What?! Then she is a miracle breeder -- and none of the researchers know about her and these very extraordinary results.she has had four generations of breeding dogs without CM!!
I would seriously question what you are being told. And I would wonder if she would send her reports to Clare Rusbridge or Dr Marino for a second opinion. I do not think a neuro familiar with grading for CM is looking at these scans.
Maybe there was some confusion about what she was saying.
Even the breeder I know of who has had some of the few CM free dogs in her lines does not have anything like four full generations of all clear puppies for CM much less SM and I don't know anyone who would risk making such a claim about a gradual onset disease.