Clin Plastic Surg 30 (2003) 307 – 318 The surgical management of facial nerve injury Terence M. Myckatyn, MD, Susan E. Mackinnon, MD, FRCS(C)* Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, Suite 17424, East Pavilion, Box 8238, One Barnes-Jewish Hospital Plaza, Saint Louis, MO 63110, USA Historical review Although the concept of repairing injured peripheral nerves is centuries old, it was not until 1821 when Sir Charles Bell demonstrated the loss of facial expression with transection of the seventh cranial nerve that surgical restoration of the facial nerve was attempted . In 1879, Drobnik diverted axons from an intact spinal accessory nerve to the distal end of a transected facial nerve, thus affecting the first nerve transfer to reinnervate the mimetic muscles of the face . The affects of nerve transfers on the cerebral cortex were critically reviewed by Kennedy in 1901 , and in 1903, Ballance et al  published a case series documenting their experience with endto-side neurorrhaphy of the transected facial nerve into an intact spinal accessory nerve and suggested a hypoglossal-to-facial nerve transfer. Initial attempts to reinnervate the facial musculature through myoneurotization were met with limited success by Lexer in 1911 , but by 1927, Sterling Bunnell reported excellent results after primary neurorrhaphy of a transected facial nerve within the temporal bone . In 1936, the Scottish neurosurgeon Norman Dott used a sural nerve graft extending from the intracranial to extratemporal facial nerve to span an intratemporal defect created by acoustic neuroma resection . Over the past 30 years, the advent and refinement of microneurosurgical techniques and free tissue No author has any financial interests associated with any aspect of this publication. * Corresponding author. E-mail address: [email protected] (S.E. Mackinnon). transfers has significantly improved treatment options for extensive or long-standing facial nerve injuries. In 1970, Tamai described free tissue transfer of innervated muscle flaps in canines , and, in 1971, Thompson reported inserting free muscle grafts first in canines and then in the clinical setting to restore facial mimetic function [9,10]. The use of the intact contralateral cervical branch of the facial nerve to reanimate the territory of the injured ipsilateral facial nerve was first presented by Scaramella in 1970 and was later modified to involve sural nerve grafts and branches of the cervical plexus [11,12]. In 1976, the microneurovascular transfer of the gracilis muscle to restore facial animation was described by Harii  and was followed by reports of successful free tissue transfer and reinnervation of the latissimus dorsi [14,15] or pectoralis minor  to restore facial animation. To produce a more symmetric and natural-looking result, these techniques have undergone multiple refinements as more attention is paid to the fascicular territories within a given muscle , the tonicity of various facial muscles , and differences in the distribution of motor endplates on facial compared with skeletal muscles . Anatomic overview The complex anatomy of the facial nerve is summarized here and can be thoroughly reviewed in other texts . The branchial motor fibers constitute the largest component of the facial nerve and provide efferent innervation to the stapedius, stylohyoid, posterior belly of digastric, and the muscles of facial expression. The remaining three components of the 0094-1298/03/$ – see front matter D 2003, Elsevier Science (USA). All rights reserved. doi:10.1016/S0094-1298(02)00102-5 308 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 facial nerve comprise the nervus intermedius, which includes visceral motor, general sensory, and special sensory fibers. A conscious or unconscious impulse is generated in the neurons of the motor cortex of the brain and is transmitted via axons traveling via the corticobulbar tracts and posterior limbs of the internal capsule toward the seventh cranial nerve nucleus within the pontine tegmentum. Impulses intended for transmission to the frontal branch of the facial nerve project to the seventh cranial nerve nucleus bilaterally, whereas impulses traveling to the remaining branches of the facial nerve project to the contralateral seventh cranial nerve nucleus. Postsynaptic branchial motor fibers exit the pons, contribute to the facial colliculus of the fourth ventricle, and emerge from the brainstem at the cerebellopontine angle before entering the internal auditory canal and the petrous part of the temporal bone. The intratemporal course of the facial nerve consists of a labyrinthine segment extending approximately 5 mm from the internal auditory canal and includes the geniculate ganglion. The intratemporal facial nerve is particularly susceptible to compression in the relatively narrow labyrinthine segment and to shearing as it makes a sharp turn, or genu, to enter the tympanic segment. The tympanic segment extends 8 to 11 mm to a second genu located between the posterior auditory canal wall and the horizontal semicircular canal of the middle ear. The nerve travels vertically another 10 to 14 mm through the mastoid segment before exiting the stylomastoid foramen [21 – 24]. The intraneural topography of the intratemporal facial nerve has been studied extensively. Clinical reports of consistent deficits of facial animation associated with nerve injuries at a particular level after mastoid , glomus tumor , and decompressive surgeries at the cerebellopontine angle suggested that the intratemporal facial nerve had a reliable spatial arrangement . These clinical findings were temporarily corroborated in pathophysiologic studies  and by May in a feline model . May later noted, however, that the reproducible facial nerve topography that he had observed histologically was at least in part due to the presence of a branch of the trigeminal nerve found in cats but not in humans and not to a consistent branch of the facial nerve . It is widely accepted that the intratemporal facial nerve possesses a variable intraneural topography [29 – 31] and that its spatial relationship to other intratemporal structures, such as the sigmoid sinus and carotid artery, are also variable . Several common branching patterns have been described for the voluntary motor component of the extratemporal facial nerve , with special attention given to the marginal mandibular  and frontal nerve branches [35 – 38]. Given the variability in location of the facial nerve branches and the overlap of facial nerve branches to any given group of facial muscles , careful dissection and a nerve stimulator should be used to confirm the presence of nerve fascicles and to decide which may be sacrificed in cross-facial nerve grafting procedures. The parasympathetic division of the facial nerve is compromised of visceral motor fibers whose cell bodies are influenced by the hypothalamus, are located in the pontine tegmentum, and are collectively known as the superior salivatory nucleus. These visceral motor fibers contribute to the nervus intermedius, penetrate the temporal bone, and then divide into the greater petrosal nerve that innervates the lacrimal gland and the chorda tympani, which innervates the submandibular and sublingual glands. Cell bodies for the general sensory component that provides sensation to the conchal skin and the special sensory component of the facial nerve that travels along the lingual and chorda tympani nerves and provides taste to the anterior two thirds of the tongue reside in the geniculate ganglion. Postsynaptic afferent impulses are transmitted from the petrous temporal bone through the nervus intermedius and synapse with the general sensory trigeminal nucleus in the rostral medulla or with cell bodies modulating taste afferents within the gustatory nucleus of the pontine tegmentum. These impulses are propagated to thalamic nuclei before projecting to the sensory cortex. Surgical management of acute facial nerve injuries Primary neurorrhaphy Acute injuries to the extratemporal facial nerve should be repaired under magnification and with adequate lighting and microsurgical equipment (Fig. 1). A nerve stimulator may be used to confirm the location of the distal end of the transected facial nerve for approximately 72 hours after nerve injury . Beyond this period, the neurotransmitter stores necessary to depolarize the motor end plates are depleted and cannot be replenished given the disruption of antegrade axoplasmic transport after nerve injury [41 – 46]. Thus, early surgery is important and should be done within the 72-hour period when the appropriate operating room, surgical team, and equipment are available. T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 309 Fig. 1. Algorithm for the management of facial nerve injuries. When possible, primary neurorrhaphy of a facial nerve injury is performed within 72 hours to enable identification of the distal end with a nerve stimulator during exploration. Procedures involving cross-facial nerve grafts (CFNG) or free tissue transfers are performed exclusively on individuals who are capable of enduring a prolonged general anesthetic and who are sufficiently motivated to remain compliant with the subsequent rehabilitation. * Partial CN XII to CN VII transfer. Ipsilateral nerve grafts are indicated in the reconstruction of segmental defects of the facial nerve when both ends of the transected nerve can be reliably identified and when it is not possible to do a primary repair (Fig. 1). In preparation for nerve grafting, neurolysis and dissection of the transected facial nerve stump to the level of clearly defined healthy fascicles proximally and equally judicious dissection of the distal facial nerve stump out of the zone of injury must occur. Once the facial nerve stumps are ready for grafting, the sural nerve, the greater auricular nerve, and the medial antebrachial cutaneous nerves are most commonly used. Our preference is to use medial or lateral antebrachial cutaneous nerve grafts. Although surgical technique is an important consideration in performing primary neurorrhaphy or nerve grafting of the facial nerve, it is its variable spatial arrangement that most significantly affects the success of the repair [20,25,28]. Although the senior author has acutely repaired transected buccal and zygomatic branches of the facial nerve medial to a perceived line drawn from the lateral corner of the eye to the lateral corner of the lip with excellent success, injuries in this region are commonly observed, and facial mimetic function tends to recover. As the facial nerve ramifies in its peripheral extent, its topography becomes less complex, and subsequent repairs are more successful, although even its distal branches may not be committed to a single muscle group . Also, unlike skeletal muscle (which possesses a single, centrically located motor end plate innervated by a single motor nerve), individual facial muscle fibers can possess multiple eccentrically located motor end plates innervated by multiple facial nerve branches [19,47]. The various facial muscles 310 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 also possess a diverse range of fiber compositions and diameters: Some (eg, the procerus) are phasic and respond rapidly when stimulated, whereas others (eg, the buccinator) are slow twitch and contribute more to underlying facial tone [18,48]. Given the complex patterns of innervation of the facial musculature and the inconsistent spatial orientation of the facial nerve, reinnervation after nerve repair is frequently accompanied by some degree of synkinesis or dyskinesis. Synkinesis is defined as the abnormal, simultaneous contraction of a group of muscles with voluntary or involuntary facial expression. Dyskinesis occurs when the facial muscles contract in an unintended fashion with facial expression. Synkinesis is the result of the successful innervation of unintended targets in addition to the intended targets, whereas dyskinesis suggests that some of the intended targets were not appropriately innervated. Some investigators have suggested that in addition to aberrant neural regeneration, synkinesis may be related to hyper-excitability of the facial nerve nucleus after injury to the facial nerve [49,50]. Synkinesis or dyskinesis becomes more common as the site of facial nerve injury becomes more proximal from the stylomastoid foramen and into the temporal bone. Cross-facial nerve graft The cross-face nerve graft, as described by Anderl [51,52] and Scaramella [11,53], can be used when the proximal stump of the injured facial nerve is unavailable (Fig. 1). By diverting extratemporal axons from the contralateral facial nerve whose cortical origins match those of the injured side, the problems of synkinesis and involuntary muscular contractions can be avoided. Exposure is gained via a preauricular incision that is carried posterior to the auricle and then caudal to the mandibular angle. Branches of the contralateral facial nerve are exposed and identified with a nerve stimulator. Typically, one or two nerve branches causing elevation of the corner of the mouth, upper lip, and ala are taken for nerve grafting. Branches that preserve eyelid function, including a prominent branch motorizing upper and lower lids and branches to the zygomaticus major and other perioral musculature, are protected to preserve the function of the nonparalyzed side. The sural nerve is used as the donor nerve graft because of its length, caliber, and relative expendability. Neurorrhaphy is performed between sural nerve graft and the transected donor facial nerves on the nonparalyzed side. The grafts are first tunneled subcutaneously across the upper lip and delivered to the contralateral side. The distal end of the graft is banked subcutaneously in the preauricular area until free tissue transfer is undertaken. If cross-facial nerve grafting is performed shortly after the period of denervation, however, neurorrhaphy to the contralateral facial nerve can be considered. Using this model, the senior author has shown that, in instances where distal neurorrhaphy was completed at the time of the initial procedure, nerve fiber diameter, myelin thickness, and the density of neural tissue was greater than when the distal end was banked in the preauricular position . When it is meticulously performed in patients with salvageable facial muscles who are capable of enduring a prolonged anesthetic and when there is sufficient donor nerve material, the cross-facial nerve graft with a distal repair is our preferred technique in restoring facial nerve function when the proximal stump is unavailable for ipsilateral grafting. Nerve transfers Defects of the facial nerve that are not amenable to primary repair, an ipsilateral nerve graft, or a crossfacial nerve graft can be reconstructed with a nerve transfer procedure. Axons from the transferred donor nerve may be delivered to the distal end of the transected facial nerve using direct neurorrhaphy or an interposition nerve graft to enable tension-free repair. Unfortunately, control of the facial mimetic musculature on the paralyzed side of the face relies upon activation of the donor nerve’s intended target. Patients treated with a hypoglossal-facial nerve transfer need to manipulate their tongues to contract their neurotized facial musculature and may develop dyskinetic facial movements with speech, chewing, and other tongue movements and hemiatrophy of the tongue on the paralyzed side. Like the hypoglossalfacial nerve transfer, other nerves transferred to the distal end of the transected facial nerve, including the trigeminal [55,56] and spinal accessory nerve, result in gross [4,57,58], unintended contractions of the facial musculature. Over time, however, a number of patients demonstrate some degree of motor re-education whereby similarly innervated facial muscles display the ability to contract independently after nerve  or muscle transfer procedures . Some authors have suggested that this process of motor re-education is related to neuronal sprouting in the region of the pontine nuclei . Others have suggested that instead of restoring facial nerve function, dormant branches of the trigeminal nerve may motorize denervated facial muscles, as suggested by rare instances of restoration of facial animation with no surgical intervention . T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 Surgical technique: partial hypoglossal-to-facial nerve transfer To minimize the deficits caused when the ipsilateral hypoglossal nerve is sacrificed to enable an end-to-end hypoglossal to facial nerve transfer, endto-side hypoglossal-to-facial nerve transfers have been described clinically [62 – 65], and a partial hypoglossal-to-facial nerve transfer is our preferred technique. Specifically, the ipsilateral hypoglossal nerve is identified proximally, where it is known to have a monofascicular pattern, and is followed distally where a polyfascicular pattern has been demonstrated in cadaveric dissections . A nerve stimulator is then used to identify fascicles of the hypoglossal nerve innervating the posterior aspect of the tongue. These fascicles are carefully protected when a neurectomy involving 25% of the remaining hypoglossal nerve is performed and the transected distal end of the facial nerve is coapted end-to-side to the neurectomized hypoglossal nerve. End-to-side neurorrhaphy of the facial nerve to the hypoglossal nerve, usually with an interposition nerve graft obtained from the medial antebrachial cutaneous nerve, is associated with adequate reinnervation of facial nerve targets and usually without appreciable loss of tongue motion, ipsilateral bulk, or significant speech deficits. Nerve transfers can be used as a definitive procedure to reanimate the paralyzed face but may also be used to provide trophic support to the denervated neuromuscular junction if a cross-facial nerve graft and subsequent prolonged period of denervation is expected [67 – 70]. The hypoglossal and accessory nerves have been used to temporarily maintain the neuromuscular junction of denervated facial mimetic muscles . Recent animal studies, however, challenge the utility of such a ‘‘baby-sitter’’ procedure, suggesting that repeated episodes of denervation followed by reinnervation leads to less muscle recovery than a single prolonged period of denervation followed by a single reinnervation . Surgical management of established facial palsy Regional muscle transfers It is well known that periods of denervation in excess of 1 year in the extremities and 1 to 2 years in the face leads to the irreversible loss of functional motor end plates and muscle contraction in response to neural stimuli. As a result, reinnervation alone does not successfully restore muscle contraction. As shown in Fig. 1, regional muscle transfers using the temporalis 311 or masseter , cross-facial nerve grafts combined with free tissue transfers in a one- or two-stage procedure, and various ancillary static procedures can be used when the motor end plates of the facial muscles are not salvageable. Regional muscle transfers are preferred in patients who do not desire a two-stage operation or are not medically suitable for a prolonged anesthetic or free tissue transfer. Some groups favor using a portion of or the entire masseter muscle alone or in combination with a temporalis muscle transfer for facial reanimation, particularly when the natural vector of the patient’s smile is in a more lateral direction [73,74]. We most frequently use a partial temporalis muscle transfer. The vector-of-pull for this transfer extends from the modiolus to the anterior zygomatic arch and resembles the vector created by contraction of the zygomaticus major muscle. Surgical technique: partial temporalis transfer Exposure for the temporalis muscle transfer begins with an incision extending from the preauricular skin cephalad over the temporalis musculature (Fig. 2). A skin flap is raised just superficial to the parotid fascia and is extended medially toward the nasolabial fold and above and below the oral commissure. If the patient has partial facial nerve palsy, care is taken to identify and preserve branches of the facial nerve that may be stimulated intraoperatively. Superiorly, the dissection continues to the deep fascia of the temporalis muscle. A superiorly based flap of deep temporal fascia, approximately 4 cm wide, is fashioned. The cephalic attachment of this fascia to the temporalis muscle is reinforced with nonabsorbable suture. This superiorly based fascial flap extends the reach of the muscle transfer and functions as a tendon that can be secured to the modiolus and orbicularis oris. After the fascial flap is mobilized, the middle third of the temporalis muscle is elevated from cephalad to caudad and is proximally based. Although care must be taken in elevating a portion of the temporalis muscle for transfer, a recent cadaveric study has confirmed that the temporalis is consistently well vascularized by three distinct arteries and in a majority of cases is simultaneously innervated by buccal, mandibular, and masseteric branches of the trigeminal nerve . With the temporalis elevated to the superior border of the zygomatic arch proximally, the flap is transposed to the modiolus, where the flap is secured to match the vector of smile noted on the contralateral side. The repair of the transferred muscle flap around the corner of the mouth is the same as for insetting a free muscle transfer. Nonabsorbable clear sutures are placed in the orbicularis oris muscle above 312 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 Fig. 2. Middle-aged woman with established facial palsy on the right side. (A) Preoperative photo while smiling. (B) Intraoperative photo demonstrating temporalis muscle transfer. (C) Two-year follow-up while smiling. T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 (three sutures), below (one or two sutures), and at the modiolus (one suture). At the time of the flap inset, it is important to overcorrect the vector by pulling up the upper lip and corner of the mouth to produce some incisor show. An intra-oral splint is placed to support the oral commissure on the affected side and is maintained for 6 weeks postoperatively. In the senior author’s experience, the temporalis muscle transfer is a reliable alternative to microsurgical techniques in restoring facial mimetic function after prolonged denervation. In addition, some animal data suggest that muscle transfers may stimulate neurotization of the facial musculature . In a recent animal study, the retrograde tracer horseradish peroxidase was identified in the trigeminal nucleus of guinea pigs after injection of the facial nerve-innervated zygomaticus major muscle. Although the possibility of duel innervation of the facial mimetics by the trigeminal and facial nerve has been mentioned previously , these investigators suggested that their results may have been due to a phenomenon whereby temporalis muscle transfers may stimulate neurotization of the facial mimetic muscles . Clinically, however, the degree of success achieved with temporalis muscle transfers depends upon the patient’s ability to independently contract the temporalis on the affected side to match the degree of facial muscle contraction on the normal side. Although involuntary facial contractions are rarely symmetric, in our experience patients do extremely well with motor re-education after these muscle transfers. Free tissue transfers To avoid synkinesis and asymmetric, unintended facial expressions in the individual with long-standing facial nerve injury, vascularized free tissue transfers motorized by an ipsilateral nerve, cross-facial nerve graft, or a long neural pedicle extending to a branch of the intact contralateral facial nerve may be used. Described free tissue transfers for facial reanimation include the gracilis , latissimus dorsi , pectoralis minor , and rectus abdominis . Our current practice is to perform a vascularized, free tissue transfer of the gracilis muscle approximately 8 months after cross-facial nerve grafting (Fig. 3). The gracilis muscle remains our muscle of choice based on ease of harvest, its parallel fiber orientation, and a reasonable length of excursion with contraction. Preparation of the recipient site involves a meticulous dissection superficial to the parotid fascia and superficial myoaponeurotic system that avoids the cross-facial nerve graft. Manktelow and Zuker have recently reported a variation on their 313 original cross-facial nerve graft technique, referred to as the ‘‘short-cross facial nerve graft’’ . Instead of performing the neurorrhaphy in the preauricular area as occurred when a 20-cm long sural nerve graft was used, a graft measuring 7 to 8 cm is used and resides superior to the incisors in the upper buccal sulcus after the first stage of cross-facial nerve grafting. The anterior branch of the obturator nerve that innervates the gracilis extends approximately 6 cm so that the neurorrhaphy is performed within the dissected buccal mucosa. One-stage free tissue transfers Over the last decade, there have been a number of reports advocating one-stage free muscle transfers to reanimate the paralyzed face. The success of onestage free tissue transfer of the abductor hallucis longus to restore facial animation in three patients was first reported in 1992  and was later updated . Koshima et al then described an innervated rectus femoris flap for facial reanimation . Nerve grafting could be avoided secondary to the length of the femoral nerve pedicle—often reaching 20 cm— that could easily extend from the muscle flap to an intact buccal branch of the contralateral facial nerve. This group subsequently described a doubly innervated rectus femoris flap whereby lip elevation was provided via the long femoral nerve segment coapted to the contralateral facial nerve. The inferior segment of the rectus femoris muscle responsible for lip depression possessed a shorter motor nerve that was coapted to the ipsilateral masseteric nerve . One-stage free tissue transfers possessing a long motor nerve that can be coapted to the contralateral side have also been described for the gracilis [83,84], latissimus dorsi, , and the internal oblique musculature . Although advocates of a two-stage approach to facial reanimation with free tissue transfers do so primarily to minimize the period of muscular denervation, none of these groups performing one-stage operations report problems with muscle reinnervation clinically or with EMG confirmation . Muscular recovery as early as 6 months after one-stage procedures has been reported, and one-stage procedures are used successfully to treat children with Moebius syndrome . Harii gives two explanations for the paradoxic acceleration in muscle reinnervation that he has observed after one-stage transfers . First, retrograde blood flows from the muscle and into its long vascular pedicle, converting it into a vascularized nerve graft. Second, a sural nerve graft possesses two suture lines, versus the single neurorrhaphy required for a one-stage transfer. 314 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 Perhaps the additional scar and technical considerations of a second neurorrhaphy limits the efficacy of a nerve graft versus the one-stage technique. One concern that we have had with the one-stage free tissue transfer technique relates to the frequent requirement of an additional anterior facial incision to gain exposure for the extended neural pedicle as it passes to the nonparalyzed side of the face [13,86]. Perhaps the buccal sulcus incision described by Manktelow and Zuker for two-stage, free tissue transfers  could be used to help pass the nerve graft to the contralateral side and could be combined with a contralateral facelift incision instead of a more anterior incision to gain exposure of the contralateral normal facial nerve. Although long-term follow-up and further study of the integrity of the neuromuscular junction in one-stage transfers is warranted, this technique is gaining favor for its shorter recovery period and reduced operative times. Gold weight for lagophthalmos Injuries to the facial nerve, most particularly the zygomatic branch, interfere with lid closure because the levator palpebrae superioris and Mueller’s muscles elevate the upper lid unopposed. Exposure keratitis and tearing are common sequelae. Although static procedures involving magnetized rods  and dynamic procedures using palpebral springs  and slips of a regional temporalis muscle transfer have been described , we frequently use a gold weight to achieve eyelid closure [91,92]. This technique has been a reliable method for treating lagophthalmos in a number of series  and relies on the weight of the implant and gravity to produce eye closure with the patient in the upright or reclined position. Preoperatively, trial weights ranging from 0.8 to 1.6 g are placed on the upper lid to determine the lightest weight consistently capable of producing eye closure. Intraoperatively, the appropriately sized 24-carat gold weight, which usually weighs 1 g, is placed immediately superficial to the tarsal plate and centered over the pupils with the patient in centric gaze. To avoid implant visibility, the weight is placed sufficiently cephalad that the resultant bulge is not visible with the eyes open. In a retrospective review, Pickford et al  noted that although patient satisfaction was generally high, selection of an excessively large weight was the most common factor contributing to 315 morbidity. Implant visibility, extrusion, downward migration, and ocular irritation are sequela noted by us and others . Fortunately, the gold weight can be downsized and repositioned as needed because this technique permits subsequent adjustments with little morbidity. Other ancillary procedures Reconstruction after facial nerve injury is not confined to a single or staged procedure but may require several ancillary procedures. Procedures that may improve facial aesthetics after facial nerve injury include debulking procedures (particularly when regional or free flaps are used), tightening or repositioning procedures, or selective denervations to restore symmetry. Static facial reconstructions with fascia lata or Gore-Tex  and common facial cosmetic procedures (eg, brow lift for eyebrow ptosis and rhytidectomy) are also implemented. Denervation of the perioral musculature may cause significant lip asymmetry, which can be restored with autologous reconstructions involving pure fat grafts , dermal fat grafts , and fascia lata grafts ; autologous forms of injectable collagen; or other alloplastic alternatives . Occasionally, facial symmetry is best restored by limiting the function of the nonparalyzed side. When overpull by muscles such as the frontalis or depressor anguli oris distorts facial harmony, for example, botulinum toxin can be used judiciously to temporarily denervate them [101,102]. Typically, any touch-up procedures are performed 18 to 24 months after the last reconstructive procedure to provide sufficient time for wound healing and scar formation and to allow the patient to identify which aspects of their facial aesthetics and function they wish to change. Summary Treatment of facial nerve injuries depends upon a detailed understanding of its anatomic course, accurate clinical examination, and timely and appropriate diagnostic studies. Reconstruction depends upon the extent of injury, the availability of the proximal stump, and the time since injury and duration of muscle denervation. Although no alternative is perfect, these techniques, in combination with static and ancillary Fig. 3. Boy with established facial palsy on the right side. (A) Preoperative photo while smiling. (B) Intra-operative photo demonstrating free tissue transfer of gracilis muscle 8 months after receiving cross facial nerve graft. (C) Two-year follow-up while smiling. (D) Seven-year follow-up while smiling. 316 T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 procedures, can protect the eye, prevent drooling, restore the smile, and improve facial symmetry. New techniques (including single-stage free tissue transfers and bioengineered nerve grafts), further research on the characteristics of the facial musculature, and methods of preserving the neuromuscular junction will undoubtedly manifest themselves as further refinements of established surgical techniques. References  Bell C. On the nerves, giving an account of some experiments on their structure and functions, which leads to a new arrangement of the system. Trans R Soc Lond 1821;3:398.  Sawicki B. The status of neurosurgery, vol. 189. Paris: J. Reuff; 1902.  Kennedy RA, McKendrick FRS. On the restoration of co-ordinated movements after nerve-crossing, with interchange of function of the cerebral cortical centres. Phil Trans Royal Soc Lond 1901;194:127 – 62.  Ballance CA, Ballance HA, Stewart P. Operative treatment of chronic facial palsy of peripheral origin. Br Med J 1903;1:1009 – 13.  Lexer E, Eden R. Uber die chirurgische Behandlung der peripheren Facialislaehmung. Beitr Klin Chir 1911;73:116.  Bunnell S. Suture of the facial nerve within the temporal bone with a report of the first successful case. Surg Gynecol Obstet 1927;45:7 – 12.  Dott NM. Facial paralysis; restitution by extrapetrous nerve graft. Proc R Soc Med 1958;51:900 – 2.  Tamai S, Komatsu S, Sakamoto H, et al. Free muscle transplants in dogs, with microsurgical neurovascular anastomoses. Plast Reconstr Surg 1970;46:219 – 25.  Thompson N. Autogenous free grafts of skeletal muscle: a preliminary experimental and clinical study. Plast Reconstr Surg 1971;48:11 – 27.  Thompson N. Investigation of autogenous skeletal muscle free grafts in the dog with a report on a successful free graft of skeletal muscle in man. Transplantation 1971;12:353 – 63.  Scaramella LF. Cross-face facial nerve anastomosis: historical notes. Ear Nose Throat J 1996;75:343 – 54.  Scaramella LF. Facial reanimation. Ear Nose Throat J 2002;81:411.  Harii K, Ohmori K, Torii S. Free gracilis muscle transplantation, with microneurovascular anastomoses for the treatment of facial paralysis: a preliminary report. Plast Reconstr Surg 1976;57:133 – 43.  Dellon AL, Mackinnon SE. Segmentally innervated latissimus dorsi muscle: microsurgical transfer for facial reanimation. J Reconstr Microsurg 1985;2:7 – 12.  Mackinnon SE, Dellon AL. Technical considerations of the latissimus dorsi muscle flap: a segmentally innervated muscle transfer for facial reanimation. Microsurgery 1988;9:36 – 45.  Terzis JK. Pectoralis minor: a unique muscle for correction of facial palsy. Plast Reconstr Surg 1989;83: 767 – 76.  Manktelow RT, Zuker RM. Muscle transplantation by fascicular territory. Plast Reconstr Surg 1984;73: 751 – 7.  Freilinger G, Happak W, Burggasser G, et al. Histochemical mapping and fiber size analysis of mimic muscles. Plast Reconstr Surg 1990;86: 422 – 8.  Happak W, Liu J, Burggasser G, et al. Human facial muscles: dimensions, motor endplate distribution, and presence of muscle fibers with multiple motor endplates. Anat Rec 1997;249:276 – 84.  May M. Anatomy for the clinician. In: May M, Schaitkin BM, editors. The facial nerve. 2nd edition. New York: Thieme; 2000. p. 19 – 56.  Donaldson JA, Anson BJ. Surgical anatomy of the facial nerve. Otolaryngol Clin North Am 1974;7: 289 – 308.  Guerrier Y. [The facial nerve: points of topographic anatomy]. Ann Otolaryngol Chir Cervicofac 1975;92: 167 – 71.  Guerrier Y, Guerrier B. [Topographic and surgical anatomy of the petrous bone]. Acta Otorhinolaryngol Belg 1976;30:22 – 50.  Lang J. Anatomy of the brainstem and the lower cranial nerves, vessels, and surrounding structures. Am J Otol 1985;Nov(Suppl):1 – 19.  May M. Anatomy of the facial nerve (spatial orientation of fibers in the temporal bone). Laryngoscope 1973;83:1311 – 29.  Kempe LG. Topical organization of the distal portion of the facial nerve. J Neurosurg 1980;52:671 – 3.  Jannetta PJ. The cause of hemifacial spasm: definitive microsurgical treatment at the brainstem in 31 patients. Trans Am Acad Ophthalmol Otolaryngol 1975;80:319 – 22.  Podvinec M, Pfaltz CR. Studies on the anatomy of the facial nerve. Acta Otolaryngol 1976;81:173 – 7.  Harris WD. Topography of the facial nerve. Arch Otolaryngol 1968;88:264 – 7.  Kukwa A, Czarnecka E, Oudghiri J. Topography of the facial nerve in the stylomastoid fossa. Folia Morphol (Warsz) 1984;43:311 – 4.  Sunderland S. The structure of the facial nerve. Anat Rec 1953;116:147.  Wysocki J. [Correlations between topography of the main structures of the temporal bone and the location of the sigmoid sinus]. Otolaryngol Pol 1998;52: 287 – 90.  Davis RA, Anson BJ, Puddinger JM, et al. Surgical anatomy of the facial nerve and parotid gland based upon study of 350 cervical facial halves. Surg Gynecol Obstet 1956;102:385 – 412.  Dingman RO, Grabb WC. Surgical anatomy of the mandibular ramus of the facial nerve based on the dissection of 100 facial halves. Plast Reconstr Surg 1962;29:266. T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318  Gosain AK. Surgical anatomy of the facial nerve. Clin Plast Surg 1995;22:241 – 51.  Gosain AK, Sewall SR, Yousif NJ. The temporal branch of the facial nerve: how reliably can we predict its path? Plast Reconstr Surg 1997;99:1224 – 33, discussion 1234 – 6.  Pitanguy I, Ramos AS. The frontal branch of the facial nerve: the importance of its variations in face lifting. Plast Reconstr Surg 1966;38:352 – 6.  Stuzin JM, Wagstrom L, Kawamoto HK, et al. Anatomy of the frontal branch of the facial nerve: the significance of the temporal fat pad. Plast Reconstr Surg 1989;83:265 – 71.  Seiler WA, Dellon AL, Mackinnon SE. Correlation of facial muscle anatomy and motor function in Maccaca fascicularis. Periph Nerve Repair Regeneration 1986;1:41 – 8.  Watchmaker GP, Mackinnon SE. Nerve injury and repair. In: Peimer CA, editor. Surgery of the hand and upper extremity. New York: McGraw-Hill; 1996. p. 1251 – 75.  Chan SY, Worth R, Ochs S. Block of axoplasmic transport in vitro by vinca alkaloids. J Neurobiol 1980;11:251 – 64.  Correia-de-Sa P, Timoteo MA, Ribeiro JA. Influence of stimulation on Ca(2+) recruitment triggering [3H]acetylcholine release from the rat motor-nerve endings. Eur J Pharmacol 2000;406:355 – 62.  Israel M, Manaranche R. The release of acetylcholine: from a cellular towards a molecular mechanism. Biol Cell 1985;55:1 – 14.  Israel M, Morel N. [Cholinergic chemical transmission: mechanisms of control]. Rev Neurol (Paris) 1987;143:89 – 97.  Ochs S, Ranish N. Metabolic dependence of fast axoplasmic transport in nerve. Science 1970;167: 878 – 9.  Sacchi O, Perri V. Quantal mechanism of transmitter release during progressive depletion of the presynaptic stores at a ganglionic synapse: the action of hemicholinium-3 and thiamine deprivation. J Gen Physiol 1973;61:342 – 60.  Happak W, Burggasser G, Liu J, et al. Anatomy and histology of the mimic muscles and the supplying facial nerve. Eur Arch Otorhinolaryngol 1994; 252:S85 – 6.  Freilinger G, Gruber H, Happak W, et al. Surgical anatomy of the mimic muscle system and the facial nerve: importance for reconstructive and aesthetic surgery. Plast Reconstr Surg 1987;80:686 – 90.  Graeber MB, Bise K, Mehraein P. Synaptic stripping in the human facial nucleus. Acta Neuropathol (Berl) 1993;86:179 – 81.  Moran CJ, Neely JG. Patterns of facial nerve synkinesis. Laryngoscope 1996;106:1491 – 6.  Anderl H. Cross-face nerve transplant. Clin Plast Surg 1979;6:433 – 49.  Anderl H. Cross-face nerve transplantation in facial palsy. Proc R Soc Med 1976;69:781 – 3. 317  Scaramella LF, Tobias E. Facial nerve anastomosis. Laryngoscope 1973;83:1834 – 40.  Mackinnon SE, Dellon AL, Hunter DA. Histological assessment of the effects of the distal nerve in determining regeneration across a nerve graft. Microsurgery 1988;9:46 – 51.  Fournier HD, Denis F, Papon X, et al. An anatomical study of the motor distribution of the mandibular nerve for a masseteric-facial anastomosis to restore facial function. Surg Radiol Anat 1997;19: 241 – 4.  Frydman WL, Heffez LB, Jordan SL, et al. Facial muscle reanimation using the trigeminal motor nerve: an experimental study in the rabbit. J Oral Maxillofac Surg 1990;48:1294 – 304.  Endo T, Hata J, Nakayama Y. Variations on the ‘‘baby-sitter’’ procedure for reconstruction of facial paralysis. J Reconstr Microsurg 2000;16:37 – 43.  Hadlock TA, Cheney ML. Update on facial nerve repair. Facial Plast Surg 1998;14:179 – 84.  Stennert EI. Hypoglossal facial anastomosis: its significance for modern facial surgery. II. Combined approach in extratemporal facial nerve reconstruction. Clin Plast Surg 1979;6:471 – 86.  Rubin LR, Rubin JP, Simpson RL, et al. The search for the neurocranial pathways to the fifth nerve nucleus in the reanimation of the paralyzed face. Plast Reconstr Surg 1999;103:1725 – 8.  Norris CW, Proud GO. Spontaneous return of facial motion following seventh cranial nerve resection. Laryngoscope 1981;91:211 – 5.  Darrouzet V, Dutkiewicz J, Chambrin A, et al. [Hypoglosso-facial anastomosis: results and technical development towards end-to-side anastomosis with rerouting of the intra-temporal facial nerve (modified May technique)]. Rev Laryngol Otol Rhinol (Bord) 1997;118:203 – 10.  Koh KS, Kim JK, Kim CJ, et al. Hypoglossal-facial crossover in facial-nerve palsy: pure end-to- sideanastomosis technique. Br J Plast Surg 2002;55:25 – 31.  Manni JJ, Beurskens CH, van de Velde C, et al. Reanimation of the paralyzed face by indirect hypoglossal-facial nerve anastomosis. Am J Surg 2001;182: 268 – 73.  Yoleri L, Songur E, Yoleri O, et al. Reanimation of early facial paralysis with hypoglossal/facial end-toside neurorrhaphy: a new approach. J Reconstr Microsurg 2000;16:347 – 55, discussion 355 – 6.  Mackinnon SE, Dellon AL. Fascicular patterns of the hypoglossal nerve. J Reconstr Microsurg 1995; 11:195 – 8.  Kalantarian B, Rice DC, Tiangco DA, et al. Gains and losses of the XII – VII component of the ‘‘baby-sitter’’ procedure: a morphometric analysis. J Reconstr Microsurg 1998;14:459 – 71.  Mersa B, Tiangco DA, Terzis JK. Efficacy of the ‘‘baby-sitter’’ procedure after prolonged denervation. J Reconstr Microsurg 2000;16:27 – 35.  Thanos PK, Terzis JK. A histomorphometric analysis 318                T.M. Myckatyn, S.E. Mackinnon / Clin Plastic Surg 30 (2003) 307–318 of the cross-facial nerve graft in the treatment of facial paralysis. J Reconstr Microsurg 1996;12:375 – 82. Thanos PK, Terzis JK. Motor endplate analysis of the denervated and reinnervated orbicularis oculi muscle in the rat. J Reconstr Microsurg 1995;11:423 – 8. Yoshimura K, Asato H, Jejurikar SS, et al. The effect of two episodes of denervation and reinnervation on skeletal muscle contractile function. Plast Reconstr Surg 2002;109:212 – 9. Baker DC, Conley J. Regional muscle transposition for rehabilitation of the paralyzed face. Clin Plast Surg 1979;6:317 – 31. Sachs ME, Conley J. Dual simultaneous systems for facial reanimation. Arch Otolaryngol 1983;109: 137 – 9. Schauss F, Schick B, Draf W. [Regional muscle flapplasty and adjuvant measures for rehabilitation of the paralyzed face]. Laryngorhinootologie 1998;77: 576 – 81. Burggasser G, Happak W, Gruber H, et al. The temporalis: blood supply and innervation. Plast Reconstr Surg 2002;109:1862 – 9. Petropoulos AE, Cheney ML. Induction of facial muscle neurotization by temporalis muscle transposition: literature review and animal model evaluation using horseradish peroxidase uptake. J Otolaryngol 2000;29:40 – 6. Hata Y, Yano K, Matsuka K, et al. Treatment of chronic facial palsy by transplantation of the neurovascularized free rectus abdominis muscle. Plast Reconstr Surg 1990;86:1178 – 87, discussion 1188 – 9. Manktelow RT, Zuker RM. Cross-facial nerve graft the long and short graft: the first stage for microneurovascular muscle transfer. Oper Tech Plastic Reconstr Surg 1999;6:174 – 9. Jiang H. [Microneurovascular free abductor hallucis muscle transplantation for resuscitation of facial paralysis in one stage]. Zhonghua Wai Ke Za Zhi 1992;30:420 – 2, 444. Jiang H, Guo ET, Ji ZL, et al. One-stage microneurovascular free abductor hallucis muscle transplantation for reanimation of facial paralysis. Plast Reconstr Surg 1995;96:78 – 85. Koshima I, Moriguchi T, Soeda S, et al. Free rectus femoris muscle transfer for one-stage reconstruction of established facial paralysis. Plast Reconstr Surg 1994;94:421 – 30. Koshima I, Umeda N, Handa T, et al. A doublemuscle transfer using a divided rectus femoris muscle for facial-paralysis reconstruction. J Reconstr Microsurg 1997;13:157 – 62. Ashayeri M, Karimi H. One-stage reversed and rotated gracilis muscle free flap for chronic facial palsy: a new technique. Plast Reconstr Surg 2002;110: 1298 – 302. Kumar PA. Cross-face reanimation of the paralysed face, with a single stage microneurovascular gracilis transfer without nerve graft: a preliminary report. Br J Plast Surg 1995;48:83 – 8.  Harii K, Asato H, Yoshimura K, et al. One-stage transfer of the latissimus dorsi muscle for reanimation of a paralyzed face: a new alternative. Plast Reconstr Surg 1998;102:941 – 51.  Wang W, Qi Z, Lin X, et al. Neurovascular musculus obliquus internus abdominis flap free transfer for facial reanimation in a single stage. Plast Reconstr Surg 2002;110:1430 – 40.  Takushima A, Harii K, Asato H, et al. Neurovascular free-muscle transfer to treat facial paralysis associated with hemifacial microsomia. Plast Reconstr Surg 2002;109:1219 – 27.  Muhlbauer WD, Segeth H, Viessman A. Restoration of lid function in facial palsy with permanent magnets. Chir Plast 1973;1:295.  Morgan LR, Rich AM. Four years’ experience with the Morel-Fatio palpebral spring. Plast Reconstr Surg 1974;53:404 – 9.  Deutinger M, Freilinger G. Transfer of the temporal muscle for lagophthalmos according to Gillies. Scand J Plast Reconstr Surg Hand Surg 1991;25:277 – 80.  Jobe RP. A technique for lid loading in the management of the lagophthalmos of facial palsy. Plast Reconstr Surg 1974;53:29 – 32.  Manktelow RT. Use of the gold weight for lagophthalmos. Oper Tech Plastic Reconstr Surg 1999;6: 157 – 8.  Fernandez-Alba J, Salmeron JI, Calderon J, et al. [Rehabilitation of facial paralysis by temporal muscle flap and implantation of gold weights]. Acta Otorrinolaringol Esp 1999;50:20 – 8.  Pickford MA, Scamp T, Harrison DH. Morbidity after gold weight insertion into the upper eyelid in facial palsy. Br J Plast Surg 1992;45:460 – 4.  Dinces EA, Mauriello Jr JA, Kwartler JA, et al. Complications of gold weight eyelid implants for treatment of fifth and seventh nerve paralysis. Laryngoscope 1997;107:1617 – 22.  Constantinides M, Galli SK, Miller PJ. Complications of static facial suspensions with expanded polytetrafluoroethylene (ePTFE). Laryngoscope 2001;111: 2114 – 21.  Guerrerosantos J. Long-term outcome of autologous fat transplantation in aesthetic facial recontouring: sixteen years of experience with 1936 cases. Clin Plast Surg 2000;27:515 – 43.  Kesselring UK. Rejuvenation of the lips. Ann Plast Surg 1986;16:480 – 6.  Burres SA. Lip augmentation with preserved fascia lata. Dermatol Surg 1997;23:459 – 62.  Singh S, Baker Jr JL. Use of expanded polytetrafluoroethylene in aesthetic surgery of the face. Clin Plast Surg 2000;27:579 – 93.  Carruthers JD. Ophthalmologic use of botulinum A exotoxin. Can J Ophthalmol 1985;20:135 – 41.  Fagien S, Brandt FS. Primary and adjunctive use of botulinum toxin type A (Botox) in facial aesthetic surgery: beyond the glabella. Clin Plast Surg 2001; 28:127 – 48.