Question about skin biopsy/diagnosis
I'm hoping someone here can share information about standard practices (and especially how standardized they really are) with punch biopsy for small fiber neuropathy.
Here is a little background: I have been experiencing symptoms consistent with neuropathy for about a year. There has been some progression (started in feet and legs, eventually included hands and then arms too) -- also started with pain and other weird sensations, but later included some numbness and decreased temperature sensations (especially on toes). There have been other symptoms too (mainly intermittent but at times severe fatigue, and headaches which have lasted over a week sometimes, but luckily have not been too severe in intensity). Neurologist tested for MS (with MRI) about 8 months ago, also then did nerve conduction studies. His report back to my GP was everything was "normal" and it looked like GP thought it might still be MS but not showing up yet on MRI (so wait and see). Recently GP sent me back to the neuro for round 2 of testing since the pains etc. had progressed and now included some numbness, and since it was not getting better. I think the GP thought the MS possibility needed to be looked at again.
In the meantime, another doctor (not a neurologist, other specialty entirely) who I happened also to have an appointment with this month, makes the connection that my symptoms seemed consistent with small fiber neuropathy, and he suggested some additional tests and named some doctors in a neuropathy specialty center. Meanwhile, neuro tracking me for possible MS had already ordered MRI number two (which came back normal again, but not before i had heard the SFN suggestion from other doc). When the neuro called me with the news the second MRI was normal, I shared with him the comment about possible SFN, and he then offered to order the punch skin biopsy himself (which seemed like a good idea at the time -- but now I am wondering whether I should have just gone directly to the neuropathy center rather than trusting this neuro who missed the possibility of SFN in the first place).
Last week I had the skin biopsy done, as ordered by the neuro, done by a doctor he sent me to who may not specialize in this. I'm waiting for results, and I am concerned about a few things: his guy only took one punch sample (isn't it more standard to take at least 2?). Looking at the chart of where the test is supposed to be done, it seems to me the location (where mine was done) is not quite where it should have been according to the info from the lab which is now processing the result (and I got a separate card from the lab, concerning insurance etc. so I know for certain where the sample is being processed, and their website shows where the samples should be taken from).
So here are my worries: is it really critical to get the sample in the right place, plus or minus 1 inch, or is it ok to be several inches off? Also, what do you think of them taking only the one sample? Wasn't it important to get two, so as to see a gradient (if any) between the different locations? Wouldn't this also potentially be important in terms of identifying causes, if the test is positive for SFN?
Clearly small fiber neuropathy was not on the radar of the neurologist at the outset, and it seems unfortunate that he bypassed a nearby neuropathy center for my biopsy in favor of someone who might not do so many of them (and might not know exactly the protocol in terms of number of samples, location, etc.)
I also think it is possibly uncomfortable for the neuro (older male) to have another doctor (especially a non-neurologist) come in with a suggestion of something the neuro seems to have missed. Does anyone have any ideas WHY the neuro would not have considered small fiber, when I had symptoms suggestive of neuropathy but the large fiber tests came back negative? Is this still so common, even in large cities, for doctors to miss this possibility?
One of my worries about only one sample -- suppose the one sample comes back "low normal" but a second sample further up the thigh might have indicated my "normal" should be closer to 50th percentile. My understanding is this would have been suggestive for the small fiber diagnosis. As it is, with one sample only, they can call it "normal" even if the number is just the tiniest amount above the lower limit of the reference range. If this happens, should I accept the result?
I guess on some level I am wondering if I got a stripped down test perhaps by doctor(s) who think SFN is not really worth testing for (or perhaps who would prefer not to be shown to have missed something -- especially by a non-neurologist who calls a likely diagnosis the neuro may have missed).
Does anyone here have any experience with any of these (neuros not bothering to consider SFN when the nerve conduction studies come back normal, or worries about how/where the biopsy was done, or # of punch biopsy sites being limited to just one)?
I expect the result in about two weeks. I'm wondering how much I will be able to trust the result, and really would be most grateful for any insight any of you can share concerning the diagnostic process for SFN. With the one scar (possibly in the wrong place) it will be uncomfortable to go for a second opinion, but I am wondering if I should prepare myself for that possibility, if the result seems questionable.
Sorry for the long post. Happy holidays to everyone.