Multiple sclerosis (MS) is an unpredictable disorder that can cause a variety of symptoms, which for many, can flare-up and then subside over the course of days, months, or even years. While MS is not contagious, its causes are not yet fully understood and researchers continue to search for answers.

The fact that symptoms flare-up and subside for many people with multiple sclerosis (MS), combined with the wide variety and unpredictability of symptoms, has made MS a difficult disease to recognize, define, and treat – right from the start. Since the late 1300s, individuals with a progressive illness suggestive of MS have been observed. It wasn’t until 1868 that the famous neurologist, Jean-Martin Charcot, lectured on the features of MS and gave it a name.

Multiple sclerosis (MS) is a disease of the central nervous system (CNS). The CNS consists of the brain, optic nerves and spinal cord. With MS, areas of the CNS become inflamed, damaging the protective covering (known as “myelin“) that surrounds and insulates the nerves (known as “axons“). In addition to the myelin, over time, the axons and nerve cells (neurons) within the CNS may also become damaged.

Approximately 400,000 individuals have been diagnosed with MS in the United States and as many as 2.5 million worldwide, with an estimated 10,000 new cases diagnosed in the United States annually. Most people with MS experience their first symptoms and are diagnosed between the ages of 15 and 50, although individuals of any age may be diagnosed with MS.

In a healthy body, nerve fibers (also referred to as “axons“) have a protective, fatty-rich protein covering known as myelin. This covering insulates the nerve fibers, similar to the insulating rubber covering of an electric wire. Myelin allows for the smooth and uninterrupted flow of nerve impulses, which in turn, enables the body to send vital instructions from the brain to the different parts of the body.

Several types of MS have been identified, from the most common form of the disease — relapsing-remitting MS (RRMS) – to the less common progressive forms. Please visit this section to learn about all of the types of MS, as well as syndromes prior to an MS diagnosis.

Relapses, also referred to as exacerbations, attacks, flare-ups, episodes, or bouts, are initially experienced by most people diagnosed with multiple sclerosis (MS). Relapses occur with relapsing-remitting, progressive-relapsing, and sometimes secondary-progressive forms of MS. Relapses do not occur with primary-progressive MS, although patients may experience day-to-day fluctuations in how they feel.

Researchers have studied a variety of possible causes for multiple sclerosis (MS), and a combination of factors appears to be involved. A popular theory looks at commonly known slow-acting viruses (one that could remain dormant for many years), such as measles, herpes, human T-cell lymphoma, and Epstein-Barr. After being exposed to one of these viruses, some researchers theorize that MS may develop in genetically susceptible people.

Diagnosing and evaluating MS disease activity is most reliably done by neurologists through a neurological history and examination. Tests that can indicate MS and rule out “MS mimickers” (other diseases that resemble MS but have other causes) are also performed.

Additional tools are available to measure disease activity. These are used mainly in clinical trials to help evaluate disease progression as well as changes in specific symptoms, such as fatigue, strength, mobility, vision, cognition, and others.