Week 10 - Myasthenia Gravis

Question 1

what is myasthenia gravis

Answer 1

• an autoimmune disease affecting the neuromuscular junction
• causes normal communication between the nerve & muscle to be interupted at the place where the nerves connect to the muscle (neuromuscular junction)

Question 2

how does the typical neuromusclar junction work

Answer 2

• signal travels down the motor nerve
• the nt Ach is released & binds to ach receptors on the muscle
• the binding then activated the muscle & causes a muscle contraction

Question 3

describe the neuromuscular junction in myasthenia gravis

Answer 3

• antibodies block or destroy the ach receptors at the neuromuscular junction = no muscle contraction

Question 4

what is the hallmark of myasthenia gravis

Answer 4

• muscle weakness that worsens after periods of activity
• but improves after periods of rest
• often wake up feeling fine in the morning, but worsens as the day progresses

Question 5

list symptoms of myasthenia gravis (6)

Answer 5

• muscle weakness
• ptosis
• diplopia
• dysphagia
• dysarthria
• difficulty breathiing

Question 6

what is ptosis

Answer 6

• drooping of the eye lid

Question 7

describe diagnosis of myasthenia gravis

Answer 7

• history & physical exam
• serum testing for ach receptor antibodies
• EMG

Question 8

what is an EMG

Answer 8

• electromyography

Question 9

describe the use of an EMG for myasthenia gravis diagnosis

Answer 9

• repetitive electrical stimulation is delivered to a motot nerve repeatedly, several times/second
• the EMG can detect impaired muscle to impaired nerve-muscle transmission

Question 10

what can trigger myasthenia gravis

Answer 10

• autoimmune disorders so

- stress, fatigue, infection

Question 11

what class of meds is used for myasthenia gravis

Answer 11

• cholinesterase inhibitor

Question 12

what type of cholinesterase inhibitor is used for myasthenia gravis

Answer 12

• neostigmine

Question 13

what is the MOA of neostigmine

Answer 13

• binds to cholinesterase & prevents breakdown of ach by the enzyme cholinesterase
  = increased amt of ach available

Question 14

what are adverse effects of neostigmine (5)

Answer 14

• excessive salivation
• increased gastric secretion
• increased GI motility
• bradycardia
• urinary urgency

Question 15

what causes the adverse effects of neostigmine

Answer 15

• accumulation of ach which is responsible for PSNS

Question 16

what can toxic doses of neostigmine cause

Answer 16

• resp depression thru paralysis of respiratory muscle

Question 17

what is an emergency associated w myasthenia gravis

Answer 17

• myasthenic crisis

Question 18

what is myasthenic crisis

Answer 18

• acute exacerbation of muscle weakness

Question 19

what can trigger myasthenic crisis (4)

Answer 19

• infection
• surgery
• stress
• fatigue/insomnia

Question 20

when does myasthenic crisis occur

Answer 20

• within the first 2 years of diagnosis

Question 21

what is the concern w myasthenic crisis

Answer 21

• the resp muscle weaken
• which can cause dyspnea, increased WOB
• and may require a ventilator & can be fatal