Impact of Glabellar Paralysis on Facial Expression of Emotion

Many prospective patients remain wary of the effects that glabellar muscle paralysis may have on their ability to normally communicate emotion with their face.

We undertook a direct empirical test of the effects of glabellar onabotulinum toxin type A injections on the ability to convey 6 universally recognized facial expressions of emotion.

Fifty-two female subjects ("expressors") were recorded on hidden camera while viewing video clips intended as a mood induction procedure that stimulates the 6 cardinal emotions (amusement, anger, disgust, fear, sadness, surprise). The subjects were then injected with 25 units of onabotulinum toxin A in the glabellar region. The subjects returned 1 month later and were again recorded while being spontaneously induced to express emotion. All video clips from both time periods from the 10 maximal expressors were extracted and shown to a group of 31 "perceivers" who rated the facial expressions for intensity (Likert 1-7) and identity of emotion (percent correct emotion identified).

Glabellar paralysis significantly diminished mean perceived intensity of anger (50.4% relative reduction, P < 0.001) and surprise (20.6% relative reduction, P < 0.001). The mean intensity of disgust increased (39.0%, P < 0.001). Importantly, however, glabellar paralysis did not result in a significant change in observers' ability to discern provoked cardinal emotions.

We believe these findings provide a measure of reassurance to patients and their providers that the use of onabotulinum toxin A to paralyze the glabellar musculature for aesthetic purposes may not pose a meaningful risk to the overall ability to express emotion during social interaction.