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ASG Specialties:

  • Hip Dysplasia
  • Patella Luxation
  • Medial Patella Luxation
  • Elbow Dysplasia
  • Fragmented Coronoid Process
  • OCD Osteochondritis Dissecans Fractures
  • Arthritis
  • Ruptured Cruciate Ligament
  • Ruptured Cranial Cruciate Ligament
  • Ruptured Anterior Cruciate Ligament


Canine Laryngeal Paralysis

Canine Laryngeal Paralysis, ASG, Los Angeles, CA

Canine laryngeal paralysis results from dysfunction of the muscles that open the airway during breathing and close it during swallowing, and can be acquired or hereditary. When severe, laryngeal paralysis may be life threatening and lead to collapse and death. Signs tend to be slowly progressive and worsen during the warmer months of the year.

by Yonatan Buks, BVSc
Surgery Resident
and Adam Strom, DVM, MS
Diplomate American College of Veterinary Surgeons


Overview:

Canine laryngeal paralysis is a common cause for upper airway obstruction in older dogs. It results from dysfunction of the muscles that open the airway during breathing and close it during swallowing. This leads to narrowing of the upper airway, and the gateway to the lower airway. The larynx is made of many muscles and series of cartilages, and is the organ guarding the tracheal (windpipe) entrance. It is responsible for protecting the airway during swallowing, controlling airway resistance, and voice production.

Laryngeal paralysis may be acquired or hereditary. The hereditary form affects young dogs, up to six months of age and has been reported in Bouvier des Flanders, Dalmatians, Siberian huskies, Rottweilers, Leonbergers and Bullterriers. The acquired form may be secondary to neoplasia (cancer), trauma, infection or surgical complication. This form has no associated breed predisposition but is commonly described as idiopathic (of unknown cause) in which Labrador retrievers are over represented. Prevalence of laryngeal paralysis increases with age as well as the severity of clinical signs. An association between laryngeal paralysis and canine hypothyroidism has been suspected, but has yet to be proven and may be coincidental.

While once believed to be an isolated entity, there is strong evidence that laryngeal paralysis is an important manifestation of a peripheral neuropathy (generalized neurologic disease affecting the long peripheral nerves in the body). The recurrent laryngeal nerve supplies the abductor muscles of the larynx and is one of the longest nerves in the dog’s body, and is therefore affected early. Other long nerves supplying the hind limbs degenerate concurrently and hind limb paresis (weakness) is commonly seen in many dogs affected by laryngeal paralysis. On a microscopic level, loss of nerve fibers and nerve fiber degeneration are seen. Laryngeal paralysis may be unilateral or bilateral, but clinical signs are commonly associated with the latter.

Clinical signs:

Clinical signs include increased upper respiratory noise (stridor), which worsens with excitement or increased ambient temperatures, exercise intolerance, respiratory distress, change of voice, cough or gag, and fever. When severe, laryngeal paralysis may be life threatening and lead to collapse and death. Signs tend to be slowly progressive and worsen during the warmer months of the year.
Laryngeal paralysis is diagnosed by direct visualization of the larynx during sedated laryngeal examination. Lack of abduction of the arytenoid cartilages (a pair of cartilage flaps acting as the gateway to the windpipe) is diagnostic. Chest radiographs are commonly performed to rule out other potential causes for the observed clinical signs and as a screening tool for concurrent diseases such as aspiration pneumonia.

Dogs may collapse and develop acute cyanosis (blue discoloration of the gums due to decreased oxygenation), and they may require intensive emergency treatment including oxygen supplementation, intravenous fluids, active cooling, sedation and anti-inflammatory steroids to decrease laryngeal swelling. On the other hand, dogs with minimal clinical signs that are asymptomatic at rest, may be managed conservatively using a combination of exercise restriction (short walks outside in the cooler hours of the day), avoiding stress with aid of sedatives, and caloric restriction/weight loss diet. As the disease progresses, clinical signs are likely to worsen.

Treatment:

Surgery is the treatment of choice for dogs with moderate to severe clinical signs and ones with decreased quality of life due to the disease. The goal of surgery is to decrease airway resistance, and there are several different techniques to do so. The most commonly performed technique is unilateral arytenoid lateralization, also known as “tie-back,” which yields the most consistent results. In this procedure, the arytenoid cartilage on one side (commonly the left) is permanently tied in abduction to open the laryngeal lumen and reduce upper airway resistance. The surgical approach is made through the side of the neck and dogs typically remain hospitalized for one to two days post-operatively.

Complications:

The most common complication from this surgery is, by far, aspiration pneumonia. Aspiration pneumonia results from food, water, saliva or other substances getting inhaled into the lungs through the permanent opening. Most dogs will cough with eating or drinking for a number of weeks to months after surgery, and this may persist for life. However, not all coughing episodes result in aspiration pneumonia. When a large amount of material, especially acidic material such as that from bringing up food or water from the stomach, reaches the lungs, the inflammatory process begins. This inflammation is very prone to becoming infected, and pneumonia can spread into the lungs. Dogs with aspiration pneumonia often need to be hospitalized and placed on IV antibiotics. Most of these dogs are treated successfully, but it can still be fatal. Other less common complications include bleeding during surgery, infection of the incision, and break down of the tie back, allowing the arytenoid cartilage to drop back into the airway.

Prognosis:

Although the complications can be serious, most dogs undergoing this procedure do very well. Many of these patients are already older and near the end of their natural lives, and studies reflect this. The majority of cases where dogs have passed away or been euthanized were due to reasons unrelated to airway disease.

Animal Specialty Group


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