A cutaneous nerve/skin biopsy is a very simple procedure performed in the outpatient setting which takes 10 to 15 minutes.
- The skin is thoroughly cleaned and a small injection of a local anesthetic to numb the skin is made.
- A sample of skin is taken by a biopsy from the numb area of the skin.
- A band-aid dressing is used to cover the biopsy site.
Generally, the skin heals easily within one to two weeks. The risk of bleeding or infection is extremely low.
Patients who are anticoagulated with INR > 2.5 should not be biopsied.
Step 1- Prepare the Area to be Biopsied
After the patient has been gowned, a clinical history has been taken, and the procedure explained, the area of skin where the biopsy is to be performed is prepared with an alcohol swab to insure sterile conditions.
Step 2 - Anesthetize the Skin
Once the skin has been prepared with alcohol, the next step is to anesthetize the area to be biopsied by injecting a solution of Lidocaine (HCL 1% and Epinephrine 1:100,000) just under the epidermis (subepidermally) using a ½ cc Tuberculin Syringe. The injection should continue until a “bleb” or bubble has formed under the skin greater than 3mm in diameter. The injection will burn slightly (much like a bee sting) due to a pH difference between the skin and the solution. The slight burning will quickly subside and the site will become numb.
Step 3 - Check for Numbness
After the initial Lidocaine injection the area to be biopsied should be checked to insure that the skin is properly anesthetized. The point of the syringe is used to poke the area of the bleb or bubble. Great care should be taken not to force the needle into the skin. The test site should be somewhere around the periphery of the bleb. Both of these precautions insure a viable biopsy for diagnosis later. If the patient experiences neither pain nor sharp sensation, the biopsy continues. A pressure sensation is normal and expected but there should be no pain. If the area requires more anesthesia, another injection (with a new syringe) is made until the skin is completely anesthetic.
Step 4 - Biopsy the Skin
After the area to be biopsied is anesthetized, the biopsy continues. Using a sterile 3mm skin punch, the physician applies pressure and twisting in a “drilling” motion until the blade of the skin punch has pierced the epidermis of the skin. The blade should be about ½ exposed. It is normal for the patient to experience a pressure and twisting sensation but no pain.
Step 5 - Remove the Skin Punch
After the blade has sufficiently “cored” or carved out a 3mm cylinder of skin the skin punch is removed. It is normal for the area to bleed after the punch is removed. Excess blood is wiped off with sterile 2 x 2 gauze to expose the biopsy site. The entire process resembles the “cookie cutter” effect. The only purpose of the skin punch is to “core” the skin and not to remove the biopsy, much like a cookie cutter.
Step 6 - Excise the Biopsy
When the skin has been cored and cleared of excess blood, the next step is to remove the biopsy from the rest of the skin. Great care should be taken not to damage the epidermis by crushing it with forceps or by cutting it with a scalpel unnecessarily. The physician uses the forceps to grab the dermis of the cored skin, pulls up the core to reveal excess dermis and subdermal fat, and uses the scalpel in one or two cutting motions to cut the cored skin free.
Step 7 - Excise the Biopsy (continued)
Notice the position of the scalpel during the excision process. The scalpel is placed under the forceps and is moved in the opposite direction of the forceps pulling on the dermis. This motion stabilizes the biopsy and aids in preventing a “chopping” or “slicing” affect when trying to free the biopsy. The physician simply utilizes one or two strokes of the scalpel to excise the biopsy with a clean cut.
Step 8 - Bandage Biopsy Site
Once the biopsy has been removed from the skin there will usually be some degree of bleeding which should be absorbed with sterile 2 x 2 gauze. The biopsy site is then covered with a standard band-aid and possibly fortified with sterile gauze and paper tape if the bleeding threatens to soak the band-aid and/or the patient’s clothing. This “hole” in the skin will continue to bleed for the rest of the day and may or may not form a scab in a few days time.
Step 8 - Biopsy Site Care
The biopsy site should be kept clean. The site should not be submerged in water (i.e. no swimming, hot tubs, baths, etc.) for a few days. The bandage should be changed at least once a day and should be changed if it should become wet or damp. Once a substantial scab has formed, or new skin begins to grow over the area and bleeding has stopped, the bandage can be removed. In the long term, minimal scaring may occur. In most cases the biopsy site is indistinguishable within a few months. In a few instances the biopsy site may form a protrusion or bump but continue to heal normally.