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)

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)

Needle biopsy

Needle biospies are performed on the neurological day unit, within the Wessex Neurological Centre. Although the procedure is short, you will often be asked to attend the ward in the morning for blood tests prior to the procedure. After the procedure two hours bedrest is advised so in practice most of the day can be spent on the ward.

The procedure involves inserting a needle, about 5mm in diameter, into the muscle. When the needle is removed a small sample of muscle remains inside the needle and this is taken for analysis. The incision through which the needle is inserted is usually only a few millimetres in length. Once the sample has been taken, the incision is held together with sterile strips and a plaster, and no stitches are required. The scar that remains is very small. The needle biopsy procedure itself is brief, often less than ten minutes, but produces a smaller sample than the open technique.

Open biopsy

This involves making an incision a few centimetres long but the size is kept to a minimum. Once the sample is taken, the incision is closed with stitches. The scar from this technique will be bigger than from the needle biopsy, but it allows a bigger specimen to be collected, which may be necessary in some cases, and makes the need for a second biopsy less likely. The technique may take about half an hour, but produces a larger sample, and allows direct vision of the muscle giving a more certain result.

Both types have their advantages and disadvantages, and the preferred method partly relates to the reason for the biopsy. Where both options are possible, patients may be asked their preference of procedure.

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.

At home after the procedure

The biopsy site may feel uncomfortable for a day or two afterwards. Simple analgesia may be required.

After an needle biopsy, the small wound is closed with steristrips. This should be kept clean and dry for 48 hours, but after that the dressing can be removed.

An open biopsy wound may be closed with stitches. The surgeon will advise when these can be removed and who will do this.

On the day of the biopsy, walking is possible but should be minimised.

Activity should gradually be resumed following the procedure. It may be necessary to take one or two days off work after the procedure, depending on activity required.

Vigorous activity or sport should be avoided for the first few days and resumed cautiously as discomfort subsides.

When to call the ward or your GP

What happens to the sample?

The sample is transported to the laboratory and most of it is frozen. Very thin slices are cut and stained with various dyes and examined under a microscope. Some of the sample is also frozen for biochemical studies. A small portion is placed in a preservative so that it can be examined under an electron microscope, if required. With the agreement of the patient, any unused portion of the sample is stored so that developments in the field can be applied, even if the faulty gene is identified.

Histology

This involves looking at the overall appearance and structure of the muscle cells. The muscle is stained using various chemicals in order to see different structures. This analysis gives information about the muscle structure and the appearance of characteristics specific to certain conditions.

Histochemistry

This technique also uses chemical stains, but looks at the action of chemicals within the muscle fibres. This includes enzymes, and so is important for the diagnosis of metabolic disorders. In addition histochemistry reveals the characteristics for the two main types of muscle fibres we all have. Changes in the normal pattern are used to identify a particular condition.

Immunohistochemistry

This procedure uses antibodies which bind to a specific protein and can show the presence or absence of important proteins within the muscle. When antibodies are tagged with a marker they can be seen under the microscope and can show if a protein is in the wrong place, or is absent. This is important for several muscular dystrophies such as Duchenne muscular dystrophy, which is caused by the absence of the protein, dystrophin. Antibodies are also used to show changes in several proteins simultaneously using a biochemical technique that separates each protein out on a special type of jelly.

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.

Muscle biopsy

Advantages and disadvantages

After the biopsy

Risks and alternatives

Risks

Is there an alternative?