Influence of dementia on multiple components of pain.

Experimental findings on the influence of dementia on pain have so far been conflicting. There is evidence for a decreased, an unchanged and even for an increased pain processing in patients with dementia. The present study was conducted to add on the description of the impact of dementia on pain processing by assessing multiple components of pain (subjective, facial, motor reflex and autonomic responses) in parallel in one group of demented patients. Subjective (rating scale), facial (FACS), motor reflex (NFR) and autonomic (SSR, heart rate) responses to noxious electrical stimulation were assessed in 35 demented patients and 46 aged-matched healthy controls. Stimulus intensities were tailored to the individual NFR threshold. Demented patients rated the stimuli similarly painful as healthy controls did; however, the ability to provide these self-report ratings was markedly diminished in demented patients. Facial responses to noxious stimulation were significantly increased in demented patients. In line with this the NFR threshold was markedly decreased in the patient group. Autonomic responses on the other hand tended to be diminished in patients with dementia. In conclusion, dementia tends to affect different pain components in different ways. Therefore, the assessment of pain in patients with dementia should be based on the measurement of multiple components of pain and not solely on subjective self-report ratings. Furthermore, taking into account our findings on facial responses and the NFR, we think that there is sufficient evidence suggesting a rather intensified processing of noxious stimulation in this patient group.

The facial expression of pain in patients with dementia.

The facial expression of pain has emerged as an important pain indicator in demented patients, who have difficulties in providing self-report ratings. In a few clinical studies an increase of facial responses to pain was observed in demented patients compared to healthy controls. However, it had to be shown that this increase can be verified when using experimental methods, which also allows for testing whether the facial responses in demented patients are still typical for pain. We investigated facial responses in 42 demented patients and 54 aged-matched healthy controls to mechanically induced pain of various intensities. The face of the subject was videotaped during pressure stimulation and was later analysed using the Facial Action Coding System. Besides facial responses we also assessed self-report ratings. Comparable to previous findings, we found that facial responses to noxious stimulation were significantly increased in demented patients compared to healthy controls. This increase was mainly due to an increase of pain-indicative facial responses in demented patients. Moreover, facial responses were closely related to the intensity of stimulation, especially in demented patients. Regarding self-report ratings, we found no significant group differences; however, the capacity to provide these self-report ratings was diminished in demented patients. The preserved pain typicalness of facial responses to noxious stimulation suggests that pain is reflected as validly in the facial responses of demented patients as it is in healthy individuals. Therefore, the facial expression of pain has the potential to serve as an alternative pain assessment tool in demented patients, even in patients who are verbally compromised.