Myasthenia gravis is a chronic neuromuscular condition. If you have myasthenia gravis, you experience weakness from using the same muscles over and over. A simple chore like brushing your teeth, for example, can become exhausting.
With myasthenia gravis, muscles return to normal after a short rest. But then with repeated use, they become weak again.
This occurs because your body is making antibodies that block nerve impulses to muscle cells. It can be dangerous when muscles involved with swallowing or breathing are affected.
The cause of myasthenia gravis is unknown. But scientists believe the thymus gland plays a role in its development.
The thymus is a butterfly-shaped gland located in front of the heart, just behind the breastbone. Its entire function is to produce immunities to disease and infection. That's why the thymus is very large in infants and small in children. It shrinks over time, getting smaller after most of its job is done.
Myasthenia gravis can be very difficult to diagnose. Someone using muscles in a repetitive motion – such as brushing hair or reading a page in a book – can start out fine, then the affected muscles become increasingly weak. Resting the muscles improves the situation – until the next set of repetitive motions.
Other symptoms and signs include:
- Drooping eyelids and facial expressions
- Blurred or double vision
- Difficulty walking, speaking, swallowing and/or breathing
Diagnostic tests may include:
- Blood tests: to identify the presence of abnormal antibodies
- Electromyography (EMG): tests to reveal abnormalities in muscle function
- Repetitive nerve stimulation: to assess muscle weakness
- Tensilon test: a dose of a medication that will briefly improve muscle weakness
A CT or MRI scan is often done to see if a thymoma is present. A thymoma is a tumor in the thymus gland. About 30 percent of people with myasthenia gravis also have thymomas.
Most people who have myasthenia gravis are under the care of a neurologist. Treatment may include medications such as:
- Mestinon, a drug used to help nerves transmit impulses to the muscles
- Steroids to suppress the immune system
- Other drugs such as azathioprine and cellcept
Thymectomy is the surgical removal of the thymus gland. It is known to be effective in helping to resolve myasthenia gravis. Good candidates for thymectomy are those who have had the condition for three years or less.
About one-third of patients who have their thymus removed will be medication-free and their myasthenia gravis will be well controlled. A third will be on dramatically less medication. And a third of patients will see no benefit.
Different methods of performing a thymectomy include:
- Sternotomy: making a long incision in the chest, then splitting the breast bone to open the chest.
- Visually Assisted Thoracic Surgery (VATS): using rigid instruments to operate through small incisions in the chest.
- Robotic thymectomy: using flexible instruments that mimic the movements of a surgeon's hand, allowing for extraordinary precision.
Patients who undergo robotic thymectomy have less pain, much shorter stays in the hospital, and quicker recovery times than possible after a sternotomy. Many surgeons prefer robotic surgery over VATS because the movements are more intuitive and the field of vision much clearer.