Structural and functional stenosis of the upper airway in Crouzon syndrome patients: A computational fluid dynamics analysis.

Objectives: This study aimed to simulate the aerodynamics and to identify the spatial correlation between anatomical and functional stenoses in Crouzon syndrome patients.

Methods: Six patients of Crouzon syndrome were included. Computational fluid dynamics (CFD) was utilized to simulate airflow dynamics, and characteristics, including the velocity, pressure intensity, wall shear stress, airflow resistance and streamline, were extracted for quantitative analysis both in overall and regionally. Structural stenosis was defined at the minimum cross-sectional area, while functional stenosis was identified at the point of maximum airflow velocity. The spatial distances between the Frankfurt plane and structural/functional stenosis were calculated and compared.

Results: Structural stenosis occurred in the palatopharynx, while the highest inspiratory resistance and peak airflow velocity during expiration identified the glossopharynx as the functional stenosis site. A steep increase in negative pressure and a significant increase in wall shear stress could be observed surrounding the functional stenosis. The intensity and diffusion range of wall shear stress are positively correlated with age. Notably, the functional stenosis was consistently 5 mm below the structural stenosis (P < 0.05).

Conclusions: CFD effectively visualized both overall and regional aerodynamics of Crouzon syndrome, providing a novel method for functional airway evaluation. The spatial distributions of structural and functional stenoses did not strictly correspond; the structural stenosis was located on the palatopharynx, while the functional stenosis was on the glossopharynx. The wall shear stress worsens pathologically with age, aggravating functional stenosis to structural stenosis. Therefore, functional stenosis should also be addressed in airway management to ensure therapeutic effectiveness.