Cricothyroid muscle function and vocal fold stability in exercising horses.
Authors: Holcombe Susan J, Rodriguez Katie, Lane Jennifer, Caron John P
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Cricothyroid muscle function and vocal fold stability in exercising horses Holcombe et al. investigated whether the cricothyroid muscle actively stabilises the vocal folds during exercise and whether loss of this function causes airway collapse in horses. Using electromyography and endoscopic examination, the researchers monitored cricothyroid muscle activity in three horses exercised at increasing intensities (50–100% maximum heart rate) and then surgically ablated both cricothyroid muscles in four additional horses to assess the functional consequences. The cricothyroid muscle demonstrated clear respiratory phasic activity during inspiration that intensified proportionally with exercise intensity, and bilateral myotomy resulted in complete vocal fold collapse in all four surgically treated horses, accompanied by significantly more negative inspiratory pressures indicating increased airway obstruction. These findings establish the cricothyroid muscle as essential for maintaining vocal fold position during work, suggesting that conditions affecting its innervation or contractile function—including recurrent laryngeal neuropathy and muscular disorders—may compromise dynamic airway stability. For practitioners managing horses with inspiratory obstruction or suspected laryngeal dysfunction, this work highlights the importance of assessing not only laryngeal nerve function but also the mechanical competence of intrinsic laryngeal muscles throughout the respiratory cycle.
Read the full abstract on PubMed
Practical Takeaways
- •Cricothyroid muscle dysfunction or denervation should be considered as a potential cause of exercise-induced vocal fold collapse and inspiratory obstruction in horses
- •Laryngeal hemiplegia (recurrent laryngeal nerve dysfunction) may not be the only neurological cause of vocal fold instability—cricothyroid innervation problems warrant investigation
- •Any condition affecting the cricothyroid muscle or its motor nerve supply could compromise upper airway stability during exercise and warrant diagnostic workup
Key Findings
- •Cricothyroid muscle EMG activity was inspiratory-related and increased proportionally with treadmill speed and respiratory effort
- •Bilateral cricothyroid myotomy resulted in vocal fold collapse in all 4 horses tested during exercise
- •Mean peak inspiratory pressures became significantly more negative post-myotomy at both maximum and 75% maximum heart rate speeds, indicating increased airway obstruction