Duration of Myasthenia Gravis Crisis
A myasthenic crisis typically lasts approximately 2 weeks (median 12-14 days of mechanical ventilation) under appropriate treatment, though prolonged courses beyond 1 month occur in about 20% of patients due to comorbidities and complications. 1
Expected Timeline and Clinical Course
- The median duration of mechanical ventilation during myasthenic crisis is 12-14 days when sufficient treatment is provided 1
- Most patients can be weaned from mechanical ventilation within 1 month 2
- Approximately 20% of patients remain mechanically ventilated after 1 month, typically due to comorbidities and complications rather than the crisis itself 1
- Clinical improvement can be achieved within a few days if immunotherapy (plasmapheresis or IVIG) is initiated early 1
Factors Affecting Crisis Duration
- Prolonged courses are not uncommon and are almost always related to comorbidities and complications, not the myasthenic crisis itself 1
- The presence of infections or other complications such as delirium significantly influences the duration and course of the crisis 1
- Early diagnosis and treatment of triggers, particularly infections, can shorten the crisis duration 1
Treatment Impact on Duration
- Plasmapheresis is preferred over IVIG as the treatment of choice for myasthenic crisis and may lead to faster improvement 2
- Early intubation to secure the airway, combined with prompt immunotherapy, can prevent prolonged respiratory failure and achieve clinical improvement within days 1
- Acute causal treatment includes immunoadsorption/plasmapheresis or alternatively immunoglobulins (IVIG 2 g/kg over 5 days), which should be initiated immediately upon ICU admission 3, 1
Prognosis and Recovery
- The outcomes of myasthenic crisis are generally favorable, with current mortality rates between 2-5% in most cohorts, though some studies report up to 16% 1, 2, 4
- Mortality is driven by age and medical comorbidities rather than the crisis itself 2
- Many patients are able to eventually achieve good MG control after recovering from crisis, and the crisis does not appear to affect long-term prognosis 2
- The lifetime risk of recurrence after one crisis is approximately 30% 1
Critical Management Considerations
- Crisis represents a temporary exacerbation, and the goal is supportive care until it subsides, typically within 2 weeks 5
- Continuous monitoring in an ICU setting with frequent pulmonary function assessments (vital capacity and negative inspiratory force) is essential throughout the crisis 3
- All acetylcholinesterase inhibitors should be withdrawn during crisis, as they do not improve outcomes and may complicate management 6