Laryngeal paralysis: a study of 375 cases in a mixed-breed population of horses.
Authors: Dixon P M, McGorum B C, Railton D I, Hawe C, Tremaine W H, Pickles K, McCann J
Journal: Equine veterinary journal
Summary
# Laryngeal Paralysis in Horses: A Large Referral Population Study Laryngeal paralysis represents a significant cause of exercise intolerance and poor performance in horses, yet the condition encompasses several distinct aetiologies requiring different clinical approaches. Dixon and colleagues examined 375 referred cases across an 13-year period to characterise the prevalence, breed predisposition, clinical presentation and underlying causes of laryngeal dysfunction. Recurrent laryngeal neuropathy (RLN) accounted for 94% of cases, predominantly affecting Thoroughbreds and Thoroughbred-crosses (85% combined) with a striking left-sided predominance (96%), whilst non-idiopathic paralysis proved far more common in ponies—notably bilateral cases secondary to hepatic encephalopathy or post-anaesthetic complications. Despite abnormal respiratory noise occurring in 90% of RLN horses, only 64% demonstrated clinically obvious reduced exercise tolerance at presentation, suggesting that many were referred based on resting or mild exercise signs before performance deterioration became severe. The substantial proportion of cases with concurrent upper and lower respiratory disease (17% overall) highlights the importance of comprehensive upper and lower airway evaluation in performance horses presenting with exercise-related respiratory dysfunction, rather than attributing all signs to laryngeal pathology alone.
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Practical Takeaways
- •RLN presents predominantly as left-sided paralysis in Thoroughbreds and performance horses; suspect this diagnosis in athletic horses with exercise-induced respiratory noise even if exercise intolerance has not yet developed
- •Bilateral laryngeal paralysis is rare in RLN but common in ponies with non-idiopathic causes—investigate hepatic disease and consider anaesthetic complications in these cases
- •Intercurrent respiratory disease affects 40% of RLN cases, so always perform complete upper and lower airway assessment rather than assuming a single diagnosis explains clinical signs
Key Findings
- •94% of 375 laryngeal paralysis cases were recurrent laryngeal neuropathy (RLN), with 96% left-sided unilateral presentation at median grade 4 severity
- •Thoroughbreds and Thoroughbred-crosses comprised 85% of RLN cases; ponies represented only 1% of RLN but 92% of bilateral paralysis cases
- •Abnormal exercise-related respiratory sounds occurred in 90% of RLN cases, but reduced exercise tolerance was reported in only 64%, with many horses referred before full exercise assessment
- •Non-idiopathic laryngeal paralysis (6% of cases) included 12 bilateral cases associated with hepatic encephalopathy (7 cases) or post-anaesthesia (2 cases), and 12 acquired unilateral cases with 7 caused by guttural pouch mycosis