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More Than Skin-Deep: The Small Nerve Fiber Problems in Fibromyalgia – A Review

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Reprinted with the kind permission of Cort Johnson and Health Rising.

We don’t generally connect fibromyalgia with skin problems. The skin, though, may present an important window into what’s going on in fibromyalgia.

We use the blood vessels and sweat glands in our skin to warm or cool us. Both blood flows and sweat glands are largely controlled by the autonomic nervous system (ANS) – a system of concern in FM. The skin also tells the brain via its sensory nerves what our body’s local environment is like. Aberrant nerve transmission along these nerves could cause pain, numbness or other symptoms. The skin contains unmyelinated nerves that appear to be under attack in some people with FM.

From the autonomic nervous system to blood flows to sensory issues, the skin is packed full of possibilities for understanding FM.

Nobody has yet attempted to use skin findings to solve a big problem in FM – how to diagnose it. FM, like ME/CFS, is diagnosed using symptoms.

The Study
This group measured different indices of the sympathetic skin response (SSR). SSR activity reflects “the electrical potential of the skin.” In simpler terms, it measures the activity of the sweat glands located in your skin. An electric pulse is applied to the hand or foot, and the response – a reflection of how the sympathetic nervous system is doing – is measured.

This test is often used to determine how well the peripheral nervous system is doing in diseases like peripheral neuropathy that knock out the nerves in the skin. If the neuropathy gets really bad, as in diabetes, no SSR at all will show up; the nerves are apparently dead. Since we have evidence of small fiber neuropathy in fibromyalgia, we would expect some changes to be found.

In total, the Turkish researchers measured a wide range of mostly commonly found lab tests. Then they attempted to determine which combination of tests diagnosed the FM patients and the healthy controls accurately.

  • physiological tests -skin temperature, heart and breathing rate

  • laboratory tests – rheumatoid factor (RF), c-reactive protein (CRP), white blood cell count (WBC), hemoglobin count (HB), platelet count (PLT) and sedimentation (sedim)

  • skin sympathetic nervous system parameters (latency response time, total time and maximum amplitude values)

If they could pull this off – and if the medical world validates their findings – we could have the first biological test for fibromyalgia ever. That would be a welcome development regarding the naysayers who still believe that FM is not real or is a psychological disease.

Results
The findings suggested that basic, easy to identify aspects of the FM patient’s physiology had been disturbed. Adding the sympathetic skin response to the mix boosted their accuracy in identifying FM patients correctly to about 98% and the sensitivity to 100%.

 

Increased latency times seen in the sympathetic skin test of FM patients indicated that their systems were responding much more slowly than usual to the electrical impulses. They didn’t manifest the kind of obliterated responses sometimes seen in diabetic patients – where no SSR response is found at all – but the increased response times suggested some damage had occurred.

Increased latency times have been associated with increased anxiety in another study. That finding brought to mind a recent post on Facebook which asked why even small things now bothered her/him so much? That’s a question I’ve been asking myself for decades. My guess is that a tweaky autonomic nervous system is involved.

Small Fiber Neuropathy and Fibromyalgia – A Short Review
A flurry of findings in 2014 suggested that from 30-40% of FM patients had a condition called small fiber neuropathy (SFN). Small fiber neuropathy refers to damage to the small, unmyelinated nerve fibers found in our skin and elsewhere.

That finding shocked researchers who’d presumed that the damage to FM patients stopped below their heads. Since that time, several studies have validated those results. The question now is not whether SFN exists in FM, but how prevalent it is and why it’s occurring. Some work is being done in both of those areas.

Just last year, a Spanish study suggested that reduced mitochondrial activity and increased oxidative stress in the skin of FM patients could play a role.

Earlier this year, Martinez-Lavin’s findings of decreased corneal nerve thickness suggested that the damage to the peripheral nerves in FM wasn’t confined to the unmyelinated C-nerve fibers in the skin. Whatever was happening to FM patients could be happening in other types of nerves. Besides, the skin unmyelinated or “C” nerve fibers are also found in the dorsal of the spinal cord and reach up into brain stem and thalamus. The study also introduced an easy to use and non-invasive testing methodology. (No skin punches needed.) (The corneal nerve issues found do not affect sight.)

The most intriguing study, however, popped up just two months in Sommer’s comparison of nerve fiber density which showed the greatest reductions in nerve fiber diameter in the FM patients.

That entirely unexpected finding suggested a different kind of pathology is occurring in FM than in other people with SFN. In fact, Sommers called what she found “small fiber pathology” instead of small fiber neuropathy to distinguish it from the more common forms of small fiber neuropathy.

At least one other study is underway. Anne Oaklander hypothesizes that the present SFN testing regimens misdiagnose over half the adults under the age of 35 experiencing widespread pain. She’s in the midst of a multi-million dollar NIH-funded study to see if that’s so.

She’ll be examining a wide variety of tests (including corneal tests) to determine which tests best identify SFN in people with widespread pain. She’ll also attempt to figure out what’s causing SFN using blood tests and a close examination of the skin. Finally, she’ll assess how effective several treatments are.

The $3 million or so study began last year, and it’s slated to end (ouch) in 2020. I imagine, though, that it’s proceeding step by step, and we’ll find out if the rates for SFN will double in younger adults soon. That result would surely focus more interest on SFN.


About the Author: ProHealth is pleased to share information from Cort Johnson.  Cort has had ME/CFS for over 30 years. The founder of Phoenix Rising and Health Rising, he has contributed hundreds of blogs on chronic fatigue syndrome, fibromyalgia and their allied disorders over the past 10 years. Find more of Cort's and other bloggers' work at Health Rising.

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