The Deep Temporal Nerve Transfer : An Anatomical Feasibility Study and Implications for Upper Facial Reanimation

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. 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. 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. 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.

This article describes facial reanimation using the transfer of the trigeminal motor nerve branch of the masseter muscle (masseter nerve) to the facial nerve (masseter-to-facial nerve transfer).

Reinnervation of the facial musculature when there is loss of the proximal facial nerve poses a difficult clinical problem. Restoration of spontaneous mimetic motion is the aim and, to this end, the use of cross-facial nerve grafts has long been considered the reconstruction of choice. The nerve to masseter has been used very successfully for reinnervation of microvascular functioning muscle transfers for facial reanimation in established facial palsy but its use as a direct nerve transfer to the facial nerve to reinnervate 'viable' facial musculature has been scarce. Electron micrographic studies of axonal counts in the nerve to masseter and nerve to gracilis in a clinical series of seven patients undergoing surgery for facial nerve palsy were made. Based on these results, and previous success with the use of the nerve to masseter for reinnervation of free gracilis transfers, we report our experience with the transfer of the nerve to masseter for direct coaptation with the ipsilateral facial nerve to restore facial motion. Our axonal counts of the nerve to masseter have, on average, 1542+/-291.70 (SD) axons. Historical data have shown that the buccal branch of the facial nerve has 834+/-285 (SD) where the distal end of a cross-facial nerve graft has 100 to 200 axons. Our clinical use of the nerve to masseter as a direct nerve transfer in three patients based on these data has resulted in significant improvement in facial symmetry in repose (at a minimum of 1 year follow up), restoration of facial motion with occasional spontaneous activity and minimal synkinesis without any donor morbidity. The advantages of this technique include the ease of dissection, constant and reliable anatomy, powerful reinnervation of the facial muscles without donor site morbidity and the potential for return of spontaneous facial movement.