Laryngeal hemiplegia is an upper respiratory disease in horses which affects their larynx. It is characterized by the collapse of the arytenoid cartilage and vocal fold into the rima glottis which causes an obstruction. Usually it is the left side which is affected but it can sometimes affect the right side or both sides.
Horses will generally show no symptoms at rest or during light exercise except on occasion may cough while eating. Once the horse increases work intensity is when symptoms of exercise intolerance and respiratory noise become apparent.