Human Diseases and Conditions

What is multiple sclerosis?

Multiple sclerosis (MS) is a disease in which the nerves of the central nervous system (brain and spinal cord) degenerate. Myelin, which provides a covering or insulation for nerves, improves the conduction of impulses along the nerves and also is important for maintaining the health of the nerves. In multiple sclerosis, inflammation causes the myelin to disappear. Consequently, the electrical impulses that travel along the nerves decelerate, that is, become slower. In addition, the nerves themselves are damaged. As more and more nerves are affected, a person experiences a progressive interference with functions that are controlled by the nervous system such as vision, speech, walking, writing, and memory.

About 350,000 people in the U.S. have multiple sclerosis. Usually, a person is diagnosed with multiple sclerosis between 20 and 50 years of age, but multiple sclerosis has been diagnosed in children and in the elderly. Multiple sclerosis is twice as likely to occur in Caucasians as in any other group. Women are twice as likely as men to be affected by multiple sclerosis earlier in life.

Sign & Symptoms

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

• Numbness or weakness in one or more limbs, which typically occurs on one side of your body at a time or the bottom half of your body
• Partial or complete loss of vision, usually in one eye at a time, often with pain during eye movement (optic neuritis)
• Double vision or blurring of vision
• Tingling or pain in parts of your body
• Electric-shock sensations that occur with certain head movements
• Tremor, lack of coordination or unsteady gait
• Fatigue
• Dizziness

Most people with multiple sclerosis, particularly in the beginning stages of the disease, experience relapses of symptoms, which are followed by periods of complete or partial remission. Signs and symptoms of multiple sclerosis often are triggered or worsened by an increase in body temperature.

Causes
Multiple sclerosis is an autoimmune disease, where the body's immune system attacks its own tissues. In multiple sclerosis, 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.
Doctors and researchers don't understand exactly why multiple sclerosis occurs in some people and not others. A combination of factors, ranging from genetics to childhood infections, may play a role

How is multiple sclerosis diagnosed?

Due to the broad range and subtleties of symptoms, multiple sclerosis may not be diagnosed for months to years after the onset of symptoms. Physicians, particularly neurologists, take detailed histories and perform complete physical and neurological examinations.

• MRI (magnetic resonance imaging) scans with intravenous gadolinium helps to identify, describe, and in some instances date lesions in the brain (plaques).
  
• An electro-physiological test, evoked potentials, examines the impulses traveling through the nerves to determine if the impulses are moving normally or too slowly.
  
• Finally, examining the cerebro-spinal fluid that surrounds the brain and spinal cord may identify abnormal chemicals (antibodies) or cells that suggest the presence of multiple sclerosis.

Collectively, these three tests help the physician in confirming the diagnosis of multiple sclerosis. For a definite diagnosis of multiple sclerosis, dissemination in time (at least two separate symptomatic events or changes on MRI over time) and in anatomical space (at least two separate locations within the central nervous system, which can be demonstrated by MRI or neurological exam) must be demonstrated.

Treatments and Pharmacology

There is no cure for multiple sclerosis. Treatment typically focuses on combating the autoimmune response and managing the symptoms. Some people have such mild symptoms that no treatment is necessary.
MedicationsDrugs that are commonly used for multiple sclerosis include:

• Corticosteroids. The most common treatment for multiple sclerosis, corticosteroids reduce the inflammation that spikes during a relapse. Examples include oral prednisone and intravenous methylprednisolone.
• Interferons. These types of drugs — such as Betaseron, Avonex and Rebif — appear to slow the rate at which multiple sclerosis symptoms worsen over time. But interferons can cause serious liver damage.
• Glatiramer (Copaxone). Doctors believe that glatiramer works by blocking your immune system's attack on myelin. You must inject this drug subcutaneously once daily. Side effects may include flushing and shortness of breath after injection.
• Natalizumab (Tysabri). This drug is designed to work by interfering with the movement of potentially damaging immune cells from your bloodstream to your brain and spinal cord. Tysabri is generally reserved for people who see no results from or can't tolerate other types of treatments. This is because Tysabri increases the risk of progressive multifocal leukoencephalopathy — a brain infection that is usually fatal.
• Mitoxantrone (Novantrone). This immunosuppressant drug can be harmful to the heart, so it's usually used only in people who have advanced multiple sclerosis.

Therapies
A physical or occupational therapist can teach you stretching and strengthening exercises, and show you how to use devices that can make it easier to perform daily tasks.
Procedures
Plasma exchange (plasmapheresis) looks a little like dialysis as it mechanically separates your blood cells from your plasma, the liquid part of your blood. Plasma exchange is sometimes used to help combat severe symptoms of multiple sclerosis relapses, especially in people who are not responding to intravenous steroids.


Last Editorial Review: 3/18/2010