Recurrent laryngeal neuropathy (RLN), also referred to commonly as roarers or laryngeal hemiplegia, is a common performance limiting neurological condition which results in reduced airflow to the horse's lungs. It leads to progressive exercise intolerance and a characteristic respiratory noise that sounds similar to "roaring" when exercised. RLN is most frequently seen in Thoroughbred race horses and large Draft horse breeds. It is usually seen in taller (over 15 hands) male horses.

The exact cause of the condition is unknown, however proposed theories include genetics or environmental (due to injury or stretching or squashing of the recurrent laryngeal nerve (which supplies nerves to the larynx). This nerve progressively weakens until it is destroyed. Usually the left side of the larynx is affected (in 95% of cases), where it is partially to completely paralyzed.

Roarers Treatment Options

Surgery is the only known treatment for horses with RLN. There are multiple surgical techniques used, with varying success rates and associated complications. Complications from these surgeries can result in poor performance themselves as they include aspiration pneumonia, lower airway diseases, and even euthanasia if the surgery is not successful.