Der Orthopäde
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Review
[Visualisation of phantom- and backpain using imaging techniques. Implication for treatment].
If patients with chronic low back pain are stimulated in the painful region, an expanded representation of the back in the primary somatosensory cortex becomes visible that increases with chronicity. This "pain memory" might play an important role in the chronicity process. In patients with phantom limb pain, e.g. subsequent to the amputation of an arm or leg, a shift in the representation of neighboring areas into the deafferented area in primary somatosensory cortex has been observed. ⋯ The modulation of plasticity and phantom limb pain by anesthesiological manipulation, the use of NMDA receptor antagonists and opioids is presented. Behaviorally relevant stimulation, e.g. by the use of a myoelectric prosthesis or sensory discrimination training can also influence the cortical somatosensory pain memory. More recent studies focus also on brain areas such as the cingulate gyrus believed to be involved in the affective processing of pain.
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The present article presents an overview of neurophysiological and neuroanatomical mechanisms that may be involved in the transition from acute to chronic muscle pain. The report is based on data that were obtained in studies on anaesthetised rats in which an acute or chronic myositis was induced experimentally. The inflamed muscle tissue was evaluated using histochemical and immunohistochemical methods, and the impulse activity of single muscle nociceptors or dorsal horn neurones was recorded in electrophysiological experiments in vivo. ⋯ Chronic spontaneous muscle pain, however, appears to be due to a lack of NO. The final step in the transition from acute to chronic pain involves structural changes that perpetuate the functional changes. In rat experiments employing nerve lesions or muscle inflammation, such morphological changes become apparent within a few hours after the lesion.