Quantitative approach to identifying abnormal variation in the human face exemplified by a study of 278 individuals with five craniofacial syndromes

We have two objectives in this study: to demonstrate the utility of two sum mary anthropometric measures for quantifying craniofacial variation and to explore some of their potential uses by physicians and clinical morphologis ts in general. The Craniofacial Variability Index (CVI) is a summary anthro pometric measure of facial "harmony.'" The mean z-score, based on craniofac ial anthropometry, is a measure of overall facial size. Both add an objecti ve component to the assessment of individual facial variation and allow us to place the individual along a scale of continuous variation with predeter mined limits of "normality" based on a reference or control series. Our res ults suggest that these summary measures coincide well with clinical assess ments of abnormality in 278 individuals representing five distinct syndrome s (Brachmann-de Lange, Prader-Willi, Rubinstein-Taybi, Smith-Magenis, and S otos), each of which has an associated craniofacial component. Although cra niofacial variation is continuous and the normal and syndromic populations overlap to varying degrees, the syndromic cases can be characterized in a v ariety of ways by using CVI as a measure of facial harmony and Mean-Z as an indicator of overall facial size. Thus, these two-objective measures offer a novel and efficient means of assessing craniofacial variation, whether t hey are used as tools in the clinical evaluation of subjects or as a means of exploring the nature of craniofacial variation within or between syndrom es. (C) 2000 Wiley-Liss, Inc.