Comprehensive Rehabilitation of Patients with Facial Expression Asymmetry and Synkinesis with Botulinum Toxin Type A and Monofilament Mesothreads

Abstract

Facial neuropathy is a lesion of the facial nerve of various nature happening at different anatomical levels, which is manifested by unilateral paralysis or paresis of the facial muscles and is complicated by synkinesis and contractures of the paretic muscles. The leading clinical symptom of this disorder is mimic asymmetry, which occurs as a result of a violation of the neuromuscular balance of both hemifaces (weakness on the side of the lesion and hypertonicity on the contralateral side). Understanding the special functional state of the unaffected hemiface made it possible to develop a pathogenetically substantiated method for the treatment of mimic asymmetry. The effect of botulinum toxin type A on the muscles of the healthy hemiface contributes to a better restoration of the motor activity of the affected muscles and the symmetry of the face. Implantation of monofilament mesothreads in the facial area was used to correct synkinesis. We have proposed a method that creates a rigid mesh frame using mesothreads between the skin and the muscles of facial expression in the area of synkinesis. This led to a significant decrease in the severity of clinical symptoms, a decrease in the frequency and amplitude of involuntary muscle contractions in the face.

1. Introduction

The face has a unique nervous system. The nervous system of the face is a single synergistic system that combines both hemifaces [1, 2, 3, 4, 5]. Clinical observations show that pathological processes in the face are most often unilateral (Bell’s palsy, trigeminal neuralgia, hemifacial spasm, etc.) [2, 3, 4, 5, 6, 7]. However, in recent years, the question of the influence of the contralateral conditionally healthy hemiface in the pathological process has been actively studied [1, 2, 3, 4, 8]. The lesion of the muscles of facial expression in facial neuropathy is also considered as a bilateral process, which involves the nervous system of both hemifaces. Besides the weakness of the muscles innervated by the facial nerve on the affected hemiface, there is an absolute hypertonicity of the muscles of facial expression of the healthy hemiface [1, 2, 3, 4, 9]. Normally, in facial neuropathy the healthy hemiface is used for the comparison. However, a special functional state of the contralateral side, manifested by increased muscle tone, is one of the causes of facial expression asymmetry (static and dynamic) [3, 8, 9, 10]. An EMG analysis of the muscle tone of the face in the “healthy” hemiface revealed a statistically significant increase in bioelectrical activity (BEA) in patients with facial nerve neuropathy in comparison to the control group (p < 0.05) [1, 11]. The data obtained allow us to assert that the true over action of muscles of facial expression is formed on the “healthy” side. Activation of the contralateral side is a maladaptive response and requires therapy [1, 2, 3, 4, 8, 9, 10]. We have used the method to influence muscle hypertonicity of the healthy hemiface in neuropathy of the facial nerve using local injections of botulinum toxin type A. Synkinesis (Greek. syn – together and kinesis – movement) is the most common complication of the facial neuropathy. Joint movements, in the form of involuntary contractions of the facial muscles that occur when performing basic facial expressions, are observed [12, 13, 14]. A patient’s quality of life significantly reduces due to the synkinesis. The treatment of synkinesis is very difficult due to the lack of a positive effect of a traditional pharmacotherapy. A local injection of botulinum toxin type A in the area of synkinesis can bring a good but temporary effect [11, 14]. However, the weakness of muscles of facial expression, which develops at the same time, causes a significant frustration in patients and creates discomfort. A joint work of neurologists and plastic surgeons allowed us to propose a method for correcting synkinesis using monofilament mesothreads, which are commonly used in esthetic practice.

2. Comprehensive rehabilitation of patients with facial expression asymmetry

2.1 The use of botulinum toxin type A in patients with facial expression asymmetry

The main task of botulinum toxin therapy of facial expression asymmetry in neuropathy of the facial nerve is to influence the hypertonicity of the muscles of the healthy hemiface by muscle relaxation. The increased activity of the muscles of the contralateral (healthy) hemiface is considered to be a mechanism for pathological compensation of the functional motor deficit on the side of the lesion and may prevent or slow down the process of recovery of facial expression activity [1, 2, 3, 4]. As a result of the treatment, after some time (10–14 days), we can observe how the affected muscles restore their functions. This contributes to the regression of facial expression asymmetry [1, 2, 3, 4, 9]. We observed two groups of patients. In group I, there were patients in the acute phase of Bell’s palsy (within 1 month after the onset of the disease), who deliberately refused corticosteroid therapy due to various reasons (diabetes mellitus, osteoporosis, poor tolerance to corticosteroids in history). Thus, monotherapy of Bell’s palsy with botulinum toxin type A was carried out. Group II included patients with facial asymmetry in the late phase of Bell’s palsy. The duration of the disease in this group of patients ranged from 3 months to 19 years.

The Sunnybrook Facial Grading Scale (SFGS) was used to assess facial symmetry and synkinesis, while the facial asymmetry was assessed using the House-Brackmann Facial Nerve Granding Sale scale (1985), which consists of six levels. The first level corresponds to the normal function of the facial nerve, and the sixth level corresponds to its complete dysfunction. Static asymmetry was assessed by the displacement of the denervated muscles in relation to the central line due to the traction of the muscles of facial expression of the unaffected hemiface. Dynamic asymmetry was assessed according to several criteria: blinking frequency (video recording was made during a conversation with a doctor), muscle activity during articulation, and facial expression tests. Clinically, in all patients on the side of the lesion, there were observed narrowing of the palpebral fissure, shortening of the zygomatic and buccal muscles, drooping of the ala of the nose, mouth angle, nasal tip deviation, and displacement of the midline of the lips toward the lesion.

2.1.1 Method of administration of botulinum toxin type A in facial expression asymmetry

To correct (weaken) the pulling effect of the active muscles of the “healthy” hemiface, we perform sequential injections of the frontal, glabellar, periorbital areas, the nasal bridge, the nasolabial fold, the middle of the face, the perioral area, and chin on one side of the face. The target muscles are determined by the facial expression tests (to raise your eyebrows up, to frown, to squint, to “wrinkle” your nose, to show your teeth, to purse your lips). The most active areas of the muscles are injected. After applying local anesthesia and treating the skin with an antiseptic, the patient is given local injections of botulinum toxin type A.

The following treatment protocol was used: 100 units of botulinum toxin type A (botulinum toxin type A complex – hemagglutinin) is reconstituted with 2.0 ml of sodium chloride injection at a concentration of 9 mg/ml (0.9%). In this case, a reconstituted colorless solution is obtained with a concentration of 5 units in 0.1 ml. The solution is injected using a 1 ml syringe with a 30 G needle. In total, 1.25–2.5 units of the drug is injected into one injection point.

Subcutaneous injections are administered in the following areas of the unaffected hemiface:

1. frontalis and glabellar muscles (total 3–4 points, 1.25 units in each point), corrugator muscle (total 1–2 points, 5 units in the head of the muscle, 1.25 units in the tail of the muscle, if necessary), procerus muscle (total 1–2 points with 1.25 units) – Figures 1 and 2;

2. periorbital area (only 4–5 points with 1.25 units, in the area of the upper eyelid the drug is injected into the pretarsal portion of orbicularis oculi muscle) – Figure 3

3. the midface, the nasal bridge, the nasolabial fold – nasalis muscle (1 point with 1.25 units), levator labii superioris muscle (1 point with 1.25 units), zygomaticus minor muscle (1–2 points with 1, 25 units), zygomaticus major muscle (1–2 points with 1.25 U) – Figure 4

4. perioral area – orbicularis oris muscle (only 1–2 points with 1.25 units), m. depressor anguli oris (1 point with 1.25 units), depressor labii inferioris muscle (total 1–2 points with 1.25 units) – Figure 5

5. mentalis area – mentalis muscle (only 1–2 points with 1.25 units).

Figure 1.

Injection pattern of botulinum toxin type A in the frontal region.

Figure 2.

Injection pattern of botulinum toxin type A in the glabellar region.

Figure 3.

Injection pattern of botulinum toxin type A in the periorbital region.

Figure 4.

Injection pattern of botulinum toxin type A in the midface.

Figure 5.

Injection pattern of botulinum toxin type A in the perioral region.

The number of injected points on the face, on average, is 15–20. During the procedure, the patient sits on a chair, resting their head against the wall. Patients sign a voluntary informed consent for medical diagnostic and treatment procedures.

2.1.2 Results of botulinum toxin therapy on facial expression asymmetry

Within 7–10 days after botulinum toxin type A injections, a muscle relaxant effect occurs as a reduction of muscle activity on the “healthy” hemiface and a decrease in the displacement of denervated muscles in relation to the central line of the face. Patients begin to notice a tendency of facial symmetry restoration and then a gradual activity in the denervated muscles. According to our observations, an earlier recovery is observed in the orbicularis oculi muscle, manifested in lagophthalmos regression, making it possible to close the eye, which in turn is important for the eyeball protection. Following, the activity of nasalis muscle and levator labii superioris muscle is restored. The asymmetry of the smile function is the latest to get restored, due to the slow recovery of the activity of the zygomaticus major and minor muscles and the orbicularis oris muscle.

Patients of group I showed the better recovery dynamic due to the treatment. Fourteen days after the injection of botulinum toxin type A, patients of group I showed the average decrease of score on the House-Brackmann scale by 1.85 times (p < 0.05), while in group II patients’ score dropped only by 1.1 times (p > 0.05). After 1 month the improvement in patients of group I was 2.6 times (p < 0.05), and in group II it was 1.5 times (p < 0.05). The general condition of the facial muscles in patients of group I, assessed using the Sunnybrook Facial Grading System, was 3.0 times better than in patients of group II (p < 0.01). It is important to note that in all subscales (symmetry of rest, symmetry of voluntary movements, synkinesis), the indicators in patients of group I were better than in group II. The dynamics of symptoms of static and dynamic facial asymmetry was also more distinct in patients of group I. Patients of group II showed a less noticeable dynamics, which prompted repeated injections of botulinum toxin type A (every 3–4 months for 1–3 years). Normally, a single injection of botulinum toxin type A is sufficient for patients of group I. The ultimate effect is observed after 1 month after the injections. We observed that the muscles of the affected hemiface get restored well enough to begin to “pull” the muscles of the “healthy” hemiface, denervated by botulinum toxin, toward themselves, which is an important detail. In such a case, a temporary asymmetry occurs on the opposite side (Figures 6–25). The patients get informed about this phenomenon prior to the treatment. The effect of botulinum toxin gets ceased, approximately, within 3–4 months. During this period, paretic muscles significantly restore their activity. Thus, the data obtained indicate a higher efficacy of botulinum toxin therapy in patients in the acute phase of Bell’s palsy.

Figure 6.

Bell’s palsy. Patient B. before injections.

Figure 7.

Patient B, 1 month after injection.

Figure 8.

Bell’s palsy. Patient B. before injections.

Figure 9.

Patient B, 1 month after injection.

Figure 10.

Bell’s palsy. Patient B. before injections.

Figure 11.

Patient B, 1 month after injection.

Figure 12.

Bell’s palsy. Patient B. before injections.

Figure 13.

Patient B, 1 month after injection.

Figure 14.

Bell’s palsy. Patient B. before injections.

Figure 15.

Patient B, 1 month after injection.

Figure 16.

Bell’s palsy. Patient А. before injections.

Figure 17.

Patient А., 1 month after injection.

Figure 18.

Bell’s palsy. Patient А. before injections.

Figure 19.

Patient А., 1 month after injection.

Figure 20.

Bell’s palsy. Patient А. before injections.

Figure 21.

Patient А., 1 month after injection.

Figure 22.

Bell’s palsy. Patient А. before injections.

Figure 23.

Patient А., 1 month after injection.

Figure 24.

Bell’s palsy. Patient А. before injections.

Figure 25.

Patient А., 1 month after injection.

We should note that in some patients suffering from the facial expression asymmetry, there was observed a poor recovery of the paretic muscles. This was registered both among patients of group I (20%) and among patients of group II (38%). Unfortunately, we were unable to identify predictors of the efficacy of botulinum therapy for patients with facial neuropathy. However, given the data obtained on a statistically significant improvement of the condition of the majority of patients studied, we believe that every patient with a damaged facial nerve should be offered to receive botulinum toxin injections. Other adverse events of botulinum therapy include temporary dryness of the eye on the side of the injection, which may occur after the drug is injected into the orbicularis oculi muscle.

2.2 The use of monofilament mesothreads for the treatment of synkinesis

Patients, suffering from the lesion of the facial nerve, develop the synkinesis and contractures on the affected side of the face in 4–6 months amid already existing weakness of muscles of facial expression. Synkinesis is involuntary movements of the facial muscles of one muscle group in response to voluntary movements of another muscle group of the face [12, 13, 15]. Currently, there are three hypotheses for the occurrence of synkinesis. The theory that has received the greatest recognition is that after damage, axons undergo aberrant regeneration forming the innervation of those muscles they had not previously been innervated. The second potential pathological mechanism involves ephaptic signaling, in which neighboring axons in the affected area stimulate each other, probably as a result of loss of myelin sheath. Finally, some studies indicate the possibility of a central mechanism of synkinesis origin as a result of overexcitation of the motor nucleus of the facial nerve [14, 15].

In clinical practice, the most common cases of synkinesis are oculo-oral (movement of the zygomaticus major and minor muscles, the orbicularis oris muscle while the arbitrary closure of the palpebral fissure) and oral-ocular (narrowing of the palpebral fissure during mouth movement). To diagnose oculo-oral synkinesis, we use the “frequent blinking” test, when the patient is asked to blink frequently. In this case, there is a contraction of the zygomatic, buccal and perioral muscles observed. To diagnose oral-ocular synkinesis, the “u-e” or “b-p” test is used, which allows to trace the narrowing of the palpebral fissure on the side of the lesion, which manifests in the patient “winking” during a conversation.

Due to the fact that synkinesis is usually manifested by interchanging hyper- and hypokinesis zones, the applied methods of treatment should be aimed both at suppressing excessive muscle activity, depending on the area of the face, and at restoring mobility. Such physiotherapy methods as physiotherapy exercises, massage, electrical stimulations are very arduous and often do not bring the desired results, because they do not influence the pathological “chain of synkinesis,” which is defined by the sequence of involvement of involuntary muscle contractions on the affected side in response to voluntary movement [12, 15]. Botulinum toxin type A is used to selectively suppress the activity of muscle fibers and is effectively used to correct synkinesis [11, 14]. However, after botulinum toxin therapy, temporary weakness of the facial muscles on the affected side may develop, which aggravates the asymmetry and causes frustration (anxiety) in patients. They start feeling as if the symptoms of the disease have reappeared, which makes many of them to refuse subsequent injections. Additionally, the effect of injections is short term (2–3 months). There are also known methods of surgical correction of synkinesis [12, 16], but they require the excision of areas of synkinesis and hospitalization in a surgical department. This can lead to persistent weakness of facial muscles and the formation of muscle contractures [11, 14].

We observed two groups of patients with Bell’s palsy. All patients had oculo-oral and oral-ocular synkinesis, which developed within a year after the disease. The first group of patients received injections of botulinum toxin type A in the areas of synkinesis, while the second group of patients underwent implantation of monofilament mesothreads. The severity of pathological synkinesis was assessed using the Synkinesis Assessment Questionaire (SAQ , 2007).

2.2.1 Method of implantation of monofilament mesothreads to treat synkinesis

Monofilament mesothreads are among the minimally invasive rejuvenation procedures in esthetic medicine, which makes it possible to improve the involutional manifestations of aging. Mesothreads got this name due to their small diameter, comparable to the diameter of a needle for mesotherapy. These threads are used to modify involutional changes in the skin and ptosis of the soft tissues of the face. The visible lifting effect of the soft tissues is determined by creation of a rigid frame consisting of a large number of mesothreads and new collagen fibers forming around them [17, 18]. Clinically, this is manifested by a decrease in the severity of wrinkles and folds and an increase in skin density and elasticity [17, 18]. Mesothreads are completely bioresorbable, often made from polydioxanone - a hypoallergenic, non-toxic material that undergoes biodegradation in 180–240 days, which gives a long-term preservation effect up to 1.5–2 years. Mesothreads are applied in different age groups. In patients younger than 30 years old, it is used to prevent aging of the skin, in the older age groups, it is used to reposition the soft tissues of the face [17, 18].

There has been some data documented about the use of polydioxanone threads in combination with botulinum toxin injections for the treatment of the facial expression asymmetry [19]. The authors used the implantation of toothed threads in the subcutaneous plane along the intended trajectory in patients with unilateral sagging of the face in the late period of facial nerve neuropathy. The authors implanted patients with unilateral sagging of the face in the late period of facial nerve neuropathy with cogged threads in the subcutaneous layer along the planned trajectory. At the same time, local injections of botulinum toxin type A were performed to treat contralateral hypertrophy and ipsilateral synkinesis. As a result, the symmetry of the face got improved. Due to the lifting effect with the help of threads, there was a rejuvenation of the sagging hemiface observed, which occurs as a result of prolonged paralysis of the muscles of facial expression [19].

In our work, we used a completely different approach. We used smooth, monofilament threads (short 3–4 cm, non-cogged threads) in the affected hemiface to correct synkinesis.

The proposed method allows creating a rigid frame-mesh between the skin and muscles of facial expression, which helps to counteract their pathological contraction. The “target” for the implantation of threads is actively contracting muscle bundles. Usually, they are located in the periorbital region, along the nasolabial fold, in the projection of the modiolus and mentalis region. Synkinesis in the periorbital region manifests in muscle contractions in the infraorbital margin, the lateral part of the orbit, the superciliary arch (in the projection of corrugator muscle), as well as in the upper eyelid region. It is not possible to install threads in the upper eyelid region in the projection of levator palpebrae superioris muscle due to the high risk of thread displacement into the orbital region and muscle injury even when implanted superficially. Therefore, the use of mesothreads to treat synkinesis in the upper eyelid, inferior to the orbital rim, is impossible due to the high risk of complications. Threads are installed in the subcutaneous layer attached to the posterior layer of the dermis in the area of synkinesis, between the skin and muscles (Figure 26). The injection site for the introduction of the thread is at a distance of 2–3 cm in each direction from the synkinesis. The threads are implanted at a distance of 1–1.5 mm from each other and in the form of mutually intersecting lines (five threads horizontally and five threads perpendicular or at an angle). The crossing point of the threads should be in the zone of synkinesis (Figure 27). The thickness and length of the thread are selected depending on the area of treatment. The qualification and experience of a plastic surgeon who performs the implantation of mesothreads are key in the successful procedure. Patients were informed about ongoing medical diagnostic and treatment procedures. During the visit, each patient signed a voluntary informed consent.

Figure 26.

Position of the threads for the treatment of synkinesis.

Figure 27.

Potential areas for the implantation of monofilament mesothreads in the synkinesis region.

2.2.2 Results of treatment of synkinesis with monofilament mesothreads

In patients of group I (who received botulinum toxin therapy), the effect appeared only 7–10 days after the administration of the drug. The amplitude and frequency of synkinesis in patients of group II (who were treated with mesothreads) decreased immediately after the completion of the procedure. A significant effect of implantation of mesothreads was also registered 7–10 days after the procedure. The amplitude and severity of synkinesis in the “u-e,” “b-p” test significantly decreased. Patients noted that they managed to communicate with other people easily. The interlocutors stopped peering, trying to discern the involuntary movements of the muscles of the face in patients, which significantly increased patients’ self-esteem, improved the quality of life.

In 1, 3, 6, and 12 months after the procedures, the general condition of the facial muscles of patients of group II, assessed using the SFGS scale, was 2.0, 2.3, 2.4, and 1.9 times better than in patients of group I (p < 0.01). In 50% of cases, the positive effect of mesothreads on synkinesis persisted even after 1.5–2 years.

Thus, a comparative analysis of two methods for treatment of motor synkinesis showed the best result in the group of patients who received monofilament mesothreads. We observed a significant decrease in the severity of clinical symptoms, manifested in a decrease of the frequency and amplitude of involuntary muscle contractions in the face.

The proposed method has limitation. It is likely to develop a hematoma at the injection sites of mesothreads (especially in the periorbital region). There is a risk of rejection of the threads within the first 2–3 days (due to the extremely superficial introduction). In such a case, it is important to remove the thread, holding it by the tip. It is likely to experience pain after thread implantation (within 1–2 days), as well as a relatively long rehabilitation period (up to 10 days).

In the later period (6–12 months), it is likely to have a migration of threads and the formation of a ligature fistula. There have been no such complications in our practice.

3. Remarks

1. Pathological process of facial nerve neuropathy affects both hemifaces. On the affected side, a pronounced motor deficit becomes apparent. On the contralateral side, hyperactivity of muscles of facial expression is determined.

2. Botulinum toxin treatment for facial expression asymmetry, which affects the neuromuscular apparatus of the “healthy” hemiface, helps to restore the balanced work of both hemifaces. This creates favorable conditions for the correct joint interaction of facial muscles, increasing the motor activity of the facial muscles of the affected hemiface.

3. To treat motor facial synkinesis, we created a mesh-frame of monofilament mesothreads between the skin and facial muscles, and new collagen fibers forming around them. This helped to significantly decrease the clinical symptoms, which were expressed by a decrease in the frequency and amplitude of involuntary muscle contractions in the face.

4. Conclusion

Thus, the signs of facial expression asymmetry in facial nerve neuropathy include weakness of the facial muscles innervated by the affected facial nerve, as well as hypertonicity of the facial expression muscles of the healthy hemiface. The proposed method of injections of botulinum toxin type A into hyperactive facial expression muscles of the unaffected (“healthy”) hemiface in case of facial nerve neuropathy contributes to the formation of a balance between both hemifaces and the joint work of the nervous structures of the face. Botulinum toxin therapy is a pathogenetically substantiated method of restoring facial symmetry. Due to this method, it is possible to achieve an increase in the motor activity of the muscles of facial expression of the affected hemiface both in the acute phase of Bell’s palsy, and with remaining effects in the long-term period. This method is also applicable for the treatment of facial expression asymmetry of another etiology, for example, as a result of an iatrogenic injury (found in cosmetology, plastic surgery, and maxillofacial surgery). The efficacy of botulinum toxin therapy is explained by other impacts besides the local muscle relaxant effect of botulinum toxin type A. It is known that the action of botulinum toxin type A causes peripheral deafferentation. This suggests a neuroplastic effect on the segmental, suprasegmental structures of the facial nerve system when performing injections in the face.

The use of the proposed method for the treatment of pathological synkinesis using monofilament mesothreads showed a good result. The creation of a mesh-frame between the facial muscles and the skin in the area of involuntary muscle contractions reduces the external manifestations of synkinesis. The use of monofilament mesothreads makes it possible to obtain a longer and more stable clinical effect, which is manifested by a decrease in the severity and amplitude of pathological muscle contractions of facial muscles, even in 2 years after the treatment.

Acknowledgments

The authors would like to thank Amina Mukhambetova for translating this article into English and Elizaveta Soikher for creating anatomical illustrations.

Conflict of interest

None of the other authors listed have any commercial associations or financial disclosures that might pose or create a conflict of interest.