Muscle biopsies

A muscle biopsy is a procedure in which a small sample of muscle – usually about the size of an orange pip – is taken and examined under a microscope. It is considered to be a ’minor’ procedure, and is usually done in outpatients under local anaesthetic or as a day case under local or general anaesthetic.

A doctor usually requests a muscle biopsy to help with diagnosis after a physical examination, blood tests, and possibly an electromyography (EMG).

What does it involve?

A muscle biopsy can be taken from any of a number of different muscles – most commonly your thigh, upper arm, shoulder or calf muscles. Your doctor will take the sample from muscle that is affected by your suspected condition, but is not severely wasted.

The muscle will re-grow in time. A muscle biopsy does not increase any muscle weakness.

There are two different types of muscle biopsy.

1. Needle biopsy

A needle biopsy involves inserting a needle, about 5mm in diameter, into your muscle. When the needle is removed, it has inside it a small sample of muscle that is taken for analysis.

The needle biopsy scar is very small, and is closed with sterile strips and a plaster. You won’t need stitches. A needle biopsy is a specialised procedure and is only performed in outpatients or as a day case at a few centres in the UK.

2. Open biopsy

An open biopsy involves making a cut in your skin to remove a muscle sample. The cut is usually just a few centimetres long. Once the sample is taken, the cut is closed with stitches.

The scar from an open biopsy is bigger than from a needle biopsy, because a bigger muscle sample has been removed. A bigger sample is sometimes necessary and makes it less likely you will need a second biopsy.

Both types of biopsy have advantages and disadvantages. Different hospitals often prefer to use different methods.

Are there any risks with muscle biopsies?

The risks associated with muscle biopsies are very small. There is a very small risk of muscle damage and infection, and you’ll often have a patch of numbness around the scar, which may last for a few weeks.

Is there an alternative to a muscle biopsy?

A muscle biopsy is a standard procedure when doctors are investigating whether you might have a muscle-wasting condition.

Molecular genetic testing is available for some conditions so in those cases a muscle biopsy may not be necessary. Doctors usually rule out any of these conditions first by analysing a blood sample. They will then decide whether or not to do a muscle biopsy too.