Muscle biopsy

A muscle biopsy is a minor surgical procedure, which involves removing a small piece of muscle for analysis. There are two types of muscle biopsy; open biopsies and needle biopsies. These are usually performed under a local anaesthetic but a general anaesthetic is sometimes used, particularly in children. The muscle sample is sent to a laboratory where it is examined for various abnormalities. Results are usually available in a few weeks, but more sophisticated analysis may take months.

A muscle biopsy is usually conducted as a day case. It is undertaken to help diagnose a condition and makes it possible to determine whether the condition is primarily a muscular problem. It can help identify inflammation and in the case of a genetic disorder, indicate if a particular gene is involved and help direct molecular analysis towards that particular gene. Neuromuscular conditions often have characteristic patterns which are visible under a microscope and these can help determine the exact condition.

A muscle biopsy can be taken from any one of  a number of different muscles. The most common is the thigh muscle (quadriceps). Often the muscle is selected because it is affected by the disorder, but not severely wasted. The sample is only a few millimetres in size and with time the sampled area re-grows. A muscle biopsy does not worsen muscle weakness.

There are two different types of muscle biopsy: needle biopsy and open biopsy.

Advantages and disadvantages

Type of biopsy Advantages Disadvantages
Needle biopsy

Quicker (about 10 minutes)

Leaves a smaller scar

Can be done by neurology staff on the ward

Only obtains a small quantity of tissue which may be insufficient for more sophisticated studies

It may sometimes not be possible to get an adequate specimen for any analysis, particularly if muscle is atrophic or fatty.

Only the quadriceps muscle can be sampled

Open biopsy

Able to sample any muscle

Guarantee of getting sample

Sample large enough to do most investigations  

A bigger procedure requiring use of operating theatre (but still a minor procedure typically lasting around 30 minutes)

Leaves a larger scar (usually less than 5cm)