"Peripheral Neuropathy" is just a catch-all term for any condition in which the nerves outside the brain and spinal cord are in some way compromised and produce symptoms, which can be motor, sensory, or autonomic.

Small-fiber neuropathy refers to problems with the small, thinly myelinated and unmyelinated fibers (myelin is a protein covering of larger nerves that helps protect them and maintain signal conduction) that subsume the sensations of temperature, pain, and a number of autonomic functions. Problems with small fiber nerves cannot be detected with nerve conduction studies of electromyography (EMG), as those nerves are too narrow (many are microscopic) to be measured that way. Nerve conduction studies generally will only reveal gross dysfunction of larger, myelinated nerves that control motor functions and the sensory modalities of mechanical touch, vibration, and position sense.

There is specialized sensory testing for small fiber problems, but the current gold standard is skin biopsy for enumeration and condition evaluation of the small fiber nerves.

Definitely take a look at the Useful Websites section at the top of this board's post list--we have accumulated numerous links to excellent sources of information about all this.