Hi BrooklynMom --
I missed on first reading that the diagnosis here is no CM but the existence of a pre-syrinx! This would be almost impossible unless he'd had a severe head injury of some type, at some point. But I just had a good look at the scan and enlarged it on my computer and for what it is worth -- I strongly think the diagnosis is mistaken about CM but that is most likely due to the neurologist not really being that familiar with 'seeing' it -- which unfortunately is not uncommon. To me at least, there looks like there's an indent at the cerebellum which means there is CM. As it is so rare for ANY cavalier not to have CM (so far there has only been one graded on the entire BVA/KC scheme, where a panel, rather than just a single neurologist, examines the scan) it would be very unusual to have such a dog and especially so if there's also a presyrinx.
I do not think anyone who is given a diagnosis of no CM can accept this as definite without submitting their scan to the BVA/KC scheme which has a panel of three neurologists familiar with CM.
There are a couple of neurologists -- who seem to be the only people routinely finding a few dogs for breeders, without CM. Having been told by one of these that one of my own dogs had no CM -- and a couple of years later, finding that CM was there in that old scan and even being able by then to clearly see it myself (!! -- the reason I asked for someone else to look at it) I just think that breeders (and pet owners if they want a definite diagnosis on CM) simply cannot accept a supposed 'clear' on CM without running it past a professional panel (or alternatively, having someone well known for diagnosing it, such as Nick Jeffrey or Clare Rusbridge or one of the other neurologists on the BVA panel, or Dr Marino in the US, examine it).
For breeders, if they accept the 'no CM' diagnosis from a neurologist (especially those who seem to have found such dogs when others do not!) and breed on the basis of that diagnosis, not seeking any confirmation -- then truly they are breeding for themselves (and sadly perhaps a premium they now feel they can charge for their puppies or their stud dogs) and NOT for the future of the breed.
Be VERY WARY of breeders claiming they have CM-free dogs!!!
I would say to anyone told by a breeder that their dog is clear of CM -- to aks if they have had a second confirmation of that from a recognised neurologist (in the US, I'd recommend either Nick Jeffrey or Dr Marino at LIVS), or submitted the scans to the BVA/KC scheme. If they have not -- think about it -- why not?
Might it be that they don't want their 'diagnosis' challenged? Might it be that they are aware that they are unlikely to get that diagnosis confirmed? Could it be that people who claim to be working for the breed's future, would really make the decision not to contribute what must be critical and deeply valuable information to the formal breeding schemes so other breeders and the breed can benefit?! The latter makes no sense at all --
unless they are well aware that their diagnosis is unlikely to stand.
For the pet owner I think being CM-free is less critical to confirm -- especially in a symptomatic dog that needs some kind of treatment. I think unless the diagnosis has been confirmed by a second opinion then anyone needs to assume their cavalier has CM. And just go ahead and treat the symptoms.
Clare Rusbridge will give second opinions on a scan but unless there's spare cash and a real desire to know this detail, I probably wouldn't bother; I'd treat on the assumption that you are dealing with CM/SM pain.