Influence of botulinum toxin type A esthetic injections on facial expressions

Botulinum toxin type A (BoNT-A) injection remains the leading medical cosmetic procedure worldwide, with a high rate of patient satisfaction. However, it still suffers from patients' fear of being unable to transmit their emotions and of looking frozen from unnatural results.

This study aimed to determine whether BoNT-A can decrease the intensity of emotions in facial expressions.

In this single-center prospective study, 42 patient investigators assessed four patients' facial expressions for six emotions and neutral faces, before and after injection of 36 IU or 48 IU of onabotulinumtoxinA, using photographs. Photographs were presented on a tablet to the investigators.

There were no statistical differences between the before and after photographs for the intensity of emotions for all expressions (P > .05) except for the expression of surprise in the group of patients that received 48 IU of the injection (protocol with injection of the frontalis muscle). All patient investigators answered negatively to the question "Do you think that this patient has a 'frozen face'?".

This study shows that esthetic injection of BoNT-A in the upper face has no negative effects on facial expressions and does not lead to the feared "frozen face" when it is injected with respect for best practice guidelines. This study can be used as an example for patients who have some reticences against BoNT-A injection.