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Principal Investigator: Dr. Heather Chalmers
Mentor(s): Dr. Normand Ducharme and Dr. Amy Yeager
Contact Information: E-mail: ngd1@cornell.edu - Phone: 607-253-3109
Sponsor: American College of Veterinary Radiology
Grant Number: N/A
Title: Accuracy of Ultrasonic Assessment of Laryngo-hyoid Conformation and Laryngeal Function in the Diagnosis of Upper Airway Diseases in Horses
Annual Direct Cost: $5,000
Project Period: 01/01/06-12/31/06
Dorsal displacement of the soft palate (DDSP) and recurrent laryngeal neuropathy (RLN) are important causes of upper airway noise and poor performance in athletic horses. Definitive diagnosis of these conditions currently relies upon upper airway video-endoscopy. Video-endoscopy at rest is used to grade laryngeal function, but has a low specificity and is a poor predictor of dorsal displacement of the soft palate at exercise. Therefore, high speed treadmill videoendoscopy is often required, but is not widely available, is invasive, and carries risk of injury to the horse. Videoendoscopy does not allow assessment of non-luminal structures, such as laryngeal musculature, or of the relation of the larynx to the hyoid apparatus or skull. The development of ultrasonography as a non-invasive test that does not require treadmill facilities would offer substantial advantages in the diagnosis of equine upper respiratory diseases. Currently, the etiopathogenesis of DDSP is not fully understood, but an altered relationship between the larynx, the hyoid apparatus, and the skull has recently been implicated in the pathogenesis of DDSP. This altered conformation may be detectable with ultrasonography. The first objective of this work is to determine if the distance between the basihyoid bone and the thyroid cartilage measured during ultrasonography of the throat is accurate diagnostic test for dorsal displacement of the soft palate at exercise. Horses with recurrent laryngeal neuropathy have altered vocal fold/arytenoid function and atrophy of the intrinsic laryngeal musculature, specifically the cricoarytenoideus lateralis muscle. These abnormalities may be detectable with ultrasonography. The second objective of this work is to determine if lack of arytenoid and/or vocal fold movement and/or decreased thickness of the cricoarytenoideus lateralis muscle during ultrasonography of the throat are accurate diagnostic tests for RLN based on correlation with laryngeal grade at exercise. The sample population will consist of all horses admitted to our institution for poor performance associated with upper airway dysfunction. A standardized ultrasonographic examination of the throat, designed to evaluate laryngo-hyoid conformation and laryngeal function, will be performed on each horse by a single examiner blinded to history, clinical signs, and endoscopic findings. Measures will be made of laryngo-hyoid conformation and arytenoid and vocal fold movement will be observed real time. Each horse will also be subjected to upper airway endoscopy, which will serve as the gold standard. The results will be analyzed for sensitivity, specificity, and positive and negative predictive values using 95% confidence intervals for all proportions.
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