Myasthenic crisis
Myasthenic crisis is acute, life-threatening respiratory and bulbar failure from severe worsening of myasthenia gravis, distinct from the chronic, ambulatory disease. Diagnosis rests on bedside respiratory monitoring (vital capacity, maximal inspiratory pressure) and distinguishing it from cholinergic crisis (anticholinesterase overtreatment); management is airway protection plus IVIG or plasma exchange.
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What this article covers
- Overview
Acute, life-threatening exacerbation of myasthenia gravis (MG): myasthenic crisis is rapid worsening of neuromuscular weakness severe enough to cause respiratory failure, from respiratory muscle…
- Epidemiology
Occurs in a minority of patients with MG over the course of their disease, and can be the initial presentation in a patient not yet diagnosed.
- Risk factors
Infection: the most common precipitant of myasthenic crisis, including respiratory infections.
- Pathophysiology
Loss of neuromuscular transmission safety factor below threshold: the same antibody-mediated destruction or dysfunction of postsynaptic acetylcholine receptors that produces chronic MG weakness can…
- Clinical features
Rapidly progressive generalized or bulbar weakness over hours to a few days, often with a preceding trigger (infection, recent medication change, recent surgery).
- Differential diagnosis
Cholinergic crisis: the essential discriminator; presence of muscarinic/autonomic symptoms (DUMBELLS), miosis, and a recent anticholinesterase dose increase points here rather than to myasthenic…
- Diagnosis
The diagnosis is established clinically in a patient with known or suspected MG who develops acute respiratory and/or bulbar failure, confirmed by objective bedside respiratory measurements rather than by waiting for blood gas abnormalities.
- Management
First, protect the airway and assess the need for mechanical ventilation using the trended vital capacity and maximal inspiratory pressure thresholds above, along with clinical signs of bulbar…
- Complications
Prolonged mechanical ventilation and its sequelae: ventilator-associated pneumonia, ICU-acquired weakness, and delayed extubation.
- Prognosis
Modern intensive care management allows most patients to be successfully extubated and to recover to their baseline functional status, though recovery can take days to weeks.
- Prevention
Medication reconciliation before prescribing in any patient with known MG: avoid aminoglycosides, fluoroquinolones, magnesium, beta-blockers, and hydroxychloroquine when alternatives exist, and flag…
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Myasthenia gravis is an autoimmune disorder of the postsynaptic neuromuscular junction, most often caused by acetylcholine receptor antibodies, producing fluctuating, fatigable weakness of ocular, bulbar, and limb muscles. Diagnosis rests on antibody testing and electrodiagnostics; first-line treatment is pyridostigmine, with glucocorticoids and steroid-sparing immunosuppression for generalized disease and thymectomy for eligible patients.
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