Effect of bilateral tenectomy of the tensor veli palatini muscle on soft palate function in horses.

OBJECTIVE

To determine the effect of bilateral tenectomy of the tensor veli palatini muscle on soft palate and nasopharyngeal function in exercising horses.

ANIMALS: 5 Standardbreds.

PROCEDURE: Treadmill videoendoscopy was performed on 5 Standardbreds exercising at 50, 75, and 100% of the speed that produced maximum heart rate; tracheal and pharyngeal pressures were measured before and after surgery. Tenectomy of the tensor veli palatini muscle was performed bilaterally on each horse while under general anesthesia, using a transoral approach.

RESULTS

Peak inspiratory tracheal pressures were significantly (P = 0.016) more negative and there was a trend (P = 0.06) for peak pharyngeal inspiratory pressure to be less negative following bilateral tenectomy of the tensor veli palatini muscle, compared with preoperative values. The rostral half of the soft palate was unstable and collapsed dorsally into the nasopharynx during inspiration, causing partial obstruction of the nasopharynx. The caudal free margin of the soft palate remained ventral to the epiglottis, and dorsal displacement of the soft palate did not occur in any horse.

CONCLUSIONS

Bilateral tenectomy of the tensor veli palatini muscle did not cause dorsal displacement of the soft palate in horses while exercising at maximum heart rate, but resulted in collapse of the nasopharynx during inspiration.

CLINICAL RELEVANCE: Results of our study indicate that the tensor veli palatini muscle functions to support and dilate the nasopharynx during intense inspiratory efforts in horses by tensing the palatine aponeurosis.