Review of objective topographic facial nerve evaluation methods.

OBJECTIVE: This study is a critical review of the described methods for objective topographic evaluation of facial nerve function to identify areas of consensus and point to future research topics. SOURCES AND STUDY SELECTION: Original research articles on the subject were identified through the Medline database and reference cross-checking. DATA EXTRACTION AND SYNTHESIS: The articles were grouped according to the methodology used for topographic facial nerve evaluation. The advantages and shortcomings of each method are evaluated. The results obtained in each publication are presented in light of the method used. CONCLUSION: Measurements localized around the facial area under investigation show maximal displacement, whereas other sites exhibit much smaller displacements. Large displacements in these locations can be used to assess synkinesis and contractures. Large intersubject variability of the same measure is found. Both linear measurement and image-subtracting techniques hold promise. but until comparative studies are performed, the best method will remain controversial. Simple systems, accurately evaluating facial motor function, are yet to be developed.