CT comparison of the nasal airway anterior and posterior to the piriform aperture in patients with and without nasal obstruction

Background Nasal airway stenosis may lie anterior and/or posterior to the piriform aperture. We intended to compare the nasal airway anterior and posterior to the piriform aperture in patients with and without nasal obstruction. Methods Segmented computed tomography cross-sectional areas of the nasal airway anterior (CT-CSAant) and posterior to the piriform aperture (at the level of the head of the inferior turbinate; CT-CSApost) were compared between patients with nasal obstruction (cases) and trauma controls. CT-CSA were approximately perpendicular to the direction of the nasal airflow. Anterior to the piriform aperture, they were tilted about 30o, 60o and 90o to the nasal floor. Posterior to the piriform aperture, they were tilted about 50o, 80o and 100o to the nasal floor. In cases, we examined the Pearson's correlation of active anterior rhinomanometry with CT-CSAant and CT-CSApost. Results Narrow and bilateral CT-CSApost were similarly large between 56 cases and 56 controls (all p > 0.2). On the contrary, narrow and bilateral CT-CSAant were significantly smaller in cases than in controls (all p < 0.001). The ratio of the size of CT-CSAant-30 to that of CT-CSApost-80 was significantly lower in cases (median: 0.84; lower to upper quartile: 0.55-1.13) than in controls (1.0; 0.88-1.16; Mann-Whitney U test; p = 0.006). Bilateral CT-CSAant correlated significantly with total inspiratory flow (all p < 0.026) in contrast to bilateral CT-CSApost (all p > 0.056). Conclusions The nasal airway anterior to the piriform aperture was smaller in patients with nasal obstruction due to skeletal nasal stenosis than that in controls. On the contrary, the nasal airway posterior to the piriform aperture was similarly large between patients with and without nasal obstruction. Furthermore, in patients with nasal obstruction, the anterior nasal airway was narrower compared to that located posterior to it. On the contrary, control patients' anterior nasal airway was as large as the posterior one.