CHAPTER 43 BOTULINUM TOXIN
MICHAEL A.C. KANE
Injections of botulinum toxin type A are the most frequently performed cosmetic procedure in the United States. The change from little-known specialty drug used by ophthalmologists to the most frequent cosmetic procedure occurred in just over a decade. Despite the widespread use, the toxin is still not completely understood and poorly used by many physicians. The paradox is not hard to understand when one considers the time allotted to teaching the various components of plastic surgery during residency training. Whereas years are spent teaching the finer points of rhytidectomy, blepharoplasty, rhinoplasty, and liposuction, only an afternoon, or perhaps 1 or 2 days, is typically spent teaching proper technique for botulinum type A injection. In 2010, more botulinum type A injections were performed than rhytidectomy, blepharoplasty, rhinoplasty, and liposuction combined.
Dr. Alan Scott, an ophthalmologist, pioneered the use of botulinum toxin type A in humans. His first publication, detailing the effect on rhesus monkeys appeared in 19731; his first publication concerning the injection of the toxin into humans was published in 1980.2 For years, the toxin was an effective, although seldom used, medication for blepharospasm and strabismus. Rare anecdotal reports of its use for wrinkle reduction are in existence.3 The first comprehensive report detailing cosmetic applicability was published by the Carruthers, an ophthalmologist/dermatologist team, in 1992.4This study reported the effects of the toxin on glabellar rhytides in 18 patients. Although the glabellar muscles are still the most commonly injected muscles for cosmetic reasons, every mimetic muscle of the face has been treated with the toxin, with varying success.
MECHANISM OF ACTION
The mechanism of action of the toxin has been carefully researched, but is often misstated. Because botulism is still a serious health threat throughout undeveloped nations and because sporadic outbreaks still occur in the United States, hundreds of publications by many different specialties are generated each year concerning botulinum toxin. The toxin is a 1,295 amino acid chain that has been fully sequenced. It consists of a heavy chain of 97 kilodaltons (kDa) connected by a disulfide bond to a light chain of 52 kDa. The heavy chain binds to the neuronal cell membrane, allowing passage of the light chain into the cytoplasm of the nerve. The light chain is a metalloprotease that cleaves the protein known as SNAP-25 (synaptosomal-associated protein 25). SNAP-25 is necessary for the transmitter vesicle containing acetylcholine to fuse with the cell membrane. Without fusion of the vesicle to the cell membrane, the neurotransmitter cannot be released into the synapse and a presynaptic neural blockade is created. Consequently, the toxin does not directly affect the skin and only indirectly affects the muscle, which loses its stimulus. Properly stated, botulinum toxin A only directly affects the nerve.
Clinically, the beneficial effects of the toxin are apparent for 3 to 6 months. However, when carefully scrutinized, it typically takes 6 to 7 months for all of the clinical effects to disappear. As patients continue to have the toxin injected on a regular basis over 2 or more years, many note an increased duration of botulinum toxin (Botox) action.5
The fact that botulinum toxin A disrupts such a basic pathway leads to its efficacy in treating a wide range of pathologic states. Any pathologic condition mediated by acetylcholine release from a peripheral nerve has the potential to be treated. As of this writing, there are more than 300 different conditions reported in the scientific literature that can be treated with the toxin, including blepharospasm, strabismus, cervical dystonia, torticollis, achalasia, spasmodic dysphonia, anal fissure, writer’s cramp, parkinsonian tremor, spasm of sphincter of Oddi, synkinesis, hyperhidrosis, migraine headache, tetanus, and cerebral palsy.
APPLIED MECHANISM OF ACTION
Because the toxin acts on presynaptic nerve terminals, it is most commonly injected into the muscle where these terminals reside. It is not an all-or-nothing phenomenon. A certain amount of toxin will block a certain number of terminals. Thus, fine control over the amount of denervation desired is possible. Despite the common use of the word paralysis when discussing about the toxin, it is rare that this is the desired effect. Rather, a selective weakening of the musculature is performed to achieve a pleasant cosmetic effect.
Facial aging consists of many components. Thinning of the dermis, elastosis, loss of facial volume, genetic factors, gravity, skeletal changes, and smoking, all play a part in the aging process, so does facial animation. Certain rhytides are primarily caused by facial movement. As long as a wrinkle is caused or partially caused by muscular action, it can be treated with botulinum toxin A. This explains why nearly all facial rhytides are treatable by the toxin with varying degrees of success. For instance, a glabellar rhytid is nearly completely caused by the actions of the corrugator and procerus muscles and can be completely eradicated in a young patient. Vertical lip rhytides in an elderly woman with thin skin, sun damage, a history of smoking, and loss of lip volume can only be partially improved by careful injection of the toxin into the orbicularis oris muscle, which contributes to the accordionlike scrunching of the overlying lip skin. How well a rhytid responds to treatment with the toxin depends on how much of the rhytid is a result of factors other than animation. Although this chapter is primarily concerned with alterations in animation, it is the overlying skin’s ability to resist these forces that is paramount when discussing rhytides. Once facility is obtained treating simple rhytids, the toxin can then be used to restore the face to a more youthful and pleasing shape.
BOTULINUM TOXINS AND PREPARATION
The Clostridium botulinum bacteria secretes eight distinguishable exotoxins.6 The most potent of these serotypes is A. Both toxins A (Botox, Allergan, Irvine, CA and Dysport, Medicis, Scottsdale, AZ) and B (Myobloc, Solstice, Louisville, KY) are available in the United States. Onabotulinum toxin A (Botox Cosmetic) is currently approved for the treatment of glabellar furrows in patients aged 65 years and younger. Another preparation of botulinum toxin type A, AbobotulinumtoxinA (Dysport), has been approved for the treatment of glabellar furrows in patients under 65 since 2009. All other applications described in this chapter are off-label uses. RimabotulinumtoxinB (Myobloc) is a type B toxin which is not approved for cosmetic purposes. It has a relatively minor role for cosmetic, off-label applications. Toxin B also exerts its effect via a presynaptic neural blockade but via a different mechanism. It does not act on SNAP-25; instead it acts on synaptobrevin. Although the onset of action is faster than that of Botox, the increased pain on injection (it is supplied premixed in a vial with a relatively low pH of 5.6) and decreased duration of action limit its cosmetic usefulness. I currently use Myobloc in isolated instances such as when a patient has a social event within 1 or 2 days of injection. Myobloc has a much faster onset of action than both type A products, usually within 24 hours. By the time this chapter is printed, another type A toxin is likely to be on the market. Xeomin (Merz Aesthetics, San Mateo, CA) is a BoNTA that is free from complexing proteins and has a dosing regimen similar to Botox. Revance (Newark, CA) has a topically applied BoNTA currently in clinical trials for lateral canthal lines (crow’s feet).
Botox injection is contraindicated in disorders of neuromuscular transmission, such as myasthenia gravis and Lambert-Eaton syndrome. It should not be used in patients taking aminoglycoside antibiotics whose use may potentiate the effects of the toxin. Although there is no evidence to suggest teratogenicity, I do not treat pregnant women, women actively attempting to become pregnant, or those who are breast-feeding. The toxin does not cross the blood–brain barrier. Complications occur from drift of the toxin to adjacent muscles, thereby weakening them. This is especially hazardous when injecting the perioral musculature. Other complications include headache, ecchymosis, and eyelid ptosis.
OnabotulinumtoxinA and abobotulinumtoxinA are supplied as vacuum dried and lyophilized complexes in glass vials. Complexing proteins, which in nature protect the toxin from stomach acid, are also present with onabotulinumtoxinA having more complexing protein present. Both preparations also contain varying amounts of excipients such as human serum albumin and sodium chloride. To be injectable, each preparation is reconstituted with normal saline. The label indicates that onabotulinumtoxinA be reconstituted with 2.5 cc of non-preserved saline and abobotulinumtoxinA with 2.5 or 1.5 cc of non-preserved saline. However, common usage for both products is primarily off-label. Reconstitution varies among providers from 1 to 10 cc dilution. Preserved saline due to its mild anesthetic agent (benzyl alcohol) is the preferred diluent for most injectors. Time period after reconstitution for use is 24 and 4 hours on label but most practitioners use the product within 5 to 7 days after reconstitution. There is one article in the literature which supports use up to 6 weeks after reconstitution. Both products are labeled as single patient use but I have been a chairman and participant at many expert consensus panels but almost no experts follow this guideline. I have used 4 cc of non-preserved saline to reconstitute onabotulinumtoxinA since 1991 and 3 cc of non-preserved saline to reconstitute abobotulinumtoxinA since 2009.
Just as dilution of BoNTA is a personal choice, so is dosage in most circumstances. Different muscles in different people have different strengths. To have a standard dose per area or muscle group makes about as much sense as having a standard amount of fat to remove during liposuction. Every patient is different and requires a different dose placed differently across the muscle being treated. For example, most practitioners inject about 25 Botox units or 60 Dysport units, on average, per glabella. Some dermatologists advocate as much as 80 Botox units. My median dose is 17.5 Botox units or 50 Dysport units, but some patients have excellent results with as little as 5/10 units. Men typically require higher doses as the muscle mass tends to be greater.1 I refer to doses in the following text with the reservation that it is up to each injector to determine the optimum dosage for an individual patient.
The difference between a proficient BoNTA injector and a technician is an understanding of the functional anatomy of the face. Anatomy texts demonstrate the location of the facial muscles. Although these texts allow for anatomic variations, they do not prepare us for the overwhelming differences in functional anatomy between individuals. A classic example is Rubin’s description of the different smile patterns.7 Even though all individuals have the same mimetic muscles, their smile patterns vary tremendously, depending on which muscles dominate within the group. Even within a single muscle, different portions of that muscle may dominate and alter animation. The key is a careful analysis of each patient’s face to discern which muscles cause unaesthetic lines or shaping of the face.
The glabella was the first area to be treated cosmetically with Botox (Figure 43.1). As with the other areas of the upper face to be treated with Botox, there was a longstanding surgical procedure upon which this treatment was based. The glabellar musculature is commonly debulked during brow lift procedures to ease glabellar furrowing and to reduce downward pull on the brow. Chemodenervation of these muscles has the same effect. My median dose for treating the corrugator and procerus muscles is 17.5 Botox/50 Dysport units for women and 20/60 units for men.
Even in a relatively straightforward area of the face such as the glabella, there is a great deal of variation in functional anatomy. When most people frown, they bring their brows together and down. In some patients, however, the brow’s movement is mostly vertical, whereas in others it is mostly horizontal.
After observing a patient through normal animation, I ask the patient to frown, relax, frown again, and then scrunch the nose as if smelling something unpleasant. The injection pattern varies depending on the frowning pattern. Horizontal frowners are not injected in the procerus muscle. Vertical frowners are injected in the medial portion of the corrugator and procerus muscles with the nasalis muscles injected as well.
The frontalis muscle is injected to weaken the forehead to relieve horizontal forehead rhytides (Figure 43.1). The frontalis also has highly variable functional anatomy. My dosage range for the frontalis is 3.75 to 30 Botox/7.5 to 60 Dysport units, although most fall within the range of 5.0 to 7.5/15 to 20 units. Care must be taken to not overly denervate the frontalis because it can lead to an overly smooth, artificial appearance, brow ptosis, and eyelid ptosis in the patient who has been using the frontalis as an accessory eyelid elevator. Despite its appearance in most anatomy texts, the frontalis is usually continuous across the forehead, with muscle present even in the midline.
After the patient is observed in normal animation, the patient is asked to raise and lower the brows several times, almost to the point of exhaustion. Upon observation of the motion, the strongest portions of this muscle are targeted, not the rhytides. No standard pattern of injection is used.
CROW’S FEET AND LOWER EYELID
The lateral and inferior orbicularis oculi is weakened to diminish crow’s feet and lower eyelid rhytides in selected patients (Figure 43.1). The effects of surgically weakening the lateral orbicularis had been known for several years prior to the cosmetic use of Botox injections.8 The confluence of the crow’s feet and lower-lid rhytides and the fact that they are both created by the same muscle makes concomitant treatment appropriate. The functional anatomy of this area leads to a classification of crow’s feet patterns.9 The most common pattern is the full-fan pattern where the lateral orbicularis contracts and wrinkles the overlying skin from the lateral brow to the lower lid–upper cheek junction; yet even this pattern occurs in less than half of all patients. The exact incidence of each pattern is not as important as the recognition that different patterns exist and that asymmetry occurs in individual patients.
This is an area where overzealous injection can yield an unpleasant deer-in-the-headlights appearance and even cheek ptosis. Although most plastic surgeons are aware that the upper lateral orbicularis oculi is a brow depressor, many fail to realize that the lower lateral portion of the muscle is an important cheek elevator. If overly denervated in its lower lateral section, malar flattening, as well as an extra “roll” of skin between the lower lid and cheek, can occur. Excessive chemodenervation of the orbicularis oculi across the lower lid can cause ectropion, lower-lid retraction, or even lymphedema. In the patient with minimal to borderline orbital fat prolapse, weakening the middle lamella can exaggerate and hasten the appearance of fat “bags” of the lower lids. Thus, these areas are injected judiciously.
FIGURE 43.1. A. This woman in her forties is seeking rejuvenation of her upper face. She is frowning prior to injection. She was last treated with BoNTA 5 months previously. She exhibits characteristic glabellar lines and musculature. B. Four weeks after injection of her corrugators and procerus muscles. She is unable to frown or lower her medial brows after injection of 20 units of Xeomin into her corrugators and procerus and 2.5 units into her nasalis muscle. C. The patient is raising her eyebrows prior to injection. Notice the asymmetry with the left forehead apparently stronger and the left brow noticeably higher than the right brow. D. The patient is raising her brows 4 weeks after injection of 5 units of Xeomin into her frontalis. Her frontalis muscle was injected asymmetrically, with 3 units into her left side and 2 units into her right side. This was done in an attempt to raise her right brow more than her left. In order to maximize brow lift, a moderate amount of motion was left resulting in small frontal rhytids. E. The patient is smiling and exhibiting a stronger orbicularis oculi along her lower eyelid than her upper eyelid. She has a classic full fan-shaped rhytid distribution. F. Four weeks after injection of 7.5 units of Xeomin into her right orbicularis oculi motion the patient has near-normal animation with a moderate reduction of rhytids. Xeomin was injected cephalad and medial to the tail of her brow to attempt to raise it more than the right brow. Caution must be taken to not overly chemodenervate the cheek elevators in an attempt to remove the rhytids which continue down the lateral cheek. Her pretarsal orbicularis was also injected laterally. G. The patient in repose prior to injection. Note her frontal and crow’s feet rhytids, glabellar rhytids and overhang, and low brows. The right brow is significantly lower than the left and causes an apparent excess of right upper lid skin. H. Four weeks after the injections described above, the patient has obvious improvement in her glabellar, frontal, and crow’s feet rhytids. She also has a pleasant small elevation of both brows (right greater than left) which open up her eyes and decrease the apparent skin excess of her upper eyelids (especially on the right).
Although there are no standard doses or dosing patterns, most patients receive between 3.75 and 5.0 Botox units/ 10 to 20 Dysport units per side. The key is to not waste your injection on relatively adynamic sections of the muscle. To do this, one must recognize that the functional anatomy of the lateral periorbita varies widely. I inject the most dynamic area of the muscle first, followed by smaller injections radiating out from this point. The idea is to create a gradient of motion so as not to have an area of no motion directly bordering an area of extreme, compensatory motion. This produces an unattractive line of demarcation.
BoNTA can easily and reliably lift the brows in excess of 6 mm but it is not always an aesthetic improvement. Two concepts are at play. The first is simple: to lift the brows, one injects muscle segments that depress the brows. The second concept is not simple: nonweakened sections of muscle react to weakened sections by increasing their pull in a compensatory fashion creating hyperactive sections. This explains why lateral orbicularis injection can cause lower-lid rhytides to increase. This is not simply an illusion as a result of smoothing of the skin laterally, but a real phenomenon caused by an increase in tone of the noninjected portion of the muscle. When the central frontalis is injected strongly, the lateral brows will often peak in an unattractive “Mr. Spock” or Mephisto appearance, with concomitant worsening of lateral suprabrow rhytides. When portions of the frontalis are weakened, the other portions of the frontalis lift more strongly. To maximize brow lift, injecting the portions of the frontalis not responsible for raising brows will induce the frontalis responsible for brow elevation to pull harder. Usually this means injecting the frontalis strongly centrally, in the zone above and medial to the brows. This causes the frontalis directly over the brows to lift more strongly. Although the frontalis directly above the brows is responsible for brow elevation, the lower frontalis is more responsible than the upper frontalis. Thus, occasionally, the upper frontalis above the brows can also be weakened to further increase the action of the lower frontalis.
There are 11 muscle segments that can depress the medial brow: the procerus, transverse heads of the corrugator, oblique heads of the corrugator, depressor supercilii, medial orbicularis oculi, and in some patients, the nasalis muscles. In most patients, the effect of the nasalis on brow position is negligible. However, in a small number of patients, I have fully injected the other medial brow depressors and been disappointed in the ensuing brow elevation. With the other segments completely nonfunctional, these patients were able to depress their brows by wrinkling their nasalis. Subsequent nasalis injection gave the brows additional elevation.
The lateral brow is depressed by the cephalic portion of the lateral orbicularis oculi. The dynamics of this phenomenon differ greatly among patients, and thus there is no single point that can be injected to reliably elevate the lateral brow. In fact, in some patients, this muscle is not a reliable brow depressor, and injecting it will not raise the brow. The problem is to determine whose brows can be elevated and what portion of the muscle should be injected. With the head in neutral position and primary gaze, the patient is asked to smile repeatedly and forcefully. When doing this, some patients will not depress their lateral brow at all. These patients will not reliably achieve brow elevation by injecting the upper lateral orbicularis. Patients who do depress their brows are studied carefully and then injected in the portion of the muscle that is pulling downward on the lateral brow. Sometimes this is at the lateral tail of the brow, sometimes directly beneath the brow more medially.Treatment is individualized based on each patient’s functional anatomy.
There is no standard pattern of injection for brow elevation. For a more medial brow elevation, the medial depressors are eliminated and the lateral frontalis is weakened, leaving the medial frontalis strong. For a more lateral elevation, the lateral depressor and the medial frontalis are injected. For a peaked and arched brow, the lateral depressor is weakened and the frontalis over the junction of the middle and lateral third of the brow is left strong. For men, a wider band of frontalis is left working to raise the brows while keeping them flat. For a unilateral brow lift, in addition to the zones not directly over the brows, the frontalis is weakened slightly over the higher brow, inducing the frontalis over the lower brow to pull harder. It is important to note that brow lifting by injection of toxins can create bizarre, unnatural appearance in some patients.
BoNTA injections in platysmal bands can yield excellent results (Figure 43.2). Two articles on neck injection were published simultaneously in 1999 with drastically different dosage, patient populations, results, and complications.10,11 One paper advocated up to 250 units be injected, noted that patients received a lift of the lower face, had better results in patients with greater skin laxity, and reported dysphagia as a complication.10 I would caution against injecting such high doses in the neck. In addition to dysphagia, high doses can also lead to dry mouth by affecting the salivary glands.
The key to evaluating the neck as a potential site for cosmetic improvement lies in the relative contributions of the skin and the platysma to banding. The best patients have minimal skin excess and relatively strong bands. Despite the results (based on 1,500 patients) of the aforementioned paper, the patient with lax neck skin is a poor candidate for injection. Even with the bands completely paralyzed, the lax neck skin will continue to hang.
My current dose range is 15 to 35 Botox units/50 to 80 Dysport units for the neck, with most patients receiving around 20/60 units. The patient is asked to show the lower teeth with teeth clenched. The platysma band becomes apparent and is grasped between the thumb and the index finger of the noninjecting hand. The patient is then told to relax and the muscle is injected starting just below the mandibular border and progressing inferiorly to the point at which the band is visible. Early horizontal “necklace” rhytides can also be very mildly improved by injecting toxin just above and below them.
Good candidates for injection fall into two basic categories. The relatively young (35 to 45 years of age) patient with strong bands and minimal skin laxity is an excellent patient. Likewise the patient of any age who has had a surgical procedure on the neck and has relatively little excess skin and recurrent bands is a good candidate. A smaller set of patients, but one that is being seen more frequently, is the young patient who has had an aggressive fat removal procedure in the neck and now has visible bands.
FIGURE 43.2. A. This woman in her mid-thirties requested neck rejuvenation. She especially complained about the cords that she would see in photographs when smiling fully. She is straining in this photo. She is an ideal candidate as she has very little skin excess. B. The patient had 20 units of Botox injected into her right primary platysmal band and 7.5 units into her left band and muscle body. She still has a mild prominence of her right secondary band at maximal strain but it is not visible in normal animation.
Treatment of the nasolabial fold demands appropriate patient selection. In addition, the patient must understand the implications of treatment in this tricky area. The levator labii superioris alaeque nasi muscle is the muscle mainly responsible for the medial nasolabial fold and the final 3 to 4 mm of central upper lip elevation. Weakening of this muscle results in smoothing of the medial nasolabial fold and a change in the smile pattern of the patient. Rubin described the three major smiling patterns in 1974. The most common, or “Mona Lisa,” smile pattern is dominated by the zygomaticus muscle and elevates the oral commissures to the highest point of the smile. The canine smile pattern is dominated by the levator labii superioris and the highest part of the smile is the central upper lip. This pattern occurs in 35% of the population and they are the potential candidates for this procedure. Because injection of the levator labii superioris alaeque nasi muscle results in a drop of the central upper lip upon smiling, it converts canine smilers into Mona Lisa smilers. Injecting Mona Lisa smile patients results in an exaggerated Mona Lisa smile that most patients find unattractive.
Patients with gummy smiles demonstrate extreme canine smile patterns. This group benefits the most from BoNTA injection.12 Gummy smilers often smile asymmetrically, requiring asymmetric injection. They also tend to have deeper medial nasolabial folds, which is the area of primary improvement with this technique. The resulting drop of the upper lip hides the gingiva and results in a more pleasing smile.
The technique for this injection is relatively straightforward. Before injection, the patient is given a preview of the proposed change. The patient looks into a mirror at eye level and smiles. Using a cotton applicator stick, I pushed the upper lip down 3 to 4 mm, giving the patient a rough approximation of the change to be expected to the smile and to the nasolabial fold. For injection, the index finger of the noninjecting hand is pressed firmly against the inferior portion of the nasal bone where it meets the maxilla. Thus, half of the finger is falling into the pyriform aperture while the other half lies in the groove between the nasal bone and maxilla. The patient is then asked to smile strongly. The levator labii superioris alaeque nasi muscle can usually be felt just lateral to this groove. It is injected once on each side, just above the periosteum. My dose range for this muscle is 5.0 to 10 Botox units/10 to 20 Dysport units total, with most patients falling closer to the 5.0/10 unit range. This technique changes the functional anatomy of the patient by changing their smile pattern.
The perioral rhytides are a common area of complaint (Figure 43.3). The radially oriented rhytides are brought about by intrinsic aging of the skin (dermal thinning, sun damage, and smoking), a loss of volume over time, and forced wrinkling of the skin caused by its densely adherent underlying muscle, the orbicularis oris. The most common rejuvenative procedure for this area is the injection of filler materials. Injection of hyaluronic acid into the lip improves the rhytides, restores lost volume, and offers immediate results with negligible recovery time. However, BoNTA is an increasingly effective rejuvenate modality for several different patient populations. First, there is the patient group that is already having BoNTA injected into other areas of the face and asks if BoNTA could help their lip lines as well. A second group wants improvement of their wrinkles but is adamant about not increasing the size of their lips at all, for fear of looking “done.” The third, and largest, group receives concomitant BoNTA and filler injection. The filler material partially obliterates the wrinkles and restores volume while the BoNTA relieves some of the force applied to the skin from the underlying orbicularis oris. In this way, combined with skin care, the patient receives the maximal amount of improvement without forced downtime. In the patient with severe perioral rhytides, maximal rhytid improvement using fillers alone would necessitate injecting high volumes, which would be unaesthetic. For combination therapy, the lip is injected with a filler material up to the point where the lip would look “done.” Botox is then used to weaken the orbicularis oris. If a filler material containing a local anesthetic is used, the filler is injected first.
FIGURE 43.3. A. This patient in her forties has a large, wide mentalis muscle when straining to elevate her lower lip. B. After 5 Botox units were injected in a threading motion across her superficial mentalis, her chin is noticeably smoother yet still strong enough to fully raise her lower lip. C. The patient is retracting her lower lip. This shows her lower gingiva and reveals her classic depressor anguli oris (DAO) dimples below the oral commissures. D. A total of 7.5 units of Botox have been injected into her DAO muscles. She can no longer reveal her gingiva and her DAO dimples are not visible. The depression of her lower lip remains symmetric. E. The patient is puckering her lips. F. After 2 units of Botox were injected into each of the upper and lower lips (4 units total), her puckering is improved but not gone. G.The patient in repose prior to injection. Her mentalis is wide and irregular. She has clear depressions and an apparent volume deficit over her DAO insertions. H. After injection, the surface of her chin is narrower and smoother due to chemodenervation of her mentalis. The area over her DAOs appears more full. The lips also appear more full due to the relaxation of the orbicularis oris which hides the lips. I. Smiling prior to injection. J. The patient maintains a natural, symmetric smile after injection. The lower lip is slightly elevated which adds to a youthful appearance. Multiple lower face injections are not for the novice injector as these patients may sometimes experience weakness.
The patient is asked to purse the lips, then relax, and purse again, repeatedly. This is done to judge the relative strength of the sphincter muscle. Beware the elderly patient with severe rhytides and decreased muscle mass. My current dosing range is only 2 to 5 Botox/5 to 10 Dysport units per lip, with most patients receiving 3/5 units per lip. As opposed to other areas of the face where precise, small drops of BoNTA are injected, this area is injected broadly to effect a diffuse, general weakening of the sphincter. The philtrum is rarely injected as it rarely contains strong rhytides. A more dilute solution is used. The extra volume allows more even placement of the Botox. The needle is inserted parallel to the vermilion border, a few millimeters above it, and the BoNTA is injected as the needle is withdrawn. The upper and lower lips can be treated in the same session. Complications can easily result in this area and are usually a result of overinjection. Overly weakening the upper lip leads to problems with plosive sounds, then general speech, and, finally, oral competence. Overinjection of the lower lip more readily leads to drooling and competence problems.
Patients who have difficulty with oral competence tend to form an unattractive, dimpled pattern on the chin during active speech or when closing the lips (Figure 43.3). This appearance results from contraction of the underlying mentalis muscle. Dimpling and occasional ridging of the skin in patients with hypertrophy of the mentalis can result. This pattern of mentalis strain is particularly common in patients with vertical maxillary excess (gummy smilers), the same patients who benefit from levator labii superioris injection.
Dosing range for the mentalis is 2.5 to 12.5 Botox/5 to 20 Dysport units, with most patients in the 5.0/10 units range. Care is taken to inject the superficial mentalis only, leaving the deep mentalis fully functional. The needle is threaded cephalad, parallel to the skin surface, aiming for the plane between the superficial muscle and its overlying fascia. Care must be taken to leave enough of the deep muscle functional so that lower lip elevation and oral competence is maintained. Injection of the mentalis is often paired with depressor anguli oris injection to maintain the height of the lower lip.
DEPRESSOR ANGULI ORIS
The depressor anguli oris is a triangularly shaped muscle that depresses the oral commissures. This action contributes to the marionette lines and often creates a distinct horizontal rhytid below the commissure. Injection of this muscle raises the oral commissures, decreasing show of the lower dentition when smiling. It also helps to improve marionette lines and the horizontal crease below the commissure.
My current dosage range for this area is between 2.5 and 12.5 Botox/5 to 20 Dysport units total, with most patients falling in the 5.0/10 units range. The patient is repeatedly asked to show the lower teeth with the dentition occluded. This usually creates a horizontal rhytid below the commissure. Each muscle is injected twice, with the first injection point at the level of the horizontal rhytid. The second point is midway between the first point and the lower border of the mandible in the direction that the muscle pulls the commissure when contracting. Most patients pull the commissures down and laterally when contracting. Some patients, however, will pull their commissures down and medially. It is along this axis of motion that the second injection is placed. Care must be taken not to attempt to inject this muscle in its cephalad portion as has been taught previously. First, there is very little active muscle there as the muscle tapers and becomes aponeurotic. Second, the muscle that is there, the lower orbicularis oris, does not tolerate concentrated injections laterally. This can easily lead to oral incompetence and drooling. The depressor labii inferioris is also cephalad and care must be taken not to inject it inadvertently. When properly injected, the depressor anguli oris is one of the safest muscles to inject in the lower face as even if it is slightly overinjected, it does not lead to oral incompetence, but rather, an actual raising of the lower lip. In fact, if a patient has oral competence problems from injection of the lower orbicularis oris or mentalis or facial nerve injury, injection of the depressor anguli oris can give the patient relief. Injection of the lower lip with a viscous hyaluronic acid product at the same time can also add some static support.
BoNTA injection can also decrease secretion of the eccrine glands in the axillae, palms, and soles of the feet. Care must be taken to inject the BoNTA intradermally in the palms and soles to minimize the risk of weakening the muscles of the hands and feet. Results for this application typically last somewhat longer, approximately 6 months.
Complications from aesthetic surgical procedures can often be treated with BoNTA. Incomplete corrugator or procerus resection after brow lift is an ideal indication. If excessive downward muscle pull on the brows is seen in the early postoperative period, it can be treated aggressively, maintaining brow elevation. Surgical misadventures with chin augmentation can lead to mentalis disinsertion and dimpling of the chin, which can be ameliorated by Botox. Overly elevated brows after brow lift can be lowered with aggressive frontalis injection. Prolonged spasm of the pectoralis major after breast augmentation can be treated with injection of the portion of the muscle. Facial nerve injuries after surgery or trauma can often be effectively masked by weakening the unaffected muscle on the contralateral side of the face. Marginal mandibular nerve injury after facelift can be disguised by injection of the contralateral depressor anguli oris muscle.
1. Scott AB, Rosenbaum A, Collins CC. Pharmacologic weakening of extraocular muscles. Invest Ophthalmol Vis Sci. 1973;12:924-927.
2. Scott AB. Botulinum toxin injection into extraocular muscles as an alternative to strabismus surgery. Ophthalmology. 1980;87:1044.
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1 Kane MAC et al. Evaluation of Variable-Dose Treatment with a New U.S. Botulinum Toxin Type A (Dysport) for Correction of Moderate to Severe Glabellar Lines: Results from a phase III, Randomized, Double-Blind, Placebo-Controlled Study.