Demyelinating Disorders

Question 1

What is the most common demyelinating disorder?

Answer 1

MS

Question 2

For MS: gender? onset?

Answer 2

female, usually before age 50

Question 3

What is MS chracterized by?

Answer 3

distinct episodes of neurologic deficits separated in time due to white matter lesions separated in space

Question 4

What is the general pathogenesis of MS?

Answer 4

immune attack on the myelin sheath

Probably caused by T-cells that autoreact against myelin antigens and secrete cytokines to turn macrophages on and eat them

B cells probably play a role too (since there are oligoclonal bands) but we don’t really know how

Question 5

Is MS totally genetic?

Answer 5

NO - there is a genetic predisposition but there is some environmental factor as well

Question 6

How is oligoclonal bands in the CSF diagnostic for MS?

Answer 6

Usually in the gamma region (where the antibodies divide out), there is just a smear through, because antibodies are normally monoclonal and ther eisn’t an abundance of any specific antibody - you want to be able to kill just about anythign that could possibly come into the system

However, in MS, you have oligoclonal bands in the gamma region when you run the CSF through.

Question 7

What will you see on gross pathology in MS?

Answer 7

plaque formation - lots of them

Question 8

How are active plaques different from inactive plaques?

Answer 8

active plaques have lipid-stuffed macrophages, T cells cuffing the vessels and axons still present

inactive plaques are when the deed is already done - no myelin left, decreased number of axons, astrocytic gliosis, and decreased oligodendrocytes

Question 9

Where do plaques typically form?

Answer 9

they can be anywhere, but they are commonly located near the ventricles and around blood vessels

Question 10

What will an MS plaque look like on histology?

Answer 10

1. plaque will stain pale on an H&E stain
2. there will be very few oligodendrocytes
3. gliosis present
4. lymphocytes cuffing the blood vessels

Question 11

What is another stain you can use when looking at an MS plaque?

Answer 11

a myelin stain - it will stain myelin dark purple

Question 12

What is an extremely common place for MS plaque to form - usually causing the precipitating symptom?

Answer 12

in the optic nerve near the chiasm

Question 13

What are the two general types of active plaque patterns you see in MS?

Answer 13

Individual patients with MS tend to have either sharply demarcated plaques around blood vessels or poorly demarcated plaques not around blood vessels - they don’t have a combination of both

Question 14

What are shadow plaques?

Answer 14

they are plaques where the border is indistinct because of thin myelin sheaths are the edges

remyelination? They’re trying to figure that out.

Question 15

What are some of the central symptoms of MS?

Answer 15

unilateral visual impairment is usually the presenting concern

cranial nerve signs

ataxia

nystagmus

Question 16

What are some of the spinal manifestations of MS?

Answer 16

motor/sensory iimpairment of trunk and limbs

spasticity

problems with voluntary bladder control

Question 17

What is acute disseminated encephalomyelitis?

Answer 17

It’s diffuse, monophasic demyelination following a viral infection - usually in children

extremely rare

Question 18

What are the symptosm of acute disseminated encephalomyelitis? Progrnosis?

Answer 18

rapid onset headache, lethargy, coma (so not very specific)

fatal in 10%, the other 90% has a complete recovery without subsequent deficit

Question 19

What do they think is the mechanism behind acute disseminated encephalomyelitis?

Answer 19

they accume is a cross-reactivity of the immune system against he myelin after aa viral infection

Question 20

What is acute necrotizing hemorrhagic encephalomyelitis?

Answer 20

It’s the bad one

You get fulminant CNS demyelination with necrosis and hemorrhage - often in yound adults or children after URI

Question 21

What is the progrnosis with acute necrotizing hemorrhagic encephalomyelitis?

Answer 21

fatal in many patients and those that survive often have deficits

Question 22

How do we cause central pontine myelinolysis?

Answer 22

By correcting hyponatremia too quickly

it’s a symmetric loss of myelin in the basis pontis and part of the pontine tegmentum

Question 23

What are the symptoms of central pontine myelinolysis?

Answer 23

It usually happens in patients that are just really sick

you treat the hyponatremia, they start to feel much better for a couple days and then they get a rapidly evolving quadriplegia and coma

it’s a monophasic disease