The situation is also complicated by SP and Relapsing Progressive. The general view is that if you have an attack (with either complete or partial recovery) then you have RRMS. However, at some stage RR moves to SP (I saw some data that said that this can vary between 1 and 33 years). Some can have an attack but move very quickly to SP. Some MS 'experts' say that SP and PP are pretty much the same. My MS nurse says that PP is a completely different disease. Not sure how Relapsing Progressive fits into this. Other terms you often see are benign ms and malignant ms. One of the top UK MS experts has suggested that it is all the same disease but reflects different responses of the individual. For RR sufferers some repair takes place during the inflammatory phase, for PP there is no repair as it's about degeneration of the nerves (as it is for SP). He also thinks that using heavy duty immuno-suppressants e.g. Campath can convert RR to PP.
At the end of the day you (we) have MS. For those with RR, steroids and CRABS can help, but these have little impact when the disease moves to SP or starts with PP. Only neuro-protective agents will benefit all the various forms of the disease. Some of these are to be trialled shortly in the UK, so fingers crossed.
PS I found the following from last year's ECTRIMS conference.
Researchers and clinicians continued to grapple with the definition of primary-progressive MS (PPMS) and RRMS by asking the question: Are these one or two diseases?
Researchers agreed that the majority of MS cases are RRMS with distinct episodes, commonly called relapses. Up to 15 years after the first onset of RRMS, about 50% of people have difficulty with mobility and enter a phase of increasing disability without necessarily having relapses. They are defining this presentation as the secondary-progressive phase of MS.
To these researchers, PPMS is a different disease which presents in about 10%-15% of people with MS who experience progressively increasing disability from the start. This presentation of PPMS differs from RRMS in several respects. The average age of onset of PPMS is significantly later by about five years and the majority of PPMS cases have progressive weakness affecting the lower extremities.
Other researchers defined RRMS and PPMS as a two-staged disease with two consecutive mechanisms underlying the progression of disability - inflammation and neurodegeneration. They report a time-difference between phase one and phase two of the disease. The early phase of the disease appears to be strongly influenced by ongoing inflammation. The second phase has a progressive course which is more suggestive of an ongoing neurodegenerative process. This progressive phase of MS is associated with irreversible disability.