A nerve biopsy is a minor operation to remove a small sample of nerve for pathological testing to aid diagnosis. The operation is performed under local anesthetic. You will be asked to lie down, and a local anesthetic will be given where the biopsy will be taken. A small cut is made, and the nerve is carefully exposed. The sample of nerve is then taken. The wound is then stitched. Self-dissolving stitches are used beneath the skin and in the skin. A plaster is then applied. You should let us know if you are allergic to any types of plaster. Sural nerve at the ankle is the most common site for nerve biopsy.
Reasons for the Procedure
If someone has neuropathic symptoms or disease, examination of a small piece of nerve may give important information on the type and severity of the disease. This procedure is usually performed for evaluation of certain hereditary, autoimmune/inflammatory, infectious, and amyloid neuropathies. Establishing a diagnosis can allow specific treatment to be given. In a portion of cases, the findings are nonspecific or reflect changes seen in an end stage nerve, and a precise diagnosis may not be made even after a biopsy.
Risks of the Procedure
The wound may ooze a little, and this is normal. If there is excessive bleeding, you should seek medical advice. The wound can sometimes become infected, so you should consult your treating physician. If the wound looks red or swollen, then treatment with antibiotics may be appropriate. If you have pain or discomfort after the biopsy, when the local anesthetic has worn off, you should take simple painkillers such as Tylenol. The sural nerve supplies sensation to a small area on the outer portion of the foot. This may lead to loss of sensation or altered sensation, including a prickling sensation and/or discomfort, and occasionally persistent pain in these areas. Patients with neuropathies already have sensory loss in these areas, and the sensory loss in these areas may not be appreciated. If pain at the biopsy site remains severe and/or becomes persistent, then you might need steroid injections or another surgical procedure to remove the tip of the biopsied nerve that may have formed neuroma (entangled nerve fibers).
Stages of the Procedure
Before the Procedure
- Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure. You will be asked to sign a consent form that provides permission to perform the procedure. Read the consent form carefully and ask questions if something is not clear.
- Notify your physician if you are sensitive to or are allergic to any medications, latex, tape, and anesthetic agents (local and general).
- Notify your physician of all medications (prescribed and over-the-counter) and herbal supplements that you are taking.
- Notify your physician if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop these medications prior to the procedure.
- You will need to arrange for someone to drive you home after the procedure.
During the Procedure
A nerve biopsy is typically performed on an outpatient basis. Procedures may vary depending on your condition and your physician’s practices.
This routine is followed generally:
- You will be asked to remove clothing and will be given a gown to wear.
- During the procedure, you will need to lie as still as possible.
- The skin over the biopsy site will be cleansed with an antiseptic solution and shaved if needed.
- As the physician injects a local anesthetic to numb the area, you will feel a needle stick and a brief stinging sensation.
- Your physician will then make an incision through the numbed skin and the fatty tissue under the skin and will expose the nerve. After this he/she will obtain the biopsy specimen. You may feel a shooting sensation during the procedure. Low level of pain is not uncommon for this procedure.
- The physician will close the opening in the skin with stitches and adhesive strips.
- A sterile bandage/dressing will be applied.
- The nerve tissue sample will be sent to the laboratory for processing and examination.
After the Procedure
- Once you are home, it is important to keep the biopsy area clean and dry.
- Since self-absorbing stitches are used, they will not be removed by anyone. Adhesive strips generally will fall off within a few days.
- The biopsy site may be tender or sore for two to three days after a nerve biopsy. Take a pain reliever for soreness as recommended by your physician. Aspirin or certain other pain medications may increase the chance of bleeding. Be sure to take only recommended medications.
- Notify your physician to report any of the following:
- Drainage from the biopsy site
- Increased pain around the biopsy site
- You may resume your usual activities as instructed by your physician. Usually you will be required not to bear any weight with the biopsied leg for 2–3 days. Please keep this in mind when planning for the procedure.
- Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.
Processing of the Muscle
The nerve biopsy is processed and examined under a microscope. Different tests are performed depending on the suspected diagnosis. The processing may take at least one week or more. This is followed by detailed analysis leading to a full report, which may take up to three to four weeks. The result is sent to the referring doctor, who will then explain the findings to you. Any sample remaining after this analysis is stored in case further analysis or re-analysis is required in the future.