The panelists agreed that all 4 agents act similarly in the glabella. In the clinical studies for the newest BoNT-A, prabotulinumtoxinA-xvfs, treating the glabella knocked out the corrugators and the procerus30 just like other BoNT-As. Some members of the group noted an observable difference between prabotulinumtoxinA-xvfs and onabotulinumtoxinA in the glabella, which could be used to some advantage.
The frontalis muscle is an elevator of the eyebrow. The muscle fibers are oriented vertically, and contraction is associated with development of horizontal forehead rhytides.29 Significant anatomic variability exists among patients, with many showing significant medial overlapping and structural difference between medial and lateral aspects.31 Some patients show several fine rhytides, where others exhibit 1 or 2 deep creases. BoNT-A treatment of this area is highly variable due to the anatomic variability of the frontalis muscle and characteristics of each patient’s animation patterns.29
Complete immobilization is generally not desirable, even if some rhytides remain, because it can prevent normal facial expression.27 The group agreed that the primary objective is to modulate the depth and magnitude of the effect of BoNT-As based on the patient’s muscle mass, thus improving rhytides and maintaining some movement of the frontalis muscle without causing brow ptosis or paralysis and a “frozen” appearance. When patients come in and express concern that they can move their forehead, the group agreed it is best to emphasize that a little bit of motion evokes natural results. But when a patient has a hyperfunctional frontalis, or wants it knocked out completely, the more extensive diffusion of abobotulinumtoxinA may be advantageous.
Treating the forehead with agents that have a smaller field of effect can be an issue in some patients, but the group agreed that the issue can be circumvented by increasing BoNT-A dilution or dose. The group recommended that in areas like the forehead, and occasionally the crow’s feet, clinicians can draw up 8 to 10 units and then draw up more diluent to increase the diffusion. Some members of the group have observed a difference between prabotulinumtoxinA-xvfs and onabotulinumtoxinA in the frontalis. For example, one panelist was able to get rid of the little “comma” above the lateral brows with prabotulinumtoxinA-xvfs, something they were unable to do with other BoNT-As.
The group agreed that it is much more important to raise and shape the brow, than to eradicate every wrinkle. Because appearance is based on shadows and light, positioning of the eyebrows and the corners of the mouth, and expression, some movement is also important. BoNT-As can also be used to correct brow asymmetry from lax skin or mild ptosis on one side and resulting compensation of the frontalis to lift the lower, sagging side.17 Brow ptosis occurs over time, due to bone loss and descent and shrinkage of the underlying fat pad in the brow area.32 In general, 2-3 units of onabotulinumtoxinA, prabotulinumtoxinA-xvfs, or incobotulinumtoxinA, or 6-9 units of abobotulinumtoxinA above the stronger brow corrects asymmetry.17
Lateral periorbital rhytides appear bilaterally upon smiling in a fan-shaped pattern that may extend as far as the temporal hair line. They are formed by a combination of lateral orbicularis oculi muscle contraction and photoaging.33 The identification of multiple fan patterns suggests that individuals may use different regions of the orbicularis oculi when smiling and, in some cases, recruit cheek elevators. Baseline severity of crow’s feet lines, age, and gender may predict fan pattern, which may progress with age from central to lower fan or full fan.34 Injection points are located based on observed muscle action and superficial landmarks; bony landmarks and anatomic diagrams also may be useful, but muscle palpation is of little value.27 Overall efficacy rates in the onabotulinumtoxinA pivotal trials35,36 suggest that 1 of the 2 distinct injection patterns used would be appropriate for the majority of individuals with moderate or severe dynamic crow’s feet lines.34
The BoNT-A dose should be adjusted based on the desired degree of effect and the expanse and number of wrinkles. Care should be used to stay 1 cm from the lateral canthus in most indications and over the lateral orbit as opposed to injecting over the eye adnexa.27 Any regional veins should be noted and avoided. It is extremely important to inject superficially in this area to avoid or minimize bruising. In patients with lax lower eyelids, caution should be used when injecting medially to avoid disrupting proper lid function.29
The panelists mentioned that over time, they see atrophy with most muscles that they treat, but that treatment of crow’s feet is different. The target is not the temporalis, yet there can be temporalis atrophy over time, especially in hyperfunctional young women. A recommendation was made to inject BoNT-A further posteriorly when targeting the temporalis muscle, beyond the hairline, so that any atrophy is hidden for the most part. By inducing muscle paresis, BoNT produces atrophy and reduction of muscle diameter.37 Muscle atrophy can be the aim of the treatment (in masseter reduction, for example) or an unintend-