Do you have small fiber neuropathy (SFN)?

Do you have small fiber neuropathy (SFN)?

  • I have ME/CFS and have SFN

    Votes: 10 33.3%

  • I have ME/CFS and do NOT have SFN

    Votes: 6 20.0%

  • I don’t have ME/CFS but I have SFN

    Votes: 0 0.0%

  • I don’t have ME/CFS but I do NOT have SFN

    Votes: 0 0.0%

  • I have ME/CFS but am not sure if I have SFN/tests inconclusive

    Votes: 14 46.7%
  • Total voters
    30
You need to include an option for 'dont know' or something similar. The neuro thinks i likely have SFN but cannot say definitively - large nerve fibres are in good nick & even skin biopsy only rarely shows SFN up so not been tested - it will remain as "SFN??" on my medical notes forever I think. So would you have me answer yes or no?
 
JemPD said:
You need to include an option for 'dont know' or something similar. The neuro thinks i likely have SFN but cannot say definitively - large nerve fibres are in good nick & even skin biopsy only rarely shows SFN up so not been tested - it will remain as "SFN??" on my medical notes forever I think. So would you have me answer yes or no?
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OK added
 
JemPD said:
You need to include an option for 'dont know' or something similar. The neuro thinks i likely have SFN but cannot say definitively - large nerve fibres are in good nick & even skin biopsy only rarely shows SFN up so not been tested - it will remain as "SFN??" on my medical notes forever I think. So would you have me answer yes or no?
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There's a 'not sure' option, which will likely apply to many of us, especially in the UK where testing is sparse.
 
I might do, as I gained some new symptoms—one being tingling feet and lower legs—after a significant vitamin B12 deficiency. But tingling feet and lower legs are probably really common in people of middle age and older, so who knows.
 
SFN, SjD, POTS, and well MECFS i would fit with CNS PEM, for the physical I cant be sure as POTS limits my mobility and I never push through that due to limb weakness.
 
Do we have a reliable test?
I note that the normal skin biopsy score drops by a factor of four by my age. So it seems that you can lose 3/4 of your small fibres and just be a normal oldish person. I have loads of symptoms of neuropathies but then I know I have lots of focal neuropathies (shown by my colleague on electropyhsiology) and maybe some general small fibre failure but I don't have ME/CFS.

It all seems a bit vague to me.
 
Jonathan Edwards said:
Do we have a reliable test?
I note that the normal skin biopsy score drops by a factor of four by my age. So it seems that you can lose 3/4 of your small fibres and just be a normal oldish person. I have loads of symptoms of neuropathies but then I know I have lots of focal neuropathies (shown by my colleague on electropyhsiology) and maybe some general small fibre failure but I don't have ME/CFS.

It all seems a bit vague to me.
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Yes it drops by age, this is why the reference range is for age groups, 20-29, 30-39, 40-49, 50-59, 60-69 etc, and for females and males separately. Male have significantly higher nerve density to begin with but even in Europe, labs pay attention to correct ref. ranges.

I agree it seems vague to someone who is not in that field.
 
The age matters, no? I presume you don't get SFN when young or middle-aged and healthy. There has to be a reason for low nerve fiber density other than aging in these age groups. The reason is a disease of some kind and the SFN is just one manifestation of it.

My grandmother also has symptoms of neuropathic pain that sounds like SFN but she does not have the other severe symptoms that are described as associated with SFN. I experienced them and they were a nightmare and there was nothing vague about them. Someone who has not experienced them cannot comprehend the experience.

Like with other tests, the result has to be interpreted in a broader context.
 
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Hoopoe said:
I presume you don't get SFN when young or middle-aged and healthy.
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I think in 5%-10% of those HCs have a positive IEFND.

IEFND is well documented to deliver positive and negative results depending on the choice of sample, sample handling and who counts the fibers and on what day of the week. I suspect you need the kind of rigorous methodlogy we hardly ever get to see in ME/CFS research. Anecdotal stories probably only confuse the picture even more. If ME/CFS involves neuropathy and even small fibers, as the case for other conditions, how do we get to somewhere where one has meaningful research and results that can tell us something?
 
I selected ‘am not sure if I have SFN/tests inconclusive’, but have never considered if there is any possibility that I might have SFN, no medic has ever suggested it as possibility, but then I have never discussed any potential underlying medical issues relating to my ME/CFS with any doctor, except more recent cardiovascular issues.

What symptoms might suggest possible SFN involvement?
 
EndME said:
I think in 5%-10% of those HCs have a positive IEFND.

IEFND is well documented to deliver positive and negative results depending on the choice of sample, sample handling and who counts the fibers and on what day of the week. I suspect you need the kind of rigorous methodlogy we hardly ever get to see in ME/CFS research. Anecdotal stories probably only confuse the picture even more. If ME/CFS involves neuropathy and even small fibers, as the case for other conditions, how do we get to somewhere where one has meaningful research and results that can tell us something?
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day of the week? Can you provide a source? How would they possibly repeat a biopsy in the same week cos you get a wound on your leg that takes weeks to heal, so you might be saying they repeated it on the other site of the body? It is still not too relevant for non-length-dependent SFN which is the autoimmune SFN linked to younger age and dysautonomias and can be 'patchy' as well..
 
Pibee said:
day of the week? Can you provide a source? How would they possibly repeat a biopsy in the same week cos you get a wound on your leg that takes weeks to heal, so you might be saying they repeated it on the other site of the body? It is still not too relevant for non-length-dependent SFN which is the autoimmune SFN linked to younger age and dysautonomias and can be 'patchy' as well..
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Nobody ever said anybody had to repeat a biopsy. Please read what people write. Intra-observer reproducibility is studied. Results actually seem good but obviously that's not the point.
 
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EndME said:
Results actually seem good but obviously that's not the point.
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If the results seem to be good, I wonder after all this back and forth, what is the point and what is the reason you were not accepting the data that 30-40% of MECFS have confirmed SFN and some claim it is a bigger number when multiple sites are biopsied, as some have non-length-dependent SFN.
 
Pibee said:
If the results seem to be good, I wonder after all this back and forth, what is the point and what is the reason you were not accepting the data that 30-40% of MECFS have confirmed SFN and some claim it is a bigger number when multiple sites are biopsied, as some have non-length-dependent SFN.
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Because obviously intra-observer reproducability is not all that matters. Which is what is already well document and has been already been discussed (obviously the number gets bigger when multiple sites are biopsied since this already applies to perfectly healthy controls as shown across studies).
 
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According to David Systrom, a skin punch biopsy should be taken from several sites and deep enough to include sweat glands. In other words, proper technique is important.


However, this diagnosis isn’t straightforward, and a doctor may need additional tests such as QSART, QST, an active standing test, and others. Some neurologists use either the Besta or NEURODIAB criteria. Unfortunately, there’s no reliable test for every condition in medicine.


Many people diagnosed by skin punch biopsy report fatigue and muscle aches [1].


I developed SFN gradually after a mild case of COVID-19—sock-and-glove aches, allodynia, muscle aches and cramps, orthostatic and exercise intolerance. I don’t have access to a skin punch biopsy, but confocal corneal microscopy is positive. Unfortunately, neurologists don’t want to hear about SFN. Even here, I feel as if I’m talking about something marginal.


I’m curious what role SFN plays in my ME/CFS. Is it just a comorbidity? A phenotype of ME/CFS? Or do I have SFN rather than ME/CFS?


The problem is that there’s almost no research. If RECOVER releases tissue-study data, we’ll probably learn more.
 
Formerhuman said:
According to David Systrom, a skin punch biopsy should be taken from several sites and deep enough to include sweat glands. In other words, proper technique is important.


However, this diagnosis isn’t straightforward, and a doctor may need additional tests such as QSART, QST, an active standing test, and others. Some neurologists use either the Besta or NEURODIAB criteria. Unfortunately, there’s no reliable test for every condition in medicine.
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The prof I saw in the UK explained my negative punch biopsy this way, along the lines of "well of course it was negative, your neuropathy is not length-dependent so you'd need biopsy samples from multiple locations to show it".

Instead I was sent for a microneurography investigation. Abnormalities there + context was enough for them to make a confident SFN diagnosis.
 
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