Living with Small Fiber Neuropathy Part 1: What is Small Fiber neuropathy?

Small Fiber Neuropathy (SFN) is a disorder that affects a large group of people but can be very poorly understood among patients and the medical community.
The onset is usually heralded by pain in both feet, often first on the soles. Sensory loss or numbness, which seems to require more nerve damage, appear later. If the condition worsens, the symptoms spread proximally as shorter axons also become affected. The hands become symptomatic at about the same time as leg symptoms ascend to the mid-calf (known as a “stocking and glove” distribution). If even short fibers are damaged, symptoms can affect the torso and head. Small-fiber sensory symptoms are a mixture of numbness (sensory loss) and pain described variously as superficial and burning, deep aching, pins-and-needles, electrical shocks, or knifelike stabbing. Innocuous contact (such as with clothing or bedclothes) can become painful, as during sunburn. Small-fiber symptoms often worsen at night (when there are few distractions) and in the cold. http://sageke.sciencemag.org/cgi/content/full/2006/6/pe7

Damage to autonomic small fibers is also common (1). Patients can develop symptoms of vascular dysregulation, such as swelling or colour and temperature changes in their feet. Their skin may become thin and shiny because keratinocyte mitosis rates depend on small-fiber innervation (2). With widespread involvement, internal organ dysregulation can develop, such as impaired gastrointestinal motility (diarrhea or constipation), bladder or sexual dysfunction, and, rarely, blood-pressure abnormalities or cardiac dysrhhythmias. Of course, many polyneuropathies affect other types of axons to a greater or lesser extent, so large-fiber symptoms such as weakness, muscle atrophy or fasciculations, or loss of touch, balance, or proprioception can appear as well.

http://sageke.sciencemag.org/cgi/content/full/2006/6/pe7

This article is meant to be an introduction. The following articles in this series will be more specific with regards to latest treatments, best practice testing, as well as other conditions that can be found alongside or can be the cause Small Fiber Neuropathy. It is far from definitive, but a starting point.
A good resource: https://www.health.harvard.edu/diseases-and-conditions/new-thinking-on-peripheral-neuropathy

Living with Small Fiber Neuropathy

Small fiber neuropathy occurs when the small fibers of the peripheral nervous system are damaged. Small fibers in the skin relay sensory information about pain and temperature. In the organs, these small fibers regulate automatic functions such as heart rate and breathing. https://www.healthline.com/health/small-fiber-neuropathy

Said something
Steve Jobs

Small fiber neuropathy is a type of peripheral neuropathy. Peripheral neuropathies affect the peripheral nervous system. This includes the nerves outside of the brain and spinal cord. With small fiber neuropathy, the narrow nerve fibers of the peripheral nervous system are affected. https://www.healthline.com/health/small-fiber-neuropathy

Small fiber neuropathy has a poorly understood pathology. It can be a result of a variety of diseases, including diabetes mellitus, autoimmune disorders such as Sjögren’s or sarcoidosis, paraproteinemia, and paraneoplastic syndrome, with diabetes mellitus being the most common cause of SFN.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5912271/

There are several other causes of SFN. This will be part of the series as well.
There are simple and more complex traditional tests run to test for peripheral neuropathies. The diagnosis of SFN requires additional testing outside of traditional peripheral neuropathy testing. The simpler tests are not effective in confirming damage found as a result of Small Fiber Neuropathy, but can confirm other types of neurological damage.

During a neurologic exam, your doctor will check your reflexes, your coordination and balance, your muscle strength and tone, and your ability to feel sensations (such as light touch or cold).  https://my.clevelandclinic.org/health/diseases/14737-neuropathy/diagnosis-and-tests

There are several types of neurologists. Seeing the wrong type of specialist (sub-specialist) can lead to a misdiagnosis, or frustration on the part of both the patient and specialist.
This link helps to define different neurological specialties. https://my.clevelandclinic.org/health/diseases/14737-neuropathy/diagnosis-and-tests

The testing required to diagnose SFN is often widely misunderstood within the medical community. This has led to difficulty for many patients seeking both recognition of the pain disorder, as well as effective treatment to treat both the pain and autonomic issues.

This link helps to define different testing. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086960/

While a skin biopsy (punch biopsy) has been considered the gold standard for a diagnosis of Small Fiber Neuropathy, many other testing methods have emerged including Peripheral Nerve Ultrasounds, Thermal Threshold Technique, Laser Doppler Flare Imaging, and specific eye tests. Bloodwork should be ordered to rule out conditions that may present with similar symptoms to SFN, or that may be found as disorders that occur with SFN. My experience with this testing occurred at the “Prosserman Family Neuromuscular Clinic” in Toronto, Ontario, Canada.

There are medical treatments that are available that will be published in future articles in this series.

I hope that this article has been helpful to you. Please feel free to share this with friends and family and in groups. I am not a medical specialist, and all information is shared on an “As is” basis.
Be well.