@helennicola The punch biopsy is the gold standard for diagnosing SFN. I found that out the hard way. Had four misdiagnoses before I had the biopsy done. By that time it was too late for me. Nearly all nerves gone and sweat glands too in my feet. My feet are on 🔥 all the time. They look like they've been through a "meat grinder". So far mine is idiopathic...Pam