--what kind of testing was done to arrive at that diagnosis?

What kind of symptoms do you have, and where?

The most common cause of small-fiber sensory syndromes is impaired glucose tolerance/diabetes, but that only accounts for about thirty percent; many are autoimmune (from gluten intolerance, anti-nuclear-antibody vascular/connective tissue disorders, cross-reactivity from blood disorders, etc.), some are from toxins (particularly chemotherapy), and many are stubbornly idiopathic . . .

Your therapeutic approach would very much depend on what the etiology is, if one can be found, though certain supplements (B12, alpha or R-lipoic acid, magnesium, possibly B1 and acetyl-l-carnitine) are pretty much standard for any sort of small-fiber problem.