Smile reconstruction in adults with free muscle transfer innervated by the masseter motor nerve: effectiveness and cerebral adaptation.

BACKGROUND: This study assesses the ability of the masseter motor nerve-innervated microneurovascular muscle transfer to produce an effective smile in adult patients with bilateral and unilateral facial paralysis.
METHODS: The operation consists of a one-stage microneurovascular transfer of a portion of the gracilis muscle that is innervated with the masseter motor nerve. The muscle is inserted into the cheek and attached to the mouth to produce a smile. The outcomes assessed were the amount of movement of the transferred muscle; the aesthetic quality of the smile; the control, use, and spontaneity of the smile; and the functional effects on eating, drinking, and speech. The study included 27 patients aged 16 to 61 years who received 45 muscle transfers.
RESULTS: All 45 muscle transfers developed movement. The commissure movement averaged 13.0 +/- 4.7 mm at an angle of 47 +/- 15 degrees above the horizontal, and the mid upper lip movement averaged 8.3 +/- 3.0 mm at 42 +/- 17 degrees. Age did not affect the amount of movement. Patients older than 50 years had the same amount of movement as patients younger than 26 years (p = 0.605). Ninety-six percent of patients were satisfied with their smile.
CONCLUSIONS: A spontaneous smile, the ability to smile without thinking about it, occurred routinely in 59 percent and occasionally in 29 percent of patients. Eighty-five percent of patients learned to smile without biting. Age did not affect the degree of spontaneity of smiling or the patient's ability to smile without biting.