Microsurgical strategies in 74 patients for restoration of dynamic depressor muscle mechanism: a neglected target in facial reanimation.

The facial depressor muscles are an essential component of a full denture smile. In addition, the depressor muscles are actively used to express other human emotions such as sadness, anger, depression, and sorrow. Despite advances in microsurgical techniques, it is surprising how little effort has been directed toward reanimation of the lower lip. This article presents innovative approaches used in 74 patients by the senior author since 1981 for the dynamic reanimation of depressor muscle function. The surgical techniques include transfer of the anterior belly of the digastric muscle (n 5 22) and transfer of the platysma muscle (n 5 26) as a pedicled muscle to the corner of the mouth. Other surgical interventions used are the mini-hypoglossal nerve transfer to the cervicofacial branch of the ipsilateral facial nerve (n 5 20), direct neurotization of the depressor muscles (n 5 6), and facialto-facial nerve transfer. The depressor muscle function was graded by four observers after reviewing standard preoperative and postoperative videotapes. Rating of the functional and aesthetic results was done according to the following arbitrary scale: excellent (2), good (1.5), moderate (1), fair (0.5), and poor (0). Sixty-nine percent of the patients who had a digastric muscle transfer displayed good to excellent results, and 24 percent showed moderate restoration of the depressor mechanism postoperatively. Eighty-three percent of patients who had platysma transfer to the lower lip demonstrated good to excellent outcome, and 11 percent had moderate depressor muscle function. In the hypoglossal nerve transfer group, 72 percent of the patients achieved good to excellent results and 15 percent had moderate function of the depressor mechanism. Of the patients who underwent direct neurotization, 34 percent showed good to excellent depressor muscle function postoperatively and 66 percent achieved fair depressor muscle function. Excellent outcome was noted in the patient with VII to VII nerve transfer. In conclusion, this article presents innovative approaches to restore dynamic depressor muscle function, which so far has been a neglected area of facial reanimation. (Plast. Reconstr. Surg. 105: 1917, 2000.) Human facial expression is vital for social interaction; humans exhibit their feelings through complex contractions of the facial musculature with or without verbal articulation. Facial paralysis leaves a person severely debilitated. A smile is perhaps one of the most important human facial expressions. Rubin1 analyzed in detail facial movements in relation to regional muscle forces and categorized smiles into three types: (1) “Mona Lisa” or zygomaticus major dominant smile, (2) “canine” or levator labii superioris dominant smile, and (3) “full denture” or all muscles dominant smile.1 Depressor muscle function is an important component of the full denture smile. In addition, the depressor muscles are actively used to express other human expressions such as sadness, anger, rage, depression, and sorrow. The drooping of the lower lip by the depressor labii inferioris, depressor angularis, and the mentalis can denote disappointment, sorrow, crying, and, in the extreme, rage and hate.1 The lower lip is animated through a complex interaction of orbicularis oris, depressor labii inferioris, depressor anguli oris, mentalis, and platysma muscles. Measurement of lower facial excursion has shown that the lower lip moves about 5.6 mm in the direction of depression.2 Damage to the mandibular branch of the facial nerve results in an inability to draw the lower lip downward and laterally or to evert the vermilion border. Thus, the resultant deformity is