Small Fiber Neuropathy

[Howie830]

I have been experiencing neuropathic pain in both feet for the last 3-4 years.  Common symptoms include burning or tingling pain, fullness, pins and needles, and extreme coldness.  Additionally, I have frequent fasciculations in both calves as well as visible pulsations on the inside of the foot.  Lyrica has helped a bit, but not enough.

I have had many investigations into foot conditions and other situations that never revealed any positive findings, including:

EMGs/NCVs
Spinal MRI (no nerve root cause found)
Ultrasound (post. tibial nerve)
Arterial ultrasound
Blood work (negative for conditions causing neuropathy, also normal levels of fasting glucose, A1C, lipids)
Neurologic examination

Finally, I turned my focus to the possibility of small fiber neuropathy and had a skin biopsy with the following report:

Distal Leg - The epidermal nerve fiber density is within a normal range.  Many of the fibers have a fragmented appearance and a few contain swellings.
Distal Thigh – The epidermal nerve fiber density is within a normal range and the distribution of nerve fibers is normal.
Prox Thigh – The epidermis is well-innervated.
Summary:  The epidermal nerve fiber density is within a normal range at all three sites and therefore there is no definitive evidence of a neuropathic process affecting small caliber sensory nerve fibers.

Unfortunately, this report leaves me guessing.  It is equivocal in that it identifies pathologies, but only concludes that it does not constitute "definitive" evidence of a small fiber neuropathy.  I also note that none of the biopsy sites were in the foot where the predominant symptoms are located, the distal leg being closest.

I would appreciate any insights you could give me as to the interpretation of these results and also your advice as to what should be done next to confirm or exclude the diagnosis.  Also, I would appreciate any suggestions for treatment or other tests to determine a cause.

[Christopher R Newey, DO]

Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.

Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.

Briefly, with small fiber neuropathies, symptoms include burning or buzzing or other vague symptoms starting in the feet and hands then in some cases spreading to other parts of the body. The EMG/nerve conduction studies (NCS) (tests done to check for neuropathy) will not show an abnormality, and a definitive diagnosis can only be made with a skin biopsy so that the number of nerve endings can literally be counted. There are other tests of the function of small nerves that can be ordered, such as QSART testing which looks at how much sweat the skin makes, since sweating is in a sense of function of these small nerves. There are several causes of small fiber neuropathy, including diabetes, vitamin deficiencies, and autoimmune problems.

It is possible that the sampling for the biopsy may not have identified the area of abnormality or the interpretation of the specimen may not have been accurate. However, small fiber neuropathy can be difficult to diagnose. I would suggest you follow up with a neuromuscular neurologist at a large academic university to have a more detailed examination and workup.

Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.

[jeff9933]

I have the same symptoms you described and have had many of the same tests.  My doctor has me on Neurontin which has little or no effect.  In addition to your symptoms, my feet feel as if they have broken bones at times and in the last few months have begun having problems with the calfs and general weakness in the legs.  Just writing to let you know you are not alone.