Dynamic ventrorostral displacement of the dorsal laryngeal mucosa in horses

The objectives of this report were to describe the occurrence and features of dynamic ventrorostral displacement of the dorsal laryngeal mucosa (VRDDLM) in a group of Thoroughbred horses presented for investigation of poor performance and/or abnormal respiratory noise. Records from 600, dynamic, endoscopic examinations of the upper respiratory tract of horses were reviewed. Horses with VRDDLM were identified as those in which the dorsal laryngeal mucosa progressively obscured the interarytenoid notch and dorsoaxial portion of the corniculate processes of the arytenoid cartilages during high-speed exercise. The condition was recognised in 12 horses. Concurrent abnormalities of the respiratory tract of eight horses were also identified and included, axial deviation of the aryepiglottic folds, vocal cord prolapse, unilateral and bilateral ventromedial luxation of the apex of the corniculate process of the arytenoid cartilage, and intermittent dorsal displacement of the soft palate. VRDDLM is a rare abnormality of the upper portion of the respiratory tract of horses that may be associated with abnormal respiratory noise and potentially poor performance. The significance of the condition is not known, but the presence of this condition in combination with other, obstructive diseases of the equine airway warrants further investigation.