Facial reanimation with masseteric to facial nerve transfer: a three-dimensional longitudinal quantitative evaluation

Facial paralysis is a severe pathological condition, negatively affecting patients' quality of life. The altered tone and mobility of the mimetic musculature provoke both functional and morphological deficits. In the present study, we longitudinally measured facial movements in 14 patients (21–69 years) affected by unilateral facial paralysis not lasting longer than 23 months. The patients were analyzed before and after surgical masseteric to facial nerve neurorrhaphy. Examinations were performed at least 3 months after they had clinically started to regain facial mimicry. The displacement of selected facial landmarks was measured using an optoelectronic three-dimensional motion analyzer during: maximum smile without clenching (pre- and postsurgery), maximum smile by clenching on their posterior teeth (only postsurgery), and spontaneous smile (recorded during the vision of a funny video in both examinations). Before facial surgery, in all smiles facial landmarks moved more in the healthy than in the paretic side; after surgery, the differences decreased for both reduction of the healthy-side motion, and increment of the paretic-side motion (motion ratio before 52%, after 87%, p < 0.05, Students' t-test). The ratio between the paretic and healthy-side total motion (asymmetry) did not modify for maximum and spontaneous smiles, but significantly increased for the maximum smiles made with teeth clenching (asymmetry before 32%, after 11%, p < 0.001). Spontaneous smiles were recorded only in a subset of patients, but their execution was modified by surgery, with more symmetrical movements of the rehabilitated-side landmarks (asymmetry before 33%, after 10%), and reduced motion of the healthy-side ones (motion ratio before 51%, after 83%). In conclusion, the significant asymmetry in the magnitude of facial movements that characterized the analyzed patients before surgery reduced after surgery, at least in those facial areas interested by the masseteric to facial nerve reanimation.