Recurrent laryngeal neuropathy (paralysis) in a sample of thoroughbred yearlings

An interesting study that, as the summary concludes, almost certainly underestimates the incidence of recurrent laryngeal paralysis (RLP) in young TB’s. In this study appx 84% of those examined at a yearling TB sale were normal (grade 1, Rakestraw scale). Another 14% were grade 2 (flutter or asynchronous opening but full opening achieved). The final 2 % were unable to fully open or even move the left arytenoid. Of note in the full article are these 4 points:
1) Due to the exclusive nature of this sale and the increasing use of presale endoscopy for RLP these numbers probably underrepresent the incidence.
2) RLP, particularly G2 or G3 may vary from exam to exam making serial exam more accurate.
3) RLP is usually progressive.
4) RLP may be hereditable
DrO

J S Afr Vet Assoc. 2020 Apr 20;91(0):e1-e5.
Endoscopic recurrent laryngeal neuropathy grade prevalence in a sample of thoroughbred yearlings at public auction in South Africa (2013-2019).
Miller SM1.

Author information:
1. Summerveld Equine Hospital, Summerveld. sean@drummondtor.co.za.
Abstract

Endoscopy of thoroughbred (TB) yearlings at public auctions is common in South Africa. Laryngeal function (LF) is a common concern of buyers of young TBs. Cancellation of sale because of LF abnormalities is a concern for both the vendor and the buyer, with recurrent laryngeal neuropathy (RLN) being a common cause of sale cancellation. The aim of this descriptive study was to determine the prevalence of RLN at South African premier TB yearling sales. This study was designed as a retrospective descriptive analysis of upper respiratory tract (URT) endoscopic examinations to determine RLN grade, performed at two premier TB yearling sales in South Africa. Results of buyer-requested endoscopic examination from 2013 to 2019 were included. Results from the yearling sales were analysed for prevalence of RLN grade (using Rakestraw’s 4-point system) and compared to similar previously published studies. For analysis of effects of gender on RLN grading, horses were grouped and Fisher’s exact test was used to determine if there was a relationship between gender and grade. For comparison of the effects of age on grade, and sales year on grade, a Kruskal-Wallis test was conducted. A value of p 0.05 was considered significant. A total of 858 horses were examined out of 4149 offered for sale; there were 57.58% colts and 42.42% fillies (mean age of 18.1 months). The annual percentage for grade 1 was 84.04% ± 9.98%, for grade 2: 14.49% ± 10.69%, for grade 3: 0.71% ± 0.57% and for grade 4: 0.76% ± 0.94%. There were no other significant findings. The exclusive nature of the sale and the increasing proclivity for pre-sale scoping may have skewed the results. This study shows that RLN grade incidences in TB yearlings at public auctions in South Africa are as follows: grade 1: 84.04%, grade 2: 14.49%, grade 3: 0.71% and grade 4: 0.76%. The results were similar to that of an adult population of horses examined in South Africa in a previous study.