Relapsing-remitting multiple sclerosis (RRMS) is the most common form of MS. About 80 percent to 85 percent of people with MS are initially diagnosed with RRMS. Most people with RRMS eventually progress to secondary progressive multiple sclerosis (SPMS). The median transition time is about 19 years in those who are not undergoing treatment.

As disease activity changes over time, it’s important to know what SPMS looks like. There are many misperceptions about RRMS and SPMS. Here’s some clarity.

You May Experience More Symptoms as MS Progresses to SPMS

Relapses can still occur in people with progressive MS. A relapse is defined as a new neurologic symptom that lasts more than 24 hours in the absence of a fever or an infection. Signs and symptoms of SPMS can manifest in a variety of ways and can differ from person to person.

People With Progressive Forms of MS Experience Fewer Relapses

The inflammation that occurs early in MS — which causes symptoms (relapses) that come and go — slowly lessens over time. As a result, fewer inflammatory changes occur in the central nervous system, leading to fewer relapses. However, MS can progress, even if there are few or no relapses. A gradual worsening of symptoms over time is common. This worsening is known as disease progression.

Learn more about MS flare-ups and managing relapses.

Progressive Forms of MS Cannot Be Diagnosed With an MRI Scan Alone

Diagnosing SPMS is difficult, and your doctor will consider the results of several types of tests and examinations during the diagnostic process. These include a medical and clinical history, a neurologic examination, and magnetic resonance imaging (MRI) scans to determine whether the transition to SPMS has occurred.

In 2013, the International MS Phenotype Group revised MS classification criteria and added three important modifiers to the description of MS:

• Disease activity refers to a new clinical MS attack (relapse) or a new bright spot (showing inflammation) on the MRI.
• Disease worsening describes changes shown in a person’s neurological examination compared to prior examinations.
• Disease progression refers to how the illness progresses, as seen through exams over time, independent from a relapse.

These modifiers help more accurately observe and diagnose disease processes in an individual with MS. Your doctor will consider all of these together when evaluating for SPMS.

SPMS May Impact Mobility

SPMS can cause worsening mobility, and some people with SPMS will go on to experience walking disability. Over time, the frequency of relapses diminishes, but disability may continue to worsen. If this occurs, talk to your doctor to see if your MS is progressing to SPMS.

Learn more about staying mobile with MS.

Most People Retain Their Walking Ability With SPMS

Over time, more than two-thirds of people with SPMS retain their ability to walk, although they may need an assistance device, such as a cane or a walker. Some people with progressive MS will experience more disability than others. A wheelchair or motorized scooter may help with walking long distances.

RRMS Treatment Can Reduce Inflammation and Delay SPMS

In RRMS, treatment has been shown to reduce inflammation (relapses) and delay disease progression to SPMS. Using long-term disease-modifying therapies (DMTs) can help prevent or delay RRMS from advancing to SPMS. Most experts recommend that individuals with relapsing forms of MS begin treatment as soon as possible after diagnosis.

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