A horse that can’t breath can’t run. So there are some conditions that can be readily identified as
problematic on a standing endoscopic exam. However a very high percentage of horses appear
to be sound of wind on this exam. Other clinical problems are most readily identified either by
listening to a horse gallop or breeze, or by doing dynamic endoscopy where the horse is scoped
while galloping.
There tends to be a lot of subjective grading on these exams: horses are graded ABCDF, or
1234. It can be very confusing. Generally the laryngeal function gets a grade of 1-4. The grade
1-4 is also broken down with grade 2 being either characterized as 2A or 2B depending on the
degree of asymmetry present on movement of the corniculate or arytenoid cartilage when it is
asked to fully open or abduct. This is in fact a critical determination as one of the most
devastating condition of an airway condition is paralysis of this cartilage; what we term a
“roarer”, where the “flap” cannot fully abduct effectively strangulating the horse.
The size and consistency of the epiglottis is also graded 1-4 with grade 1 being a normal mature
sized epiglottis. This can be relevant to a horse’s ability to displace the epiglottis under the soft
palate(“flipping the palate”) a common racehorse issue.
Also common
ly graded is pharyngitis. These are the horse equivalent to our tonsils, and almost
all horses have some level of them. They are measured 1-4 with 1 being the lowest and 4 the
highest. Typically as a horse get older the grade gets lower. Most young thoroughbreds have a
grade 2-3. Grade 4 throats need to be treated. Short term corticosteroids are effective; longer
term immune stimulants such as “Eqstim” seem to help.
Some people subjectively grade a horse’s laryngeal size, pharyngeal size and other subjective
parameters.
Also in performing standing endoscopy we attempt to ascertain the horses ability to maintain a
proper relationship of the epiglottis and the soft palate. When the soft palate comes up over the
epiglottis this is known as dorsal displacement of the soft palate or “flipping the palate”. This is a
quite common normal occurrence in young horses as one pulls them up from a gallop.It is also
the most common finding in mature racehorses having airway issues. The sound is likened to a
“gurgle”. Most common treatment or preventative is a tongue tie which pulls the larynx more
forward in an attempt to keep the proper orientation. Figure eights and nose bands help keep
the horse from swallowing which reduces the ability to displace the palate. The surgical
procedure ” Llewelyn” severs tiny muscular attachments to the larynx which normally assist in
pulling the larynx backwards which increases the chances of the palate going over the epiglottis.
In the picture above the cut portion is the soft palate and the epiglottis is under it. This horse has
a displaced palate as it should be under the epiglottis.
The important points to remember is that most horses are sound of wind on a standing
endoscopy exam and a lot of other subjective observations are made that attempt a guess at
future racing soundness. The most effective determinations are made listening to the horse
gallop and treadmill or dynamic endoscopy.
February 2, 2017
H.O. Ferguson, DVM
