What is the treatment for a myasthenia gravis crisis?

Treatment of Myasthenia Gravis Crisis

Myasthenia gravis crisis requires immediate ICU admission with aggressive respiratory support, high-dose corticosteroids (methylprednisolone 1-2 mg/kg/day IV), and plasmapheresis as the preferred rapid immunotherapy, with IVIG (2 g/kg over 5 days) as an alternative. 1

Immediate Airway and Respiratory Management

Secure the airway early through intubation if respiratory insufficiency or severe bulbar weakness with aspiration is present. 2 The rapidly progressive weakness of respiratory and bulbar muscles leads to decompensation within minutes to days, making early intubation essential to prevent aspiration and respiratory failure 2.

Respiratory Monitoring Parameters

• Apply the "20/30/40 rule" to identify patients at risk: vital capacity <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 1
• Perform frequent pulmonary function assessments with negative inspiratory force (NIF) and vital capacity (VC) measurements 1
• Monitor patients for a minimum of 24 hours in ICU even after apparent stabilization 1
• Use aggressive respiratory interventions including suction, chest physiotherapy, and bronchodilator treatments to minimize atelectasis and pneumonia 3

Rapid Immunotherapy: Plasmapheresis vs IVIG

Plasmapheresis is the preferred treatment over IVIG for myasthenic crisis. 4, 5 This recommendation is based on clinical experience showing faster response times and better outcomes in the acute setting 5.

Plasmapheresis Protocol

• Administer 5 sessions over 5 days as the standard regimen 1
• For severe cases, consider an extended regimen of 7 exchanges over 14 days 1
• Plasmapheresis requires specialized equipment and expertise, often necessitating transfer to tertiary centers 1
• Monitor for complications including hemodynamic shifts, coagulation disorders, electrolyte imbalances, and line-related bacteremia 1

IVIG as Alternative

• Administer 2 g/kg total dose over 5 days at 0.4 g/kg/day if plasmapheresis is contraindicated or unavailable 1
• IVIG may be preferred in pregnant women due to fewer monitoring requirements 6
• Do not use sequential therapy (plasmapheresis followed by IVIG) as it is no more effective than either treatment alone 6

Corticosteroid Therapy

• Start high-dose corticosteroids immediately: methylprednisolone 1-2 mg/kg/day IV or prednisone 1-1.5 mg/kg/day orally 1
• Continue corticosteroids concurrently during plasmapheresis or IVIG treatment 6
• Begin steroid taper 3-4 weeks after initiation based on symptom improvement 1

Pyridostigmine Management During Crisis

Discontinue or withhold pyridostigmine in intubated patients. 1 For non-intubated patients with myasthenic symptoms, pyridostigmine may be continued at 30 mg orally up to 600 mg daily 1.

• If IV administration is necessary: 30 mg oral pyridostigmine corresponds to 1 mg IV pyridostigmine or 0.75 mg neostigmine IM 1, 6

Critical Medication Avoidance

Immediately discontinue all medications that can worsen myasthenia gravis: 1

• IV magnesium is absolutely contraindicated 1
• Beta-blockers 1
• Fluoroquinolone antibiotics 1
• Aminoglycoside antibiotics 1
• Macrolide antibiotics 1

If severe hypomagnesemia requires treatment, mandatory neurology consultation is required before any magnesium administration 1.

Diagnostic Workup During Crisis

• Check acetylcholine receptor (AChR) antibodies and anti-striated muscle antibodies 1
• If AChR antibodies are negative, test for muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies 1
• Measure CPK, aldolase, ESR, and CRP to evaluate for concurrent myositis 1
• Perform cardiac evaluation with ECG and transthoracic echocardiogram if respiratory insufficiency or elevated CPK/troponin T is present to rule out concurrent myocarditis 1

Clinical Course and Prognosis

• Median duration of mechanical ventilation is 12-14 days under adequate treatment 2
• The majority of patients can be weaned from mechanical ventilation within 1 month 4
• Mortality rate in United States cohorts is less than 5%, primarily driven by age and medical comorbidities rather than the crisis itself 4, 2
• Approximately 20% of patients remain mechanically ventilated after 1 month, usually due to complications 2
• The lifetime risk of crisis recurrence is approximately 30% 2

Common Pitfalls to Avoid

• Do not delay intubation in patients with severe bulbar symptoms or declining respiratory parameters—early airway protection prevents aspiration and respiratory arrest 2
• Do not use IVIG for chronic maintenance therapy—it is only indicated for acute exacerbations or crisis situations 6
• Do not underestimate the importance of treating infections and other triggers—respiratory infections are the most common precipitant of crisis 4
• Do not continue pyridostigmine in intubated patients—it provides no benefit and may complicate management 1