A muscle biopsy is the removal of a small piece of muscle tissue for examination.

A muscle biopsy may be done to identify or detect:

• Diseases of the connective tissue and blood vessels (such as polyarteritis nodosa)
• Infections that affect the muscles (such as trichinosis or toxoplasmosis)
• Muscular disorders such as muscular dystrophy or congenital myopathy
• Metabolic defects of the muscle

A muscle biopsy may be 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.

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. The tissue is sent to a laboratory for examination. 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.

No special preparation is usually needed.

During the biopsy, there is usually minimal or no discomfort. You may feel some pressure or "tugging" sensations.

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.