Several studies have examined composites of quantitative facial measurements. Such studies are generally of 2 types, those reporting on differences in size (dimensions or facial measurement lengths) and those analyzing shape using 3-dimensional (3D) renderings and geometric morphometrics.
Regarding size of individual facial dimensions, various studies (which typically have used manual or digital calipers to measure distances between specific landmarks, such as the glabella, tragus, stomion, and gnathion) have reported that patients with schizophrenia have abnormal head circumference, greater skull base width, greater nasion-stomion height, smaller biocular diameter, greater interpupillary distance, smaller nasal width, smaller width of the mouth, and smaller cheilion-menton distance.8,9,15,17,18
McGrath et al19
evaluated facial measurements of 180 case-control pairs, matched by age and gender. They found that patients had greater skull base width, greater tragus-subnasale depth, and greater tragus-gnathion depth than controls. In terms of facial heights, patients had smaller glabella-subnasale, glabella-stomion, and glabella-gnathion measures. Lane et al9
assessed facial measurements in 174 patients and 80 matched controls, and patients were found to exhibit overall narrowing and elongation of the mid- and lower face. Compton et al86
found that female patients had a greater midfacial depth (tragus-subnasale) compared with female controls, whereas male patients had lesser upper facial (trichion-glabella) and lower facial (subnasale-gnathion) heights compared with male controls.
Hennessy et al87
compared craniofacial shape (rather than facial measurement lengths) by applying geometric morphometrics to 3D reconstructions88
derived from the data of Lane et al.9
Facial shapes were predictive of both gender and diagnostic group status, and there was a strong gender by diagnosis interaction. For both genders, patients exhibited a wider skull base, shortened upper midfacial height, and lengthened lower midfacial height compared with controls. Sex-specific asymmetries were noted; eg, male controls exhibited more directional asymmetry than male patients, whereas female patients exhibited more directional asymmetry than female controls. This group also is using 3D laser surface imaging and geometric morphometrics of craniofacial shape, as described in a recent publication.89
This methodology revealed that compared with controls, patients evidenced an overall widening and vertical shortening of the face, narrowing and reduction of the mid- and lower face, and widening of the mandible. Buckley et al12
evaluated 65 anthropometrically derived landmarks using 3D facial images in 14 patients with schizophrenia and 11 controls and found an overall elongation of the face.
Studies involving facial measurements may be of particular interest given that the face and some regions of the brain develop in concert from the same ectodermal tissue.9,56,60,90
Other neurodevelopmental disorders, such as VCFS, Down syndrome, and fetal alcohol syndrome also involve malformations of facial features concurrent with brain development, but they are much less subtle than those observed in schizophrenia.91
For example, the characteristic facial features of VCFS include elongation of the face, prominent nose with narrow alar base and squared nasal root, retruded mandible with chin deficiency, and microcephaly.91
Ongoing research on the genetics of craniofacial development may shed light on the underlying genetic links between MPAs and schizophrenia; eg, human cranioskeletal development has been linked to fibroblast growth factor receptor (FGFR) genes,92
and therefore, allelic variations underlying FGFR genotypes represent potentially relevant loci, among many others.