Myasthenia Gravis Tests
Reviewed
Also called: Ice pack test, Edrophonium test, Tensilon test, Nerve conduction study
Myasthenia gravis (MG) tests help diagnose a chronic autoimmune disease that causes muscle weakness. Your immune system makes antibodies that block or change the connection between your nerves and muscles. Testing can involve multiple procedures, including a blood antibody test, neurological exam, ice pack test, electromyography (EMG), nerve conduction study, imaging, edrophonium test, and lung function tests. There is no cure, but treatments can relieve symptoms and may allow periods without symptoms (remission).
Specimen: blood
Why this test may be ordered
- To diagnose myasthenia gravis when you have symptoms such as drooping eyelids, double vision, weakness in arms/legs/neck, trouble swallowing or talking, fatigue, or shortness of breath.
- Symptoms usually worsen after activity and improve with rest.
Preparation and collection
No special preparation is needed for a neurological exam, ice pack test, or antibody test. For other tests, you may need to fast or avoid certain foods and beverages. Tell your provider if you are pregnant, have metal in your body, have a pacemaker or cardiac defibrillator, or take any medicines (especially blood thinners).
A health care professional will take a blood sample from a vein in your arm using a small needle. After the needle is inserted, a small amount of blood is collected into a test tube or vial.
There is very little risk to having a blood test. You may have slight pain or bruising at the needle site, but most symptoms go away quickly.
Understanding results
Your provider will interpret your results. If one or more tests show that you have MG, your provider will work with you on a treatment plan.
- Antibodies found (positive): May indicate myasthenia gravis. Limitation: Not all people with MG have detectable antibodies; a negative result does not rule out MG. Next step: Your provider will discuss treatment options such as medicines, plasmapheresis, IV immunoglobulin, or surgery.
- No antibodies found (negative): Does not rule out myasthenia gravis. Limitation: Some people with MG do not have the antibodies tested. Next step: Your provider may order additional tests (e.g., EMG, nerve conduction study, ice pack test, edrophonium test) to help make a diagnosis.
- MG can be hard to diagnose because muscle weakness can be a symptom of many disorders. Your provider may order more than one type of test.
- A negative antibody test does not rule out MG.
- The edrophonium test may cause an allergic reaction (rare); contact your provider if you have breathing problems, vision changes, or feel faint.
- EMG may cause slight pain or cramping; if pain becomes very uncomfortable, let your provider know as it may change test results.
- Nerve conduction study may cause a mild tingling feeling; tested muscles may be sore for a few days.
What to do next
If diagnosed with MG, your provider will work with you on a treatment plan. Lifestyle changes that may help include eating a healthy diet, doing regular gentle exercise (check with your provider first), avoiding heat and stress, wearing an eye patch for double vision, and taking naps or rest breaks.
- What do my test results mean?
- Do I need any follow-up tests?
- What treatment options are available for myasthenia gravis?
- Are there any lifestyle changes I should make?