Understanding the functional anatomy of the frontalis and glabellar complex for optimal aesthetic botulinum toxin type A therapy.

BACKGROUND: Botulinum neurotoxin type A (BoNTA) is approved for the treatment of glabellar lines and also is commonly injected in an off-label fashion in the frontalis (i.e., frontalis epicranius) muscle to improve the appearance of horizontal forehead lines. This study aimed to review and discuss both the anatomy and physiology of the frontalis muscle and its relationship with antagonist muscles in the upper face and to provide a guide for the use of BoNTA to treat forehead rhytides while minimizing the occurrence of complications such as brow ptosis.
METHODS: A PubMed search was conducted to identify practitioner opinion and clinical publications on the efficacy and safety of BoNTA for aesthetic treatment of the upper face.
RESULTS: The use of BoNTA produces durable improvement in the appearance of moderate to severe horizontal forehead lines. Dose and injection technique must be adjusted and individualized based on the variable anatomy and function/mass of muscles in the forehead and upper face as well as on patient goals. Optimal aesthetic outcomes can be achieved by skillfully balancing the opposing effects of the frontalis muscle and its intricate interactions with the procerus, corrugator supercilii, depressor supercilii, and orbicularis oculi muscles.
CONCLUSIONS: The use of BoNTA to improve the aesthetic appearance of horizontal forehead lines is optimized when clinicians take into account variations in frontalis muscle function and position, anatomy of the brow, and proper injection technique when they devise individualized treatment regimens.