I would really give it a lot of thought and seek some other opinions before I would consent to a nerve biopsy. It does permanent damage because the section of nerve is cut out and many people have reported long term or even permanent pain as a result. At the least that area will be permanently numb. Unless vasculitis is suspected it will usually only confirm that you have PN rather than to find a cause. Your emg has already confirmed that you have PN so think long and hard on this one. Early in my search for a cause I was referred by a neuro for a nerve biopsy. After researching it and talking to a few people on the old board I decided not to go ahead with it and am glad that i didnt.