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Facial nerve paralysis: smile reconstruction using the masseteric nerve.

An otherwise healthy 21-year-old woman presented to the outpatient clinic with advanced cholesteatoma of the skull base involving the petrous apex (figure 1). She subsequently underwent multiple skull base cholesteatoma excisions. During one of these surgeries, the facial nerve was injured at the internal auditory canal, resulting in right-sided facial paralysis. At 1 year postoperatively, the patient had not regained any facial movement (figure 2).

Electromyography demonstrated evidence of denervation of the right facial musculature and the presence of fibrillations. In order to restore the patients smile, we performed a selective coaptation of the ipsilateral masseteric nerve to the zygomatic branch of the facial nerve. At 6 months postoperatively, the patient regained midfacial movement and was able to generate a nearly symmetric oral commissure excursion with bite (figure 3).

Management and therapeutic options for patients with facial paralysis vary depending on the timing of the paralysis as well as physician and patient preferences. Reanimation methods range from static slings and nerve transfers to dynamic muscle techniques, such as regional temporalis and free gracilis transfer.

Treatment of patients with short-term facial paralysis (<1 year) focuses on preservation of native neuromuscular junctions. Based on the early work of Bateman (1) with peripheral limb nerves, it was determined that muscular denervation beyond 12 months results in decreased motor endplate density and less chance of successful reinnervation. This forms the rationale for early reinnervation strategies. (2)

Direct motor neurotization of the facial nerve was first described by Korte in 1903 through the use of the hypoglossal nerve with an end-to-end coaptation to the facial nerve. (3) This method of facial reinnervation became widely popular and was used for many decades. (4) Over the years, however, morbidity with regard to speech and swallow resulting from tongue denervation led to various modifications of hypoglossal-facial neurotization, including introduction of jump grafting and hemihypoglossal incision. (5,6) It was not until 1978 that Spira reported using the masseteric nerve to reinnervate the lower division of the facial nerve in 3 separate cases. (7)

Hontanilla and Marre compared the results of using the hypoglossal nerve (n = 25) and the masseteric nerve (n = 21), using commissural displacement and contraction velocity as outcomes measures. (8) Smile restoration was performed with selective coaptation to the zygomatic division of the facial nerve. The authors found no statistically significant difference between the two groups with regard to outcomes, but they did note that the masseteric nerve graft group experienced less donor-site morbidity and a faster time to recovery. They subsequently recommended masseteric nerve grafting as a superior method of smile reanimation.

One potential drawback to coaptation of the masseteric nerve to the main trunk of the facial nerve is increased risk of synkinesis. Selective reinnervation of the nearest branches of the facial nerve (zygomatic or buccal) improves specificity by directing neural input to the midfacial musculature alone. This has the dual advantage of providing a strong axonal donor volume for smile restoration while avoiding synkinetic reinnervation of adjacent musculature.

Daily facial exercises and physical therapy help convert a temporal smile driven by the biting movement to a spontaneous smile. The adjacent locations of the central motor nuclei of cranial nerves V and VII within the cerebral cortex greatly aid in this process. A large proportion of patients are able to achieve a spontaneous smile with a masseteric donor nerve. (9)

The masseteric nerve is an excellent donor nerve for cases of recent-onset facial paralysis given its close anatomic proximity to the zygomatic and buccal divisions of the facial nerve, straightforward harvest technique, strong axonal volume, low morbidity, and potential for spontaneity. Selective reinnervation of the midfacial branches (zygomatic or buccal) can result in strong smile recovery with minimal risk of facial synkinesis.

References

(1.) Bateman JE. Trauma to Nerves in Limbs. Philadelphia: W.B. Saunders; 1962.

(2.) Vlastou C. Facial paralysis. Microsurgery 2006;26(4):278-87.

(3.) Korte W. Ein Fall von Nervenpropfung des Nervus facialis auf den Nervus hypoglossus. Dtsch Med Wochenschr 1903;29:293-5.

(4.) Conley J, Baker DC. Hypoglossal-facial nerve anastomosis for reinnervation of the paralyzed face. Plast Reconstr Surg 1979;63 (1):63-72

(5.) May M, Sobol SM, Mester SJ. Hypoglossal-facial nerve interpositional-jump graft for facial reanimation without tongue atrophy. Otolaryngol Head Neck Surg 1991;104(6):818-25.

(6.) Arai H, Sato K, Yanai A. Hemihypoglossal-facial nerve anastomosis in treating unilateral facial palsy after acoustic neurinoma resection. J Neurosurg 1995;82(1):51-4.

(7.) Spira M. Anastomosis of masseteric nerve to lower division of facial nerve for correction of lower facial paralysis. Preliminary report. Plast Reconstr Surg 1978;61(3):330-4.

(8.) Hontanilla B, Marre D. Comparison of hemihypoglossal nerve versus masseteric nerve transpositions in the rehabilitation of short-term facial paralysis using the Facial Clima evaluating system. Plast Reconstr Surg 2012;130(5):662e-672e.

(9.) Manktelow RT, Tomat LR, Zuker RM, Chang M. Smile reconstruction in adults with free muscle transfer innervated by the masseter motor nerve: Effectiveness and cerebral adaptation. Plast Reconstr Surg 2006;118(4):885-99.

Moustafa Mourad, MD; Christopher Linstrom, MD; Grigoriy Mashkevich, MD

From the Department of Otolaryngology-Head and Neck Surgery, New York Eye and Ear Infirmary, New York City.
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Title Annotation:FACIAL PLASTIC SURGERY CLINIC
Author:Mourad, Moustafa; Linstrom, Christopher; Mashkevich, Grigoriy
Publication:Ear, Nose and Throat Journal
Article Type:Clinical report
Geographic Code:1USA
Date:Sep 1, 2015
Words:854
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