@wjones159 that's a good question and I wished I could answer. Unfortunately I have no medical training or background. I had an EMG nerve conduction test to test for nerve damage that was used to diagnose my small fiber peripheral neuropathy. There is a discussion here on Connect about the test:

Groups > Brain & Nervous System > Nerve conduction test
-- https://connect.mayoclinic.org/discussion/nerve-conduction-test/

I agree with Chris @artscaping about getting a more definitive diagnosis. Maybe you've already done this but I like the way you listed your health history and if you haven't discussed it with the neurologist I'm wondering if that would give them more data to use.

Keep asking questions...you are your best advocate!

John

Punch biopsies are usually done on the side of the body where you experience the most symptoms (if you happen to notice a difference, and many people do). You've had the biopsy, so you know the drill, but for others who haven't, I'll elaborate. Between two and four (based on the discretion/preference of the doctor and the recommendations of the lab/kit being utilized) 3mm 'punch' biopsies are taken. Frequently three are taken, distal calf (near the ankle), proximal and distal thigh. These 3mm samples are then (again, depending on the kit/lab) frozen, sectioned into 50 micron thick samples, stained, put under a microscope, and the nerve fibers meticulously counted by a pathologist. The number of small fibers present in the samples are then compared to a reference data set for the specific locations biopsied. Taking three or four samples spanning the length of the leg allow the pathologist to differentiation between length- and non-length dependent SFN. Length-dependent SFN is more common, generally has a slower progression, and symptoms characteristically progress from the feet upwards. Non-length dependent SFN is an indicator that SFN is likely widespread throughout the body, and can cause autonomic nervous system dysfunction; affecting organs and glands along with the skin and muscle symptoms seen in length-dependent SFN. Once you have the diagnosis, there is to my knowledge, little to no significance of having it repeated in your other extremities; you know you have it, and wherever you're feeling symptoms, it's likely SFN is present. Not to mention the biopsy is quite expensive. Repeating the punch biopsies after some time has past from when the first set was taken is a great way for your neurologist to track how the disease is progressing/how well treatment is working. Bakodx and Corinthian Reference Lab's websites, can provide you with more information.

I also had nerve biopsy on one leg. It confirmed SFN. Severe pain in feet and ankles. Sometimes extends to the waist. No pain in upper extremities. But walking very painful!! Awaiting an appointment with highly recommended specialist on SFN at Mass General hospital. But it’s not till January 24. Made the appointment in February!!!! Very frustrated!!! Very depressed!!!!!