A nerve biopsy is a testing procedure in which a small sample of a nerve is removed from your body and examined in a laboratory.
Your doctor may request a nerve biopsy if you are experiencing numbness, pain, or weakness in your extremities, such as in your fingers or toes. A nerve biopsy can help your doctor determine whether your symptoms are caused by:
- damage to the covering of a nerve (called the myelin sheath)
- damage to the small nerves
- destruction of the axon in the nerve cell (the fiber-like extensions of the cell that help carry signals)
- neuropathies (inflammatory nerve conditions)
Numerous conditions and nerve dysfunctions can affect your nerves. According to the National Institutes of Health (NIH), your doctor may order a nerve biopsy if he or she believes you may have one of the following conditions (NIH, 2011):
- alcoholic neuropathy
- axillary nerve dysfunction
- brachial plexopathy
- Charcot-Marie-Tooth disease
- common peroneal nerve dysfunction
- distal median nerve dysfunction
- mononeuritis multiplex
- necrotizing vasculitis
- radial nerve dysfunction
- tibial nerve dysfunction
The major risk associated with a nerve biopsy is long-term nerve damage. However, this is extremely rare since your surgeon will be very careful when choosing which nerve to biopsy. Typically, a nerve biopsy will be done on the wrist or the ankle.
According to New York University Medical Center, it is common for a small area around the biopsy to remain numb for about six to 12 months after the procedure. In some cases, the loss of feeling will be permanent. However, because the location is small and unused, most patients are not bothered by it (NYU, 2007).
Other risks might include minor discomfort after the biopsy, allergic reaction to the anesthetic, and infection. Talk to your doctor about how to minimize your risks.
Biopsies do not require much preparation on the part of the patient. However, depending on your condition, your doctor may ask you to:
- undergo a physical examination and complete medical history
- stop taking any medications that affect bleeding (including pain relievers, anticoagulants, and certain supplements)
- have your blood drawn for a blood test
- fast (including liquids) for up to eight hours before the procedure
- arrange for someone to drive you home
Your doctor may choose from three types of nerve biopsies, depending on the area where you are having problems. These include: sensory nerve biopsy, selective motor nerve biopsy, and fascicular nerve biopsy.
Sensory Nerve Biopsy
For this procedure, a 1-inch patch of a sensory nerve is removed from your ankle or shin. This could cause temporary or permanent numbness to part of the top or side of the foot, but is not very noticeable.
Selective Motor Nerve Biopsy
This is done when a motor nerve (one that controls a muscle) is affected. A sample is typically taken from a nerve in the inner thigh.
Fascicular Nerve Biopsy
During this procedure, the nerve is exposed and separated. Each section is given a small electrical impulse to determine which sensory nerve should be removed.
For each type of biopsy, you will be given a local anesthesia that numbs the affected area. You will remain awake throughout the procedure. Your doctor will make a small surgical incision and remove a small portion of the nerve. He or she will then close the incision with stitches.
The portion of nerve sampled will be sent to a laboratory for testing.
After the biopsy, you will be free to leave the doctor’s office and go about your day. It may take up to several weeks for the results to come back from the laboratory.
You will need to care for the surgical wound by keeping it clean and bandaged until your doctor takes out the stitches. Make sure to follow your doctor’s instructions in caring for your wound.
When your biopsy results are back from the lab, your doctor will schedule a follow-up appointment to discuss the results. Depending on the findings, you may need other tests or your doctor may begin treatment for your condition.