Myasthenic crisis is a serious condition, occurring as a complication, affecting greater than 20 % of patients with myasthenia gravis. Myasthenic crisis vs cholinergic crisis can be differentiated clinically using an edrophonium test. The administration of edrophonium will improve the clinical symptom of the myasthenic crisis. Respiratory failure from an overdose of cholinesterase inhibitors was more common before the introduction of immunosuppressive therapy. The possibility that deterioration could be due to the cholinergic crisis is best excluded by temporarily stopping the anticholinesterase drugs.
Precipitating features
- Infection/ surgery
- Pregnancy or childbirth
- Tapering immunosuppressive drugs
- Medications (eg. Aminoglycoside, beta-blocker, azithromycin)
Sign/Symptoms
- Increased generalized and oropharyngeal weakness (increasing difficulty walking up, coughing up)
- Respiratory insufficiency or dyspnea
Treatment for myasthenic crisis
- Admit in the intensive care unit. Treat the intercurrent precipitating factors.
- Monitor serial FVC (forced vital capacity). An FVC of 15 mL/kg is usually an indication for intubation. Patients in myasthenic crisis have a low threshold for intubation so don’t wait until the patient is hypoxic.
- Following intubation, acetylcholinesterase inhibitors (eg pyridostigmine) used in the daily management
of Myasthenia Gravis are temporarily held to reduce excess airway secretions and the risk of aspiration. - Plasmapharesis or IVIG
- Other immunomodulatory therapy (eg, mycophenolate mofetil or azathioprine) can be considered,
especially if corticosteroid therapy is ineffective, but usually requires several weeks to reach clinical
efficacy
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