Volume 32, Issue 1 , Pages 1-7, January 2011
A systematic algorithm for the management of lower lip asymmetry☆
Article Outline
- Abstract
- 1. Introduction
- 2. Anatomy
- 3. Patients and methods
- 4. Results
- 5. Comment
- 6. Conclusions
- Acknowledgments
- References
- Copyright
Abstract
Purpose
An asymmetric smile, caused by loss of function of the lip depressors, can be functionally and cosmetically debilitating. Although some surgeons report excellent results with muscle transfer to the lower lip, many facial reanimation surgeons find that dynamic techniques do not consistently address the lower lip. Our objectives were to retrospectively review our outcomes after treatment of the asymmetric lower lip, and to propose a progressive, stepwise algorithm for the management of lower lip asymmetry in facial paralysis.
Material/Methods
Retrospective chart review was performed on all patients treated in a multidisciplinary facial nerve center with lower lip asymmetry over an eighteen month period. Treatment ranged from a temporary trial of lidocaine, to chemodenervation with botulinum toxin, to pedicled digastric muscle transfer, and/or resection of the nonparetic depressor labii inferioris (DLI).
Results
Fifty-seven patients were treated with chemodenervation with botulinum toxin, four with anterior belly of the digastric transfer, and 3 with DLI resection. All patients with DLI resection had undergone chemodenervation to the contralateral lower lip with botulinum toxin and were pleased with the appearance of their smile.
Conclusions
We have found that lower lip asymmetry is optimally managed by adherence to a standardized protocol that offers patients insight into the likely outcome of chemodenervation or surgery and progresses systematically from the reversible to the irreversible. We present our algorithm for the management of the asymmetric lower lip, which reflects this graduated approach and has resulted in high patient satisfaction.
1. Introduction
Facial paralysis can create severe debilitation and social isolation. The inability to depress the lower lip, from either an isolated marginal mandibular nerve paralysis or a complete facial paralysis, significantly limits a patient's ability to express a range of emotions. Patients with lower lip asymmetry are not able to depress, lateralize, or evert the lower lip, resulting in a smile pattern characterized by an elevated and inverted lower lip. Smile asymmetry is especially pronounced in patients with a “full denture” smile, in which all muscles are activated when smiling [1].
Techniques to manage the asymmetric lower lip revolve around either restoration of dynamic depressor muscle function on the paralyzed side [2], [3], [4], [5], [6] or the weakening of functional side to improve symmetry [7], [8], [9], [10], [11]. Methods that restore dynamic depressor muscle function have been reported in the literature, but require moderately involved surgical procedures under general anesthesia, and yield unpredictable results. Techniques that weaken the functional side, by chemodenervation with botulinum toxin or by depressor labii inferioris (DLI) resection, have been shown to be safe and effective office-based procedures, yielding high patient satisfaction [8], [10], [11]. Despite this, patients with unilateral facial weakness are frequently psychologically unprepared for the suggestion that removal of additional facial movement might provide a benefit.
Many centers manage patients with lower lip asymmetry; however, in the current literature, a systematic management strategy, using a multitude of available techniques, does not exist. Herein, we describe our management of patients with lower lip asymmetry, and suggest an algorithm for the stepwise management of the asymmetric lower lip that we have found provides improved balance of the lower lip during facial expression, and higher patient satisfaction.
2. Anatomy
The depressor muscles of the lower lip include the DLI, the depressor anguli oris (DAO), and the platysma muscle [1], [10], [11]. The mentalis muscle, located medial to this complex of muscles, acts as a lower lip elevator and everter. The DLI is the muscle most responsible for depression of the lower lip. It originates from the lower lateral surface of the body of the mandible, inferior to the mental foramen and inserts into the inferior and superficial surface of the orbicularis oris. At its origin, the DLI is 3 cm wide and covered laterally by the DAO for 1 to 2 cm, narrowing to 2 cm before insertion. The DLI everts the vermilion and depresses and lateralizes the lower lip. The DAO originates from the mandible, superficial to the DLI, and inserts onto the modiolus to depress the corner of the mouth. The platysma muscle plays a minor role in depressing the lip through its facial connections, although its resting tone can influence the resting, static position of the lower lip [1].
3. Patients and methods
A retrospective chart review was performed on all patients evaluated and treated in a multidisciplinary facial nerve center setting over an 18-month period who demonstrated lower lip asymmetry as a result of facial paralysis. Our stepwise clinical approach has evolved over the previous four years, and now begins with a one-time lidocaine injection to provide an immediate but short-lived visual sense of the potential effect of chemodenervation. If balance is improved and oral competence maintained, chemodeneravation with botulinum toxin is offered. During the study period, DLI division was offered in cases where repeat injections with botulinum toxin met with high satisfaction, and digastric transfer was offered in patients who categorically declined any “weakening” interventions or who were unhappy with the results of lower lip weakening. This study was approved by the institutional review board at the Massachusetts Eye and Ear Infirmary.
3.1. Technique for local anesthetic injection
The depressor labii inferioris muscle was identified by palpation of the lower lip, near the junction of the medial and lateral lower lip, while the patient was asked to fully animate his or her lip complex (Fig. 1). The area of maximal resistance, noted as the examiner pushed up on the vermillon border, corresponded with the location of insertion of the DLI. The point of injection of local anesthesia was into the midsection of the muscle along its lateral border, to prevent inadvertent injection into the orbicularis oris muscle [10]. The injections were performed in the office setting, with 2 mL of 1% lidocaine containing 1:100 000 epinephrine.
Fig. 1.
Demonstration of the injection site used to deliver lidocaine into the midpoint of the depressor labii inferioris (DLI) muscle.
3.2. Technique for chemodenervation with botulinum toxin
If a patient was satisfied with the results of the motor blockade by injection with lidocaine, the patient was offered chemodenervation with botulinum toxin at the next clinic visit. The DLI muscle was identified in the same fashion as described for local anesthetic injection [10]. Five units of botulinum toxin type A (100 U was mixed with 2 mL of normal saline creating a 5 U/.1 mL solution) was then injected into the midsection of the depressor labii inferioris muscle. Patients were seen in follow-up 2 to 3 weeks post injection to determine the success of the treatment. If the patient was satisfied with the results from chemodenervation, repeat injection was offered at 4- to 6-month intervals.
3.3. Technique for depressor labii inferioris division
Patients that continued to be satisfied with the results of chemodenervation after serial chemodenervation treatments were offered DLI resection (Fig. 2). Ordinarily, DLI resection was performed in the clinic under local anesthesia. The lower lip was anesthetized with 1% lidocaine with 1:100 000 epinephrine. An incision was made in the mucosa of the right lower lip, approximately 1 cm below the margin of the lip. The fibers of the DLI were identified, and a 1 cm length of muscle was excised. The incision was closed in layers.
Fig. 2.
Division of the DLI muscle. Incision site (upper). DLI muscle identification and division (middle). Incision closure (lower).
3.4. Technique for anterior belly of digastric transfer
Under general anesthesia, an incision 2 cm inferior to the inferior mandibular margin was made. The anterior belly of the digastric and the digastric tendon were mobilized to the anterior border of the mandible. Care was taken to preserve the neurovascular pedicle entering the muscle its deep, lateral surface. Care was taken to harvest the digastric tendon in its entirety to ensure adequate length of the transposed tissue. The digastric tendon was cut longitudinally into several slits, and tunneled the to the lower lip vermillon border. A 2-cm incision along the white roll was performed and the tendon was sutured to the orbicularis oris musculature, followed by closure of the incisions [6].
4. Results
Fifty-eight patients were treated for lower lip asymmetry at the MEEI Facial Nerve Center, over an approximately 18-month period. The average patient age was 48 years (range, 14–84 years; SD, 14). The average follow-up period was 18.3 months (range, 10–30; SD, 5.9). Fig. 3 summarizes the etiologies of the facial nerve paralysis. Ten patients had isolated marginal mandibular branch or segmental dysfunction, 44 had incomplete unilateral facial paresis, and 4 had unilateral complete facial paralysis.
Fig. 3.
Chart reflecting the various etiologies of facial paralysis in patients undergoing treatment of an asymmetric lower lip.
Fifty-seven patients were treated with chemodenervation with botulinum toxin, 4 with anterior belly of the digastric transfer, and three with DLI resection. Injection of 2 mL of 1% lidocaine reflected the functional and aesthetic results that a patient could expect with botox (Fig. 4). One patient with DLI resection required repeat resection; however, all were satisfied with the final result (Fig. 5). None of the patients treated with chemodenervation or DLI resection reported infection, poor aesthetic result, interference with speech, mental nerve injury, or oral incompetence.
Fig. 4.
Chemodenervation with botulinum toxin. (A and B) Note the asymmetry of the lower lip prior to chemodenervation. (C and D) Observe the improved symmetry of the lower lip after chemodenervation.
Fig. 5.
DLI division. (Left) Patient with a traumatic facial nerve injury showing asymmetry of the lower lip. (Right) Improved symmetry of the lower lip after resection of the DLI muscle.
Of the 57 patients treated with chemodenervation, 48 patients were happy with the results and received 2 or more treatments (84.2% success rate). Three of the patients who were not satisfied with the results of contralateral lower lip chemodenervation elected to have anterior belly of digastic transfer for lower lip reanimation. The other 6 patients dissatisfied with chemodenervation elected not to undergo further treatment.
Patients treated with anterior belly of digastic transfer had inconsistent results. Three of 4 were satisfied with their results (Fig. 6); however, 1 patient required reversal of the procedure for management of excessive bulk at the vermillion border.
Fig. 6.
Anterior belly of the digastric transfer. (Left) Asymmetric lower lip prior to treatment. (Right) Improved symmetry of the lower lip after muscle transfer.
5. Comment
The management of patients with facial paralysis has undergone many changes over the past thirty years. Microsurgical techniques and a deeper appreciation of neuromuscular physiology have lead to a wider variety of techniques to manage the asymmetric lower lip, amongst these instruments are free extensor digorum brevis transfer, anterior belly of the digastric transfer, minihypoglossal nerve transfer to the cervicofacial branch, direct neurotizaton of the depressor muscle, and platysma muscle transfer [2], [5], [6], [12]. Invasive management strategies for the contralateral side include neurectomy of the contralateral marginal mandibular branch [7]. All of the above procedures require general anesthesia and advanced surgical techniques with inconsistent and sometime unsatisfactory lower lip symmetry and function.
Office-based procedures for the management of the asymmetric lower lip provide safe and reliable results, without the need for general anesthesia. For 20 years, botulinum toxin has been used to treat the contralateral side in patients with facial nerve paralysis [9]. More recently, chemodenervation with botulinum toxin has been shown to produce a balanced smile without oral incompetence or interference with speech [8]. Depressor labii inferior resection has been shown to produce a more symmetric smile and decrease the amount patients bite their lower lip, without causing oral incompetence or speech problems [11]. In addition, patients preferred bilateral lack of movement of the lower lip over the lack of symmetry when expressing emotion [11]. To help to determine patient satisfaction before DLI resection, Manktelow et al [10] showed that a trial of local anesthetic before DLI resection provided patients with valuable insight into the likely outcome of the surgery.
Given the success of office-based procedures of the lower lip, we have developed a treatment algorithm to integrate existing management techniques to improve patient satisfaction and ultimate preparedness for contalateral lower lip weakening (Fig. 7). Like Manktelow, we propose that all patients considering contralateral weakening first receive a trial injection of lidocaine. If a patient is pleased with the results of the short acting muscle blockade, we recommend chemodenervation with botulinum toxin. If, after three serial chemodenervation treatments spaced 4 to 6 months apart, a patient continues to receive significant benefit, we then recommend DLI resection. This permits a prolonged decision-making period, during which a patient can see and understand the effect of contralateral lower lip weakening. Frequently, the effect has to be present for a significant period (months) and then allowed to wear off before it can be fully appreciated. Patients who underwent DLI resection preferred this procedure over recurrent chemodenervation because it produced a symmetric smile without the need for repeated treatments.
Fig. 7.
Treatment algorithm to integrate existing management techniques to improve patient satisfaction and ultimate preparedness for contalateral lower lip weakening. Note the use of repeated botox injections prior to performing DLI resection.
Patients with facial paralysis have significant distress about their decreased ability to express emotion in a social setting. Whether a patient has isolated congenital unilateral lower lip paresis or complete facial paralysis, accepting the notion of weakening the functional side is often an emotionally trying decision. Our algorithm provides an organized treatment strategy, which permits patients to be treated with proven interventions and to decide if they are likely to benefit from surgery before undergoing definitive DLI resection. Surprisingly, we have additionally found that favorable results from free gracilis transfer for smile reanimation called new attention to the lower lip area. Patients, whose initial dominant complaint was lack of smile, began to complain newly of lower lip asymmetry, after successful smile reanimation. Therefore, the algorithm is also suitable for patients in which lower lip asymmetry was not initially a dominant complaint, but who experience lower lip asymmetry after successful smile reanimation.
6. Conclusions
The management of facial nerve disorders remains a complex entity without widely excepted pathways for the management of many facial zones. Management of lower lip asymmetry can make critical differences in facial balance and should no longer be overlooked. We suggest that adherence to the management elements presented within this algorithm for lower lip asymmetry will improve outcomes, largely by permitting patients to appreciate for themselves whether decreasing the function of the contralateral lower lip provides a significant benefit in their individual clinical situation.
Acknowledgments
Dr Robin Lindsay and Dr Tessa Hadlock had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
References
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☆ Presented at the XI International Facial Nerve Symposium, Rome, Italy April 25–28, 2009.
PII: S0196-0709(09)00166-5
doi:10.1016/j.amjoto.2009.08.011
Published by Elsevier Inc.
Volume 32, Issue 1 , Pages 1-7, January 2011
