--can never rule out a small-fiber neuropathy; NCV's/EMG's are simply not designed to measure activity in nerves with less of a diameter of about 5mm or so.
Moreover, the most common presentation of a diabetic or impaired glucose tolerance neuropathy is small fibers first. That doesn't mean one can't have large fiber involvement with diabetes or impaired tolerance, but more often one gets the pain and/or numbness and/or temperature sensation disruption symptoms of small-fiber disruption early on. As the mechanism of diabetic neuropathy is primarily due to vascular insufficiency, it makes sense that narrower, more distant from body center fibers would be the first to experience toxicity or hypoxia.
Apparently this doctor needs to read a number of papers, starting with these:
http://www.medscape.com/viewarticle/418568
http://www.endotext.org/diabetes/dia...tesframe28.htm
http://www.medscape.com/viewarticle/418657_5
http://care.diabetesjournals.org/cgi...full/26/5/1553
And there are many more.
It would seem you would need a neuro or other doctor who is a bit more motivated or knowledgable; do you have any options?
And, anyway, have you had a 3-5 hour glucose tolerance test just to make really sure you have no impaired glucose metabolism issues?