Hi all,
Thank you for your replies, much appreciated. We did manage to contact the breeder, and she recommended a vet in our area that has eperience with Dogue De Bordeaux, and also recommended to find a manipulator (Chiropractor for dogs) before seeing a Neurologist. Our puppy comes from a very healthy litter and excellent pedigree, and (luckily) no other puppies from same parents had any problems. We also looked into his diet, and went for breeder's recommendation to use Purina Beniful. He hasn't been on bad or cheap diet before, but we will start supplementing with calcium now also.
As far as I know, he didn't have any serious falls or accidents. If he has pinched a nerve in his spine, manipulator should be able to sort it out, as the breeder suggests.
We've never owned a dog before. It's great to see there is a big caring dog-lovers community out there willing to help, thank you all for that. See, the vet was right to recommend to find te help on Internet. We won't need her services anymore (as valuable as they are) - 4 years of studies didn't amount to much here. What ticks me off is not the vet bill, it's the fact that if somebody else comes in with the same problem, she still would not know how to help.
Cheers.