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Neuro > Myelination Disorders > Flashcards

Myelination Disorders Flashcards

1
Q

Which cell type is responsible for myelinating axons in the CNS?

A

oligodendrocyte

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2
Q

How many axons does each oligodendrocyte myelinate?

A

multiple

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3
Q

What are the 2 major components of myelin?

A

myelin basic protein

proteolipid protein

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4
Q

What is an inherited demyelination disorder?

A

Neuromyelitis optica (NMO)

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5
Q

How is MS defined?

A

demyelination is multifocal and lesions are of different ages (disseminated in space and time)

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6
Q

What are the rapidly progressive types of MS called?

A 
acute (marburg)
concentric sclerosis (balo's disease)
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7
Q

Where to plaques usually occur in MS patients?

A 
periventricular white matter
optic nerves and chiasm
brainstem and spinal cord tracts
cerebellum
gray matter (but fewer axons so less frequent)
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8
Q

What histologic changes are found in an active plaque?

A

macrophages wtih myelin debris, perivascular lymphocytes, reactive astrocytes, relative preservation of axons

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9
Q

What histologic changes are found in inactive plaques?

A

few or no macrophages, few lymphocytes, myelin loss with axonal preservation, fibrillary astrocytes

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10
Q

What histologic changes are seen in shadow plaques?

A

partial myelin loss

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11
Q

What is acute disseminated encephalomyelitis (ADEM)?

A

monophasic demyelinating disease, acute onset

assoc w/recent viral illness of vaccines (1-2wk prior)

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12
Q

What are signs and sx of ADEM?

A

headache, lethargy, coma

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13
Q

How many ADEM pts make a complete recovery?

A

80%

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14
Q

What changes are seen histologically with ADEM?

A

perivenous demyelination with axonal preservation

PMNs early, lymphocytes later

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15
Q

What cell type likely precipitates ADEM?

A

T-cell mediated hypersensitivity rxn

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16
Q

What is seen in an ADEM pt gross specimen?

A

congested blood vessels in white matter surrounded by zones of gray discoloration

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17
Q

What is neuomyelitis optica?

A

relapsing synchronous bilateral optic neuriti and spinal cord lesions

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18
Q

What histologic changes are seen in NMO?

A

necrosis in addition to demyelination with inflammatory cells

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19
Q

What protein is affected in NMO?

A

Aquaporins (esp AQP 4)
autoantibodies induce complement depenent cytotoxicity, leukocyte infiltration, cytokine release and blod brain barrier break down—>oligodendrocyte death, myelin loss

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20
Q

Are AQP-4 specific IgG antibodies detectable in all NMO patients?

A

no, only in 60-90%

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21
Q

What is central pontine myelinosis also known as?

A

osmotic demyelination syndrome

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22
Q

What is central pontine myelinosis?

A

monophasic process leading to loss of myelin with relative preservation of the axons and neurons in basis points

23
Q

What are signs/sx of central pontine myelinosis?

A

limb weakness, gaze/speech abnormalities, dysphagia, hTN

24
Q

What causes central pontine myelinosis?

A

usually too rapid correction of hyponatremia

assoc w/alcoholic liver disease, post liver transplant, chronic malnurishment/debilitation, excessive skin burns

25
Q

What event is believed to initiate the pathogenesis of MS?

A

myelin specific T cells get activated in the periphery and cross the BBB where they are reactivated in the CNS

26
Q

What cell type is thought to drive MS?

A

autoreactive CD4 T cells with specificity for antigens expressed by oligodendrocytes, which comprise myelin (MBP, MOG, PLP)

27
Q

What factors do CD4 T cells secrete?

A

IL-17
IFN-y
TNF-a

28
Q

What types of cells can damage myelin?

A

T-cells, macrophages, PMNs

29
Q

Which factors can lead to MHC indepdent cell death via apoptosis?

A

IFN-y
TNF-a
Fas
TRAIL

30
Q

What do cytotoxic CD8 lymphoctyes release upon activation via MHC class 1?

A

granzyme and perforin

31
Q

Define excitotoxicity

A

process by which nerve cells are damaged and killed by excessive stimulation by neurotransmitters such as glutamte (NMDA and AMPA)
high levels of glutamate can cause excitotoxicity by allowing high levels of Ca2+ to enter the cell, which activates a number of enzymes that damage cell structures such as the cytoskeleton, membrane and DNA

32
Q

By what methods can oxidative stress kill cells?

A

via apoptosis or necrosis

33
Q

What are the 2 types of Ab mediated cell death?

A

antibody dependent cell mediated cytotoxicity

complement dependent cytotoxicity

34
Q

What are the 4 types of clinical courses of MS?

A 
relapsing-remitting (RRMS)
secondary progressive (SPMS)
primary progressive (PPMS)
progressive relapsing (PRMS)
35
Q

What is clinically isolated syndrome (CIS)?

A

the first clinical demyelinating event that is suggestive of MS

36
Q

What is the risk of developing MS after CIS if there are any lesions on initial MRI?

A

88%

37
Q

What is the risk of developing MS after CIS if there aren’t any lesions on initial MRI?

A

19%

38
Q

What is the most common inflammatory optic neuropathy? What is is associated with?

A

Demyelinating optic neuritis

associated with MS

39
Q

What affect do IV steroid have on demyelinating optic neuritis (DON)?

A

increase the rate at which vision recovers

may also impart short term protective effect against MS

40
Q

What is the long term of getting MS after having DON on a clean MRI?

A

25% risk in 15 yrs

41
Q

What is the longer term risk of getting MS after having DON and an MRI with 1+ lesions?

A

72% risk in 15 yrs

42
Q

What sx must ADEM have?

A

emcephalopathy (behavioral change or alteration in consciousness)

43
Q

What affect do IV steroid have on demyelinating optic neuritis (DON)?

A

increase the rate at which vision recovers

may also impart short term protective effect against MS

44
Q

How is ADEM treated?

A

high dose IV corticosteroid followed by oral steroid taper over 3-6 wks

45
Q

What is the longer term risk of getting MS after having DON and an MRI with 1+ lesions?

A

72% risk in 15 yrs

46
Q

What sx must ADEM have?

A

emcephalopathy (behavioral change or alteration in consciousness)

47
Q

How is ADEM diagnosed?

A

exclusion

48
Q

How is ADEM treated?

A

high dose IV corticosteroid

49
Q

What might NMO look like in the opthalamoscope?

A

optic disk may appear normal or swollen acutely, pallor chrnoically

50
Q

How do most patients with transverse myelitis present?

A

combo of sensory, motor and bladder/bowel-related sx

51
Q

What is lhermitte sign?

A

electircal or dysesthetic sensation in the spine of limbs elicited by neck flexion

52
Q

How can central pontine myelinosis be treated?

A

reproduce the original ostmotic state (ie/give hypotonic saline)

53
Q

What might NMO look like in the opthalamoscope?

A

optic disk may appear normal or swollen acutely, pallor chrnoically

54
Q

Which is more likely to be painless? NMO or MS assoc neuritis?

A

NMO

Neuro (14 decks)

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