Muscle biopsy

A muscle biopsy is a procedure to take a small sample of muscle for testing. The sample is usually taken from the muscle on the top of the leg (quadriceps muscle), but may be taken from the upper arm (deltoid muscle).

Please note, the description below of this procedure is for a needle biopsy, which is done at McMaster Children’s Hospital and some other Canadian hospitals. However, other hospitals may do a biopsy involving a larger incision.


  • Tell the doctor if your child is taking medication to “thin” the blood (anti-coagulants, aspirin).
  • Children under 9 years of age and people with severe developmental delay will be given a sedative to help them stay still during the procedure.
  • If sedation is required, the child or adult should have only fluids (nothing to eat) after midnight (the night before) and nothing to eat or drink after 4 am on the day of the procedure.


  • The area is “frozen” with an injection of local anesthetic medication.
  • The doctor makes a tiny incision (about ½ cm) and uses a needle to take a small piece of muscle, about the size of an eraser at the end of a pencil.
  • The incision is closed with a small stitch, which will need to be removed at home in 5 days.
  • The total procedure takes about 5 to 10 minutes. It is usually not painful, but your child may feel some pressure.
  • The sample is sent to the laboratory for testing. Any extra muscle tissue is kept frozen in case more tests are needed in the future.


  • Your child’s leg or arm will be wrapped in a tensor bandage, which can be taken off 1 hour after the procedure.
  • The freezing will wear off after 2 to 3 hours. It is usually not painful, but you can give your child acetaminophen (Tylenol) or ibuprofen (Advil or Motrin) for discomfort. Putting an ice pack on the area can also help.
  • To prevent a skin infection, clean the area with alcohol each day and keep it covered with a Band-Aid. Your child should not have a bath or swim for 5 days, until the stitch is taken out.
  • Your child may resume his or her regular activities when you get home. Regular stretching and movement can help prevent the leg or arm from getting stiff.
  • There is a small chance (1 in 3000) of developing a minor skin infection after a biopsy. Signs of infection are: redness, swelling, discharge from the incision and fever – a temperature above 38.5 If you notice these signs, take your child to the doctor. An infection may be treated with a medicated cream or antibiotics.

Leave a Comment