A Repeatable CT-Based Protocol for Nasal Cavity Volumetry and Choanal Airway Classification in Pediatric Syndromic Craniosynostosis

Syndromic craniosynostosis (SC), such as Apert and Crouzon syndromes, causes midface hypoplasia that severely limits nasal cavity development. A computed tomography (CT)-based volumetric protocol for nasal cavity volumetry and choanal airway classification in pediatric SC patients, using landmark-based image segmentation software, is described and tested for intra-rater reproducibility. The protocol was applied to 10 SC patients (5 Apert, 5 Crouzon; 2-48 months; paired pre-/postoperative CT) and 10 reference children (60-168 months), not age-matched because CT is rarely indicated in healthy children. Intra-rater reliability was excellent (ICC = 0.987 and 0.909; 95% CI 0.934-0.997 and 0.689-0.976). Preoperative nasal cavity volume was significantly lower in SC patients (median 2,063.77 mm3; Q1-Q3 1,275.53-3,457.18) than in the reference group (median 35,502.13 mm3; Q1-Q3 28,811.21-39,167.15) (Mann-Whitney U = 0.000, Z = -3.780, p < 0.001). Nasal cavity volume increased between the paired CT scans in nine of ten patients (Wilcoxon Z = -2.701, p = 0.007; difference in medians +1,584.25 mm3; +76.8%), remaining at only 10.3% of the reference group median postoperatively. A weighted regression sensitivity analysis (log[Volume] vs log[Age], w = 1/Age; n = 10), accounting for the age disparity between cohorts, yielded an exploratory, model-based, non-normative estimate of 7,580 mm3 at the SC median age (8.5 months), extrapolated below the reference group age range; the SC median represented 27.2% of this estimate. Preoperative volume varied descriptively by choanal category (normal, stenosis, atresia) without tracking narrowing severity, possibly reflecting global hypoplasia; small subgroups precluded inferential testing. Nasal cavity volume is an anatomical measure and does not by itself indicate functional airway obstruction. The protocol offers a standardized workflow for larger, age-matched multicenter studies.