Pain
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Based upon a tripartite theoretical model of pain, the Pain Rating Index (PRI) of the McGill Pain Questionnaire (MPQ) continues to be one of the most frequently used instruments to measure clinical pain. Although a number of exploratory factor analytic studies have failed to consistently support the theoretical structure of the instrument, one previous confirmatory factor analytic study of chronic pain did statistically support the a priori model. Because it has been suggested that acute pain may not involve the same dimensions as chronic pain, this study provided a direct test of the theoretical structure of the MPQ through multi-sample confirmatory factor analysis (CFA) using data provided by women experiencing pain during labor (n = 185) and women experiencing acute postoperative pain (n = 192). Results of the LISREL CFA analysis indicated that the a priori, 3-factor, oblique model originally proposed by Melzack provided the most parsimonious representation of the data across the 2 samples of acute pain.
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Fibromyalgia syndrome (FS) is a chronic pain disorder characterized by diffuse musculoskeletal soreness, stiffness, non-restorative sleep and psychological disturbance. At present, much about the etiology, pathological mechanisms and course of FS are unknown. Indeed, standardized diagnostic criteria have only been recently agreed upon. ⋯ The present paper describes the clinical presentation of FS and historical conceptualizations of the disorder. Available research on pathophysiological mechanisms in FS is then presented. In this section we have included literature concerning histology of muscle, sleep architecture, neurotransmitter anomalies and neuropeptide involvement in FS symptomatology.
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This study examined the extent to which measures of anxiety could predict pain and the length of hospitalization following surgery in 111 patients with gallstones over and above what could be predicted on the basis of biographical and medical status variables. Self-reported pain on the third day postoperative could hardly be explained by the variables measured. ⋯ Over and above these variables. A-state on the third postoperative day and also A-state and specific anxiety measured 1 day before surgery exerted a significant increase on the values of prediction of the length of postoperative hospitalization.
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In a previous report we presented a novel behavioral model of neuropathic pain disorders, produced in rat by a unilateral ligation of about half of the sciatic nerve. The model is characterized by rapid onset of behaviors suggesting spontaneous pain and disordered responses to non-noxious and noxious stimuli. These include reduced withdrawal thresholds to repetitive touch in the partially deafferented skin ('touched-evoked hyperesthesia'), touch-evoked allodynia, reduced withdrawal thresholds to noxious thermal stimuli and exaggerated responses to noxious heat and mechanical stimuli ('thermal hyperalgesia'). ⋯ Reversible sympathectomy was carried out using guanethidine injected intraperitoneally in 3 experiments, each at a different time in relation to the partial nerve injury. We found that: (1) sympathectomy performed several months postoperatively alleviated the sensory disorders bilaterally; (2) sympathectomy prior to nerve injury partially prevented the appearance of thermal hyperalgesia but did not affect hyperesthesia to repetitive touch; and (3) sympathectomy at the time of nerve injury aggravated the sensory disorders during the first few days. As maintenance and production of the sensory disorders in this animal model depended on sympathetic nervous outflow, we conclude that the rats were suffering from a syndrome analogous to sympathetically maintained causalgia in man.
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Comparative Study
Comparison of human pain sensation and flexion withdrawal evoked by noxious radiant heat.
The purpose of this study was to determine the reliability of flexion withdrawal magnitude as an indicator of pain sensation. In 10 healthy human volunteers, we compared the magnitude and latency of integrated biceps EMG with the subjects' rating of pain, using a visual analog scale, elicited by noxious radiant heat stimuli applied to the dorsal forearm. ⋯ The pain intensity and withdrawal magnitude for each stimulus were poorly correlated. Under the conditions of this experiment, mean pain intensity and mean withdrawal magnitude were both well correlated with stimulus temperature, but the magnitude of withdrawal did not reliably reflect the intensity of pain sensation.