Pain
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Seven patients diagnosed with erythromelalgia (EM) were investigated by microneurography to record from unmyelinated nerve fibers in the peroneal nerve. Two patients had characterized variants of sodium channel Nav1.7 (I848T, I228M), whereas no mutations of coding regions of Navs were found in 5 patients with EM. Irrespective of Nav1.7 mutations, more than 50% of the silent nociceptors in the patients with EM showed spontaneous activity. ⋯ The characteristic pattern of changes in conduction velocity observed in the patient with the I848T gain-of function mutation in Nav1.7 could be explained by axonal depolarization and concomitant inactivation of Nav1.7. If this were true, activity-dependent hyperpolarization would reverse inactivation of Nav1.7 and account for the supranormal CV. This mechanism might explain normal pain thresholds under resting conditions.
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Mechanical allodynia, a cardinal symptom of persistent pain, is associated with the unmasking of usually blocked local circuits within the superficial spinal or medullary dorsal horn (MDH) through which low-threshold mechanical inputs can gain access to the lamina I nociceptive output neurons. Specific interneurons located within inner lamina II (IIi) and expressing the gamma isoform of protein kinase C (PKCγ⁺) have been shown to be key elements for such circuits. However, their morphologic and electrophysiologic features are still unknown. ⋯ In addition, at least 2 morphologically and functionally different subpopulations of PKCγ⁺ interneurons can be identified: central and radial PKCγ⁺ interneurons. The former exhibit a lower membrane input resistance, rheobase and, thus, action potential threshold, and less PKCγ⁺ immunoreactivity than the latter. These 2 subpopulations might thus differently contribute to the gating of dorsally directed circuits within the MDH underlying mechanical allodynia.
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The aim of this investigation was to examine the prevalence of and factors associated with chronic pain in the pelvic area or lower extremities after rectal cancer treatment and its impact on quality of life (QoL). This is a population-based cross-sectional study of chronic pain and QoL in patients treated for rectal cancer from 2001 to 2007. A modified version of the Brief Descriptive Danish Pain Questionnaire and the European Organization for Research and Treatment of Cancer QLQ-C30 questionnaire were mailed to 1713 Danish patients. ⋯ Multivariate logistic regression analysis showed an association with chronic pain in female patients (OR 1.91 [1.51-2.43], P < 0.001) and in those who received radio(chemo)therapy (OR 1.31 [1.01-1.7], P = 0.041) or underwent abdominoperineal excision (OR 1.71 [1.19-2.44], P = 0.003), total mesorectal excision (OR 1.39 [1.01-1.90], P = 0.041), and Hartmann procedure (OR 1.72 [1.04-2.84], P = 0.33) compared with partial mesorectal excision. Ordinal regression analysis showed a strong association between all QoL subgroups and pelvic pain. Chronic pain in the pelvic region or lower extremities after rectal cancer treatment is a common but largely neglected problem that is associated with female gender, type of surgery, radio(chemo)therapy, and young age, all of which impact the patient's QoL.
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The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) has recommended that trialists evaluating treatments for chronic pain should consider reporting 9 patient-important outcome domains. We examined the extent to which clinical trials evaluating the effect of opioids for chronic non-cancer pain (CNCP) report outcome domains recommended by IMMPACT. We systematically searched electronic databases for English-language studies that randomized patients with CNCP to receive an opioid or a non-opioid control. ⋯ Trials for which the corresponding author was from North America were more likely to report treatment effects on physical functioning and participant ratings of improvement and satisfaction with treatment. Trials published in higher impact journals were more likely to report treatment effects on emotional function, but less likely to report participant ratings of improvement and satisfaction with treatment. Most IMMPACT domains showed an increased rate of reporting over time, although many patient-important outcome domains remained unreported by over half of all trials evaluating the effects of opioids for CNCP.