I had three EMGs within the first four months or so of my twitching. After three clean EMGs, I had a muscle biopsy on the same day as the third EMG. The muscle biopsy showed denervation/reinervation which is the exact thing the EMG looks for. After a year and a half since the muscle biopsy, the neurmuscular specialist who did the EMG and muscle biopsy would not order another EMG even though I still twitch. Since my symptoms haven't changed (and may even have improved a bit) he said an EMG would tell you nothing. Basically, if clinical symptoms do not change you cannot expect the EMG to change. Even if an EMG or biopsy showes nerve damage this does not lead to a diagnosis. These diagnoses have more to do with progression over time, nature of onset, blood tests, and the symptoms in combination with other findings. I wish the EMG was some definitive test but it tells you little more than a clean clinical if you have widespread twitching. I think an EMG only makes sense if you have weakness, fast progressing symptoms, or a localized problem. This is just my opinion based on my experience with all this.