Multiple Sclerosis (MS) is a disease of the central nervous system, or CNS (the brain, optic nerves, and spinal cord). Its course is unpredictable and severity can range from mild to disabling. MS disrupts communication between the brain and other parts of the body. As a result, people with MS may experience vision changes, muscle weakness, and difficulty with balance and coordination, along with many other symptoms.
MS is often considered an autoimmune disease, or a disorder where instead of attacking foreign substances such as germs, the body’s immune system attacks its own healthy tissues. In people with MS, the immune system attacks the myelin, which insulates and protects the nerves of the CNS.
MS affects both men and women but is significantly more common in women—almost twice as many women as men have MS. It’s estimated that approximately 400,000 people in the United States have MS. MS is most often diagnosed in people between the ages of 20 and 50 but can also appear in children, teenagers, and older adults.
There are four different types, or courses, of MS. Each can be mild, moderate, or severe.
This is the most common form of MS, affecting approximately 85 percent of people diagnosed with the disease. Relapsing-remitting MS is characterized by attacks (also called relapses, flares, or exacerbations) that are followed periods of complete or partial recovery (remissions).
This type of MS affects approximately 10 percent of those diagnosed with MS. Unlike relapsing-remitting MS, there are no distinct relapses or remissions. Primary-progressive MS is instead marked by progression, which may vary in severity. People may experience occasional plateaus in progression as well as temporary minor improvements.
Many people who initially have relapsing-remitting MS develop secondary-progressive MS. This type of MS involves disease that steadily worsens. There may or may not be occasional flare-ups, remissions, or plateaus.
This is a relatively rare type of MS, making up 5 percent of cases. It’s characterized by a steady worsening of the disease along with attacks of worsening symptoms. Some people do experience periods of recovery, but there are no remissions, and the disease continues to progress.
The cause of MS is not known, but researchers have identified several potential factors in its development. It’s generally believed that MS is an autoimmune disease, meaning that it is the result of abnormal activity in the immune system, where the myelin is attacked. As well, environmental factors may be involved—MS occurs more frequently in regions farther from the equator, suggesting a geographic link; and because people in these regions receive less sun exposure and therefore may have lower levels of vitamin D than people in sunnier regions, researchers are questioning the role of Vitamin D deficiency in the development of MS. There may also be genetic factors that make some people more susceptible than others. And, although MS occurs in most ethnic groups, it’s more common in Whites of northern European ancestry than in other groups. It’s also thought that certain viruses or infections may trigger MS.
More is understood about what causes the symptoms of MS than about causes of the disease itself. Symptoms of MS are the result of an immune system attack on the myelin. These attacks damage and scar the myelin in multiple places within the CNS and permanently sever some underlying nerve fibers. The scars are referred to as sclerotictissue. As a result, the CNS can’t effectively send nerve signals to other parts of the body. This altered communication between the CNS and the rest of body causes the symptoms of MS.
No one experiences MS in the same way. Symptoms vary for each person. Symptoms are also unpredictable—some may come and go, and others may remain constant.
Most Common Symptoms:
Less Common Symptoms:
Consistent with the mysterious nature of MS, there is yet no definitive test to diagnose or rule out the disease. Diagnosis is further complicated by the fact that symptoms of MS are similar to several other disorders. Doctors take several steps to make a diagnosis: a medical history, a neurologic exam, and various tests including magnetic resonance imaging (MRI), visual evoked potentials (VEP), and cerebrospinal fluid analysis. As well, several criteria are applied to make a diagnosis of MS; these include evidence of damage in at least two separate areas of the CNS, evidence that that damage occurred at least one month apart, and the ruling out of other possible diagnoses.
How the tools for diagnosis work: