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Week 2 (Neuro 2) > Myelin Disorders > Flashcards

Myelin Disorders Flashcards

1
Q

what are the three types of myelin disorders & how are they dfefined?

A
  • hypomyelinating: arrest in myelin production
  • dysmyelination: abnormal myelin production
  • demyelinating: desctruction of existing myelin
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2
Q

what is the key role of myelin?

A
  • faciliates electrical conduction by
    • increasing membrance resistance
    • decreasing membrane capacitance

(R and C inversely related)

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3
Q

myelin in the CNS

  • is what “kind”?
  • made by what cells?
  • contains which proteins?
A
  • compact myelin
  • made by: oligodendrocytes
  • contains:
    • PLP (proteolipid protein)
    • MBP (myelin basic protein)
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4
Q

myelin in the PNS

  • is what “kind” of myelin
  • made by what cells
  • includes what proteins
A
  • compact myelin
  • made by: schwann cells
  • contains
    • MPZ (myelin protein zero)
    • PMP-22 (peripheral myelin protein-22)
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5
Q

which myelin disorders are dysmyelinating diseases?

what does this mean?

A

= abnormal myelin production

  • frontal leukodystrophies
    • Alexander’s Disease
    • metachromatic leukodystrophy
  • posterior leukodystrophys
    • Krabbe’s disease
    • Adrenoleukodystrophy
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6
Q

alexander’s disease

  • what kind of myelination disorder?
  • cause?
  • presentation?
A
  • dysmeylination disorder - frontal leukodystrophy
  • cause: GFAP mutation leading to rosenthal fiber accumulation
  • presentation: infant with megalencephaly (enlarged brain)
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7
Q

metachromatic leukodystrophy

  • what kind of myelination disorder
  • cause
  • presentation
A
  • dysmyelination disorder - frontal leukodystrophy
  • causse: arysulftase A deficiency leading to cerebroside sulfate accumulation, impairing both
    • ​CNS myelination
    • PNS myelination
  • presentation:
    • juveline onset: development regression + seizures
    • adult onset: dementia + peripheral neuropathy + cholecystitis
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8
Q

krabbe’s disease

  • what kind of myelination disorder?
  • cause
  • presentation
A
  • dysmyelination disease
  • cause: galactocerebroside B-galactosidase deficiency
  • presentation: a lot goes wrong
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9
Q

adrenoleukodystrophy

  • what kind of myeliantion disorder
  • cause
  • presentation
A
  • dysmyelination disease - posteiror leukodystrophy
  • cause: adrenal neuropathy -> high plasma VLCFAS
  • presentation: adrenal insufficiency, +
    • childhood onset: behavior issues
    • adult onset: spasticity
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10
Q

which type of dysmyelination disorders leads to infants with megalencephaly?

A

Alexander’s Disease

(frontal leukodystrophy)

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11
Q

which dysmyelination disease involves cerebroside sulfate accumulation?

A

metachromatic leukodystrophy

frontal leukodystrophy

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12
Q

which dysmyelination disorder can be diagnosed with high plasma VLCFAs?

A

adrenoluekodystrophy

posterior leukodystrophy

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13
Q

list the mutation associated with each dysmyelination disease

A
  • Alexanders: GFAP
  • Metachromatic leukodstrophy: arylsulfatase A
  • Krabbe: galacterocerbrosidase B-galactosidase
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14
Q

multiple sclerosis - pathogenesis

A

autoreactive lymphocytes

  • ​​inflammatory response of Th-1, Th-17 & B-cells, causing
  • myelin dstruction + axonal destruction of the
  • gray + white matter
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15
Q

what are the major risk factors for MS?

A
  • Epstein Barr Virtus
  • Vit-D deficiency / low sunlight
  • smoking
  • adolescent obesity
  • high amplitudes
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16
Q

explain the role of amplitude in pre-disposition to MS

A
  • geographic affect on MS risk depends on age of moving
    • moving before 15 yo: adopt risks of new location (high or low altitude)
    • moving after 15 yo: adopt risks of initial location (high or low altidude)

high altitude = higher MS risk

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17
Q

what are the three categorizations of MS based on dissemination in time?

A
  • relapsing remitting (m/c): initial episode -> followed by relapses & remission
  • secondary progressive: initial episode -> remission -> gradual worsening
  • primary progressive: no initial episode -> gradual worsening
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18
Q

what is a clinically isolated syndrome (CIS)?

what are the clinical actively syndromes seen in MS?

A

definition: a solitary demylinating event lasting at least 24 hours

  • optic neuritis
  • brainstem
  • cerebellar
  • transverse myelitis
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19
Q

what is a radiologicaly isolated syndrome (RIS)?

A

an abnormal MRI in the absence of clinical symptoms

tends to preceed CIS

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20
Q

what are the common ocular manifesations of MS?

A
  • optic neuritis
  • optic atrophy (following optic neuritis)
  • internuclear opahtlmoplegia
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21
Q

optic neuritis in MS

  • demographics affected
  • clinical presentation
  • findings on work-up
A
  • demographic: F, 30s-40s
  • clinical presentation:
    1. rapid monocular vision loss of
      • depth perception
      • color saturation
    2. pain on extraocular movement
  • work-up:
    • PE:
      • significant edema
      • normal fundus
      • nosplinter hemorrhages
    • MRI: < 50% enhancement of optic nerve length
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22
Q

describe the type of vision loss caused by optic neuritis in MS

A
  • rapid onset
  • monocular
  • decreasing perception of:
    • depth
    • saturation
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23
Q

what two key ocular manifestations are NOT seen in optic neuritis?

A
  • an abnormal fundus
  • splinter hemorrhages
24
Q

identify

A

optic atrophy

MS

25
Q

internuclear opathalmolplegia in MS

  • presentation
  • mechanism
A
  • presentation: inability to adduct the eye (unilateral or bilateral)
  • cause: injury to MLF
    • ​carries fibers to oculomotor nucleus (CNIII), which
    • innervates the ipsilateral medial rectus, which
    • adducts ipsilateral eye
26
Q

list the risk of MS development based on clinical findings

A
  • low risk: CIS + normal brain MRI
  • medium risk: RIS w/ either spinal cord lesions OR oligoclonal bands
  • high risk: either
    • CIS + abnormal MRI (2+ lesions)
    • smokers
    • low Vit-D levels
    • < 30 yrs old
  • very high risk: CIS + abnormal MRI involving new disease activity
27
Q

pts with at what risk for developing MS are treated?

A

high risk and very high risk

(high risk tx with disease modifying therapy)

28
Q

which factors are associated with an aggresive presentation of MS?

A
  • male, AA, onset > 40 years
    • risk factors for eveloping MS:
      • obesity
      • smoking
      • Vit D
29
Q

what set of criteria must be met to make a diagnosis of MS?

A

McDonald Criteria

  • dissemination in time: more than one attack
  • dissemination in space: a lesion that
    • is at least 3mm in the long axis
    • at least 2 of the following areas:
      • cortical
      • juxtacortical
      • paraventircal
      • spinal cord: hemicord transverse myelitis
30
Q

describes the lesions (plaques) that characterize multiple sclerosis

A
  • > 3mm lesions
    • cortical / juxtacortical - ovoid
    • paraventricular - perpendicular, flame shaped
    • tranverse myelitis (spinal)
      • involves only one vertebral segment
      • hemicord & NOT in central canal
31
Q

MS treatment

what are the roles of DMTs (disease modifying treatments)?

A
  • NOT for symptom improvement
  • serve to delay progression from CIS to MS
32
Q

MS treatment

what is the management for patients who refuse DMTs?

A

annual MRIs for 5 years

33
Q

MS treatment

which DMTs increase PML risk?

A
  • natalizumab
  • fingolimod
  • rituximab
  • ocreliazumab
  • dimethyl fumarate

DO follow no rules

34
Q

MS treatment

when shoud switching therapies be considered?

A
  • 1 or more relapses
  • 1 year of worsening diasability
  • 2 or more new MRI lesions
35
Q

MS treatment

which MS patients should NOT be treated?

A
  • CIS with normal MRIs [low risk]
  • CIS/MIS with NEDA [no evidence of disease activity] while off therapy for 2 years
36
Q

MS treatment

treatment for acute flares?

A

methylprednisone

37
Q

progressive multifocal leukoencephlopathy (PML)

  • definition
  • cause
  • demographics
  • MRI
  • treatment:
A
  • definition: potentially fatal demyelination
  • cause: JC virus reactivation
  • demographics: I/C - HIV, transplants, chemo, natalizumab
  • MRI: gray white junction lesions that dont follow vascular territories
  • treatment:
    • PML: plasma exchange (qod x 5)
    • PML IRIS: high dose steroids (IVMP 1g/day x 5)
38
Q

identify

A

MS lesions

flame like, perpendicular to ventricles

39
Q

identify

A

MS lesions

cortical - ovoid shaped

40
Q

identify

A

PML-IRIS

41
Q

neuromyelitis optica (NMO)

  • cause
  • presentation
  • MRI
A
  • cause: antibodies to aquaporin-4, a water channel on astrocyte foot processes
  • presentation:
    • binocular optic neuritis (with > 50% optic nerve enhancement)
    • area-postrema syndrome: hiccups & N&V
  • MRI: large lesions that follow ependymal lines
    • brain - including diencephalon
    • spinal cord - LETM (longidutinally extensive transverse myelitis)
      • affects at least 3 segments
      • +/- complete, including central canal
      • may involve medulla
42
Q

identify

A

neuromyeltis optica (NMO)

lesions in diencephalon

43
Q

identify

A

neuromyelitis optica (NMO)

advancing LEMN coinciding with vomitting (area postrema) syndrome

44
Q

identify

A

neuromyelitis optica (NMO)

lesions that that are large (here - tumefactive lesions, which are > 2cm) and don’t obey ependymal lines

45
Q

contrast the ocular presentations of

  • MS
  • NMO
A
  • MS
    • monocular
    • optic nerve enhancement < 50%
  • NMO
    • binocular
    • optic nerve enhancement > 50%
46
Q

contrast the lesions seen in

  • MS
  • NMO
A
  • MS
    • brain: does not follow ependyma - ovoid, flame shaped
    • spinal cord (transverse myelitis)
      • hemicord
      • not including central canal
      • one vertebral segment
  • NMO
    • brain: follows ependyma, often includes diencehpalon, can be large
    • spinal cord: (LETM)
      • possibly complete
      • includes central canal
      • multiple vertebral levels -:> possibly up to medulla
47
Q

compare & contrast NMO based on

  • general prevalence
  • age of onset
  • co-existing autoimmunity
  • nature of optic neuritis
  • nature of myelitis
  • presence of diencephalon syndrome
  • presence of dawson’s fingers
  • presence of tumefactive lesions
  • CSF features
A
48
Q

area postrema syndrome

  • presents how?
  • is part of which syndrome? why?
A
  • presentation: hiccups, nausea & vomitting
  • NMO: d/t LETM, which can affect the medulla
49
Q

MOG antibody disease

  • cause
  • age of onset
  • presentation
  • MRI
A
  • cause: myelin oligodendrocyte glycoprotein antibody disease
  • age of onset: 25
  • presentation: binocular optic neurtiis + significant optic disc edema
  • MRI:
    • brain: involve gray matter
    • spinal cord (transverse mylitis)
      • LETM (affects multiple vertebral levels)
      • has a predilection for the conus medullaris
      • involves central canal - including gray matter
      • RARELY RECURRENT.
50
Q

ADEM

A
  • cause: triggered by inflammation - often viral infection
  • age of onset: children m/c (age 5-8 yo)
  • presentation: demylination + ENCEPHALOPATHY
  • MRI:
    • ​brain: involve gray matter (basal ganglia)
    • spinal cord (myelitis): rarely seen
51
Q

how does tranverse myelitis

  • present clinically?
  • appear on MRI in each demylination disease?
A
  • present: flaccid paralysis with decreased reflexes
  • lesions on MRI:
    • MS: single vertebral level, hemicord, no central canal
    • NMO: LETM that can include medulla, central canal involved
    • MOG: LETM w/ conus medullaris, central canal involved (up to gray matter), rarely recurrent
    • ADEM: spinal cord involvement rare
52
Q

which demylination disease can affect the gray matter of the brain?

explain

A
  • ADEM (basal ganglia involvement)
  • MOG antibody disease
53
Q

which demylenation disease commonly presents with optic disc edema?

A

MOG antibody disease

can occur in MS, but is insignificant

54
Q

which demylination disease presents with spinal cord lesions that have a predilection for the conus medularis?

A

MOG antibody disease

55
Q

which demylinating disease presents with LETM that typically does not recurr?

A

MOG antibody disease

56
Q

list the m/c age group affected by each demylinating disease

A
  • MS: 30-50, rarely > 60
  • NMO: > 40, often > 60
  • ADEM: children m/c
  • MOG antibody disease: ~25

Week 2 (Neuro 2) (9 decks)

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