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Primary progressive MS exposed What is primary progressive MS?

MS is a complex and unpredictable condition that varies widely from person to person and does not follow a set pattern. However, there are a number of 'types' of MS that have been used to try to broadly group individuals in accordance with how the condition has developed. Originally MS was classified into two main clinical subtypes:

  • relapsing remitting MS
    characterised by periods when symptoms flare up (relapses) followed by periods of good or complete recovery (remissions); and
  • progressive MS
    where progressive deterioration occurs over months or years.

However, over the years clinical evidence pointed to there being three main subtypes of MS. As well as clinical differences being noted within the group with progressive MS, there were also found to be differences on magnetic resonance imaging (MRI) scans of the brain. Therefore, in 1996, it was proposed that the group of people with progressive MS should be further sub-divided to distinguish between those with progression that occurred primarily from the outset of the condition - primary progressive MS, and those whose progression followed on secondarily after an initial relapsing remitting course - secondary progressive MS.

This classification is now widely recognised and the agreed definitions are as follows:

Primary progressive MS (PPMS):

Disease progression from outset with occasional plateaus and temporary minor improvements allowed.

For about 10-15% of people diagnosed with MS, there is an absence of relapses and remissions and progression occurs from the outset. The rate at which progression occurs varies widely between individuals. At times it may be at a standstill, or it may improve very slightly for a short period. For others the progression is more rapid.

Relapsing remitting MS (RRMS):

Clearly defined disease relapses with full recovery or with sequelae* and residual deficit upon recovery; periods between disease relapses characterised by a lack of disease progression.

[*sequelae - after effects of the condition.]

The majority of people initially follow a relapsing remitting course of MS. On average relapses (a significant worsening or re-occurrence of a symptom, or group of symptoms, that lasts for more than 24 hours in the absence of an infection) occur once or twice a year. This is followed by a period of recovery when symptoms become less severe or disappear altogether. Although symptoms may worsen gradually over time, there isn't a marked increase in the level of a person's disability.

Secondary progressive MS (SPMS):

Initial relapsing remitting disease course followed by progression with or without occasional relapses, minor remissions, and plateaus.

People with relapsing remitting MS mostly go on to develop a progressive form of the condition. Whilst the severity and frequency of relapses decrease or even stop altogether, the level of permanent disability increases over time.

Each of these 'types' of MS encompasses a wide range of experiences of MS. Even with these definitions in place it can still be difficult to determine exactly what type of MS an individual has, particularly at the point of diagnosis and it may only become apparent over time as the condition develops.

Next page - How primary progressive MS differs from the other forms of MS