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What is multiple sclerosis?
Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS), which is made up of the brain and spinal cord. The CNS is composed of nerve cells that are linked by fibers called axons. The axons are wrapped in a protective substance called myelin, which allows messages to be sent at high speed. In MS, white blood cells attack and cause inflammation and destruction of the myelin. This damage causes a communication breakdown, which in turn may cause a wide range of symptoms including weakness, fatigue, and vision problems.
What causes MS?
The exact cause of MS is unknown. Doctors believe MS is an autoimmune disease. In an autoimmune disease, the body attacks itself, thinking it is attacking viruses or bacteria. In MS, the body attacks the central nervous system, and the disease eats away at the myelin covering on the nerve fibers. Some doctors think MS may be triggered by an infection, probably a virus. But MS is not contagious.
Who gets MS?
Approximately 400,000 people in the United States have MS, and every week about 200 more are diagnosed. More than twice as many women have MS as men, and it occurs in all races – but it is most common in whites, particularly those of Northern European descent. Most people with MS are diagnosed between the ages of 20 and 40.
How is MS diagnosed?
Usually the first clues leading to a diagnosis of MS are the symptoms you describe to your doctor combined with a careful review of your medical history. Most of the time this leads to a thorough neurological examination, and will probably include MRI* scans of the central nervous system and other tests. MRI scans, or magnetic resonance imaging, are safe and painless, and can show the location and size of lesions to help doctors assess the overall damage caused by MS.
*The exact correlation between MRI findings and the current or future clinical status of patients, including disability progression, is unknown.
What is an MRI scan?
In MS, an MRI* (magnetic resonance imaging) scan is used to take detailed pictures of the brain and spinal cord. MRI scans show the amount of water in tissues. Since MS lesions have higher-than-normal water content, they appear in these detailed pictures of the central nervous system showing the areas of damage. Lesions may cause MS symptoms. How your symptoms affect you depend on where the lesions form in the brain and spinal cord. The more lesions you have, the more damage may occur. The more damage, the higher your risk of disability.
*The exact correlation between MRI findings and current or future clinical status of patients, including disability progression, is unknown.
How does MRI help diagnose and monitor the progress of MS?
MRI* scans of the brain and spinal cord show the location and size of lesions, or areas of demyelinated nerve tissue. MRI scans can be used to confirm a diagnosis of MS. They can also be used to monitor the progression of the disease by allowing your doctor to compare the results of one MRI scan with a previous one. The number and location of lesions shown in MRI scans may correlate with a person's symptoms. For example, a brainstem lesion may cause dizziness; a spinal cord lesion may cause weakness. Some lesions may be "clinically silent" and produce no symptoms. The more lesions you have, the more damage may occur. The more damage, the higher your risk of disability.
*The exact correlation between MRI findings and current or future clinical status of patients, including disability progression, is unknown.
What other tests are used to diagnose MS?
In addition to MRI* scans, other common laboratory tests used to diagnose MS are a spinal tap (to detect abnormal proteins or other substances within the cerebral spinal fluid, and evoked potentials (to measure the speed of nervous system transmissions, which may indicate damage due to MS).
*The exact correlation between MRI findings and current or future clinical status of patients, including disability progression, is unknown.
How often should I have an MRI scan?
MRI* scans are an important part of managing and treating MS. A regular (for example annual MRI) can help you and your doctor monitor the progression of your disease and how well your treatment is working. For example, if you are taking medication and your MRI scan shows an increase in lesion activity, you and your doctor may want to consider another treatment option for you. Ask your doctor when you should have your next MRI scan.
*The exact correlation between MRI findings and current or future clinical status of patients, including disability progression, is unknown.