After my diagnosis, the National Multiple Sclerosis Society (NMSS) was my first and continues to be my go-to source for information. According to NMSS, Multiple Sclerosis (MS) involves an immune-mediated process in which an abnormal response of the body’s immune system is directed against the central nervous system (CNS), which is made up of the brain, spinal cord, and optic nerves. The exact antigen—or target that the immune cells are sensitized to attack—remains unknown, which is why MS is considered by many experts to be “immune-mediated” rather than “autoimmune.”
- Within the CNS, the immune system attacks myelin—the fatty substance that surrounds and insulates the nerve fibers—as well as the nerve fibers themselves.
- The damaged myelin forms scar tissue (sclerosis), which gives the disease its name.
- When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing a wide variety of symptoms.
- The disease is thought to be triggered in a genetically susceptible individual by a combination of one or more environmental factors.
- People with MS typically experience one of four disease courses, which can be mild, moderate or severe.[i]
Relapsing-remitting MS (RRMS)
- RRMS—the most common disease course—is characterized by clearly defined attacks of worsening neurologic function. These attacks—also called relapses, flare-ups or exacerbations—are followed by partial or complete recovery periods (remissions), during which symptoms improve partially or completely and there is no apparent progression of disease. Approximately 85 percent of people with MS are initially diagnosed with relapsing-remitting MS.
Secondary-progressive MS (SPMS)
- The name for this course comes from the fact that it follows after the relapsing-remitting course. Most people who are initially diagnosed with RRMS will eventually transition to SPMS, which means that the disease will begin to progress more steadily (although not necessarily more quickly), with or without relapses. (This is where my disease is at present.)
Primary-progressive MS (PPMS)
- PPMS is characterized by steadily worsening neurologic function from the beginning. Although the rate of progression may vary over time with occasional plateaus and temporary, minor improvements, there are no distinct relapses or remissions. About 10 percent of people with MS are diagnosed with PPMS.
Progressive-relapsing MS (PRMS)
- PRMS—the least common of the four disease courses—is characterized by steadily progressing disease from the beginning and occasional exacerbations along the way. People with this form of MS may or may not experience some recovery following these attacks; the disease continues to progress without remissions.[ii]
While the cause (etiology) of MS is still not known, scientists believe that the interaction of several different factors may be involved. To answer this important question, studies are ongoing in the areas of immunology (the science of the body’s immune system), epidemiology (the study of patterns of disease in the population), and genetics. Scientists are also studying infectious agents that may play a role. Understanding what causes MS will speed the process of finding more effective ways to treat it and—ultimately—cure it, or even prevent it from occurring in the first place.
In MS, an abnormal immune-mediated response attacks the myelin coating around nerve fibers in the central nervous system, as well as the nerve fibers themselves. In recent years, researchers have been able to identify which immune cells are mounting the attack, some of the factors that cause them to attack, and some of the sites (receptors) on the attacking cells that appear to be attracted to the myelin to begin the destructive process. Ongoing efforts to learn more about the immune-mediated process in MS—what sets it in motion, how it works, and how to slow or stop it—are bringing us closer to understanding the cause of MS.[iii]
[i] (National Multiple Sclerosis Society http://www.nationalmssociety.org/What-is-MS/Definition-of-MS, February, 26, 2016)
[ii] (National Multiple Sclerosis Society, http://www.nationalmssociety.org/What-is-MS/Types-of-MS, February 26, 2016)
[iii] (National Multiple Sclerosis Society, http://www.nationalmssociety.org/What-is-MS/What-Causes-MS, February, 26, 2016)