Skin Biopsy for Small Fiber Sensory Neuropathy

Overview

What is small fiber sensory neuropathy?

Small fiber sensory neuropathy (SFSN) is a type of neuropathy that predominately affects small-caliber sensory nerve fibers, which control perception of pinprick, cold and heat stimuli. Patients with SFSN usually present with numbness, tingling (pins and needles sensation), and pain. Although the symptoms may involve any part of the body, it often affects feet the most. The pain is usually described as burning, stabbing or electric-like.

Why do I need a skin biopsy to diagnose small fiber sensory neuropathy?

Small fibers travel too slow and their conduction responses cannot be captured by nerve conduction study/EMG which is a routine test performed to evaluate for large sensory and motor nerve fibers. Therefore, skin biopsy is used to evaluate small sensory nerve fibers in the skin.

Is skin biopsy a very invasive procedure?

No. It is minimally invasive. We routinely do skin biopsy on 1 side at 3 sites, above ankle (distal leg), above knee (distal thigh), and below hip (proximal thigh) using a 3 mm (diameter) biopsy punch. Since the biopsy size is so small, no stitches are needed. The biopsy sites will be healed within 1 week, but will leave small scars.

Is skin biopsy very painful?

No. The whole procedure takes about 10–15 minutes. The only time you will feel pain is when Lidocaine is injected to numb your skin; you may feel a burning sensation for about 5 seconds. The procedure is very well tolerated.

What are the potential complications of skin biopsy?

The potential complications are bleeding and infection of biopsy sites. The risk of complications is very low if you follow the written aftercare instructions, which will be given and explained to you when you come for the biopsy.

Do I need to discontinue certain medications before the biopsy and should I limit physical activity after the biopsy?

In general, you do not need to discontinue your medications before the biopsy. If you are on an oral blood thinner such as Coumadin, you may switch it temporarily to subcutaneous injection of Heparin 2 days before the biopsy under the direction of the doctor who put you on Coumadin. You may resume Coumadin after the biopsy. You can continue activity as usual after the biopsy. You can take a shower. However, to prevent infection, you may not go swimming or take a bath in the first week.

How will my skin biopsy specimens be processed?

Skin biopsy specimens will be processed in our skin lab (CCF Cutaneous Nerve Laboratory). Each skin biopsy specimen will be cut into 50–60 sections. Some of the sections will be immunostained using an antibody against a nerve marker (PGP9.5) to highlight small sensory nerve fibers in the skin. The sections will then be viewed under a microscope to count the number of small nerve fibers in the epidermis of the skin. The diagnosis of small fiber sensory neuropathy will be made if the small nerve fiber density is reduced as compared to normal persons.