j1, here's your answers as best as I know, I'm not a doctor but I consider myself "up" on this as I have done literally thousands of hours of research on thsi stuff because that's al I could do wneh I thought I was dying of ALS and couldn't work or even function as a human being.
I don't know about the exact numbers of people who "noticed" their twitches first but here's the deal with ALS. When the nerve endings start disconnecting from the muscles (say, in your hand) the muscle then wonders what is going on and it starts twitching very finely as a last ditch attemp to reconnect itself or to continue moving. It starts out in a small place and works its way from there, then spreads to other limbs as time goes on. It is common that twitches with ALS can't be seen unless put under a special strobe light because they are so fine. The deal with twitches showing up first "without weakness" is misleading. There's no doubt in the medical world (from what I have read) that the twitches are a secondary, involuntary action of the muscle AFTER it has lost nerve conductivity. Maybe some people nboticed the twitches early-on and didn't "notice" the weakness setting in yet. I have to be careful in saying that because I don't want people to read this and freak out thinking that maybe they haven't noticed their weaknes yet. ALS is a fast progressing disease. It doesn't come and go. You WILL notice weakness very soon (probably within weeks after noticing the first twitch). I think those numbers you saw are misleading though. The bottom line with ALS is disconnecting nerve endings between the muscle itself and the brain. The weakness comes from not being able to use that particular muscle and having to rely on other muscles in say, your hand. This puts more strain on existing muscles and as more muscles become disconnected from the brain, pretty soon ( and I mean REAL soon) you will begin to notice that you can no longer hold your coffee cup or that you are dropping your toothbrush a lot because you can no longer command the disconnected muscles to do their jobs anymore.
An EMG is pretty much the only tell tale factor in whether you have ALS or not, other than an experienced neuro who knows what to look for. Like I said, ALS twitches are totally different than BFS twitches and any good doctor will know this right off the bat.
Yes, you can 100% safely rule out ALS with a clean EMG. There's a catch here thouigh. Not all abnormal EMG's mean ALS or anything else bad. Some people just show small abnormalities in their EMG's and that isn't too uncommon or anything bad. Your doctor will probably do more tewsting just to rule out anything else. They are good people those doctors, thay usually know what they are doing.
From what I have read, it does not matter which muscles they tested. Once ALS has started, it pretty much shows-up all over with an EMG test.
If you have had aclean EMG just remeber this simple equation... Clean EMG = no ALS. It's simple math that isn't wishy washy. If you had a clean EMG, you are fine
