Doctors can use several tests to diagnose muscular dystrophy.
A correct diagnosis gives patients an understanding of how their disease is likely to progress. It also helps doctors do a better job of treating the mechanisms underlying the condition and its symptoms.
Diagnosing the more common forms of muscular dystrophy tends to be easier. That’s because their recognizable set of symptoms is likely to prompt doctors to look for genetic defects associated with those forms.
If a general practitioner suspects a neuromuscular disorder after completing a thorough physical examination and reviewing a patient’s family medical history, the patient will usually be referred to a neurologist.
One of the first diagnostic exams a neurologist is likely to recommend is a blood test to check for levels of a protein called creatine kinase, or CK.
CK is an enzyme that muscles release into the bloodstream when they are damaged. The level of CK in the blood is elevated in patients with muscular dystrophies.
A CK test is not enough to confirm a muscular dystrophy diagnosis, however. The reason is that CK levels vary by age, gender, and race, and can even be elevated after a strenuous workout. A CK test can indicate whether muscle damage has occurred, and how much, however.
Doctors can use electromyography to test patients’ muscle function. An electromyograph measures muscles’ electrical activity as a patient alternates between flexing and relaxing specific muscle groups.
The test is quick and relatively non-invasive, so doctors often use it to rule out neurologic disorders as the cause of muscle weakness.
Magnetic resonance imaging
Magnetic resonance imaging, or MRI, gives doctors a glimpse of a patient’s muscle, fat, and bone.
Muscular dystrophy patients typically have a higher concentration of fat in their muscles. MRIs help neurologists understand which muscles MD is affecting the most. They also help doctors choose a suitable muscle for a biopsy, if needed.
In addition to using MRIs for an initial diagnosis, doctors use them to follow the course of a patient’s disease as it progresses. MRI scans over time help physicians track the amount of fat infiltrating muscle tissue, which tends to correlate with changing muscle strength and function.
To perform a muscle biopsy, a doctor collects a small piece of muscle with a needle or by making a small cut in the skin.
Doctors use a microscope to check the sample for muscle damage and to look at levels of different muscle proteins, certain concentrations of which can indicate muscular dystrophy. Low levels of dystrophin protein can indicate that a person has certain types of the disease, such as Duchenne muscular dystrophy and Becker muscular dystrophy.
Although a number of diagnostic tools can point toward muscular dystrophy, genetic testing is usually the most accurate way to diagnose the disease.
The tests check for mutations associated with MD. At the moment, one test is used to check for one mutation. But companies specializing in genetic testing are developing tests that can look for several types of muscular dystrophy with a single blood sample.
Scientists have yet to identify the genetic causes of a number of types of muscular dystrophy, so some patients cannot be diagnosed with genetic testing. They may be asked to submit a blood sample for research purposes, in hopes that scientists can identify a mutation that patients with similar symptoms share.
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