Articles: neuralgia.
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Acta Anaesthesiol. Sin. · Sep 1996
Case ReportsEpidural coadministration of ketamine, morphine and bupivacaine attenuates post-herpetic neuralgia--a case report.
The N-methyl-D-aspartate (NMDA) receptor system plays an important role in nociceptive signal modulation in the central nerve system. There is considerable evidence that NMDA receptor antagonists can abolish hypersensitivity of nociceptors in animal models. In this case report, we described a patient who suffered post-herpetic neuralgia with severe pain, allodynia, and hyperesthesia over right side T2 to T8 dermatomes. ⋯ The combination of relatively low doses of morphine, ketamine and bupivacaine epidurally provides effective pain relief in this case. The result strongly suggests a synergy from this combination that warrants a formal study of the dose-response relationship involved in this treatment and the mechanism by which this effect is achieved. This regimen provides a promising treatment for the neuropathic pain with limited side effects.
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The aim of the present study is to monitor the extracellular gamma-aminobutyric acid (GABA) levels in the lumbar dorsal horn of allodynic rats, which respond to spinal cord stimulation (SCS) with a normalization of the tactile withdrawal threshold. In addition, we monitored the GABA levels in nonresponding and sham-stimulated rats. ⋯ Our results indicate that the development of allodynia, a common symptom in neuropathic pain states, may be linked to a decreased spinal release of GABA. We suggest that an SCS-induced release of GABA could be important for the suppression of allodynia observed in rats after SCS. Similar mechanisms could also be involved in the SCS-induced alleviation of pain in patients with peripheral neuropathy.
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Herpes zoster occurs rarely in immunocompetent children and infrequently in immunocompetent young adults. However, its incidence increases with age, particularly after age 50. Reactivation of varicella-zoster virus (VZV) is characterized by a rash and is generally accompanied by considerable pain, dysesthesias, and skin hypersensitivity. ⋯ More than 50% of zoster patients over 60 years old will develop PHN, which may persist for months and even years. Thus, established PHN is difficult to manage, often causing serious morbidity, depression, and high costs in terms of consumption of healthcare resources. Currently, early antiviral treatment with famciclovir has shown promise of reducing the duration of PHN.
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Neuropathic pain in rats is associated with altered nitric oxide synthase activity in neural tissue.
Peripheral nerve injury may lead to a chronic neuropathic pain state that results from an increase in excitability of central neurons. This central sensitization is mediated via an N-methyl-D-aspartic acid (NMDA) receptor and may involve the production of nitric oxide (NO). As NO is suggested to play a role in nociceptive transmission following nerve injury, we examined for altered NO synthase activity at multiple levels of peripheral and spinal neural tissue in a rat model of neuropathic pain. ⋯ An increase in NOS activity in the DRG may be an early mechanism for inducing more central changes. The bilaterally decreased NOS activity in the lumbar spinal cord may be secondary to a negative feedback mechanism resulting from increased NO production in the spinal dorsal root ganglia. Multiple alterations in expression of NOS activity that occur in both peripheral and central processing may play a role in the pain behavior resulting from peripheral nerve injury. (Preliminary results of these studies have been presented in abstract form at the annual meetings of the Society for Neuroscience, 1994, and the American Society of Anesthesiologists, 1994).
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We investigated the analgesic effect of dextromethorphan (DM), a non-selective NMDA receptor antagonist, in 25 patients with postherpetic neuralgia (PHN). We administered DM 45mg.day-1 orally for 14 days and then 90mg.day-1 for next 14 days. ⋯ Side effects with no severe cases occurred in 8 patients (32%) and these were mainly digestive symptoms. We concluded that DM might be useful to treat PHN with allodynia probably due to central sensitization.