What is the definition of MS?
Multiple sclerosis (MS) is an autoimmune, cell-mediated demyelinating disease of the central nervous system.
Epidemiology of MS
What are the Risk factors of 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?
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
Relapse remitting MS
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
Progressive relapsing MS
One constant attack but there are bouts superimposed during which the disability increases even faster
Benign MS
Few relapses
Little disability
What happens in active MS
What happens in inactive MS
If plaque is distributed in cerebral hemispheres what happens
Large variety of symptoms but also silent lesions
Spinal cord plaque causes?
Visual signs of MS due to plaque distribution and demyelination of optic nerve