--that began on April 12, 2003, was at high levels for many months (though Neurontin provided some relief) and that, according to a series of skin biopsies to measure small-fiber intraepidermal nerve density, has been slowly resolving since then (the skin biopsy was the ONLY test to show anything abnormal, and I had a collection of over 100 pages of test results by then).

Cause has never been determined, though an autoimmune post-infectious molecular mimicry process was/is suspected, What kinds of autoimmunity tests have you had (not just ANA related testing, but those for antibodies to nerve gangliosides and other nerve structures)? How did this present (acute, sub-acute, more gradually)?

Do you have definitive small-fiber damage? Generally, one cannot use EMG/NCV studies for that, as they only measure larger, myelinated nerves--one generally needs specialized testing (the gold standrad being skin biopsy, of others such as quantitative sensory or sudomotor axon reflex studies, which is what I think you mean by the sweat test--and yes, autonomic neuropathy is of the small fibers, so the gastric problems do point to that as well).

This definitely sounds autoimmune, though long-term toxicity or vitamin/mineral deficiencies should also be investigated. You should take a look at the Liza Jane spreadsheets--www.lizajane.org--these were designed to be about as comprehensive listing of test for neural symptoms from whatever cause as could be compiled form current medical knowledge, and see what you have and haven't had done. (They're also good for tracking test results over time and finding patterns.)