MS Flashcards
What is the definition of MS?
Multiple sclerosis (MS) is an autoimmune, cell-mediated demyelinating disease of the central nervous system.
Epidemiology of MS
- The estimated prevalence of MS in England and Wales is 180 per 100,000
- F>M
- Most commonly diagnosed in 20-40 year olds
- More common in white populations
- More common in northern latitudes
What are the Risk factors of MS
- Age: most commonly diagnosed in 20-40 year olds
- Female gender: MS is 3 times more common in females
- Smoking
- Obesity
- Vitamin D deficiency
- Northern latitudes
- Family history: HLA-DR2 is implicated; 30% monozygotic twin concordance
- Autoimmunity: patients often have a family history of other autoimmune disorders
- EBV infection: the virus with the greatest link to MS
What factors influence who gets MS?
Environment
Genetics
Chance
What is myelin?
Myelin is the protective sheath that surrounds the axons of neurons, allowing them to quickly send electrical impulses.
This myelin is produced by oligodendrocytes in the CNS and by schwann cells in the peripheral nervous system
How does demyelination occur in MS?
demyelination happens when the immune system inappropriately attacks and destroys the myelin.
What is the pathophysiology of MS?
- T cells enter the blood brain barrier and activated by myelin
- T cell changes BB barrier and causes expression of more receptors allowing more immune cells to enter
- immune cells such as macrophages can enter
What type of hypersensitivity reaction is MS
Type IV
What happens in this type IV reaction?
T-cells release cytokines. These can recruit more immune cells as well as directly damaging the oligodendrocytes. B-cell make antibodies and macrophages can use these antibodies to attack the oligodendrocytes, ultimately destroying the myelin. This leaves behind areas of plaque/ sclera.
What can happen initially?
At first there may be remyelination but over time there is permanent damage.
A characteristic features of MS is that lesions vary in their location over time, meaning that different nerves are affected and symptoms change over time.
What is the pathogenesis of MS
The pathogenesis of MS is not well understood, although it is thought to occur due to environmental triggers in genetically susceptible individuals, comprising an inflammatory and degenerative component.
The immunopathogenic model of MS
Genetic susceptibility + Environmental trigger > Activated auto-reactive T lymphocytes
Activated Autoreactive T lymphocytes activate > Macrophages, polyclonal activated autoreactive T lymphocytes, B lymphocytes and compliment
All of these lead to complete inflammatory attack with demyelination
Which components of the immune system are relevant to MS pathogenesis?
Lymphocytes - T (CD8, CD4, Suppressor), B (Plasma cells and antibodies)
Macrophages
Complement
Cytokines - interferons, TNF, IL and others
Key features of MS
- Inflammatory, demyelinating disease
- Specific to CNS
- Commonest cause of chronic neurological disability in young adults
- Begins usually 20-40
- Early course is relapse/ remitting
- Progressive disability over time
Relapse remitting MS
- The most common pattern (85% of cases)
- Episodic flare-ups (may last days, weeks or months), separated by periods of remission.
- More frequent in first 3-4 years
- There isn’t full recovery after the flare-ups, so disability increases over time
- 60% of patients develop secondary progressive MS within 15 years
- Clearly defined - can lead to full recovery
Secondary (Chronic) progressive MS
Initially, the disease starts with a relapsing-remitting course, but then symptoms get progressively worse with no periods of remission
Slow, inexorable decline in neurological functions
- from disease onset
- following an initial relapsing/ remitting course
Primary progressive MS
- Symptoms get progressively worse from disease onset with no periods of remission
- Accounts for 10% of cases and is more common inolder patients