Hi Polar, My mom was diagnosed with PPMS. She was on a slow steady decline. Then she had serious problems walking when one of her legs stopped working about 2 months ago. The neuro gave her steroids and lo and behold she started getting better. The neuro now thinks that my mom has PRMS since she reacted to the steroids. She told my mother that she could go on Cellcept or get IVSM every 3 months for a year (I think?). Sounds like her situation is similar to yours--the PPMS getting re-diagnosed as PRMS. Good luck with the Tysbari and come see us on the Ty. board and join the crew! I'm about to get #8. After 6 months on it there was no change on my MRI. I hope you have the same luck.
Anyhow, start feeling better soon.