Myasthenic crisis is a life-threatening condition, which is defined as weakness from acquired myasthenia gravis that is severe enough to necessitate intubation or to delay extubation following surgery . The respiratory failure is due to weakness of respiratory muscles.
Severe bulbar (oropharyngeal) muscle weakness often accompanies the respiratory muscle weakness, or may be the predominant feature in some patients. When this results in upper airway obstruction or severe dysphagia with aspiration, intubation and mechanical ventilation are necessary.
This topic will review the evaluation and treatment of myasthenic crisis and rapidly worsening myasthenia gravis. Other aspects of myasthenia gravis are discussed separately. (See "Clinical manifestations of myasthenia gravis" and "Diagnosis of myasthenia gravis" and "Treatment of myasthenia gravis".)
Although data are limited, the proportion of patients with myasthenia gravis who experience at least one myasthenic crisis may be as high as 10 to 20 percent , and the annual risk of myasthenic crisis among patients with myasthenia gravis is approximately 2 to 3 percent . In 13 to 20 percent of patients who present with myasthenic crisis, it is the first manifestation of myasthenia gravis [3-5]. Most myasthenic crises occur in the first few years after the diagnosis of myasthenia gravis, when the disease is often in its most active phase. (See "Clinical manifestations of myasthenia gravis", section on 'Clinical course'.)
The epidemiology of myasthenia gravis is reviewed in detail separately. (See "Clinical manifestations of myasthenia gravis", section on 'Epidemiology'.)