EQUINE | URT endoscopy
examinations was used to obtain the data. Cases were
excluded if only a repository examination was available.
Cases with right-sided RLN abnormalities were
excluded. Horses with abnormalities other than left RLN
abnormalities were also excluded.
Materials and Methods
All of the examinations in the present study were
performed by one experienced race horse veterinarian
(SMM). The URT was examined as follows: the horses
were restrained with a head collar with the handler and
the veterinarian standing on the horse’s left, a twitch
was applied to the upper lip, and the endoscope was
passed up the right ventral meatus. Sedation was not
used because of its effect on RLN grading (Ducharme et
al. 1991:180-184). For all horses, either both nostrils were
occluded and released, or swallowing was stimulated
by touching the endoscope to the arytenoid cartilage
and was continued until sufficient swallowing cycles
were observed for a grade to be determined. For horses
graded 3 or 4, an additional independent experienced
veterinarian or South African qualified specialist equine
surgeon appointed by the auctioneers, examined the
horse to confirm the grading. This second examination
was performed as soon as possible after the first, under
the same conditions and in the same manner. The
second examining veterinarians grading was used to
confirm grade 3 and 4 RLN as per the sales requirements
and this confirmatory grade was the final grade used for
these horses in this study. Grade 1 and 2 horses were not
subjected to a second examination.
Grading of RLN used a 4-point grading system (Table
2) (Rakestraw et al. 1991:122-127; Saulez & Gummow
2009:431-435). This was used as the pass/fail criterion
of the sales as established by the auctioneers in South
Africa which considers grade 1 and 2 a ‘pass’ and grade
3 or 4 a ‘fail’, irrespective of subgrades, as outlined in the
sales agreement.
The results were tabulated using an Excel spreadsheet
Table 2: Grading of recurrent laryngeal neuropathy (Rakestraw et al. 1991:122-127; Saulez & Gummow
2009:431-435)
Grade
Description
1 Synchronous full abduction of both arytenoid cartilages during inspiration or breath holding, or after
swallowing
2 Asynchronous full abduction of the left arytenoid cartilage (hesitation, flutter or delay) can be
achieved and maintained during inspiration or breath holding, or after swallowing
3 Asynchronous abduction of the left arytenoid cartilage (hesitation, flutter or delay). Substantial
movement is present, but full abduction cannot be achieved and maintained during inspiration or
breath holding, or after swallowing
4 No appreciable abduction of the left arytenoid cartilage during any phase of respiration
26 • Equine Health Update •