Pain
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Persistent postoperative pain is a common complication of surgery, including surgical interventions for cancer. So far, there is limited information about the prevalence and clinical characteristics of pain after lymph node biopsy and dissection in patients with malignant melanoma. In this study, a questionnaire was sent out to all surviving patients (n=402) after surgery for cutaneous malignant melanoma at the Aalborg Hospital Department of Plastic Surgery, Aalborg, Denmark. ⋯ At the clinical follow-up, 10 out of 12 patients with pain both met the criteria of the recently proposed grading system for probable neuropathic pain and used descriptors on the DN4 questionnaire suggestive of neuropathic pain. Different patterns of sensory profiles were observed in single patients, suggesting heterogeneous sensory processing within single patients. This study suggested that nerve injury was the main underlying mechanism of persistent pain after lymph node excision.
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Comparative Study
Engagement of descending inhibition from the rostral ventromedial medulla protects against chronic neuropathic pain.
A puzzling observation is why peripheral nerve injury results in chronic pain in some, but not all, patients. We explored potential mechanisms that may prevent the expression of chronic pain. Sprague Dawley (SD) or Holtzman (HZ) rats showed no differences in baseline sensory thresholds or responses to inflammatory stimuli. ⋯ Thus, expression of nerve injury-induced pain may ultimately depend on descending modulation. Engagement of descending inhibition protects in the transition from acute to chronic pain. These unexpected findings might provide a mechanistic explanation for medications that engage descending inhibition or mimic its consequences.
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Spatial summation (SS) and spatial discrimination (SD) are essential for pain perception. In the cold-pain sensation, these processes have hardly been studied. Our aim was to study the SS and SD of cold pain, as well as the SS of cold-pain threshold (CPT) in hairy and glabrous skin. ⋯ CPT was significantly higher in hairy than glabrous skin, but the amount of SS of CPT was similar in the 2 skin types. Noxious cold-evoked thermal qualities were more common in the glabrous than the hairy skin. In conclusion: (1) SS and SD of cold pain are reciprocal; (2) whereas cold pain can summate over large distances, the SD of cold pain is poor; (3) SS of cold pain does not exist between contralateral body sides, however, inhibition occurs; (4) SS is independent of skin type and sensitivity to cold pain; (5) differences in pain quality between hairy and glabrous skin may reflect innervation differences.