Pain
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The gate theory of pain, published by Ronald Melzack and Patrick Wall in Science in 1965, was formulated to provide a mechanism for coding the nociceptive component of cutaneous sensory input. The theory dealt explicitly with the apparent conflict in the 1960s between the paucity of sensory neurons that responded selectively to intense stimuli and the well-established finding that stimulation of the small fibers in peripheral nerves is required for the stimulus to be described as painful. ⋯ The clarity of the model and its description gave this article immediate visibility, with numerous attempts made to test its various predictions. Although subsequent experiments and clinical findings have made clear that the model is not correct in detail, the general ideas put forth in the article and the experiments they prompted in both animals and patients have transformed our understanding of pain mechanisms.
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Randomized Controlled Trial Multicenter Study
Sensory profiles of patients with neuropathic pain based on the neuropathic pain symptoms and signs.
This manuscript aimed to characterize the clinical profile of various neuropathic pain (NeP) disorders and to identify whether patterns of sensory symptoms/signs exist, based on baseline responses on the Neuropathic Pain Symptom Inventory (NPSI) questionnaire and the quantitative sensory testing (QST). These post hoc analyses were based on data from 4 randomized, double-blind, placebo-controlled clinical studies of pregabalin (150-600mg/day) in patients with NeP syndromes: central poststroke pain, posttraumatic peripheral pain, painful HIV neuropathy, and painful diabetic peripheral neuropathy. The NPSI questionnaire includes 10 different pain symptom descriptors. ⋯ Based on QST signs, PCA identified 2 pain dimensions: evoked by cold and evoked by touch. A hierarchical cluster analysis identified 4 clusters with distinct pain characteristics profiles. These "trans-etiological" profiles may reflect distinct pathophysiological mechanisms and therefore, potential differential responses to treatment.
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Debate continues regarding the influence of litigation on pain outcomes after motor vehicle collision (MVC). In this study we enrolled European Americans presenting to the emergency department (ED) in the hours after MVC (n=948). Six weeks later, participants were interviewed regarding pain symptoms and asked about their participation in MVC-related litigation. ⋯ Initial pain severity in the ED predicted pain outcomes among both litigants and nonlitigants. Markers of socioeconomic disadvantage predicted worse pain outcomes in litigants but not nonlitigants, and individual pain and psychological symptoms were less predictive of pain outcomes among those engaged in litigation. These data demonstrate that persistent pain after MVC is common among those not engaged in litigation, and provide evidence for bidirectional influences between pain outcomes and litigation after MVC.
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Multicenter Study
Psychological, surgical and sociodemographic predictors of pain outcomes after breast cancer surgery: a population-based cohort study.
Chronic postsurgical pain (CPSP) is a common postoperative adverse event affecting up to half of women undergoing breast cancer surgery, yet few epidemiological studies have prospectively investigated the role of preoperative, intraoperative, and postoperative risk factors for pain onset and chronicity. We prospectively investigated preoperative sociodemographic and psychological factors, intraoperative clinical factors, and acute postoperative pain in a prospective cohort of 362 women undergoing surgery for primary breast cancer. Intraoperative nerve handling (division or preservation) of the intercostobrachial nerve was recorded. ⋯ At 9months, younger age, axillary node clearance (OR 2.97, 95% CI 1.09 to 8.06), and severity of acute postoperative pain (OR 1.17, 95% CI 1.00 to 1.37) were predictive of pain persistence. Of those with CPSP, 25% experienced moderate to severe pain and 40% were positive on Douleur Neuropathique 4 and Self-Complete Leeds Assessment of Neuropathic Symptoms and Signs pain scales. Overall, a high proportion of women report painful symptoms, altered sensations, and numbness in the upper body within the first 9months after resectional breast surgery and cancer treatment.