Electromyography (EMG) and Pompe Disease Diagnosis

Electromyography (EMG) is a medical test that doctors can use to assess the health of muscles and nerves, how well they are working and communicating.

An EMG may be given to diagnose late-onset Pompe disease, a rare, heritable, and progressive disorder characterized by the buildup of large sugar molecules called glycogen in muscles and other tissues. Glycogen’s accumulation affects the ability of muscles to contract, leading to weakness and pain, among other problems.

How does an EMG work?

You need to go to a hospital or clinic for the test. The doctor places a small electrode on the muscle group they want to test. The electrode has small needles that are inserted into the muscle group. The EMG machine measures the electrical impulses that your muscles send, interpreting them as a graph that your doctor can read to see how well your muscles and nerves are functioning.

What abnormalities does Pompe disease cause?

People with Pompe disease have specific changes on the EMG graph that your doctor will interpret as myopathy. The specific problems that the EMG indicates are particular to Pompe disease. EMG findings in the arms and legs may be normal. The paraspinal muscles that support your back usually show changes before other muscle groups.

As the disease progresses, these changes become more pronounced. Even if you may not have noticed changes in how you feel — how strong or weak your muscles feel, or how much trouble you have going about daily tasks — an EMG may be able to record small changes that correlate with how much glycogen is present in your muscles.

The advantage of EMG

A muscle biopsy can also give an indication of the health of your muscles, but is an invasive approach. Here, the doctor takes a sample of muscle that is then observed under a microscope for structural changes. Because an EMG is less invasive, your doctor may prefer this approach, and use it to diagnose your disease rather than a biopsy.

Last updated: Aug. 11, 2020

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