Approaches to grading facial nerve function

Systematic evaluation of facial nerve paralysis allows the clinician to determine objectively the severity of disability, record and communicate this information to colleagues, and evaluate response to therapy. An ideal grading system would be precisely calibrated-at once accurate, reliable, and conducive to use in both the clinic and the research laboratory. Developing such a system has proved difficult, however. The complexity of facial nerve anatomy allows tremendous variation in clinical presentation, and assessments of facial expression are inherently subjective in nature. Carefully defined parameters are therefore crucial in performing objective and quantitative analyses. This article reviews the clinical considerations involved in grading facial function and traces the evolution of current approaches. Emphasis is placed upon advances in computer-based facial nerve grading.