Small fiber neuropathy is something that shows up in some Long COVID and post-vax patients. If you have the symptoms and want a formal diagnosis, it’s definitely worth looking into. There are tests for SFN that do come back positive in many people.
This is one of the diagnoses that can be used to gain access to IVIG. Find more info on IVIG here.
Prevalence
SFN appears at much high rates in post-vax and Long COVID… probably over >50X the general population. There is a little data here. In a paper published by Safavi and colleagues (DOI:10.1101/2022.05.16.22274439), the team at NIH/NINDS found that 12/23 (52%) of post vac neurological patients “had objective evidence of small-fiber peripheral neuropathy”. Note that the NIH/NINDS researchers selected patients with neurological symptoms as NINDS stands for National Institute of Neurological Disorders and Stroke. The rate of (peripheral) SFN may be lower in the general post-vac population.
For post-vax patients thinking about compensation, most countries don’t recognize SFN as a side effect of the COVID vaccines. However, if we push for it, it may happen. It’s on the cusp of being recognized.
Symptoms
A person experiencing pain in their feet and hands is the most common early symptom of small fiber neuropathy. However, this condition can also reduce the body’s ability to feel pain in a concentrated area and sense temperature.
As the disease progresses, people may notice symptoms in their knees, legs, and arms.
Other symptoms of small fiber neuropathy include:
- a tingling or prickling sensation
- hypersensitivity to touch and temperature changes
- numbness in the feet, legs, or lower stomach
- bladder control issues
- constipation
- sexual dysfunction
- excessive or infrequent sweating
- skin discoloration
- dry eyes and mouth
- extremely low blood pressure that may cause fainting
- rapid or irregular heartbeat
Doctors
Ways to find a specialist who actually knows about SFN…
- The website FindExpertMD.com lists people who have published a paper that mentions SFN. It lists these people by state, province, etc. Top Published Expert Doctors for Small Fiber Neuropathy
- Neuropathy specialists directory by Neuropathy Commons - Neuropathy Specialists - US | NeuropathyCommons
- Peripheral neuropathy directory - How To Find A Neurologist In My Area | List of Neurologists
- Call an infusion center that does IVIG for CIDP and ask for doctor recommendations for a
punch biopsy and IVIG treatment - Go on r/smallfiberneuropathy and ask for doctor recommendations for a punch biopsy and
IVIG treatment - For post-vax, join the FB group “IVIG for V & C19”. The group has a SMALL list of doctors that specialize in IVIG approval; join one of the vax injury facebook groups and ask for an invite in a thread that discusses IVIG approval, TD-HDS, etc.
- Try the Burning/SFN V&C Injury Facebook group???
- If you have PSSD, try to find GoldenHour’s PSSD server. Join either the Boost or Arcanechart PSSD server listed here. Then ask for an invite to the SFN server.
Testing
Not everybody with SFN will test positive on objective tests.
Skin punch biopsy - They take a tissue sample to measure nerve fiber density.
TS-HDS and FGFR3 and MAG auto-antibodies - Positive tests for auto-antibodies against TS-HDS, FGFR3, or MAG may be helpful in providing the autoimmune component of a diagnosis.
- See Emerging autoantibody lab tests - Long Haul Wiki for information on TS-HDS and FGFR3. Due to reagent shortages, you will need to check if testing is available. WUSTL may offer both tests at the moment.
- Anti-Myelin Associated Glycoprotein (MAG) is a fairly conventional auto-antibody test that can be ordered through conventional labs such as LabCorp .
Autoimmune disease - Certain autoimmune conditions are associated with SFN (e.g. Sjogren’s).
Corneal Confocal Microscopy (CCM) - Noninvasive 
. This looks at the nerves in the eye to try to find damage to small nerve fibers. Traditionally, it was used for diabetics. However, it can still be used to diagnose SFN in non-diabetics. This is not a very conventional test right now. See this post for more information.
There are other tests.
Treatment
The people who got obsessed with IVIG are also obsessed with SFN because an autoimmune SFN diagnosis is one way to get access to IVIG. Find more info on IVIG here.
Mainstream doctors often prescribe antidepressants and antiseizure medication for SFN. However, be careful. These tend to be some of the worst-rated drugs among long haulers. To find information on specific drugs, see this post as it explains how to dig up information on specific drugs. Opiods are rated higher in the survey data (*they have downsides which are well known).
Also be aware that many antidepressants can have severe side effects such as PSSD, suicide, and terrible withdrawal symptoms. There are support groups for PSSD and withdrawal. You may want to look at alternatives first as antidepressants can be very serious drugs. Antiseizure medications and gabapentin can have similar problems. Gabapentin technically is not approved for SFN or neuropathic pain; however, almost all gabapentin prescriptions are for off-label uses.