I have just been reading the Barts Blog and on there they seem to think that there PPMS could in fact be a “benign” course of RRMS that has gone into SPMS without the person really realising that they had MS in the first place. The age at which people are dx with PPMS seems to be a similar age to when people with RRMS get SPMS. On reading posts on here over the last couple of days there are many who noticed signs or symptoms years and years before. Many would say that it would be no real difference which label you got PPMS or RRMS because there are no treatments anyway. This could change as there seem to be trials being done at the moment on SPMS. In essence people may not get the right treatment if they have the wrong label.
I myself had l’hermittes in 1990 and small episodes of it after that once every few years. After clear scans etc this was always put down to a side effect of my radiation treatment. What I have now may be down to the radiation (as one neuro believes) or as another thinks - benign MS which has gone in SPMS or PPMS. Hardly matters if there is no treatment but if treatment is there for one of those conditions I would want to try it, regardless of the label!