Pain
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The default mode network (DMN) has been proposed as a biomarker for several chronic pain conditions. Default mode network functional connectivity (FC) is typically examined during resting-state functional neuroimaging, in which participants are instructed to let thoughts wander. However, factors at the time of data collection (eg, negative mood) that might systematically impact pain perception and its brain activity, influencing the application of the DMN as a pain biomarker, are rarely reported. ⋯ However, only 1 significant cluster covering a portion of the cerebellum was identified examining a two-way repeated-measures analysis of variance for happiness > baseline (PFDR < 0.05). Overall, these findings suggest that DMN FC is affected by negative mood in individuals with and without CLBP. It is possible that DMN FC seen in patients with chronic pain is related to an affective dimension of pain, which is important to consider in future neuroimaging biomarker development and implementation.
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Randomized Controlled Trial
Long-term outcomes from training in self-management of chronic pain in an elderly population: A randomised controlled trial.
This study compares the outcomes, from pretreatment to 1-year follow-up, of an outpatient, CBT-based pain self-management program (PSM) that included exercises, pain education, and pain coping strategies, with a control condition (exercise-attention control, EAC) that included exercises and a control for the attention of the treatment team. We previously reported short-term results (to 1-month follow-up) from the same study. This new paper considers the important issue of maintenance of treatment-related gains. ⋯ The mean effect size for these gains by the pain self-management program group over the exercise-attention control group was 0.37 (range: 0.29-0.45), which is in the small effect size range. While statistically and clinically meaningful, these findings do indicate some weakening in effects over time but not to a significant degree. The study has implications for the provision of pain management interventions for community-dwelling older adults with chronic pain.
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The upregulation of the tetrodotoxin-resistant voltage-gated sodium channel NaV1.9 has previously been associated with inflammatory hyperalgesia. Na1.9 knockout (KO) mice, however, did not seem insensitive in conventional tests of acute nociception. Using electrophysiological, neurochemical, and behavioral techniques, we now show NaV1.9-null mice exhibit impaired mechanical and thermal sensory capacities and reduced electrical excitability of nociceptors. ⋯ Heat-induced calcitonin gene-related peptide release from the skin was less in the KO than in the WT group. The reduced noxious heat sensitivity was finally confirmed with the Hargreaves test using 2 rates of radiant heating of the plantar hind paws. In conclusion, NaV1.9 presumably contributes to acute thermal and mechanical nociception in mice, most likely through increasing the excitability but probably also by amplifying receptor potentials irrespective of the stimulus modality.
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Central poststroke pain (CPSP) is a severe type of neuropathic pain that can develop after stroke and is difficult to treat. Research into its underlying mechanisms and treatment options could benefit from a valid CPSP animal model. Nine different CPSP animal models have been published, but there are relatively few reports on successful reproductions of these models and so far only little advances in the understanding or the management of CPSP have been made relying on these models. ⋯ We compare the different models regarding these types of validity and discuss the robustness, reproducibility, and problems regarding the design and reporting of the articles establishing these models. We conclude with various proposals on how to improve the validity and reproducibility of CPSP animal models. Until further improvements are achieved, prudence is called for in interpreting results obtained through these models.
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Patients with fibromyalgia (FM) show characteristically enhanced unpleasantness to painful and nonpainful sensations accompanied by altered neural responses. The diagnostic potential of such neural alterations, including their sensitivity and specificity to FM (vs healthy controls) is unknown. We identify a brain signature that characterizes FM central pathophysiology at the neural systems level. ⋯ The study provides initial characterization of individual patients with FM based on pathophysiological, symptom-related brain features. If replicated, these brain features may constitute objective neural targets for therapeutic interventions. The results establish a framework for assessing therapeutic mechanisms and predicting treatment response at the individual level.