Multiple Sclerosis (MS) is the most common neurological disease in Canada. Canadians have one of the highest rates of MS in the world with a prevalence of about one case for every 500-1000 people. Anyone can develop MS, including children, however most people are diagnosed as young adults aged 20-40. Almost twice as many women develop MS as men, and MS can develop in many racial groups, although Caucasians are most commonly affected.
MS is a disabling disease because it directly affects the body's central control system, the brain and spinal cord, also known as the central nervous system (CNS). Specifically, the covering that protects nerve cells (the myelin sheath) is damaged when the body mistakenly attacks its own nervous system in an autoimmune response.
There are four types of MS. In relapsing-remitting MS, attacks or relapses are followed by periods of recovery or remission of the disease. Primary progressive MS is a form of the disease that affects about 15% of patients and is characterized by steady progression without remission. Secondary-progressive MS begins with relapses and remissions, followed by a period of progressive disease. Progressive-relapsing MS shows steady worsening from the outset with clear relapses.
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. 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 CNS has been affected and how severely. They 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.
Diagnosis of the disease is made by a physician who specializes in disease of the nervous system (neurologist) when there has been a clear indication that the disease has attacked more than one area of the CNS, as well as signs of multiple attacks separated by at least two months. The process of diagnosing the disease includes a neurological examination and medical history, and tests such as magnetic resonance imaging (MRI), evoked potentials to measure nerve conduction, and a lumbar puncture 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 MS 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; a coordinated approach that has reduced redundancy and maximized research efficiency in this country.
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. Begun in 1993, it recruited over 30 000 MS patients. 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 both nurture and nature are at play in the development of MS. Recent publications on environmental effects in MS point to major environmental influences that operate at a population level such as 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 is the work on the natural history of MS that originated at the MS Clinic in London, Ont. The first peer-reviewed article that resulted from this work has been cited over 700 times by subsequent researchers. 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 IMMUNOLOGY.