Signs and symptoms of multiple sclerosis vary, depending on the location of affected nerve fibers. MS 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
- Problems with bowel and bladder function
Most people with MS have a relapsing-remitting course, with new symptoms (relapse) that develop over days or weeks and usually improve partially or completely, followed by a quiet period (remission) that can last months or even years. Small increases in body temperature can temporarily worsen signs and symptoms of MS, but that type of event isn't a relapse.
About 60 to 70 percent of people with relapsing-remitting MS eventually develop a steady progression of symptoms, with or without periods of remission (secondary-progressive MS). The worsening symptoms usually include problems with gait. The rate of progression varies greatly among people with secondary-progressive MS.
Some people with MS experience a gradual onset and steady progression of signs and symptoms with no relapses (primary-progressive MS).
The cause of multiple sclerosis is unknown. It's believed to be an autoimmune disease, in which the body's immune system attacks its own tissues. In MS, this process destroys myelin — the fatty substance that coats and protects nerve fibers in the brain and spinal cord.
Myelin can be compared to the insulation on electrical wires. When myelin is damaged, the messages that travel along that nerve may be slowed or blocked.
It isn't clear why MS develops in some people and not others. A combination of factors, ranging from genetics to childhood infections, may play a role.
These factors may increase your risk of developing multiple sclerosis:
- Age. MS can occur at any age, but most commonly affects people between the ages of 15 and 60.
- Sex. Women are about twice as likely as men are to develop MS.
- Family history. If one of your parents or siblings has had MS, you are at higher risk of developing the disease.
- Certain infections. A variety of viruses have been linked to MS, including Epstein-Barr, the virus that causes infectious mononucleosis.
- 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.
- Climate. MS is far more common in countries with temperate climates, including southern Canada, northern United States, New Zealand, southeastern Australia and Europe.
- Certain autoimmune diseases. You have a slightly higher risk of developing MS if you have thyroid disease, type 1 diabetes or inflammatory bowel disease.
- 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.
People with multiple sclerosis also may develop:
- Muscle stiffness or spasms
- Paralysis, typically in the legs
- Problems with bladder, bowel or sexual function
- Mental changes, such as forgetfulness or mood swings