Arytenoid chondritis in horses and other species
Post Graduate Diploma in Veterinary Clinical Science
2001
Rachael Liane Smith
Abstract
Arytenoid chondritis is an inflammatory and sometimes infectious process affecting the arytenoid cartilages. Although rare, arytenoid chondritis is a serious condition in racehorses. It can produce career threatening respiratory impairment, and despite treatment, affected horses often make poor athletes.
Since 1996, post-sale endoscopic examinations of yearling racehorses at major auctions in New Zealand have been performed. This has coincided with an increase in the diagnosis of arytenoid chondritis. Mucosal contact ulcers have also become commonly recognised. These lesions are small ulcers usually bilateral, found on the mucosal covering of the vocal processes.
Arytenoid chondritis has been described in a number of species. Contact ulcers have not been reported in horses but have in humans and cattle. Contact ulcers in cattle develop into diphtheria and chondritis of the arytenoid cartilage. In humans a granulation tissue mass develops at the site of the ulcer and arytenoid chondritis is a rare complication. It is not known why contact ulcers occur in yearling horses or if they are involved in the pathogenesis of arytenoid chondritis.
Most authors have proposed that trauma is the initiating cause of arytenoid mucosal injuries and arytenoid chondritis. Human literature is the only area where immediate post-trauma laryngeal injury has been investigated and shows the trauma required for arytenoid mucosal injury formation is slight.
A pilot study was conducted on 21 horses to determine if injury caused by passage of a nasogastric tube into the trachea, produced lesions comparable to contact ulcers. The horses were videoscoped immediately after intubation and again at weekly intervals for 76 days. The study showed that injury to the laryngopharyngeal area can easily be induced but most healed uneventfully within two to four weeks. The appearance and site of the injuries were not at any stage, typical of arytenoid mucosal contact ulcers. The injuries that did not resolve, remained as focal swellings on the corniculate cartilages or the vocal cords. Factors other than trauma must therefore be involved in the development of mucosal contact ulcers in horses.
It is unknown whether contact ulcers heal uneventfully, or if they predispose to arytenoid chondritis. Because of this a retrospective study was carried out on 33 horses diagnosed with arytenoid mucosal injuries at yearling sales in 1996, 1997 and 1998. The results showed that cases were as likely to race more than three, or three or less times, as the controls. Seventy five percent of the cases had obtainable race records. A trainer survey on these horses, revealed that none had developed problems related to the respiratory tract during their race career. Horses diagnosed with mucosal contact ulcers at yearling sales, are therefore unlikely to develop arytenoid chondritis.
The aetiology of mucosal contact ulcers and arytenoid chondritis is likely to be multifactorial and possibly interrelated. Although trauma to the vocal processes may play a role in the development of contact ulcers, there must be other factors that render the mucosa over the vocal processes more susceptible to injury and result in a poor healing response. These factors could be: inflamed laryngeal mucosa due to allergy or respiratory infection; inhaled respiratory irritants such as ammonia, dust and mould; or laryngeal trauma due to vocalisation.