Bony interorbital distance (BIOD), head size, and level of the cribriform plate relative to orbital height: II. Possible pathogenesis of orbital hypertelorism.

This investigation was designed to test hypothesized pathogenetic mechanisms for orbital hypertelorism (OrH). Serial measurements of bony interorbital distance (BIOD), level of cribriform plate relative to orbital height (LOCP), and cranial width (CW) were made from postero-anterior cephalometric radiographs on two pathologic groups craniofacial clefts (FC) and premature craniofacial synostosis syndromes (PCS) compared with normal controls matched for age and sex. Both groups of malformations showed significantly larger mean values (P less than 0.01) for BIOD alone and when adjusted for CW. The LOCP relative to the orbital height was found to be positioned at a significantly lower level (P less than 0.01) than the norm in both groups. When the growth increments for BIOD were plotted to analyze rates of growth, individuals with FC showed increments similar to those seen for the normal. However, patients with Apert and Crouzon syndromes showed greater than normal increments for BIOD. In these cases, the LOCP remained at a relatively lower level in relation to orbital height. These findings support the hypothesis of a time-specific event during fetal development causing morphokinetic arrest in FC syndromes. In Apert and Crouzon, another mechanism continuing postnatally produces OrH.