Lower Lip Sling Suspension with Bidirectional Fascia Grafts For Isolated Marginal Mandibular Nerve Palsy

Procedure: The procedure in this video demonstrates a lower lip sling suspension technique for isolated marginal mandibular nerve palsy using bidirectional fascia grafts. Introduction: Facial paralysis isolated to the marginal mandibular nerve distribution results in unilateral lower lip elevation and inversion, leading to frequent lip biting, oral incompetence, and smile asymmetry. Static sling suspension using bidirectional fascia grafts on the paralyzed side is a simple, non-invasive option that avoids many of the drawbacks of procedures that weaken the non-paralyzed side as well as the more invasive dynamic reanimation surgeries. Indications/Contraindications: The indication is facial paralysis isolated to the marginal mandibular branch distribution. The static lower lip sling technique may be indicated in patients with a history of chronic facial paralysis (>2 years) and in those who wish to avoid a potentially invasive dynamic reanimation intervention. It is contraindicated in patients with paralyzed lip elevator function or when paralyzed elevators are not concurrently reconstructed. Materials/Methods: A standard facial plastics surgical instrumentation kit that includes a tendon passer and a separate general soft tissue instrument set is required. A dorsolateral thigh fascia lata graft is harvested. Facial incisions are made externally within the nasolabial fold and at the inferior border of the mandible, as well as within the wet-dry junction of the lower lip vermilion.  Horizontal and vertical subcutaneous tunnels are formed within the paralyzed lower lip. Fascia grafts are placed through the tunnels in a "T" arrangement and secured to each other as well as to the underlying mimetic muscles. Tension is adjusted to adequately displace the central aspect of the lower lip to the midline horizontally and to correct lip inversion vertically. Results: This unique approach offers the following: 1) a static reconstructive technique that aims to correct the lower lip depression, inversion, and deviation to the non-paralyzed side, and 2) potential to achieve partial dynamic reanimation. The former is due to the arrangement of fascia grafts in a "T" formation whereby the vertically oriented fascia graft is anchored to the horizontally oriented graft, similar to a fulcrum. Partial dynamic restoration may be achieved by the continuity created between the unaffected orbicularis oris to the paralyzed modiolus labii via the horizontal fascia graft, which can create the illusion of depressor function. Conclusion: Correction of lower lip asymmetry in patients with isolated marginal mandibular nerve palsy is possible with lower lip sling suspension using bidirectional fascia grafts. This technique achieves static reanimation to improve symmetry, oral competence, and lip biting, and may result in partial dynamic reanimation in select patients.

Facial paralysis limited to the marginal mandibular nerve distribution can be bothersome and debilitating for patients. Possible etiologies are secondary to congenital, traumatic, iatrogenic, and malignant causes. Injury to the nerve results in an inability to depress and evert the lower lip, which results in a smile pattern characterized by unilateral lower lip elevation, inversion, and displacement to the non-paralyzed side. Patients may also complain of oral incompetence due to weakened lip closure and recurrent trauma as the lip gets caught between the maxillary and mandibular dentition with mastication. Treatment of the lower lip asymmetry involves either restoration of dynamic lip depressor function on the paralyzed side (i.e., depressor muscle neurotization with cross-facial nerve grafting and regional or free muscle transfer), weakening of the opposite functional side (i.e., contralateral chemodenervation with botulinum toxin, selective marginal mandibular neurectomy, depressor labialis inferioris myectomy or myotomy), or static techniques to the paralyzed side that restore symmetry at rest (i.e., fascial sling suspension, lower lip wedge resection, and orbicularis oris muscle plication). Static reanimation on the affected side is advantageous because it avoids bilateral loss of emotive expression and potential worsening of oral incompetence – as with contralateral muscle weakening modalities – and is less invasive than dynamic techniques with less conspicuous scars and no donor site deficits. Static lower lip sling suspension techniques may be indicated in patients with a history of chronic facial paralysis (> 2 years) with loss of mimetic facial musculature and degenerated neuromuscular end plates and in those who wish to avoid a potentially invasive or staged dynamic reanimation surgery. One such procedure is the lower lip sling suspension using bidirectional fascia grafts. This technique employs two fascia lata grafts anchored in a "T" fashion to create static downward pull on the paralyzed lower lip particularly during mouth opening. The tension and continuity created between the orbicularis oris on the non-paralyzed side with the modiolus and lip elevators on the paralyzed side is also thought to achieve incomplete dynamic reanimation of the lower lip depressors in select patients.

Consent: Using a standard form at our institution, consent was obtained from the patient for photography and video recording for the purposes of identification, patient care, and education. Instrumentation/Setup: A standard facial plastics surgical instrumentation kit that includes a tendon passer for the lip dissection portion, as well as a separately sterile general soft tissue instrument kit for the fascia lata harvest are required. Preoperative workup: Before performing the procedure, a thorough history and a complete head and neck exam is performed, paying particular attention to facial symmetry and function of each terminal facial nerve branch. This includes visualization of symmetry both at rest and with animation (i.e., smiling and lower lip depression). No imaging is needed preoperatively. Anatomy and landmarks: An understanding of the anatomy of the facial musculature involved in lip movement is critical for this procedure. The lip is a dynamic sphincter made up of the orbicularis oris and 10 radially arranged dilator muscles, whose fibers decussate roughly 1 cm lateral to the oral commissure, termed the modiolus labii. The 3 primary lip depressors are the depressor labii inferioris (DLI), the depressor anguli oris (DAO), and the platysma. The DLI, which originates inferior to the mental foramen from the lateral surface of the body of the mandible and inserts on the inferior aspect of the orbicularis oris, is most responsible for lower lip depression; it also contributes to lip eversion and lateral displacement. The DAO originates directly from the mandible, runs superficial to the DLI, and inserts onto the modiolus to depress the corner of the mouth. While the platysma plays only a minor role in lip depression, its resting tone contributes to the static position of the lower lip. The mimetic muscles of the lower lip are all invested by the superficial muscular aponeurotic system. Detailed steps to procedure: Preoperative markings should be performed while the patient is awake and upright to determine the ideal extent of static lip suspension. The patient is placed under general anesthesia with nasotracheal intubation and supine positioning, and the entire face and thigh are prepped with sterile solution. Incisions are re-marked, and local anesthesia is infiltrated subcutaneously along the incision sites. If an assistant is available, the lip dissection and fascia lata harvest can be started simultaneously. The fascia lata graft is harvested via a left dorsolateral thigh incision. A wide area of the fascia lata is exposed and markings are made along the fascia to delineate a graft width of approximately 2.5 cm and a length that equals half of the lower lip width (i.e., 7 cm in our patient). The fascia is harvested using curved Metzenbaum scissors, and the thigh donor site is closed primarily in layers with absorbable sutures. Once harvested, the fascia graft is divided into two equal strips with a width of 1 cm, representing the horizontal and vertical grafts. Next, three separate facial and lip incisions are made on the paralyzed side for placement of the fascia grafts: at the dry-wet junction of the left lower lip vermilion extending from the midline to oral commissure, the nasolabial fold (approximately 2 cm) over the modiolus, and the inferior border of the mandible (approximately 2 cm) just below the mental tubercle. A subcutaneous tunnel is then created between the vermilion and nasolabial incisions using sharp submucosal and subcutaneous dissection to establish a plane superficial to the mimetic muscles of the face extending from the midline vermilion to the modiolus; this creates a pocket for the horizontal fascia graft. A subcutaneous tunnel is similarly created between the vermilion and mandibular incisions to create a pocked for the vertical graft. A tendon passer is used to place the horizontal graft into position, ensuring that it is not twisted or folded on itself. A combination of polydioxone (PDS) long-lasting absorbable and Prolene permanent sutures are used to secure the medial aspect of the graft into place on the underlying orbicularis oris muscle near the midline. An appropriate amount of lateral tension is then placed on the horizontal graft to bring the center of the lower lip into the midline while the lateral aspect of the graft is sutured in a similar fashion onto the underlying modiolus. Additional sutures are placed along the mid-aspect of the horizontal graft to further secure the fascia graft to the underlying mimetic muscles. Redundant graft material is excised at both ends to minimize potential bulging. The vertical fascia graft is then placed into position through the vermilion and mandibular incisions using a tendon passer. The superior aspect of the vertical graft is looped around the horizontal graft and approximated together with multiple sutures. The vermilion and nasolabial incision sites are irrigated, hemostasis is achieved, and the incisions are closed. It is critical to close the vermilion and nasolabial incisions prior to anchoring the vertical fascia graft to the mandibular periosteum as this allows for optimal estimation of the inferior tension that needs to be applied to correct the lower lip asymmetry. Finally, the vertical graft is sutured to the underlying periosteum at the inferior aspect of the mandible with Prolene sutures. Vertical tension must be carefully adjusted before anchoring the fascia to the periosteum so that the lower lip is depressed sufficiently to visualize the occlusal aspect of the mandibular dentition. Redundant graft material is excised, and the mandibular incision is irrigated and closed. Finally, the patient is extubated after emergence from anesthesia.

Lower lip sling suspension using bidirectional fascia grafts is a simple, minimally invasive approach for isolated marginal mandibular nerve paralysis. The primary goal is to achieve greater lower lip symmetry as well as simultaneous movement of the lower lip and mandible with mouth opening. Unlike most static reconstructive techniques for the lower lip, this approach attempts to restore lower lip depression and eversion while bringing the displaced central aspect of the lower lip back to the midline.  Corrective lateral displacement occurs due to tension from the horizontal fascia graft resulting in restoration of the resting position of the center of the lower lip. Depression and eversion occur as a result of the "T" arrangement of the grafts (i.e., the vertical graft is anchored onto the horizontal graft, similar to a fulcrum). This maintains a constant distance between the inferior border of the mandible and lower lip during mouth opening, which results in minimization of lip trauma with mastication. Another unique characteristic of this technique is that it has the potential to achieve incomplete depressor reanimation. Active movement can theoretically be produced due to the continuity created between the orbicularis oris on the non-paralyzed side with the modiolus labii and elevator muscles on the paralyzed side via the union of the horizontal and vertical aspects of the fascia graft. Although this does not occur in all cases, it is most common in those with a "full denture" or all muscle-dominant smile.

The lower lip asymmetry in isolated marginal mandibular nerve paralysis can be successfully reconstructed with lower lip sling suspension using bidirectional fascia grafts. The use of two grafts anchored in a "T" arrangement achieves lower lip lateral displacement, depression, and eversion leading to improved symmetry, oral competence, and lip biting, and may result in incomplete dynamic lower lip reanimation in select patients.

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