Evaluating the Impact of BoNT-A Injections on Facial Expressions: A Deep Learning Analysis.

[BACKGROUND] Botulinum toxin type A (BoNT-A) injections are widely administered for facial rejuvenation, but their effects on facial expressions remain unclear.

[OBJECTIVES] In this study, we aimed to objectively measure the impact of BoNT-A injections on facial expressions with deep learning techniques.

[METHODS] One hundred eighty patients age 25 to 60 years who underwent BoNT-A application to the upper face were included. Patients were photographed with neutral, happy, surprised, and angry expressions before and 14 days after the procedure. A convolutional neural network (CNN)-based facial emotion recognition (FER) system analyzed 1440 photographs with a hybrid data set of clinical images and the Karolinska Directed Emotional Faces (KDEF) data set.

[RESULTS] The CNN model accurately predicted 90.15% of the test images. Significant decreases in the recognition of angry and surprised expressions were observed postinjection (P < .05), with no significant changes in happy or neutral expressions (P > .05). Angry expressions were often misclassified as neutral or happy (P < .05), and surprised expressions were more likely to be perceived as neutral (P < .05).

[CONCLUSIONS] Deep learning can effectively assess the impact of BoNT-A injections on facial expressions, providing more standardized data than traditional surveys. BoNT-A may reduce the expression of anger and surprise, potentially leading to a more positive facial appearance and emotional state. Further studies are needed to understand the broader implications of these changes.