Many racehorses and some other performance horses can develop a condition that critically decreases airflow during exercise. This condition is known as laryngeal hemiplegia and the horses are known as "roarers" because of the sound they make. Laryngeal hemiplegia is a condition caused by damage or degeneration of the laryngeal nerve.
The term laryngeal hemiplegia literally means paralysis of half of the larynx. The larynx is composed of structures that guard the airway: the larynx closes to prevent food entering the airway and opens to allow maximum airflow. With paralysis, the amount of oxygen horses can inhale during exercise is decreased. Affected horses are also usually exercise intolerant.
Laryngoplasty is a procedure utilized to restore the upper airway to a more normal size in a horse with laryngeal hemiplegia. It is also known as a "tieback" procedure as the paralyzed portion of the larynx is "tied back" out of the airway.
An additional procedure often performed is ventriculectomy, removing small sacs in the larynx that can also cause noise. The horse often stays in the hospital for 48 hours receiving antibiotics and pain relievers. Following this, the horse will be confined to a stall with walking for 8 weeks. Approximately 70% of race horses have improved performance after surgery, dressage horse may experience performance improvements over 70%.