MS is an individual condition. For some people, MS is characterised by periods of relapse and remission while for others it has a progressive pattern. For everyone, it makes life unpredictable. Most people diagnosed with MS will be described as having relapsing remitting MS, except for the small number of people who have primary progressive MS.

In relapsing remitting MS, symptoms occur for a period of time - days, weeks, or months - and then improve, either partially or completely.

Many people with MS call a relapse an 'attack' because this can describe the period of time they experience new problems or begin to feel unwell. A relapse is when new symptoms occur, or old symptoms re-occur, and last for more than 24 hours.

Relapses happen when inflammatory cells attack nerve fibres in the brain and spinal cord. if inflammation blocks messages in an area that has a specific function, such as the optic nerve, then symptoms occur. the myelin sheath can be damaged and sometimes, the nerve fibre (or axon) itself is damaged, too.

When the inflammation subsides, symptoms settle down (there may be some damage left behind which can improve over time) or entirely disappear. this is known as a remission. Remissions can last any length of time, even years.

If, after ten to 15 years, your condition hasn't worsened and you have minimal or no disability, you will be said to have benign MS. This doesn't mean your MS will be free of problems - it means simply that you haven't developed major disability, despite having MS for a long time. About 20 per cent of people with MS have benign MS.

When someone with relapsing remitting MS shows a sustained deterioration for at least six months - whether or not they have relapses as well - they are said to have secondary progressive MS. The progression probably results from the loss of nerve fibres (axons) during past relapses. Although myelin can repair itself (a process known as remyelination), axons cannot fully repair themselves.

It isn't always easy for doctors to tell when somebody moves from relapsing remitting to secondary progressive MS. Some people continue to have relapses in addition to progressive deterioration, while others don't. Although nobody's MS starts off being secondary progressive, it's possible to be told you have this type at diagnosis if you've had unexplained symptoms for some time.

Not everybody with relapsing remitting MS goes on to develop the secondary progressive form. On average, buy 15 years, approximately 65 per cent of people with relapsing remitting MS will have developed secondary progressive MS.

This is an unusual form of MS, affecting overall perhaps 10 to 15 per cent of people who have MS. People with primary progressive MS tend to be diagnosed when they are a little older, usually in their forties or later. Unlike relapsing remitting MS, men are just as likely to be diagnosed with primary progressive MS as women.

While the other types of MS can affect both the brain and spinal cord, in primary progressive MS the majority of lesions tend to be found in the spinal cord. People with primary progressive MS never have any distinct attacks or remissions but begin with subtle problems that slowly worsen over time - their MS is progressive from teh beginning.

Problems tend to affect one main area and, for the majority of people, these are related to walking. However, people with primary progressive MS can experience any MS symptom.3