Pain
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Increased excitability of primary sensory neurons after peripheral nerve injury may cause hyperalgesia and allodynia. Dorsal root ganglion field stimulation (GFS) is effective in relieving clinical pain associated with nerve injury and neuropathic pain in animal models. However, its mechanism has not been determined. ⋯ After TNI, the threshold to induce AP firing by punctate mechanical stimulation (von Frey) was reduced, which was reversed to normal during GFS. These results also suggest that C-type fibers, not Aβ, mainly contribute to mechanical and thermal hypersensitivity (von Frey, brush, acetone) after injury. Ganglion field stimulation produces use-dependent blocking of afferent AP trains, consistent with enhanced filtering of APs at the sensory neuron T-junction, particularly in nociceptive units.
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Observational Study
Pain trajectory defines knee osteoarthritis subgroups: a prospective observational study.
Knee osteoarthritis (OA) is a heterogeneous disease, and identification of its subgroups/phenotypes can improve patient treatment and drug development. We aimed to identify homogeneous OA subgroups/phenotypes using pain development over time; to understand the interplay between pain and functional limitation in time course; and to investigate subgroups' responses to available pharmacological and surgical treatments. We used group-based trajectory modelling to identify pain trajectories in the phase-3 VIDEO trial (n = 474, 3-year follow-up) and also in the Osteoarthritis Initiative cohort study (n = 4796, 9-year follow-up). ⋯ Notably, we identified a phenotype with severe pain that did not benefit from available treatments, and another one most likely to benefit from knee replacement. Thus, knee OA subgroups/phenotypes can be identified based on patients' pain experiences in studies with long and regular follow-up. We provided a robust approach, reproducible between different study designs, which informs clinicians about symptom development and delivery of treatment options and opens a new avenue toward personalized medicine in OA.
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Pain-related disability is a multifaceted construct that refers to the impact of pain on an individual's capacity to fulfill their self-defined and social roles. This research examined the relationship between clinical, psychological, and pain sensitivity factors and pain-related disability among adults with chronic temporomandibular disorder (TMD). We analyzed data from a cross-sectional community-based sample of 1088 men and women with chronic TMD. ⋯ Jaw functional limitation and psychological unease was strongly related to pain-related disability. Experimental pain sensitivity was removed from our model because of weak direct effect and the burden of performing experimental pain sensitivity testing in a clinical setting. The final model explained 78% of the variance in pain-related disability.
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Randomized Controlled Trial
A digital health psychological intervention (WebMAP Mobile) for children and adolescents with chronic pain: results of a hybrid effectiveness-implementation stepped wedge cluster randomized trial.
Although psychological treatments benefit youth with chronic pain, treatment is not accessible in most communities. Digital health interventions offer promise for expanding access and reach to this population. Using a stepped-wedge cluster randomized trial design, we evaluated effectiveness and implementation of a digital health delivered psychological intervention for pediatric chronic pain. ⋯ Greater engagement (number of completed modules) was associated with significantly greater reductions in pain and disability from pre-treatment to follow-up (d's = -0.57 and -0.38, P < 0.05). Parents, youth, and providers found treatment acceptable; providers had positive attitudes and demonstrated referrals over a maintenance period. Further research is needed to understand how to enhance treatment engagement with digital health interventions and optimize implementation.
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The chronification of pain can be attributed to changes in membrane receptors and channels underlying neuronal plasticity and signal transduction largely within nociceptive neurons that initiate and maintain pathological pain states. These proteins are subject to dynamic modification by posttranslational modifications, creating a code that controls protein function in time and space. Phosphorylation is an important posttranslational modification that affects ∼30% of proteins in vivo. ⋯ This narrative review discusses the molecular mechanisms of Cdk5-mediated regulation of target proteins involved in neuropathic pain. We focus on Cdk5 substrates that have been linked to nociceptive pathways, including channels (eg, transient receptor potential cation channel and voltage-gated calcium channel), proteins involved in neurotransmitter release (eg, synaptophysin and collapsin response mediator protein 2), and receptors (eg, glutamate, purinergic, and opioid). By altering the phosphoregulatory "set point" of proteins involved in pain signaling, Cdk5 thus appears to be an attractive target for treating neuropathic pain conditions.