Multiple Sclerosis - Description
Nerve messages consist of electrical impulses that travel through the body by means of nerve cells. Nerve cells are also called neurons. Neurons are covered by a thin layer of tissue known as myelin (pronounced MY-uh-lin) that acts as an insulator. It prevents the electrical currents that pass through neurons from leaking away.
MS occurs when the myelin that surrounds neurons in the brain and spinal cord is destroyed. The loss of myelin causes electrical impulses to pass through neurons more slowly. Over time, scar tissue forms around the damaged myelin. This scar tissue, called plaque (pronounced PLAK), also reduces the neurons' ability to function normally.
Damage to myelin can cause a variety of symptoms. A person may lose the ability to use his or her senses, such as touch and vision. Loss of muscular control also occurs because movement of muscles is controlled by nerves. A person with MS may have problems with balance, strength, and coordination.
MS affects more than 250,000 people in the United States. Most people experience their first symptoms between the ages of twenty and forty. Symptoms rarely begin before the age of fifteen or after sixty. Women are twice as likely to get MS as men, especially in their early years. MS is more common among some ethnic groups than others. For example, the disease is more common in North America and northern Europe than in other parts of the world. MS is very rare among Asians, Indians of North and South America, and Eskimos.
- Evoked potential test (EPT):
- A test that measures the brain's electrical response to certain kinds of stimulation, such as light in the eyes, sound in the ears, or touch on the skin.
- A layer of tissue that surrounds nerves and acts as an insulator.
- Patches of scar tissue that form in areas where myelin tissue has been destroyed.
- Primary progressive:
- A form of multiple sclerosis in which the disease continually becomes worse without any major improvement.
- A form of multiple sclerosis in which symptoms appear for at least twenty-four hours and then disappear for a period of time.
- Secondary progressive:
- A form of multiple sclerosis in which a period of relapses and remissions is followed by another period in which the disease becomes progressively worse without improvement.