Hello! Im sorry tp hear of ypur pain. Skin punch biopsy is a simple and factual determination for SFN. Tests for underlying causes include genetic testing, multiple blood draws and spinal tap. I have full body SFN caused by B12 deficiency. Outside of Gabepentin, Lyrica is one to try. I have benefited from the controlled release version of it. I also take Cymbalta for anxiety due to the complexity of the disease and receive lidocaine infusion therapy. A multidisciplinary approach is typically used for SFN. I wish you well and hope you continue to communicate with your neurologist and find what may be able to help you.