Arytenoid Chondritis

Lee Ann Curtis, DVM

Rustin M. Moore, DVM, PhD, DACVS

Arytenoid chondritis or chondropathy is a disease affecting the upper airway of the horse. It is usually diagnosed in young horses that perform at high speeds, particularly racing Thoroughbreds. Most often the disease is associated with respiratory noise and exercise intolerance. It can also occur in middle aged to older horses, but often goes unnoticed until it is quite advanced unless the horse performs an athletic function.

Understanding the anatomy of the equine upper airway is important in understanding arytenoid chondritis. The arytenoids are paired flaps of cartilage that lie at the opening to the trachea or windpipe. During inspiration, these flaps are pulled apart to allow as much air as possible to pass through the trachea and into the lungs. They then return to a semi-open position during expiration. The arytenoids also help to prevent food from entering the trachea during swallowing.

In arytenoid chondritis, one or both of these cartilages become inflamed and swollen or disfigured. This becomes a space occupying mass and prevents the cartilage from fully opening, thereby impeding airflow. The decreased airflow causes exercise intolerance because the horse cannot breathe properly. The noise that is commonly heard during inspiration is due to the air passing across the enlarged arytenoid that obstructs the airway, causing vibration. The cause of this condition is unknown; however, it is believed to be secondary to trauma to the arytenoid cartilage or damage to the soft tissue that lies over the cartilage. This damage may occur due to ingestion of foreign bodies, trauma from nasogastric or tracheal intubation, or irritation in horses with laryngeal hemiplegia (commonly called roaring). Arytenoid chondritis most often only affects one of the arytenoid cartilages but may affect both. The inflammation may also occur secondary to infection that migrates from nearby retropharyngeal lymph nodes.

Horses with arytenoid chondritis can have similar clinical signs and histories as those with laryngeal hemiplegia, a disorder in which the arytenoids are partially or completely paralyzed and cannot function properly. These clinical signs include upper respiratory noise, exercise intolerance, and possibly respiratory distress if the inflammation is severe and the airway is obstructed. Affected horses may also have a fever during the initial stages of the disease.

Arytenoid chondritis is diagnosed using endoscopic examination in which a small camera enclosed in a tube is passed up the horse’s nasal passage in order to visualize the arytenoids. Upon examination, the affected arytenoid usually fails to completely open and is swollen or irregularly shaped. It may also have erosions or ulcerations, and the inflammation may extend into the adjacent soft tissues. Horses with arytenoid chondritis have also been shown using radiography to have excessive mineralization (calcification) of their laryngeal cartilages.

The most common treatment for arytenoid chondritis involves surgery; however, medical therapy may be of value in some cases. It has been suggested that if the arytenoid cartilage is inflamed or if there are obvious draining tracts, therapy consisting of rest, nonsteroidal anti-inflammatory drugs, antibiotics, and throat sprays containing anti-inflammatory medications may be helpful. There are two surgical procedures that may be performed. If the affected arytenoid can function adequately but has excessive tissue, the tissue can be removed using an endoscopic-guided laser. In cases where the cartilage is malformed and function is reduced, an arytenoidectomy, or removal of all or part of the arytenoid is indicated. In some cases where both arytenoids are severely affected, the damage is so extensive that surgery will not provide relief. In these cases a permanent tracheostomy may be necessary; however, this can be accompanied by complications. In some cases, the disease may be so severe that it requires euthanasia.

There are complications associated with surgical treatment of arytenoid chondritis. Inspiratory obstruction is often present, most likely due to collapse of the unsupported adjacent soft tissues. Some horses will develop an intermittent to persistent cough when eating. Aspiration of food particles may then result in severe pneumonia. Wetting the horse’s hay prior to feeding may reduce the risk of aspiration pneumonia. Also, it is recommended that horses be muzzled for 1 to 2 hours prior to exercise to reduce coughing during exercise and therefore, reduce tracheal irritation.

Surgical intervention most often relieves the inspiratory obstruction at rest and at low levels of exercise. Only approximately 50% of horses treated surgically will return to their previous level of athletic performance. Horses in which both arytenoids are affected usually do not return to competitive racing ability. An increase in mineralization of the laryngeal cartilages may be an important prognostic indicator, as many of these horses fail to return to racing.

Arytenoid chondritis should be considered especially in performance horses that exhibit exercise intolerance and inspiratory noise. It is important for owners to realize that horses treated for this disorder may not return to their previous level of athletic performance. Since the exact cause of arytenoid chondritis is unknown, there are no preventive measures available.