This is the usual algorithm for EMG's, though it can change depending upon which muscles are more weak.

When they do an RNS, it's normally done on the EDC muscle (forearm) but it can be done anywhere depending upon your clinical weakness.

Regular EMG's can be done anywhere but they're normally done on the arms and legs and not the face. Yeah, there are exceptions but I'm talking about MG specifically.

SFEMG are often done on the EDC, frontalis (forehead), deltoid (shoulder) or the facial/ocular muscles. They can be done on the leg muscles too. It's too dangerous to do them on the chest wall muscles.

From what I've read and have been told, a SFEMG can be normal on a clinically weak muscle and abnormal on one that's not weak. There are so many variables that come into play when doing a SFEMG: Hydration, warmth of muscles, technician's experience, how results are analyzed, etc. Subcutaneous fat of 9mm, which lies above the muscles and under the skin, can reduce the signal by 80%, exactly what can happen with an ECG of the heart. Some studies show that men's muscles fatigue more quickly than women's do, which might be why women are in charge of "the household." Just kidding. That might be why women often have a negative SFEMG and might need a longer one to show weakness.

The EMG result will not necessarily show the severity of your disease. Your symptoms and a good clinical exam are best to do that! And breathing tests too.

Questions, even if you're babbling, aren't annoying!!! And YOU aren't annoying. MG is. I hope the test goes well.


Annie