--I will chime in that negative NCV/EMG studies and/or negative skin biopsies does not necessarily mean that there is no nerve damage--just that it is not gross enough yet, or is not gross enough now (it may have been once), to fall outside the test norms.

EMG/NCV studies tend not to go into abnormal ranges until at least 6-8 weeks after an initial damage, and the damage has to be fairly extensive to be picked up.

With skin biopsy, the MacArthur protocols "norm" intraepidermal nerve fiber density at the 5th and 95th percentiles of a control group--those are what is defined on most reports as pathology. But since there are individual differeneces, a person who started in, say, the 70th percentile but had damage that took him/her to the 25th percentile might be undergoing a nerve damage process, yet be considered "normal" for purposes of the report, and be considerably symptomatic.

Sometime this can be qualified by noticing the condition of the small-fiber nerves from a skin biopsy--excessive branching and swelling tends to point to a neuropathic process whatever the numbers are.