--you're a member of a very large club. Approximately one-quarter to one-third of all documentable peripheral neuropathies (depending on which medical review you're reading) are idiopathic, meaning that they currently hve no known cause. For sensory neuropathies that affect primarily the small, unmyelinated fibers that subsume pain and temperature sensations, the fraction is probably even higher.

For many such neuropathies, autoimmune and/or impaired glucose tolerance/metabolic syndromes (short of diabetes) are often suspected, but it's difficult to tease these out if one is receiving "normal" test results. It's why investigations into causes of neuropathic symptoms--inclduing those due to problems of the central nervous system, for which the symptoms can exactly mimic those caused by problems with the peripheral--are often so long (and expensive).

What nobody needs are doctors who are unfamiliar with the range of testing that needs to be involved to try to find a cause. There are many docs out there (even neurologists) who have a frighteningly limited idea of what causes neuropathy and what tests can be brought to bear. It's why many of us use the spreadsheets at www.lizajane.org; they are not only comprehensive as to neuro symptom testing, but are great for tracking one's own test results over time, to see patterns.

Also, from our Useful websites, these documents might be helpful:


http://www.neuro.wustl.edu/neuromuscular/naltbrain.html

This is the diagnostics entry point for the huge neuromuscular conditions database at Washington University of St. Louis' medical website. It is written primarily in outline form, and mostly for medical professionals, but it is extraordinarily comprehensive; going through the links and sub links reveals a wealth of info on neuropathy (and other neuromuscular conditions).

http://www.aafp.org/afp/980215ap/poncelet.html

The famous Poncelet protocols. Outside of neurology textbooks, this article has become the "gold-standard" guideline for many physicians and neuros for investigating the causes of potential neuropathies. The flow charts are particularly instructive (and good to show ingorant physicians).

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

One of the best articles I know written about small-fiber neuropathies, which can be difficult to diagnose, as "standard" tests for neuropathy often come up "normal" and fail to reveal them (and meanwhile patients suffer). The reference list is excellent--it includes many of the seminal papers on skin biopsy, autonomic testing, and small-fiber vasculitis and other causes of small-fiber dysfunction (these can themselves be investigated if one wants).

http://www.questdiagnostics.com/hcp/...a lNeurop.htm

A small but dense clinical application paper about laboratory tests to investigate causes of peripheral neuropathy. Dr. Latov heads the Cornell Weill Center for Peripheral Neuropathy in New York City, and he and his staff may be the world's leading experts on immune-mediated neuropathies (not that they're slouches in other realms, either). (All docs there are both researchers and clinicians--and, I can tell you from personal experience, an informed patient can have great discussions with them.)

http://www.dcmsonline.org/jax-medici...uropathies.htm

Another good paper--this one form Dr. Alan Berger and his colleagues at Jacksonville Shands. It provides a good overview of diagnosis and treatment options for various kinds of neuropathies, and suggests a particular categorizing method to understand them.


Still, even with all this, a good fraction of neuropathies remain stubbornly idiopathic--the nerve damage can be documented, but the cause remains stubbornly elusive.

Carpal Tunnel is merely one type of neuropathy, caused by compressive forces on the nerves that pass through the rather narrow/crowded wrist area. People with impaired glucose tolerance/diabetes and various vasculitic autoimmune disorders have higher rates of carpal tunnel (and other neuropathies) than others, so it's really worth a very detailed workup for these as described in the spreadsheets (three-plus hour glucose tolerance testing aand a really thorough antibody check). Ischemic damage tends to make it more likely that compressive forces will cause symptoms that "normals" would not experience--sort of like a double whammy on the nerves (neither alone might cause much symptomology, but together . . .)

Can you give us a run-down on exactly what testing you've had so far?