What is the management approach for acute myasthenia gravis?

Management of Acute Myasthenia Gravis

The first-line treatment for acute myasthenia gravis crisis is respiratory support combined with either plasmapheresis or intravenous immunoglobulin (IVIG), with concurrent administration of prednisone at 0.5-1 mg/kg per day. 1

Initial Assessment and Stabilization

• Respiratory evaluation is critical:

  • Monitor for signs of respiratory compromise (decreased vital capacity, oxygen saturation)
  • Consider early non-invasive positive pressure ventilation (NIPPV) even in patients with bulbar weakness 2
  • If intubation becomes necessary, avoid depolarizing paralytics or use reduced doses of non-depolarizing agents 2

• Identify and treat precipitating factors:

  • Infection is the most common trigger (respiratory, urinary tract) 3, 4
  • Medication changes, surgery, pregnancy, or emotional stress
  • Rule out infection with appropriate cultures and imaging

Acute Phase Treatment

1. Discontinue acetylcholinesterase inhibitors during crisis 5, 2

   • Continuing these medications during crisis can mask signs of cholinergic crisis
   • Resumption should occur after stabilization

2. Immunomodulatory therapy 1, 6:

   • Plasmapheresis: First-line for severe cases with respiratory compromise
   • IVIG: Alternative when plasmapheresis is unavailable or contraindicated (slower onset)
   • Typical IVIG dosing: 2 g/kg divided over 2-5 days

3. Corticosteroid therapy 1:

   • Prednisone 0.5-1 mg/kg per day
   • Initiate concurrently with plasmapheresis or IVIG
   • Caution: May cause temporary worsening of symptoms in first 1-2 weeks

Differential Diagnosis: Myasthenic vs. Cholinergic Crisis

• Critical distinction: Myasthenic crisis (disease worsening) vs. cholinergic crisis (medication overdose) 5
• Cholinergic crisis signs: Increased secretions, abdominal cramping, diarrhea, bradycardia
• Diagnostic approach: May require edrophonium testing (with caution) to differentiate 5
• Management differs radically:
  • Myasthenic crisis: Intensify immunotherapy
  • Cholinergic crisis: Withdraw acetylcholinesterase inhibitors, consider atropine

Long-term Management After Crisis Resolution

• Restart acetylcholinesterase inhibitors 1:

  • Pyridostigmine bromide: Start at 30 mg orally three times daily
  • Titrate gradually to maximum of 120 mg four times daily based on symptom response

• Initiate steroid-sparing agents 1:

  • Start concurrently with corticosteroids to minimize steroid exposure
  • Options include:
    • Methotrexate: 15 mg weekly
    • Azathioprine: 2 mg/kg ideal body weight in divided doses
    • Mycophenolate mofetil: Start 500 mg twice daily, increase to 1000 mg twice daily

Monitoring and Precautions

• Regular neurological assessments 1:

  • Daily during acute phase
  • Monitor pulmonary function tests
  • Watch for signs of deterioration

• Medication precautions 1:

  • Avoid medications that can worsen myasthenia gravis:
    • Aminoglycosides, fluoroquinolones, macrolides
    • Beta-blockers, IV magnesium, daptomycin
  • Safer alternatives include penicillins, cephalosporins, and tetracyclines

Prognosis

• Mortality rate has significantly improved to approximately 4-8% with modern management 4
• Good to satisfactory outcomes can be expected in most patients with appropriate treatment 3
• Cardiac monitoring is essential as arrhythmias can occur and may be fatal in some cases 7