What is a muscle biopsy?

A muscle biopsy is a procedure used to diagnose muscle-wasting conditions. During the procedure, a small sample of muscle tissue is collected to be examined under a microscope. The specimen typically is collected from a muscle that is moderately affected by the suspected condition. It is a minor procedure, completed either with local anesthesia or at an outpatient clinic with general anesthesia. The sample can be collected in two ways: A needle biopsy or an open biopsy.

In a needle biopsy, a small muscle sample is collected through a needle or syringe, which is inserted into the muscle. It is a quick procedure, typically lasting only about 10 minutes, and it leaves a very small scar. This procedure is preferred. However, it only collects a small quantity of muscle tissue, which may be insufficient for some types of analysis. This type of biopsy is usually done on the quadriceps or thigh muscle, areas that often are not initially affected by all types of muscular dystrophy.

An open biopsy involves making a cut through the skin to retrieve a muscle sample. The patient will require stitches afterward, as the incision is several centimeters long. Open biopsies can be completed on any muscle and will provide enough specimen for most assessments, reducing the risk of needing further specimen collections.

How is the sample analyzed?

Once harvested, the biopsy sample is sent to a laboratory, frozen, and cut into very thin slices. Pathologists have several methods of analyzing the muscle specimens.

Histology involves the analysis of the cell structure. In muscular dystrophy patients, a pathologist might be able to use this method to recognize structural damage to the muscle fibers.

Pathologists use histochemistry analyses to review the activity of chemicals in the cells. In this technique, the specimen is dyed with chemicals. Because this method of analysis is most effective in diagnosing metabolic disorders, it usually cannot be used to diagnose patients with particular types of muscular dystrophy. It can, however, help to rule out other possible diagnoses.

Immunohistochemistry is the most precise method of diagnosing certain types of muscular dystrophies, such as Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), in which patients have reduced quantities of a protein called dystrophin. This method uses antibodies that bind to specific proteins, indicating the quantity and locations of those proteins in the muscle sample.

Are there risks associated with a muscle biopsy?

There are minimal risks associated with a muscle biopsy. Healthcare providers may recommend pain relievers for potential soreness in the two or three days following the procedure. Infection or muscle damage is rare, but indications of these risks should be reported to a member of the clinical team immediately.

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