Management of Myasthenia Gravis Exacerbation
For myasthenia gravis exacerbation, the management approach should be stratified based on severity, with immediate hospitalization and intensive treatment for severe cases, while milder exacerbations can be managed with medication adjustments on an outpatient basis. 1, 2
Assessment and Diagnosis of Exacerbation
- Evaluate for fatigable or fluctuating muscle weakness, particularly with ocular and/or bulbar involvement (ptosis, extraocular movement abnormalities, dysphagia, dysarthria, facial muscle weakness) 1
- Assess for neck and/or respiratory muscle weakness which may indicate a more severe exacerbation 1
- Perform pulmonary function assessment with negative inspiratory force (NIF) and vital capacity (VC) measurements to evaluate respiratory status 1, 3
- Check for laboratory markers including AChR and anti-striated muscle antibodies; if AChR antibodies are negative, consider muscle-specific kinase and lipoprotein-related 4 antibodies 1, 4
- Consider concurrent conditions such as myositis (check CPK, aldolase, ESR, CRP) and myocarditis (ECG and TTE) if respiratory insufficiency or elevated CPK/troponin T is present 1
- Obtain neurologic consultation for all grades of exacerbation 1, 3
Management Based on Severity
Mild to Moderate Exacerbation (Grade 2)
- Hold immune checkpoint inhibitors (if applicable) and may resume only if symptoms resolve 1
- Initiate or adjust pyridostigmine starting at 30 mg orally three times daily, gradually increasing to maximum of 120 mg four times daily based on symptoms and tolerance 1, 2, 5
- Administer corticosteroids (prednisone 1-1.5 mg/kg orally daily) and wean based on symptom improvement 1, 2
- Warning: Monitor for cholinergic crisis which may result from pyridostigmine overdosage and can be difficult to distinguish from myasthenic crisis 5
Severe Exacerbation/Crisis (Grade 3-4)
- Permanently discontinue immune checkpoint inhibitors (if applicable) 1
- Admit patient immediately, with potential ICU-level monitoring 1, 3
- Continue corticosteroids (methylprednisolone 1-2 mg/kg daily) 1, 3
- Initiate either IVIG (2 g/kg IV over 5 days at 0.4 g/kg/day) or plasmapheresis for 5 days 1, 2, 3
- Perform frequent pulmonary function assessment and daily neurologic review 1, 3
- Consider intubation and mechanical ventilation for respiratory failure 6
Important Precautions
- Avoid medications that can worsen myasthenia symptoms: β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides 1, 2, 3
- Differentiate between myasthenic crisis (disease worsening requiring more anticholinesterase therapy) and cholinergic crisis (overdosage requiring withdrawal of anticholinesterase drugs) 5
- For cholinergic crisis, promptly withdraw all anticholinesterase drugs and consider atropine to manage muscarinic effects 5
- Be cautious with atropine use as it can mask signs of overdosage and lead to inadvertent induction of cholinergic crisis 5
Long-term Management After Exacerbation
- Consider immunosuppressive therapies such as azathioprine for long-term management to prevent future exacerbations 7, 8
- Evaluate for thymectomy in AChR antibody-positive generalized MG patients, particularly those with thymoma 7, 8
- Implement regular neurological follow-up to adjust treatment as needed 2
- Consider physical therapy for management of fatigue, which is common in MG 7
Special Considerations
- For ocular MG exacerbations, early treatment with corticosteroids is recommended when ocular motility is abnormal and fails to respond to symptomatic treatment 7
- For refractory cases, consider rituximab as an additional treatment option 7, 9
- Tailor treatment approach based on MG subtype (early-onset, late-onset, thymoma-associated, MuSK-positive, etc.) 9, 8
By following this structured approach to management, mortality rates in myasthenic crisis have significantly improved to approximately 4-8% 6.