What is Small Fiber Neuropathy

In the last few years we’ve seen many articles about the overlap of small fiber neuropathy (or small fiber polyneuropathy – same thing) in Fibromyalgia and the hope that we may be able to use skin biopsies of these small fiber nerves to diagnose Fibromyalgia. I’ll be honest I thought for a while we were just seeing the same study popping back up in the news (and it frustrated me); however, I’ve realized I was wrong. There have actually been a couple of studies in as many years that have made this connection. That said all of the studies I’ve read have been very small (less than 30 participants), and they are not finding that all of the Fibromyalgia patients have this (only about 50% of those in the studies). However, these studies may be a stepping stone to uncovering one potential cause for the pain associated with Fibromyalgia.

But, what is Small Fiber Neuropathy?

Small Fiber Polyneuropathy (SFPN) is a disease (yes, an actual disease) that cause degeneration in the small fiber neurons. The small fiber nerves are the ones that transmit the information about pain and temperature. These small fibers are also involved in many areas of the autonomic nervous system (the part that controls the automatic features like breathing, digestion, blood flow), so it’s a little more than just burning and itching in the feet.

Small Fiber Neuropathy is more than just burning and itching hands and feet.

Unlike problems in the large nerves small fiber neuropathies don’t show up in EMG and nerve conduction studies. SFPN is most commonly associated with diabetes, but can be caused by a variety of other diseases and illnesses, and can even be genetic. A skin biopsy is the primary way of diagnosing SFPN. Unfortunately, diagnosis of SFPN doesn’t do much for those of us with Fibromyalgia except perhaps make us feel like we have a better diagnosis than just Fibromyalgia. The treatments for SFPN are basically the same ones that we already use for Fibromyalgia (anti-depressants, anti-convulsants, topical pain treatments, gabapentin, and tramadol to name a few.

What are the symptoms of Small Fiber Neuropathy?

  • Painful burning/ itching feeling in the hands and feet – this seemsto be the primary symptom
    • Often worse at night and/or made worse with heat or cold – often people can’t stand to have the sheets touching their feet.
    • Alcohol can also increase this symptom
  • Digestive symptoms including diarrhea, constipation, nausea, vomiting
  • Urinary incontinence
  • Periods of increased heartbeat
  • Dry eyes/ mouth
  • Abnormal sweating
  • orthostatic hypotension
  • erectile dysfunction
  • Skin changes in affected areas

 

Interestingly, I have pretty much all of the symptoms listed, and so many of these are symptoms we often attribute to “just Fibro”. My diagnosis journey began with burning and tingling in my hands, a variety of tests turned up nothing. I’ve often had a burning in my feet (and they get red and puffy) if I do much walking but I just wrote it off as the effects of walking too much in poorly fitted shoes. Then in December I noticed that I was waking up with this extreme burning in my feet. They would feel like they were burning but also as if they were extremely dry, even if I’d put lotion on them just before I went to sleep. To feel my feet the skin didn’t feel dry to the touch, but that’s the sensation that was being transmitted to my brain (along with the severe burning). I noticed that more and more often they were also very red and puffy looking. After doing some research I found that this is a (rare) side effect of the medication I was on for migraines (Verapamil) and when I told my neurologist about the symptoms he had me stop the med. The symptoms did decrease after about a month off of Verapamil but they haven’t completely disappeared. I think they were there all along I just hadn’t really connected them. I have noticed that the tingling in my hands and the burning in my feet are much worse on nights when I’ve been drinking. I would never have thought to connect the other issues like the urinary and digestive issues had I not read it for myself in the NIH documentation.

Do you also have painful tingling and burning in your hands and feet? How many of the other symptoms do you have?

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