Myasthenic Crisis: A Serious Complication of Myasthenia Gravis

Medically Reviewed by Michael W. Smith, MD on September 22, 2021

Myasthenic crisis is a life-threatening complication of myasthenia gravis. It’s when the muscles that you use to breathe get so weak that you can’t get air in and out of your lungs.

It isn’t the same as a myasthenia gravis flare, an all-over muscle weakness that may cause double vision or a wobbly walk. Myasthenic crisis only affects the muscles you use to breathe.

Who’s Affected?

As many as 20% of people with myasthenia gravis have at least one myasthenic crisis at some point. Some people don’t know they have myasthenia gravis until they have a myasthenic crisis. Women with myasthenia gravis are twice as likely to have a myasthenic crisis as men with this disease. Before age 55, women are far more likely to have one than men.

What Causes a Myasthenic Crisis?

Respiratory infections are a common trigger of myasthenic crisis. Half the time, there’s no clear reason why people with myasthenia gravis develop this complication.

Possible triggers include:

  • Not taking your myasthenia gravis medication
  • Tapering off drugs that control your immune system
  • Medications like antibiotics, anti-seizure drugs, or steroids like prednisone
  • Pregnancy
  • Giving birth
  • Premenstrual syndrome (PMS)
  • Stress
  • Not getting enough sleep
  • Pain
  • Surgery
  • Extreme hot or cold weather

Myasthenic Crisis Symptoms

A myasthenic crisis may come on slowly or very quickly. Difficult or labored breathing is the main symptom. You may notice that your breaths are shallow or your muscles seem too weak to move air in and out as you try to breathe.

Other possible symptoms:

  • Saliva builds up in your throat.
  • You can’t swallow.
  • Jaw or tongue weakness.
  • Nasal tone to your voice.
  • Your airways feel blocked.

How Is Myasthenic Crisis Diagnosed?

If you have myasthenia gravis and have trouble breathing, go to the hospital right away. Doctors will give you some tests to be sure you’re having a myasthenic crisis and not a heart or lung problem like heart failure or a blood clot.

First, you’ll have a physical exam so the doctor can go over your symptoms and your medical history.

Other tests to diagnose myasthenic crisis include:

  • Chest X-ray
  • Echocardiogram (EKG)
  • Lung ultrasound
  • Spirometry lung function test to check how much air you exhale with each breath, or your forced vital capacity (FVC)

Your doctor will rule out a rare complication called a cholinergic crisis that’s caused by a high dose of your myasthenia gravis medications. Cholinergic crisis symptoms are different from myasthenic crisis, and include heavy sweating, nausea, vomiting, and diarrhea.

Treating Myasthenic Crisis

To treat a myasthenic crisis, you’ll need emergency treatment at the hospital. Doctors will intubate you, which means they’ll insert a tube into your airways. The tube is connected to a machine called a ventilator that helps you breathe.

If your breathing and muscle strength improve, the doctor can slowly wean you off the ventilator until you can breathe on your own. Many people in a myasthenic crisis need to be intubated for 2 weeks or more. About 25% of people have to be intubated again after they’ve stopped using a ventilator.

Sometimes, myasthenic crisis can be treated with a bilevel positive airway pressure (BiPAP) device, which doesn’t require a tube to be inserted. It’s a type of ventilator that helps you breathe by sending air into your lungs through a snug mask or nasal plugs.

Can You Prevent Myasthenic Crisis?

Take these steps to help prevent or lower your risk of a myasthenic crisis:

  • Take your myasthenia gravis medicines as your doctor prescribes to help your muscles stay strong.
  • Take your meds around a half-hour before meals to prevent food from getting into your airways.
  • Eat healthy food to keep your body weight and muscles healthy.
  • Avoid crowded places or events where you’re more likely to catch a cold, flu, or other respiratory infection.
  • Get enough rest and sleep.
  • Find ways to manage your stress.
WebMD Medical Reference



Myasthenia Gravis Foundation of Michigan: “What Is Myasthenic Crisis?”

Myasthenia Gravis Foundation of America: “MG Exacerbations & Crisis.”

The Neurohospitalist: “Myasthenic Crisis.”

Johns Hopkins Medicine: “BiPap,” “Myasthenia Gravis.”

Stanford Children’s Health: “Myasthenia Gravis and Pregnancy.”

Internet Book of Critical Care: “Myasthenia gravis & myasthenic crisis.”

American Lung Association: “Lung Capacity and Aging.”

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