Facial Pain Expression in Dementia: A Review of the Experimental and Clinical Evidence

Abstract

The analysis of the facial expression of pain promises to be one of the most sensitive tools for the detection of pain in patients with moderate to severe forms of dementia, who can no longer self-report pain. Fine-grain analysis using the Facial Action Coding System (FACS) is possible in research but not feasible for clinical use at the moment because it is too time and effort consuming. Studies using the FACS showed either enhanced facial responses or no alterations of facial activity during pain in patients with cognitive impairment. Pain assessment in the clinical context relies strongly on the use of observational scales when self-report has become invalid. All of the established scales include items describing facial responses to pain. Despite this agreement, the content of these face items is very different, ranging from anatomically-based descriptions to inference of internal states. Recent studies let the anatomical orientation appear more promising. Automated video systems for the detection of pain in patients with dementia may lead to ground-breaking improvements of pain care in the future.

Keywords: Alzheimer's disease; Dementia; facial action coding system; facial expression; observational scales; pain.