A 67-year-old woman arrives speaking in short, breathy phrases, her eyelids drooping as she tries to keep them open under the fluorescent lights. Her daughter says the patient was eating breakfast normally but began choking on tea and could no longer finish a sentence. She has no fever, chest pain, or unilateral weakness, but her neck seems too tired to hold her head upright. The room quiets as her respiratory effort becomes visibly shallower, and the next move has not yet been made.
— What’s your move? Read on.
Before you read
- Which drugs can rapidly worsen neuromuscular transmission?
- When is noninvasive support unsafe?
When to Think of It
Fluctuating, fatigable weakness: ptosis, diplopia, dysarthria, dysphagia, nasal speech, neck flexion weakness, and proximal limb weakness. Ask about counting aloud, sustained upgaze, repeated arm elevation, and the ability to handle secretions. Crisis is suggested by bulbar dysfunction, weak cough, orthopnea, paradoxical breathing, or rapidly declining respiratory measurements.
Sick or Not Sick
The call that matters most: Can the patient protect the airway and sustain ventilation? Do not use pulse oximetry alone. Obtain serial forced vital capacity (FVC) and negative inspiratory force (NIF) when feasible; concerning thresholds are FVC <15–20 mL/kg or NIF weaker than −20 to −30 cm H₂O, but the trajectory and bulbar function outrank a single number. A weak cough, pooling secretions, hypercapnia, or inability to speak in full sentences means ICU-level care and early airway planning.
The First Fifteen Minutes
- Place on continuous cardiac, oxygen-saturation, and end-tidal CO₂ monitoring; sit upright, suction ready, two IVs, bedside glucose, blood gas, CBC/CMP, ECG, and chest radiograph.
- If hypoxemic or in respiratory distress: oxygen by nasal cannula or face mask, titrated to adequate oxygenation, because hypoxemia signals impending ventilatory failure—not merely a need for more oxygen.
- If ventilation is failing but airway protection is intact: initiate BiPAP, commonly IPAP 10–15/EPAP 5–8 cm H₂O, because positive pressure reduces work of breathing; avoid it with copious secretions, vomiting, severe bulbar weakness, or declining mental status.
- If unable to protect the airway, has worsening hypercapnia, exhaustion, or copious secretions: perform controlled endotracheal intubation with an experienced airway team; use the lowest effective dose of a short-acting sedative such as etomidate 0.3 mg/kg IV if hemodynamically tenuous, because it generally preserves blood pressure. Neuromuscular blockers are unusually unpredictable; if paralysis is essential, use rocuronium 0.6–1.2 mg/kg IV, recognizing prolonged effect and checking a reference/institutional airway protocol.
- If infection, fever, or another trigger is suspected: obtain cultures when indicated and give empiric antibiotics based on the suspected source; avoid fluoroquinolones, macrolides, and aminoglycosides when reasonable because they can impair neuromuscular transmission.
- Do not reflexively give extra pyridostigmine during impending crisis: excess acetylcholine can worsen secretions, bronchospasm, and weakness, while the intubated patient needs specialist-directed adjustment.
Definitive Care & Disposition
Admit crisis or significant bulbar dysfunction to the ICU. Neurology should guide IVIG 2 g/kg total divided over 2–5 days or plasma exchange, typically 5 exchanges over 7–10 days; dosing and access strategy vary, so confirm with neurology/institutional protocol. Treat triggers—especially infection, surgery, medication exposure, or thyroid disease. Corticosteroids and steroid-sparing immunotherapy are usually started or adjusted after specialist input; steroids can transiently worsen weakness. Noncrisis patients require neurology follow-up, medication review, respiratory assessment, and admission when swallowing, ambulation, or respiratory mechanics are unreliable.
How This One Kills
The fatal error is waiting for oxygen saturation to fall. A patient with severe bulbar weakness can silently aspirate or develop hypercapnic arrest while pulse oximetry remains normal on supplemental oxygen.
The Differential — What Else Looks Like This
- Cholinergic excess — miosis, diaphoresis, diarrhea, fasciculations, and bronchorrhea; confusing it with crisis can worsen secretions and respiratory failure with more cholinesterase inhibitor.
- Botulism — fixed or dilated pupils, autonomic symptoms, and descending paralysis; missing it delays antitoxin and public-health evaluation.
- Guillain-Barré syndrome — progressive, relatively nonfluctuating weakness with areflexia and sensory symptoms; confusing the two can misdirect testing and treatment.
- Brainstem stroke — abrupt focal deficits, ataxia, or altered consciousness; attributing it to fatigue delays reperfusion evaluation.
The Second-Day Story
Older adults may present with isolated dysphagia, dysarthria, falls, head drop, or unexplained respiratory failure rather than obvious ptosis. Sedatives, pneumonia, electrolyte abnormalities, and recently started antibiotics can erase the classic fluctuating pattern. Repeated examination—counting aloud, sustained upgaze, single-breath counting, cough strength, secretion handling, and serial FVC/NIF—often reveals fatigability that a single normal strength test misses.
Back to Our Patient
Back to our 67-year-old woman: her fatigable dysarthria, choking, neck weakness, and shallow respirations make myasthenic crisis the leading diagnosis. Recognize the emergency through bulbar and respiratory fatigue, then risk-stratify her as sick because she cannot reliably handle secretions or sustain ventilation, regardless of her initially normal oxygen saturation. She is placed upright on continuous monitoring, has serial respiratory mechanics and suction prepared, and undergoes controlled ICU intubation when her cough weakens and hypercapnia appears; neurology then starts IVIG and investigates pneumonia as the trigger. She remains in the ICU for ventilatory support and definitive immunotherapy.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
“This is a 67-year-old woman with known fluctuating eyelid and swallowing weakness presenting with rapidly worsening dysarthria, choking, and short phrases. Her daughter reports abrupt progression over several hours, without fever, chest pain, sensory loss, or unilateral deficits. She has bilateral ptosis, weak neck flexion, pooled secretions, a weak cough, and shallow respirations; oxygen saturation is initially preserved on supplemental oxygen. Serial testing shows falling FVC and rising CO₂, concerning for myasthenic crisis rather than isolated fatigue or stroke. I’m placing her in the ICU pathway with airway and suction support, avoiding neuromuscular-transmission–impairing medications, and proceeding with controlled intubation; neurology will start IVIG or plasma exchange and we’ll search for an infectious trigger.”
Study Directive
- Practice a 60-second bedside MG respiratory exam: single-breath count, cough, secretion handling, neck flexion, and serial FVC/NIF.
- Memorize the crisis triggers and medication classes that impair neuromuscular transmission.
- Review your institution’s IVIG, plasma-exchange, and airway protocols; write down the local ICU and neurology activation pathway.
- Work through two cases distinguishing myasthenic crisis, cholinergic excess, botulism, and brainstem stroke.
Recent Literature
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Review or guideline Myasthenia gravis-Pathophysiology, diagnosis, and treatment
A current comprehensive reference for recognizing myasthenic weakness, confirming the diagnosis, and managing acute deterioration with respiratory monitoring and crisis-directed therapy.