Board Questions



1. You have a 9 month old patient who comes in with new onset weakness. He has a poor suck, a weak cry, and enlarged, sluggishly reactive pupils? Where in the diagram above is the likely etiology of his disease process? 

a) 1
b) 3
c) 5
d) 7

2. Your patient comes in for followup of a known neuromuscular disorder. She is treated with daily pyridostigmine, which improves her symptoms of generalized weakness, ptosis, and fatigability. Where in the diagram above is the likely etiology of her disease process? 

a) 2
b) 3
c) 5
d) 6

3. Which of the following agents is NOT known to exacerbate neuromuscular weakness? 

a) methylprednisone
b) rocuronium
c) aminogylcosides
d) cephalosporins


ANSWERS & EXPLANATIONS

1. D- this infant has classic signs of infant botulism, caused by ingestion of botulinum spores which subsequently germinate and produce toxin. Botulinum toxin works by inhibiting fusion of the vesicle containing Ach with the presynaptic membrane, thus preventing release of acetylcholine to propagate muscular contraction. Hence, "7" is the correct answer. 

2. C- this patient has myasthenia gravis, caused by antibodies which attack the Ach receptor at the postsynaptic membrane. Myasthenia gravis is treated using Acetylcholinesterase inhibitors such as pyridostigmine. Hence, "5" is the correct answer. 

3. D- all the other agents are known to exacerbate neuromuscular weakness and should be used with caution in patients with neuromuscular weakness. Cephalosporins, in contrast to aminoglycosides, are not thought to exacerbate neurmouscular weakness.

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