Laryngeal paralysis results when the muscles of the larynx fail to abduct or open the arytenoid cartilages during inspiration and signs of upper airway obstruction occur. This is characterized by loud breathing and panting resulting from difficulty with movement of air. Some patients have complete paralysis and others may have paresis or partial paralysis of the arytenoid cartilage. It may be bilateral or unilateral: however, since clinical signs are usually absent in unilateral paralysis, bilateral paralysis is typically observed. Older, large breed animals are more commonly affected, but it has been reported in small dogs and cats and as congenital disease in Bouvier des Flanders, Dalmatians, Siberian Huskies, (Husky cross breeds), Bull Terriers, and Rottweilers.
WHAT CAUSES THIS?
Many cases are usually idiopathic, meaning the cause is unknown, but other causes should be ruled out which include: injury to the recurrent laryngeal nerve from trauma to the cervical or neck region, mass lesions or tumors in the neck and mediastinum (chest area), and generalized polyneuropathies/neuromuscular disease. Although most are idiopathic, it is felt that many are associated with a more generalized neuromuscular problem. This may be manifested as weakness in the legs, and perhaps a megaesophagus problem whereby the esophageal motility is abnormal and the esophagus is more dilated. Hypothyroidism may or may not contribute to the disease.
WHAT ARE THE CLINICAL SIGNS?
Clinical signs are related to upper airway obstruction, which includes: stridor (noisy breathing), respiratory distress, exercise intolerance, and a change in bark. A chronic cough or gag may be seen and regurgitation with aspiration pneumonia can occur with patients having concurrent laryngeal paralysis and megaesophagus. The signs vary depending on the severity of the problem and are often gradual in onset over months to years.
HOW IS THIS DIAGNOSED?
Definitive diagnosis is determined by visualization of the inability of the arytenoids cartilages to equally abduct or open during inspiration or cough during a LIGHT plane of anesthesia. The patient should maintain the gag and cough reflex when making this conclusion or the risk of too deep of anesthesia may result in an inaccurate diagnosis of laryngeal paralysis. Laryngoscopy is not the only diagnostic which should be performed. Other diagnostic tests include: 1.) adequate palpation throughout the cervical and laryngeal areas looking for masses, 2.) cervical and thoracic radiographs looking for masses, aspiration pneumonia, mega esophagus, or other cardiac and pulmonary changes, 3.) CBC, chemistry panel, and urinalysis for determining any underlying metabolic abnormalities and advisability for general anesthesia, 4.) neurologic exam looking for other related generalized neuromuscular diseases, 5.) and possible additional laboratory and diagnostic tests such as a thyroid stimulation test, blood tests to screen for myasthenia gravis, and an esophagram may be performed if indicated to confirm megaesophagus.
HOW CAN THIS BE TREATED?
The goal of treating laryngeal paralysis is to alleviate signs of upper airway obstruction while minimizing complications allowing the patient to breathe more comfortably and return to a level of normal activity for their age. This goal can be achieved through surgery on the larynx (laryngoplasty). Laryngoplasty has been performed with a variety of surgical methods. These include partial arytenoidectomy (removal of a portion of the airway opening), ventriculochordectomy (remove the vocal folds), modified castellated laryngofissure (widening the larynx), and arytenoid lateralization or “tie back”. Arytenoid lateralization is where sutures are placed in the larynx to mimic or replace the nonfunctional muscle which normally opens the airway resulting in a permanent widened opening.
ARYTENOID LATERALIZATION “TIE-BACK”
This technique utilizes the placement of two monofilament nonabsorbable sutures in the same location as the nonfunctional cricoarytenoideus dorsalis muscle, from the muscular process of the arytenoid cartilage to the caudal portion of the cricoid cartilage. The approach is usually on the left side for surgeon’s consistency and the incision is about 8 cm long caudal to the angle of the mandible or lower jaw. Either during surgery or immediately after surgery the patient is extubated and the opening of the airway is visualized for acceptable width of opening. “Bigger is not always better”.
WHAT KIND OF POST OPERATIVE CARE IS REQUIRED?
Continuous monitoring post operatively is important. Food and water is withheld for 12-24 hours and intravenous fluids are maintained. Pre and post operative antibiotics are given. Sometimes steroids may be given preoperatively to control swelling. Additionally drugs that control nausea and decrease the risk of vomiting or regurgitation are given. The difficulty in breathing or stridor is alleviated immediately and the patient can often go home the same day or the following day.
WHAT IS THE PROGNOSIS WITH THIS SURGERY?
Owners report the disappearance of abnormal respiratory signs and that attitude and activity levels are much improved. Most patients tolerate canned moist food the best for minimizing aspiration pneumonia (not liquid food). Some patients will also tolerate dry food. Finding the correct consistency of the food that is tolerated the best is recommended. Aspiration pneumonia can occur at any time. The pneumonia is often treatable. The problematic cases of pneumonia are those with underlying megaesophagus. The combined problem warrants concern and the prognosis decreases. Owners should be advised on the possibilities of slow progression of generalized neuromuscular disease. The owners should be advised that by performing this surgery, the sound of the bark will change, as if they had been debarked. This is due to the wider opening of the airway. The literature reports that approximately 25% of the patients will have bouts of aspiration pneumonia. In my clinical experience reviewing the last 25 cases that we have performed this surgery on, 3 owners have reported bouts of aspiration pneumonia, all treatable and one case had megaesophagus and one patient had an obvious generalized neuromuscular disease affecting the strength of walking. In our caseload experience, we see approximately a 90% success rate (without concurrent megaesophagus) and owners are pleased that they made this choice for their pet.
HOME DISCHARGE INSTRUCTION SHEET (EXAMPLE)
When a patient has laryngeal paralysis, the airway does not open well and this causes patients to have difficulty breathing and it will sometimes cause life threatening overheating in certain conditions. After this type of surgery, I would recommend that we limit activity to no running jumping or no exertional activity for 4-6 weeks. This allows for some fibrosis or healing at the site to occur. Post surgery the left arytenoid is abducted adequately. We should understand that a normal larynx will close when a pet drinks and eats to prevent food and water particles from going into the airway. With this surgery, the airway is held open on one side. The risks are aspiration pneumonia and breakdown of the repair. These patients when drinking will hack a little because water trickles into the airway. Additionally, dry food can crumble and do the same therefore, I would recommend a softer meatball size food be provided where the patient can swallow and not chew so much on the dry food, risking pieces to fall into airway. Over time, it seems as though they improve with the function and less hacking occurs. Keep the water bowl at the ground level so when drinking, gravity helps prevent water from trickling down the airway. Food bowls should be kept at ground level too. Most of our patients will have a noticeable improvement and increased activity levels after the surgery with a good acceptable result.
No food tonight. Start feeding in the morning. No swimming, at least for the first 6 weeks. Some dogs have swum with success; however, the risk is that water will go into the airway. No neck leads or collars should be used for the first 4-6 weeks, use a chest harness.
Send home on 10-14 days of cephalosporin and oral pain meds such as tramadol for 3-5 days and Rimadyl for 3-5 days. Staple removal in 10-14 days