Electrolyte imbalance such as low potassium and low calcium causes perioral numbness.

As far as sfn goes, I do think the most likely place for it to show is the ankle or the calf punch. My calves are worse than my feet! Much worse!

I know that you do not have insurance right now... but something to think about for the future.

Mayo Clinic diagnosed me with small fiber neuropathy (and large fiber and limited autonomic). I never had a skin biopsy done. The results of other tests were conclusive enough. I don't know specifically which tests, since I had so many done in the 4 days I was there. But when I looked it up online, it said "Skin biopsy (with an evaluation of the density of intraepidermal nerve fibers) and tests of autonomic nerve function are useful for the diagnosis." (http://www.ccjm.org/content/76/5/297.full)

So, if you get health insurance again.. or if you try several things and get to the point where you decide you want to find out if it is SFN and be tested even without insurance, there are other options for testing. I have no idea how much the tests cost in comparison to each other--but one may be a more reasonable price. Just a thought.

Though the current gold standard for diagnosing small-fiber neuropathy is the skin punch biopsy to check the condition and density of intraepidermal nerves, there are other tests that are available and were done frequently before this test came along, and are still done at some locations. Even so, many of these tests are specialized enough that the average doctor will not be familiar with them. They include:

Quantitative Sensory Testing--a small thermal electrode is placed on various body parts and it's voltage is adjusted so that its tmeperature is raised and lowered; the patient reports what sensations of hot/cold/pain are felt and at what levels they can notice small differences. This is a rough guide of the sensitivity of the small nerves that control pain and temperature sensations. People who cannot notice differences easily or who cannot distinguish temperatures likely have some small-fiber damage.

The Sudomotor Axon Reflex Test--this is used to see if the small-fiber autonomic nerves that regulate sweating are in good working order. The test has three parts and measures resting skin temperature, resting sweat output, and stimulated sweat output. Measurements are typically taken on arms, legs or both. A small plastic cup is placed on the skin and the temperature and amounts of sweat under the skin are measured. To stimulate sweat a chemical is delivered electrically through the skin to a sweat gland.

There is also the bodypowder sweat test, in which one is covered in a fine powder which turns purple when sweat on--the idea here is to see if, when exposed to heat, one sweats within a normal range on various body parts, or too much (hyperhdrosis) or too little (anhydrosis).

There are also autonomic tests to measure blood pressure and heart rate variation under various conditions. These include the tilt table test, a deep breathing test and the Valsalva maneuver. The tilt table test requires that the patient lie on a table that is then raised. The deep breathing test requires the patient to take deep breaths for a minute. The Valsalva maneuver requires that the patient blow into a tube to increase pressure in the chest.

Some places--not as advanced, in my opinion--still do more invasive nerve/muscle biopsies. I don't think these are as warranted or useful for those with smal-fiber symtpoms, but some places love to practice surgery (and bill for it) . . .

BTW, since small-fiber neuropathy certainly doesn't have to show up in a length-dependent pattern--it can show up anywhere in the body--taking only one sample at an ankle seems to show a lack of understanding. Most standard protocols take three smaples--at ankle, thigh, and upper arm--and some can take more, including the face; in fact, a skin sample can be taken any place there is hairy skin.

Yes, thank you! I was trying to find the specific tests, but was having a hard time.

I had theses ones:

Quantitative sensory testing
Body powder sweat test
Tilt table test
Deep breathing test
and I can't remember but it sounds like I may have also had the valsalva maneuver one done, too.

Thank you for explaining the other ways of testing for SFN.