I am so sorry! I've PM'd you with a lady's email that has gone through this and has done wonders with her Yorkie.
Back in '04 I had purchased a Show male from a breeder. I Showed him myself and he was only 1 Major away from his AKC Championship, and I decided to breed him during a break in Shows. No puppies.. So I had him tested and he was completely STERILE
Although devastated, I knew there was no sense finishing his Championship and I placed him with a very loving family. I got several emails and updates and all went well for a few years. She then called me to let me know that he had Encephalitis. Thank God, he was sterile, and had produced no offspring because it was confirmed hereditary Encephalitis. He had terrible symptoms, and they all went through hell. She emailed updates as things progressed, and just yesterday sent pics of how well he was doing. She will be of great help to you, I am sure.
Good luck and God Bless!