Myasthenic crisis is a complication of myasthenia gravis (MG) that can cause a breathing emergency. Prevention can involve avoiding known triggers, such as infection, trauma, surgery, or medication side effects.

MG is a chronic autoimmune disease of the nerves and muscles. This means the immune system attacks otherwise healthy tissue. Symptoms may affect tissues that play a direct role in breathing and, as such, can cause breathing difficulties.

In severe cases, a person living with MG may experience complications. This can include a myasthenic crisis, which can occur if the muscles linked to breathing weaken too much. It requires immediate emergency care and can be life threatening. Recognizing and avoiding known triggers can help prevent an episode of myasthenic crisis.

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A myasthenic crisis is a breathing emergency that occurs when the muscles controlling breathing become too weak to function. People experiencing a myasthenic crisis will need mechanical ventilation to support breathing while they recover.

Around 15% to 20%Trusted Source of people with MG experience one or more myasthenic crises, often in response to a trigger. Even though it can be dangerous, around 95% of people in the United States who have one survive, according to a 2023 reviewTrusted Source.

Around halfTrusted Source of all people who experience a myasthenic crisis can identify a specific trigger that causes it. A respiratory infection is the most commonTrusted Source trigger. Pneumonia is a particularly common cause of crisis-linked infections. However, other triggers might include:

  • stress
  • surgery
  • adverse medication effects
  • not taking MG medications according to the doctor’s instructions
  • reducing the dosage of immune-system-suppressing medications
  • starting or stopping steroids
  • electrolyte imbalance
  • thyroid hormone imbalances
  • trauma
  • pregnancy, including delivery

Up to 50% of all people with MG do not have a known trigger. However, certain risk factors make severe disease progression, including myasthenic crises, more likely. According to a 2022 study, these include:

  • how severe the disease is when a person receives an MG diagnosis
  • the presence of certain immune proteins, or antibodies, known as muscle-specific kinase (MuSK) antibodies
  • having a chest tumor called a thymoma
  • a history of previous myasthenic crises
  • MG-related weakness in the throat muscles
  • being an older adult
  • having infections
  • experiencing other health conditions alongside MG

Despite myasthenic crisis affecting breathing, the early symptoms may not directly seemTrusted Source to affect breathing. However, this can quickly lead to a full crisis due to factors such as choking on food or airway blockage. People with MG who show severe limb weakness require monitoring for breathing issues.

Doctors may check the following areas for weakness during an exam:

  • drooping eyelids and difficulties moving the eyes
  • a “myasthenic snarl,” which means that facial muscle weakness may lead to difficulties forming a smile
  • difficulty holding air in the cheek
  • not being able to fully close the jaw after chewing, or holding it shut with a hand
  • nasal or hoarse speech
  • swallowing difficulties, including food coming out through the nose
  • noisy breathing
  • vocal cord paralysis
  • finding it difficult to push the tongue against the cheek
  • weak neck muscles

In rare cases, respiratory failure may be the only sign of a myasthenic crisis. Symptoms of respiratory failure may include:

  • a diaphragm that moves inward instead of outward during breathing due to weakness
  • a chest that does not expand fully during breaths, with the possible use of other muscles to support breathing, such as the neck or abdomen muscles
  • increased breathing or heart rate
  • general weakness and high carbon dioxide levels
  • distress or increased effort during breathing
  • a reduced ability to cough and clear the airways

Avoiding specific triggers can help people reduce the risk of a myasthenic crisis. These may include:

  • preventing tiredness by getting enough rest and avoiding overexertion
  • managing stress
  • staying up to date with vaccines, such as the pneumococcal vaccine or annual flu jab
  • avoiding medicines with a known link to triggering MG symptoms, including the antibiotic telithromycin, drugs that interact with the nervous system, medications for psychiatric disorders, and a rheumatoid arthritis drug called penicillamine
  • continuing to take MG medications as prescribed, including pyridostigmine, steroids, or immune-system-suppressing medications
  • avoiding surgery where possible

Be sure to discuss any vaccines containing live viruses or bacteria with a healthcare professional before getting them, and make them aware of underlying MG.

Although people may be aware of possible triggers, they may not be able to prevent a crisis. Myasthenic crisis is sometimes a person’s first sign of MGTrusted Source.

Doctors diagnose a myasthenic crisisTrusted Source using lung function tests, imaging scans, and clinical judgment. However, severe facial or throat weakness can reduce the accuracy of lung function tests.

They may carry out the single-breath test, which is quick and helpful for measuring respiratory function. It involves counting aloud after taking a deep breath. Usually, a score of 25 or higher suggests normal respiratory muscle function.

A physician may assess swallowing by checking for choking or coughing as the person drinks water.

Doctors also use spirometry to measure breathing strength while breathing in and out. Reduced breathing strength while lying down may suggest muscle weakness in the diaphragm. Using blood tests, oxygen level checks, and imaging scans, doctors will investigate other possible causes of respiratory issues, including:

  • blood clots
  • heart failure
  • infections
  • botulism
  • Guillain-Barré syndrome

Treatment often starts before a doctor diagnoses a myasthenic crisis to prevent symptoms from getting worse. However, antibody tests and nerve function studies can confirm MG.

A myasthenic crisis requires emergency treatment in the hospital. This includes ventilation, such as external ventilation through an oxygen mask or internal ventilation through breathing tubes.

People may also receive treatments to reduce the number of harmful antibodies in their blood. This may include intravenous immunoglobulin (IVIg) therapy, in which the emergency team infuses donated blood to improve immune system function and reduce muscle weakness.

However, plasmapheresis is the preferred treatment optionTrusted Source over IVIg therapy. Doctors may circulate blood through a machine, filtering the antibodies and returning the blood to the body.

Following a crisis, people can gradually wean off ventilation machines after around a month. As long as an individual receives emergency care, a myasthenic crisis does not seem to affect the long-term outlook of MG. Many people with MG can successfully control the condition.

Myasthenic crisis is a complication of myasthenia gravis (MG). It occurs due to excessive weakness in muscles linked to breathing, often in response to triggers. These can include viral infections, trauma, surgery, and medication side effects. Avoiding these triggers may help to reduce the risk of a myasthenic crisis in those who know they have MG.

People will require emergency treatment if they have symptoms of myasthenic crisis. These can include changes or increased effort while breathing and signs of facial or eye weakness. Treatment involves ventilation, plasmapheresis, and IVIg therapy.