Last updated Jan. 11, 2022, by Marisa Wexler, MS
Fact-checked by José Lopes, PhD
Muscular dystrophy refers to a group of genetic diseases that cause muscle weakness and loss that worsen over time. Different types of muscular dystrophy are caused by different genetic mutations, and a proper diagnosis can involve a range of tests, such as blood tests, functional tests, muscle biopsies, and magnetic resonance imaging (MRI).
What is an MRI?
An MRI is a noninvasive diagnostic technique using a magnetic field and radio waves to produce detailed images of the organs and tissues (such as muscle, fat, and bone) within the body.
The MRI scanner is a tube-shaped device that uses strong magnetic fields and radio waves to produce images in good detail. The magnetic field temporarily realigns hydrogen atoms (often called protons) in the body, while short bursts of radio waves break the alignment continuously (because the magnets re-establish alignment between the bursts). This sequence sends out weak radio signals that are picked up and used to create cross-sectional and three-dimensional images of organs and tissues.
MRI in muscular dystrophy
In muscular dystrophies, as the disease progresses, muscle tissue gradually is lost and gets replaced by fatty tissue. Edema, or swelling, and inflammation also can occur as muscle tissue is lost. All of these changes can be visualized with an MRI scan.
The specific changes and patterns of muscle damage vary depending on the type of muscular dystrophy. For example, the most common type of muscular dystrophy, Duchenne muscular dystrophy (DMD), is commonly characterized early on by involvement of the muscles in the gluteus and upper thighs.
MRI imaging of muscle tissue may be useful for diagnosing muscular dystrophy. The technique also can be used to monitor changes in disease progression over time. MRI scans also may be useful for figuring out the best area(s) for a muscle biopsy, by identifying affected muscles, limiting the risk of false negative results, or needing to take another biopsy.
MRI may be complemented with other imaging techniques, such as ultrasound — which uses sound waves to view the body’s internal structures — or computer tomography (CT), which uses ionizing radiation.
MRI is generally considered a safe procedure, and it doesn’t expose a patient to X-ray radiation. People with claustrophobia, who experience anxiety in confined spaces, might be uncomfortable during the procedure and should discuss any concerns with the specialist working the machine.
Because the MRI scanner uses powerful magnets, people with metal objects implanted in their bodies — such as some insulin pumps or pacemakers — should not undergo MRI.
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