Fibromyalgia small fiber neuropathy – Brainless Blogger

There was older research on this topic Small-fiber neuropathy and fibromyalgia. But the studies have been small and different in criteria. So what could we really say about this issue and fibromyalgia? Something anyway?

But with more research, it has become clear small fiber neuropathy (SFN) has a role to play with fibromyalgia.

Fibromyalgia and small fiber neuropathy

So now we have, from a previous researcher in this area, a new study: Reduction of skin innervation is associated with a severe fibromyalgia phenotype.

This study looks at 117 women with fibromyalgia. And they did:

  • Fibromyalgia questionnaires
  • Neurological exams
  • And 5 small fiber nerve tests (including skin punch biopsy (in two places), corneal confocal, microscopy, microneurography, and quantitative sensory testing (which examined C-tactile afferents, and pain-related evoked potentials).) Prohealth

And they compared to a group with widespread pain and major depression, which also produces similar pain symptoms. I find this comparison interesting to include, because yes, major depression does have very similar widespread pain (from experience) so if you are going to have a similar control group it works quite well for that.

The results

Types of pain Prohealth


  • Pressing – 40%
  • Burning – 38%
  • Stabbing – 25%
  • Muscle soreness – 25%

With depression and widespread pain

  • Pressing – 73%
  • Burning – 55%
  • Stabbing – 36%

Small fiber nerve density


  • 37% had normal small fiber levels
  • 17% had reduced lower leg small fiber levels
  • 31% had reduced thigh small fiber levels
  • 15% had both reduced lower leg and thigh levels

Depression and widespread pain

There was only 1 patient with small fiber neuropathy presenting in the thigh


The Eyes

Small nerve fiber levels were significantly reduced in the eyes of FM patients relative to healthy controls. The small fiber levels in the eyes of people with major depressive disorder and widespread pain were, again, similar to those in the healthy controls. Prohealth

This study showed our sensitivity to heat was reduced while sensitivity to cold was increased. And that is particularly weird because “The thermal finding highlighted how different the SFN in FM is; small fiber neuropathy in other diseases is usually associated with increased heat sensitivity – but the FM patients demonstrated decreased sensitivity to heat stimuli. It’s not clear why this is.” Prohealth

Widespread nerve loss group

This group is concerning in the sense one wonders if nerve loss continues as time progresses but I suppose research will have to answer that speculation. So most of the group didn’t experience increased pain or more loss in functionality but 15% with widespread nerve loss, well, they Did. More pain and more loss of functionality. And we all know fibromyalgia is a spectrum with some of us high functioning than others.

The FM patients with the most widespread small fiber loss (in their lower legs, thighs and eyes) were in significantly more pain that FM patients without small fiber loss. They reported higher levels of pain in several areas of their body, more widespread pain, different kinds of pain (stabbing pains associated with pins and needles), plus they had higher pain intensity overall. Also, the questionnaires indicated that this group reported greater impairment and disability, had more severe symptoms overall (Fibromyalgia Impact Quotient), and were more anxious.Prohealth

Prohealth also mentions the meta-research that has been going on. I love meta-reviews where they look at all the research and make some conclusions on them all combined in data. And basically, this is an issue with us. And it affects pain and functionality in fibromyalgia.

“Our findings underscore the importance of the peripheral nervous system for FMS symptoms” – The authors

In conclusion, the biggest and most complete SNP study done yet in FM found that unusual small nerve problems and stimuli responses are commonly found and significantly upped the prevalence of small nerve fiber pathology to 63%.  Plus, the study indicated that small fiber pathology may not be, as has been suggested, a mostly benign problem. More widespread small nerve pathology was associated with increased pain, disability, functionality, etc.

My thoughts

What we have here is something that is quite important to fibromyalgia research and management. And quite important to us when it comes to pain and functionality levels. I have long been fascinated with this research because of the spontaneous peripheral neuropathy I developed that couldn’t be explained. Different, yes, but it made me interested in nerve issues and fibromyalgia. Yes, we know fibromyalgia is a pain processing issue. We have seen research it might involve neuroinflammation. But this research shows fibromyalgia is also IN the body and it is also causing its own set of complex issues with us. And again… is this something we have and then it gets worse over time or is it something we have at a certain level that just maintains over time? That is a question I would like answered because that could say a lot about what fibromyalgia is doing to the body and What type of condition it Is. Not progressive vs. progressive. A question we have all wondered about and as it stands it has always been said it is not progressive and does not over time get worse. But one wonders.

I have to say this avenue of research is the most important line of research I have seen. Because of the fact it shows something is going on with us that can explain multiple issues. And I do hope it leads to some sort of treatment or management.

Now there was also research that suggested some people with fibromyalgia are misdiagnosed and actually have small-fiber polyneuropathy. And certainly, that made me wonder as well. Do we have a neuropathic condition, or syndrome in our case, and are some of us misdiagnosed with fibromyalgia when they have a different neuropathic condition?

See more:

Fibromyalgia and sensory sensitivity

Fibromyalgia: Why do we itch?

Peripheral neuropathy awareness week
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