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Multiple sclerosis (MS) is a chronic, potentially debilitating disease that affects the central nervous system, which is made up of the brain and spinal cord. Doctors and researchers think the illness is probably an autoimmune disease, which means that your immune system attacks part of your body as if it's a foreign substance.

In multiple sclerosis, the body incorrectly directs antibodies and white blood cells against proteins in the myelin sheath, which surrounds nerves in your brain and spinal cord. This causes inflammation and injury to the sheath and ultimately to the nerves that it surrounds. The result may be multiple areas of scarring (sclerosis). Eventually, this damage can slow or block the nerve signals that control muscle coordination, strength, sensation and vision.

Multiple sclerosis affects more than 1 million people around the world - including twice as many women as men. Most people experience their first symptoms between ages 20 and 40. This disease is unpredictable and varies in severity. In some people, MS is a mild illness, but, for others, it results in permanent disability. Treatments can modify the course of the disease and relieve symptoms.

Symptoms of multiple sclerosis vary widely, depending on the location of affected nerve fibers. Signs and symptoms of multiple sclerosis may include:

• Numbness or weakness in one or more limbs, which typically occurs on one side of the body at a time or the bottom half of the body
• 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 numb areas of the body
• Electric-shock sensations that occur with certain head movements
• Tremor, lack of coordination or unsteady gait
• Fatigue
• Dizziness

In some cases, people with MS may also develop muscle stiffness or spasticity, slurred speech, paralysis, or problems with bladder, bowel or sexual function. Mental changes such as forgetfulness or difficulties with concentration also can occur.

Your central nervous system contains millions of nerve cells joined together by nerve fibers. Electrical impulses originate in nerve cells and travel along the nerve fibers to and from your brain. Myelin is the fatty substance that coats and protects these fibers, similar to the way insulation shields electrical wires.

In people with MS, the immune system mistakenly destroys the cells that produce the myelin sheath. As a result, myelin becomes inflamed and swollen and detaches from the fibers. The detached myelin may eventually be destroyed. Firm or hardened (sclerosed) patches of scar tissue form over the fibers. When nerve impulses reach a damaged area, some impulses are blocked or delayed from traveling to or from your brain. Ultimately, this process leads to degeneration of the nerves themselves, which likely accounts for the permanent disabilities that may develop in MS.

Doctors and researchers don't understand what causes this autoimmune reaction. Some evidence suggests that genetic factors make certain people more susceptible to MS than others are. But genetic susceptibility is only part of the explanation. Something seems to trigger the condition in susceptible people. Some researchers believe the disorder is related to a protein that mimics the myelin protein, which may be introduced into the body by a virus. Other researchers believe that the immune system is somehow disrupted in people with MS, which leads to an abnormal tendency to develop autoimmune disease. The disease can also be exacerbated by hormonal changes after pregnancy.

Whatever the cause or trigger, multiple sclerosis occurs in four main patterns:

• Relapsing remitting. This type of MS is characterized by clearly defined flare-ups, followed by periods of remission. The flare-ups typically appear suddenly, last a few weeks or months, and then gradually disappear. Most people with MS have this form at the time of diagnosis.
• Primary progressive. People with this less common form of MS experience a gradual decline, without periods of remission. People with this form of MS are usually older than 40 when symptoms begin.
• Secondary progressive. More than half the people with relapsing remitting MS eventually enter a stage of continuous deterioration referred to as secondary progressive MS. Sudden relapses may occur, superimposed upon the continuous deterioration that characterizes this type of MS.
• Progressive relapsing. This is primary progressive MS with the addition of sudden episodes of new symptoms or worsened existing ones. This form is relatively rare.

These factors may increase your risk of developing multiple sclerosis:

• Heredity. Multiple sclerosis is more common in people of Northern European descent. There also appears to be a genetic component to the condition, although it's not strictly inherited. Researchers suspect that the tendency to develop MS is inherited, but the disease manifests itself only when environmental triggers are present.
• Environmental factors. Environmental factors have some influence on MS. Many viruses and bacteria have been suspected of causing MS. Some researchers believe that environmental factors may trigger the disease in susceptible people.
• Geographical factors. Multiple sclerosis is more common in countries with temperate climates, including Europe, southern Canada, northern United States, New Zealand and southeastern Australia.

One of the early indications of MS is numbness and tingling in your arms, legs or elsewhere in your body. Although numbness most often doesn't indicate MS, it's important to see your doctor if you experience numbness or tingling that persists for days or weeks — especially if it involves large parts of your body. Your doctor can determine whether MS or another neurological disorder may be the cause. Also see your doctor if you experience persistent double vision, persistent loss of balance or visual loss.

Multiple sclerosis can be difficult to diagnose. Your doctor may base a diagnosis of MS on the following:

• Medical history. Your doctor reviews your symptoms and the pattern of the symptoms.
• Neurological examination. This examination systematically tests various parts of your nervous system, including your reflexes, muscle strength, muscle tone, and sensations of pain, heat, touch and vibration. Your doctor may also observe your gait, posture, coordination and balance, and ask you questions to help determine the clarity of your thinking, judgment and memory.
• Magnetic resonance imaging (MRI) scan. The cylinder-shaped MRI scanner creates tissue-slice images on a computer from data generated by a powerful magnetic field and radio waves. Your doctor can view these images from any direction or plane. This imaging technique may reveal MS lesions, which are caused by myelin loss. Newer MRI techniques can provide even greater detail.
• Spinal tap (lumbar puncture). In this procedure, a doctor or nurse removes a small sample of cerebrospinal fluid from within your spinal canal for laboratory analysis. This sample can show abnormalities associated with MS, such as abnormal levels of white blood cells or proteins. This procedure can also help rule out viruses and other conditions that can cause neurological symptoms.
• Evoked potential test. This test measures the electrical signals sent by the brain in response to stimuli. An evoked potential test may use visual stimuli or electrical stimuli, in which short electrical impulses are applied to the legs or arms.

If your attacks are mild or infrequent, your doctor may advise a wait-and-see approach, with counseling and observation. However, if you have a relapsing form of the disease, your doctor may recommend treatment with disease-modifying medications as soon as possible. These medications can't be used if you are pregnant or may become pregnant. They include:

• Beta interferons. Interferon beta-1b (Betaseron) and interferon beta-1a (Avonex, Rebif) are genetically engineered copies of proteins that occur naturally in your body. They help fight viral infection and regulate your immune system. If you use Betaseron, you inject yourself under your skin (subcutaneously) every other day. If you use Rebif, you inject yourself subcutaneously three times a week. Avonex is self-injected into your muscle (intramuscularly) once a week. These medications reduce flare-ups of MS. It's uncertain which of their many actions lead to a reduction in disease activity and what their long-term benefits are. Beta interferons should never be used in combination with one another. Only one of these medications should be used at a time.

  The Food and Drug Administration (FDA) has approved beta interferons only for people with relapsing forms of MS who can still walk. Beta interferons don't reverse damage and haven't been proved to prevent permanent disability. Some people develop antibodies to beta interferons, which may make them less effective. Other people can't tolerate the side effects, which may include symptoms similar to those of the flu (influenza).

  Doctors generally recommend beta interferons for people who have more than one attack of MS a year and for those who don't recover well from flare-ups. The treatment may also be used for people who have a significant buildup of new lesions as seen on an MRI scan, even when there may not be major new symptoms of disease activity.

• Glatiramer (Copaxone). This medication is an alternative to beta interferons if you have relapsing remitting MS. Doctors believe that glatiramer works by blocking your immune system's attack on myelin. You must inject glatiramer subcutaneously once daily. Side effects may include flushing and shortness of breath after injection.
• Other medications. Mitoxantrone (Novantrone) is a chemotherapy drug used for many cancers. This drug is also FDA-approved for treatment of aggressive forms of relapsing remitting MS, as well as certain forms of progressive MS. It's given intravenously, typically every three months. However, mitoxantrone may cause serious side effects, such as heart damage, after long-term use, so it's typically not used for longer than two years. And it's typically reserved for people with severe attacks or rapidly advancing disease who don't respond to other treatments. Close monitoring is critical for anyone on this medication. Some doctors are also prescribing other chemotherapy drugs, such as cyclophosphamide (Cytoxan), for people with severe, rapidly progressing MS. However, these medications aren't approved for treatment of MS.

Some medications may relieve symptoms of progressive MS. They include:

• Corticosteroids. Doctors most often prescribe short courses of oral or intravenous corticosteroids to reduce inflammation in nerve tissue and to shorten the duration of flare-ups. Prolonged use of these medications, however, may cause side effects such as osteoporosis and high blood pressure (hypertension).
• Muscle relaxants. Baclofen and tizanidine (Zanaflex) are oral treatments for muscle spasticity. If you have MS, you may experience muscle stiffening or spasms, particularly in your legs, which can be painful and uncontrollable. Baclofen often increases weakness in the legs. Zanaflex appears to control muscle spasms without leaving your legs feeling weak but can be associated with drowsiness or a dry mouth.
• Medications to reduce fatigue. To help combat fatigue, your doctor may prescribe an antidepressant medication, the antiviral drug amantadine (Symmetrel) or a medication for narcolepsy called modafinil (Provigil). All appear to work because of their stimulant properties.
• Other medications. Many medications are used for the muscle stiffness, depression, pain and bladder control problems often associated with MS. Drugs for arthritis and medications that suppress the immune system may slow MS in some cases.

In addition to medications, these treatments may also be helpful:

• Physical and occupational therapy. A physical or occupational therapist can teach you strengthening exercises and show you how to use devices that can ease daily tasks. This can help preserve your independence.
• Counseling. Individual or group therapy may help you cope with MS and relieve emotional stress. Your family members or caregivers may also benefit from seeing a counselor.
• Plasma exchange (plasmapheresis). Plasma exchange may help restore neurological function in people with sudden severe attacks of MS-related disability who don't respond to high doses of steroid treatment. This procedure involves removing some of your blood and mechanically separating the blood cells from the fluid (plasma). Your blood cells then are mixed with a replacement solution, typically albumin, or a synthetic fluid with properties like plasma. The solution with your blood is then returned to your body.

  Replacing your plasma may dilute the activity of the destructive factors in your immune system, including antibodies that attack myelin, and help you to recover. Plasma exchange has no proven benefit beyond three months from the onset of the neurological symptoms.

These steps may help relieve some symptoms of multiple sclerosis:

• Get enough rest. Fatigue is a common symptom of MS, and getting your rest may make you feel less tired.
• Exercise. Regular aerobic exercise may offer some benefits if you have mild to moderate MS. Benefits include improved strength, muscle tone, balance and coordination, and help with depression. Swimming is a good option for people with MS who are bothered by heat.
• Be careful with heat. Extreme heat may cause extreme muscle weakness. Although some people with MS aren't bothered by heat and may enjoy warm baths and showers, be very careful before exposing yourself to extreme heat until you know how you'll react. Don't get into a hot tub or sauna unless there's someone nearby who can pull you out if necessary. If you do experience heat-related worsening of signs or symptoms, merely cooling down for a few hours usually will return you to your normal state.
• Cool down. Many people with MS experience heat-related worsening of MS symptoms. If you live in a hot and humid area, consider having air conditioning in your home. Tepid or cool baths also may provide some relief.
• Eat a well-balanced diet. Eating a healthy diet and taking the recommended daily dose of vitamins can help keep your immune system strong.

As is true with other chronic diseases, living with multiple sclerosis can place you on a roller coaster of emotions. Here are some suggestions to help you even out the ups and downs:

• Maintain normal daily activities as best you can.
• Stay connected with friends and family.
• Continue to pursue hobbies that you enjoy and are able to do.

If multiple sclerosis impairs your ability to do things you enjoy, talk with your doctor about possible ways to get around the obstacles.

Remember that your physical health can directly impact your mental health. Denial, anger and frustration are not uncommon when you learn life has dealt you something painful and unexpected. Professionals such as therapists or behavioral psychologists may help you put things in perspective. They can also teach you coping skills and relaxation techniques that may be helpful.

Sometimes, joining a support group, where you can share experiences and feelings with other people, is a good approach. Ask your doctor what support groups are available in your community.

Many chronic illnesses, including MS, are associated with an increased risk of depression. This isn't a failure to cope but may indicate a disruption in the body's neurochemistry that can be helped with appropriate medical treatment.

If you have a chronic illness such as MS, there's no denying that it affects your life. But how much you allow it to determine the quality of your life depends, to some extent, on the way you choose to live day to day.