Hello. I am undergoing testing for small fiber neuropathy and am wondering if anyone has had a similar experience. I have had several evoked potentials (EVPs) done that have had abnormalities. In the beginning both my legs and eyes showed delays which is common with people with MS. MRI was clear however I had a B12 defficiency. The last 2 years I have suffered with burning sensation all over my body and testing began again.Most recently the evoked potenials showed delays in legs only, the right more so than the left. They did and EMG and although the EMG results were normal, the left leg was in excruciating pain each time they "zapped" it, but the right side I could hardly feel at all. It. Is amzing to me that my legs would feel so completely different and yet the results would be normal. Next step they are doing skin biopsy. Has anyone had these types of sensations during EMG? You would think I would have the same feeling in both legs if it was normal. Also has anyone had abnormal EVPs that has been dx'd with SFN? Thanks!

I do not know if evoked potentials are similar to nerve conduction studies. I certainly have abnormal NCS as well as EMG's. I also feel almost nothing during the tests, even after hours of it, but I will have zapping and buzzing for weeks afterwards. Both legs are similarly insensitive,but i have no feeling in either leg now to above the knee. I hope you are not as affected. Small fiber neuropathies commonly do not show up on the tests, the skin biopsy is the preferred method of diagnosis, so that will give you more info.

I have both small and large fiber hereditary neuropathy, so it shows up on both tests. Nerve conduction studies are only useful to diagnose large fiber types, as far as I know.

Sounds like you'll get more answers possibly with the skin biopsy (best test for SFN). However, it's obvious that you need to address the B-12 regardless of what the biopsy (or any other test) shows. This may resolve the problem all together.

MrsD will probably provide some input. But it would be best if you post the level so she can better help you.

--differ from electromyography (EMG) and peripheral nerve conduction studies in that they measure the processing rate for sensory modes (sight, hearing, mechanical touch--VEP, AEP, and SSEP, respectively) in the central nervous system. As such, they are normally used to help diagnose central nervous system (brain, spinal cord) problems rather than peripheral ones. They are sometimes used to check for possible demyelination, as in transverse myelitis or multiple sclerosis.

It is possible to have damage both to peripheral nerves and the central nervous system, however, and B12 deficiency is certainly on the list of candidates for that.

The current gold standard for discovering small-fiber neuropathy is the skin biopsy to enumerate intraepidermal nerve fiber density and condition, although there are other tests, such as quantitative sensory testing and certain autonomic tests that are also sometimes tried.