For about 85% of those affected, MS starts in the form of relapses. This is an acute neurological dysfunction that lasts at least 24 hours and comes with a variety of symptoms. Often, the symptoms fully subside after a relapses, though they may sometimes persist to some extent. Between relapses, a person's health does not deteriorate. This form is also known as relapsing-remitting multiple scleroris (RRMS).

After several years of RRMS, some patients develop secondary progressive multiple sclerosis (SPMS), i.e. a progressive course begins. In this stage, the disease progresses even independent of relapses – often, these MS symptoms are not clearly noticeable (e.g. increasing difficulty with attention and concentration during
conversations, worsening daytime fatigue, deteriorating balance while walking). The timing of the transition from RRMS to SPMS cannot be predicted. With appropriate treatment, this transition can be delayed. About 40% of those affected transition to SPMS after 10 years.

In about 15% of people with MS, the disease is progressive from the onset, that is, becomes more advanced over time. This is called primary progressive multiple sclerosis (PPMS). PPMS mainly affects patients whose disease started later and in whom multiple sclerosis first appears in people over the age of 40.