That's really interesting. You might want to contact the MDA's research department:
Grants Manager
MDA Research Department
3300 E. Sunrise Drive
Tucson, AZ 85718
(520) 529-2000
(520) 529-5454 (fax)
grants@mdausa.org
There might be a researcher in touch with them who would like to do a study on other patients who have had stem cell transplants. It's probably a bit too drastic to do for routine treatment, but it could be the foundation for future treatment.
I don't know much about stem cells at this time, but I do know they frequently try to coax them into the type of cell they want them to become before they inject them. I think a lot of things can affect the severity of the myotonia, but I couldn't even begin to speculate in this instance, except to say, maybe it shifted something with your biochemistry.
You might try e-mailing some researchers. I doubt they will have much of an answer but they might find it interesting.