Hole-Punch Biopsy Testing for Peripheral Neuropathy

Many cases of Peripheral Neuropathy (PN) first begin affecting the small fiber sensory nerves that conduct physical sensations experienced in the body and that are transmitted back to the brain. This allows the brain to process these sensations, by identifying them, so that further bodily responses can be triggered in response to them. If for example, the sensory nerves detect extreme heat, that part of the body comes in contact with, a voluntary response that might follow would be to move away from the heat-source to prevent discomfort or bodily damage.

These sensory nerves, allow us to feel all kinds of sensory perceptions, such as temperature, pain, pleasure and body position. With cases of PN, these nerves can become damaged, due to a disease process within the body. Once damage occurs, the sensory perceptions can become abnormal or distorted and symptoms will result.

Symptoms of Small Fiber Sensory Neuropathy

Once enough damage to small fiber nerves has occurred, symptoms may include those in the list that follows below. Symptoms usually begin in the extremities but they can eventually affect the trunk of the body and/or organs within the body, if small fiber autonomic nerves also become affected (those controlling involuntary bodily functions):

*Tingling in the extremities

*Burning sensations

*Stabbing pains

*Numbness

*Hypersensitivity to certain normal physical sensations

*Inability to sense the position of the limbs (arms, legs, hands and feet)

*Change in function of major organs or mechanisms, such as the kidneys, heart, blood pressure and lungs (autonomic neuropathy)

The degree of symptoms experienced, varies between patients with small fiber neuropathy. Some patients may only experience tingling and numbness, while others may develop chronic pain in their limbs that requires daily medication or other pain-control therapies. In worse case scenarios, the function of major organs may become inadequate over time, causing an eventual failure of them. This however, is rare and is usually a scenario occurring in patients with sever, underlying diseases that are not well-controlled, such as chronic diabetes, or those causing autoimmunity in the body (antibodies that attack normal tissues in the body).

Confirming Small Fiber Neuropathy with a Hole-Punch Biopsy

When peripheral neuropathy of small nerves is suspected, a biopsy may be ordered, which consists of taking a small tissue sample from the lower leg, usually a few inches above the ankle from the side of the calf. This is accomplished using a small circle-shaped incisor (surgical cutting device), for extracting a very small area of epidermis (skin) from the body. The sample is then analyzed, to see if the density of small fiber nerves has decreased.

The lab conducting the analysis, will use a normal values range that tells them how many nerves should be found within the tissue sample and if the number of them falls below the reference range, small fiber neuropathy would be the likely diagnosis. This test is approximately 90% accurate for diagnosing peripheral neuropathy, meaning nerve disease that has resulted in an abnormally low number of healthy nerves present to conduct normal sensory functions.

While other tests, such as Electromyogram testing (EMG) and Nerve Conduction Velocity tests (NCV) are also commonly ordered to evaluate patients with symptoms of PN, these are directed at finding problems within large fiber nerves, while a hole-punch biopsy is specific toward finding damage in small fiber nerves.

What Causes Small Fiber Sensory Neuropathy?

According to the U.S. National Institutes of Health, no determinable cause is found in many cases of peripheral neuropathy (some sources estimate that up to 40% of cases are "idiopathic" -- no cause found). Causes that are commonly found include: diabetes, thyroid disorders, autoimmune diseases, chronic or acute viral infections, exposure to toxins, nutritional deficiencies, certain types of prescription and illegal drugs, alcohol abuse and nerve compression (pinched or physically damaged nerves).

It is important if small fiber nerve disease is suspected or peripheral neuropathy of any type is experienced, to see a medical doctor for a physical examination and possible recommendations for diagnostic tests and treatments.

Source:

The U.S. National Institutes of Health: MedLinePlus