Some articles and textbooks recommend using a dose of 20-40 U of botulinum toxin type A (Vistabel) in the glabella, 15-30 U in the forehead, and 12-30 U in the crow's feet.2,3 We use 30% less in the glabella, 50% less in the forehead, and the same dose in the crow's feet. On the lower third of the face, we usually use 50% less than the generally recommended dose. With this approach, the results are more natural and side effects are less frequent; however, patients should be informed that the effect of the procedure will last for a shorter time (approximately 3-4 months).

In our protocol, we ask patients to return for a follow-up appointment 2 weeks after the initial treatment. At this visit, we reassess the patient and, if necessary, administer additional injections in certain areas. However, it is important to educate patients to help them understand that “less is more” (ie, the goal is not to completely paralyze the facial muscles).

The 5 traditional glabellar injection sites appear in many articles and textbooks (Fig. 1). In reality, however, the 2 most superior of these injection sites are not located on the corrugator supercilii muscle—for which the insertion site is almost at eyebrow level—but rather on the frontalis muscle. Relaxation of the frontalis muscle causes the medial portion of the brow to descend and lifts the lateral portion of the brow as a result of the compensatory contraction of the lateral fibers of the frontalis muscle. The result is the well-known Mephisto effect (Fig. 2).

Figure 1.

The 5 traditional injection sites for treatment of the glabellar region. Doctors attempting to inject the corrugator supercilii muscle often inject the lower portion of the frontalis muscle instead, causing the medial portion of the brow to descend and the lateral portion of the brow to arch upward unnaturally, generating a Mephisto effect.

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Figure 2.

Typical Mephisto effect or “devil brow.”

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In some cases, we use a higher concentration of botulinum toxin in order to achieve greater precision and relax only the corrugator supercilii muscle. In our experience, this approach allows us to inject a smaller volume of liquid, thereby decreasing the likelihood of diffusion to unintended muscles (in this case, the frontalis).

Infiltration of botulinum toxin into the superior-lateral fibers of the orbicularis oculi muscle (Fig. 3) relaxes those fibers and lifts the lateral portion of the brow. The problem is that, in many patients, the position of the eyebrows moves upward with age as a result of the physiological contraction of the frontalis muscle.

Figure 3.

Injection at point 2 can result in the Mephisto effect. Injection at point 3 lifts the lateral portion of the brow; in some patients, it may lift the brow excessively. Injection at point 4 can relax the frontalis muscle; in some patients, it can cause eyelid ptosis. Injection at point 5 can relax the orbicularis oculi muscle and exacerbate the undereye bags.

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In one study,4 photographs were analyzed in order to compare eyebrow position in young patients and in patients 30 or 40 years older. Paradoxically, the study found that a physiological elevation of the eyebrows tends to occur with age in most patients. Therefore, for natural results, the superior-lateral fibers of the orbicularis oculi muscle should only be injected in patients in whom the lateral portion of the brow has descended.

In our experience, we have observed that many patients aged 65 years or older use the frontalis muscle to keep their eyes open. In these patients, relaxation of the frontalis muscle with botulinum toxin (Fig. 3) results in ptosis of the brows and/or eyelids. Therefore, in patients aged 65 years or older, the physician should examine the frontalis muscle and avoid injecting it if the patient uses it to open the eyes.

Some patients have undereye bags as a result of herniated fat or fluid retention. In either case, botulinum toxin injection can exacerbate these bags if the inferior fibers of the orbicularis oculi muscle are relaxed excessively. Therefore, in patients with a tendency to develop undereye bags, injection of the most inferior portion of the crow's feet should be avoided in order to preserve the tone of the corresponding region of the orbicularis oculi muscle.

When administering botulinum toxin injections, the physician should consider the patient's face as a whole, with the aim of relaxing the main depressor muscles in both the upper third—where the results are most gratifying—and the lower third. The problem is that undesired effects in the lower third of the face can lead to both cosmetic and functional deficiencies. It is therefore essential to use low doses in order to avoid complications.

In the lower third of the face, we can relax the platysma muscle at the jawline (a technique known as the “Nefertiti lift”),5 the depressor septi nasi muscle (in patients who have a plunging nasal tip when they smile),6 the depressor anguli oris muscle (to lift the corners of the mouth),7 the mentalis muscle (to relax the “pebbly” effect caused by the insertion of this muscle on the skin),8 etc.

The masseter muscle, which is used for chewing, is hypertrophied in some patients, causing both functional alterations (bruxism) and cosmetic alterations (square face). Injecting botulinum toxin into this muscle not only improves the symptoms of bruxism but also transforms a square face into a more oval shape.9,10 When injecting the masseter muscle, the location of the risorius muscle should be taken into account because diffusion of the toxin into this muscle can result in an asymmetrical smile.11

When certain muscles are relaxed with botulinum toxin, the adjacent muscles increase in tone as they compensate for the inactivity of the treated muscles. This compensation has a desirable lifting effect, but it can also lead to new telltale wrinkles. The classic wrinkles caused by botulinum toxin—“bunny lines”—are caused by the contraction of the nasalis muscle (Fig. 4),12 but the contraction of fibers in the inferior portion of the orbicularis oculi muscle, in the frontalis muscle just above the eyebrows or at the hairline, etc., can also cause new wrinkles. These wrinkles should be corrected with botulinum toxin treatment.

Figure 4.

After treatment with botulinum toxin, improvement is observed in the crow's feet but a new contraction of the nasalis muscle also appears, resulting in “bunny lines.”

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The appropriate injection sites vary from patient to patient. The “one size fits all” approach does not work in botulinum toxin treatment. Physicians should be familiar with the basic contraction patterns of the glabella,13–15 the forehead,16 and the crow's feet17 so that they can personalize the injection pattern for each patient, thereby achieving more natural results and using a smaller amount of botulinum toxin.

The “seagull wing” is the classic eyebrow shape in women, whereas men's eyebrows are straighter and closer to the upper eyelids. The eyebrows can be shaped by relaxing the frontalis muscle, which lowers the brow at the injection site, or by relaxing the superior-lateral fibers of the orbicularis oculi muscle, which lifts the lateral portion of the brow. To lift the medial portion of the brow, botulinum toxin should be injected into the 3 depressor muscles in this area: the procerus, the corrugator supercilii, and the depressor supercilii.

Botulinum toxin is an excellent treatment for controlling certain expression lines and adjusting the position of certain facial features, including the brows, the nose, and the mouth. However, in the interest of achieving an excellent outcome, physicians should explain to patients that a prudent combination of botulinum toxin injection and other cosmetic treatments yields the best results.

One of the most important signs of facial aging is the loss of volume caused by changes in the fat compartments and bones of the face.18 In light of these changes, it is easy to see why the combination of botulinum toxin, dermal fillers, and collagen induction therapy—a “3-dimensional” approach—achieves the most natural results.

By combining this approach with fractional laser treatment, focused ultrasound treatment, and laser treatment of pigmented and vascular lesions, it is possible to safely and effectively correct the various signs of facial aging.19