By Matthew Kearns, DVM
During this hot weather I am always concerned with heat stroke and predisposing factors: heat, humidity, and underlying disease.
One condition that is a risk factor for heatstroke is laryngeal paralysis. The larynx, or voicebox, is not only essential for communication but also plays a protective role in preventing aspiration. When food or water gets caught in the back of the throat the larynx snaps shut and the body stimulates a cough to clear the food/liquid to prevent aspiration.
The larynx also helps control body temperature. When a dog starts to overheat, they pant to release heat and reduce body temperature. The larynx aids in this function by dilating to allow more air to pass. If the entrance to the larynx is no longer able to dilate, the dog cannot control body temperature and is at risk for heat stroke.
The most common cause of laryngeal paralysis is considered idiopathic degeneration of the recurrent laryngeal nerve. “Idiopathic” is a medical term for “we don’t know.” We know there is a cause but just do not have the diagnostic test to identify it. The recurrent largyngeal nerve atrophies and signals to the muscles of the larynx no longer transmit. Trauma to the neck and neoplasia (tumors/cancer) are also causes. Hypothyroidism has been linked to laryngeal paralysis.
Large to giant breed dogs are more at-risk including Labrador Retrievers, Golden Retrievers, St. Bernards, Bouvier des Flandres, Bull Terriers, Rottweilers, Huskies, Malamute and many others.
Symptoms of laryngeal paralysis early on are subtle and include a change in the pitch of the dog’s bark and intermittent coughing when eating or drinking. Later symptoms include stridor and difficulty breathing. Stridor is also described as “roaring” where rather than just panting, one hears a harsher, coarser sound.
Diagnosis of laryngeal paralysis is made by direct examination of the larynx while breathing. This involves a very light plane of anesthesia. Other diagnostics like bloodwork and imaging (x-rays, etc) of the neck are also indicated to rule out secondary disease processes.
Surgery is the treatment of choice for laryngeal paralysis. The procedure is called a crico-arytenoid laryngoplasty where one side of the larynx is permanently sutured open. Most dogs do very well after surgery. However, the surgery does increase the risk of aspiration. A change in lifestyle (how and what your dog is fed) is indicated. The use of a medication called doxepin (Sinaquen®) has shown improvement of laryngeal function in some cases but no controlled study has been performed to confirm its efficacy.
Laryngeal paralysis is not a death sentence but diagnosis of this condition and intervention early on is key. Stay cool everyone.
Dr. Kearns practices veterinary medicine from his Port Jefferson office and is pictured with his son Matthew and his dog Jasmine. Have a question for the vet? Email it to [email protected] and see his answer in an upcoming column.