Laryngeal Paralysis in Dogs
By Dr. Beth Guerra
The larynx is the opening to the trachea, and is flanked by two flaps known as arytenoid cartilages. When an animal inhales, these cartilage flaps should abduct, or pull away from each other, to open the airway. They should also close tightly during swallowing to prevent food or fluids from being aspirated into the lungs. Laryngeal paralysis, or ‘lar par’ as it commonly called in veterinary circles, is characterized by failure of these flaps to move during inspiration and leads to upper respiratory obstruction. Affected animals often have loud stridor, or constricted, noisy breathing, as they try to pull air past the obstruction. Coughing, gagging, retching, or change in voice can also occur. The condition can be exacerbated by exercise, heat, obesity, or excitement. In severe cases, dogs present with cyanosis (blue color to the gums/tongue) from lack of oxygen and often collapse during activity. In these cases, emergency care is essential.
The exact origin of laryngeal paralysis is often not determined but can be caused by dysfunction of the nerves innervating the larynx, degeneration of laryngeal muscles, or by stiffening of the cartilage folds. Certain breeds are prone to congenital laryngeal paralysis and include Bouvier des Flandres, Huskies, bull terriers, and Dalmatians, however, this condition is commonly seen in middle aged to older, large breed dogs. Trauma, neurological diseases such as Myasthenia gravis or polyneuropathy can also lead to laryngeal paralysis.
Dogs suspected to have laryngeal paralysis should be examined under light sedation or general anesthesia so that the arytenoids cartilage movement can be observed during breathing. In general, one or both sides can be affected, and examination shows cartilages that fail to abduct, or open away from each other, during normal inspiration. Bloodwork or X-rays of the neck and chest may also be recommended to further investigate any other underlying causes.
In the case of severely affected animals, immediate sedation is often required to allow intubation of the airway. The arytenoids cartilages can be observed during this time, and the veterinarian can also make sure there are no other causes of upper airway obstruction such as masses or foreign objects blocking the airw ay. These dogs usually benefit from low level sedation or anesthesia for 30-60 minutes with the tracheal tube in place to improve oxygenation and allow inflammation of the tissues around the larynx to subside. Occasionally low dose steroids are given, and the patient is allowed to recover slowly from anesthesia.
Several surgical options exist, but the most common is referred to as a ‘tie back’ surgery, where one of the arytenoids folds is secured in an open position. This serves to keep the airway open and avoid respiratory crises, however, these patients are at an increased risk for aspiration pneumonia. Soft food is often introduced in small amounts, and exercise should be restricted for about eight weeks. These dogs can have some post-operative coughing and a hoarse bark. Studies have shown that about 90% of these dogs have excellent long-term results.
(Below: Picture of the Larynx with laryngeal paralysis and some swelling.)