What is Multiple sclerosis?

Multiple sclerosis

What is multiple sclerosis?

If you have multiple sclerosis (MS), the nerves in your brain and spinal cord slowly lose their coating. Over time, these nerves get damaged and may stop working properly. This can affect you in all sorts of ways. For example, MS can affect the way you move your body. You may at times find it hard to reach out for something or to walk properly.

Key points for people with MS

Some people with MS are hardly affected at all. But the disease is more serious for other people.
The most common symptoms are feeling very tired and weak and having numb or "tingling" areas.
You may have flare-ups (or relapses) when your symptoms get worse and other periods when you feel fine.
MS affects everyone differently. Just because you have this disease, it doesn't mean you'll be very disabled or need a wheelchair.
There's no cure for MS, but drugs such as interferon beta can reduce flare-ups, slow down the disease and help you stay active.

Your central nervous system

To understand what happens when you get MS and how it's treated, it helps to know a bit about your central nervous system (or CNS for short).

Your CNS has two main parts:

Source:
Martini FH, Ober WC, Garrison CW, et al.
Fundamentals of anatomy and physiology.
5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Your brain sends messages to nerves throughout your body.

Your brain controls everything your body does. For example, your brain lets you move your arm to pick up your coffee, speak, recognize your family, think and remember things.
Your spinal cord is the main highway of your CNS. It's the big bundle of nerves that runs down your back from your brain. It sits inside the bones of your spine.

Your brain and spinal cord are made up of billions of nerve cells that share information. The information moves from one nerve cell to another as chemical signals.

Groups of nerve cells have specific jobs. For example, some let you think, learn, remember and plan. Others let you see and hear. And others manage the millions of actions that keep your body working.

Many of the nerves in your brain and spinal cord have a coating called myelin. Myelin is made mainly of fat. It's important because it helps signals travel quickly and smoothly along your nerves.

What happens in MS?

Here's what happens if you have MS.

Source:
Keegan BM, Noseworthy JH.
Multiple sclerosis.
Annual Review of Medicine. 2002; 53: 285-302.

Source:
Hauser SL, Goodkin DE.
Multiple sclerosis and other demyelinating diseases.
In: Braunwald E, Fauci AS, Kasper DL, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw Hill, New York, USA; 2001.

Your

immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.

immune system normally helps protect you by fighting off

infection
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.

infections. But if you have MS, your immune system makes a mistake. It attacks the myelin coating around the nerves in your brain and spinal cord.
This causes

inflammation
If your skin or some other part of your body becomes red, swollen, hot or sore, we say it is inflamed. It means that your body is trying to protect you from germs, from something in your body tissues that can hurt you (like a thorn or sliver), or from things that cause allergies (allergens). Inflammation is part of the way the body heals an infection or injury.

inflammation, and the myelin coating may be damaged or even destroyed.
If this happens, signals traveling along your nerves can slow down, get blocked, speed up or get mixed up.
This can affect how different parts of your body work. For example, your brain may send a message to your hand to pick up a cup. But if the signal gets mixed up, your hand may not move the way you want it to. Or the movement may be too weak or jerky for you to pick up the cup.
MS can cause many different symptoms. This is because what symptoms you get depends on where in your brain and spinal cord the inflammation happens. For more, see What are the symptoms of multiple sclerosis?
The inflammation from MS can come and go. But if it keeps coming back, your nerves may get damage that doesn't go away.

Types of MS

There are four main types of MS:

Relapsing-remitting MS
Secondary progressive MS
Primary progressive MS
Progressive relapsing MS.

Most people with MS get the relapsing-remitting type, then go on to have secondary progressive type.

³ To learn more, see Types of multiple sclerosis.

What causes MS?

Scientists don't know exactly what causes MS. But a lot of research is going on to try to find out.

Why me?

Certain things increase your chances of getting MS. Doctors call these things risk factors for MS. Having a risk factor doesn't mean you'll get MS for sure. It just means you're more likely to get it than someone who doesn't have the risk factor.

The main risk factors for MS are having a close relative with the disease and living in a cooler climate rather than a warm one. To learn more, see Risk factors for multiple sclerosis.

Sources for the information on this page:

Martini FH, Ober WC, Garrison CW, et al.Fundamentals of anatomy and physiology.5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Keegan BM, Noseworthy JH.Multiple sclerosis.Annual Review of Medicine. 2002; 53: 285-302.

Hauser SL, Goodkin DE.Multiple sclerosis and other demyelinating diseases.In: Braunwald E, Fauci AS, Kasper DL, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw Hill, New York, USA; 2001.

This information was last updated on Jul 25, 2008

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