Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion.

This research study investigates a specific type of cartilage dislocation in the throat of horses which only becomes apparent under certain circumstances like swallowing or nasal blockage. The researchers aimed to describe this phenomenon, its circumstances, as well as the morphologic characteristics of the larynx in an affected horse.

Subjects and Methods

• The retrospective study was conducted on 8 horses. The subjects consisted of 7 Clydesdale horses that underwent endoscopic examination as part of a survey, and 1 Thoroughbred horse investigated for poor performance.
• One of the Clydesdale horses was euthanatized for a more detailed analysis of the larynx. To compare findings, four larynges from cadaver horses were also examined.

Findings

• The ventroaxial luxation (dislocation) of a part of the arytenoid cartilage, known as the corniculate process, was not noticeable during quiet breathing. It could only be observed during induced actions such as swallowing or nasal occlusion.
• The prevalence of this specific luxation among Clydesdales studied was estimated at 5.2% (7 from a total of 133 examined).
• Similar observations were made with the Thoroughbred whose laryngeal appearance at rest was the same. However, progressive luxation of the arytenoid cartilage was detected during high-speed treadmill endoscopy. This condition was associated with abnormal respiratory noise.
• An autopsy of the affected Clydesdale’s larynx revealed a notably wide (10mm) transverse arytenoid ligament – a fibrous connection that typically keeps the arytenoid cartridges in place. This wide ligament allowed easy separation of the apices of the corniculate processes. In comparison, the apices in normal larynges examined could not be separated with abaxial traction.

Conclusions

• The clinical importance of this laryngeal observation in horses while resting remains unclear, given that the condition only becomes perceptible during induced actions like swallowing, nasal occlusion, or intense exercise.
• The observed dislocation of the corniculate process may be caused by an abnormal width of the transverse arytenoid ligament. This structural irregularity was detected in the examined case and could potentially explain the phenomenon.