It galls me that people breed dogs and don't know about such things. This condition is not necessarily common in yorkies like it is in the king charles...but it does happen.
There are varying degrees. Did they mention Syringomyelia? One symptom of it is the neck scratching you are talking about. Often it is hand in hand with chiari.
I had a foster pup who had multiple neuro issues....AAI, syringomyelia, chiari and some other things. He was a senior when he came to me. I am sharing this with you to let you know that it can happen that they live to be older. I don't know what Sammy's age was nor do I know what treatments he had; but he did fairly well and was a little charmer. Following is a thread about him that may give you some hope:
http://www.yorkietalk.com/forums/sic...ro-issues.html
YT member Lillymae has some experience with Chiari I believe. Perhaps she can add to this.
Please keep us posted. I will keep your Teddy in my thoughts and prayers.