Abby, I thought of a couple more things. If something does run in your family and it's a CMS, it's more likely a dominant inheritance (versus recessive). Though if I've learned anything about this "family" of diseases, it's that they have not even skimmed the surface of the gene pool yet.

Also, there's a classic sign in some of the CMS's called a Repetitive Compound Muscle Action Potential. It's an extra little blip that some doctors would miss.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924514/

Not that you'd want another test again!