Myasthenia Gravis and Related Disorders

Question 1

T/F

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

Answer 1

true

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

Question 2

Cogan’s signs

Answer 2

lid-twitch

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

Question 3

T/F

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

Answer 3

true

Question 4

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

Answer 4

80%

Question 5

In MG, which muscles of the trunk are mostly affected

Answer 5

erector spinae

Question 6

T/F

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

Answer 6

True

Question 7

T/F

In MG, smooth and cardiac muscles are involved

Answer 7

False

Question 8

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

Answer 8

those with MuSK

muscle-specific tyrosine kinase

Question 9

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

Answer 9

10%

Question 10

MG

peak age of first symptoms in women? men?

Answer 10

women 20-30

men 50-60

Question 11

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

Answer 11

Class IVb

Question 12

Periods of danger in MG (2)

Answer 12

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

Question 13

T/F

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

Answer 13

True

Question 14

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.

Answer 14

True

Question 15

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

Answer 15

60%

16%

Question 16

T/F

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

Answer 16

True

Question 17

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

Answer 17

1 yr 67%

3 yrs 83%

Question 18

How many % of MG patients have

nonneoplastic lymphofollicular hyperpalasia of the thymic medulla?
thymic tumors?

Answer 18

65%

10-15%

Question 19

Cells found in the centers of follicles in hyperplasia of thymus

Answer 19

helper T lymphocytes
B lymphocytes
plasma cells

Question 20

2 forms of thymic tumors

Answer 20

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

Question 21

T/F

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

Answer 21

True

Question 22

In MG, the main ultrastructural alterations occur in the

Answer 22

motor endplate

Question 23

describe changes in the motor endplate of MG

Answer 23

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

Question 24

True or False

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

Answer 24

True

Question 25

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

Answer 25

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

Question 26

How many percent of Patients with MG have AChR antibodies generalized ocular

Answer 26

generalized - 85% | ocular - 60%

Question 27

Neuromuscular transmission is impaired in MG in 3 ways

Answer 27

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

Question 28

RNS in MG

Answer 28

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

Question 29

Muscarinic effects of Neostigmine

Answer 29

``` salivation sweating bronchorhea borborygmi bowel cramps diarrhea ```

Question 30

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

Answer 30

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

Question 31

dosing of pyridostigmine and neostigmine

Answer 31

30-90 mg given every 6 hrs; rarely exceeds 120mg every 3h neostigmine 7.5-45mg given every 2-6 hrs

Question 32

remission rate after thymectomy in MG

Answer 32

35% if done in the first 2 years of disease onset | to 50% will improve to some extent

Question 33

Plasma exchange

Answer 33

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

Question 34

IV Ig

Answer 34

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

Question 35

how many weeks before deciding to do a tracheostomy

Answer 35

2-3 weeks

Question 36

Physiologic mechanism in Lambert-Eaton myasthenic syndrome

Answer 36

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

Question 37

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

Answer 37

Neonatal Myasthenia Gravis

Question 38

defects in congenital myasthenic syndromes

Answer 38

presynaptic synaptic postsynaptic (3/4 of cases)

Question 39

drugs which can cause myasthenic weakness

Answer 39

neomycin, kanamycin, colistin, streptomycin, polymyxin B, some tetracyclines ciprofloxacin affects pre and postsynaptic activity

Question 40

MOA of botolinum toxin

Answer 40

binds to cholinergic motor endings, blocking quantal release of ACh

Question 41

MOA black widow spider venom

Answer 41

massive release of ACh resulting in muscular contraction and paralysis

Question 42

MOA d-tubocurarine

Answer 42

binds to AChR

Question 43

MOA suxamethonium and decamethonium

Answer 43

bind to AChR

Question 44

MOA organophosphates

Answer 44

binds irreversibly to AChE

Question 45

MOA malathion and parathion

Answer 45

inhibit AChE

Question 46

Presynaptic Congenital Myasthenic Syndrome

Answer 46

Episodic apnea Paucity of synaptic vesicles reduced quantal release of acetylcholine

Question 47

Synaptic Congenital Myasthenic Syndrome

Answer 47

AChE Deficiency | DOK-7 synopathy

Question 48

Postsynaptic Congenital Myasthenic Syndrome

Answer 48

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