Demyelinating Disorders including MS Flashcards
What is the key cell that myelinates the axons in the CNS and in the PNS?
In CNS, it is the oligodendrocytes, and in the PNS it is the Schwann cells.
What is a common feature among demyelinating diseases?
Since the myelin is what is damaged, the axons are intact, however the conduction speed of the axons are impaired (since myelin accelerates the rate of conduction through the axons).
What are “Leukodystrophies?”
Inherent mutations in the enzymes necessary for production or maintenance of myelin.
What is the most common leukodystrophy and what happens here?
Metachromatic Leukodystrophy is the most common, and here we have a deficiency of arylsulfatase. Therefore, myelin cannot be degraded and accumulates in the lysosomes.
What is the purpose of arylsulfatase?
To break down myelin, recall that myelin has a regular rate of turnover so if they are not properly degraded it will accumulate and lead to Metachromatic Leukodystrophy.
What is Multiple Sclerosis?
Autoimmune disorder where the CNS myelin and oligodendrocytes are destroyed.
What gene is MS associated with?
HLA-DR2
What is the population distribution of people with MS?
Most common CNS degenerative disorder of young adults, most common in women (autoimmune tends to hit women more).
What is the double whammy responsible for MS?
HLA-DR2 gene (genetic) in association with living far away from the equator (environmental).
If a patient has MS and complains of blurred vision what can we deduce?
There is a lesion in the optic tract where the optic tract is demyelinated.
If MS lesions involve the brainstem what should we expect to see?
Vertigo and Scanning speech (as if the patient is drunk).
What happens if the Medial Longitudinal Fasciculus gets involved in MS?
Patient will get Internuclear opthalmoplegia.
What is “internuclear Opthalmoplegia?”
CN6 attaches to the lateral rectus, of each eyeball, and in addition it has connections to CN3 which innervate the medial rectus via the MLF. If MLF is damaged via MS, the lateral rectus (via CN6) will still fire for left eye to look left for example, but CN6 will fail to fire CN3 to turn the medial rectus of the right eye to also look left. As a result, left eye looks left, right eye does not = condition known as internuclear opthalmoplegia.
What happens if we have MS plaques in the cerebral white matter?
Hemiparesis (weakness to one side of the body) or unilateral loss of sensation of one side of body.
What happens if there are MS plaques in spinal cord?
Lower extremity loss of sensation or weakness.
