Definition

Myasthenia gravis is an autoimmune disease characterized by muscle weakness in various parts of the body, occurring without our control. It is a rare and chronic condition. Typically, there is progressive muscle weakness in frequently used muscles, such as those in the eyes, mouth, throat, and limbs.

According to data from the United States, myasthenia gravis affects 20 out of 100,000 people. It is commonly found in women under the age of 40 and men over the age of 60, though it can affect individuals of any age. The cause of myasthenia gravis is the disrupted connection between nerves and muscles due to antibodies produced by the patient’s body. Currently, there is no cure for myasthenia gravis, but symptoms can be controlled with medication.

One of the urgent complications of myasthenia gravis is a myasthenic crisis. This occurs when there is sudden weakness in the respiratory muscles, making it difficult for a person to breathe. This differs from a myasthenia gravis flare, where weakness occurs in all muscles, leading to symptoms such as limping or double vision. In a myasthenic crisis, the respiratory muscles suddenly become weak. When the respiratory muscles are extremely weak and the patient cannot breathe, mechanical ventilation is provided to assist breathing.

Causes

The most common cause of a myasthenic crisis is infection, although it can occur without a clear cause. Myasthenic crises occur in patients with myasthenia gravis, and non-compliance with treatment can worsen symptoms. Other factors that can trigger a myasthenic crisis include emotional stress, extreme weather conditions, and certain surgical procedures. In some cases, medication side effects can also exacerbate myasthenia gravis symptoms.

Risk factor

Infection is the most frequent risk factor for a myasthenic crisis in myasthenia gravis patients. Other risk factors include:

• Thymectomy (surgical removal of the thymus)
• Pregnancy and premenstrual syndrome (PMS)
• Lack of sleep
• Childbirth
• Reduction in immunosuppressive medication dosage
• Use of certain medications such as antibiotics, antihypertensives, or specific antipsychotics
• Extreme temperature changes

A myasthenic crisis can also occur suddenly as part of the disease's progression. It is estimated that 20% of myasthenia gravis patients experience at least one myasthenic crisis in their lifetime. Women with myasthenia gravis are twice as likely to experience a myasthenic crisis compared to male patients.

Symptoms

Diagnosis

The doctor will inquire about the patient’s medical history and current medications. It is crucial to disclose all ongoing treatments and provide a complete health history. Myasthenic crises occur in individuals already diagnosed with myasthenia gravis and receiving regular treatment. Following a brief interview with the patient or accompanying family members, the doctor will conduct additional tests such as laboratory examinations, radiological assessments, and electrocardiograms (EKGs). Once the patient’s airway is secured with intubation, further tests to determine the cause of the myasthenic crisis can be performed, including:

• Chest X-ray: to check for lung infections or foreign objects in the lungs (aspiration)
• CT scan or MRI: to detect abnormalities in the thymus
• Blood oxygen level measurement using an oximeter
• Muscle and lung function tests

Management

Patients experiencing a myasthenic crisis must be treated in the Emergency Room (ER) and may be admitted to the Intensive Care Unit (ICU) for close respiratory function monitoring. In suspected respiratory failure, adequate ventilation and oxygenation are critical as the patient can stop breathing at any time.

To keep the airway open, a doctor or trained healthcare professional may perform intubation by inserting a tube into the respiratory tract, which will be connected to a ventilator to support the patient’s breathing. Once the patient’s respiratory function improves, the ventilator will be gradually withdrawn. Most patients need a ventilator for about two weeks.

Determining the cause of the myasthenic crisis is crucial. If diagnosed, treatment may include intravenous immunoglobulin (IVIg) for autoimmune conditions like myasthenia gravis and its crises, or plasma exchange (PE) to replace the patient’s blood plasma. For patients with myasthenia gravis and a thymus tumor, thymectomy is a recommended therapy. Treatment choices depend on facility availability and the doctor’s judgment. Neurologists or specialists in neurology manage myasthenic crisis patients.

Complications

The most frequent complications from a myasthenic crisis are fever and infections, particularly lower respiratory tract infections like pneumonia and bronchitis. Other common infections include urinary tract infections and gastrointestinal infections. Severe complications from infection can lead to sepsis, where infectious microorganisms enter the bloodstream.

Myasthenia gravis patients are also at high risk for deep vein thrombosis (blood clots in deep veins), heart failure, heart attacks, abnormal heart rhythms, and cardiac arrest. The most severe complication of a myasthenic crisis is death.

Prevention

Myasthenic crises can be prevented by regular health check-ups to monitor the progression of myasthenia gravis. Additional preventive measures include:

• Taking medications regularly and as prescribed to maintain respiratory muscle strength
• Taking anticholinesterase medications about half an hour before meals to prevent food aspiration into the respiratory tract
• Eating a balanced and nutritious diet to maintain weight and muscle strength
• Avoiding crowded and cold places to prevent upper respiratory infections
• Balancing physical activity with adequate rest
• Having effective stress management techniques to prevent extreme emotional changes

When to see a doctor?

If you or a loved one has a history of myasthenia gravis and experiences any of the following symptoms, seek immediate medical attention:

• Sudden drooping of the eyelids
• Blurred or double vision
• Nasal voice
• Difficulty chewing and swallowing
• Weakness in limbs such as hands and feet
• Persistent fatigue
• Increasing difficulty breathing

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