What is multiple sclerosis?

Multiple sclerosis (MS) is a chronic and often disabling disease of the central nervous system. Symptoms may be episodic and mild, such as numbness in a limb, or severe, including paralysis, cognitive loss, or loss of vision.

MS involves decreased nerve function associated with scar formation on myelin, the covering of nerve cells. Repeated episodes of inflammation destroy myelin, leaving multiple areas of scar tissue along the covering of the nerve cells. This results in slowing or blockage of transmissions in that area.

Multiple sclerosis often progresses with episodes (called "exacerbations") that last days, weeks, or months. Exacerbations may alternate with times of reduced or no symptoms (remission). Recurrence (relapse) is common.

A relapsing-remitting course, the most common form of MS, is characterized by partial or total recovery after attacks. About 75 percent of people with MS begin with a relapsing-remitting course.

Relapsing-remitting MS may become steadily progressive with continued attacks and partial recoveries. This is called secondary-progressive MS. Of those who start with relapsing-remitting, more than half will develop secondary-progressive MS within ten years; 90 percent within 25 years.

A progressive course from onset of the disease is called primary-progressive MS. In this case, symptoms generally do not remit.

Although the disorder is chronic and incurable, life expectancy can be normal or nearly so, with a lifespan of 35 or more years after diagnosis occurring commonly. Most people with MS continue to walk and function at work with minimal disability for 20 or more years.


Multiple sclerosis varies greatly from person to person and in the severity and the course of the disease. Symptoms of MS include:

  • Weakness, tremor, or paralysis of one or more extremities
  • Movement problems, loss of coordination and balance
  • Numbness, tingling, and spasticity
  • Pain
  • Loss of vision
  • Loss of memory or judgment
  • Bladder, bowel, and sexual dysfunction
  • Fatigue

Fatigue, occurring in about 80 percent of people with MS, can significantly interfere with a person's ability to work and function. It may be the most prominent symptom in a person who has otherwise been minimally affected by the disease.

MS-related fatigue generally occurs on a daily basis and tends to worsen as the day progresses. It tends to be aggravated by heat and humidity. It does not, however, appear to be correlated with depression or the degree of physical impairment.

Attempts should be made to avoid fatigue, stress, physical deterioration, temperature extremes, and illness to reduce factors that may trigger an MS attack.

Causes of MS

The exact cause of MS is unknown. Studies indicate an environmental factor may be involved. There is a higher incidence in northern Europe, northern United States, southern Australia, and New Zealand than in other areas of the world.

As people in sunnier climates are less likely to get MS, research has targeted some link between lower levels of vitamin D and MS. Vitamin D is synthesized naturally by the skin as it is exposed to sunlight. Studies show that people in northern climates often have reduced vitamin D levels.

In fact, babies born in less sunny April have the highest risk of developing multiple sclerosis later in life while those born in sunnier October have the lowest risk. There may also be a familial tendency toward the disorder.

MS affects approximately 1 out of 1,000 people. Women are affected more commonly than men. The disorder most commonly begins between 20 to 40 years old but can happen at any age. The progress, severity, and symptoms of MS in any individual cannot yet be predicted.

Multiple sclerosis is believed to be an abnormal immune response directed against the central nervous system (CNS). The cells and proteins of the body's immune system, which normally defend the body against infections,turn against the brain and spinal cord, destroying myelin.

The specific triggering mechanism that causes the immune system to attack its own myelin remains unknown, although a viral infection combined with an inherited genetic susceptibility is a leading suspect. While many different viruses have been thought to cause MS, there has been no definitive evidence linking its cause to any one virus.

Treatments and clinical trials

While there is no known cure for multiple sclerosis, there are promising new therapies that may decrease exacerbations and delay progression of the disease. Treatment is aimed at controlling symptoms and maintaining function to prolong maximum quality of life.

Clinical trials have led to approvals of several drugs shown to affect immune response, and thus the course of MS.

  • Betaseron helps reduce the severity and frequency of attacks.
  • Avonex, approved in 1996, slows the development of disability and reduces the severity and frequency of attacks.
  • Copaxone treats relapsing-remitting MS.
  • Rebif reduces the number and frequency of relapses and slows the progression of disability.
  • Novantrone treats advanced or chronic MS and reduces the number of relapses.
  • Tysabri was approved for relapsing-remitting multiple sclerosis, with very restrictive prescription policies due to a high risk for immune-related side effects.

Recently, three oral medications have been approved for treating MS:

  • Gilenya, for reducing the frequency of relapses and delaying physical disability in relapsing forms of MS.
  • Aubagio, which inhibits the function of specific immune cells implicated in MS.
  • Tecfidera, shown to reduce relapses and development of brain lesions, and to slow disability progression over time.

A drug called Ampyra was approved to improve walking speed in people with MS. The active ingredient, 4AP, has been widely used for many years as a nerve stimulant by people with MS or spinal cord injury and is available by prescription from compounding pharmacies.

Steroids are often given to decrease the severity of an attack. Other common MS medicines include baclofen, tizanidine or diazepam may be used to reduce muscle spasticity. Cholinergic medications may be helpful to reduce urinary problems. Antidepressant medications may be helpful for mood or behavior symptoms. Amantadine may be given for fatigue.

Physical therapy, speech therapy or occupational therapy may improve the person’s outlook, reduce depression, maximize function, and improve coping skills. A planned exercise program early in the course of MS helps to maintain muscle tone.

Research efforts

There are many studies underway to accelerate the development of treatments for MS, below is a snapshot of current research efforts:

  • Minocycline (an antibiotic) has showed promising results as an anti-inflammatory agent in trials with relapsing-remitting MS.
  • Plasmapheresis is used to treat myasthenia gravis, Guillain-Barré, and other demyelinating diseases. Studies of plasmapheresis in people with primary and secondary progressive MS have had mixed results.
  • By wiping out the immune cells in a patient's bone marrow with chemotherapy and then repopulating it with healthy mesenchymal stem cells, researchers hope the rebuilt immune system will stop attacking its own nerves.
  • Immune system defenders called T-cells erode myelin by producing small chemical signals (cytokines) that activate cells known as macrophages, which destroy the myelin. A man-made antibody called Zenapax (approved for use in people with kidney transplants) attaches itself to the rogue T-cells, blocking their role in the damage process. Results have been encouraging in early relapsing-remitting MS trials.
  • A drug called Tcelna is in clinical trials as a sort of MS vaccine; it is manufactured from the blood of each MS patient and thus specifically tailored to each patient's immune response to myelin-reactive T-cells (MRTC), known to attack myelin.
  • Rituxan, a drug that is already used to treat cancer and rheumatoid arthritis, reduced by more than half the chance that people with MS would have symptom flare-ups over a six-month period.
  • It may be possible to repair damage to myelin (a process called remyelinization). Various cell types, including Schwann cells, can migrate and remyelinate brain and spinal cord nerves after transplantation directly into experimental lesions.


If you are looking for more information on multiple sclerosis or have a specific question, our information specialists are available business weekdays, Monday through Friday, toll-free at 800-539-7309 from 9am to 5pm ET.

Additionally, the Reeve Foundation maintains a fact sheet on MS with resources from trusted Reeve Foundation sources. Check out our repository of fact sheets on hundreds of topics ranging from state resources to secondary complications of paralysis.

We encourage you to also reach out to MS support groups and organizations, including:

    This project was supported, in part, by grant number 90PRRC0002, from the U.S. Administration for Community Living, Department of Health and Human Services, Washington, D.C. 20201. Grantees undertaking projects under government sponsorship are encouraged to express freely their findings and conclusions. Points of view or opinions do not, therefore, necessarily represent official Administration for Community Living policy.