My mother has suffered from non-diabetic neuropathy in her feet & legs for many years. No drugs help her, really, except Gabapentin a bit. Pain meds do little to touch nerve pain, in reality. When my ex had chemo for cancer, he too developed neuropathy in his feet and started using Penetrex cream which you can get on Amazon. It helped him quite a bit so I ordered it for my mother & it helped her too. You might want to give it a try. I don't think it matters where neuropathy comes from; whether it's due to diabetes or other causes; it's the fact that the nerves are damaged and the pain is stemming from that that's the issue which is so very hard to find relief from. I would think the epidural blocks help your mother? If not, I can't imagine anything else would help!
Where is the neuropathy: hands or feet? How long ago was the surgery? My husband (64) has non-diabetic neuropathy in his left hand from nerve damage (docs think due to years of a hockey glove pressing on his nerve). Doc did a carpal tunnel surgery with no success. Not to the point of chronic pain but he hasn't been able to get relief from the "buzzing and tingling" sensation.
Good luck!