Reduced facial expressiveness in Parkinson's disease: A pure motor disorder?

Impaired emotional facial expressiveness is an important feature in Parkinson's disease (PD). Although there is evidence of a possible relationship between reduced facial expressiveness and altered emotion recognition or imagery in PD, it is unknown whether other aspects of the emotional processing, such as subjective emotional experience (alexithymia), might influence hypomimia in this condition. In this study wee aimed to investigate possible relationship between reduced facial expressiveness and altered emotion processing (including facial recognition and alexithymia) in patients with PD.

Forty PD patients and seventeen healthy controls were evaluated. Facial expressiveness was rated on video recordings, according to the UPDRS-III item 19 and using an ad hoc scale assessing static and dynamic facial expression and posed emotions. Six blind raters evaluated the patients' videos. Emotion facial recognition was tested using the Ekman Test; alexithymia was assessed using Toronto Alexithymia Scale (TAS-20).

PD patients had a significantly reduced static and dynamic facial expressiveness and a deficit in posing happiness and surprise. They performed significantly worse than healthy controls in recognizing surprise (p=0.03). The Ekman total score positively correlated with the global expressiveness (R^2=0.39, p=0.01) and with the expressiveness of disgust (R^2=0.32, p=0.01). The occurrence of alexithymia was not different between PD patients and HC; however, a significant negative correlation between the expressiveness of disgust was found for a subscore of TAS (R^2=-.447, p=0.007).

Reduced facial expressiveness in PD may be in part related to difficulties with emotional recognition in a context of an unimpaired subjective emotional experience.