Hi Matthew glad to hear your mother is doing better on her present regime.
Can't comment on the new treatment she is about to go on except to say it sounds like the 'c' you are talking about is likely to be entacapone/Comtan (brand name). This will get more l-dopa to the brain, basically makes it more bio available. So she may need to re-adjust down once she settles on it. If she avoids the side effects it is a very useful drug. We are all so different and there are probably people who are msa but closer to pd and vice versa, so it's good that her condition isn't put into a box just yet, leaving it open helps. It sounds like you are all starting to understand what is happening a lot better, and that always helps too. Best wishes to you all.
Lindy