Laryngeal Paresis and Paralysis

Dogs

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Laryngeal paralysis is a dysfunction of the larynx, or voicebox. The larynx is located at the entrance to the trachea or windpipe and is covered by a movable, valve-like structure or flap called the epiglottis, which covers the windpipe when we swallow to prevent food from entering the trachea. The larynx itself also closes to prevent aspiration of food and water and acts to control airflow into the windpipe.

Laryngeal paresis (weakness) is caused by malfunction either of the muscles that move the two halves of the larynx into an open position, the nerves that control those muscles, or both. In laryngeal paresis/paralysis the larynx fails to open properly during inhaling, and this leads to airway obstruction.

Acquired idiopathic (unknown cause) laryngeal paralysis, the most common form of the disorder, occurs more commonly in middle aged or older, large breed dogs, such as Labrador retrievers, golden retrievers, and St. Bernards. Less commonly, the disease can occur secondary to injury to the larynx or laryngeal nerves, neuromuscular disease, or it may be congenital in some breeds.

If the disease is allowed to progress over time, the quality of the pet's life decreases because of the inability to inhale sufficient oxygen to permit even the simplest of activities. Fainting, severe respiratory distress, or death may result.

What to Watch For

  • Voice change
  • Gagging or coughing during eating or drinking
  • Exercise intolerance
  • Respiratory stridor or noisy breathing
  • Difficulty breathing (dyspnea)
  • Cyanosis (blue color due to lack of oxygen)
  • Fainting (syncope)

    Diagnosis

    Diagnostic tests are needed to recognize laryngeal paralysis and differentiate it from other causes of respiratory difficulty. These may include:

  • Physical examination, including auscultation of the chest with a stethoscope

  • Thoracic radiographs to rule out primary heart or lung disease

  • Thyroid gland function tests to rule out hypothyroidism (low levels of thyroid hormone).

  • Direct examination of the larynx. This is the definitive diagnosis and is made while the dog is breathing and under a light plane of general anesthesia.

    Treatment in mild cases

  • Mild cases may respond well to medical management which includes maintaining a healthy body weight and sedentary lifestyle, and avoiding stressful situations (such as exercise during hot, humid weather).

  • Occasionally oral sedatives or tranquilizers may be administered.

  • Avoid using a neck collar – use a harness instead.

    Treatment in moderate to severe cases

  • Dogs that have severe difficulty breathing are considered to be in a cyanotic crisis and must be stabilized initially with oxygen. Initial treatment also includes body cooling if the temperature is abnormally high, corticosteroids to reduce laryngeal swelling, and in very severe cases with a temporary tracheostomy, which is a quick surgical opening into the trachea to allow breathing.

  • Once stabilized, definitive surgical treatment is usually recommended. Procedures that may be performed include either removal of the part of the larynx that is obstructing the airway (a partial arytenoidectomy) or suturing part of the larynx in an open position out of the flow of the airway (arytenoid lateralization or"tie back").

    Home Care and Prevention

    Take your dog to the veterinarian as soon as the first signs of respiratory difficulty arise. If your veterinarian prescribes medical management, keep your dog from overly stressful situations, avoid excessively warm days outside, avoid letting your dog become overweight, and always use a harness-type leash instead of a neck collar. Watch your dog to make sure his condition does not worsen.

    If surgical management is prescribed, watch for potential complications after surgery such as:

  • Drainage, swelling, or redness of the incision
  • Recurrence of respiratory difficulty
  • Gagging or coughing during eating or drinking

    Because most cases of laryngeal paralysis are acquired later in life and have no known cause (idiopathic) prevention is not possible.

    • Surgical treatment is usually recommended and is performed through an incision in the neck.

    • The larynx can be visualized through the mouth.

    • In laryngeal paresis/paralysis the larynx fails to open properly during inspiration leading to airway obstruction. This larynx opens only partially.

    • Acquired idiopathic laryngeal paralysis, the most common form of the disorder, occurs more commonly in middle aged or older, large breed dogs, such as Labrador retrievers, golden retrievers, and St. Bernards.

    Laryngeal disease is just one of many causes of difficult breathing. Other causes of respiratory distress include:

  • Upper respiratory neoplasia. Tumors of the nasal cavity, pharynx, larynx, or trachea can cause respiratory difficulty as the air passage is partially obstructed by the mass.

  • Laryngeal collapse. A very severe, end-stage condition of the larynx caused by chronic increased inspiratory effort and subsequent weakening of the laryngeal cartilages that would normally hold the walls of the larynx out of the airway.

  • Cardiac disease. Ineffective pumping of oxygenated blood to the body because of a faulty heart can cause dyspnea and weakness.

  • Pulmonary disease. Ineffective oxygenation of the blood caused by lung disease can cause shortness of breath and dyspnea.

  • Tracheal collapse. Usually found in small dog breeds, tracheal collapse is caused by weakness of the cartilage rings that normally hold the trachea open during breathing leading to a severe "honking" cough and dyspnea.

  • Brachycephalic syndrome. A group of conditions that cause resistance to airflow through the upper respiratory tract in short-nosed dog breeds.

  • Hypothyroidism. An endocrine disorder in which insufficient thyroid hormone is secreted by the thyroid gland. It can be a cause of neuromuscular disorders and is sometimes found concurrently in dogs with laryngeal paralysis.

  • Veterinary care should include diagnostic tests and subsequent treatment recommendations.

    Diagnosis

    Diagnostic tests are needed to recognize laryngeal paralysis from other causes of respiratory difficulty, including:

  • A complete medical history and thorough physical examination. It is especially important that your veterinarian examine the chest with a stethoscope (auscultation) to listen for abnormalities in the lungs or irregularities in the heartbeat.

  • Thoracic radiographs also may be taken, particularly if auscultation of the chest was questionable or abnormal in order to confirm or refute cardiac or pulmonary causes of the respiratory difficulty.

  • Concurrent hypothyroidism can complicate the treatment and prognosis of a dog with laryngeal paralysis. Thyroid gland hormone levels and function tests may be done to rule out this condition.

  • In order to verify the presence of laryngeal paralysis, the dog must be lightly anesthetized and the veterinarian must watch the motion of the larynx while the dog breathes. The diagnosis is confirmed when the arytenoid cartilages of the larynx fail to abduct (move outward) when the dog inhales.

    Treatment

  • Although most cases of laryngeal paralysis are not diagnosed until the dog is brought to the veterinarian in a state of dyspnea, cases in the early stages of the disease with only mild clinical signs may respond well to conservative medical management. Conservative management is directed at preventing excessive respiratory effort that would require the dog to move air faster than the airways will allow.

  • Obesity makes it more difficult for the dog to move air in and out of his lungs due to compression on the diaphragm and chest wall. Excess fat in the tissues around the airways also impedes airflow through the airways. Obese dogs also have trouble ridding themselves of excess heat and are forced to pant more than usual. These all subsequently cause the dog to have an increased respiratory effort and exacerbate the problem.

  • Excessively stressful situations increase the tissues' oxygen demands and cause the dog to increase his respiratory effort. This is true of hot, humid weather, so they should be kept quiet in an air-conditioned environment whenever possible.

  • Some mild cases of laryngeal paralysis can benefit from the occasional use of oral sedatives when the dogs become overly excited. Acepromazine given orally is often used for this purpose.

  • A very important management technique to prevent difficult breathing is to avoid the use of a neck collar. When the dog pulls on the collar, it compresses part of the trachea, further exacerbating the airway obstruction. An over-the-shoulders-type harness should be used instead.

  • Because the disease tends to progress over time, it is essential to monitor the dog's condition closely for worsening symptoms that might indicate the need for surgical intervention.

  • Usually the first the veterinarian sees the dog is often during an episode of severe respiratory distress. Owners frequently do not recognize or consider that the early mild symptoms, such as voice change or noisy breathing, are significant enough to warrant a visit to the veterinarian. When they finally do visit the veterinarian, they must be stabilized before definitive therapy can be undertaken.

  • Supplemental oxygen therapy allows the dog to decrease his respiratory effort and treats cyanosis.

  • Dogs in respiratory distress can easily overheat, as they expend a great deal of energy breathing heavily and are unable to rid their bodies of excess heat by panting. If the animal is hyperthermic (body temperature greater than 105 degrees Fahrenheit) the dog will be cooled with a cool water or alcohol bath.

  • The larynx often becomes edematous or swollen in periods of dyspnea and can further obstruct the movement of air during breathing. The administration of corticosteroids can help reduce this swelling.

  • Very severe cases that do not respond to initial treatment may require a temporary tracheostomy to bypass the non-functional larynx. The tracheostomy is created under the neck and a plastic tube is placed through the opening to allow unobstructed flow of air and facilitate breathing.

    After the dog has been stabilized and the crisis situation is over, surgical treatment is recommended. There are several different surgeries that accomplish the same basic thing – to create a larger air passage through the larynx. The two most popular are:

  • Partial arytenoidectomy (also called partial laryngectomy). The dog is anesthetized and a temporary tracheostomy tube is placed if not already present. The larynx is visualized through the mouth and part of the arytenoid cartilage and vocal fold is removed from one side. The tracheostomy tube is removed one to two days after surgery and is allowed to heal on its own (it is not sutured closed).

  • Arytenoid lateralization ("tie back"). The dog is anesthetized and has a tube passed into the trachea in the normal fashion through the mouth. An incision is made on one side of the dog's neck and the arytenoid cartilage on that side is sutured in an open position.

  • Take your dog to the veterinarian as soon as the first signs of respiratory difficulty arise. Minor abnormalities such as change in the character of the dog's bark or loud breathing noises should be brought to the veterinarian's attention during the annual check-up if they are not causing difficulty breathing before then.

    Your veterinarian's recommendations for medical management should be followed closely to avoid respiratory crisis situations. If medical management is pursued, protect your dog from overly stressful situations, avoid excessively warm days outside, avoid letting your dog become overweight, and always use a harness-type leash instead of a neck collar. Watch for deterioration of clinical signs. If the dog becomes dyspneic or cyanotic, or collapses, visit your veterinarian immediately. Severe respiratory distress leads to periods of hypoxia (low oxygen in the blood) and can cause irreversible injury to the body.

    If surgical management is done, watch for potential complications after surgery. After partial arytenoidectomy, the tracheostomy site must be monitored until it is completely healed.

    After a surgical procedure, the dog must be monitored for recurrence of respiratory difficulty that could indicate failure of the surgery or aspiration pneumonia. Aspiration pneumonia is a relatively common complication of any surgical treatment for laryngeal paralysis because moving or removing part of the larynx out of the airway leaves the airway unprotected from food or vomit entering from the pharynx.

    Gagging or coughing during eating or drinking may occur during the recovery period as the animal accommodates to the permanently open larynx. Try different food types to find the one that minimizes these problems in your dog. If drinking water causes gagging, you may need to mix in with the food so it is easier to swallow.

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