Computerized objective measurement of facial motion: normal variation and test-retest reliability.

OBJECTIVE: Objective quantitative measurements of facial motion for the assessment of outcomes in patients with facial paralysis have been elusive. This paper will reintroduce an objective computerized program for measurement of facial motion and present data on symmetry in healthy subjects and test-retest reliability in patients with facial paralysis. STUDY DESIGN: Cross-sectional analysis of archived images. SETTING: Tertiary referral center. PATIENTS: Good quality video-recordings of 38 healthy subjects and 30 facial paralysis subjects with a wide range of paralysis that had been tested twice were selected. INTERVENTION: Using image subtraction techniques of digital video recordings, computer-generated strength-duration curves of prescribed facial movements were automatically constructed. MAIN OUTCOME MEASURES: The areas under the curve for specific regions of each side of the face were compared as a proportion described as a percentage (left/right in healthy subjects, abnormal/normal side in paralysis) in which 100% would be perfect symmetry. RESULTS: Thirty-eight healthy subjects had the following left/right symmetry means (95% confidence interval): brow, 98.95 (93.94-103.95); eye, 99.18 (96.31-102.06); and mouth, 96.87 (93.10-100.63).Thirty patients with varying degrees of facial paralysis, tested twice, were evaluated to determine the degree of agreement between trials as measured by the intraclass correlation coefficient. The results showed the intraclass correlation coefficient (95% confidence interval) for brow was 0.972 (0.943-0.987), eye 0.950 (0.898-0.976), and mouth 0.951 (0.901-0.976). CONCLUSION: These results demonstrate no substantial side bias in healthy subjects and excellent test-retest reliability in patients with facial paralysis. This program may be made available for interested investigators upon request.