Most people who have been around horses long enough have heard a few make abnormal respiratory noises while exercising. These horses usually draw attention to themselves by the sheer volume of noise they create as they go around the show jumping course or trot and canter around the show ring. Other times, the noise is more subtle and the rider will complain about a horse which just runs out of energy and tends to stop. In other horses, the noise isn’t loud until the rider asks the horse for more collection and bending at the poll. All of these horses have one thing in common–laryngeal hemiplegia.

In this article, we will explain the condition laryngeal hemiplegia (otherwise known as roaring), what the known causes are, how a diagnosis is made, and what the treatment options are for horses with this disorder. Although there are other abnormal conditions of the horse’s upper airway that can cause respiratory noise, laryngeal hemiplegia is one of the more common disorders.

A Normal Larynx

Before we begin a description of this abnormal condition, you must have an understanding of the normal larynx. We will confine this description to the anatomy pertaining to laryngeal hemiplegia.

The larynx of the horse is a structure composed of cartilage and muscle tissue, and it makes the transition between the pharynx (food tube) and trachea (windpipe) of the horse. The larynx serves a multitude of very important functions in the horse. During exercise, its cartilages (sometimes called flappers) open as wide as possible to allow a greater amount of air to enter the trachea and reach the lungs. These arytenoid cartilages ar