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Equine veterinary journal2004; 36(4); 318-323; doi: 10.2746/0425164044890553

Effects of stylopharyngeus muscle dysfunction on the nasopharynx in exercising horses.

Abstract: Nasopharyngeal collapse has been observed in horses as a potential cause of exercise intolerance and upper respiratory noise. No treatment is currently available and affected horses are often retired from performance. Objective: To determine the effect of bilateral glossopharyngeal nerve block and stylopharyngeus muscle dysfunction on nasopharyngeal function and airway pressures in exercising horses. Methods: Endoscopic examinations were performed on horses at rest and while running on a treadmill at speeds corresponding to HRmax50, HRmax75 and HRmax, with upper airway pressures measured with and without bilateral glossopharyngeal nerve block. Results: Bilateral glossopharyngeal nerve block caused stylopharyngeus muscle dysfunction and dorsal nasopharyngeal collapse in all horses. Peak inspiratory upper airway pressure was significantly (P = 0.0069) more negative at all speeds and respiratory frequency was lower (P = 0.017) in horses with bilateral glossopharyngeal nerve block and stylopharyngeus muscle dysfunction compared to control values. Conclusions: Bilateral glossopharyngeal nerve anaesthesia produced stylopharyngeus muscle dysfunction, dorsal pharyngeal collapse and airway obstruction in all horses. Conclusions: The stylopharyngeus muscle is probably an important nasopharyngeal dilating muscle in horses and dysfunction of this muscle may be implicated in clinical cases of dorsal nasopharyngeal collapse. Before this information can be clinically useful, further research on the possible aetiology of stylopharyngeus dysfunction and dysfunction of other muscles that dilate the dorsal and lateral walls of the nasopharynx in horses is needed.
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Publication Date: 2004-05-28 PubMed ID: 15163038DOI: 10.2746/0425164044890553Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research study investigates the effects of dysfunction in the stylopharyngeus muscle, a muscle in the horse’s throat, on the function of the nasopharynx, particularly in relation to exercise. The researchers found that the impairment of this muscle might contribute to the collapse of the nasopharynx, a condition that can lead to exercise intolerance and abnormal respiratory noise in horses.

Objective of the Study

  • The main aim of this study was to observe the impact of malfunctioning stylopharyngeus muscle on the functioning of the nasopharynx and the pressure in the airway of horses during exercise.

Research Methodology

  • The researchers carried out endoscopic examinations on horses while at rest and during exercise on a treadmill. The levels of exercise were determined according to different heart rate maximums (HRmax50, HRmax75, and HRmax).
  • To induce stylopharyngeus muscle dysfunction, the researchers performed a bilateral glossopharyngeal nerve block in the horses and compared the findings with control values.
  • Pressure in the upper airway was measured before and after the bilateral glossopharyngeal nerve block to assess the change.

Results

  • The results signified that dysfunction in the stylopharyngeus muscle caused by the bilateral glossopharyngeal nerve block led to a collapse of the nasopharynx in all the horses.
  • Moreover, it was found that the peak inspiratory upper airway pressure became significantly more negative at all speeds after the nerve block, and the respiratory frequency was lower compared to the control values.

Conclusions

  • The conclusions drawn from this research indicate that the stylopharyngeus muscle plays a crucial role in maintaining the openness of the nasopharynx in horses. Any dysfunction of this muscle can cause a dorsal collapse of the nasopharynx, leading to the obstruction of the airway.
  • Therefore, it is suggested that for improving the clinical understanding and for potential treatment development, further studies are required to understand better the causes leading to stylopharyngeus dysfunction and other muscles that affect the dilation of the nasopharynx.

Cite This Article

APA
Tessier C, Holcombe SJ, Derksen FJ, Berney C, Boruta D. (2004). Effects of stylopharyngeus muscle dysfunction on the nasopharynx in exercising horses. Equine Vet J, 36(4), 318-323. https://doi.org/10.2746/0425164044890553

Publication

Equine veterinary journal
ISSN: 0425-1644
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 36
Issue: 4
Pages: 318-323

Researcher Affiliations

Tessier, C
  • Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824, USA.
Holcombe, S J
    Derksen, F J
      Berney, C
        Boruta, D

          MeSH Terms

          • Airway Obstruction / etiology
          • Airway Obstruction / physiopathology
          • Airway Obstruction / veterinary
          • Animals
          • Exercise Test / veterinary
          • Female
          • Forced Expiratory Flow Rates
          • Glossopharyngeal Nerve / physiology
          • Horse Diseases / etiology
          • Horse Diseases / physiopathology
          • Horses
          • Male
          • Nasopharynx / physiopathology
          • Nerve Block / methods
          • Nerve Block / veterinary
          • Pharyngeal Muscles / innervation
          • Pharyngeal Muscles / physiopathology
          • Physical Conditioning, Animal / physiology
          • Pressure
          • Respiration
          • Respiratory Sounds / etiology
          • Respiratory Sounds / physiopathology
          • Respiratory Sounds / veterinary
          • Running

          Citations

          This article has been cited 5 times.
          1. Jeong S, Bond S, Bayly W, Sole-Guitart A. Laser fenestration of the dorsal pharyngeal recess does not correct experimentally induced dorsal nasopharyngeal collapse in horses. Vet Surg 2026 Jan;55(1):88-100.
            doi: 10.1111/vsu.70023pubmed: 41074232google scholar: lookup
          2. Rubin JA, Holt DE, Reetz JA, Clarke DL. Signalment, clinical presentation, concurrent diseases, and diagnostic findings in 28 dogs with dynamic pharyngeal collapse (2008-2013). J Vet Intern Med 2015 May-Jun;29(3):815-21.
            doi: 10.1111/jvim.12598pubmed: 25903658google scholar: lookup
          3. Go LM, Barton AK, Ohnesorge B. Objective classification of different head and neck positions and their influence on the radiographic pharyngeal diameter in sport horses. BMC Vet Res 2014 May 23;10:118.
            doi: 10.1186/1746-6148-10-118pubmed: 24886564google scholar: lookup
          4. Go LM, Barton AK, Ohnesorge B. Pharyngeal diameter in various head and neck positions during exercise in sport horses. BMC Vet Res 2014 May 23;10:117.
            doi: 10.1186/1746-6148-10-117pubmed: 24886465google scholar: lookup
          5. Cao Y, Liu C, Ling L. Glossopharyngeal long-term facilitation requires serotonin 5-HT2 and NMDA receptors in rats. Respir Physiol Neurobiol 2010 Feb 28;170(2):164-72.
            doi: 10.1016/j.resp.2009.12.005pubmed: 20026287google scholar: lookup
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