Although multiple sclerosis affects each individual differently, there are four broad groups into which MS is categorised:

1. Clinically isolated syndrome (CIS)

CIS is the term used to describe the first neurological episode that lasts at least 24 hours and is caused by inflammation or demyelination in one or more sites in the central nervous system. Approximately 60-80 per cent of people with CIS, who present with brain lesions, will go on to develop MS within 10 years. 

2. Relapsing remitting MS (RRMS)

This is the more common type of MS affecting as many as 85 per cent of diagnosed individuals. People with RRMS experience relapses (episodes of new or worsening symptoms) periodically, often months or years apart. When a relapse resolves, the person moves
into a period of remission.

3. Secondary progressive MS (SPMS)

People who are initially diagnosed with RRMS may transition to SPMS, in which there is a progressive worsening of neurological function over time. People may or may not continue to experience relapses caused by inflammation. For those people who may still get relapses, remission following a relapse is less complete. The disease gradually changes from the inflammatory process seen in RRMS to a more steadily progressive phase characterised by nerve damage or loss. 

4. Primary progressive MS (PPMS)

Approximately 10-15 per cent of people with MS are diagnosed with PPMS. This is characterised by a gradual, but continuous, worsening of symptoms and disease progression from the start. People with PPMS tend to experience more problems with walking and also require more assistance with their everyday activities.