Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder that leads to the loss of nerve cells. The disease is caused by genetic mutations, but also may be caused by environmental factors such as smoking or alcohol use.

Diagnosing ALS can be difficult and multiple tests usually are required to confirm a diagnosis.

A muscle biopsy can be used to diagnose ALS, but is more likely to be used to eliminate other possible diagnoses and to monitor the progression of the disease by comparing muscle biopsies taken over the lifetime of the patient.

What is a muscle biopsy?

A muscle biopsy is the surgical removal of a small piece of muscle that will then be analyzed in the laboratory. Generally, the procedure is performed either on the bicep (the muscle of the upper arm) or the quadriceps (the muscle of the upper thigh).

How is a muscle biopsy performed?

The procedure is very quick. The surgical site is first numbed by injecting a local anesthetic. A small incision of one to two inches in length is then made in the skin, and three to five small pieces of muscle tissue are removed. Finally, the surgical incision is sealed. Depending on the surgeon, this could be done with stitches, staples, or surgical glue.

The patient should not feel the surgical procedure at all. Patients should not use the limb that has been biopsied for about 24 hours. Pain after the procedure should be minimal and is usually manageable with over-the-counter pain medications. Patients will not need to stay in the hospital after the procedure unless they experience complications like uncontrolled bleeding.

What information can be obtained from a muscle biopsy?

The muscle pieces obtained with a biopsy can be stained and examined under a microscope allowing the medical team to visualize the nerves directly. The extent of nerve damage can be seen and compared to previous biopsies if there are any.

The muscle biopsy also may be used to distinguish between different forms of ALS, which are caused by different mutations, as well as muscular dystrophy. The nerve bundles present in each small slice of tissue obtained with the biopsy can be visualized with a stain and counted under a microscope. In ALS nerve atrophy (shrinkage) is present, i.e., instead of a nerve web spreading into the muscle like the roots of a tree, the nerves are blunted, or withered, and may cluster together. Researchers also may see changes in muscle morphology (the appearance and shape of the muscle cells) such as muscular atrophy or abnormalities in the mitochondria, which can affect the amount of energy available to the muscle.

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ALS News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.