Multiple Sclerosis | The Canadian Encyclopedia


Multiple Sclerosis

Multiple Sclerosis (MS) is an autoimmune disease that impacts the body’s central nervous system. As of September 2020 an estimated 2.8 million people are living with MS worldwide. Canada has one of the highest rates of MS in the world with over 90,000 Canadians living with the disease. There is no known cure for MS, but treatments can help address symptoms and slow the progression of the disease.

Multiple Sclerosis

Multiple Sclerosis (MS) is a potentially disabling disease because it directly affects the body's central control system, the brain, spinal cord and optic nerves, also known as the central nervous system (CNS). The body’s immune system mistakenly attacks the myelin (the protective sheath that covers and protects nerve cells). This damages the ability of the central nervous system to communicate with the rest of the body. (See also Neuroscience.)

Canada has one of the highest rates of MS in the world with a prevalence of approximately 290 cases per 100,000 population. Anyone can develop MS, including children, however most people are diagnosed as adults between the ages of 20 to 49. Women are two to three times more likely to be diagnosed with MS compared to men.

Causes and Symptoms

Although the exact cause of MS is unknown and a specific trigger for the autoimmune response that attacks the myelin sheath has not been found, most specialists in the field think that the cause may be multifactorial. This means that MS is likely linked to genetic and environmental factors. In other words, something in an individual's environment triggers an immune response against myelin if that person is genetically predisposed to getting the disease.

When the protective covering (myelin) of the brain and spinal cord is attacked, inflammation occurs that frequently damages the myelin in patches. This disrupts the normal flow of impulses along the nerve fibres (axons) and it is this disruption that causes the symptoms of MS. The symptoms of MS vary depending on which part of the central nervous system has been affected and how severely. Symptoms frequently include: altered sensation such as numbness, tingling and pain; problems with vision; bowel and bladder problems; balance and co-ordination problems; speech problems; weakness; and fatigue.


There are four types of MS: Clinically Isolated Syndrome, Relapsing-remitting MS, Secondary progressive MS and Primary progressive MS. Clinically Isolated Syndrome (CIS) refers to the first episode of neurological symptoms caused by damage to the myeline. CIS typically lasts 24 hours. It is possible that individuals who experience CIS will not develop MS. Relapsing-remitting MS (RRMS) is characterized by relapses or attacks of new or worsening neurological symptoms. These relapses are followed by periods of recovery or remission of the disease. Secondary-progressive MS (SPMS) begins with relapses and remissions, followed by a period of progressive disease. Primary progressive MS (PPMS) is a form of the disease that affects about 15 per cent of MS patients and is characterized by worsening neurological function without remission.


Diagnosis of the disease is made by a neurologist (a physician that specializes in disease of the nervous system). (See also Neuroscience.) A diagnosis requires a clear indication that the disease has attacked more than one area of the central nervous system. In addition, diagnosis requires signs of multiple attacks that occurred during different points in times. The process of diagnosing the disease includes a neurological examination, medical history and tests such as magnetic resonance imaging (MRI), evoked potential tests to measure nerve conduction, and a lumbar puncture (spinal tap) to measure the antibodies in the fluid surrounding the brain (cerebrospinal fluid).

There is no known cure for this disease. Treatments for MS can specifically address symptoms of the disease or can alter immune system activity and thereby possibly slow the progression of the disease.


There has been a great deal of MS research in Canada that has been facilitated by the Canadian Network of Multiple Sclerosis Clinics, which is a national network established for the advancement of patient services, education and research. This model of multi-disciplinary and comprehensive care was spearheaded by the Multiple Sclerosis Society of Canada. The Canadian Network of MS Clinics has allowed for recruitment of patients to multiple clinical studies and for national collaborations in research. This coordinated approach has reduced redundancy and maximized research efficiency in this country. (See also Medical Research.)

The Canadian Collaborative Project on Genetic Susceptibility to Multiple Sclerosis (CCPGSMS) is an example of research made possible by the Canadian Network of MS Clinics. Beginning in 1993, MS patients were recruited to participate in the CCPGSMS. The identification and availability of Canadian patients and their family members willing to participate in studies of genetic epidemiology have provided a growing body of evidence that demonstrates that both nurture and nature are at play in the development of MS. Similarly, Publications on environmental effects in MS point to major environmental influences that operate at a population level, such as exposure to sunshine and Vitamin D.

One of the very important long-term Canadian research endeavors that has contributed to the planning and interpretation of therapeutic trials in MS includes work on the natural history of MS that originated at the MS Clinic in London, Ontario. These studies in the progression and accumulating disability in a population of patients with MS have led to a better understanding of the clinical course and possible outcomes for patients. (See also George C. Ebers.)

Further Reading

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