I have been sent for nerve tests, as some of my fingers are permanantly numb on one hand and occasionally numb on the other. What would a Dr be looking for by saying hold your arms and hands out straight together for a few seconds with your eyes shut?
I’m assuming your asking about a nerve conductivity test, in which they send electrical impulses through various port of suspected nerves. I have one of these scheduled for next week.
As to the putting your arms out, etc, there are a whole bunch of tests these kinds of diagnostic tests. The doc may be attempting to determine a suspected impingement is located in the wrist, shoulder, or neck, for example. I once had to go to a neurologist (so that work could feel better about a guy with hand tremors carrying a gun). I spent about 2 hours duck-walking and doing all kinds of silly things that didn’t make much sense to me. But then again, I’m not an MD.
I my case, I had the same symptoms and the surgeon performed an ulnar nerve transposition (sounds like you may be in the same boat, if the fingers you can’t feel are your pinky and ring fingers). Sometimes, they’ll attempt to treat with NSAIDS and/or physical therapy (depending on severity and your doctor’s personal inclination). 6 months later, I’ve got a nice big incision (and a sore elbow), but still no feeling in my fingers. So off to the nerve test center I go!
What is an ulnar nerve transposition? Like, do they open you up and actually try to re-wire or re-route some nerves?
This sounds like you were being tested for “pronator drift” - were you specificallly told to keep your palms pointed to the ceiling? If yes, then that’s what it was.
A positive test is when, without you being aware of it, and despite thinking that you are holding your palms facing the ceiling, one hand/arm (usually only one) rotates such that the back of your hand begins to face the ceiling instead (the wrist “pronates”). That would indicate a so-called upper motor neuron lesionin the rotating arm. And that is a sign of damage somewhere between the brain and the nerve cells in the spinal cord which control that limb.
Hey look, there’s even a wiki article on ‘pronator drift’. I’m impressed.
Why not ask your treating Doctor this question? You will get an authorative answer.
Yup. It’s also called cubital tunnel syndrome. Basically, the nerve gets pinched (aka, “f’d up”). In my case, if I understand correctly, they opened up my elbow, cut off some of the bone, and repositioned the nerve so that my “funny bone” nerve is now in a different position.
Heh. Unless your doctor kind of scratches his head and says, “there’s something not right here…” as his voice trails off. 
Might they also be looking to see if you can keep the arms at the same height without visual input? I’ve had this same screening and I assumed that was what they were looking for. Never bothered to ask, of course…
Yes, you are absolutely right. In that case, one is looking for “cerebellar drift” or “sensory drift”. In other words, just as you said, if the person can’t keep the arms at the same height in the absence of visual input, it suggests that there may be a problem in the cerebellum (that part of the brain involved in coordination and ‘smoothness’ of movement) or a problem with the nerves (proprioception) responsible for telling the brain where the limbs are in space.