There really isn't an entity of long fiber neuropathy. Small fibers are unmyelinated, those are referred to as C-fibers....C fiber neuropathy is hard to diagnose, as EMGs, evoked potentials, MRIs will not show small fiber neuropathy. Many, many people diagnosed with other conditions likely have small fiber or C fiber neuropathy. C fiber or small fiber neuropathy causes sensory symptoms of all kinds AND can cause autonomic symptoms of ALL kinds such as anhidrosis and POTS. C fibers or small fibers permeate the entire body.

The fibers to which you refer as long fibers, can be motor or sensory nerves that are myelinated. Usually those myelinated nerves will show some abnormalities on EMGs, MRI etc, altho not always. Abnormalities of the larger myelinated nerves are more detectable.

Then there are some 'thinly myelinated' fibers, those are included with small fibers....they generally deteriorate along with the unmyelinated ones giving rise to the name 'small fiber neuropathy'.

No one type of neuropathy is any better or worse than the other in terms of discomfort or functionality...they are both problems.

Glenntaj gave a good explanation in his post on CIDP. Both axons (the nerve cell) and myelin the nerve cell covering can deteriorate independently...and in small fiber neuropathy, there is no myelin to deteriorate...it is axonopathy or neuronopathy.

A non-invasive, cheap test will be revolutionary for diagnosing pain syndromes and will help to identify people who may be having autonomic dysfunction a lot sooner. It would be wonderful it this test is as good as it claims to be and becomes available to all.

Also having small fiber neuropathy does not preclude a person from developing a demyelinating neuropathy, and visa versa....some people have both.

This website might explain it better than I can.

http://www.neuro.wustl.edu/neuromusc...ory-large.html

neuro.wustl is chock full of good information. I highly recommend it.