Can small fiber neuropathy present like ME/CFS?

I was diagnosed with small fiber neuropathy via skin biopsy. I'm trying to understand my health issues and I'm wondering if it's possible to have a painless form of SFN that presents with fatigue, poor sleep, exertion intolerance, mild intolerance of upright position.

I later developed more typical symptoms of SFN that include pain, but could it be that it was SFN all along?

I visited a forum for SFN patients and read patient descriptions of symptom aggravation that occurs with a delay after exertion.

 

Do SFN patients feel really unwell. Like, really unwell ME-unwell? Physical *and cognitive* exhaustion? Immune (flu-like) symptoms, sore throat, tender lymph nodes, worse in PEM/crashes..? From what I've read that's not the case, although there is of course significant symptom overlap.

I guess what I'm saying is: is there a severe 'malaise' in SFN, of the type that characterises PEM (rather than just symptom exacerbation)? I've not read anything to suggest there is.

One study found 1/3 of ME/CFS patients have SFN, so you could have both.

 

I think there may be a problem with using skin biopsies for diagnosing SFN. As I understand it the number of small nerve fibres is counted. Whether it is really possible together a reliable number out or not I don't know. I would expect the method to be very open to subjective bias.

I would not expect SFN in itself to produce fatigue, poor sleep or malaise as in PEM. Whatever caused the SFN might do but I am not sure we have much idea what the causes are, other than maybe standard things like diabetes.

 

@Hoopoe,

I have been diagnosed with SFN and have PEM like symptoms also and have wondered about this. As Jonathan says, there doesn’t seem to be any good understanding of causitive factors.

You might find this of interest. Dr. Todd Levine in the USA has a classification system he’s developed:

https://www.youtube.com/watch?v=WbvhPa-l4W4

 

I apparently have both as I get significant pem/malaise/flu like symptoms along with widespread pain and pots. I started off with mild pain and autonomic symptoms post virally which are now severe. The neuropathic pain has spread post covid from just my arms and legs to my entire face and scalp which is really unpleasant along with chronic migraines.

I’ve had a specialised neurophysiology test called microneurography which looked at the function of the varying small fibre nerves, C-fibre nerves which generate pain, along with autonomic and sudomotor nerves. All have spontaneous depolarisation meaning they were essentially over active or dysfunctional apparently not seen in healthy controls. They think the remaining “nerve sprouts” after the nerves have been damaged and regenerated cause the spontaneous activity. But it’s a specialised test so not widely in use and not been replicated much to my knowledge.

Anecdotally some of my friends who’ve had microneurography too have had over-activity of their autonomic nerves but not the c-fibre pain nerves but both were affected in my case. This seemed to correlate with whether or not they had significant pain.

This was in addition to a skin biopsy showing reduced nerve fibre density too. Genetic tests have ruled out a genetic neuropathy and other bloods for metabolic causes like diabetes and so it has been deemed idiopathic.

As I’m sure you know David Systrom/Fluge and Mella and co have speculated that SFN of the autonomic nerves can impair blood flow to the muscle and return of blood flow back to the heart so question whether hypoxia in exercising muscle is the cause of some of the symptoms like exertion intolerance.

I haven’t seen anything that has hypothesised the cause of flu like symptoms/malaise although some researchers assume that the nerves release things like CGRP/histamine/cytokines in excess. Although there’s no data to support this yet from what I know.

As my SFN has worsened I’ve developed flushing and red ear syndrome too which some class as erythromelalgia possibly due to dysfunctional small fibre nerves not controlling blood flow as they should. This has been classified as a “neurogenic flare response” of small fibre nerves by researchers such as Dr Anne Oaklander at Harvard. I have also developed what is thought of as neuropathic itch so something isn’t right with my nerves to cause all of the above.

But the question is, is the SFN a cause or consequence and what role does it play in ME especially as not all have it. Most of this is unanswered frustratingly and it’s even harder when you see yourself declining over many years.

 

Surly there is, though? It's not uncommon in diabetes, and another causal factor is long term vitamin B12 deficiency (that's why I have it). It's linked with some medications, and post-chemotherapy it can be quite severe. There are probably other known causes too.

 

Certain causes of neuropathy are quite well understood, yes. Although generally not small fibre specific. B12 goes for dorsal columns. Diabetes hits all nerve types I think. Vincristine neuropathy has a specific pattern etc.

The small fibre neuropathy said to be associated with fibromyalgia or with pain syndromes or even ME/CFS is, as far as I know, of completely unknown origin. About 50% of neuropathies have no discoverable cause - maybe the majority.