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The symptoms of small fiber neuropathy often will appear first in the feet. ALTO IMAGES/Stocksy
  • The number of people with small fiber neuropathy has been increasing over the past 20 years.
  • The increase could be due to greater awareness as well as the increase in obesity.
  • People with small fiber neuropathy should be screened for diabetes and heart disease.

The incident rate of small fiber neuropathy (SFN) seems to have increased over the past 20 years, according to a study published today in the journal Neurology.

And one of the first signs that you might have this condition could be in your feet.

The reasons for the increase aren’t entirely clear, but there are some theories.

“I have noticed an increase in SFN over the past decade,” Dr. John Markman, a fellow of the American Academy of Neurology, told Healthline. “This might be attributable to rising rates of obesity, which is associated with SFN. There is also a greater awareness of SFN as a specific, painful condition, and that might be a factor.”

Researchers say increasing levels of obesity could also contribute to the rising number of diagnoses.

The symptoms of SFN include:

  • numbness
  • tingling
  • “pins and needles” feeling
  • pain
  • dizziness
  • fainting

Symptoms usually begin in the hands or feet and move to other areas of the body. They often worsen at night or while you’re resting.

One of the leading causes of neuropathy is diabetes. Researchers reported that about 50 percent of participants in their study with neuropathy had diabetes compared to 22 percent of those without neuropathy.

Other causes include:

  • autoimmune disorders such as Sjogren’s syndrome, lupus, or Celiac disease
  • genetic factors
  • vitamin deficiencies
  • chemotherapy drugs

However, researchers said about two-thirds of study participants with the condition had idiopathic SFN, meaning there was no known underlying cause.

Despite the potentially severe symptoms, most people do not develop significant impairments, loss of mobility, or disability from SFN.

However, they are more likely to have other health conditions. For people with SFN, there is an increased risk of heart attack, so prevention and treatment are essential.

Researchers looked at medical records of everyone diagnosed with SFN in Olmsted County, Minnesota, and the adjacent counties over 20 years.

There were 94 people with SFN and 282 participants without the condition in a control group. Researchers compared the two groups and followed them over 6 years.

The incident rate was 13 per 100,000 people, with the rate increasing throughout the study. Study findings for people with SFN include:

  • an average BMI of 30, which is considered obesity
  • more likely to have insomnia
  • more likely to have a heart attack
  • about one-half had diabetes
  • more likely to take opioids for pain

“Based on these findings, people with SFN should be screened for heart problems, and their blood glucose should be monitored for signs of diabetes,” said Dr. Christopher J. Klein, a neurologist at the Mayo Clinic in Minnesota and a fellow of the American Academy of Neurology.

“While diabetes has long been known to be the most common cause of peripheral neuropathy, obesity has more recently been demonstrated to be associated with peripheral neuropathy,” Dr. Brian C. Callaghan and Dr. J. Robinson Singleton wrote in an editorial accompanying the study in Neurology. “Treatment of metabolic risk factors is one potential intervention.”

The most definitive test when diagnosing SFN is a skin biopsy.

Medical professionals count the number of nerve fibers in the sample to determine whether SFN is present. Another diagnostic analysis is an EMG nerve conduction test. However, this is typically used to rule out large fiber neuropathy.

Many people are diagnosed based on clinical features without further testing or biopsies.

What should you do if you think you have small fiber neuropathy?

“People who think they might have SFN should consult with a neurologist as there are rare cases for which there are specific treatments that could improve or even reverse the symptoms,” explained Markman. “For patients with SFN, diagnosis of possible diabetes mellitus is particularly important as involvement of the small nerve fibers is associated with more widespread involvement with other organs, such as the heart.”

For the pain caused by idiopathic SFN, anti-seizure medication, antidepressants, or analgesics, including opiate drugs, often helps. Some people might find help with ongoing treatment at a chronic pain clinic.

“Some patients will require symptomatic treatment for neuropathic pain,” Markman noted. “Few studies have been conducted in idiopathic SFN populations, so patients and clinicians must rely on studies in other nerve pain conditions like diabetic neuropathy and postherpetic neuralgia to inform treatment decisions related to symptoms such as pain.”