Myasthenia Gravis Tests
Reviewed
Also called: Ice pack test, Edrophonium test, Tensilon test, Nerve conduction study
Myasthenia gravis (MG) tests are used to diagnose MG, a chronic (long-lasting) autoimmune disease that causes weakness in muscles throughout your body.
Specimen: blood
Urgent safety information
If the muscles that control your breathing are affected, this is called a myasthenic crisis. It is a life-threatening emergency.
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
You don't need any special preparations for a neurological exam, ice pack test, or antibody test. For the other tests, you may need to fast (not eat or drink) or avoid certain foods and beverages before the test. Tell your provider if you are pregnant, have pieces of metal in your body, or if you have a pacemaker or cardiac defibrillator. Also, tell your provider if you take any medicines. If you're taking blood thinners, you may need to watch for more bleeding from the needle.
So, your health care provider may order more than one type of MG test to help make a diagnosis. This is a blood test that looks for certain types of antibodies that are found in people with MG. Your provider will place an ice pack or bag filled with ice on your eyelid. The ice will be removed after two minutes.
There is no risk to having a neurological exam or an ice pack test. There is very little risk to having a blood test. You may feel a little pain or cramping during an EMG test. An edrophonium test may cause an allergic reaction. It is not common, but contact your provider if you have breathing problems, vision changes, and/or feel faint after taking the medicine.
Understanding results
MG can be hard to diagnose because muscle weakness can be a symptom of many disorders.
- Tests show MG: If one or more of the tests show that you have MG, your provider will work with you on a treatment plan. Limitation: So, your health care provider may order more than one type of MG test to help make a diagnosis. Next step: Treatments can help reduce your symptoms and improve muscle weakness.
- Ice pack test: drooping eyelid improves: If drooping improves, it may mean you have MG. This is because cooling temporarily improves muscle weakness that's caused by MG. Limitation: So, your health care provider may order more than one type of MG test to help make a diagnosis. Next step: If you have questions about your results, talk to your provider.
- 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 you have questions about your results, talk to your provider.
- 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?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.