Definition and Symmetrical Correction Using Botulinum Toxin A

Figure 1 - Measurement of eyebrow height with a caliper.

Between 2002 and 2005, we recruited, from among 245 patients who answered the questionnaire and in whom eyebrow asymmetry was found to be 2 mm or more (Table 1), 106 women and nine men as a study group. The average age of patients in this group was 42 years. Only patients with aesthetic indications for botulinum toxin injection were selected; those who had received treatment for facial palsy or trauma or who had undergone previous surgery around the region were excluded. Standardized photographs were taken of all patients before the treatment. Preintervention brow measurements were taken by use of calipers with millimeter gradations, as described above. All measurements were taken by the primary investigator. The patients were instructed not to alter their brow position or shape during the course of the study.

Table 1

The distribution of asymmetry among patients (n = 638) who answered the questionnaire

Lyophilized Toxin treatments was dissolved in 2.5 mL sterile saline solution to achieve a final concentration of 4 U/0.1 mL. Prepared Toxin treatments was administered with a 30-gauge needle on an insulin syringe within 24 hours of dilution. A total of 30 to 45 units of Toxin treatments were injected to all patients bilaterally and symmetrically to both brow regions, regardless of their brow height measurements (Figure 2). Injections were administered to frontal, glabellar, and orbicular regions bilaterally, with equal doses used on both sides in the usual fashion.

Figure 2 - Injection sites for botulinum toxin.

All patients were examined 2 weeks after treatment, when posttreatment measurements were again taken by the primary investigator. Posttreatment standardized photographs were also taken. Each patient was evaluated for specific side effects. Three sets of data were collected: the pretreatment bilateral brow height at the lateral canthus; posttreatment brow height at the lateral canthus; and the discrepancy between the brow heights. For the statistical analysis, the SPSS (Statistical Package for Social Sciences) for Windows 10.0 program was used. The Wilcoxon signed test was used for quantitative comparison of the data.

Results

All 115 patients selected for the study group completed the study. Both eyebrows were treated symmetrically. Pretreatment mean brow height was 18.59 mm at the right lateral canthus and 18.55 mm at the left lateral canthus. Posttreatment mean brow height was 21.91 mm on the right and 21.89 mm on the left (Table 2). The decrease in discrepancy between the right and left brow heights before and after Toxin treatments treatment was measured and found to be statistically significant (P < .01) (Table 3). Successful correction was achieved in 83 of 115 cases (72.1%), with success defined as posttreatment asymmetry of either 0 or 1 mm (Figures 3 to 5, Table 4). In 11 cases (9.5%), no improvement was obtained. In 21 cases (18.2%), some improvement was obtained, but posttreatment asymmetry was still 2 mm or more. The only complication reported was mild bruising in 12 patients (10.4%), which resolved by 1 week after treatment.

Figure 3 - A, Pretreatment view of a 43-year-old woman with brow asymmetry. B, Posttreatment view of eyebrows 2 weeks after Toxin treatments injections.

Table 2

Mean brow height of the eyebrows before and after Toxin treatments treatment

Table 3

Statistical analysis of discrepancy ratio before and after Toxin treatments treatment

*Z, Wilcoxon sign test.

Table 4

The distribution of asymmetry in the study group after Toxin treatments injections

Discussion

As has been the case with all surgical subspecialty fields, there has been a trend in aesthetic surgery toward use of less-invasive techniques. Newer techniques, such as endoscopic forehead lift and botulinum toxin A treatment of hyperfunctional facial lines, effect changes by altering the dynamic muscular forces that act on the upper third of the face. The ability of botulinum toxin A treatment to efface hyperfunctional lines of the face depends on the resultant denervation of the facial mimetic muscles. With respect to the dynamic muscular forces affecting the height and the shape of the eyebrows, a relative weakening of the muscular depressors of the brow (orbicularis oculi, depressor supercilii, procerus, and corrugator muscles) against the primary brow levator, the frontalis muscle, results in a visibly appreciable amount of brow elevation. To determine the objective amount of brow elevation, it is necessary to take the preintervention brow measurements, which is a routine procedure in our clinic. The triggering factor for this study was the high incidence of eyebrow asymmetry in healthy individuals seeking cosmetic enhancement in the upper face region.

Many surgical procedures for correction of eyebrow asymmetry have been described. A high-riding eyebrow may be lowered to the level of the normal side through a superselective neurotomy of the final branches of the frontal nerve on the affected site.7 In cases in which the asymmetry was caused by trauma or previous surgery, this method may be the treatment of choice. But when the asymmetry is caused by excessive muscle dynamics, as is most often the case in healthy individuals, it is much easier and less risky to correct the underlying disease instead of creating an irreversible injury to the healthy tissue. The open brow lift is a rare indication in cases of asymmetrical ptosis of the eyebrow with additional surplus of skin. The overall results are good and permanent. Endoscopic brow lift is another option, but in our view it is an unnecessarily aggressive one, especially if it is proposed for young patients without any profound complaints other than mild asymmetry and mild aging of the face.

The unilateral injection of Toxin treatments for correction of eyebrow asymmetry has been described in the literature discussing facial nerve paralysis cases as well. In one study, the author experienced difficulty in finding the exact dosage to correct the disorder unilaterally without creating a reversed asymmetry. This difficulty was the result of the unilateral treatment of asymmetry. Furthermore, complications developed in three of the five patients in this study, an exceptionally high rate. This was probably due to the use of additional procedures to achieve the desired symmetry because of the difficulty of the unilateral correction. On the other hand, our data demonstrate that significant correction of asymmetry can be achieved simply by bilateral and symmetrical chemodenervation of the primary depressors and elevators of the eyebrows, resulting in a symmetrical standstill of the eyebrows in a neutral position, a technique that avoids the difficulties and risks of unilateral treatment.

In our series, 83 of 115 patients were successfully treated, whereas no improvement was seen in 11 patients. The failure in these cases is probably due to underlying congenital skeletal asymmetries. According to our experience, those patients with an asymmetry of more than 4 mm should be warned that secondary injections might be needed. After a trial of two Toxin treatments injections, if asymmetry still continues, it is necessary to recommend another method to solve the problem. In all the other individuals, an improvement to some degree of existing asymmetry was noted.

Conclusion

Hyperkinetic eyebrow asymmetry is a common problem in patients seeking periorbital rejuvenation. Aesthetic surgeons need to draw attention to this problem in preoperative consultations to minimize postoperative dissatisfaction with respect to brow symmetry after surgery or Toxin treatments treatments.

In most cases, eyebrow asymmetry is due to muscle dynamics that affect eyebrow height and shape. As a result, any treatment should focus on both eyebrows. We propose that bilateral chemodenervation of the primary depressors and elevators of the eyebrows results in a symmetrical standstill of the eyebrows in a neutral position. Botulinum toxin A therapy is a problem-oriented, safe, and reproducible method for correction of eyebrow asymmetry that provides significant control over eyebrow symmetry, height, and shape.

The authors have no financial interest in and receive no compensation from manufacturers of products mentioned in this article.