What is Laryngeal Paralysis?
Laryngeal paralysis describes a failure of the larynx (also known as the voice box) to open the vocal cords during inspiration (breathing in).
The larynx is important for three main reasons; it opens the vocal cords during inspiration to allow air to enter the lungs, it closes the vocal cords during swallowing to prevent food and water from entering the lungs and it enables vocalisation.
What causes Laryngeal Paralysis?
Laryngeal paralysis is the result of a dysfunction in one or both nerves that innervate the larynx. These are called the recurrent laryngeal nerves and they supply the muscles that hold the laryngeal cartilages open during inspiration. Failure to open these vocal cords results in obstruction of the upper airway and difficulty breathing. The result is an overall loss of O2 to the body
Laryngeal paralysis may be congenital (present at birth) or acquired (develops throughout life).
Congenital laryngeal paralysis is due to degeneration of the laryngeal nerves. Acquired laryngeal paralysis is associated with chronic endocrine, infectious or immune mediated polyneuropathy. However, most commonly the underlying cause cannot be identified.
What breeds are predisposed to developing Laryngeal Paralysis?
Congenital laryngeal paralysis has been diagnosed in Bull Terriers, Dalmatians, Rottweilers, Pyrenean Mountain Dogs and Huskies.
Acquired laryngeal paralysis commonly occurs in Labrador Retrievers, Border Collies, Golden Retrievers, Saint Bernard’s and Irish Setters, at an average age of 9 years.
What clinical signs will my pet show?
The first signs you may see in your pet is a change in their voice, gagging and coughing. You may then notice that your pets endurance decreases, and they have an increased exercise intolerance. The progression of clinical signs is very slow, and many will be put down to signs of old age. Eventually your pet will have an increased inspiratory noise (loud rasping noise when your pet breathes in), and they may have some episodes of collapse and difficulty in swallowing food and water.
Fifty percent of dogs will develop hindlimb weakness or wobbliness.
As the condition worsens, your pet will have a decreased tolerance of hot temperatures as this condition decreases their ability to pant. They may suffer from sudden respiratory distress when subjected to a warm environment. This is a serious emergency as dogs will overheat rapidly
How is Laryngeal Paralysis diagnosed?
Your veterinary specialist will have a suspicion of laryngeal paralysis from the age and breed of the patient, and the clinical signs seen during consultation.
Definitive diagnosis requires careful examination of the larynx under a light plane of general anaesthesia. General anaesthesia in animals with laryngeal paralysis can be risky, particularly when they are recovering. For this reason if a definitive diagnosis is made, the animal is normally kept anaesthetised and surgery performed immediately under the same anaesthetic.
Thoracic radiographs may be performed to rule out any other causes of breathing difficulty, including tumours, and to look for concurrent disease such as aspiration pneumonia, pulmonary oedema or megaoesophagus. In addition blood samples including thyroid levels will be performed before surgery.
How is Laryngeal Paralysis treated?
Surgical treatment is indicated for animals with moderate to severe clinical signs. The surgery aims to decrease airway resistance by permanently fixing one of the patients cartilages of the larynx in such a position to stop further collapse. This is called a “tieback” procedure or Unilateral Arytenoid Lateralisation.
Dogs that are only mildly affected can occasionally be managed with weight loss, stress reduction, exercise restriction and a reduction in temperature.
What post-operative care is required?
Following surgery, your pet will be recovered from anaesthesia and surgery and under continuous monitoring until they go home.
They will not be allowed food for 12-24 hours following surgery to enable any swelling to begin to subside. Your pet will be offered small boluses of soft food to ensure that they are able to swallow correctly, before being offered any water. It is only once we are satisfied that your pet is able to swallow food and water correctly that they will be able to be discharged. This is usually only 1-2 days following surgery.
Long term, there will be a number of management changes that will make for a better outcome for your pet. This includes a harness rather than a collar. Avoiding dusty dry food, and instead feeding soft foods to prevent dust entering the airways. Avoiding heat stress is still imperative as there will be a degree of airway compromise remaining. Milk products need to avoided completely.
Antibiotics and anti-inflammatory medications are given for a short period post-surgery. Thyroid replacement medication will be dispensed if necessary.
What complications can occur?
Complications that can occur in a small number of cases include haemorrhage, airway swelling, infection, aspiration pneumonia, seroma formation (fluid accumulation in the neck tissue), suture failure or cartilage fracture.
This procedure greatly improves the airflow in an animal suffering from laryngeal paralysis, however the procedure will also decrease the patients ability to cough and increases the risk of food and water being aspirated. For this reason, the benefits and risks will be clearly discussed to you during consultation.
What is the prognosis?
The long term outcome for patients with laryngeal paralysis is generally excellent with 95% of patients having a dramatically improve their quality of life