A muscle biopsy is the removal of a small piece of muscle tissue for examination.
This procedure is usually done while you are awake. The health care provider will apply a numbing medicine (local anesthesia) to the biopsy area.
There are two types of muscle biopsy:
A needle biopsy involves inserting a needle into the muscle. When the needle is removed, a small piece of tissue remains in the needle. More than one needle stick may be needed to get a large enough sample.
An open biopsy involves making a small cut in the skin and into the muscle. The muscle tissue is then removed.
After either type of biopsy, the tissue is sent to a laboratory for examination.
No special preparation is usually needed. If you will have anesthesia, follow instructions on not eating or drinking anything before the test.
During the biopsy, there is usually little or no discomfort. You may feel some pressure or tugging.
The anesthetic may burn or sting when injected (before the area becomes numb). After the anesthetic wears off, the area may be sore for about a week.
A muscle biopsy may be done to identify or detect:
A muscle biopsy may also be done to tell the difference between nerve and muscle disorders.
A muscle that has recently been injured, such as by an EMG needle, or is affected by a pre-existing condition, such as nerve compression, is not a good choice for a biopsy.
A normal result means the muscle is normal.
A muscle biopsy can help diagnose the following conditions:
Additional conditions under which the test may be performed include:
The risks are small, but may include:
Reviewed By: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.