Overview

Multiple sclerosis (MS) is a potentially disabling disease of the brain and spinal cord (central nervous system).

In MS, the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body. Eventually, the disease can cause permanent damage or deterioration of the nerve fibers.

Signs and symptoms of MS vary widely between patients and depend on the location and severity of nerve fiber damage in the central nevous system. Some people with severe MS may lose the ability to walk independently or ambulate at all. Other individuals may experience long periods of remission without any new symptoms depending on the type of MS they have.

There's no cure for multiple sclerosis. However, there are treatments to help speed the recovery from attacks, modify the course of the disease and manage symptoms.

Symptoms

Multiple sclerosis signs and symptoms may differ greatly from person to person and over the course of the disease depending on the location of affected nerve fibers.

Common symptoms include:

  • Numbness or weakness in one or more limbs that typically occurs on one side of your body at a time
  • Tingling
  • Electric-shock sensations that occur with certain neck movements, especially bending the neck forward (Lhermitte sign)
  • Lack of coordination
  • Unsteady gait or inability to walk
  • Partial or complete loss of vision, usually in one eye at a time, often with pain during eye movement
  • Prolonged double vision
  • Blurry vision
  • Vertigo
  • Problems with sexual, bowel and bladder function
  • Fatigue
  • Slurred speech
  • Cognitive problems
  • Mood disturbances

When to see a doctor

See a doctor if you experience any of the above symptoms for unknown reasons.

Disease course

Most people with MS have a relapsing-remitting disease course. They experience periods of new symptoms or relapses that develop over days or weeks and usually improve partially or completely. These relapses are followed by quiet periods of disease remission that can last months or even years.

Small increases in body temperature can temporarily worsen signs and symptoms of MS. These aren't considered true disease relapses but pseudorelapses.

At least 20% to 40% of those with relapsing-remitting MS can eventually develop a steady progression of symptoms, with or without periods of remission, within 10 to 20 years from disease onset. This is known as secondary-progressive MS.

The worsening of symptoms usually includes problems with mobility and gait. The rate of disease progression varies greatly among people with secondary-progressive MS.

Some people with MS experience a gradual onset and steady progression of signs and symptoms without any relapses, known as primary-progressive MS.

Causes

The cause of multiple sclerosis is unknown. It's considered an immune mediated disease in which the body's immune system attacks its own tissues. In the case of MS, this immune system malfunction destroys the fatty substance that coats and protects nerve fibers in the brain and spinal cord (myelin).

Myelin can be compared to the insulation coating on electrical wires. When the protective myelin is damaged and the nerve fiber is exposed, the messages that travel along that nerve fiber may be slowed or blocked.

It isn't clear why MS develops in some people and not others. A combination of genetics and environmental factors appears to be responsible.

Risk factors

These factors may increase your risk of developing multiple sclerosis:

  • Age. MS can occur at any age, but onset usually occurs around 20 and 40 years of age. However, younger and older people can be affected.
  • Sex. Women are more than 2 to 3 times as likely as men are to have relapsing-remitting 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. A recent study suggests that the number of Black and Hispanic young adults with multiple sclerosis may be greater than previously thought.
  • Climate. MS is far more common in countries with temperate climates, including Canada, the northern United States, New Zealand, southeastern Australia and Europe. Your birth month may also affect the chances of developing multiple sclerosis, since exposure to the sun when a mother is pregnant seems to decrease later development of multiple sclerosis in these children.
  • Vitamin D. Having low levels of vitamin D and low exposure to sunlight is associated with a greater risk of MS.
  • Your genes. A gene on chromosome 6p21 has been found to be associated with multiple sclerosis.
  • Obesity. An association with obesity and multiple sclerosis has been found in females. This is especially true for female childhood and adolescent obesity.
  • Certain autoimmune diseases. You have a slightly higher risk of developing MS if you have other autoimmune disorders such as thyroid disease, pernicious anemia, psoriasis, type 1 diabetes or inflammatory bowel disease.
  • Smoking. Smokers who experience an initial symptom that may signal MS are more likely than nonsmokers to develop a second event that confirms relapsing-remitting MS.

Complications

People with multiple sclerosis may also develop:

  • Muscle stiffness or spasms
  • Severe weakness or paralysis, typically in the legs
  • Problems with bladder, bowel or sexual function
  • Cognitive problems, like forgetfulness or word finding difficulties
  • Mood problems, such as depression, anxiety or mood swings
  • Seizures, though very rare