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Multiple Sclerosis

Content provided by the Faculty of the Harvard Medical School

What Is It?

Multiple sclerosis (MS) is a disabling neurological illness. It affects the brain and spinal cord. The disease is usually progressive. This means it worsens over time.

An insulating sheath called myelin normally surrounds nerve cells. Myelin helps to transmit nerve impulses.

In MS, the myelin sheath becomes inflamed or damaged. This disrupts or slows nerve impulses. The inflammation leaves areas of scarring called sclerosis.

Multiple sclerosis may also damage nerve cells, not just their myelin lining.

The disruption of nerve signals causes a variety of symptoms. MS can affect a person's vision, ability to move parts of the body, and ability to feel sensations (such as pain and touch).

Symptoms usually come and go. Periods when symptoms suddenly get worse are called relapses. They alternate with periods when symptoms improve, called remissions.

Many people have a long history of MS attacks over several decades. In these cases, the disease may worsen in "steps," when the attacks occur. For others, the disease worsens steadily. In a minority of patients, MS causes relatively few problems.

Scientists believe MS is an autoimmune disease. This means the immune system mistakenly attacks its own body. In this case, the body attacks the myelin sheaths of the nerves.

In some cases, the trigger for an MS attack seems to be a viral infection. At other times, other physical or emotional stress may be to blame. The timing, duration and damage of MS attacks are unpredictable.

The symptoms of MS usually begin before age 40. But people between ages 40 and 60 sometimes are affected. Having a close relative with MS increases your chances of developing the disease.


Symptoms of MS vary depending on which areas of the brain and spinal cord are affected.

MS can cause:

  • Sudden loss of vision

  • Blurred or double vision

  • Slurred speech

  • Clumsiness, especially on one side

  • Unsteady gait

  • Loss of coordination

  • Hand trembling

  • Extreme tiredness

  • Facial symptoms including numbness, weakness or pain

  • Loss of bladder control

  • Inability to empty the bladder

  • Tingling, numbness or a feeling of constriction in the arms, legs or elsewhere

  • Weakness or a heavy feeling in the arms or legs


Your doctor will look for signs of neurological problems. These include:

  • Vision changes

  • Difficulty walking

  • Difficulty coordinating body movements

  • Muscle weakness

  • Trembling hands

  • Loss of sensation

To confirm the diagnosis, your doctor probably will order a magnetic resonance imaging (MRI) scan. The MRI will check for inflammation and myelin sheath destruction in your brain and spinal cord.

Other possible diagnostic tests include:

  • A detailed eye examination by an ophthalmologist.

  • Special tests called evoked potentials. These record electrical activity in the brain.

  • Lumbar puncture (spinal tap) to obtain spinal fluid. Spinal fluid may show abnormal types of proteins called immunoglobulins. This is a characteristic finding in MS.

Expected Duration

MS is a lifelong illness. It can follow one of several different patterns.

The three most common patterns seen in MS patients are:

  • Relapsing remitting MS. There are relapses (episodes when symptoms suddenly get worse), followed by remissions (periods of recovery). Between relapses, the patient's condition usually is stable, without deterioration.

    This type accounts for the vast majority of cases at disease onset. About half of people with relapsing remitting MS enter a secondary progressive phase (described below) over time.

  • Primary progressive MS. Symptoms worsen gradually and continuously. There are no episodes of relapses and remissions.

  • Secondary progressive MS. Someone who originally had relapsing remitting MS begins to have gradual deterioration in nerve function. This may occur with or without relapses.

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Did You Know?

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Which of these age groups is more likely to experience initial symptoms of multiple sclerosis?