DDx - Botulism vs Myasthenia gravis

[loveoforganic2]

Strictly referring to signs and symptoms, how would these two present differently? Is the main distinction that botulism can also affect autonomics via inhibiting release of presynaptic ACh?

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[VCorp]

MGravis - gets tired as the day progresses, usually see signs of ptosis as the first s/s. Honestly, the question will give a good amount of information to distinguish between the MG and botulism. After doing so many questions, there is always extra information given in the question to help you ddx between MG and CB.

Some of the extra things I've seen include for MG:
- talks about the tensilon test
- talks about being tired and feels more tired through the day
- talks about no ach is found in the synaptic cleft

As for botulinum, I've seen questions mention:
- bulging can
- giving some description about the bacteria and how it's ingestion of "pre-formed toxin" similar to that of s. aureus

 

[loveoforganic2]

MGravis - gets tired as the day progresses, usually see signs of ptosis as the first s/s. Honestly, the question will give a good amount of information to distinguish between the MG and botulism. After doing so many questions, there is always extra information given in the question to help you ddx between MG and CB.

Some of the extra things I've seen include for MG:
- talks about the tensilon test
- talks about being tired and feels more tired through the day
- talks about no ach is found in the synaptic cleft

As for botulinum, I've seen questions mention:
- bulging can
- giving some description about the bacteria and how it's ingestion of "pre-formed toxin" similar to that of s. aureus

Thanks for the reply. I know there are a bunch of epidemiology and clues that usually come up, I was just curious about the actual presentations. Don't think you'd need to know it for making a diagnosis, but they could make the diagnosis very obvious, then say something like "which of the following is a likely additional finding on physical exam?" or some such. I think the one I bolded you meant to put under botulinum

 

[operaman]

Thanks for the reply. I know there are a bunch of epidemiology and clues that usually come up, I was just curious about the actual presentations. Don't think you'd need to know it for making a diagnosis, but they could make the diagnosis very obvious, then say something like "which of the following is a likely additional finding on physical exam?" or some such. I think the one I bolded you meant to put under botulinum

Botulinum can present a number of ways depending on how it was administered. Ingestion is the usmle classic but you can also get iatrogenic presentations after treàtment with btx for dystonia, hyperhidrosus, cosmetic, etc. Classic ingestion clues are floppy baby, dysphasia, dyspnea, weakness, paresis/paralysis. You can get all the same from btx injections, minus the baby of course. Btx is more severe and acute while MG chronically worsens.

Context is really everything as they have significant overlap. Step 1 will always give you enough to figure out the difference, and if not then they'll ask you what test you would order to figure it out.

 

[VCorp]

Thanks for the reply. I know there are a bunch of epidemiology and clues that usually come up, I was just curious about the actual presentations. Don't think you'd need to know it for making a diagnosis, but they could make the diagnosis very obvious, then say something like "which of the following is a likely additional finding on physical exam?" or some such. I think the one I bolded you meant to put under botulinum

lol yes...good catch on that. 👍