These are also in LizaJane's site but not as well organized here:
http://neuromuscular.wustl.edu/over/labdis.html#Ab
http://neuromuscular.wustl.edu/lab/nvworkup.htm#lab

The basic site runs down dozens of myopathies and neuropathies starting with the symptoms. If you slog thru it all, and prepare to be a bit confused in the process, you mite be able to narrow some things down in your situation.
http://neuromuscular.wustl.edu/naltbrain.html
It's pretty much the most comprehensive of sites that describes the different neuropathies and myopathies....

This way you can see what tests have been done and why...sometimes doctors don't go to the next step tho.

Fatigue is common in many neuropathies! Often it is a primary symptom. Thing is, it is symptom of soo many other neurological and other medical conditions as well! That's what makes it so hard to zero in on what YOUR issues are. As good as many neuro's are, it's going to be/GOT TO BE up to you to keep persisting in getting a diagnosis.
My first diagnosis was a 'simple PN' and that neuro did nothing further despite a rapid progression of numbness throughout my body. I went and got second and THIRD opinions and found I had an auto-immune PN called CIDP. IF I had not known that things plain old 'weren't right' and gotten those other opinions, I could now be in a wheelchair - or worse. I am not there and I am grateful to ever so many here for helping me learn that YES! Things weren't right. I was and I'm lucky that I kept at it while I could get all the testing needed. You can and will too - end of pep talk.

If your docs are continuing to do 'another' test, then yet 'another'...that's a good sign...They've not given up or admitted that they don't know what to do - and do nothing. Getting a top notch second opinion is cheap, really cheap [even if it's out of your insurance plans' coverages] in the long run because it'll spur your plans' docs to keep up with the 'experts'! You'd be surprised at how many 'results' you can get that way.

's - j