Metabolism: clinical and experimental
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Review
Fibromyalgia and the complex regional pain syndrome: similarities in pathophysiology and treatment.
Although the pain of fibromyalgia usually is not preceded by an injury to the involved tissue, whereas that of the complex regional pain syndrome usually starts at a site of prior trauma or surgery, both disorders may share a common mechanism-pathologic sensitization of brain mechanisms that integrate nociceptive signals-and both apparently respond to treatment with ketamine, an anesthetic-analgesic agent whose actions include blockade of N-methyl-D-aspartate receptors. Ketamine's widespread illegal use as a recreational agent probably precludes developing it as a general treatment of centrally mediated pain disorders; however, its efficacy suggests that related, to-be-discovered agents could be useful.
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Intractable pain may require neurosurgical intervention. This review provides a critical update of neurosurgical techniques available to treat this condition. Neurosurgery can affect pain's pathways from the receptor up to the "centers" of its reception and perception, either by destroying or by stimulating them. ⋯ The indications for undertaking an ablative vs a neurostimulative procedure, as well as selection of the anatomical target, depend largely on whether pain is nociceptive or neuropathic, given that most of these indications overlap to some extent. In addition, because the published outcomes are not based on universal criteria, it is difficult for the attending physician to select the type of procedure most suitable to the pain problem. This brief review surveys the various neurosurgical procedures together with their corresponding indications in the hope that the information provided will help practitioners choose (1) the type of neurosurgical therapy most appropriate to their patients' needs and (2) the neurosurgical group best equipped to implement that choice.
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During 2007, 11.7 million US men and women of all ages suffered from some form of invasive cancer. During their illness, at least 70% (8.2 million) will experience pain sufficiently severe to require chronic opioid treatment. Cancer-induced pain is usually described under 3 headings: acute pain, chronic pain, and breakthrough pain. ⋯ The existence of a number of opioid receptor subtypes, each with its own repertoire of responses, has given rise to the hope (as yet unrealized) that an opioid can be found (or engineered) that will selectively produce adequate analgesia and sedation without, at the same time, causing unwanted adverse effects. Furthermore, suitable neurostimulatory or neuroinhibitive methods involving the central nervous system are being sought that can amplify the analgesic action of opioids. In the search for antinociceptive agents as efficacious as currently available opioids, but without their troublesome adverse effects, the endogenous opioids, such as the endomorphins, are being examined as offering possible solutions to the adverse effect problem.
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Arthritic pain and disability are at or near the top of the list of reasons adult patients seek medical attention. At least 47.8 million US residents have arthritis. In Europe, the magnitude of the problem is similar, affecting 8 million in the United Kingdom and 108 million across the continent. ⋯ Analysis of joint fluid is mandatory to rule out septic arthritis, which can rapidly become lethal. Because of its special ability to identify and quantitate urate deposits in peripheral tissues, dual-energy computed tomography should prove valuable in the differential diagnosis of gout. Gout mimics a variety of illnesses; for example, spinal gout may masquerade as metastatic cancer, epidural abscess, and nerve compression syndrome.
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Therapeutic management of chronic pain has not been widely successful owing to a lack of understanding of factors that initiate and maintain the chronic pain condition. Efforts to delineate the mechanisms underlying pain long have focused on neuronal elements of pain pathways, and both opiate- and non-opiate-based therapeutics are thought largely to target neurons. Abnormal neuronal activity at the level of spinal cord "pain centers" in the dorsal horn leads to hypersensitivity or a hyperalgesic response subsequent to the initial painful stimulus. ⋯ Recent evidence even suggests that opioid tolerance and withdrawal hyperalgesia may be initiated and maintained via actions of microglia and astroglia. Together, these recent findings suggest that glia will serve as novel therapeutic targets for the treatment of chronic pain. To fully exploit glia as novel therapeutic targets will require a greater understanding of glial biology, as well as the identification of agents able to control the glial reactions involved in chronic pain, without interfering with beneficial glial functions.