Local muscle transfers can be utilized to support the corner of the mouth and to re-establish some degree of active smiling. They are indicated for treating individuals whose facial paralysis is associated with damage or irreversible atrophy of the facial muscles. Segments of the chewing muscles on the side of the facial nerve paralysis can be rerouted and attached to the corner of the mouth.
Clenching ones teeth together activates these muscle segments elevating the corner of the mouth. The procedure works because the innervation to the chewing muscles is different from the muscles of facial expression. The temporalis muscle is often chosen because its vector or angle of pull produces an upwardly oriented smile. The masseter muscle transfer creates a more horizontal movement at the corner of the mouth. Utilizing the temporalis and masseter transfers in combination has the potential to produce a multidirectional smile of increased strength.
Muscle transfer procedures are often reserved for individuals whose age, general medical condition or previous surgeries prohibit more complex microsurgical procedures.
The combined temporalis-masseter muscle transfer performed through a face lift style incision that is created in front of the ear and extends into the hair. The central segment of the temporalis muscle is released on three sides leaving its base attached.
The dense leathery tissue encasing the muscle (fascia) is unfurled to extend its reach. The temporalis muscle segment is then tunneled beneath the skin of the cheek and secured to the upper lip. The temporal void created by borrowing the muscle segment can be filled by rearranging local tissues or utilizing a number of biological or synthetic implants.
Attention is now focused on the masseter muscle. The anterior one half of the masseter muscle is released from its attachment to the jaw and redirected to the corner of the mouth and then secured with sutures. Preservation of the posterior segment of the muscle prevents creation of a hollow depression at the angle of the jaw.
The period of hospitalization with the temporalis-masseter muscle transfer typically ranges from 24 to 72 hours. Patients are required to eat a soft diet for 4 weeks after surgery and avoid pressure on the operated side of the face.
The corner of the mouth is intentionally over suspended at the time of surgery. The operated side of the face gradually relaxes and better symmetry is usually present by the third postoperative week. Practice is essential to achieving a natural efficient smile. Over time, highly motivated individuals may even learn to smile without biting down.