Assessment of the Deformity

Physical examination includes complete head and neck examination with attention to cranial nerve function and the presence of functional masseter and temporalis muscles. The degree of facial nerve function is recorded using the House-Brackmann Facial Grading System² (Table 172-1). A number of facial nerve grading scales have been developed, but the House-Brackmann scale was adopted by the Facial Nerve Disorders Committee of the American Academy of Otolaryngology–Head and Neck Surgery in 1985 because of its reproducibility and ease of use.² This scale is useful for evaluation of overall function, but it is insufficient for precise assessment of defects affecting one or more branches of the facial nerve, and it does not allow precise measurement of effectiveness of treatments isolated to one region of the face. Therefore, the examination should assess deformity of the upper, middle, and lower thirds of the face independently. This approach allows more precise characterization of defects, aids the decision-making process for rehabilitation, and allows more precise assessment of treatment results. Facial tone also is noted, as is the presence of any reinnervation. Thorough assessment of the eye also is performed. Visual acuity, corneal integrity, eyelid closure, tearing, Bell’s phenomenon, lagophthalmos, lower lid laxity, position of the lacrimal puncta, and eyebrow position are noted. Nasal examination focuses on the position of the ala and nasal septum and the presence or absence of nasal obstruction. Oral competence and height and position of the lower lip are carefully reviewed. In long-term paralysis (of more than 1 year’s duration), electromyography (EMG) of the facial muscles is performed before reinnervation procedures. Occasionally, muscle biopsy provides additional information about the presence of viable muscle for innervation. If nerve fibrosis is suspected, nerve biopsy occasionally is indicated.

Table 172-1 House-Brackmann Grading System

Time since Transection

A chronic, long-standing paralysis with complete muscle degeneration poses several problems with regard to eventual reinnervation surgery. The facial muscles may undergo denervation atrophy. Severe atrophy renders the reasonably normal muscles incapable of reinnervation and contraction. Such severe atrophy may occur after 18 months of complete denervation, although in some clinical situations, muscles have been known to persist inexplicably for many years without incurring such atrophy.⁴ EMG is the most helpful method for assessing facial muscle atrophy and is therefore a preoperative prerequisite for all reanimation candidates if the paralysis is of more than 12 months’ duration. The presence of nascent, polyphasic, or normal voluntary action potentials in a patient with facial paralysis indicates the occurrence of reinnervation. If more than 12 months have passed since the facial nerve injury, the situation can be assumed to be stable, and an attempt at surgical reanimation may be warranted. Within the first 12 months, however, the presence of potentials may mean that reinnervation is occurring and that facial movements may return in the next few months. Reanimation surgery should therefore be postponed. Fibrillation or denervation potentials mean that the EMG electrode is positioned in denervated muscle. This is an optimal situation for cable nerve grafting or, when no viable proximal facial nerve is available, for hypoglossal-facial anastomosis.

One of the most significant EMG findings is electrical silence, reflecting denervation atrophy of the facial muscles. The surgical implication is that nerve grafting or transfer is futile and therefore contraindicated. If the facial muscles are absent or atrophied, muscle transfers are indicated.

Another effect of time includes endoneural scarring within distal nerve segments. It is not known whether endoneural scarring acts as an impediment to nerve regeneration, but when associated with muscular atrophy, it probably further precludes nerve grafting or transfer.

Presence of Partial Regeneration

Partial regeneration often is overlooked but is extremely important in determining which operation to perform. If the facial nerve has undergone enough regeneration to permit a few axons to reach the facial muscles, this partial innervation may be sufficient to preserve the muscles for many years, even though they may be totally paralyzed. In these clinical circumstances, results with hypoglossal-facial anastomosis, which generally is preferable to muscle transfer, will be optimized.

Status of the Proximal and Distal Facial Nerve

The optimal source for rejuvenation of the paralyzed face is the ipsilateral facial nerve. Anastomosis or grafting to the ipsilateral nerve has no donor consequence (other than the minor hypesthesia or anesthesia from the harvesting of a nerve graft) and facilitates natural voluntary and involuntary control. Exceptions to this general rule are those cases in which the patient needs prompt relief from corneal exposure or drooling, and a tissue transfer or sling technique may be preferred because its effects are immediate.

Accordingly, the integrity of the proximal facial nerve is critical. As with other motor nerves, no reliable electrical tests exist to confirm the viability of the proximal nerve when it is discontinuous with its distal portion. Factors that affect proximal nerve viability and are therefore important considerations in the clinical evaluation include (1) nature of the nerve injury (e.g., clean transection versus crush), (2) location of injury (proximal versus distal), (3) age (younger nerves tend to regenerate more quickly and fully), (4) nutritional status (which directly affects nerve regeneration), and (5) history of irradiation (which may impede neural regeneration).

The facial nerve distal to the injury site serves as a conduit for neural regeneration to the facial muscles after neurorrhaphy, grafting, or hypoglossal-facial anastomosis. With acute injuries (incurred less than 72 hours previous), the electrical stimulator may be used to identify the distal nerve and the muscular innervation of distal branches. After this “golden period,” however, the surgeon must rely on visual identification of the divisions and branches of the distal nerve, because the capability of being stimulated electrically generally is lost after approximately 72 hours. For this reason, transected nerve branches in trauma or tumor cases should be tagged for identification by placing a small colored suture around or adjacent to each nerve branch. Any anatomic or surgical landmarks should be precisely dictated in the operative note. If no suture markers are available, and the golden period has elapsed, careful surgical searching (preferably with use of loupes or an operating microscope) may reveal each of the divisions or branches of the facial nerve. A topographic map is essential in guiding the dissection. A review by Bernstein and Nelson⁵ describes the variability with which these branches are placed. The following landmarks are helpful (Fig. 172-1).

Figure 172-1. Topographic map of distal facial nerve anatomy, useful as a guide in finding nonstimulatable nerve branches for grafting. Pes anserinus is 2 cm inferior to a point 1 cm anterior to tragus. Marginal mandibular branch courses from the pes anserinus to the angle of the mandible: buccal branch parallels the zygomatic arch 1 cm below its inferior border. Superior division arcs from pes anserinus toward lateral end of the eyebrow, under a line that is convex superiorly.

(From House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985;93:146.)

As an example of selective routing, when a parotid tumor operation results in excision of the pes anserinus and the proximal facial branches, a branched nerve graft may be placed to reinnervate the zygomatic and the buccal branches, excluding unimportant branches. Fisch⁶ advises clipping branches of cervical branches in order to route innervation to the more important portions of the face. Data confirming the efficacy of this technique, however, are very limited.

If no nerve branches are found, and EMG shows that denervated facial muscles are present, the nerve graft may be sutured directly to the muscles targeted for reinnervation (muscular neurotization). In these instances, the most important muscles are those of the midface (zygomaticus major and minor, levator labii superioris) and orbicularis oculi muscles. Reinnervation will not be as complete as in routine nerve grafting because the regenerating axons must form new connections to the old motor endplates, or they must create their own.⁷

Viability of Facial Muscles

Four types of EMG responses are observed⁸:

Donor Consequences

Many surgical procedures designed for facial reanimation borrow neural elements or signals from other systems (i.e., the hypoglossal and trigeminal systems). The consequences of sacrificing the donor nerve (known as donor deficit) are most important in planning for the overall needs of the patient. Certainly, the surgeon must assess the donor nerve preoperatively in all cases. The hypoglossal nerve must be tested for strength and vitality before it is transected and anastomosed to the distal facial nerve. Similarly, the trigeminal nerve must be intact and functional when its muscles, either masseter or temporalis, are considered for transposition into the facial muscle system.

The donor effects of facial reanimation surgery may be quite detrimental to the patient’s welfare. For example, a patient with previous hypoglossal nerve injury on the opposite side could become an “oral cripple” if the remaining hypoglossal nerve were to be transected for use in a XII-VII anastomosis.

The ideal reanimation procedure is one that yields the following results: (1) no donor deficit; (2) immediate restitution of facial movement; (3) appropriate involuntary emotional response; (4) normal voluntary motion; and (5) facial symmetry. No currently available operative procedure satisfies all of these parameters. In fact, even with a bacteriologically sterile and precise surgical transection and immediate microsurgical repair of the facial nerve, completely normal neurologic function cannot be restored. Therefore, the surgeon must have a clear understanding of all operations available, including potential outcomes and sequelae.

Status of Donor Nerves

The hypoglossal nerve is the most frequently used nerve source for transfer. Reflex and physiologic similarities between the hypoglossal and facial nerves have been described.⁹ The integrity of the hypoglossal nerve must be determined before it is transferred for reinnervation. Irradiation of the brainstem, lesions of the skull base and hypoglossal canal, and surgical procedures of the upper neck may affect the integrity and function of this nerve.

The trigeminal nerve has been used for facial reanimation in many ways. The methods currently used most often involve masseter or temporalis muscle transfer (necessitating that the motor portions of the trigeminal nerves be intact). Palpation of the muscle during jaw clenching confirms whether the muscle is functional.

The cross-face nerve graft procedure (faciofacial anastomosis) initially was thought to be the most appropriate and ingenious facial reanimation procedure.^10,11 The procedure is unique in that it borrows appropriate neural input from the contralateral normal side and routes it to the paralyzed side. Such a procedure requires a fully intact (contralateral) facial nerve.

Age

The proximal neuron’s ability to regenerate declines with time because of denervation and aging-related changes. The etiologic mechanism probably involves diminishing regenerative vitality of the perikaryon (cell body), although peripheral scarring may play a role. The clinical implication is that facial reanimation surgery should always be performed as soon as possible, provided that the operative procedure does not interfere with or injure existing innervation or ongoing reinnervation.¹²

Health Status

Among patients with diabetes, regeneration of injured nerves is notoriously poor. Microangiopathy is an additional factor that may affect the grafted segment. These factors do not preclude a nerve graft procedure in a diabetic patient, but when combined with radiation, advancing age, and other factors, they may cause the surgeon to consider muscle transfer or a suspensory operation, rather than a neural anastomosis.

Prior Radiotherapy

Radiotherapy, a necessary component of treatment for certain salivary gland malignancies, appears to have a deleterious effect on reinnervation through facial nerve grafts. McCabe¹³ demonstrated satisfactory muscle reinnervation from grafting despite irradiation in animals. These investigators subsequently have documented return of facial function in nine patients who received post-grafting radiotherapy. McGuirt and McCabe¹³ and Conley and Miehlke¹⁴ have published reports indicating that facial nerve grafts function well even though irradiated, and that nerves are among the most radioresistant tissues of the human body. Pillsbury and Fisch¹⁵ found that radiotherapy reduced the average outcome from 75% to 25% of nerve function recovery in a review of 42 grafted patients. Irradiation probably affects the neovascularization of the nerve graft by decreasing vascularity of the tissue bed and probably injures the proximal and distal segments of the nerve as well. The most radiosensitive portion of the nerve—the pontine nucleus—should be assessed to determine whether it was present in the field of irradiation.

Congenital Paralysis

In a series of 95 infants with neonatal paralysis, Smith and associates⁸ found 74 of the cases to be secondary to intrauterine injury or birth trauma, whereas 21 were thought to be congenital. These infants should be studied with nerve excitability and EMG testing early in life to ascertain the status of nerves and muscles. Most patients with injury-related neonatal paralysis recover rapidly, whereas the paralysis associated with other congenital anomalies (such as Möbius syndrome) is permanent. Nerve exploration or transfer generally is futile in the latter cases.

Eye Protection: Evaluation and Treatment of Eyelid Paralysis

Paralysis of the orbicularis oculi results in exposure and drying of the cornea. Patients at increased risk for exposure keratitis may be identified by applying the acronym BAD—absence of Bell’s phenomenon, corneal anesthesia, and history of dry eye. An inability to protect the cornea is the result of incomplete eye closure, preventing effective distribution of the tear film across the surface of the eye, and ectropion occurs because the atonic lower lid and lacrimal punctum fail to appose the globe and bulbar conjunctiva. This causes faulty eyelid closure and improper distribution of tears across the cornea.

Epiphora may result from failure of tears to enter the lacrimal punctum, secondary to pooling of tears due to ectropion and the loss of the orbicularis oculi tear-pumping mechanism. The response to abnormal corneal sensation may be reflex tear hypersecretion, which will further increase the epiphora.

Any patient with facial paralysis who demonstrates a poor Bell’s phenomenon is at risk for the development of exposure keratitis. Eye pain may herald the onset of keratitis. In patients with diminished corneal sensation, however, exposure keratitis may asymptomatically progress to corneal ulceration. Accordingly, all patients with diminished orbicularis oculi function require ophthalmologic consultation.

Initial eye care is directed toward moisturizing the dry eye and preventing exposure. It is important to communicate to the patient the potential consequences of failure to protect the eye, in hopes of improved compliance. If the eyelid paralysis is temporary or partial, these local measures may be all that are necessary to adequately protect the eye. Regular use of artificial tears commonly is the first-line method used to keep the eye moist. Ointments also may be used, but they are less practical in the daytime because they tend to blur vision.

Lacriserts, contact lenses, and occlusive bubbles commonly are used, although patient compliance may be problematic¹⁶ (Fig. 172-2). The eyelids frequently are patched or taped, but if incorrectly used, these methods may result in corneal injuries. Tape should not be placed vertically across the eyelashes, but applied horizontally above the eyelashes on the upper eyelid, or supporting the lateral canthal portions of the lower eyelid.¹⁷ When an eye patch is used, care must be taken to ensure that the eye cannot open, because this would allow contact between the patch and the cornea.

Figure 172-2. Occlusive bubble worn by a patient after acoustic neuroma surgery. The appliance has a foam rubber skin contact surface that is firmly attached to a thin Plexiglas lens. In our experience, patient compliance is relatively high with this type of device.

(Courtesy of Moisture Chamber, Pro-optics, Palatine, Illinois.)

Procedures to Treat Paralysis of the Lower Lid (Ectropion)

Tarsorrhaphy

The temporary lateral tarsorrhaphy is an expeditious and effective method for protecting the eye in patients with mild lagophthalmos and mild corneal exposure. A horizontal mattress suture of 7-0 silk or nylon is placed laterally to approximate the gray line (mucocutaneous junction) of the upper and lower lids. Tarsorrhaphy sutures will remain effective longer if they are placed through bolsters made of rubber (Robinson) catheters.

For longer-lasting protection, the lid adhesion tarsorrhaphy is preferred. The lid margin (gray line) of each lid is denuded 4 to 6 mm from the lateral canthus, and a similar suture technique is used to approximate the denuded mucocutaneous junctions of upper and lower lids (Fig. 172-3). Like the temporary lateral tarsorrhaphy, this procedure can be reversed if function returns. The cosmetic deformity of tarsorrhaphy and the availability of improved, alternative techniques to rehabilitate the eyelids have reduced the use of tarsorrhaphies.

Figure 172-3. A, Tiny single skin hook being used to evert the lower lid for denuding of “gray line” (mucocutaneous junction). Note that a gray line of upper lid has been denuded. B, Healed tarsorrhaphy at 4 months. Increased eye closure may be achieved by extending the denudation and sutures medially.

Procedures to Treat Paralysis of the Upper Lid (Lagophthalmos)

Surgical Planning

In planning the surgical procedure, the proximal site of nerve transection frequently is found to be in the intraparotid portion proximal to the pes anserinus. This location may present technical difficulties because the proximal stump may not be adequate for technical ease in suturing. In other instances, the nerve may be transected at the stylomastoid foramen. If it is seen to be transected at the stylomastoid foramen, a mastoidectomy should be performed. Distal to the mastoid portion, the nerve’s sheath merges with periosteum of the stylomastoid foramen and temporal bone, making this portion difficult to dissect free for suture. This difficult region exists roughly from 1 cm above to 1 cm below the stylomastoid foramen. Use of the mastoid portion of the facial nerve may require use of the longer sural or medial antebrachial cutaneous nerve, rather than the greater auricular nerve, for a cable graft.

Distally, several situations may be encountered that require some ingenuity in effecting reanimation. When the distal anastomotic site is at or proximal to the pes anserinus, a simple nerve-to-nerve suture will suffice. More frequently, however, after resection for parotid malignancy, several branches or divisions may require anastomosis. In such cases, priority must be given to the zygomatic and buccal branches, sometimes to the exclusion of other, less important facial nerve branches. Frequently, a two-branch graft can be prepared from the greater auricular nerve or the sural nerve. This situation favors suturing of one branch of the nerve graft to the buccal branch and the other graft branch to the zygomatic branch or superior division. This technique will direct innervation to the important orbicularis oculi muscle and the muscles of the buccal-smile complex (Fig. 172-4).

Figure 172-4. Facial muscles. A, The most important muscles for reanimation: The levator labii superioris, along with the lesser zygomatic muscle, probably is the most significant muscle for elevation of the upper lip. The greater zygomatic muscle also is critical as the strongest elevator of the oral commissura. B to F, Example of a delayed nerve graft in a patient in whom a parotid malignancy was removed without immediate reconstruction (because of intraoperative anesthesia considerations). B, The patient was referred for nerve grafting after 9 months elapsed. Note elongation of the buccal-smile complex of muscles (greater and lesser zygomatics, levator labii superioris) and paralysis of orbicular eye muscle. C, Preoperative surface markings for nerve branches. Nerve stimulator cannot be used to locate distal branches after 9-month time lapse. Markings are for the superior division and buccal branch, based on landmarks described in Figure 172-1 and the previous operative report. D, Superior division is found; it is ready for transection and anastomosis to sural graft (from midmastoid nerve segment). E, Result at 1 year after operation—typical for a delayed nerve graft. Orbicular eye and buccal branch muscle function is improved, but the muscles are not normally or completely reinnervated. F, Voluntary motion in both zygomatic and buccal branches, with synkinesia. This result also is typical for most nerve grafts in that the temporal branch (to occipitofrontal muscle) shows no reinnervation. Note the hairstyle designed to camouflage occipitofrontal muscle paralysis.

Surgical Technique

For the surgical technique of neurorrhaphy, interrupted sutures using 9-0 or 10-0 monofilament nylon are preferred. A straight and a curved pair of jeweler’s forceps as well as a Castroviejo needle holder are satisfactory instruments for performing the anastomosis. Both ends of the nerve graft and the proximal and distal stumps should be transected cleanly with a fresh sterile blade.¹³ For nerve trunk anastomosis, four simple epineural sutures will usually coapt the nerve ends accurately. However, obvious discrepancies in size or other epineural gaps should be closed with additional sutures. The needle should pass through epineurium only to avoid injury to the fascicular neural contents. The nerve graft should lie in the healthiest possible bed of supporting tissue, with approximately 8 to 10 mm of extra length for each anastomosis. Thus, the graft should lie in a somewhat “lazy S” configuration (see Fig. 172-4), which appears to minimize tension during healing. Suction drainage systems should be placed away from any portions of the nerve graft.

When one division is excised or injured and other portions of the nerve remain intact, it may be desirable to graft from a fascicle within the pes anserinus to a distal branch. To accomplish this, fascicular dissection is performed in parallel and along the plane of the nerve fascicles with curved jewler’s forceps into the pes anserinus (Fig. 172-5). The distal buccal branch often has several small filaments, so it may be necessary to select the larger of these for distal anastomosis.

Figure 172-5. A, Hypoglossal-facial anastomosis showing selective reinnervation of the inferior division, leaving the superior division innervation intact. Inset shows fascicular dissection before anastomosis (see D and E). B and C, Preoperative photographs of patient with long-standing segmental paralysis of inferior division of facial nerve. Zygomatic branch to orbicular eye muscle shows preservation of innervation. D to F, Intraoperative photographs. D, Perineural dissection of pes anserinus reveals fascicles destined for zygomatic and buccal branches (see A). E, Buccal branch and inferior division transected. Neurosurgical loop protects intact superior division under background piece of polymeric silicone (Silastic). Hypoglossal nerve (at lower right) is ready for anastomosis. F, Completed anastomosis of hypoglossal nerve to the buccal branch and inferior division of the facial nerve. The superior division is intact and in continuity with proximal facial nerve. G and H, Strong reinnervation to entire face, 1 year after operation. G, Patient uses hypoglossal innervation to buccal branch muscles to enhance eye closure. H, Upward movement of oral commissura mediated by hypoglossal nerve, without associated or synkinetic eye closure.

Approximation of the nerve ends using an acrylic glue has been described (Histacryl or cyano-butyl-acrylate)²⁸ with subsequent investigators revealing that neural anastomosis with tissue adhesive yields results similar to nerve suture. This technique is most helpful in the confined surgical considerations of the temporal bone rather than in distal facial anastomosis.²⁹ Others have described using biodegradable nerve tubules.

Following temporal bone resection, the nerve may be routed from the tympanic or the labyrinthine portions directly to the face through a bony window near the posterior root of the zygomatic arch. This will shorten the necessary length of the nerve graft. However, when using this technique it is important to ensure the nerve graft’s protection from trauma at the temporomandibular joint if the joint is preserved. Conley and Baker^30,31 have reported excellent results using similar techniques.

Millesi³² introduced interfascicular nerve repair, reasoning that the exact microsurgical approximation of nerve fascicles or fascicle groups may minimize synkinesis or mass movement. It is well known that this type of repair is preferred in nerve injuries in the extremities; however, such repairs have not been universally accepted for use in the facial nerve. Several reasons underlie this limited acceptance. The tympanic and, in many cases, the mastoid portions of the nerve have only one or two fascicles, and the intraneural topography is questionable. Few, if any, sensory fibers are present in the extratemporal portion of the facial nerve, so performing sensory-to-sensory fascicular repair is not of value.

Along with May and Miehlke, we have reported (independently) that discrete, spatially oriented fascicles are present in the nerve near the stylomastoid foramen.^33–35 Other authors, notably Sir Sidney Sunderland³⁶ and Tomander and colleagues,³⁷ have reported conflicting data demonstrating that various portions of the face are represented in a random fashion in the proximal nerve. At present, it probably is best to perform fascicular repair when the injury obviously lends itself to the technique (e.g., clean lacerations through the pes anserinus and branch nerve grafts that require fascicular dissection in the pes). Basic research has yet to reveal the exact neural topography of the more proximal portions of the nerve.

Cross-Face Nerve Grafting

Hypoglossal Nerve Transfer

Of the various nerves available for anastomosis with the facial nerve, the hypoglossal nerve is preferred, because an anatomic and functional relationship exists between the facial and the hypoglossal nerves. They both arise from a similar collection of neurons in the brainstem, and they also share similar reflex responses to trigeminal nerve stimulation.⁹ In addition, the hypoglossal nerve is in close anatomic proximity and is readily available during other operations on the facial nerve. Hypoglossal nerve transection results in less donor disability than that typical with sacrifice of the spinal accessory, phrenic, or other regional nerves that have been used for facial reanimation. The most common criticism of hypoglossal nerve transfer is that it results in a lack of voluntary emotional control. Although this is true, ipsilateral facial nerve anastomosis often is associated with a similar drawback: Mass movements and spasms preclude any voluntary control of eye closure, smiling, or other emotional movements. In our practice, we have used hypoglossal nerve transfer for reanimation of the upper or lower division selectively by performing fascicular dissection in the pes anserinus to identify the specific fascicles that required reinnervation (see Fig. 172-5).

May and coworkers⁴³ attempted to decrease morbidity from tongue atrophy by performing partial transection of the hypoglossal nerve with use of a jump graft from the partially transected nerve to the distal facial nerve. Decreased effectiveness of partial transection with jump graft has been reported by some investigators.⁴⁴

Recently, “pure” end-to-side anastomosis of the facial nerve or a jump graft into the donor hypoglossal nerve has been rediscovered⁴⁵ and reported in a small series of patients.⁴⁶ The study investigators performed anastomosis of facial nerve either mobilized from the mastoid or bridged by interposition graft into the intact hypoglossal nerve, without removal of epineurium or perineurium. This technique relies on the presumed axon sprouting across intact epineurium of the hypoglossal nerve. Some evidence indicates lateral axonal growth after end-to-side nerve anastomosis occurs. Rat studies demonstrate axonal penetration of endoneurium, perineurium, and epineurium.^47–49 Whether this technique will be applicable in humans who have decreased nerve regenerative capacity and much thicker perineurium and epineurium than in the rat remains to be seen. It may be more effective to remove an epineurial window and perform the anastomosis without disruption of nerve fibers yet still induce enough axonal regrowth to provide tone and function. Further animal and human studies will be necessary to determine the usefulness and role of end-to-side neurorrhaphy for facial rehabilitation.

Results

In the largest series to date, involving 137 patients, approximately 95% regained satisfactory tone in repose and regained some mass facial movement.⁵⁰ Of these patients, 15% demonstrated hypertonia and excessive movement in the middle third of the face; however, none of these patients requested that the transferred nerve be reoperated. This excessive movement was found to decrease gradually over 10 to 20 years. However, Dressler and Schonle⁵¹ and Borodic and coworkers⁵² have had success treating facial hyperkinesia with selective injection of botulinum toxin. Seventy-eight percent of the patients had moderate to severe tongue atrophy, whereas 22% showed minimal atrophy; this wide variability in response of the tongue to hypoglossal nerve transection has been confirmed in other series⁵³ (Fig. 172-6). Use of the interpositional jump graft with partial hypoglossal nerve preservation preserved tongue function in a majority of patients and provided satisfactory function. In a series of 20 patients, good facial tone and symmetry were observed at follow-up evaluation in all patients, and 13 had “excellent” restoration of facial movement, with development of 12th nerve deficits noted in only 3 patients.⁴³

Figure 172-6. A, Patient with facial paralysis after acoustic neuroma excision. Lateral tarsorrhaphy is in place. B, Exposure of hypoglossal nerve. Note exit of ansa cervicalis branch at lower right. This may be transected and sutured to the distal hypoglossal, although preservation of tongue innervation usually is weak with this technique. C, Repose. Note elevated commissura and reconstitution of nasolabial fold. D, Movement instigated by pushing tongue tip against lingual aspect of mandible in canine region. This maneuver usually results in strongest facial movement after anastomosis of cranial nerves XII and VII. E, Typical lingual deviation after the procedure.

Other Nerve Transfers

The spinal accessory nerve was used before the hypoglossal nerve in nerve transposition techniques. Drobnik performed the first anastomosis of cranial nerves XI and VII in 1879.⁹ The phrenic nerve has been similarly used, but this technique causes paralysis of the diaphragm and induces undesirable involuntary inspiratory movements in the facial muscles.⁵⁴ The technique is now obsolete.

The neuromuscular pedicle technique described by Tucker transfers a branch of the ansa hypoglossi nerve and a small muscle bloc directly to paralyzed facial muscles. According to Tucker,⁵⁵ this procedure is valuable only for the perioral, depressor anguli oris, and zygomaticus muscles. The procedure is described as transferring innervated motor endplates to the denervated facial muscles without the usual delay period seen with free nerve grafts and nerve transfers. The technique allows limited reanimated strength because of the small number of axons present in the donor nerve. In addition, sound electrophysiologic confirmation that the technique produces reinnervation is somewhat lacking, despite a report by Anonsen and colleagues on this topic.⁵⁶ Until physiologic data are presented and confirmation by other surgeons is obtained, the procedure has potential but remains unproved.

Neurotropic Factors

With several growth factors known to promote neuronal survival, application and delivery of the these factors constitute an attractive therapy for nerve injury and surgical repair. The trophic effects of nerve growth factor (NGF), glial cell–derived neurotropic factor (GDNF), brain-derived neurotropic factor (BDNF), and insulin growth factors I and II all are under current investigation.⁵⁷ In ongoing rat experiments, embyronic stem cells are used to provide the trophic support factors to the host motor neurons in restitution of the neuromuscular junction.⁵⁸ These preliminary findings provide a model for motor unit restoration and a potential therapeutic intervention in the treatment of paralysis. However, these studies are limited to the rat model and require further basic and clinical investigation.

Masseter Transfer

Although masseter and temporalis muscle transfer techniques are effective, generally they should be used only if ipsilateral cable nerve grafting is not possible. For most patients with viable facial muscle endplates, a nerve transfer such as hypoglossal facial anastomosis also is preferable to muscle transposition. However, when the proximal facial nerve and the hypoglossal nerve are unavailable, or when facial muscles are surgically absent or atrophied, new contractile muscle must be delivered into the face. A large group of patients who fit into this category are those whose complete paralysis has lasted 2 years or more. These patients usually are characterized by severe denervation atrophy as documented by EMG. In these situations, muscle transfer is the preferred technique of reanimation.

Since the masseter was first used for facial reanimation in 1908, many modifications have been described.⁵⁹ Many authors, notably Conley and Baker, prefer the masseter muscle for rehabilitation of the lower face and midface.³⁰

The masseter transfer procedure generally is performed for rehabilitation of the sagging paralyzed oral commissure and the buccal-smile complex of muscles. The masseter’s upper origin from the zygomatic arch allows a predominantly posterosuperior pull on the lower midface. Transfer of the muscle can be accomplished externally through a rhytidectomy-parotidectomy incision, or intraorally using a mucosal incision in the gingivobuccal sulcus lateral to the ascending ramus of the mandible (Fig. 172-7). The masseter’s blood supply is medial and deep, and its nerve supply passes through the sigmoid notch between the condylar and the coronoid processes of the mandible to reach the upper deep surface of the muscle. The nerve supply then ramifies and courses distally and inferiorly, terminating near the periosteal attachments on the lateral aspect of the mandibular angle and body. In general, the external approach is preferred, insofar as the intraoral approach is associated with somewhat limited access, poorer muscle mobilization, and less vascular control.

Figure 172-7. Masseter transfer procedure. A to D, Schematic depiction of key surgical principles. A, Intraoral approach to masseter. The procedure is more difficult when performed in this manner; an external approach is preferred. B, Correct incisions in muscle and periosteum. Periosteum must be incorporated in the lower portion of the muscle flap to leave the tissue secure for suturing to the lip region. C and D, Entire muscle, rather than only anterior elements, is transposed, so that the masseteric nerve supply is transferred intact with muscle belly. E to G, Use of intraoral masseter transfer for correction of complete left peripheral facial paralysis in an elderly woman. E, Note severe brow ptosis, medial tarsorrhaphy, and severe redundancy of cheek, paranasal, and lateral lip tissues on the left. F, Intraoperative photograph showing intraoral masseter transfer. Large Kelly clamp is used to grasp the inferior portion of the masseter, which will be passed through the cheek tissues to a nasolabial fold incision (see A through D). G, Photograph taken after browlift procedure (tarsorrhaphy has been left for eye safety). Masseter transfer has successfully raised the corner of the mouth and the nasolabial fold. The patient declined further excision of the nasolabial fold for improved cosmesis.

A generous parotidectomy incision is made and extended inferiorly below the mastoid tip. The parotid gland and masseteric fascia are exposed. The posterior border of the muscle is freed from the mandible’s ascending ramus and at the lower border of the mandible. The nerve supply courses along the deep surface approximately midway between the anterior and the posterior borders of the muscle (see Fig. 172-7). It is advisable to preserve the deep fascial layer in dissecting the muscle free from the mandible. Mobilization of the periosteal attachments along the inferior border will provide secure tissue for anchoring sutures and will provide greater length of the transposed muscle.

Dissection is then carried forward to the nasolabial fold in the subcutaneous plane using large Metzenbaum or rhytidectomy scissors. The external incisions are made at or just medial to the nasolabial fold, the lateral oral commissure, and the vermilion cutaneous junction of the lower lip. Each of these incisions is connected to the cheek tunnel, allowing transfer of the masseter muscle. The muscle may be divided into three slips for attachment at these sites, or the entire periosteal end of the muscle may be used to suture the remnants of the orbicularis oris muscle from the lateral upper lip to the commissure and below. These muscle slips are sutured to the dermis and the orbicularis oris muscle using 3-0 clear nylon sutures. The best results depend on gross overcorrection with hyperelevation of the oral commisure, preservation of masseteric nerve supply, secure suture stabilization of the transposed muscle, supportive tape dressing to maintain overcorrection of the oral commissure, and nasogastric feedings to minimize masseteric movement.

Results from the masseteric procedure are quite gratifying and usually yield a high degree of facial symmetry. However, the masseter’s arc of rotation will not allow for rehabilitation around the orbit. For this reason, the temporalis transfer can be combined with masseter transfer, or the reanimation of the orbital region can be approached separately with such procedures as canthoplasty and gold weights.

Temporalis Transfer

Although Gillies⁶⁰ usually is given credit for introducing the temporalis procedure, Rubin^61,62 deserves much credit for refining the goals of the procedure and the operative technique in the United States. Like the masseter transfer, the temporalis transfer procedure requires an intact ipsilateral V₃ nerve. The nerve supply to the temporalis lies along the deep surface of the muscle. The blood supply comes from the deep temporal vessels from the external carotid artery. Thus, with total parotidectomy, extensive neck dissection, or infratemporal fossa dissection, the neurovascular supply may be tenuous at best. The upper origin of the temporalis muscle is fan-shaped and arises from the periosteum of the entire temporal fossa. The muscle belly converges on a short tendinous portion deep to the zygomatic arch and inserts on the coronoid process. The muscle is best exposed through an incision that passes above the ear, slightly posteriorly, and then in an anteromedial arc. This will expose the entire upper portion of the muscle (Fig. 172-8). A convenient aponeurotic dissection plane exists lateral to the temporalis fascia.

Figure 172-8. Temporalis muscle transposition. A, Dotted line illustrates the incision in the pericranium peripheral to the edge of the muscle. This results in strong periosteum to hold sutures in the transposed position. Nerve supply on deep side of muscle is not shown. B, Temporalis muscle divided into four slips. Note pericranium at the end of the slips sutured to the muscle to reinforce the suture site. Temporal fascia superficial to the muscle can be used in the same way. C, Transposed slips sutured to perioral muscles. Creativity and compulsivity are crucial during this portion of procedure. Overcorrection is mandatory. Sutures (A) must be placed in subdermis inferior to incision or in the submucosal portion of the wound deep to the orbicularis oris muscle. D, Completed procedure. Wide tunnel over the zygomatic arch precludes an unsightly bulge of muscle, which would otherwise be produced. Superior pull of temporalis muscle is somewhat preferred to posterolateral pull of masseter muscle (see Fig. 172-7).

In Rubin’s technique, the muscle is dissected free from the periosteum and attached to fascial strips, which are turned down inferiorly to reach the oral commissure and eyelid area. If these fascial strips are omitted, the transposed muscle’s length will be insufficient to reach the lateral oral commissure. More recently, Rubin⁶² refined his temporalis transfer technique by including a slip of masseter muscle that is sutured to the oral commissure and lower lip. The resulting masseteric pull improves results by providing more posterior and lateral vectors to the oral commissure.

We prefer to use the technique described by Baker and Conley,⁵⁰ who describe retaining the integrity of the upper muscle and its overlying fascia. The latter is dissected free and then turned inferiorly for suturing to the oral commissure.

A tunnel at least 1 to 1.5 inches wide must be made over the zygomatic arch to allow the muscle to turn inferiorly and eliminate an unsightly bulge. The attachment of the strip should be just medial to the nasolabial fold so that the natural crease is reproduced by the muscle pull. As with the masseteric procedure, a marked overcorrection is necessary on the operating table. A soft silicone block or a temporoparietal fascia flap may be used to fill the temporal hollow. A modification of this technique by Sherris⁶³ is performed by extending the transfer into the midregion of the upper and lower lips, to reduce stretching and thinning of the lips over time.

Several modifications of the temporalis transfer have been reported in attempts to avoid folding of the temporalis muscle over the zygomatic arch. Labbé and Huault⁶⁴ describe partial inferior mobilization of the temporalis muscle from the skull by elevation of the posterior and superior attachments of the muscle. The coronoid attachments of the muscle are detached, and the muscle is inferiorly mobilized toward the upper lip. The coronoid insertion of the inferiorly displaced muscle is secured to the perioral musculature.

Although the gold weight–canthoplasty technique often is preferred, the temporalis muscle can be used for orbital rehabilitation. The anterior third of the temporalis muscle is turned laterally into the eyelids (see Fig. 172-8). Subcutaneous tunnel dissection between the paralyzed orbicularis oculi and the eyelid skin allows passage of the fascial strips medially through both eyelids to the medial canthus, where they are sutured. As with any reconstructive procedure, adjustments and suture revisions should be checked carefully on the operating table to ensure proper eyelid contour.

With both masseter and temporalis transfer, facial muscle activation originates from the trigeminal nerve. Patients need to learn, through videotape, biofeedback, or similar methods, the proper way to contract the muscles by chewing or biting. Some younger patients may actually learn how to incorporate these movements into their own facial expressions (e.g., smiles, grimaces). However, patients should be told preoperatively that muscle transfer procedures will not allow any emotional or involuntary reanimation. When performed in the best hands, these techniques provide symmetry and tone in repose, with some learned and induced movements on attempted chewing.

Microneurovascular Muscle Transfer

Microneurovascular muscle transfer was popularized in the 1970s and has been combined with cross-face nerve grafting to restore some facial movement.⁶⁵ Because facial movements are highly complex and interrelated, enthusiasm for free muscle transfer was stimulated by the potential to use muscles that may provide isolated or independent segmental contractions, such as for superior elevation of the oral commissure. In patients with absence of facial musculature (such as those with congenital paralysis as in Möbius syndrome), microneurovascular muscle transfer seems to have strong potential.

A number of muscles and their respective nerve supply have been used for microneurovascular transfers. The most popular muscles include the gracilis, latissimus dorsi, and pectoralis minor muscle flaps.⁶⁶ Ideally, the proximal stump of the ipsilateral facial nerve is used, but this often is not possible. Traditionally, reinnervation has been accomplished in two stages, with a preliminary cross-face nerve graft performed approximately 1 year before muscle transfer. Neural ingrowth within the grafted nerve is monitored by recording progression of Tinel’s sign along the path of the graft. When reinnervation of the graft has occurred, microvascular muscle transfer is then performed. One-stage procedures using long neurovascular pedicles connected directly to the contralateral facial nerve have been described.^67–70 A recent comparison study found favorable outcomes with the one-stage reconstruction compared to the more traditional two-stage reconstruction.⁷⁰ Muscle preservation using implantable intramuscular stimulators is under investigation and may allow preservation of facial muscles while reinnervation occurs.⁷¹ This technique shows promise in management of peripheral nerve injuries, and exploratory studies on the facial nerve have been initiated. When facial nerve input is not available, alternative nerves can be used for input, including the masseteric branch of V₃, ansa hypoglossi, or the hypoglossal nerve.^66,72

Composite tissue allograft procedures have gained considerable interest over the last 10 years. Devauchelle⁷³ and Dubernard⁷⁴ and their colleagues detailed the preliminary functional improvements of the first human partial face transplant, with the return of light touch, heat and cold perception, and mouth closure. These functional milestones were obtained by 10 months postoperatively; a normal smile was observed at 18 months. As with all tissue transplantation, however, immunosuppression is an essential adjunct and not without consequence. After transplantation, the patient suffered two episodes of acute rejection, two infectious complications (type 1 herpes simplex virus infection and molluscum contagiosum), renal failure, moderate thrombotic microanigiopathy, and hemolytic anemia. These preliminary findings reveal a new dimension of reconstructive surgery while also underscoring the inherent benefits of native tissues in facial reconstruction.

Significant advances in microvascular techniques and one-stage microneurovascular facial rehabilitation have greatly improved the functional outcome for appropriately selected patients. These techniques are complex, requiring expertise in both microvascular techniques and facial reconstruction. In general, patients with absent distal facial nerve fibers or intact facial musculature who are motivated to attain dynamic function are potential candidates for these procedures.

Static Facial Sling

Procedures for Upper Third of the Face

Paralysis of the upper third of the face produces significant functional and cosmetic deformities. Brow ptosis may cause superior visual field deficits as well significant facial asymmetry. This asymmetry may be further accentuated after procedures to address the lower face. Browlift techniques to manage paralytic ptosis are the same as for a cosmetic browlift, the only significant technical difference being exercise of restraint to avoid further compromising eyelid closure. Direct, mid-forehead, endoscopic, and indirect browlifts are all effective. When not overdone, a browlift in conjunction with lid loading or lower eyelid tightening, or both, generally produces satisfactory cosmetic and functional results. Brow ptosis associated with normal aging may be accentuated unnaturally by a unilateral lift, and in older patients, improved results are seen when bilateral browlifts are performed.⁷⁹

Many patients with facial paralysis, particularly older persons, will express interest in additional adjunctive procedures in the periocular region. In patients with excessive redundant eyelid skin, conservative blepharoplasty can decrease superior visual field defects while cosmetically addressing brow ptosis and excessive tissue folds. Extreme caution is necessary in performing blepharoplasty in conjunction with browlift procedures. The risk of further impairing eye closure mandates a conservative approach. A maneuver to help assess the amount of skin to be safely removed consists of manually holding the paralyzed brow in the normal position with observation for impairment of eyelid closure. Similarly, it also is helpful to pinch together the excessive eyelid skin to be resected while holding the brow superiorly and observing its effect on eye closure.

Procedures for Middle Third of the Face

The middle third of the face is most commonly rehabilitated using reinnervation techniques, dynamic slings, or static slings. A number of additional procedures are available to fine-tune the results obtained with these procedures, and selection of the appropriate procedure(s) is determined by both the defect and the desires of the patient.

Nasal obstruction after facial paralysis can occur because of collapse of the alar sidewall from adjacent soft tissue ptosis and loss of intrinsic dilator naris tone. As described, a properly designed static sling may alleviate this problem. Alar batten grafting also may provide relief.

Midface soft tissue laxity and sagging, characteristic of the aging midface, is abnormally pronounced in the paralyzed face. In older patients with significant skin laxity, performing a facelift enhances the results of other treatments for midface deformity. Facelifts can be performed concurrently with other procedures, whether dynamic or static, and some patients will benefit from and prefer a bilateral facelift (Fig. 172-9).

Figure 172-9. Result with static rehabilitation techniques in a patient with right facial paralysis:. Preoperative (A) and postoperative (B) photographs. Patient underwent direct browlift, lateral transorbital canthopexy, alloderm facial sling repair, and gold weight placement.

Like the aging patient, the patient with facial paralysis acquires ptotic palpebral-malar and nasojugal sulci, producing a hollowed-out appearance to these areas. The lower eyelid fat may bulge, and the suborbicularis oculi fat (SOOF) and midface complex descend, producing a “double convexity” sign on lateral view. In the youthful patient, the suborbicularis oculi fat typically lies at the inferior orbital rim between the orbicularis oculi muscle and the periosteum. The midface lift repositions the SOOF and associated midface soft tissue superior to its preexisting position. The lift has become a popular technique in facial rejuvenation surgery, and also has shown utility in the treatment of facial paralysis. The midface lift can be performed through a transconjunctival incision, with a lateral canthotomy and inferior cantholysis. The periosteum is incised near the orbital rim and is elevated down to the inferior maxilla, where it is released. It also is important to release the attachment to the masseter muscle. Care is taken to avoid injury to the infraorbital nerve. The periosteum and overlying soft tissue are then elevated and secured superiorly to the deep temporal fascia.

Procedures for Lower Third of the Face

The functional deficits with paralysis of the lower face are dominated by manifestations of oral incompetence. Drooling, air escape with speech, and difficulty with mastication may be present. The asymmetry also produces a significant aesthetic deformity. This is due to the lack of a smile (loss of zygomaticus function) as well as the lack of depressor anguli oris (marginal mandibular nerve) function. These defects can be worsened by performance of static procedures on the middle third of the face, which can produce a troublesome gap in the region of the commissure from elevation of the upper lip.

Reinnervation, free tissue transfer, dynamic slings, and to some degree even static slings assist in repositioning the oral commissure to re-create a more symmetric smile. The asymmetry of depressor function, the so-called “marginal mandibular lip,” is more troublesome and difficult to improve. The most commonly used procedures are wedge resection and transposition of the posterior belly of the digastric muscle. The wedge resection, with or without supplemental cheiloplasty technique to improve symmetry and oral competence, has been described by Glenn and Goode.⁸⁰ A 2- to 2.5-cm full-thickness excision is performed 7 to 10 mm lateral to the commissure (Fig. 172-10).

Figure 172-10. Lip wedge excision and cheiloplasty. A, Outline of incisions for lip wedge excision. Excision tightens the lower lip and removes part of the denervated muscle. B, Appearance after lip resection. Note the intentional asymmetry of vermilion border during closure to evert the lower lip. C, Outline of incisions for cheiloplasty. D, Appearance of cheiloplasty after resection. Note lowering and outward rotation of the lower lip

(Adapted from Glenn MG, Goode RL. Surgical treatment of the “marginal mandibular lip” deformity. Otolaryngol Head Neck Surg. 1987;97:464-465.)

The most common dynamic technique for depressor dysfunction is the digastric transposition, first described by Conley and colleagues.⁸¹ The digastric tendon is identified using a submandibular approach. It is released from the hyoid bone, transected near the mastoid tip, transposed superiorly, and attached to the orbicularis oris through a separate vermilion border incision. Care is taken to preserve the mylohyoid nerve innervating the anterior belly of the digastric muscle. The anterior belly of the digastric muscle may not be available after extirpative cancer surgery, however.⁸²

Management of Synkinesis

Patients with incomplete recovery from facial paralysis typically are troubled by both weakness and hyperkinesis, or synkinesis. Synkinesis develops in many patients after facial paralysis of any cause. These uncoordinated mass movements may begin within weeks after paralysis as regeneration occurs. Although the classic description of synkinesis places the etiologic mechanism in aberrant axonal regeneration, it is now known that the sites of pathology are multiple. Synaptic stripping also occurs in the facial nucleus of the brainstem, and ephaptic (nonsynaptic) transmission among axons contributes to synkinesis. Future efforts to prevent or treat synkinesis will require addressing each of these areas. Synkinesis ranges in severity from a mild, barely noticeable tic to painful and debilitating mass facial movements.

Careful assessment of each region of the face is performed. It is esssential to identify the patient’s most troublesome symptoms and then determine which symptoms result from decreased function and which from synkinesis. The treatment plan can then be individualized to address the patient’s needs.

Traditionally, neurolysis has been a mainstay in the management of synkinesis, but it has been largely abandoned as safer and more conservative yet effective techniques have evolved. Such techniques include chemodenervation with botulinum A toxin injections and selective myectomies to target affected muscles.