Investigations into the role of the thyrohyoid muscles in the pathogenesis of dorsal displacement of the soft palate in horses.
Authors: Ducharme N G, Hackett R P, Woodie J B, Dykes N, Erb H N, Mitchell L M, Soderholm L V
Journal: Equine veterinary journal
Summary
# Editorial Summary: Thyrohyoid Muscle Function and Dorsal Displacement of the Soft Palate Dorsal displacement of the soft palate (DDSP) remains a significant cause of upper airway obstruction during exercise, yet the underlying mechanisms remain incompletely understood. Ducharme and colleagues used high-speed treadmill trials in ten horses to investigate whether thyrohyoid muscle dysfunction contributes to DDSP pathogenesis, employing videoendoscopy and pressure measurements across four conditions: baseline control, post-resection of the thyrohyoid muscles, sham surgery, and surgical restoration of thyrohyoid function via prosthesis. Surgical resection of the thyrohyoid muscles induced DDSP in 7 of 10 horses during exercise, whilst five of six horses showed resolution of the condition following prosthesis-based functional restoration, with airway pressures and respiratory parameters returning to control values. These findings provide compelling evidence that thyrohyoid muscle dysfunction directly contributes to laryngopharyngeal instability during exercise, suggesting that therapeutic strategies aimed at restoring or augmenting thyrohyoid function—rather than addressing the soft palate itself—may offer a more mechanistically sound approach to managing DDSP in clinical cases.
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Practical Takeaways
- •DDSP can be experimentally induced by thyrohyoid muscle dysfunction, supporting a targeted surgical approach to treatment beyond traditional methods
- •Horses with exercise-induced DDSP may benefit from surgical procedures aimed at restoring thyrohyoid muscle function rather than palatal support alone
- •Monitoring for thyrohyoid muscle dysfunction should be considered in horses presenting with recurrent or persistent DDSP during exercise
Key Findings
- •7 of 10 horses (70%) developed DDSP after thyrohyoid muscle resection, compared to 0 of 10 in control conditions
- •Surgical restoration of thyrohyoid muscle function via prosthesis-treatment eliminated DDSP in 5 of 6 horses (83%)
- •Thyrohyoid muscle dysfunction causes significant anomalies in airway pressures and respiratory frequency during exercise
- •Restoration of thyrohyoid muscle function normalizes all measured parameters to control condition levels