I too have this. As a result of SFN caused by Sjogren's Disease. According to my Drs. if you have SFN long enough the large fibers get effected, too. They are a part of your autonomic nervous system that tells your body where it is in space. The nerves exit the spine at the lumbar level and if there is any nerve pinching (and most of are old enough to have that) then it effects your balance. Interestingly, it causes no pain-just the balance issues. I don't know how long I've had SFN as it usally causes pain but I have none. Go figure. Took a while to figure this out. I take IvIg every 3 weeks and Retuximab twice a year and the positive results are very slow in coming. But they come and I am very determined to make it to 100.