Der Schmerz
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Functional neuroimaging methods such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) provide fascinating insights into the cerebral processing of pain. Neuroimaging studies have shown that no clearly defined "pain centre" exists. ⋯ Sophisticated study designs nowadays permit the characterisation of different components of pain processing. In this review, we summarise neuroimaging studies, which contributed to the characterisation of these different aspects of cerebral pain processing, such as somatosensory (discrimination of different stimulus modalities, noxious vs non-noxious, summation), emotional, cognitive (attention, anticipation, distraction), vegetative (homeostasis) and motor aspects.
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Neuroplasticity is the ability of the central nervous system to induce functional and microstructural changes in order to adapt to a new environment. However, so-called maladaptive neuroplasticity can also bring disadvantages, such as reduced inhibition of input signals, one of the suspected causes of chronic pain. With the method of repetitive transcranial magnetic stimulation (rTMS) a technique has been developed that makes it possible to study cortical excitability changes in the human brain non-invasively over a long time. ⋯ In phase II trials its efficacy has been demonstrated. Ongoing studies are focusing on management of the placebo effect; however, it is easier to control this effect in tDCS compared to rTMS. Phase III trials are currently in preparation.
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Nociceptive information processing and related pain perception are subject to substantial pro- and antinociceptive modulation. Research on the involved circuitry and the implemented mechanisms is a major focus of contemporary neuroscientific studies in the field of pain and will provide new insights into the prevention and treatment of chronic pain states. Placebo analgesia is a powerful clinical example of the cognitive modulation of pain perception. ⋯ This cognitively triggered endogenous modulation of pain involves, at least in part, the endogenous opioid system. Most recently, functional magnetic resonance imaging data of the human spinal cord revealed that these mechanisms involve the inhibition of nociceptive processing at the level of the dorsal horn of the spinal cord. Here we discuss recent advances in pain imaging research focusing on cognitively triggered endogenous pain control mechanisms and respective implications for future research strategies.
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Chronic pain patients using opioids frequently suffer from constipation which compromises well-being. Such an opioid-induced gastro-intestinal complication can occur regularly in patients in palliative care as well as in analgesic sedated intensive care patients or during prolonged perioperative pain therapy. Discomfort and distress in the affected patients can be so severely pronounced that they would rather suffer from the pain than from the side effect of constipation. ⋯ An interference with central analgesia does not occur as the molecules cannot pass the blood-brain barrier due to their charged states. A reduction of opioid therapy or the development of withdrawal symptoms can be avoided. Studies have shown that methylnaltrexone is not only safe and efficient for chronically constipated palliative care patients but offers promising therapeutic options for further patient collectives.
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Multimodal pain therapy describes an integrated multidisciplinary treatment in small groups with a closely coordinated therapeutical approach. Somatic and psychotherapeutic procedures cooperate with physical and psychological training programs. For chronic pain syndromes with complex somatic, psychological and social consequences, a therapeutic intensity of at least 100 hours is recommended. ⋯ Medical indications are given for patients with chronic pain syndromes, but also if there is an elevated risk of chronic pain in the early stadium of the disease and aiming at delaying the process of chronification. Relative contraindications are a lack of motivation for behavioural change, severe mental disorders or psychopathologies and addiction problems. The availability of multimodal pain treatment centers in Germany is currently insufficient.