Dynamic bilateral arytenoid and vocal fold collapse associated with head flexion in 5 Norwegian Coldblooded Trotter racehorses

Abstract

Dynamic obstruction of the upper airway is a common cause of poor performance in racehorses, often associated with abnormal respiratory noise during exercise (Morris and Seeherman 1991; Kannegieter and Dore 1995). Welldocumented upper respiratory tract disorders diagnosed using traditional resting upper airway endoscopy include left laryngeal hemiplegia (LLH), dorsal displacement of the soft palate (DDSP), epiglottic entrapment, subepiglottic cyst, epiglottic hypoplasia, pharyngeal lymphoid hyperplasia, arytenoid chondritis and rostral displacement of the palatopharyngeal arch. High-speed treadmill (HST) videoendoscopy has improved our ability to appreciate previously unrecognised forms of dynamic airway obstruction (King et al. 2001). Recently described forms of upper airway obstruction diagnosed using HST videoendoscopy are dynamic collapse of the roof of the nasopharynx (Strand and Staempfli 1993), epiglottic retroversion (Holcombe et al. 1997; Parente et al. 1998), intermittent epiglottic entrapment (Weishaupt et al. 1998) and axial deviation of the aryepiglottic folds (King et al. 2001). This report describes 5 cases of upper airway obstruction due to dynamic bilateral collapse of the vocal folds and arytenoid cartilages in Norwegian Coldblooded Trotter (NCT) racehorses, diagnosed by use of slowmotion playback of HST videoendoscopic recordings.