Myasthenic crisis

Myasthenic crisis is a life-threatening condition in myasthenia gravis with worsening weakness, often due to infection, surgery, or medications. Treatment includes intensive care, respiratory support, plasma exchange or IVIG, and immunomodulating therapy to improve strength and manage triggers.

2024-01-08 16:09:10 - Editor

Introduction to Myasthenic Crisis

Myasthenic crisis is a life- threatening condition which is defined as worsening of myasthenic weakness, leading to generalised weakness, respiratory failure and requiring intubation or noninvasive ventilation. Severe bulbar palsy often accompanies respiratory muscle weakness. (1)

Precipitating Factors and Triggers of Myasthenic Crisis

Myasthenic crisis may be precipitated by a variety of factors, most often concurrent infection, surgical intervention, pregnancy, childbirth, tapering of immunosuppressive agents or by medications including aminoglycosides, fluoroquinolones, erythromycin, beta blockers, procainamide, quinidine and magnesium. (2, 3)

Treatment of Myasthenic Crisis

Treatment of patients with myasthenic crisis include admission to intensive care unit, frequently monitor respiratory muscle strength, electively intubate patients if clinically or tests (vital capacity (VC)< 30mL/kg of ideal body weight, maximum inspiratory pressure [MIP] less negative than -25 to -30 cmH20) suggest impending respiratory failure, stop anticholinesterase medications for intubated patients, begin rapid therapy with plasma exchange or intravenous immune globulin (IVIG). Then, begin immunomodulating therapy. Thereafter, initiate weaning from mechanical ventilation when respiratory muscle strength is improving, but only after starting rapid therapy with either plasma exchange or IVIG. Concurrent infections should be treated aggressively, as should stopping any drugs that may have precipitated or exacerbated the patient's weakness. (4, 5)

Immunomodulating Therapy in Myasthenic Crisis

Plasma exchange (plasmapheresis) directly removes acetylcholine receptor antibodies from the circulation, and its clinical efficacy roughly correlates with the reduction in antibody levels. A typical course of treatment consists of five exchanges (3 to 5 L of plasma each) over 7 to 14 days. IVIG is the pooled immunoglobulins from thousands of donors and acts in myasthenia via uncertain mechanisms. The total dose of IVIG is 2 g/kg, usually over five days (400 mg/kg per day for five days). (6, 7)

Plasma Exchange and IVIG

Immunomodulating therapy includes either high- dose glucocorticoids (prednisolone 60- 80 mg daily), or, alternatively, if glucocorticoids are contraindicated or were previously ineffective, then consider azathioprine (target dose of 2.5 mg/kg/day ), mycophenolate mofetil (500 mg twice daily), or cyclosporine (starting at 100 mg twice daily). (8, 9)

References

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