Der Schmerz
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Anxieties and emotional disturbances associated with cancer often cause pain therapy to be unsuccessful. When psychological support is required it is mostly aimed at supporting cancer patients in attempts to cope with their disease so as to improve the efficiency of pain therapy. In our study we focused on the barriers to cancer pain management that lie in patient's beliefs about pain and their coping behavior. ⋯ Those patients who used cognitive coping strategies and did not communicate often received inadequate pain therapy. Those who talked about pain but did not use any other coping strategies were mostly well treated. We have designed a brochure, "What tumour patients should know about pain" directly oriented on the above pain beliefs; this is now being evaluated with reference to its educational effect.
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Cerebral potentials evoked by cutaneous heat stimuli from an infrared laser (LEP) enable overall controls of thin fibre function and anterolateral tract projection, which is of special meaning in the diagnosis of normal and disturbed pain pathways. Owing to the long-wave radiation, the laser energy is completely absorbed within the most superficial skin layers only a few 100 mum in depth and activates only the most superficial afferents, i.e. the thermo- and nociceptive A, delta and C fibres. According to the particular fibre spectrum activated, a single laser stimulus elicits a typical double pain sensation: the first pain appears with a mean reaction time of approximately 400 ms and is described as a sharp and stinging, well-localizable pinprick sensation; this pain is induced by A delta fibre activity with a mean conduction velocity of 14 m/s. ⋯ Both sensations and both evoked potentials can emerge to very different degrees in healthy subjects and in patients with neurological diseases. The diagnostic practicability of LEP is individuals illustrated with reference to patients with syringomyelia suffering from a dissociated sensory loss in cutaneous sensibility. In contrast to conventional electrical nerve stimuli, the laser stimuli allow monitoring of disturbances in the protopathic system projected to the anterolateral columns.
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In the present article aspects of reflex sympathetic dystrophy (RSD) and sympathetically maintained pain (SMP) are discussed from the point of view of a basic scientist. The main focus is on the sympathetic nervous system. ⋯ Finally, clinical observations are discussed that seem to bear little or no relation to the models that are available. The general synopsis puts the problem into a wider context.
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The gate-control theory of pain, as originally proposed by Melzack and Wall [8], is nothing but a hypothesis concerning the spinal processing of non-noxious and noxious afferent information. Its basic tenant is that the P cells (projecting neurons) convey noxious information to supraspinal pain systems only after a critical threshold of excitation has been passed, and that access to the P cells is controlled by the SG cells (cells of the substantia gelatinosa Rolandi) or, in other words, the SG cells act as the gate. Since the primary afferent fibres have monosynaptic connections with the P cells the gate can only operate-and this is the critical point of the whole hypothesis-via presynaptic inhibition exerted by axoaxonic contacts on these afferents (Fig. 1). ⋯ As a consequence, Melzack and Wall [9] have now modified their hypothesis considerably. Its present formulation is not much more than a very general statement to the effect that all kinds of afferent input, including noxious input, is under the modulating influence of various mechanisms operating both at the spinal level and from supraspinal (descending) structures. No implications for therapy can be derived directly from such an undefined, in many ways trivial, assumption.