Proceedings of a Workshop on - The Havemeyer Foundation

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Havemeyer Foundation Monograph Series No. 11 itself difficult. This creates a small risk <strong>of</strong> injury to the horse or the people involved with the procedure. Sedation is usually not an option. Thus, experienced handlers become very important. To address the above concerns, some vendors will allow only a few experienced veterinarians to examine endoscopically certain yearlings. They may ask other veterinarians wanting to examine the UA to contact the few veterinarians who did examine the horse, for their opinion. However, in general, most vendors allow as many UA examinations as requested. There is a direct relationship between the number <strong>of</strong> veterinary examinations <strong>of</strong> the UA and the number <strong>of</strong> potential buyers. INTERPRETING UPPER AIRWAY FINDINGS Accurate interpretation <strong>of</strong> the findings from UA examination is not difficult for most horses as they are well within normal limits. However, for some horses this can be challenging. A veterinarian is expected to determine suitability <strong>of</strong> the UA for racing during a brief single examination. The pharynx/larynx is observed at rest, after swallowing, and usually during nasal occlusion. In most immature horses the arytenoids are well abducted throughout much <strong>of</strong> the UA examination, or easily maximally abduct following swallowing, or when the UA is stressed during nasal occlusion. Rarely is complete paralysis <strong>of</strong> an arytenoid found in a yearling. In the experience <strong>of</strong> the author’s practice this occurs in less than 0.2% <strong>of</strong> the general population <strong>of</strong> thoroughbred yearlings examined during the first three-quarters <strong>of</strong> their yearling year. The arytenoid function <strong>of</strong> yearlings that fall between complete paralysis and relatively easily achieved maximal abduction can be difficult to interpret and requires good judgment to determine suitability for purchase. It is recognised that many normally functioning arytenoids that are neither perfectly symmetrical nor synchronous, do not become dysfunctional. It is also generally believed that complete arytenoid paralysis is usually preceded by progressive, deterioration <strong>of</strong> arytenoid function <strong>of</strong> variable duration. Thus, when evaluating the UA <strong>of</strong> a sales yearling the arytenoids that do not function in an ideal fashion do raise the level <strong>of</strong> concern. It has been noted that arytenoid movement in some yearlings can change mildly over a few to several months, over a few days, or even from morning to afternoon. This may change the opinion <strong>of</strong> the examining veterinarian <strong>of</strong> whether the UA is acceptable. Some yearlings are uncooperative and cannot be induced to fully abduct the left and right arytenoids even with nasal occlusion. The author considers this within normal limits for this age if they are relatively symmetrical and synchronous. In some yearlings one arytenoid (usually the left) does not fully abduct, even with nasal occlusion. The author considers this normal if the arytenoid abducts to at least 95% <strong>of</strong> what would be considered maximal abduction. Is a yearling within normal limits if an arytenoid can fully abduct briefly after swallowing and fully abduct briefly with nasal occlusion, but not maintain abduction? This becomes a judgment call on whether the abduction was maintained long enough to be considered acceptable by the examining veterinarian. RECORDING FINDINGS (GRADING SYSTEMS) Being able to record endoscopic findings in a consistent manner is important. This allows subsequent review <strong>of</strong> notes to determine accurately the status <strong>of</strong> the UA during that examination. The veterinarian can then explain to a client or another veterinarian what was seen at that time. This also provides a comparative reference for a subsequent examination <strong>of</strong> the same horse and for UA findings <strong>of</strong> other horses. Different grading systems for arytenoid movement have been used. This can make communication between veterinarians difficult unless the actual description <strong>of</strong> the arytenoid movement is used. Some <strong>of</strong> the grading systems proposed and used have had from 4 to 10 different categories for arytenoid movement. Some veterinarians have abandoned these grading systems and just describe what was seen. Some veterinarians combine all the findings <strong>of</strong> the UA endoscopic examination and give the entire pharynx/larynx a letter grade. A relatively simple grading scale that is easy to use and widely accepted is needed. The problem with having too few categories is the broad range <strong>of</strong> arytenoid movements that fit in a single category. A system with too many categories becomes too complicated to use easily. Regardless <strong>of</strong> the grading system used, some arytenoids will not fit precisely into a specific category. However, a widely accepted grading 43
Equine Recurrent Laryngeal Neuropathy system used by veterinarians all over the world, will provide consistent and more accurate communication between veterinarians. PREDICTING FUTURE FUNCTION OF THE ARYTENOID It is now well recognised that arytenoid movement within an individual can change over variable periods <strong>of</strong> time, both for the better and for the worse. Thus, making accurate predictions in immature horses for future function can be difficult. In general the younger the horse, the more difficult this becomes. It is important for buyers and sellers to understand that regarding arytenoid movement, opinions on suitability for athletic function are based on the examination performed that day. This may result (has resulted) in horses that appear normal having subsequent problems, and in horses that do not quite appear normal, having no subsequent problems. There is less risk for the veterinarian and the buyer to purchase a horse with what is considered a normal UA and avoid purchasing a horse with a questionable UA, than to take a chance on a horse with a questionable UA. In summary, although the knowledge regarding arytenoid movements in young horses has improved, there will continue to be very good racehorses that had less than ideal arytenoid function as a young horse. 44
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