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Use of the masseter motor nerve in facial animation with free muscle transfer
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British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
Use of the masseter motor nerve in facial animation with free muscle transfer Bernardo Bianchi, Chiara Copelli ∗ , Silvano Ferrari, Andrea Ferri, Enrico Sesenna Maxillofacial Surgery, Head and Neck Department, University of Parma, Ospedale Maggiore, Via Gramsci, 14-43100 Parma (Pr), Italy Accepted 24 July 2011 Available online 31 August 2011
Abstract Facial paralysis is either congenital or acquired, and of varying severity, which leads to an asymmetrical or absent facial expression. It is an important disability both from the aesthetic and functional points of view. Between 2003 and 2008, at the Department of Maxillofacial Surgery, University of Parma, Italy, 21 patients with facial paralysis had their faces reanimated with a gracilis transplant reinnervated by the masseter motor nerve. All free-muscle transplants survived the transfer, and no flap was lost. Facial symmetry at rest and while smiling was excellent or good in most cases, and we found an appreciable improvement in both speech and oral competence. We consider that the masseter motor nerve is a powerful and reliable donor nerve, which allows us to obtain movement of the commissure and upper lip similar to those of the normal site for degree and direction. There may be a role for the masseter motor nerve in innervation of patients with facial paralysis. © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Facial animation; Gracilis transplantation; Motor nerve to masseter
Introduction Facial paralysis is an important disability from both the aesthetic and functional points of view.1–3 The totally or partially paralysed face is characterised by generalised laxity and atonicity, an asymmetrical smile, drooping of the corner of the mouth, difficulty with chewing, inability to purse the lips, and impaired articulation. When the zygomatic branch of the nerve is involved there is ectropion with keratitis and lagophthalmos. Dynamic reanimation of the paralysed midface aims at a symmetrical and coordinated smile. Reanimation of the midface also increases tone in the cheeks, which assists the lower eyelid against gravity, and facilitates speech and eating.The microneurovascular transfer of a free-muscle transplant is the procedure of choice for facial animation and, specifically, the
gracilis muscle has been used as a dynamic functioning free tissue transfer with considerable success.2,4–7 One of the critical factors of this procedure is the selection of a motor nerve to innervate the transplanted muscle. It must provide a strong muscular contraction, and allow control of the movement and achievement of synchronous and spontaneous activity.1,2,7–12 We report patients with facial paralysis who were seen and treated surgically with gracilis transplants innervated by the motor branch to the masseter muscle, from 2003 to 2008 at the Operative Unit of Maxillofacial Surgery, Head and Neck Department, University of Parma, Italy. We have evaluated the effectiveness of the masseter motor nerve in providing adequate innervation to a muscle transfer for reanimation of the lower face.
Patients and methods ∗
Corresponding author. Tel.: +39 0521 703107. E-mail addresses: [email protected] (B. Bianchi), [email protected] (C. Copelli), [email protected] (S. Ferrari), [email protected] (A. Ferri), [email protected] (E. Sesenna).
We reviewed the records of patients with facial paralysis who were seen between 2003 and 2008 at the Operative Unit of Maxillofacial Surgery of the University of Parma, Italy. We
0266-4356/$ – see front matter © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2011.07.019
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
651
Table 2 Evaluation of the smile in 21 patients.
Table 1 Types of facial paralysis in 21 patients. Type
Number of patients
Smile
Number of patients
Moebius (bilateral) Moebius (unilateral) Iatrogenic Failure of previous animation Other congenital
10 3 3 3 2
Excellent Good Moderate Fair Poor
14 6 0 1 0
focused on patients treated by transplantation of the gracilis muscle innervated by the motor nerve to the masseter muscle. To evaluate the functional and aesthetic results of microsurgical reconstruction, we considered only patients with a minimum follow-up of 12 months. The results were analysed for the patient’s response, clinical examination, and preoperative and postoperative videotaping of patients filmed at rest and illustrating several standard facial movements to show muscular action, spontaneity, independence, and fine facial movements during speech. The smile was evaluated from the functional and aesthetic points of view using the facial grading system proposed by Terzis et al in 1997.6,13,14 This included excellent-indicating symmetrical smile with teeth showing, and full contraction; moderate-indicating moderate symmetry, moderate contraction, and mass movement; fair-indicating no symmetry, bulk, and minimal contraction; and poor-indicating deformity and no contraction. Dynamic measurements (smiling) were made on each side to evaluate the movements of the commissure. As reported by Manktelow et al.,15 these movements are considered to be the distance moved by the commissure from the rest position to a maximum smile as measured in the plane of movement of this point. The surgical technique in all cases was the same as described by us previously.16,17
Results Between 2003 and September 2008, 21 patients with facial paralysis were seen and treated at the Department of Maxillofacial Surgery, University of Parma, Italy, by gracilis muscle transplantation reinnervated by the motor nerve to the masseter. There were 11 male and 10 female patients (mean age 21 years (range 7–60)), and the different types of facial paralysis are shown in Table 1. All patients had microsurgical reconstruction with a gracilis muscle transplant reinnervated by the motor nerve to the masseter. All free-muscle transplants survived, and the reinnervation of the gracilis muscle took about 3.5 months. Two patients developed hypertrophic scars at the site of the incision in the neck. There were no complications or morbidity at the donor site. Postoperatively all patients had smile training by the speech–language pathologist using mirror exercises and biofeedback. All patients who had complained of preoperative difficulties regarding oral competence reported a considerable
Fig. 1. A 33-year-old woman with complete bilateral Moebius syndrome showing her preoperative appearance attempting to smile. She had the gracilis muscle on the right side transplanted in November 2008 and the left one in November 2009.
improvement as evaluated by the grading system developed by Terzis et al.6,13,14 (Table 2), and it was excellent or good in most patients. In one case we had a fair result as a result of displacement of one pericommissural suture with the development of an asymmetrical, not aesthetic, movement. The mean commissural movement measured on the treated sides was 16 mm (range 13–20). In patients with bilateral facial paralysis the mean difference between the two sides was 2.5 mm (range 2–3). The results of 2 of our patients are shown in Figs. 1–4.
Discussion The lack of facial animation in patients with facial paralysis poses a serious barrier to interpersonal communication, creates severe aesthetic and functional problems,1,3 and the microneurovascular transfer of a free-muscle transplant is the treatment of choice.4–7 Specifically, the gracilis muscle has been used as a dynamic functioning free tissue transfer with considerable success.2,5 One of the critical factors of this procedure is the selection of a motor nerve to innervate the transplanted
652
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
Fig. 4. Postoperative appearance smiling 10 months postoperatively.
Fig. 2. Postoperative appearance smiling a year after the second operation.
muscle. Not only must sufficient innervation be present to power the muscle, it must achieve spontaneity, synchronicity, and symmetry. Many different donor motor nerves have been used with varying success. For those patients who have sufficiently strong contralateral facial nerves, a crossfacial nerve graft is the ideal choice.1,7–11 For the remainder of patients, hypoglossal nerve, nerve to the masseter, and nerve to the accessory nerve, are available options. Though we have
Fig. 3. A 7-year-old boy with a congenital left facial paralysis showing his preoperative appearance attempting to smile. In September 2008 he had a microsurgical reconstruction with the gracilis muscle, which was innervated by the ipsilateral motor nerve to the masseter muscle.
already partly described the use of the masseter motor nerve used for Moebius syndrome and for unilateral facial paralysis,16,17 we wanted to present a systematic review of all its indications and applications. The aim is to help surgeons to make the correct choice of the donor nerve in facial reanimation, and to propose a wider use of the masseter nerve, as in selected cases it should be preferred to that of the contralateral facial nerve in the treatment of unilateral facial paralysis. Like other authors,1,2,6,8 we have used the nerve to the masseter for the following indications: bilateral facial paralysis (Moebius syndrome); unilateral facial paralysis; inadequate VII nerve on the same side; for older patients in whom crossfacial reinnervation by nerve graft is difficult; for a patient who does not wish to have two operations; for a patient who has a strong smile on the normal side; and in the case of a previously failed crossfacial graft. In patients with classic Moebius syndrome the bilateral involvement of the facial nerves does not allow the crossfacial nerve grafting using the contralateral VII nerve. The masseteric nerve in these patients is rarely impaired, and is a tempting source because free-muscle transplants can be connected directly, so avoiding transplantation of a nerve. The lack of spontaneity makes the masseteric nerve a second choice of donor nerve in unilateral facial paralysis, and the crossfacial nerve graft with the contralateral facial nerve is preferred. Nevertheless, the contraction obtained in this way is much less than that obtained with masseteric reinnervation, and that of the normal side. The necessity for dissection of the facial nerve safely, and two anastomoses of nerves, increases the risk of damage to the contralateral VII nerve and also the risk of unsatisfactory activity or a lack of reinnervation. This is why in patients with a strong contraction on the normal side and in high-risk cases (an inadequate VII contralateral nerve, or older patients) we consider the masseteric nerve a safe and reliable option preferable to the cross nerve graft. We also consider this donor nerve the first choice in patients who have had previously failed grafts. The technical difficulty of dissecting the nerves in the fibrous tissue left by the previous operation contraindicates a new cross-nerve graft. The masseteric nerve can easily be identified on the undersurface
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
of the masseter muscle, and safely anastomosed to the nerve of the new muscular transplant. The single-stage procedure spares the patients two further operations, and is also an indication to use the masseteric nerve in all those patients who do not wish to have the two procedures of the crossfacial nerve graft. As in earlier reports using the masseteric nerve, we found that the movement produced was within the normal range, and consistently good enough to obtain symmetry.8,9 When we evaluated the movement of the commissure on the operated sides, like Manktelow et al.,15 we obtained a measure ranging from 13 to 20 mm (mean 16). The normal range of movement of the commissure is 7–22 mm (mean 14). Historically, the use of non-facial motor nerve donors has been thought to preclude spontaneous facial expression, and the patient has not been thought to be able to move the facial muscles independently from the original muscle of the donor nerve. We are unable to comment on emotional expression in the present series. Nevertheless, as reported by Manktelow et al.,10 we found that some patients were able to move their transferred muscles independently from their jaws. They also reported that they no longer had to think about activating their facial muscles while laughing, suggesting that they have developed involuntary facial expressions of emotion. According to Manktelow et al.,10 the ability to smile without biting and thinking about it, brings up the issue of cerebral plasticity, or cerebral cortical reorganisation. This is the ability of the human brain to reorganise, adapt, and compensate for injury or changes in the environment. Actually cortical plasticity has been illustrated in multiple instances of sensory and motor reinnervation and in many clinical conditions, including Braille reading, after nerve injuries, amputations of limbs, or nerve transfers in patients with injuries to the brachial plexus.10,16 It is likely that there is a similar process, with the facial nerve centre taking over control by activating connections to the V nerve centre and, through this centre, activating the motor axons of the masseter branch of the trigeminal nerve, causing gracilis muscle contractions and a smile.10,16–19 In the future, functional magnetic resonance imaging may be used to study this process in facial paralysis and to find out whether the cortical area that is activated during smiling in patients who have undergone facial reanimation innervated by the nerve to the masseter is different from that of the cortical area activated in control patients when contracting the masseter muscle.10,16–18 To achieve a spontaneous and symmetrical smile, an important part is played by postoperative smile training by a speech–language pathologist using mirror exercises and biofeedback. When r the muscle reinnervates 3–6 months after transfer, an active exercise programme must be started. In this way, progress in strength, excursion, and – most importantly – symmetry, can be achieved. The age of the patient when operated on did not influence the results from an aesthetic or functional point of view. In adults, we
653
found that reinnervation took longer (5–6 months) than in children (3.5 months).16,17 As reported by other authors,6,8,9 we found that the masseter motor nerve is a powerful and reliable donor nerve, which allowed us to obtain movement of the commissure and upper lip similar to those of the normal site for amount and direction. Our clinical experience, like that of other studies, has shown that an independent smile and closure of the jaw is attainable in these patients, refuting previous speculation.10–12,18
References 1. Hoffman WY. Reanimation of the paralyzed face. Otolaryngol Clin North Am 1992;25:649–67. 2. O’Brien BM, Pederson WC, Khazanchi RK, Morrison WA, MacLeod AM, Kumar V. Results of management of facial palsy with microvascular free-muscle transfer. Plast Reconstr Surg 1990;86:12–24. 3. Westin LM, Zuker R. A new classification system for facial paralysis in the clinical setting. J Craniofac Surg 2003;14:672–9. 4. Terzis JK, Noah EM. Dynamic restoration in Möbius and Möbius-like patients. Plast Reconstr Surg 2003;111:40–55. 5. Johnson PJ, Bajaj-Luthra A, Llull R, Johnson PC. Quantitative facial motion analysis after functional free muscle reanimation procedures. Plast Reconstr Surg 1997;100:1710–22. 6. Terzis JK, Noah ME. Analysis of 100 cases of free-muscle transplantation for facial paralysis. Plast Reconstr Surg 1997;99:1905–21. 7. Ueda K, Harii K, Asato H, Yamada A. Neurovascular free muscle transfer combined with cross-face nerve grafting for the treatment of facial paralysis in children. Plast Reconstr Surg 1998;101:1765–73. 8. Bae YC, Zuker RM, Manktelow RT, Wade S. A comparison of commissure excursion following gracilis muscle transplantation for facial paralysis using a cross-face nerve graft versus the motor nerve to the masseter nerve. Plast Reconstr Surg 2006;117:2407–13. 9. Lee EI, Hurvitz KA, Evans GR, Wirth GA. Cross-facial nerve graft: past and present. J Plast Reconstr Aesthet Surg 2008;61:250–6. 10. Manktelow RT, Tomat LR, Zuker RM, Chang M. Smile reconstruction in adults with free muscle transfer innervated by the masseter motor nerve: effectiveness and cerebral adaptation. Plast Reconstr Surg 2006;118:885–99. 11. Zuker RM. Facial paralysis in children. Clin Plast Surg 1990;17:95–9. 12. Zuker RM, Goldberg CS, Manktelow RT. Facial animation in children with Möbius syndrome after segmental gracilis muscle transplant. Plast Reconstr Surg 2000;106:1–9. 13. Terzis JK, Olivares FS. Long term outcomes of free-muscle transfer for smile restoration in adults. Plast Reconstr Surg 2009;123:877–88. 14. Terzis JK, Olivares FS. Long term outcomes of free-muscle transfer for smile restoration in children. Plast Reconstr Surg 2009;123:543–55. 15. Manktelow RT, Zuker RM, Tomat LR. Facial paralysis measurement with a handheld ruler. Plast Reconstr Surg 2008;121:435–42. 16. Bianchi B, Copelli C, Ferrari S, Ferri A, Sesenna E. Facial animation in children with Moebius and Moebius-like syndromes. J Pediatr Surg 2009;44:2236–42. 17. Bianchi B, Copelli C, Ferrari S, Ferri A, Bailleul C, Se senna E. Facial animation with free muscle transfer innervated by the masseter motor nerve in unilateral facial paralysis. J Oral Maxillofac Surg 2010;68:1524–9. 18. Lifchez SD, Matloub HS, Gosain AK. Cortical adaptation to restoration of smiling after free muscle transfer innervated by the nerve to the masseter. Plast Reconstr Surg 2005;115:1472–82. 19. Gosain AK, Birn RM, Hyde JS. Localization of the cortical response to smiling using new imaging paradigms with functional magnetic resonance imaging. Plast Reconstr Surg 2001;108:1136–44.
British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
Use of the masseter motor nerve in facial animation with free muscle transfer Bernardo Bianchi, Chiara Copelli ∗ , Silvano Ferrari, Andrea Ferri, Enrico Sesenna Maxillofacial Surgery, Head and Neck Department, University of Parma, Ospedale Maggiore, Via Gramsci, 14-43100 Parma (Pr), Italy Accepted 24 July 2011 Available online 31 August 2011
Abstract Facial paralysis is either congenital or acquired, and of varying severity, which leads to an asymmetrical or absent facial expression. It is an important disability both from the aesthetic and functional points of view. Between 2003 and 2008, at the Department of Maxillofacial Surgery, University of Parma, Italy, 21 patients with facial paralysis had their faces reanimated with a gracilis transplant reinnervated by the masseter motor nerve. All free-muscle transplants survived the transfer, and no flap was lost. Facial symmetry at rest and while smiling was excellent or good in most cases, and we found an appreciable improvement in both speech and oral competence. We consider that the masseter motor nerve is a powerful and reliable donor nerve, which allows us to obtain movement of the commissure and upper lip similar to those of the normal site for degree and direction. There may be a role for the masseter motor nerve in innervation of patients with facial paralysis. © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Facial animation; Gracilis transplantation; Motor nerve to masseter
Introduction Facial paralysis is an important disability from both the aesthetic and functional points of view.1–3 The totally or partially paralysed face is characterised by generalised laxity and atonicity, an asymmetrical smile, drooping of the corner of the mouth, difficulty with chewing, inability to purse the lips, and impaired articulation. When the zygomatic branch of the nerve is involved there is ectropion with keratitis and lagophthalmos. Dynamic reanimation of the paralysed midface aims at a symmetrical and coordinated smile. Reanimation of the midface also increases tone in the cheeks, which assists the lower eyelid against gravity, and facilitates speech and eating.The microneurovascular transfer of a free-muscle transplant is the procedure of choice for facial animation and, specifically, the
gracilis muscle has been used as a dynamic functioning free tissue transfer with considerable success.2,4–7 One of the critical factors of this procedure is the selection of a motor nerve to innervate the transplanted muscle. It must provide a strong muscular contraction, and allow control of the movement and achievement of synchronous and spontaneous activity.1,2,7–12 We report patients with facial paralysis who were seen and treated surgically with gracilis transplants innervated by the motor branch to the masseter muscle, from 2003 to 2008 at the Operative Unit of Maxillofacial Surgery, Head and Neck Department, University of Parma, Italy. We have evaluated the effectiveness of the masseter motor nerve in providing adequate innervation to a muscle transfer for reanimation of the lower face.
Patients and methods ∗
Corresponding author. Tel.: +39 0521 703107. E-mail addresses: [email protected] (B. Bianchi), [email protected] (C. Copelli), [email protected] (S. Ferrari), [email protected] (A. Ferri), [email protected] (E. Sesenna).
We reviewed the records of patients with facial paralysis who were seen between 2003 and 2008 at the Operative Unit of Maxillofacial Surgery of the University of Parma, Italy. We
0266-4356/$ – see front matter © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2011.07.019
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
651
Table 2 Evaluation of the smile in 21 patients.
Table 1 Types of facial paralysis in 21 patients. Type
Number of patients
Smile
Number of patients
Moebius (bilateral) Moebius (unilateral) Iatrogenic Failure of previous animation Other congenital
10 3 3 3 2
Excellent Good Moderate Fair Poor
14 6 0 1 0
focused on patients treated by transplantation of the gracilis muscle innervated by the motor nerve to the masseter muscle. To evaluate the functional and aesthetic results of microsurgical reconstruction, we considered only patients with a minimum follow-up of 12 months. The results were analysed for the patient’s response, clinical examination, and preoperative and postoperative videotaping of patients filmed at rest and illustrating several standard facial movements to show muscular action, spontaneity, independence, and fine facial movements during speech. The smile was evaluated from the functional and aesthetic points of view using the facial grading system proposed by Terzis et al in 1997.6,13,14 This included excellent-indicating symmetrical smile with teeth showing, and full contraction; moderate-indicating moderate symmetry, moderate contraction, and mass movement; fair-indicating no symmetry, bulk, and minimal contraction; and poor-indicating deformity and no contraction. Dynamic measurements (smiling) were made on each side to evaluate the movements of the commissure. As reported by Manktelow et al.,15 these movements are considered to be the distance moved by the commissure from the rest position to a maximum smile as measured in the plane of movement of this point. The surgical technique in all cases was the same as described by us previously.16,17
Results Between 2003 and September 2008, 21 patients with facial paralysis were seen and treated at the Department of Maxillofacial Surgery, University of Parma, Italy, by gracilis muscle transplantation reinnervated by the motor nerve to the masseter. There were 11 male and 10 female patients (mean age 21 years (range 7–60)), and the different types of facial paralysis are shown in Table 1. All patients had microsurgical reconstruction with a gracilis muscle transplant reinnervated by the motor nerve to the masseter. All free-muscle transplants survived, and the reinnervation of the gracilis muscle took about 3.5 months. Two patients developed hypertrophic scars at the site of the incision in the neck. There were no complications or morbidity at the donor site. Postoperatively all patients had smile training by the speech–language pathologist using mirror exercises and biofeedback. All patients who had complained of preoperative difficulties regarding oral competence reported a considerable
Fig. 1. A 33-year-old woman with complete bilateral Moebius syndrome showing her preoperative appearance attempting to smile. She had the gracilis muscle on the right side transplanted in November 2008 and the left one in November 2009.
improvement as evaluated by the grading system developed by Terzis et al.6,13,14 (Table 2), and it was excellent or good in most patients. In one case we had a fair result as a result of displacement of one pericommissural suture with the development of an asymmetrical, not aesthetic, movement. The mean commissural movement measured on the treated sides was 16 mm (range 13–20). In patients with bilateral facial paralysis the mean difference between the two sides was 2.5 mm (range 2–3). The results of 2 of our patients are shown in Figs. 1–4.
Discussion The lack of facial animation in patients with facial paralysis poses a serious barrier to interpersonal communication, creates severe aesthetic and functional problems,1,3 and the microneurovascular transfer of a free-muscle transplant is the treatment of choice.4–7 Specifically, the gracilis muscle has been used as a dynamic functioning free tissue transfer with considerable success.2,5 One of the critical factors of this procedure is the selection of a motor nerve to innervate the transplanted
652
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
Fig. 4. Postoperative appearance smiling 10 months postoperatively.
Fig. 2. Postoperative appearance smiling a year after the second operation.
muscle. Not only must sufficient innervation be present to power the muscle, it must achieve spontaneity, synchronicity, and symmetry. Many different donor motor nerves have been used with varying success. For those patients who have sufficiently strong contralateral facial nerves, a crossfacial nerve graft is the ideal choice.1,7–11 For the remainder of patients, hypoglossal nerve, nerve to the masseter, and nerve to the accessory nerve, are available options. Though we have
Fig. 3. A 7-year-old boy with a congenital left facial paralysis showing his preoperative appearance attempting to smile. In September 2008 he had a microsurgical reconstruction with the gracilis muscle, which was innervated by the ipsilateral motor nerve to the masseter muscle.
already partly described the use of the masseter motor nerve used for Moebius syndrome and for unilateral facial paralysis,16,17 we wanted to present a systematic review of all its indications and applications. The aim is to help surgeons to make the correct choice of the donor nerve in facial reanimation, and to propose a wider use of the masseter nerve, as in selected cases it should be preferred to that of the contralateral facial nerve in the treatment of unilateral facial paralysis. Like other authors,1,2,6,8 we have used the nerve to the masseter for the following indications: bilateral facial paralysis (Moebius syndrome); unilateral facial paralysis; inadequate VII nerve on the same side; for older patients in whom crossfacial reinnervation by nerve graft is difficult; for a patient who does not wish to have two operations; for a patient who has a strong smile on the normal side; and in the case of a previously failed crossfacial graft. In patients with classic Moebius syndrome the bilateral involvement of the facial nerves does not allow the crossfacial nerve grafting using the contralateral VII nerve. The masseteric nerve in these patients is rarely impaired, and is a tempting source because free-muscle transplants can be connected directly, so avoiding transplantation of a nerve. The lack of spontaneity makes the masseteric nerve a second choice of donor nerve in unilateral facial paralysis, and the crossfacial nerve graft with the contralateral facial nerve is preferred. Nevertheless, the contraction obtained in this way is much less than that obtained with masseteric reinnervation, and that of the normal side. The necessity for dissection of the facial nerve safely, and two anastomoses of nerves, increases the risk of damage to the contralateral VII nerve and also the risk of unsatisfactory activity or a lack of reinnervation. This is why in patients with a strong contraction on the normal side and in high-risk cases (an inadequate VII contralateral nerve, or older patients) we consider the masseteric nerve a safe and reliable option preferable to the cross nerve graft. We also consider this donor nerve the first choice in patients who have had previously failed grafts. The technical difficulty of dissecting the nerves in the fibrous tissue left by the previous operation contraindicates a new cross-nerve graft. The masseteric nerve can easily be identified on the undersurface
B. Bianchi et al. / British Journal of Oral and Maxillofacial Surgery 50 (2012) 650–653
of the masseter muscle, and safely anastomosed to the nerve of the new muscular transplant. The single-stage procedure spares the patients two further operations, and is also an indication to use the masseteric nerve in all those patients who do not wish to have the two procedures of the crossfacial nerve graft. As in earlier reports using the masseteric nerve, we found that the movement produced was within the normal range, and consistently good enough to obtain symmetry.8,9 When we evaluated the movement of the commissure on the operated sides, like Manktelow et al.,15 we obtained a measure ranging from 13 to 20 mm (mean 16). The normal range of movement of the commissure is 7–22 mm (mean 14). Historically, the use of non-facial motor nerve donors has been thought to preclude spontaneous facial expression, and the patient has not been thought to be able to move the facial muscles independently from the original muscle of the donor nerve. We are unable to comment on emotional expression in the present series. Nevertheless, as reported by Manktelow et al.,10 we found that some patients were able to move their transferred muscles independently from their jaws. They also reported that they no longer had to think about activating their facial muscles while laughing, suggesting that they have developed involuntary facial expressions of emotion. According to Manktelow et al.,10 the ability to smile without biting and thinking about it, brings up the issue of cerebral plasticity, or cerebral cortical reorganisation. This is the ability of the human brain to reorganise, adapt, and compensate for injury or changes in the environment. Actually cortical plasticity has been illustrated in multiple instances of sensory and motor reinnervation and in many clinical conditions, including Braille reading, after nerve injuries, amputations of limbs, or nerve transfers in patients with injuries to the brachial plexus.10,16 It is likely that there is a similar process, with the facial nerve centre taking over control by activating connections to the V nerve centre and, through this centre, activating the motor axons of the masseter branch of the trigeminal nerve, causing gracilis muscle contractions and a smile.10,16–19 In the future, functional magnetic resonance imaging may be used to study this process in facial paralysis and to find out whether the cortical area that is activated during smiling in patients who have undergone facial reanimation innervated by the nerve to the masseter is different from that of the cortical area activated in control patients when contracting the masseter muscle.10,16–18 To achieve a spontaneous and symmetrical smile, an important part is played by postoperative smile training by a speech–language pathologist using mirror exercises and biofeedback. When r the muscle reinnervates 3–6 months after transfer, an active exercise programme must be started. In this way, progress in strength, excursion, and – most importantly – symmetry, can be achieved. The age of the patient when operated on did not influence the results from an aesthetic or functional point of view. In adults, we
653
found that reinnervation took longer (5–6 months) than in children (3.5 months).16,17 As reported by other authors,6,8,9 we found that the masseter motor nerve is a powerful and reliable donor nerve, which allowed us to obtain movement of the commissure and upper lip similar to those of the normal site for amount and direction. Our clinical experience, like that of other studies, has shown that an independent smile and closure of the jaw is attainable in these patients, refuting previous speculation.10–12,18
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