The larynx is the opening to the trachea at the back of the throat. During normal breathing it opens when a dog breathes in and closes when they swallow. Laryngeal paralysis (LP) is failure of the larynx to open when the pet breathes in. Other features of the problem include:
- The failure to open occurs in degrees, ranging from slight to severe, and the symptoms correspondingly range from slightly harsh breathing to suffocation.
- LP is a degenerative, progressive problem; it gets worse with time. Most of our patients but a more rapid decline is possible, as is a sudden, complete collapse. The rate at which a pets problem will progress is not predictable.
- Symptoms of LP usually start in old age.
In our experience, almost every case of LP is an idiopathic (unknown cause) polyneuropathy (problem affecting multiple nerves, not just the ones to the larynx). Other possible causes include:
- immune-mediated disease
- hypothyroidism (low thyroid hormone levels)
- injury to the larynx
- cancer of the larynx
- congenital diseases
- myasthenia gravis
Four important problems can occur along with laryngeal paralysis:
- Aspiration pneumonia: inhalation of food and/or fluid into the lungs.
- Laryngeal collapse: weakened by the prolonged physical stress of LP, the larynx can collapse in on itself. It is sometimes difficult for us to determine if a case of LP has progressed to laryngeal collapse. We are very careful to try to make this distinction during diagnostic testing for LP, because the surgical procedures available for LP (discussed below) will not usually help laryngeal collapse.
- Megaesophagus: an enlarged esophagus that has lost the ability to effectively move food and drink from the mouth to the stomach.
- General weakness and lameness: Most cases of LP are a polyneuropathy, a nerve problem affecting more than just the larynx. Signs of weakness usually appear within a year after the signs of laryngeal paralysis are first noted, beginning with the back legs and eventually progressing to involve the front legs.
Dogs with LP will have one or more of the following symptoms:
- Harsh-sounding breathing
- Decreased tolerance for exercise and hot, humid weather (dogs cool themselves by panting,and, even though they might be panting more with LP, they are not panting as effectively)
- Change in voice
- Gagging or coughing, especially with eating and/or drinking
- General muscle weakness
- Extreme respiratory distress, fainting, and sudden death (these signs are rare, but do occur)
A dog's history and physical exam allow us to make a strong but tentative diagnosis of LP. However, other problems can have the same symptoms as LP, LP has several different possible causes, and there can be one or more related problems occuring simultaneously with LP. Diagnostic testing in addition to the physical exam
A patient's history and physical exam allow often allow us to make a tentative diagnosis of laryngeal paralysis. Observation of the pet's larynx while they are under a light level of general anesthesia is needed to confirm the diagnosis of LP, and, at the same time, rule out other possible causes of the pet's symptoms.
At YVC we provide the most careful and thorough version of this testing, because we are uniquely equipped with endoscopes that allow us to image the larynx and examine the trachea and esophagus as well.
Diagnostic tests in addition to laryngoscopy are important in order to:
- Uncover the specific cause of LP, in patients that do not have the idiopathic form
- Diagnose illnesses that are occuring simultaneously with LP
- Diagnose complications of LP, in particular aspiration pneumonia
Tests we recommend in addition to laryngoscopy include:
- General laboratory screening blood tests, including cbc, blood profile, urinalysis, and thyroid level
- X-rays of the chest and neck
- Occasionally specific blood tests for tick-borne diseases and myasthenia gravis
Treatment options are medical and surgical therapy. Because the patient is usually an older pet, and because the signs are usually very gradually progressive, many of the owners we work with choose to pursue medical therapy first and surgical therapy if the signs are worsening and the concern of a possible emergency situation is high.
MEDICAL THERAPY Except in uncommon cases when a particular cause for LP can be determined, such as low thyroid hormone levels, medical therapy will not cure LP. It is still very helpful to pursue though, because it can significantly improve a patient’s quality of life and help to prevent a respiratory crisis.
Medical therapy options that we consider most important are:
- weight loss and maintenance at a lean weight
- avoidance of high-stress activities and high temperature and humidity situations (these factors must be considered relative to the patient's LP: an activity or environment that a dog without LP can easily tolerate might provoke a respiratory crisis for an LP patient)
- oral cortisone for control of inflammation of the larynx
- oral tranquilizers for control of stress and distress
SURGERY We believe surgery is appropriate to consider whenever an LP patient’s quality of life has become unacceptable or when LP appears to be progressing so rapidly that there is concern about a respiratory crisis.
The decision on whether or not to pursue LP surgery is a difficult one. Some patients live excellent quality lives without surgery, some make quick and excellent recovery from surgery and their respiratory distress is relieved, but, on the other hand, the incidence of post-surgical complications is fairly high.
There are different types of surgery used for control of LP. The most common one in veterinary medicine today is a laryngeal tie-back. In this surgery part of the larynx is tied in a fixed position, permanently opening the airway. A less-commonly used surgery is ventriculocordectomy - removal of the vocal cords. We can perform either surgery at YVC. (Laryngeal tie-back $1400; Ventriculocordectomy $1200; prices subject to change)
Some recent veterinary studies compared the outcomes of laryngeal tie-back and ventriculocordectomy. The percentage of patients that developed aspiration pneumonia post-operatively was the same, or perhaps slightly less for the patients that had ventriculocordectomy. This does not mean this generally lesser-used procedure is the best one, but it is evidence that this alternative to the laryngeal tie-back may be a reasonable option. We believe it is important to consider the possible benefits and contraindications for each surgery for each individual pet that has LP.
Because of the complex nature LP, the possibility that a pet with LP might have additional significant health problems simultaneously, and the relatively (compared to most other veterinary surgeries) high incidence of pre- and post-surgical complications, we only offer LP surgery at YVC for pets for whom we have performed the preliminary diagnostic testing. We also only offer this surgery for pets whose owners live within a reasonable distance of YVC so that we, along with our local animal emergency clinics, are easily accessible for follow-up care.
SURGICAL COMPLICATIONS Regardless of which surgery is used, the patient’s ability to prevent food and water from going down the trachea (windpipe) to the lungs when swallowing is likely to be somewhat compromised following surgery. If some food and/or water gets into the lungs it creates a problem called aspiration pneumonia. Aspiration pneumonia produces signs that vary from mild to severe and occasionally it is life-threatening. Various veterinary studies have placed the incidence of aspiration pneumonia at 10% to 58% of patients that have LP surgery.
Other serious complications are possible, including death. Failure of the surgery to correct the problem is also possible.
Any of the complications, and failure of the surgery, can occur quickly or gradually, and can occur within hours, days, weeks, months or years of surgery.
As mentioned here earlier, patients with LP most likely have a polyneuropathy, and, usually within a year or less after the diagnosis of LP, the pet will have significant trouble with mobility, and possibly trouble swallowing or other signs of muscular weakness.
YARMOUTH VETERINARY CENTER