I have a question that I've been wondering about for a week, especially in light of the fact that my own sfemg came back negative. My question is, why is it that some patients, particularly those with hereditary myasthenia gravis and, as Rach recently wrote, with sero-negative mg tend to have negative emgs and sfemgs?

I asked the neurophysiologist who did my sfemg why that test and the regular emg would come back negative when I clearly had a problem with either my nerves or muscles (my eyebrow can fall so far down my eye is almost covered and weakness in my lower facial muscles can cause my mouth to sort of curve up or pull down depending on, well, I don't know what!). I didn't really get an answer from him - he told me to see a plastic surgeon. Which besides being completely illogical left my question unanswered.
Anyway, I'm still left wondering. If someone could explain this in a not too master's degree in physiology way, I'd really appreciate it.

Also, is it true that if there is any weakness at all somewhere then the sfemg will show up even in a non-weak muscle? What about the regular emg? I was told that it would almost certainly be positive in a person with mg - around 90% of the time. Of course I've had two negative emg's . . .

Thanks for any help!

Ally