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Asymmetrical Smiles Corrected by Botulinum Toxin Serotype A
ANTHONY V. BENEDETTO, DO, FACP�
OBJECTIVE The objective was to identify the cause of an asymmetrical smile and to ascertain whether ornot it would be correctable by injections of Botulinum toxin A (BTX-A).
METHODS Five patients with asymmetrical smiles were identified and found to lower one side of theirlower lip in an exaggerated fashion when smiling or laughing. After close observation, it was determinedthat the ipsilateral depressor labii inferioris of the lower lip was hyperkinetic and retracted that side of thelips lower than its contralateral side when smiling or laughing. Injections of low-volume and low-dose BTX-A (BOTOX, Allergan, Inc.) were placed into the depressor labii inferioris on the side where the lower lipretracted the lowest.
RESULTS All of the five patients with asymmetrical smiles presented with unilateral hyperkinetic de-pressor labii inferioris and responded to injections of BOTOX. Their lower lips became level and theirsmiles were symmetrical within 1 week of the BOTOX treatments. Their lip symmetry lasted for at least 6months after their initial treatment. With each additional treatment, the duration of BOTOX lasted evenlonger, averaging approximately 7 months.
CONCLUSION BOTOX is an effective, safe, and long-lasting treatment for lower lip asymmetries causedby a hyperkinetic depressor labii inferioris.
Dr. Benedetto is a stock holder, is on the Speakers Bureau for Allergan, and has been a member of the BOTOXNational Education Faculty Network since 2002.
Facial asymmetry (FA) can result from many dif-
ferent causes, which will determine whether or
not it can be reversible. There are three basic types of
facial asymmetries. Acquired FA is the result of a
medical or physical episode, e.g., a cerebral vascular
accident or facial nerve (Bell’s) palsy. FA can be the
result of iatrogenic causes as in the case of facial nerve
palsy resulting from the severance of the facial nerve
during a parotidectomy or other types of surgery on
the face (e.g., deep surgical resection of skin cancer).
A temporary paresis can be iatrogenically produced
by the inadvertent diffusion to adjacent muscles of
botulinum toxin (BTX) injected for therapeutic or
cosmetic reasons. In the case of a parotidectomy, or
deep tissue surgical resections and severance of the
facial nerve, the palsy is usually irreversible depending
on the location of the nerve trunk interruption. In the
case of the inadvertent paresis resulting from a
treatment of BTX, however, the palsy is temporary
and reversible. A third type of FA can be idiosyncratic
or familial, whereby one of a pair of muscles on one
side of the face can be comparatively stronger or
weaker than its partner muscle on the contralateral
side of the face.1 This is seen as a subtle displacement
in the level of the eyebrows or, more obviously, as an
asymmetrical smile.2 In many, a naturally occurring
asymmetrical smile usually is a familial trait passed
down from one generation to the next, typifying a
certain characteristic trait such as the ‘‘family smile’’
(Figure 1). In this pilot study, patients with idiosyn-
cratic asymmetrical smiles were treated with injec-
tions of botulinum toxin serotype A (BTX-A),
specifically BOTOX (Allergan, Inc., Irvine, CA),
which produced a symmetrical, more balanced smile.
& 2007 by the American Society for Dermatologic Surgery, Inc. � Published by Blackwell Publishing �ISSN: 1076-0512 � Dermatol Surg 2007;33:S32–S36 � DOI: 10.1111/j.1524-4725.2006.32329.x
3 2
�Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania School of Medicine, and MedicalDirector, Dermatologic SurgiCenter, Philadelphia, Pennsylvania
Case 1
A 46-year-old professional woman was always
bothered by her obviously ‘‘crooked’’ or asymmet-
rical smile, which was present for as long as the
patient can remember and as early as preadoles-
cence. Because of her status in the work place,
smiling or laughing was an anxiety provoking emo-
tive response. This caused the patient to always
cover her mouth when the occasion for laughing or
smiling presented itself. The asymmetrical smile was
determined to be caused by a unilateral hyperkinetic
depressor labii inferioris (DLI) on the left when
compared to the strength and activity of its paired
DLI on the contralateral right side (Figure 2). After
identifying the reason for the patient’s asymmetrical
smile, 3 U of BOTOX were injected into the belly of
the hyperkinetic DLI on the left side of the lower lip.
Within 96 hours the stronger left DLI was weakened
and resulted in a leveling of the lower lip margin
causing the lower lip to appear normal and sym-
metrical when the patient smiled or laughed. The
symmetrical smile lasted approximately 5 1/2
months after the first treatment and 6 to 8 months
after subsequent treatments (see Table 1).
Figure 1. Father (A) and daughter (B) have the same asymmetrical smile that manifests as an uneven lower lip margin on theright.
Figure 2. Asymmetrical smile with depressed lower lip margin on the left before (A), 3 weeks after (B), and 6 months after(C) 3 U of BOTOX. Note the reduction of the lower ‘‘dental show.’’
3 3 : S 1 : J A N U A RY 2 0 0 7 S 3 3
B E N E D E T T O
Case 2
A 49-year-old woman was unaware of her asym-
metrical smile that was characterized by an uncon-
scious excessive lowering of the right side of the
lower lip when she smiled or laughed. This was
brought to her attention during a treatment session
of BOTOX injections for her upper face wrinkles
(Figure 3). After determining the right DLI was
hyperkinetic compared to its contralateral paired
muscle, 2 U of BOTOX were injected into the belly
of her right DLI. In approximately 1 week, the pa-
tient’s smile was noticeably even and symmetrical.
The effects of the BOTOX lasted approximately 5
months after the first treatment and 7 to 8 months
after subsequent treatments (see Table 1).
Case 3
A 21-year-old female presented with a right sided
lower lip hyperkinetic DLI causing an asymmetrical
smile that was present since birth. This patient’s
smile closely resembled that of her father’s smile,
which was identical in location and appearance
(Figures 1 and 4). None of her other three siblings
(two older brothers and one younger sister) or her
mother exhibited such an asymmetrical smile. After
identifying the right DLI as hyperkinetic and the
cause of her asymmetrical smile, 1 U of BOTOX was
then injected intramuscularly into it. This produced
a symmetrical smile that lasted more than 8 months
with the first treatment (see Table 1).
Methods
BOTOX was the only BTX-A used to treat the
hyperkinetic DLI of the patients presented. A vial of
100 U of BOTOX was reconstituted with 1 mL of
preserved normal saline. After the causal hyperkin-
etic DLI was identified and confirmed, 1 to 3 U of
BOTOX were injected into the belly of the muscle
just below the mental crease to avoid injecting the
lower fibers of the orbicularis oris and at a point that
was medial to the depressor anguli oris and lateral to
the mentalis. Individual dosing was selected accord-
ing to the severity of the asymmetry and the per-
ceived strength of the hyperkinetic DLI.
TABLE 1. Details of Cases
Case Sex Age of onset Age (years) Location BOTOX units Duration (months)
I Female Childhood 46 Left DLI 3 U 6
II Female Unknown 49 Right DLI 2 U 7
III Female Birth 21 Right DLI 1 U 8
IV Male Childhood 55 Right DLI 3 U 6.5
V Female Childhood 32 Right DLI 2 U 7.5
Figure 3. Patient with lower right asymmetry before (A) and 3 weeks after (B) 2 U of BOTOX. Note the elimination of thelower ‘‘dental show.’’
D E R M AT O L O G I C S U R G E RYS 3 4
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Results
In less than 5 days a typical low dose of 1 to 3 U of
BOTOX weakened the hyperkinetic side of the lower
lip and made the smiles of the patients symmetrical.
The effects of the injected BOTOX lasted at least 4
to 5 months after the first treatment and much
longer with subsequent treatments, producing a
symmetrical smile that lasted a mean of 7 months for
each patient (see Table 1).
Discussion
FAs when acquired as a result of nerve injury can be
reversible or permanent. Facial nerve (Bell’s) palsy
caused by an inflammatory process usually is re-
versible, but it also can be recurrent. When FA is the
result of damage to the facial nerve because of an
accidental episode or an incidental surgical resection,
the FA usually is permanent but eventually can be
reversible. This depends on how completely severed
the facial nerve is, how distal the injury is from the
main trunk of the facial nerve, and how well the
damaged nerve can repair and reanimate itself. Iat-
rogenically acquired FAs that result from a segmen-
tal facial palsy produced by the unintentional but
inadvertent diffusion of BTX into nontargeted ad-
jacent muscle fibers after a therapeutic or cosmetic
treatment are temporary and reversible. Finally,
there is another type of FA that is idiosyncratic to a
particular person and can manifest either randomly
in isolated individuals or in persons in different
generations of a particular family.2
These familial traits frequently can be disconcerting
and embarrassing to [by] the bearer. Before BTX such
FAs were correctable only by surgical intervention.
Now BTX can provide a simple, noninvasive, safe
way of correcting obtrusively distracting asymmet-
rical smiles.3 Four of our patients were aware of their
lip asymmetry; one was not. When the asymmetrical
smile was identified and brought to the attention of
the one patient who was unaware of it, that patient
became a faithful and regular recipient of the cor-
rective BOTOX treatments, especially when she
realized how easily and painlessly it was to treat. It is
essential that a physician possess a comprehensive
understanding of the functional anatomy of the mi-
metic muscles of the face when treating patients with
BTX.4,5 When evaluating the patients in this pilot
study, it became apparent that the asymmetries of
their lower lips were created by the enhanced down-
ward pull of one of the paired DLIs.6 The idiosyn-
cratic, unilateral, hyperkinetic DLI of the lower lip
caused an ipsilateral retraction of the lip margin
lower than its contralateral side, which resulted in lip
asymmetry during a smile or while laughing. A few
units of highly concentrated BOTOX injected into the
overactive muscle fibers of the DLI responsible for the
asymmetry of the lower lip produced a gentle relax-
ation of the ipsilateral DLI which then functioned in
unison with its contralateral DLI partner resulting in
symmetry to the patients’ smile. Such corrections are
easily accomplished when one can identify the source
of the asymmetry. Accurate injections of precise
amounts of low-volume BOTOX can then be utilized
Figure 4. Patient with a characteristic ‘‘family smile’’ before (A) and 7 months after (B) her first treatment with 1 U of BOTOX.Note the elimination of the lower ‘‘dental show.’’
3 3 : S 1 : J A N U A RY 2 0 0 7 S 3 5
B E N E D E T T O
to produce a very long-lasting, well-appreciated cor-
rection of naturally occurring, but unwanted, lower
lip asymmetry.
When the hyperkinetic DLI is weakened, the result-
ant leveling of the lower lip in an asymmetrical smile
may diminish and even eliminate the lower ‘‘dental
show’’ that the patient has become accustomed to
seeing during a smile or laughter. This dental show
commonly is present only on the side of the hyper-
kinetic DLI and only because that DLI is hyperactive.
When the smile becomes symmetrical the dental
show commonly is eliminated. Likewise, when the
asymmetry occurs in the upper lip there frequently is
a ‘‘gingival show’’ instead. The releveling of an upper
lip asymmetry, however, is not as straightforward as
it is in the lower lip, because of the different levators
that might be producing the asymmetry.
Before any correction of lower lip asymmetry, the
patient must be advised of the possible reduction in
lower lip dental show. Also there are times when the
first treatment with BOTOX does not exactly pro-
duce the expected outcome, i.e., a perfectly sym-
metrical smile. Rather, what usually is produced is a
‘‘more symmetrical’’ smile. Informing the patient of
this beforehand will avoid disappointment afterward.
It is also possible that just 1 or 2 U of BOTOX in a
particular patient will overly weaken the ipsilateral
hyperkinetic DLI, especially in subsequent treatments
during maintenance, whereby the contralateral DLI
may or may not overly compensate and create a sec-
ondary asymmetrical smile. In such situations 0.5 to
1 U of BOTOX in the contralateral DLI may be
needed to maintain dynamic symmetry. Therefore,
perfect results should never be guaranteed particu-
larly when treating for the first time any new ana-
tomic site with BOTOX, especially in the lower face.
In this pilot study, none of the patients experienced
any complications. What probably can occur as a
complication is the overtreatment of a DLI by an
overzealous injector.7 Minimal doses in minimal vol-
umes of BOTOX should be injected because it is also
possible that an exaggerated response of the treated
DLI to 1, 2, or more units of BOTOX might occur,
particularly with subsequent maintenance treatments.
This would result in an inability of the patient to
retract the lower lip. An adynamic DLI would inter-
fere with the daily activities of eating, drinking, and
speaking. Biting of the lower lip while eating or
speaking conceivably could occur. Incontinence of li-
quid and solid food could also result. Large volumes
of injected BOTOX could diffuse peripherally and
inadvertently affect the mentalis, the contralateral
DLI, or even the ipsilateral depressors anguli oris and
orbicularis oris depending on the volume injected.
None of these complications, however, were ever ex-
perienced by any of the patients in this study.
Because the use of BOTOX in clinical medicine has
become more readily acceptable by physicians and
patients, simple and safe treatments such as the
noninvasive correction of an asymmetrical smile can
become an indispensable component of a dermatol-
ogist’s therapeutic armamentarium.
References
1. Benedetto A. Cosmetic uses of botulinum toxin a in the upper face.
In: Benedetto AV, editor. Botulinum toxin in clinical dermatology.
London: Taylor & Francis Group, 2005:p. 78–95.
2. Benedetto A. Cosmetic uses of botulinum toxin in the mid face. In:
Benedetto AV, editor. Botulinum toxin in clinical dermatology.
London: Taylor & Francis Group, 2005:p. 156–61.
3. Blitzer A, Binder WJ, Aviv JE, et al. The management of hyper-
functional facial lines with botulinum toxin. Arch Otolaryngol
Head Neck Surgery 1997;123:389–92.
4. Carruthers J, Carruthers A. Botox use in mid and lower face and
neck. Semin Cutan Med Surg 2001;20:8592.
5. Fagien S. Botulinum toxin type A for facial aesthetic enhancement:
role in facial shaping. Plast Reconstr Surg 2003;112:65–185.
6. Hoefflin SM. Anatomy of the platysma and lip depressor muscles: a
simplified mnemonic approach. Dermatol Surg 1998;24:1223–31.
7. Klein AW. Complications and adverse reactions with the use of
botulinum toxin. Semin Cutan Med Surg 2001;20:109–20.
Address correspondence and reprint requests to: Addresscorrespondence and reprint requests to: Anthony V.Benedetto, DO, FACP, Dermatologic SurgiCenter, 1200Locust Street, Philadelphia, PA, or e-mail:[email protected].
D E R M AT O L O G I C S U R G E RYS 3 6
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