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 veil palatini muscle on soft palate and nasopharyngeal function in ex ercising horses.Animals-5 Standardbreds. Procedure-Treadmill videoendo scopy 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 te nsor veli palatini muscle was performed bilaterally on each horse whil e under general anesthesia, using a transoral approach. Results-Peak i nspiratory tracheal pressures were significantly (P = 0.016) more nega tive and there was a trend (P = 0.06) for peak pharyngeal inspiratory pressure sure to be less negative following bilateral tenectomy of the tensor veil palatini muscle, compared with preoperative values. The r ostral half of the soft palate was unstable and collapsed dorsally int o the nasopharynx during inspiration, causing partial obstruction of t he nasopharynx. The caudal free margin of the soft palate remained ven tral 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 pa late in horses while exercising at maximum heart rate, but resulted in collapse of the nasopharynx during inspiration. Clinical Relevance-Re sults of our study indicate that the tensor veli palatini muscle funct ions to support and dilate the nasopharynx during intense inspiratory efforts in horses by tensing the palatine aponeurosis.