Imaging Tests For Myasthenia Gravis

Reviewed by: HU Medical Review Board | Last reviewed: May 2021

Myasthenia gravis (MG) is a chronic autoimmune condition that causes weakness in specific muscles. Because MG symptoms often come and go, and have changing levels of severity, imaging tests may be used to identify what is going on.

With MG, imaging tests are most often used to take pictures of the thymus gland, neck, and base of the skull. These tests may be ordered after a physical exam and blood work has already confirmed myasthenia gravis (MG). Or, these tests may help doctors rule out other causes for MG-like symptoms.

The tests most often used in people with MG are:1,2

  • X-ray
  • CT scan
  • MRI

Chest X-ray

A chest X-ray uses a small beam of radiation to create an image on a special film. It creates an image of the thymus, heart, lungs, and bones of the chest. Chest X-rays can sometimes show the doctor if the thymus gland is larger than normal. However, since the thymus is small, a chest X-ray may not be accurate, and a CT scan or MRI may be needed instead.

Computerized tomography (CT scan)

A CT scan is a more detailed type of X-ray. The test is performed inside a doughnut-shaped machine. It can be performed with or without contrast iodine dye depending on the reason the study is being obtained. This dye is used to map blood flow through the vessels, organs, and glands. A CT scan can show the doctor if the thymus is enlarged or has tumors.

Magnetic resonance imaging (MRI)

MRI is a noninvasive test using a magnetic field and radio waves to create images of the body. MRIs can be used to get detailed images of the body such as anatomy, tissue damage, reduced blood flow, and tumors.

An MRI of the head and neck area may help rule out cancer or other lesions that might press on nerves and cause similar symptoms to ocular MG.

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