Laryngeal paralysis is a pathology that affects the upper respiratory tract in which the laryngeal cartilages do not open (abduct) correctly during inspiration. It can have a congenital or acquired origin and, in turn, can be unilateral or bilateral. In animals that remain asymptomatic, no treatment is necessary. However, in those patients in whom the disease produces respiratory insufficiency that compromises the quality of life and well-being of the animal, it is necessary to carry out an adequate surgical treatment.
If you want to know more about laryngeal paralysis in dogs, keep reading the following article on our site where we explain what its symptoms, causes and treatment.
What is laryngeal paralysis in dogs?
Laryngeal paralysis is an obstructive disorder of the upper airways in which the arytenoid cartilages of the larynx do not open (abduct) correctly during inspiration, 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 rhyme glottis (opening of the larynx) narrows during inspiration, increasing inspiratory effort.
Depending on the affected muscles, we find the following types of laryngeal paralysis in dogs:
- If only the dorsal cricoarytenoid muscle on one side of the larynx is affected (unilateral), we speak of laryngeal hemiplegia.
- If the muscles on both sides of the larynx are affected (bilateral) we speak of complete paralysis.
It should be noted that laryngeal paralysis is one of the alterations that can form part of the brachycephalic syndrome, being present in 30% of dogs suffering from this syndrome.
Symptoms of laryngeal paralysis in dogs
The clinical signs that can be found in dogs with laryngeal paralysis are:
- Laryngeal stridor: Abnormal breath sound that occurs during inspiration. As the rima glottis narrows, resistance to the passage of air increases and turbulence is generated, which causes laryngeal stridor.
- Exercise intolerance: in some cases, syncope may occur.
- Dysphagia: difficulty swallowing. Coughing fits are common during intake of food or water. In some animals, aspiration pneumonia can occur due to the passage of food into the respiratory tract.
- Alteration of phonation: variations can be detected with respect to the usual barking, and can reach aphonia in some cases.
- Inspiratory dyspnea: respiratory distress that affects only the inspiratory phase of breathing.
- Tachypnea: increased respiratory rate.
- Cyanosis: bluish discoloration of the mucous 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 phonation variation (39%).
It should be noted that the symptoms can be aggravated by intense physical exercise, stressful situations or environments with high temperatures and humidity.
Causes of laryngeal paralysis in dogs
Laryngeal paralysis can be of two types:
- Congenital: when dogs are born with this pathology.
- Acquired: when dogs develop this pathology throughout their lives as a result of very diverse causes.
Congenital laryngeal paralysis
Appears in breeds such as the Siberian Husky, Rottweiler, Cattle Dog, Bull Terrier, and Dalmatian. In some cases, the existence of an autosomal dominant gene has been shown to be responsible for the heritability of this disease.
Dogs with congenital laryngeal paralysis present this alteration from birth, although the signs associated with it do not usually appear until they are 5 -8 months old.
Acquired laryngeal paralysis
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 that can cause acquired laryngeal paralysis in dogs are very varied:
- Traumatisms (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 must be taken into account that in most cases the cause that triggers the paralysis is not known, but in many cases it is a pathology idiopathic, that is, of unknown origin.
Diagnosis of laryngeal paralysis in dogs
The diagnosis of laryngeal paralysis in dogs should be based on the following points:
- Physical examination, paying special attention to the neurological examination in order to evaluate possible myopathies or neuropathies. Neurological examination will look for signs such as weakness or paresis, decreased spinal reflexes, or muscle atrophy.
- Laryngoscopy (endoscopy at the level of the larynx) to observe that during inspiration there is no opening (abduction) of the cartilage arytenoids of the larynx. In addition, a lack of tone in the vocal cords and an alteration of the adjacent tissues, with edema and erythema, can be observed. Laryngoscopy should be done under light sedation, since, in case of deep sedation, the reflexes of the larynx will be annulled and a false positive will be diagnosed.
- Chest x-rays 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.
Treatment for laryngeal paralysis in dogs
Unilateral hemiplegia or paralysis are not usually treated, since they do not normally compromise the life of the animal. However, in case of complete or bilateral paralysis, a surgical treatment should be resorted to, since animals usually present 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 ones:
- Unilateral or bilateral lateralization of the arytenoid cartilage or “tie back”.
- Ventriculo-cordectomy.
- Partial laryngectomy.
All of them are intended to enlarge the rhyme of the glottis (laryngeal opening) to facilitate the passage of air. The opening must be sufficient to favor the passage of air, but not excessive, as it could increase the risk of aspiration pneumonia. Therefore, more aggressive surgical techniques should be ruled out. Currently, the technique of choice is unilateral lateralization of the arytenoid cartilage using low-tension sutures. Both ventriculocordectomy and partial laryngectomy produce inconsistent results with a high rate of complications, making them less recommended techniques.
Postoperative care
After laryngeal paralysis surgery, the following care must be taken into account:
- It is important to achieve gentle anesthetic recovery to avoid patient agitation. In addition, in the immediate postoperative period it is a priority to guarantee the correct oxygenation of the patient.
- Corticosteroid treatment will be instituted 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 correctly, wet feeding After two weeks, dry food can be offered. In case dry feed is not tolerated (cough appears, dysphagia, etc.), moist food will be kept for another two weeks. If you follow a homemade diet, it will be equally important to offer it as bland as possible, as well as 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 harnesses instead of a 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 due to excessive manipulation. To avoid this complication, corticosteroid therapy is usually started in the postoperative period.
- Minor complications: continued cough or stridor, exercise intolerance, vomiting or seromas.
- Major complications: aspiration pneumonia (the risk is greater during the first days after the operation, although it remains throughout life, since the greater opening of the larynx can favor the passage of food to the respiratory tract).
Forecast
Although post-surgical complications are quite frequent, most are not serious and the short and medium-term prognosis is favourableIn fact, nearly 90% of caregivers of dogs with laryngeal paralysis notice 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.
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. Therefore, 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, preventing acquired laryngeal paralysis is much more difficult On the one hand, because many of the causes that produce it (neoplasms, polyneuropathies, polymyositis) cannot be prevented and, on the other hand, because in most cases the pathology is idiopathic, that is, it has an unknown origin.
