Myasthenia Gravis

Question 1

Myasthenia Gravis

describe

Answer 1

autoimmune disorder of post synaptic membrane at neuromuscular junction

Question 2

Myasthenia Gravis

characteristics

commonality,epi, key sx (4 total)

Answer 2

• rare
• presents at any age
• males & females equally
• fatigable muscle weakness (ptosis, EOM fatigue, neck)

Question 3

Myasthenia Gravis

pathophys

Answer 3

body develops an auto antibody to ACh receptors

Question 4

Myasthenia Gravis

typical first symptoms

3

Answer 4

• partial paralysis of eye movements
• double vision
• droopy eyelids

Question 5

Myasthenia Gravis

of those who present with ocular sx, what % will develop generalized disease within 2 yrs?

Answer 5

50%

Question 6

Myasthenia Gravis

Other sx

5

Answer 6

• weakness/fatigue in neck
• Bulbar weakness
• dysarthria
• dysphagia
• difficulty holding up head

Question 7

Myasthenia Gravis

which CN are bulbar?

Answer 7

CN IX, X, XI, XII

Question 8

Myasthenia Gravis

describe generalized myasthenia

Answer 8

• weakness spreads from face/neck to upper limbs, hands, then lower limbs

Question 9

Myasthenia Gravis

describe the purpose for the ice pack test

Answer 9

• part of neuro exam if ptosis is found
• based on principle that neuromuscular transmission improves at lower muscle temperatures

Question 10

Myasthenia Gravis

how do you perform the ice pack test?

Answer 10

• assess ptosis
• fill surgical glove w/ ice
• place of closed lid for 2 min
• remove ice- if ptosis improved, test is positve

Question 11

Myasthenia Gravis

describe the Edrophonium test

Answer 11

• drug (acetylcholinesterase inhibitor) w/ rapid onset (30-45s) and short duration of action (5 to 10 min)
• prolongest presence of acetylcholine in NMJ and results in immediate increase in muscle strength

Question 12

Myasthenia Gravis

work up

Answer 12

• serum anti-AChR antibodies
• anti-muscle-specific tyrosine kinase antibodies
• EMG testing
• CT/MRI

Question 13

Myasthenia Gravis

what % will be neg for both antibodies?

Answer 13

~10%

Question 14

Myasthenia Gravis

describe EMG testing

Answer 14

repetitive nerve stimulation which shows decremental change in amplitude of muscle response

Question 15

Myasthenia Gravis

what would CT/MRI show?

Answer 15

thymus gland abnormality

Question 16

Myasthenia Gravis

tx options

Answer 16

• sx: acetylcholinesterase inhibitor
• chronic immunosuppressive therapies
• rapid, short-acting immunomodulating tx (IV IG)

Question 17

Myasthenia Gravis

why do you give acetylcholinesterase inhibitors

Answer 17

to increase amount of ACh available at NMJ

Question 18

Myasthenia Gravis

which chronic immunosuppressive therapy do you give? why?

Answer 18

• glucocorticoids
• to target underlying immune dysregulation

Question 19

Myasthenia Gravis

what surgical tx can be done?

Answer 19

thymectomy

Question 20

Myasthenia Gravis

management of mild disease

Answer 20

• some people don’t need tx
• pyridostigmine (cholinesterase inhibitor)
• add corticosteroids if unresponsive to CI

Question 21

Myasthenia Gravis

management of MG crisis

describe + meds

Answer 21

• pt presenting w/ severe weakness, respiratory failure
• intubation & mechanical ventilation
• plasma exchange + IV IG

Question 22

Myasthenia Gravis

management for moderate disease

Answer 22

• pyridostigmine
• immunosuppressant (steroid, cyclosporine, tacrolimus)

Question 23

Myasthenia Gravis

Thymectomy management

Answer 23

• perform on pts w/ thymoma (any age)
• pts with generalized MG and AChR antibodies who are < 60 y/o

Question 24

Myasthenia Gravis

who may not benefit from thymectomy?

Answer 24

pts who are MuSK pos