What the small fibers do.
Your peripheral nerves are not all the same size. NINDS describes small-fiber neuropathy as affecting the small fibers that carry pain and temperature sensation. Standard nerve conduction studies and EMG assess the larger fibers, which is why they can miss a problem confined to the small ones.
When those small fibers are damaged, NINDS describes the sensory consequence plainly: an inability to feel pain or changes in temperature. Peer-reviewed descriptions add the other half — burning pain and pins-and-needles sensations, often starting in the feet.
Here is the part that explains a lot of frustrating appointments. Because nerve conduction studies and EMG read only the large fibers, a neuropathy confined to the small ones can leave those tests looking entirely normal. A normal EMG does not rule it out — that is a limit of the instrument, not evidence that nothing is wrong.
Why this comes up in POTS conversations.
Small autonomic fibers also help blood vessels tighten when you stand. One hypothesis under study is that when they underperform in the legs, blood pools rather than returning to the heart and the heart speeds up to compensate. That is a proposed mechanism for one subtype, not a settled explanation of POTS.
The numbers are substantial. The Heart Rhythm Society's consensus statement reports that up to 50 percent of patients with POTS have a restricted autonomic neuropathy of small and distal postganglionic sudomotor fibers, predominantly of the feet and toes. Researchers sometimes call this the neuropathic subtype of POTS.
But hold that loosely. The 2019 NIH expert consensus meeting on POTS is candid that the syndrome's mechanisms are incompletely understood and undoubtedly multifaceted, and that no data show long-term prognosis or treatment response differing by mechanism. Finding small fiber involvement names something real; it does not yet come with a different prognosis attached.
How it is actually established.
Skin biopsy is the established method. NINDS describes a neurodiagnostic skin biopsy as examining nerve fiber endings after removing a tiny piece of skin under local anesthesia, and notes it is used most often for small fiber neuropathies that nerve conduction studies and EMG do not detect. A clinician takes a small punch of skin — typically 3 to 5 millimeters, usually from the lower leg — and a lab counts the nerve fibers in it. That count is the intraepidermal nerve fiber density. Peer-reviewed work describes skin biopsy as the most sensitive method available for diagnosing small fiber neuropathy.
Sweat testing is the common companion. NINDS notes that QSART measures the ability to sweat at several sites on the arm and leg, and that abnormalities on it are associated with small fiber neuropathies. One Cleveland Clinic review of POTS patients found reduced sweat output in 33 percent of those given QSART and reduced nerve fiber density in 24 percent of those biopsied — a real subset, not everyone.
Corneal confocal microscopy comes up as a noninvasive future option that skips the punch biopsy. Be careful with it: the first study applying it to POTS patients was a preliminary analysis of nine people and found no statistically significant difference between groups. It is a research tool, not a substitute for biopsy.
The Heart Rhythm Society consensus adds a caution worth repeating — detailed autonomic testing should not be done routinely, because there is no evidence it improves care for most patients. Whether it is worth doing in your case is a conversation with a neurologist or autonomic specialist.
Where this practice fits — and where it does not.
Gates Brain Health does not diagnose small fiber neuropathy. Establishing it takes skin biopsy and laboratory analysis, and that pathway runs through a neurologist or autonomic specialist. If that is the question you need answered, ask your primary care provider for a neurology referral. It is the right route, and it is not this office.
Care here is complementary functional neurology, provided by Dr. Randall Gates, D.C., DACNB — a board-certified chiropractic neurologist, not a medical doctor. The practice's published focus includes POTS among the chronic neurological conditions it works with. It runs alongside your primary care provider and any specialist you see rather than replacing them, and medication decisions stay with the prescribing clinician. Nothing here regenerates nerves or resolves symptoms, and whether an evaluation makes sense for you is decided on a call.
Fainting that causes injury, fainting during exercise, chest pain, or severe shortness of breath need urgent medical attention now. Call 911 or get to an emergency room rather than waiting for any office appointment.
Questions worth asking.
What an examination here involves is described on the treatment page rather than repeated here. If you are considering calling (775) 507-2000, these are worth raising:
- Has anyone tested my small fiber function, or has my normal EMG been treated as the end of the question?
- Should I ask my primary care provider for a neurology referral before doing anything else?
- Does an evaluation here make sense alongside what my cardiologist or neurologist has already found?
- Which records should I bring — biopsy or autonomic testing results, tilt-table findings, recent labs?
- What does the free consultation cover before I commit to anything?