67.1 Introduction

In patients with vestibular schwannoma (VS), facial paralysis can be caused by compression of the facial nerve, traction or transection of the nerve during tumor resection, or as a rare complication of stereotactic radiosurgery (SRS). Temporary and permanent facial paralysis imparts significant social and psychological consequences. Facial expression is an integral aspect of social integration and communication, leading healthy individuals to state that they would be willing to sacrifice eight years of life to correct unilateral facial paralysis.s. Literatur Free gracilis muscle transfer is one surgical approach to restore dynamic and spontaneous facial expression when salvaging native facial muscles is not possible or when the results of nerve transfers or cross-face nerve grafting have yielded suboptimal outcomes.

Gracilis free muscle transfer was first utilized by Pickrell et al in 1952 for rectal sphincter reconstruction.s. Literatur In 1976, Harii and colleagues utilized the gracilis muscle to restore facial animation, coapting the muscle to the deep temporal branch of the trigeminal nerve so that a smile was elicited upon biting.s. Literatur Reanimating the smile using a one-stage procedure has been performed, commonly utilizing the motor branch to the masseter to innervate the gracilis, and continues to have a role when cross-face nerve grafting is likely to yield poor outcomes. Mostly, this is true for older patients where reinnervation from the contralateral side is slower and less optimal,s. Literatur in patients with bilateral facial paralysis for whom cross-face nerve grafting is not possible, or in patients who may develop paralysis on the contralateral side due to neurofibromatosis type 2 or other causes.s. Literatur

In 1990, the two-stage cross-face nerve graft technique was pioneered by Thompson and Gustavson.s. Literatur A cross-face nerve graft utilizing the sural nerve is coapted to branches of the contralateral functional facial nerve. The sural nerve graft is tunneled under the skin of the upper lip, and buried in the subcutaneous tissue for 6 to 12 months followed by the second stage, where the gracilis muscle is transferred to restore smile function through upper lip elevation and lateral and upward movement of the oral commissure. Cross-face nerve grafting enables axonal fibers from the facial nerve to traverse the nerve graft to the nonfunctional side of the face. In the second stage of the procedure, a free muscle flap is harvested and inset into the paralyzed face and coapted to the previously placed cross-face nerve graft. The initial report of the cross-face nerve graft utilized an extensor digitorum free flap.s. Literatur Terzis described the pectoralis minor as a favorable muscle for facial reanimation,s. Literatur particularly in children, and later Harrison and Grobbelaar published a large series on the use of this muscle for reanimating the paralyzed face.s. Literatur In 1990, O’Brien and colleagues pioneered utilizing the gracilis free muscle transfer in the second stage of the procedure.s. Literatur Pairing a cross-face nerve graft procedure with gracilis free muscle transfer enables restoration of dynamic and spontaneous facial animation. Despite the advantages of the pectoralis minor, the gracilis free muscle transfer is more commonly used due to the ease of harvest and the ability to easily work in two teams.

In patients younger than 60 years with unilateral facial paralysis who are willing to undergo a two-stage procedure, the authors recommend cross-face nerve grafting followed by a gracilis muscle transfer in a second stage, as the spontaneity is clearly better than the one-stage procedure utilizing the branch to the masseter. More recently, we have been performing cross-face nerve grafting and, in the second stage, when the gracilis muscle transfer is performed, we transfer the branch to the masseter to the cross-face nerve graft in an end-to-side fashion to improve strength (see Chapter 66).s. Literatur

67.2 Advantages and Limitations of This Surgical Approach and Rationale for Use

The gracilis free flap has several distinct advantages when utilized for facial reanimation. The muscle has consistent anatomy with a reliably located neurovascular pedicle. Following some debulking, its size and volume are ideal for use in the face. Furthermore, two teams can work simultaneously to harvest the flap and prepare the recipient site, thus reducing operative time. Flap harvest does not create a functional deficit and the donor site is closed primarily leaving a discrete scar on the medial thigh.s. Literatur The proximal attachment of the fascia to the pubic bone can be harvested with the flap and utilized to anchor to the upper lip as described by Terzis and Karypidis.s. Literatur This provides thin tissue at the upper lip and solid tissue capable of suture retention (Fig. 67‑1 ). A skin island can be harvested with the flap and utilized to augment an external or intraoral soft-tissue defect.s. Literatur These positive aspects of gracilis transfer have made it most surgeons’ preference for free muscle transfer for facial reanimation.

67.3 Patient Evaluation and Selection

The timing and approach of facial reanimation intervention following VS resection is critical. There are three distinct clinical subgroups of patients presenting with facial palsy following VS resection: the first has completely reversible facial paralysis, with viable facial muscle fibers that will respond to reinnervation by ingrowing nerve axons. These patients have polyphasic action potentials on needle electromyogram (EMG), demonstrating active facial nerve regeneration and the presence of healthy facial muscles.s. Literatur If the facial nerve is anatomically disrupted in these patients, nerve repair, supplementary nerve grafting, or cross-face nerve grafting should be performed as soon as possible to minimize muscle denervation time. If the facial nerve is anatomically intact, the patient should first be observed for spontaneous recovery.

The timing of facial nerve reanimation is a controversial issue. The most common recommendation is to wait for 1 year for spontaneous recovery in cases of facial paralysis with an intact facial nerve. This decision is based on many reports that intraoperative and postoperative electrodiagnostic tests are not reliable enough to predict facial nerve functional status 1 year after VS surgery. However, one disadvantage of this standard approach is that a long waiting period delays nerve grafting and often yields inadequate functional outcomes, ultimately requiring further procedures to achieve the desired final outcome. Long delays lead to loss of motor endplate function of facial muscles.s. Literatur A different approach has been proffered which utilizes a predictive model introduced by Rivas and colleagues, based on an outcomes review of 281 patients. They recommended determining the intervention timeline based on the rate of recovery during the 6 months following VS resection.s. Literatur This model recommends planning for nerve repair at 6 months for patients with anatomically intact facial nerves and a House–Brackmann (HB) grade V or worse who show no improvement of at least one grade at 6 months. This model is also supported by Albathi et al, who advocated for intervention at 6 months should there be no clinical sign of reinnervation.s. Literatur Neither of these most recent studies advocating intervention at 6 months incorporate postoperative EMG findings, but rather are solely based on clinical recovery rates.

The second clinical subgroup of patients presents with completely irreversible damage to the facial muscles as a result of long-standing denervation. Many of these patients had intact facial nerves following resection, with the expectation of spontaneous muscle function recovery. Patients in this subgroup likely have dysfunctional facial muscle contractile units, atrophic muscle fibers, and loss of muscle satellite cells, and thus would be unresponsive to reinnervation attempts.s. Literatur These patients show no EMG potentials, yielding what is commonly called a “silent EMG.” This subgroup is best treated with a free-muscle transfer or a regional muscle transfer to replace the nonfunctional muscles. In this subgroup, the timing of intervention depends on convenience to the patients. There is no true urgency to performing the surgery, as the denervation of the facial muscles is permanent. This subgroup is the focus of this chapter. Smile restoration with a gracilis muscle transfer,s. Literatur in a two-stage procedure, innervated by a cross-face nerve graft, is our preferred method of reconstruction. We also perform, in select patients, a gracilis free muscle transfer in one stage innervated by the branch to the masseter.

The third clinical subgroup of patients are those who present with partial recovery of facial nerve function, which leads to a more complex decision regarding intervention. These patients have muscle function but weakness that can be addressed through additional innervation via nerve grafting or through functional muscle transfer. Additional reinnervation procedures, through supplementary nerve grafting or cross-face nerve grafting, may be considered in this subgroup of patients who present with poorly defined melolabial folds, droopy oral commissure and eyelids, but some evidence of muscle movement upon attempted facial expression.s. Literatur For nerve transfers to be considered, fibrillations on EMG should be present. Nevertheless, even in patients with the above-mentioned criteria, it is not clear which patients will do well enough with nerve transfers that they will not require further reconstruction. Muscle transfer, alternatively, should be performed when patients present with a stable result for over 1 year and in patients without evidence of fibrillations on EMG. Rarely, muscle transfer could also be considered in patients with severe spastic muscle function or synkinesis. These patients have hypercontracted levator and zygomatic muscles, manifesting as exaggerated melolabial folds, and no excursion upon attempted smile.s. Literatur

Functional muscle transfer, including gracilis free muscle transfer, is indicated in patients who present with complete irreversible facial paralysis from long-term muscle denervation and in patients with partial recovery of facial nerve function, for whom nerve grafting is not expected to yield improvement.

67.4 Relevant Anatomy Specific to Approach

Gracilis, derived from the Latin word gracile, meaning slender, is a thin, strap-like muscle located most superficially in the thigh adductor group. The muscle’s origin is at the pubic symphysis, medial and posterior to the adductor longus muscle tendon. The adductor longus tendon can be palpated in the medial thigh in front of the pubis when the patient is in the frog leg position. The gracilis has a wide origin, from the inferior ramus of the pubis to the lower symphysis. It lies posterior to the sartorius and anterior to the semitendinosus in its lower half. Its insertion onto the medial tibial condyle is immediately posterior to the sartorius muscle. The gracilis muscle size is dependent on the size and build of the patient and averages 30 cm long, 5 to 8 cm wide proximally (3–4 cm in children), and 3 cm thick.s. Literatur The muscle tapers superiorly to inferiorly.

The dominant vascular pedicle of the gracilis muscle flap is the branch of the medial femoral circumflex artery or a direct branch from the profunda femoris artery.s. Literatur ^,​ s. Literatur This dominant pedicle enters the medial aspect of the muscle between the adductor longus and adductor magnus at approximately 10 cm inferior to the pubic tubercle. The gracilis muscle also has a minor pedicle in the distal half of the muscle, which is a branch from the superficial femoral artery (Fig. 67‑2 ), and in 10% of cases a branch from the descending genicular artery also supplies this flap.s. Literatur The dominant pedicle has two vena comitantes that are located alongside the artery, draining into the profunda femoris vein either separately or by converging into a common vein.s. Literatur

The single motor nerve of the gracilis is the anterior branch of the obturator nerve. This enters the gracilis on the medial surface 1 to 2 cm superior to the vascular pedicle (6–7 cm from the pubic tubercle). The nerve has an average of three fascicles, and often divides into two branches that supply the superior and inferior muscle.s. Literatur The bifurcation of the nerve is located, on average, 2 cm proximal to the vascular bifurcation. The superior branch is usually the larger branch, and runs first transverse then inferior and posterior. The inferior branch runs parallel to the anterior muscle border, with a mean distance of 2 cm from this edge.s. Literatur This anatomical bifurcation has been utilized to divide the gracilis into two separate motor units upon free muscle transfer.s. Literatur

The gracilis muscle functions to flex the knee and adduct the thigh. However, there is no functional deficit noticed clinically following removal of the muscle. The scar is usually around 10 to 15 cm and inconspicuously placed on the medial aspect of the thigh. By performing meticulous reapproximation of the superficial fascia of the thigh as well and by taking breaks from retracting the skin during the harvest, excellent scar healing can be expected.