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.