Small fiber neuropathy in fibromyalgia

Many Fibromyalgia Patients Have Small-Fiber Polyneuropathy – October 18, 2012 – medscape.com – Daniel M. Keller, PhD

In a small study of patients labeled as having fibromyalgia, almost half actually had small-fiber polyneuropathy (SFPN), a potentially treatable condition.

Dr. Oaklander noted that despite an emphasis on central mechanisms as the cause of fibromyalgia, these findings suggest that a specific — and sometimes treatable — type of peripheral neuropathy is a common cause of the condition.

It seems like quite a leap to assume the neuropathy is the *cause* of fibromyalgia. Another article from 4 years later (summarized below) suggests the opposite: that fibromyalgia is the cause of the peripheral neuropathy. 

“This is exciting for us because it’s the beginning of objective data on what the actual cause of patients’ symptoms may be,” she said.

Widespread Chronic Pain

her laboratory tested the hypothesis that some patients with fibromyalgia may have SFPN, which “produces widespread chronic pain and very similar symptoms.

The difference though is that small-fiber polyneuropathy is a true disease, meaning that there are objective tests for it, known causes, and the possibility of disease-modifying treatments and cure,” Dr. Oaklander told Medscape Medical News.

“The diagnostic criterion, universally accepted around the world, is that someone whose nerve fiber density in their biopsy is below the fifth centile of predicted value is considered to have definite small-fiber polyneuropathy,” Dr. Oaklander said

“The major finding of our study is that half of the cohort of fibromyalgia patients but none of an age-matched control group had evidence of nerve loss. And so to neurologists this meets the diagnostic criteria for small-fiber polyneuropathy.”

For the various tests overall, 46% of the patients with fibromyalgia and 17% of controls (P < .001) met the rigorous criteria for SFPN.

Link to Diabetes

“The significance of this finding is that unlike with fibromyalgia there are known causes of small-fiber polyneuropathy, many of which are amenable to treatment,” Dr. Oaklander pointed out.

In all of her studies, she said that when she found small-fiber polyneuropathy, “a substantial proportion of patients turn out to have either diabetes or pre-diabetes. Most of them don’t even know that. It’s so common.

“We noticed that virtually all of the patients that we were able to give an ultimate diagnosis of small-fiber [polyneuropathy] in fact said, ‘Oh, I’ve been told I have fibromyalgia for the last 10 years’.”

Although fibromyalgia is purely a clinical diagnosis, this new information may add to the understanding of the pain syndrome “so it could be useful,”

Small fiber neuropathy in fibromyalgia: cause or consequence? – March 8, 2016 – BodyInMind

Dan Clauw recently wrote an insightful editorial for Pain, in which he highlighted an important finding about the idea that people with fibromyalgia show signs of ‘small fibre neuropathy’.

Changes in intra-epidermal nerve fibres (‘small fibres’) have been shown in many clinical conditions, including conditions that are characterised by chronic pain.  

So the idea that people with fibromyalgia show such changes is not revolutionary.

However, the study Clauw refers to also examined the nature of the changes, comparing small fibre biopsies in people with fibromyalgia to healthy controls and to people with the classic signs and symptoms of ‘small fibre neuropathy’.  

Unsurprisingly, the nature of the changes in fibromyalgia differ from those in classic small fibre neuropathy, which the authors interpreted as suggesting that the mechanisms driving the changes probably differ, too.

There is sufficient evidence to firmly support the view that chronic pain conditions like fibromyalgia cannot be caused exclusively by peripheral disease: the central nervous system appears to be a major player.

Indeed, it is far more likely that the central nervous system drives the changes in intra-epidermal nerve fibres (concomitant with probable changes in many other peripheral structures) that are seen in people with fibromyalgia and in other chronic pain conditions.

Source: BodyinMind was developed by Professor Lorimer Moseley and Digital Publishing Consultant Heidi Allen, as a method to promote better understanding of the clinical pain sciences.

 

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