Laryngeal paralysis is a condition that affects the upper respiratory tract in dogs. When it occurs, the laryngeal cartilages do not open (abduct) properly during inspiration. It can be due to congenital or acquired causes, as well as unilateral or bilateral. Some dogs may have the problem, but remain asymptomatic. In these cases, no treatment is required. However, there is a risk of respiratory failure in some cases that will require appropriate treatment, usually in the form of surgical intervention.
At Glòries Veterinary Hospital, we closely observe laryngeal paralysis in dogs. Read on to learn about its causes, symptoms, and treatment, as well as which breeds are most likely to be affected by the condition.
What is laryngeal paralysis in dogs?
Laryngeal paralysis is an obstructive disorder of the upper respiratory tract. Within this tract are the arytenoid cartilages of the larynx. These cartilages must abduct (open) to let in air and adduct (closer together) to keep it there, before abducting again to complete breathing. Laryngeal paralysis prevents these processes from occurring due to a loss of innervation of the dorsal cricoarytenoid muscle.
The dorsal cricoarytenoid muscle is responsible for the movement of the larynx. When the innervation of this muscle is lost, its contraction is inhibited and it atrophies. Consequently, the arytenoid cartilages of the larynx do not open properly and the glottis rhyme (opening of the larynx) narrows during inspiration, increasing the inspiratory effort.
Depending on the muscles affected, we find the following types of laryngeal paralysis in dogs:
- Laryngeal hemiplegia: in the case that only the dorsal cricoarytenoid muscle is affected on one side of the larynx (unilateral).
- Complete paralysis: when the muscles on both sides of the larynx (bilateral) are affected.
It should be noted that laryngeal paralysis is one of the common conditions in dogs with brachycephalic syndrome. It has been recorded that it is present in 30% of dogs that suffer from this problem.
Symptoms of laryngeal paralysis in dogs
The clinical signs that we can find in dogs with laryngeal paralysis are:
- Laryngeal stridor: abnormal breathing sound that occurs during inspiration. As the glottis rhyme narrows, the resistance to the passage of air increases and turbulence is generated that causes laryngeal stridor.
- Exercise intolerance: In some cases, syncope (fainting in dogs) can occur.
- Dysphagia: difficulty swallowing. Coughing fits are common during food or water intake. In some animals, cases of aspiration pneumonia occur due to the passage of food into the respiratory tract.
- Vocalization alteration: variations can be detected in contrast to their usual barking. It can cause aphonia in some cases.
- Inspiratory dyspnea: respiratory distress that affects only the inspiratory phase of respiration.
- Tachypnea: increased respiratory rate.
- Cyanosis: bluish discoloration of the mucous membranes due to insufficient oxygenation of the blood.
Causes of laryngeal paralysis in dogs
Laryngeal paralysis can be of two types:
- Congenital: when dogs are born with this pathology due to genetic inheritance.
- Acquired: when dogs develop this pathology throughout their lives as a consequence of various causes.
Congenital laryngeal paralysis
It appears in breeds such as the Siberian Husky, the Rottweiler, the Flandres Mountain Dog, the Bull Terrier and the Dalmatian. In some cases, the existence of an autosomal dominant gene responsible for the heritability of this disease has been found. Dogs with congenital laryngeal paralysis present this alteration from birth, although the signs associated with it do not usually appear until 5-8 months of age.
Acquired laryngeal paralysis
It appears in breeds such as the Labrador Retriever, the Golden Retriever, the Saint Bernard or the Irish Setter. It is more common than the congenital form of the disease.
The causes of acquired laryngeal paralysis in dogs are varied:
- Trauma (bites, wounds, foreign bodies, surgeries) that affect the recurrent laryngeal nerve.
- Recurrent laryngeal nerve compression due to thyroid neoplasms, masses, or abscesses in the neck or mediastinum.
- Polymyositis or myasthenia gravis.
- Polyneuropathies of metabolic, toxic, or infectious origin
- Immune-mediated causes.
However, it should be noted that in most cases the cause that triggers the paralysis is unknown. This means that many of the cases of laryngeal paralysis in dogs are idiopathic.
Diagnosis of laryngeal paralysis in dogs
The diagnosis of laryngeal paralysis in dogs should be based on the following tests and evaluations:
- Physical examination: paying special attention to the neurological examination to evaluate possible myopathies or neuropathies. The neurological exam will look for signs such as paresis (weakness in movement), decreased spinal reflexes, or muscle atrophy.
- Laryngoscopy: This is a type of endoscopy that examines the larynx. It is used to observe that during inspiration there is no opening (abduction) of the arytenoid cartilages of the larynx. A lack of tone can be observed in the vocal cords and an alteration of the adjacent tissues, with edema and erythema. Laryngoscopy should be performed under light sedation. If the dog is under heavy sedation, the laryngeal reflexes will be canceled and a false positive will be diagnosed.
- Chest X-rays: These are used to detect other muscle abnormalities (such as megaesophagus), mediastinal or intrathoracic masses, and aspiration pneumonia.
- Blood test with thyroid profile: it is important to rule out that the cause of the paralysis is hypothyroidism, since in these cases the treatment does not reverse the paralysis. In addition, specific laboratory tests can be performed to detect generalized neuromuscular diseases or myasthenia gravis.
Treatment for laryngeal paralysis in dogs
Unilateral hemiplegia or paralysis is rarely treated, as it is not normally life-threatening for the animal. However, in cases of complete or bilateral paralysis, surgical treatment is almost always required. With the latter, animals often have moderate to severe respiratory failure that greatly compromises their quality of life and well-being.
Currently, there are multiple surgical techniques to treat laryngeal paralysis in dogs. These are the three most important:
- Unilateral or bilateral lateralization of the arytenoid cartilage (tie back).
- Partial laryngectomy.
All of them are intended to enlarge the glottis rhyme (laryngeal opening) to facilitate the passage of air. The opening should be large enough to allow air to pass through, but not excessive, as it could increase the risk of aspiration pneumonia. Therefore, the most aggressive surgical techniques should be ruled out. Currently, the technique of choice is unilateral lateralization of the arytenoid cartilage with low tension sutures. Both ventriculo-cordectomy and partial laryngectomy produce inconsistent results with a high complication rate and are therefore less recommended.
After surgery for laryngeal paralysis, the following care guidelines should be considered:
- Overriding any agitation of the patient assists in anesthetic recovery. Oxygen may be required during the immediate postoperative period.
- Corticosteroid treatment will be started to reduce the risk of edema and swelling of the larynx.
- After 24 hours, a small amount of water should be offered to the animal. If the patient tolerates it well, wet feeding can be started. After two weeks, dry food can be offered. If dry feed is not tolerated (cough, dysphagia, etc.), the feed will remain moist for another two weeks. If you follow a homemade diet, it will be equally important to make it as bland as possible, as well as to opt for easily digestible foods.
- Physical exercise should be restricted for 3 weeks, although improvement in respiratory failure is usually immediate.
- During walks it is preferable to use a harness instead of a collar.
How to prevent laryngeal paralysis in dogs?
In the case of congenital laryngeal paralysis, it has been shown that in some breeds there is an autosomal dominant gene that is responsible for the heritability of this disease. As a preventive measure, dogs born with this pathology should be prevented from reproducing to prevent the disease from being transmitted to their offspring.
However, prevention of acquired laryngeal paralysis is much more difficult. Due to its many possible causes, many of which are idiopathic, we cannot specifically prevent it. Instead, we must do everything we can to make sure our dog is healthy and happy. This means providing basic care needs, observing possible symptoms, and ensuring that we provide regular veterinary check-ups.