I had that nerve test and it stings a little in areas where you don't have RSD and is definitely noticeable pain where you have RSD. It wasn't as bad as cold water or a cold breeze or someone grabbing me in an area where I have RSD...but it did hurt so probably better to be prepared and know that going in. Not horrific so I wouldn't worry too much about it and hopefully it is useful in figuring out what's happening...but no spot lasts that long and if they are just checking your arms then it should be pretty quick (they checked all over my body and it took about an hour).