Multiple sclerosis is a disease of the central nervous system that affects the brain and spinal cord. It causes your immune system to attack the myelin sheath that covers your nerves. When myelin becomes damaged, it interferes with the pathway between your brain and the rest of your body that allows the two to communicate. Eventually, the nerves gradually deteriorate. Unfortunately, multiple sclerosis is irreversible and there is currently no cure as of yet.

The signs and symptoms of multiple sclerosis vary depending on how much damage it causes the nerves and which nerves are affected. Some people who develop a severe case of multiple sclerosis may no longer be able to walk. Others may go into remission for a period of time and have no symptoms at all. Signs and symptoms may include numbness or weakness in one or more limbs that typically occurs on one side of your body at a time, or the legs and trunk, partial or complete loss of vision, usually in one eye at a time, often with pain during eye movement, double vision or blurring of vision, tingling or pain in parts of your body, electric-shock sensations that occur with certain neck movements, especially bending the neck forward, tremor, lack of coordination or unsteady gait, slurred speech, fatigue, dizziness, or problems with bowel and bladder function.

It is unknown what the cause of multiple sclerosis is. For now, it is believed to be an autoimmune disease. This means that the body's immune system attacks itself. As for who is at risk, it is unclear as to why some people get it and some people don’t. What we know for now is that there are risk factors that may increase your risk of developing the disease. They include:
Family history. If one of your parents or siblings has had MS, you are at higher risk of developing the disease.

Race. White people, particularly those of Northern European descent, are at highest risk of developing MS. People of Asian, African or Native American descent have the lowest risk.
Age. MS can occur at any age, but most commonly affects people between the ages of 15 and 60.
Smoking. Smokers who experience an initial event of symptoms that may signal MS are more likely than nonsmokers to develop a second event that confirms relapsing-remitting MS.
Sex. Women are about twice as likely as men are to develop MS.

Climate. MS is far more common in countries with temperate climates, including southern Canada, northern United States, New Zealand, southeastern Australia and Europe.

Certain infections. A variety of viruses have been linked to MS, including Epstein-Barr, the virus that causes infectious mononucleosis.

Certain autoimmune diseases. You have a higher risk of developing MS if you have thyroid disease, type 1 diabetes or inflammatory bowel disease.