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Myasthenia Gravis

Myasthenia gravis (MG) is a chronic neuromuscular condition that causes weakness in voluntary muscles (skeletal muscles) that worsens with activity and improves with rest. It is caused by an abnormal response in the immune system.


The weakness occurs when the nerve impulses that initiate or sustain movement do not adequately reach the muscle cells because the immune system targets the body's own cells. This is called an autoimmune response. An immune system produces antibodies that attach to one’s own cells, which prevents muscles from receiving the message from the nerves.

Myasthenia gravis can occur at any time, but is more common in young women and older men.


The earliest symptoms of myasthenia gravis usually affect vision and include:

  • Double vision
  • Difficulty maintaining a steady gaze
  • Eyelid drooping

Other symptoms include:

  • A drooping head
  • Difficulty breathing
  • Difficulty chewing and swallowing
  • Difficulty climbing stairs
  • Difficulty talking
  • Facial paralysis
  • Difficulty lifting objects
  • Hoarseness
  • Difficulty standing from a seated position
  • Muscle weakness that improves with rest
  • Gagging or choking


The cause of myasthenia gravis is unknown.

Factors that can make myasthenia gravis worse include:

  • Fatigue
  • Illness
  • Stress
  • Extreme heat
  • Some medications, including beta-blockers, calcium channel blockers, quinine, and some antibiotics


The first method of diagnosis is the physical exam and medical history. The main indication of myasthenia gravis is weakness that worsens with activity and improves with rest. Tests that the physician may order to confirm a diagnosis include:

  • Edrophonium Test

    A test that blocks the enzyme that breaks down a chemical called acetylcholine, which helps nerves transmit messages to the muscles.

  • Blood Tests

    A common tool for disease screening, blood tests provide information about many substances in the body, such as blood cells, hormones, minerals, and proteins.

  • Repetitive Nerve Stimulation

    This measures how well the nerves send electrical signals to the muscles.

  • EMG (Electromyogram)

    Electromyography (EMG) is a diagnostic test to evaluate the health of muscles and the nerve cells that control them. Motor neurons transmit electrical signals that cause muscles to contract. An EMG uses tiny devices called electrodes to transmit or detect electrical signals. These are then interpreted by a specialist. EMGs can include placing a needle electrode into a specific muscle to measure its electrical activity, and a nerve conduction study, which is using electrodes taped to the skin to measure the speed and strength of signals traveling between two or more points.

The physician will also order a:

Computed Tomography (CT) Scan

CT scans use x-ray equipment and computer processing to produce 2-dimensional images of the body. The patient lies on a table and passes through a machine that looks like a large, squared-off donut. Doctors order CT scans when they want to see a two-dimensional image of the body to look for tumors and examine lymph nodes and bone abnormalities. If contrast dye is used to improve the computer image, the patient may need to avoid eating or drinking for 4 to 6 hours before the test. Patients should tell their provider before the test if they have any allergies or kidney problems.


Magnetic Resonance Imaging (MRI)

This test uses a magnetic field, radiofrequency pulses, and a computer to produce detailed images of body structures in multiple places. You may be asked to drink a contrast solution for better imaging, and you will most likely lie on a moving table as pictures are taken. MRI is a more detailed tool than x-ray and ultrasound and for certain organs or areas of the body, it provides better images than CT. MRI may not be recommended if you have a pacemaker or other metal implant.



Doctors use a variety of treatments—alone or in combination—to relieve symptoms of myasthenia gravis.

Treatment for myasthenia gravis includes:

  • Medication, including cholinesterase inhibitors, corticosteroids and immunosuppressants
  • Plasmapheresis

    Plasmapheresis is a process in which the plasma (liquid) of the blood is separated from the cells and removed from the body.  Then, healthy plasma is placed back into the body.  People who have antibodies in their plasma that are attacking their immune system may benefit from plasmapheresis

  • Thymectomy

    This is the surgical removal of part or all of the thymus.

There are several techniques for performing a thymectomy, including:

  • VATS

    VATS stands for video-assisted thorascopic surgery. This minimally invasive alternative to open chest surgery greatly reduces patient’s pain, recovery time and risk for infection. When using VATS, the physician makes tiny incisions in the patient’s chest and inserts a thorascope (a fiber-optic camera) as well as surgical instruments. As the physician turns the thorascope, its views are displayed on a video monitor to guide surgery. The surgeon has no need to stress or cut ribs, because all movements are performed at the tip of the instrument, at the point of contact with the cancerous tissue.

  • Robotic thymectomy. The surgeon makes three tiny incisions, usually on the left side of the chest. A small camera and robotically controlled surgical instruments are advanced through these incisions. The surgeon’s hand movements control the robotic instruments using a control console and computer. The benefits of robotic thymectomy include briefer hospital stays, less pain and risk of infection, and faster healing and recovery time.
  • Transsternal radical thymectomy. The surgeon makes a lengthwise incision in the center of the chest and separates the breastbone (sternum) to gain access to the chest. The thymus is then removed. This procedure is performed under general anesthesia, and is the most invasive form of thymectomy and requires the longest recovery time.