The journal of pain : official journal of the American Pain Society
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Transcutaneous electric nerve stimulation (TENS) is a noninvasive treatment used in physiotherapy practice to promote analgesia in acute and chronic inflammatory conditions. The aim of the present study was to investigate the action mechanism of TENS at high (HF: 130 Hz) and low (LF: 10 Hz) frequencies in an inflammation model produced by the injection of carrageenan in rat paws (Cg; 250 microg). After carrageenan administration (0 time), either HF or LF TENS was applied to the inflamed paw of rats for 20 minutes, and hyperalgesia was assessed hourly using the modified Randall-Selitto method (1957). HF and LF TENS inhibited the carrageenan-induced hyperalgesia by 100%. Pretreatment of animals with intraplantar naltrexone (Nx; 50 microg) reversed the analgesic effect of the LF TENS but did not alter the effect of HF TENS. The application of HF and LF TENS to the contralateral paw reversed the hyperalgesia of the inflamed paw similar to that observed when TENS was applied to the inflamed paw. However, LF TENS presented a longer-lasting analgesic effect than HF TENS. Our data demonstrate that HF and LF TENS induced antihyperalgesia. We also report that the antihyperalgesia provoked by LF TENS is partially due to the local release of endogenous opioids. ⋯ This study offers important information about physiotherapy practices aimed at pain relieving. TENS is a noninvasive treatment that promotes analgesia in acute and chronic inflammatory conditions. Scientists, patients, and the general population may benefit from this knowledge.
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A randomized, double-blind, placebo-controlled trial was conducted to determine the benefit of nabilone in pain management and quality of life improvement in 40 patients with fibromyalgia. After a baseline assessment, subjects were titrated up on nabilone, from 0.5 mg PO at bedtime to 1 mg BID over 4 weeks or received a corresponding placebo. At the 2- and 4-week visits, the primary outcome measure, visual analog scale (VAS) for pain, and the secondary outcome measures, number of tender points, the average tender point pain threshold, and the Fibromyalgia Impact Questionnaire (FIQ), were evaluated. After a 4-week washout period, subjects returned for reassessment of the outcome measures. There were no significant differences in population demographics between groups at baseline. There were significant decreases in the VAS (-2.04, P < .02), FIQ (-12.07, P < .02), and anxiety (-1.67, P < .02) in the nabilone treated group at 4 weeks. There were no significant improvements in the placebo group. The treatment group experienced more side effects per person at 2 and 4 weeks (1.58, P < .02 and 1.54, P < .05), respectively. Nabilone appears to be a beneficial, well-tolerated treatment option for fibromyalgia patients, with significant benefits in pain relief and functional improvement. ⋯ To our knowledge, this is the first randomized, controlled trial to assess the benefit of nabilone, a synthetic cannabinoid, on pain reduction and quality of life improvement in patients with fibromyalgia. As nabilone improved symptoms and was well-tolerated, it may be a useful adjunct for pain management in fibromyalgia.
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Review
Pain and stress in a systems perspective: reciprocal neural, endocrine, and immune interactions.
This paper advances a psychophysiological systems view of pain in which physical injury, or wounding, generates a complex stress response that extends beyond the nervous system and contributes to the experience of pain. Through a common chemical language comprising neurotransmitters, peptides, endocannabinoids, cytokines, and hormones, an ensemble of interdependent nervous, endocrine, and immune processes operates in concert to cope with the injury. These processes act as a single agent and comprise a supersystem. Acute pain in its multiple dimensions, and the related symptoms that commonly occur with it, are products of the supersystem. Chronic pain can develop as a result of unusual stress. Social stressors can compound the stress resulting from a wound or act alone to dysregulate the supersystem. When the supersystem suffers dysregulation, health, function, and sense of well-being suffer. Some chronic pain conditions are the product of supersystem dysregulation. Individuals vary and are vulnerable to dysregulation and dysfunction in particular organ systems due to the unique interactions of genetic, epigenetic and environmental factors, as well as the past experiences that characterize each person. ⋯ Acute tissue injury activates an ensemble of interdependent nervous, endocrine, and immune processes that operate in concert and comprise a supersystem. Some chronic pain conditions result from supersystem dysregulation. Individuals vary and are vulnerable to dysregulation due to the unique interactions of genetic, epigenetic, and environmental factors and past experiences that characterize each person. This perspective can potentially assist clinicians in assessing and managing chronic pain patients.
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The present study is an in vivo investigation into the time course of inflammation-induced axonal mechanical sensitivity (AMS) in intact C-fiber axons. After induction of a localized neuritis in the rat sciatic nerve, AMS developed in C-fiber axons at 1 (18.2%) and 4 weeks (11.6%). By 8 weeks, AMS was virtually absent (2.1%). AMS was also tested in intact L5 neurons after L4 spinal nerve transection, which induces a diffuse inflammation within the sciatic nerve. At 1 week, AMS developed in 10% of neurons. No AMS was observed in unoperated animals. The localized neuritis also caused changes in L5 dorsal root conduction velocities (CVs). CVs decreased at 1 week (-7.7%) and 4 weeks (-17.6%) and returned to normal by 8 weeks. L4 transection similarly reduced CVs (-13.7%) of L5 dorsal root axons. There were no significant changes among any groups in the proportion or rate of ongoing activity. These results demonstrate that the axonal changes due to neuritis are not permanent. Therefore, in patients with persistent movement-induced radiating limb pain with few clinically apparent signs of nerve damage, there may be a persisting inflammatory lesion affecting the nerve. ⋯ Nerve inflammation, or neuritis, causes axonal mechanical sensitivity, which is the neural substrate for radiating limb pain induced by movement. This study examined the time course of induced axonal mechanical sensitivity and conduction velocity changes in intact C-fiber axons after nerve inflammation. The results suggest that treatment to reduce nerve inflammation may be beneficial to patients with radiating pain.
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A consensus meeting was convened by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) to provide recommendations for interpreting clinical importance of treatment outcomes in clinical trials of the efficacy and effectiveness of chronic pain treatments. A group of 40 participants from universities, governmental agencies, a patient self-help organization, and the pharmaceutical industry considered methodologic issues and research results relevant to determining the clinical importance of changes in the specific outcome measures previously recommended by IMMPACT for 4 core chronic pain outcome domains: (1) Pain intensity, assessed by a 0 to 10 numerical rating scale; (2) physical functioning, assessed by the Multidimensional Pain Inventory and Brief Pain Inventory interference scales; (3) emotional functioning, assessed by the Beck Depression Inventory and Profile of Mood States; and (4) participant ratings of overall improvement, assessed by the Patient Global Impression of Change scale. It is recommended that 2 or more different methods be used to evaluate the clinical importance of improvement or worsening for chronic pain clinical trial outcome measures. Provisional benchmarks for identifying clinically important changes in specific outcome measures that can be used for outcome studies of treatments for chronic pain are proposed. ⋯ Systematically collecting and reporting the recommended information needed to evaluate the clinical importance of treatment outcomes of chronic pain clinical trials will allow additional validation of proposed benchmarks and provide more meaningful comparisons of chronic pain treatments.