Did you have 'contrast' administered? Sometimes that can cause [tho rarely] a skin reaction. I'd had a whopper earlier because it wasn't administered properly. Hives that drive you crazier when you've neuropathy! That itch on a working nerve? Well, it's not fun! Now, for me? No more MRI's w/contrast...Pet Scans only...much more expensive, but better for diagnostics in the long run.
My only other question would be...how long were you tested? i.e. on that dreaded table? I've found that being 'still' in that cold room and also for Cats, and Pets and whatevers.. that WALKING out of there can be a challenge in the best of times! Up until this year's current round of tests, I've always experienced techs who were sensitive to severe neuropathies, and who understood that I mite not be able to tolerate for long periods of time that 'being' still wasn't conducive to the rest of the tests or the day or the week! Some test 'contrasts' can cause 'allergic' responses, as they are fish based. While I don't like fish? I don't seem to be allergic to it either-go figger.
Also, keep in mind that 'small fiber neuropathies' cannot be detected via any MRI? What they are doing it for is to see if there are any other gross spinal or other impingements to your basic nerve trunks to diagnose causes/non-causes for your issues. Remember, Diagnosing SFN IS a process of elimination! As long as it's Small fiber? Count your stars in your favor!
This is in the stickies? But the graphs show how difficult it can be to diagnose: http://www.aafp.org/afp/980215ap/poncelet.html
I do hope that soon there will be 'updates' on this tho.
I hope this helps and keep faith.