Articles: neuralgia.
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J. Auton. Nerv. Syst. · Mar 1997
Skin blood flow abnormalities in a rat model of neuropathic pain: result of decreased sympathetic vasoconstrictor outflow?
Loose ligation of a sciatic nerve in rats provokes signs and symptoms like those observed in human conditions of neuropathic pain. Some of these have been associated with sympathetic dysfunction. Since the skin microcirculation in the rat is strongly influenced by sympathetic tone, abnormalities in skin blood flow may be used as an indirect measure of sympathetic dysfunction. ⋯ As compared to the values obtained before ligation (= 100%): (1) the vasoconstrictor response was impaired (65%, P < 0.01) from day 1 onwards, whereas (2) basal skin blood flow was increased (171%; P < 0.01) from day 3 until day 5, and decreased (51%, P < 0.0001) from day 7 until day 28. At day 28, blockade of impulse propagation in the loosely ligated sciatic nerve (by means of lidocaine) did not increase the lowered level of skin blood flow. These findings suggest that in the chronic construction injury model loose ligation of a sciatic nerve reduces sympathetic vasoconstrictor outflow, which, in turn may induce supersensitivity of skin microvessels to catecholamines.
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Acta Anaesthesiol Scand · Mar 1997
Case ReportsFour years' treatment with ketamine and a trial of dextromethorphan in a patient with severe post-herpetic neuralgia.
N-methyl-D-aspartate (NMDA) receptors are involved in the development of neuropathic pain. Ketamine, a non-competitive NMDA receptor antagonist, has in several case reports given pain relief but efficacy in dosages tolerated in long-term ketamine treatment is unknown. Another substance with an antagonist action at NMDA receptors and which is approved for peroral administration is dextromethorphan. ⋯ We report a patient with severe post-herpetic pain resistant to conventional pain treatment which was treated with ketamine for 4 years with good pain relief. The practical application of long-term treatment in different administration forms of ketamine is described. The patient also responded with pain relief in a double-blind trial with oral dextromethorphan.
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Neuropathic pains arising from peripheral nerve injury can result in increased sensitivity to both noxious and non-noxious stimuli and are accompanied by a number of neuroplastic alterations at the level of the spinal cord including upregulation of neurotransmitters including dynorphin, cholecystokinin and neuropeptide Y. Additionally, such pain states appear to be associated with activation of excitatory amino acid receptors including the N-methyl-D-aspartate (NMDA) receptor. Neuropathic pains have often been classified as 'opioid resistant' in both clinical and laboratory settings. ⋯ Co-administration, however, of i.t. morphine with MK-801, or i.t. antisera to dynorphin A (1-13) given prior to morphine elicited both a full antiallodynic response and a complete block of the tail-flick reflex in nerve-injured animals. These results suggest that tonic activation of NMDA receptors, following peripheral nerve injury, is involved with the attenuation of the effectiveness of spinal morphine in a model of neuropathic pain. Additionally, this tonic NMDA activity may be mediated, in part, by increased levels of endogenous dynorphin associated with peripheral nerve injury.
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Herpes zoster is a common disease primarily affecting the elderly. Although some individuals experience no symptoms beyond the duration of the acute infection, many develop chronic pain [postherpetic neuralgia (PHN)], which is the commonest complication of herpes zoster infection and remains notoriously difficult to treat once established. It may persist until death and has major implications for quality of life and use of healthcare resources. ⋯ In the future, vaccines may have an important place in reducing the incidence of chickenpox in the population or, through the vaccination of middle-aged individuals, in boosting immunity to varicella zoster virus, thus preventing or modifying the replication of the virus from its latent phase that results in herpes zoster. Developments in the understanding of the pathophysiology of PHN indicate possible directions for improved drug management of established PHN, although no evidence yet exists for efficacy of the drugs concerned. Such agents include new generation anticonvulsants and N-methyl-D-aspartate antagonists.
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Clin Neurol Neurosurg · Feb 1997
Case ReportsCoiling of the vertebral artery presenting with neuralgic pain.
A rare case of radicular pain in the arm due to compression of the C6 nerve root by coiling of the vertebral artery is reported; the diagnosis was confirmed by computed tomography (CT), magnetic resonance (MR) angiography and echocolordoppler. Although the enlargement of an intervertebral foramen by a tortuous vertebral artery has been described previously, the occurrence of radicular pain is exceptional. Magnetic resonance imaging (MRI), MR angiography and echocolordoppler allow to differentiate foraminal enlargement due to vascular anomalies of the vertebral artery from that more commonly due to tumor compression, mainly from neurinoma. Surgical decompression may be considered in symptomatic cases.