Myasthenia Gravis Flashcards
Myasthenia Gravis
describe
autoimmune disorder of post synaptic membrane at neuromuscular junction
Myasthenia Gravis
characteristics
commonality,epi, key sx (4 total)
- rare
- presents at any age
- males & females equally
- fatigable muscle weakness (ptosis, EOM fatigue, neck)
Myasthenia Gravis
pathophys
body develops an auto antibody to ACh receptors
Myasthenia Gravis
typical first symptoms
3
- partial paralysis of eye movements
- double vision
- droopy eyelids
Myasthenia Gravis
of those who present with ocular sx, what % will develop generalized disease within 2 yrs?
50%
Myasthenia Gravis
Other sx
5
- weakness/fatigue in neck
- Bulbar weakness
- dysarthria
- dysphagia
- difficulty holding up head
Myasthenia Gravis
which CN are bulbar?
CN IX, X, XI, XII
Myasthenia Gravis
describe generalized myasthenia
- weakness spreads from face/neck to upper limbs, hands, then lower limbs
Myasthenia Gravis
describe the purpose for the ice pack test
- part of neuro exam if ptosis is found
- based on principle that neuromuscular transmission improves at lower muscle temperatures
Myasthenia Gravis
how do you perform the ice pack test?
- assess ptosis
- fill surgical glove w/ ice
- place of closed lid for 2 min
- remove ice- if ptosis improved, test is positve
Myasthenia Gravis
describe the Edrophonium test
- 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
Myasthenia Gravis
work up
- serum anti-AChR antibodies
- anti-muscle-specific tyrosine kinase antibodies
- EMG testing
- CT/MRI
Myasthenia Gravis
what % will be neg for both antibodies?
~10%
Myasthenia Gravis
describe EMG testing
repetitive nerve stimulation which shows decremental change in amplitude of muscle response
Myasthenia Gravis
what would CT/MRI show?
thymus gland abnormality
Myasthenia Gravis
tx options
- sx: acetylcholinesterase inhibitor
- chronic immunosuppressive therapies
- rapid, short-acting immunomodulating tx (IV IG)
Myasthenia Gravis
why do you give acetylcholinesterase inhibitors
to increase amount of ACh available at NMJ
Myasthenia Gravis
which chronic immunosuppressive therapy do you give? why?
- glucocorticoids
- to target underlying immune dysregulation
Myasthenia Gravis
what surgical tx can be done?
thymectomy
Myasthenia Gravis
management of mild disease
- some people don’t need tx
- pyridostigmine (cholinesterase inhibitor)
- add corticosteroids if unresponsive to CI
Myasthenia Gravis
management of MG crisis
describe + meds
- pt presenting w/ severe weakness, respiratory failure
- intubation & mechanical ventilation
- plasma exchange + IV IG
Myasthenia Gravis
management for moderate disease
- pyridostigmine
- immunosuppressant (steroid, cyclosporine, tacrolimus)
Myasthenia Gravis
Thymectomy management
- perform on pts w/ thymoma (any age)
- pts with generalized MG and AChR antibodies who are < 60 y/o
Myasthenia Gravis
who may not benefit from thymectomy?
pts who are MuSK pos
