Pain
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Severe neuropathic pain is a hallmark of Fabry disease, a genetic disorder caused by a deficiency in lysosomal α-galactosidase A. Pain experienced by these patients significantly impacts their quality of life and ability to perform everyday tasks. Patients with Fabry disease suffer from peripheral neuropathy, sensory abnormalities, acute pain crises, and lifelong ongoing pain. ⋯ This review will detail the types of pain, sensory abnormalities, influence of demographics on pain, and current strategies to treat pain experienced by patients with Fabry disease. In addition, we discuss the current knowledge of Fabry pain pathogenesis and which aspects of the disease preclinical models accurately recapitulate. Understanding the commonalities and divergences between humans and preclinical models can be used to further interrogate mechanisms causing the pain and sensory abnormalities as well as advance development of the next generation of therapeutics to treat pain in patients with Fabry disease.
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It has been proposed that complex regional pain syndrome (CRPS) is a posttraumatic autoimmune disease. Previously, we observed that B cells contribute to CRPS-like changes in a mouse tibia fracture model, and that early (<12 months duration) CRPS patient IgM antibodies have pronociceptive effects in the skin and spinal cord of muMT fracture mice lacking B cells. The current study evaluated the pronociceptive effects of intraplantar or intrathecal injections of early CRPS IgM (5 µg) in muMT fracture mice. ⋯ Intrathecal IgM injection also had pronociceptive effects with increased spinal cytokine expression, effects that were blocked by PMX53 or pentoxifylline treatment. Intrathecal injection of chronic (>12 months duration) CRPS patient IgM (but not IgG) caused nociceptive sensitization in muMT fracture mice, but intraplantar injection of chronic CRPS IgM or IgG had no effect. We postulate that CRPS IgM antibodies bind to neoantigens in the fracture limb skin and corresponding spinal cord to activate C5a complement signaling in macrophages and microglia, evoking proinflammatory cytokine expression contributing to nociceptive sensitization in the injured limb.
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This study examines the importance of length of follow-up on the association between pain and incident dementia. Further objective was to characterize pain trajectories in the 27 years preceding dementia diagnosis and compare them with those among persons free of dementia during the same period. Pain intensity and pain interference (averaged as total pain) were measured on 9 occasions (1991-2016) using the Short-Form 36 Questionnaire amongst 9046 (women = 31.4%) dementia-free adults aged 40 to 64 years in 1991; 567 dementia cases were recorded between 1991 and 2019. ⋯ These associations were stronger when the mean follow-up for incidence of dementia was 3.2 years. Twenty-seven-year pain trajectories differed between dementia cases and noncases with small differences in total pain and pain interference evident 16 years before dementia diagnosis (difference in the total pain score = 1.4, 95% confidence intervals = 0.1-2.7) and rapidly increasing closer to diagnosis. In conclusion, these findings suggest that pain is a correlate or prodromal symptom rather than a cause of dementia.
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Randomized Controlled Trial
Reduction in movement-evoked pain and fatigue during initial 30-minute TENS treatment predicts TENS responders in women with fibromyalgia.
We previously showed that 1 month of transcutaneous electrical nerve stimulation (TENS) reduces movement-evoked pain and fatigue in women with fibromyalgia (FM). Using data from this study (Fibromyalgia Activity Study with TENS [FAST]), we performed a responder analysis to identify predictors of clinical improvement in pain and fatigue with TENS, validated these models using receiver operator characteristic, and determined number needed to treat and number needed to harm. Participants were randomly assigned to active-TENS (2-125 Hz; highest-tolerable intensity), placebo-TENS, or no-TENS for 1 month. ⋯ Number needed to harm ranged from 20 to 100 for minor TENS-related adverse events. The response to an initial 30-minute TENS treatment predicts who responds to longer-term TENS use in women with FM, making this a clinically useful procedure. Number needed to treat and number needed to harm suggest that TENS is effective and safe for managing pain and fatigue in FM.
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Randomized Controlled Trial
A randomized, controlled trial of a β2-agonist in painful polyneuropathy.
Experimental data have suggested that in neuropathic pain, tricyclic antidepressants may work solely through a β2-agonist action. The aim of this study was to test if the β2-agonist terbutaline relieves painful polyneuropathy. The study was a randomized, double-blind, placebo-controlled and active-controlled, 3-way, cross-over trial among patients with painful polyneuropathy. ⋯ The median score for total pain on imipramine changed from NRS 6.6 to 4.8 with an average effect as compared with placebo of -1.17 (95% confidence interval -1.42 to -0.92, P < 0.001). Secondary outcomes were also unaltered by terbutaline but improved by imipramine. The β2-agonist terbutaline has no effect in painful polyneuropathy. β2-agonism seems not to be an important mechanism of action of tricyclic antidepressants in neuropathic pain.