Hi Joanna,
Somatosensory evoked potentials tracks amount of time nerve impulses take to travel up and down the nerve pathways and it isn't the same as an emg.
I've had it, it is very relaxing. It is done to rule out ms and peripheral neuropathy.
It takes about an hour, and you have to wear sticky goop on your head, plus you have to make sure you shampoo in advance so the sticky goop will stick properly. They also place little stickies all along your limbs. You won't be able to wear shoes. Bring warm, comfortable clothing and remember to relax. I kept clenching my jaw and the tech kept hollering at me to stop because she could tell (without even looking at me,) from my results that I was clenching, lol.
It's a piece of cake, don't worry. I got my results on the spot, but it should be within a day or so.
Blessings,
Sue