Dynamic Reanimation for Facial Paralysis Treatment & Management
- Author: Steven M Parnes, MD; Chief Editor: Arlen D Meyers, MD, MBA more...
Before attempting any surgical repair, the surgeon must consider eye protection to prevent exposure keratitis, which could lead to blindness. The conservative measures that afford this protection include the use of moisture chambers, artificial tears, and ointments. Artificial eye closure techniques may be necessary. These techniques include taping or providing hermetically sealed chambers to protect the eye until a more effective procedure is used. Immediate surgical procedures can be considered to obtain eye closure regardless of prognosis and are discussed in the Surgical Procedures section.
Physical therapy (mechanical vs electrical) and steroids are likely beneficial. Most authors recommend these interventions, particularly in patients with Bell palsy or trauma. These ancillary therapies may improve function and seem to encourage the patients to participate actively in their care.
Many factors have to be considering when choosing a surgical procedure for a patient with facial paralysis. The algorithm below identifies some of the important factors in the decision-making process. Please note, proximal system signifies the proximal facial nerve and the motor nucleus in the brainstem, while distal system signifies the mimetic musculature and their associated motor endplates.
Facial plastics surgical procedures
Surgical therapies include facial plastic surgical techniques (rhytidectomy, blepharoplasty, brow lift), the prosthetic gold implant, canthopexy, and lid-tightening techniques. Although these therapies have similar indications as the transposition techniques, they can be used to supplement the transposition techniques, particularly to protect the eye during the facial recovery period. This is particularly true as an alternative to tarsorrhaphy, which is standard care in patients who have facial nerve preservation, but in whom recovery is not expected for several months to a year.
The gold implant is a very simple procedure that consistently offers satisfactory results. Initially, corneal protection is used. A small incision is made in the supratarsal crease or 8-10 mm cephalad to the upper lid margin. Using a sharp scissor, the tarsal plate is exposed directly.
Prefabricated gold implants ranging in size from 0.6-1.6 g are available. Most of the time, 1- to 1.2-g implants are sufficient and do not have to be sized preoperatively. With the tarsal plate exposed, 8-0 nylon sutures are used directly on top of the plate in order to secure the implant in place.
The wound is closed in 2 layers with 5-0 chromic sutures followed by 6-0 mild chromic sutures. This yields very good eye closure in most cases. If incomplete closure is anticipated, a mullerectomy may be performed just prior to placement of the gold weight. The Müller muscle that originates from the levator muscle provides tonic elevation to the lid and adheres tightly to the conjunctiva. The muscle can be incised easily through the conjunctiva with a sharp blade, after which the conjunctiva is closed with a 5-0 plain suture, as shown below.
Lateral tarsal strip
Patients with a great laxity of the lower eyelid and resulting ectropion may benefit from the lateral tarsal strip procedure. Performing a lateral canthotomy followed by an inferior cantholysis begins the relatively simple technique. The lateral portion of the lower eyelid is divided into musculocutaneous and tarsoconjunctival layers.
The tarsoconjunctival layer is grasped with a skin hook, and the overlying conjunctiva is abraded with a sharp blade to promote adherence and to avoid the formation of epithelial deposits. The resulting tarsal strip is sutured to the periosteum inside the lateral rim of the orbit. This is performed in order to shorten and elevate the lower eyelid. The resultant excess tissue of the musculocutaneous layer is removed, followed by wound closure using mild chromic sutures, as shown below.
An alternative technique is to elevate the lower lid with cartilage or scleral spacers. The spacer is placed between the lower lid retractor (capsulopalpebral fascia) and the inferior border of the tarsal plate. A subciliary or a transconjunctional approach can provide the surgical exposure to insert the spacer.
The rhytidectomy, blepharoplasty, and brow lift is not discussed in this article; however, certain principles of the brow lift are worth mentioning here. Brow ptosis due to unilateral facial paralysis is usually corrected with a direct brow lift; however, a supraciliary scar is needed and can be combined with a fixation device. Although endoscopic brow suspension provides an alternative technique, this requires special equipment and expertise and provides decreased durability and symmetry. Botulinum toxin injections provide a chemical brow lift without the need for surgery, yet several injections are needed. More recently, a minimally invasive brow suspension has been proposed for the treatment of brow ptosis secondary to unilateral facial paralysis. This procedure has shown promising results.
Facial nerve anastomosis
When the facial nerve is disrupted, either due to trauma, benign tumors, or an iatrogenic condition, re-approximating the nerve without tension is important. Rerouting the nerve within the temporal bone or releasing it in the area of the parotid gland, which would lengthen the nerve, may help re-approximate the nerve. The best time to perform this technique is within the first few days after the disruption, if feasible, because degeneration has not yet occurred, and the surgeon can stimulate the distal ends of the nerve for assistance in identification. If that is not feasible, to prevent scarring and fibrosis within the facial nerve defect, a repair should be completed within 30 days of injury.
Operating microscope or loupes are used for magnification while performing this repair. The nerve endings are freshened, and sutures of 8-0 nylon or a smaller size are applied, with 2 or 3 sutures applied to the epineurium. If the injury occurs in the temporal bone, sutures are unnecessary. Placing the ends of the nerve in contact with one another is sufficient to facilitate anastomosis.
In situations in which one of the main branches of the facial nerve is injured, the defect can be repaired in a similar fashion. If, however, the injury is medial to a line drawn down from the lateral canthus, spontaneous recovery often occurs without surgical intervention, as pictured below.
Facial nerve repair with grafts
Choice of donor nerve
Facial nerve repair with a nerve graft is necessary in patients who cannot achieve a direct anastomosis without tension. Most commonly, patients who undergo repair with grafts have undergone some type of tumor resection, such as a malignant parotid tumor, during which part of the nerve has been sacrificed.
The most commonly used graft is the great auricular nerve due to its proximity to the facial nerve, diameter match, and minimal donor morbidity. Drawing an imaginary line between the mastoid tip and the angle of the mandible aids in locating the great auricular nerve, as the nerve usually bisects this mark and runs perpendicular to it, lying on the superficial surface of the sternocleidomastoid muscle, as shown below. Cervical plexus nerves in this area can also be used for interposition grafts.
If the length of the defect is too long for the greater auricular nerve to bridge, or if multiple branches have been injured, the sural nerve is often harvested. The sural cutaneous nerve lies 1-2 cm lateral to the saphenous vein, medial and posterior to the lateral malleolus of the ankle, depicted in the image below. The shortcoming with using the sural nerve is that there is a significant diameter mismatch and that harvesting the nerve results in a significant scar. Endoscopic harvest of the sural nerve has been described and uses a small horizontal incision at the donor ankle.
Nerve transfer techniques have the advantage of consistently providing some restoration of function, although results are often unpredictable. The available techniques are the following: hypoglossal to facial, masseteric to facial, spinal accessory to facial, and cross-facial to facial. All techniques require the following conditions:
Irreversible facial nerve injury
Intact mimetic function
Intact motor endplate function
Intact proximal donor nerve
Intact distal facial nerve
Hypoglossal nerve transfer
The hypoglossal to facial technique is the most popular and commonly used technique. This technique is indicated most commonly in patients who lose their facial nerve during excision of acoustic neuromas. As a result of this method, many patients have synkinesis or mass movement with unappealing results, and, therefore, some authors advocate the use of this technique in only one of the major branches with adjunctive techniques used for other parts of the face. Biofeedback and the judicious use of botulinum toxin also are used to improve the results.
In performing the hypoglossal-to-facial nerve anastomosis, the 2 nerves frequently are long enough to preclude exposing the facial nerve within the temporal bone; instead, the nerve is transected as it exits the stylomastoid foramen. To identify the facial nerve, the surgeon proceeds with a typical parotidectomy approach.
A Blair or lazy-S incision is typically used, but an extended facelift incision can be substituted. Once the appropriate flaps are raised, the anterior border of the sternocleidomastoid muscle is identified and separated from the parotid gland. The cartilaginous auditory canal is skeletonized and further delineated to identify the pointer. With visualization and palpation, the facial nerve can be identified as it exits the stylomastoid foramen, usually several millimeters inferior to the tragal pointer. By palpating the mastoid and styloid process, the precise location of the facial nerve can be determined. The nerve is skeletonized up to the pes anserinus and, if necessary, to the 2 major branches to provide further mobility and lengthening.
The surgeon then directs attention to the hypoglossal nerve, usually found just inferior to the digastric muscle. The fibers of the digastric muscle run perpendicular to the sternocleidomastoid muscle and are located deep to the muscle. Once the nerve is identified and confirmed by nerve stimulation, it is further skeletonized distally towards the tongue for lengthening. The nerve then is transected as distal as possible and sutured directly to the main trunk or, if necessary, to a secondary division of the facial nerve. Direct anastomosis is completed as described above.
Some authors advocate splitting the hypoglossal nerve to reduce the degree of hemiglossal atrophy; nevertheless, no significant morbidity is associated with transecting the entire hypoglossal nerve. Occasionally, a patient may experience some subtle articulation problems and, therefore, must be warned of this possible sequela. Also, patients who undergo this procedure must participate in physical therapy to help activate the hypoglossal nerve during planned facial movement. Emotional activation of the mimetic muscles is otherwise impossible.
Masseteric nerve transposition
Transposition of the masseteric nerve has been described in reanimating the smile. The main advantages of using the masseteric nerve as a donor are as follows:
The position of the nerve, which often allows direct anastomosis without the need for grafting
The strong motor impulse, which ensures strong muscular activation
Fast reinnervation time, which is usually less than 3 months
The absence of morbidity related to its sectioning
Although some anecdotal reports suggest that cortical adaptation can lead to emotional activation of the effected side, there has been insufficient clinical evidence of the above.
Much like the hypoglossal nerve transfer, a parotid or modified facelift incision is made and flaps are elevated anteriorly until the anterior margin of the parotid gland and the zygomaticofacial trunk are seen. The facial nerve branches are dissected distally. Particular attention is paid to exposing and isolating the zygomatic and buccal branches, as these are the main neural inputs to the muscles responsible for smiling. The masseteric nerve is then isolated 4 cm anterior to the tragus, 1 cm inferior to the zygomatic branch, and 1.5 cm deep. The fibers of the masseter muscle are bluntly dissected until the nerve is isolated on its undersurface. The nerve is then distally dissected until adequate length is obtained, then finally transected and transposed superficially. End-to-end neurorrhaphy is then completed under microscopy, as previously described.
The cross-facial technique is the only nerve transfer technique that can predictably preserve emotional animation. Facial nerve branches from the healthy side are isolated and stimulated to confirm redundant function. The branch is sectioned distally, and the grafting nerve, often the sural, is anastomosed to the facial branch and tunneled to the contralateral side. Although direct anastomosis to the paralyzed facial nerve has been described, muscle atrophy often results secondary to the long reinnervation time. "Babysitter" procedures have been described that innervate the paralyzed side with the masseteric nerve, so, as the cross-facial graft regenerates, the paralyzed muscle receives motor input from the masseteric nerve, thereby preventing atrophy.
Multiple branches can be reanimated with separate sural nerve grafts, thereby preventing synkinesis and resulting in more symmetric facial movement.
Muscle transposition techniques
Muscle transposition techniques are used when the neural techniques are unsuitable. Reasons for this include the following:
An intact facial neuromuscular system is absent, such as in congenital facial paralysis (Möbius syndrome)
Longstanding facial nerve interruption (at least 3 y) results in loss of motor endplates
Other cranial nerves are sacrificed; therefore, a cross-over technique cannot be tolerated
The trigeminal nerve innervation to the temporalis and masseter muscle must remain intact. Early rehabilitation of the patient may be desirable if prolonged recovery with the neural technique is anticipated.
Temporalis muscle transposition
The temporalis is a fan-shaped muscle radiating from the narrow coronoid process of the mandible to the broad temporal fossa of the temporal bone. Because of its large area, the temporalis can be used for multiple areas of the face. Additional length can be obtained by using the fascia and suturing it to the edge of the muscle. Because eyelid procedures have proved to be superior, temporalis muscle transposition techniques are typically reserved for reanimation of the corner of the mouth.[2, 3, 4]
An incision is made in the preauricular crease and is extended into the superior temporal line, exposing the temporalis muscle and fascia, as seen below. The plane of dissection is above the superficial muscular aponeurotic system in order to avoid injuring the nerve.
After obtaining a wide exposure of the temporalis muscle, an incision is made down to the periosteum, elevating the muscle fibers. The middle one third of the muscle is elevated and folded on itself towards the corner of the mouth and a large tunnel is made over the zygomatic arch. This tunnel must be able to admit at least 2 fingerbreadths to prevent bunching up, causing a large mass in the face.
A second incision is made in the vermilion border at the oral commissure to expose the orbicularis muscle. As an alternative, this incision can be placed in the melolabial line to produce a symmetrical crease. The edge of the temporalis muscle then is attached to the orbicularis muscle with a permanent 2-0 chromic suture and is pulled up superiorly and laterally in an overcorrected position. In some patients, a temporoparietal fascial flap may be rotated in the temporalis fossa to fill the defect created by the harvested muscle.
The vermilion incision can be closed with 4-0 chromic sutures and running 6-0 nylon sutures. The preauricular incision may be closed with 3-0 chromic sutures and staples. The dressing must contain Steri-strips that will continue to pull up the corner of the mouth for overcorrection, as shown below.
As an alternative to the temporalis muscle transfer, temporalis tendon transfer has regained popularity. Compared with muscle transfer, the tendon transfer only necessitates a single facial incision in the nasolabial fold. Marking the incision preoperatively, while the patient is in an upright position, aids in camouflaging the scar. Once the subcutaneous layer is reached, the buccal fat pad is approached with blunt dissection. The Stensen duct and the fat pad are retracted superiorly until the coronoid process is identified. The coronoid is then sawed off of the mandible, taking care to preserve the tendon insertion. The coronoid/tendon complex is then grasped with an Allis clamp and stretched toward the modiolus. If a gap exists between the coronoid and the modiolus, a facia lata graft can be harvested to bridge the gap. A hold is drilled into the coronoid process to aid in suturing the complex to the modiolus or the fascia lata.
The benefits of using a tendon transfer as opposed to a muscle transposition are as follows:
Single skin incision
Prevents bulky appearance over the zygoma often seen in muscle transposition
Retained natural vector of pull
Masseter muscle transposition
The masseter muscle transposition technique is used when the temporalis muscle is unavailable due to either resection, such as temporal bone resection, or reconstruction. This technique may be a surgeon's preference because a large facial incision can be avoided in the intraoral application. The disadvantage of this technique is that less muscle is available to use, and the vector force of the muscle is in a more horizontal plane. This provides less superior angulation to the corner of the mouth.
In the intraoral approach, the masseter muscle is exposed by making a large incision in the gingival mucosa along the sulcus of the mandible, as depicted below. Creating a plane between the mucosa and the muscle exposes the muscle. The muscle then is freed immediately by raising it off the mandible with periosteal elevators. Once the masseter muscle is freed medially and laterally, it is detached from its insertion at the inferolateral edge of the mandible with curved right-angle scissors. Do not extend this vertical incision of the masseter muscle too far superiorly or posteriorly; otherwise, the nerve supply to the muscle could be jeopardized.
The anterior half is split again to fashion 2 slips of the masseter muscle. These slips ultimately are tunneled into the small external incisions made along the vermilion border. The external incisions, each measuring 1 cm, are placed in the lateral inferior lip half the distance between the melolabial line in the upper lip and the vermilion border.
Using a pair of sharp scissors, a lateral tunnel then is created in a plane just above the masseteric fascia and medial to the soft tissues of the face. Two clamps are passed through the lip incisions to the intraoral area. The slips of the masseter muscle are grasped and guided into place.
The muscles are fixed to the lips and the commissure, pulling the commissure upward and laterally for overcorrection. The lips and muscles are secured in place with permanent sutures directly into the deep dermal layers of the skin to avoid later relaxation. The wounds are closed with dressing that contains Steri-strips, which support the overcorrection.
The masseter muscle also may be exposed through an extraoral approach, usually through a rhytidectomy or Blair incision. This is used as an adjunct technique along with some other reanimation procedure.
Free muscle flaps
Indications for free muscle transfers are identical to those of the muscle transposition techniques. Examples of muscles that can be used for free muscle flaps include the gracilis, serratus anterior, latissimus dorsi, and extensor digitorum brevis. Additionally, the gracilis muscle has been used as a compound flap to include a skin paddle for repair of skin defects to help reanimate the eye with good result.
Use of the gracilis muscle to reanimate the face was first described in 1976. This is an ideal donor muscle because of the ease of dissection, lack of donor morbidity, adequate neurovascular pedicle, and muscle fiber length. The donor neurovascular pedicle is derived from the medial circumflex artery and the anterior branch of the obturator nerve, which provide 8 and 10 cm of length, respectively.
Typically, the donor muscle is innervated by a cross-facial graft and therefore is completed in 2 stages. First, the cross-facial graft is set in place and, 6-9 months later, the free flap is inset. The distal end of the cross-facial graft is sent for frozen pathologic analysis to confirm the presence of viable axons, and then the muscle is anchored to the periosteum of the zygoma and the modiolus. Neurovascular anastomosis is completed with care taken to anastomose the nerve as close to the donor muscle as possible. Movement can be expected in 6-9 months, with progressive motor strength in 2-3 years.
The masseteric nerve can serve as an alternative to cross-facial grafting, which simplifies the above procedure into a single stage. Studies comparing the 2 techniques, including a report by Snyder-Warwick et al on 91 pediatric patients, found that excursion with the masseteric nerve was greater than with the cross-facial nerve graft. However, the cross-facial technique was able to achieve spontaneity of movement, while the masseteric nerve transfer could not.[6, 7]
A one-stage procedure using the abductor hallucis muscle can also be performed. The results are good to excellent; however, only experienced surgeons with extensive knowledge of microvascular techniques should perform these technically difficult procedures.
Complications can occur with all of these techniques; however, they are rare. Always be on guard for either infection or hematomas. A most disconcerting complication would be lack of effect. Examples of lack of effect include no movement noted after a dynamic procedure or an undesirable result, such as continued eye exposure and problems with mastication. The outcome of the procedure is very technique dependent. If the nerve actually is transected, the prognosis is poor, and the best result one can expect when a neuro-technique is used is a grade 3 on the House-Brackmann scale. This is due to anticipated synkinesis and residual paresis. Muscle transpositions and other ancillary techniques are helpful in improving the aesthetics and, perhaps, can effect eye protection; however, these techniques cannot reproduce the voluntary symmetric and discreet facial movement.
Outcome and Prognosis
To evaluate facial nerve function, the House-Brackmann Scale is used. Classification includes the following:
- Mild dysfunction (slight weakness, normal symmetry at rest)
- Moderate dysfunction (obvious but not disfiguring weakness with synkinesis, normal symmetry at rest)
- Moderately severe dysfunction (obvious and disfiguring asymmetry, significant synkinesis)
- Severe dysfunction (barely perceptible motion)
- Total paralysis (no movement)
Keep in mind that this is a dynamic scale, and the patient's facial nerve status can change depending on the etiology.
Future and Controversies
When the patient presents with total facial paralysis, particularly when the nerve is disrupted entirely, total restoration with a natural spontaneous expression, full motor power, and perfect congruent movement may be impossible. When possible, dynamic repair is preferred over static techniques because the outcomes are better.
The techniques described above can provide marked cosmetic improvement and can restore function, particularly in the areas of eye protection, mastication, and articulation.
As these procedures evolve, patients will be afforded the possibility of leading normal lives without the stigma of facial disfigurement.
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