Laryngeal Paralysis in Dogs - Causes & Treatment

Laryngeal paralysis consists of an obstructive disorder of the upper respiratory tract. Within this tract are the arytenoid cartilages of the larynx. These cartilages should go through abduction (open apart) to let air in and adduction (closer together) to hold it there, before abducting again to complete respiration. Laryngeal paralysis prevents these processes from happening due to a loss of innervation of the dorsal cricoarytenoid muscle.

The dorsal cricoarytenoid muscle is responsible for 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 rima glottis (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 event that only the dorsal cricoarytenoid muscle on one side of the larynx (unilateral) is affected.
• 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 conditions common to dogs with brachycephalic syndrome. It has been recorded as being present in 30% of dogs that suffer from this problem.

The clinical signs that we can find in dogs with laryngeal paralysis are:

• Laryngeal stridor: abnormal breathing sound that occurs during inspiration. As the rima glottis narrows, the resistance to the passage of air increases and turbulence is generated, which causes laryngeal stridor.
• Exercise intolerance: in some cases, syncope (fainting in dogs) can occur.
• Dysphagia: difficulty swallowing. Coughing spells 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.
• Alteration of vocalization: variations can be detected in contrast to their usual barking. It can lead to 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 mucus membranes due to insufficient oxygenation of the blood.

The most frequent clinical sign is laryngeal stridor (present in 97% of cases), followed by exercise intolerance (87%), dysphagia (41%) and variation in phonation (39%). It should be noted that the symptoms can be aggravated by intense physical exercise, stressful situations or environments with high temperatures and humidity.

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 diverse causes.

Congenital laryngeal paralysis

It appears in breeds such as the Siberian Husky, the Rottweiler, the Bouvier des Flandres, 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) affecting the recurrent laryngeal nerve.
• Recurrent laryngeal nerve compression due to thyroid neoplasms, masses, or abscesses in the neck or mediastinum.
• Hypothyroidism
• Polymyositis or myasthenia gravis
  
• Polyneuropathies of metabolic, toxic or infectious origin
• Immune-mediated causes

However, it should be taken into account that in most cases the cause that triggers the paralysis is unknown. These means many of the cases of laryngeal paralysis in dogs are idiopathic.

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 in order to evaluate possible myopathies or neuropathies. The neurological examination will look for signs such as paresis (weakness in movement), decreased spinal reflexes or muscle atrophy.
• Laryngoscopy: this is a type endoscopy which 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 done 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: used to check for 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 may be performed to detect generalized neuromuscular diseases or myasthenia gravis.

It is important to know that the handling of these dogs in the veterinary clinic must be especially careful, since stressful situations can trigger a cyanotic crisis.

Unilateral hemiplegia or paralysis are not usually treated, since they are not normally life-threatening for the animal. However, in the event 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. Here are the three most important:

• Unilateral or bilateral lateralization of the arytenoid cartilage (tie back)
• Ventricle-cordectomy
• Partial laryngectomy

All of them are intended to enlarge the rima glottis (laryngeal opening) to facilitate the passage of air. The opening should be sufficient to allow the passage of air, but not excessive, as it could increase the risk of aspiration pneumonia. For this reason, 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 ventricle-cordectomy and partial laryngectomy produce inconsistent results with a high rate of complications, which is why they are less recommended.

Postoperative care

After surgery for laryngeal paralysis, the following care guidelines should be taken into account:

• Voiding any agitation of the patient aids anesthetic recovery. Oxygen may be required during the immediate postoperative period.
• Corticosteroid treatment will be started to reduce the risk of edema and inflammation 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 begin. After two weeks, dry food can be offered. If the dry feed is not tolerated (coughing, dysphagia, etc.), the feed will be kept 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 opting 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 collar.

Postoperative complications

In the postoperative period of laryngeal paralysis surgery in dogs, it is important to attend to the appearance of possible complications, since they occur in almost 35% of cases. The main complications are:

• Laryngeal edema from excessive manipulation: to avoid this complication, corticosteroid therapy is usually established in the postoperative period.
• Minor complications: continued cough or stridor, exercise intolerance, vomiting, or seromas.
• Major complications: the risk of aspiration pneumonia is greater during the first days after the operation, although it persists throughout life. This is due to the larger opening of the larynx which can cause food to enter the respiratory tract.

Prognosis after laryngeal paralysis surgery

Despite the fact that postoperative complications are relatively frequent, most are not serious and the prognosis in the short and medium term is favorable. In fact, almost 90% of caregivers of dogs suffering from laryngeal paralysis notice a marked clinical improvement in their companion after surgery.

However, it should be taken into account that the presence of other concomitant pathologies (neoplasms, megaesophagus, polyneuropathies, etc.) worsens the prognosis of these patients.

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 prevent it specifically. Instead, we need to do all we can to ensure our dog is healthy and happy. This means providing basic care needs, observing for possible symptoms and ensuring we provide regular veterinary checkups.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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