If the neurologist already confirmed that you have SFN, the punch test will not improve the diagnosi, since he has already Dx you with SFN. Now if for instance, you were to get the DNA test that showed CMT then he would be able to give you a more definitive answer. But even then, there wouldn't be a cure... The only time a Dx is real important is if it can be reversed in time, or if it proves to be suggestive of having more serious life threatening results. Right now Neurologists and Rheumitologists are just poking a stick in a dark room, they have no clue how to treat or cure PN.