Facial motor abnormalities in individuals at risk for psychotic onset

Abstract

Background: Earlier studies have indicated that individuals at risk for psychotic onset have facial motor abnormalities. Moreover, more severe facial motor abnormalities predict a higher probability of subsequent transition to full-blown psychotic diseases in at-risk individuals. It is of clinical value to explore existence of other motor abnormalities in at-risk individuals because results will greatly benefit future studies identifying reliable risk factors of psychotic onset. In drug-naïve first-episode schizophrenia patients, bradykinesia and dyskinesia are common motor abnormalities. However, earlier studies examining facial motor abnormalities in at-risk individuals mainly focused on dyskinesia. Little has been known about whether both facial bradykinesia and facial dyskinesia exist in at-risk individuals. Therefore, this study was to examine whether at-risk individuals had facial bradykinesia and facial dyskinesia. Measuring facial motor abnormalities in at-risk individuals is challenging because their facial motor impairments are subtle and easily missed if observation-based measures are used. In order to overcome this measuring challenge and be able to sensitively and objectively measure facial bradykinesia and dyskinesia in at-risk individuals, this study used motion analysis technology. Methods: A total of 13 at-risk individuals and 13 healthy controls were recruited in this study. A score of or larger than 17 in Schizotypal Personality Questionnaire-Brief was used to identify at-risk individuals from the community. The VICON motion capture system was used to capture three-dimensional trajectory data of the reflective marker attached to the medial side of the left eyebrow of the participant when s/he showed facial expression of surprise to the maximal level. On the basis of captured data, the normalized movement time (nMT) and the normalized number of movement units (nNMU) were calculated to reflect bradykinesia and dyskinesia respectively. The independent sample t test was used to compare nMT and nNMU between at-risk individuals and healthy controls. Results: At-risk individuals (age: 20.46±3.09 years; 5 men and 8 women) and healthy controls (age: 20.06±1.80 years; 5 men and 8 women) were matched by age (t=-.41, p=.687) and sex. Significant differences between at-risk individuals and healthy controls were found in nMT (.08±.05 and .05±.02 respectively; t=-2.08, p=.049) and nNMU (.34±.19 and .20±.10 respectively; t=-2.21, p=.040). Discussion: Individuals at risk for psychotic onset have both facial bradykinesia and facial dyskinesia. Results of this study and earlier research show that both bradykinesia and dyskinesia in the face exist across different stages of schizophrenia, including the at-risk stage, the drug-naïve first-episode stage, and the chronic stage. These results reflect that facial bradykinesia and facial dyskinesia are core manifestations of the schizophrenia disease. Future studies further examining whether facial bradykinesia, like facial dyskinesia, is a predictor of the imminent onset of psychotic diseases in at-risk individuals are warranted.