I have Primary Progressive MS. I have never had an exacerbation. My syptoms never go away, they just worsen over time.
My symptoms seem to worsen all at once and then for a long period of time I have no worsening at all.

I have been on what my neurologist calls a "plateau" for almost two years. My symptoms seem to have remained at the same intensity for that period of time. I keep my fingers crossed that I remain on this plateau for a good long while.

With PPMS the doctors only treat the symptoms. I take Flexeril and Neurontin and sublingual B12.

Apparently, to add to my MS, I have a B12 deficiency. That causes its own set of problems including a peripheral neuropathy.