Hi Manny
Welcome! You don't say how old your puppy is - has he finished all his shots and being taken for walks? Ear mites are VERY common with Cavaliers and can cause intense irritation. At this time of year he could also have got a grass seed in his ear, which can be really painful and would cause him to flinch when touched. Biting his feet could be harvest mites. Chasing his tail could mean he's trying to lick or nibble his backside and needs his anal glands emptied - again, a very common condition with Cavaliers. Although you don't want your vet to waste years looking for allergies etc and missing SM symptoms (as some have done), there are - as I've indicated - a lot of other conditions that produce similar symptoms. This is part of the difficulty of diagnosing SM - some of us have wasted several years treating our dog for other things when it was really SM, but conversely, some of us have worried ourselves sick about what seem to be symptoms of SM and turn out not to be! A lot of vets still don't know much about it. And some dogs with SM never scratch (including my Oliver), so that in itself is not necessarily a symptom.
I should ask your vet to check for ear problems and anal glands before going to a neurologist. If nothing is found, then talk to your vet about taking it further. If your vet is unfamiliar with SM, you will find a lot of helpful stuff on the website of Clare Rusbridge, the leading UK researcher into SM -
www.veterinary-neurologist.co.uk - which you can either print off to show your vet or suggest he or she looks at the website themselves.
Meanwhile, enjoy your puppy - even if he has got SM, it is not a death sentence and many Cavaliers with it lead normal, happy lives with medication or, in the case of younger dogs, surgery. My Oliver was diagnosed with SM when he was 6 (though with hindsight he had symptoms long before that) and is now 10 and still loves his 5-mile walks and camping holidays. Our vet keeps exclaiming how fit he is!
Kate, Oliver and Aled
PS Your breeder is in denial! And woefully ignorant - Oliver has only just retired from doing competition obedience, and his brain is very much still alert - he's becoming a very naughty old man, always thinking of new sorts of mischief!