Clinical and endoscopic evidence of progression in 152 cases of equine recurrent laryngeal neuropathy (RLN).
Authors: Dixon P M, McGorum B C, Railton D I, Hawe C, Tremaine W H, Pickles K, McCann J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Progression in Equine Recurrent Laryngeal Neuropathy Recurrent laryngeal neuropathy (RLN) is typically considered a static condition in horses, yet this longitudinal study of 351 affected animals reveals a more complex picture: 52 cases (15%) demonstrated measurable progression of laryngeal dysfunction over a median 12-month period, with deterioration commencing at around 7 years of age. In 30 horses, both endoscopic examination and clinical signs deteriorated concurrently, with endoscopic grading worsening by a median of three grades; notably, 97% of these animals developed sudden-onset abnormal respiratory noises during exercise and 43% showed reduced performance. The remaining 22 cases exhibited clinical progression without corresponding endoscopic changes at examination, though 59% subsequently revealed marked laryngeal collapse that appeared inconsistent with their historical work capacity, suggesting the dynamic nature of the condition may be underrecognised. These findings carry significant implications for pre-purchase veterinary assessments—a normal endoscopic examination does not guarantee the horse will remain unaffected—and support a more cautious approach to surgical intervention in milder cases, where progression cannot be reliably predicted. For practitioners, this evidence highlights the importance of establishing a thorough baseline assessment and maintaining detailed clinical records, particularly in performance horses, to identify deterioration early and counsel owners appropriately regarding prognosis.
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Practical Takeaways
- •RLN is not always static—15% of cases progress over time, so repeat endoscopic examination may be warranted in horses with worsening clinical signs months or years after initial diagnosis
- •Sudden onset of respiratory noise or performance decline in a previously diagnosed RLN horse should prompt re-evaluation, as significant endoscopic deterioration may not always match clinical presentation
- •Pre-purchase evaluations showing normal laryngeal function do not exclude future RLN development or progression, which is relevant for liability and warranty disputes
Key Findings
- •15% (52/351) of RLN cases showed progression of laryngeal dysfunction over median 12 months, with onset at median age 7 years
- •30 cases with both endoscopic and clinical progression showed median deterioration of 3 endoscopic grades, with 97% developing abnormal exercise-related respiratory sounds and 43% showing reduced performance
- •22 cases with solely clinical evidence of progression demonstrated sudden-onset or worsening respiratory sounds (96%) and reduced exercise performance in 59%
- •59% of cases with clinical-only evidence had marked total or near-total RLN endoscopically that was incompatible with their previous exercise histories