The relation of pain responses and brain function in a sample of patients with Alzheimer's disease

Pain in patients with Alzheimer's disease is often underassessed, with many patients' pain conditions remaining undiagnosed. It is postulated that this is due to communication deficits that occur as a result of the dementing process. Pain is therefore often undertreated and undermanaged. More reflexive responses to pain (e.g., facial responses) become increasingly important for pain assessment among patients with Alzheimer's disease as self-report becomes progressively more unreliable (due to cognitive declines). In this study the Facial Action Coding System (FACS; Ekman & Friesen, 1978) was used to identify reflexive facial responses to specifically determined noxious stimulation at varying levels of intensity for two different types of stimulation (i.e., electrical shock and mechanical pressure stimulation). This is the first study of seniors with (N=27) and without dementia (N=36) that investigated the ability of FACS to differentiate among different levels of precisely measured painful stimulation. Moreover, the relationship between the FACS, self-report of affective pain and fMRI activation was investigated. Consistent with previous research, we did not find any group differences in pain threshold (i.e., Alzheimer's Disease vs. age-matched control group). Additionally, the FACS intensity index correlated significantly with fMRI activation in the medial temporal lobe whereas self-report did not relate to fMRI activation. The implications of these findings are discussed. Results show that, as hypothesized, the FACS can be used effectively for pain assessment at conservative levels of pain, regardless of the presence of Alzheimer's disease.