Laryngeal paralysis is the failure of abduction of both arytenoid cartilages.  It leads to dyspnea to the point of suffocation, along with a miserable quality of life.  Sadly, few owners perceive it that way until the disease is very advanced. 

Two forms

Congenital laryngeal paralysis is rare, and mostly reported in Dalmatians, Huskies, Bouvier des Flandres, and bull terriers.  Clinical signs usually present before 1 year of age.

Acquired laryngeal paralysis is much more common, and mostly seen in Labrador and Golden retrievers, Saint Bernards, and Irish Setters.  FYI I have seen a significant number of Greyhounds...  The median age of affected animals is 9 years of age.

Etiology of acquired lar par is most often idiopathic, and rarely traumatic, neoplastic or iatrogenic.

Presenting signs for congenital and acquired forms are (logically) exactly the same.

Interestingly, male dogs are affected 2-3 times more often than females.

The bad news

Recent evidence suggests that (some?) dogs with idiopathic lar par may have an underlying chronic progressive polyneuropathy.  In one study (Stanley et al, Vet Surgery 2010), 10 of 32 dogs with idiopathic lar par had generalized neurologic signs at the time of presentation. All dogs showed hind leg weakness (not to be thought to be a disc hernia!) more than one year after surgery. 

Another study showed that lar par dogs had or will have megaesophagus.  This is the reason why every client should be quizzed very carefully about a history of vomiting vs. regurgitation.

Based on the information we have, we have not observed this commonly in our patient population.

Clinical signs

Presenting signs may be acute or chronic.  They include exercise intolerance, inspiratory stridor, excessive inspiratory effort, loss of or change in phonation, coughing (mainly after eating or drinking), cyanosis, and at worst, collapse.

These signs worsen with obesity, exercise, excitement, and high temperatures.  And car rides.

In cats, the most common clinical sign is tachypnea or dyspnea.

Thoracic X-rays (while awake or sedated, never under anesthesia) are taken to rule out other causes of dyspnea, detect underlying etiologies, and look for concurrent pathology such as aspiration pneumonia and megaesophagus.

Diagnosis

Laryngeal paralysis is diagnosed by performing a laryngeal exam under sedation.  Propofol is one of the very few drugs of choice.  The patient should be sedated to the magic point at which the mouth can be easily opened but a laryngeal reflex is still present.

In normal patients, arytenoid cartilages and vocal folds should abduct during inspiration and relax during expiration.

In patients with laryngeal paralysis, one and/or both arytenoid cartilages and vocal folds are immobile and drawn toward midline during inspiration.   Edema and erythema of the arytenoid cartilage mucosa are typically present in the dorsal larynx.

Diagnostic trick

What to do if the patient holds his/her breath?  You can give doxapram as a quick bolus. Within 3 seconds, the patient should start to take deep breaths.  It's quite fascinating.

The dose is 1 mg/lb, but FYI we are currently trying to use 1 ml only and so far it seems to work.

Treatment

Surgery is the treatment of choice for patients with overt clinical signs or a decreased quality of life.  The purpose of laryngeal surgery is to decrease airway resistance.  There are multiple options, but only one is widely accepted: the "tie back" i.e. opening up the left or right arytenoid cartilage with 2 nylon sutures.

Preferred medications to be administered preoperatively include:

Acepromazine (0.5 mg/kg IV), butorphanol (0.2 mg/kg IV), atropine
(0.02 mg/kg IV), metoclopramide (0.2 mg/kg subcutaneously),
dexamethasone-SP (0.5 mg/kg IV), and cefazolin (10 mg/kg IV)

A recent paper (von Pfeil DJ et al.) describing a less invasive surgical approach for the "tie back" procedure and same day admission, surgery and discharge revealed a 95% success rate in those patients.  So don't be fooled that these cases can't be performed in your hospital and sent home that evening. They actually do better according to the most recent literature.

Complications

The long term outcome after surgical treatment is generally good to excellent, but patients are at risk for aspiration pneumonia their entire lives. To be fair, they are also at risk BEFORE surgery.

Other complications include persistent cough, vomiting/regurgitating, increased respiratory stridor, exercise intolerance, and surgical failure from suture breakage or arytenoid cartilage fragmentation.

The good news

Success rates for unilateral arytenoid lateralization is about 95%.  A recent report suggests those patients treated on an outpatient surgery routine tend to do recover better and have less complications (arrive and go home same day as surgery is performed).  See: Less invasive unilateral arytenoid lateralization: a modified technique for treatment of idiopathic laryngeal paralysis in dogs: technique description and outcome.

Bottom line

* Lar par is not a death sentence!

* Owners of lar par patients are some of the happiest and most faithful clients.

* If you meet an older Lab with dyspnea, think lar par - until proven otherwise.

If you'd like to give a handout or a link to clients, here is one option:

http://www.pethealthnetwork.com/dog-health/dog-diseases-conditions-a-z/laryngeal-paralysis-not-a-death-sentence (there is only 1 part)

If you have any question or doubt about a patient, feel free to call me.

See you in the OR.