Quantification of osseous facial dysmorphology in untreated unilateral coronal synostosis

Unilateral coronal synostosis results in dysmorphology of the midface in ad dition to well-characterized cranial and orbital deformities. Because most American infants with this problem have undergone cranio-orbital surgery wi thin their first year of life for the past 25 years, a paucity of data exis t regarding the natural history of untreated unilateral coronal synostosis. In an attempt to remedy this void, an international search was conducted t o identify computed tomography data sets of living individuals with untreat ed unilateral coronal synostosis; data were obtained from two European cent ers and one center in the United States. Results limited to the study of th e midface are presented here. Digital data from high-resolution head computed tomography scans of 11 livi ng, white individuals with untreated unilateral coronal synostosis were obt ained from three craniofacial centers (in Denmark, The Netherlands, and the United States). Image volumes were constructed from each scan using ANALYZ E biomedical imaging software. Fourteen pairs of three-dimensional distance s were calculated on the ipsilateral (the side of the synostosis) and the c ontralateral (the side opposite to the synostosis) hemifaces using 11 osseo us landmarks. The resulting measurements were expressed as a ratio of the i psilateral: contralateral sides. Descriptive statistics were derived for th e untreated unilateral coronal synostosis population and compared with anal ogous measurements performed on dried skulls. Age at computed tomography ra nged from 1.1 to 21.1 years (mean, 6.6 years; median, 4.1 years). Twelve of the 14 measured distances differed by greater than 5 percent on the ipsila teral side, and all but one of these measurements were decreased on the ips ilateral side when compared with contralateral values. The results of this study support the following conclusions: (1) There are discrete and measurable differences in the facial morphology between patien ts with untreated unilateral coronal synostosis and normal skulls. (2) Inte rcenter and international collaboration can provide a sufficient number of individuals with rare craniofacial anomalies to quantitatively determine gr oup characteristics. (3) Quantitative documentation of rare anomaly natural history is necessary for quantitative outcome assessment of treated patien ts.