Multiple sclerosis, often called MS, is a disease that affects the central nervous system—the brain, spinal cord, and optic nerves. It can cause problems with muscle control and strength, vision, balance, feeling, and thinking.

Your nerve fibres have a protective covering called myelin. Without myelin, the brain and spinal cord can't communicate with the nerves in the rest of the body. MS slowly destroys myelin and nerve cells in the central nervous system, causing muscle weakness and other symptoms.

Most of the time, MS is not diagnosed unless a doctor can be sure you have had at least two attacks affecting at least two different areas of your central nervous system. Your doctor will examine you, ask you questions about your symptoms, and do some tests. An MRI scan is often used to confirm the diagnosis, because the patches of damage (lesions) caused by MS attacks can be seen with MRI.

MS is different for each person. You may go through life with only minor problems. Or you may become seriously disabled. Most people are somewhere in between. In general, MS follows one of four courses:

• Clinically isolated syndrome. The symptoms last for 24 hours or longer and go away.
• Secondary progressive, which at first follows a relapsing-remitting course and then becomes progressively worse. "Progressive" means it gets worse over time.
• Primary progressive, which means the disease is progressive from the start.
• Progressive relapsing, which means the symptoms are progressive at first and are relapsing later.

Disease-modifying therapy means treatment to delay, change, or interrupt the natural course of the disease. For MS, this means taking medicine over a long period of time to reduce not only the number of attacks but also how bad they are.

Depending on the practice in your province, your doctor may suggest medicines after your first attack or when you are first diagnosed with MS. People treated soon after being diagnosed with MS may have better results than those who delay treatment. Lasting damage to the nervous system can occur in the early stages of MS. Early treatment may prevent or delay some of this damage.

Medicines for MS can be costly. They don't work for everyone. And it's hard to know who will benefit.

Some examples include:

• Interferon beta (such as Betaseron).
• Glatiramer (Copaxone).
• Ocrelizumab (Ocrevus).

Making a decision about starting disease-modifying therapy can be hard, especially if your symptoms have been mild. Some people wait to see if their symptoms get worse before they make a decision to start therapy. A small number of people with MS may never have more than a few mild episodes and never have any disability. But there is no way to know who will fall into this group.

Medicines can't cure MS. They don't stop disease activity or reverse nervous system damage that has already happened. But drugs may reduce relapses and delay disability in many people with relapsing forms of MS.

If you decide not to try disease-modifying therapy at this time, work with your doctor to monitor your health through regular checkups and periodic MRI scans to evaluate whether the disease is progressing. If new lesions are developing or existing lesions are growing, you may want to reconsider your decision and begin treatment.

If you decide not to take MS medicines, there are some other things you can do.

• Take other medicine, such as steroid medicine, to relieve symptoms during attacks or relapses.
• Try physiotherapy, occupational therapy, and other treatment you can do at home to help you manage your symptoms and adjust to living and working with MS.
• Do what you can to stay well. Eat a healthy diet, get plenty of rest, and try to reduce stress.
• Some people try alternative therapy to lessen their symptoms. Discuss your treatment options with your doctor before trying any type of alternative treatment for MS. You can also get reliable advice from an MS treatment centre or the Multiple Sclerosis Society of Canada.

This section focuses on glatiramer and interferon beta, the most commonly used MS medicines.

*Based on the best available evidence (evidence quality: borderline to inconclusive)

*Based on the best available evidence (evidence quality: moderate to borderline)

Benefits

The evidence suggests a slight positive effect for people with relapsing-remitting multiple sclerosis. But the quality of the evidence isn't good. It is borderline to inconclusive.

If you have had some early symptoms of MS but don't have a clear diagnosis yet, medicine may reduce the chance that your symptoms will progress to full-blown MS. Take a group of 100 people who have had an MS-like episode but do not yet have an MS diagnosis:

• Without medicines, 45 to 58 out of 100 may progress to an MS diagnosis. This means that 42 to 55 may not.
• With MS medicines, 34 to 35 out of 100 may progress to an MS diagnosis. This means that 65 to 66 may not.

Your risk of needing a hospital stay over the next 2 years may be lower if you take medicines than if you don't. Take a group of 100 people who have MS:

• Without MS medicines, 20 people out of 100 may need to be hospitalized over the next 2 years, while 80 out of 100 may not.
• With MS medicines, 12 out of 100 may need to be hospitalized over the next 2 years, while 88 out of 100 may not.

Risks

Many people who take MS medicines have uncomfortable side effects. Take a group of 100 people who have MS:

• With interferon beta, 48 out of 100 may have flu-like symptoms. This means that 52 out of 100 may not. The quality of the evidence about this is moderate.
• With glatiramer, 24 out of 100 may have symptoms such as flushing, chest tightness, sweating, heart palpitations, anxiety, and shortness of breath. This means that 76 out of 100 may not. The quality of the evidence about this is borderline.

Understanding the evidence

Some evidence is better than other evidence. Evidence comes from studies that look at how well treatments and tests work and how safe they are. For many reasons, some studies are more reliable than others. The better the evidence is—the higher its quality—the more we can trust it.

The information shown here is based on the best available evidence. ^{footnote 1footnote 2footnote 3footnote 4} The evidence is rated using four quality levels: high, moderate, borderline, and inconclusive.

Another thing to understand is that the evidence can't predict what's going to happen in your case. When evidence tells us that 2 out of 100 people who have a certain test or treatment may have a certain result and that 98 out of 100 may not, there's no way to know if you will be one of the 2 or one of the 98.

The U.S. National Multiple Sclerosis Society recommends that people with a definite diagnosis of MS and active, relapsing disease start treatment with medicine as soon as possible after receiving a diagnosis. Most neurologists support this recommendation and now agree that permanent damage to the nervous system may occur early on, even while symptoms are still quite mild. Early treatment may help prevent or delay some of this damage. In general, treatment is recommended until it no longer provides a clear benefit.

The U.S. National MS Society also says that treatment with medicine may be considered after the first attack in some people who are at a high risk for MS (before MS is definitely diagnosed).^{footnote 5}

Your doctor may suggest that you take MS medicines because:

• You have had symptoms that are most likely caused by multiple sclerosis, tests show you most likely have MS, and your doctor is confident that you have MS.
• You have just been diagnosed with multiple sclerosis, and early treatment may delay damage to your central nervous system.
• These medicines are the only ones proved to reduce the frequency and severity of relapses and delay disability.