Pediatric Facial Reanimation Using a Functional Gracilis Muscle Transfer
Pediatric Facial Reanimation Using a Functional Gracilis Muscle Transfer
Brad M. Gandolfi
Jeffrey R. Marcus
Michael R. Zenn
The facial nerve exits the stylomastoid foramen and enters the posterior parotid gland, dividing the gland into superficial and deep components.
The facial nerve divides into two main branches within the parotid gland: the frontozygomatic and the cervicofacial trunks. These branches further divide before exiting the parotid gland.
Five branches are classically described as exiting the parotid (frontal/temporal, zygomatic, buccal, marginal mandibular, and cervical). However, the branching pattern for each individual is unique, and many of the abovenamed nerves exist in multiples.3
The average number of branches exiting the parotid is 7 (FIG 1
Buccal and zygomatic branches begin to arborize and cross within and beyond the parotid, resulting in redundancy in the functional territory of these buccal-zygomatic branches.3,4
It is difficult to separate the activity of these branches as purely buccal or zygomatic because stimulation often results in a mixed response. Due to mixed nerve function, sacrifice of one nerve for end-to-end coaptation does not result in functional loss.
The target for reanimation of smile is a buccal or zygomatic branch, selected based on targeted muscle stimulation. Stimulation should ideally identify a branch that produces vertical and horizontal movement of the commissure and upper lip consistent with the patient’s natural smile, with minimal extraneous movement.
Zuker point describes a relatively consistent buccal-zygomatic branch that meets the needs for facial reanimation.4
It is found at the center of a line drawn from the oral commissure to the helical root.
Nerve to the Masseter
The nerve to the masseter arises as a branch of the trigeminal nerve (V3), passing posterior to the temporalis muscle en route to the deep surface of the masseter (FIG 2
FIG 1 • The anatomy of the facial nerve.
The nerve is reliably found 3 cm anterior to the tragus, 1 cm inferior to the zygomatic arch, and 1.5 mm deep to the SMAS.5,6
The gracilis muscle originates along the body and inferior ramus of the pubis, just below the pubic tubercle.7
It runs along the medial thigh and inserts into the medial tibial condyle, immediately deep to the sartorius muscle (FIG 3A
The gracilis lies immediately posterior to the much larger adductor longus, which is easily palpated on most patients.
FIG 2 • The nerve to the masseter is found by splitting the temporalis and masseter muscles, under the zygoma. (Reprinted from Borschel GH, et al. The motor nerve to the masseter muscle: an anatomic and histomorphometric study to facilitate its use in facial reanimation. J Plast Reconstr Aesthet Surg. 2012;65(3):363-366, with permission from Elsevier.)
FIG 3 • Gracilis muscle with the pedicle ex vivo. Note the length of obturator nerve (left side of image).
The muscle is supplied by the medial circumflex femoral artery, a branch of the deep femoral artery. The pedicle runs underneath the adductor longus en route to the gracilis.
The artery enters the muscle 5 to 12 cm inferior to the pubic tubercle. It is generally 1 to 2 mm in diameter and may have two or three branches at the level of the muscle (FIG 3B
The artery is accompanied by two vena comitantes.
The artery and the accompanying vein are 5 to 6 cm when dissected to the deep femoral vessels.
The muscle has a minor pedicle at its distal aspect that is not appropriate for microvascular transfer.
A branch of the obturator nerve supplies the gracilis muscle. It splits from the anterior branch of the obturator behind the pectineus and runs with the branch to the adductor longus. The nerve joins the muscle from its lateral aspect, generally at a 45-degree angle to the vascular pedicle. The nerve pierces the muscle and arborizes within it.
The gracilis muscle has a tendinous origin from the pubis, which can be included with the flap. The muscle can be 3 to 4 cm wide at the level of the pedicle, requiring some muscle splitting to avoid bulky reconstructions.
PATIENT HISTORY AND PHYSICAL FINDINGS
The most important initial distinction in the preoperative evaluation of pediatric patients with facial paralysis is whether the condition is congenital or acquired. For those with congenital paralysis, the condition may have been apparent at birth or recognized shortly thereafter (FIG 4
). For those with acquired paralysis, the circumstances and details of the inciting event(s) should be carefully noted. The timing of functional loss is the most critical detail.
FIG 4 • Photo taken shortly after birth, depicting a left-side congenital facial nerve paralysis.
Functional impairment, including the following, should be noted:
Excessive tearing and/or dryness requiring frequent use of lubricating drops
Inability to close the eyes fully at night requiring the use of viscous eye lubricant
Oral incompetence (drooling) or speech articulation difficulties
Presence and extent of dental caries, which are predisposed on the affected side
Any prior treatments should be noted as well as any progression or improvement in the condition.
Prior medical, neurologic, or surgical history that would potentially be associated with the condition or the potential surgical treatments that may be considered should be noted.
A focused examination of the function of the facial nerve is performed, taking care to document both static and dynamic deficiencies. The motor territory associated with each branch should be graded relative to the completeness of the paralysis. We prefer the Toronto Facial Grading System to track our progress.2
If etiology of paralysis is unclear, level of injury can be elucidated using the Schirmer test, stapedius reflex test, salivary flow test, and taste examination.
Photographs and video of the following should be included in the initial evaluation:
The ability to close the eyelids such that the cornea is protected must be assessed. Those who are unable to close fully and require viscous lubrication should be identified early and treated with priority ahead of smile reanimation.
Amblyopia may be seen in as many as 50% of patients with facial nerve palsies, and thus a thorough ophthalmologic examination is warranted.1
The eye examination should also assess for corneal pathology due to exposure.
The presence of the facial artery should be confirmed. It is palpable in most patients regardless of age.
The temporalis and masseter muscles should be palpated, particularly if considering the motor nerve to the masseter as a potential donor nerve. Normal strength and mass should be present.
Syndromic associations can be seen in congenital facial paralysis and can include hemifacial microsomia, Mobius syndrome, and Poland syndrome among others. Therefore, the examination should include an evaluation of the facial bones (orbits, zygoma, maxilla, and mandible), soft tissues, and ear. Mobius syndrome includes the presence of a cranial nerve VI deficit and can also be associated with a Poland deformity and congenital hand anomalies. Thus, cranial nerves VI, VII, IX, X, and XII should be evaluated for disability.
For candidate patients with long-standing or congenital paralysis, a radiographic workup is generally unnecessary. For those with associated congenital anomalies, such as craniofacial microsomia, craniofacial CT may be valuable for the comprehensive workup.
In cases of recently acquired facial paralysis, an EMG may be useful to establish a baseline, demonstrate improvement, or predict recovery. In congenital or long-standing cases, EMG does not provide information that contributes to treatment planning and therefore is not necessary.
Nonoperative management plays an important role in partial paralysis. A facial rehabilitation specialist may be able to obtain a more symmetric smile by strengthening weaker muscles and de-emphasizing stronger, more active muscles. Such treatment requires participation of the child.
In certain instances of incomplete paralysis, neurotoxins can be used on the unaffected side as an adjunct to obtain symmetry.
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