i am assuming that what you are referring to is actually an EMG?if you actually have true nerve impingment/compression it would indeed show it with this test.only direct impingment and or compression is what will only show with this type of test.it checks the nerve flow and whether or not a signal can get thru to your brain.the things it wont show are pain caused by things like intermittant compression unless it is actually going on during the test,or pain from stenosis or other things,just direct nerve issues will show.if you actually have numbness,this test should be able to tell which nerve is actually being compromised.but in alot of people who are actually suffering with some pretty excruciating pain,you can still end up with a perfect EMG,only becaue of things i ststed above?there are many things that can be wrong wiothin our spines and with the nerves that don't actually cause direct compression so the test looks great and you are left scratching your head wondering why you are having this much pain.that is the way my very first EMG went when i had a herniated disc.but my EMG looked great according to the neuro i was seeing.this was because it had not compressed the nerve yet but was irritating the hell out of it and i also had stenosis which in and of itself can be very painful.so you can be having alot of pain and just intermittant(posisitional)impingment or compressionbut still have a 'good' test.an MRI actually gives you much better 'reasons' for pain and the EMG gives better info on actual nerve affectation,you know what i mean?good luck and please let me know how it all goes for you.you should be able to find out right away what may be up.my physiatrist always tells me as we go along what looks good or bad so i always know before i leave his office how bad my deterioration has gotten.i have had to have three seperate EMGs done over the past five years or so.Marcia