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Primary progressive MS Progression

It is a common misconception that the course of primary progressive MS can be predicted and that a diagnosis implies a rapid downhill course for everyone. This has fuelled the belief that primary progressive is the 'worst' type of MS. In reality, just as with other types of MS, considerable individual variation is seen in the course of primary progressive MS.

Whilst for some people progression can be very rapid, primary progressive MS onset is typically slow with symptoms steadily increasing over a period of months or years. The changes can be very subtle over a long period of time and some people experience long periods of relative stability. Indeed some consider the condition to be more 'predictable' than relapsing remitting MS, where a person can be struck down by a disabling relapse at any time without any prior warning.

I have seen a slow but sure deterioration over the two years since I was diagnosed. I'm still walking, working full time, but I get more tired.

Rosemary, W Sussex

Progression usually occurs in the same functional 'system' of the body, for example mobility and bladder function, both of which are caused by lesions in the spinal cord, whilst other systems such as vision and cognition tend to be unaffected in the majority of people.

Researchers have compared the course of primary progressive and secondary progressive MS to see if there are any major differences between the rates of progression. It was found they are in fact very similar, with the average rate of deterioration being the same. The time at which benchmarks such as needing assistance to walk are reached, were found to be related to the age of the person and were independent of any previous relapse history of the person with secondary progressive MS. This means that on average, regardless of the number of relapses they had previously experienced, a person who entered the secondary progressive phase at the age of 45 would progress at a similar rate to someone with primary progressive MS who experienced their first symptoms at the age of 45.


Predicting how primary progressive MS might progress

To see if it is possible to predict how someone's MS might progress studies have been carried out to look at the natural progression of primary progressive MS in several different populations. These are known as natural history studies. One such study published by Canadian researchers found that although 25% of their study group needed assistance to walk seven and a half years after their symptoms began, 25% were still able to walk unaided after living for 25 years with the condition.

The following factors have been found to influence the rate of progression:

  • Initial rate of progression - the Expanded Disability Status Scale (EDSS) is used in MS as a method of quantifying and monitoring changes in the level of disability over time. The first major 'landmark' on this scale is a score of 3.0 -'mild' disability, but able to walk without any assistance. The longer a person takes to reach a score of 3.0 on the scale, the more likely it is they will have a slower rate of progression in the future.
  • The number of symptoms experienced at onset - someone whose symptoms are caused by damage to three or more different areas within the CNS, for example problems with walking, vision and cognition, are at risk for a higher rate of progression than someone with problems associated with damage in only one area, such as walking.
  • Gender - men generally progress at a faster rate than women.
  • Number of brain lesions - those with a lower number of brain lesions and less brain atrophy (a decrease in the amount of tissue in the brain) tend to do better.
  • Amount of inflammation in the early stages - people who had primary progressive MS for less than five years and had gadolinium enhancement of their lesions (a marker of inflammation) were found to have a greater level of disability and more brain atrophy than those without enhancing lesions.

Although the above factors have been shown to influence the rate of progression, it must be emphasised that every person is unique and these predictors will not hold true for everyone with primary progressive MS. There will be some men who progress at a slow rate and similarly women who progress more rapidly than the average. There will be people who reach a plateau in their condition after initially having a swift deterioration and so on.


Next page - Management of primary progressive MS