Pain
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Comparative Study
The dimensions of pain: a multidimensional scaling comparison of cancer patients and healthy volunteers.
This paper presents a new approach to the measurement and understanding of clinical pain. A multidimensional scaling (MDS) procedure was used to analyze pairwise similarity judgments made to 9 pain descriptors by 24 cancer pain patients and 24 healthy volunteers. The question was whether the dimensions of the global pain space differed between the 2 groups. ⋯ The subject weight space revealed that the Pain Intensity dimension was the most important dimension for the patients, while Emotional Quality was more salient for the volunteers. Wide differences were found in the salience of the various dimensions to different individuals; this information may prove useful for tailoring patient treatment. The study demonstrates that MDS procedures such as INDSCAL, in which the subjects (rather than the researcher) determine the number and characteristics of the global pain dimensions, will improve our understanding and treatment of pain.
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In the first part of the study 20 subjects (11 headache, 9 normals) free-sorted descriptors from the intensity and affect scales of the Tursky pain perception profile (PPP) into groups on the basis of similar meaning. In part 2 they made similarity ratings of all pairs of words within the intensity and affect scales. In the third part of the study subjects completed a cross-modal matching task to scale the intensity and affect words. ⋯ An MDS analysis showed that the groups could be located in 2-dimensional space in which the dimensions of intensity and affective distress could be easily discerned. When the descriptors from the intensity and affect scales were rated within each scale, a second MDS analysis showed that, whereas the intensity descriptors could be fitted by a 1-dimensional representation, the affect descriptors required a 3-dimensional model. There was evidence that subjects with extensive pain experience placed greater weight on the second and third affective dimensions compared with relatively pain-free subjects.
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Intrathecal administration of glycine (strychnine) or GABA (bicuculline) but not opioid (naloxone), adrenergic (phentolamine) or serotonin (methysergide) receptor antagonists resulted in a dose-dependent organized agitation response to light tactile stimulation. This effect was maximally evoked by oscillating but not continuous stimulation applied to a dermatome corresponding to the levels of spinal cord acted upon by the intrathecal antagonist. Similar results were observed in chloralose-urethane anesthetized rats in which tactile stimulation evoked hypertensive responses following local tactile stimuli. ⋯ At doses below those which produced motor dysfunction, however, these agents had no effects on the hot-plate response latency. These data emphasize that low threshold afferent input is likely subject to an ongoing modulation, the loss of which results in a miscoding of the afferent stimulus yielding a pain relevant message. The lack of effect of agents having a powerful effect on somatic pain stimuli and the converse effects of glutamate receptor antagonists on the strychnine hyperesthesia at doses which do not affect the somatic pain response indicate discriminable processing systems, the characteristics of which resemble the clinical phenomenon observed in patients suffering from sensory dysesthesia following central and peripheral horn injury.
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The use of strategies for coping with chronic pain was assessed by means of the Coping Strategy Questionnaire (CSQ) in a Dutch sample of 108 chronic low back pain (LBP) patients referred for behavioral treatment. The 3 factors of the CSQ were related to measurements of behavioral and emotional adjustment to LBP above and beyond the effects of demographic and medical status variables. Especially patients high on the factor Helplessness reported higher levels of pain, functional impairment, anxiety, depression and psychoneuroticism, while patients high on the factor Perceived Control reported lower levels of pain, functional impairment and also manifested a higher level of uptime. The causal role of coping strategies in adjustment to pain, the selectivity of focusing on LBP patients selected through referral and implications for pain management are discussed.