Myasthenic crisis is a common complication in patients with myasthenia gravis (MG), marked by exacerbation of MG symptoms and respiratory failure. But with the rarity of MG, and its similarity to a range of other neuromuscular diseases, proper detection and treatment might fail, researchers argue.
To make it easier for fellow physicians in the emergency room to handle patients who develop the condition, a research team at the University of Texas Southwestern Medical Center authored a review, presenting available data of its diagnosis and treatment.
The review, “Myasthenia Gravis and Crisis: Evaluation and Management in the Emergency Department,” was published in the Journal of Emergency Medicine.
Up to 30 percent of patients with MG develop myasthenic crisis at some point, most often in the first two or three years after diagnosis.
Nearly any form of stress, physical or emotional, can trigger the failure of muscles to adequately maintain breathing. Among the most common factors, however, is infection, which contributes to about 30 percent of cases.
Importantly, the condition can be the first sign of MG in a previously undiagnosed patient, making diagnosis and treatment even more difficult. Moreover, common MG medications — corticosteroids and cholinesterase inhibitors — can trigger the condition in patients with severe MG.
Physical examination, including examining the lungs, in combination with a review of the patient’s disease and medication history, may help in diagnosing the condition. Affected patients often appear clearly distressed and use accessory muscles to maintain breathing.
But the diagnosis might become difficult in some patients, as signs of breathing difficulties can be very subtle. In these cases, which often involve patients with severe MG, problems with phonation, a quiet voice, or weak neck muscles may flag respiratory distress.
Importantly, the reviewers underscored that oxygen and carbon dioxide levels often are normal until late in the crisis, and should not be used to exclude the possibility of an MG crisis.
The team further underscored that noninvasive positive pressure ventilation (NIPPV) should be the first treatment choice in these patients, and may be used while physical examinations are still ongoing.
If intubation is needed, researchers underscored that emergency physicians should avoid paralytic drugs, particularly those called depolarizing paralytics, which act on the so-called motor end-plate where a motor neuron and muscle meet. Also corticosteroids and cholinesterase inhibitors should be avoided.
Instead, low-dose nondepolarizing drugs should be used, they said.
The review further underscored that a range of other medications can exacerbate the condition, listing several antibiotics, anticonvulsants, antipsychotics, and heart medications among the drugs that should be avoided.