Asymmetrical Smiles Corrected by Botulinum Toxin Serotype A

OBJECTIVE The objective was to identify the cause of an asymmetrical smile and to ascertain whether or not it would be correctable by injections of Botulinum toxin A (BTX-A).
METHODS Five patients with asymmetrical smiles were identified and found to lower one side of their lower lip in an exaggerated fashion when smiling or laughing. After close observation, it was determined that the ipsilateral depressor labii inferioris of the lower lip was hyperkinetic and retracted that side of the lips lower than its contralateral side when smiling or laughing. Injections of low-volume and low-dose BTX-A (BOTOX, Allergan, Inc.) were placed into the depressor labii inferioris on the side where the lower lip retracted the lowest.
RESULTS All of the five patients with asymmetrical smiles presented with unilateral hyperkinetic depressor labii inferioris and responded to injections of BOTOX. Their lower lips became level and their smiles were symmetrical within 1 week of the BOTOX treatments. Their lip symmetry lasted for at least 6 months after their initial treatment. With each additional treatment, the duration of BOTOX lasted even longer, averaging approximately 7 months.
CONCLUSION BOTOX is an effective, safe, and long-lasting treatment for lower lip asymmetries caused by a hyperkinetic depressor labii inferioris.