It is generally very difficult to predict the course of MS. The condition varies greatly in each individual but most people with MS can expect 95% of the normal life expectancy.
Some studies have shown that people who have few attacks in the first several years after diagnosis; long intervals between attacks; complete recovery from attacks and attacks that are sensory in nature (i.e. numbness or tingling) tend to have better outcomes in the long run.
People who have early symptoms of tremor, difficulty in walking, or who have frequent attacks with incomplete recoveries tend to have a more progressive disease course.
MS tends to take one of three clinical courses each of which might be mild, moderate or severe:
1. Relapsing-remitting (RRMS)
Relapsing-remitting (RRMS) - characterised by partial or total recovery after attacks (also called exacerbations, relapses, or flares). The most common form of MS. 70 to 75% of people with MS initially begin with a relapsing-remitting course.
2. Secondary progressive (SPMS)
Secondary progressive (SPMS) – a relapsing-remitting course which later becomes steadily progressive. Attacks and partial recoveries may continue to occur. Of the 70-75% who start with relapsing-remitting disease, more than 50% will develop SPMS within 10 years; 90% within 25 years.
3. Primary progressive (PPMS)
Primary progressive (PPMS) - a progressive course from onset. Symptoms generally do not remit. 15% of people with MS are diagnosed with PPMS, although the diagnosis usually needs to be made after the fact, when the person has been living for a period of time with progressive disability but not acute attacks.
Clinically Isolated Syndrome (CIS) refers to a first episode of inflammatory demyelination in the central nervous system that could become MS if additional activity occurs.
The National MS Society in the USA have provided a table which outlines the three courses of MS along with charts that show what happens in MS over time:
The MS Information Sourcebook produced by the Information Resource Center and Library of the National Multiple Sclerosis Society. © 2001 The National Multiple Sclerosis Society. All rights reserved. Reproduced with permission.