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.

The medial eyebrow depressors include the procerus, the corrugators supercilii, the depressor supercilii, and the medial portion of the orbicularis oculi. Lateral brow depression is performed by the lateral aspect of the orbicularis oculi muscle, which also is responsible for producing crows feet.

The corrugator supercilii is a 2–3 cm, small but strong, pyramidal muscle arising at the glabellar prominence of the frontal bone, about 7 mm from the midline and 11 mm above the orbital margin. It sits beneath the frontalis muscle and passes upward and laterally between the palpebral and orbital fibers of the orbicularis oculi to insert into the skin of the eyebrow at the mid-pupillary line. With contraction, the corrugator supercilii pulls the medial eyebrow downward and medially, causing a frown. The corrugator supercilii is thickest 2 cm from the nasion at the center of the medial brow.

The orbicularis oculi is a sphincteric muscle responsible for closing the eyelids. The thicker, outer portion of the orbicularis oculi arises from the medial orbit and extends both superiorly and inferiorly around the eye to form a ring. Contraction of the thicker, outer ring will close the eyes tightly, and can pull the brows downward. The thin, inner palpebral portion of the orbicularis oculi muscle closes the eyes more gently. This often occurs involuntarily, as in blinking.

For a more detailed review of the anatomy of the glabella please refer to the relevant preceding sections.

Technique

At the initial visit the subject should undergo a resting and dynamic evaluation of the brows. In addition to this observation, the corrugator supercilli and procerus muscle should be palpated to find the belly of these target muscles. This assessment can also be helpful in choosing a starting dose depending on the strength of the glabellar muscles as measured by range and blanching of the furrowed skin. We recommend pretreatment photographs as a part of this assessment. Any brow asymmetries noted should be pointed out to the patient. The patient’s face shape, age, treatment goals, and asymmetries should be taken into account when determining treatment goals.

The standard injection pattern for glabella typically has five to seven injection sites and most studies looking at brow height have used this template (Figs 13.3, 13.4). We recommend an initial total dose of 20–30 units for women and 40–60 units for men (Box 13.2), distributed as shown in Figure 13.3. The first injection is typically 5–10 units into the belly of the procerus muscle. The site of the injection can be found at the center of an imaginary X drawn between the top of the medial brow and the contralateral medial canthus. The next injections are 7–10 units (15–20 units in men) bilaterally into the belly of the corrugator supercilii, which overlies the depressor supercilii and medial portion of the orbicularis oculi. The site for this injection is directly above the inner canthus, just above the supraorbital ridge. Although this landmark is typically just superior to the medial brow, the site should be chosen based on the muscular and bony landmarks regardless of the brow position. The supratrochlear artery runs just medial to this injection site so proper landmarking and post-injection pressure are important to avoid excess bruising. Next 4–5 units are injected bilaterally 1 cm above the supraorbital rim in the mid-pupillary line. This injection is the most likely to cause lid ptosis so it is important to measure 1 cm above the supraorbital rim, to inject strictly intradermally in an upwards direction, and to avoid firm massage that may displace the botulinum toxin, since the ptosis is likely caused by diffusion of the botulinum toxin into the levator palpebrae superioris (Fig. 13.5).

Figure 13.3 Botulinum toxin brow lift – subject 1: (A) Typical glabella markings (black: 5 units, red: 2.5 units) plus 10 units per side in the upper lateral orbicularis oculi (yellow: 10 units). (B) The result, with good elevation and shaping of the brows. This patient also had concurrent treatment of the crow’s feet.

Figure 13.4 (A, B) Botulinum toxin brow lift – subject 2: same dose and pattern as in Figure 13.3.

Figure 13.5 Left upper eyelid ptosis following botulinum toxin treatment and immediate correction with apraclonidine eye drops.

In addition to lid ptosis, another possible complication of brow treatment is monolateral or bilateral hyperelevation of the brow’s apex, known as a ‘mephisto brow’ (Figs 13.6, 13.7).

Figure 13.6 Prevention of mephisto eyebrow: (A) Deep glabella lines, mild frontal lines. (B) When the patient activates the frontalis, a significant lateral elevation is apparent. (C) The index and middle fingers block elevation of the central part of frontalis, while the lateral part remains active and in fact elevates even more for compensation. In this subject a 1–2 U injection is indicated to prevent mephisto eyebrow where the frontalis lines are more visible above the peak of the eyebrow.

Figure 13.7 Treating mephisto eyebrow: (A) Mephisto eyebrow on the right side. (B) With full frontalis action, the injection point is determined at the peak of the brow, where the lines appear strongest (1 U is usually enough). (C) Correction is achieved.

When treating eyebrows, lateral brow elevation is a common goal because it gives a more youthful appearance. In addition to the standard injection pattern previously described, some authors have achieved lateral brow elevation by treating the lateral orbicularis oculi. To achieve this 7–10 units of botulinum toxin A can be injected intradermally just inferior to the lateral brow (see Figs 13.3, 13.4). Concurrent treatment of the crow’s feet will also help to weaken the lateral orbital orbicularis oculi and contribute to brow lift. When performing this procedure it is important not to treat the lateral frontalis since this is the muscle elevating the brow. Risks with this technique include diffusion of the botulinum toxin into the levator palpebrae superioris leading to ptosis and bruising if the injections are too deep.

In men, and in women with particularly long faces, a more horizontal brow is preferable, so an injection at the mid-pupillary line will prevent a more pronounced apex. The lateral aspect of the frontalis muscle will also likely need to be treated in order to maintain a horizontal brow position as the increase in resting tone of this muscle will cause a brow elevation. In contrast, a patient with a round face will benefit from a high arched brow with a lateral apex. In addition to the standard injection pattern, treatment inferior to the lateral brow may help to elevate the lateral brow and give the face a more oval appearance. This must also be a consideration when treating horizontal forehead lines in these patients as they will need the lateral frontalis left largely untreated so as to lift the brow. A peaked brow with a slightly more medial apex draws the eyes upward, making a diamond-shaped face appear more oval. To achieve this it may be necessary to omit the injection above the mid-pupillary line.

As an adjunct to the brow elevation and contouring achieved with botulinum toxin A, Lambros suggests that adding some volume to the brows with hyaluronic acid can restore a more youthful appearance (Fig. 13.8). This is achieved by adding small amounts in several deep passes beneath the brows, never going below the supraorbital rim. The amount of hyaluronic acid used is very subject specific. The ideal candidates for this procedure are those who have lost volume medially, giving them a worried appearance, and those patients who have lost volume across the entire length of the brow. This is also typically seen in upper blepharoplasty patients, especially when over-resection of fat has been performed. In these cases, the use of botulinum toxin to elevate the brows and of hyaluronic acid to compensate for iatrogenic volume loss is particularly beneficial. Intravascular injections are the most serious complication from this treatment. This risk can be lessened by using lidocaine with epinephrine for vasoconstriction and injecting small amounts at low pressure. The fine blunt-tipped cannulas may also help to minimize this risk.

Figure 13.8 The same usual dose and pattern of BoNT-A, but to achieve extra elevation and fullness 0.3 mL of hyaluronic acid was injected just below the lateral portion of the brow.

Eyebrow asymmetry

Eyebrow asymmetry is common in the general population, although minimal data exist regarding the incidence. The minimum asymmetry noticeable to individuals is 2 mm, so many people with mild eyebrow asymmetry may not be aware of it. Box 13.3 lists the many potential causes of eyebrow asymmetry.

Case Study 1

A 40-year-old woman visits your office for the first time to discuss the possibility of cosmetic treatment with botulinum toxin. Her primary concern is that she would like to have a younger appearance. She does not have any significant horizontal forehead lines at rest, but has static glabellar lines and has significant glabellar blanching when she furrows her brow. You also note she has a round face, slightly wider set eyes, and her eyebrows are horizontal with a slight apex just lateral to the mid-pupillary line.

This patient would benefit from treatment of the glabella to reduce her glabellar lines and to elevate the lateral brows. The ideal eyebrow shape for this patient would be a high arching brow with a lateral apex, and the brow beginning just medial to the medial canthus. These adjustments to the brow will give her face a more oval appearance and make the increased intercanthal distance less noticeable.

Conclusion

The eyebrows have a subtle but important role in an individual’s perceived attractiveness, age, and mood. Understanding the dynamic interplay of the muscles affecting the brows allows us to use a non-surgical approach, botulinum toxin, to effectively improve the height, position, and symmetry of the brows. By altering the contour of the brows, it is possible to enhance a subject’s appearance. Botulinum toxin is a simple, safe and effective instrument to achieve this goal.