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Fundamentals of neuroscience > Myelin disorders (diseases of NS) > Flashcards

Myelin disorders (diseases of NS) Flashcards

1
Q

LOs:

A
  • Understand the peripheral myelin diseases –> Guillain Barre Syndrome, CIDP and Charcot-Marie-Tooth disease
  • Understand the key features of central nervous myelin disorders
  • Understand MS
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2
Q

What is myelin?

A

Surrounds axons on nerve cells to allow signals to be trnasmitted faster

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3
Q

What are the functions of myelin?

A
  • Provides PROTECTIVE BARRIER between axons & extracellular space
  • INCREASES CONDUCTION VELOCITY
  • Enables GREATER nervous system COMPACTNESS
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4
Q

How does myelin increase conduction velocity?

A

It increases the rm without needing to increase the axon diameter

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5
Q

How does myelin enable for greater nervous system compactness?

A

Maintains small diameter on axons

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6
Q

How does demylination affect conduction?

A
  • Decreases rm
  • Which reduces λ
  • Lenght constant is too small resulting in insufficient spread of voltage to excite the subsequent node
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7
Q

What does λ mean in the context of axons?

A

The mathematical constant used to quantify the distance that a graded potential will travel along a neurone via passive electrical conduction

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8
Q

What are the collected symptoms of demyelination?

A
  • Ataxia
  • Clonus
  • Fatigue
  • Paralysis
  • Incoordination
  • Impaired muscle condition
  • Weakness
  • Loss of sensation
  • Blurred vision
  • Hearing problems
  • Speech problems
  • Cognitive problems
  • Incontinence
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9
Q

What is the cause of Guillain Barre Syndrome?

A
  • Autoimmune response that attacks peripheral nerves
  • Ofter proceeds a respiratory infection
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10
Q

What is the incidence of Guillain Barre Syndrome?

A

Rare –> ~2 in 100,000

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11
Q

What is the diagnosis for Guillain Barre Syndrome?

A
  • Rapid onset muscle weakness in the arms & legs
  • Without sensory disturbance
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12
Q

What is the treatment for Guillain Barre Syndrome?

A
  • Plasma exchange (5 volumes over 2 weeks)
  • Intravenous immunoglobulin
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13
Q

What is the prognosis for Guillain Barre Syndrome?

A
  • The vast majority recover within a year
  • Outlook worse in older ppl
  • The more severe the attack the poorer the outcome
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14
Q

What are the 2 subtypes of Guillain Barre Syndrome?

A
  • Demylenating
  • Axonal
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15
Q

What is demylenating Guillain Barre Syndrome like?

A

(Acute inflammatory demylenating polyneuropathy)

Antibody injures MYELIN membranes

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16
Q

What is axonal Guillain Barre Syndrome like?

A

(Acute motor axonal neuropathy or acute motor and sensory axonal neuropathy)

Antibody injures AXONAL membranes

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17
Q

What is axonal Guillain Barre Syndrome like?

A

(Acute motor axonal neuropathy or acute motor and sensory axonal neuropathy)

Antibody injures axonal membranes

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18
Q

What does CIDP stand for?

A

Chronic Inflammatory Demyelinating Polyradiculoneuropathy

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19
Q

What is the cause od CIDP?

A

Immune origin (inflammation of nerve roots and autoimmune destruction of perpheral nerve myelin)

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20
Q

What is the incidence of CIDP?

A

Rare –> ~1 in 100,000 in UK

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21
Q

What is the diagnosis of CIDP?

A
  • Slower progression of sensory and motor symptoms in the distal & proximal segments of the 4 limbs evolving over 8 weeks
  • Progressive or relapsing in nature
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22
Q

What is the treatment for CIDP?

A
  • Steroids
  • Intravenous immunoglobulin
23
Q

What is the prognosis for CIDP?

A

Best in young adults who respons to treament –> can fully recover

24
Q

May need to watch the video to see if it decribes CIDP actions

25
What is the cause of Charcot-Marie-Tooth disease?
Hereditary Defects in genes encoding for myelin, Schwann cells & axons
26
What is the incidence of Charcot-Marie-Tooth disease?
- Most common inherited neuromuscular disorder - 40 in 100,000
27
What is the diagnosis for Charcot-Marie-Tooth disease?
- Occur in first or second decade - Slower progression of sensory & motor symptoms - Symptoms usually begin in feet & legs, but they may eventually affect the hands & arms
28
What are the treatments for Charcot-Marie-Tooth disease?
- Physio - Surgery
29
What is the prognosis for Charcot-Marie-Tooth disease?
Not life threatening but living w a long term progressive condition can have significant emotional impact
30
Which peripheral myelin disease has these traits: Autoimmune Acute Motor
Guillain Barre Syndrome
31
Which peripheral myelin disease has these traits: Hereditary Chronic Motor and sensory
Charcot-Marie-Tooth disease
32
Which peripheral myelin disease has these traits: Immune Chronic Motor and sensory
CIDP
33
What are the 3 types of central myelin disorders?
- Genetic abnormalities - Inflammatory diseases - Preventricular leukomalacia
34
Central myelin disorders: What are genetic abnormalities?
- General lesions - Leukodystrophies (DYSMYELINATION)
35
Central myelin disorders: What are inflammatory diseases?
- Focal lesions - Mutiple sclerosis (DEMYLENATION)
36
Central myelin disorders: What are preventricular leukomalacia?
- Cerebral palsy (HYPOMYELINATION)
37
What is Multiple Sclerosis (MS)?
Neurological disease that results in progressive pathology (peripheral symptoms) exclusively associated w central myelin
38
What is the cause of MS?
- Immune mediated - Inflammatory mediated demyelination
39
How is MS diagnosed?
- MRI used to detect multiple lesions - Lumbar puncture to axamine CSF for signal of inflammatory cells & antibodies - Neurological exams & evoked potentials for functional assessment
40
What are the 4 classificationf for MS?
- Relapsing remitting (RRMS) - Secondary progressive (SPMS) - Primary progressive (PPMS) - Progressive relamsing (PRMS)
41
Which form of MS is the most common?
Relapsing remitting ~85% of ppl with MS are diagnosed w RRMS
42
What is remitting relapsing MS like? (e.g. how does it affect the individual) RRMS
- Experience clearly defined attacks of worsening neurological function - Temporary periods when new symptoms appear (RELAPSE) - Followed by periods of partial or complete recovery (REMISSION) (Graph looks like a series of peaks and plateaus - gradually increass over time)
43
What is secondary progressive MS like? (e.g. how does it affect the individual) SPMS
- Tends to follow initial period of RRMS - Slow worsening of symptoms - Without periods of relapses or remissions (Graph looks like RRMS but then will continually escalate without plateaus)
44
What does primary progressive MS like? (e.g. how does it affect the individual) PPMS
- Very uncommon; ~10% of ppl with MS are diagnosed with PPMS - Slow worsening of symptoms from the beginning - W/o periods of relapses or remissions (Graph is a stright continuous line)
45
Can remylenation occur in MS patients?
Yes in the central axons it has been seen in MS patients However --> new myelin sheaths are thinner & shorter in length Does allow the axon to adequately regain conduction properties Unclear whether remylenation is associates w clinal outcome
46
What age does MS onset generally happen?
20-40
47
Which gender is more likely to suffer from MS?
Twice as common in females
48
Which part of the world has a higher incidence for MS?
- Further away from the equator (North and South) = higher the incidence - More in the Northern hemisphere bc of the greater landmass - Moving before, not after, puberty affects your risk of MS
49
What are the 3 main treatments for MS?
- ABC - Vitamin D - Stem cells
50
How is ABC used to treat MS?
- Avonex - B interferon - Copaxone - Treat immune effects
51
How is vitamin D used to treat MS?
- Effect of latitude could the the effect of sunlight - Modulates the immune system
52
How are stem cells used to treat MS?
- Ablate immune system w chemotherapy - Harvest own patients stem cells from bone marrow & inject into the patient - Stem cells differentiate into immune cells to rebuit immune system
53
MS summary:
Cause: Immune & inflammatory mediated demylination of central axons Types: - RRMS - SPMS - PPMS - PRMS Incidence: - 20-40 years old - 2x as common in females Diagnosis: - Peripheral neurological symptoms - MRI to detect central white matter lesions Treatment: - ABC - Vitamin D - Stem cell therapy Prognosis: - Most cases isn't fatal - Progressively debilitating

Fundamentals of neuroscience (38 decks)

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