Infant Midnasal Stenosis: Reliability of Nasal Metrics

Abstract

Background and purpose: Midnasal stenosis is a poorly defined entity that may be a component of other conditions of nasal obstruction contributing to respiratory distress in infants. We sought to establish whether midnasal vault narrowing is a component of well-defined syndromes of nasal narrowing, such as bilateral choanal atresia and pyriform aperture stenosis, and to characterize the nasal anatomy of patients with syndromic craniosynostosis.

Materials and methods: A convenience sample of patients with pyriform aperture stenosis, bilateral choanal atresia, and Apert and Crouzon syndromes with maxillofacial CT scans was identified. Patients with Pierre Robin Sequence were used as controls. Nasal measurements were performed at the pyriform aperture, choana, and defined midnasal points on axial and coronal CT scans. Intra- and interrater reliability was quantified with the intraclass correlation coefficient. T tests with Bonferroni adjustment were used to assess differences from controls.

Results: The study included 50 patients: Eleven had pyriform aperture stenosis, 10 had Apert and Crouzon syndromes, 9 had choanal atresia, and 20 were controls. Measurements in patients with pyriform aperture stenosis and Apert and Crouzon syndromes were narrower than those of controls at all measured points (P < .001). Measurements in patients with choanal atresia were only narrow in the posterior half of the nose (P < .001). The intra- and interrater reliability of midnasal and pyriform measurements was very good to excellent (intraclass correlation coefficient > 0.87). The choanal measurement was good (intraclass correlation coefficient = 0.76-0.77).

Conclusions: Pyriform aperture stenosis, Apert and Crouzon patients were narrower at all measured points compared to controls. Bilateral choanal atresia patients were only narrower in the posterior half of the nose. More research is needed to evaluate the clinical implications of these radiographic findings.

Fig 1.

Measurement landmarks. Axial scans (A) were measured from bony lateral nasal wall to bony lateral nasal wall at the level of the pyriform aperture (PA), the choana, and at points 50% and 75% posteriorly between these two landmarks. An additional measurement on axial scan was obtained between the medial pterygoid plates. On coronal views, measurements were obtained from bony lateral nasal wall to bony lateral nasal wall at the pyriform aperture (not shown), just posterior to the lacrimal duct (B), and at the last molar (C).

Fig 2.

Mean nasal measurements. Measurements are given in millimeters. Asterisks indicate statistical significance (P < .001).

Fig 3.

Trends seen in the nasal cavity of pyriform aperture stenosis (A), syndromic craniosynostosis (B), and bilateral choanal atresia (C). Note the more global narrowing in patients with PAS and SC versus a more posterior narrowing in patients with BCA. Although the pyriform aperture in patients with BCA appears narrower than that in controls (Fig 1A) visually, this difference is not statistically significant.

Fig 4.

3D reconstructions of maxillofacial CT scans highlighting the pyriform aperture, in particular in patients with PAS (A), Apert syndrome (B), and PRS (C).