Myasthenia Crisis

Myasthenia crisis is a complication of myasthenia gravis. It is defined as worsening of myasthenic weakness requiring intubation or noninvasive ventilation. Myasthenia crisis has a mortality rate of 5%

Primary Category
Secondary Category


  • Myasthenia crisis is a complication of myasthenia gravis
  • Defined as worsening of myasthenic weakness requiring intubation or noninvasive ventilation
  • Myasthenia crisis has a mortality rate of 5%
  • 10 to 20% of myasthenia gravis patients experience myasthenic crisis at least once in their lifetime

Cholinergic crisis

  • Paradoxical weakening with anticholinesterase medications is called "cholinergic crisis."
  • It can be difficult to distinguish from worsening myasthenia gravis.
  • Develops as a result of overstimulation of nicotinic and muscarinic receptors at the neuromuscular junctions and synapses
  • It is a major side effect of excessive anticholinesterase medication if the dose limitation of pyridostigmine is exceeded above 120 mg every three hours. .


  • concurrent infection
  • post-surgical intervention (eg, thymectomy)
  • pregnancy
  • childbirth
  • tapering of immunosuppressive medications
  • Certain drugs

Table 1: Other causes of acute neuromuscular respiratory failure

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Table 2: Drugs that precipitate myasthenia gravis

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  • Admit in ICU for frequent monitoring of respiratory function
  • Vital capacity (VC) and/or maximal inspiratory pressure (MIP) should be measured frequently, typically every four hours.
  • Diaphragm thickness measurements by using ultrasound
  • Elective intubation if suspecting impending respiratory failure
  • Dyspnea on lying down that can be expressed as suffocation or drowning.
  • Severe dysphagia with weak cough and difficulty clearing secretions.
  • Signs of respiratory muscle weakness, such as hypophonia, pausing during speech to take a breath, poor respiratory effort, increased respiratory rate with shallow breaths, use of accessory muscles of respiration, and paradoxical abdominal breathing. However the signs of respiratory muscle weakness not always apparent.
  • VC falls below 15 to 20 mL/kg
  • MIP is less negative than -25 to -30 cmH20
  • Decreased diaphragm thickening fraction
  • Progressive respiratory acidosis despite therapy
  • Arterial blood gases are insensitive tests to measure respiratory muscle weakness because they often develop only after the onset of life-threatening respiratory failure
  • For patients with myasthenic crisis who are intubated, anticholinesterase medications used for myasthenia gravis (eg, pyridostigmine) should be withdrawn to reduce airway secretions. These medications can be restarted at a low dose after the patient has shown a response to plasma exchange (PLEX) or intravenous immune globulin (IVIG).
  • Rapid therapy with PLEX or IVIG
  • Expert consensus suggests that PLEX is more effective and works more quickly. The choice between the 2 therapies depends on patient comorbidity (e.g., PLEX cannot be used in sepsis and IVIg is contraindicated in hypercoagulable states, renal failure, or hypersensitivity to immunoglobulin) and other factors, including availability.
  • Plasma exchange directly removes acetylcholine receptor antibodies from the circulation
  • Generally the course of treatment consists of five exchanges (3 to 5 L of plasma each) over 7 to 14 days
  • Dosage of IVIG is 2 g/kg, usually over 2-5 days.
  • Concurrent initiation of chronic immunomodulating therapy with high-dose glucocorticoids; if glucocorticoids are contraindicated or less effective consider azathioprine, mycophenolate mofetil, or cyclosporine.
  • Weaning from mechanical ventilation with spontaneous breathing trials considered after treatment with plasma exchange or IVIG has been started and respiratory muscle strength has been improved (VC >15 to 20 mL/kg and a MIP more negative than -25 to -30 cmH2O)
  • Remove any precipitating factors such as drugs or infections exacerbating the disease.
  • Workup for concurrent infections including CBC, UA, CXR and blood cultures.
  • Treat any infection if present
  • IV Magnesium added as allergy

Mechanical Ventilation in Myasthenia Crisis

  • The key to the greatest chance of recovery in patients with neuromuscular disease is quick assessment and prompt treatment.
  • Identifying patient with impending respiratory failure and prompt endotracheal intubation with positive pressure mechanical ventilation should be considered while managing myasthenia crisis
  • Invasive mechanical ventilation has the advantage of adequate secretion clearance and full support for those suspected to have prolonged courses of crisis
  • The mode of mechanical ventilation generally utilized for managing myasthenia crisis is assist control modes of volume controlled ventilation and low levels of positive end-expiratory pressure (PEEP) with subsequent adjustments.
  • The median duration of mechanical ventilation is 14 days in myasthenia crisis

Complications of Myasthenia crisis

  • Fever and infection, including pneumonia, bronchitis, urinary tract infection, colitis caused by Clostridium difficile, bacteremia, and sepsis.
  • Increased risk for vascular complications including deep vein thrombosis, heart failure, acute myocardial infarction, cardiac arrhythmias, and cardiac arrest.

Further Reading

  • Excellent Review Article - Getting Rid of Weakness in the ICU: An Updated Approach to the Acute Management of Myasthenia Gravis and Guillain-Barré Syndrome (Lizarraga, Lizarraga, & Benatar, 2016)


  • Boon, A. J., Harper, C.J., et al. Two-dimensional ultrasound imaging of the diaphragm: quantitative values in normal subjects. Muscle Nerve. 2013;47(6):884-889
  • Sanders, D. B., Wolfe, G. I., Benatar, M., et al. International consensus guidance for management of myasthenia gravis: Executive summary. Neurology 2016; 87:419.
  • Lizarraga, A. A., Lizarraga, K. J., & Benatar, M. (2016). Getting Rid of Weakness in the ICU: An Updated Approach to the Acute Management of Myasthenia Gravis and Guillain-Barré Syndrome. Seminars in Neurology, 36(6), 615–624.
  • Weinberg, M., Cavalcante, J. A., Choy, T., & Ahmad, S. (2019). A 23-Year-Old Man With Dyspnea During Myasthenia Crisis. Chest, 155(6), e155–e157.
Umair Hamid MD

Written by

Umair Hamid MD

Neurology Resident at University of Illinois College of Medicine Peoria

    Danish Batti MD

    Written by

    Danish Batti MD

    Movement Disorders Neurologists and teaches physicians internationally, Directs an online mini-fellowship in Movement Disorders since 2017, Founding director of the International Neurology program at University of Nebraska Medical Center

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