Diseases & Conditions
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
- 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:
- 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
- Blood Tests
- Repetitive Nerve Stimulation
- Single-fiber Electromyography (EMG)
The physician will also order a computed tomography (CT) scan or magnetic resonance imaging (MRI).
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
- Therapies, such as plasmapheresis, which removes antibodies from the blood that block nerve signals, and intravenous immune globulin, which adds normal antibodies to the immune system
- Thymectomy, which is surgical removal of the thymus
There are several techniques for performing a thymectomy, including:
- 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.
- Video-assisted thoracotomy (VATS) thymectomy. This is a less invasive form of thymectomy. The surgeon makes several small incisions on the right or left side of the chest and inserts fiber-optic instruments through the incisions. The fiber-optic instruments are flexible tubes that can include a light or camera. The camera transmits images to a monitor, which allows the surgeon to see inside the chest. Surgical instruments are put through the incisions to remove the thymus. Because of its minimally invasive nature, this procedure is less painful and requires less recovery time than the transsternal approach.
- 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.