Hi Carly...
A regular EMG/NCS tests multiple nerve sites and muscles and that's what sets it apart from a SFEMG. Single-fiber electromyography (SFEMG) is a selective EMG recording technique that allows identification of action potentials from individual muscle fibers. Both of these studies are unreliable as a single method of diagnosis and most MG experienced Neuro docs should tell you that from the get go. You can use it as a tool to get confirmation for the clinical diagnosis. Clinical diagnosis is based on current symptoms, personal and family history, symptoms, date of onset, etc. Basically, a patient can be negative for the blood titers and EMG/SFEMG but still have a clinical diagnosis of MG. This is not the only autoimmune disease that is like that. You can also be negative for Lupus through blood work but clinically positive too. There are a couple of other diseases that are like that but this is why it is so important to have a well experienced MG neuro.
I hope you get some answers from these studies. I haven't done the SFEMG but I've had the EMG/NCS a couple of times as a test subject when we ordered anew machine and then as an MG patient with the repetitive stimulation included. I did not find it to be terribly unpleasant but I have a high tolerance for pain. The NCS I always tell patients it feels like when you are wearing socks and walking on carpet and then get shocked when you touch something metal. They should start of on with softer shocks and the idea is to get the best possible response from your nerves so they increase the shocks until they reach that maximum response. The EMG portion of the study is done with a very fine needle (slightly smaller than an acupuncture needle, if you've ever seen one of those) and they just go to the surface of the muscle. During that part they will have you first start out in a relaxed state. They will look at the muscles response to stimulation while relaxed and then ask you to activate the muscle. The doctor or tech will tell you exactly what you need to do to activate the muscle. For example; Testing your lower leg, they will poke you with the needle (sorry, that sounds bad) while you are relaxed and then when they have seen the data from the relaxed state they will ask you to do something like point your toes like you are pressing down on the gas peddle. Then they should tell you to relax just before they remove the needle.

I know that the neuro that I work with is very thorough and our experience is that nobody here in Hawaii does a more complete study than we do but that may be a local issue. We diagnose a lot of conditions that other local doctors have missed because they didn't do a complete study. So I hope that yours is a complete one for the best possible outcome.

I'm sorry that this is so detailed. I have a unique perspective being on both sides of the study so sometimes that can be helpful. I hope that this information is helpful and good luck with your testing. Let us know how you did once it's over with.
Aloha,
Angie

Thanks for this post Carly and your information Angie - we are so lucky to have you and your knowledge!!

I have had the NCS/EMG but not a SFEMG, I am also double seronegative (sigh!) and diagnosed by Clinical Symptoms and response to mestinon - mestinon worked wonderfully for 3 months but now the effects are waning and so I may have to go for a SFEMG on my face (as this is my predominant weakness) to get any further help.....although I have sent a pleading letter to my Neuro to see if he will consider any other treatment without the need for more tests, I am praying he will consider it...but, if I.m honest, I am not holding out much hope!

Have you had any other tests apart from the bloods Carly??

Eve.x

I have even had EMG done to rest my diaphragm, which I think was somehow done through the neck. I do not find EMG painful in anyway, though, like Angie, I have a high pain tolerance. I am seronegative, negative on SFEMG (which was done when I was quite healthy yet), have a slightly irregular repstim, and a clinical diagnosis. Clinical symptoms, unless you are seropositive, seem to be the best indicator of MG, so it is good to know your body well. I hope your tests will give your neuro the objective data he or she seeks so you can move forward.

ALL-Thanks for your informative and kind replies!!

I've had many EMGs/NCVs. The NCVs are always normal, but the EMGs show myopathy in the face, paraspinus, and limbs. My RNS testing was normal, so one neuro doubts MG dx. Other neuro that originally dxed it goes on clinical (eye droop, weakness, speech/swallow isues, etc...) Thank God for my opthaneuro who
dx'd me and gave me the Mestinon. I'm hoping the SFEMG will give me a firm dx or not. We'll see next week!

Carly