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) |
After the biopsy
There might be some bleeding straight after the procedure, but this will stop when pressure is applied to the site. There is a certain risk for an infection around the surgical site. This risk is very small. There may be some pain afterwards, requiring paracetamol or other pain medication.
We usually advise bed rest for 2 hours immediately after the procedure. It's wise to have a friend or relative to drive you home after the procedure to minimise walking. We advise that you should not drive yourself home after the procedure.
Risks and alternatives
Risks
The risks associated with muscle biopsies are very small. The commonest problem after needle biopsy is bleeding, usually resulting in some localised bruising. Rarely the bruising may be more extensive causing swelling of the region and very rarely this may require medical attention. With all neuromuscular conditions, care must be taken when using general anaesthetics, and for this reason local anaesthetics are preferred where possible. For all muscle biopsies it is assumed that the patient is at risk for malignant hyperthermia (an adverse reaction) and the precipitating anaesthetic agents are avoided, so the risk is negligible There is a small risk of muscle damage and infection, but these are very rare. It is not uncommon to have a patch of numbness around the scar which may last for a few weeks.
Special arrangement are required for patients on Warfarin or other anticoagulants, and a clear plan made prior to biopsy.
Is there an alternative?
A muscle biopsy is a standard procedure when testing for most muscle conditions. Molecular genetic testing is available for some conditions and a muscle biopsy may not be necessary, but this applies to only a few disorders. It is common for these conditions to be excluded using a blood sample before a muscle biopsy is performed.