I can speak to this as I have this very thing! Known PN, ideopathic since 2004 or so. Then the end of 2012 a dramatic increase of symptoms in my left foot. My lumbar MRI showed some defects in L5-S1 especially with a conjoined nerve root on the left. After about 8 months of PT, injections and the like, I ended up doing a single level fusion.

Was it worth it? Maybe. I have less burning type pain. Numbness, transient tingling and some lateral muscle weakness are still there. It is hard knowing what symptoms would have been there anyway and what were from a pinched nerve. Heck, I didn't have any consesus from different neurologists on if it was a radiculopathy. That's the hard thing when you have underlying PN.

I guess make sure you get several opinions if you choose to have surgery, and know chances are it may not fix your issues.

As for an autoimmune cause, they assume that is my underlying reason based on family history, but I have no strong bloodwork to back this up. I suppose if you have a doctor willing to do a steroid trial, & you are willing, go for it. IVIG will be hard to come by through insurance unless you have a firm autoimmune diagnosis.