YYC and Mat, you can test for small fiber neuropathy through a QSART test. It's true that you can't find SFN through EMG, and other sweat tests can pick it up. This is how my SFN was Dx. More clinics/hospitals do the QSART now. I didn't need any biopsies to Dx this.
Basically, they stimulate your sweat glands with a chemical to see if they respond properly. Either way (whatever you have), *if* your Neuro problems are coming from an AI disorder, the Neuro is correct in saying that treatment of the AI will help the Neuro stuff. However, *how* it's treated varies depending on the Neuro symptoms
For instance, IVIG does help with SFN, but would not help (is is not shown to help) other neuropathies. Taking the typical Plaquenil (and or Prednisone, methotrexate, imuran, etc.) might help your underlying condition (AI disorder). AI inflammation will cause all sorts of problems, including Neuro symptoms.
Hope this helps. Sometimes it gets pretty confusing before it becomes clear. Take care now and keep us posted.
Peace and blessings to you both.
~Andrea