Around 85% of people with multiple sclerosis (MS) are diagnosed first with the relapsing-remitting form of the disease (RRMS). This type of MS is defined by periods of relapses, followed by periods of remissions.
A relapse is defined by the appearance of new symptoms or the return of past symptoms for 24 hours or more, without a change in body temperature or infection. These periods of new symptoms can last anywhere from a few days to a few months, but usually patients experience them for about four to six weeks.
Relapses are caused by the immune system launching an inflammatory attack against nerve fibers. During attacks, new parts of the nervous system can become damaged, leading to new symptoms. Thus, symptoms vary person-to-person, depending on which parts of the nervous system are most affected.
These relapses (also called exacerbations) are followed by periods of partial or complete recovery from symptoms, called remissions. During remissions, all of the symptoms may disappear, or some may continue and become permanent. However, there is no apparent disease progression (symptoms do not continually worsen) during this time.
Relapsing-remitting MS can be characterized as active (with relapses or evidence of new activity seen on an MRI) or not active. It also can be described as worsening or not worsening, meaning there may be an increase in disability following the relapse or no evidence of worsening disability.
Differences between RRMS and other subtypes
RRMS differs from progressive types of MS because relapses represent new inflammatory attacks on the nervous system. By contrast, much less inflammation is present in the progressive forms of the disease, which result from a slow infiltration of immune cells into certain regions of the brain and a slow expansion of pre-existing lesions.
Also, people with RRMS usually have more brain lesions with more inflammatory cells, whereas individuals with progressive types of MS generally experience more spinal cord lesions with fewer inflammatory cells.
Women are up to three times more affected by RRMS than men. The diagnosis is usually made earlier (when patients are in their 20s and 30s) than progressive types of MS, which are usually diagnosed when people are in their 40s and 50s.
Last updated: July 6, 2021
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