Neuropathy questions, answered
Small fiber neuropathy: why it gets missed
By Dr. Jill Althoff, DC, founder of Althoff Wellness Clinic in Cheyenne, Wyoming. In practice since 2003 and author of two books on neuropathy.Short answer
Small fiber neuropathy affects the tiny sensory nerves that carry pain and temperature. It often causes burning, alternating hot and cold sensations, numbness, or sensitivity in the feet. Standard EMG and nerve conduction tests measure larger nerve fibers, so results can come back normal even when symptoms are real. A careful sensory exam that compares how different areas of your body feel can show what those tests miss.
What patients describe
Small fiber neuropathy can feel different from person to person. Some of the things I hear most:
- Burning. Some people say their feet feel like they're on fire.
- Hot, then cold. Feet that burn, then feel cold, then burn again.
- Mixed signals. The feet feel like they're burning, but when the person touches them, they're actually cold.
- Numbness or sensitivity. Some people mostly feel numb. Others are hypersensitive, so even sheets or socks feel uncomfortable.
Why it gets missed
The test most people get for neuropathy is an EMG, often with a nerve conduction study. These tests are useful, but they measure the larger nerve fibers, including the motor nerves that make your muscles contract. Small fiber damage doesn't show up on them. That's why some people are told their test was normal when they still have burning, numb feet.
Many routine office checks, like muscle strength and reflexes, also look mostly at motor function. We check those too, because they matter. But they don't tell the whole story about the sensory nerves.
The specialized test
There is a specialized test for small fiber neuropathy: a small skin biopsy, usually taken from the lower leg and sometimes compared with one from the thigh. A lab counts the tiny nerve fibers in the skin. It is ordered by medical providers, and many patients are never offered it. We don't perform biopsies at our clinic.
How we test the sensory nerves
At our clinic, we use a standardized scoring system called the Toronto Clinical Neuropathy Score, along with hands-on sensory testing. The hard part with neuropathy is that sensation is personal: how hot is hot, how cold is cold, how sharp is sharp? So we compare an area of your body that feels normal with the area that doesn't. That comparison shows which types of sensory fibers are affected and how much.
You can read more about what happens at a neuropathy evaluation.
When to see your medical doctor
If your symptoms came on suddenly, are getting worse quickly, or are joined by weakness or a foot wound that isn't healing, see your medical provider promptly. We work alongside your physician.
More from Dr. A on neuropathy
This page is educational and is not a substitute for medical advice. Individual results vary.