What is Multiple Sclerosis?

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Canada has one of the highest rates of multiple sclerosis (MS) in the world, with an estimated 90,000 Canadians living with the disease. On average, 12 Canadians are diagnosed with MS every day. Most people are diagnosed with MS between the ages of 20 and 49 and the unpredictable effects of the disease will last for the rest of their lives.

MS is a chronic autoimmune disease of the central nervous system. Since that includes the brain, spinal cord and optic nerve, MS can affect vision, memory, balance and mobility. It is considered an episodic disability meaning that the severity and duration of illness and disability can vary and are often followed by periods of wellness. It can also be progressive.

The disease attacks myelin, the protective covering of the nerves, causing inflammation and often damaging the myelin. Myelin is necessary for the transmission of nerve impulses through nerve fibres. If damage to myelin is slight, nerve impulses travel with minor interruptions; however, if damage is substantial and if scar tissue replaces the myelin, nerve impulses may be completely disrupted, and the nerve fibres themselves can be damaged.

MS is unpredictable and may cause symptoms such as extreme fatigue, lack of coordination, weakness, tingling, impaired sensation, vision problems, bladder problems, cognitive impairment and mood changes. Its effects can be physical, emotional and financial. Currently there is no cure, but each day researchers are learning more about what causes MS and are zeroing in on ways to prevent it.

We are here to help. No one needs to face MS alone. In communities across Canada, MS Canada provides information, support, educational events and other resources for people living with MS and their families. Learn more about the programs and services we offer.

Researchers funded by MS Canada are working to find the cause of MS, develop better treatments with less side effects, and ultimately cure the disease for everyone who is affected by it. Learn more about the research we fund.


Despite decades of research, the cause of MS remains a mystery. The best current evidence suggests that lifestyle, environmental, genetic and biological factors all contribute. All these areas are being actively examined. Studies funded by MS Canada are asking if certain risk factors, such as gender, age, family history or lifestyle habits impact a person’s susceptibility to MS.


60% of adults diagnosed with MS are between the ages of 20 and 49 years old. While it is most often diagnosed in adults aged 20 to 49, younger children and older adults are also diagnosed with the disease. In Canada, 43 is the average age of MS diagnosis. 75% of people in Canada living with MS are women. Women are three times more likely to be diagnosed with MS than men.

Read more about diagnosing MS

Types of MS

The majority of people who develop MS are initially diagnosed with relapsing-remitting MS (RRMS), characterized by clearly defined attacks (relapses) followed by complete or partial recovery (remissions); in Canada about 90 per cent of all people living with MS are diagnosed with RRMS. Over time, most people with RRMS will transition to a phase of the disease called secondary progressive MS (SPMS). This phase of the disease has fewer relapses with variable disability progression. About 10 per cent of people, will be diagnosed with primary progressive MS (PPMS). Individuals diagnosed with this type of MS will experience a continuous worsening of symptoms from the beginning usually without clear relapses or remissions. Some people living with early PPMS will experience occasional relapses with steadily worsening disease from the beginning (active PPMS).

Learn more about the various types of MS


MS is thought to be an autoimmune disease, which means the immune system - designed to protect against intruders such as viruses and bacteria - attacks tissues in the body. In the case of MS, the tissue that is targeted is myelin. Without myelin the communication between nerve cells is disrupted, and the body does not receive the instructions necessary to perform basic functions like speaking, seeing, walking and learning. Myelin damage can also lead to deterioration of the exposed nerves, resulting in irreversible damage to them. As a chronic neurological disease, MS can also have a dramatic effect on energy levels, sleep and overall quality of life. 

Learn more about MS symptoms

Additional Information

MS is not fatal for the vast majority of people living with the disease. Most people who have MS can expect a normal or near-normal lifespan, thanks to improvements in symptom management and the MS disease-modifying therapies.

Researchers are zeroing in on what causes MS and exploring ways to repair the damage it causes and ways to prevent MS from occurring. We fund investigation into many aspects of the disease including:

  1. Progression/therapies – Examines current or potential therapies for MS and seeks to improve imaging technology to better visualize what happens in the brain.
  2. Cause/risk factors – Investigates potential triggers of MS and why some factors may increase susceptibility to MS.
  3. Nerve damage/repair – Focuses on the cellular mechanisms that result in either damage or repair of myelin and underlying nerve cells.
  4. Symptom management/quality of life – Probes how MS affects day-to-day living and develops treatments that more effectively manage symptoms.

Learn more about the latest news in MS research