Pain
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The aim of the present study was to investigate the role of primary afferent fibres with polymodal nociceptors in the various pain symptoms and signs associated with post-herpetic neuralgia (PHN). Forty-four patients with PHN affecting thoracic dermatomes were examined clinically for evidence of sensory disturbance to touch and pinprick and compared to 14 normal subjects and 9 subjects with evidence of past herpes zoster infection but no pain. ⋯ The 2 groups with allodynia had significantly decreased neurogenic flare responses compared to PHN subjects without allodynia and the 2 control groups. These results suggest that allodynia in patients with post-herpetic neuralgia may be a consequence of disrupted function of primary afferent fibres.
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We present a revised taxonomic system for disorders previously called reflex sympathetic dystrophy (RSD) and causalgia. The system resulted from a special consensus conference that was convened on this topic and is based upon the patient's history, presenting symptoms, and findings at the time of diagnosis. The disorders are grouped under the umbrella term CRPS: complex regional pain syndrome. ⋯ Two types of CRPS have been recognized: type I, corresponds to RSD and occurs without a definable nerve lesion, and type II, formerly called causalgia refers to cases where a definable nerve lesion is present. The term sympathetically maintained pain (SMP) was also evaluated and considered to be a variable phenomenon associated with a variety of disorders, including CRPS types I and II. These revised categories have been included in the 2nd edition of the IASP Classification of Chronic Pain Syndromes.
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We have tested the effects of cutaneous application of noradrenaline in 35 patients presenting with neuropathic pain. Depending on the outcome of sympatholytic interventions the patients were considered to have sympathetically maintained pain (SMP; n = 25) or sympathetically independent pain (SIP; n = 10). Iontophoretic application or cutaneous injection of noradrenaline into symptomatic skin aggravated pain and mechanical or thermal hyperalgesia in 7/25 SMP patients. ⋯ None of these 4 and none of the 7 initially noradrenaline-unresponsive patients experienced pain to the noradrenaline challenge at follow-up. Thus, cutaneous noradrenaline application can aggravate the pain in some, but not all SMP patients. THe abnormal noradrenaline reaction can change over time as can the pain relieving effects of sympatholytic therapy.
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The present study describes the development of the Chronic Pain Self-Efficacy Scale (CPSS), a 22-item questionnaire designed to measure chronic pain patients' perceived self-efficacy to cope with the consequences of chronic pain. The CPSS and other measures of psychosocial functioning were administered to 141 consecutive patients who were referred to an outpatient multidisciplinary pain treatment program. An exploratory factor analysis of the CPSS responses identified 3 factors: self-efficacy for pain management (PSE), self-efficacy for coping with symptoms (CSE), and self-efficacy for physical function (FSE). ⋯ The subscale scores derived from the factor analysis were significantly correlated with measures of depression, hopelessness, somatic preoccupation, and adaptation to the chronic pain experience. Multiple regression analyses provided further support for the concurrent and construct validity of the CPSS. The scale may aid in the evaluation of the self-efficacy beliefs of chronic pain patients.
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The antinociceptive efficacy of different opioid-receptor agonists following their intrathecal (i.t.) administration was examined in awake, unanesthetized rats in a model of visceral pain. Cumulative i.t. doses of the mu-preferring opioid-receptor agonist morphine produced dose-dependent attenuation of the change (increase) in mean arterial pressure (delta MAP) and elevation of the visceromotor threshold to colorectal distension (CRD). Similar dose-dependent antinociceptive effects were produced after i.t. administration of the mu opioid-receptor-selective agonist DAMPGO. ⋯ The kappa opioid-receptor-selective agonist U 50488H was without antinociceptive efficacy after i.t. administration, but did attenuate responses to CRD after systemic administration. The antinociceptive effects produced by morphine and DAMPGO were antagonized by i.t. pretreatment with naloxone and the effects produced by DPDPE were antagonized by i.t. pretreatment with the delta opioid-receptor-selective antagonist naltrindole. These data indicate that local mu and delta, but not kappa, opioid receptors can modulate visceral nociceptive transmission in the spinal cord.