Did you know there are three different types of multiple sclerosis (MS)? Each type has a risk of relapses and unique characteristics. Relapses — also known as flare-ups, exacerbations, or attacks — are periods of new or worsening symptoms of MS. Although the relapsing forms of MS are different, they are often treated with the same medications to lower the chance of relapses and slow the progression of the disease.

The three types of relapsing MS are clinically isolated syndrome (CIS), relapsing-remitting MS (RRMS), and active secondary progressive MS (SPMS). Keep reading to learn about their differences.

1. Clinically Isolated Syndrome

CIS is often the first episode of symptoms a person will experience that eventually lead to an MS diagnosis. CIS is diagnosed when neurological MS symptoms last for at least 24 hours. These symptoms must be caused by demyelination (damage to the myelin that sheathes nerve fibers) or inflammation in the central nervous system (CNS), which includes the brain, spinal cord, and optic nerve.

CIS is a condition that can convert (or progress) to MS, but it doesn’t always. The risk of conversion often depends on the quantity and size of lesions, as seen on initial baseline MRI scans. CIS usually occurs in people between the ages of 20 and 40. Effective treatment soon after a diagnosis of CIS is important to delay or prevent the conversion to MS.

CIS is a first episode of MS-like symptoms. If a relapse occurs, it may then be diagnosed as relapsing-remitting MS.

Although CIS is considered a type of relapsing MS, it’s different because it’s not officially MS unless there’s another relapse or an MS attack later on.

2. Relapsing-Remitting Multiple Sclerosis

RRMS is the most common type of MS. However, no two people experience RRMS the same way. This is because lesions can occur in different locations within the CNS and affect different functions in the body.

RRMS is characterized by defined attacks with new symptoms or symptoms worsening in severity. This type of MS is different from other types because after each attack, the condition will go into remission. During remission, symptoms will either go away completely or become significantly less intense, but the disease will not progress further during remission.

In RRMS, there are relapses of new or worsening symptoms followed by periods of remission, in which symptoms improve or go away.

There are several risk factors for RRMS. Women are approximately two to three times more likely than men to be diagnosed with RRMS, according to Mayo Clinic. RRMS usually starts at around the same age as CIS — between ages 20 and 40. However, children can also be diagnosed with this course of MS. Genetics are another risk factor, as RRMS often runs in families.

Learn more about what MS relapses feel and look like.

3. Active Secondary Progressive Multiple Sclerosis

After some time, RRMS can progress to SPMS. In people with SPMS, neurological symptoms continue to get worse. Unlike people with RRMS, those who have SPMS don’t have clear periods of remission. SPMS is considered active if relapses continue to occur and inactive if there have been no relapses for a while.

In SPMS, symptoms slowly progress without periods of remission. However, some people still experience relapses in which symptoms worsen.

Whether SPMS is active or inactive, symptoms and disability generally continue to gradually worsen over time, with fewer relapses than RRMS. SPMS is also a different type of MS from primary progressive MS (PPMS), which starts as a progressive disease, rather than converting from a relapsing form of MS.

Although there may be periods when inactive SPMS doesn’t progress, eventually the disease will likely continue to progress, and symptoms and disability will increase. Disability can also worsen without obvious signs of disease activity or MRI changes.

Read about how long MS relapses last.

Treatment Options for Relapsing Forms of MS

Although CIS, RRMS, and SPMS are distinct forms of relapsing MS, they have similar treatment options.

Disease-modifying therapies (DMTs) are the main way to slow the progression of relapsing forms of MS. They work by targeting immune system cells that attack the CNS. The U.S. Food and Drug Administration (FDA) has approved more than 20 DMTs for treating relapsing forms of MS.

According to the National Multiple Sclerosis Society, without the use of approved DMTs, 50 percent of people diagnosed with RRMS will likely transition to SPMS within 10 years, and 90 percent tend to transition within 25 years.

DMTs cannot cure MS, but treatment with DMTs aims at the following:

• Reducing the frequency of MS relapses
• Limiting new MS activity, such as new lesions or plaques on the brain and spinal cord, as shown on MRI scans
• Slowing disease progression and disability

People diagnosed with any type of relapsing MS should discuss DMTs with a neurologist as soon as possible. DMTs have a risk of side effects, some of which can be serious. It’s important to discuss potential side effects in detail before starting any medication.

Sometimes, an MS flare may require emergency treatment or hospitalization.

Classes of DMTs for Relapsing Forms of MS

There are several different classes of DMTs for the relapsing MS treatment. Be sure to talk to your doctor about which treatment option may be best for you. ​

Classes of DMT drugs include:

• Interferons, such as interferon beta-1a (Avonex) and interferon beta-1b (Betaseron)
• Monoclonal antibodies, such as ofatumumab (Kesimpta), ocrelizumab (Ocrevus), and natalizumab (Tysabri)
• Fumarates, such as dimethyl fumarate (Tecfidera) and diroximel fumarate (Vumerity)
• Cladribine (Mavenclad), an adenosine analog
• Sphingosine-1-phosphate receptor modulators, such as fingolimod (Gilenya) and siponimod (Mayzent)

• Pyrimidine synthesis inhibitors, such as teriflunomide (Aubagio)

Delaying MS Progression

MS is a debilitating disease that usually progresses as time goes by. Although there is not yet a cure for MS, DMT treatment as early as possible after diagnosis can help delay the progression from one type of relapsing MS to another. Long-term treatment with a DMT is the most important way to slow down MS progression.

New treatments for relapsing forms of MS are becoming approved or in clinical trials as research scientists learn more about disease courses in relapsing types of MS. Talk to your doctor about new treatment options and if a clinical trial may be appropriate for you. ​

Talk With Others Who Understand

MyMSTeam is the social network for people with multiple sclerosis and their loved ones. On MyMSTeam, more than 218,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you living with a relapsing form of multiple sclerosis? Have you talked to your doctor about how you can delay progression of the disease? Share your experience in the comments below, or start a conversation by posting on your Activities page.