What Is Multiple Sclerosis?

MS is thought to be an autoimmune disease that affects the central nervous system (CNS). The CNS consists of the brain, spinal cord, and the optic nerves. Surrounding and protecting the nerve fibers of the CNS is a fatty tissue called myelin, which helps nerve fibers conduct electrical impulses. In MS, myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also known as plaques or lesions. Sometimes the nerve fiber itself is damaged or broken. Myelin not only protects nerve fibers, but makes their job possible. When myelin or the nerve fiber is destroyed or damaged, the ability of the nerves to conduct electrical impulses to and from the brain is disrupted, and this produces the various symptoms of MS.

• Relapsing-Remitting
  Characteristics: People with this type of MS experience clearly defined flare-ups (also called relapses, attacks, or exacerbations). These are episodes of acute worsening of neurologic function. They are followed by partial or complete recovery periods (remissions) free of disease progression.
  Frequency: Most common form of MS at time of initial diagnosis. Approximately 85%.

• Primary-Progressive
  Characteristics: People with this type of MS experience a slow but nearly continuous worsening of their disease from the onset, with no distinct relapses or remissions. However, there are variations in rates of progression over time, occasional plateaus, and temporary minor improvements.
  Frequency: Relatively rare. Approximately 10%.

• Secondary-Progressive
  Characteristics: People with this type of MS experience an initial period of relapsing-remitting MS, followed by a steadily worsening disease course with or without occasional flare-ups, minor recoveries (remissions), or plateaus.
  Frequency: 50% of people with relapsing-remitting MS developed this form of the disease within 10 years of their initial diagnosis, before introduction of the "disease-modifying" drugs. Long-term data are not yet available to demonstrate if this is significantly delayed by treatment.

• Progressive-Relapsing
  Characteristics: People with this type of MS experience a steadily worsening disease from the onset but also have clear acute relapses (attacks or exacerbations), with or without recovery. In contrast to relapsing-remitting MS, the periods between relapses are characterized by continuing disease progression.
  Frequency: Relatively rare. Approximately 5%.

What Causes MS?
While the exact cause of MS is unknown, most researchers believe that the damage to myelin results from an abnormal response by the body’s immune system. Normally, the immune system defends the body against foreign invaders such as viruses or bacteria. In autoimmune diseases, the body attacks its own tissue. It is believed that MS is an autoimmune disease. In the case of MS, myelin is attacked. Scientists do not yet know what triggers the immune system to do this. Most agree that several factors are involved, including: Genetics Gender Environmental Triggers [Possibilities include viruses, trauma, and heavy metals( toxicology)]		Scientists have long been searching for an infectious agent that might trigger MS. While many different viruses have been suggested, none has yet been confirmed. Chlamydia pneumoniae, a bacterial agent, has also been suggested but never proven. Although no trigger has yet been identified, most MS experts believe that some infectious agent is involved in initiating the disease process.

Who Gets MS?

Anyone may develop MS, but there are some patterns. Most people with MS are diagnosed between the ages of 20 and 50. Two-three times as many women as men have MS. Studies indicate that genetic factors make certain individuals more susceptible than others, but there is no evidence that MS is directly inherited. MS occurs more commonly among people with northern European ancestry, but people of African, Asian, and Hispanic backgrounds are not immune. Approximately 400,000 Americans acknowledge having MS, and every week about 200 people are diagnosed. Worldwide, MS may affect 2.5 million individuals. © 2007 The National Multiple Sclerosis Society. All rights reserved.