It is well known now--though it should be better known, especially among neurologists--that a nerve conduction/EMG test series will only reveal damage to the larger, myelinated nerves, if that ddamage is sufficiently advanced; the technology is not yet advanced enough to measure problems with the smaller, thinly-myelinated or unmyelinated nerves that subsume the sensations of pain and temperature. And people can have small-fiber syndromes and come up (depressingly) "normal" on most of the first-line tests neuros tend to perform, including the reflex/pinprick/tuning fork parts of the standard neuro exam.

Small fiber damage may be revealed through qualitative sensory testing (QST), sudomotor axon reflex testing (QSART--know as the sweat test--this is because autonomic functions generally are mediated through small fiber nerves), or through a skin biopsy designed to enumerate the density and conditon of intraepidermal nerve fibers.

Take a look at:

http://www.thecni.org/reviews/13-2-p07-treihaft.htm

The reference list with this paper is also excellent to look through.