It's not painful, it's just unpleasant
Electric current is put through your nerves and it feels weird, but I can name plenty of greatest pain sources

I don't believe you'll feel anything after it ends and I'm pretty sure 2 weeks time you'll forget about it totally
It's very important diagnostic tool and if your neuro wants to do it just go for it

Let me also put it like this, you're a women a have a child, I can't potentially imagine the PAIN of birth, you went through it, EMG is a tickle :-)

I have many tattoos and they definitely hurt more
EMG is annoying but although it takes some time only fraction of that time is when they actually put current through your nerves
So it's an impulse that last few seconds and then rest
It's not constant electric chair experience