Articles: neuralgia.
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Neuroscience letters · May 1998
Motor denervation induces altered muscle fibre type densities and atrophy in a rat model of neuropathic pain.
Loose ligation of a sciatic nerve in rats (chronic constriction injury; CCI) provokes sensory, autonomic, and motor disturbances like those observed in humans with partial peripheral nerve injury. So far, it is unknown whether these motor disturbances result from (mechanical) allodynia or from damage to the motor neuron. These considerations prompted us to assess, in CCI rats, the density of motor axons in both the ligated sciatic nerve and the ipsilateral femoral nerve. ⋯ In line with these findings, we observed altered fibre type densities in muscle tissue innervated by the ligated sciatic nerve as well as the non-ligated femoral nerve indicative of motor denervation rather than hypokinesia. The findings of this study suggest that the motor disorder induced by partial nerve injury involves degeneration of motor nerve fibres not only within the primarily affected nerve but also within adjacent large peripheral nerves. This spread outside the territory of the primarily affected nerve suggests degeneration of motor neurons at the level of the central nervous system.
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Clinical Trial
Neural activation during acute capsaicin-evoked pain and allodynia assessed with PET.
The PET H2 15O-bolus method was used to image regional brain activity in normal human subjects during intense pain induced by intradermal injection of capsaicin and during post-capsaicin mechanical allodynia (the perception of pain from a normally non-painful stimulus). Images of regional cerebral blood flow were acquired during six conditions: (i) rest; (ii) light brushing of the forearm; (iii) forearm intradermal injection of capsaicin, (iv) and (v) the waning phases of capsaicin pain; and (vi) allodynia. Allodynia was produced by light brushing adjacent to the capsaicin injection site after ongoing pain from the capsaicin injection had completely subsided. ⋯ The cerebellar vermis was strongly activated by capsaicin, whereas light brush and experimental allodynia produced little or no activation, suggesting a selective association with C-fibre stimulation and nociceptive second-order spinal neurons. The experimental allodynia activated a network that partially overlapped those activated by both pain and light brush alone. Unlike capsaicin-induced pain, allodynia was characterized by bilateral activation of inferior prefrontal cortex, suggesting that prefrontal responses to pain are context dependent.
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A local inflammatory reaction may play an important role in the development of neuropathic pain following peripheral nerve injury. One important participant in the inflammatory response of injured peripheral nerve may be nitric oxide (NO). In this work, we examined physiological and morphological evidence for nitric oxide synthase (NOS) activation in the chronic constriction injury model of neuropathic pain in rats. ⋯ NOS-like immunoreactivity of the neuronal and endothelial isoforms was identified just proximal to the constriction at 48 h. iNOS-like immunoreactivity was observed at 7 and 14 days at the constriction and distal sites, respectively. This work provides evidence for local NOS expression and NO action in the chronic constriction injury model of neuropathic pain. NO has local physiological actions that include vasodilatation of microvessels and that may be important in the development of pain sensitivity.
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J Assoc Physicians India · Apr 1998
Comparative Study Clinical TrialHerpes zoster and post-herpetic neuralgia--a clinical trial of aspirin in chloroform for anodyne.
Pain associated with Herpes Zoster (HZ) and Post-herpetic Neuralgia (PHN) has been a challenging task to manage with ease. Topical aspirin dissolved in chloroform is an effective means of reducing pain due to HZ and PHN in most patients. The locus of pain origin and analgesia induced by topical aspirin is supposed to be at cutaneous free nerve ending pain receptors. ⋯ Most of the patients experienced relief of pain within 1-5 minutes after the aspirin-chloroform application. Maximum relief was achieved in about 30-40 minutes and persisted for 5-6 hrs. In the beginning 3-4 applications were required but frequency decreased gradually as the pain abated.
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This report details the course of a 77-year-old patient suffering mild pain from operated tongue cancer and excruciating, intractable pain from thoracic (T6-T8) post-herpetic neuralgia (PHN), The mouth pain was treated with nonopioid analgesics, as the patient had personal objections to opioid treatment. All the components of the pain from his PHN (continuous burning pain, intermittent lancinating stabbing pain, and tactile allodynia) were successfully treated with an Intrathecal Infusion of buprenorphine (0.03 mg/ml) and bupivacaine (4.75 mg/ml) administered via an externalized intrathecal catheter with the tip located at T9-T10 intervertebral disc. The treatment started three months after the appearance of the herpetic eruption and lasted 294 days until the patient died of malnutrition and the progression of his tongue cancer. ⋯ The patient could ambulate without support while on 90-100 mg/day of intrathecal bupivacaine. During a series of high-pressure oxygen treatments in a pressure chamber to treat an infection at the site of his tumor, the intrathecal infusion was interrupted. Thus, repeated observation of the intervals of severe pain and of analgesia were possible.