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NSB > Intro to Demyelinating Disorders > Flashcards

Intro to Demyelinating Disorders Flashcards

1
Q

What cells are shown below?

A

insert diagram

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2
Q

What are glial cells?

A

neural tissue cells that do not propagate an action potential but support and protect neurons

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3
Q

When does myelination begin?

A
  • third trimester
  • increases rapidly at birth
  • continues throughout life
  • oligodendrocyte = neuroepithelial
    origin from neural tube
  • schwann cell = neural crest origin
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4
Q

Myelin is

A

a membranous cytoplasmic projection (lamellipodum) of an oligodendrocyte or a schwann cell that surrounds a neuronal axon forming the protective sheath

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5
Q

Schwann cell

A

insert diagram

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6
Q

Myelination in the CNS vs PNS

A
  • CNS: one oligodendrocyte can
    myelinate up to 50 axons
  • PNS: one schwann cell myelinates one
    axon
  • PNS: myelin sheaths are thicker in
    diameter
  • CNS: axon >0.2 micrometers to be
    myelinated
  • PNS: 1-2 micrometers to be myelinated
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7
Q

Oligodendrocyte and Schwann cell origin

A

insert diagram

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8
Q

Which fibers are myelinated earlier in development? Sensory or Motor fibers?

A

Sensory fibers

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9
Q

Myelination in the CNS can be intrinsic or adaptive.

A
  • intrinsic = early on during birth and
    early childhood
  • adaptive = as neuronal network forms
  • dwindles with age
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10
Q

What promotes the proliferation of oligodendrocytes?

A

Astrocytes

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11
Q

In the PNS how is myelination initiated?

A

proteins expressed on axon surface interact with glial cell receptors and promote the differentiation of progenitor cells to mature myelinating schwann cells

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12
Q

What is the main component of the myelin sheath?

A

primarily plasma membrane so
Lipid

like cholesterol

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13
Q

How is adaptive myelination initiated?

A

proteins expressed on axon surface interact with receptors on glial cells and promote the differentiation of progenitor cells to mature myelinating cells

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14
Q

Myelin Sheath

A

insert diagram

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15
Q

The juxtaparanodal area of the axon is rich in

A

K+ voltage gated ion channels

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16
Q

What is the bare area of the axon called?

A

Node/nodal area

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17
Q

Schmidt-Lanterman incisures are found

A

between the internodal lamellae formed by schwann cells in the pns

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18
Q

Nodes of Ranvier:
- are
- contain

A
  • gap between two adjacenet myelin
    sheaths across an axon is called the
    node of Ranvier
  • nodes of ranvier contain clusters of
    voltage gated sodium channels
  • electrical current generated ollowing
    depolarisation travels across the
    insulated internode segment, with little
    change to the next node causing
    depolarisation
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19
Q

Label the diagram below

A

insert node of ranvier diagram

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20
Q

Saltatory Conduction:
- is
- advantages

A
  • action potentials leap from node to node,
    increasing conduction velocity
  • reduces loss of electrical current across axon
  • unmyelinated = 0.5-2m/s, myelinated = 70-
    100 m/s
  • increased efficiency of electrical
    transmission as less ion channels are
    needed (only ones at nodes) -> saves energy
    for cell
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21
Q

Saltatory Conduction:

A

insert diagram

22
Q

Demyelinating Diseases:

A

damage to the myelin sheath

23
Q

Dysmyelinating Disease:

A

abnormal formation of the myelin sheath

24
Q

Demyelinating Diseases: Pathological Effects:

A
  • reduced conduction velocity
  • reduced distance in propagation of signal
    across an axon
  • both efferent and afferent neurons can be
    affected as well as higher functions, such as
    cognition
25
Q

Pathology of Demyelinating Diseases: Causes:

A
  • brain injury or ischaemia
  • toxins/chemicals
  • metabolic
  • neurodegenerative
  • infection
  • autoimmune effects (myelin sheath proteins
    are antigenic)
26
Q

Demyelinating Diseases: Symptoms:

A
  • visual impairment
  • cognitive changes
  • speech impairment
  • balance problems
  • incoordination
  • sensory loss
  • weakness
  • incontinence
  • pain
  • fatigue
27
Q

Multiple Sclerosis:
- is
- incidence
- causes

A
  • autoimmune demyelinating disease
  • most common demyelinating disease with 1
    in 1000 incidence
  • increased incidence in females
  • genetic susceptibility and environmental
    triggers
28
Q

Multiple Sclerosis: Subtypes (3):

A
  • relapsing-remitting = episodes of relapse
    followed by remission, in the majority of
    cases without complete repair
  • primary progressive = no periods of
    improvement or relapse
  • secondary progressive = with relapse-
    remission phase followed by progressive
    disease years later with no remission phase
29
Q

Multiple Sclerosis:

What leads to ongoing symptoms, accumulation of neurologic deficits and disability?

A

failure of remyelination

30
Q

Multiple Sclerosis: Clinical Features:

A
  • earliest presentation generally visual
    impairment due to optic nerve affected
  • not all cases of optic neuritis develop MS
  • ataxia
  • nystagmus
  • sensory and motor impairment of trunk and
    limbs
  • loss of bladder control
31
Q

Multiple Sclerosis: Treatment:

A
  • steroids
  • disease modifying treatments
  • aim to control immune response to
    decrease the rate and severity of replace
    episodes
  • social prescribers
32
Q

Multiple Sclerosis: Pathophysiology:

A
  • T helper and B cells involved
  • secrete cytokines that recruit macrophages
    and other leucocytes that destroy myelin
  • leading to the formation of white matter
    lesions called plaques
  • plaques can be active; containing
    macrophages, broken down myelin and
    lymphocytes
  • inactive plaques = resolved inflammation,
    astrocyte proliferation and no myelin-gliosis
    that can lead to the formation of a glial scar
33
Q

Multiple Sclerosis:

A

insert images

34
Q

As age increases, remyelination is

A

less efficient

35
Q

Autoimmune Demyelinating Diseases:

A
  • demyelination due to immune function can
    follow viral infections, even mild ones
  • caused by cross reactivity between myelin
    proteins and immune cells/antibodies
  • the resulting diseases are acute and
    monophasic
36
Q

Acute Disseminated Encephalomyelitis (ADEM):

A
  • autoimmune demyelinating disease
    following viral infection
  • non-localised symptoms (headache,
    lethargy, coma)
  • rapid progression with either complete
    recovery or fatality in a minority of cases
37
Q

Neuromyelitis optica:

A

optic nerve and spinal cord affected by autoimmune demyelination

38
Q

Gullian-Barre Syndrome:

A
  • autoimmune demyelinating disease of the
    PNS
39
Q

Guillain-Barre Syndrome: Presentation:

A
  • often following infection like diarrhoeal
    illness (campylobacter), upper respiratory
    tract infection, COVID, hep E
  • progressive weakness over 2-4 weeks,
    reaches nadir by 4-6 weeks
  • affects arms/legs/facial
    muscles/speech/swallowing/breathing
  • may affect autonomic nervous system
  • varying degrees of severity
  • recovery thereafter (may not be complete)
40
Q

Gullian-Barre Syndrome is a monophasic illness.

True or False?

A

True

41
Q

Guillain-Barre Syndrome: Treatment:

A
  • plasma exchange
  • IV immunoglobulins
42
Q

Guillain-Barre Syndrome: Subtypes:

A
  • acute demyelinating polyradiculoneuropathy
    (AIDP): europe, north ameria
  • acute motor axonal neuropathy (AMAN):
    asia
43
Q

Dysmyelinating Diseases: Leukodystrophies:
- are, cause, nature

A
  • inherited diseases that emerge at a young
    age and are progressive
44
Q

Krabbe Disease:

A
  • dysmyelinating leukodystrophy
  • autosomal recessive
  • causes by build up of cytotoxic metabolic
    compound which inhibits myelin sheath
    formation
  • appears between 3-6 months of age, survival
    beyond 2 years is rare
  • loss of myelination in both CNS and PNS;
    loss of oligodendrocytes
45
Q

Metachromatic Leukodystrophy:

A
  • dysmyelinating leukodystrophy
  • autosomal recessive
  • affects macrophages
46
Q

Adrenoleukodystrophy:

A
  • dysmyelinating leukodystrophy
  • x linked recessive
  • young males affects
  • 10 years of life max
47
Q

Charcot-Marie-Tooth Disease:

A
  • hereditary heterogenous (dominant) disease
  • dysmyelinating leukodystrophy in some
    subtypes
  • mutations in different proteins linked
  • progressive disease that usually presents
    between 0-20 years of age
  • CMT1 are subtypes caused by demyelination
    when the mutation is autosomal dominant
  • CMT4 when autosomal recessive which is the
    most rare and severe
  • CMT2 subtypes affect neuronal axons
48
Q

Remyelination: CNS:

A
  • regenerative process
  • axon regeneration is limited in CNS but
    remyelination occurs
  • remyelination relies on oligodendrocytes
    and the differentiation of oligodendrocyte
    precursor cells (OPCs)
  • success of remyelination depends on the
    location of a lesion, presence of OPCs,
    degree of inflammation and the presence of
    gliosis
49
Q

Remyelination does occur in MS patients however is negatively affected by

A

disease progression

50
Q

Remyelination: PNS:

A
  • schwann cells can proliferate and
    remyelinate axons
  • depends on the presence of progenitor cells
    and successful differentiation
  • in comparison with CNS, schwann cells
    create a positive growth environment that
    promotes both axon growth and
    remyelination in the event of injury

NSB (50 decks)

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