To understand laryngeal paralysis, it’s first necessary to understand the anatomy of the larynx itself. Commonly known as the voice box, the larynx consists of two main parts – the vocal cords and the cartilages. The vocal cords allow vocalization, while the cartilages, stabilized by the surrounding muscles, provide the semi-flexible structure of the larynx. The arytenoid cartilages form the structural “doors” of the larynx, with the glottis serving as the opening through which air passes from the mouth, through the larynx, into the windpipe, and then into the lungs.
There are two sets of muscles that attach to the arytenoid cartilages to control the larynx – one set to open the “doors” and the other set to close them. The epiglottis is a flap or valve that covers the larynx during the act swallowing to help prevent food or water from traveling down the windpipe. When the nerves of the muscles that support the larynx cartilages become weak or paralyzed, the muscles relax and the cartilages tend to collapse inwards. Certain respiratory and neurologic disorders can cause paralysis of these muscles, preventing the cartilages from opening and closing. This condition is known as laryngeal paralysis.
Some causes of the condition include trauma to the throat or neck; tumors or space-occupying lesions in the neck or chest area; and endocrine or hormonal diseases such as hypothyroidism. Some dogs are born with congenital laryngeal paralysis. The nerve paralysis rapidly leads to laryngeal muscle wasting, which can also be congenital and is most commonly seen in Bouvier des Flandres, Siberian Huskies, and Dalmatians. This problem does not commonly affect cats.
In the majority of cases of laryngeal paralysis, the cause is unknown, and affects older large breed dogs more than other pets. Idiopathic laryngeal paralysis (ILP) is an insidiously progressive disease with a high death rate, in which affected pets develop signs of upper airway obstruction, often resulting in severe difficulty breathing. Recent studies at Michigan State University suggest that many older dogs diagnosed with ILP are in fact suffering from chronic, progressive, and widespread neurological disease (polyneuropathy), in which case the more accurate diagnosis is Geriatric Onset Laryngeal Paralysis Polyneuropathy:
GOLPP is most commonly seen in older, large breed dogs and typically has a slow, subtle, progressive onset with chronic history. Historical complaints mimic ILP and can include noisy and/or difficult breathing; change or loss in bark; coughing and/or gagging (especially when eating or drinking); and intolerance of exercise and heat. Some dogs will present in acute respiratory distress or suffering from severe heat exhaustion. Neurologic dysfunction is exhibited as regurgitation, abnormal body positions or movements resulting from problems with normal perception, problems coordinating voluntary muscle movements, hindlimb weakness, and muscle atrophy. Neurologic dysfunction is often overlooked as it may be misinterpreted in an older pet as weakness from lack of oxygen or orthopedic conditions.
Laryngeal paralysis is most commonly seen in older large breed dogs, although small breed dogs and cats can also be affected. Symptoms of laryngeal paralysis are related to the failure of the vocal cords to properly pull apart from each other during breathing, making the opening of the airway smaller than usual. This means that your pet is not able to get as much air into the lungs as is needed.
Historical complaints of idiopathic laryngeal paralysis can include noisy and/or difficulty breathing; change or loss in voice; some coughing; and/or gagging (especially when eating or drinking), as well as exercise and heat intolerance. More severe signs include continued coughing/gagging, vomiting, and sometimes a near inability to breathe.
Although laryngeal paralysis usually develops slowly over time, the symptoms may come on suddenly. The signs of laryngeal paralysis are easier to detect in hot, humid weather and include exercise intolerance; difficulty inhaling; and raspy or noisy breathing sounds. In severe cases, exercise or excitement may cause a dog’s tongue or gums to develop a blue or gray color due to a lack of oxygen. Collapse and subsequent death may occur if the problem is untreated. Cats may initially display signs of hoarse purring, which may progress to exercise intolerance. Occasionally, laryngeal paralysis is only one sign of GOLPP, but often it is a problem that occurs by itself.
Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from laryngeal paralysis or another serious condition, a veterinary specialist is available at an ExpertVet certified or affiliated hospital.