I am so sorry that you are facing this with your first cavalier and I do hope that your puppy can be treated and kept comfortable.
These poor little dogs & the pet owning public are getting a very raw deal from cavalier breeders. This is not what should happen when someone buys a dog for their family.
One of the excuses breeders make is that they don't set out to breed unhealthy puppies. The problem is that they won't do the tests that they know will give their puppies the best chance of being healthy.
Here in the UK I have been contacted by owners of puppies that have needed to be PTS because they have SM and the pain could not be controlled and unfortunately I think we will hear of this even more often, until 'reputable' breeders realise that seeing no signs of SM in their dogs is no substitute for a MRI scan.
Cavaliers......Faith, The Ginger Tank and Woody.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.
Remembered with love......... Tommy Tuppence and Fonzi