Diseases & Conditions
At Boston Medical Center's Division of Thoracic Surgery, we treat a broad range of conditions, including myasthenia gravis. We combine medical excellence, technologically advanced facilities and equipment, and a patient-centered approach to provide fast, accurate diagnoses and effective treatments.
What is Myasthenia Gravis?
Myasthenia gravis (MG) is a chronic neuromuscular condition that causes weakness in your voluntary muscles (skeletal muscles) that worsens with activity and improves with rest. It is caused by an abnormal response in your immune system.
The weakness occurs when the nerve impulses that initiate or sustain movement do not adequately reach the muscle cells because your immune system targets your body's own cells. This is called an autoimmune response. Your immune system produces antibodies that attach to your own cells, which prevents your muscles from receiving the message from your nerves.
Myasthenia gravis affects about three out of every 10,000 people in the United States. It 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. Scientists believe that the thymus gland, which is part of the immune system, produces antibodies that target your own cells. Typically, the thymus is large in infants and children and small in healthy adults. However, the thymus is abnormally large in some adults with myasthenia gravis. In addition, some people with myasthenia gravis have tumors of the thymus. Most often, these are noncancerous.
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. Your physician will ask you a series of questions and examine you. The main indication of myasthenia gravis is weakness that worsens with activity and improves with rest. Tests your physician may order to confirm the diagnosis include:
- An edrophonium (Tensilon) test, which blocks the enzyme that breaks down a chemical called acetylcholine, which helps nerves transmit messages to your muscles
- A blood test for abnormal antibodies that disrupt the electrical signals traveling from your nerves to your muscles
- Repetitive nerve stimulation, which measures how well your nerves send electrical signals to your muscles
- Single-fiber electromyography (EMG), which measures the electrical energy traveling between your brain and your muscles
Your physician will also order a computed tomography (CT) scan or magnetic resonance imaging (MRI).
After a careful evaluation of your condition, we will recommend the treatment that is appropriate to your particular circumstances. 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 your blood that block nerve signals, and intravenous immune globulin, which adds normal antibodies to your 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.