by: Matthew O'Donnell, DVM, DACVS-SA
We are coming upon the time of year when people and dogs are spending more time outdoors. As the weather warms, this can lead to an increase in the number of episodes of dyspnea for patients with laryngeal paralysis. This condition is commonly acquired and is seen in older dogs (median age 9 years). Labrador retrievers, Golden retrievers, and Irish Setters. Male dogs are two to three times more likely to be affected.
Laryngeal paralysis is a manifestation of recurrent laryngeal nerve dysfunction. Terminal branches of this nerve are responsible for innervation and contraction of the cricoarytenoideus dorsalis muscle and abduction of the laryngeal cartilages. This effectively reduces the upper airway diameter and increases airway resistance.
Early clinical signs include dysphonia (change in bark) and a gagging or retching cough. The latter is often associated with eating or drinking but can often be heard at other times due to secretions in the upper airway. Some patients are intolerant of activity. More severe cases may present for dyspnea, cyanosis, and syncope. As the condition interrupts normal thermoregulation, severe cases can suffer concurrently from hyperthermia.
Laryngeal paralysis is often a component of a more diffuse degenerative polyneuropathy (geriatric onset laryngeal paralysis and polyneuropathy). Many, patients present with rear limb weakness and proprioceptive deficits that may be perceived by owners as age related or the result of degenerative joint disease. Some patients may have a history of difficulty swallowing or regurgitation that can be associated with megaesophagus.
When laryngeal paralysis is suspected, a neurologic exam should be performed to look for signs of polyneuropathy. Thoracic radiographs should be performed to assess for aspiration pneumonia and megaesophagus, both of which are contraindications for surgery. Thyroid levels should be checked, as laryngeal paralysis can be secondary to hypothyroidism. Definitive diagnosis is made on sedated laryngeal examination, which is often immediately prior to surgical intervention.
Mild cases can be treated conservatively, however owners should be warned that the condition is progressive and acute exacerbation may lead to a need for emergency intervention. Conservative management generally entails avoidance of warmer ambient temperatures, exuberant activity, and excitement that results in barking. For some dogs, treatment with sedatives (e.g., acepromazine, trazodone) can help to avoid acute episodes. The mainstays of treatment of acute episodes of upper airway obstruction include sedation (e.g., combination of butorphanol and acepromazine), oxygen administration, and treatment of hyperthermia. Dogs should be fed from an elevated platform and from bowls that encourage them to eat slowly. Some dogs require emergency surgical intervention.
Surgical treatment of laryngeal paralysis is arytenoid lateralization and is generally recommended for dogs that fail conservative management or for which a severe, acute episode is considered likely. Arytenoid lateralization is performed unilaterally, most commonly on the left side. Bilateral lateralization has shown no significant benefit in terms of reduction of airway resistance but has been associated with a higher incidence of postoperative aspiration pneumonia. Postoperative recovery at home is generally centered on minimizing excitement and after two weeks, most patients are ready to resume normal activities. Long term management is related to avoiding aspiration pneumonia and management of the generalized polyneuropathy. Dogs should be fed from elevated bowls and encouraged to eat slowly.
Prognosis for the relief of upper airway obstruction is good with surgical intervention, however if a polyneuropathy is present, owners should be warned that it will progress. The absence of signs of polyneuropathy at the time of diagnosis of laryngeal paralysis does not rule it out, as laryngeal paralysis is commonly an early manifestation. Physical rehabilitation may slow progression of a polyneuropathy. Avoidance of stairs and slick surfaces as well as the use of high friction paw-wear (i.e., booties, ToeGrips) can help with mobility. Generally, with a combination of medical and surgical management of laryngeal paralysis and palliative management of polyneuropathy, patients can have good outcomes.