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M&M Test 2 > B6-058 CBCL Trouble at the Junction > Flashcards

B6-058 CBCL Trouble at the Junction Flashcards

1
Q

list the anatomic possibilities for a lesion causing weakness from proximal to distal

A

motor cortex
internal capsule
brainstem
corticospinal tract (in spinal cord)
anterior horn cell
nerve roots
spinal nerves
plexus
peripheral nerves
neuromuscular junction
skeletal muscle

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2
Q

protein that plays a role in the coordination of clustering acetylcholine receptors on the postsynaptic side

A

MuSK

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3
Q

what is the key function of MuSK?

A

clustering acetycholine receptors on the motor end plate

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4
Q

what is the sensitivity of repetitive nerve stimulation for generalized MG?

A

75-80%

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5
Q

what is the sensitivity of repetitive nerve stimulation for occular MG?

A

15-45%

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6
Q

what percentage of patients with generalized MG have AChR Ab?

A

80-90%

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7
Q

what percentage of patients with generalized MG have anti-MuSK antibodies?

A

4-5%

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8
Q

rapid acting therapies used to control MG during a myasthenic crisis [2]

A

IVIG
plasma exchange

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9
Q

first line treatment for MG patients that do not adequately respond to pyridostigmine

A

prednisone

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10
Q

cholinesterase inhibitor used for symptomatic management of MG

A

pyridostigmine

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11
Q

drug that is particularly effective in MuSK MG patients who did not respond to pyridostigmine and prednisone

A

rituximab

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12
Q

MG patients that receive […] have less severe disease symptoms and require less prednisone

A

thymectomy

**regardless of whether thymoma is present

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13
Q

in LEMS, loss of voltage gated calcium channels results in…

A

decreased release of acetylcholine containing vesicles

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14
Q

nerve conduction shows low amplitude motor potentials and >100% increase in amplitude after 10s of exercise

A

LEMS

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15
Q

rapid repetitive nerve stimulation at 10-50 Hz frequently shows increment of >100%

A

LEMS

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16
Q

sensory nerve conduction should be […] in LEMS patients

A

unaffected

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17
Q

85-95% of LEMS patients have autoantibodies to

A

voltage gated calcium channels

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18
Q

associated with autonomic features

A

LEMS

**dry mouth, ED, sluggish pupillary response

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19
Q

dry mouth
erectile dysfunction
sluggish pupillary response

A

LEMS

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20
Q

associated with small cell lung cancer

A

LEMS

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21
Q

associated with thymoma

A

MG

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22
Q

postsynaptic NMJ disorder

A

MG

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23
Q

presynaptic NMJ disorder

A

LEMS

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24
Q

associated with ocular and bulbar symptoms

A

MG

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25
Q

associated with proximal weakness in lower extremities

A

LEMS

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26
Q

describe the first steps of management of LEMS patients [3]

A
  1. screen for/treat SCLC
  2. amifampridine
  3. immunomodulatory therapy
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27
Q

cause hydrolytic cleavage of SNARE proteins essential for presynaptic calcium mediated vesicle exocytosis

A

botulinum toxin

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28
Q

binding and accelerated internalization of the postsynaptic acetylcholine receptor

A

MG

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29
Q

binding and accelerated internalization of the presynaptic voltage-gated calcium channel

A

LEMS

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30
Q

what part of the nervous system is not affected by botulinum toxin

A

CNS

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31
Q

would you expect to see seizures in a patient with botulism?

A

no, spares the CNS

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32
Q

presynaptic toxin mediated disease

A

botulism

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33
Q

presynaptic immune mediated disease

A

LEMS

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34
Q

postsynaptic immune mediated disease

A

MG

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35
Q

hereditary disorders of neuromuscular transmission that can affect presynaptic, synaptic, or post synaptic NMJ

A

congenital mysathenic syndrome

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36
Q

proximal to distal anatomic sequence of the motor unit

A

anterior horn cell
motor axon
motor axon twig branches
NMJ
muscle fibers

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37
Q

have a specialized synapse with muscle fibers

A

lower motor neurons

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38
Q

relay excitatory electrical signals down through the motor axon

A

lower motor neurons

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39
Q

decussate in the brainstem at the level of the medulla

A

upper motor neurons

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40
Q

originate in the frontal lobe cortex

A

upper motor neurons

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41
Q

upper motor neurons synapse with lower motor neurons at the

A

anterior horn of the spinal cord

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42
Q

cardinal manifestations of lower motor neuron weakness

A

muscle atrophy
hypotonia
diminished/absent reflexes

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43
Q

cardinal manifestations of upper motor neuron weakness

A

preserved muscle bulk
spastic muscle tone
hyperreflexive

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44
Q

positive Babinski reflex in adults indicates damage to

A

upper motor neuron

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45
Q

sequence of event during neuromuscular transmission:

A
  1. motor axon depolarization
  2. voltage gated calcium channel activation
  3. influx of calcium on motor axon
  4. vesicle fusion with presynaptic membrane
  5. ACh release into the NMJ
  6. activation of the ligand gated AChR on the muscle membrane
  7. sodium ion influx into the muscle sarcolemma
  8. calcium release from endoplasmic reticulum
  9. activation of actin-myosin contraction
46
Q

bind and block ACh receptors on postsynaptic membrane

A

ACh-R Ab

47
Q

reduced end plate potentials below the minimum necessary to activate muscle contraction

A

MG

48
Q

interfere with NMJ development and maintenance leading to endplate degradation and blocking of NMJ

A

MuSK Ab

49
Q

protein that directs aggregation of AChR on the muscle during development

A

agrin

50
Q

for [….] studies, a peripheral nerve is stimulated with an electrical pulse and the evoked potential is recorded over a distal muscle innervated by the stimulated one

A

motor nerve conduction studies

51
Q

for [….] studies, a peripheral nerve is stimulated with an electrical pulse and the evoked potential is recorded over a proximal or distal sensory fibers innervated by the stimulated one

A

sensory nerve conduction studies

52
Q

key bioelectric potential characteristics analyzed during nerve conduction studies [3]

A

distal latency
amplitude
conduction velocity

53
Q

[…] greatly influences the accuracy of nerve conduction studies

A

technical factors

**produces false positive/negative

54
Q

what percentage of patients with ocular MG have AChR Ab?

A

40-50%

55
Q

what degree of decrement is expected on RNS studies in patients with MG?

A

> 10%

**must be reproducible

56
Q

thymectomy is an evidence based treatment strategy for patients with what type of MG?

A

AChR Ab MG

57
Q

when should thymectomy be performed in an eligible patient?

A

after disease is in control

**if not controlled, there is increased risk of myasthenic crises

58
Q

autoantibodies found to be pathogenic in MG patients [3]

A

AChR Ab
MuSK
LRP4 Ab

59
Q

CMAP decrement >10% is associated with

A

MG

60
Q

CMAP increment is associated with

A

LEMS

61
Q

organized protein secreted from the motor nerve terminal

A

agrin

62
Q

agrin binds to […] which forms a receptor complex with […]

A

LRP4
MuSK

63
Q

agrin signal is transmitted through […], Dok-7, and rapsyn to promote the accumulation, organization, and clustering of AChR

A

MuSK

64
Q

all patients diagnosed with MG should have chest imaging to evaluate for

A

thymoma

65
Q

MOA of pyridostigmine

A

inhibition of the hydrolysis of ACh within the synapse

**enhances availability for binding

66
Q

the AChR has a central pore that can open and allow […] entry to the sarcolemma

A

sodium

67
Q

the AChR has […] binding sites

A

2

68
Q

opening of the AChR creates the endplate potential to initiate

A

muscle fiber action potential

69
Q

hyperreflexia
spasticity
plantar extensor sign

A

upper motor neuron dysfunction

70
Q

fatiguable weakness with sustained upward gaze is associated with

A

MG

71
Q

slurred speech
swallowing difficulty
are associated with

A

MG

72
Q

what is the correct path of electrical and chemical activation along a motor unit?

A

anterior horn cell
motor axon
axon twigs
NMJ
muscle fibers

73
Q

assesses for evidence of impairment of neuromuscular transmission from motor nerve endings to skeletal muscle tissue

A

RNS (repetitive nerve stimulation)

74
Q

commonly used prednisone sparing agent

A

azathioprine

75
Q

first line immunosuppressant used for MG

A

prednisone

76
Q

drug frequently used for symptom management of MG

A

pyridostigmine

77
Q

side effects of azathioprine [2]

A

hepatotoxicity
bone marrow suppression

78
Q

side effects of prednisone

A

weight gain
fluid retention
hyperglycemia
osteoporosis

79
Q

most common side effect of rituximab

A

injection site reaction

80
Q

proximal weakness
autonomic dysfunction
diminished relexes

A

LEMS

81
Q

most common malignancy associated with LEMS

A

SCLC

82
Q

low motor amplitude but normal sensory amplitude would suggest..

A

LEMS

83
Q

EMG shows active denervation

A

ALS

84
Q

associated with voltage gated calcium channel antibodies

A

LEMS

85
Q

post exercise increased of CMAP amplitudes

A

LEMS

86
Q

fasciculations are associated with

A

ALS

87
Q

slows acetylcholine breakdown in the synaptic cleft and reduces myasthenic symptoms

A

pyridostigmine

88
Q

reversible cholinesterase inhibitor

A

pyridostigmine

89
Q

what is the MOA of the botulinum toxin?

A

hydrolytic cleavage of different SNARE proteins

90
Q

gram positive, rod shaped anaerobe

A

C. botulinum

91
Q

C. botulinum has the ability to differentiate into […] in stressful environmental conditions

A

inert endospores

92
Q

why can home canning put you at risk of foodborne botulism?

A

C. botulinum spores are heat resistant

93
Q

C. botulinum spores can be destroyed at […] C for 5 min

A

120 degrees C

94
Q

most common NMJ disorder

A

MG

95
Q

autoantibodies to postsynaptic ACh receptor

A

MG

96
Q

in MG, bulbar muscle weakness causes [2]

A

dysphagia
difficulty chewing

97
Q

in MG, respiratory muscle weakness causes [1]

A

dyspnea

98
Q

in MG, fatiguable weakness causes [3]

A

ptosis
diplopia
proximal weakness

99
Q

in MG, the reflexes are

A

spared

100
Q

in LEMS, the reflexes are

A

hyporeflexive

101
Q

[MG or LEMS] worsens with muscle use

A

MG

102
Q

[MG or LEMS] better with muscle use

A

LEMS

103
Q

associated with thymoma/thymic hyperplasia

A

MG

104
Q

associated with SCLC

A

LEMS

105
Q

potassium channel blocker that blocks K+ from exiting the motor axon, prolonging depolarization

A

amifampridine

106
Q

amifamprine is used for symptom management of

A

LEMS

107
Q

flaccid limb weakness
fasiculations
atrophy
hyperreflexia

A

ALS

108
Q

terminal complement inhibitors [2]

A

eculizumab
raulizumab

109
Q

selective B cell depleting agent that suppresses humoral immunity

A

rituximab

110
Q

neonatal Fc receptor inhibitor used in MG treatment

A

Efgartgimod

111
Q

subacute proximal limb weakness is associated with

A

LEMS

112
Q
A

M&M Test 2 (18 decks)

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