From the Guidelines
Myasthenia crisis is a life-threatening condition characterized by severe muscle weakness that affects breathing muscles, requiring immediate medical attention, as evidenced by the need for inpatient admission and potential ICU-level monitoring in patients with G3-4 symptoms, such as limiting self-care, weakness limiting walking, ANY dysphagia, facial weakness, respiratory muscle weakness, or rapidly progressive symptoms 1. The primary signs and symptoms include severe respiratory muscle weakness leading to respiratory failure, difficulty breathing, shortness of breath, and inability to clear secretions. Patients may experience extreme fatigue, severe generalized muscle weakness, difficulty swallowing (dysphagia), slurred speech (dysarthria), and inability to hold up the head. Some key signs and symptoms to look out for include:
- Severe respiratory muscle weakness
- Difficulty breathing
- Shortness of breath
- Inability to clear secretions
- Extreme fatigue
- Severe generalized muscle weakness
- Difficulty swallowing (dysphagia)
- Slurred speech (dysarthria)
- Inability to hold up the head
- Facial muscle weakness, often presenting as drooping eyelids (ptosis), double vision (diplopia), and a weak smile or expressionless face. Objective measurements, such as decreased vital capacity below 15-20 mL/kg or negative inspiratory force less than -20 cm H2O, indicate impending respiratory failure, and patients with these symptoms should be admitted for close monitoring and potential intervention, as outlined in the management guidelines for immune-related adverse events in patients treated with immune checkpoint inhibitor therapy 1. Paradoxical breathing (abdomen moves inward during inspiration) and use of accessory respiratory muscles are concerning signs, and anxiety, restlessness, and confusion may develop due to hypoxia. These symptoms typically develop rapidly over hours to days, often triggered by infection, surgery, pregnancy, medication changes, or emotional stress, and prompt recognition is crucial as patients require ICU admission, possible mechanical ventilation, and specific treatments such as plasma exchange, intravenous immunoglobulin, and high-dose corticosteroids to address the underlying autoimmune process targeting acetylcholine receptors at the neuromuscular junction, as recommended for patients with G3-4 symptoms 1.
From the Research
Signs and Symptoms of Myasthenia Crises
- Myasthenic crisis (MC) is a life-threatening state with respiratory failure in patients with myasthenia gravis (MG) 2, 3, 4, 5
- Muscle weakness can involve any voluntary muscle, and can be severe enough to result in respiratory failure 4
- MC can be differentiated from other neuromuscular junction diseases by the presence of normal reflexes, normal sensation, lack of autonomic symptoms, lack of fasciculations, and worsening weakness with repetitive motion 4
- The clinical diagnosis of MC is defined by respiratory failure caused by exacerbation of MG 4
- Infection is the most common stressor that can precipitate MC 4
Treatment and Management
- Treatment should target the inciting event and airway support 4
- All acetylcholinesterase inhibitors should be avoided in crisis, including edrophonium testing and corticosteroids initially 4
- Respiratory support can begin with noninvasive positive-pressure ventilation, as this has been successful even in patients with bulbar weakness 4
- If intubation is necessary, consider avoiding paralytics or use a reduced dose of nondepolarizing agents 4
- Plasma exchange is more effective than intravenous immunoglobulin in the treatment of myasthenia gravis involving respiratory failure 5
- Intravenous immunoglobulin or plasmapheresis can be used as fast-acting immunomodulatory therapies for treating MC 2, 3, 6