Muscular dystrophy - Diagnosing muscular dystrophy

Many different methods can be used to diagnose the various types of muscular dystrophy (MD). The age at which MD is diagnosed will vary depending on when symptoms first start to appear.

Diagnosis will involve some or all of these stages:

• investigating any symptoms
• discussing any family history of MD
• physical examination
• blood tests
• electrical tests on the nerves and muscles
• a muscle biopsy (when a sample of tissue is removed for testing)

In the first instance, visit your GP if you or your child have any symptoms of MD. If necessary, your GP may refer you to a hospital for further tests.

Investigating symptoms

Your GP will need to know about any symptoms of MD that you or your child have noticed and when they began to appear. For example, you may be:

• finding it hard to climb the stairs
• unable to play sports as you used to
• finding it hard to lift objects

Identifying when symptoms first appeared and determining which muscles are affected is particularly useful in helping to diagnose different types of MD.

Symptoms in young children

Duchenne MD is the most common type of MD in boys. Symptoms can be present from birth, but this is unusual and signs usually appear between 12 months and three years of age. You may notice that your child has difficulty walking or climbing stairs, or that they fall down more frequently than other children.

Your child might also find it difficult to stand up from sitting on the floor. They may use what is known as the Gower's manoeuvre to do this. The Gower's manoeuvre is where a child stands up by:

• facing the floor
• placing their feet wide apart
• lifting their bottom first
• using their hands to "walk up" their legs by placing their hands first on their knees, then on their thighs

Visit your GP if you suspect that your child may have MD. Your GP will look at the following when they examine your child:

• the way your child stands
• the way your child walks – children with Duchenne MD often have a typical style of walking, which is sometimes described as "waddling"; later on, they may tend to stand and walk on the front part of their foot, with their heels off the ground
• whether your child has an exaggerated inward curve of their lower back – the medical term for this is lordosis, although it is also sometimes called "sway back"
• whether your child has a sideways curvature of their spine, known as scoliosis
• whether your child's calves and other leg muscles look large compared with other muscles

Family history

If there is a history of MD in your family, it is important to discuss it with your GP. This can help determine which type of MD you or your child might have.

For example, discussing the family history of limb-girdle MD will help your GP determine if your type of MD is inherited as a recessive or a dominant condition (see causes of muscular dystrophy for more information).  

Blood tests

A sample of blood may be taken from a vein in your or your child's arm to test it for creatine kinase, a protein usually found in muscle fibres.

When muscle fibres are damaged, creatine kinase is released into the blood. The muscle damage caused by some types of MD means that the level of creatine kinase in the blood will often be higher than normal.

A blood sample may also be used for genetic testing, and this can sometimes identify the cause of muscle problems without the need for a muscle biopsy.

Muscle biopsy

A muscle biopsy is when a small sample of muscle tissue is removed through a small cut (incision) or a hollow needle so it can be examined under a microscope and tested for proteins. The sample will usually be taken from the leg or arm, depending on the type of MD.

Analysing the protein in the muscle can help determine which gene is causing the MD and therefore which type of MD you have. For example, people with Duchenne MD and Becker MD have too little of the protein dystrophin in their muscles and it is usually an altered size.

Examining the muscle tissue under a microscope can also help diagnose limb-girdle MD. Healthy muscle consists of closely packed, evenly sized fibres. In people with limb-girdle MD, these fibres may be missing, different sizes, or have been replaced with fat.

Other tests

A number of other tests can be used to find out more about the spread and extent of any muscle damage. This will help your doctor to identify or confirm which type of MD you have. Treatment can then be directed where it is most needed. Some tests are explained below.

• nerve conduction studies and electromyography (EMG) – tests used to examine the electrical activity in nerves and muscles at rest and when the muscles are contracting; this can help decide whether the underlying problem is in the spinal cord, in the muscles themselves, or in the nerves carrying impulses between the spinal cord and the muscles
• magnetic resonance imaging (MRI) scan – a test that uses a strong magnetic field and radio waves to produce detailed pictures of the inside of your body; this can help identify the affected muscles and will also show the extent of any muscle damage
• computerised tomography (CT) scan – where a series of X-rays are taken to create a detailed image of the inside of your body; this will reveal any muscle damage.
• chest X-ray – this can be useful for looking for breathing or heart symptoms, as it will show up any abnormal enlargement of the heart, plus any fluid in or around the lungs
• electrocardiogram (ECG) – where electrodes (flat metal discs) are attached to the arms, legs and chest to measure the electrical activity of the heart; this is used to check for an irregular heartbeat and reveal any damage
• echocardiogram – an ultrasound scan of the heart using sound waves; it gives a clear picture of the heart muscles and valves so the heart structure and function can be checked