L8 Multiple Sclerosis Flashcards
What is MS?
An acquired, inflammatory disease of the CNS where there is an inflammation against myelin.
Describe the risks of MS.
MS is more common in men and occurs more in colder climates.
Your risk of MS is related to the climate you lived in for the first 10 years of your life. If you move to a country with a cooler climate after 10 years of age, your risk of MS will not be increased.
The risk of MS is also increased if your immediate family has MS.
What are the five phases of MS?
1) Initiation. Occurs between 5-10 years of age.
2) Latent phase. Occurs between 10-50 years of age. This is where asymptomatic lesions appear in the brain before the appearance of symptoms. The latent phase is often discovered accidentally.
3) Disease onset. This occurs between 20-50 years of age. This is where the symptoms start to appear.
4) Remitting and relapsing phase (RRMS). This is where you have frequent episodes of demyelination followed by recovery.
5) Progressive phase (SPMS). This is where you have a steady progression of deterioration.
What is the hypothetical theory of MS initiation?
It is thought than an antigen gets into the body, binds to antigen-presenting dendritic cells which then activate DCs. These then communicate to CD4 and T cells.
This antigen is similar to myelin (it shows molecular mimicry) so the T-cells that are produced stay within the system, detect myelin as a foreign object and destroys it.
How do lymphocytes get into the CNS?
They interact with adhesion molecules (selectin and integrins) on the endothelial cells that make up the BBB and make their way through.
Once inside, they activate macrophages and microglia that produce the immune response and destroy myelin.
What happens to the BBB during an episode?
The inflammation seen in the body causes the BBB to become leaky.
Describe AP conductance in normal nerves in the CNS.
AP’s jump along nerves via the Nodes of Ranvier. These are areas along nerves that have no myelin so allows very fast conduction.
There are also K channels either side of the Nodes of Ranvier that hyperpolarise the membrane preventing the impulse from moving too far from the node.
What areas of the body are affected in MS and what are the symptoms?
- Brain = cognition, speech, hemiplegia (paralysis on one side of the body).
- Optic nerve = blurred vision.
- Brain stem = double vision, ataxia (lack of voluntary coordination of muscle movements), weakness, dizziness.
- Spinal cord = weakness, loss of sensation, abnormal sensations, bladder and bowel dysfunction.
Why will a lesion in the spinal cord cause more severe symptoms than the brain?
There is a lot of grey matter in the brain which doesn’t have any myelin. The white matter that is affected in the brain spreads out like a fan, not a chord like in the spinal chord.
What are the four types of MS?
- Relapsing-Remitting = where you have numerous periods of symptoms and then recovery. However, the recovery is not always complete so each new relapse is a bit worse than the first.
- Secondary Progressive = an initial stage of relapsing and remitting, followed by a progressive phase (very slow worsening of symptoms with no recovery). Most common form of MS.
- Primary Progressive = slow worsening of symptoms with no recovery.
- Progressive - Relapsing
What criteria do you need to fill in order to be certain that a relapse is occuring?
Need to have acute symptoms lasting more than 24 hours that are not caused by:
- Infection
- Exercise
- Menstruation
- Head and Humidity
- Stress
If the symptoms are caused by the above things, it is called a psuedo-relapse.
There should also be at least one month between relapses. Symptoms more frequent than this are due to the same relapse.
What tests can you use to diagnose MS?
- A MRI to look for lesions in the brain.
- Inject a dye into the blood and then scan the brain with a MRI to see if the dye has crossed the BBB.
- Check the CSF using oligoclonal bands. If the IgG bands are present, this indicates that the lymphocytes have travelled into the CNS.
What is secondary progression?
Steady deterioration in the function of axons that are unrelated to the acute relapses.
This progression occurs in two parts: demyelination and then loss of primary axons.
How do you treat an acute relapse of MS?
With methylprednisolone. This is a very high dose of steriods to ensure the drug passes through the BBB. This drug has lots of side effects and only reduces the duration of the relapse, not recovery.
What drugs to you use to prevent relapses from happening? What criteria must you meet you be able to take them?
Disease modifying drugs. These drugs are continuous and not dependant on relapses. You are given different lines of drugs depending on the number of relapses the patient has after starting the drugs.
You must have two or more relapses in two years and be able to walk for 20 metres.
