A twenty year old quarterhorse gelding presented to PHD veterinary services for a complaint of chronic coughing and exercise intolerance. There was no nasal discharge noted during the physical exam however the amount of air that was exiting the nares during expiration was subjectively reduced. An endoscopic exam was performed to evaluated the nasal passages, pharynx and larynx. In Figure 1, a "normal" airway of a horse is pictured. There is a large opening within the larynx (green arrow) which corresponds to the opening to the proximal trachea which provides air into the lungs. The small blister-like structures seen along the dorsal pharyngeal wall are common in young horses and considered lymphatic tissues. .
In Figure 2, the endoscopic images correspond to the 20 year-old horse with a cough and exercise intolerance. Notice the airway (green arrow) is significantly reduced compared to the "normal horse" in Figure 1. The clinically relevant anatomy includes the arytenoid cartilage (blue stars), vocal cords (red cross), and the laryngeal cicatrix (yellow arrows). In this horse, the arytenoid cartilage is thicker than normal and the vocal cords are adhered to each other. In addition, a thick scar or cicatrix has developed between the arytenoid cartilage and the epiglottis. Hence, the cause for the recurrent cough and exercise intolerance is due to a significant reduction in the airway at the level of the larynx. The airway reduction is caused by the narrowing of the laryngeal opening due to cicatrix formation between the arytenoid cartilage and between the vocal cords.
