Small fiber neuropathy is damage to the small nerve fibers that carry pain, temperature and autonomic signals (the automatic ones, like sweating). It causes burning, tingling and prickling in the feet. Strength, reflexes and vibration sense stay normal. A standard nerve conduction study cannot see it.
This is the neuropathy that standard nerve testing misses. If you have burning feet and a normal nerve conduction study, this is usually why.
What is small fiber neuropathy?
Peripheral nerves (the nerves in the arms and legs) hold two kinds of fibers. Large fibers are wrapped in a thick coat called myelin. Small fibers have a thin coat or none. The small fibers carry pain, temperature and autonomic signals. They are the first to be damaged in diabetes and in most metabolic and toxic neuropathies.
Damage to them causes burning, tingling, electric or prickling feelings. Touch can feel too sharp. Sweating is often off. Yet strength, reflexes and vibration sense stay fully normal.
Why is my nerve conduction test normal?
Nerve conduction studies measure large fibers only. They cannot test small fibers at all. So a patient with real, severe small-fiber neuropathy gets a normal study. He is told the nerves are fine. He is left to think the pain is in his head.
That is a limit of the test, not a finding about the patient. Nerve conduction testing is still useful. It rules out large-fiber damage and finds pinched nerves. But a normal result does not rule out small-fiber disease.
What a normal nerve study actually rules out
It argues against large-fiber neuropathy, a pinched nerve root and a trapped nerve. It says nothing at all about small fibers. You may be told ‘your nerve test was normal’ after a study that never looked at the fibers causing your symptoms. That is one of the more crushing moments in this condition. It is avoidable if someone explains what was measured.
What test confirms small fiber neuropathy?
- The clinical pattern, which stands out. It is the same on both sides, starts in the feet, burns, is worse at night and at rest, and is better with movement.
- Bedside small-fiber testing: pinprick and hot-versus-cold tests in the office. They map the small fibers directly.
- Autonomic signs: changes in sweating, skin color and temperature in the affected area.
- Skin biopsy to count the nerve fibers in the skin (intraepidermal nerve fiber density). It is the gold standard when the diagnosis truly matters and is still unclear.
What causes small fiber neuropathy?
Diabetes and prediabetes are the most common causes in this region. Sugar starts to damage small fibers well below the diabetes cutoff. Other causes: B12 deficiency, thyroid disease, alcohol, chemotherapy, HIV, autoimmune conditions including Sjögren’s, and several medications.
A real share of people have no cause found after a full workup. That is honest to say. It does not stop us from treating the pain.
Does small fiber neuropathy ever go away?
It can, because small fibers regrow. Long-standing large-fiber loss does not. But small-fiber damage caught early can truly improve once the cause is corrected — see can diabetic neuropathy be reversed. Missing the diagnosis wastes the exact window when that is possible.
To get checked, call or text us. We are at 12174 Natural Bridge Rd, Suite 110, St. Louis, MO 63044.
Common questions
What are the symptoms of small fiber neuropathy?
Burning, tingling, electric or prickling feelings, touch that feels too sharp, and often off sweating. It is the same on both sides and starts farthest from the body, in the feet. It is worse at night and at rest and better with movement. Strength, reflexes and vibration sense stay fully normal. That is why a standard nerve conduction study can miss it.
What autoimmune disease causes small fiber neuropathy?
Sjögren’s is one. Autoimmune conditions as a group are a known cause. Diabetes and prediabetes are the most common causes in this region. B12 deficiency, thyroid disease, alcohol, chemotherapy, HIV and several medications also cause it. A real share of patients have no cause found after a full workup.
Can small fiber neuropathy be treated if no cause is found?
Yes. A real share of patients have no cause found after a full workup. That is honest to say. It does not stop us from treating the pain. The workup still matters, because when a cause such as diabetes, prediabetes or B12 deficiency is found and corrected, small fibers can regrow and early damage can truly improve.
My nerve test was normal, so why do my feet burn?
Because nerve conduction studies measure large fibers, and your symptoms come from small ones. A normal study does not rule out small-fiber neuropathy.
Do I need a skin biopsy?
Not usually. The symptom pattern plus office testing is enough in most cases. Biopsy is kept for truly unclear cases where the answer would change the treatment.
Is it progressive?
It can be. It often spreads to the large fibers if the cause goes untreated. That is the case for finding the cause early.
The Stages of Diabetic Neuropathy sets out how small-fiber damage progresses to large-fiber loss.
Can it happen without diabetes?
Yes. B12 deficiency, thyroid disease, alcohol, chemotherapy and autoimmune conditions all cause it. Some people have no cause found.
Small fiber loss is one input into balance. Inner-ear function is another, and the two fail independently — see balance and fall-risk assessment.
Alcohol injures nerve directly and nutritionally at the same time.
Sources
- Kool D et al. Small fiber neuropathy. International review of neurobiology, 2024. PubMed 39580213
- Devigili G et al. Clinical diagnosis and management of small fiber neuropathy: an update on best practice. Expert review of neurotherapeutics, 2020. PubMed 32654574
- Finsterer J et al. Small fiber neuropathy. Acta neurologica Scandinavica, 2022. PubMed 35130356
- Furia A et al. Small-Fiber Neuropathy: An Etiology-Oriented Review. Brain sciences, 2025. PubMed 40002491
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