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School of Medicine
Multiple Sclerosis (MS)
Multiple sclerosis is a chronic disease of the central nervous system (the brain, spinal cord, and nerves). It occurs when the immune system attacks nerve fibers and myelin sheathing in the brain and spinal cord, resulting in abnormal nervous system function. Myelin is a fatty substance that surrounds healthy nerve fibers, insulating the fibers to help transmission of electrical messages along the nerves to various parts of the body. Nerve cell processes and myelin sheathing are destroyed by the inflammation that occurs with this abnormal immune attack, causing an interruption or distortion of the electrical impulses to and from the brain.
Types of multiple sclerosis:
There are several types of MS that reflect different courses of illness:
Relapsing-Remitting Multiple Sclerosis:
At the time of diagnosis, 90% of patients will have a relapsing-remitting pattern of MS. This form of multiple sclerosis is characterized by the onset of the following symptoms over a period of hours to days:
- Blurred vision
- Unsteady gait
These symptoms tend to persist for days or weeks, and then disappear partially or completely on their own or with treatment. Patients may then remain symptom-free for weeks, months or even years. The periods of disease activity are called exacerbations or “relapses.” The periods without symptoms are called “remissions.” Without treatment, most people with MS will develop disease symptoms that will gradually worsen over time. In most cases, this will be without discernible relapses and remissions.
Secondary Progressive Multiple Sclerosis:
If the condition progresses to a point where there are no discernible relapses and remissions, the diagnosis is secondary progressive MS.
Primary Progressive Multiple Sclerosis:
About 10-15% of patients will have a gradual worsening from the start of their MS disease. This is referred to as primary progressive MS.
Benign Multiple Sclerosis:
Benign MS is a mild course where an individual will have mild disease symptoms after having MS for about 15 years. This occurs in about 5-10% of patients. There is no good way of predicting which patients will follow this course.
What causes multiple sclerosis?
Multiple Sclerosis typically affects those with the following characteristics:
- Young adults, typically between the ages of fifteen and fifty
- Women more often than men
- Occurs more frequently in temperate zones than states near the equator (environmental factors)
- People of European descent more often than individuals of African or Asian ancestry (genetic factors)
- People with family members diagnosed with MS are at a slightly higher risk for developing the disease (genetic factors)
The exact cause of MS is unknown. It appears to be an autoimmune disease in which the immune system is stimulated to attack myelin in the central nervous system. The source of the initial stimulus has not been clearly identified. In certain people who inherit a predisposition to MS, the trigger may be infections (such as viruses) or other factors in the environment. Individuals may also have a genetic predisposition for developing the disease as people with family members diagnosed with MS are at a slightly higher risk.
Symptoms vary greatly from person to person, over time and in intensity. They may include:
- sensory symptoms, such as paresthesia (numbness and tingling) and pain
- visual symptoms such as double vision
- motor symptoms such as weakness, tremor, dizziness, spasticity
- autonomic symptoms such as frequent urination, urgency
- other symptoms, such as fatigue
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