Facial mimicry after conservative parotidectomy: a three-dimensional optoelectronic study

Facial nerve paralysis is one of several possible complications following conservative parotidectomy. To assess three-dimensional facial movements non-invasively in patients with unilateral facial palsy following parotidectomy for benign tumours, the three-dimensional coordinates of 21 soft-tissue facial landmarks were recorded in 32 patients (21 HB I, 5 HB II, 6 HB III-IV; 3 months post-surgery follow-up), and 40 control subjects, during the performance of facial movements (smile, 'surprise', eye closure, single eye closure). For all symmetric animations, control subjects had larger total mobility than patients; mobility progressively decreased in patients with larger clinical grades. For asymmetric eye closures, HB I patients and control subjects had similar total movements, while HB II patients had smaller movements, especially for the paretic side eye closure; smaller total movements were found in HB III-IV patients. The method allowed the quantitative detection of alterations in facial movements. Significant differences between patients and control subjects in the magnitude and asymmetry of movements were found.