As far as I know, tests for SFN may include skin biopsy, sural nerve biopsy, QSART and something called a tilt test. I've never had any of these as my symptoms are classic SFN and all other possible causes for the symptoms have been ruled out. The Gabapentin and Cymbalta I take control the pain, tingling, stabbing, etc. symptoms, but no drugs cure the disease so the numbness progresses. - Ruby