[The impact of Alzheimer's disease on the pain processing].

It is well known that patients with Alzheimer's disease report less pain in comparison to their age group. However, little is yet known about the underlying mechanisms causing the decreased pain report. In order to learn more about these mechanisms, experimental studies are indispensable, since only in experimental settings, noxious input and pain experience can be assessed independently. We therefore report on experimental data on pain perception in Alzheimer's disease in this review. The experimental data suggest that the threshold for pain tolerance is markedly increased and the autonomic pain reaction is, at least in part, considerably diminished. On the other hand, pain threshold and pain event-related brain potentials remain largely unchanged. As possible explanations we discuss age-related changes in pain perception and neuroanatomical changes in Alzheimer's disease. Particularly the atrophy of limbic structures may have a modifying impact on the pain experience. We also discuss what influence communicational deficits have on pain report.