Info from verywellhealth.com/multiple...
There are three main types of MS. They vary in their symptoms, disease course, and how they are treated.
Relapsing-remitting MS: About 85 to 90 percent of people with MS are first diagnosed with this form. During relapses, you'll experience neurological symptoms and functionality will decline. During remissions, symptoms may disappear or just become milder. Remission may last weeks or months.
Secondary-progressive MS: Some people with relapsing-remitting MS eventually develop secondary-progressive MS. It has a more progressive disease course in which symptoms become chronic and irreversible.
Primary-progressive MS: Symptoms slowly, but steadily get worse over time. Relapses don't occur, and the rate of worsening varies greatly. This is a less common type, accounting for about ten percent of cases. It tends to affect the spinal cord more than the brain.
You may also hear about clinically isolated syndrome (CIS). This is when a person has experienced a single episode that looks like an MS relapse but doesn't meet the criteria for a proper MS diagnosis. Some people with CIS go on to develop MS while others don't.
In the past, when specific treatments weren't available, the vast majority of patients with relapsing-remitting MS developed secondary progressive MS within 15 to 20 years of their diagnoses. However, since the development of disease-modifying medications, that has changed.
The prognosis for MS patients continues to improve.: Some people with relapsing-remitting MS eventually develop secondary-progressive MS. It has a more progressive disease course in which symptoms become chronic and irreversible.
The prognosis for MS patients continues to improve.