Some of the diagnosis is your history of relapse / recovery. If you’ve had some, even partial, recovery from relapses, then you’d probably be fairly safely diagnosed as RRMS. But even if you’ve had very little remission, the neurologist might prefer to call it RR in the first place anyway. The reason for that would be that you only qualify for DMDs if you are diagnosed with relapsing MS.
Also, if you had an MRI with ‘contrast dye’, new inflammation lights up as ‘enhancing’ lesions and tells the neurologist that your MS is ‘active’, ie relapsing.
With me, I was diagnosed with RR, and stayed like that for about 18+ years. From the very first relapse, I didn’t get complete remission, I soon forgot what feet without neurological damage felt like - but you soon adapt to sensory changes, and the nerves do a reasonable job of compensating for deficits. Eventually, about 2 or 3 years ago, my neurologist decided (together with me), that I’d transitioned to SP. This was mostly because I’d not had any real relapses for a long time, plus, I’d more or less run out of disease modifying drugs that didn’t give me crappy side effects.
Then this year I’ve had two definite relapses, and have had a) quite rapid and significant remission following a course of steroids, and b) an MRI with new ‘enhancing’ (aka showing current inflammation) lesions on my brain.
So I have a new label, that of relapsing progressive MS. And I’ve been offered a couple of DMDs. One of which I’ve had before and didn’t get side effects from (Copaxone) and the other which could give me side effects (Gilenya). Even though I stopped taking Copaxone more than 10 years ago because I thought it had stopped working, I’m going to start back on that for safety’s sake. If it doesn’t work, then I can try the more effective, but riskier (for me due to my stupid body’s reaction to drugs) Gilenya.
So you see, it’s a mixture of MRI plus experiential evidence that tells the neurologist what kind of MS you have. The labels to some extent can seem a bit meaningless. It’s time that will show what your MS is doing and how it’s behaving. In particular, the labels are ever changing if you fall into the RR/SP continuum (which it seems you do as you had earlier symptoms which remitted).
I hope that helps a bit. It is all a bit of a learning curve when you are first diagnosed. And an unnerving one at that.