Diagnoses & Conditions

Myasthenia Gravis (MG)

Understanding MG

Myasthenia gravis (MG) is believed to be an autoimmune disorder. An autoimmune disorder develops when the immune system malfunctions and creates antibodies that attack and cause damage to a part of the body. In MG, the neuromuscular junction, the place where nerve cells connect with the muscles they control, is attacked. There are several antibodies associated with MG, including acetylcholine receptor antibodies (AChR) and muscle specific kinase (MuSK) antibodies. Some patients do not test positive for antibodies. Both antibodies cause interference in the transmission of a nerve signal to the muscle resulting in muscle weakness. This mostly affects voluntary muscles, which are the muscles a person can control. MG can affect any voluntary muscle but especially affects those that control the eyes, mouth, throat and limbs.

Symptoms of MG

Symptoms of myasthenia gravis (MG) include weakness and fatigue and decreased tolerance of physical activity. Because MG affects the voluntary muscles, movements such as blinking, chewing, swallowing and holding your head up become difficult. Additional symptoms may include droopy eyes and slurred speech. People with MG can experience periods where symptoms are controlled as well as periods of exacerbation, or worsening. In some cases, exacerbations can occur rapidly and require quick intervention. Severe exacerbations can affect swallowing to the point where aspiration (inhaling something such as food into the lungs) can occur and can become dangerous. Breathing can also become affected, leading to an emergency.

Diagnosing MG

Diagnosing myasthenia gravis (MG) is difficult because weakness and fatigue can be indicative of many different conditions. A physician will look at the patterns of weakness and areas affected and decide what tests to perform to make a definitive diagnosis.

Diagnostic testing may include:

  • Electromyography (EMG) to measure muscle activity.
  • Nerve conduction studies (NCS) to measure efficiency and speed of nerve signals. Special forms of an EMG and NCS specific to diagnosing MG are performed.
  • Blood work to test for antibodies that may be present in MG.
  • Tensilon test to measure effectiveness of tensilon, a drug that supplies acetylcholine. If MG is suspected, and a person is experiencing fatigue, administering tensilon will alleviate the fatigue for a very short period of time.

Treating MG

Treatment of myasthenia gravis (MG) may involve steroids, immunosuppressants and/or immune globulin therapy administered into the blood stream intravenously (IVIG). Additionally, a thymectomy (removal of the thymus gland) may be appropriate for some. IVIG treatment is given for MG primarily when an exacerbation occurs to prevent any complications, or if steroids and/or immunosuppressants are not working, cause intolerable side effects or are contraindicated. Your doctor will assess your response to therapy and determine how long you will need to continue receiving it.



The information provided on this website is not medical advice, nor is it intended to be a substitute for medical advice, diagnosis, and treatment. Always seek the advice of a physician or other qualified health provider with questions concerning a medical condition. Never disregard professional medical advice, or delay seeking it based on information provided on this website.