I've had 3 done.
FOR ME:
I was laying on a table face down. They put me out. Then the inserted needles into my back. They woke me up when they were done doing that. They asked me questions...."Can you feel this, can you feel that" etc.... They send something thru those needles. Not sure if it's electricity or they send a shock through it. It's not painful whatsoever. It's just an unpleasant vision of what they're doing. When the questions were done they put me out again and I woke up.

They have to determine where your pain is at. What nerve your pain is going through so the can help that specific area.

Hope that helps!
Heather