How Is Myasthenia Gravis Diagnosed and Treated?

Medically Reviewed by Christopher Melinosky, MD on May 12, 2023
3 min read

During a physical exam for myasthenia gravis, your health care provider may observe signs such as a droopy eyelid, difficulty holding your arms out at shoulder length for a reasonable length of time, or a weak grasp. Blood tests may reveal the presence of acetylcholine-receptor or muscle-specific tyrosine kinase-seropositive (MuSK) antibodies. Specialized tests use electricity to stimulate muscles, and at the same time, measure the strength of muscle contraction.

If you have myasthenia gravis, muscle strength will decrease predictably over the course of testing. You may be given certain medications -- edrophonium or neostigmine -- as part of a diagnostic exam. In a patient with myasthenia gravis, these drugs will significantly and noticeably improve muscle strength for a short time. This helps to further confirm the diagnosis.

Because other conditions sometimes occur along with myasthenia gravis and can interfere with treatment, your health care provider may order other tests. You may need a CT scan or an MRI to check for a thymoma. You'll be checked for high blood pressure and glaucoma, and you'll probably have your blood tested to see if you have thyroid disease, other autoimmune diseases (such as rheumatoid arthritis or systemic lupus erythematosus), diabetes, kidney problems, or any infections.

There is no cure for myasthenia gravis, but it is treated with medications and sometimes surgery. You may be put on a drug called pyridostigmine (Mestinon), that increases the amount of acetylcholine available to stimulate the receptors.

If you continue to have symptoms on pyridostigmine, an immunotherapeutic agent is usually added. These include azathioprine (Imuran), cyclosporine (Neoral), eculizumab (Solaris), efgartigimod alfa-fcab (Vyvgart), mycophenolate (CellCept), and prednisone to suppress the immune system.

In severe cases, you may need to have your blood sent through a special machine that removes the antibody-containing plasma and replaces it with antibody-free plasma. This is called plasmapheresis. You may also be given a preparation called intravenous immunoglobulin (IVIg) through a needle in a vein.

If you have a thymoma, you will need surgery to remove your thymus (thymectomy). In fact, your doctor may recommend that you undergo this surgery even if no tumor is present because removal of the thymus seems to improve symptoms in many patients.

Myasthenic crisis is a sudden worsening of symptoms, often with difficulty breathing and/or swallowing. It is life-threatening and requires treatment in the intensive care unit with temporary placement on a respirator. Myasthenic crisis can occur during a severe infection, so you'll probably need to be treated with antibiotics, as well.

Situations that affect myasthenia gravis include:

  • Changes in thyroid function
  • Surgery
  • Radiation therapy
  • Infection

Certain medications can exacerbate symptoms of myasthenia gravis, including:

  • Antibiotics (particularly those called aminoglycosides)
  • Narcotic drugs
  • Penicillamine
  • Magnesium
  • Anesthesia
  • Muscle relaxants
  • Beta-blockers to treat heart arrhythmias

Some women notice that their symptoms worsen around the time of their menstrual period. Pregnancy's effect on myasthenia gravis is unpredictable. About one-third of all women have an improvement in their symptoms, one-third have no change, and one-third get worse.

There are no known ways to prevent myasthenia gravis. If you already have the condition, take these steps to avoid an exacerbation:

  • Try to prevent infections with careful hygiene and by avoiding sick people.
  • Treat infections promptly.
  • Do not become overheated or too cold.
  • Avoid overexertion.
  • Learn effective methods of dealing with stress.