Results of upper airway radiography and ultrasonography predict dynamic laryngeal collapse in affected horses.

This study investigated how the position of a horse’s head affects the larynx and breathing in horses diagnosed with dynamic bilateral laryngeal collapse (DLC), a condition that can affect performance in harness racing. Diagnostic imaging techniques, including radiography and ultrasound, were used to explore the condition and possibly establish a new diagnostic approach for restful horses.

Research Objective and Methodology

• The main objective of this research was to determine differences in laryngeal positioning and airway size between healthy horses and those diagnosed with DLC under varying head positions. The researchers hoped to establish diagnostic criteria for DLC using imaging technologies.
• The study involved a sample of 50 horses; 25 cases were diagnosed with DLC, while the remaining 25 served as controls with no recorded abnormalities.
• Diagnostic imaging, employing laryngeal radiography and ultrasonography, was utilised under both neutral and flexed head positions for all participating horses.

Results of the Study

• Upon flexing the head (poll flexion), horses with DLC demonstrated much more forward movement of the larynx as related to the hyoid bone when compared to unaffected animals.
• Measured at the level of the vocal folds, the width of the opening of the larynx (laryngeal lumen), shrinks significantly for the horses diagnosed with DLC during poll flexion.
• In poll flexion, a correlation was found linking a longer thyrohyoid bone to thyroid cartilage distance of ≥12 mm and DLC diagnosis. Here, the risk was multiplied by a factor of 21.3.
• When the width of laryngeal lumen was smaller during poll flexion than in neutral position, the odds of having DLC increased by a factor of 8.4.

Conclusions

• The researchers found that horses with DLC experienced a more forward movement of the larynx and a smaller airway when their heads were flexed, compared with horses not diagnosed with the condition.
• The study indicates that ultrasound and radiography could potentially be effective diagnostic tools to identify DLC, even when horses are at rest.