Assessment of functional outcomes of temporalis muscle transfers for patients with longstanding facial paralysis

Background. Usually, clinical evaluation of facial reanimation provides accurate information about contraction of the mimetic muscles and phonation but fails to identify smile recovery and to quantify the motility of the lower third of the face during a smile. The purpose of this study was to verify that, in longstanding facial palsy, the modified temporalis muscle transfer (MTMT) can result in the ability to smile, not only voluntarily with chewing, but also spontaneously with a sudden emotional stimulus, and to confirm that a symmetric smile can be obtained. Methods. Ten patients of the treated group (group T; 4 women and 6 men) were randomly selected from a population of 24 patients with longstanding facial palsy treated by MTMT. Five normal subjects of the control group (group C; 3 women and 2 men) were enrolled as the control population. Functional outcomes after transposed temporalis muscle were examined and measured through clinical assessment by using a scored smile symmetry grading system, video recording, and surface electromyography (sEMG). In addition, the voluntary smile test (VST) and the not-voluntary smile test (NVST) were performed to study voluntary and spontaneous smiling. Results. Subjects in the VST group (group T) were able to smile voluntarily and the expression was characterized by symmetry. In the NVST group, they were able to smile spontaneously and the symmetry of the smile was maintained for 8 subjects and only partially for 2 subjects. During both tests, the temporalis muscle of the treated side and the orbicularis oris muscle of the not-treated side were activated during smiling, indicating spontaneous activity of the transposed temporalis muscle with an emotional stimulus. For the control group, smiles during VST and NVST were symmetric and the temporalis muscles were not activated during smiling, whereas the orbicularis oris muscles were. Conclusion. Our study shows that the Morrison MTMT is able to restore the voluntary smile ability. Particularly, this technique allows for recovery of the spontaneous smile with symmetry. This assessment would seem to suggest that the transposed temporalis muscle might adapt from a chewing to a mimetic muscle.