Myasthenic Crisis During Sedation Leads to Diagnosis

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by Margarida Maia PhD |

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A recent case report describes an elderly woman who was first diagnosed with myasthenia gravis (MG) after experiencing a myasthenic crisis while being sedated for a surgical procedure.

“This case reports a form of discovery of [a] myasthenic crisis outside the usual circumstance,” its authors wrote. “The prognosis depends on early and appropriate management.”

The report, “Myasthenia gravis in an old woman discovered during sedation for diagnostic digestive fibroscopy: case report,” was published in the Annals of Medicine and Surgery.

A myasthenic crisis is a complication of MG, in which a severe worsening of muscle weakness typically results in respiratory failure requiring intubation (the insertion of a tube down the throat) and mechanical ventilation (the use of a special machine to assist with breathing).

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It is more common among women younger than 40 and men older than 60, but can occur in women or men at any age.

Researchers in Morocco reported the case of an 85-year-old woman who showed signs of a myasthenic crisis while being sedated for a surgical procedure.

“Myasthenia gravis is rare in women of advanced age,” the researchers wrote, adding that a “myasthenic crisis can be inaugural of the disease whatever the age without distinction of sex.”

The woman was scheduled for a diagnostic gastrointestinal fibroscopy — a procedure that allows doctors to see the inside of the digestive tract — to pinpoint the cause of her swallowing difficulties. She appeared healthy otherwise.

Prior to the surgical procedure, the woman was given 2 mg of midazolam to induce sedation and 1 mg/kg of propofol to induce and maintain sedation.

After being given the medication, however, the woman developed acute respiratory failure followed by cardiopulmonary arrest, during which blood flow and breathing stopped. She was intubated and ventilated, and then transferred to the intensive care unit. Her blood flow returned to normal, but a first attempt to wean her off intubation failed.

She had drooping of the upper eyelids (ptosis), double vision (diplopia), and difficulty swallowing (dysphagia), which are three common symptoms of MG.

A chest CT scan revealed she had a thymoma, which is a tumor in the thymus. While the role of the thymus in the development of MG is unclear, it is thought that it may trigger or help maintain the production of disease-causing self-reactive antibodies, namely those against the acetylcholine receptor (AChR).

The diagnosis of MG was confirmed by a blood test, which detected high levels of AChR antibodies, and an electromyography, which detected a blockade of the electrical signals traveling in three nerve-muscle pairs.

The woman was treated with pyridostigmine (sold as Mestinon, among other brand names), a medication that prevents the breakdown of acetylcholine — a signaling molecule that triggers muscle contraction. She also received immunoglobulins, which are antibodies that destroy and neutralize self-reactive AChR antibodies. One week later, she was weaned off intubation.

She also was scheduled for surgery to remove her thymoma under general anesthesia, while respecting the contraindications of anesthetic products that could trigger a myasthenic crisis.

“The myasthenic crisis was revealing of the disease and probably had several triggers including stress and premedication with midazolam,” the researchers wrote. “The evolution was favorable as a result of early and appropriate management.”

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Myasthenia Gravis News conducted a survey from Feb. 11-March 28 to gain greater insight into the characteristics of the MG community and disease management. Results of the survey have now been published. Click on the image to view the infographic, and click here to read the story.