[Pain and dementia].

Dementia and pain are both common in the elderly and then frequently associated. The literature review shows that pain in dementia is underdiagnosed and consequently undertreated. This can be linked to: 1) the difficulty of pain assessment in patients with cognitive disorders and altered communication skills; 2) changes of pain processing and especially in the motivational-affective domain; 3) modified efficacy of analgesic drugs. This has been documented in Alzheimer's disease but remains to be investigated in the other types of dementia in order that all patients can be treated whatever their diagnosis, illness duration and type of pain (acute versus chronic).