Pharyngeal contraction secondary to its collapse in dogs with brachycephalic airway syndrome.

Brachycephalic airway syndrome (BAS) is a common disease in certain "flat-faced" dog breeds. This syndrome includes stenotic nares, elongated and thickened soft palate, laryngeal collapse, and tracheal hypoplasia. Pharyngeal collapse is also commonly observed, but it is unclear if laryngopharynx motions are merely sequelae or actually contribute to BAS respiratory symptoms. Laryngopharynx motion was imaged using dynamic four-dimensional computed tomography (4D-CT) during spontaneous respiration in four dogs with different BAS types. Dynamic 4D-CT showed laryngopharynx motion in the following order during inspiration: pharyngeal collapse, contraction, and laryngospasm. We concluded that dynamic 4D-CT is a highly-detailed diagnostic approach for detecting laryngopharynx motion. Pharyngeal contraction during inspiration appears to contribute toward the worsening of clinical respiratory signs of BAS.