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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

A

Cool

25
Q

What is the cause of Charcot-Marie-Tooth disease?

A

Hereditary

Defects in genes encoding for myelin, Schwann cells & axons

26
Q

What is the incidence of Charcot-Marie-Tooth disease?

A
  • Most common inherited neuromuscular disorder
  • 40 in 100,000
27
Q

What is the diagnosis for Charcot-Marie-Tooth disease?

A
  • 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
Q

What are the treatments for Charcot-Marie-Tooth disease?

A
  • Physio
  • Surgery
29
Q

What is the prognosis for Charcot-Marie-Tooth disease?

A

Not life threatening but living w a long term progressive condition can have significant emotional impact

30
Q

Which peripheral myelin disease has these traits:

Autoimmune
Acute
Motor

A

Guillain Barre Syndrome

31
Q

Which peripheral myelin disease has these traits:

Hereditary
Chronic
Motor and sensory

A

Charcot-Marie-Tooth disease

32
Q

Which peripheral myelin disease has these traits:

Immune
Chronic
Motor and sensory

A

CIDP

33
Q

What are the 3 types of central myelin disorders?

A
  • Genetic abnormalities
  • Inflammatory diseases
  • Preventricular leukomalacia
34
Q

Central myelin disorders:

What are genetic abnormalities?

A
  • General lesions
  • Leukodystrophies (DYSMYELINATION)
35
Q

Central myelin disorders:

What are inflammatory diseases?

A
  • Focal lesions
  • Mutiple sclerosis (DEMYLENATION)
36
Q

Central myelin disorders:

What are preventricular leukomalacia?

A
  • Cerebral palsy (HYPOMYELINATION)
37
Q

What is Multiple Sclerosis (MS)?

A

Neurological disease that results in progressive pathology (peripheral symptoms) exclusively associated w central myelin

38
Q

What is the cause of MS?

A
  • Immune mediated
  • Inflammatory mediated demyelination
39
Q

How is MS diagnosed?

A
  • 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
Q

What are the 4 classificationf for MS?

A
  • Relapsing remitting (RRMS)
  • Secondary progressive (SPMS)
  • Primary progressive (PPMS)
  • Progressive relamsing (PRMS)
41
Q

Which form of MS is the most common?

A

Relapsing remitting ~85% of ppl with MS are diagnosed w RRMS

42
Q

What is remitting relapsing MS like? (e.g. how does it affect the individual)

RRMS

A
  • 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
Q

What is secondary progressive MS like? (e.g. how does it affect the individual)

SPMS

A
  • 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
Q

What does primary progressive MS like? (e.g. how does it affect the individual)

PPMS

A
  • 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
Q

Can remylenation occur in MS patients?

A

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
Q

What age does MS onset generally happen?

A

20-40

47
Q

Which gender is more likely to suffer from MS?

A

Twice as common in females

48
Q

Which part of the world has a higher incidence for MS?

A
  • 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
Q

What are the 3 main treatments for MS?

A
  • ABC
  • Vitamin D
  • Stem cells
50
Q

How is ABC used to treat MS?

A
  • Avonex
  • B interferon
  • Copaxone
  • Treat immune effects
51
Q

How is vitamin D used to treat MS?

A
  • Effect of latitude could the the effect of sunlight
  • Modulates the immune system
52
Q

How are stem cells used to treat MS?

A
  • 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
Q

MS summary:

A

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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