Leonbeck Leonbergers
Last update 30 oct 2017
What Is LPN1 & LPN 2
Polyneuropathy Nando was diagnosed as being affected for the LPN1 gene back in November, 2010. In early 2011 he commenced an exercise programme designed to help him keep muscle tone at our local vets rehabilitation centre where he goes on the water treadmill each week. Below is the link which shows Nando showing signs of the characteristic high step gait and also him working hard on the water treadmill. Nando is 2 years old in these video's. To visit Nando's story Click here Laryngeal Paralysis in Leonbergers The Leonberger breed has sadly been shown to suffer from an inherited (poly)neuropathy (nerve disorder) in which nerves gradually degenerate and lose function. As is the case in most neuropathies, the longer the nerve, the more vulnerable it is to the disease. The longest nerves tend to run from the brain to the hindlimbs as these two areas are furthest apart and so symptoms of the polyneuropathy include a loss of coordination of the hindlimbs together with a "high stepping gait" and significant hindlimb muscle wastage. What is less obvious, perhaps, is why these dogs often present with breathing problems as the larynx ("voicebox") is very close to the brain and so you would expect the nerves to run between the two structures to be relatively short. There is only one nerve that supplies the abductor (opening) muscle (Cricoarytenoideus dorsalis- DCA) of the larynx. These paired muscles are supplied by a single nerve – the "recurrent laryngeal nerve". Due to a quirk of evolution, this nerve leaves the brain, goes down the dog’s neck, into the chest cavity, wraps around a major artery and then goes back up the neck and supplies the DCA muscle. This tortuous route means that the recurrent laryngeal is one of the longest nerves in the body and so it, too, is very vulnerable to any neuropathy. When affected, the nerve cannot function properly meaning that the dog is unable to open its larynx to aid breathing. This is the definition of laryngeal paralysis (LP) and this will be the focus of the rest of this article. Laryngeal paralysis affects dogs to different extents, presumably depending on the severity of the underlying neuropathy. Dogs do not simply "either have it or they don’t". Many dogs with a mild form will not show any clinical signs. The disease normally progresses however and eventually causes the dog to develop characteristic symptoms. Symptoms of LP are all caused by the inability of the larynx to open fully. This causes a difference in "voice" – LP dogs often will develop a higher pitched bark. Dogs may also become dysphagic – that is they can have difficulty eating and swallowing their food. The main symptoms however, concern the respiratory/breathing system. If the dog cannot open its larynx then it cannot increase the airflow into the lungs when needed, also the vocal folds are not pulled out of the way and so they tend to "dangle" in the way causing a characteristic fluttering sound. The symptoms, therefore, include a progressively worsening exercise intolerance (ie unable to run around as much as they used to), loud ("stertorous") harsh breathing (especially when excited), coughing and collapse. Dogs with LP are also very prone to heatstroke due to an inability to pant and therefore cool themselves efficiently. Dogs can collapse due to insufficient oxygen being delivered to the brain and it can sadly prove fatal if not treated promptly. A strong suspicion of laryngeal paralysis can be made from clinical examination alone. The vet normally places the stethoscope over the larynx and listens for the characteristic "fluttering" sound of paralysis. Together with the history of events, this may or may not be enough to make a definite diagnosis of LP. If in any doubt, then further investigations are often necessary and these include ultrasound scans of the larynx and also direct visualisation of the larynx under a very light anaesthetic. This is easier said than done, too much anaesthetic agent and the larynx is anaesthetised and doesn’t move at all, too little and the dog tries to move too much and you can’t see what’s going on! If the diagnosis of LP is confirmed then the treatment of choice is surgery. Surgery is not straightforward and should only be carried out by a vet who has received appropriate specialist training. The normal surgery done in the UK is an arytenoid lateralisation procedure (thyroarytenoid or cricoarytenoid depending on surgeon’s preference), What this means is that one of the cartilages that makes up the larynx opening is stitched to the outer edge of the larynx – permanently pulling open the main airway to allow the dog to breathe easier and get enough oxygen into the blood stream. When done well, the surgery has very good results with the vast majority of dogs having a significantly improved quality of life and being able to do more exercise. Crucially, it also allows the dog to control its body temperature more effectively and so it lessens the risk of heatstroke in the summer. Another surgical procedure that can be done is a tracheostomy – this is the creation of a permanent new opening into the trachea (windpipe) which effectively bypasses the obstructive problems in the larynx. Surgical outcome can be very good although dogs need more post-operative management than the traditional lateralisation techniques above. We do see dogs with laryngeal paralysis relatively commonly. We see relatively mildly affected dogs brought in to us for investigation of coughing or inability to exercise but we also see dogs brought in to us as emergencies especially in the summer months as the hot weather often tips affected dogs over the edge and produces severe clinical signs in what had been previously been normal (symptomless) dogs. These dogs need medical stabilisation and surgery as soon as possible. In summary, laryngeal paralysis should be suspected in any Leonberger with a progressive inability to exercise, loud, harsh breathing sounds or changing bark tone. If LP is at all suspected then the dog must not be over exerted (this may produce a crisis), the dog should be kept cool and taken to a vet as soon as possible. Dogs should be walked early am and late pm to avoid the heat of the day. Not all dogs need surgery, if the dogs are only mildly affected then sometimes the best course of action is to monitor them and change their lifestyle as above. The disease is progressive however, and it is often prudent to operate on known affected dogs before the hot summer months to avoid a possible emergency situation. LP in Leonbergers is part of an overall polyneuropathy, although the airway problems can be "bypassed" by appropriate surgery, it must be remembered that the underlying disease will inevitably progress. Sadly more and more nerves will become affected causing the dog increasing difficulty primarily through progressive himdlimb weakness. If the dog deteriorates to the point of not being able to stand and walk then, given the lack of an effective "cure", it is sadly sometimes necessary to have the dog put to sleep if its quality of life is poor. Other dogs, however, are very slow to deteriorate and may not lose the ability to walk within their lifespan. Tim Charlesworth MA VetMB CertSAS MRCVS About the author: Tim graduated from Cambridge Veterinary School in 2001 and currently works in small animal first opinion and referral practice. He obtained the RCVS certificate in small animal surgery in 2006 and is currently studying towards the specialist diploma in soft tissue surgery (DSAS(ST)) spending most of the year at Eastcott Veterinary Hospital in Swindon and 2 months a year at Anderson Sturgess Veterinary Specialists in Winchester. Many thanks to Racquel Walker of Condalf Leonbergers for allowing me to use this information from her website.
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