As you will see, I have been diagnosed as having Small Fiber Sensory Neuropathy, and the possible cause would appear to be my Gadolinium Toxicity. This posting explains a bit about Small Fiber Sensory Neuropathy.
The Small Fiber Neuropathy was diagnosed at the Cleveland Clinic with two tests. First is a skin biopsy (actually three) just above your ankle, one just above the knee, and one near the top of the thigh. They then count the nerves per millimeter. In my case the count at the top of the thigh was OK, the one above the knee was marginal and the one above the ankle was bad (a positive test for SFN). the second test is less invasive, it is called QSART, and it requires special equipment that attaches to your legs, and provides an electrical stimulus to make you sweat. it them measures the sweat. In my case this test had normal results.
I actually had them re-test about a year later, and the results were all in the normal range. But my symptoms were worse. They could not explain, and they did not try.
The big difference with SFN is that there is normally no involvement of the large nerves, so it cannot be diagnosed with and EMG. It is just that the ends of the nerves are dying. And this can be anywhere in your body, but normally first in your feet/legs. The problem is that whenever I have any sort of strange feeling or burning pain ANYWHERE in my body, the doctors just say “well it could be the SFN”. Not very helpful.
I do not have Diabetes (the most common cause of SFSN) and have had negative tests for all the other known causes. Although the doctors would deem it idiopathic, metal toxicity is also a possible cause. My SFSN is likely caused by Gadolinium Toxicity from the Gadolinium I retained from contrast MRIs. It was 5 years ago when I had my last contrast and the amount of Gadolinium in my urine is still double the limit that Mayo Clinic has on their test. If you go for a contrast MRI, they will tell you it is gone in a couple days. They are wrong as I am evidence of it still being in me 5 YEARS later.