Pain
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The formalin test in mice is a valid and reliable model of nociception and is sensitive for various classes of analgesic drugs. The noxious stimulus is an injection of dilute formalin (1% in saline) under the skin of the dorsal surface of the right hindpaw. The response is the amount of time the animals spend licking the injected paw. ⋯ It is suggested that the early phase is due to a direct effect on nociceptors and that prostaglandins do not play an important role during this phase. The late phase seems to be an inflammatory response with inflammatory pain that can be inhibited by anti-inflammatory drugs. ASA and paracetamol seem to have actions independent of their inhibition of prostaglandin synthesis and they also have effects on non-inflammatory pain.
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Pressure threshold is the minimal pressure (force) which induces pain. The pressure threshold meter (PTM) is a force gauge with a rubber disc of 1 cm2 surface. The instrument has been proven to be useful in clinical practice for quantification of deep muscle tenderness. ⋯ Results serve as a reference for clinical diagnosis of abnormal tenderness and for documentation of treatment results. The sensitivity of individual muscles varies. Therefore the results presented should be kept in mind when diagnosis of pathological tenderness by palpation is attempted.
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The heat beam dolorimeter (HBD) was developed to evaluate cutaneous pain thresholds in humans. In the present study, the hypothesis that a patient's underlying pain status affects his pain tolerance to an incident HBD stimulus was tested. Twenty-seven chronic pain patients with a variety of clinical problems unresponsive to conventional algological therapy were scheduled for neurosurgical procedures. ⋯ Twenty-four of the 27 patients reported significant pain relief following surgery. Our results show that, in chronic pain patients, endogenous pain significantly affected incident pain perception in the HBD test when compared with the responses of normal pain-free volunteers. Consequently, HBD may be useful in objectively assessing chronic pain and its relief by neurosurgical procedures.
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In sciatalgic patients and before any treatment, the goal of this work was to compare the amplitude of the late component (N150-P220) of the brain evoked potential (BEP) between resting pain-free conditions and a neurological induced pain produced by the Lasègue manoeuvre. The study was carried out with 8 inpatients affected with a unilateral sciatica resulting from an X-ray identified dorsal root compression from discal origin. The sural nerve was electrically stimulated at the ankle level while BEPs were recorded monopolarly from the vertex. ⋯ Results show that the Lasègue manoeuvre performed on the affected side induced a significant increase in the amplitude of N150-P220; performed on the normal side, this same manoeuvre resulted in a significant decrease of the N150-P220 amplitude. These variations were observed whatever was the side (normal or affected) under sural nerve stimulation. The possible neural mechanisms of these changes and clinical implications of these data are then discussed.
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We applied calcitonin in a single-shot treatment to 10 patients with persistent or acute phantom limb pain. Nine patients responded immediately and noted a clear analgesic effect. In contrast a group of non-phantom pain patients of heterogeneous composition did not respond at all, except 1 patient with chronic stump pain. We believe that this could be an exciting new approach to the treatment of phantom limb pain.