Our precious cavaliers may encounter this devastating disease. Reputable breeders are working hard to minimize the odds of this in their bloodlines, but it is not an exact science. CM is a complex disease. There is so much we don’t know about it. We can have dogs who don’t exhibit symptoms produce it,. There are some who are diagnosed by MRI with it, who are asymptomatic (no symptoms), and others who do have it and exhibit symptoms.
Unfortunately we can not genetically test for it, so we have no way to predict which puppies may or may not get it. We do know it is polygenic. This means that it must be inherited from both sides, and it does seem to look like it can be passed hidden through many generations before popping up in the “perfect storm” in one puppy who exhibits the symptoms.
So, lets talk about what CM actually is. The best way I can describe it would be to liken it to try to put your foot into a shoe that is too small for your foot. It is when the brain is too large for when the skull to the point that the cerebellum and brain stem are herniated into or via the foramen magnum.
Some people believe it is because the cavalier head shape has changed, but I am not entirely convinced by this theory as I have seen CM in both “domed” shaped heads as well as “flat” shaped heads. Some vets have talked about diagnosing CM by the shape of a cavalier’s head (not through MRI) and I believe that there is plenty of evidence that proves that there is CM (and clears) in many different head shapes and so i think we need to be careful of that.
Really, as a breeder, just do your research – ask questions about if your breeder does scanning and which dogs in your puppy’s bloodline have been scanned.