Myasthenic crisis is a complication of a condition known as myasthenia gravis, which is characterized by weakness and rapid fatigue of voluntarily controlled muscles. It’s considered a neuromuscular autoimmune disease that can affect the muscles of the eyes, face, and eventually other parts of the body.
Suffering from a myasthenia gravis crisis can be an extremely hazardous situation, requiring emergency medical assistance. Between one-fifth and one-third of all patients with generalized autoimmune myasthenia gravis can be affected.
Epidemiology of Myasthenic Crisis
The percentage of myasthenic patients who progress to myasthenic crisis is between 15 to 20 percent. Women are twice as likely to experience myasthenic crisis than men, with women having a higher rate prior to the age of 55 and men and women have equal rates post-55.
Signs and Symptoms of Myasthenic Crisis
Understanding the background of myasthenia gravis will give some context as to how myasthenia gravis with acute exacerbation can lead to a myasthenic crisis. In this condition, antibodies either block or destroy nicotinic acetylcholine receptors at the neuromuscular junction between the nerve and muscle. This structure serves to communicate the control of muscular contraction.
The breakdown of normal communication between nerves and muscles is the hallmark of myasthenia gravis and is characterized by symptoms such as weakness of the arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing, and breathing.
A myasthenic crisis is characterized by muscle weakness that may extend to the respiratory muscles, causing respiratory failure. This requires intubation and mechanical ventilation. Without this medical intervention, a myasthenic crisis is considered life-threatening.
The following are common myasthenic crisis symptoms:
- Difficulty breathing or speaking
- The skin between your ribs, around your neck, or on your abdomen pulls in when you breathe
- Morning headaches or daytime fatigue
- Frequent nighttime awakenings or feeling unrested during the day
- A weak cough with increased secretions (mucus or saliva)
- Weak tongue, trouble swallowing, or trouble chewing
- Weight loss
Diagnosis of Myasthenic Crisis
Pulmonary function tests (PFTs): An evaluation of how well your lungs are working by measuring lung volume, capacity, rate of flow, and gas exchange.
Arterial blood gases (ABG): A test to assess the amount of oxygen and carbon dioxide in your blood. It is an accurate measurement of how well your lungs are working. Having increased levels of carbon dioxide will tell doctors that you’re not perfusing enough oxygen into your bloodstream due to mechanical failure of the lungs.
Chest x-ray: Used to rule out any other possible causes for your presenting symptoms. An x-ray of the chest will allow doctors to view the heart and lung structure, looking for signs of pneumonia or possible fluid that has accumulated around the heart or lungs.
Computer tomography (CT) scan: A more detailed imaging machine that allows doctors to get a better view of internal organs. CT scans are better for looking at soft tissue, such as the lungs and heart. CT is also great for looking at the thymus gland, of which myasthenia gravis patients are known for having issues with.
MRI: The best imaging scan that gives an even more detailed image compared to a CT scan. It uses powerful magnets and a computer to take pictures of the desired body part. Because of this, having any type of metal in the body may cause serious injury and should be disclosed to your doctor beforehand.
Treatment for Myasthenic Crisis
Myasthenic crisis treatment is one that needs to be implemented quickly with the goal of treatment to make respiratory muscles stronger to breathe better. If this is not done in a timely fashion, lungs may begin to fail and endanger the patient’s life due to suffocation. The following are the most common strategies when facing a myasthenic crisis.
- Endotracheal tube: An emergency intervention that places a tube into the windpipe (trachea) through the mouth or nose to keep the airway open. Sometimes, a mechanical ventilator may be attached, supplying extra oxygen through this tube and helping you breathe.
- Bilevel positive airway pressure (BiPAP): Works in a similar fashion as a CPAP for the treatment of sleep apnea, as it helps to regulate varying pressures in the lungs to keep them open and functioning properly.
- Suctioning: To help remove airway secretions for better ventilation
- Anticholinesterase medication: Helps increase the level of acetylcholine at the neuromuscular junction in an attempt to improve muscle weakness.
- Immunosuppressants: Used to slow down the immune system, slowing down the progression of myasthenia gravis.
- Intravenous immunoglobulins (IVIg): A medication given intravenously that’s used to treat various autoimmune conditions, such as myasthenia gravis. IVIg provides the body with normal antibodies that can alter an immune response.
- IV fluids: Given to prevent dangerously low blood pressure states. They may also be useful for replacing any fluid and electrolyte loss from the body.
- Plasma exchange: A procedure that aims to remove plasma from your blood and replace it with healthy plasma from a donor. This is done to remove a disease substance that is circulating in the plasma itself.
Prevention of Myasthenic Crisis
Myasthenic crisis prevention comes in the form of decreasing the risk of myasthenia gravis. However, about 50 percent of patients developing a myasthenic crisis will not present with any precipitating factors. Factors such as an infection should be identified and treated as quickly as possible.
The following are actions taken to prevent myasthenia gravis:
- Take anticholinesterase medication as prescribed
- Avoid respiratory infections
- Maintain strength and weight with proper nutrition
- When exercising, plan intermittent rest periods
- Reduce emotional stress
- All currently used medications should be disclosed to your doctor to help avoid medications that interfere with myasthenia gravis treatment
Risk Factors for Myasthenic Crisis
Having myasthenia gravis is a major risk factor for developing myasthenic crisis, however, it may still occur for unknown reasons. The following triggers may trigger or increase your risks for a myasthenic crisis:
- Thyroid disease
- A tumor of the thymus gland
- Lung infections, such as pneumonia
- Aspiration pneumonitis
- Stress from trauma, surgery, or emotional upset
- A change in medicines
- Monthly periods or pregnancy
- Some contract dyes used in imaging studies, such as during CT or MRI