Muscle Biopsy

What is a muscle biopsy?

A muscle biopsy is a procedure and test that can help diagnose muscle-related conditions (myopathies). A healthcare provider takes a small sample of your skeletal muscle and sends it to a lab for analysis under a microscope.

When would I need a muscle biopsy?

Your healthcare provider may recommend a muscle biopsy if you have symptoms of myopathy (like muscle weakness) and need a more definitive diagnosis. Providers usually start the path to diagnosis with other tests, like:

• Physical and neurological exams.
• Blood tests, like a creatine kinase test or genetic testing.
• Imaging tests.
• Nerve conduction studies and electromyography.

But a muscle biopsy can provide further information and pinpoint a diagnosis. You may need a muscle biopsy if your provider suspects you have one of the following conditions:

• Muscular dystrophies, like Duchenne muscular dystrophy, Becker muscular dystrophy and myotonic dystrophy.
• Parasitic infections that affect your muscles, like trichinosis and toxoplasmosis.
• Inflammatory muscle conditions, like polymyositis and dermatomyositis.
• Metabolic myopathies, like Pompe disease and other glycogen storage diseases.
• Congenital myopathies, like nemaline myopathy.
• Toxic myopathies, like those related to steroid or statin use.

Which muscles are tested in a muscle biopsy?

Healthcare providers typically only take muscle biopsies from one of the following muscles:

• Quadricep (the large set of muscles in the front of your thigh).
• Deltoid (the muscles attached to the front, side and rear of your shoulder).
• Bicep (the muscle on the front of your upper arm between your shoulder and elbow).

The muscle your provider biopsies must have weakness or other symptoms. But your provider will make sure the muscle doesn’t have excessive weakness or recently experienced injections or injury, which could interfere with the results.

How do I prepare for a muscle biopsy?

Your healthcare provider will go over the procedure and give you instructions to prepare. Be sure to follow them, and don’t hesitate to ask questions.

In general:

• It’s important to let your healthcare provider know if you’ve received any muscle injections or muscle testing (like electromyography) in the past six months. Also, let them know if you have any muscle injuries.
• Your provider may ask you not to take aspirin or any other anticoagulant (blood thinner) medications before the procedure to prevent bleeding issues. Only stop taking prescribed medications if they tell you so.
• You may also have to fast (not eat or drink anything except water) for several hours before the biopsy.
• If you’re undergoing sedation or general anesthesia, you’ll need someone else to drive you home after the procedure.

What should I expect during a muscle biopsy procedure?

The steps of a muscle biopsy procedure differ based on the type: open or needle. You (or your child) may receive sedation or general anesthesia before either type.

Open muscle biopsy procedure

In general, the steps of an open muscle biopsy procedure include:

1. Your provider will clean the area where they’ll make the incision (cut) with an antiseptic solution.
2. They’ll then inject a local anesthetic to that area, so you won’t feel pain when they make the incision.
3. They’ll make an incision into your skin that’s about 4 to 6 centimeters long.
4. The provider will separate your skin, subcutaneous fat and muscle fascia (connective tissue) to access the underlying muscle.
5. They’ll cut out a small sample of muscle tissue.
6. Your provider will then close the fascia and your skin with sutures (stitches).
7. They’ll cover the wound with bandages and gauze.

Needle muscle biopsy procedure

In general, the steps of a needle muscle biopsy procedure include:

1. Your provider will clean the area where they’ll do the biopsy with an antiseptic solution.
2. They’ll then inject a local anesthetic to that area, so you won’t feel pain when they do the biopsy.
3. Your provider will make a small incision (cut) in your skin.
4. They’ll insert the needle biopsy instrument through the skin opening. It’s about the width of a pencil. They’ll use ultrasound imaging to guide the instrument to the muscle.
5. Your provider will then make small cuts or snips with the instrument to collect samples of muscle tissue. Once they have enough tissue — usually three to four samples — they’ll remove the instrument.
6. They’ll apply pressure to the site to stop bleeding and then cover the wound with bandages and gauze.

How painful is a muscle biopsy?

If you have general anesthesia for the procedure, you won’t feel any pain during it. If you just have a local anesthetic, you should feel little or no pain during the procedure. But you may feel uncomfortable pressure or tugging.

After the procedure, you may experience some pain for two to three days. It may be sore for up to a week if you have an open biopsy. You may also have some bruising.

Talk to your healthcare provider about how to manage pain after the procedure.

What should I expect after a needle biopsy procedure?

If you had sedation or general anesthesia, you’ll go to a recovery room to rest until the medication wears off. You can then leave, but someone else will need to drive you home. Your healthcare provider will give you instructions for caring for the biopsy wound.

After the biopsy, your healthcare provider will “flash freeze” the muscle sample with chemicals to preserve the tissue for examination. They’ll then send it to a lab where a pathologist specializing in neuromuscular diseases will examine it under a microscope. The pathologist may do other tests on the sample, like applying stains or testing for the presence of certain antibodies.

What are the risks of a muscle biopsy procedure?

Complications are rare for muscle biopsies but can include:

• Infection.
• Muscle protruding through the fascia (muscle hernia).
• Re-opening of the wound.
• Accidental injury to your muscle, nerves or blood vessels.

You may experience a scar at the biopsy site. Some people are more prone to scarring than others.

When will I get my muscle biopsy results?

Waiting for results may be the hardest part of having a muscle biopsy. Your healthcare provider will explain how and when you’ll receive results. The results may be available within a few days or more than a week. Follow up with your provider if you haven’t received the results when you expected to.

What do the results of a muscle biopsy mean?

The results of a muscle biopsy will include information on the characteristics of the muscle sample. This includes factors like:

• The structure, health and “age” of the muscle fibers (cells).
• Descriptions of other cells in the tissue, like neurons (nerve cells).
• Signs of inflammation, mitochondrial abnormalities, and glycogen and lipid storage abnormalities.

Your healthcare provider will go over the results with you and what they mean.

In some cases, the biopsy may appear normal with only minimal signs of disease. The pathologist may refer to this as “unspecified myopathy.” This could be because the biopsy didn’t get an affected part of your muscle, or because the condition is in its early stages. You may need to have another muscle biopsy.

If the muscle biopsy results are abnormal, what are the next steps?

Muscle biopsy results often lead to a diagnosis of a specific myopathy. If this is the case for you, your healthcare provider will explain the condition to you and be by your side for the next steps. Together, you’ll develop a treatment plan that’s best for you.

When should I call my healthcare provider?

If you notice signs of infection of the biopsy wound, call your healthcare provider. Symptoms can include:

• Swelling, skin discoloration or redness around the wound.
• Warmer-than-usual skin around the wound.
• Pus or drainage from the wound.
• Fever.
• Fatigue.

Will a muscle biopsy show MS?

Healthcare providers don’t typically use muscle biopsies to confirm a multiple sclerosis (MS) diagnosis. But they may recommend one to rule out other conditions that have similar symptoms to MS.