Multiple sclerosis (MS) is a chronic disease that affects the central nervous system. It affects more than 2 million people worldwide and is 50 per cent more common in women than men. There is an increased risk if you have a close relative with MS.
The cause of the disease is not known, but theories include that it is an autoimmune disease, it is caused by genetic or environmental factors (it is more common the further away from the equator you live), or that it is caused by a virus.
There is currently no known cure for MS. It is an unpredictable disease that affects different people in different ways.
Most people have episodes where new symptoms appear or existing symptoms worsen over a period of days, weeks or even months, followed by partial or complete recovery, followed by another relapse. This is known as relapsing-remitting MS.
For some people, those relapses get worse and the disability stays. Their health gradually declines. This is known as secondary progressive MS.
A smaller number of people find that their symptoms just become gradually worse, with no separate attacks. This is known as primary progressive MS.
A small number of people find their health gradually deteriorates from the start, with a few attacks along the way. This is known as relapsing progressive MS.
And some people find they have one or two attacks, but completely recover with no disability, and no more attacks. This is known as benign MS.
MS is diagnosed by a range of tests including MRI to detect lesions in the central nervous system, a physical examination to check reflexes and responses, blood tests, lumbar punctures and a range of other tests to measure nerve activity.
Sometimes it can take years to reach a diagnosis because there is no one test for MS. You will be diagnosed as having MS if there is evidence of lesions in different parts of the central nervous system, at different times, with no alternative explanation other than MS.
Last reviewed: November 2016