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e-learning IV - Transmission
MS is the most common auto-immune disease in Northern Europe. It can be particularly devastating because it is a disease of younger adults that can lead to decades of disability. Its cause is not fully understood and whilst it can be treated, there is no cure.
MS is interesting to neuroscientists for many reasons. For example, it is a perfect illustration of the importance of myelination in nerve conduction. It is also an example of what happens when the "immune privilege" of the brain is compromised. When this occurs, the immune system is allowed too much access to the brain and an inflammatory response is generated. It is inflammation that causes much of the damage in MS and many of the treatment strategies are aimed at reducing this response.
There is a good overview of MS, its symptoms and its treatments on the Multiple Sclerosis
Association of America website. The NHS Choices website is also very good.
Diagnosing Multiple Sclerosis
Visual Evoked Potential Test
The defining feature of MS is that there is a loss of myelin from the CNS neurones.
Often, one of the first systems to be affected is the visual system. A simple test that can indicate MS is the Visual Evoked Potential (VEP) test. This is similar to an EEG, except that it is stimulated brain activity, rather than spontaneous activity, that is measured. In a VEP
test, electrodes are placed on the scalp and the patient is shown a checkerboard pattern.
The electrical activity that this stimulus provokes is picked up by the electrodes and recorded. In patients with MS, there is a delay in the response. This is because demyelinated neurones conduct slower than normal.
Evoked potential tests are not just used in MS. A similar system, but using auditory, rather than visual, stimuli can be used to test for hearing loss.
The "gold-standard" for diagnosing MS is an MRI scan. This obviously requires a much more complicated and expensive equipment than a VEP test.
MRI scans can reveal the presence of sclerotic plaques in the brain and spinal cord (yellow arrows on the figure below). These are hallmarks of MS and can help distinguish it from disorders with similar clinical symptoms.
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