The most serious complication of myasthenia gravis (MG) is called a myasthenic crisis. A myasthenic crisis happens when a person with MG has severe weakness of the breathing muscles. When this happens, the person needs urgent medical help.1,2
What is a myasthenic crisis?
Myasthenic crisis is not a common problem of MG, but it does happen to about 1 in 5 people with MG at least once.1,2
A myasthenic crisis leads to weakness of the breathing (respiratory) muscles. It is a potentially life-threatening situation that requires emergency care. A crisis often develops after days or weeks of slowly worsening symptoms but can also come on quickly. It may also develop in up to 1 in 3 people after thymectomy surgery.1,2
Treatment
Treatment for a myasthenic crisis requires a hospital stay. That is because the person needs to be watching closely and may need help breathing as they receive other treatments. The other treatments used include:1
- Breathing support
- Intravenous immunoglobulin (IVIG)
- Plasmapheresis
- High doses of steroids
- Correcting nutritional issues
- Treating underlying infections or other triggers
Breathing support
Helping the person breathe better is the first part of responding to a myasthenic crisis. If caught early enough, the person may only need breathing support from a bilevel positive airway pressure (BiPAP) machine. A BiPAP machine looks like a CPAP machine that people with sleep apnea wear at night, but it works differently.1
However, up to 9 out of 10 people in a myasthenic crisis need to be intubated. This means a tube is inserted into the mouth and then into the airway, then connected to a ventilator. Once the person’s muscle weakness improves, the person is weaned off the ventilator.1
Studies show that using a BiPAP machine early in a myasthenic crisis leads to fewer days on a ventilator and less time in intensive care.1
Intravenous immunoglobulin (IVIG)
Intravenous immunoglobulin (IVIG) is an injection filled with healthy antibodies. IVIG is most often given to people who have severe MG symptoms (a severe flare or myasthenic crisis) for a short time. It is a treatment that helps reduce the body’s attack on the nervous system.1
A course of IVIG often lasts for 5 days. The most common side effects include:1
- Headache
- Fever
- Nausea
- Discomfort at the IV site
- Rash
- Tiredness
- Body aches and pains
IVIG usually starts to work in 4 to 5 days, and the benefits last for 4 to 8 weeks.1
IVIG may also be used on a regular basis if someone’s MG is more serious or does not get better using other treatments.
Plasma exchange
Plasma is one of the building blocks of blood. Among its many jobs, plasma carries antibodies, which are chemicals the body makes to fight germs. In an autoimmune condition like MG, abnormal antibodies attack healthy tissue. Plasma exchange is a process in which a machine removes the abnormal antibodies in your plasma and replaces them with healthy plasma. It is also called plasmapheresis.1
Plasma exchange is most often used when symptoms are temporarily severe. It can also be used on a regular basis if someone’s MG is more serious or not responding to other treatments. It may be given 5 times over 10 days.1
Plasma exchange usually starts to work in 2 days, and the benefits last for 3 to 4 weeks. Common side effects include:1
- Fever
- Feeling tingling or prickling skin
- Low blood pressure
- Fast heart rate
High doses of steroids
Steroids are usually given at the same time the person receives IVIG or plasma exchange. The benefits of steroids begin to work after 2 weeks. This means the steroids start to kick in about the time the effects of IVIG or plasma exchange are starting to decrease. Once the person is improving, the steroid dose is lowered.1
After a myasthenic crisis, the person often goes home from the hospital taking a higher dose of steroids than they were taking before the crisis. Their treatment plan may need to change to prevent future crises.1
Cyclosporine, a different type of immune system drug, may be given to people who cannot take steroids. Other immune system drugs used to treat MG are not typically used in a crisis because they take a long time to begin working.1
Nutritional issues
Blood tests will be used to monitor other health issues that may make muscle weakness worse. For example, having low levels of potassium, magnesium, or phosphate can make a myasthenic crisis worse. Low levels of red blood cells will also need to be corrected.1,2
