Pain
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Randomized Controlled Trial
Extended-release gabapentin for failed back surgery syndrome: results from a randomized double-blind cross-over study.
Extended-release gabapentin does not improve persistent pain after unsuccessful lumbar spine surgery.
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Mechanical allodynia is pain caused by normally innocuous mechanical stimuli and is a cardinal and intractable symptom of neuropathic pain. Roles of low-threshold mechanoreceptors (LTMRs), including Aβ fibers, in mechanical allodynia have previously been proposed, but the necessity and sufficiency of LTMRs in allodynia have not been fully determined. Recent technological advances have made it possible to achieve subpopulation-specific ablation, silencing or stimulation, and to dissect and elucidate complex neuronal circuitry. ⋯ Whole-cell recording has revealed that optical Aβ stimulation after nerve injury causes excitation of lamina I dorsal horn neurons, which are normally silent by this stimulation. Moreover, Aβ stimulation after nerve injury results in activation of central amygdaloid neurons and produces aversive behaviors. In summary, these findings indicate that optogenetics is a powerful approach for investigating LTMR-derived pain (resembling mechanical allodynia) with sensory and emotional features after nerve injury and for discovering novel and effective drugs to treat neuropathic pain.
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Randomized Controlled Trial
Effectiveness and safety of 5% lidocaine-medicated plaster on localized neuropathic pain after knee surgery: a randomized, double-blind controlled trial.
Localized neuropathic pain symptoms are reported after knee surgery in 30% to 50% of patients. 5% lidocaine plaster (LP5) is recommended for localized neuropathic pain, but evidence in postsurgery neuropathic pain is missing. This study focuses on the effectiveness of LP5 on allodynia, hyperalgesia, and thermal stimuli in postsurgery knee localized neuropathic pain. A randomized double-blind, 2 parallel groups, controlled trial (NCT02763592) took place in 36 patients (age, 69.4 ± 7.3 years) at the Clinical Pharmacology Center, University Hospital Clermont-Ferrand, France. ⋯ Cold pain and maximal mechanical pain thresholds improved over 3 months (P = 0.001 and P = 0.007, respectively). This study shows for the first time the effectiveness of LP5 on dynamic mechanical allodynia, pain, pressure, and cold thresholds over 3 months in knee localized neuropathic pain. Beyond the inhibition of sodium channels by LP5, these findings suggest the involvement of cold and mechanical receptors that participate to pain chronicisation and also of the non-negligible placebo effect of the patch, items that need to be explored further and challenged in other etiologies of localized neuropathic pain.
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Numerous studies have examined how alexithymia (difficulty identifying and describing one's emotions and a preference for externally oriented thinking) relates to chronic pain and associated disability. We conducted a systematic review and meta-analysis to summarize individual studies that either assessed alexithymia in individuals with chronic pain vs controls or related alexithymia to pain intensity, physical interference, depression, and anxiety. We searched MEDLINE, Embase, and PsycINFO from inception through June 2017; 77 studies met the criteria (valid assessment of alexithymia in adults or children with any chronic pain condition) and were included in analyses (n = 8019 individuals with chronic pain). ⋯ Secondary meta-analyses of 14 studies that conducted partial correlations that controlled for negative affect-related measures revealed that alexithymia was no longer significantly related to pain intensity or interference. Meta-analysis findings demonstrated that alexithymia is elevated in individuals with chronic pain and related to greater pain intensity and physical interference, although the latter relationships may be accounted for by negative affect. Critical future work is needed that examines alexithymia assessed using non-self-report measures, develops a person-centered perspective on this construct, and identifies how alexithymia is relevant to the assessment and treatment of individuals with chronic pain.
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Neurofibromatosis type 1 (NF1) is the most common of a group of rare diseases known by the term, "Neurofibromatosis," affecting 1 in 3000 to 4000 people. NF1 patients present with, among other disease complications, café au lait patches, skin fold freckling, Lisch nodules, orthopedic complications, cutaneous neurofibromas, malignant peripheral nerve sheath tumors, cognitive impairment, and chronic pain. Although NF1 patients inevitably express pain as a debilitating symptom of the disease, not much is known about its manifestation in the NF1 disease, with most current information coming from sporadic case reports. ⋯ As therapy for NF1 pain remains in various clinical and preclinical stages, we present current treatments available for patients and highlight the importance of future therapeutic development. Equally important, NF1 pain is accompanied by psychological complications in comorbidities with sleep, gastrointestinal complications, and overall quality of life, lending to the importance of investigation into this understudied phenomenon of NF1. In this review, we dissect the presence of pain in NF1 in terms of psychological implication, anatomical presence, and discuss mechanisms underlying the onset and potentiation of NF1 pain to evaluate current therapies and propose implications for treatment of this severely understudied, but prevalent symptom of this rare disease.