Demyelinating Disorders

Question 1

What are the 4 main demyelinating disorders?

Answer 1

MS Acute disseminated encephalomyelitis Acute necrotizing hemorrhagic encephalomyelitis Central pontine myelinolysis

Question 2

What is MS?

Answer 2

The most common demyelinating disorder

F > M

Before age 50

Question 3

What is MS characterized by and what is it due to?

Answer 3

distinct episodes of neurologic deficits (separated in time)

Due to white matter lesions (separated in space)

Question 4

What is the pathology of MS?

Answer 4

1. Immune attack on myelin sheath: T cells react against myelin agntigens and secrete cytokines
2. Linked to HLA- DR2 (very polymorpohic, w/ some polymorphisms are more likely to get MS)

Due to GENETIC plus ENVIRONMENTAL factors.

Question 5

Do B cells play a role in MS?

Answer 5

If you deplete B cells you are LESS likely to get MS.

Question 6

How are oligoclonal bands incicative of MS?

Answer 6

In MS there are a small number of clones of B cells. Each clonal polpulation makes the exact same antibody that descends from the same B cell. Antibodies migrate to the gamma region and find a specific spot depending on size/weight.These multiple B cell bands–> oligoclonal (multiple clones of B cells). Not a normal finding in CSF

Question 7

What does MS cause in the CNS?

Answer 7

Plaques!

These are regions of demyleination.

Question 8

What are the two different types of plaques?

Answer 8

Active plaques:

Lipid stuffed macrophages

T cells cuffing vessels

Axons preserved

Inactive plaques:

NO myelin

decreased oligodendrocytes

Gliosis–proliferation of astrocytes

decreased number of axons

Question 9

Is MS monophasic?

Answer 9

NO

Lesions can be at different stages throughout the body.

Question 10

What is the purpose of the mylein stain?

Answer 10

To determine if there is demyelination.

Myelin stain deep dark blue or purple.

Question 11

Where is one of the more common locations to see plaques?

Answer 11

The optic nerve.

One of the more common signs of MS is eye problems.

Question 12

What are the types of active plaque patterns?

Answer 12

Sharply demarcated I and II

or

poorly demarcated III and IV

People usualy have I/II or III/IV

Question 13

What are shadow plaques?

Answer 13

Plaques that have an indistinct border–remyelination occurs at edges

Question 14

What are the clinical features of MS?

Answer 14

Central Manifestations:

Unilateral visual impairment

Cranial nerve signs

ataxia (cerebellum)

nystagmus (brainstem involved)

Spinal Manifestations:

Motor/sensory impairment of trunk and limbs, spasticity, problems w/ voluntary bladder control

Question 15

What is acute disseminated encephalomyelitis?

Answer 15

Diffuse, MONOPHASIC demyelination

Follows a viral infection

usually in children

An accute autoimmune reaction against myelin precipitated by infection usually seen in kids.

Fatal in 10%

Question 16

What is Acute Necrotizing Hemorrhagic Encephalomyelitis?

Answer 16

The WORST–rare

Fulminant (rapid) CNS demyelination

Young adults and hcildren

Preceeded by upper respiratory infection

Usually FATAL

Question 17

What is central pontine myelinolysis and how is it OUR fault?

Is it monophasic?

Answer 17

The symmetric loss of myelin in basis pontis and part of pontine tegmentum

Usually due to a RAPID correction of hyponatremia

Leads to quadriplegia

MONOPHASIC

*Demyelination in the pons is caused by correting los Na levels too fast. This causes Na diuresis and cells to shrink in pons. Often occurs in very sick patients.