What is small fiber neuropathy?

Neuropathy No More By JODI KNAPP Neuropathy No More is an eBook which is a compilation of all the essential information and details about the nervous system and how to keep it active and healthy. With the help of this program, one can get a relief from the symptoms of neuropathy. This eBook not only tells you about the nervous system, but also helps to provide essential information to get relief from the condition of neuropathy. It also provides information about how you can prevent this condition from coming back in the near future.

What is small fiber neuropathy?

Small fiber neuropathy (SFN) is a type of peripheral neuropathy that specifically affects the small nerve fibers in the peripheral nervous system. These small fibers, known as C fibers and A-delta fibers, are responsible for transmitting sensory information about pain, temperature, and autonomic functions (such as sweating, heart rate, and blood pressure regulation). In SFN, these fibers become damaged, leading to a variety of sensory and autonomic symptoms. Unlike large fiber neuropathy, SFN typically does not affect muscle strength or reflexes, as these functions are controlled by larger nerve fibers.

Causes of Small Fiber Neuropathy:

Small fiber neuropathy can have a variety of causes, including underlying medical conditions, genetic factors, or unknown origins (idiopathic). Some of the most common causes include:

Diabetes:
- Diabetic neuropathy is one of the most common causes of SFN. Chronically high blood sugar levels can damage small nerve fibers over time, leading to sensory and autonomic symptoms.
Pre-diabetes (Impaired Glucose Tolerance):
- Some individuals with pre-diabetes can develop SFN due to fluctuations in blood sugar levels, even before developing full-blown diabetes.
Autoimmune Diseases:
- Conditions like Sjogren’s syndrome, lupus, and sarcoidosis can cause the immune system to attack small nerve fibers, resulting in neuropathy.
Vitamin Deficiencies:
- Deficiencies in vitamins that are essential for nerve health, particularly vitamin B12, can lead to small fiber damage. Other deficiencies, such as vitamin D or folate, can also contribute.
Genetic Causes:
- Some forms of SFN are hereditary, such as Fabry disease or other rare genetic disorders that affect small nerve fibers.
Infections:
- Certain infections, such as HIV, Lyme disease, and hepatitis C, can lead to small fiber damage.
Toxins or Medications:
- Exposure to certain toxins (e.g., heavy metals, chemotherapy drugs) or medications can damage small nerve fibers.
Idiopathic Small Fiber Neuropathy:
- In many cases, the cause of SFN remains unknown, and the condition is classified as idiopathic. This is particularly common in older adults.

Symptoms of Small Fiber Neuropathy:

The symptoms of SFN are primarily sensory and autonomic in nature and can range from mild to severe. The condition often affects the extremities (feet and hands) first but can also impact other areas of the body.

Sensory Symptoms:
- Pain: People with SFN often experience burning, stabbing, or shooting pain, particularly in the feet or hands.
- Tingling and Numbness: Tingling sensations or numbness may develop in the affected areas, usually starting in the feet and progressing upwards (a “stocking-glove” pattern).
- Increased Sensitivity (Hyperalgesia): Many individuals become overly sensitive to pain. Even light touch, such as the brushing of clothes against the skin, can cause discomfort (a phenomenon known as allodynia).
- Temperature Sensitivity: Patients may have difficulty distinguishing between hot and cold, or they may experience exaggerated reactions to temperature changes.
Autonomic Symptoms:
- Sweating Abnormalities: People with SFN may experience excessive sweating (hyperhidrosis) or a lack of sweating (anhidrosis), which can affect their ability to regulate body temperature.
- Heart Rate and Blood Pressure Changes: Some individuals may have orthostatic hypotension (a sudden drop in blood pressure upon standing), which can cause dizziness or fainting.
- Gastrointestinal Symptoms: Autonomic dysfunction can affect digestion, leading to symptoms such as bloating, constipation, or diarrhea.
- Urinary and Sexual Dysfunction: SFN can cause difficulty with bladder control or sexual function, including erectile dysfunction or vaginal dryness.

Diagnosis of Small Fiber Neuropathy:

Diagnosing SFN can be challenging, as standard tests for peripheral neuropathy (such as nerve conduction studies) typically do not detect small fiber damage. Therefore, the diagnosis often relies on a combination of clinical evaluation and specialized tests, such as:

Clinical Examination:
- A neurologist will evaluate symptoms, perform a physical exam, and assess the patient’s medical history. The doctor will look for sensory changes, especially in response to pain or temperature.
Skin Biopsy:
- One of the most definitive diagnostic tools for SFN is a skin biopsy, which involves taking a small sample of skin to assess the density of small nerve fibers. In people with SFN, the nerve fiber density is usually reduced.
Quantitative Sudomotor Axon Reflex Test (QSART):
- This test measures the autonomic function of small fibers by evaluating the body’s ability to sweat in response to stimulation. Abnormal sweating patterns can indicate small fiber damage.
Other Autonomic Function Tests:
- Tests such as heart rate variability (to assess autonomic control of the heart) and tilt-table tests (to evaluate blood pressure regulation) may be used if autonomic symptoms are present.
Blood Tests:
- Blood tests can be used to rule out underlying causes, such as diabetes, vitamin deficiencies, autoimmune diseases, or infections.

Treatment for Small Fiber Neuropathy:

The treatment for SFN depends largely on the underlying cause. If a treatable condition like diabetes or a vitamin deficiency is identified, addressing the root cause can slow the progression or even reverse some symptoms. However, if the cause is unknown or cannot be treated, the focus is on managing symptoms.

Medications for Pain Relief:
- Anticonvulsants: Medications like gabapentin and pregabalin are often prescribed to manage nerve pain.
- Antidepressants: Amitriptyline, duloxetine, and other tricyclic or serotonin-norepinephrine reuptake inhibitors (SNRIs) can be effective in treating neuropathic pain.
- Topical Treatments: Capsaicin cream or lidocaine patches can be applied to the skin to reduce localized pain.
- Pain Relievers: Over-the-counter pain relievers, such as ibuprofen or acetaminophen, may be used for mild discomfort, but they are generally not effective for severe neuropathic pain.
Treating Underlying Conditions:
- If SFN is caused by diabetes, controlling blood sugar levels is essential to prevent further nerve damage.
- Vitamin supplementation (e.g., B12, folate) may be necessary if deficiencies are contributing to nerve damage.
- Autoimmune disorders may require treatment with immunosuppressants or corticosteroids to reduce inflammation affecting the nerves.
Lifestyle Modifications:
- Exercise: Regular physical activity can help improve circulation and reduce pain. Low-impact exercises like swimming or walking are particularly beneficial.
- Healthy Diet: A balanced diet rich in essential vitamins and nutrients supports overall nerve health.
- Smoking Cessation and Limiting Alcohol: Smoking and alcohol use can worsen neuropathy, so avoiding these habits is important.
Physical Therapy:
- Physical therapy can help maintain muscle strength and flexibility, and improve balance for those who experience numbness or pain in the extremities.
Managing Autonomic Symptoms:
- Autonomic dysfunction, such as blood pressure irregularities or gastrointestinal issues, may require specific treatments, such as medications to regulate heart rate or dietary changes to manage digestion.

Prognosis:

The prognosis for small fiber neuropathy depends on the underlying cause and how well it is managed. In some cases, addressing the root cause (such as controlling diabetes or correcting vitamin deficiencies) can lead to improvement or stabilization of symptoms. However, if the cause remains unknown or untreatable, SFN can progress over time, leading to chronic pain or disability. Early diagnosis and treatment are crucial in preventing further nerve damage and managing symptoms effectively.

In summary, small fiber neuropathy is a condition that affects the small sensory and autonomic nerve fibers, leading to pain, sensory disturbances, and autonomic dysfunction. It can be caused by various underlying conditions or remain idiopathic, and treatment focuses on managing symptoms and addressing the root cause when possible.

Jodi Knapp