Skin Biopsy for Diagnosing Small Fiber Sensory Neuropathy
This web page tells you about having a punch biopsy to diagnose small fiber neuropathy. It explains what is involved and what the possible risks are. It is not meant to replace information discussed between you and your doctor but can act as a starting point for such discussions.
The sample taken from a skin biopsy is examined to provide information about your medical condition. A doctor uses a skin biopsy to diagnose or rule out certain skin conditions and diseases as well as to evaluate if your treatment is effective.
If you have any questions about the procedure please ask your doctor who has referred you to the test or the department which is going to perform it.
Why It’s Done
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, the skin biopsy is used to evaluate small sensory nerve fibers in the skin.
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 the perception of pain (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.
What are the potential complications of skin biopsy?
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.
A skin biopsy is a generally safe procedure, but complications can occur, including:
Allergic reaction to the topical antibiotic
How You Prepare
Shower before seeing your doctor for the procedure and be sure to cleanse the area with soap and water. There is no need to shave prior to the biopsy.
Before the skin biopsy, tell your doctor if you:
Have been diagnosed with a bleeding disorder
Have experienced excessive bleeding after other medical procedures
Are taking blood-thinning medications, such as aspirin, aspiring-containing medications, warfarin (Coumadin) or heparin
Have a history of skin infections, including impetigo
Are taking medications that suppress the immune system, such as diabetes medications or medications used after an organ transplant
What You Can Expect
Depending on the location of the skin biopsy, you may be asked to undress and change into a clean gown. A doctor or nurse will then clean the area of the skin to be biopsied. Your skin may be marked with a surgical marker or marking pen to outline the biopsy area.
You then receive a local anesthetic to numb the biopsy site. This is can be given as a topical cream or be given by injection with a thin needle. If injected, the numbing medication can cause a burning sensation in the skin for a few seconds. Afterward, the biopsy site is numb and you shouldn’t feel any pain or discomfort during the skin biopsy.
During the skin biopsy
For a punch biopsy, the procedure involves cutting into the top layer of fat beneath the skin, so typically stitches are not needed to close the wound. However, a stitch may be placed if a larger punch biopsy is needed or there is increased risk of infection (such as if you are diabetic or are on steroid medication).
A dressing or adhesive bandage is then placed over the site to protect the wound and prevent bleeding.
A skin biopsy typically takes about 15 minutes total, including the preparation time, dressing the wound and instructions for at-home care.
After The Skin Biopsy
Should I limit physical activity after the biopsy?
You can continue normal 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.
Try not to bump the biopsy site area or do activities that might stretch the skin. Stretching the skin could cause the wound to bleed or enlarge the scar.
How To Care For The Biopsy Site:
Your doctor may instruct you to keep the bandage over the biopsy site until the next day. Occasionally, the biopsy site bleeds after you leave the doctor’s office. This is more likely in people taking blood-thinning medications. If this occurs, apply direct pressure to the wound for 10 to 20 minutes. If bleeding continues, contact your health care provider.
All biopsies cause a small scar. Some people develop a prominent, raised scar. The risk of this is increased when a biopsy is done on the neck or upper torso, such as the back or chest. Initially, the scar will be pink and then fade to white or sometimes brown. Scars fade gradually. The scar’s permanent color will be evident one or two years after the biopsy.
Healing of the wound can take several weeks but is usually complete within two months. Wounds on legs and feet tend to heal slower than those in other areas of the body.
How to care for the biopsy site while it heals:
Keep the biopsy site bandage on until recommended by your doctor.
Wash your hands with soap and water before touching the biopsy site.
Wash the biopsy site with soap and water.
Rinse the site well.
Pat the site dry with a clean towel.
Cover the site with an adhesive bandage that allows the skin to ventilate.
Continue caring for the biopsy site until the skin is healed.
After the biopsy procedure, your doctor sends the sample to a laboratory for testing.
Your doctor may schedule an office appointment to discuss the results of the test.
Write down questions that you want to ask your doctor. Don’t be afraid to ask questions or to speak up when you don’t understand something. Questions you may want to ask include:
Based on the results, what are my next steps?
What kind of follow-up, if any, should I expect?
Are there any factors that might have affected the results of this test and, therefore, may have altered the results?
Will I need to repeat the test at some point?
How long does it take to get the biopsy report?
The biopsy report is usually generated and sent to the referring physician in 1–2 weeks.
Whom should I contact to find out and discuss the biopsy result?
You should contact your doctor who orders the skin biopsy to find out and discuss the biopsy result.
Costs & Insurance
Please contact your insurance company to verify medical coverage and to obtain any needed authorization prior to your visit. Often, your insurer’s customer service number is printed on the back of your insurance card.
Frequently Asked Questions
What is a punch biopsy?
A punch biopsy is a way of taking a small sample of tissue from your skin, using a special instrument called a punch. The name punch comes from the fact that a small, punch-size piece of skin is taken as a sample.
Is skin biopsy a very invasive procedure?
No. It is minimally invasive. Physicians routinely do a skin biopsy on 1 side at one to three sites, above the ankle (distal leg), above the knee (distal thigh), and below the hip (proximal thigh) using a 3 mm (diameter) biopsy punch. Since the biopsy size is so small, typically 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 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.
How long will it take?
Every patient is different, and it is not always easy to predict; however, the whole procedure typically takes about 10-20 minutes including the preparation time, dressing the wound and instructions for at-home care.
Do I need to discontinue certain medications before 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, your doctor 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.
How will my skin biopsy specimens be processed?
Skin biopsy specimens will be processed in our lab (Nova Labs) or locally at a pathologic lab determined by your physician. 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.
Some of your questions should have been answered by this web page or our brochure, but remember that this is only a starting point for discussion about your treatment with the doctors looking after you. Make sure you are satisfied that you have received enough information about the procedure.