Multiple Sclerosis and Amyotrophic Lateral Sclerosis Flashcards
What is Multiple Sclerosis (MS)?
MS is one of the most common non-traumatic neurological conditions affecting young and middle-aged adults, characterized by discrete areas of damage in the brain, spinal cord, and optic nerves.
How common is MS in Canada?
Canada has one of the highest rates of MS per capita in the world. Most people are diagnosed between ages 20 and 49, with the average age being 43.
Who is more likely to be diagnosed with MS?
75% of people in Canada living with MS are female, and females are three times more likely to be diagnosed than males.
What body functions are most commonly affected by MS?
Vision, coordination, speech, strength, sensation, bladder control, and sexual function.
Is MS a terminal disease?
No, MS is not terminal, and most people live normal lifespans. However, it can greatly affect quality of life, with an unemployment rate of 60-80% among those with MS.
What is the primary contribution of massage therapy for people with MS?
Easing secondary effects of the disease in the body’s soft tissue, which can impair mobility and function and reduce quality of life.
What is myelin?
Myelin is a proteolipid sheath covering most axons in the CNS, made by oligodendrocytes. It insulates neurons, prevents impulse mixing, and speeds up conduction of nerve signals.
What is demyelination?
Demyelination is the process by which myelin sheaths are lost or destroyed. MS is the most common demyelinating condition in the CNS.
What are plaques in MS?
Plaques are characteristic lesions of MS, appearing as greyish spots in white matter where myelin destruction occurs. They average 1-15 mm in size.
What happens at an active plaque site?
Active plaques are edematous inflammatory lesions with infiltrating lymphocytes and macrophages. These immune cells consume myelin, attack oligodendrocytes, and rapidly kill them.
What is the role of astrocytes in plaque formation?
Astrocytes synthesize fiber processes to form a living scar (gliosis) at the plaque site, making the tissue harder than the surrounding area.
What characterizes old, inactive plaques in MS?
Old plaques are fields of permanently demyelinated axons filled with glial fibers in spaces where myelin bundles used to be.
What is an exacerbation in MS?
Exacerbation, also called a relapse or flare-up, is a period of active demyelination with sudden onset of neurological symptoms, lasting 6-8 weeks and resolving over 2-3 months.
What is remission in MS?
Remission is the period between exacerbations, which may return a person to normal or near-normal function, or leave considerable new disability depending on the disease stage.
What is the average frequency of MS exacerbations?
The average rate of exacerbations is every eighteen months.
What causes MS exacerbations?
MS exacerbations are caused by an autoimmune reaction where immune cells accumulate in CNS venules, breach the blood-brain barrier, and attack myelin, leaving behind plaques.
Where are MS plaques typically found?
MS plaques are denser around blood vessels and the ventricles. They may be new or reactivations of old sites.
How do immune cells attack in MS?
Immune cells release chemicals that cause inflammation and damage to myelin, neurons, and oligodendrocytes, perceiving myelin as an antigen and producing antibodies against it.
What happens when myelin is stripped away?
Uncovered axon sections transmit poorly or erratically due to lost insulation, causing dysfunction in pathways dependent on those signals.
What role do oligodendrocytes play during MS remission?
Oligodendrocytes remyelinate axons, often restoring normal or near-normal function in the early stages of MS.
Why does remyelination become less effective over time in MS?
Repeated attacks and cumulative damage reduce oligodendrocyte effectiveness, eventually leading to their dysfunction or disappearance.
What replaces oligodendrocytes in chronic MS plaques?
Glial scars (astrocytic fibrillary gliosis) fill the plaques, as astrocytes produce glial fibers after inflammation decreases and microglia disappear.
What happens when nearby plaques join in MS?
Larger fields of tissue form where impulse conduction is disrupted, leading to more severe symptoms and deficits.
What determines the severity of neurological deficits in MS?
Axonal damage/loss and the development of permanent inactive plaques are major determinants of profound neurological deficits.
When are exacerbations in MS more likely to occur?
Exacerbations are more likely if the person’s overall health is impaired, or during periods of illness.
Do all individuals with MS experience a well-defined course of exacerbations and remissions?
No, some have an extreme form of the disease with little or no remission, while others may only have one or two exacerbations in their lifetimes or experience a low-grade chronic type.
How does the progression of MS affect the distinction between flare-ups and remissions?
As the disease progresses, the distinction between states of flare-up and remission becomes less clear.
What are the possible disability outcomes in MS?
Disability outcomes range from clinically insignificant to total physical disability, with a variety of acute, subacute, and inactive lesions scattered throughout the CNS.
What is the suspected cause of MS?
MS is believed to result from a combination of immunological, environmental, infectious, and genetic factors.
How is MS succinctly described in terms of its cause?
MS is an immune-mediated neurological disorder precipitated in a genetically susceptible individual by exposure to an environmental factor, likely a virus.
Which genetic factor is strongly linked to MS development?
Changes in HLA genes, especially the HLA-DRB1*1501 variation, are strongly linked to increased MS risk.
Which immune cells play a significant role in MS?
T cells and B cells are the key immune cells involved in the abnormal immune response in MS.
What happens when T and B cells enter the CNS in MS?
Once in the CNS, T and B cells release chemicals that cause inflammation and damage.
How many genes have been identified that contribute to MS risk?
About 200 genes contribute a small amount to the overall risk, including HLA-DRB1*1501, the most strongly associated variation.
What is the risk of developing MS in the general population, and how does it compare for identical twins?
The risk in the general population is about 1 in 750–1,000. For identical twins, if one has MS, the other has about a 1 in 4 risk.
Which ethnic group has the highest prevalence of MS?
White people of Northern European descent have the highest prevalence of MS.
How does geography influence the risk of developing MS?
MS occurs more frequently in areas farther from the equator. People moving before age 15 assume the risk of their new area; those moving later retain the risk of their origin area.
Why might vitamin D levels be linked to MS risk?
People living closer to the equator have higher vitamin D levels due to greater sun exposure, which may support immune function and protect against MS.
How does obesity influence the risk of developing MS?
Obesity in childhood, adolescence, or early adulthood increases the risk of MS and may contribute to inflammation and MS activity.
How does smoking affect MS risk and progression?
Smoking increases the risk of developing MS, speeds up disability progression, and worsens relapsing MS. Stopping smoking slows disability progression.
