How Do You Test For Muscular Dystrophy?
There are several tests done for muscular dystrophy (MD). Tests are done to see whether the problem is due to muscular dystrophy, if it is due to a sub type of muscular dystrophy and to exclude other causes of muscle weakness like toxic exposure, drugs, surgery and other muscle diseases.
Blood Tests
Serum Creatinine Kinase
Creatinine kinase (CK) is an enzyme that is seen in the skeletal muscles, heart muscles and brain. CK levels increase with ischemic attacks, traumatic injury, and infections. If you do not have any other problem but muscle weakness the increase in CK levels suggestive of a skeletal muscle cause. High levels of CK can be seen with muscle weakness, traumatic muscle injury, excessive exercises and muscle infections. Muscle weakness and elevated levels of CK suggest muscular dystrophy, but we cannot specifically say the underlying cause for the muscle weakness by the increased CK levels.1
In the initial stages of muscular dystrophy the CK levels are higher because the muscle degradation is more during the initial stages. With time the muscle mass reduce, therefore CK levels tend to be low. The severity of muscular dystrophy cannot be assessed by the CK levels.
Serum Aldolase
Aldolase is an enzyme that breaks down sugars to produce energy. Higher aldolase levels means there is some muscle disease. This test is done usually when muscular dystrophy is suspected.2 Serum aldolase is highest In DMD.
Muscle Biopsy
Sample of muscle tissue is taken through needle biopsy or open biopsy. This muscle sample is assessed under the microscope and tested for proteins to diagnose muscular dystrophy and the type of muscular dystrophy.
In needle biopsy small piece of muscle tissue is taken from the thigh by using a needle and a syringe. Minimally invasive procedure, it usually take about 10 minutes and leaves a small scar. However, the sample may not be adequate for some types of analysis.
In open biopsy skin incision is made and muscle sample retrieved, sutures are needed to close the skin incision. The sample taken form any site through open biopsy is adequate for all types of analysis.
Electromyography (EMG)
The electrical activity of the skeletal muscles are assessed from this test.3 Electrodes are placed on the muscles and you are asked to contract the muscles then the electrical activity of the muscles is recorded through the electrodes as a wave. From this test doctors can differentiate muscle weakness due to muscular dystrophy from nerve damage.
Genetic Testing
Genetic testing is done using a blood sample to check if there are mutations in the dystrophin gene. The test can confirm muscular dystrophy and identify certain types of muscular dystrophy. It also helps to check if the woman with a family history is a carrier and whether the fetus has got muscular dystrophy (prenatal diagnosis). Genetic testing takes a longer time to give results (weeks or months).
Imaging Tests
Magnetic resonance imaging (MRI) give images of the shape, volume of the muscles and the replacement of muscle tissue by fat. In asymptomatic patient early detection is possible with MRI. Disease progression can be measured by MRI combined with Ultrasound scan (USS).
Summary
There are several tests done for muscular dystrophy (MD). Tests are done to see whether the problem is due to muscular dystrophy, if it is due to muscular dystrophy the type of muscular dystrophy and to exclude other causes of muscle weakness like toxic exposure, drugs, surgery and other muscle diseases. High serum creatinine and aldolase levels are suggestive of muscle disease, but we cannot say it is exactly muscular dystrophy. Muscle biopsy and genetic testing are the tests that can confirm muscular dystrophy and identify certain types of muscular dystrophy. Genetic testing can also be used to check the carrier status of a woman and to do a prenatal diagnosis. EMG is helpful to differentiate muscle weakness due to muscular dystrophy from nerve damage. Magnetic resonance imaging (MRI) give images of the shape, volume of the muscles and the replacement of muscle tissue by fat. Disease progression can be measured by MRI combined with Ultrasound scan (USS).
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