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ADAMS > Myasthenia Gravis and Related Disorders > Flashcards

Myasthenia Gravis and Related Disorders Flashcards

1
Q

T/F

Diplopia is common in MG but it does not correspond to the innervatory pattern of nerve

A

true

it is the result of asymmetrical weakness of several muscles in both eyes

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2
Q

Cogan’s signs

A

lid-twitch

twitching of the upper eyelid that appears a moment after the patient moves the eyes from a downward to the primary position

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3
Q

T/F

Bright sunlight aggravates the ocular signs and cold has been said to improve them

A

true

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4
Q

In MG, muscles of facial expressions, mastication, swallowing, speech, are affected in ____ of patients

A

80%

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5
Q

In MG, which muscles of the trunk are mostly affected

A

erector spinae

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6
Q

T/F

In advanced cases of MG, the sphincters of the bladder and bowel may be affected

A

True

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7
Q

T/F

In MG, smooth and cardiac muscles are involved

A

False

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8
Q

In MG, the tongue may atrophy as seen in which type of MG patients

A

those with MuSK

muscle-specific tyrosine kinase

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9
Q

How many percent of MG are seen in children younger than 10

A

10%

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10
Q

MG

peak age of first symptoms in women? men?

A

women 20-30

men 50-60

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11
Q

Clinical Grading of MG wherein use of feeding tube is indicated but without intubation

A

Class IVb

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12
Q

Periods of danger in MG (2)

A
  1. danger of death from generalized MG is greatest in 1st year after onset of disease
  2. 2nd danger in progressive case is 4-7 years after onset
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13
Q

T/F

An increasing duration of purely ocular myasthenia is associated with a decreasing risk of late generalization of weakness

A

True

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14
Q

T/F

A later age at onset was also associated with a higher incidence of fatal respiratory distress. In general, a patient whose disease begins at a younger age run a more benign course.

A

True

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15
Q

Localized ocular myasthenia present for a month was associated with a ___% likelihood of generalization

ocular myasthenia restricted for 1 year was associated with _____% to generalize

A

60%

16%

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16
Q

T/F

Progression of symptoms is more rapid in male than in female patients.

A

True

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17
Q

How many percent of MG patients attained maximun severity in 1 year? 3 years?

A

1 yr 67%

3 yrs 83%

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18
Q

How many % of MG patients have

nonneoplastic lymphofollicular hyperpalasia of the thymic medulla?
thymic tumors?

A

65%

10-15%

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19
Q

Cells found in the centers of follicles in hyperplasia of thymus

A

helper T lymphocytes
B lymphocytes
plasma cells

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20
Q

2 forms of thymic tumors

A
  1. composed of histiocytic cells like the reticulum cells in the center of the follicles
  2. lymphocytic and considered lymphosarcomatous
21
Q

T/F

Myasthenia may develop after thymic tumors have been removed, even after 15-20 yrs.

A

True

22
Q

In MG, the main ultrastructural alterations occur in the

A

motor endplate

23
Q

describe changes in the motor endplate of MG

A

reduction and simplification in the surface area of the postsynaptic membrane (sparse, shallow, abnormally wide, or absent, secondary synaptic clefts)
widening of synaptic cleft

24
Q

True or False

The number and size of the presynaptic vesicles and their quanta of acetylcholine ACh are normal.

A

True

25
Q

Reason why the ocular and cranial muscles are usually the first to be affected in MG

A

these muscles are the most continuously active and have the fewest AChRs per motor unit

26
Q

How many percent of Patients with MG have AChR antibodies

generalized
ocular

A

generalized - 85%

ocular - 60%

27
Q

Neuromuscular transmission is impaired in MG in 3 ways

A
  1. the antibodies block the binding of ACh to the AChR
  2. serum IgG from myasthenic patients has been shown to induce an increase in the degradation of AChR
  3. antibodies cause a complement-mediated destruction of the postsynaptic folds
28
Q

RNS in MG

A

rapid reduction in the amplitude of CMAPs during a series of repetitive nerve stimulation of a peripheral nerve at a rate of 3 Hz

reversal of response by neostigmine or edrophonium

29
Q

Muscarinic effects of Neostigmine

A 
salivation
sweating
bronchorhea
borborygmi
bowel cramps
diarrhea
30
Q

after how many minutes of injection with neostigmine can we detect improvement

A

objective improvement occurs after 10-15 mins
reaches peak at 20 mins
lasts up to 1 hr

31
Q

dosing of pyridostigmine and neostigmine

A

30-90 mg given every 6 hrs; rarely exceeds 120mg every 3h

neostigmine 7.5-45mg given every 2-6 hrs

32
Q

remission rate after thymectomy in MG

A

35% if done in the first 2 years of disease onset

to 50% will improve to some extent

33
Q

Plasma exchange

A

several exchanges 2 to 3.5 L each (125mL/kg) performed over a week

34
Q

IV Ig

A

2g/kg in divided doses over 3 to 5 days

35
Q

how many weeks before deciding to do a tracheostomy

A

2-3 weeks

36
Q

Physiologic mechanism in Lambert-Eaton myasthenic syndrome

A

loss of voltage-gated calcium channels on the presynaptic motor nerve terminal
calcium channels become cross-linked and aggregated by functioning channels
These antibodies against a specific component of the presynaptic membrane have the effect of reducing the presynaptic release of ACh

37
Q

transitory phenomenon apparent at birth and has a mean duration of about 2-5 weeks; recovery is usually complete within 2 months of birth without later relapse

seen in 10-20 percent of babies born to mothers with myasthenia

A

Neonatal Myasthenia Gravis

38
Q

defects in congenital myasthenic syndromes

A

presynaptic
synaptic
postsynaptic (3/4 of cases)

39
Q

drugs which can cause myasthenic weakness

A

neomycin, kanamycin, colistin, streptomycin, polymyxin B, some tetracyclines

ciprofloxacin affects pre and postsynaptic activity

40
Q

MOA of botolinum toxin

A

binds to cholinergic motor endings, blocking quantal release of ACh

41
Q

MOA black widow spider venom

A

massive release of ACh resulting in muscular contraction and paralysis

42
Q

MOA d-tubocurarine

A

binds to AChR

43
Q

MOA suxamethonium and decamethonium

A

bind to AChR

44
Q

MOA organophosphates

A

binds irreversibly to AChE

45
Q

MOA malathion and parathion

A

inhibit AChE

46
Q

Presynaptic Congenital Myasthenic Syndrome

A

Episodic apnea
Paucity of synaptic vesicles
reduced quantal release of acetylcholine

47
Q

Synaptic Congenital Myasthenic Syndrome

A

AChE Deficiency

DOK-7 synopathy

48
Q

Postsynaptic Congenital Myasthenic Syndrome

A 
Slow Channel Syndrome
Fast Channel Syndrome
Primary AChR Deficiency
Rapsyn Deficiency
Plectin Deficiency
Escobar Syndrome

ADAMS (29 decks)

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