Small Fiber Neuropathy - Underlying Causes, Symptoms, Diagnosis, and Treatment

What Is Small Fiber Neuropathy?

It is a painful condition where the small nerve fibers of the body get damaged. These small fibers belong to the peripheral nervous system, including all the nerves that branch out from the brain and spinal cord. Small fiber neuropathy causes pain, tingling, and burning in different body parts. Affected individuals suffer altered sensations in their hands and feet on both sides. It tends to start in the feet and move up to the legs and eventually affects the hands. As time passes, the symptoms grow severe. Neuropathy may affect other areas and functions of the body as well, leading to issues with digestion, sweating, and urination. The symptoms associated with small fiber neuropathy can be mildly annoying to extremely painful and debilitating.

What Are the Causes for Small Fiber Neuropathy?

The small fibers of the peripheral nervous system belong to two categories. There are somatic nerves that go into the skin and muscles. And there are autonomic nerves that connect the brain and spinal cord to the internal organs such as; the heart, stomach, etc. Peripheral nerves send sensory information from various body parts to the brain and spinal cord. They also pass on the commands from the brain to different organs. Damage to these nerves can be the initial symptom of some undiagnosed disease conditions in the individual as well.

The affected individual is more sensitive to pain than an unaffected individual. This increased sensitivity is termed hyperalgesia. They even feel pain from simulations that are not normally painful. Also, they are seen to lose the ability to tell the difference between hot and cold. There are several other symptoms too. Following are the possible causes for small fiber neuropathy:

• The most common cause of small fiber neuropathy is diabetes.

• Hormone disorders, hypothyroidism (due to low thyroid levels), or immune system disorders.

• Hereditary diseases such as; amyloidosis, sensory, autonomic neuropathy, and more.

• Metabolic syndrome involves high blood pressure, high blood cholesterol, obesity, and abnormal glucose metabolism.

• Syndromes such as Guillain-Barre syndrome or Sjogren’s syndrome.

• Infectious diseases such as; hepatitis, human immunodeficiency virus (HIV), Lyme disease,

• Conditions like Fabry disease, Tangier disease, celiac disease, inflammatory bowel disease, lupus, and mixed connective tissue disease.

• Disorders like sarcoidosis, scleroderma, vasculitis, psoriasis.

• Adverse reactions to medications like chemotherapy drugs.

• Alcohol abuse.

• Chronic kidney disease.

• Vitamin deficiencies, specifically vitamin B12.

• Those with impaired glucose tolerance (body’s response to sugar), age above 65 years, and male gender are at a higher risk.

• Sometimes small fiber neuropathy starts without any known underlying cause too.

What Are the Symptoms Suggestive of Small Fiber Neuropathy?

Pain is the major symptom associated with small fiber neuropathy. In the early stages, symptoms may be mild. As it typically affects the feet first and then moves up to affect the hand, the condition is always mentioned as a ‘stocking-and-glove’ pattern of symptom distribution.

When the somatic nerve fibers are affected, one suffers the following symptoms:

1. Sudden pain in the form of severe short bursts.

2. Neuropathic symptoms such as itching, burning, prickling, tingling, and numbness on the hand and legs.

3. Sensations like sunburn or frostbite.

4. Tightening or squeezing sensation at the feet, as if there is a sock stuffed at the end of the shoe.

5. Occasional spasms or cramps.

6. Muscle weakness, lack of coordination, and tendency to stumble.

7. Loss of sensation in the affected body part.

8. Symptoms get worse at the end of the day.

9. It is worse while sitting down or lying in bed.

10. Even the slightest touches of bed linen or cool air trigger the pain.

11. Cold weather makes the symptoms worse.

12. Some suffer electric shock-like sensations on the face along with tingling in the arms, lasting for minutes to hours.

When autonomic nerve fibers are affected, one suffers:

1. Dryness of mouth and eyes.

2. Lack of sweat or too much sweating.

3. Constipation.

4. Incontinence.

5. Sexual dysfunction.

6. Discolorations in the skin.

7. Occasional dizziness due to low blood pressure.

How Is Small Fiber Neuropathy Diagnosed?

As small fiber neuropathy may be the starting symptom of an undetected disease condition, the diagnosis often aims at identifying the underlying cause. The doctor will review the medical history and family history of the affected individual and listen to their symptoms. There are several tests conducted to diagnose small fiber neuropathy, such as:

• Skin Biopsy - This is the most effective test of all. The doctor will obtain small samples of skin tissue from the affected areas. These samples are microscopically examined to identify signs of neuropathy. The test aims to look at the number of nerve cells present in a given quantity of skin (intraepidermal nerve fiber density). Usually, the samples are taken from the legs where the symptoms often start.

• Reflex Testing - This tests the neuropathy involving the autonomic nerves. Here, a mild electric shock is used to stimulate the skin to measure the sweat output. If the amount of sweat produced is low, it is indicative of small fiber neuropathy.

• Electromyography Test - Is done to evaluate the nerve function by measuring the electrical signals sent from the nerve to the muscles.

• Lab Tests - Additionally, one may order necessary lab tests to identify the underlying causes of diabetes and others.

What Are the Treatment Strategies for Small Fiber Neuropathy?

The primary goal of treating small fiber neuropathy is alleviating the symptoms by treating the underlying cause of the disease. The treatment involves:

1. Medical management of diabetes or glucose tolerance issues by drugs to regulate blood sugar levels, lifestyle changes, and special diet plans.

2. The agonizing pain caused by small fiber neuropathy can be treated with topical pain creams and pain-relieving drugs. In addition, immunosuppressive drugs like corticosteroids help reduce nerve damage by suppressing the immune system.

3. Doctors may prescribe antidepressants and anticonvulsants as well, according to the individual's requirements.

Conclusion:

Small fiber neuropathy is a slowly progressing condition in most affected individuals. The pain symptoms may worsen as the disease progresses, though some people have shown spontaneous recovery. Treating the underlying disease condition is the best way to resolve the symptoms. There are several methods available to manage pain medically. Discussing the symptoms with a qualified medical practitioner is the first step toward managing the complications of small fiber neuropathy.