Which symptom is most associated with a myasthenic crisis?

• A. Headache
• B. Nausea
• C. Cough without weakness
• D. Shortness of breath

Answer: (D)

Shortness of breath signals respiratory muscle weakness that defines a myasthenic crisis. In myasthenia gravis, weakness worsens with use, and a crisis is an acute deterioration where the diaphragm and intercostal muscles can no longer sustain ventilation. This leads to dyspnea, rapid or shallow breathing, and the risk of respiratory failure requiring urgent ventilatory support. Headache and nausea are nonspecific symptoms and don’t reflect the critical loss of ventilatory function. A cough alone doesn’t indicate crisis, since an effective cough relies on strong respiratory muscles, which are compromised in a crisis. So, the presence of shortness of breath best identifies a myasthenic crisis.