Laryngeal paralysis is a condition which affects the voice box (larynx). The voice box is found at the back of the throat connected to the top of the windpipe. One of the many functions of the voice box is to open wider when dogs are breathing (to maximise air flow into the lungs) and to close when they are swallowing (to protect the lungs from saliva and ingested items). Laryngeal paralysis is a condition where the voice box cannot open and close normally.
Causes of Laryngeal paralysis
There are many causes of laryngeal paralysis. They can broadly be categorised into congenital or acquired. Congenital laryngeal paralysis is very uncommon, it means the dog was born with laryngeal paralysis and this affects very specific breeds such as Huskies and Bouvier de Flanders (amongst others).
Acquired means laryngeal paralysis has occurred secondary to another problem. These other problems vary in cause but include: trauma (e.g. bites) damaging nerves which control the larynx, tumours either in the neck or in the cheek which either compress or grow into the nerves supplying the larynx, altering the function of the nerves, or even hormonal causes such as an underactive thyroid gland. In fact, the most common form of acquired laryngeal paralysis secondary to a progressive and generalised nerve dysfunction (termed degenerative polyneuropathy). This is thought to be an age-related change and can affect more nerves in the body but causes problems in the larynx first as the nerves that control the larynx happen to be amongst the longest in the body so anything that slows transmission of signals down these long nerves has a more noticeable effect than in shorter nerves.
Signs of Laryngeal paralysis
Laryngeal paralysis is most commonly seen in larger breed dogs but occasionally is seen in smaller dogs and even cats on rare occasions. Most often the signs of laryngeal paralysis are very slow and gradual in onset and so it is common for people not to notice these signs. As it is most commonly a condition associated with older dogs these signs are sometimes attributed to old age, concurrent ailments (e.g. arthritis or heart problems) or just “slowing down”. Not all signs are always seen but common signs include a change in bark, gagging when eating, coughing and exercise intolerance (reluctance to go for long walks, struggling to keep up on walks, tiring on walks very quickly). Dogs will also often have much noisier breathing which may be more laboured than usual, especially when breathing in. All of these are often worse in hot weather as panting which is a dog’s main way of controlling temperature (they cannot sweat like us!) is impaired by the larynx not opening properly, reducing airflow in and out of the lungs. It is important to understand that although these signs are slow and progressive in nature, dogs can also have sudden deterioration and can rapidly have acute life-threatening signs (such as collapse, heat stroke or marked difficulty in breathing). This typically happens in either hot weather or following periods of excitement and or exercise.
Diagnosis of laryngeal paralysis
A specialist surgeon will often have a good idea of the diagnosis from the sound and pattern of a dog’s breathing when assessed in conjunction with recent history from the owner and a thorough examination. Further tests are usually advised to assess for any underlying conditions which could be causing the laryngeal paralysis – such as blood tests to rule out hormone imbalances and X-rays or scans to exclude tumours and look for signs of pneumonia (more about this below). Often an examination to assess other nerves in the body is performed, as on some occasions other nerves can also be affected by the age-related dysfunction (that is the most common cause of laryngeal paralysis) either at the time of diagnosis or indeed in the future.
Ultimately a diagnosis can only be made by visualisation of the larynx while under a very light anaesthetic. Please be aware it is necessary for a specialist surgeon to repeat this even if your local vet has performed this already; as different medications, anaesthetic drugs/protocols and the experience of the assessor can affect the findings – it is particularly important to be absolutely confident of the diagnosis before surgery is advised.
If an underlying condition is present some form of treatment will be specifically directed to this. In most instances this is not the case. Surgery is usually recommended if dogs are clinically affected (i.e. having problems associated with laryngeal paralysis) as there are no effective medical treatments and this is a condition that will only progressively worsen with time.
There are many different surgical options for management. The most common procedure is referred to by many different names (e.g. unilateral arytenoid lateralisation or cricoarytenoid lateralisation) but most easily is called a “tie-back”. In this procedure a permanent stitch is placed in the larynx to hold one side of the larynx open, increasing the space for air flow into the windpipe and the lungs.
Overall more than 90% of dogs are markedly improved following surgery and approximately 70% will still be alive after five years – which is very encouraging given this condition is most commonly seen in old dogs.
Like all surgical procedures there are some risks associated with a tie-back procedure. In common with most surgical procedures bleeding, infection and post-operative swelling are possible but rare. Specific complications include failure of the stitch holding open the larynx, either due to the stitch breaking or fracture of the part of the larynx it is placed through. This is thankfully a very rare complication but important to appreciate as it results in a failure of the surgery. As this is a condition usually caused by dysfunction of the nerves, occasionally in the long-term other nerves can be affected, such as the nerves controlling the back legs leading to back leg weakness.
The most important aspect to appreciate is the possibility of aspiration pneumonia. This is pneumonia (an infection within the lungs) secondary to inhaled material. As the larynx is permanently held open following surgery, and often the dog’s coughing is not as effective as normal due to the underlying nerve dysfunction, there is an increased risk of material such as saliva or food being inhaled. In fact, it is not uncommon for dogs to have aspiration pneumonia at the time of diagnosis – due to the dysfunction associated with the larynx. This is one of the reasons for pre-operative X-rays as the short-term outcome for dogs with pre-operative aspiration pneumonia is not quite as good. The risk of aspiration pneumonia increases with time from surgery. If it should occur it is commonly mild and either self-limiting or managed with medication but it has the potential to be life threatening. Dogs should be monitored for coughing, lethargy and being off colour long term following surgery.
There are several things which can be done to minimise the risk of aspiration pneumonia and maximise the outcome. Following diagnosis dogs should be walked on a harness rather than neck collar. Heat should be avoided, and exercise managed sensibly – such as walking in the cool of evening and going at a relaxed pace for a sensible distance. Avoiding rapid eating or stress at feeding times is sensible as well as choosing and storing food in a dust free fashion to minimise the change of food inhalation.
Overall with appropriate care this is a disease that can be managed and the vast majority of dogs will go on to have a significantly improved quality of life.