Anatomical consideration of the congenital nasal pyriform aperture stenosis: localized dysostosis without interorbital hypoplasia.

Congenital nasal pyriform aperture stenosis may be isolated or associated with other midline anomalies. The aim of the study was to describe the measurements and features of the interorbital structure and midface in congenital nasal pyriform aperture stenosis. The computed tomography scans of eight patients (two girls and six boys) were retrospectively reviewed. Several distances were obtained at the orbital and midface levels and compared with normative data. The average width of the pyriform aperture was 5.5 mm +/- 1.6, and there was overgrowth of the pyriform aperture rim (nasal process of the maxilla). No skeletal anomalies were present other than the congenital nasal pyriform aperture stenosis. It was associated with a single median maxillary central incisor in two cases. The anterior and lateral interorbital distances were normal (17.4 mm and 65.4 mm, respectively). The midface was not hypoplastic. There was no brain malformation. Congenital nasal pyriform aperture stenosis is a localized dysostosis of the pyriform aperture rim without interorbital or midface hypoplasia. It may be associated with a single median maxillary central incisor but cannot be viewed as a minor form of holoprosencephaly.