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 the symptoms first start to appear.
Diagnosis will involve some or all of the following stages:
- investigating any symptoms
- discussing any family history of MD
- physical examination
- blood tests
- electrical tests on the nerves and muscles
- a muscle biopsy (where a sample of tissue is removed for testing)
In the first instance, see a GP if you or your child have symptoms like muscle weakness or mobility problems. If necessary, they may refer you for further tests at a hospital.
The 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 or your child may be:
- finding it difficult to climb the stairs
- unable to play sports as you used to
- finding it difficult 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.
Duchenne MD is the most common type of MD in boys. Symptoms can be present from birth, but this is unusual.
Signs usually appear between 12 months and 3 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 may also find it difficult to stand up from sitting on the floor. They may use what's known as Gowers' manoeuvre to do this. This 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 first placing their hands on their knees and then on their thighs
See a GP if you think your child may have MD. The 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 "waddling" style of walking; later on, they may 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's 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
If there's a history of MD in your family, it's important to discuss it with your GP. This can help to 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 whether your type of MD is inherited as a recessive or a dominant condition (see causes of MD for more information).
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.
A muscle biopsy involves removing a small sample of muscle tissue through a small cut (incision), or using 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 to determine which gene is causing 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's usually an altered size.
Examining the muscle tissue under a microscope can also help to diagnose limb-girdle MD. Healthy muscle consists of closely packed, evenly sized fibres. In people with limb-girdle MD, these fibres may be missing, may be different sizes or may have been replaced with fat.
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's most needed. Some tests include:
- 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 to determine 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.
- 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 to identify the affected muscles and will also show the extent of any muscle damage.
- CT scan – where a series of X-rays are taken to create a detailed image of the inside of your body, which 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 – a 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.
Once the doctor – usually a geneticist or neurologist – has an idea about what type of MD may be affecting you or your child, they may arrange genetic testing to look into this.
Genetic testing is simpler for some types of muscle conditions, so it may be arranged at an early stage if a specific condition is suspected, or after many other tests if it's more difficult to diagnose.
There are many different genes that could potentially be responsible for MD, so it would be expensive and time-consuming to test them all. However, genetic testing can sometimes confirm a diagnosis.
For example, if you're diagnosed with Duchenne MD, tests can be carried out to check for a mutation in the dystrophin gene, because mutations in this gene are directly responsible for the condition.
Genetic testing can also be used to identify carriers of MD and to perform prenatal diagnosis (when a foetus is diagnosed before the baby is born).
