What is the larynx?
The larynx is a complex structure composed of cartilage, muscle, and mucosa that connects the pharynx (the space behind the nasal and oral cavities) to the trachea (windpipe). It houses the glottis, a structure formed by the paired vocal cords and arytenoid cartilages which opens and closes in a coordinated fashion to allow air to move in and out of the windpipe with inhalation and exhalation and protects the airway during swallowing.
What is laryngeal paralysis?
Laryngeal paralysis is a disorder causing loss of function of the nerves that govern opening of the glottis during inspiration. When the glottis fails to fully open as a dog breathes in, airflow into the windpipe through this narrowed aperture is reduced, requiring the dog to breathe faster and harder to move a normal amount of air. This is commonly exacerbated by inflammation of the larynx that results from the generation of an increased pressure gradient and turbulent airflow. In addition, failure of the glottis to fully close when swallowing results in an increased risk of aspiration pneumonia.
What causes laryngeal paralysis?
Most cases of laryngeal paralysis are classified as idiopathic, meaning no underlying cause can be found. A small percentage of cases are congenital and appear to have a genetic basis. Trauma, cancer, and several neuromuscular diseases can also cause laryngeal paralysis.
Recent case studies have led to the conclusion that in most dogs with acquired idiopathic laryngeal paralysis, this is actually the earliest sign of a generalized neuromuscular disease, the characteristics of which have not yet been well-defined. A new term, geriatric onset laryngeal paralysis and polyneuropathy (GOLPP), has recently been developed to describe this condition. It is believed that most dogs) diagnosed with acquired laryngeal paralysis will eventually develop megaesophagus (a weak and stretched-out esophagus that fails to convey food and water effectively into the stomach) and generalized weakness.
Do certain dog breeds more commonly develop laryngeal paralysis?
Congenital laryngeal paralysis is usually evident by 6 months of age and is most commonly seen in the Siberian Husky, Bouvier de Flanders, Bull Terrier, Great Pyrenees, and Dalmation. Acquired (adult-onset) idiopathic laryngeal paralysis is most frequently encountered in large and giant breed dogs over 10 years old. Labrador Retrievers appear to be at particularly high risk for developing this condition.
What are the clinical signs of laryngeal paralysis in dogs and cats?
The clinical signs of laryngeal paralysis in dogs and cats can vary widely. Unfortunately, laryngeal paralysis is probably under-recognized and underdiagnosed. The hallmark of laryngeal paralysis is noisy breathing (called “stridor”) that worsens with excitement and physical activity. Many owners also notice a change to the pitch of their bark (dysphonia), as well as coughing and gagging when eating and drinking.
In severe cases a dog may suddenly develop respiratory distress, blue or lavender-colored gums (cyanosis), and may even collapse. If these signs are noted, it is essential to seek emergency veterinary attention.
How is laryngeal paralysis diagnosed?
A diagnosis is based on medical history and a laryngeal exam. Diagnostic tests needed to determine laryngeal paralysis that may be recommended include blood and urine tests and chest radiographs (X-rays).
How is laryngeal paralysis treated in dogs and cats?
Mild cases of laryngeal paralysis in dogs and cats can often be managed with medications and lifestyle changes. Anti-inflammatory medication helps to reduce secondary laryngeal swelling, while sedative and/or anti-anxiety medications are also helpful in reducing respiratory distress. Anecdotally, a tricyclic antidepressant called doxepin (brand name Sinequan®) has proven helpful in some cases; however, more studies are needed to prove its effectiveness. Lifestyle changes that are useful in managing laryngeal paralysis include limiting physical activity, avoiding highly stimulating or stressful situations, avoiding hot conditions, and using a chest harness rather than a collar around the neck.
In more severe cases, surgery is indicated. Patients with laryngeal paralysis are at a slightly increased risk of anesthetic complications. Surgical correction is usually successful at significantly reducing or eliminating clinical signs.
What does the surgery involve?
The most commonly-used surgical procedure for laryngeal paralysis is called the Arytenoid Lateralization Laryngoplasty, or “Laryngeal Tie-Back.” This surgery involves permanently securing one side of the glottis in a partially open position by suturing the edge of the arytenoid cartilage to the cartilage forming the wall of the larynx. While securing both sides of the glottis in the open position would further improve airflow, it significantly increases the risk of complications. For most patients, tying back just one side is sufficient to significantly alleviate symptoms while minimizing the risk of complications.
Surgery will often dramatically improve a dog’s quality of life with laryngeal paralysis but won’t restore laryngeal function to the dog. Your veterinarian will discuss any anesthetic concerns with surgery and the specific surgical technique needed prior to surgery. Canine and feline patients with laryngeal paralysis are at a slightly increased risk of anesthetic complications, but surgical correction is usually successful at significantly reducing or eliminating clinical signs of laryngeal paralysis in dogs and cats.
What are the possible complications of surgery?
In the immediate post-operative period, potential complications include airway swelling and breakdown of the lateralization. Airway swelling is usually minimal, and is easily controlled with anti-inflammatory medications. Breakdown of the repair can occur if too much stress is placed on it in the first few weeks after surgery. For this reason, it is particularly important to avoid moderate and intense physical activity and to minimize barking as much as possible for at least three weeks after surgery. Some dogs may require sedative and anti-anxiety medications during this period. Coughing is also commonly encountered in the first couple of weeks after surgery, but usually goes away as the healing process progresses.
The most common and serious long-term complication of both laryngeal paralysis and laryngeal tie back surgery is aspiration pneumonia. About one in four patients who have had a laryngeal tie back surgery will develop aspiration pneumonia at some point. This results from the inability of the glottis to fully close when swallowing, which can result in small amounts of food and water entering the windpipe and contaminating the lungs. The abnormal esophageal function present in many of these patients further increases their risk of aspiration pneumonia. Precautions that can reduce the risk of aspiration include feeding several small meals of canned food throughout the day, preventing rapid drinking of large volumes of water, and avoiding swimming.
What is the prognosis?
The prognosis for dogs following laryngeal tie back surgery is generally very good. While laryngeal paralysis appears to be the earliest manifestation of a more generalized neuromuscular condition, this disease appears to be very slow to advance, and many dogs will reach their full natural lifespan before significant progression occurs.
Although it is important to remain vigilant for signs of aspiration pneumonia and take precautions to reduce this risk, most dogs who do develop aspiration pneumonia respond well to treatment. In a small percentage of cases, particularly those with concurrent megaesophagus, recurrent or particularly severe aspiration pneumonia may occur. The prognosis for these patients is much more guarded, and sometimes euthanasia becomes the only option.
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