--are interpreted according to the McArthur protocols, named after the main researcher at Johns Hopkins where the procedure was invented.

There are specific "norms" that were set up at the time to make diagnostic classification easier (and possibly insurance re-imburseable). In short, after a lot of samples were taken from both "normal" peopkle and neuropathy sufferers, it was decided that if one had an intraepddermal nerve fiber density belows the fifth percentile determined from these many samples, or above the ninety-fifth percentile, that would be considered an indication of definite nerve dysfunction. Other factors go into the diagnosis, including whether the nerves show swelling or excessive branching, but the numerical criteria has been the one most reported when the results are compiled.

Of course, as my neuro pointed out, owing to individual variation, one might have nerve damage that hasn't yet reached either of those percentiles, as it's very difficult to know at what level of density one started at before one's damage process, as none of us have the procedure until we have symptoms. To me, if one began at the fifttieth percentile (if we could know that) andhas dropped to the twelfth, that's an indication of damage, though it likely wouldn't meet the criteria for a definite diganosis of small-fiber neuropathy.

Since I have the protocols and the numbers, I ask people to report the numbers from their biopsies; I think anything near the percentiles is likely an indication that something has happened.