What is laryngeal paralysis?

The larynx, often referred to as the ‘voice box’ in people, is made up of several separate cartilages.  Its main functions include:

• Open the vocal folds when breathing in (inspiration)
• Closing the vocal folds when eating and drinking to prevent food and water entering the trachea
• allowing vocalisation such as barking 

The muscles controlling the larynx are supplied by one of the longest nerves in the body - the recurrent laryngeal nerve, which is a branch of the vagus nerve.  This nerve leaves the brain, travels down the neck to wrap around the heart before passing back up the neck to the larynx.  Damage to any part of this nerve supply can result in paralysis of the larynx, and the vocal folds can then no longer abduct (open) in response to respiratory demands during exercise or excitement. 

What causes laryngeal paralysis?

Most cases of laryngeal paralysis occur later in life (acquired cases), however a small number of cases are congenital, meaning the changes are present from birth.  Most acquired cases are seen in middle to old aged larger breed dogs as the result of declining nerve function, however the condition can also occur due to:

• Trauma to the neck causing damage to the recurrent laryngeal nerve
• Tumours of the neck or chest, putting pressure on the recurrent laryngeal nerve
• Hormonal imbalances; an underactive thyroid gland (hypothyroidism) which isn’t properly controlled can result in a peripheral neuropathy, and can cause reduced function of the recurrent laryngeal nerve

Laryngeal paralysis is more common in certain breeds, including Labradors, Golden Retrievers, Irish Setters and Saint Bernards. It can also occur in cats, however this is much less common.      

What are the signs of laryngeal paralysis?

The clinical signs of laryngeal paralysis often appear gradually, and as such they can often be attributed to ‘old age’ changes. Signs include:

• Reduced exercise tolerance
• Increased inspiratory noise
• Coughing
• Changes in their bark
• Problems swallowing food and water
• Sudden respiratory distress, particularly in hot weather or when excited
• Collapse

Whilst many patients are asymptomatic when calm and resting, exercise or excitement can result in an acute deterioration with subsequent severe respiratory distress which can rapidly become life threatening. 

How is laryngeal paralysis diagnosed?

A large number of cases can be diagnosed based on the clinical examination and history, however further investigation is always required to confirm this diagnosis and to rule out underlying causes.

 Definitive diagnosis requires laryngoscopy – examination of the vocal folds under light anaesthesia. CT imaging of the head and thorax is performed to check for the presence of tumours, pneumonia and megaoesophagus (enlarged food pipe) which, if present, may later the prognosis following surgery  Recovery from anaesthesia with laryngeal paralysis carries a higher risk, and as such we always endeavour to proceed with surgery under the same anaesthetic. 

How is laryngeal paralysis treated?

Definitive management of laryngeal paralysis requires surgical intervention to perform a ‘Tie Back’ procedure which permanently secures one of the vocal folds in an open position. This greatly improves the airflow through the larynx of patients and as such results in a better quality of life. 

Whilst successful surgery results in a great clinical improvement in the vast majority of patients, a small number of patients can experience complications post-operatively. These include:

• Seroma formation; a non-painful build up of fluid under the skin which rarely requires treatment
• Suture failure or cartilage fracture; this results in failure of the procedure, and in some cases the procedure needs to be repeated on the other side
• Aspiration pneumonia; passage of food or liquid through the open larynx can result in infection of the lungs. This can occur at any point following surgery. 

What happens after surgery?

Patients will often take time to learn how to swallow after surgery and so need to be closely monitored during this time.  In many cases this will take a few days, however in some cases it may take several weeks, during which the patient needs to be carefully hand fed ‘meatballs’ of dog food which tend to be better tolerated than biscuits.

Post-operatively there are a number of changes which can be made at home to increase the chances of ongoing success following surgery:

• Always use a harness for walking, never a neck collar
• Avoid very dry, dusty food which can easily be inhaled
• Avoid very strenuous exercise and hot weather