Myasthenia Gravis

Question 1

what is MG

Answer 1

an autoimmune disease that attacks ACh receptors at the neuromuscular junction
- characterized by fluctuating weakness of certain muscle groups
- can be short term remission, stabilization, severe/progressive

Question 2

who is at risk for MG

Answer 2

10-65
women

Question 3

what is the pathogenesis of MG

Answer 3

• antibodies attack ACh receptors which dec nerve impulses bc dec ACh at junction
• ACh unable to bind and stimulate muscle contraction
• receptors eventually go away bc they arent even being used

Question 4

what are the clinical manifestations of MG

Answer 4

• fluctuating skeletal muscle
• strength comes back after resting
• eyes, face, speaking, and breathing are affected
• malnutrition, aspiration

Question 5

what is myasthenic crisis

Answer 5

an acute exacerbation of muscle weakness
- triggered by infection, surgery, emotional distress, inadequate pharm
- major complication: breathing muscle weakness –> resp insufficiency and arrest

Question 6

what is the pharm of MG

Answer 6

immunosuppressants (steroids)
cholinesterase inhibitors (prevent inactivation of ACh by cholinesterase which intensifies the effects of ACh released from motor neurons which inc muscle strength
- provide sx relief

Question 7

what is the class of neostigmine

Answer 7

cholinesterase inhibitor

Question 8

what is the moa of neostigmine

Answer 8

enhances cholinergic activity by
- facilitating transmission of impulses across neuromuscular junctions
- affects both muscarinic and nicotinic receptor

Question 9

where are muscarinic receptors found

Answer 9

glands
sweat

Question 10

where are nicotinic receptors found

Answer 10

adrenal
skeletal muscles
blood vessels

Question 11

how do cholinergics affect the body

Answer 11

inc motility and D
inc secretions
urinary urgency
bradycardia
bronchial constriction
miosis (constriction)

Question 12

how do anticholinergics affect the body

Answer 12

dec motility and constipation
dry mouth
urinary retention
tachycardia
brochodilation
mydriasis

Question 13

what are the adverse effects of neostigmine

Answer 13

muscarinic
- inc secretions, GI motility
- urinary urgency
- bradycardia
- bronchial constriction
- miosis, near sightedness
nicotinic (neuromuscular)
- inc muscular contraction with therapeutic doses
- toxic doses will reduce contraction –> could lead to cholinergic crisis

Question 14

what is cholinergic crisis

Answer 14

too much ACh or mystigmine which overstimulates muscles and they can become worn out leading to resp failure
- extreme muscle weakness or paralysis –> excessive muscarinic stimulation

Question 15

what is the treatment for cholinergic crisis

Answer 15

mechanical ventilation
atropine is the antidote

Question 16

what should MG wear?

Answer 16

a medical alert bracelet

Question 17

what is a MG crisis

Answer 17

not enough stimulation or ACh
- muscles arent stimulated and weak which leads to resp failure

Question 18

how do you tell the difference between MG and cholinergic crisis

Answer 18

when a pt shows up with resp failure give edrophonium
- its a short acting AChase inhibitor which inc ACh temporarily
- MG crisis: will improve bc there is an inc in ACh, the drug will dec the breakdown of ACh
- cholinergic crisis: they will worsen bc already have too much ACh so sx will worsen