain sensation intensity with a delayed-discrimination task using pairs of heat pain, warm and cool stimulation in healthy volunteers. Performance decreased as a function of the inter-stimulus interval (ISI), indicating a robust deterioration of sensory information over the test period of 4-14 s. ⋯ Importantly, performance declined steadily with increasing ISI (from 6 to 14 s)--but only for pairs of heat pain stimuli that were relatively difficult to discriminate (Delta-T < or = 1.0 degree C; perceptual difference < or = 32/100 pain rating units) while no deterioration in performance was observed for the largest temperature difference tested (Delta T = 1.5 degrees C; perceptual difference of 50 units). These results are consistent with the possibility that short-term memory for pain and temperature sensation intensity relies on a transient analog representation that is quickly degraded and transformed into a more resistant but less precise categorical format. This implies that retrospective pain ratings obtained even after very short delays may be rather inaccurate but relatively reliable.
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To investigate neglect, extinction, and body-perception in patients suffering from complex regional pain syndrome (CRPS). So-called 'neglect-like' symptoms have been reported in CRPS, however no studies have yet analyzed this phenomenon which might substantiate the theory of the central nervous system involvement in the pathophysiology of CRPS. A total of 114 patients with CRPS of the upper limb underwent bedside neurological examination. 'Neglect-like' symptoms were determined by asking all patients what kind of feeling they had toward the affected hand (feeling of foreignness). ⋯ A large proportion of CRPS patients have disturbances of the self-perception of the hand, indicating an alteration of higher central nervous system processing. There are no indicators that classic neglect or extinction contribute to these findings. Physical therapy of such patients should take this observation into consideration.
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Randomized Controlled Trial Multicenter Study Comparative Study Clinical Trial
Venlafaxine extended release in the treatment of painful diabetic neuropathy: a double-blind, placebo-controlled study.
To evaluate the efficacy and safety of 6 weeks of venlafaxine extended-release (ER) (75 mg and 150-225 mg) treatment in patients with painful diabetic neuropathy. This multicenter, double-blind, randomized, placebo-controlled study included 244 adult outpatients with metabolically stable type 1 or 2 diabetes with painful diabetic neuropathy. Primary efficacy measures were scores on the daily 100 mm Visual Analog Pain Intensity (VAS-PI) and Pain Relief (VAS-PR) scales. ⋯ Seven patients on venlafaxine had clinically important ECG changes during treatment. Venlafaxine ER appears effective and safe in relieving pain associated with diabetic neuropathy. NNT values for higher dose venlafaxine ER are comparable to those of tricyclic antidepressants and the anticonvulsant gabapentin.
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Comparative Study
Role of TNF-alpha in sensitization of nociceptive dorsal horn neurons induced by application of nucleus pulposus to L5 dorsal root ganglion in rats.
Herniation of the nucleus pulposus (NP) from lumbar intervertebral discs commonly results in radiculopathic pain and paresthesia (sciatica). While traditionally considered the result of mechanical compression of the dorsal root ganglion (DRG) and/or spinal nerve root, recent studies implicate pro-inflammatory mediators released from or evoked by NP, a possibility that was presently investigated. Single-unit recordings were made from L5 wide dynamic range dorsal horn neurons in pentobarbital-anesthetized rats. ⋯ Thermally and mechanically evoked responses were not significantly affected in control rats or those treated with NP + soluble TNF-alpha receptor type 1. These results indicate that sensitization of nociceptive spinal neuronal responses develops quickly following exposure of the DRG to NP, and that TNF-alpha is involved. This electrophysiological model of herniated NP may prove useful in further characterizing the role of inflammatory mediators in hyperalgesia and allodynia resulting from lumbar disc herniation.
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This study continued the validation of a Whiplash Specific Disability Questionnaire (WDQ) that was developed from the Neck Disability Index (NDI) using self-reported disabilities in a group of participants experiencing whiplash-associated disorders [J Manipulative Physiol Ther 14 (1991) 409]. Previous research has established the content, construct and face validity and internal consistency of the WDQ. The aim of this study was to establish the short-term and medium-term test-retest reliability and responsiveness of the WDQ. ⋯ Correlation between change in WDQ score over 1 month and participant perceived change was r(s) = 0.64, the effect size was 0.03, the SRM was 0.08 and the responsiveness statistics were 0.90 (participants who improved) and -1.60 (participants who deteriorated). The minimal detectable change of the WDQ was established at 15 points. These results demonstrate that the WDQ has excellent short- and medium-term reproducibility and responsiveness in a population seeking treatment for WAD.