About multiple sclerosis

• What is multiple sclerosis?
• Types of MS
• Risk factors for multiple sclerosis
• Multiple sclerosis symptoms
• Diagnosing multiple sclerosis

What is multiple sclerosis?

Multiple sclerosis (MS) is a chronic, progressive, and disabling disease that affects the central nervous system (CNS). This system includes the brain and spinal cord. MS affects about one in 1,000 people and is usually diagnosed between the ages of 15 and 40. There are an estimated 55,000 to 75,000 Canadians living with MS. In fact, Canada has one of the highest rates of people living with MS in the world.

Healthy nerves are covered by a protective layer known as the myelin sheath. This covering helps to speed electrical signals in the brain. In MS, researchers think that the immune system sees the myelin sheath as foreign and attacks it, leading to patches of damage and inflammation. It is not known what chain of events starts this damage, but once the injury occurs, electrical signals in the brain are slowed down or interrupted.

MS cannot be spread from person to person. It is an autoimmune disease, which means that the body's immune system attacks a part of the body that it sees as foreign. In this case, it attacks the myelin sheath.

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Types of MS

Relapsing-remitting MS: This type shows clearly defined relapses (attacks) with partial or complete recovery. It affects around 75% of all people with MS.

Secondary progressive MS: Within 10 years, about half of patients with relapsing-remitting MS will go on to develop secondary progressive MS. People with this form of MS may experience fewer relapses, but with a steady increase in disability.

Primary progressive MS: This type shows no clear relapses, but over a period of years, there is gradual loss of physical and cognitive functions. This form of MS affects about 10% to 15% of all people with MS.

Progressive-relapsing MS: This type has relapses with or without some recovery and steadily worsens over time. It affects about 5% of people with MS.

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Risk factors for multiple sclerosis

The cause of MS is still unknown. However, there are certain factors associated with an increased risk of developing MS. These include:

• gender - MS affects approximately 3 times as many women as men.
   
• race - MS affects mostly people of Caucasian descent in northern climates (northern European ancestry). However, it can also develop in individuals of African, Asian, and Hispanic descent.
   

• family history of MS - MS is not directly inherited, but a family history of MS increases the chance of getting the disease. The closer the relationship, the higher the risk. For example, if an immediate family member (i.e., parent or sibling) has MS, your risk is about 3%. If your identical twin develops the illness, your chances are about 1 in 4. However, while genetics may play a role, there are other factors involved.
   

  The cause of MS is still unknown.

• environmental factors - environmental factors seem to act as a trigger for MS. MS is most common in northern temperate climates, which includes Canada, northern Europe, and northern United States. People of African and Asian descent have the lowest incidence of developing MS. MS is also rare for Inuits and other First Nations peoples, even though they have lived for thousands of years in high-risk (northern) areas.

  People who move from an area that is considered high-risk to a low-risk area early in life, before the age of 15, are less at risk of getting MS than those who do not move. This suggests that exposure to some environmental factors at an early age may increase their risk of developing the disease.

• viral infections - viral infections probably also have a hand in the development of MS. Researchers have been looking at a variety of viruses and other infectious agents (e.g., bacteria) as possible triggers. Most agree that MS involves an environmental agent encountered during childhood that probably triggers the disease in individuals who are already at risk of MS due to the makeup of their genes.

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Multiple sclerosis symptoms

MS symptoms are unpredictable and vary greatly from person to person. Not all people with MS will experience all symptoms, and often the symptoms will improve during periods of remission.

Symptoms will depend on the location of the myelin damage (myelin is the protective layer surrounding your nerves), and can include:

• weakness, numbness, and tingling (in the arms, legs, or other body areas)
• extreme fatigue
• muscle stiffness or spasticity
• shaking and loss of coordination
• poor balance and unsteadiness, which can cause a staggering gait
• speech disorders such as slurred speech
• depression
• pain
• troubles with memory, concentration, thinking, or solving problems
• vision changes or vision loss
• vertigo and dizziness
• bladder problems
• bowel problems
• sexual problems

Although the majority of people with MS do not have severe disability, as MS progresses some of these symptoms can lead to some form of physical disability (e.g., loss of motor skills) that can have a large impact on your life. One goal of MS treatment is to ensure that disability symptoms don't progress and that you preserve your ability so that you can live a productive life.

Having one or more of these symptoms does not necessarily mean that you have MS. However, if you are experiencing these symptoms, talk to your doctor to find out what may be causing them.

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Diagnosing multiple sclerosis

There is no single test that can diagnose multiple sclerosis. Doctors make a diagnosis based on the results of a number of tests such as brain imaging and neurologic exams.

If your family doctor suspects MS, you may be sent to see a neurologist for a number of tests. Neurological tests examine reflexes, eye movements, limb strength, sensation, and coordination. Your medical and family history is also very important

Further tests that might be done include:

• magnetic resonance imaging (MRI), a type of scan that can take pictures of your brain
• evoked potential, which measures nerve signals from your body to your brain (in MS, signals are slower and weaker)
• spinal fluid examination, which may give doctors more information about what may be causing your symptoms

To find out more about the tests used to diagnose MS, talk to your doctor.

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