In MS, the immune system, which normally helps to fight off infections, mistakes the myelin sheath which normally protects nerve cells, for a foreign body and attacks it. This damages the myelin and strips it off the nerve fibres, either partially or completely, leaving scars known as lesions or plaques. This damage disrupts messages travelling along nerve fibres – they can slow down, become distorted, or not get through at all.
As well as myelin loss, there can also sometimes be damage to the actual nerve fibres. It is this nerve damage that causes the accumulation of disability that can occur over time.
No one knows the exact cause of MS, but it is likely that a mixture of genetic and environmental factors including viruses and vitamin D deficiency may play a role.
There are many different types of MS:
- Relapsing Remitting (RRMS) is the most common type of MS, affecting around 85 per cent of everyone diagnosed with MS. It means that symptoms appear (a relapse), and then fade away, either partially or completely (remitting).
- Primary Progressive (PPMS) affects about 10 to 15 per cent of people diagnosed with MS. It has this name because from the first (primary) symptoms and it is progressive. Symptoms gradually get worse over time, rather than appearing as sudden attacks (relapses).
- Secondary Progressive MS (SPMS) is a stage of MS which comes after relapsing remitting MS in many cases. Neurologists generally agree secondary progressive MS is a “sustained build up of disability, independent of any relapses