--one can have a completely normal EMG/nerve conduction study and still have small-fiber or autonomic neuropathy, as the unmyelinated, small-fiber nerves that subsume the sensations of pain and temperature are too small to be measured by those kinds of studies.

If it gets to that point, specific kinds of testing for small-fiber syndromes, from sudomotor axon reflex (sweat) testing, to qualitative sensory testing, to a skin punch biopsy to look at the microscopic nerve fibers, may be done. But I imagine that a lot of blood work would be done first.

It's very hard to tease out peripheral nerve problems from those of the spinal cord or brain, as the symptoms may be exactly the same. MRI's of brain and spine might also be indicated.