RRMS – the most common disease course – is characterized by clearly defined attacks of new or increasing neurologic symptoms. These attacks – also called relapses or exacerbations
– are followed by periods of partial or complete recovery (remissions). During remissions, all symptoms may disappear, or some symptoms may continue and become permanent. However, there is no apparent progression of the disease during the periods of remission.
At different points in time, RRMS can be further characterized as either active
(with relapses and/or evidence of new MRI activity) or not active
, as well as worsening
(a confirmed increase in disability over a specified period of time following a relapse) or not worsening
. An increase in disability is confirmed when the person exhibits the same level of disability at the next scheduled neurological evaluation, typically 6 to 12 months later.
Approximately 85 percent of people with MS are initially diagnosed with RRMS.
This graphic shows the kinds of disease activity that can occur in RRMS; however, each person's experience with RRMS will be unique. Following a relapse, the new symptoms may disappear without causing any increase in level of disability, or the new symptoms may only partially disappear, resulting in an increase in disability. New lesions on MRI, as shown by the arrows, often occur as part of a relapse. However, new MRI lesions indicating MS activity may also occur without symptoms of which the person is aware.
Relapsing-remitting MS is defined by inflammatory attacks on myelin (the layers of insulating membranes surrounding nerve fibers in the central nervous system (CNS)), as well as the nerve fibers themselves. During these inflammatory attacks, activated immune cells cause small, localized areas of damage which produce the symptoms of MS
. Because the location of the damage is so variable, no two people have exactly the same symptoms.
Why are modifiers used to characterize RRMS?
Disease activity and progression should be evaluated at regular intervals by neurologic examination and MRI. Being able to characterize the course of your disease at different points in time helps you and your MS care provider discuss your treatment options and expected outcomes. For example:
- If you have RRMS that is active and worsening, you and your MS care provider will likely want to consider a more aggressive treatment approach than if there were no evidence of activity or worsening. Together, you can weigh the potential risks and benefits of other treatment options.
- If your symptoms have not worsened on the treatment you are currently taking, but you have evidence of new disease activity on your MRI, you and your healthcare provider may discuss switching to another treatment with a different mechanism of action in order to control the disease activity more effectively and help prevent worsening.
- If your RRMS is stable without evidence of MRI activity or worsening, you and your healthcare provider can feel confident that the current treatment regimen is working effectively.
How does RRMS differ from progressive types of MS?
While RRMS is defined by attacks of inflammation (relapses) in the CNS, progressive forms of MS involve much less of this type of inflammation.
- People with RRMS tend to have more brain lesions — also called plaques or scars — on magnetic resonance imaging (MRI) scans, and these lesions contain more inflammatory cells.
- People with primary progressive MS (PPMS) tend to have more spinal cord lesions, which contain fewer inflammatory cells.
In RRMS, women are affected two to three times as often as men; in PPMS, the number of women and men are approximately equal.
RRMS is diagnosed earlier than the progressive disease courses:
- Most people with RRMS are diagnosed in their 20s and 30s (although it can occur in childhood or later adulthood), while the onset of PPMS tends to be in ones 40s or 50s.
- The transition to SPMS generally occurs in people who have been living with RRMS for at least 10 years.
The most common symptoms reported in RRMS include episodic bouts of fatigue, numbness, vision problems, spasticity or stiffness, bowel and bladder problems, and problems with cognition (learning and memory or information processing). People with progressive forms of MS are more likely to experience gradually worsening problems with walking and mobility, along with whatever other symptoms they may have.