Introduction

Eyebrow height and shape are key determinants of perceived youthfulness and beauty. They also play a central role in an individual’s ability to convey expression to others. Botulinum toxin offers a simple and effective way to subtly enhance brow height and contour, thereby augmenting the subject’s apparent attractiveness.

Following the first published report of glabellar frown lines treated with botulinum toxin in 1992, several clinicians began to note a subtle brow elevation with treatment of the glabella. Frankel and Kamer postulated that, because medial eyebrow height and shape were a result of the interplay between the brow-elevating frontalis muscle and the brow depressors, selective treatment of the depressors with botulinum toxin A would result in medial brow elevation. To test this they injected 20 units of botulinum toxin A in the corrugator supercilii and procerus muscle of 30 patients and found that the eyebrow height at the mid-pupillary and medial canthal level rose in 48 and 32% of patients. Virtually all subsequent studies on eyebrow height in which the brow depressors were treated without concurrent treatment of the forehead have confirmed this finding.

In 2007 Alastair and Jean Carruthers published their dose-ranging randomized controlled trial assessing brow height following glabellar injections of botulinum toxin A. In this study they used a standard glabellar injection pattern, with seven sites treated with 10, 20, 30, or 40 units of botulinum toxin A. Brow height was assessed retrospectively with photographs at baseline, and then every 2 weeks until week 20. Statistically significant increases in brow height were seen at all sites in the subjects treated with 20, 30, and 40 units. In the patients treated with doses of 20 or more units there was a dramatic elevation of the lateral brow within the first 2 weeks, followed by a gradual elevation of the medial brow that peaked at 12 weeks. Interestingly, the patients randomized to 10 units had an initial, significant, decrease in brow height. The brows of these patients gradually elevated until the 16th week, beginning with the lateral brow.

Of note, despite the fact that the most lateral injection in this study was above the mid-pupillary line, the earliest and most dramatic elevation was at the lateral brow. It seems, then, that brow elevation following treatment of the glabella with botulinum toxin A has less to do with weakening of the brow depressors as this would not impact the lateral brow. The brow elevation is more likely a result of the weakening of the inferomedial frontalis, causing a compensatory increase in the resting tone of the lateral remainder of this muscle. Knowing that the untreated frontalis compensates with increased elevation, adjustments to the shape of the brow can be made by changing the dose or site of the injections in the medial aspect of this muscle.

Ahn et al produced mid-pupillary and lateral brow elevations of 1 mm and 4.8 mm by injecting 7–10 units of botulinum toxin A into the superolateral orbicularis oculi at three sites inferior to the lateral brow (superior and lateral to the orbital rim). Huang et al used a similar technique, injecting 10 units along four sites inferior to the lateral brow, and an additional 5 units in each corrugator above the medial brow. The mean increase was 3.9 mm on the left and 1.9 mm on the right, with the greatest elevation in the central brow.

Eyebrows and attractiveness

The importance of the eyebrow should not be underestimated. It is one of the primary determinants of static facial attractiveness. In addition to this, it plays an essential role in the human ability to convey emotion to others. The ideal brow is influenced by many factors including gender, age, culture, ethnicity, and current fashion trends. In ancient Greece an ideal brow extended across the midline over the nose, known today in popular culture as a ‘uni-brow’. Unfortunately for Bert, from Sesame Street, this style of eyebrow is no longer considered to be the ideal.

The modern concept of the ideal contour of the female brow was proposed by Westmore in 1974 (Fig. 13.1). This schema applies best to an oval-shaped face, and serves as a good starting point since there is no clear definition of an ‘ideal brow’ that can be applied to all faces (Fig. 13.2). Several authors have suggested that the ideal apex of the brow is actually more lateral than the lateral limbus as Westmore had proposed. If the apex is too medial and overelevated it creates a surprised appearance.

Figure 13.1 The medial aspect of the brow should begin on a vertical plane with the nasal ala, and curve with the apex above the lateral limbus. The lateral brow ends on a horizontal plane with the medial brow at a point where an oblique line can be drawn from the ala through the lateral canthus.

Figure 13.2 Face shapes.

Key:

Oval face – ideal.

Round face – to make the face appear more oval eyebrow lines should go up. A high arched brow with a lateral apex is ideal.

Long face – horizontal eyebrows draw the eye from side to side, making the face appear more oval.

Square face – angled brows balance the strong jaw line. The apex of the brow should be above the square of the jaw if possible.

Heart-shaped face – a rounded brow adds curves, softens the appearance, and emphasizes the shape.

Diamond face – a rounded brow will soften the angular face. If the face is particularly wide a peaked brow will draw the eyes up and make the face appear more oval.

Variations to Westmore’s ideal brow have been suggested to account for variations in face shape and intercanthal distance. Baker et al confirmed that, in the case of a long face and square face, observers preferred eyebrows planned by a makeup artist who accounted for these factors, rather than the Westmore ideal (see Fig. 13.2, Box 13.1).

In contrast to what one might expect, Matros et al found that as women age there is a paradoxical increase in the resting medial eyebrow height. Younger women tend to have more lateral elevation of the brow, and lower medial eyebrows. This finding helps explain the disappointing cosmetic results of surgical brow lifts when they elevate the entire brow.

The ideal eyebrow in men sits lower than the female brow, just above the superior orbital rim. The brow shape is more horizontal with minimal arching.

Anatomy

The height and shape of the eyebrows are determined by the opposing forces of the brow elevating frontalis muscle, and the brow depressors. The paired frontalis muscle originates superiorly at the galea aponeurotica and has no bony insertion points. Instead, it is continuous medially with the procerus muscle, and attaches centrally to the corrugator supercilii and laterally to the orbicularis oculi. The frontalis muscle is connected to the skin of the eyebrows through its attachment to these brow depressors, which in turn insert to the skin of the brows.