title: Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion.
abstract: OBJECTIVE
  To report ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage under the contralateral corniculate process during resting endoscopic examination, and morphologic features of the larynx of 1 affected horse.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Horses (n=8).
  
  
  METHODS
  Horses had endoscopic examination as part of a survey of Clydesdale horses (n=7), or investigation of poor performance in Thoroughbred horses (1). One Clydesdale was euthanatized and the larynx examined; 4 cadaver larynges from normal horses were also examined.
  
  
  RESULTS
  Ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage was not detected during quiet breathing but was induced by swallowing or nasal occlusion. Prevalence in Clydesdales was 5.2% (7/133). A Thoroughbred with identical endoscopic appearance of the larynx at rest had progressive ventroaxial luxation of the apex of the arytenoid cartilage during high-speed treadmill endoscopy, associated with abnormal respiratory noise. Necropsy examination of an affected Clydesdale larynx revealed an excessively wide (10 mm) transverse arytenoid ligament that allowed easy separation of the apices of the corniculate processes. In normal cadaver larynges, the apices could not be separated with abaxial traction.
  
  
  CONCLUSIONS
  The clinical relevance of this laryngeal observation in resting horses is unclear. Ventroaxial luxation of the corniculate process of the arytenoid cartilage during induced swallowing or nasal occlusion in resting horses or during high-speed treadmill exercise may be caused by an abnormally wide transverse arytenoid ligament.
authors.affiliation: Division of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Scotland, UK. safia.barakzai@ed.ac.uk
authors.forename: S Z
authors.initials: SZ
authors.lastname: Barakzai
authors.forename: Cert
authors.initials: C
authors.lastname: Es
authors.forename: E M
authors.initials: EM
authors.lastname: Milne
authors.forename: Padraic
authors.initials: P
authors.lastname: Dixon
mesh_terms: D000818:Animals; D001193:Arytenoid Cartilage / Q000473:pathology / Q000503:physiopathology*; D003679:Deglutition; D004724:Endoscopy / Q000662:veterinary; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis* / Q000473:pathology; D006736:Horses; D007818:Laryngeal Diseases / Q000175:diagnosis / Q000662:veterinary*; D008022:Ligaments / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D015508:Nasal Obstruction / Q000175:diagnosis / Q000662:veterinary*; D010805:Physical Conditioning, Animal; D012146:Rest / Q000502:physiology; D012189:Retrospective Studies