by Barry B. Burtis D.V.M.
The larynx or voicebox, as it is more commonly known, is a very important structure in all mammals. It regulates airflow to and from the trachea or windpipe, is responsible for voice production and prevents the inhalation of food. Those are some very important tasks and if the larynx fails to work properly serious problems will result. Failure of the larynx to function normally is usually the result of a malfunction of the muscles and/or the nerve supply of the larynx. The result of such problems causes a paralysis of the larynx. Laryngeal paralysis can occur in both dogs and cats. Sometimes animals are born with the disorder, sometimes it develops later in life.
Congenital (present from birth) laryngeal paralysis has been reported in Bouvier des Flandres, bull terriers, Dalmatians, Rottweillers and huskies. However, in general practice, it is more common to see the acquired (later in life development) form of the disease. Labrador retrievers, golden retrievers, St. Bernards and Irish setters are the most commonly affected breeds. Usually dogs who develop laryngeal paralysis are nine years of age or older. It has also been reported in cats.
In most cases, no specific cause can be found for the failure of laryngeal function. However, traumas in the neck area or certain diseases that cause nerve and muscle failure in the body sometimes are identified as a reason for the dysfunction.
The earliest signs in an affected pet that would be noticed by an owner include a change in voice and a developing gag or cough especially during eating or drinking. Progression of signs is often slow; months to years may pass before an animal develops severe breathing distress. Gradually the pet's endurance decreases and air intake becomes more difficult, causing much noisier breathing efforts. Episodes of breathing difficulty, cyanosis and collapse occur in severely affected patients. Male dogs are approximately three times more likely to be affected by the problem than females.
Confirmation of a diagnosis of laryngeal paralysis is often rather difficult. A general physical examination, by a veterinarian, will often reveal nothing remarkably changed, at least early in the course of the problem. Laboratory blood tests, unless an under active thyroid is involved, are usually within normal limits. X-rays of the larynx usually show no changes from normal. An examination of the larynx under general anesthesia is required for the diagnosis. When laryngeal function is evaluated at a light or shallow level of anesthesia, changes in the normal movement of the larynx can be detected.
Often animals with laryngeal paralysis are taken to a veterinarian having suffered collapse and cyanosis as the result of an obstruction of their upper airway caused by the malfunctioning larynx. Emergency medical care that includes the use of drugs to reduce the edema and swelling that can develop in the larynx is required to resolve the crisis. Medical therapy in patients affected in this way is usually successful. Occasionally, a tracheostomy to bypass the obstruction is necessary.
Surgical management, in the long term, is the treatment of choice. Laryngeal surgery is directed at removing or repositioning laryngeal cartilage in the malfunctioning larynx. This is certainly necessary for patients who develop these more serious effects of the disease. In most cases, this surgery would be done at a referral hospital by a board certified specialist in veterinary surgery or someone very experienced in respiratory surgery. With successful surgery, the prognosis for the patient is good to excellent.