What’s a nerve biopsy?
A nerve biopsy is a procedure where 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’re experiencing numbness, pain, or weakness in your extremities. You might experience these symptoms in your fingers or toes.
A nerve biopsy can help your doctor determine whether your symptoms are caused by:
- damage to the myelin sheath, which covers the nerves
- damage to the small nerves
- destruction of the axon, the fiber-like extensions of the nerve cell that help carry signals
Numerous conditions and nerve dysfunctions can affect your nerves. Your doctor may order a nerve biopsy if they believe you may have one of the following conditions:
- alcoholic neuropathy
- axillary nerve dysfunction
- brachial plexus neuropathy, which affects the upper shoulder
- Charcot-Marie-Tooth disease, a genetic disorder affecting the peripheral nerves
- common peroneal nerve dysfunction, such as drop foot
- distal median nerve dysfunction
- mononeuritis multiplex, which affects at least two separate areas of the body
- necrotizing vasculitis, which occurs when the blood vessel walls are inflamed
- neurosarcoidosis, a chronic inflammatory disease
- radial nerve dysfunction
- tibial nerve dysfunction
The major risk associated with a nerve biopsy is long-term nerve damage. But this is extremely rare since your surgeon will be very careful when choosing which nerve to biopsy. Typically, a nerve biopsy will be performed on the wrist or the ankle.
It’s common for a small area around the biopsy to remain numb for about 6 to 12 months after the procedure. In some cases, the loss of feeling will be permanent. But because the location is small and unused, most people aren’t bothered by it.
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 don’t require much preparation for the person being biopsied. But 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, such as pain relievers, anticoagulants, and certain supplements
- have your blood drawn for a blood test
- refrain from eating and drinking 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’re having problems. These include a:
- sensory nerve biopsy
- selective motor nerve biopsy
- fascicular nerve biopsy
For each type of biopsy, you’ll be given a local anesthetic that numbs the affected area. You’ll likely remain awake throughout the procedure. Your doctor will make a small surgical incision and remove a small portion of the nerve. They will then close the incision with stitches.
The portion of nerve sampled will be sent to a laboratory for testing.
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 isn’t very noticeable.
Selective motor nerve biopsy
A motor nerve is one that controls a muscle. This procedure is done when a motor nerve is affected, and 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.
After the biopsy, you’ll 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’ll 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 treatment for your condition.