One of the most common uses for the well known aesthetic drug, Botox, is injection into the forehead. While it is most commonly used to treat horizontal forehead lines and vertical glabellar rhytids, it is also used to create a chemical brow lift. While such injections can be very effective, it it not uncommon for some patients to develop adverse aesthetic effects such as brow asymmetry and even the opposite effect of brows getting lower rather than elevated.
Like all facial injections there is an art form to doing them. But it really based on an understanding of the anatomy of the muscles and how they work. Brow shape and position one the brow bone is because of an interactive relationship between the multiple inner and outer depressor muscles and the one main forehead elevator. (frontalis muscle) Thus to create a complete brow lift the inner and outer depressor muscles must be theoretically injected.
In the January 2018 issue of the journal Plastic and Reconstructive Surgery an article was published entitled ‘The Impact of Botulinum Toxin on Brow Height and Morphology: A Randomized Controlled Trial’. The authors evaluated the effects of injecting both inner and outer depressor muscles (Group 2) or just the lateral depressor muscles (Group 1)on brow height and shape. Fifteen patients (30 eyebrows) were done in each injected group with 25 units injected into the lateral depressors and 10 units into the medial depressors.
Their results showed that the brow was elevated up to 2mms across the entire brow in Group 1. In Group 2 the brows elevated up to 1.7mms in the outer half of the eyebrow with no change in its inner 1/3.
These study results initially seem counterintuitive. How could injecting both sides of the eyebrow result in electing only its outer portion? And how could just injecting the outer depressors result in more complete brow elevation? The authors hypothesis that there is diffusion of the drug into the lower frontalis muscle with injection into the medial depressors leading to partial deactivation. This results in no change in the medial brow position but increased resting tone of the frontal, raising the lateral brow.
These study findings provide guidance as to how to inject Botox for eyebrow elevation to meet patient expectations. For those seeking lateral brow elevation along, both the inner and outer depressors should be injected. But for those seeking total brow elevation only the lateral depressors should be injected.
Dr. Barry Eppley