Small Fiber Peripheral Neuropathy: Prognosis (What Studies Say)

What are the symptoms of small fiber neuropathy?

Imagine your nerves as electrical wires transmitting information between different parts of your body and your brain.

Neuropathy occurs when these wires (nerves) are damaged, leading to communication problems between different parts of the body.

Our body’s nerves consist of various types of fibers, some larger and others smaller.

Small fiber neuropathy means that these finer nerve fibers closer to the surface of the skin are damaged or not functioning properly.

Symptoms of Small Fiber Peripheral Neuropathy

Small fiber neuropathy can cause the following symptoms:

• Tingling, prickling, twitching, or numbness in affected areas, like “pins and needles” in the skin.
• A sensation of burning or stabbing pain.
• Intense and persistent itching, even without obvious skin irritation.
• Excessive sensitivity to heat, cold, and light touch.
• Numbness or reduced pain perception, which can lead to injuries going unnoticed immediately.
• General symptoms such as fatigue, sleep disturbances, anxiety, or depression, as a subtype of these small fibers regulates organs and other body components managing these aspects.

These symptoms primarily affect the feet, lower limbs, and hands, but they can also occur in other parts of the body.

Diagnosis of Small Fiber Peripheral Neuropathy

The diagnosis is often made in several steps. After observations and questions, your general practitioner or neurologist has likely conducted additional examinations.

There are no very clear and consensus criteria for this disease to definitively determine whether it is small fiber neuropathy or not.

Electromyogram: This test assesses whether large nerve fibers are functioning properly. However, it does not evaluate the functioning of small fibers. Sometimes it is still performed to rule out another disease.

Skin biopsy: Cells are taken from your skin to analyze under the microscope how nerve endings function.

Other less-known tests, including those assessing your sweating.

Blood tests: Mainly to rule out other health problems.

Source: Cascio 2022

On the left, the image shows that there are fewer nerve fibers in the skin than what is considered normal (on the right). Image: Mastropaolo 2023

What are the causes of small fiber neuropathy?

In half of the people affected, there is no identified underlying cause of small fiber neuropathy.

In such cases, it is termed “idiopathic,” and it’s likely that there were genetic predispositions to develop this type of disease.

In the other half of individuals, something is at the origin:

• A hereditary disease, such as Fabry’s disease.
• Infection: Lyme disease, hepatitis C, HIV.
• Toxic cause: alcohol, chemotherapy, certain medications, or vaccines.
• Autoimmune disease: Ehlers-Danlos syndrome, lupus, chronic inflammatory demyelinating polyneuropathy, rheumatic diseases (undifferentiated connective tissue disorders, rheumatoid arthritis, psoriatic arthropathy), Sjögren’s syndrome, etc.
• Metabolic problem: diabetes mellitus (Type II), vitamin B12 deficiency, etc.

Source: Cascia 2022

Small fiber neuropathy and COVID vaccine: Is there a link?

Several hundred people per month, in United-States alone, wonder if there is a link between receiving a COVID-19 vaccine and the onset of small fiber neuropathy.

Several research teams have reported cases of small fiber neuropathy diagnosed after receiving a vaccine.

However, this is merely an association between the COVID vaccine and small fiber disease, without a clearly established causal link.

Similar to cases of Guillain-Barré syndrome (another type of neuropathy), which is more extensively studied:

“Our study reports an association between COVID-19 vaccination with the ChAdOx1 nCoV-19 vaccine after the first dose and Guillain-Barré syndrome, representing an estimated excess incidence of 5.8 cases of the syndrome per million first doses administered. The cause of this association remains unclear, and the excessive risk remains comparable to previous cases of Guillain-Barré syndrome associated with other vaccines.

The risk compared to the benefits of vaccination is very low. Further studies are needed to confirm these observations, establish a causal relationship, explore pathogenic mechanisms, and examine the effects of other COVID-19 vaccine preparations used elsewhere in the world.”

Keh 2023

There are even fewer studies and less data on the link between the COVID vaccine and small fiber neuropathy compared to the link with Guillain-Barré syndrome.

Here’s what a research team says on this matter:

“Over 220 million Americans have been fully vaccinated with the Pfizer, Moderna, or Janssen vaccine. However, only 338 incidents have been reported as ‘peripheral neuropathy’ or ‘paresthesia’ with the Pfizer vaccine in the Vaccine Adverse Event Reporting System, 257 with the Moderna vaccine, and 34 with the Janssen vaccine.

Moreover, the broader symptomatic categories in the database likely overestimate the incidence of small fiber neuropathy confirmed by skin biopsy.

Therefore, the rare incidence of this potential complication should not discourage vaccination to prevent the higher risks of morbidity and mortality associated with SARS-CoV-2 infection.”

Bernheimer 2023

What is the prognosis of small fiber neuropathy?

People I have met who had this type of neuropathy were often uncertain about its usual prognosis.

According to my perception, they even painted a bleaker picture than what is known about the evolution of people diagnosed with this condition (and followed for years in some cases).

Here’s what we know about the progression of small fiber neuropathy:

• Symptoms become more noticeable over time, but the progression is slow.
• 13 to 36% of affected people also have their larger fibers affected over time (which can lead to more symptoms).
• A few years after the onset of symptoms, you often reach a plateau: the disease no longer progresses.
• Even better: over half of the patients with this disease who were followed for two years either remained stable or improved.

Source: Cascio 2022

Here is the conclusion of the main study that follows people with this neurological disease:

“Our data suggest that small fiber neuropathy has a benign course in the majority of patients and does not severely restrict the quality of life.”

Flossdorf 2018

Of course, my goal is not to downplay the impact that small fiber neuropathy can have on some individuals but simply to reassure that symptoms may sometimes not worsen and may even regress (become less significant).

Is life expectancy reduced due to small fiber neuropathy?

There isn’t much data on whether people with this condition tend to die earlier on average than those without it. This is already a positive aspect: it implies that life expectancy is unlikely to be significantly reduced with this condition, which has been known and studied for over 40 years.

It appears that mortality is increased by 18% in individuals with small fiber neuropathy compared to those without it. However, this increase is particularly prominent in individuals who have another disease, with diabetes being a significant factor for half of them.

In reality, people more often succumb to complications related to diabetes or other underlying health issues rather than to small fiber neuropathy itself.

Source : Johnson 2021

Is disability common in the case of small fiber neuropathy?

Some people may experience reduced functionality due to small fiber neuropathy. This can be explained by at least three factors:

1. Their muscles and muscle control function less effectively due to nerve damage.
2. They move less due to pain, which can lead to complications related to inactivity and sedentary behavior.
3. They have other associated pathologies that cause disability.

If you face challenges in your daily life, personal or professional, your doctor may suggest submitting a file to the Department of Rehabilitation (DOR) or Disability Determination Services (DDS) (in the United States). These agencies provide support and services for people with disabilities, including the evaluation of disability claims and the determination of eligibility for assistance programs.

Additionally, the Social Security Administration (SSA) plays a role in disability-related matters in the United States. If someone is unable to work due to a disability, they may apply for Social Security Disability Insurance (SSDI) or Supplemental Security Income (SSI) through the SSA.

It doesn’t matter whether the difficulties you encounter are due to small fiber neuropathy or something else; what is evaluated is your health condition and difficulties, regardless of their cause.

What treatments are available for small fiber neuropathy?

A reassuring fact is that there are dozens of research teams worldwide specifically focusing on this neurological condition.

Look below: it represents the number of studies on small fiber neuropathy published in scientific journals.

These studies form the basis of my entire article, particularly this section dedicated to treatments.

However, the primary axis of treatment remains the management of associated or underlying conditions of neuropathy, such as diabetes. I won’t delve into those treatments here.

Immunoglobulins (Ig)

“Ig” stands for immunoglobulins, which are proteins produced by the immune system to help combat infections and other health issues.

In the context of small fiber neuropathy, treatment with intravenous immunoglobulins (IVIG) is sometimes employed.

IVIG is a preparation containing numerous antibodies derived from blood donations of healthy individuals.

The use of IVIG is occasionally attempted to alleviate symptoms and reduce inflammation that may contribute to nerve damage in this type of neuropathy.

However, it is a treatment whose risk-benefit balance has been relatively understudied.

The highest-quality study I identified on the subject (Gibbons 2023) shows no superior effect of IVIG treatment compared to a placebo in patients with small fiber neuropathy.

Pain Management

Medicinal and non-medicinal treatments are sometimes suggested, especially when pain is the primary concern:

• Anticonvulsants (gabapentin and pregabalin)
• Tricyclic antidepressants (amitriptyline and nortriptyline)
• Topical anesthetics (applied to the skin): 5% lidocaine
• Narcotic and non-narcotic medications
• Antiarrhythmics
• Cold
• Heat
• Massage
• Transcutaneous electrical nerve stimulation (TENS)
• Non-steroidal anti-inflammatory drugs and selective serotonin reuptake inhibitors may also be used; they are often less effective than the medications mentioned earlier
• Opioid medications: due to the risk of dependence and significant side effects, they should be reserved for refractory cases
• Relaxation
• Physical activity
• Cognitive-behavioral therapy

Source: Johnson 2021

How to “choose” among all these treatments? Should you try everything?

Depending on your specific case, not all solutions may be suitable for you.

However, there are no objectively good or bad combinations of solutions. You are the only person capable of deciding what suits you best.

In practice, you likely do this using a more or less conscious set of criteria.

You probably consider that, ideally, the solutions to adopt for managing your pain should:

• Seem effective at first glance, be plausible (vs. fanciful)
• Be likely to be genuinely effective (in light of available scientific knowledge)
• Be financially affordable
• Be pleasant to implement
• Be free of the risk of side effects
• Make you autonomous
• Be practical to apply
• Generate positive collateral effects for your physical and mental health (such as regular physical activity)
• Be deemed acceptable by your environment (family, friends, etc.)
• Be deemed acceptable by the healthcare professionals who may be caring for you (your doctor, your physiotherapist, etc.)

According to our respective sensitivities, it is perfectly normal to assign different importance to each of these criteria. That’s why there are no right or wrong solutions for you, independent of your own appreciation.

For some, taking medications will be out of the question due to a strong fear of the risk of side effects (justified or not, that’s not the issue).

For others, it is an indispensable solution.

For some, considering doing more physical activity will be perceived as very unpleasant.

For others, it will be a real pleasure. For some, resorting to professional massages is obvious. For others, it means entering a situation of dependence.

My position as a professional is that I prefer not to judge the values and preferences of others. Consequently, I do not judge the bouquet of solutions that people choose to manage their pain.

Is there a natural treatment for small fiber neuropathy?

Here is a non-exhaustive list of solutions or home remedies presented as natural and sometimes recommended by health or wellness professionals to alleviate the pain of small fiber neuropathy:

• Osteopathy
• Chiropractic care
• A healer/magnetizer
• Acupuncture
• Homeopathy
• Certain dietary supplements or diets
• Balms or creams to apply, especially plant-based ones

Here’s my honest opinion: it’s already challenging to be sure that there is a significant effect from treatments that are more studied and based on more solid theoretical foundations.

Therefore, these treatments are not the ones I recommend turning to. Of course, you are free to form your own opinion on the subject!

Can physical therapy make a difference?

Physical therapy sessions are quite often prescribed in cases of neuropathy causing significant discomfort.

Depending on the physical therapists you encounter, very different things can be offered to you. Often several. A small sample:

• Advice on coping with pain and discomfort in your daily life. This is the approach I most often adopt, and I refer to other physiotherapists if people do not adhere to this approach.
• An assessment of our daily physical activity level, and a discussion of the potential benefits for you to increase it, to help you identify if the benefit/risk/constraint balance is favorable in your case. This is also something I always propose. I am talking about physical activity (= moving) and not necessarily sports.
• Muscle strengthening or stretching exercises. Without a specific approach name, or Pilates, McKenzie type. I also offer self-rehabilitation exercises to people who explicitly request them.
• Massage, mobilizations/manipulations/manual therapy, TENS, ultrasound, or other techniques to relieve pain in the short term.

There are no studies evaluating the effect of physiotherapy specifically on people with this type of neuropathy.

Where to find testimonials on small fiber neuropathy?

In United-States, there are several associations bringing together people affected by small fiber neuropathy:

• The Foundation for Peripheral Neuropathy (La Fondation pour la Neuropathie Périphérique)
  • Website: https://www.foundationforpn.org/
• Neuropathy Action Foundation (Fondation d’Action pour la Neuropathie)
  • Website: https://www.neuropathyaction.org/
• The Neuropathy Commons
  • Website: https://www.neuropathycommons.org/
• The Peripheral Neuropathy Support Group
  • Website: https://www.neuropathy.org/

Perhaps you are one of the people who do not wish to join an association but want to exchange with others in an even less formal setting. For this, you can find testimonials in Facebook groups.

Small fiber neuropathy and knee replacement surgery?

You can also, of course, freely exchange comments here.

Here’s what I respond to Évelyne today, now that I’ve delved deeper into the subject.

You mentioned that several surgeons had deemed the operation relevant a priori.

But only one deemed it irrelevant, based on a result for a single patient.

In 2018, approximately 100,000 people received a knee replacement in France (source: health actors).

And the number of people with small fiber neuropathy is about 53 per 10,000.

This means that it is reasonable to think that about fifty people undergo surgery each year with this neuropathy (which is not a formal contraindication to the operation).

It is true that having sensory disturbances and neuropathic pain potentially exposes to more pain after the operation: those related to the knee prosthesis operation + neuropathic pain.

However, no case report has been published in the literature to support a significantly worse outcome of knee prosthesis placement in the case of small fiber neuropathy.

A study conducted on people with Sjögren’s syndrome shows that there is no significant difference in terms of outcome, provided some medical precautions are taken before the operation (Songlin 2022).

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I hope this article has addressed some of your questions! If you have remarks, additional information to provide, a testimony to share, or questions: feel free to comment 🙂.