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NSB! > Introduction to demyelinating disorders > Flashcards

Introduction to demyelinating disorders Flashcards

1
Q

When does myelination being in babies?

1 1st trimester
2 - 2nd trimester
3 - 3rd trimester

A

3 - 3rd trimester
- rapid increase at birth and continues throughout life

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2
Q

Do oligodendrocytes form myelin in set places?

A
  • no
  • oligodendrocytes move to where they are needed
  • then myelin is laid down
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3
Q

What is myelin?

1 - cytoplasm of neuronal cells
2 - extensions of schwann and oligodendrocytes lipid membranes
3 - protein laid down by neutrophils on neurons
3 - lipid and protein laid down during foetal development but stops when born

A

2 - extensions of schwann + oligodendrocytes lipid membranes
- mixture of lipid and proteins

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4
Q

What is myelin sheath?

A
  • the myelin that has wrapped around the axons
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5
Q

Where can oligodendrocytes be found and how many axons can they myelineate?

A
  • CNS
  • multiple
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6
Q

Where can schwann cells be found and how many axons can they myelineate?

A
  • PNS
  • one axon per schwann cell
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7
Q

Are all axons in the CNS and PNS myelineated?

A
  • no
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8
Q

In the CNS which axons are myelineated?

1 - CNS axons >1-2um
2 - CNS axons <1-2um
3 - CNS axons >0.2um
4 - CNS axons <0.2um

A

3 - axons >0.2um
- small axons are small enough & don’t need help transmitting signal

In CNS axons >0.2µm myelinated.

In PNS axons >1-2µm myelinated

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9
Q

Which cells in the PNS are myelineated?

1 - PNS axons >0.2um
2 - PNS axons <0.2um
3 - PNS axons >1-2um
4 - PNS axons <1-2um

A

3 - PNS axons >1-2um
- small axons are small enough and do not need help transmitting signal

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10
Q

Some axons have more wraps of myelin than others. What determines how many layers of myelin the axons have?

1 - location of axon
2 - length of the axon
3 - type of axon (multi, uni-polar etc.)
4 - diameter of axon

A

4 - diameter of the axon

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11
Q

What role do gliotransmitters have in myelination?

A
  • communication between neuronal + glial cells
  • myelination is dependent on neuronal activity
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12
Q

What are the 3 functions of myelin?

1 - reduce loss of charge, increase speed of action potential, increase transmission efficacy
2 - increase loss of charge, increase speed of action potential, increase transmission efficacy
3 - reduce loss of charge, decrease speed of action potential, increase transmission efficacy
4 - increase loss of charge, increase speed of action potential, decrease transmission efficacy

A

3 functions of Myelin:
1. reduce loss of charge,
2. increase speed of action potential,
3. increase transmission efficacy

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13
Q

The nodes of ranvier are spaces between where axons are myelinated. What is highly concentrated at the nodes of ranvier?

1 - voltage gated Ca2+ channels
2 - voltage gated K+ channels
3 - voltage gates Mg+ channels
4 - voltage gated Na+ channels

A

4 - voltage gated Na+ channels

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14
Q

When a neuronal cell body receives an action potential from a dendrite it causes depolarisation inside the cell. How does this then move from the cell body of the neuron to the axon hillock (where axon and cell body meet) and move down the axon?

A
  • Na+ voltage gated channels open
  • depolarisation spreads and Na+ gated channels further down the axon begin to open
  • acts like a domino effect
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15
Q

Are voltage gated channels generally found on the sections of axon that are myelinated?

A
  • no
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16
Q

How does myelin reduce the loss of charge in the axons and therefore facilitate the movement of the action potential down the axon?

1 - no voltage gated channels in myelin areas and decreased axon permeability
2 - only Na+ and Ca2+ voltage gates channels in myelinated areas
3 - permeability to just K+ leaving the axon
4 - increased permeability and increased voltage gated channels in myelin areas

A

1 - no voltage gated channels in myelin areas and decreased axon permeability

  • no voltage gated channels in myelin areas means no ions can leave or enter the already depolarised neuron
  • permeability is decreased in myelin areas, meaning ions cannot leave, so depolarised neuron remains depolarised
  • positive charge (action potential) must move down the axon
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17
Q

What is capacitance in relation to an action potential?

A
  • relates to the ability of an electrical system to store charge or the charge required to initiate an action potential/electrical impulse
  • high capacitance = high positive charge required for an action potential
  • low capacitance = less positive charge required for an action potential
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18
Q

Capacitance relates to the ability of an electrical system to store charge or the charge required to initiate an action potential/electrical impulse.

  • high capacitance = high positive charge required for an action potential
  • low capacitance = less positive charge required for an action potential

How does myelin affect the capacitance of an axon?

1 - capacitance is high meaning meaning low charge required for action potential
2 - capacitance is high meaning meaning high charge required for action potential
3 - capacitance is low meaning meaning low charge required for action potential
4 - capacitance is low meaning meaning high charge required for action potential

A

3 - capacitance is low meaning meaning low charge required for action potential
- myelinated regions have lower capacitance (less negative charge)
- less negative charge in myelin areas means less positive charge required for action potential
- therefore less positive charge is required to initiate an action potential

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19
Q

When we look at the flow of an action potential along an axon, do small or larger diameter axons have faster flow of action potential?

A
  • axons are part of a neurons cytoplasm, which means they contain cytoplasmic proteins, vesicles, etc.
  • larger diameter have more room for cytoplasmic vesicles to spread out
  • large diameter axons will have faster conductance as there is less resistance for ions to flow
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20
Q

What is the relationship between the diameter of the axon and the resistance to the flow of ions that move down the axon following an action potential?

A
  • ⬆️ diameter = ⬇️ resistance = ⬆️ flow
  • ⬇️ diameter = ⬆️ resistance = ⬇️ flow
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21
Q

What are the 2 terms used to describe the propagation of an action potential down a myelinated and non-myelinated axon?

A
  • saltatory conduction = myelinated fast conduction
  • continuous conduction = unmyelinated slow conduction
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22
Q

If we break down the word leukodystrophies, what does this term mean?

A
  • leuko = white
  • dyst = abnormal (muscle dystrophy)
  • trophies = growth
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23
Q

Leukodystrophies is a rare neurological disorder. What happens?

  • leuko = white
  • dyst = abnormal
  • trop = growth
A
  • demyelinating disease
  • degeneration/loss of the white matter of the nervous system (myelin)
  • causes slow or no nerve message or action potential
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24
Q

Leukodystrophies is a rare neurological disorder.

  • leuko = white
  • dyst = abnormal
  • trop = growth

This is a dysmyelinating disease causing degeneration/loss of the white matter of the nervous system, which is myelin meaning action potentials are unable to travel along axons, or if they do it is very slow. Is this a congenital or acquired disease?

A
  • congenital
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25
Q

Leukodystrophies is a rare neurological disorder that causes loss of myelin sheaths, termed demyelination. Does this always cause loss of myelin?

A
  • it can do
  • but it can be where myelin is not formed when a baby is born
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26
Q

Leukodystrophies is a rare neurological disorder that causes loss of myelin sheaths, termed demyelination. What does this do to nerves?

A
  • can cause complete loss of nerve activity
  • can cause slowing of nerve activity
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27
Q

In patients with demyelination, do symptoms always present the same in all patients?

A
  • no
  • depends on the nerve affected
  • if visual nerve then eye sight is affected
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28
Q

Multiple sclerosis, whose name is based on multiple sclerae (multiple glial scars which is what is formed when glial cells (astrocytes) try to repair damaged neurons) is a demyelinating disease. Does this disease affect the CNS or PNS?

A
  • affects CNS, so the brain and spine
  • does not affect the PNS
29
Q

Multiple sclerosis is a common neurological disease that is an immune based disorder. Is it more common in males or females?

A
  • females 3:1 ratio
  • common in western world
30
Q

Although the specific cause of multiple sclerosis is unknown, what are some of the most common risk factors that have been linked?

A
  • genetics (aprox 30%)
  • lifestyle (obesity, smoking)
  • environment (sun/vit D exposure)
31
Q

Multiple sclerosis is an immune mediated demyelinating disease. What immune cell is able to cross the blood brain barrier and enter the brain, that generally would not be present?

1 - B cells
2 - dendritic cells
3 - T cells
4 - neutrophils

A

3 - T cells
- once in they are activated by myelin
- more T cell receptors on BBB and more T cells enter and attack myelin

32
Q

Multiple sclerosis is an immune mediated demyelinating disease. What type of hypersensitivity is this disease?

1 - type I (IgE related)
2 - type II
3 - type III
4 - type IV

A

4 - type IV (4)
- cell mediated so T cells stimulate inflammation
- damage the myelin in CNS

33
Q

Multiple sclerosis is an immune mediated demyelinating disease. This is a type 4 hypersensitivity. Does this cause a continuous demyelination or are there periods of demyelination, and are these linked with clinical symptoms?

A
  • periods of demyelination are linked with symptoms
  • periods of remission where demyelination stops and CNS tries to repair the damaged neurons
  • relapse when demyelination starts again
34
Q

If a patient has multiple sclerosis, does that mean demyelination will be continuous?

A
  • no
  • if demyelination stops, neurons could remyelinate
  • failure to remyelinate leads to further symptoms
35
Q

In a patient who has multiple sclerosis, and has not had any relapse of demyelination, then remyelination can occur. Is this remyelinate as good as the original demyelination?

A
  • no
  • not as good and can cause glial scars
  • can improve nerve signals though
36
Q

What is relapsing remitting disease in multiple sclerosis?

A
  • when demyelination occurs
  • remission of demyelination occurs
  • demyelination occurs again and this continues
  • patients symptoms will link with demyelination
37
Q

What is secondary progressive multiple sclerosis?

A
  • relapsing and remitting demyelination
  • but course is deteriorating
38
Q

In the image below is a patients with multiple sclerosis sagittal scan from the brain. What are the white area in this image a sign of?

1 - myelinated areas
2 - neuronal cell bodies
3 - unmyelinated areas
4 - glial scars called sclerela

A

4 - glial scars called sclerela

39
Q

Although there are a myriad of symptoms that patients with multiple sclerosis can present with, what are the most common patterns of disease?

A
  • optic neuritis (vision loss)
  • cerebellar (balance, tremor, co-ordination)
  • spinal cord (muscle weakness, spasticity, bladder/bowel dysfunction)
40
Q

In patients with optic neuritis, swelling and inflammation of the optic nerve can occur, what can patients experience?

A
  • reduced vision and colour loss
  • pain on eye movement (due to inflammation)
41
Q

In patients with multiple sclerosis, optic neuritis is one of the most common symptoms. This can cause swelling and inflammation of the optic nerve causing reduced vision and colour loss and pain on eye movement (due to inflammation). Is this permanent?

A
  • no can be affected during phases of demyelination
  • however, in remission (when demyelination has stopped) vision can return
42
Q

Patients with multiple sclerosis can experience Lhermittes sign, what is this?

1 - inability to make hand signals with their hands
2 - pain felt in the upper limbs
3 - electric shock felt in back and limbs
4 - electric shock felt in upper limbs

A

3 - electric shock felt in back and limbs
- felt when we bend out heads towards our chest
- causes by lesion on the cervical region of the spinal cord

43
Q

Multiple sclerosis can have a significant impact on a patients health and quality of life. What scale can be used to determine the level of disability and impact the disease has on their quality of life?

1 - MRC scale
2 - Expanded Disability Status Scale (EDSS)
3 - Disease Severity Scale (DSS)

A

2 - Expanded Disability Status Scale (EDSS)

44
Q

Multiple sclerosis causes significant inflammation. What drugs can be given to these patients to treat the inflammation?

A
  • steroid (acute relapse) such as glucocorticoids
  • increase recovery speed
  • do not get better than prior to relapse though
45
Q

Multiple sclerosis causes is generally progressive. What drugs are trying to be developed?

A
  • disease modifying agents
  • essentially stop or reverse the disease
46
Q

What is Guillain-Barre syndrome?

A
  • demyelinating disease of the PNS
47
Q

Guillain-Barré syndrome is a demyelinating disease that is an immune based condition. Although we do not know exactly what causes this condition, but it is linked with infections. What are a few of the most common infections?

A
  • diarrhoeal illness (campylobacter causes 1/3)
  • upper respiratory tract infection, covid
  • hepatitis E
48
Q

Guillain-Barré syndrome is a demyelinating disease that is an immune based condition. Although we do not know exactly what causes this condition, but it often follows infections. Why is this?

A
  • antibodies are produced to target an infection
  • antibodies then target myelin due similarity in antigens
49
Q

What is ‘molecular mimicry?

A
  • foreign bodies and/or pathogens share similar antigen structure to self antigens
  • this is a leading mechanisms by which infectious or chemical agents may induce autoimmunity
50
Q

Guillain-Barré syndrome is caused by antibodies binding to the myelin. which then initiates an immune response. The immune cells then attack the myelin in the PNS. There are different forms of Guillain-Barré syndrome. Which is the most common in the UK?

1 - acute demyelinating polyradiculoneuropathy (AIDP)
2 - acute motor axonal neuropathy (AMAN)

A

1 - acute demyelinating polyradiculoneuropathy (AIDP)

  • poly = many nerves
  • radiculon = roots, relating to nerve roots and spine
  • neuropathy = disease of the neurons
51
Q

Guillain-Barré syndrome (GBS) that is caused by antibodies targeting the nerve itself is the most common form of GBS in asian countries, what is this called?

1 - acute demyelinating polyradiculoneuropathy (AIDP)
2 - acute motor axonal neuropathy (AMAN)

A

2 - AMAN: acute motor axonal neuropathy

52
Q

In Guillain-Barré syndrome patients tend to present with weakness (may be tingling as well) over how many weeks?

1 - 2-4 days
2 - 2-4 weeks
3 - 2-4 months
4 - 2-4 years

A

2 - 2-4 weeks
- affects anything with muscles
- patients can deteriorate and die within days

53
Q

In Guillain-Barré syndrome patients tend to present with weakness (may be tingling as well) over 2-4 weeks. How long before this reaches the lowest point?

1 - 4-6 weeks
2 - 6-12 weeks
3 - 12-24 weeks
4 - >24 weeks

A

2 - 4-6 weeks

54
Q

In Guillain-Barré syndrome once a patient has presented with weakness (may be tingling as well) over 2-6 weeks, what tends to occur?

A
  • patients recover and stabilise, but may not be to normal levels
  • some people can deteriorate and die though
55
Q

Guillain-Barré syndrome is a monophasic condition, what does this mean?

A
  • patient will have one episode of inflammation on PNS
  • unlikely to have another
56
Q

Label the dermatomes of the upper limbs using the labels below:

  • T1
  • C5
  • C8
  • C7
  • C6
A

1 - C5
2 - C6
3 - C7
4 - C8
5 - T1

57
Q

Label the dermatomes of the leg using the labels below:

  • S1
  • L5
  • L4
  • L3
  • L2
A

1 - L2
2 - L3
3 - L4
4 - L5
5 - S1

58
Q

T4 and T10 are 2 important landmark dermatomes on the upper body. What do each of these dermatomes link with?

A
  • T4 = nipples
  • T10 = umbilicus
59
Q

If a patient presents with optic neuritis (inflammation or demyelination), what is the most likely diagnosis?

1 - UMN = multiple sclerosis
2 - LMN = guillain barre syndrome

A

1 - UMN = multiple sclerosis

60
Q

What is clinically isolated syndrome?

1 - patient has one nerve affected
2 - first episode of multiple sclerosis
3 - first episode of a neurological symptoms that lasts > 24 hours
4 - first episode of Guillain-Barré syndrome

A

3 - first episode of a neurological symptoms that lasts > 24 hours

61
Q

Clinically isolated syndrome (CIS) is the first episode of a neurological symptoms that lasts > 24 hours. If a patient presents with optic neuritis as part of the their CIS there is a 50% chance the patient will then go on and develop what?

1 - Guillain-Barré syndrome
2 - dementia
3 - cerebral vascular disease
4 - multiple sclerosis

A

4 - multiple sclerosis

62
Q

What is cataplexy?

1 - patient develops cat like features
2 - sudden loss of sensations
3 - sudden loss of muscle tone whilst awake
4 - sudden spasticity when awake

A

3 - sudden loss of muscle tone whilst awake
- leads to weakness and a loss of voluntary muscle control

63
Q

Cataplexy is the sudden loss of muscle tone while a person is awake leads to weakness and a loss of voluntary muscle control. What is the most likely cause of this?

A
  • a sudden, strong emotions such as laughter, fear, anger, stress, or excitement
  • should be sleep and have narcolepsy
64
Q

What is bells palsy?

1 - patients experiences sound in ears like a bell ringing
2 - patient experiences complete facial muscle weakness
3 - patient experiences episodic loss of facial muscle weakness/paralysis
4 - patients face becomes infected

A

3 - patient experiences episodic loss of facial muscle weakness/paralysis
- can begin suddenly and worsen over 48 hours

65
Q

Bells palsy is an unexplained episode of facial muscle weakness or paralysis. It normally affects entire face and can begin suddenly and worsen over 48 hours. Although damage to the facial nerve can cause this, what is the most common cause?

1 - bacterial infection
2 - molecular mimicry
3 - trauma
4 - herpes virus

A

4 - secondary to herpes virus
- caused by virus

66
Q

What is the Wada test?

A
  • looks at language and memory on one side of the brain at a time
  • brain is infused with pentobarbital (slows the activity of the brain) through carotid artery
  • one side of the brains activity will be suppressed
67
Q

The Wada test is a test to look at language and memory on one side of the brain at a time. The brain is infused with pentobarbital (slows the activity of the brain) through carotid artery causing one side of the brains activity to be suppressed in the temporal and frontal lobes. How do we know which side is affected?

A
  • even with pentobarbital if they answer questions correctly then the opposite side that is being treated is the one controlling language and memory
68
Q

What does the name Myasthenia Gravis translate as?

A
  • my = muscle
  • asthenia = weakness
  • gravis = grave
    SO MUSCLE WEAKNESS
69
Q

Myasthenia Gravis translates as muscle weakness.

  • my = muscle
  • asthenia = weakness
  • gravis = grave

What causes myasthenia gravis?

A
  • autoimmune disease
  • type II hypersensitivity = antibody mediated hypersensitivity
  • B cells produce antibodies that bind nicotinic receptors

NSB! (53 decks)

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