Botox, Masseter

Scientific Foundations Lower Facial Contouring With Botulinum Toxin Type A Gianpaolo Tartaro, MD, FACS, Raffaele Rauso, MD, Mario Santagata, MD, Vincenzo Santillo, MD, Angelo Itro, MD, DDS Naples, Italy

The use of botulinum toxin (BoNT) is well established in medical practice. The application of BoNT extends over many indications such as strabismus, blepharospasm, hemifacial spasm, and others. Another indication for the use of BoNT type A is the masseteric muscle hypertrophy to obtain a lower facial contouring. Authors report the treatment of 5 patients with intramuscular injection of BoNT. A high degree of patient and physician satisfaction was noted after the treatment. Authors concluded that BoNT type A can safely be considered as a noninvasive drug treatment for patients with MMH. Key Words: Botulinum toxin type A, masseteric muscle hypertrophy, lower facial contouring

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owadays the use of botulinum toxin (BoNT) is well established in medical practice, not only for aesthetic purpose. The application of BoNT extends over many indications and medical specialties such as hemifacial spasm, strabismus and other ophthalmic disorders, bruxism, rhinitis, lacrimation, wrinkles, focal dystonias, foot dystonias, Tourette syndrome and other kinds of tics, hyperhidrosis, urologic disorders (hyperreflexive bladder, detrusor-sphincter dyssynergia, spasticity of the vescical sphincter, etc), gastrointestinal and proctologic disorders (achalasia, anal fissure, etc), and others.1 In several indications, the use of BoNT is well established and is considered the treatment of choice. The mode of approval varies from continent to continent and from country to country.

From the Department of Head and Neck Pathology, Oral Cavity and Audio-Verbal Communication, 2nd University of Naples, Naples, Italy. Address correspondence and reprint requests to Raffaele Rauso, MD, Corso Aldo Moro, 100. 81055 S.M. Capua Vetere (CE), Naples, Italy; E-mail: [email protected]

Another indication for the use of BoNT type A is the masseteric muscle hypertrophy (MMH) to obtain a lower facial contouring. Masseteric muscle hypertrophy is a relatively uncommon condition that may present as either a unilateral or bilateral painless swelling in the region of the angle of the mandible.2Y6 The etiology of this anomaly is not yet clear.2,4 The diagnosis is usually clinical; however, conventional radiography, ultrasonography, and electromyographic examination may be helpful.2,5,6 Surgical treatment consists in the resection of a portion of the masseteric muscle and/or the removal of exostosis of the mandibular angle that are frequently associated with this condition.2,4 Botulinum toxin type A is a potent bacterial neurotoxin produced by anaerobic bacterium Clostridium botulinum that produces muscle paralysis, atrophy, and weakness.3,5,7 The use of BoNT has been reported as a successful method of treatment of MMH that offers some advantages over conventional surgical treatment.3Y5,8Y11 Authors report the treatment of 4 patients with intramuscular injection of BoNT associated or not with surgical treatment. PATIENTS

AND

METHODS

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his study was conducted as a clinical prospective study. Patients were recruited consecutively between April 2006 and March 2007 at the Department of Head and Neck Pathology, Oral Cavity and AudioVerbal Communication, Naples, Italy. Patients were included if they presented widened lower facial profile with hypertrophic masseteric muscles (or bilateral MMH). The exclusion criteria are listed in Table 1. All data and parameters considered for investigation in this study were captured during pretreatment investigations, treatment course, and recall visit. Five patients (2 men and 3 women) were included in the study. The median age was 53 years (range, 46Y56 years). Table 2 shows the patients’ demographic data. All patients complied for esthetic nature, none of them report pain. Two patients had a sign of bruxism on a tooth. 1613

Copyright @ 2008 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.

THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 19, NUMBER 6 November 2008 Table 1. Exclusion Criteria &Pregnancy (or pregnancy attempt) &Breastfeeding &Concurrent administration of quinine, calcium-channel blocker, penicillamine, or aminoglycoside antibiotics &Neuromuscular disorders (myasthenia gravis, Eaton-Lambert disease) &Peripheral neuropathy (diabetes mellitus, alcoholism)

Diagnosis was confirmed through clinical and radiographic examination, which included posteroanterior telecranium for hyperostosis diagnosis. Percutaneus intramuscular injections of BoNT were selected to treat the patients, and none of them had already received this form of treatment. The nature and the established use of BoNT, as well as its potential side effects, were explained in detail to the patients. The drug used for injections was C. botulinum type A toxin (Botox; Allergan Inc., Irvine, CA). Each Botox vial, containing 50 U of BoNT, was dissolved in 1.25 mL of normal saline solution with a final concentration of 40 U/mL. With the use of a 1.0mL syringe and a 25-G needle, the toxin was administered percutaneously in varying doses, in the thickest portion of the hypertrophied masseter muscle. This point was identified by palpation on the patient during clenching. Aspiration of the syringe was performed to avoid intravenous injection. After the injection, the muscles were massaged for 5 minutes to spread the drug. After each seat of injection, a therapy with tiocolchicoside (4 mg twice a day) and ciclobenzaprina (10 mg/die before sleeping) was performed for 10 days. Electromyographic study of the masseteric muscle was performed before and after 20 days from the injection. In 2 cases was associated a therapy with bite plane, where signs of bruxism were present, 8 hours per die during the night. Recurrence was considered when relapse of hypertrophy was noted or when result was not satisfactory (after 30 days on average) through clinical and photographic evaluation of the patients (Figs 1Y4). RESULTS

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lectromyographic examination after injections of BoNT denotes a reduction of contraction of the

Fig 1 A patient before BoNT injection.

masseter muscle during swallowing, clenching, mastication, and at rest. All patients presented with satisfactory regression of MMH after 20 days on average. Only in 1 case we performed a second injection monolaterally, after 23 days, to reach a satisfactory result (Table 3). There were no local or systemic complications associated with the injection of BoNT. The masseteric muscle was clinically reduced. The followup was, on average, 12 months; only in 1 case, after 6 months, a relapse was noted and a second injection was performed. Electromyographic examination denotes after 5 months, on average, a resumption of muscular tone, but there was no esthetical change found. DISCUSSION

Table 2. Patients’ Demographic Data Patient No. 1 2 3 4 5

Sex

Age, y

Male Male Female Female Female

54 53 56 46 48

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o achieve a slim and smooth contour line of the lower face, conventional treatment has concentrated on 2 approaches: surgical resection of the masseteric muscle or modeling ostectomy of squareangled mandibula. In 1951, Converse12 finally announced for the first time that the resection of both the bone and

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BOTULINUM TOXIN TYPE A FOR THE LOWER FACE / Tartaro et al

Fig 4 Electromyographic study of the masseteric muscle 21 days after injection.

Fig 2 Follow-up of the patients after 9 months from the injection.

the muscle could be done at the same time through the intraoral incision. Whitaker13 reported in 1989 that the width of the lower face could be reduced

Fig 3 Electromyographic study of the masseteric muscle before injection of BoNT.

through the ostectomy of cortical bone of the mandibula, together with the resection of the masseteric muscle. Baek14 found that the masseteric muscle volume is reduced over time as the muscle tone deteriorates when only the mandibula was resected, whereas Hong et al15 proved that after the ostectomy of the mandibula, the nonused masseteric muscle becomes atrophied over time through the Gato experiment. The resection of the masseteric muscle is likely to cause a variety of side effects such as bleeding, hematoma, facial nerve injury, and asymmetric resection. Although the operation itself is relatively simple, it is difficult to predict the outcome. Moreover, muscle resection may result in unwelcome side effect such as bleeding, asymmetry, and uneven contour lines.16 In this respect, even in the case of muscular hypertrophy, surgical treatments for the square-angled jawbone have been frequently applied. If muscular dystrophy is not as much as expected, however, the change in the lower face from the front is minimal. Thus, the need to reduce the lower muscular volume in a safe manner has been raised. In 2001, von Lindern et al17 announced that the masseter muscle can be reduced using BoNT A in the case of masticatory hypertrophy. Botulinum toxin A is a well-known potent bacterial substance naturally produced by C. botulinum. The toxin binds to the presynaptic cholinergic nerve terminals and inhibits the release of acetylcholine, causing paralysis and subsequent functional denervated muscle atrophy. However, the axon terminal begins to proliferate within 2 days of exposure to the toxin and forms new extrajunctional 1615

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THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 19, NUMBER 6 November 2008 Table 3. Results of the Study Patient No.

Sex

Age, y

Clinical Findings

Treatment

Improvement

Relapse

1 2 3

M M F

54 53 56

R-L MMH R-L MMH stg R-L MMH stg

Yes Yes Yes

No No Yes

4

F

46

R MMH stg

Yes

No

5

F

48

R-L MMH

1st A: 50 U Botox 1st A: 50 U Botox Bite plane 1st A: 50 U Botox 2nd A: 50 U Botox Bite plane 1st A: 50 U Botox Bite plane 1st A: 50 U Botox

Yes

No

R indicates right; L, Left; stg, sign of tooth grinding; A, application.

acetylcholine receptors as new synapses make contact with the adjacent muscle fibers.18Y20 Therefore, the effect of binding of the toxin to the neuromuscular junction, causing muscle atrophy, is a temporary event, and new neuromuscular synapses can be resynthesized during a period of a few months. Another possible reason for the temporary nature of the action is that antibodies may develop after repeated injections.21 In fact, there are 2 kinds of therapy failure after a BoNT injection22; the first is primary therapy failure, which means that BoNT therapy fails from its first application. Secondary therapy failure implies that it is initially successful but fails in its further course. The causes of primary therapy failure include BoNT-insensitive cases such as myasthenia gravis, reduced BoNT sensitivity cases such as antecolis, technical problems such as inadequate dosing or improper placement, and possible preexisting antibodies against BoNT. Secondary therapy failure is mainly caused by antibodies against BoNT, which can be either the neurotoxin component or, theoretically, the nontoxic proteins of BoNT. Antibodies against nontoxic proteins can occur, but the effects are not clearly understood currently.23 Lee in a study affirms that the 2 common factors implied in antibody formation are high single doses and short interinjection intervals.24,25 In our experience, BoNT injection for the contouring of the lower third of the face is a safe treatment with respect to surgical muscle resection, and an asymmetry developed from the first injection can be solved with a second one, after 21 days on average.26,27 No antibody formation was developed after short interinjection intervals. An aesthetic satisfactory result was reached in the 100% of cases, and a resumption of muscular tone was evidenced with an electromyographic examination; it was not associated with a lost of aesthetic result. Probably the patient should be educated in his occlusion to get a long-term result. In most MMH cases, the etiology is unexplained; it has been attributed to many causes

such as malocclusion, bruxism, clenching, and TMJ disorders.28 In the 60% of the patients presented, the treatment included the control of parafunctional activities involving the masticatory musculature of patients. Only in 1 case where we performed the control of parafunctional activities we had a relapse, but probably this is related to a noncompliance of the patients after first injection; in fact, after the second one, no relapse was noted. From our study, we can affirm that BoNT type A can safely be considered as a noninvasive drug treatment for patients with MMH, but the reduction in the thickness of the masseter can provoke relative prominence of the malar and mandible angle, so before the injection, it is very important to study the facial bones and desire of the patients. From published literature, similar results are reached; we also performed a management of occlusal and muscular parameters. Probably, in patients with deleterious habits for occlusion and mastication control, the association with this treatment can give a longer result with BoNT injection.26Y28 Therefore, the results from this study suggest that the use of BoNT type A for contouring of the lower face can be established as a simple, predictable, alternative facial contouring procedure. REFERENCES 1. Jost WH. Other indications of Botulinum toxin therapy. Eur J Neur 2006;13:65Y69 2. Rocenvic R. Masseter muscle hypertrophy. Aetiology and therapy. J Maxillofac Surg 1986;14:344 3. Moore AP, Wood GD. The medical management of masseteric hypertrophy with botulinum toxin type A. Br J Oral Maxillofac Surg 1994;32:26 4. Smyth AG. Botulinum toxin treatment of bilateral masseteric hypertrophy. Br J Oral Maxillofac Surg 1994;32:29 5. Mandel L, Tharakan M. Treatment of unilateral masseteric hypertrophy with botulinum toxin: case report. J Oral Maxillofac Surg 1999;57:1017 6. Newton JP, Cowpe JG, McClure IJ, et al. Masseteric hypertrophy: preliminary report. Br J Oral Maxillofac Surg 1999;37:405 7. National Institutes of Health (NIH). Clinical use of botulinum

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BOTULINUM TOXIN TYPE A FOR THE LOWER FACE / Tartaro et al

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