Pain
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(1) Electrophysiological properties of dorsal horn neurones have been investigated in decerebrate, immobilized spinal rats rendered polyarthritic by intradermal injection of Freund's adjuvant. Since arthritis is associated with pronounced erythema and oedema of the foot sole and ankle areas, this particular study was devoted to the induced modifications of responses of units driven by cutaneous inputs. It allowed comparison with previous studies performed in healthy animals. (2) Superficial dorsal horn cells could be separated in: those driven from non-oedematous skin and which had properties similar to those observed in healthy animals; and those driven from oedematous skin and which characterized by unclassical electrophysiological properties such as: (a) a relatively high level of background activity, frequently with bursting pattern and sometimes exhibiting dramatic increases; these neurones are normally silent in healthy animals; (b) a high degree of responsivity to light mechanical stimuli associated with a clear decrease in threshold. ⋯ Responses to radiant heat showed an increase in threshold, sometimes associated with a very high degree of adaptation. (6) Another group of neurones displayed fading responses to repetitive mechanical stimuli. All were located in the deeper two-thirds of the dorsal horn. (7) These data indicate that chronic pathological conditions related to articular and/or cutaneous diseases strongly modify the responses of dorsal horn neurones, some being at the origin of ascending tracts. This model seems to be a promising approach to study the fundamental mechanisms involved in chronic pain in order to approach these problems in human beings.
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Twelve chronic pain patients were employed in an investigation of the accuracy of memory for chronic pain. Subjects first made pain ratings before entering a treatment program. ⋯ Results show that patients remembered having significantly more pain than they actually rated during the baseline period. Caution is therefore warranted when using post-hoc pain measures with chronic pain patients.
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Comparative Study
A comparison of the McGill Pain Questionnaire in chronic and acute pain.
The McGill Pain Questionnaire (MPQ) is widely used in pain research and treatment. The internal structure of the questionnaire has been subjected to empirical investigation, with sensory and reactive factors documented. In the present study, questionnaire responses of 95 women experiencing acute (post episiotomy) pain are analyzed. ⋯ It is suggested that acute pain involves less differentiation of sensory, affective and evaluative language dimensions. Rating scales were also administered. Ratings of labor and episiotomy pain were uncorrelated indicating the importance of distinguishing between these in studying pain in the puerperium.
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Low back pain patients' responses to the McGill Pain Questionnaire (MPQ) were factor analyzed using the principal factor method and direct oblique rotation procedures. Four factors were extracted that accounted for 55% of the total variance. ⋯ The results provided positive evidence that the sensory pressure, evaluative, and affective-sensory factors that were previously identified are stable dimensions underlying the MPQ responses of low back pain patients. However, it is necessary to conduct further cross-validation studies using patients from a wide variety of treatment settings.
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In the population of chronic pain patients seen at multidisciplinary pain clinics, excessive and/or inappropriate medication use is a frequent problem. This study examined differences between chronic pain patients who used no addicting medication (30% of the sample of 131 patients), those who used narcotic but not sedative medications (33%) and those who used both narcotic and sedative medications (37%). ⋯ Narcotic-sedative patients spent significantly more money on pain medication per month, reported significantly greater physical impairment, and had higher MMPI hypochondriasis and hysteria scores when compared to the other patients. The findings are interpreted in light of the hypothesis that certain patients show greater readiness to complain of and seek help for physical symptoms.