Myasthenia GravisEmergency

Known myasthenia gravis, chest infection; worsening ptosis, nasal speech, choking on liquids, breathless lying flat; single-breath count 14

• FVC <20 mL/kg
• Weak cough, pooling secretions, nasal regurgitation
• Paradoxical breathing
• Neck flexion weakness

• Lambert–Eaton syndrome
• Guillain–Barré (Miller Fisher)
• Botulism
• Brainstem stroke
• Cholinergic crisis (miosis, secretions, fasciculations)

• Admit: Bulbar symptoms, breathlessness, rapidly worsening weakness
• ICU: Myasthenic crisis: falling FVC, bulbar failure
• Intubate: FVC <15–20 mL/kg, NIF weaker than −20 to −30 cmH₂O, aspiration or exhaustion
• Ventilate: Respiratory failure; avoid succinylcholine-type doses and reduce non-depolarising relaxants

• A single-breath count <20 or FVC <20 mL/kg is a warning; <15 mL/kg usually needs ventilation (20/30/40 rule).
• Infection is the commonest trigger — treat it with a β-lactam.
• Thymectomy improves outcomes in AChR-positive generalised MG (MGTX trial).

• Give aminoglycosides, fluoroquinolones, macrolides, IV magnesium or β-blockers in MG
• Wait for desaturation or hypercapnia before intubating
• Start high-dose steroids alone in a crisis without rescue therapy
• Give edrophonium as a bedside test in crisis

• Trusting SpO₂
• MG-worsening antibiotics
• Steroids without IVIG/PLEX in crisis
• Missing thymoma

HDU/ICU during crisis; neurology-led; thymectomy and long-term immunotherapy planned.