A nerve biopsy is a procedure in which a piece of a nerve is removed and examined under a microscope. It is used to help identify the cause of a patient’s symptoms or to confirm a diagnosis.
Prior to a nerve biopsy, the physician is likely to perform a physical examination and obtain the patient’s medical history. The patient should provide a comprehensive medical and medication history to the physician.
A nerve biopsy is usually is performed on an outpatient basis at a clinic or a hospital. A local anesthetic is used to numb the area of interest. In some biopsies, the physician makes a small incision a few inches long into the skin and removes a small portion of the nerve. In other biopsies, a hollow needle is used to withdraw a sample of nerve tissue.
Samples obtained during biopsies are examined under a microscope, and a report is prepared based on the findings of this analysis. Patients may feel minor pain or discomfort for a few days following the procedure. Patients are typically required to keep the incision dry for seven to 10 days.
Potential risks associated with a nerve biopsy are small. There is a slight risk of infection whenever the skin is broken, and some individuals can experience an allergic reaction to the anesthetic or bandaging used during the nerve biopsy. In rare cases, patients may experience permanent nerve damage following the biopsy.
About nerve biopsy
A nerve biopsy is a procedure to remove a small piece of a nerve for examination under a microscope for diagnostic purposes. It most often involves the sural nerve, which is located in ankle. The superficial radial nerve (located just above the wrist) is also sometimes used.
In some cases, nerve biopsies are performed to help diagnose the source of a patient’s symptoms that appear to be related to the nervous system. In general, nerve biopsies may identify nerve inflammation or damage (either of the axon or myelin sheath) that can be caused by a wide variety of neurological conditions. These include:
- Neuropathy. Damage, disease or inflammation of nerves. There are different types of neuropathies, including peripheral neuropathy (nerve damage that affects the limbs), focal neuropathy (localized nerve damage such as carpal tunnel syndrome) and autonomic neuropathy (nerve damage that affects involuntary body processes and internal organs).
- Neurosarcoidosis. Disease in which abnormal collections of inflammatory cells form in the tissue of the nervous system, including the brain, spinal cord and other nerves.
- Amyloidosis. Condition in which buildup of protein in body tissue (including nerves) can impair functioning.
- Necrotizing vasculitis. Inflammatory condition of blood vessels that causes tissue death, scarring and blockage of blood flow. This in turn may cause the death of tissues (including nerve tissues) supplied by the affected blood vessels.
Nerve biopsies are performed by either making a small incision and removing a nerve sample, or using a hollow needle to do the same. The nerves selected for biopsy are generally located close to the surface of the skin, requiring only small, shallow incisions to access them. In some cases, tissue from an adjacent muscle may also be extracted at the same time.
Before the nerve biopsy
Prior to a nerve biopsy, a physician will perform a physical examination and compile a thorough medical history of the patient. Blood tests may be performed, and the muscles and nerves may be tested (e.g., with an electromyography and nerve conduction velocity test). Patients typically undergo a complete neurological examination.
Patients should disclose any allergies or other medical conditions they have and information about all medications they are taking. Of particular concern are medications that can cause prolonged bleeding, including aspirin and aspirin-based products.
Typically, any preparation for a nerve biopsy is minimal. Patients may be asked to refrain from taking certain medications for a period of time prior to the biopsy.
Children may need extra parental attention and support to calm fears about the testing. It is best to be honest with children and to warn them that the test may involve minor discomfort or pain.
During the nerve biopsy
A nerve biopsy is usually performed on an outpatient basis at a medical provider’s facility or at a hospital. Prior to the biopsy, a local anesthetic is used to numb the area of interest. There may be a slight burning or stinging discomfort as the anesthesia is injected.
In some biopsies, the physician makes a small incision a few inches long into the skin and removes a small portion of the nerve. The area of the incision is closed with sutures or special adhesive strips. A pressure dressing such as an elasticized bandage will be applied to reduce bleeding and swelling during the first 24 hours after the test.
In other biopsies, a hollow needle is used. The needle is inserted into the nerve and withdrawn with a sample of nerve tissue attached.
In some cases, a muscle biopsy will also be performed at the same time as the nerve biopsy. This usually involves taking a sample of muscle tissue adjacent to the area where the nerve tissue was taken.
In general, a nerve biopsy takes less than an hour to perform. However, the length of the procedure may depend on the area of the body from which a nerve sample is taken.
Once the biopsy sample has been obtained, it is analyzed using a microscope. In some cases, individual nerve fibers within the sample also may be examined.