Dynamic computed tomography evaluation of the nasopharynx in normal Beagle dogs

Abstract

Pharyngeal collapsibility has been used as diagnostic criteria in dogs, whereas the normal range and quantitative method have not been studied. Dynamic and static computed tomography (CT) was performed in 23 normal Beagle dogs to quantify the nasopharyngeal collapsibility at different locations. Using dynamic CT, maximum and minimum nasopharyngeal cross-sectional areas (CSAs) were measured at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The ratio of all maximum and minimum CSA to nasopharyngeal CSA at the level of the caudal hard palate (rCSAmax and rCSAmin) and the nasopharyngeal collapsibility were calculated. The differences of rCSAmax, rCSAmin, and nasopharyngeal collapsibility were analyzed at various locations. The nasopharyngeal collapsibility at the level of foramen lacerum, bony labyrinth, and caudal end of soft palate were higher than the others. At the level of the caudal end of the soft palate, rCSAmin was lower than that of the foramen lacerum and bony labyrinth, whereas rCSAmax at foramen lacerum was higher than that of the caudal end of the soft palate. These results indicated that the nasopharynx at the level of foramen lacerum and caudal end of the soft palate were considered notable locations for evaluating collapsibility. Dynamic CT could show the nasopharyngeal dynamic profile and will be an adequate modality for evaluating nasopharynx. Our results will be helpful for further comparative studies in dogs with and without nasopharyngeal collapse.

Nasopharyngeal collapse can be identified on radiography in healthy male Beagle dogs without cardiopulmonary diseases

“…This study objectively described the method for evaluating change in nasopharyngeal lumen on the inspiratory and expiratory cervical radiographs and identified nasopharyngeal collapse in Beagle way, open mouth condition, head posture, and gravity. [12][13][14][15][16][17][18][19][20] The upper airway lacks a fixed rigid structural support compared to the trachea and bronchi, which are supported by cartilage. 13,14 Nasopharyngeal collapsibility is negatively correlated with soft palate length and positively correlated with soft palate thickness.…”

“…13,14 Nasopharyngeal collapsibility is negatively correlated with soft palate length and positively correlated with soft palate thickness. 15 Additionally, nasopharyngeal collapsibility is larger in dogs with epiglottis under the soft palate. 15 The volume of the air-filled nasopharynx differed significantly with mouth position, and was greater in dogs with opened mouth compared to closed.…”

“…15 Additionally, nasopharyngeal collapsibility is larger in dogs with epiglottis under the soft palate. 15 The volume of the air-filled nasopharynx differed significantly with mouth position, and was greater in dogs with opened mouth compared to closed. 16 In humans, oral breathing causing uneven airflow could result in pharyngeal airway collapse.…”

Severity of nasopharyngeal collapse before and after corrective upper airway surgery in brachycephalic dogs

“…A minority of dogs returned for re‐evaluation and fluoroscopy, limiting the size of this cohort. An additional possible limitation was the use of fluoroscopy for evaluation of pharyngeal collapse as opposed to magnetic resonance imaging, which has documented utility in humans with obstructive sleep apnea, or computed tomography which has been used to evaluate normal Beagles, and Pugs and French Bulldogs with BOAS 65–67 …”

“…An additional possible limitation was the use of fluoroscopy for evaluation of pharyngeal collapse as opposed to magnetic resonance imaging, which has documented utility in humans with obstructive sleep apnea, or computed tomography which has been used to evaluate normal Beagles, and Pugs and French Bulldogs with BOAS. [65][66][67] Nasopharyngeal collapse reflects both the anatomy of the upper airway and the function of its neuromuscular components. The results of this study showed that nasopharyngeal collapse occurred in brachycephalic dogs in our study population and was often severe.…”