Anthropometric indices of facial features in Down’s syndrome subjects

Down’s Syndrome (DS) is the most frequent live-born autosomal aneuploidy in humans,and it is characterized by a distinctive craniofacial phenotype. Qualitative reports and quantitative investigations comparing subjects with DS to normal subjects found modifications in head size (overall reduction) and shape (brachycephaly with a flattened occipital bone). The faces of subjects with DS are narrower, less deep, and shorter than normal faces, with a global anomalous relationship between individual measurements. In the upper part of the face, the interorbital width is decreased, the palpebral fissures are reduced with slanted eyelids, and the forehead is prominent with a depressed nasal bridge. The middle part of the face (maxillary region) is hypoplasic, with reduced vertical, lateral, and anteroposterior dimensions. Overall, the nose is significantly smaller; its vertical and anteroposterior dimensions are reduced, but its horizontal dimensions are increased. In DS subjects the nose is shorter and less protruding, but with larger nostrils, a flatter angle of alar slope, and a more acute nasal tip angle. The mandible is small, with more acute gonial angles, and a more prominent position. Overall, there is a tendency toward a skeletal Class III pattern; the prominent forehead and mandible, associated with midfacial hypoplasia, may result in a concave sagittal plane facial profile. In the horizontal plane, the face is less prominent. Mouth width is reduced, with a smaller lower lip and a larger upper lip, with increased vermilion area and height. The lips are prominent, with reduced nasolabial, interlabial (soft tissues), and interincisal (teeth) angles. There are alterations in ear dimensions (global reduction), position and shape, with a significant larger asymmetry than in normal subjects. The ears are usually more prominent from head surface in DS subjects than in normal subjects. Persons with DS also possess several alterations in the hard- and soft-tissue structures of the oral cavity (teeth and dental arches, palate, tongue, oral mucosa), with reduced hard tissue palatal dimensions. In conclusion, the facial soft-tissue of subjects with Down’ syndrome can be successfully measured and monitored with noninvasive computerized anthropometry. A global, three-dimensional, quantitative assessment of the craniofacial characteristics may help in clinical diagnosis.